Organic light-emitting device, display device, electronic device, in-vehicle display, and vehicle

Abstract

To provide an organic light-emitting device of which the lifetime under a high-temperature environment is prolonged, a display device, an electronic apparatus, an on-vehicle display and a vehicle.SOLUTION: An organic light-emitting device comprises: an anode electrode and a cathode electrode which are disposed oppositely; a light-emitting layer disposed between the anode electrode and the cathode electrode; and a hole transporting layer which is disposed between the anode electrode and the light-emitting layer in contact with the light-emitting layer. The light-emitting layer contains a first host material and a second host material. An energy difference ΔE1 between a HOMO level 14aH of the first host material and a HOMO level 13H of the hole transporting layer is smaller than an energy difference ΔE2 between a HOMO level 14bH of the second host material and the HOMO level 13H of the hole transporting layer, and a difference between the HOMO level 13H of the hole transporting layer and the HOMO level 14aH of the first host material is equal to or less than 0.37 eV.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to an organic light-emitting device, a display device, an electronic device, an in-vehicle display, and a vehicle. [Background technology]

[0002] Organic light-emitting devices called organic EL (Electro-Luminescence) devices are used in displays and the like. The organic EL device includes a light-emitting layer containing an organic light-emitting material, and an anode electrode and a cathode electrode sandwiching the light-emitting layer. In order to improve the light-emitting efficiency of the organic EL device, a hole transport layer or a hole injection layer is provided between the anode electrode and the light-emitting layer, and an electron transport layer or an electron injection layer is provided between the cathode electrode and the light-emitting layer (for example, Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2008-535266 [Patent Document 2] Special Publication No. 2014-513418 [Patent Document 3] JP 2017-022369 A Summary of the Invention [Problem to be solved by the invention]

[0004] It is known that the lifespan of an organic EL device is shortened in a high-temperature environment. For an organic EL device exposed to various environments (for example, an organic EL device mounted on a vehicle), it is preferable that the lifespan in a high-temperature environment is longer.

[0005] The present disclosure has been made in view of the above-mentioned problems, and has an object to provide an organic light-emitting device, a display device, an electronic device, an in-vehicle display, and a vehicle that have a long life in a high-temperature environment. [Means for solving the problem]

[0006] In order to achieve the above object, an organic light-emitting device according to a first embodiment of the present disclosure includes: an anode electrode and a cathode electrode disposed opposite each other; a light-emitting layer disposed between the anode electrode and the cathode electrode; a hole transport layer disposed between the anode electrode and the light emitting layer and in contact with the light emitting layer; Equipped with the light-emitting layer comprises a first host material and a second host material; a difference between a HOMO level of the hole transport layer and a HOMO level of the first host material is smaller than a difference between a HOMO level of the hole transport layer and a HOMO level of the second host material; The difference between the HOMO level of the hole transport layer and the HOMO level of the first host material is Beyond 0 0.37 eV or less, The weight ratio of the first host material to the second host material is 55:45 to 70:30.

[0007] A display device according to a second embodiment of the present disclosure includes the organic light-emitting device according to the first embodiment.

[0008] An in-vehicle display according to a third embodiment of the present disclosure includes the display device according to the second aspect.

[0009] An electronic device according to a fourth embodiment of the present disclosure includes the display device according to the second aspect.

[0010] A vehicle according to a fifth embodiment of the present disclosure includes an in-vehicle display according to the third aspect. Effect of the Invention

[0011] According to the present disclosure, it is possible to extend the life of organic light-emitting devices, display devices, electronic devices, in-vehicle displays, and vehicles in high-temperature environments. [Brief description of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view showing a structure of an organic light-emitting device according to a first embodiment. [Diagram 2] FIG. 2 is an energy state diagram of a hole transport layer and a first host material and a second host material in an emission layer of the organic light-emitting device according to the first embodiment. [Diagram 3] 1 is a graph showing the relationship between the energy difference ΔE1 obtained by subtracting the HOMO level of the light-emitting layer from the HOMO level of the hole-transporting layer, and the lifetime in a high-temperature environment (high-temperature lifetime). [Figure 4] 1 is a graph showing the relationship between the difference ΔE3 between the HOMO level of a first host material and the HOMO level of a second host material in an emitting layer and the lifetime in a high-temperature environment (high-temperature lifetime). [Diagram 5] 1 is a graph showing the relationship between the content of the first host material and the lifetime in a high-temperature environment (high-temperature lifetime). [Figure 6] FIG. 11 is a diagram illustrating a configuration example of a display device according to a third embodiment. [Figure 7] FIG. 2 is a plan view showing a part of a display area of ​​the display device. [Figure 8] FIG. 11 is a diagram showing a configuration example of an in-vehicle display according to a fourth embodiment. [Figure 9] FIG. 13 is a diagram illustrating an example of the configuration of an electronic device according to a fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an organic light-emitting device 10, a display device 20, an electronic device, an in-vehicle display 30, and a vehicle according to the present embodiment will be described with reference to the drawings.

[0014] (Embodiment 1) As shown in Fig. 1, the organic light-emitting device 10 includes an anode electrode 12 disposed on a substrate 11, a hole transport layer 13 disposed on the anode electrode 12, a light-emitting layer 14 disposed on the hole transport layer 13, an electron transport layer 15 disposed on the light-emitting layer 14, an electron injection layer 16 disposed on the electron transport layer 15, and a cathode electrode 17 disposed on the electron injection layer 16. The organic light-emitting device 10 may be used as a monochromatic light-emitting device. It may also be used as a display device having pixels with different chromaticities such as red, green, and blue, and is used, for example, in mobile products such as smartphones and tablets, in-vehicle displays, and the like.

[0015] The substrate 11 is an insulating substrate, such as a glass substrate. As shown in Fig. 1, an anode electrode 12, a hole transport layer 13, a light emitting layer 14, and the like are laminated on the substrate 11. As the substrate 11, any substrate, such as a flexible substrate made of polyimide, polycarbonate, or the like, can be used.

[0016] The anode electrode 12 is disposed on the substrate 11, and faces the cathode electrode 17 via the hole transport layer 13, the light emitting layer 14, the electron transport layer 15, and the electron injection layer 16, as shown in FIG. 1. The anode electrode 12 is connected to a power source (not shown) and supplies holes to the hole transport layer 13. A material having translucency and conductivity is used as a material for forming the anode electrode 12, and examples of the material that can be used include indium tin oxide (ITO), tin oxide (SnO2), and indium zinc oxide (IZO). When the organic light emitting device 10 has a top emission structure, the substrate 11 side reflects light and emits the light to the cathode electrode 17 side. In this case, the anode electrode 12 can be an electrode in which ITO or IZO is disposed on the surface of a reflective metal such as silver (Ag).

[0017] The hole transport layer 13 is disposed between the anode electrode 12 and the light emitting layer 14 in contact with the light emitting layer 14. The hole transport layer 13 efficiently transports holes injected from the anode electrode 12 to the light emitting layer 14. In general, the band gap of the hole transport layer 13 is larger than the band gap of the light emitting layer 14. The band gap refers to the energy difference between the energy level of the lowest unoccupied molecular orbital, that is, the LUMO (Lowest Unoccupied Molecular Orbital) level, and the energy level of the highest occupied molecular orbital, that is, the HOMO (Highest Occupied Molecular Orbital) level. The HOMO level can be measured using a commonly known atmospheric photoelectron yield spectroscopy. The band gap of each layer can be measured using a commonly known ultraviolet-visible-near infrared spectroscopy, and the LUMO level of each layer can be calculated from the measured HOMO level and band gap of each layer.

[0018] In this embodiment, a known material can be used as the material for forming the hole transport layer 13. For example, the hole transport layer 13 can be formed using α-NPD (trade name: 2,2′-Dimethyl-N,N′-di-[(1-naphthyl)-N,N′-diphenyl]-1,1′-biphenyl-4,4′-diamine), TAPC (trade name: 4,4′-Cyclohexylidenebis[N,N-bis(4-methylphenyl)benzenamine]), TPD (trade name: N,N′-Bis(3-methylphenyl)-N,N′-diphenylbenzidine), or the like. The hole transport layer 13 is not limited to being a single layer, and can have multiple layers.

[0019] The light-emitting layer 14 is disposed between the anode electrode 12 and the cathode electrode 17. In the light-emitting layer 14, holes injected from the anode electrode 12 and electrons injected from the cathode electrode 17 are efficiently recombined, and light is emitted by the recombination. The light-emitting layer 14 contains two types of host materials, a first host material and a second host material, and a light-emitting material.

[0020] The luminescent material may be a known material such as a fluorescent material, a thermally activated delayed fluorescent material, or a phosphorescent material. The luminescent material may be, for example, a bisstyrylbenzene derivative, Alq3 (Tris-(8-hydroxyquinoline)aluminum), rubrene, dimethylquinacridone, FIrpic (Bis[2-(4,6-difluorophenyl)pyridinato-C2,N](picolinato)iridium(III)), Ir(ppy)3 (Tris[2-phenylpyridinato-C2,N]iridium(III)), (ppy)2Ir(acac) (Bis[2-(2-pyridinyl-N)phenyl-C](2,4-pentanedionato-O2,O4)iridium(III)), or the like.

[0021] As the first host material, a known host material having a hole transporting property or an electron transporting property can be used. The same applies to the second host material.

[0022] The hole-transporting host material is selected from pyrrole, indole, carbazole, azaindole, azacarbazole, triazole, oxazole, oxadiazole, pyrazole, imidazole, thiophene, polyarylalkane, pyrazoline, pyrazolone, phenylenediamine, arylamine, amino-substituted chalcone, styrylanthracene, fluorenone, hydrazone, stilbene, silazane, aromatic tertiary amine compound, styrylamine compound, aromatic dimethylidine-based compound, porphyrin-based compound, polysilane-based compound, poly(N-vinylcarbazole), aniline-based copolymer, conductive polymer oligomer such as thiophene oligomer or polythiophene, organic silane, carbon film, or derivatives thereof.

[0023] The electron transporting host material is selected from pyridine, pyrimidine, triazine, imidazole, pyrazole, triazole, oxazole, oxadiazole, fluorenone, anthraquinodimethane, anthrone, diphenylquinone, thiopyran dioxide, carbodiimide, fluorenylidenemethane, distyrylpyrazine, fluorine-substituted aromatic compounds, heterocyclic tetracarboxylic acid anhydrides such as naphthaleneperylene, phthalocyanine or derivatives thereof (which may form a condensed ring with another ring), metal complexes of 8-quinolinol derivatives, metal phthalocyanine, benzoxazole, and various metal complexes typified by metal complexes having benzothiazole as a ligand.

[0024] The first host material and the second host material may both be selected from hole-transporting host materials, or both may be selected from electron-transporting host materials. Alternatively, one of the first host material and the second host material may be selected from hole-transporting host materials, and the other may be selected from electron-transporting materials. As an example, the first host material is selected from hole-transporting materials, and the second host material is selected from electron-transporting materials. In addition, in the light-emitting layer 14, when the total weight of the first host material and the second host material is 100, the weight ratio of the first host material to the second host material (first host material:second host material) is 10:90 to 90:10. In other words, the first host material is contained in the light-emitting layer 14 in an amount of 10% by weight to 90% by weight with respect to the total weight of the first host material and the second host material.

[0025] The electron transport layer 15 efficiently transports electrons injected from the electron injection layer 16 to the light emitting layer 14. In this embodiment, a known material can be used as a material for forming the electron transport layer 15. The electron transport layer 15 can be formed using, for example, Alq3, BCP (product name: 3-Benzidino-6-(4-chlorophenyl)pyridazine), a silole derivative, or the like. In addition, the electron transport layer 15 is not limited to being a single layer, and can include multiple layers.

[0026] The electron injection layer 16 efficiently injects electrons injected from the cathode electrode 17 into the electron transport layer 15. Examples of materials that can be used to form the electron injection layer 16 include lithium fluoride (LiF), ytterbium (Yb), and Liq (name: 8-Hydroxyquinolinolato-lithium).

[0027] The cathode electrode 17 is connected to a power source (not shown) and supplies electrons to the electron injection layer 16. The cathode electrode 17 may be made of a material such as aluminum, a magnesium-silver alloy, ITO, or IZO.

[0028] Next, the energy states of the hole transport layer 13 and the first and second host materials of the light emitting layer 14 are shown in Fig. 2. In Fig. 2, reference numeral 13H denotes the HOMO level of the hole transport layer 13, and reference numeral 13L denotes the LUMO level of the hole transport layer 13. Reference numeral 14aH denotes the HOMO level of the first host material of the light emitting layer 14, and reference numeral 14aL denotes the LUMO level of the first host material of the light emitting layer 14. Reference numeral 14bH denotes the HOMO level of the second host material of the light emitting layer 14, and reference numeral 14bL denotes the LUMO level of the second host material of the light emitting layer 14.

[0029] In this embodiment, the energy states of the hole transport layer 13 and the first and second host materials of the light emitting layer 14 have particularly notable features in the following two respects.

[0030] First, the difference between the HOMO level 13H of the hole transport layer 13 and the HOMO level 14aH of the first host material of the light emitting layer 14 is 0.37 eV or less. The HOMO level 13H of the hole transport layer 13 in contact with the light emitting layer 14 is higher than the HOMO level 14aH of the first host material of the light emitting layer 14. Referring to Fig. 2, ΔE1 is the energy difference obtained by subtracting the HOMO level 14aH of the first host material of the light emitting layer 14 from the HOMO level 13H of the hole transport layer 13, and ΔE1 is in the range of more than 0 eV and less than or equal to 0.37 eV (0 eV<ΔE1≦0.37 eV). Moreover, the energy difference ΔE1 is preferably in the range of more than 0 eV and not more than 0.34 eV (0 eV<ΔE1≦0.34 eV), and more preferably in the range of more than 0 eV and not more than 0.32 eV (0 eV<ΔE1≦0.32 eV).

[0031] Secondly, the absolute value of the difference between the HOMO level of the first host material and the HOMO level of the second host material is 0.3 eV or less. Also, the difference between the HOMO level of the first host material and the HOMO level of the hole transport layer 13 is smaller than the difference between the HOMO level of the second host material and the HOMO level of the hole transport layer 13. In other words, the HOMO level of the first host material is closer to the HOMO level of the hole transport layer 13 than the HOMO level of the second host material. Referring to FIG. 2, ΔE1 is the energy difference obtained by subtracting the HOMO level 14aH of the first host material of the light-emitting layer 14 from the HOMO level 13H of the hole transport layer 13, and ΔE2 is the energy difference obtained by subtracting the HOMO level 14bH of the second host material of the light-emitting layer 14 from the HOMO level 13H of the hole transport layer 13. In this case, ΔE1 is smaller than ΔE2 (ΔE1<ΔE2). Also, ΔE3 is the energy difference obtained by subtracting the HOMO level 14bH of the second host material from the HOMO level 14aH of the first host material. In this case, ΔE3 is 0.3 eV or less (ΔE3≦0.3 eV).

[0032] Next, the effects achieved by having such a remarkable feature will be described with reference to the high-temperature life characteristics of the organic light-emitting device 10.

[0033] 3 shows a graph showing the relationship between the energy difference ΔE1 [eV] (horizontal axis) and the high-temperature lifetime [h] (vertical axis). Note that in the present disclosure, the high-temperature lifetime is measured when the organic light-emitting device 10 is driven at 10 mA / cm in an environment of 85° C. 2 The HOMO level refers to the time (hours) required for the intensity of light emitted by the organic light-emitting device 10 to decrease by 20% compared to the initial intensity when the device is continuously driven at a current density of 1000 . The HOMO level is measured using atmospheric photoelectron yield spectroscopy. In FIG. 3, the energy difference (ΔE3) between the first host material and the second host material, obtained by subtracting the HOMO level of the second host material from the HOMO level of the first host material, is 0.3 eV or less.

[0034] As shown in FIG. 3, when the energy difference ΔE1 is in the range of more than 0.37 eV, the high-temperature lifetime is about 200 hours, but when the energy difference ΔE1 is in the range of 0.37 eV to 0.32 eV, the high-temperature lifetime increases as the energy difference ΔE1 decreases. When the energy difference ΔE1 is 0.34 eV or less, the high-temperature lifetime exceeds 500 hours. Also, when the energy difference ΔE is 0.32 eV or less, the high-temperature lifetime exceeds 800 hours in both cases. In addition, as shown in FIG. 3, when the energy difference ΔE1 is less than 0 eV, that is, when the HOMO level 13H of the hole transport layer 13 in contact with the light-emitting layer 14 is lower than the HOMO level 14aH of the first host material of the light-emitting layer 14, the high-temperature lifetime decreases to about 200 hours. This is expected to be because when ΔE1 is 0 eV or less, it becomes difficult for holes flowing through the hole transport layer 13 to overcome the barrier of the light-emitting layer 14. Therefore, it is preferable that the energy difference ΔE1 is larger than 0 eV.

[0035] Therefore, the high-temperature life can be further extended by setting the energy difference ΔE1 in the range of more than 0 eV and not more than 0.37 eV (0 eV<ΔE1≦0.37 eV). In addition, when the energy difference ΔE1 is set to 0 eV<ΔE1≦0.34 eV, the high-temperature life exceeds 500 hours, which is preferable. Furthermore, when the energy difference ΔE1 is set to 0 eV<ΔE1≦0.32 eV, the high-temperature life can be further extended, which is particularly preferable.

[0036] Next, a graph showing the relationship between the energy difference ΔE3 [eV] (horizontal axis) obtained by subtracting the HOMO level 14bH of the second host material from the HOMO level 14aH of the first host material, and the high-temperature lifetime [h] (vertical axis) is shown in Figure 4. The legend in Figure 4 indicates the value of ΔE1 at each point. As shown in the legend, the energy differences ΔE1 at all points satisfy 0 eV<ΔE1≦0.37 eV.

[0037] As shown in Figure 4, when the energy difference ΔE3 is 0.3 eV or less, a high-temperature lifetime exceeding 800 hours is obtained. However, when the energy difference ΔE3 exceeds 0.3 eV, the high-temperature lifetime decreases as the energy difference ΔE3 increases, and when the energy difference ΔE3 is 0.4 eV, the high-temperature lifetime decreases to about 250 hours. In addition, even if ΔE1 is 0.32 eV or less, when ΔE3 exceeds 0.3 eV, the high-temperature lifetime decreases.

[0038] For these reasons, by setting the energy difference ΔE1 in the range of more than 0 eV and not more than 0.37 eV (0 eV<ΔE1≦0.37 eV) and additionally setting the energy difference ΔE3 to 0.3 eV or less, the high-temperature life of organic light-emitting device 10 can be extended.

[0039] The organic light-emitting device 10 of the present embodiment has an advantage in that it can have a long high-temperature life, and is therefore suitable for use as an element having a short emission wavelength, particularly as a green element. Generally, as the range of uses for displays expands, deeper blues and greens are required to broaden the chromaticity range, but elements having a short emission wavelength tend to have a short life.

[0040] The organic light-emitting device 10 can be produced by the following manufacturing method.

[0041] First, a substrate 11 is prepared. Next, an anode electrode 12 made of, for example, ITO is formed on the surface of the substrate 11 by sputtering. Next, a hole transport layer 13 is formed on the anode electrode 12 by, for example, vacuum deposition. Next, a light emitting layer 14 is formed on the hole transport layer 13 by a dry process, for example, vacuum deposition. The first host material and the second host material of the hole transport layer 13 and the light emitting layer 14 are selected so that the energy difference ΔE1 is in the range of more than 0 eV and not more than 0.37 eV. In addition, the first host material and the second host material of the hole transport layer 13 and the light emitting layer 14 are selected so that the energy difference ΔE3 is not more than 0.3 eV. The weight ratio of the first host material to the second host material is 10:90 to 90:10.

[0042] Next, the electron transport layer 15, the electron injection layer 16 and the cathode electrode 17 are formed in this order on the light emitting layer 14 by a known method such as vacuum deposition.

[0043] The present disclosure can also be applied to an organic light-emitting device having pixels for each light-emitting element with different chromaticity, such as red, green, and blue. In this case, first, an anode electrode 12 is formed by sputtering on a substrate 11 on which a transistor is formed. Then, a pixel definition layer is formed using an organic film. Then, a hole transport layer 13 to a cathode electrode 17 are formed in this order on the anode electrode 12 in the open region of the pixel definition layer by vacuum deposition or the like. In this way, an organic light-emitting device composed of pixels using red, green, and blue light-emitting elements can be fabricated.

[0044] (Embodiment 2) Hereinafter, a description will be given of the organic light-emitting device 10 according to embodiment 2. Note that since the organic light-emitting device 10 according to embodiment 2 has the same structure as the organic light-emitting device 10 according to embodiment 1 (the structure shown in FIG. 1), detailed description of the features common to embodiment 1 will be omitted.

[0045] In the organic light-emitting device 10 according to the second embodiment, the light-emitting layer 14 includes a light-emitting material, a first host material, and a second host material, similarly to the first embodiment. In the light-emitting layer 14, when the total weight of the first host material and the second host material is taken as 100, the weight ratio of the first host material to the second host material (first host material:second host material) is preferably 20:80 to 75:25, and more preferably 45:55 to 70:30. In other words, the first host material is preferably contained in an amount of 20% by weight to 75% by weight, and more preferably 45% by weight to 70% by weight, based on the total weight of the first host material and the second host material. The HOMO level of the hole transport layer, the HOMO level of the first host material, and the HOMO level of the second host material satisfy 0<ΔE1≦0.37 and ΔE3≦0.3, similarly to the first embodiment.

[0046] Next, the effects achieved by having such a remarkable feature will be described with reference to the high-temperature life characteristics of the organic light-emitting device 10.

[0047] A graph showing the relationship between the proportion [%] of the first host material (horizontal axis) and the high-temperature lifetime [h] (vertical axis) is shown in Fig. 5. The proportion [%] of the first host material is the weight (% by weight) of the first host material relative to the total weight of the first host material and the second host material in the light-emitting layer 14. As shown in Fig. 5, when the proportion of the first host material is 20% to 75%, the high-temperature lifetime exceeds 500 hours. Furthermore, when the proportion of the first host material is 45% to 70%, the high-temperature lifetime exceeds 800 hours.

[0048] As described above, by setting the weight ratio of the first host material to the second host material (first host material:second host material) in the light-emitting layer 14 to 20:80 to 75:25, the high-temperature life of the organic light-emitting device 10 can be extended. Furthermore, by setting the weight ratio of the first host material to the second host material to 45:55 to 70:30, the high-temperature life can be further extended.

[0049] (Embodiment 3) Next, a third embodiment will be described. This embodiment relates to an OLED display device (display device) 20 using the organic light-emitting device 10 according to each of the above-described embodiments. An example of the configuration of the display device 20 according to this embodiment is shown in FIG.

[0050] The display device 20 includes a TFT (Thin Film Transistor) substrate 100, a sealing substrate 200, and a bonding portion (glass frit seal portion) 300. An organic light emitting device 10 serving as an OLED element is formed on the TFT substrate 100. The sealing substrate 200 is disposed opposite the TFT substrate 100. The bonding portion 300 is provided between the TFT substrate 100 and the sealing substrate 200, and bonds the TFT substrate 100 and the sealing substrate 200 together to seal the OLED element.

[0051] A scan driver 131, an emission driver 132, a protection circuit 133, and a driver IC (Integrated Circuit) 134 are arranged around a cathode electrode forming region 114 outside a display region 125 of the TFT substrate 100. These are connected to an external device via an FPC (Flexible Printed Circuit) 135.

[0052] The scan driver 131 drives the scan lines of the TFT substrate 100. The emission driver 132 drives the emission control lines to control the light emitting period of each sub-pixel. The driver IC 134 is implemented using, for example, an anisotropic conductive film (ACF).

[0053] The driver IC 134 provides power and timing signals (control signals) to the scan driver 131 and the emission driver 132, and also provides data voltages corresponding to video data to the data lines. That is, the driver IC 134 has a display control function.

[0054] The sealing substrate 200 is a transparent insulating substrate, such as a glass substrate. A λ / 4 retardation plate and a polarizing plate are disposed on the light exit surface (front surface) of the sealing substrate 200 to suppress reflection of light incident from the outside.

[0055] A plurality of subpixels are arranged in the display region 125. FIG. 7 is a plan view showing a part of the display region 125. FIG. 7 shows a plurality of subpixels arranged in a matrix. At least three subpixels emit different first to third colors. The first color is, for example, blue, the second color is, for example, red, and the third color is, for example, green. FIG. 7 shows a red subpixel (light-emitting region) 251R, a blue subpixel (light-emitting region) 251B, and a green subpixel (light-emitting region) 251G. The entire region of each subpixel (light-emitting region) is covered with an organic light-emitting layer of the same color. Specifically, the red subpixel 251R, the blue subpixel 251B, and the green subpixel 251G are completely covered with an organic light-emitting layer 269R, a blue organic light-emitting layer 269B, and a green organic light-emitting layer 269G, respectively. Of the subpixels in FIG. 7, only one red, one blue, and one green subpixel are indicated by a symbol. Each sub-pixel displays either red, blue, or green. The red, blue, and green sub-pixels form one pixel (main pixel).

[0056] In this embodiment, each subpixel is formed of the organic light-emitting device 10 according to embodiment 1 or 2. Therefore, by virtue of the action of the configuration described in embodiment 1 or 2, the high-temperature life of the display device 20 can be extended.

[0057] (Embodiment 4) Next, a fourth embodiment will be described. This embodiment relates to an in-vehicle display 30 using the display device 20 according to the third embodiment. Fig. 8 is a diagram showing a configuration example of a vehicle equipped with the in-vehicle display according to this embodiment and the in-vehicle display.

[0058] The in-vehicle display 30 is a display that is provided inside an automobile 35 as a vehicle shown in Fig. 8 and displays various information. The in-vehicle display 30 is, for example, a CID (Center Information Display) 301, a cluster display 302, and a side display 303 shown in Fig. 8. In this embodiment, the CID 301, the cluster display 302, and the side display 303 are displays that use the display device 20.

[0059] CID 301 is provided in the center of the dashboard of automobile 35, and displays information from the audio, navigation system, automobile status management system, etc. Cluster display 302 displays the speedometer, etc. Side displays 303 are provided on the left and right sides of the dashboard, and function as side mirrors by displaying images from cameras.

[0060] The interior of an automobile 35 in which these in-vehicle displays 30 are installed can become a high-temperature environment due to the influence of sunlight, etc. The in-vehicle display 30 can have a long high-temperature life by using the display device 20 including the organic light-emitting device 10. Therefore, the in-vehicle display 30 exposed to a high-temperature environment can provide good display for a long period of time.

[0061] (Embodiment 5) Next, a fifth embodiment will be described. This embodiment relates to an electronic device using the display device according to the third embodiment. FIG. 9 is a perspective view of a smartphone 40 as an electronic device. In this smartphone 40, the display device 20 according to the third embodiment is provided inside a housing 401, and a cover glass 402 is provided on the display surface side of the display device 20. In addition, these housings are provided with devices having functions required for a smartphone, such as a transmitting / receiving device, various control devices, a storage device, an audio device including a speaker and a microphone, a battery, etc.

[0062] The smartphone 40 may be used in a high-temperature environment, such as outdoors. The smartphone 40 can have a long high-temperature life by using the display device 20. Therefore, the smartphone 40 exposed to a high-temperature environment can provide good display for a long period of time.

[0063] Although the present disclosure has been described in accordance with the embodiments, the present disclosure is not limited to these embodiments. It will be obvious to those skilled in the art that various modifications, improvements, combinations, and the like are possible.

[0064] The materials used for each layer constituting the organic light-emitting device 10 are not limited to the materials exemplified in the above embodiment. As long as the relationships 0 eV<ΔE1≦0.37 and ΔE3≦0.3 are satisfied, the materials used for the hole transport layer 13, the first host material, and the second host material can be appropriately selected. As described above, the HOMO levels of the hole transport layer 13, the first host material, and the second host material can be measured using atmospheric photoelectron yield spectroscopy or the like. By using such a measurement method, it is possible to select a suitable material for each layer.

[0065] In addition, the anode electrode 12, the electron transport layer 15, the electron injection layer 16, and the cathode electrode 17 are not limited to a single-layer structure, and may have a multilayer structure. In addition, the materials used for the anode electrode 12, the electron transport layer 15, the electron injection layer 16, and the cathode electrode 17 are not limited to the above-mentioned materials, and may be selected arbitrarily. The electron injection layer 16 does not necessarily have to be formed.

[0066] In the fourth embodiment, the CID 301, the cluster display 302, and the side display 303 are given as examples of the in-vehicle display 30, but the in-vehicle display 30 is not limited to these. The in-vehicle display 30 can be any display provided in a vehicle.

[0067] In embodiment 5, a smartphone is given as an example of an electronic device, but the present invention is not limited to this, and the electronic device may be, for example, a personal computer, a PDA (Personal Digital Assistance), a tablet terminal, a head-mounted display, a projector, a digital (video) camera, etc. [Explanation of symbols]

[0068] 10 Organic light-emitting device 11 Substrate 12 Anode electrode 13 Hole transport layer 14 Emitting layer 15 Electron transport layer 16 Electron injection layer 17 Cathode Electrode 20 Display device 30 In-vehicle display 35 Automobiles 40 Smartphone 100 TFT Substrate 114 Cathode electrode formation area 125 Display area 131 Scan Driver 132 Emission Driver 133 Protection circuit 134 Driver IC 135 FPC 200 Sealing substrate 251R Red subpixel 251G Green subpixel 251B Blue subpixel 269R Organic light-emitting layer 269B Blue organic light-emitting layer 269G Green organic light-emitting layer 300 joint 301 CID 302 Cluster Display 303 Side Display 401 Case 402 Cover glass

Claims

1. an anode electrode and a cathode electrode disposed opposite each other; a light-emitting layer disposed between the anode electrode and the cathode electrode; a hole transport layer disposed between the anode electrode and the light emitting layer and in contact with the light emitting layer; Equipped with the light-emitting layer includes a first host material and a second host material; a difference between a HOMO level of the hole transport layer and a HOMO level of the first host material is smaller than a difference between a HOMO level of the hole transport layer and a HOMO level of the second host material; a difference between a HOMO level of the hole transport layer and a HOMO level of the first host material is greater than 0 and is not greater than 0.37 eV; The weight ratio of the first host material to the second host material is 55:45 to 70:

30. Organic light-emitting device.

2. The weight ratio of the first host material to the second host material is 60:40 to 70:

30.

10. The organic light emitting device of claim 1.

3. a difference between a HOMO level of the first host material and a HOMO level of the second host material is 0.3 eV or less; 3. An organic light-emitting device according to claim 1 or 2.

4. a difference between a HOMO level of the hole transport layer and a HOMO level of the first host material is 0.34 eV or less; An organic light-emitting device according to any one of claims 1 to 3.

5. A display device comprising the organic light-emitting device according to claim 1 .

6. An in-vehicle display comprising the display device according to claim 5.

7. An electronic device comprising the display device according to claim 5.

8. A vehicle comprising the on-board display according to claim 6.

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