JP4423585B2 - Organic EL device and method for manufacturing the same - Google Patents

Description

【００２２】
なお、有機半導体は、単独で、または、光照射、加熱、電界の付与等によって導電性を示す有機物であり、炭素（Ｃ）、窒素（Ｎ）、水素（Ｈ）、イオウ（Ｓ）等の原子を含む。
【００２３】
上記の構成を有する有機ＥＬ素子２０について、発光層１５を６５℃程度に加熱して６−ＴＴＰ−１２をスメクティックＦ相にし、電極２ａ、２ｂ間に直流電圧を印加して、発光特性を調べた。このとき、電極２ａを陽極とし、電極２ｂを陰極として、電極２ａ、２ｂ間での電界強度を４×１０⁵ Ｖ／ｃｍとした。電極２ａ、２ｂ間の電流値は、２．８μＡであった。その結果、２０ｃｄ／ｍ² 程度の輝度を有する緑色の発光が観察された。
【００２４】
図２は、このとき観察された発光の分光分布を示す。同図から明らかなように、有機ＥＬ素子２０からの発光のピーク波長は５１０ｎｍ付近である。
【００２５】
図３は、発光している有機ＥＬ素子２０での電極２ａ、２ｂ付近の顕微鏡観察結果を模式的に示す。同図に示すように、陰極として用いた電極２ｂでの電極２ａ側端面を覆っている配向膜４付近に、平面視上、輝点ＬＳが点在していた。
【００２６】
また、電極３ａ、３ｂ間に直流電圧を印加して、その発光特性を調べた。このとき、電極３ａ、３ｂ間の電流値は、０．６μＡであった。その結果、電極２ａ、２ｂ間に直流電圧を印加した場合に比べて発光強度は低かったものの、緑色の発光が観察された。
【００２７】
電極２ａ、２ｂ間に直流電圧を印加したときの発光特性と電極３ａ、３ｂ間に直流電圧を印加したときの発光特性との対比から明らかなように、有機ＥＬ素子２０においては、電界方向と配向膜４での配向方向との相対的な関係によって、発光特性、特に発光輝度を制御することが可能である。
【００２８】
すなわち、配向膜４での配向方向を電界方向と平面視上直交する方向にすることによって発光輝度を高めることができ、配向膜４での配向方向を電界方向と平面視上平行にすることによって発光輝度を低めることができる。
【００２９】
有機ＥＬ素子２０においては、絶縁破壊や、電極間に長時間電圧を印加することに伴う輝度の低下は認められなかった。反対に、輝度については学習効果が認められた。すなわち、連続して電圧を印加することにより、あるいは繰り返し電圧を印加することにより輝度が向上する、という現象が認められた。
【００３０】
次に、第２の実施例による有機ＥＬ素子について説明する。
【００３１】
図４は、第２の実施例による有機ＥＬ素子の断面を概略的に示す。同図に示した有機ＥＬ素子２５は、電極２ｂおよび３ｂが第２透明ガラス基板５側に配置されると共に、これらの電極２ｂ、３ｂが配向膜４ｂによって覆われている点を除いて、図１に示した有機ＥＬ素子２０と同様の構成を有する。ただし、図４においては、電極３ａ、３ｂのみが見えている。
【００３２】
図４に示した構成部材のうちで図１に示した構成部材と共通するものについては、図１で用いた参照符号と同じ参照符号を付してその説明を省略する。発光層１５を収容している容器については、電極２ｂ、３ｂの配置および配向膜４ｂの有無が図１に示した容器１０とは異なるので、新たな参照符号１０ａを付してある。
【００３３】
図示の有機ＥＬ素子２５においては、電極２ａと電極３ａとが第１透明ガラス基板１の内表面上に配置され、電極２ｂと電極３ｂとが第２透明ガラス基板５の内表面上に配置される。これらの電極２ａ、２ｂおよび電極３ａ、３ｂは、発光層を形成する前の段階で平面視したときに、電極２ａ、２ｂの間および電極３ａ、３ｂの間にそれぞれ細隙Ｓ３が形成されるように配置される。電極２ａ、２ｂ間または電極３ａ、３ｂ間に直流電圧を印加すると、これらの電極間に斜め電界が形成される。配向膜４ｂの配向方向は、配向膜４での配向方向と同じである。
【００３４】
この有機ＥＬ素子２５も、電極２ａ、２ｂ間または電極３ａ、３ｂ間に直流電圧を印加することにより、発光するものと期待される。
【００３５】
次に、第３の実施例による有機ＥＬ素子について説明する。
【００３６】
図５は、第３の実施例による有機ＥＬ素子の断面を概略的に示す。同図に示した有機ＥＬ素子４０は、配向膜４に代えて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'−ジアミン等のトリフェニルジアミン誘導体からなる正孔輸送層３３が設けられている点、および、６−ＴＴＰ−１２に代えて高分子系ＥＬ材料（ポリ−ｐ−フェニレンビニレン（ＰＰＶ）等のフェニレンビニレン誘導体）によって発光層３５が形成されている点で、図１に示した有機ＥＬ素子２０と異なる。
【００３７】
また、陽極として用いる電極がＩＴＯ（酸化インジウム・スズ）、金（Ａｕ）、白金（Ｐｔ）、銀（Ａｇ）、Ｃｕ等によって形成され、陰極として用いる電極が、陽極材料よりもイオン化エネルギーが小さい材料、例えばアルミニウム（Ａｌ）、インジウム（Ｉｎ）、マグネシウム（Ｍｇ）、カルシウム（Ｃａ）、リチウム（Ｌｉ）、Ｍｇ−Ａｌ合金、Ｍｇ−Ｌｉ合金、Ａｌ−Ｌｉ合金、グラファイト薄膜等によって形成されているという点でも、図１に示した有機ＥＬ素子２０と異なる。
【００３８】
これらの相違点を除いた他の構成は有機ＥＬ素子２０と同様であるので、図５に示した構成部材のうちで図１に示した構成部材と共通するものについては、図１で用いた参照符号と同じ参照符号を付してその説明を省略する。
【００３９】
正孔輸送層３３は電極２ａと電極３ａとを覆い、電極２ｂと電極３ｂとは覆わない。ただし、図５においては電極３ａ、３ｂのみが見えている。正孔輸送層３３の膜厚は、概ね０．１〜１．０μｍの範囲内で適宜選択可能である。この正孔輸送層３３は、例えば、所定形状のマスクを用いた真空蒸着法やスパッタリング法等によって形成される。例えば電界重合法によれば、所望の電極上のみに容易に正孔輸送層を形成することができる。
【００４０】
電極対を構成する２つの電極２ａ、２ｂおよび電極３ａ、３ｂは、正孔輸送層３３および発光層３５を形成する前の段階で、これらの電極２ａ、２ｂの間および電極３ａ、３ｂの間に幅（間隔）数十ｎｍ〜２μｍ程度の細隙Ｓ４が形成されるように配置される。正孔輸送層３３は、陰極として利用する電極２ｂ、３ｂに接しないように形成される。
【００４１】
発光層３５は非晶質であり、その膜厚は、概ね０．０１〜０．１μｍとすることが好ましい。この発光層３５は、例えば、スピンコート、キャスティング、ディッピング、バーコート、ロールコート等の塗布法によって形成される。
【００４２】
図示の有機ＥＬ素子４０においても、電極２ａ、２ｂ間または電極３ａ、３ｂ間に直流電圧を印加することにより、発光するものと期待される。この有機ＥＬ素子４０では、図１に示した有機ＥＬ素子２０に比べて、発光させるのに要する印加電圧値が大きくなるものと予想される。
【００４３】
なお、必要に応じて、陰極として利用する電極２ｂ、３ｂ上に電子輸送層を形成してもよい。
【００４４】
次に、第４の実施例による有機ＥＬ素子について説明する。
【００４５】
図６は、第４の実施例による有機ＥＬ素子の断面を概略的に示す。同図に示した有機ＥＬ素子５０は、第１透明ガラス基板１の内表面上に配置される部材の種類と、これらの部材の配置とを除き、図１に示した有機ＥＬ素子２０と同様の構成を有する。
【００４６】
図６に示した構成部材のうちで図１に示した構成部材と共通するものについては、図１で用いた参照符号と同じ参照符号を付してその説明を省略する。ただし、発光層１５を収容している容器については、第１透明ガラス基板１の内表面上に配置されている部材自体と各部材の配置とが図１に示した容器１０と異なるので、新たな参照符号４５を付してある。
【００４７】
同図に示すように、有機ＥＬ素子５０では、複数のゲート電極４３ａと、これらのゲート電極４３ａを覆うゲート絶縁膜４４とが第１透明ガラス基板１の内表面上に配置され、複数の電極対が平坦化膜４４上に配置される。ゲート絶縁膜４４は、例えばシリコン酸化膜によって形成される。
【００４８】
個々の電極対は、２つの電極４３ｂ、４３ｃによって構成され、これらの電極４３ｂ、４３ｃは、配向膜４および発光層１５を形成する前の段階で細隙Ｓ５を介して相隣るように配置される。
【００４９】
１つのゲート電極４３ａに１つの電極対が対応して、１つのトランジスタを構成する。各ゲート電極４３ａは、平面視上、対応する電極対を構成している２つの電極４３ａ、４３ｂの間に位置する。配向膜４は、電気絶縁性をもたないように薄く成膜され、細隙Ｓ５を埋め尽くすことなく、ゲート電極４３ａの各々と電極対４３ｂ、４３ｃの各々とを覆う。配向膜４での配向処理方向は、細隙Ｓ５の延在方向と平行であり、個々の電極対での電界方向と平面視上直交する方向である。
【００５０】
図示の有機ＥＬ素子５０においても、電極対を構成する２つの電極４３ｂ、４３ｃ間に直流電圧を印加することにより、発光するものと期待される。
【００５１】
さらに、有機ＥＬ素子５０では、個々のゲート電極４３ａに印加する直流電圧の大きさを制御することにより、このゲート電極４３ａに対応する電極対を構成している２つの電極４３ｂ、４３ｃ間に形成される電界の強さや向きを制御することが可能である。ゲート電極４３ａに印加する直流電圧の大きさによって、発光強度を制御することが可能である。
【００５２】
以上説明した実施例による有機ＥＬ素子では、主として、電極対を構成している２つの電極の平面視上の間に分布する有機発光材料が発光に寄与する。このため、従来の積層構造の有機ＥＬ素子に比べて、素子の性能が電極表面の性状の影響を受けにくい。黒点（ダークスポット）の発生、輝度の低下、絶縁破壊等を容易に防止することができる。
【００５３】
また、透明電極を用いる必要性がないことから、種々の電極材料を利用することが可能になり、電極材料の選択の自由度が高くなる。発光層で生じた光が素子外に出射するにあたって透明電極を透過する必要がないため、電極での光の吸収や反射に起因する実効的な発光強度の低下が小さい。
【００５４】
このような利点を有する有機ＥＬ素子は、微小な線幅でライン状に発光できるため、例えば液晶表示装置でのバックライト（サイドライト）やホログラフィックな光学素子の再生光用光源として利用することが可能である。また、種々の書込み光源、例えば、静電転写方式を用いたプリンタの線状光源、銀塩カメラでフィルムに日付等を書き込むための光源、画像データ等を感光紙や感光フィルム等に書き込むための光源等、として利用することも可能である。さらには、表示装置の画素、照明装置を含む各種の光源装置、光通信素子、光センサ素子等として利用することも可能である。例えば図６に示した有機ＥＬ素子５０のように、電極対を構成する２つの電極とゲート電極とを組み合わせることにより、アクティブマトリックス駆動方式の表示装置を構成することも可能である。
【００５５】
なお、本発明は、上述した実施例による有機ＥＬ素子およびその製造方法に限定されるものではない。
【００５６】
例えば、発光層を収容するための容器を構成する基板は、ガラス以外の透明材料、例えば透明樹脂や透光性セラミクスによって形成することも可能である。基板は板状である他、シートないしフィルム状であってもよい。容器の形状は、平板状に限らず、棒状、円柱状、半円柱状、半球状等、適宜選定可能である。
【００５７】
電極材料はモリブデンに限定されるものではなく、使用する有機発光材料の種類等に応じてＩＴＯ、ＩＭＯ（酸化インジウム・モリブデン）、クロム（Ｃｒ）、金（Ａｕ）、銀（Ａｇ）、銅（Ｃｕ）、ニッケル（Ｎｉ）、白金（Ｐｔ）、アルミニウム（Ａｌ）、タングステン（Ｗ）、カルシウム（Ｃａ）等、適宜選択可能である。陰極と陽極とで電極材料を変えてもよい。その場合、陰極材料の仕事関数が陽極材料の仕事関数よりも小さくなるように、電極材料を組み合わせることが好ましい。
【００５８】
電極対を構成する２つの電極の間に介在させる細隙の幅（間隔）を狭くすることにより、低電圧駆動の下でも高輝度に発光する有機ＥＬ素子が得られるものと考えられる。これらの電極間に印加する直流電圧の値を大きくすれば、細隙の幅を狭くしなくても、有機ＥＬ素子の発光強度を高めることができるものと考えられる。
【００５９】
上記の細隙は、電極対を構成する２つの電極同士を短絡させることなく、配向膜や正孔輸送層、あるいは電子輸送層によって平面視上埋め尽くされていてもよい。
【００６０】
液晶状態の有機半導体によって発光層を形成する場合には、配向膜を設けることが好ましい。この配向膜は、電極対を構成する２つの電極の間に介在する細隙部分で有機半導体の分子を所定方向に配向させるためのものである。したがって配向膜は、少なくとも前記２つの電極の間の基板表面上に形成される。
【００６１】
液晶状態の有機半導体の分子と配向膜とのアンカリング強度は、比較的高く設定することが好ましい。ラビングによって配向膜に配向処理を施す場合には、例えば、１つの配向膜に対して複数回繰り返し、比較的高い荷重をかけながらラビング処理を施すことにより、上記のアンカリング強度を比較的高くすることができる。
【００６２】
配向膜の材料としては、第１の実施例による有機ＥＬ素子２０で使用した日産化学社製のポリイミド（ＲＮ−１１９９）の他に、同社製の他のポリイミドであるＲＮ−１１７５も好適である。
【００６３】
発光層の材料として使用される有機半導体は、キャリア輸送性を有し、かつ、液晶相になり得るものであることが望まれる。このような有機半導体の具体例としては、ターチオフェン誘導体を主骨格とするもの、フェニルナフタレン誘導体を主骨格とするもの、バイフェニル誘導体を主骨格とするもの等が挙げられる。
【００６４】
上述した有機半導体は、分子の配向方向を電圧によって制御することが可能であるので、配向制御用の電極を別途設けることにより、配向膜を省略することも可能である。特に、上述した有機半導体に不斉炭素等を導入して誘電率異方性を付与した材料では、分子の配向方向を低電圧で制御することが可能である。
【００６５】
これらの有機半導体は、その温度に応じて、液晶状態または液体状態となる。加熱することによって流動状態（例えば等方性液相状態）にした有機半導体は、毛管現象を利用した方法以外にも、真空注入や減圧加圧注入等によって容器内に充填することができる。
【００６６】
第１の基板の一面に当該基板の縁に沿ってシール剤を塗布し、このシール剤によって囲まれた領域内に液晶状態または液体状態の有機半導体を充填した後に、その上から第２の基板を重ね合わせることによっても、発光層を形成することができる。
【００６７】
液晶状態の有機半導体を発光材料として用いた有機ＥＬ素子では、有機半導体の分子の配向方向を制御することにより、発光輝度や、発光の偏光状態を制御することが可能である。第１の実施例による有機ＥＬ素子２０からの発光は偏光ではなかったが、１つの電極対を構成する２つの電極のうちで陰極として利用する電極付近での有機半導体分子の配向性を向上させることにより、偏光を発光させることも可能であると思われる。
【００６８】
その他、種々の変更、改良、組み合わせ、応用等が可能なことは当業者に自明であろう。
【００６９】
【発明の効果】
以上説明したように、本発明によれば、素子性能が電極表面の性状の影響を受けにくく、電極材料の選択の自由度が高く、電極での光の吸収や反射に起因する実効的な発光強度の低下が小さい有機ＥＬ素子が提供される。素子性能を向上させやすい有機ＥＬ素子を得ることができる。
【図面の簡単な説明】
【図１】図１（Ａ）は第１の実施例による有機ＥＬ素子を概略的に示す断面図であり、図１（Ｂ）は、図１（Ａ）に示した有機ＥＬ素子を構成している第１透明ガラス基板上での電極の平面配置を示す概略図である。
【図２】図１（Ａ）に示した有機ＥＬ素子からの発光の分光分布を示すグラフである。
【図３】図１（Ａ）に示した有機ＥＬ素子が発光しているときの顕微鏡観察結果を示す模式図である。
【図４】第２の実施例による有機ＥＬ素子を概略的に示す断面図である。
【図５】第３の実施例による有機ＥＬ素子を概略的に示す断面図である。
【図６】第４の実施例による有機ＥＬ素子を概略的に示す断面図である。
【符号の説明】
１…第１透明ガラス基板、 ２ａ、２ｂ…電極対を構成する２つの電極、 ３ａ、３ｂ…電極対を構成する２つの電極、 ４、４ｂ…配向膜、 ５…第２透明ガラス基板、 １０、１０ａ、３０、４５…容器、 １５…発光層、 ２０、２５、４０、５０…有機ＥＬ素子、 ４３ａゲート電極、 ４３ｂ、４３ｃ…電極対を構成する２つの電極、 Ｓ１、Ｓ２、Ｓ３、Ｓ４、Ｓ５…細隙。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an organic electroluminescent element and a method for manufacturing the same. In this specification, “electroluminescence (electroluminescence)” may be abbreviated as “EL”.
[0002]
[Prior art]
Solid organic light emitting materials have relatively low charge mobility. For this reason, in a conventional organic EL element in which a light emitting layer is formed of a solid organic light emitting material, electroluminescence at a low voltage is enabled by thinning the light emitting layer to, for example, about several tens of nm.
[0003]
As a result of reducing the thickness of the light emitting layer, the conventional organic EL element basically has a structure in which an electrode, a light emitting layer, and an electrode (counter electrode) are sequentially laminated on a substrate in this order. This is an injection-type device that excites the emission center by the recombination energy of electrons and holes. In general, in order to increase luminous efficiency, a hole transport layer is provided between the anode and the light emitting layer, and an electron transport layer is provided between the cathode and the light emitting layer.
[0004]
[Problems to be solved by the invention]
In the organic EL device having the above structure, the property of the electrode surface on the light emitting layer side greatly affects the performance of the device. For example, unevenness on the surface of the electrode on the light emitting layer side can cause black spots (dark spots), a decrease in luminance, dielectric breakdown, and the like.
[0005]
In addition, in order for the light generated in the light emitting layer to be emitted outside the element, it must be transmitted through the anode or the cathode. Therefore, the electrode on the light emitting side needs to be a transparent electrode. As a result, the degree of freedom in selecting the electrode material is reduced, and the effective light emission intensity is reduced due to light absorption and reflection (including multiple reflections) at the transparent electrode.
[0006]
The object of the present invention is that the device performance is not easily affected by the properties of the electrode surface, the degree of freedom in selecting the electrode material is high, and the decrease in effective light emission intensity due to light absorption and reflection at the electrode is small. It is to provide an EL element.
[0007]
Another object of the present invention is that the device performance is not easily affected by the properties of the electrode surface, the degree of freedom in selecting an electrode material is high, and the effective emission intensity is reduced due to light absorption and reflection at the electrode. It is providing the manufacturing method of a small organic EL element.
[0008]
[Means for Solving the Problems]
According to one aspect of the present invention,
A container in which two substrates are arranged opposite to each other with a space therebetween, and a space between the two substrates is an accommodation space;
An electrode pair which is arranged on the inner surface of one of the two substrates and is constituted by two electrodes adjacent to each other through a slit;
A light emitting layer formed of an organic light emitting material made of an organic semiconductor in a liquid crystal state , housed in the container ;
An organic EL device comprising: an alignment film formed on a substrate surface between the two electrodes and having an alignment direction in a direction orthogonal to the direction of the electric field generated in the slit in plan view Is done.
[0009]
According to another aspect of the present invention, two substrates are arranged to face each other with a space therebetween, and a space between the two substrates is disposed on a container serving as a storage space, and inner surfaces of the two substrates. An organic EL comprising a pair of electrodes that are adjacent to each other via a slit in plan view, and a light-emitting layer that is housed in the container and formed of an organic light-emitting material. An element is provided.
[0010]
According to yet another aspect of the present invention,
(A) Two substrates are arranged opposite to each other with a space therebetween, and an electrode pair constituted by two electrodes adjacent to each other through a slit is formed on the inner surface of one of the two substrates. An alignment film having an alignment direction in a direction orthogonal to the direction of the electric field generated in the slit in a plan view is disposed on the substrate surface between the two electrodes, and a space between the two substrates is formed A step of preparing a container to be a storage space;
(B) A method of manufacturing an organic EL element is provided which includes injecting an organic light emitting material that can be in a liquid crystal state into the container in a fluid state.
[0011]
According to still another aspect of the present invention, there is provided (A) an electrode pair in which two substrates are arranged to be opposed to each other with a space therebetween, and are constituted by two electrodes adjacent to each other through a slit when viewed in plan. A step of preparing a container which is arranged separately on the inner surfaces of the two substrates and in which the space between the two substrates serves as an accommodation space; and (B) injecting the organic light emitting material into the container in a fluidized state. The manufacturing method of the organic EL element including a process is provided.
[0012]
In the organic EL element having the above configuration, the organic light emitting material distributed mainly between the two electrodes constituting the electrode pair in plan view contributes to light emission. For this reason, compared with the organic EL element of the conventional laminated structure, the light emission characteristic of an element is hard to be influenced by the property of an electrode surface.
[0013]
In addition, since there is no need to use a transparent electrode, various electrode materials can be used, and the degree of freedom in selecting the electrode material is increased. Since light generated in the light emitting layer does not need to be transmitted through the transparent electrode when it is emitted outside the element, a decrease in effective light emission intensity due to light absorption and reflection at the electrode is small.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 (A) schematically shows a cross section of the organic EL element according to the first embodiment, and FIG. 1 (B) shows a first transparent glass constituting the organic EL element shown in FIG. 1 (A). 1 schematically shows a planar arrangement of electrodes on a substrate.
[0015]
An organic EL element 20 shown in FIG. 1A includes a plate-like hollow container 10 and a light emitting layer 15 formed of an organic light emitting material accommodated in the container 10.
[0016]
The container 10 includes a first transparent glass substrate 1 and a second transparent glass substrate 5. On the inner surface of the first transparent glass substrate 1, two electrode pairs and an alignment film 4 covering them are provided. FIG. 1A shows only two electrodes 3a and 3b constituting one electrode pair. The alignment film 4 is rubbed. The first transparent glass substrate 1 and the second transparent glass substrate 5 are arranged to face each other with a space T of 2 μm by a thermosetting sealant 7 to which a gap control material 7a is added in several%.
[0017]
As shown in FIG. 1B, two electrodes 2a and 2b constituting one of two electrode pairs provided on the inner surface of the first transparent glass substrate 1 are adjacent to each other via a slit S1. The two electrodes 3a and 3b constituting the other electrode pair are adjacent to each other through the slit S2. In FIG. 1B, the electrodes 2a, 2b, 3a, and 3b are hatched so that the first transparent glass substrate 1 and the electrodes 2a, 2b, 3a, and 3b can be easily distinguished from each other.
[0018]
The electrodes 2a, 2b and the electrodes 3a, 3b are all made of molybdenum, the film thickness is 0.2 μm, and the line width at the portion facing the slit S1 or S2 is 2 mm. The widths (intervals) D of the individual slits S1 and S2 are both 25 μm (width without the alignment film 4).
[0019]
The alignment film 4 is formed of polyimide (RN-1199 manufactured by Nissan Chemical Industries, Ltd.), and its film thickness is 0.01 μm. The alignment treatment direction (rubbing direction) in the alignment film 4 is a direction parallel to the extending direction of the slit S1, as indicated by an arrow A in FIG. They are orthogonal in plan view.
[0020]
The light emitting layer 15 is formed by using a capillary phenomenon of hexadodecyl terthiophene (hereinafter abbreviated as “6-TTP-12”) that has been made isotropic liquid phase by heating after the formation of the container 10. It is formed by filling. 6-TTP-12 is a known terthiophene derivative represented by the following formula, and is a kind of organic semiconductor. This 6-TTP-12 can be in either a liquid crystal state or a liquid state depending on the temperature.
[0021]
[Chemical 1]

[0022]
Note that an organic semiconductor is an organic substance that exhibits conductivity by light irradiation, heating, application of an electric field, or the like, such as carbon (C), nitrogen (N), hydrogen (H), sulfur (S), or the like. Contains atoms.
[0023]
For the organic EL element 20 having the above-described configuration, the light emitting layer 15 is heated to about 65 ° C. to make 6-TTP-12 a smectic F phase, and a direct current voltage is applied between the electrodes 2a and 2b to examine the light emission characteristics. It was. At this time, the electrode 2a was an anode, the electrode 2b was a cathode, and the electric field strength between the electrodes 2a and 2b was 4 × 10 ⁵ V / cm. The current value between the electrodes 2a and 2b was 2.8 μA. As a result, green light emission having a luminance of about 20 cd / m ² was observed.
[0024]
FIG. 2 shows the spectral distribution of the light emission observed at this time. As is clear from the figure, the peak wavelength of light emission from the organic EL element 20 is around 510 nm.
[0025]
FIG. 3 schematically shows the microscopic observation results near the electrodes 2a and 2b in the organic EL element 20 that emits light. As shown in the figure, bright spots LS are scattered in the vicinity of the alignment film 4 covering the electrode 2a side end face of the electrode 2b used as the cathode in plan view.
[0026]
Further, a direct current voltage was applied between the electrodes 3a and 3b, and the light emission characteristics were examined. At this time, the current value between the electrodes 3a and 3b was 0.6 μA. As a result, green light emission was observed although the light emission intensity was lower than when a DC voltage was applied between the electrodes 2a and 2b.
[0027]
As is clear from the comparison between the light emission characteristics when a DC voltage is applied between the electrodes 2a and 2b and the light emission characteristics when a DC voltage is applied between the electrodes 3a and 3b, in the organic EL element 20, the electric field direction and The light emission characteristics, particularly the light emission luminance, can be controlled by the relative relationship with the alignment direction in the alignment film 4.
[0028]
That is, the emission luminance can be increased by making the alignment direction in the alignment film 4 orthogonal to the electric field direction in plan view, and by making the alignment direction in the alignment film 4 parallel to the electric field direction in plan view. Luminance can be lowered.
[0029]
In the organic EL element 20, neither dielectric breakdown nor a decrease in luminance due to applying a voltage for a long time between the electrodes was observed. On the other hand, a learning effect was observed for luminance. That is, a phenomenon was observed in which luminance was improved by applying a voltage continuously or by applying a voltage repeatedly.
[0030]
Next, an organic EL element according to the second embodiment will be described.
[0031]
FIG. 4 schematically shows a cross section of an organic EL device according to the second embodiment. The organic EL element 25 shown in the figure is similar to that shown in FIG. 2 except that the electrodes 2b and 3b are disposed on the second transparent glass substrate 5 side, and the electrodes 2b and 3b are covered with the alignment film 4b. 1 has the same configuration as that of the organic EL element 20 shown in FIG. However, only the electrodes 3a and 3b are visible in FIG.
[0032]
4 that are the same as those shown in FIG. 1 are assigned the same reference numerals as those used in FIG. 1 and description thereof is omitted. The container containing the light emitting layer 15 is given a new reference numeral 10a because the arrangement of the electrodes 2b and 3b and the presence or absence of the alignment film 4b are different from the container 10 shown in FIG.
[0033]
In the illustrated organic EL element 25, the electrode 2a and the electrode 3a are disposed on the inner surface of the first transparent glass substrate 1, and the electrode 2b and the electrode 3b are disposed on the inner surface of the second transparent glass substrate 5. The When these electrodes 2a, 2b and electrodes 3a, 3b are viewed in plan before the formation of the light emitting layer, slits S3 are formed between the electrodes 2a, 2b and between the electrodes 3a, 3b, respectively. Are arranged as follows. When a DC voltage is applied between the electrodes 2a and 2b or between the electrodes 3a and 3b, an oblique electric field is formed between these electrodes. The alignment direction of the alignment film 4 b is the same as the alignment direction in the alignment film 4.
[0034]
This organic EL element 25 is also expected to emit light when a DC voltage is applied between the electrodes 2a and 2b or between the electrodes 3a and 3b.
[0035]
Next, an organic EL element according to a third embodiment will be described.
[0036]
FIG. 5 schematically shows a cross section of an organic EL device according to the third embodiment. The organic EL device 40 shown in the figure is replaced with the alignment film 4 by N, N′-diphenyl-N, N′-bis (3-methylphenyl) -1,1′-biphenyl-4,4′-diamine. A hole transport layer 33 made of a triphenyldiamine derivative such as, and a polymer EL material (a phenylene vinylene derivative such as poly-p-phenylene vinylene (PPV) instead of 6-TTP-12) ) Is different from the organic EL element 20 shown in FIG. 1 in that the light emitting layer 35 is formed.
[0037]
The electrode used as the anode is formed of ITO (indium tin oxide), gold (Au), platinum (Pt), silver (Ag), Cu, etc., and the electrode used as the cathode has a lower ionization energy than the anode material. Formed of materials such as aluminum (Al), indium (In), magnesium (Mg), calcium (Ca), lithium (Li), Mg—Al alloy, Mg—Li alloy, Al—Li alloy, graphite thin film, etc. This is also different from the organic EL element 20 shown in FIG.
[0038]
Since other configurations excluding these differences are the same as those of the organic EL element 20, among the components shown in FIG. 5, the components common to those shown in FIG. 1 are used in FIG. The same reference numerals as those of the reference numerals are attached and the description thereof is omitted.
[0039]
The hole transport layer 33 covers the electrodes 2a and 3a and does not cover the electrodes 2b and 3b. However, only the electrodes 3a and 3b are visible in FIG. The film thickness of the hole transport layer 33 can be appropriately selected within a range of approximately 0.1 to 1.0 μm. The hole transport layer 33 is formed by, for example, a vacuum deposition method or a sputtering method using a mask having a predetermined shape. For example, according to the electric field polymerization method, the hole transport layer can be easily formed only on the desired electrode.
[0040]
The two electrodes 2a and 2b and the electrodes 3a and 3b constituting the electrode pair are formed between the electrodes 2a and 2b and between the electrodes 3a and 3b before the formation of the hole transport layer 33 and the light emitting layer 35. The slits S4 having a width (interval) of about several tens of nm to 2 μm are formed. The hole transport layer 33 is formed so as not to contact the electrodes 2b and 3b used as the cathode.
[0041]
The light emitting layer 35 is amorphous, and the film thickness is preferably about 0.01 to 0.1 μm. The light emitting layer 35 is formed by a coating method such as spin coating, casting, dipping, bar coating, or roll coating.
[0042]
The illustrated organic EL element 40 is also expected to emit light when a DC voltage is applied between the electrodes 2a and 2b or between the electrodes 3a and 3b. In this organic EL element 40, compared to the organic EL element 20 shown in FIG.
[0043]
If necessary, an electron transport layer may be formed on the electrodes 2b and 3b used as the cathode.
[0044]
Next, an organic EL element according to a fourth embodiment will be described.
[0045]
FIG. 6 schematically shows a cross section of an organic EL device according to the fourth embodiment. The organic EL element 50 shown in the figure is the same as the organic EL element 20 shown in FIG. 1 except for the types of members arranged on the inner surface of the first transparent glass substrate 1 and the arrangement of these members. It has the composition of.
[0046]
6 that are the same as those shown in FIG. 1 are given the same reference numerals as those used in FIG. 1 and description thereof is omitted. However, for the container containing the light emitting layer 15, the members themselves arranged on the inner surface of the first transparent glass substrate 1 and the arrangement of each member are different from the container 10 shown in FIG. Reference numeral 45 is assigned.
[0047]
As shown in the figure, in the organic EL element 50, a plurality of gate electrodes 43a and a gate insulating film 44 covering these gate electrodes 43a are disposed on the inner surface of the first transparent glass substrate 1, and a plurality of electrodes A pair is disposed on the planarization film 44. The gate insulating film 44 is formed of, for example, a silicon oxide film.
[0048]
Each electrode pair is constituted by two electrodes 43b and 43c, and these electrodes 43b and 43c are arranged so as to be adjacent to each other through the slit S5 before the alignment film 4 and the light emitting layer 15 are formed. Is done.
[0049]
One electrode pair corresponds to one gate electrode 43a to form one transistor. Each gate electrode 43a is located between two electrodes 43a and 43b constituting a corresponding electrode pair in plan view. The alignment film 4 is formed thin so as not to have electrical insulation, and covers each of the gate electrode 43a and each of the electrode pairs 43b and 43c without filling the slit S5. The alignment treatment direction in the alignment film 4 is parallel to the extending direction of the slits S5 and is orthogonal to the electric field direction in each electrode pair in plan view.
[0050]
The illustrated organic EL element 50 is also expected to emit light when a DC voltage is applied between the two electrodes 43b and 43c constituting the electrode pair.
[0051]
Further, in the organic EL element 50, by controlling the magnitude of the DC voltage applied to each gate electrode 43a, it is formed between the two electrodes 43b and 43c constituting the electrode pair corresponding to the gate electrode 43a. It is possible to control the strength and direction of the applied electric field. The light emission intensity can be controlled by the magnitude of the DC voltage applied to the gate electrode 43a.
[0052]
In the organic EL element according to the embodiment described above, the organic light emitting material distributed between the two electrodes constituting the electrode pair in plan view mainly contributes to light emission. For this reason, compared with the organic EL element of the conventional laminated structure, the performance of an element is hard to be influenced by the property of an electrode surface. Generation of black spots (dark spots), reduction in luminance, dielectric breakdown, and the like can be easily prevented.
[0053]
Further, since there is no need to use a transparent electrode, various electrode materials can be used, and the degree of freedom in selecting the electrode material is increased. Since light generated in the light emitting layer does not need to be transmitted through the transparent electrode when it is emitted outside the element, a decrease in effective light emission intensity due to light absorption and reflection at the electrode is small.
[0054]
Since the organic EL element having such advantages can emit light in a line shape with a minute line width, it can be used as a light source for reproducing light of a backlight (side light) in a liquid crystal display device or a holographic optical element. Is possible. Also, various writing light sources, for example, linear light sources for printers using an electrostatic transfer system, light sources for writing dates and the like on films with a silver salt camera, and for writing image data etc. on photosensitive paper or photosensitive films, etc. It can also be used as a light source or the like. Furthermore, it can also be used as a pixel of a display device, various light source devices including a lighting device, an optical communication element, an optical sensor element, and the like. For example, as in the organic EL element 50 shown in FIG. 6, it is possible to configure an active matrix drive type display device by combining two electrodes constituting a pair of electrodes and a gate electrode.
[0055]
In addition, this invention is not limited to the organic EL element by the Example mentioned above, and its manufacturing method.
[0056]
For example, the substrate constituting the container for housing the light emitting layer can be formed of a transparent material other than glass, for example, a transparent resin or translucent ceramics. The substrate may be in the form of a sheet or a film other than a plate. The shape of the container is not limited to a flat plate shape, and can be appropriately selected from a rod shape, a cylindrical shape, a semi-cylindrical shape, a hemispherical shape, and the like.
[0057]
The electrode material is not limited to molybdenum, but ITO, IMO (indium oxide / molybdenum), chromium (Cr), gold (Au), silver (Ag), copper (depending on the type of organic light-emitting material used, etc. Cu), nickel (Ni), platinum (Pt), aluminum (Al), tungsten (W), calcium (Ca), and the like can be appropriately selected. The electrode material may be changed between the cathode and the anode. In that case, it is preferable to combine the electrode materials so that the work function of the cathode material is smaller than the work function of the anode material.
[0058]
It is considered that an organic EL element that emits light with high luminance even under low voltage driving can be obtained by narrowing the width (interval) of the slit interposed between the two electrodes constituting the electrode pair. If the value of the DC voltage applied between these electrodes is increased, the light emission intensity of the organic EL element can be increased without reducing the width of the slit.
[0059]
The above-mentioned slit may be filled with an alignment film, a hole transport layer, or an electron transport layer in a plan view without short-circuiting the two electrodes constituting the electrode pair.
[0060]
In the case where the light emitting layer is formed of an organic semiconductor in a liquid crystal state, an alignment film is preferably provided. This alignment film is for orienting the molecules of the organic semiconductor in a predetermined direction at the slits interposed between the two electrodes constituting the electrode pair. Therefore, the alignment film is formed on at least the substrate surface between the two electrodes.
[0061]
The anchoring strength between the organic semiconductor molecules in the liquid crystal state and the alignment film is preferably set to be relatively high. When the alignment film is subjected to an alignment process by rubbing, for example, the above anchoring strength is relatively high by repeatedly performing a rubbing process while applying a relatively high load to a single alignment film. be able to.
[0062]
As the material for the alignment film, in addition to the polyimide (RN-1199) manufactured by Nissan Chemical Co., Ltd. used in the organic EL element 20 according to the first embodiment, RN-1175, which is another polyimide manufactured by the same company, is also suitable. .
[0063]
It is desirable that the organic semiconductor used as the material for the light emitting layer has carrier transport properties and can be a liquid crystal phase. Specific examples of such an organic semiconductor include those having a terthiophene derivative as a main skeleton, those having a phenylnaphthalene derivative as a main skeleton, and those having a biphenyl derivative as a main skeleton.
[0064]
Since the organic semiconductor described above can control the orientation direction of molecules by voltage, the alignment film can be omitted by separately providing an electrode for controlling the orientation. In particular, in a material in which asymmetric carbon or the like is introduced into the organic semiconductor described above to impart dielectric anisotropy, the molecular orientation direction can be controlled with a low voltage.
[0065]
These organic semiconductors are in a liquid crystal state or a liquid state depending on the temperature. The organic semiconductor that has been brought into a fluidized state (for example, isotropic liquid phase state) by heating can be filled into the container by vacuum injection, reduced pressure injection, or the like, in addition to a method utilizing capillary action.
[0066]
A sealing agent is applied to one surface of the first substrate along the edge of the substrate, and a region surrounded by the sealing agent is filled with an organic semiconductor in a liquid crystal state or a liquid state. The light emitting layer can also be formed by overlapping the layers.
[0067]
In an organic EL element using an organic semiconductor in a liquid crystal state as a light emitting material, it is possible to control the light emission luminance and the polarization state of light emission by controlling the alignment direction of the molecules of the organic semiconductor. The light emitted from the organic EL element 20 according to the first embodiment is not polarized light, but improves the orientation of the organic semiconductor molecules in the vicinity of the electrode used as the cathode among the two electrodes constituting one electrode pair. Thus, it seems possible to emit polarized light.
[0068]
It will be apparent to those skilled in the art that other various modifications, improvements, combinations, applications, and the like are possible.
[0069]
【The invention's effect】
As described above, according to the present invention, the device performance is not easily affected by the properties of the electrode surface, the degree of freedom in selecting the electrode material is high, and effective light emission due to light absorption or reflection at the electrode. An organic EL element having a small decrease in strength is provided. An organic EL element that can easily improve the element performance can be obtained.
[Brief description of the drawings]
FIG. 1A is a cross-sectional view schematically showing an organic EL element according to a first embodiment, and FIG. 1B shows the organic EL element shown in FIG. It is the schematic which shows the planar arrangement | positioning of the electrode on the 1st transparent glass substrate.
FIG. 2 is a graph showing a spectral distribution of light emission from the organic EL element shown in FIG.
FIG. 3 is a schematic diagram showing a microscopic observation result when the organic EL element shown in FIG. 1A emits light.
FIG. 4 is a cross-sectional view schematically showing an organic EL element according to a second embodiment.
FIG. 5 is a cross-sectional view schematically showing an organic EL element according to a third embodiment.
FIG. 6 is a cross-sectional view schematically showing an organic EL element according to a fourth embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... 1st transparent glass substrate, 2a, 2b ... Two electrodes which comprise electrode pair, 3a, 3b ... Two electrodes which comprise electrode pair, 4, 4b ... Alignment film, 5 ... 2nd transparent glass substrate, 10 10a, 30, 45 ... container, 15 ... light emitting layer, 20, 25, 40, 50 ... organic EL element, 43a gate electrode, 43b, 43c ... two electrodes constituting an electrode pair, S1, S2, S3, S4 , S5 ... slit.

Claims (8)

A container in which two substrates are arranged opposite to each other with a space therebetween, and a space between the two substrates is an accommodation space;
An electrode pair that is arranged on the inner surface of one of the two substrates and is constituted by two electrodes adjacent to each other through a slit;
A light emitting layer formed of an organic light emitting material made of an organic semiconductor in a liquid crystal state , housed in the container ;
An organic EL element , comprising: an alignment film formed on a substrate surface between the two electrodes and having an alignment direction in a direction perpendicular to an electric field direction generated in the slit in a plan view . The organic EL device according to claim 1 , wherein the organic semiconductor is a terthiophene derivative. The organic EL device according to claim 1 or 2, wherein the electrode pair is formed of molybdenum. A container in which two substrates are arranged opposite to each other with a space therebetween, and a space between the two substrates is an accommodation space;
An electrode pair composed of two electrodes respectively disposed on the inner surfaces of the two substrates, the two electrodes being adjacent to each other through a slit in plan view;
An organic EL device comprising a light emitting layer housed in the container and formed of an organic light emitting material. The organic light emitting material is an organic semiconductor in a liquid crystal state,
further,
The organic EL element according to claim 4, further comprising an alignment film formed on surfaces of the substrate facing each other and having an alignment direction in a direction orthogonal to an electric field direction generated in the slit in a plan view. (A) Two substrates are arranged opposite to each other with a space therebetween, and an electrode pair constituted by two electrodes adjacent to each other through a slit is formed on the inner surface of one of the two substrates. An alignment film having an alignment direction in a direction orthogonal to the direction of the electric field generated in the slit in a plan view is disposed on the substrate surface between the two electrodes, and a space between the two substrates is formed. A step of preparing a container to be a storage space;
(B) A method of manufacturing an organic EL element, including a step of injecting into the container an organic light emitting material that can be in a liquid crystal state in a fluid state. (A) Two substrates are arranged opposite to each other with a space therebetween, and an electrode pair constituted by two electrodes adjacent to each other through a slit when viewed in plan is divided and arranged on the inner surfaces of the two substrates. A step of preparing a container in which a space between the two substrates serves as an accommodation space;
(B) The manufacturing method of an organic EL element including the process of inject | pouring into a container the organic light emitting material in a fluid state. The organic light emitting material is an organic semiconductor that can be in a liquid crystal state,
further,
8. The method of manufacturing an organic EL element according to claim 7, wherein an alignment film having an alignment direction in a direction orthogonal to the direction of the electric field generated in the slit in a plan view is disposed on the mutually opposing surfaces of the substrate. .

Images