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

Abstract

A light-emitting device with high luminous efficiency is provided. The light-emitting device includes 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, and the electron transport layer includes an organic compound with electron transport properties and a metal complex of an alkali metal. The light emitted by the light-emitting material containing the organic compound with electron transport properties has an ordinary refractive index at the peak wavelength of light of 1.50 or more and 1.75 or less, and the light emitted by the alkali metal complex of the light-emitting material has an ordinary refractive index at the peak wavelength of light of 1.45 or more and 1.70 or less.

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 equipment, and an electronic device. Note that one embodiment of the present invention is not limited to the above-described technical fields. The technical field of one embodiment of the invention disclosed in this specification relates to an object, method, or manufacturing method. Furthermore, one embodiment of the present invention relates to a process, machine, manufacture, or composition of matter. Therefore, more specifically, 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 equipment, energy storage devices, memory devices, imaging devices, and methods for driving or manufacturing these devices. Prior Technology

[0002] In recent years, the practical application of light-emitting devices (organic EL devices) that utilize organic compounds and electroluminescence (EL) has been very active. In the basic structure of these light-emitting devices, an organic compound layer (EL layer) containing luminescent material is sandwiched between a pair of electrodes. By applying a voltage to the device and injecting carriers, light emission from the luminescent material can be obtained using the recombination energy of these carriers.

[0003] Because this type of light-emitting device is self-emissive, it offers advantages over liquid crystal displays (LCDs) in terms of higher visibility and the elimination of the need for a backlight when used for display pixels, making it particularly suitable for flat panel displays. Furthermore, displays using this type of device can be manufactured to be thin and lightweight, which is a significant advantage. Moreover, its extremely high response time is also a characteristic of this light-emitting device.

[0004] Furthermore, because the light-emitting layer of this type of light-emitting device can be continuously formed in two dimensions, surface light emission can be achieved. Since this is a characteristic that is difficult to obtain in point light sources represented by incandescent lamps or LEDs, or in line light sources represented by fluorescent lamps, the above-mentioned light-emitting device is also highly valuable as a surface light source that can be applied to lighting and other applications.

[0005] As mentioned above, although displays or lighting devices using light-emitting devices are suitable for a wide variety of electronic devices, research and development of light-emitting devices with better characteristics is becoming increasingly active.

[0006] Low light extraction efficiency is a common problem in organic EL devices. In particular, attenuation caused by reflection due to the difference in refractive index between adjacent layers is the main reason for the decrease in the efficiency of light-emitting devices. To reduce this effect, a structure in which a layer of low refractive index material is formed inside the EL layer has been proposed (for example, see Non-Patent Literature 1).

[0007] [Non-Patent Literature 1] Jaeho Lee, 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

[0008] One embodiment of the present invention aims to provide a light-emitting device with high luminous efficiency. Another embodiment of the present invention aims to provide any one of a light-emitting device, light-emitting apparatus, electronic device, display device, and electronic apparatus that has low power consumption.

[0009] Furthermore, another embodiment of the present invention aims to provide a novel organometallic complex (metal complex). Another embodiment of the present invention aims to provide a metal complex that can be used in light-emitting devices with low driving voltages. Another embodiment of the present invention aims to provide a metal complex that can be used in light-emitting devices comprising an electron transport layer with a low refractive index and a low driving voltage.

[0010] The present invention can achieve any one of the above objectives.

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

[0012] Another embodiment of the present invention is a light-emitting device, which includes 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, and the electron transport layer includes an organic compound with electron transport properties and a metal complex of an alkali metal. The value obtained by dividing the sum of the ordinary refractive index at the peak wavelength of the light emitted by the light-emitting material of the organic compound with electron transport properties and the ordinary refractive index at the peak wavelength of the light emitted by the light-emitting material of the alkali metal complex by 2 is 1.50 or more and less than 1.75.

[0013] Another embodiment of the present invention is a light-emitting device, which includes 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, and the electron transport layer includes an organic compound and an alkali metal complex with electron transport properties. The light emitted by the light-emitting material of the electron transport layer has an ordinary refractive index of 1.50 or more and less than 1.75 at the peak wavelength.

[0014] Another embodiment of the present invention is a light-emitting device, which includes 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 electron transport layer includes an organic compound with electron transport properties and a metal complex of an alkali metal. The ordinary refractive index of the organic compound with electron transport properties is 1.50 or more and 1.75 or less relative to any wavelength of light in the range of 455 nm or more and 465 nm or less. The ordinary refractive index of the metal complex of the alkali metal is 1.45 or more and 1.70 or less relative to any wavelength of light 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, which includes 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 electron transport layer includes an organic compound with electron transport properties and a metal complex of an alkali metal. The sum of the ordinary refractive index of the organic compound with electron transport properties relative to any wavelength of light in the range of 455 nm to 465 nm and the ordinary refractive index of the metal complex of the alkali metal relative to any wavelength of light in the range of 455 nm to 465 nm, divided by 2, yields a value of 1.50 or more and less than 1.75.

[0016] Another embodiment of the present invention is a light-emitting device, which includes 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 electron transport layer includes an organic compound and an alkali metal complex with electron transport properties. The ordinary optical refractive index of the electron transport layer relative to any wavelength in the range of 455 nm or higher and 465 nm or lower is 1.50 or higher and less than 1.75.

[0017] Another embodiment of the present invention is a light-emitting device, which includes 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 electron transport layer includes an organic compound with electron transport properties and a metal complex of an alkali metal. The ordinary refractive index of the organic compound with electron transport properties relative to light with a wavelength of 633 nm is 1.45 or more and 1.70 or less, and the ordinary refractive index of the metal complex of the alkali metal relative to light with a wavelength of 633 nm is 1.40 or more and 1.65 or less.

[0018] Another embodiment of the present invention is a light-emitting device, which includes 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 electron transport layer includes an organic compound with electron transport properties and a metal complex of an alkali metal. The sum of the ordinary refractive index of the organic compound with electron transport properties relative to light at a wavelength of 633 nm and the ordinary refractive index of the metal complex of the alkali metal relative to light at a wavelength of 633 nm, divided by 2, yields a value of 1.45 or more and less than 1.70.

[0019] Another embodiment of the present invention is a light-emitting device, which includes 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 electron transport layer includes an organic compound and an alkali metal complex with electron transport properties. The ordinary optical refractive index of the electron transport layer relative to light with a wavelength of 633 nm is greater than 1.45 and less than 1.70.

[0020] Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the organic compound and the alkali metal complex having electron transport properties each have an alkyl or cycloalkyl group.

[0021] Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein 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, and the alkyl group of the alkali metal complex 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-described structure, wherein the alkyl group of the organic compound having electron transport properties is tert-butyl, and the alkyl group of the alkali metal complex is methyl.

[0023] Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the proportion of carbon atoms bonded by sp3 hybrid orbitals in the organic compound having electron transport properties is more than 10% and less than 60% of the total number of carbon atoms in the organic compound.

[0024] Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the integral value of a signal less than 4 ppm in the 1 H-NMR measurement results of an organic compound with electron transport properties exceeds the integral value of a signal greater than 4 ppm.

[0025] Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the organic compound having electron transport properties has a triazine backbone or a diazine backbone.

[0026] Another embodiment of the present invention is a light-emitting device with a benzene ring in an organic compound having electron transport properties.

[0027] Another embodiment of the present invention is a light-emitting device, which includes 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, and the electron transport layer includes an organic compound having a π-electron-deficient heteroaromatic ring skeleton and a metal complex of an alkali metal. The value obtained by dividing the sum of the ordinary refractive index at the peak wavelength of the light emitted by the light-emitting material of the organic compound having a π-electron-deficient heteroaromatic ring skeleton and the ordinary refractive index at the peak wavelength of the light emitted by the light-emitting material of the alkali metal complex by 2 is 1.50 or more and less than 1.75.

[0028] Another embodiment of the present invention is a light-emitting device, which includes 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 a π-electron-deficient heteroaromatic ring skeleton and a metal complex of an alkali metal. The light emitted by the light-emitting material of the electron transport layer has an ordinary refractive index of 1.50 or more and less than 1.75 at the peak wavelength.

[0029] Another embodiment of the present invention is a light-emitting device, which includes 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 electron transport layer includes an organic compound having a π-electron-deficient heteroaromatic ring skeleton and an alkali metal complex. The ordinary refractive index of the organic compound having a π-electron-deficient heteroaromatic ring skeleton relative to any wavelength in the range of 455 nm to 465 nm is 1.50 or more and 1.75 or less. The ordinary refractive index of the alkali metal complex relative to any wavelength in the range of 455 nm to 465 nm is 1.45 or more and 1.70 or less.

[0030] Another embodiment of the present invention is a light-emitting device, which includes 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 electron transport layer includes an organic compound having a π-electron-deficient heteroaromatic ring skeleton and a metal complex of an alkali metal. The value obtained by dividing the sum of the ordinary refractive index of the organic compound having a π-electron-deficient heteroaromatic ring skeleton with light of any wavelength in the range of 455 nm or more and 465 nm or less, and the ordinary refractive index of the metal complex of the alkali metal with light of any wavelength in the range of 455 nm or more and 465 nm or less, by 2 is 1.50 or more and less than 1.75.

[0031] Another embodiment of the present invention is a light-emitting device, which includes 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 electron transport layer includes an organic compound having a π-electron-deficient heteroaromatic ring skeleton and a metal complex of an alkali metal. The ordinary refractive index of the electron transport layer relative to any wavelength of light in the range of 455 nm or more and 465 nm or less is 1.50 or more and less than 1.75.

[0032] Another embodiment of the present invention is a light-emitting device, which includes 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 electron transport layer includes an organic compound having a π-electron-deficient heteroaromatic ring skeleton and an alkali metal complex. The ordinary refractive index of the organic compound having a π-electron-deficient heteroaromatic ring skeleton relative to light with a wavelength of 633 nm is 1.45 or more and 1.70 or less, and the ordinary refractive index of the alkali metal complex relative to light with a wavelength of 633 nm is 1.40 or more and 1.65 or less.

[0033] Another embodiment of the present invention is a light-emitting device, which includes 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 electron transport layer includes an organic compound having a π-electron-deficient heteroaromatic ring skeleton and an alkali metal complex. The value obtained by dividing the sum of the ordinary refractive index of the organic compound having a π-electron-deficient heteroaromatic ring skeleton relative to light at a wavelength of 633 nm and the ordinary refractive index of the alkali metal complex relative to light at a wavelength of 633 nm by 2 is 1.45 or more and less than 1.70.

[0034] Another embodiment of the present invention is a light-emitting device, which includes 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 electron transport layer includes an organic compound having a π-electron-deficient heteroaromatic ring skeleton and a metal complex of an alkali metal. The ordinary optical refractive index of the electron transport layer relative to light with a wavelength 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-described structure, wherein the organic compound having a π-electron-deficient heteroaromatic ring skeleton and the metal complex of the alkali metal each have an alkyl or cycloalkyl group.

[0036] Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the alkyl group of 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 of the alkali metal complex is an alkyl group having 1 to 3 carbon atoms.

[0037] In addition, another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the alkyl group of the organic compound having a π-electron-deficient heteroaromatic ring skeleton is tertiary butyl, and the alkyl group of the alkali metal complex is methyl.

[0038] Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the proportion of carbon atoms bonded by sp3 hybrid orbitals in the organic compound having a π-electron-deficient heteroaromatic ring backbone is more than 10% and less than 60% of the total number of carbon atoms in the organic compound.

[0039] Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the integral value of a signal less than 4 ppm in the 1 H-NMR measurement results of an organic compound having a π-electron-deficient heteroaromatic ring skeleton exceeds the integral value of a signal greater than 4 ppm.

[0040] Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein 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-described structure, wherein the alkali metal complex is a metal complex comprising a ligand having an 8-hydroxyquinoline structure.

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

[0043] Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the alkali metal complex is a lithium metal complex.

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

[0045] [Chemical Formula 1]

[0046] Note that in the above general formula (G0), M represents an alkali metal, R1 represents an alkyl group with 1 to 3 carbon atoms, and R2 represents hydrogen or an alkyl group with 1 to 3 carbon atoms.

[0047] Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein R2 is a methyl group.

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

[0049] [Chemical Formula 2]

[0050] Note that in the above general formulas (G1) to (G3), R1 represents an alkyl group having 1 to 3 carbon atoms, and in general formula (G3), R2 represents an alkyl group having 1 to 3 carbon atoms.

[0051] Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein R1 is a methyl group.

[0052] Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein R1 is an ethyl group.

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

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

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

[0056] [Chemical Formula 3]

[0057] Note that in the above general formula (G0), M represents an alkali metal, R1 represents an alkyl group with 1 to 3 carbon atoms, and R2 represents hydrogen or an alkyl group with 1 to 3 carbon atoms.

[0058] Another embodiment of the present invention is a metal complex having the above-described structure, wherein R2 is methyl.

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

[0060] [Chemical Formula 4]

[0061] Note that in the above general formulas (G1) to (G3), R1 and R2 independently represent alkyl groups having 1 to 3 carbon atoms.

[0062] Another embodiment of the present invention is a metal complex having the above-described structure, wherein R1 is methyl.

[0063] Another embodiment of the present invention is a metal complex having the above-described structure, wherein R1 is an ethyl group.

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

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

[0066] Another embodiment of the present invention is a light-emitting device having the above-mentioned metal complex.

[0067] Another embodiment of the present invention is a light-emitting device in which the light emitted by the light-emitting material of the metal complex represented by the above general formula (G1) has an ordinary refractive index of 1.45 or more and 1.70 or less at the peak wavelength.

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

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

[0070] In addition, another embodiment of the present invention is an electronic device comprising: the light-emitting device described in any of the preceding claims; and at least one of a sensor, an operation button, a speaker, and a microphone.

[0071] In addition, another embodiment of the present invention is a light-emitting device, comprising: the light-emitting device described in any of the above items; and at least one of a transistor and a substrate.

[0072] In addition, another embodiment of the present invention is a lighting device, comprising: the light-emitting device described in any of the above items; and a housing.

[0073] In this specification, a light-emitting device includes an image display device that uses a light-emitting element. Additionally, a light-emitting device sometimes includes modules such as: modules in which the light-emitting element is mounted with connectors such as anisotropic conductive films or TCP (Tape Carrier Package); modules in which printed circuit boards are provided at the ends of the TCP; or modules in which ICs (integrated circuits) are directly mounted on the light-emitting element using COG (Chip On Glass) bonding. Furthermore, lighting equipment sometimes includes a light-emitting device.

[0074] One embodiment of the present invention can provide a light-emitting device with high luminous efficiency. Another embodiment of the present invention can 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.

[0075] Another embodiment of the present invention can provide a novel organometallic complex (metal complex). Additionally, another embodiment of the present invention can provide a metal complex that can be used in light-emitting devices with low driving voltages. Furthermore, another embodiment of the present invention can provide a metal complex that can be used in light-emitting devices comprising a low-refractive-index electron transport layer and with low driving voltages.

[0076] Note that the description of these effects does not preclude the existence of other effects. Furthermore, one embodiment of the present invention does not require all of the above-described effects to be achieved. Additionally, effects other than those described above can be derived from the description in the specification, drawings, claims, etc. Simple Explanation of the Diagram

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

[0078] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the following description, and those skilled in the art will readily understand that its methods and details can be varied in many ways without departing from the spirit and scope of the invention. Therefore, the present invention should not be construed as being limited to the contents described in the embodiments shown below.

[0079] Implementation Method 1

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

[0081] The light-emitting layer 113 includes at least a light-emitting material, and the electron transport layer 114 includes an organic compound with electron transport properties and a metal complex of an alkali metal.

[0082] In one embodiment of the present invention, the electron transport layer 114 of the light-emitting device comprises an organic compound and an alkali metal complex with electron transport properties, preferably in the following combination: the sum of the ordinary refractive indices of the light emitted by the light-emitting materials included in the light-emitting layer 113 divided by 2 is 1.50 or more and less than 1.75, preferably 1.50 or more and less than 1.70.

[0083] Note that the refractive index of the aforementioned electron-transporting organic compounds and alkali metal complexes is determined by measuring the thin film of the material. When anisotropy occurs in such a thin film, the ordinary refractive index and the extraordinary refractive index may differ. When the measured thin film is in the aforementioned state, the ordinary refractive index and the extraordinary refractive index can be calculated separately by performing anisotropic analysis. Note that in this specification, when the measured material has both an ordinary and extraordinary refractive indices, the ordinary refractive index is used as the indicator.

[0084] The electron transport layer 114 using this material can be a layer with a low refractive index. By setting a layer with a low refractive index in the EL layer, the light extraction efficiency is improved, thus a light-emitting device with high luminous efficiency can be obtained. Generally, the refractive index of the organic compound constituting the light-emitting device is about 1.8 to 1.9. Because the light-emitting device of one embodiment of the present invention includes an electron transport layer with a low refractive index, a light-emitting device with high luminous efficiency can be realized.

[0085] In particular, because the electron transport layer 114 is disposed between the light-emitting layer 113 and the cathode 102, it is suitable for top-emitting light-emitting devices.

[0086] In addition, the ordinary light refractive index of the electron transport layer 114 of the light-emitting device according to one embodiment of the present invention is preferably 1.50 or more and less than 1.75, and more preferably 1.50 or more and less than 1.70.

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

[0088] Furthermore, in the blue light-emitting device, the aforementioned light-emitting material emits light of any wavelength (λB) within the blue light-emitting region (455 nm and above and 465 nm and below). Therefore, the combination of the organic compound and the alkali metal complex with electron transport properties is preferably as follows: the sum of the ordinary refractive indices of the light relative to λB divided by 2 yields a value of 1.50 or more and less than 1.75, more preferably 1.50 or more and less than 1.70.

[0089] Furthermore, similarly, the ordinary refractive index of the electron transport layer 114 of the blue light-emitting device relative to λB is preferably 1.50 or higher and less than 1.75, more preferably 1.50 or higher and less than 1.70. In particular, the organic compound with electron transport properties is preferably a substance with an ordinary refractive index of 1.50 or higher and less than 1.75 relative to λB, more preferably 1.50 or higher and less than 1.70, and the metal complex of the alkali metal is preferably a substance with an ordinary refractive index of 1.45 or higher and less than 1.70 relative to λB.

[0090] Furthermore, since the refractive index is high on the short wavelength side and low on the long wavelength side in principle, the electron transport layer 114 used in one embodiment of the present invention preferably has the following combination of an organic compound and an alkali metal complex with electron transport properties, where the sum of their respective ordinary refractive indices relative to light at a wavelength of 633 nm is divided by 2 to obtain a value of 1.45 or more and less than 1.70. Similarly, the ordinary refractive index of the electron transport layer 114 used in one embodiment of the present invention relative to light at a wavelength of 633 nm is preferably 1.45 or more and less than 1.70. Moreover, it is particularly preferred that the ordinary refractive index of the organic compound with electron transport properties used in the electron transport layer 114 used in one embodiment of the present invention is 1.45 or more and less than 1.70 relative to light at a wavelength of 633 nm, and the ordinary refractive index of the alkali metal complex used in the electron transport layer 114 used in one embodiment of the present invention is 1.40 or more and less than 1.65 relative to light at a wavelength of 633 nm.

[0091] Furthermore, the electron transport layer 114 used in one embodiment of the present invention preferably comprises an organic compound and an alkali metal complex having electron transport properties, each having an alkyl or cycloalkyl group. When they have alkyl or cycloalkyl groups, the refractive index can be reduced, thus achieving an electron transport layer 114 with a low refractive index.

[0092] Here, it is generally believed that the presence of alkyl or cycloalkyl groups hinders the interaction (also known as docking) between organic compounds with electron transport properties and metal complexes of alkali metals, leading to an increase in driving voltage. However, in a light-emitting device according to one embodiment of the present invention, there is no significant increase in driving voltage, and a light-emitting device with a low refractive index electron transport layer and high luminous efficiency can be realized.

[0093] Note that the alkyl group in the electron-transporting organic compound is preferably a branched alkyl group, particularly preferably an alkyl group with 3 or 4 carbon atoms, with tert-butyl being especially preferred. Additionally, the alkyl group in the alkali metal complex preferably has any one of 1 to 3 carbon atoms, with methyl being particularly preferred.

[0094] Preferably, the electron transportable organic compound constituting the electron transport layer 114 has at least one six-membered heteroaromatic ring with 1 to 3 nitrogen atoms, including a plurality of fused aromatic hydrocarbon rings with 6 to 14 cyclic carbon atoms, at least two of the plurality of fused aromatic hydrocarbon rings being benzene rings, and comprising a plurality of organic compounds having hydrocarbon groups bonded by sp3 hybrid orbitals.

[0095] Furthermore, in such organic compounds, the proportion of carbon atoms bonded by sp3 hybrid orbitals in the total carbon atoms of the molecule is preferably 10% or more and 60% or less, more preferably 10% or more and 50% or less. Alternatively, in such organic compounds, the integral value of a signal less than 4 ppm in the results of 1H-NMR measurements is preferably more than half the integral value of a signal greater than 4 ppm.

[0096] Note that, preferably, all the hydrocarbon groups in the organic compound that are bonded by sp3 hybrid orbitals are bonded to the aforementioned fused aromatic ring with 6 to 14 carbon atoms, and the LUMO of the organic compound is not distributed on the fused aromatic ring.

[0097] Note that the above-mentioned organic compounds are equivalent to organic compounds with electron transport properties included in the electron transport layer 114.

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

[0099] [Chemical Formula 5]

[0100] In the general formula, A represents a six-membered heteroaromatic ring with 1 to 3 nitrogen atoms, preferably a pyridine ring, pyrimidine ring, pyrazine ring, pyrazine ring, or triazine ring.

[0101] Additionally, R0 represents hydrogen, an alkyl group having 1 to 6 carbon atoms, an alicyclic group having 3 to 10 carbon atoms, or a substituent represented by formula (G1-1).

[0102] At least one of R1 to R15 is a phenyl group with a substituent, and the others independently represent hydrogen, an alkyl group having 1 to 6 carbon atoms, an alicyclic group having 3 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 14 carbon atoms, or a substituted or unsubstituted pyridyl group. R1, R3, R5, R6, R8, R10, R11, R13, and R15 are preferably hydrogen. The aforementioned phenyl group with a substituent has one or two substituents, which are independently 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.

[0103] The organic compound represented by the above 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 proportion of carbon atoms bonded by sp3 hybrid orbitals in the total number of carbon atoms of the molecule is more than 10% and less than 60%.

[0104] In addition, the organic compound with electron transport capability is preferably an organic compound represented by the following general formula (G3).

[0105] [Chemical Formula 6]

[0106] In the general formula, two or three of Q1 to Q3 represent N. When two of Q1 to Q3 are N, the remaining one represents CH.

[0107] Furthermore, at least one of R1 to R15 is a phenyl group with a substituent, and the others independently represent hydrogen, an alkyl group having 1 to 6 carbon atoms, an alicyclic group having 3 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 14 carbon atoms, or a substituted or unsubstituted pyridyl group. R1, R3, R5, R6, R8, R10, R11, R13, and R15 are preferably hydrogen. The aforementioned phenyl group with a substituent has one or two substituents, which are independently 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.

[0108] Preferably, the organic compound represented by the above 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 proportion of carbon atoms bonded by sp3 hybrid orbitals in the total number of carbon atoms of the molecule is more than 10% and less than 60%.

[0109] In addition, in organic compounds represented by the above general formula (G1) or (G3), the phenyl group having a substituent is preferably represented by the following formula (G1-2).

[0110] [Chemical Formula 7]

[0111] In the formula, α represents a substituted or unsubstituted phenyl group, with meta-substituted phenyl groups being preferred. Furthermore, when a meta-substituted phenyl group has one substituent, it is preferable that the substituent is also meta-substituted. 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 tert-butyl group.

[0112] R20 represents an alkyl group with 1 to 6 carbon atoms, an alicyclic group with 3 to 10 carbon atoms, or a substituted or unsubstituted cyclic aromatic group with 6 to 14 carbon atoms.

[0113] Additionally, m and n represent 1 or 2. Note that when m is 2, multiple α groups can be the same or different. Similarly, when n is 2, multiple R20 groups can be the same or different. R20 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 in one or both of the two meta positions. The substituent in one or both of the meta positions of this phenyl group is more preferably an alkyl group having 1 to 6 carbon atoms, and even more preferably a tributyl group.

[0114] Furthermore, the alkali metal complex is preferably a lithium metal complex or a sodium metal complex. Additionally, the ligand of the metal complex is preferably a ligand having an 8-hydroxyquinoline structure.

[0115] When a lithium or sodium complex having an 8-hydroxyquinoline structure contains an alkyl group, the complex preferably contains one or two alkyl groups. 8-hydroxyquinoline-lithium with alkyl groups can achieve metal complexes with low refractive indices. Specifically, in the thin film state, the ordinary optical refractive index relative to light wavelengths in the range of 455 nm to 465 nm can be 1.45 or higher and 1.70 or lower, and the ordinary optical refractive index relative to light wavelengths of 633 nm can be 1.40 or higher and 1.65 or lower.

[0116] Furthermore, in particular, the use of alkali metal complexes comprising an 8-hydroxyquinoline ligand having an alkyl group at the 6-position has the effect of reducing the driving voltage of the light-emitting device. Light-emitting devices using alkali metal complexes comprising a 6-alkyl-8-hydroxyquinoline ligand or alkali metal complexes comprising a 3,6-dialkyl-8-hydroxyquinoline ligand exhibit good characteristics and are therefore preferred. The aforementioned alkyl group is more preferably methyl or ethyl.

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

[0118] [Chemical Formula 8]

[0119] Note that in the above general formula (G0), M represents an alkali metal, R1 represents an alkyl group with 1 to 3 carbon atoms, and R2 represents hydrogen or an alkyl group with 1 to 3 carbon atoms.

[0120] Furthermore, the metal complex represented by the above general formula (G0) is particularly preferably a metal complex represented by any one of the following general formulas (G1) to (G3).

[0121] [Chemical Formula 9]

[0122] Note that in the above general formulas (G1) to (G3), R1 and R2 independently represent alkyl groups having 1 to 3 carbon atoms. By utilizing metal complexes with such structures, light-emitting devices with high luminous efficiency and low driving voltage can be obtained. Furthermore, the evaporation rate in vacuum evaporation of metal complexes represented by general formula (G3) is very stable, which is preferable. Moreover, it is even more preferable that the number of carbon atoms in R1 and R2 is 1 independently, which results in a lower driving voltage compared to the case where the number of carbon atoms is 2 or more.

[0123] Furthermore, among the metal complexes represented by the above general formulas (G1) to (G3), a more preferred approach is to represent metal complexes represented by the following structural formulas (100), (101), (102), and (200).

[0124] [Chemical Formula 10]

[0125] [Chemical Formula 11]

[0126] [Chemical Formula 12]

[0127] [Chemical Formula 13]

[0128] As described above, the electron transport layer 114 of the light-emitting device according to one embodiment of the present invention preferably comprises an alkyl group having 3 or 4 carbon atoms, and more preferably comprises a plurality of such alkyl groups. However, carrier transport decreases when there are too many alkyl groups in the molecule. Therefore, the proportion of carbons bonded by sp3 hybrid orbitals in the electron transport organic compound is preferably 10% or more and 60% or less of the total number of carbon atoms in the organic compound, more preferably 10% or more and 50% or less. An electron transport organic compound with this structure can achieve a low refractive index without a significant decrease in electron transport.

[0129] When this organic compound was measured using 1H-NMR (proton nuclear magnetic resonance), the results showed that the integral value of the signal less than 4 ppm exceeded the integral value of the signal above 4 ppm.

[0130] When the electron transport layer 114 of the light-emitting device used in one embodiment of the present invention has a triazine or diazine backbone, the carrier transport properties are good, which is preferred.

[0131] By including, as described above, an electron transport layer comprising an organic compound with low refractive index and an alkali metal complex with low refractive index, a low refractive index layer can be achieved without significant degradation of the driving voltage, etc. As a result, the extraction efficiency of light emitted from the light-emitting layer 113 is improved, and the light-emitting device according to one embodiment of the present invention can be a light-emitting device with high luminous efficiency.

[0132] Next, examples of other structures or materials of the light-emitting device according to one embodiment of the present invention will be described. As described above, the light-emitting device according to one embodiment of the present invention includes an EL layer 103 composed of multiple layers between a pair of electrodes, an anode 101 and a cathode 102. The EL layer 103 includes a light-emitting layer 113 containing a light-emitting material and an 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 with a high work function (specifically 4.0 eV or higher). Specifically, examples include indium tin oxide (ITO), indium tin oxide containing silicon or silicon oxide, indium zinc oxide, and indium oxide (IWZO) containing tungsten oxide and zinc oxide. While these conductive metal oxide films are typically formed by sputtering, they can also be formed using sol-gel methods. Examples of formation methods include sputtering an indium oxide-zinc oxide film using a target containing 1 wt% to 20 wt% zinc oxide. Alternatively, indium oxide (IWZO) containing tungsten oxide and zinc oxide can be formed by sputtering a target containing 0.5 wt% to 5 wt% tungsten oxide and 0.1 wt% to 1 wt% zinc oxide. Furthermore, materials used for the anode 101 can include, for example, gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), or nitrides of metallic materials (e.g., titanium nitride). Additionally, graphene can also be used as a material for the anode 101. Moreover, by using the composite material described later in the EL layer 103 in contact with the anode 101, the work function does not need to be considered when selecting the electrode material.

[0134] The EL layer 103 preferably has a stacked structure. There are no particular limitations on this stacked structure; it can be any layer structure, such as a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer, a carrier barrier layer (hole barrier layer and electron barrier layer), an exciton barrier layer, or a charge generation layer. It is also possible to omit any layers. In this embodiment, two structures are described: as shown in FIG1A, a structure that includes 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; and as shown in FIG1B, a structure that includes 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. The materials constituting each layer are shown in detail below.

[0135] The hole injection layer 111 is a layer containing a substance with acceptor properties. Organic and inorganic compounds can be used as the acceptor material.

[0136] Compounds with electron-withdrawing groups (halogen or cyano groups) can be used as acceptor substances. Examples include 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinone dimethylethane (F4-TCNQ), chloroquinone, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazabitribenzene (HAT-CN), 1,3,4,5,7,8-hexafluorotetracyano-naphthoquinodimethane (F6-TCNNQ), and 2-(7-dicyanomethylene-1,3,4,5,6,8,9,10-octafluoro-7H-pyrene-2-ylidene)malononitrile. In particular, compounds with electron-withdrawing groups bonded to fused aromatic rings containing multiple heteroatoms, such as HAT-CN, are thermally stable and therefore preferred. In addition, electron-withdrawing groups (especially halogen groups such as fluorine groups and cyano groups) [3] axialene derivatives have very high electron accepting properties and are therefore particularly preferred. Specifically, examples include: α,α',α''-1,2,3-cycloalkyltrimethylenetri[4-cyano-2,3,5,6-tetrafluorophenylacetonitrile], α,α',α''-1,2,3-cyclopropyltrimethylenetri[2,6-dichloro-3,5-difluoro-4-(trifluoromethyl)phenylacetonitrile], α,α',α''-1,2,3-cycloalkyltrimethylenetri[2,3,4,5,6-pentafluorophenylacetonitrile], etc. In addition to the above-mentioned organic compounds, molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, manganese oxide, etc. can be used as acceptor substances. Alternatively, phthalocyanine complexes such as phthalocyanine (H2Pc) and copper phthalocyanine (CuPc) can be used; aromatic amine compounds such as 4,4'-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (DPAB) and N,N'-bis{4-[bis(3-methylphenyl)amino]phenyl}-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine (DNTPD) can be used; or polymers such as poly(3,4-ethylenedioxythiophene) / poly(styrenesulfonic acid) (PEDOT / PSS) can be used to form the hole injection layer 111. Substances with acceptor properties can extract electrons from adjacent hole transport layers (or hole transport materials) by means of an applied electric field.

[0137] Furthermore, as the hole injection layer 111, a composite material containing the aforementioned acceptor substance in a material with hole transport properties can be used. Note that by using a composite material containing an acceptor substance in a material with hole transport properties, the work function of the electrode can be disregarded when selecting the material to form the electrode. In other words, as the anode 101, not only materials with high work functions but also materials with low work functions can be used.

[0138] Various organic compounds, such as aromatic amine compounds, carbazole derivatives, aromatic hydrocarbons, and polymers (oligomers, dendritic polymers, polymers, etc.), can be used as hole-transporting materials for composite materials. Preferably, substances with a hole mobility of 1 × 10⁻⁶ cm² / Vs or higher are used. The following are specific examples of organic compounds that can be used as hole-transporting materials in composite materials.

[0139] Examples of aromatic amine compounds that can be used in composite materials include N,N'-bis(p-tolyl)-N,N'-diphenyl-p-phenylenediamine (DTDPPA), 4,4'-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (DPAB), N,N'-bis{4-[bis(3-methylphenyl)amino]phenyl}-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine (DNTPD), and 1,3,5-tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene (DPA3B). Specific examples of carbazole derivatives include 3-[N-(9-phenylcarbazole-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviated as PCzPCA1), 3,6-bis[N-(9-phenylcarbazole-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviated as PCzPCA2), 3-[N-(1-naphthyl)-N-(9-phenylcarbazole-3-yl)amino]-9-phenylcarbazole (abbreviated as PCzPCN1), 4,4'-bis(N-carbazole)biphenyl (abbreviated as CBP), 1,3,5-tris[4-(N-carbazole)phenyl]benzene (abbreviated as TCPB), 9-[4-(10-phenylanthracene-9-yl)phenyl]-9H-carbazole (abbreviated as CzPA), and 1,4-bis[4-(N-carbazole)phenyl]-2,3,5,6-tetraphenylbenzene, etc. Examples of aromatic hydrocarbons include 2-tertiary butyl-9,10-bis(2-naphthyl)anthracene (t-BuDNA), 2-tertiary butyl-9,10-bis(1-naphthyl)anthracene, 9,10-bis(3,5-diphenylphenyl)anthracene (DPPA), 2-tertiary butyl-9,10-bis(4-phenylphenyl)anthracene (t-BuDBA), 9,10-bis(2-naphthyl)anthracene (DNA), 9,10-diphenylanthracene (DPAnth), 2-tertiary butylanthracene (t-BuAnth), and 9,10-bis(4-methyl-1-naphthyl)anthracene (DMNA). Anthracene, 2-tert-butyl-9,10-bis[2-(1-naphthyl)phenyl]anthracene, 9,10-bis[2-(1-naphthyl)phenyl]anthracene, 2,3,6,7-tetramethyl-9,10-bis(1-naphthyl)anthracene, 2,3,6,7-tetramethyl-9,10-bis(2-naphthyl)anthracene, 9,9'-bianthracene, 10,10'-diphenyl-9,9'-bianthracene, 10,10'-bis(2-phenylphenyl)-9,9'-bianthracene, 10,10'-bis[(2,3,4,5,6-pentaphenyl)phenyl]-9,9'-bianthracene, anthracene, condensed tetraphenylene, red fluorene, perylene, 2,5,8,11-tetra(tert-butyl)perylene, etc. In addition, condensed pentaphenylene, keratin, etc., can also be used. Furthermore, it can also have a vinyl backbone.Examples of aromatic hydrocarbons containing vinyl groups include 4,4'-bis(2,2-diphenylvinyl)biphenyl (abbreviated as DPVBi) and 9,10-bis[4-(2,2-diphenylvinyl)phenyl]anthracene (abbreviated as DPVPA). Additionally, organic compounds from one embodiment of the present invention may also be used.

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

[0141] As a material with hole-transporting properties for use in composite materials, it is more preferably any one of a carbazole backbone, a dibenzofuran backbone, a dibenzothiophene backbone, and an anthracene backbone. In particular, it can be an aromatic amine having substituents including a dibenzofuran ring or a dibenzothiophene ring, an aromatic monoamine including a naphthyl ring, or an aromatic monoamine with a 9-pyrenyl group bonded to the nitrogen of the amine via an aryl group. Note that when these second organic compounds are substances including N,N-bis(4-biphenyl)amine groups, it is preferable to manufacture light-emitting devices with good lifetimes. Specifically, examples of the aforementioned second organic compounds include N-(4-biphenyl)-6,N-diphenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviated as: BnfABP), N,N-bis(4-biphenyl)-6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviated as: BBABnf), 4,4'-bis(6-phenylbenzo[b]naphtho[1,2-d]furan-8-yl)-4”-phenyltriphenylamine (abbreviated as: BnfBB1BP), and 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-(dibenzothiophene-4-yl)] [Phenyl]-N-phenyl-4-benzidine (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'-binathyl-2-yl)triphenylamine (abbreviation: BBAαNβNB), 4,4'-diphenyl-4”-(7;1'-binathyl-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'-binathyl-1-yl)triphenylamine (abbreviation: BBAβNαNB-02), 4-(4-biphenyl)-4'-(2-naphthyl)-4'-phenyltriphenylamine (abbreviation: TPBiAβNB), 4-(3-biphenyl)-4'-[4-(2-naphthyl)phenyl]-4'-phenyltriphenylamine (abbreviation: mTPBiAβNBi), 4-(4-biphenyl)-4'-[4-(2-naphthyl)phenyl]-4'-phenyltriphenylamine (abbreviation: TPBiAβNBi), 4-phenyl-4'-(1-naphthyl)triphenylamine (abbreviation: αNBA1BP), 4,4'-bis(1-naphthyl)triphenylamine (abbreviation: αNBB1B) P), 4,4'-diphenyl-4”-[4'-(carbazole-9-yl)biphenyl-4-yl]triphenylamine (abbreviation: YGTBi1BP), 4'-[4-(3-phenyl-9H-carbazole-9-yl)phenyl]tri(1,1'-biphenyl-4-yl)amine (abbreviation: YGTBi1BP-02), 4-diphenyl-4'-(2-naphthyl)-4”-{9-(4-biphenyl)carbazole}triphenylamine (abbreviation: YGTBiβNB), N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-N-[4-(1-naphthyl)phenyl]-9,9'-spirodi(9H-enyl)-2-amine (abbreviation: PCBNBSF), N,N-bis(4-biphenyl)-9,9'-spirodi(9H-enyl)-2-amine (abbreviation: PCBNBSF), N,N-bis(4-biphenyl)-9,9'-spirodi(9H-enyl)-2-yl) Bis[9H-furan]-2-amine (abbreviation: BBASF), N,N-bis(1,1'-biphenyl-4-yl)-9,9'-spirobis[9H-furan]-4-amine (abbreviation: BBASF(4)), N-(1,1'-biphenyl-2-yl)-N-(9,9-dimethyl-9H-furan-2-yl)-9,9'-spirobis(9H-furan)-4-amine (abbreviation: oFBiSF), N-(4-biphenyl)-N-(dibenzofuran-4-yl)-9,9-dimethyl-9H-furan-2-amine (abbreviation: FrBiF), N-[4-(1-naphthyl)phenyl]-N-[3-(6-phenyldibenzofuran-4-yl)phenyl]-1-naphthylamine (abbreviation: mPDBfBNBN) 4-Phenylacetyl-4'-(9-phenylenylacetyl-9-yl)triphenylamine (abbreviation: BPAFLP), 4-Phenylacetyl-3'-(9-phenylenylacetyl-9-yl)triphenylamine (abbreviation: mBPAFLP), 4-Phenylacetyl-4'-[4-(9-phenylenylacetyl-9-yl)phenyl]triphenylamine (abbreviation: BPAFLBi), 4-Phenylacetyl-4'-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4'-diphenyl-4”-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCCBI1BP), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBANB), 4,4'-Di(1-naphthyl)-4”-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCCNBB), N-phenyl-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9,9'-spirodi[9H-furan]-2-amine (abbreviation: PCBASF), N-(1,1'-biphenyl-4-yl)-9,9-dimethyl-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9H-furan-2-amine (abbreviation: PCB) BiF), N,N-bis(9,9-dimethyl-9H-fumon-2-yl)-9,9'-spirodi-9H-fumon-4-amine, N,N-bis(9,9-dimethyl-9H-fumon-2-yl)-9,9'-spirodi-9H-fumon-3-amine, N,N-bis(9,9-dimethyl-9H-fumon-2-yl)-9,9'-spirodi-9H-fumon-2-amine, N,N-bis(9,9-dimethyl-9H-fumon-2-yl)-9,9'-spirodi-9H-fumon-1-amine, etc.

[0142] Note that the hole-transporting material used in the composite material is preferably a material with a deep HOMO level, having a HOMO level above -5.7 eV and below -5.4 eV. When the hole-transporting material used in the composite material has a deep HOMO level, holes are easily injected into the hole transport layer 112, and a long-lifetime light-emitting device can be easily obtained. Furthermore, when the hole-transporting material used in the composite material has a deep HOMO level, hole induction is appropriately suppressed, thus enabling a light-emitting device with an even longer lifetime.

[0143] Note that by further mixing alkali metal or alkaline earth metal fluorides into the above composite material (preferably, the atomic ratio of fluorine atoms in the layer is 20% or more), the refractive index of the layer can be reduced. Therefore, a layer with a low refractive index can be formed inside the EL layer 103, and the external quantum efficiency of the light-emitting device can be improved.

[0144] By forming a hole injection layer 111, hole injection can be improved, thereby obtaining a light-emitting device with a low driving voltage.

[0145] Furthermore, organic compounds with receptor properties can be easily formed in substances with receptor properties using vapor deposition, making them easy-to-use materials.

[0146] The hole transport layer 112 is formed by including a material with hole transport properties. The material with hole transport properties preferably has a hole mobility of 1×10-6 cm2 / Vs or higher.

[0147] Examples of materials exhibiting hole transport properties include: 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB), N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (TPD), 4,4'-bis[N-(spiro-9,9'-dien-2-yl)-N-phenylamino]biphenyl (BSPB), 4-phenyl-4'-(9-phenylenen-9-yl)triphenylamine (BPAFLP), 4-phenyl-3'-(9-phenylenen-9-yl)triphenylamine (mBPAFLP), 4-phenyl-4 '-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4'-diphenyl-4”-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBANB), 4,4'-di(1-naphthyl)-4”-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCCNBB), 9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]furo-2-amine (abbreviation: PCBAF), N- Compounds with an aromatic amine skeleton, such as phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9'-spirobi[9H-furan]-2-amine (abbreviated as: PCBASF); compounds with a carbazole skeleton, such as 1,3-bis(N-carbazolyl)benzene (abbreviated as: mCP), 4,4'-bis(N-carbazolyl)biphenyl (abbreviated as: CBP), 3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviated as: CzTP), and 3,3'-bis(9-phenyl-9H-carbazole) (abbreviated as: PCCP); and compounds with a carbazole skeleton, such as 4,4',4”-(benzyl-1,3,5-triyl)tris(dibenzothiophene) (abbreviated as: DBT3). Compounds with a thiophene skeleton, such as 2,8-diphenyl-4-[4-(9-phenyl-9H-prostaglandin-9-yl)phenyl]dibenzothiophene (abbreviated as DBTFLP-III) and 4-[4-(9-phenyl-9H-prostaglandin-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviated as DBTFLP-IV); and compounds with a furan skeleton, such as 4,4',4”-(phenyl-1,3,5-triyl)tris(dibenzofuran) (abbreviated as DBF3P-II) and 4-{3-[3-(9-phenyl-9H-prostaglandin-9-yl)phenyl]phenyl}dibenzofuran (abbreviated as mmDBFFLBi-II). Among these, compounds with aromatic amine skeletons and compounds with carbazole skeletons have good reliability and high hole transport properties and help reduce driving voltage, so they are preferred.Note that materials with hole-transporting properties, such as those used in the hole injection layer 111, can also be appropriately used as the material constituting the hole transport layer 112.

[0148] The light-emitting layer 113 contains a light-emitting substance and a host material. Note that the light-emitting layer 113 may also contain other materials. Furthermore, it may be a two-layer stack with different compositions.

[0149] The luminescent material can be a fluorescent luminescent material, a phosphorescent luminescent material, a material exhibiting thermally activated delayed fluorescence (TADF), or other luminescent materials. In one embodiment of the present invention, it is more suitable to use a luminescent layer 113 that exhibits fluorescent emission, especially a layer that exhibits blue fluorescent emission.

[0150] In the luminescent layer 113, materials that can be used as fluorescent luminescent substances include, for example, the following substances. Note that other fluorescent luminescent substances can also be used.

[0151] Examples include 5,6-bis[4-(10-phenyl-9-anthrayl)phenyl]-2,2'-bipyridine (abbreviated as: PAP2BPy), 5,6-bis[4'-(10-phenyl-9-anthrayl)biphenyl-4-yl]-2,2'-bipyridine (abbreviated as: PAPP2BPy), N,N'-diphenyl-N,N'-bis[4-(9-phenyl-9H-enta-9-yl)phenyl]pyrene-1,6-diamine (abbreviated as: 1,6FLPAPrn), N,N'-bis(3-methylphenyl)-N,N'-bis[3-(9-phenyl-9H-enta-9-yl)phenyl]pyrene-1,6-diamine (abbreviated as: 1,6mMemFLPAPrn), and N,N'-bis[4-(9H-carboxylic acid)-2,2'-bipyridine (abbreviated as: PAP2BPy). [9-[4-(10-phenyl-9-anthrayl)phenyl]-N,N'-diphenylstilbene-4,4'-diamine (abbreviation: YGA2S), 4-(9H-carbazol-9-yl)-4'-(10-phenyl-9-anthrayl)triphenylamine (abbreviation: YGAPA), 4-(9H-carbazol-9-yl)-4'-(9,10-diphenyl-2-anthrayl)triphenylamine (abbreviation: 2YGAPPA), N,9-diphenyl-N-[4-(10-phenyl-9-anthrayl)phenyl]-9H-carbazol-3-amine (abbreviation: PCAPA), perylene, 2,5,8,11-tetra-tertiary butylperylene (abbreviation: TBP), 4-(10-phenyl-9-anthrayl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (Abbreviation: PCPAPA), N,N”-(2-tert-butylanthracene-9,10-diyl-4,1-epenylphenyl)bis[N,N',N'-triphenyl-1,4-phenylenediamine] (Abbreviation: DPABPA), N,9-diphenyl-N-[4-(9,10-diphenyl-2-anthrayl)phenyl]-9H-carbazole-3-amine (Abbreviation: 2PCAPPA), N-[4-(9,10-diphenyl-2-anthrayl)phenyl]-N,N',N'-triphenyl-1,4-phenylenediamine (Abbreviation: 2DPAPPA), N,N,N',N',N”,N”,N”',N”'-octaphenyldibenzo[g,p] ⇌ chrysene-2,7,10,15-tetracycline Amine (abbreviation: DBC1), Coumarin 30, N-(9,10-diphenyl-2-anthrayl)-N,9-diphenyl-9H-carbazole-3-amine (abbreviation: 2PCAPA), N-[9,10-bis(1,1'-biphenyl-2-yl)-2-anthrayl]-N,9-diphenyl-9H-carbazole-3-amine (abbreviation: 2PCABPhA), N-(9,10-diphenyl-2-anthrayl)-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPA), N-[9,10-bis(1,1'-biphenyl-2-yl)-2-anthrayl]-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPABPhA), 9,10-bis(1,1'-Biphenyl-2-yl)-N-[4-(9H-carbazole-9-yl)phenyl]-N-phenylanthracene-2-amine (abbreviation: 2YGABPhA), N,N,9-triphenylanthracene-9-amine (abbreviation: DPhAPhA), coumarin 545T, N,N'-diphenylquinacridone (abbreviation: DPQd), fluorene, 5,12-bis(1,1'-biphenyl-4-yl)-6,11-diphenyltetraphenyl (abbreviation: BPT), 2-(2-{2-[4-(dimethylamino)phenyl]vinyl}-6-methyl-4H-pyran-4-yl)malononitrile (abbreviation: DCM1), 2-{2-methyl-6-[2-(2,3,6,7-tetrahydro- 1H,5H-Benzo[ij]quinazine-9-yl)vinyl]-4H-pyran-4-ylidene}malonitrile (abbreviation: DCM2), N,N,N',N'-tetra(4-methylphenyl)tetraphenyl-5,11-diamine (abbreviation: p-mPhTD), 7,14-diphenyl-N,N,N',N'-tetra(4-methylphenyl)acenaphthene[1,2-a]propadiene-3,10-diamine (abbreviation: p-mPhAFD), 2-{2-isopropyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-Benzo[ij]quinazine-9-yl)vinyl]-4H-pyran-4-ylidene}malonitrile (abbreviation: DCJTI), 2-{2-tert-butyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinazin-9-yl)vinyl]-4H-pyran-4-ylidene}malonium (abbreviated: DCJTB), 2-(2,6-bis{2-[4-(dimethylamino)phenyl]vinyl}-4H-pyran-4-ylidene)malonium (abbreviated: BisDCM), 2-{2,6-bis[2-(8-methoxy-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinazin-9-yl)vinyl]-4H-pyran-4-ylidene}malonium (abbreviated: BisDCJTM), N,N'-diphenyl-N,N'-(1,6-pyrene-diyl)bis[(6-phenylbenzo[b]naphtho[1,2-d]furan)-8-amine] (abbreviation: 1,6BnfAPrn-03), 3,10-bis[N-(9-phenyl-9H-carbazole-2-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviation: 3,10PCA2Nbf(IV)-02), 3,10-bis[N-(dibenzofuran-3-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviation: 3,10FrA2Nbf(IV)-02), etc. In particular, 1,6FLPAPrn, 1,6mMemFLPAPrn, 1,Fused aromatic diamine compounds, represented by pyrene diamine compounds such as 6BnfAPrn-03, possess suitable hole-trapping properties, high luminescent efficiency, and high reliability, making them a superior choice.

[0152] When a phosphorescent material is used as a luminescent material in the luminescent layer 113, the following materials can be used as examples.

[0153] For example, materials 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-triazole)iridium(III) (abbreviated as: [Ir(Mptz)3]), and tris[4-(3-biphenyl)-5-isopropyl-3-phenyl-4H-1,2,4-triazole]iridium(III) (abbreviated as: [Ir(iPrptz-3b)3]) and organometallic iridium complexes with a 4H-triazole skeleton can be used; tris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazole]iridium(III) (abbreviated as: [Ir(Mptz1-mp)3]) Organometallic iridium complexes with a 1H-triazole skeleton, such as tris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazole)iridium(III) (abbreviated as [Ir(Prptz1-Me)3]); organometallic iridium complexes with an imidazole skeleton, such as fac-tris[1-(2,6-diisopropylphenyl)-2-phenyl-1H-imidazolium]iridium(III) (abbreviated as [Ir(iPrpmi)3]) and tris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridium(III) (abbreviated as [Ir(dmpimpt-Me)3]); and bis[2-(4',6'-difluorophenyl)pyridinium-N,C2' Organometallic iridium complexes with electron-withdrawing phenylpyridine derivatives as ligands include iridium(III) tetratetra(1-pyrazolyl)borate (FIr6), bis[2-(4',6'-difluorophenyl)pyridin-N,C2']iridium(III)pyridinecarboxylate (FIrpic), bis{2-[3',5'-bis(trifluoromethyl)phenyl]pyridin-N,C2'}iridium(III)pyridinecarboxylate ([Ir(CF3 ppy)2 (pic)]), and bis[2-(4',6'-difluorophenyl)pyridin-N,C2']iridium(III) acetoacetone (Fir(acac)). These substances are blue phosphorescent compounds with emission peaks in the wavelength region of 440 nm to 520 nm.

[0154] Additionally, examples include: tris(4-methyl-6-phenylpyrimidine)iridium(III) (abbreviated as [Ir(mppm)3]), tris(4-tert-butyl-6-phenylpyrimidine)iridium(III) (abbreviated as [Ir(tBuppm)3]), acetylacetone-bis(6-methyl-4-phenylpyrimidine)iridium(III) (abbreviated as [Ir(mppm)2 (acac)]), acetylacetone-bis(6-tert-butyl-4-phenylpyrimidine)iridium(III) (abbreviated as [Ir(tBuppm)2 (acac)]), and acetylacetone-bis[6-(2-norborneol)-4-phenylpyrimidine]iridium(III) (abbreviated as [Ir(nbppm)2]). Organometallic iridium complexes with a pyrimidine skeleton, such as (acac)], (acetyl acetone)bis[5-methyl-6-(2-methylphenyl)-4-phenylpyrimidine]iridium(III) (abbreviated as: Ir(mpmppm)2 (acac)), (acetyl acetone)bis(4,6-diphenylpyrimidine)iridium(III) (abbreviated as: [Ir(dppm)2 (acac)]); organometallic iridium complexes with a pyrazine skeleton, such as (acetyl acetone)bis(3,5-dimethyl-2-phenylpyrazine)iridium(III) (abbreviated as: [Ir(mppr-Me)2 (acac)]), (acetyl acetone)bis(5-isopropyl-3-methyl-2-phenylpyrazine)iridium(III) (abbreviated as: [Ir(mppr-iPr)2 (acac)]); tri(2-phenylpyridinium-N,C2' Organometallic iridium complexes with a pyridine skeleton, including iridium(III) (abbreviated as [Ir(ppy)3]), bis(2-phenylpyridinium-N,C2')iridium(III)acetoacetone (abbreviated as [Ir(ppy)2(acac)]), bis(benzo[h]quinoline)iridium(III)acetoacetone (abbreviated as [Ir(bzq)2(acac)]), tri(benzo[h]quinoline)iridium(III) (abbreviated as [Ir(bzq)3]), tri(2-phenylquinoline-N,C2')iridium(III)(abbreviated as [Ir(pq)3]), bis(2-phenylquinoline-N,C2')iridium(III)acetoacetone (abbreviated as [Ir(pq)2(acac)]), and tri(acetoacetone-N,C2')iridium(III)acetoacetone (abbreviated as [Ir(pq)2(acac)]); and tri(acetoacetone-(monophorone)thionyl(III) (abbreviated as [Tb(acac)3]). Rare earth metal complexes such as (Phen) are mentioned. These substances are primarily compounds exhibiting green phosphorescence and possessing emission peaks in the 500 nm to 600 nm wavelength region. Furthermore, organometallic iridium complexes with a pyrimidine framework are particularly preferred due to their exceptionally superior reliability and luminescence efficiency.

[0155] In addition, examples include organometallic iridium complexes with a pyrimidine skeleton such as (diisobutylmethane)bis[4,6-bis(3-methylphenyl)pyrimidinyl]iridium(III) (abbreviated as: [Ir(5mdppm)2 (dibm)]), (bis[4,6-bis(3-methylphenyl)pyrimidinyl)(dineopentylmethane)iridium(III) (abbreviated as: [Ir(5mdppm)2 (dpm)]), and (bis[4,6-di(naphth-1-yl)pyrimidinyl](dineopentylmethane)iridium(III) (abbreviated as: [Ir(d1npm)2 (dpm)]); and (acetylacetone)bis(2,3,5-triphenylpyrazine)iridium(III) (abbreviated as: [Ir(tppr)2)). Organometallic iridium complexes with pyrazine skeletons, such as bis(2,3,5-triphenylpyrazine)(dinepentylmethane)iridium(III) (abbreviated as: [Ir(tppr)2 (dpm)]), (acetylacetone)bis[2,3-bis(4-fluorophenyl)quinoline]iridium(III) (abbreviated as: [Ir(Fdpq)2 (acac)]); tri(1-phenylisoquinoline-N,C2')iridium(III) (abbreviated as: [Ir(piq)3]), bis(1-phenylisoquinoline-N,C2')iridium(III)acetylacetone (abbreviated as: [Ir(piq)2]), etc. Organometallic iridium complexes with a pyridine framework, such as [acac]; platinum complexes such as 2,3,7,8,12,13,17,18-octaethyl-21H,23H-violet platinum(II) (abbreviated as PtOEP); and rare earth metal complexes such as tris(1,3-diphenyl-1,3-propanedionato) (monoporphyrin) europium(III) (abbreviated as [Eu(DBM)3 (Phen)]) and tris[1-(2-thiophenecarboxyl)-3,3,3-trifluoroacetone] (monoporphyrin) europium(III) (abbreviated as [Eu(TTA)3 (Phen)]). These substances are compounds that exhibit red phosphorescence and have emission peaks in the wavelength region of 600 nm to 700 nm. Furthermore, organometallic iridium complexes with a pyrazine framework can obtain red emission with good colorimetry.

[0156] In addition to the phosphorescent compounds mentioned above, other known phosphorescent compounds may also be used.

[0157] Fullerenes and their derivatives, acridines and their derivatives, and eosin derivatives can be used as TADF materials. Additionally, metallic violets containing magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), or palladium (Pd) can also be cited. Examples of such metallic violets include, for instance, the following structural formulas: protoviolet-tin fluoride complex (SnF2 (Proto IX)), mesoviolet-tin fluoride complex (SnF2 (Meso IX)), hematoviolet-tin fluoride complex (SnF2 (Hemato IX)), tetramethyl copropisyl ester-tin fluoride complex (SnF2 (Copro III-4Me), octaethylviolet-tin fluoride complex (SnF2 (OEP)), protoviolet-tin fluoride complex (SnF2 (Etio I)), and octaethylviolet-platinum chloride complex (PtCl2 OEP).

[0158] [Chemical Formula 14]

[0159] Alternatively, the following structural formulas can also be used: 2-(biphenyl-4-yl)-4,6-bis(12-phenylindol[2,3-a]carbazole-11-yl)-1,3,5-triazine (abbreviated as: PIC-TRZ), 9-(4,6-diphenyl-1,3,5-triazin-2-yl)-9'-phenyl-9H,9'H-3,3'-bicarbazole (abbreviated as: PCCzTzn), 9-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-9'-phenyl-9H,9'H-3,3'-bicarbazole (abbreviated as: PCCzPTzn), 2-[4-(10H-phenanthro-10-yl)phenyl]-4,6-diphenyl-1,3,5 Heterocyclic compounds such as triazine (PXZ-TRZ), 3-[4-(5-phenyl-5,10-dihydrophenanthrene-10-yl)phenyl]-4,5-diphenyl-1,2,4-triazole (PPZ-3TPT), 3-(9,9-dimethyl-9H-acridin-10-yl)-9H-oxazanthracene-9-one (ACRXTN), bis[4-(9,9-dimethyl-9,10-dihydroacridin)phenyl]thiosulfate (DMAC-DPS), and 10-phenyl-10H,10'H-spiro[acridin-9,9'-anthracene]-10'-one (ACRSA) are heterocyclic compounds with one or both of π-electron-rich and π-electron-deficient heterocyclic rings. This heterocyclic compound possesses both π-electron-rich and π-electron-deficient heteroaromatic rings, exhibiting high electron transport and hole transport properties, making it preferred. Among the skeletons with π-electron-deficient heteroaromatic rings, pyridine, diazine (pyrimidine, pyrazine, and triazine) skeletons are stable and reliable, thus preferred. In particular, benzofuran-pyrimidine, benzothiophene-pyrimidine, benzofuran-pyrazine, and benzothiophene-pyrazine skeletons exhibit high acceptability and reliability, thus preferred. Furthermore, among the skeletons with π-electron-rich heteroaromatic rings, acridine, phenanthrene, phenanthrene-thiophene, furan, thiophene, and pyrrole skeletons are stable and reliable, thus having at least one of these skeletons is preferred. Additionally, dibenzofuran skeletons are preferred as furan skeletons, and dibenzothiophene skeletons are preferred as thiophene skeletons. As the pyrrole skeleton, indole, carbazole, indole-carbazole, bicarbazole, and 3-(9-phenyl-9H-carbazole-3-yl)-9H-carbazole skeletons are particularly preferred. In substances where π-electron-rich and π-electron-deficient heteroaromatic rings are directly bonded, the electron-donating capacity of the π-electron-rich heteroaromatic ring and the electron-accepting capacity of the π-electron-deficient heteroaromatic ring are both high, and the energy difference between the S1 and T1 energy levels is smaller, resulting in efficient acquisition of thermally activated delayed fluorescence, making it particularly preferred. Note that aromatic rings bonded with electron-withdrawing groups such as cyano groups can also be used instead of π-electron-deficient heteroaromatic rings. Furthermore, aromatic amine skeletons, phenazine skeletons, etc., can be used as π-electron-rich skeletons.Furthermore, as π-electron-deficient skeletons, the following can be used: oxanthracene skeleton, thioxanthene dioxide skeleton, diazole skeleton, triazole skeleton, imidazole skeleton, anthraquinone skeleton, boron-containing skeletons such as phenylborane or boranthrene, aromatic or heteroaromatic rings with nitrile or cyanobenzene, carbonyl skeletons such as benzophenone, phosphine oxide skeleton, and uranium skeleton. Thus, π-electron-deficient and π-electron-rich skeletons can be used to replace at least one of the π-electron-deficient and π-electron-rich heteroaromatic rings.

[0160] [Chemical Formula 15]

[0161] TADF materials refer to materials with a small difference between the S1 and T1 energy levels and the ability to convert triple excitation energy into single excitation energy via antisystem crossing. Therefore, they can upconvert triple excitation energy into single excitation energy (antisystem crossing) with minimal thermal energy, efficiently generating singlet excited states. Furthermore, triple excitation energy can be converted into luminescence.

[0162] Exciplexes formed by two substances in an excited state have the function of converting triple excitation energy into single excitation energy due to the extremely small difference between the S1 and T1 energy levels.

[0163] Note that the phosphorescence spectrum observed at low temperatures (e.g., 77 K to 10 K) can be used as an indicator of the T1 energy level. For TADF materials, it is preferable that the difference between S1 and T1 is less than 0.3 eV, more preferably less than 0.2 eV, when the wavelength energy of the extrapolated line obtained by drawing a tangent at the tail of the short-wavelength side of the fluorescence spectrum is taken as the S1 energy level and the wavelength energy of the extrapolated line obtained by drawing a tangent at the tail of the short-wavelength side of the phosphorescence spectrum is taken as the T1 energy level.

[0164] Furthermore, when using TADF material as the luminescent material, the S1 energy level of the host material is preferably higher than that of the TADF material. Additionally, the T1 energy level of the host material is preferably higher than that of the TADF material.

[0165] As the main material of the light-emitting layer, various carrier transport materials such as materials with electron transport properties, materials with hole transport properties, and the aforementioned TADF material can be used.

[0166] As materials with hole transport properties, organic compounds having an amine skeleton or a π-electron-rich heteroaromatic ring skeleton are preferred. Examples include: 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB), N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (TPD), 4,4'-bis[N-(spiro-9,9'-dien-2-yl)-N-phenylamino]biphenyl (BSPB), 4-phenyl-4'-(9-phenylenen-9-yl)triphenylamine (BPAFLP), 4-phenyl-3'-(9-phenylenen-9-yl)triphenylamine (mBPAFLP), 4-phenyl-4'-(9-phenylenen-9-yl)triphenylamine, and 4-phenyl-4'-(9-phenylenen-9-yl)triphenylamine. H-Carbazole-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4'-diphenyl-4”-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBANB), 4,4'-di(1-naphthyl)-4”-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCCNBB), 9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]enazine-2-amine (abbreviation: PCBAF), N-phenyl-N-[ Compounds with an aromatic amine skeleton, such as 4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9,9'-spirobis[9H-furan]-2-amine (abbreviated as: PCBASF); compounds with a carbazole skeleton, such as 1,3-bis(N-carbazole)benzene (abbreviated as: mCP), 4,4'-bis(N-carbazole)biphenyl (abbreviated as: CBP), 3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviated as: CzTP), and 3,3'-bis(9-phenyl-9H-carbazole) (abbreviated as: PCCP); and compounds with a carbazole skeleton, such as 4,4',4”-(benzene-1,3,5-triyl)tris(dibenzothiophene) (abbreviated as: DBT3P-I). Compounds with a thiophene skeleton, such as 2,8-diphenyl-4-[4-(9-phenyl-9H-peroxy-9-yl)phenyl]dibenzothiophene (abbreviated: DBTFLP-III) and 4-[4-(9-phenyl-9H-peroxy-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviated: DBTFLP-IV); and compounds with a furan skeleton, such as 4,4',4”-(phenyl-1,3,5-triyl)tris(dibenzofuran) (abbreviated: DBF3P-II) and 4-{3-[3-(9-phenyl-9H-peroxy-9-yl)phenyl]phenyl}dibenzofuran (abbreviated: mmDBFFLBi-II). Among these, compounds with an aromatic amine skeleton and compounds with a carbazole skeleton have good reliability and high hole transport properties and help reduce the driving voltage, so they are preferred.Alternatively, organic compounds, which are examples of materials with hole-transporting properties, can be used as the hole-transporting layer 112.

[0167] Examples of materials with electron transport properties include: bis(10-hydroxybenzo[h]quinoline)beryllium(II) (abbreviated as BeBq2), bis(2-methyl-8-hydroxyquinoline)(4-phenylphenol)aluminum(III) (abbreviated as BAlq), bis(8-hydroxyquinoline)zinc(II) (abbreviated as Znq), bis[2-(2-benzothiazolyl)phenol]zinc(II) (abbreviated as ZnPBO), bis[2-(2-benzothiazolyl)phenol]zinc(II) (abbreviated as ZnBTZ), and other metal complexes or organic compounds including π-electron-deficient heteroaromatic ring skeletons.Examples of organic compounds that include π-electron-deficient heterocyclic aromatic ring skeletons include: 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-diazole (abbreviated: PBD), 3-(4-biphenyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviated: TAZ), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-diazole-2-yl]benzene (abbreviated: OXD-7), 9-[4-(5-phenyl-1,3,4-diazole-2-yl)phenyl]-9H-carbazole (abbreviated: CO11), and 2,2',2”-(1,3,5-phenyltriyl)tris(1-phenyl-1H-benzimidazole) (abbreviated: TPBI). Heterocyclic compounds with polyazole skeletons, such as 2-[3-(dibenzothiophene-4-yl)phenyl]-1-phenyl-1H-benzimidazole (abbreviated as: mDBTBIm-II); 2-[3-(dibenzothiophene-4-yl)phenyl]dibenzo[f,h]quinoline (abbreviated as: 2mDBTPDBq-II), 2-[3'-(dibenzothiophene-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoline (abbreviated as: 2mDBTBPDBq-II), 2-[3'-(9H-carbazol-9-yl)biphenyl-3-yl]dibenzo[f,h]quinoline (abbreviated as: 2mCzBPDBq), 4,6-bis[3-(phenanthrene-9-yl)phenyl]pyrimidine (abbreviated as: 4,6mPnP) Heterocyclic compounds with a diazine skeleton, such as 2Pm), 4,6-bis[3-(4-dibenzothiophene)phenyl]pyrimidine (abbreviated as: 4,6mDBTP2Pm-II); heterocyclic compounds with a pyridine skeleton, such as 3,5-bis[3-(9H-carbazole-9-yl)phenyl]pyridine (abbreviated as: 35DCzPPy), 1,3,5-tris[3-(3-pyridyl)-phenyl]benzene (abbreviated as: TmPyPB); and heterocyclic compounds with a pyridine skeleton, such as 2-[3'-(9,9-dimethyl-9H-furo-2-yl)-1,1'-biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviated as: mFBPTzn), 2-[(1,1'-biphenyl)-4-yl]-4-phenyl-6-[9,9' Heterocyclic compounds with triazine skeletons include spirodi(9H-furan)-2-yl]-1,3,5-triazine (abbreviated as BP-SFTzn), 2-{3-[3-(benzo[b]naphtho[1,2-d]furan-8-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviated as mBnfBPTzn), and 2-{3-[3-(benzo[b]naphtho[1,2-d]furan-6-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviated as mBnfBPTzn-02). Among these, heterocyclic compounds with diazine skeletons, pyridine skeletons, or triazine skeletons exhibit good reliability and are therefore preferred.In particular, heterocyclic compounds with a diazine (pyrimidine or pyrazine) skeleton and heterocyclic compounds with a triazine skeleton exhibit high electron transport properties, which also helps to reduce the driving voltage.

[0168] As a TADF material that can be used as the host material, the same materials mentioned above as TADF materials can be used. When a TADF material is used as the host material, the triple excitation energy generated by the TADF material is converted into a single excitation energy via antisystem crossing and further transferred to the luminescent material, thereby improving the luminous efficiency of the light-emitting device. In this case, the TADF material is used as an energy donor, and the luminescent material is used as an energy acceptor.

[0169] This is highly effective when the aforementioned luminescent material is a fluorescent material. Furthermore, to achieve high luminescent efficiency, the S1 energy level of the TADF material is preferably higher than that of the fluorescent material. Additionally, the T1 energy level of the TADF material is preferably higher than that of the S1 energy level of the fluorescent material. Therefore, the T1 energy level of the TADF material is preferably higher than that of the fluorescent material.

[0170] Furthermore, it is preferable to use a TADF material that emits light at a wavelength that overlaps with the wavelength of the absorption band on the lowest energy side of the fluorescent material. This allows for efficient transfer of excitation energy from the TADF material to the fluorescent material, resulting in highly efficient luminescence.

[0171] To efficiently generate a singlet excitation energy from a triplet excitation energy via anti-system jumps, it is preferable to generate carrier recombination within the TADF material. Furthermore, it is preferable that the triplet excitation energy generated in the TADF material does not transfer to the fluorescent luminescent material. For this purpose, the fluorescent luminescent material preferably has a protecting group surrounding its luminescent body (the framework that causes luminescence). This protecting group is preferably a substituent without π bonds, preferably a saturated hydrocarbon; specifically, examples include alkyl groups with 3 or more but less than 10 carbon atoms, substituted or unsubstituted cycloalkyl groups with 3 or more but less than 10 carbon atoms, and trialkylsilyl groups with 3 or more but less than 10 carbon atoms; more preferably, it has multiple protecting groups. Substituents without π bonds have almost no carrier transport function, so they have little effect on carrier transport or carrier recombination, allowing the TADF material and the luminescent body of the fluorescent luminescent material to be kept apart. Here, the luminescent body refers to the atomic group (backbone) in the fluorescent luminescent material that causes luminescence. The luminescent material preferably has a π-bonded framework, preferably contains an aromatic ring, and preferably has a fused aromatic ring or a fused heteroaromatic ring. Examples of fused aromatic rings or fused heteroaromatic rings include phenanthrene frameworks, stilbene frameworks, acridinone frameworks, phenanthrene-acridinium frameworks, and phenanthrene-thiacridinium frameworks. In particular, fluorescent materials having naphthalene frameworks, anthracene frameworks, benzo[a]ene frameworks, benzo[b]ene frameworks, triphenylene frameworks, fused tetraphenylene frameworks, pyrene frameworks, perylene frameworks, coumarin frameworks, quinacridone frameworks, and naphthobisbenzofuran frameworks are preferred due to their high fluorescence quantum yield.

[0172] When using fluorescent materials as the luminescent material, materials with an anthracene framework are preferably used as the host material. By using materials with an anthracene framework as the host material of the fluorescent material, a luminescent layer with high luminous efficiency and durability can be achieved. Among the anthracene framework materials used as host materials, those with a diphenylanthracene framework (especially 9,10-diphenylanthracene framework) are chemically stable and therefore preferred. Furthermore, when the host material has a carbazole framework, hole injection / transport is improved, which is also preferred. In the case of a benzo[a]carbazole framework containing a benzene ring fused to a carbazole, its HOMO level is about 0.1 eV shallower than that of carbazole, facilitating hole injection, which is even better. In particular, when the host material has a dibenzo[a]carbazole framework, its HOMO level is about 0.1 eV shallower than that of carbazole, which not only facilitates hole injection but also improves hole transport and heat resistance, making it even more desirable. Therefore, it is further preferred that the material used as the host material be a substance having a 9,10-diphenylanthracene skeleton and a carbazole skeleton (or a benzo[a]carbazole skeleton or a dibenzo[a]carbazole skeleton). Note that from the viewpoint of the aforementioned hole injection / transportation, a benzo[a]carbazole skeleton or a dibenzo[a]carbazole skeleton can also be used instead of a carbazole skeleton. Examples of such substances include 9-phenyl-3-[4-(10-phenyl-9-anthrayl)phenyl]-9H-carbazole (abbreviated: PCzPA), 3-[4-(1-naphthyl)-phenyl]-9-phenyl-9H-carbazole (abbreviated: PCPN), 9-[4-(10-phenyl-9-anthrayl)phenyl]-9H-carbazole (abbreviated: CzPA), and 7-[4-(10-phenyl-9-anthrayl)phenyl]-7H-dibenzo[c,g] Carbazole (abbreviated as cgDBCzPA), 6-[3-(9,10-diphenyl-2-anthrayl)phenyl]-benzo[b]naphtho[1,2-d]furan (abbreviated as 2mBnfPPA), 9-phenyl-10-{4-(9-phenyl-9H-en-9-yl)-biphenyl-4'-yl}-anthracene (abbreviated as FLPPA), 9-(1-naphthyl)-10-[4-(2-naphthyl)phenyl]anthracene (abbreviated as αN-βNPAnth), etc. In particular, CzPA, cgDBCzPA, 2mBnfPPA, and PCzPA exhibit very good properties and are therefore preferred.

[0173] Alternatively, the host material can be a mixture of multiple substances. When using a mixed host material, it is preferable to mix materials with electron transport properties and materials with hole transport properties. By mixing materials with electron transport properties and materials with hole transport properties, it is easier to adjust the transport properties of the light-emitting layer 113 and to more easily control the rebinding region. The weight ratio of the materials with hole transport properties to the materials with electron transport properties can be 1:19 to 19:1.

[0174] Note that phosphorescent materials can be used as part of the above-mentioned mixture. When phosphorescent materials are used as fluorescent materials, they can be used as energy donors to supply excitation energy to the fluorescent materials.

[0175] Alternatively, these mixed materials can be used to form excited-state complexes. By selecting mixed materials in a way that creates excited-state complexes whose wavelengths overlap with the absorption bands on the lowest energy side of the luminescent material, energy transfer can be facilitated, resulting in efficient luminescence, which is preferable. Furthermore, this structure allows for a reduction in driving voltage, which is also preferable.

[0176] Note that at least one of the materials forming the excited-state complex can be a phosphorescent material. This allows for the efficient conversion of triple excitation energy into single excitation energy via antisystem crosstalk.

[0177] Regarding the combination of materials for efficiently forming excited-state complexes, the HOMO level of the material with hole transport is preferably higher than that of the material with electron transport. Furthermore, the LUMO level of the material with hole transport is preferably higher than that of the material with electron transport. Note that the LUMO and HOMO levels of the material can be determined from the electrochemical properties (reduction potential and oxidation potential) of the material measured by cyclic voltammetry (CV).

[0178] Note that the formation of excited-state complexes can be confirmed, for example, by comparing the emission spectra of materials with hole transport properties, materials with electron transport properties, and the emission spectra of a mixed film formed by mixing these materials. When the emission spectrum of the mixed film is observed to shift towards a longer wavelength (or to have a new peak at a longer wavelength) compared to the emission spectra of each material, it indicates the formation of excited-state complexes. Alternatively, by comparing the transient photoluminescence (PL) of materials with hole transport properties, the transient PL of materials with electron transport properties, and the transient PL of a mixed film formed by mixing these materials, when a difference in transient response is observed, such as the mixed film having a longer lifetime component or a higher proportion of delayed components compared to the transient PL lifetimes of each material, it indicates the formation of excited-state complexes. Furthermore, the aforementioned transient PL can be referred to as transient electroluminescence (EL). In other words, by comparing the transient EL of materials with hole transport properties, the transient EL of materials with electron transport properties, and the transient EL of a mixed film of these materials, and observing the differences in transient response, the formation of excited-state complexes can be confirmed.

[0179] When the electron transport layer 114 has the structure of the present invention, it can be a layer with a low refractive index. Therefore, a layer with a low refractive index can be formed in the EL layer 103 without a significant drop in driving voltage, which can improve the external quantum efficiency of the light-emitting device.

[0180] Note that the electron transport layer 114 with this structure sometimes also serves as the electron injection layer 115.

[0181] Furthermore, the electron transport layer 114 preferably has an electron mobility of 1×10⁻⁷ cm² / Vs or more and 5×10⁻⁵ cm² / Vs or less when the square root of the electric field strength [V / cm] is 600. By reducing the electron transportability in the electron transport layer 114, the amount of electrons injected into the light-emitting layer can be controlled, thereby preventing the light-emitting layer from becoming an electron-overloaded state. When this structure is used, a long lifetime can be obtained, and it is particularly preferred when a hole injection layer is formed using a composite material and the HOMO level of the hole-transporting material in the composite material is a relatively deep HOMO level of -5.7 eV or more and -5.4 eV or less. Note that in this case, the HOMO level of the electron-transporting material is preferably -6.0 eV or more.

[0182] Furthermore, it is preferable that there is a concentration difference (including the case of 0) in the alkali metal or alkaline earth metal complex in the electron transport layer 114 in the thickness direction.

[0183] An electron injection layer 115 may be provided between the electron transport layer 114 and the cathode 102, consisting of an alkali metal, alkaline earth metal, or its compound or complex, such as lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF2), or 8-hydroxyquinoline-lithium (Liq). The electron injection layer 115 may be a layer or electron compound in which an alkali metal, alkaline earth metal, or its compound is contained within a layer composed of a substance with electron transport properties. Examples of electron compounds include, for instance, a mixture of calcium and aluminum oxides to which electrons are added at a high concentration.

[0184] Note that, as the electron injection layer 115, a layer containing fluorides of the aforementioned alkali metal or alkaline earth metal in a microcrystalline state at a concentration of 50 wt% or higher can also be used, which is a material with electron transport properties (preferably an organic compound with a bipyridine framework). Since this layer has a low refractive index, it can provide a light-emitting device with better external quantum efficiency.

[0185] Alternatively, a charge generation layer 116 can be provided instead of the electron injection layer 115 in FIG. 1A (FIG. 1B). The charge generation layer 116 is a layer that, by applying a potential, can inject holes into the layer in contact with the cathode side of the layer and inject electrons into the layer in contact with the anode side of the layer. 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 that constitutes the hole injection layer 111 described above. Alternatively, the P-type layer 117 can also be formed by laminating a film containing an acceptor material and a film containing a hole transport material as the composite material. By applying a potential to the P-type layer 117, electrons and holes are injected into the electron transport layer 114 and the cathode 102, respectively, causing the light-emitting device to operate.

[0186] In addition to the P-type layer 117, the charge generation layer 116 preferably includes either or both of the electron relay layer 118 and the electron injection buffer layer 119.

[0187] The electron relay layer 118 contains at least an electron-transporting material and is capable of preventing the interaction between the electron injection buffer layer 119 and the p-type layer 117, while facilitating electron transfer. Preferably, the LUMO level of the electron-transporting material contained in the electron relay layer 118 is set between the LUMO level of the acceptor material in the p-type layer 117 and the LUMO level of the material contained in the layer in the electron transport layer 114 that is in contact with the charge-generating layer 116. Specifically, the LUMO level of the electron-transporting material in the electron relay layer 118 is preferably -5.0 eV or higher, more preferably -5.0 eV or higher and -3.0 eV or lower. Furthermore, the electron-transporting material in the electron relay layer 118 is preferably a phthalocyanine-based material or a metal complex having metal-oxygen bonds and aromatic ligands.

[0188] The electron injection buffer layer 119 can use alkali metals, alkaline earth metals, rare earth metals and their compounds (alkali metal compounds (including oxides such as lithium oxide, halides, carbonates such as lithium carbonate or cesium carbonate), alkaline earth metal compounds (including oxides, halides, carbonates) or rare earth metal compounds (including oxides, halides, carbonates)) and other materials with high electron injection properties.

[0189] In addition, when the electron injection buffer layer 119 contains electron transport substances and donor substances, the donor substances may include alkali metals, alkaline earth metals, rare earth metals and compounds of these substances (alkali metal compounds (including oxides such as lithium oxide, halides, carbonates such as lithium carbonate or cesium carbonate), alkaline earth metal compounds (including oxides, halides, carbonates) or rare earth metal compounds (including oxides, halides, carbonates)), as well as organic compounds such as tetrathianaphthacene (TTN), nickel dicene, and decamethylnickel dicene.

[0190] Furthermore, the material with electron transport properties can be formed using the same material as the one described above for the electron transport layer 114. Since this material is an organic compound with a low refractive index, by using it for the electron injection buffer layer 119, a light-emitting device with good external quantum efficiency can be obtained.

[0191] As the material forming the cathode 102, metals, alloys, conductive compounds, and mixtures thereof with low work functions (specifically below 3.8 eV) can be used. Specific examples of such cathode materials include alkali metals such as lithium (Li) or cesium (Cs), elements belonging to Group 1 or Group 2 of the periodic table such as magnesium (Mg), calcium (Ca), or strontium (Sr), alloys containing them (MgAg, AlLi), rare earth metals such as europium (Eu) and ytterbium (Yb), and alloys containing them. 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 oxide-tin oxide containing silicon or silicon oxide can be used as the cathode 102 regardless of the work function. These conductive materials can be formed by vacuum evaporation, dry processing such as sputtering, inkjet printing, spin coating, etc. Alternatively, the cathode 102 can be formed by wet processing such as sol-gel method or by wet processing of a paste of metal material.

[0192] Furthermore, various methods can be used to form the EL layer 103, whether dry or wet processing. For example, vacuum evaporation, gravure printing, photogravure printing, screen printing, inkjet printing, or spin coating can also be used.

[0193] Alternatively, the electrodes or layers described above can be formed by using different film-forming methods.

[0194] Note that the structure of the layer disposed between the anode 101 and the cathode 102 is not limited to the structure described above. However, it is preferable to adopt a structure in which a light-emitting region for the recombination of holes and electrons is provided in the portion far from the anode 101 and the cathode 102, so as to suppress quenching that occurs due to the proximity of the light-emitting region to the metal used for the electrode or carrier injection layer.

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

[0196] Next, a light-emitting device (hereinafter also referred to as a stacked element or series element) having a structure with multiple light-emitting units stacked will be described with reference to FIG1C. This light-emitting device has multiple light-emitting units between the anode and the cathode. One light-emitting unit has a structure that is substantially the same as that of the EL layer 103 shown in FIG1A. That is to say, it can be said that the light-emitting device shown in FIG1C is a light-emitting device with multiple light-emitting units, while the light-emitting devices shown in FIG1A or FIG1B are light-emitting devices with one light-emitting unit.

[0197] In Figure 1C, 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-generating layer 513 is disposed 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 cathode 102 in Figure 1A, respectively, and can be made of the same materials as described in Figure 1A. Furthermore, the first light-emitting unit 511 and the second light-emitting unit 512 can have the same structure or different structures.

[0198] The charge generation layer 513 has the function of injecting electrons into one light-emitting unit and holes into the other light-emitting unit when a voltage is applied to the anode 501 and the cathode 502. That is, in FIG1C, when a voltage is applied in such a way that the potential of the anode is higher than that of the cathode, the charge generation layer 513 only needs to be a layer that injects electrons into the first light-emitting unit 511 and holes into the second light-emitting unit 512.

[0199] The charge generation layer 513 preferably has the same structure as the charge generation layer 116 shown in FIG. 1B. Because the composite material of organic compound and metal oxide has good carrier injection and carrier transport properties, low-voltage driving and low-current driving can be achieved. Note that when the surface of the light-emitting unit on the anode side contacts the charge generation layer 513, the charge generation layer 513 can function as a hole injection layer of the light-emitting unit, so a hole injection layer may not be provided in the light-emitting unit.

[0200] In addition, when an electron injection buffer layer 119 is provided in the charge generation layer 513, since the electron injection buffer layer 119 has the function of an electron injection layer in the light-emitting unit on the anode side, it is not necessary to provide an electron injection layer in the light-emitting unit on the anode side.

[0201] Although a light-emitting device with two light-emitting units is illustrated in Figure 1C, light-emitting devices with three or more light-emitting units stacked can be applied similarly. As in the light-emitting device according to this embodiment, by separating and arranging multiple light-emitting units between a pair of electrodes using a charge-generating layer 513, the device can achieve high brightness emission while maintaining low current density and can achieve a long lifespan. Furthermore, a light-emitting device capable of low-voltage driving and low power consumption can be realized.

[0202] Furthermore, by making each light-emitting unit emit a different color, the desired color of light can be obtained from the entire light-emitting device. For example, by obtaining red and green light emission colors from the first light-emitting unit and blue light emission color from the second light-emitting unit in a light-emitting device with two light-emitting units, a light-emitting device that emits white light throughout the entire device can be obtained.

[0203] Furthermore, the aforementioned EL layer 103, first light-emitting unit 511, second light-emitting unit 512, charge-generating layer, and electrodes can be formed using methods such as vapor deposition (including vacuum vapor deposition), droplet jetting (also known as inkjet printing), coating, and gravure printing. Additionally, they may contain low-molecular-weight materials, medium-molecular-weight materials (including oligomers and dendritic polymers), or high-molecular-weight materials.

[0204] Furthermore, this embodiment can be freely combined with other embodiments.

[0205] Implementation Method 2 In this embodiment, a light-emitting device using the light-emitting device shown in Embodiment 1 will be described.

[0206] In this embodiment, a light-emitting device manufactured using the light-emitting device shown in Embodiment 1 will be described with reference to FIGS. 2A and 2B. Note that FIG. 2A is a top view showing the light-emitting device, and FIG. 2B is a cross-sectional view taken along the dotted lines AB and CD in FIG. 2A. The light-emitting device includes a driving circuit section (source line driving circuit) 601, a pixel section 602, and a driving circuit section (gate line driving circuit) 603, indicated by dashed lines, which are used to control the light emission of the light-emitting device. In addition, component symbol 604 is a sealing substrate, component symbol 605 is a sealing material, and the inner side surrounded by the sealing material 605 is a space 607.

[0207] Note that the guide wiring 608 is used to transmit signals input to the source line drive circuit 601 and the gate line drive circuit 603, and to receive video signals, clock signals, start signals, reset signals, etc., from the FPC (Flexible Printed Circuit) 609, which serves as an external input terminal. Note that although only the FPC is shown here, the FPC can also be equipped with a printed circuit board (PWB). The light-emitting device in this specification includes not only the main body of the light-emitting device, but also the light-emitting device equipped with an FPC or PWB.

[0208] The cross-sectional structure will now be described with reference to FIG2B. Although a driving circuit section and a pixel section are formed on the component substrate 610, a pixel is shown here as the source line driving circuit 601 of the driving circuit section and one of the pixels 602.

[0209] In addition to substrates made of glass, quartz, organic resin, metal, alloy, semiconductor, etc., the component substrate 610 can also use plastic substrates made of FRP (fiber reinforced plastics), PVF (polyvinyl fluoride), polyester or acrylic resin, etc.

[0210] There are no particular restrictions on the structure of the transistors used in the pixel or driving circuitry. For example, anti-interlaced or interlaced transistors can be used. Additionally, top-gate or bottom-gate transistors can also be used. There are no particular restrictions on the semiconductor materials used for the transistors; for example, silicon, germanium, silicon carbide, gallium nitride, etc., can be used. Alternatively, oxide semiconductors containing at least one of indium, gallium, and zinc, such as In-Ga-Zn metal oxides, can be used.

[0211] There are no particular restrictions on the crystallinity of the semiconductor material used for transistors; amorphous semiconductors or crystalline semiconductors (microcrystalline semiconductors, polycrystalline semiconductors, single-crystal semiconductors, or semiconductors with a portion of crystalline regions) can be used. Crystalline semiconductors are preferred because they can suppress transistor performance degradation.

[0212] Here, oxide semiconductors are preferably semiconductor devices such as transistors used in the aforementioned pixels or driving circuits, and transistors used in touch sensors, etc., as described later. Particularly preferred are oxide semiconductors with a band gap wider than silicon. By using oxide semiconductors with a band gap wider than silicon, the off-state current of the transistor can be reduced.

[0213] The aforementioned oxide semiconductor preferably contains at least indium (In) or zinc (Zn). Furthermore, the aforementioned oxide semiconductor is more preferably an oxide semiconductor containing oxides represented by In-M-Zn type oxides (M being metals such as Al, Ti, Ga, Ge, Y, Zr, Sn, La, Ce, or Hf).

[0214] In particular, as a semiconductor layer, it is preferable to use an oxide semiconductor film having a plurality of crystal portions, the c-axis of which are all oriented in a direction perpendicular to the surface to which the semiconductor layer is formed or the top surface of the semiconductor layer, and there are no grain boundaries between adjacent crystal portions.

[0215] By using the above materials as a semiconductor layer, it is possible to achieve highly reliable transistors whose electrical characteristics are suppressed.

[0216] Furthermore, because the transistor with the aforementioned semiconductor layer has a low off-state current, it can retain the charge stored in the capacitor through the transistor for a long period of time. By using such a transistor in pixels, the driving circuit can be stopped while maintaining the grayscale of the image displayed in each display area. As a result, electronic devices with extremely low power consumption can be realized.

[0217] To stabilize the characteristics of the transistor, a base film is preferably provided. As the base film, inorganic insulating films such as silicon oxide films, silicon nitride films, silicon oxynitride films, and silicon oxynitride films can be used and fabricated as a single layer or in layers. The base film can be formed by sputtering, CVD (Chemical Vapor Deposition) methods (plasma CVD, thermal CVD, MOCVD (Metal Organic CVD), etc.), ALD (Atomic Layer Deposition), coating, printing, etc. Note that a base film is optional if not required.

[0218] Note that FET623 represents one of the transistors formed in the drive circuit section 601. Alternatively, the drive circuit can also be formed using various CMOS, PMOS, or NMOS circuits. Furthermore, although this embodiment shows an integrated driver type with the drive circuit formed on the substrate, this structure is not mandatory; the drive circuit can also be formed externally instead of on the substrate.

[0219] In addition, the pixel unit 602 is formed by multiple pixels, each of which includes a switching FET 611, a current control FET 612, and an anode 613 electrically connected to the drain of the current control FET 612. However, it is not limited to this and a pixel unit combining three or more FETs and capacitors can also be used.

[0220] Note that an insulator 614 is formed to cover the end of the anode 613. Here, a positive photosensitive acrylic resin film can be used to form the insulator 614.

[0221] Furthermore, the upper or lower end of the insulator 614 is formed as a curved surface to obtain good coverage for the subsequently formed EL layer, etc. For example, when using a positive photosensitive acrylic resin as the material of the insulator 614, it is preferable that only the upper end of the insulator 614 includes a curved surface with a radius of curvature (0.2 μm to 3 μm). As the insulator 614, either a negative photosensitive resin or a positive photosensitive resin can be used.

[0222] An EL layer 616 and a cathode 617 are formed on the anode 613. Here, a material with a high work function is preferably used as the material for the anode 613. For example, in addition to single-layer films such as ITO films, indium tin oxide films containing silicon, indium oxide films containing 2 wt% to 20 wt% zinc oxide, titanium nitride films, chromium films, tungsten films, Zn films, and Pt films, multilayer films composed of titanium nitride films and films with aluminum as the main component, as well as three-layer structures composed of titanium nitride films, films with aluminum as the main component, and titanium nitride films, can also be used. Note that by adopting a multilayer structure, the resistance of the wiring can be lower, good ohmic contact can be obtained, and it can be used as an anode.

[0223] Furthermore, the EL layer 616 is formed by various methods such as vapor deposition using a vapor deposition mask, inkjet printing, spin coating, etc. The EL layer 616 includes the structure shown in Embodiment 1. In addition, low molecular weight compounds or high molecular weight compounds (including oligomers and dendritic polymers) can also be used as other materials constituting the EL layer 616.

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

[0225] Furthermore, the light-emitting device is formed of an anode 613, an EL layer 616, and a cathode 617. This light-emitting device is the light-emitting device shown in Embodiment 1. Additionally, the pixel portion includes multiple light-emitting devices, and the light-emitting device of this embodiment may also include both the light-emitting device shown in Embodiment 1 and light-emitting devices with other structures.

[0226] Furthermore, by attaching the sealing substrate 604 to the element substrate 610 using the sealing material 605, the light-emitting device 618 is disposed within the space 607 surrounded by the element substrate 610, the sealing substrate 604, and the sealing material 605. Note that the space 607 is filled with a filler, which can be an inert gas (such as nitrogen or argon) or a sealing material. It is preferable to form a recess in the sealing substrate and place a desiccant therein to suppress deterioration caused by moisture.

[0227] Furthermore, epoxy resin or glass powder is preferably used as the sealing material 605. These materials are also preferably those that minimize the permeability of moisture or oxygen. Additionally, as the material used for the sealing substrate 604, besides glass substrates or quartz substrates, plastic substrates made of FRP (fiber reinforced plastics), PVF (polyvinyl fluoride), polyester, acrylic resin, etc., can also be used.

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

[0229] As a protective membrane, materials that are not easily permeable to water and other impurities can be used. Therefore, it is possible to effectively prevent water and other impurities from diffusing from the outside into the inside.

[0230] Materials constituting the protective film can include oxides, nitrides, fluorides, sulfides, ternary compounds, metals, or polymers. For example, materials 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, and indium oxide can be used; materials containing aluminum nitride, hafnium nitride, silicon nitride, tantalum nitride, titanium nitride, niobium nitride, molybdenum nitride, zirconium nitride, and gallium nitride can be used; materials containing titanium and aluminum nitrides; oxides containing titanium and aluminum; oxides containing aluminum and zinc; sulfides containing manganese and zinc; sulfides containing cerium and strontium; oxides containing erbium and aluminum; and oxides containing yttrium and zirconium can be used.

[0231] The protective film is preferably formed using a film-forming method with good step coverage. One such method is atomic layer deposition (ALD). It is preferable to use a material that can be formed by ALD for the protective film. ALD can form a dense protective film with reduced or uniform thickness, minimizing defects such as cracks or pinholes. Furthermore, it can reduce damage to the machined component during the formation of the protective film.

[0232] For example, the ALD method can be used to form a uniform protective film with few defects on the top, sides and back of a surface or touch panel with a complex uneven shape.

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

[0234] Because the light-emitting device in this embodiment uses the light-emitting device shown in Embodiment 1, a light-emitting device with excellent characteristics can be obtained. Specifically, the light-emitting device shown in Embodiment 1 has high luminous efficiency, thereby enabling a low-power light-emitting device.

[0235] Figures 3A and 3B show examples of light-emitting devices that achieve full-color illumination by forming a white light-emitting device and providing a color layer (color filter). Figure 3A shows a substrate 1001, a substrate insulating film 1002, a gate insulating film 1003, gate electrodes 1006, 1007, 1008, a first interlayer insulating film 1020, a second interlayer insulating film 1021, a peripheral portion 1042, a pixel portion 1040, a driving circuit portion 1041, an anode of the light-emitting device 1024W, 1024R, 1024G, 1024B, a separator wall 1025, an EL layer 1028, a cathode of the light-emitting device 1029, a sealing substrate 1031, a sealing material 1032, etc.

[0236] In Figure 3A, color layers (red color layer 1034R, green color layer 1034G, and blue color layer 1034B) are disposed on a transparent substrate 1033. A black matrix 1035 may also be disposed thereon. The transparent substrate 1033, on which the color layers and black matrix are disposed, is aligned and fixed to the substrate 1001. The color layers and black matrix 1035 are covered by a protective layer 1036. Figure 3A also shows a light-emitting layer that transmits light to the outside without passing through the color layers, and a light-emitting layer that transmits light through each color layer. The light that does not pass through the color layers becomes white light, and the light that passes through the color layers becomes red, green, and blue light, thus enabling the display of images using pixels of four colors.

[0237] Figure 3B shows an example in which colored layers (red colored layer 1034R, green colored layer 1034G, and blue colored layer 1034B) are formed between the gate insulating film 1003 and the first interlayer insulating film 1020. As described above, the colored layers may also be disposed between the substrate 1001 and the sealing substrate 1031.

[0238] Furthermore, although the above description describes a light-emitting device with a structure that emits light from the side of the substrate 1001 where the FET is formed (bottom-emitting type), a light-emitting device with a structure that emits light from the side of the sealing substrate 1031 (top-emitting type) can also be used. Figure 4 shows a cross-sectional view of the top-emitting type light-emitting device. In this case, the substrate 1001 can be a substrate that does not allow light to pass through. The process up to manufacturing the connection electrode for connecting the FET to the anode of the light-emitting device is performed in the same way as for the bottom-emitting type light-emitting device. Then, a third interlayer insulating film 1037 is formed in a manner that covers the electrode 1022. This insulating film may also have a planarization function. The third interlayer insulating film 1037 can be formed using the same material as the second interlayer insulating film 1021 or other known materials.

[0239] The anodes 1024W, 1024R, 1024G, and 1024B of the light-emitting device can also be cathodes. Alternatively, in the case of a top-emitting light-emitting device as shown in Figure 4, the anode is preferably a reflective electrode. The structure of the EL layer 1028 adopts the structure of the EL layer 103 shown in Embodiment 1, and employs an element structure capable of obtaining white light emission.

[0240] When using the top-emitting structure shown in Figure 4, a sealing substrate 1031 with color layers (red color layer 1034R, green color layer 1034G, and blue color layer 1034B) can be used for sealing. The sealing substrate 1031 may also have a black matrix 1035 located between pixels. The color layers (red color layer 1034R, green color layer 1034G, and blue color layer 1034B) and the black matrix 1035 may also be covered by a protective layer 1036. Furthermore, a light-transmitting substrate is used as the sealing substrate 1031. Although an example of full-color display using four colors (red, green, blue, and white) is shown here, it is not limited to this; full-color display using four colors (red, yellow, green, and blue) or three colors (red, green, and blue) can also be performed.

[0241] Microcavity structures are particularly suitable for top-emitting light-emitting devices. By using a reflective electrode as the anode and a semi-transparent / semi-reflective electrode as the cathode, a light-emitting device with a microcavity structure can be obtained. At least an EL layer is present between the reflective electrode and the semi-transparent / semi-reflective electrode, and at least a light-emitting layer that forms the light-emitting region is also present.

[0242] Note that the reflective electrode has a visible light reflectance of 40% to 100%, preferably 70% to 100%, and a resistivity of 1×10⁻² Ωcm or less. Additionally, the semi-transmissive / semi-reflective electrode has a visible light reflectance of 20% to 80%, preferably 40% to 70%, and a resistivity of 1×10⁻² Ωcm or less.

[0243] Light emitted from the light-emitting layer contained in the EL layer is reflected by the reflective electrode and the semi-transmissive and semi-reflective electrode, and resonates.

[0244] In this light-emitting device, the optical path between the reflective electrode and the semi-transparent / semi-reflective electrode can be changed by altering the thickness of the transparent conductive film, the aforementioned composite material, or the carrier transport material. This allows for the enhancement of resonant wavelengths of light between the reflective electrode and the semi-transparent / semi-reflective electrode, while attenuating non-resonant wavelengths of light.

[0245] The light reflected back by the reflecting electrode (the first reflected light) will cause significant interference to the light directly incident from the emissive layer to the semi-transmissive and semi-reflective electrode (the first incident light). Therefore, it is preferable to adjust the optical path between the reflecting electrode and the emissive layer to (2n-1)λ / 4 (note that n is a natural number greater than 1, and λ is the wavelength of the light to be enhanced). By adjusting this optical path, the phase of the first reflected light and the first incident light can be made synchronized, thereby further enhancing the light emitted from the emissive layer.

[0246] Furthermore, in the above structure, the EL layer may contain multiple light-emitting layers or only one light-emitting layer. For example, the above structure can be combined with the structure of the above-described series-type light-emitting device, wherein multiple EL layers are arranged in a light-emitting device with charge-generating layers sandwiched between them, and one or more light-emitting layers are formed in each EL layer.

[0247] By employing a microcavity structure, the luminous intensity in the front direction at a specified wavelength can be enhanced, thereby achieving low power consumption. Note that in the case of a light-emitting device that displays images using sub-pixels of four colors—red, yellow, green, and blue—the increased brightness due to yellow luminescence can be achieved, and microcavity structures suitable for the wavelengths of each color can be used in all sub-pixels, thus enabling a light-emitting device with excellent characteristics.

[0248] Because the light-emitting device in this embodiment uses the light-emitting device shown in Embodiment 1, a light-emitting device with excellent characteristics can be obtained. Specifically, the light-emitting device shown in Embodiment 1 has high luminous efficiency, thereby enabling a low-power light-emitting device.

[0249] Although an active matrix type light-emitting device has been described here, a passive matrix type light-emitting device will be described below. Figures 5A and 5B show a passive matrix type light-emitting device manufactured using the present invention. Note that Figure 5A is a perspective view showing the light-emitting device, and Figure 5B is a cross-sectional view obtained by cutting along the dashed line XY of Figure 5A. In Figures 5A and 5B, an EL layer 955 is disposed between electrodes 952 and 956 on a substrate 951. The end of electrode 952 is covered by an insulating layer 953. An insulating layer 954 is disposed on the insulating layer 953. The sidewalls of the insulating layer 954 have an inclination such that the closer to the substrate surface, the narrower the gap between the two sidewalls. In other words, the cross-section of the short side of the insulating layer 954 is trapezoidal, and the bottom side (the side facing the same direction as the surface direction of the insulating layer 953 and in contact with the insulating layer 953) is shorter than the top side (the side facing the same direction as the surface direction of the insulating layer 953 and not in contact with the insulating layer 953). Thus, by providing the isolation layer 954, malfunctions of the light-emitting device caused by static electricity or the like can be prevented. Furthermore, in a passive matrix type light-emitting device, by using the light-emitting device shown in Embodiment 1, a light-emitting device with high reliability or low power consumption can also be obtained.

[0250] The light-emitting device described above can control each of a plurality of tiny light-emitting devices arranged in a matrix, so it can be appropriately used as a display device for displaying images.

[0251] Furthermore, this embodiment can be freely combined with other embodiments.

[0252] Implementation Method 3 In this embodiment, an example of using the light-emitting device shown in Embodiment 1 in a lighting device will be described with reference to FIGS. 6A and 6B. FIG. 6B is a top view of the lighting device, and FIG. 6A is a cross-sectional view along line ef shown in FIG. 6B.

[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 using a light-transmitting material.

[0254] Additionally, pads 412 for supplying voltage to the cathode 404 are formed on the substrate 400.

[0255] An EL layer 403 is formed on the anode 401. The EL layer 403 corresponds to the structure of the EL layer 103 in Embodiment 1 or the structure of the light-emitting unit 511, the light-emitting unit 512, and the charge-generating layer 513, etc. Note that their structures are described in the respective descriptions.

[0256] A cathode 404 is formed by covering an EL layer 403. The cathode 404 corresponds to the cathode 102 in Embodiment 1. When light is extracted from the anode 401 side, the cathode 404 is formed using a material with high reflectivity. Voltage is supplied to the cathode 404 by connecting it to the pad 412.

[0257] As described above, the lighting device shown in this embodiment includes a light-emitting device comprising an anode 401, an EL layer 403, and a cathode 404. Since this light-emitting device is a high-efficiency light-emitting device, the lighting device of this embodiment can be a low-power lighting device.

[0258] The light-emitting device having the above-described structure is formed on a substrate 400 and a sealing substrate 407, which are fixed together using sealing materials 405 and 406, thereby manufacturing a lighting device. Alternatively, only one of the sealing materials 405 and 406 may be used. Furthermore, the inner sealing material 406 (not shown in FIG. 6B) may be mixed with a desiccant, thereby absorbing moisture and improving reliability.

[0259] Furthermore, by providing a portion of the pad 412 and the anode 401 extending to the exterior of the sealing materials 405 and 406, they can be used as external input terminals. Additionally, an IC chip 420, on which a converter or similar device is mounted, can also be provided on the external input terminal.

[0260] In summary, the lighting device described in this embodiment uses the light-emitting device shown in Embodiment 1 in the EL element, which enables a low-power lighting device.

[0261] Furthermore, this embodiment can be freely combined with other embodiments.

[0262] Implementation Method 4 In this embodiment, an example of an electronic device that includes the light-emitting device shown in Embodiment 1 in a portion thereof will be described. The light-emitting device shown in Embodiment 1 is a light-emitting device with high luminous efficiency and low power consumption. As a result, the electronic device described in this embodiment can realize an electronic device including a light-emitting part with low power consumption.

[0263] Examples of electronic devices employing the aforementioned light-emitting devices include television sets (also called television sets or television receivers), monitors for computers, digital cameras, digital camcorders, digital photo frames, mobile phones (also called mobile phones or mobile phone devices), portable game consoles, portable information terminals, audio playback devices, and large game machines such as pinball machines. Specific examples of these electronic devices are shown below.

[0264] Figure 7A shows an example of a television set. In the television set, a display unit 7103 is assembled in the housing 7101. Furthermore, a structure in which the housing 7101 is supported by a bracket 7105 is shown here. Images can be displayed using the display unit 7103, and the display unit 7103 is constructed by arranging the light-emitting devices shown in Embodiment 1 in a matrix.

[0265] The television can be operated using the operation switch provided in the casing 7101 or the separately provided remote control 7110. Using the operation keys 7109 provided in the remote control 7110, channels and volume can be controlled, thereby controlling the images displayed on the display unit 7103. Alternatively, a display unit 7107 for displaying information output from the remote control 7110 can be provided in the remote control 7110. Furthermore, the light-emitting devices described in Embodiment 1 can be arranged in a matrix and used in the display unit 7107.

[0266] In addition, television sets are structured with receivers, modems, and other components. The receiver can receive general television broadcasts. Furthermore, the modem connects to wired or wireless communication networks, enabling one-way (from sender to receiver) or two-way (between sender and receiver, or between receivers, etc.) information communication.

[0267] Figure 7B1 shows a computer, which includes a main body 7201, a casing 7202, a display unit 7203, a keyboard 7204, an external connection port 7205, and a pointing device 7206. This computer is manufactured by arranging the light-emitting devices shown in Embodiment 1 in a matrix and using them in the display unit 7203. The computer in Figure 7B1 can also be configured as shown in Figure 7B2. The computer shown in Figure 7B2 has a display unit 7210 instead of the keyboard 7204 and the pointing device 7206. The display unit 7210 is a touch panel, allowing input by using a finger or a special stylus to operate the input display shown on the display unit 7210. Furthermore, the display unit 7210 can display not only the input display but also other images. Additionally, the display unit 7203 can also be a touch panel. Because the two screens are connected by a hinge, problems such as screen damage or breakage during storage or transportation can be prevented.

[0268] Figure 7C shows an example of a portable terminal. The mobile phone includes a display 7402, operation buttons 7403, an external connection port 7404, a speaker 7405, a microphone 7406, etc., all assembled in a housing 7401. Furthermore, the mobile phone includes a display 7402 manufactured by arranging the light-emitting devices shown in Embodiment 1 in a matrix.

[0269] The portable terminal shown in Figure 7C can also have a structure that allows information to be input using a touch display unit 7402 such as a finger. In this case, operations such as making phone calls or composing emails can be performed using the touch display unit 7402 such as a finger.

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

[0271] For example, when making a phone call or composing an email, the text displayed on the screen can be entered using the text input mode primarily used for inputting text on the display unit 7402. In this case, it is preferable to display a keyboard or number buttons in most of the screen of the display unit 7402.

[0272] In addition, by installing a detection device with sensors such as gyroscopes and accelerometers to detect tilt inside the portable terminal, the orientation (vertical or horizontal) of the portable terminal can be determined and the screen display of the display unit 7402 can be switched automatically.

[0273] Additionally, the screen mode can be switched by touching the display unit 7402 or by operating the operation buttons 7403 on the housing 7401. Alternatively, the screen mode can be switched according to the type of image displayed on the display unit 7402. For example, when the image signal displayed on the display unit is moving image data, the screen mode is switched to display mode, and when the image signal is text data, the screen mode is switched to input mode.

[0274] In addition, when in input mode, if the light sensor of display unit 7402 detects a signal and it is known that there is no touch operation input on display unit 7402 within a certain period of time, control can be performed to switch the screen mode from input mode to display mode.

[0275] The display unit 7402 can also be used as an image sensor. For example, by touching the display unit 7402 with the palm or fingers, palm prints, fingerprints, etc., can be captured for personal identification. In addition, by using a backlight that emits near-infrared light or a sensing light source that emits near-infrared light in the display unit, finger veins, palm veins, etc., can also be captured.

[0276] Furthermore, the structure shown in this embodiment can be used in appropriate combinations with the structures shown in Embodiments 1 to 3.

[0277] As described above, the light-emitting device equipped with the light-emitting device shown in Embodiment 1 or Embodiment 2 has a very wide range of applications, and can be used in electronic devices in various fields. By using the light-emitting device shown in Embodiment 1 or Embodiment 2, electronic devices with low power consumption can be obtained.

[0278] Figure 8A is a schematic diagram showing an example of a robotic vacuum cleaner.

[0279] The robotic vacuum cleaner 5100 includes a display 5101 on its top surface, multiple cameras 5102 on its sides, a brush 5103, and operation buttons 5104. Although not shown, the bottom of the robotic vacuum cleaner 5100 has tires and a suction port. Furthermore, the robotic vacuum cleaner 5100 includes various sensors such as infrared sensors, ultrasonic sensors, accelerometers, piezoelectric sensors, light sensors, and gyroscope sensors. Additionally, the robotic vacuum cleaner 5100 includes a wireless communication unit.

[0280] The 5100 robotic vacuum cleaner can walk automatically, and the 5120 can detect garbage and suck it up from the suction port on the bottom.

[0281] In addition, the robot vacuum cleaner 5100 analyzes the images captured by the camera 5102 to determine the presence or absence of obstacles such as walls, furniture, or steps. Furthermore, if it detects objects such as wiring that may get tangled in the brush 5103 through image analysis, it can stop the rotation of the brush 5103.

[0282] The display 5101 can show the remaining battery power and the amount of debris collected. The display 5101 can also show the robot vacuum cleaner's path. Additionally, the display 5101 can be a touch panel, displaying the operation buttons 5104.

[0283] The robotic vacuum cleaner 5100 can communicate with portable electronic devices 5140 such as smartphones. Images captured by the camera 5102 can be displayed on the portable electronic device 5140. Therefore, the owner of the robotic vacuum cleaner 5100 can know the status of the room even when leaving home. Additionally, the content displayed on the monitor 5101 can be checked using a portable electronic device such as a smartphone.

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

[0285] The robot 2100 shown in Figure 8B includes a computing unit 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] Microphone 2102 has the function of detecting the user's voice and ambient sounds. Additionally, speaker 2104 has the function of emitting sound. Robot 2100 can use microphone 2102 and speaker 2104 to communicate with the user.

[0287] The display 2105 has the function of displaying various information. The robot 2100 can display the information desired by the user on the display 2105. The display 2105 may be equipped with a touch panel. The display 2105 can be a detachable information terminal, which can be charged and send and receive data by setting it at a designated position on the robot 2100.

[0288] The upper camera 2103 and the lower camera 2106 are capable of capturing images of the surrounding environment of the robot 2100. Additionally, the obstacle sensor 2107 can detect the presence or absence of obstacles in front of the robot 2100 when it moves using the mobility mechanism 2108. The robot 2100 can use the upper camera 2103, the lower camera 2106, and the obstacle sensor 2107 to perceive its surrounding environment and move safely. The light-emitting device of one embodiment of the present invention can be used in the display 2105.

[0289] Figure 8C 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 light 5004, a connection terminal 5006, a sensor 5007 (which has the function of measuring factors such as force, displacement, position, velocity, acceleration, angular velocity, rotational speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, tilt, vibration, odor, or infrared radiation), a microphone 5008, a display unit 5002, a support unit 5012, and headphones 5013, etc.

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

[0291] Figure 9 shows an example of a table lamp using the light-emitting device shown in Embodiment 1 as a lighting device. The table lamp shown in Figure 9 includes a housing 2001 and a light source 2002, and the lighting device described in Embodiment 3 can also be used as the light source 2002.

[0292] Figure 10 shows an example of using the light-emitting device shown in Embodiment 1 in an indoor lighting device 3001. Since the light-emitting device shown in Embodiment 1 is a high-efficiency light-emitting device, a low-power lighting device can be provided. Furthermore, because the light-emitting device shown in Embodiment 1 can be made in a large area, it can be used in large-area lighting devices. Additionally, because the light-emitting device shown in Embodiment 1 is thin, a thin lighting device can be manufactured.

[0293] The light-emitting device shown in Embodiment 1 can also be installed on the windshield or dashboard of a car. Figure 11 shows one embodiment of using the light-emitting device shown in Embodiment 1 on the windshield or dashboard of a car. Display areas 5200 to 5203 are displays set using the light-emitting device shown in Embodiment 1.

[0294] Display areas 5200 and 5201 are display devices mounted on the windshield of an automobile and equipped with the light-emitting device shown in Embodiment 1. By using electrodes with light transmittance to manufacture the anode and cathode of the light-emitting device shown in Embodiment 1, a so-called see-through display device that allows the view of the opposite side can be obtained. With a see-through display, even when mounted on the windshield of an automobile, the view is not obstructed. Furthermore, when using transistors or the like for driving the device, it is preferable to use transistors with light transmittance, such as organic transistors using organic semiconductor materials or transistors using oxide semiconductors.

[0295] Display area 5202 is a display device installed on the pillar portion and equipped with the light-emitting device shown in Embodiment 1. By displaying images from the imaging unit installed on the passenger compartment on display area 5202, the view obstructed by the pillar can be compensated. Similarly, display area 5203 installed on the dashboard portion can compensate for blind spots obstructed by the passenger compartment by displaying images from the imaging unit installed on the exterior of the vehicle, thereby improving safety. By displaying images to compensate for unseen parts, safety can be confirmed more naturally and simply.

[0296] Display area 5203 can also provide various information such as navigation information, speedometer, tachometer, and air conditioning settings. Users can appropriately change the display content and layout. Additionally, this information can also be displayed on display areas 5200 to 5203. Furthermore, display areas 5200 to 5203 can also be used as lighting equipment.

[0297] Figures 12A and 12B illustrate a foldable portable information terminal 5150. The foldable portable information terminal 5150 includes a housing 5151, a display area 5152, and a bending portion 5153. Figure 12A shows the portable information terminal 5150 in its unfolded state. Figure 12B shows the portable information terminal 5150 in its folded state. Although the portable information terminal 5150 has a relatively large display area 5152, by folding the portable information terminal 5150, it becomes smaller and more portable.

[0298] The display area 5152 can be folded in half by the bending portion 5153. The bending portion 5153 is composed of a telescopic component and multiple support components. When folding, the telescopic component is stretched, and the bending portion 5153 is folded in such a way that it has a radius of curvature of 2 mm or more, preferably 3 mm or more.

[0299] Alternatively, the display area 5152 can also be a touch panel (input / output device) equipped with a touch sensor (input device). A light-emitting device according to one embodiment of the present invention can be used in the display area 5152.

[0300] Furthermore, Figures 13A to 13C illustrate a foldable portable information terminal 9310. Figure 13A shows the portable information terminal 9310 in its unfolded state. Figure 13B shows the portable information terminal 9310 in a state transitioning between the unfolded and folded states. Figure 13C shows the portable information terminal 9310 in its folded state. The portable information terminal 9310 offers good portability in its folded state and provides a strong sense of overview in its unfolded state due to its large, seamlessly integrated display area.

[0301] The display panel 9311 is supported by three housings 9315 connected by a hinge portion 9313. Note that the display panel 9311 can also be a touch panel (input / output device) equipped with a touch sensor (input device). Furthermore, by bending the display panel 9311 at the hinge portion 9313 between two housings 9315, the portable information terminal 9310 can be reversibly changed from an unfolded state to a folded state. A light-emitting device according to one embodiment of the present invention can be used in the display panel 9311. Example 1

[0302] In this embodiment, 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 formula of the organic compound used in this embodiment is shown below.

[0303] [Chemical Formula 16]

[0304] (Manufacturing method of light-emitting device 1) First, an alloy film (Ag-Pd-Cu (APC) film) of silver (Ag), palladium (Pd), and copper (Cu) is formed on a glass substrate as a reflective electrode with a thickness of 100 nm by sputtering. Then, an indium tin oxide (ITSO) containing silicon oxide is formed as a transparent electrode with a thickness of 85 nm by sputtering to form the anode 101. Note that its electrode area is 4 mm² (2 mm × 2 mm).

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

[0306] Then, the substrate is placed in a vacuum evaporation apparatus where the pressure is reduced to about 10⁻⁴ Pa, and vacuum-baked at 170°C for 30 minutes in the heating chamber of the vacuum evaporation apparatus, and then cooled for about 30 minutes.

[0307] Next, the substrate with the anode 101 formed thereon is fixed on a substrate support provided in a vacuum evaporation apparatus with the anode 101 facing downwards. A hole injection layer 111 is formed on the anode 101 by evaporation with N-(1,1'-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9,9-dimethyl-9H-furo-2-amine (abbreviated as: PCBBiF) and electron acceptor material (OCHD-001) in a weight ratio of 1:0.05 (=PCBBiF:OCHD-001) and a thickness of 10 nm.

[0308] PCBBiF is deposited on the hole injection layer 111 with a thickness of 20 nm, and then N,N-bis[4-(dibenzofuran-4-yl)phenyl]-4-amino-p-terphenyl (abbreviated as: DBfBB1TP) represented by the above structural formula (ii) is deposited with a thickness of 10 nm, thereby forming the hole transport layer 112.

[0309] Next, 3,3'-(naphthalene-1,4-diyl)bis(9-phenyl-9H-carbazole) (abbreviated as PCzN2) represented by the above structural formula (iii) is vapor-deposited on the hole transport layer 112 with a thickness of 10 nm, thereby forming an electron barrier layer.

[0310] Then, a co-evaporation process is performed with 2-(10-phenyl-9-anthrayl)-benzo[b]naphtho[2,3-d]furan (abbreviated as Bnf(II)PhA) represented by the above structural formula (iv) and 3,10-bis[N-(9-phenyl-9H-carbazole-2-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviated as 3,10PCA2Nbf(IV)-02) represented by the above structural formula (v) in a weight ratio of 1:0.015 (=Bnf(II)PhA:3,10PCA2Nbf(IV)-02) and a thickness of 25 nm, thereby forming the light-emitting layer 113.

[0311] Then, after depositing 2-{(3',5'-di-tert-butyl)-1,1'-biphenyl-3-yl}-4,6-bis(3,5-di-tert-butylphenyl)-1,3,5-triazine (abbreviated as: mmtBumBP-dmmtBuPTzn) with a thickness of 10 nm to form an electron transport layer 114, a co-deposition is performed with a weight ratio of mmtBumBP-dmmtBuPTzn to 6-methyl-8-hydroxyquinoline-lithium (abbreviated as: Li-6mq) with a thickness of 20 nm at 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, an electron injection layer 115 is formed by depositing Li-6mq with a thickness of 1 nm. Finally, a cathode 102 is formed by co-evaporating silver (Ag) and magnesium (Mg) with a thickness of 15 nm and a volume ratio of 1:0.1, thereby manufacturing the light-emitting device 1. Note that the cathode 102 is a semi-transmissive and semi-reflective electrode that has the function of reflecting light and allowing light to pass through. The light-emitting device in this embodiment is a top-emitting device that extracts light from the cathode 102. In addition, 1,3,5-tris(dibenzothiophene-4-yl)-benzene (abbreviated as DBT3P-II) represented by the above structural formula (xi) is evaporated on the cathode 102 with a thickness of 70 nm to improve the light extraction efficiency.

[0313] (Compare the manufacturing methods of light-emitting device 1) Except for the following points, the manufacturing conditions of the light-emitting device 1 are the same as those of the light-emitting device 2: the thickness of PCBBiF in the hole transport layer 112 is changed to 15 nm; 2-[3'-(9,9-dimethyl-9H-en-2-yl)-1,1'-biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviated as: mFBPTzn) represented by the above structural formula (vi) is used in the hole barrier layer to replace mmtBumBP-dmmtBuPTzn; The 2-[3-(2,6-dimethyl-3-pyridyl)-5-(9-phenanthyl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviated as mPn-mDMePyPTzn), represented by structural formula (xix), is used in electron transport layer 114 instead of mmtBumBP-dmmtBuPTzn; 8-hydroxyquinoline-lithium (abbreviated as Liq), represented by the above structural formula (ix), is used in electron transport layer 114 and electron injection layer 115 instead of Li-6mq. The thickness of the hole transport layer is adjusted to ensure uniform chromaticity between the elements.

[0314] The following shows the element structure of light-emitting device 1 and a comparison of light-emitting device 1.

[0315] [Table 1]

[0316] Furthermore, Figure 14 and Table 2 below show the refractive indices of mmtBumBP-dmmtBuPTzn, mPn-mDMePyPTzn, Li-6mq, and Liq, as well as the refractive index at 456 nm. Measurements were performed using a spectroellipsometry (JA Woollam Japan M-2000U). As the measurement sample, films formed on a quartz substrate with each layer of material at a thickness of approximately 50 nm using vacuum evaporation were used. Figure 14 also shows the ordinary refractive index n, Ordinary, and the extraordinary refractive index n, Extra-ordinary.

[0317] As shown in Figure 14, the ordinary refractive index of mmtBumBP-dmmtBuPTzn across the entire blue emission region (above 455 nm and below 465 nm) is 1.60 to 1.61, which is within the range of 1.50 to 1.75. Furthermore, the ordinary refractive index at 633 nm is 1.57, which is within the range of 1.45 to 1.70. Therefore, mmtBumBP-dmmtBuPTzn is a material with a low refractive index. Similarly, the ordinary refractive index of Li-6mq across the entire blue emission region (above 455 nm and below 465 nm) is 1.67, which is within the range of 1.45 to 1.70. Moreover, the ordinary refractive index at 633 nm is 1.61, which is within the range of 1.40 to 1.65. Therefore, Li-6mq is also a material with a low refractive index.

[0318] Therefore, the light-emitting device 1 is as follows: the ordinary light refractive index of the electron transport layer 114 in the entire blue light-emitting region (above 455nm and below 465nm) is in the range of above 1.50 and less than 1.75, and the ordinary light refractive index of the electron transport layer 114 at 633nm is in the range of above 1.45 and less than 1.70.

[0319] [Table 2]

[0320] In a nitrogen-atmospheric glove box, the light-emitting device 1 and the comparative light-emitting device 1 were sealed using a glass substrate in a manner that prevented them from being exposed to the atmosphere (UV-curable sealing material was applied around the components, and UV radiation was applied to the sealing material without irradiating the light-emitting device, followed by heat treatment 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 treatment to improve light extraction efficiency was performed on the sealed glass substrate.

[0321] Figure 15 shows the luminance-current density characteristics of light-emitting device 1 and the comparative light-emitting device 1; Figure 16 shows the current efficiency-luminance characteristics; Figure 17 shows the luminance-voltage characteristics; Figure 18 shows the current-voltage characteristics; Figure 19 shows the blue index-luminance characteristics; and Figure 20 shows the emission spectrum. Furthermore, Table 3 shows the main characteristics of light-emitting device 1 and the comparative light-emitting device 1 near 1000 cd / m². Note that luminance, CIE chromaticity, and emission spectrum were measured at room temperature using a spectroradiometer (Topcon SR-UL1R).

[0322] Note that the Blue Index (BI) is the value obtained by dividing the current efficiency (cd / A) by the chromaticity (y) (cd / A / y), and it is one of the indicators representing the luminous emission characteristics of blue light. Blue light emission tends to have higher color purity as the chromaticity (y) decreases. High-purity blue light emission can display a wider range of blue hues even with fewer luminance components. When using high-purity blue light emission, the brightness required to display blue is reduced, thus achieving a reduction in power consumption. Therefore, appropriately using the BI, which takes into account the chromaticity (y) as one of the indicators of blue purity, as a method to represent the efficiency of blue light emission can be said to indicate that the higher the BI of a light-emitting device, the better its efficiency as a blue light-emitting device used in displays.

[0323] [Table 3]

[0324] As shown in Figures 15 to 20 and Table 3, in one embodiment of the present invention, the light-emitting device 1 using a low refractive index material is an EL device that exhibits an emission spectrum almost identical to that of the comparative light-emitting device 1 but has better current efficiency than the comparative light-emitting device 1.

[0325] Furthermore, the blue index (BI) near 1000 cd / m² for light-emitting device 1 and the comparative light-emitting device 1 are 153 (cd / A / y) and 148 (cd / A / y), respectively, with maximum BIs of 161 (cd / A / y) and 149 (cd / A / y), respectively. Thus, it can be said that light-emitting device 1 is a light-emitting device with particularly good BI. Therefore, one embodiment of the present invention is suitable for use as a light-emitting device for a display. Example 2

[0326] In this embodiment, 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 formula of the organic compound used in this embodiment is shown below.

[0327] [Chemical Formula 17]

[0328] (Manufacturing method of light-emitting device 2) First, an alloy film (Ag-Pd-Cu (APC) film) of silver (Ag), palladium (Pd), and copper (Cu) is formed on a glass substrate as a reflective electrode with a thickness of 100 nm by sputtering. Then, an indium tin oxide (ITSO) containing silicon oxide is formed as a transparent electrode with a thickness of 10 nm by sputtering to form the anode 101. Note that its electrode area is 4 mm² (2 mm × 2 mm).

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

[0330] Then, the substrate is placed in a vacuum evaporation apparatus where the pressure is reduced to about 10⁻⁴ Pa, and vacuum-baked at 170°C for 30 minutes in the heating chamber of the vacuum evaporation apparatus, and then cooled for about 30 minutes.

[0331] Next, the substrate with the anode 101 formed thereon is fixed on a substrate support provided in a vacuum evaporation apparatus with the anode 101 facing downwards. A hole injection layer 111 is formed on the anode 101 by evaporation with N-(1,1'-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9,9-dimethyl-9H-furo-2-amine (abbreviated as: PCBBiF) and electron acceptor material (OCHD-001) in a weight ratio of 1:0.05 (=PCBBiF:OCHD-001) and a thickness of 10 nm.

[0332] PCBBiF is deposited on the hole injection layer 111 with a thickness of 105 nm, and then N,N-bis[4-(dibenzofuran-4-yl)phenyl]-4-amino-p-terphenyl (abbreviated as: DBfBB1TP) represented by the above structural formula (ii) is deposited with a thickness of 10 nm, thereby forming the hole transport layer 112.

[0333] Next, 3,3'-(naphthalene-1,4-diyl)bis(9-phenyl-9H-carbazole) (abbreviated as PCzN2) represented by the above structural formula (iii) is vapor-deposited on the hole transport layer 112 with a thickness of 10 nm, thereby forming an electron barrier layer.

[0334] Then, a co-evaporation process is performed with 2-(10-phenyl-9-anthrayl)-benzo[b]naphtho[2,3-d]furan (abbreviated as Bnf(II)PhA) represented by the above structural formula (iv) and 3,10-bis[N-(9-phenyl-9H-carbazole-2-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviated as 3,10PCA2Nbf(IV)-02) represented by the above structural formula (v) in a weight ratio of 1:0.015 (=Bnf(II)PhA:3,10PCA2Nbf(IV)-02) and a thickness of 25 nm, thereby forming the light-emitting layer 113.

[0335] Then, after forming an electron transport layer 114 by evaporating 2-{(3',5'-di-tert-butyl)-1,1'-biphenyl-3-yl}-4,6-bis(3,5-di-tert-butylphenyl)-1,3,5-triazine (abbreviated as mmtBumBP-dmmtBuPTzn) with a thickness of 10 nm, co-evaporation is performed with a weight ratio of mmtBumBP-dmmtBuPTzn to 6-methyl-8-hydroxyquinoline-lithium (abbreviated as Li-6mq) with a thickness of 20 nm at a weight ratio of 1:1 (=mmtBumBP-dmmtBuPTzn:Li-6mq).

[0336] After forming the electron transport layer 114, an electron injection layer 115 is formed by depositing Li-6mq with a thickness of 1 nm. Finally, a cathode 102 is formed by co-evaporating silver (Ag) and magnesium (Mg) with a thickness of 15 nm and a volume ratio of 1:0.1, thereby manufacturing the light-emitting device 2. Note that the cathode 102 is a semi-transmissive and semi-reflective electrode that has the function of reflecting light and allowing light to pass through. The light-emitting device in this embodiment is a top-emitting device that extracts light from the cathode 102. In addition, 1,3,5-tris(dibenzothiophene-4-yl)-benzene (abbreviated as DBT3P-II) represented by the above structural formula (xi) is evaporated on the cathode 102 with a thickness of 70 nm to improve the light extraction efficiency.

[0337] (Compare the manufacturing methods of light-emitting device 2) Except for the following points, the manufacturing conditions of the comparative light-emitting device 2 are the same as those of the light-emitting device 2: 8-hydroxyquinoline-lithium (Liq), represented by the above structural formula (ix), is used instead of Li-6mq in the electron transport layer 114 and the electron injection layer 115; the thickness of PCBBiF in the hole transport layer 112 is changed to 100 nm. The thickness of the hole transport layer is adjusted to make the chromaticity of the components the same.

[0338] The following shows the element structure of light-emitting device 2 and a comparison of light-emitting device 2.

[0339] [Table 4]

[0340] Furthermore, Figure 21 and Table 5 below show the refractive indices of mmtBumBP-dmmtBuPTzn, Li-6mq, and Liq, as well as the refractive index at 456 nm. Measurements were performed using a spectroscopic ellipsometry (JA Woollam Japan M-2000U). As the measurement sample, a film obtained by vacuum evaporation, in which each layer of material was formed on a quartz substrate to a thickness of approximately 50 nm, was used. Figure 21 also shows the ordinary refractive index n, Ordinary, and the extraordinary refractive index n, Extra-ordinary.

[0341] As shown in Figure 21, the ordinary refractive index of mmtBumBP-dmmtBuPTzn in the entire blue emission region (above 455nm and below 465nm) is 1.60 to 1.61, which is within the range of 1.50 to 1.75. Furthermore, the ordinary refractive index at 633nm is 1.57, which is within the range of 1.45 to 1.70. Therefore, mmtBumBP-dmmtBuPTzn is a material with a low refractive index. Similarly, the ordinary refractive index of Li-6mq in the entire blue emission region (above 455nm and below 465nm) is 1.67 to 1.67, which is within the range of 1.45 to 1.70. Furthermore, the ordinary refractive index at 633nm is 1.61, which is within the range of 1.40 to 1.65. Therefore, Li-6mq is also a material with a low refractive index.

[0342] Therefore, the light-emitting device 2 is as follows: the ordinary light refractive index of the electron transport layer 114 in the entire blue light-emitting region (above 455nm and below 465nm) is in the range of above 1.50 and less than 1.75, and the ordinary light refractive index of the electron transport layer 114 at 633nm is in the range of above 1.45 and less than 1.70.

[0343] [Table 5]

[0344] In a nitrogen-atmospheric glove box, the light-emitting device 2 and the comparative light-emitting device 2 were sealed using glass substrates in a manner that prevented them from being exposed to the atmosphere (UV-curable sealing material was applied around the components, and UV radiation was applied to the sealing material without irradiating the light-emitting devices, followed by heat treatment 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 treatment to improve light extraction efficiency was performed on the sealed glass substrates.

[0345] Figure 22 shows the luminance-current density characteristics of light-emitting device 2 and the comparison light-emitting device 2; Figure 23 shows the current efficiency-luminance characteristics; Figure 24 shows the luminance-voltage characteristics; Figure 25 shows the current-voltage characteristics; Figure 26 shows the blue index-luminance characteristics; and Figure 27 shows the emission spectrum. Furthermore, Table 6 shows the main characteristics of light-emitting device 2 and the comparison light-emitting device 2 near 1000 cd / m². Note that luminance, CIE chromaticity, and emission spectrum were measured at room temperature using a spectroradiometer (Topcon SR-UL1R).

[0346] Note that the Blue Index (BI) is the value obtained by dividing the current efficiency (cd / A) by the chromaticity (y) (cd / A / y), and it is one of the indicators representing the luminous emission characteristics of blue light. Blue light emission tends to have higher color purity as the chromaticity (y) decreases. High-purity blue light emission can display a wider range of blue hues even with fewer luminance components. When using high-purity blue light emission, the brightness required to display blue is reduced, thus achieving a reduction in power consumption. Therefore, appropriately using the BI, which takes into account the chromaticity (y) as one of the indicators of blue purity, as a method to represent the efficiency of blue light emission can be said to indicate that the higher the BI of a light-emitting device, the better its efficiency as a blue light-emitting device used in displays.

[0347] [Table 6]

[0348] As shown in Figures 22 to 27 and Table 6, in one embodiment of the present invention, the light-emitting device 2 using a low refractive index material is an EL device that exhibits an emission spectrum almost identical to that of the comparative light-emitting device 2, but has a lower driving voltage and higher current efficiency than the comparative light-emitting device 2.

[0349] It is evident that by using the alkali metal organometallic complex Li-6mq, which has an alkyl group at the 6-position, together with an electron transport material having a relatively high number of alkyl groups in the electron transport layer 114, a significant reduction in driving voltage is achieved. It is generally believed that the presence of alkyl groups hinders intermolecular stacking, suppresses interactions, and leads to an increase in driving voltage. However, in the light-emitting device of one embodiment of the present invention, the effect of reducing driving voltage is particularly pronounced when both the aforementioned alkali metal organometallic complex and the aforementioned electron transport material have alkyl groups. This is a significant effect characteristic of alkali metal organometallic complexes that include ligands with an 8-hydroxyquinoline structure having an alkyl group at the 6-position. Compared to the same metal complex having an 8-hydroxyquinoline structure with an unsubstituted (hydrogen) group at the 6-position, the driving voltage is reduced. The organometallic complex is preferably 6-alkyl-8-hydroxyquinoline-lithium, and particularly preferably 6-methyl-8-hydroxyquinoline-lithium (abbreviated as: Li-6mq).

[0350] Furthermore, the blue index (BI) near 1000 cd / m² for light-emitting device 2 and the comparative light-emitting device 2 are 145 (cd / A / y) and 119 (cd / A / y), respectively. Thus, it can be said that light-emitting device 2 is a light-emitting device with particularly good BI. Therefore, one embodiment of the present invention is suitable for use as a light-emitting device for a display.

[0351] Furthermore, the power efficiencies of light-emitting device 2 and the comparative light-emitting device 2 near 1000 cd / m2 are 4.5 (lm / W) and 2.5 (lm / W), respectively. Thus, it can be said that light-emitting device 2 is a light-emitting device with particularly low power consumption. Example 3

[0352] In this embodiment, 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 formula of the organic compound used in this embodiment is shown below.

[0353] [Chemical Formula 18]

[0354] (Manufacturing method of light-emitting device 3) First, an alloy film (Ag-Pd-Cu (APC) film) of silver (Ag), palladium (Pd), and copper (Cu) is formed on a glass substrate as a reflective electrode with a thickness of 100 nm by sputtering. Then, an indium tin oxide (ITSO) containing silicon oxide is formed as a transparent electrode with a thickness of 10 nm by sputtering to form the anode 101. Note that its electrode area is 4 mm² (2 mm × 2 mm).

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

[0356] Then, the substrate is placed in a vacuum evaporation apparatus where the pressure is reduced to about 10⁻⁴ Pa, and vacuum-baked at 170°C for 30 minutes in the heating chamber of the vacuum evaporation apparatus, and then cooled for about 30 minutes.

[0357] Next, the substrate with the anode 101 formed thereon is fixed on a substrate support provided in a vacuum evaporation apparatus with the anode 101 facing downwards. A hole injection layer 111 is formed on the anode 101 by evaporation with N-(1,1'-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9,9-dimethyl-9H-furo-2-amine (abbreviated as: PCBBiF) and electron acceptor material (OCHD-001) in a weight ratio of 1:0.05 (=PCBBiF:OCHD-001) and a thickness of 10 nm.

[0358] PCBBiF is deposited on the hole injection layer 111 with a thickness of 100 nm, and then N,N-bis[4-(dibenzofuran-4-yl)phenyl]-4-amino-p-terphenyl (abbreviated as: DBfBB1TP) represented by the above structural formula (ii) is deposited with a thickness of 10 nm, thereby forming the hole transport layer 112.

[0359] Next, 3,3'-(naphthalene-1,4-diyl)bis(9-phenyl-9H-carbazole) (abbreviated as PCzN2) represented by the above structural formula (iii) is vapor-deposited on the hole transport layer 112 with a thickness of 10 nm, thereby forming an electron barrier layer.

[0360] Then, a co-evaporation process is performed with 2-(10-phenyl-9-anthrayl)-benzo[b]naphtho[2,3-d]furan (abbreviated as Bnf(II)PhA) represented by the above structural formula (iv) and 3,10-bis[N-(9-phenyl-9H-carbazole-2-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviated as 3,10PCA2Nbf(IV)-02) represented by the above structural formula (v) in a weight ratio of 1:0.015 (=Bnf(II)PhA:3,10PCA2Nbf(IV)-02) and a thickness of 25 nm, thereby forming the light-emitting layer 113.

[0361] Then, after depositing a hole barrier layer with a thickness of 10 nm using 2-[3'-(9,9-dimethyl-9H-piro-2-yl)-1,1'-biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviated as mFBPTzn) represented by the above structural formula (vi), co-depositing is performed with a thickness of 20 nm using 2-[3-(2,6-dimethyl-3-pyridyl)-5-(9-phenanthyl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviated as mPn-mDMePyPTzn) represented by the above structural formula (xix) and 6-methyl-8-hydroxyquinoline-lithium (abbreviated as Li-6mq) represented by the above structural formula (vii) in a weight ratio of 1:1 (=mPn-mDMePyPTzn:Li-6mq), thereby forming an electron transport layer 114.

[0362] After forming the electron transport layer 114, an electron injection layer 115 is formed by depositing Li-6mq with a thickness of 1 nm. Finally, a cathode 102 is formed by co-evaporating silver (Ag) and magnesium (Mg) with a thickness of 15 nm and a volume ratio of 1:0.1, thereby manufacturing the light-emitting device 3. Note that the cathode 102 is a semi-transmissive and semi-reflective electrode that has the function of reflecting light and allowing light to pass through. The light-emitting device in this embodiment is a top-emitting element that extracts light from the cathode 102. In addition, 1,3,5-tris(dibenzothiophene-4-yl)-benzene (abbreviated as DBT3P-II) represented by the above structural formula (xi) is evaporated on the cathode 102 with a thickness of 70 nm to improve the light extraction efficiency.

[0363] (Compare the manufacturing methods of light-emitting device 3) Except for the following points, the manufacturing conditions of the light-emitting device 3 are the same as those of the light-emitting device 3: 8-hydroxyquinoline-lithium (abbreviated as Liq) represented by the above structural formula (ix) is used instead of Li-6mq for the electron transport layer.

[0364] The following shows the element structure of light-emitting device 3 and a comparison of light-emitting device 3.

[0365] [Table 7]

[0366] Furthermore, Figure 28 and Table 8 below show the refractive indices of mPn-mDMePyPTzn, Li-6mq, and Liq, as well as the refractive index at 456 nm. Measurements were performed using a spectroscopic ellipsometry (JA Woollam Japan M-2000U). As the measurement sample, films formed on a quartz substrate with each layer of material at a thickness of approximately 50 nm using vacuum evaporation were used. Figure 28 also shows the ordinary refractive index n, Ordinary, and the extraordinary refractive index n, Extra-ordinary.

[0367] [Table 8]

[0368] In a nitrogen-atmospheric glove box, the light-emitting device 3 and the comparative light-emitting device 3 were sealed using a glass substrate in a manner that prevented them from being exposed to the atmosphere (UV-curable sealing material was applied around the components, and UV radiation was applied to the sealing material without irradiating the light-emitting device, followed by heat treatment 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 treatment to improve light extraction efficiency was performed on the sealed glass substrate.

[0369] Figure 29 shows the luminance-current density characteristics of light-emitting device 3 and the comparative light-emitting device 3; Figure 30 shows the current efficiency-luminance characteristics; Figure 31 shows the luminance-voltage characteristics; Figure 32 shows the current-voltage characteristics; Figure 33 shows the emission spectrum; and Figure 34 shows the blue index (BI)-luminance characteristics. Furthermore, Table 9 shows the main characteristics of light-emitting device 3 and the comparative light-emitting device 3 near 1000 cd / m². Note that luminance, CIE chromaticity, and emission spectrum were measured at room temperature using a spectroradiometer (Topcon SR-UL1R).

[0370] Note that the Blue Index (BI) is the value obtained by dividing the current efficiency (cd / A) by the chromaticity (y) (cd / A / y), and it is one of the indicators representing the luminous emission characteristics of blue light. Blue light emission tends to have higher color purity as the chromaticity (y) decreases. High-purity blue light emission can display a wider range of blue hues even with fewer luminance components. When using high-purity blue light emission, the luminance required to display blue is reduced, thus achieving a reduction in power consumption. Therefore, appropriately using the BI, which takes into account chromaticity (y) as one of the indicators of blue purity, as a method to represent the efficiency of blue light emission can be said to indicate that the higher the BI of a light-emitting device, the better the efficiency of the blue light-emitting device used in displays.

[0371] [Table 9]

[0372] As shown in Figures 29 to 34 and Table 9, in one embodiment of the present invention, the light-emitting device 3 using a low refractive index material is an EL device that 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] It is understood that by using the alkali metal organometallic complex Li-6mq, which has an alkyl group at the 6-position, together with an electron transport material in the electron transport layer 114, a driving voltage reduction effect is achieved. This is a characteristic effect of alkali metal organometallic complexes that include ligands with an alkyl group at the 6-position of 8-hydroxyquinoline. The organometallic complex is preferably 6-alkyl-8-hydroxyquinoline-lithium, and particularly preferably 6-methyl-8-hydroxyquinoline-lithium (abbreviated as Li-6mq).

[0374] Furthermore, the blue index (BI) near 1000 cd / m2 for light-emitting device 3 and the comparative light-emitting device 3 are 152.3 (cd / A / y) and 149.4 (cd / A / y) respectively, with the maximum BI being 153.3 (cd / A / y) and 150.4 (cd / A / y) respectively. Thus, it can be said that light-emitting device 3 is a light-emitting device with particularly good BI.

[0375] Note that in this embodiment, the low-refractive-index material is used only in the organometallic complex to confirm the low driving voltage effect of 6-alkyl-8-hydroxyquinoline-lithium (preferably Li-6mq). As shown in Example 1, by using the low-refractive-index material in both the electron transport layer and the electron transport layer of the organometallic complex with electron transport properties, a significant improvement in light extraction effect can be obtained, which leads to an increase in current efficiency or BI.

[0376] Furthermore, as shown in Example 2, by using an alkyl-containing organic compound with electron transport properties in conjunction with 6-alkyl-8-hydroxyquinoline-lithium (preferably Li-6mq), a significant low driving voltage effect can be obtained. Additionally, it is known that by using an alkyl-containing organic compound with low refractive index and electron transport properties, along with 6-alkyl-8-hydroxyquinoline-lithium (preferably Li-6mq), a significant low driving voltage effect and a significant improvement in luminous efficiency can be achieved. Example 4

[0377] <<Synthesis Example 1>> In this embodiment, a method for synthesizing the metal complex 6-methyl-8-hydroxyquinoline-lithium (hereinafter referred to as Li-6mq) according to one embodiment of the present invention is described. The structural formula of Li-6mq is shown below.

[0378] [Chemical Formula 19]

[0379] <Step 1: Synthesis of Li-6mq> 2.0 g (12.6 mmol) of 8-hydroxy-6-methylquinoline and 130 mL of dehydrated tetrahydrofuran (THF) were placed in a three-necked flask and stirred. 10.1 mL (10.1 mmol) of 1M lithium butoxide (tBuOLi) THF solution was added to the solution, and the mixture was stirred at room temperature for 47 hours. The reaction solution was concentrated to give a yellow solid. Acetonitrile was added to the solid, and the mixture was ultrasonically irradiated and filtered to give a pale yellow solid. This washing operation was performed twice. 1.6 g (95% yield) of pale yellow solid Li-6mq was obtained as the filter residue. The synthetic scheme is shown below.

[0380] [Chemical Formula 20]

[0381] Next, Figure 35 shows the measurement results of the absorption and emission spectra of Li-6mq in dehydrated acetone solution. The absorption spectrum was measured using a UV-Vis spectrophotometer (V550 model manufactured by Nippon Spectroscopy Co., Ltd.), and the spectrum shown is the result of subtracting the spectrum measured when only the dehydrated acetone was placed in a quartz dish. The emission spectrum was measured using a fluorescence spectrophotometer (FP-8600 manufactured by Nippon Spectroscopy Co., Ltd.).

[0382] As shown in Figure 35, Li-6mq in the dehydrated acetone solution has an absorption peak at 390 nm and an emission peak at 540 nm (excitation wavelength 385 nm). Example 5

[0383] In this embodiment, a light-emitting device 4, a comparison light-emitting device 4, and a comparison light-emitting device 5 according to one embodiment of the present invention will be described. The structural formula of the organic compound used in this embodiment is shown below.

[0384] [Chemical Formula 21]

[0385] (Manufacturing method of light-emitting device 4) First, silver (Ag) is sputtered to a thickness of 100 nm on a glass substrate as a reflective electrode. Then, indium tin oxide (ITSO) containing silicon oxide is sputtered to a thickness of 95 nm as a transparent electrode to form the anode 101. Note that its electrode area is 4 mm² (2 mm × 2 mm).

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

[0387] Then, the substrate is placed in a vacuum evaporation apparatus where the pressure is reduced to about 10⁻⁴ Pa, and vacuum-baked at 170°C for 30 minutes in the heating chamber of the vacuum evaporation apparatus, and then cooled for about 30 minutes.

[0388] Next, the substrate with the anode 101 formed thereon is fixed on a substrate support provided in a vacuum evaporation apparatus with the anode 101 facing downwards. A hole injection layer 111 is formed on the anode 101 by evaporation with N-(1,1'-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9,9-dimethyl-9H-furo-2-amine (abbreviated as: PCBBiF) and electron acceptor material (OCHD-001) in a weight ratio of 1:0.05 (=PCBBiF:OCHD-001) and a thickness of 10 nm.

[0389] PCBBiF is deposited on the hole injection layer 111 with a thickness of 10 nm, and then N,N-bis(4-biphenyl)-6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviated as BBABnf) represented by the above structural formula (xii) is deposited on the hole transport layer 112 with a thickness of 10 nm.

[0390] Next, 3,3'-(naphthalene-1,4-diyl)bis(9-phenyl-9H-carbazole) (abbreviated as PCzN2) represented by the above structural formula (iii) is vapor-deposited on the hole transport layer 112 with a thickness of 10 nm, thereby forming an electron barrier layer.

[0391] Then, a co-evaporation process is performed with 2-(10-phenyl-9-anthrayl)-benzo[b]naphtho[2,3-d]furan (abbreviated as Bnf(II)PhA) represented by the above structural formula (iv) and 3,10-bis[N-(9-phenyl-9H-carbazole-2-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviated as 3,10PCA2Nbf(IV)-02) represented by the above structural formula (v) in a weight ratio of 1:0.015 (=Bnf(II)PhA:3,10PCA2Nbf(IV)-02) and a thickness of 25 nm, thereby forming the light-emitting layer 113.

[0392] Then, after forming an electron transport layer 114 by evaporating 2-{(3',5'-di-tert-butyl)-1,1'-biphenyl-3-yl}-4,6-diphenyl-1,3,5-triazine (abbreviated as mmtBumBPTzn) represented by the above structural formula (xiii) with a thickness of 10 nm, co-evaporation is performed with a weight ratio of mmtBumBPTzn to 6-methyl-8-hydroxyquinoline-lithium (abbreviated as Li-6mq) represented by the above structural formula (vii) of 1:1 (=mmtBumBPTzn:Li-6mq).

[0393] After forming the electron transport layer 114, lithium fluoride is deposited to form the electron injection layer 115 with a thickness of 1 nm. Finally, silver (Ag) and magnesium (Mg) are co-evaporated with a thickness of 15 nm in a volume ratio of 1:0.1 to form the cathode 102, thereby manufacturing the light-emitting device 4. Note that the cathode 102 is a semi-transmissive and semi-reflective electrode that has the function of reflecting light and allowing light to pass through. The light-emitting device in this embodiment is a top-emitting element that extracts light from the cathode 102. In addition, 1,3,5-tris(dibenzothiophene-4-yl)-benzene (abbreviated as DBT3P-II) represented by the above structural formula (xi) is evaporated on the cathode 102 with a thickness of 70 nm to improve the light extraction efficiency.

[0394] (Compare the manufacturing methods of light-emitting device 4) Except for the following points, the manufacturing conditions of the light-emitting device 4 are the same as those of the light-emitting device 4: 8-hydroxyquinoline-lithium (abbreviated as Liq) represented by the above structural formula (ix) is used instead of Li-6mq in the electron transport layer 114.

[0395] (Compare the manufacturing methods of light-emitting device 5) Except for the following points, the manufacturing conditions of the comparative light-emitting device 5 are the same as those of the comparative light-emitting device 4: 2-[3'-(9,9-dimethyl-9H-piro-2-yl)-1,1'-biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviated as mFBPTzn), represented by the above structural formula (vi), is used in place of mmtBumBPTzn in the hole barrier layer; 2-[3-(2,6-dimethyl-3-pyridyl)-5-(9-phenanthyl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviated as mPn-mDMePyPTzn), represented by the above structural formula (xix), is used in place of mmtBumBPTzn in the electron transport layer 114. The thickness of the hole transport layer is adjusted to make the chromaticity of the elements the same.

[0396] The following shows the component structures of light-emitting device 4, comparison light-emitting device 4, and comparison light-emitting device 5.

[0397] [Table 10]

[0398] Furthermore, Figure 37 and Table 11 below show the refractive indices of mmtBumBPTzn, mPn-mDMePyPTzn, Li-6mq, and Liq, as well as the refractive index at 456 nm. Measurements were performed using a spectroscopic ellipsometry (JA Woollam Japan M-2000U). As the measurement sample, films formed on a quartz substrate with each layer of material at a thickness of approximately 50 nm using vacuum evaporation were used. Figure 37 also shows the ordinary refractive index n, Ordinary, and the extraordinary refractive index n, Extra-ordinary.

[0399] As shown in Figure 37, the ordinary refractive index of mmtBumBPTzn across the entire blue emission region (above 455 nm and below 465 nm) is 1.68, 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. Therefore, mmtBumBPTzn is a material with a low refractive index. Similarly, the ordinary refractive index of Li-6mq across the entire blue emission region (above 455 nm and below 465 nm) is 1.67, falling within the range of 1.45 to 1.70. Moreover, the ordinary refractive index at 633 nm is 1.61, falling within the range of 1.40 to 1.65. Therefore, Li-6mq is also a material with a low refractive index.

[0400] Therefore, the light-emitting device 4 is as follows: the ordinary light refractive index of the electron transport layer 114 in the entire blue light-emitting region (above 455nm and below 465nm) is in the range of above 1.50 and less than 1.75, and the ordinary light refractive index of the electron transport layer 114 at 633nm is in the range of above 1.45 and less than 1.70.

[0401] [Table 11]

[0402] In a nitrogen-atmospheric glove box, the light-emitting devices 4 and 5 were sealed using glass substrates in a manner that prevented them from being exposed to the atmosphere (UV-curable sealing material was applied around the components, and UV radiation was applied to the sealing material without irradiating the light-emitting devices, followed by heat treatment at 80°C under atmospheric pressure for 1 hour). The initial characteristics of these light-emitting devices were then measured. Note that no special treatment to improve light extraction efficiency was performed on the sealed glass substrates.

[0403] Figure 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 shows the current efficiency-luminance characteristics; Figure 40 shows the luminance-voltage characteristics; Figure 41 shows the current density-voltage characteristics; Figure 42 shows the emission spectrum; and Figure 43 shows the blue index-luminance characteristics. Furthermore, Table 12 shows the main characteristics of light-emitting device 4, comparative light-emitting device 4, and comparative light-emitting device 5 near 1000 cd / m². Note that luminance, CIE chromaticity, and emission spectrum were measured at room temperature using a spectroradiometer (Topcon SR-UL1R).

[0404] Note that the Blue Index (BI) is the value obtained by dividing the current efficiency (cd / A) by the chromaticity (y) (cd / A / y), and it is one of the indicators representing the luminous emission characteristics of blue light. Blue light emission tends to have higher color purity as the chromaticity (y) decreases. High-purity blue light emission can display a wider range of blue hues even with fewer luminance components. When using high-purity blue light emission, the luminance required to display blue is reduced, thus achieving a reduction in power consumption. Therefore, appropriately using the BI, which takes into account chromaticity (y) as one of the indicators of blue purity, as a method to represent the efficiency of blue light emission can be said to indicate that the higher the BI of a light-emitting device, the better the efficiency of the blue light-emitting device used in displays.

[0405] [Table 12]

[0406] As shown in Figures 38 to 43 and Table 12, the light-emitting device 4 of one embodiment of the present invention exhibits an emission spectrum almost identical to that of the comparative light-emitting device 5, but has better current efficiency than the comparative light-emitting device 5. Furthermore, it can be seen that the light-emitting device 4 of one embodiment of the present invention has a lower driving voltage than the comparative light-emitting device 4.

[0407] Furthermore, the blue index (BI) near 1000 cd / m² for light-emitting device 4, comparison light-emitting device 4, and comparison light-emitting device 5 are 178 (cd / A / y), 164 (cd / A / y), and 160 (cd / A / y), respectively. Thus, it can be said that light-emitting device 4 is a light-emitting device with particularly good BI. Therefore, one embodiment of the present invention is suitable for use as a light-emitting device for a display.

[0408] Furthermore, the power efficiencies of light-emitting device 4, comparison light-emitting device 4, and comparison light-emitting device 5 near 1000 cd / m2 are 6.8 (lm / W), 5.9 (lm / W), and 5.9 (lm / W), respectively. Thus, it can be said that light-emitting device 4 is a light-emitting device with particularly low power consumption.

[0409] Furthermore, bottom-emitting light-emitting devices 15 and 16 were fabricated, and initial characteristic measurements were performed. Light-emitting device 15 has almost the same structure as light-emitting device 4, but a 20nm thick PCBBiF layer and a 10nm thick N,N-bis[4-(dibenzofuran-4-yl)phenyl]-4-amino-p-terphenyl (abbreviated as DBfBB1TP) are stacked to form a hole transport layer, and a 1nm lithium fluoride layer is formed as an electron injection layer. Light-emitting device 16 is fabricated using 2-methyl-8-hydroxyquinoline-lithium (abbreviated as Li-mq) instead of Li-6mq in light-emitting device 15. At 4V, the current values ​​of light-emitting devices 15 and 16 are 0.36mA and 0.27mA, respectively, meaning that the current value of light-emitting device 15 is more than 30% higher than that of light-emitting device 16. Thus, compared with the case of using metal complexes including ligands having an alkyl group at the 2-position of an 8-hydroxyquinoline structure, light-emitting devices using metal complexes including ligands having an alkyl group at the 6-position of an 8-hydroxyquinoline structure having 1 to 3 carbon atoms can be light-emitting devices with particularly low driving voltages. Example 6

[0410] <<Synthesis Example 2>> In this embodiment, a method for synthesizing the metal complex 6-methyl-8-hydroxyquinoline-lithium (hereinafter referred to as Li-6eq) according to one embodiment of the present invention is described. The structural formula of Li-6eq is shown below.

[0411] [Chemical Formula 22]

[0412] <Step 1: Synthesis of 6-ethyl-8-hydroxyquinoline> 5.21 g (38.0 mmol) of 2-amino-5-ethylphenol and 135 mL of 1N hydrochloric acid were placed in a three-necked flask and stirred at 100 °C for 30 minutes. A solution of 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, and the mixture was heated at 100 °C for 5 hours. After the reaction was complete, the reaction solution was heated at 100 °C for 120 minutes. After adding dichloromethane to the reaction solution, the pH of the aqueous layer was adjusted to pH 7 using a 10% sodium hydroxide aqueous solution and 1N hydrochloric acid. After filtering the solution, the organic layer was removed, and the aqueous layer was extracted with dichloromethane. The extract and organic layer were then mixed, washed with water, and the organic layer was dehydrated with magnesium sulfate and concentrated to obtain a black solid containing the target compound.

[0413] The obtained solid was purified by silicone column chromatography using an developing solvent whose polarity was changed from hexane:ethyl acetate = 10:0 to hexane:ethyl acetate = 10:1. This purification was performed twice, yielding 3.4 g of the target white-yellow solid (yield: 51%). The synthetic scheme for step 1 is shown below.

[0414] [Chemical Formula 23]

[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-necked flask and stirred. 13.9 mL (13.9 mmol) of 1M lithium butoxide (tBuOLi) THF solution was added to the solution, and the mixture was stirred at room temperature for 68 hours. The reaction solution was concentrated to obtain a yellow solid. Acetonitrile was added to the solid, and the mixture was ultrasonically irradiated and filtered to obtain a yellow solid. This washing operation was performed twice. 2.6 g of yellow solid (yield 104%) was obtained as the filter residue.

[0416] The obtained yellow solid (2.58 g) was purified by sublimation using a gradient sublimation method, heating at 2.8 Pa and 335 °C for 15.5 hours. After sublimation purification, 1.94 g of yellow solid was obtained with a recovery rate of 75%. The synthetic scheme for step 2 is shown below.

[0417] [Chemical Formula 24]

[0418] The following shows the analytical results of the yellow solid obtained by nuclear magnetic resonance spectroscopy (1H-NMR). From these results, it can be seen that in this embodiment, the organic compound Li-6eq, represented by structural formula (101) of one embodiment of the present invention, was obtained.

[0419] H1 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, Figure 45 shows the measurement results of the absorption and emission spectra of Li-6eq in dehydrated acetone solution. The absorption spectrum was measured using a UV-Vis spectrophotometer (V550 model manufactured by Nippon Spectroscopy Co., Ltd.), and the spectrum shown is the result of subtracting the spectrum measured when only dehydrated acetone was placed in a quartz dish. The emission spectrum was measured using a fluorescence spectrophotometer (FP-8600 manufactured by Nippon Spectroscopy Co., Ltd.).

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

[0422] Furthermore, Figure 46 shows the measurement results of the refractive index of Li-6eq using a spectroelastic polarimeter (JA Woollam Japan M-2000U). In the measurement, a film was formed on a quartz substrate with each layer of material at a thickness of approximately 50 nm using a vacuum evaporation method. Figure 46 also shows the ordinary refractive index n, Ordinary, and the extraordinary refractive index n, Extra-ordinary.

[0423] As shown in Figure 46, the ordinary refractive index of Li-6eq in the entire blue emission region (above 455 nm and below 465 nm) is 1.68, which is in the range of above 1.45 and below 1.70. Moreover, the ordinary refractive index at 633 nm is 1.63, which is in the range of above 1.40 and below 1.65. Therefore, Li-6eq is a material with a low refractive index. Example 7

[0424] <<Synthesis Example 3>> In this embodiment, a method for synthesizing the metal complex 6-methyl-8-hydroxyquinoline-sodium (Na-6mq) according to one embodiment of the present invention is described. The structural formula of Na-6mq is shown below.

[0425] [Chemical Formula 25]

[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 placed in a three-necked flask and stirred at 80 °C for 8 hours. The reaction solution was heated and distilled at atmospheric pressure. After the solvent decreased, 140 mL of toluene was added. This process was repeated a total of three times. The reaction solution was cooled with ice water and filtered. 3.4 g (98% yield) of the yellow-green solid of the target compound was obtained as the filter residue.

[0427] The obtained yellow-green solid (1.3 g) was purified by sublimation at a pressure of 3.2 × 10⁻² Pa and a temperature of 358 °C for 16.5 hours. After sublimation purification, a yellow solid (1.0 g) was obtained with a recovery rate of 77%.

[0428] Furthermore, 1.0 g of the obtained yellow solid was purified by sublimation for 16 hours using a gradient sublimation method under a pressure of 2.0 × 10⁻² Pa and a temperature of 356 °C. After sublimation purification, 0.84 g of the yellow solid was obtained with a recovery rate of 84%. The synthesis scheme for step 1 is shown below.

[0429] [Chemical Formula 26]

[0430] The following shows the analytical results of the yellow solid obtained by nuclear magnetic resonance spectroscopy (1H-NMR). From these results, it can be seen that in this embodiment, the organic compound Na-6mq, represented by structural formula (102) of one embodiment of the present invention, was obtained.

[0431] H1 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] Figure 47 shows the absorption and emission spectra of Na-6mq in a dehydrated acetone solution. The absorption spectrum was measured using a UV-Vis spectrophotometer (V550 model, manufactured by Nippon Spectrophotometer Co., Ltd.), and the spectrum shown is the result of subtracting the spectrum measured when only the dehydrated acetone was placed in a quartz dish. The emission spectrum was measured using a fluorescence spectrophotometer (FP-8600, manufactured by Nippon Spectrophotometer Co., Ltd.). Na-6mq in the dehydrated acetone solution exhibits an absorption peak at 405 nm and an emission peak at 551 nm (excitation wavelength 405 nm). Example 8

[0433] In this embodiment, light-emitting devices 5 and 6 according to one embodiment of the present invention will be described. The structural formula of the organic compound used in this embodiment is shown below.

[0434] [Chemical Formula 27]

[0435] (Manufacturing method of light-emitting device 5) First, an anode 101 is formed on a glass substrate by sputtering indium tin oxide (ITSO) containing silicon oxide to a thickness of 70 nm. Note that its electrode area is 4 mm² (2 mm × 2 mm).

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

[0437] Then, the substrate is placed in a vacuum evaporation apparatus where the pressure is reduced to about 10⁻⁴ Pa, and vacuum-baked at 170°C for 30 minutes in the heating chamber of the vacuum evaporation apparatus, and then cooled for about 30 minutes.

[0438] Next, the substrate with the anode 101 formed thereon is fixed on a substrate support provided in a vacuum evaporation apparatus with the anode 101 facing downwards. A hole injection layer 111 is formed on the anode 101 by evaporation with N-(1,1'-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9,9-dimethyl-9H-furo-2-amine (abbreviated as: PCBBiF) and electron acceptor material (OCHD-001) in a weight ratio of 1:0.05 (=PCBBiF:OCHD-001) and a thickness of 10 nm.

[0439] PCBiF is deposited on the hole injection layer 111 with a thickness of 20 nm to form the hole transport layer 112.

[0440] Next, N-[4-(9H-carbazol-9-yl)phenyl]-N-[4-(4-dibenzofuran)phenyl]-[1,1':4',1''-terphenyl]-4-amine (abbreviated as YGTPDBfB) represented by the above structural formula (xii) is vapor-deposited on the hole transport layer 112 with a thickness of 10 nm, thereby forming an electron barrier layer.

[0441] Then, a co-evaporation process is performed with 2-(10-phenyl-9-anthrayl)-benzo[b]naphtho[2,3-d]furan (abbreviated as Bnf(II)PhA) represented by the above structural formula (iv) and 3,10-bis[N-(9-phenyl-9H-carbazole-2-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviated as 3,10PCA2Nbf(IV)-02) represented by the above structural formula (v) in a weight ratio of 1:0.015 (=Bnf(II)PhA:3,10PCA2Nbf(IV)-02) and a thickness of 25 nm, thereby forming the light-emitting layer 113.

[0442] Then, after forming an electron transport layer 114 by evaporating 2-{(3',5'-di-tert-butyl)-1,1'-biphenyl-3-yl}-4,6-diphenyl-1,3,5-triazine (abbreviated as mmtBumBPTzn) represented by the above structural formula (xiii) with a thickness of 10 nm, co-evaporation is performed with a weight ratio of mmtBumBPTzn to 6-methyl-8-hydroxyquinoline-lithium (abbreviated as Li-6mq) represented by the above structural formula (vii) of 1:1 (=mmtBumBPTzn:Li-6mq).

[0443] After forming the electron transport layer 114, lithium fluoride is deposited with a thickness of 1 nm to form the electron injection layer 115, and finally aluminum is evaporated with a thickness of 200 nm to form the cathode 102, thereby manufacturing the light-emitting device 5. Note that the light-emitting device in this embodiment is a bottom-emitting element from the anode 101 side.

[0444] (Manufacturing method of light-emitting device 6) Except for the following points, the manufacturing conditions of the light-emitting device 6 are the same as those of the light-emitting device 5: 6-tert-butyl-8-hydroxyquinoline-lithium (abbreviated as: Li-6tBuq) represented by the above structural formula (xiii) is used instead of Li-6mq.

[0445] The ordinary refractive index of Li-6tBuq in the entire blue emission region (above 455 nm and below 465 nm) is above 1.63 and below 1.64, that is, in the range of 1.45 to 1.70. Moreover, the ordinary refractive index at 633 nm is 1.59, that is, in the range of 1.40 and below 1.65. Therefore, Li-6tBuq is a material with a low refractive index.

[0446] The following shows the component structure of light-emitting device 5 and light-emitting device 6.

[0447] [Table 13]

[0448] In a nitrogen-atmospheric glove box, the light-emitting devices 5 and 6 were sealed using a glass substrate in a manner that prevented them from being exposed to the atmosphere (UV-curable sealing material was applied around the components, and UV radiation was applied to the sealing material without irradiating the light-emitting devices, followed by heat treatment at 80°C under atmospheric pressure for 1 hour). The initial characteristics of these light-emitting devices were then measured. Note that no special treatment to improve light extraction efficiency was performed on the sealed glass substrate.

[0449] Figure 48 shows the luminance-current density characteristics of light-emitting devices 5 and 6; Figure 49 shows the current efficiency-luminance characteristics; Figure 50 shows the luminance-voltage characteristics; Figure 51 shows the current density-voltage characteristics; Figure 52 shows the external quantum efficiency-luminance characteristics; Figure 53 shows the power efficiency-luminance characteristics; and Figure 54 shows the emission spectrum. Furthermore, Table 14 shows the main characteristics of light-emitting devices 5 and 6 near 1000 cd / m². Note that luminance, CIE chromaticity, and emission spectrum were measured at room temperature using a spectroradiometer (Topcon SR-UL1R).

[0450] [Table 14]

[0451] As shown in Figures 48 to 54 and Table 14, both light-emitting devices 5 and 6, which are embodiments of the present invention, are light-emitting devices with excellent characteristics. Furthermore, it is evident that, in particular, the light-emitting device 5 using Li-6mq exhibits better external quantum efficiency and a particularly low driving voltage compared to the light-emitting device 6. Therefore, the light-emitting device 5 is a light-emitting device with good current efficiency and power efficiency. Thus, it is clear that, compared to the case of using metal complexes comprising ligands with an 8-hydroxyquinoline structure having 4 or more carbon atoms at the 6-position, the light-emitting device using metal complexes comprising ligands with an 8-hydroxyquinoline structure having 1 to 3 carbon atoms at the 6-position can be a light-emitting device with a particularly low driving voltage. Example 9

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

[0453] [Chemical Formula 28]

[0454] (Manufacturing method of light-emitting device 7) First, an anode 101 is formed on a glass substrate by sputtering indium tin oxide (ITSO) containing silicon oxide to a thickness of 70 nm. Note that its electrode area is 4 mm² (2 mm × 2 mm).

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

[0456] Then, the substrate is placed in a vacuum evaporation apparatus where the pressure is reduced to about 10⁻⁴ Pa, and vacuum-baked at 170°C for 30 minutes in the heating chamber of the vacuum evaporation apparatus, and then cooled for about 30 minutes.

[0457] Next, the substrate with the anode 101 formed thereon is fixed on a substrate support provided in a vacuum evaporation apparatus with the anode 101 facing downwards. A hole injection layer 111 is formed on the anode 101 by evaporation with N-(1,1'-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9,9-dimethyl-9H-furo-2-amine (abbreviated as: PCBBiF) and electron acceptor material (OCHD-001) in a weight ratio of 1:0.05 (=PCBBiF:OCHD-001) and a thickness of 10 nm.

[0458] PCBBiF is deposited on the hole injection layer 111 with a thickness of 10 nm, and then N,N-bis(4-biphenyl)-6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviated as BBABnf) represented by the above structural formula (xii) is deposited on the hole transport layer 112 with a thickness of 10 nm.

[0459] Next, 3,3'-(naphthalene-1,4-diyl)bis(9-phenyl-9H-carbazole) (abbreviated as PCzN2) represented by the above structural formula (iii) is vapor-deposited on the hole transport layer 112 with a thickness of 10 nm, thereby forming an electron barrier layer.

[0460] Then, a co-evaporation process is performed with 2-(10-phenyl-9-anthrayl)-benzo[b]naphtho[2,3-d]furan (abbreviated as Bnf(II)PhA) represented by the above structural formula (iv) and 3,10-bis[N-(9-phenyl-9H-carbazole-2-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviated as 3,10PCA2Nbf(IV)-02) represented by the above structural formula (v) in a weight ratio of 1:0.015 (=Bnf(II)PhA:3,10PCA2Nbf(IV)-02) and a thickness of 25 nm, thereby forming the light-emitting layer 113.

[0461] Then, after depositing 2-[3'-(9,9-dimethyl-9H-furo-2-yl)-1,1'-biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviated as mFBPTzn) with a thickness of 10 nm to form an electron transport layer, co-depositing is performed with 2-{(3',5'-ditributyl)-1,1'-biphenyl-3-yl}-4,6-diphenyl-1,3,5-triazine (abbreviated as mmtBumBPTzn) with a weight ratio of 1:1 (=mmtBumBPTzn:Li-6mq) and a thickness of 20 nm to form an electron transport layer 114.

[0462] After forming the electron transport layer 114, lithium fluoride is deposited with a thickness of 1 nm to form the electron injection layer 115, and finally aluminum is co-deposited with a thickness of 200 nm to form the cathode 102, thereby manufacturing the light-emitting device 7. Note that the light-emitting device in this embodiment is a bottom-emitting element from the anode 101 side.

[0463] (Manufacturing method of light-emitting device 8) Except for the following points, the manufacturing conditions of the light-emitting device 8 are the same as those of the light-emitting device 7: 6-methyl-8-hydroxyquinoline-sodium (abbreviated as Na-6mq) represented by the above structural formula (xiv) is used instead of Li-6mq.

[0464] (Compare the manufacturing methods of light-emitting device 6) Except for the following points, the manufacturing conditions of the light-emitting device 6 are the same as those of the light-emitting device 7: 8-hydroxyquinoline-lithium (abbreviated as Liq) represented by the above structural formula (ix) is used instead of Li-6mq.

[0465] The following shows the component structures of light-emitting device 7, light-emitting device 8, and comparative light-emitting device 6.

[0466] [Table 15]

[0467] In a nitrogen-atmospheric glove box, the light-emitting devices 7 and 8, as well as the comparative light-emitting device 6, were sealed using glass substrates in a manner that prevented them from being exposed to the atmosphere (UV-curable sealing material was applied around the components, and UV radiation was applied to the sealing material without irradiating the light-emitting devices; the mixture was then heat-treated at 80°C under atmospheric pressure for 1 hour). The initial characteristics of these light-emitting devices were then measured. Note that no special treatment to improve light extraction efficiency was performed on the sealed glass substrates.

[0468] Figure 55 shows the luminance-current density characteristics of light-emitting devices 7, 8, and the comparative light-emitting device 6; Figure 56 shows the current efficiency-luminance characteristics; Figure 57 shows the luminance-voltage characteristics; Figure 58 shows the current density-voltage characteristics; Figure 59 shows the external quantum efficiency-luminance characteristics; Figure 60 shows the power efficiency-luminance characteristics; and Figure 61 shows the emission spectrum. Furthermore, Table 16 shows the main characteristics of light-emitting devices 7, 8, and the comparative light-emitting device 6 near 1000 cd / m². Note that luminance, CIE chromaticity, and emission spectra were measured at room temperature using a spectroradiometer (Topcon SR-UL1R).

[0469] [Table 16]

[0470] As shown in Figures 55 to 61 and Table 16, the light-emitting devices 7, 8, and comparative light-emitting device 6, which are embodiments of the present invention, are all light-emitting devices exhibiting good characteristics. In particular, light-emitting devices 7 and 8, which use a hydroxyquinoline complex of a metal having an alkyl group at the 6-position, have low driving voltages and are therefore light-emitting devices with good current efficiency and power efficiency. Furthermore, it can be seen that, in particular, light-emitting device 8, which utilizes a hydroxyquinoline complex using sodium metal, is a light-emitting device with low driving voltage, good current efficiency, and good power efficiency. Example 10

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

[0472] [Chemical Formula 29]

[0473] (Manufacturing method of light-emitting device 9) First, an anode 101 is formed on a glass substrate by sputtering indium tin oxide (ITSO) containing silicon oxide to a thickness of 55 nm. Note that its electrode area is 4 mm² (2 mm × 2 mm).

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

[0475] Then, the substrate is placed in a vacuum evaporation apparatus where the pressure is reduced to about 10⁻⁴ Pa, and vacuum-baked at 170°C for 30 minutes in the heating chamber of the vacuum evaporation apparatus, and then cooled for about 30 minutes.

[0476] Next, the substrate with the anode 101 formed thereon is fixed on a substrate support provided in a vacuum evaporation apparatus with the anode 101 facing downwards. A hole injection layer 111 is formed on the anode 101 by evaporation with N-(1,1'-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9,9-dimethyl-9H-furo-2-amine (abbreviated as: PCBBiF) and electron acceptor material (OCHD-001) in a weight ratio of 1:0.05 (=PCBBiF:OCHD-001) and a thickness of 10 nm.

[0477] PCBBiF is deposited on the hole injection layer 111 with a thickness of 20 nm, and then N,N-bis[4-(dibenzofuran-4-yl)phenyl]-4-amino-p-terphenyl (abbreviated as: DBfBB1TP) represented by the above structural formula (ii) is deposited with a thickness of 10 nm, thereby forming the hole transport layer 112.

[0478] Next, 3,3'-(naphthalene-1,4-diyl)bis(9-phenyl-9H-carbazole) (abbreviated as PCzN2) represented by the above structural formula (iii) is vapor-deposited on the hole transport layer 112 with a thickness of 10 nm, thereby forming an electron barrier layer.

[0479] Then, a co-evaporation process is performed with 2-(10-phenyl-9-anthrayl)-benzo[b]naphtho[2,3-d]furan (abbreviated as Bnf(II)PhA) represented by the above structural formula (iv) and 3,10-bis[N-(9-phenyl-9H-carbazole-2-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviated as 3,10PCA2Nbf(IV)-02) represented by the above structural formula (v) in a weight ratio of 1:0.015 (=Bnf(II)PhA:3,10PCA2Nbf(IV)-02) and a thickness of 25 nm, thereby forming the light-emitting layer 113.

[0480] Then, after depositing 2-[3'-(9,9-dimethyl-9H-furo-2-yl)-1,1'-biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviated as mFBPTzn) with a thickness of 10 nm to form an electron transport layer, co-depositing is performed with 2-{(3',5'-ditributyl)-1,1'-biphenyl-3-yl}-4,6-diphenyl-1,3,5-triazine (abbreviated as mmtBumBPTzn) with a weight ratio of 0.5:0.5 (=mmtBumBPTzn:Li-mq) and a thickness of 20 nm to form an electron transport layer 114.

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

[0482] (Manufacturing method of light-emitting device 10) Except for the following points, the manufacturing conditions of the light-emitting device 10 are the same as those of the light-emitting device 9: 5-methyl-8-hydroxyquinoline-lithium (abbreviated as Li-5mq) represented by the above structural formula (xvi) is used instead of Li-mq in the electron transport layer 114.

[0483] (Manufacturing method of light-emitting device 11) Except for the following points, the manufacturing conditions of the light-emitting device 11 are the same as those of the light-emitting device 9: 6-methyl-8-hydroxyquinoline-lithium (abbreviated as: Li-6mq) represented by the above structural formula (vii) is used in the electron transport layer 114 instead of Li-mq; the weight ratio is changed to 0.4:0.6 (=mmtBumBPTzn:Li-6mq).

[0484] (Manufacturing method of light-emitting device 12) Except for the following points, the manufacturing conditions of the light-emitting device 12 are the same as those of the light-emitting device 9: 7-methyl-8-hydroxyquinoline-lithium (abbreviated as Li-7mq) represented by the above structural formula (xvii) is used instead of Li-mq in the electron transport layer 114.

[0485] The following shows the component structure of light-emitting devices 9 to 12.

[0486] [Table 17]

[0487] Furthermore, Figure 75 and Table 18 below show the refractive indices of mmtBumBPTzn, Li-mq, Li-5mq, Li-6mq, and Li-7mq, as well as the refractive index at 456 nm. Measurements were performed using a spectroscopic ellipsometry (JA Woollam Japan M-2000U). As the measurement sample, films formed on a quartz substrate with each layer of material at a thickness of approximately 50 nm using vacuum evaporation were used. Figure 75 also shows the ordinary refractive index n, Ordinary, and the extraordinary refractive index n, Extra-ordinary.

[0488] [Table 18]

[0489] As shown in Figure 75 and Table 18, the ordinary refractive index of mmtBumBPTzn across the entire blue emission region (above 455 nm and below 465 nm) is 1.68, which falls within the range of 1.50 to 1.75. Furthermore, the ordinary refractive index at 633 nm is 1.64, which falls within the range of 1.45 to 1.70. Therefore, mmtBumBPTzn is a material with a low refractive index. Similarly, the ordinary refractive index of Li-mq across the entire blue emission region (above 455 nm and below 465 nm) ranges from 1.67 to 1.68, which falls within the range of 1.45 to 1.70. Moreover, the ordinary refractive index at 633 nm is 1.62, which falls within the range of 1.40 to 1.65. Therefore, Li-mq is also a material with a low refractive index. Furthermore, the ordinary refractive index of Li-6mq across its entire blue emission region (above 455nm and below 465nm) is 1.67, falling within the range of 1.45 to 1.70. Its ordinary refractive index at 633nm is 1.61, also falling within the range of 1.40 to 1.65. This indicates that Li-6mq is a material with a low refractive index. Similarly, the ordinary refractive index of Li-7mq across its entire blue emission region (above 455nm and below 465nm) is between 1.68 and 1.69, falling within the range of 1.45 to 1.70. Its ordinary refractive index at 633nm is 1.63, also falling within the range of 1.40 to 1.65. This also indicates that Li-7mq is a material with a low refractive index.

[0490] Here, the ordinary refractive index of Li-5mq at 633 nm is 1.65, that is, in the range of 1.40 to 1.65. The ordinary refractive index of the entire blue emitting region (above 455 nm and below 465 nm) is 1.71 to 1.72, that is, above 1.70. It can be seen that Li-5mq is a material with a higher refractive index than other Li complexes in this embodiment. However, since the refractive index of the electron-transporting organic compound mmtBumBPTzn in the blue emitting region is low, that is, 1.68, and the sum of the refractive indices divided by 2 yields a value of 1.75 or less, the light-emitting device 10 using Li-5mq exhibits very good characteristics.

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

[0492] In a nitrogen-atmospheric glove box, the light-emitting devices 9 to 12 were sealed using a glass substrate in a manner that prevented them from being exposed to the atmosphere (UV-curable sealing material was applied around the components, and UV radiation was applied to the sealing material without irradiating the light-emitting devices, followed by heat treatment 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 treatment to improve light extraction efficiency was performed on the sealed glass substrate.

[0493] Figure 62 shows the luminance-current density characteristics of light-emitting devices 9 to 12, Figure 63 shows the current efficiency-luminance characteristics, Figure 64 shows the luminance-voltage characteristics, Figure 65 shows the current density-voltage characteristics, Figure 66 shows the external quantum efficiency-luminance characteristics, and Figure 67 shows the emission spectrum. Furthermore, Table 19 shows the main characteristics of light-emitting devices 9 to 12 near 1000 cd / m². Note that luminance, CIE chromaticity, and emission spectra were measured at room temperature using a spectroradiometer (Topcon SR-UL1R).

[0494] [Table 19]

[0495] As can be seen from Figures 62 to 67 and Table 19, the light-emitting devices 9 to 12 of the light-emitting device according to one embodiment of the present invention are light-emitting devices with good characteristics.

[0496] Furthermore, as shown in Figure 65, in particular, the light-emitting device 10 using Li-5mq and the light-emitting device 11 using Li-6mq are light-emitting devices with low driving voltage and good characteristics. Thus, by having the methyl group of the 8-hydroxyquinoline complex bonded to lithium located at a position far from the lithium atom or the nitrogen atom of the quinoline backbone, a light-emitting device with low driving voltage can be obtained. Note that Li-5mq tends to have a high refractive index, therefore, it is easier to obtain a light-emitting device with high external quantum efficiency and good characteristics when using Li-6mq, making Li-6mq a very useful material. This embodiment is a light-emitting device with a bottom-emitting structure, but in the case of a light-emitting device with a top-emitting structure, the improvement in external quantum efficiency due to the low refractive index is greater, therefore Li-6mq is particularly suitable for light-emitting devices with a top-emitting structure. Thus, it can be seen that, compared to the case of using metal complexes including ligands with alkyl groups at substitution positions other than 6, light-emitting devices using metal complexes including ligands with alkyl groups having 1 to 3 carbon atoms at the 6 position can be light-emitting devices with good characteristics. Example 11

[0497] <<Synthesis Example 4>> In this embodiment, a method for synthesizing the metal complex 3,6-dimethyl-8-hydroxyquinoline-lithium (hereinafter referred to as Li-3,6dmq) according to one embodiment of the present invention is described. The structural formula of Li-3,6dmq is shown below.

[0498] [Chemical Formula 30]

[0499] <Step 1: Synthesis of 8-hydroxy-3,6-dimethylquinoline> 6.28 g (51.0 mmol) of 6-amino-m-cresol and 175 mL of 1N hydrochloric acid were placed in a three-necked flask and stirred at 100 °C for 30 minutes. A solution of 5.36 g (76.5 mmol) (6.38 mL) of methacrolein and 15 mL of ethanol was added dropwise to the reaction solution over 1 hour, and the mixture was heated at 100 °C for 2 hours. After the reaction was complete, the reaction solution was heated at 100 °C for 2 hours. After adding dichloromethane to the reaction solution, the pH of the aqueous layer was adjusted to pH 7 using a 10% sodium hydroxide aqueous solution and 1N hydrochloric acid. After filtering the solution, the organic layer was removed, and the aqueous layer was extracted with dichloromethane. The extract and organic layer were then mixed, washed with water, and the organic layer was dehydrated with magnesium sulfate and concentrated to obtain a black solid containing the target compound.

[0500] The obtained solid was purified by silicone column chromatography using an developing solvent whose polarity was changed from hexane:ethyl acetate = 10:0 to hexane:ethyl acetate = 10:1. This purification was performed twice, yielding 4.3 g of the target white-yellow solid (yield: 49%). The synthetic scheme for step 1 is shown below.

[0501] [Chemical Formula 31]

[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 dehydrated tetrahydrofuran (THF) were placed in a three-necked flask and stirred. 9.24 mL (9.24 mmol) of 1M lithium butoxide (tBuOLi) THF solution was added to the solution, and the mixture was stirred at room temperature for 96 hours. The reaction solution was concentrated to obtain a yellow solid. Acetonitrile was added to the solid, and the mixture was ultrasonically irradiated and filtered to obtain a yellow solid. This washing operation was performed twice. 1.7 g (100% yield) of a yellow solid of Li-3,6 dmq was obtained as the filter residue.

[0503] The obtained yellow solid (1.65 g) was purified by sublimation at 2.7 Pa and 330 °C for 17 hours using a gradient sublimation method. After sublimation purification, 1.40 g of the target yellow solid was obtained with a recovery rate of 84%.

[0504] Furthermore, methacrolein, used as a starting material in this synthesis, is a cheaper material than acrolein diethyl acetal. Therefore, it can be said that materials with a methyl group at the 3-position of 8-hydroxyquinoline can be formed more cheaply than materials without a methyl group. That is, it can be said that the hydroxyquinoline complexes such as Li-3,6dmq synthesized using 8-hydroxy-3,6-dimethylquinoline, an embodiment of the present invention, are inexpensive and readily available materials, synthesized using methacrolein.

[0505] [Chemical Formula 32]

[0506] The following shows the analytical results of the yellow solid obtained by nuclear magnetic resonance spectroscopy (1H-NMR). From these results, it can be seen that in this embodiment, the organic compound Li-3,6dmq, represented by structural formula (200) of one embodiment of the present invention, was obtained.

[0507] H1 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] Figure 68 shows the absorption and emission spectra of Li-3,6 dmq in a dehydrated acetone solution. The absorption spectrum was measured using a UV-Vis spectrophotometer (V550 model, manufactured by Nippon Spectroscopy Co., Ltd.), and the spectrum shown is the result of subtracting the spectrum measured when only the dehydrated acetone was placed in a quartz dish. The emission spectrum was measured using a fluorescence spectrophotometer (FP-8600, manufactured by Nippon Spectroscopy Co., Ltd.). Li-3,6 dmq in the dehydrated acetone solution exhibits an absorption peak at 376 nm and an emission peak at 533 nm (excitation wavelength 378 nm). Example 12

[0509] In this embodiment, light-emitting devices 13 and 14, which use an organometallic complex of the present invention described in the embodiments, and a comparative light-emitting device 7, which uses a conventional organometallic complex, will be described. The structural formulas of the organic compounds used in this embodiment are shown below.

[0510] [Chemical Formula 33]

[0511] (Manufacturing method of light-emitting device 13) First, an anode 101 is formed on a glass substrate by sputtering indium tin oxide (ITSO) containing silicon oxide to a thickness of 70 nm. Note that its electrode area is 4 mm² (2 mm × 2 mm).

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

[0513] Then, the substrate is placed in a vacuum evaporation apparatus where the pressure is reduced to about 10⁻⁴ Pa, and vacuum-baked at 170°C for 30 minutes in the heating chamber of the vacuum evaporation apparatus, and then cooled for about 30 minutes.

[0514] Next, the substrate with the anode 101 formed thereon is fixed on a substrate support provided in a vacuum evaporation apparatus with the anode 101 facing down. On the anode 101, a co-evaporation method is used to form a hole injection layer 111 by means of N,N-bis(4-biphenyl)-6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviated as BBABnf) and electron acceptor material (OCHD-001) in a weight ratio of 1:0.1 (=BBABnf:OCHD-001) and a thickness of 10 nm.

[0515] BBABnf is deposited on the hole injection layer 111 with a thickness of 20 nm to form the hole transport layer 112.

[0516] Next, 3,3'-(naphthalene-1,4-diyl)bis(9-phenyl-9H-carbazole) (abbreviated as PCzN2) represented by the above structural formula (iii) is vapor-deposited on the hole transport layer 112 with a thickness of 10 nm, thereby forming an electron barrier layer.

[0517] Then, a co-evaporation process is performed with 9-(1-naphthyl)-10-[4-(2-naphthyl)phenyl]anthracene (abbreviated as αN-βNPAnth) represented by the above structural formula (xviii) and 3,10-bis[N-(9-phenyl-9H-carbazole-2-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviated as 3,10PCA2Nbf(IV)-02) represented by the above structural formula (v) in a weight ratio of 1:0.015 (=αN-βNPAnth:3,10PCA2Nbf(IV)-02) and a thickness of 20 nm, thereby forming the luminescent layer 113.

[0518] Then, after depositing a hole barrier layer with a thickness of 10 nm using 2-[3'-(9,9-dimethyl-9H-piro-2-yl)-1,1'-biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviated as mFBPTzn) represented by the above structural formula (vi), co-depositing is performed with a thickness of 20 nm using 2-[3-(2,6-dimethyl-3-pyridyl)-5-(9-phenanthyl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviated as mPn-mDMePyPTzn) represented by the above structural formula (xix) and 6-methyl-8-hydroxyquinoline-lithium (abbreviated as Li-6mq) represented by the above structural formula (vii) in a weight ratio of 1:1 (=mPn-mDMePyPTzn:Li-6mq), thereby forming an electron transport layer 114.

[0519] After forming the electron transport layer 114, an electron injection layer 115 is formed by depositing 8-hydroxyquinoline-lithium (Liq) represented by the above structural formula (ix) with a thickness of 1 nm. Finally, aluminum is deposited with a thickness of 200 nm to form the cathode 102, thereby manufacturing the light-emitting device 13. Note that the light-emitting device in this embodiment is a bottom-emitting element that emits light from the anode 101 side.

[0520] (Manufacturing method of light-emitting device 14) Except for the following points, the manufacturing conditions of the light-emitting device 14 are the same as those of the light-emitting device 13: 3,6-dimethyl-8-hydroxyquinoline-lithium (abbreviated as: Li-3,6dmq) represented by the above structural formula (xx) is used instead of Li-6mq.

[0521] (Compare the manufacturing methods of light-emitting device 7) Except for the following points, the manufacturing conditions of the light-emitting device 7 are the same as those of the light-emitting device 13: 8-hydroxyquinoline-lithium (abbreviated as Liq) represented by the above structural formula (ix) is used instead of Li-6mq.

[0522] The following shows the component structures of light-emitting device 13, light-emitting device 14, and comparative light-emitting device 7.

[0523] [Table 20]

[0524] In a nitrogen-atmospheric glove box, the light-emitting devices 13, 14, and 7 were sealed using glass substrates in a manner that prevented them from being exposed to the atmosphere (UV-curable sealing material was applied around the components, and UV radiation was applied to the sealing material without irradiating the light-emitting devices; the devices were then heat-treated at 80°C under atmospheric pressure for 1 hour). The initial characteristics of these light-emitting devices were then measured. Note that no special treatment to improve light extraction efficiency was applied to the sealed glass substrates.

[0525] Figure 69 shows the luminance-current density characteristics of light-emitting devices 13, 14, and the comparative light-emitting device 7; Figure 70 shows the current efficiency-luminance characteristics; Figure 71 shows the luminance-voltage characteristics; Figure 72 shows the current density-voltage characteristics; Figure 73 shows the external quantum efficiency-luminance characteristics; and Figure 74 shows the emission spectrum. Furthermore, Table 21 shows the main characteristics of light-emitting devices 13, 14, and the comparative light-emitting device 7 near 1000 cd / m². Note that luminance, CIE chromaticity, and emission spectrum were measured at room temperature using a spectroradiometer (Topcon SR-UL1R).

[0526] [Table 21]

[0527] As can be seen from Figures 69 to 74 and Table 21, the light-emitting devices 13 and 14 of the light-emitting device using metal complexes in one embodiment of the present invention are both light-emitting devices with low driving voltage and high luminous efficiency.

[0528] Furthermore, in particular, Li-3,6dmq exhibits high deposition rate stability during vacuum evaporation in component manufacturing, making it a superior material.

[0529] <<Reference Synthesis Example 1>> The synthesis method of 2-{(3',5'-di-tertiary-butyl)-1,1'-biphenyl-3-yl}-4,6-bis(3,5-di-tertiary-butylphenyl)-1,3,5-triazine (abbreviated as: mmtBumBP-dmmtBuPTzn) used in Examples 1 and 2 is described below. The structure of mmtBumBP-dmmtBuPTzn is shown below.

[0530] [Chemical Formula 34]

[0531] <Step 1: Synthesis of 3-bromo-3',5'-di-tertiary butylbiphenyl> 1.0 g (4.3 mmol) of 3,5-di- and tri-butylphenylboronic acid, 1.5 g (5.2 mmol) of 1-bromo-3-iodobenzene, 4.5 mL of 2 mol / L potassium carbonate aqueous solution, 20 mL of toluene, and 3 mL of ethanol were placed in a three-necked flask and degassed by stirring under reduced pressure. Then, 52 mg (0.17 mmol) of tris(2-methylphenyl)phosphine and 10 mg (0.043 mmol) of palladium(II) acetate were added, and the reaction was carried out 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 with magnesium sulfate. The mixture was gravity filtered, and the filtrate was purified by silicone column chromatography (developing solvent: hexane) to give 1.0 g of the desired white solid (yield: 68%). The synthetic scheme for step 1 is shown below.

[0532] [Chemical Formula 35]

[0533] <Step 2: Synthesis of 2-(3',5'-di-tertiary-butylbiphenyl-3-yl)-4,4,5,5,-tetramethyl-1,3,2-dioxaborolane> 1.0 g (2.9 mmol) of 3-bromo-3',5'-di-tert-butylbiphenyl, 0.96 g (3.8 mmol) of bis(pinacol ester) diboron, 0.94 g (9.6 mmol) of potassium acetate, and 30 mL of 1,4-dioxane were placed in a three-necked flask and degassed by stirring under reduced pressure. Then, 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) dichloromethane adduct were added, and the reaction was carried out at 110 °C for 24 hours under a nitrogen atmosphere. After the reaction was complete, the mixture was extracted with toluene, and the resulting organic layer was dried using magnesium sulfate. The mixture was then gravity filtered. The filtrate was purified by silicone column chromatography (developing solvent: toluene) to obtain 0.89 g of the desired yellow oil (yield: 78%). The synthesis scheme for step 2 is shown below.

[0534] [Chemical Formula 36]

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

[0536] [Chemical Formula 37]

[0537] The obtained white solid (0.87 g) was purified by sublimation using a gradient sublimation method. The solid was heated to 230 °C under an argon gas supply at a pressure of 5.8 Pa. After sublimation purification, 0.82 g of the target white solid was obtained with a recovery rate of 95%.

[0538] Furthermore, Figure 36 shows the measurement results of the refractive index of mmtBumBP-dmmtBuPTzn obtained by the above synthesis method using a spectroelastic polarimeter (JA Woollam Japan M-2000U). In the measurement, a film was formed on a quartz substrate with each layer of material at a thickness of approximately 50 nm using a vacuum evaporation method. Figure 36 also shows the ordinary refractive index n, Ordinary, and the extraordinary refractive index n, Extra-ordinary.

[0539] As shown in Figure 36, the ordinary refractive index of mmtBumBP-dmmtBuPTzn in the entire blue emission region (above 455nm and below 465nm) is in the range of above 1.50 and below 1.75, and the ordinary refractive index at 633nm is in the range of above 1.45 and below 1.70. Therefore, mmtBumBP-dmmtBuPTzn is a material with a low refractive index.

[0540] <<Reference Synthesis Example 2>> The synthesis method of 2-{(3',5'-di-tertiary-butyl)-1,1'-biphenyl-3-yl}-4,6-diphenyl-1,3,5-triazine (abbreviated as mmtBumBPTzn) used in Example 5 is described below. The structure of mmtBumBPTzn is shown below.

[0541] [Chemical Formula 38]

[0542] <Step 1: Synthesis of 3-bromo-3',5'-di-tertiary butylbiphenyl> Perform the synthesis in the same manner as step 1 of the 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-diaxopentane> Perform the synthesis in the same manner as step 2 of the reference synthesis example 1.

[0544] <Step 3: Synthesis of mmtBumBPTzn> 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-dihexane (6.2 mmol), 2.4 g (11 mmol) of tripotassium phosphate, 10 mL of water, 28 mL of toluene, and 10 mL of 1,4-dioxane were placed in a three-necked flask and degassed by stirring under reduced pressure. Then, 13 mg (0.056 mmol) of palladium(II) acetate and 34 mg (0.11 mmol) of tris(2-methylphenyl)phosphine were added, and the mixture was heated under reflux for 14 hours under a nitrogen atmosphere. After the reaction was complete, the mixture was extracted with ethyl acetate, and the water in the resulting organic layer was removed using magnesium sulfate. The filtrate obtained by gravity filtration of the mixture was purified by silicone column chromatography (the ratio of chloroform:hexane was changed from 1:5 to 1:3 as the developing solvent), and then recrystallized with hexane to obtain 2.0 g of the desired white solid (yield: 51%). The synthetic scheme of step 3 is shown in equation (b-1) below.

[0545] [Chemical Formula 39]

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

[0547] The following shows the analytical results of the white solid obtained in step 3 above using nuclear magnetic resonance spectroscopy (1H-NMR). From these results, it can be seen that in this embodiment, mmtBumBPTzn was obtained.

[0548] H1 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] Additionally, Figure 44 shows the refractive index measurement results of mmtBumBPTzn using a spectroscopic ellipsometry (JA Woollam Japan M-2000U). In the measurement, a film was formed on a quartz substrate with each layer of material at a thickness of approximately 50 nm using a vacuum evaporation method. Furthermore, Figure 44 shows the ordinary refractive index n, Ordinary, and the extraordinary refractive index n, Extra-ordinary.

[0550] As shown in Figure 44, the ordinary refractive index of mmtBumBPTzn in the entire blue emission region (above 455nm and below 465nm) is 1.68, which is in the range of above 1.50 and below 1.75. The ordinary refractive index at 633nm is 1.64, which is in the range of above 1.45 and below 1.70. Therefore, mmtBumBPTzn is a material with a low refractive index.

[0551] 101: Anode 102: Cathode 103: EL layer 111: Hole Injection Layer 112: Hole Transport Layer 113: Emissive 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:Substrate 401: Anode 403: EL layer 404: Cathode 405: Sealing material 406: Sealing material 407:Sealing substrate 412: Solder pad 420: IC chip 501: Anode 502: Cathode 511: First light-emitting unit 512: Second light-emitting unit 513: Charge Generation Layer 601: Drive Circuit Section (Source Line Drive 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: Component substrate 611: Switching FET 612: Current-controlled FET 613: Anode 614: Insulator 616: EL layer 617: Cathode 618: Light-emitting devices 951:Substrate 952: Electrode 953: Insulation layer 954: Isolation Layer 955: EL layer 956: Electrode 1001:Substrate 1002: Substrate 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: Partition Wall 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: Protective layer 1037: Third interlayer insulating film 1040: Pixels 1041: Drive Circuit Section 1042: Surrounding Area 2001: Outer Shell 2002: Light Source 2100: Robot 2110: Computing device 2101: Illuminance sensor 2102: Microphone 2103: Upper camera 2104: Speaker 2105: Monitor 2106: Lower camera 2107: Obstacle Sensor 2108: Mobile organization 3001: Lighting equipment 5000: Casing 5001: Display Section 5002: Display Section 5003: Speaker 5004: LED lights 5006: Connecting terminal 5007: Sensor 5008: Microphone 5012: Support section 5013: Headphones 5100: Robotic Vacuum Cleaner 5101: Monitor 5102: Camera 5103: Brush 5104: Operation button 5150: Portable Information Terminal 5151: Outer shell 5152: Display area 5153: Bending section 5120: Garbage 5200: Display area 5201: Display area 5202: Display area 5203: Display area 7101: Outer casing 7103: Display Unit 7105: Bracket 7107: Display Unit 7109: Operation Keys 7110: Remote Control 7201: Main Body 7202: Outer shell 7203: Display Unit 7204: Keyboard 7205: External connection port 7206: Pointing device 7210: Second Display Unit 7401: Outer casing 7402: Display Unit 7403: Operation button 7404: External connection port 7405: Speaker 7406: Microphone 9310: Portable Information Terminal 9311: Display panel 9313: Hinges 9315: Outer casing

Claims

1. A light-emitting device, comprising: Anode; Cathode; The EL layer between the anode and the cathode includes a light-emitting layer and an electron transport layer. The light-emitting layer includes a light-emitting material, and the electron transport layer includes an organic compound and an alkali metal complex with electron transport properties. The light emitted by the light-emitting material of the organic compound with electron transport properties has an ordinary refractive index of 1.50 or more and 1.75 or less at the peak wavelength, and the light emitted by the light-emitting material of the alkali metal complex has an ordinary refractive index of 1.45 or more and 1.70 or less at the peak wavelength.

2. The light-emitting device of claim 1, wherein the sum of the ordinary refractive index at the peak wavelength of the light emitted by the light-emitting material of the organic compound having the electron transport property and the ordinary refractive index at the peak wavelength of the light emitted by the light-emitting material of the alkali metal complex, divided by 2, yields a value of 1.50 or more and less than 1.

75.

3. The light-emitting device of claim 1, wherein the ordinary refractive index of the light emitted by the light-emitting material of the electron transport layer at the peak wavelength is 1.50 or more and less than 1.

75.

4. A light-emitting device, comprising: Anode; Cathode; The EL layer between the anode and the cathode includes a light-emitting layer and an electron transport layer. The electron transport layer includes an organic compound and an alkali metal complex with electron transport properties. The ordinary refractive index of the organic compound with electron transport properties is 1.50 or more and 1.75 or less relative to any wavelength of light in the range of 455 nm or more and 465 nm or less. The ordinary refractive index of the alkali metal complex with respect to any wavelength of light in the range of 455 nm or more and 465 nm or less is 1.45 or more and 1.70 or less.

5. The light-emitting device of claim 4, wherein the sum of the ordinary refractive index of the organic compound having the electron transport property with respect to any wavelength of light in the range of 455 nm or more and 465 nm or less, and the ordinary refractive index of the metal complex of the alkali metal with respect to any wavelength of light in the range of 455 nm or more and 465 nm or less, divided by 2, yields a value of 1.50 or more and less than 1.

75.

6. The light-emitting device of claim 4, wherein the ordinary optical refractive index of the electron transport layer relative to any wavelength in the range of 455 nm or more and 465 nm or less is 1.50 or more and less than 1.

75.

7. A light-emitting device, comprising: Anode; Cathode; The EL layer between the anode and the cathode includes a light-emitting layer and an electron transport layer. The electron transport layer includes an organic compound and an alkali metal complex with electron transport properties. The ordinary refractive index of the organic compound with electron transport properties is 1.45 or more and 1.70 or less relative to light with a wavelength of 633 nm. The ordinary refractive index of the alkali metal complex with respect to light with a wavelength of 633 nm is 1.40 or more and 1.65 or less.

8. The light-emitting device of claim 7, wherein the sum of the ordinary refractive index of the organic compound having the electron transport property relative to the light of the 633 nm wavelength and the ordinary refractive index of the metal complex of the alkali metal relative to the light of the 633 nm wavelength, divided by 2, yields a value of 1.45 or more and less than 1.

70.

9. The light-emitting device of claim 7, wherein the ordinary refractive index of the electron transport layer relative to the light of the 633nm wavelength is greater than 1.45 and less than 1.

70.

10. A light-emitting device as claimed in any of claims 1, 4 and 7, wherein the organic compound having the electron transport property and the metal complex of the alkali metal each have an alkyl or cycloalkyl group.

11. The light-emitting device of claim 10, wherein the alkyl group of the organic compound having the electron transport property is either a branched alkyl group or an alkyl group having 3 or 4 carbon atoms, and the alkyl group of the metal complex of the alkali metal is an alkyl group having 1 to 3 carbon atoms.

12. The light-emitting device of claim 10, wherein the alkyl group of the organic compound having the electron transport property is tert-butyl, and the alkyl group of the metal complex of the alkali metal is methyl.

13. The light-emitting device according to any one of claims 1, 4 and 7, wherein the proportion of carbon atoms bonded by sp3 hybrid orbitals in the organic compound having the electron transport property is more than 10% and less than 60% of the total number of carbon atoms.

14. The light-emitting device of any one of claims 1, 4 and 7, wherein the integral value of a signal less than 4 ppm in the 1H-NMR measurement of the organic compound having the electron transport property exceeds the integral value of a signal greater than 4 ppm.

15. A light-emitting device as claimed in any of claims 1, 4 and 7, wherein the organic compound having the electron transport property has a π-electron-deficient heteroaromatic ring backbone.

16. The light-emitting device of claim 15, wherein the π-electron-deficient heteroaryl ring backbone has a triazine backbone or a diazine backbone.

17. A light-emitting device as claimed in any of claims 1, 4 and 7, wherein the metal complex comprises a ligand having an 8-hydroxyquinoline structure.

18. The light-emitting device of claim 17, wherein the metal complex has one or two alkyl groups, and each of the one or two alkyl groups has 1 to 3 carbon atoms.

19. A light-emitting device as claimed in any of claims 1, 4 and 7, wherein the metal complex is a lithium metal complex.

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