JP2004311205A

JP2004311205A - Passive matrix type organic thin-film light emitting display, and manufacturing method of passive matrix type organic thin-film light emitting display

Info

Publication number: JP2004311205A
Application number: JP2003102889A
Authority: JP
Inventors: Takatoshi Onoda; 貴稔小野田
Original assignee: Fuji Electric Holdings Ltd
Current assignee: Fuji Electric Co Ltd
Priority date: 2003-04-07
Filing date: 2003-04-07
Publication date: 2004-11-04

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate a short circuit between electrodes caused by a structural defect of a passive matrix type organic thin-film light emitting display by self-repair. <P>SOLUTION: An electrode part in a unit pixel of this passive matrix type organic thin-film light emitting display is so structured that a second electrode 11, an organic layer 12 including an organic light emitting layer, a first electrode 13 and a power feed part 16 are mainly stacked on a surface of a transparent substrate 10. When a short circuit is generated between both the electrodes in a pixel, a short-circuit current significantly exceeding a normal value flows, so that the short-circuited position generates heat. When the thickness of the first electrode 13 is reduced, the first electrode 13 around the short-circuited part is raised by thermal expansion caused by the heat generation to resolve the short circuit. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、パッシブマトリクス型有機薄膜発光ディスプレイおよびその製造方法に関し、特に消費電力を低く抑えたパッシブマトリクス型有機薄膜発光ディスプレイおよびその製造方法に関する。
【０００２】
【従来の技術】
有機発光素子は、自己発光型素子であるため視認性が高く、低電圧で駆動できるという特徴を持つ（Ａｐｐｌ．Ｐｈｙｓ．Ｌｅｔｔ．，５１，９１３，１９８７）ため、実用化研究が積極的になされている。有機発光素子としては、透明基板上に、陽極の透明導電性膜、有機物から成る正孔輸送層と発光層、陰極の金属膜、を形成した有機層が２層の構造や、有機層が正孔輸送層、発光層、電子輸送層の３層からなる構造が知られている。
【０００３】
有機発光素子の発光機構は次のように考えられている。陰極から注入された電子と、陽極から注入された正孔とが、発光層中の蛍光性色素分子で励起子を生成し、この励起子が輻射再結合する過程でエレクトロルミネセンスを放つ。このエレクトロルミネセンスが、陽極である透明導電性膜および透明基板を通して外部に放出される。
【０００４】
有機発光素子を用いたディスプレイの一つに、パッシブマトリクス型（単純マトリクス型）有機薄膜発光ディスプレイがある。図３は、パッシブマトリクス型有機薄膜発光ディスプレイの一般的な構造の概略図である。この図のように、パッシブマトリクス型有機薄膜発光ディスプレイは、透明基板３０上の複数の陽極３１と、陽極３１に交差する複数の陰極３３、これらに挟持された有機発光層を含む有機層３２から構成される。陽極３１と陰極３３の交差領域が画素を形成し、この画素が複数個配列することにより表示部分が形成される。陽極３１および陰極３３を表示部より基板周囲へ延長し形成した接続部を介して、外部駆動回路と表示部分を接続することによりディスプレイ装置が構成される。
【０００５】
近年では、有機発光素子の発光応答速度の速さを活かした高精細なパッシブマトリクス型カラーディスプレイの研究がなされ、フルカラー表示や動画表示といった情報機器用途での低コストの高品位ディスプレイ実現への期待が高まってきている。
【０００６】
前述したように有機発光素子は電流注入によりエレクトロルミネセンスを得るデバイスであり、液晶ディスプレイ等の電界デバイスに比して大きな電流を制御しうる駆動回路と、大きな電流を流しうる陽極、陰極を必要とする。
【０００７】
パッシブマトリクス型有機薄膜発光ディスプレイに用いられる電極として、陽極には、インジウム錫酸化物（ＩＴＯ）やインジウム亜鉛酸化物、酸化錫等の透明導電性金属酸化物が用いられ、陰極にはＡｌ合金、Ｍｇ合金等の低仕事関数金属が用いられる。透明金属酸化物の抵抗率は、金属配線材料として用いられるＡｌ等に比較して大きく、また透明導電性膜としてある程度の可視光透過性を保つ必要があるため膜厚が制限される。陰極に用いられる金属電極は、複数の陽極から電流が流れ込むため、その抵抗値を小さくして電圧降下を低く抑える必要がある。陰極は主に発光を取り出さない方向であるため、金属電極の膜厚を調整することで抵抗値を小さくすることが可能である。
【０００８】
有機発光素子は、その膜厚が数１００ｎｍ程度と薄いため、透明基板や下地層の平滑性、クリーンルームのパーティクル等に起因する構造欠陥が存在しやすい。この構造欠陥は陽極と陰極間で電界集中による短絡を生じさせ、パッシブマトリクス型有機薄膜発光ディスプレイにおいては、短絡画素を中心に陽極方向に明線もしくは輝線と呼ばれる現象が発生する。
【０００９】
例えば画素ピッチ０．１１ｍｍ×０．３３ｍｍで開口率７０％、陽極をデータラインとしデータライン数が２４０、陰極をアドレスラインとしアドレスライン数が６０、両極の交点で形成される画素数が１４，４００の１．２５型パッシブマトリクス型有機薄膜発光ディスプレイを考える。簡単の為、データライン電位は選択時Ｈ（正電位）で非選択時ゼロ（グランド）のＰｕｓｈ−Ｐｕｌｌ駆動、アドレスライン電位は選択時ゼロ（グランド）で非選択時Ｈ（正電位）のＰｕｓｈ−Ｐｕｌｌ駆動、走査線の選択ライン数は常に１ラインの駆動を考える。
【００１０】
電気的短絡欠陥のない状態では、電極配線抵抗あるいは駆動回路内部インピーダンスは、有機発光層を有する画素の抵抗に比して十分小さい。例の場合には、選択時（発光状態、順バイアス）での画素抵抗が数１００ＫΩ、非選択時（消灯状態、順バイアス）あるいは逆バイアス時の画素抵抗が数１０ＭΩ以上に対して、電極配線抵抗あるいは駆動回路内部インピーダンスは高々数ｋΩである。パネルに印加される電圧のほとんどは、画素すなわち有機発光層への電荷注入に必要な電界強度を得るために画素内の両電極間で電圧降下しているので、配線構造設計の設計指針としては前述したように配線抵抗と駆動回路の内部インピーダンスを低減することで、低消費電力で画質の均質性に優れるパネルを実現することが可能になる。
【００１１】
しかし、画素中に電気的な短絡が存在する場合には、上述画素抵抗がほとんど失われ高々数１００Ω程度となる。このため欠陥画素を経由する電気経路には配線抵抗と駆動回路内部インピーダンスで決定される大電流（以下短絡電流と称す）が流れるという欠点を持っている。例の場合、正常動作時の画素電流が高々１００ｕＡであるのに対して、短絡電流は数ｍＡから数１０ｍＡにも達する。
【００１２】
この短絡電流は消費電力を増やすばかりでなく、熱的に弱い有機層を変質させ、短絡画素内での電極短絡面積を増大させ、さらには近隣画素へ伝搬し新たな電気的短絡画素を誘起することになる。また電気的短絡の存在する画素は、発光に必要な電極間電圧を得られなくなるために非点灯となり、表示中で黒点の表示欠陥となるばかりでなく、画像を表示する場合に様々な画質欠陥を引き起こす。例えば、短絡画素を含むデータラインが明るい線状に点灯し続ける輝線、短絡画素を含むアドレスラインに大電流が流れることで画素のカソード電位が上昇し、そのアドレスライン全体が暗くなる、などの画質不良がよく知られている。
【００１３】
透明基板や下地層の平滑性、クリーンルームのパーティクル等を完全に解決し、これらの画質不良の原因となる構造欠陥を皆無とすることは工業的に困難であり、長期の駆動に際して安定した画質を得るためには、構造欠陥を起因とする短絡の解消が必要となる。
【００１４】
従来、作製直後のパッシブマトリクス型有機薄膜発光ディスプレイの短絡画素を修復する方法として、レーザーを用いて短絡電極を部分破壊して修復する方法（例えば、特許文献１参照）がある。また、発光電圧を超える高電圧を与えて短絡部分の修復を行う方法（例えば、特許文献２参照）などがある。
【００１５】
【特許文献１】
特開２００１−３１３１７０号公報（段落番号〔０００４〕〜〔００１２〕、第２図）
【特許文献２】
特開２００１−２３７０８２号公報（段落番号〔００２５〕〜〔００３１〕、第２図）
【００１６】
【発明が解決しようとする課題】
しかし、これらの方法はレーザーの照射や高電圧の印加など特別な条件下で行う必要があり、仮に短絡画素の検出もれが発生した場合、容易に修復できないという問題点があった。
【００１７】
本発明はこのような点に鑑みてなされたものであり、連続駆動状態においての短絡箇所の自己修復を可能とすることで、駆動時の輝線発生等による画質低下を防止したパッシブマトリクス型有機薄膜発光ディスプレイを提供することを目的とする。
【００１８】
また、本発明の他の目的は、連続駆動状態においての短絡箇所の自己修復を可能とすることで、駆動時の輝線発生等による画質低下を防止したパッシブマトリクス型有機薄膜発光ディスプレイの製造方法を提供することである。
【００１９】
【課題を解決するための手段】
本発明では上記課題を解決するために、透明基板に少なくとも、複数の矩形状に配置された第１の電極と、複数の矩形状に配置された第２の電極とを有し、前記第１の電極と第２の電極との交点は各々画素を構成し、かつ前記第１の電極と第２の電極間に有機層を挟持してなり、所望の画素を構成する両電極間に電圧を印加し電流を注入することで得るエレクトロルミネセンスを取り出すことで情報を表示するパッシブマトリクス型有機薄膜発光ディスプレイにおいて、前記第１の電極は、前記第２の電極との間の短絡箇所を短絡電流によって自己修復する機能を有する程度に薄く、かつ前記第１の電極に給電するための給電部は、前記第１の電極を薄くしたことによる抵抗を補償するために、膜厚を厚く高導電率材料で構成したこと、を特徴とするパッシブマトリクス型有機薄膜発光ディスプレイが提供される。
【００２０】
上述の構造を取ることで、画素内で第１の電極および第２の電極間で短絡が発生した場合にはその短絡電流により発熱し、その熱膨張により短絡部分を中心に電極を持ち上げる力が働き、短絡を解除する。給電部は、膜厚を厚く高導電率材料で構成して、第一の電極を薄くしたことによる抵抗を補償する。
【００２１】
【発明の実施の形態】
以下、本発明の実施の形態を、図面を参照して説明する。
図１は、本発明の実施の形態における単位画素部分の概略断面図である。図に示すように、透明基板１０の表面に第２の電極１１、有機発光層を含む有機層１２、第１の電極１３、陰極隔壁１４、絶縁膜１５、給電部１６が積層された構成となっている。第１の電極１３の上に給電部１６が積層され、両者は電気的に接続しているため、駆動回路から第１の電極１３への給電は給電部１６を介して行われることになる。
【００２２】
先に説明したように、有機層１２に接する第１の電極１３の熱膨張を利用して短絡を自己修復させるには、短絡電流の発熱によって膜が持ち上がる程度に第１の電極１３の膜厚を薄くする。ここで、第１の電極１３の上に給電部１６を積層する構成としたことで、第１の電極１３の抵抗が大きくなっても、給電部１６の膜厚を厚く、かつ導電率の高い材料を使用することにより、それを補償することが可能となる。給電部１６と第１の電極１３の抵抗値は、パッシブマトリクス型有機薄膜発光ディスプレイのマトリクス数、給電部１６の給電抵抗、有機発光素子の電気的特性、駆動回路に用いられるドライバＩＣの内部インピーダンスなどを考慮して、設計されるものである。
【００２３】
次に、画素数８０×６０ドット、画素ピッチ０．３３×０．３３ｍｍ、ドット数４８００として、本形態の実施例および比較例の有機薄膜発光ディスプレイパネルについて説明する。
【００２４】
【実施例１】
（製造方法）
ガラスを用いた透明基板１０上に、陽極となる第２の電極１１を形成する。陽極は透明電極であり、抵抗率４．１×１０^−３（Ω・ｃｍ）のインジウム錫酸化物を膜厚２２０ｎｍ、幅３００ｕｍで形成した。成膜にはＤＣマグネトロンスパッタ法を用い、パターニングには通常のフォトリソグラフィ法を用いた。
【００２５】
次に、絶縁膜１５を画素の非発光部全体に形成する。材料はレジストであり、これを膜厚１ｕｍ形成した。成膜にはスピンコート法を用い、パターニングには通常のフォトリソグラフィ法を用いた。
【００２６】
次に、陰極隔壁１４を第２の電極１１とは直交する配置で絶縁膜１５上に形成する。材料はレジストであり、これを膜厚３ｕｍ形成した。成膜にはスピンコート法を用い、パターニングには通常のフォトリソグラフィ法を用いた。
【００２７】
次に、有機層１２を表示領域全面に形成する。抵抗過熱式蒸着法にて１０Ｅ−５Ｐａ台の真空を破ることなく連続で、有機正孔注入層、有機発光層、有機電子注入層の順に成膜を行った。
【００２８】
続いて、陰極となる第１の電極１３を形成する。材料はＡｌＬｉ合金であり、これを真空蒸着にて５０ｎｍ形成した。
次に給電部１６をマスク形成する。マスクは幅５０ｕｍのスリットが形成された電鋳形成Ｎｉマスクを用い、このスリットを陰極隔壁１４に平行に配置した。給電部１６の材料はＡｌであり、これを膜厚２００ｎｍ形成した。このとき給電部１６を絶縁膜１５上に位置するように形成することで、開口率（フィルファクター）の低下を最小限に抑えることができる。
【００２９】
成膜を終了した基板は、大気にさらすことなく窒素ガス雰囲気下のグローブボックスに移送し、ＵＶ硬化／熱硬化併用型シール剤とガラス封止板とを用いて封止した。封止内にはグローブボックス内環境ガスである窒素ガス（水分量５ｐｐｍ以下、酸素分量５ｐｐｍ以下）を充填した。
【００３０】
封止を完了した基板は大気中に取り出し、異方導電性フィルム（ＡＣＦ）を用いて駆動回路端子と接続した。
（性能の評価）
上述のように製造した有機薄膜発光ディスプレイパネルから構成される有機薄膜発光ディスプレイに対し、パッシブマトリクス駆動（駆動周波数６０Ｈｚ、駆動デューティ１／６０、階調数１６、階調方式はパルス幅変調）を全てのデータラインが選択された全点灯状態にて行い、電源投入直後および１００時間駆動後の非点灯画素数（電気的短絡を伴う欠陥画素数に相当する）を調べた。なお、各基板構成によって駆動電圧−輝度特性が異なることから、比較のために全点灯状態でのエリア輝度が１００ｃｄ／ｍ^２となるように規格化して評価した。結果を表１に示す。
【００３１】
（比較例１）
図２は、本発明の比較例における単位画素部分の概略断面図である。透明基板２０の表面に第２の電極２１、有機層２２、第１の電極２３、陰極隔壁２４、絶縁膜２５が積層された構成になっている。実施例１と異なり給電部１６が存在しないため、駆動回路から第１の電極２３へは直接給電される。
【００３２】
第１の電極２３の膜厚は１００ｎｍにし、給電部１６は積層しない。それ以外は上記実施例１と同様に有機薄膜発光ディスプレイパネルを製造し、性能の評価を行った。結果を表１に示す。
【００３３】
【表１】

【００３４】
（比較結果）
電源投入直後の非点灯画素数の差は、電源投入時に自己修復した数の差と考えられる。１００時間後の非点灯画素数の差は、連続駆動における自己修復のしやすさの差と考えられる。本発明の適用により、エージングを行うことで短絡画素の自己修復が起こり、表示画質の低下が防止される。
【００３５】
以上の点から、本発明の目的が達成されたことが確かめられた。
なお、給電部はその延長方向に位置する第１の電極と電気的に接続されていれば良く、給電部の配置はこの実施例１に限定されない。また第１の電極は給電部と電気的に接続され、かつ短絡時の短絡電流による発熱をもって自己修復すれば良く、第１の電極の配置、形成方法および画素の構造はこの実施例１に限定されない。
【００３６】
また、上記の実施例１では給電部にＡｌ（２．６５５×１０^−６Ω・ｃｍ）を用いたが、他にＭｇ（４．４５×１０^−６Ω・ｃｍ）、Ａｇ（１．５９×１０^−６Ω・ｃｍ）、Ｃｕ（１．６７×１０^−６Ω・ｃｍ）、Ｎｉ（６．８４×１０^−６Ω・ｃｍ）、Ｍｏ（５．２×１０^−６Ω・ｃｍ）、Ｃｒ（１２．９×１０^−６Ω・ｃｍ）など配線材料として挙げられる様々な高導電率材料を用いることができる（各（）内数値は、電気抵抗率を示す）。特に、高融点かつ機械的強度の高い材料が好ましく、形成する膜厚を厚くすることでさらに抵抗値低減と機械的強度向上が達成される。
【００３７】
また、上記の実施例１では第１の電極にＡｌＬｉ合金を用いたが、他にＭｇＡｇ合金など仕事関数の小さい導電性材料を用いることができる。
また、上記の実施例１では第２の電極にインジウム錫酸化物を用いたが、他にインジウム亜鉛酸化物、酸化錫などを用いることもできる。
【００３８】
さらに、上記の実施例１では第１の電極の膜厚を５０ｎｍとしたが、膜厚略７０ｎｍまでは同様の効果が得られる。薄くする場合は、透過率の増加に従って発光効率が低下するため、その影響が実用上問題とならない略１０ｎｍが限界と考えられる。
【００３９】
【発明の効果】
以上説明したように本発明では、第１の電極の厚さを自己修復可能な厚さに構成したので、第１の電極および第２の電極間で短絡が発生した場合にはその短絡電流により発熱し、その熱膨張により短絡部分を中心に電極を持ち上げる力が働き、短絡を解除して自己修復がなされ、駆動時の輝線発生による表示画質の低下を防止できる。また、給電部を膜厚を厚く高導電率材料で構成したので、第１の電極の抵抗を補償できる。
【図面の簡単な説明】
【図１】本発明の実施の形態における単位画素部分の概略断面図である。
【図２】本発明の比較例における単位画素部分の概略断面図である。
【図３】一般的なパッシブマトリクス型有機薄膜発光ディスプレイの電極構造の概略図である。
【符号の説明】
１０透明基板
１１第２の電極
１２有機層
１３第１の電極
１４陰極隔壁
１５絶縁膜
１６給電部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a passive matrix type organic thin film light emitting display and a method of manufacturing the same, and more particularly to a passive matrix type organic thin film light emitting display with low power consumption and a method of manufacturing the same.
[0002]
[Prior art]
Organic light emitting devices are self-luminous devices and have high visibility and can be driven at a low voltage (Appl. Phys. Lett., 51, 913, 1987). ing. The organic light-emitting device has a two-layer structure in which a transparent conductive film of an anode, a hole transport layer and a light-emitting layer made of an organic substance, and a metal film of a cathode are formed on a transparent substrate. A structure including three layers, a hole transport layer, a light emitting layer, and an electron transport layer, is known.
[0003]
The light emitting mechanism of the organic light emitting device is considered as follows. The electrons injected from the cathode and the holes injected from the anode generate excitons in the fluorescent dye molecules in the light emitting layer, and emits electroluminescence in the process of radiative recombination of the excitons. This electroluminescence is emitted to the outside through the transparent conductive film and the transparent substrate as the anode.
[0004]
As one of displays using an organic light emitting element, there is a passive matrix type (simple matrix type) organic thin film light emitting display. FIG. 3 is a schematic view of a general structure of a passive matrix organic thin film light emitting display. As shown in this figure, a passive matrix type organic thin film light emitting display is composed of a plurality of anodes 31 on a transparent substrate 30, a plurality of cathodes 33 intersecting the anodes 31, and an organic layer 32 including an organic light emitting layer sandwiched therebetween. Be composed. The intersection area between the anode 31 and the cathode 33 forms a pixel, and a plurality of pixels are arranged to form a display portion. A display device is configured by connecting an external drive circuit and a display portion via a connection portion formed by extending the anode 31 and the cathode 33 from the display portion to the periphery of the substrate.
[0005]
In recent years, research has been conducted on high-definition passive matrix color displays that take advantage of the fast light-emitting response speed of organic light-emitting devices, and expectations for the realization of low-cost, high-quality displays for information equipment applications such as full-color display and moving image display. Is increasing.
[0006]
As described above, an organic light emitting device is a device that obtains electroluminescence by current injection, and requires a drive circuit that can control a large current compared to an electric field device such as a liquid crystal display, and an anode and a cathode that can flow a large current. And
[0007]
Transparent conductive metal oxides such as indium tin oxide (ITO), indium zinc oxide, and tin oxide are used for an anode as an electrode used in a passive matrix type organic thin-film light emitting display, and an aluminum alloy is used for a cathode. A low work function metal such as an Mg alloy is used. The resistivity of the transparent metal oxide is larger than that of Al or the like used as a metal wiring material, and the film thickness is limited because it is necessary to maintain a certain level of visible light transmission as a transparent conductive film. Since a current flows from a plurality of anodes to a metal electrode used as a cathode, it is necessary to reduce the resistance value to suppress the voltage drop. Since the cathode has a direction in which light emission is not mainly taken out, the resistance value can be reduced by adjusting the thickness of the metal electrode.
[0008]
Since the organic light-emitting element has a thin film thickness of about several hundreds of nm, structural defects due to smoothness of a transparent substrate or an underlayer, particles in a clean room, and the like are likely to be present. This structural defect causes a short circuit due to electric field concentration between the anode and the cathode, and in a passive matrix type organic thin film light emitting display, a phenomenon called a bright line or a bright line occurs in the direction of the anode around the short-circuited pixel.
[0009]
For example, the pixel pitch is 0.11 mm × 0.33 mm, the aperture ratio is 70%, the number of data lines is 240 with the anode as the data line, the number of address lines is 60 with the cathode as the address line, and the number of pixels formed at the intersection of the two poles is 14. Consider a 400 1.25 passive matrix organic thin film light emitting display. For simplicity, the data line potential is H (positive potential) when selected and the non-selection is zero (ground) Push-Pull drive. The address line potential is zero (ground) when selected and the H (positive potential) Push when not selected. -Pull driving, the number of selected scanning lines always considers driving one line.
[0010]
In a state where there is no electrical short-circuit defect, the electrode wiring resistance or the internal impedance of the driving circuit is sufficiently smaller than the resistance of the pixel having the organic light emitting layer. In the case of the example, the electrode wiring is selected when the pixel resistance at the time of selection (light emitting state, forward bias) is several hundred KΩ, and the pixel resistance at the time of non-selection (light off state, forward bias) or reverse bias is several tens MΩ or more. The resistance or the internal impedance of the drive circuit is at most several kΩ. Most of the voltage applied to the panel drops between the two electrodes in the pixel in order to obtain the electric field strength necessary for injecting the charge into the pixel, that is, the organic light emitting layer. As described above, by reducing the wiring resistance and the internal impedance of the driving circuit, a panel with low power consumption and excellent image quality uniformity can be realized.
[0011]
However, when an electric short circuit exists in the pixel, the above-described pixel resistance is almost lost, and the resistance is at most several hundred ohms. For this reason, there is a disadvantage that a large current (hereinafter referred to as a short-circuit current) determined by the wiring resistance and the internal impedance of the driving circuit flows through the electric path passing through the defective pixel. In the case of the example, while the pixel current in the normal operation is 100 μA at most, the short-circuit current reaches several mA to several tens mA.
[0012]
This short-circuit current not only increases the power consumption, but also alters the thermally weak organic layer, increases the electrode short-circuit area within the short-circuit pixel, and further propagates to neighboring pixels to induce a new electric short-circuit pixel. Will be. In addition, a pixel having an electrical short circuit is not lit because it is impossible to obtain a voltage between electrodes required for light emission, which causes not only a black dot display defect during display but also various image quality defects when displaying an image. cause. For example, image quality such as a bright line in which a data line including a short-circuited pixel continues to light up in a bright line, a cathode potential of a pixel increases due to a large current flowing through an address line including a short-circuited pixel, and the entire address line becomes dark. Bad is well known.
[0013]
It is industrially difficult to completely resolve the smoothness of the transparent substrate and the underlayer, particles in the clean room, etc., and to eliminate any structural defects that cause these image quality defects. In order to obtain it, it is necessary to eliminate short circuits caused by structural defects.
[0014]
2. Description of the Related Art Conventionally, as a method of repairing a short-circuit pixel of a passive matrix type organic thin-film light emitting display immediately after fabrication, there is a method of partially destroying and repairing a short-circuit electrode using a laser (for example, see Patent Document 1). Further, there is a method of restoring a short-circuit portion by applying a high voltage exceeding a light emission voltage (for example, see Patent Document 2).
[0015]
[Patent Document 1]
JP-A-2001-313170 (paragraph numbers [0004] to [0012], FIG. 2)
[Patent Document 2]
JP 2001-237082 A (paragraph numbers [0025] to [0031], FIG. 2)
[0016]
[Problems to be solved by the invention]
However, these methods need to be performed under special conditions such as laser irradiation or application of a high voltage, and if short-circuited pixels are missed, they cannot be easily repaired.
[0017]
The present invention has been made in view of such a point, and enables a self-repair of a short-circuited portion in a continuous driving state, thereby preventing a deterioration in image quality due to generation of a bright line at the time of driving. It is an object to provide a light emitting display.
[0018]
Another object of the present invention is to provide a method of manufacturing a passive matrix type organic thin-film light emitting display capable of preventing self-healing of a short-circuit portion in a continuous driving state, thereby preventing image quality deterioration due to generation of bright lines during driving. To provide.
[0019]
[Means for Solving the Problems]
In order to solve the above problem, the present invention has at least a first electrode arranged in a plurality of rectangular shapes on a transparent substrate, and a second electrode arranged in a plurality of rectangular shapes, Each of the intersections of the first electrode and the second electrode constitutes a pixel, and an organic layer is sandwiched between the first electrode and the second electrode. A voltage is applied between both electrodes constituting a desired pixel. In a passive matrix organic thin film light emitting display that displays information by taking out electroluminescence obtained by applying and injecting a current, the first electrode forms a short-circuit current between the second electrode and a short-circuited portion. The power supply unit for supplying power to the first electrode is thin enough to have a function of self-healing, and has a large film thickness and high conductivity in order to compensate for resistance due to the thinning of the first electrode. Made of material, Passive matrix type organic thin film light emitting display according to is provided.
[0020]
With the above-described structure, when a short circuit occurs between the first electrode and the second electrode in the pixel, heat is generated by the short-circuit current, and a force for lifting the electrode around the short-circuited portion due to thermal expansion. Work and release short circuit. The power supply section is made of a high-conductivity material having a large film thickness, and compensates for resistance due to the thinning of the first electrode.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic sectional view of a unit pixel portion according to an embodiment of the present invention. As shown in the figure, a structure in which a second electrode 11, an organic layer 12 including an organic light emitting layer, a first electrode 13, a cathode partition 14, an insulating film 15, and a power supply unit 16 are laminated on the surface of a transparent substrate 10 is shown. Has become. Since the power supply unit 16 is stacked on the first electrode 13 and both are electrically connected, power supply from the drive circuit to the first electrode 13 is performed via the power supply unit 16.
[0022]
As described above, the self-repair of a short circuit using the thermal expansion of the first electrode 13 in contact with the organic layer 12 requires the film thickness of the first electrode 13 to be raised to such an extent that the film is lifted by the heat generated by the short-circuit current. Thinner. Here, since the power supply unit 16 is stacked on the first electrode 13, even if the resistance of the first electrode 13 increases, the thickness of the power supply unit 16 is increased and the electric conductivity is high. The use of a material makes it possible to compensate for it. The resistance values of the power supply unit 16 and the first electrode 13 are determined by the number of matrices of the passive matrix type organic thin film light emitting display, the power supply resistance of the power supply unit 16, the electric characteristics of the organic light emitting element, and the internal impedance of the driver IC used in the drive circuit. It is designed in consideration of such factors.
[0023]
Next, the organic thin-film light-emitting display panels of the example of the present embodiment and the comparative example will be described with a pixel number of 80 × 60 dots, a pixel pitch of 0.33 × 0.33 mm, and a dot number of 4800.
[0024]
Embodiment 1
(Production method)
A second electrode 11 serving as an anode is formed on a transparent substrate 10 using glass. The anode was a transparent electrode, and was formed of indium tin oxide having a resistivity of 4.1 × 10 ⁻³ (Ω · cm) with a thickness of 220 nm and a width of 300 μm. DC magnetron sputtering was used for film formation, and normal photolithography was used for patterning.
[0025]
Next, the insulating film 15 is formed on the entire non-light emitting portion of the pixel. The material was a resist, which was formed to a thickness of 1 μm. A spin coating method was used for film formation, and a normal photolithography method was used for patterning.
[0026]
Next, a cathode partition wall 14 is formed on the insulating film 15 in an arrangement orthogonal to the second electrode 11. The material was a resist, which was formed to a thickness of 3 μm. A spin coating method was used for film formation, and a normal photolithography method was used for patterning.
[0027]
Next, the organic layer 12 is formed on the entire display area. Film formation was successively performed in the order of an organic hole injecting layer, an organic light emitting layer, and an organic electron injecting layer without breaking a vacuum of the order of 10E-5 Pa by a resistance heating evaporation method.
[0028]
Subsequently, a first electrode 13 serving as a cathode is formed. The material was an AlLi alloy, which was formed to a thickness of 50 nm by vacuum evaporation.
Next, the power supply unit 16 is formed as a mask. The mask used was an electroformed Ni mask in which a slit having a width of 50 μm was formed, and this slit was arranged in parallel with the cathode partition wall 14. The material of the power supply section 16 was Al, which was formed to a thickness of 200 nm. At this time, by forming the power supply portion 16 so as to be located on the insulating film 15, a decrease in the aperture ratio (fill factor) can be suppressed to a minimum.
[0029]
The substrate on which the film formation was completed was transferred to a glove box under a nitrogen gas atmosphere without being exposed to the air, and sealed using a UV curing / thermo curing combined sealant and a glass sealing plate. The inside of the seal was filled with nitrogen gas (water content 5 ppm or less, oxygen content 5 ppm or less), which is an environmental gas in the glove box.
[0030]
The sealed substrate was taken out to the atmosphere, and connected to a drive circuit terminal using an anisotropic conductive film (ACF).
(Evaluation of performance)
Passive matrix driving (drive frequency 60 Hz, drive duty 1/60, gradation number 16, gradation method is pulse width modulation) is applied to the organic thin film light emitting display composed of the organic thin film light emitting display panel manufactured as described above. All data lines were selected in the fully lit state, and the number of non-lit pixels (corresponding to the number of defective pixels with an electrical short) immediately after power-on and after driving for 100 hours was examined. Since the driving voltage-luminance characteristics differ depending on the configuration of each substrate, for comparison, evaluation was performed by standardizing the area luminance in all lighting states to be 100 cd / m ² . Table 1 shows the results.
[0031]
(Comparative Example 1)
FIG. 2 is a schematic sectional view of a unit pixel portion in a comparative example of the present invention. The structure is such that a second electrode 21, an organic layer 22, a first electrode 23, a cathode partition 24, and an insulating film 25 are stacked on the surface of a transparent substrate 20. Unlike the first embodiment, since the power supply unit 16 does not exist, power is directly supplied from the drive circuit to the first electrode 23.
[0032]
The thickness of the first electrode 23 is set to 100 nm, and the power supply unit 16 is not stacked. Otherwise, an organic thin film light emitting display panel was manufactured in the same manner as in Example 1 and the performance was evaluated. Table 1 shows the results.
[0033]
[Table 1]

[0034]
(Comparison result)
The difference in the number of non-lighting pixels immediately after the power is turned on is considered to be the difference in the number of self-repairs when the power is turned on. The difference in the number of non-lighting pixels after 100 hours is considered to be the difference in the ease of self-repair in continuous driving. By applying the present invention, self-repair of a short-circuit pixel occurs by performing aging, and deterioration of display image quality is prevented.
[0035]
From the above points, it was confirmed that the object of the present invention was achieved.
Note that the power supply unit only needs to be electrically connected to the first electrode positioned in the extension direction, and the arrangement of the power supply unit is not limited to the first embodiment. The first electrode may be electrically connected to the power supply unit and may be self-repaired by heat generated by a short-circuit current at the time of short-circuit. The arrangement, formation method, and pixel structure of the first electrode are limited to the first embodiment. Not done.
[0036]
Further, in the first embodiment, Al (2.655 × 10 ⁻⁶ Ω · cm) was used for the power supply unit, but Mg (4.45 × 10 ⁻⁶ Ω · cm) and Ag (1.59 × 10 ⁻⁶ Ω · cm), Cu (1.67 × 10 ⁻⁶ Ω · cm), Ni (6.84 × 10 ⁻⁶ Ω · cm), Mo (5.2 × 10 ⁻⁶ Ω · cm) , Cr (12.9 × 10 ⁻⁶ Ω · cm), and various high conductivity materials listed as wiring materials can be used (each value in parentheses indicates an electrical resistivity). In particular, a material having a high melting point and high mechanical strength is preferable. By increasing the thickness of the formed film, the resistance value is further reduced and the mechanical strength is further improved.
[0037]
In the first embodiment, the AlLi alloy is used for the first electrode. However, a conductive material having a small work function, such as an MgAg alloy, can be used.
Further, in the first embodiment, indium tin oxide is used for the second electrode. Alternatively, indium zinc oxide, tin oxide, or the like may be used.
[0038]
Further, in the first embodiment, the thickness of the first electrode is set to 50 nm, but the same effect can be obtained up to a thickness of about 70 nm. When the thickness is reduced, the luminous efficiency decreases as the transmittance increases. Therefore, it is considered that the limit is about 10 nm, the effect of which is not a practical problem.
[0039]
【The invention's effect】
As described above, in the present invention, since the thickness of the first electrode is configured to be self-repairable, when a short circuit occurs between the first electrode and the second electrode, the short-circuit current Heat is generated and the thermal expansion causes a force to lift the electrode around the short-circuited portion, thereby canceling the short-circuit and performing self-repair, thereby preventing a reduction in display quality due to the generation of bright lines during driving. In addition, since the power supply section is made of a thick and high-conductivity material, the resistance of the first electrode can be compensated.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of a unit pixel portion according to an embodiment of the present invention.
FIG. 2 is a schematic sectional view of a unit pixel portion in a comparative example of the present invention.
FIG. 3 is a schematic view of an electrode structure of a general passive matrix organic thin film light emitting display.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Transparent substrate 11 2nd electrode 12 Organic layer 13 1st electrode 14 Cathode partition 15 Insulating film 16 Power supply part

Claims

The transparent substrate has at least a plurality of first electrodes arranged in a rectangular shape and a plurality of second electrodes arranged in a rectangular shape, and an intersection of the first electrode and the second electrode is Each pixel is formed, and an organic layer is sandwiched between the first electrode and the second electrode. Electroluminescence is obtained by applying a voltage and injecting a current between both electrodes forming a desired pixel. In a passive matrix organic thin film light emitting display that displays information by taking out the sense,
The first electrode is thin enough to have a function of self-repairing a short-circuited portion between the first electrode and a second electrode by a short-circuit current, and the power supply unit for supplying power to the first electrode includes the first electrode. A passive matrix type organic thin-film light emitting display characterized in that it is made of a thick and high-conductivity material in order to compensate for the resistance caused by making the electrodes thinner.

2. The passive matrix type organic thin film light emitting display according to claim 1, wherein a thickness of said first electrode is in a range of 10 nm or more and 70 nm or less.

2. The passive matrix type organic thin film light emitting display according to claim 1, wherein said first electrode is made of an aluminum / lithium alloy or a magnesium / silver alloy.

The passive matrix type organic thin film light emitting display according to claim 1, wherein the power supply unit is formed of any one of aluminum, magnesium, silver, copper, nickel, molybdenum, and chromium.

2. The passive matrix type organic thin film light emitting display according to claim 1, wherein the thickness of the power supply unit is 200 nm or more.

The transparent substrate has at least a first electrode arranged in a plurality of rows in a rectangular shape, and a second electrode arranged in a plurality of rows in a rectangular shape, wherein the first electrode and the second electrode are The intersections are obtained by forming a pixel and sandwiching an organic layer between the first electrode and the second electrode, and applying a voltage between the two electrodes forming the desired pixel and injecting a current. In a method of manufacturing a passive matrix type organic thin film light emitting display for displaying information by extracting electroluminescence,
Forming a transparent electrode on the transparent substrate,
Forming the organic layer over the entire display area,
Forming a first electrode having a thickness of 10 nm or more and 70 nm or less on the organic layer by vacuum deposition;
A method for manufacturing a passive matrix organic thin film light emitting display, comprising: forming a power supply portion on the first electrode.