JP2004039531A - Organic electroluminescence element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL element in which a leak current and the resistance value are small, a transmission factor in a visible light wavelength (around 400 to 700 nm) is high, and stable light emitting characteristics can be maintained for a long period. <P>SOLUTION: This is an organic EL element provided with at least a positive electrode 2, an organic layer 9 containing a light emitting material, and a negative electrode 3 on the substrate 1. The positive electrode 2 is formed with ITO as a main component by ion plating method, the film thickness of the positive electrode 2 is 2,700 Å to 3,500 Å, the transmission factor of the transmitting light in the visible light wavelength of the positive electrode 2 is 80% or more, and the surface roughness of a face joined to at least an organic layer 9 of the positive electrode 2 is 250 Å or less of Rp-v and 20 Å or less of Ra by a measurement with an atomic force microscope. <P>COPYRIGHT: (C)2004,JPO

Description

【００２２】
表１より、抵抗値は膜厚が厚い程低いこと、表面粗さの平均値Ｒａはどの膜厚でも１０Å程度で差は見られないが、表面粗さの最大値Ｒｐ−ｖは膜厚が薄い程大きい傾向にあることが判明した。すなわち、平均粗さＲａのみで表面粗さを規定すると、突起部の発生を見逃すことになることが判った。したがって、表面粗さは平均値Ｒａと最大値Ｒｐ−ｖの両者を規定する必要があることが判った。
【００２３】
後述する実施例で説明するが、表面粗さの最大値Ｒｐ−ｖが３００Å以上の場合にはリーク電流が発生し易いため、陽極の膜厚としては２７００Å以上が良いと言える。
【００２４】
また、可視光波長（４００〜７００ｎｍ程度）における透過率は、３５００Å以下であれば８０％以上であることが判った。透過率は高いほど良いが、８０％以上あれば表示パネルの設計上充分と言える。
【００２５】
以上の結果から、イオンプレーティング法によるＩＴＯの最適な膜厚は、シート抵抗値については２７００Å以上、表面粗さＲｐ−ｖ、Ｒａについては２７００Å以上、透過率については３５００Å以下が良いことが判った。すなわち、２７００Å〜３５００Åが最も良い条件であることが判明した。また、この範囲の膜厚のＩＴＯを用いてダークスポットの発生状況についても調査したが、ダークスポットは発生し難いことが判った。これは、後述する実施例においても明らかとなる。
【００２６】
以下に、本実施形態の有機ＥＬ素子における他の構成要素について説明する。
【００２７】
光透過性を有する基板１としては、一般的に使用されているガラスが用いられ、例えば、無アルカリガラス、石英、ホウ珪酸ガラス、ソーダガラスが挙げられる。また、可撓性を有する基板でも良く、例えば、ポリエチレンテレフタレート（ＰＥＴ）、ポリカーボネート（ＰＣ）、ポリエーテルスルフォンサン（ＰＥＳ）、ポリエーテルエチルケトン（ＰＥＥＫ）、ポリエチレン（ＰＥ）、ポリプロピレン（ＰＰ）トリアセチルセルロース（ＴＡＣ）、ポリビニルアルコール（ＰＶＡ）、ポリフッ化ビニル（ＰＦＶ）、ポリアクリレート（ＰＡ）、非晶質ポリオレフィン、フッ素樹脂などの高分子フィルムを用いてもよい。
【００２８】
陰極３を構成する電子注入層４としては、仕事関数の小さい（４ｅＶ以下）金属、金属合金などを用いることができ、具体的にはマグネシウム、マグネシウムと銀との合金、ナトリウム、ナトリウムとカリウムとの合金、アルミニウムとリチウムとの合金、インジウムや希土類金属などが挙げられる。また、電子注入層４の上に電極５として、例えば、ＡｌやＭｇなどの金属を形成する。
【００２９】
有機物層９とは、実質的に１種類または多種類の有機発光材料のみからなる薄膜や、１種類または多種類の有機発光材料と正孔輸送材料、電子注入材料との混合物からなる薄膜など、発光層として機能する単層構造や、発光層以外に正孔輸送材料、電子注入材料を個別に２層以上の多層構造を有するものをいう。有機物層９の構成材料には、従来より有機ＥＬ素子で用いられている正孔輸送材料、有機発光材料、電子注入材料をそのまま使用することができる。
【００３０】
正孔輸送層６としては、例えば、トリアゾール誘導体、オキサジアゾール誘導体、イミダゾール誘導体、フェニレンジアミン誘導体、アリールアミン誘導体、ピラゾリン誘導体、ピラゾロン誘導体、アニリン系共重合体、ポリアリールアルカン誘導体、スチルベン誘導体、ヒドラゾン誘導体、アミノ置換カルコン誘導体、オキサゾール誘導体、スチリルアントランセン誘導体、フルオレノン誘導体、シラザン誘導体、ポリシラン系化合物などが挙げられる。
【００３１】
発光層７としては、例えば、ベンゾチアゾール系、金属キレート化オキシノイド化合物、スチルベンゼン系化合物、芳香族ジメチルリジン化合物、ジスチルピラジン誘導体ベンゾイミダゾール系、ベンゾオイサゾール系などが挙げられる。
【００３２】
電子輸送層８としては、例えば、ニトロ置換フルオレノン誘導体、アントラキノジメタン誘導体、チオピランジオイシド誘導体などの複素環テトラカルボン酸無水物、フレオレニリンデンメタン誘導体、オキサジアゾール誘導体、８−キノリノール誘導体、カルボジイミド、アントロン誘導体などが挙げられる。
【００３３】
以上説明したように、本実施形態における有機物層９は、有機化合物からなる発光材料を含む有機単層薄膜、もしくは有機多層薄膜であり、陰極３は公知の構成である。
【００３４】
【実施例】
以下に、本発明の一実施例を詳細に説明するが、本発明は本実施例に限るものではない。
【００３５】
図２は、本実施例の有機ＥＬ素子における層構成を示す模式図である。図２に示すように、板厚が０．７ｍｍで、１０ｍｍ角のガラス基板（ＳｉＯ_２系）１上に、イオンプレーティング法により、表１に示した種類と同じ膜厚１２００Å、２０００Å、２７００Å、３５００Å、４０００ÅのＩＴＯ品を作製した。
【００３６】
蒸着ソースには、Ｉｎ_２Ｏ_３が９０％とＳｎＯ_２が１０％との混合焼結品を使用した。成膜条件は、基板温度、酸素分圧、及び蒸着速度を種々変更して作製した。その後、フォトリソグラフィ工程で３ｍｍ角の形状とし、この基板をイソプロピルアルコール（ＩＰＡ）溶液で５分間洗浄し、純水中で超音波洗浄した後、ＵＶオゾン洗浄機で１０分間洗浄した。
【００３７】
このＩＴＯ蒸着ガラスを蒸着機の基板ホルダーに固定し、１×１０^−４Ｐａの真空中でＩＴＯ側にＮ，Ｎ’−ビス（３−メチルフェニル−Ｎ，Ｎ’−ジフェニル〔１，１’−ビフェニル〕−４，４’−ジアミン（以下、「ＴＰＤ」という。）を１００Å蒸着して正孔輸送層６を積層した。
【００３８】
次に、発光層７としてトリス（８−キノリノール）アルミニウム（以下、「Ａｌｑ_３」という。）にキナクリドンを共蒸着により５％ドーピングした層を２００Å設けた。次に電子輸送層８であるＡｌｑ_３を５００Å蒸着した。
【００３９】
そして、陰極３として、アルミニウムとリチウムとの混合金属を６０Å蒸着して電子注入層４を積層した後、さらにアルミニウムを１２００Å蒸着して電極５を積層し、有機ＥＬ素子を作成した。
【００４０】
その後、大気中の水分の影響を受けないように、窒素雰囲気中で各有機ＥＬ素子を封止容器１２で覆い、接着剤１４によりガラス基板１と接合した。すなわち、封止容器１２とガラス基板１とで区画される空間には窒素ガス１３が封入されている。
【００４１】
各有機ＥＬ素子のサンプルにＤＣ定電流を流し、発光輝度を１００ｃｄ／ｍ^２で１００時間駆動して、ダークスポット試験を行った。
【００４２】
表２は、発光部の初期（素子作成直後）及びダークスポット試験後（１００時間駆動後）におけるダークスポットの数を示している。ダークスポットの数の測定は、倍率１００倍の暗視野で、０．５ｍｍ角内に０．２μｍ以上のパーティクルの数を数えて行った。
【００４３】
【表２】

【００４４】
表２に示すように、２０００Å以下の場合は、ダークスポットが発生し易い。また、駆動後には素子作製直後のダークスポットの拡大が見られ、また、数が増加し易いことが判った。
【００４５】
図３はＩＴＯ厚みが１２００Å品の素子作成直後におけるダークスポットの発生状況を示す説明図であり、図４はＩＴＯ厚みが１２００Å品の１００時間駆動後におけるダークスポットの発生状況を示す説明図である。また、図５はＩＴＯ厚みが３５００Å品の素子作成直後におけるダークスポットの発生状況を示す説明図であり、図６はＩＴＯ厚みが３５００Å品の１００時間駆動後におけるダークスポットの発生状況を示す説明図である。図３乃至図６において、１１はダークスポットであり、１００時間駆動後におけるダークスポットの発生状況が、３５００Å品よりも１２００Å品の方が多数見られる。すなわち、ＩＴＯの膜厚が２７００Å〜４０００Åの範囲のものは、ダークスポットが発生し難いことが判った。これは、ＩＴＯ表面の突起部が小さいからである。
【００４６】
【発明の効果】
以上説明したように、本発明によれば、陽極の不具合による有機ＥＬ素子のショート破壊、輝度劣化の原因となるリーク電流の発生を防止することができ、長時間に亘って安定した発光特性を維持することができる有機ＥＬ素子を提供することができるものである。
【図面の簡単な説明】
【図１】本発明の一実施形態の有機ＥＬ素子における層構成を示す模式図である。
【図２】本発明の実施例の有機ＥＬ素子における層構成を示す模式図である。
【図３】本発明の実施例において、ＩＴＯ厚みが１２００Å品の素子作成直後のダークスポット発生状況を示す説明図である。
【図４】本発明の実施例において、ＩＴＯ厚みが１２００Å品の１００時間駆動後のダークスポット発生状況を示す説明図である。
【図５】本発明の実施例において、ＩＴＯ厚みが３５００Å品の素子作成直後のダークスポット発生状況を示す説明図である。
【図６】本発明の実施例において、ＩＴＯ厚みが３５００Å品の１００時間駆動後のダークスポット発生状況を示す説明図である。
【符号の説明】
１　基板
２　陽極
３　陰極
４　電子注入層
５　電極
６　正孔輸送層
７　発光層
８　電子輸送層
９　有機物層
１０　突起部
１１　ダークスポット
１２　封止容器
１３　窒素ガス
１４　接着剤[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an organic electroluminescence device (hereinafter, referred to as “organic EL device”) in which at least an anode, an organic material layer containing a luminescent material, and a cathode are stacked on a substrate.
[0002]
[Prior art]
2. Description of the Related Art In recent years, a display device constituted by an organic EL element has advantages such as thinness, a wide viewing angle, and a fast response speed as compared with a so-called LCD module in which a liquid crystal (LCD) and a backlight are combined because of a self-luminous property. Therefore, practical application is being promoted.
[0003]
In this type of organic EL device, an anode is formed on a light-transmitting substrate, and a hole transport layer, a light-emitting layer, an electron transport layer, and an electron injection layer, which is a cathode, and an electrode are formed on the anode. Indium tin oxide (hereinafter, referred to as “ITO”), which is a transparent electrode and has low resistance, is generally used for the anode.
[0004]
However, if a protrusion is present on the ITO surface, the distance from the cathode is reduced only at that portion, and when a voltage is applied to the element, current flows intensively at that portion. That is, when a leak current occurs and the time elapses, the projection and the cathode are short-circuited, and current flows only to that portion, and the luminance is deteriorated and light emission stops.
[0005]
Therefore, Japanese Patent Application Laid-Open No. 09-245965 discloses that after the anode is formed, the surface of the anode is polished and flattened by using a technique such as polishing, lapping, or tape lapping, thereby reducing the surface roughness of the anode. The specified invention has been proposed. Further, Japanese Patent Application Laid-Open No. 09-007770 proposes an invention in which the surface roughness of the anode is defined by the contact angle with water.
[0006]
[Problems to be solved by the invention]
However, it is important for the anode of the organic EL element to have a small leakage current due to the influence of the projections on the anode surface, but it also has a small resistance value and a low transmittance at a visible light wavelength (about 400 to 700 nm). It is required to be high, but no proposal has been made to properly define these values.
[0007]
SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object a low leakage current and a low resistance value, a high transmittance at a visible light wavelength (about 400 to 700 nm), and a long term. It is an object of the present invention to provide an organic EL device capable of maintaining stable light-emitting characteristics.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, an organic EL device of the present invention is an organic EL device comprising at least an anode, an organic material layer containing a luminescent material, and a cathode on a substrate.
The anode is formed by indium tin oxide as a main component by an ion plating method, the thickness of the anode is 2700 ° to 3500 °, and the transmittance of transmitted light at a visible light wavelength (400 to 700 nm) of the anode is 80% or more; The surface roughness of at least the surface of the anode bonded to the organic material layer is characterized in that the maximum value Rp-v is 250 ° or less and the average value Ra is 20 ° or less as measured by an atomic force microscope.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
The organic electroluminescent device of the present invention is an organic electroluminescent device comprising at least an anode, an organic material layer containing a luminescent material, and a cathode on a substrate, wherein the anode mainly comprises indium tin oxide by an ion plating method. The anode has a film thickness of 2700-3500 °, a transmittance of transmitted light at a visible light wavelength (400-700 nm) of 80% or more, and a surface roughness of at least a surface of the anode that is bonded to an organic material layer. The maximum value Rp-v is 250 ° or less and the average value Ra is 20 ° or less as measured by an atomic force microscope.
[0010]
Such an organic electroluminescent element has a small leak current and a low resistance, a high transmittance at a visible light wavelength (about 400 to 700 nm), and a long period of time, as will be apparent from the examination results described later. As a result, stable light emission characteristics can be maintained.
[0011]
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings and examination results, but the present invention is not limited to the embodiments.
[0012]
FIG. 1 is a schematic diagram illustrating a layer configuration in the organic EL device of the present embodiment. As shown in FIG. 1, the organic EL device of the present embodiment includes at least an anode 2, an organic material layer 9 containing a luminescent material, and a cathode 3 on a light-transmitting substrate 1. In this example, the organic material layer 9 is composed of a hole transport layer 6, a light emitting layer 7, and an electron transport layer 8 made of an organic compound, and the cathode 3 is composed of an electron injection layer 4 and an electrode 5.
[0013]
The properties required for the anode 2 are that the surface is smooth (small leakage current due to the influence of the protrusions), the resistance value is small (lower current consumption, measures against uneven brightness during light emission of the display panel), and High transmittance at a visible light wavelength (about 400 to 700 nm). Considering that the inorganic material has a large work function (4 eV or more) in addition to the above, examples thereof include CuI, ITO, SnO ₂ , and ZnO. In addition, examples of the organic material include conductive polymer systems such as polythiophene, polypyrrole, and polyaniline.
[0014]
In the present invention, among these constituent materials, the study was focused on ITO having a characteristic of having a low resistance value and a large transmittance at a visible light wavelength (about 400 to 700 nm).
[0015]
ITO is formed by a sputtering method, an ion plating method, or the like. The surface state and the resistance value of the formed ITO are determined by a film forming method, a film forming material, a substrate temperature, an oxygen partial pressure, a deposition rate, and the like. It varies greatly depending on conditions.
[0016]
Therefore, an ITO product having a thickness of 3000 mm was manufactured by a sputtering method and an ion plating method, and the surface roughness and the resistance value were examined. The film formation conditions are as follows: in the case of sputtering, the target material is ITO containing 7 wt% of tin oxide, the substrate temperature is 250 ° C., the pressure during film formation is 5 × 10 ⁻¹ Pa, and the oxygen partial pressure is 3 × 10 ⁻² Pa. In the ion plating method, the target material was ITO containing 7 wt% of tin oxide, the substrate temperature was 230 ° C., the pressure during film formation was 5 × 10 ⁻¹ Pa, and the oxygen partial pressure was 3 × 10 ⁻² Pa.
[0017]
The surface state of the ITO is evaluated using a nuclear microscope. In this case, the length measurement range is 100 μm, and the scan speed is 0.5 Hz. The maximum value Rp-v of the surface roughness of the ion-plated product was 164 °, and the average value Ra of the surface roughness was 12 °. On the other hand, the maximum value Rp-v of the surface roughness of the sputtered product was 273 °, and the average value Ra of the surface roughness was 26 °. Thus, it was found that the ion-plated product had fewer protrusions (lower roughness) on the surface.
[0018]
When measuring the surface roughness, an atomic force microscope was used, but the measurement mode is preferably a non-contact mode. In the case of the contact mode, a very small amount of splash may adhere to the substrate when the ITO film is formed. This is because, during measurement of the portion of the splash object, the splash object may peel off and stick to the tip of the probe, so that the reliability of subsequent measurement data is lost.
[0019]
Next, the sheet resistance was measured. The ion plating was 4Ω / □, and the sputtered product was 5Ω / □. Therefore, it has been found that the ion plating method is suitable for ITO film formation because the surface roughness is small and the resistance value is small.
[0020]
ITO having a film thickness of 1200 °, 2000 °, 2700 °, 3500 °, and 4000 ° was prepared by an ion plating method, and the resistance value, surface roughness, and light transmittance at a visible light wavelength (about 400 to 700 nm) were measured. The transmittance is measured according to JIS R 1635. A test piece is placed perpendicular to the measurement light, and the measurement light is incident from the ITO side at an incident angle of 0 ° and transmitted to the substrate side (substrate defined by JIS). It is a value measured as described above. Table 1 shows the results, which are average values of 10 samples.
[0021]
[Table 1]

[0022]
From Table 1, it can be seen that the resistance value is lower as the film thickness is larger, and that the average value of surface roughness Ra is about 10 ° at any film thickness and no difference is observed, but the maximum surface roughness value Rp-v is It turned out that the thinner the film, the larger the tendency. In other words, it was found that if the surface roughness was defined only by the average roughness Ra, the occurrence of the projection would be overlooked. Therefore, it was found that the surface roughness needed to define both the average value Ra and the maximum value Rp-v.
[0023]
As will be described in the examples described later, when the maximum value of the surface roughness Rp-v is 300 ° or more, a leak current is likely to occur, so it can be said that the anode film thickness is preferably 2700 ° or more.
[0024]
Further, it was found that the transmittance at a visible light wavelength (about 400 to 700 nm) was 80% or more if it was 3500 ° or less. The higher the transmittance, the better, but if it is 80% or more, it can be said that the design of the display panel is sufficient.
[0025]
From the above results, it is found that the optimum film thickness of ITO by the ion plating method is 2700 ° or more for the sheet resistance value, 2700 ° or more for the surface roughness Rp-v and Ra, and 3500 ° or less for the transmittance. Was. That is, it turned out that 2700-3500 degrees is the best condition. The occurrence of dark spots was also investigated using ITO having a film thickness in this range, and it was found that dark spots were unlikely to occur. This will be clear in the embodiments described later.
[0026]
Hereinafter, other components of the organic EL device of the present embodiment will be described.
[0027]
As the substrate 1 having optical transparency, generally used glass is used, and examples thereof include non-alkali glass, quartz, borosilicate glass, and soda glass. Further, a flexible substrate may be used. For example, polyethylene terephthalate (PET), polycarbonate (PC), polyethersulfonesan (PES), polyetherethylketone (PEEK), polyethylene (PE), polypropylene (PP) A polymer film such as acetyl cellulose (TAC), polyvinyl alcohol (PVA), polyvinyl fluoride (PFV), polyacrylate (PA), amorphous polyolefin, or a fluororesin may be used.
[0028]
As the electron injection layer 4 constituting the cathode 3, a metal, a metal alloy, or the like having a small work function (4 eV or less) can be used, and specifically, magnesium, an alloy of magnesium and silver, sodium, sodium and potassium, and the like. Alloys, alloys of aluminum and lithium, indium and rare earth metals, and the like. Further, as the electrode 5, for example, a metal such as Al or Mg is formed on the electron injection layer 4.
[0029]
The organic layer 9 may be a thin film substantially composed of only one or more kinds of organic light emitting materials, a thin film composed of a mixture of one or more kinds of organic light emitting materials and a hole transport material, an electron injection material, and the like. It refers to a single-layer structure functioning as a light-emitting layer, or a multilayer structure having two or more layers of a hole transport material and an electron injection material separately from the light-emitting layer. As a constituent material of the organic material layer 9, a hole transport material, an organic light emitting material, and an electron injection material conventionally used in an organic EL device can be used as they are.
[0030]
Examples of the hole transport layer 6 include a triazole derivative, an oxadiazole derivative, an imidazole derivative, a phenylenediamine derivative, an arylamine derivative, a pyrazoline derivative, a pyrazolone derivative, an aniline-based copolymer, a polyarylalkane derivative, a stilbene derivative, and a hydrazone. Derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styryl anthracene derivatives, fluorenone derivatives, silazane derivatives, polysilane compounds and the like.
[0031]
Examples of the light emitting layer 7 include a benzothiazole compound, a metal chelated oxinoid compound, a stilbenzene compound, an aromatic dimethyl lysine compound, a distilpyrazine derivative benzimidazole compound, and a benzooisazole compound.
[0032]
Examples of the electron transport layer 8 include a heterocyclic tetracarboxylic anhydride such as a nitro-substituted fluorenone derivative, an anthraquinodimethane derivative, and a thiopyrandioiside derivative, a fluorenylidene methane derivative, an oxadiazole derivative, and 8-quinolinol. Derivatives, carbodiimides, anthrone derivatives and the like.
[0033]
As described above, the organic layer 9 in the present embodiment is an organic single-layer thin film or an organic multilayer thin film containing a light emitting material made of an organic compound, and the cathode 3 has a known configuration.
[0034]
【Example】
Hereinafter, one embodiment of the present invention will be described in detail, but the present invention is not limited to this embodiment.
[0035]
FIG. 2 is a schematic diagram showing a layer configuration in the organic EL device of this example. As shown in FIG. 2, on a glass substrate (SiO ₂ system) 1 having a thickness of 0.7 mm and a square of 10 mm, the same film thicknesses as those shown in Table 1 were formed by ion plating at 1200 °, 2000 °, and 2700 °. An ITO product having a thickness of 3500 ° and 4000 ° was prepared.
[0036]
As a deposition source, a mixed sintered product of 90% of In ₂ O ₃ and 10% of SnO ₂ was used. The film was formed by changing the substrate temperature, the oxygen partial pressure, and the deposition rate variously. Thereafter, the substrate was formed into a 3 mm square shape by a photolithography process, and this substrate was washed with an isopropyl alcohol (IPA) solution for 5 minutes, ultrasonically washed in pure water, and then washed with a UV ozone washing machine for 10 minutes.
[0037]
This ITO vapor-deposited glass was fixed to a substrate holder of a vapor deposition machine, and N, N′-bis (3-methylphenyl-N, N′-diphenyl [1,1 ′) was placed on the ITO side in a vacuum of 1 × 10 ⁻⁴ Pa. -Biphenyl] -4,4'-diamine (hereinafter referred to as "TPD") was deposited at 100 [deg.] To laminate the hole transport layer 6.
[0038]
Next, as the light-emitting layer 7, a layer formed by doping 5% of quinacridone into tris (8-quinolinol) aluminum (hereinafter, referred to as “Alq ₃ ”) by co-evaporation was provided at 200 °. Next, Alq ₃ as the electron transport layer 8 was deposited at 500 °.
[0039]
Then, as the cathode 3, a mixed metal of aluminum and lithium was deposited at 60 ° to deposit the electron injection layer 4, and then aluminum was deposited at 1200 ° to deposit the electrode 5, thereby producing an organic EL device.
[0040]
Thereafter, each organic EL element was covered with a sealing container 12 in a nitrogen atmosphere so as not to be affected by moisture in the air, and bonded to the glass substrate 1 with an adhesive 14. That is, the space defined by the sealing container 12 and the glass substrate 1 is filled with the nitrogen gas 13.
[0041]
A dark spot test was performed by applying a DC constant current to each organic EL element sample and driving the emission luminance at 100 cd / m ² for 100 hours.
[0042]
Table 2 shows the number of dark spots in the initial stage of the light emitting unit (immediately after the device was created) and after the dark spot test (after driving for 100 hours). The number of dark spots was measured by counting the number of particles of 0.2 μm or more within a 0.5 mm square in a dark field with a magnification of 100 times.
[0043]
[Table 2]

[0044]
As shown in Table 2, when the angle is 2000 ° or less, a dark spot is easily generated. In addition, it was found that the dark spots were enlarged immediately after the device was manufactured after driving, and the number was likely to increase.
[0045]
FIG. 3 is an explanatory diagram showing the state of occurrence of dark spots immediately after the device having an ITO thickness of 1200 mm is produced, and FIG. 4 is an explanatory diagram showing the occurrence of dark spots after driving an ITO product of 1200 mm thickness for 100 hours. . FIG. 5 is an explanatory view showing the state of occurrence of dark spots immediately after the production of an element having an ITO thickness of 3500 mm, and FIG. 6 is an explanatory view showing the occurrence of dark spots after 100 hours of driving of an ITO thickness of 3500 mm. It is. In FIG. 3 to FIG. 6, reference numeral 11 denotes a dark spot. The occurrence of dark spots after 100 hours of driving is found more frequently for 1200 mm products than for 3500 mm products. That is, it was found that when the ITO film thickness was in the range of 2700 ° to 4000 °, dark spots were hardly generated. This is because the protrusions on the ITO surface are small.
[0046]
【The invention's effect】
As described above, according to the present invention, it is possible to prevent the short-circuit destruction of the organic EL element due to the failure of the anode and the occurrence of the leak current which causes the luminance degradation, and to achieve the stable light emission characteristics for a long time. It is possible to provide an organic EL element that can be maintained.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a layer configuration in an organic EL device according to an embodiment of the present invention.
FIG. 2 is a schematic diagram showing a layer configuration in an organic EL device according to an example of the present invention.
FIG. 3 is an explanatory view showing a state of occurrence of a dark spot immediately after a device having an ITO thickness of 1200 mm is produced in an example of the present invention.
FIG. 4 is an explanatory diagram showing a state of occurrence of dark spots after driving for 100 hours for a product having an ITO thickness of 1200 mm in an example of the present invention.
FIG. 5 is an explanatory diagram showing a state of occurrence of dark spots immediately after an element having an ITO thickness of 3500 mm is formed in an example of the present invention.
FIG. 6 is an explanatory diagram showing a state of occurrence of dark spots after driving for 100 hours for a product having an ITO thickness of 3500 mm in an example of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Substrate 2 Anode 3 Cathode 4 Electron injection layer 5 Electrode 6 Hole transport layer 7 Emission layer 8 Electron transport layer 9 Organic layer 10 Projection part 11 Dark spot 12 Sealing container 13 Nitrogen gas 14 Adhesive

Claims (1)

On a substrate, at least an anode, an organic material layer containing a light-emitting material, and an organic electroluminescent device comprising a cathode,
The anode is formed by indium tin oxide as a main component by an ion plating method, the thickness of the anode is 2700 ° to 3500 °, and the transmittance of transmitted light at a visible light wavelength (400 to 700 nm) of the anode is 80% or more; An organic electroluminescent device characterized in that the surface roughness of at least the surface of the anode which is bonded to the organic material layer has a maximum value Rp-v of 250 ° or less and an average value Ra of 20 ° or less as measured by an atomic force microscope. .

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