JP2012059962A - Organic el element - Google Patents

Organic el element Download PDF

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JP2012059962A
JP2012059962A JP2010202379A JP2010202379A JP2012059962A JP 2012059962 A JP2012059962 A JP 2012059962A JP 2010202379 A JP2010202379 A JP 2010202379A JP 2010202379 A JP2010202379 A JP 2010202379A JP 2012059962 A JP2012059962 A JP 2012059962A
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Toyoyasu Tadokoro
豊康 田所
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Nippon Seiki Co Ltd
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    • 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
    • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/14—Carrier transporting layers
    • H10K50/16—Electron transporting layers
    • H10K50/165—Electron transporting layers comprising dopants
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    • H10K2101/00—Properties of the organic materials covered by group H10K85/00
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Abstract

PROBLEM TO BE SOLVED: To provide an organic EL element having high reliability at low power operation under high temperature environment.SOLUTION: An organic EL element is formed by laminating at least an organic light-emitting layer 3b and an electron transport layer 3c between a positive electrode 2 and a negative electrode 4, where the electron transport layer 3c is composed of a mixed layer of an electron transporting material and a lithium complex. The electron transporting material has an electron mobility of 10cm/V s or higher, and LUMO energy of less than 3.0 eV.

Description

本発明は、有機ＥＬ（Electro Luminescence）素子に関し、特に有機ＥＬ素子の低電圧化及び高効率化に関するものである。   The present invention relates to an organic EL (Electro Luminescence) element, and particularly relates to a reduction in voltage and an increase in efficiency of an organic EL element.

従来、有機材料によって形成される自発光素子として知られる有機ＥＬ素子は、例えば、陽極となるＩＴＯ（Indium Tin Oxide）等からなる第一電極と、少なくとも発光層を有する有機層と、陰極となるアルミニウム（Ａｌ）等からなる非透光性の第二電極と、を順次積層してなるものである（特許文献１参照）。   Conventionally, an organic EL element known as a self-luminous element formed of an organic material is, for example, a first electrode made of ITO (Indium Tin Oxide) or the like serving as an anode, an organic layer having at least a light emitting layer, and a cathode. A non-translucent second electrode made of aluminum (Al) or the like is sequentially laminated (see Patent Document 1).

かかる有機ＥＬ素子は、第一電極から正孔を注入し、また、第二電極から電子を注入して正孔及び電子が前記発光層にて再結合することによって光を発するものである。有機ＥＬ素子を用いた有機ＥＬディスプレイは、自己発光のため視認性に優れ、完全固体素子であるため耐衝撃性や低温環境下での応答性に優れているため表示の瞬間判読が必要な車両用計器などの車載表示装置に採用されている。   Such an organic EL element emits light by injecting holes from the first electrode and injecting electrons from the second electrode, and the holes and electrons recombine in the light emitting layer. An organic EL display using an organic EL element has excellent visibility due to self-emission, and is a completely solid element, so it has excellent impact resistance and responsiveness in a low temperature environment. It is used for in-vehicle display devices such as measuring instruments.

特開昭５９−１９４３９３号公報JP 59-194393 A 特開２０００−１８２７７４号公報JP 2000-182774 A

特に車載表示装置に採用される有機ＥＬ素子は、広範囲な温度環境下での高信頼性が要求されるとともに低電力化が求められている。低電力で高温環境下での信頼性を高めるためには、低電圧化と高効率化が重要な課題である。これに対し、低電圧化と高効率を達成するための方法として、発光層と陰極との間に形成される電子輸送層に電子移動度の高い電子輸送性材料やＬＵＭＯ（最低空位分子軌道）エネルギーが小さい電子輸送性材料を適用することで電子輸送層内での電子移動効率を高めるあるいは電子輸送層から発光層への電子注入障壁を小さくすることが考えられる。しかし、電子輸送性材料としてよく知られるアルミキノリノール（Ａｌｑ３）の電子移動度（μｅ＝５×１０−６ｃｍ２／Ｖｓ）よりも電子輸送層の電子移動度が高い、あるいはＡｌｑ３のＬＵＭＯエネルギー（Ｅａ＝３．０ｅＶ）よりも電子輸送層のＬＵＭＯエネルギーが小さいと、電子の供給が過剰となりキャリアバランスが崩れて発光層と陽極との間に形成される正孔輸送層が電子によって劣化し、発光ムラが生じたり、寿命が短くなるという問題点があり、キャリアバランスを保つ点でなお改善の余地があった。 In particular, organic EL elements employed in in-vehicle display devices are required to have high reliability in a wide range of temperature environments and to have low power consumption. Low voltage and high efficiency are important issues in order to improve reliability in low temperature and high temperature environments. On the other hand, as a method for achieving low voltage and high efficiency, an electron transporting material or LUMO (lowest vacancy molecular orbital) having a high electron mobility is formed in the electron transporting layer formed between the light emitting layer and the cathode. It is conceivable to increase the electron transfer efficiency in the electron transport layer or to reduce the electron injection barrier from the electron transport layer to the light emitting layer by applying an electron transport material having low energy. However, the electron mobility of the electron transport layer is higher than the electron mobility (μe = 5 × 10 −6 cm 2 / Vs) of aluminum quinolinol (Alq 3 ) well known as an electron transport material, or the LUMO of Alq 3 If the LUMO energy of the electron transport layer is lower than the energy (Ea = 3.0 eV), the supply of electrons will be excessive, the carrier balance will be lost, and the hole transport layer formed between the light emitting layer and the anode will be deteriorated by electrons. However, there is a problem that uneven light emission occurs and the life is shortened, and there is still room for improvement in terms of maintaining the carrier balance.

また、特許文献２には、有機ＥＬ素子の低電圧化に関し、陰極に接する部分の有機層が、アルカリ金属イオン、アルカリ土類金属イオン、希土類金属イオンの少なくとも１種を含有する有機金属錯体化合物と電子輸送性有機物との混合層から構成される点が開示されている。しかしながら、特許文献２に開示される技術は、電子注入層の構成に関するものであり、また、電子輸送性有機物としてはＡｌｑ３が上げられるのみであって、Ａｌｑ３よりも電子移動度が高いあるいはＬＵＭＯエネルギーが小さい電子輸送性材料を電子輸送層に適用した構成におけるキャリアバランスの保持に関するものではない。 In addition, Patent Document 2 discloses an organic metal complex compound in which the organic layer in contact with the cathode contains at least one of alkali metal ions, alkaline earth metal ions, and rare earth metal ions with regard to lowering the voltage of the organic EL element. The point which is comprised from the mixed layer of an electron transport organic substance is disclosed. However, the technique disclosed in Patent Document 2 relates to the configuration of the electron injection layer, and only Alq 3 can be raised as an electron transporting organic substance, and the electron mobility is higher than that of Alq 3 or It does not relate to maintenance of carrier balance in a configuration in which an electron transporting material having low LUMO energy is applied to the electron transport layer.

そこで本発明は、この問題に鑑みなされたものであり、低電力で高温環境下での信頼性が高い有機ＥＬ素子を提供することを目的とする。   Therefore, the present invention has been made in view of this problem, and an object thereof is to provide an organic EL element having low power and high reliability in a high temperature environment.

本発明は、前記課題を解決するために、少なくとも有機発光層と電子輸送層とを陽極と陰極との間に積層形成してなる有機ＥＬ素子であって、
前記電子輸送層は、電子輸送性材料とリチウム錯体との混合層からなることを特徴とする有機ＥＬ素子。 The present invention is an organic EL device comprising at least an organic light emitting layer and an electron transport layer laminated between an anode and a cathode in order to solve the above-mentioned problem,
The electron transport layer is an organic EL element comprising a mixed layer of an electron transport material and a lithium complex.

また、前記電子輸送性材料は、電子移動度が１０−５ｃｍ２／Ｖ・ｓ以上であることを特徴とする。 The electron transporting material has an electron mobility of 10 −5 cm 2 / V · s or more.

また、前記電子輸送性材料は、ＬＵＭＯエネルギーが３．０ｅＶより小さいことを特徴とする。   The electron transporting material has a LUMO energy of less than 3.0 eV.

また、前記リチウム錯体は、リチウム８−キノリノラート（Ｌｉｑ）からなることを特徴とする。   The lithium complex is made of lithium 8-quinolinolate (Liq).

また、前記電子輸送層と前記陰極との間に、電子注入層が形成されてなることを特徴とする。   Further, an electron injection layer is formed between the electron transport layer and the cathode.

また、前記電子注入層は、アルカリ金属化合物あるいはアルカリ金属錯体からなることを特徴とする。   The electron injection layer is made of an alkali metal compound or an alkali metal complex.

本発明は、低電力で高温環境下での信頼性の高い有機ＥＬ素子を提供することが可能となるものである。   The present invention can provide an organic EL element with low power and high reliability in a high temperature environment.

本発明の実施形態である有機ＥＬ素子を示す図。The figure which shows the organic EL element which is embodiment of this invention. 本発明の実施例１〜５及び比較例１〜１２の試験結果を示す図。The figure which shows the test result of Examples 1-5 of this invention and Comparative Examples 1-12.

以下、添付図面に基づいて本発明の実施形態について説明する。   Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

図１は、本発明の実施形態を示す図である。本実施形態である有機ＥＬ素子は、支持基板１と、陽極となる第一電極２と、有機層３と、陰極となる第二電極４と、を有するものである。なお、有機ＥＬ素子は、吸湿剤が塗布される封止基板を支持基板１上に配設して封止されるものであるが、図１ではこの封止基板を省略している。   FIG. 1 is a diagram showing an embodiment of the present invention. The organic EL element which is this embodiment has the support substrate 1, the 1st electrode 2 used as an anode, the organic layer 3, and the 2nd electrode 4 used as a cathode. Note that the organic EL element is sealed by disposing a sealing substrate to which a hygroscopic agent is applied on the support substrate 1, but this sealing substrate is omitted in FIG.

支持基板１は、例えば透光性のガラス材料からなる矩形状の基板である。支持基板１上には、第一電極２，有機層３及び第二電極４が順に積層形成される。   The support substrate 1 is a rectangular substrate made of a translucent glass material, for example. On the support substrate 1, the 1st electrode 2, the organic layer 3, and the 2nd electrode 4 are laminated | stacked in order.

第一電極２は、正孔を注入する陽極となるものであり、支持基板１上にＩＴＯ等の透明導電材料をスパッタリング法あるいは蒸着法等の手段によって層状に形成し、フォトエッチング等の手段によって所定の形状にパターニングされてなる。また、第一電極２は、表面がＵＶ／Ｏ３処理やプラズマ処理等の表面処理を施されてなる。 The first electrode 2 serves as an anode for injecting holes, and a transparent conductive material such as ITO is formed in layers on the support substrate 1 by means such as sputtering or vapor deposition, and by means such as photoetching. Patterned into a predetermined shape. The surface of the first electrode 2 is subjected to a surface treatment such as UV / O 3 treatment or plasma treatment.

有機層３は、少なくとも有機発光層を含む多層からなり、第一電極２上に形成されるものである。本実施形態においては、第一電極２側から順に正孔注入輸送層３ａ，発光層（有機発光層）３ｂ，電子輸送層３ｃ及び電子注入層３ｄが順に積層形成されてなる。   The organic layer 3 is formed of a multilayer including at least an organic light emitting layer, and is formed on the first electrode 2. In the present embodiment, a hole injection / transport layer 3a, a light emitting layer (organic light emitting layer) 3b, an electron transport layer 3c, and an electron injection layer 3d are sequentially stacked from the first electrode 2 side.

正孔注入輸送層３ａは、第一電極２から正孔を取り込み発光層３ｂへ伝達する機能を有し、例えばアミン系化合物等の正孔輸送性材料を蒸着法等の手段によって膜厚１５〜４０ｎｍ程度の層状に形成してなる。   The hole injecting and transporting layer 3a has a function of capturing holes from the first electrode 2 and transmitting the holes to the light emitting layer 3b. For example, a hole transporting material such as an amine compound is formed with a film thickness of 15 to 15 by means such as vapor deposition. It is formed in a layer shape of about 40 nm.

発光層３ｂは、ホスト材料に少なくとも発光を呈する発光ドーパントを共蒸着等の手段によって添加してなるものである。前記ホスト材料は、通常発光層３ｂ中で最も高い比率で含まれるものであり、正孔及び電子の輸送が可能であり、その分子内で正孔及び電子が再結合することで前記発光ドーパントを発光させる機能を有し、３．０ｅＶ程度のエネルギーギャップを有する。前記発光ドーパントは、正孔と電子との再結合に反応して発光する機能を有し、所定の発光色を示す蛍光材料からなる。また、発光層３ｂは、さらに正孔輸送性ドーパントを添加するものであってもよい。前記正孔輸送性ドーパントは、第一電極２から発光層３ｂへの正孔の注入効率を向上させる機能を有し、発光層３ｂ中の濃度が５０ｗｔ％以下で、ガラス転移温度が８５℃以上で好ましくは１１０℃以上の材料である。   The light emitting layer 3b is formed by adding at least a light emitting dopant that emits light to a host material by means such as co-evaporation. The host material is usually contained at the highest ratio in the light emitting layer 3b, and can transport holes and electrons. The holes and electrons are recombined in the molecule so that the light emitting dopant is added. It has a function of emitting light and has an energy gap of about 3.0 eV. The light emitting dopant is made of a fluorescent material having a function of emitting light in response to recombination of holes and electrons and exhibiting a predetermined emission color. Moreover, the light emitting layer 3b may further contain a hole transporting dopant. The hole transporting dopant has a function of improving the efficiency of hole injection from the first electrode 2 to the light emitting layer 3b, the concentration in the light emitting layer 3b is 50 wt% or less, and the glass transition temperature is 85 ° C. or higher. Preferably, the material is 110 ° C. or higher.

電子輸送層３ｃは、電子を発光層３ｂへ伝達する機能を有し、電子移動度μｅが１０−５ｃｍ２／Ｖｓ以上（μｅ≧１０−５ｃｍ２／Ｖｓ）である及び／あるいはＬＵＭＯエネルギー（電子親和力）Ｅａが３．０ｅＶより小さい（Ｅａ＜３．０ｅＶ）電子輸送性材料と例えばリチウム８−キノリノラート（Ｌｉｑ）等のリチウム錯体とを共蒸着等の手段によって混合し、膜厚８〜３０ｎｍ程度の層状に形成した混合層である。なお、前記電子輸送性材料とリチウム錯体とは例えばｗｔ％比率が１：１で混合されるものであるが、この比率を変更することでキャリアバランスを変化させることも可能である。 The electron transport layer 3c has a function of transmitting electrons to the light emitting layer 3b, and has an electron mobility μe of 10 −5 cm 2 / Vs or more (μe ≧ 10 −5 cm 2 / Vs) and / or LUMO energy. (Electron affinity) Ea is smaller than 3.0 eV (Ea <3.0 eV) An electron transporting material and a lithium complex such as lithium 8-quinolinolato (Liq) are mixed by means such as co-evaporation, and the film thickness is 8 to It is a mixed layer formed in a layer shape of about 30 nm. The electron transporting material and the lithium complex are mixed at a wt% ratio of 1: 1, for example, but the carrier balance can be changed by changing this ratio.

電子注入層３ｄは、電子を第二電極４から取り込む機能を有し、例えばフッ化リチウム（ＬｉＦ）やＬｉｑを真空蒸着法等の手段によって薄膜状に形成してなる。   The electron injection layer 3d has a function of taking electrons from the second electrode 4, and is formed, for example, by forming lithium fluoride (LiF) or Liq into a thin film by means such as vacuum deposition.

第二電極４は、電子を注入する陰極となるものであり、電子注入層３ｄ上に例えばＡｌ等の低抵抗導電材料を蒸着法等の手段によって層状に形成した導電膜からなるものである。   The second electrode 4 serves as a cathode for injecting electrons, and is composed of a conductive film in which a low-resistance conductive material such as Al is formed in layers on the electron injection layer 3d by means such as vapor deposition.

以上の各部によって有機ＥＬ素子が構成されている。   The organic EL element is comprised by the above each part.

本願発明者らは、鋭意検討した結果、電子輸送能力の高い電子輸送性材料を電子輸送層に適用する構成においては、電子輸送層にリチウム錯体を混合することで有機ＥＬ素子のキャリアバランスを安定化させ、低電力で高温環境下での信頼性の高い素子を得ることが可能であることを見いだし、本発明に達した。特に、電子移動度μｅが１０−５ｃｍ２／Ｖｓ以上である及び／あるいはＬＵＭＯエネルギーＥａが３．０ｅＶより小さい電子輸送性材料とリチウム錯体とを混合して電子輸送層を形成することによって、キャリアバランスを安定させて低電圧と高効率を達成することができ、低電力で高温環境下での信頼性の高い有機ＥＬ素子を得ることができる。 As a result of intensive studies, the inventors of the present invention have stabilized the carrier balance of the organic EL element by mixing a lithium complex in the electron transport layer in a configuration in which an electron transport material having a high electron transport capability is applied to the electron transport layer. And the inventors have found that it is possible to obtain an element with low power and high reliability in a high-temperature environment, and reached the present invention. In particular, by forming an electron transport layer by mixing an electron transport material and a lithium complex having an electron mobility μe of 10 −5 cm 2 / Vs or more and / or a LUMO energy Ea of less than 3.0 eV, The carrier balance can be stabilized to achieve low voltage and high efficiency, and an organic EL element with low power and high reliability in a high temperature environment can be obtained.

以下、さらに本発明の実施例について説明するが、本発明はこれらによって限定されるものではない。図２は各実施例及び各比較例の性能比較を示している。   Examples of the present invention will be further described below, but the present invention is not limited thereto. FIG. 2 shows a performance comparison between each example and each comparative example.

支持基板１上にＩＴＯからなる第一電極２を膜厚１４５ｎｍで形成し、第一電極２上に正孔輸送性材料ＨＴ１からなる正孔注入輸送層３ａを膜厚３０ｎｍで形成した。また、正孔注入輸送層３ａ上に、ホスト材料ＥＭ１と緑色発光を示す蛍光ドーパントＧＤ１からなる前記発光ドーパントと正孔輸送性材料ＨＴ１からなる前記正孔輸送性ドーパントを、ＥＭ１：ＧＤ１：ＨＴ１＝３６：１．２：４のｗｔ％比率で含有させて発光層３ｂを膜厚５０ｎｍで形成した。ホスト材料ＥＭ１は、Ｉｐ（イオン化ポテンシャル）＝５．９ｅＶ、Ｅａ（ＬＵＭＯエネルギー、すなわち電子親和力）＝２．９ｅＶ、μｅ（電子移動度）＝３×１０−３ｃｍ２／Ｖｓ、μｈ（正孔移動度）＝２×１０−３ｃｍ２／Ｖｓである。蛍光ドーパントＧＤ１は、Ｅｇ（エネルギーギャップ）＝２．４ｅＶ、Ｉｐ＝５．８ｅＶである。正孔輸送性材料ＨＴ１は、Ｔｇ（ガラス転移温度）＝１３０℃、Ｉｐ＝５．４ｅＶ、μｈ＝４×１０−４ｃｍ２／Ｖｓである。さらに、発光層３ｂ上に電子輸送層３ｃとして電子輸送性材料ＥＴ１とＬｉｑとを、ＥＴ１：Ｌｉｑ＝１：１のｗｔ％比率で混合して膜厚１０ｎｍで形成した。電子輸送性材料ＥＴ１は、Ｉｐ＝６．０ｅＶ、Ｅａ＝３．０ｅＶ、電子移動度μｅ＝４×１０−４ｃｍ２／Ｖｓである。さらに、電子輸送層３ｃ上に電子注入層３ｄとしてＬｉＦを膜厚1ｎｍで形成し、電子注入層３ｄ上に第二電極４としてＡｌを膜厚１００ｎｍで形成して有機ＥＬ素子を作製した。実施例１は緑色発光を示し、その特性はピーク輝度Ｌｐ＝１６０００ｃｄ／ｍ２での駆動電圧Ｖ＝４．７Ｖ、電流効率Ｌ／Ｊ＝１８ｃｄ／Ａであり、８５℃の高温環境下における初期輝度Ｌｐ＝３０００ｃｄ／ｍ２でのＤＣ駆動時の半減寿命は２０００時間を越えた。また、１１０℃の高温環境下での２時間の高温放置試験において、２ｍｍ２の発光部に発光ムラが発生することはなかった。尚、発光ムラの測定は、ミノルタ製２次元色分布測定装置（CA-1500）で行った。 A first electrode 2 made of ITO was formed on the support substrate 1 with a film thickness of 145 nm, and a hole injection transport layer 3a made of a hole transport material HT1 was formed on the first electrode 2 with a film thickness of 30 nm. Further, on the hole injecting and transporting layer 3a, the light emitting dopant made of the host material EM1 and the fluorescent dopant GD1 that emits green light and the hole transporting dopant made of the hole transporting material HT1 are changed to EM1: GD1: HT1 = The light emitting layer 3b was formed with a thickness of 50 nm by containing 36: 1.2: 4 in a wt% ratio. The host material EM1 has Ip (ionization potential) = 5.9 eV, Ea (LUMO energy, that is, electron affinity) = 2.9 eV, μe (electron mobility) = 3 × 10 −3 cm 2 / Vs, μh (hole) Mobility) = 2 × 10 −3 cm 2 / Vs. The fluorescent dopant GD1 has Eg (energy gap) = 2.4 eV and Ip = 5.8 eV. The hole transporting material HT1 has Tg (glass transition temperature) = 130 ° C., Ip = 5.4 eV, and μh = 4 × 10 −4 cm 2 / Vs. Further, the electron transporting material ET1 and Liq were mixed as the electron transporting layer 3c on the light emitting layer 3b at a wt% ratio of ET1: Liq = 1: 1 to form a film with a thickness of 10 nm. The electron transporting material ET1 has Ip = 6.0 eV, Ea = 3.0 eV, and electron mobility μe = 4 × 10 −4 cm 2 / Vs. Furthermore, LiF was formed with a film thickness of 1 nm as the electron injection layer 3d on the electron transport layer 3c, and Al was formed with a film thickness of 100 nm as the second electrode 4 on the electron injection layer 3d to produce an organic EL device. Example 1 shows green light emission, and its characteristics are a driving voltage V = 4.7 V at a peak luminance Lp = 16000 cd / m 2 , a current efficiency L / J = 18 cd / A, and an initial condition in a high temperature environment of 85 ° C. The half-life at the time of DC driving with luminance Lp = 3000 cd / m 2 exceeded 2000 hours. Further, in the high temperature standing test for 2 hours in a high temperature environment of 110 ° C., no light emission unevenness occurred in the 2 mm 2 light emitting part. The measurement of light emission unevenness was performed with a Minolta two-dimensional color distribution measuring device (CA-1500).

（比較例１）
比較例１として、電子輸送層３ｃを電子輸送性材料ＥＴ１のみで形成したほかは、実施例１と同様に有機ＥＬ素子の作製及び特性の測定を行った。比較例１は緑色発光を示し、その特性はピーク輝度Ｌｐ＝１６０００ｃｄ／ｍ２での駆動電圧Ｖ＝４．９Ｖ、電流効率Ｌ／Ｊ＝１７ｃｄ／Ａであり、８５℃の高温環境下における初期輝度Ｌｐ＝３０００ｃｄ／ｍ２でのＤＣ駆動時の半減寿命は１５００時間であった。また、１１０℃の高温環境下での２時間の高温放置試験において、２ｍｍ２の発光部に中央部が明るく周辺部が暗くなる発光ムラが発生し、ディスプレイとしては使用に堪えない発光状態であった。 (Comparative Example 1)
As Comparative Example 1, an organic EL device was produced and properties were measured in the same manner as in Example 1 except that the electron transport layer 3c was formed only from the electron transport material ET1. Comparative Example 1 shows green light emission, and its characteristics are a driving voltage V = 4.9 V at a peak luminance Lp = 16000 cd / m 2 , a current efficiency L / J = 17 cd / A, and an initial condition in a high temperature environment of 85 ° C. The half life at the time of DC driving at a luminance Lp = 3000 cd / m 2 was 1500 hours. Further, in a high temperature standing test for 2 hours in a high temperature environment of 110 ° C., a light emission unevenness in which the central portion is bright and the peripheral portion is dark occurs in the 2 mm 2 light emitting portion, and the light emitting state is unbearable as a display. It was.

（比較例２）
比較例２として、電子注入層３ｄを形成しないほかは、実施例１と同様に有機ＥＬ素子の作製及び特性の測定を行った。比較例２は緑色発光を示し、その特性はピーク輝度Ｌｐ＝１６０００ｃｄ／ｍ２での駆動電圧Ｖ＝５．５Ｖ、電流効率Ｌ／Ｊ＝１６ｃｄ／Ａであり、８５℃の高温環境下における初期輝度Ｌｐ＝３０００ｃｄ／ｍ２でのＤＣ駆動時の半減寿命は１９００時間を超えた。また、１１０℃の高温環境下での２時間の高温放置試験において、２ｍｍ２の発光部に発光ムラが発生することはなかった。 (Comparative Example 2)
As Comparative Example 2, an organic EL element was produced and characteristics were measured in the same manner as in Example 1 except that the electron injection layer 3d was not formed. Comparative Example 2 shows green light emission, and its characteristics are a driving voltage V = 5.5 V at a peak luminance Lp = 16000 cd / m 2 , a current efficiency L / J = 16 cd / A, and an initial condition in a high temperature environment of 85 ° C. The half-life at the time of DC driving with luminance Lp = 3000 cd / m 2 exceeded 1900 hours. Further, in the high temperature standing test for 2 hours in a high temperature environment of 110 ° C., no light emission unevenness occurred in the 2 mm 2 light emitting part.

（比較例３）
比較例３として、電子輸送層３ｃを電子輸送性材料ＥＴ２とＬｉｑとの混合層としたほかは、実施例１と同様に有機ＥＬ素子の作製及び特性の測定を行った。電子輸送性材料ＥＴ２はＡｌｑ３であり、Ｉｐ＝５．８ｅＶ、Ｅａ＝３．０ｅＶ、電子移動度μｅ＝５×１０−６ｃｍ２／Ｖｓである。比較例３は緑色発光を示し、その特性はピーク輝度Ｌｐ＝１６０００ｃｄ／ｍ２での駆動電圧Ｖ＝７．０Ｖ、電流効率Ｌ／Ｊ＝１７ｃｄ／Ａであり、８５℃の高温環境下における初期輝度Ｌｐ＝３０００ｃｄ／ｍ２でのＤＣ駆動時の半減寿命は２０００時間を超えた。また、１１０℃の高温環境下での２時間の高温放置試験において、２ｍｍ２の発光部に発光ムラが発生することはなかった。 (Comparative Example 3)
As Comparative Example 3, an organic EL device was produced and properties were measured in the same manner as in Example 1 except that the electron transport layer 3c was a mixed layer of the electron transport material ET2 and Liq. Electron transporting material ET2 is Alq 3, is Ip = 5.8eV, Ea = 3.0eV, the electron mobility μe = 5 × 10-6cm2 / Vs. Comparative Example 3 shows green light emission, and its characteristics are a driving voltage V = 7.0 V at a peak luminance Lp = 16000 cd / m 2 , a current efficiency L / J = 17 cd / A, and an initial condition in a high temperature environment of 85 ° C. The half-life at the time of DC driving with luminance Lp = 3000 cd / m 2 exceeded 2000 hours. Further, in the high temperature standing test for 2 hours in a high temperature environment of 110 ° C., no light emission unevenness occurred in the 2 mm 2 light emitting part.

かかる測定結果が示すように、実施例１は、比較例３に対して駆動電圧が低く、また、比較例１に見られるような発光ムラは発生していない。したがって、少なくともＡｌｑ３よりも電子輸送能力の高い電子輸送性材料を電子輸送層３ｃに適用する構成においては、電子輸送層３ｃにリチウム錯体を混合することで有機ＥＬ素子のキャリアバランスを安定化させ、低電力で高温環境下での信頼性の高い素子を得ることが可能であることがわかる。また、比較例２は比較例１に対して駆動電圧Ｖが高く、電子輸送層３ｃが直接第二電極４と接する構成ではリチウム錯体を混合することで電子輸送性材料のみで電子輸送層３ｃを形成する場合よりも駆動電圧Ｖの低減効果が低くなることがわかるが、実施例１のようにさらに電子注入層３ｄを形成することで電子輸送性材料のみで電子輸送層３ｃを形成するのと同程度に駆動電圧Ｖを低減することができる。 As shown by the measurement results, the driving voltage in Example 1 is lower than that in Comparative Example 3, and the light emission unevenness as seen in Comparative Example 1 does not occur. Therefore, in the configuration in which an electron transport material having a higher electron transport capability than Alq 3 is applied to the electron transport layer 3c, the carrier balance of the organic EL element is stabilized by mixing the lithium complex with the electron transport layer 3c. It can be seen that an element having low power and high reliability in a high temperature environment can be obtained. Further, in Comparative Example 2, the driving voltage V is higher than that of Comparative Example 1, and in the configuration in which the electron transport layer 3c is in direct contact with the second electrode 4, the electron transport layer 3c can be formed only by the electron transport material by mixing the lithium complex. It can be seen that the effect of reducing the driving voltage V is lower than that in the case of forming, but the electron transport layer 3c is formed only by the electron transport material by further forming the electron injection layer 3d as in the first embodiment. The drive voltage V can be reduced to the same extent.

支持基板１上にＩＴＯからなる第一電極２を膜厚１００ｎｍで形成し、第一電極２上に正孔輸送性材料ＨＴ１からなる正孔注入輸送層３ａを膜厚３０ｎｍで形成した。また、正孔注入輸送層３ａ上に、発光層３ｂとして第一，第二の発光層を積層形成した。前記第一の発光層は、ホスト材料ＥＭ１と橙色発光を示す蛍光ドーパントＡＤ１からなる前記発光ドーパントと正孔輸送性材料ＨＴ１からなる前記正孔輸送性ドーパントを、ＥＭ１：ＡＤ１：ＨＴ１＝６：１．２：６のｗｔ％比率で含有させて膜厚１５ｎｍで形成した。蛍光ドーパントＡＤ１は、Ｅｇ＝２．０ｅＶ、Ｉｐ＝５．２ｅＶである。前記第二の発光層は、ホスト材料ＥＭ１と青緑色発光を示す蛍光ドーパントＢＤ１からなる前記発光ドーパントと正孔輸送性材料ＨＴ１からなる前記正孔輸送性ドーパントを、ＥＭ１：ＢＤ１：ＨＴ１＝２０：１．２：１０のｗｔ％比率で含有させて膜厚３０ｎｍで形成した。蛍光ドーパントＢＤ１は、Ｅｇ＝２．７ｅＶ、Ｉｐ＝５．６ｅＶである。さらに、発光層３ｂ上に電子輸送層３ｃとして電子輸送性材料ＥＴ１とＬｉｑとを、ＥＴ１：Ｌｉｑ＝１：１のｗｔ％比率で混合して膜厚１０ｎｍで形成した。さらに、電子輸送層３ｃ上に電子注入層３ｄとしてＬｉＦを膜厚1ｎｍで形成し、電子注入層３ｄ上に第二電極４としてＡｌを膜厚１００ｎｍで形成して有機ＥＬ素子を作製した。実施例２は白色発光を示し、その特性はピーク輝度Ｌｐ＝１６０００ｃｄ／ｍ２での駆動電圧Ｖ＝４．５Ｖ、電流効率Ｌ／Ｊ＝１３ｃｄ／Ａであり、８５℃の高温環境下における初期輝度Ｌｐ＝３０００ｃｄ／ｍ２でのＤＣ駆動時の半減寿命は２０００時間を越えた。また、１１０℃の高温環境下での２時間の高温放置試験において、２ｍｍ２の発光部に発光ムラが発生することはなかった。 A first electrode 2 made of ITO was formed on the support substrate 1 with a film thickness of 100 nm, and a hole injection transport layer 3a made of a hole transport material HT1 was formed on the first electrode 2 with a film thickness of 30 nm. In addition, the first and second light emitting layers were stacked as the light emitting layer 3b on the hole injecting and transporting layer 3a. The first light-emitting layer includes the light-emitting dopant made of the host material EM1 and the fluorescent dopant AD1 that emits orange light, and the hole-transporting dopant made of the hole-transport material HT1, EM1: AD1: HT1 = 6: 1. .2: 6 wt% ratio to form a film with a thickness of 15 nm. The fluorescent dopant AD1 has Eg = 2.0 eV and Ip = 5.2 eV. The second light-emitting layer is composed of the light-emitting dopant made of the host material EM1 and the fluorescent dopant BD1 exhibiting blue-green light emission and the hole-transporting dopant made of the hole-transport material HT1, EM1: BD1: HT1 = 20: The film was contained at a thickness of 30 nm with a wt% ratio of 1.2: 10. The fluorescent dopant BD1 has Eg = 2.7 eV and Ip = 5.6 eV. Further, the electron transporting material ET1 and Liq were mixed as the electron transporting layer 3c on the light emitting layer 3b at a wt% ratio of ET1: Liq = 1: 1 to form a film with a thickness of 10 nm. Furthermore, LiF was formed with a film thickness of 1 nm as the electron injection layer 3d on the electron transport layer 3c, and Al was formed with a film thickness of 100 nm as the second electrode 4 on the electron injection layer 3d to produce an organic EL device. Example 2 shows white light emission, and its characteristics are a driving voltage V = 4.5 V at a peak luminance Lp = 16000 cd / m 2 , a current efficiency L / J = 13 cd / A, and an initial state in a high temperature environment of 85 ° C. The half-life at the time of DC driving with luminance Lp = 3000 cd / m 2 exceeded 2000 hours. Further, in the high temperature standing test for 2 hours in a high temperature environment of 110 ° C., no light emission unevenness occurred in the 2 mm 2 light emitting part.

実施例３として、電子輸送層３ｃを電子輸送性材料ＥＴ３とＬｉｑとの混合層としたほかは、実施例２と同様に有機ＥＬ素子の作製及び特性の測定を行った。電子輸送性材料ＥＴ３は、Ｉｐ＝６．３ｅＶ、Ｅａ＝２．９ｅＶ、電子移動度μｅ＝４×１０−５ｃｍ２／Ｖｓである。実施例３は白色発光を示し、その特性はピーク輝度Ｌｐ＝１６０００ｃｄ／ｍ２での駆動電圧Ｖ＝５．５Ｖ、電流効率Ｌ／Ｊ＝１４ｃｄ／Ａであり、８５℃の高温環境下における初期輝度Ｌｐ＝３０００ｃｄ／ｍ２でのＤＣ駆動時の半減寿命は２０００時間であった。また、１１０℃の高温環境下での２時間の高温放置試験において、２ｍｍ２の発光部に発光ムラが発生することはなかった。 As Example 3, an organic EL device was prepared and characteristics were measured in the same manner as in Example 2 except that the electron transport layer 3c was a mixed layer of the electron transport material ET3 and Liq. The electron transport material ET3 has Ip = 6.3 eV, Ea = 2.9 eV, and electron mobility μe = 4 × 10 −5 cm 2 / Vs. Example 3 shows white light emission, and its characteristics are a driving voltage V = 5.5 V at a peak luminance Lp = 16000 cd / m 2 , a current efficiency L / J = 14 cd / A, and an initial condition in a high temperature environment of 85 ° C. The half-life at the time of DC driving at a luminance Lp = 3000 cd / m 2 was 2000 hours. Further, in the high temperature standing test for 2 hours in a high temperature environment of 110 ° C., no light emission unevenness occurred in the 2 mm 2 light emitting part.

実施例４として、電子輸送層３ｃを電子輸送性材料ＥＴ４とＬｉｑとの混合層としたほかは、実施例２と同様に有機ＥＬ素子の作製及び特性の測定を行った。電子輸送性材料ＥＴ４は、Ｉｐ＝６．１ｅＶ、Ｅａ＝２．８ｅＶ、電子移動度μｅ＝６×１０−６ｃｍ２／Ｖｓである。実施例４は白色発光を示し、その特性はピーク輝度Ｌｐ＝１６０００ｃｄ／ｍ２での駆動電Ｖ＝６Ｖ、電流効率Ｌ／Ｊ＝１４ｃｄ／Ａであり、８５℃の高温環境下における初期輝度Ｌｐ＝３０００ｃｄ／ｍ２でのＤＣ駆動時の半減寿命は２０００時間であった。また、１１０℃の高温環境下での２時間の高温放置試験において、２ｍｍ２の発光部に発光ムラが発生することはなかった。 As Example 4, an organic EL device was produced and properties were measured in the same manner as in Example 2, except that the electron transport layer 3c was a mixed layer of the electron transport material ET4 and Liq. The electron transport material ET4 has Ip = 6.1 eV, Ea = 2.8 eV, and electron mobility μe = 6 × 10 −6 cm 2 / Vs. Example 4 shows white light emission, and its characteristics are a driving power V = 6V at a peak brightness Lp = 16000 cd / m 2 , a current efficiency L / J = 14 cd / A, and an initial brightness Lp in a high temperature environment of 85 ° C. = The half life at the time of DC drive at 3000 cd / m 2 was 2000 hours. Further, in the high temperature standing test for 2 hours in a high temperature environment of 110 ° C., no light emission unevenness occurred in the 2 mm 2 light emitting part.

実施例５として、電子輸送層３ｃを電子輸送性材料ＥＴ５とＬｉｑとの混合層としたほかは、実施例２と同様に有機ＥＬ素子の作製及び特性の測定を行った。電子輸送性材料ＥＴ５は、Ｉｐ＝６．１ｅＶ、Ｅａ＝２．８ｅＶ、電子移動度μｅ＝６×１０−４ｃｍ２／Ｖｓである。実施例５は白色発光を示し、その特性はピーク輝度Ｌｐ＝１６０００ｃｄ／ｍ２での駆動電圧Ｖ＝４．５Ｖ、電流効率Ｌ／Ｊ＝１４ｃｄ／Ａであり、８５℃の高温環境下における初期輝度Ｌｐ＝３０００ｃｄ／ｍ２でのＤＣ駆動時の半減寿命は２０００時間であった。また、１１０℃の高温環境下での２時間の高温放置試験において、２ｍｍ２の発光部に発光ムラが発生することはなかった。 As Example 5, an organic EL device was produced and characteristics were measured in the same manner as in Example 2 except that the electron transport layer 3c was a mixed layer of the electron transport material ET5 and Liq. The electron transport material ET5 has Ip = 6.1 eV, Ea = 2.8 eV, and electron mobility μe = 6 × 10 −4 cm 2 / Vs. Example 5 shows white light emission, and its characteristics are a driving voltage V = 4.5 V at a peak luminance Lp = 16000 cd / m 2 , a current efficiency L / J = 14 cd / A, and an initial condition in a high-temperature environment of 85 ° C. The half-life at the time of DC driving at a luminance Lp = 3000 cd / m 2 was 2000 hours. Further, in the high temperature standing test for 2 hours in a high temperature environment of 110 ° C., no light emission unevenness occurred in the 2 mm 2 light emitting part.

（比較例４）
比較例４として、電子輸送層３ｃを電子輸送性材料ＥＴ１のみで形成したほかは、実施例２と同様に有機ＥＬ素子の作製及び特性の測定を行った。比較例４は白色発光を示し、その特性はピーク輝度Ｌｐ＝１６０００ｃｄ／ｍ２での駆動電圧Ｖ＝４．４Ｖ、電流効率Ｌ／Ｊ＝１４ｃｄ／Ａであり、８５℃の高温環境下における初期輝度Ｌｐ＝３０００ｃｄ／ｍ２でのＤＣ駆動時の半減寿命は１０００時間であった。また、１１０℃の高温環境下での２時間の高温放置試験において、２ｍｍ２の発光部に中央部が明るく周辺部が暗くなる発光ムラが発生し、ディスプレイとしては使用に堪えない発光状態であった。 (Comparative Example 4)
As Comparative Example 4, an organic EL device was prepared and characteristics were measured in the same manner as in Example 2 except that the electron transport layer 3c was formed only from the electron transport material ET1. Comparative Example 4 shows white light emission, and its characteristics are a driving voltage V = 4.4 V at a peak luminance Lp = 16000 cd / m 2 , a current efficiency L / J = 14 cd / A, and an initial condition in a high temperature environment of 85 ° C. The half-life at the time of DC driving at a luminance Lp = 3000 cd / m 2 was 1000 hours. Further, in a high temperature standing test for 2 hours in a high temperature environment of 110 ° C., a light emission unevenness in which the central portion is bright and the peripheral portion is dark occurs in the 2 mm 2 light emitting portion, and the light emitting state is unbearable as a display. It was.

（比較例５）
比較例５として、電子注入層３ｄを形成しないほかは、実施例２と同様に有機ＥＬ素子の作製及び特性の測定を行った。比較例５は白色発光を示し、その特性はピーク輝度Ｌｐ＝１６０００ｃｄ／ｍ２での駆動電圧Ｖ＝５．０Ｖ、電流効率Ｌ／Ｊ＝１３ｃｄ／Ａであり、８５℃の高温環境下における初期輝度Ｌｐ＝３０００ｃｄ／ｍ２でのＤＣ駆動時の半減寿命は１９００時間を超えた。また、１１０℃の高温環境下での２時間の高温放置試験において、２ｍｍ２の発光部に発光ムラが発生することはなかった。 (Comparative Example 5)
As Comparative Example 5, an organic EL element was produced and characteristics were measured in the same manner as in Example 2 except that the electron injection layer 3d was not formed. Comparative Example 5 shows white light emission, and its characteristics are a driving voltage V = 5.0 V at a peak luminance Lp = 16000 cd / m 2 , a current efficiency L / J = 13 cd / A, and an initial condition in a high temperature environment of 85 ° C. The half-life at the time of DC driving with luminance Lp = 3000 cd / m 2 exceeded 1900 hours. Further, in the high temperature standing test for 2 hours in a high temperature environment of 110 ° C., no light emission unevenness occurred in the 2 mm 2 light emitting part.

（比較例６）
比較例６として、電子輸送層３ｃを電子輸送性材料ＥＴ２とＬｉｑとの混合層としたほかは、実施例２と同様に有機ＥＬ素子の作製及び特性の測定を行った。比較例６は白色発光を示し、その特性はピーク輝度Ｌｐ＝１６０００ｃｄ／ｍ２での駆動電圧Ｖ＝８．０Ｖ、電流効率Ｌ／Ｊ＝１１ｃｄ／Ａであり、８５℃の高温環境下における初期輝度Ｌｐ＝３０００ｃｄ／ｍ２でのＤＣ駆動時の半減寿命は２０００時間であった。また、１１０℃の高温環境下での２時間の高温放置試験において、２ｍｍ２の発光部に発光ムラが発生することはなかった。 (Comparative Example 6)
As Comparative Example 6, an organic EL device was produced and characteristics were measured in the same manner as in Example 2 except that the electron transport layer 3c was a mixed layer of the electron transport material ET2 and Liq. Comparative Example 6 shows white light emission, and its characteristics are a driving voltage V = 8.0 V at a peak luminance Lp = 16000 cd / m 2 , a current efficiency L / J = 11 cd / A, and an initial value in a high temperature environment of 85 ° C. The half-life at the time of DC driving at a luminance Lp = 3000 cd / m 2 was 2000 hours. Further, in the high temperature standing test for 2 hours in a high temperature environment of 110 ° C., no light emission unevenness occurred in the 2 mm 2 light emitting part.

（比較例７）
比較例７として、電子輸送層３ｃを電子輸送性材料ＥＴ３のみで形成したほかは、実施例３と同様に有機ＥＬ素子の作製及び特性の測定を行った。比較例７は白色発光を示し、その特性はピーク輝度Ｌｐ＝１６０００ｃｄ／ｍ２での駆動電圧Ｖ＝５．５Ｖ、電流効率Ｌ／Ｊ＝１４ｃｄ／Ａであり、８５℃の高温環境下における初期輝度Ｌｐ＝３０００ｃｄ／ｍ２でのＤＣ駆動時の半減寿命は１４００時間であった。また、１１０℃の高温環境下での2時間の高温放置試験において、２ｍｍ２の発光部に中央部が明るく周辺部が暗くなる発光ムラが発生し、ディスプレイとしては使用に堪えない発光状態であった。 (Comparative Example 7)
As Comparative Example 7, an organic EL device was produced and properties were measured in the same manner as in Example 3 except that the electron transport layer 3c was formed only from the electron transport material ET3. Comparative Example 7 shows white light emission, and its characteristics are a driving voltage V = 5.5 V at a peak luminance Lp = 16000 cd / m 2 , a current efficiency L / J = 14 cd / A, and an initial condition in a high temperature environment of 85 ° C. The half life at the time of DC driving at a luminance Lp = 3000 cd / m 2 was 1400 hours. Also, in a 2-hour high-temperature standing test under a high-temperature environment of 110 ° C., a light-emitting unevenness in which the central portion is bright and the peripheral portion is dark occurs in the 2 mm 2 light-emitting portion, which is a light-emitting state that cannot be used as a display. It was.

（比較例８）
比較例８として、電子注入層３ｄを形成しないほかは、実施例３と同様に有機ＥＬ素子の作製及び特性の測定を行った。比較例８は白色発光を示し、その特性はピーク輝度Ｌｐ＝１６０００ｃｄ／ｍ２での駆動電圧Ｖ＝６．０Ｖ、電流効率Ｌ／Ｊ＝１３ｃｄ／Ａであり、８５℃の高温環境下における初期輝度Ｌｐ＝３０００ｃｄ／ｍ２でのＤＣ駆動時の半減寿命は１９００時間を超えた。また、１１０℃の高温環境下での高温放置試験において、２ｍｍ２の発光部に発光ムラが発生することはなかった。 (Comparative Example 8)
As Comparative Example 8, an organic EL element was produced and characteristics were measured in the same manner as in Example 3 except that the electron injection layer 3d was not formed. Comparative Example 8 shows white light emission, and the characteristics are a driving voltage V = 6.0 V at a peak luminance Lp = 16000 cd / m 2 , a current efficiency L / J = 13 cd / A, and an initial condition in a high temperature environment of 85 ° C. The half-life at the time of DC driving with luminance Lp = 3000 cd / m 2 exceeded 1900 hours. Further, in the high temperature standing test under a high temperature environment of 110 ° C., no light emission unevenness occurred in the 2 mm 2 light emitting part.

（比較例９）
比較例９として、電子輸送層３ｃを電子輸送性材料ＥＴ４のみで形成したほかは、実施例４と同様に有機ＥＬ素子の作製及び特性の測定を行った。比較例９は白色発光を示し、その特性はピーク輝度Ｌｐ＝１６０００ｃｄ／ｍ２での駆動電圧Ｅ＝６．０Ｖ、電流効率Ｌ／Ｊ＝１４ｃｄ／Ａであり、８５℃の高温環境下における初期輝度Ｌｐ＝３０００ｃｄ／ｍ２でのＤＣ駆動時の半減寿命は１４００時間であった。また、１１０℃の高温環境下での２時間の高温放置試験において、２ｍｍ２の発光部に中央部が明るく周辺部が暗くなる発光ムラが発生し、ディスプレイとしては使用に堪えない発光状態であった。 (Comparative Example 9)
As Comparative Example 9, an organic EL device was produced and properties were measured in the same manner as in Example 4 except that the electron transport layer 3c was formed only from the electron transport material ET4. Comparative Example 9 shows white light emission, and its characteristics are a driving voltage E = 6.0 V at a peak luminance Lp = 16000 cd / m 2 , a current efficiency L / J = 14 cd / A, and an initial condition in a high temperature environment of 85 ° C. The half life at the time of DC driving at a luminance Lp = 3000 cd / m 2 was 1400 hours. Further, in a high temperature standing test for 2 hours in a high temperature environment of 110 ° C., a light emission unevenness in which the central portion is bright and the peripheral portion is dark occurs in the 2 mm 2 light emitting portion, and the light emitting state is unbearable as a display. It was.

（比較例１０）
比較例１０として、電子注入層３ｄを形成しないほかは、実施例４と同様に有機ＥＬ素子の作製及び特性の測定を行った。比較例１０は白色発光を示し、その特性はピーク輝度Ｌｐ＝１６０００ｃｄ／ｍ２での駆動電圧Ｖ＝６．７Ｖ、電流効率Ｌ／Ｊ＝１３ｃｄ／Ａであり、８５℃の高温環境下における初期輝度Ｌｐ＝３０００ｃｄ／ｍ２でのＤＣ駆動時の半減寿命は１９００時間を超えた。また、１１０℃の高温環境下での２時間の高温放置試験において、２ｍｍ２の発光部に発光ムラが発生することはなかった。 (Comparative Example 10)
As Comparative Example 10, an organic EL device was produced and characteristics were measured in the same manner as in Example 4 except that the electron injection layer 3d was not formed. Comparative Example 10 shows white light emission, and its characteristics are a driving voltage V = 6.7 V at a peak luminance Lp = 16000 cd / m 2 , a current efficiency L / J = 13 cd / A, and an initial value in a high-temperature environment of 85 ° C. The half-life at the time of DC driving with luminance Lp = 3000 cd / m 2 exceeded 1900 hours. Further, in the high temperature standing test for 2 hours in a high temperature environment of 110 ° C., no light emission unevenness occurred in the 2 mm 2 light emitting part.

（比較例１１）
比較例１１として、電子輸送層３ｃを電子輸送性材料ＥＴ５のみで形成したほかは、実施例５と同様に有機ＥＬ素子の作製及び特性の測定を行った。比較例１１は白色発光を示し、その特性はピーク輝度Ｌｐ＝１６０００ｃｄ／ｍ２での駆動電圧Ｖ＝４．５Ｖ、電流効率Ｌ／Ｊ＝１４ｃｄ／Ａであり、８５℃の高温環境下における初期輝度Ｌｐ＝３０００ｃｄ／ｍ２でのＤＣ駆動時の半減寿命は１０００時間であった。また、１１０℃の高温環境下での２時間の高温放置試験において、２ｍｍ２の発光部に中央部が明るく周辺部が暗くなる発光ムラが発生し、ディスプレイとしては使用に堪えない発光状態であった。 (Comparative Example 11)
As Comparative Example 11, an organic EL device was produced and properties were measured in the same manner as in Example 5 except that the electron transport layer 3c was formed only from the electron transport material ET5. Comparative Example 11 shows white light emission, and its characteristics are a driving voltage V = 4.5 V at a peak luminance Lp = 16000 cd / m 2 , a current efficiency L / J = 14 cd / A, and an initial condition in a high temperature environment of 85 ° C. The half-life at the time of DC driving at a luminance Lp = 3000 cd / m 2 was 1000 hours. Further, in a high temperature standing test for 2 hours in a high temperature environment of 110 ° C., a light emission unevenness in which the central portion is bright and the peripheral portion is dark occurs in the 2 mm 2 light emitting portion, and the light emitting state is unbearable as a display. It was.

（比較例１２）
比較例１２として、電子注入層３ｄを形成しないほかは、実施例５と同様に有機ＥＬ素子の作製及び特性の測定を行った。比較例１２は白色発光を示し、その特性はピーク輝度Ｌｐ＝１６０００ｃｄ／ｍ２での駆動電圧Ｖ＝５．５Ｖ、電流効率Ｌ／Ｊ＝１３ｃｄ／Ａであり、８５℃の高温環境下における初期輝度Ｌｐ＝３０００ｃｄ／ｍ２でのＤＣ駆動時の半減寿命は１９００時間を超えた。また、１１０℃の高温環境下での２時間の高温放置試験において、２ｍｍ２の発光部に発光ムラが発生することはなかった。 (Comparative Example 12)
As Comparative Example 12, an organic EL element was produced and characteristics were measured in the same manner as in Example 5 except that the electron injection layer 3d was not formed. Comparative Example 12 shows white light emission, and the characteristics are a driving voltage V = 5.5 V at a peak luminance Lp = 16000 cd / m 2 , a current efficiency L / J = 13 cd / A, and an initial condition in a high temperature environment of 85 ° C. The half-life at the time of DC driving with luminance Lp = 3000 cd / m 2 exceeded 1900 hours. Further, in the high temperature standing test for 2 hours in a high temperature environment of 110 ° C., no light emission unevenness occurred in the 2 mm 2 light emitting part.

かかる測定結果が示すように、実施例２〜５は、比較例６に対して駆動電圧が低く、また、比較例４，７，９及び１１に見られるような発光ムラは発生していない。したがって、発光層３ｂとして複数の発光層を積層する場合でも、少なくともＡｌｑ３よりも電子輸送能力の高い電子輸送性材料を電子輸送層３ｃに適用する構成においては、電子輸送層３ｃにリチウム錯体を混合することで有機ＥＬ素子のキャリアバランスを安定化させ、低電力で高温環境下での信頼性の高い素子を得ることが可能であることがわかる。また、比較例５，８，１０及び１２はそれぞれ比較例４，７，９及び１１に対して駆動電圧Ｖが高く、電子輸送層３ｃが直接第二電極４と接する構成ではリチウム錯体を混合することで電子輸送性材料のみで電子輸送層３ｃを形成する場合よりも駆動電圧Ｖの低減効果が低くなることがわかるが、実施例２〜５のようにさらに電子注入層３ｄを形成することで電子輸送性材料のみで電子輸送層３ｃを形成するのと同程度に駆動電圧Ｖを低減することができる。 As shown in the measurement results, the driving voltages of Examples 2 to 5 are lower than those of Comparative Example 6, and light emission unevenness as seen in Comparative Examples 4, 7, 9, and 11 does not occur. Therefore, even when stacking a plurality of light emitting layers as the light emitting layer 3b, in the structure for applying at least an electron transporting material having a high electron transporting capability than the Alq 3 electron transporting layer 3c, a lithium complex electron transporting layer 3c It can be seen that mixing makes it possible to stabilize the carrier balance of the organic EL element and to obtain an element with low power and high reliability in a high temperature environment. Further, Comparative Examples 5, 8, 10 and 12 have a higher driving voltage V than Comparative Examples 4, 7, 9 and 11, respectively, and in the configuration where the electron transport layer 3c is in direct contact with the second electrode 4, a lithium complex is mixed. Thus, it can be seen that the effect of reducing the driving voltage V is lower than that in the case of forming the electron transport layer 3c only with the electron transport material, but by further forming the electron injection layer 3d as in Examples 2-5. The drive voltage V can be reduced to the same extent as when the electron transport layer 3c is formed using only the electron transport material.

なお、本実施形態は、正孔注入輸送層３ａが単一層にて形成されるものであったが、本発明の有機ＥＬ素子は、正孔注入層及び正孔輸送層がそれぞれ順次積層されるものであってもよい。また、本発明は、電子輸送層が複数層形成される構成であっても適用可能であり、その場合、少なくとも最も陰極側に位置する電子輸送層に本発明を適用する。   In the present embodiment, the hole injection / transport layer 3a is formed as a single layer. However, in the organic EL device of the present invention, the hole injection layer and the hole transport layer are sequentially stacked. It may be a thing. The present invention can also be applied to a configuration in which a plurality of electron transport layers are formed. In this case, the present invention is applied to at least the electron transport layer located on the most cathode side.

本発明は、有機ＥＬ素子に関し、特に車載用表示器などの高温環境下での使用が想定される機器に用いられる有機ＥＬ素子に好適である。   The present invention relates to an organic EL element, and is particularly suitable for an organic EL element used in a device that is assumed to be used in a high-temperature environment such as a vehicle-mounted display.

１ 支持基板
２ 第一電極（陽極）
３ 有機層
３ａ 正孔注入輸送層
３ｂ 発光層（有機発光層）
３ｃ 電子輸送層
３ｄ 電子注入層
４ 第二電極（陰極）
1 Support substrate 2 First electrode (anode)
3 Organic layer 3a Hole injection transport layer 3b Light emitting layer (organic light emitting layer)
3c Electron transport layer 3d Electron injection layer 4 Second electrode (cathode)

Claims (6)

少なくとも有機発光層と電子輸送層とを陽極と陰極との間に積層形成してなる有機ＥＬ素子であって、
前記電子輸送層は、電子輸送性材料とリチウム錯体との混合層からなることを特徴とする有機ＥＬ素子。 An organic EL element formed by laminating at least an organic light emitting layer and an electron transport layer between an anode and a cathode,
The electron transport layer is an organic EL element comprising a mixed layer of an electron transport material and a lithium complex. 前記電子輸送性材料は、電子移動度が１０−５ｃｍ２／Ｖ・ｓ以上であることを特徴とする請求項１に記載の有機ＥＬ素子。 2. The organic EL device according to claim 1, wherein the electron transporting material has an electron mobility of 10 −5 cm 2 / V · s or more. 前記電子輸送性材料は、ＬＵＭＯエネルギーが３．０ｅＶより小さいことを特徴とする請求項１に記載の有機ＥＬ素子。 The organic EL device according to claim 1, wherein the electron transporting material has LUMO energy of less than 3.0 eV. 前記リチウム錯体は、リチウム８−キノリノラート（Ｌｉｑ）からなることを特徴とする請求項１に記載の有機ＥＬ素子。 The organic EL device according to claim 1, wherein the lithium complex is made of lithium 8-quinolinolate (Liq). 前記電子輸送層と前記陰極との間に、電子注入層が形成されてなることを特徴とする請求項１に記載の有機ＥＬ素子。 The organic EL device according to claim 1, wherein an electron injection layer is formed between the electron transport layer and the cathode. 前記電子注入層は、アルカリ金属化合物あるいはアルカリ金属錯体からなることを特徴とする請求項５に記載の有機ＥＬ素子。 The organic EL device according to claim 5, wherein the electron injection layer is made of an alkali metal compound or an alkali metal complex.
JP2010202379A 2010-09-09 2010-09-09 Organic el element Pending JP2012059962A (en)

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US9204511B2 (en) 2012-10-10 2015-12-01 Panasonic Intellectual Property Management Co., Ltd. Lighting apparatus and lighting fixture using same
JP2015044792A (en) * 2013-07-30 2015-03-12 東ソー株式会社 Triazine compound having azanaphthyl group and phenanthryl group, and organic electroluminescent element containing the same
JP2019071249A (en) * 2017-10-11 2019-05-09 Dic株式会社 Light-emitting device and image display apparatus
WO2020174301A1 (en) * 2019-02-26 2020-09-03 株式会社半導体エネルギー研究所 Display panel, and information processing device

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