JPH11224783A - Organic electroluminescence element - Google Patents
Organic electroluminescence elementInfo
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- JPH11224783A JPH11224783A JP10022871A JP2287198A JPH11224783A JP H11224783 A JPH11224783 A JP H11224783A JP 10022871 A JP10022871 A JP 10022871A JP 2287198 A JP2287198 A JP 2287198A JP H11224783 A JPH11224783 A JP H11224783A
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、一対の電極間に正
孔輸送層、有機材料からなる発光層を備え、両電極から
発光層にキャリアを注入することによって発光層を発光
させる有機エレクトロルミネッセンス素子（以下、有機
ＥＬ素子という）に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescence having a hole transport layer and a light emitting layer made of an organic material between a pair of electrodes, and emitting light from the light emitting layer by injecting carriers from both electrodes into the light emitting layer. The present invention relates to an element (hereinafter, referred to as an organic EL element).
【０００２】[0002]
【従来の技術】有機ＥＬ素子を利用した平面ディスプレ
イや、平面光源は、次世代のディスプレイ材料として大
きな注目を浴びており、研究開発が盛んに行われてお
り、単純ドットマトリクスディスプレイについては実用
化のための開発が進んでいる。2. Description of the Related Art A flat display using an organic EL element and a flat light source have received a great deal of attention as a next-generation display material, and have been actively researched and developed. The development for is progressing.
【０００３】有機ＥＬ素子は、図７に示すように、ガラ
ス基板１０上に陽極を構成する透明導電材料（ＩＴＯ、
ＳｎＯ2、ＩｎＯ3、ＺｎＯ：Ａｌ等）が用いられた透明
電極１２が形成され、この透明電極１２上に有機材料を
用いた複数の有機層（正孔輸送層１４、発光層１６、電
子輸送層１７）、有機層の上に、陰極を構成するための
ＭｇＡｇ、Ｃａ、Ａｌ、ＭｇＩｎなどからなる金属電極
５０が形成されている。そして、透明電極１２から発光
層１６に注入される正孔と、金属電極５０から発光層１
６に注入される電子とが、発光層１６で再結合すること
によって発光する。図７に示すように、発光層１６で発
生した光は、透明電極１２を通過し、ガラス基板１０を
通して外部に出る。また、不透明な金属電極５０側へ進
んだ光は、この金属電極５０で反射され、これによりガ
ラス基板側に進んでガラス基板を通って外部に出る。As shown in FIG. 7, an organic EL element is composed of a transparent conductive material (ITO, ITO) forming an anode on a glass substrate 10.
A transparent electrode 12 using SnO 2 , InO 3 , ZnO: Al or the like is formed, and a plurality of organic layers (hole transport layer 14, light emitting layer 16, electron transport) using an organic material are formed on the transparent electrode 12. A metal electrode 50 made of MgAg, Ca, Al, MgIn or the like for forming a cathode is formed on the layer 17) and the organic layer. The holes injected from the transparent electrode 12 into the light emitting layer 16 and the metal electrode 50 from the light emitting layer 1
The electrons injected into 6 emit light by recombination in the light emitting layer 16. As shown in FIG. 7, light generated in the light emitting layer 16 passes through the transparent electrode 12 and exits through the glass substrate 10. Light that has proceeded to the opaque metal electrode 50 side is reflected by the metal electrode 50, and thereby travels to the glass substrate side and exits through the glass substrate.
【０００４】また、有機ＥＬ素子としては、図７に示す
ものに限らず、図８に示すように微小共振器構造を持つ
ものも知られている。共振器構造を備えた有機ＥＬ素子
では、ガラス基板１０と陽極をなす透明電極１２との間
に多層膜からなる誘電体ミラー４０が設けられ、発光層
１６での発光光が、この誘電体ミラー４０と金属電極５
０との間を往復し、共振波長の光だけが増強されてガラ
ス基板１０を通して外部へ出る。Further, as the organic EL element, not only the one shown in FIG. 7 but also one having a micro-resonator structure as shown in FIG. 8 is known. In an organic EL device having a resonator structure, a dielectric mirror 40 composed of a multilayer film is provided between a glass substrate 10 and a transparent electrode 12 serving as an anode. 40 and metal electrode 5
Reciprocating between zero and zero, only the light of the resonance wavelength is enhanced and exits through the glass substrate 10.
【０００５】[0005]
【発明が解決しようとする課題】しかし、このような有
機ＥＬ素子内で発生した発光光がガラス基板１０を通し
て外部へ射出される割合は、素子内の屈折率ｎに対し、
理論的には１／（２ｎ２）である。従って、屈折率ｎが
１．５の場合、射出割合は約２０％程度であり、残りの
８０％近くは、有機層（１６、１４）やガラス基板１０
を導波して金属面で吸収されたり基板の端から放出され
てしまう。However, the ratio of the emitted light generated in such an organic EL device to the outside through the glass substrate 10 is smaller than the refractive index n in the device.
Theoretically, it is 1 / (2n2). Therefore, when the refractive index n is 1.5, the emission ratio is about 20%, and the remaining 80% is near the organic layer (16, 14) or the glass substrate 10.
And is absorbed by the metal surface or emitted from the edge of the substrate.
【０００６】また、１９９６年、５月６日のApply Phys
ics Letter 68(19)「Transparent organic light emitt
ing devices」には、透過型の素子を得るために、陰極
として一般的に用いられているＭｇＡｇ層の厚さを例え
ば１００Å程度に薄くし、このＭｇＡｇ層上をＩＴＯ層
で覆う構造とすることが記載されている。しかし、陰極
としてＭｇＡｇ層が存在しているため、素子の透過率は
６０％程度にしか得られず、光の利用効率は低い。[0006] Also, Apply Phys on May 6, 1996.
ics Letter 68 (19) `` Transparent organic light emitt
In order to obtain a transmissive element, the thickness of the MgAg layer generally used as a cathode is reduced to, for example, about 100 °, and the MgAg layer is covered with an ITO layer. Is described. However, since the MgAg layer is present as a cathode, the transmittance of the device is only about 60%, and the light use efficiency is low.
【０００７】また、図８に示すような微小光共振器構造
を備えた有機ＥＬ素子においても、有機発光層１６から
の発光光が金属電極面と誘電体ミラー４０との間で多重
往復するため、金属電極面での光損失がさらに大きく、
共振器構造が光増強効果を十分に発揮することができな
い。Also, in the organic EL device having the micro optical resonator structure as shown in FIG. 8, the light emitted from the organic light emitting layer 16 reciprocates between the metal electrode surface and the dielectric mirror 40. , The light loss on the metal electrode surface is even greater,
The resonator structure cannot sufficiently exhibit the light enhancement effect.
【０００８】本発明は、上記課題を解決するためになさ
れたものであり、素子内で発生した光をより効率よく素
子外部に取り出して発光効率を改善することを目的とす
る。SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to improve the luminous efficiency by more efficiently extracting light generated in an element to the outside of the element.
【０００９】[0009]
【課題を解決するための手段】上記目的を達成するため
に本発明はなされたものであり、基板上に形成された透
明な陽極電極と、陰極電極との間に、有機材料からなる
発光層を備え、前記陽極電極から前記発光層に正孔を注
入し、前記陰極電極から前記発光層に電子を注入して前
記発光層を発光させる有機エレクトロルミネッセンス素
子であり、前記陰極電極として、少なくとも発光波長に
対して透明な透明導電性材料を用いることを特徴とす
る。In order to achieve the above object, the present invention has been made, and a light emitting layer made of an organic material is provided between a transparent anode electrode formed on a substrate and a cathode electrode. An organic electroluminescence element that injects holes from the anode electrode into the light emitting layer and injects electrons from the cathode electrode into the light emitting layer to cause the light emitting layer to emit light. It is characterized in that a transparent conductive material transparent to the wavelength is used.
【００１０】更に、本発明では、上記透明な陰極電極と
発光層との間に電子注入層を備えることが好ましい。電
子注入層を設ければ、陰極電極から発光層への電子注入
が容易となり、電子注入効率が向上し、素子の駆動電圧
を低くでき、高い発光効率を実現することができる。Further, in the present invention, it is preferable to provide an electron injection layer between the transparent cathode electrode and the light emitting layer. When the electron injection layer is provided, electron injection from the cathode electrode to the light emitting layer is facilitated, the electron injection efficiency is improved, the driving voltage of the element can be reduced, and high light emission efficiency can be realized.
【００１１】また、電子注入層としては、アルカリ金属
又はアルカリ土類金属の酸化物やフッ化物を含む材料が
好ましい。Further, as the electron injection layer, a material containing an oxide or a fluoride of an alkali metal or an alkaline earth metal is preferable.
【００１２】[0012]
【発明の実施の形態】以下、本発明の実施の形態（以下
実施形態という）について、図面に基づいて説明する。Embodiments of the present invention (hereinafter referred to as embodiments) will be described below with reference to the drawings.
【００１３】［実施形態１］図１は、実施形態１に係る
有機ＥＬ素子の構成を示す図である。ガラス基板１０の
上面には、透明な陽極電極１２が形成されている。この
陽極電極１２は、ＩＴＯ（Indium Tin Oxid）、Ｓｎ
Ｏ2、ｌｎ2Ｏ3などが利用される。[First Embodiment] FIG. 1 is a diagram showing a configuration of an organic EL device according to a first embodiment. On the upper surface of the glass substrate 10, a transparent anode electrode 12 is formed. This anode electrode 12 is made of ITO (Indium Tin Oxid), Sn
O 2 , In 2 O 3 and the like are used.
【００１４】また、陽極電極１２上には、有機材料から
なる正孔輸送層１４及び発光層１６が積層形成される。
正孔輸送層１４には、主として芳香族アミン系材料が用
いられる。例えばＴＰＴＥ（トリフェニルアミン４量
体）や、α−ＮＰＢ（Bis [N-(1-naphthyl)-N-phenyl]
benzidine）等が好適である。また、発光層１６には、
これまでに報告されている既知のどの材料を用いてもよ
く、青色から黄緑発光までの発光材料が利用可能であ
る。On the anode electrode 12, a hole transport layer 14 and a light emitting layer 16 made of an organic material are laminated.
For the hole transport layer 14, an aromatic amine-based material is mainly used. For example, TPTE (triphenylamine tetramer) and α-NPB (Bis [N- (1-naphthyl) -N-phenyl]
benzidine) and the like are preferred. In addition, the light emitting layer 16 includes
Any of the known materials reported so far may be used, and light emitting materials from blue to yellow-green emission can be used.
【００１５】発光層１６の上には、電子注入層１８が形
成され、この電子注入層１８の上に陰極電極２０が形成
されている。この陰極電極２０は、従来のように不透明
な金属材料ではなく、陽極と同様、ＩＴＯ（Indium Tin
Oxid）、ＳｎＯ2、ｌｎ2Ｏ3或いはこれらの酸化物の複
合体などからなる透明導電材料が用いられている。An electron injection layer 18 is formed on the light emitting layer 16, and a cathode electrode 20 is formed on the electron injection layer 18. The cathode electrode 20 is not made of an opaque metal material as in the prior art.
Oxid), SnO 2 , In 2 O 3, or a transparent conductive material composed of a composite of these oxides is used.
【００１６】ここで、本実施形態のように陰極電極２０
としてＩＴＯ等からなる透明導電材料を用いると、透明
陰極電極２０の仕事関数が大きく、エネルギー障壁が高
くなり、低電圧駆動では、透明陰極電極２０から発光層
１６へ直接電子を注入することが難しい。陰極電極材料
として仕事関数の比較的小さいＺｎＯ系の材料を用いて
も、電子注入のためには陰極電極２０と陽極電極１２と
の間かなり高い電圧を印加する必要がある。発光層１６
と透明陰極電極２０との間に電子注入層１８を設け、こ
の電子注入層１８をアルカリ金属やアルカリ土類金属の
酸化物、フッ化物（例えばＬｉＦやＮａＦ、ＬｉＯ2）
を材料として形成すれば、低電圧での電子注入が容易と
なる。特に、この電子注入層１８として、アルカリ土類
金属のフッ化物（ＭｇＦ2、ＣａＦ2、ＳｒＦ2、Ｂａ
Ｆ2）を材料として形成することにより、有機ＥＬ素子
の安定性と素子の寿命の改善が図られる。これは、アル
カリ土類金属のフッ化物がアルカリ金属の化合物或いは
アルカリ土類金属の酸化物に比べて水との反応性が低
く、成膜中或いは成膜後における吸水が少ないためであ
る。更に、アルカリ土類金属のフッ化物は、アルカリ金
属の化合物に比べて融点が高いため、耐熱安定性も改善
されるためである。電子注入層１８は、概ね数Å〜数百
Åの厚さとすればよいが、透明陰極電極２０の成膜（ス
パッタ法、イオンプレーティング法、ＥＢ法）に際し
て、発光層１６がその表面に受けるダメージを低減する
ため、発光層１６の表面を完全に覆うような厚み（約数
十Å）が適切である。余り厚くすると、駆動電圧が高く
なってしまう。Here, the cathode electrode 20 as in this embodiment is used.
When a transparent conductive material made of ITO or the like is used, the work function of the transparent cathode electrode 20 is large, the energy barrier is high, and it is difficult to inject electrons directly from the transparent cathode electrode 20 to the light emitting layer 16 at low voltage driving. . Even if a ZnO-based material having a relatively small work function is used as the cathode electrode material, it is necessary to apply a considerably high voltage between the cathode electrode 20 and the anode electrode 12 for electron injection. Light emitting layer 16
An electron injection layer 18 is provided between the transparent cathode electrode 20 and the electron injection layer 18. The electron injection layer 18 is formed of an oxide or a fluoride of an alkali metal or an alkaline earth metal (eg, LiF, NaF, LiO 2 ).
Is formed as a material, which facilitates electron injection at a low voltage. Particularly, as the electron injection layer 18, fluorides of alkaline earth metals (MgF 2 , CaF 2 , SrF 2 , Ba)
By forming F 2 ) as a material, the stability of the organic EL device and the life of the device can be improved. This is because the fluoride of the alkaline earth metal has lower reactivity with water than the alkali metal compound or the oxide of the alkaline earth metal, and absorbs less water during or after film formation. Furthermore, since the fluoride of the alkaline earth metal has a higher melting point than the alkali metal compound, the heat stability is also improved. The electron injecting layer 18 may have a thickness of approximately several to several hundreds of mm, but the surface of the light emitting layer 16 is applied to the transparent cathode electrode 20 during the film formation (sputtering, ion plating, EB). In order to reduce the damage, a thickness (about several tens of mm) that completely covers the surface of the light emitting layer 16 is appropriate. If the thickness is too large, the driving voltage will increase.
【００１７】以上のように、陰極として透明陰極電極２
０を用いることで、素子の上部電極となる透明陰極電極
２０側から発光層１６の発光光を取り出すことが可能と
なる。図２（ａ）に示すように、発光層１６での発光光
をガラス基板を通して得る場合には、基板中を導波して
失われる導波光が発生するが、本実施形態のように上部
陰極電極を透明電極で構成すると、図２（ｂ）のように
導波成分となるガラス基板等を介すことなく発光光を取
り出すことが可能となる。更に、光を反射する金属電極
を使用しないので、発光層と金属陰極電極との界面での
光吸収（光損失）が発生しない。従って、この点でも発
光効率の向上を図ることが可能となる。As described above, the transparent cathode electrode 2 is used as the cathode.
By using 0, light emitted from the light emitting layer 16 can be extracted from the side of the transparent cathode electrode 20 serving as an upper electrode of the element. As shown in FIG. 2A, when light emitted from the light emitting layer 16 is obtained through a glass substrate, guided light that is lost while being guided in the substrate is generated. When the electrode is formed of a transparent electrode, it is possible to extract emitted light without passing through a glass substrate or the like serving as a waveguide component as shown in FIG. Furthermore, since a metal electrode that reflects light is not used, light absorption (light loss) does not occur at the interface between the light emitting layer and the metal cathode electrode. Therefore, it is possible to improve the luminous efficiency also in this respect.
【００１８】［実施形態２］上述の実施形態１では、発
光層１６からの発光光を透明陰極電極２０側から取り出
す構成を示しているが、微小光共振器構造を備える有機
ＥＬ素子にも適用可能である。図３は、このような共振
器構造を備える実施形態２に係る有機ＥＬ素子の構造を
示している。なお、既に説明した図面と対応する構成に
は同一符号を付して説明を省略する。[Embodiment 2] In Embodiment 1 described above, a configuration is described in which light emitted from the light emitting layer 16 is extracted from the transparent cathode electrode 20 side. However, the present invention is also applicable to an organic EL device having a micro optical resonator structure. It is possible. FIG. 3 shows a structure of an organic EL device according to Embodiment 2 having such a resonator structure. Note that the same reference numerals are given to configurations corresponding to the drawings described above, and description thereof will be omitted.
【００１９】図２に示す有機ＥＬ素子では、ガラス基板
１０上に多層膜からなる誘電体ミラー３０が形成され、
この誘電体ミラー３０上に陽極として透明陽極電極１
２、有機材料からなる発光層１６、電子注入層１８、陰
極として透明陰極電極２０が形成され、透明陰極電極２
０上に更に多層膜からなる誘電体ミラー３２が形成され
ている。この有機ＥＬ素子は、２つの誘電体ミラー３
０、３２によって微小光共振器が形成され、この共振器
によって発光層１６での発光光の発光スペクトルの内、
単一又は複数の特定波長が選択的に増幅され、素子の上
部（陰極側）及び下部（陽極側）から放射される。素子
の上部又は下部の片側からのみ放射させる場合には、放
射側と反対側に位置する誘電体ミラーの最終層を金属層
とする。なお、導波成分を成すガラス基板による光損失
を防止するには、誘電体ミラー３０のガラス基板側の最
終層を金属層として、上部（陰極側）から光を放射させ
る構成とすればよい。In the organic EL device shown in FIG. 2, a dielectric mirror 30 composed of a multilayer film is formed on a glass substrate 10,
A transparent anode electrode 1 is formed on the dielectric mirror 30 as an anode.
2. A light emitting layer 16 made of an organic material, an electron injection layer 18, and a transparent cathode electrode 20 as a cathode are formed.
Further, a dielectric mirror 32 made of a multilayer film is formed on 0. This organic EL element has two dielectric mirrors 3
A micro-optical resonator is formed by 0 and 32, and this resonator makes the emission spectrum of the emission light in the emission layer 16
One or more specific wavelengths are selectively amplified and emitted from the top (cathode side) and bottom (anode side) of the device. When light is emitted only from one side of the upper or lower part of the element, the final layer of the dielectric mirror located on the side opposite to the emission side is a metal layer. In order to prevent light loss due to the glass substrate forming the waveguide component, a configuration may be adopted in which the final layer on the glass substrate side of the dielectric mirror 30 is a metal layer and light is emitted from the upper side (cathode side).
【００２０】[0020]
【実施例】［実施例１］次に、実施例１として上記実施
形態１に係る有機ＥＬ素子について図４及び図５を参照
して説明する。[Example 1] Next, as Example 1, the organic EL device according to Embodiment 1 will be described with reference to FIGS.
【００２１】図４に示す素子では、基板としてガラス基
板１０を用い、この基板を洗浄してその上にマグネトロ
ンスパッタ法によってＩＴＯ電極１２を１５０ｎｍの厚
さに形成した。ＩＴＯ電極１２上には、有機材料である
トリフェニルアミン四量体（ＴＰＴＥ）を用いて正孔輸
送層１４を６０ｎｍの厚さに形成し、続いて、有機材料
であるキノリノールアルミ錯体（Ａｌｑ）を用いて発光
層１６を６０ｎｍの厚さに形成した。In the device shown in FIG. 4, a glass substrate 10 was used as a substrate, and the substrate was washed and an ITO electrode 12 was formed thereon by magnetron sputtering to a thickness of 150 nm. On the ITO electrode 12, a hole transport layer 14 is formed to a thickness of 60 nm using triphenylamine tetramer (TPTE) as an organic material, and subsequently, a quinolinol aluminum complex (Alq) as an organic material is formed. Was used to form the light emitting layer 16 to a thickness of 60 nm.
【００２２】次に、真空蒸着法により、ＬｉＦを用いて
電子注入層１８を５Åの厚さに形成し、更に、真空蒸着
法により、ＩＴＯ電極２０を３ｎｍ／ｍｉｎの速度で１
００ｎｍの厚さに形成した。Next, an electron injection layer 18 is formed to a thickness of 5 ° using LiF by a vacuum evaporation method, and the ITO electrode 20 is formed at a speed of 3 nm / min by a vacuum evaporation method at a speed of 3 nm / min.
It was formed to a thickness of 00 nm.
【００２３】図５は、このようにして得られた有機ＥＬ
素子に対し、下部ＩＴＯ電極１２がプラス、上部ＩＴＯ
電極２０がマイナスとなるように電圧を印加した場合
に、発光層１６への注入電流密度（ｍＡ／ｃｍ2）に対
する上部ＩＴＯ電極側とガラス基板側との発光輝度の違
いを示している。また、両電極間に５Ｖの電圧を印加し
たところ、１０ｃｄ／ｍ2の輝度の緑色発光が、陽極と
なった下部ＩＴＯ電極１２からガラス基板１０を介して
得られ、上部ＩＴＯ電極２０からは２０ｃｄ／ｍ2の緑
色発光が得られた。FIG. 5 shows the organic EL thus obtained.
The lower ITO electrode 12 is positive and the upper ITO
When the voltage is applied so that the electrode 20 becomes negative, the difference in the light emission luminance between the upper ITO electrode side and the glass substrate side with respect to the injection current density (mA / cm 2 ) into the light emitting layer 16 is shown. When a voltage of 5 V was applied between both electrodes, green light emission with a luminance of 10 cd / m 2 was obtained from the lower ITO electrode 12 serving as an anode through the glass substrate 10, and 20 cd from the upper ITO electrode 20. / M 2 of green light was obtained.
【００２４】これらの結果から、陰極となった上部ＩＴ
Ｏ電極２０側から直接放射される発光層１６での光は、
ガラス基板１０を介して外部に放射される光の２倍程度
であることがわかる。従って、陰極を透明電極とし、陰
極側から発光光を取り出すことにより、素子の発光効率
を向上させることが分かる。From these results, it can be seen that the upper IT
Light in the light emitting layer 16 radiated directly from the O electrode 20 side is:
It can be seen that the light is about twice as much as the light radiated outside through the glass substrate 10. Therefore, it can be seen that the emission efficiency of the device is improved by using the cathode as a transparent electrode and extracting emitted light from the cathode side.
【００２５】［実施例２］次に、実施例２として、上記
実施形態２に係る有機ＥＬ素子について説明する。実施
例２において、上述の図３に示すような構成の有機ＥＬ
素子は、まず、ガラス基板１０上に、スパッタ法によっ
て屈折率の異なるＳｉＯ2膜とＴｉＯ2膜とを交互に形成
して誘電体ミラー３０を形成した。次に、この誘電体ミ
ラー３０の上にＩＴＯ陽極電極１２を５０ｎｍ形成し
た。次に、真空蒸着法でＴＰＴＥを用いて５０ｎｍの厚
さの正孔輸送層（図示せず）、Ａｌｑを用いて４０ｎｍ
の厚さの発光層１６を形成した。更にＬｉＯ2を用いて
１ｎｍの厚さの電子注入層１８を形成し、更にＩＴＯを
用いて５０ｎｍの厚さにＩＴＯ陰極電極２０を形成し
た。最後にガラス基板１０側に形成した誘電体ミラー３
０と同様の誘電体ミラー３２をＩＴＯ陰極電極２０の上
にスパッタ法によって形成した。Example 2 Next, as Example 2, an organic EL device according to Embodiment 2 will be described. In the second embodiment, the organic EL having the configuration as shown in FIG.
First, the dielectric mirror 30 was formed by alternately forming SiO 2 films and TiO 2 films having different refractive indexes on the glass substrate 10 by a sputtering method. Next, an ITO anode electrode 12 having a thickness of 50 nm was formed on the dielectric mirror 30. Next, a hole transport layer (not shown) having a thickness of 50 nm using TPTE by vacuum evaporation and 40 nm using Alq.
The light-emitting layer 16 having a thickness of 5 mm was formed. Further, an electron injection layer 18 having a thickness of 1 nm was formed using LiO 2 , and an ITO cathode electrode 20 was formed to a thickness of 50 nm using ITO. Finally, the dielectric mirror 3 formed on the glass substrate 10 side
A dielectric mirror 32 similar to 0 was formed on the ITO cathode electrode 20 by sputtering.
【００２６】図６は、このようにして作成した有機ＥＬ
素子を５Ｖで駆動した場合における発光波長と外部に放
射される光の発光強度との関係を示している。共振器構
造を備えない有機ＥＬ素子に対し、陰極として金属電極
を用いた従来の共振器構造の有機ＥＬ素子においても、
特定波長の光が増幅されてこれが出力されている。しか
し、実施例２のように両側電極を透明電極とした共振器
構造の素子は、従来のように片側に金属電極を用いた有
機ＥＬ素子に対して、共振波長がより選択的に増幅さ
れ、半値幅（最大ピークが半分の値になるまでの幅）の
小さい単色光が得られている。また、素子の上方及び下
方への指向性を示した。更に、図６から明らかなよう
に、実施例２の素子で得られる単色光の発光強度は、片
側が金属電極である従来の有機ＥＬ素子に比較して非常
に高くなっている。このことからも、本実施例２の構成
により発光効率が向上することが理解できる。FIG. 6 shows the organic EL device thus prepared.
The relationship between the emission wavelength and the emission intensity of light emitted outside when the element is driven at 5 V is shown. In contrast to an organic EL element having no resonator structure, an organic EL element having a conventional resonator structure using a metal electrode as a cathode,
Light of a specific wavelength is amplified and output. However, in the device having a resonator structure in which both electrodes are transparent electrodes as in Example 2, the resonance wavelength is more selectively amplified than in the conventional organic EL device using a metal electrode on one side, Monochromatic light having a small half-value width (width until the maximum peak becomes a half value) is obtained. In addition, directivity upward and downward of the element was shown. Further, as is clear from FIG. 6, the emission intensity of monochromatic light obtained by the device of Example 2 is much higher than that of a conventional organic EL device in which one side is a metal electrode. From this, it can be understood that the luminous efficiency is improved by the configuration of the second embodiment.
【００２７】なお、以上の実施形態、実施例において発
光層の有機材料としては、低分子系材料に限らず、例え
ば、ポリパラフェニレンビニレンのような高分子系材料
を用いることも可能である。In the embodiments and examples described above, the organic material of the light emitting layer is not limited to a low molecular weight material, and for example, a high molecular weight material such as polyparaphenylene vinylene can be used.
【００２８】更に、本発明では、上記本実施形態に係る
有機ＥＬ素子を有機材料や無機材料化合物からなる保護
膜で覆う、更に不活性ガスで素子を封入するなどによ
り、素子の信頼性を一層高めることができる。なお、素
子の封止にあたっては、不活性ガスの封入に限らず、シ
リコン系やフッ素系の液体を封入してもよい。Further, in the present invention, the reliability of the device is further improved by covering the organic EL device according to the present embodiment with a protective film made of an organic material or an inorganic material compound, and further sealing the device with an inert gas. Can be enhanced. The sealing of the element is not limited to sealing with an inert gas, but may be sealing with a silicon-based or fluorine-based liquid.
【００２９】[0029]
【発明の効果】以上説明したように本発明では、陰極と
して透明導電材料を用いることで、光損失を低減し、素
子の発光効率の向上を可能としている。また、この陰極
と発光層との間に電子注入層を設け、この層をアルカリ
金属やアルカリ土類金属の酸化物やフッ化物などの材料
を用いて形成すれば、低電圧駆動が可能でかつ信頼性の
高い有機ＥＬ素子を得ることが可能となる。As described above, in the present invention, by using a transparent conductive material for the cathode, light loss can be reduced and the luminous efficiency of the device can be improved. If an electron injection layer is provided between the cathode and the light emitting layer, and this layer is formed using a material such as an oxide or a fluoride of an alkali metal or an alkaline earth metal, low voltage driving is possible and It is possible to obtain a highly reliable organic EL element.
【図１】 本発明の実施形態１に係る有機ＥＬ素子の構
成を示す図である。FIG. 1 is a diagram showing a configuration of an organic EL device according to a first embodiment of the present invention.
【図２】 本発明と従来の有機ＥＬ素子の光放射機構の
相違を説明する図である。FIG. 2 is a diagram for explaining a difference between a light emitting mechanism of the present invention and a conventional organic EL element.
【図３】 本発明の実施形態２に係る光共振器構造を有
する有機ＥＬ素子の構成を示す図である。FIG. 3 is a diagram showing a configuration of an organic EL device having an optical resonator structure according to a second embodiment of the present invention.
【図４】 実施例１に係る有機ＥＬ素子の構成を示す図
である。FIG. 4 is a diagram showing a configuration of an organic EL device according to Example 1.
【図５】 実施例１に係る有機ＥＬ素子の上部電極側と
下部電極側における注入電流密度に対する発光輝度の相
違を示す図である。FIG. 5 is a diagram showing a difference in light emission luminance with respect to an injection current density on the upper electrode side and the lower electrode side of the organic EL element according to Example 1.
【図６】 実施例２及び従来の光共振器構造を備える有
機ＥＬ素子の発光波長に対する発光強度を示す図であ
る。FIG. 6 is a diagram showing the emission intensity with respect to the emission wavelength of the organic EL device having the optical resonator structure of Example 2 and the conventional optical resonator structure.
【図７】 陰極として金属電極を用いた従来の有機ＥＬ
素子の構成を示す図である。FIG. 7 shows a conventional organic EL using a metal electrode as a cathode.
FIG. 3 is a diagram illustrating a configuration of an element.
【図８】 陰極として金属電極を用いた従来の光共振器
構造の有機ＥＬ素子の構造を示す図である。FIG. 8 is a diagram showing the structure of an organic EL element having a conventional optical resonator structure using a metal electrode as a cathode.
１０ ガラス基板、１２ 透明陽極電極、１４ 正孔輸
送層、１６ 発光層、１８ 電子注入層、２０ 透明陰
極電極、３０，３２ 誘電体ミラー。Reference Signs List 10 glass substrate, 12 transparent anode electrode, 14 hole transport layer, 16 light emitting layer, 18 electron injection layer, 20 transparent cathode electrode, 30, 32 dielectric mirror.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 野田 浩司 愛知県愛知郡長久手町大字長湫字横道41番 地の１ 株式会社豊田中央研究所内 (72)発明者 藤川 久喜 愛知県愛知郡長久手町大字長湫字横道41番 地の１ 株式会社豊田中央研究所内 (72)発明者 多賀 康訓 愛知県愛知郡長久手町大字長湫字横道41番 地の１ 株式会社豊田中央研究所内 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Koji Noda 41-cho, Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture Inside of Toyota Central Research Laboratory Co., Ltd. 41, Yokomichi, Toyota Central Research Laboratory Co., Ltd. (72) Inventor Yasunori Taga 41, Yokomichi, Yoji, Nagakute-cho, Aichi-gun, Aichi Prefecture
Claims (1)
陰極電極との間に、有機材料からなる発光層を備え、前
記陽極電極から前記発光層に正孔を注入し、前記陰極電
極から前記発光層に電子を注入して前記発光層を発光さ
せる有機エレクトロルミネッセンス素子であり、 前記陰極電極として、少なくとも発光波長に対して透明
な透明導電性材料を用いる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 transparent anode electrode formed on a substrate;
A light-emitting layer made of an organic material between the cathode electrode, an organic material that injects holes from the anode electrode into the light-emitting layer, and injects electrons from the cathode electrode into the light-emitting layer to cause the light-emitting layer to emit light. An organic electroluminescent element, which is an electroluminescent element, wherein a transparent conductive material transparent to at least an emission wavelength is used as the cathode electrode.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10022871A JPH11224783A (en) | 1998-02-04 | 1998-02-04 | Organic electroluminescence element |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10022871A JPH11224783A (en) | 1998-02-04 | 1998-02-04 | Organic electroluminescence element |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH11224783A true JPH11224783A (en) | 1999-08-17 |
Family
ID=12094769
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP10022871A Pending JPH11224783A (en) | 1998-02-04 | 1998-02-04 | Organic electroluminescence element |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH11224783A (en) |
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