JP3601760B2 - Organic electroluminescence device - Google Patents
Organic electroluminescence device Download PDFInfo
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- JP3601760B2 JP3601760B2 JP32087598A JP32087598A JP3601760B2 JP 3601760 B2 JP3601760 B2 JP 3601760B2 JP 32087598 A JP32087598 A JP 32087598A JP 32087598 A JP32087598 A JP 32087598A JP 3601760 B2 JP3601760 B2 JP 3601760B2
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- organic electroluminescence
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- 238000005401 electroluminescence Methods 0.000 title claims description 13
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- 229910000287 alkaline earth metal oxide Inorganic materials 0.000 claims description 4
- 125000000325 methylidene group Chemical group [H]C([H])=* 0.000 claims description 4
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Classifications
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K50/00—Organic light-emitting devices
- H10K50/80—Constructional details
- H10K50/84—Passivation; Containers; Encapsulations
- H10K50/846—Passivation; Containers; Encapsulations comprising getter material or desiccants
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- Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Electroluminescent Light Sources (AREA)
- Compositions Of Macromolecular Compounds (AREA)
Description
【0001】
【発明の属する技術分野】
本発明は、各種情報機器に使用される表示素子や発光素子において好適に用いられる有機エレクトロルミネッセンス(電界発光)素子(以下、「EL素子」と略記する)に関し、詳しくは、長期にわたって安定した発光特性を維持することが可能な有機EL素子に関する。
【0002】
【従来の技術】
近年、情報の多様化が進んでいる。その中で情報分野における表示デバイスは「美、軽、薄、優」が追求され、かつ低消費電力化、高速応答化へ向けて活発な開発が進められている。特に、高精細なフルカラー化への表示デバイスが各種考案されている。
【0003】
視野角依存性、高速応答性等の特徴を有する素子として、1980年の後半にタン(Tang)らによって、印加電圧10Vにおいて1000cd/m2以上の高輝度が得られる積層型有機EL素子が報告されてから(Appl.Phys.Lett.,51,913(1987))、有機EL素子は実用化に向けての研究が活発に行われている。また、有機高分子材料を用いた同様の素子も活発に開発が進められている。
【0004】
有機EL素子は低電圧で高い電流密度が実現できるため、無機EL素子やLEDに比べて高い発光輝度と発光効率が期待でき、更に、自発光型素子であるという利点も有している。
【0005】
従って、有機EL素子を用いた(多色発光)表示素子は、▲1▼高輝度と高コントラスト、▲2▼低電圧駆動と高い発光効率、▲3▼高解像度、▲4▼高視野性、▲5▼速い応答速度、▲6▼微細化とカラー化、▲7▼軽さと薄さ等の優れた特徴を有し、以上の点から「美、軽、薄、優」を満足するフラットパネルディスプレイへの応用が期待されている。
【0006】
有機EL発光素子の構成は、陽極2上に有機高分子薄膜を積層する、代表的な積層構造をとり、例えば、
(1)陽極(透明電極)/有機発光層/陰極(電極)
(2)陽極(透明電極)/正孔注入層/有機発光層/陰極(電極)
(3)陽極(透明電極)/有機発光層/電子注入層/陰極(電極)
(4)陽極(透明電極)/正孔注入層/有機発光層/電子注入層/陰極(電極)
などの層構成が挙げられ、かかる層構成は、特開平5−21163号、特開平5−114487号、特開平5−94876号、特開平5−94877号、特開平5−125360号、特開平5−134430号、特開平6−200242号、特開平6−234969号、特開平7−11245号、特開平7−11246号、特開平7−142168号、特開平7−282975号、特開平8−213171号、特開平8−227276号、特開平8−236273号、特開平8−279394号、特開平8−302340号、特開平8−315981号、特開平9−022782号、特開平9−102393号、特開平9−153395号、特開平9−204983号、特開平9−204984号、特開平9−204985号、特開平9−209127号、特開平9−232075号、特開平9−283279号、特開平9−293589号、特開平9−298090号、特開平9−306666号、特開平9−306668号、特開平9−330791号、特開平9−330792号、特開平10−012378号、特開平10−012379号、特開平10−012380号、特開平10−012383号、特開平10−022072号、特開平10−022076号、特開平10−039792号、特開平10−069981号、特開平10−083889号、特開平10−092583号、特開平10−106746号、特開平10−106753号、特開平10−125471号、特開平10−125472号、特開平10−125473号等の各公報に開示された手法にて形成することができる。
【0007】
かかる有機EL素子の課題は、▲1▼内部にキャリアを有しない有機絶縁体からなるが故に外部から効率よくキャリアを注入しなければいけないこと、▲2▼注入された正孔/電子キャリアの輸送効率の向上と再結合の確率を高め発光効率の向上を図る必要があること、▲3▼多色発光のカラーバランス、高輝度および高発光効率を得る必要があることであり、特に、▲4▼有機薄膜材料が、熱、水分、ガス等による膜質の変化を防ぎ得、物理的、化学的に安定で、形成された膜の界面および表面が平滑であることが必要である。
【0008】
しかし、今日では、既に東北パイオニア社によって、車搭載用の緑色モノクロ有機ELデイスプレイが1997年の11月より製品化されており、今後は多様化する社会のニーズに応えるべく、上記要求を満足し、長期安定性、高速応答性、多色表示、高精細なフルカラー表示として有機ELデイスプレイの実用化が急がれる。特に、高性能表示デバイスとして欠かせない性能は精細なカラー表示機能であり、その長期にわたり安定なことが実用化する上で重要である(機能材料、Vol.18、No.2、96頁以降に記載)。
【0009】
電極間に有機高分子材料からなる層を積層した積層構造をとる有機EL素子は、電流駆動型の素子であるがために、発光させるためには電極間(陽極、陰極)に電流を流さなければならない。しかし、一定期間駆動すると、発光輝度等の初期発光特性が著しく低下するという欠点がある。
【0010】
この発光特性の低下は、通電中はもちろん保存中にも進行し、特に、▲1▼素子の周囲に存在する酸素や水分により加速され、▲2▼有機積層膜中に吸着物として存在する酸素や水分に影響され、▲3▼素子作製時の部品に吸着している水分や製造時等における水分の浸入にも影響され、▲4▼封止層の欠陥部等から透過浸入する水分等にも影響されると考えられる。
【0011】
素子中に酸素や水分があった場合には、酸素や水分により素子積層構成材料の酸化や凝集等が促進されて、素子が劣化する要因となる。この酸化や水分による素子の劣化の代表的なものはダークスポットの発生と成長である。このダークスポットとは、発光欠陥点のことである。駆動時および保存中に酸化が進むと既存のダークスポットの成長が進み、発光面全体に広がる。かかるダークスポットの発生を抑えるためには、素子構造において、封止を行うことが重要となる。
【0012】
ダークスポットの発生を抑えるために、気密容器内に乾燥剤としての五酸化リンを配設して中空封止する方法(特開平3−261091号)、更にこの五酸化リンを含有する保護層および封止層を積層した構造を採用する方法(特開平7−169567号)が提案されているが、これらの方法では水分によりリン酸が生じ、有機積層体に悪影響を及ぼすことがある。更に、乾燥剤を含有した不活性液体を積層体上および気密容器内に充填させる方法(特開平5−41281号、特開平9−35868号)、感圧接着剤を用いた方法(米国特許第5,304,419号)等も提案されている。
【0013】
【発明が解決しようとする課題】
しかし、未だ、長期にわたって安定した発光特性を維持する有機EL素子を提供するには至っていない。即ち、上記の方法でもリーク電流やクロストークが発生することはないが、長期安定な発光特性を得るためには、ダークスポットの生成や成長を十分に抑えることが必要である。
【0014】
そのためには上述した発光特性の低下原因▲1▼〜▲4▼を解消することが重要であり、長期持続性効果のある乾燥手段を講じなければならない。
【0015】
単に乾燥剤を用いるだけでは持続性がなく、また乾燥剤が有機発光素子上に粉落ち等により付着することがあってはならない。そのためには均一で持続性のある吸着膜が必要であり、また、コストや工程的にも容易に入手できるものでなければならない。
【0016】
即ち、素子への水分等の影響を持続性よく抑えることができ、工程的かつコスト的にも優れた有機EL素子が求められている。
【0017】
そこで、本発明の目的は、製造工程並びに駆動中および保存時等において、素子に浸入する酸素や水分から素子積層構造材料の酸化等を長期にわたり持続性よく抑えることが可能な乾燥手段としての均一な吸着膜を設け、素子に悪影響を及ぼすことがないようにするとともに、封入の際の取り扱い等の工程を容易とした有機EL素子を提供することにある。これにより、素子のダークスポットの成長を持続性よく、強く抑制し、長期にわたって安定した発光特性を維持できるようにする。
【0018】
【課題を解決するための手段】
本発明者らは、上記多くの課題を解決するために鋭意研究した結果、乾燥手段として特定のポリマーを採用し、そのポリマーマトリックス中に乾燥剤化合物を分散させることにより上記目的を達成し得ることを見出し、本発明を完成するに至った。
即ち、本発明は以下の通りである。
【0019】
(1)有機化合物を含む有機発光層が互いに対向する電極間に配置されてなる積層体が支持体上に形成され、該積層体の周囲に空間をあけて気密容器を設けた有機エレクトロルミネッセンス素子において、前記気密容器内面の少なくとも一部に、下記一般式(I)、
(式中、Rは炭素数1〜6のメチレン鎖、mは1〜12の整数、nは1以上の整数を夫々表す)で示される構成単位を有する、官能基を有するアルコール可溶性直鎖脂肪族ポリアミドを主成分とするポリマーマトリックス中に無機系乾燥剤化合物を1重量%以上分散してなる吸着膜を形成したことを特徴とするものである。
【0020】
(2)前記有機エレクトロルミネッセンス素子において、前記乾燥剤化合物がアルカリ金属酸化物またはアルカリ土類金属酸化物の単独または複合物である有機エレクトロルミネッセンス素子である。
【0021】
(3)前記有機エレクトロルミネッセンス素子において、前記乾燥剤化合物の主成分が粒径1〜200ミクロンのγ型活性アルミナである有機エレクトロルミネッセンス素子である。
【0022】
(4)前記有機エレクトロルミネッセンス素子において、前記一般式(I)で示される直鎖脂肪族ポリアミド成分が単独で、または50重量%以上の混合形態でポリマーマトリックスを形成する有機エレクトロルミネッセンス素子である。
【0023】
(5)前記有機エレクトロルミネッセンス素子において、前記気密容器がガラス又は金属材料からなる有機エレクトロルミネッセンス素子である。
【0024】
【発明の実施の形態】
本発明の一実施の形態である有機EL素子は、図1に示すように、支持体1上に有機発光層3(正孔注入層3−1、正孔輸送層3−2、発光層3−3、電子注入層3−4)が互いに対向する電極間2、4に挟持されて設けられ、積層体を構成し、この積層体からなる発光素子が外気からの遮断のために気密容器5内に収納されている。この気密容器5の内面には、乾燥手段として、前記一般式(I)で表される官能基(N−メトキシアルキル基)を有する直鎖脂肪族ポリアミドを主成分としたマトリックスポリマー中に固体乾燥剤を分散したコーティング剤が印刷法、スピンコート法、またはキャスト法等で形成され、酸素や水分に対する吸着膜7を成す。尚、図中の符号8は外部回路を表している。
【0025】
本発明において乾燥手段として形成する吸着膜7は、封止後において外部から有機EL素子中に酸素や水分が浸入するのを防ぎ、また素子の作製工程中に浸入した酸素や水分等と、内部に当初から存する酸素や水分とを吸着し、かつ一度吸着した酸素や水分等を放出しにくい性質であることが、その効果として、ダークスポットの生成や成長を良好に抑制する上で好ましい。
【0026】
上述の如き観点から、本発明に係る吸着膜7中に分散し使用する無機乾燥剤は、形状は特に限定されるものではないが、粉体状のものの方が吸着面積が大きくなるので望ましい。
【0027】
本発明に使用可能な無機系乾燥剤化合物としては、例えば、アルカリ金属酸化物、アルカリ土類金属酸化物、硫酸塩、金属ハロゲン化物、過塩素酸塩を挙げることができ、特には、アルカリ金属酸化物またはアルカリ土類金属酸化物が好ましい。具体的には、活性アルミナ、珪素土、活性炭、五酸化リン、過塩素酸マグネシウム、水酸化カリウム、酸化カルシウム、塩化亜鉛、酸化バリウム、リチウム、ベリリウム、カリウム、マグネシウム、カルシウム、ゼオライト、シリカゲル等の金属等が挙げられる。この化合物は単独でも2種以上を併用してもよい。
【0028】
かかる乾燥剤化合物は十分な吸着能力を保持した状態下で使用しなければならないために、使用する前に、吸着している酸素や水分を除去する活性化処理を行っておくことが好ましい。この活性化処理方法は、例えば、外気から遮断された状態で、真空下にて150℃以上の加熱処理を行い、酸素や水分を除去する等、いろいろな方法を採用することができる。
【0029】
本発明においては、γ型活性アルミナを主成分とした系が、各特性や、安定性、本発明に係る共重合体との相溶性の面で、また取り扱い易さの点から、特に好ましい。
【0030】
かかる乾燥剤化合物の使用量は、所望の効果を得る上でマトリックスポリマー中に1重量%以上は必要であり、多い程効果が高い。粒径と効果との間にも相関があり、また、分散系のポリマーとの関係もあるが、2〜180重量%が、流動性や容器への密着性、また膜形成性から好ましい。粒径についても同様のことが関係し、表面積が大きい程効果が大きく、また、マトリックスポリマーとの関係からも適切な粒径があり、以上の観点から本発明では、平均粒径が、好ましくは1〜200ミクロン、より好ましくは2〜130ミクロンである。
【0031】
本発明においては、吸着膜7を形成するポリマーマトリックスの主成分として上記一般式(I)で表されるアルコール可溶性直鎖脂肪族ポリアミドを用いるが、アクリル系樹脂、エポキシ樹脂、アルキッド樹脂、ポリビニル樹脂、ポリウレタン樹脂、イミド樹脂等の汎用のコーティング樹脂を併用することができる。
【0032】
本発明に係る吸着膜7に用いられる上記アルコール可溶性直鎖脂肪族ポリアミドは、直鎖脂肪族ポリアミド(ナイロン)をホルムアミドと目的のアルキルアルコールで化学反応させて、部分的にアミド結合をN−メトキシメチル化したものである。アミド結合のメトキシメチル化度(MM化度)は5〜50%程度が好ましく、またメチレン鎖のmは2〜7が好ましく、更にアミド結合鎖中のRは炭素数1〜5のメチレン鎖が好ましい。かかるアルコール可溶性直鎖脂肪族ポリアミドの分子量は特に限定されない。このアルコール可溶性直鎖脂肪族ポリアミド自身も酸素や水分を吸着する機能を有しており、保持性に優れ、容器への密着性等に優れている。
【0033】
本発明に係るアルコール可溶性直鎖脂肪族ポリアミドの具体例としては、
ユニチカ(株)製:タイプ8ナイロン 品名「T−8−5、T−8−E」
日本リルサン(株)製:プラタボンド 品名「M995、M1276」
帝国化学産業(株)製:トレジン 品名「F−30、MF−30、EF−30T、FS−350、FS−500」
等が挙げられるが、この限りではない。
【0034】
上記乾燥剤をかかるアルコール可溶性直鎖脂肪族ポリアミドを主成分とするポリマーマトリックス中に分散させることで、酸素や水分の吸着性を高め、かつ吸着物の放出を防ぐ等の効果を著しく増すことができる。このようにして、素子内の酸素や水分を化学的に除去することで、ダークスポットの生成と成長とを大幅に抑制することができる。上記アルコール可溶性直鎖脂肪族ポリアミドは、上述のように単独でも他のポリマーと併用してもよいが、本発明に係るマトリックスポリマーは、不純物に対する処理を施すとともに、乾燥剤化合物の活性処理と同様にして、真空下、120℃で1時間以上乾燥し、水分を除去することが好ましい。このようにして得たポリマーと乾燥剤化合物とを溶存酸素が2ppm以下のグローブボックス内で分散し、上記方法で気密容器の内部に膜を形成することで吸着膜7が得られる。
【0035】
本発明の素子構造における支持体1は、光透過性に優れていればよく、例えばガラスの他に、ポリアクリル、ポリカーボネート等のプラスチック基板でもよいが、ガラス基板が一般的である。また、有機発光素子を外気より遮断する気密容器5は、ガラス製、またはステンレス、アルミ等の金属製とすることができる。
【0036】
支持体1上に有機発光素子として陽極2、有機発光層3、陰極4を積層し、さらに上述のようにしてこれに吸着膜7を形成した気密容器5を、水分と酸素濃度とを管理した環境雰囲気下(各々2ppm以下)で封止する。この際の封止剤としては液晶等の封止剤として使用されている接着剤、例えばエポキシ樹脂に代表される常温硬化タイプまたは生産性から紫外線硬化タイプ、あるいはカチオン重合タイプの紫外線硬化/温度併用タイプの接着剤等を用い、さらに、この接着剤中にギャップ剤としてガラス製スペーサー材、またはプラスチック製スペーサー材を分散させ、封止層6として接合を行うことで、本発明の有機EL素子を得ることができる。
【0037】
本発明の有機EL素子においては、乾燥手段としての上記吸着膜を、積層体からなる有機発光素子を外気から遮断する気密容器の内面に形成することで、ダークスポットの生成や成長がなく、長期にわたり安定的に発光特性を維持し、実用化に十分に耐えることができる。
【0038】
【実施例】
以下、本発明の有機EL素子を、実施例に基づきより詳細に説明する。
最初に、有機EL発光積層体の作製例を示す。
図1は、今回の試作評価用の有機EL層の層構成を示す概略的断面図である。支持体1としての透明ガラス基板上に、まず、陽極2として、スパッタ法にて透明電極(ITO)を全面成膜した。パターニングはITO上にレジスト剤(東京応化(株)製:OPPR−800)を塗布した後、0.096mmライン、0.11mmピッチのラインパターンが得られるマスクをガラス基板上に200mJ/cm2(365nm)で露光し、現像液(東京応化(株)製:NMD−3)により前記のITOラインパターンを得た。
【0039】
次いで、基板を抵抗加熱蒸着装置内に装着し、有機EL発光層3として、正孔注入層3−1、正孔輸送層3−2、発光層3−3、電子注入層3−4と真空を破らずに順次成膜し、有機EL発光積層体を得た。成膜に際して真空槽内圧は1×10−4Paまで減圧した。正孔注入層3−1は銅フタロシアニン(CuPc)を100nm積層した。正孔輸送層3−2は4,4’−ビス[N−(1−ナフチル)−N−フェニルアミノ]ビフェニル(α−NPD)を20nm積層した。発光層3−3は4,4’−ビス(2,2−ジフェニルビニル)ビフェニル(DPVBi)を30nm積層した。電子注入層3−4はアルミキレート(Alq)を20nm積層した。
【0040】
この後、この基板を真空槽から取り出し、新たに抵抗加熱蒸着装置内に装着した後、陰極4として、陽極2と直交する方向にMg/Ag(10:1の重量比率)を200nm形成した。有機EL発光積層体の材料は、上述の材料に限定されないのは勿論のことである。
【0041】
実施例1
本発明の構成要素であるポリマーマトリックス材料として、N−メトキシメチル化ポリアミド樹脂(トレジン:F30K、帝国化学産業(株)製)を、120℃で1.5時間真空下で乾燥し吸着水分を除去した後、無水エチルアルコールを用いて固形分15重量%に溶解し、ポリマー溶液を作製した。また、乾燥剤として平均粒径50ミクロンのγ型アルミナを200℃の真空下で2時間活性化処理を行った後、酸素溶存濃度が2ppm以下のグローブボックス内で、上記ポリマー溶液の固形分100重量部に対して上記処理された乾燥剤を100重量部分散させた。
【0042】
このようにして得られた吸着膜用溶液を、ガラス製の気密容器(封止ガラス)5の内面に成膜し、約120℃のホットプレート上で乾燥した。得られた気密容器で、ガラス支持体上において電極間に有機発光層を積層して形成した上記有機EL発光積層体を封止した。かかる封止は、ガラススぺーサーを分散したカチオン重合タイプの紫外線硬化型の接着剤(スリーボンド(株)製:3025G)を封止剤として用い、これを上記封止ガラス5の外周にディスペンサーを用いて塗布し、上記環境下でガラス基板に接合し、紫外線ランプ3000mJ/cm2の照度で硬化させることにより行った。
【0043】
得られた有機EL素子の評価方法として、発光させてダークスポットの発光状態を拡大写真で初期観察し、また60℃、90%の温湿度環境下でのダークスポットの促進テストで、その生成と成長を観察した。その結果、ダークスポットの生成と成長はほとんど観察されなかった。図2にその結果を示す。
【0044】
実施例2
実施例1における乾燥剤を上記マトリックスポリマー100重量部に対して50重量部分散させて、実施例1と同様に吸着膜を形成し、かつ実施例1と同じ方法で封止して、有機EL発光素子を形成した。
【0045】
実施例3
実施例1における乾燥剤の代りに、活性化処理を施したγ型アルミナと酸化バリウム(BaO)とを2:1の割合(重量%)で混合した混合乾燥剤を用い、かつ上記マトリックスポリマーの代りに、上記と同様の乾燥処理を施したユニチカ(株)製ポリマー(商品名:T−8−E)を用い、上記混合乾燥剤100重量部を上記ポリマー100重量部中に分散させて、実施例1と同様に吸着膜を形成し、かつ実施例1と同じ方法で封止して、有機EL発光素子を形成した。
【0046】
実施例4
実施例1におけるマトリックスポリマーの代りに、実施例1で用いたポリマーと汎用のヒドロキシ変性ポリアクリル樹脂とを2:1の割合(重量%)で併用した混合ポリマーを用い、この混合ポリマー100重量部に対して、実施例1と同様の乾燥剤を100重量部分散させて、実施例1と同様に吸着膜を形成し、同じ方法で封止して、有機EL発光素子を形成した。
【0047】
比較例1
吸着膜を気密容器の内面に形成しない他は、実施例1と同じ方法で封止して、有機EL発光素子を作製した。
【0048】
比較例2
実施例1における乾燥剤を用いずに、実施例1で用いたポリマーだけを気密容器の内面に形成し、他は実施例1と同様の方法で封止して、有機EL発光素子を作製した。
【0049】
比較例3
実施例1における乾燥剤を粘着テープ上に固定し、この粘着剤を用いて容器の内面に吸着膜を形成し、他は実施例1と同様の方法で封止して、有機EL発光素子を作製した。
【0050】
実施例2〜4および比較例1〜3についても実施例1と同様のダークスポット促進テストを行い、評価した。その結果、図2に示すように本発明に伴う実施例1〜4は比較例1〜3に比べてダークスポットの成長がほとんど観察されなかった。
【0051】
【発明の効果】
以上に詳述した通り、本発明によれば、素子に悪影響を及ぼす酸素や水分の存在を持続性よく、強く抑制することができ、かつ工程上も安価に作製することが可能である。その結果、リーク電流やクロストークの発生を招かずに、ダークスポットの生成と成長とを持続性よく、強く抑制することができる。よって、長期にわたって安定した発光特性を維持した、素子寿命の長い有機EL発光素子を提供することが可能になった。
【図面の簡単な説明】
【図1】本発明の一実施の形態に係る有機EL素子の断面図である。
【図2】実施例および比較例における時間とダークスポット径との関係を示すグラフである。
【符号の説明】
1 支持体
2 陽極
3 有機発光層
3−1 正孔注入層
3−2 正孔輸送層
3−3 発光層
3−4 電子注入層
4 陰極
5 気密容器
6 封止層
7 吸着膜
8 外部回路[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an organic electroluminescence (electroluminescence) element (hereinafter, abbreviated as “EL element”) suitably used in a display element or a light-emitting element used for various information devices, and more particularly, to stable light emission for a long time. The present invention relates to an organic EL device capable of maintaining characteristics.
[0002]
[Prior art]
In recent years, information has been diversified. Among them, display devices in the information field are pursuing “beauty, lightness, thinness, and excellence”, and active development is being promoted for low power consumption and high speed response. In particular, various display devices for high-definition full-color display have been devised.
[0003]
In the latter half of 1980, Tang et al. Reported a stacked organic EL device capable of obtaining a high luminance of 1000 cd / m 2 or more at an applied voltage of 10 V as a device having characteristics such as viewing angle dependence and high-speed response. Since that time (Appl. Phys. Lett., 51, 913 (1987)), research on practical use of organic EL devices has been actively conducted. Further, similar devices using organic polymer materials are also being actively developed.
[0004]
Since an organic EL element can realize a high current density at a low voltage, higher luminous luminance and luminous efficiency can be expected as compared with an inorganic EL element and an LED, and further, it has an advantage of being a self-luminous element.
[0005]
Therefore, a display element using an organic EL element (multicolor light emission) includes (1) high luminance and high contrast, (2) low voltage driving and high luminous efficiency, (3) high resolution, (4) high field of view, Flat panel that has excellent characteristics such as (5) fast response speed, (6) miniaturization and colorization, (7) lightness and thinness, and satisfies "beauty, lightness, thinness, and excellentness" from the above points. It is expected to be applied to displays.
[0006]
The configuration of the organic EL element has a typical laminated structure in which an organic polymer thin film is laminated on the
(1) Anode (transparent electrode) / organic light emitting layer / cathode (electrode)
(2) anode (transparent electrode) / hole injection layer / organic light emitting layer / cathode (electrode)
(3) Anode (transparent electrode) / organic light emitting layer / electron injection layer / cathode (electrode)
(4) anode (transparent electrode) / hole injection layer / organic light emitting layer / electron injection layer / cathode (electrode)
Such layer configurations include those described in JP-A-5-21163, JP-A-5-114487, JP-A-5-94876, JP-A-5-94877, JP-A-5-125360, and JP-A-5-125360. 5-134430, JP-A-6-200242, JP-A-6-234969, JP-A-7-112245, JP-A-7-112246, JP-A-7-142168, JP-A-7-282975, JP-A-8-208 JP-A-213171, JP-A-8-227276, JP-A-8-236273, JP-A-8-279394, JP-A-8-302340, JP-A-8-315981, JP-A-9-022782, and JP-A-9- 102393, JP-A-9-153395, JP-A-9-204983, JP-A-9-204498, JP-A-9-204985, JP-A-9-2 9127, JP-A-9-23275, JP-A-9-283279, JP-A-9-293589, JP-A-9-298090, JP-A-9-306666, JP-A-9-306668, JP-A-9-330791 JP-A-9-330792, JP-A-10-012378, JP-A-10-012379, JP-A-10-012380, JP-A-10-012383, JP-A-10-022072, and JP-A-10-022076 JP-A-10-039792, JP-A-10-069881, JP-A-10-088889, JP-A-10-092583, JP-A-10-106746, JP-A-10-106675, JP-A-10-125471, Techniques disclosed in JP-A-10-125472, JP-A-10-125473, etc. It is possible to form Te.
[0007]
The problems of such an organic EL device are that (1) the carrier must be efficiently injected from the outside because it is made of an organic insulator having no carrier inside, and (2) transport of the injected hole / electron carrier. It is necessary to increase the efficiency and the probability of recombination to increase the luminous efficiency, and (3) it is necessary to obtain a color balance of multicolor light emission, high luminance and high luminous efficiency, and in particular, (4) ▼ It is necessary that the organic thin film material can prevent a change in film quality due to heat, moisture, gas, etc., be physically and chemically stable, and have smooth interfaces and surfaces of the formed film.
[0008]
However, today, Tohoku Pioneer has already commercialized a green monochrome organic EL display for use in vehicles since November 1997, and will satisfy the above requirements in order to meet the diversifying needs of society. Organic EL displays are urgently required for long-term stability, high-speed response, multi-color display, and high-definition full-color display. In particular, the performance indispensable as a high-performance display device is a fine color display function, and its long-term stability is important for practical use (functional materials, Vol. 18, No. 2, pp. 96 et seq.). Described).
[0009]
An organic EL element having a layered structure in which a layer made of an organic polymer material is laminated between electrodes is a current-driven element. Therefore, in order to emit light, a current must be passed between the electrodes (anode and cathode). Must. However, when driven for a certain period, there is a disadvantage that initial light emission characteristics such as light emission luminance are significantly reduced.
[0010]
This decrease in light emission characteristics proceeds not only during energization but also during storage. In particular, (1) accelerated by oxygen and moisture existing around the element, and (2) oxygen present as an adsorbate in the organic laminated film. (3) is affected by moisture adsorbed on parts during device fabrication and moisture infiltration during manufacturing. Is also thought to be affected.
[0011]
When oxygen or moisture is present in the element, the oxidation or aggregation of the element laminated constituent material is promoted by the oxygen or moisture, which causes deterioration of the element. A typical example of the deterioration of the element due to oxidation or moisture is the generation and growth of dark spots. The dark spot is a light emission defect point. As oxidation proceeds during driving and storage, the existing dark spots grow and spread over the entire light emitting surface. In order to suppress the occurrence of such dark spots, it is important to seal the element structure.
[0012]
In order to suppress the occurrence of dark spots, a method of disposing phosphorus pentoxide as a desiccant in an airtight container and sealing it in a hollow state (Japanese Patent Laid-Open No. Hei 3-261109), a protective layer containing this phosphorus pentoxide and Although a method employing a structure in which a sealing layer is laminated has been proposed (JP-A-7-169567), in these methods, phosphoric acid is generated by moisture, which may adversely affect the organic laminate. Furthermore, a method of filling an inert liquid containing a desiccant on the laminate and in an airtight container (Japanese Patent Application Laid-Open Nos. 5-41281 and 9-35868), a method using a pressure-sensitive adhesive (US Pat. No. 5,304,419) have been proposed.
[0013]
[Problems to be solved by the invention]
However, there has not yet been provided an organic EL device that maintains stable light-emitting characteristics for a long period of time. That is, no leak current or crosstalk occurs even in the above method, but it is necessary to sufficiently suppress the generation and growth of dark spots in order to obtain long-term stable light emission characteristics.
[0014]
For that purpose, it is important to eliminate the above-mentioned causes (1) to (4) of deterioration of the light emission characteristics, and it is necessary to take drying means having a long-lasting effect.
[0015]
The mere use of a desiccant is not persistent, and the desiccant must not adhere to the organic light-emitting device due to powder falling or the like. For that purpose, a uniform and persistent adsorption film is required, and it must be easily available in terms of cost and process.
[0016]
That is, there is a demand for an organic EL device that can suppress the influence of moisture and the like on the device with good sustainability and is excellent in process and cost.
[0017]
Therefore, an object of the present invention is to provide a uniform drying means as a drying means which can suppress oxidation and the like of an element laminated structure material from oxygen and moisture entering the element for a long time with good durability in the manufacturing process and during driving and storage. It is an object of the present invention to provide an organic EL device which is provided with a simple adsorption film so as not to adversely affect the device, and which facilitates a process such as handling during encapsulation. As a result, the growth of dark spots in the element is suppressed with good sustainability and can maintain stable light emission characteristics over a long period of time.
[0018]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to solve the above many problems, and as a result, have found that the above object can be achieved by employing a specific polymer as a drying means and dispersing a desiccant compound in the polymer matrix. And completed the present invention.
That is, the present invention is as follows.
[0019]
(1) An organic electroluminescence device in which a laminate in which an organic light emitting layer containing an organic compound is arranged between electrodes facing each other is formed on a support, and a space is provided around the laminate with an airtight container provided. In at least a part of the inner surface of the hermetic container, the following general formula (I):
(Wherein, R is a methylene chain having 1 to 6 carbon atoms, m is an integer of 1 to 12, and n is an integer of 1 or more). An adsorption film formed by dispersing 1% by weight or more of an inorganic desiccant compound in a polymer matrix containing an aromatic polyamide as a main component.
[0020]
(2) The organic electroluminescence device, wherein the desiccant compound is an alkali metal oxide or an alkaline earth metal oxide alone or in a composite.
[0021]
(3) The organic electroluminescence device, wherein the main component of the desiccant compound is γ-type activated alumina having a particle size of 1 to 200 μm.
[0022]
(4) The organic electroluminescent element, wherein the linear aliphatic polyamide component represented by the general formula (I) forms a polymer matrix alone or in a mixed form of 50% by weight or more.
[0023]
(5) In the organic electroluminescence element, the airtight container is an organic electroluminescence element made of glass or a metal material.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
As shown in FIG. 1, an organic EL device according to an embodiment of the present invention includes an organic light emitting layer 3 (a hole injection layer 3-1, a hole transport layer 3-2, a light emitting layer 3) on a support 1. -3, the electron injection layer 3-4) is provided between the
[0025]
The adsorption film 7 formed as a drying means in the present invention prevents oxygen and moisture from entering the organic EL element from the outside after sealing, and prevents oxygen and moisture from entering during the manufacturing process of the element. It is preferable to have a property of adsorbing oxygen or moisture existing from the beginning and hardly releasing oxygen or moisture once adsorbed from the viewpoint of favorably suppressing generation and growth of dark spots.
[0026]
From the above-mentioned viewpoints, the shape of the inorganic desiccant dispersed and used in the adsorption film 7 according to the present invention is not particularly limited, but a powdery one is preferable because the adsorption area becomes larger.
[0027]
Examples of the inorganic desiccant compound that can be used in the present invention include alkali metal oxides, alkaline earth metal oxides, sulfates, metal halides, and perchlorates. Oxides or alkaline earth metal oxides are preferred. Specifically, activated alumina, silicon earth, activated carbon, phosphorus pentoxide, magnesium perchlorate, potassium hydroxide, calcium oxide, zinc chloride, barium oxide, lithium, beryllium, potassium, magnesium, calcium, zeolite, silica gel, etc. Metal and the like. These compounds may be used alone or in combination of two or more.
[0028]
Since such a desiccant compound must be used while maintaining a sufficient adsorption capacity, it is preferable to perform an activation treatment for removing adsorbed oxygen and moisture before use. For this activation treatment method, for example, various methods can be adopted, such as performing a heat treatment at 150 ° C. or more under vacuum in a state of being shielded from the outside air to remove oxygen and moisture.
[0029]
In the present invention, a system containing γ-type activated alumina as a main component is particularly preferable in view of each property, stability, compatibility with the copolymer according to the present invention, and ease of handling.
[0030]
The amount of the desiccant compound used is required to be 1% by weight or more in the matrix polymer in order to obtain a desired effect, and the larger the effect, the higher the effect. There is a correlation between the particle size and the effect, and there is also a relationship with the polymer of the dispersion system, but 2 to 180% by weight is preferable from the viewpoint of fluidity, adhesion to a container, and film forming property. The same is related to the particle size, the larger the surface area, the greater the effect, and there is also an appropriate particle size from the relationship with the matrix polymer.In view of the above, in the present invention, the average particle size is preferably It is between 1 and 200 microns, more preferably between 2 and 130 microns.
[0031]
In the present invention, an alcohol-soluble linear aliphatic polyamide represented by the above general formula (I) is used as a main component of the polymer matrix forming the adsorption film 7, but an acrylic resin, an epoxy resin, an alkyd resin, a polyvinyl resin A general-purpose coating resin such as a polyurethane resin and an imide resin can be used in combination.
[0032]
The alcohol-soluble linear aliphatic polyamide used for the adsorption membrane 7 according to the present invention is obtained by chemically reacting a linear aliphatic polyamide (nylon) with formamide and a target alkyl alcohol to partially form an amide bond with N-methoxy. It is methylated. The methoxy methylation degree (MM degree) of the amide bond is preferably about 5 to 50%, m of the methylene chain is preferably 2 to 7, and R in the amide bond chain is a methylene chain having 1 to 5 carbon atoms. preferable. The molecular weight of such an alcohol-soluble linear aliphatic polyamide is not particularly limited. The alcohol-soluble linear aliphatic polyamide itself also has a function of adsorbing oxygen and moisture, is excellent in holding properties, is excellent in adhesion to a container, and the like.
[0033]
Specific examples of the alcohol-soluble linear aliphatic polyamide according to the present invention,
Unitika Ltd .:
Nippon Rilsan Co., Ltd .: Platabond Product name "M995, M1276"
Teikoku Chemical Industry Co., Ltd .: Toresin Product name "F-30, MF-30, EF-30T, FS-350, FS-500"
And the like, but not limited thereto.
[0034]
By dispersing the desiccant in a polymer matrix containing alcohol-soluble linear aliphatic polyamide as a main component, it is possible to increase the adsorptivity of oxygen and moisture and to significantly increase the effect of preventing the release of adsorbed substances. it can. In this manner, the generation and growth of dark spots can be significantly suppressed by chemically removing oxygen and moisture in the device. The alcohol-soluble linear aliphatic polyamide may be used alone or in combination with another polymer as described above.However, the matrix polymer according to the present invention is subjected to a treatment for impurities and is similar to the activation treatment of the desiccant compound. Then, it is preferable to dry under vacuum at 120 ° C. for 1 hour or more to remove water. The polymer and the desiccant compound thus obtained are dispersed in a glove box having a dissolved oxygen concentration of 2 ppm or less, and a film is formed inside the hermetic container by the above method, whereby the adsorption film 7 is obtained.
[0035]
The support 1 in the element structure of the present invention may be any material that is excellent in light transmittance. For example, besides glass, a plastic substrate such as polyacryl or polycarbonate may be used, but a glass substrate is generally used. In addition, the
[0036]
The
[0037]
In the organic EL device of the present invention, by forming the adsorption film as a drying means on the inner surface of an airtight container that shields the organic light-emitting device made of a laminate from the outside air, no dark spots are generated or grown, For a long time, and can sufficiently withstand practical use.
[0038]
【Example】
Hereinafter, the organic EL device of the present invention will be described in more detail based on examples.
First, an example of manufacturing an organic EL light-emitting laminate will be described.
FIG. 1 is a schematic cross-sectional view showing a layer configuration of an organic EL layer for evaluation of a prototype this time. First, a transparent electrode (ITO) was entirely formed as an
[0039]
Next, the substrate is mounted in a resistance heating evaporation apparatus, and as the organic EL
[0040]
Thereafter, the substrate was taken out of the vacuum chamber, and was newly mounted in a resistance heating evaporation apparatus. As a
[0041]
Example 1
An N-methoxymethylated polyamide resin (Tresin: F30K, manufactured by Teikoku Chemical Industry Co., Ltd.) as a polymer matrix material which is a component of the present invention is dried under vacuum at 120 ° C. for 1.5 hours to remove adsorbed moisture. After that, the polymer was dissolved in 15% by weight of solid content using anhydrous ethyl alcohol to prepare a polymer solution. Further, after activating γ-type alumina having an average particle diameter of 50 μm as a desiccant under vacuum at 200 ° C. for 2 hours, the solid content of the polymer solution was reduced to 100 ppm in a glove box having an oxygen dissolved concentration of 2 ppm or less. 100 parts by weight of the treated desiccant was dispersed in parts by weight.
[0042]
The adsorption film solution thus obtained was formed into a film on the inner surface of an airtight container (sealing glass) 5 made of glass and dried on a hot plate at about 120 ° C. In the obtained airtight container, the organic EL light-emitting laminate formed by laminating an organic light-emitting layer between electrodes on a glass support was sealed. Such sealing is performed by using a cationic polymerization type ultraviolet-curing adhesive (3025G, manufactured by Three Bond Co., Ltd.) in which a glass spacer is dispersed as a sealing agent, and using a dispenser on the outer periphery of the sealing
[0043]
As an evaluation method of the obtained organic EL device, the light emission state of the dark spot was observed by an enlarged photograph at an early stage, and the formation and the formation of the dark spot were examined by an accelerated test of the dark spot in a 60 ° C., 90% temperature and humidity environment. Growth was observed. As a result, generation and growth of dark spots were hardly observed. FIG. 2 shows the result.
[0044]
Example 2
50 parts by weight of the desiccant in Example 1 was dispersed with respect to 100 parts by weight of the matrix polymer to form an adsorption film in the same manner as in Example 1 and sealed in the same manner as in Example 1 to obtain an organic EL. A light emitting element was formed.
[0045]
Example 3
Instead of the desiccant in Example 1, a mixed desiccant obtained by mixing activated γ-type alumina and barium oxide (BaO) at a ratio of 2: 1 (% by weight) was used, and the above-mentioned matrix polymer was used. Instead, using a polymer (trade name: T-8-E) manufactured by Unitika Ltd. which has been subjected to the same drying treatment as above, 100 parts by weight of the mixed desiccant is dispersed in 100 parts by weight of the polymer, An adsorption film was formed in the same manner as in Example 1, and sealed by the same method as in Example 1, to form an organic EL light emitting device.
[0046]
Example 4
Instead of the matrix polymer in Example 1, a mixed polymer in which the polymer used in Example 1 and a general-purpose hydroxy-modified polyacrylic resin were used in a ratio of 2: 1 (% by weight) was used, and 100 parts by weight of the mixed polymer was used. On the other hand, the same desiccant as in Example 1 was dispersed in 100 parts by weight, an adsorption film was formed in the same manner as in Example 1, and sealing was performed by the same method to form an organic EL light emitting device.
[0047]
Comparative Example 1
An organic EL light emitting device was manufactured by sealing in the same manner as in Example 1 except that the adsorption film was not formed on the inner surface of the airtight container.
[0048]
Comparative Example 2
Without using the desiccant in Example 1, only the polymer used in Example 1 was formed on the inner surface of the airtight container, and the other components were sealed in the same manner as in Example 1 to produce an organic EL light emitting device. .
[0049]
Comparative Example 3
The desiccant in Example 1 was fixed on an adhesive tape, an adsorption film was formed on the inner surface of the container using the adhesive, and the other components were sealed in the same manner as in Example 1 to obtain an organic EL light emitting device. Produced.
[0050]
Examples 2 to 4 and Comparative Examples 1 to 3 were also evaluated by performing the same dark spot acceleration test as in Example 1. As a result, as shown in FIG. 2, in Examples 1 to 4 according to the present invention, dark spot growth was hardly observed as compared with Comparative Examples 1 to 3.
[0051]
【The invention's effect】
As described in detail above, according to the present invention, the presence of oxygen or moisture that adversely affects the element can be suppressed with good sustainability and can be manufactured at low cost. As a result, the generation and growth of dark spots can be suppressed with good continuity without causing leakage current or crosstalk. Therefore, it has become possible to provide an organic EL light-emitting element having a long element life while maintaining stable light-emitting characteristics for a long time.
[Brief description of the drawings]
FIG. 1 is a sectional view of an organic EL device according to an embodiment of the present invention.
FIG. 2 is a graph showing a relationship between time and a dark spot diameter in Examples and Comparative Examples.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1
Claims (5)
前記気密容器内面の少なくとも一部に、下記一般式(I)、
(式中、Rは炭素数1〜6のメチレン鎖、mは1〜12の整数、nは1以上の整数を夫々表す)で示される構成単位を有する、官能基を有するアルコール可溶性直鎖脂肪族ポリアミドを主成分とするポリマーマトリックス中に無機系乾燥剤化合物を1重量%以上分散してなる吸着膜を形成したことを特徴とする有機エレクトロルミネッセンス素子。A laminate in which an organic light-emitting layer containing an organic compound is disposed between electrodes facing each other is formed on a support, and an organic electroluminescence device in which a space is provided around the laminate and an airtight container is provided.
At least a part of the inner surface of the hermetic container has the following general formula (I):
Wherein R is a methylene chain having 1 to 6 carbon atoms, m is an integer of 1 to 12, and n is an integer of 1 or more. An organic electroluminescent device comprising an adsorption film formed by dispersing an inorganic desiccant compound in an amount of 1% by weight or more in a polymer matrix containing an aromatic polyamide as a main component.
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JP32087598A JP3601760B2 (en) | 1998-11-11 | 1998-11-11 | Organic electroluminescence device |
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JP2002043055A (en) * | 2000-05-17 | 2002-02-08 | Tohoku Pioneer Corp | Organic electroluminescent element and method of manufacturing the same |
US6465953B1 (en) * | 2000-06-12 | 2002-10-15 | General Electric Company | Plastic substrates with improved barrier properties for devices sensitive to water and/or oxygen, such as organic electroluminescent devices |
JP2002175881A (en) * | 2000-12-07 | 2002-06-21 | Fuji Photo Film Co Ltd | Luminous element |
JP4272819B2 (en) * | 2001-01-10 | 2009-06-03 | キヤノン株式会社 | Organic light emitting device |
JP2011142099A (en) * | 2001-01-12 | 2011-07-21 | Nihon Gore Kk | Porous adsorbing sheet made of polytetrafluoroethylene |
JP2002280166A (en) * | 2001-01-12 | 2002-09-27 | Japan Gore Tex Inc | Organic el element |
US6936131B2 (en) | 2002-01-31 | 2005-08-30 | 3M Innovative Properties Company | Encapsulation of organic electronic devices using adsorbent loaded adhesives |
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