JP4239523B2 - Organic electroluminescence device - Google Patents

Description

【００１３】
一般式（Ｉ−１）及び（Ｉ−２）中、Ｘは置換または未置換のビフェニルもしくターフェニルを表す。Ｔは炭素数１〜６の２価の直鎖状炭化水素、または炭素数２〜１０の分枝状炭化水素を表し、ｉ、ｊは０または１、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】

式中、Ａは上記一般式（Ｉ−１）及び（Ｉ−２）で示される構造から選択された少なくとも１種を表し、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２価のアルコール残基を表し、Ｚは２価のカルボン酸残基を表し、ｍは１〜５の整数を表し、ｐは５〜５０００の整数を表す。Ｂ及びＢ’は、それぞれ独立に−Ｏ−（Ｙ−Ｏ） _m −Ｒまたは−Ｏ−（Ｙ−Ｏ） _m −ＣＯ−Ｚ−ＣＯ−Ｏ−Ｒ’（ここで、Ｒ、Ｙ、Ｚ、ｍ、ｐは上記と同様であり、Ｒ’はアルキル基、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す。）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）及び（Ｉ−２）で示される構造から選択された少なくとも１種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エステルを、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）及び（Ｉ−２）で示される構造から選択された少なくとも１種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エステルを、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）及び（Ｉ−２）で示される構造から選択された少なくとも１種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エステルを、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）及び（Ｉ−２）で示される構造から選択された少なくとも１種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エステルを、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、前記電荷輸送性ポリエステル以外のホール輸送性材料または電子輸送性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、前記電荷輸送性ポリエステル以外のホール輸送性材料または電子輸送性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、前記電荷輸送性ポリエステル以外のホール輸送性材料または電子輸送性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、電荷輸送性ポリエステル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、前記一般式（Ｉ−１）及び（Ｉ−２）で示される構造から選択された少なくとも１種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エステルは、機能分離された複数の層が積層されたもの、例えば、少なくともホール輸送層及び発光層が積層された積層型、あるいは有機化合物層がキャリア輸送能と発光能を兼ね備えた単層型のいずれにも用いられる。また、積層型の発光層、あるいは単層型の有機化合物層に含有される場合には、他に電荷輸送性材料や発光性化合物を同時に含有してもよい。
【００３４】
【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）及び（Ｉ−２）で示される構造から選択された少なくとも１種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エステル（以下、単に「電荷輸送性ポリエステル」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。
【００３５】
【化５】

【００３６】
一般式（Ｉ−１）及び（Ｉ−２）中、Ｘは置換または未置換の２価のビフェニルもしくはターフェニルを表す。Ｔは炭素数１〜６の２価の直鎖状炭化水素、または炭素数２〜１０の分枝状炭化水素を表し、ｉ、ｊは０または１、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。
【００３７】
上記電荷輸送性ポリエステル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。
【００３８】
一般式（Ｉ−１）及び（Ｉ−２）中、Ｘは、置換または未置換のビフェニルもしくはターフェニルを表し、具体的な例としては下記の式（４）、（５）が挙げられる。
【００３９】
【化６】

【００４０】
式（４）、（５）中、Ｒ _９ は、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。
【００４１】
【化７】

【００４２】
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。
【００４３】
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。
【００４４】
【化８】

【００４５】
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、または炭素数２〜１０の分枝状炭化水素を表し、具体的な例としては以下の構造を挙げることができる。
【００４６】
【化９】

【００４７】
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１３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１〜表５における構造番号１３〜４４は一般式（Ｉ−１）で示される構造の具体例を示し、表１０〜表１３における構造番号８６〜１０９は一般式（Ｉ−２）で示される構造の具体例を示す。
【００４９】
【表２】

【００５０】
【表３】

【００５１】
【表４】

【００５２】
【表５】

【００５７】
【表１０】

【００５８】
【表１１】

【００５９】
【表１２】

【００６０】
【表１３】

【００６５】
一般式（Ｉ−１）及び（Ｉ−２）で示される構造から選択された少なくとも１種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エステルとしては、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。
【００６６】
【化１０】

【００６７】
式中、Ａは上記一般式（Ｉ−１）及び（Ｉ−２）で示される構造から選択された少なくとも１種を表し、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２価のアルコール残基を表し、Ｚは２価のカルボン酸残基を表し、ｍは１〜５の整数を表し、ｐは５〜５０００の整数を表すが、ｐは１０〜１０００の範囲であることが好ましい。Ｂ及びＢ’は、それぞれ独立に−Ｏ−（Ｙ−Ｏ）_m−Ｒまたは−Ｏ−（Ｙ−Ｏ）_m−ＣＯ−Ｚ−ＣＯ−Ｏ−Ｒ’（ここで、Ｒ、Ｙ、Ｚ、ｍ、ｐは上記と同様であり、Ｒ’はアルキル基、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す。）を表す。
【００６８】
一般式（II−１）または（II−２）式中の、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。
【００６９】
【化１１】

【００７０】
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。
【００７１】
以下、表１８〜表２５に、一般式（II−１）及び（II−２）で示される電荷輸送性ポリエステル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１３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エステルの具体例を示し、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エステルの具体例を示す。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。
【００７２】
【表１８】

【００７３】
【表１９】

【００７４】
【表２０】

【００７６】
【表２２】

【００７７】
【表２３】

【００７８】
【表２４】

【００７９】
【表２５】

【００８０】
前記電荷輸送性ポリエステルの質量平均分子量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。
【００８１】
前記電荷輸送性ポリエステルは、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、構造式（III−１）〜（IV−２）中、Ｔ、ｍは、各々前記一般式（Ｉ−１）、（Ｉ−２）、（II−１）、及び（II−２）におけるＴ、ｍと各々同様である。また、Ａ’は脱アルコールにより重合（エステル結合形成）させるため、前記モノマー末端をアルコール化するための２価アルコール等との反応基を表す。
【００８２】
【化１２】

【００８３】
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、電荷輸送性ポリエステルは、次のようにして合成することができる。Ａ’が水酸基の場合には、ＨＯ−（Ｙ−Ｏ）_m−Ｈで示される２価アルコール類をほぼ当量混合し、酸触媒を用いて重合する。
【００８４】
酸触媒としては、硫酸、トルエンスルホン酸、トリフルオロ酢酸等、通常のエステル化反応に用いるものが使用でき、触媒量としては、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。
【００８５】
重合中に生成する水を除去するために、水と共沸可能な溶剤を用いることが好ましく、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、電荷輸送性モノマー１質量部に対して、１〜１００質量部、好ましくは２〜５０質量部の範囲で用いられる。反応温度は任意に設定できるが、重合中に生成する水を除去するために、溶剤の沸点で反応させることが好ましい。
【００８６】
反応終了後、溶剤を用いなかった場合には溶解可能な溶剤に溶解させる。溶剤を用いた場合には、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、電荷輸送性ポリエステルを析出させ、電荷輸送性ポリエステルを分離した後、水や有機溶剤で十分洗浄し、乾燥させる。更に、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、電荷輸送性ポリエステル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、効率よく撹拌しながら行うことが好ましい。
【００８７】
上記再沈殿処理の際に電荷輸送性ポリエステルを溶解させる溶剤の量は、電荷輸送性ポリエステル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、貧溶剤の量は、電荷輸送性ポリエステル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。
【００８８】
前記Ａ’がハロゲンの場合には、ＨＯ−（Ｙ−Ｏ）_m−Ｈで示される２価アルコール類をほぼ当量混合し、ピリジンやトリエチルアミン等の有機塩基性触媒を用いて重合する。上記有機塩基性触媒の量は、電荷輸送性モノマー１当量に対して、１〜１０当量の範囲であることが好ましく、２〜５当量の範囲であることがより好ましい。
【００８９】
溶剤としては、塩化メチレン、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、前述のように再沈殿処理し、精製する。
【００９０】
また、ビスフェノール等の酸性度の高い２価アルコール類の場合には、界面重合法も用いることができる。すなわち、２価アルコール類を水に加え、当量の塩基を加えて溶解させた後、激しく撹拌しながら２価アルコール類と当量の電荷輸送性モノマー溶液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、２価アルコール類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、２〜５００質量部の範囲であることがより好ましい。
【００９１】
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。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。
【００９２】
前記Ａ’がアルコキシル基の場合には、前述の構造式（III−１）及び（III−２）で示される電荷輸送性ポリマーに、ＨＯ−（Ｙ−Ｏ）_m−Ｈで示される２価アルコール類を過剰に加え、硫酸、リン酸等の無機酸、チタンアルコキシド、カルシウム及びコバルト等の酢酸塩あるいは炭酸塩、亜鉛や鉛の酸化物を触媒に用いて加熱し、エステル交換により合成することができる。
【００９３】
前記２価アルコール類の量は、電荷輸送性モノマー１当量に対して、２〜１００当量の範囲であることが好ましく、３〜５０当量の範囲であることがより好ましい。また、触媒の量は、ホール輸送性モノマー１質量部に対して１／１０,０００〜１質量部の範囲であることが好ましく、１／１,０００〜１／２質量部の範囲であることがより好ましい。
【００９４】
反応は、反応温度２００〜３００℃の範囲で行い、前記アルコキシル基から−Ｏ−（Ｙ−Ｏ）_m−Ｈへのエステル交換終了後は、ＨＯ−（Ｙ−Ｏ）_m−Ｈの脱離による重合を促進するため、減圧下で反応させることが好ましい。また、ＨＯ−（Ｙ−Ｏ）_m−Ｈと共沸可能な１−クロロナフタレン等の高沸点溶剤を用いて、常圧下でＨＯ−（Ｙ−Ｏ）_m−Ｈを共沸で除きながら反応させることもできる。
【００９５】
また、一般式（II−２）で示される電荷輸送性ポリエステルは、次のようにして合成することができる。上記の一般式（II−１）で示される電荷輸送性ポリエステルの合成におけるそれぞれの場合において、２価アルコール類を過剰に加えて反応させることによって、下記構造式（IV−１）及び（IV−２）で示される化合物を生成した後、これを電荷輸送性モノマーとして用いて上記と同様の方法で、２価カルボン酸または２価カルボン酸ハロゲン化物等と反応させればよく、それによって電荷輸送性ポリエステルを得ることができる。
【００９６】
【化１３】

【００９７】
なお、上記式中、Ｒ₁、Ｒ₂、Ｘ、Ｙ、Ｔ、ｉ、ｊ、ｍ及びｋは前述の通りである。
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とから構成され、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エステルを含有してなる。
【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、有機化合物層はキャリア輸送能を持つ発光層を意味し、該発光層が前記電荷輸送性ポリエステルを含有してなる。また、有機化合物層が複数の場合（機能分離型の場合）は、その少なくとも１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よりなるものを意味し、これらの少なくとも１層が前記電荷輸送性ポリエステルを含有してなる。
【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エステルを含有してなるもの等が挙げられる。
【０１００】
本発明の有機ＥＬ素子においては、発光層が、低分子の電荷輸送性材料（前記電荷輸送性ポリエステル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、より詳細に説明するが、本発明の有機ＥＬ素子は、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エステル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エステルを含有してなる有機化合物層は発光層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エステル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エステル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工程数を大きく削減できるため、コスト的に好ましい。
【０１０５】
前記電荷輸送性ポリエステル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、電荷輸送性ポリエステルの特性を反映でき、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エステルが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で表される有機ＥＬ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記（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エステルを含有する有機化合物層であることが好ましい。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エステル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エステル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エステル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。
【０１０９】
【化１５】

【０１１０】
同様にホール移動度を調節するために、電荷輸送性ポリエステル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。
【０１１１】
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エステル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。
【０１１２】
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）が用いられるが、これらに限定されたものではない。
【０１１３】
【化１６】

【０１１４】
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。
【０１１５】
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、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。
【０１１６】
【化１７】

【０１１７】
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、前記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。
【０１１８】
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、電荷輸送性ポリエステル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が、これらに限定されるものではない。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。
【０１１９】
【化１８】

【０１２０】
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。
【０１２１】
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。
【０１２２】
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。
【０１２３】
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。
【０１２４】
上記各材料（前記電荷輸送性ポリエステル、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。
【０１２５】
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。
【０１２６】
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。
【０１２７】
【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エステルは、例えば以下のようにして得た。
【０１２８】
−合成例１〔例示化合物（４）〕−
表１の１７に記載のモノマー２．０ｇ、エチレングリコール８．０ｇ及びテトラブトキシチタン０．１ｇを、容量５０ｍｌのフラスコに入れ、窒素気流下、２００℃で３時間加熱攪拌した。原料モノマーが消費されたことを確認した後、６６．６６Ｐａに減圧してエチレングリコールを留去しながら２００℃に加熱し、４時間反応を続けた。その後、室温まで冷却し、反応物をトルエン５０ｍｌに溶解して不溶物を０．１μｍのポリテトラフルオロエチレン（ＰＴＦＥ）フィルターにて濾過し、その濾液を撹拌されたメタノール２５０ｍｌ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、１．８ｇの電荷輸送性ポリエステル（例示化合物４）を得た。分子量はＧＰＣにて測定したところ、Ｍｗ＝９．８７×１０⁴（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。
【０１２９】
−合成例２〔例示化合物（３８）〕−
表１の４３に記載のモノマー２．０ｇ、エチレングリコール８．０ｇ及びテトラブトキシチタン０．１ｇを、容量５０ｍｌのフラスコに入れ、窒素気流下、２００℃で３時間加熱攪拌した。原料モノマーが消費されたことを確認した後、６６．６６Ｐａに減圧してエチレングリコールを留去しながら２００℃に加熱し、４時間反応を続けた。その後、室温まで冷却し、トルエン５０ｍｌに溶解して不溶物を０．１μｍのＰＴＦＥフィルターにて濾過し、その濾液を撹拌されてメタノール２５０ｍｌ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、１．９ｇの電荷輸送性ポリエステル（例示化合物３８）を得た。分子量はＧＰＣにて測定したところ、Ｍｗ＝１．２９×１０⁵（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１３８であった。
【０１３０】
−合成例３〔例示化合物（１０９）〕−
表１の１０１に記載のモノマー２．０ｇ、エチレングリコール８．０ｇ及びテトラブトキシチタン０．１ｇを、容量５０ｍｌのフラスコに入れ、窒素気流下、２００℃で３時間加熱攪拌した。原料モノマーが消費されたことを確認した後、６６．６６Ｐａに減圧してエチレングリコールを留去しながら２００℃に加熱し、４時間反応を続けた。その後、室温まで冷却し、トルエン５０ｍｌに溶解して不溶物を０．１μｍのＰＴＦＥフィルターにて濾過し、その濾液を撹拌されたメタノール２５０ｍｌ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、１．８ｇの電荷輸送性ポリエステル（例示化合物１０９）を得た。分子量はＧＰＣにて測定したところ、Ｍｗ＝８．５５×１０⁴（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８２であった。
【０１３１】
（実施例１）
合成例１に記載の電荷輸送性ポリエステルの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。
【０１３２】
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４００ｃｄ／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。
【０１３３】
（実施例２）
合成例１に記載の電荷輸送性ポリエステル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。
【０１３４】
（実施例３）
合成例１に記載の電荷輸送性ポリエステルを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。
【０１３５】
（実施例４）
合成例１に記載の電荷輸送性ポリエステルの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。
【０１３６】
（実施例５）
合成例２の電荷輸送性ポリエステル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。
【０１３７】
（実施例６）
合成例２の電荷輸送性ポリエステル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。
【０１３８】
（実施例７）
合成例２の電荷輸送性ポリエステル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。
【０１３９】
（実施例８）
合成例２の電荷輸送性ポリエステル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。
【０１４０】
（実施例９）
合成例３の電荷輸送性ポリエステル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。
【０１４１】
（実施例１０）
合成例３の電荷輸送性ポリエステル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。
【０１４２】
（実施例１１）
合成例３の電荷輸送性ポリエステル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。
【０１４３】
（実施例１２）
合成例３の電荷輸送性ポリエステル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。
【０１４４】
（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。
【０１４５】
（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例示化合物（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。
【０１４６】
【表２６】

【０１４７】
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３、１０、１１においては、９００ｃｄ／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。
【０１４８】
【発明の効果】
前記一般式（Ｉ−１）及び（Ｉ−２）で示される構造から選択された少なくとも１種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エステルは、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. The included charge transporting polyester not only has suitable charge injection characteristics, charge mobility, and thin film forming ability as an organic EL device, but also has extremely good light emission characteristics in a solid state, so that it is used as a light emitting material. 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 Contains at least one charge transporting polyester comprising a repeating unit containing at least one selected from the structures represented by the following general formulas (I-1) and (I-2) as a partial structureThe charge transporting polyester has the following general formula ( II -1) or ( II -2)This is an organic electroluminescent element characterized by the above.
[0012]
[Chemical 3]

[0013]
  In general formulas (I-1) and (I-2), X is substituted or unsubstituted.Biphenyl or terphenylRepresents. T represents a divalent linear hydrocarbon having 1 to 6 carbon atoms or a branched hydrocarbon having 2 to 10 carbon atoms, i, jIs 0 or 1, KIs 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]

  In the formula, A represents at least one selected from the structures represented by the general formulas (I-1) and (I-2), and R represents a hydrogen atom, an alkyl group, a substituted or unsubstituted aryl group, or Represents a substituted or unsubstituted aralkyl group, Y represents a divalent alcohol residue, Z represents a divalent carboxylic acid residue, m represents an integer of 1 to 5, and p represents an integer of 5 to 5000 Represents. B and B ′ are each independently —O— (YO). _m -R or -O- (YO) _m —CO—Z—CO—O—R ′ (wherein R, Y, Z, m and p are the same as above, R ′ is an alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted group) Represents an aralkyl group.
[0014]
<2> The organic compound layer is composed of at least a light emitting layer and an electron transport layer having a carrier transport ability, and the light emitting layer is selected from the structures represented by the general formulas (I-1) and (I-2). <1> The organic electroluminescent element according to <1>, wherein the organic electroluminescent element comprises at least one charge transporting polyester comprising a repeating unit containing at least one kind as a partial structure.
[0015]
<3> 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 selected from the structures represented by the general formulas (I-1) and (I-2). <1> The organic electroluminescence device according to <1>, wherein the organic electroluminescence device comprises at least one charge transporting polyester comprising a repeating unit including at least one kind as a partial structure.
[0016]
<4> The organic compound layer includes at least a light emitting layer having a carrier transporting ability, and the light emitting layer is at least one selected from the structures represented by the general formulas (I-1) and (I-2). <1> The organic electroluminescent device according to <1>, wherein the organic electroluminescent device comprises at least one kind of charge transporting polyester composed of a repeating unit containing 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 is represented by the general formulas (I-1) and (I The organic electroluminescence according to <1>, comprising at least one charge transporting polyester comprising a repeating unit containing at least one selected from the structure represented by -2) as a partial structure It is an element.
[0018]
<6> The light emitting layer isHole transport material or electron transport material other than the charge transport polyester<2> The organic electroluminescent element according to <2>.
[0019]
<7> The light emitting layer isHole transport material or electron transport material other than the charge transport polyester<3> The organic electroluminescent element according to <3>.
[0020]
<8> The light emitting layer isHole transport material or electron transport material other than the charge transport polyester<4> The organic electroluminescence device according to <4>, wherein
[0021]
<9> The light emitting layer isHole transport material or electron transport material other than charge transporting polyester<5> The organic electroluminescent device according to <5>.
[0033]
In the organic EL device of the present invention, the charge transporting polyester comprising a repeating unit containing at least one selected from the structures represented by the general formulas (I-1) and (I-2) as a partial structure is: Any of those in which a plurality of functionally separated layers are laminated, for example, a laminate type in which at least a hole transport layer and a light emitting layer are laminated, or a single layer type in which an organic compound layer has both carrier transport ability and light emission ability Used. In addition, when it is contained in a laminated light emitting layer or a single layer organic compound layer, it may contain a charge transporting material or a light emitting compound at the same time.
[0034]
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 a charge transporting polyester comprising a repeating unit containing at least one selected from the structures represented by the following general formulas (I-1) and (I-2) as a partial structure (hereinafter simply referred to as “charge transporting polyester”). 1) or more).
[0035]
[Chemical formula 5]

[0036]
  In general formulas (I-1) and (I-2), X is a substituted or unsubstituted divalent divalent group.Biphenyl or terphenylRepresents. T represents a divalent linear hydrocarbon having 1 to 6 carbon atoms or a branched hydrocarbon having 2 to 10 carbon atoms, i, jIs 0 or 1, KIs 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.
[0037]
By using the charge transporting polyester in at least one layer of the organic compound layer, the mobility of charges can be increased, and thus 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.
[0038]
  In general formulas (I-1) and (I-2), X is substituted or unsubstituted.Biphenyl or terphenylAs a specific example, the following formula (4), (5)Is mentioned.
[0039]
[Chemical 6]

[0040]
  formula(4), (5)During ~, R ₉ IsA 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 a and b are 0 or 1 V represents a group selected from the following formulas (14) to (31).
[0041]
[Chemical 7]

[0042]
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.
[0043]
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.
[0044]
[Chemical 8]

[0045]
In general formulas (I-1) and (I-2), T represents a divalent straight-chain hydrocarbon having 1 to 6 carbon atoms or a branched hydrocarbon having 2 to 10 carbon atoms. Specific examples include the following structures.
[0046]
[Chemical 9]

[0047]
  Specific examples of the structures represented by the general formulas (I-1) and (I-2) are shown below.2~table13Although shown, the present invention is not limited to these specific examples. Table 1 to Table5Structure number in13~44Shows specific examples of the structure represented by formula (I-1), and Tables 10 to 1013Structure number in86~109Is a specific example of the structure represented by formula (I-2).
[0049]
[Table 2]

[0050]
[Table 3]

[0051]
[Table 4]

[0052]
[Table 5]

[0057]
[Table 10]

[0058]
[Table 11]

[0059]
[Table 12]

[0060]
[Table 13]

[0065]
  Examples of the charge transporting polyester comprising a repeating unit containing at least one selected from the structures represented by the general formulas (I-1) and (I-2) as a partial structure include the following general formula (II-1) or ( II-2)UsedUsed.
[0066]
[Chemical Formula 10]

[0067]
In the formula, A represents at least one selected from the structures represented by the general formulas (I-1) and (I-2), and R represents a hydrogen atom, an alkyl group, a substituted or unsubstituted aryl group, or Represents a substituted or unsubstituted aralkyl group, Y represents a divalent alcohol residue, Z represents a divalent carboxylic acid residue, m represents an integer of 1 to 5, and p represents an integer of 5 to 5000 P is preferably in the range of 10 to 1000. B and B 'are each independently -O- (YO)_m-R or -O- (YO)_m—CO—Z—CO—O—R ′ (wherein R, Y, Z, m and p are the same as above, R ′ is an alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted group) Represents an aralkyl group.
[0068]
Specific examples of Y and Z in the formula (II-1) or (II-2) include groups selected from the following formulas (34) to (40).
[0069]
Embedded image

[0070]
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).
[0071]
  Hereinafter, specific examples of the charge transporting polyesters represented by the general formulas (II-1) and (II-2) are shown in Tables 18 to 25, but the present invention is not limited to these specific examples. Absent. In addition,In the tableThe numbers in the A column of the monomer column are tables that are specific examples of the structures represented by the general formulas (I-1) and (I-2).2~table13This corresponds to the structure number indicated by. In addition, the case where the column of Z is “-” indicates a specific example of the charge transporting polyester 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 polyester 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).
[0072]
[Table 18]

[0073]
[Table 19]

[0074]
[Table 20]

[0076]
[Table 22]

[0077]
[Table 23]

[0078]
[Table 24]

[0079]
[Table 25]

[0080]
The mass average molecular weight Mw of the charge transporting polyester is preferably in the range of 10,000 to 300,000, and more preferably in the range of 50,000 to 200,000.
[0081]
Examples of the charge transporting polyester include charge transporting monomers represented by the following structural formulas (III-1) to (IV-2), 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 structural formulas (III-1) to (IV-2), T and m are the general formulas (I-1), (I-2), (II-1), and (II-2), respectively. The same as T and m in FIG. A 'represents a reactive group with a dihydric alcohol or the like for alcoholation of the monomer terminal in order to cause polymerization (ester bond formation) by dealcoholization.
[0082]
Embedded image

[0083]
Specifically, for example, in the case of the charge transporting monomers represented by the general formulas (III-1) and (III-2), the charge transporting polyester can be synthesized as follows. When A 'is a hydroxyl group, HO- (YO)_mAlmost the same amount of dihydric alcohol represented by —H is mixed and polymerized using an acid catalyst.
[0084]
As the acid catalyst, those used for usual esterification reaction such as sulfuric acid, toluenesulfonic acid, trifluoroacetic acid and the like can be used, and the amount of the catalyst is 1 / 10,000 to It is preferably in the range of 1/10 parts by mass, more preferably in the range of 1/1000 to 1/50 parts by mass.
[0085]
In order to remove water generated during the polymerization, it is preferable to use a solvent that can be azeotroped with water, and toluene, chlorobenzene, 1-chloronaphthalene and the like are effective, and with respect to 1 part by mass of the charge transporting monomer, It is used in the range of 1 to 100 parts by mass, preferably 2 to 50 parts by mass. The reaction temperature can be arbitrarily set, but it is preferable to carry out the reaction at the boiling point of the solvent in order to remove water generated during the polymerization.
[0086]
When the solvent is not used after completion of the reaction, it is dissolved in a soluble solvent. When a solvent is used, the reaction solution is dropped as it is in a poor solvent in which alcohols such as methanol and ethanol, and polymers such as acetone are difficult to dissolve, to precipitate the charge transporting polyester, After separation, wash thoroughly with water or organic solvent and dry. Furthermore, if necessary, the reprecipitation treatment may be repeated in which it is dissolved in a suitable organic solvent, dropped into a poor solvent, and the charge transporting polyester is precipitated. The reprecipitation treatment is preferably carried out with efficient stirring with a mechanical stirrer or the like.
[0087]
The amount of the solvent for dissolving the charge transporting polyester in 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 polyester. It is more preferable that The amount of the poor solvent is preferably in the range of 1 to 1,000 parts by mass, more preferably in the range of 10 to 500 parts by mass with respect to 1 part by mass of the charge transporting polyester.
[0088]
When A ′ is halogen, HO— (Y—O)_mDivalent alcohols represented by —H are mixed in an approximately equivalent amount and polymerized using an organic basic catalyst such as pyridine or triethylamine. The amount of the organic basic catalyst is preferably in the range of 1 to 10 equivalents and more preferably in the range of 2 to 5 equivalents with respect to 1 equivalent of the charge transporting monomer.
[0089]
As the solvent, methylene chloride, tetrahydrofuran (THF), toluene, chlorobenzene, 1-chloronaphthalene and the like are effective, and the amount of the solvent is in the range of 1 to 100 parts by mass with respect to 1 part by mass of the charge transporting monomer. It is preferable, 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, reprecipitation treatment is performed as described above, and purification is performed.
[0090]
In the case of dihydric alcohols with high acidity such as bisphenol, an interfacial polymerization method can also be used. That is, after adding a dihydric alcohol to water, adding an equivalent base and dissolving it, it can superpose | polymerize by adding a bivalent alcohol and an equivalent charge transportable monomer solution, stirring vigorously. At this time, the amount of water is preferably in the range of 1 to 1,000 parts by mass, more preferably in the range of 2 to 500 parts by mass with respect to 1 part by mass of the dihydric alcohol.
[0091]
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 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.
[0092]
In the case where A ′ is an alkoxyl group, the charge transporting polymer represented by the structural formulas (III-1) and (III-2) is added to HO— (Y—O)._mAdd an excess of dihydric alcohol represented by -H and heat using inorganic acid such as sulfuric acid and phosphoric acid, titanium alkoxide, acetate or carbonate such as calcium and cobalt, oxide of zinc and lead as catalyst. Can be synthesized by transesterification.
[0093]
The amount of the dihydric alcohol is preferably in the range of 2 to 100 equivalents and more preferably in the range of 3 to 50 equivalents with respect to 1 equivalent of the charge transporting monomer. The amount of the catalyst is preferably in the range of 1 / 10,000 to 1 part by mass, and in the range of 1 / 1,000 to 1/2 part by mass with respect to 1 part by mass of the hole transporting monomer. Is more preferable.
[0094]
The reaction is carried out at a reaction temperature in the range of 200 to 300 ° C. From the alkoxyl group, —O— (YO)_mAfter transesterification to -H, HO- (YO)_mIn order to promote polymerization due to elimination of -H, it is preferable to carry out the reaction under reduced pressure. HO- (YO)_mHO- (YO) under normal pressure using a high boiling point solvent such as 1-chloronaphthalene that can be azeotroped with -H_mThe reaction can be carried out while azeotropically removing -H.
[0095]
The charge transporting polyester represented by the general formula (II-2) can be synthesized as follows. In each case in the synthesis of the charge transporting polyester represented by the general formula (II-1), by adding an excess of dihydric alcohols and reacting them, the following structural formulas (IV-1) and (IV- After the compound represented by 2) is formed, it may be reacted with a divalent carboxylic acid or a divalent carboxylic acid halide in the same manner as described above using this as a charge transporting monomer, whereby charge transport is performed. Can be obtained.
[0096]
Embedded image

[0097]
In the above formula, R₁, R₂, X, Y, T, i, j, m, and k are as described above.
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 polyester 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 means a light emitting layer having a carrier transporting ability, and the light emitting layer contains the charge transporting polyester. 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 a carrier transporting ability). The other organic compound layer means 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 has the charge transport property. It contains polyester.
[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 transporting layer, electron transporting layer) contains the charge transporting polyester.
[0100]
In the organic EL device of the present invention, the light emitting layer preferably contains a low molecular charge transport material (a hole transport material other than the charge transport polyester, an electron transport material). Details will be described later.
[0101]
Hereinafter, although it demonstrates in detail, referring drawings, the organic EL element of this invention is not necessarily limited to these.
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 polyester 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 polyester can be used as both 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 polyester as the light emitting layer 6 having a carrier transporting ability. Furthermore, in the case of the layer structure of the organic EL element shown in FIG. 4, the organic compound layer containing the charge transporting polyester is, for example, a hole transport layer 3 or a light emitting layer 6 having a carrier transport capability. However, it is preferable in terms of cost to use the light emitting layer 6 having a carrier transporting capability because the number of steps can be greatly reduced.
[0105]
As the organic EL element of the present invention using the charge transporting polyester as an organic compound layer, the structure shown in FIGS. 3 and 4 is easy to produce as the element among the above-described layer structures, and the characteristics of the charge transporting polyester are as follows. This configuration is preferable in that it can be reflected and sufficient luminance, stability, and durability can be achieved.
[0106]
In addition, the organic compound layer formed by the charge transporting polyester in the present invention has a good hole transporting ability. For example, as described above, the hole transporting layer 3 of the organic EL element shown in FIG. Can be used. 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 thereof include the compounds shown in the following (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 polyester is preferable. The organic compound layer in this case is basically formed of the charge transporting polyester alone, but in order to adjust the balance between holes and electrons injected into the organic EL element, other than the charge transporting polyester. 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 polyester, and more preferably, the following exemplified compound (VI) is used, but it is not limited thereto. is not.
[0109]
Embedded image

[0110]
Similarly, in order to adjust the hole mobility, a hole transporting material other than the charge transporting polyester, 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.
[0111]
In addition, 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 polyester 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.
[0112]
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.
[0113]
Embedded image

[0114]
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.
[0115]
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.
[0116]
Embedded image

[0117]
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 is a polymer, it is a material selection condition that a good thin film can be formed by applying and drying a solution or dispersion containing itself.
[0118]
As the charge transporting material exhibiting hole transporting ability, tetraphenylenediamine derivatives, triphenylamine derivatives, carbazole derivatives, stilbene derivatives, aryl hydrazone derivatives, porphyrin compounds, and the like are preferably used. 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 polyester. It is not done. Moreover, you may use the said compound mixed with other general purpose resin.
[0119]
Embedded image

[0120]
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.
[0121]
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 a carrier transport capability are formed by depositing the above materials on the surface of the transparent electrode 2 by using a vacuum deposition method or by dissolving or dispersing them in an organic solvent. It is formed by a spin coating method, a dip method or the like.
[0122]
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.
[0123]
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.
[0124]
The dispersion state of each of the materials (the charge transporting polyester, 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.
[0125]
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.
[0126]
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.
[0127]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not restrict | limited to these Examples.
First, the charge transporting polyester used in each example was obtained as follows, for example.
[0128]
-Synthesis example 1 [Exemplary compound (4)]-
2.0 g of a monomer described in 17 in Table 1, 8.0 g of ethylene glycol and 0.1 g of tetrabutoxytitanium were placed in a 50 ml capacity flask and heated and stirred at 200 ° C. for 3 hours in a nitrogen stream. After confirming that the raw material monomer was consumed, the pressure was reduced to 66.66 Pa and the mixture was heated to 200 ° C. while distilling off ethylene glycol, and the reaction was continued for 4 hours. After cooling to room temperature, the reaction product is dissolved in 50 ml of toluene, the insoluble matter is filtered through a 0.1 μm polytetrafluoroethylene (PTFE) filter, and the filtrate is dropped into 250 ml of stirred methanol to form a polymer. Was precipitated. The obtained polymer was filtered, washed thoroughly with methanol, and then dried to obtain 1.8 g of a charge transporting polyester (Exemplary Compound 4). Molecular weight measured by GPC was Mw = 9.87 × 10.^FourThe value of p calculated from the molecular weight of the monomer was about 103.
[0129]
-Synthesis example 2 [Exemplary compound (38)]-
2.0 g of the monomer described in 43 of Table 1, 8.0 g of ethylene glycol and 0.1 g of tetrabutoxytitanium were placed in a 50 ml capacity flask and heated and stirred at 200 ° C. for 3 hours in a nitrogen stream. After confirming that the raw material monomer was consumed, the pressure was reduced to 66.66 Pa and the mixture was heated to 200 ° C. while distilling off ethylene glycol, and the reaction was continued for 4 hours. Then, it cooled to room temperature, melt | dissolved in 50 ml of toluene, and filtered the insoluble matter with a 0.1 micrometer PTFE filter, the filtrate was stirred and it was dripped in 250 ml of methanol, and the polymer was deposited. The obtained polymer was filtered, washed thoroughly with methanol, and then dried to obtain 1.9 g of a charge transporting polyester (Exemplary Compound 38). Molecular weight measured by GPC was Mw = 1.29 × 10.^FiveThe value of p obtained from the molecular weight of the monomer was about 138.
[0130]
-Synthesis example 3 [Exemplary compound (109)]-
2.0 g of the monomer described in 101 of Table 1, 8.0 g of ethylene glycol, and 0.1 g of tetrabutoxytitanium were placed in a 50 ml capacity flask and heated and stirred at 200 ° C. for 3 hours in a nitrogen stream. After confirming that the raw material monomer was consumed, the pressure was reduced to 66.66 Pa and the mixture was heated to 200 ° C. while distilling off ethylene glycol, and the reaction was continued for 4 hours. Thereafter, the mixture was cooled to room temperature, dissolved in 50 ml of toluene, and the insoluble matter was filtered through a 0.1 μm PTFE filter. The filtrate was dropped into 250 ml of stirred methanol to precipitate a polymer. The obtained polymer was filtered, washed sufficiently with methanol, and then dried to obtain 1.8 g of a charge transporting polyester (Exemplary Compound 109). The molecular weight was measured by GPC, Mw = 8.55 × 10^FourThe value of p calculated from the molecular weight of the monomer was about 82.
[0131]
Example 1
A 5% by mass dichloroethane solution of the charge transporting polyester 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.
[0132]
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. The evaluation of the light emission lifetime is 400 cd / m for the initial luminance.²The 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.
[0133]
(Example 2)
99 parts by mass of the charge transporting polyester described in Synthesis Example 1 and 1 part by mass of the 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.
[0134]
(Example 3)
2 parts by mass of the charge transporting polyester 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.
[0135]
(Example 4)
A 5% by mass dichloroethane solution of the charge transporting polyester 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.
[0136]
(Example 5)
An organic EL device was produced in the same manner as in Example 1 except that the charge transporting polyester of Synthesis Example 2 was used.
Evaluation similar to Example 1 was performed about the said organic EL element. The results are shown in Table 26.
[0137]
(Example 6)
An organic EL device was produced in the same manner as in Example 2 except that the charge transporting polyester of Synthesis Example 2 was used.
Evaluation similar to Example 1 was performed about the said organic EL element. The results are shown in Table 26.
[0138]
(Example 7)
An organic EL device was produced in the same manner as in Example 3 except that the charge transporting polyester of Synthesis Example 2 was used.
Evaluation similar to Example 1 was performed about the said organic EL element. The results are shown in Table 26.
[0139]
(Example 8)
An organic EL device was produced in the same manner as in Example 4 except that the charge transporting polyester of Synthesis Example 2 was used.
Evaluation similar to Example 1 was performed about the said organic EL element. The results are shown in Table 26.
[0140]
Example 9
An organic EL device was produced in the same manner as in Example 1 except that the charge transporting polyester of Synthesis Example 3 was used.
Evaluation similar to Example 1 was performed about the said organic EL element. The results are shown in Table 26.
[0141]
(Example 10)
An organic EL device was produced in the same manner as in Example 2 except that the charge transporting polyester of Synthesis Example 3 was used.
Evaluation similar to Example 1 was performed about the said organic EL element. The results are shown in Table 26.
[0142]
(Example 11)
An organic EL device was produced in the same manner as in Example 3 except that the charge transporting polyester of Synthesis Example 3 was used.
Evaluation similar to Example 1 was performed about the said organic EL element. The results are shown in Table 26.
[0143]
Example 12
An organic EL device was produced in the same manner as in Example 4 except that the charge transporting polyester of Synthesis Example 3 was used.
Evaluation similar to Example 1 was performed about the said organic EL element. The results are shown in Table 26.
[0144]
(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.
[0145]
(Comparative Example 2)
2 parts by mass of polyvinyl carbazole (PVK) as a hole transporting polymer compound, 0.1 part by mass of the exemplified compound (V-1) as a light emitting material, and 1 part by mass of the compound (VI) as an electron transporting material Then, 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.
[0146]
[Table 26]

[0147]
As shown in the above examples, the organic EL device of the present invention has a high maximum luminance despite a low driving current density, and particularly in Examples 3, 10 and 11, 900 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.
[0148]
【The invention's effect】
A charge transporting polyester comprising a repeating structural unit containing at least one selected from the structures represented by the general formulas (I-1) and (I-2) as a partial structure is an ionization potential suitable for an organic EL device. Since it has charge mobility and light emission characteristics, and it is possible to form a good thin film by using a spin coating method, a dip method, etc., the organic EL device of the present invention formed by using this is sufficient. In addition, since the film thickness can be set relatively large, there are few defects such as pinholes, the area can be easily increased, and excellent durability is achieved.
[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 device composed of one or more 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 Containing at least one charge transporting polyester comprising a repeating unit containing at least one selected from the structures represented by the general formulas (I-1) and (I-2) as a partial structure ;
The organic electroluminescent element, wherein the charge transporting polyester is a polyester represented by the following general formula ( II- 1) or ( II- 2) .

[In general formulas (I-1) and (I-2), X represents substituted or unsubstituted biphenyl or terphenyl . T represents a divalent linear hydrocarbon having 1 to 6 carbon atoms or a branched hydrocarbon having 2 to 10 carbon atoms, i and j are 0 or 1 , and k is 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. ]

[Wherein, A represents at least one selected from the structures represented by the above general formulas (I-1) and (I-2), R represents a hydrogen atom, an alkyl group, a substituted or unsubstituted aryl group, Or a substituted or unsubstituted aralkyl group, Y represents a divalent alcohol residue, Z represents a divalent carboxylic acid residue, m represents an integer of 1 to 5, and p represents 5 to 5000. Represents an integer. B and B ′ are each independently —O— (Y—O) _m —R or —O— (Y—O) _m —CO—Z—CO—O—R ′ (where R, Y, Z , M and p are as defined above, and R ′ represents an alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted aralkyl group. ]   The organic compound layer is composed of at least a light emitting layer having a carrier transport ability and an electron transport layer, and the light emitting layer is at least one selected from the structures represented by the general formulas (I-1) and (I-2). The organic electroluminescent element according to claim 1, comprising at least one charge transporting polyester comprising a repeating unit containing a seed as a partial structure.   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 at least one selected from the structures represented by the general formulas (I-1) and (I-2) The organic electroluminescent element according to claim 1, wherein the organic electroluminescent element comprises at least one kind of charge-transporting polyester comprising a repeating unit containing as a partial structure.   The organic compound layer is composed of at least a light emitting layer having a carrier transport ability, and the light emitting layer has at least one selected from the structures represented by the general formulas (I-1) and (I-2) as a partial structure. The organic electroluminescent element according to claim 1, wherein the organic electroluminescent element comprises at least one kind of charge transporting polyester comprising repeating units.   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 or the hole transport layer is represented by the general formulas (I-1) and (I-2). The organic electroluminescent device according to claim 1, comprising at least one charge transporting polyester comprising a repeating unit containing at least one selected from the structure represented by the above as a partial structure. 3. The organic electroluminescent element according to claim 2, wherein the light emitting layer contains a hole transporting material or an electron transporting material other than the charge transporting polyester . The organic light emitting device according to claim 3, wherein the light emitting layer contains a hole transporting material or an electron transporting material other than the charge transporting polyester . The organic electroluminescent element according to claim 4, wherein the light emitting layer contains a hole transporting material or an electron transporting material other than the charge transporting polyester . The organic electroluminescent element according to claim 5, wherein the light emitting layer contains a hole transporting material or an electron transporting material other than the charge transporting polyester .

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