JP2008243669A - Organic electroluminescent element - Google Patents
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Classifications
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K50/00—Organic light-emitting devices
- H10K50/80—Constructional details
- H10K50/85—Arrangements for extracting light from the devices
- H10K50/858—Arrangements for extracting light from the devices comprising refractive means, e.g. lenses
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K2102/00—Constructional details relating to the organic devices covered by this subclass
- H10K2102/301—Details of OLEDs
- H10K2102/331—Nanoparticles used in non-emissive layers, e.g. in packaging layer
Abstract
Description
本発明は、有機電界発光素子に関し、より詳しくは、面状光源、情報表示装置等に用いられる発光素子として有用な有機電界発光素子に関する。 The present invention relates to an organic electroluminescent element, and more particularly to an organic electroluminescent element useful as a light emitting element used in a planar light source, an information display device, and the like.
有機電界発光素子は、自発光素子としてディスプレイ等の映像表示装置や面光源として期待されている。このような有機電界発光素子は、一般的には、透明基板と、透明電極からなる第一電極と、有機層と、第二電極とを順に積層した構造をとる。そして、このような有機電界発光素子においては、第一電極と第二電極との間で印加された電圧により有機層が発光し、発光した光は透明基板側から外部に取り出される。しかしながら、このような有機電界発光素子は、上記のような構成のまま用いた場合には、透明電極／透明基板／空気の各界面における全反射のため、有機層（発光層）にて発光した光の２０％程度しか外部に取り出すことができなかった。そのため、光の取り出し効率を高めて有機電界発光素子の輝度低下を抑制するために、回折格子機能を有する層等を積層させた種々の構成の有機電解発光素子の研究が進められてきた。 Organic electroluminescent elements are expected as self-luminous elements such as video display devices such as displays and surface light sources. Such an organic electroluminescent element generally has a structure in which a transparent substrate, a first electrode composed of a transparent electrode, an organic layer, and a second electrode are sequentially laminated. In such an organic electroluminescent element, the organic layer emits light by a voltage applied between the first electrode and the second electrode, and the emitted light is extracted outside from the transparent substrate side. However, when such an organic electroluminescent element is used as it is, the organic layer (light emitting layer) emits light due to total reflection at each interface of the transparent electrode / transparent substrate / air. Only about 20% of the light could be taken out. Therefore, in order to increase the light extraction efficiency and suppress the decrease in luminance of the organic electroluminescent element, researches on organic electroluminescent elements having various configurations in which layers having a diffraction grating function or the like are laminated have been advanced.
例えば、特開平６−１５１０６１号公報（特許文献１）においては、電場を加えると発光する発光層と、前記発光層の両側に配置された電極層とを備える有機電界発光素子であって、発光層からの伝搬光を有機電界発光素子外に散乱させる光散乱手段としてガラスなどの透明材料や顔料粒子等の散乱粒子を分散させた光伝搬層を発光層と連続的に形成した有機電界発光素子が開示されている。しかしながら、特許文献１に記載のような有機電界発光素子においては、前記光伝搬層中に散乱粒子を分散させることで光の取り出し効率の向上を図るが、発光層で基板垂直方向に発光した光も様々な方向に散乱されるため，正面輝度が著しく低下してしまうという問題があった。 For example, in Japanese Patent Application Laid-Open No. 6-151061 (Patent Document 1), an organic electroluminescence device including a light emitting layer that emits light when an electric field is applied and electrode layers disposed on both sides of the light emitting layer, An organic electroluminescence device in which a light propagation layer in which scattering materials such as transparent materials such as glass and pigment particles are dispersed is continuously formed as a light scattering means for scattering light propagating from the layer to the outside of the organic electroluminescence device Is disclosed. However, in the organic electroluminescence device as described in Patent Document 1, light extraction efficiency is improved by dispersing scattering particles in the light propagation layer. Is scattered in various directions, and there is a problem that the front brightness is significantly reduced.
また、特開平１１−２８３７５１号公報（特許文献２）においては、透明基板と、透明電極からなる第一電極と、有機層と、第二電極とを順に積層した有機電界発光素子であって、前記透明基板と、前記透明電極との間に回折格子を更に積層させた構造の有機電界発光素子が開示されている。また、特開２００４−３１１４１９号公報（特許文献３）においては、有機電界発光素子の内部に規則性のある屈折率分布を持つ光学的構造を形成した有機電界発光素子が開示されている。更に、特開２００６−１９０５７３号公報（特許文献４）においては、基板と、前記基板上に設けられ、第一の電極および第二の電極により有機層が狭持されてなる発光部と、前記発光部に隣接して設けられた回折格子部とを備える有機電界発光素子が開示されている。しかしながら、特許文献２〜４に記載のような有機電界発光素子においては、回折格子に微細な凹凸パターンを形成させるために複雑な製造工程を経る必要があった。例えば、特許文献２〜３に記載の有機電界発光素子においては、光リソグラフィー法によってピッチが１μｍ程度以下の回折格子を形成させていたため、工程が複雑であるばかりか、高額な露光装置が必要となり製造コストも高くなってしまうという問題があった。また、特許文献４に記載の有機電界発光素子においては、基板上に微粒子からなる単粒子層を形成した後、この単粒子層をエッチングマスクとして用いて基板をエッチングし、基板表面に凹凸を形成した後、残留した微粒子を除去し、前記凹凸の凹部に前記基材とは屈折率の異なる媒質を充填することによって回折格子部を形成しており、製造工程が複雑であった。また、特許文献２〜４に記載の有機発光素子においては、製造時に回折格子部の格子定数を取り出す光の波長に応じて調整することが困難であった。
本発明は、上記従来技術の有する課題に鑑みてなされたものであり、透明基板に対して垂直な方向に出射される光の取り出し効率が十分に高く、高輝度の発光が可能であり、回折格子機能を有する層の格子定数を発光色の光の波長に対応させて容易に調整することができ、しかも簡便な方法で製造することが可能な有機電界発光素子を提供することを目的とする。 The present invention has been made in view of the above-described problems of the prior art. The extraction efficiency of light emitted in a direction perpendicular to the transparent substrate is sufficiently high, high-luminance light emission is possible, and diffraction is performed. An object of the present invention is to provide an organic electroluminescence device capable of easily adjusting the lattice constant of a layer having a lattice function in accordance with the wavelength of light of emission color and capable of being manufactured by a simple method. .
本発明者らは、上記目的を達成すべく鋭意研究を重ねた結果、透明基板と、前記透明基板上に配置された透明電極からなる第一電極と、前記第一電極上に配置された少なくとも１層の有機層と、前記有機層上に配置された第二電極とを備える有機電界発光素子において、下記条件（Ａ）〜（Ｃ）を満たす粒子からなる単粒子層を前記透明基板と前記第一電極との間に形成することにより、透明基板に対して垂直な方向に出射される光の取り出し効率が十分に高く、高輝度の発光が可能であり、回折格子機能を有する層（単粒子層）の格子定数を発光色の光の波長に対応させて容易に調整することができ、しかも簡便な方法で製造することが可能な有機電界発光素子が得られることを見出し、本発明を完成するに至った。 As a result of intensive studies to achieve the above object, the inventors have made a transparent substrate, a first electrode composed of a transparent electrode disposed on the transparent substrate, and at least disposed on the first electrode. In an organic electroluminescent device comprising a single organic layer and a second electrode disposed on the organic layer, a single particle layer made of particles satisfying the following conditions (A) to (C) is formed on the transparent substrate and the transparent substrate: By forming between the first electrode and the first electrode, the extraction efficiency of light emitted in a direction perpendicular to the transparent substrate is sufficiently high, light emission with high luminance is possible, and a layer having a diffraction grating function (single It has been found that an organic electroluminescent device can be easily prepared by adjusting the lattice constant of the particle layer) in accordance with the wavelength of light of the luminescent color, and can be manufactured by a simple method. It came to be completed.
すなわち、本発明の有機電界発光素子は、透明基板と、前記透明基板上に配置された透明電極からなる第一電極と、前記第一電極上に配置された少なくとも１層の有機層と、前記有機層上に配置された第二電極とを備える有機電界発光素子であって、
下記条件（Ａ）〜（Ｃ）：
（Ａ）平均粒径が０．０５〜１．０μｍの範囲にあること、
（Ｂ）下記式（１）：
［単分散度（単位：％）］＝（［粒径の標準偏差］／［平均粒径］）×１００ （１）
で表される単分散度が１０％以下となること、
（Ｃ）波長５２０ｎｍの光に対する屈折率が前記透明電極の材料の波長５２０ｎｍの光に対する屈折率と比較して０．１以上の差がある材料からなること、
を満たす粒子によって形成された単粒子層が、前記透明基板と前記第一電極との間に形成されていること、
を特徴とするものである。
That is, the organic electroluminescent element of the present invention includes a transparent substrate, a first electrode composed of a transparent electrode disposed on the transparent substrate, at least one organic layer disposed on the first electrode, An organic electroluminescent device comprising a second electrode disposed on the organic layer,
The following conditions (A) to (C):
(A) The average particle size is in the range of 0.05 to 1.0 μm,
(B) The following formula (1):
[Monodispersity (unit:%)] = ([standard deviation of particle size] / [average particle size]) × 100 (1)
The monodispersity represented by
(C) The refractive index for light having a wavelength of 520 nm is made of a material having a difference of 0.1 or more compared to the refractive index for light having a wavelength of 520 nm of the material of the transparent electrode,
A single particle layer formed of particles satisfying the above condition is formed between the transparent substrate and the first electrode;
It is characterized by.
上記本発明にかかる単粒子層としては、前記粒子が三角格子状又は正方格子状に配列した二次元配列構造を有することが好ましい。 The single particle layer according to the present invention preferably has a two-dimensional arrangement structure in which the particles are arranged in a triangular lattice shape or a square lattice shape.
また、上記本発明においては、前記単粒子層を形成する各粒子の最近接粒子間の距離の平均が、該粒子の平均粒径の１．０〜２．０倍の範囲にあることが好ましい。 In the present invention, the average distance between the closest particles of each particle forming the single particle layer is preferably in the range of 1.0 to 2.0 times the average particle size of the particles. .
さらに、上記本発明にかかる粒子としては、シリカ、ポリスチレン又はポリメチル酸メタクリレートからなるものが好ましい。 Furthermore, the particles according to the present invention are preferably those made of silica, polystyrene or polymethyl acid methacrylate.
なお、本発明の有機電界発光素子によって、上記目的が達成される理由は必ずしも定かではないが、本発明者らは以下のように推察する。すなわち、本発明においては、先ず、透明基板と第一の電極との間に形成された単粒子層によって、導波光が回折されて、光の取り出し効率が向上するものと推察する。このような単粒子層においては、微細な粒子によって二次元周期構造が形成される。このような二次元周期構造は、回折格子として機能し、通常であれば素子内部を導波して取り出せない導波光を基板垂直方向に回折させる。そのため、本発明の有機電界発光素子においては、単粒子層によって導波光の抑制と回折した光の外部放射とが可能となり、光取出し効率が向上される。また、本発明においては、このような単粒子層によって、透明基板と第一の電極との間に凹凸が形成され、このような凹凸によってもたらされる擬似的屈折率傾斜領域によって反射防止効果が発揮されて、光の取り出し効率が向上するものと推察される。このような擬似的屈折率傾斜領域によって反射防止効果については、例えば、Ｙ．Ｋａｎａｍｏｒｉ，ｅｔ ａｌ．，Ｊｐｎ．Ｊ．Ａｐｐｌ．Ｐｈｙｓ．，Ｖｏｌ．３９，２０００年発行、７３５頁（非特許文献１）に開示されている。すなわち、このような効果は、ガラス表面に形成された二次元のｓｕｂｗａｖｅｌｅｎｇｔｈ−ｓｔｒｕｃｔｕｒｅｄ（ＳＷＳ）表面における反射防止効果と同様の効果である。そして、二次元周期構造を形成する粒子の屈折率が透明基板を構成する材料の屈折率に近い場合には、このような効果がより有効に得られ、光の取り出し効率がより向上されるものと推察される。なお、単粒子層と透明基板との間に大きな屈折率差がある場合には、輝度向上の効果は主に前述の回折効果によるところが大きいものと推察される。また、本発明においては、単粒子層に回折格子機能を発揮させるが、その単粒子層が微細な粒子を配列させて形成するものであるため、簡便な方法で製造することが可能
となるとともに、粒子の配列を変更することで容易にその格子定数を調整することが可能となる。例えば、粒子同士が接触するようにして配列させたり、粒子同士が互いに接触しないように配列させたりすることで、均一な粒子径を有する粒子を用いて可視光領域のいかなる発光色に対しても光取り出し効率の向上を可能にするように格子定数の調整が可能な素子構造を形成させることが可能となる。従って、本発明においては、回折格子機能を有する単粒子層の格子定数を発光色の光の波長に対応させて容易に調整することができ、しかも簡便な方法で製造することが可能となるものと本発明者らは推察する。
The reason why the above-described object is achieved by the organic electroluminescent element of the present invention is not necessarily clear, but the present inventors speculate as follows. That is, in the present invention, it is presumed that the guided light is diffracted by the single particle layer formed between the transparent substrate and the first electrode, and the light extraction efficiency is improved. In such a single particle layer, a two-dimensional periodic structure is formed by fine particles. Such a two-dimensional periodic structure functions as a diffraction grating, and normally diffracts guided light that cannot be extracted by being guided inside the element in the direction perpendicular to the substrate. Therefore, in the organic electroluminescent element of the present invention, the single particle layer can suppress the guided light and emit the diffracted light to the outside, thereby improving the light extraction efficiency. Further, in the present invention, such a single particle layer forms unevenness between the transparent substrate and the first electrode, and the anti-reflective effect is exhibited by the pseudo refractive index gradient region caused by such unevenness. Thus, it is assumed that the light extraction efficiency is improved. Regarding the antireflection effect by such a pseudo refractive index gradient region, see, for example, Y.S. Kanamori, et al. , Jpn. J. et al. Appl. Phys. , Vol. 39, 2000, page 735 (Non-Patent Document 1). That is, such an effect is the same as the antireflection effect on the two-dimensional subwavelength-structured (SWS) surface formed on the glass surface. When the refractive index of the particles forming the two-dimensional periodic structure is close to the refractive index of the material constituting the transparent substrate, such an effect can be obtained more effectively and the light extraction efficiency can be further improved. It is guessed. In addition, when there is a large refractive index difference between the single particle layer and the transparent substrate, it is presumed that the effect of improving the luminance is mainly due to the diffraction effect described above. Further, in the present invention, the single particle layer exhibits a diffraction grating function, but since the single particle layer is formed by arranging fine particles, it can be manufactured by a simple method. The lattice constant can be easily adjusted by changing the particle arrangement. For example, by arranging particles so that they are in contact with each other, or arranging particles so that they are not in contact with each other, using particles having a uniform particle diameter for any emission color in the visible light region It is possible to form an element structure in which the lattice constant can be adjusted so that the light extraction efficiency can be improved. Therefore, in the present invention, the lattice constant of a single particle layer having a diffraction grating function can be easily adjusted in accordance with the wavelength of light of the emission color, and can be manufactured by a simple method. The present inventors speculate.
本発明によれば、透明基板に対して垂直な方向に出射される光の取り出し効率が十分に高く、高輝度の発光が可能であり、回折格子機能を有する層の格子定数を発光色の光の波長に対応させて容易に調整することができ、しかも簡便な方法で製造することが可能な有機電界発光素子を提供することが可能となる。 According to the present invention, the extraction efficiency of light emitted in a direction perpendicular to the transparent substrate is sufficiently high, high-luminance light emission is possible, and the lattice constant of the layer having the diffraction grating function is set to the light of the emission color. Therefore, it is possible to provide an organic electroluminescence device that can be easily adjusted according to the wavelength of the light and can be manufactured by a simple method.
以下、図面を参照しながら本発明の好適な実施形態について詳細に説明する。なお、以下の説明及び図面中、同一又は相当する要素には同一の符号を付し、重複する説明は省略する。 Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the following description and drawings, the same or corresponding elements are denoted by the same reference numerals, and duplicate descriptions are omitted.
本発明の有機電界発光素子は、透明基板と、前記透明基板上に配置された透明電極からなる第一電極と、前記第一電極上に配置された少なくとも１層の有機層と、前記有機層上に配置された第二電極とを備える有機電界発光素子であって、
下記条件（Ａ）〜（Ｃ）：
（Ａ）平均粒径が０．０５〜１．０μｍの範囲にあること、
（Ｂ）下記式（１）：
［単分散度（単位：％）］＝（［粒径の標準偏差］／［平均粒径］）×１００ （１）
で表される単分散度が１０％以下となること、
（Ｃ）波長５２０ｎｍの光に対する屈折率が前記透明電極の材料の波長５２０ｎｍの光に対する屈折率と比較して０．１以上の差がある材料からなること、
を満たす粒子によって形成された単粒子層が、前記透明基板と前記第一電極との間に形成されていること、
を特徴とするものである。
The organic electroluminescent device of the present invention includes a transparent substrate, a first electrode comprising a transparent electrode disposed on the transparent substrate, at least one organic layer disposed on the first electrode, and the organic layer An organic electroluminescent device comprising a second electrode disposed on the top,
The following conditions (A) to (C):
(A) The average particle size is in the range of 0.05 to 1.0 μm,
(B) The following formula (1):
[Monodispersity (unit:%)] = ([standard deviation of particle size] / [average particle size]) × 100 (1)
The monodispersity represented by
(C) The refractive index for light having a wavelength of 520 nm is made of a material having a difference of 0.1 or more compared to the refractive index for light having a wavelength of 520 nm of the material of the transparent electrode,
A single particle layer formed of particles satisfying the above condition is formed between the transparent substrate and the first electrode;
It is characterized by.
図１は、本発明の有機電界発光素子の好適な一実施形態の構成を示す模式図である。 FIG. 1 is a schematic diagram showing the configuration of a preferred embodiment of the organic electroluminescent element of the present invention.
図１に示す実施形態の有機電界発光素子１は、透明基板１１と、単粒子層１２と、第一の電極１３と、有機層１４と、第二の電極１５とを備えるものである。このような有機電界発光素子１は、電極１３及び１５の間に電圧を印加して有機層１４を発光させ、透明基板１１側から面発光させるボトムエミッション型の構造を有するものである。 The organic electroluminescent element 1 according to the embodiment shown in FIG. 1 includes a transparent substrate 11, a single particle layer 12, a first electrode 13, an organic layer 14, and a second electrode 15. Such an organic electroluminescent element 1 has a bottom emission type structure in which a voltage is applied between the electrodes 13 and 15 to cause the organic layer 14 to emit light and to emit light from the transparent substrate 11 side.
透明基板１１は、可視光に対して透光性を有する材質からなる基板であればよく、特に制限されず、公知の透明基板を適宜用いることができ、例えば、ガラス基板、プラスチック基板、半導体基板等が挙げられる。また、透明基板１１の面の大きさや厚みは特に制限されず、目的とする有機電界発光素子の設計に応じて適宜変更することが可能である。 The transparent substrate 11 may be a substrate made of a material having translucency with respect to visible light, and is not particularly limited, and a known transparent substrate can be used as appropriate, for example, a glass substrate, a plastic substrate, a semiconductor substrate. Etc. Further, the size and thickness of the surface of the transparent substrate 11 are not particularly limited, and can be appropriately changed according to the design of the target organic electroluminescent element.
単粒子層１２は、下記条件（Ａ）〜（Ｃ）：
（Ａ）平均粒径が０．０５〜１．０μｍの範囲にあること、
（Ｂ）下記式（１）：
［単分散度（単位：％）］＝（［粒径の標準偏差］／［平均粒径］）×１００ （１）
で表される単分散度が１０％以下となること、
（Ｃ）波長５２０ｎｍの光に対する屈折率が前記透明電極の材料の波長５２０ｎｍの光に対する屈折率と比較して０．１以上の差がある材料からなること、
を満たす粒子が、基板面に平行に二次元配列した層である。このような単粒子層１２は、主に導波光を基板垂直方向に回折する回折格子としての機能を有し、二次的に擬似的屈折率傾斜領域による反射防止機能も有する層である。
The single particle layer 12 has the following conditions (A) to (C):
(A) The average particle size is in the range of 0.05 to 1.0 μm,
(B) The following formula (1):
[Monodispersity (unit:%)] = ([standard deviation of particle size] / [average particle size]) × 100 (1)
The monodispersity represented by
(C) The refractive index for light having a wavelength of 520 nm is made of a material having a difference of 0.1 or more compared to the refractive index for light having a wavelength of 520 nm of the material of the transparent electrode,
The particles satisfying the above condition are two-dimensionally arranged in parallel to the substrate surface. Such a single particle layer 12 is a layer that mainly has a function as a diffraction grating that diffracts guided light in a direction perpendicular to the substrate, and also has a secondary antireflection function by a pseudo refractive index gradient region.
前記粒子は、平均粒径が０．０５〜１．０μｍ（より好ましくは０．１〜０．５μｍ）の範囲にある粒子である。このような粒子の平均粒径が前記下限未満では、単粒子層によって形成される回折格子の周期が、可視光域の波長よりも短波長側に著しくずれる傾向にあり、他方、前記上限を超えると、単粒子層によって形成される回折格子の周期が、長波長側に著しくずれ、更には、透明電極の膜厚を粒子径よりも厚くする必要があることから実用的な厚さではなくなる傾向にある。 The particles are particles having an average particle size in the range of 0.05 to 1.0 μm (more preferably 0.1 to 0.5 μm). When the average particle size of such particles is less than the lower limit, the period of the diffraction grating formed by the single particle layer tends to be significantly shifted to the shorter wavelength side than the wavelength in the visible light region, and on the other hand, exceeds the upper limit. And the period of the diffraction grating formed by the single particle layer is significantly shifted to the longer wavelength side, and further, the thickness of the transparent electrode needs to be larger than the particle diameter, so that the thickness is not practical. It is in.
また、前記粒子は、下記式（１）：
［単分散度（単位：％）］＝（［粒径の標準偏差］／［平均粒径］）×１００ （１）
で表される単分散度が１０％以下の粒子である。すなわち、前記粒子は、このような単分散度を有する粒径が極めて均一な粒子である。また、このような粒子としては、単分散度がより小さな値となるほど、より高い特性が得られる傾向にあることから、前記単分散度は８％以下であることがより好ましく、５％以下であることが特に好ましい。
Further, the particles have the following formula (1):
[Monodispersity (unit:%)] = ([standard deviation of particle size] / [average particle size]) × 100 (1)
The monodispersity represented by the particle is 10% or less. That is, the particles are particles having such a monodispersity and a very uniform particle size. Further, as such particles, the smaller the monodispersity value, the higher the tendency to obtain higher characteristics. Therefore, the monodispersity is more preferably 8% or less, and 5% or less. It is particularly preferred.
単粒子層１２を構成する前記粒子は、波長５２０ｎｍの光に対する屈折率が前記透明電極の材料の波長５２０ｎｍの光に対する屈折率と比較して０．１以上の差がある材料からなる。このような屈折率の差が０．１未満では、単粒子層１２によって形成される回折格子の回折効率が小さくなり、十分な輝度向上効果が得られなくなる。このような粒子の材料としては、発光スペクトルに対して著しい吸収がない材料が好ましい。また、このような粒子の材料は、その材料からなる粒子を配列させた際に回折格子として機能させることが可能な公知の有機材料、無機材料、有機−無機複合材料及び無機−無機複合材料の中から適宜選択して用いることができる。このような有機材料としては、例えば、ポリスチレン誘導体、アクリル樹脂等の有機高分子材料等が挙げられ、前記無機材料としては、例えば、シリカ、アルミナ、酸化チタン、酸化亜鉛等が挙げられる。また、前記有機−無機複合材料としては、例えば、ポリスチレン誘導体又はアクリル樹脂からなる粒子を酸化チタン、酸化セリウム、酸化亜鉛等で覆ったコアシェル型の有機−無機複合粒子などが挙げられる。また、前記無機−無機複合材料としては、例えば、シリカからなる粒子を酸化チタン、酸化セリウム又は酸化亜鉛等で覆ったコアシェル型の無機−無機複合粒子等が挙げられる。 The particles constituting the single particle layer 12 are made of a material having a difference in refractive index with respect to light with a wavelength of 520 nm of 0.1 or more compared with the refractive index with respect to light with a wavelength of 520 nm of the material of the transparent electrode. When the difference in refractive index is less than 0.1, the diffraction efficiency of the diffraction grating formed by the single particle layer 12 becomes small, and a sufficient brightness enhancement effect cannot be obtained. As the material of such particles, a material that does not significantly absorb the emission spectrum is preferable. Further, the material of such particles is a known organic material, inorganic material, organic-inorganic composite material, or inorganic-inorganic composite material that can function as a diffraction grating when the particles made of the material are arranged. It can be appropriately selected from among them. Examples of such an organic material include organic polymer materials such as polystyrene derivatives and acrylic resins, and examples of the inorganic material include silica, alumina, titanium oxide, and zinc oxide. Examples of the organic-inorganic composite material include core-shell type organic-inorganic composite particles in which particles made of a polystyrene derivative or an acrylic resin are covered with titanium oxide, cerium oxide, zinc oxide, or the like. Examples of the inorganic-inorganic composite material include core-shell type inorganic-inorganic composite particles in which particles made of silica are covered with titanium oxide, cerium oxide, zinc oxide, or the like.
また、このような粒子の材料としては、単粒子層１２の擬似的屈折率傾斜領域による反射防止効果をより向上させるという観点からは、透明基板１１を構成する材料の屈折率に近い屈折率を有する材料からなる粒子を用いることが好ましく、透明基板１１の材料の５２０nｍの光に対する屈折率と比較して屈折率差が０．１以下となる材料を用いることがより好ましい。このような材料としては、例えば、透明基板がガラス基板である場合にはシリカ粒子が挙げられ、透明基板がプラスチック基板である場合にはポリスチレン誘導体からなる粒子を用いることが挙げられる。さらに、このような粒子の材料としては、擬似的屈折率傾斜領域による反射防止効果をより効率よく向上させることが可能であるという観点から、シリカ、ポリスチレン又はポリメチル酸メタクリレートが特に好ましい。なお、このような材料を用いて上記条件（Ａ）〜（Ｃ）を満たす粒子を製造する方法は特に制限されず、例えば、ポリスチレン又はポリメチル酸メタクリレートからなる粒子を製造する場合にはエマルション重合により製造してもよく、シリカからなる粒子を製造する場合には、いわゆるストーバー法により製造してもよい。また、このような製造方法により製造された市販の粒子を用いてもよい。 Moreover, as a material of such particles, from the viewpoint of further improving the antireflection effect by the pseudo refractive index gradient region of the single particle layer 12, a refractive index close to the refractive index of the material constituting the transparent substrate 11 is used. It is preferable to use particles made of a material having a refractive index difference of 0.1 or less compared to the refractive index of the material of the transparent substrate 11 with respect to light of 520 nm. Examples of such a material include silica particles when the transparent substrate is a glass substrate, and use of particles made of a polystyrene derivative when the transparent substrate is a plastic substrate. Furthermore, as a material of such particles, silica, polystyrene, or polymethyl acid methacrylate is particularly preferable from the viewpoint that the antireflection effect by the pseudo refractive index gradient region can be improved more efficiently. In addition, the method in particular which manufactures the particle | grains which satisfy | fill said conditions (A)-(C) using such a material is not restrict | limited, For example, when manufacturing the particle | grains which consist of polystyrene or a polymethyl acid methacrylate, it is by emulsion polymerization. You may manufacture, and when manufacturing the particle which consists of silica, you may manufacture by what is called a Stover method. Moreover, you may use the commercially available particle | grains manufactured by such a manufacturing method.
更に、前記粒子の二次元配列構造としては、前記粒子が三角格子状又は正方格子状に配列した二次元配列構造であることが好ましい。図２に三角格子状の二次元配列構造を模式的に示し、図３に正方格子状の二次元配列構造を模式的に示す。また、このような二次元配列は、有機電界発光素子の発光面全体を覆っていてもよいが、図４に模式的に示すように、発光面内でモザイクパターン状に形成されていてもよい。なお、前述の三角格子状又は正方格子状に配列した二次元配列構造としては、図２及び図３に模式的に示すような粒子同士が互いに接触して配列された構造の他、図５及び図６に模式的に示すように、粒子同士が互いに接触することなく三角格子状又は正方格子状に配列された構造であってもよい。このようにして粒子同士を互いに接触させずに配列させることで、最近接粒子の中心間距離を適宜変更することが可能となり、二次元配列の周期（格子定数）を容易に調整することが可能である。 Furthermore, the two-dimensional arrangement structure of the particles is preferably a two-dimensional arrangement structure in which the particles are arranged in a triangular lattice shape or a square lattice shape. FIG. 2 schematically shows a two-dimensional array structure having a triangular lattice shape, and FIG. 3 schematically shows a two-dimensional array structure having a square lattice shape. Further, such a two-dimensional array may cover the entire light emitting surface of the organic electroluminescent element, but may be formed in a mosaic pattern within the light emitting surface as schematically shown in FIG. . In addition, as the two-dimensional array structure arranged in the above-described triangular lattice shape or square lattice shape, in addition to the structure in which particles are schematically arranged in contact with each other as shown in FIGS. As schematically shown in FIG. 6, the particles may be arranged in a triangular lattice shape or a square lattice shape without contacting each other. By arranging the particles without contacting each other in this way, the distance between the centers of the closest particles can be changed as appropriate, and the period (lattice constant) of the two-dimensional arrangement can be easily adjusted. It is.
また、このような粒子の配列構造において、前記単粒子層を形成する各粒子の最近接粒子間の距離の平均が、該粒子の平均粒径の１．０〜２．０倍の範囲にあることが好ましく、１．０〜１．５倍の範囲にあることがより好ましい。このような最近接粒子間の距離を前記範囲とすることで、形成される二次元配列の周期によって、可視光域の光に対する取り出し効率をより向上させることが可能となる傾向にある。すなわち、可視光域の波長３５０ｎｍ〜８００ｎｍの範囲の光に対する単粒子層の二次元配列の周期が、目的とする波長の光学長（波長を屈折率で除した値）に対して大き過ぎても小さ過ぎても光が素子内部を導波してしまうため、最近接粒子間の距離が前記範囲外になると、形成される周期構造によって導波光を基板垂直方向に回折することが困難となり、素子前方方向への光の取り出し効率が低下してしまう傾向にある。 Further, in such an array structure of particles, the average distance between the closest particles of each particle forming the single particle layer is in the range of 1.0 to 2.0 times the average particle diameter of the particles. It is preferable that it is in the range of 1.0 to 1.5 times. By setting the distance between the closest particles in the above range, the extraction efficiency with respect to light in the visible light range tends to be further improved by the period of the two-dimensional array formed. That is, even if the period of the two-dimensional arrangement of the single particle layer for light in the visible light wavelength range of 350 nm to 800 nm is too large for the optical length of the target wavelength (the value obtained by dividing the wavelength by the refractive index). Even if the distance is too small, the light will be guided inside the device. If the distance between the nearest particles is outside the above range, it will be difficult to diffract the guided light in the direction perpendicular to the substrate due to the periodic structure formed. The light extraction efficiency in the forward direction tends to decrease.
また、このような単粒子層１２の形成させる方法としては特に限定されず、例えば、前記粒子が溶媒中に分散された分散液を透明基板１１上に塗布した後、溶媒を乾燥して、粒子が二次元配列された単粒子層を形成する方法を挙げることができる。このような溶媒としては特に制限されず、水や有機溶媒（例えばアルコール類等）を適宜用いることができる。また、前記分散液を塗布する方法も特に制限されず、公知の塗布方法を適宜採用することができ、例えば、キャスト法、スピンコート法、ディップコート法等を採用してもよい。 In addition, the method for forming such a single particle layer 12 is not particularly limited. For example, after a dispersion liquid in which the particles are dispersed in a solvent is applied on the transparent substrate 11, the solvent is dried to form particles. Can be mentioned as a method of forming a single particle layer in which two-dimensionally arranged. Such a solvent is not particularly limited, and water or an organic solvent (for example, alcohols) can be appropriately used. The method for applying the dispersion is not particularly limited, and a known application method can be appropriately employed. For example, a cast method, a spin coating method, a dip coating method, or the like may be employed.
また、単粒子層１２を形成させる他の方法としては、例えば、前記粒子として前記無機材料からなる粒子を用いる場合に好適な方法として、アクリルモノマー等のモノマー中に前記粒子を分散させた分散液を調製し、これを透明基板１１上にスピンコート法により塗布した後、モノマーを重合させて内部に前記粒子が配列された樹脂層を形成せしめ、その後、樹脂をエッチングして除去し、粒子が二次元配列された単粒子層を形成する方法が挙げられる。このような方法は、粒子同士を互いに接触することなく三角格子状又は正方格子状に配列させた構造の単粒子層を形成するのに好適な方法である。 Further, as another method for forming the single particle layer 12, for example, as a method suitable when using particles made of the inorganic material as the particles, a dispersion liquid in which the particles are dispersed in a monomer such as an acrylic monomer After coating this on the transparent substrate 11 by spin coating, the monomers are polymerized to form a resin layer in which the particles are arranged, and then the resin is etched away to remove the particles. Examples include a method of forming a two-dimensionally arranged single particle layer. Such a method is a method suitable for forming a single particle layer having a structure in which particles are arranged in a triangular lattice shape or a square lattice shape without contacting each other.
このようなモノマー中に前記粒子を分散させた分散液を調製する方法としては特に制限されないが、前記粒子をエタノール等のアルコール中に分散させた後、これにモノマーを加え、アルコールを３０〜８０％程度揮発させて調製することが好ましい。このようなモノマーとしては特に制限されないが、アクリルモノマー等のビニル系モノマーを用いることが好ましい。また、このような分散液を調製する際に前記アルコール中に添加する前記粒子の量はアルコール１００質量部に対して前記粒子が５０〜２００質量部であることが好ましい。更に、前記モノマーの添加量としては、前記粒子の質量の０．５〜１０倍とすることが好ましい。このような含有割合で分散液中に前記粒子及び前記モノマーを含有させることで、形成される二次元配列において、各粒子の最近接粒子間の距離の平均を前記粒子の平均粒径の１．０〜２．０倍の範囲に容易に調整することが可能となる。 A method for preparing a dispersion in which the particles are dispersed in such a monomer is not particularly limited, but after dispersing the particles in an alcohol such as ethanol, the monomer is added thereto, and the alcohol is added in an amount of 30-80. It is preferable to prepare by volatilizing about%. Such a monomer is not particularly limited, but a vinyl monomer such as an acrylic monomer is preferably used. The amount of the particles added to the alcohol when preparing such a dispersion is preferably 50 to 200 parts by mass with respect to 100 parts by mass of the alcohol. Furthermore, the addition amount of the monomer is preferably 0.5 to 10 times the mass of the particles. By adding the particles and the monomer in the dispersion at such a content ratio, the average of the distances between the closest particles of each particle in the two-dimensional array formed is 1. It is possible to easily adjust to a range of 0 to 2.0 times.
また、このようなモノマー中に前記粒子を分散させた分散液を透明基板１２にスピンコートする際には、より均一な二次元配列構造を形成させるという観点から、段階的に回転数を上げながらスピンコートすることが好ましい。なお、このようなスピンコートの際の回転数の調整方法は、均一な二次元構造を形成させることが可能な方法であればよく特に制限されず、分散液の濃度や粒子及びモノマーの種類等に応じて適宜変更できる。また、前記モノマーを重合させる方法は特に制限されず、公知の方法を適宜採用でき、例えば、窒素ガス雰囲気下において紫外光を照射する光重合方法を採用してもよい。更に、前記樹脂をエッチングする方法としては、特に制限されず、公知のエッチング方法を適宜採用でき、例えば、酸素プラズマエチング法等を採用することができる。 Further, when spin-coating the dispersion liquid in which the particles are dispersed in such a monomer onto the transparent substrate 12, while increasing the rotational speed stepwise from the viewpoint of forming a more uniform two-dimensional array structure. Spin coating is preferred. The method for adjusting the number of revolutions during spin coating is not particularly limited as long as it is a method capable of forming a uniform two-dimensional structure, and the concentration of dispersion liquid, types of particles and monomers, and the like. It can be changed appropriately according to the situation. The method for polymerizing the monomer is not particularly limited, and a known method can be appropriately employed. For example, a photopolymerization method in which ultraviolet light is irradiated in a nitrogen gas atmosphere may be employed. Furthermore, the method for etching the resin is not particularly limited, and a known etching method can be appropriately employed. For example, an oxygen plasma etching method or the like can be employed.
さらに、単粒子層１２を形成させる別の方法としては、例えば、ポリスチレン等の有機材料からなる粒子を用いる場合に好適な方法として、前記粒子の表面にイニフェータ法（Ｔ．Ｏｔｓｕ，Ｊ．Ｐｏｌｙｍ．Ｓｃｉ．Ａ３８，２０００年発行、２１２１頁（非特許文献）によりｐｏｌｙ（Ｎ−ｉｓｏｐｒｏｐｙｌａｃｒｙｌａｍｉｄｅ）（ＰＮＩＰＡＭ）等の高分子化合物をグラフト重合した後、得られた粒子の水分散液を調製し、これを透明基板１１上に滴下し、乾燥することにより、前記粒子が二次元配列された単粒子層を形成する方法を挙げることができる。なお、このような方法は、用いる粒子の表面が改質されており、粒子間距離が重合したＰＮＩＰＡＭの鎖長によって制御されることから、粒子同士を互いに接触することなく配列させた構造の単粒子層を形成するのに好適な方法である。 Further, as another method for forming the single particle layer 12, for example, as a method suitable for using particles made of an organic material such as polystyrene, an iniferter method (T. Otsu, J. Polym. Sci. A38, published in 2000, page 2121 (non-patent document), after graft polymerization of a polymer compound such as poly (N-isopropylacycle) (PNIPAM), an aqueous dispersion of the obtained particles was prepared, A method of forming a single particle layer in which the particles are two-dimensionally arranged by dropping and drying on the transparent substrate 11 can be mentioned.In this method, the surface of the particles to be used is modified. Since the distance between the particles is controlled by the chain length of the polymerized PNIPAM, the particles do not contact each other. Is the preferred method for forming a single particle layer of the column is allowed structure.
また、第一の電極１３は、透明電極からなるものであり、有機電界発光素子において陽極として正孔を有機層１４中に注入する役割を担うものである。このような透明電極の材料としては特に制限されず、公知の材料を適宜用いることができ、例えば、酸化インジウム錫合金（ＩＴＯ）、酸化錫、酸化亜鉛、金、銀、白金、銅等の金属、これらの酸化物並びにこれらの混合物等を適宜用いることができる。このような電極の形成方法は特に制限されず、公知の方法を適宜採用することができ、例えば、前記単粒子層１２上に前記金属の膜をスパッタリング法により形成させて透明電極を形成する方法を採用してもよい。 The first electrode 13 is made of a transparent electrode and plays a role of injecting holes into the organic layer 14 as an anode in the organic electroluminescence device. A material for such a transparent electrode is not particularly limited, and a known material can be used as appropriate. For example, a metal such as indium tin oxide alloy (ITO), tin oxide, zinc oxide, gold, silver, platinum, copper, or the like. These oxides and mixtures thereof can be used as appropriate. A method for forming such an electrode is not particularly limited, and a known method can be appropriately employed. For example, a method of forming a transparent electrode by forming the metal film on the single particle layer 12 by a sputtering method. May be adopted.
また、有機層１４は、第一の電極（透明電極）１３と第二の電極１５との間に配置され、少なくとも一層の発光層を含む層である。ここで、発光層とは、前記電極間に電流又は電圧を印加することで、正孔と電子とが再結合することに起因して発光する領域をいう。このような発光層の材料は特に限定されず、有機電界発光素子において通常用いられる公知の発光層材料を適宜用いることができる。また、このような有機層は、前記発光層を含んでいればよく、他の構成は特に制限されず、正孔と電子との再結合効率を向上させるために、例えば、正孔輸送層及び／又は電子輸送層を更に配置させた多層構造のものとしてもよい。この場合、正孔輸送層は発光層と透明電極の間に配置し，電子輸送層は発光層と第二の電極との間に配置することが好ましい。また、このような有機層においては、更に発光効率や安定性を向上させるために、前記正孔輸送層とともに、正孔注入層を更に配置することが好ましい。この場合、透明電極と正孔輸送層との間に正孔注入層を配置することが好ましい。また、これらの層の材料としては特に制限されず、有機電界発光素子において通常用いられる公知の正孔輸送材料、電子輸送材料及び正孔注入材料を適宜用いることができる。 The organic layer 14 is a layer that is disposed between the first electrode (transparent electrode) 13 and the second electrode 15 and includes at least one light emitting layer. Here, the light emitting layer refers to a region that emits light due to recombination of holes and electrons when a current or voltage is applied between the electrodes. The material of such a light emitting layer is not particularly limited, and a known light emitting layer material that is usually used in an organic electroluminescent element can be appropriately used. Further, such an organic layer only needs to include the light emitting layer, and other configurations are not particularly limited. For example, in order to improve recombination efficiency between holes and electrons, for example, a hole transport layer and A multilayer structure in which an electron transport layer is further arranged may be used. In this case, the hole transport layer is preferably disposed between the light emitting layer and the transparent electrode, and the electron transport layer is preferably disposed between the light emitting layer and the second electrode. Further, in such an organic layer, it is preferable to further dispose a hole injection layer together with the hole transport layer in order to further improve the light emission efficiency and stability. In this case, it is preferable to arrange a hole injection layer between the transparent electrode and the hole transport layer. The materials for these layers are not particularly limited, and known hole transport materials, electron transport materials, and hole injection materials that are usually used in organic electroluminescent devices can be used as appropriate.
さらに、第二の電極１５は、陰極として電子を有機薄膜層４中に注入する役割を担うものである。このような第二の電極１５の材料としては特に制限されず、陰極を製造することが可能な公知の材料を適宜用いることができ、例えば，インジウム、アルミニウム、マグネシウム、リチウム、スカンジウム等の金属並びにこれらの混合物等を用いることができる。このような第二の電極の形成方法としては、特に制限されず、公知の方法を適宜採用することができ、例えば、前記金属を前記有機層上に蒸着させることにより陰極を形成する方法を採用することができる。また、このような第二の電極１５は、電子注入層が積層された構造としてもよい。このような電子注入層の材料及びその製造方法は特に制限されず、公知の材料（例えばフッ化リチウム）及び製造方法を利用して適宜積層させればよい。 Furthermore, the second electrode 15 serves to inject electrons into the organic thin film layer 4 as a cathode. The material of the second electrode 15 is not particularly limited, and a known material capable of manufacturing a cathode can be appropriately used. For example, a metal such as indium, aluminum, magnesium, lithium, scandium, and the like Mixtures of these can be used. A method for forming such a second electrode is not particularly limited, and a known method can be appropriately employed. For example, a method of forming a cathode by vapor-depositing the metal on the organic layer is employed. can do. Such a second electrode 15 may have a structure in which electron injection layers are stacked. The material for the electron injection layer and the manufacturing method thereof are not particularly limited, and may be appropriately laminated using a known material (for example, lithium fluoride) and a manufacturing method.
以上、本発明の有機電界発光素子の好適な実施形態について説明したが、本発明の有機電界発光素子は上記実施形態に限定されるものではない。例えば、上記実施形態の有機電界発光素子においては第一の電極１３を正極としているが、本発明においては第一の電極１３は透明電極であればよく、第一の電極１３を負極として、第二の電極１５を正極としてもよい。 As mentioned above, although preferred embodiment of the organic electroluminescent element of this invention was described, the organic electroluminescent element of this invention is not limited to the said embodiment. For example, in the organic electroluminescence device of the above embodiment, the first electrode 13 is a positive electrode. However, in the present invention, the first electrode 13 may be a transparent electrode, and the first electrode 13 is a negative electrode. The second electrode 15 may be a positive electrode.
以下、実施例及び比較例に基づいて本発明をより具体的に説明するが、本発明は以下の実施例に限定されるものではない。 EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.
（実施例１）
図１に示すような透明基板１１と、単粒子層１２と、透明電極１３と、有機層１４と、第二の電極１５とが順に積層された構造を有する有機電界発光素子を製造した。なお、有機層１４は、透明電極１３側から順に正孔注入層／正孔輸送層／発光層／電子輸送層が積層された構造とし、第二の電極は、有機層側から順に電子注入層／金属電極が積層された構造とした。以下に製造工程を説明する。
Example 1
An organic electroluminescence device having a structure in which a transparent substrate 11, a single particle layer 12, a transparent electrode 13, an organic layer 14, and a second electrode 15 as shown in FIG. The organic layer 14 has a structure in which a hole injection layer / a hole transport layer / a light emitting layer / an electron transport layer are stacked in order from the transparent electrode 13 side, and the second electrode is an electron injection layer in order from the organic layer side. / A structure in which metal electrodes are laminated. The manufacturing process will be described below.
先ず、透明基板１１としてガラス基板（パイレックスガラス（登録商標）、屈折率１．４７、両面光学研磨、大きさ：縦２５ｍｍ、横３５ｍｍ、厚み１ｍｍ）を準備した。次に、シリカ粒子の水分散液（日本触媒製ＫＥ−Ｗ３０、粒子の平均粒子径２８０ｎｍ、粒子の屈折率１．４５、粒子の含有量２０．４質量％）を、更に水で希釈して粒子の固形分換算による含有量を５質量％とした分散液を調製した。そして、前記分散液を、前記ガラス基板上に回転数３０００ｒｐｍにて１分間スピンコートし、乾燥させて透明基板１１上に単粒子層１２を形成した。このような単粒子層を走査型電子顕微鏡（ＳＥＭ）で観察した結果、単粒子層１２は、六方最密充填構造に配列したシリカ粒子の単粒子層が形成されていることを確認された。 First, a glass substrate (Pyrex glass (registered trademark), refractive index 1.47, double-sided optical polishing, size: 25 mm length, 35 mm width, 1 mm thickness) was prepared as the transparent substrate 11. Next, an aqueous dispersion of silica particles (KE-W30 manufactured by Nippon Shokubai, average particle diameter of particles 280 nm, refractive index of particles 1.45, particle content 20.4% by mass) is further diluted with water. A dispersion having a content of particles in terms of solid content of 5% by mass was prepared. Then, the dispersion was spin-coated on the glass substrate at a rotational speed of 3000 rpm for 1 minute and dried to form a single particle layer 12 on the transparent substrate 11. As a result of observing such a single particle layer with a scanning electron microscope (SEM), it was confirmed that the single particle layer 12 was formed with a single particle layer of silica particles arranged in a hexagonal close-packed structure.
次に、単粒子層１２が形成されたガラス基板１１上に、スパッタリング法により２．５ｍｍ幅の帯状パターンを有し且つ平均膜厚が３５０ｎｍのＩＴＯ電極（透明電極１３、屈折率２．１２）を形成した。なお、このようなスパッタリングの際には、雰囲気をアルゴン（９９容量％）と酸素（１容量％）の混合ガス雰囲気（圧力１．６×１０−３Ｔｏｒｒ）とし、基板温度を３００℃とし、１３．５６ＭＨｚの高周波を３００Ｗ印加して、前記帯状パターンを形成させるためにメタルマスクを用いた。 Next, on the glass substrate 11 on which the single particle layer 12 is formed, an ITO electrode (transparent electrode 13, refractive index 2.12) having a band-like pattern with a width of 2.5 mm by sputtering and an average film thickness of 350 nm. Formed. In such sputtering, the atmosphere is a mixed gas atmosphere of argon (99% by volume) and oxygen (1% by volume) (pressure 1.6 × 10 −3 Torr), the substrate temperature is 300 ° C., A metal mask was used to form a strip pattern by applying a high frequency of 13.56 MHz to 300 W.
次いで、前述のようにして形成された透明電極１３上に真空蒸着（真空度：３×１０−７Ｔｏｒｒ）により、銅フタロシアニン（ＣｕＰｃ）の膜を１０ｎｍの厚みで成膜し、正孔注入層を形成した後、前記正孔注入層上に、下記一般式（１）： Next, a film of copper phthalocyanine (CuPc) having a thickness of 10 nm is formed on the transparent electrode 13 formed as described above by vacuum deposition (degree of vacuum: 3 × 10 −7 Torr), and a hole injection layer is formed. Then, on the hole injection layer, the following general formula (1):
で表されるテトラアリールジアミン誘導体（以下「ＴＰＴＥ」と記載する）を真空蒸着（真空度：３×１０−７Ｔｏｒｒ）により３０ｎｍの膜厚となるようにして堆積させて正孔輸送層を形成した。次に、前記正孔輸送層上に下記一般式（２）： A hole-transporting layer is formed by depositing a tetraaryldiamine derivative represented by the formula (hereinafter referred to as “TPTE”) to a thickness of 30 nm by vacuum deposition (degree of vacuum: 3 × 10 −7 Torr). did. Next, on the hole transport layer, the following general formula (2):
で表される電子輸送性材料であるトリス（８−キノリノール）アルミニウム錯体（以下「Ａｌｑ３」と記載する）と、下記一般式（３）： A tris (8-quinolinol) aluminum complex (hereinafter referred to as “Alq3”), which is an electron transporting material represented by the following general formula (3):
で表される緑色発光色素であるジメチルキナクリドンを同時に真空蒸着（真空度：３×１０−７Ｔｏｒｒ）により蒸着して、膜厚が２０ｎｍの発光層を形成させた。なお、発光層中での電子輸送性材料と緑色発光色素の混合比は、Ａｌｑ３が９９容量％、ジメチルキナクリドンが１容量％となるようにした。そして、形成された発光層上に、Ａｌｑ３を真空蒸着（真空度：３×１０−７Ｔｏｒｒ）により４０ｎｍの膜厚で蒸着して電子輸送層を形成し、透明電極１３上に有機層１４を形成した。 Dimethylquinacridone, which is a green luminescent dye represented by the following, was simultaneously deposited by vacuum deposition (vacuum degree: 3 × 10 −7 Torr) to form a light emitting layer having a thickness of 20 nm. The mixing ratio of the electron transporting material and the green light emitting pigment in the light emitting layer was such that Alq3 was 99% by volume and dimethylquinacridone was 1% by volume. Then, Alq3 is deposited on the formed light emitting layer by vacuum deposition (vacuum degree: 3 × 10 −7 Torr) to a thickness of 40 nm to form an electron transport layer, and the organic layer 14 is formed on the transparent electrode 13. Formed.
次に、前記有機層上に、ＬｉＦを真空蒸着（真空度：３×１０−７Ｔｏｒｒ）により０．５ｎｍの膜厚で蒸着して電子注入層を形成した後、Ａｌを真空蒸着（真空度：３×１０−７Ｔｏｒｒ）により１５０ｎｍの膜厚で蒸着して金属電極を形成して、第二の電極１５を形成した。 Next, LiF was deposited on the organic layer by vacuum deposition (vacuum degree: 3 × 10 −7 Torr) to a thickness of 0.5 nm to form an electron injection layer, and then Al was vacuum deposited (vacuum degree). : 3 × 10 −7 Torr) to form a metal electrode by vapor deposition with a film thickness of 150 nm to form the second electrode 15.
そして、上述のようにして透明基板１１／単粒子層１２／透明電極１３／有機層１４／第二の電極１５が順に積層された構造の素子部を製造した後、前記素子部を高真空排気したチャンバーに搬送し、チャンバー内を窒素置換した後、エポキシ樹脂を用いて金属製の封止キャップの端部を透明電極の表面に接着し密封して、有機電界発光素子とした。なお、得られた素子の１画素の発光面積は２．５×２．５ｍｍである。 And after manufacturing the element part of the structure where the transparent substrate 11 / single particle layer 12 / transparent electrode 13 / organic layer 14 / second electrode 15 were laminated in order as described above, the element part was evacuated to high vacuum. Then, the inside of the chamber was purged with nitrogen, and then an end portion of a metal sealing cap was bonded to the surface of the transparent electrode using an epoxy resin and sealed to obtain an organic electroluminescence device. The light emitting area of one pixel of the obtained element is 2.5 × 2.5 mm.
（実施例２）
単粒子層１２の形成方法を変更した以外は実施例１と同様にして有機電界発光素子を製造した。なお、単粒子層１２の形成方法を以下に示す。
(Example 2)
An organic electroluminescent element was produced in the same manner as in Example 1 except that the method for forming the single particle layer 12 was changed. In addition, the formation method of the single particle layer 12 is shown below.
先ず、真空エバポレータと電気炉とを用いて、平均粒子径２１０ｎｍのシリカ粒子の水分散液（日本触媒製ＫＥ−Ｗ２０、粒子の固形分換算による含有量２０．４質量％）から水を揮発させてシリカ粒子を得た。次に、前記シリカ粒子の固形分換算による含有量が４０質量％となるようにして、前記シリカ粒子をエタノール中に分散させた後、アクリルモノマー（東亞合成，アロニックスＭ−３５０）を、その含有量が前記シリカ粒子の固形分換算による質量の１．５倍の質量となるようにして加えてモノマー含有液を得た。その後、前記モノマー含有液を４５℃の温度条件の乾燥機中に置き、エタノールの約５０％を揮発させて、単粒子層製造用の分散液を得た。 First, using a vacuum evaporator and an electric furnace, water is volatilized from an aqueous dispersion of silica particles having an average particle diameter of 210 nm (KE-W20 manufactured by Nippon Shokubai, content 20.4% by mass in terms of solid content of particles). Thus, silica particles were obtained. Next, after the silica particles are dispersed in ethanol so that the content of the silica particles in terms of solid content is 40% by mass, an acrylic monomer (Toagosei Co., Aronix M-350) is contained. The monomer was added in such a way that the amount was 1.5 times the mass of the silica particles in terms of solid content. Thereafter, the monomer-containing liquid was placed in a dryer having a temperature condition of 45 ° C., and about 50% of ethanol was volatilized to obtain a dispersion for producing a single particle layer.
次に、前記単粒子層製造用の分散液を透明基板１１上にスピンコート法にて塗布し、透明基板１１上にアクリルモノマーに分散したシリカ粒子の単層二次元配列膜を形成させた。なお、スピンコートの際には、先ず、２００ｒｐｍで２分間回転させた後、０．５秒かけて３００ｒｐｍに回転数を上げ、３００ｒｐｍで２分間回転させ、次いで、３．５秒かけて１０００ｒｐｍに回転数を上げ、１０００ｒｐｍで１分間回転させ、その後、更に１０秒かけて３０００ｒｐｍに回転数を上げ、３０００ｒｐｍで２０秒間回転させ、次に、３秒かけて６０００ｒｐｍに回転数を上げ、６０００ｒｐｍで２０秒間回転させ、最後に２秒かけて８０００ｒｐｍに回転数を上げ、８０００ｒｐｍで６分間回転させた。 Next, the dispersion for producing the single particle layer was applied onto the transparent substrate 11 by a spin coating method, and a single layer two-dimensional array film of silica particles dispersed in an acrylic monomer was formed on the transparent substrate 11. In spin coating, first, after rotating at 200 rpm for 2 minutes, the rotational speed is increased to 300 rpm over 0.5 seconds, rotated at 300 rpm for 2 minutes, and then increased to 1000 rpm over 3.5 seconds. Increase the rotation speed and rotate at 1000 rpm for 1 minute, then increase the rotation speed to 3000 rpm over 10 seconds, rotate at 3000 rpm for 20 seconds, then increase the rotation speed to 6000 rpm over 3 seconds and 20 rotation at 6000 rpm. The rotation speed was increased to 8000 rpm over 2 seconds, and the rotation was continued at 8000 rpm for 6 minutes.
次いで、前記単層二次元配列膜が形成された透明基板１１を、窒素雰囲気のグローブボックスに搬送した後、グローブボックス内にて紫外線硬化ランプ（アズワン、ＨＬＲ１００Ｔ−２）を１分間照射することにより光重合を行い、単層二次元配列膜中でアクリル樹脂を硬化させた。次に、アクリル樹脂を硬化させた膜が形成された透明基板１１をグローブボックスから取り出し、真空容器内に搬入し、１×１０−３Ｔｏｒｒの酸素雰囲気下で１３．５６ＭＨｚの高周波（５０Ｗ）を３０秒印加して、アクリル樹脂をエッチング除去し、透明基板上にシリカ粒子が二次元配列した単粒子層を形成した。なお、このようにして形成された単粒子層をＳＥＭ観察した結果、ガラス基板上に、シリカ粒子が三角格子状に粒子同士は互いに接触することなく配列していることを確認され、更に、最近接の粒子同士の中心間距離が３００ｎｍとなっていることが確認された。 Next, the transparent substrate 11 on which the single-layer two-dimensional array film is formed is transferred to a glove box in a nitrogen atmosphere, and then irradiated with an ultraviolet curing lamp (As One, HLR100T-2) for 1 minute in the glove box. Photopolymerization was performed to cure the acrylic resin in the single layer two-dimensional array film. Next, the transparent substrate 11 on which a film obtained by curing the acrylic resin is formed is taken out of the glove box and loaded into a vacuum container, and a high frequency (50 W) of 13.56 MHz is applied in an oxygen atmosphere of 1 × 10 −3 Torr. By applying for 30 seconds, the acrylic resin was removed by etching to form a single particle layer in which silica particles were two-dimensionally arranged on a transparent substrate. As a result of SEM observation of the single particle layer thus formed, it was confirmed that the silica particles were arranged in a triangular lattice pattern on the glass substrate without contacting each other. It was confirmed that the center-to-center distance between adjacent particles was 300 nm.
（比較例１）
単粒子層１２を積層させなかった以外は実施例１と同様にして、比較のための有機電界発光素子（素子構成：透明基板１１／透明電極１３／有機層１４／第二の電極１５）を製造した。
(Comparative Example 1)
An organic electroluminescent element (element structure: transparent substrate 11 / transparent electrode 13 / organic layer 14 / second electrode 15) for comparison was prepared in the same manner as in Example 1 except that the single particle layer 12 was not laminated. Manufactured.
［実施例１〜２及び比較例１で得られた有機電界発光素子の性能評価］
実施例１〜２及び比較例１で得られた有機電界発光素子を用い、それぞれの素子に１１ｍＡ／ｃｍ２の電流を流し、素子をそれぞれ発光させて発光性能を比較した。このような試験の結果、いずれの素子も緑色の発光が観察された。次に、各素子の発光輝度を発光面に対して垂直な方向で測定した。得られた結果を表１に示す。なお、表１には、素子に印加された電圧も合わせて記載した。
[Performance evaluation of organic electroluminescent elements obtained in Examples 1 and 2 and Comparative Example 1]
Using the organic electroluminescent elements obtained in Examples 1 and 2 and Comparative Example 1, a current of 11 mA / cm 2 was passed through each of the elements to emit light, and the light emission performance was compared. As a result of such a test, green light emission was observed in all the elements. Next, the light emission luminance of each element was measured in a direction perpendicular to the light emitting surface. The obtained results are shown in Table 1. Table 1 also shows the voltage applied to the element.
表１に示す結果からも明らかなように、比較のための有機電界発光素子においては、輝度が７８０ｃｄ／ｍ２であるのに対して、実施例１で得られた有機電界発光素子においては輝度が１１５０ｃｄ／ｍ２であり、実施例２で得られた有機電界発光素子においては輝度が１３４０ｃｄ／ｍ２であった。すなわち、比較例１で得られた有機電界発光素子に対して、実施例１で得られた有機電界発光素子の輝度は１．４７倍であり、実施例２で得られた有機電界発光素子の輝度は１．７２倍であった。このような結果から、本発明の有機電界発光素子（実施例１〜２）においては、発光面に対して垂直な方向への光の取り出し効率が高く、高輝度で発光できることが分かった。また、本発明においては、上述のような製造方法で単粒子層を形成して有機電界発光素子が製造されるため、単粒子層の格子定数を変更することが容易であるとともに、素子を簡便な製造方法で製造できることが分かった。 As is clear from the results shown in Table 1, the organic electroluminescent device for comparison has a luminance of 780 cd / m 2 , whereas the organic electroluminescent device obtained in Example 1 has a luminance. Was 1150 cd / m 2 , and the organic electroluminescent element obtained in Example 2 had a luminance of 1340 cd / m 2 . That is, the luminance of the organic electroluminescent element obtained in Example 1 is 1.47 times that of the organic electroluminescent element obtained in Comparative Example 1, and the organic electroluminescent element obtained in Example 2 The luminance was 1.72 times. From these results, it was found that the organic electroluminescent elements (Examples 1 and 2) of the present invention have high light extraction efficiency in a direction perpendicular to the light emitting surface and can emit light with high luminance. In the present invention, since the organic electroluminescence device is manufactured by forming the single particle layer by the above-described manufacturing method, it is easy to change the lattice constant of the single particle layer and the device can be simplified. It turned out that it can manufacture with a simple manufacturing method.
（実施例３）
単粒子層１２をポリスチレン粒子の二次元配列膜とし、更に、透明電極３（ＩＴＯ電極）を室温にてスパッタ成膜して形成させた以外は、実施例１と同様にして有機電界発光素子を製造した。なお、単粒子層１２の形成方法を以下に示す。
(Example 3)
An organic electroluminescent element was prepared in the same manner as in Example 1 except that the single particle layer 12 was formed as a two-dimensional array film of polystyrene particles and the transparent electrode 3 (ITO electrode) was formed by sputtering at room temperature. Manufactured. In addition, the formation method of the single particle layer 12 is shown below.
単粒子層１２（ポリスチレン粒子の二次元配列膜）は、ポリスチレン粒子の水分散液（Ｄｕｋｅ Ｓｃｉｅｎｔｉｆｉｃ Ｃｏｒｐｏｒａｔｉｏｎ製の商品名「Ｗ０３０ＰＢ」、平均粒子径２９０ｎｍ、粒子の屈折率１．５９、粒子の含有量４質量％）を、透明基板１１に対して回転数３０００ｒｐｍで１分間スピンコートし、乾燥することにより形成した。このようにして形成された単粒子層１２を走査型電子顕微鏡（ＳＥＭ）観察した結果、ポリスチレン粒子が、六方最密充填構造に配列していることを確認された。 Single particle layer 12 (two-dimensional array film of polystyrene particles) is an aqueous dispersion of polystyrene particles (trade name “W030PB” manufactured by Duke Scientific Corporation, average particle diameter 290 nm, particle refractive index 1.59, content of particles. 4 mass%) was formed by spin-coating the transparent substrate 11 at 3000 rpm for 1 minute and drying. As a result of observing the single particle layer 12 thus formed with a scanning electron microscope (SEM), it was confirmed that the polystyrene particles were arranged in a hexagonal close-packed packed structure.
（実施例４）
単粒子層１２の形成方法を変更した以外は実施例３と同様にして有機電界発光素子を製造した。なお、単粒子層１２の形成方法を以下に示す。
Example 4
An organic electroluminescent element was produced in the same manner as in Example 3 except that the method for forming the single particle layer 12 was changed. In addition, the formation method of the single particle layer 12 is shown below.
先ず、ポリスチレン粒子の水分散液（Ｄｕｋｅ Ｓｃｉｅｎｔｉｆｉｃ Ｃｏｒｐｏｒａｔｉｏｎ製Ｗ０３０ＰＢ、平均粒子径１９０ｎｍ、粒子の含有量４質量％）を用い、前記水分散液中にＮ，Ｎ−ジエチルジチオカルバミド酸ナトリウム三水和物（和工純薬工業、９２％）を添加し、１０時間反応させることにより、前記粒子の表面にグラフト重合の開始点となるイニファータ基を固定化して表面を改質した。次に、表面の改質された粒子をN−イソプロピルアクリルアミド（ＮＩＰＡＭ）を１質量％含有する水溶液中に、粒子の含有量が０．３質量％となるようにして分散させた後、室温で紫外光を照射することによりグラフト重合させて、粒子表面にポリイソプロピルアクリルアミド（ＰＮＩＰＡＭ）鎖を導入した。そして、ＰＮＩＰＡＭ鎖が表面に導入された粒子を取り出し、その粒子を含有量が０．０１質量％となるようにして水中に分散させた水分散液を調製し、得られた分散液を透明基板１１上に滴下し、室温で乾燥させることにより、粒子同士が互いに離れた状態で三角格子状に配列した構造の単粒子層１２（二次元粒子配列膜）を得た。このようにして形成された単粒子層１２を走査型電子顕微鏡（ＳＥＭ）観察した結果、ガラス基板上に三角格子状に粒子が互いに接触することなく配列していることを確認され、更に、最近接の粒子同士の中心間距離が約３５０ｎｍとなっていることが確認された。 First, an aqueous dispersion of polystyrene particles (Duke Scientific Corporation W030PB, average particle diameter 190 nm, particle content 4% by mass) was used, and sodium N, N-diethyldithiocarbamate trihydrate was added to the aqueous dispersion. (Wako Pure Chemical Industries, 92%) was added and reacted for 10 hours to immobilize the iniferter group serving as the starting point of graft polymerization on the surface of the particles, thereby modifying the surface. Next, the surface-modified particles are dispersed in an aqueous solution containing 1% by mass of N-isopropylacrylamide (NIPAM) so that the particle content becomes 0.3% by mass, and then at room temperature. Graft polymerization was performed by irradiating with ultraviolet light to introduce polyisopropylacrylamide (PNIPAM) chains on the particle surface. And the particle | grains by which the PNIPAM chain | strand was introduce | transduced on the surface are taken out, the water dispersion liquid which prepared the particle | grains and was made to disperse | distribute in water so that content may be 0.01 mass%, and the obtained dispersion liquid is transparent substrate The solution was dropped on the substrate 11 and dried at room temperature to obtain a single particle layer 12 (two-dimensional particle arrangement film) having a structure in which the particles are arranged in a triangular lattice pattern in a state of being separated from each other. As a result of observing the single particle layer 12 thus formed with a scanning electron microscope (SEM), it was confirmed that the particles were arranged in a triangular lattice pattern on the glass substrate without contacting each other. It was confirmed that the distance between the centers of the contact particles was about 350 nm.
（比較例２）
単粒子層１２を積層させなかった以外は実施例３と同様にして、比較のための有機電界発光素子（素子構成：透明基板１１／透明電極１３／有機層１４／第二の電極１５）を製造した。
(Comparative Example 2)
An organic electroluminescent element (element structure: transparent substrate 11 / transparent electrode 13 / organic layer 14 / second electrode 15) for comparison was prepared in the same manner as in Example 3 except that the single particle layer 12 was not laminated. Manufactured.
［実施例３〜４及び比較例２で得られた有機電界発光素子の性能評価］
実施例３〜４及び比較例２で得られた有機電界発光素子を用い、それぞれの素子に１１ｍＡ／ｃｍ２の電流を流し、素子をそれぞれ発光させて発光性能を比較した。このような試験の結果、いずれの素子も緑色の発光が観察された。次に、各素子の発光輝度を発光面に対して垂直な方向で測定した。得られた結果を表２に示す。なお、表２には、素子に印加された電圧も合わせて記載した。
[Performance evaluation of organic electroluminescent elements obtained in Examples 3 to 4 and Comparative Example 2]
Using the organic electroluminescent elements obtained in Examples 3 to 4 and Comparative Example 2, a current of 11 mA / cm 2 was passed through each element to cause the elements to emit light, and the light emission performance was compared. As a result of such a test, green light emission was observed in all the elements. Next, the light emission luminance of each element was measured in a direction perpendicular to the light emitting surface. The obtained results are shown in Table 2. Table 2 also shows the voltage applied to the element.
表２に示す結果からも明らかなように、比較のための有機電界発光素子（比較例２）においては輝度が６６０ｃｄ／ｍ２であるのに対して、実施例３で得られた有機電界発光素子においては輝度が８８０ｃｄ／ｍ２であり、実施例４で得られた有機電界発光素子においては輝度が１０８０ｃｄ／ｍ２であった。すなわち、比較例２で得られた有機電界発光素子に対して、実施例３で得られた有機電界発光素子の輝度は１．３３倍であり、実施例４で得られた有機電界発光素子の輝度は１．６４倍であった。このような結果から、本発明の有機電界発光素子（実施例３〜４）においては、発光面に対して垂直な方向への光の取り出し効率が高く、高輝度で発光できることが分かった。また、本発明においては、上述のような製造方法で単粒子層を形成して有機電界発光素子が製造されるため、単粒子層の格子定数を変更することが容易であるとともに、素子を簡便な製造方法で製造できることが分かった。 As is clear from the results shown in Table 2, the organic electroluminescence device obtained in Example 3 has a luminance of 660 cd / m 2 in the organic electroluminescence device for comparison (Comparative Example 2). The device had a luminance of 880 cd / m 2 , and the organic electroluminescent device obtained in Example 4 had a luminance of 1080 cd / m 2 . That is, the luminance of the organic electroluminescent element obtained in Example 3 was 1.33 times that of the organic electroluminescent element obtained in Comparative Example 2, and the organic electroluminescent element obtained in Example 4 The luminance was 1.64 times. From these results, it was found that the organic electroluminescence device of the present invention (Examples 3 to 4) has high light extraction efficiency in a direction perpendicular to the light emitting surface and can emit light with high luminance. In the present invention, since the organic electroluminescence device is manufactured by forming the single particle layer by the above-described manufacturing method, it is easy to change the lattice constant of the single particle layer and the device can be simplified. It turned out that it can manufacture with a simple manufacturing method.
以上説明したように、本発明によれば、透明基板に対して垂直な方向に出射される光の取り出し効率が十分に高く、高輝度の発光が可能であり、回折格子機能を有する層の格子定数を発光色の光の波長に対応させて容易に調整することができ、しかも簡便な方法で製造することが可能な有機電界発光素子を提供することが可能となる。 As described above, according to the present invention, the extraction efficiency of light emitted in a direction perpendicular to the transparent substrate is sufficiently high, high-luminance light emission is possible, and a grating having a diffraction grating function. It is possible to provide an organic electroluminescent element that can be easily adjusted in accordance with the wavelength of light of the emission color and that can be manufactured by a simple method.
したがって、本発明の有機電界発光素子は、高輝度の発光が可能であるため、ディスプレイ等の映像表示装置や面光源に用いる素子として特に有用である。 Accordingly, the organic electroluminescent element of the present invention is particularly useful as an element used in a video display device such as a display or a surface light source because it can emit light with high luminance.
１…有機電界発光素子、１１…透明基板、１２…単粒子層、１３…第一の電極、１４…有機層、１５…第二の電極。 DESCRIPTION OF SYMBOLS 1 ... Organic electroluminescent element, 11 ... Transparent substrate, 12 ... Single particle layer, 13 ... 1st electrode, 14 ... Organic layer, 15 ... 2nd electrode.
Claims (5)
下記条件（Ａ）〜（Ｃ）：
（Ａ）平均粒径が０．０５〜１．０μｍの範囲にあること、
（Ｂ）下記式（１）：
［単分散度（単位：％）］＝（［粒径の標準偏差］／［平均粒径］）×１００ （１）
で表される単分散度が１０％以下となること、
（Ｃ）波長５２０ｎｍの光に対する屈折率が前記透明電極の材料の波長５２０ｎｍの光に対する屈折率と比較して０．１以上の差がある材料からなること、
を満たす粒子によって形成された単粒子層が、前記透明基板と前記第一電極との間に形成されていること、
を特徴とする有機電界発光素子。 A transparent substrate; a first electrode comprising a transparent electrode disposed on the transparent substrate; at least one organic layer disposed on the first electrode; and a second electrode disposed on the organic layer; An organic electroluminescent device comprising:
The following conditions (A) to (C):
(A) The average particle size is in the range of 0.05 to 1.0 μm,
(B) The following formula (1):
[Monodispersity (unit:%)] = ([standard deviation of particle size] / [average particle size]) × 100 (1)
The monodispersity represented by
(C) The refractive index for light having a wavelength of 520 nm is made of a material having a difference of 0.1 or more compared to the refractive index for light having a wavelength of 520 nm of the material of the transparent electrode,
A single particle layer formed of particles satisfying that is formed between the transparent substrate and the first electrode,
An organic electroluminescent device characterized by the above.
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