JP2004296154A - Electrode, its manufacturing method, and organic electroluminescent element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode capable of restraining non-luminescence in the entire area of a luminescent surface due to a short circuit of an organic EL element constituting respective pixels, simply manufacturable at a low cost, and capable of easily forming respective layers constituting the organic EL element by application or printing; to provide its manufacturing method; and to provide an organic EL element using the electrode. <P>SOLUTION: This island-shaped electrode is formed by being separated on a substrate, and is characterized by that the electrode is connected to a wire for feeding a current to the electrode through a wire melted down or broken down by an overcurrent to be electrically insulated. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００７６】
【化２】

【００７７】
【化３】

【００７８】
これらの発光層は、上記化合物を、例えば真空蒸着法、スピンコート法、キャスト法、ＬＢ法などの公知の薄膜化法により製膜して形成することができる。発光層としての膜厚は、特に制限はないが、通常は５ｎｍ〜５μｍの範囲で選ばれる。
【００７９】
発光層は、これらの発光材料一種又は二種以上からなる一層構造であってもよいし、あるいは、同一組成又は異種組成の複数層からなる積層構造であってもよい。
【００８０】
また、これらの発光層は、特開昭５７−５１７８１号公報に記載されているように、樹脂などの結着材と共に上記発光材料を溶剤に溶かして溶液としたのち、これをスピンコート法などにより薄膜化して形成することができる。
【００８１】
又、この発光層は、例えば真空蒸着法、スピンコート法、キャスト法、Ｌａｎｇｍｕｉｒ−Ｂｌｏｄｇｅｔｔ法（ＬＢ法）などの公知の薄膜化法により製膜して形成することができる。発光層としての膜厚は、特に制限はないが、通常は５ｎｍ〜５μｍの範囲で選ばれる。これらの発光層は、これらの発光材料一種又は二種以上からなる一層構造であってもよいし、あるいは、同一組成又は異種組成の複数層からなる積層構造であってもよい。
【００８２】
次に正孔注入層、正孔輸送層および電子注入層、電子輸送層について説明する。
【００８３】
正孔注入層、正孔輸送層は、陽極より注入された正孔を発光層に伝達する機能を有し、この正孔輸送層を陽極と発光層の間に介在させることにより、より低い電界で多くの正孔が発光層に注入され、そのうえ、発光層に陰極、陰極バッファー層、電子注入層または電子輸送層より注入された電子は、発光層と正孔輸送層の界面に存在する電子の障壁により、発光層内の界面に累積され発光効率が向上するなど発光性能の優れた素子となる。この正孔輸送層の材料（以下、正孔注入材料、正孔輸送材料という）については、前記の好ましい性質を有するものであれば特に制限はなく、従来、光導伝材料において、正孔の電荷注入輸送材料として慣用されているものやＥＬ素子の正孔輸送層に使用される公知のものの中から任意のものを選択して用いることができる。
【００８４】
上記正孔注入材料、正孔輸送材料は、正孔の注入もしくは輸送、電子の障壁性のいずれかを有するものであり、有機物、無機物のいずれであってもよい。この正孔輸送材料としては、例えばトリアゾール誘導体、オキサジアゾール誘導体、イミダゾール誘導体、ポリアリールアルカン誘導体、ピラゾリン誘導体及びピラゾロン誘導体、フェニレンジアミン誘導体、アリールアミン誘導体、アミノ置換カルコン誘導体、オキサゾール誘導体、スチリルアントラセン誘導体、フルオレノン誘導体、ヒドラゾン誘導体、スチルベン誘導体、シラザン誘導体、アニリン系共重合体、また、導電性高分子オリゴマー、特にチオフェンオリゴマーなどが挙げられる。正孔輸送材料としては、上記のものを使用することができるが、ポルフィリン化合物、芳香族第三級アミン化合物及びスチリルアミン化合物、特に芳香族第三級アミン化合物を用いることが好ましい。
【００８５】
上記芳香族第三級アミン化合物及びスチリルアミン化合物の代表例としては、Ｎ，Ｎ，Ｎ′，Ｎ′−テトラフェニル−４，４′−ジアミノフェニル；Ｎ，Ｎ′−ジフェニル−Ｎ，Ｎ′−ビス（３−メチルフェニル）−〔１，１′−ビフェニル〕−４，４′−ジアミン（ＴＰＤ）；２，２−ビス（４−ジ−ｐ−トリルアミノフェニル）プロパン；１，１−ビス（４−ジ−ｐ−トリルアミノフェニル）シクロヘキサン；Ｎ，Ｎ，Ｎ′，Ｎ′−テトラ−ｐ−トリル−４，４′−ジアミノビフェニル；１，１−ビス（４−ジ−ｐ−トリルアミノフェニル）−４−フェニルシクロヘキサン；ビス（４−ジメチルアミノ−２−メチルフェニル）フェニルメタン；ビス（４−ジ−ｐ−トリルアミノフェニル）フェニルメタン；Ｎ，Ｎ′−ジフェニル−Ｎ，Ｎ′−ジ（４−メトキシフェニル）−４，４′−ジアミノビフェニル；Ｎ，Ｎ，Ｎ′，Ｎ′−テトラフェニル−４，４′−ジアミノジフェニルエーテル；４，４′−ビス（ジフェニルアミノ）クオードリフェニル；Ｎ，Ｎ，Ｎ−トリ（ｐ−トリル）アミン；４−（ジ−ｐ−トリルアミノ）−４′−〔４−（ジ−ｐ−トリルアミノ）スチリル〕スチルベン；４−Ｎ，Ｎ−ジフェニルアミノ−（２−ジフェニルビニル）ベンゼン；３−メトキシ−４′−Ｎ，Ｎ−ジフェニルアミノスチルベンゼン；Ｎ−フェニルカルバゾール、さらには、米国特許第５，０６１，５６９号明細書に記載されている２個の縮合芳香族環を分子内に有するもの、例えば４，４′−ビス〔Ｎ−（１−ナフチル）−Ｎ−フェニルアミノ〕ビフェニル（ＮＰＤ）、特開平４−３０８６８８号公報に記載されているトリフェニルアミンユニットが３つスターバースト型に連結された４，４′，４″−トリス〔Ｎ−（３−メチルフェニル）−Ｎ−フェニルアミノ〕トリフェニルアミン（ＭＴＤＡＴＡ）などが挙げられる。
【００８６】
さらにこれらの材料を高分子鎖に導入した、またはこれらの材料を高分子の主鎖とした高分子材料を用いることもできる。
【００８７】
また、ｐ型−Ｓｉ、ｐ型−ＳｉＣなどの無機化合物も正孔注入材料、正孔輸送材料として使用することができる。この正孔注入層、正孔輸送層は、上記正孔注入材料、正孔輸送材料を、例えば真空蒸着法、スピンコート法、キャスト法、ＬＢ法などの公知の方法により、薄膜化することにより形成することができる。正孔注入層、正孔輸送層の膜厚については特に制限はないが、通常は５ｎｍ〜５μｍ程度である。この正孔注入層、正孔輸送層は、上記材料の一種又は二種以上からなる一層構造であってもよく、同一組成又は異種組成の複数層からなる積層構造であってもよい。さらに、必要に応じて用いられる電子輸送層は、陰極より注入された電子を発光層に伝達する機能を有していればよく、その材料としては従来公知の化合物の中から任意のものを選択して用いることができる。
【００８８】
電子注入層、電子輸送層に用いられる材料（以下、電子注入材料、電子輸送材料という）の例としては、ニトロ置換フルオレン誘導体、ジフェニルキノン誘導体、チオピランジオキシド誘導体、ナフタレンペリレンなどの複素環テトラカルボン酸無水物、カルボジイミド、フレオレニリデンメタン誘導体、アントラキノジメタン及びアントロン誘導体、オキサジアゾール誘導体、トリアゾール誘導体、フェナントロリン誘導体などが挙げられる。さらに、上記オキサジアゾール誘導体において、オキサジアゾール環の酸素原子を硫黄原子に置換したチアジアゾール誘導体、電子吸引基として知られているキノキサリン環を有するキノキサリン誘導体も、電子注入材料、電子輸送材料として用いることができる。
【００８９】
さらにこれらの材料を高分子鎖に導入した、またはこれらの材料を高分子の主鎖とした高分子材料を用いることもできる。
【００９０】
また、８−キノリノール誘導体の金属錯体、例えばトリス（８−キノリノール）アルミニウム（Ａｌｑ３）、トリス（５，７−ジクロロ−８−キノリノール）アルミニウム、トリス（５，７−ジブロモ−８−キノリノール）アルミニウム、トリス（２−メチル−８−キノリノール）アルミニウム、トリス（５−メチル−８−キノリノール）アルミニウム、ビス（８−キノリノール）亜鉛（Ｚｎｑ）など、及びこれらの金属錯体の中心金属がＩｎ、Ｍｇ、Ｃｕ、Ｃａ、Ｓｎ、Ｇａ又はＰｂに置き替わった金属錯体も、電子注入材料、電子輸送材料として用いることができる。その他、メタルフリー若しくはメタルフタロシアニン、又はそれらの末端がアルキル基やスルホン酸基などで置換されているものも、電子注入材料、電子輸送材料として好ましく用いることができる。また、発光層の材料として用いられるジスチリルピラジン誘導体も、電子輸送材料として用いることができるし、正孔注入層、正孔輸送層と同様に、ｎ型−Ｓｉ、ｎ型−ＳｉＣなどの無機半導体も電子輸送材料として用いることができる。
【００９１】
この電子注入層、電子輸送層は、上記化合物を、例えば真空蒸着法、スピンコート法、キャスト法、ＬＢ法などの公知の薄膜化法により製膜して形成することができる。電子注入層、電子輸送層としての膜厚は、特に制限はないが、通常は５ｎｍ〜５μｍの範囲で選ばれる。この電子注入層、電子輸送層は、これらの電子注入材料、電子輸送材料一種又は二種以上からなる一層構造であってもよいし、あるいは、同一組成又は異種組成の複数層からなる積層構造であってもよい。
【００９２】
さらに、陽極と発光層または正孔注入層の間、および、陰極と発光層または電子注入層との間にはバッファー層（電極界面層）を存在させてもよい。
【００９３】
バッファー層とは、駆動電圧低下や発光効率向上のために電極と有機層間に設けられる層のことで、「有機ＥＬ素子とその工業化最前線（１９９８年１１月３０日 エヌ・ティー・エス社発行）」の第２編第２章「電極材料」（第１２３頁〜第１６６頁）に詳細に記載されており、陽極バッファー層と陰極バッファー層とがある。
【００９４】
陽極バッファー層は、特開平９−４５４７９号、同９−２６００６２号、同８−２８８０６９号等にもその詳細が記載されており、具体例として、銅フタロシアニンに代表されるフタロシアニンバッファー層、酸化バナジウムに代表される酸化物バッファー層、アモルファスカーボンバッファー層、ポリアニリン（エメラルディン）やポリチオフェン等の導電性高分子を用いた高分子バッファー層等が挙げられる。
【００９５】
陰極バッファー層は、特開平６−３２５８７１号、同９−１７５７４号、同１０−７４５８６号等にもその詳細が記載されており、具体的にはストロンチウムやアルミニウム等に代表される金属バッファー層、フッ化リチウムに代表されるアルカリ金属化合物バッファー層、フッ化マグネシウムに代表されるアルカリ土類金属化合物バッファー層、酸化アルミニウムに代表される酸化物バッファー層等が挙げられる。
【００９６】
特に、本発明の有機ＥＬ素子において、陰極バッファー層が存在した場合、駆動電圧低下や発光効率向上が大きく得られた。
【００９７】
上記バッファー層はごく薄い膜であることが望ましく、素材にもよるが、その膜厚は０．１〜１００ｎｍの範囲が好ましい。
【００９８】
さらに上記基本構成層の他に必要に応じてその他の機能を有する層を積層してもよく、本発明においては、例えば特開平１１−２０４２５８号、同１１−２０４３５９号、および「有機ＥＬ素子とその工業化最前線（１９９８年１１月３０日 エヌ・ティー・エス社発行）」の第２３７頁等に記載されている正孔ブロック層などのような機能層を有しているのが好ましい。
【００９９】
正孔ブロック層は、発光層と電子輸送層の間に、又、発光層を正孔輸送層が兼ねる場合には、正孔輸送層と電子輸送層の間に設けられ、ホールの輸送を制御するためのものである。代表的にはバソクプロイン（ＢＣ）やフェナントロリン誘導体、トリアゾール誘導体等の化合物がもちいられているが（前記特開平８−１０９３７３号及び特開平１０−２３３２８４号等）、正孔ブロック層の存在により、注入されたホールは電子輸送層に移動しにくくなるため、正孔ブロック層に充満するようになり、正孔ブロック層に充満した正孔によって、発光層中に正孔が効率よく蓄積し、発光層での電子−正孔の再結合確率を向上させ、発光の高効率化を達成する。
【０１００】
次に有機ＥＬ素子で使用する電極について説明する。有機ＥＬ素子の電極は、陰極と陽極からなる。
【０１０１】
この有機ＥＬ素子における陽極としては、仕事関数の大きい（４ｅＶ以上）金属、合金、電気伝導性化合物及びこれらの混合物を電極物質とするものが好ましく用いられる。このような電極物質の具体例としてはＡｕなどの金属、ＣｕＩ、インジウムチンオキシド（ＩＴＯ）、ＳｎＯ_２、ＺｎＯなどの導電性透明材料が挙げられる。
【０１０２】
上記陽極は、これらの電極物質を蒸着やスパッタリングなどの方法により、薄膜を形成させ、フォトリソグラフィー法で所望の形状のパターンを形成してもよく、あるいはパターン精度をあまり必要としない場合は（１００μｍ以上程度）、上記電極物質の蒸着やスパッタリング時に所望の形状のマスクを介してパターンを形成してもよい。この陽極より発光を取り出す場合には、透過率を１０％より大きくすることが望ましく、また、陽極としてのシート抵抗は数百Ω／□以下が好ましい。さらに膜厚は材料にもよるが、通常１０ｎｍ〜１μｍ、好ましくは１０ｎｍ〜２００ｎｍの範囲で選ばれる。
【０１０３】
一方、陰極としては、仕事関数の小さい（４ｅＶ以下）金属（電子注入性金属と称する）、合金、電気伝導性化合物及びこれらの混合物を電極物質とするものが用いられる。このような電極物質の具体例としては、ナトリウム、ナトリウムーカリウム合金、マグネシウム、リチウム、マグネシウム／銅混合物、マグネシウム／銀混合物、マグネシウム／アルミニウム混合物、マグネシウム／インジウム混合物、アルミニウム／酸化アルミニウム（Ａｌ_２Ｏ_３）混合物、インジウム、リチウム／アルミニウム混合物、希土類金属などが挙げられる。これらの中で、電子注入性及び酸化などに対する耐久性の点から、電子注入性金属とこれより仕事関数の値が大きく安定な金属である第二金属との混合物、例えばマグネシウム／銀混合物、マグネシウム／アルミニウム混合物、マグネシウム／インジウム混合物、アルミニウム／酸化アルミニウム（Ａｌ_２Ｏ_３）混合物、リチウム／アルミニウム混合物などが好適である。
【０１０４】
更に本発明の有機ＥＬ素子に用いる陰極としては、アルミニウム合金が好ましく、特にアルミニウム含有量が９０質量％以上１００質量％未満であることが好ましく、最も好ましくは９５質量％以上１００質量％未満である。これにより、有機ＥＬ素子の発光寿命や、最高到達輝度を非常に向上させることができる。
【０１０５】
上記陰極は、これらの電極物質を蒸着やスパッタリングなどの方法により、薄膜を形成させることにより、作製することができる。また、陰極としてのシート抵抗は数百Ω／□以下が好ましく、膜厚は通常１０ｎｍ〜１μｍ、好ましくは５０〜２００ｎｍの範囲で選ばれる。なお、発光を透過させるため、有機ＥＬ素子の陽極又は陰極のいずれか一方が、透明又は半透明であれば発光効率が向上し好都合である。
【０１０６】
本発明の有機ＥＬ素子に好ましく用いられる基板は、ガラス、プラスチックなどの種類には特に限定はなく、また、透明のものであれば特に制限はない。本発明のエレクトロルミネッセンス素子に好ましく用いられる基板としては例えばガラス、石英、光透過性プラスチックフィルムを挙げることができる。
【０１０７】
光透過性プラスチックフィルムとしては、例えばポリエチレンテレフタレート（ＰＥＴ）、ポリエチレンナフタレート（ＰＥＮ）、ポリエーテルスルホン（ＰＥＳ）、ポリエーテルイミド、ポリエーテルエーテルケトン、ポリフェニレンスルフィド、ポリアリレート、ポリイミド、ポリカーボネート（ＰＣ）、セルローストリアセテート（ＴＡＣ）、セルロースアセテートプロピオネート（ＣＡＰ）等からなるフィルム等が挙げられるが、可撓性を有し軽量で好ましい。
【０１０８】
次に、該有機ＥＬ素子を作製する好適な例を説明する。例として、前記の陽極／陽極バッファー層／正孔輸送層／発光層／正孔ブロック層／電子輸送層／陰極バッファー層／陰極からなるＥＬ素子の作製法について説明する。まず適当な基板上に、所望の電極物質、例えば陽極用物質からなる薄膜を、１μｍ以下、好ましくは１０〜２００ｎｍの範囲の膜厚になるように、蒸着やスパッタリングなどの方法により形成させ、陽極を作製する。次に、この上に陽極バッファー層、正孔輸送層、発光層、正孔ブロック層、電子輸送層、陰極バッファー層の材料からなる薄膜を形成させる。
【０１０９】
この有機薄膜層の製膜法としては、前記の如くスピンコート法、キャスト法、蒸着法などがあるが、均質な膜が得られやすく、かつピンホールが生成しにくいなどの点から、真空蒸着法またはスピンコート法が特に好ましい。さらに層ごとに異なる製膜法を適用しても良い。製膜に蒸着法を採用する場合、その蒸着条件は、使用する化合物の種類、分子堆積膜の目的とする結晶構造、会合構造などにより異なるが、一般にボート加熱温度５０〜４５０℃、真空度１０^−６〜１０^−２Ｐａ、蒸着速度０．０１〜５０ｎｍ／秒、基板温度−５０〜３００℃、膜厚５ｎｍ〜５μｍの範囲で適宜選ぶことが望ましい。
【０１１０】
これらの層の形成後、その上に陰極用物質からなる薄膜を、１μｍ以下好ましくは５０〜２００ｎｍの範囲の膜厚になるように、例えば蒸着やスパッタリングなどの方法により形成させ、陰極を設けることにより、所望のＥＬ素子が得られる。この有機ＥＬ素子の作製は、一回の真空引きで一貫して正孔注入層から陰極まで作製するのが好ましいが、途中で取り出して異なる製膜法を施してもかまわないが、その際には作業を乾燥不活性ガス雰囲気下で行う等の配慮が必要となる。
【０１１１】
また作製順序を逆にして、陰極、陰極バッファー層、電子輸送層、正孔ブロック層、発光層、正孔輸送層、陽極バッファー層、陽極の順に作製することも可能である。このようにして得られたＥＬ素子に、直流電圧を印加する場合には、陽極を＋、陰極を−の極性として電圧５〜４０Ｖ程度を印加すると、発光が観測できる。また、逆の極性で電圧を印加しても電流は流れずに発光は全く生じない。さらに、交流電圧を印加する場合には、陽極が＋、陰極が−の状態になったときのみ発光する。なお、印加する交流の波形は任意でよい。
【０１１２】
本発明の電極を用いた有機ＥＬ素子においては、照明用や露光光源のような一種のランプとして使用するのが好ましいが、画像を投影するタイプのプロジェクション装置や、静止画像や動画像を直接視認するタイプの表示装置（ディスプレイ）として使用しても良い。動画再生用の表示装置として使用する場合の駆動方式は単純マトリクス（パッシブマトリクス）方式でもアクティブマトリクス方式でもどちらでも良いが。前述のように、直接駆動線に電極が接続する、単純マトリクス（パッシブマトリクス）方式の場合に効果が大きく好ましい。また、異なる発光色を有する本発明の有機ＥＬ素子を２種以上使用することにより、多色を発光させることが可能である。
【０１１３】
【発明の実施の形態】
以下、本発明に係わる電極及び有機ＥＬ素子の実施の形態について具体的に説明するが、本発明はこれらに限定されるものではない。
【０１１４】
図１は、ガラス基板上にマスク材を形成した後、金等の金属を蒸着或いはスパッタリングすることで形成した、金等の金属からなる島状の電極１と該電極に電流を供給する配線２、そして、該電極と電流を供給する配線間を電気的に接続し過電流によって溶断もしくは破壊されるヒューズ型配線３からなる本発明の電極の概略図である。また、均一な、例えば金等の金属膜形成の後、エッチングにより形成しても良い。
【０１１５】
例えば、電極及び配線を構成する金属膜は、厚みが２００ｎｍ（５０ｎｍから５００ｎｍの範囲が好ましい）になるように蒸着或いはスパッタリング形成され、島状の電極１は６００μｍ×６００μｍの矩形、該電極１に電流を供給する配線２は幅８０μｍ、電極及び電流を供給する配線の間隔は２０μｍとなるようにパターニングされる。
【０１１６】
過電流によって溶断もしくは破壊されるヒューズ型配線３は導電性高分子化合物ＰＥＤＯＴ／ＰＳＳの水性懸濁液（Ｂａｙｅｒ製 Ｂｙｔｒｏｎ Ｐ ＴＰ ＡＩ ４０８３）を用いインクジェット法により島状の電極１と電流を供給する配線２の間に乾燥時の厚みが例えば１００ｎｍ、配線幅が例えば１５μｍとなるように印字形成される。この配線を細くすることで過電流が流れたときにこの部分が破断し、電極を電流を供給する配線から絶縁できる。このヒューズ型配線は、又、スクリーン印刷法によって、ＰＥＤＯＴ／ＰＳＳ等の導電性高分子化合物をペースト状としてパターン様に印刷することでも形成できる。
【０１１７】
図１（ａ）は電極及び配線を上面からみた概略図であり、（ｂ）はインクジェット法により導電性高分子化合物懸濁液を島状の電極１及び電流を供給する配線２間に印字したところ、（ｃ）は乾燥されヒューズ型配線が形成されたされたところを示すそれぞれ電極及び配線のａ−ａ′断面図である。金のような仕事関数の大きい金属からなる電極は有機ＥＬ素子の陽極として用いることができる。この場合、有機ＥＬ素子の陰極は光を取り出せるようにＩＴＯのような透明導電膜を用いた電極で構成される。
【０１１８】
図２はＩＴＯの様な透明導電性材料で島状の電極を形成した、本発明の有機ＥＬ素子の一例を示す概略図である。ＩＴＯ膜を全面ガラス基板上に形成した後（厚み１５０ｎｍ）、フォトリソグラフィーによりマスクを形成し、エッチング（エッチング液としては水、濃塩酸及び４０質量％第二塩化鉄溶液を質量比で８５：８：７で混合したものをもちいた）によりパターニングを行い複数の島状の電極１を形成する（６００μｍ×６００μｍの矩形）。次いで、フォトマスク形成の後、銅或いは金等の金属膜をスパッタリングにより形成した後（厚み１５０ｎｍ）、マスクを除き、金或いは銅等の金属膜による電流を供給する配線２のパターンを形成する。電流を供給する配線の幅は８０μｍとなるように、又、各島状の電極との間隔が４０μｍになるようにパターニングした。ＩＴＯ膜による島状の電極及び金属からなる電流を供給する配線パターンに、前記と同様、ＰＥＤＯＴ／ＰＳＳ懸濁液（Ｂａｙｅｒ製Ｂｙｔｒｏｎ Ｐ ＴＰ ＡＩ ４０８３）を用いてインクジェット法により、ＩＴＯからなる電極及び電流を供給する配線の間に幅３０μｍ、乾燥時の厚みで５０ｎｍのヒューズ型配線３を形成してこれらを接続する。
【０１１９】
これら、ＩＴＯ膜による島状の電極及び金属からなる配線等をパターニングした基板を洗浄容器に入れ、ＩＰＡ洗浄した後、以下の様に有機ＥＬ層４（有機ＥＬ素子を構成する電極以外の正孔輸送層、電子輸送層又は発光層等の各層を併せてこう呼ぶ）を一様に順次有機溶媒系の塗布により形成した。
【０１２０】
即ち、正孔輸送材料としてポリビニルカルバゾール（Ｍｗ＝６３，０００ アルドリッチ製）をジクロロメタンに溶解して得た液をスピンコーターを用いて塗布し乾燥させた４０ｎｍの正孔輸送層を形成した。
【０１２１】
次いで、更に、湖の正孔輸送層上にポリメチルメタクリレート（ＰＭＭＡ、Ｍｗ＝１２０，０００ アルドリッチ製）と電子輸送材料としての４，４′−Ｎ，Ｎ′−ジカルバゾールビフェニル（ＣＢＰ）と、トリス（２−フェニルピリジン）イリジウム錯体とを、１０：２０：１の質量比で、メチルエチルケトン／トルエン混合溶液に溶解して得た液を、スピンコーターを用いて塗布し、真空乾燥させることで厚みが４０ｎｍの発光層を形成した。
【０１２２】
次いで有機ＥＬ層４をステンレス鋼製のマスク材により覆った後、真空蒸着装置中において、例えば、Ｍｏ製抵抗加熱ボート中にマグネシウムを又タングステン製の蒸着用バスケットに銀を入れて、２×１０^−４Ｐａの条件下それぞれを加熱してマグネシウム及び銀を共蒸着して（厚み１１０ｎｍ）銀／マグネシウム混合物からなる陰極５のパターンを、前記陽極である島状の電極１に略対応する幅で電極に対向させるように、且つ、該各島状の電極１に電流を供給する配線２と重ならないように平行に形成する。
【０１２３】
図２（ａ）はこの様にして形成した有機ＥＬ素子の主に電極及び配線の配置を示す上面概略図であり、図２（ｂ）がｂ−ｂ′断面図を示す。
【０１２４】
照明用として用いることを前提としているため。陽極に電流を供給する配線と、陰極を構成する帯が平行に重ならないように形成される。
【０１２５】
又、全て配線をＩＴＯ膜で形成しても良いが、ＩＴＯ膜は金属膜に比べ抵抗率が稍大きいので、これに電流を供給する配線は金属で形成している。仕事関数の低い金属電極が有機ＥＬ素子の陰極には用いられるが、透過率の高い陰極材料を得ることは難しい。一方ＩＴＯ等の膜は陽極として用いることができるため陽極を透明導電膜とする構成が普通である。
【０１２６】
図３は前記のＩＴＯ膜を用いた島状の電極１のパターニングの後、電流を供給する配線２を金属で形成する際に、電流を供給する配線と同じ材料で過電流により溶断若しくは破壊されるヒューズ型配線３を同時にパターニング形成した例である。
【０１２７】
即ち、ＩＴＯ膜からなる島状の電極１の形成の後、フォトマスク形成、銅或いは金等の金属膜を蒸着又はスパッタリングにより形成し、マスクを除いて、金或いは銅等の金属からなるで電流を供給する配線２及び過電流によって溶断もしくは破壊されるヒューズ型配線３を同時に形成する。
図３（ａ）はこの様にして形成した有機ＥＬ素子の主に電極及び配線の配置を示す上面概略図であり、図３（ｂ）がｃ−ｃ′断面図を示す。
【０１２８】
この例においてはヒューズ型配線と電流を供給する配線が同じ金属材料となるためヒューズ型配線の断面積を電流を供給する配線の１／５以下とすればよい。
【０１２９】
その後に有機ＥＬ層４及び陰極５を図２における説明と同様に形成して、有機ＥＬ素子が得られる。電極及び各配線のサイズ、幅等については図２と基本的に同じである。
【０１３０】
図４には、島状の電極、該電極に電流を供給する配線及びこれらを接続する過電流によって溶断若しくは破壊されるヒューズ型配線を同時に形成した例を示す。
【０１３１】
ガラス基盤上に形成されたＩＴＯ膜（厚み１００ｎｍ）から基板上に第１の電極Ａを幅５００μｍに帯状にパターニング形成した後（陽極として用いる）該電極を有するガラス基板上に以下の各層からなる有機ＥＬ層Ｂを積層した。
【０１３２】
即ち、該ガラス基板を市販の真空蒸着装置の基板ホルダーに固定し、α−ＮＰＤ（４，４′−ビス〔Ｎ−（１−ナフチル）−Ｎ−フェニルアミノ〕ビフェニル）、ＣＢＰ（４，４′−（Ｎ，Ｎ′−ビスカルバゾリル）ビフェニル）、Ｉｒ（ｐｐｙ）_３（トリス（２−フェニルピリジン）イリジウム錯体）、ＢＣ（バソキュプロイン）、Ａｌｑ３（トリス（８−キノリノラート）アルミニウム（ＩＩＩ））をそれぞれモリブデン製抵抗加熱ボートに入れ真空蒸着装置に取り付けた。
【０１３３】
真空槽を４×１０^−４Ｐａまで減圧した後、α−ＮＰＤの入った前記加熱ボートに通電して加熱し、ＩＴＯ上に正孔輸送層としてα−ＮＰＤを蒸着速度０．１〜０．２ｎｍ／ｓｅｃで４０ｎｍの厚さに蒸着した。さらに、ＣＢＰの入った前記加熱ボートとＩｒ（ｐｐｙ）_３の入ったボートをそれぞれ独立に通電してＣＢＰとＩｒ（ｐｐｙ）_３の蒸着速度が１００：７になるように調節し、２０ｎｍの厚さに蒸着し発光層を設けた。
【０１３４】
次いで、ＢＣの入った前記加熱ボートに通電して加熱し、蒸着速度０．１〜０．２ｎｍ／ｓｅｃで厚さ１０ｎｍの正孔ブロック層を設けた。更に、Ａｌｑ３の入った前記加熱ボートを通電して加熱し、蒸着速度０．１〜０．２ｎｍ／ｓｅｃで膜厚４０ｎｍの電子輸送層を設けた。さらに、酸化リチウム（Ｌｉ_２Ｏ）を０．５ｎｍ蒸着した。以上により形成した有機ＥＬ層Ｂの上に、ステンレス鋼性のマスク材により覆った後、アルミニウムを真空蒸着によって、１１０ｎｍ積層し、前記第１の電極Ａに対向した島状の第２の電極Ｃ、電流を供給する配線Ｄ及び該第２の電極と電流を供給する配線を接続する過電流により破断するヒューズ型配線Ｅを同時に形成した。図４に示すように第２の電極は前記ＩＴＯ膜からなる第１の電極と対向させるように、５００×５００μｍの矩形に、又、これと平行に電流を供給する配線を８０μｍの幅で、島状の電極との間隔が２０μｍ、接続するヒューズ型配線の幅が１５μｍとなるようにパターニングした。この例では、有機ＥＬ素子の陰極を本発明に係わる過電流によって電流を供給する配線から絶縁される電極として用いている。
図４（ａ）はこの様にして形成した有機ＥＬ素子の主に電極及び配線の配置を示す上面概略図であり、図４（ｂ）がｄ−ｄ′断面図を示す。
ちなみに、この有機ＥＬ素子からは、イリジウム錯体であるＩｒ（ｐｐｙ）_３からの緑色の発光が得られる。
【０１３５】
図５には、ガラス基板上に島状の電極及び電流を供給する配線の両方をＩＴＯ膜で１度にパターニング形成しヒューズ型配線として導電性高分子化合物でこれらを接続し、陽極として用いた有機ＥＬ素子例を示す。（ａ）はガラス等の基板１０上にＩＴＯ透明導電膜を蒸着により形成したところを示す。また、ＮＨテクノグラス社製（ＮＡ−４５）等の様にガラス上にＩＴＯを１５０ｎｍ成膜した上市されているガラス基板を用いてもよい。（ｂ）はこれにパターニングを行って、ＩＴＯ膜からなる島状の電極１及び電流を供給する配線２をパターンを形成したところである。
【０１３６】
島状の電極は５００μｍ×５００μｍの矩形、又、電流を供給する配線は幅８０μｍとし、電極及び電流を供給する配線の間隔は２０μｍとなるようにパターニングする。
（ｃ）は形成した島状の電極１及び電流を供給する配線２間を前記同様にＰＥＤＯＴ／ＰＳＳ水系懸濁液（Ｂａｙｅｒ製 Ｂｙｔｒｏｎ Ｐ ＴＰ ＡＩ ４０８３）を用いてインクジェット法によりパターン印字したところを示す。
（ｄ）は真空乾燥により島状の電極１と電流を供給する配線２間を接続するヒューズ型配線３が形成されたところを示す。乾燥時の厚みはＩＴＯ膜と同じ、且つ、配線幅は１０μｍとする。
【０１３７】
次いで、該電極パターン上に、図４の有機ＥＬ層と同じ有機ＥＬ層を順次、蒸着により形成する（図５（ｅ））。
【０１３８】
更に該有機ＥＬ層４上にマスク材を用いて、アルミニウムを真空蒸着によって、１１０ｎｍ積層し、前記の島状の電極と対向させ、略５００μｍの幅にパターニング形成して陰極５とする。
【０１３９】
電極に電流を供給する配線及びヒューズ型配線と同時に形成された島状の電極を陰極とした有機ＥＬ素子の一例を示す概略図である。
【０１４０】
図６は、一度のパターニングによって同時にガラス基板上に形成された、電流を供給する配線Ｄ、該配線に接続する過電流によって溶断若しくは破壊され電極を電流を供給する配線から絶縁するヒューズ型配線Ｅ及びヒューズ型配線と接続する島状の第１の電極Ａ（図６（ｄ）に得られたパターンを示す）を陰極として、該陰極上に、前記図４の説明における順序と逆に有機ＥＬ層Ｂを積層し、該有機ＥＬ層上に、ＩＴＯ膜からなる第２の電極Ｃを陽極としてマスクパターンを介して、スパッタリングにより形成（厚み１００ｎｍ）し有機ＥＬ素子を形成した例である。前記同様、陰極となる島状の第１の電極Ａは６００μｍ×６００μｍの矩形、又、これに電流を供給する配線２は幅８０μｍとし、電極及び電流を供給する配線の間隔は２０μｍ、島状の電極と電流を供給する配線を接続するヒューズ型配線は１５μｍの幅となるようパターニングし、又、陽極である第１の電極Ａに対向する帯状のＩＴＯ膜からなる第２の電極Ｃの幅は第１の電極Ａと略同じ幅とした。
【０１４１】
図６（ａ）は基板１０上に第１の電極Ａ、電流を供給する配線Ｄ及びヒューズ型配線Ｅを同時に形成したところを、（ｂ）は該電極パターンを有する基板上に有機ＥＬ層Ｂを形成したところを、更に（ｃ）が第２の電極Ｃを形成して有機ＥＬ素子を構成したところを示す。
【０１４２】
以上の様な構成によって、有機ＥＬ素子における画素の電極間のショートによって過電流が流れたとき、断面積が小さく形成されたヒューズ型配線が溶断もしくは破壊され、短絡した有機ＥＬ素子が電流を供給する配線から絶縁されることで切り離されるために、他の発光単位（画素となる有機ＥＬ素子）は影響を受けることがないので、有機ＥＬ素子全体としては発光を維持し、全面的なダメージを受けることがない。照明用の光源に用いる有機ＥＬ素子の場合にはトランジスタによって駆動されておらず電流を供給する配線と直接接続する構成となっているので特に効果が高い。
【０１４３】
本発明を用いることにより、有機ＥＬ（主に照明）用電極を容易に作製することができる。
【０１４４】
【発明の効果】
各々の発光単位を構成する有機ＥＬ素子の短絡による発光面全域の非発光を抑制でき、かつ、塗布、印刷により、簡単に、低コストで有機ＥＬ素子を構成する各層が形成できる有機ＥＬ素子が得られた。
【図面の簡単な説明】
【図１】本発明の電極の概略図である。
【図２】本発明の有機ＥＬ素子の一例を示す概略図である。
【図３】電流を供給する配線とヒューズ型配線を同時に形成した有機ＥＬ素子の一例を示す概略図である。
【図４】島状の電極、電流を供給する配線及びヒューズ型配線を同時に形成した有機ＥＬ素子の一例を示す概略図である。
【図５】島状の電極及び電流を供給する配線の両方をＩＴＯ膜で１度に形成した有機ＥＬ素子の一例を示す概略図である。
【図６】電流を供給する配線及びヒューズ型配線と同時に形成された島状の電極を陰極とした有機ＥＬ素子の一例を示す概略図である。
【符号の説明】
１ 島状の電極
２，Ｄ 電流を供給する配線
３，Ｅ ヒューズ型配線
４，Ｂ 有機ＥＬ層
５ 陰極
１０ ガラス基板
Ａ 第１の電極
Ｃ 第２の電極[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electrode connected by a fuse-type wiring that is blown or broken by an overcurrent and is electrically insulated, and an organic electroluminescent element using the electrode.
[0002]
[Prior art]
2. Description of the Related Art An organic electroluminescence element (hereinafter, sometimes referred to as an organic EL element) is a current-driven light-emitting element that emits light by passing a current between a very thin thin film between an anode and a cathode.
[0003]
Normally, an organic substance is an insulator, but by making the thickness of the organic layer extremely thin, current can be injected and the organic layer can be driven.
[0004]
However, since the thickness of the organic layer is extremely small, the anode and the cathode may be short-circuited due to dust on the electrode, unevenness of the electrode, and the like.
[0005]
In such a case, the short-circuited portion may be broken down due to overcurrent and become insulated due to the short-circuit of the electrode, but in the worst case, the short-circuited portion may be further increased, and as a result, almost all of the current is short-circuited The whole element may not emit light by flowing through the portion.
[0006]
Such a phenomenon will be a serious problem when the organic EL element is applied not only to a display but also to lighting in the future.
[0007]
This is because the entire light emitting surface becomes non-luminous due to one short circuit.
[0008]
In order to solve the problem of non-light emission of the entire EL element due to such a short circuit, in the disclosure of Patent Document 1 (Japanese Patent Application Laid-Open No. 2001-319778), a light-emitting region is composed of a plurality of EL elements by a partition for forming small pixels. Each pixel is divided into small pixels, and a part of a pixel forming partition forming each pixel is cut out, and a planar electrode in the small pixel passes a current outside the partition through the cutout. It has a configuration connected to the wiring to be supplied. When a short circuit occurs in an electrode in each pixel, the cutout portion is blown and the electrode and the wiring for supplying current are cut off, so that the inside of the small pixel and the outside of the small pixel are electrically connected. It is designed to be shut off.
[0009]
However, in the organic EL element disclosed in the above-mentioned publication, a partition for forming small pixels is provided, and a part of the partition is cut out, so that the manufacturing method becomes very complicated.
[0010]
Moreover, since the partition is used, the organic EL element formed thereon cannot be formed by application such as spin coating, printing, or the like.
[0011]
Also, recently, it has been reported that an etchant for producing a partition wall remains in the partition wall portion, which affects the element life of the organic EL element.
[0012]
[Patent Document 1]
JP 2001-319778 A
[0013]
[Problems to be solved by the invention]
Therefore, an object of the present invention is to suppress non-emission of light over the entire light-emitting surface due to short-circuiting of the organic electroluminescence element constituting each pixel, and it is possible to manufacture it simply and at low cost. An object of the present invention is to provide an electrode capable of easily forming each layer constituting an organic EL element by using the method, a method for manufacturing the same, and an organic EL element using the electrode.
[0014]
[Means for Solving the Problems]
The above object of the present invention is achieved by the following means.
[0015]
1. An island-shaped electrode formed separately on a substrate and connected to a wiring for supplying a current to the electrode by a fuse-type wiring which is melted or broken by an overcurrent and electrically insulated. Electrode.
[0016]
2. 2. The electrode according to the above item 1, wherein the wiring that is melted or broken by an overcurrent flowing through the electrode and electrically insulated is made of a conductive polymer compound.
[0017]
3. In a method of manufacturing an island-shaped electrode connected to a wiring that is formed separately on a substrate and that is melted or broken by an overcurrent and electrically insulated from a wiring for supplying an electric current, the fusing is caused by an overcurrent. A method of manufacturing an electrode, wherein a fuse-type wiring that is broken and electrically insulated is made of a conductive polymer compound and is formed by an inkjet method or a printing method.
[0018]
4. 2. The electrode according to the above item 1, wherein the fuse-type wiring which is melted or broken by an overcurrent to be electrically insulated is made of the same metal material as the wiring or the electrode for supplying a current to the electrode.
[0019]
5. A method of manufacturing an island-shaped electrode, which is formed on a substrate and is separated by a fuse-type wiring which is melted or broken by an overcurrent and electrically insulated from a wiring for supplying a current, the method comprising: The electrode is formed in the same shape, the wiring for supplying current to the electrode, and the fuse type wiring which is blown or broken by overcurrent and electrically insulated are formed from the same metal material, and are formed at one time by vapor deposition or sputtering. Method for manufacturing an electrode.
[0020]
6. 3. The electrode according to 1 or 2, wherein the electrode is made of a transparent conductive film.
7. 7. An organic electroluminescence device using the electrode according to 1, 2, 4 or 6.
[0021]
8. 8. The organic electroluminescence device according to the above 7, wherein the electroluminescence is based on phosphorescence.
[0022]
9. 7. A method for manufacturing an organic electroluminescent device, comprising: sequentially stacking an organic compound layer composed of a single layer or a plurality of layers, and a second electrode on the electrode described in 1, 2, 4 or 6.
[0023]
10. 10. The method for producing an organic electroluminescence device according to the item 9, wherein a single layer or an organic compound layer including a plurality of layers is formed by coating.
[0024]
11. In an organic EL element in which a first electrode, an organic compound layer including a single layer or a plurality of layers, and a second electrode are sequentially stacked on a substrate, the second electrode is blown or broken by an overcurrent. An organic electroluminescent element, wherein the organic electroluminescent element is connected to a wiring for supplying a current through a fuse-type wiring which is electrically insulated.
[0025]
12. 12. The organic electroluminescence device according to the above item 11, wherein the fuse-type wiring which is blown or broken by an overcurrent to be electrically insulated is made of a metal material.
[0026]
13. A fuse type wiring which is blown or broken by overcurrent flowing and is electrically insulated is formed by depositing a metal material film by vapor deposition or sputtering and then patterning using a mask material. The organic electroluminescent device according to the above.
[0027]
14． 12. The organic electroluminescent device according to the above item 11, wherein the fuse-type wiring which is blown or broken by an overcurrent to be electrically insulated is made of a conductive polymer compound.
[0028]
15. 15. The organic electroluminescence device according to the above 14, wherein the fuse-type wiring which is blown or broken and electrically insulated by flowing an overcurrent made of a conductive polymer compound is patterned by an inkjet method or a printing method. .
[0029]
16. The organic electroluminescence device according to any one of items 11 to 15, wherein the substrate is a flexible resin substrate.
[0030]
17. The organic electroluminescence device according to any one of the items 11 to 16, wherein the organic electroluminescence device is used as a light source for illumination.
[0031]
Hereinafter, the present invention will be described in detail.
When an organic EL element is used as a display element, as disclosed in the above-mentioned JP-A-2001-319778, it is preferable to provide partition walls between pixels in order to prevent color turbidity or the like between pixels, It is necessary to provide a portion and conduct the conduction to the driving transistor from there. Since the partitions must be formed by etching or the like, both of them are provided with an improved configuration in which the formation of the partitions and short-circuiting (short-circuit) in each pixel prevent the entire light emitting region from emitting light due to overcurrent. This means that, especially in applications such as lighting, the cost becomes high and the production becomes difficult. Further, it is difficult to easily form the organic EL element on the electrode by coating, printing, etc. due to the presence of the partition.
[0032]
The present invention can solve the phenomenon that the entire light emitting region does not emit light due to short-circuiting between electrodes without providing any partition between the electrodes, and in particular, an electrode suitable for an organic EL element used for lighting Is provided.
[0033]
In an organic EL element for display use, at least one of an anode and a cathode is formed and used in an isolated island shape so as to constitute a plurality of organic EL elements corresponding to respective pixel units such as BGR. I have.
[0034]
Also, when an organic EL element is used as a light source for illumination, it is difficult to manufacture the entire surface with a single electrode from the viewpoint of uniformity. It is divided into elements (thus having a plurality of electrodes) to form this.
[0035]
When an element for display use or a light source for illumination is constituted by the plurality of organic EL elements, when an electrode is short-circuited in, for example, one of the organic EL elements, each electrode is connected to a wiring for supplying a current. As a result, current concentrates on the short-circuited portion, current does not flow to other elements constituting the pixel, and light emission may be reduced or may not be emitted at all.
[0036]
The present invention solves such a drawback, and is useful as an electrode for an organic EL device or the like by adopting the following structure, and a phenomenon in which the entire light emitting region becomes non-light emitting due to a short circuit between the electrodes. Can be obtained.
[0037]
In the present invention, at least one of the electrodes constituting each pixel of the organic EL element (a pixel such as a BGR in a display application, or a plurality of separated small pixels also in an illumination application). The isolated island-shaped electrode corresponding to each pixel is connected to a wiring for supplying current through a fuse-type wiring (hereinafter, also simply referred to as a fuse-type wiring) that is blown or broken by an overcurrent and is electrically insulated. To do.
[0038]
That is, one of the electrodes is connected to an electrode formed in a form of an island on a substrate and connected by a fuse-type wiring which is melted or broken by overcurrent and electrically insulated from a wiring for supplying current. The organic EL element may be used as a cathode (cathode or anode).
[0039]
By using such an electrode as at least one electrode of the organic EL element, when the electrodes are short-circuited, only the electrode of the short-circuited organic EL element (pixel) is blown by an overcurrent connected to a wiring for supplying current. Alternatively, the destroyed fuse-type wiring is electrically insulated from the current supply wiring, so that only the pixel does not emit light and does not affect the electroluminescence of the entire organic EL element. .
[0040]
For example, in the case of an organic EL element for display use, between an ITO electrode serving as an anode (a transparent electrode is usually used because it is observed from the anode side) and a source or drain electrode of a transistor connected to a drive line (wiring for supplying current). Is used as a wiring for connecting the fuses, which is blown or broken when the overcurrent flows.
[0041]
When used as an illumination light source, a wiring for supplying current and one of the electrodes constituting the organic EL element are directly connected by a fuse-type wiring which is blown or broken when an overcurrent flows. Thereby, the above effects can be obtained.
[0042]
The electrode according to the present invention is preferably highly effective when applied to an organic EL element for an illumination light source in which a current supply wiring and an electrode are directly connected without the intervention of a transistor or the like. Therefore, also in the organic EL element for display use, the simple matrix method is more directly affected by the overcurrent than the organic EL element of the active matrix driving method using the driving transistor, and the effect of the present invention is large.
[0043]
Fuse-type wiring that is blown or destroyed by the flow of an overcurrent is defined as a cross-sectional area of the island-shaped electrode and a wiring for supplying current, for example, thinner, narrower, or thinner. What is necessary is just to form wiring so that there may be blown or destroyed when an overcurrent flows by forming a thin film etc., and the same as the material forming the island-shaped electrode or the wiring supplying current. It may be formed of a material. For example, when the electrode material is formed of a cathode material of an organic EL element, for example, a mixture of Al or Mg / Ag or the like, a wiring for supplying a current is also formed of the same metal material, and the wiring for connecting the wiring and the electrode is formed. The fuse type wiring is also formed of the same material, and its width, thickness or thickness is reduced so that the portion is destroyed by overcurrent. When the same metal material is used, a metal film is uniformly formed, and then patterned using a mask material, and a cross-sectional area of the wiring portion is formed so as to function as a fuse-type wiring which is blown or broken by an overcurrent. It is preferable to make it small.
[0044]
Fusing refers to melting of the wiring due to the heat generated by the wiring, disconnection of the wiring, and insulation between the island-shaped electrode and the wiring supplying current to the electrode. Destruction refers to the breaking of the wiring without going through the molten state. This means that the electrodes are insulated from the wires supplying the current.
[0045]
Since the cathode material of the organic EL element is a metal having a small work function, a stable metal material can be used as a wiring for supplying a current such as a drive line, and the material of the island-shaped electrode is used. A metal material having a small work function suitable for a cathode of an organic EL element is used, and another wiring for supplying a current is made of a stable, highly conductive (low resistivity) metal material such as gold, silver, or copper. May be formed. In this case, it is preferable to use the same material as that of the electrode or the wiring for supplying the current as the fuse type wiring for connecting the electrode and the wiring for supplying the current.
[0046]
When an island-shaped electrode, a wiring for supplying a current, and a fuse-type wiring connecting the electrode and the wiring for supplying a current are formed of the same metal material, the cross-sectional area is made smaller than other wirings. For example, after a metal film of gold, silver, copper, or the like having a thickness of 100 nm to 300 nm is uniformly formed on a substrate, an island-shaped electrode (corresponding to one pixel) is formed into a rectangle having a side of 600 μm by patterning. The width of the wiring for supplying the current is set to 50 to 300 μm, and the width of the fuse type wiring connecting the electrode and the wiring for supplying the current is set to 2 to 50 μm, preferably 1 to 20 μm. The fuse-type wiring has a smaller cross-sectional area than a wiring for supplying current, thereby facilitating breakage when an overcurrent flows.
[0047]
In order to form a fuse type wiring which is blown or destroyed by the overcurrent, it is not always necessary to form the fuse type wiring together with an electrode or a wiring for supplying an electric current and using the same material. After the wiring for supplying the current is formed, each island-shaped electrode and the wiring for supplying the current can be electrically connected by forming a fuse-type wiring using various conductive materials.
[0048]
That is, after simultaneously forming an island-shaped electrode made of a metal film and a wiring for supplying current on the substrate by patterning, printing between the island-shaped electrode and the wiring for supplying current with ink or paste made of a conductive material. A fuse type wiring which is blown or broken by an overcurrent by a method or an ink jet method may be formed by patterning and connected.
[0049]
At the current value flowing between the electrodes during normal driving, the fuse-type wiring hardly generates heat, and when a short-circuit current flows, the fuse-type wiring is given a somewhat large resistance value by other wiring materials, and the temperature due to the heat generation is increased. It is necessary to select the material and the cross-sectional area so that the rise is large, and to select the fusing or breaking temperature so that the material is blown or broken by the short-circuit current. The short-circuit current of the organic EL element varies depending on the organic EL material used, its configuration, the electrode area, and the like, but it should be broken when it becomes several to several tens times that of the operation. If the resistance value of the fuse-type wiring is too low than the current supply wiring, a load is applied to the current supply wiring, which is not preferable, and also it is not preferable from the viewpoint of protecting the current supply unit. On the other hand, if it is too large, the short-circuit current value will not be so large, and it is conceivable that the temperature does not reach the temperature at which the wiring breaks. Therefore, the resistance value of the fuse-type wiring, the cross-sectional area of the wiring that determines the same, and the like, depend on factors such as the value of the short-circuit current, the electrical conductivity of the material forming the fuse-type wiring to be used, and the temperature at which fusing or breaking occurs. It is chosen experimentally taking into account. As a material, a material having high electric conductivity (low resistivity) and being blown or broken by the short-circuit current is preferable.
[0050]
As a material having an electric conductivity of a certain level or more, a metal material is preferable, and a material which is relatively easily blown or broken is selected. Also, in order to prevent the current supply wiring from being blown, when using a metal, particularly when using the same material, the cross-sectional area of the fuse type wiring is made smaller than that of the current supply wiring, and the resistance is slightly reduced. The value can be increased so that fusing occurs here. The cross-sectional area is preferably 1/3 or less, more preferably 1/5 or less, of the current supply wiring.
[0051]
When using a material with a low melting point that is easily melted by a short-circuit current, or when using the same material as the electrode material or the wiring that supplies current, the heat generated by the short-circuit current is increased, and the temperature at which the material is melted or broken The wiring must be thin so that the temperature rises up to that point. In addition, the resistance value of the wiring is selected so that the temperature rises to a temperature at which the short circuit current is sufficiently blown or broken. On the other hand, if the resistance value is excessively increased, the current itself decreases.
[0052]
As a material of the fuse-type wiring that is blown or broken when an overcurrent flows between the plurality of island-shaped electrodes and a wiring that supplies a current to the electrodes, a conductive material as described above is used. It is not particularly limited as long as it is made of the same metal material as the electrode or the wiring supplying the current similarly to the above, and the fuse type wiring is made of a metal paste such as a silver paste, and another conductive substance such as a carbon paste. In particular, an organic conductive polymer compound is preferred for melting or breaking at a relatively low temperature. The conductive polymer compound is preferable because the electric conductivity, the fusing or breaking temperature, and the like can be selected from a relatively wide range depending on the degree of polymerization and the doping material.
[0053]
Examples of the conductive polymer compound that is advantageously used in the present invention include conductive polymers such as conductive polyaniline, conductive polypyrrole, and conductive polythiophene, or a conductive polymer whose conductivity has been improved by doping or the like. A polymer, for example, a conductive polymer such as a complex of polyethylenedioxythiophene and polystyrenesulfonic acid (PEDOT / PSS) is preferably used.
Of these, the electrical conductivity is 10 ³ Materials of S / m or more are preferred.
[0054]
Further, even when the fuse type electrode is formed of a conductive polymer, similarly to the case of the above-mentioned metal, since the resistance value is too low, heat generation of other wirings is increased, so that there is no fusing or breakage. In addition, the conductive polymer material is selected so that the resistance value is not so large that the value of the overcurrent becomes small enough not to blow or break the fuse type wiring. When a fuse-type wiring is formed of a conductive polymer material having the above-described electrical conductivity, the cross-sectional area is preferably smaller than that of a wiring supplying current, more preferably 1/3 or less, further preferably 1/5 or less. preferable.
[0055]
As a method for forming a wiring using these conductive polymers, a solution or dispersion or suspension of the conductive polymer may be directly patterned by an inkjet method, or may be formed from a coating film by lithography or laser ablation. . Further, a method of patterning an ink, a paste, or the like containing a conductive polymer by a printing method such as letterpress, intaglio, lithographic, or screen printing can also be used. The cross-sectional area of the fuse type wiring can be adjusted by the width and layer thickness of patterning.
[0056]
Among the conductive polymers, PEDOT / PSS is particularly preferable, and a commercially available product (eg, Baytron Bytron) can be obtained as an aqueous suspension or paste. A method of patterning by an ink-jet method or a method of patterning a conductive polymer paste by, for example, a screen printing method or the like is preferable because it can be performed with a simple procedure with high accuracy.
[0057]
Further, in the case of a conductive polymer, even if the material is blown or broken by an overcurrent, the breakage does not proceed during light emission and there is no problem in the durability as a wiring. As the temperature, a conductive polymer of 100 ° C. or higher, more preferably 150 ° C. or higher is selected.
[0058]
Further, the island-shaped electrode insulated from the wiring supplying the current by overcurrent may be a transparent electrode made of, for example, an ITO thin film used as an anode in the organic EL element, and the ITO thin film is deposited on the substrate. Then, both the island-shaped transparent electrode serving as an anode and the wiring for supplying current may be formed of an ITO thin film by patterning. However, as an electrode material of the organic EL element, a material such as gold, platinum, or an ITO film having a large work function must be used as an anode. On the other hand, sodium, which has a small work function, must be used as a cathode. Since it is necessary to use a metal such as magnesium or aluminum, and it is difficult to use a transparent material as a cathode material, it is preferable to use an ITO thin film as a transparent conductive film as an anode material and pattern and form island-shaped electrodes. Since the thin film has a higher resistivity as a material constituting a circuit than a metal such as gold or copper, it is preferable to use a metal film having a low resistivity as a wiring for supplying a current. After forming an island-shaped electrode, a mask material is separately formed using a photoresist or the like, and a thin film of a highly stable metal such as copper is sputtered. Adult, preferably separately formed wiring for supplying a current and patterned. If the wiring for supplying current is formed of ITO, the fuse-type wiring must be made of a material having a lower conductivity than this, and the value of the overcurrent is inevitably reduced. Limited. Although a metal material having good conductivity is not transparent like an ITO thin film, for example, when each pixel is separated by a shadow mask such as a black matrix, a wiring for supplying a current can be hidden behind the pixel. . Further, also in lighting applications, a wiring for supplying a current can be formed using a material having good conductivity, so that the width of the wiring is less noticeable than each pixel.
[0059]
After the island-shaped electrode and the wiring for supplying the current are formed of the ITO film, or the island-shaped electrode is formed of the ITO film, and the wiring for supplying the current is formed of a low-resistance metal such as gold or copper. After being formed of another metal film, a fuse-type wiring between these electrodes and a wiring for supplying current can be formed of another conductive material as described above. However, it is preferable that the fuse-type wiring is formed of another metal film such as gold, copper or the like, which is the same as the wiring for supplying a current. Further, for example, the aqueous dispersion of the conductive polymer compound such as PEDOT / PSS is preferable. It is preferable to use a liquid or suspension, paste, or the like to directly pattern by an ink-jet method, or to form a paste by patterning by screen printing or the like because a fuse-type wiring can be formed easily and accurately.
[0060]
The island-shaped electrode, the wiring for supplying a current to the electrode, and the fuse-type wiring for electrically connecting the electrode and fusing or breaking due to overcurrent have been described above. In many cases, the present invention relates to an organic material in which the island-shaped electrode is used as an anode or a cathode when the island-shaped electrode is short-circuited with a counter electrode. A second element which electrically insulates and separates the EL element by an overcurrent and supplies a current to the electrode formed in an island shape, for example, is a second electrode serving as a counter electrode of the electrode formed in the island shape. Since it is preferable that the second electrode serving as the counter electrode is arranged so as not to overlap with the electrode, the second electrode serving as the counter electrode does not overlap with the wiring for supplying the current and is arranged in parallel. In the case of orthogonal arrangement, it is preferable to coat a highly reliable insulating film on an overlapping portion of a wiring for supplying current and a second electrode which is a counter electrode orthogonal to the wiring.
[0061]
Therefore, in an organic EL element for display use, for example, when an ITO electrode serving as an anode is patterned in an island shape, the second electrode serving as a cathode is preferably formed in a band shape, and the anode is used as the anode. Since it is necessary to orthogonally arrange a row of ITO electrodes patterned in each island shape and a wiring (drive line) for supplying current, an overlapping portion of the wiring for supplying current and the second electrode serving as a cathode is provided. When a short circuit occurs in this portion, the short circuit occurs on the power supply side rather than the fuse type wiring, and the light emission of the entire organic EL element is affected. Therefore, in this case, it is necessary to completely insulate the overlapping portion, and the configuration becomes complicated.
[0062]
In the case of an organic EL element for illumination, it is not necessary to perform the time-division operation of each pixel, so there is no need for such orthogonal arrangement, and when a plurality of separated island-shaped electrodes are used as anodes, It is preferable that the pattern is formed in parallel, and a wiring for supplying a current for supplying a current to the electrode and a strip-shaped pattern of a cathode of the organic EL element serving as a counter electrode are arranged in parallel so as not to overlap.
[0063]
Next, an organic EL device using the electrode according to the present invention will be described.
The organic electroluminescence (EL) element includes a single layer or an organic compound layer composed of a plurality of layers, specifically, a light emitting layer, and if necessary, a hole transport layer, an electron transport layer, A structure in which layers such as an anode buffer layer and a cathode buffer layer are sandwiched between a cathode and an anode is adopted. The electrode according to the present invention is used as at least one of an anode and a cathode to constitute an organic EL device of the present invention.
[0064]
In particular,
(I) anode / light-emitting layer / cathode
(Ii) anode / hole transport layer / light-emitting layer / cathode
(Iii) anode / light-emitting layer / electron transport layer / cathode
(Iv) anode / hole transport layer / light-emitting layer / electron transport layer / cathode
(V) anode / anode buffer layer / hole transport layer / emission layer / electron transport layer / cathode buffer layer / cathode
(Vi) anode / anode buffer layer / hole transport layer / emission layer / hole block layer / electron transport layer / cathode buffer layer / cathode
There are such structures.
[0065]
The light emitting layer is an electrode or an electron transporting layer, a layer in which electrons and holes injected from the hole transporting layer are recombined to emit light, and a light emitting portion is a light emitting layer even in the light emitting layer. It may be an interface with an adjacent layer.
[0066]
The material used for the light-emitting layer (hereinafter, referred to as a light-emitting material) is preferably an organic compound or complex that emits fluorescence or phosphorescence, and is appropriately selected from known materials used for the light-emitting layer of the organic EL device. Can be used. Such a light emitting material is mainly an organic compound, and according to a desired color tone, for example, Macromol. Synth. And the like, vol. 125, pp. 17-25.
[0067]
The light emitting material may have a hole transport function and an electron transport function in addition to the light emitting performance, and most of the hole transport material and the electron transport material can be used as the light emitting material.
[0068]
The light-emitting material may be a polymer material such as polyvinyl carbazole, p-polyphenylenevinylene, polyfluorene, or the like. Further, a polymer in which the light-emitting material is introduced into a polymer chain or the light-emitting material is a polymer main chain. Materials may be used.
[0069]
This light emitting layer can be formed by forming the above compound into a thin film by a known thinning method such as a vacuum evaporation method, a spin coating method, a casting method, and an LB method. The thickness of the light emitting layer is not particularly limited, but is usually selected in the range of 5 nm to 5 μm, preferably 5 nm to 200 nm. This light-emitting layer may have a single-layer structure composed of one or two or more of these light-emitting materials, or may have a laminated structure composed of a plurality of layers having the same composition or different compositions.
[0070]
When the light emitting layer is made of two or more materials, the main component is called a host compound, and the other components are called dopants. It is preferable to use a dopant (guest material) in combination in the light emitting layer, and any one of known ones used as a dopant for an organic EL device can be used.
[0071]
Specific examples of the dopant include, for example, quinacridone, DCM (4-dicyanomethylene-2-methyl-6- (p-dimethylaminostyryl) -4H-pyran), coumarin derivative, rhodamine, rubrene, decyclene, pyrazoline derivative, and squarylium derivative. , Europium complex and the like are typical examples.
[0072]
Also, for example, an iridium complex described in JP-A-2001-247859 or a tris (2-phenylpyridine) iridium or an osmium complex represented by a formula as shown in pages 16 to 18 of WO0070655, or Platinum complexes such as 2,3,7,8,12,13,17,18-octaethyl-21H, 23H-porphyrin platinum complexes are also mentioned as dopants. By using such a phosphorescent compound as a dopant, a light-emitting organic EL device having high internal quantum efficiency based on phosphorescence can be realized.
[0073]
Particularly preferred as these phosphorescent compounds are, in particular, complex compounds containing a metal belonging to Group VIII in the periodic table of the elements as a central metal. More preferably, the central metal is an osmium, iridium or platinum complex compound. Most preferably, it is an iridium complex.
[0074]
These phosphorescent compound dopants include the following compounds.
[0075]
Embedded image

[0076]
Embedded image

[0077]
Embedded image

[0078]
These light-emitting layers can be formed by forming the above compound by a known thinning method such as a vacuum evaporation method, a spin coating method, a casting method, and an LB method. The thickness of the light emitting layer is not particularly limited, but is usually selected in the range of 5 nm to 5 μm.
[0079]
The light-emitting layer may have a single-layer structure composed of one or two or more of these light-emitting materials, or may have a laminated structure composed of a plurality of layers having the same composition or different compositions.
[0080]
As described in JP-A-57-51781, these light-emitting layers are prepared by dissolving the light-emitting material together with a binder such as a resin in a solvent to form a solution, and then spin-coating the solution. Can be formed as a thin film.
[0081]
The light emitting layer can be formed by a known thinning method such as a vacuum evaporation method, a spin coating method, a casting method, and a Langmuir-Blodgett method (LB method). The thickness of the light emitting layer is not particularly limited, but is usually selected in the range of 5 nm to 5 μm. These light-emitting layers may have a single-layer structure composed of one or two or more of these light-emitting materials, or may have a laminated structure composed of a plurality of layers having the same composition or different compositions.
[0082]
Next, the hole injection layer, the hole transport layer, the electron injection layer, and the electron transport layer will be described.
[0083]
The hole injection layer and the hole transport layer have a function of transmitting holes injected from the anode to the light emitting layer. By interposing the hole transport layer between the anode and the light emitting layer, a lower electric field can be obtained. In addition, many holes are injected into the light emitting layer, and the electrons injected from the cathode, the cathode buffer layer, the electron injection layer or the electron transport layer into the light emitting layer are electrons existing at the interface between the light emitting layer and the hole transport layer. By the above barrier, the device is excellent in light emitting performance, for example, accumulated at the interface in the light emitting layer to improve light emitting efficiency. The material of the hole transport layer (hereinafter, referred to as a hole injection material and a hole transport material) is not particularly limited as long as it has the above preferable properties. Any material can be selected from those commonly used as an injection transport material and known materials used for a hole transport layer of an EL device.
[0084]
The hole injection material and the hole transport material have any of hole injection or transport and electron barrier properties, and may be any of an organic substance and an inorganic substance. Examples of the hole transport material include triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives and pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styryl anthracene derivatives Fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline-based copolymers, and conductive polymer oligomers, particularly thiophene oligomers. As the hole transporting material, those described above can be used, but it is preferable to use a porphyrin compound, an aromatic tertiary amine compound and a styrylamine compound, particularly an aromatic tertiary amine compound.
[0085]
Representative examples of the aromatic tertiary amine compound and styrylamine compound include N, N, N ', N'-tetraphenyl-4,4'-diaminophenyl; N, N'-diphenyl-N, N' -Bis (3-methylphenyl)-[1,1'-biphenyl] -4,4'-diamine (TPD); 2,2-bis (4-di-p-tolylaminophenyl) propane; 1,1- Bis (4-di-p-tolylaminophenyl) cyclohexane; N, N, N ', N'-tetra-p-tolyl-4,4'-diaminobiphenyl; 1,1-bis (4-di-p- Tolaminophenyl) -4-phenylcyclohexane; bis (4-dimethylamino-2-methylphenyl) phenylmethane; bis (4-di-p-tolylaminophenyl) phenylmethane; N, N'-diphenyl-N, N -Di (4-methoxyphenyl) -4,4'-diaminobiphenyl; N, N, N ', N'-tetraphenyl-4,4'-diaminodiphenyl ether; 4,4'-bis (diphenylamino) quadri Phenyl; N, N, N-tri (p-tolyl) amine; 4- (di-p-tolylamino) -4 '-[4- (di-p-tolylamino) styryl] stilbene; 4-N, N-diphenyl Amino- (2-diphenylvinyl) benzene; 3-methoxy-4'-N, N-diphenylaminostilbenzene; N-phenylcarbazole, and further described in U.S. Pat. No. 5,061,569. Those having two condensed aromatic rings in the molecule, for example, 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (NPD); No. 8688, 4,4 ′, 4 ″ -tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine in which three triphenylamine units are linked in a starburst form. MTDATA).
[0086]
Further, a polymer material in which these materials are introduced into a polymer chain, or a polymer material in which these materials are used as a polymer main chain, can also be used.
[0087]
Further, inorganic compounds such as p-type Si and p-type SiC can also be used as the hole injection material and the hole transport material. The hole injecting layer and the hole transporting layer are formed by thinning the hole injecting material and the hole transporting material by a known method such as a vacuum evaporation method, a spin coating method, a casting method, and an LB method. Can be formed. The thickness of the hole injection layer and the hole transport layer is not particularly limited, but is usually about 5 nm to 5 μm. The hole injecting layer and the hole transporting layer may have a single-layer structure composed of one or more of the above materials, or may have a laminated structure composed of a plurality of layers having the same composition or different compositions. Furthermore, the electron transporting layer used as needed may have a function of transmitting electrons injected from the cathode to the light emitting layer, and any material may be selected from conventionally known compounds. Can be used.
[0088]
Examples of materials used for the electron injecting layer and the electron transporting layer (hereinafter, referred to as an electron injecting material and an electron transporting material) include heterocyclic tetracyclics such as nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, and naphthalene perylene. Examples thereof include carboxylic anhydride, carbodiimide, fluorenylidenemethane derivative, anthraquinodimethane and anthrone derivative, oxadiazole derivative, triazole derivative, and phenanthroline derivative. Further, in the oxadiazole derivative, a thiadiazole derivative in which an oxygen atom of an oxadiazole ring is substituted with a sulfur atom, and a quinoxaline derivative having a quinoxaline ring known as an electron withdrawing group are also used as an electron injection material and an electron transport material. be able to.
[0089]
Further, a polymer material in which these materials are introduced into a polymer chain, or a polymer material in which these materials are used as a polymer main chain, can also be used.
[0090]
Also, metal complexes of 8-quinolinol derivatives, such as tris (8-quinolinol) aluminum (Alq3), tris (5,7-dichloro-8-quinolinol) aluminum, tris (5,7-dibromo-8-quinolinol) aluminum, Tris (2-methyl-8-quinolinol) aluminum, tris (5-methyl-8-quinolinol) aluminum, bis (8-quinolinol) zinc (Znq), and the like, and the central metals of these metal complexes are In, Mg, Cu , Ca, Sn, Ga or Pb can also be used as an electron injection material and an electron transport material. In addition, metal free or metal phthalocyanine, or those whose terminals are substituted with an alkyl group, a sulfonic acid group, or the like, can also be preferably used as an electron injection material and an electron transport material. Further, a distyrylpyrazine derivative used as a material for the light-emitting layer can also be used as an electron transporting material, and like the hole injection layer and the hole transport layer, inorganic materials such as n-type Si and n-type SiC. Semiconductors can also be used as electron transport materials.
[0091]
The electron injection layer and the electron transport layer can be formed by forming the above compound by a known thinning method such as a vacuum evaporation method, a spin coating method, a casting method, and an LB method. The thickness of the electron injection layer and the electron transport layer is not particularly limited, but is usually selected in the range of 5 nm to 5 μm. The electron injecting layer and the electron transporting layer may have a single layer structure composed of one or two or more of these electron injecting materials and electron transporting materials, or may have a laminated structure composed of a plurality of layers having the same composition or different compositions. There may be.
[0092]
Further, a buffer layer (electrode interface layer) may be present between the anode and the light emitting layer or the hole injection layer, and between the cathode and the light emitting layer or the electron injection layer.
[0093]
The buffer layer is a layer provided between the electrode and the organic layer for lowering the driving voltage and improving the luminous efficiency. “The organic EL device and the forefront of its industrialization (NTS, November 30, 1998, published by NTT )), Vol. 2, Chapter 2, "Electrode Materials" (pages 123 to 166), and includes an anode buffer layer and a cathode buffer layer.
[0094]
The details of the anode buffer layer are described in JP-A-9-45479, JP-A-9-260062, JP-A-8-288069 and the like. Specific examples thereof include a phthalocyanine buffer layer represented by copper phthalocyanine, and vanadium oxide. And a polymer buffer layer using a conductive polymer such as polyaniline (emeraldine) or polythiophene.
[0095]
The details of the cathode buffer layer are also described in JP-A-6-325871, JP-A-9-17574, and JP-A-10-74586. Specifically, a metal buffer layer represented by strontium, aluminum, and the like; Examples include an alkali metal compound buffer layer represented by lithium fluoride, an alkaline earth metal compound buffer layer represented by magnesium fluoride, and an oxide buffer layer represented by aluminum oxide.
[0096]
In particular, in the organic EL device of the present invention, when a cathode buffer layer was present, a large reduction in driving voltage and improvement in luminous efficiency were obtained.
[0097]
The buffer layer is desirably an extremely thin film, and the thickness is preferably in the range of 0.1 to 100 nm, depending on the material.
[0098]
Further, layers having other functions may be laminated as necessary in addition to the above-mentioned basic constituent layers. In the present invention, for example, JP-A-11-204258, JP-A-11-204359, and It is preferable to have a functional layer such as a hole blocking layer described on page 237 of the Industrialization Forefront (published by NTT Corporation on November 30, 1998).
[0099]
The hole blocking layer is provided between the light emitting layer and the electron transporting layer, or when the light emitting layer also functions as the hole transporting layer, between the hole transporting layer and the electron transporting layer to control hole transport. It is for doing. Typically, compounds such as bathocuproin (BC), a phenanthroline derivative, and a triazole derivative are used (for example, JP-A-8-109373 and JP-A-10-233284). The holes that have become difficult to move to the electron transport layer, so that the holes are filled in the hole blocking layer, and the holes filled in the hole blocking layer efficiently accumulate holes in the light emitting layer, and To improve the probability of electron-hole recombination in the semiconductor device, thereby achieving high efficiency of light emission.
[0100]
Next, the electrodes used in the organic EL element will be described. The electrodes of the organic EL element are composed of a cathode and an anode.
[0101]
As the anode in this organic EL element, a metal, an alloy, an electrically conductive compound, or a mixture thereof having a large work function (4 eV or more) as an electrode material is preferably used. Specific examples of such an electrode material include metals such as Au, CuI, indium tin oxide (ITO), and SnO. ₂ And a transparent conductive material such as ZnO.
[0102]
The above-mentioned anode may be formed by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering, and forming a pattern of a desired shape by a photolithography method, or (100 μm Above), a pattern may be formed through a mask having a desired shape at the time of vapor deposition or sputtering of the electrode material. When light is extracted from the anode, the transmittance is desirably greater than 10%, and the sheet resistance of the anode is preferably several hundred Ω / □ or less. Further, although the thickness depends on the material, it is usually selected in the range of 10 nm to 1 μm, preferably 10 nm to 200 nm.
[0103]
On the other hand, as a cathode, a metal having a small work function (4 eV or less) (referred to as an electron injecting metal), an alloy, an electrically conductive compound, and a mixture thereof are used as an electrode material. Specific examples of such an electrode material include sodium, sodium-potassium alloy, magnesium, lithium, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al ₂ O ₃ ) Mixtures, indium, lithium / aluminum mixtures, rare earth metals and the like. Among them, a mixture of an electron injecting metal and a second metal which is a metal having a large work function and a stable work function, such as a magnesium / silver mixture, magnesium, / Aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al ₂ O ₃ ) Mixtures, lithium / aluminum mixtures and the like are preferred.
[0104]
Further, as the cathode used in the organic EL device of the present invention, an aluminum alloy is preferable, and the aluminum content is particularly preferably from 90% by mass to less than 100% by mass, and most preferably from 95% by mass to less than 100% by mass. . As a result, the emission life of the organic EL element and the maximum achievable luminance can be significantly improved.
[0105]
The cathode can be manufactured by forming a thin film from these electrode substances by a method such as vapor deposition or sputtering. Further, the sheet resistance as the cathode is preferably several hundred Ω / □ or less, and the film thickness is usually selected in the range of 10 nm to 1 μm, preferably 50 to 200 nm. In order to transmit light, if either the anode or the cathode of the organic EL element is transparent or translucent, the luminous efficiency is advantageously improved.
[0106]
The substrate preferably used for the organic EL device of the present invention is not particularly limited in the type of glass, plastic, and the like, and is not particularly limited as long as it is transparent. Substrates preferably used for the electroluminescent device of the present invention include, for example, glass, quartz, and light-transmitting plastic films.
[0107]
Examples of the light-transmitting plastic film include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), polyetherimide, polyetheretherketone, polyphenylene sulfide, polyarylate, polyimide, and polycarbonate (PC). And a film made of cellulose triacetate (TAC), cellulose acetate propionate (CAP), and the like.
[0108]
Next, a preferred example of manufacturing the organic EL device will be described. As an example, a method for manufacturing an EL device including the above-described anode / anode buffer layer / hole transport layer / emission layer / hole block layer / electron transport layer / cathode buffer layer / cathode will be described. First, a thin film made of a desired electrode material, for example, a material for an anode is formed on an appropriate substrate by a method such as evaporation or sputtering so as to have a thickness of 1 μm or less, preferably in the range of 10 to 200 nm. Is prepared. Next, a thin film made of a material for the anode buffer layer, the hole transport layer, the light emitting layer, the hole block layer, the electron transport layer, and the cathode buffer layer is formed thereon.
[0109]
As a method for forming the organic thin film layer, there are a spin coating method, a casting method, a vapor deposition method, and the like as described above. However, from the viewpoint that a uniform film is easily obtained and a pinhole is not easily generated, vacuum deposition is performed. The method or the spin coating method is particularly preferred. Further, a different film forming method may be applied to each layer. When a vapor deposition method is employed for film formation, the vapor deposition conditions vary depending on the type of compound used, the target crystal structure of the molecular deposition film, the association structure, and the like. ^-6 -10 ^-2 It is desirable to appropriately select Pa, a deposition rate of 0.01 to 50 nm / sec, a substrate temperature of −50 to 300 ° C., and a film thickness of 5 nm to 5 μm.
[0110]
After the formation of these layers, a thin film made of a material for a cathode is formed thereon by a method such as vapor deposition or sputtering so as to have a thickness of 1 μm or less, preferably in the range of 50 to 200 nm, and a cathode is provided. As a result, a desired EL element is obtained. In the production of this organic EL device, it is preferable that the hole injection layer to the cathode are produced consistently by one evacuation, but it is also possible to take out and apply a different film forming method in the middle. It is necessary to consider that the work is performed in a dry inert gas atmosphere.
[0111]
In addition, the production order can be reversed, and the cathode, the cathode buffer layer, the electron transport layer, the hole block layer, the light emitting layer, the hole transport layer, the anode buffer layer, and the anode can be produced in this order. When a DC voltage is applied to the thus obtained EL device, light emission can be observed by applying a voltage of about 5 to 40 V with the positive polarity of the anode and the negative polarity of the cathode. Also, even if a voltage is applied in the opposite polarity, no current flows and no light emission occurs. Further, when an AC voltage is applied, light is emitted only when the anode is in the + state and the cathode is in the-state. The waveform of the applied AC may be arbitrary.
[0112]
In the organic EL device using the electrode of the present invention, it is preferable to use it as a kind of lamp such as an illumination light source or an exposure light source. However, a projection device of an image projection type or a still image or a moving image can be directly viewed. It may be used as a type of display device (display). When used as a display device for reproducing moving images, the driving method may be either a simple matrix (passive matrix) method or an active matrix method. As described above, the effect is large and preferable in the case of a simple matrix (passive matrix) system in which the electrodes are directly connected to the drive lines. Further, by using two or more kinds of the organic EL elements of the present invention having different emission colors, it is possible to emit light of multiple colors.
[0113]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the electrode and the organic EL device according to the present invention will be specifically described, but the present invention is not limited thereto.
[0114]
FIG. 1 shows an island-shaped electrode 1 made of a metal such as gold formed by depositing or sputtering a metal such as gold after forming a mask material on a glass substrate, and a wiring 2 for supplying a current to the electrode. FIG. 2 is a schematic view of an electrode of the present invention comprising a fuse type wiring 3 which is electrically connected between the electrode and a wiring for supplying a current and is blown or broken by an overcurrent. Further, after a uniform metal film such as gold is formed, it may be formed by etching.
[0115]
For example, a metal film forming an electrode and a wiring is formed by vapor deposition or sputtering so as to have a thickness of 200 nm (preferably in the range of 50 nm to 500 nm). The island-shaped electrode 1 is a rectangle of 600 μm × 600 μm. The wiring 2 for supplying the current is patterned so as to have a width of 80 μm, and the interval between the electrode and the wiring for supplying the current is 20 μm.
[0116]
The fuse-type wiring 3 which is blown or broken by an overcurrent is supplied with an island-shaped electrode 1 and a current by an ink-jet method using an aqueous suspension of a conductive polymer compound PEDOT / PSS (Bytron PTP AI 4083 manufactured by Bayer). Printing is performed between the wirings 2 so that the dry thickness is, for example, 100 nm and the wiring width is, for example, 15 μm. By making this wiring thin, when an overcurrent flows, this part is broken, and the electrode can be insulated from the wiring supplying the current. This fuse-type wiring can also be formed by printing a conductive polymer compound such as PEDOT / PSS into a paste by pattern printing by a screen printing method.
[0117]
FIG. 1A is a schematic view of an electrode and a wiring as viewed from above, and FIG. 1B is a diagram in which a conductive polymer compound suspension is printed between an island-like electrode 1 and a wiring 2 for supplying a current by an inkjet method. Here, (c) is a sectional view taken along line aa ′ of the electrode and the wiring, respectively, showing a state where the fuse wiring is formed by drying. An electrode made of a metal having a large work function such as gold can be used as an anode of an organic EL device. In this case, the cathode of the organic EL element is formed of an electrode using a transparent conductive film such as ITO so that light can be extracted.
[0118]
FIG. 2 is a schematic view showing an example of the organic EL device of the present invention in which island-shaped electrodes are formed of a transparent conductive material such as ITO. After the entire surface of the ITO film was formed on the glass substrate (thickness: 150 nm), a mask was formed by photolithography, and etching was performed (as an etching solution, water, concentrated hydrochloric acid and a 40% by mass ferric chloride solution in a mass ratio of 85: 8). : Using a mixture of 7) to form a plurality of island-shaped electrodes 1 (rectangular 600 μm × 600 μm). Next, after forming a photomask, a metal film such as copper or gold is formed by sputtering (thickness: 150 nm), and then, except for the mask, a pattern of the wiring 2 for supplying a current with the metal film such as gold or copper is formed. The patterning was performed so that the width of the wiring supplying the current was 80 μm, and the distance between each island-shaped electrode was 40 μm. Similarly to the above, an ITO electrode and a wiring pattern for supplying a current made of a metal are formed on the ITO film by an inkjet method using a PEDOT / PSS suspension (Bytron PTP AI 4083 manufactured by Bayer). A fuse type wiring 3 having a width of 30 μm and a dry thickness of 50 nm is formed between wirings for supplying a current, and these are connected.
[0119]
The substrate in which the island-shaped electrodes formed of the ITO film and the wiring made of metal or the like are patterned is placed in a cleaning container and subjected to IPA cleaning, and then the organic EL layer 4 (holes other than the electrodes constituting the organic EL element) are formed as follows. Each layer such as a transport layer, an electron transport layer, and a light-emitting layer is collectively referred to as such).
[0120]
That is, a liquid obtained by dissolving polyvinyl carbazole (Mw = 63,000, manufactured by Aldrich) as a hole transport material in dichloromethane was applied using a spin coater and dried to form a 40 nm hole transport layer.
[0121]
Next, polymethyl methacrylate (PMMA, Mw = 120,000, manufactured by Aldrich) and 4,4′-N, N′-dicarbazole biphenyl (CBP) as an electron transport material were further provided on the hole transport layer of the lake. A solution obtained by dissolving tris (2-phenylpyridine) iridium complex at a mass ratio of 10: 20: 1 in a mixed solution of methyl ethyl ketone / toluene is applied using a spin coater, and dried by vacuum drying to obtain a thickness. Formed a light emitting layer having a thickness of 40 nm.
[0122]
Next, after covering the organic EL layer 4 with a stainless steel mask material, in a vacuum evaporation apparatus, for example, magnesium is put in a Mo resistance heating boat and silver is put in a tungsten evaporation basket, and 2 × 10 ^-4 Under the conditions of Pa, each was heated to co-evaporate magnesium and silver (thickness: 110 nm) to form a pattern of the cathode 5 composed of a silver / magnesium mixture with an electrode having a width substantially corresponding to the island-shaped electrode 1 as the anode. They are formed in parallel so as to face each other and not to overlap with the wiring 2 for supplying a current to each of the island-shaped electrodes 1.
[0123]
FIG. 2A is a schematic top view mainly showing the arrangement of electrodes and wirings of the organic EL element thus formed, and FIG. 2B is a cross-sectional view taken along the line bb '.
[0124]
Because it is assumed to be used for lighting. The wiring for supplying a current to the anode and the band constituting the cathode are formed so as not to overlap in parallel.
[0125]
Further, all the wirings may be formed of an ITO film. However, since the ITO film has a slightly higher resistivity than the metal film, the wiring for supplying a current thereto is formed of a metal. Although a metal electrode having a low work function is used for a cathode of an organic EL element, it is difficult to obtain a cathode material having a high transmittance. On the other hand, since a film such as ITO can be used as an anode, a structure in which the anode is a transparent conductive film is usually used.
[0126]
FIG. 3 shows that, after patterning of the island-shaped electrode 1 using the ITO film, when the wiring 2 for supplying current is formed of metal, it is blown or broken by overcurrent with the same material as the wiring for supplying current. This is an example in which fuse type wirings 3 are simultaneously formed by patterning.
[0127]
That is, after the formation of the island-shaped electrode 1 made of an ITO film, a photomask is formed, a metal film such as copper or gold is formed by vapor deposition or sputtering, and the current is reduced by using a metal such as gold or copper except for the mask. And a fuse-type wiring 3 that is blown or destroyed by an overcurrent is formed at the same time.
FIG. 3A is a schematic top view showing mainly the arrangement of electrodes and wirings of the organic EL element thus formed, and FIG. 3B is a cross-sectional view taken along the line cc '.
[0128]
In this example, since the fuse-type wiring and the wiring supplying the current are made of the same metal material, the cross-sectional area of the fuse-type wiring may be set to 1/5 or less of the wiring supplying the current.
[0129]
After that, the organic EL layer 4 and the cathode 5 are formed in the same manner as described in FIG. 2 to obtain the organic EL element. The sizes and widths of the electrodes and the respective wirings are basically the same as those in FIG.
[0130]
FIG. 4 shows an example in which an island-shaped electrode, a wiring for supplying current to the electrode, and a fuse-type wiring for connecting and connecting the electrodes, which are blown or broken by an overcurrent, are formed at the same time.
[0131]
After the first electrode A is patterned and formed into a strip shape with a width of 500 μm on the substrate from the ITO film (thickness 100 nm) formed on the glass substrate (used as an anode), the following electrodes are formed on the glass substrate having the electrodes. Organic EL layer B was laminated.
[0132]
That is, the glass substrate was fixed to a substrate holder of a commercially available vacuum evaporation apparatus, and α-NPD (4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl) and CBP (4,4 '-(N, N'-biscarbazolyl) biphenyl), Ir (ppy) ₃ (Tris (2-phenylpyridine) iridium complex), BC (vasocuproine), and Alq3 (tris (8-quinolinolate) aluminum (III)) were each placed in a molybdenum resistance heating boat and attached to a vacuum evaporation apparatus.
[0133]
4 × 10 vacuum chamber ^-4 After reducing the pressure to Pa, the heating boat containing α-NPD was energized and heated to deposit α-NPD as a hole transport layer on ITO at a deposition rate of 0.1 to 0.2 nm / sec and a thickness of 40 nm. Was deposited. Further, the heating boat containing CBP and Ir (ppy) ₃ Energized independently for each boat containing CBP and Ir (ppy) ₃ Was adjusted so that the vapor deposition rate became 100: 7, and vapor deposition was performed to a thickness of 20 nm to provide a light emitting layer.
[0134]
Next, the heating boat containing BC was energized and heated to form a hole blocking layer having a thickness of 10 nm at a deposition rate of 0.1 to 0.2 nm / sec. Further, the heating boat containing Alq3 was energized and heated to form an electron transport layer having a thickness of 40 nm at a deposition rate of 0.1 to 0.2 nm / sec. In addition, lithium oxide (Li ₂ O) was deposited to a thickness of 0.5 nm. After covering the organic EL layer B formed as described above with a stainless steel mask material, 110 nm of aluminum is laminated by vacuum evaporation, and an island-shaped second electrode C facing the first electrode A is formed. Then, a wiring D for supplying a current and a fuse-type wiring E which is broken by an overcurrent and connects the second electrode and the wiring for supplying a current were formed at the same time. As shown in FIG. 4, the second electrode has a rectangular shape of 500 × 500 μm and a wiring for supplying a current in parallel with this, having a width of 80 μm, facing the first electrode made of the ITO film. The patterning was performed so that the distance between the island-shaped electrodes was 20 μm and the width of the connected fuse-type wiring was 15 μm. In this example, the cathode of the organic EL element is used as an electrode that is insulated from the wiring that supplies current due to overcurrent according to the present invention.
FIG. 4A is a schematic top view mainly showing the arrangement of electrodes and wirings of the organic EL element formed in this manner, and FIG. 4B is a sectional view taken along the line dd '.
Incidentally, from this organic EL element, Ir (ppy) which is an iridium complex ₃ Green light is obtained.
[0135]
In FIG. 5, both an island-shaped electrode and a wiring for supplying current are patterned and formed at once with an ITO film on a glass substrate, and they are connected as a fuse type wiring with a conductive polymer compound and used as an anode. An example of an organic EL device will be described. (A) shows a state in which an ITO transparent conductive film is formed on a substrate 10 such as glass by vapor deposition. Alternatively, a commercially available glass substrate having a 150 nm ITO film formed on glass, such as NH-Technoglass (NA-45), may be used. (B) is a pattern in which an island-like electrode 1 made of an ITO film and a wiring 2 for supplying a current are formed by patterning.
[0136]
The island-shaped electrodes are rectangular with a size of 500 μm × 500 μm, the wiring for supplying current is 80 μm in width, and the pattern between the electrodes and the wiring for supplying current is patterned to be 20 μm.
(C) shows a pattern printed by an inkjet method using a PEDOT / PSS aqueous suspension (Bytron PTP AI 4083 manufactured by Bayer) in the same manner as described above between the island-shaped electrode 1 and the wiring 2 for supplying current. Show.
(D) shows a state where a fuse-type wiring 3 for connecting between the island-shaped electrode 1 and the wiring 2 for supplying current is formed by vacuum drying. The thickness at the time of drying is the same as that of the ITO film, and the wiring width is 10 μm.
[0137]
Next, the same organic EL layer as the organic EL layer of FIG. 4 is sequentially formed on the electrode pattern by vapor deposition (FIG. 5E).
[0138]
Further, aluminum is laminated on the organic EL layer 4 by vacuum evaporation using a mask material to a thickness of 110 nm, and is patterned to have a width of about 500 μm so as to face the island-shaped electrode, thereby forming the cathode 5.
[0139]
FIG. 2 is a schematic diagram illustrating an example of an organic EL element having a cathode as an island-shaped electrode formed simultaneously with a wiring for supplying a current to the electrode and a fuse-type wiring.
[0140]
FIG. 6 shows a wiring D for supplying a current, which is simultaneously formed on a glass substrate by one patterning, and a fuse-type wiring E which is blown or broken by an overcurrent connected to the wiring and insulates the electrode from the wiring for supplying a current. And an island-shaped first electrode A (showing the pattern obtained in FIG. 6D) connected to the fuse-type wiring as a cathode, and an organic EL on the cathode in the reverse order of the description in FIG. This is an example in which a layer B is laminated and formed on the organic EL layer by sputtering (thickness: 100 nm) through a mask pattern using a second electrode C made of an ITO film as an anode to form an organic EL element. Similarly to the above, the first island-shaped electrode A serving as a cathode has a rectangular shape of 600 μm × 600 μm, the wiring 2 for supplying a current to the first electrode A has a width of 80 μm, and the interval between the electrode and the wiring for supplying the current is 20 μm. The fuse type wiring for connecting the current supplying electrode and the current supplying wiring is patterned so as to have a width of 15 μm, and the width of the second electrode C made of a band-shaped ITO film opposed to the first electrode A which is an anode. Has a width substantially equal to that of the first electrode A.
[0141]
FIG. 6A shows a state in which a first electrode A, a wiring D for supplying a current, and a fuse wiring E are simultaneously formed on a substrate 10, and FIG. 6B shows an organic EL layer B on a substrate having the electrode pattern. (C) shows a state in which the second electrode C is formed to constitute an organic EL element.
[0142]
With the above configuration, when an overcurrent flows due to a short circuit between the pixel electrodes in the organic EL element, the fuse type wiring having a small cross-sectional area is blown or broken, and the short-circuited organic EL element supplies a current. Since other light-emitting units (organic EL elements serving as pixels) are not affected because they are separated from each other by being insulated from the wiring, the organic EL element as a whole maintains the light emission and the overall damage is reduced. I will not receive it. In the case of an organic EL element used for a light source for illumination, the effect is particularly high because the organic EL element is not driven by a transistor and is directly connected to a wiring for supplying current.
[0143]
By using the present invention, an electrode for organic EL (mainly illumination) can be easily manufactured.
[0144]
【The invention's effect】
An organic EL element capable of suppressing non-emission of light over the entire light emitting surface due to short-circuiting of the organic EL element constituting each light emitting unit and capable of easily forming each layer constituting the organic EL element at low cost by coating and printing. Obtained.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of an electrode of the present invention.
FIG. 2 is a schematic view showing an example of the organic EL device of the present invention.
FIG. 3 is a schematic view showing an example of an organic EL element in which a current supply wiring and a fuse type wiring are simultaneously formed.
FIG. 4 is a schematic view showing an example of an organic EL element in which island-shaped electrodes, wirings for supplying current, and fuse-type wirings are simultaneously formed.
FIG. 5 is a schematic view showing an example of an organic EL element in which both an island-like electrode and a wiring for supplying a current are formed at once by an ITO film.
FIG. 6 is a schematic view showing an example of an organic EL element using an island-shaped electrode formed at the same time as a wiring for supplying a current and a fuse type wiring as a cathode.
[Explanation of symbols]
1 island electrode
2, D Wiring to supply current
3, E fuse type wiring
4, B Organic EL layer
5 Cathode
10 Glass substrate
A First electrode
C second electrode

Claims (17)

An island-shaped electrode formed separately on a substrate and connected to a wiring for supplying a current to the electrode by a fuse-type wiring which is melted or broken by an overcurrent and electrically insulated. Electrode. 2. The electrode according to claim 1, wherein the wiring which is melted or broken by an overcurrent flowing through the electrode and which is electrically insulated is made of a conductive polymer compound. In a method of manufacturing an island-shaped electrode connected to a wiring that is formed separately on a substrate and that is melted or broken by an overcurrent and electrically insulated from a wiring for supplying an electric current, the fusing is caused by an overcurrent. A method of manufacturing an electrode, wherein a fuse-type wiring that is broken and electrically insulated is made of a conductive polymer compound and is formed by an inkjet method or a printing method. 2. The electrode according to claim 1, wherein the fuse-type wiring that is blown or broken by an overcurrent to be electrically insulated is made of the same metal material as the wiring or the electrode that supplies current to the electrode. In a method of manufacturing an island-shaped electrode connected by a fuse-type wiring that is formed by being separated on a substrate and is electrically blown or broken by an overcurrent and electrically insulated from a wiring that supplies current,
The island-shaped electrode, the wiring for supplying current to the electrode, and the fuse-type wiring that is blown or broken by overcurrent and electrically insulated are formed from the same metal material and formed at one time by vapor deposition or sputtering. A method for producing an electrode, comprising: 3. The electrode according to claim 1, comprising a transparent conductive film. An organic electroluminescence device using the electrode according to claim 1. The organic electroluminescent device according to claim 7, wherein the electroluminescence is based on phosphorescence. A method for manufacturing an organic electroluminescent device, comprising: sequentially stacking a single layer or a plurality of layers of an organic compound layer and a second electrode on the electrode according to claim 1, 2, 4 or 6. . The method for manufacturing an organic electroluminescence device according to claim 9, wherein a single layer or an organic compound layer including a plurality of layers is formed by coating. In an organic EL element in which a first electrode, an organic compound layer including a single layer or a plurality of layers, and a second electrode are sequentially stacked on a substrate, the second electrode is blown or broken by an overcurrent. An organic electroluminescence device, wherein the organic electroluminescence device is connected to a wiring for supplying a current through a fuse-type wiring which is electrically insulated. The organic electroluminescence device according to claim 11, wherein the fuse-type wiring that is blown or broken by an overcurrent to be electrically insulated is made of a metal material. 13. The fuse-type wiring which is blown or broken by an overcurrent to be electrically insulated, and formed by depositing a metal material film by vapor deposition or sputtering and then patterning using a mask material. 3. The organic electroluminescent device according to 1.). The organic electroluminescence device according to claim 11, wherein the fuse-type wiring which is blown or broken by an overcurrent to be electrically insulated is made of a conductive polymer compound. 15. The organic electroluminescence according to claim 14, wherein the fuse-type wiring which is blown or broken and electrically insulated by flowing an overcurrent made of a conductive polymer compound is patterned by an inkjet method or a printing method. element. The organic electroluminescence device according to any one of claims 11 to 15, wherein the substrate is a flexible resin substrate. The organic electroluminescence device according to any one of claims 11 to 16, which is used as a light source for illumination.

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