JP2004079421A - Organic el element - Google Patents
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- JP2004079421A JP2004079421A JP2002240751A JP2002240751A JP2004079421A JP 2004079421 A JP2004079421 A JP 2004079421A JP 2002240751 A JP2002240751 A JP 2002240751A JP 2002240751 A JP2002240751 A JP 2002240751A JP 2004079421 A JP2004079421 A JP 2004079421A
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- 239000010410 layer Substances 0.000 claims abstract description 326
- 239000000758 substrate Substances 0.000 claims abstract description 61
- 239000012044 organic layer Substances 0.000 claims abstract description 54
- 238000002347 injection Methods 0.000 claims description 32
- 239000007924 injection Substances 0.000 claims description 32
- 239000000463 material Substances 0.000 claims description 22
- 238000000605 extraction Methods 0.000 claims description 12
- 239000003086 colorant Substances 0.000 claims description 6
- 230000003287 optical effect Effects 0.000 abstract description 14
- 150000001875 compounds Chemical class 0.000 description 54
- 239000010408 film Substances 0.000 description 52
- 229910052751 metal Inorganic materials 0.000 description 12
- 238000001704 evaporation Methods 0.000 description 11
- 239000002184 metal Substances 0.000 description 11
- 239000000126 substance Substances 0.000 description 11
- DCZNSJVFOQPSRV-UHFFFAOYSA-N n,n-diphenyl-4-[4-(n-phenylanilino)phenyl]aniline Chemical compound C1=CC=CC=C1N(C=1C=CC(=CC=1)C=1C=CC(=CC=1)N(C=1C=CC=CC=1)C=1C=CC=CC=1)C1=CC=CC=C1 DCZNSJVFOQPSRV-UHFFFAOYSA-N 0.000 description 10
- 230000005525 hole transport Effects 0.000 description 9
- 150000002894 organic compounds Chemical class 0.000 description 9
- 230000008020 evaporation Effects 0.000 description 8
- 239000000203 mixture Substances 0.000 description 8
- 238000000151 deposition Methods 0.000 description 7
- 239000011521 glass Substances 0.000 description 7
- 239000000470 constituent Substances 0.000 description 6
- 238000007789 sealing Methods 0.000 description 6
- 230000007423 decrease Effects 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 238000001228 spectrum Methods 0.000 description 5
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 4
- 229910052782 aluminium Inorganic materials 0.000 description 4
- AIYUHDOJVYHVIT-UHFFFAOYSA-M caesium chloride Chemical compound [Cl-].[Cs+] AIYUHDOJVYHVIT-UHFFFAOYSA-M 0.000 description 4
- ZYGHJZDHTFUPRJ-UHFFFAOYSA-N coumarin Chemical compound C1=CC=C2OC(=O)C=CC2=C1 ZYGHJZDHTFUPRJ-UHFFFAOYSA-N 0.000 description 4
- 230000008021 deposition Effects 0.000 description 4
- 229910003437 indium oxide Inorganic materials 0.000 description 4
- PJXISJQVUVHSOJ-UHFFFAOYSA-N indium(iii) oxide Chemical compound [O-2].[O-2].[O-2].[In+3].[In+3] PJXISJQVUVHSOJ-UHFFFAOYSA-N 0.000 description 4
- 239000002356 single layer Substances 0.000 description 4
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 3
- 229910052783 alkali metal Inorganic materials 0.000 description 3
- 150000001340 alkali metals Chemical class 0.000 description 3
- -1 aluminum quinolinol Chemical compound 0.000 description 3
- 238000000295 emission spectrum Methods 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- 229910052709 silver Inorganic materials 0.000 description 3
- 238000004544 sputter deposition Methods 0.000 description 3
- 239000010409 thin film Substances 0.000 description 3
- 229910052718 tin Inorganic materials 0.000 description 3
- TVIVIEFSHFOWTE-UHFFFAOYSA-K tri(quinolin-8-yloxy)alumane Chemical compound [Al+3].C1=CN=C2C([O-])=CC=CC2=C1.C1=CN=C2C([O-])=CC=CC2=C1.C1=CN=C2C([O-])=CC=CC2=C1 TVIVIEFSHFOWTE-UHFFFAOYSA-K 0.000 description 3
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 2
- NRCMAYZCPIVABH-UHFFFAOYSA-N Quinacridone Chemical compound N1C2=CC=CC=C2C(=O)C2=C1C=C1C(=O)C3=CC=CC=C3NC1=C2 NRCMAYZCPIVABH-UHFFFAOYSA-N 0.000 description 2
- 229910006404 SnO 2 Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 230000004888 barrier function Effects 0.000 description 2
- 229910052804 chromium Inorganic materials 0.000 description 2
- 229960000956 coumarin Drugs 0.000 description 2
- 235000001671 coumarin Nutrition 0.000 description 2
- 239000002019 doping agent Substances 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 229910052737 gold Inorganic materials 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 150000007857 hydrazones Chemical class 0.000 description 2
- 150000002460 imidazoles Chemical class 0.000 description 2
- 229910052741 iridium Inorganic materials 0.000 description 2
- AMXOYNBUYSYVKV-UHFFFAOYSA-M lithium bromide Chemical compound [Li+].[Br-] AMXOYNBUYSYVKV-UHFFFAOYSA-M 0.000 description 2
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 description 2
- PQXKHYXIUOZZFA-UHFFFAOYSA-M lithium fluoride Chemical compound [Li+].[F-] PQXKHYXIUOZZFA-UHFFFAOYSA-M 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 229910052750 molybdenum Inorganic materials 0.000 description 2
- 230000007935 neutral effect Effects 0.000 description 2
- 150000004767 nitrides Chemical class 0.000 description 2
- 150000004866 oxadiazoles Chemical class 0.000 description 2
- 230000006798 recombination Effects 0.000 description 2
- 238000005215 recombination Methods 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- YYMBJDOZVAITBP-UHFFFAOYSA-N rubrene Chemical compound C1=CC=CC=C1C(C1=C(C=2C=CC=CC=2)C2=CC=CC=C2C(C=2C=CC=CC=2)=C11)=C(C=CC=C2)C2=C1C1=CC=CC=C1 YYMBJDOZVAITBP-UHFFFAOYSA-N 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 238000002834 transmittance Methods 0.000 description 2
- 125000005259 triarylamine group Chemical group 0.000 description 2
- 238000007740 vapor deposition Methods 0.000 description 2
- 229910052725 zinc Inorganic materials 0.000 description 2
- VERMWGQSKPXSPZ-BUHFOSPRSA-N 1-[(e)-2-phenylethenyl]anthracene Chemical class C=1C=CC2=CC3=CC=CC=C3C=C2C=1\C=C\C1=CC=CC=C1 VERMWGQSKPXSPZ-BUHFOSPRSA-N 0.000 description 1
- 125000001637 1-naphthyl group Chemical group [H]C1=C([H])C([H])=C2C(*)=C([H])C([H])=C([H])C2=C1[H] 0.000 description 1
- BRSRUYVJULRMRQ-UHFFFAOYSA-N 1-phenylanthracene Chemical class C1=CC=CC=C1C1=CC=CC2=CC3=CC=CC=C3C=C12 BRSRUYVJULRMRQ-UHFFFAOYSA-N 0.000 description 1
- YWLAKGDPVNCEES-UHFFFAOYSA-N 2-(2h-pyran-2-yl)propanedinitrile Chemical compound N#CC(C#N)C1OC=CC=C1 YWLAKGDPVNCEES-UHFFFAOYSA-N 0.000 description 1
- DQFBYFPFKXHELB-UHFFFAOYSA-N Chalcone Natural products C=1C=CC=CC=1C(=O)C=CC1=CC=CC=C1 DQFBYFPFKXHELB-UHFFFAOYSA-N 0.000 description 1
- 229910001218 Gallium arsenide Inorganic materials 0.000 description 1
- WTKZEGDFNFYCGP-UHFFFAOYSA-N Pyrazole Chemical class C=1C=NNC=1 WTKZEGDFNFYCGP-UHFFFAOYSA-N 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- ONMRPBVKXUYVER-UHFFFAOYSA-N [Ge+2].[O-2].[In+3] Chemical compound [Ge+2].[O-2].[In+3] ONMRPBVKXUYVER-UHFFFAOYSA-N 0.000 description 1
- 239000004840 adhesive resin Substances 0.000 description 1
- 229920006223 adhesive resin Polymers 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 229910052784 alkaline earth metal Inorganic materials 0.000 description 1
- 150000001342 alkaline earth metals Chemical class 0.000 description 1
- 125000003277 amino group Chemical group 0.000 description 1
- 239000010405 anode material Substances 0.000 description 1
- 150000004982 aromatic amines Chemical class 0.000 description 1
- 230000002238 attenuated effect Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 239000000872 buffer Substances 0.000 description 1
- XJHCXCQVJFPJIK-UHFFFAOYSA-M caesium fluoride Inorganic materials [F-].[Cs+] XJHCXCQVJFPJIK-UHFFFAOYSA-M 0.000 description 1
- 125000000609 carbazolyl group Chemical class C1(=CC=CC=2C3=CC=CC=C3NC12)* 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 235000005513 chalcones Nutrition 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 238000010549 co-Evaporation Methods 0.000 description 1
- 230000000295 complement effect Effects 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- UKJLNMAFNRKWGR-UHFFFAOYSA-N cyclohexatrienamine Chemical group NC1=CC=C=C[CH]1 UKJLNMAFNRKWGR-UHFFFAOYSA-N 0.000 description 1
- 239000003599 detergent Substances 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 238000005401 electroluminescence Methods 0.000 description 1
- 239000000284 extract Substances 0.000 description 1
- 150000008376 fluorenones Chemical class 0.000 description 1
- 150000004820 halides Chemical class 0.000 description 1
- 229910052738 indium Inorganic materials 0.000 description 1
- 229940079865 intestinal antiinfectives imidazole derivative Drugs 0.000 description 1
- 238000007733 ion plating Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000010030 laminating Methods 0.000 description 1
- 239000002346 layers by function Substances 0.000 description 1
- 239000003446 ligand Substances 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- HSZCZNFXUDYRKD-UHFFFAOYSA-M lithium iodide Inorganic materials [Li+].[I-] HSZCZNFXUDYRKD-UHFFFAOYSA-M 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 239000012788 optical film Substances 0.000 description 1
- 239000011368 organic material Substances 0.000 description 1
- 125000002524 organometallic group Chemical group 0.000 description 1
- 150000007978 oxazole derivatives Chemical class 0.000 description 1
- 229960003540 oxyquinoline Drugs 0.000 description 1
- 125000001037 p-tolyl group Chemical group [H]C1=C([H])C(=C([H])C([H])=C1*)C([H])([H])[H] 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 125000002080 perylenyl group Chemical group C1(=CC=C2C=CC=C3C4=CC=CC5=CC=CC(C1=C23)=C45)* 0.000 description 1
- 150000004986 phenylenediamines Chemical class 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 229920000123 polythiophene Polymers 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
- 150000003222 pyridines Chemical class 0.000 description 1
- 150000003230 pyrimidines Chemical class 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- MCJGNVYPOGVAJF-UHFFFAOYSA-N quinolin-8-ol Chemical compound C1=CN=C2C(O)=CC=CC2=C1 MCJGNVYPOGVAJF-UHFFFAOYSA-N 0.000 description 1
- 150000003252 quinoxalines Chemical class 0.000 description 1
- 230000009103 reabsorption Effects 0.000 description 1
- 238000002310 reflectometry Methods 0.000 description 1
- SBIBMFFZSBJNJF-UHFFFAOYSA-N selenium;zinc Chemical compound [Se]=[Zn] SBIBMFFZSBJNJF-UHFFFAOYSA-N 0.000 description 1
- 229910052814 silicon oxide Inorganic materials 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
- 238000010025 steaming Methods 0.000 description 1
- PJANXHGTPQOBST-UHFFFAOYSA-N stilbene Chemical class C=1C=CC=CC=1C=CC1=CC=CC=C1 PJANXHGTPQOBST-UHFFFAOYSA-N 0.000 description 1
- 229910052712 strontium Inorganic materials 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
- 229940042055 systemic antimycotics triazole derivative Drugs 0.000 description 1
- IFLREYGFSNHWGE-UHFFFAOYSA-N tetracene Chemical compound C1=CC=CC2=CC3=CC4=CC=CC=C4C=C3C=C21 IFLREYGFSNHWGE-UHFFFAOYSA-N 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 150000003852 triazoles Chemical class 0.000 description 1
- 238000004506 ultrasonic cleaning Methods 0.000 description 1
- 238000007738 vacuum evaporation Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
Images
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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
- H10K50/80—Constructional details
- H10K50/85—Arrangements for extracting light from the devices
- H10K50/856—Arrangements for extracting light from the devices comprising reflective means
-
- 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
- H10K2102/302—Details of OLEDs of OLED structures
- H10K2102/3023—Direction of light emission
- H10K2102/3026—Top emission
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- Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Electroluminescent Light Sources (AREA)
Abstract
Description
【０００１】
【発明の属する技術分野】
本発明は、有機化合物を用いた有機ＥＬ素子に関し、さらに詳細には、発光を有効に取り出すことができ発光輝度のバラツキの少ない有機ＥＬ素子を提供するための光学モデルを適用した有機ＥＬ素子に関する。
【０００２】
【従来の技術】
有機ＥＬ素子は、ホール注入電極上にトリフェニルジアミン（ＴＰＤ）などのホール輸送材料を蒸着により薄膜とし、さらにアルミキノリノール錯体（Ａｌｑ３）などの蛍光物質を発光層として積層し、さらにＭｇなどの仕事関数の小さな金属電極（電子注入電極）を形成した基本構成を有する素子である。有機ＥＬ素子は、自発光型の薄膜構造物であって、１０Ｖ前後の電圧で数１００から数１００００ｃｄ／ｍ２ときわめて高い輝度が得られることで注目されている。
【０００３】
有機ＥＬ素子は、前述のように基板上に電子注入電極、有機層、ホール注入電極等を有する有機ＥＬ構造体が成膜されている基本構成を有し、通常、発光した光はホール注入電極を介して基板側から取り出される。
【０００４】
ところで、一般に有機ＥＬ素子では、発光種の発光スペクトルは外部に出る間に素子内部で光学的な干渉を起こし、変調されることが知られている。このため、同一の発光材料を持つ有機ＥＬ素子であっても、光学系が異なれば外部に発光されるスペクトルやその強度が変化してしまう。
【０００５】
この光学変調の最も大きなものとしては、特開平４−３２８２９５号公報に開示されているように、前方に発光された光と、後方に発光され金属面（電子注入電極）で反射した光との干渉によるものである。この効果は、発光点と金属面との距離で決まる関数で表せるので、所望の変調スペクトルを得るための光学的構成がわかる。しかし、さらに精密な予想を行う場合には誤差が大きく、これでも不十分であり、さらに考慮すべきパラメータを必要としていた。
【０００６】
さらに、特開平７−２４０２７７号公報において、ガラス／透明電極界面での反射光が干渉して有機ＥＬ素子の発光光を変調するという問題が明らかになった。しかし、同公報中にはある狭い範囲の特定波長の発光強度を、光学変調を利用して強くするためには、ガラス／透明導電膜界面と有機多層部を挟む金属面までの光学膜厚を特定の値にすればよいことが述べられているにすぎない。
【０００７】
ある任意の光学系があったとき、上記したパラメータ以外の干渉により、どの程度変調されるのかが予想できなくては、スペクトル変調についての詳細な検討は困難であり、素子のさらなる最適化への光学設計を困難にしていた。また、上記モデルは何れも基板側から光を取り出す素子を対象としており、基板と反対側である上面から光を取り出す構造の素子についての検討はなされていない。
【０００８】
上述のように、有機ＥＬ素子の構成膜厚が変わると外部に発せられる光のスペクトルや輝度が変化する。特に複数の発光層を有する白色発光素子においては、各発光層からの発光スペクトルが変化すると、最終的に外部に現れる白色の色純度が変化してしまい、高効率かつ高純度のディスプレーとすることが困難であり、均一な製品を供給することを困難にしていた。
【０００９】
なお、特開２０００−２４３５７３号公報には、透光性の基板上に少なくとも、透明電極と、発光層を含む有機化合物材料層と、金属電極と、が順に積層されて形成され、発光層の発光界面を境にした透明電極側の有機化合物材料層又は透明電極に最大屈折率段差の界面を有する有機エレクトロルミネッセンス素子であって、透明電極側の有機化合物材料層は、有機化合物材料層の透明電極側の膜厚に対する発光効率特性における１次極大値及び２次極大値の発光効率の間の極小値を生じる膜厚以上となるように、形成されている有機エレクトロルミネッセンス素子が記載されている。
【００１０】
しかし、この文献で検討されているのは基板側から光り取り出しを行うボトムタイプの素子であり、上面光取り出しに関する検討はなされていない。しかも、検討されている発光色は単独のピーク波長λを有する単色光であり、この波長の１／４の奇数倍として素子構造内の厚さを規定しているが、２層以上の発光層から得られる発光色を合成して白色発光を得る素子に関する検討はなされていない。また、素子の積層構成により白色の色バランスが悪化するといった課題も提示されてはいない。
【００１１】
一方、特開２０００−３２３２７７号公報には、製造が簡単で、光の外部取り出し効率の高い有機エレクトロルミネッセンス多色ディスプレイとその製造方法を提供することを目的として、各々が透明基板上に順に積層された、透明電極と、発光層を含む有機化合物材料層と、金属電極と、からなり、発光層が異なる有機化合物材料からなりかつ異なる発光色を呈する有機エレクトロルミネッセンス素子の複数からなる有機エレクトロルミネッセンス多色ディスプレイであって、発光層を除く有機化合物材料層の同一機能を有する何れかの機能層は発光色に対応してそれぞれ異なる膜厚を有する有機エレクトロルミネッセンス多色ディスプレイが開示されている。
【００１２】
しかし、この文献で検討されているのはボトム取り出しで、しかもＲ、Ｇ、Ｂ塗り分けタイプのフルカラーディスプレイであり、２種以上の発光層を積層した白色発光に関する検討はなされていない。
【００１３】
【発明が解決しようとする課題】
本発明の目的は、従来検討されていない上面光取り出し型の構造を有する有機ＥＬ素子において、好ましくは２層以上の発光層から白色発光を得る素子において、素子内部での光学モデルを確立し、効率の良い、白色の色度に優れた有機ＥＬ素子を提供することである。
【００１４】
【課題を解決するための手段】
すなわち上記目的は以下の本発明の構成により達成される。
（１） 少なくとも１つの発光ピークを持つ１種の発光層を有し、基板と反対側の上面から取り出し光を得る有機ＥＬ素子であって、
前記基板とこの基板上に可視光反射率５０％以上を有する反射層と、陽極と、発光層を有する有機層と、陰極である透明電極とを少なくとも順次有し、
前記発光層の中間点から陽極下端面までの総膜厚が４５ｎｍ〜１６０ｎｍであり、前記発光層中間点から陰極上端面までの総膜厚が１２０ｎｍ〜２９０ｎｍである有機ＥＬ素子。
（２） 前記反射層が陽極であり、
前記発光層中間点から陽極上端面までの総膜厚が４５ｎｍ〜１６０ｎｍであり、前記発光層中間点から陰極上端面までの総膜厚が１２０ｎｍ〜２９０ｎｍである上記（１）の有機ＥＬ素子。
（３） 前記発光層を２種以上有し、この２種以上の発光層の合成光により基板と反対側の上面から白色の取り出し光を得、
少なくとも最も陽極側に位置する下部発光層と最も陰極側に位置する上部発光層との界面あるいはこれらの中間点から陽極下端面までの総膜厚が４５ｎｍ〜１００ｎｍであり、前記界面あるいは中間点から陰極上端面までの総膜厚が１００ｎｍ〜２６０ｎｍである上記（１）の有機ＥＬ素子。
（４） 前記下部発光層と上部発光層との界面あるいはこれらの中間点から陽極下端面までの総膜厚が４５ｎｍ〜１３０ｎｍであり、
陽極の膜厚が２５〜７０ｎｍである上記（３）の有機ＥＬ素子。
（５） 前記下部発光層と上部発光層との界面あるいはこれらの中間点から陰極上端面までの総膜厚が１００ｎｍ〜２６０ｎｍであり、
陰極である透明電極の膜厚が５０ｎｍ〜１４０ｎｍである上記（３）または（４）の有機ＥＬ素子。
（６） 前記陰極の少なくとも一部が透明電極であって、その屈折率が１．７〜２．０、前記発光層を含む有機層の屈折率が１．６〜１．８、前記陽極が透明電極でありその屈折率が１．６〜２．０である上記（１）〜（５）のいずれかの有機ＥＬ素子。
（７） 前記下部発光層と上部発光層との界面あるいはこれらの中間点から陽極下端面までの膜厚（ｎｍ）と屈折率の積の総和をＡ、
Ａ＝（ａ１×ｎ２）＋（ａ２×ｎ３）
（ａ１は陽極の膜厚、ｎ２は陽極の屈折率、ａ２は下部発光層を含む下側有機層の膜厚、ｎ３は下部発光層５を含む下側有機層の屈折率）、
前記界面あるいは中間点から陰極上端面までの膜厚（ｎｍ）と屈折率の積の総和をＢ、
Ｂ＝（ｂ１×ｎ４）＋（ｂ２×ｎ５）
（ｂ１は上部発光層を含む上側有機層の膜厚、ｎ４は上部発光層を含む上側有機層の屈折率、ｂ２は透明陰極の膜厚、ｎ５は透明陰極の屈折率、）
とすると、
Ａ＝７２〜２４８、
Ｂ＝１６５〜４９６、
である上記（３）の有機ＥＬ素子。
（８） 前記反射層が陽極であり、
前記下部発光層と上部発光層との界面あるいはこれらの中間点から陽極上端面までの総膜厚が４５ｎｍ〜１３０ｎｍであり、前記界面あるいは中間点から陰極上端面までの総膜厚が１００ｎｍ〜２９０ｎｍである上記（３）の有機ＥＬ素子。
（９） 前記下部発光層と上部発光層との界面あるいはこれらの中間点から陰極上端面までの総膜厚が１００ｎｍ〜２６０ｎｍであり、陰極である透明電極の膜厚が４０ｎｍ〜１４０ｎｍである上記（８）の有機ＥＬ素子。
（１０） 前記陰極の少なくとも一部が透明陰極であって、その屈折率が１．７〜２．０、前記発光層を含む有機層の屈折率が１．６〜１．８である上記（８）または（９）の有機ＥＬ素子。
（１１） 前記下部発光層と上部発光層の界面あるいはこれらの中間点から陽極上端部までの膜厚（ｎｍ）と屈折率の積の総和をＡ、
Ａ＝（ａ２×ｎ３）
（ａ２は下部発光層を含む下側有機層の膜厚、ｎ３は下部発光層を含む下側有機層の屈折率）、
前記界面あるいはこれらの中間点から陰極上端部までの膜厚（ｎｍ）と屈折率の積の総和をＢ、
Ｂ＝（ｂ１×ｎ４）＋（ｂ２×ｎ５）
（ｂ１は上部発光層を含む上側有機層の膜厚、ｎ２は上部発光層を含む上側有機層の屈折率、ｂ２は透明電極の膜厚、ｎ３は透明電極の屈折率）、
とすると、
Ａ＝７２〜２３４
Ｂ＝１６４〜４９６
である上記（８）の有機ＥＬ素子。
【００１５】
（１２） 異なる発光ピークを有する２種以上の発光層を有し、この２種以上の発光層の合成光により基板と反対側の上面から白色の取り出し光を得る有機ＥＬ素子であって、
前記基板と、この基板上に可視光反射率５０％以上を有する反射層と、陽極と、少なくとも最も陽極側に位置する下部発光層と最も陰極側に位置する上部発光層とを有する有機層と、陰極である透明電極とを順次有し、
前記下部発光層と上部発光層との界面あるいはこれらの中間点から陽極下端面までの膜厚（ｎｍ）と屈折率の積の総和をＡ、
Ａ＝（ａ１×ｎ２）＋（ａ２×ｎ３）
（ａ１は陽極の膜厚、ｎ２は陽極の屈折率、ａ２は下部発光層を含む下側有機層の膜厚、ｎ３は下部発光層５を含む下側有機層の屈折率）、
前記界面あるいは中間点から陰極上端面までの膜厚（ｎｍ）と屈折率の積の総和をＢ、
Ｂ＝（ｂ１×ｎ４）＋（ｂ２×ｎ５）
（ｂ１は上部発光層を含む上側有機層の膜厚、ｎ４は上部発光層を含む上側有機層の屈折率、ｂ２は透明陰極の膜厚、ｎ５は透明陰極の屈折率、）
とすると、
Ａ＝７２〜２４８、
Ｂ＝１６５〜４９６、
である有機ＥＬ素子。
（１３） 前記反射層が陽極であり、
前記下部発光層と上部発光層の界面あるいはこれらの中間点から陽極上端部までの膜厚（ｎｍ）と屈折率の積の総和をＡ、
Ａ＝（ａ２×ｎ３）
（ａ２は下部発光層を含む下側有機層の膜厚、ｎ３は下部発光層を含む下側有機層の屈折率）、
前記界面あるいはこれらの中間点から陰極上端部までの膜厚（ｎｍ）と屈折率の積の総和をＢ、
Ｂ＝（ｂ１×ｎ４）＋（ｂ２×ｎ５）
（ｂ１は上部発光層を含む上側有機層の膜厚、ｎ２は上部発光層を含む上側有機層の屈折率、ｂ２は透明電極の膜厚、ｎ３は透明電極の屈折率）、
とすると、
Ａ＝７２〜２３４
Ｂ＝１６４〜４９６
である上記（１２）の有機ＥＬ素子。
（１４） 前記２種以上の発光層を構成するホスト材料が同一である上記（３）〜（１３）のいずれかの有機ＥＬ素子。
（１５） 前記２種以上の発光層の発光色は、４５０ｎｍ〜５００ｎｍの青色、及び５６０ｎｍ〜６００ｎｍの黄色である上記（３）〜（１４）のいずれかの有機ＥＬ素子。
（１６） １種類または２種類以上の発光層を有し、基板と反対側の上面から白色の取り出し光を得る有機ＥＬ素子であって、
前記基板とこの基板上に可視光反射率５０％以上を有する反射層と、この反射層を陽極とし、少なくとも最も陽極側に位置する下部発光層と最も陰極側に位置する上部発光層とを有する有機層と、無機電子注入層と、陰極である透明電極とを順次有し、
前記無機電子注入層の膜厚が０．１ｎｍ〜５ｎｍで、屈折率が１．６〜２．６である有機ＥＬ素子。
【００１６】
【発明の実施の形態】
本発明の有機ＥＬ素子は、少なくとも１つの発光ピークを持つ１種の発光層を有し、基板と反対側の上面から取り出し光を得る有機ＥＬ素子であって、
前記基板とこの基板上に可視光反射率５０％以上を有する反射層と、陽極と、発光層を有する有機層と、陰極である透明電極とを少なくとも順次有し、
前記発光層の中間点から陽極下端面までの総膜厚が４５ｎｍ〜１６０ｎｍであり、前記発光層中間点から陰極上端面までの総膜厚が１２０ｎｍ〜２９０ｎｍであるものである。
【００１７】
また、好ましくは前記発光層を２種以上有し、この２種以上の発光層の合成光により基板と反対側の上面から白色の取り出し光を得、少なくとも最も陽極側に位置する下部発光層と最も陰極側に位置する上部発光層との界面あるいはこれらの中間点から陽極下端面までの総膜厚が４５ｎｍ〜１００ｎｍであり、前記界面あるいは中間点から陰極上端面までの総膜厚が１００ｎｍ〜２６０ｎｍであるものである。
【００１８】
このように、基板と反対側の上面から取り出し光、好ましくは２種以上の発光層の合成光により白色の取り出し光を得る有機ＥＬ素子において、発光層あるいは２種以上の発光層の場合には上部発光層および下部発光層より、基板側と陰極側の各界面までの距離を規制することにより、高効率で高純度の白色発光を取り出すことができる。
【００１９】
すなわち、本発明者らの検討によると、発光層の中点、または２層以上の発光層同士の界面、あるいは最外層発光層同士の中間点から基板側である陽極下端面までの総膜厚と、その反対側である陰極上端面までの総膜厚を最適化することで、発光光取り出しの効率を向上させ、白色の色バランスを整えて高純度の白色発光を得ることができる。
【００２０】
次ぎに、図を参照しつつ、本発明の有機ＥＬ素子についてより詳細に説明する。図１は、本発明の有機ＥＬ素子の基本構成を示す概略断面図である。図において、有機ＥＬ素子は基板１上に、光反射層２と、透明電極である陽極３と、有機ホール注入輸送層４と、第１の発光層（下部発光層）５と、第２の発光層（上部発光層）６と、有機電子注入輸送層７と、無機電子注入層８と、透明電極である陰極９とが順次積層されている。なお、発光層５，６は単層であってもよい。
【００２１】
本発明では、発光層は好ましくは図示例のように第１の発光層（下部発光層）５、第２の発光層（上部発光層）６の２層構造、または単層構造、あるいは３層以上の複数層により構成される。そして、これら複数の発光層５，６からの発光光が合成され、好ましくは白色の取り出し光が得られる。このため、図示例のような２層の発光層から白色光を得る場合、例えば青色と橙色等のように、互いに補色関係にある発光が得られるよう、それぞれの発光層の発光を調製することが望ましい。また、発光層が３層以上ある場合には、例えばＲＧＢの３原色を発光させ、白色を得るようにしても良いし、最終的な合成光が白色になるように各発光層の発光色を調製すればよい。
【００２２】
本発明では、単層、あるいは上記のような複数の発光層からの発光色により、取り出し光、好ましくは白色の取り出し光を得る素子であって、基板と反対側の上面（陰極側）から光を取り出す構造の素子において、効率よく、白色の純度に優れた取り出し光が得られる素子構成を提供する。
【００２３】
本発明者らの検討によると、白色取り出し光の効率、色純度を最適化するためには、構成層の膜厚が以下の関係にあると良いことが判明した。すなわち、前記下部発光層と上部発光層との界面あるいはこれらの中間点から陽極下端面ないし反射層上端面までの総膜厚をａ、前記界面あるいは中間点から陰極上端面（つまり陰極と空気との界面）までの総膜厚をｂとすると、
〔単一発光層の場合〕
ａ＝４５ｎｍ〜１６０ｎｍ、好ましくは６０〜１４０ｎｍ、
ｂ＝１２０ｎｍ〜２９０ｎｍ、好ましくは１４０〜２５０ｎｍ、
〔２種以上の発光層の場合〕
ａ＝４５ｎｍ〜１３０ｎｍ、好ましくは６０〜１１０ｎｍ、
ｂ＝１００ｎｍ〜２６０ｎｍ、好ましくは１１０〜１８０ｎｍ、
の範囲とするとよい。
【００２４】
また、反射層が陽極を兼ねる場合には、以下のようになる。
〔単一発光層の場合〕
ａ＝４５ｎｍ〜１６０ｎｍ、好ましくは６０〜１４０ｎｍ、
ｂ＝１２０ｎｍ〜２９０ｎｍ、好ましくは１４０〜２５０ｎｍ、
〔２種以上の発光層の場合〕
ａ＝４５ｎｍ〜１３０ｎｍ、好ましくは６０〜１１０ｎｍ、
ｂ＝１００ｎｍ〜２９０ｎｍ、好ましくは１１０〜１８０ｎｍ、
である。
【００２５】
ここで、前記発光層の中間点とは単一発光層の膜厚方向における中間点をいう。また、前記界面あるいは中間点とは、第１の発光層（下部発光層）５、第２の発光層（上部発光層）６の２層構造の場合には、これらの界面であり、２層以上有する場合には下部発光層５と上部発光層６の間の中間点をいう。通常、発光は２つの発光層の界面で発生すると想定して問題ないが、発光層を２層以上有する場合にも最上部の発光層と最下部の発光層の中間地点を界面と擬制しても問題はない。
【００２６】
また、上記膜厚範囲において、特に陽極の膜厚が２５〜５０ｎｍ、より好ましくは３５〜４５ｎｍであり、陰極である透明電極の膜厚が４０ｎｍ〜１４０ｎｍ、より好ましくは９０〜１２０ｎｍとするとよい。
【００２７】
ここで、各構成層の屈折率について検討する。基板１の屈折率ｎ１としては、通常ガラス基板等が用いられ、この場合にはｎ１＝１．５０〜１．５４程度である。次ぎに陽極２，３は、通常、ＩＴＯ等の透明導電膜が用いられ、この場合にはｎ２＝１．６〜２．０程度である。さらに、下部発光層５を含む有機層５，４の屈折率は、通常１．６〜１．８であり、上部発光層６を含む有機層６，７の屈折率は、同様に１．６〜１．８である。なお、無機電池注入層８は、極めて膜厚が薄いため、ここでは無視する。そして、陰極である透明電極の屈折率は、通常１．７〜２．０程度である。なお、空気の屈折率は、この明細書では１．０として扱うこととする。
【００２８】
上記各構成層の屈折率の関係を見ると、基板１／透明電極（陽極）３の界面、および透明電極（陰極）９／空気の界面での屈折率の変化が最も大きくなることがわかる。従って、発光光は主にこれらの界面で反射することとなるが、本発明では反射層を有するので、陽極方向に進んだ光はこの反射層の表面で反射する。このため、発光中心である発光層界面からこれらの界面、反射層表面までの距離を規制することで、取り出される発光光の効率と、白色の純度を最適化できることがわかる。
【００２９】
すなわち、発光中心で生じた発光は、基板側と基板と反対側の上面側に向かう。なお、ここでは基板面と垂直方向以外の光はモデルを単純化するために無視することとする。そして、上面側に向かった光は、透明陰極９と外気との界面でその一部が反射される。一方、基板側に向かった光は、反射層２で少なくともその一部が反射され、上面側に向かう。従って、これら２つの光路長を最適化することで、上面に向かう光と、基板側に向かう光の干渉を極力抑え、効率の良い光取り出しを行わせることができる。
【００３０】
このため、上記膜厚と屈折率との関係を表すと以下のようになる。
前記下部発光層と上部発光層との界面あるいはこれらの中間点から陽極下端面までの膜厚（ｎｍ）と屈折率の積の総和をＡ、
Ａ＝（ａ１×ｎ２）＋（ａ２×ｎ３）
（ａ１は陽極の膜厚、ｎ２は陽極の屈折率、ａ２は下部発光層５を含む有機層４，５の膜厚、ｎ３は下部発光層５を含む有機層４，５の屈折率）、
前記界面あるいは中間点から陰極上端面までの膜厚（ｎｍ）と屈折率の積の総和をＢ、
Ｂ＝（ｂ１×ｎ４）＋（ｂ２×ｎ５）
（ｂ１は上部発光層６を含む有機層６，７の膜厚、ｎ４は上部発光層６を含む有機層６，７の屈折率、ｂ２は透明陰極の膜厚、ｎ５は透明陰極の屈折率、）とすると、
Ａ＝７２〜１９０、好ましくは１０３〜１５３、
Ｂ＝１６４〜５２０、好ましくは２４９〜４５６、
となる。
【００３１】
なお、本発明において、上記屈折率、および光取り出し光率など取り出し光の評価は、波長４００〜７００ｎｍの帯域の光について、これを満たすものであることが好ましい。
【００３２】
本発明において、有機ＥＬ構造体を形成する基板としては、非晶質基板（例えばガラス、石英など）、結晶基板（例えば、Ｓｉ、ＧａＡｓ、ＺｎＳｅ、ＺｎＳ、ＧａＰ、ＩｎＰなど）、あるいは透明プラスチックなどの樹脂が挙げられ、また、これらの結晶基板に結晶質、非晶質あるいは金属のバッファ層を形成した基板も用いることができる。また、金属基板としては、Ｍｏ、Ａｌ、Ｐｔ、Ｉｒ、Ａｕ、Ｐｄなどを用いることができ、好ましくはガラス基板が用いられる。また、基板側から光を取り出さない構造であるため、Ｓｉ等の結晶基板も好ましい。
【００３３】
反射層は、発光層から発した光の５０％以上、好ましくは８０％以上、さらに好ましくは９０％以上の光を反射する機能を有する。反射層の反射率が低下すると外部への取り出し光が減少し、光取り出し効率が低下してくる。一方、反射率があまり高すぎると、逆にコントラスト比が低下するなどの弊害が生じる場合もある。
【００３４】
反射層の材質としては、特に限定されるものではないが、金属、またはその酸化物、窒化物等を挙げることができる。具体的には、Ｍｏ，Ｃｒ，Ａｌ，Ａｇ，Ｔｉ等の金属元素単体、あるいはその合金、酸化物、窒化物等を挙げることができ、これらのなかでもＡｇ，Ａｌ等が反射率が高いことから好ましい。しかし、陽極にＩＴＯ等を使用する場合には電触を防止するため、ＴｉＮ等のバリア層あるいはバリア機能を有する反射層が必要になる。反射層の膜厚は、用いる材料や、設計する反射率により異なるが、通常３０〜３００ｎｍ、特に５０〜２５０ｎｍ程度である。
【００３５】
陽極は、導電性を有する電極材料であれば特に限定されるものではないが、ホール注入性を有し、素子設計上要求される仕事関数等を最適化できる材料が好ましい。このような陽極材料としては、具体的には、錫ドープ酸化インジウム（ＩＴＯ）、亜鉛ドープ酸化インジウム（ＩＺＯ）、ＺｎＯ、ＳｎＯ２、Ｉｎ２Ｏ３などの透明電極を用いることが好ましい。本来、陽極側から積極的に光を取り出すものではないが、上記特性を有する材料である点からこれらの材料が好ましく、特に上記屈折率の関係からは、ＩＴＯ、ＩＺＯ等が好ましい。
【００３６】
また、陽極の厚さは２５〜５０ｎｍ程度とすることが好ましい。素子の信頼性を向上させるために駆動電圧が低いことが必要であるが、好ましいシート抵抗のものとして、２０〜６０Ω／□（膜厚５０〜３００ｎｍ）のＩＴＯが挙げられる。実際に使用する場合には、ＩＴＯ等の陽電極界面での反射による干渉効果が、光取り出し効率や色純度を十分に満足するように、電極の膜厚や光学定数を設定すればよい。
【００３７】
さらに、陽極と反射層とが一体となっていてもよい。つまり、陽極が反射層として機能してもよい。このような陽極兼反射層の構成材料としては、酸化ゲルマニウムインジウム（ＧｅＯＩｎ）、あるいは酸化ケイ素（ＳｉＯ２ ）に金属（例えばＦｅ，Ｎｉ，Ｃｒ，Ｉｎ，Ｚｎ，Ａｇ，Ａｕ，Ｃｕ等）元素を添加したもの等を用いることができる。
【００３８】
陽極兼反射層の膜厚も、上記陽極と同様である。
【００３９】
無機電子注入輸送層は、有機の電子注入輸送層等との組み合わせにおいては電子注入性を有するものとして必要に応じて下記のものを用いることができる。例えば、Ｋ、Ｌｉ、Ｎａ、Ｍｇ、Ｌａ、Ｃｅ、Ｃａ、Ｓｒ、Ｂａ、Ｓｎ、Ｚｎ、Ｚｒ等の金属元素単体、または安定性を向上させるためにそれらを含む２成分、３成分の合金系、例えばＡｇ・Ｍｇ（Ａｇ：０．１〜５０ａｔ％）、Ａｌ・Ｌｉ（Ｌｉ：０．０１〜１４ａｔ％）、Ｉｎ・Ｍｇ（Ｍｇ：５０〜８０ａｔ％）、Ａｌ・Ｃａ（Ｃａ：０．０１〜２０ａｔ％）等が挙げられる。
【００４０】
さらに、アルカリ金属またはアルカリ士類金属のハロゲン化物も好ましく、例えば、アルカリ金属では、ＬｉＦ、ＬｉＣｌ、ＬｉＢｒ、ＬｉＩ、ＣｓＦ、ＣｓＣｌ、ＣｓＢｆ、ＣｓＩ、また、アルカリ土類金属ではＭｇＦ２ 、ＭｇＣｌ２ 、ＭｇＢｒ２ 、ＭｇＩ２ 等がある。取扱の簡易さと、抵抗率の低さから好ましくはＣｓＩ、ＣｓＣｌ、ＬｉＦが選択される。
【００４１】
無機電子注入層の膜厚としては、好ましくは、０．１ｎｍ〜５．０ｎｍ、より好ましくは０．５〜１．０ｎｍが好ましい。膜厚はこれより薄いと効果が十分ではなくなり、これより厚いと駆動電圧の上昇が顕著になる為である。前記無機電子注入層の屈折率は、好ましくは１．６〜２．６である。
【００４２】
上記無機電子注入層の作製方法はスパッタ法、ＥＢ蒸着法、イオンプレーティング法、抵抗加熱蒸着法等が考えられるが、有機ＥＬ素子に与えるダメージを考慮して、抵抗加熱蒸着法を用いた蒸着や、多元蒸着源による共蒸着が好ましい。
【００４３】
陰極は、光透過性を必要とすることから透明電極が好ましい。また、無機電子注入層との組み合わせでは、電子注入性はあまり問題にならないが、電極としての性能面でシート抵抗が低いか、導電率が高いことが要求される。
【００４４】
具体的には、上記陽極で例示された透明電極、すなわち錫ドープ酸化インジウム（ＩＴＯ）、亜鉛ドープ酸化インジウム（ＩＺＯ）、ＺｎＯ、ＳｎＯ２ 、
Ｉｎ２Ｏ３ などを用いることが好ましい。
【００４５】
また、シート抵抗を減少させ、導電率を向上させるためには、これらの材料に不純物をドーピングするとよい。具体的には、Ａｌ、Ｉｒ等の元素の１種または２種以上を総計５ ｍｏｌ％以下、特に３ ｍｏｌ％以下、さらには２〜１ ｍｏｌ％添加するとよい。
【００４６】
このようにして不純物をドーピングすることで、１００ｎｍ以下の膜厚でも、２０Ω／□以下のシート抵抗とすることができる。従って、上記光学設計を行う上でも有効である。
【００４７】
陰極は、通常光取り出し側の電極となる。光を取り出す側の電極は、発光波長帯域、通常４００〜７００ｎｍの波長の光に対する光透過率が５０％以上、さらには８０％以上、特に９０％以上であることが好ましい。透過率が低くなりすぎると、発光層からの発光自体が減衰され、発光素子として必要な輝度を得難くなってくる。
【００４８】
本発明において、有機発光層は、単層もしくは２層以上の積層体により構成され、好ましくは各発光層からの発光光の合成スペクトルが白色発光になるように調製される。なお、本発明における白色とは、ＣＩＥ色座標において、ｘ＝０．２９〜０．３７、ｙ＝０．３０〜０．４５、好ましくはｘ＝０．３２〜０．３６、ｙ＝０．３０〜０．４０で表される範囲のものであり、４００〜７００ｎｍの波長帯域でブロードな発光スペクトルを有するものである。また、複数の発光ピークを有する発光層からの合成光であるため、上記波長帯域内において完全にフラットな特性とはならず、ある程度のピークが数カ所に点在したスペクトルとなる。
【００４９】
白色発光を得るための具体的な発光層としては、例えば４５０ｎｍ〜５００ｎｍの青色、及び５６０ｎｍ〜６００ｎｍの黄色の２層構造とするとよい。
【００５０】
発光層は、正孔輸送性化合物もしくは電子輸送性化合物またはこれらの混合物であるホスト物質を含み、正孔および電子の注入機能、正孔および電子の輸送機能ならびに正孔および電子の再結合により、励起子を生成させる機能を有しており、電子的に比較的ニュートラルな化合物を含んでいることが好ましい。
【００５１】
有機発光層のホスト物質として用いられる正孔輸送性化合物としては、トリアゾール誘導体、オキサジアゾール誘導体、イミダゾール誘導体、ポリアリールアルカン誘導体、ビラゾリン誘導体、ビラゾロン誘導体、フェニレンジアミン誘導体、アリールアミン誘導体、アミノ置換カルコン誘導体、オキサゾール誘導体、スチリルアントラセン誘導体、フルオレノン誘導体、ヒドラゾン誘導体、スチルベン誘導体が挙げられ、さらに、トリフェニルジアミン誘導体が好ましく使用できる。
【００５２】
トリフェニルジアミン誘導体の例としては、テトラアリールべンジシン化合物（トリアリールジアミンないしトリフェニルジアミン：ＴＰＤ）がとくに好ましい。
【００５３】
有機発光層のホスト物質として用いられる電子輸送性化合物としては、下記に示すようなジスチリルアリーレン誘導体を好ましく使用することがでる。また、フェニルアントラセン誘導体やテトラアリールエテン誘導体も、電子輸送性化合物として使用することができる。
【００５４】
【化１】
本発明において、有機発光層は、正孔輸送性化合物もしくは電子輸送性化合物またはこれらの混合物であるホスト物質に、蛍光物質であるドーバントがドープされた構造を有していることが好ましい。
【００５６】
また、本発明にかかる有機ＥＬ素子は、好ましくは、互いに積層された２層以上の有機発光層を備えている。２層以上の有機発光層を形成する場合には、それぞれに、異なった発光波長を有する蛍光物質をドーピングすることによって、広い発光波長帯域を確保し、また、発光色の色彩の自由度を向上させることができる。
【００５７】
本発明において、ドーバントとして含有させる蛍光物質としては、たとえば、特開昭６３−２６４６９２号公報に開示された化合物、具体的には、ルブレン系化合物、クマリン系化合物、キナクリドン系化合物、ジシアノメチルビラン系化合物などの化合物よりなる群から選ばれる１種以上の化合物が好ましく使用できる。
【００５８】
本発明に好ましく使用できる蛍光物質の例を挙げると、以下のとおりである。
【００５９】
【化２】
【化３】
【化４】
【化５】
さらに、本発明においては、特開２０００−２６３３４号公報および特開２０００−２６３３７号公報に記載されているナフタセン系化合物も、ドーバントとして含有させる蛍光物質として、好ましく使用することができ、ルブレン系化合物、クマリン系化合物、キナクリドン系化合物、ジシアノメチルピラン系化合物などと併用することによって、有機ＥＬ素子の寿命を飛澤的に向上させることができる。
【００６４】
２層以上の有機発光層を設ける場合、各有機発光層が、２種以上のこれらの蛍光物質を含み、２種以上の蛍光物質が、異なった発光波長を有していることが好ましい。
【００６５】
本発明において、有機発光層におけるドーバントの含有量は、０．０１〜２０質量％であることが好ましく、さらに好ましくは、０．１〜１５質量％である。
【００６６】
本発明において、好ましくは、有機発光層は蒸着によって形成される。
【００６７】
本発明において、好ましくは、有機発光層は、正孔輸送性化合物と電子注入輸送性化合物の混合物を含んでいる。
【００６８】
有機発光層が、正孔輸送性化合物と電子注入輸送性化合物の混合物を含んでいる場合には，キャリアのホッピング伝導パスが形成されるため、各キャリアは極性的に優勢な物質中を移動し、逆の極性のキャリア注入が起こり難くなり、したがって、有機発光層に含まれた化合物がダメージを受けることが防止されるので、素子の寿命を向上させることができるという利点がある。
【００６９】
さらに、蛍光物質からなるドーバントを、正孔輸送性化合物および電子注入輸送性化合物の混合物を含んだ有機発光層に含有させることによって、有機発光層自体が有する発光波長特性を変化させることができ、発光波長を長波長側に移行させるとともに、発光強度を向上させ、さらには、有機ＥＬ素子の安定性を向上させることが可能になる。
【００７０】
有機発光層が、正孔輸送性化合物および電子注入輸送性化合物の混合物を含んでいる場合、正孔輸送性化合物と電子注入輸送性化合物の混合比は、それぞれのキャリア移動度とキャリア濃度にしたがって決定されるが、一般的には、質量比で、１／９９〜９９／１、好ましくは、１０／９０〜９０／１０、さらに好ましくは、２０／８０〜８０／２０、最も好ましくは、４０／６０〜６０／４０が選ばれる。
【００７１】
正孔輸送性化合物および電子注入輸送性化合物の混合物を含む有機発光層を形成する場合には、正孔輸送性化合物と電子注入輸送性化合物を、異なる蒸着源に入れて、蒸発させ、共蒸著することが好ましいが、正孔輸送性化合物と電子注入輸送性化合物の蒸気圧が同程度あるいは非常に近い場合には、あらかじめ同じ蒸着源内で混合させておき、蒸著することもできる。
【００７２】
正孔輸送性化合物および電子注入輸送性化合物の混合物を含む有機発光層を形成する場合、有機発光層内で、正孔輸送性化合物と電子注入輸送性化合物とが均一に混合していることが好ましいが、均一に混合していることは必ずしも必要でない。
【００７３】
本発明において、有機物層は、好ましくは、少なくとも一層の有機発光層に加えて、正孔を安定的に輸送する機能を有する正孔輸送層、ならびに、電子を安定的に輸送する機能を有する電子輸送層を備えている。これらの層を備えることによって、有機発光層に注入される正孔や電子を増大させるとともに、有機発光層内に閉じ込めさせ、再結合領域を最適化させ、発光効率を向上させることが可能になる。
【００７４】
本発明において、正孔輸送層に、好ましく使用することができる化合物としては、例えば、テトラアリールベンジシン化合物（トリアリールジアミンないしトリフェニルジアミン：ＴＰＤ）、芳香族三級アミン、ヒドラゾン誘導体、カルバゾール誘導体、トリアゾール誘導体」イミダゾール誘導体、アミノ基を有するオキサジアゾール誘導体、ポリチオフェンなどを挙げることができる。これらのうち、テトラアリールべンジシン化合物（トリアリールジアミンないしトリフェニルジアミン：ＴＰＤ）、ＷＯ／９８／３００７１号に記載されているトリアリールアミン多量体（ＡＴＰ）が、とくに好ましく使用することができる。
【００７５】
トリアリールアミン多量体（ＡＴＰ）の好ましい具体例は、以下のとおりである。
【００７６】
【化６】
【化７】
【化８】
本発明において、さらには、特開昭６３−２９５６９５号公報、特開平２−１９１６９４号公報、特開平３−７９２号公報、特開平５−２３４６８１号公報、特開平５−２３９４５５号公報、特開平５−２９９１７４号公報、特開平７−１２６２２５号公報、特開平７−１２６２２６号公報、特開平８−１００１７２号公報、ＥＰＯ６５０９５５Ａｌなどに記載されている各種有機化合物も、正孔注入輸送層、正孔注入層および正孔輸送層に使用することができる。
【００８０】
本発明において、２種以上のこれらの化合物を併用してもよく、２種以上のこれらの化合物を併用する場合には、一層中に混合しても、また、２以上の層として、積層してもよい。
【００８１】
本発明において、正孔輸送層は、前記化合物を蒸着することによって形成することができる。蒸着によって、素子化する場合には、均一で、ピンホールのない１〜１０ｎｍ程度の薄膜を形成することができるため、正孔注入層にイオン化ポテンシャルが小さく、可視波長の光を吸収する化合物を用いても、発光色の色調変化や再吸収による発光効率の低下を防止することができる。
【００８２】
本発明において、電子輸送層に、好ましく使用することができる化合物としては、たとえば、トリス（８−キノリノラト）アルミニウム（Ａｌｑ３）などの８−キノリノールないしその誘導体を配位子とする有機金属錯体、オキサジアゾール誘導体、ペリレン誘導体、ピリジン誘導体、ピリミジン誘導体、キノキサリン誘導体などを挙げることができる。
【００８３】
本発明において、電子輸送層は、前記化合物を蒸着することによって形成することができる。
【００８４】
本発明において、有機発光層、正孔注入輸送層あるいは正孔注入層および正孔輸送層、ならびに、電子注入輸送層あるいは電子注入層および電子輸送層の各層を、蒸着によって形成する条件はとくに限定されるものではないが、１×１０−４パスカル以下で、蒸着速度を０．０１〜１ｎｍ／秒程度とすることが好ましい。各層は、１×１０−４パスカル以下の減圧下で、連続して、形成されることが好ましい。１×１０−４パスカル以下の減圧下で、連続して、各層を形成することによって、各層の界面に不純物が吸着されることを防止することができるから、高特性の有機ＥＬ素子を得ることが可能になるとともに、有機ＥＬ素子の駆動電圧を低下させ、ダークスポットが発生し、成長することを抑制することができる。
【００８５】
さらに、素子の有機層や電極の劣化を防ぐために、素子上を封止板等により封止することが好ましい。封止板は、湿気の浸入を防ぐために、接着性樹脂層を用いて、封止板を接着し密封する。封止ガスは、Ａｒ、Ｈｅ、Ｎ２ 等の不活性ガス等が好ましい。また、この封止ガスの水分含有量は、１００ｐｐｍ 以下、より好ましくは１０ｐｐｍ 以下、特には１ｐｐｍ 以下であることが好ましい。この水分含有量に下限値は特にないが、通常０．１ｐｐｍ 程度である。
【００８６】
さらに、本発明の素子を、平面上に多数並べてもよい。平面上に並べられたそれぞれの素子の発光色を変えて、カラーのディスプレーにすることができる。
【００８７】
素子基板または封止基板に色フィルター膜や蛍光性物質を含む色変換膜、あるいは誘電体反射膜を用いて発光色をコントロールしてもよい。
【００８８】
【実施例】
〔実施例１〕
ガラス基板上に反射層としてＴｉＮをスパッタ法により、膜厚５０ｎｍに成膜した。このとき、反射層の波長４００〜７００ｎｍにおける反射率は４５％であった。
【００８９】
次いで、表１に示す厚さにＩＴＯ透明電極（陽極）を成膜し、この反射層、ＩＴＯ付きガラス基板を、中性洗剤、アセトン、エタノールを用いて超音波洗浄し、煮沸エタノール中から引き上げて乾燥した。この透明電極付き基板をＵＶ／Ｏ３ 洗浄した後、真空蒸着装置の基板ホルダーに固定して、チャンバー内を１０−４Ｐａ以下の減圧状態とした。なお、ＩＴＯの屈折率ｎ１＝１．９であった。なお、サンプル９のみＩＴＯを設けず、ＴｉＮ反射層を陽極としてＩＴＯに代えてホール注入性を確保するためにＧｅＯＩｎを膜厚２ｎｍに成膜して用いた。
【００９０】
次に、ホール注入層として、減圧状態を保ったまま、Ｎ，Ｎ’−ジフェニル−Ｎ，Ｎ’−ビス［Ｎ−（４−メチルフェニル）−Ｎ−フェニル（４−アミノフェニル）］−１，１’−ビフェニル−４，４′−ジアミンを蒸音速度０．１ｎｍ／ｓｅｃで２０ｎｍの厚さに形成した。
【００９１】
次いで、減圧状態を保ったまま、ホール輸送層として、Ｎ，Ｎ’−ジフェニル−Ｎ，Ｎ’−ビス（１−ナフチル）−１，１’−ジフェニル−４．４’−ジアミンを蒸着速度０．１ｎｍ／ｓｅｃ で１０ｎｍの厚さに形成した。
【００９２】
さらに、減圧状態を保ったまま、下部発光属として下記の化合物１と化合物２を、１００：３の体積比率、蒸着速度０．１ｎｍ／ｓｅｃ で共蒸着し、３０ｎｍの厚さに形成した。これら、ホール注入層、ホール輸送層、下部発光層のうち、ホール輸送層の膜厚を変えることで、総膜厚が表１に示す各サンプルの膜厚となるように形成した。なお、これらの有機層の屈折率ｎ３＝１．７であった。
【００９３】
【化９】
【化１０】
さらに、減圧状態を保ったまま、発光属として下記の化合物３と化合物４を、１００：３の体積比率、蒸着速度０．１ｎｍ／ｓｅｃ で共蒸着し、３０ｎｍの厚さに形成した。
【００９６】
【化１１】
【化１２】
次に、電子注入層として、上記ＩＤＥ１２０を蒸着速度０．１ｎｍ／ｓｅｃ で３０ｎｍの厚さに形成した。これら、上部発光層、有機の電子注入層のうち、電子注入層の膜厚を変えることで、総膜厚が表１に示す各サンプルの膜厚となるように形成した。なお、これらの有機層の屈折率ｎ４＝１．７であった。
【００９９】
次に、減圧状態を保ったまま、無機電子注入層としてＬｉＦを蒸着速度０．０１ｎｍ／ｓｅｃ で３ｎｍの厚さに形成した後、ＺｎＯにＡｌを５ ｍｏｌ％ドープした透明電極を、スパッタ法にて速度０．０５ｎｍ／ｓｅｃ で表１に示す厚さに形成した。この透明電極の屈折率はｎ５＝１．８であった。
【０１００】
この有機ＥＬ素子に電圧を印加して電流を流し評価した。得られた発光輝度、電圧、色度（ＣＩＥ色座標）を表１に示す。
【０１０１】
【表１】
表１から明らかなように、各構成層の膜厚、あるいは膜厚と屈折率との積が本発明範囲のサンプルは輝度、色度ともに優れた値が得られていることがわかる。また、電極の膜厚が厚くなる駆動電圧が上昇してしまう。
【０１０３】
【発明の効果】
以上のように本発明によれば、従来検討されていない２層以上の発光層から白色発光を得る上面光取り出し型の構造を有する有機ＥＬ素子において、素子内部での光学モデルを確立し、効率の良い、白色の色度に優れた有機ＥＬ素子を提供することができる。
【図面の簡単な説明】
【図１】本発明の有機ＥＬ素子の基本構成を示す概略断面図である。
【符号の説明】
１ 基板
２ 光反射層
３ 陽極
４ 有機ホール注入輸送層
５ 第１の発光層（下部発光層）
６ 第２の発光層（上部発光層）
７ 有機電子注入輸送層
８ 無機電子注入層８
９ 陰極[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an organic EL device using an organic compound, and more particularly, to an organic EL device to which an optical model is applied to provide an organic EL device capable of effectively extracting light emission and having less variation in light emission luminance. .
[0002]
[Prior art]
The organic EL element is formed by depositing a hole transporting material such as triphenyldiamine (TPD) on a hole injecting electrode to form a thin film, further laminating a fluorescent substance such as an aluminum quinolinol complex (Alq3) as a light emitting layer, and further forming a work such as Mg. This is an element having a basic configuration in which a metal electrode (electron injection electrode) having a small function is formed. The organic EL element is a self-luminous type thin film structure, and has a voltage of about 10 V to several hundreds to several 10,000 cd / m. 2 And extremely high brightness.
[0003]
The organic EL element has a basic structure in which an organic EL structure having an electron injection electrode, an organic layer, a hole injection electrode, and the like is formed on a substrate as described above. Is taken out from the substrate side.
[0004]
By the way, it is generally known that, in an organic EL device, the emission spectrum of a light-emitting species causes optical interference inside the device while being emitted, and is modulated. For this reason, even if the organic EL elements have the same light emitting material, if the optical system is different, the spectrum emitted outside and the intensity thereof change.
[0005]
The largest type of the optical modulation is, as disclosed in Japanese Patent Application Laid-Open No. 4-328295, between light emitted forward and light emitted backward reflected by a metal surface (electron injection electrode). This is due to interference. Since this effect can be expressed by a function determined by the distance between the light emitting point and the metal surface, an optical configuration for obtaining a desired modulation spectrum can be understood. However, when making a more precise prediction, the error is large, which is still insufficient, and further requires parameters to be considered.
[0006]
Furthermore, Japanese Patent Application Laid-Open No. 7-240277 has revealed a problem that reflected light at the glass / transparent electrode interface interferes to modulate light emitted from the organic EL element. However, in the publication, in order to increase the emission intensity of a specific wavelength in a certain narrow range by using optical modulation, the optical film thickness between the glass / transparent conductive film interface and the metal surface sandwiching the organic multilayer portion is required. It merely states that a specific value is required.
[0007]
If there is a certain arbitrary optical system, it is difficult to consider in detail the spectral modulation unless it is possible to predict how much the signal will be modulated due to interference other than the above-mentioned parameters. Optical design was difficult. Further, each of the above models targets an element for extracting light from the substrate side, and no study is made on an element having a structure for extracting light from the upper surface opposite to the substrate.
[0008]
As described above, when the constituent film thickness of the organic EL element changes, the spectrum and luminance of light emitted to the outside change. In particular, in a white light-emitting element having a plurality of light-emitting layers, when the emission spectrum from each light-emitting layer changes, the color purity of white finally appearing outside changes, and a display with high efficiency and high purity should be obtained. And it has been difficult to supply a uniform product.
[0009]
Japanese Patent Application Laid-Open No. 2000-243573 discloses that at least a transparent electrode, an organic compound material layer including a light emitting layer, and a metal electrode are sequentially laminated on a light-transmitting substrate. An organic electroluminescence element having an organic compound material layer on the transparent electrode side or a transparent electrode bordering the light-emitting interface, the organic compound material layer on the transparent electrode side being transparent to the organic compound material layer. An organic electroluminescent element is described which is formed so as to have a film thickness at or above which a minimum value between the luminous efficiency of the primary maximum value and the luminous efficiency of the secondary maximum value in the luminous efficiency characteristics with respect to the film thickness on the electrode side is obtained. .
[0010]
However, what is studied in this document is a bottom-type element that extracts light from the substrate side, and no study on light extraction from the top surface is made. Moreover, the emission color under consideration is monochromatic light having a single peak wavelength λ, and the thickness in the element structure is defined as an odd multiple of 1/4 of this wavelength. No study has been made on an element that obtains white light emission by synthesizing the light emission colors obtained from. Further, there is no problem that the white color balance is deteriorated due to the layered structure of the elements.
[0011]
On the other hand, Japanese Patent Application Laid-Open No. 2000-323277 discloses an organic electroluminescent multicolor display that is easy to manufacture and has high light extraction efficiency and a method of manufacturing the same. An organic electroluminescent element comprising a transparent electrode, an organic compound material layer including a light emitting layer, and a metal electrode, wherein the light emitting layer is formed of a different organic compound material and has a different emission color. There is disclosed an organic electroluminescent multicolor display, which is a multicolor display, in which any functional layer having the same function as the organic compound material layer except for the light-emitting layer has a different thickness corresponding to the emission color.
[0012]
However, what is studied in this document is a bottom-out, full color display of R, G, and B colors, and white light emission in which two or more light-emitting layers are stacked has not been studied.
[0013]
[Problems to be solved by the invention]
An object of the present invention is to establish an optical model inside an element in an organic EL element having a top light extraction type structure which has not been studied conventionally, preferably in an element which obtains white light emission from two or more light emitting layers, An object of the present invention is to provide an efficient organic EL device having excellent white chromaticity.
[0014]
[Means for Solving the Problems]
That is, the above object is achieved by the following configuration of the present invention.
(1) An organic EL element having one kind of light emitting layer having at least one light emission peak and obtaining light extracted from the upper surface opposite to the substrate,
Having at least the substrate and a reflective layer having a visible light reflectance of 50% or more on the substrate, an anode, an organic layer having a light emitting layer, and a transparent electrode serving as a cathode;
An organic EL device wherein the total film thickness from the midpoint of the light emitting layer to the lower end surface of the anode is 45 nm to 160 nm, and the total film thickness from the midpoint of the light emitting layer to the upper end surface of the cathode is 120 nm to 290 nm.
(2) the reflection layer is an anode;
The organic EL device according to the above (1), wherein the total film thickness from the midpoint of the light emitting layer to the upper end surface of the anode is 45 nm to 160 nm, and the total film thickness from the midpoint of the light emitting layer to the upper end surface of the cathode is 120 nm to 290 nm.
(3) having two or more light-emitting layers, and obtaining white light from the upper surface on the side opposite to the substrate by the combined light of the two or more light-emitting layers;
At least the total thickness from the interface between the lower light-emitting layer located closest to the anode side and the upper light-emitting layer positioned closest to the cathode side or an intermediate point thereof to the lower end surface of the anode is 45 nm to 100 nm, and from the interface or the intermediate point. The organic EL device according to the above (1), wherein the total film thickness up to the upper end surface of the cathode is 100 nm to 260 nm.
(4) a total film thickness from the interface between the lower light emitting layer and the upper light emitting layer or an intermediate point thereof to the lower end surface of the anode is 45 nm to 130 nm;
The organic EL device according to the above (3), wherein the thickness of the anode is 25 to 70 nm.
(5) a total film thickness from the interface between the lower light emitting layer and the upper light emitting layer or an intermediate point thereof to the upper end surface of the cathode is 100 nm to 260 nm;
The organic EL device according to the above (3) or (4), wherein the thickness of the transparent electrode serving as the cathode is 50 nm to 140 nm.
(6) At least a part of the cathode is a transparent electrode, the refractive index of which is 1.7 to 2.0, the refractive index of the organic layer including the light emitting layer is 1.6 to 1.8, and the anode is The organic EL device according to any one of the above (1) to (5), which is a transparent electrode and has a refractive index of 1.6 to 2.0.
(7) The sum of the product of the film thickness (nm) and the refractive index from the interface between the lower light-emitting layer and the upper light-emitting layer or an intermediate point thereof to the anode lower end surface is A,
A = (a1 × n2) + (a2 × n3)
(A1 is the thickness of the anode, n2 is the refractive index of the anode, a2 is the thickness of the lower organic layer including the lower light emitting layer, n3 is the refractive index of the lower organic layer including the lower light emitting layer 5),
The sum of the product of the film thickness (nm) from the interface or the intermediate point to the cathode upper end surface and the refractive index is B,
B = (b1 × n4) + (b2 × n5)
(B1 is the thickness of the upper organic layer including the upper light emitting layer, n4 is the refractive index of the upper organic layer including the upper light emitting layer, b2 is the thickness of the transparent cathode, and n5 is the refractive index of the transparent cathode.)
Then
A = 72-248,
B = 165-496,
The organic EL device according to (3) above.
(8) the reflection layer is an anode;
The total film thickness from the interface between the lower light emitting layer and the upper light emitting layer or an intermediate point thereof to the upper end face of the anode is 45 nm to 130 nm, and the total film thickness from the interface or the intermediate point to the upper end face of the cathode is 100 nm to 290 nm. The organic EL device according to (3) above.
(9) The total film thickness from the interface between the lower light emitting layer and the upper light emitting layer or an intermediate point thereof to the upper end face of the cathode is 100 nm to 260 nm, and the thickness of the transparent electrode serving as the cathode is 40 nm to 140 nm. The organic EL device according to (8).
(10) At least a part of the cathode is a transparent cathode, the refractive index of which is 1.7 to 2.0, and the refractive index of the organic layer including the light emitting layer is 1.6 to 1.8. 8) or the organic EL device according to (9).
(11) The sum of the product of the refractive index and the film thickness (nm) from the interface between the lower light emitting layer and the upper light emitting layer or an intermediate point thereof to the upper end of the anode is represented by A,
A = (a2 × n3)
(A2 is the thickness of the lower organic layer including the lower light emitting layer, n3 is the refractive index of the lower organic layer including the lower light emitting layer),
The sum of the product of the film thickness (nm) from the interface or the intermediate point thereof to the upper end of the cathode and the refractive index is B
B = (b1 × n4) + (b2 × n5)
(B1 is the thickness of the upper organic layer including the upper light emitting layer, n2 is the refractive index of the upper organic layer including the upper light emitting layer, b2 is the thickness of the transparent electrode, and n3 is the refractive index of the transparent electrode),
Then
A = 72 to 234
B = 164-496
The organic EL device according to the above (8), wherein
[0015]
(12) An organic EL device having two or more light-emitting layers having different light emission peaks, and obtaining white light extracted from the upper surface on the side opposite to the substrate by a combined light of the two or more light-emitting layers,
An organic layer having the substrate, a reflective layer having a visible light reflectance of 50% or more on the substrate, an anode, and at least a lower light-emitting layer positioned closest to the anode and an upper light-emitting layer positioned closest to the cathode; , A transparent electrode which is a cathode,
The sum of the product of the film thickness (nm) and the refractive index from the interface between the lower light emitting layer and the upper light emitting layer or the midpoint thereof to the lower end face of the anode is represented by A,
A = (a1 × n2) + (a2 × n3)
(A1 is the thickness of the anode, n2 is the refractive index of the anode, a2 is the thickness of the lower organic layer including the lower light emitting layer, n3 is the refractive index of the lower organic layer including the lower light emitting layer 5),
The sum of the product of the film thickness (nm) from the interface or the intermediate point to the cathode upper end surface and the refractive index is B,
B = (b1 × n4) + (b2 × n5)
(B1 is the thickness of the upper organic layer including the upper light emitting layer, n4 is the refractive index of the upper organic layer including the upper light emitting layer, b2 is the thickness of the transparent cathode, and n5 is the refractive index of the transparent cathode.)
Then
A = 72-248,
B = 165-496,
An organic EL device.
(13) the reflection layer is an anode;
The sum of the product of the film thickness (nm) and the refractive index from the interface between the lower light emitting layer and the upper light emitting layer or the midpoint thereof to the upper end of the anode is represented by A,
A = (a2 × n3)
(A2 is the thickness of the lower organic layer including the lower light emitting layer, n3 is the refractive index of the lower organic layer including the lower light emitting layer),
The sum of the product of the film thickness (nm) from the interface or the intermediate point thereof to the upper end of the cathode and the refractive index is B
B = (b1 × n4) + (b2 × n5)
(B1 is the thickness of the upper organic layer including the upper light emitting layer, n2 is the refractive index of the upper organic layer including the upper light emitting layer, b2 is the thickness of the transparent electrode, and n3 is the refractive index of the transparent electrode),
Then
A = 72 to 234
B = 164-496
The organic EL device according to the above (12), wherein
(14) The organic EL device according to any one of the above (3) to (13), wherein the host materials constituting the two or more light emitting layers are the same.
(15) The organic EL device according to any one of (3) to (14), wherein the emission colors of the two or more light emitting layers are blue at 450 nm to 500 nm and yellow at 560 to 600 nm.
(16) An organic EL element having one or two or more types of light-emitting layers and obtaining white light extracted from the upper surface opposite to the substrate,
The substrate, a reflective layer having a visible light reflectance of 50% or more on the substrate, an anode having the reflective layer as an anode, and at least a lower light emitting layer located closest to the anode and an upper light emitting layer located closest to the cathode. An organic layer, an inorganic electron injection layer, and a transparent electrode which is a cathode in order,
An organic EL device wherein the inorganic electron injecting layer has a thickness of 0.1 nm to 5 nm and a refractive index of 1.6 to 2.6.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
The organic EL device of the present invention is an organic EL device that has one kind of light emitting layer having at least one light emission peak and obtains light extracted from the upper surface opposite to the substrate,
Having at least the substrate and a reflective layer having a visible light reflectance of 50% or more on the substrate, an anode, an organic layer having a light emitting layer, and a transparent electrode serving as a cathode;
The total film thickness from the midpoint of the light emitting layer to the lower end face of the anode is 45 nm to 160 nm, and the total film thickness from the midpoint of the light emitting layer to the upper end face of the cathode is 120 nm to 290 nm.
[0017]
Further, preferably, the light-emitting layer has two or more light-emitting layers, and white light is obtained from the upper surface on the side opposite to the substrate by a combined light of the two or more light-emitting layers, and at least a lower light-emitting layer located closest to the anode. The total film thickness from the interface with the upper light-emitting layer located closest to the cathode or the intermediate point thereof to the lower end face of the anode is 45 nm to 100 nm, and the total film thickness from the interface or the intermediate point to the upper end face of the cathode is 100 nm to 100 nm. It is 260 nm.
[0018]
As described above, in an organic EL device that obtains white light by combining light from the upper surface opposite to the substrate, preferably by combining two or more kinds of light emitting layers, in the case of a light emitting layer or two or more kinds of light emitting layers, By regulating the distance from the upper light emitting layer and the lower light emitting layer to each interface between the substrate side and the cathode side, highly efficient and highly pure white light emission can be obtained.
[0019]
That is, according to the study of the present inventors, the total film thickness from the middle point of the light emitting layer, the interface between two or more light emitting layers, or the intermediate point between the outermost light emitting layers to the anode lower end surface on the substrate side. By optimizing the total film thickness up to the upper end face of the cathode on the opposite side, the efficiency of taking out emitted light can be improved, the white color balance can be adjusted, and high-purity white light emission can be obtained.
[0020]
Next, the organic EL device of the present invention will be described in more detail with reference to the drawings. FIG. 1 is a schematic sectional view showing the basic structure of the organic EL device of the present invention. In the figure, an organic EL element has a light reflection layer 2, an anode 3, which is a transparent electrode, an organic hole injection / transport layer 4, a first light emitting layer (lower light emitting layer) 5, a second light emitting layer A light emitting layer (upper light emitting layer) 6, an organic electron injection / transport layer 7, an inorganic electron injection layer 8, and a cathode 9 as a transparent electrode are sequentially laminated. The light emitting layers 5 and 6 may be a single layer.
[0021]
In the present invention, the light-emitting layer is preferably a two-layer structure of a first light-emitting layer (lower light-emitting layer) 5, a second light-emitting layer (upper light-emitting layer) 6, a single-layer structure, or a three-layer structure as shown in the illustrated example. It is composed of a plurality of layers as described above. Then, the emitted lights from the plurality of light emitting layers 5 and 6 are combined, and preferably, white extracted light is obtained. For this reason, when white light is obtained from two light-emitting layers as in the illustrated example, the light emission of each light-emitting layer should be adjusted so as to obtain light having complementary colors, such as blue and orange. Is desirable. When there are three or more light emitting layers, for example, three primary colors of RGB may be emitted to obtain white light, or the light emission color of each light emitting layer may be adjusted so that the final combined light becomes white. It may be prepared.
[0022]
In the present invention, an element for obtaining extracted light, preferably white extracted light, by the color of light emitted from a single layer or a plurality of light emitting layers as described above, wherein light is emitted from the upper surface (cathode side) opposite to the substrate. Provided is an element configuration which efficiently obtains light with excellent white purity in an element having a structure for extracting light.
[0023]
According to the study of the present inventors, it has been found that the film thickness of the constituent layers preferably satisfies the following relationship in order to optimize the efficiency of white light extraction and the color purity. That is, the total film thickness from the interface between the lower light emitting layer and the upper light emitting layer or an intermediate point thereof to the lower end surface of the anode or the upper end surface of the reflective layer is a, and the upper end surface of the cathode from the interface or the intermediate point (that is, Where b is the total film thickness up to the interface of
(In the case of a single light emitting layer)
a = 45 nm to 160 nm, preferably 60 to 140 nm,
b = 120 nm to 290 nm, preferably 140 to 250 nm,
[In the case of two or more light emitting layers]
a = 45 nm to 130 nm, preferably 60 to 110 nm,
b = 100 nm to 260 nm, preferably 110 to 180 nm,
Should be within the range.
[0024]
When the reflective layer also serves as the anode, the following is performed.
(In the case of a single light emitting layer)
a = 45 nm to 160 nm, preferably 60 to 140 nm,
b = 120 nm to 290 nm, preferably 140 to 250 nm,
[In the case of two or more light emitting layers]
a = 45 nm to 130 nm, preferably 60 to 110 nm,
b = 100 nm to 290 nm, preferably 110 to 180 nm,
It is.
[0025]
Here, the intermediate point of the light emitting layer means an intermediate point in the thickness direction of the single light emitting layer. In the case of a two-layer structure of the first light-emitting layer (lower light-emitting layer) 5 and the second light-emitting layer (upper light-emitting layer) 6, the interface or the intermediate point means these interfaces. In the case where the light emitting layer has the above, it means an intermediate point between the lower light emitting layer 5 and the upper light emitting layer 6. Usually, there is no problem assuming that light emission occurs at the interface between the two light emitting layers. However, even when the light emitting layer has two or more light emitting layers, the intermediate point between the uppermost light emitting layer and the lowermost light emitting layer is simulated as the interface. No problem.
[0026]
In the above thickness range, the thickness of the anode is preferably 25 to 50 nm, more preferably 35 to 45 nm, and the thickness of the transparent electrode serving as the cathode is preferably 40 to 140 nm, more preferably 90 to 120 nm.
[0027]
Here, the refractive index of each constituent layer will be examined. As the refractive index n1 of the substrate 1, a glass substrate or the like is usually used, and in this case, n1 is about 1.50 to 1.54. Next, the anodes 2 and 3 are usually made of a transparent conductive film such as ITO. In this case, n2 is about 1.6 to 2.0. Further, the refractive index of the organic layers 5 and 4 including the lower light emitting layer 5 is usually 1.6 to 1.8, and the refractive index of the organic layers 6 and 7 including the upper light emitting layer 6 is similarly 1.6. １1.8. Note that the inorganic battery injection layer 8 has a very small thickness, and is therefore ignored here. The refractive index of the transparent electrode serving as the cathode is usually about 1.7 to 2.0. The refractive index of air is assumed to be 1.0 in this specification.
[0028]
Looking at the relationship between the refractive indices of the respective constituent layers, it can be seen that the change in the refractive index at the interface of the substrate 1 / transparent electrode (anode) 3 and the interface of the transparent electrode (cathode) 9 / air is greatest. Therefore, the emitted light is mainly reflected at these interfaces, but since the present invention has a reflective layer, light traveling toward the anode is reflected at the surface of the reflective layer. For this reason, it is understood that the efficiency of the emitted light to be extracted and the purity of white light can be optimized by regulating the distance from the interface of the light emitting layer, which is the light emission center, to these interfaces and the surface of the reflective layer.
[0029]
That is, the light emitted at the light emission center goes to the substrate side and the upper surface side opposite to the substrate. Here, light in directions other than the direction perpendicular to the substrate surface is neglected to simplify the model. Then, part of the light traveling toward the upper surface is reflected at the interface between the transparent cathode 9 and the outside air. On the other hand, the light traveling toward the substrate is at least partially reflected by the reflection layer 2 and travels toward the upper surface. Therefore, by optimizing these two optical path lengths, interference between light traveling toward the upper surface and light traveling toward the substrate can be suppressed as much as possible, and efficient light extraction can be performed.
[0030]
Therefore, the relationship between the film thickness and the refractive index is as follows.
The sum of the product of the film thickness (nm) and the refractive index from the interface between the lower light emitting layer and the upper light emitting layer or the midpoint thereof to the lower end face of the anode is represented by A,
A = (a1 × n2) + (a2 × n3)
(A1 is the thickness of the anode, n2 is the refractive index of the anode, a2 is the thickness of the organic layers 4 and 5 including the lower light emitting layer 5, and n3 is the refractive index of the organic layers 4 and 5 including the lower light emitting layer 5).
The sum of the product of the film thickness (nm) from the interface or the intermediate point to the cathode upper end surface and the refractive index is B,
B = (b1 × n4) + (b2 × n5)
(B1 is the thickness of the organic layers 6 and 7 including the upper light emitting layer 6, n4 is the refractive index of the organic layers 6 and 7 including the upper light emitting layer 6, b2 is the thickness of the transparent cathode, and n5 is the refractive index of the transparent cathode. ))
A = 72 to 190, preferably 103 to 153,
B = 164-520, preferably 249-456,
It becomes.
[0031]
In the present invention, it is preferable that the evaluation of the extracted light such as the refractive index and the light extraction light rate satisfy the light in the wavelength band of 400 to 700 nm.
[0032]
In the present invention, as a substrate on which an organic EL structure is formed, an amorphous substrate (eg, glass, quartz, etc.), a crystalline substrate (eg, Si, GaAs, ZnSe, ZnS, GaP, InP, etc.), or a transparent plastic, etc. In addition, a substrate in which a crystalline, amorphous or metal buffer layer is formed on these crystalline substrates can also be used. As a metal substrate, Mo, Al, Pt, Ir, Au, Pd, or the like can be used, and a glass substrate is preferably used. Further, a crystal substrate made of Si or the like is also preferable because it has a structure in which light is not extracted from the substrate side.
[0033]
The reflective layer has a function of reflecting 50% or more, preferably 80% or more, more preferably 90% or more of light emitted from the light-emitting layer. When the reflectivity of the reflective layer decreases, the amount of light extracted to the outside decreases, and the light extraction efficiency decreases. On the other hand, if the reflectance is too high, adverse effects such as a decrease in contrast ratio may occur.
[0034]
The material of the reflective layer is not particularly limited, but may be a metal, or an oxide or nitride thereof. Specifically, metal elements such as Mo, Cr, Al, Ag, Ti, and the like, or alloys, oxides, nitrides, and the like can be given. Among them, Ag, Al, and the like have high reflectance. Is preferred. However, when ITO or the like is used for the anode, a barrier layer of TiN or the like or a reflective layer having a barrier function is required to prevent electric contact. The thickness of the reflective layer varies depending on the material to be used and the designed reflectance, but is usually 30 to 300 nm, especially about 50 to 250 nm.
[0035]
The anode is not particularly limited as long as it is an electrode material having conductivity. However, a material having hole injection properties and capable of optimizing a work function and the like required in element design is preferable. As such an anode material, specifically, tin-doped indium oxide (ITO), zinc-doped indium oxide (IZO), ZnO, SnO 2 , In 2 O 3 It is preferable to use a transparent electrode such as Originally, light is not actively extracted from the anode side, but these materials are preferable because they have the above characteristics, and ITO, IZO, and the like are particularly preferable in view of the refractive index.
[0036]
The thickness of the anode is preferably about 25 to 50 nm. It is necessary that the driving voltage be low in order to improve the reliability of the element. As a preferable sheet resistance, ITO having a thickness of 20 to 60 Ω / □ (film thickness of 50 to 300 nm) is exemplified. When actually used, the film thickness and optical constant of the electrode may be set so that the interference effect due to the reflection at the positive electrode interface such as ITO sufficiently satisfies the light extraction efficiency and the color purity.
[0037]
Further, the anode and the reflective layer may be integrated. That is, the anode may function as a reflective layer. As a constituent material of such an anode / reflection layer, germanium indium oxide (GeOIn) or silicon oxide (SiO 2 ) To which a metal (for example, Fe, Ni, Cr, In, Zn, Ag, Au, Cu, or the like) is added.
[0038]
The thickness of the anode / reflection layer is also the same as that of the anode.
[0039]
As the inorganic electron injecting and transporting layer, in combination with an organic electron injecting and transporting layer, the following materials can be used, if necessary, as having electron injecting properties. For example, a metal element such as K, Li, Na, Mg, La, Ce, Ca, Sr, Ba, Sn, Zn, Zr, or a two-component or three-component alloy system containing them for improving stability. For example, Ag.Mg (Ag: 0.1 to 50 at.%), Al.Li (Li: 0.01 to 14 at.%), In.Mg (Mg: 50 to 80 at.%), Al.Ca (Ca: 0. 01 to 20 at%).
[0040]
Further, a halide of an alkali metal or an alkali metal is also preferable. For example, for an alkali metal, LiF, LiCl, LiBr, LiI, CsF, CsCl, CsBf, CsI, and for an alkaline earth metal, MgF 2 , MgCl 2 , MgBr 2 , MgI 2 Etc. CsI, CsCl, and LiF are preferably selected from the viewpoint of ease of handling and low resistivity.
[0041]
The thickness of the inorganic electron injection layer is preferably from 0.1 nm to 5.0 nm, more preferably from 0.5 to 1.0 nm. If the film thickness is smaller than this, the effect is not sufficient, and if the film thickness is larger than this, the driving voltage rises remarkably. The refractive index of the inorganic electron injection layer is preferably from 1.6 to 2.6.
[0042]
As a method for forming the inorganic electron injecting layer, a sputtering method, an EB evaporation method, an ion plating method, a resistance heating evaporation method, or the like can be considered. However, in consideration of damage to an organic EL element, evaporation using a resistance heating evaporation method is considered. Alternatively, co-evaporation using a multi-source evaporation source is preferable.
[0043]
The cathode is preferably a transparent electrode because light transmission is required. In addition, in combination with an inorganic electron injection layer, the electron injection property does not matter so much, but in terms of performance as an electrode, a low sheet resistance or high conductivity is required.
[0044]
Specifically, the transparent electrodes exemplified by the above-mentioned anode, that is, tin-doped indium oxide (ITO), zinc-doped indium oxide (IZO), ZnO, SnO 2 ,
In 2 O 3 It is preferable to use such as.
[0045]
In order to reduce the sheet resistance and improve the conductivity, it is preferable to dope these materials with impurities. Specifically, one or more elements such as Al and Ir may be added in a total amount of 5 mol% or less, particularly 3 mol% or less, and more preferably 2-1 mol%.
[0046]
By doping impurities in this way, a sheet resistance of 20 Ω / □ or less can be achieved even with a film thickness of 100 nm or less. Therefore, it is effective in performing the above optical design.
[0047]
The cathode is usually an electrode on the light extraction side. It is preferable that the electrode on the light extraction side has a light transmittance of 50% or more, more preferably 80% or more, particularly 90% or more with respect to light in a light emission wavelength band, usually 400 to 700 nm. If the transmittance is too low, the light emission itself from the light emitting layer is attenuated, and it becomes difficult to obtain the luminance required for the light emitting element.
[0048]
In the present invention, the organic light-emitting layer is composed of a single layer or a laminate of two or more layers, and is preferably prepared so that the combined spectrum of light emitted from each light-emitting layer emits white light. In the present invention, white means x = 0.29 to 0.37, y = 0.30 to 0.45, preferably x = 0.32 to 0.36, and y = 0. It is in the range of 30 to 0.40 and has a broad emission spectrum in a wavelength band of 400 to 700 nm. In addition, since the light is a composite light from a light emitting layer having a plurality of light emission peaks, it does not have completely flat characteristics in the above wavelength band, and has a spectrum in which a certain number of peaks are scattered at several places.
[0049]
As a specific light-emitting layer for obtaining white light emission, for example, a two-layer structure of blue having a wavelength of 450 nm to 500 nm and yellow having a wavelength of 560 nm to 600 nm may be used.
[0050]
The light-emitting layer includes a host substance that is a hole-transporting compound or an electron-transporting compound or a mixture thereof, and has a hole and electron injection function, a hole and electron transport function, and a hole and electron recombination. It preferably has a function of generating excitons and contains an electronically relatively neutral compound.
[0051]
Examples of the hole transporting compound used as a host material of the organic light emitting layer include a triazole derivative, an oxadiazole derivative, an imidazole derivative, a polyarylalkane derivative, a virazoline derivative, a virazolone derivative, a phenylenediamine derivative, an arylamine derivative, and an amino-substituted chalcone. Derivatives, oxazole derivatives, styryl anthracene derivatives, fluorenone derivatives, hydrazone derivatives, and stilbene derivatives can be mentioned, and a triphenyldiamine derivative can be preferably used.
[0052]
As an example of the triphenyldiamine derivative, a tetraarylbendicine compound (triaryldiamine or triphenyldiamine: TPD) is particularly preferable.
[0053]
As the electron transporting compound used as a host material of the organic light emitting layer, a distyryl arylene derivative as shown below can be preferably used. Further, a phenylanthracene derivative or a tetraarylethene derivative can also be used as the electron transporting compound.
[0054]
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In the present invention, the organic light-emitting layer preferably has a structure in which a host material, which is a hole-transport compound or an electron-transport compound, or a mixture thereof, is doped with dovant, which is a fluorescent material.
[0056]
Further, the organic EL device according to the present invention preferably includes two or more organic light emitting layers stacked on each other. When two or more organic light-emitting layers are formed, a wide light-emitting wavelength band is secured and the degree of freedom of the color of the emitted light is improved by doping a fluorescent substance having a different light-emitting wavelength into each of the organic light-emitting layers. Can be done.
[0057]
In the present invention, examples of the fluorescent substance to be contained as a dovant include compounds disclosed in JP-A-63-264692, specifically, rubrene-based compounds, coumarin-based compounds, quinacridone-based compounds, and dicyanomethylbiran-based compounds. One or more compounds selected from the group consisting of compounds such as compounds can be preferably used.
[0058]
Examples of the fluorescent substance that can be preferably used in the present invention are as follows.
[0059]
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Further, in the present invention, the naphthacene-based compounds described in JP-A-2000-26334 and JP-A-2000-26337 can also be preferably used as a fluorescent substance contained as a dopant, and the rubrene-based compound When used in combination with a coumarin-based compound, a quinacridone-based compound, a dicyanomethylpyran-based compound, or the like, the life of the organic EL device can be significantly improved.
[0064]
When two or more organic light emitting layers are provided, it is preferable that each organic light emitting layer contains two or more kinds of these fluorescent substances, and the two or more kinds of fluorescent substances have different emission wavelengths.
[0065]
In the present invention, the content of the dopant in the organic light emitting layer is preferably from 0.01 to 20% by mass, and more preferably from 0.1 to 15% by mass.
[0066]
In the present invention, preferably, the organic light emitting layer is formed by vapor deposition.
[0067]
In the present invention, the organic light emitting layer preferably contains a mixture of a hole transporting compound and an electron injecting and transporting compound.
[0068]
When the organic light-emitting layer contains a mixture of a hole transporting compound and an electron injecting and transporting compound, a hopping conduction path for carriers is formed, and each carrier moves through a predominantly polar substance. In addition, carrier injection of the opposite polarity is less likely to occur, and therefore, the compound included in the organic light emitting layer is prevented from being damaged, so that there is an advantage that the life of the device can be improved.
[0069]
Further, by containing a doughant made of a fluorescent substance in an organic light emitting layer containing a mixture of a hole transporting compound and an electron injecting and transporting compound, the emission wavelength characteristics of the organic light emitting layer itself can be changed, The emission wavelength can be shifted to the longer wavelength side, the emission intensity can be improved, and further, the stability of the organic EL element can be improved.
[0070]
When the organic light-emitting layer contains a mixture of a hole transporting compound and an electron injecting and transporting compound, the mixing ratio of the hole transporting compound and the electron injecting and transporting compound is determined according to the respective carrier mobility and carrier concentration. Although it is determined, it is generally 1 / 99-99 / 1, preferably 10 / 90-90 / 10, more preferably 20 / 80-80 / 20, most preferably 40/90 by mass ratio. / 60 to 60/40 are selected.
[0071]
In the case of forming an organic light emitting layer containing a mixture of a hole transporting compound and an electron injecting and transporting compound, the hole transporting compound and the electron injecting and transporting compound are put in different evaporation sources, evaporated, and co-evaporated. However, when the hole transporting compound and the electron injecting and transporting compound have similar or very close vapor pressures, they can be mixed in advance in the same evaporation source and then subjected to evaporation.
[0072]
When forming an organic light emitting layer containing a mixture of a hole transporting compound and an electron injecting and transporting compound, the hole transporting compound and the electron injecting and transporting compound must be uniformly mixed in the organic light emitting layer. Although preferred, uniform mixing is not necessary.
[0073]
In the present invention, the organic material layer preferably has, in addition to at least one organic light emitting layer, a hole transport layer having a function of stably transporting holes, and an electron having a function of stably transporting electrons. It has a transport layer. By providing these layers, it is possible to increase the number of holes and electrons injected into the organic light emitting layer, confine it in the organic light emitting layer, optimize the recombination region, and improve the light emission efficiency. .
[0074]
In the present invention, compounds that can be preferably used in the hole transport layer include, for example, tetraarylbendicine compounds (triaryldiamine or triphenyldiamine: TPD), aromatic tertiary amines, hydrazone derivatives, carbazole derivatives , Triazole derivatives ", imidazole derivatives, oxadiazole derivatives having an amino group, polythiophenes and the like. Of these, a tetraarylbendicine compound (triaryldiamine or triphenyldiamine: TPD) and a triarylamine polymer (ATP) described in WO / 98/30071 can be particularly preferably used.
[0075]
Preferred specific examples of the triarylamine multimer (ATP) are as follows.
[0076]
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In the present invention, furthermore, JP-A-63-295695, JP-A-2-191694, JP-A-3-792, JP-A-5-234681, JP-A-5-239455, and JP-A-5-239455 Various organic compounds described in JP-A-5-299174, JP-A-7-126225, JP-A-7-126226, JP-A-8-100172, EPO650955Al, etc. also include a hole injection / transport layer, It can be used for injection layers and hole transport layers.
[0080]
In the present invention, two or more of these compounds may be used in combination, and when two or more of these compounds are used in combination, they may be mixed in one layer or laminated as two or more layers. You may.
[0081]
In the present invention, the hole transport layer can be formed by depositing the compound. When a device is formed by vapor deposition, a uniform, thin film having a thickness of about 1 to 10 nm without pinholes can be formed. Therefore, a compound having a low ionization potential and absorbing light of a visible wavelength is formed in the hole injection layer. Even if it is used, it is possible to prevent a decrease in luminous efficiency due to a change in the color tone of the luminescent color or reabsorption.
[0082]
In the present invention, examples of the compound that can be preferably used for the electron transport layer include, for example, an organometallic complex having 8-quinolinol such as tris (8-quinolinolato) aluminum (Alq3) or a derivative thereof as a ligand; Examples thereof include a diazole derivative, a perylene derivative, a pyridine derivative, a pyrimidine derivative, and a quinoxaline derivative.
[0083]
In the present invention, the electron transport layer can be formed by depositing the compound.
[0084]
In the present invention, the conditions for forming the organic light emitting layer, the hole injection transport layer or the hole injection layer and the hole transport layer, and the electron injection transport layer or the electron injection layer and the electron transport layer by evaporation are not particularly limited. Is not done, but 1 × 10 -4 It is preferable to set the deposition rate to about 0.01 to 1 nm / sec at Pascal or less. Each layer is 1 × 10 -4 It is preferably formed continuously under a reduced pressure of Pascal or less. 1 × 10 -4 By continuously forming each layer under a reduced pressure of Pascal or less, it is possible to prevent impurities from being adsorbed at the interface of each layer, so that it is possible to obtain a high-performance organic EL element. In addition, the driving voltage of the organic EL element is reduced, and the generation and growth of dark spots can be suppressed.
[0085]
Furthermore, in order to prevent deterioration of the organic layer and the electrodes of the element, it is preferable to seal the element with a sealing plate or the like. The sealing plate adheres and seals the sealing plate using an adhesive resin layer in order to prevent moisture from entering. The sealing gas is Ar, He, N 2 And the like. Further, the moisture content of the sealing gas is preferably 100 ppm or less, more preferably 10 ppm or less, and particularly preferably 1 ppm or less. Although there is no particular lower limit for this water content, it is usually about 0.1 ppm.
[0086]
Further, a number of the devices of the present invention may be arranged on a plane. By changing the emission color of each element arranged on a plane, a color display can be obtained.
[0087]
The emission color may be controlled by using a color filter film, a color conversion film containing a fluorescent substance, or a dielectric reflection film on the element substrate or the sealing substrate.
[0088]
【Example】
[Example 1]
TiN was formed as a reflective layer to a thickness of 50 nm on a glass substrate by a sputtering method. At this time, the reflectance of the reflective layer at a wavelength of 400 to 700 nm was 45%.
[0089]
Next, an ITO transparent electrode (anode) was formed into a film having the thickness shown in Table 1, and the reflective layer and the glass substrate with ITO were subjected to ultrasonic cleaning using a neutral detergent, acetone, and ethanol, and pulled up from boiling ethanol. And dried. This substrate with transparent electrode is UV / O 3 After cleaning, it is fixed to the substrate holder of the vacuum evaporation apparatus, -4 The pressure was reduced to Pa or less. In addition, the refractive index n1 of ITO was 1.9. It should be noted that only Sample 9 was not provided with ITO, and instead of ITO using the TiN reflective layer as an anode, GeOIn was formed to a thickness of 2 nm and used in order to ensure hole injection properties.
[0090]
Next, as a hole injection layer, N, N'-diphenyl-N, N'-bis [N- (4-methylphenyl) -N-phenyl (4-aminophenyl)]-1 was maintained while maintaining a reduced pressure. , 1'-biphenyl-4,4'-diamine was formed to a thickness of 20 nm at a steaming rate of 0.1 nm / sec.
[0091]
Next, while maintaining the reduced pressure state, N, N′-diphenyl-N, N′-bis (1-naphthyl) -1,1′-diphenyl-4.4′-diamine was deposited at a deposition rate of 0 as a hole transport layer. A film was formed at a thickness of 10 nm at a thickness of 0.1 nm / sec.
[0092]
Further, while maintaining the reduced pressure state, the following compounds 1 and 2 were co-evaporated at a volume ratio of 100: 3 at an evaporation rate of 0.1 nm / sec to form a 30 nm thick layer. By changing the thickness of the hole transport layer among the hole injection layer, the hole transport layer, and the lower light emitting layer, the film was formed so that the total thickness was the thickness of each sample shown in Table 1. In addition, the refractive index n3 of these organic layers was 1.7.
[0093]
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Further, while maintaining the reduced pressure state, the following compounds 3 and 4 as luminous elements were co-evaporated at a volume ratio of 100: 3 at an evaporation rate of 0.1 nm / sec to form a film having a thickness of 30 nm.
[0096]
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Next, as the electron injection layer, the IDE 120 was formed to a thickness of 30 nm at a deposition rate of 0.1 nm / sec. By changing the thickness of the electron injecting layer among the upper light emitting layer and the organic electron injecting layer, the film was formed so that the total film thickness became the thickness of each sample shown in Table 1. In addition, the refractive index n4 of these organic layers was 1.7.
[0099]
Next, while maintaining the reduced pressure state, LiF is formed as an inorganic electron injection layer to a thickness of 3 nm at a deposition rate of 0.01 nm / sec, and then a transparent electrode obtained by doping ZnO with 5 mol% of Al is formed by sputtering. At a speed of 0.05 nm / sec to a thickness shown in Table 1. The refractive index of this transparent electrode was n5 = 1.8.
[0100]
A voltage was applied to this organic EL element to flow a current, and the evaluation was performed. Table 1 shows the obtained light emission luminance, voltage, and chromaticity (CIE color coordinates).
[0101]
[Table 1]
As is evident from Table 1, the samples in which the film thickness of each constituent layer or the product of the film thickness and the refractive index falls within the range of the present invention have excellent values in both luminance and chromaticity. In addition, the drive voltage at which the film thickness of the electrode becomes large increases.
[0103]
【The invention's effect】
As described above, according to the present invention, in an organic EL device having a top light extraction type structure that emits white light from two or more light emitting layers, which has not been studied, an optical model inside the device is established, and efficiency is improved. It is possible to provide an organic EL device which is excellent in white chromaticity and excellent in chromaticity.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing a basic configuration of an organic EL device of the present invention.
[Explanation of symbols]
1 substrate
2 Light reflection layer
3 Anode
4 Organic hole injection transport layer
5 First light emitting layer (lower light emitting layer)
6 Second light emitting layer (upper light emitting layer)
7 Organic electron injection transport layer
8 Inorganic electron injection layer 8
9 Cathode
Claims (16)
前記基板とこの基板上に可視光反射率５０％以上を有する反射層と、陽極と、発光層を有する有機層と、陰極である透明電極とを少なくとも順次有し、
前記発光層の中間点から陽極下端面までの総膜厚が４５ｎｍ〜１６０ｎｍであり、前記発光層中間点から陰極上端面までの総膜厚が１２０ｎｍ〜２９０ｎｍである有機ＥＬ素子。An organic EL element having one kind of light emitting layer having at least one light emission peak and obtaining light extracted from an upper surface opposite to a substrate,
Having at least the substrate and a reflective layer having a visible light reflectance of 50% or more on the substrate, an anode, an organic layer having a light emitting layer, and a transparent electrode serving as a cathode;
An organic EL device wherein the total film thickness from the midpoint of the light emitting layer to the lower end surface of the anode is 45 nm to 160 nm, and the total film thickness from the midpoint of the light emitting layer to the upper end surface of the cathode is 120 nm to 290 nm.
前記発光層中間点から陽極上端面までの総膜厚が４５ｎｍ〜１６０ｎｍであり、前記発光層中間点から陰極上端面までの総膜厚が１２０ｎｍ〜２９０ｎｍである請求項１の有機ＥＬ素子。The reflective layer is an anode,
2. The organic EL device according to claim 1, wherein a total thickness from the midpoint of the light emitting layer to the upper end face of the anode is 45 nm to 160 nm, and a total thickness from the midpoint of the light emitting layer to the upper end face of the cathode is 120 nm to 290 nm.
少なくとも最も陽極側に位置する下部発光層と最も陰極側に位置する上部発光層との界面あるいはこれらの中間点から陽極下端面までの総膜厚が４５ｎｍ〜１００ｎｍであり、前記界面あるいは中間点から陰極上端面までの総膜厚が１００ｎｍ〜２６０ｎｍである請求項１の有機ＥＬ素子。It has two or more kinds of the light emitting layers, and obtains white extraction light from the upper surface opposite to the substrate by a combined light of the two or more kinds of light emitting layers,
At least the total thickness from the interface between the lower light-emitting layer located closest to the anode side and the upper light-emitting layer located closest to the cathode side or the middle point thereof to the lower end face of the anode is 45 nm to 100 nm, and from the interface or the middle point. 2. The organic EL device according to claim 1, wherein the total film thickness up to the upper end surface of the cathode is 100 nm to 260 nm.
陽極の膜厚が２５〜７０ｎｍである請求項３の有機ＥＬ素子。A total film thickness from the interface between the lower light-emitting layer and the upper light-emitting layer or an intermediate point thereof to the lower end surface of the anode is 45 nm to 130 nm;
4. The organic EL device according to claim 3, wherein the thickness of the anode is 25 to 70 nm.
陰極である透明電極の膜厚が５０ｎｍ〜１４０ｎｍである請求項３または４の有機ＥＬ素子。A total film thickness from the interface between the lower light-emitting layer and the upper light-emitting layer or an intermediate point thereof to the upper end surface of the cathode is 100 nm to 260 nm;
5. The organic EL device according to claim 3, wherein the transparent electrode serving as a cathode has a thickness of 50 nm to 140 nm.
Ａ＝（ａ１×ｎ２）＋（ａ２×ｎ３）
（ａ１は陽極の膜厚、ｎ２は陽極の屈折率、ａ２は下部発光層を含む下側有機層の膜厚、ｎ３は下部発光層５を含む下側有機層の屈折率）、
前記界面あるいは中間点から陰極上端面までの膜厚（ｎｍ）と屈折率の積の総和をＢ、
Ｂ＝（ｂ１×ｎ４）＋（ｂ２×ｎ５）
（ｂ１は上部発光層を含む上側有機層の膜厚、ｎ４は上部発光層を含む上側有機層の屈折率、ｂ２は透明陰極の膜厚、ｎ５は透明陰極の屈折率、）
とすると、
Ａ＝７２〜２４８、
Ｂ＝１６５〜４９６、
である請求項３の有機ＥＬ素子。The sum of the product of the film thickness (nm) and the refractive index from the interface between the lower light emitting layer and the upper light emitting layer or the midpoint thereof to the lower end face of the anode is represented by A,
A = (a1 × n2) + (a2 × n3)
(A1 is the thickness of the anode, n2 is the refractive index of the anode, a2 is the thickness of the lower organic layer including the lower light emitting layer, n3 is the refractive index of the lower organic layer including the lower light emitting layer 5),
The sum of the product of the film thickness (nm) from the interface or the intermediate point to the cathode upper end surface and the refractive index is B,
B = (b1 × n4) + (b2 × n5)
(B1 is the thickness of the upper organic layer including the upper light emitting layer, n4 is the refractive index of the upper organic layer including the upper light emitting layer, b2 is the thickness of the transparent cathode, and n5 is the refractive index of the transparent cathode.)
Then
A = 72-248,
B = 165-496,
The organic EL device according to claim 3, wherein
前記下部発光層と上部発光層との界面あるいはこれらの中間点から陽極上端面までの総膜厚が４５ｎｍ〜１３０ｎｍであり、前記界面あるいは中間点から陰極上端面までの総膜厚が１００ｎｍ〜２９０ｎｍである請求項３の有機ＥＬ素子。The reflective layer is an anode,
The total film thickness from the interface between the lower light emitting layer and the upper light emitting layer or the intermediate point thereof to the upper end face of the anode is 45 nm to 130 nm, and the total film thickness from the interface or the intermediate point to the upper end face of the cathode is 100 nm to 290 nm. The organic EL device according to claim 3, wherein
Ａ＝（ａ２×ｎ３）
（ａ２は下部発光層を含む下側有機層の膜厚、ｎ３は下部発光層を含む下側有機層の屈折率）、
前記界面あるいはこれらの中間点から陰極上端部までの膜厚（ｎｍ）と屈折率の積の総和をＢ、
Ｂ＝（ｂ１×ｎ４）＋（ｂ２×ｎ５）
（ｂ１は上部発光層を含む上側有機層の膜厚、ｎ２は上部発光層を含む上側有機層の屈折率、ｂ２は透明電極の膜厚、ｎ３は透明電極の屈折率）、
とすると、
Ａ＝７２〜２３４
Ｂ＝１６４〜４９６
である請求項８の有機ＥＬ素子。The sum of the product of the film thickness (nm) and the refractive index from the interface between the lower light emitting layer and the upper light emitting layer or the midpoint thereof to the upper end of the anode is represented by A,
A = (a2 × n3)
(A2 is the thickness of the lower organic layer including the lower light emitting layer, n3 is the refractive index of the lower organic layer including the lower light emitting layer),
The sum of the product of the film thickness (nm) from the interface or the intermediate point thereof to the upper end of the cathode and the refractive index is B
B = (b1 × n4) + (b2 × n5)
(B1 is the thickness of the upper organic layer including the upper light emitting layer, n2 is the refractive index of the upper organic layer including the upper light emitting layer, b2 is the thickness of the transparent electrode, and n3 is the refractive index of the transparent electrode),
Then
A = 72 to 234
B = 164-496
The organic EL device according to claim 8, wherein
前記基板と、この基板上に可視光反射率５０％以上を有する反射層と、陽極と、少なくとも最も陽極側に位置する下部発光層と最も陰極側に位置する上部発光層とを有する有機層と、陰極である透明電極とを順次有し、
前記下部発光層と上部発光層との界面あるいはこれらの中間点から陽極下端面までの膜厚（ｎｍ）と屈折率の積の総和をＡ、
Ａ＝（ａ１×ｎ２）＋（ａ２×ｎ３）
（ａ１は陽極の膜厚、ｎ２は陽極の屈折率、ａ２は下部発光層を含む下側有機層の膜厚、ｎ３は下部発光層５を含む下側有機層の屈折率）、
前記界面あるいは中間点から陰極上端面までの膜厚（ｎｍ）と屈折率の積の総和をＢ、
Ｂ＝（ｂ１×ｎ４）＋（ｂ２×ｎ５）
（ｂ１は上部発光層を含む上側有機層の膜厚、ｎ４は上部発光層を含む上側有機層の屈折率、ｂ２は透明陰極の膜厚、ｎ５は透明陰極の屈折率、）
とすると、
Ａ＝７２〜２４８、
Ｂ＝１６５〜４９６、
である有機ＥＬ素子。An organic EL device having two or more light-emitting layers having different light emission peaks, and obtaining white light extracted from the upper surface on the side opposite to the substrate by a combined light of the two or more light-emitting layers,
An organic layer having the substrate, a reflective layer having a visible light reflectance of 50% or more on the substrate, an anode, and at least a lower light-emitting layer positioned closest to the anode and an upper light-emitting layer positioned closest to the cathode; , A transparent electrode which is a cathode,
The sum of the product of the film thickness (nm) and the refractive index from the interface between the lower light emitting layer and the upper light emitting layer or the midpoint thereof to the lower end face of the anode is represented by A,
A = (a1 × n2) + (a2 × n3)
(A1 is the thickness of the anode, n2 is the refractive index of the anode, a2 is the thickness of the lower organic layer including the lower light emitting layer, n3 is the refractive index of the lower organic layer including the lower light emitting layer 5),
The sum of the product of the film thickness (nm) from the interface or the intermediate point to the cathode upper end surface and the refractive index is B,
B = (b1 × n4) + (b2 × n5)
(B1 is the thickness of the upper organic layer including the upper light emitting layer, n4 is the refractive index of the upper organic layer including the upper light emitting layer, b2 is the thickness of the transparent cathode, and n5 is the refractive index of the transparent cathode.)
Then
A = 72-248,
B = 165-496,
An organic EL device.
前記下部発光層と上部発光層の界面あるいはこれらの中間点から陽極上端部までの膜厚（ｎｍ）と屈折率の積の総和をＡ、
Ａ＝（ａ２×ｎ３）
（ａ２は下部発光層を含む下側有機層の膜厚、ｎ３は下部発光層を含む下側有機層の屈折率）、
前記界面あるいはこれらの中間点から陰極上端部までの膜厚（ｎｍ）と屈折率の積の総和をＢ、
Ｂ＝（ｂ１×ｎ４）＋（ｂ２×ｎ５）
（ｂ１は上部発光層を含む上側有機層の膜厚、ｎ２は上部発光層を含む上側有機層の屈折率、ｂ２は透明電極の膜厚、ｎ３は透明電極の屈折率）、
とすると、
Ａ＝７２〜２３４
Ｂ＝１６４〜４９６
である請求項１２の有機ＥＬ素子。The reflective layer is an anode,
The sum of the product of the film thickness (nm) and the refractive index from the interface between the lower light emitting layer and the upper light emitting layer or the midpoint thereof to the upper end of the anode is represented by A,
A = (a2 × n3)
(A2 is the thickness of the lower organic layer including the lower light emitting layer, n3 is the refractive index of the lower organic layer including the lower light emitting layer),
The sum of the product of the film thickness (nm) from the interface or the intermediate point thereof to the upper end of the cathode and the refractive index is B
B = (b1 × n4) + (b2 × n5)
(B1 is the thickness of the upper organic layer including the upper light emitting layer, n2 is the refractive index of the upper organic layer including the upper light emitting layer, b2 is the thickness of the transparent electrode, and n3 is the refractive index of the transparent electrode),
Then
A = 72 to 234
B = 164-496
The organic EL device according to claim 12, wherein
前記基板とこの基板上に可視光反射率５０％以上を有する反射層と、この反射層を陽極とし、少なくとも最も陽極側に位置する下部発光層と最も陰極側に位置する上部発光層とを有する有機層と、無機電子注入層と、陰極である透明電極とを順次有し、
前記無機電子注入層の膜厚が０．１ｎｍ〜５ｎｍで、屈折率が１．６〜２．６である有機ＥＬ素子。An organic EL element having one or more kinds of light-emitting layers and obtaining white light extracted from the upper surface opposite to the substrate,
The substrate, a reflective layer having a visible light reflectance of 50% or more on the substrate, an anode having the reflective layer as an anode, and at least a lower light emitting layer located closest to the anode and an upper light emitting layer located closest to the cathode. An organic layer, an inorganic electron injection layer, and a transparent electrode which is a cathode in order,
An organic EL device wherein the inorganic electron injecting layer has a thickness of 0.1 nm to 5 nm and a refractive index of 1.6 to 2.6.
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