JP2005026057A

JP2005026057A - Organic light-emitting display device

Info

Publication number: JP2005026057A
Application number: JP2003190038A
Authority: JP
Inventors: Takahiro Nakayama; 隆博中山; Sukekazu Araya; 介和荒谷; Kazutaka Tsuji; 和隆辻
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 2003-07-02
Filing date: 2003-07-02
Publication date: 2005-01-27
Anticipated expiration: 2023-07-02
Also published as: JP3898163B2

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a display with high brightness by efficiently utilizing the emission light of an organic thin film of an upside-emission light take-out organic light-emitting display device. <P>SOLUTION: A minute resonator structure having an optical length D corresponding to a wave length of intended light is formed between a metal electrode serving as a total reflection mirror 102 formed on a substrate 101 on which a light-emitting layer made of an organic thin film is formed, and an inside face of a transparent sealing plate 106. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、自発光型の表示装置に係り、特に有機発光素子を用いた有機発光表示装置に関する。
【０００２】
【従来の技術】
有機発光表示装置を構成する有機発光素子は、該有機発光素子の発光前面に半透明反射鏡を設置し往復する光の光学的長さが所望の発光波長の数倍になる共振器（微小共振器）にすることにより、発光スペクトルを単色化し、同時に発光ピーク強度をエンハンスすることが可能である（「特許文献１」）。また、共振器構造に関係した物性については「非特許文献１」に詳説されている。
【０００３】
図９は上部発光取り出し構造の有機発光表示装置の代表的な構造を説明する模式断面図である。図中、参照符号１０１は絶縁基板（以下、単に基板と称する）であり、この基板１０１上に第１電極である金属電極兼全反射鏡１０２を有し、この上に有機材料からなるホール注入層と発光層および電子注入層からなる有機薄膜（有機発光層とも称する）１０３が形成され、さらに第２電極である複数（ここでは３個）の透明電極１０４が積層されている。各透明電極１０４は図示しないアクティブ素子（薄膜トランジスタ等）で個別に駆動される画素単位を構成する。
【０００４】
有機薄膜１０３の上方には、該有機薄膜１０３を覆って外部環境からの湿気やガスの影響を遮断すると共に表示面を形成する透明封止板１０６がスペーサ１０７で有機薄膜１０３に対して所定の空隙１０５をもって配置されている。有機薄膜１０３の発光光は透明封止板１０６から出射して表示を形成する。このような上部発光取り出し構造の有機発光装置では、有機発光層を構成する有機薄膜１０３を保護する透明板である透明封止板１０６が該有機薄膜１０３の膜面上方に十分な距離だけ離されて設置されていた。
【０００５】
【特許文献１】
特開平８−２１３１７４号公報
【非特許文献１】
Ｔ．Ｎａｋａｙａｍａ： ”Ｏｒｇａｎｉｃｌｕｍｉｎｅｓｃｅｎｔｄｅｖｉｃｅｓｗｉｔｈａｍｉｃｒｏｃａｖｉｔｙｓｔｒｕｃｔｕｒｅ”，ｉｎｃｌｕｄｅｄｉｎ ”Ｏｒｇａｎｉｃｅｌｅｃｔｒｏｌｕｍｉｎｅｓｃｅｎｔｍａｔｅｒｉａｌｓａｎｄｄｅｖｉｃｅｓ ”，ｅｄｉｔｅｄｂｙＳ．Ｍｉｙａｔａ，ｐｕｂｌｉｓｈｅｄｂｙＧｏｒｄｅｎ＆ＢｒｅａｃｈＳｃｉｅｎｃｅＰｕｂｌｉｓｈｅｒ（１９９７）。
【０００６】
【発明が解決しようとする課題】
従来の共振器構造有りの有機発光表示装置においては、この有機薄膜を保護する透明封止板は共振器の構成体としては利用されていなかった。また、有機薄膜１０３の発光光の一部は透明封止板１０６の内面および外面とでそれぞれ約５％程度反射して戻る反射光Ｌｒ１，Ｌｒ２を有し、表示のための光Ｌｍの光量はこれらの反射光により損失され、表示面の輝度向上を低下させる原因となっている。本発明の目的は、透明封止板を共振器の構成体としては利用することによって有機薄膜の発光光を効率よく表示に利用して高輝度の有機発光表示装置を提供することにある。
【０００７】
【課題を解決するための手段】
上記目的を達成するため、本発明は、有機薄膜の保護用の透明封止板の光透過・反射機能を利用して発光素子である有機薄膜と一体の微小な共振器を構成する点に特徴を有する。すなわち、本発明は、有機薄膜を保護する部分反射機能を有する透明封止板を透過して直接上部に出る直接出力光と、該透明封止板の反射により一度素子側に戻る光を有機薄膜の下部にある基板側に設けられた金属電極兼全反射鏡等の反射膜で反射させ、上記直接出力光とは別光路で透明封止板の上部に光を出射させる構造とした。
【０００８】
別光路を経て上部より出力される光（別光路光）と直接出力光との間で干渉が生じる構造が必要要件である。そのためには直接出力光と別光路光との光路および反射により生じる光路長シフト相当分の光学的長さの差の総和が、有機薄膜の発光波長の整数倍（および可干渉な作成誤差の範囲内）であることが必要である。
【０００９】
仮に、基板側反射板（金属電極兼全反射鏡）にアルミニウム等を用い、基板上の有機発光素子（有機薄膜）の最上部の設ける第２の電極を透明電極ＩＴＯ（ＩｎｄｉｕｍＴｉｎＯｘｉｄｅ）とし、この透明電極ＩＴＯの上部に空隙（減圧ガスなどを封入）を設けるとすると、金属電極兼全反射鏡上の反射時に光の位相が１／２波長分シフトするので、該金属電極兼全反射鏡の反射面から透明電極ＩＴＯの最上部までの光学的長さは、所望の共振波長の１／４、３／４、１、（２ｎ−１）／４倍の何れかであることが必要となる。なお、ｎは自然数である。また、透明電極ＩＴＯの上部にある空隙にＩＴＯより屈折率の大きい媒体を入れた場合は、そこでの反射でも光の位相が１／２波長分シフトするので、２／４、４／４、１、２ｎ／４倍の何れかであることが必要になる。
【００１０】
さらに、基板側の有機発光素子である有機薄膜の上部と空隙との界面での反射と、空隙と有機薄膜保護用の透明封止板の表面との界面の反射が干渉により所望の波長の反射を果たす為には、透明電極−空隙−空隙（減圧ガスなど）−有機薄膜保護用の透明封止板の各屈折率の大小関係が大−小−大（または、小−大−小）の関係を満たすときは、空隙の光学的長さが所望の共振波長の１／４、３／４、１、（２ｎ−１）／４倍の何れかであることが必要となる。また、小−中−大の関係の時は２／４、４／４、１、２ｎ／４倍の何れかである。
【００１１】
有機薄膜保護用の透明封止板の表面構造のみで十分な反射機能を付与し、透明電極上面での反射がその反射強度に対して十分小さい場合は、基板側にある反射板（金属電極兼全反射鏡）から有機薄膜保護用の透明封止板の表面までの光学的長さが所望の波長に対応する共振器長であることが必要である。なお、基板側に有する素子構造（金属電極兼全反射鏡１０２、有機薄膜１０３、透明電極１０４）の最上部が透明電極１０４であるのは必要要件ではなく、透明電極１０４上方に透明材料を積層して基板側素子の最上部とすることができる。共振器構造の有機発光素子の発光原理と構成例は前記「非特許文献１」に詳説されている。共振器の光学的長さは、発光の角度依存性や発光素子を構成する有機薄膜等の膜厚を変えたサンプルとの比較などから検証できる。
【００１２】
【発明の実施の形態】
以下、本発明の実施の形態について、添付の図面を参照して詳細に説明する。図１は本発明による有機発光表示装置の第１実施例を説明する模式断面図である。図１において、透明基板１０１上に金属電極兼全反射鏡１０２として厚さ１５０ｎｍのアルミニウム（Ａｌ）が形成され、その上に厚さ０．６ｎｍのフッ化リチウム（ＬｉＦ）をこの順で積層した積層膜が形成されている。また、有機薄膜１０３として厚さ５０ｎｍの電子輸送層ＡＬＱを、発光層として厚さ２０ｎｍのＣＢＰにＩｒ（ｐｐｙ）_３を６体積％混入させた膜を、ホール注入層として厚さ４０ｎｍのα−ＮＰＤを形成してある。
【００１３】
また、有機１０３の上層に透明電極１０４として、厚さ１１０ｎｍのＩＴＯが形成されている。上記有機薄膜を構成するＡＬＱの分子構造は「化１」に、ＣＢＰの分子構造は「化２」に、Ｉｒ（ｐｐｙ）_３の分子構造は「化３」に示した。
【００１４】
【化１】

【化２】

【化３】

【００１５】
このとき、金属電極兼全反射鏡１０２の表面から基板に形成された積層膜構造の最上部までの光学的距離（光学的長さ）ＤはＩｒ（ｐｐｙ）_３の発光ピーク波長５２０ｎｍの３／４倍になっている。ここで言う光学的長さとは、積層膜構造の厚さと屈折率の積である。
【００１６】
この上部発光取り出し構造の有機発光表示装置においては、外部環境からの湿気やガスの影響を遮断する有機薄膜保護のために透明封止板１０６が設置されている。本実施例においては、この透明封止板１０６を有機薄膜１０３の発光波長の３／４倍の間隔である３９０ｎｍの間隔を持つように、両者間にＳｉＯ_２からなるフィラー１０７（ビーズなど）を介在させて基板１０１と透明封止板１０６の間（基板間間隙）を減圧状態に維持して該基板１０１と透明封止板１０６を貼り合わせている。
【００１７】
透明封止板１０６として、０．１ｍｍ厚のガラス板を用い、外気と基板間間隙との圧力差により該透明封止板が有機薄膜構造を有する基板１０１に対して一様な間隙を維持するように変形させて密着させる。これにより、透明電極１０４の最表面の当該基板に有する薄膜構造の内部方向に戻る反射光と透明封止板１０６の内面での反射光は波長５２０ｎｍで可干渉となり、反射光を効率よく薄膜構造の内部に戻し、金属電極兼全反射鏡１０２との間で微小な共振器を構成することができる。なお、透明封止板１０６としては、上記したような減圧下で基板１０１の最表面の形状に倣うフレキシブルな材料が適しており、上記したガラス板の他、樹脂板なども採用できる。
【００１８】
図２は本発明の実施例の効果を有機薄膜の発光スペクトルの差で従来技術と比較して示す説明図であり、横軸に発光波長（ｎｍ）を、縦軸に発光の強度（相対値）を取って示す。図２に示されたように、図１に示した本実施例の構造によれば、基板１０１と透明封止板１０６との間の間隔を約１ｍｍで貼り付けた従来構造（前記図９の構造に相当）と比較して、共振が発生している３９０ｎｍでの発光スペクトルの単色化とそのピーク強度の上昇が得られていることが分かる。このように、本実施例によれば、透明封止板１０６を共振器の構成体としては利用することによって有機薄膜１０３の発光光を効率よく表示に利用して高輝度の有機発光表示装置を提供することができる。
【００１９】
図３は本発明による有機発光表示装置の第２実施例を説明する模式断面図である。図３に示した実施例では、図１で説明した本発明の第１実施例の構造に加えて、透明封止板１０６の内面に、膜厚の光学的長さが所望の発光波長の１／４倍になる膜厚で高屈折率薄膜１０９による反射層を形成した。この高屈折率薄膜１０９を設けることによって反射に寄与する面が増加し、基板１０１と透明封止板１０６の両基板間に形成される共振器の光閉じ込め効率を上げることができる。
【００２０】
高屈折率薄膜１０９としては、酸化チタン、酸化ジルコニアなど、基板１０１より屈折率の高い薄膜を用いる。この高屈折率薄膜１０９の屈折率は高いほど反射率は向上する。また、この高屈折率薄膜１０９を低屈折率の薄膜と交互積層して形成することにより、反射率を上げることもできる（この原理に関しては、前掲の「非特許文献１」を参照されたい）。
【００２１】
この高屈折率薄膜１０９による反射層形成により透明封止板１０６の内面での反射率が十分大きくなる。基板間間隙下面での反射の効果が重要でない程度に小さいと考えられるときは、透明封止板１０６の内面と金属電極兼全反射鏡１０２の間の距離を共振条件にとることが重要になり、透明封止板１０６の内面と基板１０１に形成された積層構造の最上面との距離は重要ではなくなる。
【００２２】
また、図３の実施例に示したように、透明封止板１０６の上面に、所望の発光波長の透過を向上させると共に外部からの入射光の使用者への戻りを防止する機能を有する表面薄膜（表面コート薄膜）１１０を形成することもでき、この表面コート薄膜１１０を設けることで、さらに表示品質を向上することができる。本実施例によれば、透明封止板１０６を共振器の構成体としては利用することによっても、有機薄膜１０３の発光光を効率よく表示に利用して高輝度の有機発光表示装置を提供することができる。
【００２３】
図４は本発明による有機発光表示装置の第３実施例を説明する模式断面図である。図４に示した実施例では、図３の実施例におけるフィラーに代えて、ＰＩＱなどを用いてパターニングしたスペーサ１０７を設け、基板１０１と透明封止板１０６の間の間隔を所定値に規制したものである。本実施例では、スペーサ１０７を基板１０１に有する有機薄膜１０３の上に形成したが、これに限るものではなく、透明封止板１０６の内面に形成してもよい。スペーサ１０７を透明封止板１０６の内面に形成することで、製造プロセス途上で有機薄膜１０３に及ぼされるダメージを軽減できる。本実施例によっても、透明封止板１０６を共振器の構成体としては利用することによっても、有機薄膜１０３の発光光を効率よく表示に利用して高輝度の有機発光表示装置を提供することができる。
【００２４】
図５は本発明による有機発光表示装置の第４実施例を説明する模式断面図である。本実施例では、基板１０１と透明封止板１０６の間の間隔すなわち基板間間隔を前記したようなスペーサを使用せずに、透明封止板１０６を基板１０１の内面に有する薄膜層の最上層に密着させたものである。透明封止板１０６を基板１０１密着させるためには、透明封止板１０６と基板１０１の間の空隙を減圧することが有効である。しかし、他の方法として、所謂マッチングリキッド１２１を当該空隙に注入して透明電極１０４とマッチングリキッド１２１の間、またはマッチングリキッド１２１と高屈折率薄膜１０９の間の界面反射を０に近づけて基板間間隔の不均一から生じる不要な光反射を低減することができる。
【００２５】
透明電極１０４と同じ屈折率のマッチングリキッド１２１を用いた場合は、高屈折率薄膜１０９の下面、高屈折率薄膜１０９と同じ屈折率のマッチングリキッド１２１を用いた場合は、透明電極１０４の上面が共振器の上部反射面となる。共振器の上面と下面の長さは、高屈折率薄膜１０９の代わりに低屈折率薄膜を用いる場合は、共振器の上面と下面の長さは（２ｎ−１）λ／４ではなく、２ｎλ／４となる。
【００２６】
本実施例によっても、透明封止板１０６を共振器の構成体としては利用することによっても、有機薄膜１０３の発光光を効率よく表示に利用して高輝度の有機発光表示装置を提供することができる。
【００２７】
図６は本発明による有機発光表示装置の第５実施例を説明する模式断面図である。図６に示した実施例は、フルカラーの表示装置のように、例えば、赤（Ｒ）、緑（Ｇ）、青（Ｂ）の各画素で光の共振波長が異なる場合の構造の一例である。本実施例では、波長が異なる赤（Ｒ）、緑（Ｇ）、青（Ｂ）の各画素の共振器長（共振器の光学的長さ）を各該当する光の波長に合わせて、それぞれＤｒ、Ｄｇ、Ｄｂとした。この共振器長の調整を行うため、基板１０１に形成する金属電極兼反射鏡１０２の膜厚を変えた。なお、透明封止板１０６の内面に有する高屈折率薄膜１０９は必須ではなく、高屈折率薄膜１０９を設けない場合の各画素の共振器は透明封止板１０６の内面と膜厚が異なる各画素の金属電極兼反射鏡１０２との間に形成される。また、表面コート薄膜１１０の形成も任意であるが、表示品質の向上のためには、これを設けることが望ましい。本実施例により、赤（Ｒ）、緑（Ｇ）、青（Ｂ）の各画素毎に最適な共振器構造を付与でき、各色の有機薄膜１０３の発光光を効率よく表示に利用して高輝度の有機発光表示装置を提供することができる。
【００２８】
図７は本発明による有機発光表示装置の第６実施例を説明する模式断面図である。図７に示した実施例も図６の実施例と同様に、フルカラーの表示装置を構成する場合の他例である。本実施例では、波長が異なる赤（Ｒ）、緑（Ｇ）、青（Ｂ）の各画素の共振器長（共振器の光学的長さ）を各該当する光の波長に合わせて、それぞれＤｒ、Ｄｇ、Ｄｂとした。この共振器長の調整を行うため、透明封止板１０６の内面に共振器長調整層１０８を設け、この膜厚を波長が異なる赤（Ｒ）、緑（Ｇ）、青（Ｂ）の各画素の共振器長Ｄｒ、Ｄｇ、Ｄｂとなるように変えたものである。共振器長調整層１０８は、透明封止板１０６との間の界面での反射率を下げるために該透明封止板１０６の屈折率に近い材質であることが望ましく、透明封止板１０６がガラス板の場合は共振器長調整層１０８を酸化シリコンとするのが適当である。酸化シリコン以外の適当な材料を用いることができることは言うまでもない。なお、表面コート薄膜１１０の形成は任意であるが、表示品質の向上のためには、これを設けることが望ましい。本実施例により、赤（Ｒ）、緑（Ｇ）、青（Ｂ）の各画素毎に最適な共振器構造を付与でき、各色の有機薄膜１０３の発光光を効率よく表示に利用して高輝度の有機発光表示装置を提供することができる。
【００２９】
上記した第６実施例と第７実施例では、赤（Ｒ）、緑（Ｇ）、青（Ｂ）の各画素を分離するために画素分離壁１０７を設けている。この画素分離壁１０７は基板１０１と透明封止板１０６との間隔（基板間間隔）を規制するスペーサとしても機能する。しかし、基板間間隔の規制に図１などで説明したフィラーも用いることもできる。
【００３０】
図８は本発明の有機波高表示装置の回路構成を説明する等価回路である。図８に示したように、データ線２０１（２０１ｍ＋１，２０１ｍ，２０１ｍ−１・・・）とゲート線２０２（２０１ｎ＋１，２０１ｎ，２０１ｎ−１・・・）で囲まれた画素ＰＸには、スイッチング素子（コントロール・トランジスタ）ＳＷ１、電流供給トランジスタ（ドライブ・トランジスタ）ＤＴ、コンデンサＣ、および有機発光素子ＬＥＤが配置される。スイッチング素子ＳＷ１の制御電極（ゲート）はゲート線２０２に、チャネルの一端（ドレイン）はデータ線２０１に接続されている。電流供給トランジスタＤＴのゲートはスイッチング素子ＳＷ１のチャネルの他端（ソース）に接続され、この接続点にはコンデンサＣの一方の電極（＋極）が接続されている。電流供給トランジスタＤＴのチャネルの一端（ドレイン）は電流供給線２０３に、その他端（ソース）は有機発光素子ＬＥＤの陽極に接続されている。データ線２０１はデータ駆動回路２０４で駆動され、走査線（ゲート線）２０２は走査駆動回路２０５で駆動される。また、電流供給線２０３は共通電位供給バスライン２０６を通して電流供給回路（ＰＷ）２０７に接続される。
【００３１】
図８において、１つの画素ＰＸが走査線２０２で選択されて、そのスイッチング素子（コントロール・トランジスタ）ＳＷ１がターン・オンすると、データ線２０１から供給される画像信号がコンデンサＣに蓄積される。その後、スイッチング素子ＳＷ１がターン・オフした時点で電流供給トランジスタＤＴがターン・オンし、電流供給線２０３から有機発光素子ＬＥＤに、ほぼ１フレーム期間に亘って電流が流れる。有機発光素子ＬＥＤに流れる電流は電流供給トランジスタＤＴにより調整され、また、電流供給トランジスタＤＴのゲートには、コンデンサＣに蓄積されている電荷に応じた電圧が印加される。これにより、画素ＰＸの発光が制御される。
【００３２】
【発明の効果】
以上説明したように、本発明によれば、発光上部取り出し構造の有機発光素子を共振器構造にすることで、透明封止板の下部（内面）の反射を有効利用でき、有機発光素子の発光の色調調整や単色化、発光ピーク強度のエンハンスの効果が得られる。また、透明封止板を共振器構造に用いることで反射膜やスペーサ、共振器長調整層といった構成部材を発光部を構成する有機薄膜と分離して作製できると言う利点があり、これにより製造プロセスでの有機薄膜へのダメージを回避できるという効果もあり、高輝度の有機発光表示装置を提供することができる。
【図面の簡単な説明】
【図１】本発明による有機発光表示装置の第１実施例を説明する模式断面図である。
【図２】本発明の実施例の効果を有機薄膜の発光スペクトルの差で従来技術と比較して示す説明図である。
【図３】本発明による有機発光表示装置の第２実施例を説明する模式断面図である。
【図４】本発明による有機発光表示装置の第３実施例を説明する模式断面図である。
【図５】本発明による有機発光表示装置の第４実施例を説明する模式断面図である。
【図６】本発明による有機発光表示装置の第５実施例を説明する模式断面図である。
【図７】本発明による有機発光表示装置の第６実施例を説明する模式断面図である。
【図８】本発明の有機波高表示装置の回路構成を説明する等価回路である。
【図９】上部発光取り出し構造の有機発光表示装置の代表的な構造を説明する模式断面図である。
【符号の説明】
１０１・・・基板
１０２・・・金属電極兼全反射鏡
１０３・・・有機薄膜
１０４・・・透明電極
１０５・・・基板間空隙（間隔）
１０６・・・透明封止板
１０７・・・フィラー、スペーサ、又は画素分離壁
１０８・・・高屈折率薄膜
１１０・・・表面薄膜（表面コート薄膜）
１１１・・・共振器長調整層。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a self-luminous display device, and more particularly to an organic light-emitting display device using an organic light-emitting element.
[0002]
[Prior art]
An organic light-emitting device constituting an organic light-emitting display device is a resonator (microresonance) in which a translucent reflector is installed in front of the light-emitting surface of the organic light-emitting device and the optical length of the light traveling back and forth is several times the desired emission wavelength. ), It is possible to make the emission spectrum monochromatic and at the same time enhance the emission peak intensity ("Patent Document 1"). The physical properties related to the resonator structure are described in detail in “Non-Patent Document 1”.
[0003]
FIG. 9 is a schematic cross-sectional view illustrating a typical structure of an organic light emitting display device having an upper light emission extraction structure. In the figure, reference numeral 101 denotes an insulating substrate (hereinafter simply referred to as a substrate), which has a metal electrode / total reflection mirror 102 as a first electrode on the substrate 101, and a hole injection made of an organic material thereon. An organic thin film (also referred to as an organic light emitting layer) 103 including a layer, a light emitting layer, and an electron injection layer is formed, and a plurality of (here, three) transparent electrodes 104 as second electrodes are stacked. Each transparent electrode 104 constitutes a pixel unit that is individually driven by an active element (not shown) such as a thin film transistor.
[0004]
Above the organic thin film 103, a transparent sealing plate 106 that covers the organic thin film 103 and blocks the influence of moisture and gas from the external environment and forms a display surface is provided on the organic thin film 103 with a spacer 107. The air gap 105 is disposed. Light emitted from the organic thin film 103 is emitted from the transparent sealing plate 106 to form a display. In the organic light emitting device having such an upper light emission extraction structure, the transparent sealing plate 106, which is a transparent plate for protecting the organic thin film 103 constituting the organic light emitting layer, is separated by a sufficient distance above the film surface of the organic thin film 103. It was installed.
[0005]
[Patent Document 1]
JP-A-8-213174 [Non-Patent Document 1]
T.A. Nakayama: “Organic luminous devices with a microcavity structure”, included in “Organic electroluminescent materials and devices. Miyata, published by Gorden & Breach Science Publisher (1997).
[0006]
[Problems to be solved by the invention]
In a conventional organic light emitting display device having a resonator structure, the transparent sealing plate for protecting the organic thin film has not been used as a component of the resonator. Further, a part of the emitted light of the organic thin film 103 has reflected lights Lr1 and Lr2 which are reflected by about 5% on the inner surface and the outer surface of the transparent sealing plate 106 respectively, and the amount of the light Lm for display is It is lost by these reflected lights, and causes a reduction in luminance improvement of the display surface. An object of the present invention is to provide a high-luminance organic light-emitting display device by using a light emitting light of an organic thin film efficiently for display by using a transparent sealing plate as a constituent of a resonator.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is characterized in that a microresonator integrated with an organic thin film as a light emitting element is formed by utilizing a light transmission / reflection function of a transparent sealing plate for protecting the organic thin film. Have That is, the present invention relates to direct output light that passes through a transparent sealing plate having a partial reflection function for protecting an organic thin film and directly goes to the upper part, and light that returns to the element side once by reflection of the transparent sealing plate. The light is reflected by a reflective film such as a metal electrode / total reflection mirror provided on the substrate side at the lower part of the substrate, and light is emitted to the upper part of the transparent sealing plate through an optical path different from the direct output light.
[0008]
A structure in which interference occurs between light output from the upper part via another optical path (another optical path light) and direct output light is a necessary requirement. For that purpose, the sum of the optical length difference corresponding to the optical path length shift caused by the optical path and reflection between the direct output light and the separate optical path light is an integral multiple of the emission wavelength of the organic thin film (and the range of coherent creation error) Within).
[0009]
Temporarily, the second electrode provided on the uppermost portion of the organic light-emitting element (organic thin film) on the substrate is made of a transparent electrode ITO (Indium Tin Oxide) using aluminum or the like for the substrate-side reflector (metal electrode and total reflector), If a gap (enclosed with reduced pressure gas or the like) is provided above the transparent electrode ITO, the phase of light shifts by ½ wavelength during reflection on the metal electrode / total reflection mirror. The optical length from the reflective surface to the top of the transparent electrode ITO needs to be any one of 1/4, 3/4, 1, and (2n-1) / 4 times the desired resonance wavelength. Become. Note that n is a natural number. In addition, when a medium having a refractive index larger than that of ITO is put in the gap above the transparent electrode ITO, the phase of the light is shifted by ½ wavelength even in the reflection, so that 2/4, 4/4, 1 It is necessary to be either 2n / 4 times.
[0010]
Furthermore, the reflection at the interface between the upper part of the organic thin film, which is the organic light emitting element on the substrate side, and the gap, and the reflection at the interface between the gap and the surface of the transparent sealing plate for protecting the organic thin film cause reflection of a desired wavelength. In order to achieve this, the relationship between the refractive indexes of the transparent electrode, the gap, the gap (reduced pressure gas, etc.) and the transparent sealing plate for protecting the organic thin film is large-small-large (or small-large-small). When the relationship is satisfied, it is necessary that the optical length of the air gap is 1/4, 3/4, 1 or (2n-1) / 4 times the desired resonance wavelength. In the case of a small-medium-large relationship, it is either 2/4, 4/4, or 1,2n / 4 times.
[0011]
If the surface structure of the transparent sealing plate for protecting the organic thin film only provides a sufficient reflection function, and the reflection on the upper surface of the transparent electrode is sufficiently small relative to the reflection intensity, the reflection plate on the substrate side (also serves as a metal electrode) The optical length from the total reflection mirror) to the surface of the transparent sealing plate for protecting the organic thin film needs to be a resonator length corresponding to a desired wavelength. Note that it is not a requirement that the uppermost portion of the element structure (metal electrode / total reflection mirror 102, organic thin film 103, transparent electrode 104) on the substrate side is a transparent electrode 104, and a transparent material is laminated above the transparent electrode 104. Thus, the uppermost portion of the substrate side element can be obtained. The light emission principle and configuration example of the organic light emitting device having the resonator structure are described in detail in the above-mentioned “Non-Patent Document 1”. The optical length of the resonator can be verified from the angle dependency of light emission and comparison with a sample in which the film thickness of the organic thin film constituting the light emitting element is changed.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic cross-sectional view illustrating a first embodiment of an organic light emitting display device according to the present invention. In FIG. 1, aluminum (Al) having a thickness of 150 nm is formed on a transparent substrate 101 as a metal electrode and total reflection mirror 102, and lithium fluoride (LiF) having a thickness of 0.6 nm is stacked thereon in this order. A laminated film is formed. Further, an electron transport layer ALQ having a thickness of 50 nm is used as the organic thin film 103, a film in which 6% by volume of Ir (ppy) ₃ is mixed in CBP having a thickness of 20 nm as a light emitting layer, and an α-layer having a thickness of 40 nm as a hole injection layer. NPD is formed.
[0013]
In addition, 110 nm thick ITO is formed as the transparent electrode 104 on the upper layer of the organic layer 103. The molecular structure of ALQ constituting the organic thin film is shown in “Chemical Formula 1”, the molecular structure of CBP is shown in “Chemical Formula 2”, and the molecular structure of Ir (ppy) ₃ is shown in “Chemical Formula 3”.
[0014]
[Chemical 1]

[Chemical 2]

[Chemical 3]

[0015]
At this time, the optical distance (optical length) D from the surface of the metal electrode / total reflection mirror 102 to the top of the laminated film structure formed on the substrate is 3 / of the emission peak wavelength 520 nm of Ir (ppy) _3. It has quadrupled. The optical length referred to here is the product of the thickness and refractive index of the laminated film structure.
[0016]
In the organic light emitting display device having the upper light emission extraction structure, a transparent sealing plate 106 is installed to protect the organic thin film that blocks the influence of moisture and gas from the external environment. In this embodiment, the transparent sealing plate 106 is filled with a filler 107 (beads or the like) made of SiO ₂ so as to have an interval of 390 nm, which is an interval of 3/4 times the emission wavelength of the organic thin film 103. The substrate 101 and the transparent sealing plate 106 are bonded together while maintaining a reduced pressure between the substrate 101 and the transparent sealing plate 106 (inter-substrate gap).
[0017]
A glass plate having a thickness of 0.1 mm is used as the transparent sealing plate 106, and the transparent sealing plate maintains a uniform gap with respect to the substrate 101 having the organic thin film structure due to a pressure difference between the outside air and the gap between the substrates. So that it is deformed and brought into close contact. As a result, the reflected light returning to the inside of the thin film structure on the substrate on the outermost surface of the transparent electrode 104 and the reflected light on the inner surface of the transparent sealing plate 106 become coherent at a wavelength of 520 nm, and the reflected light is efficiently converted into the thin film structure. And a minute resonator can be formed between the metal electrode and the total reflection mirror 102. As the transparent sealing plate 106, a flexible material that conforms to the shape of the outermost surface of the substrate 101 under reduced pressure as described above is suitable, and a resin plate or the like can be employed in addition to the glass plate described above.
[0018]
FIG. 2 is an explanatory view showing the effect of the embodiment of the present invention in comparison with the prior art by the difference in the emission spectrum of the organic thin film, where the horizontal axis indicates the emission wavelength (nm) and the vertical axis indicates the emission intensity (relative value). ) As shown in FIG. 2, according to the structure of the present embodiment shown in FIG. 1, the conventional structure in which the distance between the substrate 101 and the transparent sealing plate 106 is pasted at about 1 mm (see FIG. 9). It can be seen that monochromatization of the emission spectrum at 390 nm where resonance occurs and an increase in peak intensity thereof are obtained as compared to the structure). As described above, according to this embodiment, by using the transparent sealing plate 106 as a resonator structure, the light emitted from the organic thin film 103 can be efficiently used for display, and a high-luminance organic light-emitting display device can be obtained. Can be provided.
[0019]
FIG. 3 is a schematic cross-sectional view illustrating a second embodiment of the organic light emitting display device according to the present invention. In the embodiment shown in FIG. 3, in addition to the structure of the first embodiment of the present invention described with reference to FIG. 1, the optical length of the film thickness is 1 at the desired emission wavelength on the inner surface of the transparent sealing plate 106. A reflective layer made of the high refractive index thin film 109 was formed with a film thickness of / 4 times. By providing the high refractive index thin film 109, the number of surfaces contributing to reflection increases, and the optical confinement efficiency of the resonator formed between the substrate 101 and the transparent sealing plate 106 can be increased.
[0020]
As the high refractive index thin film 109, a thin film having a higher refractive index than that of the substrate 101 such as titanium oxide or zirconia oxide is used. The higher the refractive index of the high refractive index thin film 109, the higher the reflectance. Further, the high refractive index thin film 109 can be alternately laminated with a low refractive index thin film to increase the reflectance (refer to the above-mentioned “Non-patent Document 1”). .
[0021]
By forming the reflective layer with the high refractive index thin film 109, the reflectance on the inner surface of the transparent sealing plate 106 becomes sufficiently large. When the effect of reflection at the lower surface of the inter-substrate gap is considered to be insignificant, it is important to set the distance between the inner surface of the transparent sealing plate 106 and the metal electrode / total reflection mirror 102 as a resonance condition. The distance between the inner surface of the transparent sealing plate 106 and the uppermost surface of the laminated structure formed on the substrate 101 is not important.
[0022]
Also, as shown in the embodiment of FIG. 3, the surface having the function of improving the transmission of a desired emission wavelength and preventing the return of incident light from the outside to the user on the upper surface of the transparent sealing plate 106 A thin film (surface-coated thin film) 110 can also be formed. By providing this surface-coated thin film 110, display quality can be further improved. According to the present embodiment, a high-luminance organic light-emitting display device can be provided by efficiently using the light emitted from the organic thin film 103 for display even when the transparent sealing plate 106 is used as a resonator structure. be able to.
[0023]
FIG. 4 is a schematic cross-sectional view illustrating a third embodiment of the organic light emitting display device according to the present invention. In the embodiment shown in FIG. 4, a spacer 107 patterned using PIQ or the like is provided instead of the filler in the embodiment of FIG. 3, and the interval between the substrate 101 and the transparent sealing plate 106 is regulated to a predetermined value. Is. In this embodiment, the spacer 107 is formed on the organic thin film 103 having the substrate 101, but the present invention is not limited to this, and the spacer 107 may be formed on the inner surface of the transparent sealing plate 106. By forming the spacer 107 on the inner surface of the transparent sealing plate 106, damage to the organic thin film 103 during the manufacturing process can be reduced. Also according to the present embodiment, a high-luminance organic light emitting display device can be provided by efficiently using the light emitted from the organic thin film 103 for display even by using the transparent sealing plate 106 as a component of the resonator. Can do.
[0024]
FIG. 5 is a schematic cross-sectional view illustrating a fourth embodiment of the organic light emitting display device according to the present invention. In this embodiment, the uppermost layer of the thin film layer having the transparent sealing plate 106 on the inner surface of the substrate 101 without using the spacer as described above for the interval between the substrate 101 and the transparent sealing plate 106, that is, the interval between the substrates. It is made to adhere to. In order to bring the transparent sealing plate 106 into close contact with the substrate 101, it is effective to reduce the pressure between the transparent sealing plate 106 and the substrate 101. However, as another method, a so-called matching liquid 121 is injected into the gap so that the interface reflection between the transparent electrode 104 and the matching liquid 121 or between the matching liquid 121 and the high refractive index thin film 109 is close to 0, and between the substrates. Unnecessary light reflection caused by non-uniform spacing can be reduced.
[0025]
When the matching liquid 121 having the same refractive index as that of the transparent electrode 104 is used, the lower surface of the high refractive index thin film 109 is used. When the matching liquid 121 having the same refractive index as that of the high refractive index thin film 109 is used, the upper surface of the transparent electrode 104 is changed. It becomes the upper reflective surface of the resonator. When the low refractive index thin film is used instead of the high refractive index thin film 109, the length of the top and bottom surfaces of the resonator is 2nλ instead of (2n−1) λ / 4. / 4.
[0026]
Also according to the present embodiment, a high-luminance organic light emitting display device can be provided by efficiently using the light emitted from the organic thin film 103 for display even by using the transparent sealing plate 106 as a component of the resonator. Can do.
[0027]
FIG. 6 is a schematic sectional view for explaining a fifth embodiment of the organic light emitting display device according to the present invention. The embodiment shown in FIG. 6 is an example of a structure in which, for example, red (R), green (G), and blue (B) pixels have different resonance wavelengths of light as in a full-color display device. . In this embodiment, the resonator length (optical length of the resonator) of each pixel of red (R), green (G), and blue (B) having different wavelengths is adjusted to the wavelength of the corresponding light, respectively. Dr, Dg, and Db were used. In order to adjust the resonator length, the film thickness of the metal electrode / reflecting mirror 102 formed on the substrate 101 was changed. Note that the high refractive index thin film 109 provided on the inner surface of the transparent sealing plate 106 is not essential, and the resonator of each pixel in the case where the high refractive index thin film 109 is not provided is different in thickness from the inner surface of the transparent sealing plate 106. It is formed between the metal electrode and reflecting mirror 102 of the pixel. Further, the formation of the surface coat thin film 110 is optional, but it is desirable to provide it for improving the display quality. According to this embodiment, an optimum resonator structure can be provided for each pixel of red (R), green (G), and blue (B), and light emitted from the organic thin film 103 of each color can be efficiently used for display. A luminance organic light-emitting display device can be provided.
[0028]
FIG. 7 is a schematic cross-sectional view illustrating a sixth embodiment of the organic light emitting display device according to the present invention. The embodiment shown in FIG. 7 is another example in the case of configuring a full-color display device, similarly to the embodiment of FIG. In this embodiment, the resonator length (optical length of the resonator) of each pixel of red (R), green (G), and blue (B) having different wavelengths is adjusted to the wavelength of the corresponding light, respectively. Dr, Dg, and Db were used. In order to adjust the resonator length, a resonator length adjusting layer 108 is provided on the inner surface of the transparent sealing plate 106, and the film thicknesses of red (R), green (G), and blue (B) having different wavelengths are set. This is changed so that the resonator lengths Dr, Dg, Db of the pixel are obtained. The resonator length adjusting layer 108 is preferably made of a material close to the refractive index of the transparent sealing plate 106 in order to reduce the reflectance at the interface with the transparent sealing plate 106. In the case of a glass plate, it is appropriate that the resonator length adjusting layer 108 is made of silicon oxide. Needless to say, any suitable material other than silicon oxide can be used. The formation of the surface coat thin film 110 is optional, but it is desirable to provide it in order to improve display quality. According to this embodiment, an optimum resonator structure can be provided for each pixel of red (R), green (G), and blue (B), and light emitted from the organic thin film 103 of each color can be efficiently used for display. A luminance organic light-emitting display device can be provided.
[0029]
In the sixth embodiment and the seventh embodiment described above, a pixel separation wall 107 is provided to separate red (R), green (G), and blue (B) pixels. The pixel separation wall 107 also functions as a spacer that regulates the distance between the substrate 101 and the transparent sealing plate 106 (inter-substrate distance). However, the filler described with reference to FIG.
[0030]
FIG. 8 is an equivalent circuit for explaining the circuit configuration of the organic wave height display device of the present invention. As shown in FIG. 8, the pixel PX surrounded by the data line 201 (201m + 1, 201m, 201m-1...) And the gate line 202 (201n + 1, 201n, 201n-1. (Control transistor) SW1, current supply transistor (drive transistor) DT, capacitor C, and organic light emitting element LED are arranged. The control electrode (gate) of the switching element SW1 is connected to the gate line 202, and one end (drain) of the channel is connected to the data line 201. The gate of the current supply transistor DT is connected to the other end (source) of the channel of the switching element SW1, and one electrode (+ electrode) of the capacitor C is connected to this connection point. One end (drain) of the channel of the current supply transistor DT is connected to the current supply line 203 and the other end (source) is connected to the anode of the organic light emitting element LED. The data line 201 is driven by the data driving circuit 204, and the scanning line (gate line) 202 is driven by the scanning driving circuit 205. The current supply line 203 is connected to a current supply circuit (PW) 207 through a common potential supply bus line 206.
[0031]
In FIG. 8, when one pixel PX is selected by the scanning line 202 and its switching element (control transistor) SW1 is turned on, the image signal supplied from the data line 201 is accumulated in the capacitor C. After that, when the switching element SW1 is turned off, the current supply transistor DT is turned on, and a current flows from the current supply line 203 to the organic light emitting element LED for almost one frame period. The current flowing through the organic light emitting element LED is adjusted by the current supply transistor DT, and a voltage corresponding to the electric charge accumulated in the capacitor C is applied to the gate of the current supply transistor DT. Thereby, the light emission of the pixel PX is controlled.
[0032]
【The invention's effect】
As described above, according to the present invention, by making the organic light emitting device having the light emitting upper extraction structure into a resonator structure, the reflection of the lower portion (inner surface) of the transparent sealing plate can be effectively used, and the light emission of the organic light emitting device is achieved. Color tone adjustment, monochromatization, and enhancement of emission peak intensity can be obtained. In addition, by using a transparent sealing plate for the resonator structure, there is an advantage that components such as a reflective film, a spacer, and a resonator length adjusting layer can be manufactured separately from the organic thin film that constitutes the light emitting part. There is also an effect that damage to the organic thin film in the process can be avoided, and a high-luminance organic light-emitting display device can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view illustrating a first embodiment of an organic light emitting display device according to the present invention.
FIG. 2 is an explanatory view showing the effect of the embodiment of the present invention in comparison with the prior art by the difference in the emission spectrum of the organic thin film.
FIG. 3 is a schematic cross-sectional view illustrating a second embodiment of the organic light emitting display device according to the present invention.
FIG. 4 is a schematic cross-sectional view illustrating a third embodiment of the organic light emitting display device according to the present invention.
FIG. 5 is a schematic cross-sectional view illustrating a fourth embodiment of the organic light emitting display device according to the present invention.
FIG. 6 is a schematic cross-sectional view illustrating a fifth embodiment of the organic light emitting display device according to the present invention.
FIG. 7 is a schematic cross-sectional view illustrating a sixth embodiment of the organic light emitting display device according to the present invention.
FIG. 8 is an equivalent circuit illustrating a circuit configuration of the organic wave height display device of the present invention.
FIG. 9 is a schematic cross-sectional view illustrating a typical structure of an organic light emitting display device having an upper light emission extraction structure.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 101 ... Substrate 102 ... Metal electrode and total reflection mirror 103 ... Organic thin film 104 ... Transparent electrode 105 ... Inter-substrate gap (interval)
106 ... Transparent sealing plate 107 ... Filler, spacer, or pixel separation wall 108 ... High refractive index thin film 110 ... Surface thin film (surface coat thin film)
111: Resonator length adjustment layer.

Claims

An insulating substrate in which a first electrode, an organic light emitting layer and a transparent second electrode are formed in this order;
A transparent sealing plate installed above the second electrode;
An organic light emitting display device that emits light emitted from the organic light emitting layer from a surface opposite to the transparent sealing plate,
The first electrode has a first reflecting surface that reflects the light emitted from the organic light emitting layer toward the transparent sealing plate,
A second reflecting surface that reflects the light emitted from the organic light emitting layer toward the first reflecting surface of the first electrode on the second electrode side of the transparent sealing plate;
An organic light emitting display device, wherein a resonator structure for light having a predetermined wavelength emitted from the organic light emitting layer is formed between the first reflective surface and the second reflective surface.

2. The organic light emitting device according to claim 1, wherein a resonance condition for light having a predetermined wavelength emitted from the organic light emitting layer is satisfied between the first reflective surface and the second reflective surface. Display device.

The resonance condition is the sum of the optical distance between the first reflecting surface and the second reflecting surface and the length of the phase shift that occurs at the first reflecting surface and the second reflecting surface. The organic light emitting display device according to claim 2, wherein the organic light emitting display device is an integral multiple of a wavelength of the predetermined light.

An insulating substrate in which a first electrode provided in common for a plurality of pixels, an organic light emitting layer and a transparent second electrode provided for each of the plurality of pixels are formed in this order;
A transparent sealing plate installed above the second electrode;
An organic light emitting display device that emits light emitted from the organic light emitting layer from a surface opposite to the insulating substrate of the transparent sealing plate,
The first electrode has a first reflecting surface that reflects the light emitted from the organic light emitting layer toward the transparent sealing plate,
A second reflecting surface that reflects the light emitted from the organic light emitting layer toward the first reflecting surface of the first electrode on the second electrode side of the transparent sealing plate;
A resonator for light of a predetermined wavelength emitted from each organic light emitting layer of each of the plurality of pixels is configured for each pixel between the first reflecting surface and the second reflecting surface. Luminescent display device.

The optical distance between the first reflecting surface and the second reflecting surface corresponding to the plurality of pixels is a resonance condition of light having a predetermined wavelength emitted from each organic light emitting layer of the plurality of pixels. The organic light-emitting display device according to claim 4, wherein the organic light-emitting display device is different depending on the organic light-emitting display device.

The size relationship between the second electrode formed on the insulating substrate, the gap between the first reflecting surface and the second reflecting surface, and the refractive index of the transparent sealing plate is, in order, large-small-large, Or small-large-small
An interval between the transparent sealing plate and the second electrode is an optical distance of 1/4, 3/4, 1, (2n-1) / 4 times (n is a natural number) of a predetermined emission wavelength. The organic light emitting display device according to claim 1, wherein the organic light emitting display device is any one of the above.

The organic light emitting display device according to claim 1, wherein a distance between the second electrode and the transparent sealing plate is zero.

The size relationship between the second electrode formed on the insulating substrate, the gap between the first reflective surface and the second reflective surface, and the refractive index of the transparent sealing plate is large-medium-small in order. Or when small-medium-large
The distance between the transparent sealing plate and the second electrode is an optical distance of 2/4, 2/4, 1 or (2n) / 4 times the predetermined emission wavelength (n is a natural number) The organic light-emitting display device according to claim 1 or 4, wherein