JP4192422B2 - Organic electroluminescence device - Google Patents
Organic electroluminescence device Download PDFInfo
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- JP4192422B2 JP4192422B2 JP2000402884A JP2000402884A JP4192422B2 JP 4192422 B2 JP4192422 B2 JP 4192422B2 JP 2000402884 A JP2000402884 A JP 2000402884A JP 2000402884 A JP2000402884 A JP 2000402884A JP 4192422 B2 JP4192422 B2 JP 4192422B2
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- 238000006862 quantum yield reaction Methods 0.000 description 1
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- 150000004053 quinones Chemical class 0.000 description 1
- 238000005215 recombination Methods 0.000 description 1
- 230000006798 recombination Effects 0.000 description 1
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- JWHOQZUREKYPBY-UHFFFAOYSA-N rubonic acid Natural products CC1(C)CCC2(CCC3(C)C(=CCC4C5(C)CCC(=O)C(C)(C)C5CC(=O)C34C)C2C1)C(=O)O JWHOQZUREKYPBY-UHFFFAOYSA-N 0.000 description 1
- YYMBJDOZVAITBP-UHFFFAOYSA-N rubrene Chemical class C1=CC=CC=C1C(C1=C(C=2C=CC=CC=2)C2=CC=CC=C2C(C=2C=CC=CC=2)=C11)=C(C=CC=C2)C2=C1C1=CC=CC=C1 YYMBJDOZVAITBP-UHFFFAOYSA-N 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 150000003335 secondary amines Chemical class 0.000 description 1
- FZHAPNGMFPVSLP-UHFFFAOYSA-N silanamine Chemical class [SiH3]N FZHAPNGMFPVSLP-UHFFFAOYSA-N 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
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- 229910052708 sodium Inorganic materials 0.000 description 1
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- 238000004544 sputter deposition Methods 0.000 description 1
- PJANXHGTPQOBST-UHFFFAOYSA-N stilbene Chemical compound C=1C=CC=CC=1C=CC1=CC=CC=C1 PJANXHGTPQOBST-UHFFFAOYSA-N 0.000 description 1
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- 125000001424 substituent group Chemical group 0.000 description 1
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- 150000003513 tertiary aromatic amines Chemical group 0.000 description 1
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- OCKFCYARHPIGDV-UHFFFAOYSA-N tetraphenylene-1,2-diamine Chemical class C1=CC=C2C3=C(N)C(N)=CC=C3C3=CC=CC=C3C3=CC=CC=C3C2=C1 OCKFCYARHPIGDV-UHFFFAOYSA-N 0.000 description 1
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Description
【０００１】
【発明の属する技術分野】
本発明は、有機電界発光素子（以下、「有機ＥＬ素子」という）に関し、詳しくは特定の電子輸送性材料を用いることにより素子作製を容易にし、さらに安定性が向上した有機電界発光素子に関する。
【０００２】
【従来の技術】
ＥＬ素子は、自発光性の全固体素子であり、視認性が高く衝撃にも強いため、広く応用が期待されている。現在は無機螢光体を用いたものが主流であるが、２００Ｖ以上の交流電圧が駆動に必要なため製造コストが高く、また輝度が不十分等の問題点を有している。
【０００３】
一方、有機化合物を用いた有機ＥＬ素子研究は、最初アントラセン等の単結晶を用いて始まったが、単結晶の場合、膜厚が１ｍｍ程度と厚く１００Ｖ以上の駆動電圧が必要であった。そのため蒸着法による薄膜化が試みられている（Ｔｈｉｎ Ｓｏｌｉｄ Ｆｉｌｍｓ，Ｖｏｌ．９４，１７１（１９８２））。しかしながら、この方法で得られた薄膜は、駆動電圧が３０Ｖと未だ高く、また、膜中における電子・ホールキャリアの密度が低く、キャリアの再結合によるフォトンの生成確率が低いため十分な輝度が得られなかった。
【０００４】
ところが、近年、ホール輸送性有機低分子化合物と電子輸送能を持つ螢光性有機低分子化合物の薄膜を真空蒸着法により順次積層した機能分離型の有機ＥＬ素子において、１０Ｖ程度の低電圧で１０００ｃｄ／ｍ2以上の高輝度が得られるものが報告されており（Ａｐｐｌ．Ｐｈｙｓ．Ｌｅｔｔ．，Ｖｏｌ．５１，９１３（１９８７））、以来、積層型のＥＬ素子の研究・開発が活発に行われている。
【０００５】
しかしながら、このタイプの有機ＥＬ素子では、複数の蒸着工程において０．１μｍ以下の薄膜を形成していくためピンホールを生じ易く、十分な性能を得るためには厳しく管理された条件下で膜厚の制御を行うことが必要である。従って、生産性が低くかつ大面積化が難しいという問題がある。また、有機ＥＬ素子は数ｍＡ／ｃｍ2という高い電流密度で駆動されるため、大量のジュール熱を発生する。このため、蒸着によってアモルファスガラス状態で製膜されたホール輸送性低分子化合物や螢光性有機低分子化合物が次第に結晶化して最後には融解し、輝度の低下や絶縁破壊が生じるという現象が多く見られ、その結果素子の寿命が低下するという問題も有している。例えば、電子輸送性材料の場合、これまで特開平７−１０９４５４号公報等に記載されているように、２−（４−ビフェニルイル）−５−（４−ｔｅｒｔ−ブチルフェニル）−１，３，４−オキサジアゾール（ＰＢＯ）を初めとするオキサジアゾール誘導体を電子輸送性材料として使用することが提案されているものの、得られた薄膜は結晶化しやすく、電荷輸送・注入特性の面からも充分とはいえない。また、電子輸送性材料はオキサジアゾール化合物以外に種類が乏しく、低電圧駆動・高効率化の面からも電荷輸送・注入特性にも優れたさらなる材料の開発が望まれているのが現状である。
【０００６】
一方、積層型有機ＥＬ素子における生産性と大面積化に関する問題の解決を目指し、単層構造の有機ＥＬ素子についても研究・開発が進められ、ポリ（ｐ−フェニレンビニレン）等の導電性高分子を用いたり（Ｎａｔｕｒｅ，Ｖｏｌ．３５７，４７７（１９９２）等）、ホール輸送性ポリビニルカルバゾール中に電子輸送性材料と螢光色素を混入した（第３８回応用物理学関係連合講演会予稿集３１ｐ−Ｇ−１２（１９９１））素子が提案されているが、未だ輝度、発光効率等が有機低分子化合物を用いた積層型有機ＥＬ素子には及ばない。
【０００７】
【発明が解決しようとする課題】
本発明は、従来の技術の上記問題点に鑑みてなされたものであって、その目的は素子製造が容易で十分な輝度が得られ、耐久性に優れた有機ＥＬ素子を提供することにある。
【０００８】
【課題を解決するための手段】
上記目的を達成するため電子輸送性材料に関し鋭意検討した結果、下記一般式（Ｉ）で示される繰り返し単位を有するポリエステル化合物が、有機ＥＬ素子として好適な電子注入特性、電子移動度、薄膜形成能を有することを見出し、本発明を完成するに至った。
【０００９】
すなわち、本発明の有機ＥＬ素子は、少なくとも一方が透明又は半透明である一対の電極間に挾持された一つ又は複数の有機化合物層より構成されるものであって、有機化合物層の少なくとも一層が、下記一般式（１）で示される繰り返し単位を有するポリエステル化合物の少なくとも１種を含有してなり、前記ポリエステル化合物が、Ａが下記構造１を表しＢが２価の脂肪族炭化水素を表す化合物、Ａが２価の脂肪族炭化水素を表しＢが下記構造２を表す化合物、Ａが下記構造３を表しＢが下記構造４を表す化合物、又は、Ａが２価の脂肪族炭化水素を表しＢが下記構造１を表す化合物であることを特徴とする。
【００１０】
【化３】
【００１１】
［一般（Ｉ）式中、ｎは１０〜２０００を表す。］
【００１２】
【化４】
【００１３】
本発明の有機ＥＬ素子において、前記一般式（Ｉ）で示される繰り返し単位を有するポリエステル化合物を含有する有機化合物層は、さらに有機低分子化合物を含有してなることが好ましい。この有機低分子化合物は電子受容性化合物又は電子供与性化合物であることが好ましい。
【００１４】
本発明の有機ＥＬ素子において、前記一般式（Ｉ）で示される繰り返し単位を有するポリエステル化合物は、他の繰り返し単位を含む共重合ポリエステル化合物であってもよい。
【００１５】
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、少なくとも発光層及び電子輸送層から構成、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、或いは、少なくともホール輸送層及び発光層から構成され、発光層又は電子輸送層が前記一般式（Ｉ）で示される繰り返し単位を有するポリエステル化合物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、有機化合物層が少なくとも発光層から構成されてなり、該発光層が前記一般式（Ｉ）で示される繰り返し単位を有するポリエステル化合物を含有してなるもののいずれでもよい。なお、機能分離型における発光層はキャリア輸送能と発光能を兼ね備えたものであってもよいし、発光能のみ備えたものでもよい。
【００１６】
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（ホール輸送性材料、前記一般式（Ｉ）で示される繰り返し単位を有するポリエステル化合物以外の電子輸送性材料）を含有してもよく、この電荷輸送性材料（ホール輸送性材料）としては、ホール輸送性高分子であることが好ましい。また、ホール輸送層が、ホール輸送性高分子を含有してなることが好ましい。
【００１７】
【発明の実施の形態】
以下に、本発明をさらに詳細に説明する。
本発明の有機ＥＬ素子は、少なくとも一方が透明又は半透明である一対の電極間に挾持された一つ又は複数の有機化合物層より構成されるものであって、有機化合物層の少なくとも一層が、下記一般式（１）で示される繰り返し単位を有するポリエステル化合物の少なくとも１種を含有してなる。そして、前記一般式（Ｉ）で示される繰り返し単位を有するポリエステル化合物は、Ａが下記構造１を表しＢが２価の脂肪族炭化水素を表す化合物、Ａが２価の脂肪族炭化水素を表しＢが下記構造２を表す化合物、Ａが下記構造３を表し Ｂが下記構造４を表す化合物、又は、Ａが２価の脂肪族炭化水素を表しＢが下記構造１を表す化合物である。前記一般式（Ｉ）で示される繰り返し単位を有するポリエステル化合物は、優れた電子注入特性、電子移動度、薄膜形成能を示すので、これを含有する層を有する本発明の有機ＥＬ素子は、素子製造が容易で十分な輝度が得られ、耐久性に優れる。
【００１８】
【化５】
【００１９】
一般（Ｉ）式中、ｎは１０〜２０００を表す。
【００２０】
【化６】
【００２１】
一般（Ｉ）式中、ＡおよびＢを表す２価の脂肪族炭化水素としては、炭素数１〜２０の２価の直鎖状炭化水素基または炭素数２〜２０の２価の分枝鎖状炭化水素基等が挙げられる。これらの中でも、炭素数４〜１２の２価の直鎖状炭化水素基および炭素数３〜７の２価の分枝鎖状炭化水素基等が好適である。これら２価の脂肪族炭化水素の置換基としては、アルコキシル基やハロゲン原子等が挙げられる。
【００２２】
以下、一般式（Ｉ）で示される繰り返し単位の具体例を示すが、これら具体例に限定されるわけではない。なお、表中に示す「化合物Ｎｏ」で示す繰り返し単位を有するポリエステル化合物を、例示化合物（Ｎｏ）という。例えば、化合物Ｎｏ１２で示す繰り返し単位を有するポリエステル化合物を例示化合物（１２）という。
【００２３】
【表１】
【００２４】
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又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一つ又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層が一般式（Ｉ）で示される繰り返し単位を有するポリエステル化合物を含有してなる。
【００２５】
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、該発光層が一般式（Ｉ）で示される繰り返し単位を有するポリエステル化合物を含有してなる。また、有機化合物層が複数の場合（機能分離型の場合）は、その少なくとも一つは発光層（この発光層はキャリア輸送能を持っていてもよいし、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、又は、ホール輸送層及び電子輸送層よりなるものを意味し、これらのホール輸送層を除く少なくとも一層が前記一般式（Ｉ）で示される繰り返し単位を有するポリエステル化合物を含有してなる。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、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、或いは、少なくともホール輸送層及び発光層から構成され、発光層又は電子輸送層が前記一般式（Ｉ）で示される繰り返し単位を有するポリエステル化合物を含有してなるものが挙げられる。さらに、例えば、有機化合物層が発光層から構成されてなり、該発光層が前記一般式（Ｉ）で示される繰り返し単位を有するポリエステル化合物を含有してなるものも挙げられる。
【００２６】
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（ホール輸送性材料、前記一般式（Ｉ）で示される繰り返し単位を有するポリエステル化合物以外の電子輸送性材料）を含有してもよく、この電荷輸送性材料（ホール輸送性材料）としては、ホール輸送性高分子であることが好ましい。また、ホール輸送層が、ホール輸送性高分子を含有してなることが好ましい。詳しくは、後述する。
【００２７】
本発明の有機ＥＬ素子において、一般式（Ｉ）で示される繰り返し単位を有するポリエステル化合物を含有する有機化合物層は、電気的特性をさらに改善する等の目的で、電子移動度を調節するために、さらに、前記一般式（Ｉ）で示される繰り返し単位を有するポリエステル化合物（電子輸送性材料）と併せて、有機低分子化合物を含有してもよい。この特定の有機低分子化合物の添加量は１重量％ないし３０重量％の範囲でよい。この特定の有機低分子化合物としては、低分子系の電子受容性化合物、電子供与性化合物又は金属錯塩等が挙げられる。これらの中でも電子受容性化合物又は電子供与性化合物が好ましく、特に前記一般式（Ｉ）で示される繰り返し単位を有するポリエステル化合物とは独立の作用により、あるいは前記一般式（Ｉ）で示される繰り返し単位を有するポリエステル化合物と電荷移動錯体の形成等の相互作用により、電子伝導性を増強若しくは制御する機能を有する化合物が好ましい。これら有機低分子化合物は１種を単独で用いても２種以上を組み合わせて用いてもよい。
【００２８】
電子受容性化合物の例としては、４−ニトロベンズアルデヒド等の芳香族ニトロ化合物、無水マレイン酸等の環状カルボン酸無水物、Ｎ−（ｎ−ブチル）−１，８−ナフタルイミド等の芳香族カルボン酸イミド類、ｐ−クロラニル、２，３−ジクロロアントラキノン等のキノン類、テトラシアノアントラキノンジメタン等のテトラシアノキシジメタン誘導体、９−ジシアノメチレンフルオレン−４−カルボン酸−ｎ−オクチル等のフルオレノン誘導体等が挙げられる。
電子供与性化合物の例としては、２，５−ビス（４−ジメチルアミノフェニル）−１，３，４−オキサジアゾールに代表されるオキサジアゾ−ル類、９−（４−ジエチルアミノスチリル）アントラセンのようなスチリル系化合物、Ｎ−メチル−Ｎ−フェニルヒドラゾン−３−メチリデン−９−エチルカルバゾールのようなカルバゾール化合物、１−フェニル−３−（ｐ−ジメチルアミノスチリル）−５−（ｐ−ジメチルアミノフェニル）−ピラゾリンのようなピラゾリン系化合物、Ｎ，Ｎ’−ジフェニル−Ｎ，Ｎ’−ビス（３−メチルフェニル）ベンジジンやトリ（４−メチルフェニル）アミン、Ｎ，Ｎ−ビス（３，４−ジメチルフェニル）ビフェニル−４−アミン等のトリフェニルアミン系化合物、あるいは、テトラチアフルバレン、Ｎ，Ｎ，Ｎ’，Ｎ’−テトラエチルフェニレンジアミン等が挙げられる。
有機金属錯塩の例としては、遷移金属元素又はＩＩＩ族、ＩＶ族金属元素等のアセチルアセトン錯体、アセト酢酸エステル錯体、オキシキノリン錯体、フェナントロリン錯体等の各種キレート錯体、あるいは、フェロセン等のシクロペンタジエニル錯体等が挙げられる。
【００２９】
以下、図面を参照しつつ、より詳細に説明するが、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の場合は、有機化合物層が複数の場合の一例であり、図３の場合は、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。
【００３０】
図１に示す有機ＥＬ素子は、透明絶縁体基板１上に、透明電極２、発光層４、電子輸送層及び背面電極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上に、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上に、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上に、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。
【００３１】
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。透明電極２は、透明絶縁体基板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行うため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、及び蒸着或いはスパッタされた金、白金、パラジウム等が用いられる。
【００３２】
本発明における前記一般式（Ｉ）で示される繰り返し単位を有するポリエステル化合物を含有してなる有機化合物層は、図１及び図２に示される有機ＥＬ素子の層構成の場合、電子輸送層５として作用し、また、図３及び図４に示される有機ＥＬ素子の層構成の場合、キャリア輸送能を持つ発光層６として作用する。
【００３３】
図１及び図２に示される有機ＥＬ素子の層構成の場合、電子輸送層５は前記一般式（Ｉ）で示される繰り返し単位を有するポリエステル化合物単独で形成されていてもよいが、電気的特性をさらに改善する等の目的で、電子移動度を調節するために、上述のように一般式（Ｉ）で示される繰り返し単位を有するポリエステル化合物（電子輸送性材料）と併せて、有機低分子化合物を含有してもよい。また、成膜性の向上のため、他の汎用の樹脂等との混合でもよい。具体的な樹脂としては、ポリカーボネート樹脂、ポリエステル樹脂、メタクリル樹脂、アクリル樹脂、ポリ塩化ビニル樹脂、セルロース樹脂、ウレタン樹脂、エポキシ樹脂、ポリススチレン樹脂、ポリビニルアセテート樹脂、スチレンブタジエン共重合体、塩化ビニルデン−アクリロニトリル共重合体、塩化ビニル−酢酸ビニル−無水マレイン酸共重合体、シリコン樹脂、ポリ−Ｎ−ビニルカルバゾール樹脂、ポリシラン樹脂、ポリチオフェン、ポリピロール等の導電性樹脂等を用いることができる。これらの樹脂を併用する場合、前記一般式（Ｉ）で示される繰り返し単位を有するポリエステル化合物が電子輸送層５を構成する材料の６０重量％以上となるよう混合することが好ましい。また、添加剤としては、公知の酸化防止剤、紫外線吸収剤、可塑剤等を用いることができる。
【００３４】
図１及び図２に示される有機ＥＬ素子の層構成の場合、発光層４には、固体状態で高い蛍光量子収率を示す化合物が発光材料として用いられる。発光材料が有機低分子の場合、真空蒸着法もしくは低分子と結着樹脂を含む溶液又は分散液を塗布・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。また、高分子の場合、それ自身を含む溶液又は分散液を塗布・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。好適には、有機低分子の場合、キレート型有機金属錯体、多核又は縮合芳香環化合物、ペリレン誘導体、クマリン誘導体、スチリルアリーレン誘導体、シロール誘導体、オキサゾール誘導体、オキサチアゾール誘導体、オキサジアゾール誘導体等が、高分子の場合、ポリパラフェニレン誘導体、ポリパラフェニレンビニレン誘導体、ポリチオフェン誘導体、ポリアセチレン誘導体等が挙げられる。好適な具体例として、下記例示化合物（Ｘ−１）〜（Ｘ−１５）が用いられるが、これらに限定されたものではない。なお、例示化合物（Ｘ−１３）〜（Ｘ−１５）中、ｎ及びｘはそれぞれ独立に１以上の整数を示す。
【００３５】
【化７】
【００３６】
【化８】
【００３７】
また、発光層４には、有機ＥＬ素子の耐久性向上或いは発光効率の向上を目的として、上記発光材料中にゲスト材料として発光材料と異なる色素化合物をドーピングしてもよい。真空蒸着によって発光層を形成する場合、共蒸着によってドーピングを行い、溶液又は分散液を塗布・乾燥することで発光層を形成する場合、溶液又は分散液中に混合することでドーピングを行う。発光層４中における色素化合物のドーピングの割合としては０．００１重量％〜４０重量％程度、好ましくは０．０１重量％〜１０重量％程度である。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、発光材料との相容性が良く、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、好適には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挙げられる。好適な具体例として、下記例示化合物（ＸＩ−１）〜（ＸＩ−４）が用いられるが、これらに限定されたものではない。
【００３８】
【化９】
【００３９】
図２及び図４に示される有機ＥＬ素子の層構成の場合、ホール輸送層３には、電子供与性を示す化合物がホール輸送性材料として用いられる。ホール輸送性材料が有機低分子の場合、真空蒸着法もしくは低分子と結着樹脂を含む溶液又は分散液を塗布・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。好適には、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、カルバゾール誘導体等の芳香族アミン系低分子の場合、１，１‐ビス｛４‐（ジ−ｐ−トリルアミノ）フェニル｝シクロヘキサンの３級芳香族アミンユニットを連結した芳香族ジアミン化合物（特開昭５９−１９４３９３号公報）、４，４，−ビス［（Ｎ−１−ナフチル）−Ｎ−フェニルアミノ〕ビフェニルで代表される２個以上の３級アミンを含み２個以上の縮合芳香族環が窒素原子に置換した芳香族アミン（特関平５‐２３４６８１号公報）、トリフェニルベンゼンの誘導体でスターバースト構造を有する芳香族トリアミン（米国特許第４，９２３，７７４号）、Ｎ，Ｎ’−ジフェニル−Ｎ，Ｎ’−ビス（３‐メチルフェニル）−（１，１’−ビフェニル）−４，４’−ジアミン等の芳香族ジアミン（米国特許第４，７６４，６２５号）、α，α，α’，α’−テトラメチル−α，α’−ビス（４‐ジ−ｐ−トリルアミノフェニル）‐ｐ−キシレン（特開平３−２６９０８４号公報）、分子全体として立体的に非対称なトリフェニルアミン誘導体（特開平４−１２９２７１号公報）、ピレニル基に芳香族ジアミノ基が複数個置換した化合物（特開平４−１７５３９５号公報）、エチレン基で３級芳香族アミンユニットを連結した芳香族ジアミン（特開平４−２６４１８９号公報）、スチリル構造を有する芳香族ジアミン（特開平４−２９０８５１号公報）、チオフェン基で芳香族３級アミンユニットを連結したもの（特開平４−３０４４６６号公報）、スターバースト型芳香族トリアミン（特開平４−３０８６８８号公報）、ベンジルフェニル化合物（特開平４−３６４１５３号公報）、フルオレン基で３級アミンを連結したもの（特開平５‐２５４７３号公報）、トリアミン化合物（特開平５−２３９４５５号公報）、ビスジピリジルアミノビフェニル（特開平５‐３２０６３４号公報）、Ｎ，Ｎ’，Ｎ”−トリフェニルアミン誘導体（特開平６−１９７２号公報）、フェノキザジン構造を有する芳香族ジアミン（特開平５−２９０７２８号公報）、ジアミノフェニルフェナントリジン誘導体（特願平６−４５６６９号公報）に示される化合物、誘導体等を使用することができる。また、芳香族アミン系低分子以外の有機低分子化合物である場合、ヒドラゾン化合物（特開平２−３１１５９１号公報）、シラザン化合物（米国特許第４，９５０，９５０号明細書）、シラナミン誘導体（特開平６−４９０７９号公報）、ホスファミン誘導体（特開平６−２５６５９号公報）、キナクリドン化合物、４‐ジ−ｐ−トリルアミノスチルベン、４−（ジ−ｐ−トリルアミノ）−４’−［４−（ジ−ｐ−トリルアミノ）スチリル］スチルベン等のスチルベン化合物、トリアゾール誘導体、オキサジアゾール誘導体、イミダゾール誘導体、ポリアリールアルカン誘導体、ピラゾリン誘導体、ピラゾロン誘導体、アミノ置換カルコン誘導体、オキサゾール誘導体、スチリルアントラセン誘導体、フルオレノン誘導体、ポリシラン誘導体等を使用することができる。また、上記の有機低分子化合物以外に、ホール輸送性高分子も好適に用いることができ、具体的には、例えば、ポリビニルカルバゾールやポリシラン（Ａｐｐｌ．Ｐｈｙｓ．Ｌｅｔｔ．，５９巻、２７６０頁，１９９１年等が挙げられる）、ポリフォスファゼン（特開平５−３１０９４９号公報）、ポリアミド（特開平５−１０９４９号公報）、ポリビニルトリフェニルアミン（特願平５‐２０５３７７号明細書）、トリフェニルアミン骨格を有する高分子（特開平４−１３３０６５号公報）トリフェニルアミン単位をメチレン基等で連結した高分子（Ｓｙｎｔｈｅｔｉｃ Ｍｅｔａｌｓ，５５−５７巻，４１６３頁，１９９３年）、芳香族アミンを含有するポリエステル（特開平８−２１１６４０号公報）、芳香族アミンを含有するポリエーテル（特開平８‐１７６２９３号公報）、芳香族アミンを含有するポリメタクリレート（Ｊ．Ｐｏｌｙｍ．Ｓｃｉ．，Ｐｏｌｙｍ．Ｃｈｅｍ．Ｅｄ．，２１巻、９６９頁、１９８３年）等の高分子材料を用いることもできる。これらの化合物は、単独で用いてもよいし、必要に応じて、各々、混合して用いてもよい。好適な具体例として、下記例示化合物（ＸＩＩ−１）〜（ＸＩＩ−７）が挙げられるが、これらに限定されたものではない。
【００４０】
【化１０】
【００４１】
【化１１】
【００４２】
図３及び図４に示される有機ＥＬ素子の層構成の場合、キャリア輸送能を持つ発光層６は、例えば、少なくとも前記一般式（Ｉ）で示される繰り返し単位を有するポリエステル化合物（電子輸送性材料）中に発光材料を５０重量％以下分散させた有機化合物層であり、発光材料としては前記例示化合物（Ｘ−１）ないし化合物（Ｘ−１２）が好適に用いられるが、有機ＥＬ素子に注入されるホールと電子のバランスを調節するために、前記一般式（Ｉ）で示される繰り返し単位を有するポリエステル化合物以外の特定の電荷輸送性材料（例えば、上述したホール輸送性高分子等）を併用してもよい。また、発光材料と異なる色素化合物をドーピングしてもよい。さらに、図１に示される有機ＥＬ素子の層構成の場合と同様、成膜性の向上のため、他の汎用の樹脂等との混合でもよい。
【００４３】
背面電極７には、真空蒸着可能で、電子注入を行うため仕事関数の小さな金属が使用されるが、特に好ましくはマグネシウム、アルミニウム、銀、インジウム及びこれらの合金である。また、素子の水分や酸素による劣化を防ぐために背面電極上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。
【００４４】
これら図１〜図４に示される有機ＥＬ素子は、まず透明電極２の上に各有機ＥＬ素子の層構成に応じて、ホール輸送層３或いは発光層４を形成する。ホール輸送層３及び発光層４は、それぞれ、ホール輸送性材料、発光材料を真空蒸着法、もしくは有機溶媒中に溶解或いは分散し、得られた塗布液を用いて前記透明電極２上にスピンコーティング法、ディップ法等を用いて製膜することにより形成する。
【００４５】
次に、電子輸送層５及びキャリア輸送能を持つ発光層６は、まず前記一般式（Ｉ）で示される繰り返し単位を有するポリエステル化合物単独、或いはこれらの電子輸送性材料と発光材料、及び必要に応じて電子輸送性材料、ホール輸送性材料を有機溶媒中に溶解或いは分散し、得られた塗布液を用いて前記透明電極上にスピンコーティング法、ディップ法等を用いて製膜することによって形成される。これにより容易に有機ＥＬ素子を作製することが可能である。
【００４６】
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、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程度が好ましい。ホール輸送性材料、発光材料、電子輸送性材料及び前記一般式（Ｉ）で示される繰り返し単位を有するポリエステル化合物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、分散溶媒はホール輸送性材料、発光材料、電子輸送性材料及び前記一般式（Ｉ）で示される繰り返し単位を有するポリエステル化合物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分散溶媒はホール輸送性材料、発光材料、電子輸送性材料の分散性及び溶解性、ならびに前記一般式（Ｉ）で示される繰り返し単位を有するポリエステル化合物の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。
【００４７】
そして、最後に、電子輸送層５或いはキャリア輸送能を持つ発光層６の上に背面電極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。
【００４８】
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発光させることができる。
【００４９】
【実施例】
以下、実施例によって本発明を説明する。用いた一般式（Ｉ）で示される繰り返し単位を有するポリエステル化合物（電子輸送性材料）は、例えば以下のようにして得た。
【００５０】
（合成例１〔例示化合物（１）の合成〕）
１，１０−デカンジオール１．７４ｇ（１０ｍｍｏｌ）及びピリジン２．０ｍｌ（２５ｍｍｏｌ）を３０ｍｌの１，１，２，２−テトラクロロエタンに溶解し、約５０℃に加温、撹拌しながら、ベンゾフェノン−４，４’−ジカルボン酸塩化物３．０７ｇ（１０ｍｍｏｌ）を３０ｍｌの１，１，２，２−テトラクロロエタンに溶解した溶液を約１時間かけて滴下した。滴下終了後、４時間撹拌を続けた後、混合物をメタノール３００ｍｌ中に注ぎ、析出した沈殿を濾過、メタノール、水、アセトンで洗浄、減圧乾燥し、白色固体３．１４ｇを得た（収率：７７％）。得られた白色固体の赤外吸収スペクトルを測定したところ、赤外吸収スペクトル：７２６，１６６６，１２６６ｃｍ-1であり、例示化合物（１）であった。
【００５１】
（合成例２〔例示化合物（７）の合成〕）
２，５−ジヒドロキシ−１，４−ベンゾキノン１．４０ｇ（１０ｍｍｏｌ）及び水酸化ナトリウム０．８２ｇ（２０ｍｍｏｌ）を３０ｍｌの水に溶解し、ヨウ化テトラ（ｎ−ブチル）アンモニウム５０ｍｇを加え、急速に撹拌しながら、塩化スベリロイル１．８０ｍｌ（１０ｍｍｏｌ）をジクロロメタン３０ｍｌに溶解した溶液を一度に加え、室温（〜２０℃）で２時間撹拌を続けた。反応終了後、有機相を分取し、水で洗浄した後、メタノール４００ｍｌ中に注ぎ、析出した沈殿を濾取、メタノール及び水で洗浄、減圧乾燥し、黄褐色固体２．７０ｇを得た（収率：９７％相当）。得られた黄褐色固体の赤外吸収スペクトルを測定したところ、赤外吸収スペクトル：２９４０，２８６８，１７７６，１６８４ｃｍ-1であり。例示化合物（７）であった。
【００５２】
（合成例３〔例示化合物（２３）の合成）
１，４−ジヒドロキシアントラキノン２．４０ｇ（１０ｍｍｏｌ）及び水酸化ナトリウム０．８４ｇ（２１ｍｍｏｌ）を水４０ｍｌに溶解し、ヨウ化テトラ（ｎ−ブチル）アンモニウム５０ｍｇを加え、急速に撹拌しながら、２，２−ジフェニル−１，１，１，３，３，３−ヘキサフルオロプロパン−４’，４’−ジカ
ルボン酸塩化物４．３０ｇ（１０ｍｍｏｌ）をジクロロメタン３０ｍｌに溶解した溶液を一度に加え、室温で２時間撹拌を続けた。反応終了後、有機相を分取し水で洗浄した後、メタノール５００ｍｌ中に注ぎ、析出した沈殿を濾取、メタノール及び水で洗浄、減圧乾燥し、黄褐色固体５．６６ｇを得た（収率：９５％相当）。得られた黄褐色固体の赤外吸収スペクトルを測定したところ、赤外吸収スペクトル：１７５２，１６８２，１５９２ｃｍ-1であり、例示化合物（２３）であった。
【００５３】
（合成例４〔例示化合物（３２）の合成）
４，４’−ジヒドロキシベンゾフェノン２．１４ｇ（１０ｍｍｏｌ）、水酸化
ナトリウム０．８２ｇ（２０ｍｍｏｌ）、及びヨウ化テトラ（ｎ−ブチル）アンモニウム５０ｍｇを水３０ｍｌに溶解し、急速に撹拌しながら、塩化セバコイル２．４０ｇ（１０ｍｍｏｌ）をジクロロメタン５０ｍｌに溶解した溶液を加え、室温で３時間撹拌を続けた。反応終了後、混合物をジクロロメタン５０ｍｌ及び水１００ｍｌで希釈し、有機相を分取し水で洗浄した後、メタノール２００ｍｌ中に注ぎ、析出した沈殿を濾過、メタノール、水、アセトンで洗浄、減圧乾燥し、白色固体３．０３ｇを得た（収率：７９％）。得られた白色固体の赤外吸収スペクトルを測定したところ、赤外吸収スペクトル：２９３２，２８５６，１７６０，１６５２，１６０２ｃｍ-1であり、例示化合物（３２）であった。
【００５４】
（実施例１）
２ｍｍ幅の短冊型にエッチングしたＩＴＯガラス基板を２−プロパノール（電子工業用、関東化学製）で超音波洗浄した後、乾燥させた。この基板上に前記例示化合物（ＸＩＩ−２）で示されるホール輸送性材料より構成される厚さ０．０５０μｍのホール輸送層を、さらに前記例示化合物（Ｘ−１）で示される発光材料より構成される厚さ０．０６５μｍの発光層を順次真空蒸着法により形成した。続いて、合成例１で得られた例示化合物（１）を５重量％の割合でｍ−クレゾールに溶解し、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て得られた溶液をスピンコーター法により塗布して膜厚０．０５０μｍの電子輸送層を形成し、最後に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。形成された有機ＥＬ素子の有効面積は０．０４ｃｍ2であった。
【００５５】
（実施例２）
前記例示化合物（ＸＩＩ−６）で示されるホール輸送性高分子を５重量％の割合でジクロロエタンに溶解し溶液を調製し、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て得られた溶液をスピンコーター法により塗布して膜厚０．０５０μｍのホール輸送層を形成した以外は、実施例１と同様にして有機ＥＬ素子を作製した。この有機ＥＬ素子の有効面積は０．０４ｃｍ2であった。
【００５６】
（実施例３）
前記例示化合物（ＸＩＩ−７）で示されるホール輸送性高分子を５重量％の割合でジクロロエタンに溶解し溶液を調製し、０．１μｍのポリテトラフルオロエチレン（ＰＴＦＥ）フイルターで濾過して得られた溶液をスピンコーター法により塗布して膜厚０．０５０μｍのホール輸送層を形成した以外は、実施例１と同様にして有機ＥＬ素子を作製した。この有機ＥＬ素子の有効面積は０．０４ｃｍ2であった。
【００５７】
（実施例４）
実施例１に用いた合成例１で得られた例示化合物（１）を１重量部、発光材料として前記例示化合物（ＸＩＩ−５）１重量部、ホール輸送性材料としてポリ（Ｎ−ビニルカルバゾール）２重量部を混合し、１０重量％ｍ−クレゾール分散液を１ｍｍφのガラスビーズを用いたサンドミルで２時間分散して分散液を調製して、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上に、スピンコーター法により塗布して膜厚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、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。形成された有機ＥＬ素子の有効面積は０．０４ｃｍ2であった。
【００５８】
（実施例５）
実施例１に用いた合成例１で得られた例示化合物（１）を２重量部、発光材料として前記例示化合物（Ｘ−１）１重量部を混合し、１０重量％ｍ−クレゾール分散液を１ｍｍφのガラスビーズを用いたサンドミルで２時間分散して調製して、０．１μｍのＰＴＦＥフィルターで濾過した。次に、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上に前記例示化合物（ＸＩＩ−２）で示されるホール輸送性材料より構成される厚さ０．０５０μｍのホール輸送層を真空蒸着法により形成し、続いて、スピンコーター法により先の１０重量％ｍ−クレゾール分散液を塗布して膜厚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、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て有機ＥＬ素子を作製した。この有機ＥＬ素子の有効面積は０．０４ｃｍ2であった。
【００５９】
（実施例６）
例示化合物（１）の代わりに、合成例２で得られた例示化合物（７）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。
【００６０】
（実施例７）
例示化合物（１）の代わりに、合成例２で得られた例示化合物（７）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。
【００６１】
（実施例８）
例示化合物（１）の代わりに、合成例３で得られた例示化合物（２３）を用い、電子輸送層の塗布溶剤として１，１，２，２−テトラクロロエ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。
【００６２】
（実施例９）
例示化合物（１）の代わりに、合成例３で得られた化合物（２３）を用い、発光層の塗布溶剤として１，１，２，２−テトラクロロエ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。
【００６３】
（実施例１０）
例示化合物（１）の代わりに、合成例４で得られた化合物（３２）を用い、電子輸送層の塗布溶剤として１，１，２，２−テトラクロロエ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。
【００６４】
（実施例１１）
例示化合物（１）の代わりに、合成例４で得られた化合物（３２）を用い、発光層の塗布溶剤として１，１，２，２−テトラクロロエ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。
【００６５】
（比較例１）
２ｍｍ幅の短冊型にエッチングしたＩＴＯガラス基板を２−プロパノール（電子工業用、関東化学製）で超音波洗浄した後、乾燥させた。この基板上に前記例示化合物（ＸＩＩ−２）で示されるホール輸送性材料より構成される厚さ０．０５０μｍのホール輸送層を、前記例示化合物（Ｘ−１）より構成される厚さ０．０６５μｍの発光層を順次真空蒸着法により形成した。続いて、下記構造式に示される化合物（ＸＩＩＩ）より構成される厚さ０．０５０μｍの電子輸送層を真空蒸着法により形成し、最後に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。形成された有機ＥＬ素子の有効面積は０．０４ｃｍ2であった。
【００６６】
【化１２】
【００６７】
（比較例２）
ホール輸送性材料として前記例示化合物（ＸＩＩ−５）を２重量部、発光材料として前記例示化合物（Ｘ−１）を０．１重量部、電子輸送性材料として前記例示化合物（ＸＩＩＩ）を１重量部混合し、１０重量％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上に、スピンコーター法により塗布して膜厚０．１５μｍの発光層を形成した。十分乾燥させた後、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。形成された有機ＥＬ素子の有効面積は０．０４ｃｍ2であった。
【００６８】
（比較例３）
電子輸送層の形成を省略した以外は、比較例１と同様にして有機ＥＬ素子を作製した。
【００６９】
（比較例４）
発光層の形成において電子輸送性材料の混合を省略した以外は、比較例２と同様にして有機ＥＬ素子を作製した。
【００７０】
（評価）
以上のように作製した実施例１〜１１、比較例１〜４の有機ＥＬ素子を、真空中（１３３．３×１０-3Ｐａ（１０-3Ｔｏｒｒ））でＩＴＯ電極側をプラス、Ｍｇ−Ａｇ背面電極をマイナスとして直流電圧を印加し、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２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５０ｃｄ／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２に示す。
【００７１】
【表２】
【００７２】
実施例、比較例から、前記上記一般式（Ｉ）で示される繰り返し単位を有するポリエステル化合物を用いた、有機ＥＬ素子は、高輝度、高効率が可能であることがわかる。また、スピンコーティング法、ディップ法等を用いてピンホール等の不良も少なく、大面積化も容易で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、製造コストの面でも有利であることがわかる。
【００７３】
【発明の効果】
以上、本発明によれば、素子製造が容易で十分な輝度が得られ、耐久性に優れた有機電界発光素子を提供することができる。
【図面の簡単な説明】
【図１】 本発明の有機電界発光素子の層構成の一例を示した概略構成図である。
【図２】 本発明の有機電界発光素子の層構成の他の一例を示した概略構成図である。
【図３】 本発明の有機電界発光素子の層構成の他の一例を示した概略構成図である。
【図４】 本発明の有機電界発光素子の層構成の他の一例を示した概略構成図である。
【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 electroluminescent device that facilitates device fabrication by using a specific electron transporting material and further improves stability.
[0002]
[Prior art]
An EL element is a self-luminous all-solid-state element, and has high visibility and resistance to impacts. At present, the one using an inorganic phosphor is the mainstream, but since an AC voltage of 200 V or more is required for driving, there are problems such as high manufacturing cost and insufficient brightness.
[0003]
On the other hand, research on organic EL devices using organic compounds first started using a single crystal such as anthracene. However, in the case of a single crystal, a film thickness of about 1 mm and a driving voltage of 100 V or more were necessary. For this reason, attempts have been made to reduce the thickness by vapor deposition (Thin Solid Films, Vol. 94, 171 (1982)). However, the thin film obtained by this method still has a high driving voltage of 30 V, a low density of electrons and hole carriers in the film, and a low probability of photon generation due to carrier recombination, resulting in sufficient luminance. I couldn't.
[0004]
However, in recent years, in a function-separated organic 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 1000 cd is obtained at a low voltage of about 10V. / M2What has obtained the above high luminance has been reported (Appl. Phys. Lett., Vol. 51, 913 (1987)), and research and development of stacked EL devices have been actively conducted since then.
[0005]
However, in this type of organic EL element, a thin film having a thickness of 0.1 μm or less is formed in a plurality of vapor deposition processes, so that pinholes are likely to occur, and the film thickness is under strictly controlled conditions in order to obtain sufficient performance. It is necessary to perform control. Therefore, there are problems that productivity is low and it is difficult to increase the area. The organic EL element is several mA / cm.2Because it is driven at a high current density, a large amount of Joule heat is generated. For this reason, there are many phenomena in which hole transporting low molecular weight compounds and fluorescent organic low molecular weight compounds formed in an amorphous glass state by vapor deposition gradually crystallize and eventually melt, resulting in a decrease in luminance and dielectric breakdown. As a result, there is a problem that the lifetime of the device is reduced. For example, in the case of an electron transporting material, 2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3 as described in JP-A-7-109454 and the like so far. Although it has been proposed to use oxadiazole derivatives such as 1,4-oxadiazole (PBO) as an electron transporting material, the obtained thin film is easily crystallized from the viewpoint of charge transport / injection characteristics. Is not enough. In addition, there are few types of electron transport materials other than oxadiazole compounds, and it is currently desired to develop further materials with excellent charge transport and injection characteristics from the viewpoint of low voltage drive and high efficiency. is there.
[0006]
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 organic EL devices with a single-layer structure are also underway, and conductive polymers such as poly (p-phenylene vinylene). (Nature, Vol. 357, 477 (1992), etc.), electron transporting materials and fluorescent dyes were mixed in hole transporting polyvinyl carbazole (Proceedings of the 38th Joint Conference on Applied Physics, 31p- G-12 (1991)) devices have been proposed, but the luminance, light emission efficiency, etc. are still not as good as those of a stacked organic EL device using an organic low molecular weight compound.
[0007]
[Problems to be solved by the invention]
The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide an organic EL element that is easy to manufacture, has sufficient luminance, and has excellent durability. .
[0008]
[Means for Solving the Problems]
As a result of intensive studies on an electron transporting material to achieve the above object, a polyester compound having a repeating unit represented by the following general formula (I) is suitable for an organic EL device: electron injection characteristics, electron mobility, thin film forming ability As a result, the present invention has been completed.
[0009]
That is, 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, at least one of which is transparent or translucent, and includes at least one organic compound layer. Contains at least one polyester compound having a repeating unit represented by the following general formula (1),The polyester compound is a compound in which A represents the following structure 1 and B represents a divalent aliphatic hydrocarbon, A represents a divalent aliphatic hydrocarbon and B represents the following structure 2, and A represents the following structure 3 And B represents the following structure 4 or A represents a divalent aliphatic hydrocarbon and B represents the following structure 1.It is characterized by that.
[0010]
[Chemical 3]
[0011]
[General Formula (I)NRepresents 10-2000. ]
[0012]
[Formula 4]
[0013]
In the organic EL device of the present invention, the organic compound layer containing the polyester compound having the repeating unit represented by the general formula (I) preferably further contains an organic low molecular weight compound. The organic low molecular weight compound is preferably an electron accepting compound or an electron donating compound.
[0014]
In the organic EL device of the present invention, the polyester compound having a repeating unit represented by the general formula (I) may be a copolyester compound containing another repeating unit.
[0015]
In the organic EL device of the present invention, the organic compound layer is a function-separated type, for example, composed of at least a light emitting layer and an electron transport layer, at least composed of a hole transport layer, a light emitting layer and an electron transport layer, or at least hole transport. A layer composed of a layer and a light emitting layer, wherein the light emitting layer or the electron transport layer contains a polyester compound having a repeating unit represented by the general formula (I), or has both a carrier transport ability and a light emission ability, The organic compound layer may be composed of at least a light emitting layer, and the light emitting layer may contain any polyester compound having a repeating unit represented by the general formula (I). Note that the light-emitting layer in the function separation type may have both the carrier transport ability and the light emission ability, or may have only the light emission ability.
[0016]
In the organic EL device of the present invention, the light emitting layer may contain a charge transporting material (a hole transporting material, an electron transporting material other than a polyester compound having a repeating unit represented by the general formula (I)). The charge transporting material (hole transporting material) is preferably a hole transporting polymer. The hole transport layer preferably contains a hole transporting polymer.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in further detail below.
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, at least one of which is transparent or translucent, and at least one of the organic compound layers is It comprises at least one polyester compound having a repeating unit represented by the following general formula (1).The polyester compound having the repeating unit represented by the general formula (I) is a compound in which A represents the following structure 1 and B represents a divalent aliphatic hydrocarbon, and A represents a divalent aliphatic hydrocarbon. B represents a compound representing the following structure 2, and A represents the following structure 3. A compound in which B represents the following structure 4 or a compound in which A represents a divalent aliphatic hydrocarbon and B represents the following structure 1.Since the polyester compound having the repeating unit represented by the general formula (I) exhibits excellent electron injection properties, electron mobility, and thin film forming ability, the organic EL device of the present invention having a layer containing the same is an element. Manufacture is easy, sufficient brightness is obtained, and durability is excellent.
[0018]
[Chemical formula 5]
[0019]
In general formula (I), n represents 10-2000.
[0020]
[Chemical 6]
[0021]
In the general formula (I), the divalent aliphatic hydrocarbon representing A and B is a divalent linear hydrocarbon group having 1 to 20 carbon atoms or a divalent branched chain having 2 to 20 carbon atoms. A hydrocarbon group and the like. Among these, a divalent linear hydrocarbon group having 4 to 12 carbon atoms and a divalent branched hydrocarbon group having 3 to 7 carbon atoms are preferable. Examples of the substituent of these divalent aliphatic hydrocarbons include an alkoxyl group and a halogen atom..
[0022]
Specific examples of the repeating unit represented by formula (I) are shown below, but are not limited to these specific examples. In addition, the polyester compound which has a repeating unit shown by "compound No" shown in a table | surface is called exemplary compound (No). For example, a polyester compound having a repeating unit represented by compound No12 is referred to as exemplary compound (12).
[0023]
[Table 1]
[0024]
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 sandwiched between the electrodes, and at least one of the organic compound layers Contains a polyester compound having a repeating unit represented by formula (I).
[0025]
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 has a repeating unit represented by the general formula (I). It contains a compound. 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 others The organic compound layer means a carrier transport layer, that is, a hole transport layer, an electron transport layer, or a layer comprising a hole transport layer and an electron transport layer, and at least one layer excluding these hole transport layers has the general formula ( It comprises a polyester compound having a repeating unit represented by I). Specifically, for example, it is composed of at least a light emitting layer and an electron transport layer, is composed of at least a hole transport layer, a light emitting layer and an electron transport layer, or is composed of at least a hole transport layer and a light emitting layer. Which contain a polyester compound having a repeating unit represented by the general formula (I). Furthermore, for example, the organic compound layer is composed of a light emitting layer, and the light emitting layer contains a polyester compound having a repeating unit represented by the general formula (I).
[0026]
In the organic EL device of the present invention, the light emitting layer may contain a charge transporting material (a hole transporting material, an electron transporting material other than a polyester compound having a repeating unit represented by the general formula (I)). The charge transporting material (hole transporting material) is preferably a hole transporting polymer. The hole transport layer preferably contains a hole transporting polymer. Details will be described later.
[0027]
In the organic EL device of the present invention, the organic compound layer containing the polyester compound having the repeating unit represented by the general formula (I) is used for adjusting the electron mobility for the purpose of further improving the electrical characteristics. Furthermore, in addition to the polyester compound (electron transporting material) having the repeating unit represented by the general formula (I), an organic low molecular weight compound may be contained. The specific organic low molecular weight compound may be added in an amount of 1 to 30% by weight. Examples of the specific organic low molecular weight compound include a low molecular weight electron accepting compound, an electron donating compound, and a metal complex salt. Among these, an electron-accepting compound or an electron-donating compound is preferable, and the repeating unit represented by the general formula (I) or an independent action from the polyester compound having the repeating unit represented by the general formula (I). A compound having a function of enhancing or controlling electron conductivity by an interaction such as formation of a charge transfer complex with a polyester compound having a hydrogen atom is preferable. These organic low molecular weight compounds may be used alone or in combination of two or more.
[0028]
Examples of electron accepting compounds include aromatic nitro compounds such as 4-nitrobenzaldehyde, cyclic carboxylic acid anhydrides such as maleic anhydride, and aromatic carboxylic acids such as N- (n-butyl) -1,8-naphthalimide. Acid imides, p-chloranil, quinones such as 2,3-dichloroanthraquinone, tetracyanoxydimethane derivatives such as tetracyanoanthraquinone dimethane, fluorenones such as 9-dicyanomethylenefluorene-4-carboxylic acid-n-octyl Derivatives and the like.
Examples of electron donating compounds include oxadiazols represented by 2,5-bis (4-dimethylaminophenyl) -1,3,4-oxadiazole, 9- (4-diethylaminostyryl) anthracene. Styryl compounds such as: carbazole compounds such as N-methyl-N-phenylhydrazone-3-methylidene-9-ethylcarbazole, 1-phenyl-3- (p-dimethylaminostyryl) -5- (p-dimethylamino) Pyrazoline compounds such as phenyl) -pyrazoline, N, N′-diphenyl-N, N′-bis (3-methylphenyl) benzidine and tri (4-methylphenyl) amine, N, N-bis (3,4) -Dimethylphenyl) biphenyl-4-amine and other triphenylamine compounds, or tetrathiafulvalene, N, , N ', N'-tetra ethyl-phenylenediamine, and the like.
Examples of the organometallic complex salts include transition metal elements or acetylacetone complexes such as group III and group IV metal elements, various chelate complexes such as acetoacetate complexes, oxyquinoline complexes, and phenanthroline complexes, or cyclopentadienyl such as ferrocene. A complex etc. are mentioned.
[0029]
Hereinafter, although it demonstrates in detail, referring drawings, it 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. In the case of FIGS. 1, 2, and 4, an example in which there are a plurality of organic compound layers is shown. 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.
[0030]
The organic EL element shown in FIG. 1 is formed by sequentially laminating a transparent electrode 2, a light emitting layer 4, an electron transport layer and a back electrode 7 on 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 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 transporting ability, and a back electrode 7 on 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 a transparent insulator substrate 1. Each will be described in detail below.
[0031]
The transparent insulator substrate 1 is preferably transparent in order to extract emitted light, and glass, plastic film or the like is used. The transparent electrode 2 is transparent in order to extract emitted light in the same manner as the transparent insulator substrate, and preferably has a large work function for injecting holes. Indium tin oxide (ITO), tin oxide (NESA), oxide An oxide film such as indium or zinc oxide and gold, platinum, palladium or the like deposited or sputtered are used.
[0032]
The organic compound layer containing the polyester compound having the repeating unit represented by the general formula (I) in the present invention has an electron transport layer 5 in the case of the layer structure of the organic EL element shown in FIGS. In the case of the layer structure of the organic EL element shown in FIG. 3 and FIG. 4, it acts as the light emitting layer 6 having a carrier transport capability.
[0033]
In the case of the layer structure of the organic EL device shown in FIG. 1 and FIG. 2, the electron transport layer 5 may be formed of a polyester compound having a repeating unit represented by the general formula (I) alone. In order to adjust the electron mobility for the purpose of further improving the organic compound, the organic low molecular weight compound is combined with the polyester compound (electron transporting material) having the repeating unit represented by the general formula (I) as described above. It may contain. Further, in order to improve the film formability, it may be mixed with other general-purpose resins. Specific resins include polycarbonate resin, polyester resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, cellulose resin, urethane resin, epoxy resin, polystyrene styrene resin, polyvinyl acetate resin, styrene butadiene copolymer, vinyl chloride- An acrylonitrile copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicon resin, poly-N-vinylcarbazole resin, polysilane resin, polythiophene, polypyrrole, or other conductive resin can be used. When these resins are used in combination, it is preferable to mix so that the polyester compound having the repeating unit represented by the general formula (I) is 60% by weight or more of the material constituting the electron transport layer 5. Moreover, as an additive, a well-known antioxidant, a ultraviolet absorber, a plasticizer, etc. can be used.
[0034]
In the case of the layer structure of the organic EL element shown in FIGS. 1 and 2, a compound showing a high fluorescence quantum yield in the solid state is used as the light emitting material for the light emitting layer 4. In the case where the light emitting material is an organic low molecule, it is a condition that a good thin film can be formed by applying and drying a solution or dispersion containing a low molecular weight and a binder resin. 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. Preferably, in the case of small organic molecules, chelate-type organometallic complexes, polynuclear or condensed aromatic ring compounds, perylene derivatives, coumarin derivatives, styrylarylene derivatives, silole derivatives, oxazole derivatives, oxathiazole derivatives, oxadiazole derivatives, etc. In the case of a polymer, examples include polyparaphenylene derivatives, polyparaphenylene vinylene derivatives, polythiophene derivatives, polyacetylene derivatives, and the like. As preferred specific examples, the following exemplified compounds (X-1) to (X-15) are used, but are not limited thereto. In the exemplified compounds (X-13) to (X-15), n and x each independently represent an integer of 1 or more.
[0035]
[Chemical 7]
[0036]
[Chemical 8]
[0037]
The light emitting layer 4 may be doped with a dye compound different from the light emitting material as a guest material in the light emitting material for the purpose of improving the durability of the organic EL element or improving the light emitting efficiency. When the light emitting layer is formed by vacuum deposition, doping is performed by co-evaporation, and when the light emitting layer is formed by applying and drying a solution or dispersion, doping is performed by mixing in the solution or dispersion. The doping ratio of the dye compound in the light emitting layer 4 is about 0.001 to 40% by weight, preferably about 0.01 to 10% by weight. As the coloring compound used for such doping, an organic compound that is compatible with the light emitting material and does not interfere with the formation of a good thin film of the light emitting layer is used, preferably a DCM derivative, a quinacridone derivative, a rubrene derivative. And porphyrin-based compounds. As preferred specific examples, the following exemplified compounds (XI-1) to (XI-4) are used, but are not limited thereto.
[0038]
[Chemical 9]
[0039]
In the case of the layer structure of the organic EL element shown in FIGS. 2 and 4, a compound showing an electron donating property is used for the hole transport layer 3 as the hole transport material. In the case where the hole transporting material is an organic low-molecular material, it is a condition that a favorable thin film can be formed by applying and drying a vacuum deposition method or a solution or dispersion containing a low-molecular material and a binder resin. Preferably, in the case of an aromatic amine-based low molecule such as a tetraphenylenediamine derivative, a triphenylamine derivative, or a carbazole derivative, a tertiary aromatic of 1,1-bis {4- (di-p-tolylamino) phenyl} cyclohexane An aromatic diamine compound in which amine units are linked (Japanese Patent Laid-Open No. 59-194393), two or more 3 represented by 4,4, -bis [(N-1-naphthyl) -N-phenylamino] biphenyl Aromatic amines containing a secondary amine and having two or more condensed aromatic rings substituted with nitrogen atoms (Japanese Patent Publication No. 5-234681), triphenylbenzene derivatives and aromatic triamines having a starburst structure (US Pat. 4,923,774), N, N'-diphenyl-N, N'-bis (3-methylphenyl)-(1,1'-biphenyl) -4 Aromatic diamines such as 4′-diamine (US Pat. No. 4,764,625), α, α, α ′, α′-tetramethyl-α, α′-bis (4-di-p-tolylaminophenyl) ) -P-xylene (Japanese Patent Laid-Open No. 3-269084), a sterically asymmetric triphenylamine derivative as a whole molecule (Japanese Patent Laid-Open No. 4-129271), a compound in which a pyrenyl group is substituted with a plurality of aromatic diamino groups (Japanese Patent Laid-Open No. 4-175395), an aromatic diamine having a tertiary aromatic amine unit linked by an ethylene group (Japanese Patent Laid-Open No. 4-264189), and an aromatic diamine having a styryl structure (Japanese Patent Laid-Open No. 4-290851) ), Aromatic tertiary amine units linked by a thiophene group (Japanese Patent Laid-Open No. 4-304466), starburst type aromatic triamine (Japanese Patent Laid-Open No. 4-30) 688), a benzylphenyl compound (JP-A-4-364153), a tertiary amine linked with a fluorene group (JP-A-5-25473), a triamine compound (JP-A-5-239455), Bisdipyridylaminobiphenyl (JP-A-5-320634), N, N ′, N ″ -triphenylamine derivative (JP-A-6-1972), aromatic diamine having a phenoxazine structure (JP-A-5-290728) Gazette), diaminophenylphenanthridine derivatives (Japanese Patent Application No. Hei 6-45669), derivatives and the like, and organic low-molecular compounds other than aromatic amine-based low molecules. Hydrazone compounds (JP-A-2-311591), silazane compounds (US Pat. No. 4,950, 950), silanamine derivatives (JP-A-6-49079), phosphamine derivatives (JP-A-6-25659), quinacridone compounds, 4-di-p-tolylaminostilbene, 4- (di-p- Stilbene compounds such as tolylamino) -4 ′-[4- (di-p-tolylamino) styryl] stilbene, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, amino-substituted chalcone derivatives Oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, polysilane derivatives, and the like can be used. In addition to the above-mentioned organic low molecular weight compounds, hole transporting polymers can also be suitably used. Specifically, for example, polyvinyl carbazole and polysilane (Appl. Phys. Lett., 59, 2760, 1991). Polyphosphazene (JP-A-5-310949), polyamide (JP-A-5-10949), polyvinyltriphenylamine (Japanese Patent Application No. 5-205377), triphenylamine Polymer having a skeleton (Japanese Patent Laid-open No. Hei 4-133065) Polymer (Synthetic Metals, 55-57, 4163, 1993) in which triphenylamine units are linked by a methylene group or the like, polyester containing aromatic amine (JP-A-8-21640), a polyester containing an aromatic amine Polymer materials such as Teru (JP-A-8-176293) and polymethacrylates containing aromatic amines (J. Polym. Sci., Polym. Chem. Ed., 21, 969, 1983) are used. You can also. These compounds may be used alone or in combination as necessary. Preferable specific examples include the following exemplary compounds (XII-1) to (XII-7), but are not limited thereto.
[0040]
[Chemical Formula 10]
[0041]
Embedded image
[0042]
In the case of the layer structure of the organic EL element shown in FIGS. 3 and 4, the light emitting layer 6 having a carrier transporting ability is, for example, a polyester compound (electron transporting material) having at least a repeating unit represented by the general formula (I). ) Is an organic compound layer in which a light emitting material is dispersed in an amount of 50% by weight or less, and the exemplified compound (X-1) to compound (X-12) are preferably used as the light emitting material, but injected into the organic EL device. In order to adjust the balance of holes and electrons, a specific charge transporting material other than the polyester compound having the repeating unit represented by the general formula (I) (for example, the above-described hole transporting polymer) is used in combination May be. Moreover, you may dope the pigment | dye compound different from a luminescent material. Furthermore, as in the case of the layer structure of the organic EL element shown in FIG. 1, it may be mixed with other general-purpose resins or the like for improving the film formability.
[0043]
For the back electrode 7, a metal that can be vacuum-deposited and has a small work function is used for electron injection, and magnesium, aluminum, silver, indium, and alloys thereof are particularly preferable. Further, a protective layer may be provided on the back electrode 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, SiO2, and TiO.2Examples thereof include resins such as 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.
[0044]
In the organic EL elements shown in FIGS. 1 to 4, the hole transport layer 3 or the light emitting layer 4 is first formed on the transparent electrode 2 according to the layer structure of each organic EL element. The hole transport layer 3 and the light emitting layer 4 are respectively spin-coated on the transparent electrode 2 using the obtained coating solution by dissolving or dispersing the hole transporting material and the light emitting material in a vacuum deposition method or an organic solvent. The film is formed by using a method, a dip method or the like.
[0045]
Next, the electron transport layer 5 and the light emitting layer 6 having a carrier transport ability are first a polyester compound having a repeating unit represented by the general formula (I) alone, or these electron transporting material and light emitting material, and as necessary. According to the formation, the electron transporting material and the hole transporting material are dissolved or dispersed in an organic solvent, and the obtained coating solution is used to form a film on the transparent electrode using a spin coating method, a dip method, or the like. Is done. Thereby, an organic EL element can be easily produced.
[0046]
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. The film thickness of the light emitting layer 6 having carrier transporting ability is preferably about 0.03 to 0.2 μm. The dispersed state of the hole transporting material, the light emitting material, the electron transporting material, and the polyester compound having the repeating unit represented by the general formula (I) may be a molecular dispersion state or a fine particle dispersion state. In the case of a film forming method using a coating solution, in order to obtain a molecular dispersion state, a dispersion solvent is a hole transporting material, a light emitting material, an electron transporting material, and a polyester having a repeating unit represented by the general formula (I). It is necessary to use a common solvent for the compound, and in order to obtain a fine particle dispersed state, the dispersion solvent is a hole transporting material, a light emitting material, the dispersibility and solubility of the electron transporting material, and the repetition represented by the general formula (I). It is necessary to select in consideration of the solubility of the polyester compound having units. 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.
[0047]
Finally, the back electrode 7 is formed on the electron transport layer 5 or the light emitting layer 6 having carrier transport ability by a vacuum deposition method, thereby completing the device.
[0048]
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.2It is possible to emit light by applying a direct current voltage.
[0049]
【Example】
Hereinafter, the present invention will be described by way of examples. The polyester compound (electron transporting material) having the repeating unit represented by the general formula (I) used was obtained as follows, for example.
[0050]
(Synthesis Example 1 [Synthesis of Exemplified Compound (1)])
1.74 g (10 mmol) of 1,10-decanediol and 2.0 ml (25 mmol) of pyridine were dissolved in 30 ml of 1,1,2,2-tetrachloroethane, and the mixture was heated to about 50 ° C. while stirring and benzophenone- A solution prepared by dissolving 3.07 g (10 mmol) of 4,4′-dicarboxylic acid chloride in 30 ml of 1,1,2,2-tetrachloroethane was added dropwise over about 1 hour. After completion of the dropwise addition, stirring was continued for 4 hours, and then the mixture was poured into 300 ml of methanol, and the deposited precipitate was filtered, washed with methanol, water and acetone, and dried under reduced pressure to obtain 3.14 g of a white solid (yield: 77%). When the infrared absorption spectrum of the obtained white solid was measured, the infrared absorption spectrum: 726, 1666, 1266 cm.-1It was Exemplified Compound (1).
[0051]
(Synthesis Example 2 [Synthesis of Exemplified Compound (7)])
1.40 g (10 mmol) of 2,5-dihydroxy-1,4-benzoquinone and 0.82 g (20 mmol) of sodium hydroxide are dissolved in 30 ml of water, and 50 mg of tetra (n-butyl) ammonium iodide is added rapidly. While stirring, a solution prepared by dissolving 1.80 ml (10 mmol) of subericyl chloride in 30 ml of dichloromethane was added at once, and stirring was continued at room temperature (˜20 ° C.) for 2 hours. After completion of the reaction, the organic phase was separated and washed with water, then poured into 400 ml of methanol, and the deposited precipitate was collected by filtration, washed with methanol and water, and dried under reduced pressure to obtain 2.70 g of a tan solid ( Yield: equivalent to 97%). When the infrared absorption spectrum of the obtained tan solid was measured, the infrared absorption spectrum: 2940, 2868, 1776, 1684 cm.-1It is. It was exemplary compound (7).
[0052]
(Synthesis Example 3 [Synthesis of Exemplified Compound (23))
1.40 g (10 mmol) of 1,4-dihydroxyanthraquinone and 0.84 g (21 mmol) of sodium hydroxide are dissolved in 40 ml of water, and 50 mg of tetra (n-butyl) ammonium iodide is added thereto. 2-diphenyl-1,1,1,3,3,3-hexafluoropropane-4 ′, 4′-dica
A solution of 4.30 g (10 mmol) of rubonic acid chloride dissolved in 30 ml of dichloromethane was added all at once, and stirring was continued at room temperature for 2 hours. After completion of the reaction, the organic phase was separated and washed with water, then poured into 500 ml of methanol, and the deposited precipitate was collected by filtration, washed with methanol and water, and dried under reduced pressure to obtain 5.66 g of a tan solid (yield). Rate: 95% equivalent). When an infrared absorption spectrum of the obtained tan solid was measured, an infrared absorption spectrum: 1752, 1682, 1592 cm.-1It was Exemplified Compound (23).
[0053]
(Synthesis Example 4 [Synthesis of Exemplified Compound (32))
4,4'-dihydroxybenzophenone 2.14 g (10 mmol), hydroxylated
Dissolve 0.82 g (20 mmol) of sodium and 50 mg of tetra (n-butyl) ammonium iodide in 30 ml of water and add a solution of 2.40 g (10 mmol) of sebacoyl chloride in 50 ml of dichloromethane while stirring rapidly. Stirring was continued at room temperature for 3 hours. After completion of the reaction, the mixture was diluted with 50 ml of dichloromethane and 100 ml of water, the organic phase was separated and washed with water, poured into 200 ml of methanol, and the deposited precipitate was filtered, washed with methanol, water and acetone, and dried under reduced pressure. As a result, 3.03 g of a white solid was obtained (yield: 79%). When the infrared absorption spectrum of the obtained white solid was measured, the infrared absorption spectrum: 2932, 2856, 1760, 1652, 1602 cm.-1It was Exemplified Compound (32).
[0054]
Example 1
The ITO glass substrate etched into a 2 mm wide strip was ultrasonically cleaned with 2-propanol (for electronics industry, manufactured by Kanto Chemical) and then dried. A 0.050 μm-thick hole transport layer composed of the hole transporting material represented by the exemplary compound (XII-2) is further formed from the light emitting material represented by the exemplary compound (X-1) on the substrate. A 0.065 μm thick light emitting layer was sequentially formed by vacuum deposition. Subsequently, the exemplified compound (1) obtained in Synthesis Example 1 was dissolved in m-cresol at a ratio of 5% by weight, and a solution obtained by filtering through a 0.1 μm polytetrafluoroethylene (PTFE) filter was obtained. An electron transport layer having a thickness of 0.050 μm is formed by applying by a spin coater method, and finally a Mg—Ag alloy is vapor-deposited by co-evaporation so that a back electrode having a width of 2 mm and a thickness of 0.15 μm intersects the ITO electrode. Formed. The effective area of the formed organic EL element is 0.04 cm.2Met.
[0055]
(Example 2)
It is obtained by dissolving a hole transporting polymer represented by the exemplified compound (XII-6) in 5% by weight in dichloroethane to prepare a solution and filtering through a 0.1 μm polytetrafluoroethylene (PTFE) filter. An organic EL device was produced in the same manner as in Example 1 except that the solution was applied by a spin coater method to form a hole transport layer having a thickness of 0.050 μm. The effective area of this organic EL element is 0.04 cm.2Met.
[0056]
(Example 3)
It is obtained by dissolving a hole transporting polymer represented by the exemplified compound (XII-7) in dichloroethane at a ratio of 5% by weight, preparing a solution, and filtering through a 0.1 μm polytetrafluoroethylene (PTFE) filter. An organic EL device was produced in the same manner as in Example 1 except that the solution was applied by a spin coater method to form a hole transport layer having a thickness of 0.050 μm. The effective area of this organic EL element is 0.04 cm.2Met.
[0057]
Example 4
1 part by weight of the exemplified compound (1) obtained in Synthesis Example 1 used in Example 1, 1 part by weight of the exemplified compound (XII-5) as a light emitting material, and poly (N-vinylcarbazole) as a hole transporting material 2 parts by weight were mixed, and a 10% by weight m-cresol dispersion was dispersed for 2 hours with a sand mill using glass beads of 1 mmφ to prepare a dispersion, which was then filtered through a 0.1 μm PTFE filter. Using this solution, a light emitting layer having a thickness of 0.15 μm and having a carrier transporting ability was formed on a glass substrate on which a 2 mm wide strip-shaped ITO electrode was formed by etching, and was applied by a spin coater method. After sufficiently drying, a Mg—Ag alloy was vapor-deposited 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 formed organic EL element is 0.04 cm.2Met.
[0058]
(Example 5)
2 parts by weight of Exemplified Compound (1) obtained in Synthesis Example 1 used in Example 1 and 1 part by weight of Exemplified Compound (X-1) as a luminescent material were mixed to prepare a 10 wt% m-cresol dispersion. It was prepared by dispersing in a sand mill using 1 mmφ glass beads for 2 hours and filtered through a 0.1 μm PTFE filter. Next, a 0.050 μm thick hole transport layer composed of the hole transport material represented by the exemplary compound (XII-2) is vacuum-deposited on a glass substrate formed by etching a 2 mm wide strip-shaped ITO electrode. Subsequently, the above 10 wt% m-cresol dispersion was applied by a spin coater method to form a light emitting layer having a carrier transport ability of 0.15 μm. After sufficiently drying, an Mg-Ag alloy was vapor-deposited by co-evaporation, and a back electrode having a width of 2 mm and a thickness of 0.15 μm was formed so as to intersect with the ITO electrode to produce an organic EL device. The effective area of this organic EL element is 0.04 cm.2Met.
[0059]
(Example 6)
An organic EL device was produced in the same manner as in Example 1 except that the exemplified compound (7) obtained in Synthesis Example 2 was used instead of the exemplified compound (1).
[0060]
(Example 7)
An organic EL device was produced in the same manner as in Example 4 except that the exemplified compound (7) obtained in Synthesis Example 2 was used instead of the exemplified compound (1).
[0061]
(Example 8)
Example 1 except that Example Compound (23) obtained in Synthesis Example 3 was used instead of Example Compound (1), and 1,1,2,2-tetrachloroethane was used as a coating solvent for the electron transport layer. In the same manner, an organic EL device was produced.
[0062]
Example 9
The same as Example 4 except that the compound (23) obtained in Synthesis Example 3 was used instead of the exemplified compound (1) and 1,1,2,2-tetrachloroethane was used as the coating solvent for the light emitting layer. Thus, an organic EL element was produced.
[0063]
(Example 10)
Example 1 except that instead of the exemplified compound (1), the compound (32) obtained in Synthesis Example 4 was used, and 1,1,2,2-tetrachloroethane was used as a coating solvent for the electron transport layer. Similarly, an organic EL device was produced.
[0064]
(Example 11)
The same as Example 4 except that the compound (32) obtained in Synthesis Example 4 was used instead of the exemplified compound (1), and 1,1,2,2-tetrachloroethane was used as the coating solvent for the light emitting layer. Thus, an organic EL element was produced.
[0065]
(Comparative Example 1)
The ITO glass substrate etched into a 2 mm wide strip was ultrasonically cleaned with 2-propanol (for electronics industry, manufactured by Kanto Chemical) and then dried. On this substrate, a 0.050 μm-thick hole transport layer composed of a hole transporting material represented by the exemplary compound (XII-2) is formed with a thickness of 0.05 μm composed of the exemplary compound (X-1). A 065 μm light emitting layer was sequentially formed by vacuum deposition. Subsequently, an electron transport layer having a thickness of 0.050 μm composed of the compound (XIII) represented by the following structural formula is formed by a vacuum deposition method, and finally a Mg—Ag alloy is deposited by co-evaporation to have a width of 2 mm. A back electrode having a thickness of 0.15 μm was formed so as to cross the ITO electrode. The effective area of the formed organic EL element is 0.04 cm.2Met.
[0066]
Embedded image
[0067]
(Comparative Example 2)
2 parts by weight of the exemplified compound (XII-5) as a hole transporting material, 0.1 part by weight of the exemplified compound (X-1) as a light emitting material, and 1 weight of the exemplified compound (XIII) as an electron transporting material A 10 wt% dichloroethane solution was prepared and filtered through a 0.1 μm PTFE filter. Using this solution, a light emitting layer having a thickness of 0.15 μm was formed on a glass substrate on which a 2 mm wide strip-shaped ITO electrode was formed by etching, by spin coating. After sufficiently drying, a Mg—Ag alloy was vapor-deposited 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 formed organic EL element is 0.04 cm.2Met.
[0068]
(Comparative Example 3)
An organic EL device was produced in the same manner as in Comparative Example 1 except that the formation of the electron transport layer was omitted.
[0069]
(Comparative Example 4)
An organic EL device was produced in the same manner as in Comparative Example 2 except that the mixing of the electron transporting material was omitted in the formation of the light emitting layer.
[0070]
(Evaluation)
The organic EL elements of Examples 1 to 11 and Comparative Examples 1 to 4 manufactured as described above were subjected to vacuum (133.3 × 10 6-3Pa (10-3Torr)), the ITO electrode side was positive and the Mg-Ag back electrode was negative, a DC voltage was applied, and light emission was measured, and the maximum luminance and emission color at this time were evaluated. Those resultsTable 2Shown in Moreover, the light emission lifetime of the organic EL element was measured in dry nitrogen. The evaluation of the light emission lifetime is an initial luminance of 50 cd / m.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 2 together with the element lifetime.
[0071]
[Table 2]
[0072]
From the examples and comparative examples, it can be seen that the organic EL device using the polyester compound having the repeating unit represented by the general formula (I) can have high luminance and high efficiency. In addition, since there are few defects such as pinholes using a spin coating method, a dip method, etc., it is easy to increase the area, and a good thin film can be formed. It can be seen that the EL element is advantageous in terms of manufacturing cost.
[0073]
【The invention's effect】
As described above, according to the present invention, it is possible to provide an organic electroluminescence device that is easy to manufacture, has sufficient luminance, and has excellent durability.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an example of a layer configuration of an organic electroluminescent element of the present invention.
FIG. 2 is a schematic configuration diagram showing another example of the layer configuration of the organic electroluminescent element of the present invention.
FIG. 3 is a schematic configuration diagram showing another example of the layer configuration of the organic electroluminescent element of the present invention.
FIG. 4 is a schematic configuration diagram showing another example of the layer configuration of the organic electroluminescent 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 (12)
前記ポリエステル化合物が、Ａが下記構造１を表しＢが２価の脂肪族炭化水素を表す化合物、Ａが２価の脂肪族炭化水素を表しＢが下記構造２を表す化合物、Ａが下記構造３を表しＢが下記構造４を表す化合物、又は、Ａが２価の脂肪族炭化水素を表しＢが下記構造１を表す化合物であることを特徴とする有機電界発光素子。
The polyester compound is a compound in which A represents the following structure 1 and B represents a divalent aliphatic hydrocarbon, A represents a divalent aliphatic hydrocarbon and B represents the following structure 2, and A represents the following structure 3 An organic electroluminescent device, wherein B represents a compound represented by the following structure 4, or A represents a divalent aliphatic hydrocarbon and B represents the following structure 1 .
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