JP2004002740A - Polymer compound, 1,4-phenylenediamine derivative, charge-transporting material, organic electroluminescent element material and organic electroluminescent element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic electroluminescent element drivable at a low voltage and in high luminous efficiency, having good heat resistance and capable of keeping stable luminous characteristics over a long period, in which defect causing short circuit in preparation of element result from surface roughness of an anode is prevented. <P>SOLUTION: In the organic electroluminescent element, a hole-injecting layer 3 containing a polymer compound having a recurring unit represented by formula (I) and an electron-accepting compound is provided. <P>COPYRIGHT: (C)2004,JPO

Description

（式中、環Ｂ１，環Ｂ２，環Ｂ４および環Ｂ５は各々独立してベンゼン環を表し、このベンゼン環は、置換基を有していてもよいアシル基、および置換基を有していてもよいアルコキシカルボニル基よりなる群から選ばれる１種または２種以上の置換基で置換されていてもよい。
環Ｂ３は、置換基を有していてもよいアシル基で置換されていてもよいベンゼン環を表す。
Ｘは、２価の連結基を表す。）
【００２２】
本発明の電荷輸送材料は、このような本発明の高分子化合物を含むものである。
【００２３】
本発明の有機電界発光素子材料は、このような本発明の高分子化合物を含むものである。
【００２４】
本発明の有機電界発光素子は、基板上に陽極、陰極、および該両極間に存在する発光層を有する有機電界発光素子において、このような本発明の高分子化合物を含む層を有することを特徴とする。
【００２５】
即ち、本発明者らは、従来の問題点を解決し、高温において安定な発光特性を維持できる有機電界発光素子を提供するべく鋭意検討した結果、基板上に、陽極および陰極により挟持された発光層を有する有機電界発光素子において、陽極と発光層との間に、電子受容性化合物を含有し、かつ、高いＴｇを有する高分子化合物からなる層を設けることで、上記課題を解決することができることを知見し、上記一般式（Ｉ）で表される繰り返し単位を有する高分子化合物は、ガラス転移温度Ｔｇ≧　１２０℃を容易に達成することができ、このような高いＴｇを有する高分子化合物と電子受容性化合物を混合して用いることで、素子の発光特性と耐熱性を同時に改善することができることを見出し、本発明を完成させた。
【００２６】
本発明の高分子化合物は電子供与性であり、この高分子化合物に電子受容性化合物を混合することにより、電荷移動が起こり、結果としてフリーキャリアである正孔が生成し、この層の電気伝導度が高くなる。このような層を設けることで、発光層と陽極との電気的接合が改善され、駆動電圧が低下すると同時に連続駆動時の安定性も向上する。
【００２７】
しかも、このような高分子化合物を主成分とする層を、塗布プロセスにて陽極上に形成することにより、前述の陽極の表面粗さが緩和され、良好な表面平滑化効果が得られ、素子作製時の短絡欠陥が防止されるという効果も奏される。
【００２８】
なお、本発明に係る高分子化合物と電子受容性化合物を含む層は、正孔輸送性を示す層であり、陽極と発光層との間であればどこにあっても良く、後掲の図１〜３に示す如く、陽極上に直接設けるものに何ら限定されないが、陽極（無機材料）との電気的接合が良く、耐熱性が高いというこの層の長所を十分に生かすためには、陽極と接する位置に正孔注入層として形成するのが最も有利である。
【００２９】
本発明の有機電界発光素子においては、この高分子化合物のイオン化ポテンシャルから電子受容性化合物の電子親和力を引いた値は０．７ｅＶ以下であることが好ましく、また、これらを含有する層中の電子受容性化合物の含有量は、この高分子化合物に対して０．１〜５０重量％の範囲であることが好ましい。
【００３０】
本発明の有機電界発光素子において、電子受容性化合物は、下記化合物群から選ばれる化合物の少なくとも１種であることが好ましい。
【００３１】
【化７】

【００３２】
本発明の１，４−フェニレンジアミン誘導体は、本発明の高分子化合物の合成中間体として有用な単量体であり、下記一般式（ＩＩＩ）で表される。
【００３３】
【化８】

（式中、Ｒ^１，Ｒ^２，Ｒ^４，Ｒ^５は、各々独立して、水素原子、置換基を有していてもよいアシル基、または置換基を有していてもよいアルコキシカルボニル基を表し、
Ｒ^３は、水素原子、または置換基を有していてもよいアシル基を表す。）
【００３４】
【発明の実施の形態】
以下に本発明の実施の形態を詳細に説明する。
まず、本発明の高分子化合物について説明する。
本発明の高分子化合物は、前記一般式（Ｉ）で表される繰り返し単位を有するものである。
【００３５】
前記一般式（Ｉ）中の環Ｂ１，環Ｂ２，環Ｂ４および環Ｂ５は各々独立して、置換されていてもよいベンゼン環である。このベンゼン環が有しうる置換基は、置換基を有していてもよいアシル基、および置換基を有していてもよいアルコキシカルボニル基よりなる群から選ばれる１種または２種以上であり、より具体的には、置換基を有していてもよい、アセチル基等の炭素数１〜６のアシル基；置換基を有していてもよい、メトキシカルボニル基；メトキシカルボニル基等の炭素数２〜７のアルコキシカルボニル基である。
【００３６】
これらの置換基が有していてもよい置換基としては、例えば、下記の置換基群Ｚの１種または２種以上が挙げられる。
［置換基群Ｚ］
メチル基、エチル基等の炭素数１〜６のアルキル基；ビニル基等の炭素数１〜６のアルケニル基；エチニル基等の炭素数１〜６のアルキニル基；メトキシカルボニル基、エトキシカルボニル基等の炭素数２〜７のアルコキシカルボニル基；ジメチルアミノ基、ジエチルアミノ基等の炭素数１〜１０のジアルキルアミノ基；ジフェニルアミノ基、ジトリルアミノ基、カルバゾリル基等のジアリールアミノ基；フェニルメチルアミノ基等のアリールアルキルアミノ基；アセチル基等の炭素数１〜６のアシル基；フッ素原子等のハロゲン原子；トリフルオロメチル基等のハロアルキル基；フェノキシ基、ベンジルオキシ基等のアリールオキシ基；シアノ基；フェニル基、ナフチル基等の芳香族炭化水素環基
【００３７】
環Ｂ１，Ｂ２，Ｂ４，Ｂ５の置換基としては、好ましくは水素原子（即ち、無置換）が挙げられる。
【００３８】
１つの繰り返し単位中に含まれる環Ｂ１，Ｂ２，Ｂ４，Ｂ５は各々同一であっても異なるものであってもよいが、高分子化合物の非晶質性の点からは互いに異なる方が好ましい。
【００３９】
前記一般式（Ｉ）中の環Ｂ３は、置換されていてもよいベンゼン環である。
【００４０】
環Ｂ３が有しうる置換基としては、置換基を有していてもよいアシル基が挙げられ、より具体的には、置換基を有していてもよい、アセチル基等の炭素数１〜６のアシル基である。
【００４１】
これらの置換基が有していてもよい置換基としては、前述の置換基群Ｚの１種または２種以上が挙げられる。
【００４２】
環Ｂ３の置換基としては、好ましくは水素原子（即ち、無置換）が挙げられる。
【００４３】
Ｘは２価の連結基、好ましくは下記構造式で表される部分構造から選ばれた２価の連結基が挙げられる。
【００４４】
【化９】

【００４５】
上記式中、Ａｒ^１１ないしＡｒ^１８は各々独立して、置換基を有していてもよい芳香族環、好ましくは置換基を有していてもよい、５または６員環の単独または２〜３縮合環の、芳香族炭化水素環または芳香族複素環であり、具体的には、ベンゼン環、ナフタレン環、フェナントレン環、アントラセン環、ピリジン環、キノリン環、チオフェン環、ベンゾチオフェン環、フラン環、ピロール環、インドール環、ベンゾフラン環、カルバゾール環が挙げられる。
【００４６】
このような芳香族環が有しうる置換基としては、以下にＲ^２１，Ｒ^２２として例示するものが挙げられる。
【００４７】
Ｒ^２１およびＲ^２２は各々独立して、水素原子、置換基を有していてもよいアルキル基、置換基を有していてもよいアルケニル基、置換基を有していてもよいアルキニル基、置換基を有していてもよいアラルキル基、置換基を有していてもよいアルコキシ基、置換基を有していてもよいアリールオキシ基、置換基を有していてもよいアミノ基、置換基を有していてもよい芳香族炭化水素環基、または置換基を有していてもよい芳香族複素環基を表し、より具体的には、水素原子、メチル基、エチル基等の炭素数１〜６のアルキル基；置換基を有していてもよい、ビニル基等の炭素数１〜６のアルケニル基；置換基を有していてもよい、エチニル基等の炭素数１〜６のアルキニル基；置換基を有していてもよい、ベンジル基等のアラルキル基；置換基を有していてもよい、メトキシ基、エトキシ基等の炭素数１〜６のアルコキシ基；置換基を有していてもよい、フェノキシ基、ベンジルオキシ基等のアリールオキシ基；置換基を有していてもよいアミノ基、例えばジメチルアミノ基、ジエチルアミノ基等の炭素数１〜１０のジアルキルアミノ基；ジフェニルアミノ基、ジトリルアミノ基、カルバゾリル基等のジアリールアミノ基；フェニルメチルアミノ基等のアリールアルキルアミノ基；置換基を有していてもよい、フェニル基、ナフチル基等の芳香族炭化水素環基；置換基を有していてもよい、チエニル基等の芳香族複素環基である。
【００４８】
これらの置換基が有していてもよい置換基としては、前述の置換基群Ｚの１種または２種以上が挙げられる。
【００４９】
Ａｒ^１１〜Ａｒ^１８の置換基、Ｒ^２１，Ｒ^２２として好ましいものは、水素原子（即ち、無置換）、メチル基、エチル基、メトキシ基である。
【００５０】
Ｘは、好ましくは
【化１０】

であり、特に、
【化１１】

であることが好ましい。なお、Ｒ^１１〜Ｒ^１７は、Ａｒ^１１〜Ａｒ^１８が有しうる置換基として前述したものであり、好ましい基についても同様である。
【００５１】
このような本発明の高分子化合物は、好ましくは下記一般式（ＩＩ）で表される単量体、特に好ましくは、下記一般式（ＩＩＩ）で表される、本発明の１，４−フェニレンジアミン誘導体より合成される。
【００５２】
【化１２】

（上記式中、環Ｂ１ないし環Ｂ５は前記一般式（Ｉ）におけると同義である。）
【００５３】
【化１３】

【００５４】
上記式中Ｒ^１，Ｒ^２，Ｒ^４，Ｒ^５は各々独立して、水素原子、置換基を有していてもよいアシル基、置換基を有していてもよいアルコキシカルボニル基、より具体的には、置換基を有していてもよい、アセチル基等の炭素数１〜６のアシル基；置換基を有していてもよい、メトキシカルボニル基、エトキシカルボニル基等の炭素数２〜７のアルコキシカルボニル基である。
【００５５】
また、Ｒ^３は、水素原子、置換基を有していてもよいアシル基であり、より具体的には、置換基を有していてもよい、アセチル基等の炭素数１〜６のアシル基である。
【００５６】
これらの置換基が有していてもよい置換基としては、前述の置換基群Ｚの１種または２種以上が挙げられる。
【００５７】
Ｒ^１ないしＲ^５としては、好ましくは水素原子（即ち、無置換）、フェニル基、ｔ−ブチルフェニル基、スチリル基、ジメチルアミノ基、ジフェニルアミノ基が挙げられる。
【００５８】
以下に本発明の高分子化合物の繰り返し単位の好ましい具体例を示すが、本発明は何らこれらに限定されるものではない。
【００５９】
【化１４】

【００６０】
本発明の高分子化合物は、１種または２種以上の一般式（Ｉ）で表される繰り返し単位からなる高分子化合物である。
【００６１】
更に、本発明の高分子化合物は、その性能を損なわない範囲で、他の種々のモノマー由来の繰り返し単位を含有していてもよい。他のモノマー由来の繰り返し単位としては、例えば前記一般式（Ｉ）で表される繰り返し単位において、
【化１５】

の代わりに
【化１６】

とした繰り返し単位が挙げられるが、有機電界発光素子の製造に有用な化合物としては、前記一般式（Ｉ）で表される繰り返し単位の含有量が、１分子あたり通常２０モル％以上、好ましくは５０モル％以上、さらに好ましくは８０モル％以上のものである。
【００６２】
なお、上記式中、Ｒ^ａ，Ｒ^ｂ，Ｒ^ｃは、各々独立して、置換基を有していてもよいアルキル基、置換基を有していてもよいアルケニル基、置換基を有していてもよいアルキニル基、置換基を有していてもよいアラルキル基、置換基を有していてもよいアシル基、置換基を有していてもよいアミノ基、置換基を有していてもよいアルコキシカルボニル基、置換基を有していてもよい芳香族炭化水素環基、または置換基を有していてもよい芳香族複素環基であり、より具体的には、置換基を有していてもよい、メチル基、エチル基等の炭素数１〜６のアルキル基；置換基を有していてもよい、ビニル基等の炭素数１〜６のアルケニル基；置換基を有していてもよい、エチニル基等の炭素数１〜６のアルキニル基；置換基を有していてもよい、ベンジル基等のアラルキル基；置換基を有していてもよい、アセチル基等の炭素数１〜６のアシル基；置換基を有していてもよいアミノ基、例えばジメチルアミノ基、ジエチルアミノ基等の炭素数１〜１０のジアルキルアミノ基；ジフェニルアミノ基、ジトリルアミノ基、カルバゾリル基等のジアリールアミノ基；フェニルメチルアミノ基等のアリールアルキルアミノ基；置換基を有していてもよい、メトキシカルボニル基；エトキシカルボニル基等の炭素数２〜７のアルコキシカルボニル基；置換基を有していてもよい、フェニル基、ナフチル基等の芳香族炭化水素環基；置換基を有していてもよい、チエニル基等の芳香族複素環基である。
【００６３】
これらの置換基が有していてもよい置換基としては、前述の置換基群Ｚの１種または２種以上が挙げられる。
【００６４】
これらの高分子化合物のうち、特に重量平均分子量が１，０００〜１，０００，０００のものが有機電界発光素子の製造に有用である。また、この高分子化合物を含む層を、塗布法により形成する場合には、架橋度により差があるが、通常は、溶解性の点から重量平均分子量が１０，０００〜２００，０００程度のものが好ましい。
【００６５】
本発明の高分子化合物は、例えば、先ずヒドロキシフェニル基を有する１，４−フェニレンジアミン誘導体を合成し、それと、４，４’−ジフルオロベンゾフェノン、ビス（４−フルオロフェニル）スルホン等の芳香族二フッ化物とを反応させることにより得られる。
【００６６】
本発明の高分子化合物は、高い電荷輸送性を有するため、電荷輸送材料として電子写真感光体、有機電界発光素子、光電変換素子、有機太陽電池、有機整流素子等に好適に使用できる。特に正孔輸送性に優れることから、正孔輸送材料として好適である。
【００６７】
また本発明の高分子化合物を用いることにより、耐熱性に優れ、長期間安定に駆動（発光）する有機電界発光素子が得られるため、有機電界発光素子材料として好適である。
【００６８】
次に、図面を参照して本発明の有機電界発光素子の実施の形態を詳細に説明する。
【００６９】
図１〜３は本発明の有機電界発光素子の実施の形態を示す模式的な断面図であり、１は基板、２は陽極、３は正孔注入層、４は正孔輸送層、５は発光層、６は電子輸送層、７は陰極を各々表わす。
【００７０】
基板１は有機電界発光素子の支持体となるものであり、石英やガラスの板、金属板や金属箔、プラスチックフィルムやシートなどが用いられる。特にガラス板や、ポリエステル、ポリメタクリレート、ポリカーボネート、ポリスルホンなどの透明な合成樹脂の板が好ましい。合成樹脂基板を使用する場合にはガスバリア性に留意する必要がある。基板のガスバリア性が低すぎると、基板を通過する外気により有機電界発光素子が劣化することがあるので好ましくない。このため、合成樹脂基板のどちらか片側もしくは両側に緻密なシリコン酸化膜等を設けてガスバリア性を確保してもよい。
【００７１】
基板１上には陽極２が設けられるが、陽極２は正孔注入層３への正孔注入の役割を果たすものである。この陽極２は、通常、アルミニウム、金、銀、ニッケル、パラジウム、白金等の金属、インジウムおよび／またはスズの酸化物などの金属酸化物、ヨウ化銅などのハロゲン化金属、カーボンブラック等により構成される。陽極２の形成は通常、スパッタリング法、真空蒸着法などにより行われることが多い。また、銀などの金属微粒子、ヨウ化銅などの微粒子、カーボンブラック、導電性の金属酸化物微粒子等を適当なバインダー樹脂溶液に分散し、基板１上に塗布することにより陽極２を形成することもできる。陽極２は異なる物質で積層して形成することも可能である。陽極２の厚みは、必要とされる透明性により異なる。透明性が必要とされる場合は、可視光の透過率を、通常、６０％以上、好ましくは８０％以上とすることが望ましく、この場合、陽極２の厚みは、通常、１０００ｎｍ以下、好ましくは　５００ｎｍ以下であり、下限は１０ｎｍ程度、好ましくは２０ｎｍ程度である。不透明でよい場合には陽極２は基板１と同一でもよい。また、さらには上記の陽極２の上に異なる導電材料を積層することも可能である。
【００７２】
本発明では、図１の素子構造においては、陽極２の上に正孔注入層３が設けられる。この正孔注入層３に用いられる材料に要求される条件としては、陽極２からの正孔注入効率が高く、かつ、注入された正孔を効率よく輸送することができる材料であることが挙げられる。そのためには、イオン化ポテンシャルが小さく、可視光の光に対して透明性が高く、しかも正孔移動度が大きく、さらに安定性に優れ、トラップとなる不純物が製造時や使用時に発生しにくいことが要求される。上記の一般的要求以外に、車載表示用の応用を考えた場合、素子にはさらに１２０℃以上の耐熱性が要求される。
【００７３】
本発明の有機電界発光素子は、好ましくはこの正孔注入層３が前記一般式（Ｉ）で表わされる繰り返し単位を有する本発明の高分子化合物と、電子受容性化合物とを含有するものである。
【００７４】
本発明においては、通常、　１２０℃以上のＴｇを有する本発明の高分子化合物と電子受容性化合物を混合して用いることで、素子の発光特性と耐熱性を同時に改善することを可能とした。即ち、電子供与性の前記高分子化合物に電子受容性化合物を混合することにより、電荷移動が起こり、結果としてフリーキャリアである正孔が生成し、正孔注入層の電気電導度が高くなる。このため、発光層５と陽極２との電気的接合が、本発明による正孔注入層３を設けることで改善され、駆動電圧が低下すると同時に連続駆動時の安定性も向上する。また、
１２０℃以上のＴｇを有する高分子化合物を正孔注入層３の母体とすることにより、素子の耐熱性も大きく改善される。
【００７５】
しかも、このような本発明の高分子化合物を主成分とする正孔注入層３を、塗布プロセスにて陽極２上に形成することにより、前述の陽極２の表面粗さが緩和され、良好な表面平滑化効果が得られ、素子作製時の短絡欠陥が防止されるという効果も奏される。
【００７６】
正孔注入層３に、本発明の高分子化合物と組み合わせて用いる電子受容性化合物としては、該高分子化合物との間で電荷移動を起こすものであればよいが、本発明者らが鋭意検討した結果、正孔注入層３に用いる本発明の高分子化合物のイオン化ポテンシャル：ＩＰ（本発明の高分子化合物）、と電子受容性化合物（アクセプタ）の電子親和力：ＥＡ（アクセプタ）の２つの物性値が、
ＩＰ（本発明の高分子化合物）−ＥＡ（アクセプタ）≦０．７ｅＶ、
の関係式で表される時に、本発明の目的に特に有効であることを見出した。
【００７７】
このことを図４のエネルギー準位図を用いて説明する。一般に、イオン化ポテンシャルおよび電子親和力は真空準位を基準として決定される。イオン化ポテンシャルは物質のＨＯＭＯ（最高被占分子軌道）レベルにある電子を真空準位に放出するのに必要なエネルギーで定義され、電子親和力は真空準位にある電子が物質のＬＵＭＯ（最低空分子軌道）レベルに落ちて安定化するエネルギーで定義される。
【００７８】
図４に示す本発明の高分子化合物のＨＯＭＯレベルのイオン化ポテンシャルと、電子受容性化合物のＬＵＭＯレベルの電子親和力の差が　０．７ｅＶ以下であることが好ましい。イオン化ポテンシャルは光電子分光法で直接測定されるか、電気化学的に測定した酸化電位を基準電極に対して補正しても求められる。後者の方法の場合は、例えば、飽和甘コウ電極（ＳＣＥ）を基準電極として用いたとき、
イオン化ポテンシャル＝酸化電位（ｖｓ．ＳＣＥ）＋４．３ｅＶ、
で表される（“Ｍｏｌｅｃｕｌａｒ　Ｓｅｍｉｃｏｎｄｕｃｔｏｒｓ”，Ｓｐｒｉｎｇｅｒ−Ｖｅｒｌａｇ，１９８５年、９８頁）。電子親和力は、上述のイオン化ポテンシャルから光学的バンドギャップを差し引いて求められるか、電気化学的な還元電位から上記の式で同様に求められる。
【００７９】
前記イオン化ポテンシャルと電子親和力の関係式は、酸化電位と還元電位を用いて、
（本発明の高分子化合物の酸化電位）−（アクセプタの還元電位）≦０．７Ｖ、と表現することもできる。
【００８０】
なお、後述する発光層や正孔輸送層など、隣接する有機層への効率よい正孔注入の観点からは、イオン化ポテンシャルがあまり低すぎない方が更に好ましく、−０．１ｅＶ≦｛ＩＰ（本発明の高分子化合物）−ＥＡ（アクセプタ）｝
すなわち
−０．１Ｖ≦｛ＩＰ（本発明の高分子化合物の酸化電位）−ＥＡ（アクセプタの還元電位）｝
であることが好ましい。
【００８１】
また、正孔注入層３中の電子受容性化合物の含有量は、本発明の高分子化合物に対して０．１〜５０重量％の範囲にあることが好ましい。さらに好ましくは、１〜３０重量％の濃度範囲が実用特性上望ましい。
【００８２】
電子受容性化合物としては、前述の関係を満たすものであれば特に限定はされないが、好ましい例を、以下に省略名とともに示す。
【００８３】
【化１７】

【００８４】
本発明の高分子化合物と電子受容性化合物を含有する正孔注入層３は塗布法により前記陽極２上に形成される。即ち、前記一般式（Ｉ）で表される繰り返し単位を有する本発明の高分子化合物と電子受容性化合物の所定量に、必要により正孔のトラップにならないバインダー樹脂や塗布性改良剤などの添加剤を添加し、適当な溶媒に溶解して塗布溶液を調製し、スピンコート法、ディップコート法やインクジェット法などの方法により陽極２上に塗布し、乾燥して正孔注入層３を形成する。
【００８５】
正孔注入・輸送能の点から、正孔注入層３中の本発明の高分子化合物と電子受容性化合物との合計の含有量は２０重量％以上、特に５０重量％以上であることが好ましい。
【００８６】
正孔注入層３の膜厚の上限は、通常１０００ｎｍ、好ましくは５００　ｎｍであり、下限は、通常５　ｎｍ、好ましくは１０ｎｍである。
【００８７】
正孔注入層３の上には発光層５が設けられる。発光層５は、電界を与えられた電極間において陰極７からの注入された電子と正孔注入層３から輸送された正孔を効率よく再結合し、かつ、再結合により効率よく発光する材料から形成される。
【００８８】
このような条件を満たす材料としては、８−ヒドロキシキノリンのアルミニウム錯体などの金属錯体（特開昭５９−１９４３９３号公報）、１０−ヒドロキシベンゾ〔ｈ〕キノリンの金属錯体（特開平６−３２２３６２号公報）、ビススチリルベンゼン誘導体（特開平１−２４５０８７号公報、同２−２２２４８４号公報）、ビススチリルアリーレン誘導体（特開平２−２４７２７８号公報）、（２−ヒドロキシフェニル）ベンゾチアゾールの金属錯体（特開平８−３１５９８３号公報）、シロール誘導体等が挙げられる。これらの発光層材料は、通常は真空蒸着法により正孔注入層３上に積層される。
【００８９】
素子の発光効率を向上させるとともに発光色を変える目的で、例えば、８−ヒドロキシキノリンのアルミニウム錯体をホスト材料として、クマリン等のレーザ用蛍光色素をドープすること（Ｊ．　Ａｐｐｌ．　Ｐｈｙｓ．，　６５巻，　３６１０頁，　１９８９年）等が行われている。
【００９０】
素子の駆動寿命を改善する目的においても、前記発光層材料をホスト材料として、蛍光色素をドープすることは有効である。例えば、８−ヒドロキシキノリンのアルミニウム錯体などの金属錯体をホスト材料として、ルブレンに代表されるナフタセン誘導体（特開平４−３３５０８７号公報）、キナクリドン誘導体（特開平５−７０７７３号公報）、ペリレン等の縮合多環芳香族炭化水素環（特開平５−１９８３７７号公報）を、ホスト材料に対して　０．１〜１０重量％ドープすることにより、素子の発光特性、特に駆動安定性を大きく向上させることができる。発光層のホスト材料に上記ナフタセン誘導体、キナクリドン誘導体、ペリレン等の蛍光色素をドープする方法としては、共蒸着による方法と蒸着源を予め所定の濃度で混合しておく方法がある。
【００９１】
高分子系の発光層材料としては、先に挙げたポリ（ｐ−フェニレンビニレン）、ポリ［２−メトキシ−５−（２−エチルヘキシルオキシ）−１，４−フェニレンビニレン］、ポリ（３−アルキルチオフェン）等の高分子材料や、ポリビニルカルバゾール等の高分子に発光材料と電子移動材料を混合した系等が挙げられる。これらの材料は正孔注入層３と同様にスピンコートやディップコート等の方法により正孔注入層３上に塗布して薄膜化される。
【００９２】
発光層５の膜厚の上限は、通常２００　ｎｍ、好ましくは１００　ｎｍであり、下限は通常１０ｎｍ、好ましくは３０ｎｍである。
【００９３】
素子の発光特性を向上させるために、図２に示す様に、正孔輸送層４を正孔注入層３と発光層５との間に設けたり、さらには、図３に示す様に電子輸送層６を発光層５と陰極７の間に設けるなどして機能分離型の有機電解発光素子とすることが行われる。
【００９４】
図２および図３の機能分離型素子において、正孔輸送層４の材料としては、正孔注入層３からの正孔注入効率が高く、かつ、注入された正孔を効率よく輸送することができる材料であることが必要である。そのためには、イオン化ポテンシャルが小さく、しかも正孔移動度が大きく、さらに安定性に優れ、トラップとなる不純物が製造時や使用時に発生しにくいことが要求される。また、発光層５と直接接する層であるために、発光を消光する物質が含まれていないことが望ましい。
【００９５】
このような正孔輸送材料としては、例えば、４，４’−ビス［Ｎ−（９−ナフチル）−Ｎ−フェニルアミノ］ビフェニルで代表される２個以上の３級アミンを含み２個以上の縮合芳香族炭化水素環が窒素原子に置換した芳香族ジアミン（特開平５−２３４６８１号公報）、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等のスターバースト構造を有する芳香族アミン化合物（Ｊ．　Ｌｕｍｉｎ．，　７２−７４巻、９８５頁、１９９７年）、トリフェニルアミンの四量体から成る芳香族アミン化合物（Ｃｈｅｍ．Ｃｏｍｍｕｎ．，　２１７５頁、１９９６年）、２，２’，７，７’−テトラキス−（ジフェニルアミノ）−９，９’−スピロビフルオレン等のスピロ化合物（Ｓｙｎｔｈ．　Ｍｅｔａｌｓ，　９１巻、２０９頁、１９９７年）等が挙げられる。これらの化合物は、単独で用いてもよいし、必要に応じて２種以上を混合して用いてもよい。
【００９６】
上記の化合物以外に、正孔輸送層４の材料として、ポリビニルカルバゾール、ポリビニルトリフェニルアミン（特開平７−５３９５３号公報）、テトラフェニルベンジジンを含有するポリアリーレンエーテルサルホン（Ｐｏｌｙｍ．　Ａｄｖ．　Ｔｅｃｈ．，
７巻、３３頁、１９９６年）等の高分子材料が挙げられる。
【００９７】
正孔輸送層４は、上記の正孔輸送材料を塗布法あるいは真空蒸着法により前記正孔注入層３上に積層することにより形成される。
【００９８】
塗布法の場合は、正孔輸送材料の１種または２種以上と、必要により正孔のトラップにならないバインダー樹脂や塗布性改良剤などの添加剤とを添加し、適当な溶媒に溶解して塗布溶液を調製し、スピンコート法などの方法により陽極２上に塗布し、乾燥して正孔輸送層４を形成する。この場合、バインダー樹脂としては、ポリカーボネート、ポリアリレート、ポリエステル等を用いることができる。バインダー樹脂は添加量が多いと正孔移動度を低下させるので、少ない方が望ましく、通常、正孔輸送層４中の割合で５０重量％以下が好ましい。
【００９９】
真空蒸着法の場合には、正孔輸送材料を真空容器内に設置されたルツボに入れ、真空容器内を適当な真空ポンプで１０^−４Ｐａ程度にまで排気した後、ルツボを加熱して、正孔輸送材料を蒸発させ、ルツボと向き合って置かれた、正孔注入層３が形成された基板１上に正孔輸送層４を形成させる。
【０１００】
正孔輸送層４の膜厚の上限は、通常３００　ｎｍ、好ましくは１００　ｎｍであり、下限は通常１０ｎｍ、好ましくは３０ｎｍである。このように薄い膜を一様に形成するためには、一般に真空蒸着法がよく用いられる。
【０１０１】
有機電界発光素子の発光効率をさらに向上させる方法として、図３に示すように発光層４の上にさらに電子輸送層６を積層することもできる。この電子輸送層６に用いられる化合物には、陰極７からの電子注入が容易で、電子の輸送能力がさらに大きいことが要求される。この様な電子輸送材料としては、既に発光層材料として挙げた８−ヒドロキシキノリンのアルミ錯体、オキサジアゾール誘導体（Ａｐｐｌ．　Ｐｈｙｓ．　Ｌｅｔｔ．，　５５巻，　１４８９頁，　１９８９年）やそれらをポリメタクリル酸メチル（ＰＭＭＡ）等の樹脂に分散した系、フェナントロリン誘導体（特開平５−３３１４５９号公報）、２−ｔ−ブチル−９，１０−Ｎ，Ｎ’−ジシアノアントラキノンジイミン、ｎ型水素化非晶質炭化シリコン、ｎ型硫化亜鉛、ｎ型セレン化亜鉛等が挙げられる。
【０１０２】
電子輸送層６の膜厚の上限は、通常２００　ｎｍ、好ましくは１００　ｎｍであり、下限は通常５ｎｍ、好ましくは１０ｎｍである。
【０１０３】
陰極７は、発光層５に電子を注入する役割を果たす。陰極７の形成材料としては、前記陽極２に使用される材料を用いることが可能であるが、効率よく電子注入を行なうには、仕事関数の低い金属が好ましく、スズ、マグネシウム、インジウム、カルシウム、アルミニウム、銀等の適当な金属またはそれらの合金が用いられる。具体例としては、マグネシウム−銀合金、マグネシウム−インジウム合金、アルミニウム−リチウム合金等の低仕事関数合金電極が挙げられる。さらに、陰極７と発光層５または電子輸送層６の界面にＬｉＦ、ＭｇＦ_２、Ｌｉ_２Ｏ等の極薄絶縁膜（０．１〜５ｎｍ）を挿入することも、素子の効率を向上させる有効な方法である（Ａｐｐｌ．　Ｐｈｙｓ．　Ｌｅｔｔ．，　７０巻，１５２頁，１９９７年；特開平１０−７４５８６号公報；ＩＥＥＥ　Ｔｒａｎｓ．　Ｅｌｅｃｔｒｏｎ．　Ｄｅｖｉｃｅｓ，４４巻，１２４５頁，１９９７年）。
【０１０４】
陰極７の膜厚は通常、陽極２と同様である。低仕事関数金属から成る陰極を保護する目的で、この上にさらに、仕事関数が高く大気に対して安定な金属層を積層することは素子の安定性を増す。この目的のために、アルミニウム、銀、銅、ニッケル、クロム、金、白金等の金属が使われる。
【０１０５】
図１〜３は、本発明で採用される素子構造の一例であって、本発明は何ら図示のものに限定されるものではない。例えば、図１とは逆の構造、即ち、基板上に陰極７、発光層５、正孔注入層３、陽極２の順に積層することも可能であり、既述したように少なくとも一方が透明性の高い２枚の基板の間に本発明の有機電界発光素子を設けることも可能である。同様に、図２および図３に示した前記各層構成とは逆の構造に積層することも可能である。
【０１０６】
更に、本発明の有機電界発光素子の性能を損なわない限り、図１、図２および図３に示した各層間に任意の層を有していてもよい。
【０１０７】
このような本発明の有機電界発光素子は、単一の素子、アレイ状に配置された構造からなる素子、陽極と陰極がＸ−Ｙマトリックス状に配置された構造のいずれにも適用することができる。
【０１０８】
【実施例】
次に、本発明を合成例、実験例、実施例および比較例によって更に具体的に説明するが、本発明はその要旨を超えない限り、以下の実施例の記載に限定されるものではない。
【０１０９】
まず、一般式（Ｉ）で表される繰り返し単位を有する高分子化合物の原料となる、本発明の１，４−フェニレンジアミン誘導体の合成例を示す。
【０１１０】
合成例１
（１−１）Ｎ，Ｎ’−ジフェニル−Ｎ，Ｎ’−ビス（４−メトキシフェニル）−１，４−フェニレンジアミン（ＢＭＰＰ）の合成
【０１１１】
【化１８】

【０１１２】
Ｎ，Ｎ’−ジフェニル−１，４−フェニレンジアミン（７７．０ミリモル）と４−ヨードアニソール（２３１ミリモル）とをテトラグライム１５０ミリリットルに溶かし、銅粉末（１５４ミリモル）および炭酸カリウム（１１２ミリモル）の存在下、窒素雰囲気中２００℃で８時間反応を行った。その結果、式（Ｖ）で示されるＢＭＰＰ（３４．８ｇ、収率９６％）を得た。
【０１１３】
（１−２）Ｎ，Ｎ’−ジフェニル−Ｎ，Ｎ’−（４−ヒドロキシフェニル）−１，４−フェニレンジアミン（ＢＨＰＰ）の合成
【０１１４】
【化１９】

【０１１５】
ＢＭＰＰ（５０．０ミリモル）を３６０ミリリットルの塩化メチレンに溶かし、窒素雰囲気下、ドライアイス−エタノールバスで系内を−６５℃以下に冷やし、これに三臭化ほう素（１００ミリモル）の塩化メチレン溶液（１００ミリリットル）を滴下した。滴下終了後、冷媒バスを外し２時間撹拌した後、酢酸エチルで抽出し、シリカゲルカラムクロマトフラフィーによって精製した。その結果、式（ＶＩ）で示されるＢＨＰＰ（１６．２ｇ、収率７３％）を得た。
【０１１６】
以下に、ＢＨＰＰの^１Ｈ−ＮＭＲ（ＤＭＳＯ−ｄ_６）データを示す。
９．３６１（２Ｈ，Ｓ）
７．１８９（４Ｈ，ｄｄ，Ｊ＝６．７，６．６）
６．９３６（４Ｈ，ｄｄ，Ｊ＝５．７，１．７）
６．８７５（４Ｈ，Ｓ）
６．８６５−６．８３７（６Ｈ，ｍ）
６．７５１（４Ｈ，ｄｄ，Ｊ＝５．７，１．７）
【０１１７】
次に本発明の高分子化合物の合成例を示す。
【０１１８】
合成例２
１，４−フェニレンジアミン含有高分子化合物（ＰＰＰＥＫ）の合成
【０１１９】
【化２０】

【０１２０】
ＢＨＰＰ（２０．０ミリモル）と４，４’−ジフルオロベンゾフェノン（２０．０ミリモル）とを２００ミリリットルの１−メチル２−ピロリジノン（ＮＭＰ）に溶かし、炭酸カリウム（１２０ミリモル）の存在下、窒素雰囲気中１４５℃で２０時間、縮合反応させた。放冷後、酢酸１０ミリリットルを反応系に加え、メタノール中に放出し、得られたポリマーを水洗いし、無機塩を除いた。６０℃で減圧乾燥させた後、ポリマーを３００ミリリットルのクロロホルムに溶かし、メタノールに放出し再沈殿させた。最後に、４００ミリリットルのアセトンで懸洗することにより、低分子量成分を除き、繰り返し単位（ＩＸ）からなるホモポリマーＰＰＰＥＫ（収量１１．８ｇ、収率９５％）を得た。
【０１２１】
このポリマーのＴｇは１８３℃、窒素雰囲気下の熱分解温度は５５０℃以上であり、重量平均分子量（Ｍｗ）は４６，７００、数平均分子量（Ｍｎ）７，５２０であった。なお、分子量はクロロホルム中でＧＰＣ測定により、ポリスチレンを標準試料として求めた。
【０１２２】
次に、合成例２で得られた１，４−フェニレンジアミン含有高分子化合物のイオン化ポテンシャルを測定する実験例を示す。
【０１２３】
実験例１
ガラス基板をアセトンで超音波洗浄、純水で水洗した後、イソプロピルアルコールで超音波洗浄し、次いで乾燥窒素で乾燥後、紫外線／オゾン洗浄を行った後、合成例２にて得られた１，４−フェニレンジアミン含有高分子化合物（ＰＰＰＥＫ）を下記の条件で、上記ガラス基板上にスピンコートした：
溶媒　　　　　：シクロヘキサノン
塗布液濃度　　：５．０　ｍｇ／ｍｌ
スピナ回転数　：１５００　ｒｐｍ
スピナ回転時間：３０秒
乾燥条件　　　：１２０℃で２時間
【０１２４】
上記のスピンコートにより２０ｎｍの膜厚の均一な薄膜が形成された。この薄膜試料のイオン化ポテンシャルを理研計器（株）製の紫外線電子分析装置（ＡＣ−１）を用いて測定したところ、５．１８ｅＶの値を示した。
【０１２５】
いくつかの電子受容性化合物について、還元電位が報告されているものについての電子親和力と、上記１，４−フェニレンジアミン含有高分子化合物（ＰＰＰＥＫ）のイオン化ポテンシャルとの差を表１に示す。
【０１２６】
【表１】

【０１２７】
以下に、合成された１，４−フェニレンジアミン含有高分子化合物を用いた有機電界発光素子の性能評価を行う実施例と比較例を挙げる。
【０１２８】
実施例１
図３に示す構造を有する有機電界発光素子を以下の方法で作製した。
【０１２９】
ガラス基板１上にインジウム・スズ酸化物（ＩＴＯ）透明導電膜を　１２０ｎｍ堆積したもの（ジオマテック社製；電子ビーム成膜品；シート抵抗１５Ω／ｓｑ）を通常のフォトリソグラフィ技術と塩酸エッチングを用いて２ｍｍ幅のストライプにパターニングして陽極２を形成した。パターン形成したＩＴＯ基板を、アセトンによる超音波洗浄、純水による水洗、イソプロピルアルコールによる超音波洗浄の順で洗浄後、窒素ブローで乾燥させ、最後に紫外線／オゾン洗浄を行った。
【０１３０】
このＩＴＯガラス基板上に、１，４−フェニレンジアミン含有高分子化合物（ＰＰＰＥＫ）とＰＰＢの混合物を下記の条件でスピンコートした。
［スピンコート条件］
溶媒　　　　　：シクロヘキサノン
ＰＰＰＥＫ　　：５．０　ｍｇ／ｍｌ
ＰＰＢ　　　　：０．５　ｍｇ／ｍｌ
スピナ回転数　：１５００　ｒｐｍ
スピナ回転時間：３０秒
乾燥条件　　　：１２０℃で２時間
【０１３１】
上記のスピンコートにより２０ｎｍの膜厚の均一な薄膜形状を有する正孔注入層３を形成した。
【０１３２】
次に、上記正孔注入層３を塗布成膜した基板を真空蒸着装置内に設置した。この装置の粗排気を油回転ポンプにより行った後、装置内の真空度が２×１０^−６Ｔｏｒｒ（約２．７×１０^−４Ｐａ）以下になるまで液体窒素トラップを備えた油拡散ポンプを用いて排気した。この装置内に配置されたセラミックるつぼに入れた以下に示す芳香族ジアミン化合物：４，４’−ビス［Ｎ−（９−フェナンチル）−Ｎ−フェニルアミノ］ビフェニルを加熱して蒸着を行った。蒸着時の真空度は１．３×１０^−６Ｔｏｒｒ（約１．７×１０^−４Ｐａ）、蒸着速度は０．３ｎｍ／秒で、膜厚２０ｎｍの膜を正孔注入層３の上に積層して正孔輸送層４を完成させた。
【０１３３】
【化２１】

【０１３４】
引続き、発光層５の材料として、以下の構造式に示すアルミニウムの８−ヒドロキシキノリン錯体：Ａｌ（Ｃ_９Ｈ_６ＮＯ）_３、とルブレンとを同時に蒸着した。
【０１３５】
【化２２】

【０１３６】
アルミニウムの８−ヒドロキシキノリン錯体に対するルブレンの割合は２．５ｖｏｌ．％になるようにした。この時のアルミニウムの８−ヒドロキシキノリン錯体のるつぼ温度は２７５〜２８５℃の範囲で制御し、蒸着時の真空度は１．２×１０^−６Ｔｏｒｒ（約１．６×１０^−４Ｐａ）、蒸着速度は０．４ｎｍ／秒であった。またルブレンのるつぼ温度は２４０〜２５０℃の範囲で制御し、蒸着速度は０．０１ｎｍ／秒であった。このように蒸着された発光層５の膜厚は３０ｎｍであった。
【０１３７】
続いて、電子輸送層６としてアルミニウムの８−ヒドロキシキノリン錯体：Ａｌ（Ｃ_９Ｈ_６ＮＯ）_３を正孔輸送層４と同様にして蒸着を行った。この時のアルミニウムの８−ヒドロキシキノリン錯体のるつぼ温度は２７５〜２８５℃の範囲で制御し、蒸着時の真空度は１．１×１０^−６Ｔｏｒｒ（約１．５×１０^−４Ｐａ）、蒸着速度は０．４ｎｍ／秒で、蒸着された電子輸送層６の膜厚は４５ｎｍであった。
【０１３８】
なお、上記の正孔輸送層４および発光層５、電子輸送層６を真空蒸着する時の基板温度は室温に保持した。
【０１３９】
ここで、電子輸送層６までの蒸着を行った素子を一度前記真空蒸着装置内より大気中に取り出して、陰極蒸着用のマスクとして　２ｍｍ幅のストライプ状シャドーマスクを、陽極２のＩＴＯストライプと直交するように素子に密着させた後、別の真空蒸着装置内に設置して、各有機層形成時と同様にして装置内の真空度が２×１０^−６Ｔｏｒｒ（約２．７×１０^−４Ｐａ）以下になるまで排気した。
【０１４０】
その後、陰極７として、先ず、フッ化リチウム（ＬｉＦ）をモリブデンボートを用いて、蒸着速度０．０２ｎｍ／秒、真空度７．０×１０^−６Ｔｏｒｒ（約９．３×１０^−４Ｐａ）で、０．５ｎｍの膜厚となるように電子輸送層６の上に成膜した。次に、アルミニウムを同様にモリブデンボートにより加熱して、蒸着速度０．５ｎｍ／秒、真空度１×１０^−５Ｔｏｒｒ（約１．３×１０^−３Ｐａ）で、膜厚８０ｎｍのアルミニウム層を形成して、陰極７を完成させた。以上の２層型陰極７の蒸着時の基板温度は室温に保持した。
【０１４１】
以上の様にして、２ｍｍ×２ｍｍのサイズの発光面積部分を有する有機電界発光素子が得られた。この素子の発光特性を表２に示す。表２において、発光輝度は２５０ｍＡ／ｃｍ^２の電流密度での値、発光効率は１００ｃｄ／ｍ^２での値、輝度／電流は輝度−電流密度特性の傾きを、電圧は
１００ｃｄ／ｍ^２での値を各々示す。
【０１４２】
表２より、駆動電圧の低い、高輝度かつ高発光効率で発光する素子が得られたことが明らかである。
【０１４３】
【表２】

【０１４４】
比較例１
１，４−フェニレンジアミン含有高分子化合物（ＰＰＰＥＫ）の代わりに、特開平９−１８８７５６号公報中９頁に記載されている、下記の繰り返し単位（ＸＩ）のみからなるホモポリマー（重量平均分子量（Ｍｗ）７４７００，数平均分子量（Ｍｎ）１５０００）を用い、正孔注入層３を形成する際の、ＩＴＯガラス基板上へのスピンコートの条件を以下の通りとした他は、実施例１と同様に素子を作成した。
【０１４５】
【化２３】

【０１４６】
［スピンコート条件］
溶媒　　　　　　：シクロヘキサノン
高分子化合物（ＸＩ）：５．０　ｍｇ／ｍｌ
ＰＰＢ　　　　　：０．５　ｍｇ／ｍｌ
スピナ回転数　　：１５００　ｒｐｍ
スピナ回転時間　：３０秒
乾燥条件　　　　：１２０℃で２時間
【０１４７】
比較例１にて得られた素子と、実施例１にて得られた素子について、駆動寿命を評価した。駆動寿命は、初期輝度３００ｃｄ／ｍ^２、８５℃で駆動した時の輝度半減時間で表した。結果を表３に示す。
【０１４８】
【表３】

【０１４９】
表３より、本発明の有機電界発光素子は、駆動寿命が長く、耐熱性に優れることが示された。
【０１５０】
以上の結果から明らかなように、塗布プロセスに有利な、本発明の高分子化合物と電子受容性化合物を含有する正孔注入層を形成することにより、低電圧で駆動可能かつ耐熱性の向上した素子を得ることができる。
【０１５１】
【発明の効果】
以上詳述した通り、本発明の新規高分子化合物、好ましくは本発明の新規１，４−フェニレンジアミン誘導体より合成される高分子化合物を用いることにより、低電圧、高発光効率で駆動させることができ、かつ良好な耐熱性を有し、長期間にわたって安定な発光特性を維持することができる有機電界発光素子であって、陽極の表面粗さに起因する素子作製時の短絡欠陥を防止した有機電界発光素子が提供される。
【０１５２】
従って、本発明による有機電界発光素子は、フラットパネル・ディスプレイ（例えばＯＡコンピュータ用や壁掛けテレビ）や面発光体としての特徴を生かした光源（例えば、複写機の光源、液晶ディスプレイや計器類のバックライト光源）、表示板、標識灯への応用が考えられ、特に、高耐熱性が要求される車載用表示素子としては、その技術的価値は大きいものである。
【図面の簡単な説明】
【図１】本発明の有機電界発光素子の実施の形態の一例を示す模式的な断面図である。
【図２】本発明の有機電界発光素子の実施の形態の他の例を示す模式的な断面図である。
【図３】本発明の有機電界発光素子の実施の形態の別の例を示す模式的な断面図である。
【図４】本発明の高分子化合物のイオン化ポテンシャルと電子受容性化合物の電子親和力との関係を示したエネルギー準位図である。
【符号の説明】
１　基板
２　陽極
３　正孔注入層
４　正孔輸送層
５　発光層
６　電子輸送層
７　陰極[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a novel polymer compound, a novel 1,4-phenylenediamine derivative as a combined intermediate of the polymer compound, a charge transport material using the polymer compound, an organic electroluminescent device material, and an organic electroluminescence. The present invention relates to an element, that is, a thin film device that emits light by applying an electric field to a light emitting layer made of an organic compound.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, thin-film electroluminescence (EL) devices include inorganic materials such as ZnS, CaS, and SrS, which are group II-VI compound semiconductors, as well as Mn as a luminescence center and rare earth elements (Eu, Ce, Tb, and Sm) ) Is generally used, but an EL device made from the above inorganic material is
1) AC drive is required (50-1000Hz)
2) high driving voltage (up to 200 V);
3) It is difficult to make full color,
4) The cost of the peripheral drive circuit is high,
There is a problem that.
[0003]
However, in recent years, EL devices using organic thin films have been developed to improve the above problems. In particular, in order to enhance the luminous efficiency, the type of the electrode is optimized for the purpose of improving the efficiency of carrier injection from the electrode, and a hole transport layer composed of an aromatic diamine and a luminescent layer composed of an aluminum complex of 8-hydroxyquinoline are provided. The development of an organic electroluminescent device provided with (see Non-Patent Document 1) greatly improved the luminous efficiency as compared with a conventional EL device using a single crystal such as anthracene, and is approaching practical characteristics.
[0004]
In addition to the electroluminescent device using a low molecular material as described above, poly (p-phenylenevinylene) and poly [2-methoxy-5- (2-ethylhexyloxy) -1,4 may be used as the material of the light emitting layer. -Phenylenevinylene], development of an electroluminescent device using a polymer material such as poly (3-alkylthiophene) and polyfluorene, and mixing and dispersing a low-molecular light-emitting material and an electron transfer material in a polymer such as polyvinylcarbazole. Devices are also being developed.
[0005]
By the way, the biggest problem of the organic electroluminescent device is the life during driving. The instability during driving includes a decrease in light emission luminance, an increase in voltage during constant current driving, generation of a non-light emitting portion (dark spot), and the like. Although there are several causes of these instabilities, deterioration of the thin film shape of the organic layer is dominant. It is considered that the deterioration of the thin film shape is caused by crystallization (or aggregation) of the organic amorphous film due to heat generated during element driving. In particular, the contact between the anode and the hole transport layer is important for increasing the drive voltage.
[0006]
In order to improve the contact between the anode and the hole transport layer, it has been studied to provide a hole injection layer between the two layers to lower the driving voltage. The conditions required for the material used for the hole injection layer are that a uniform thin film can be formed with good contact with the anode and that it is thermally stable, that is, the melting point and the glass transition temperature (Tg) are high. It is required to have a melting point of 300 ° C. or more and a glass transition temperature of 120 ° C. or more. Further, it is required that holes are easily injected from the anode and that the holes have an appropriate ionization potential so that the injected holes can be efficiently transferred to the hole transport layer. In a series of hole injection / transport processes, high hole mobility is required. Various materials have been studied as materials for the hole injection layer, such as porphyrin derivatives and phthalocyanine compounds (Patent Document 1), starburst type aromatic triamines (Patent Document 2), sputtered carbon films, and vanadium oxides. And metal oxides such as ruthenium oxide and molybdenum oxide.
[0007]
However, when a porphyrin derivative or a phthalocyanine compound is used as the hole injection layer in the method of inserting the hole injection layer between the anode and the hole transport layer, the spectrum changes due to light absorption by these films themselves. In addition, there is a problem that the color is not transparent in appearance.
[0008]
Starburst-type aromatic triamines have the advantage of having an appropriate ionization potential and good transparency, but have low heat resistance due to their low glass transition point and melting point.
[0009]
Also, many hole injection layers containing various conjugated / non-conjugated polymer compounds have been proposed. In general, indium tin oxide (ITO) used as an anode of an organic electroluminescent device has a surface roughness (Ra) of about 10 nm and often has local projections. Although there was a problem of causing short-circuit defects, an effect of reducing the defects can be obtained by applying a solution containing a polymer compound on the anode to provide a hole injection layer.
[0010]
As such a hole injection layer material, for example, use of a conjugated polymer such as polythienylenevinylene, polythiophene, or polyaniline has been proposed. However, these have a problem in solubility in a solvent, and therefore have a problem in a production process.
[0011]
Further, it has been proposed to use a non-conjugated polymer in which an electron-accepting compound is not mixed as a hole transport layer (Patent Documents 3, 4, 5, 6, and 7). Such an element is 20 cd / m at 6 V as described in FIG. ² And the driving voltage is high, and the luminous efficiency at that time is as low as 1 cd / A.
[0012]
Further, it is disclosed that a device can be driven at a low voltage by mixing an electron-accepting compound with a non-conjugated hole-transporting polymer and using it as a hole-injecting layer (Patent Document 7). However, the polymer disclosed in Patent Document 7 has a low glass transition temperature Tg, and has a problem in heat resistance.
[0013]
Most of the non-conjugated polymers disclosed in the above-mentioned documents contain two diarylamino structures linked by a biphenylene group. Due to the part.
[0014]
However, the monomer component that forms the structure is harmful to the human body, and since the structure has a large reorientation energy in charge transfer, the energy barrier for hole injection / transport is large. It is expected that an organic electroluminescent device having a hole injecting layer using the compound has insufficient driving life.
[0015]
An electron-accepting compound is mixed with a non-conjugated polymer having a 1,4-phenylenediamine moiety, which is expected to have a low reorientation energy and a large hole mobility as a hole transporting moiety, and mix it with a hole injection layer. Patent Literature 8 describes an example of using the above. However, compounds in which an electron donating alkoxy group or alkyl group is directly bonded to the 1,4-phenylenediamine moiety, such as specific examples (I-10) and (I-22), have a low ionization potential. There is a possibility that charge transfer to the hole transport layer is not performed efficiently. X in the linking group between 1,4-phenylenediamine moieties as in specific example (I-2), and a direct bond as in specific example (I-6). Those partially having a naphthyl group tend to have low solubility in a solvent, which may make it difficult to purify the compound or to form a layer containing the compound by a coating method.
[0016]
An example of using a non-conjugated polymer having a 1,4-phenylenediamine moiety as a hole transport layer is also disclosed in Patent Document 4. However, the polymer disclosed here also has a low ionization potential because the electron-donating alkyl group is directly bonded to the 1,4-phenylenediamine site, and the compound and the electron-accepting compound are added to the hole injection layer. When used in combination, charge transfer to the hole transport layer is not expected to be performed efficiently. In addition, the polymers disclosed herein are believed to have low heat resistance due to the alkyl groups. In the presence of an electron accepting compound, an absorption band associated with charge transfer from the polymer to the electron accepting compound exists in a low energy region, and photocrosslinking does not occur. Therefore, the insolubilization technique as disclosed in Patent Document 4 cannot be employed in the presence of an electron accepting compound.
[0017]
[Patent Document 1]
JP-A-63-295695
[Patent Document 2]
JP-A-4-308688
[Patent Document 3]
JP-A-9-188756
[Patent Document 4]
JP-A-9-255774
[Patent Document 5]
JP-A-11-135262
[Patent Document 6]
WO97 / 33193
[Patent Document 7]
JP-A-11-283750
[Patent Document 8]
JP 2000-36390 A
[Non-patent document 1]
Appl. Phys. Lett. , 51, 913, 1987
[0018]
[Problems to be solved by the invention]
The high voltage at the time of driving the organic electroluminescent device and the low stability including heat resistance are major problems for a light source such as a facsimile, a copying machine, and a backlight of a liquid crystal display. It is not desirable as a display element such as a panel display.
[0019]
The present invention solves the above-mentioned conventional problems, and can be driven at low voltage and high luminous efficiency, has good heat resistance, and can maintain stable luminescent characteristics for a long period of time. A light-emitting element, an organic electroluminescent element that prevents short-circuit defects at the time of element production due to the surface roughness of the anode, and a novel polymer compound suitable as a hole injection layer material of the organic electroluminescent element; It is an object of the present invention to provide a novel 1,4-phenylenediamine derivative as a synthetic intermediate of the polymer compound, a charge transport material containing the polymer compound, and an organic electroluminescent device material.
[0020]
[Means for Solving the Problems]
The polymer compound of the present invention is characterized by containing a repeating unit represented by the following general formula (I).
[0021]
Embedded image

(Wherein, ring B1, ring B2, ring B4 and ring B5 each independently represent a benzene ring, and this benzene ring has an optionally substituted acyl group and a substituted May be substituted with one or more substituents selected from the group consisting of alkoxycarbonyl groups.
Ring B3 represents a benzene ring which may be substituted with an acyl group which may have a substituent.
X represents a divalent linking group. )
[0022]
The charge transport material of the present invention contains such a polymer compound of the present invention.
[0023]
The organic electroluminescent device material of the present invention contains such a polymer compound of the present invention.
[0024]
The organic electroluminescent device of the present invention is characterized in that, in an organic electroluminescent device having an anode, a cathode, and a light emitting layer present between the two electrodes on a substrate, such a layer containing the polymer compound of the present invention is provided. And
[0025]
That is, the present inventors have solved the conventional problems, and as a result of intensive studies to provide an organic electroluminescent device capable of maintaining stable light-emitting characteristics at high temperatures, as a result, the light emission sandwiched between an anode and a cathode on a substrate. In an organic electroluminescent device having a layer, the above problem can be solved by providing a layer containing a polymer compound having an electron-accepting compound and having a high Tg between an anode and a light-emitting layer. The polymer compound having a repeating unit represented by the general formula (I) can easily achieve a glass transition temperature Tg ≧ 120 ° C., and has a polymer compound having such a high Tg. The inventors have found that the use of a mixture of the compound and an electron-accepting compound can simultaneously improve the light-emitting characteristics and heat resistance of the device, and have completed the present invention.
[0026]
The polymer compound of the present invention is electron-donating. By mixing the polymer compound with an electron-accepting compound, charge transfer occurs, and as a result, holes serving as free carriers are generated. The degree increases. By providing such a layer, the electrical connection between the light emitting layer and the anode is improved, and the driving voltage is reduced, and at the same time, the stability during continuous driving is also improved.
[0027]
In addition, by forming a layer containing such a polymer compound as a main component on the anode in a coating process, the surface roughness of the anode is reduced, and a good surface smoothing effect is obtained. There is also an effect that a short-circuit defect during fabrication is prevented.
[0028]
The layer containing the polymer compound and the electron-accepting compound according to the present invention is a layer exhibiting a hole transporting property, and may be anywhere between the anode and the light emitting layer. As shown in Nos. 3 to 3, the material is not limited to those directly provided on the anode, but in order to make full use of the advantages of this layer such as good electrical bonding with the anode (inorganic material) and high heat resistance, the anode and the Most advantageously, it is formed as a hole injection layer at the contact position.
[0029]
In the organic electroluminescent device of the present invention, the value obtained by subtracting the electron affinity of the electron-accepting compound from the ionization potential of the polymer compound is preferably 0.7 eV or less. The content of the receptive compound is preferably in the range of 0.1 to 50% by weight with respect to the polymer compound.
[0030]
In the organic electroluminescent device of the present invention, the electron accepting compound is preferably at least one compound selected from the following compound group.
[0031]
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[0032]
The 1,4-phenylenediamine derivative of the present invention is a monomer useful as a synthetic intermediate for the polymer compound of the present invention, and is represented by the following general formula (III).
[0033]
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(Where R ¹ , R ² , R ⁴ , R ⁵ Each independently represents a hydrogen atom, an acyl group which may have a substituent, or an alkoxycarbonyl group which may have a substituent,
R ³ Represents a hydrogen atom or an acyl group which may have a substituent. )
[0034]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
First, the polymer compound of the present invention will be described.
The polymer compound of the present invention has a repeating unit represented by the general formula (I).
[0035]
In formula (I), ring B1, ring B2, ring B4 and ring B5 are each independently a benzene ring which may be substituted. The substituent which the benzene ring may have is one or more selected from the group consisting of an acyl group which may have a substituent, and an alkoxycarbonyl group which may have a substituent. More specifically, an acyl group having 1 to 6 carbon atoms such as an acetyl group which may have a substituent; a methoxycarbonyl group which may have a substituent; It is an alkoxycarbonyl group of the formulas 2 to 7.
[0036]
Examples of the substituent which these substituents may have include, for example, one or more of the following substituent groups Z.
[Substituent group Z]
C1-C6 alkyl groups such as methyl group and ethyl group; C1-C6 alkenyl groups such as vinyl group; C1-C6 alkynyl groups such as ethynyl group; methoxycarbonyl group, ethoxycarbonyl group and the like An alkoxycarbonyl group having 2 to 7 carbon atoms; a dialkylamino group having 1 to 10 carbon atoms such as a dimethylamino group and a diethylamino group; a diarylamino group such as a diphenylamino group, a ditolylamino group and a carbazolyl group; Arylalkylamino group; acyl group having 1 to 6 carbon atoms such as acetyl group; halogen atom such as fluorine atom; haloalkyl group such as trifluoromethyl group; aryloxy group such as phenoxy group and benzyloxy group; cyano group; And aromatic hydrocarbon ring groups such as naphthyl group
[0037]
The substituents on the rings B1, B2, B4, and B5 preferably include a hydrogen atom (that is, unsubstituted).
[0038]
The rings B1, B2, B4, and B5 contained in one repeating unit may be the same or different, but are preferably different from each other in view of the amorphous nature of the polymer compound.
[0039]
Ring B3 in the general formula (I) is a benzene ring which may be substituted.
[0040]
Examples of the substituent which the ring B3 may have include an acyl group which may have a substituent, and more specifically, an acyl group which may have a substituent and has 1 to 1 carbon atoms such as an acetyl group. And 6 acyl groups.
[0041]
Examples of the substituent which these substituents may have include one or more of the above-described substituent group Z.
[0042]
The substituent for ring B3 preferably includes a hydrogen atom (that is, unsubstituted).
[0043]
X is a divalent linking group, preferably a divalent linking group selected from partial structures represented by the following structural formulas.
[0044]
Embedded image

[0045]
In the above formula, Ar ¹¹ Or Ar ¹⁸ Are each independently an aromatic ring which may have a substituent, preferably an aromatic hydrocarbon which may or may not have a 5- or 6-membered ring, or a 2- or 3-condensed ring Ring or aromatic heterocyclic ring, specifically, benzene ring, naphthalene ring, phenanthrene ring, anthracene ring, pyridine ring, quinoline ring, thiophene ring, benzothiophene ring, furan ring, pyrrole ring, indole ring, benzofuran ring And a carbazole ring.
[0046]
Examples of the substituent which the aromatic ring may have include the following R ²¹ , R ²² Are exemplified.
[0047]
R ²¹ And R ²² Each independently has a hydrogen atom, an alkyl group which may have a substituent, an alkenyl group which may have a substituent, an alkynyl group which may have a substituent, An aralkyl group which may be substituted, an alkoxy group which may have a substituent, an aryloxy group which may have a substituent, an amino group which may have a substituent, Represents an aromatic hydrocarbon ring group which may be, or an aromatic heterocyclic group which may have a substituent, more specifically, a hydrogen atom, a methyl group, an ethyl group or the like having 1 to 6 carbon atoms. An alkyl group; an alkenyl group having 1 to 6 carbon atoms such as a vinyl group which may have a substituent; an alkynyl group having 1 to 6 carbon atoms such as an ethynyl group which may have a substituent; An aralkyl group such as a benzyl group which may have a group; A C1-C6 alkoxy group such as a methoxy group and an ethoxy group; an aryloxy group such as a phenoxy group and a benzyloxy group which may have a substituent; an amino group which may have a substituent A dialkylamino group having 1 to 10 carbon atoms such as a dimethylamino group and a diethylamino group; a diarylamino group such as a diphenylamino group, a ditolylamino group and a carbazolyl group; an arylalkylamino group such as a phenylmethylamino group; An aromatic hydrocarbon ring group such as a phenyl group and a naphthyl group which may be possessed; and an aromatic heterocyclic group such as a thienyl group which may have a substituent.
[0048]
Examples of the substituent which these substituents may have include one or more of the above-described substituent group Z.
[0049]
Ar ¹¹ ~ Ar ¹⁸ A substituent of R ²¹ , R ²² Are preferably a hydrogen atom (that is, unsubstituted), a methyl group, an ethyl group, and a methoxy group.
[0050]
X is preferably
Embedded image

And, in particular,
Embedded image

It is preferable that Note that R ¹¹ ~ R ¹⁷ Is Ar ¹¹ ~ Ar ¹⁸ Are the same as those described above as the substituent which may have, and the same applies to preferred groups.
[0051]
Such a polymer compound of the present invention is preferably a monomer represented by the following general formula (II), particularly preferably a 1,4-phenylene of the present invention represented by the following general formula (III) It is synthesized from a diamine derivative.
[0052]
Embedded image

(In the above formula, the rings B1 to B5 have the same meaning as in the above general formula (I).)
[0053]
Embedded image

[0054]
R in the above formula ¹ , R ² , R ⁴ , R ⁵ Are each independently a hydrogen atom, an acyl group which may have a substituent, an alkoxycarbonyl group which may have a substituent, more specifically, may have a substituent, An acyl group having 1 to 6 carbon atoms such as an acetyl group; an alkoxycarbonyl group having 2 to 7 carbon atoms such as a methoxycarbonyl group and an ethoxycarbonyl group which may have a substituent;
[0055]
Also, R ³ Is a hydrogen atom or an acyl group which may have a substituent, more specifically, an acyl group having 1 to 6 carbon atoms such as an acetyl group which may have a substituent.
[0056]
Examples of the substituent which these substituents may have include one or more of the above-described substituent group Z.
[0057]
R ¹ Or R ⁵ Preferred examples include a hydrogen atom (that is, unsubstituted), a phenyl group, a t-butylphenyl group, a styryl group, a dimethylamino group, and a diphenylamino group.
[0058]
Preferred specific examples of the repeating unit of the polymer compound of the present invention are shown below, but the present invention is not limited thereto.
[0059]
Embedded image

[0060]
The polymer compound of the present invention is a polymer compound comprising one or more kinds of repeating units represented by the general formula (I).
[0061]
Further, the polymer compound of the present invention may contain a repeating unit derived from other various monomers as long as its performance is not impaired. As the repeating unit derived from another monomer, for example, in the repeating unit represented by the general formula (I),
Embedded image

Instead of
Embedded image

The compound useful for the production of the organic electroluminescent device has a content of the repeating unit represented by the general formula (I) of usually 20 mol% or more per molecule, preferably It is at least 50 mol%, more preferably at least 80 mol%.
[0062]
In the above formula, R ^a , R ^b , R ^c Are each independently an alkyl group which may have a substituent, an alkenyl group which may have a substituent, an alkynyl group which may have a substituent, Aralkyl group, an acyl group which may have a substituent, an amino group which may have a substituent, an alkoxycarbonyl group which may have a substituent, A good aromatic hydrocarbon ring group or an aromatic heterocyclic group which may have a substituent, and more specifically, a carbon atom such as a methyl group or an ethyl group which may have a substituent. An alkyl group having 1 to 6 carbon atoms; an alkenyl group having 1 to 6 carbon atoms such as a vinyl group which may have a substituent; 1 to 6 carbon atoms such as an ethynyl group which may have a substituent. Alkynyl group; aralkyl group such as benzyl group which may have a substituent; An optionally substituted acyl group having 1 to 6 carbon atoms such as an acetyl group; an optionally substituted amino group such as a dialkylamino group having 1 to 10 carbon atoms such as a dimethylamino group and a diethylamino group; Diarylamino group such as diphenylamino group, ditolylamino group, carbazolyl group; arylalkylamino group such as phenylmethylamino group; methoxycarbonyl group which may have a substituent; An aromatic hydrocarbon ring group such as a phenyl group or a naphthyl group which may have a substituent; an aromatic heterocyclic group such as a thienyl group which may have a substituent. .
[0063]
Examples of the substituent which these substituents may have include one or more of the above-described substituent group Z.
[0064]
Among these high molecular compounds, those having a weight average molecular weight of 1,000 to 1,000,000 are particularly useful for producing an organic electroluminescent device. Further, when the layer containing the polymer compound is formed by a coating method, there is a difference depending on the degree of crosslinking, but usually the weight average molecular weight is about 10,000 to 200,000 from the viewpoint of solubility. Is preferred.
[0065]
The polymer compound of the present invention is prepared, for example, by first synthesizing a 1,4-phenylenediamine derivative having a hydroxyphenyl group, and then synthesizing it with an aromatic diamine such as 4,4′-difluorobenzophenone and bis (4-fluorophenyl) sulfone. It is obtained by reacting with fluoride.
[0066]
Since the polymer compound of the present invention has a high charge transporting property, it can be suitably used as a charge transporting material in an electrophotographic photosensitive member, an organic electroluminescent device, a photoelectric conversion device, an organic solar cell, an organic rectifying device, and the like. In particular, since it has excellent hole transportability, it is suitable as a hole transport material.
[0067]
In addition, by using the polymer compound of the present invention, an organic electroluminescent element which has excellent heat resistance and can be driven (emitted) stably for a long period of time can be obtained, and thus is suitable as an organic electroluminescent element material.
[0068]
Next, embodiments of the organic electroluminescent device of the present invention will be described in detail with reference to the drawings.
[0069]
1 to 3 are schematic sectional views showing an embodiment of the organic electroluminescent device of the present invention, wherein 1 is a substrate, 2 is an anode, 3 is a hole injection layer, 4 is a hole transport layer, and 5 is A light emitting layer, 6 represents an electron transport layer, and 7 represents a cathode.
[0070]
The substrate 1 serves as a support for the organic electroluminescent element, and is made of a quartz or glass plate, a metal plate or a metal foil, a plastic film or a sheet, or the like. Particularly, a glass plate or a plate of a transparent synthetic resin such as polyester, polymethacrylate, polycarbonate, and polysulfone is preferable. When using a synthetic resin substrate, it is necessary to pay attention to gas barrier properties. If the gas barrier property of the substrate is too low, the organic electroluminescent element may be deteriorated by outside air passing through the substrate, which is not preferable. For this reason, a gas barrier property may be ensured by providing a dense silicon oxide film or the like on one or both sides of the synthetic resin substrate.
[0071]
The anode 2 is provided on the substrate 1, and the anode 2 plays a role of injecting holes into the hole injection layer 3. The anode 2 is usually made of a metal such as aluminum, gold, silver, nickel, palladium, and platinum; a metal oxide such as an oxide of indium and / or tin; a metal halide such as copper iodide; Is done. Usually, the formation of the anode 2 is often performed by a sputtering method, a vacuum evaporation method, or the like. Further, the anode 2 is formed by dispersing metal fine particles such as silver, fine particles such as copper iodide, carbon black, conductive metal oxide fine particles, and the like in a suitable binder resin solution and applying the dispersion on the substrate 1. You can also. The anode 2 can be formed by laminating different materials. The thickness of the anode 2 depends on the required transparency. When transparency is required, it is desirable that the transmittance of visible light is usually 60% or more, preferably 80% or more. In this case, the thickness of the anode 2 is usually 1000 nm or less, preferably, 1000 nm or less. 500 nm or less, and the lower limit is about 10 nm, preferably about 20 nm. The anode 2 may be the same as the substrate 1 if it is opaque. Further, it is also possible to stack different conductive materials on the anode 2.
[0072]
In the present invention, the hole injection layer 3 is provided on the anode 2 in the device structure of FIG. Conditions required for the material used for the hole injection layer 3 include a material having high hole injection efficiency from the anode 2 and capable of transporting the injected holes efficiently. Can be For that purpose, the ionization potential is small, the transparency to visible light is high, the hole mobility is large, the stability is excellent, and impurities serving as traps are unlikely to be generated during production or use. Required. In addition to the above general requirements, when considering applications for in-vehicle display, the element is further required to have a heat resistance of 120 ° C. or higher.
[0073]
The organic electroluminescent device of the present invention is preferably such that the hole injection layer 3 contains the polymer compound of the present invention having the repeating unit represented by the general formula (I) and an electron accepting compound. .
[0074]
In the present invention, it is possible to simultaneously improve the luminous characteristics and the heat resistance of the device by using a mixture of the polymer compound of the present invention having a Tg of 120 ° C. or higher and an electron-accepting compound. That is, by mixing an electron-accepting compound with the electron-donating polymer compound, charge transfer occurs, and as a result, holes serving as free carriers are generated, and the electric conductivity of the hole-injecting layer increases. For this reason, the electrical connection between the light emitting layer 5 and the anode 2 is improved by providing the hole injection layer 3 according to the present invention, and the driving voltage is reduced and the stability during continuous driving is also improved. Also,
By using a polymer compound having a Tg of 120 ° C. or higher as the base of the hole injection layer 3, the heat resistance of the device is greatly improved.
[0075]
In addition, by forming such a hole injection layer 3 containing the polymer compound of the present invention as a main component on the anode 2 by a coating process, the surface roughness of the anode 2 described above is reduced, and a favorable An effect of obtaining a surface smoothing effect and preventing a short circuit defect at the time of manufacturing an element is also exerted.
[0076]
The electron-accepting compound used in the hole injection layer 3 in combination with the polymer compound of the present invention may be any as long as it causes charge transfer between the polymer and the electron-accepting compound. As a result, the ionization potential of the polymer compound of the present invention used for the hole injection layer 3: IP (polymer compound of the present invention), and the electron affinity of the electron accepting compound (acceptor): EA (acceptor) value,
IP (polymer compound of the present invention) -EA (acceptor) ≦ 0.7 eV,
Was found to be particularly effective for the purpose of the present invention.
[0077]
This will be described with reference to the energy level diagram of FIG. Generally, the ionization potential and the electron affinity are determined based on the vacuum level. The ionization potential is defined as the energy required to emit electrons at the HOMO (highest occupied molecular orbital) level of a substance to a vacuum level, and the electron affinity is determined by the LUMO (lowest empty molecule) of the substance at the vacuum level. Orbit) defined by the energy that falls to a level and stabilizes.
[0078]
It is preferable that the difference between the ionization potential at the HOMO level of the polymer compound of the present invention shown in FIG. 4 and the electron affinity at the LUMO level of the electron-accepting compound is 0.7 eV or less. The ionization potential is directly measured by photoelectron spectroscopy, or can be obtained by correcting an electrochemically measured oxidation potential with respect to a reference electrode. In the case of the latter method, for example, when a saturated sweet pepper electrode (SCE) is used as a reference electrode,
Ionization potential = oxidation potential (vs. SCE) +4.3 eV,
("Molecular Semiconductors", Springer-Verlag, 1985, p. 98). The electron affinity can be obtained by subtracting the optical band gap from the above-mentioned ionization potential, or similarly from the above-mentioned formula from the electrochemical reduction potential.
[0079]
The relational expression between the ionization potential and the electron affinity uses an oxidation potential and a reduction potential,
(Oxidation potential of the polymer compound of the present invention) − (reduction potential of acceptor) ≦ 0.7 V.
[0080]
In addition, from the viewpoint of efficient hole injection into an adjacent organic layer such as a light emitting layer and a hole transport layer described below, it is more preferable that the ionization potential is not too low, and -0.1 eV ≦ IP Polymer compound of the invention) -EA (acceptor)
Ie
−0.1 V ≦ {IP (oxidation potential of polymer compound of the present invention) −EA (reduction potential of acceptor)}
It is preferable that
[0081]
Further, the content of the electron accepting compound in the hole injection layer 3 is preferably in the range of 0.1 to 50% by weight based on the polymer compound of the present invention. More preferably, a concentration range of 1 to 30% by weight is desirable in practical characteristics.
[0082]
The electron-accepting compound is not particularly limited as long as it satisfies the above-mentioned relationship, but preferred examples are shown below with abbreviations.
[0083]
Embedded image

[0084]
The hole injection layer 3 containing the polymer compound of the present invention and the electron accepting compound is formed on the anode 2 by a coating method. That is, a predetermined amount of the polymer compound of the present invention having the repeating unit represented by the general formula (I) and the electron-accepting compound may be added to a predetermined amount of a binder resin or a coating property improving agent which does not trap holes as necessary. A coating solution is prepared by adding an agent and dissolving in a suitable solvent, applying the solution on the anode 2 by a method such as spin coating, dip coating or ink jetting, and drying to form the hole injection layer 3. .
[0085]
From the viewpoint of hole injection / transport ability, the total content of the polymer compound of the present invention and the electron accepting compound in the hole injection layer 3 is preferably 20% by weight or more, particularly preferably 50% by weight or more. .
[0086]
The upper limit of the thickness of the hole injection layer 3 is usually 1000 nm, preferably 500 nm, and the lower limit is usually 5 nm, preferably 10 nm.
[0087]
The light emitting layer 5 is provided on the hole injection layer 3. The light-emitting layer 5 is a material that efficiently recombines electrons injected from the cathode 7 and holes transported from the hole injection layer 3 between electrodes to which an electric field is applied, and emits light efficiently by the recombination. Formed from
[0088]
Materials satisfying such conditions include metal complexes such as an aluminum complex of 8-hydroxyquinoline (JP-A-59-194393) and metal complexes of 10-hydroxybenzo [h] quinoline (JP-A-6-322362). Publication), bisstyrylbenzene derivatives (Japanese Patent Application Laid-Open Nos. 1-245087 and 2-222484), bisstyrylylene derivatives (Japanese Patent Application Laid-Open No. 2-247278), and metal complexes of (2-hydroxyphenyl) benzothiazole ( JP-A-8-315983), silole derivatives and the like. These light emitting layer materials are usually laminated on the hole injection layer 3 by a vacuum evaporation method.
[0089]
For the purpose of improving the luminous efficiency of the device and changing the luminescent color, for example, doping a fluorescent dye for laser such as coumarin using an aluminum complex of 8-hydroxyquinoline as a host material (J. Appl. Phys., Vol. 65) , P. 3610, 1989).
[0090]
Doping a fluorescent dye with the light emitting layer material as a host material is effective also for the purpose of improving the driving life of the device. For example, using a metal complex such as an aluminum complex of 8-hydroxyquinoline as a host material, a naphthacene derivative represented by rubrene (JP-A-4-335087), a quinacridone derivative (JP-A-5-70773), perylene, etc. By doping a condensed polycyclic aromatic hydrocarbon ring (Japanese Unexamined Patent Publication No. 5-198377) in an amount of 0.1 to 10% by weight with respect to a host material, the light emitting characteristics of the device, particularly the driving stability, are greatly improved. Can be. As a method of doping the fluorescent material such as the naphthacene derivative, the quinacridone derivative, or the perylene into the host material of the light emitting layer, there are a method of co-evaporation and a method of previously mixing an evaporation source at a predetermined concentration.
[0091]
Examples of the polymer-based light-emitting layer materials include poly (p-phenylenevinylene), poly [2-methoxy-5- (2-ethylhexyloxy) -1,4-phenylenevinylene], and poly (3-alkyl). A polymer material such as thiophene), a system in which a light emitting material and an electron transfer material are mixed with a polymer such as polyvinyl carbazole, and the like. These materials are applied on the hole injection layer 3 by a method such as spin coating or dip coating in the same manner as the hole injection layer 3 to be thinned.
[0092]
The upper limit of the thickness of the light emitting layer 5 is usually 200 nm, preferably 100 nm, and the lower limit is usually 10 nm, preferably 30 nm.
[0093]
In order to improve the light emitting characteristics of the device, a hole transport layer 4 is provided between the hole injection layer 3 and the light emitting layer 5 as shown in FIG. By providing the layer 6 between the light emitting layer 5 and the cathode 7, for example, a function-separated type organic electroluminescent device is obtained.
[0094]
In the function-separated element of FIGS. 2 and 3, the material of the hole transport layer 4 is such that the hole injection efficiency from the hole injection layer 3 is high and the injected holes are transported efficiently. It must be a material that can be used. For that purpose, it is required that the ionization potential is small, the hole mobility is large, the stability is further improved, and impurities serving as traps are hardly generated at the time of manufacture or use. Further, since the layer is in direct contact with the light emitting layer 5, it is preferable that a substance that quenches light emission is not included.
[0095]
Examples of such a hole transport material include, for example, two or more tertiary amines including two or more tertiary amines represented by 4,4′-bis [N- (9-naphthyl) -N-phenylamino] biphenyl. Starburst structures such as aromatic diamines in which a condensed aromatic hydrocarbon ring is substituted with a nitrogen atom (JP-A-5-234681) and 4,4 ', 4 "-tris (1-naphthylphenylamino) triphenylamine Aromatic amine compound (J. Lumin., Vol. 72-74, p. 985, 1997), aromatic amine compound composed of a tetramer of triphenylamine (Chem. Commun., P. 2175, 1996), 2 , 2 ', 7,7'-tetrakis- (diphenylamino) -9,9'-spirobifluorene and other spiro compounds (Synth. Metals, 91, 209; 1997) etc. These compounds may be used alone or as a mixture of two or more as necessary.
[0096]
In addition to the above compounds, as a material for the hole transport layer 4, polyarylene ether sulfone containing polyvinyl carbazole, polyvinyl triphenylamine (Japanese Patent Application Laid-Open No. 7-53953), and tetraphenylbenzidine (Polym. Adv. Tech. ,
7, p. 33, 1996).
[0097]
The hole transport layer 4 is formed by laminating the above hole transport material on the hole injection layer 3 by a coating method or a vacuum evaporation method.
[0098]
In the case of the coating method, one or more hole transport materials and, if necessary, an additive such as a binder resin or a coating property improving agent which does not trap holes are added and dissolved in an appropriate solvent. A coating solution is prepared, applied on the anode 2 by a method such as spin coating, and dried to form the hole transport layer 4. In this case, as the binder resin, polycarbonate, polyarylate, polyester, or the like can be used. Since a large amount of the binder resin decreases the hole mobility, a small amount is desirable. Usually, the content of the binder resin in the hole transport layer 4 is preferably 50% by weight or less.
[0099]
In the case of the vacuum evaporation method, the hole transporting material is put into a crucible installed in a vacuum container, and the inside of the vacuum container is pumped by a suitable vacuum pump. ^-4 After evacuation to about Pa, the crucible is heated to evaporate the hole transport material, and the hole transport layer 4 is formed on the substrate 1 on which the hole injection layer 3 is formed, which is placed facing the crucible. Let it.
[0100]
The upper limit of the thickness of the hole transport layer 4 is usually 300 nm, preferably 100 nm, and the lower limit is usually 10 nm, preferably 30 nm. In order to uniformly form such a thin film, generally, a vacuum deposition method is often used.
[0101]
As a method for further improving the luminous efficiency of the organic electroluminescent element, an electron transport layer 6 can be further laminated on the light emitting layer 4 as shown in FIG. The compound used for the electron transport layer 6 is required to be capable of easily injecting electrons from the cathode 7 and having a higher electron transport ability. Examples of such an electron transport material include aluminum complexes of 8-hydroxyquinoline, oxadiazole derivatives (Appl. Phys. Lett., Vol. 55, p. 1489, 1989), which have already been mentioned as a light-emitting layer material, and polymethacrylic acid. Phenanthroline derivative (JP-A-5-331559), 2-t-butyl-9,10-N, N'-dicyanoanthraquinone diimine, n-type hydrogenated Amorphous silicon carbide, n-type zinc sulfide, n-type zinc selenide, and the like.
[0102]
The upper limit of the thickness of the electron transport layer 6 is usually 200 nm, preferably 100 nm, and the lower limit is usually 5 nm, preferably 10 nm.
[0103]
The cathode 7 plays a role of injecting electrons into the light emitting layer 5. As a material for forming the cathode 7, the material used for the anode 2 can be used. However, for efficient electron injection, a metal having a low work function is preferable, and tin, magnesium, indium, calcium, A suitable metal such as aluminum or silver or an alloy thereof is used. Specific examples include a low work function alloy electrode such as a magnesium-silver alloy, a magnesium-indium alloy, and an aluminum-lithium alloy. Further, the interface between the cathode 7 and the light emitting layer 5 or the electron transporting layer 6 is LiF, MgF ₂ , Li ₂ Inserting an ultrathin insulating film (0.1 to 5 nm) of O or the like is also an effective method for improving the efficiency of the element (Appl. Phys. Lett., 70, 152, 1997; No. 10-74586; IEEE Trans. Electron Devices, 44, 1245, 1997).
[0104]
The thickness of the cathode 7 is usually the same as that of the anode 2. In order to protect the cathode made of a low work function metal, further laminating a metal layer having a high work function and being stable to the atmosphere increases the stability of the device. For this purpose, metals such as aluminum, silver, copper, nickel, chromium, gold, platinum and the like are used.
[0105]
1 to 3 show an example of an element structure employed in the present invention, and the present invention is not limited to those shown in the drawings. For example, it is also possible to stack the cathode 7, the light emitting layer 5, the hole injection layer 3, and the anode 2 in this order on the substrate, that is, as described above, at least one of which is transparent. It is also possible to provide the organic electroluminescent device of the present invention between two substrates having a high density. Similarly, it is also possible to laminate in a structure opposite to the above-mentioned respective layer constitutions shown in FIG. 2 and FIG.
[0106]
Further, as long as the performance of the organic electroluminescent device of the present invention is not impaired, an arbitrary layer may be provided between the respective layers shown in FIGS. 1, 2 and 3.
[0107]
Such an organic electroluminescent device of the present invention can be applied to any of a single device, a device having a structure arranged in an array, and a structure in which an anode and a cathode are arranged in an XY matrix. it can.
[0108]
【Example】
Next, the present invention will be described more specifically with reference to Synthesis Examples, Experimental Examples, Examples and Comparative Examples, but the present invention is not limited to the description of the following Examples unless it exceeds the gist thereof.
[0109]
First, a synthesis example of the 1,4-phenylenediamine derivative of the present invention, which is a raw material of a polymer compound having a repeating unit represented by the general formula (I), will be described.
[0110]
Synthesis Example 1
(1-1) Synthesis of N, N′-diphenyl-N, N′-bis (4-methoxyphenyl) -1,4-phenylenediamine (BMPP)
[0111]
Embedded image

[0112]
N, N'-diphenyl-1,4-phenylenediamine (77.0 mmol) and 4-iodoanisole (231 mmol) were dissolved in 150 ml of tetraglyme, copper powder (154 mmol) and potassium carbonate (112 mmol). Was reacted at 200 ° C. for 8 hours in a nitrogen atmosphere in the presence of. As a result, BMPP (34.8 g, yield 96%) represented by the formula (V) was obtained.
[0113]
(1-2) Synthesis of N, N′-diphenyl-N, N ′-(4-hydroxyphenyl) -1,4-phenylenediamine (BHPP)
[0114]
Embedded image

[0115]
Dissolve BMPP (50.0 mmol) in 360 ml of methylene chloride, cool the system to −65 ° C. or lower in a dry ice-ethanol bath under a nitrogen atmosphere, and add boron tribromide (100 mmol) in methylene chloride. The solution (100 ml) was added dropwise. After completion of the dropwise addition, the mixture was stirred for 2 hours after removing the refrigerant bath, extracted with ethyl acetate, and purified by silica gel column chromatography. As a result, BHPP represented by the formula (VI) (16.2 g, yield 73%) was obtained.
[0116]
Below, BHPP ¹ H-NMR (DMSO-d ₆ ) Shows data.
9.361 (2H, S)
7.189 (4H, dd, J = 6.7, 6.6)
6.936 (4H, dd, J = 5.7, 1.7)
6.875 (4H, S)
6.865-6.837 (6H, m)
6.751 (4H, dd, J = 5.7, 1.7)
[0117]
Next, a synthesis example of the polymer compound of the present invention will be described.
[0118]
Synthesis Example 2
Synthesis of 1,4-phenylenediamine-containing polymer compound (PPPEK)
[0119]
Embedded image

[0120]
BHPP (20.0 mmol) and 4,4'-difluorobenzophenone (20.0 mmol) are dissolved in 200 ml of 1-methyl 2-pyrrolidinone (NMP) and a nitrogen atmosphere is present in the presence of potassium carbonate (120 mmol). A condensation reaction was performed at 145 ° C. for 20 hours. After cooling, 10 ml of acetic acid was added to the reaction system, released into methanol, and the obtained polymer was washed with water to remove inorganic salts. After drying under reduced pressure at 60 ° C., the polymer was dissolved in 300 ml of chloroform, released into methanol and reprecipitated. Finally, the resultant was washed with 400 ml of acetone to remove a low molecular weight component, thereby obtaining a homopolymer PPPEK (11.8 g, 95% yield) composed of the repeating unit (IX).
[0121]
The Tg of this polymer was 183 ° C., the thermal decomposition temperature in a nitrogen atmosphere was 550 ° C. or higher, the weight average molecular weight (Mw) was 46,700, and the number average molecular weight (Mn) was 7,520. The molecular weight was determined by GPC measurement in chloroform using polystyrene as a standard sample.
[0122]
Next, an experimental example for measuring the ionization potential of the 1,4-phenylenediamine-containing polymer compound obtained in Synthesis Example 2 will be described.
[0123]
Experimental example 1
The glass substrate was subjected to ultrasonic cleaning with acetone, water cleaning with pure water, ultrasonic cleaning with isopropyl alcohol, drying with dry nitrogen, and ultraviolet / ozone cleaning. A 4-phenylenediamine-containing polymer compound (PPPEK) was spin-coated on the above glass substrate under the following conditions:
Solvent: cyclohexanone
Coating solution concentration: 5.0 mg / ml
Spinner rotation speed: 1500 rpm
Spinner rotation time: 30 seconds
Drying condition: 2 hours at 120 ° C
[0124]
A uniform thin film having a thickness of 20 nm was formed by the spin coating. The ionization potential of this thin film sample was measured using an ultraviolet electron analyzer (AC-1) manufactured by Riken Keiki Co., Ltd., and showed a value of 5.18 eV.
[0125]
Table 1 shows the difference between the electron affinity of some of the electron accepting compounds for which the reduction potential is reported and the ionization potential of the 1,4-phenylenediamine-containing polymer compound (PPPEK).
[0126]
[Table 1]

[0127]
Examples and comparative examples for evaluating the performance of an organic electroluminescent device using the synthesized 1,4-phenylenediamine-containing polymer compound will be described below.
[0128]
Example 1
An organic electroluminescent device having the structure shown in FIG. 3 was manufactured by the following method.
[0129]
An indium tin oxide (ITO) transparent conductive film deposited on a glass substrate 1 with a thickness of 120 nm (manufactured by Geomatics Co .; electron beam film-formed product; sheet resistance 15 Ω / sq) using a normal photolithography technique and hydrochloric acid etching. The anode 2 was formed by patterning into a stripe having a width of 2 mm. The patterned ITO substrate was cleaned in the order of ultrasonic cleaning with acetone, water cleaning with pure water, and ultrasonic cleaning with isopropyl alcohol, dried with nitrogen blow, and finally cleaned with ultraviolet / ozone.
[0130]
On this ITO glass substrate, a mixture of 1,4-phenylenediamine-containing polymer compound (PPPEK) and PPB was spin-coated under the following conditions.
[Spin coating conditions]
Solvent: cyclohexanone
PPPEK: 5.0 mg / ml
PPB: 0.5 mg / ml
Spinner rotation speed: 1500 rpm
Spinner rotation time: 30 seconds
Drying condition: 2 hours at 120 ° C
[0131]
The hole injection layer 3 having a uniform thin film shape with a thickness of 20 nm was formed by the spin coating described above.
[0132]
Next, the substrate on which the hole injection layer 3 was applied and formed was set in a vacuum evaporation apparatus. After rough exhaust of this device was performed by an oil rotary pump, the degree of vacuum in the device was 2 × 10 ^-6 Torr (about 2.7 × 10 ^-4 Evacuation was performed using an oil diffusion pump equipped with a liquid nitrogen trap until Pa) or below. The following aromatic diamine compound: 4,4′-bis [N- (9-phenanthyl) -N-phenylamino] biphenyl placed in a ceramic crucible placed in this apparatus was heated to perform vapor deposition. The degree of vacuum during vapor deposition is 1.3 × 10 ^-6 Torr (about 1.7 × 10 ^-4 Pa), the deposition rate was 0.3 nm / sec, and a film having a thickness of 20 nm was laminated on the hole injection layer 3 to complete the hole transport layer 4.
[0133]
Embedded image

[0134]
Subsequently, an 8-hydroxyquinoline complex of aluminum represented by the following structural formula: Al (C ₉ H ₆ NO) ₃ , And rubrene were simultaneously deposited.
[0135]
Embedded image

[0136]
The ratio of rubrene to the 8-hydroxyquinoline complex of aluminum was 2.5 vol. %. At this time, the crucible temperature of the 8-hydroxyquinoline complex of aluminum was controlled in the range of 275 to 285 ° C., and the degree of vacuum at the time of vapor deposition was 1.2 × 10 5 ^-6 Torr (about 1.6 × 10 ^-4 Pa), the deposition rate was 0.4 nm / sec. The crucible temperature of rubrene was controlled in the range of 240 to 250 ° C., and the deposition rate was 0.01 nm / sec. The thickness of the light emitting layer 5 thus deposited was 30 nm.
[0137]
Subsequently, an 8-hydroxyquinoline complex of aluminum: Al (C ₉ H ₆ NO) ₃ Was deposited in the same manner as in the hole transport layer 4. At this time, the crucible temperature of the aluminum 8-hydroxyquinoline complex was controlled in the range of 275 to 285 ° C., and the degree of vacuum at the time of vapor deposition was 1.1 × 10 5 ^-6 Torr (about 1.5 × 10 ^-4 Pa), the deposition rate was 0.4 nm / sec, and the thickness of the deposited electron transport layer 6 was 45 nm.
[0138]
In addition, the substrate temperature at the time of vacuum-depositing the hole transport layer 4, the light emitting layer 5, and the electron transport layer 6 was kept at room temperature.
[0139]
Here, the element on which the electron transport layer 6 has been vapor-deposited is once taken out of the vacuum vapor deposition apparatus into the atmosphere, and a stripe shadow mask having a width of 2 mm as a mask for cathode vapor deposition is orthogonal to the ITO stripe of the anode 2. After that, it is placed in another vacuum evaporation apparatus, and the degree of vacuum in the apparatus is set to 2 × 10 ^-6 Torr (about 2.7 × 10 ^-4 Pa).
[0140]
Thereafter, as a cathode 7, lithium fluoride (LiF) was first deposited using a molybdenum boat at a deposition rate of 0.02 nm / sec and a degree of vacuum of 7.0 × 10 ^-6 Torr (about 9.3 × 10 ^-4 Pa), a film was formed on the electron transport layer 6 so as to have a thickness of 0.5 nm. Next, the aluminum was similarly heated by a molybdenum boat, and the deposition rate was 0.5 nm / sec and the degree of vacuum was 1 × 10 5 ^-5 Torr (about 1.3 × 10 ^-3 Pa), an aluminum layer having a thickness of 80 nm was formed, and the cathode 7 was completed. The substrate temperature during the deposition of the two-layer cathode 7 was kept at room temperature.
[0141]
As described above, an organic electroluminescent device having a light emitting area of 2 mm × 2 mm was obtained. Table 2 shows the light emission characteristics of this device. In Table 2, the emission luminance was 250 mA / cm. ² The value at the current density of luminous efficiency is 100 cd / m ² , The luminance / current is the slope of the luminance-current density characteristic, and the voltage is
100 cd / m ² The values at are shown below.
[0142]
It is apparent from Table 2 that an element which emits light with high driving efficiency, low luminance, and high luminance was obtained.
[0143]
[Table 2]

[0144]
Comparative Example 1
Instead of the 1,4-phenylenediamine-containing polymer compound (PPPEK), a homopolymer comprising only the following repeating unit (XI) described on page 9 in JP-A-9-188756 (weight-average molecular weight: (Mw) 74700, number average molecular weight (Mn) 15000), and the same as Example 1 except that the conditions for spin coating on the ITO glass substrate when forming the hole injection layer 3 were as follows: An element was prepared.
[0145]
Embedded image

[0146]
[Spin coating conditions]
Solvent: cyclohexanone
Polymer compound (XI): 5.0 mg / ml
PPB: 0.5 mg / ml
Spinner rotation speed: 1500 rpm
Spinner rotation time: 30 seconds
Drying condition: 2 hours at 120 ° C
[0147]
The driving life of the device obtained in Comparative Example 1 and the device obtained in Example 1 was evaluated. The driving life is 300 cd / m of initial luminance. ² , And a luminance half time when driven at 85 ° C. Table 3 shows the results.
[0148]
[Table 3]

[0149]
Table 3 shows that the organic electroluminescent device of the present invention has a long driving life and excellent heat resistance.
[0150]
As is clear from the above results, the hole injection layer containing the polymer compound of the present invention and the electron-accepting compound, which is advantageous for the coating process, can be driven at a low voltage and has improved heat resistance. An element can be obtained.
[0151]
【The invention's effect】
As described in detail above, by using the novel polymer compound of the present invention, preferably a polymer compound synthesized from the novel 1,4-phenylenediamine derivative of the present invention, it can be driven at low voltage and high luminous efficiency. An organic electroluminescent device that has good heat resistance and can maintain stable light-emitting characteristics for a long period of time, and is capable of preventing short-circuit defects at the time of device fabrication due to surface roughness of an anode. An electroluminescent device is provided.
[0152]
Therefore, the organic electroluminescent device according to the present invention can be used as a light source (for example, a light source of a copier, a back light of a liquid crystal display or an instrument) utilizing a feature as a flat panel display (for example, for an OA computer or a wall-mounted television) or a surface light emitter. It can be applied to a light source, a display panel, and a sign lamp. The technical value of the display element for a vehicle which requires high heat resistance is great.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing one example of an embodiment of an organic electroluminescent device of the present invention.
FIG. 2 is a schematic sectional view showing another example of the embodiment of the organic electroluminescent device of the present invention.
FIG. 3 is a schematic sectional view showing another example of the embodiment of the organic electroluminescent device of the present invention.
FIG. 4 is an energy level diagram showing the relationship between the ionization potential of the polymer compound of the present invention and the electron affinity of the electron-accepting compound.
[Explanation of symbols]
1 substrate
2 Anode
3 hole injection layer
4 Hole transport layer
5 Light-emitting layer
6 electron transport layer
7 Cathode

Claims (12)

A polymer compound comprising a repeating unit represented by the following general formula (I).

(Wherein, ring B1, ring B2, ring B4 and ring B5 each independently represent a benzene ring, and this benzene ring has an optionally substituted acyl group and a substituted May be substituted with one or more substituents selected from the group consisting of alkoxycarbonyl groups.
Ring B3 represents a benzene ring which may be substituted with an acyl group which may have a substituent.
X represents a divalent linking group. ) The polymer compound according to claim 1, wherein X in the general formula (I) is a divalent linking group selected from partial structures represented by the following structural formulas.

(Wherein, Ar ¹¹ to Ar ¹⁸ each independently represent an aromatic ring which may have a substituent,
R ²¹ and R ²² are each independently a hydrogen atom, an alkyl group optionally having a substituent, an alkenyl group optionally having a substituent, an alkynyl group optionally having a substituent, An aralkyl group which may have a substituent, an alkoxy group which may have a substituent, an aryloxy group which may have a substituent, an amino group which may have a substituent, Represents an aromatic hydrocarbon ring group which may have a group, or an aromatic heterocyclic group which may have a substituent. ) 3. The polymer compound according to claim 1, wherein the weight average molecular weight is 1,000 to 1,000,000. The polymer compound according to any one of claims 1 to 3, wherein the polymer compound is synthesized using a monomer represented by the following general formula (II).

(Wherein, ring B1 to ring B5 have the same meaning as in the above formula (I).) A 1,4-phenylenediamine derivative represented by the following general formula (III).

(Wherein, R ¹ , R ² , R ⁴ , and R ⁵ each independently represent a hydrogen atom, an acyl group optionally having a substituent, or an alkoxycarbonyl group optionally having a substituent. Represents
R ³ represents a hydrogen atom or an acyl group which may have a substituent. ) A charge transport material comprising the polymer compound according to claim 1. An organic electroluminescent device material comprising the polymer compound according to claim 1. An organic electroluminescent device having an anode, a cathode, and a light emitting layer present between the two electrodes on a substrate, comprising a layer containing the polymer compound according to any one of claims 1 to 4. Organic electroluminescent device. 9. The organic electroluminescent device according to claim 8, wherein a layer containing the polymer compound and the electron accepting compound is provided between the light emitting layer and the anode. 10. The organic electroluminescent device according to claim 9, wherein a value obtained by subtracting the electron affinity of the electron-accepting compound from the ionization potential of the polymer compound is not more than 0.7 eV. The content of the electron accepting compound in the layer containing the polymer compound and the electron accepting compound according to claim 9 or 10, wherein the content of the electron accepting compound is 0.1 to 50% by weight based on the polymer compound. An organic electroluminescent device, which is in a range. The organic electroluminescent device according to any one of claims 9 to 11, wherein the electron accepting compound is at least one selected from the following compound group.

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