JP4221973B2 - Organic electroluminescence device - Google Patents

Description

【００１３】
一般式（Ｉ−１）中、Ｘは置換または未置換のビフェニルもしくはアントラセンを表す。Ｔは炭素数１〜６の２価の直鎖状炭化水素基、または炭素数２〜１０の２価の分枝状炭化水素基を表し、ｋは１を表す。Ｒ₁は炭素数１〜１０の飽和もしくは不飽和炭化水素基、または置換もしくは未置換の芳香族基を表し、Ｒ₂は水素原子、炭素数１〜１０の飽和もしくは不飽和炭化水素基、炭素数１〜４のアルコキシ基、シアノ基、ハロゲン原子、置換アミノ基、置換もしくは未置換のアリール基、または置換もしくは未置換のアラルキル基を表す。
【化４】

一般式（ II −１）及び（ II −２）中、Ａは上記一般式（Ｉ−１）で示される構造を表し、Ｒは水素原子、アルキル基、置換もしくは未置換のアリール基、または置換もしくは未置換のアラルキル基を表し、Ｙはジイソシアネート残基を表し、Ｚは２価アルコール残基を表し、ｐは５〜５０００の整数を表す。
【００１４】
＜２＞ 前記有機化合物層が少なくともキャリア輸送能を持つ発光層及び電子輸送層から構成され、前記発光層が、前記一般式（Ｉ−１）で示される構造を部分構造として含む繰り返し単位よりなる電荷輸送性ポリウレタンを、少なくとも１種含有してなることを特徴とする＜１＞に記載の有機電界発光素子である。
【００１５】
＜３＞ 前記有機化合物層が少なくともホール輸送層、発光層及び電子輸送層から構成され、前記発光層が、前記一般式（Ｉ−１）で示される構造を部分構造として含む繰り返し単位よりなる電荷輸送性ポリウレタンを、少なくとも１種含有してなることを特徴とする＜１＞に記載の有機電界発光素子である。
【００１６】
＜４＞ 前記有機化合物層が少なくともキャリア輸送能を持つ発光層から構成され、前記発光層が、前記一般式（Ｉ−１）で示される構造を部分構造として含む繰り返し単位よりなる電荷輸送性ポリウレタンを、少なくとも１種含有してなることを特徴とする＜１＞に記載の有機電界発光素子である。
【００１７】
＜５＞ 前記有機化合物層が少なくともホール輸送層及びキャリア輸送能を持つ発光層から構成され、前記発光層もしくはホール輸送層のうち少なくとも１つの層が、前記一般式（Ｉ−１）で示される構造を部分構造として含む繰り返し単位よりなる電荷輸送性ポリウレタンを、少なくとも１種含有してなることを特徴とする＜１＞に記載の有機電界発光素子である。
【００１８】
＜６＞ 前記発光層が、電荷輸送性ポリウレタン以外のホール輸送材料または電子輸送材料を含むことを特徴とする＜２＞に記載の有機電界発光素子である。
【００１９】
＜７＞ 前記発光層が、電荷輸送性ポリウレタン以外のホール輸送材料または電子輸送材料を含むことを特徴とする＜３＞に記載の有機電界発光素子である。
【００２０】
＜８＞ 前記発光層が、電荷輸送性ポリウレタン以外のホール輸送材料または電子輸送材料を含むことを特徴とする＜４＞に記載の有機電界発光素子である。
【００２１】
＜９＞ 前記発光層が、電荷輸送性ポリウレタン以外のホール輸送材料または電子輸送材料を含むことを特徴とする＜５＞に記載の有機電界発光素子である。
【００３３】
なお、本発明の有機ＥＬ素子において、有機化合物層は、機能分離型のもの、例えば、少なくともホール輸送層及び発光層から構成され、該ホール輸送層が前記一般式（Ｉ−１）で示される構造を部分構造として含む繰り返し単位よりなる電荷輸送性ポリウレタンを含有してなるものや、キャリア輸送能と発光能を兼ね備えたもの、すなわち、有機化合物層が発光層のみから構成されてなり、該発光層が前記一般式（Ｉ−１）で示される構造を部分構造として含む繰り返し単位よりなる電荷輸送性ポリウレタンを含有してなるもののいずれでもよい。
【００３４】
また、本発明の有機ＥＬ素子において、有機化合物層が発光層のみから構成される場合、該発光層には、電荷輸送性材料（電荷輸送性ポリウレタン以外のホール輸送材料、電子輸送材料）を含んでもよい。
【００３５】
【発明の実施の形態】
本発明の有機ＥＬ素子は、少なくとも一方が透明または半透明である陽極及び陰極よりなる一対の電極間に挾持された、一つまたは複数の有機化合物層より構成され、該有機化合物層の少なくとも一層が、下記一般式（Ｉ−１）で示される構造を部分構造として含む繰り返し単位よりなる電荷輸送性ポリウレタン（以下、単に「電荷輸送性ポリウレタン」ということがある）を１種以上含有することを特徴とする。なお、前記電荷輸送性ポリウレタンは、下記一般式（Ｉ−２）で示される部分構造をさらに含有してもよい。
【００３６】
【化５】

【００３７】
一般式（Ｉ−１）中、Ｘは置換または未置換のビフェニルもしくはアントラセンを表し、一般式（Ｉ−２）中、Ｘは置換または未置換の２価の芳香族基を表す。Ｔは炭素数１〜６の２価の直鎖状炭化水素基、または炭素数２〜１０の２価の分枝状炭化水素基を表し、ｋは１を表す。Ｒ₁は炭素数１〜１０の飽和もしくは不飽和炭化水素基、または置換もしくは未置換の芳香族基を表し、Ｒ₂は水素原子、炭素数１〜１０の飽和もしくは不飽和炭化水素基、炭素数１〜４のアルコキシ基、シアノ基、ハロゲン原子、置換アミノ基、置換もしくは未置換のアリール基、または置換もしくは未置換のアラルキル基を表す。
【００３８】
本発明の有機ＥＬ素子は、前記電荷輸送性ポリウレタンを含有してなる層を有することで、十分な輝度を有し、安定性および耐久性に優れる。さらに、前記電荷輸送性ポリウレタンを用いることで、大面積化可能であり、容易に製造可能である。
【００３９】
具体的には、上記電荷輸送性ポリウレタンを有機化合物層の少なくとも一層に用いることにより、電荷の移動度を大きくすることができるため、低電流で高い発光輝度を有する有機ＥＬ素子を得ることができる。また、電荷輸送層形成にあたり、低分子の電荷輸送材料を高分子材料中に分散（相溶）させる必要がないため、高分子材料のガラス転移温度を低下させることがなく、有機ＥＬ素子の耐熱性、耐久性を向上させることができる。
【００４０】
一般式（Ｉ−１）中、Ｘは置換または未置換のビフェニルもしくはアントラセンを表し、一般式（Ｉ−２）中、Ｘは、置換または未置換の２価の芳香族基を表し、具体的な例としては下記の式（１）〜（１３）が挙げられる。
【００４１】
【化６】

【００４２】
式（１）〜（１３）中、Ｒ₃は、水素原子、炭素数１〜４のアルキル基、置換もしくは未置換のフェニル基、または置換もしくは未置換のアラルキル基を表し、Ｒ₄〜Ｒ₁₂は、それぞれ水素原子、炭素数１〜４のアルキル基、炭素数１〜４のアルコキシル基、置換もしくは未置換のフェニル基、置換もしくは未置換のアラルキル基、またはハロゲン原子を表し、ａ、ｂは０または１を表し、Ｖは下記の式（１４）〜（３１）から選択される基を表す。
【００４３】
【化７】

【００４４】
式（１４）〜（３１）中、ｃ、ｄ、ｅは１〜１０の整数、ｆ、ｇ、ｈは０〜１０の整数を表す。
【００４５】
これらの中でも、前記Ｘが下記構造式（３２）または（３３）で示されるビフェニレン構造を有する場合、「Ｔｈｅ Ｓｉｘｔｈ ＩｎｔｅｒｎａｔｉｏｎａｌＣｏｎｇｒｅｓｓ ｏｎ Ａｄｖａｎｃｅｓ ｉｎ Ｎｏｎ−ｉｍｐａｃｔ Ｐｒｉｎｔｉｎｇ Ｔｅｃｈｎｏｌｏｇｉｅｓ，３０６，（１９９０） 」にも報告されているように、モビリティーが高いポリマーが得られることから、特に好ましい。
【００４６】
【化８】

【００４７】
なお、一般式（Ｉ−１）及び（Ｉ−２）中、Ｔは炭素数１〜６の２価の直鎖状炭化水素基、または炭素数２〜１０の２価の分枝状炭化水素基を表し、具体的な例としては以下の構造を挙げることができる。
【００４８】
【化９】

【００４９】
以下、一般式（Ｉ−１）及び（Ｉ−２）で示される構造の具体例を表２〜表５、表７、表１０〜表１７示すが、本発明はこれら具体例に限定されるわけではない。なお、表２〜表５、表７における構造番号１３〜１９、２０〜４０、４４、５７〜５９は一般式（Ｉ−１）で示される構造の具体例を示し、表１０〜表１７における構造番号７７〜１４０は一般式（Ｉ−２）で示される構造の具体例を示す。
【００５１】
【表２】

【００５２】
【表３】

【００５３】
【表４】

【００５４】
【表５】

【００５６】
【表７】

【００５９】
【表１０】

【００６０】
【表１１】

【００６１】
【表１２】

【００６２】
【表１３】

【００６３】
【表１４】

【００６４】
【表１５】

【００６５】
【表１６】

【００６６】
【表１７】

【００６７】
一般式（Ｉ−１）で示される構造を部分構造として含む繰り返し単位よりなる電荷輸送性ポリウレタンとしては、下記一般式（II−１）または（II−２）で示されるものが使用される。
【００６８】
【化１０】

【００６９】
一般式（II−１）及び（II−２）中、Ａは上記一般式（Ｉ−１）で示される構造を表し、Ｒは水素原子、アルキル基、置換もしくは未置換のアリール基、または置換もしくは未置換のアラルキル基を表し、Ｙはジイソシアネート残基を表し、Ｚは２価アルコール残基を表し、ｐは５〜５０００の整数を表す。
【００７０】
一般式（II−１）または（II−２）中の、Ｙ及びＺの具体的な例としては下記の式（３４）〜（４０）から選択された基が挙げられる。
【００７１】
【化１１】

【００７２】
式（３４）〜（４０）中、Ｒ₁₃及びＲ₁₄は、それぞれ水素原子、炭素数１〜４のアルキル基、炭素数１〜４のアルコキシル基、置換もしくは未置換のフェニル基、置換もしくは未置換のアラルキル基、またはハロゲン原子を表し、α及びβはそれぞれ１〜１０の整数を、γ及びδはそれぞれ０、１または２の整数を、η及びρはそれぞれ０または１を表す。また、Ｖの具体例としては、前記式（１４）〜（３１）を挙げることができる。
【００７３】
以下、表１８〜表２０、表２４〜表２５に、一般式（II−１）及び（II−２）で示される電荷輸送性ポリウレタンの具体的な例を示すが、本発明はこれら具体例に限定されるわけではない。なお、表１８〜表２０、表２４〜表２５において、モノマー列のＡ欄の番号は、前記一般式（Ｉ−１）及び（Ｉ−２）で示される構造の具体例である表２〜表５、表７、表１０〜表１７で示した構造番号に対応している。また、Ｚの欄が「−」であるものは一般式（II−１）で示される電荷輸送性ポリウレタンの具体例を示し、Ｚの欄が「−」以外であるものは一般式（II−２）で示される電荷輸送性ポリウレタンの具体例を示す。以下、各番号を付した具体例、例えば、１５の番号を付した具体例は例示化合物（１５）という。
【００７４】
【表１８】

【００７５】
【表１９】

【００７６】
【表２０】

【００８０】
【表２４】

【００８１】
【表２５】

【００８２】
前記電荷輸送性ポリウレタンの質量平均分子量Ｍｗは、１０，０００〜３００，０００の範囲にあることが好ましく、５０，０００〜２００，０００の範囲にあることがより好ましい。
【００８３】
前記電荷輸送性ポリウレタンは、下記構造式（III−１）〜（IV−２）で示される電荷輸送性モノマーを、例えば、第４版実験化学講座第２８巻（丸善、１９９２）、新高分子実験学第２巻（共立出版、１９９５）、等に記載された公知の方法で重合させることによって合成することができる。なお、下記構造式（III−１）及び（III−２）中、Ａ、Ｔは、前記一般式（II−１）または（II−２）におけるＡ、前記一般式（Ｉ−１）または（Ｉ−２）におけるＴと同様である。
【００８４】
【化１２】

【００８５】
具体的には、例えば、一般式（III−１）及び（III−２）で示される電荷輸送性モノマーの場合、電荷輸送性ポリウレタンは、次のようにして合成することができる。例えば、電荷輸送性モノマーが一般式（III−１）で示される２価アルコールの場合には、ＯＣＮ−Ｙ−ＮＣＯで示されるジイソシアネート類と当量混合し、また例えば、電荷輸送性モノマーが一般式（III−２）で示されるジイソシアネート類の場合には、ＨＯ−Ｙ−ＯＨで示される２価アルコール類と当量混合し、重付加する。
【００８６】
触媒としては、ジラウリル酸ジブチルスズ（II）、二酢酸ジブチルスズ（II）、ナフテン酸鉛等の有機金属化合物といった通常の重付加によるポリウレタン合成反応に用いるものが使用できる。また、芳香族系のジイソシアネートを電荷輸送性ポリウレタンの合成に用いる場合には、トリエチレンジアミン等の第三アミンを触媒として用いることができる。これら有機金属化合物と第三アミンとは、触媒として混合して用いてもよい。
【００８７】
上記触媒の添加量は、電荷輸送性モノマー１質量部に対して、１／１０，０００〜１／１０質量部の範囲であることが好ましく、１／１，０００〜１／５０質量部の範囲であることがより好ましい。
【００８８】
溶剤としては、電荷輸送性モノマーとジイソシアネート、もしくは２価アルコール類とを溶解するものであれば、任意の溶剤を用いることができるが、反応性の点から極性の低い溶媒やアルコールとの水素結合を生じない溶媒を用いることが好ましく、トルエン、クロロベンゼン、ジクロロベンゼン、１−クロロナフタレン等が有効である。用いられる溶剤の量は、電荷輸送性モノマー１質量部に対して、１〜１００質量部の範囲であることが好ましく、２〜５０質量部の範囲であることがより好ましい。なお、反応温度は任意に設定できる。
【００８９】
反応終了後は、反応溶液をそのまま、メタノール、エタノール等のアルコール類や、アセトン等のポリマーが溶解しにくい貧溶剤中に滴下し、電荷輸送性ポリウレタンを析出させて分離した後、水や有機溶剤で十分洗浄し、乾燥させる。さらに、必要であれば適当な有機溶剤に溶解させ、貧溶剤中に滴下し、電荷輸送性ポリウレタンを析出させる再沈殿処理を繰り返してもよい。再沈殿処理の際には、メカニカルスターラー等で、貧溶剤を効率よく撹拌しながら行うことが好ましい。
【００９０】
上記再沈殿処理の際に電荷輸送性ポリウレタンを溶解させる溶剤量は、電荷輸送性ポリウレタン１質量部に対して、１〜１００質量部の範囲であることが好ましく、２〜５０質量部の範囲であることがより好ましい。また、前記貧溶剤の量は電荷輸送性ポリウレタン１質量部に対して、１〜１，０００質量部の範囲であることが好ましく、１０〜５００質量部の範囲であることがより好ましい。
【００９１】
次に、下記構造式（IV−１）及び（IV−２）で示される電荷輸送性モノマーを用いた場合の電荷輸送性ポリウレタンの合成について説明する。なお、構造式（IV−１）及び（IV−２）におけるＡ、Ｔも、前記一般式（II−１）または（II−２）におけるＡ、前記一般式（Ｉ−１）または（Ｉ−２）におけるＴと同様である。
【００９２】
【化１３】

【００９３】
電荷輸送性モノマーが一般式（IV−１）で示されるビスクロロホルメートの場合には、₂ＨＮ−Ｙ−ＮＨ₂で示されるジアミン類と当量混合し、また、電荷輸送性モノマーが一般式（IV−２）で示されるジアミン類の場合には、ＣｌＯＣＯ−Ｙ−ＯＣＯＣｌで示されるビスクロロホルメート類と当量混合し、重縮合する。
【００９４】
溶剤としては、塩化メチレン、ジクロロエタン、トリクロロエタン、テトラヒドロフラン（ＴＨＦ）、トルエン、クロロベンゼン、１−クロロナフタレン等が有効であり、溶剤量としては電荷輸送性モノマー１質量部に対して、１〜１００質量部の範囲であることが好ましく、２〜５０質量部の範囲であることがより好ましい。反応温度は任意に設定できる。重合後は、前述のように再沈殿処理により精製する。
【００９５】
また、前記₂ＨＮ−Ｙ−ＮＨ₂で示されるジアミン類の塩基性度の高い場合には、界面重合法も用いることができる。すなわち、ジアミン類を水に加え、当量の酸を加えて溶解させた後、激しく撹拌しながらジアミン類と前記一般式（IV−１）で示される当量の電荷輸送性モノマー溶液とを加えることによって重合することができる。この際、水の量はジアミン類１質量部に対して、１〜１，０００質量部の範囲であることが好ましく、１０〜５００質量部の範囲であることがより好ましい。
【００９６】
電荷輸送性モノマーを溶解させる溶剤としては、塩化メチレン、ジクロロエタン、トリクロロエタン、トルエン、クロロベンゼン、１−クロロナフタレン等が有効である。反応温度は任意に設定でき、反応を促進するために、アンモニウム塩、スルホニウム塩等の相間移動触媒を用いることが効果的である。用いられる相間移動触媒の量は、電荷輸送性モノマー１質量部に対して、０．１〜１０質量部の範囲であることが好ましく、０．２〜５質量部の範囲であることがより好ましい。
【００９７】
次に、本発明の有機ＥＬ素子の層構成について詳記する。
本発明の有機ＥＬ素子は、少なくとも一方が透明または半透明である一対の電極と、それら電極間に挾持された発光層を含む一つまたは複数の有機化合物層より構成され、該有機化合物層の少なくとも１層に前記電荷輸送性ポリウレタンを含有してなる。
【００９８】
本発明の有機ＥＬ素子においては、有機化合物層が１つの場合は、該有機化合物層はキャリア輸送能を持つ発光層であり、該発光層が前記電荷輸送性ポリウレタンを含有してなる。また、有機化合物層が複数の場合（機能分離型の場合）は、それらの少なくとも一つは発光層（この発光層はキャリア輸送能を有していてもよいし、有していなくてもよい）であり、他の有機化合物層は、キャリア輸送層、すなわち、ホール輸送層、電子輸送層、または、ホール輸送層及び電子輸送層として構成され、これらの少なくとも一層が、前記電荷輸送性ポリウレタンを含有してなる。
【００９９】
具体的には、例えば、少なくとも発光層及び電子輸送層から構成される有機ＥＬ素子、少なくともホール輸送層、発光層及び電子輸送層から構成される有機ＥＬ素子、あるいは、少なくともホール輸送層及び発光層から構成される有機ＥＬ素子において、これらの少なくとも一層（発光層、ホール輸送層、電子輸送層）が前記電荷輸送性ポリウレタンを含有してなるもの等が挙げられる。さらに、例えば、有機化合物層が発光層のみから構成されてなり、該発光層が前記電荷輸送性ポリウレタンを含有してなるものも挙げることができる。
【０１００】
また、本発明の有機ＥＬ素子においては、発光層が、電荷輸送性材料（前記電荷輸送性ポリウレタン以外のホール輸送性材料、電子輸送性材料）を含有していることが好ましい。詳しくは、後述する。
【０１０１】
以下、図面を参照しつつ、本発明の有機ＥＬ素子の構成をより詳細に説明するが、本発明はこれらに限定されるわけではない。
図１〜図４は、本発明の有機ＥＬ素子の層構成を説明するための模式的断面図であって、図１、図２、図４は、有機化合物層が複数の場合の一例であり、図３は、有機化合物層が１つの場合の例を示す。なお、図１〜図４において、同様の機能を有するものは同じ符号を付して説明する。
【０１０２】
図１に示す有機ＥＬ素子は、透明絶縁体基板１表面に、透明電極２、キャリア輸送能を持つ発光層６、電子輸送層５及び背面電極７を順次積層してなる。図２に示す有機ＥＬ素子は、透明絶縁体基板１表面に、透明電極２、ホール輸送層３、発光層４、電子輸送層５及び背面電極７を順次積層してなる。図３に示す有機ＥＬ素子は、透明絶縁体基板１表面に、透明電極２、キャリア輸送能を持つ発光層６及び背面電極７を順次積層してなる。図４に示す有機ＥＬ素子は、透明絶縁体基板１表面に、透明電極２、ホール輸送層３、キャリア輸送能を持つ発光層６及び背面電極７を順次積層してなる。以下、各々を詳しく説明する。
【０１０３】
なお、図１、図２及び図４に示す有機ＥＬ素子は、発光材料（発光層）が、明確なキャリア輸送性を示さないものを用いる場合に、有機ＥＬ素子の耐久性向上あるいは発光効率の向上を図る目的で、発光層４あるいはキャリア輸送能を持つ発光層６と透明電極２との間にホール輸送層を設けたり、発光層４あるいはキャリア輸送能を持つ発光層６と背面電極７との間に電子輸送層を設けたりした層構成のものである。
【０１０４】
本発明における前記電荷輸送性ポリウレタンを含有してなる有機化合物層は、図１に示される有機ＥＬ素子の層構成の場合には、例えば、キャリア輸送能を持つ発光層６として用いることが好ましい。また、図２に示される有機ＥＬ素子の層構成の場合には、前記電荷輸送性ポリウレタンを含有してなる有機化合物層を発光層４、ホール輸送層３としていずれにも用いることができるが、発光層４として用いることが好ましい。また、図３に示される有機ＥＬ素子の層構成の場合には、前記電荷輸送性ポリウレタンを含有してなる有機化合物層をキャリア輸送能を持つ発光層６として用いることが好ましい。さらに、図４に示される有機ＥＬ素子の層構成の場合には、前記電荷輸送性ポリウレタンを含有してなる有機化合物層を、例えば、ホール輸送層３、キャリア輸送能を持つ発光層６としていずれも用いることができるが、キャリア輸送能を持つ発光層６として用いることが好ましい。
【０１０５】
前記電荷輸送性ポリウレタンを有機化合物層として用いる本発明の有機ＥＬ素子としては、上記各層構成の中で図３、図４の構成が、素子として作製が容易であり、電荷輸送性ポリウレタンの特性を反映でき、十分な輝度、安定性、耐久性を達成できる点で好ましい構成である。
【０１０６】
なお、本発明における前記電荷輸送性ポリウレタンを含有してなる有機化合物層は良好なホール輸送能を有し、例えば前記のように図４で表される発光素子のホール輸送層３にも用いることができる。この場合、キャリア輸送能を持つ発光層６には電子輸送性の発光層が設けられ、代表的な例としては下図（Ｖ−１〜９）に示される化合物を挙げることができる。
【０１０７】
【化１４】

【０１０８】
図１〜図４に示される有機ＥＬ素子の層構成の場合、発光層４もしくはキャリア輸送能を持つ発光層６は、目的に応じて機能（ホール輸送能、あるいは電子輸送能）が付与された前記電荷輸送性ポリウレタンを含有する有機化合物層であることが好ましい。
【０１０９】
この場合の有機化合物層は、基本的には前記電荷輸送性ポリウレタン単独で形成されるが、有機ＥＬ素子に注入されるホールと電子とのバランスを調節するために、前記電荷輸送性ポリウレタン以外の電子輸送材料を層全体の質量に対して１０〜５０質量％の範囲で分散させてもよい。このような電子輸送材料としては、前記電荷輸送性ポリウレタンと強い電子相互作用を示さない有機化合物を用いることが好ましく、より好ましくは下記例示化合物（VI）が用いられるが、これに限定されるものではない。
【０１１０】
【化１５】

【０１１１】
同様にホール移動度を調節するために、電荷輸送性ポリウレタン以外のホール輸送材料、好ましくはテトラフェニレンジアミン誘導体を層全体の質量に対して１０〜５０質量％の範囲で同時に分散させて用いてもよい。
【０１１２】
また、発光層４もしくはキャリア輸送能を持つ発光層６には、有機ＥＬ素子の耐久性向上あるいは発光効率の向上を目的として、前記電荷輸送性ポリウレタンと異なる色素化合物をドーピングしてもよい。ドーピングは溶液または分散液中に所定の色素を混合することで行う。発光層中における色素化合物のドーピングの割合としては、層全体の質量の０．００１〜４０質量％の範囲であることが好ましく、０．０１〜１０質量％の範囲であることがより好ましい。
【０１１３】
このようなドーピングに用いられる色素化合物としては、発光材料との相溶性がよく、かつ発光層の良好な薄膜形成を妨げない有機化合物が用いられ、ＤＣＭ誘導体、キナクリドン誘導体、ルブレン誘導体、ポルフィリン系化合物等が好適に用いられる。具体例として、下記の化合物（VII−１）〜（VII−４）を挙げることができるが、これらに限定されるものではない。
【０１１４】
【化１６】

【０１１５】
図１〜図４に示される層構成の有機ＥＬ素子の場合、透明絶縁体基板１は、発光を取り出すため透明なものが好ましく、ガラス、プラスチックフィルム等が用いられる。また、透明電極２は、透明絶縁体基板１と同様に発光を取り出すため透明であって、かつホールの注入を効率よく行うために仕事関数の大きなものが好ましく、酸化スズインジウム（ＩＴＯ）、酸化スズ（ＮＥＳＡ）、酸化インジウム、酸化亜鉛等の酸化膜、及び蒸着あるいはスパッタされた金、白金、パラジウム等が好ましく用いられる。
【０１１６】
図１及び図２に示される層構成の有機ＥＬ素子の場合、電子輸送層５には、電子輸送能を示す化合物が電荷輸送性材料として用いられる。このような電子輸送層に用いられる電子輸送性材料としては、有機低分子の場合、真空蒸着法により良好な薄膜形成が可能な有機化合物が好ましく用いられ、具体的にはオキサジアゾール誘導体、ニトロ置換フルオレノン誘導体、ジフェノキノン誘導体、チオピランジオキシド誘導体、フルオレニリデンメタン誘導体等を挙げることができる。また、高分子の場合には、それ自身を含む溶液または分散液を塗布・乾燥することにより良好な薄膜形成が可能であることが条件である。電子輸送性材料としては、具体的に下記の化合物（VIII−１）〜（VIII−３）が好ましく用いられるが、これらに限定されるものではない。また、他の汎用の樹脂等と混合して用いてもよい。
【０１１７】
【化１７】

【０１１８】
図２及び図４に示される層構成の有機ＥＬ素子の場合、ホール輸送層３には、ホール輸送能を示す化合物が電荷輸送性材料として用いられる。該電荷輸送性材料が有機低分子の場合には、真空蒸着法、もしくは低分子と結着樹脂を含む溶液または分散液を塗布・乾燥することにより良好な薄膜形成が可能であることが材料選択の条件とされる。また、ホール輸送能を示す電荷輸送性材料が高分子の場合には、それ自身を含む溶液または分散液を塗布・乾燥することにより良好な薄膜形成が可能であることが材料選択の条件である。
【０１１９】
ホール輸送能を示す電荷輸送性材料としては、テトラフェニレンジアミン誘導体、トリフェニルアミン誘導体、カルバゾール誘導、スチルベン誘導体、アリールヒドラゾン誘導体、ポルフィリン系化合物等が好ましく用いられるが、特に好適な具体例として、下記例示化合物（IX−１）〜（IX−８）を挙げることができるが、これらの中では、電荷輸送性ポリウレタンとの相溶性がよいことから、テトラフェニレンジアミン誘導体が好ましく用いられる。また、上記化合物を他の汎用の樹脂等と混合して用いてもよい。
【０１２０】
【化１８】

【０１２１】
図１〜図４に示される層構成の有機ＥＬ素子の場合、背面電極７には、真空蒸着可能で、かつ電子注入を効率よく行うために仕事関数の小さな金属が使用されるが、特にマグネシウム、アルミニウム、銀、インジウム及びこれらの合金が好ましく用いられる。また、背面電極７の表面には、さらに素子の水分や酸素による劣化を防ぐために保護層を設けてもよい。具体的な保護層の材料としては、Ｉｎ、Ｓｎ、Ｐｂ、Ａｕ、Ｃｕ、Ａｇ、Ａｌ等の金属、ＭｇＯ、ＳｉＯ₂、ＴｉＯ₂等の金属酸化物、ポリエチレン樹脂、ポリウレア樹脂、ポリイミド樹脂等の樹脂等が挙げられる。保護層の形成には、真空蒸着法、スパッタリング法、プラズマ重合法、ＣＶＤ法、コーティング法が適用できる。
【０１２２】
これら図１〜図４に示される有機ＥＬ素子の各層形成は以下のように行われる。まず、透明電極２の表面に各有機ＥＬ素子の層構成に応じて、ホール輸送層３あるいはキャリア輸送能を持つ発光層６を形成する。ホール輸送層３及びキャリア輸送能を持つ発光層６は、上記各材料を真空蒸着法、もしくは有機溶媒中に溶解あるいは分散し、得られた塗布液を用いて前記透明電極２表面に製膜するスピンコーティング法、ディップ法等により形成される。
【０１２３】
次に、各有機ＥＬ素子の層構成に応じて、ホール輸送層３、発光層４、電子輸送層５あるいはキャリア輸送能を持つ発光層６は、上記各材料を、真空蒸着法、もしくは有機溶媒中に溶解あるいは分散し、得られた塗布液を用いて前記透明電極２表面に製膜するスピンコーティング法、ディップ法等を用いることによって形成される。
【０１２４】
形成されるホール輸送層３、発光層４及び電子輸送層５の膜厚は、各々０．１μｍ以下であることが好ましく、特に０．０３〜０．０８μｍの範囲であることが好ましい。また、キャリア輸送能を持つ発光層６の膜厚は、０．０３〜０．２μｍの範囲であることが好ましく、０．０５〜０．１μｍの範囲であることがより好ましい。
【０１２５】
上記各材料（前記電荷輸送性ポリウレタン、発光材料等）の分散状態は分子分散状態でも微粒子分散状態でも構わない。塗布液を用いた製膜法の場合、分子分散状態とするためには、分散溶媒は上記各材料の共通溶媒を用いる必要があり、微粒子分散状態とするためには、分散溶媒は上記各材料の分散性及び溶解性を考慮して選択する必要がある。微粒子状に分散するためには、ボールミル、サンドミル、ペイントシェイカー、アトライター、ボールミル、ホモジェナイザー、超音波法等が利用できる。
【０１２６】
そして、最後に、電子輸送層５あるいはキャリア輸送能を持つ発光層６の表面に、背面電極７を真空蒸着法により形成することにより素子が完成される。
【０１２７】
本発明の有機ＥＬ素子は、一対の電極間に、例えば、４〜２０Ｖで、電流密度１〜２００ｍＡ／ｃｍ²の直流電圧を印加することによって、１００ｃｄ／ｍ²程度以上に十分発光させることができる。
【０１２８】
【実施例】
以下、実施例によって本発明を説明するが、本発明はこれらの実施例に制限されるものではない。
まず、各実施例に用いた電荷輸送性ポリウレタンは、例えば以下のようにして得た。
【０１２９】
−合成例１〔例示化合物（４）〕−
表１の１７に記載のモノマー２．０ｇとクロロベンゼン３０ｍｌとを、容量５０ｍｌのフラスコに入れて攪拌し溶解させ、該フラスコ中に、ヘキサメチレンジイソシアネート０．５４ｇをクロロベンゼン１０ｍｌに溶解した溶液を３０分かけて滴下した後、窒素気流下、１５０℃で２時間加熱攪拌した。反応終了後、室温まで冷却し、反応溶液を撹拌されたメタノール３００ｍｌ中に滴下してポリマーを析出させた。得られたポリマーを濾過し、十分にメタノールで洗浄し乾燥させた後、テトラヒドロフラン（ＴＨＦ）３０ｍｌに溶解し、この溶液をメタノール３００ｍｌ中に滴下する再沈殿を３回繰り返すことによって、１．７ｇの電荷輸送性ポリウレタンを得た。分子量はＧＰＣにて測定したところ、Ｍｗ＝８．８２×１０⁴（スチレン換算）であり、モノマーの分子量から求めたｐの値は約１０３であった。
【０１３０】
−合成例２〔例示化合物（１３）〕−
表１の３２に記載のモノマー２．０ｇとクロロベンゼン３０ｍｌとを、容量５０ｍｌのフラスコに入れて攪拌し溶解させ、該フラスコ中に、ヘキサメチレンジイソシアネート０．５２ｇをクロロベンゼン１０ｍｌに溶解した溶液を３０分かけて滴下した後、窒素気流下、１５０℃で２時間加熱攪拌した。反応終了後、室温まで冷却し、反応溶液を撹拌されたメタノール３００ｍｌ中に滴下してポリマーを析出させた。得られたポリマーを濾過し、十分にメタノールで洗浄し乾燥させた後、テトラヒドロフラン（ＴＨＦ）３０ｍｌに溶解し、この溶液をメタノール３００ｍｌ中に滴下する再沈殿を３回繰り返すことによって、１．７ｇの電荷輸送性ポリウレタンを得た。分子量はＧＰＣにて測定したところ、Ｍｗ＝１．５２×１０⁵（スチレン換算）であり、モノマーの分子量から求めたｐの値は約１７０であった。
【０１３１】
−合成例３〔例示化合物（３８）〕−
表１の５８に記載のモノマー２．０ｇとクロロベンゼン３０ｍｌとを、容量５０ｍｌのフラスコに入れて攪拌し溶解させ、該フラスコ中に、ヘキサメチレンジイソシアネート０．５２ｇをクロロベンゼン１０ｍｌに溶解した溶液を３０分かけて滴下した後、窒素気流下、１５０℃で３時間加熱攪拌した。反応終了後、室温まで冷却し、反応溶液を撹拌されたメタノール３００ｍｌ中に滴下してポリマーを析出させた。得られたポリマーを濾過し、十分にメタノールで洗浄した後乾燥させた後、テトラヒドロフラン（ＴＨＦ）３０ｍｌに溶解し、この溶液をメタノール３００ｍｌに滴下する再沈殿を３回繰り返すことによって、２．１ｇの電荷輸送性ポリウレタンを得た。分子量はＧＰＣにて測定したところ、Ｍｗ＝１．２１×１０⁵（スチレン換算）であり、モノマーの分子量から求めたｐの値は約１４０であった。
【０１３２】
（実施例１）
合成例１に記載の電荷輸送性ポリウレタンの５質量％ジクロロエタン溶液を調製し、０．１μｍのポリテトラフルオロエチレン（ＰＴＦＥ）フィルターで濾過した。この溶液を用いて、２ｍｍ幅の短冊型ＩＴＯ電極をエッチングにより形成したガラス基板表面に、ディップ法により塗布し、膜厚約０．１μｍのホール輸送層を形成した。十分乾燥させたこのホール輸送層の表面に、発光材料として昇華精製した前記例示化合物（Ｖ−１）をタングステンボートに入れ、真空蒸着法により蒸着して、膜厚０．０５μｍのキャリア輸送能を持つ発光層を形成した。この時の真空度は１．３３×１０^-3Ｐａ、ボート温度は３００℃であった。続いてこの発光層の表面にＭｇ−Ａｇ合金を共蒸着により蒸着して、２ｍｍ幅、０．１５μｍ厚の背面電極をＩＴＯ電極と交差するように形成した。作製された有機ＥＬ素子の有効面積は０．０４ｃｍ²であった。
【０１３３】
以上のように作製した有機ＥＬ素子を、真空中（１．３３×１０^-1Ｐａ）でＩＴＯ電極側をプラス、Ｍｇ−Ａｇ背面電極をマイナスとして１０Ｖの直流電圧を印加し、発光について測定を行い、このときの最高輝度、及び発光色を評価した。それらの結果を表２６に示す。また、乾燥窒素中で有機ＥＬ素子の発光寿命の測定を行った。発光寿命の評価は、初期輝度が３５０ｃｄ／ｍ²となるように電流値を設定し、定電流駆動により輝度が初期値から半減するまでの時間を素子寿命（ｈｏｕｒ）とした。この時の駆動電流密度を素子寿命と共に表２６に示す。
【０１３４】
（実施例２）
合成例１に記載の電荷輸送性ポリウレタン９９質量部と、発光材料として化合物（VII−３）１質量部とを混合し、１０質量％ジクロロエタン溶液を調製し、０．１μｍのＰＴＦＥフィルターで濾過した。この溶液を用いて、２ｍｍ幅の短冊型ＩＴＯ電極をエッチングにより形成したガラス基板表面に、ディップ法により膜厚約０．１５μｍのキャリア輸送能を持つ発光層を形成した。充分乾燥させた後、該キャリア輸送能を持つ発光層表面にＭｇ−Ａｇ合金を共蒸着により蒸着して、２ｍｍ幅、０．１５μｍ厚の背面電極をＩＴＯ電極と交差するように形成した。作製された有機ＥＬ素子の有効面積は０．０４ｃｍ²であった。
上記有機ＥＬ素子について実施例１と同様の評価を行った。結果を表２６に示す。
【０１３５】
（実施例３）
合成例１に記載の電荷輸送性ポリウレタンを２質量部と、発光材料として化合物（VII−１）を０．１質量部と、電子輸送材料として前記化合物（VI）を１質量部とを混合し、１０質量％ジクロロエタン溶液を調製し、０．１μｍのＰＴＦＥフィルターで濾過した。この溶液を用いて、２ｍｍ幅の短冊型ＩＴＯ電極をエッチングにより形成したガラス基板表面に、ディップ法により塗布して、膜厚約０．１５μｍのキャリア輸送能を持つ発光層を形成した。十分乾燥させた後、該キャリア輸送能を持つ発光層表面にＭｇ−Ａｇ合金を共蒸着により蒸着して、２ｍｍ幅、０．１５μｍ厚の背面電極をＩＴＯ電極と交差するように形成した。作製された有機ＥＬ素子の有効面積は０．０４ｃｍ²であった。
上記有機ＥＬ素子について実施例１と同様の評価を行った。結果を表２６に示す。
【０１３６】
（実施例４）
合成例１に記載の電荷輸送性ポリウレタンの５質量％ジクロロエタン溶液を調製し、０．１μｍのポリテトラフルオロエチレン（ＰＴＦＥ）フィルターで濾過した。この溶液を用いて、２ｍｍ幅の短冊型ＩＴＯ電極をエッチングにより形成したガラス基板表面に、ディップ法により塗布し、膜厚約０．１μｍのキャリア輸送能を持つ発光層を形成した。十分乾燥させた後、該キャリア輸送能を持つ発光層表面にＭｇ−Ａｇ合金を共蒸着により蒸着して、２ｍｍ幅、０．１５μｍ厚の背面電極をＩＴＯ電極と交差するように形成した。作製された有機ＥＬ素子の有効面積は０．０４ｃｍ²であった。
上記有機ＥＬ素子について実施例１と同様の評価を行った。結果を表２６に示す。
【０１３７】
（実施例５）
合成例１の電荷輸送性ポリウレタンの代わりに、合成例２の電荷輸送性ポリウレタンを用いた以外は実施例１と同様にして有機ＥＬ素子を作製した。
上記有機ＥＬ素子について実施例１と同様の評価を行った。結果を表２６に示す。
【０１３８】
（実施例６）
合成例１の電荷輸送性ポリウレタンの代わりに、合成例２の電荷輸送性ポリウレタンを用いた以外は実施例２と同様にして有機ＥＬ素子を作製した。
上記有機ＥＬ素子について実施例１と同様の評価を行った。結果を表２６示す。
【０１３９】
（実施例７）
合成例１の電荷輸送性ポリウレタンの代わりに、合成例２の電荷輸送性ポリウレタンを用いた以外は実施例３と同様にして有機ＥＬ素子を作製した。
上記有機ＥＬ素子について実施例１と同様の評価を行った。結果を表２６に示す。
【０１４０】
（実施例８）
合成例１の電荷輸送性ポリウレタンの代わりに、合成例２の電荷輸送性ポリウレタンを用いた以外は実施例４と同様にして有機ＥＬ素子を作製した。
上記有機ＥＬ素子について実施例１と同様の評価を行った。結果を表２６に示す。
【０１４１】
（実施例９）
合成例１の電荷輸送性ポリウレタンの代わりに、合成例３の電荷輸送性ポリウレタンを用いた以外は実施例１と同様にして有機ＥＬ素子を作製した。
上記有機ＥＬ素子について実施例１と同様の評価を行った。結果を表２６に示す。
【０１４２】
（実施例１０）
合成例１の電荷輸送性ポリウレタンの代わりに、合成例３の電荷輸送性ポリウレタンを用いた以外は実施例２と同様にして有機ＥＬ素子を作製した。
上記有機ＥＬ素子について実施例１と同様の評価を行った。結果を表２６に示す。
【０１４３】
（実施例１１）
合成例１の電荷輸送性ポリウレタンの代わりに、合成例３の電荷輸送性ポリウレタンを用いた以外は実施例３と同様にして有機ＥＬ素子を作製した。
上記有機ＥＬ素子について実施例１と同様の評価を行った。結果を表２６に示す。
【０１４４】
（実施例１２）
合成例１の電荷輸送性ポリウレタンの代わりに、合成例３の電荷輸送性ポリウレタンを用いた以外は実施例４と同様にして有機ＥＬ素子を作製した。
上記有機ＥＬ素子について実施例１と同様の評価を行った。結果を表２６に示す。
【０１４５】
（比較例１）
前記ホール輸送能を示す化合物（IX−２）を１質量部と、発光材料として前記の化合物（Ｖ−１）を１質量部と、結着樹脂としてポリメチルメタクリレート（ＰＭＭＡ）を１質量部とを混合し、１０質量％ジクロロエタン溶液を調製し、０．１μｍのＰＴＦＥフィルターで濾過した。この溶液を用いて、２ｍｍ幅の短冊型ＩＴＯ電極をエッチングにより形成したガラス基板表面に、ディップ法により塗布して膜厚０．１５μｍのホール輸送層を形成した。十分乾燥させたホール輸送層表面に、Ｍｇ−Ａｇ合金を共蒸着により蒸着して、２ｍｍ幅、０．１５μｍ厚の背面電極をＩＴＯ電極と交差するように形成した。作製された有機ＥＬ素子の有効面積は０．０４ｃｍ²であった。
上記有機ＥＬ素子について実施例１と同様の評価を行った。結果を表２６に示す。
【０１４６】
（比較例２）
ホール輸送性高分子化合物として、ポリビニルカルバゾール（ＰＶＫ）を２質量部、発光材料として前記化合物（Ｖ−１）を０．１質量部、電子輸送材料として前記化合物（VI）を１質量部混合し、１０質量％ジクロロエタン溶液を調製し、０．１μｍのＰＴＦＥフィルターで濾過した。この溶液を用いて、２ｍｍ幅の短冊型ＩＴＯ電極をエッチングにより形成したガラス基板表面に、ディップ法により塗布して膜厚０．１５μｍのホール輸送層を形成した。十分乾燥させた後、該ホール輸送層表面にＭｇ−Ａｇ合金を共蒸着により蒸着して、２ｍｍ幅、０．１５μｍ厚の背面電極をＩＴＯ電極と交差するように形成した。作製された有機ＥＬ素子の有効面積は０．０４ｃｍ²であった。
上記有機ＥＬ素子について実施例１と同様の評価を行った。結果を表２６に示す。
【０１４７】
【表２６】

【０１４８】
上記実施例に示すように、本発明の有機ＥＬ素子は、駆動電流密度が低いにもかかわらず高い最高輝度を示し、特に実施例２、６、９、１２においては、８００ｃｄ／ｍ²以上の最高輝度が得られた。これに対し、比較例の有機ＥＬ素子では、十分な最高輝度、素子寿命が得られなかった。
【０１４９】
【発明の効果】
前記一般式（Ｉ−１）で示される構造を部分構造として含む繰り返し構造単位からなる電荷輸送性ポリウレタンは、有機ＥＬ素子に好適なイオン化ポテンシャルや電荷移動度及び発光特性を持ち、また、スピンコーティング法、ディップ法等を用いて良好な薄膜を形成することが可能であるので、これを用いて形成された本発明の有機ＥＬ素子は、十分に高い輝度を示し、また、膜厚を比較的厚く設定できるため、ピンホール等の不良も少なく、大面積化も容易であり、しかも優れた耐久性を有する。
【図面の簡単な説明】
【図１】 本発明の積層型有機ＥＬ素子の一例を示す模式的断面図である。
【図２】 本発明の積層型有機ＥＬ素子の他の一例を示す模式的断面図である。
【図３】 本発明の有機ＥＬ素子の他の一例を示す模式的断面図である。
【図４】 本発明の積層型有機ＥＬ素子の他の一例を示す模式的断面図である。
【符号の説明】
１ 透明絶縁体基板
２ 透明電極
３ ホール輸送層
４ 発光層
５ 電子輸送層
６ キャリア輸送能を持つ発光層
７ 背面電極[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an organic electroluminescent device (hereinafter referred to as “organic EL device”), and more particularly to an organic EL device using a specific charge transporting polymer.
[0002]
[Prior art]
An electroluminescent element (hereinafter referred to as an “EL element”) is a self-luminous all-solid-state element, and is highly visible and resistant to impacts. As the EL element, an inorganic phosphor is mainly used at present, but since an AC voltage of 200 V or more is necessary for driving, there are problems such as high manufacturing cost and insufficient luminance. is doing.
[0003]
On the other hand, research on EL devices using organic compounds first started with a single crystal such as anthracene, but in the case of a single crystal, the film thickness was as thick as about 1 mm and a driving voltage of 100 V or more was required. For this reason, attempts have been made to reduce the film thickness by vapor deposition (Thin Solid Films, Vol. 94, 171 (1982)), but the thin film obtained by this method still has a high drive voltage of 30 V, Sufficient brightness could not be obtained because the electron / hole carrier density was low and the photon generation probability due to carrier recombination was low.
[0004]
However, in recent years, in a function-separated EL device in which thin films of a hole-transporting organic low-molecular compound and a fluorescent organic low-molecular compound having an electron-transporting capability are sequentially stacked by a vacuum deposition method, a low driving voltage of about 10V is used. 1000 cd / m²It has been reported that the above high luminance can be obtained (Appl. Phys. Lett., Vol. 51, 913 (1987), Japanese Patent Laid-Open No. 59-194393). Development is active. In these stacked EL devices, holes and electrons are made of a light-emitting layer made of a fluorescent organic compound while maintaining the carrier balance between the holes and electrons through a charge transport layer made of an organic compound having a charge-transport property from the electrode. High-luminance light emission is realized by recombination of the holes and electrons injected into the light-emitting layer and confined in the light-emitting layer.
[0005]
However, in this type of EL device, a thin film having a film thickness of 0.1 μm or less is formed in a plurality of vapor deposition processes, so that pinholes are likely to occur, and under strictly controlled conditions to obtain sufficient performance. It is necessary to control the film thickness. Therefore, there are problems that productivity is low and it is difficult to increase the area. In addition, this EL element has several mA / cm.²Because it is driven at a high current density, a large amount of Joule heat is generated. For this reason, there is a phenomenon that the charge transporting low molecular weight compound or the fluorescent organic low molecular weight compound formed in an amorphous glass state by vapor deposition gradually crystallizes and finally melts, resulting in a decrease in luminance and dielectric breakdown. There was also a problem that the lifetime of the device was reduced as a result.
[0006]
Therefore, in order to solve the problems related to the thermal stability of the EL element, a starburst amine that can obtain a stable amorphous glass state is used as a hole transporting material (Preliminary Proceedings of the 40th Joint Conference on Applied Physics, 30a-SZK-14 (1993), etc.), and EL elements using a polymer in which triphenylamine is introduced into the side chain of polyphosphazene (The 42nd Polymer Science Conference Proceedings, 20J21 (1993)) have been reported. ing.
[0007]
However, since these alone have an energy barrier due to the ionization potential of the hole transport material, the hole injection property from the anode or the hole injection property to the light emitting layer cannot be satisfied. Further, in the case of the former starburst amine, it is difficult to purify due to low solubility, and it is difficult to increase the purity, and in the case of the latter polymer, a high current density cannot be obtained and sufficient. There is also a problem that the luminance is not obtained.
[0008]
On the other hand, with the aim of solving the problems related to productivity and large area in stacked organic EL devices, research and development of EL devices with a single-layer structure have also been promoted, and conductive polymers such as poly (p-phenylene vinylene). (Nature, Vol. 357, 477 (1992), Nature, Vol. 397, 121 (1999)), a device in which an electron transporting material and a fluorescent dye are mixed in hole transporting polyvinyl carbazole (38th) Proceedings of the Applied Physics Related Lecture, 31p-G-12 (1991)) has been proposed, but the luminance, light emission efficiency, and the like are still not as good as those of a stacked EL device using an organic low molecular weight compound. Furthermore, it has been reported that the manufacturing method is preferably a wet coating method from the viewpoint of simplification of manufacturing, workability, large area, cost, etc., and an element can also be obtained by a casting method (No. 50). Proceedings of the Japan Society of Applied Physics, 29p-ZP-5 (1989), Proceedings of the 51st Japan Society of Applied Physics, 28a-PB-7 (1990)). However, since the charge transport material has poor solubility and compatibility with solvents and resins, it is easy to crystallize, and there is a problem in production or characteristics.
[0009]
[Problems to be solved by the invention]
The object of the present invention is to solve the above-mentioned problems of the prior art. That is, an object of the present invention is to provide an organic EL device that has sufficient luminance, is excellent in stability and durability, can be increased in area, and can be easily manufactured.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the present inventors have conducted extensive studies on charge transport materials, and as a result, have at least one selected from structures represented by the following general formulas (I-1) and (I-2) as a partial structure. When the charge transporting polyurethane is used as a light emitting material, it has not only excellent charge injection characteristics, charge mobility, and thin film forming ability as an organic EL device, but also extremely excellent light emission characteristics in a solid state. Has been found to function as an element excellent in luminance and luminous efficiency, and has completed the present invention.
[0011]
  That is, the present invention
<1> In an electroluminescent element composed of one or a plurality of organic compound layers, sandwiched between a pair of electrodes composed of an anode and a cathode, at least one of which is transparent or translucent, at least one of the organic compound layers Is the following general formula(I-1)IndicatedStructureContains one or more charge-transporting polyurethanes consisting of repeating units included as a partial structureThe charge transporting polyurethane has the following general formula ( II -1) or ( II -2)This is an organic electroluminescent element characterized by the above.
[0012]
[Chemical 3]

[0013]
  General formula(I-1) Medium, X is substituted or unsubstitutedBiphenyl or anthraceneRepresents. T represents a divalent linear hydrocarbon group having 1 to 6 carbon atoms or a divalent branched hydrocarbon group having 2 to 10 carbon atoms;Is 1Represents. R₁Represents a saturated or unsaturated hydrocarbon group having 1 to 10 carbon atoms, or a substituted or unsubstituted aromatic group, and R₂Is a hydrogen atom, a saturated or unsaturated hydrocarbon group having 1 to 10 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a cyano group, a halogen atom, a substituted amino group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted group Represents an aralkyl group.
[Formula 4]

  General formula ( II -1) and ( II -2), A represents the structure represented by the general formula (I-1), R represents a hydrogen atom, an alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted aralkyl group, Y Represents a diisocyanate residue, Z represents a dihydric alcohol residue, and p represents an integer of 5 to 5000.
[0014]
<2> The organic compound layer is composed of at least a light emitting layer having a carrier transporting ability and an electron transporting layer, and the light emitting layer has the general formula(I-1)IndicatedStructure<1> The organic electroluminescence device according to <1>, wherein the organic electroluminescence device comprises at least one kind of charge transporting polyurethane composed of repeating units included as a partial structure.
[0015]
<3> The organic compound layer includes at least a hole transport layer, a light-emitting layer, and an electron transport layer, and the light-emitting layer has the general formula.(I-1)IndicatedStructure<1> The organic electroluminescence device according to <1>, wherein the organic electroluminescence device comprises at least one kind of charge transporting polyurethane composed of repeating units included as a partial structure.
[0016]
<4> The organic compound layer is composed of a light emitting layer having at least a carrier transport ability, and the light emitting layer has the general formula.(I-1)IndicatedStructure<1> The organic electroluminescence device according to <1>, wherein the organic electroluminescence device comprises at least one kind of charge transporting polyurethane composed of repeating units included as a partial structure.
[0017]
<5> The organic compound layer is composed of at least a hole transport layer and a light emitting layer having a carrier transport ability, and at least one of the light emitting layer and the hole transport layer has the general formula.(I-1)IndicatedStructure<1> The organic electroluminescence device according to <1>, wherein the organic electroluminescence device comprises at least one kind of charge transporting polyurethane composed of repeating units included as a partial structure.
[0018]
<6> The light emitting layer isHole transport materials or electron transport materials other than charge transporting polyurethane<2> The organic electroluminescent element according to <2>.
[0019]
<7> The light emitting layer isHole transport materials or electron transport materials other than charge transporting polyurethane<3> The organic electroluminescent element according to <3>.
[0020]
<8> The light emitting layer isHole transport materials or electron transport materials other than charge transporting polyurethane<4> The organic electroluminescence device according to <4>, wherein
[0021]
<9> The light emitting layer isHole transport materials or electron transport materials other than charge transporting polyurethane<5> The organic electroluminescent device according to <5>.
[0033]
  In the organic EL device of the present invention, the organic compound layer is a function-separated type, for example, at least a hole transport layer and a light-emitting layer, and the hole transport layer has the general formula(I-1)IndicatedStructureThose containing a charge transporting polyurethane comprising a repeating unit included as a partial structure, or those having both carrier transporting ability and light emitting ability, that is, the organic compound layer is composed only of a light emitting layer, General formula(I-1)IndicatedStructureAny of those containing a charge transporting polyurethane comprising repeating units included as a partial structure may be used.
[0034]
In the organic EL device of the present invention, when the organic compound layer is composed only of the light emitting layer, the light emitting layer contains a charge transporting material (a hole transporting material other than the charge transporting polyurethane, an electron transporting material). But you can.
[0035]
DETAILED DESCRIPTION OF THE INVENTION
  The organic EL device of the present invention is composed of one or a plurality of organic compound layers sandwiched between a pair of electrodes composed of an anode and a cathode, at least one of which is transparent or translucent, and at least one of the organic compound layers. Is the following general formula(I-1)IndicatedStructureIt is characterized by containing one or more types of charge transporting polyurethane (hereinafter sometimes simply referred to as “charge transporting polyurethane”) comprising repeating units included as a partial structure.The charge transporting polyurethane may further contain a partial structure represented by the following general formula (I-2)..
[0036]
[Chemical formula 5]

[0037]
  Formula (I-1)Wherein X represents substituted or unsubstituted biphenyl or anthracene,In (I-2), X represents a substituted or unsubstituted divalent aromatic group. T represents a divalent linear hydrocarbon group having 1 to 6 carbon atoms or a divalent branched hydrocarbon group having 2 to 10 carbon atoms;Is 1Represents. R₁Represents a saturated or unsaturated hydrocarbon group having 1 to 10 carbon atoms, or a substituted or unsubstituted aromatic group, and R₂Is a hydrogen atom, a saturated or unsaturated hydrocarbon group having 1 to 10 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a cyano group, a halogen atom, a substituted amino group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted group Represents an aralkyl group.
[0038]
The organic EL device of the present invention has a layer containing the charge transporting polyurethane, thereby having sufficient luminance and excellent stability and durability. Further, by using the charge transporting polyurethane, the area can be increased and the production can be easily performed.
[0039]
Specifically, by using the charge transporting polyurethane in at least one of the organic compound layers, the charge mobility can be increased, so that an organic EL element having high emission luminance at a low current can be obtained. . In addition, since it is not necessary to disperse (compatible) a low molecular charge transport material in the polymer material for forming the charge transport layer, the glass transition temperature of the polymer material is not lowered, and the heat resistance of the organic EL device is reduced. Property and durability can be improved.
[0040]
  Formula (I-1)Wherein X represents substituted or unsubstituted biphenyl or anthracene,In (I-2), X represents a substituted or unsubstituted divalent aromatic group, and specific examples thereof include the following formulas (1) to (13).
[0041]
[Chemical 6]

[0042]
In formulas (1) to (13), R_ThreeRepresents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted phenyl group, or a substituted or unsubstituted aralkyl group;_Four~ R₁₂Each represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxyl group having 1 to 4 carbon atoms, a substituted or unsubstituted phenyl group, a substituted or unsubstituted aralkyl group, or a halogen atom; 0 or 1 is represented, and V represents a group selected from the following formulas (14) to (31).
[0043]
[Chemical 7]

[0044]
In formulas (14) to (31), c, d, and e are integers of 1 to 10, and f, g, and h are integers of 0 to 10.
[0045]
Among these, when the X has a biphenylene structure represented by the following structural formula (32) or (33), it is also reported in “The Sixth International Congress on Non-impact Printing Technologies, 306, (1990)”. As described above, a polymer having high mobility can be obtained, which is particularly preferable.
[0046]
[Chemical 8]

[0047]
In general formulas (I-1) and (I-2), T represents a divalent linear hydrocarbon group having 1 to 6 carbon atoms or a divalent branched hydrocarbon group having 2 to 10 carbon atoms. Represents a group, and specific examples thereof include the following structures.
[0048]
[Chemical 9]

[0049]
  Hereinafter, specific examples of the structures represented by the general formulas (I-1) and (I-2)Table 2 to Table 5, Table 7, Table 10Although shown in Table 17, the present invention is not limited to these specific examples. In addition,Table 2 to Table 5, Table 7Structure number in13-19, 20-40, 44, 57-59Indicates specific examples of the structure represented by the general formula (I-1), and structure numbers 77 to 140 in Tables 10 to 17 indicate specific examples of the structure represented by the general formula (I-2).
[0051]
[Table 2]

[0052]
[Table 3]

[0053]
[Table 4]

[0054]
[Table 5]

[0056]
[Table 7]

[0059]
[Table 10]

[0060]
[Table 11]

[0061]
[Table 12]

[0062]
[Table 13]

[0063]
[Table 14]

[0064]
[Table 15]

[0065]
[Table 16]

[0066]
[Table 17]

[0067]
  General formula(I-1)IndicatedStructureThe charge transporting polyurethane comprising repeating units contained as a partial structure is represented by the following general formula (II-1) or (II-2)UsedIs done.
[0068]
[Chemical Formula 10]

[0069]
  In general formulas (II-1) and (II-2), A represents the above general formula.(I-1)IndicatedStructureR represents a hydrogen atom, an alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted aralkyl group, Y represents a diisocyanate residue, Z represents a dihydric alcohol residue, and p represents 5 Represents an integer of ˜5000.
[0070]
Specific examples of Y and Z in the general formula (II-1) or (II-2) include groups selected from the following formulas (34) to (40).
[0071]
Embedded image

[0072]
In formulas (34) to (40), R₁₃And R₁₄Each represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxyl group having 1 to 4 carbon atoms, a substituted or unsubstituted phenyl group, a substituted or unsubstituted aralkyl group, or a halogen atom, and α and β are Each represents an integer of 1 to 10, γ and δ each represent an integer of 0, 1 or 2, and η and ρ each represents 0 or 1. Specific examples of V include the above formulas (14) to (31).
[0073]
  Table 18 ~Table 20, Table 24-Table 25 shows specific examples of the charge transporting polyurethane represented by the general formulas (II-1) and (II-2), but the present invention is not limited to these specific examples. Table 18 ~Table 20, Table 24-In Table 25, the numbers in the column A of the monomer column are specific examples of the structures represented by the general formulas (I-1) and (I-2).Table 2 to Table 5, Table 7, Table 10Corresponds to the structure numbers shown in Table 17. The case where the column of Z is “−” indicates a specific example of the charge transporting polyurethane represented by the general formula (II-1), and the case where the column of Z is other than “−” is the general formula (II- Specific examples of the charge transporting polyurethane represented by 2) are shown below. Hereinafter, the specific example which attached | subjected each number, for example, the specific example which attached | subjected the number of 15, is called illustration compound (15).
[0074]
[Table 18]

[0075]
[Table 19]

[0076]
[Table 20]

[0080]
[Table 24]

[0081]
[Table 25]

[0082]
The mass average molecular weight Mw of the charge transporting polyurethane is preferably in the range of 10,000 to 300,000, and more preferably in the range of 50,000 to 200,000.
[0083]
For the charge transporting polyurethane, charge transporting monomers represented by the following structural formulas (III-1) to (IV-2) are used, for example, 4th edition Experimental Chemistry Course Vol. 28 (Maruzen, 1992), New Polymer Experiment. It can be synthesized by polymerization by a known method described in Gaku 2nd volume (Kyoritsu Shuppan, 1995). In the following structural formulas (III-1) and (III-2), A and T are A in the general formula (II-1) or (II-2), the general formula (I-1) or ( The same as T in I-2).
[0084]
Embedded image

[0085]
Specifically, for example, in the case of the charge transporting monomers represented by the general formulas (III-1) and (III-2), the charge transporting polyurethane can be synthesized as follows. For example, when the charge transporting monomer is a dihydric alcohol represented by the general formula (III-1), it is mixed in an equivalent amount with a diisocyanate represented by OCN-Y-NCO. In the case of diisocyanates represented by (III-2), they are mixed in an equivalent amount with dihydric alcohols represented by HO—Y—OH and polyadded.
[0086]
As a catalyst, what is used for the polyurethane synthesis reaction by normal polyadditions, such as organometallic compounds, such as dibutyltin (II) dilaurate, dibutyltin diacetate, and lead naphthenate, can be used. Further, when an aromatic diisocyanate is used for the synthesis of a charge transporting polyurethane, a tertiary amine such as triethylenediamine can be used as a catalyst. These organometallic compounds and tertiary amines may be mixed and used as a catalyst.
[0087]
The addition amount of the catalyst is preferably in the range of 1 / 10,000 to 1/10 parts by mass, and in the range of 1 / 1,000 to 1/50 parts by mass with respect to 1 part by mass of the charge transporting monomer. It is more preferable that
[0088]
As the solvent, any solvent can be used as long as it dissolves the charge transporting monomer and diisocyanate or dihydric alcohol. However, from the viewpoint of reactivity, a hydrogen bond with a less polar solvent or alcohol. It is preferable to use a solvent that does not generate water, and toluene, chlorobenzene, dichlorobenzene, 1-chloronaphthalene, and the like are effective. The amount of the solvent used is preferably in the range of 1 to 100 parts by mass, more preferably in the range of 2 to 50 parts by mass with respect to 1 part by mass of the charge transporting monomer. The reaction temperature can be arbitrarily set.
[0089]
After completion of the reaction, the reaction solution is dropped as it is into a poor solvent in which alcohols such as methanol and ethanol, and polymers such as acetone are difficult to dissolve, and the charge transporting polyurethane is precipitated and separated, and then water or an organic solvent. Wash thoroughly and dry. Furthermore, if necessary, the reprecipitation treatment may be repeated in which it is dissolved in a suitable organic solvent and dropped into a poor solvent to precipitate the charge transporting polyurethane. In the reprecipitation treatment, it is preferable to carry out the poor solvent efficiently with a mechanical stirrer or the like.
[0090]
The amount of the solvent that dissolves the charge transporting polyurethane during the reprecipitation treatment is preferably in the range of 1 to 100 parts by weight, and in the range of 2 to 50 parts by weight with respect to 1 part by weight of the charge transporting polyurethane. More preferably. The amount of the poor solvent is preferably in the range of 1 to 1,000 parts by mass and more preferably in the range of 10 to 500 parts by mass with respect to 1 part by mass of the charge transporting polyurethane.
[0091]
Next, the synthesis of the charge transporting polyurethane when the charge transporting monomers represented by the following structural formulas (IV-1) and (IV-2) are used will be described. In the structural formulas (IV-1) and (IV-2), A and T are the same as A in the general formula (II-1) or (II-2), the general formula (I-1) or (I- The same as T in 2).
[0092]
Embedded image

[0093]
When the charge transporting monomer is bischloroformate represented by the general formula (IV-1),₂HN-Y-NH₂In the case where the charge transporting monomer is a diamine represented by the general formula (IV-2), it is mixed in an equivalent amount with a bischloroformate represented by ClOCO-Y-OCOCl. And polycondensate.
[0094]
As the solvent, methylene chloride, dichloroethane, trichloroethane, tetrahydrofuran (THF), toluene, chlorobenzene, 1-chloronaphthalene and the like are effective, and the amount of the solvent is 1 to 100 parts by mass with respect to 1 part by mass of the charge transporting monomer. It is preferable that it is the range of this, and it is more preferable that it is the range of 2-50 mass parts. The reaction temperature can be arbitrarily set. After the polymerization, purification is performed by reprecipitation as described above.
[0095]
Also, the above₂HN-Y-NH₂When the basicity of the diamine represented by is high, an interfacial polymerization method can also be used. That is, by adding diamines to water and adding an equivalent amount of acid to dissolve, diamines and an equivalent amount of the charge transporting monomer solution represented by the general formula (IV-1) are added with vigorous stirring. Can be polymerized. Under the present circumstances, it is preferable that it is the range of 1-1000 mass parts with respect to 1 mass part of diamines, and, as for the quantity of water, it is more preferable that it is the range of 10-500 mass parts.
[0096]
As the solvent for dissolving the charge transporting monomer, methylene chloride, dichloroethane, trichloroethane, toluene, chlorobenzene, 1-chloronaphthalene and the like are effective. The reaction temperature can be arbitrarily set, and in order to promote the reaction, it is effective to use a phase transfer catalyst such as an ammonium salt or a sulfonium salt. The amount of the phase transfer catalyst used is preferably in the range of 0.1 to 10 parts by mass and more preferably in the range of 0.2 to 5 parts by mass with respect to 1 part by mass of the charge transporting monomer. .
[0097]
Next, the layer structure of the organic EL element of the present invention will be described in detail.
The organic EL device of the present invention comprises a pair of electrodes, at least one of which is transparent or translucent, and one or a plurality of organic compound layers including a light emitting layer sandwiched between the electrodes. The charge transporting polyurethane is contained in at least one layer.
[0098]
In the organic EL device of the present invention, when there is one organic compound layer, the organic compound layer is a light emitting layer having a carrier transport ability, and the light emitting layer contains the charge transporting polyurethane. Further, when there are a plurality of organic compound layers (in the case of function separation type), at least one of them is a light emitting layer (this light emitting layer may or may not have carrier transporting ability). And the other organic compound layer is configured as a carrier transport layer, that is, a hole transport layer, an electron transport layer, or a hole transport layer and an electron transport layer, and at least one of these layers comprises the charge transport polyurethane. It contains.
[0099]
Specifically, for example, an organic EL device composed of at least a light emitting layer and an electron transport layer, an organic EL device composed of at least a hole transport layer, a light emitting layer and an electron transport layer, or at least a hole transport layer and a light emitting layer In the organic EL device composed of the above, there may be mentioned those in which at least one of these layers (light emitting layer, hole transport layer, electron transport layer) contains the charge transporting polyurethane. Furthermore, for example, the organic compound layer may be composed only of a light emitting layer, and the light emitting layer may contain the charge transporting polyurethane.
[0100]
In the organic EL device of the present invention, the light emitting layer preferably contains a charge transporting material (a hole transporting material other than the charge transporting polyurethane, an electron transporting material). Details will be described later.
[0101]
Hereinafter, the configuration of the organic EL device of the present invention will be described in more detail with reference to the drawings, but the present invention is not limited thereto.
1 to 4 are schematic cross-sectional views for explaining the layer structure of the organic EL element of the present invention, and FIGS. 1, 2, and 4 are examples of the case where there are a plurality of organic compound layers. FIG. 3 shows an example in the case of one organic compound layer. In FIG. 1 to FIG. 4, components having similar functions are described with the same reference numerals.
[0102]
The organic EL element shown in FIG. 1 is formed by sequentially laminating a transparent electrode 2, a light emitting layer 6 having a carrier transport ability, an electron transport layer 5 and a back electrode 7 on the surface of a transparent insulator substrate 1. The organic EL element shown in FIG. 2 is formed by sequentially laminating a transparent electrode 2, a hole transport layer 3, a light emitting layer 4, an electron transport layer 5 and a back electrode 7 on the surface of a transparent insulator substrate 1. The organic EL element shown in FIG. 3 is formed by sequentially laminating a transparent electrode 2, a light emitting layer 6 having a carrier transport capability, and a back electrode 7 on the surface of a transparent insulator substrate 1. The organic EL element shown in FIG. 4 is formed by sequentially laminating a transparent electrode 2, a hole transport layer 3, a light emitting layer 6 having a carrier transport capability, and a back electrode 7 on the surface of the transparent insulator substrate 1. Each will be described in detail below.
[0103]
1, 2, and 4, when the light emitting material (light emitting layer) does not show a clear carrier transport property, the durability of the organic EL element is improved or the light emission efficiency is improved. For the purpose of improvement, a hole transport layer is provided between the light-emitting layer 4 or the light-emitting layer 6 having carrier transport capability and the transparent electrode 2, or the light-emitting layer 4 or the light-emitting layer 6 having carrier transport capability and the back electrode 7 A layer structure in which an electron transport layer is provided between the layers.
[0104]
In the case of the layer structure of the organic EL device shown in FIG. 1, the organic compound layer containing the charge transporting polyurethane in the present invention is preferably used, for example, as the light emitting layer 6 having a carrier transporting ability. In the case of the layer structure of the organic EL element shown in FIG. 2, the organic compound layer containing the charge transporting polyurethane can be used as the light emitting layer 4 and the hole transporting layer 3, It is preferable to use as the light emitting layer 4. Further, in the case of the layer structure of the organic EL element shown in FIG. 3, it is preferable to use the organic compound layer containing the charge transporting polyurethane as the light emitting layer 6 having a carrier transporting ability. Further, in the case of the layer structure of the organic EL element shown in FIG. 4, the organic compound layer containing the charge transporting polyurethane is, for example, a hole transport layer 3 or a light emitting layer 6 having a carrier transport ability. Can also be used, but it is preferably used as the light emitting layer 6 having a carrier transporting ability.
[0105]
As the organic EL device of the present invention using the charge transporting polyurethane as the organic compound layer, the configurations of FIGS. 3 and 4 among the above-described layer configurations are easy to manufacture as the device, and the characteristics of the charge transporting polyurethane are as follows. This configuration is preferable in that it can be reflected and sufficient luminance, stability, and durability can be achieved.
[0106]
Note that the organic compound layer containing the charge transporting polyurethane in the present invention has a good hole transporting ability, and is used, for example, in the hole transporting layer 3 of the light emitting device shown in FIG. 4 as described above. Can do. In this case, the light-emitting layer 6 having a carrier transporting ability is provided with an electron-transporting light-emitting layer, and typical examples include compounds shown in the following figures (V-1 to 9).
[0107]
Embedded image

[0108]
In the case of the layer structure of the organic EL element shown in FIGS. 1 to 4, the light emitting layer 4 or the light emitting layer 6 having a carrier transport ability is given a function (hole transport ability or electron transport ability) depending on the purpose. An organic compound layer containing the charge transporting polyurethane is preferred.
[0109]
The organic compound layer in this case is basically formed of the charge transporting polyurethane alone, but in order to adjust the balance between holes and electrons injected into the organic EL element, other than the charge transporting polyurethane is used. You may disperse | distribute an electron transport material in 10-50 mass% with respect to the mass of the whole layer. As such an electron transporting material, it is preferable to use an organic compound that does not exhibit a strong electron interaction with the charge transporting polyurethane. More preferably, the following exemplified compound (VI) is used, but the organic compound is not limited thereto. is not.
[0110]
Embedded image

[0111]
Similarly, in order to adjust the hole mobility, a hole transporting material other than charge transporting polyurethane, preferably a tetraphenylenediamine derivative, may be simultaneously dispersed in the range of 10 to 50% by mass with respect to the total mass of the layer. Good.
[0112]
Further, the light emitting layer 4 or the light emitting layer 6 having a carrier transporting ability may be doped with a dye compound different from the charge transporting polyurethane for the purpose of improving the durability of the organic EL device or improving the light emitting efficiency. Doping is performed by mixing a predetermined dye in a solution or dispersion. The doping ratio of the dye compound in the light emitting layer is preferably in the range of 0.001 to 40% by mass, more preferably in the range of 0.01 to 10% by mass, based on the total mass of the layer.
[0113]
As the dye compound used for such doping, an organic compound that has good compatibility with the light emitting material and does not prevent the formation of a good thin film of the light emitting layer is used. DCM derivatives, quinacridone derivatives, rubrene derivatives, porphyrin compounds Etc. are preferably used. Specific examples include the following compounds (VII-1) to (VII-4), but are not limited thereto.
[0114]
Embedded image

[0115]
In the case of the organic EL element having the layer structure shown in FIGS. 1 to 4, the transparent insulator substrate 1 is preferably transparent in order to extract emitted light, and glass, plastic film, or the like is used. Further, the transparent electrode 2 is preferably transparent for extracting light emission like the transparent insulator substrate 1 and has a high work function for efficient hole injection, such as indium tin oxide (ITO), oxidized An oxide film such as tin (NESA), indium oxide, and zinc oxide, and gold, platinum, palladium, or the like deposited or sputtered is preferably used.
[0116]
In the case of the organic EL element having the layer structure shown in FIGS. 1 and 2, a compound exhibiting an electron transport ability is used as the charge transport material for the electron transport layer 5. As an electron transport material used for such an electron transport layer, in the case of an organic low molecule, an organic compound capable of forming a good thin film by a vacuum deposition method is preferably used. Specifically, an oxadiazole derivative, a nitro compound, Substituted fluorenone derivatives, diphenoquinone derivatives, thiopyran dioxide oxide derivatives, fluorenylidenemethane derivatives and the like can be mentioned. In the case of a polymer, it is a condition that a good thin film can be formed by applying and drying a solution or dispersion containing itself. Specifically, the following compounds (VIII-1) to (VIII-3) are preferably used as the electron transporting material, but are not limited thereto. Moreover, you may mix and use with other general purpose resin etc.
[0117]
Embedded image

[0118]
In the case of the organic EL element having the layer structure shown in FIGS. 2 and 4, a compound exhibiting hole transport ability is used as the charge transport material for the hole transport layer 3. When the charge transporting material is a low molecular weight organic material, it is possible to form a good thin film by vacuum deposition or by applying and drying a solution or dispersion containing a low molecular weight and a binder resin. It is assumed that In addition, when the charge transporting material exhibiting hole transporting ability is a polymer, the material selection condition is that a good thin film can be formed by applying and drying a solution or dispersion containing itself. .
[0119]
As the charge transporting material exhibiting hole transporting ability, tetraphenylenediamine derivatives, triphenylamine derivatives, carbazole derivatives, stilbene derivatives, arylhydrazone derivatives, porphyrin compounds, and the like are preferably used. Illustrative compounds (IX-1) to (IX-8) can be mentioned, and among these, a tetraphenylenediamine derivative is preferably used because of its good compatibility with the charge transporting polyurethane. Moreover, you may use the said compound mixed with other general purpose resin.
[0120]
Embedded image

[0121]
In the case of the organic EL element having the layer structure shown in FIGS. 1 to 4, the back electrode 7 is made of a metal that can be vacuum-deposited and has a small work function in order to efficiently perform electron injection. Aluminum, silver, indium and alloys thereof are preferably used. Further, a protective layer may be provided on the surface of the back electrode 7 in order to prevent deterioration of the element due to moisture or oxygen. Specific protective layer materials include metals such as In, Sn, Pb, Au, Cu, Ag, and Al, MgO, and SiO.₂TiO₂Examples thereof include metal oxides such as polyethylene resins, polyurea resins, and polyimide resins. For forming the protective layer, a vacuum deposition method, a sputtering method, a plasma polymerization method, a CVD method, or a coating method can be applied.
[0122]
Each layer formation of the organic EL element shown in FIGS. 1 to 4 is performed as follows. First, the hole transport layer 3 or the light emitting layer 6 having a carrier transport capability is formed on the surface of the transparent electrode 2 according to the layer structure of each organic EL element. The hole transport layer 3 and the light emitting layer 6 having carrier transport capability are formed by depositing the above materials on the surface of the transparent electrode 2 using a vacuum deposition method or by dissolving or dispersing in an organic solvent.RuIt is formed by a spin coating method, a dip method or the like.
[0123]
Next, depending on the layer structure of each organic EL element, the hole transport layer 3, the light-emitting layer 4, the electron transport layer 5 or the light-emitting layer 6 having a carrier transport capability is obtained by using the above-mentioned materials by vacuum deposition or organic It is formed by using a spin coating method, a dip method, or the like that dissolves or disperses therein and forms a film on the surface of the transparent electrode 2 using the obtained coating solution.
[0124]
The film thicknesses of the hole transport layer 3, the light emitting layer 4 and the electron transport layer 5 to be formed are each preferably 0.1 μm or less, and particularly preferably in the range of 0.03 to 0.08 μm. Further, the film thickness of the light emitting layer 6 having a carrier transporting ability is preferably in the range of 0.03 to 0.2 μm, and more preferably in the range of 0.05 to 0.1 μm.
[0125]
The dispersion state of each of the materials (the charge transporting polyurethane, the light emitting material, etc.) may be a molecular dispersion state or a fine particle dispersion state. In the case of a film forming method using a coating solution, it is necessary to use a common solvent of each of the above materials as a dispersion solvent in order to obtain a molecular dispersion state. It is necessary to select it in consideration of the dispersibility and solubility. In order to disperse into fine particles, a ball mill, a sand mill, a paint shaker, an attritor, a ball mill, a homogenizer, an ultrasonic method, or the like can be used.
[0126]
Finally, the device is completed by forming the back electrode 7 on the surface of the electron transport layer 5 or the light emitting layer 6 having carrier transport ability by a vacuum deposition method.
[0127]
The organic EL element of the present invention has a current density of 1 to 200 mA / cm between a pair of electrodes, for example, at 4 to 20 V.²By applying a direct current voltage of 100 cd / m²It can be made to emit enough light.
[0128]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not restrict | limited to these Examples.
First, the charge transport polyurethane used in each example was obtained as follows, for example.
[0129]
-Synthesis example 1 [Exemplary compound (4)]-
2.0 g of the monomer described in 17 of Table 1 and 30 ml of chlorobenzene were placed in a 50 ml flask and stirred to dissolve, and a solution of 0.54 g of hexamethylene diisocyanate dissolved in 10 ml of chlorobenzene was added to the flask for 30 minutes. After dropwise addition, the mixture was heated and stirred at 150 ° C. for 2 hours under a nitrogen stream. After completion of the reaction, the reaction solution was cooled to room temperature, and the reaction solution was dropped into 300 ml of stirred methanol to precipitate a polymer. The polymer obtained was filtered, washed thoroughly with methanol and dried, and then dissolved in 30 ml of tetrahydrofuran (THF), and this solution was added dropwise to 300 ml of methanol. A charge transporting polyurethane was obtained. The molecular weight was measured by GPC and found to be Mw = 8.82 × 10.^FourThe value of p calculated from the molecular weight of the monomer was about 103.
[0130]
-Synthesis example 2 [Exemplary compound (13)]-
2.0 g of the monomer described in 32 of Table 1 and 30 ml of chlorobenzene were placed in a 50 ml flask and stirred to dissolve, and a solution of 0.52 g of hexamethylene diisocyanate dissolved in 10 ml of chlorobenzene was added to the flask for 30 minutes. After dropwise addition, the mixture was heated and stirred at 150 ° C. for 2 hours under a nitrogen stream. After completion of the reaction, the reaction solution was cooled to room temperature, and the reaction solution was dropped into 300 ml of stirred methanol to precipitate a polymer. The polymer obtained was filtered, washed thoroughly with methanol and dried, and then dissolved in 30 ml of tetrahydrofuran (THF), and this solution was added dropwise to 300 ml of methanol. A charge transporting polyurethane was obtained. The molecular weight was measured by GPC, Mw = 1.52 × 10^FiveThe value of p calculated from the molecular weight of the monomer was about 170.
[0131]
-Synthesis example 3 [Exemplary compound (38)]-
2.0 g of the monomer described in 58 of Table 1 and 30 ml of chlorobenzene were placed in a 50 ml flask and stirred to dissolve, and a solution of 0.52 g of hexamethylene diisocyanate dissolved in 10 ml of chlorobenzene was added to the flask for 30 minutes. After dropwise addition, the mixture was heated and stirred at 150 ° C. for 3 hours under a nitrogen stream. After completion of the reaction, the reaction solution was cooled to room temperature, and the reaction solution was dropped into 300 ml of stirred methanol to precipitate a polymer. The polymer obtained was filtered, washed thoroughly with methanol and dried, and then dissolved in 30 ml of tetrahydrofuran (THF), and this solution was added dropwise to 300 ml of methanol. A charge transporting polyurethane was obtained. The molecular weight was measured by GPC, Mw = 1.21 × 10^FiveThe value of p calculated from the molecular weight of the monomer was about 140.
[0132]
Example 1
A 5 mass% dichloroethane solution of the charge transporting polyurethane described in Synthesis Example 1 was prepared and filtered through a 0.1 μm polytetrafluoroethylene (PTFE) filter. Using this solution, a 2 mm wide strip-shaped ITO electrode was applied to the surface of a glass substrate formed by etching by a dipping method to form a hole transport layer having a thickness of about 0.1 μm. The exemplified compound (V-1) purified by sublimation as a light-emitting material is put on a tungsten boat on the surface of this hole transport layer that has been sufficiently dried, and is deposited by a vacuum deposition method to provide a carrier transport ability of 0.05 μm in thickness. A light emitting layer was formed. The degree of vacuum at this time is 1.33 × 10^-3Pa and boat temperature were 300 degreeC. Subsequently, a Mg—Ag alloy was vapor-deposited on the surface of the light emitting layer by co-evaporation to form a back electrode having a width of 2 mm and a thickness of 0.15 μm so as to cross the ITO electrode. The effective area of the produced organic EL element is 0.04 cm.²Met.
[0133]
The organic EL device produced as described above was subjected to vacuum (1.33 × 10 6^-1Pa), the ITO electrode side was positive, the Mg-Ag back electrode was negative, a DC voltage of 10 V was applied, and light emission was measured, and the maximum luminance and light emission color at this time were evaluated. The results are shown in Table 26. Moreover, the light emission lifetime of the organic EL element was measured in dry nitrogen. In the evaluation of the light emission lifetime, the initial luminance is 350 cd / m²The current value was set such that the time until the luminance was halved from the initial value by constant current driving was defined as the element lifetime. The drive current density at this time is shown in Table 26 together with the element lifetime.
[0134]
(Example 2)
99 parts by mass of the charge transporting polyurethane described in Synthesis Example 1 and 1 part by mass of Compound (VII-3) as a luminescent material were mixed to prepare a 10% by mass dichloroethane solution, which was filtered through a 0.1 μm PTFE filter. . Using this solution, a light emitting layer having a carrier transport ability of about 0.15 μm thickness was formed by a dipping method on the surface of a glass substrate on which a 2 mm wide strip-shaped ITO electrode was formed by etching. After sufficiently drying, a Mg—Ag alloy was vapor-deposited on the surface of the light emitting layer having the carrier transporting ability to form a back electrode having a width of 2 mm and a thickness of 0.15 μm so as to cross the ITO electrode. The effective area of the produced organic EL element is 0.04 cm.²Met.
Evaluation similar to Example 1 was performed about the said organic EL element. The results are shown in Table 26.
[0135]
(Example 3)
2 parts by mass of the charge transporting polyurethane described in Synthesis Example 1, 0.1 part by mass of the compound (VII-1) as a light emitting material, and 1 part by mass of the compound (VI) as an electron transporting material were mixed. A 10% by mass dichloroethane solution was prepared and filtered through a 0.1 μm PTFE filter. Using this solution, a 2 mm wide strip-shaped ITO electrode was coated on the surface of a glass substrate formed by etching by a dipping method to form a light emitting layer having a thickness of about 0.15 μm and having a carrier transport capability. After sufficiently drying, a Mg—Ag alloy was vapor-deposited on the surface of the light emitting layer having the carrier transporting ability to form a back electrode having a width of 2 mm and a thickness of 0.15 μm so as to cross the ITO electrode. The effective area of the produced organic EL element is 0.04 cm.²Met.
Evaluation similar to Example 1 was performed about the said organic EL element. The results are shown in Table 26.
[0136]
(Example 4)
A 5 mass% dichloroethane solution of the charge transporting polyurethane described in Synthesis Example 1 was prepared and filtered through a 0.1 μm polytetrafluoroethylene (PTFE) filter. Using this solution, a 2 mm wide strip-shaped ITO electrode was applied to the surface of a glass substrate formed by etching by a dipping method to form a light-emitting layer having a thickness of about 0.1 μm and having a carrier transport capability. After sufficiently drying, a Mg—Ag alloy was vapor-deposited on the surface of the light emitting layer having the carrier transporting ability to form a back electrode having a width of 2 mm and a thickness of 0.15 μm so as to cross the ITO electrode. The effective area of the produced organic EL element is 0.04 cm.²Met.
Evaluation similar to Example 1 was performed about the said organic EL element. The results are shown in Table 26.
[0137]
(Example 5)
An organic EL device was produced in the same manner as in Example 1 except that the charge transporting polyurethane of Synthesis Example 2 was used instead of the charge transporting polyurethane of Synthesis Example 1.
Evaluation similar to Example 1 was performed about the said organic EL element. The results are shown in Table 26.
[0138]
(Example 6)
An organic EL device was produced in the same manner as in Example 2 except that the charge transporting polyurethane of Synthesis Example 2 was used instead of the charge transporting polyurethane of Synthesis Example 1.
Evaluation similar to Example 1 was performed about the said organic EL element. The results are shown in Table 26.
[0139]
(Example 7)
An organic EL device was produced in the same manner as in Example 3 except that the charge transporting polyurethane of Synthesis Example 2 was used instead of the charge transporting polyurethane of Synthesis Example 1.
Evaluation similar to Example 1 was performed about the said organic EL element. The results are shown in Table 26.
[0140]
(Example 8)
An organic EL device was produced in the same manner as in Example 4 except that the charge transporting polyurethane of Synthesis Example 2 was used instead of the charge transporting polyurethane of Synthesis Example 1.
Evaluation similar to Example 1 was performed about the said organic EL element. The results are shown in Table 26.
[0141]
Example 9
An organic EL device was produced in the same manner as in Example 1 except that the charge transporting polyurethane of Synthesis Example 3 was used instead of the charge transporting polyurethane of Synthesis Example 1.
Evaluation similar to Example 1 was performed about the said organic EL element. The results are shown in Table 26.
[0142]
(Example 10)
An organic EL device was produced in the same manner as in Example 2 except that the charge transporting polyurethane of Synthesis Example 3 was used instead of the charge transporting polyurethane of Synthesis Example 1.
Evaluation similar to Example 1 was performed about the said organic EL element. The results are shown in Table 26.
[0143]
(Example 11)
An organic EL device was produced in the same manner as in Example 3 except that the charge transporting polyurethane of Synthesis Example 3 was used instead of the charge transporting polyurethane of Synthesis Example 1.
Evaluation similar to Example 1 was performed about the said organic EL element. The results are shown in Table 26.
[0144]
Example 12
An organic EL device was produced in the same manner as in Example 4 except that the charge transporting polyurethane of Synthesis Example 3 was used instead of the charge transporting polyurethane of Synthesis Example 1.
Evaluation similar to Example 1 was performed about the said organic EL element. The results are shown in Table 26.
[0145]
(Comparative Example 1)
1 part by mass of the compound (IX-2) exhibiting the hole transport ability, 1 part by mass of the compound (V-1) as a light emitting material, and 1 part by mass of polymethyl methacrylate (PMMA) as a binder resin Were mixed to prepare a 10% by mass dichloroethane solution, which was filtered through a 0.1 μm PTFE filter. Using this solution, a hole transport layer having a thickness of 0.15 μm was formed on the surface of a glass substrate on which a 2 mm wide strip-shaped ITO electrode was formed by etching, by a dipping method. An Mg—Ag alloy was vapor-deposited on the sufficiently dried hole transport layer surface by co-evaporation to form a back electrode having a width of 2 mm and a thickness of 0.15 μm so as to cross the ITO electrode. The effective area of the produced organic EL element is 0.04 cm.²Met.
Evaluation similar to Example 1 was performed about the said organic EL element. The results are shown in Table 26.
[0146]
(Comparative Example 2)
2 parts by mass of polyvinyl carbazole (PVK) as a hole transporting polymer compound, 0.1 part by mass of the compound (V-1) as a light emitting material, and 1 part by mass of the compound (VI) as an electron transporting material are mixed. A 10% by mass dichloroethane solution was prepared and filtered through a 0.1 μm PTFE filter. Using this solution, a hole transport layer having a thickness of 0.15 μm was formed on the surface of a glass substrate on which a 2 mm wide strip-shaped ITO electrode was formed by etching, by a dipping method. After sufficiently drying, a Mg—Ag alloy was vapor-deposited on the surface of the hole transport layer by co-evaporation to form a back electrode having a width of 2 mm and a thickness of 0.15 μm so as to cross the ITO electrode. The effective area of the produced organic EL element is 0.04 cm.²Met.
Evaluation similar to Example 1 was performed about the said organic EL element. The results are shown in Table 26.
[0147]
[Table 26]

[0148]
As shown in the above examples, the organic EL device of the present invention exhibits a high maximum luminance despite a low driving current density, and particularly in Examples 2, 6, 9, and 12, 800 cd / m.²The above maximum brightness was obtained. On the other hand, in the organic EL element of the comparative example, sufficient maximum luminance and element life could not be obtained.
[0149]
【The invention's effect】
  General formula(I-1)IndicatedStructureCharge transportable polyurethane consisting of repeating structural units included as a partial structure has ionization potential, charge mobility and light emission characteristics suitable for organic EL devices, and forms good thin films using spin coating, dipping, etc. Therefore, the organic EL element of the present invention formed using this exhibits sufficiently high luminance, and since the film thickness can be set relatively thick, there are few defects such as pinholes, It is easy to enlarge the area and has excellent durability.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing an example of a stacked organic EL element of the present invention.
FIG. 2 is a schematic cross-sectional view showing another example of the stacked organic EL element of the present invention.
FIG. 3 is a schematic cross-sectional view showing another example of the organic EL element of the present invention.
FIG. 4 is a schematic cross-sectional view showing another example of the stacked organic EL element of the present invention.
[Explanation of symbols]
1 Transparent insulator substrate
2 Transparent electrode
3 Hole transport layer
4 Light emitting layer
5 Electron transport layer
6 Light emitting layer with carrier transport ability
7 Back electrode

Claims (9)

In an electroluminescent element composed of one or a plurality of organic compound layers sandwiched between a pair of electrodes consisting of an anode and a cathode, at least one of which is transparent or translucent, at least one of the organic compound layers is: a charge transport polyurethane consisting repeating units contain one or more containing the structure represented by the general formula (I-1) as a partial structure,
The organic electroluminescent device, wherein the charge transporting polyurethane is a polyurethane represented by the following general formula ( II- 1) or ( II- 2) .

[In General Formula (I-1) , X represents substituted or unsubstituted biphenyl or anthracene . T represents a divalent linear hydrocarbon group having 1 to 6 carbon atoms or a divalent branched hydrocarbon group having 2 to 10 carbon atoms, and k represents 1 . R ₁ represents a saturated or unsaturated hydrocarbon group having 1 to 10 carbon atoms, or a substituted or unsubstituted aromatic group, R ₂ represents a hydrogen atom, a saturated or unsaturated hydrocarbon group having 1 to 10 carbon atoms, carbon It represents an alkoxy group of formulas 1 to 4, a cyano group, a halogen atom, a substituted amino group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted aralkyl group. ]

[In General Formulas ( II- 1) and ( II- 2), A represents the structure represented by General Formula (I-1), and R represents a hydrogen atom, an alkyl group, a substituted or unsubstituted aryl group, or It represents a substituted or unsubstituted aralkyl group, Y represents a diisocyanate residue, Z represents a dihydric alcohol residue, and p represents an integer of 5 to 5000. ] The organic compound layer is composed of at least a light emitting layer having an electron transporting property and an electron transporting layer, and the light emitting layer comprises a repeating unit containing the structure represented by the general formula ( I-1) as a partial structure. The organic electroluminescent element according to claim 1, comprising at least one polyurethane. The organic compound layer is composed of at least a hole transport layer, a light-emitting layer, and an electron transport layer, and the light-emitting layer is composed of a repeating unit containing the structure represented by the general formula (I-1) as a partial structure. The organic electroluminescent element according to claim 1, wherein at least one kind is contained. The organic compound layer is composed of a light emitting layer having at least a carrier transporting ability, and the light emitting layer comprises at least a charge transporting polyurethane comprising a repeating unit containing the structure represented by the general formula (I-1) as a partial structure. The organic electroluminescent element according to claim 1, comprising one kind. The organic compound layer is composed of at least a hole transport layer and a light-emitting layer having carrier transport ability, and at least one of the light-emitting layer and the hole transport layer is a part of the structure represented by the general formula (I-1) 2. The organic electroluminescent device according to claim 1, wherein the organic electroluminescent device comprises at least one kind of charge transporting polyurethane comprising repeating units included as a structure. The organic light emitting device according to claim 2, wherein the light emitting layer contains a hole transport material or an electron transport material other than the charge transporting polyurethane . The organic light emitting device according to claim 3, wherein the light emitting layer contains a hole transport material or an electron transport material other than the charge transporting polyurethane . The organic light emitting device according to claim 4, wherein the light emitting layer contains a hole transport material or an electron transport material other than the charge transporting polyurethane . The organic electroluminescent element according to claim 5, wherein the light emitting layer contains a hole transport material or an electron transport material other than the charge transporting polyurethane .

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