Light emitting device, electronic device and television device

The invention disclosed below relates to a light emitting device having a light emitting layer between a pair of electrodes. The present invention also relates to a light emitting device using the light emitting element, and a lighting device and an electronic device using the light emitting device.

In recent years, the development of light emitting devices using luminescent organic compounds and inorganic compounds as light emitting substances has been active. In particular, the configuration of a light emitting element called an electroluminescence (EL) element has a simple structure in which a light emitting layer containing a light emitting substance is provided between electrodes, and is thin and lightweight, has high-speed responsiveness, and is driven by a low-voltage DC. Because of its characteristics, it is attracting attention as a next-generation flat panel display element. In addition, a display using such a light emitting element has excellent contrast and image quality, and has a wide viewing angle. Further, since these light emitting elements are planar light sources, application as a light source for a backlight or lighting of a liquid crystal display is also considered.

The light emitting element can obtain a predetermined light emitting color by applying an electric current to the light emitting layer provided between the pair of electrodes to excite the light emitting substance contained in the light emitting layer. In order to increase the emission brightness of such a light emitting element, a method of supplying a large amount of current to the light emitting layer can be considered, but the merit of low power consumption is impaired. Further, by passing a large amount of current through the light emitting layer, the deterioration of the light emitting element is accelerated.

Therefore, a light emitting element has been proposed in which a plurality of light emitting layers are laminated and a current having the same current density as that of a single layer is passed to increase the light emitting brightness (for example, Patent Document 1).

<p><patcit num="1"><text>Japanese Patent No. 3933591</text></patcit></p>

<p> Patent Document 1 proposes a light emitting device having a plurality of light emitting units (hereinafter, also referred to as EL layers in the present specification), and each light emitting unit is partitioned by a charge generation layer. More specifically, a charge generation layer made of vanadium pentaoxide is provided on a metal doping layer that functions as an electron injection layer of the first light emitting unit, and a second light generation unit is further passed through the charge generation layer. A light emitting element having a structure in which is laminated is disclosed. However, in a light emitting device having such a structure, an interaction occurs at the interface between the metal doping layer and the charge generation layer made of oxide, and the interface becomes a strong electric field, so that a high voltage is required to drive the light emitting device. It becomes.</p><p> In view of the above-mentioned problems, one of the problems is to provide a light emitting element that emits high-luminance light and can be driven at a low voltage. Another issue is to provide a light emitting device or an electronic device with reduced power consumption.</p>

<p> One of the configurations of the light emitting element disclosed in the present specification has an EL layer of n (n is a natural number of 2 or more) layer between the anode and the cathode, and m (m is a natural number, 1 m n-). Between the 1) th EL layer and the (m + 1) th EL layer, in order from the anode side, alkali metal, alkaline earth metal, rare earth metal, alkali metal compound, alkaline earth metal compound, or A first layer containing any of the rare earth metal compounds, a second layer containing a highly electron-transporting substance in contact with the first layer, and a hole-transporting layer in contact with the second layer. It has a region containing high substances and acceptor substances.</p><p> Further, one of the other configurations of the light emitting element disclosed in the present specification has an EL layer of n (n is a natural number of 2 or more) layer between the anode and the cathode, and m (m is a natural number, 1 m). Between the n-1) th EL layer and the (m + 1) th EL layer, in order from the anode side, a first layer containing a substance having a high electron transport property and a donor substance, and a first layer. It has a second layer in contact with the first layer and containing a substance having a high electron transport property, and a region in contact with the second layer and containing a substance having a high hole transport property and an acceptor property.</p><p> Further, in the first layer containing the above-mentioned substance having high electron transportability and the donor substance, the donor substance is added at a mass ratio of 0.001 or more and 0.1 or less to the substance having high electron transport property. May be. Further, the donor substance is preferably an alkali metal, an alkaline earth metal, a rare earth metal, an alkali metal compound, an alkaline earth metal compound, or a compound of a rare earth metal.</p><p> Further, in the above configuration, the region containing the substance having a high hole transporting property and the accepting substance is a region to which the substance having the accepting property is added at a mass ratio of 0.1 or more and 4.0 or less with respect to the substance having a high hole transporting property. Is. Of the carriers generated in this region, holes are injected into the (m + 1) th EL layer, and electrons move to the second layer.</p><p> Further, in the above configuration, the region containing the substance having a high hole transporting property and the accepting substance may be a region in which a layer containing the substance having a high hole transporting property and a layer containing the accepting substance are laminated. ..</p><p>Further, in the above configuration, as the substance having high electron transport property contained in the second layer, a substance having a LUMO level of -5.0 eV or more, more preferably -5.0 eV or more and -3.0 eV or less is preferably used. Is preferable.</p><p> Further, since the light emitting element having the above configuration can realize a low drive voltage, a light emitting device (image display device or light emitting device) using this as a light emitting element can realize low power consumption. Therefore, a light emitting device using a light emitting element having the above configuration, and a lighting device and an electronic device using the light emitting device are also included as one aspect of the present invention.</p><p> The above configuration solves at least one of the above problems.</p><p> The light emitting device in the present specification includes an electronic device such as an image display device using a light emitting element or a lighting device. In addition, a module in which a connector, for example, an anisotropic conductive film, a TAB (Tape Automated Bonding) tape, or a TCP (Tape Carrier Package) is attached to a light emitting element, or a module in which a printed wiring board is provided at the tip of the TAB tape or TCP. Alternatively, the light emitting device shall include all modules in which an IC (integrated circuit) is directly mounted on the light emitting element by the COG (Chip On Glass) method.</p><p> In this specification, the ordinal numbers attached as the first or second are used for convenience, and do not indicate the process order or the stacking order. In addition, this specification does not indicate a unique name as a matter for specifying the invention.</p>

<p> It is possible to provide a light emitting element having a plurality of light emitting layers and capable of being driven at a low voltage.</p><p> Further, by manufacturing a light emitting device using the above-mentioned light emitting element, it is possible to provide a light emitting device having low power consumption. Further, by applying such a light emitting device to a lighting device or an electronic device, it is possible to provide a lighting device or an electronic device having low power consumption.</p>

<figref num="1">The figure which shows an example of the element structure of a light emitting element, and the band diagram.</figref><figref num="2">The figure which shows an example of the element structure of a light emitting element, and the band diagram.</figref><figref num="3">The figure which shows an example of the element structure of a light emitting element, and the band diagram.</figref><figref num="4">The figure which shows an example of the element structure of a light emitting element.</figref><figref num="5">The figure which shows the active matrix type light emitting device.</figref><figref num="6">The figure which shows the passive matrix type light emitting device.</figref><figref num="7">The figure which shows the electronic device.</figref><figref num="8">The figure which shows the lighting apparatus.</figref><figref num="9">The figure which shows the element structure of the light emitting element of an Example and the comparative light emitting element.</figref><figref num="10">The figure which shows the characteristic of the light emitting element of Example 1.</figref><figref num="11">The figure which shows the characteristic of the light emitting element of Example 1.</figref><figref num="12">The figure which shows the element structure of the light emitting element of an Example and the comparative light emitting element.</figref><figref num="13">The figure which shows the characteristic of the light emitting element of Example 2.</figref><figref num="14">The figure which shows the characteristic of the light emitting element of Example 2.</figref><figref num="15">The figure which shows the characteristic of the light emitting element of Example 3.</figref><figref num="16">The figure which shows the characteristic of the light emitting element of Example 3.</figref><figref num="17">The figure which shows the characteristic of the light emitting element of Example 4.</figref><figref num="18">The figure which shows the characteristic of the light emitting element of Example 4.</figref><figref num="19">The figure which shows the characteristic of the light emitting element of Example 5.</figref><figref num="20">The figure which shows the characteristic of the light emitting element of Example 5.</figref><figref num="21">The figure which shows the element structure of the comparative light emitting element of Example 6.</figref><figref num="22">The figure which shows the characteristic of the light emitting element of Example 6.</figref><figref num="23">The figure which shows the characteristic of the light emitting element of Example 6.</figref><figref num="24">The figure which shows an example of the element structure of a light emitting element, and the light emission spectrum.</figref><figref num="25">The figure which shows the characteristic of the light emitting element of Example 7.</figref><figref num="26">The figure which shows the characteristic of the light emitting element of Example 7.</figref><figref num="27">The figure which shows the characteristic of the light emitting element of Example 8.</figref><figref num="28">The figure which shows the characteristic of the light emitting element of Example 8.</figref><figref num="29">The figure which shows the characteristic of the light emitting element of Example 8.</figref><figref num="30">The figure which shows the characteristic of the light emitting element of Example 9.</figref><figref num="31">The figure which shows the characteristic of the light emitting element of Example 9.</figref><figref num="32">The figure which shows the characteristic of the light emitting element of Example 9.</figref>

Hereinafter, embodiments will be described in detail with reference to the drawings. However, the invention disclosed in the present specification is not limited to the following description, and those skilled in the art can easily change the form and details thereof without departing from the spirit and scope of the present invention. Understood. Therefore, the interpretation is not limited to the description of the embodiments and examples of the present specification. In all the drawings for explaining the embodiment, the same parts or parts having the same functions are designated by the same reference numerals, and the repeated description thereof will be omitted.

(Embodiment 1) In the present embodiment, one aspect of the light emitting element will be described with reference to FIG.

In the device structure shown in FIG. 1 (A), a first EL layer 103 and a second EL layer 107 including a light emitting region are sandwiched between a pair of electrodes (anode 101, cathode 102), and the first EL The layer 103 and the second EL layer 107 have a structure in which an electron injection buffer 104, an electron relay layer 105, and a charge generation region 106 are sequentially laminated from the anode 101 side.

The charge generation region 106 is a region containing a substance having a high hole transport property and an acceptor substance, and generates holes and electrons which are carriers of the light emitting element. The holes generated in the charge generation region 106 move to the second EL layer 107, and the electrons move to the electron relay layer 105. Further, since the electron relay layer 105 has high electron transportability, it is possible to quickly send electrons to the electron injection buffer 104. Further, since the electron injection buffer 104 can relax the injection barrier when injecting electrons into the first EL layer 103, it is possible to increase the efficiency of electron injection into the first EL layer 103.

The electron injection buffer 104 contains alkali metals, alkaline earth metals, rare earth metals, and compounds thereof (alkali metal compounds (including oxides such as lithium oxide, halides, and carbonates such as lithium carbonate and cesium carbonate). It is possible to use a substance having high electron injection properties such as an alkaline earth metal compound (including oxides, halides and carbonates) or a rare earth metal compound (including oxides, halides and carbonates). Alternatively, the electron infusion buffer 104 may be configured to contain a substance having a high electron transport property and a donor substance.

FIG. 1 (B) shows a band diagram in the device structure of FIG. 1 (A). In FIG. 1 (B), 111 is the Fermi level of the anode 101, 112 is the Fermi level of the cathode 102, and 113 is the LUMO (Lowest Unoccupied Molecular Orbital) level of the first EL layer 103. The position 114 indicates the LUMO level of the electron relay layer 105, 115 indicates the acceptor level of the acceptor in the charge generation region 106, and 116 indicates the LUMO level of the second EL layer 107.

In FIG. 1B, the holes injected from the anode 101 are injected into the first EL layer 103. On the other hand, the electrons generated in the charge generation region 106 move to the electron relay layer 105, are injected into the first EL layer 103 via the electron injection buffer 104, recombine with holes, and emit light. Further, the holes generated in the charge generation region 106 move to the second EL layer 107, and in the second EL layer 107, they recombine with the electrons injected from the cathode 102 to emit light.

In the light emitting element shown in the present embodiment, the electron relay layer 105 functions as a layer for efficiently injecting the electrons generated in the charge generation region 106 into the first EL layer 103. Therefore, the electron relay layer 105 has a LUMO. It is preferable to use a material in which the level occupies a level between the acceptor level of the acceptor in the charge generation region 106 and the LUMO level of the first EL layer 103. Specifically, it is preferable to use a material having a LUMO level of about -5.0 eV or more, and more preferably to use a material having a LUMO level of -5.0 eV or more and -3.0 eV or less.

Since the acceptor substance contained in the charge generation region 106 and the highly electron injectable substance or donor substance contained in the electron injection buffer 104 have a strong acceptor property or a strong donor property, respectively, the charge generation region 106 and the electron When the injection buffer 104 comes into contact with it, electrons are transferred at the interface and the drive voltage of the light emitting element rises. Further, the drive voltage of the light emitting element may increase due to the formation of the PN junction at the interface where the charge generation region 106 and the electron injection buffer 104 are in contact with each other. However, in the light emitting device shown in the present embodiment, the electron relay layer 105 can prevent the charge generation region 106 from coming into contact with the electron injection buffer 104, and the acceptor substance contained in the charge generation region 106 and the electron injection It is possible to prevent the highly electron-injectable substance or the donor substance contained in the buffer 104 from interacting with each other. Further, by using a material having a LUMO level in the above range for the electron relay layer 105, it is possible to suppress the interface with the electron injection buffer 104 from becoming a strong electric field, and to generate electrons in the charge generation region 106. It can be efficiently injected into the first EL layer 103.

Further, as shown in the band diagram of FIG. 1 (B), the electrons that have moved from the charge generation region 106 to the electron relay layer 105 are relaxed by the electron injection buffer 104, so that the injection barrier is relaxed, so that the first EL layer 103 Easily injected into LUMO level 113. The holes generated in the charge generation region 106 move to the second EL layer 107.

Next, the materials that can be used for the above-mentioned light emitting device will be specifically described.

As the anode 101, it is preferable to use a metal, an alloy, an electrically conductive compound, a mixture thereof, or the like having a large work function (specifically, 4.0 eV or more is preferable). Specifically, for example, indium tin oxide (ITO: Indium Tin Oxide), indium tin oxide containing silicon or silicon oxide, indium tin oxide (IZO: Indium Zinc Oxide), tungsten oxide and oxidation. Examples thereof include indium oxide containing zinc.

These conductive metal oxide films are usually formed by sputtering, but may be produced by applying a sol-gel method or the like. For example, indium oxide-zinc oxide (IZO) can be formed by sputtering using a target in which 1 to 20 wt% zinc oxide is added to indium oxide. Further, indium oxide containing tungsten oxide and zinc oxide can be formed by a sputtering method using a target containing 0.5 to 5 wt% of tungsten oxide and 0.1 to 1 wt% of zinc oxide with respect to indium oxide.

Also, gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd). ), Titanium (Ti), or a nitride of a metallic material (eg, titanium nitride, etc.), molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, manganese oxide, titanium oxide, etc. It is also possible to form. Further, conductive polymers such as poly (3,4-ethylenedioxythiophene) / poly (styrene sulfonic acid) (PEDOT / PSS) and polyaniline / poly (styrene sulfonic acid) (PAni / PSS) may be used. However, when a charge generation region in contact with the anode 101 is provided as a part of the first EL layer 103, Al, Ag, and various conductive materials may be used for the anode 101 regardless of the magnitude of the work function. it can.

As the cathode 102, it is preferable to use a metal having a small work function (specifically, preferably 3.8 eV or less), an alloy, an electrically conductive compound, or a mixture thereof. Specific examples of such a cathode material include elements belonging to Group 1 or Group 2 of the Periodic Table of the Elements, that is, alkali metals such as lithium (Li) and cesium (Cs), magnesium (Mg), and calcium (Ca). ), Alkaline earth metals such as strontium (Sr), and rare earth metals such as alloys containing them (MgAg, AlLi), europium (Eu), ytterbium (Yb), and alloys containing these. A film of an alkali metal, an alkaline earth metal, or an alloy containing these can be formed by using a vacuum vapor deposition method. Further, an alloy containing an alkali metal or an alkaline earth metal can also be formed by a sputtering method. It is also possible to form a film of silver paste or the like by an inkjet method or the like.

Also, alkali metal compounds, alkaline earth metal compounds, or rare earth metal compounds (eg, lithium fluoride (LiF), lithium oxide (LiOx), cesium fluoride (CsF), calcium fluoride (CaF).₂), Erbium Fluoride (ErF)₃) Etc.) and a metal film such as aluminum are laminated to form the cathode 102. However, when a charge generation region in contact with the cathode 102 is provided as a part of the second EL layer 107, indium oxide containing Al, Ag, ITO, silicon or silicon oxide-regardless of the magnitude of the work function. Various conductive materials such as tin oxide can be used for the cathode 102.

In the light emitting device shown in the present embodiment, at least one of the anode and the cathode may have translucency. Translucency can be ensured by using a transparent electrode such as ITO or by reducing the film thickness of the electrode.

The first EL layer 103 and the second EL layer 107 may be formed so as to include at least a light emitting layer, and may have a laminated structure further having a layer other than the light emitting layer. The light emitting layer contained in the first EL layer 103 and the light emitting layer contained in the second EL layer 107 may be different from each other. Further, the first EL layer 103 and the second EL layer 107 may each independently have a laminated structure having a layer other than the light emitting layer. In addition to the light emitting layer, a substance with high hole injection property, a substance with high hole transport property or a substance with high electron transport property, a substance with high electron injection property, and a bipolar substance (a substance with high electron and hole transport property). Examples include layers made of the above substances. Specific examples thereof include a hole injection layer, a hole transport layer, a light emitting layer, a hole blocking layer (hole blocking layer), an electron transport layer, an electron injection layer, and the like, and these are appropriately combined from the anode side. can do. Further, a charge generation region can be provided on the side of the first EL layer 103 in contact with the anode 101.

Specific examples of the materials constituting each layer included in the EL layer described above are shown below.

The hole injection layer is a layer containing a substance having a high hole injection property. As the substance having high hole injection property, for example, molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, manganese oxide and the like can be used. In addition, phthalocyanine (abbreviation: H)₂Holes are also formed by phthalocyanine compounds such as Pc) and copper phthalocyanine (abbreviation: CuPc), or polymers such as poly (3,4-ethylenedioxythiophene) / poly (styrene sulfonic acid) (PEDOT / PSS). An injection layer can be formed.

The hole transport layer is a layer containing a substance having a high hole transport property. Examples of substances having high hole transport properties include 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (abbreviation: NPB or α-NPD) and N, N'-bis (abbreviation: NPB or α-NPD). 3-Methylphenyl) -N, N'-diphenyl- [1,1'-biphenyl] -4,4'-diamine (abbreviation: TPD), 4,4', 4''-tris (carbazole-9-yl) ) Triphenylamine (abbreviation: TCTA), 4,4', 4''-Tris (N, N-diphenylamino) Triphenylamine (abbreviation: TDATA), 4,4', 4''-Tris [N- (3-Methylphenyl) -N-Phenylamino] Triphenylamine (abbreviation: MTDATA), 4,4'-bis [N- (spiro-9,9'-bifluoren-2-yl) -N-phenylamino] Aromatic amine compounds such as biphenyl (abbreviation: BSPB), 3- [N- (9-phenylcarbazole-3-yl) -N-phenylamino] -9-phenylcarbazole (abbreviation: PCzPCA1), 3,6-bis [N- (9-Phenylcarbazole-3-yl) -N-Phenylamino] -9-Phenylcarbazole (abbreviation: PCzPCA2), 3- [N- (1-naphthyl) -N- (9-Phenylcarbazole-3) -Il) Amino] -9-Phenylcarbazole (abbreviation: PCzPCN1) and the like. In addition, 4,4'-di (N-carbazolyl) biphenyl (abbreviation: CBP), 1,3,5-tris [4- (N-carbazolyl) phenyl] benzene (abbreviation: TCPB), 9- [4- ( 10-Phenyl-9-anthracenyl) phenyl] -9H-carbazole (abbreviation: CzPA) and other carbazole derivatives can be used. The substances mentioned here are mainly 10^-6cm²It is a substance with hole mobility of / Vs or more. However, any substance other than these may be used as long as it is a substance having a higher hole transport property than electrons. The layer containing the substance having a high hole transport property is not limited to a single layer, but may be a layer in which two or more layers made of the above substances are laminated.

In addition to this, poly (N-vinylcarbazole) (abbreviation: PVK), poly (4-vinyltriphenylamine) (abbreviation: PVTPA), poly [N- (4- {N'-[4- (4- (4- (4- (4-) Diphenylamino) phenyl] phenyl-N'-phenylamino} phenyl) methacrylamide] (abbreviation: PTPDMA) poly [N, N'-bis (4-butylphenyl) -N, N'-bis (phenyl) benzidine] ( A polymer compound such as (abbreviation: Poly-TPD) can be used for the hole transport layer.

The light emitting layer is a layer containing a light emitting substance. As the luminescent substance, the following fluorescent compounds can be used. For example, N, N'-bis [4- (9H-carbazole-9-yl) phenyl] -N, N'-diphenylstylben-4,4'-diamine (abbreviation: YGA2S), 4- (9H-carbazole- 9-yl) -4'-(10-phenyl-9-anthril) triphenylamine (abbreviation: YGAPA), 4- (9H-carbazole-9-yl) -4'-(9,10-diphenyl-2- Anthryl) Triphenylamine (abbreviation: 2YGAPPA), N, 9-diphenyl-N- [4- (10-phenyl-9-anthril) phenyl] -9H-carbazole-3-amine (abbreviation: PCAPA), perylene, 2 , 5,8,11-Tetra-tert-butylperylene (abbreviation: TBP), 4- (10-phenyl-9-anthril) -4'-(9-phenyl-9H-carbazole-3-yl) triphenylamine (Abbreviation: PCBAPA), N, N''-(2-tert-butylanthracene-9,10-diyldi-4,1-phenylene) Bis [N, N', N'-triphenyl-1,4-phenylene Diamine] (abbreviation: DPABPA), N,9-diphenyl-N- [4- (9,10-diphenyl-2-anthryl) phenyl] -9H-carbazole-3-amine (abbreviation: 2PCAPPA), N- [4 -(9,10-diphenyl-2-anthryl) phenyl] -N, N', N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPPA), N, N, N', N', N' ', N'', N''', N'''-octaphenyldibenzo [g, p] chrysene-2,7,10,15-tetraamine (abbreviation: DBC1), coumarin 30, N- (9,10) -Diphenyl-2-anthril) -N,9-diphenyl-9H-carbazole-3-amine (abbreviation: 2PCAPA), N- [9,10-bis (1,1'-biphenyl-2-yl) -2- Anthril] -N, 9-diphenyl-9H-carbazole-3-amine (abbreviation: abbreviation:

-N, N', N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPABPhA), 9,10-bis (1,1'-biphenyl-2-yl) -N- [4- (9H-) Carbazole-9-yl) phenyl] -N-Phenylanthracen-2-amine (abbreviation: 2YGABPhA), N, N, 9-triphenylanthracene-9-amine (abbreviation: DPhAPhA) Kumarin 545T, N, N'-diphenyl Kinacridone, (abbreviation: DPQd), rubrene, 5,12-bis (1,1'-biphenyl-4-yl) -6,11-diphenyltetracene (abbreviation: BPT), 2- (2- {2- [4 -(Dimethylamino) Phenyl] Ethenyl} -6-Methyl-4H-Pyran-4-Ilidene) Propanedinitrile (abbreviation: DCM1), 2- {2-Methyl-6- [2- (2,3,6,, 7-Tetrahydro-1H, 5H-benzo [ij] quinolidine-9-yl) ethenyl] -4H-pyran-4-iriden} propandinitrile (abbreviation: DCM2), N, N, N', N'-tetrakis 4-Methylphenyl) tetracene-5,11-diamine (abbreviation: p-mPhTD), 7,14-diphenyl-N, N, N', N'-tetrakis (4-methylphenyl) acenaft [1,2-a ] Fluorantene-3,10-diamine (abbreviation: p-mPhAFD), 2- {2-isopropyl-6- [2- (1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-) 1H, 5H-benzo [ij] quinolidine-9-yl) ethenyl] -4H-pyran-4-ylidene} propandinitrile (abbreviation: DCJTI), 2- {2-tert-butyl-6- [2- (1) , 1,7,7-Tetramethyl-2,3,6,7-Tetrahydro-1H, 5H-benzo [ij] quinolysin-9-yl) ethenyl] -4H-pyran-4-ylidene} propandinitrile (abbreviation) : DCJTB), 2- (2,6-bis {2- [4- (dimethylamino) phenyl] ethenyl} -4H-pyran-4-ylidene) propandinitrile (abbreviation: BisDCM), 2- {2,6-bis [2- (8-methoxy-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H, 5H-benzo [ij] quinolizidine-9-yl) ethenyl] -4H -Pyran-4-iriden} Propanedinitrile (abbreviation: BisDCJTM) and the like.

Further, as the luminescent substance, the phosphorescent compounds shown below can also be used. For example, bis [2- (4', 6'-difluorophenyl) pyridinato-N, C^2’] Iridium (III) Tetrakis (1-pyrazolyl) Borato (abbreviation: FIr6), Bis [2- (4', 6'-difluorophenyl) Pyrizinato-N, C^2’] Iridium (III) picolinate (abbreviation: F Irpic), bis [2- (3', 5'-bistrifluoromethylphenyl) pyridinate-N, C^2’] Iridium (III) picolinate (abbreviation: Ir (CF)₃ppy)₂(pic)), Bis [2- (4', 6'-difluorophenyl) pyridinato-N, C^2’] Iridium (III) Acetylacetonate (abbreviation: FIracac), Tris (2-phenylpyridinato) Iridium (III) (abbreviation: Ir (ppy)₃), Bis (2-phenylpyridinato) Iridium (III) Acetylacetonate (abbreviation: Ir (ppy)₂(acac)), bis (benzo [h] quinolinato) iridium (III) acetylacetoneate (abbreviation: Ir (bzq))₂(acac)), bis (2,4-diphenyl-1,3-oxazolato-N, C^2’) Iridium (III) Acetylacetoneate (abbreviation: Ir (dpo))₂(acac)), bis [2- (4'-perfluorophenylphenyl) pyridinate] iridium (III) acetylacetonate (abbreviation: Ir (p-PF-ph))₂(acac)), bis (2-phenylbenzothiazolato-N, C^2’) Iridium (III) Acetylacetoneate (abbreviation: Ir (bt))₂(acac)), bis [2- (2'-benzo [4,5-α] thienyl) pyridinato-N, C^3’] Iridium (III) Acetylacetoneate (abbreviation: Ir (btp))₂(acac)), Bis (1-Phenylisoquinolinato-N, C^2’) Iridium (III) Acetylacetoneate (abbreviation: Ir (piq))₂(acac)), (Acetylacetoneto) bis [2,3-bis (4-fluorophenyl) quinoxalinato] Iridium (III) (abbreviation: Ir (Fdpq)₂(acac)), (Acetylacetoneto) Bis (2,3,5-triphenylpyrazinato) Iridium (III) (Abbreviation: Ir (tppr)₂(acac)), 2,3,7,8,12,13,17,18-octaethyl-21H, 23H-porphyrin platinum (II) (abbreviation: PtOEP), tris (acetylacetoneto) (monophenanthroline) terbium ( III) (Abbreviation: Tb (acac)₃(Phen)), Tris (1,3-diphenyl-1,3-propanedionat) (monophenanthroline) Europium (III) (abbreviation: Eu (DBM))₃(Phen)), Tris [1- (2-tenoyl) -3,3,3-trifluoroacetonato] (monophenanthroline) Europium (III) (abbreviation: Eu (TTA))₃(Phen)) and so on.

In addition, it is preferable to use these luminescent substances dispersed in a host material. Examples of the host material include aromatic amine compounds such as NPB (abbreviation), TPD (abbreviation), TCTA (abbreviation), TDATA (abbreviation), MTDATA (abbreviation), and BSPB (abbreviation), PCzPCA1 (abbreviation), and PCzPCA2 (abbreviation). Abbreviation), PCzPCN1 (abbreviation), CBP (abbreviation), TCPB (abbreviation), CzPA (abbreviation), 4- (1-naphthyl) -4'-(9-phenyl-9H-carbazole-3-yl) -triphenyl Carbazole derivatives such as amine (abbreviation; PCBANB), substances with high hole transport properties including high molecular compounds such as PVK (abbreviation), PVTPA (abbreviation), PTPDMA (abbreviation), Poly-TPD (abbreviation), and tris (abbreviation) 8-quinolinolato) aluminum (abbreviation: Alq), tris (4-methyl-8-quinolinolato) aluminum (abbreviation: Almq)₃), Bis (10-hydroxybenzo [h] quinolinato) beryllium (abbreviation: BeBq)₂), Bis (2-methyl-8-quinolinolato) (4-phenylphenolato) Aluminum (abbreviation: BAlq), a metal complex having a quinoline skeleton or a benzoquinoline skeleton, bis [2- (2-hydroxyphenyl) benzoxa Zorato] Zinc (abbreviation: Zn (BOX))₂), Bis [2- (2-Hydroxyphenyl) benzothiazolate] Zinc (abbreviation: Zn (BTZ))₂) And other metal complexes with oxazole-based and thiazole-based ligands 2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole (abbreviation: PBD), 1 , 3-Bis [5- (p-tert-butylphenyl) -1,3,4-oxadiazole-2-yl] benzene (abbreviation: OXD-7), 9- [4- (5-phenyl-1) , 3,4-Oxadiazole-2-yl) phenyl] Carbazole (abbreviation: CO11), 3- (4-biphenylyl) -4-phenyl-5- (4-tert-butylphenyl) -1,2,4 -Triazole (abbreviation: TAZ), vasofenantroline (abbreviation: BPhen), vasocuproin (abbreviation: BCP), poly [(9,9-dihexylfluorene-2,7-diyl)-co- (pyridine-3,5-diyl) )] (Abbreviation: PF-Py), Poly [(9,9-Dioctylfluorene-2,7-Diyl) -co- (2,2'-Bipyridine-6,6'-Diyl)] (Abbreviation: PF- A substance having high electron transport property such as BPy) can be used.

The electron transport layer is a layer containing a substance having a high electron transport property. Examples of substances with high electron transport properties include Alq (abbreviation) and Almq.₃(Abbreviation), BeBq₂A metal complex having a quinoline skeleton or a benzoquinoline skeleton such as (abbreviation) and BAlq (abbreviation) can be used. In addition, Zn (BOX)₂(Abbreviation), Zn (BTZ)₂Oxazole-based and thiazole-based ligand-based metal complexes such as (abbreviation) can also be used. Further, in addition to the metal complex, PBD (abbreviation), OXD-7 (abbreviation), CO11 (abbreviation), TAZ (abbreviation)), BPhen (abbreviation), BCP (abbreviation) and the like can also be used. The substances mentioned here are mainly 10^-6cm²It is a substance with electron mobility of / Vs or more. A substance other than these may be used as long as it is a substance having a higher electron transport property than holes. Further, the electron transport layer may be not limited to a single layer, but may be a stack of two or more layers made of the above substances.

In addition to this, polymer compounds such as PF-Py (abbreviation) and PF-BPy (abbreviation) can be used for the electron transport layer.

The electron injection layer is a layer containing a substance having a high electron injection property. Lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF) are highly electron-injectable substances.₂) And other alkali metals, alkaline earth metals, or compounds thereof. Further, a substance having an electron transporting property containing an alkali metal or an alkaline earth metal or a compound thereof, for example, a substance containing magnesium (Mg) in Alq or the like can also be used. With such a structure, the electron injection efficiency from the cathode 102 can be further improved.

When the charge generation region is provided in the first EL layer 103 or the second EL layer 107, the charge generation region is a region containing a substance having a high hole transport property and an acceptor substance. In the charge generation region, not only when a substance having a high hole transport property and an acceptor substance are contained in the same film, but also a layer containing a substance having a high hole transport property and a layer containing an acceptor substance are laminated. It may have been done. However, in the case of the laminated structure provided on the anode side, the layer containing the acceptor substance is in contact with the anode 101, and in the case of the laminated structure provided on the cathode side, the layer containing the substance having high hole transport property is the cathode. It has a structure in contact with 102.

By forming a charge generation region in the first EL layer 103 or the second EL layer 107, the anode 101 or the cathode 102 can be formed without considering the work function of the material forming the electrode.

Examples of the acceptor substance used in the charge generation region include transition metal oxides and oxides of metals belonging to Groups 4 to 8 in the Periodic Table of the Elements. Specifically, molybdenum oxide is particularly preferable. Molybdenum oxide has a feature of low hygroscopicity.

Further, as a substance having high hole transport property used in the charge generation region, various organic compounds such as an aromatic amine compound, a carbazole derivative, an aromatic hydrocarbon, and a polymer compound (oligomer, dendrimer, polymer, etc.) are used. Can be done. Specifically, 10^-6cm²It is preferable that the substance has a hole mobility of / Vs or more. However, any substance other than these may be used as long as it is a substance having a higher hole transport property than electrons.

The first EL layer 103 or the second EL layer 107 can be formed by appropriately combining and laminating these layers. Further, as a method for forming the first EL layer 103 or the second EL layer 107, various methods (for example, a dry method, a wet method, etc.) can be appropriately selected depending on the material used. For example, a vacuum deposition method, an inkjet method, a spin coating method, or the like can be used. Moreover, each layer may be formed by using a different method.

Further, between the first EL layer 103 and the second EL layer 107, an electron injection buffer 104, an electron relay layer 105, and a charge generation region 106 are provided in this order from the anode 101 side. The charge generation region 106 is formed in contact with the second EL layer 107, and the electron relay layer 105 is formed in contact with the charge generation region 106, and the electron relay layer 105 and the first EL are formed. Formed in contact between layers 103 is an electron injection buffer 104.

The charge generation region 106 is a region containing a substance having a high hole transport property and an acceptor substance. The charge generation region 106 is formed with the same structure by using the same material as the charge generation region that can be formed in a part of the first EL layer 103 or the second EL layer 107 described above. can do. Therefore, in the charge generation region 106, not only when a substance having a high hole transport property and an acceptor substance are contained in the same film, but also a layer containing the substance having a high hole transport property and a layer containing the acceptor substance are formed. It is also possible to have a laminated structure. However, in the case of a laminated structure, the layer containing a substance having high hole transport property is in contact with the second EL layer 107.

In the charge generation region 106, it is preferable to add the acceptor substance at a mass ratio of 0.1 or more and 4.0 or less with respect to the substance having high hole transport property.

The electron relay layer 105 is a layer capable of quickly receiving the electrons extracted by the acceptor substance in the charge generation region 106. Therefore, the electron relay layer 105 is a layer containing a substance having high electron transportability, and its LUMO level is the acceptor level of the acceptor in the charge generation region 106 and the LUMO level of the first EL layer 103. It is preferably formed using a material that occupies a level between and. Specifically, it is preferable to use a material having a LUMO level of about -5.0 eV or more, and more preferably to use a material having a LUMO level of about -5.0 eV or more and -3.0 eV or less. Examples of the substance used for the electron relay layer 105 include a perylene derivative and a nitrogen-containing condensed aromatic compound. Since the nitrogen-containing condensed aromatic compound is a stable compound, it is preferable as a substance used for the electron relay layer 105. Further, among the nitrogen-containing condensed aromatic compounds, it is preferable to use a compound having an electron-withdrawing group such as a cyano group or a fluoro group because the electron relay layer 105 can receive electrons more easily.

Specific examples of the perylene derivative include 3,4,9,10-perylenetetracarboxylic dianhydride (abbreviation: PTCDA), 3,4,9,10-perylenetetracarboxylic bisbenzoimidazole (abbreviation: PTCBI), N, N'-Dioctylu 3,4,9,10-Perylenetetracarboxylic dianimide (abbreviation: PTCDI-C8H), N, N'-dihexyl-3,4,9,10-perylenetetracarboxylic dianimide (abbreviation:: HexPTC) and the like.

Specific examples of nitrogen-containing condensed aromatic compounds include pyradino [2,3-f] [1,10].

Phenanthroline-2,3-dicarbonitrile (abbreviation: PPDN), 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation: HAT (CN)) )₆), 2,3-Diphenylpyrazine [2,3-b] pyrazine (abbreviation: 2PYPR) 2,3-bis (4-fluorophenyl) pyrazine [2,3-b] pyrazine (abbreviation: F2PYPR), etc. Be done. In addition, perfluoropentacene, 7,7,8,8, -tetracyanoquinodimethane (abbreviation: TCNQ), 1,4,5,8, -naphthalenetetracarboxylic dianhydride (abbreviation: NTCDA), Copper hexadecafluorophthalocyanine (abbreviation: F)₁₆CuPc), N, N'-bis (2,2,3,3,4,4,5,5,6,6,7,7,8,8,8, pentadecafluorooctyl-1,4,5 , 8-Naphthalene tetracarboxylic acid diimide (abbreviation: NTCDI-C8F), 3', 4'-dibutyl-5,5''-bis (dicyanomethylene) -5,5''-dihydro-2,2': 5 ', 2''-terthiophene) (abbreviation: DCMT), metanofullerene (eg [6,6]-phenyl C₆₁Methyl butyrate (abbreviation: PCBM)) or the like can be used for the electronic relay layer 105.

The electron injection buffer 104 is a layer capable of injecting electrons received by the electron relay layer 105 into the first EL layer 103. By providing the electron injection buffer 104, the injection barrier between the charge generation region 106 and the first EL layer 103 can be relaxed, so that the electrons generated in the charge generation region 106 can be transferred to the first EL layer 103. Can be easily injected into.

The electron injection buffer 104 contains alkali metals, alkaline earth metals, rare earth metals, and compounds thereof (alkali metal compounds (including oxides such as lithium oxide, halides, and carbonates such as lithium carbonate and cesium carbonate). It is possible to use substances with high electron injectability such as alkaline earth metal compounds (including oxides, halides and carbonates) or rare earth metal compounds (including oxides, halides and carbonates). ..

When the electron injection buffer 104 is formed by containing a substance having a high electron transport property and a donor substance, the electron injection buffer 104 has a mass ratio of 0.001 or more and 0.1 or less as a donor property to the substance having a high electron transport property. It is preferable to add a substance. The donor substances include alkali metals, alkaline earth metals, rare earth metals, and compounds thereof (alkali metal compounds (including oxides such as lithium oxide, halides, and carbonates such as lithium carbonate and cesium carbonate). , Alkaline earth metal compounds (including oxides, halides, carbonates), or rare earth metal compounds (including oxides, halides, carbonates), as well as tetrathianaphthalcene (abbreviation: TTN), Organic compounds such as nickerosen and decamethyl nickerosen can also be used. As the substance having high electron transportability, it can be formed by using the same material as the material of the electron transport layer that can be formed in a part of the first EL layer 103 described above.

By combining the above materials, the light emitting device shown in the present embodiment can be manufactured. From this light emitting element, light emission from the above-mentioned light emitting substance can be obtained, and various light emitting colors can be obtained by changing the type of the light emitting substance used for the light emitting layer. Further, by using a plurality of light emitting substances having different light emitting colors as the light emitting substance, it is possible to obtain light emission having a broad spectrum or white light emission.

In this embodiment, a light emitting device provided with two EL layers is described, but the number of EL layers is not limited to two, and there are two or more layers, for example, three layers. You may. When an EL layer of n (n is a natural number of 2 or more) is provided in the light emitting element, between the m (m is a natural number, 1 m n-1) th EL layer and the (m + 1) th EL layer. By stacking the electron injection buffer, the electron relay layer, and the charge generation region in this order from the anode side, it is possible to suppress an increase in the drive voltage of the light emitting element.

Further, the light emitting element shown in the present embodiment can be formed on various substrates. As the substrate, for example, glass, plastic, a metal plate, a metal foil, or the like can be used. When the light emitted from the light emitting element is taken out from the substrate side, a translucent substrate may be used. However, the substrate may be other than these as long as it functions as a support in the process of manufacturing the light emitting element.

As for the element structure of the light emitting element shown in the present embodiment, a passive matrix type light emitting device in which both electrodes are formed in a grid pattern on one substrate can be manufactured. It is also possible to manufacture an active matrix type light emitting device having a light emitting element electrically connected to a thin film transistor (TFT) or the like acting as a switch and controlling the driving of the light emitting element by the TFT. The structure of the TFT is not particularly limited. It may be a staggered type TFT or an inverted staggered type TFT. Further, the drive circuit composed of TFTs may also be composed of N-type and P-type TFTs, or may be composed of only one of N-type TFTs and P-type TFTs. .. Further, the crystallinity of the semiconductor film used for the TFT is not particularly limited. An amorphous semiconductor film may be used, or a crystalline semiconductor film may be used. Further, a single crystal semiconductor film or a microcrystal semiconductor (microcrystal semiconductor) may be used. Furthermore, oxide semiconductors, such as oxide semiconductors containing indium, gallium, and zinc, can be used.

Further, the method for manufacturing the light emitting element shown in the present embodiment is not limited to a dry process (for example, vacuum deposition method, sputtering method, etc.) or a wet process (for example, an inkjet method, spin coating method, coating method, etc.). It can be formed using various methods.

By adopting the element structure shown in the present embodiment, it is possible to make the drive voltage less affected by the film thickness of the charge generation region 106, so that the increase in the drive voltage in the light emitting element can be suppressed and the optics can be suppressed. It is possible to improve the color purity by adjusting.

Further, by adopting the element structure shown in the present embodiment, the electron relay layer 105 is sandwiched between the charge generation region 106 and the electron injection buffer 104, so that the acceptor included in the charge generation region 106 can be used. , The structure is such that the highly electron-injectable substance or the donor substance contained in the electron-injection buffer 104 is less likely to interact with each other and hinder each other's functions. Therefore, it is possible to drive the light emitting element at a low voltage.

It should be noted that the configuration shown in this embodiment can be used in combination with the configurations shown in other embodiments as appropriate.

(Embodiment 2) In the second embodiment, an example of the light emitting element included in the basic configuration described in the first embodiment will be described with reference to FIGS. 2 (A) and 2 (B). Specifically, among the light emitting elements shown in the first embodiment, a case where the electron injection buffer 104 is a single layer of an alkali metal, an alkaline earth metal, a rare earth metal, or a compound thereof will be described.

In the light emitting element shown in the present embodiment, as shown in FIG. 2A, a first EL layer 103 and a second EL layer 107 including a light emitting region are sandwiched between a pair of electrodes (anode 101, cathode 102). The structure is such that the electron injection buffer 104, the electron relay layer 105, and the charge generation region 106 are sequentially laminated from the anode 101 side between the first EL layer 103 and the second EL layer 107.

The anode 101, cathode 102, first EL layer 103, second EL layer 107, charge generation region 106, and electron relay layer 105 in the second embodiment are the same as those described in the first embodiment. Materials can be used.

In the present embodiment, the substances used for the electron injection buffer 104 include alkali metals such as lithium (Li) and cesium (Cs), and alkaline earth metals such as magnesium (Mg), calcium (Ca) and strontium (Sr). , Rare earth metals such as Europium (Eu) and Itterbium (Yb), alkali metal compounds (including oxides such as lithium oxide, halides, carbonates such as lithium carbonate and cesium carbonate), alkaline earth metal compounds (oxides) , Halogens, carbonates), or rare earth metal compounds (including oxides, halides, carbonates) and other highly electron-injectable substances.

The light emitting device shown in the present embodiment is provided with a single layer of the above metal or a compound thereof as an electron injection buffer 104, and the film thickness thereof is very thin in order to avoid an increase in the driving voltage ( Specifically, it is formed at 1 nm or less). In the present embodiment, it is preferable that the first EL layer 103 is in contact with the electron injection buffer 104 to form the electron transport layer 108, and the electron injection buffer 104 is one of the electron relay layer 105 and the EL layer 103. It exists almost at the interface with the electron transport layer 108, which is a part. However, when the electron injection buffer 104 is formed on the electron transport layer 108 after the electron transport layer 108 is formed, a part of the substance forming the electron injection buffer 104 is a part of the EL layer 103. It can also be present in transport layer 108.

FIG. 2 (B) shows a band diagram in the element structure of FIG. 2 (A). By providing the electron injection buffer 104 at the interface between the electron relay layer 105 and the first EL layer 103 in FIG. 2B, the injection barrier between the charge generation region 106 and the first EL layer 103 is relaxed. Therefore, the electrons generated in the charge generation region 106 can be easily injected into the first EL layer 103. Further, the holes generated in the charge generation region 106 move to the second EL layer 107.

By adopting the structure of the electron injection buffer shown in the present embodiment, the light emitting device has a structure as compared with the electron injection buffer (formed by adding a donor substance to a substance having high electron transport property) shown in the third embodiment. The drive voltage can be reduced. In the present embodiment, the highly electron-injectable substances in the electron injection buffer 104 include alkali metal compounds (including oxides such as lithium oxide, halides, and carbonates such as lithium carbonate and cesium carbonate) and alkalis. It is preferable to use an earth metal compound (including oxides, halides and carbonates), a rare earth metal compound (including oxides, halides and carbonates) and the like. Since these substances having high electron injectability are stable substances in air, they have good productivity and are suitable for mass production.

It should be noted that the configuration shown in this embodiment can be used in combination with the configurations shown in other embodiments as appropriate.

(Embodiment 3) In the third embodiment, an example of the light emitting element included in the basic configuration described in the first embodiment will be described with reference to FIGS. 3 (A) and 3 (B). Specifically, among the light emitting devices shown in the first embodiment, a case where the electron injection buffer 104 is formed by including a substance having a high electron transport property and a donor substance will be described.

In the light emitting element shown in the present embodiment, as shown in FIG. 3A, a first EL layer 103 and a second EL layer 107 including a light emitting region are sandwiched between a pair of electrodes (anode 101, cathode 102). The structure is such that the electron injection buffer 104, the electron relay layer 105, and the charge generation region 106 are sequentially laminated from the anode 101 side between the first EL layer 103 and the second EL layer 107. Further, the electron injection buffer 104 is formed by containing a substance having a high electron transport property and a donor substance.

In the present embodiment, it is preferable to add the donor substance at a mass ratio of 0.001 or more and 0.1 or less with respect to the substance having high electron transport property. As a result, an electron injection buffer 104 having a good film quality can be obtained, and an electron injection buffer 104 having a good reactivity can be obtained.

The same materials as those described in the first embodiment can be used for the anode 101, the cathode 102, the EL layer 103, the charge generation region 106, and the electron relay layer 105 in the third embodiment.

In the present embodiment, examples of the highly electron-transporting substance used in the electron injection buffer 104 include tris (8-quinolinolato) aluminum (abbreviation: Alq) and tris (4-methyl-8-quinolinolato) aluminum (abbreviation::). Almq₃), Bis (10-hydroxybenzo [h] quinolinato) beryllium (abbreviation: BeBq)₂), Bis (2-methyl-8-quinolinolato) (4-phenylphenolato) aluminum (abbreviation: BAlq) and the like, a metal complex having a quinoline skeleton or a benzoquinoline skeleton can be used. In addition, bis [2- (2-hydroxyphenyl) benzoxazolato] zinc (abbreviation: Zn (BOX))₂), Bis [2- (2-Hydroxyphenyl) benzothiazolate] Zinc (abbreviation: Zn (BTZ))₂) And other oxazole-based and thiazole-based ligand-bearing metal complexes can also be used. In addition to metal complexes, 2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole (abbreviation: PBD) and 1,3-bis [5 -(P-tert-butylphenyl) -1,3,4-oxadiazole-2-yl] benzene (abbreviation: OXD-7), 9- [4- (5-phenyl-1,3,4-oxa) Diazole-2-yl) phenyl] Oxadiazole (abbreviation: CO11), 3- (4-biphenylyl) -4-phenyl-5- (4-tert-butylphenyl) -1,2,4-triazole (abbreviation: TAZ) ), Basophenanthroline (abbreviation: BPhen), vasocuproin (abbreviation: BCP), etc. can also be used. The substances mentioned here are mainly 10^-6cm²It is a substance with electron mobility of / Vs or more.

In addition to this, poly [(9,9-dihexylfluorene-2,7-diyl) -co- (pyridine-3,5-diyl)] (abbreviation: PF-Py), poly [(9,9-dioctyl) High molecular weight compounds such as fluorene-2,7-diyl) -co- (2,2'-bipyridine-6,6'-diyl)] (abbreviation: PF-BPy) can be used.

Further, in the present embodiment, the donor substances used in the electron injection buffer 104 include alkali metals, alkaline earth metals, rare earth metals, and compounds thereof (alkali metal compounds (oxides such as lithium oxide, halides, etc.). With carbonates such as lithium carbonate and cesium carbonate), alkaline earth metal compounds (including oxides, halides and carbonates), or rare earth metal compounds (including oxides, halides and carbonates), etc. It can also be used. Further, organic compounds such as tetrathianaphthalene (abbreviation: TTN), nickerosen, and decamethyl nickerosen can also be used.

In the present embodiment, the first EL layer 103 may be in contact with the electron injection buffer 104 to form the electron transport layer 108, and when the electron transport layer 108 is formed, the electrons used for the electron injection buffer 104 may be formed. The highly transportable substance and the highly transportable substance used for the electron transport layer 108, which is a part of the EL layer 103, may be the same or different.

In the light emitting device shown in the present embodiment, as shown in FIG. 3A, an electron injection buffer 104 containing a substance having high electron transport property and a donor substance is formed between the EL layer 103 and the electron relay layer 105. It is a feature that it is done. A band diagram for this device structure is shown in FIG. 3 (B).

That is, by forming the electron injection buffer 104, the injection barrier between the electron relay layer 105 and the EL layer 103 can be relaxed, so that the electrons generated in the charge generation region 106 are transferred to the EL layer 103. It can be easily injected. Further, the holes generated in the charge generation region 106 move to the second EL layer 107.

It should be noted that the configuration shown in this embodiment can be used in combination with the configurations shown in other embodiments as appropriate.

(Embodiment 4) In the fourth embodiment, the configuration of the charge generation region 106 will be described with reference to FIGS. 4 (A) and 4 (B) as an example of the light emitting element included in the basic configuration described in the first embodiment. To do.

In the element structure shown in FIGS. 4 (A) and 4 (B), a first EL layer 103 and a second EL layer 107 including a light emitting region are sandwiched between a pair of electrodes (anode 101, cathode 102). Between the EL layer 103 of 1 and the second EL layer 107, an electron injection buffer 104, an electron relay layer 105, and a charge generation region 106 are sequentially laminated from the anode 101 side. In FIGS. 4A and 4B, the anode 101, the cathode 102, the first EL layer 103, the electron injection buffer 104, the electron relay layer 105, and the second EL layer 107 have been described in the first embodiment. The same material as that of the one can be used and the same composition can be obtained.

In the light emitting device shown in FIGS. 4A and 4B, the charge generation region 106 is a region containing a substance having a high hole transport property and an acceptor substance. In the charge generation region 106, holes and electrons are generated by the acceptor substance extracting electrons from the substance having high hole transport property.

The charge generation region 106 shown in FIG. 4 (A) has a structure in which a substance having a high hole transport property and an acceptor substance are contained in the same film. In this case, it is preferable to add the acceptor substance at a mass ratio of 0.1 or more and 4.0 or less with respect to the substance having a high hole transport property because carriers can be easily generated in the charge generation region 106.

In FIG. 4A, since the acceptor substance is doped with a substance having a high hole transport property, it is possible to suppress an increase in the drive voltage even when the charge generation region 106 is thickened. Therefore, it is possible to suppress an increase in the driving voltage of the light emitting element and improve the color purity by optical adjustment. Further, by thickening the charge generation region 106, it is possible to prevent a short circuit of the light emitting element.

On the other hand, the charge generation region 106 shown in FIG. 4B has a structure in which a layer 106a containing a substance having a high hole transport property and a layer 106b containing an acceptor substance are laminated. In the charge generation region 106 of the light emitting element shown in FIG. 4 (B), the electron transfer complex formed by the contact between the substance having high hole transport property and the acceptor substance and the transfer of electrons occurs is the hole transport property. It is formed only at the interface between the layer 106a containing the high material and the layer 106b containing the accepting material. Therefore, the light emitting element shown in FIG. 4B is preferable because an absorption band for visible light is unlikely to be formed even when the film thickness of the charge generation region 106 is increased.

Further, the light emitting device shown in FIG. 4 (B) and the configuration described in the second embodiment are combined to form the electron injection buffer 104 as a single layer of an alkali metal, an alkaline earth metal, a rare earth metal, or a compound thereof. Therefore, the layer between the first EL layer 103 and the second EL layer 107, that is, the electron injection buffer 104, the electron relay layer 105, and the charge generation region 106 can be prepared without using doping. , The total thickness of these layers can be reduced to about 5 nm or less.

Examples of substances having high hole transport properties used for forming the charge generation region 106 include various organic compounds such as aromatic amine compounds, carbazole derivatives, aromatic hydrocarbons, and polymer compounds (oligomers, dendrimers, polymers, etc.). Can be used. Specifically, 10^-⁶cm²It is preferable that the substance has a hole mobility of / Vs or more. However, any substance other than these may be used as long as it is a substance having a higher hole transport property than electrons.

Specific examples of aromatic amine compounds include 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (abbreviation: NPB or α-NPD) and N, N'-bis (3-). Methylphenyl) -N, N'-diphenyl- [1,1'-biphenyl] -4,4'-diamine (abbreviation: TPD), 4,4', 4''-tris (carbazole-9-yl) tri Phenylamine (abbreviation: TCTA), 4,4', 4''-Tris (N, N-diphenylamino) Triphenylamine (abbreviation: TDATA), 4,4', 4''-Tris [N- (3) -Methylphenyl) -N-phenylamino] Triphenylamine (abbreviation: MTDATA), N, N'-bis (4-methylphenyl) -N, N'-diphenyl-p-phenylenediamine (abbreviation: DTDPPA), 4 , 4'-bis [N- (4-diphenylaminophenyl) -N-phenylamino] biphenyl (abbreviation: DPAB), 4,4'-bis [N- (3-methylphenyl) -N-phenylamino] biphenyl (Abbreviation: DNTPD), 1,3,5-tris [N- (4-diphenylaminophenyl) -N-phenylamino] benzene (abbreviation: DPA3B) and the like can be mentioned.

Specific examples of the carbazole derivative include 3- [N- (9-phenylcarbazole-3-yl) -N-phenylamino] -9-phenylcarbazole (abbreviation: PCzPCA1) and 3,6-bis [N- (9). -Phenylcarbazole-3-yl) -N-Phenylamino] -9-Phenylcarbazole (abbreviation: PCzPCA2), 3- [N- (1-naphthyl) -N- (9-Phenylcarbazole-3-yl) amino] -9-Phenylcarbazole (abbreviation: PCzPCN1) and the like can be mentioned. In addition, 4,4'-di (N-carbazolyl) biphenyl (abbreviation: CBP), 1,3,5-tris [4- (N-carbazolyl) phenyl] benzene (abbreviation: TCPB), 9- [4- ( 10-Phenyl-9-anthracenyl) phenyl] -9H-carbazole (abbreviation: CzPA), 1,4-bis [4- (N-carbazolyl) phenyl] -2,3,5,6-tetraphenylbenzene, etc. Be done.

Specific examples of aromatic hydrocarbons include 2-tert-butyl-9,10-di (2-naphthyl) anthracene (abbreviation: t-BuDNA) and 2-tert-butyl-9,10-di (1-naphthyl). ) Anthracene, 9,10-bis (3,5-diphenylphenyl) anthracene (abbreviation: DPPA), 2-tert-butyl-9,10-bis (4-phenylphenyl) anthracene (abbreviation: t-BuDBA), 9 , 10-di (2-naphthyl) anthracene (abbreviation: DNA), 9,10-diphenylanthracene (abbreviation: DPAnth), 2-tert-butylanthracene (abbreviation: t-BuAnth), 9,10-bis (4-) Methyl-1-naphthyl) anthracene (abbreviation: DMNA), 9,10-bis [2- (1-naphthyl) phenyl] -2-tert-butylanthracene, 9,10-bis [2- (1-naphthyl) phenyl ] Anthracene, 2,3,6,7-Tetramethyl-9,10-di (1-naphthyl) anthracene, 2,3,6,7-Tetramethyl-9,10-di (2-naphthyl) anthracene, 9 , 9'-Bianthracene, 10,10'-Diphenyl-9,9'-Bianthracene, 10,10'-Bis (2-phenylphenyl) -9,9'-Bianthracene, 10,10'-Bis [(2,, 3,4,5,6-pentaphenyl) phenyl] -9,9'-bianthracene, anthracene, tetracene, rubrene, perylene, 2,5,8,11-tetra (tert-butyl) perylene and the like. In addition, pentacene, coronene and the like can also be used. Thus, 1x10^-6cm²It is more preferable to use an aromatic hydrocarbon having a hole mobility of / Vs or more and having 14 to 42 carbon atoms.

Further, the aromatic hydrocarbon may have a vinyl skeleton. Examples of aromatic hydrocarbons having a vinyl group include 4,4'-bis (2,2-diphenylvinyl) biphenyl (abbreviation: DPVBi) and 9,10-bis [4- (2,2-). Diphenylvinyl) phenyl]

Anthracene (abbreviation: DPVPA) and the like can be mentioned.

Further, polymer compounds such as poly (N-vinylcarbazole) (abbreviation: PVK) and poly (4-vinyltriphenylamine) (abbreviation: PVTPA) can also be used.

The accepting material used to form the charge generation region 106 is 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F).₄-TCNQ), chloranil, etc. can be mentioned. In addition, transition metal oxides can be mentioned. In addition, oxides of metals belonging to Group 4 to Group 8 in the Periodic Table of the Elements can be mentioned. Specifically, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, and renium oxide are preferable because they have high electron acceptability.

It should be noted that the configuration shown in this embodiment can be used in combination with the configurations shown in other embodiments as appropriate.

(Embodiment 5) In the fifth embodiment, another example of the light emitting element included in the basic configuration described in the first embodiment will be described with reference to FIG. 24.

In the light emitting element shown in the present embodiment, as shown in FIG. 24A, a first EL layer 103 and a second EL layer 107 including a light emitting region are sandwiched between a pair of electrodes (anode 101, cathode 102). The structure is such that the electron injection buffer 104, the electron relay layer 105, and the charge generation region 106 are sequentially laminated from the anode 101 side between the first EL layer 103 and the second EL layer 107.

The same materials as those described in the first embodiment can be used for the anode 101, the cathode 102, the electron injection buffer 104, the electron relay layer 105, and the charge generation region 106 in the present embodiment.

In the present embodiment, the first EL layer 103 includes the first light emitting layer 103-1 showing an emission spectrum having a peak in the blue to blue-green wavelength region and light emission having a peak in the yellow to orange wavelength region. It has a second light emitting layer 103-2 showing the spectrum. Further, the second EL layer 107 has a third light emitting layer 107-1 having a peak in a blue-green to green wavelength region and a third light emitting spectrum having a peak in an orange to red wavelength region. It has 4 light emitting layers 107-2. The first light emitting layer 103-1 and the second light emitting layer 103-2 may be stacked in the reverse order. Further, the third light emitting layer 107-1 and the fourth light emitting layer 107-2 may be stacked in the reverse order.

When a bias is applied to such a light emitting element with the anode 101 side positive and the cathode 102 side negative, holes injected from the anode 101 and charge generation regions 106 are generated, and electrons are injected into the electron relay layer 105 and electrons. The electrons injected through the buffer 104 are recombined in the first light emitting layer 103-1 or the second light emitting layer 103-2 to obtain the first light emitting 330. Further, the electrons injected from the cathode 102 and the holes generated in the charge generation region 106 are recombined in the third light emitting layer 107-1 or the fourth light emitting layer 107-2 to obtain the second light emitting 340. ..

Since the first light emitting 330 is a combination of light emitted from both the first light emitting layer 103-1 and the second light emitting layer 103-2, blue to blue-green as shown in FIG. 24 (B). The emission spectrum having peaks in both the wavelength region of No. 1 and the wavelength region of yellow to orange is shown. That is, the first EL layer 103 exhibits two-wavelength type white or near-white light emission. Further, since the second light emitting 340 is a combination of light emitted from both the third light emitting layer 107-1 and the fourth light emitting layer 107-2, it is bluish green as shown in FIG. 24 (B). It shows an emission spectrum having peaks in both the ~ green wavelength region and the orange ~ red wavelength region. That is, the second EL layer 107 exhibits a two-wavelength type white or near-white color emission different from that of the first EL layer 103.

Therefore, in the light emitting element of the present embodiment, as a result of the first light emitting 330 and the second light emitting 340 being superposed, the blue to blue-green wavelength region, the blue-green to green wavelength region, the yellow to orange wavelength region, and the orange color. ~ Emission that covers the red wavelength region can be obtained.

In the present embodiment, for example, even if the emission brightness of the first light emitting layer 103-1 (showing an emission spectrum having a peak in the blue to blue-green wavelength region) changes with time or due to current density, the spectrum Since the contribution of the first light emitting layer 103-1 to the whole is about 1/4, the deviation of the chromaticity can be relatively small.

In the above description, the first EL layer 103 shows a spectrum having peaks in both the blue to bluish green wavelength region and the yellow to orange wavelength region, and the second EL layer 107 is bluish green to green. Although the case of showing a spectrum having peaks in both the wavelength region and the orange to red wavelength region has been described as an example, the relationship may be opposite to each other. That is, the second EL layer 107 shows a spectrum having peaks in both the blue to turquoise wavelength region and the yellow to orange wavelength region, and the first EL layer 103 shows the turquoise to green wavelength region and the orange to orange. It may be configured to show a spectrum having peaks in both red wavelength regions. Further, the first EL layer 103 and the second EL layer 107 may each have a laminated structure in which a layer other than the light emitting layer is formed.

Next, a material that can be used as a luminescent organic compound in the EL layer of the light emitting device shown in the present embodiment will be described. However, the materials applicable to the light emitting device shown in the present embodiment are not limited to these.

For blue to turquoise emission, for example, perylene, 2,5,8,11-tetra-t-butylperylene (abbreviation: TBP), 9,10-diphenylanthracene, etc. are used as guest materials as appropriate host materials. Obtained by dispersing. In addition, styrylallylen derivatives such as 4,4'-bis (2,2-diphenylvinyl) biphenyl (abbreviation: DPVBi), 9,10-di-2-naphthylanthracene (abbreviation: DNA), 9,10-bis It can be obtained from anthracene derivatives such as (2-naphthyl) -2-t-butylanthracene (abbreviation: t-BuDNA). Further, a polymer such as poly (9,9-dioctylfluorene) may be used. Further, as the guest material for blue emission, a styrylamine derivative is preferable, and N, N'-bis [4- (9H-carbazole-9-yl) phenyl] -N, N'-diphenylstilbene-4,4'- Diamine (abbreviation: YGA2S), N, N'-diphenyl-N, N'-bis (9-phenyl-9H-carbazole-3-yl) stilbene-4,4'-diamine (abbreviation: PCA2S), etc. Be done. In particular, YGA2S has a peak near 450 nm, which is preferable. Further, as the host material, an anthracene derivative is preferable, and 9,10-bis (2-naphthyl) -2-t-butylanthracene (abbreviation: t-BuDNA) and 9- [4- (10-phenyl-9-). Anthracene phenyl] -9H-carbazole (abbreviation: CzPA) is suitable. In particular, CzPA is preferable because it is electrochemically stable.

The turquoise to green luminescence is, for example, coumarin pigments such as coumarin 30 and coumarin 6, bis [2- (2,4-difluorophenyl) pyridinato] picolinatoiridium (abbreviation: FIrpic), and bis (2-phenyl). Pyridinato) Acetylacetonatoiridium (abbreviation: Ir (ppy)₂(acac))) is used as a guest material and dispersed in an appropriate host material. It can also be obtained by dispersing the above-mentioned perylene or TBP in a suitable host material at a high concentration of 5 wt% or more. Also, BAlq, Zn (BTZ)₂, Bis (2-methyl-8-quinolinolato) chlorogallium (Ga (mq))₂It can also be obtained from metal complexes such as Cl). Further, a polymer such as poly (p-phenylene vinylene) may be used. Further, as a guest material of the blue-green to green light emitting layer, an anthracene derivative is preferable because highly efficient light emission can be obtained. For example, by using 9,10-bis {4- [N- (4-diphenylamino) phenyl-N-phenyl] aminophenyl} -2-tert-butylanthracene (abbreviation: DPABPA), highly efficient blue-green color is used. Luminescence is obtained. In addition, an anthracene derivative in which the amino group is substituted at the 2-position is preferable because it can obtain highly efficient green light emission, and N- (9,10-diphenyl-2-anthryl) -N, 9-diphenyl-9H-carbazole-3. -Amine (abbreviation: 2PCAPA) has a particularly long life and is suitable. Anthracene derivatives are preferable as these host materials, and CzPA described above is preferable because it is electrochemically stable. In addition, when a light emitting element having two peaks in the blue to green wavelength region is produced by combining green light emission and blue light emission, an electron transporting anthracene derivative such as CzPA is used as the host of the blue light emitting layer to emit green light. It is preferable to use a hole-transporting aromatic amine compound such as NPB as the host of the layer because light emission can be obtained at the interface between the blue light emitting layer and the green light emitting layer. That is, in this case, an aromatic amine compound such as NPB is preferable as a host for a green light emitting material such as 2PCAPA.

The yellow to orange luminescence is, for example, rubrene, 4- (dicyanomethylene) -2- [p- (dimethylamino) styryl] -6-methyl-4H-pyran (abbreviation: DCM1), 4- (dicyanomethylene)- 2-Methyl-6- (9-juloridyl) ethynyl-4H-pyran (abbreviation: DCM2), bis [2- (2-thienyl) pyridinato] acetylacetonatoiridium (Ir (thp))₂(acac)), Bis (2-phenylquinolinato) Acetylacetonatoiridium (Ir (pq))₂(acac))) is used as a guest material and dispersed in an appropriate host material. In particular, a tetracene derivative such as rubrene is preferable as a guest material because it is highly efficient and chemically stable. As the host material in this case, an aromatic amine compound such as NPB is preferable. Other host materials include bis (8-quinolinolato) zinc (abbreviation: Znq).₂) And bis [2-cinnamoyl-8-quinolinolato] zinc (abbreviation: Znsq)₂) And other metal complexes can be used. Further, a polymer such as poly (2,5-dialkoxy-1,4-phenylene vinylene) may be used.

The orange to red emission is, for example, 4- (dicyanomethylene) -2,6-bis [p- (dimethylamino) styryl] -4H-pyran (abbreviation: BisDCM), 2- (2- {2- [4 -(Dimethylamino) Phenyl] Ethenyl} -6-Methyl-4H-Pyran-4-Ilidene) Propanedinitrile (abbreviation: DCM1), 4- (dicyanomethylene) -2-methyl-6- (9-juloridyl) ethynyl -4H-pyran (abbreviation: DCM2), bis [2- (2-thienyl) pyridinato] acetylacetonatoiridium (Ir (thp))₂(acac))), etc. are used as guest materials and dispersed in an appropriate host material. Bis (8-Kinorinorat) Zinc (abbreviation: Znq)₂) And bis [2-cinnamoyl-8-quinolinolato] zinc (abbreviation: Znsq)₂) And other metal complexes. Further, a polymer such as poly (3-alkylthiophene) may be used. Guest materials that emit red light include 4- (dicyanomethylene) -2,6-bis [p- (dimethylamino) styryl] -4H-pyran (abbreviation: BisDCM), 2- (2- {2- [4 -(Dimethylamino) phenyl] ethenyl} -6-methyl-4H-pyran-4-idene) propandinitrile (abbreviation: DCM1), 4- (dicyanomethylene) -2-methyl-6- (9-juloridyl) ethynyl -4H-pyran (abbreviation: DCM2), {2-isopropyl-6- [2- (2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H, 5H-benzo [ij]] Kinolysin-9-yl) ethenyl] -4H-pyran-4-iriden} propandinitrile (abbreviation: DCJTI), {2,6-bis [2- (2,3,6,7-tetrahydro-8-methoxy-) 1,1,7,7-Tetramethyl-1H, 5H-benzo [ij] quinolidine-9-yl) ethenyl] -4H-pyran-4-ylidene} 4H-pyran such as propandinitrile (abbreviation: BisDCJTM) Derivatives are highly efficient and preferred. In particular, DCJTI and BisDCJTM are preferable because they have an emission peak near 620 nm.

In the above configuration, the suitable host material may be one having a shorter emission color than the luminescent organic compound or a material having a larger energy gap. Specifically, it can be appropriately selected from the hole transport material and the electron transport material represented by the example shown in the first embodiment. In addition, 4,4'-bis (N-carbazolyl) biphenyl (abbreviation: CBP), 4,4', 4''-tris (N-carbazolyl) triphenylamine (abbreviation: TCTA), 1,3,5- Tris [4- (N-carbazolyl) phenyl] benzene (abbreviation: TCPB) or the like may be used.

The light emitting element shown in the present embodiment has a blue to bluish green wavelength region, a bluish green to green wavelength region, and a yellow color as a result of superimposing the emission spectrum of the first EL layer and the emission spectrum of the second EL layer. White light emission that covers a wide range of ~ orange wavelength range and orange ~ red wavelength range can be obtained.

By adjusting the film thickness of each laminate and intentionally slightly interfering with light, the generation of protruding sharp peaks is suppressed and a trapezoidal emission spectrum is obtained, resulting in natural light having a continuous spectrum. You may bring them closer. Further, the position of the peak of the emission spectrum can also be changed by adjusting the film thickness of each laminate and intentionally slightly interfering with the light. By adjusting the film thickness of each laminate so that the multiple peak intensities appearing in the emission spectrum are substantially the same, and further narrowing the distance between the peaks of each other, it is possible to obtain white emission having an emission spectrum closer to a trapezoid. it can.

In the present embodiment, in each of the plurality of light emitting layers, an EL layer capable of obtaining white light emission by superimposing emission colors complementary to each other is shown. In the following, a specific configuration of the EL layer that emits white light due to the complementary color relationship will be described.

The EL layer provided in the light emitting device shown in the present embodiment is, for example, a first layer containing a substance having a high hole transport property and a first light emitting substance, a substance having a high hole transport property, and a second layer. A second layer containing the luminescent substance of the above, and a third layer containing the substance having high electron transportability and the second luminescent substance can be laminated in order from the anode 101.

In the EL layer of the light emitting device shown in the present embodiment, in order to obtain white light emission, both the first light emitting substance and the second light emitting substance need to emit light. Therefore, in order to regulate the transportability of carriers in the EL layer, it is preferable to use both the substance having high hole transportability and the substance having high electron transportability as host materials. As a substance having a high hole transport property or a substance having a high electron transport property that can be used for the EL layer, the substance exemplified in the first embodiment can be appropriately used.

Further, as the first luminescent substance and the second luminescent substance, a substance having a complementary color relationship with each luminescent color can be selected and used. The relationship between complementary colors includes blue and yellow, or blue-green and red. As the substance that emits blue, yellow, blue-green, or red, for example, it may be appropriately selected from the luminescent substances listed above. By setting the emission wavelength of the second luminescent substance to be shorter than the emission wavelength of the first luminescent substance, a part of the excitation energy of the second luminescent substance is transferred to the first luminescent substance. The first luminescent substance can emit light. Therefore, in the light emitting device of the present embodiment, it is preferable that the emission peak wavelength of the second light emitting substance is shorter than the emission peak wavelength of the first light emitting substance.

The configuration of the light emitting element shown in the present embodiment can obtain both light emission from the first light emitting substance and light emission from the second light emitting substance, and also emits light from the first light emitting substance and the second light emitting substance. Since the colors are complementary colors to each other, white light emission can be obtained. Further, by adopting the configuration of the light emitting element shown in the present embodiment, it is possible to obtain a light emitting element having a long life.

It should be noted that the configuration shown in this embodiment can be used in combination with the configurations shown in other embodiments as appropriate.

(Embodiment 6) In the present embodiment, one aspect of the light emitting device including the light emitting element shown in the above embodiment will be described with reference to FIG. FIG. 5 is a cross-sectional view of the light emitting device.

In FIG. 5, what is surrounded by the dotted dotted line is the transistor 11 provided for driving the light emitting element 12. The light emitting element 12 has a layer 15 containing an organic compound between the first electrode 13 and the second electrode 14, and the layer containing the organic compound is an EL layer of n (n is a natural number of 2 or more). Between the m (m is a natural number, 1 m n-1) th EL layer and the (m + 1) th EL layer, the electron injection buffer and the electrons are placed in order from the anode side. It is a layer including a relay layer and a charge generation region. Further, each EL layer is provided with at least a light emitting layer, and in addition to the light emitting layer, a hole injection layer, a hole transport layer, an electron transport layer, or an electron injection layer is appropriately provided. That is, the light emitting element 12 has a configuration as shown in the first to fourth embodiments. The drain region of the transistor 11 and the first electrode 13 are electrically connected by a wiring 17 penetrating the first interlayer insulating film 16 (16a, 16b, 16c). Further, the light emitting element 12 is separated from another light emitting element provided adjacent to the light emitting element 12 by the partition wall layer 18. The light emitting device of the present embodiment having such a configuration is provided on the substrate 10 in the present embodiment.

The transistor 11 shown in FIG. 5 is a top-gate type in which a gate electrode is provided on the opposite side of the substrate with the semiconductor layer as the center. However, the structure of the transistor 11 is not particularly limited, and may be, for example, a bottom gate type. In the case of a bottom gate, a protective film may be formed on the semiconductor layer forming the channel (channel protection type), or a part of the semiconductor layer forming the channel may be concave (channel protection type). Channel etch type) may be used.

Further, the semiconductor layer constituting the transistor 11 may be either crystalline or non-crystalline. Further, a microcrystal semiconductor (microcrystal semiconductor), an oxide semiconductor, or the like may be used.

As the oxide semiconductor layer, a composite oxide of an element selected from indium, gallium, aluminum, zinc and tin can be used. For example, zinc oxide (ZnO), indium oxide containing zinc oxide (IZO), and oxide composed of indium oxide, gallium oxide, and zinc oxide (IGZO) can be mentioned as examples. Further, specific examples of the semiconductor layer having a crystalline layer include those made of single crystal or polycrystalline silicon, silicon germanium, or the like. These may be those formed by laser crystallization or, for example, those formed by crystallization by a solid phase growth method using nickel or the like.

When the semiconductor layer is formed of an amorphous substance, for example, amorphous silicon, the transistor 11 and other transistors (transistors constituting a circuit for driving a light emitting element) are all composed of N-channel transistors. It is preferable that the light emitting device has the circuit. In addition, many oxide semiconductors, such as zinc oxide (ZnO), indium oxide containing zinc oxide (IZO), and oxides consisting of indium oxide, gallium oxide, and zinc oxide (IGZO), are N-type semiconductors. Transistors having these compounds in the active layer are N-channel type. Other than that, it may be a light emitting device having a circuit composed of either N channel type or P channel type transistors, or a light emitting device having a circuit composed of both transistors.

Further, the first interlayer insulating film 16 may be a multilayer or a single layer as shown in FIGS. 5 (A) and 5 (C). 16a is composed of inorganic substances such as silicon oxide and silicon nitride, and 16b is an organic group whose skeleton structure is composed of bonds of acrylic or siloxane (silicon (Si) and oxygen (O), and contains at least hydrogen as a substituent. ), It is composed of a substance having self-flatness such as silicon oxide that can be applied and formed. In addition, 16c consists of a silicon nitride film containing argon (Ar). The substances constituting each layer are not particularly limited, and substances other than those described here may be used. Further, layers made of substances other than these may be further combined. As described above, the first interlayer insulating films 16a to 16c may be formed by using both an inorganic substance and an organic substance, or may be formed by either an inorganic film or an organic film.

The partition wall layer 18 preferably has a shape in which the radius of curvature changes continuously at the edge portion. The partition wall layer 18 is formed by using acrylic, siloxane, resist, silicon oxide, or the like. The partition wall layer 18 may be formed of either an inorganic film or an organic film, or may be formed by using both of them.

In addition, in FIGS. 5 (A) and 5 (C), only the first interlayer insulating films 16a to 16c are provided between the transistor 11 and the light emitting element 12, but as shown in FIG. 5 (B), the first interlayer insulating film 16a to 16c is provided. In addition to the one interlayer insulating film 16 (16a, 16b), a second interlayer insulating film 19 (19a, 19b) may be provided. In the light emitting device shown in FIG. 5B, the first electrode 13 penetrates the second interlayer insulating film 19 and is connected to the wiring 17.

The second interlayer insulating film 19 may be a multilayer or a single layer, similarly to the first interlayer insulating film 16. 19a has self-flatness such as acrylic, siloxane (organic group whose skeletal structure is composed of bonds of silicon (Si) and oxygen (O) and contains at least hydrogen as a substituent), silicon oxide that can be applied and deposited. It consists of substances. In addition, 19b consists of a silicon nitride film containing argon (Ar). The substances constituting each layer are not particularly limited, and substances other than those described here may be used. Further, layers made of substances other than these may be further combined. As described above, the second interlayer insulating films 19a and 19b may be formed by using both an inorganic substance and an organic substance, or may be formed by either an inorganic film or an organic film.

In the light emitting element 12, when both the first electrode and the second electrode are made of a translucent substance, the first electrode is as shown by the white arrow in FIG. 5 (A). Light can be extracted from both the electrode 13 side and the second electrode 14 side. When only the second electrode 14 is composed of a translucent substance, light is emitted only from the second electrode 14 side as shown by the white arrow in FIG. 5 (B). be able to. In this case, it is preferable that the first electrode 13 is made of a material having a high reflectance, or a film (reflective film) made of a material having a high reflectance is provided below the first electrode 13. Further, when only the first electrode 13 is composed of a translucent substance, light emission is extracted only from the first electrode 13 side as shown by the white arrow in FIG. 5 (C). be able to. In this case, it is preferable that the second electrode 14 is made of a highly reflective material, or a reflective film is provided above the second electrode 14.

Further, the light emitting element 12 may have layers 15 laminated so as to operate when a voltage is applied so that the potential of the second electrode 14 is higher than the potential of the first electrode 13. Alternatively, the layers 15 may be laminated so as to operate when a voltage is applied so that the potential of the second electrode 14 is lower than the potential of the first electrode 13. In the former case, the transistor 11 is an N-channel transistor, and in the latter case, the transistor 11 is a P-channel transistor.

Although only one light emitting element is shown in the cross-sectional view shown in FIG. 5, it is assumed that a plurality of light emitting elements are arranged in a matrix in the pixel portion. Further, when performing a color display consisting of R (red) G (green) B (blue) color elements, a plurality of light emitting elements capable of obtaining three types (R, G, B) of light emission are formed in the pixel portion. Will be done. Further, the color element is not limited to three colors, and four or more colors may be used, or a color other than RGB may be used. For example, it is possible to add white to make RGBW (W is white).

As a method of manufacturing light emitting elements having different color elements, a method of painting each EL layer separately, forming all EL layers so as to obtain white light emission, and combining with a color filter to emit light of different color elements. A method of obtaining an element, a method of forming all EL layers so as to obtain blue light emission or light emission having a shorter wavelength than that, and combining with a color conversion layer to obtain a light emitting element having different color elements can be used.

As described above, in the present embodiment, the active matrix type light emitting device in which the driving of the light emitting element is controlled by the transistor has been described, but in addition, the driving element such as the transistor is provided on the same substrate as the light emitting element. It may be a passive matrix type light emitting device that drives a light emitting element without using it. FIG. 6A shows a perspective view of a passive matrix type light emitting device manufactured by applying the light emitting elements shown in the first to fourth embodiments. Further, FIG. 6 (B) is a cross-sectional view taken along the broken line XY of FIG. 6 (A).

In FIG. 6, a layer 955 containing an organic compound is provided between the electrode 952 and the electrode 956 on the substrate 951. The layer containing the organic compound has an EL layer of n (n is a natural number of 2 or more), an m (m is a natural number, 1 m n-1) th EL layer, and a (m + 1) th layer. Between the EL layers of the above, a layer including an electron injection buffer, an electron relay layer, and a charge generation region in this order from the anode side. Further, each EL layer is provided with at least a light emitting layer, and in addition to the light emitting layer, a hole injection layer, a hole transport layer, an electron transport layer, or an electron injection layer is appropriately provided. The end of the electrode 952 is covered with an insulating layer 953. A partition layer 954 is provided on the insulating layer 953. The side wall of the partition wall layer 954 preferably has an inclination such that the distance between one side wall and the other side wall becomes narrower as it gets closer to the substrate surface. That is, the cross section in the short side direction of the partition wall layer 954 is trapezoidal, and the bottom side (the side facing the same direction as the surface direction of the insulating layer 953 and in contact with the insulating layer 953) is the upper side (the surface of the insulating layer 953). It faces in the same direction as the direction, and is shorter than the side that does not contact the insulating layer 953). By providing the partition wall layer 954 in this way, it is possible to prevent defects in the light emitting element due to static electricity or the like. Even in the passive matrix type light emitting device, a light emitting device having low power consumption can be obtained by including the light emitting elements shown in the first to fourth embodiments.

Since the light emitting device shown in the present embodiment uses the light emitting element shown as an example in the above embodiment, it can be a light emitting device having high brightness, low drive voltage, and low power consumption.

(Embodiment 7) In the present embodiment, an electronic device including the light emitting device shown in the sixth embodiment as a part thereof will be described. The electronic device shown in the present embodiment includes the light emitting elements shown in the first to fourth embodiments, and has a display unit having high brightness, a low drive voltage, and reduced power consumption.

The electronic devices of the present embodiment include a video camera, a digital camera, a goggle type display, a navigation system, a sound reproduction device (car audio, audio component, etc.), a computer, a game device, and a mobile information terminal (mobile computer, mobile phone, mobile device). Type game machines or electronic books, etc.), image playback devices equipped with recording media (specifically, devices equipped with display devices that can play back recording media such as Digital Versatile Disc (DVD) and display the images), etc. Can be mentioned. Specific examples of these electronic devices are shown in FIG.

FIG. 7 (A) shows an example of the personal digital assistant device 9200. Portable information terminals device 9200 incorporates a computer, it is possible to perform various data processing. Examples of such a personal digital assistant 9200 include a PDA (Personal Digital Assistance).

The personal digital assistant device 9200 is composed of two housings, a housing 9201 and a housing 9203. The housing 9201 and the housing 9203 are foldably connected by a connecting portion 9207. The display 9202 is incorporated in the housing 9201, and the housing 9203 is equipped with a keyboard 9205. Of course, the configuration of the mobile information terminal device 9200 is not limited to the above, and other auxiliary equipment may be appropriately provided. The display unit 9202 is configured by arranging light emitting elements similar to those described in the above embodiment in a matrix. The light emitting element has features of high brightness, low drive voltage, and low power consumption. Since the display unit 9202 composed of the light emitting element has the same characteristics, the power consumption of this portable information terminal device is reduced.

FIG. 7B shows an example of the digital video camera 9500 according to the present embodiment. The digital video camera 9500 has a display unit 9503 incorporated in the housing 9501, and various other operation units are provided. The configuration of the digital video camera 9500 is not particularly limited, and other auxiliary equipment may be appropriately provided.

In this digital video camera, the display unit 9503 is configured by arranging light emitting elements similar to those described in the above embodiment in a matrix. The light emitting element has the features of low drive voltage, high brightness, and low power consumption. Since the display unit 9503 composed of the light emitting element has the same characteristics, the power consumption of this digital video camera is reduced.

FIG. 7C shows an example of the mobile phone 9100 according to the present embodiment. The mobile phone 9100 is composed of two housings, a housing 9102 and a housing 9101, and is foldably connected by a connecting portion 9103. A display unit 9104 is incorporated in the housing 9102, and an operation key 9106 is provided in the housing 9101. The configuration of the mobile phone 9100 is not particularly limited, and other auxiliary equipment may be appropriately provided.

In this mobile phone, the display unit 9104 is configured by arranging light emitting elements similar to those described in the above embodiment in a matrix. The light emitting element has features of high brightness, low drive voltage, and low power consumption. Since the display unit 9104 composed of the light emitting element has the same characteristics, the power consumption of this mobile phone is reduced. Further, the light emitting element shown in the above embodiment may be used as the backlight of the display provided in the mobile phone or the like.

Figure 7 (D) shows an example of a portable computer 9400. The computer 9400 has a housing 9401 and a housing 9404 that are openably connected. The display unit 9402 is incorporated in the housing 9401, and the housing 9404 is equipped with a keyboard 9403 and the like. The configuration of the computer 9400 is not particularly limited, and other auxiliary equipment may be appropriately provided.

In this computer, the display unit 9402 is configured by arranging light emitting elements similar to those described in the above embodiment in a matrix. The light emitting element has features of high brightness, low drive voltage, and low power consumption. Since the display unit 9402 composed of the light emitting element has the same characteristics, the power consumption of this computer is reduced.

FIG. 7 (E) shows an example of the television device 9600. In the television device 9600, the display unit 9603 is incorporated in the housing 9601. The display unit 9603 makes it possible to display an image. Further, here, a configuration in which the housing 9601 is supported by the stand 9605 is shown.

The operation of the television device 9600 can be performed by the operation switch provided in the housing 9601 or the separate remote control operation device 9610. The operation key 9609 provided on the remote controller 9610 can be used to control the channel and volume, and the image displayed on the display unit 9603 can be operated. Further, the remote controller 9610 may be provided with a display unit 9607 that displays information output from the remote controller 9610.

The television device 9600 is configured to include a receiver, a modem, and the like. The receiver allows the reception of general television broadcasts, and by connecting to a wired or wireless communication network via a modem, one-way (sender to receiver) or two-way (sender and receiver). It is also possible to perform information communication between (or between recipients, etc.).

In this television device, at least one of the display unit 9607 and the display unit 9603 is configured by arranging light emitting elements similar to those described in the above embodiment in a matrix. The light emitting element has features of high brightness, low drive voltage, and low power consumption. The display unit composed of the light emitting element has the same characteristics.

As described above, the applicable range of the light emitting device shown in the above embodiment is extremely wide, and this light emitting device can be applied to electronic devices in all fields. By using the light emitting elements shown in the first to fourth embodiments, it is possible to provide an electronic device that emits high-intensity light and has a display unit with low power consumption.

Further, the light emitting device shown in the above embodiment can also be used as a lighting device. An aspect of using the light emitting device shown in the above embodiment as a lighting device will be described with reference to FIG.

FIG. 8 shows an example in which the light emitting device shown as an example in the above embodiment is used as a desk lamp which is a lighting device and an indoor lighting device. The desk lamp shown in FIG. 8 has a light source 3000, and as the light source 3000, the light emitting device shown as an example in the above embodiment is used. Therefore, the light emitting device with low power consumption can be obtained. Further, since this light emitting device can have a large area, the lighting device can be used as a large area lighting. Further, since this light emitting device is thin and has low power consumption, it can be used as a thin and low power consumption lighting device. Further, since this light emitting device can be made flexible, it is possible to use roll-type lighting such as the lighting device 3002. As described above, the television device as described with reference to FIG. 7 (E) can be installed in the room in which the light emitting device shown in the present embodiment is used as the indoor lighting devices 3001 and 3002.

As described above, the range of application of the light emitting device shown in the sixth embodiment is extremely wide, and it can be used for electronic devices in all fields. In addition, this embodiment can be used in combination with Embodiment 1 to Embodiment 5 as appropriate.

<p> In this embodiment, a light emitting device according to an aspect of the present invention will be described with reference to FIG. The chemical formulas of the materials used in Examples 2 to 6 are shown below.</p><p><chemistry num="1"><img file="JP2019040887A_D0001.tif" /></chemistry></p><p>The manufacturing method of the light emitting element 1 and the comparative light emitting element 1 of this embodiment is shown below.</p><p>First, the light emitting element 1 will be described (see FIG. 9A). Indium tin oxide containing silicon oxide was formed on the glass substrate 2100 by a sputtering method to form the first electrode 2101. The film thickness was 110 nm, and the electrode area was 2 mm × 2 mm.</p><p> Next, the substrate on which the first electrode 2101 is formed is fixed to a substrate holder provided in the vacuum vapor deposition apparatus so that the surface on which the first electrode 2101 is formed faces downward.^-4After depressurizing to about Pa, 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (abbreviation: NPB), which is a highly hole-transporting substance, is placed on the first electrode 2101. And molybdenum oxide (VI), which is an accepting substance, were co-deposited to form a first charge generation region 2103a containing a composite material formed by combining an organic compound and an inorganic compound. The film thickness was 50 nm, and the ratio of NPB to molybdenum oxide (VI) was adjusted to be 4: 1 (= NPB: molybdenum oxide) by weight. The co-evaporation method is a vapor deposition method in which vapor deposition is performed simultaneously from a plurality of evaporation sources in one processing chamber.</p><p> Next, a hole transport layer 2103b was formed by forming a film of NPB on the first charge generation region 2103a so as to have a film thickness of 10 nm by a vapor deposition method using resistance heating.</p><p> In addition, 9- [4- (N-carbazolyl)] phenyl-10-phenylanthracene (abbreviation: CzPA) and 9,10-bis {4- [N- (4-diphenylaminophenyl) -N-phenylamino] By co-depositing phenyl} -2-tert-butylanthracene (abbreviation: DPABPA), a light emitting layer 2103c having a thickness of 30 nm was formed on the hole transport layer 2103b. Here, the weight ratio of CzPA and DPABPA was adjusted to be 1: 0.1 (= CzPA: DPABPA). CzPA is a substance having electron transportability, and DPABPA, which is a guest material, is a substance that emits blue-green light.</p><p> Then, using a thin-film deposition method by resistance heating, tris (8-quinolinolato) aluminum (abbreviation: Alq) was formed on the light emitting layer 2103c so as to have a film thickness of 10 nm to form an electron transport layer 2103d. As a result, the first EL layer 2103 including the first charge generation region 2103a, the hole transport layer 2103b, the light emitting layer 2103c, and the electron transport layer 2103d was formed.</p><p> Then, by co-depositing bassophenanthroline (abbreviation: BPhen) and lithium (Li), an electron injection buffer 2104 having a film thickness of 10 nm was formed on the electron transport layer 2103d. Here, the weight ratio of BPhen and Li was adjusted to be 1: 0.02 (= BPhen: Li).</p><p> Then, by vapor deposition of 3,4,9,10-perylenetetracarboxylic bisbenzimidazole (abbreviation: PTCBI), an electron relay layer 2105 having a thickness of 3 nm was formed on the electron injection buffer 2104. The LUMO level of PTCBI is about -4.0 eV from the result of cyclic voltammetry (CV) measurement.</p><p> Next, a second charge generation region 2106 was formed by co-depositing NPB, which is a substance with high hole transportability, and molybdenum oxide (VI), which is an acceptor substance, on the electron relay layer 2105. .. The film thickness was 20 nm, and the ratio of NPB to molybdenum oxide (VI) was adjusted to be 4: 1 (= NPB: molybdenum oxide) by weight.</p><p> Next, a second EL layer 2107 was formed on the second charge generation region 2106. First, a hole transport layer 2107a was formed by forming a film of NPB on the second charge generation region 2106 so as to have a film thickness of 10 nm by a vapor deposition method using resistance heating.</p><p> After that, tris (8-quinolinolato) aluminum (abbreviation: Alq) and 4-dicyanomethylene-2-isopropyl-6- [2- (1,1,7,7-tetramethyl-2,3,6,7-) Tetrahydro-1H, 5H-benzo [ij] quinolidine-9-yl) ethenyl] -4H-pyran (abbreviation: DCJTI) is co-deposited with a light emitting layer having a film thickness of 40 nm on the hole transport layer 2107a. Formed 2107b. Here, the weight ratio of Alq and DCJTI was adjusted to be 1: 0.01 (= Alq: DCJTI). Alq is a substance having electron transportability, and DCJTI, which is a guest material, is a substance that emits red light.</p><p> Next, an electron transport layer 2107c was formed by depositing Alq at a film thickness of 10 nm and then BPhen at 20 nm on the light emitting layer 2107b. An electron injection layer 2107d was formed by depositing lithium fluoride (LiF) on the electron transport layer 2107c at a film thickness of 1 nm. As a result, a second EL layer 2107 including a hole transport layer 2107a, a light emitting layer 2107b, an electron transport layer 2107c, and an electron injection layer 2107d was formed.</p><p> Finally, a light emitting device 1 was produced by forming a second electrode 2102 by forming aluminum on the electron injection layer 2107d so as to have a film thickness of 200 nm by using a vapor deposition method by resistance heating. ..</p><p> Next, the comparative light emitting device 1 will be described (see FIG. 9B). The comparative light emitting element 1 has a structure in which the electronic relay layer 2105 is removed from the light emitting element 1, and the other layers are formed by the same manufacturing method as that of the light emitting element 1. In the comparative light emitting device 1, after the electron injection buffer 2104 was formed, a second charge generation region 2106 was formed on the electron injection buffer 2104. From the above, the comparative light emitting device 1 of this example was obtained.</p><p> Table 1 below shows the element structures of the light emitting element 1 and the comparative light emitting element 1.</p><p><tables num="1"><img file="JP2019040887A_D0002.tif" /></tables></p><p> After performing the work of sealing the light emitting element 1 and the comparative light emitting element 1 obtained above in a glove box having a nitrogen atmosphere so that each light emitting element is not exposed to the atmosphere, the operating characteristics of these light emitting elements are measured. Was done. The measurement was performed at room temperature (atmosphere maintained at 25 ° C).</p><p> The voltage-luminance characteristics of the light emitting element 1 and the comparative light emitting element 1 are shown in FIG. In FIG. 10, the horizontal axis is the applied voltage (V) and the vertical axis is the brightness (cd / m).²). The current density-luminance characteristics are shown in FIG. In FIG. 11, the horizontal axis represents voltage (V) and the vertical axis represents current density (mA / cm).²). Also 1000 cd / m²Table 2 below summarizes the main initial characteristic values of each element in the vicinity.</p><p><tables num="2"><img file="JP2019040887A_D0003.tif" /></tables></p><p> As can be seen from the CIE chromaticity coordinates in Table 2, both the light emitting element 1 and the comparative light emitting element 1 show white light emission. This is because both the blue-green light emission derived from DPABPA contained in the first EL layer 2103 and the red light emission derived from DCJTI contained in the second EL layer 2107 were obtained.</p><p> From FIG. 10, it can be seen that the light emitting element 1 can obtain high brightness with respect to the voltage by providing the electronic relay layer. Further, from FIG. 11, it can be seen that the light emitting element 1 has a higher current density than the comparative light emitting element 1.</p><p>From the above, it was confirmed that the light emitting element 1 of this embodiment has characteristics as a light emitting element and functions sufficiently. Further, it was confirmed that the light emitting element 1 is a light emitting element that can be driven at a low voltage.</p>

<p> In this embodiment, a light emitting device according to an aspect of the present invention will be described with reference to FIG. In the light emitting element and the comparative light emitting element shown in this embodiment, the same parts as those in the above-described embodiment or parts having the same functions are designated by the same reference numerals, and the repeated description thereof will be omitted.</p><p>The manufacturing method of the light emitting element 2 and the comparative light emitting element 2 of this embodiment is shown below.</p><p>First, the light emitting element 2 will be described (see FIG. 12 (A)). The light emitting element 2 of this example was manufactured in the same manner as the light emitting element 1 shown in Example 1 up to the electronic relay layer 2105. In the light emitting device 2 of the present embodiment, molybdenum oxide (VI), which is an acceptor substance, is deposited at 20 nm on the electron relay layer 2105, and then NPB, which is a substance with high hole transportability, is deposited at 10 nm and laminated. A second charge generation region 2106 was formed.</p><p> Next, a second EL layer 2108 was formed on the second charge generation region 2106. First, Alq and DCJTI were co-deposited to form a light emitting layer 2108a having a film thickness of 40 nm on the second charge generation region 2106. Here, the weight ratio of Alq and DCJTI was adjusted to be 1: 0.01 (= Alq: DCJTI). Alq is a substance having electron transportability, and DCJTI, which is a guest material, is a substance that emits red light.</p><p> Next, an electron transport layer 2108b was formed by depositing Alq at a film thickness of 10 nm and then BPhen at 20 nm on the light emitting layer 2108a. An electron injection layer 2108c was formed by depositing lithium fluoride (LiF) on the electron transport layer 2108b at a film thickness of 1 nm. As a result, a second EL layer 2108 including the light emitting layer 2108a, the electron transport layer 2108b, and the electron injection layer 2108c was formed.</p><p> Finally, a light emitting device 2 was produced by forming a second electrode 2102 by forming aluminum on the electron injection layer 2108c so as to have a film thickness of 200 nm using a thin-film deposition method by resistance heating. ..</p><p> Next, the comparative light emitting device 2 will be described (see FIG. 12B). The comparative light emitting element 2 of this embodiment has a structure in which the electronic relay layer 2105 is removed from the light emitting element 2, and the other layers are formed by the same manufacturing method as that of the light emitting element 2. In the comparative light emitting device 2, after the electron injection buffer 2104 was formed, a second charge generation region 2106 was formed on the electron injection buffer 2104. From the above, the comparative light emitting device 2 of this example was obtained.</p><p> Table 3 below shows the element structures of the light emitting element 2 and the comparative light emitting element 2.</p><p><tables num="3"><img file="JP2019040887A_D0004.tif" /></tables></p><p> After performing the work of sealing the light emitting element 2 and the comparative light emitting element 2 obtained as described above in a glove box having a nitrogen atmosphere so that each light emitting element is not exposed to the atmosphere, the operating characteristics of these light emitting elements are measured. Was done. The measurement was performed at room temperature (atmosphere maintained at 25 ° C).</p><p> The voltage-luminance characteristics of the light emitting element 2 and the comparative light emitting element 2 are shown in FIG. In FIG. 13, the horizontal axis is the applied voltage (V) and the vertical axis is the brightness (cd / m).²). The current density-luminance characteristics are shown in FIG. In FIG. 14, the horizontal axis represents voltage (V) and the vertical axis represents current density (mA / cm).²). Also 1000 cd / m²Table 4 below summarizes the main initial characteristic values of each element in the vicinity.</p><p><tables num="4"><img file="JP2019040887A_D0005.tif" /></tables></p><p> As can be seen from the CIE chromaticity coordinates in Table 4, both the light emitting element 2 and the comparative light emitting element 2 show white light emission. This is because both the blue-green light emission derived from DPABPA contained in the first EL layer 2103 and the red light emission derived from DCJTI contained in the second EL layer 2108 were obtained.</p><p> From FIG. 13, it can be seen that the light emitting element 2 can obtain high brightness with respect to the voltage by providing the electronic relay layer. Further, from FIG. 14, it can be seen that the light emitting element 2 has a higher current density than the comparative light emitting element 2.</p><p>From the above, it was confirmed that the light emitting element 2 of this embodiment has characteristics as a light emitting element and functions sufficiently. Further, it was confirmed that the light emitting element 2 is a light emitting element that can be driven at a low voltage.</p>

<p> In this embodiment, a light emitting device according to an aspect of the present invention will be described with reference to FIG. In the light emitting element and the comparative light emitting element shown in this embodiment, the same parts as those in the above-described embodiment or parts having the same functions are designated by the same reference numerals, and the repeated description thereof will be omitted.</p><p>The manufacturing method of the light emitting element 3 and the comparative light emitting element 3 of this embodiment is shown below.</p><p>First, the light emitting element 3 will be described (see FIG. 9A). The light emitting device 3 of this example was manufactured in the same manner as the light emitting device 1 shown in Example 1 except for the electron transport layer 2103d of the first EL layer 2103 and the electron injection buffer 2104. In the light emitting device 3 of this example, the electron transport layer 2103d was formed by laminating Alq with a film thickness of 10 nm and then BPhen with a thickness of 10 nm on the light emitting layer 2103c.</p><p> Then, on the electron transport layer 2103d, lithium oxide (Li)₂Electron injection buffer 2104 was formed by vapor deposition of O) at 0.1 nm. From the above, the light emitting element 3 of this example was obtained.</p><p> Next, the comparative light emitting device 3 will be described (see FIG. 9B). The comparative light emitting element 3 of this embodiment has a structure in which the electronic relay layer 2105 is removed from the light emitting element 3, and the other layers are formed by the same manufacturing method as that of the light emitting element 3. In the comparative light emitting device 3, after the electron injection buffer 2104 was formed, a second charge generation region 2106 was formed on the electron injection buffer 2104. From the above, the comparative light emitting device 3 of this example was obtained.</p><p> Table 5 below shows the element structures of the light emitting element 3 and the comparative light emitting element 3.</p><p><tables num="5"><img file="JP2019040887A_D0006.tif" /></tables></p><p> After performing the work of sealing the light emitting element 3 and the comparative light emitting element 3 obtained above in a glove box having a nitrogen atmosphere so that each light emitting element is not exposed to the atmosphere, the operating characteristics of these light emitting elements are measured. Was done. The measurement was performed at room temperature (atmosphere maintained at 25 ° C).</p><p> FIG. 15 shows the voltage-luminance characteristics of the light emitting element 3 and the comparative light emitting element 3. In FIG. 15, the horizontal axis is the applied voltage (V) and the vertical axis is the brightness (cd / m).²). The current density-luminance characteristics are shown in FIG. In FIG. 16, the horizontal axis represents voltage (V) and the vertical axis represents current density (mA / cm).²). Also 1000 cd / m²Table 6 below summarizes the main initial characteristic values of each element in the vicinity.</p><p><tables num="6"><img file="JP2019040887A_D0007.tif" /></tables></p><p> As can be seen from the CIE chromaticity coordinates in Table 6, both the light emitting element 3 and the comparative light emitting element 3 show white light emission. This is because both the blue-green emission derived from DPABPA contained in the first EL layer 2103 and the red emission derived from DCJTI contained in the second EL layer 2107 were obtained.</p><p> From FIG. 15, it can be seen that the light emitting element 3 can obtain high brightness with respect to the voltage by providing the electronic relay layer. Further, from FIG. 16, it can be seen that the light emitting element 3 has a higher current density than the comparative light emitting element 3.</p><p>From the above, it was confirmed that the light emitting element 3 of this embodiment has characteristics as a light emitting element and functions sufficiently. Further, it was confirmed that the light emitting element 3 is a light emitting element that can be driven at a low voltage.</p>

<p> In this embodiment, a light emitting device according to an aspect of the present invention will be described with reference to FIG. In the light emitting element and the comparative light emitting element shown in this embodiment, the same parts as those in the above-described embodiment or parts having the same functions are designated by the same reference numerals, and the repeated description thereof will be omitted.</p><p>The manufacturing method of the light emitting element 4 and the comparative light emitting element 4 of this embodiment is shown below.</p><p>First, the light emitting element 4 will be described (see FIG. 12 (A)). The light emitting device 4 of this example was manufactured in the same manner as the light emitting device 2 shown in Example 2 except for the electron transport layer 2103d of the first EL layer 2103 and the electron injection buffer 2104. In the light emitting device 4 of this example, the electron transport layer 2103d was formed by depositing Alq at a film thickness of 10 nm and then BPhen at 10 nm on the light emitting layer 2103c.</p><p> Then, on the electron transport layer 2103d, lithium oxide (Li)₂Electron injection buffer 2104 was formed by vapor deposition of O) at 0.1 nm. From the above, the light emitting element 4 of this example was obtained.</p><p> Next, the comparative light emitting device 4 will be described (see FIG. 12B). The comparative light emitting element 4 of this embodiment has a structure in which the electronic relay layer 2105 is removed from the light emitting element 4, and the other layers are formed by the same manufacturing method as that of the light emitting element 4. In the comparative light emitting device 4, after the electron injection buffer 2104 was formed, a second charge generation region 2106 was formed on the electron injection buffer 2104. From the above, the comparative light emitting device 4 of this example was obtained.</p><p> Table 7 below shows the element structures of the light emitting element 4 and the comparative light emitting element 4.</p><p><tables num="7"><img file="JP2019040887A_D0008.tif" /></tables></p><p> The light emitting elements 4 and the comparative light emitting elements 4 obtained as described above are sealed in a glove box having a nitrogen atmosphere so that each light emitting element is not exposed to the atmosphere, and then the operating characteristics of these light emitting elements are measured. Was done. The measurement was performed at room temperature (atmosphere maintained at 25 ° C).</p><p> The voltage-luminance characteristics of the light emitting element 4 and the comparative light emitting element 4 are shown in FIG. In FIG. 17, the horizontal axis is the applied voltage (V) and the vertical axis is the brightness (cd / m).²). The current density-luminance characteristics are shown in FIG. In FIG. 18, the horizontal axis represents voltage (V) and the vertical axis represents current density (mA / cm).²). Also 1000 cd / m²Table 8 below summarizes the main initial characteristic values of each element in the vicinity.</p><p><tables num="8"><img file="JP2019040887A_D0009.tif" /></tables></p><p> As can be seen from the CIE chromaticity coordinates in Table 8, both the light emitting element 4 and the comparative light emitting element 4 show white light emission. This is because both the blue-green light emission derived from DPABPA contained in the first EL layer 2103 and the red light emission derived from DCJTI contained in the second EL layer 2108 were obtained.</p><p> From FIG. 17, it can be seen that the light emitting element 4 can obtain high brightness with respect to the voltage by providing the electronic relay layer. Further, from FIG. 18, it can be seen that the light emitting element 4 has a higher current density than the comparative light emitting element 4.</p><p>From the above, it was confirmed that the light emitting element 4 of this embodiment has characteristics as a light emitting element and functions sufficiently. Further, it was confirmed that the light emitting element 4 is a light emitting element that can be driven at a low voltage.</p>

<p> In this embodiment, a light emitting device according to an aspect of the present invention will be described with reference to FIG. 9A. In the light emitting element and the comparative light emitting element shown in this embodiment, the same parts as those in the above-described embodiment or parts having the same functions are designated by the same reference numerals, and the repeated description thereof will be omitted.</p><p>The manufacturing method of the light emitting element 3 and the comparative light emitting element 5 of this embodiment is shown below.</p><p> The light emitting element 3 of this example was manufactured in the same manner as the light emitting element 3 shown in Example 3 (see FIG. 9 (A)). Further, the comparative light emitting device 5 of this example was manufactured in the same manner as the light emitting device 3 except for the second charge generation region 2106. In the comparative light emitting device 5 of this embodiment, a second charge generation region 2106 was formed by depositing NPB on the electron relay layer 2105 with a thickness of 20 nm (see FIG. 9 (A)). From the above, the comparative light emitting device 5 of this example was obtained.</p><p> Table 9 below shows the element structures of the light emitting element 3 and the comparative light emitting element 5.</p><p><tables num="9"><img file="JP2019040887A_D0010.tif" /></tables></p><p> The light emitting elements 3 and the comparative light emitting elements 5 obtained as described above are sealed in a glove box having a nitrogen atmosphere so that each light emitting element is not exposed to the atmosphere, and then the operating characteristics of these light emitting elements are measured. Was done. The measurement was performed at room temperature (atmosphere maintained at 25 ° C).</p><p> FIG. 19 shows the voltage-luminance characteristics of the light emitting element 3 and the comparative light emitting element 5. In FIG. 19, the horizontal axis is the applied voltage (V) and the vertical axis is the brightness (cd / m).²). The current density-luminance characteristics are shown in FIG. In FIG. 20, the horizontal axis represents voltage (V) and the vertical axis represents current density (mA / cm).²). Also 1000 cd / m²The main initial characteristic values of each element in the vicinity are summarized in Table 10 below.</p><p><tables num="10"><img file="JP2019040887A_D0011.tif" /></tables></p><p> As described in Example 3, the light emitting device 3 emitted white light emission, but the comparative light emitting element 5 exhibited blue-green light emission due to the weak red spectral intensity derived from DCJTI (Table 10). See chromaticity coordinates of). This suggests that when the second charge generation region 2106 consists only of a substance with high hole transportability (NPB in this example), it is difficult for holes to be injected into the second EL layer 2107. To.</p><p> On the other hand, since the light emitting element 3 contains a substance having a high hole transport property (NPB in this example) and an acceptor substance (molybdenum oxide in this example) in the second charge generation region 2106, it is second. Electrons are exchanged in the charge generation region 2106 of the above, and holes and electrons are generated in the second charge generation region 2106. The generated holes easily move on the NPB by applying a voltage and are injected into the second EL layer 2107. Further, the electrons are easily injected into the electron relay layer 2105 by applying a voltage and reach the first EL layer 2103. Therefore, as shown in FIG. 19, the light emitting element 3 can obtain higher brightness than the comparative light emitting element 5. Further, as shown in FIG. 20, the light emitting element 3 can flow a larger current at a lower voltage than the comparative light emitting element 5.</p><p>From the above, it was confirmed that the light emitting element 3 of this embodiment has characteristics as a light emitting element and functions sufficiently. Further, it was confirmed that the light emitting element 3 is a light emitting element that can be driven at a low voltage.</p>

<p> In this embodiment, a light emitting device according to an aspect of the present invention will be described with reference to FIGS. 9 (A) and 21. In the light emitting element and the comparative light emitting element shown in this embodiment, the same parts as those in the above-described embodiment or parts having the same functions are designated by the same reference numerals, and the repeated description thereof will be omitted.</p><p>The chemical formulas of the materials used in this example are shown below. The material whose structural formula has already been shown will be omitted.</p><p><chemistry num="2"><img file="JP2019040887A_D0012.tif" /></chemistry></p><p>The manufacturing method of the light emitting element 5 and the comparative light emitting element 6 of this embodiment is shown below.</p><p>First, the light emitting element 5 will be described (see FIG. 9A). The light emitting element 5 of this example was manufactured in the same manner as the light emitting element 3 shown in Example 3 except for the light emitting layer 2103c of the first EL layer 2103 and the light emitting layer 2107b of the second EL layer 2107. In the light emitting device 5 of this embodiment, CzPA, coumarin 30, N- (9,10-diphenyl-2-anthryl) -N, 9-diphenyl-9H-carbazole-3-amine (abbreviation: 2PCAPA), and Was co-deposited to form a light emitting layer 2103c having a thickness of 30 nm on the hole transport layer 2103b. Further, similarly to the light emitting layer 2103c, CzPA and 2PCAPA were co-deposited to form a light emitting layer 2107b having a film thickness of 30 nm on the hole transport layer 2107a. In the light emitting layer 2103c and the light emitting layer 2107b, the weight ratio of CzPA and 2PCAPA was adjusted to be 1: 0.05 (= CzPA: 2PCAPA). CzPA is a substance having electron transport properties, and 2PCAPA, which is a guest material, is a substance that emits green light. From the above, the light emitting element 5 of this example was obtained.</p><p> Next, the comparative light emitting device 6 will be described (see FIG. 21). The comparative light emitting element 6 of this embodiment has a structure in which the electron relay layer 2105, the charge generation region 2106, and the second EL layer 2107 are removed from the light emitting element 5, and the other layers are the same as those of the light emitting element 5. It was formed by the manufacturing method. As shown in FIG. 21, the comparative light emitting device 6 of this embodiment has a structure having one EL layer between a pair of electrodes.</p><p>In the comparative light emitting device 6, after the electron injection buffer 2104 was formed, the second electrode 2102 was formed on the electron injection buffer 2104. From the above, the comparative light emitting device 6 of this example was obtained.</p><p> Table 11 below shows the element structures of the light emitting element 5 and the comparative light emitting element 6.</p><p><tables num="11"><img file="JP2019040887A_D0013.tif" /></tables></p><p> The light emitting elements 5 and the comparative light emitting elements 6 obtained as described above are sealed in a glove box having a nitrogen atmosphere so that each light emitting element is not exposed to the atmosphere, and then the operating characteristics of these light emitting elements are measured. Was done. The measurement was performed at room temperature (atmosphere maintained at 25 ° C).</p><p> The voltage-current density characteristics of the light emitting element 5 and the comparative light emitting element 6 are shown in FIG. In FIG. 22, the horizontal axis is the applied voltage (V) and the vertical axis is the current density (mA / cm).²). The current density-luminance characteristics are shown in FIG. In FIG. 23, the horizontal axis is the current density (mA / cm).²), The vertical axis is the brightness (cd / m)²). Also 1000 cd / m²The main initial characteristic values of each element in the vicinity are summarized in Table 12 below.</p><p><tables num="12"><img file="JP2019040887A_D0014.tif" /></tables></p><p> From FIG. 22, the light emitting element 5 of the present embodiment having two EL layers can be driven at almost twice the voltage when the EL layer carries a current having the same current density as the one-layer comparative light emitting element 6. I understand that. Further, from FIG. 23, it can be seen that the light emitting element 5 exhibits almost twice the brightness (that is, the current efficiency is almost double) when a current having the same current density as that of the comparative light emitting element 6 is passed. This suggests that in the light emitting device 5 of this embodiment, there is almost no extra voltage increase due to the introduction of the electron injection buffer, the electron relay layer, and the charge generation region between the two EL layers. ..</p><p>From the above, it was confirmed that the light emitting element 5 of this embodiment has characteristics as a light emitting element and functions sufficiently. Further, the light emitting element 5 is a light emitting element that can be driven at a low voltage with almost no extra voltage rise due to the introduction of an electron injection buffer, an electron relay layer, and a charge generation region between the two EL layers. I was able to confirm that.</p>

<p>In this embodiment, a light emitting device according to an aspect of the present invention will be described with reference to FIGS. 9 (A) and 9 (B). In the light emitting element and the comparative light emitting element shown in this embodiment, the same parts as those in the above-described embodiment or parts having the same functions are designated by the same reference numerals, and the repeated description thereof will be omitted.</p><p>The chemical formulas of the materials used in this example are shown below. The material whose structural formula has already been shown will be omitted.</p><p><chemistry num="3"><img file="JP2019040887A_D0015.tif" /></chemistry></p><p>The manufacturing method of the light emitting element 6 and the comparative light emitting element 7 of this embodiment is shown below.</p><p>First, the light emitting element 6 will be described (see FIG. 9A). The light emitting element 6 of this example was manufactured in the same manner as the light emitting element 5 shown in Example 6 except for the electronic relay layer 2105. In the light emitting device 6 of this embodiment, a film thickness of 3 nm is formed on the electron injection buffer 2104 by depositing N, N'-dihexylu 3,4,9,10-perylenetetracarboxylic acid diimide (abbreviation: HexPTC). The electronic relay layer 2105 was formed. From the above, the light emitting element 6 of this example was obtained.</p><p>Next, the comparative light emitting device 7 will be described (see FIG. 9B). The comparative light emitting element 7 of this embodiment has a structure in which the electronic relay layer 2105 is removed from the light emitting element 6, and the other layers are formed by the same manufacturing method as that of the light emitting element 6. In the comparative light emitting device 7, after the electron injection buffer 2104 was formed, the charge generation region 2106 was formed on the electron injection buffer 2104. From the above, the comparative light emitting device 7 of this example was obtained.</p><p> Table 13 below shows the element structures of the light emitting element 6 and the comparative light emitting element 7.</p><p><tables num="13"><img file="JP2019040887A_D0016.tif" /></tables></p><p> The light emitting elements 6 and the comparative light emitting elements 7 obtained as described above are sealed in a glove box having a nitrogen atmosphere so that each light emitting element is not exposed to the atmosphere, and then the operating characteristics of these light emitting elements are measured. Was done. The measurement was performed at room temperature (atmosphere maintained at 25 ° C).</p><p> FIG. 25 shows the voltage-luminance characteristics of the light emitting element 6 and the comparative light emitting element 7. In FIG. 25, the horizontal axis is the applied voltage (V) and the vertical axis is the brightness (cd / m).²). The voltage-current density characteristics are also shown in FIG. In FIG. 26, the horizontal axis represents voltage (V) and the vertical axis represents current density (mA / cm).²). Also 1000 cd / m²Table 14 below summarizes the main initial characteristic values of each element in the vicinity.</p><p><tables num="14"><img file="JP2019040887A_D0017.tif" /></tables></p><p>From FIG. 25, it can be seen that the light emitting element 6 can obtain higher brightness with respect to the voltage than the comparative light emitting element 7 by providing the electronic relay layer. Further, from FIG. 26, it can be seen that the light emitting element 6 has a higher current density than the comparative light emitting element 7.</p><p>From the above, it was confirmed that the light emitting element 6 of this embodiment has characteristics as a light emitting element and functions sufficiently. Further, it was confirmed that the light emitting element 6 is a light emitting element that can be driven at a low voltage.</p>

<p>In this embodiment, a light emitting device according to an aspect of the present invention will be described with reference to FIGS. 9 (A) and 9 (B). In the light emitting element and the comparative light emitting element shown in this embodiment, the same parts as those in the above-described embodiment or parts having the same functions are designated by the same reference numerals, and the repeated description thereof will be omitted.</p><p>The chemical formulas of the materials used in this example are shown below. The material whose structural formula has already been shown will be omitted.</p><p><chemistry num="4"><img file="JP2019040887A_D0018.tif" /></chemistry></p><p>The manufacturing method of the light emitting element 7 and the comparative light emitting element 8 of this embodiment is shown below.</p><p>First, the light emitting element 7 will be described (see FIG. 9A). The light emitting device 7 of this embodiment includes a light emitting layer 2103c and an electron transport layer 2103d in the first EL layer 2103, a second charge generation region 2106, and a light emitting layer 2107b and an electron transport layer 2107c in the second EL layer 2107. Other than that, it was produced in the same manner as the light emitting element 3 in Example 3.</p><p>In the light emitting element 7 of this embodiment, the light emitting layer 2103c is 4- (10-phenyl-9-anthryl) -4'-(9-phenyl-9H-carbazole-3-yl) triphenylamine (abbreviation: PCBAPA). And 4 (1-naphthyl) -4'(9-phenyl-9H-carbazole-3-yl) -triphenylamine (abbreviation; PCBANB) were co-deposited with a film thickness of 20 nm, and then CzPA and SD1 were further deposited. It was formed by co-depositing and laminating (trade name; manufactured by SFC Co., Ltd) with a film thickness of 30 nm. The weight ratio of PCBAPA and PCBANB was adjusted to be 1: 1 (= PCBAPA: PCBANB). The weight ratio of CzPA and SD1 was adjusted to 1: 0.05 (= CzPA: SD1).</p><p> Next, an electron transport layer 2107c was formed by depositing BPhen at 30 nm on the light emitting layer 2103c.</p><p>Further, in the light emitting device 7, the second charge generation region 2106 co-deposits NPB, which is a substance having high hole transport property, and molybdenum oxide (VI), which is an acceptor substance, on the electron relay layer 2105. Formed by The film thickness was 40 nm, and the ratio of NPB to molybdenum oxide (VI) was adjusted to be 4: 1 (= NPB: molybdenum oxide) by weight.</p><p>Further, in the light emitting element 7, the light emitting layer 2107b is composed of 4- (9H-carbazole-9-yl) -4'-(5-phenyl-1,3,4-oxadiazole-2-yl) triphenylamine ( Abbreviation: YGAO11) and (acetylacetone) bis (2,3,5-triphenylpyrazinato) iridium (III) (abbreviation: Ir (tppr))₂(acac)) is co-deposited with a film thickness of 10 nm, and then YGAO11 and bis (2-phenylpyridinato-N, C2') iridium (acetylacetonate) (abbreviation: Ir (ppy))₂(acac)) was formed by co-depositing with a film thickness of 20 nm. In addition, YGAO11 and Ir (tppr)₂The weight ratio with (acac) is 1: 0.03 (= YGAO11: Ir (tppr))₂(acac)) was adjusted. Also, YGAO11 and Ir (ppy)₂The weight ratio with (acac) is 1: 0.06 (= YGAO11: Ir (ppy)₂(acac)) was adjusted.</p><p>Next, the electron transport layer 2107c was formed by laminating BAlq with a film thickness of 10 nm and then BPhen with a thickness of 20 nm on the light emitting layer 2107b. From the above, the light emitting element 7 of this example was obtained.</p><p>Next, the comparative light emitting device 8 will be described (see FIG. 9B). The comparative light emitting element 8 of this embodiment has a structure in which the electronic relay layer 2105 is removed from the light emitting element 7. Further, in the comparative light emitting device 8, the electron injection buffer 2104 was formed to have a film thickness of 20 nm by co-depositing BPhen and lithium (Li). Here, the weight ratio of BPhen and Li was adjusted to be 1: 0.02 (= BPhen: Li). The other layers were formed by the same manufacturing method as that of the light emitting device 7. In the comparative light emitting device 8, after the electron injection buffer 2104 was formed, the charge generation region 2106 was formed on the electron injection buffer 2104. From the above, the comparative light emitting device 8 of this example was obtained.</p><p> Table 15 below shows the element structures of the light emitting element 7 and the comparative light emitting element 8.</p><p><tables num="15"><img file="JP2019040887A_D0019.tif" /></tables></p><p>The light emitting elements 7 and the comparative light emitting elements 8 obtained as described above are sealed in a glove box having a nitrogen atmosphere so that each light emitting element is not exposed to the atmosphere, and then the operating characteristics of these light emitting elements are measured. Was done. The measurement was performed at room temperature (atmosphere maintained at 25 ° C).</p><p> FIG. 27 shows the voltage-luminance characteristics of the light emitting element 7 and the comparative light emitting element 8. In FIG. 27, the horizontal axis is the applied voltage (V) and the vertical axis is the brightness (cd / m).²). The voltage-current density characteristics are shown in FIG. In FIG. 28, the horizontal axis represents voltage (V) and the vertical axis represents current density (mA / cm).²). Also 1000 cd / m²The main initial characteristic values of each element in the vicinity are summarized in Table 16 below.</p><p><tables num="16"><img file="JP2019040887A_D0020.tif" /></tables></p><p>From FIG. 27, it can be seen that the light emitting element 7 can obtain higher brightness with respect to the voltage than the comparative light emitting element 8 by providing the electronic relay layer. Further, from FIG. 28, it can be seen that the light emitting element 7 has a higher current density than the comparative light emitting element 8.</p><p> As can be seen from the CIE chromaticity coordinates in Table 16 and FIG. 29, both the light emitting element 7 and the comparative light emitting element 8 show white light emission. This is the blue emission derived from PCBAPA and SD1 contained in the first EL layer 2103 and Ir (tppr) contained in the second EL layer 2107.₂Red emission derived from (acac) and Ir (ppy)₂This is because a green luminescence derived from (acac) was obtained.</p><p>From the above, it was confirmed that the light emitting element 7 of this embodiment has characteristics as a light emitting element and functions sufficiently. Further, it was confirmed that the light emitting element 7 is a light emitting element that can be driven at a low voltage. Further, it was found that one form of the configuration of the present invention is effective even when applied to a white light emitting device in which each EL layer exhibits a different emission spectrum.</p>

<p>In this embodiment, a light emitting device according to an aspect of the present invention will be described with reference to FIGS. 9 (A) and 9 (B). In the light emitting element and the comparative light emitting element shown in this embodiment, the same parts as those in the above-described embodiment or parts having the same functions are designated by the same reference numerals, and the repeated description thereof will be omitted.</p><p>The chemical formulas of the materials used in this example are shown below. The material whose structural formula has already been shown will be omitted.</p><p><chemistry num="5"><img file="JP2019040887A_D0021.tif" /></chemistry></p><p>The manufacturing method of the light emitting element 8 and the comparative light emitting element 9 of this embodiment is shown below.</p><p>First, the light emitting element 8 will be described (see FIG. 9A). The light emitting device 8 of this embodiment is the same as that of the eighth example except for the light emitting layer 2103c in the first EL layer 2103, the second charge generation region 2106, the light emitting layer 2107b in the second EL layer 2107, and the electron transport layer 2107c. It was manufactured in the same manner as the light emitting element 7.</p><p>In the light emitting element 8 of this embodiment, the light emitting layer 2103c is composed of 2,3-bis {4- [N- (4-biphenylyl) -N-phenylamino] phenyl} quinoxaline (abbreviation: BPAPQ) and (acetylacetonato). ) Bis [2,3-bis (4-fluorophenyl) quinoxalineato] Iridium (III) (abbreviation: Ir (Fdpq)₂(acac)) was co-deposited to a film thickness of 10 nm, and then NPB and N,9-diphenyl-N- [4- (9,10-diphenyl-2-anthryl) phenyl] -9H-carbazole-3-amine ( Abbreviation: 2PCAPPA) was co-deposited with a film thickness of 5 nm, and CzPA and 2PCAPPA were co-deposited with a film thickness of 30 nm and laminated.</p><p>BPAPQ and Ir (Fdpq)₂The weight ratio with (acac) is 1: 0.06 (= BPAPQ: Ir (Fdpq))₂(acac)) was adjusted. The weight ratio of NPB and 2PCAPPA was adjusted to 1: 0.1 (= NPB: 2PCAPPA). The weight ratio of CzPA and 2PCAPPA was adjusted to 1: 0.1 (= CzPA: 2PCAPPA).</p><p>Further, in the light emitting device 7, the second charge generation region 2106 co-deposits NPB, which is a substance having high hole transport property, and molybdenum oxide (VI), which is an acceptor substance, on the electron relay layer 2105. Formed by The film thickness was 70 nm, and the ratio of NPB to molybdenum oxide (VI) was adjusted to be 4: 1 (= NPB: molybdenum oxide) by weight.</p><p>Further, in the light emitting element 7, the light emitting layer 2107b is formed by co-depositing NPB and stilbene at a film thickness of 20 nm, and then 9-phenyl-9'-[4- (10-phenyl-9-anthryl) phenyl]-. 3,3'-bi (9H-carbazole) (abbreviation: PCCPA) and N, N'-bis [4- (9H-carbazole-9-yl) phenyl] -N, N'-diphenylstilbene-4,4 It was formed by co-depositing'-diamine (abbreviation: YGA2S) with a film thickness of 10 nm, and further co-depositing CzPA and YGA2S with a film thickness of 20 nm. The weight ratio of NPB and rubrene was adjusted to be 1: 0.015 (= NPB: rubrene). The weight ratio of PCCPA and YGA2S was adjusted to 1: 0.05 (= PCCPA: YGA2S). The weight ratio of CzPA and YGA2S was adjusted to 1: 0.05 (= CzPA: YGA2S).</p><p>Next, an electron transport layer 2107c was formed by depositing and laminating BPhen at 30 nm on the light emitting layer 2107b. From the above, the light emitting element 8 of this example was obtained.</p><p>Next, the comparative light emitting device 9 will be described (see FIG. 9B). The comparative light emitting element 9 of this embodiment has a structure in which the electronic relay layer 2105 is removed from the light emitting element 8. Further, in the comparative light emitting device 9, the electron injection buffer 2104 was formed to have a film thickness of 20 nm by co-depositing BPhen and lithium (Li). Here, the weight ratio of BPhen and Li was adjusted to be 1: 0.02 (= BPhen: Li). The other layers were formed by the same manufacturing method as that of the light emitting device 8. In the comparative light emitting device 9, after the electron injection buffer 2104 was formed, the charge generation region 2106 was formed on the electron injection buffer 2104. From the above, the comparative light emitting device 9 of this example was obtained.</p><p> Table 17 below shows the element structures of the light emitting element 8 and the comparative light emitting element 9.</p><p><tables num="17"><img file="JP2019040887A_D0022.tif" /></tables></p><p>The light emitting elements 8 and the comparative light emitting elements 9 obtained as described above are sealed in a glove box having a nitrogen atmosphere so that each light emitting element is not exposed to the atmosphere, and then the operating characteristics of these light emitting elements are measured. Was done. The measurement was performed at room temperature (atmosphere maintained at 25 ° C).</p><p> The voltage-luminance characteristics of the light emitting element 8 and the comparative light emitting element 9 are shown in FIG. In FIG. 30, the horizontal axis is the applied voltage (V) and the vertical axis is the brightness (cd / m).²). The voltage-current density characteristics are shown in FIG. In FIG. 31, the horizontal axis represents voltage (V) and the vertical axis represents current density (mA / cm).²). Also 1000 cd / m²Table 18 below summarizes the main initial characteristic values of each element in the vicinity.</p><p><tables num="18"><img file="JP2019040887A_D0023.tif" /></tables></p><p>From FIG. 30, it can be seen that the light emitting element 8 can obtain higher brightness with respect to the voltage than the comparative light emitting element 9 by providing the electronic relay layer. Further, from FIG. 31, it can be seen that the light emitting element 8 has a higher current density than the comparative light emitting element 9.</p><p> As can be seen from the CIE chromaticity coordinates in Table 18 and FIG. 32, both the light emitting element 8 and the comparative light emitting element 9 show white light emission. This is Ir (Fdpq) contained in the first EL layer 2103.₂Because red emission from (acac), blue-green emission from 2PCAPPA, yellow emission from rubrene contained in the second EL layer 2107, and blue emission from YGA2S were obtained. Is. In addition, by combining these four types of emission colors, a high color rendering index (CRI) of 92 was obtained.</p><p>From the above, it was confirmed that the light emitting element 8 of this embodiment has characteristics as a light emitting element and functions sufficiently. Further, it was confirmed that the light emitting element 8 is a light emitting element that can be driven at a low voltage. Further, it was found that one form of the configuration of the present invention is effective even when applied to a white light emitting device in which each EL layer exhibits a different emission spectrum.</p><p>(Reference Example) In this reference example, the method for synthesizing the materials used in the above examples will be specifically described. &lt;&lt; Synthesis example of 4 (1-naphthyl) -4'(9-phenyl-9H-carbazole-3-yl) -triphenylamine (abbreviation; PCBANB) &gt;&gt;</p><p>The synthesis scheme of 4 (1-naphthyl) -4'(9-phenyl-9H-carbazole-3-yl) -triphenylamine is shown in (A-1) below.</p><p><chemistry num="6"><img file="JP2019040887A_D0024.tif" /></chemistry></p><p> 1.2 g (3.0 mmol) of 3- (4-bromophenyl) -9-phenyl-9H-carbazole, 0.9 g (3.0 mmol) of 4- (1-naphthyl) diphenylamine, 0.5 g (5.0 mmol) of sodium tert-butoxide ), Bis (dibenzylideneacetone) palladium (0) was placed in a 6.0 mg (0.01 mmol), 50 mL three-necked flask, and 15 mL of dehydrated xylene was added to this mixture. The mixture was degassed with stirring under reduced pressure, and after degassing, 0.06 mL (0.03 mmol) of tri (tert-butyl) phosphine (10 wt% hexane solution) was added. The mixture was heated and stirred at 120 ° C. for 4.5 hours under a nitrogen atmosphere to react.</p><p> After the reaction, 250 mL of toluene was added to the reaction mixture and the suspension was filtered through Florisil, silica gel, alumina and Celite. The obtained filtrate was washed with water, and magnesium sulfate was added to remove water. This suspension was filtered through Florisil, alumina, silica gel and Celite to obtain a filtrate. The obtained filtrate was concentrated, acetone and methanol were added, ultrasonic waves were applied, and the mixture was recrystallized to obtain the desired white powder in a yield of 1.5 g and a yield of 82%.</p><p> The Rf value (developing solvent ethyl acetate: hexane = 10: 10) in silica gel thin layer chromatography (TLC) was 0.34 for the target product, 0.46 for 3- (4-bromophenyl) -9-phenyl-9H-carbazole, The 4- (1-naphthyl) diphenylamine was 0.25.</p><p> The compound obtained in the above step is subjected to nuclear magnetic resonance spectroscopy (¹It was measured by 1 H NMR). The measurement data is shown below. From the measurement results, it was found that the target product, PCBANB (abbreviation), was obtained.</p><p>¹1 H NMR (CDCl₃, 300MHz): δ (ppm) = 7.07 (t, J = 6.6Hz, 1H), 7.25-7.67 (m, 26H), 7.84 (d, J = 7.8Hz, 1H), 7.89-7.92 (m, 1H) , 8.03-8.07 (m, 1H), 8.18 (d, J = 7.8Hz, 1H), 8.35 (d, J = 0.9Hz, 1H).</p>

10 Substrate 11 Transistor 12 Light emitting element 13 Electrode 14 Electrode 15 Layer containing organic compound 16 Interlayer insulating film 17 Wiring 18 Partition layer 19 Interlayer insulating film 101 Anode 102 Cathode 103 EL layer 103-1 First light emitting layer 103-2 Second Light emitting layer 104 Electron injection buffer 105 Electron relay layer 106 Charge generation region 107 EL layer 107-1 Third light emitting layer 107-2 Fourth light emitting layer 108 Electron transport layer 111 Anode Fermi level 112 Electrode Fermi level 113 LUMO level of the first EL layer 114 LUMO level of the electron relay layer 115 Acceptor level of the acceptor in the charge generation region 116 LUMO level of the second EL layer 330 First emission 340 Second emission 951 Substrate 952 Electrode 953 Insulation layer 954 Partition layer 955 Layer containing organic compounds 956 Electrode 2100 Glass substrate 2101 Electrode 2102 Electron 2103 EL layer 2103a Charge generation region 2103b Hole transport layer 2103c Light emitting layer 2103d Electron transport layer 2104 Electron injection buffer 2105 Electron relay layer 2106 Charge generation region 2107 EL layer 2107a Hole transport layer 2107b Light emitting layer 2107c Electron transport layer 2107d Electron injection Layer 2108 EL layer 2108a Light emitting layer 2108b Electronic transport layer 2108c Electronic injection layer 3000 Light source 3001 Lighting device 3002 Lighting device 9100 Mobile phone 9101 Housing 9102 Housing 9103 Connecting part 9104 Display 9106 Operation key 9200 Mobile information terminal device 9201 Housing 9202 Display 9203 Housing 9205 Keyboard 9207 Connection 9400 Computer 9401 Housing 9402 Display 9403 Keyboard 9404 Housing 9500 Digital Video Camera 9501 Housing 9503 Display unit 9600 Television device 9601 Housing 9603 Display unit 9605 Stand 9607 Display unit 9609 Operation key 9610 Remote control operation unit 9703 Display unit