JP2005347004A - Light emitting device and display apparatus - Google Patents
Light emitting device and display apparatus Download PDFInfo
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- JP2005347004A JP2005347004A JP2004162948A JP2004162948A JP2005347004A JP 2005347004 A JP2005347004 A JP 2005347004A JP 2004162948 A JP2004162948 A JP 2004162948A JP 2004162948 A JP2004162948 A JP 2004162948A JP 2005347004 A JP2005347004 A JP 2005347004A
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Abstract
Description
本発明は、有機化合物を用いた発光素子に関するものであり、さらに詳しくは素子内の金属配位化合物に由来する不純物を低減することによって安定した効率の高い発光が得られる有機エレクトロルミネッセンス素子（有機ＥＬ素子）に関するものである。 The present invention relates to a light-emitting device using an organic compound, and more specifically, an organic electroluminescence device (organic) capable of obtaining stable and efficient light emission by reducing impurities derived from a metal coordination compound in the device. EL element).
有機ＥＬ素子は、高速応答性や高効率の発光素子として、応用研究が精力的に行われている。その基本的な構成を図１（ａ）、（ｂ）に示した。図中、１１は金属電極、１２は発光層、１３はホール輸送層、１４は透明電極、１５は透明基板、１６は電子輸送層、１７は励起子拡散防止層である。 Organic EL devices have been intensively studied for application as light-emitting devices with high-speed response and high efficiency. The basic configuration is shown in FIGS. 1 (a) and 1 (b). In the figure, 11 is a metal electrode, 12 is a light emitting layer, 13 is a hole transport layer, 14 is a transparent electrode, 15 is a transparent substrate, 16 is an electron transport layer, and 17 is an exciton diffusion preventing layer.
図１に示したように、一般に有機ＥＬ素子は、透明電極１４と金属電極１１の間に複数層の有機化合物層を挟持した積層体を透明基板１５上に配置してなる。
As shown in FIG. 1, the organic EL element is generally formed by arranging a laminated body having a plurality of organic compound layers sandwiched between a
図１（ａ）では、有機層が発光層１２とホール輸送層１３からなる。透明電極１４としては、仕事関数が大きなＩＴＯなどが用いられ、透明電極１４からホール輸送層１３への良好なホール注入特性を持たせている。金属電極１１としては、アルミニウム、マグネシウム或いはそれらを用いた合金などの仕事関数の小さな金属材料を用い有機層への良好な電子注入性を持たせる。これら電極には、５０〜２００ｎｍの膜厚が用いられる。
In FIG. 1A, the organic layer is composed of a
発光層１２には、電子輸送性と発光特性を有するアルミキノリノール錯体など（代表例は、化１に示すＡｌｑ3）が用いられる。また、ホール輸送層１３には、例えばビフェニルジアミン誘導体（代表例は、化１に示すα−ＮＰＤ）など電子供与性を有する材料が用いられる。
For the
以上の構成を有する有機ＥＬ素子は整流性を示し、金属電極１１を陰極に、透明電極１４を陽極になるように電界を印加すると、金属電極１１から電子が発光層１２に注入され、透明電極１５からはホールが注入される。
The organic EL element having the above configuration exhibits rectifying properties. When an electric field is applied so that the
注入されたホールと電子は発光層１２内で再結合により励起子が生じ発光する。この時ホール輸送層１３は電子のブロッキング層の役割を果たし、発光層１２／ホール輸送層１３界面の再結合効率が上がり、発光効率が上がる。
The injected holes and electrons emit light by recombination in the
さらに、図１（ｂ）では、図１（ａ）の金属電極１１と発光層１２の間に、電子輸送層１６が設けられており、発光と電子・ホール輸送を分離して、より効果的なキャリアブロッキング構成にすることで、効率的な発光を行うことができる。電子輸送層１６としては、例えば、オキサジアゾール誘導体などを用いることができる。
Further, in FIG. 1 (b), an
これまで、一般に有機ＥＬ素子に用いられている発光は、発光中心の分子の一重項励起子から基底状態になる時の蛍光が取り出されている。一方、一重項励起子を経由した蛍光発光を利用するのでなく、三重項励起子を経由したりん光発光を利用する素子の検討がなされている（非特許文献１，２参照）。 Until now, the light emitted from the singlet exciton of the molecule at the emission center has been extracted from the light emission generally used in the organic EL element. On the other hand, an element that utilizes phosphorescence emission via a triplet exciton rather than using fluorescence emission via a singlet exciton has been studied (see Non-Patent Documents 1 and 2).
これらの文献では、図１（ｃ）に示す有機化合物層の４層構成が主に用いられている。それは、陽極側からホール輸送層１３、発光層１２、励起子拡散防止層１７、電子輸送層１６からなる。用いられている材料は、化１に示すキャリア輸送材料とりん光発光性材料である。
In these documents, the four-layer structure of the organic compound layer shown in FIG. 1C is mainly used. It consists of a
Ａｌｑ3：アルミ−キノリノール錯体
α−ＮＰＤ：Ｎ，Ｎ’−ｄｉ（１−ｎａｐｈｔｈｙｌ）−Ｎ，Ｎ’−ｄｉｐｈｅｎｙｌｂｅｎｚｉｄｉｎｅ
ＣＢＰ：４，４’−Ｎ，Ｎ’−ｄｉｃａｒｂａｚｏｌｅ−ｂｉｐｈｅｎｙｌ
ＢＣＰ：２，９−ｄｉｍｅｔｈｙｌ−４，７−ｄｉｐｈｅｎｙｌ−１，１０−ｐｈｅｎａｎｔｈｒｏｌｉｎｅ
ＰｔＯＥＰ：白金−オクタエチルポルフィリン錯体
Ｉｒ（ｐｐｙ）3：イリジウム−フェニルピリジン錯体
Alq 3 : Aluminum-quinolinol complex α-NPD: N, N′-di (1-naphthyl) -N, N′-diphenylbenzidine
CBP: 4,4′-N, N′-dicarbazole-biphenyl
BCP: 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline
PtOEP: Platinum-octaethylporphyrin complex Ir (ppy) 3 : Iridium-phenylpyridine complex
非特許文献１，２に開示された素子において、高効率が得られたのは、ホール輸送層１３にα−ＮＰＤ、電子輸送層１６にＡｌｑ3、励起子拡散防止層１７にＢＣＰ、発光層１２にＣＢＰをホスト材料として、６質量％程度の濃度で、りん光発光性材料であるＰｔＯＥＰまたはＩｒ（ｐｐｙ）3を混入して構成したものである。
In the devices disclosed in Non-Patent Documents 1 and 2, high efficiency was obtained because the
りん光性発光材料が特に注目されている理由は、原理的に高発光効率が期待できるからである。その理由は、キャリア再結合により生成される励起子は一重項励起子と三重項励起子からなり、その確率は１：３である。これまでの有機ＥＬ素子は、一重項励起子から基底状態に遷移する際の蛍光を発光として取り出していたが、原理的にその発光収率は生成された励起子数に対して２５％であり、これが原理的上限であった。しかし、三重項から発生する励起子からのりん光を用いれば、原理的に少なくとも３倍の収率が期待され、さらに、エネルギー的に高い一重項から三重項への項間交差による転移を考え合わせれば、原理的には４倍の１００％の発光収率が期待できる。 The reason why phosphorescent light-emitting materials are particularly attracting attention is that high luminous efficiency can be expected in principle. The reason is that excitons generated by carrier recombination are composed of singlet excitons and triplet excitons, and the probability is 1: 3. Conventional organic EL devices have taken out fluorescence when transitioning from a singlet exciton to a ground state as light emission. In principle, the light emission yield is 25% of the number of excitons generated. This was the upper limit in principle. However, if phosphorescence from excitons generated from triplets is used, a yield of at least three times is expected in principle, and transition due to intersystem crossing from singlet to triplet, which is high in energy, is considered. In combination, a 100% light emission yield of 4 times can be expected in principle.
他にも、特許文献１〜３に三重項からの発光を利用した有機ＥＬ素子が開示されている。 In addition, Patent Documents 1 to 3 disclose organic EL elements using light emission from triplets.
上記、りん光発光を用いた有機ＥＬ素子では、特に通電状態の発光劣化が問題となる。りん光発光素子の発光劣化の原因は明らかではないが、一般に三重項寿命が一重項寿命より３桁以上長いために、分子がエネルギーの高い状態に長く置かれるため、周辺物質との反応、励起多量体の形成、分子微細構造の変化、周辺物質の構造変化などが起こるのではないかと考えられている。 In the organic EL element using phosphorescence emission described above, there is a problem of light emission deterioration particularly in an energized state. The cause of light emission degradation of phosphorescent light emitting devices is not clear, but in general, the triplet lifetime is more than three orders of magnitude longer than the singlet lifetime, so the molecule is placed in a high energy state for a long time. It is thought that formation of multimers, changes in molecular microstructure, structural changes in surrounding substances, etc. may occur.
いずれにしても、りん光発光素子は高発光効率が期待されるが、一方で通電劣化が問題となる。 In any case, the phosphorescent light emitting element is expected to have high luminous efficiency, but on the other hand, deterioration of energization becomes a problem.
本発明の課題は、高効率発光で、耐久性に優れ、長い期間高輝度を保つ発光素子及びこれを用いた表示装置を提供することを目的とする。 An object of the present invention is to provide a light-emitting element that has high-efficiency light emission, excellent durability, and maintains high luminance for a long period of time, and a display device using the light-emitting element.
本発明者等は、上記課題を解決すべく鋭意検討した結果、特に金属錯体化合物に着目して、金属錯体化合物からの分解生成物が、強く初期の特性や耐久性能に影響を与えていることを見出し、本発明を完成するに至った。 As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention pay particular attention to the metal complex compound, and the decomposition products from the metal complex compound strongly influence the initial characteristics and durability performance. As a result, the present invention has been completed.
即ち、本発明の発光素子は、一対の電極間に少なくとも一層の有機化合物層を有する発光素子において、該有機化合物層の少なくとも一層が金属配位化合物を少なくとも一種有し、該金属配位化合物を有する有機化合物層に含まれる前記金属配位化合物の分解生成物または原料物の含有量が０．５質量％以下であることを特徴とする。 That is, the light-emitting element of the present invention is a light-emitting element having at least one organic compound layer between a pair of electrodes, wherein at least one of the organic compound layers has at least one metal coordination compound, The content of the decomposition product or raw material of the metal coordination compound contained in the organic compound layer is 0.5% by mass or less.
また、本発明の表示装置は、上記本発明の発光素子を表示素子として備えたことを特徴とする。 In addition, a display device of the present invention includes the light-emitting element of the present invention as a display element.
本発明の発光素子は、高効率発光で、耐久性に優れ、長い期間高輝度を保つことができる。よって、本発明の発光素子を用いてなる表示装置においては、低消費電力で長期間高画質の画像を表示することができる。さらに、本発明においては、りん光発光を用いて発光素子を構成することにより、初期特性も改善される。 The light-emitting element of the present invention has high-efficiency light emission, excellent durability, and can maintain high luminance for a long period. Thus, a display device using the light-emitting element of the present invention can display a high-quality image for a long time with low power consumption. Furthermore, in the present invention, the initial characteristics are also improved by configuring the light emitting element using phosphorescence emission.
有機ＥＬ素子の発光効率を高めるためには、発光中心材料そのものの発光量子収率が大きいことは言うまでもない。しかしながら、ホスト−ホスト間、或いはホスト−ゲスト間のエネルギー移動が如何に効率的にできるかも大きな問題となる。また、通電による発光劣化は今のところ原因は明らかではないが、少なくとも発光中心材料そのもの、または、その周辺分子による発光材料の環境変化に関連したもの、或いは、キャリア輸送層の材料などの劣化によるものと想定される。 Needless to say, the emission quantum yield of the luminescent center material itself is large in order to increase the luminous efficiency of the organic EL element. However, how to efficiently transfer energy between the host and the host or between the host and the guest is also a big problem. In addition, although the cause of light emission deterioration due to energization is not clear at present, it is due to deterioration of at least the light emission center material itself, those related to the environmental change of the light emission material due to its peripheral molecules, or the material of the carrier transport layer, etc. It is assumed.
本発明の発光素子は、一対の電極間に少なくとも一層の有機化合物層を有する発光素子である。発光素子の層構成としては特に限定されず、図１に示す構成が好ましく適用される。 The light-emitting element of the present invention is a light-emitting element having at least one organic compound layer between a pair of electrodes. The layer structure of the light emitting element is not particularly limited, and the structure shown in FIG. 1 is preferably applied.
また、本発明の発光素子においては、上記した金属配位化合物を有する有機化合物層に含まれる該金属配位化合物の分解生成物または原料物の含有量が０．５質量％以下、好ましくは０．１質量％以下である。金属配位化合物の分解生成物または原料物の含有量が０．５質量％以下であれば、耐久性に優れ、りん光発光を用いた発光素子の場合には、初期特性にも優れる。 In the light emitting device of the present invention, the content of the decomposition product or raw material of the metal coordination compound contained in the organic compound layer having the metal coordination compound described above is 0.5% by mass or less, preferably 0. .1% by mass or less. If the content of the decomposition product or raw material of the metal coordination compound is 0.5% by mass or less, the durability is excellent, and in the case of a light emitting device using phosphorescence, the initial characteristics are also excellent.
ここで、金属配位化合物の分解生成物または原料物とは、例えば金属配位化合物の合成の際に用いる配位子となる合成原料等であり、精製が不十分で最初から未反応物質として金属配位化合物中に混入しているもの、蒸着時の加熱による熱分解で発生するもののいずれをも含む。 Here, the decomposition product or raw material of the metal coordination compound is, for example, a synthetic raw material that becomes a ligand used in the synthesis of the metal coordination compound, etc. It includes both those mixed in metal coordination compounds and those generated by thermal decomposition by heating during vapor deposition.
本発明にかかる金属配位化合物及びその分解生成物または原料物は、特に限定されないが、発光材料であることが好ましく、りん光発光性発光材料であることがより好ましく、例えば、以下に示すようなものが挙げられる。 The metal coordination compound and the decomposition product or raw material thereof according to the present invention are not particularly limited, but are preferably luminescent materials, more preferably phosphorescent luminescent materials, for example as shown below. The thing is mentioned.
Ｉｒ錯体Ａ：イリジウム−ベンゾチエニル−４−トリフルオロメチル−ピリジン−錯体
Ｉｒ錯体Ｂ：イリジウム−チエニル−４−チエニル−ピリジン−錯体
Ir complex A: iridium-benzothienyl-4-trifluoromethyl-pyridine-complex Ir complex B: iridium-thienyl-4-thienyl-pyridine-complex
りん光発光とは、励起三重項状態からの発光であり、励起三重項状態から基底状態への発光遷移確率をいかに大きくするかが重要になる。この発光遷移確率を上げるには、本発明に用いられる上記発光材料のように、イリジウムや白金などを用いて重原子効果を利用するのが一般的な方法である。さらに可視光領域に発光を持たせるには、配位子は芳香環などの比較的分子量の大きな共役系を持つものを使う。金属・配位子ともに重い原子団を用いるためイリジウムを中心金属とする金属配位化合物では分子量が大きくなる。また、分子量が大きくなると昇華温度も高くなる傾向にある。本発明に使用される分子量８０５のＩｒ（ｐｉｑ）3では、蒸着時に分解することが確認されており、分子量４５９の蛍光発光素子の代表的有機材料であるＡｌｑ3等の金属配位化合物より昇華温度が高くなり、真空蒸着時の熱分解が問題となる。特に赤色発光材料では、配位子に置換基を導入し共役長を伸ばすためさらに分子量は増加する。これは、他のりん光発光の金属配位化合物全てで問題となる。例えば、レニウム、白金、ユウロピウム、銅、等の配位化合物が挙げられる。 Phosphorescence emission is light emission from the excited triplet state, and how to increase the light emission transition probability from the excited triplet state to the ground state is important. In order to increase the light emission transition probability, it is a common method to use the heavy atom effect using iridium, platinum or the like, as in the light emitting material used in the present invention. Furthermore, in order to give light emission in the visible light region, a ligand having a conjugated system having a relatively large molecular weight such as an aromatic ring is used. Since a heavy atomic group is used for both the metal and the ligand, the molecular weight of the metal coordination compound having iridium as the central metal is large. Further, as the molecular weight increases, the sublimation temperature tends to increase. Ir (piq) 3 having a molecular weight of 805 used in the present invention has been confirmed to decompose during vapor deposition, and is sublimated from a metal coordination compound such as Alq 3 which is a typical organic material of a fluorescent light-emitting device having a molecular weight of 459. The temperature becomes high, and thermal decomposition during vacuum deposition becomes a problem. In particular, in a red light emitting material, a substituent is introduced into the ligand to increase the conjugation length, and thus the molecular weight further increases. This is a problem with all other phosphorescent metal coordination compounds. For example, coordination compounds, such as rhenium, platinum, europium, copper, etc. are mentioned.
本発明で使用される金属配位化合物を真空蒸着する時の蒸着温度は、昇華温度と関係がある。使用する材料の昇華温度が低ければ蒸着温度も低くなり、蒸着時の不純物量が低下し素子に通電し発光させる際の素子寿命を長くできる。また、本発明に使用される発光材料を蒸着する際、長時間熱を加え続けると分解量が増加することを本発明者等は確認している。従って、蒸着温度の低下は大量生産する際の生産安定性という面で重要になってくる。また、蒸着温度が蒸着中の蒸着距離、角度、ボート形状、真空度、粉末試料の置き方、試料量によっても左右される。本発明では、蒸着速度を０．１ｎｍ／ｓｅｃと０．５ｎｍ／ｓｅｃの速度で蒸着した際の基板蒸着物とボート内残渣の分解物割合の比較を行った結果、０．１ｎｍ／ｓｅｃの方が分解物の割合が少なく素子寿命が長くなることも見出した。これらのデータ等は、後述の実施例１７、比較例９に示す。 The deposition temperature when the metal coordination compound used in the present invention is vacuum deposited is related to the sublimation temperature. If the sublimation temperature of the material to be used is low, the vapor deposition temperature will be low, the amount of impurities during vapor deposition will be reduced, and the device life when the device is energized to emit light can be extended. In addition, the present inventors have confirmed that the amount of decomposition increases when heat is applied for a long time when the light emitting material used in the present invention is deposited. Therefore, the lowering of the deposition temperature becomes important in terms of production stability in mass production. The deposition temperature also depends on the deposition distance, angle, boat shape, degree of vacuum, how to place the powder sample, and the amount of sample during deposition. In the present invention, as a result of comparing the ratio of decomposition products of the substrate deposit and the residue in the boat when the deposition rate was 0.1 nm / sec and 0.5 nm / sec, the direction of 0.1 nm / sec However, it has also been found that the percentage of decomposition products is small and the device life is extended. These data are shown in Example 17 and Comparative Example 9 described later.
最近、イリジウムを中心金属とする金属配位化合物で、アセチルアセトナト配位子を持ち発光効率の良いものが発表された（Ｈｉｇｈ−ｅｆｆｉｃｉｅｎｃｙ ｒｅｄ ｅｌｅｃｔｒｏｐｈｏｓｐｈｏｒｅｓｃｅｎｃｅ ｄｅｖｉｃｅｓ（Ｃｈｉｈａｙａ Ａｄａｃｈｉら、Ａｐｐｌ．Ｐｈｙｓ．Ｌｅｔｔ．，Ｖｏｌ．７８，Ｎｏ．１１，１２ Ｍａｒｃｈ ２００１）参照）。しかし、アセチルアセトナト配位子を持ちフェニルイソキノリンが二つ配位した２配位体とフェニルイソキノリンが三つ配位した３配位体では、ある同一条件下で蒸着を行うと３配位体を用いた素子の方が素子寿命が長い。本発明では、ある同一条件下で素子作成した場合に蒸着時のボート内残渣、基板蒸着物の両方で３配位体の方が分解物割合が少なく分解割合が０．５質量％以下であった。その結果、素子寿命を比較しても３配位体の方が長命になることを見出した。 Recently, a metal coordination compound having iridium as a central metal and having an acetylacetonate ligand and having high luminous efficiency has been announced (High-efficiency red electrophoresis devices (Chihaya Adachi et al., Appl. Phys. Lett., Vol.78, No.11, 12 March 2001)). However, a 2-coordination product with two acetylacetonato ligands and two coordinated phenylisoquinolines and a tri-coordination product with three phenylisoquinoline coordinations are tricoordinated by vapor deposition under the same conditions. The element using the element has a longer element life. In the present invention, when an element is fabricated under the same conditions, the tricoordinated body has a lower decomposition ratio and a decomposition ratio of 0.5% by mass or less for both the residue in the boat during vapor deposition and the substrate deposition. It was. As a result, it has been found that even when the device lifetimes are compared, the tridentate has a longer life.
本発明者等の実験において、直接導入型質量分析装置を用いて昇華温度を調べた結果、アセチルアセトナト配位子を持つ２配位体は、昇華時にアセチルアセトナト配位子が外れ金属配位化合物より低温で昇華していく。また、３配位体でも昇華時の加熱で配位子が外れて昇華していくが、配位子が外れて昇華する温度と金属配位化合物の昇華温度の差はほぼ無いに等しい。しかし、同一の蒸着スピードに設定した場合、その分解割合は配位子が外れて昇華していく温度と金属配位化合物が昇華する温度の差が大きいアセチルアセトナト配位子を有する２配位体の方が多くなり、その結果素子寿命が短命になることを見出した。 In the experiments by the present inventors, as a result of examining the sublimation temperature using a direct introduction type mass spectrometer, it was found that a bicoordinator having an acetylacetonate ligand was released from the acetylacetonate ligand during the sublimation. Sublimates at a lower temperature than the coordination compound. Further, even in the tricoordinate body, the ligand is removed and sublimates by heating at the time of sublimation, but the difference between the temperature at which the ligand is removed and sublimates and the sublimation temperature of the metal coordination compound is almost equal. However, when the same deposition rate is set, the decomposition rate is a 2-coordination having an acetylacetonate ligand with a large difference between the temperature at which the ligand is removed and sublimates and the temperature at which the metal coordination compound is sublimated. It has been found that the body becomes larger, and as a result, the device life is shortened.
前記した様に、蒸着温度は昇華温度と関係がある。そこで、昇華させる金属配位化合物の熱分解を低減させることが重要になってくる。 As described above, the deposition temperature is related to the sublimation temperature. Therefore, it is important to reduce the thermal decomposition of the metal coordination compound to be sublimated.
本発明者等は、ある同一蒸着スピード条件で配位子骨格が二つの芳香環を持つ二座配位子で、どちらか一方の芳香環が縮合環（縮合環の例としては、イソキノリン環、キノリン環、ベンゾチエニル環、ベンゾイミダゾール環、ベンゾフラン環などがあり、この他の複素環から成る縮合環も含む）である有機フッ素化物でフッ素を導入したもの（例えば、Ｉｒ（４Ｆｐｉｑ）3の分子量は８５９で、Ｉｒ（４ＣＦ3ｐｉｑ）3の分子量は１００９である。）と導入しないもの（例えば、Ｉｒ（ｐｉｑ）3の分子量は８０５で、Ｉｒ（４ｍｐｉｑ）3の分子量８４７である。）では、導入したものの方が分子間相互作用が低減され、昇華温度が低下し蒸着後のボート内残渣及び蒸着物の分解割合も低下することを見出した。さらに、素子寿命もフッ素を導入したものの方が、長寿命になることがわかった。このような効果は、特に配位子の分子量が増加し、その結果、金属配位化合物全体で分子量が増加してしまう赤色発光材料で特に顕著である。配位子に縮合環を有する金属配位化合物は、そもそも分子量が大きいため、昇華温度が高く一定の蒸着条件下では、分解量が無視できない量になり、特に素子寿命を短命化させる。生産性を向上させるには、蒸着速度に制限がないような蒸着性の良い分子設計が必要であり、配位子に縮合環を有する金属配位化合物にフッ素系置換基を導入し、分解物を低減することはきわめて重要である。また、配位子に縮合環を有する金属配位化合物は、分子形状が大きくなり、隣接分子との分子間相互作用がしやすくなる。従って、ＥＬ素子内での不純物との分子間相互作用を抑制するためにも、フッ素系置換基は有効に働く。実際に直接導入型質量分析装置を用いて、昇華温度を測定した結果、Ｉｒ（４ｍｐｉｑ）3は２２３℃、Ｉｒ（４ＣＦ3ｐｉｑ）3は２１３℃であった。 The inventors of the present invention are bidentate ligands having a ligand skeleton having two aromatic rings under a certain vapor deposition speed condition, and either one of the aromatic rings is a condensed ring (an example of a condensed ring is an isoquinoline ring, Organic fluorinated compounds, such as quinoline ring, benzothienyl ring, benzimidazole ring, benzofuran ring, etc., including condensed rings composed of other heterocycles, in which fluorine is introduced (for example, molecular weight of Ir (4Fpiq) 3 Is 859, Ir (4CF 3 piq) 3 has a molecular weight of 1009) and non-introduced (for example, Ir (piq) 3 has a molecular weight of 805 and Ir (4mpiq) 3 has a molecular weight of 847). It has been found that the intermolecular interaction is reduced in the introduced one, the sublimation temperature is lowered, and the decomposition rate of the residue in the boat and the deposited material after the vapor deposition is also lowered. Furthermore, it was found that the element lifetime was longer when fluorine was introduced. Such an effect is particularly remarkable in a red light emitting material in which the molecular weight of the ligand increases, and as a result, the molecular weight of the entire metal coordination compound increases. Since the metal coordination compound having a condensed ring as a ligand has a large molecular weight in the first place, the decomposition amount is not negligible under a certain vapor deposition condition with a high sublimation temperature, and particularly shortens the device life. In order to improve productivity, it is necessary to design a molecule with good vapor deposition properties that does not limit the vapor deposition rate. By introducing a fluorine-based substituent into a metal coordination compound having a condensed ring as a ligand, a decomposition product is obtained. It is extremely important to reduce this. In addition, a metal coordination compound having a condensed ring as a ligand has a large molecular shape and facilitates intermolecular interaction with adjacent molecules. Therefore, the fluorine-based substituent works effectively in order to suppress intermolecular interaction with impurities in the EL element. As a result of actually measuring the sublimation temperature using a direct introduction type mass spectrometer, Ir (4mpiq) 3 was 223 ° C. and Ir (4CF 3 piq) 3 was 213 ° C.
本発明の発光素子は、高効率・高耐久性であり、省エネルギーや高輝度が必要な製品に応用が可能である。応用例としては表示装置・照明装置やプリンターの光源、液晶表示装置のバックライトなどが考えられる。表示装置としては、省エネルギーや高視認性・軽量なフラットパネルディスプレイが可能となる。また、プリンターの光源としては、現在広く用いられているレーザビームプリンタのレーザー光源部を、本発明の発光素子に置き換えることができる。独立にアドレスできる素子をアレイ上に配置し、感光ドラムに所望の露光を行うことで、画像形成する。本発明の素子を用いることで、装置体積を大幅に減少することができる。照明装置やバックライトに関しては、本発明による省エネルギー効果が期待できる。 The light-emitting element of the present invention has high efficiency and high durability, and can be applied to products that require energy saving and high luminance. Application examples include light sources for display devices / illuminators and printers, backlights for liquid crystal display devices, and the like. As a display device, energy-saving, high visibility and lightweight flat panel display can be realized. Further, as the light source of the printer, the laser light source unit of the laser beam printer that is widely used at present can be replaced with the light emitting element of the present invention. Elements that can be independently addressed are arranged on the array, and an image is formed by performing desired exposure on the photosensitive drum. By using the element of the present invention, the volume of the apparatus can be greatly reduced. With respect to the lighting device and the backlight, the energy saving effect according to the present invention can be expected.
＜実施例１〜４、比較例１〜２＞
以下に示す層構成の素子を作製した。（ ）内は膜厚である。
ガラス基板／ＩＴＯ（７０ｎｍ）／α−ＮＰＤ（５０ｎｍ）／Ａｌｑ3（５０ｎｍ）／ＡｌＬｉ（Ｌｉ：１．８質量％、３ｎｍ）／Ａｌ（１００ｎｍ）
<Examples 1-4, Comparative Examples 1-2>
An element having the following layer structure was produced. Figures in parentheses are film thicknesses.
Glass substrate / ITO (70 nm) / α-NPD (50 nm) / Alq 3 (50 nm) / AlLi (Li: 1.8 mass%, 3 nm) / Al (100 nm)
有機化合物層及びＡｌ電極は、真空蒸着法（真空度１０-4Ｐａ以下）で形成した。 The organic compound layer and the Al electrode were formed by a vacuum vapor deposition method (vacuum degree: 10 −4 Pa or less).
原料の金属配位化合物であるＡｌｑ3に関して、純度が９９．９質量％以上であることを確認し、Ａｌｑ3の分解生成物である配位子にプロトンが付加された、８−キノリノールが不純物として存在しないことを確認した。さらに、本例の蒸着条件で蒸着したＡｌｑ3層には８−キノリノールが存在しないことを確認した。同じ蒸着条件で、Ａｌｑ3層形成時に、８−キノリノールを表１に示す割合で共蒸着し、意図的に８−キノリノールが含有されるＡｌｑ3層を形成した。 Regarding Alq 3 which is a metal coordination compound as a raw material, it was confirmed that the purity was 99.9% by mass or more, and 8-quinolinol in which a proton was added to a ligand which is a decomposition product of Alq 3 was an impurity. As confirmed that it does not exist. Furthermore, it was confirmed that 8-quinolinol was not present in the Alq 3 layer deposited under the deposition conditions of this example. In the same deposition conditions, when Alq 3 layer formed, 8-quinolinol was co-deposited at a ratio shown in Table 1, is deliberately 8-quinolinol was formed Alq 3 layer contained.
各例の素子に電圧を印加するとＡｌｑ3からの発光が確認された。また、１０ｍＡ／ｃｍ2の直流電流を、ＩＴＯを陽極として、乾燥窒素中で印加して、耐久特性を評価した。結果を表１に示す。 When voltage was applied to the device of each example, light emission from Alq 3 was confirmed. In addition, a DC current of 10 mA / cm 2 was applied in dry nitrogen using ITO as an anode, and durability characteristics were evaluated. The results are shown in Table 1.
表１に示す様に、８−キノリノールの含有量が０．５質量％以下で耐久性が特に良好になり、０．１質量％でさらに良くなっており、８−キノリノールの含有量が耐久性能に強く影響していることがわかった。特に、８−キノリノールはＡｌｑ3の配位子と水素原子以外は同じ形状をしており、金属配位化合物と会合しやすく電流特性や発光特性を阻害すると考えられる。それら阻害因子である金属配位化合物の配位子に由来する化合物を取り除くことが重要である。 As shown in Table 1, the durability is particularly good when the content of 8-quinolinol is 0.5% by mass or less, and even better when the content is 0.1% by mass. The content of 8-quinolinol is the durability performance. It was found to have a strong influence on In particular, 8-quinolinol has the same shape except for the ligand of Alq 3 and a hydrogen atom, and is likely to associate with a metal coordination compound and inhibit current characteristics and light emission characteristics. It is important to remove compounds derived from the ligands of the metal coordination compounds that are those inhibitors.
本実施例では、故意に８−キノリノールを混入させたが、現実にＡｌｑ3蒸着時に８−キノリノールが混入されるのは、精製が不十分で蒸着前から材料中に８−キノリノールが未反応物質として残っている場合と、蒸着時に加熱され、その熱で分解される場合が考えられる。いずれの場合も、耐久性能は金属配位化合物の分解生成物の含有量が、０．５％質量以下、好ましくは０．１質量％以下が好ましい。 In this example, 8-quinolinol was intentionally mixed, but 8-quinolinol was actually mixed during the deposition of Alq 3 because the purification was insufficient and 8-quinolinol was not reacted in the material before the deposition. The case where it is left as it is, and the case where it is heated at the time of vapor deposition and decomposed by the heat can be considered. In any case, the durability performance is such that the content of the decomposition product of the metal coordination compound is 0.5% by mass or less, preferably 0.1% by mass or less.
＜実施例５〜８、比較例３〜４＞
以下に示す層構成のりん光発光素子を作製した。
ガラス基板／ＩＴＯ（７０ｎｍ）／α−ＮＰＤ（５０ｎｍ）／ＣＢＰ：Ｉｒ（ｐｐｙ）3（７％）／ＢＣＰ（２０ｎｍ）／Ａｌｑ3（５０ｎｍ）／ＡｌＬｉ（Ｌｉ：１．８質量％、３ｎｍ）／Ａｌ（１００ｎｍ）
<Examples 5-8, Comparative Examples 3-4>
A phosphorescent light emitting device having the following layer structure was produced.
Glass substrate / ITO (70 nm) / α-NPD (50 nm) / CBP: Ir (ppy) 3 (7%) / BCP (20 nm) / Alq 3 (50 nm) / AlLi (Li: 1.8 mass%, 3 nm) / Al (100 nm)
本実施例に用いられるＩｒ（ｐｐｙ）3は、Ｉｒ（ａｃａｃ）3（トリス−アセチルアセトナト−イリジウム錯体）を用いて、以下の合成経路で合成した。 Ir (ppy) 3 used in this example was synthesized by the following synthetic route using Ir (acac) 3 (tris-acetylacetonato-iridium complex).
Ｉｒ（ａｃａｃ）3＋フェニルピリジン→Ｉｒ（ｐｐｙ）3 Ir (acac) 3 + phenylpyridine → Ir (ppy) 3
実施例１〜４と同様に、原料である金属配位化合物であるＩｒ（ｐｐｙ）3とＡｌｑ3を９９．９質量％以上の純度に精製した。また、実施例１〜４と同様にして、ＣＢＰ：Ｉｒ（ｐｐｙ）3層形成時に、意図的にフェニルピリジンを表２に示す割合で原料に混入させた。 In the same manner as in Examples 1 to 4, Ir (ppy) 3 and Alq 3 which are metal coordination compounds as raw materials were purified to a purity of 99.9% by mass or more. Further, in the same manner as in Examples 1 to 4, phenylpyridine was intentionally mixed into the raw material at the ratio shown in Table 2 when the CBP: Ir (ppy) 3 layer was formed.
本例の素子に電圧を印加すると、Ｉｒ（ｐｐｙ）3からの発光が確認された。また、実施例１〜４と同様に、耐久特性を評価した。結果を表２に示す。 When voltage was applied to the device of this example, light emission from Ir (ppy) 3 was confirmed. Moreover, the durability characteristic was evaluated similarly to Examples 1-4. The results are shown in Table 2.
表２に示す様に、実施例１〜４と同様、耐久性能を向上させるためには、金属配位化合物であるＩｒ（ｐｐｙ）3からの分解生成物であるフェニルピリジンの含有量が、０．５質量％以下、好ましくは０．１質量％以下が良い。 As shown in Table 2, the content of phenylpyridine, which is a decomposition product from Ir (ppy) 3 , which is a metal coordination compound, is 0 to improve durability as in Examples 1 to 4. .5% by mass or less, preferably 0.1% by mass or less.
また、このりん光発光素子では、初期特性が分解生成物が０．５質量％以下で著しく改善される。即ちフェニルピリジン含有量が０．５質量％と１．０質量％を比較すると同じ電圧をかけた場合に、発光輝度が２倍以上になる。この不純物の濃度が低い場合の初期特性が改善する現象は、実施例１〜４の蛍光発光素子にはない現象であり、りん光発光素子特有の現象である。 In this phosphorescent light emitting device, the initial characteristics are remarkably improved when the decomposition product is 0.5 mass% or less. That is, when the phenylpyridine content is compared between 0.5% by mass and 1.0% by mass, when the same voltage is applied, the emission luminance is doubled or more. The phenomenon that the initial characteristics are improved when the impurity concentration is low is a phenomenon that the fluorescent light emitting elements of Examples 1 to 4 do not have, and is a phenomenon peculiar to the phosphorescent light emitting element.
本実施例により、りん光発光素子にも、本発明が有用であることが確認された。さらに、蛍光素子にはない初期特性も改善されることが明らかになった。 This example confirmed that the present invention is also useful for phosphorescent light emitting devices. Furthermore, it has been clarified that initial characteristics not found in the fluorescent element are also improved.
＜実施例９〜１２、比較例５〜６＞
発光材料として化２に示すＩｒ錯体Ｂ（純度９９．９質量％以上）を用い、チエニル−４−チエニル−ピリジンを表３に示す割合で混入させた以外は実施例５〜８と同様にして素子を作製し、耐久特性を評価した。結果を表３に示す。
<Examples 9 to 12 and Comparative Examples 5 to 6>
Except that Ir complex B shown in Chemical Formula 2 (purity: 99.9% by mass or more) was used as the luminescent material, and thienyl-4-thienyl-pyridine was mixed at the ratio shown in Table 3, the same as in Examples 5-8. An element was fabricated and durability characteristics were evaluated. The results are shown in Table 3.
＜実施例１３〜１５，比較例７＞
実施例５〜８と同様の材料を用いて、同様の層構成のりん光発光素子を作製した。但し、発光材料であるＩｒ（ｐｐｙ）3は、カラム精製したもの、再結晶にて生成した物、昇華生成した物の３種を用い、精製度の差により蒸着前の純度に差を持たせた。
<Examples 13 to 15, Comparative Example 7>
Using the same material as in Examples 5 to 8, phosphorescent light emitting elements having the same layer structure were produced. However, Ir (ppy) 3 , which is a luminescent material, uses three types of purified column, recrystallized product, and sublimated product, and the purity before vapor deposition varies depending on the degree of purification. It was.
予備実験として、ガラス基板にホスト材料と共にＩｒ（ｐｐｙ）3を真空蒸着した物を成分分析すると、不純物含有量は０．９質量％（比較例７）、０．５質量％（実施例１５）、０．２質量％（実施例１４）、０．０７質量％（実施例１３）であった。これら不純物は、フェニルピリジンが主成分であった。 As a preliminary experiment, component analysis of a vacuum-deposited Ir (ppy) 3 together with a host material on a glass substrate revealed an impurity content of 0.9 mass% (Comparative Example 7) and 0.5 mass% (Example 15). And 0.27 mass% (Example 14) and 0.07 mass% (Example 13). These impurities were mainly phenylpyridine.
これらの素子を用いて、これまでの実施例同様、耐久特性を評価した。結果を表４に示す。 Using these elements, durability characteristics were evaluated as in the previous examples. The results are shown in Table 4.
表４に示す様に、これまでの実施例と同様、本実施例においても、不純物（フェニルピリジン）含有量が０．５質量％以下、より好ましくは０．１質量％以下で、耐久性能が著しく向上することが明らかになった。 As shown in Table 4, as in the previous examples, in this example as well, the impurity (phenylpyridine) content was 0.5 mass% or less, more preferably 0.1 mass% or less, and the durability performance was It became clear that it improved remarkably.
＜実施例１６，比較例８＞
実施例５〜８と同様の材料を用いて、同様の層構成のりん光発光素子を作製した。本実施例では、発光層の真空蒸着時の速度を０．１ｎｍ／ｓｅｃ（実施例１６）と０．７ｎｍ／ｓｅｃ（比較例７）とした。
<Example 16, comparative example 8>
Using the same material as in Examples 5 to 8, phosphorescent light emitting elements having the same layer structure were produced. In this example, the speed during vacuum deposition of the light emitting layer was set to 0.1 nm / sec (Example 16) and 0.7 nm / sec (Comparative Example 7).
予備実験として、ガラス基板上に発光層を蒸着した物を分析したところ、不純物含有量が０．１ｎｍ／ｓｅｃ（実施例１６）では０．２質量％、０．７ｎｍ／ｓｅｃ（比較例７）では０．７質量％であった。不純物の主成分は、フェニルピリジンであった。 As a preliminary experiment, a product obtained by evaporating a light emitting layer on a glass substrate was analyzed. As a result, when the impurity content was 0.1 nm / sec (Example 16), 0.2% by mass, 0.7 nm / sec (Comparative Example 7). It was 0.7 mass%. The main component of the impurity was phenylpyridine.
これらの素子を用いて、これまでの実施例同様、耐久特性を評価した。結果を表５に示す。 Using these elements, durability characteristics were evaluated as in the previous examples. The results are shown in Table 5.
表５に示す様に、蒸着速度による不純物（フェニルピリジン）濃度の差で、耐久性能が異なる。この理由は、真空蒸着の速度により、金属から外れた配位子が主たる成分の不純物が、同時に蒸着される程度に差が生じ、耐久性能を低下させたためである。 As shown in Table 5, the durability performance varies depending on the impurity (phenylpyridine) concentration difference depending on the deposition rate. The reason for this is that due to the speed of vacuum deposition, a difference in the degree to which impurities mainly composed of ligands deviated from the metal are deposited simultaneously reduces durability.
＜実施例１７，比較例９＞
実施例５〜８と同様の材料を用いて、同様の層構成のりん光発光素子を作製した。本実施例では、発光材料にＩｒ（ｐｉｑ）3を用い発光層の真空蒸着速度を１ｎｍ／ｓｅｃ（実施例１７）と０．５ｎｍ／ｓｅｃ（比較例９）の速度で行った。
<Example 17, comparative example 9>
Using the same material as in Examples 5 to 8, phosphorescent light emitting elements having the same layer structure were produced. In this example, Ir (piq) 3 was used as the light emitting material, and the vacuum deposition rate of the light emitting layer was 1 nm / sec (Example 17) and 0.5 nm / sec (Comparative Example 9).
予備実験として、ガラス基板上に発光層を蒸着した物を液体クロマトグラフィーで分析したところ、不純物含有量が０．１ｎｍ／ｓｅｃ（実施例１７）では０．３質量％、０．５ｎｍ／ｓｅｃ（比較例９）では２．０質量％であった。 As a preliminary experiment, a product obtained by evaporating a light emitting layer on a glass substrate was analyzed by liquid chromatography. As a result, when the impurity content was 0.1 nm / sec (Example 17), 0.3 mass% and 0.5 nm / sec ( In Comparative Example 9), it was 2.0% by mass.
これらの素子を用いて、初期輝度３００ｃｄ／ｍ2に設定し耐久特性を評価した。結果を表６に示す。 Using these elements, the initial luminance was set to 300 cd / m 2 and the durability characteristics were evaluated. The results are shown in Table 6.
表６に示す様に、蒸着速度による不純物濃度の差で、耐久性能が異なる。この理由は、実施例１６と同様に真空蒸着の速度により、金属から外れた配位子が主たる成分の不純物が、同時に蒸着される程度に差が生じ、耐久性能を低下させたためである。 As shown in Table 6, the durability performance varies depending on the difference in impurity concentration depending on the deposition rate. This is because, as in Example 16, due to the rate of vacuum deposition, a difference occurs in that the impurities mainly composed of ligands deviated from the metal are deposited at the same time, thereby reducing the durability.
＜実施例１８，比較例１０＞
実施例５〜８と同様の材料を用いて、同様の層構成のりん光発光素子を作製した。本実施例では、発光材料にＩｒ（４ｍｐｉｑ）3（実施例１８）を用いたものとＩｒ（４ｍｐｉｑ）2ａｃａｃ（比較例１０）を用いたものを０．１ｎｍ／ｓｅｃ真空蒸着速度で行った。
<Example 18, Comparative Example 10>
Using the same material as in Examples 5 to 8, phosphorescent light emitting elements having the same layer structure were produced. In this example, a material using Ir (4mpiq) 3 (Example 18) and a material using Ir (4mpiq) 2 acac (Comparative Example 10) as the light-emitting material were performed at a vacuum deposition rate of 0.1 nm / sec. .
予備実験として、ガラス基板上に発光層を蒸着した物を液体クロマトグラフィーで分析した。 As a preliminary experiment, the thing which vapor-deposited the light emitting layer on the glass substrate was analyzed by the liquid chromatography.
これらの素子を用いて、初期輝度３００ｃｄ／ｍ2に設定し耐久特性を評価した。結果を表７に示す。 Using these elements, the initial luminance was set to 300 cd / m 2 and the durability characteristics were evaluated. The results are shown in Table 7.
表７に示す様にアセチルアセトナト配位子があるａｃａｃ体と３配位体では、蒸着時の熱安定性に違いがあり、３配位体の方が蒸着時の熱分解を少なくすることができる。以上のことから、ａｃａｃ体で素子寿命を長くするには真空蒸着速度を低下する必要があり、生産性が低下する問題があることが確認された。 As shown in Table 7, there is a difference in thermal stability between the acac and tricoordination with acetylacetonate ligand, and the tricoordination has less thermal decomposition during vapor deposition. Can do. From the above, it has been confirmed that in order to increase the device life of the acac body, it is necessary to reduce the vacuum deposition rate, and there is a problem that productivity is lowered.
＜実施例１９，比較例１１＞
実施例５〜８と同様の材料を用いて、同様の層構成のりん光発光素子を作製した。本実施例では、発光材料にＩｒ（４ＣＦ3ｐｉｑ）3（実施例１９）を用いたものとＩｒ（４ｍｐｉｑ）3（比較例１１）を用いたものを通常の真空蒸着速度で行った。
<Example 19, Comparative example 11>
Using the same material as in Examples 5 to 8, phosphorescent light emitting elements having the same layer structure were produced. In this example, a material using Ir (4CF 3 piq) 3 (Example 19) and a material using Ir (4mpiq) 3 (Comparative Example 11) as the light emitting material were performed at a normal vacuum deposition rate.
これらの素子を用いて、初期輝度３００ｃｄ／ｍ2に設定し耐久特性を評価した。結果を表８に示す。 Using these elements, the initial luminance was set to 300 cd / m 2 and the durability characteristics were evaluated. The results are shown in Table 8.
表８に示す様にフッ素化したＩｒ（４ＣＦ3ｐｉｑ）3とＩｒ（４ｍｐｉｑ）3では、蒸着時の昇華性に違いがありフッ素化することにより昇華温度を低下させ蒸着時の熱分解を少なくすることができ、発光素子を長命化することができた。 As shown in Table 8, fluorinated Ir (4CF 3 piq) 3 and Ir (4 mpiq) 3 have different sublimation properties during vapor deposition, and the fluorination reduces the sublimation temperature and reduces thermal decomposition during vapor deposition. Thus, the life of the light emitting element can be extended.
１１ 金属電極
１２ 発光層
１３ ホール輸送層
１４ 透明電極
１５ 透明基板
１６ 電子輸送層
１７ 励起子拡散防止層
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2010184876A (en) * | 2009-02-10 | 2010-08-26 | Mitsubishi Chemicals Corp | Organometallic complex, composition for organic electroluminescent device and organic electroluminescent device |
| JP2010209317A (en) * | 2009-02-10 | 2010-09-24 | Mitsubishi Chemicals Corp | Metal complex, composition for organic electroluminescent element, and organic electroluminescent element |
| JP4590020B1 (en) * | 2009-07-31 | 2010-12-01 | 富士フイルム株式会社 | Charge transport material and organic electroluminescent device |
| US8426042B2 (en) | 2009-09-30 | 2013-04-23 | Udc Ireland Limited | Material for organic electroluminescence device, and organic electroluminescence device |
| JP2016086171A (en) * | 2014-10-28 | 2016-05-19 | 株式会社半導体エネルギー研究所 | Light-emitting element, light-emitting device, electronic device, and illuminating device |
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2010184876A (en) * | 2009-02-10 | 2010-08-26 | Mitsubishi Chemicals Corp | Organometallic complex, composition for organic electroluminescent device and organic electroluminescent device |
| JP2010209317A (en) * | 2009-02-10 | 2010-09-24 | Mitsubishi Chemicals Corp | Metal complex, composition for organic electroluminescent element, and organic electroluminescent element |
| JP4590020B1 (en) * | 2009-07-31 | 2010-12-01 | 富士フイルム株式会社 | Charge transport material and organic electroluminescent device |
| WO2011013681A1 (en) * | 2009-07-31 | 2011-02-03 | 富士フイルム株式会社 | Charge transport material and organic electroluminescent element |
| JP2011071474A (en) * | 2009-07-31 | 2011-04-07 | Fujifilm Corp | Charge transport material and organic electroluminescent element |
| US8426042B2 (en) | 2009-09-30 | 2013-04-23 | Udc Ireland Limited | Material for organic electroluminescence device, and organic electroluminescence device |
| JP2016086171A (en) * | 2014-10-28 | 2016-05-19 | 株式会社半導体エネルギー研究所 | Light-emitting element, light-emitting device, electronic device, and illuminating device |
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