Organic light-emitting device

Abstract

To provide an organic light-emitting device that improves the movement of carriers and triplet energy between stacked luminous layers, and has improved drive durability.SOLUTION: Luminous layers include a first luminous layer 4a and a second luminous layer 4b in contact with each other. The first luminous layer 4a includes a first organic compound, a first metal complex, and a second metal complex. The second luminous layer 4b includes a second organic compound and a third metal complex, and does not include the first metal complex. When the triplet energies of the first metal complex, second metal complex, and third metal complex are defined as T1D1, T1D2, and T1D3, respectively, the relationships of the following formulas [a] to [c] are satisfied. [a] T1D2>T1D1; [b] T1D3≥T1D2; [c] T1D2-T1D1>T1D3-T1D2.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an organic light-emitting element and various devices having the organic light-emitting element. [Background technology]

[0002] An organic light-emitting element (hereinafter sometimes referred to as an "organic electroluminescent element" or an "organic EL element") is an element that emits light when electricity is passed through an organic EL (electroluminescent) layer that includes an anode, a cathode, and a light-emitting layer disposed between these electrodes. In recent years, research and development of full-color displays using organic light-emitting elements has been actively pursued. Organic light-emitting elements are known to be roughly classified into fluorescent light-emitting elements and phosphorescent light-emitting elements depending on the type of compound contained in the light-emitting layer, and it is necessary to design an energy diagram suitable for each of them. On the other hand, when manufacturing a full-color display, there are two known methods: a method in which the light-emitting layer is painted for each pixel (element), and a method in which the light-emitting layer emits white light and a color filter is painted for each pixel. When a white-light-emitting light-emitting layer is used, it is known that the organic light-emitting element uses two or more types of light-emitting materials. Patent Document 1 discloses an organic light-emitting device in which an emission layer made of an exciplex host and a phosphorescent material is laminated. Patent Document 2 discloses an organic light-emitting device in which an emission layer made of a hole-transporting host and a phosphorescent material and an emission layer made of an electron-transporting host and a phosphorescent material are laminated. Patent Document 3 discloses an organic light-emitting device in which two emission layers containing a blue phosphorescent material, a green phosphorescent material, and a red phosphorescent material are laminated. Patent Document 4 discloses an organic light-emitting device in which an emission layer containing a blue phosphorescent material and a green phosphorescent material and an emission layer containing a red phosphorescent material are laminated. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-96557 A [Patent Document 2] JP 2013-200939 A [Patent Document 3] JP 2011-171269 A [Patent Document 4] JP 2010-34484 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the organic light-emitting device described in the above patent document is an organic light-emitting device in which carrier transfer and triplet energy transfer between two light-emitting layers in contact with each other are difficult to occur, and therefore the durability characteristics of the organic light-emitting device are subject to improvement. The present invention has been made in view of the above problems, and an object of the present invention is to provide an organic light-emitting element which improves carrier transfer and triplet energy transfer between two adjacent light-emitting layers and thereby improves driving durability. [Means for solving the problem]

[0005] The organic light-emitting device of the present invention is an organic light-emitting device including a first electrode, a first light-emitting layer, a second light-emitting layer, and a second electrode, the first light-emitting layer and the second light-emitting layer are in contact with each other, the first light-emitting layer includes a first organic compound, a first metal complex, and a second metal complex; the second light-emitting layer contains a second organic compound and a third metal complex, but does not contain the first metal complex; When the triplet energies of the first metal complex, the second metal complex, and the third metal complex are T1D1, T1D2, and T1D3, respectively, the relationships of the following formulas [a] to [c] hold. T1D2>T1D1 [a] T1D3 ≥ T1D2 [b] T1D2-T1D1>T1D3-T1D2 [c] Effect of the Invention

[0006] According to the present invention, it is possible to provide an organic light-emitting device having improved durability characteristics. [Brief description of the drawings]

[0007] [Figure 1] 1 is a schematic cross-sectional view of an organic light-emitting device according to one embodiment of the present invention. [Diagram 2] 1 is an energy diagram showing a schematic energy level around an emission layer of an organic light-emitting element according to one embodiment of the present invention. [Diagram 3] FIG. 2 is a diagram showing a triplet energy level of a metal complex contained in a light-emitting layer of an organic light-emitting element according to one embodiment of the present invention. [Figure 4] 1A and 1B are schematic diagrams illustrating a display device according to an embodiment of the present invention; [Diagram 5] 1 is a schematic diagram of a display device according to an embodiment of the present invention; [Figure 6] 1A is a schematic diagram of an imaging device according to an embodiment of the present invention, and FIG. [Figure 7] 1A is a schematic diagram of a display device according to an embodiment of the present invention, and FIG. 1B is a schematic diagram of a foldable display device according to an embodiment of the present invention. [Figure 8] 1A is a schematic diagram of an illumination device according to an embodiment of the present invention, and FIG. 1B is a schematic diagram of an automobile having a vehicle lamp according to an embodiment of the present invention. [Figure 9] 1A is a schematic diagram showing an example of a wearable device according to an embodiment of the present invention, and FIG. 1B is a schematic diagram showing an example of a wearable device according to an embodiment of the present invention, the wearable device having an imaging device. [Figure 10] 1 is a schematic diagram showing an example of an image forming apparatus according to an embodiment of the present invention and an example of an exposure light source thereof; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] An organic light-emitting element according to one embodiment of the present invention includes a first electrode, a stacked light-emitting layer including a first light-emitting layer and a second light-emitting layer, and a second electrode. At least one of the first electrode and the second electrode may be a light-transmitting electrode, and either one may be a reflective electrode. The first light-emitting layer and the second light-emitting layer are in contact with each other, and either one is an anode side and either one is a cathode side.

[0009] The first light-emitting layer includes a first organic compound, a first metal complex, and a second metal complex, and the second light-emitting layer includes a second organic compound and a third metal complex, but does not include the first metal complex. That is, the first metal complex and the third metal complex are different metal complexes and have different triplet energies. Therefore, the first light-emitting layer and the second light-emitting layer show different emission colors.

[0010] [Stacked Light-Emitting Layer] An organic light-emitting device according to one embodiment of the present invention is characterized in that the relationships of the following formulas [a] to [c] hold. T1D2>T1D1 [a] T1D3 ≥ T1D2 [b] T1D2-T1D1>T1D3-T1D2 [c] The above T1D1, T1D2, and T1D3 represent the triplet energies of the first metal complex, the second metal complex, and the third metal complex, respectively.

[0011] The above formula [a] indicates that the first metal complex has a smaller triplet energy than the second metal complex, and therefore indicates that light emission from the first metal complex is mainly observed in the first emitting layer. The above formula [b] indicates that the triplet energy of the third metal complex contained in the second light-emitting layer is equal to or greater than the triplet energy of the second metal complex contained in the first light-emitting layer. In addition, this, together with the above formula [a], indicates that the third metal complex has a higher triplet energy than the first metal complex. Therefore, it indicates that the second light-emitting layer is an emitting layer in which light having a shorter wavelength than the first light-emitting layer is observed. The above formula [c] indicates that the difference in triplet energy between the third metal complex and the second metal complex is smaller than the difference in triplet energy between the first metal complex and the second metal complex. As described below, this indicates that the energy transfer is more likely to occur between the third metal complex and the second metal complex than between the third metal complex and the first metal complex.

[0012] In addition, the third metal complex and the second metal complex are metal complexes with a small or no difference in triplet energy, and therefore have a similar energy gap. Therefore, the positional relationship of the HOMO and LUMO energy levels is also close, which indicates that carrier transfer is more likely to occur between the third metal complex and the second metal complex than between the third metal complex and the first metal complex. As described later, this makes it easier to adjust the exciton density generated in the first and second emitting layers between the emitting layers, and improves driving durability.

[0013] In this specification, the triplet energy is the energy of the lowest excited triplet state, and is expressed in eV. The larger the value, the higher the energy. When converted to wavelength, the higher the energy, the shorter the wavelength. In this specification, the energy gap refers to the energy gap between the energy level of the highest occupied molecular orbital (HOMO) and the energy level of the lowest unoccupied molecular orbital (LUMO), and is also called a band gap. The energy level of the HOMO and the energy level of the LUMO may be referred to as "HOMO" or "HOMO level", "LUMO" or "LUMO level", respectively.

[0014] Hereinafter, an embodiment of the present invention will be described in more detail with reference to FIGS. Fig. 1 is a schematic cross-sectional view of an organic light-emitting device according to this embodiment. The organic light-emitting device in Fig. 1 has an anode 2, a hole transport layer 3, a first light-emitting layer 4a, a second light-emitting layer 4b, an electron transport layer 5, and a cathode 6 disposed in this order on an insulating layer 1.

[0015] In this embodiment, the light-emitting layer refers to a layer that emits light among the organic compound layers provided between the electrodes. Among the compounds contained in the light-emitting layer, the compound with the largest mass ratio may be called a host, and the compound that contributes to the main emission may be called a dopant or a guest. More specifically, the host refers to a material contained in the light-emitting layer whose content in the light-emitting layer exceeds 50 mass%, and the dopant refers to a material contained in the light-emitting layer whose content in the light-emitting layer is less than 50 mass%. The concentration of the dopant in the light-emitting layer is preferably 0.1 mass% or more and 40 mass% or less, and further, it is desirably 30 mass% or less in order to suppress concentration quenching. In the present invention, the first organic compound and the second organic compound are hosts, and the first metal complex and the third metal complex are dopants.

[0016] Among the compounds contained in the light-emitting layer, the assist material is a compound that has a mass ratio smaller than that of the host among the compounds constituting the light-emitting layer and assists the light emission of the guest. The assist material is also called a second host. Alternatively, if the guest is the first compound, the assist can be called the second compound. The second metal complex in the present invention is an assist material.

[0017] 2 is an energy diagram showing a schematic representation of the energy levels around the light-emitting layer constituting the organic light-emitting device of the present invention, in which HOMOD1, LUMOD1, HOMOD2, LUMOD2, HOMOD3, LUMOD3, HOMOH1, LUMOH1, HOMOH2, and LUMOH2 represent the HOMO level and LUMO level of the first metal complex, the HOMO level and LUMO level of the second metal complex, the HOMO level and LUMO level of the third metal complex, the HOMO level and LUMO level of the first host, and the HOMO level and LUMO level of the second host, respectively.

[0018] Fig. 3 is a diagram showing the triplet energy level relationship of the metal complexes contained in the light-emitting layer constituting the organic light-emitting device according to one embodiment of the present invention. The vertical axis of Fig. 3 represents the energy level, and the upward direction of the figure represents higher energy. In the figure, D1, D2, and D3 represent the first metal complex, the second metal complex, and the third metal complex, respectively, and T1D1, T1D2, and T1D3 represent the triplet energy levels of the first metal complex, the second metal complex, and the third metal complex, respectively.

[0019] As shown in FIG. 3, in the present invention, the relationships of the following formulas [a] to [c] hold among the first metal complex and the second metal complex contained in the first emitting layer 4a, and the third metal complex contained in the second emitting layer 4b.

[0020] T1D2>T1D1 [a] T1D3 ≥ T1D2 [b] T1D2-T1D1>T1D3-T1D2 [c]

[0021] In the present invention, the triplet energy of the metal complex may be an actual measured value or a value calculated by molecular orbital calculation. In this specification, the calculation method for the metal complex using the molecular orbital calculation method is the density functional theory (DFT), which is widely used at present. The functional used is B3PW91, and the basis set used is LANL2DZ.In particular, the free-flowing spectroscopy is based on Gaussian09(Gaussian 09,Revision D.01, MJ Frisch, GWTrucks, HBSchlegel, GEScuseria, MARobb, JRCheeseman, G. Scalmani, V. Barone, B. Mennucci, GPetersson, H. Nakatsuji, M. Caricato, X. Li, HHPratchian, AFIzmaylov, J. Bloino, G. Zheng, JLSonne nberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nak ai,T.Vreven,JAMontgomery,Jr.,JEPeralta,F.Ogliaro,M.Bearpark,JJHeyd,E.Brothers,KNKudin,VNStar overov, T. Keith, R. Kobayashi, J. Normand, K. Raghavachari, A. Rendell, JCBurant, SSIyengar, J. Thomas, M. Cossi, N. Rega, JMMillam, M. Klene, JEKnox, JBCross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, REStra p DJFox,Gaussian,Inc.,Wallingford CT,2013.) Then there is a lot of information The snow-white snowflakes are based on a snowstorm.

[0022] An organic light-emitting device according to one embodiment of the present invention has an element configuration having two or more light-emitting layers, and has the following configuration.

[0023] <1> Two light-emitting layers are stacked, each of which contains a metal complex that is a phosphorescent material that emits different emission colors, and one of the light-emitting layers contains a metal complex that is an assist material for triplet energy transfer. In an organic light-emitting device according to one embodiment of the present invention, two light-emitting layers are laminated, and each light-emitting layer has a phosphorescent metal complex. Each light-emitting layer exhibits a different emission wavelength. Phosphorescence is light emission derived from triplet energy. That is, the triplet energy generated in each light-emitting layer is different, and there is a relationship in magnitude. Therefore, energy transfer occurs from a light-emitting layer having a higher triplet energy to a light-emitting layer having a lower triplet energy. The first light-emitting layer and the second light-emitting layer may be laminated in a direction from the first electrode to the second electrode, and the first light-emitting layer may be disposed closer to the first electrode than the second light-emitting layer, or the first light-emitting layer may be disposed closer to the second electrode than the second light-emitting layer.

[0024] Here, the present inventors have found that the durability of the device can be improved by quickly transferring the excess triplet energy generated in the light-emitting layer having a higher triplet energy to the adjacent light-emitting layer having a lower triplet energy. More specifically, a metal complex having a triplet energy that is an intermediate value between the metal complexes contained in each light-emitting layer is included in the light-emitting layer to which the energy is transferred. By adopting such a configuration, it is possible to promote the energy transfer from the high-energy light-emitting layer to the adjacent low-energy light-emitting layer. In other words, it can be said that the device contains an assist material for triplet energy transfer.

[0025] In general, phosphorescent light-emitting devices are prone to triplet-triplet annihilation (TTA) due to the long emission life of the phosphorescent light-emitting material. TTA occurs when excess triplet excitons that do not transition to the emission process collide with each other. The high-order excited state generated by TTA has high energy and is therefore likely to cause material degradation and reduce the durability of the device.

[0026] The high energy generated by TTA is proportional to the triplet energy of the light-emitting layer. Therefore, in light-emitting layers with higher triplet energy, the TTA generates a higher excited state with higher energy, which increases the risk of material degradation. Therefore, it is believed that material degradation can be suppressed by reducing the TTA in the light-emitting layer with higher energy and increasing the TTA in the light-emitting layer with lower energy instead.

[0027] Here, in the present invention, the relationship between the above formulas [a] and [b] is established. That is, in order to facilitate energy transfer from the second light-emitting layer containing a third metal complex having a higher triplet energy to the first light-emitting layer containing a first metal complex having a lower triplet energy among two adjacent light-emitting layers, the first light-emitting layer contains a second metal complex having an intermediate energy level for promoting triplet energy transfer. This can reduce TTA that may occur in the second light-emitting layer containing a third metal complex having a higher triplet energy, thereby suppressing material deterioration. As a result, an organic light-emitting device with excellent durability can be obtained.

[0028] <2> The triplet energy of the assisting material that promotes energy transfer has a value closer to the triplet energy of the light-emitting material that is the source of the energy transfer than to the light-emitting material that is the destination of the energy transfer. As described above, the present invention provides an organic light-emitting device having a stacked light-emitting layer that can improve driving durability by promoting triplet energy transfer with an assist material. In general, the energy transfer of triplet excitons is believed to occur via Dexter energy transfer. As shown in the following formula [A], the rate constant of Dexter energy transfer is proportional to the overlap between the emission spectrum of the energy transfer source (donor) and the absorption spectrum of the energy transfer destination (acceptor). It is also exponentially inversely proportional to the intermolecular distance between the donor and acceptor.

[0029]

number

[0030] Here, the present inventors have found that the Dexter energy transfer between the first light-emitting layer and the second light-emitting layer can be promoted by satisfying the relationship of the above formula [c]. That is, in the stacked light-emitting layer configuration according to the present invention, the triplet energy of the second metal complex, which is an assist material for promoting energy transfer, has a value closer to the third metal complex, which is the source of energy transfer, than to the first metal complex, which is the destination of energy transfer, thereby promoting energy transfer.

[0031] In the present invention, the second metal complex, which is an assist material, is contained in the first light-emitting layer. Meanwhile, the third metal complex, which is the source of energy transfer, is contained in the second light-emitting layer. Therefore, the opportunity for contact between the donor (third metal complex) and the acceptor (second metal complex) is limited to the interface between the first light-emitting layer and the second light-emitting layer.

[0032] According to the above formula [A], in Dexter energy transfer, the shorter the intermolecular distance between the donor (third metal complex) and the acceptor (second metal complex), the easier the energy transfer is, so it is preferable that the distance between the donor (third metal complex) and the acceptor (second metal complex) is short. Therefore, the present inventors have found that by reducing the difference in triplet energy between the donor (third metal complex) and the acceptor (second metal complex), compatibility is increased and the intermolecular distance is shortened.

[0033] This is presumably because the two metal complexes have similar molecular structure characteristics, and because they are both metal complexes, they have similar energies and their dipole moments tend to align, making it easier for the molecules to approach each other.

[0034] For example, when a second light-emitting layer is laminated after the formation of a first light-emitting layer containing an acceptor (second metal complex), the donor (third metal complex) tends to gather on the acceptor (second metal complex), which is a molecule with a closer energy level and is more likely to be energetically stable. As a result, the intermolecular distance between the donor (third metal complex) and the acceptor (second metal complex) becomes shorter. In addition, since the difference in triplet energy between the donor (third metal complex) and the acceptor (second metal complex) is small, the overlap between the emission spectrum (phosphorescence) of the donor and the absorption spectrum of the acceptor becomes sufficiently large.

[0035] From the above, when the relationship in the above formula [c] is satisfied, the intermolecular distance between the donor (third metal complex) and the acceptor (second metal complex) is shortened and the overlap between the emission spectrum of the donor and the absorption spectrum of the acceptor is sufficiently large, promoting Dexter energy transfer.

[0036] After the energy transfer from the third metal complex to the second metal complex, the energy transfer occurs from the second metal complex to the first metal complex in the first light-emitting layer, and the first metal complex starts emitting light. In this way, by forming a laminated light-emitting layer that continuously undergoes the triplet energy transfer process, it is expected that the accumulation of excess triplet excitons that do not reach the light-emitting process can be reduced. In other words, the diffusion of triplet excitons in the laminated light-emitting layer is likely to occur. That is, the TTA itself, in which excess triplet excitons collide with each other, can be reduced, and the organic light-emitting device can have improved durability, which is also a feature of the present invention.

[0037] In addition to the above-mentioned features (1) and (2), the organic light-emitting device according to one embodiment of the present invention preferably has the following structure. <3> The concentration of the second metal complex in the first emitting layer is higher than the concentration of the third metal complex in the second emitting layer. <4> The concentration of the second metal complex in the first emitting layer is higher than the concentration of the first metal complex. <5> The second metal complex and the third metal complex have at least one identical ligand. <6> The second metal complex and the third metal complex have a HOMO level difference of within 0.2 eV and a LUMO level difference of within 0.2 eV. <7> The first metal complex is a red phosphorescent material, and the third metal complex is a green phosphorescent material. <8> The second light-emitting layer contains a second organic compound (assist material) that is not a metal complex. <9> The first electrode is an anode, the second electrode is a cathode, the first light-emitting layer is on the anode side, and the second light-emitting layer is on the cathode side. <10> The concentration of the third metal complex in the second emitting layer is higher than the concentration of the first metal complex in the first emitting layer. <11> The second metal complex and the third metal complex are the same compound. <12> The first organic compound (the host of the first emitting layer) and the second organic compound (the host of the second emitting layer) are the same compound. These will be explained below.

[0038] <3> The concentration of the second metal complex is higher than the concentration of the third metal complex. As described above, the third metal complex (donor) contained in the second light-emitting layer and the second metal complex (acceptor) contained in the first light-emitting layer come into contact only at the interface between the first light-emitting layer and the second light-emitting layer. Here, by increasing the concentration of the second metal complex (acceptor) compared to the third metal complex (donor), it is possible to promote the energy transfer between the first light-emitting layer and the second light-emitting layer. The second metal complex that has accepted the energy must then transfer the energy to the first metal complex. Here, when the third metal complex (donor) has a higher concentration, it accepts a lot of triplet energy from the third metal complex (donor), so the second metal complex (acceptor) has a lot of triplet excitons before transferring energy to the first metal complex, which makes it easier to cause TTA. If TTA occurs in the second metal complex, it is not preferable because it is not possible to transfer energy to the first metal complex.

[0039] Therefore, the concentration of the second metal complex is preferably higher than the concentration of the third metal complex, and it is preferable that the relationship of the following formula [d] holds. C1D2 ≧ C1D3 [d] C1D2 and C1D3 respectively represent the concentration of the second metal complex in the first emitting layer and the concentration of the third metal complex in the second emitting layer.

[0040] <4> The concentration of the second metal complex in the first emitting layer is higher than the concentration of the first metal complex. A feature of the organic light-emitting device of the present invention is that triplet energy transfer is continuous. Specifically, energy transfer occurs from the third metal complex to the second metal complex, and then from the second metal complex to the first metal complex. In this way, by forming a stacked light-emitting layer that continuously undergoes triplet energy transfer processes, it is expected that the accumulation of excess triplet excitons that do not reach the light-emitting process can be reduced.

[0041] Here, the concentration of the second metal complex is preferably higher than that of the first metal complex, since when the concentration of the first metal complex is high, the triplet energy transfer from the third metal complex is transferred to the first metal complex, not to the second metal complex, making it difficult to undergo the diffusion of excitons through the above-mentioned continuous energy transfer process.

[0042] Therefore, the concentration of the second metal complex is preferably higher than the concentration of the first metal complex, and it is preferable that the relationship of the following formula [e] holds. C1D2 ≧ C1D1 [e] C1D1 and C1D2 respectively represent the concentrations of the first metal complex and the second metal complex in the first emitting layer.

[0043] <5> The second metal complex and the third metal complex have at least one identical ligand. As described above, the compatibility between the third metal complex (donor) contained in the second emitting layer and the second metal complex (acceptor) contained in the first emitting layer is improved, thereby promoting energy transfer between the first emitting layer and the second emitting layer. Here, as a means for enhancing the compatibility between the third metal complex (donor) and the second metal complex (acceptor), it is preferable that they have the same partial structure in the molecule. Specifically, it is preferable that at least one of the ligands forming the metal complex has the same structure. This makes it easier for the ligands having the same structure to approach each other, and as a result, it is expected that the intermolecular distance between the third metal complex (donor) and the second metal complex (acceptor) will be shortened. For example, it is preferable that the second metal complex and the third metal complex are metal complexes that simultaneously have any of the following molecular structures. The following example is an example using a phenylpyridine skeleton, which is a representative skeleton of a bidentate ligand, and a pyridylpyridine skeleton, a phenylpyrimidine skeleton, and a phenylpyrazine skeleton, and a ligand having a condensed ring structure, a monodentate ligand, a tridentate ligand, or a tetradentate ligand can be used. In addition, in the following structural formula. The two bonds between the ligand and the Ir metal are both represented by dotted lines, but one is a covalent bond and the other is a coordinate bond.

[0044] [ka]

[0045] <6> The second metal complex and the third metal complex have a HOMO level difference of within 0.2 eV and a LUMO level difference of within 0.2 eV. In Fig. 2, the light-emitting layer 4a contains a host (first organic compound), an assist material (second metal complex), and a dopant (first metal complex). The light-emitting layer 4b contains a host (second organic compound) and a dopant (third metal complex). For this reason, it is considered that the dopant or the assist material becomes a trap level for the carriers (holes and electrons) moving in the light-emitting layer.

[0046] Here, it is preferable that the HOMO level difference between the second metal complex and the third metal complex is within 0.2 eV, and the LUMO level difference is within 0.2 eV. This is because such a relationship promotes carrier movement between the first light-emitting layer and the second light-emitting layer. That is, the second metal complex, which is the carrier trap level of the first light-emitting layer, and the third metal complex, which is the carrier trap level of the second light-emitting layer, have similar HOMO and LUMO levels, thereby promoting carrier movement. Here, if there is an extreme difference in the HOMO level or LUMO level between the second metal complex and the third metal complex, carriers are accumulated at the interface between the first light-emitting layer and the second light-emitting layer, and the recombination region is concentrated, which is disadvantageous to the luminous efficiency and the durability of the device. By promoting carrier movement, unnecessary charge accumulation is eliminated, and exciton concentration is also eliminated, so that TTA generation can be reduced and durability characteristics can be improved.

[0047] Therefore, it is preferable that the relationship between the following formulas [f] and [g] holds. |LUMOD3-LUMOD2|≦0.2 eV [f] |HOMOD3-HOMOD2|≦0.2 eV [g] In [f] and [g], HOMOD2, LUMOD2, HOMOD3, and LUMOD3 represent the HOMO level and LUMO level of the second metal complex and the HOMO level and LUMO level of the third metal complex, respectively. In addition, the relationship between the above formulas [f] and [g] is also advantageous in that the carrier balance between the first emitting layer and the second emitting layer can be easily adjusted.

[0048] <7> The first metal complex is a red phosphorescent material, and the third metal complex is a green phosphorescent material. From the viewpoint of maximizing the luminous efficiency of each of the first emitting layer and the second emitting layer while satisfying the relationship of formulas [a] and [b], it is preferred that the first metal complex is a red phosphorescent light-emitting material and the third metal complex is a green phosphorescent light-emitting material. In the organic light-emitting device according to one embodiment of the present invention, the recombination region is slightly biased toward the second emitting layer, thereby providing a stacked structure that enables efficient energy transfer to the first emitting layer, and it becomes easier to realize light emission with a good balance between green and red emission.

[0049] In this specification, the blue light-emitting material refers to a light-emitting material whose emission spectrum has a maximum peak wavelength of 430 nm to 480 nm. The green light-emitting material refers to a light-emitting material whose emission spectrum has a maximum peak wavelength of 500 nm to 570 nm. The red light-emitting material refers to a light-emitting material whose emission spectrum has a maximum peak wavelength of 580 nm to 680 nm. The emission spectrum is preferably measured using a dilute toluene solution or the like to reduce the influence of other compounds and crystalline states.

[0050] Yellow emission means that the main part of the emission spectrum is in the range of 565 nm to 590 nm. For example, yellow emission can be obtained by mixing green emission and red emission. Cyan emission means that the main part of the emission spectrum is in the range of 485 nm to 500 nm. For example, cyan emission can be obtained by mixing blue emission and green emission.

[0051] <8> The second light-emitting layer contains an assist material that is not a metal complex. As described above, in the organic light-emitting element according to one embodiment of the present invention, the recombination region is biased slightly toward the second light-emitting layer, which enables efficient energy transfer to the first light-emitting layer. As a result, well-balanced light emission can be obtained from each light-emitting layer.

[0052] Here, the second emitting layer preferably contains a second organic compound that is not a metal complex as an assist material. If the assist material of the second emitting layer is also a phosphorescent metal complex, due to the above-mentioned phenomenon, the energy transfer between the third metal complex and the assist material of the second emitting layer, that is, the energy transfer in the second emitting layer is promoted, and the energy transfer to the first emitting layer is inhibited, so this is not preferable. The assist material of the second emitting layer is preferably not a metal complex and is a material that injects carriers, either holes or electrons, into the emitting layer and adjusts the recombination region slightly toward the center of the second emitting layer. Specifically, a material having any one of a triarylamine skeleton, a carbazole skeleton, an azine ring, and a xanthone skeleton is preferable. These materials are preferable because they have excellent electron donating and electron withdrawing properties, and therefore the HOMO level and LUMO level can be easily adjusted, and the injection of carriers from the surrounding layers can be promoted.

[0053] <9> The first light-emitting layer is on the anode side, and the second light-emitting layer is on the cathode side. As shown in Fig. 2, the light-emitting layer 4a on the anode side satisfies the above-mentioned condition <7> and preferably contains a host (first organic compound), an assist material (second metal complex), and a dopant (first metal complex). The light-emitting layer 4b on the cathode side preferably contains a host (second organic compound) and a dopant (third metal complex). In this case, the first metal complex, which is a red phosphorescent light-emitting material, traps holes, and the third metal complex, which is a green phosphorescent light-emitting material, traps electrons, resulting in a layered structure with the best carrier balance.

[0054] <10> The concentration of the third metal complex in the second emitting layer is higher than the concentration of the first metal complex in the first emitting layer. In addition to the above-mentioned condition <9>, the concentration of the third metal complex is preferably higher than that of the first metal complex. The first metal complex is a red phosphorescent light-emitting material, and therefore has a small band gap, so that it is easy to have a high carrier trapping property. In this embodiment, the hole trapping property is high. Therefore, when the first metal complex, which is a red phosphorescent light-emitting material, is high in concentration, the hole concentration in the first light-emitting layer is localized, which is not preferable. Therefore, the first metal complex is made low in concentration, and the role of hole transport in the first light-emitting layer is carried out by the second metal complex, which is an assist material, to adjust the carrier balance. On the other hand, for the second light-emitting layer, the third metal complex is responsible for electron transport, and as described above, smooth transfer of carriers with the second metal complex can be expected. Therefore, the concentration of the third metal complex is preferably higher than that of the first metal complex, and it is preferable that the relationship of the following formula [h] is satisfied. C1D3>C1D1 [h] C1D1 and C1D3 respectively represent the concentration of the first metal complex in the first emitting layer and the concentration of the third metal complex in the second emitting layer.

[0055] <11> The second metal complex and the third metal complex are the same compound. As described above, in the embodiment of the present invention, it is preferable that carrier movement and energy movement between the first light-emitting layer and the second light-emitting layer are good. Therefore, it is preferable that the second metal complex and the third metal complex are the same compound. In this case, it is possible to promote carrier movement and energy movement between the first light-emitting layer and the second light-emitting layer in particular.

[0056] <12> The first organic compound and the second organic compound are the same compound. As described above, in the embodiment of the present invention, it is preferable that the carrier movement and energy movement between the first light-emitting layer and the second light-emitting layer are good. Therefore, it is preferable that the host (first organic compound) of the first light-emitting layer and the host (second organic compound) of the second light-emitting layer are the same compound. In this case, it is possible to particularly promote the carrier movement and energy movement between the first light-emitting layer and the second light-emitting layer.

[0057] [First to third metal complexes] Next, the first to third metal complexes used in one embodiment of the organic light-emitting device of the present invention will be specifically described. The first to third metal complexes used in one embodiment of the present invention are preferably compounds represented by the following general formula [I]. Ir(L) q (L') r (L'') s [I] In the general formula [1], L, L', and L'' each represent a different bidentate ligand. q is an integer of 1 to 3, and r and s are each an integer of 0 to 2, provided that q+r+s=3. When r is 2, multiple L's may be the same or different. When s is 2, multiple L''s may be the same or different. Substructure Ir(L) q are structures represented by the following general formulas [Ir-1] to [Ir-16].

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[0060] In the general formulae [Ir-1] to [Ir-16], Ar1 and Ar2 are each independently a deuterium atom, a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heterocyclic group, a substituted or unsubstituted silyl group, or a cyano group. Specifically, Ar1 to Ar2 are preferably a deuterium atom, a fluorine atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, an aryl group having 6 to 10 carbon atoms, a silyl group substituted with an alkyl group, or a cyano group, and more preferably a methyl group, a tert-butyl group, or a phenyl group. p1 and p2 each independently represent an integer of 0 to 4.

[0061] In the general formulas [Ir-5] to [Ir-16], X is selected from an oxygen atom, a sulfur atom, C(R1)(R2), or NR3. R1 to R3 are each independently selected from a hydrogen atom, a deuterium atom, a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted amino group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heterocyclic group, a substituted or unsubstituted silyl group, and a cyano group. R1 and R2 may be bonded to each other to form a ring. Specifically, R1 to R3 are preferably an alkyl group having 1 to 3 carbon atoms or a phenyl group, and more preferably a methyl group.

[0062] As described above, the metal complex used in the present invention is a dopant or assist material, but it is particularly preferable that the skeleton is one that facilitates carrier and energy transfer. Therefore, by using a highly planar compound having a fused ring structure in the ligand, the intermolecular distance is shortened. This is because the highly planar partial structures are easily brought close to each other. Therefore, energy transfer by the Dexter mechanism is easily caused, and an organic light-emitting element having driving durability and highly efficient light-emitting characteristics can be provided. Specifically, metal complexes represented by the general formulas [Ir-5] to [Ir-16] are preferably used.

[0063] More specifically, the first to third metal complexes preferably have a triphenylene skeleton, a phenanthrene skeleton, a fluorene skeleton, a benzofluorene skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, a benzoisoquinoline skeleton, or a naphthoisoquinoline skeleton as a ligand. By using a metal complex having at least one of these skeletons as a ligand, the organic compound according to this embodiment can provide an organic light-emitting element with higher luminous efficiency.

[0064] Specific examples of the first to third metal complexes according to this embodiment are shown below. However, the present invention is not limited to these. In the following structural formulas, the two bonds between the ligand and the iridium atom may be represented by solid lines, in which case one bond may be a covalent bond and the other bond may be a coordinate bond. On the other hand, when solid and dotted lines are mixed, the solid line may be a covalent bond and the dotted line may be a coordinate bond. Among the following specific examples, JJ1 to JJ30 are specific examples of general formulas [Ir-1] to [Ir-4], and the others are specific examples of general formulas [Ir-5] to [Ir-16].

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[0082] Of the above organometallic complexes, the exemplified compounds belonging to groups AA and BB are compounds having at least a phenanthrene skeleton in the ligand of the Ir complex, and are compounds that are particularly excellent in stability. Among the above organometallic complexes, the exemplary compounds belonging to the CC group are compounds having at least a triphenylene skeleton in the ligand of the Ir complex, and are compounds that are particularly excellent in stability. Among the above-mentioned organometallic complexes, the exemplary compounds belonging to the DD group are compounds having at least a dibenzofuran skeleton or a dibenzothiophene skeleton in the ligand of the Ir complex. These compounds contain oxygen atoms and sulfur atoms in the condensed ring, and therefore can enhance the charge transportability due to the abundant unshared electron pairs of these atoms. Therefore, it is particularly easy to adjust the carrier balance of these compounds.

[0083] Among the above-mentioned organometallic complexes, the exemplary compounds belonging to the EE group, FF group, and GG group are compounds having at least a benzofluorene skeleton in the ligand of the Ir complex. These compounds further have a substituent at the 9-position of the fluorene. Therefore, since the substituent is in the direction perpendicular to the in-plane direction of the fluorene ring, it is possible to particularly prevent the overlapping of the condensed rings. Therefore, these compounds have particularly excellent sublimation properties.

[0084] Among the above-mentioned organometallic complexes, the exemplary compounds belonging to the HH group are compounds having at least a benzoisoquinoline skeleton in the ligand of the Ir complex. These compounds contain nitrogen atoms in the condensed ring, and therefore can enhance charge transportability due to the unshared electron pairs and high electronegativity of these atoms. Therefore, these compounds are particularly easy to adjust the carrier balance.

[0085] Among the above-mentioned organometallic complexes, the exemplary compounds belonging to group II are compounds having at least naphthoisoquinoline skeleton in the ligand of Ir complex. These compounds contain nitrogen atoms in the condensed ring, and therefore can enhance charge transportability due to the unshared electron pair and high electronegativity of these atoms. Therefore, it is a compound that is particularly easy to adjust the carrier balance.

[0086] In this embodiment, examples of luminescent materials mainly involved in the luminescence function include, in addition to the organometallic complexes represented by the above general formulas [Ir-1] to [Ir-16], condensed ring compounds (e.g., fluorene derivatives, naphthalene derivatives, pyrene derivatives, perylene derivatives, tetracene derivatives, anthracene derivatives, rubrene, etc.), quinacridone derivatives, coumarin derivatives, stilbene derivatives, organoaluminum complexes such as tris(8-quinolinolato)aluminum, iridium complexes, platinum complexes, rhenium complexes, copper complexes, europium complexes, ruthenium complexes, and polymer derivatives such as poly(phenylenevinylene) derivatives, poly(fluorene) derivatives, and poly(phenylene) derivatives.

[0087] Specific examples of compounds used as luminescent materials are shown below, but are of course not limited to these. Among the specific examples below, BD9, GD10 to GD19, and RD3 to RD11 are metal complexes, and can also be used as the first to third metal complexes according to this embodiment. Compounds other than metal complexes can be used as luminescent materials in combination with the first and third metal complexes.

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[0091] [First and second organic compounds] In the embodiment according to the present invention, carrier transfer and energy transfer between the first emitting layer and the second emitting layer are excellent, and therefore the first and second organic compounds used as the first and second hosts according to the present invention are preferably compounds having excellent carrier transport ability. Therefore, the first and second hosts are preferably materials having any one of a dibenzothiophene skeleton, a dibenzofuran skeleton, a triphenylene skeleton, and a phenanthrene skeleton. These materials have highly planar skeletons and can promote carrier movement between light-emitting layers. Therefore, by using these materials, an organic light-emitting element having excellent light-emitting efficiency can be obtained. When these host materials are combined with the element configuration according to the present invention, a good carrier balance can be achieved, and an organic light-emitting element having superior element durability can be provided.

[0092] [Third organic compound] In the embodiment according to the present invention, carrier transfer and energy transfer between the first emitting layer and the second emitting layer are excellent, and therefore, the second emitting layer according to the present invention preferably contains a third organic compound as an assist material, and the assist material is preferably a compound that can easily adjust the carrier balance. Specifically, a material having any one of a triarylamine skeleton, a carbazole skeleton, an azine skeleton, and a xanthone skeleton is preferable. These materials have excellent electron donating and electron withdrawing properties, so that it is easy to adjust the HOMO level and the LUMO level, and it is possible to promote the injection of carriers from the surrounding layers. Therefore, by using these materials, an organic light-emitting element having excellent luminous efficiency can be obtained. When these assist materials are combined with the element configuration according to the present invention, a good carrier balance can be achieved, and an organic light-emitting element having superior element durability can be provided.

[0093] Examples of the host material or assist material contained in the light-emitting layer include, in addition to the materials described above in [First and Second Organic Compounds] and [Third Organic Compound], aromatic hydrocarbon compounds or derivatives thereof, carbazole derivatives, dibenzofuran derivatives, dibenzothiophene derivatives, organoaluminum complexes such as tris(8-quinolinolato)aluminum, and organoberyllium complexes.

[0094] In particular, the assist material is preferably a material having a carbazole skeleton, a material having an azine ring, or a material having a xanthone skeleton. These materials have high electron donating and withdrawing properties, and therefore the HOMO level and LUMO level can be easily adjusted. Therefore, when these assist materials are combined with the metal complex according to the present invention, a good carrier balance can be achieved. Specific examples of compounds that can be used as the host or assist material in the light-emitting layer are shown below, but the present invention is not limited to these. Among the specific examples below, materials having a carbazole skeleton are EM32 to EM38, materials having an azine ring are EM35 to EM40, and materials having a xanthone skeleton are EM28 and EM30.

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[0097] [Other compounds] In the organic light-emitting device of this embodiment, a hole injection layer, a hole transport layer, an electron blocking layer, an electron injection layer, an electron transport layer, and a hole blocking layer may be disposed between the light-emitting layer and the electrode, as necessary. As the hole injection transport material suitably used for the hole injection layer or the hole transport layer, a material having a high hole mobility is preferred so as to facilitate the injection of holes from the anode and transport the injected holes to the light emitting layer. In addition, a material having a high glass transition temperature is preferred so as to suppress deterioration of the film quality such as crystallization in the organic light emitting device. Examples of low molecular weight and polymeric materials having hole injection and transport performance include triarylamine derivatives, arylcarbazole derivatives, phenylenediamine derivatives, stilbene derivatives, phthalocyanine derivatives, porphyrin derivatives, poly(vinylcarbazole), poly(thiophene), and other conductive polymers. Furthermore, the above-mentioned hole injection transport material is also suitably used for the electron blocking layer. Specific examples of compounds usable as the hole injection transport material are shown below, but the invention is not limited to these.

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[0099] The electron transporting material preferably used in the electron injection layer or electron transport layer can be arbitrarily selected from those capable of transporting electrons injected from the cathode to the light emitting layer, and is selected in consideration of the balance with the hole mobility of the hole transporting material. Examples of materials having electron transporting properties include oxadiazole derivatives, oxazole derivatives, pyrazine derivatives, triazole derivatives, triazine derivatives, quinoline derivatives, quinoxaline derivatives, phenanthroline derivatives, organic aluminum complexes, and condensed ring compounds (e.g., fluorene derivatives, naphthalene derivatives, chrysene derivatives, anthracene derivatives, etc.). Furthermore, the above electron transporting materials are also preferably used in the hole blocking layer. Specific examples of compounds usable as the electron transporting material are shown below, but the present invention is not limited to these.

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[0101] [Configuration of Organic Light-Emitting Element] Hereinafter, the constituent members of the organic light-emitting device of this embodiment other than the organic compound layer will be described. The organic light-emitting element is provided by forming an insulating layer, a first electrode, an organic compound layer, and a second electrode on a substrate. A protective layer, a color filter, a microlens, etc. may be provided on the second electrode. When a color filter is provided, a planarizing layer may be provided between the protective layer. The planarizing layer may be made of acrylic resin, etc. The same applies when a planarizing layer is provided between the color filter and the microlens.

[0102] <substrate> Examples of the substrate include quartz, glass, silicon wafer, resin, and metal. In addition, a switching element such as a transistor and wiring may be provided on the substrate, and an insulating layer may be provided thereon. As the insulating layer, any material can be used as long as it can form a contact hole so that wiring can be formed between the first electrode and the insulating layer, and insulation from wiring that is not connected can be ensured. For example, resin such as polyimide, silicon oxide, silicon nitride, etc. can be used.

[0103] <electrode> A pair of electrodes can be used. The pair of electrodes may be an anode and a cathode. When an electric field is applied in the direction in which the organic light-emitting element emits light, the electrode with a higher potential is the anode, and the other is the cathode. It can also be said that the electrode that supplies holes to the light-emitting layer is the anode, and the electrode that supplies electrons is the cathode.

[0104] The material constituting the anode should have as large a work function as possible. For example, metals such as gold, platinum, silver, copper, nickel, palladium, cobalt, selenium, vanadium, tungsten, etc., mixtures containing these metals, alloys combining these metals, metal oxides such as tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO), and indium zinc oxide can be used. Conductive polymers such as polyaniline, polypyrrole, and polythiophene can also be used. These electrode materials may be used alone or in combination of two or more kinds. The anode may be composed of one layer or multiple layers.

[0105] When used as a reflective electrode, for example, chromium, aluminum, silver, titanium, tungsten, molybdenum, or alloys or laminates thereof can be used. The above materials can also function as a reflective film without serving as an electrode. When used as a transparent electrode, a transparent conductive layer of oxide such as indium tin oxide (ITO) or indium zinc oxide can be used, but is not limited to these. Photolithography technology can be used to form the electrode.

[0106] On the other hand, the material for the cathode should have a small work function. Examples of the material include alkali metals such as lithium, alkaline earth metals such as calcium, aluminum, titanium, manganese, silver, lead, chromium, and other metals or mixtures containing these metals. Alternatively, alloys combining these metals can be used. For example, magnesium-silver, aluminum-lithium, aluminum-magnesium, silver-copper, zinc-silver, and the like can be used. Metal oxides such as indium tin oxide (ITO) can also be used. These electrode materials may be used alone or in combination of two or more types. The cathode may have a single layer structure or a multi-layer structure. Among these, it is preferable to use silver, and it is even more preferable to use a silver alloy to reduce the aggregation of silver. As long as the aggregation of silver can be reduced, the ratio of the alloy is not important. For example, the ratio of silver to other metals may be 1:1, 3:1, and the like.

[0107] The cathode may be a top-emission element using an oxide conductive layer such as ITO, or a bottom-emission element using a reflective electrode such as aluminum (Al), and is not particularly limited. The method for forming the cathode is not particularly limited, but it is more preferable to use a direct current or alternating current sputtering method, etc., since the film coverage is good and the resistance can be easily reduced.

[0108] <Organic compound layer> The organic compound layer according to this embodiment is disposed between the first electrode and the second electrode, and includes the stacked light-emitting layer consisting of the first light-emitting layer and the second light-emitting layer described above, and, if necessary, a hole injection layer, a hole transport layer, an electron blocking layer, an electron injection layer, an electron transport layer, and a hole blocking layer. The organic compound layer is mainly composed of an organic compound, but may also contain inorganic atoms and inorganic compounds. For example, it may contain copper, lithium, magnesium, aluminum, iridium, platinum, molybdenum, zinc, etc.

[0109] The organic compound layers (hole injection layer, hole transport layer, electron blocking layer, light emitting layer, hole blocking layer, electron transport layer, electron injection layer, etc.) can be formed by a dry process such as vacuum deposition, ionization deposition, sputtering, plasma, etc. Also, instead of the dry process, a wet process can be used in which a layer is formed by dissolving the compound in an appropriate solvent and applying a known coating method (e.g., spin coating, dipping, casting, LB method, inkjet method, etc.). Here, when the layer is formed by a vacuum deposition method or a solution coating method, crystallization is unlikely to occur and the layer has excellent stability over time. When the layer is formed by a coating method, the layer can be formed by combining with a suitable binder resin.

[0110] Examples of the binder resin include, but are not limited to, polyvinylcarbazole resin, polycarbonate resin, polyester resin, ABS resin, acrylic resin, polyimide resin, phenol resin, epoxy resin, silicone resin, and urea resin. These binder resins may be used alone or in combination as homopolymers or copolymers, and may further include known additives such as plasticizers, antioxidants, and ultraviolet absorbers, if necessary.

[0111] <Protective layer> A protective layer may be provided on the cathode. For example, by bonding glass provided with a moisture absorbent on the cathode, the intrusion of water and the like into the organic compound layer can be reduced, and the occurrence of display defects can be reduced. In another embodiment, a passivation film such as silicon nitride may be provided on the cathode to reduce the intrusion of water and the like into the organic compound layer. For example, after forming the cathode, the cathode may be transported to another chamber without breaking the vacuum, and a silicon nitride film having a thickness of 2 μm may be formed by the CVD method to form a protective layer. A protective layer may be provided using the atomic deposition method (ALD method) after the film formation by the CVD method. The material of the film by the ALD method is not limited, and may be silicon nitride, silicon oxide, aluminum oxide, etc. Silicon nitride may be further formed by the CVD method on the film formed by the ALD method. The film by the ALD method may have a smaller thickness than the film formed by the CVD method. Specifically, it may be 50% or less, or even 10% or less.

[0112] Color Filters A color filter may be provided on the protective layer. For example, a color filter taking into consideration the size of the organic light-emitting element may be provided on another substrate and then bonded to the substrate on which the organic light-emitting element is provided, or a color filter may be patterned on the protective layer described above using a photolithography technique. The color filter may be made of a polymer.

[0113] <Planarization layer> A planarization layer may be provided between the color filter and the protective layer. The planarization layer is provided for the purpose of reducing unevenness of the layer below. It may also be called a material resin layer without limiting the purpose. The planarization layer may be composed of an organic compound, and may be either a low molecular weight or a high molecular weight, but is preferably a high molecular weight.

[0114] The planarization layer may be provided above and below the color filter, and may be made of the same or different materials.Specific examples of the materials include polyvinylcarbazole resin, polycarbonate resin, polyester resin, ABS resin, acrylic resin, polyimide resin, phenol resin, epoxy resin, silicone resin, and urea resin.

[0115] <Microlens> The organic light-emitting element may have an optical member such as a microlens on its light-emitting side. The microlens may be made of acrylic resin, epoxy resin, or the like. The microlens may be intended to increase the amount of light extracted from the organic light-emitting element and control the direction of the extracted light. The microlens may have a hemispherical shape. When the microlens has a hemispherical shape, among the tangents to the hemisphere, there is a tangent that is parallel to the insulating layer, and the tangent and the hemisphere are the vertices of the microlens. The vertex of the microlens can be determined in the same manner in any cross-sectional view. That is, among the tangents to the semicircle of the microlens in the cross-sectional view, there is a tangent that is parallel to the insulating layer, and the tangent and the semicircle are the vertices of the microlens.

[0116] It is also possible to define the midpoint of the microlens. In the cross section of the microlens, a line segment is imaginary from a point where an arc shape ends to a point where another arc shape ends, and the midpoint of the line segment can be called the midpoint of the microlens. The cross section for determining the vertex and midpoint may be a cross section perpendicular to the insulating layer.

[0117] <Opposite substrate> A counter substrate may be provided on the planarization layer. The counter substrate is called a counter substrate because it is provided at a position corresponding to the aforementioned substrate. The constituent material of the counter substrate may be the same as that of the aforementioned substrate. When the aforementioned substrate is a first substrate, the counter substrate may be a second substrate.

[0118] <Light-emitting device> A pixel circuit may be connected to the organic light-emitting element according to one embodiment of the present invention to form a light-emitting device. The pixel circuit may be an active matrix type that controls the emission of a plurality of organic light-emitting elements independently. The active matrix type circuit may be voltage programming or current programming. The drive circuit has a pixel circuit for each pixel. The pixel circuit may have a light-emitting element, a transistor that controls the emission luminance of the light-emitting element, a transistor that controls the emission timing, a capacitance that holds the gate voltage of the transistor that controls the emission luminance, and a transistor for connecting to GND without passing through the light-emitting element.

[0119] The light-emitting device has a display region and a peripheral region disposed around the display region. The display region has a pixel circuit, and the peripheral region has a display control circuit. The mobility of a transistor constituting the pixel circuit may be smaller than the mobility of a transistor constituting the display control circuit.

[0120] The slope of the current-voltage characteristic of the transistor constituting the pixel circuit may be smaller than the slope of the current-voltage characteristic of the transistor constituting the display control circuit. The slope of the current-voltage characteristic can be measured by the so-called Vg-Ig characteristic. The transistor constituting the pixel circuit is a transistor connected to an organic light-emitting element.

[0121] Pixels A display device having a plurality of pixels may be formed by using a plurality of organic light-emitting devices according to an embodiment of the present invention. Each pixel has sub-pixels that emit different colors. The sub-pixels may each emit, for example, RGB colors.

[0122] The pixel emits light in an area also called the pixel aperture. This area is the same as the first area. The pixel aperture may be 15 μm or less, or 5 μm or more. More specifically, it may be 11 μm, 9.5 μm, 7.4 μm, 6.4 μm, etc. The distance between the subpixels may be 10 μm or less, more specifically, it may be 8 μm, 7.4 μm, 6.4 μm.

[0123] The pixels may have a known arrangement in plan view. For example, they may be a stripe arrangement, a delta arrangement, a pentile arrangement, or a Bayer arrangement. The shape of the subpixels in plan view may be any known shape. For example, they may be a rectangle, a quadrangle such as a diamond, or a hexagon. Of course, if the shape is not an exact shape but is close to a rectangle, it is included in the rectangle. The shape of the subpixels and the pixel arrangement may be used in combination.

[0124] [Uses of organic light-emitting devices] The organic light-emitting device according to an embodiment of the present invention can be used as a component of a display device or a lighting device, and can also be used as an exposure light source for an electrophotographic image forming device, a backlight for a liquid crystal display device, a light-emitting device having a white light source and a color filter, etc.

[0125] The display device may be an image information processing device having an image input unit that inputs image information from an area CCD, a linear CCD, a memory card, etc., an information processing unit that processes the input information, and displays the input image on a display unit.

[0126] The display unit of the imaging device or inkjet printer may have a touch panel function. The driving method of the touch panel function may be an infrared type, a capacitance type, a resistive film type, or an electromagnetic induction type, and is not particularly limited. The display device may be used in the display unit of a multifunction printer.

[0127] Next, the display device according to the present embodiment will be described with reference to the drawings. 4(a) shows an example of a pixel, which is a component of the display device according to this embodiment. The pixel has sub-pixels 40. The sub-pixels are divided into 40R, 40G, and 40B according to their light emission. The emitted light color is determined by selectively transmitting or color-converting the light emitted from the sub-pixels by a color filter. Each sub-pixel has a reflective electrode 32, which is a first electrode, on an interlayer insulating layer 31, an insulating layer 33 covering the edge of the reflective electrode 32, an organic compound layer 34 covering the first electrode and the insulating layer, a transparent electrode 35, a protective layer 36, and a color filter 37.

[0128] A transistor and a capacitor may be disposed below or inside the interlayer insulating layer 31. The transistor and the first electrode may be electrically connected via a contact hole or the like (not shown). The insulating layer 33 is also called a bank or a pixel separation film. It covers the edge of the first electrode and is disposed so as to surround the first electrode. The part where the insulating layer is not disposed contacts the organic compound layer 34 and becomes a light-emitting region.

[0129] The protective layer 36 reduces the penetration of moisture into the organic compound layer. Although the protective layer is illustrated as being a single layer, it may be a multi-layer. Each layer may include an inorganic compound layer and an organic compound layer. The color filters 37 are divided into 37R, 37G, and 37B according to their colors. The color filters 37 may be formed on a planarization film (not shown). Also, a resin protective layer (not shown) may be provided on the color filters 37. Also, the color filters 37 may be formed on the protective layer 36, or may be provided on an opposing substrate such as a glass substrate and then bonded thereto.

[0130] 4(b) is a cross-sectional view showing a configuration of an example of a display device having an organic light-emitting element according to one embodiment of the present invention and a transistor connected to the organic light-emitting element. The transistor is an example of an active element.

[0131] The display device 100 in FIG. 4(b) includes an organic light-emitting element 26 and a TFT 18 as an example of a transistor. The organic light-emitting element 26 has an anode 21, a cathode 23, and an organic compound layer 22 disposed between them. A substrate 11 made of glass, silicon, or the like is provided with an insulating layer 12 disposed thereon. A gate electrode 13, a gate insulating film 14, and a semiconductor layer 15 of the TFT 18 are disposed on the insulating layer 12. The TFT 18 is also composed of the semiconductor layer 15, a drain electrode 16, and a source electrode 17. An insulating film 19 is provided on the top of the TFT 18. The anode 21 and source electrode 17 constituting the organic light-emitting element 26 are connected via a contact hole 20 provided in the insulating film 19.

[0132] The electrical connection method between the electrodes (anode, cathode) included in the organic light-emitting element 26 and the electrodes (source electrode, drain electrode) included in the TFT is not limited to the embodiment shown in FIG. 4(b). In other words, it is sufficient that either the anode or the cathode is electrically connected to either the source electrode or the drain electrode of the TFT 18. TFT stands for thin film transistor. The organic light-emitting element according to this embodiment has its emission brightness controlled by the TFT, which is an example of a switching element, and by providing the organic light-emitting elements on multiple planes, an image can be displayed based on the emission brightness of each element. A first protective layer 24 and a second protective layer 25 are provided on the cathode 23 in order to reduce deterioration of the organic light-emitting element.

[0133] In the display device 100 of FIG. 4(b), transistors are used as switching elements, but other switching elements may be used instead.

[0134] The transistor used in the display device 100 of Fig. 4(b) may be a transistor using a single crystal silicon wafer, a thin film transistor having an active layer on an insulating surface of a substrate, a transistor formed of low-temperature polysilicon, or an active matrix driver formed on a substrate such as a Si substrate. Examples of the active layer include single crystal silicon, amorphous silicon, non-single crystal silicon such as microcrystalline silicon, and non-single crystal oxide semiconductors such as indium zinc oxide and indium gallium zinc oxide.

[0135] The transistors included in the display device 100 of FIG. 4(b) may be formed in a substrate such as a Si substrate. Formed in a substrate here means that the substrate such as a Si substrate itself is processed to produce the transistors. In other words, having a transistor in a substrate can be seen as the substrate and the transistor being integrally formed. Whether to provide a transistor in the substrate or to use a TFT is selected according to the size of the display unit. For example, if the size is about 0.5 inches, it is preferable to provide an organic light-emitting element on a Si substrate.

[0136] 5 is a schematic diagram showing an example of a display device according to this embodiment. The display device 1000 has a touch panel 1003, a display panel 1005, a frame 1006, a circuit board 1007, and a battery 1008 between an upper cover 1001 and a lower cover 1009. Flexible printed circuits FPC1002 and 1004 are connected to the touch panel 1003 and the display panel 1005, respectively. A transistor is printed on the circuit board 1007. The battery 1008 may not be provided if the display device is not a portable device, and may be provided in a different position even if the display device is a portable device.

[0137] The display device according to this embodiment may have a color filter having red, green, and blue colors, and the red, green, and blue colors may be arranged in a delta arrangement in the color filter.

[0138] The display device according to the present embodiment may be used as a display unit of a mobile terminal. In this case, the display device may have both a display function and an operation function. Examples of the mobile terminal include mobile phones such as smartphones, tablets, and head-mounted displays.

[0139] The display device according to the present embodiment is used in a display unit of an imaging device having an optical unit with a plurality of lenses and an imaging element that receives light that has passed through the optical unit. The imaging device may have a display unit that displays information acquired by the imaging element, and the display unit may be a display unit exposed to the outside of the imaging device or a display unit disposed within a viewfinder. The imaging device may be a digital camera or a digital video camera.

[0140] 6(a) is a schematic diagram showing an example of an imaging device according to this embodiment. The imaging device 1100 has a viewfinder 1101, a rear display 1102, an operation unit 1103, and a housing 1104. The viewfinder 1101 has a display device according to this embodiment, which may display not only an image to be captured, but also environmental information, imaging instructions, and the like. The environmental information includes the intensity of external light, the direction of external light, the moving speed of the subject, the possibility that the subject will be blocked by an obstruction, and the like.

[0141] Since the optimal timing for capturing an image is very short, it is better to display information as soon as possible. Therefore, a display device using an organic light-emitting element with a fast response speed can be suitably used in an image capturing device or the like that requires a high display speed.

[0142] The imaging device 1100 has an optical section (not shown). The optical section has a plurality of lenses, which form an image on an imaging element housed in a housing 1104. The focus of the plurality of lenses can be adjusted by adjusting their relative positions. This operation can also be performed automatically. The imaging device is also called a photoelectric conversion device. The photoelectric conversion device can include an imaging method that does not capture images sequentially, but detects the difference from the previous image, cuts out an image from an image that is always recorded, and the like.

[0143] FIG. 6(b) is a schematic diagram showing an example of an electronic device according to the present embodiment. The electronic device 1200 has a display unit 1201, an operation unit 1202, and a housing 1203. The display unit 1201 has the organic light-emitting element according to the present embodiment. The housing 1203 may have a circuit, a printed circuit board having the circuit, a battery, and a communication unit. The operation unit 1202 may be a button or a touch panel type reaction unit. The operation unit may be a biometric recognition unit that recognizes a fingerprint and releases a lock. An electronic device having a communication unit can also be called a communication device. The electronic device may further have a camera function by including a lens and an image sensor. An image captured by the camera function is displayed on the display unit. Examples of the electronic device include a smartphone and a notebook computer.

[0144] Fig. 7 is a schematic diagram showing an example of a display device according to this embodiment. Fig. 7(a) shows a display device such as a television monitor or a PC monitor. The display device 1300 has a frame 1301 and a display unit 1302. The display unit 1302 has an organic light-emitting element according to this embodiment. It has a frame 1301 and a base 1303 that supports a display unit 1302. The base 1303 is not limited to the form shown in Fig. 7(a). The lower side of the frame 1301 may also serve as the base. The frame 1301 and the display unit 1302 may be curved. The radius of curvature may be 5000 mm or more and 6000 mm or less.

[0145] FIG. 7(b) is a schematic diagram showing another example of the display device according to the present embodiment. The display device 1310 in FIG. 7(b) is configured to be bendable, and is a so-called foldable display device. The display device 1310 has a first display unit 1311, a second display unit 1312, a housing 1313, and a bending point 1314. The first display unit 1311 and the second display unit 1312 have the organic light-emitting element according to the present embodiment. The first display unit 1311 and the second display unit 1312 may be a single display unit without a joint, or may be separated at the bending point. The first display unit 1311 and the second display unit 1312 may display different images, or the first and second display units may display one image.

[0146] FIG. 8(a) is a schematic diagram showing an example of a lighting device according to this embodiment. The lighting device 1400 has a housing 1401, a light source 1402, a circuit board 1403, an optical filter 1404, and a light diffusion unit 1405. The light source has an organic light-emitting element according to this embodiment. The optical filter is a filter that improves the color rendering of the light source, and the light diffusion unit can effectively diffuse the light of the light source for lighting up, etc., and deliver the light to a wide range. The optical filter and the light diffusion unit are provided on the light emission side of the lighting, and a cover may be provided on the outermost part as necessary.

[0147] The lighting device is, for example, a device that illuminates a room. The lighting device may emit white light, neutral white light, or any other color from blue to red, and may have a dimming circuit for dimming the light. The lighting device has the organic light-emitting element of the present invention and a power supply circuit connected thereto. The power supply circuit is a circuit that converts AC voltage into DC voltage. Moreover, white has a color temperature of 4200K, and neutral white has a color temperature of 5000K. The lighting device may have a color filter. Furthermore, the lighting device according to this embodiment may have a heat dissipation section, which dissipates heat inside the device to the outside, and examples of the heat dissipation section include metals with high specific heat, liquid silicon, and the like.

[0148] 8(b) is a schematic diagram of an automobile, which is an example of a moving body according to this embodiment. The automobile has tail lamps, which are an example of a lamp. The automobile 1500 has tail lamps 1501, and may be configured to turn on the tail lamps when braking or the like is performed. The tail lamp 1501 has the organic light-emitting element according to this embodiment, and may have a protective member for protecting the organic light-emitting element. The protective member may be made of any material as long as it has a certain degree of strength and is transparent, but is preferably made of polycarbonate or the like, and polycarbonate may be mixed with a furandicarboxylic acid derivative, an acrylonitrile derivative, or the like.

[0149] An automobile 1500 has a body 1503 and a window 1502 attached thereto. The window may be a transparent display as long as it is not a window for checking the front and rear of the automobile. The transparent display has an organic light-emitting element according to this embodiment. In this case, the constituent materials of the electrodes and the like of the organic light-emitting element are made of transparent materials.

[0150] The moving body according to the present embodiment may be a ship, an aircraft, a drone, or the like. The moving body may have a body and a lamp provided on the body. The lamp may emit light to indicate the position of the body. The lamp has the organic light-emitting element according to the present embodiment.

[0151] An application example of the display device of each of the above-mentioned embodiments will be described with reference to Fig. 9. The display device according to this embodiment can be applied to a system that can be worn as a wearable device such as smart glasses, HMD, and smart contacts. The display device used in such an application example is an image capturing and displaying device having an image capturing device capable of photoelectrically converting visible light and a display device capable of emitting visible light.

[0152] 9(a) illustrates glasses 1600 (smart glasses) according to one application example. An imaging device 1602 such as a CMOS sensor or a SPAD is provided on the front side of a lens 1601 of the glasses 1600. In addition, a display device according to each of the above-mentioned embodiments is provided on the back side of the lens 1601.

[0153] The glasses 1600 further include a control device 1603. The control device 1603 functions as a power source that supplies power to the image capture device 1602 and the display device. The control device 1603 also controls the operations of the image capture device 1602 and the display device. The lens 1601 is formed with an optical system for focusing light on the image capture device 1602.

[0154] FIG. 6(b) illustrates glasses 1610 (smart glasses) according to one application example. The glasses 1610 have a control device 1612, which is equipped with an imaging device corresponding to the imaging device 1602 in FIG. 6(a) and a display device. The lens 1611 is formed with an optical system for projecting light emitted from the imaging device in the control device 1612 and the display device, and an image is projected onto the lens 1611. The control device 1612 functions as a power source that supplies power to the imaging device and the display device, and controls the operations of the imaging device and the display device.

[0155] The control device 1612 may have a gaze detection unit that detects the gaze of the wearer, and infrared rays may be used to detect the gaze. A gaze detection unit using infrared rays includes an infrared light emitting unit that emits infrared light toward the eyeball of the user gazing at the display image. An imaging unit having a light receiving element detects the reflected light of the emitted infrared light from the eyeball to obtain an image of the eyeball. By having a reduction means for reducing the light from the infrared light emitting unit to the display unit in a planar view, deterioration of image quality is reduced. The gaze of the user with respect to the display image is detected from the image of the eyeball obtained by imaging with infrared light.

[0156] Any known method can be applied to gaze detection using a captured image of the eyeball. As an example, a gaze detection method based on a Purkinje image produced by reflection of irradiated light on the cornea can be used. More specifically, a gaze detection process based on a pupil-corneal reflex method is performed. Using the pupil-corneal reflex method, a gaze vector representing the direction (rotation angle) of the eyeball is calculated based on the image of the pupil and the Purkinje image included in the captured image of the eyeball, thereby detecting the user's gaze.

[0157] A display device according to an embodiment of the present invention may have an imaging device having a light receiving element, and may control a display image on the display device based on information about a user's line of sight from the imaging device. Specifically, the display device determines a first field of view area to which the user gazes and a second field of view area other than the first field of view area based on the line-of-sight information. The first field of view area and the second field of view area may be determined by a control device of the display device, or may be received from an external control device. In the display area of ​​the display device, the display resolution of the first field of view area may be controlled to be higher than the display resolution of the second field of view area. In other words, the resolution of the second field of view area may be lower than that of the first field of view area.

[0158] The display area includes a first display area and a second display area different from the first display area, and an area having a high priority is determined from the first display area and the second display area based on line-of-sight information. The first field of view area and the second field of view area may be determined by a control device of the display device, or may be received from an external control device. The resolution of the area having a high priority may be controlled to be higher than the resolution of areas other than the area having a high priority. In other words, the resolution of an area having a relatively low priority may be lowered.

[0159] In addition, AI may be used to determine the first field of view area and the area with high priority. The AI ​​may be a model configured to estimate the angle of the line of sight and the distance to an object at the end of the line of sight from the image of the eyeball, using the image of the eyeball and the direction in which the eyeball in the image was actually looking as teacher data. The AI ​​program may be included in the display device, the imaging device, or an external device. If included in the external device, it is transmitted to the display device via communication.

[0160] When display control is performed based on visual recognition detection, the present invention is preferably applicable to smart glasses that further include an imaging device for capturing images of the outside world. The smart glasses can display captured outside information in real time.

[0161] FIG. 10(a) is a schematic diagram showing an example of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus is an electrophotographic image forming apparatus, and includes a photoconductor 1707, an exposure light source 1708, a charging unit 1706, a developing unit 1701, a transfer unit 1702, a transport roller 1703, and a fixing unit 1705. Light 1709 is irradiated from the exposure light source 1708, and an electrostatic latent image is formed on the surface of the photoconductor 1707. The exposure light source 1708 includes an organic light-emitting element according to this embodiment. The developing unit 1701 includes a toner and the like. The charging unit 1706 charges the photoconductor 1707. The transfer unit 1702 transfers the developed image to a recording medium 1704. The transport roller 1703 transports the recording medium 1704. The recording medium 1704 is, for example, paper. The fixing unit 1705 fixes the image formed on the recording medium 1704.

[0162] 10(b) and 10(c) are diagrams showing an exposure light source 1708, and are schematic diagrams showing a state in which a plurality of light-emitting sections 1710 having organic light-emitting elements according to this embodiment are arranged on a long substrate. An arrow 1711 indicates the column direction in which the organic light-emitting elements are arranged. This column direction is the same as the axis direction of the rotation of the photoconductor 1707. This direction can also be called the long axis direction of the photoconductor 1707. FIG. 10(b) shows a form in which the light-emitting sections 1710 are arranged along the long axis direction of the photoconductor 1707. FIG. 10(c) shows a form different from FIG. 10(b), in which the light-emitting sections 1710 are alternately arranged in the column direction in each of the first column and the second column. The first column and the second column are arranged at different positions in the row direction. In the first column, a plurality of light-emitting sections 1710 are arranged at intervals. In the second column, the light-emitting sections 1710 are arranged at positions corresponding to the intervals between the light-emitting sections 1710 in the first column. That is, the light-emitting units 1710 are also spaced apart in the row direction. The arrangement in Fig. 10(c) can also be described as a grid arrangement, a houndstooth arrangement, or a checkerboard pattern.

[0163] As described above, by using a device using the organic light-emitting element according to this embodiment, it is possible to achieve a display with good image quality and stability even over a long period of time.

[0164] [Included configuration] The disclosure of this embodiment includes the following configuration. (Configuration 1) An organic light-emitting device including a first electrode, a first light-emitting layer, a second light-emitting layer, and a second electrode, the first light-emitting layer and the second light-emitting layer are in contact with each other, the first light-emitting layer includes a first organic compound, a first metal complex, and a second metal complex; the second light-emitting layer contains a second organic compound and a third metal complex, but does not contain the first metal complex; An organic light-emitting element characterized in that, when the triplet energies of the first metal complex, the second metal complex, and the third metal complex are T1D1, T1D2, and T1D3, respectively, the relationships of the following formulas [a] to [c] hold.

[0165] T1D2>T1D1 [a] T1D3 ≥ T1D2 [b] T1D2-T1D1>T1D3-T1D2 [c]

[0166] (Structure 2) The organic light-emitting element according to Structure 1, wherein when the concentration of the second metal complex in the first light-emitting layer and the concentration of the third metal complex in the second light-emitting layer are C1D2 and C1D3, respectively, the relationship of the following formula [d] holds: C1D2 ≧ C1D3 [d]

[0167] (Structure 3) The organic light-emitting element according to Structure 1 or 2, characterized in that when the concentrations of the first metal complex and the second metal complex in the first light-emitting layer are C1D1 and C1D2, respectively, the relationship of the following formula [e] holds: C1D2 ≧ C1D1 [e]

[0168] (Configuration 4) The organic light-emitting device according to any one of configurations 1 to 3, wherein the second metal complex and the third metal complex have at least one identical ligand.

[0169] (Structure 5) The organic light-emitting element according to any one of Structures 1 to 4, characterized in that when the HOMO energy level and LUMO energy level of the second metal complex, and the HOMO energy level and LUMO energy level of the third metal complex are HOMOD2, LUMOD2, HOMOD3, and LUMOD3, respectively, the relationship between the following formulas [f] and [g] holds: |LUMOD3-LUMOD2|≦0.2 eV [f] |HOMOD3-HOMOD2|≦0.2 eV [g]

[0170] (Configuration 6) The organic light-emitting device according to any one of configurations 1 to 5, wherein the first metal complex is a red phosphorescent light-emitting material, and the third metal complex is a green phosphorescent light-emitting material. (Configuration 7) The organic light-emitting device according to any one of configurations 1 to 6, wherein the second light-emitting layer contains a third organic compound which is not a metal complex. (Structure 8) The organic light-emitting element according to any one of Structures 1 to 7, wherein the first electrode is an anode, the second electrode is a cathode, and the first light-emitting layer is disposed closer to the anode than the second light-emitting layer.

[0171] (Structure 9) The organic light-emitting element according to any one of Structures 1 to 8, wherein when the concentration of the first metal complex in the first light-emitting layer and the concentration of the third metal complex in the second light-emitting layer are C1D1 and C1D3, respectively, the relationship of the following formula [h] holds: C1D3>C1D1 [h]

[0172] (Configuration 10) The organic light-emitting device according to any one of configurations 1 to 9, wherein the second metal complex and the third metal complex are the same compound. (Configuration 11) The organic light-emitting device according to any one of configurations 1 to 10, wherein the first organic compound and the second organic compound are the same compound. (Configuration 12) The organic light-emitting device according to any one of Configurations 1 to 11, wherein the light emitted from the first light-emitting layer and the second light-emitting layer is yellow light.

[0173] (Configuration 13) A display device having a plurality of pixels, wherein at least one of the plurality of pixels has an organic light-emitting element according to any one of Configurations 1 to 12 and a transistor connected to the organic light-emitting element. (Configuration 14) An imaging device having an optical unit having a plurality of lenses, an imaging element that receives light that has passed through the optical unit, and a display unit that displays an image captured by the imaging element. The display unit has an organic light-emitting element according to any one of Configurations 1 to 12. (Configuration 15) An electronic device having a display unit having an organic light-emitting element according to any one of Configurations 1 to 12, a housing in which the display unit is provided, and a communication unit provided in the housing for communicating with the outside. (Configuration 16) An illumination device having a light source having an organic light-emitting element according to any one of Configurations 1 to 12 and a light diffusing unit or an optical filter that transmits light emitted by the light source. (Configuration 17) A moving body having a lighting fixture having an organic light-emitting element according to any one of Configurations 1 to 12 and a body in which the lighting fixture is provided. (Configuration 18) An exposure light source of an electrophotographic image forming apparatus having an organic light-emitting element according to any one of Configurations 1 to 12.

Examples

[0174] (Example 1) <Evaluation of Triplet Energy> The T1 energy of the dopant was evaluated by the method shown below. The results are shown in Table 1. Using Hitachi F-4500, photoluminescence (PL) measurement of a diluted toluene solution at 77 K and an excitation wavelength of 300 nm was performed by the built-in phosphorescence mode measurement. It was calculated from the maximum emission wavelength of the obtained emission spectrum.

[0175] <Evaluation of HOMO·LUMO> The HOMO level and LUMO level of the host and the dopant were evaluated by the method shown below. The results are shown in Table 1.

[0176] A) Method for evaluating HOMO levels 5×10 -4 A 30 nm thick film was formed by vapor deposition on an aluminum substrate under a vacuum of 0.1 Pa or less, and this thin film was measured using an AC-3 (manufactured by Riken Keiki Co., Ltd.).

[0177] B) Method for evaluating LUMO levels 5×10 -4 A 30 nm thick film was formed on a quartz substrate under a vacuum of 10 Pa or less, and the optical band gap (absorption edge) of the material to be measured was determined using a spectrophotometer (V-560, manufactured by JASCO Corporation). The optical band gap value was added to the above-mentioned HOMO level value to determine the LUMO level. The results are shown in Table 1.

[0178] [Table 1]

[0179] Example 2 An organic light-emitting device of bottom emission type structure was produced by sequentially forming an anode, a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer, and a cathode on a substrate. First, an ITO film was formed on a glass substrate, and the desired patterning process was performed to form an ITO electrode (anode). At this time, the film thickness of the ITO electrode was set to 100 nm. The substrate on which the ITO electrode was formed was used as an ITO substrate in the following process. Next, a 1.33×10 -4 The organic compound layer and the electrode layer shown in Table 2 were successively formed on the ITO substrate by vacuum deposition using resistance heating in a vacuum chamber at 1000 Pa. Note that at this time, the electrode area of ​​the opposing electrode (metal electrode layer, cathode) was 3 mm 2 Thereafter, the substrate was transferred to a glove box and sealed with a glass cap containing a desiccant in a nitrogen atmosphere to obtain an organic light-emitting element.

[0180] [Table 2]

[0181] The properties of the obtained organic light-emitting device were measured and evaluated. The light-emitting color of the organic light-emitting device was yellow, and the maximum external quantum efficiency (EQE) was 18%. Furthermore, the current density is 100mA / cm 2 A continuous driving test was performed at 100° C., and the time when the luminance degradation rate reached 5% was measured. When the time when the luminance degradation rate of Comparative Example 1 reached 5% was taken as 1.0, the luminance degradation ratio of this example was 2.3. In this example, the measuring device was a microammeter 4140B manufactured by Hewlett-Packard Company to measure the current-voltage characteristics, and a BM7 manufactured by Topcon Corporation to measure the luminance.

[0182] (Examples 3 to 20, Comparative Examples 1 to 7) Organic light-emitting devices of Examples 3 to 20 and Comparative Examples 1 to 7 were produced in the same manner as in Example 2, except that the compounds constituting the organic compound layer were appropriately changed to compounds shown in Tables 3 and 4. The characteristics of the obtained organic light-emitting devices were measured and evaluated in the same manner as in Example 2. The measurement results are shown in Tables 3 and 4.

[0183] When the second emitting layer contained an assist material, the mass ratio was adjusted to second host:assist material:third metal complex=55:30:15.

[0184] [Table 3]

[0185] [Table 4]

[0186] From Tables 3 and 4, the EQEs of Comparative Examples 1 to 7 were 18%, 7%, 12%, 15%, 15%, 13%, and 8%, respectively. The luminance degradation ratios of Comparative Examples 1 to 7 were 1.0, 0.3, 0.8, 1.3, 1.1, 1.4, and 1.3, respectively. These are considered to have poor luminous properties and durability properties because carrier transfer and triplet energy transfer between the first emitting layer and the second emitting layer are difficult to occur. On the other hand, the organic light-emitting device according to the present invention exhibited excellent light-emitting efficiency and excellent device life. This is because the stacked light-emitting layer according to the present invention has a relationship that facilitates energy transfer with the carrier.

[0187] Furthermore, by selecting a host material and a light-emitting material suitable for combination with the stacked light-emitting layer of the present invention, an organic light-emitting device having a particularly excellent device life could be obtained.

[0188] As described above, by using the organic compound according to the present invention, it is possible to provide an organic light-emitting device excellent in luminous efficiency and device life.

[0189] Example 21 An organic light-emitting device was produced in the same manner as in Example 2, except that the thickness of the first emitting layer was changed to 10 nm. The characteristics of the obtained organic light-emitting device were measured and evaluated in the same manner as in Example 2. The maximum external quantum efficiency (EQE) was 16%, and the luminance degradation ratio was 2.0.

[0190] Example 22 An organic light-emitting device was produced in the same manner as in Example 2, except that the thickness of the first emitting layer was changed to 10 nm and the thickness of the second emitting layer was changed to 10 nm. The characteristics of the obtained organic light-emitting device were measured and evaluated in the same manner as in Example 2. The maximum external quantum efficiency (EQE) was 18%, and the luminance degradation ratio was 1.8.

[0191] Example 23 An organic light-emitting device was produced in the same manner as in Example 2, except that the mass ratio of the first emitting layer was changed to EM10:AA1:HH1 = 81:15:4 and the mass ratio of the second emitting layer was changed to EM14:AA2 = 85:15. The characteristics of the obtained organic light-emitting device were measured and evaluated in the same manner as in Example 2. The maximum external quantum efficiency (EQE) was 16%, and the luminance degradation ratio was 2.0.

[0192] (Example 24) An organic light-emitting device was produced in the same manner as in Example 2, except that the mass ratio of the first emitting layer was changed to EM10:AA1:HH1 = 75:20:5 and the mass ratio of the second emitting layer was changed to EM14:AA2 = 95:5. The characteristics of the obtained organic light-emitting device were measured and evaluated in the same manner as in Example 2. The maximum external quantum efficiency (EQE) was 14%, and the luminance degradation ratio was 2.2. [Explanation of symbols]

[0193] 2: anode, 4a: first light-emitting layer, 4b: second light-emitting layer, 6: cathode, 10: display device, 18: transistor, 1000: display device, 1100: imaging device, 1200: electronic device, 1201: display unit, 1203: housing, 1300: display device, 1310: display device, 1313: housing, 1400: lighting device, 1401: housing, 1402: light source, 1404: optical filter, 1405: light diffusion unit, 1708: exposure light source

Claims

1. An organic light-emitting device comprising a first electrode, a first light-emitting layer, a second light-emitting layer, and a second electrode, the first light-emitting layer and the second light-emitting layer are in contact with each other, the first light-emitting layer includes a first organic compound, a first metal complex, and a second metal complex; the second light-emitting layer contains a second organic compound and a third metal complex, but does not contain the first metal complex; An organic light-emitting element characterized in that, when the triplet energies of the first metal complex, the second metal complex, and the third metal complex are T1D1, T1D2, and T1D3, respectively, the relationships of the following formulas [a] to [c] hold. T1D2>T1D1 [a] T1D3≧T1D2 [b] T1D2-T1D1>T1D3-T1D2 [c]

2. 2. The organic light-emitting element according to claim 1, wherein when the concentration of the second metal complex in the first light-emitting layer is C1D2 and the concentration of the third metal complex in the second light-emitting layer is C1D3, the relationship of the following formula [d] holds: C1D2≧C1D3 [d]

3. 2. The organic light-emitting element according to claim 1, wherein when the concentrations of the first metal complex and the second metal complex in the first light-emitting layer are C1D1 and C1D2, respectively, the relationship of the following formula [e] holds: C1D2≧C1D1 [e]

4. The organic light-emitting device according to claim 1 , wherein the second metal complex and the third metal complex have at least one identical ligand.

5. 2. The organic light-emitting element according to claim 1, wherein the relationship between the following formulas [f] and [g] holds when the HOMO energy level and LUMO energy level of the second metal complex and the HOMO energy level and LUMO energy level of the third metal complex are HOMOD2, LUMOD2, HOMOD3, and LUMOD3, respectively: |LUMOD3-LUMOD2|≦0.2eV [f] |HOMOD3-HOMOD2|≦0.2eV [g]

6. 2. The organic light-emitting element according to claim 1, wherein the first metal complex is a red phosphorescent material, and the third metal complex is a green phosphorescent material.

7. The organic light-emitting device according to claim 1 , wherein the second light-emitting layer comprises a third organic compound that is not a metal complex.

8. 2. The organic light-emitting element according to claim 1, wherein the first electrode is an anode, the second electrode is a cathode, and the first light-emitting layer is disposed closer to the anode than the second light-emitting layer.

9. 2. The organic light-emitting element according to claim 1, wherein when the concentration of the first metal complex in the first light-emitting layer is C1D1 and the concentration of the third metal complex in the second light-emitting layer is C1D3, the relationship of the following formula [h] holds: C1D3>C1D1 [h]

10. The organic light-emitting device according to claim 1 , wherein the second metal complex and the third metal complex are the same compound.

11. The organic light-emitting device according to claim 1 , wherein the first organic compound and the second organic compound are the same compound.

12. 2. The organic light-emitting device according to claim 1, wherein the light emitted from the first light-emitting layer and the second light-emitting layer is yellow.

13. The first metal complex is selected from the group consisting of HH1, HH19, II8, II9, RD3, RD7, and RD10 shown below, the second metal complex is selected from the group consisting of AA1, AA21, BB21, CC1, CC21, FF11, JJ4, and JJ19 shown below, The organic light-emitting element according to claim 1, wherein the third metal complex is selected from the group consisting of AA2, CC2, CC22, DD2, DD7, DD30, JJ2, JJ4, JJ14, JJ17, JJ19, JJ20, GD20, and GD11 shown below. 【Chemical 1】 【Chemistry 2】 【Chemistry 3】

14. A display device comprising a plurality of pixels, at least one of the plurality of pixels comprising the organic light-emitting element according to claim 1 and a transistor connected to the organic light-emitting element.

15. an optical unit having a plurality of lenses, an image pickup element that receives light that has passed through the optical unit, and a display unit that displays an image picked up by the image pickup element; An imaging device, wherein the display unit comprises the organic light-emitting element according to claim 1 .

16. 14. An electronic device comprising: a display unit having the organic light-emitting element according to claim 1; a housing in which the display unit is provided; and a communication unit provided in the housing and communicating with an external device.

17. 14. A lighting device comprising: a light source having the organic light-emitting element according to claim 1; and a light diffusion section or an optical filter that transmits light emitted by the light source.

18. A moving body comprising: a lamp having the organic light-emitting element according to claim 1; and a vehicle on which the lamp is provided.

19. An exposure light source for an electrophotographic image forming apparatus, comprising the organic light-emitting element according to claim 1 .

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