Light-emitting device, light-emitting apparatus, electronic device and lighting apparatus

Abstract

To provide a light-emitting device with high luminous efficiency.SOLUTION: A light-emitting device includes an anode, a cathode, and an EL layer existing between the anode and the cathode. The EL layer includes a light-emitting layer and an electron-transporting layer. The light-emitting layer contains a light-emitting material. The electron-transporting layer contains an organic compound with an electron-transporting property and metal complex of alkali metal. In the organic compound with an electron-transporting property, the normal light refractive index of the light emitted from the light-emitting material at a peak wavelength is 1.50 or more and 1.75 or less. In the metal complex of alkali metal, the normal light refractive index of the light emitted from the light-emitting material at the peak wavelength is 1.45 or more and 1.70 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] One embodiment of the present invention relates to an organic compound, a light-emitting element, a light-emitting device, a display module, a lighting module, a display device, a light-emitting device, an electronic device, a lighting device, and an electronic device. Note that one embodiment of the present invention is not limited to the above technical field. The technical field of one embodiment of the invention disclosed in this specification etc. relates to an object, a method, or a manufacturing method. Alternatively, one embodiment of the present invention relates to a process, a machine, manufacture, or a composition of matter. Therefore, more specific examples of the technical field of one embodiment of the present invention disclosed in this specification include semiconductor devices, display devices, liquid crystal display devices, light-emitting devices, lighting devices, power storage devices, memory devices, imaging devices, driving methods thereof, and manufacturing methods thereof. [Background technology]

[0002] Light-emitting devices (organic EL devices) that utilize electroluminescence (EL) using organic compounds are becoming more and more common. The basic structure of these light-emitting devices is a pair of electrodes sandwiching an organic compound layer (EL layer) containing a light-emitting material between them. By applying a voltage to this device, carriers are injected, and the recombination energy of these carriers is utilized to emit light from the light-emitting material.

[0003] Since such light-emitting devices are self-luminous, when used as display pixels, they offer advantages such as higher visibility and no need for backlighting compared to liquid crystal displays, making them particularly suitable for flat panel displays. Another major advantage of displays using such light-emitting devices is that they can be fabricated to be thin and lightweight. Another feature is their extremely fast response time.

[0004] Furthermore, these light-emitting devices can emit light continuously in two dimensions, making it possible to obtain surface light emission. This is a feature that is difficult to obtain with point light sources such as incandescent bulbs and LEDs, or linear light sources such as fluorescent lamps, making them highly useful as surface light sources for lighting applications.

[0005] Displays and lighting devices using such light-emitting devices are suitable for a variety of electronic devices, but research and development is ongoing to find light-emitting devices with even better characteristics.

[0006] One of the problems often cited when discussing organic EL devices is their low light extraction efficiency. In particular, attenuation due to reflection caused by differences in the refractive index of adjacent layers is a major factor in reducing the efficiency of light-emitting devices. To reduce this effect, a structure has been proposed in which a layer made of a low-refractive-index material is formed inside the EL layer (see, for example, Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] Jaeho Lee and 12 others, "Synergetic electrode architecture for efficient graphene-based flexible organic light-emitting diodes," Nature Communications, June 2, 2016, DOI: 10.1038 / ncomms11791 Summary of the Invention [Problem to be solved by the invention]

[0008] An object of one embodiment of the present invention is to provide a light-emitting device with high emission efficiency, or to provide any one of a light-emitting device, a light-emitting apparatus, an electronic device, a display device, and an electronic device with low power consumption.

[0009] Another object of another embodiment of the present invention is to provide a novel organometallic complex (metal complex). Another object of another embodiment of the present invention is to provide a metal complex that can be used in a light-emitting device with a low driving voltage. Another object of another embodiment of the present invention is to provide a metal complex that has an electron-transporting layer with a low refractive index and can be used in a light-emitting device with a low driving voltage.

[0010] The present invention is intended to solve any one of the above problems. [Means for solving the problem]

[0011] One embodiment of the present invention is a light-emitting device including an anode, a cathode, and an EL layer located between the anode and the cathode. The EL layer includes a light-emitting layer and an electron-transport layer. The light-emitting layer includes a light-emitting material. The electron-transport layer includes an organic compound having electron-transport properties and a metal complex of an alkali metal. The organic compound having electron-transport properties has an ordinary refractive index of 1.50 or more and 1.75 or less at a peak wavelength of light emitted from the light-emitting material, and the metal complex of the alkali metal has an ordinary refractive index of 1.45 or more and 1.70 or less at the peak wavelength of light emitted from the light-emitting material.

[0012] Another embodiment of the present invention is a light-emitting device comprising an anode, a cathode, and an EL layer located between the anode and the cathode, the EL layer comprising a light-emitting layer and an electron-transporting layer, the light-emitting layer comprising a light-emitting material, the electron-transporting layer comprising an organic compound having electron-transporting properties and a metal complex of an alkali metal, wherein the sum of the ordinary refractive index at the peak wavelength of light emitted by the light-emitting material of the organic compound having electron-transporting properties and the ordinary refractive index at the peak wavelength of light emitted by the light-emitting material of the alkali metal complex, divided by 2, is 1.50 or greater and less than 1.75.

[0013] Another embodiment of the present invention is a light-emitting device comprising an anode, a cathode, and an EL layer located between the anode and the cathode, the EL layer comprising a light-emitting layer and an electron-transporting layer, the light-emitting layer comprising a light-emitting material, the electron-transporting layer comprising an organic compound having electron-transporting properties and a metal complex of an alkali metal, and the ordinary refractive index at the peak wavelength of light emitted by the light-emitting material of the electron-transporting layer is 1.50 or more and less than 1.75.

[0014] Another embodiment of the present invention is a light-emitting device comprising an anode, a cathode, and an EL layer located between the anode and the cathode. The EL layer comprises an emitting layer and an electron-transporting layer. The electron-transporting layer comprises an organic compound having electron-transporting properties and a metal complex of an alkali metal. The organic compound having electron-transporting properties has an ordinary refractive index of 1.50 or more and 1.75 or less for light having a wavelength in the range of 455 nm or more and 465 nm or less, and the metal complex of the alkali metal has an ordinary refractive index of 1.45 or more and 1.70 or less for light having a wavelength in the range of 455 nm or more and 465 nm or less.

[0015] Another embodiment of the present invention is a light-emitting device comprising an anode, a cathode, and an EL layer located between the anode and the cathode, wherein the EL layer comprises an emitting layer and an electron-transporting layer, and the electron-transporting layer comprises an organic compound having electron-transporting properties and a metal complex of an alkali metal, wherein the sum of the ordinary refractive index of the organic compound having electron-transporting properties for light of a wavelength in the range of 455 nm to 465 nm and the ordinary refractive index of the alkali metal complex for light of a wavelength in the range of 455 nm to 465 nm, and divided by 2, is 1.50 or greater and less than 1.75.

[0016] Another embodiment of the present invention is a light-emitting device comprising an anode, a cathode, and an EL layer located between the anode and the cathode, the EL layer comprising an emitting layer and an electron-transporting layer, the electron-transporting layer comprising an organic compound having electron-transporting properties and a metal complex of an alkali metal, and the electron-transporting layer has an ordinary refractive index of 1.50 or more and less than 1.75 for light of any wavelength in the range of 455 nm or more and 465 nm or less.

[0017] Another embodiment of the present invention is a light-emitting device comprising an anode, a cathode, and an EL layer located between the anode and the cathode. The EL layer comprises an emitting layer and an electron-transporting layer. The electron-transporting layer comprises an organic compound having electron-transporting properties and a metal complex of an alkali metal, wherein the organic compound having electron-transporting properties has an ordinary refractive index for light of 633 nm of 1.45 or more and 1.70 or less, and the alkali metal complex has an ordinary refractive index for light of 633 nm of 1.40 or more and 1.65 or less.

[0018] Another embodiment of the present invention is a light-emitting device comprising an anode, a cathode, and an EL layer located between the anode and the cathode, wherein the EL layer comprises an emitting layer and an electron-transporting layer, and the electron-transporting layer comprises an organic compound having electron-transporting properties and a metal complex of an alkali metal, wherein the sum of the ordinary refractive index of the organic compound having electron-transporting properties for light of 633 nm and the ordinary refractive index of the metal complex of the alkali metal for light of 633 nm divided by 2 is 1.45 or greater but less than 1.70.

[0019] Another embodiment of the present invention is a light-emitting device comprising an anode, a cathode, and an EL layer located between the anode and the cathode, the EL layer comprising an emitting layer and an electron-transporting layer, the electron-transporting layer comprising an organic compound having electron-transporting properties and a metal complex of an alkali metal, and the ordinary refractive index of the electron-transporting layer for light of 633 nm is 1.45 or more and less than 1.70.

[0020] Another embodiment of the present invention is a light-emitting device having the above structure, in which both the organic compound having an electron-transporting property and the metal complex of an alkali metal have an alkyl group or a cycloalkyl group.

[0021] Another embodiment of the present invention is a light-emitting device having the above structure, in which the alkyl group included in the organic compound having electron-transport properties is either a branched alkyl group or an alkyl group having 3 or 4 carbon atoms, and the alkyl group included in the metal complex of the alkali metal is an alkyl group having 1 to 3 carbon atoms.

[0022] Another embodiment of the present invention is a light-emitting device having the above structure, in which the alkyl group included in the organic compound having an electron-transporting property is a t-butyl group, and the alkyl group included in the metal complex of the alkali metal is a methyl group.

[0023] Another embodiment of the present invention is a method for manufacturing a semiconductor device comprising the steps of: 3 The light-emitting device is one in which the ratio of carbon atoms that form bonds through hybrid orbitals is 10% to 60% of the total number of carbon atoms in the organic compound.

[0024] Another embodiment of the present invention is a method for manufacturing a semiconductor device using the above structure, wherein an organic compound having an electron-transport property is added to the semiconductor device. 1 Measurement by H-NMR showed that the integral value of signals below 4 ppm exceeded the integral value of signals above 4 ppm, indicating that this is a light-emitting device.

[0025] Another embodiment of the present invention is a light-emitting device having any of the above structures, in which the organic compound having an electron-transport property has a triazine skeleton or a diazine skeleton.

[0026] Another embodiment of the present invention is a light-emitting device in which an organic compound having an electron-transporting property has a benzene ring.

[0027] Another embodiment of the present invention is a light-emitting device including an anode, a cathode, and an EL layer located between the anode and the cathode, the EL layer including a light-emitting layer and an electron-transport layer, the light-emitting layer including a light-emitting material, and the electron-transport layer including an organic compound having a π-electron-deficient heteroaromatic ring skeleton and a metal complex of an alkali metal, wherein the sum of the ordinary refractive index at a peak wavelength of light emitted by the light-emitting material, the organic compound having a π-electron-deficient heteroaromatic ring skeleton, and the ordinary refractive index at the peak wavelength of light emitted by the light-emitting material, the metal complex of an alkali metal, divided by 2 is 1.50 or greater and less than 1.75.

[0028] Another embodiment of the present invention is a light-emitting device including an anode, a cathode, and an EL layer located between the anode and the cathode, the EL layer including a light-emitting layer and an electron-transport layer, the light-emitting layer including a light-emitting material, the electron-transport layer including an organic compound having a π-electron-deficient heteroaromatic skeleton and a metal complex of an alkali metal, and the ordinary refractive index at the peak wavelength of light emitted by the light-emitting material of the electron-transport layer is 1.50 or more and less than 1.75.

[0029] Another embodiment of the present invention is a light-emitting device comprising an anode, a cathode, and an EL layer located between the anode and the cathode. The EL layer comprises an emitting layer and an electron-transporting layer. The electron-transporting layer comprises an organic compound having a π-electron-deficient heteroaromatic ring skeleton and a metal complex of an alkali metal. The organic compound having the π-electron-deficient heteroaromatic ring skeleton has an ordinary refractive index of 1.50 or more and 1.75 or less for light having a wavelength in the range of 455 nm or more and 465 nm or less, and the metal complex of the alkali metal has an ordinary refractive index of 1.45 or more and 1.70 or less for light having a wavelength in the range of 455 nm or more and 465 nm or less.

[0030] Another embodiment of the present invention is a light-emitting device including an anode, a cathode, and an EL layer located between the anode and the cathode, wherein the EL layer includes an light-emitting layer and an electron-transporting layer, and the electron-transporting layer includes an organic compound having a π-electron-deficient heteroaromatic ring skeleton and a metal complex of an alkali metal, wherein the sum of the ordinary refractive index of the organic compound having the π-electron-deficient heteroaromatic ring skeleton for light of a wavelength in the range of 455 nm to 465 nm and the ordinary refractive index of the metal complex of the alkali metal for light of a wavelength in the range of 455 nm to 465 nm, and the sum divided by 2, is 1.50 or greater and less than 1.75.

[0031] Another embodiment of the present invention is a light-emitting device comprising an anode, a cathode, and an EL layer located between the anode and the cathode, the EL layer comprising an emitting layer and an electron-transporting layer, the electron-transporting layer comprising an organic compound having a π-electron-deficient heteroaromatic ring skeleton and a metal complex of an alkali metal, and the ordinary refractive index of the electron-transporting layer for light having a wavelength in the range of 455 nm to 465 nm is 1.50 or more and less than 1.75.

[0032] Another embodiment of the present invention is a light-emitting device comprising an anode, a cathode, and an EL layer located between the anode and the cathode. The EL layer comprises an emitting layer and an electron-transporting layer. The electron-transporting layer comprises an organic compound having a π-electron-deficient heteroaromatic ring skeleton and a metal complex of an alkali metal. The organic compound having the π-electron-deficient heteroaromatic ring skeleton has an ordinary refractive index for 633 nm light of 1.45 to 1.70, and the metal complex of the alkali metal has an ordinary refractive index for 633 nm light of 1.40 to 1.65.

[0033] Another embodiment of the present invention is a light-emitting device including an anode, a cathode, and an EL layer located between the anode and the cathode, wherein the EL layer includes an emitting layer and an electron-transporting layer, and the electron-transporting layer includes an organic compound having a π-electron-deficient heteroaromatic ring skeleton and a metal complex of an alkali metal, wherein the sum of the ordinary refractive index of the organic compound having a π-electron-deficient heteroaromatic ring skeleton for light of 633 nm and the ordinary refractive index of the metal complex of the alkali metal for light of 633 nm, divided by 2, is 1.45 or greater and less than 1.70.

[0034] Another embodiment of the present invention is a light-emitting device including an anode, a cathode, and an EL layer located between the anode and the cathode, the EL layer including a light-emitting layer and an electron-transporting layer, the electron-transporting layer including an organic compound having a π-electron-deficient heteroaromatic skeleton and a metal complex of an alkali metal, and the ordinary refractive index of the electron-transporting layer for light of 633 nm is 1.45 or more and less than 1.70.

[0035] Another embodiment of the present invention is a light-emitting device having the above structure, in which both the organic compound having a π-electron-deficient heteroaromatic ring skeleton and the metal complex of an alkali metal have an alkyl group or a cycloalkyl group.

[0036] Another embodiment of the present invention is a light-emitting device having the above structure, in which the alkyl group included in the organic compound having a π-electron-deficient heteroaromatic ring skeleton is either a branched alkyl group or an alkyl group having 3 or 4 carbon atoms, and the alkyl group included in the metal complex of the alkali metal is an alkyl group having 1 to 3 carbon atoms.

[0037] Another embodiment of the present invention is a light-emitting device having the above structure, in which the alkyl group included in the organic compound having a π-electron-deficient heteroaromatic ring skeleton is a t-butyl group, and the alkyl group included in the metal complex of the alkali metal is a methyl group.

[0038] Another embodiment of the present invention is a compound having the above structure, wherein the organic compound having a π-electron-deficient heteroaromatic ring skeleton is sp 3 The light-emitting device is one in which the ratio of carbon atoms that form bonds through hybrid orbitals is 10% to 60% of the total number of carbon atoms in the organic compound.

[0039] Another embodiment of the present invention is a compound having the above structure, wherein the compound further comprises an organic compound having a π-electron-deficient heteroaromatic ring skeleton. 1 Measurement by H-NMR showed that the integral value of signals below 4 ppm exceeded the integral value of signals above 4 ppm, indicating that this is a light-emitting device.

[0040] Another embodiment of the present invention is a light-emitting device having any of the above structures, in which the organic compound having a π-electron-deficient heteroaromatic ring skeleton has a triazine skeleton or a diazine skeleton.

[0041] Another embodiment of the present invention is a light-emitting device having the above structure, in which the metal complex of an alkali metal is a metal complex having a ligand including an 8-quinolinolato structure.

[0042] Another embodiment of the present invention is a light-emitting device having any of the above structures, in which the metal complex of an alkali metal has one alkyl group, and the one alkyl group has 1 to 3 carbon atoms.

[0043] Another embodiment of the present invention is a light-emitting device having any of the above structures, in which the metal complex of an alkali metal is a metal complex of lithium.

[0044] Another embodiment of the present invention is a light-emitting device having the above structure, in which the metal complex is a metal complex represented by the following general formula (G0):

[0045] [ka]

[0046] In the above general formula (G0), M is an alkali metal, R 1 is an alkyl group having 1 to 3 carbon atoms, R 2 represents hydrogen or an alkyl group having 1 to 3 carbon atoms.

[0047] Alternatively, another embodiment of the present invention is a method for manufacturing a semiconductor device according to the above-described embodiment, wherein R 2 is a methyl group.

[0048] Another embodiment of the present invention is a light-emitting device having the above structure, in which the metal complex is a metal complex represented by any one of the following general formulas (G1) to (G3).

[0049] [ka]

[0050] However, in the above general formulas (G1) to (G3), R 1 represents an alkyl group having 1 to 3 carbon atoms, and in general formula (G3), R 2 represents an alkyl group having 1 to 3 carbon atoms.

[0051] Alternatively, another embodiment of the present invention is a method for manufacturing a semiconductor device according to the above-described embodiment, wherein R 1 is a methyl group.

[0052] Alternatively, another embodiment of the present invention is a method for manufacturing a semiconductor device according to the above-described embodiment, wherein R 1 is an ethyl group.

[0053] Another embodiment of the present invention is a light-emitting device having the above structure, in which M is lithium.

[0054] Another embodiment of the present invention is a light-emitting device having the above structure, in which M is sodium.

[0055] Another embodiment of the present invention is a metal complex represented by the following general formula (G0).

[0056] [ka]

[0057] In the above general formula (G0), M is an alkali metal, R 1 is an alkyl group having 1 to 3 carbon atoms, R 2 represents hydrogen or an alkyl group having 1 to 3 carbon atoms.

[0058] Alternatively, another embodiment of the present invention is a method for manufacturing a semiconductor device according to the above-described embodiment, wherein R 2 is a metal complex in which the methyl group is

[0059] Another embodiment of the present invention is a metal complex represented by any one of the following general formulas (G1) to (G3).

[0060] [ka]

[0061] However, in the above general formulas (G1) to (G3), R 1 and R 2each independently represents an alkyl group having 1 to 3 carbon atoms.

[0062] Alternatively, another embodiment of the present invention is a method for manufacturing a semiconductor device according to the above-described embodiment, wherein R 1 is a metal complex in which the methyl group is

[0063] Alternatively, another embodiment of the present invention is a method for manufacturing a semiconductor device according to the above-described embodiment, wherein R 1 is a metal complex in which the methyl group is an ethyl group.

[0064] Another embodiment of the present invention is a metal complex having the above structure, in which M is lithium.

[0065] Another embodiment of the present invention is a metal complex having the above structure, in which M is sodium.

[0066] Another embodiment of the present invention is a light-emitting device including any of the above metal complexes.

[0067] Another embodiment of the present invention is a light-emitting device in which the ordinary refractive index at the peak wavelength of light emitted from a light-emitting material that is a metal complex represented by General Formula (G1) is 1.45 to 1.70.

[0068] Another embodiment of the present invention is a light-emitting device including the above metal complex between a light-emitting layer and a cathode.

[0069] Another embodiment of the present invention is a light-emitting device including the above metal complex in an electron-transporting layer.

[0070] Another embodiment of the present invention is an electronic device including any of the above light-emitting devices and at least one of a sensor, an operation button, a speaker, and a microphone.

[0071] Another embodiment of the present invention is a light-emitting device including any of the above light-emitting devices and at least one of a transistor and a substrate.

[0072] Another embodiment of the present invention is a lighting device including any of the above light-emitting devices and a housing.

[0073] In this specification, the term "light-emitting device" includes an image display device using a light-emitting device. The term "light-emitting device" may also include a module in which a connector, such as an anisotropic conductive film or TCP (Tape Carrier Package), is attached to a light-emitting device, a module in which a printed wiring board is provided at the end of the TCP, or a module in which an IC (integrated circuit) is directly mounted on a light-emitting device using a COG (Chip On Glass) method. Furthermore, lighting fixtures and the like may include a light-emitting device. [Effects of the Invention]

[0074] According to one embodiment of the present invention, a light-emitting device with high emission efficiency or a light-emitting device, a light-emitting apparatus, an electronic device, a display device, or an electronic device with low power consumption can be provided.

[0075] Another embodiment of the present invention provides a novel organometallic complex (metal complex). Alternatively, another embodiment of the present invention provides a metal complex applicable to a light-emitting device with a low driving voltage. Alternatively, another embodiment of the present invention provides a metal complex applicable to a light-emitting device having an electron transport layer with a low refractive index and a low driving voltage.

[0076] Note that the description of these effects does not preclude the existence of other effects. Note that one embodiment of the present invention does not necessarily have all of these effects. Note that effects other than these will become apparent from the description in the specification, drawings, claims, etc., and it is possible to extract other effects from the description in the specification, drawings, claims, etc. [Brief explanation of the drawings]

[0077] [Figure 1]1(A), 1(B) and 1(C) are schematic diagrams of light-emitting devices. [Figure 2] 2(A) and 2(B) are diagrams showing an active matrix light emitting device. [Figure 3] 3(A) and 3(B) are diagrams showing an active matrix light emitting device. [Figure 4] FIG. 4 is a diagram showing an active matrix light emitting device. [Figure 5] 5(A) and 5(B) are diagrams showing a passive matrix light emitting device. [Figure 6] 6(A) and 6(B) are diagrams showing the lighting device. [Figure 7] 7(A), 7(B1), 7(B2) and 7(C) are diagrams showing electronic devices. [Figure 8] 8(A), 8(B) and 8(C) are diagrams showing electronic devices. [Figure 9] FIG. 9 is a diagram showing a lighting device. [Figure 10] FIG. 10 is a diagram showing a lighting device. [Figure 11] FIG. 11 is a diagram showing an in-vehicle display device and a lighting device. [Figure 12] 12(A) and 12(B) are diagrams showing electronic devices. [Figure 13] 13(A), 13(B) and 13(C) are diagrams showing electronic devices. [Figure 14] FIG. 14 shows data obtained by measuring the refractive index of mmtBumBP-dmmtBuPTzn, mPn-mDMePyPTzn, Li-6mq, and Liq. [Figure 15] FIG. 15 shows the luminance-current density characteristics of the light-emitting device 1 and the comparative light-emitting device 1. [Figure 16] FIG. 16 shows the current efficiency-luminance characteristics of the light-emitting device 1 and the comparative light-emitting device 1. [Figure 17] FIG. 17 shows the luminance-voltage characteristics of the light-emitting device 1 and the comparative light-emitting device 1. [Figure 18]FIG. 18 shows the current-voltage characteristics of the light-emitting device 1 and the comparative light-emitting device 1. [Figure 19] FIG. 19 shows the blue index-luminance characteristics of the light-emitting device 1 and the comparative light-emitting device 1. [Figure 20] FIG. 20 shows the emission spectra of the light-emitting device 1 and the comparative light-emitting device 1. [Figure 21] FIG. 21 shows data obtained by measuring the refractive index of mmtBumBP-dmmtBuPTzn, Li-6mq, and Liq. [Figure 22] FIG. 22 shows the luminance-current density characteristics of the light-emitting device 2 and the comparative light-emitting device 2. [Figure 23] FIG. 23 shows the current efficiency-luminance characteristics of the light-emitting device 2 and the comparative light-emitting device 2. [Figure 24] FIG. 24 shows the luminance-voltage characteristics of the light-emitting device 2 and the comparative light-emitting device 2. [Figure 25] FIG. 25 shows the current-voltage characteristics of the light-emitting device 2 and the comparative light-emitting device 2. [Figure 26] FIG. 26 shows the blue index-luminance characteristics of the light-emitting device 2 and the comparative light-emitting device 2. [Figure 27] FIG. 27 shows the emission spectra of the light-emitting device 2 and the comparative light-emitting device 2. [Figure 28] FIG. 28 shows data obtained by measuring the refractive index of mPn-mDMePyPTzn, Li-6mq, and Liq. [Figure 29] FIG. 29 shows the luminance-current density characteristics of the light-emitting device 3 and the comparative light-emitting device 3. [Figure 30] FIG. 30 shows the current efficiency-luminance characteristics of the light-emitting device 3 and the comparative light-emitting device 3. [Figure 31] FIG. 31 shows the luminance-voltage characteristics of the light-emitting device 3 and the comparative light-emitting device 3. [Figure 32] FIG. 32 shows the current-voltage characteristics of the light-emitting device 3 and the comparative light-emitting device 3. [Figure 33] FIG. 33 shows the emission spectra of the light-emitting device 3 and the comparative light-emitting device 3. [Figure 34] FIG. 34 shows the blue index-luminance characteristics of the light-emitting device 3 and the comparative light-emitting device 3. [Figure 35] FIG. 35 shows the absorption and emission spectra of Li-6mq in a dehydrated acetone solution. [Figure 36] FIG. 36 shows data obtained by measuring the refractive index of mmtBumBP-dmmtBuPTzn. [Figure 37] FIG. 37 shows data obtained by measuring the refractive index of mmtBumBPTzn, mPn-mDMePyPTzn, Li-6mq, and Liq. [Figure 38] FIG. 38 shows the luminance-current density characteristics of light-emitting device 4, comparative light-emitting device 4, and comparative light-emitting device 5. [Figure 39] FIG. 39 shows the current efficiency-luminance characteristics of light-emitting device 4, comparative light-emitting device 4, and comparative light-emitting device 5. [Figure 40] FIG. 40 shows the luminance-voltage characteristics of light-emitting device 4, comparative light-emitting device 4, and comparative light-emitting device 5. [Figure 41] FIG. 41 shows the current density-voltage characteristics of light-emitting device 4, comparative light-emitting device 4, and comparative light-emitting device 5. [Figure 42] FIG. 42 shows the emission spectra of Light-Emitting Device 4, Comparative Light-Emitting Device 4, and Comparative Light-Emitting Device 5. [Figure 43] FIG. 43 shows the blue index-luminance characteristics of Light-Emitting Device 4, Comparative Light-Emitting Device 4, and Comparative Light-Emitting Device 5. [Figure 44] FIG. 44 shows data obtained by measuring the refractive index of mmtBumBPTzn. [Figure 45] FIG. 45 shows the absorption and emission spectra of Li-6eq in a dehydrated acetone solution. [Figure 46] Figure 46 shows the data obtained by measuring the refractive index of Li-6eq. [Figure 47] Figure 47 shows the absorption and emission spectra of Na-6mq in a dehydrated acetone solution. [Figure 48]FIG. 48 is a graph showing the luminance-current density characteristics of light-emitting device 5 and light-emitting device 6. As shown in FIG. [Figure 49] FIG. 49 is a diagram showing the luminance-voltage characteristics of the light-emitting device 5 and the light-emitting device 6. As shown in FIG. [Figure 50] FIG. 50 is a graph showing the current efficiency-luminance characteristics of the light-emitting device 5 and the light-emitting device 6. As shown in FIG. [Figure 51] FIG. 51 is a graph showing the current density-voltage characteristics of light-emitting device 5 and light-emitting device 6. As shown in FIG. [Figure 52] FIG. 52 is a graph showing the external quantum efficiency-luminance characteristics of the light-emitting device 5 and the light-emitting device 6. As shown in FIG. [Figure 53] FIG. 53 is a graph showing the power efficiency-luminance characteristics of the light-emitting device 5 and the light-emitting device 6. As shown in FIG. [Figure 54] FIG. 54 shows the emission spectra of light-emitting device 5 and light-emitting device 6. As shown in FIG. [Figure 55] FIG. 55 is a graph showing the luminance-current density characteristics of the light-emitting device 7, the light-emitting device 8, and the comparative light-emitting device 6. As shown in FIG. [Figure 56] FIG. 56 is a graph showing the luminance-voltage characteristics of the light-emitting device 7, the light-emitting device 8, and the comparative light-emitting device 6. In FIG. [Figure 57] FIG. 57 is a graph showing the current efficiency-luminance characteristics of the light-emitting device 7, the light-emitting device 8, and the comparative light-emitting device 6. [Figure 58] FIG. 58 is a graph showing the current density-voltage characteristics of the light-emitting device 7, the light-emitting device 8, and the comparative light-emitting device 6. [Figure 59] FIG. 59 is a graph showing the external quantum efficiency-luminance characteristics of the light-emitting device 7, the light-emitting device 8, and the comparative light-emitting device 6. [Figure 60] FIG. 60 is a graph showing the power efficiency-luminance characteristics of the light-emitting device 7, the light-emitting device 8, and the comparative light-emitting device 6. [Figure 61] FIG. 61 shows the emission spectra of the light-emitting device 7, the light-emitting device 8, and the comparative light-emitting device 6. As shown in FIG. [Figure 62]FIG. 62 is a diagram showing the luminance-current density characteristics of light-emitting device 9, light-emitting device 10, light-emitting device 11, and light-emitting device 12. In FIG. [Figure 63] FIG. 63 is a diagram showing the luminance-voltage characteristics of light-emitting device 9, light-emitting device 10, light-emitting device 11, and light-emitting device 12. In FIG. [Figure 64] FIG. 64 is a graph showing the current efficiency-luminance characteristics of light-emitting device 9, light-emitting device 10, light-emitting device 11, and light-emitting device 12. [Figure 65] FIG. 65 is a diagram showing the current density-voltage characteristics of light-emitting device 9, light-emitting device 10, light-emitting device 11, and light-emitting device 12. [Figure 66] FIG. 66 is a graph showing the external quantum efficiency-luminance characteristics of light-emitting device 9, light-emitting device 10, light-emitting device 11, and light-emitting device 12. [Figure 67] FIG. 67 is a diagram showing the emission spectra of light-emitting device 9, light-emitting device 10, light-emitting device 11, and light-emitting device 12. [Figure 68] Figure 68 shows the absorption and emission spectra of Li-3,6dmq in a dehydrated acetone solution. [Figure 69] FIG. 69 is a graph showing the luminance-current density characteristics of light-emitting device 13, light-emitting device 14, and comparative light-emitting device 7. [Figure 70] FIG. 70 is a graph showing the luminance-voltage characteristics of the light-emitting device 13, the light-emitting device 14, and the comparative light-emitting device 7. In FIG. [Figure 71] FIG. 71 is a graph showing the current efficiency-luminance characteristics of light-emitting device 13, light-emitting device 14, and comparative light-emitting device 7. [Figure 72] FIG. 72 is a graph showing the current density-voltage characteristics of light-emitting device 13, light-emitting device 14, and comparative light-emitting device 7. [Figure 73] FIG. 73 is a graph showing the external quantum efficiency-luminance characteristics of the light-emitting device 13, the light-emitting device 14, and the comparative light-emitting device 7. [Figure 74]FIG. 74 is a diagram showing the emission spectra of the light-emitting device 13, the light-emitting device 14, and the comparative light-emitting device 7. [Figure 75] FIG. 75 shows data obtained by measuring the refractive indexes of mmtBumBPTzn, Li-mq, Li-5mq, Li-6mq, and Li-7mq. DETAILED DESCRIPTION OF THE INVENTION

[0078] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and it will be readily understood by those skilled in the art that various changes in form and details can be made without departing from the spirit and scope of the present invention. Therefore, the present invention should not be interpreted as being limited to the description of the embodiments shown below.

[0079] (Embodiment 1)

[0080] 1A illustrates a light-emitting device according to one embodiment of the present invention. The light-emitting device includes an anode 101, a cathode 102, and an EL layer 103. The EL layer 103 includes a light-emitting layer 113 and an electron-transporting layer 114.

[0081] The light-emitting layer 113 contains at least a light-emitting material, and the electron-transporting layer 114 contains an organic compound having an electron-transporting property and a metal complex of an alkali metal.

[0082] The organic compound having electron-transport properties and the metal complex of an alkali metal contained in the electron-transport layer 114 in the light-emitting device of one embodiment of the present invention are preferably combined such that the sum of their ordinary refractive indices at the peak wavelength (λp) of light emitted from the light-emitting material contained in the light-emitting layer 113 divided by 2 is 1.50 or greater and less than 1.75, preferably 1.50 or greater and less than 1.70.

[0083] The refractive index of the organic compound having electron transport properties and the metal complex of an alkali metal is determined by measuring a thin film of the material. However, if anisotropy occurs in the material in such a thin film, the refractive index for ordinary light and the refractive index for extraordinary light may differ. If the thin film to be measured is in such a state, anisotropy analysis can be performed to separate the ordinary refractive index and the extraordinary refractive index and calculate each refractive index. In this specification, if the measured material has both an ordinary refractive index and an extraordinary refractive index, the ordinary refractive index is used as the index.

[0084] The electron-transport layer 114 using such a material can be a layer with a low refractive index, and by providing a layer with a low refractive index inside the EL layer, the light extraction efficiency can be improved, resulting in a light-emitting device with high emission efficiency. Generally, the refractive index of an organic compound constituting a light-emitting device is about 1.8 to 1.9, and the light-emitting device of one embodiment of the present invention can be a light-emitting device with high emission efficiency by including an electron-transport layer with a low refractive index.

[0085] In particular, since the electron transport layer 114 is provided between the light-emitting layer 113 and the cathode 102, it is suitable for a top-emission light-emitting device.

[0086] Note that the ordinary refractive index of the electron-transport layer 114 for light with λp in the light-emitting device of one embodiment of the present invention is preferably 1.50 or greater and less than 1.75, more preferably 1.50 or greater and less than 1.70.

[0087] In particular, the organic compound having electron transport properties contained in the electron transport layer 114 is preferably a substance having an ordinary refractive index for λp light of 1.50 or more and 1.75 or less, and the metal complex of an alkali metal is preferably a substance having an ordinary refractive index for λp light of 1.45 or more and 1.70 or less.

[0088] In the blue light-emitting device, the light-emitting material emits light having a wavelength (λ ) in the blue light-emitting region (455 nm or more and 465 nm or less). B), the organic compound having electron transport properties and the metal complex of the alkali metal emit light of λ B The sum of the ordinary refractive indices of the respective light components and divided by 2 is preferably 1.50 or more and less than 1.75, and more preferably 1.50 or more and less than 1.70.

[0089] Similarly, the λ of the electron transport layer 114 in the blue light-emitting device B The ordinary refractive index for light of λ is preferably 1.50 or more and less than 1.75, and more preferably 1.50 or more and less than 1.70. B Preferably, the ordinary refractive index for light of λ is 1.50 or more and 1.75 or less, more preferably 1.50 or more and 1.70 or less, and the metal complex of the alkali metal is B It is preferable that the material has an ordinary refractive index of 1.45 or more and 1.70 or less for the light.

[0090] In principle, the refractive index is larger on the short wavelength side and smaller on the long wavelength side, so that the organic compound having electron-transport properties and the metal complex of an alkali metal used in the electron-transport layer 114 of one embodiment of the present invention are preferably combined such that the sum of their ordinary refractive indices for light with a wavelength of 633 nm divided by two is 1.45 or more and less than 1.70. Similarly, the ordinary refractive index of the electron-transport layer 114 of one embodiment of the present invention for light with a wavelength of 633 nm is preferably 1.45 or more and less than 1.70. In particular, the ordinary refractive index of the organic compound having electron-transport properties used in the electron-transport layer 114 of one embodiment of the present invention for light with a wavelength of 633 nm is preferably 1.45 or more and 1.70 or less, and the ordinary refractive index of the alkali metal complex used in the electron-transport layer 114 of one embodiment of the present invention for light with a wavelength of 633 nm is preferably 1.40 or more and 1.65 or less.

[0091] Note that the organic compound having an electron-transport property and the metal complex of an alkali metal used in the electron-transport layer 114 of one embodiment of the present invention preferably have an alkyl group or a cycloalkyl group. When these have an alkyl group or a cycloalkyl group, the refractive index can be reduced, and the electron-transport layer 114 with a low refractive index can be realized.

[0092] Here, it has generally been thought that the presence of an alkyl group or a cycloalkyl group inhibits the interaction (also referred to as docking) between an organic compound having electron-transport properties and a metal complex of an alkali metal, resulting in an increase in driving voltage. However, in the light-emitting device of one embodiment of the present invention, there is no significant increase in driving voltage, and the light-emitting device can be provided with an electron-transport layer having a small refractive index and has good emission efficiency.

[0093] The alkyl group contained in the organic compound having electron transport properties is preferably a branched alkyl group, particularly preferably an alkyl group having 3 or 4 carbon atoms, and particularly preferably a tert-butyl group. The alkyl group contained in the metal complex of an alkali metal is preferably an alkyl group having any one of 1 to 3 carbon atoms, and particularly preferably a methyl group.

[0094] The organic compound having electron transport properties that constitutes the electron transport layer 114 has at least one six-membered heteroaromatic ring containing one to three nitrogen atoms, and has a plurality of aromatic hydrocarbon rings that form the ring and have 6 to 14 carbon atoms, at least two of the aromatic hydrocarbon rings being benzene rings, and sp 3 It is preferable that the compound contains an organic compound having a plurality of hydrocarbon groups that form bonds through hybrid orbitals.

[0095] In addition, the sp ratio of such organic compounds to the total number of carbon atoms in the molecule of the organic compound is 3 The ratio of the number of carbon atoms forming bonds through hybrid orbitals is preferably 10% or more and 60% or less, and more preferably 10% or more and 50% or less. Alternatively, such an organic compound is 1In the results of measuring the organic compound by H-NMR, the integral value of signals below 4 ppm is preferably at least half the integral value of signals at 4 ppm or higher.

[0096] In addition, all sp 3 It is preferred that the hydrocarbon group forming a bond via a hybrid orbital is bonded to the aromatic hydrocarbon ring having 6 to 14 carbon atoms forming the ring, and that the LUMO of the organic compound is not distributed in the aromatic hydrocarbon ring.

[0097] The organic compound corresponds to the organic compound contained in the electron transport layer 114 and having an electron transport property.

[0098] The organic compound having an electron transport property is preferably an organic compound represented by the following general formula (G1).

[0099] [ka]

[0100] In the formula, A represents a 6-membered heteroaromatic ring containing 1 to 3 nitrogen atoms, and is preferably a pyridine ring, a pyrimidine ring, a pyrazine ring, a pyridazine ring, or a triazine ring.

[0101] Also, R 0 represents any one of hydrogen, an alkyl group having 1 to 6 carbon atoms, an alicyclic group having 3 to 10 carbon atoms, and a substituent represented by formula (G1-1).

[0102] R 1 ~R 15 At least one of R is a phenyl group having a substituent, and the others each independently represent any one of hydrogen, an alkyl group having 1 to 6 carbon atoms, an alicyclic group having 3 to 10 carbon atoms, a substituted or unsubstituted ring-forming aromatic hydrocarbon group having 6 to 14 carbon atoms, and a substituted or unsubstituted pyridyl group. 1 , R 3 , R 5 , R 6 , R 8, R 10 , R 11 , R 13 and R 15 is preferably hydrogen. The phenyl group having a substituent has one or two substituents, each of which is independently any one of an alkyl group having 1 to 6 carbon atoms, an alicyclic group having 3 to 10 carbon atoms, and a substituted or unsubstituted aromatic hydrocarbon group having 6 to 14 carbon atoms in a ring.

[0103] The organic compound represented by the general formula (G1) has a plurality of hydrocarbon groups selected from alkyl groups having 1 to 6 carbon atoms and alicyclic groups having 3 to 10 carbon atoms, and the ratio of sp 3 The proportion of carbon atoms that form bonds through hybrid orbitals is between 10% and 60%.

[0104] Moreover, the organic compound having the electron transport property is preferably an organic compound represented by the following general formula (G3).

[0105] [ka]

[0106] In the formula, Q 1 ~Q 3 2 or 3 of the groups represent N, and the Q 1 ~Q 3 If two of the groups are N, the remaining group represents CH.

[0107] Also R 1 ~R 15 At least one of R is a phenyl group having a substituent, and the others each independently represent any one of hydrogen, an alkyl group having 1 to 6 carbon atoms, an alicyclic group having 3 to 10 carbon atoms, a substituted or unsubstituted ring-forming aromatic hydrocarbon group having 6 to 14 carbon atoms, and a substituted or unsubstituted pyridyl group. 1 , R 3 , R 5 , R 6 , R 8 , R 10 , R 11 , R 13and R 15 is preferably hydrogen. The phenyl group having a substituent has one or two substituents, each of which is independently any one of an alkyl group having 1 to 6 carbon atoms, an alicyclic group having 3 to 10 carbon atoms, and a substituted or unsubstituted aromatic hydrocarbon group having 6 to 14 carbon atoms in a ring.

[0108] The organic compound represented by the general formula (G3) has a plurality of hydrocarbon groups selected from alkyl groups having 1 to 6 carbon atoms and alicyclic groups having 3 to 10 carbon atoms, and the ratio of sp 3 The ratio of the number of carbon atoms forming bonds via hybrid orbitals is preferably 10% or more and 60% or less.

[0109] In the organic compound represented by the general formula (G1) or (G3), the substituted phenyl group is preferably a group represented by the following formula (G1-2).

[0110] [ka]

[0111] In the formula, α represents a substituted or unsubstituted phenylene group, and is preferably a meta-substituted phenylene group. Furthermore, when the meta-substituted phenylene group has one substituent, the substituent is preferably also substituted at the meta-position. The substituent is preferably an alkyl group having 1 to 6 carbon atoms or an alicyclic group having 3 to 10 carbon atoms, more preferably an alkyl group having 1 to 6 carbon atoms, and even more preferably a t-butyl group.

[0112] R 20 represents an alkyl group having 1 to 6 carbon atoms, an alicyclic group having 3 to 10 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 14 carbon atoms in a ring.

[0113] Furthermore, m and n represent 1 or 2. When m is 2, the multiple α may be the same or different. When n is 2, the multiple R20 may be the same or different. 20 is preferably a phenyl group, more preferably a phenyl group having an alkyl group having 1 to 6 carbon atoms or an alicyclic group having 3 to 10 carbon atoms at one or both of the two meta positions. The substituent that the phenyl group has at one or both of the two meta positions is more preferably an alkyl group having 1 to 6 carbon atoms, and even more preferably a t-butyl group.

[0114] The alkali metal complex is preferably a lithium complex or a sodium complex, and the ligand of the metal complex is preferably a ligand containing an 8-quinolinolato structure.

[0115] When the lithium complex or sodium complex containing the 8-quinolinolato structure has an alkyl group, the complex preferably has one or two alkyl groups. 8-quinolinolato-lithium having an alkyl group can be a metal complex with a low refractive index. Specifically, in a thin film state, the ordinary refractive index for light with a wavelength in the range of 455 nm to 465 nm can be 1.45 to 1.70, and the ordinary refractive index for light with a wavelength of 633 nm can be 1.40 to 1.65.

[0116] In particular, the use of an alkali metal complex having an 8-quinolinolato ligand with an alkyl group at the 6-position is effective in reducing the driving voltage of a light-emitting device. Among these, alkali metal complexes having a 6-alkyl-8-quinolinolato ligand or an alkali metal complex having a 3,6-dialkyl-8-quinolinolato ligand are preferred because they provide good light-emitting device characteristics. The alkyl group is more preferably a methyl group or an ethyl group.

[0117] Here, the alkali metal complex having an 8-quinolinolato ligand having an alkyl group at the 6-position can be represented by the following general formula (G0).

[0118] [ka]

[0119] In the above general formula (G0), M is an alkali metal, R 1 is an alkyl group having 1 to 3 carbon atoms, R 2 represents hydrogen or an alkyl group having 1 to 3 carbon atoms.

[0120] The metal complex represented by the general formula (G0) is preferably a metal complex represented by any one of the following general formulae (G1) to (G3).

[0121] [ka]

[0122] However, in the above general formulas (G1) to (G3), R 1 and R 2 Each independently represents an alkyl group having 1 to 3 carbon atoms. By using a metal complex having such a structure, a light-emitting device with high luminous efficiency and low driving voltage can be obtained. In addition, the metal complex represented by general formula (G3) is preferable because it has a stable deposition rate during vacuum deposition. In addition, R 1 and R 2 is a more preferable structure since each independently has one carbon atom, the driving voltage is lower than when each has two or more carbon atoms.

[0123] Among the metal complexes represented by the above general formulae (G1) to (G3), more preferred embodiments are metal complexes represented by the following structural formulae (100), (101), (102), and (200).

[0124] [ka]

[0125] [ka]

[0126] [ka]

[0127] [ka]

[0128] As described above, the organic compound having electron-transport properties used in the electron-transport layer 114 of the light-emitting device of one embodiment of the present invention preferably has an alkyl group having 3 or 4 carbon atoms. In particular, the organic compound having electron-transport properties preferably has a plurality of such alkyl groups. However, if the number of alkyl groups in the molecule is too large, the carrier transport property is reduced. Therefore, the sp 3 The ratio of carbon atoms forming bonds through hybrid orbitals to the total number of carbon atoms in the organic compound is preferably 10% to 60%, and more preferably 10% to 50%. An organic compound having electron transport properties and having such a structure can achieve a low refractive index without significantly impairing the electron transport properties.

[0129] In addition, such organic compounds 1 When measured by H-NMR (proton nuclear magnetic resonance), the integral value of signals below 4 ppm exceeds the integral value of signals above 4 ppm.

[0130] The organic compound having an electron-transport property used for the electron-transport layer 114 in the light-emitting device of one embodiment of the present invention preferably has a triazine skeleton or a diazine skeleton because of its favorable carrier-transport property.

[0131] As described above, the electron-transport layer contains an organic compound having a low refractive index and electron-transporting properties and a metal complex of an alkali metal having a low refractive index, so that the electron-transport layer can have a low refractive index without significantly deteriorating the driving voltage, etc. As a result, the efficiency of extracting light from the light-emitting layer 113 is improved, and the light-emitting device of one embodiment of the present invention can have high emission efficiency.

[0132] Next, other examples of the structure and materials of the light-emitting device of one embodiment of the present invention will be described. As described above, the light-emitting device of one embodiment of the present invention includes the EL layer 103 composed of multiple layers between a pair of electrodes, the anode 101 and the cathode 102. The EL layer 103 includes the light-emitting layer 113 containing a light-emitting material and the electron-transport layer 114 having the above-described structure.

[0133] The anode 101 is preferably formed using a metal, alloy, conductive compound, or mixture thereof having a large work function (specifically, 4.0 eV or higher). Specific examples include indium tin oxide (ITO), indium tin oxide containing silicon or silicon oxide, indium zinc oxide, and indium oxide containing tungsten oxide and zinc oxide (IWZO). These conductive metal oxide films are typically formed by sputtering, but they may also be formed by applying a sol-gel method. For example, indium zinc oxide may be formed by sputtering using a target containing indium oxide and 1 to 20 wt% zinc oxide. Indium oxide containing tungsten oxide and zinc oxide (IWZO) may also be formed by sputtering using a target containing indium oxide and 0.5 to 5 wt% tungsten oxide and 0.1 to 1 wt% zinc oxide. Other examples of materials that can be used for the anode 101 include gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), and nitrides of metal materials (e.g., titanium nitride). Graphene can also be used as the material for the anode 101. By using a composite material (described later) in the layer of the EL layer 103 that is in contact with the anode 101, it becomes possible to select an electrode material regardless of the work function.

[0134] The EL layer 103 preferably has a stacked layer structure, but the stacked layer structure is not particularly limited, and various layer structures, such as a hole-injection layer, a hole-transport layer, a light-emitting layer, an electron-transport layer, an electron-injection layer, a carrier-blocking layer (hole-blocking layer, electron-blocking layer), an exciton-blocking layer, and a charge-generation layer, can be used. Note that any of the layers may not be provided. In this embodiment, two types of structures are described: a structure including a hole-injection layer 111 and a hole-transport layer 112 in addition to the electron-transport layer 114, the electron-injection layer 115, and the light-emitting layer 113, as shown in FIG. 1A; and a structure including a charge-generation layer 116 in addition to the electron-transport layer 114, the light-emitting layer 113, the hole-injection layer 111, and the hole-transport layer 112, as shown in FIG. 1B. Materials constituting each layer are specifically described below.

[0135] The hole-injection layer 111 is a layer containing a substance having acceptor properties. As the substance having acceptor properties, either an organic compound or an inorganic compound can be used.

[0136] As the acceptor substance, a compound having an electron-withdrawing group (a halogen group or a cyano group) can be used, and examples thereof include 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F4-TCNQ), chloranil, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation: HAT-CN), 1,3,4,5,7,8-hexafluorotetracyano-naphthoquinodimethane (abbreviation: F6-TCNNQ), and 2-(7-dicyanomethylene-1,3,4,5,6,8,9,10-octafluoro-7H-pyren-2-ylidene)malononitrile. In particular, compounds in which an electron-withdrawing group is bonded to a fused aromatic ring having multiple heteroatoms, such as HAT-CN, are thermally stable and preferred. Radialene derivatives having electron-withdrawing groups (especially halogen groups such as fluoro groups or cyano groups) are also preferred because of their extremely high electron-accepting properties. Specific examples include α,α',α''-1,2,3-cyclopropanetriylidene tris[4-cyano-2,3,5,6-tetrafluorobenzeneacetonitrile], α,α',α''-1,2,3-cyclopropanetriylidene tris[2,6-dichloro-3,5-difluoro-4-(trifluoromethyl)benzeneacetonitrile], and α,α',α''-1,2,3-cyclopropanetriylidene tris[2,3,4,5,6-pentafluorobenzeneacetonitrile]. In addition to the organic compounds described above, other materials having acceptor properties can include molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, manganese oxide, etc. The hole injection layer 111 can also be formed from phthalocyanine complex compounds such as phthalocyanine (abbreviated as HPc) and copper phthalocyanine (CuPc), aromatic amine compounds such as 4,4'-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviated as DPAB) and N,N'-bis{4-[bis(3-methylphenyl)amino]phenyl}-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine (abbreviated as DNTPD), or polymers such as poly(3,4-ethylenedioxythiophene) / poly(styrenesulfonic acid) (PEDOT / PSS).A substance having acceptor properties can extract electrons from an adjacent hole transport layer (or hole transport material) when an electric field is applied.

[0137] Furthermore, a composite material in which a material having a hole-transporting property contains the above-mentioned acceptor substance can also be used for the hole-injection layer 111. Note that by using a composite material in which a material having a hole-transporting property contains an acceptor substance, a material for forming an electrode can be selected regardless of the work function. In other words, not only a material with a high work function but also a material with a low work function can be used for the anode 101.

[0138] As a material having hole transport properties to be used in the composite material, various organic compounds such as aromatic amine compounds, carbazole derivatives, aromatic hydrocarbons, and polymer compounds (oligomers, dendrimers, polymers, etc.) can be used. Note that as a material having hole transport properties to be used in the composite material, -6 cm 2 A substance having a hole mobility of 1 / Vs or more is preferred. Specific examples of organic compounds that can be used as a material having a hole transport property in a composite material are listed below.

[0139] Examples of aromatic amine compounds that can be used in composite materials include N,N'-di(p-tolyl)-N,N'-diphenyl-p-phenylenediamine (abbreviation: DTDPPA), 4,4'-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation: DPAB), N,N'-bis{4-[bis(3-methylphenyl)amino]phenyl}-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine (abbreviation: DNTPD), and 1,3,5-tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene (abbreviation: DPA3B). Specific examples of the carbazole derivative include 3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA1), 3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA2), 3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole, and Examples of suitable carbazoles include PCzPCN1, 4,4'-di(N-carbazolyl)biphenyl (CBP), 1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (TCPB), 9-[4-(10-phenylanthracen-9-yl)phenyl]-9H-carbazole (CzPA), and 1,4-bis[4-(N-carbazolyl)phenyl]-2,3,5,6-tetraphenylbenzene.Examples of aromatic hydrocarbons include 2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA), 2-tert-butyl-9,10-di(1-naphthyl)anthracene, 9,10-bis(3,5-diphenylphenyl)anthracene (abbreviation: DPPA), 2-tert-butyl-9,10-bis(4-phenylphenyl)anthracene (abbreviation: t-BuDBA), 9,10-di(2-naphthyl)anthracene (abbreviation: DNA), 9,10-diphenylanthracene (abbreviation: DPAnth), 2-tert-butylanthracene (abbreviation: t-BuAnth), 9,10-bis(4-methyl-1-naphthyl)anthracene (abbreviation: DMNA), 2-tert- Examples of suitable anthracene include butyl-9,10-bis[2-(1-naphthyl)phenyl]anthracene, 9,10-bis[2-(1-naphthyl)phenyl]anthracene, 2,3,6,7-tetramethyl-9,10-di(1-naphthyl)anthracene, 2,3,6,7-tetramethyl-9,10-di(2-naphthyl)anthracene, 9,9'-bianthryl, 10,10'-diphenyl-9,9'-bianthryl, 10,10'-bis(2-phenylphenyl)-9,9'-bianthryl, 10,10'-bis[(2,3,4,5,6-pentaphenyl)phenyl]-9,9'-bianthryl, anthracene, tetracene, rubrene, perylene, and 2,5,8,11-tetra(tert-butyl)perylene. Pentacene and coronene may also be used. The aromatic hydrocarbon having a vinyl group may also have a vinyl skeleton. Examples of the aromatic hydrocarbon having a vinyl group include 4,4'-bis(2,2-diphenylvinyl)biphenyl (abbreviation: DPVBi) and 9,10-bis[4-(2,2-diphenylvinyl)phenyl]anthracene (abbreviation: DPVPA). Note that the organic compound of one embodiment of the present invention can also be used.

[0140] In addition, polymer compounds such as poly(N-vinylcarbazole) (abbreviation: PVK), poly(4-vinyltriphenylamine) (abbreviation: PVTPA), poly[N-(4-{N'-[4-(4-diphenylamino)phenyl]phenyl-N'-phenylamino}phenyl)methacrylamide] (abbreviation: PTPDMA), and poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine] (abbreviation: Poly-TPD) can also be used.

[0141] The hole-transporting material used in the composite material preferably has a carbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, or an anthracene skeleton. In particular, the second organic compound may be an aromatic amine having a substituent containing a dibenzofuran ring or a dibenzothiophene ring, an aromatic monoamine having a naphthalene ring, or an aromatic monoamine in which a 9-fluorenyl group is bonded to the nitrogen of the amine via an arylene group. It is preferable that the second organic compound has an N,N-bis(4-biphenyl)amino group, since this allows the fabrication of a light-emitting device with a long lifetime. Specific examples of the second organic compound include N-(4-biphenyl)-6,N-diphenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BnfABP), N,N-bis(4-biphenyl)-6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BBABnf), 4,4'-bis(6-phenylbenzo[b]naphtho[1,2-d]furan- 8-yl-4''-phenyltriphenylamine (abbreviation: BnfBB1BP), N,N-bis(4-biphenyl)benzo[b]naphtho[1,2-d]furan-6-amine (abbreviation: BBABnf(6)), N,N-bis(4-biphenyl)benzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BBABnf(8)), N,N-bis(4-biphenyl)benzo[b]naphtho[2,3-d] Furan-4-amine (abbreviation: BBABnf(II)(4)), N,N-bis[4-(dibenzofuran-4-yl)phenyl]-4-amino-p-terphenyl (abbreviation: DBfBB1TP), N-[4-(dibenzothiophen-4-yl)phenyl]-N-phenyl-4-biphenylamine (abbreviation: ThBA1BP), 4-(2-naphthyl)-4',4''-diphenyltriphenylamine (abbreviation: : BBAβNB), 4-[4-(2-naphthyl)phenyl]-4',4''-diphenyltriphenylamine (abbreviation: BBAβNBi), 4,4'-diphenyl-4''-(6;1'-binaphthyl-2-yl)triphenylamine (abbreviation: BBAαNβNB), 4,4'-diphenyl-4''-(7;1'-binaphthyl-2-yl)triphenylamine (abbreviation: BBAαNβNB-03), 4,4'-Diphenyl-4''-(7-phenyl)naphthyl-2-yltriphenylamine (abbreviation: BBAPβNB-03), 4,4'-diphenyl-4''-(6;2'-binaphthyl-2-yl)triphenylamine (abbreviation: BBA(βN2)B), 4,4'-diphenyl-4''-(7;2'-binaphthyl-2-yl)triphenylamine (abbreviation: BBA(βN2)B-03), 4,4'-diphenyl-4''-(4;2'-binaphthyl-1-yl)triphenylamine (abbreviation: BBAβNαNB), 4,4'-diphenyl-4''-(5;2'- (binaphthyl-1-yl)triphenylamine (abbreviation: BBAβNαNB-02), 4-(4-biphenylyl)-4'-(2-naphthyl)-4''-phenyltriphenylamine (abbreviation: TPBiAβNB), 4-(3-biphenylyl)-4'-[4-(2-naphthyl)phenyl]-4''-phenyltriphenylamine (abbreviation: mTPBiAβNBi), 4-(4-biphenylyl)-4'-[4-(2-naphthyl)phenyl]-4''-phenyltriphenylamine (abbreviation: TPBiAβNBi), 4-phenyl-4'-(1-naphthyl)triphenylamine 4,4'-Bis(1-naphthyl)triphenylamine (abbreviated as αNBA1BP), 4,4'-Bis(1-naphthyl)triphenylamine (abbreviated as αNBB1BP), 4,4'-diphenyl-4''-[4'-(carbazol-9-yl)biphenyl-4-yl]triphenylamine (abbreviated as YGTBi1BP), 4'-[4-(3-phenyl-9H-carbazol-9-yl)phenyl]tris(1,1'-biphenyl-4-yl)amine (abbreviated as YGTBi1BP-02), 4-diphenyl-4'-(2-naphthyl)-4''-{9-(4-biphenylyl)carbazole}triphenylamine N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-N-[4-(1-naphthyl)phenyl]-9,9'-spirobi[9H-fluorene]-2-amine (abbreviation: PCBNBSF), N,N-bis(4-biphenylyl)-9,9'-spirobi[9H-fluorene]-2-amine (abbreviation: BBASF), N,N-bis(1,1'-biphenyl-4-yl)-9,9'-spirobi[9H-fluorene]-4-amine (abbreviation: BBASF(4)), N-(1,1'-biphenyl-2-yl)-N-(9,9-Dimethyl-9H-fluoren-2-yl)-9,9'-spirobi(9H-fluorene)-4-amine (abbreviation: oFBiSF), N-(4-biphenyl)-N-(dibenzofuran-4-yl)-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: FrBiF), N-[4-(1-naphthyl)phenyl]-N-[3-(6-phenyldibenzofuran-4-yl)phenyl]-1-naphthylamine (abbreviation: mPDBfBNBN), 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP), 4-furan phenyl-3'-(9-phenylfluoren-9-yl)triphenylamine (abbreviated as mBPAFLP), 4-phenyl-4'-[4-(9-phenylfluoren-9-yl)phenyl]triphenylamine (abbreviated as BPAFLBi), 4-phenyl-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviated as PCBA1BP), 4,4'-diphenyl-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviated as PCBBi1BP), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviated as PCBBi1BP), N-(1,1'-biphenyl-4-yl)-9,9-dimethyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9H-fluorene-2-amine (abbreviation: PCBASF), 4,4'-di(1-naphthyl)-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBANB), 4,4'-di(1-naphthyl)-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBNBB), N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9'-spirobi[9H-fluorene]-2-amine (abbreviation: PCBASF), N-(1,1'-biphenyl-4-yl)-9,9-dimethyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9H-fluorene-2-amine Examples of suitable amines include PCBBiF (abbreviation: PCBBiF), N,N-bis(9,9-dimethyl-9H-fluoren-2-yl)-9,9'-spirobi-9H-fluoren-4-amine, N,N-bis(9,9-dimethyl-9H-fluoren-2-yl)-9,9'-spirobi-9H-fluoren-3-amine, N,N-bis(9,9-dimethyl-9H-fluoren-2-yl)-9,9'-spirobi-9H-fluoren-2-amine, and N,N-bis(9,9-dimethyl-9H-fluoren-2-yl)-9,9'-spirobi-9H-fluoren-1-amine.

[0142] Note that the material having hole-transporting properties used in the composite material is more preferably a substance having a relatively deep HOMO level of -5.7 eV or more and -5.4 eV or less. When the material having hole-transporting properties used in the composite material has a relatively deep HOMO level, injection of holes into the hole-transport layer 112 becomes easy, and a light-emitting device with a long lifetime can be easily obtained. Furthermore, when the material having hole-transporting properties used in the composite material has a relatively deep HOMO level, hole induction is appropriately suppressed, and a light-emitting device with a long lifetime can be obtained.

[0143] The refractive index of the layer can be reduced by further mixing an alkali metal or alkaline earth metal fluoride into the composite material (preferably with an atomic ratio of fluorine atoms of 20% or more in the layer), which also allows a layer with a low refractive index to be formed inside the EL layer 103, thereby improving the external quantum efficiency of the light-emitting device.

[0144] By forming the hole injection layer 111, the hole injection property becomes good, and a light emitting device with a low driving voltage can be obtained.

[0145] Among substances having acceptor properties, organic compounds having acceptor properties are easy to use because they can be easily vapor-deposited and formed into a film.

[0146] The hole transport layer 112 is formed by including a material having a hole transport property. -6 cm 2 It is preferable that the hole mobility is / Vs or more.

[0147] Examples of the material having hole transport properties include 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB), N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (abbreviation: TPD), 4,4'-bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenylamino]biphenyl (abbreviation: BSPB), 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPA), and 4,4'-bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenylamino]biphenyl (abbreviation: BSPB). FLP), 4-phenyl-3'-(9-phenylfluoren-9-yl)triphenylamine (abbreviated as mBPAFLP), 4-phenyl-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviated as PCBA1BP), 4,4'-diphenyl-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviated as PCBBi1BP), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviated as PCB Aromatic amines such as 4,4'-di(1-naphthyl)-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviated as PCBNBB), 9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]fluoren-2-amine (abbreviated as PCBAF), and N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9'-spirobi[9H-fluorene]-2-amine (abbreviated as PCBASF) Compounds with a benzophenone skeleton, compounds with a carbazole skeleton such as 1,3-bis(N-carbazolyl)benzene (abbreviation: mCP), 4,4'-di(N-carbazolyl)biphenyl (abbreviation: CBP), 3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP), and 3,3'-bis(9-phenyl-9H-carbazole) (abbreviation: PCCP), and compounds with a benzophenone skeleton such as 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation: DBT3P-II), 2,Examples of suitable compounds include compounds having a thiophene skeleton, such as 8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene (abbreviation: DBTFLP-III) and 4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviation: DBTFLP-IV), and compounds having a furan skeleton, such as 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation: DBF3P-II) and 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran (abbreviation: mmDBFFLBi-II). Among the above, compounds having an aromatic amine skeleton and compounds having a carbazole skeleton are preferred because they have good reliability, high hole transport properties, and contribute to reducing driving voltage. Note that the substances listed as materials having hole transport properties used in the composite material of the hole injection layer 111 can also be suitably used as materials for forming the hole transport layer 112.

[0148] The light-emitting layer 113 contains a light-emitting substance and a host material. The light-emitting layer 113 may also contain other materials. Alternatively, the light-emitting layer 113 may be a laminate of two layers with different compositions.

[0149] The light-emitting substance may be a fluorescent substance, a phosphorescent substance, a substance that exhibits thermally activated delayed fluorescence (TADF), or other light-emitting substances. Note that one embodiment of the present invention is more preferably applicable to the case where the light-emitting layer 113 is a layer that exhibits fluorescent light, particularly a layer that exhibits blue fluorescent light.

[0150] Examples of materials that can be used as the fluorescent substance in the light-emitting layer 113 include the following: Other fluorescent substances can also be used.

[0151] 5,6-bis[4-(10-phenyl-9-anthryl)phenyl]-2,2'-bipyridine (abbreviation: PAP2BPy), 5,6-bis[4'-(10-phenyl-9-anthryl)biphenyl-4-yl]-2,2'-bipyridine (abbreviation: PAPP2BPy), N,N'-diphenyl-N,N'-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6FLPAPrn), N,N'-bis(3-methylphenyl)-N,N'-bis[3-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine )phenyl]pyrene-1,6-diamine (abbreviation: 1,6mMemFLPAPrn), N,N'-bis[4-(9H-carbazol-9-yl)phenyl]-N,N'-diphenylstilbene-4,4'-diamine (abbreviation: YGA2S), 4-(9H-carbazol-9-yl)-4'-(10-phenyl-9-anthryl)triphenylamine (abbreviation: YGAPA), 4-(9H-carbazol-9-yl)-4'-(9,10-diphenyl-2-anthryl)triphenylamine (abbreviation: 2YGAPPA), N,9-diphenyl-N-[4-( 10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine (abbreviation: PCAPA), perylene, 2,5,8,11-tetra-tert-butylperylene (abbreviation: TBP), 4-(10-phenyl-9-anthryl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBAPA), N,N''-(2-tert-butylanthracene-9,10-diyldi-4,1-phenylene)bis[N,N',N'-triphenyl-1,4-phenylenediamine] (abbreviation: DPABPA), N,9 -diphenyl-N-[4-(9,10-diphenyl-2-anthryl)phenyl]-9H-carbazol-3-amine (abbreviated as 2PCAPPA), N-[4-(9,10-diphenyl-2-anthryl)phenyl]-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviated as 2DPAPPA), N,N,N',N',N'',N'',N''',N'''-octaphenyldibenzo[g,p]chrysene-2,7,10,15-tetraamine (abbreviated as DBC1), Coumarin 30, N-(9,10-diphenyl-2-anthryl)-N,9-Diphenyl-9H-carbazol-3-amine (abbreviation: 2PCAPA), N-[9,10-bis(1,1'-biphenyl-2-yl)-2-anthryl]-N,9-diphenyl-9H-carbazol-3-amine (abbreviation: 2PCABPhA), N-(9,10-diphenyl-2-anthryl)-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPA), N-[9,10-bis(1,1'-biphenyl-2-yl)-2-anthryl]-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPA BPhA), 9,10-bis(1,1'-biphenyl-2-yl)-N-[4-(9H-carbazol-9-yl)phenyl]-N-phenylanthracen-2-amine (abbreviation: 2YGABPhA), N,N,9-triphenylanthracen-9-amine (abbreviation: DPhAPhA), Coumarin 545T, N,N'-diphenylquinacridone (abbreviation: DPQd), rubrene, 5,12-bis(1,1'-biphenyl-4-yl)-6,11-diphenyltetracene (abbreviation: BPT), 2-(2-{2-[4-(dimethylamino)phenyl]ethenyl}-6 -methyl-4H-pyran-4-ylidene)propanedinitrile (abbreviation: DCM1), 2-{2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCM2), N,N,N',N'-tetrakis(4-methylphenyl)tetracene-5,11-diamine (abbreviation: p-mPhTD), 7,14-diphenyl-N,N,N',N'-tetrakis(4-methylphenyl)acenaphtho[1,2-a]fluoranthene-3,10-diamine amine (abbreviation: p-mPhAFD), 2-{2-isopropyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCJTI), 2-{2-tert-butyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCJTB),6-Bis{2-[4-(dimethylamino)phenyl]ethenyl}-4H-pyran-4-ylidene)propanedinitrile (abbreviation: BisDCM), 2-{2,6-bis[2-(8-methoxy-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: BisDCJTM), N,N'-diphenyl-N,N'-(1,6-pyren-diyl)bis[(6-phenylbenzo[b ]naphtho[1,2-d]furan)-8-amine] (abbreviated as 1,6BnfAPrn-03), 3,10-bis[N-(9-phenyl-9H-carbazol-2-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviated as 3,10PCA2Nbf(IV)-02), and 3,10-bis[N-(dibenzofuran-3-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviated as 3,10FrA2Nbf(IV)-02). In particular, condensed aromatic diamine compounds, such as pyrenediamine compounds, such as 1,6FLPAPrn, 1,6mMemFLPAPrn, and 1,6BnfAPrn-03, are preferred because of their high hole-trapping properties, excellent luminous efficiency, and reliability.

[0152] When a phosphorescent material is used as the light-emitting material in the light-emitting layer 113, examples of materials that can be used include the following.

[0153] Organometallic iridium complexes with a 4H-triazole skeleton, such as tris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-κN2]phenyl-κC}iridium(III) (abbreviated as [Ir(mpptz-dmp)3]), tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazolato)iridium(III) (abbreviated as [Ir(Mptz)3]), and tris[4-(3-biphenyl)-5-isopropyl-3-phenyl-4H-1,2,4-triazolato]iridium(III) (abbreviated as [Ir(iPrptz-3b)3]), and tris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazolato]iridium(III) Organometallic iridium complexes with a 1H-triazole skeleton, such as tris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazolato)iridium(III) (abbreviation: [Ir(Mptz1-mp)3]) and tris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazolato)iridium(III) (abbreviation: [Ir(Prptz1-Me)3]), organometallic iridium complexes with an imidazole skeleton, such as fac-tris[(1-2,6-diisopropylphenyl)-2-phenyl-1H-imidazole]iridium(III) (abbreviation: [Ir(iPrpmi)3]) and tris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridium(III) (abbreviation: [Ir(dmpimpt-Me)3]), and bis[2-(4',6'-difluorophenyl)pyridinato-N,C 2’ ]iridium(III) tetrakis(1-pyrazolyl)borate (abbreviation: FIr6), bis[2-(4',6'-difluorophenyl)pyridinato-N,C 2’ ]iridium(III) picolinate (abbreviation: FIrpic), bis{2-[3',5'-bis(trifluoromethyl)phenyl]pyridinato-N,C 2’}iridium(III) picolinate (abbreviation: [Ir(CF3ppy)2(pic)]), bis[2-(4',6'-difluorophenyl)pyridinato-N,C 2’] Organometallic iridium complexes with phenylpyridine derivatives bearing electron-withdrawing groups as ligands, such as iridium(III) acetylacetonate (abbreviated as FIr(acac)), are compounds that exhibit blue phosphorescence, with peak emission in the wavelength range from 440 nm to 520 nm.

[0154] Also, tris(4-methyl-6-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(mppm)3]), tris(4-t-butyl-6-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(tBuppm)3]), (acetylacetonato)bis(6-methyl-4-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(mppm)2(acac)]), (acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(tBuppm)2(acac)]), (acetylacetonato)bis[6-(2-norbornyl)-4-phenylpyrimidinato]iridium(III) (abbreviation: [Ir(nbppm)2(acac)]), (acetylacetonato)bis[5-methyl-6-( Organometallic iridium complexes with a pyrimidine skeleton, such as (acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III) (abbreviation: [Ir(mpmppm)2(acac)]) and (acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III) (abbreviation: [Ir(dppm)2(acac)]), organometallic iridium complexes with a pyrazine skeleton, such as (acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinato)iridium(III) (abbreviation: [Ir(mppr-Me)2(acac)]) and (acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinato)iridium(III) (abbreviation: [Ir(mppr-iPr)2(acac)]), and tris(2-phenylpyridinato-N,C 2’ ) Iridium(III) (abbreviation: [Ir(ppy)3]), bis(2-phenylpyridinato-N,C 2’) Iridium(III) acetylacetonate (abbreviation: [Ir(ppy)2(acac)]), bis(benzo[h]quinolinato)iridium(III) acetylacetonate (abbreviation: [Ir(bzq)2(acac)]), tris(benzo[h]quinolinato)iridium(III) (abbreviation: [Ir(bzq)3]), tris(2-phenylquinolinato-N,C 2’ ) Iridium(III) (abbreviation: [Ir(pq)3]), bis(2-phenylquinolinato-N,C 2’ Examples include organometallic iridium complexes with a pyridine skeleton, such as iridium(III) acetylacetonate (abbreviated as [Ir(pq)2(acac)]), and rare earth metal complexes, such as tris(acetylacetonato)(monophenanthroline)terbium(III) (abbreviated as [Tb(acac)3(Phen)]). These compounds primarily exhibit green phosphorescence, with an emission peak in the wavelength range of 500 to 600 nm. Organometallic iridium complexes with a pyrimidine skeleton are particularly preferred, as they are remarkably superior in reliability and luminous efficiency.

[0155] In addition, organometallic iridium complexes having a pyrimidine skeleton, such as (diisobutyrylmethanato)bis[4,6-bis(3-methylphenyl)pyrimidinato]iridium(III) (abbreviation: [Ir(5mdppm)2(dibm)]), bis[4,6-bis(3-methylphenyl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: [Ir(5mdppm)2(dpm)]), and bis[4,6-di(naphthalen-1-yl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: [Ir(d1npm)2(dpm)]), Organometallic iridium complexes with a pyrazine skeleton, such as (acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III) (abbreviation: [Ir(tppr)2(acac)]), bis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III) (abbreviation: [Ir(tppr)2(dpm)]), and (acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III) (abbreviation: [Ir(Fdpq)2(acac)]), and tris(1-phenylisoquinolinato-N,C 2’ ) Iridium(III) (abbreviation: [Ir(piq)3]), bis(1-phenylisoquinolinato-N,C 2’ Examples include organometallic iridium complexes with a pyridine skeleton, such as iridium(III) acetylacetonate (abbreviated as [Ir(piq)2(acac)]), platinum complexes such as 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrinplatinum(II) (abbreviated as PtOEP), and rare earth metal complexes such as tris(1,3-diphenyl-1,3-propanedionato)(monophenanthroline)europium(III) (abbreviated as [Eu(DBM)3(Phen)]) and tris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III) (abbreviated as [Eu(TTA)3(Phen)]). These compounds exhibit red phosphorescence, with peak emission in the wavelength range of 600 to 700 nm. Furthermore, organometallic iridium complexes having a pyrazine skeleton can emit red light with good chromaticity.

[0156] In addition to the phosphorescent compounds described above, known phosphorescent compounds may be selected and used.

[0157] TADF materials include fullerene and its derivatives, acridine and its derivatives, eosin derivatives, etc. Also available are metal-containing porphyrins containing magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), or palladium (Pd). Examples of the metal-containing porphyrin include protoporphyrin-tin fluoride complex (SnF2(Proto IX)), mesoporphyrin-tin fluoride complex (SnF2(Meso IX)), hematoporphyrin-tin fluoride complex (SnF2(Hemato IX)), coproporphyrin tetramethyl ester-tin fluoride complex (SnF2(Copro III-4Me)), octaethylporphyrin-tin fluoride complex (SnF2(OEP)), etioporphyrin-tin fluoride complex (SnF2(Etio I)), and octaethylporphyrin-platinum chloride complex (PtCl2OEP), all of which are shown in the following structural formulas.

[0158] [ka]

[0159] In addition, 2-(biphenyl-4-yl)-4,6-bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1,3,5-triazine (abbreviation: PIC-TRZ), 9-(4,6-diphenyl-1,3,5-triazin-2-yl)-9'-phenyl-9H,9'H-3,3'-bicarbazole (abbreviation: PCCzTzn), 9-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-9'-phenyl-9H,9'H-3,3'-bicarbazole (abbreviation: PCCzPTzn), 2-[4-(10H-phenoxazin-10-yl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: P Heterocyclic compounds having either or both of a π-electron rich heteroaromatic ring and a π-electron deficient heteroaromatic ring, such as 3-[4-(5-phenyl-5,10-dihydrophenazin-10-yl)phenyl]-4,5-diphenyl-1,2,4-triazole (abbreviation: PPZ-3TPT), 3-(9,9-dimethyl-9H-acridin-10-yl)-9H-xanthen-9-one (abbreviation: ACRXTN), bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone (abbreviation: DMAC-DPS), and 10-phenyl-10H,10'H-spiro[acridine-9,9'-anthracene]-10'-one (abbreviation: ACRSA), can also be used. The heterocyclic compound has a π-electron-rich heteroaromatic ring and a π-electron-deficient heteroaromatic ring, and therefore has high electron transport and hole transport properties, and is therefore preferred. Among the skeletons having a π-electron-deficient heteroaromatic ring, pyridine skeleton, diazine skeleton (pyrimidine skeleton, pyrazine skeleton, pyridazine skeleton), and triazine skeleton are preferred because they are stable and reliable. In particular, benzofuropyrimidine skeleton, benzothienopyrimidine skeleton, benzofuropyrazine skeleton, and benzothienopyrazine skeleton are preferred because they have high acceptor properties and good reliability. Furthermore, among the skeletons having a π-electron-rich heteroaromatic ring, acridine skeleton, phenoxazine skeleton, phenothiazine skeleton, furan skeleton, thiophene skeleton, and pyrrole skeleton are preferred because they are stable and reliable.The furan skeleton is preferably a dibenzofuran skeleton, and the thiophene skeleton is preferably a dibenzothiophene skeleton. The pyrrole skeleton is particularly preferably an indole skeleton, a carbazole skeleton, an indolocarbazole skeleton, a bicarbazole skeleton, or a 3-(9-phenyl-9H-carbazol-3-yl)-9H-carbazole skeleton. Substances in which a π-electron-rich heteroaromatic ring and a π-electron-deficient heteroaromatic ring are directly bonded are particularly preferred because the electron-donating ability of the π-electron-rich heteroaromatic ring and the electron-accepting ability of the π-electron-deficient heteroaromatic ring are both enhanced, thereby reducing the energy difference between the S1 level and the T1 level, thereby enabling efficient thermally activated delayed fluorescence. Instead of the π-electron-deficient heteroaromatic ring, an aromatic ring bonded to an electron-withdrawing group such as a cyano group may be used. The π-electron-rich skeleton may be, for example, an aromatic amine skeleton or a phenazine skeleton. Examples of usable π-electron-deficient skeletons include a xanthene skeleton, a thioxanthene dioxide skeleton, an oxadiazole skeleton, a triazole skeleton, an imidazole skeleton, an anthraquinone skeleton, a boron-containing skeleton such as phenylborane or boranthrene, an aromatic ring or heteroaromatic ring having a nitrile group or a cyano group such as benzonitrile or cyanobenzene, a carbonyl skeleton such as benzophenone, a phosphine oxide skeleton, a sulfone skeleton, etc. In this way, a π-electron-deficient skeleton or a π-electron-rich skeleton can be used in place of at least one of a π-electron-deficient heteroaromatic ring and a π-electron-rich heteroaromatic ring.

[0160] [ka]

[0161] TADF materials are materials with a small difference between the S1 and T1 levels, and have the ability to convert triplet excitation energy to singlet excitation energy through reverse intersystem crossing. Therefore, triplet excitation energy can be upconverted to singlet excitation energy (reverse intersystem crossing) using a small amount of thermal energy, allowing for efficient generation of a singlet excited state. Triplet excitation energy can also be converted into light emission.

[0162] Furthermore, exciplexes (also known as exciplexes), which form an excited state with two types of substances, have an extremely small difference between the S1 and T1 levels and function as TADF materials that can convert triplet excitation energy into singlet excitation energy.

[0163] The phosphorescence spectrum observed at low temperatures (for example, 77 K to 10 K) can be used as an indicator of the T1 level. For a TADF material, when a tangent line is drawn at the base of the fluorescence spectrum on the short wavelength side and the energy of the wavelength of the extrapolated line is defined as the S1 level, and a tangent line is drawn at the base of the phosphorescence spectrum on the short wavelength side and the energy of the wavelength of the extrapolated line is defined as the T1 level, the difference between S1 and T1 is preferably 0.3 eV or less, and more preferably 0.2 eV or less.

[0164] When a TADF material is used as a light-emitting material, the S1 level of the host material is preferably higher than the S1 level of the TADF material, and the T1 level of the host material is preferably higher than the T1 level of the TADF material.

[0165] As the host material of the light-emitting layer, various carrier transporting materials such as a material having an electron transporting property, a material having a hole transporting property, or the above-mentioned TADF material can be used.

[0166] As a material having hole transport properties, an organic compound having an amine skeleton or a π-electron-rich heteroaromatic ring skeleton is preferable. For example, 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB), N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (abbreviation: TPD), 4,4'-bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenylamino]biphenyl (abbreviation: BSPB), 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP ... mBPAFLP), 4-phenyl-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (PCBA1BP), 4,4'-diphenyl-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (PCBBi1BP), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (PCBANB), 4, Aromatic amine skeletons such as 4'-di(1-naphthyl)-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBNBB), 9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]fluoren-2-amine (abbreviation: PCBAF), and N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9'-spirobi[9H-fluorene]-2-amine (abbreviation: PCBASF) and compounds with a carbazole skeleton such as 1,3-bis(N-carbazolyl)benzene (abbreviation: mCP), 4,4'-di(N-carbazolyl)biphenyl (abbreviation: CBP), 3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP), and 3,3'-bis(9-phenyl-9H-carbazole) (abbreviation: PCCP), as well as 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation: DBT3P-II), 2,Examples of suitable materials include compounds having a thiophene skeleton, such as 8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene (abbreviation: DBTFLP-III) and 4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviation: DBTFLP-IV), and compounds having a furan skeleton, such as 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation: DBF3P-II) and 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran (abbreviation: mmDBFFLBi-II). Among the above, compounds having an aromatic amine skeleton and compounds having a carbazole skeleton are preferred because they have good reliability, high hole transport properties, and contribute to reducing driving voltage. The organic compounds listed as examples of materials having hole transport properties for the hole transport layer 112 can also be used. ,

[0167] Examples of materials having electron transport properties include metal complexes such as bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq2), bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III) (abbreviation: BAlq), bis(8-quinolinolato)zinc(II) (abbreviation: Znq), bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO), and bis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ), as well as organic compounds having a π-electron-deficient heteroaromatic ring skeleton. Examples of organic compounds having a π-electron-deficient heteroaromatic ring skeleton include 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazole] (abbreviation: 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,2,4-triazole] ... [oxadiazol-2-yl]benzene (abbreviation: OXD-7), 9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation: CO11), 2,2',2''-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole) (abbreviation: TPBI), 2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1 Heterocyclic compounds with polyazole skeletons such as H-benzimidazole (abbreviated as mDBTBIm-II), 2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviated as 2mDBTPDBq-II), 2-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviated as 2mDBTBPDBq-II), and 2-[3' Heterocyclic compounds with diazine skeletons such as 4,6-bis[3-(4-dibenzothienyl)phenyl]pyrimidine (abbreviation: 4,6mDBTP2Pm-II), 4,6-bis[3-(4-dibenzothienyl)phenyl]pyrimidine (abbreviation: 4,6mDBTP2Pm-II), and 3,Heterocyclic compounds with a pyridine skeleton, such as 5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine (abbreviation: 35DCzPPy) and 1,3,5-tri[3-(3-pyridyl)phenyl]benzene (abbreviation: TmPyPB), 2-[3'-(9,9-dimethyl-9H-fluoren-2-yl)-1,1'-biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mFBPTzn), 2-[(1,1'-biphenyl)-4-yl]-4-phenyl-6-[9,9'-spirobi(9 Examples of heterocyclic compounds having a triazine skeleton include 2-{3-[3-(benzo[b]naphtho[1,2-d]furan-8-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mBnfBPTzn), and 2-{3-[3-(benzo[b]naphtho[1,2-d]furan-6-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mBnfBPTzn-02). Among the above, heterocyclic compounds having a diazine skeleton, heterocyclic compounds having a pyridine skeleton, and heterocyclic compounds having a triazine skeleton are preferred because of their high reliability. In particular, heterocyclic compounds having a diazine (pyrimidine or pyrazine) skeleton and heterocyclic compounds having a triazine skeleton have high electron transport properties and contribute to reducing driving voltage.

[0168] The TADF materials that can be used as host materials are the same as those listed above. When a TADF material is used as a host material, the triplet excitation energy generated in the TADF material is converted to singlet excitation energy through reverse intersystem crossing, and the energy is then transferred to the light-emitting material, thereby improving the luminous efficiency of the light-emitting device. In this case, the TADF material functions as an energy donor, and the light-emitting material functions as an energy acceptor.

[0169] This is very effective when the luminescent material is a fluorescent luminescent material. In this case, in order to obtain high luminous efficiency, the S1 level of the TADF material is preferably higher than the S1 level of the fluorescent luminescent material. In addition, the T1 level of the TADF material is preferably higher than the S1 level of the fluorescent luminescent material. Therefore, the T1 level of the TADF material is preferably higher than the T1 level of the fluorescent luminescent material.

[0170] It is also preferable to use a TADF material that emits light at a wavelength that overlaps with the wavelength of the lowest-energy absorption band of the fluorescent material, as this allows for smooth transfer of excitation energy from the TADF material to the fluorescent material, resulting in efficient light emission.

[0171] Furthermore, to efficiently generate singlet excitation energy from triplet excitation energy through reverse intersystem crossing, carrier recombination is preferred in the TADF material. It is also preferable that the triplet excitation energy generated in the TADF material does not transfer to triplet excitation energy in the fluorescent material. To achieve this, the fluorescent material preferably has a protecting group around the luminophore (the skeleton responsible for light emission) of the fluorescent material. The protecting group is preferably a substituent without a π bond, and is preferably a saturated hydrocarbon. Specific examples include alkyl groups with 3 to 10 carbon atoms, substituted or unsubstituted cycloalkyl groups with 3 to 10 carbon atoms, and trialkylsilyl groups with 3 to 10 carbon atoms. Multiple protecting groups are even more preferred. Substituents without a π bond have poor carrier transport properties, allowing for the distance between the TADF material and the luminophore of the fluorescent material to be increased without significantly affecting carrier transport or carrier recombination. Here, the term "luminophore" refers to the atomic group (skeleton) responsible for light emission in the fluorescent material. The luminophore preferably has a skeleton having a π bond, preferably contains an aromatic ring, and preferably has a fused aromatic ring or a fused heteroaromatic ring. Examples of the fused aromatic ring or the fused heteroaromatic ring include a phenanthrene skeleton, a stilbene skeleton, an acridone skeleton, a phenoxazine skeleton, and a phenothiazine skeleton. In particular, fluorescent substances having a naphthalene skeleton, an anthracene skeleton, a fluorene skeleton, a chrysene skeleton, a triphenylene skeleton, a tetracene skeleton, a pyrene skeleton, a perylene skeleton, a coumarin skeleton, a quinacridone skeleton, or a naphthobisbenzofuran skeleton are preferred because of their high fluorescence quantum yield.

[0172] When a fluorescent emitting substance is used as the emitting substance, a material having an anthracene skeleton is suitable as the host material. Using a substance having an anthracene skeleton as the host material for a fluorescent emitting substance makes it possible to realize an emitting layer with both excellent luminous efficiency and durability. As a substance having an anthracene skeleton to be used as a host material, a diphenylanthracene skeleton, particularly a 9,10-diphenylanthracene skeleton, is preferred due to its chemical stability. Furthermore, host materials having a carbazole skeleton are preferred because of their enhanced hole injection and transport properties. However, host materials containing a benzocarbazole skeleton, in which a benzene ring is further condensed to carbazole, are even more preferred because their HOMO is approximately 0.1 eV shallower than that of carbazole, facilitating hole insertion. In particular, host materials containing a dibenzocarbazole skeleton are preferred because their HOMO is approximately 0.1 eV shallower than that of carbazole, facilitating hole insertion, and also exhibiting excellent hole transport properties and high heat resistance. Therefore, a more preferable host material is a substance having both a 9,10-diphenylanthracene skeleton and a carbazole skeleton (or a benzocarbazole skeleton or a dibenzocarbazole skeleton). From the viewpoint of the hole injection / transport property, a benzofluorene skeleton or a dibenzofluorene skeleton may be used instead of the carbazole skeleton. Examples of such a substance include 9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: PCzPA), 3-[4-(1-naphthyl)-phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPN), 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA), and 7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole. Examples include benzo[b]naphtho[1,2-d]furan (abbreviation: 2mBnfPPA), 9-phenyl-10-{4-(9-phenyl-9H-fluoren-9-yl)biphenyl-4'-yl}anthracene (abbreviation: FLPPA), and 9-(1-naphthyl)-10-[4-(2-naphthyl)phenyl]anthracene (abbreviation: αN-βNPAnth).In particular, CzPA, cgDBCzPA, 2mBnfPPA, and PCzPA are preferable choices because they exhibit very good properties.

[0173] The host material may be a mixture of multiple substances, and when a mixture of host materials is used, it is preferable to mix a material having electron-transporting properties with a material having hole-transporting properties. By mixing a material having electron-transporting properties with a material having hole-transporting properties, the transport properties of the light-emitting layer 113 can be easily adjusted, and the recombination region can also be easily controlled. The weight ratio of the content of the material having hole-transporting properties to the material having electron-transporting properties may be 1:19 to 19:1 (material having hole-transporting properties:material having electron-transporting properties).

[0174] A phosphorescent material can be used as part of the mixed material. The phosphorescent material can be used as an energy donor that provides excitation energy to a fluorescent material when the fluorescent material is used as a light-emitting material.

[0175] Furthermore, these mixed materials may form an exciplex. It is preferable to select a combination that forms an exciplex that emits light that overlaps with the wavelength of the lowest-energy absorption band of the light-emitting material, because this allows for smooth energy transfer and efficient light emission. Furthermore, using this structure is also preferable because it reduces the driving voltage.

[0176] At least one of the materials forming the exciplex may be a phosphorescent material, which allows efficient conversion of triplet excitation energy into singlet excitation energy through reverse intersystem crossing.

[0177] As a combination of materials that efficiently form an exciplex, it is preferable that the HOMO level of the hole-transporting material is equal to or higher than the HOMO level of the electron-transporting material. It is also preferable that the LUMO level of the hole-transporting material is equal to or higher than the LUMO level of the electron-transporting material. The LUMO and HOMO levels of the materials can be derived from the electrochemical properties (reduction potential and oxidation potential) of the materials measured by cyclic voltammetry (CV).

[0178] The formation of exciplexes can be confirmed by, for example, comparing the emission spectra of a hole-transporting material, an electron-transporting material, and a mixed film of these materials and observing the phenomenon that the emission spectrum of the mixed film is shifted to longer wavelengths than the emission spectra of each material (or has a new peak at longer wavelengths). Alternatively, it can be confirmed by comparing the transient photoluminescence (PL) of a hole-transporting material, the transient PL of an electron-transporting material, and a mixed film of these materials and observing differences in transient response, such as the transient PL lifetime of the mixed film having a longer-lived component or a larger proportion of delayed components than the transient PL lifetimes of the individual materials. The above-mentioned transient PL can also be interpreted as transient electroluminescence (EL). In other words, the formation of exciplexes can also be confirmed by comparing the transient EL of a hole-transporting material, the transient EL of an electron-transporting material, and a mixed film of these materials and observing differences in transient response.

[0179] Since the electron transport layer 114 has the configuration of the present invention, it can be made a layer with a low refractive index. Therefore, a layer with a low refractive index can be formed inside the EL layer 103 without significantly reducing the driving voltage, and the external quantum efficiency of the light-emitting device can be improved.

[0180] The electron transport layer 114 having this structure may also serve as the electron injection layer 115.

[0181] The electron transport layer 114 has an electron mobility of 1×10 when the square root of the electric field strength [V / cm] is 600. -7 cm 2 / Vs or more 5×10 -5 cm 2 / Vs or less. By reducing the electron transport property of the electron-transport layer 114, the amount of electrons injected into the light-emitting layer can be controlled, and the light-emitting layer can be prevented from becoming electron-excessive. This configuration is particularly preferable because it improves the lifetime when the hole-injection layer is formed of a composite material and the HOMO level of the material having hole-transport properties in the composite material is a substance having a relatively deep HOMO level of -5.7 eV or more and -5.4 eV or less. In this case, the HOMO level of the material having electron-transport properties is preferably -6.0 eV or more.

[0182] In addition, it is preferable that the alkali metal or the metal complex of the alkali metal in the electron transport layer 114 has a concentration difference (including a case where the difference is 0) in the thickness direction.

[0183] Between the electron transport layer 114 and the cathode 102, a layer containing an alkali metal or alkaline earth metal, such as lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF), or 8-hydroxyquinolinato-lithium (abbreviated as Liq), or a compound or complex thereof, may be provided as the electron injection layer 115. The electron injection layer 115 may be a layer made of a substance having electron transport properties containing an alkali metal or alkaline earth metal or a compound thereof, or an electride. Examples of the electride include a substance in which a high concentration of electrons is added to a mixed oxide of calcium and aluminum.

[0184] Note that a layer containing a fluoride of the alkali metal or alkaline earth metal in a concentration (50 wt % or more) sufficient to form a microcrystalline state in a substance having an electron transport property (preferably an organic compound having a bipyridine skeleton) can also be used as the electron-injection layer 115. Since this layer has a low refractive index, it is possible to provide a light-emitting device with better external quantum efficiency.

[0185] Furthermore, a charge generation layer 116 may be provided instead of the electron injection layer 115 of FIG. 1(A) (FIG. 1(B)). The charge generation layer 116 is a layer that can inject holes into a layer in contact with the cathode side of the layer and electrons into a layer in contact with the anode side of the layer by applying a potential. The charge generation layer 116 includes at least a P-type layer 117. The P-type layer 117 is preferably formed using the composite material listed above as a material that can form the hole injection layer 111. The P-type layer 117 may also be formed by laminating a film containing an acceptor material and a film containing a hole transport material, both of which are materials that form the composite material. By applying a potential to the P-type layer 117, electrons are injected into the electron transport layer 114 and holes are injected into the cathode 102, and the light-emitting device operates.

[0186] It is preferable that the charge generating layer 116 be provided with either or both of an electron relay layer 118 and an electron injection buffer layer 119 in addition to the P-type layer 117 .

[0187] The electron relay layer 118 contains at least a substance having electron transport properties and has the function of preventing interaction between the electron injection buffer layer 119 and the P-type layer 117 and smoothly transferring electrons. The LUMO level of the substance having electron transport properties contained in the electron relay layer 118 is preferably between the LUMO level of the acceptor substance in the P-type layer 117 and the LUMO level of the substance contained in the layer of the electron transport layer 114 that is in contact with the charge generation layer 116. The specific energy level of the LUMO level of the substance having electron transport properties used in the electron relay layer 118 is −5.0 eV or higher, preferably −5.0 eV or higher and −3.0 eV or lower. Note that the substance having electron transport properties used in the electron relay layer 118 is preferably a phthalocyanine-based material or a metal complex having a metal-oxygen bond and an aromatic ligand.

[0188] The electron injection buffer layer 119 can be made of a material with high electron injection properties, such as alkali metals, alkaline earth metals, rare earth metals, and compounds thereof (alkali metal compounds (including oxides such as lithium oxide, halides, and carbonates such as lithium carbonate and cesium carbonate), alkaline earth metal compounds (including oxides, halides, and carbonates), or rare earth metal compounds (including oxides, halides, and carbonates)).

[0189] Furthermore, when the electron injection buffer layer 119 is formed to contain a substance having electron transport properties and a donor substance, examples of the donor substance that can be used include alkali metals, alkaline earth metals, rare earth metals, and compounds thereof (alkali metal compounds (including oxides such as lithium oxide, halides, and carbonates such as lithium carbonate and cesium carbonate), alkaline earth metal compounds (including oxides, halides, and carbonates), and rare earth metal compounds (including oxides, halides, and carbonates)), as well as organic compounds such as tetrathianaphthacene (abbreviation: TTN), nickelocene, and decamethylnickelocene.

[0190] The substance having an electron-transporting property can be formed using the same material as the material for forming the electron-transporting layer 114 described above. Since the material is an organic compound with a low refractive index, by using the material for the electron-injection buffer layer 119, a light-emitting device with good external quantum efficiency can be obtained.

[0191] Materials that can be used to form the cathode 102 include metals, alloys, electrically conductive compounds, and mixtures thereof that have a low work function (specifically, 3.8 eV or less). Specific examples of such cathode materials include alkali metals such as lithium (Li) and cesium (Cs), elements belonging to Group 1 or Group 2 of the periodic table such as magnesium (Mg), calcium (Ca), and strontium (Sr), alloys containing these (MgAg, AlLi), rare earth metals such as europium (Eu) and ytterbium (Yb), and alloys containing these. However, by providing an electron injection layer between the cathode 102 and the electron transport layer, various conductive materials, such as Al, Ag, ITO, and indium tin oxide containing silicon or silicon oxide, can be used as the cathode 102, regardless of the magnitude of the work function. These conductive materials can be formed into films using dry methods such as vacuum deposition and sputtering, inkjet printing, spin coating, and the like. Alternatively, the layer may be formed by a wet method using a sol-gel method, or by a wet method using a paste of a metal material.

[0192] In addition, various methods, whether dry or wet, can be used to form the EL layer 103. For example, vacuum deposition, gravure printing, offset printing, screen printing, inkjet printing, or spin coating may be used.

[0193] Furthermore, the above-mentioned electrodes or layers may be formed using different film formation methods.

[0194] The configuration of the layer provided between the anode 101 and the cathode 102 is not limited to the above. However, a configuration in which a light-emitting region where holes and electrons recombine is provided at a location away from the anode 101 and the cathode 102 is preferable, so as to suppress quenching caused by the proximity of the light-emitting region to the metals used in the electrodes and the carrier injection layer.

[0195] Furthermore, the hole transport layer and electron transport layer in contact with the light-emitting layer 113, particularly the carrier transport layer close to the recombination region in the light-emitting layer 113, are preferably made of a material having a band gap larger than the band gap of the light-emitting material constituting the light-emitting layer or the light-emitting material contained in the light-emitting layer, in order to suppress energy transfer from excitons generated in the light-emitting layer.

[0196] Next, an embodiment of a light-emitting device having a configuration in which multiple light-emitting units are stacked (also referred to as a stacked element or a tandem element) will be described with reference to FIG. 1(C). This light-emitting device has multiple light-emitting units between an anode and a cathode. One light-emitting unit has a configuration substantially similar to that of the EL layer 103 shown in FIG. 1(A). In other words, the light-emitting device shown in FIG. 1(C) is a light-emitting device having multiple light-emitting units, and the light-emitting device shown in FIG. 1(A) or 1(B) can be said to be a light-emitting device having one light-emitting unit.

[0197] 1(C), a first light-emitting unit 511 and a second light-emitting unit 512 are stacked between an anode 501 and a cathode 502, and a charge generation layer 513 is provided between the first light-emitting unit 511 and the second light-emitting unit 512. The anode 501 and the cathode 502 correspond to the anode 101 and the cathode 102 in FIG. 1(A), respectively, and the same components as those described in the description of FIG. 1(A) can be applied. The first light-emitting unit 511 and the second light-emitting unit 512 may have the same structure or different structures.

[0198] The charge generation layer 513 has a function of injecting electrons into one light-emitting unit and injecting holes into the other light-emitting unit when a voltage is applied between the anode 501 and the cathode 502. That is, in FIG. 1C, when a voltage is applied so that the potential of the anode is higher than the potential of the cathode, the charge generation layer 513 may inject electrons into the first light-emitting unit 511 and inject holes into the second light-emitting unit 512.

[0199] The charge generation layer 513 is preferably formed to have the same structure as the charge generation layer 116 described in FIG. 1B. A composite material of an organic compound and a metal oxide has excellent carrier injection and carrier transport properties, and therefore can achieve low-voltage driving and low-current driving. Note that when the anode side surface of the light-emitting unit is in contact with the charge generation layer 513, the charge generation layer 513 can also serve as a hole injection layer for the light-emitting unit, and therefore the light-emitting unit does not need to be provided with a hole injection layer.

[0200] Furthermore, when the electron injection buffer layer 119 is provided in the charge generation layer 513, the electron injection buffer layer 119 plays the role of an electron injection layer in the light-emitting unit on the anode side, so that it is not necessarily necessary to form an electron injection layer in the light-emitting unit on the anode side.

[0201] 1C illustrates a light-emitting device having two light-emitting units, but the present invention can also be applied to a light-emitting device having three or more stacked light-emitting units. By disposing a plurality of light-emitting units between a pair of electrodes and separating them with a charge-generating layer 513, as in the light-emitting device according to this embodiment, high-luminance light emission can be achieved while maintaining a low current density, and an element with a long life can be realized. Furthermore, a light-emitting device that can be driven at a low voltage and consumes low power can be realized.

[0202] Furthermore, by making each light-emitting unit emit a different light color, the light-emitting device as a whole can emit light of a desired color. For example, in a light-emitting device having two light-emitting units, it is possible to obtain a light-emitting device that emits white light as a whole by obtaining red and green light from the first light-emitting unit and blue light from the second light-emitting unit.

[0203] The layers and electrodes, such as the EL layer 103, the first light-emitting unit 511, the second light-emitting unit 512, and the charge generation layer, can be formed by, for example, an evaporation method (including a vacuum evaporation method), a droplet discharge method (also called an ink-jet method), a coating method, a gravure printing method, etc. They may also contain low-molecular-weight materials, medium-molecular-weight materials (including oligomers and dendrimers), or polymer materials.

[0204] This embodiment mode can be freely combined with other embodiment modes.

[0205] (Embodiment 2) In this embodiment, a light-emitting apparatus using the light-emitting device described in Embodiment 1 will be described.

[0206] In this embodiment, a light-emitting device manufactured using the light-emitting device described in Embodiment 1 will be described with reference to FIGS. 2A and 2B. FIG. 2A is a top view of the light-emitting device, and FIG. 2B is a cross-sectional view taken along dashed lines AB and CD in FIG. 2A. This light-emitting device includes a driver circuit section (source line driver circuit) 601, a pixel section 602, and a driver circuit section (gate line driver circuit) 603, all of which are shown by dotted lines, to control light emission from the light-emitting device. Reference numeral 604 denotes a sealing substrate, 605 denotes a sealant, and the inside surrounded by the sealant 605 forms a space 607.

[0207] The routing wiring 608 is wiring for transmitting signals input to the source line driver circuit 601 and the gate line driver circuit 603, and receives video signals, clock signals, start signals, reset signals, etc. from an FPC (flexible printed circuit) 609, which serves as an external input terminal. Although only the FPC is shown here, a printed wiring board (PWB) may be attached to this FPC. In this specification, the light-emitting device includes not only the light-emitting device itself, but also a state in which an FPC or PWB is attached to it.

[0208] Next, the cross-sectional structure will be described with reference to Fig. 2(B) . A driver circuit portion and a pixel portion are formed on an element substrate 610, and here, a source line driver circuit 601, which is the driver circuit portion, and one pixel in the pixel portion 602 are shown.

[0209] The element substrate 610 may be made of a substrate made of glass, quartz, organic resin, metal, alloy, semiconductor, or a plastic substrate made of FRP (Fiber Reinforced Plastics), PVF (Polyvinyl Fluoride), polyester, acrylic resin, or the like.

[0210] The structure of the transistors used in the pixels and driver circuits is not particularly limited. For example, they may be inverted staggered transistors or staggered transistors. Furthermore, they may be top-gate or bottom-gate transistors. The semiconductor material used for the transistors is not particularly limited, and examples thereof include silicon, germanium, silicon carbide, and gallium nitride. Alternatively, an oxide semiconductor containing at least one of indium, gallium, and zinc, such as an In-Ga-Zn-based metal oxide, may be used.

[0211] The crystallinity of a semiconductor material used for a transistor is not particularly limited, and any of an amorphous semiconductor and a crystalline semiconductor (a microcrystalline semiconductor, a polycrystalline semiconductor, a single crystal semiconductor, or a semiconductor having a crystalline region in part) may be used. The use of a crystalline semiconductor is preferable because it can suppress deterioration of transistor characteristics.

[0212] Here, it is preferable to use an oxide semiconductor for semiconductor devices such as transistors provided in the pixels and driver circuits, as well as transistors used in touch sensors, which will be described later. In particular, it is preferable to use an oxide semiconductor having a wider band gap than silicon. By using an oxide semiconductor having a wider band gap than silicon, the current in the off state of the transistor can be reduced.

[0213] The oxide semiconductor preferably contains at least indium (In) or zinc (Zn), and more preferably contains an oxide represented by In-M-Zn oxide (M is a metal such as Al, Ti, Ga, Ge, Y, Zr, Sn, La, Ce, or Hf).

[0214] In particular, it is preferable to use, as the semiconductor layer, an oxide semiconductor film having a plurality of crystal parts whose c-axes are oriented perpendicular to the surface on which the semiconductor layer is formed or the top surface of the semiconductor layer and which does not have grain boundaries between adjacent crystal parts.

[0215] By using such a material for the semiconductor layer, fluctuations in electrical characteristics are suppressed, and a highly reliable transistor can be realized.

[0216] Furthermore, a transistor having the above-described semiconductor layer can retain charge stored in a capacitor through the transistor for a long period of time due to its low off-state current. By applying such a transistor to a pixel, it is possible to stop the driver circuit while maintaining the gray level of an image displayed in each display region. As a result, an electronic device with extremely low power consumption can be realized.

[0217] To stabilize the characteristics of the transistor, it is preferable to provide an underlayer film. The underlayer film can be formed as a single layer or a multilayer using an inorganic insulating film such as a silicon oxide film, a silicon nitride film, a silicon oxynitride film, or a silicon nitride oxide film. The underlayer film can be formed by a sputtering method, a CVD (Chemical Vapor Deposition) method (such as a plasma CVD method, a thermal CVD method, or a MOCVD (Metal Organic CVD) method), an ALD (Atomic Layer Deposition) method, a coating method, a printing method, or the like. Note that the underlayer film need not be provided if it is not necessary.

[0218] Note that FET 623 represents one of the transistors formed in the drive circuit section 601. The drive circuit may be formed of various CMOS circuits, PMOS circuits, or NMOS circuits. In addition, although this embodiment shows a driver-integrated type in which the drive circuit is formed on a substrate, this is not necessarily required, and the drive circuit may also be formed externally rather than on the substrate.

[0219] Furthermore, the pixel section 602 is formed by a plurality of pixels each including a switching FET 611, a current control FET 612, and an anode 613 electrically connected to the drain of the FET, but is not limited to this, and the pixel section may be formed by combining three or more FETs and a capacitance element.

[0220] An insulator 614 is formed to cover the end of the anode 613. Here, it can be formed by using a positive photosensitive acrylic resin film.

[0221] Furthermore, in order to improve the coverage of an EL layer or the like to be formed later, a curved surface having a curvature is formed at the upper or lower end of the insulator 614. For example, when a positive photosensitive acrylic resin is used as the material for the insulator 614, it is preferable that only the upper end of the insulator 614 has a curved surface having a radius of curvature (0.2 μm to 3 μm). Furthermore, either a negative photosensitive resin or a positive photosensitive resin can be used as the insulator 614.

[0222] An EL layer 616 and a cathode 617 are formed on the anode 613. It is desirable to use a material with a large work function for the anode 613. For example, a single layer film such as an ITO film, an indium tin oxide film containing silicon, an indium oxide film containing 2 to 20 wt % zinc oxide, a titanium nitride film, a chromium film, a tungsten film, a Zn film, or a Pt film can be used. It is also possible to use a laminated structure of a titanium nitride film and a film mainly composed of aluminum, or a three-layer structure of a titanium nitride film, a film mainly composed of aluminum, and a titanium nitride film. The laminated structure provides low resistance as wiring, good ohmic contact, and the anode can function well.

[0223] The EL layer 616 is formed by various methods such as a vapor deposition method using a vapor deposition mask, an inkjet method, or a spin coating method. The EL layer 616 includes the components described in Embodiment 1. Other materials constituting the EL layer 616 may be low-molecular compounds or high-molecular compounds (including oligomers and dendrimers).

[0224] Furthermore, it is preferable to use a material with a small work function (Al, Mg, Li, Ca, or alloys or compounds thereof (MgAg, MgIn, AlLi, etc.)) as a material formed on the EL layer 616. When light generated in the EL layer 616 is transmitted through the cathode 617, it is preferable to use a laminate of a thin metal thin film and a transparent conductive film (ITO, indium oxide containing 2 to 20 wt % zinc oxide, indium tin oxide containing silicon, zinc oxide (ZnO), etc.) as the cathode 617.

[0225] Note that a light-emitting device is formed with the anode 613, the EL layer 616, and the cathode 617. The light-emitting device is the light-emitting device described in Embodiment 1. Note that a pixel portion is formed with a plurality of light-emitting devices, but the light-emitting device in this embodiment may include both the light-emitting device described in Embodiment 1 and light-emitting devices having other structures.

[0226] Furthermore, by bonding the sealing substrate 604 to the element substrate 610 with a sealing material 605, a structure is formed in which a light-emitting device 618 is provided in a space 607 surrounded by the element substrate 610, the sealing substrate 604, and the sealing material 605. The space 607 is filled with a filler, and in some cases, it is filled with an inert gas (nitrogen, argon, etc.), or with a sealing material. A recess is formed in the sealing substrate, and by providing a desiccant there, deterioration due to the influence of moisture can be suppressed, which is a preferable configuration.

[0227] It is preferable to use epoxy resin or glass frit for the sealing material 605. It is also desirable that these materials are as moisture and oxygen impermeable as possible. In addition to glass and quartz substrates, plastic substrates made of FRP (Fiber Reinforced Plastics), PVF (Polyvinyl Fluoride), polyester, acrylic resin, etc. can be used for the sealing substrate 604.

[0228] Although not shown in Figures 2(A) and 2(B), a protective film may be provided on the cathode. The protective film may be formed of an organic resin film or an inorganic insulating film. The protective film may also be formed so as to cover the exposed portion of the sealing material 605. The protective film may also be provided so as to cover the surfaces and side surfaces of the pair of substrates, the exposed side surfaces of the sealing layer, the insulating layer, etc.

[0229] The protective film can be made of a material that is impermeable to impurities such as water, and therefore can effectively prevent impurities such as water from diffusing from the outside to the inside.

[0230] The protective film may be made of an oxide, a nitride, a fluoride, a sulfide, a ternary compound, a metal, a polymer, or the like. For example, a material containing aluminum oxide, hafnium oxide, hafnium silicate, lanthanum oxide, silicon oxide, strontium titanate, tantalum oxide, titanium oxide, zinc oxide, niobium oxide, zirconium oxide, tin oxide, yttrium oxide, cerium oxide, scandium oxide, erbium oxide, vanadium oxide, indium oxide, or the like; a material containing aluminum nitride, hafnium nitride, silicon nitride, tantalum nitride, titanium nitride, niobium nitride, molybdenum nitride, zirconium nitride, gallium nitride, or the like; a nitride containing titanium and aluminum; an oxide containing titanium and aluminum; an oxide containing aluminum and zinc; a sulfide containing manganese and zinc; a sulfide containing cerium and strontium; an oxide containing erbium and aluminum; or an oxide containing yttrium and zirconium.

[0231] The protective film is preferably formed using a film formation method that provides good step coverage. One such method is atomic layer deposition (ALD). It is preferable to use a material that can be formed using the ALD method for the protective film. By using the ALD method, it is possible to form a dense protective film with reduced defects such as cracks and pinholes, or with a uniform thickness. In addition, it is possible to reduce damage to the workpiece when forming the protective film.

[0232] For example, by forming a protective film using the ALD method, it is possible to form a uniform protective film with few defects on surfaces with complex uneven shapes, as well as on the top, side, and back surfaces of a touch panel.

[0233] In the above manner, a light-emitting device manufactured using the light-emitting device described in Embodiment 1 can be obtained.

[0234] The light-emitting device in this embodiment can have favorable characteristics because it uses the light-emitting device described in Embodiment 1. Specifically, the light-emitting device described in Embodiment 1 has favorable luminous efficiency, and therefore can have low power consumption.

[0235] 3A and 3B show an example of a full-color light-emitting device in which a light-emitting device that emits white light is formed and a colored layer (color filter) is provided, etc. Fig. 3A shows a substrate 1001, a base insulating film 1002, a gate insulating film 1003, gate electrodes 1006, 1007, and 1008, a first interlayer insulating film 1020, a second interlayer insulating film 1021, a peripheral portion 1042, a pixel portion 1040, a driver circuit portion 1041, anodes 1024W, 1024R, 1024G, and 1024B of the light-emitting device, a partition wall 1025, an EL layer 1028, a cathode 1029 of the light-emitting device, a sealing substrate 1031, a sealant 1032, etc.

[0236] In FIG. 3A, the colored layers (a red colored layer 1034R, a green colored layer 1034G, and a blue colored layer 1034B) are provided on a transparent base material 1033. A black matrix 1035 may also be provided. The transparent base material 1033 on which the colored layers and the black matrix are provided is aligned and fixed to the substrate 1001. The colored layers and the black matrix 1035 are covered with an overcoat layer 1036. In FIG. 3A, there are light-emitting layers from which light does not pass through the colored layers and exits to the outside, and light-emitting layers from which light passes through the colored layers of each color and exits to the outside. Light that does not pass through the colored layers is white, and light that passes through the colored layers is red, green, and blue, so that an image can be displayed using four color pixels.

[0237] 3B shows an example in which colored layers (a red colored layer 1034R, a green colored layer 1034G, and a blue colored layer 1034B) are formed between the gate insulating film 1003 and the first interlayer insulating film 1020. In this way, the colored layers may be provided between the substrate 1001 and the sealing substrate 1031.

[0238] Furthermore, the light-emitting device described above has a structure in which light is extracted from the substrate 1001 side on which the FET is formed (bottom emission type), but it may also have a structure in which light is extracted from the sealing substrate 1031 side (top emission type). A cross-sectional view of a top emission type light-emitting device is shown in FIG. 4. In this case, a light-opaque substrate can be used as the substrate 1001. The process is the same as for a bottom emission type light-emitting device up to the formation of a connection electrode that connects the FET and the anode of the light-emitting device. Thereafter, a third interlayer insulating film 1037 is formed to cover the electrode 1022. This insulating film may also serve as a planarizing film. The third interlayer insulating film 1037 can be formed using the same material as the second interlayer insulating film 1021, as well as other known materials.

[0239] The anodes 1024W, 1024R, 1024G, and 1024B of the light-emitting device may be cathodes. In the case of a top-emission light-emitting device as shown in FIG. 4, the anodes are preferably reflective electrodes. The EL layer 1028 has the same structure as that of the EL layer 103 in the first embodiment, and has an element structure that allows white light emission.

[0240] In the top-emission structure shown in FIG. 4, sealing can be performed using a sealing substrate 1031 provided with colored layers (a red colored layer 1034R, a green colored layer 1034G, and a blue colored layer 1034B). The sealing substrate 1031 may be provided with a black matrix 1035 positioned between pixels. The colored layers (the red colored layer 1034R, the green colored layer 1034G, and the blue colored layer 1034B) and the black matrix 1035 may be covered with an overcoat layer 1036. Note that a light-transmitting substrate is used as the sealing substrate 1031. In addition, although an example of full-color display using four colors, red, green, blue, and white, is shown here, this is not particularly limited, and full-color display using four colors, red, yellow, green, and blue, or three colors, red, green, and blue, may also be performed.

[0241] A microcavity structure is suitable for use in top-emission light-emitting devices. A light-emitting device with a microcavity structure can be obtained by using a reflective electrode as the anode and a semi-transparent / semi-reflective electrode as the cathode. At least an EL layer is present between the reflective electrode and the semi-transparent / semi-reflective electrode, and at least an emissive layer that serves as the light-emitting region is present.

[0242] The reflectance of the reflective electrode to visible light is 40% to 100%, preferably 70% to 100%, and the resistivity is 1×10 -2 The semi-transmitting and semi-reflective electrode has a visible light reflectance of 20% to 80%, preferably 40% to 70%, and a resistivity of 1×10 -2 It is assumed that the film has a resistance of Ωcm or less.

[0243] The light emitted from the light-emitting layer included in the EL layer is reflected by the reflective electrode and the semi-transmissive and semi-reflective electrode, causing resonance.

[0244] In this light-emitting device, the optical distance between the reflective electrode and the semi-transparent / semi-reflective electrode can be changed by changing the thickness of the transparent conductive film, the composite material described above, the carrier transport material, etc. This makes it possible to intensify light with resonant wavelengths and attenuate light with non-resonant wavelengths between the reflective electrode and the semi-transparent / semi-reflective electrode.

[0245] Note that, since the light reflected by the reflective electrode and returned (first reflected light) significantly interferes with the light (first incident light) that directly enters the semi-transmissive-semi-reflective electrode from the light-emitting layer, it is preferable to adjust the optical distance between the reflective electrode and the light-emitting layer to (2n-1)λ / 4 (where n is a natural number greater than or equal to 1, and λ is the wavelength of the emitted light to be amplified). By adjusting this optical distance, the phases of the first reflected light and the first incident light can be matched, thereby further amplifying the light emitted from the light-emitting layer.

[0246] In the above configuration, the EL layer may have a structure having multiple light-emitting layers or a structure having a single light-emitting layer. For example, it may be combined with the above-mentioned tandem light-emitting device configuration, in which multiple EL layers are provided in one light-emitting device with a charge-generating layer sandwiched therebetween, and one or more light-emitting layers are formed in each EL layer.

[0247] The microcavity structure makes it possible to increase the light emission intensity of specific wavelengths in the front direction, thereby reducing power consumption. In the case of a light-emitting device that displays images using four sub-pixels of red, yellow, green, and blue, not only is the yellow light emitted effective in improving brightness, but the microcavity structure that matches the wavelength of each color can be applied to all sub-pixels, resulting in a light-emitting device with good characteristics.

[0248] The light-emitting device in this embodiment can have favorable characteristics because it uses the light-emitting device described in Embodiment 1. Specifically, the light-emitting device described in Embodiment 1 has favorable luminous efficiency, and therefore can have low power consumption.

[0249] Up to this point, active matrix light-emitting devices have been described. Below, passive matrix light-emitting devices will be described. FIGS. 5A and 5B show a passive matrix light-emitting device manufactured by applying the present invention. FIG. 5A is a perspective view of the light-emitting device, and FIG. 5B is a cross-sectional view of FIG. 5A taken along the dashed-dotted line XY. In FIG. 5, an EL layer 955 is provided between an electrode 952 and an electrode 956 on a substrate 951. An end of the electrode 952 is covered with an insulating layer 953. A partition layer 954 is provided on the insulating layer 953. The sidewalls of the partition layer 954 are inclined such that the distance between one sidewall and the other sidewall becomes narrower as the distance becomes closer to the substrate surface. That is, the cross section of the partition layer 954 in the short side direction is trapezoidal, and the bottom side (the side facing the same direction as the surface of the insulating layer 953 and in contact with the insulating layer 953) is shorter than the top side (the side facing the same direction as the surface of the insulating layer 953 and not in contact with the insulating layer 953). By providing the partition layer 954 in this manner, defects in the light-emitting device due to static electricity or the like can be prevented. Furthermore, the light-emitting device described in Embodiment 1 is used in a passive matrix light-emitting device, and the light-emitting device can be highly reliable or consumes less power.

[0250] The light emitting device described above is capable of individually controlling a large number of minute light emitting devices arranged in a matrix, and is therefore suitable for use as a display device for displaying images.

[0251] This embodiment mode can be freely combined with other embodiment modes.

[0252] (Embodiment 3) In this embodiment, an example in which the light-emitting device described in Embodiment 1 is used as a lighting device will be described with reference to Fig. 6. Fig. 6(B) is a top view of the lighting device, and Fig. 6(A) is a cross-sectional view taken along line ef shown in Fig. 6(B).

[0253] In the lighting device of this embodiment, an anode 401 is formed on a light-transmitting substrate 400, which serves as a support. The anode 401 corresponds to the anode 101 in Embodiment 1. When light is extracted from the anode 401 side, the anode 401 is formed from a light-transmitting material.

[0254] A pad 412 for supplying a voltage to the cathode 404 is formed on the substrate 400 .

[0255] An EL layer 403 is formed on the anode 401. The EL layer 403 corresponds to the configuration of the EL layer 103 in Embodiment 1, or a configuration in which the light-emitting units 511 and 512 and the charge generation layer 513 are combined. For details of these configurations, please refer to the relevant descriptions.

[0256] Cathode 404 is formed to cover EL layer 403. Cathode 404 corresponds to cathode 102 in Embodiment 1. When light is extracted from the anode 401 side, cathode 404 is formed of a material with high reflectivity. Cathode 404 is connected to pad 412 to supply voltage.

[0257] As described above, the lighting device described in this embodiment has a light-emitting device including the anode 401, the EL layer 403, and the cathode 404. Since the light-emitting device has high luminous efficiency, the lighting device in this embodiment can be a lighting device with low power consumption.

[0258] The lighting device is completed by bonding and sealing the substrate 400 on which the light-emitting device having the above structure is formed and a sealing substrate 407 using sealants 405 and 406. Either one of the sealants 405 and 406 may be used. Also, a desiccant may be mixed into the inner sealant 406 (not shown in FIG. 6(B)), which can absorb moisture and improve reliability.

[0259] Furthermore, an external input terminal can be formed by extending a portion of the pad 412 and the anode 401 outside the sealing materials 405 and 406. An IC chip 420 equipped with a converter or the like may also be provided thereon.

[0260] As described above, the lighting device described in this embodiment uses the light-emitting device described in Embodiment 1 as its EL element, and can be a lighting device with low power consumption.

[0261] This embodiment mode can be freely combined with other embodiment modes.

[0262] (Fourth embodiment) In this embodiment, an example of an electronic device including the light-emitting device described in Embodiment 1 as a part thereof will be described. The light-emitting device described in Embodiment 1 has good light-emitting efficiency and low power consumption. As a result, the electronic device described in this embodiment can be an electronic device having a light-emitting portion with low power consumption.

[0263] Examples of electronic devices to which the light-emitting devices are applied include television sets (also called televisions or television receivers), computer monitors, digital cameras, digital video cameras, digital photo frames, mobile phones (also called mobile phones or mobile phone devices), portable game machines, personal digital assistants, sound players, large game machines such as pachinko machines, etc. Specific examples of these electronic devices are shown below.

[0264] 7A illustrates an example of a television set. The television set includes a display portion 7103 built in a housing 7101. Here, the housing 7101 is supported by a stand 7105. The display portion 7103 can display images, and the light-emitting devices described in Embodiment 1 are arranged in a matrix.

[0265] The television set can be operated using operation switches provided on the housing 7101 or a separate remote control 7110. Channels and volume can be controlled using operation keys 7109 provided on the remote control 7110, and images displayed on the display portion 7103 can be controlled. The remote control 7110 may be provided with a display portion 7107 that displays information output from the remote control 7110. Note that the light-emitting devices described in Embodiment 1 arranged in a matrix can also be applied to the display portion 7107.

[0266] The television device is configured to include a receiver, a modem, etc. The receiver can receive general television broadcasts, and by connecting to a wired or wireless communication network via the modem, it is also possible to perform one-way (from sender to receiver) or two-way (between sender and receiver, or between receivers, etc.) information communication.

[0267] FIG. 7B1 shows a computer including a main body 7201, a housing 7202, a display portion 7203, a keyboard 7204, an external connection port 7205, a pointing device 7206, and the like. Note that this computer is manufactured by using the light-emitting devices described in Embodiment 1 arranged in a matrix for the display portion 7203. The computer in FIG. 7B1 may have a configuration as shown in FIG. 7B2. The computer in FIG. 7B2 is provided with a display portion 7210 instead of the keyboard 7204 and the pointing device 7206. The display portion 7210 is a touch panel type, and input can be performed by operating an input display on the display portion 7210 with a finger or a dedicated pen. The display portion 7210 can display not only an input display but also other images. The display portion 7203 may also be a touch panel. The two screens are connected by a hinge, which can prevent the screens from being scratched or broken during storage or transportation.

[0268] 7C shows an example of a mobile terminal. The mobile phone includes a display portion 7402 incorporated in a housing 7401, operation buttons 7403, an external connection port 7404, a speaker 7405, a microphone 7406, and the like. Note that the mobile phone has the display portion 7402 in which the light-emitting devices described in Embodiment 1 are arranged in a matrix.

[0269] 7C can be configured so that information can be input by touching the display portion 7402 with a finger or the like. In this case, operations such as making a call or creating an e-mail can be performed by touching the display portion 7402 with a finger or the like.

[0270] The screen of the display unit 7402 has three main modes. The first is a display mode that mainly displays images, the second is an input mode that mainly inputs information such as characters, and the third is a display+input mode that combines the display mode and the input mode.

[0271] For example, when making a call or creating an e-mail, the display portion 7402 may be set to a character input mode mainly for inputting characters, and characters displayed on the screen may be input. In this case, it is preferable to display a keyboard or number buttons on most of the screen of the display portion 7402.

[0272] Furthermore, by providing a detection device having a sensor for detecting tilt, such as a gyroscope or an acceleration sensor, inside the mobile terminal, the orientation of the mobile terminal (portrait or landscape) can be determined and the screen display of the display portion 7402 can be automatically switched.

[0273] The screen mode can be switched by touching the display portion 7402 or by operating the operation buttons 7403 on the housing 7401. The screen mode can also be switched depending on the type of image displayed on the display portion 7402. For example, if the image signal to be displayed on the display portion is moving image data, the display mode is selected, and if it is text data, the input mode is selected.

[0274] In addition, in the input mode, a signal detected by an optical sensor of the display portion 7402 may be detected, and if there is no input by touch operation on the display portion 7402 for a certain period of time, the screen mode may be controlled to switch from the input mode to the display mode.

[0275] The display portion 7402 can also function as an image sensor. For example, personal authentication can be performed by touching the display portion 7402 with a palm or a finger to capture an image of a palm print, fingerprint, or the like. Furthermore, by using a backlight that emits near-infrared light or a sensing light source that emits near-infrared light for the display portion, finger veins, palm veins, or the like can also be captured.

[0276] Note that the structure described in this embodiment mode can be used by combining the structures described in any of Embodiment Modes 1 to 3 as appropriate.

[0277] As described above, the light-emitting device having the light-emitting device described in Embodiment 1 or 2 has a very wide range of application, and this light-emitting device can be applied to electronic devices in a wide range of fields. By using the light-emitting device described in Embodiment 1 or 2, electronic devices with low power consumption can be obtained.

[0278] FIG. 8(A) is a schematic diagram showing an example of a cleaning robot.

[0279] The cleaning robot 5100 has a display 5101 arranged on its top surface, multiple cameras 5102 arranged on its side, a brush 5103, and an operation button 5104. Although not shown, the cleaning robot 5100 is also provided with tires, a suction port, and the like on its bottom surface. The cleaning robot 5100 also has various other sensors such as an infrared sensor, an ultrasonic sensor, an acceleration sensor, a piezoelectric sensor, an optical sensor, and a gyro sensor. The cleaning robot 5100 also has wireless communication means.

[0280] The cleaning robot 5100 can move by itself, detect dust 5120, and suck up the dust from a suction port provided on the bottom surface.

[0281] Furthermore, the cleaning robot 5100 can analyze the image captured by the camera 5102 to determine whether there are any obstacles such as walls, furniture, or steps. Furthermore, if the image analysis detects an object that may become tangled in the brush 5103, such as a wire, the rotation of the brush 5103 can be stopped.

[0282] The display 5101 can display the remaining battery level, the amount of dust that has been sucked up, etc. The path traveled by the cleaning robot 5100 may be displayed on the display 5101. The display 5101 may also be a touch panel, and an operation button 5104 may be provided on the display 5101.

[0283] The cleaning robot 5100 can communicate with a portable electronic device 5140 such as a smartphone. Images captured by the camera 5102 can be displayed on the portable electronic device 5140. Therefore, the owner of the cleaning robot 5100 can know the state of the room even when he or she is away from home. In addition, the display on the display 5101 can be confirmed on the portable electronic device such as a smartphone.

[0284] The light-emitting device according to one embodiment of the present invention can be used for the display 5101 .

[0285] The robot 2100 shown in FIG. 8(B) includes a computing device 2110, an illuminance sensor 2101, a microphone 2102, an upper camera 2103, a speaker 2104, a display 2105, a lower camera 2106, an obstacle sensor 2107, and a movement mechanism 2108.

[0286] The microphone 2102 has a function of detecting the user's speaking voice, environmental sounds, etc. The speaker 2104 has a function of emitting sound. The robot 2100 can communicate with the user using the microphone 2102 and the speaker 2104.

[0287] The display 2105 has a function of displaying various information. The robot 2100 can display information desired by the user on the display 2105. The display 2105 may be equipped with a touch panel. The display 2105 may also be a detachable information terminal, which can be installed in a fixed position on the robot 2100 to enable charging and data transfer.

[0288] The upper camera 2103 and the lower camera 2106 have a function of capturing images of the surroundings of the robot 2100. In addition, the obstacle sensor 2107 can detect the presence or absence of an obstacle in the moving direction when the robot 2100 moves forward using the moving mechanism 2108. The robot 2100 can recognize the surrounding environment and move safely using the upper camera 2103, the lower camera 2106, and the obstacle sensor 2107. The light-emitting device of one embodiment of the present invention can be used for the display 2105.

[0289] 8(C) is a diagram showing an example of a goggle-type display. The goggle-type display includes, for example, a housing 5000, a display unit 5001, a speaker 5003, an LED lamp 5004, a connection terminal 5006, a sensor 5007 (including a function for measuring force, displacement, position, velocity, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, odor, or infrared ray), a microphone 5008, a display unit 5002, a support unit 5012, and earphones 5013.

[0290] The light-emitting device of one embodiment of the present invention can be used for the display portion 5001 and the display portion 5002 .

[0291] 9 shows an example in which the light-emitting device described in Embodiment 1 is used in a desk lamp, which is a lighting device. The desk lamp shown in FIG. 9 includes a housing 2001 and a light source 2002, and the lighting device described in Embodiment 3 may be used as the light source 2002.

[0292] FIG. 10 shows an example in which the light-emitting device described in Embodiment 1 is used as an indoor lighting device 3001. The light-emitting device described in Embodiment 1 has high emission efficiency and can therefore be used as a lighting device with low power consumption. In addition, the light-emitting device described in Embodiment 1 can be made large in area and can therefore be used as a large-area lighting device. In addition, the light-emitting device described in Embodiment 1 is thin and can therefore be used as a thin lighting device.

[0293] The light-emitting device described in Embodiment 1 can also be mounted on a windshield or dashboard of an automobile. Figure 11 shows one mode in which the light-emitting device described in Embodiment 1 is used on a windshield or dashboard of an automobile. Display regions 5200 to 5203 are displays provided using the light-emitting device described in Embodiment 1.

[0294] The display region 5200 and the display region 5201 are display devices equipped with the light-emitting device described in Embodiment 1 and provided on the windshield of an automobile. The light-emitting device described in Embodiment 1 can be a so-called see-through display device, in which the opposite side can be seen through, by fabricating the anode and cathode using light-transmitting electrodes. A see-through display can be installed on the windshield of an automobile without obstructing the view. Note that when a transistor or the like is provided for driving the device, a light-transmitting transistor such as an organic transistor made of an organic semiconductor material or a transistor using an oxide semiconductor is preferably used.

[0295] The display area 5202 is a display device provided on a pillar and incorporating the light-emitting device described in Embodiment 1. By displaying an image from an imaging means provided on the vehicle body in the display area 5202, the view blocked by the pillar can be complemented. Similarly, the display area 5203 provided on the dashboard can complement the view blocked by the vehicle body by displaying an image from an imaging means provided on the outside of the vehicle, thereby compensating for blind spots and improving safety. By displaying an image to complement the invisible parts, safety can be confirmed more naturally and without discomfort.

[0296] The display area 5203 can also provide various information such as navigation information, a speedometer, a tachometer, and air conditioning settings. The display items and layout can be changed as needed to suit the user's preferences. This information can also be provided in the display areas 5200 to 5203. The display areas 5200 to 5203 can also be used as lighting devices.

[0297] 12A and 12B show a foldable mobile information terminal 5150. The foldable mobile information terminal 5150 has a housing 5151, a display area 5152, and a bending portion 5153. FIG. 12A shows the mobile information terminal 5150 in an unfolded state. FIG. 12B shows the mobile information terminal 5150 in a folded state. Although the mobile information terminal 5150 has a large display area 5152, it is compact and highly portable when folded.

[0298] Display area 5152 can be folded in half by bending portion 5153. Bending portion 5153 is composed of an expandable member and multiple support members, and when folding, the expandable member stretches and bending portion 5153 is folded with a curvature radius of 2 mm or more, preferably 3 mm or more.

[0299] Note that the display region 5152 may be a touch panel (input / output device) equipped with a touch sensor (input device). The light-emitting device of one embodiment of the present invention can be used for the display region 5152.

[0300] 13(A) to 13(C) show a foldable mobile information terminal 9310. Fig. 13(A) shows the mobile information terminal 9310 in an unfolded state. Fig. 13(B) shows the mobile information terminal 9310 in a state in the process of changing from one of an unfolded state and a folded state to the other. Fig. 13(C) shows the mobile information terminal 9310 in a folded state. The mobile information terminal 9310 has excellent portability in a folded state, and has excellent display visibility due to a seamless, wide display area in an unfolded state.

[0301] The display panel 9311 is supported by three housings 9315 connected by hinges 9313. Note that the display panel 9311 may be a touch panel (input / output device) equipped with a touch sensor (input device). The display panel 9311 can be reversibly transformed from an unfolded state of the mobile information terminal 9310 to a folded state by bending the two housings 9315 via the hinges 9313. The light-emitting device of one embodiment of the present invention can be used for the display panel 9311. [Example]

[0302] Example 1 In this example, a light-emitting device 1 according to one embodiment of the present invention and a comparative light-emitting device 1 will be described. The structural formulae of organic compounds used in this example are shown below.

[0303] [ka]

[0304] (Method for fabricating light-emitting device 1) First, a silver (Ag), palladium (Pd), and copper (Cu) alloy film (Ag-Pd-Cu (APC) film) was formed on a glass substrate by sputtering to a thickness of 100 nm as a reflective electrode, and then an indium tin oxide (ITSO) film containing silicon oxide was formed by sputtering to a thickness of 85 nm as a transparent electrode to form an anode 101. The electrode area was 4 mm 2 (2mm x 2mm).

[0305] Next, as a pretreatment for forming a light-emitting device on the substrate, the substrate surface was washed with water, baked at 200°C for 1 hour, and then subjected to UV ozone treatment for 370 seconds.

[0306] Then, 10 -4 The substrate was introduced into a vacuum deposition apparatus whose internal pressure had been reduced to about Pa, and after vacuum baking at 170°C for 30 minutes in the heating chamber of the vacuum deposition apparatus, the substrate was allowed to cool for about 30 minutes.

[0307] Next, the substrate on which the anode 101 was formed was fixed to a substrate holder installed in a vacuum deposition apparatus so that the surface on which the anode 101 was formed faced downward. N-(1,1'-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF) represented by the above structural formula (i) and an electron acceptor material (OCHD-001) were co-deposited on the anode 101 by a deposition method to a thickness of 10 nm at a weight ratio of 1:0.05 (= PCBBiF:OCHD-001) to form a hole injection layer 111.

[0308] After PCBBiF was deposited on the hole injection layer 111 to a thickness of 20 nm, N,N-bis[4-(dibenzofuran-4-yl)phenyl]-4-amino-p-terphenyl (abbreviation: DBfBB1TP) represented by the above structural formula (ii) was deposited to a thickness of 10 nm to form the hole transport layer 112.

[0309] Subsequently, 3,3'-(naphthalene-1,4-diyl)bis(9-phenyl-9H-carbazole) (abbreviation: PCzN2) represented by the above structural formula (iii) was vapor-deposited on the hole transport layer 112 to a thickness of 10 nm to form an electron blocking layer.

[0310] Thereafter, 2-(10-phenyl-9-anthracenyl)-benzo[b]naphtho[2,3-d]furan (abbreviation: Bnf(II)PhA) represented by the above structural formula (iv) and 3,10-bis[N-(9-phenyl-9H-carbazol-2-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviation: 3,10PCA2Nbf(IV)-02) represented by the above structural formula (v) were co-deposited to a thickness of 25 nm in a weight ratio of 1:0.015 (=Bnf(II)PhA:3,10PCA2Nbf(IV)-02) to form the light-emitting layer 113.

[0311] After that, 2-{(3',5'-di-tert-butyl)-1,1'-biphenyl-3-yl}-4,6-bis(3,5-di-tert-butylphenyl)-1,3,5-triazine (abbreviation: mmtBumBP-dmmtBuPTzn) represented by the above structural formula (x) was evaporated to a thickness of 10 nm to form a hole blocking layer, and then mmtBumBP-dmmtBuPTzn and 6-methyl-8-quinolinolato-lithium (abbreviation: Li-6mq) represented by the above structural formula (vii) were co-evaporated to a thickness of 20 nm to give a weight ratio of 1:1 (= mmtBumBP-dmmtBuPTzn:Li-6mq) to form an electron transport layer 114.

[0312] After forming the electron transport layer 114, Li-6mq was deposited to a thickness of 1 nm to form the electron injection layer 115. Finally, silver (Ag) and magnesium (Mg) were co-deposited in a volume ratio of 1:0.1 to a thickness of 15 nm to form the cathode 102, thereby producing the light-emitting device 1. The cathode 102 is a semi-transparent / semi-reflective electrode that has the functions of reflecting and transmitting light, and the light-emitting device of this example is a top-emission device that extracts light from the cathode 102. In addition, 1,3,5-tri(dibenzothiophen-4-yl)-benzene (abbreviation: DBT3P-II) represented by the above structural formula (xi) was deposited to a thickness of 70 nm on the cathode 102 to improve the light extraction efficiency.

[0313] (Method for producing comparative light-emitting device 1) The comparative light-emitting device 1 was fabricated by changing the thickness of PCBBiF in the hole transport layer 112 of the light-emitting device 1 to 15 nm, changing the mmtBumBP-dmmtBuPTzn used in the hole blocking layer to 2-[3'-(9,9-dimethyl-9H-fluoren-2-yl)-1,1'-biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mFBPTzn) represented by the above structural formula (vi), and changing the mmtBumBP-dmmtBuPTzn used in the electron transport layer 114 to Light-emitting device 1 was fabricated in the same manner as light-emitting device 1, except that tBuPTzn was replaced with 2-[3-(2,6-dimethyl-3-pyridinyl)-5-(9-phenanthrenyl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mPn-mDMePyPTzn) represented by the above structural formula (xix), and Li-6mq used in the electron transport layer 114 and the electron injection layer 115 was replaced with 8-quinolinolato-lithium (abbreviation: Liq) represented by the above structural formula (ix). The thickness of the hole transport layer was adjusted so that the chromaticity was similar between the devices.

[0314] The device structures of the light-emitting device 1 and the comparative light-emitting device 1 are summarized in the table below.

[0315] [Table 1]

[0316] The refractive indices of mmtBumBP-dmmtBuPTzn, mPn-mDMePyPTzn, Li-6mq, and Liq are shown in Figure 14, and their refractive indices at 456 nm are shown in Table 2 below. Measurements were performed using a spectroscopic ellipsometer (M-2000U, manufactured by J.A. Woollam Japan). The measurement samples used were films of each layer formed by vacuum deposition onto a quartz substrate to a thickness of approximately 50 nm. Figure 14 also lists the refractive index for ordinary rays, n, Ordinary, and the refractive index for extraordinary rays, n, Extraordinary.

[0317] As shown in Figure 14, the ordinary refractive index of mmtBumBP-dmmtBuPTzn was 1.60 to 1.61 in the entire blue emission region (455 nm to 465 nm), ranging from 1.50 to 1.75. Furthermore, the ordinary refractive index at 633 nm was 1.57, ranging from 1.45 to 1.70, indicating that mmtBumBP-dmmtBuPTzn is a low-refractive-index material. Furthermore, the ordinary refractive index of Li-6mq was 1.67 in the entire blue emission region (455 nm to 465 nm), ranging from 1.45 to 1.70. Furthermore, the ordinary refractive index at 633 nm was 1.61, ranging from 1.40 to 1.65, indicating that Li-6mq is a low-refractive-index material.

[0318] This shows that the light-emitting device 1 is a light-emitting device in which the ordinary refractive index of the electron transport layer 114 is in the range of 1.50 or more and less than 1.75 throughout the entire blue light-emitting region (455 nm or more and 465 nm or less), and in the range of 1.45 or more and less than 1.70 at 633 nm.

[0319] [Table 2]

[0320] The above-mentioned light-emitting device 1 and comparative light-emitting device 1 were sealed with glass substrates in a nitrogen-atmosphere glove box to prevent the light-emitting devices from being exposed to the atmosphere (a UV-curable sealant was applied around the elements, UV was irradiated only on the sealant without irradiating the light-emitting device, and heat-treated at 80°C under atmospheric pressure for 1 hour), and then the initial characteristics of these light-emitting devices were measured. Note that no special measures were taken on the sealed glass substrates to improve light extraction efficiency.

[0321] The luminance-current density characteristics of light-emitting device 1 and comparative light-emitting device 1 are shown in Figure 15, the current efficiency-luminance characteristics in Figure 16, the luminance-voltage characteristics in Figure 17, the current-voltage characteristics in Figure 18, the blue index-luminance characteristics in Figure 19, and the emission spectra in Figure 20. The 1000 cd / m 2 The main characteristics in this range are shown in Table 3. The luminance, CIE chromaticity, and emission spectrum were measured using a spectroradiometer (SR-UL1R, manufactured by Topcon Corporation) at room temperature.

[0322] The blue index (BI) is the current efficiency (cd / A) divided by the chromaticity y (cd / A / y), and is one index that represents the luminous characteristics of blue light emission. The smaller the chromaticity y, the higher the color purity of blue light emission tends to be. Blue light emission with high color purity can express a wide range of blue colors even with a small luminance component. By using blue light emission with high color purity, the required luminance to express blue colors is reduced, resulting in reduced power consumption. Therefore, the BI, which takes into account the chromaticity y, an index of blue purity, is preferably used as a means of expressing the efficiency of blue light emission. Therefore, it can be said that light-emitting devices with a higher BI have better efficiency as blue light-emitting devices used in displays.

[0323] [Table 3]

[0324] 15 to 20 and Table 3, it can be seen that the light-emitting device 1 using the low refractive index material of one embodiment of the present invention is an EL device with better current efficiency than the comparative light-emitting device 1, while showing almost the same emission spectrum as the comparative light-emitting device 1.

[0325] Furthermore, the light-emitting device 1 and the comparative light-emitting device 1 have a luminance of 1000 cd / m 2 The blue index (BI) values ​​at the 0.01 and 0.02 nm wavelengths were 153 (cd / A / y) and 148 (cd / A / y), respectively, and the maximum BI values ​​were 161 (cd / A / y) and 149 (cd / A / y), respectively. Thus, light-emitting device 1 can be said to be a light-emitting device with particularly good BI. Therefore, one embodiment of the present invention is suitable for light-emitting devices used in displays. [Example]

[0326] In this example, a light-emitting device 2 according to one embodiment of the present invention and a comparative light-emitting device 2 will be described. The structural formulae of organic compounds used in this example are shown below.

[0327] [ka]

[0328] (Method for fabricating light-emitting device 2) First, a silver (Ag), palladium (Pd), and copper (Cu) alloy film (Ag-Pd-Cu (APC) film) was formed on a glass substrate by sputtering to a thickness of 100 nm as a reflective electrode, and then an indium tin oxide (ITSO) film containing silicon oxide was formed by sputtering to a thickness of 10 nm as a transparent electrode to form an anode 101. The electrode area was 4 mm 2 (2mm x 2mm).

[0329] Next, as a pretreatment for forming a light-emitting device on the substrate, the substrate surface was washed with water, baked at 200°C for 1 hour, and then subjected to UV ozone treatment for 370 seconds.

[0330] Then, 10-4 The substrate was introduced into a vacuum deposition apparatus whose internal pressure had been reduced to about Pa, and after vacuum baking at 170°C for 30 minutes in the heating chamber of the vacuum deposition apparatus, the substrate was allowed to cool for about 30 minutes.

[0331] Next, the substrate on which the anode 101 was formed was fixed to a substrate holder installed in a vacuum deposition apparatus so that the surface on which the anode 101 was formed faced downward. N-(1,1'-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF) represented by the above structural formula (i) and an electron acceptor material (OCHD-001) were co-deposited on the anode 101 by a deposition method to a thickness of 10 nm at a weight ratio of 1:0.05 (= PCBBiF:OCHD-001) to form a hole injection layer 111.

[0332] After PCBBiF was deposited on the hole injection layer 111 to a thickness of 105 nm, N,N-bis[4-(dibenzofuran-4-yl)phenyl]-4-amino-p-terphenyl (abbreviation: DBfBB1TP) represented by the above structural formula (ii) was deposited to a thickness of 10 nm to form the hole transport layer 112.

[0333] Subsequently, 3,3'-(naphthalene-1,4-diyl)bis(9-phenyl-9H-carbazole) (abbreviation: PCzN2) represented by the above structural formula (iii) was vapor-deposited on the hole transport layer 112 to a thickness of 10 nm to form an electron blocking layer.

[0334] Thereafter, 2-(10-phenyl-9-anthracenyl)-benzo[b]naphtho[2,3-d]furan (abbreviation: Bnf(II)PhA) represented by the above structural formula (iv) and 3,10-bis[N-(9-phenyl-9H-carbazol-2-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviation: 3,10PCA2Nbf(IV)-02) represented by the above structural formula (v) were co-deposited to a thickness of 25 nm in a weight ratio of 1:0.015 (=Bnf(II)PhA:3,10PCA2Nbf(IV)-02) to form the light-emitting layer 113.

[0335] After that, 2-{(3',5'-di-tert-butyl)-1,1'-biphenyl-3-yl}-4,6-bis(3,5-di-tert-butylphenyl)-1,3,5-triazine (abbreviation: mmtBumBP-dmmtBuPTzn) represented by the above structural formula (x) was evaporated to a thickness of 10 nm to form a hole blocking layer, and then mmtBumBP-dmmtBuPTzn and 6-methyl-8-quinolinolato-lithium (abbreviation: Li-6mq) represented by the above structural formula (vii) were co-evaporated to a thickness of 20 nm to give a weight ratio of 1:1 (= mmtBumBP-dmmtBuPTzn:Li-6mq) to form an electron transport layer 114.

[0336] After forming the electron transport layer 114, Li-6mq was deposited to a thickness of 1 nm to form the electron injection layer 115. Finally, silver (Ag) and magnesium (Mg) were co-deposited in a volume ratio of 1:0.1 to a thickness of 15 nm to form the cathode 102, thereby producing the light-emitting device 2. The cathode 102 is a semi-transparent / semi-reflective electrode that has the functions of reflecting and transmitting light, and the light-emitting device of this example is a top-emission device that extracts light from the cathode 102. In addition, 1,3,5-tri(dibenzothiophen-4-yl)-benzene (abbreviation: DBT3P-II) represented by the above structural formula (xi) was deposited to a thickness of 70 nm on the cathode 102 to improve the light extraction efficiency.

[0337] (Method for producing comparative light-emitting device 2) Comparative light-emitting device 2 was fabricated in the same manner as light-emitting device 2, except that Li-6mq used in the electron transport layer 114 and the electron injection layer 115 in light-emitting device 2 was replaced with 8-quinolinolato-lithium (abbreviation: Liq) represented by the above structural formula (ix), and the thickness of PCBBiF in the hole transport layer 112 was set to 100 nm. The thickness of the hole transport layer was adjusted so that the chromaticity was similar between the devices.

[0338] The device structures of light-emitting device 2 and comparative light-emitting device 2 are summarized in the table below.

[0339] [Table 4]

[0340] The refractive indices of mmtBumBP-dmmtBuPTzn, Li-6mq, and Liq are shown in Figure 21, and their refractive indices at 456 nm are shown in Table 5 below. Measurements were performed using a spectroscopic ellipsometer (M-2000U, manufactured by J.A. Woollam Japan). The measurement samples used were films of approximately 50 nm thickness formed by vacuum deposition of each layer material on a quartz substrate. Figure 21 also lists the refractive index for ordinary rays, n, Ordinary, and the refractive index for extraordinary rays, n, Extraordinary.

[0341] 21, mmtBumBP-dmmtBuPTzn have an ordinary refractive index ranging from 1.60 to 1.61 and from 1.50 to 1.75 throughout the entire blue emission region (455 nm to 465 nm), and the ordinary refractive index at 633 nm is 1.57, ranging from 1.45 to 1.70, indicating that they are low-refractive-index materials. Similarly, Li-6mq has an ordinary refractive index ranging from 1.67 to 1.45 and from 1.70 throughout the entire blue emission region (455 nm to 465 nm), and the ordinary refractive index at 633 nm is 1.61, ranging from 1.40 to 1.65, indicating that they are low-refractive-index materials.

[0342] This shows that the light-emitting device 2 is a light-emitting device in which the ordinary refractive index of the electron transport layer 114 is in the range of 1.50 or more and less than 1.75 throughout the entire blue light-emitting region (455 nm or more and 465 nm or less), and in the range of 1.45 or more and less than 1.70 at 633 nm.

[0343] [Table 5]

[0344] The above-mentioned light-emitting device 2 and comparative light-emitting device 2 were sealed with glass substrates in a nitrogen-atmosphere glove box to prevent the light-emitting devices from being exposed to the atmosphere (a UV-curable sealant was applied around the elements, UV was irradiated only on the sealant without irradiating the light-emitting device, and heat-treated at 80°C under atmospheric pressure for 1 hour), and then the initial characteristics of these light-emitting devices were measured. Note that no special measures were taken on the sealed glass substrates to improve light extraction efficiency.

[0345] The luminance-current density characteristics of light-emitting device 2 and comparative light-emitting device 2 are shown in Figure 22, the current efficiency-luminance characteristics in Figure 23, the luminance-voltage characteristics in Figure 24, the current-voltage characteristics in Figure 25, the blue index-luminance characteristics in Figure 26, and the emission spectra in Figure 27. 2 The main characteristics in this range are shown in Table 6. The luminance, CIE chromaticity, and emission spectrum were measured using a spectroradiometer (SR-UL1R, manufactured by Topcon Corporation) at room temperature.

[0346] The blue index (BI) is the current efficiency (cd / A) divided by the chromaticity y (cd / A / y), and is one index that represents the luminous characteristics of blue light emission. The smaller the chromaticity y, the higher the color purity of blue light emission tends to be. Blue light emission with high color purity can express a wide range of blue colors even with a small luminance component. By using blue light emission with high color purity, the required luminance to express blue colors is reduced, resulting in reduced power consumption. Therefore, the BI, which takes into account the chromaticity y, an index of blue purity, is preferably used as a means of expressing the efficiency of blue light emission. Therefore, it can be said that light-emitting devices with a higher BI have better efficiency as blue light-emitting devices used in displays.

[0347] [Table 6]

[0348] 22 to 27 and Table 6, it can be seen that the light-emitting device 2 using the low refractive index material of one embodiment of the present invention is an EL device that has a lower driving voltage and higher current efficiency than the comparative light-emitting device 2, while exhibiting an emission spectrum almost identical to that of the comparative light-emitting device 2.

[0349] As described above, the use of Li-6mq, an alkali metal organic complex having an alkyl group at the 6-position, together with an electron-transporting material having many alkyl groups in the electron-transporting layer 114, significantly reduces the driving voltage. While the presence of alkyl groups is generally thought to inhibit molecular stacking, suppress interactions, and increase the driving voltage, the presence of alkyl groups at both positions in the light-emitting device of one embodiment of the present invention significantly reduces the driving voltage. This significant effect is unique to alkali metal organic complexes containing a ligand containing an 8-quinolinolato structure with an alkyl group at the 6-position. In fact, the driving voltage was found to be lower than that of similar metal complexes containing an 8-quinolinolato structure with an unsubstituted (hydrogen) 6-position. As the organic metal complex, 6-alkyl-8-quinolinolato-lithium, particularly 6-methyl-8-quinolinolato-lithium (abbreviated as Li-6mq), is preferred.

[0350] Furthermore, the light-emitting device 2 and the comparative light-emitting device 2 have a luminance of 1000 cd / m 2 The blue index (BI) at around 145 (cd / A / y) and 119 (cd / A / y), respectively, was 145 (cd / A / y) and 119 (cd / A / y). Thus, light-emitting device 2 can be said to be a light-emitting device with particularly good BI. Therefore, one embodiment of the present invention is suitable for light-emitting devices used in displays.

[0351] Furthermore, the light-emitting device 2 and the comparative light-emitting device 2 have a luminance of 1000 cd / m 2 The power efficiencies in the vicinity of 1000 W and 1000 W were 4.5 (lm / W) and 2.5 (lm / W), respectively. Thus, light-emitting device 2 can be said to be a light-emitting device with particularly low power consumption. [Example]

[0352] In this example, a light-emitting device 3 according to one embodiment of the present invention and a comparative light-emitting device 3 will be described. The structural formulae of organic compounds used in this example are shown below.

[0353] [ka]

[0354] (Method for fabricating light-emitting device 3) First, a silver (Ag), palladium (Pd), and copper (Cu) alloy film (Ag-Pd-Cu (APC) film) was formed on a glass substrate by sputtering to a thickness of 100 nm as a reflective electrode, and then an indium tin oxide (ITSO) film containing silicon oxide was formed by sputtering to a thickness of 10 nm as a transparent electrode to form an anode 101. The electrode area was 4 mm 2 (2mm x 2mm).

[0355] Next, as a pretreatment for forming a light-emitting device on the substrate, the substrate surface was washed with water, baked at 200°C for 1 hour, and then subjected to UV ozone treatment for 370 seconds.

[0356] Then, 10 -4 The substrate was introduced into a vacuum deposition apparatus whose internal pressure had been reduced to about Pa, and after vacuum baking at 170°C for 30 minutes in the heating chamber of the vacuum deposition apparatus, the substrate was allowed to cool for about 30 minutes.

[0357] Next, the substrate on which the anode 101 was formed was fixed to a substrate holder installed in a vacuum deposition apparatus so that the surface on which the anode 101 was formed faced downward. N-(1,1'-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF) represented by the above structural formula (i) and an electron acceptor material (OCHD-001) were co-deposited on the anode 101 by a deposition method to a thickness of 10 nm at a weight ratio of 1:0.05 (= PCBBiF:OCHD-001) to form a hole injection layer 111.

[0358] After PCBBiF was deposited on the hole injection layer 111 to a thickness of 100 nm, N,N-bis[4-(dibenzofuran-4-yl)phenyl]-4-amino-p-terphenyl (abbreviation: DBfBB1TP) represented by the above structural formula (ii) was deposited to a thickness of 10 nm to form the hole transport layer 112.

[0359] Subsequently, 3,3'-(naphthalene-1,4-diyl)bis(9-phenyl-9H-carbazole) (abbreviation: PCzN2) represented by the above structural formula (iii) was vapor-deposited on the hole transport layer 112 to a thickness of 10 nm to form an electron blocking layer.

[0360] Thereafter, 2-(10-phenyl-9-anthracenyl)-benzo[b]naphtho[2,3-d]furan (abbreviation: Bnf(II)PhA) represented by the above structural formula (iv) and 3,10-bis[N-(9-phenyl-9H-carbazol-2-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviation: 3,10PCA2Nbf(IV)-02) represented by the above structural formula (v) were co-deposited to a thickness of 25 nm in a weight ratio of 1:0.015 (=Bnf(II)PhA:3,10PCA2Nbf(IV)-02) to form the light-emitting layer 113.

[0361] After that, 2-[3'-(9,9-dimethyl-9H-fluoren-2-yl)-1,1'-biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mFBPTzn) represented by the above structural formula (vi) was deposited to a thickness of 10 nm to form a hole blocking layer, and then 2-[3-(2,6-dimethyl-3-pyridinyl)-5-(9-phenanthrenyl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mPn-mDMePyPTzn) represented by the above structural formula (xix) and 6-methyl-8-quinolinolato-lithium (abbreviation: Li-6mq) represented by the above structural formula (vii) were co-deposited to a thickness of 20 nm in a weight ratio of 1:1 (=mPn-mDMePyPTzn:Li-6mq) to form an electron transport layer 114.

[0362] After forming the electron transport layer 114, Li-6mq was deposited to a thickness of 1 nm to form the electron injection layer 115. Finally, silver (Ag) and magnesium (Mg) were co-deposited in a volume ratio of 1:0.1 to a thickness of 15 nm to form the cathode 102, thereby producing the light-emitting device 3. The cathode 102 is a semi-transparent / semi-reflective electrode that has the functions of reflecting and transmitting light, and the light-emitting device of this example is a top-emission device that extracts light from the cathode 102. In addition, 1,3,5-tri(dibenzothiophen-4-yl)-benzene (abbreviation: DBT3P-II) represented by the above structural formula (xi) was deposited to a thickness of 70 nm on the cathode 102 to improve the light extraction efficiency.

[0363] (Method for producing comparative light-emitting device 3) Comparative light-emitting device 3 was fabricated in the same manner as light-emitting device 3, except that Li-6mq used in the electron transport layer in light-emitting device 3 was replaced with 8-quinolinolato-lithium (abbreviation: Liq) represented by the above structural formula (ix).

[0364] The device structures of light-emitting device 3 and comparative light-emitting device 3 are summarized in the table below.

[0365] [Table 7]

[0366] The refractive indices of mPn-mDMePyPTzn, Li-6mq, and Liq are shown in Figure 28, and their refractive indices at 456 nm are shown in Table 8 below. Measurements were performed using a spectroscopic ellipsometer (M-2000U, manufactured by J.A. Woollam Japan). The measurement samples used were films of approximately 50 nm thickness formed by vacuum deposition of each layer material on a quartz substrate. Figure 28 also lists the refractive index of ordinary light, n, Ordinary, and the refractive index of extraordinary light, n, Extraordinary.

[0367] [Table 8]

[0368] The above-mentioned light-emitting device 3 and comparative light-emitting device 3 were sealed with glass substrates in a nitrogen-atmosphere glove box to prevent the light-emitting devices from being exposed to the atmosphere (a UV-curable sealant was applied around the elements, UV was irradiated only on the sealant without irradiating the light-emitting device, and heat-treated at 80°C under atmospheric pressure for 1 hour), and then the initial characteristics of these light-emitting devices were measured. Note that no special measures were taken on the sealed glass substrates to improve light extraction efficiency.

[0369] The luminance-current density characteristics of light-emitting device 3 and comparative light-emitting device 3 are shown in Figure 29, the current efficiency-luminance characteristics in Figure 30, the luminance-voltage characteristics in Figure 31, the current-voltage characteristics in Figure 32, the emission spectra in Figure 33, and the blue index (BI)-luminance characteristics in Figure 34. The 1000 cd / m 2 The main characteristics in this range are shown in Table 9. The luminance, CIE chromaticity, and emission spectrum were measured using a spectroradiometer (SR-UL1R, manufactured by Topcon Corporation) at room temperature.

[0370] The blue index (BI) is the current efficiency (cd / A) divided by the chromaticity y (cd / A / y), and is one index that represents the luminous characteristics of blue light emission. The smaller the chromaticity y, the higher the color purity of blue light emission tends to be. Blue light emission with high color purity can express a wide range of blue colors even with a small luminance component. By using blue light emission with high color purity, the required luminance to express blue colors is reduced, resulting in reduced power consumption. Therefore, the BI, which takes into account the chromaticity y, an index of blue purity, is preferably used as a means of expressing the efficiency of blue light emission. Therefore, it can be said that light-emitting devices with a higher BI have better efficiency as blue light-emitting devices used in displays.

[0371] [Table 9]

[0372] 29 to 34 and Table 9, it can be seen that the light-emitting device 3 using the low refractive index material of one embodiment of the present invention exhibits an emission spectrum almost identical to that of the comparative light-emitting device 3, but has a lower driving voltage and a better blue index than the comparative light-emitting device 3.

[0373] As described above, it can be seen that the use of Li-6mq, an organic complex of an alkali metal having an alkyl group at the 6-position, together with an electron transport material in the electron transport layer 114, results in a reduction in driving voltage. This effect is unique to an organic metal complex of an alkali metal having a ligand containing an 8-quinolinolato structure with an alkyl group at the 6-position. As the organic metal complex, 6-alkyl-8-quinolinolato-lithium, particularly 6-methyl-8-quinolinolato-lithium (abbreviation: Li-6mq), is preferred.

[0374] Furthermore, the light-emitting device 3 and the comparative light-emitting device 3 exhibited a luminance of 1000 cd / m 2 The blue index (BI) in the vicinity of 152.3 (cd / A / y) and 149.4 (cd / A / y), respectively, and the maximum BI was 153.3 (cd / A / y) and 150.4 (cd / A / y), respectively. Thus, light-emitting device 3 can be said to be a light-emitting device with particularly good BI.

[0375] In this example, only the organometallic complex was used as a material with a low refractive index, and the effect of 6-alkyl-8-quinolinolato-lithium (preferably Li-6mq) in reducing the driving voltage was confirmed. However, by using low refractive index materials for both the organic compound having electron transport properties and the metal complex in the electron transport layer, as in Example 1, a significant improvement in light extraction efficiency can be achieved, leading to improvements in current efficiency and BI.

[0376] Furthermore, a significant driving voltage reduction effect can be obtained by using an organic compound having an alkyl group and electron transporting properties together with 6-alkyl-8-quinolinolato-lithium (preferably Li-6mq) as in Example 2. It was also found that a significant driving voltage reduction effect and a significant improvement in luminous efficiency can be obtained by using an organic compound having an alkyl group and low refractive index and electron transporting properties together with 6-alkyl-8-quinolinolato-lithium (preferably Li-6mq). [Example]

[0377] <Synthesis Example 1> Example 1 In this example, a synthesis method of 6-methyl-8-quinolinolato-lithium (abbreviation: Li-6mq), which is a metal complex of one embodiment of the present invention, is described. The structural formula of Li-6mq is shown below.

[0378] [ka]

[0379] <Step 1: Synthesis of Li-6mq> 2.0 g (12.6 mmol) of 8-hydroxy-6-methylquinoline and 130 mL of anhydrous tetrahydrofuran (THF) were placed in a three-neck flask and stirred. 10.1 mL (10.1 mmol) of a 1 M THF solution of lithium tert-butoxide (tBuOLi) was added to this solution and stirred at room temperature for 47 hours. The reaction solution was concentrated to give a yellow solid. Acetonitrile was added to this solid, and the mixture was subjected to ultrasonic irradiation and filtration to give a pale yellow solid. This washing procedure was repeated twice. 1.6 g (95% yield) of a pale yellow solid of Li-6mq was obtained as the filtrate. The synthesis scheme is shown below.

[0380] [ka]

[0381] Next, the absorption spectrum and emission spectrum of Li-6mq in anhydrous acetone solution were measured, and the results are shown in Figure 35. The absorption spectrum was measured using a UV-visible spectrophotometer (V550, manufactured by JASCO Corporation), and the spectrum measured by placing only anhydrous acetone in a quartz cell was subtracted from the absorption spectrum. The emission spectrum was measured using a fluorometer (FP-8600, manufactured by JASCO Corporation).

[0382] As can be seen from FIG. 35, the dehydrated acetone solution of Li-6mq exhibited an absorption peak at 390 nm, and the emission wavelength peak was 540 nm (excitation wavelength 385 nm). [Example]

[0383] In this example, a light-emitting device 4 according to one embodiment of the present invention, a comparative light-emitting device 4, and a comparative light-emitting device 5 will be described. The structural formulae of organic compounds used in this example are shown below.

[0384] [ka]

[0385] (Method for fabricating light-emitting device 4) First, a silver (Ag) film was formed on a glass substrate by sputtering to a thickness of 100 nm as a reflective electrode, and then an indium tin oxide (ITSO) film containing silicon oxide was formed on the glass substrate by sputtering to a thickness of 95 nm as a transparent electrode to form an anode 101. The electrode area was 4 mm 2 (2mm x 2mm).

[0386] Next, as a pretreatment for forming a light-emitting device on the substrate, the substrate surface was washed with water, baked at 200°C for 1 hour, and then subjected to UV ozone treatment for 370 seconds.

[0387] Then, 10 -4 The substrate was introduced into a vacuum deposition apparatus whose internal pressure had been reduced to about Pa, and after vacuum baking at 170°C for 30 minutes in the heating chamber of the vacuum deposition apparatus, the substrate was allowed to cool for about 30 minutes.

[0388] Next, the substrate on which the anode 101 was formed was fixed to a substrate holder installed in a vacuum deposition apparatus so that the surface on which the anode 101 was formed faced downward. N-(1,1'-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF) represented by the above structural formula (i) and an electron acceptor material (OCHD-001) were co-deposited on the anode 101 by a deposition method to a thickness of 10 nm at a weight ratio of 1:0.05 (= PCBBiF:OCHD-001) to form a hole injection layer 111.

[0389] After PCBBiF was deposited on the hole injection layer 111 to a thickness of 10 nm, N,N-bis(4-biphenyl)-6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BBABnf) represented by the above structural formula (xii) was deposited to a thickness of 10 nm to form the hole transport layer 112.

[0390] Subsequently, 3,3'-(naphthalene-1,4-diyl)bis(9-phenyl-9H-carbazole) (abbreviation: PCzN2) represented by the above structural formula (iii) was vapor-deposited on the hole transport layer 112 to a thickness of 10 nm to form an electron blocking layer.

[0391] Thereafter, 2-(10-phenyl-9-anthracenyl)-benzo[b]naphtho[2,3-d]furan (abbreviation: Bnf(II)PhA) represented by the above structural formula (iv) and 3,10-bis[N-(9-phenyl-9H-carbazol-2-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviation: 3,10PCA2Nbf(IV)-02) represented by the above structural formula (v) were co-deposited to a thickness of 25 nm in a weight ratio of 1:0.015 (=Bnf(II)PhA:3,10PCA2Nbf(IV)-02) to form the light-emitting layer 113.

[0392] After that, 2-{(3',5'-di-tert-butyl)-1,1'-biphenyl-3-yl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mmtBumBPTzn) represented by the above structural formula (xiii) was deposited to a thickness of 10 nm to form a hole blocking layer, and then mmtBumBPTzn and 6-methyl-8-quinolinolato-lithium (abbreviation: Li-6mq) represented by the above structural formula (vii) were co-deposited to a thickness of 20 nm in a weight ratio of 1:1 (= mmtBumBPTzn:Li-6mq) to form an electron transport layer 114.

[0393] After forming the electron transport layer 114, lithium fluoride was deposited to a thickness of 1 nm to form the electron injection layer 115. Finally, silver (Ag) and magnesium (Mg) were co-deposited in a volume ratio of 1:0.1 to a thickness of 15 nm to form the cathode 102, thereby producing the light-emitting device 4. The cathode 102 is a semi-transparent / semi-reflective electrode that has the functions of reflecting and transmitting light, and the light-emitting device of this example is a top-emission device that extracts light from the cathode 102. In addition, 1,3,5-tri(dibenzothiophen-4-yl)-benzene (abbreviation: DBT3P-II) represented by the above structural formula (xi) was deposited to a thickness of 70 nm on the cathode 102 to improve the light extraction efficiency.

[0394] (Method for producing comparative light-emitting device 4) Comparative light-emitting device 4 was fabricated in the same manner as light-emitting device 4, except that Li-6mq used in electron transport layer 114 in light-emitting device 4 was replaced with 8-quinolinolato-lithium (abbreviation: Liq) represented by the above structural formula (ix).

[0395] (Method for producing comparative light-emitting device 5) Comparative light-emitting device 5 was fabricated in the same manner as comparative light-emitting device 4, except that the mmtBumBPTzn used in the hole-blocking layer in comparative light-emitting device 4 was changed to 2-[3'-(9,9-dimethyl-9H-fluoren-2-yl)-1,1'-biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mFBPTzn) represented by the above structural formula (vi), and the mmtBumBPTzn used in the electron-transporting layer 114 was changed to 2-[3-(2,6-dimethyl-3-pyridinyl)-5-(9-phenanthrenyl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mPn-mDMePyPTzn) represented by the above structural formula (xix). The thickness of the hole-transporting layer was adjusted so that the chromaticity was similar between the devices.

[0396] The device structures of light-emitting device 4, comparative light-emitting device 4, and comparative light-emitting device 5 are summarized in the table below.

[0397] [Table 10]

[0398] The refractive indices of mmtBumBPTzn, mPn-mDMePyPTzn, Li-6mq, and Liq are shown in Figure 37, and their refractive indices at 456 nm are shown in Table 11 below. Measurements were performed using a spectroscopic ellipsometer (M-2000U, manufactured by J.A. Woollam Japan). The measurement samples used were films of each layer formed by vacuum deposition onto a quartz substrate to a thickness of approximately 50 nm. Figure 37 also lists the refractive index for ordinary rays, n, Ordinary, and the refractive index for extraordinary rays, n, Extraordinary.

[0399] From Figure 37, it can be seen that the ordinary refractive index of mmtBumBPTzn is 1.68 throughout the entire blue emission region (455 nm to 465 nm), falling within the range of 1.50 to 1.75. Furthermore, the ordinary refractive index at 633 nm is 1.64, falling within the range of 1.45 to 1.70, indicating that mmtBumBPTzn is a low refractive index material. Furthermore, the ordinary refractive index of Li-6mq is 1.67 throughout the entire blue emission region (455 nm to 465 nm), falling within the range of 1.45 to 1.70, and the ordinary refractive index at 633 nm is 1.61, falling within the range of 1.40 to 1.65, indicating that it is a low refractive index material.

[0400] This shows that the light-emitting device 4 is a light-emitting device in which the ordinary refractive index of the electron transport layer 114 is in the range of 1.50 or more and less than 1.75 throughout the entire blue light-emitting region (455 nm or more and 465 nm or less), and in the range of 1.45 or more and less than 1.70 at 633 nm.

[0401] [Table 11]

[0402] The above light-emitting device 4 and comparative light-emitting devices 4 and 5 were sealed with glass substrates in a nitrogen-atmosphere glove box to prevent the light-emitting devices from being exposed to the atmosphere (a UV-curable sealant was applied around the elements, UV was irradiated only on the sealant without irradiating the light-emitting devices, and heat-treated at 80°C under atmospheric pressure for 1 hour), and then the initial characteristics of these light-emitting devices were measured. Note that no special measures were taken on the sealed glass substrates to improve light extraction efficiency.

[0403] The luminance-current density characteristics of light-emitting device 4, comparative light-emitting device 4, and comparative light-emitting device 5 are shown in Figure 38, their current efficiency-luminance characteristics in Figure 39, their luminance-voltage characteristics in Figure 40, their current density-voltage characteristics in Figure 41, their emission spectra in Figure 42, and their blue index-luminance characteristics in Figure 43. Furthermore, the 1000 cd / m 2 The main characteristics in this range are shown in Table 12. The luminance, CIE chromaticity, and emission spectrum were measured using a spectroradiometer (SR-UL1R, manufactured by Topcon Corporation) at room temperature.

[0404] The blue index (BI) is the current efficiency (cd / A) divided by the chromaticity y (cd / A / y), and is one index that represents the luminous characteristics of blue light emission. The smaller the chromaticity y, the higher the color purity of blue light emission tends to be. Blue light emission with high color purity can express a wide range of blue colors even with a small luminance component. By using blue light emission with high color purity, the required luminance to express blue colors is reduced, resulting in reduced power consumption. Therefore, the BI, which takes into account the chromaticity y, an index of blue purity, is preferably used as a means of expressing the efficiency of blue light emission. Therefore, it can be said that light-emitting devices with a higher BI have better efficiency as blue light-emitting devices used in displays.

[0405] [Table 12]

[0406] 38 to 43 and Table 12 show that light-emitting device 4, which is a light-emitting device of one embodiment of the present invention, is a light-emitting device with better current efficiency than comparative light-emitting device 5, while exhibiting almost the same emission spectrum as comparative light-emitting device 5. Furthermore, light-emitting device 4, which is a light-emitting device of one embodiment of the present invention, is a light-emitting device with a lower driving voltage than comparative light-emitting device 4.

[0407] Furthermore, the light-emitting device 4, the comparative light-emitting device 4, and the comparative light-emitting device 5 have a luminance of 1000 cd / m2 The blue index (BI) at around 178 (cd / A / y), 164 (cd / A / y), and 160 (cd / A / y), respectively. Thus, light-emitting device 4 can be said to be a light-emitting device with particularly good BI. Therefore, one embodiment of the present invention is suitable for light-emitting devices used in displays.

[0408] Furthermore, the light-emitting device 4, the comparative light-emitting device 4, and the comparative light-emitting device 5 have a luminance of 1000 cd / m 2 The power efficiencies in the vicinity of 1000 W were 6.8 (lm / W), 5.9 (lm / W), and 5.9 (lm / W), respectively. Thus, light-emitting device 4 can be said to be a light-emitting device with particularly low power consumption.

[0409] We also fabricated two bottom-emission light-emitting devices, Device 15, which has a similar configuration to Device 4, but with a hole-transport layer consisting of 20 nm of PCBBiF and 10 nm of N,N-bis[4-(dibenzofuran-4-yl)phenyl]-4-amino-p-terphenyl (DBfBB1TP) and an electron-injection layer consisting of 1 nm of lithium fluoride. We also fabricated Device 16, which uses 2-methyl-8-quinolinolato-lithium (Li-mq) instead of Li-6mq. The initial current at 4 V was 0.36 mA for Device 15 and 0.27 mA for Device 16, resulting in Device 15 delivering a current that is more than 30% higher than Device 16. Thus, a light-emitting device using a metal complex having a ligand containing an 8-quinolinolato structure with an alkyl group having 1 to 3 carbon atoms at the 6th position can be made into a light-emitting device with a particularly lower driving voltage than a light-emitting device using a metal complex having a ligand containing an 8-quinolinolato structure with an alkyl group at the 2nd position. [Example]

[0410] <Synthesis Example 2> Example 1 In this example, a synthesis method for 6-ethyl-8-quinolinolato-lithium (abbreviation: Li-6eq), which is a metal complex of one embodiment of the present invention, is described. The structural formula of Li-6eq is shown below.

[0411] [ka]

[0412] <Step 1: Synthesis of 6-ethyl-8-hydroxyquinoline> A three-neck flask was charged with 5.21 g (38.0 mmol) of 2-amino-5-ethylphenol and 135 mL of 1N hydrochloric acid, followed by stirring at 100°C for 30 minutes. A solution containing 7.42 g (57.0 mmol) (8.73 mL) of acrolein diethyl acetal and 10 mL of ethanol was added dropwise to the reaction solution over 1 hour, followed by heating at 100°C for 5 hours. After completion of the reaction, the reaction solution was heated at 100°C for 120 minutes. Dichloromethane was added to the reaction solution, and the aqueous layer was adjusted to pH 7 using 10% aqueous sodium hydroxide and 1N hydrochloric acid. The solution was filtered, the organic layer was removed, and the aqueous layer was further extracted with dichloromethane. The extracted solution was then combined with the organic layer and washed with water. The organic layer was dehydrated over magnesium sulfate and concentrated to obtain a black solid containing the target compound.

[0413] The resulting solid was purified by silica gel column chromatography using a developing solvent whose polarity was changed from hexane:ethyl acetate = 10:0 to hexane:ethyl acetate = 10:1. This purification was performed twice to obtain 3.4 g (yield: 51%) of the target whitish-yellow solid. The synthesis scheme for Step 1 is shown below.

[0414] [ka]

[0415] <Step 2: Synthesis of Li-6eq> 3.0 g (17.4 mmol) of 6-ethyl-8-hydroxyquinoline obtained in Step 1 and 200 mL of dehydrated tetrahydrofuran (THF) were placed in a three-neck flask and stirred. 13.9 mL (13.9 mmol) of lithium tert-butoxide (tBuOLi) in 1 M THF was added to this solution and stirred at room temperature for 68 hours. The reaction solution was concentrated to obtain a yellow solid. Acetonitrile was added to this solid, which was then subjected to ultrasonic irradiation and filtered to obtain a yellow solid. This washing procedure was repeated twice. 2.6 g of a yellow solid (yield 104%) was obtained as the filtered product.

[0416] The resulting yellow solid (2.58 g) was purified by train sublimation at 335°C and 2.8 Pa for 15.5 hours. After sublimation, a yellow solid (1.94 g) was obtained with a recovery rate of 75%. The synthesis scheme for Step 2 is shown below.

[0417] [ka]

[0418] Nuclear magnetic resonance spectroscopy ( 1 The analysis results by H-NMR are shown below. From these results, it was found that in this example, an organic compound Li-6eq, which is one embodiment of the present invention and is represented by the above structural formula (101), was obtained.

[0419] H 1 NMR (DMSO-d6, 300MHz): δ = 1.21 (t, 3H), 2.54 (t, 2H), 6.29 (s, 1H), 6.37 (s, 1H), 7.22 (q, 1H), 7.96 (d, 1H), 8.30 (d, 1H).

[0420] Next, the absorption spectrum and emission spectrum of Li-6eq in anhydrous acetone solution were measured, and the results are shown in Figure 45. The absorption spectrum was measured using a UV-visible spectrophotometer (V550, manufactured by JASCO Corporation), and the spectrum measured by placing only anhydrous acetone in a quartz cell was subtracted from the absorption spectrum. The emission spectrum was measured using a fluorometer (FP-8600, manufactured by JASCO Corporation).

[0421] The dehydrated acetone solution of Li-6eq showed an absorption peak at 369 nm and an emission wavelength peak at 532 nm (excitation wavelength 375 nm).

[0422] Figure 46 shows the results of measuring the refractive index of Li-6eq using a spectroscopic ellipsometer (M-2000U manufactured by J.A. Woollam Japan). For the measurements, films of approximately 50 nm thickness were formed on a quartz substrate using vacuum deposition of the materials for each layer. Figure 46 also lists the refractive index of ordinary light, n, Ordinary, and the refractive index of extraordinary light, n, Extraordinary.

[0423] From Figure 46, it can be seen that Li-6eq has an ordinary refractive index of 1.68 throughout the entire blue emission region (455 nm or more and 465 nm or less), which is in the range of 1.45 to 1.70, and also has an ordinary refractive index of 1.63 at 633 nm, which is in the range of 1.40 to 1.65, making it a material with a low refractive index. [Example]

[0424] <Synthesis Example 3> Example 1 This example describes a synthesis method for 6-methyl-8-quinolinolato-sodium (abbreviation: Na-6mq), which is a metal complex of one embodiment of the present invention. The structural formula of Na-6mq is shown below.

[0425] [ka]

[0426] <Step 1: Synthesis of Na-6mq> 3.8 g (23.7 mmol) of 8-hydroxy-6-methylquinoline, 0.76 g (18.9 mmol) of sodium hydroxide, and 240 mL of methanol were added to a three-neck flask and stirred at 80°C for 8 hours. The reaction solution was heated and distilled at atmospheric pressure. When the solvent had decreased, 140 mL of toluene was added. This was repeated three times. The reaction solution was cooled with ice water and filtered. 3.4 g (98% yield) of the target yellow-green solid was obtained as the filtrate.

[0427] The resulting yellow-green solid (1.3 g) was subjected to a pressure of 3.2 × 10 -2 Sublimation purification was carried out for 16.5 hours by train sublimation under conditions of Pa and 358°C. After sublimation purification, 1.0 g of a yellow solid was obtained, with a recovery rate of 77%.

[0428] Further, 1.0 g of the obtained yellow solid was subjected to a pressure of 2.0 × 10 -2 The product was purified by train sublimation at 356°C and 1000kJ / Pa for 16 hours. After sublimation purification, a yellow solid was obtained in a yield of 0.84g, with a recovery rate of 84%. The synthesis scheme for Step 1 is shown below.

[0429] [ka]

[0430] Nuclear magnetic resonance spectroscopy ( 1 The results of the analysis by H-NMR are shown below. From these results, it was found that in this example, an organic compound Na-6mq, which is one embodiment of the present invention and is represented by the above structural formula (102), was obtained.

[0431] H 1 NMR (DMSO-d6, 300MHz): δ = 2.24 (s, 3H), 6.32 (d, 2H), 7.18 (q, 1H), 7.86 (d, 1H), 8.37 (d, 1H).

[0432] The absorption and emission spectra of Na-6mq in anhydrous acetone solution are shown in Figure 47. The absorption spectrum was measured using a UV-visible spectrophotometer (V550, manufactured by JASCO Corporation) and is shown after subtracting the spectrum measured using only anhydrous acetone in a quartz cell. The emission spectrum was measured using a fluorometer (FP-8600, manufactured by JASCO Corporation). The Na-6mq in anhydrous acetone solution exhibited an absorption peak at 405 nm and an emission wavelength peak at 551 nm (excitation wavelength 405 nm). [Example]

[0433] In this example, a light-emitting device 5 and a light-emitting device 6 according to one embodiment of the present invention will be described. The structural formulae of organic compounds used in this example are shown below.

[0434] [ka]

[0435] (Method for fabricating light-emitting device 5) First, a film of indium tin oxide containing silicon oxide (ITSO) was formed on a glass substrate by sputtering to a thickness of 70 nm to form an anode 101. The electrode area was 4 mm 2 (2mm x 2mm).

[0436] Next, as a pretreatment for forming a light-emitting device on the substrate, the substrate surface was washed with water, baked at 200°C for 1 hour, and then subjected to UV ozone treatment for 370 seconds.

[0437] Then, 10 -4 The substrate was introduced into a vacuum deposition apparatus whose internal pressure had been reduced to about Pa, and after vacuum baking at 170°C for 30 minutes in the heating chamber of the vacuum deposition apparatus, the substrate was allowed to cool for about 30 minutes.

[0438] Next, the substrate on which the anode 101 was formed was fixed to a substrate holder installed in a vacuum deposition apparatus so that the surface on which the anode 101 was formed faced downward. N-(1,1'-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF) represented by the above structural formula (i) and an electron acceptor material (OCHD-001) were co-deposited on the anode 101 by a deposition method to a thickness of 10 nm at a weight ratio of 1:0.05 (= PCBBiF:OCHD-001) to form a hole injection layer 111.

[0439] On the hole injection layer 111, PCBBiF was evaporated to a thickness of 20 nm to form a hole transport layer 112.

[0440] Next, N-[4-(9H-carbazol-9-yl)phenyl]-N-[4-(4-dibenzofuranyl)phenyl]-[1,1':4',1''-terphenyl]-4-amine (abbreviation: YGTPDBfB) represented by the above structural formula (xii) was vapor-deposited on the hole transport layer 112 to a thickness of 10 nm to form an electron blocking layer.

[0441] Thereafter, 2-(10-phenyl-9-anthracenyl)-benzo[b]naphtho[2,3-d]furan (abbreviation: Bnf(II)PhA) represented by the above structural formula (iv) and 3,10-bis[N-(9-phenyl-9H-carbazol-2-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviation: 3,10PCA2Nbf(IV)-02) represented by the above structural formula (v) were co-deposited to a thickness of 25 nm in a weight ratio of 1:0.015 (=Bnf(II)PhA:3,10PCA2Nbf(IV)-02) to form the light-emitting layer 113.

[0442] After that, 2-{(3',5'-di-tert-butyl)-1,1'-biphenyl-3-yl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mmtBumBPTzn) represented by the above structural formula (xiii) was deposited to a thickness of 10 nm to form a hole blocking layer, and then mmtBumBPTzn and 6-methyl-8-quinolinolato-lithium (abbreviation: Li-6mq) represented by the above structural formula (vii) were co-deposited to a thickness of 20 nm in a weight ratio of 1:1 (= mmtBumBPTzn:Li-6mq) to form an electron transport layer 114.

[0443] After the formation of the electron transport layer 114, lithium fluoride was deposited to a thickness of 1 nm to form the electron injection layer 115, and finally, aluminum was evaporated to a thickness of 200 nm to form the cathode 102, thereby producing the light-emitting device 5. The light-emitting device of this example is a bottom-emission element in which light is extracted from the anode 101 side.

[0444] (Method for fabricating light-emitting device 6) Light-emitting device 6 was fabricated in the same manner as light-emitting device 5, except that Li-6mq in light-emitting device 5 was replaced with 6-tert-butyl-8-quinolinolato-lithium (abbreviation: Li-6tBuq) represented by the above structural formula (xiii).

[0445] The ordinary refractive index of Li-6tBuq is 1.63 or more and 1.64 or less throughout the entire blue emission region (455 nm or more and 465 nm or less), in the range of 1.45 to 1.70. The ordinary refractive index at 633 nm is also 1.59, in the range of 1.40 or more and 1.65 or less, indicating that it is a material with a low refractive index.

[0446] The device structures of light-emitting device 5 and light-emitting device 6 are summarized in the table below.

[0447] [Table 13]

[0448] The above light-emitting devices 5 and 6 were sealed with glass substrates in a nitrogen-atmosphere glove box to prevent the light-emitting devices from being exposed to the atmosphere (a UV-curable sealant was applied around the elements, UV was irradiated only on the sealant without irradiating the light-emitting devices, and heat-treated at 80°C under atmospheric pressure for 1 hour), and then the initial characteristics of these light-emitting devices were measured. Note that no special measures were taken on the sealed glass substrates to improve light extraction efficiency.

[0449] The luminance-current density characteristics of light-emitting device 5 and light-emitting device 6 are shown in Figure 48, the current efficiency-luminance characteristics in Figure 49, the luminance-voltage characteristics in Figure 50, the current density-voltage characteristics in Figure 51, the external quantum efficiency-luminance characteristics in Figure 52, the power efficiency-luminance characteristics in Figure 53, and the emission spectra in Figure 54. 2 The main characteristics in this range are shown in Table 14. The luminance, CIE chromaticity, and emission spectrum were measured using a spectroradiometer (SR-UL1R, manufactured by Topcon Corporation) at room temperature.

[0450] [Table 14]

[0451] 48 to 54 and Table 14 show that light-emitting device 5 and light-emitting device 6, which are light-emitting devices according to one embodiment of the present invention, both have favorable characteristics. Furthermore, light-emitting device 5 using Li-6mq in particular has better external quantum efficiency than light-emitting device 6, and is a light-emitting device with particularly low driving voltage, current efficiency, and power efficiency. Thus, it has been found that a light-emitting device using a metal complex having a ligand including an 8-quinolinolato structure with an alkyl group having 1 to 3 carbon atoms at the 6-position can be a light-emitting device with a particularly low driving voltage compared to a light-emitting device using a metal complex having a ligand including an 8-quinolinolato structure with an alkyl group having 4 or more carbon atoms (such as a t-butyl group) at the 6-position. [Example]

[0452] In this example, a light-emitting device 7, a light-emitting device 8, and a comparative light-emitting device 6 according to one embodiment of the present invention will be described. The structural formulae of organic compounds used in this example are shown below.

[0453] [ka]

[0454] (Method for fabricating light-emitting device 7) First, a film of indium tin oxide containing silicon oxide (ITSO) was formed on a glass substrate by sputtering to a thickness of 70 nm to form an anode 101. The electrode area was 4 mm 2 (2mm x 2mm).

[0455] Next, as a pretreatment for forming a light-emitting device on the substrate, the substrate surface was washed with water, baked at 200°C for 1 hour, and then subjected to UV ozone treatment for 370 seconds.

[0456] Then, 10 -4 The substrate was introduced into a vacuum deposition apparatus whose internal pressure had been reduced to about Pa, and after vacuum baking at 170°C for 30 minutes in the heating chamber of the vacuum deposition apparatus, the substrate was allowed to cool for about 30 minutes.

[0457] Next, the substrate on which the anode 101 was formed was fixed to a substrate holder installed in a vacuum deposition apparatus so that the surface on which the anode 101 was formed faced downward. N-(1,1'-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF) represented by the above structural formula (i) and an electron acceptor material (OCHD-001) were co-deposited on the anode 101 by a deposition method to a thickness of 10 nm at a weight ratio of 1:0.05 (= PCBBiF:OCHD-001) to form a hole injection layer 111.

[0458] After PCBBiF was deposited on the hole injection layer 111 to a thickness of 10 nm, N,N-bis(4-biphenyl)-6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BBABnf) represented by the above structural formula (xii) was deposited to a thickness of 10 nm to form the hole transport layer 112.

[0459] Subsequently, 3,3'-(naphthalene-1,4-diyl)bis(9-phenyl-9H-carbazole) (abbreviation: PCzN2) represented by the above structural formula (iii) was vapor-deposited on the hole transport layer 112 to a thickness of 10 nm to form an electron blocking layer.

[0460] Thereafter, 2-(10-phenyl-9-anthracenyl)-benzo[b]naphtho[2,3-d]furan (abbreviation: Bnf(II)PhA) represented by the above structural formula (iv) and 3,10-bis[N-(9-phenyl-9H-carbazol-2-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviation: 3,10PCA2Nbf(IV)-02) represented by the above structural formula (v) were co-deposited to a thickness of 25 nm in a weight ratio of 1:0.015 (=Bnf(II)PhA:3,10PCA2Nbf(IV)-02) to form the light-emitting layer 113.

[0461] After that, 2-[3'-(9,9-dimethyl-9H-fluoren-2-yl)-1,1'-biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mFBPTzn) represented by the above structural formula (vi) was deposited to a thickness of 10 nm to form a hole blocking layer, and then 2-{(3',5'-di-tert-butyl)-1,1'-biphenyl-3-yl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mmtBumBPTzn) represented by the above structural formula (xiii) and 6-methyl-8-quinolinolato-lithium (abbreviation: Li-6mq) represented by the above structural formula (vii) were co-deposited to a thickness of 20 nm in a weight ratio of 1:1 (=mmtBumBPTzn:Li-6mq) to form an electron transport layer 114.

[0462] After the formation of the electron transport layer 114, lithium fluoride was deposited to a thickness of 1 nm to form the electron injection layer 115, and finally, aluminum was evaporated to a thickness of 200 nm to form the cathode 102, thereby producing the light-emitting device 7. The light-emitting device of this example is a bottom-emission type element in which light is extracted from the anode 101.

[0463] (Method for fabricating light-emitting device 8) Light-emitting device 8 was fabricated in the same manner as light-emitting device 7, except that Li-6mq in light-emitting device 7 was replaced with 6-methyl-8-quinolinolato-sodium (abbreviation: Na-6mq) represented by the above structural formula (xiv).

[0464] (Method for producing comparative light-emitting device 6) Comparative light-emitting device 6 was fabricated in the same manner as light-emitting device 7, except that Li-6mq in light-emitting device 7 was replaced with 8-quinolinolato-lithium (abbreviation: Liq) represented by the above structural formula (ix).

[0465] The device structures of light-emitting device 7, light-emitting device 8, and comparative light-emitting device 6 are summarized in the table below.

[0466] [Table 15]

[0467] The above light-emitting devices 7 and 8 and comparative light-emitting device 6 were sealed with glass substrates in a nitrogen-atmosphere glove box to prevent the light-emitting devices from being exposed to the atmosphere (a UV-curable sealant was applied around the elements, UV was irradiated only on the sealant without irradiating the light-emitting devices, and heat-treated at 80°C under atmospheric pressure for 1 hour), and then the initial characteristics of these light-emitting devices were measured. Note that no special measures were taken on the sealed glass substrates to improve light extraction efficiency.

[0468] The luminance-current density characteristics of light-emitting device 7, light-emitting device 8, and comparative light-emitting device 6 are shown in Figure 55, their current efficiency-luminance characteristics in Figure 56, their luminance-voltage characteristics in Figure 57, their current density-voltage characteristics in Figure 58, their external quantum efficiency-luminance characteristics in Figure 59, their power efficiency-luminance characteristics in Figure 60, and their emission spectra in Figure 61. Furthermore, the 1000 cd / m 2 The main characteristics in this range are shown in Table 16. The luminance, CIE chromaticity, and emission spectrum were measured using a spectroradiometer (SR-UL1R, manufactured by Topcon Corporation) at room temperature.

[0469] [Table 16]

[0470] 55 to 61 and Table 16 show that light-emitting device 7 and light-emitting device 8, which are light-emitting devices according to one embodiment of the present invention, and comparative light-emitting device 6 all exhibit favorable characteristics. In particular, light-emitting device 7 and light-emitting device 8, which use a quinolinol complex of a metal having an alkyl group at the 6-position, exhibit low driving voltage and favorable current efficiency and power efficiency. In particular, light-emitting device 8, which uses a quinolinol complex of sodium metal, exhibits low driving voltage and favorable current efficiency and power efficiency. [Example]

[0471] In this example, light-emitting devices 9 to 12 according to embodiments of the present invention will be described. The structural formulae of organic compounds used in this example are shown below.

[0472] [ka]

[0473] (Method for fabricating light-emitting device 9) First, a film of indium tin oxide containing silicon oxide (ITSO) was formed on a glass substrate by sputtering to a thickness of 55 nm to form an anode 101. The electrode area was 4 mm 2 (2mm x 2mm).

[0474] Next, as a pretreatment for forming a light-emitting device on the substrate, the substrate surface was washed with water, baked at 200°C for 1 hour, and then subjected to UV ozone treatment for 370 seconds.

[0475] Then, 10 -4 The substrate was introduced into a vacuum deposition apparatus whose internal pressure had been reduced to about Pa, and after vacuum baking at 170°C for 30 minutes in the heating chamber of the vacuum deposition apparatus, the substrate was allowed to cool for about 30 minutes.

[0476] Next, the substrate on which the anode 101 was formed was fixed to a substrate holder installed in a vacuum deposition apparatus so that the surface on which the anode 101 was formed faced downward. N-(1,1'-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF) represented by the above structural formula (i) and an electron acceptor material (OCHD-001) were co-deposited on the anode 101 by a deposition method to a thickness of 10 nm at a weight ratio of 1:0.05 (= PCBBiF:OCHD-001) to form a hole injection layer 111.

[0477] After PCBBiF was deposited on the hole injection layer 111 to a thickness of 20 nm, N,N-bis[4-(dibenzofuran-4-yl)phenyl]-4-amino-p-terphenyl (abbreviation: DBfBB1TP) represented by the above structural formula (ii) was deposited to a thickness of 10 nm to form the hole transport layer 112.

[0478] Subsequently, 3,3'-(naphthalene-1,4-diyl)bis(9-phenyl-9H-carbazole) (abbreviation: PCzN2) represented by the above structural formula (iii) was vapor-deposited on the hole transport layer 112 to a thickness of 10 nm to form an electron blocking layer.

[0479] Thereafter, 2-(10-phenyl-9-anthracenyl)-benzo[b]naphtho[2,3-d]furan (abbreviation: Bnf(II)PhA) represented by the above structural formula (iv) and 3,10-bis[N-(9-phenyl-9H-carbazol-2-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviation: 3,10PCA2Nbf(IV)-02) represented by the above structural formula (v) were co-deposited to a thickness of 25 nm in a weight ratio of 1:0.015 (=Bnf(II)PhA:3,10PCA2Nbf(IV)-02) to form the light-emitting layer 113.

[0480] After that, 2-[3'-(9,9-dimethyl-9H-fluoren-2-yl)-1,1'-biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mFBPTzn) represented by the above structural formula (vi) was deposited to a thickness of 10 nm to form a hole blocking layer, and then 2-{(3',5'-di-tert-butyl)-1,1'-biphenyl-3-yl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mmtBumBPTzn) represented by the above structural formula (xiii) and 2-methyl-8-quinolinolato-lithium (abbreviation: Li-mq) represented by the above structural formula (xv) were co-deposited to a thickness of 20 nm in a weight ratio of 0.5:0.5 (=mmtBumBPTzn:Li-mq) to form an electron transport layer 114.

[0481] After the electron transport layer 114 was formed, lithium fluoride was deposited to a thickness of 1 nm to form the electron injection layer 115, and finally, aluminum was evaporated to a thickness of 200 nm to form the cathode 102, thereby producing the light-emitting device 9.

[0482] (Method of Making Light-Emitting Device 10) Light-emitting device 10 was fabricated in the same manner as light-emitting device 9, except that the Li-mq used in electron transport layer 114 in light-emitting device 9 was replaced with 5-methyl-8-quinolinolato-lithium (abbreviation: Li-5mq) represented by the above structural formula (xvi).

[0483] (Method for fabricating light-emitting device 11) Light-emitting device 11 was fabricated in the same manner as light-emitting device 9, except that the Li-mq used in the electron transport layer 114 in light-emitting device 9 was replaced with 6-methyl-8-quinolinolato-lithium (abbreviated as Li-6mq) represented by the above structural formula (vii), and the weight ratio was set to 0.4:0.6 (=mmtBumBPTzn:Li-6mq).

[0484] (Method of manufacturing light-emitting device 12) Light-emitting device 12 was fabricated in the same manner as light-emitting device 9, except that the Li-mq used in electron transport layer 114 in light-emitting device 9 was replaced with 7-methyl-8-quinolinolato-lithium (abbreviation: Li-7mq) represented by the above structural formula (xvii).

[0485] The device structures of light-emitting devices 9 to 12 are summarized in the table below.

[0486] [Table 17]

[0487] The refractive indices of mmtBumBPTzn, Li-mq, Li-5mq, Li-6mq, and Li-7mq are shown in Figure 75, and their refractive indices at 456 nm are shown in Table 18 below. Measurements were performed using a spectroscopic ellipsometer (M-2000U, manufactured by J.A. Woollam Japan). The measurement samples used were films of each layer formed by vacuum deposition onto a quartz substrate to a thickness of approximately 50 nm. Figure 75 also lists the refractive index for ordinary rays, n, Ordinary, and the refractive index for extraordinary rays, n, Extraordinary.

[0488] [Table 18]

[0489] From Figure 75 and Table 18, it can be seen that the ordinary refractive index of mmtBumBPTzn was 1.68 throughout the entire blue emission region (455 nm to 465 nm), falling within the range of 1.50 to 1.75. Furthermore, the ordinary refractive index at 633 nm was 1.64, falling within the range of 1.45 to 1.70, indicating that mmtBumBPTzn is a low refractive index material. Furthermore, the ordinary refractive index of Li-mq was 1.67 to 1.68 throughout the entire blue emission region (455 nm to 465 nm), falling within the range of 1.45 to 1.70, and the ordinary refractive index at 633 nm was 1.62, falling within the range of 1.40 to 1.65, indicating that it is a low refractive index material. Furthermore, Li-6mq was found to be a low-refractive index material, with an ordinary refractive index of 1.67 across the entire blue emission region (455nm to 465nm), falling within the range of 1.45 to 1.70, and 1.61 at 633nm, falling within the range of 1.40 to 1.65. Li-7mq was found to be a low-refractive index material, with an ordinary refractive index of 1.68 to 1.69 across the entire blue emission region (455nm to 465nm), falling within the range of 1.45 to 1.70, and 1.63 at 633nm, falling within the range of 1.40 to 1.65.

[0490] Here, the ordinary refractive index of Li-5mq at 633 nm is 1.65, which is in the range of 1.40 to 1.65, but the ordinary refractive index across the entire blue emission region (455 nm to 465 nm) is 1.71 to 1.72, which is above 1.70, indicating that Li-5mq has a higher refractive index than the other Li complexes in this example. However, because the refractive index of mmtBumBPTzn, an organic compound with electron transport properties, in the blue emission region is low at 1.68, the sum of the refractive indices divided by 2 is 1.75 or less, and therefore light-emitting device 10 using Li-5mq exhibits sufficiently good characteristics.

[0491] From the above, it can be seen that light-emitting devices 9 to 12 are light-emitting devices in which the ordinary refractive index of the electron transport layer 114 is in the range of 1.50 or more and less than 1.75 throughout the entire blue light emission region (455 nm or more and 465 nm or less), and in the range of 1.45 or more and less than 1.70 at 633 nm.

[0492] The above light-emitting devices 9 to 12 were sealed with glass substrates in a nitrogen-atmosphere glove box to prevent the light-emitting devices from being exposed to the atmosphere (a UV-curable sealant was applied around the elements, UV was irradiated only on the sealant without irradiating the light-emitting devices, and heat-treated at 80°C under atmospheric pressure for 1 hour), and then the initial characteristics of these light-emitting devices were measured. Note that no special measures were taken on the sealed glass substrates to improve light extraction efficiency.

[0493] The luminance-current density characteristics of light-emitting devices 9 to 12 are shown in Figure 62, the current efficiency-luminance characteristics in Figure 63, the luminance-voltage characteristics in Figure 64, the current density-voltage characteristics in Figure 65, the external quantum efficiency-luminance characteristics in Figure 66, and the emission spectra in Figure 67. 2 The main characteristics in this range are shown in Table 19. The luminance, CIE chromaticity, and emission spectrum were measured using a spectroradiometer (SR-UL1R, manufactured by Topcon Corporation) at room temperature.

[0494] [Table 19]

[0495] 62 to 67 and Table 19 show that light-emitting devices 9 to 12, which are light-emitting devices according to one embodiment of the present invention, have favorable characteristics.

[0496] Furthermore, Figure 65 reveals that light-emitting device 10 using Li-5mq and light-emitting device 11 using Li-6mq are particularly light-emitting devices with low driving voltage and excellent characteristics. Thus, the methyl group bonded to the lithium 8-quinolinolato complex is located away from the lithium atom or the nitrogen atom in the quinoline skeleton, enabling the production of light-emitting devices with low driving voltage. Furthermore, because Li-5mq tends to have a relatively high refractive index, Li-6mq is more useful as it facilitates the production of light-emitting devices with high external quantum efficiency and excellent characteristics. While this example illustrates a light-emitting device with a bottom-emission structure, Li-6mq is particularly suitable for top-emission light-emitting devices because its low refractive index significantly improves the external quantum efficiency of top-emission light-emitting devices. Thus, it was found that light-emitting devices using metal complexes containing a ligand including an 8-quinolinolato structure with an alkyl group having 1 to 3 carbon atoms at the 6th position can be used to produce light-emitting devices with better characteristics than those using metal complexes containing a ligand including an 8-quinolinolato structure with an alkyl group at a substitution position other than the 6th position. [Example]

[0497] <Synthesis Example 4> Example 1 In this example, a synthesis method of 3,6-dimethyl-8-quinolinolato-lithium (abbreviation: Li-3,6dmq), which is a metal complex of one embodiment of the present invention, is described. The structural formula of Li-3,6dmq is shown below.

[0498] [ka]

[0499] <Step 1: Synthesis of 8-hydroxy-3,6-dimethylquinoline> A three-neck flask was charged with 6.28 g (51.0 mmol) of 6-amino-m-cresol and 175 mL of 1N hydrochloric acid, followed by stirring at 100°C for 30 minutes. A solution containing 5.36 g (76.5 mmol) of methacrolein (6.38 mL) and 15 mL of ethanol was added dropwise to the reaction solution over 1 hour, followed by heating at 100°C for 2 hours. After completion of the reaction, the reaction solution was heated at 100°C for 2 hours. Dichloromethane was added to the reaction solution, and the aqueous layer was adjusted to pH 7 using 10% aqueous sodium hydroxide and 1N hydrochloric acid. The solution was filtered, the organic layer was removed, and the aqueous layer was further extracted with dichloromethane. The extracted solution was then combined with the organic layer and washed with water. The organic layer was dehydrated over magnesium sulfate and concentrated to obtain a black solid containing the target product.

[0500] The resulting solid was purified by silica gel column chromatography using a developing solvent whose polarity was changed from hexane:ethyl acetate = 10:0 to hexane:ethyl acetate = 10:1. This purification was performed twice in total to obtain 4.3 g (yield: 49%) of the target whitish-yellow solid. The synthesis scheme for Step 1 is shown below.

[0501] [ka]

[0502] <Step 2: Synthesis of Li-3,6dmq> 2.00 g (11.6 mmol) of 8-hydroxy-3,6-dimethylquinoline obtained in Step 1 and 130 mL of anhydrous tetrahydrofuran (THF) were placed in a three-neck flask and stirred. 9.24 mL (9.24 mmol) of lithium tert-butoxide (tBuOLi) in 1 M THF was added to this solution and stirred at room temperature for 96 hours. The reaction solution was concentrated to obtain a yellow solid. Acetonitrile was added to this solid, which was then subjected to ultrasonic irradiation and filtered to obtain a yellow solid. This washing procedure was repeated twice. 1.7 g (100% yield) of a yellow solid, Li-3,6dmq, was obtained as the filtered product.

[0503] 1.65 g of the obtained yellow solid was purified by train sublimation for 17 hours under conditions of a pressure of 2.7 Pa and 330° C. After sublimation purification, 1.40 g of the target yellow solid was obtained with a recovery rate of 84%.

[0504] The raw material methacrolein used in this synthesis was a cheaper material than acrolein diethyl acetal. Therefore, it can be said that a compound having a methyl group at the 3-position of the 8-hydroxyquinoline skeleton can be synthesized more cheaply than one without a methyl group. In other words, quinolinol complexes such as Li-3,6dmq, which is one embodiment of this invention, synthesized using 8-hydroxy-3,6-dimethylquinoline synthesized using methacrolein, can be said to be inexpensive and good materials.

[0505] [ka]

[0506] Nuclear magnetic resonance spectroscopy ( 1 The results of H-NMR analysis are shown below. These results demonstrate that the organic compound Li-3,6dmq, which is one embodiment of the present invention and is represented by structural formula (200), was obtained in this example.

[0507] H 1 NMR (DMSO-d6, 300MHz): δ = 2.23 (s, 3H), 2.36 (s, 3H), 6.17 (s, 1H), 6.23 (s, 1H), 7.69 (s, 1H), 8.14 (s, 1H).

[0508] The absorption and emission spectra of Li-3,6dmq in anhydrous acetone solution are shown in Figure 68. The absorption spectrum was measured using a UV-visible spectrophotometer (V550, manufactured by JASCO Corporation) and is shown after subtracting the spectrum measured with only anhydrous acetone in a quartz cell. The emission spectrum was measured using a fluorometer (FP-8600, manufactured by JASCO Corporation). The anhydrous acetone solution of Li-3,6dmq exhibited an absorption peak at 376 nm and an emission peak at 533 nm (excitation wavelength 378 nm). [Example]

[0509] In this example, light-emitting device 13 and light-emitting device 14, which are light-emitting devices using the organometallic complex of one embodiment of the present invention described in the embodiment, and comparative light-emitting device 7, which is a light-emitting device using a known organometallic complex, will be described. The structural formulas of the organic compounds used in this example are shown below.

[0510] [ka]

[0511] (Method for fabricating light-emitting device 13) First, a film of indium tin oxide containing silicon oxide (ITSO) was formed on a glass substrate by sputtering to a thickness of 70 nm to form an anode 101. The electrode area was 4 mm 2 (2mm x 2mm).

[0512] Next, as a pretreatment for forming a light-emitting device on the substrate, the substrate surface was washed with water, baked at 200°C for 1 hour, and then subjected to UV ozone treatment for 370 seconds.

[0513] Then, 10 -4 The substrate was introduced into a vacuum deposition apparatus whose internal pressure had been reduced to about Pa, and after vacuum baking at 170°C for 30 minutes in the heating chamber of the vacuum deposition apparatus, the substrate was allowed to cool for about 30 minutes.

[0514] Next, the substrate on which the anode 101 was formed was fixed to a substrate holder installed in a vacuum deposition apparatus so that the surface on which the anode 101 was formed faced downward. N,N-bis(4-biphenyl)-6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BBABnf) represented by the above structural formula (xii) and an electron acceptor material (OCHD-001) were co-deposited on the anode 101 by a deposition method to a thickness of 10 nm in a weight ratio of 1:0.1 (=BBABnf:OCHD-001), thereby forming a hole injection layer 111.

[0515] On the hole injection layer 111, BBABnf was evaporated to a thickness of 20 nm to form a hole transport layer 112.

[0516] Subsequently, 3,3'-(naphthalene-1,4-diyl)bis(9-phenyl-9H-carbazole) (abbreviation: PCzN2) represented by the above structural formula (iii) was vapor-deposited on the hole transport layer 112 to a thickness of 10 nm to form an electron blocking layer.

[0517] Thereafter, 9-(1-naphthyl)-10-[4-(2-naphthyl)phenyl]anthracene (abbreviation: αN-βNPAnth) represented by the above structural formula (xviii) and 3,10-bis[N-(9-phenyl-9H-carbazol-2-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviation: 3,10PCA2Nbf(IV)-02) represented by the above structural formula (v) were co-deposited to a thickness of 20 nm in a weight ratio of 1:0.015 (=αN-βNPAnth:3,10PCA2Nbf(IV)-02) to form the light-emitting layer 113.

[0518] After that, 2-[3'-(9,9-dimethyl-9H-fluoren-2-yl)-1,1'-biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mFBPTzn) represented by the above structural formula (vi) was deposited to a thickness of 10 nm to form a hole blocking layer, and then 2-[3-(2,6-dimethyl-3-pyridinyl)-5-(9-phenanthrenyl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mPn-mDMePyPTzn) represented by the above structural formula (xix) and 6-methyl-8-quinolinolato-lithium (abbreviation: Li-6mq) represented by the above structural formula (vii) were co-deposited to a thickness of 20 nm in a weight ratio of 1:1 (=mPn-mDMePyPTzn:Li-6mq) to form an electron transport layer 114.

[0519] After the formation of the electron transport layer 114, 8-quinolinolato-lithium (abbreviation: Liq) represented by the above structural formula (ix) was deposited to a thickness of 1 nm to form the electron injection layer 115, and finally, aluminum was evaporated to a thickness of 200 nm to form the cathode 102, thereby producing the light-emitting device 13. The light-emitting device of this example is a bottom-emission element in which light is extracted from the anode 101.

[0520] (Method of Making Light-Emitting Device 14) Light-emitting device 14 was fabricated in the same manner as light-emitting device 13, except that Li-6mq in light-emitting device 13 was replaced with 3,6-dimethyl-8-quinolinolato-lithium (abbreviation: Li-3,6dmq) represented by the above structural formula (xx).

[0521] (Method for producing comparative light-emitting device 7) Comparative light-emitting device 7 was fabricated in the same manner as light-emitting device 13, except that Li-6mq in light-emitting device 13 was replaced with 8-quinolinolato-lithium (abbreviation: Liq) represented by the above structural formula (ix).

[0522] The device structures of light-emitting device 13, light-emitting device 14 and comparative light-emitting device 7 are summarized in the table below.

[0523] [Table 20]

[0524] Light-emitting device 13, light-emitting device 14, and comparative light-emitting device 7 were sealed with glass substrates in a nitrogen-atmosphere glove box to prevent the light-emitting devices from being exposed to the atmosphere (a UV-curable sealant was applied around the elements, UV was irradiated only on the sealant without irradiating the light-emitting devices, and heat-treated at 80°C under atmospheric pressure for 1 hour), and then the initial characteristics of these light-emitting devices were measured. Note that no special measures were taken on the sealed glass substrates to improve light extraction efficiency.

[0525] The luminance-current density characteristics of light-emitting device 13, light-emitting device 14, and comparative light-emitting device 7 are shown in Figure 69, their current efficiency-luminance characteristics in Figure 70, their luminance-voltage characteristics in Figure 71, their current density-voltage characteristics in Figure 72, their external quantum efficiency-luminance characteristics in Figure 73, and their emission spectra in Figure 74. Furthermore, the 1000 cd / m 2 The main characteristics in this range are shown in Table 21. The luminance, CIE chromaticity, and emission spectrum were measured using a spectroradiometer (SR-UL1R, manufactured by Topcon Corporation) at room temperature.

[0526] [Table 21]

[0527] 69 to 74 and Table 21 show that the light-emitting devices 13 and 14, which are light-emitting devices of one embodiment of the present invention and which include a metal complex, each have low driving voltage and high emission efficiency.

[0528] In particular, Li-3,6dmq has good deposition rate stability during vacuum deposition during device fabrication, making it a good material.

[0529] ≪Reference synthesis example 1≫ This section describes a synthesis method for 2-{(3',5'-di-tert-butyl)-1,1'-biphenyl-3-yl}-4,6-bis(3,5-di-tert-butylphenyl)-1,3,5-triazine (abbreviation: mmtBumBP-dmmtBuPTzn) used in Examples 1 and 2. The structure of mmtBumBP-dmmtBuPTzn is shown below.

[0530] [ka]

[0531] <Step 1: Synthesis of 3-bromo-3',5'-di-tert-butylbiphenyl> A three-neck flask was charged with 1.0 g (4.3 mmol) of 3,5-di-t-butylphenylboronic acid, 1.5 g (5.2 mmol) of 1-bromo-3-iodobenzene, 4.5 mL of 2 mol / L aqueous potassium carbonate, 20 mL of toluene, and 3 mL of ethanol. The mixture was degassed by stirring under reduced pressure. 52 mg (0.17 mmol) of tris(2-methylphenyl)phosphine and 10 mg (0.043 mmol) of palladium(II) acetate were added and reacted at 80 °C for 14 hours under a nitrogen atmosphere. After the reaction was complete, the mixture was extracted with toluene, and the resulting organic layer was dried over magnesium sulfate. The mixture was gravity filtered, and the filtrate was purified by silica gel column chromatography (eluent: hexane) to obtain 1.0 g of the desired white solid (yield: 68%). The synthesis scheme for Step 1 is shown below.

[0532] [ka]

[0533] <Step 2: Synthesis of 2-(3',5'-di-tert-butylbiphenyl-3-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane> A three-neck flask was charged with 1.0 g (2.9 mmol) of 3-bromo-3',5'-di-tert-butylbiphenyl, 0.96 g (3.8 mmol) of bis(pinacolato)diboron, 0.94 g (9.6 mmol) of potassium acetate, and 30 mL of 1,4-dioxane. The mixture was degassed by stirring under reduced pressure. 0.12 g (0.30 mmol) of 2-dicyclohexylphosphino-2',6'-dimethoxybiphenyl and 0.12 g (0.15 mmol) of [1,1'-bis(diphenylphosphino)ferrocene]palladium(II) dichloride dichloromethane adduct were then added and reacted under a nitrogen atmosphere at 110°C for 24 hours. After the reaction was complete, the mixture was extracted with toluene, and the resulting organic layer was dried over magnesium sulfate. The mixture was gravity filtered. The obtained filtrate was purified by silica gel column chromatography (developing solvent: toluene) to obtain 0.89 g of the target yellow oil (yield: 78%). The synthesis scheme of Step 2 is shown below.

[0534] [ka]

[0535] <Step 3: Synthesis of 2-{(3',5'-di-tert-butyl)-1,1'-biphenyl-3-yl}-4,6-bis(3,5-di-tert-butylphenyl)-1,3,5-triazine (abbreviation: mmtBumBP-dmmtBuPTzn)> A three-neck flask was charged with 0.8 g (1.6 mmol) of 4,6-bis(3,5-di-tert-butylphenyl)-2-chloro-1,3,5-triazine, 0.89 g (2.3 mmol) of 2-(3',5'-di-tert-butylbiphenyl-3-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane, 0.68 g (3.2 mmol) of tripotassium phosphate, 3 mL of water, 8 mL of toluene, and 3 mL of 1,4-dioxane. The mixture was degassed by stirring under reduced pressure. 3.5 mg (0.016 mmol) of palladium(II) acetate and 10 mg (0.032 mmol) of tris(2-methylphenyl)phosphine were added and heated to reflux under a nitrogen atmosphere for 12 hours. After the reaction was complete, the mixture was extracted with ethyl acetate, and the resulting organic layer was dried over magnesium sulfate. The mixture was gravity filtered. The resulting filtrate was concentrated and purified by silica gel column chromatography (eluent: ethyl acetate:hexane = 1:20) to obtain a solid. This solid was purified by silica gel column chromatography (eluent: chloroform:hexane = 5:1 changed to 1:0). The resulting solid was recrystallized with hexane to obtain 0.88 g of the desired white solid in 76% yield. The synthesis scheme for Step 3 is shown below.

[0536] [ka]

[0537] 0.87 g of the resulting white solid was purified by train sublimation. The conditions were a pressure of 5.8 Pa, and the solid was heated to 230 °C while flowing argon gas. After sublimation purification, 0.82 g of the target white solid was obtained with a recovery rate of 95%.

[0538] Figure 36 shows the refractive index of mmtBumBP-dmmtBuPTzn obtained by the synthesis method described above, measured using a spectroscopic ellipsometer (M-2000U manufactured by J.A. Woollam Japan). For the measurements, films of approximately 50 nm thickness were formed on a quartz substrate using vacuum deposition of the materials for each layer. Figure 36 also shows the refractive index for ordinary rays, n, Ordinary, and the refractive index for extraordinary rays, n, Extraordinary.

[0539] From Figure 36, it can be seen that mmtBumBP-dmmtBuPTzn has an ordinary refractive index in the range of 1.50 to 1.75 throughout the entire blue emission region (455 nm to 465 nm), and that the ordinary refractive index at 633 nm is also in the range of 1.45 to 1.70, making it a material with a low refractive index.

[0540] ≪Reference synthesis example 2≫ This section describes a method for synthesizing 2-{(3',5'-di-tert-butyl)-1,1'-biphenyl-3-yl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mmtBumBPTzn) used in Example 5. The structure of mmtBumBPTzn is shown below.

[0541] [ka]

[0542] <Step 1: Synthesis of 3-bromo-3',5'-di-tert-butylbiphenyl> The synthesis was carried out in the same manner as in Step 1 of Reference Synthesis Example 1.

[0543] <Step 2: Synthesis of 2-(3',5'-di-tert-butylbiphenyl-3-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane> The synthesis was carried out in the same manner as in Step 2 of Reference Synthesis Example 1.

[0544] <Step 3: Synthesis of mmtBumBPTzn> A three-neck flask was charged with 1.5 g (5.6 mmol) of 4,6-diphenyl-2-chloro-1,3,5-triazine, 2.4 g (6.2 mmol) of 2-(3',5'-di-tert-butylbiphenyl-3-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane, 2.4 g (11 mmol) of tripotassium phosphate, 10 mL of water, 28 mL of toluene, and 10 mL of 1,4-dioxane. The mixture was degassed by stirring under reduced pressure. To this mixture was added 13 mg (0.056 mmol) of palladium(II) acetate and 34 mg (0.11 mmol) of tris(2-methylphenyl)phosphine. The mixture was heated under reflux for 14 hours under a nitrogen atmosphere. After completion of the reaction, the mixture was extracted with ethyl acetate, and the resulting organic layer was dehydrated with magnesium sulfate. The mixture was gravity filtered, and the resulting filtrate was purified by silica gel column chromatography (the developing solvent was changed from chloroform:hexane = 1:5 to 1:3), followed by recrystallization with hexane to obtain 2.0 g of the target white solid (yield: 51%). The synthesis scheme of Step 3 is shown in the following formula (b-1).

[0545] [ka]

[0546] 2.0 g of the obtained white solid was purified by train sublimation under argon gas flow at a pressure of 3.4 Pa and 220°C. The solid was heated. After sublimation purification, 1.8 g of the target white solid was obtained with a recovery rate of 80%.

[0547] The white solid obtained in step 3 was analyzed by nuclear magnetic resonance spectroscopy ( 1 The results of the analysis by H-NMR are shown below. From these results, it was found that mmtBumBPTzn was obtained in this synthesis example.

[0548] H 1 NMR (CDCl3, 300MHz): δ = 1.44 (s, 18H), 7.51-7.68 (m, 10H), 7.83 (d, 1H), 8.73-8.81 (m, 5H), 9.01 (s, 1H).

[0549] Figure 44 shows the results of measuring the refractive index of mmtBumBPTzn using a spectroscopic ellipsometer (M-2000U manufactured by J.A. Woollam Japan). For the measurements, films of approximately 50 nm thickness were formed on a quartz substrate using vacuum deposition of the materials for each layer. Figure 44 also lists the refractive index of ordinary light, n, Ordinary, and the refractive index of extraordinary light, n, Extraordinary.

[0550] 44, mmtBumBPTzn has an ordinary refractive index of 1.68 throughout the entire blue emission region (455 nm to 465 nm), which is in the range of 1.50 to 1.75. The ordinary refractive index at 633 nm is also 1.64, which is in the range of 1.45 to 1.70, indicating that mmtBumBPTzn is a material with a low refractive index. [Explanation of symbols]

[0551] 101 Anode 102 Cathode 103 EL layer 111 Hole injection layer 112 Hole transport layer 113 Light-emitting layer 114 Electron transport layer 115 Electron injection layer 116 Charge generation layer 117 P type layer 118 Electronic Relay Layer 119 Electron injection buffer layer 400 boards 401 Anode 403 EL layer 404 Cathode 405 Sealing material 406 Sealing material 407 Sealing substrate 412 Pad 420 IC chip 501 Anode 502 Cathode 511 First Light Emitting Unit 512 Second Light Emitting Unit 513 Charge generation layer 601 Driver circuit section (source line driver circuit) 602 Pixel section 603 Drive circuit section (gate line drive circuit) 604 Sealing substrate 605 Sealing material 607 Space 608 Wiring 609 FPC (Flexible Printed Circuit) 610 Element substrate 611 Switching FET 612 Current control FET 613 Anode 614 Insulators 616 EL layer 617 Cathode 618 Light-emitting devices 951 PCB 952 Electrode 953 Insulation Layer 954 Partition layer 955 EL layer 956 Electrode 1001 board 1002 Undercoat insulating film 1003 Gate insulating film 1006 Gate electrode 1007 Gate electrode 1008 gate electrode 1020 First interlayer insulating film 1021 Second interlayer insulating film 1022 Electrode 1024W anode 1024R Anode 1024G anode 1024B Anode 1025 Bulkhead 1028 EL layer 1029 Cathode 1031 Sealing substrate 1032 Sealing material 1033 Transparent substrate 1034R Red color layer 1034G Green color layer 1034B Blue color layer 1035 Black Matrix 1036 Overcoat layer 1037 Third interlayer insulating film 1040 pixel section 1041 Drive circuit section 1042 Periphery 2001 Case 2002 light source 2100 Robot 2110 Arithmetic equipment 2101 Illuminance sensor 2102 Microphone 2103 Upper Camera 2104 Speaker 2105 Display 2106 Lower Camera 2107 Obstacle Sensor 2108 Moving mechanism 3001 Lighting equipment 5000 cabinets 5001 Display section 5002 Display section 5003 Speaker 5004 LED lamp 5006 Connection terminal 5007 Sensor 5008 Microphone 5012 Support part 5013 Earphones 5100 Cleaning Robot 5101 Display 5102 Camera 5103 Brush 5104 Operation button 5150 Personal Digital Assistant 5151 Case 5152 Display area 5153 Bend 5120 Garbage 5200 display area 5201 Display area 5202 Display area 5203 Display area 7101 Housing 7103 Display section 7105 Stand 7107 Display section 7109 Operation key 7110 Remote control device 7201 Main unit 7202 Case 7203 Display section 7204 keyboard 7205 External connection port 7206 Pointing Device 7210 Display section 7401 Housing 7402 Display section 7403 Operation button 7404 External connection port 7405 Speaker 7406 Microphone 9310 Mobile Information Terminal 9311 Display Panel 9313 Hinge 9315 Housing

Claims

1. an anode, a cathode, and an EL layer located between the anode and the cathode; the EL layer has a light-emitting layer and an electron transport layer, the light-emitting layer comprises a light-emitting material; the electron transport layer includes an organic compound having electron transport properties and a metal complex of an alkali metal; the alkali metal complex is a metal complex having a ligand containing an 8-quinolinolato structure, The alkali metal complex has one or two alkyl groups, the one or two alkyl groups are alkyl groups having 1 to 3 carbon atoms; the organic compound having electron transport properties has an ordinary refractive index of 1.50 or more and 1.75 or less at the peak wavelength of light emitted by the light-emitting material; A light-emitting device, wherein the metal complex of the alkali metal has an ordinary refractive index of 1.45 or more and 1.70 or less at the peak wavelength of light emitted by the light-emitting material.

2. In claim 1, a light-emitting device in which the organic compound having electron transport properties and the metal complex of an alkali metal both have an alkyl group or a cycloalkyl group;

3. In claim 2, the alkyl group of the organic compound having electron transport properties is either a branched alkyl group or an alkyl group having 3 or 4 carbon atoms; The alkyl group of the metal complex of the alkali metal is any one of alkyl groups having 1 to 3 carbon atoms.

4. In claim 2, the alkyl group of the organic compound having electron transport properties is a t-butyl group; A light-emitting device, wherein the alkyl group of the metal complex of the alkali metal is a methyl group.

5. In any one of claims 1 to 4, The sp of the organic compound having electron transport properties ３ A light-emitting device in which the ratio of carbon atoms forming bonds through hybrid orbitals is 10% to 60% of the total number of carbon atoms in the organic compound.

6. In any one of claims 1 to 4, The organic compound having electron transport properties １ The results of H-NMR measurements show that the integral value of signals below 4 ppm exceeds the integral value of signals above 4 ppm.

7. an anode, a cathode, and an EL layer located between the anode and the cathode; the EL layer has a light-emitting layer and an electron transport layer, the light-emitting layer comprises a light-emitting material; the electron transport layer comprises an organic compound having a π-electron-deficient heteroaromatic ring skeleton and a metal complex of an alkali metal; the alkali metal complex is a metal complex having a ligand containing an 8-quinolinolato structure, The alkali metal complex has one or two alkyl groups, the one or two alkyl groups are alkyl groups having 1 to 3 carbon atoms; the organic compound having a π-electron-deficient heteroaromatic ring skeleton has an ordinary refractive index of 1.50 or more and 1.75 or less at a peak wavelength of light emitted by the light-emitting material; A light-emitting device, wherein the metal complex of the alkali metal has an ordinary refractive index of 1.45 or more and 1.70 or less at the peak wavelength of light emitted by the light-emitting material.

8. In claim 7, A light-emitting device in which the organic compound having a π-electron-deficient heteroaromatic ring skeleton and the metal complex of an alkali metal both have an alkyl group or a cycloalkyl group.

9. In claim 8, the alkyl group contained in the organic compound having a π-electron-deficient heteroaromatic ring skeleton is either a branched alkyl group or an alkyl group having 3 or 4 carbon atoms; The alkyl group of the metal complex of the alkali metal is any one of alkyl groups having 1 to 3 carbon atoms.

10. In claim 8, the alkyl group of the organic compound having a π-electron-deficient heteroaromatic ring skeleton is a t-butyl group, The light-emitting device wherein the alkyl group in the metal complex of the alkali metal is a methyl group.

11. In any one of claims 7 to 10, The sp of the organic compound having a π-electron-deficient heteroaromatic ring skeleton ３ A light-emitting device in which the ratio of carbon atoms forming bonds through hybrid orbitals is 10% or more and 60% or less of the total number of carbon atoms in the organic compound.

12. In any one of claims 7 to 10, The organic compound having the π-electron-deficient heteroaromatic ring skeleton is １ The results of H-NMR measurements show that the integral value of signals below 4 ppm exceeds the integral value of signals above 4 ppm.

13. In any one of claims 7 to 12, The organic compound having a π-electron-deficient heteroaromatic ring skeleton has a triazine skeleton or a diazine skeleton.

14. In any one of claims 1 to 13, The light-emitting device wherein the metal complex of an alkali metal is a metal complex of lithium.

15. In any one of claims 1 to 13, The light-emitting device, wherein the alkali metal complex is a metal complex represented by the following general formula (G0): 【Chemistry 1】 (In the above general formula (G0), M is an alkali metal, R １ is an alkyl group having 1 to 3 carbon atoms, R ２ represents hydrogen or an alkyl group having 1 to 3 carbon atoms.

16. In claim 15, R ２ is a methyl group in light-emitting devices.

17. In claim 15 or claim 16, M is a lithium light-emitting device.

18. In claim 15 or claim 16, M is sodium light-emitting device.

19. In any one of claims 1 to 13, The light-emitting device, wherein the alkali metal complex is a metal complex represented by any one of the following general formulas (G1) to (G3): 【Chemistry 2】 (However, in the above general formulae (G1) to (G3), R １ and R ２ each independently represents an alkyl group having 1 to 3 carbon atoms.

20. In any one of claims 15 to 19, R １ is a methyl group in light-emitting devices.

21. In any one of claims 15 to 19, R １ is an ethyl group light-emitting device.

22. A light emitting device according to any one of claims 1 to 21; An electronic device having at least one of a sensor, an operation button, a speaker, and a microphone.

23. A light emitting device according to any one of claims 1 to 21; a transistor and / or a substrate;

24. A lighting device comprising: a light-emitting device according to any one of claims 1 to 21; and a housing.

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