JP4164251B2

JP4164251B2 - Organic EL color display and manufacturing method thereof

Info

Publication number: JP4164251B2
Application number: JP2001334343A
Authority: JP
Inventors: 輝一渡辺
Original assignee: Tohoku Pioneer Corp
Current assignee: Tohoku Pioneer Corp
Priority date: 2001-10-31
Filing date: 2001-10-31
Publication date: 2008-10-15
Anticipated expiration: 2021-10-31
Also published as: JP2003142277A

Description

【０００１】
【発明の属する技術分野】
本発明は、複数の発光色を呈する発光層からる有機ＥＬ（エレクトロルミネッセンス）素子を要素とした有機ＥＬカラーディスプレイ及びその製造方法に関する。
【０００２】
【従来の技術】
有機ＥＬディスプレイは、有機ＥＬ素子を基本要素とするもので、平面基板上に形成された有機ＥＬ素子を点灯又は非点灯することで、画像表示を行うものである。有機ＥＬ素子とは、所定面積の電極を対向配置して、一方を正電圧が印加される陽極、他方を負電圧が印加される陰極とし、この電極間に発光層を含む有機化合物材料層を介在させたものであり、電極間に電圧を印加することで、陰極から電子が、陽極から正孔がそれぞれ発光層に注入され、この発光層中で電子−正孔の再結合が起こることにより発光が生じる面発光素子である。この有機ＥＬ素子を単位面発光要素として平面基板上にマトリクス状に形成し、これをドットマトリクス駆動することにより、高精細な画像が表示できるフラットパネルディスプレイを形成することができる。
【０００３】
また、有機化合物材料の研究によって、色純度の高いＲ，Ｇ，Ｂ各発光色を呈する有機ＥＬ素子が開発されたことを受けて、この各色の素子を画素毎に配設して、フルカラー表示を行う有機ＥＬカラーディスプレイが開発されている。図８は、その素子構造を示す説明図である。
【０００４】
同図において、透明なガラス等から成る基板１上には、ＴＦＴ２が形成されており、更にはＩＴＯ等の透明導電材料からなる透明電極３（陽極）が１つの要素毎に独立して形成されている。この透明電極３間には、ポリイミド等からなる絶縁膜４が形成されている。そして、この透明電極３上に、複数の有機化合物材料層５が形成され、その有機化合物材料層５の上を覆って、Ａｌ等からなる金属電極（陰極）６が形成されている。有機化合物材料層５は、基板１上の透明電極３及び絶縁膜４上に形成される正孔輸送機能層（正孔注入層５１，正孔輸送層５２）、その上に形成される、異なる有機化合物材料によって異なる色を発光する発光層５０Ｂ，５０Ｇ，５０Ｒ、その上に形成される電子輸送機能層（電子輸送層５３，電子注入層５４）からなる。また、破線間の矢印の領域はＲＧＢ各色の発光領域を示している。
【０００５】
このような素子構造からなる有機ＥＬカラーディスプレイにおいては、発光層５２Ｂ，５２Ｇ，５２Ｒから放射して基板１から出射する光として、直接透明電極３を介して基板１から出射する光、金属電極６側に出射して金属電極３の表面で反射されて基板１から出射する光、基板１，透明電極３及び多層化された有機化合物材料層５の各界面で反射して基板１から出射する光が存在し、これらの光が干渉して出力に影響を及ぼすことが知られている。特開平２０００−３２３２７７号公報には、発光層を除く有機化合物材料層の各層を発光色に対応してそれぞれ異なる膜厚に設定し、反射干渉現象を利用することで各色取り出し光の高効率化を図ることが記載されている。
【０００６】
上述の説明では、アクティブマトリクス型の有機ＥＬカラーディスプレイを例にして説明したが、単純マトリクス（パッシブ）型の有機ＥＬカラーディスプレイも、素子構造自体には大きな違いはなく、同様に反射干渉現象を利用した出力の高効率化が図られている。
【０００７】
【発明が解決しようとする課題】
前述の特開平２０００−３２３２７７号公報に記載されたものでは、透明電極の膜厚を一定にすることを前提としているので、有機化合物材料層と透明電極との境界で反射する反射光を対象とした反射干渉現象と、透明電極と基板との境界で反射する反射光を対象にした反射干渉現象とを共に考慮した取り出し光の高効率化ができないという問題がある。また、発光層を除いた有機化合物材料層を各色に対応して異なる膜厚に設定しているが、有機化合物材料層の膜厚は、本来その機能を充分に発揮するために設定されるべきものであり、この膜厚を反射干渉現象を考慮して設定した場合には、各色発光層の電圧輝度効率が低下してしまう問題があった。
【０００８】
更には、発光層を除いた有機化合物材料層である正孔輸送機能層及び電子輸送機能層は一般には各色に拘わらず各機能毎に同じ材料で且つ均一な膜厚とすることがなされており、この各機能層の膜厚を各色毎に異なる膜厚にすると生産性が悪化する問題が生じる。
【０００９】
本発明は、このような事情に対処するために提案されたものであって、各種の反射光を考慮して取り出し光の高効率化を達成することができると共に、発光層を除いた有機化合物材料層はその機能に応じた膜厚を設定することができ、また良好な生産性を確保できる有機ＥＬカラーディスプレイ及びその製造方法を提供することを目的とするものである。
【００１０】
【課題を解決するための手段】
上記目的を達成するために、本発明の有機ＥＬカラーディスプレイ又はその製造方法は、以下の特徴を具備するものである。
【００１１】
一つには、透明電極と少なくとも発光層を含む複数の有機化合物材料層と金属電極とを透明基板上に順次積層してなる有機ＥＬ素子を要素として、異なる有機化合物材料によって異なる発光色を呈する前記発光層からなる前記有機ＥＬ素子を複数配列してなる有機ＥＬカラーディスプレイにおいて、前記透明電極は、発光色に対応した異なる膜厚を有し、前記発光層を除く前記有機化合物材料層のうちで同一機能を有するいずれかの機能層の少なくとも一層が一定膜厚を有し、前記各有機ＥＬ素子の前記透明電極と前記有機化合物材料層は、波長λを中心波長として発光する前記発光層の発光界面から前記透明電極と前記透明基板との境界までの光学距離がλ／４の偶数倍と略等しくなるような膜厚で、成膜されていることを特徴とする。
【００１２】
また一つには、透明電極と少なくとも発光層を含む複数の有機化合物材料層と金属電極とを透明基板上に順次積層してなる有機ＥＬ素子を要素として、異なる有機化合物材料によって異なる発光色を呈する前記発光層からなる前記有機ＥＬ素子を複数配列してなる有機ＥＬカラーディスプレイにおいて、前記透明電極は、発光色に対応した異なる膜厚を有し、前記発光層を除く前記有機化合物材料層のうちで同一機能を有するいずれかの機能層の少なくとも一層が一定膜厚を有し、前記各有機ＥＬ素子の前記透明電極と前記有機化合物材料層は、波長λを中心波長として発光する前記発光層の発光界面から前記透明電極と前記透明基板との境界までの光学距離がλ／４の偶数倍と略等しく、且つ前記発光層の発光界面から前記金属電極と前記有機化合物材料層との境界までの光学距離がλ／４の奇数倍と略等しくなるような膜厚で、成膜されていることを特徴とする。
【００１３】
また一つには、前述の特徴に併せて、前記発光層の発光界面から前記有機化合物材料層と前記透明電極との境界までの光学距離がλ／４の奇数倍と略等しくなるような膜厚で、前記有機化合物材料層が成膜されていることを特徴とする。
【００１４】
また一つには、透明電極と少なくとも発光層を含む複数の有機化合物材料層と金属電極とを透明基板上に順次積層してなる有機ＥＬ素子を要素として、異なる有機化合物材料によって異なる発光色を呈する前記発光層からなる前記有機ＥＬ素子を複数配列してなる有機ＥＬカラーディスプレイにおいて、前記透明電極は、発光色に対応した異なる膜厚を有し、前記発光層を除く前記有機化合物材料層のうちで同一機能を有するいずれかの機能層の少なくとも一層が一定膜厚を有し、前記各有機ＥＬ素子の前記透明電極と前記有機化合物材料層は、波長λを中心波長として発光する前記発光層の発光界面から前記透明電極と前記有機化合物材料層との境界までの光学距離、前記発光層の発光界面から前記金属電極と前記有機化合物材料層との界面までの光学距離、且つ前記透明電極の前記有機化合物材料層との界面と前記透明基板の前記透明電極との界面までの光学距離がλ／４と略等しくなるような膜厚で、成膜されていることを特徴とする。
【００１５】
また一つには、屈折率ｎ３，膜厚ｄ３である透明電極、少なくとも屈折率ｎ１，膜厚ｄ１である電子輸送層、屈折率ｎ２，膜厚ｄ２である正孔輸送層、発光層を含む複数の有機化合物材料層と金属電極とを透明基板上に順次積層してなる有機ＥＬ素子を要素として、異なる有機化合物材料によって異なる発光色を呈する前記発光層からなる前記有機ＥＬ素子を複数配列してなる有機ＥＬカラーディスプレイにおいて、前記透明電極は、発光色に対応した異なる膜厚を有し、前記発光層を除く前記有機化合物材料層のうちで同一機能を有するいずれかの機能層の少なくとも一層が一定膜厚を有し、異なる発光色を呈する前記有機ＥＬ素子毎に、波長λを各発光色の中心波長として各発光層の発光界面から前記金属電極と前記有機化合物材料層との境界までの光学距離（ｎ１・ｄ１）、各発光層の発光界面から前記透明電極と前記有機化合物材料層との界面までの光学距離（ｎ２・ｄ２）、且つ前記透明電極の前記有機化合物材料層の界面と前記透明基板の前記透明電極との界面までの光学距離（ｎ３・ｄ３）がλ／４と略等しくなるような膜厚で成膜されていることを特徴とする。
【００１６】
また一つには、透明電極と少なくとも発光層を含む複数の有機化合物材料層と金属電極とを透明基板上に順次積層してなる有機ＥＬ素子を要素として、異なる有機化合物材料によって異なる発光色を呈する前記発光層からなる前記有機ＥＬ素子を複数配列してなる有機ＥＬカラーディスプレイの製造方法において、前記透明電極を発光色に対応してそれぞれ異なる膜厚に成膜する工程を有すると共に、前記有機ＥＬ素子のすべてについて、同一の有機化合物材料からなる連続した一定膜厚を有する共通層を積層する共通積層工程を少なくとも１工程以上有し、波長λを中心波長として発光する前記発光層の発光界面から前記透明電極と前記透明基板との境界までの光学距離がλ／４の偶数倍と略等しくなるような膜厚で、前記有機化合物材料層と前記透明電極が成膜されることを特徴とする。
【００１７】
透明電極と少なくとも発光層を含む複数の有機化合物材料層と金属電極とを透明基板上に順次積層してなる有機ＥＬ素子を要素として、異なる有機化合物材料によって異なる発光色を呈する前記発光層からなる前記有機ＥＬ素子を複数配列してなる有機ＥＬカラーディスプレイの製造方法において、前記透明電極を発光色に対応してそれぞれ異なる膜厚に成膜する工程を有すると共に、前記有機ＥＬ素子のすべてについて、同一の有機化合物材料からなる連続した一定膜厚を有する共通層を積層する共通積層工程を少なくとも１工程以上有し、波長λを中心波長として発光する前記発光層の発光界面から前記透明電極と前記透明基板との境界までの光学距離がλ／４の偶数倍と略等しく、且つ前記発光層の発光界面から前記金属電極と前記有機化合物材料層との境界までの光学距離がλ／４の奇数倍と略等しくなるような膜厚で、前記有機化合物材料層と透明電極が成膜されていることを特徴とする。
【００１８】
また一つには、前記発光層の発光界面から前記有機化合物材料層と前記透明電極との境界までの光学距離がλ／４の奇数倍と略等しくなるような膜厚で、前記有機化合物材料層が成膜されていることを特徴とする。
【００２８】
前記各請求項に係る発明は以下の作用を奏するものである。
【００２９】
本発明によると、透明電極の膜厚を発光色に対応させて異なる膜厚に設定することにより、有機化合物材料層と透明電極との境界で反射する反射光と、透明電極と基板との境界で反射する反射光との両方を考慮して、取り出し光の干渉による高効率化を設定することができる。また、透明電極のみによって干渉による高効率化を達成する場合には、有機化合物材料層の各機能層は、各機能の応じた膜厚又は生産性を考慮に入れた均一な膜厚とすることが可能になる。これによって、生産性又は発光層の発光効率の最適化を図りながら、取り出し光の高効率化を達成することが可能になる。
【００３０】
特に、有機化合物材料層の各機能層の少なくとも一層を、ディスプレイの全面において一定膜厚とするか又は同一の有機化合物材料により形成することにより、生産性の向上を図ることが可能になる。この一定膜厚又は同一材料の機能層としては、発光層から陽極側に積層された正孔輸送層或いは正孔注入層、又は発光層から陰極側に積層された電子輸送層とすることができる。
【００３１】
また、発光層から放射して透明電極と透明基板との境界で反射して再び発光層側に戻る光を対象にした反射干渉現象を考慮して取り出し光の高効率化を達成することができる。
【００３２】
また、発光層から放射して透明電極と透明基板との境界で反射して再び発光層側に戻る光及び発光層から後面方向に放射して金属電極の界面で反射して前面基板側に向けられる光を対象とした反射干渉現象を考慮して取り出し光の高効率化を達成することができる。
【００３３】
また、発光層から放射して有機化合物材料層と透明電極との境界で反射して再び発光層側に戻る光を対象にした反射干渉現象を考慮して、取り出し光の高効率化を達成することができる。
【００３４】
【発明の実施の形態】
以下、本発明の実施形態を図面を参照して説明する。図１は本発明の有機ＥＬカラーディスプレイにおける第１の実施形態を示す説明図である。図はＲＧＢ各色の発光領域における層構造を示している。この実施形態は、各色の有機化合物材料層及び透明電極の膜厚を全て光学膜厚としたものである。有機ＥＬカラーディスプレイは複数の有機ＥＬ素子を要素としており、各々の有機ＥＬ素子は、異なる有機化合物材料によって異なる発光色を呈する発光層を備えており、各色の有機ＥＬ素子が複数配列して有機ＥＬカラーディスプレイを形成している。そして、各有機ＥＬ素子は、透明なガラス等から成る基板１、その上に形成されたＩＴＯ等の透明電極３、有機化合物材料層５を形成する正孔輸送機能層５Ａ，発光層５０Ｒ（５０Ｇ，５０Ｂ），電子輸送機能層５Ｂ、及びＡｌ等から成る金属電極６から構成され、この金属電極６が図示省略したＳｉＮ₄等から成る封止材で覆われている。
【００３５】
各有機ＥＬ素子において、独立して別個に積層された発光層５０Ｒ，５０Ｇ，５０Ｂはそれぞれ電流印加時に異なる発光色の赤，緑，青を呈する異なる有機化合物材料から成っており、有機ＥＬカラーディスプレイは、赤，緑及び青の発光色の有機ＥＬ素子の組を一つの画素として、例えば、これら複数画素をマトリクス配列することによりカラー表示を行うものである。
【００３６】
まず、図２によって、有機ＥＬ素子における反射干渉現象について説明する。ここで、電子輸送機能層５Ｂ，正孔輸送機能層５Ａ，透明電極３はそれぞれｎ１，ｎ２，ｎ３の屈折率を有し、各膜厚がｄ１，ｄ２，ｄ３であるとする。そして、基板１の屈折率をｎ４とすると、ｎ１≒ｎ２＜ｎ３＞ｎ４の関係にあるとする。
【００３７】
この場合に、反射干渉現象の対象として考慮すべき光の態様は、発光層５０の発光界面５０ａ（発光層５０と正孔輸送機能層５Ａとの界面を発光界面とする。）から前面に放射される光ａ、発光界面５０ａから後面に放射される光ａ’、発光界面５０ａから後面に放射されて金属電極の界面で反射する光ｂ、発光界面５０ａから前面に放射されて正孔輸送機能層５Ａと透明電極３との境界で反射して再び発光界面５０ａに戻る光ｃ、発光界面５０ａから前面に放射されて透明電極３と基板１との境界で反射して再び発光界面５０ａに戻る光ｄとなる。実際上の発光領域は素子構造や使用する有機化合物材料に大きく依存するが、発光層５０と正孔輸送機能層５Ａとの界面から数〜数十ｎｍに分布していると考えられるので、前述の発光界面５０ａを定義して、そこからの光学距離によって反射干渉現象を検討するものとする。
【００３８】
そして、波長λの光ａと光ｂが強め合う条件は（１）式のとおり、すなわち、波長λを中心波長として発光する発光層の発光界面５０ａから金属電極６の界面までの光学距離ｎ１・ｄ１がλ／４の奇数倍である。
【００３９】
【数１】

【００４０】
また、波長λの光ａ’と光ｄが強め合う条件は（２）式のとおり、すなわち、波長λを中心波長として発光する発光層の発光界面５０ａから透明電極３と基板１との境界までの光学距離（ｎ２・ｄ２＋ｎ３・ｄ３）がλ／４の偶数倍である。
【００４１】
【数２】

【００４２】
更に、中心波長λの光ａ’と光ｃが強め合う条件は（３）式のとおり、すなわち、波長λを中心波長として発光する発光層の発光界面５０ａから有機化合物材料層５と透明電極３との境界までの光学距離（ｎ２・ｄ２）がλ／４の奇数倍である。
【００４３】
【数３】

【００４４】
したがって、（１）〜（３）式を全て満足する光学距離の関係は、以下のとおりである。
【００４５】
【数４】

【００４６】
【数５】

図１の実施形態では、ＲＧＢの各色における電子輸送機能層５Ｂ，正孔輸送機能層５Ａ，透明電極３に対して、ＲＧＢに相当する中心波長（λ_Ｒ＝６５０ｎｍ，λ_Ｇ＝５２０ｎｍ，λ_Ｂ＝４６０ｎｍ）からλ_Ｒ／４，λ_Ｇ／４，λ_Ｂ／４を求めて（５）式より各層の光学距離を以下のように設定している。
【００４７】
【数６】

【００４８】
ここで、透明電極３（ＩＴＯ）の各色毎の屈折率は、ｎ３（λ_Ｒ）＝１.８１，ｎ３（λ_Ｇ）＝１.９４，ｎ４（λ_Ｂ）＝２.００であるから、透明電極３の各色毎の膜厚（ｎｍ）は、ｄ３（λ_Ｒ）＝９０，ｄ３（λ_Ｇ）＝６７，ｄ４（λ_Ｂ）＝５８となる。このように透明電極３の各色における膜厚ｄ３を発光色に対応した異なる厚さにすることで、（１）〜（３）式を全て満たして、考慮した全ての光が互いに強め合うような設定が可能になり、各色発光層から放射した光を最も効率よく取り出すことができる。
【００４９】
［設定例１］電子輸送機能層をＡｌｑ、正孔輸送機能層をＮＰＢ、透明電極をＩＴＯ、基板をＡＳガラスとして、図１の実施形態における設定例を以下に示す。ここでｎ１〜ｎ４は各波長（λ_Ｒ＝６５０ｎｍ，λ_Ｇ＝５２０ｎｍ，λ_Ｂ＝４６０ｎｍ）における屈折率の実測値を示している。
【００５０】
【表１】

【００５１】
次に、本発明の有機ＥＬカラーディスプレイの第２の実施形態を図３を参照して説明する（以下の各実施形態において、前述の実施形態と同一の部位には同一の符号を付して一部説明を省略する。また、図はＲＧＢ各色の発光領域における層構造を示しており、発光層を図示省略している。）。この実施形態は、発光界面５０ａから前面に放射されて正孔輸送機能層５Ａと透明電極３との境界で反射して再び発光界面５０ａに戻る光ｃを無視して、反射光としては、発光界面５０ａから後面に放射されて金属電極の界面で反射する光ｂ及び発光界面５０ａから前面に放射されて透明電極３と基板１との境界で反射して再び発光界面５０ａに戻る光ｄのみを考慮したものである。
【００５２】
以下に、前述の設定例１における各層境界（電子輸送機能層；Ａｌｑ，正孔輸送機能層；ＮＰＢ，透明電極；ＩＴＯ，基板；ＡＳガラス）での電界振幅反射率の実測値を示す。
【００５３】
【表２】

【００５４】
この表から明らかなように、実際には、有機化合物材料層間又は有機化合物材料層と透明電極３との境界での反射率は、透明電極３と基板１との境界における反射率と比較するとかなり小さく、前者の反射光を無視することは実用上問題にならない。したがって、前述の（１）式と（２）式のみ、すなわち、波長λを中心波長として発光する発光層の発光界面５０ａから透明電極３と基板１との境界までの光学距離（ｎ２・ｄ２＋ｎ３・ｄ３）がλ／４の偶数倍であり、且つ発光界面５０ａから金属電極６の界面までの光学距離ｄ１がλ／４の奇数倍となる関係から、ｍ＝１として以下の関係を得る。
【００５５】
【数７】

【００５６】
ここで、ｄ２とｄ３については、例えば各色で駆動電圧をそろえるように膜厚設定を行う。すなわち、正孔輸送機能層を厚く形成し、透明電極を薄くすると、電流輝度特性は変わらないが電圧輝度特性は劣化するので、これを利用して、駆動条件が各色毎に同じになるように正孔輸送機能層ｄ２の膜厚を設定することができる。そして、透明電極膜厚ｄ３を各色毎に異なる値とすることで（７）式を満足することが可能になり、実用的な取り出し光の高効率化も併せて達成することができるものである。
【００５７】
次に、本発明の有機ＥＬカラーディスプレイにおける第３の実施形態を図４によって説明する。この実施形態では、図３の実施形態と同様に有機化合物材料層間の反射及び有機化合物材料層と透明電極との境界での反射を無視して、（１）式と（２）式のみからｎ１・ｄ１＝λ／４、ｎ２・ｄ２＋ｎ３・ｄ３＝λ／２の条件を求め、これに対して、正孔輸送機能層５Ａの膜厚ｄ２を各色共通の一定値として設定したものである。これによると、透明電極３膜形成後に正孔輸送機能層５Ａをパネル一面に一様に形成することができるので生産性の向上を図ることができる。正孔輸送機能層５ＡはＮＰＢ等の単一材料からなる正孔輸送層の単層であっても良いし、正孔輸送層と透明電極との間にＣｕＰＣ等から成る単一材料の正孔注入層を積層させたものでもよい。
【００５８】
［設定例２］電子輸送機能層をＡｌｑ、正孔輸送機能層をＮＰＢ、透明電極をＩＴＯ、基板をＡＳガラスとして、図４の実施形態における設定例を以下に示す。ここでｎ１〜ｎ４は各波長（λ_Ｒ＝６５０ｎｍ，λ_Ｇ＝５２０ｎｍ，λ_Ｂ＝４６０ｎｍ）における屈折率の実測値を示している。
【００５９】
【表３】

【００６０】
次に、本発明の有機ＥＬカラーディスプレイにおける第４の実施形態を図５によって説明する。この実施形態においては、透明電極３、正孔輸送機能層５Ａについては図４の実施形態と同様であり、陰極側の電子輸送機能層５Ｂの膜厚ｄ１を各色共通の一定値として設定したものである。この場合には、膜厚ｄ１を各色共通の一定値にすることにより、前述の（１）式を全ての色において満足することはできなくなる。したがって、特定の色のみで（１）式を満足させた膜厚ｄ１を設定すると共に、透明電極３の膜厚ｄ３を各色毎に異なる値に設定し、（２）式を満足するように正孔輸送機能層５Ａの膜厚ｄ２を設定する。これによると、実用的に取り出し光の高効率化を達成しながら、正孔輸送機能層５Ａと電子輸送機能層５Ｂを共に一定膜厚とすることで、更に生産性の向上を図ることができる。この際の電子輸送機能層５Ｂは、Ａｌｑ等からなる単一材料の電子輸送層の単層であっても良いし、電子輸送層と金属電極６との間にＬｉ₂Ｏ等から成る単一材料の電子注入層を積層させたものでもよい。
【００６１】
［設定例３］電子輸送機能層をＡｌｑ、正孔輸送機能層をＮＰＢ、透明電極をＩＴＯ、基板をＡＳガラスとして、図５の実施形態における設定例を以下に示す。ここでｎ１〜ｎ４は各波長（λ_Ｒ＝６５０ｎｍ，λ_Ｇ＝５２０ｎｍ，λ_Ｂ＝４６０ｎｍ）における屈折率の実測値を示している。
【００６２】
【表４】

【００６３】
以下に、本発明に係る有機ＥＬカラーディスプレイの製造方法を説明する。図６において、まず、同図（ａ）に示すように、それぞれＩＴＯからなるＲＧＢ用の透明電極３をガラス基板１上に形成する。透明電極の膜厚ｄ３は表４に示すようにＲＧＢの各発光色に対応して異なる値となるように予め設定されており、各色毎のマスクを用いて蒸着時間を各色毎に設定して所望の膜厚を形成する。
【００６４】
次に同図（ｂ）に示すように、真空蒸着等によって正孔輸送機能層５Ａを透明電極３の上に一様に形成する。この正孔輸送機能層５Ａは前述のようにＮＰＢの単層であってもよいし、正孔注入層としてＣｕＰＣ等の単層を積層した後のＮＰＢを積層するようにしてもよい。いずれにしても、この正孔輸送機能層５Ａの形成は、同一の有機化合物材料からなる連続した一定膜厚を有する共通層を積層する工程とする。
【００６５】
次に同図（ｃ）に示すように、各色毎に発光層５０を形成し、更にその上に真空蒸着等によって電子輸送機能層５Ｂを一様に形成する。この電子輸送機能層５Ｂは前述のようにＡｌｑの単層であってもよいし、この単層を積層した後に電子注入層としてＬｉ_２Ｏ等の単層を積層するようにしてもよい。いずれにしても、この電子輸送機能層５Ｂの形成は、同一の有機化合物材料からなる連続した一定膜厚を有する共通層を積層する工程とする。そして、同図（ｄ）に示すように、電子輸送機能層５Ｂ上にＡｌ−Ｌｉ等の低仕事関数の金属電極６を蒸着又はスパッタ等の手段で成膜し、更にその上を図示省略した封止材で覆う。
【００６６】
この製造方法によると、透明電極３の形成工程はマスク等を用いた各色毎に膜厚を設定する煩雑な工程を要するが、その後の成膜工程を簡略化することが可能になる。特に、基板上に透明電極３を形成した状態で資材を流通させることを考えると、ディスプレイの生産性を著しく向上させることが可能になる。
【００６７】
そして、正孔輸送機能層５Ａ及び電子輸送機能層５Ｂを表４の膜厚ｄ２及び膜厚ｄ１となるように設定することで、実用的に有効な範囲で反射干渉現象による取り出し光の高効率化を達成することも可能になる。
【００６８】
図７は、本発明に係る有機ＥＬカラーディスプレイの製造方法における他の実施形態を示す説明図である。これは、各色取り出し光の高効率化を最も重要視した［設定例１］を得るための実施形態である。まず、同図（ａ）に示すように、それぞれＩＴＯからなるＲＧＢ用の透明電極３をガラス基板１上に膜厚ｄ３が表１に示す値となるように形成する。そして、この透明電極３上に正孔輸送機能層の共通層５Ａ’を同一の有機化合物材料からなる連続した一定膜厚で形成する。この共通層５Ａ’の膜厚は、表１におけるｄ２の最小値（５９ｎｍ）に設定されている。
【００６９】
次に同図（ｂ）に示すように、Ｒ及びＧに対して正孔輸送機能層を必要な厚さだけ付加して、ＲＧＢ各色の膜厚ｄ２が表１に示す値になるように、正孔輸送機能層５Ａを形成する。更に同図（ｃ）に示すように、各色毎の発光層５０を形成した後、電子輸送機能層の共通層５Ｂ’を同一の有機化合物材料からなる連続した一定膜厚で形成する。この共通層５Ｂ’の膜厚は、表１におけるｄ１の最小値（６２ｎｍ）に設定されている。
【００７０】
そして、同図（ｄ）に示すように、Ｒ及びＧに対して電子輸送機能層を必要な厚さだけ付加して、ＲＧＢ各色の膜厚ｄ１が表１に示す値になるように、電子輸送機能層５Ｂを形成する。以下、前述の実施形態と同様に電子輸送機能層５Ｂ上に金属電極６を成膜し、更にその上を封止材で覆う。また、この実施形態においても、前述の実施形態と同様に、正孔輸送機能層５ＡはＮＰＢ等の単層であってもよいし、正孔注入層としてＣｕＰＣ等の単層を積層した後のＮＰＢを積層するようにしてもよく、電子輸送機能層５Ｂは、Ａｌｑ等の単層であってもよいし、この単層を積層した後に電子注入層としてＬｉ_２Ｏ等の単層を積層するようにしてもよい。
【００７１】
この製造方法によると、前述の（１）〜（３）式を全て満足する膜厚の設定をすることで、各色の取り出し光を最大限高効率化することが可能になると共に、有機化合物材料層の形成に際して共通層を先に形成して、その後に各色の層を付加するようにしたので、膜形成の時間を短縮化することが可能になり、生産性の向上を図ることができる。
【００７２】
【発明の効果】
本発明は、このように構成されるので、各種の反射光を考慮して取り出し光の高効率化を達成することができると共に、発光層を除いた有機化合物材料層はその機能に応じた膜厚を設定することができ、また良好な生産性を確保することができる。
【図面の簡単な説明】
【図１】本発明の有機ＥＬカラーディスプレイにおける実施形態を示す説明図である。
【図２】有機ＥＬ素子における反射干渉現象を説明する説明図である。
【図３】本発明の有機ＥＬカラーディスプレイにおける実施形態を示す説明図である。
【図４】本発明の有機ＥＬカラーディスプレイにおける実施形態を示す説明図である。
【図５】本発明の有機ＥＬカラーディスプレイにおける実施形態を示す説明図である。
【図６】本発明の有機ＥＬカラーディスプレイの製造方法における実施形態を示す説明図である。
【図７】本発明の有機ＥＬカラーディスプレイの製造方法における実施形態を示す説明図である。
【図８】従来の有機ＥＬカラーディスプレイの素子構造を示す説明図である。
【符号の説明】
１基板
２ＴＦＴ
３透明電極
４絶縁膜
５有機化合物材料層
５Ａ正孔輸送機能層
５Ｂ電子輸送機能層
５０発光層
６金属電極[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an organic EL color display having an organic EL (electroluminescence) element composed of a light emitting layer exhibiting a plurality of emission colors as an element and a method for manufacturing the same.
[0002]
[Prior art]
An organic EL display has an organic EL element as a basic element, and displays an image by turning on or off an organic EL element formed on a flat substrate. An organic EL element is an organic compound material layer including a light emitting layer between electrodes, with electrodes of a predetermined area facing each other, one being an anode to which a positive voltage is applied and the other being a cathode to which a negative voltage is applied. When a voltage is applied between the electrodes, electrons are injected from the cathode and holes from the anode are injected into the light-emitting layer, and electron-hole recombination occurs in the light-emitting layer. It is a surface light emitting element that emits light. A flat panel display capable of displaying a high-definition image can be formed by forming the organic EL element as a unit surface light-emitting element in a matrix on a flat substrate and driving it in a dot matrix.
[0003]
Further, in response to the development of organic EL elements that exhibit R, G, and B emission colors with high color purity through research on organic compound materials, each color element is arranged for each pixel to provide a full color display. An organic EL color display has been developed. FIG. 8 is an explanatory view showing the element structure.
[0004]
In the figure, a TFT 2 is formed on a substrate 1 made of transparent glass or the like, and a transparent electrode 3 (anode) made of a transparent conductive material such as ITO is formed independently for each element. ing. An insulating film 4 made of polyimide or the like is formed between the transparent electrodes 3. A plurality of organic compound material layers 5 are formed on the transparent electrode 3, and a metal electrode (cathode) 6 made of Al or the like is formed so as to cover the organic compound material layer 5. The organic compound material layer 5 is formed on the hole transport function layer (hole injection layer 51, hole transport layer 52) formed on the transparent electrode 3 and the insulating film 4 on the substrate 1 and different from each other. It comprises

light emitting layers

50B, 50G, and 50R that emit different colors depending on the organic compound material, and an electron transport function layer (electron transport layer 53 and electron injection layer 54) formed thereon. Moreover, the area | region of the arrow between broken lines has shown the light emission area | region of each color of RGB.
[0005]
In the organic EL color display having such an element structure, the light emitted from the substrate 1 through the transparent electrode 3 as the light emitted from the light emitting layers 52B, 52G, 52R and emitted from the substrate 1, the metal electrode 6 Light emitted to the side and reflected from the surface of the metal electrode 3 and emitted from the substrate 1, light reflected from each interface of the substrate 1, the transparent electrode 3, and the multilayered organic compound material layer 5 and emitted from the substrate 1 It is known that these lights interfere and affect the output. In JP-A-2000-323277, the organic compound material layers excluding the light emitting layer are set to have different film thicknesses corresponding to the light emission colors, and the reflection interference phenomenon is used to increase the efficiency of each color extraction light. Is described.
[0006]
In the above description, the active matrix type organic EL color display has been described as an example. However, the simple matrix (passive) type organic EL color display has no significant difference in the element structure itself, and similarly exhibits a reflection interference phenomenon. The efficiency of the used output is improved.
[0007]
[Problems to be solved by the invention]
In the above-described Japanese Patent Application Laid-Open No. 2000-323277, it is assumed that the film thickness of the transparent electrode is constant, so that the reflected light reflected at the boundary between the organic compound material layer and the transparent electrode is targeted. Therefore, there is a problem in that it is impossible to increase the efficiency of the extracted light in consideration of both the reflected interference phenomenon and the reflected interference phenomenon for the reflected light reflected at the boundary between the transparent electrode and the substrate. In addition, the organic compound material layer excluding the light emitting layer is set to have a different film thickness corresponding to each color. However, the film thickness of the organic compound material layer should be originally set in order to fully exhibit its function. However, when this film thickness is set in consideration of the reflection interference phenomenon, there is a problem that the voltage luminance efficiency of each color light emitting layer is lowered.
[0008]
Furthermore, the hole transporting functional layer and the electron transporting functional layer, which are organic compound material layers excluding the light emitting layer, are generally made of the same material and uniform film thickness for each function regardless of the color. When the film thickness of each functional layer is made different for each color, there arises a problem that productivity is deteriorated.
[0009]
The present invention has been proposed in order to cope with such a situation, and can achieve high efficiency of extracted light in consideration of various reflected light, and an organic compound excluding a light emitting layer An object of the material layer is to provide an organic EL color display capable of setting a film thickness according to its function and ensuring good productivity, and a manufacturing method thereof.
[0010]
[Means for Solving the Problems]
  To achieve the above objective,The organic EL color display of the present invention or the manufacturing method thereof has the following characteristics.
[0011]
  For one thing, an organic EL element formed by sequentially laminating a transparent electrode, a plurality of organic compound material layers including at least a light-emitting layer, and a metal electrode on a transparent substrate as an element exhibits different emission colors depending on different organic compound materials. In an organic EL color display formed by arranging a plurality of the organic EL elements composed of the light emitting layer,The transparent electrode has a different film thickness corresponding to the emission color,At least one of the functional layers having the same function among the organic compound material layers excluding the light emitting layer has a constant film thickness, and the transparent electrode and the organic compound material layer of each organic EL element are: The optical distance from the light emitting interface of the light emitting layer that emits light having the wavelength λ as the central wavelength to the boundary between the transparent electrode and the transparent substrate is formed so as to be substantially equal to an even multiple of λ / 4. It is characterized by being.
[0012]
  Also, for one element, an organic EL element in which a transparent electrode, a plurality of organic compound material layers including at least a light emitting layer, and a metal electrode are sequentially laminated on a transparent substrate is used as an element. In the organic EL color display formed by arranging a plurality of the organic EL elements including the light emitting layer to be exhibited, the transparent electrode has a different film thickness corresponding to a light emission color, and the organic compound material layer excluding the light emitting layer Among them, at least one of the functional layers having the same function has a certain film thickness, and the transparent electrode and the organic compound material layer of each organic EL element emit light having a wavelength λ as a central wavelength. The optical distance from the light emitting interface to the boundary between the transparent electrode and the transparent substrate is substantially equal to an even multiple of λ / 4, and from the light emitting interface of the light emitting layer to the metal electrodeAnd the organic compound material layerThe film thickness is such that the optical distance is approximately equal to an odd multiple of λ / 4.
[0013]
  In addition, in addition to the above-described characteristics, a film in which an optical distance from a light emitting interface of the light emitting layer to a boundary between the organic compound material layer and the transparent electrode is substantially equal to an odd multiple of λ / 4. Thick, said organic compound materiallayerIs formed into a film.
[0014]
  Also, for one element, an organic EL element in which a transparent electrode, a plurality of organic compound material layers including at least a light emitting layer, and a metal electrode are sequentially laminated on a transparent substrate is used as an element. In the organic EL color display formed by arranging a plurality of the organic EL elements including the light emitting layer to be exhibited, the transparent electrode has a different film thickness corresponding to a light emission color, and the organic compound material layer excluding the light emitting layer Among them, at least one of the functional layers having the same function has a certain film thickness, and the transparent electrode and the organic compound material layer of each organic EL element emit light having a wavelength λ as a central wavelength. From the light emitting interface of the transparent electrode and theOrganic compound material layerThe optical distance to the boundary with the metal electrode from the light emitting interface of the light emitting layerAnd the organic compound material layerAnd the organic compound of the transparent electrode.materialThe interface with the layer and saidTransparentThe film is formed in such a film thickness that the optical distance to the interface with the transparent electrode of the substrate is substantially equal to λ / 4.
[0015]
  One of them includes a transparent electrode having a refractive index n3 and a film thickness d3, at least an electron transport layer having a refractive index n1 and a film thickness d1, a hole transport layer having a refractive index n2 and a film thickness d2, and a light emitting layer. A plurality of the organic EL elements composed of the light-emitting layers exhibiting different emission colors depending on different organic compound materials are arranged using an organic EL element formed by sequentially laminating a plurality of organic compound material layers and metal electrodes on a transparent substrate. In the organic EL color display, the transparent electrode has a different film thickness corresponding to an emission color, and at least one of the functional layers having the same function among the organic compound material layers excluding the light emitting layer. For each of the organic EL elements having a constant film thickness and exhibiting different emission colors, the metal electrode from the emission interface of each emission layer with the wavelength λ as the center wavelength of each emission colorAnd the organic compound material layerOptical distance to (n1・d1) The transparent electrode from the light emitting interface of each light emitting layerAnd the organic compound material layerOptical distance to the interface (n2・d2) and the organic compound of the transparent electrodematerialLayer interface and saidTransparentOptical distance to the interface of the substrate with the transparent electrode (n3・The film is formed with a film thickness such that d3) is substantially equal to λ / 4.
[0016]
Also, for one element, an organic EL element in which a transparent electrode, a plurality of organic compound material layers including at least a light emitting layer, and a metal electrode are sequentially laminated on a transparent substrate is used as an element. In the manufacturing method of the organic EL color display formed by arranging a plurality of the organic EL elements composed of the light emitting layers to be exhibited, the method includes forming the transparent electrodes in different film thicknesses corresponding to light emission colors, The light emitting interface of the light emitting layer that has at least one common lamination step of laminating a common layer having a constant film thickness made of the same organic compound material and emits light having a wavelength λ as a central wavelength for all EL elements The organic compound material layer has a film thickness such that the optical distance from the transparent electrode to the boundary between the transparent substrate and the transparent substrate is substantially equal to an even multiple of λ / 4. The transparent electrode is formed into a film.
[0017]
  Consists of the light-emitting layer exhibiting different emission colors depending on different organic compound materials, with an organic EL element formed by sequentially laminating a transparent electrode, a plurality of organic compound material layers including at least a light-emitting layer, and a metal electrode on a transparent substrate. In the method for producing an organic EL color display in which a plurality of the organic EL elements are arranged, the method includes forming the transparent electrodes in different film thicknesses corresponding to emission colors, and for all the organic EL elements, The transparent electrode and the transparent electrode from the light emitting interface of the light emitting layer having at least one common lamination step of laminating a common layer having a constant film thickness made of the same organic compound material and having a wavelength λ as a central wavelength The optical distance to the boundary with the transparent substrate is substantially equal to an even multiple of λ / 4, and the metal electrode from the light emitting interface of the light emitting layerAnd the organic compound material layerThe organic compound material layer and the transparent electrode are formed in such a film thickness that the optical distance to the boundary is substantially equal to an odd multiple of λ / 4.
[0018]
In another aspect, the organic compound material has a film thickness such that an optical distance from a light emitting interface of the light emitting layer to a boundary between the organic compound material layer and the transparent electrode is substantially equal to an odd multiple of λ / 4. A layer is formed.
[0028]
The invention according to each of the claims has the following effects.
[0029]
BookAccording to the invention, by setting the film thickness of the transparent electrode to a different film thickness corresponding to the emission color, the reflected light reflected at the boundary between the organic compound material layer and the transparent electrode, and the boundary between the transparent electrode and the substrate Considering both the reflected light and the reflected light, it is possible to set high efficiency by interference of the extracted light. In addition, when achieving high efficiency by interference only with transparent electrodes, each functional layer of the organic compound material layer should have a uniform film thickness that takes into account the film thickness or productivity of each function. Is possible. This makes it possible to achieve high extraction light efficiency while optimizing productivity or light emission efficiency of the light emitting layer.
[0030]
In particular, it is possible to improve productivity by forming at least one of the functional layers of the organic compound material layer to have a constant film thickness over the entire surface of the display or using the same organic compound material. The functional layer of the constant thickness or the same material can be a hole transport layer or a hole injection layer laminated from the light emitting layer to the anode side, or an electron transport layer laminated from the light emitting layer to the cathode side. .
[0031]
Also,Considering the reflection interference phenomenon for the light radiated from the light emitting layer, reflected at the boundary between the transparent electrode and the transparent substrate, and returning to the light emitting layer side again, it is possible to achieve high efficiency of the extracted light.
[0032]
Also,Light emitted from the light emitting layer, reflected at the boundary between the transparent electrode and the transparent substrate, and returned to the light emitting layer again, and light emitted from the light emitting layer toward the rear surface and reflected at the interface of the metal electrode and directed to the front substrate side Considering the reflection interference phenomenon for the above, it is possible to achieve high efficiency of extracted light.
[0033]
Also,Considering the reflection interference phenomenon for the light radiated from the light emitting layer, reflected at the boundary between the organic compound material layer and the transparent electrode, and returning to the light emitting layer side, it is possible to achieve high efficiency of the extracted light it can.
[0034]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an organic EL color display according to the present invention.FirstIt is explanatory drawing which shows embodiment. The figure shows the layer structure in the light emitting region of each color of RGB. In this embodiment, the thicknesses of the organic compound material layers and the transparent electrodes of the respective colors are all optical thicknesses. An organic EL color display has a plurality of organic EL elements as elements, and each organic EL element has a light emitting layer that exhibits different emission colors depending on different organic compound materials, and a plurality of organic EL elements of each color are arranged in an organic manner. An EL color display is formed. Each organic EL element includes a substrate 1 made of transparent glass or the like, a transparent electrode 3 such as ITO formed thereon, a hole transport function layer 5A for forming an organic compound material layer 5, and a light emitting layer 50R (50G). , 50B), an electron transporting functional layer 5B, and a metal electrode 6 made of Al or the like._FourIt is covered with a sealing material made of or the like.
[0035]
In each organic EL element, the

light emitting layers

50R, 50G, and 50B, which are separately laminated independently, are made of different organic compound materials that exhibit red, green, and blue light emission colors when current is applied. In this case, a set of organic EL elements having emission colors of red, green and blue is used as one pixel, and color display is performed by, for example, arranging these plural pixels in a matrix.
[0036]
First, the reflection interference phenomenon in the organic EL element will be described with reference to FIG. Here, it is assumed that the electron transport function layer 5B, the hole transport function layer 5A, and the transparent electrode 3 have refractive indexes of n1, n2, and n3, respectively, and the film thicknesses are d1, d2, and d3. When the refractive index of the substrate 1 is n4, it is assumed that the relationship is n1≈n2 <n3> n4.
[0037]
In this case, the mode of light to be considered as a target of the reflection interference phenomenon is emitted from the light emitting interface 50a of the light emitting layer 50 (the interface between the light emitting layer 50 and the hole transport functional layer 5A is the light emitting interface) to the front. Light a emitted from the light emitting interface 50a to the rear surface, light b emitted from the light emitting interface 50a to the rear surface and reflected from the interface of the metal electrode, and emitted from the light emitting interface 50a to the front surface to transport holes. Light c reflected at the boundary between the layer 5A and the transparent electrode 3 and returned to the light emitting interface 50a again, emitted from the light emitting interface 50a to the front surface, reflected at the boundary between the transparent electrode 3 and the substrate 1, and returned to the light emitting interface 50a again. It becomes light d. Although the actual light emitting region largely depends on the element structure and the organic compound material to be used, it is considered to be distributed from several to several tens of nanometers from the interface between the light emitting layer 50 and the hole transporting functional layer 5A. The light emission interface 50a is defined, and the reflection interference phenomenon is examined according to the optical distance from the light emission interface 50a.
[0038]
The condition that the light a and the light b having the wavelength λ are intensified is as shown in the equation (1), that is, the optical distance n1 · from the light emitting interface 50a of the light emitting layer that emits light having the wavelength λ as the central wavelength to the interface of the metal electrode 6. d1 is an odd multiple of λ / 4.
[0039]
[Expression 1]

[0040]
Further, the condition that the light a ′ and the light d having the wavelength λ are intensified is as shown in the equation (2), that is, from the light emitting interface 50a of the light emitting layer that emits light having the wavelength λ as the central wavelength to the boundary between the transparent electrode 3 and the substrate 1. The optical distance (n2 · d2 + n3 · d3) is an even multiple of λ / 4.
[0041]
[Expression 2]

[0042]
Further, the condition that the light a ′ and the light c having the central wavelength λ are intensified is as shown in the equation (3), that is, the organic compound material layer 5 and the transparent electrode 3 from the light emitting interface 50a of the light emitting layer that emits light having the wavelength λ as the central wavelength. The optical distance (n2 · d2) to the boundary is an odd multiple of λ / 4.
[0043]
[Equation 3]

[0044]
Therefore, the relationship between the optical distances satisfying all the expressions (1) to (3) is as follows.
[0045]
[Expression 4]

[0046]
[Equation 5]

In the embodiment of FIG. 1, the center wavelength (λ corresponding to RGB) with respect to the electron transport function layer 5B, the hole transport function layer 5A, and the transparent electrode 3 in each color of RGB._R= 650 nm, λ_G= 520 nm, λ_B= 460 nm) to λ_R/ 4, λ_G/ 4, λ_B/ 4 is obtained, and the optical distance of each layer is set as follows from the equation (5).
[0047]
[Formula 6]

[0048]
Here, the refractive index for each color of the transparent electrode 3 (ITO) is n3 (λ_R) = 1.81, n3 (λ_G) = 1.94, n4 (λ_B) = 2.00, the film thickness (nm) for each color of the transparent electrode 3 is d3 (λ_R) = 90, d3 (λ_G) = 67, d4 (λ_B) = 58. In this way, by setting the film thickness d3 of each color of the transparent electrode 3 to a different thickness corresponding to the light emission color, all the considered light is intensified by satisfying all the expressions (1) to (3). Setting is possible, and light emitted from each color light emitting layer can be extracted most efficiently.
[0049]
[Setting Example 1] A setting example in the embodiment of FIG. 1 is shown below, assuming that the electron transporting functional layer is Alq, the hole transporting functional layer is NPB, the transparent electrode is ITO, and the substrate is AS glass. Here, n1 to n4 are each wavelength (λ_R= 650 nm, λ_G= 520 nm, λ_B= Measurement value of refractive index at 460 nm).
[0050]
[Table 1]

[0051]
Next, the organic EL color display of the present inventionSecondThe embodiment will be described with reference to FIG. 3 (in the following embodiments, the same parts as those of the above-described embodiment are denoted by the same reference numerals, and a part of the description will be omitted. The layer structure in the light emitting region is shown, and the light emitting layer is not shown). In this embodiment, light c emitted from the light emitting interface 50a to the front surface, reflected at the boundary between the hole transporting functional layer 5A and the transparent electrode 3 and returning to the light emitting interface 50a again is ignored, and reflected light is emitted. Only light b emitted from the interface 50a to the rear surface and reflected from the interface of the metal electrode and light d emitted from the light emitting interface 50a to the front surface, reflected from the boundary between the transparent electrode 3 and the substrate 1 and returned to the light emitting interface 50a again. It is taken into consideration.
[0052]
The measured values of the electric field amplitude reflectivity at each layer boundary (electron transport function layer: Alq, hole transport function layer; NPB, transparent electrode: ITO, substrate: AS glass) in the setting example 1 described above are shown below.
[0053]
[Table 2]

[0054]
As is apparent from this table, in practice, the reflectance at the organic compound material layer or the boundary between the organic compound material layer and the transparent electrode 3 is considerably larger than the reflectance at the boundary between the transparent electrode 3 and the substrate 1. Neglecting the former reflected light is not a problem in practice. Therefore, only the above-described formulas (1) and (2), that is, the optical distance (n2 · d2 + n3 ·) from the light emitting interface 50a of the light emitting layer that emits light with the wavelength λ as the center wavelength to the boundary between the transparent electrode 3 and the substrate 1 From the relationship where d3) is an even multiple of λ / 4 and the optical distance d1 from the light emitting interface 50a to the interface of the metal electrode 6 is an odd multiple of λ / 4, the following relationship is obtained with m = 1.
[0055]
[Expression 7]

[0056]
Here, with respect to d2 and d3, for example, the film thickness is set so that the drive voltages are aligned for each color. In other words, if the hole transporting functional layer is formed thick and the transparent electrode is thin, the current luminance characteristic does not change, but the voltage luminance characteristic deteriorates. Therefore, using this, the driving conditions are the same for each color. The film thickness of the hole transport functional layer d2 can be set. Then, by setting the transparent electrode film thickness d3 to a different value for each color, the expression (7) can be satisfied, and practically high efficiency of extracted light can be achieved. .
[0057]
Next, in the organic EL color display of the present inventionThirdThe embodiment will be described with reference to FIG. In this embodiment, as in the embodiment of FIG. 3, the reflection between the organic compound material layers and the reflection at the boundary between the organic compound material layer and the transparent electrode are ignored, and only n1 is obtained from the equations (1) and (2). The conditions of d1 = λ / 4 and n2 · d2 + n3 · d3 = λ / 2 are obtained, and the film thickness d2 of the hole transport function layer 5A is set as a constant value common to each color. According to this, since the hole transporting functional layer 5A can be uniformly formed on the entire surface of the panel after forming the transparent electrode 3 film, the productivity can be improved. The hole transport functional layer 5A may be a single layer of a hole transport layer made of a single material such as NPB, or a single material hole made of CuPC or the like between the hole transport layer and the transparent electrode. It may be a laminate of injection layers.
[0058]
[Setting Example 2] A setting example in the embodiment of FIG. 4 is shown below, assuming that the electron transporting functional layer is Alq, the hole transporting functional layer is NPB, the transparent electrode is ITO, and the substrate is AS glass. Here, n1 to n4 are each wavelength (λ_R= 650 nm, λ_G= 520 nm, λ_B= Measurement value of refractive index at 460 nm).
[0059]
[Table 3]

[0060]
Next, in the organic EL color display of the present invention4thThe embodiment will be described with reference to FIG. In this embodiment, the transparent electrode 3 and the hole transport function layer 5A are the same as those in the embodiment of FIG. 4, and the film thickness d1 of the electron transport function layer 5B on the cathode side is set as a constant value common to each color. It is. In this case, by setting the film thickness d1 to a constant value common to each color, the above-described expression (1) cannot be satisfied for all colors. Accordingly, the film thickness d1 that satisfies the expression (1) with only a specific color is set, and the film thickness d3 of the transparent electrode 3 is set to a different value for each color, so that the expression (2) is satisfied. The film thickness d2 of the hole transport function layer 5A is set. According to this, productivity can be further improved by setting both the hole transporting functional layer 5A and the electron transporting functional layer 5B to a constant film thickness while achieving practically high efficiency of extracted light. . In this case, the electron transporting functional layer 5B may be a single layer of a single material electron transporting layer made of Alq or the like, or a Li layer between the electron transporting layer and the metal electrode 6.₂A single material electron injection layer made of O or the like may be laminated.
[0061]
[Setting Example 3] A setting example in the embodiment shown in FIG. 5 is shown below, assuming that the electron transporting functional layer is Alq, the hole transporting functional layer is NPB, the transparent electrode is ITO, and the substrate is AS glass. Here, n1 to n4 are each wavelength (λ_R= 650 nm, λ_G= 520 nm, λ_B= Measurement value of refractive index at 460 nm).
[0062]
[Table 4]

[0063]
Below, the manufacturing method of the organic electroluminescent color display which concerns on this invention is demonstrated. In FIG. 6, first, RGB transparent electrodes 3 each made of ITO are formed on a glass substrate 1 as shown in FIG. As shown in Table 4, the thickness d3 of the transparent electrode is set in advance so as to have a different value corresponding to each of the RGB emission colors, and the deposition time is set for each color using a mask for each color. A desired film thickness is formed.
[0064]
Next, as shown in FIG. 2B, the hole transporting functional layer 5A is uniformly formed on the transparent electrode 3 by vacuum deposition or the like. The hole transporting functional layer 5A may be a single layer of NPB as described above, or may be formed by stacking NPB after a single layer of CuPC or the like is stacked as the hole injection layer. In any case, the formation of the hole transporting functional layer 5A is a step of laminating a common layer having a continuous constant film thickness made of the same organic compound material.
[0065]
Next, as shown in FIG. 2C, the light emitting layer 50 is formed for each color, and the electron transporting functional layer 5B is uniformly formed thereon by vacuum deposition or the like. The electron transporting functional layer 5B may be a single layer of Alq as described above, and after this single layer is laminated, Li as an electron injection layer.₂A single layer such as O may be laminated. In any case, the formation of the electron transporting functional layer 5B is a step of laminating a common layer having a continuous constant film thickness made of the same organic compound material. Then, as shown in FIG. 4D, a metal electrode 6 having a low work function such as Al—Li is formed on the electron transporting functional layer 5B by means of vapor deposition or sputtering, and the upper portion thereof is not shown. Cover with sealing material.
[0066]
According to this manufacturing method, the formation process of the transparent electrode 3 requires a complicated process of setting the film thickness for each color using a mask or the like, but the subsequent film formation process can be simplified. In particular, considering the distribution of materials with the transparent electrode 3 formed on the substrate, the productivity of the display can be remarkably improved.
[0067]
Then, by setting the hole transporting functional layer 5A and the electron transporting functional layer 5B so as to have the film thickness d2 and the film thickness d1 shown in Table 4, high efficiency of extracted light due to the reflection interference phenomenon within a practically effective range. Can also be achieved.
[0068]
FIG. 7 is an explanatory view showing another embodiment of the method for producing an organic EL color display according to the present invention. This is an embodiment for obtaining [Setting Example 1] that places the highest importance on increasing the efficiency of each color extraction light. First, as shown in FIG. 1A, RGB transparent electrodes 3 each made of ITO are formed on a glass substrate 1 so that the film thickness d3 has a value shown in Table 1. Then, the common layer 5A ′ of the hole transport function layer is formed on the transparent electrode 3 with a continuous film thickness made of the same organic compound material. The film thickness of the common layer 5A ′ is set to the minimum value (59 nm) of d2 in Table 1.
[0069]
Next, as shown in FIG. 6B, the hole transporting functional layer is added to R and G by a necessary thickness so that the film thickness d2 of each color of RGB becomes a value shown in Table 1. A hole transporting functional layer 5A is formed. Further, as shown in FIG. 3C, after the light emitting layer 50 for each color is formed, the common layer 5B 'of the electron transport function layer is formed with a continuous constant film thickness made of the same organic compound material. The film thickness of the common layer 5B ′ is set to the minimum value (62 nm) of d1 in Table 1.
[0070]
Then, as shown in FIG. 4D, the electron transport function layer is added to R and G by a necessary thickness, and the film thickness d1 of each color of RGB becomes the value shown in Table 1 so that the electrons The transport function layer 5B is formed. Thereafter, the metal electrode 6 is formed on the electron transporting functional layer 5B in the same manner as in the above-described embodiment, and further covered with a sealing material. Also in this embodiment, the hole transporting functional layer 5A may be a single layer such as NPB, or after a single layer such as CuPC is stacked as the hole injection layer in the same manner as in the previous embodiment. NPB may be laminated, and the electron transporting functional layer 5B may be a single layer such as Alq, and after this single layer is laminated, Li as an electron injection layer₂A single layer such as O may be laminated.
[0071]
According to this manufacturing method, by setting the film thickness to satisfy all the above-mentioned formulas (1) to (3), it is possible to maximize the efficiency of the extracted light of each color, and the organic compound material When the layers are formed, the common layer is formed first, and then the layers of each color are added. Therefore, the time for forming the film can be shortened, and the productivity can be improved.
[0072]
【The invention's effect】
Since the present invention is configured as described above, it is possible to achieve high efficiency of extracted light in consideration of various reflected light, and the organic compound material layer excluding the light emitting layer is a film corresponding to its function. The thickness can be set, and good productivity can be secured.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an embodiment of an organic EL color display of the present invention.
FIG. 2 is an explanatory diagram for explaining a reflection interference phenomenon in an organic EL element.
FIG. 3 is an explanatory diagram showing an embodiment of the organic EL color display of the present invention.
FIG. 4 is an explanatory diagram showing an embodiment of the organic EL color display of the present invention.
FIG. 5 is an explanatory diagram showing an embodiment of the organic EL color display of the present invention.
FIG. 6 is an explanatory view showing an embodiment in a method for producing an organic EL color display of the present invention.
FIG. 7 is an explanatory view showing an embodiment in a method for producing an organic EL color display of the present invention.
FIG. 8 is an explanatory diagram showing an element structure of a conventional organic EL color display.
[Explanation of symbols]
1 Substrate
2 TFT
3 Transparent electrodes
4 Insulating film
5 Organic compound material layer
5A hole transporting functional layer
5B Electron transport functional layer
50 Light emitting layer
6 Metal electrodes

Claims

Consists of the light-emitting layer exhibiting different emission colors depending on different organic compound materials, with an organic EL element formed by sequentially laminating a transparent electrode, a plurality of organic compound material layers including at least a light-emitting layer, and a metal electrode on a transparent substrate. In an organic EL color display formed by arranging a plurality of the organic EL elements,
The transparent electrode has a different film thickness corresponding to the emission color,
At least one of the functional layers having the same function among the organic compound material layers excluding the light emitting layer has a constant film thickness,
The transparent electrode and the organic compound material layer of each organic EL element have an optical distance of λ / 4 from a light emitting interface of the light emitting layer that emits light having a wavelength λ as a center wavelength to a boundary between the transparent electrode and the transparent substrate. An organic EL color display having a film thickness that is substantially equal to an even multiple of the thickness.

Consists of the light-emitting layer exhibiting different emission colors depending on different organic compound materials, with an organic EL element formed by sequentially laminating a transparent electrode, a plurality of organic compound material layers including at least a light-emitting layer, and a metal electrode on a transparent substrate. In an organic EL color display formed by arranging a plurality of the organic EL elements,
The transparent electrode has a different film thickness corresponding to the emission color,
At least one of the functional layers having the same function among the organic compound material layers excluding the light emitting layer has a constant film thickness,
The transparent electrode and the organic compound material layer of each organic EL element have an optical distance of λ / 4 from a light emitting interface of the light emitting layer that emits light having a wavelength λ as a center wavelength to a boundary between the transparent electrode and the transparent substrate. And a film thickness such that the optical distance from the light emitting interface of the light emitting layer to the boundary between the metal electrode and the organic compound material layer is substantially equal to an odd multiple of λ / 4. Organic EL color display characterized by being made.

A film thickness as substantially equal optical distance between an odd multiple of lambda / 4 to the boundary between the transparent electrode and the organic compound material layer from the light emitting surface of the light-emitting layer, the organic compound material layers is deposited The organic EL color display according to claim 2, wherein:

Consists of the light-emitting layer exhibiting different emission colors depending on different organic compound materials, with an organic EL element formed by sequentially laminating a transparent electrode, a plurality of organic compound material layers including at least a light-emitting layer, and a metal electrode on a transparent substrate. In an organic EL color display formed by arranging a plurality of the organic EL elements,
The transparent electrode has a different film thickness corresponding to the emission color,
At least one of the functional layers having the same function among the organic compound material layers excluding the light emitting layer has a constant film thickness,
The transparent electrode and the organic compound material layer of each organic EL element have an optical distance from a light emitting interface of the light emitting layer that emits light having a wavelength λ as a central wavelength to a boundary between the transparent electrode and the organic compound material layer , The optical distance from the light emitting interface of the light emitting layer to the boundary between the metal electrode and the organic compound material layer and the optical distance from the interface between the organic compound material layer of the transparent electrode and the transparent electrode of the transparent substrate An organic EL color display having a film thickness such that the distance is substantially equal to λ / 4.

A transparent electrode having a refractive index n3, a film thickness d3, an electron transport layer having at least a refractive index n1, a film thickness d1, a hole transport layer having a refractive index n2, a film thickness d2, and a plurality of organic compound material layers including a light emitting layer An organic EL color display in which a plurality of organic EL elements composed of the light emitting layers exhibiting different light emission colors by different organic compound materials are arranged using an organic EL element formed by sequentially laminating a metal electrode on a transparent substrate. In
The transparent electrode has a different film thickness corresponding to the emission color,
At least one of the functional layers having the same function among the organic compound material layers excluding the light emitting layer has a constant film thickness,
Optical distance (n1 · d1) from the light emitting interface of each light emitting layer to the boundary between the metal electrode and the organic compound material layer with the wavelength λ as the center wavelength of each light emitting color for each of the organic EL elements exhibiting different light emission colors An optical distance (n 2 · d 2) from the light emitting interface of each light emitting layer to the interface between the transparent electrode and the organic compound material layer, and the interface of the organic compound material layer of the transparent electrode and the transparent electrode of the transparent substrate An organic EL color display having a film thickness such that an optical distance (n3 · d3) to the interface with the substrate is substantially equal to λ / 4.

A plurality of organic compound material layers including a transparent electrode and at least a light-emitting layer; Manufacture of an organic EL color display in which a plurality of organic EL elements composed of the light-emitting layers exhibiting different emission colors by different organic compound materials are arranged using an organic EL element formed by sequentially laminating electrodes on a transparent substrate as elements. In the method
A step of forming the transparent electrodes in different film thicknesses corresponding to light emission colors and laminating a common layer having a constant constant film thickness made of the same organic compound material for all of the organic EL elements. Having at least one common lamination step,
The organic compound material having a film thickness such that an optical distance from a light emitting interface of the light emitting layer emitting light having a wavelength λ as a central wavelength to a boundary between the transparent electrode and the transparent substrate is substantially equal to an even multiple of λ / 4 A method of manufacturing an organic EL color display, comprising forming a layer and the transparent electrode.

Consists of the light-emitting layer exhibiting different emission colors depending on different organic compound materials, with an organic EL element formed by sequentially laminating a transparent electrode, a plurality of organic compound material layers including at least a light-emitting layer, and a metal electrode on a transparent substrate. In the manufacturing method of an organic EL color display formed by arranging a plurality of the organic EL elements,
A step of forming the transparent electrodes in different film thicknesses corresponding to light emission colors and laminating a common layer having a constant constant film thickness made of the same organic compound material for all of the organic EL elements. Having at least one common lamination step,
The optical distance from the light emitting interface of the light emitting layer that emits light having a wavelength λ as the center wavelength to the boundary between the transparent electrode and the transparent substrate is substantially equal to an even multiple of λ / 4, and from the light emitting interface of the light emitting layer to the metal The organic compound material layer and the transparent electrode are formed in such a film thickness that an optical distance to the boundary between the electrode and the organic compound material layer is substantially equal to an odd multiple of λ / 4. Manufacturing method of organic EL color display.

The organic compound material layer is formed in such a film thickness that an optical distance from the light emitting interface of the light emitting layer to the boundary between the organic compound material layer and the transparent electrode is substantially equal to an odd multiple of λ / 4. The method for producing an organic EL color display according to claim 7.