Organic electroluminescent device and compounds thereof

Abstract

The purpose of this invention is to prevent internal degradation of organic electroluminescent devices and significantly improve light extraction efficiency by providing a compound that absorbs sunlight with wavelengths from 400 nm to 410 nm without affecting the internal materials of the device, and has a high refractive index in the wavelength range of 450 nm to 750 nm. This invention focuses on the excellent stability and durability of thin films of aromatic amine materials, and designs a diamine compound with a high refractive index and a specific benzoazole ring structure for use as a material constituting the capping layer, thereby obtaining an organic electroluminescent device with excellent luminous efficiency.

Description

Technical Field

[0001] This invention relates to compounds suitable for self-emissive elements in various display devices, and more particularly to compounds suitable for organic electroluminescent elements (hereinafter referred to as organic EL elements), and organic EL elements, electronic devices or electronic components using the compounds. Prior Technology

[0002] Organic EL elements are self-emissive, so they are brighter and have better visibility than liquid crystal elements, making them more vivid and thus they have been actively studied.

[0003] In 1987, CWTang et al. of Eastman Kodak developed a multilayer structure element that distributed various functions to each material, thus making organic EL elements using organic materials practical. They achieved high brightness of over 1000 cd / m2 at voltages below 10V by multiplying a phosphor that can transport electrons with an organic material that can transport holes and injecting the charge of both into the phosphor layer to make it emit light (see, for example, Patent Document 1 and Patent Document 2).

[0004] To date, many improvements have been made to make organic EL devices practical. The various functions of the stacked structure have been further subdivided. In the electric field light-emitting element with an anode, hole injection layer, hole transport layer, light-emitting layer, electron transport layer, electron injection layer and cathode arranged in sequence on the substrate, high efficiency and durability have been achieved by the light-emitting element with a bottom light-emitting structure that emits light from the bottom (see, for example: Non-Patent Literature 1).

[0005] In recent years, light-emitting elements with a top-emitting structure, employing a metal with a high work function as the anode and emitting light from above, have gradually begun to be used. In bottom-emitting structures, where light is extracted from the bottom containing the pixel circuitry, the area of ​​the light-emitting portion is limited. In contrast, top-emitting structures allow for a larger light-emitting portion because the pixel circuitry does not block light from the top. In top-emitting structures, the cathode system uses semi-transparent electrodes such as LiF / Al / Ag (e.g., see Non-Patent Document 2), Ca / Mg (e.g., see Non-Patent Document 3), and LiF / MgAg.

[0006] In such a light-emitting element, when light emitted from the light-emitting layer is incident on other films, if it is incident at an angle greater than a certain angle, it will be totally reflected at the interface between the light-emitting layer and other films. Therefore, only a portion of the emitted light can be utilized. In recent years, in order to improve the light extraction efficiency, some have proposed a scheme for a light-emitting element in which a high-refractive-index "capping layer" is placed outside a semi-transparent electrode with a low refractive index (see, for example, Non-Patent Literature 2 and Non-Patent Literature 3).

[0007] Regarding the effect of the capping layer on the light-emitting element of the top-emitting structure, in light-emitting elements using Ir(ppy)3 as the light-emitting material, the current efficiency without the capping layer is 38 cd / A, while the light-emitting element using ZnSe with a film thickness of 60 nm as the capping layer achieves 64 cd / A, representing an efficiency improvement of approximately 1.7 times. Furthermore, it has been shown that the maximum transmittance of the semi-transparent electrode and the capping layer does not necessarily coincide with the maximum efficiency; the maximum light extraction efficiency is determined by the interference effect (see, for example, Non-Patent Literature 3).

[0008] Previously, proposals have suggested using high-precision metal masks during the formation of the cover layer. However, under high-temperature conditions, the metal mask can strain due to heat, leading to a decrease in alignment accuracy. Since ZnSe has a melting point exceeding 1100°C (see, for example, Non-Patent Document 3), a high-precision metal mask cannot be deposited in the correct position, potentially affecting the light-emitting element itself. Furthermore, film formation using sputtering methods can also impact the light-emitting element; therefore, cover layers made from inorganic materials are unsuitable.

[0009] Furthermore, when using aluminum (8-hydroxyquinoline) (Alq 3) as a capping layer to adjust the refractive index (e.g., refer to Non-Patent Document 2), although Alq 3 is known to be an organic EL material commonly used as a green light-emitting material or an electron transport material, it has weak absorption around 450 nm when used in blue light-emitting materials. Therefore, in the case of blue light-emitting elements, there will be problems of decreased color purity and reduced light extraction efficiency.

[0010] Furthermore, components made with conventional cover layers will allow sunlight with wavelengths of 400nm to 410nm to pass through, affecting the materials inside the component and causing problems such as decreased color purity and reduced light extraction efficiency.

[0011] In order to improve the characteristics of organic EL devices, especially to absorb sunlight with wavelengths of 400nm to 410nm without affecting the internal materials of the device, and to significantly improve the light extraction efficiency, materials with high absorption coefficient, high refractive index, and excellent thin film stability and durability are sought for the cover layer. [Previous Technical Documents] [Patent Literature]

[0012] [Patent Document 1] Japanese Patent Application Publication No. 8-048656 [Patent Document 2] Japanese Patent No. 3194657 [Patent Document 3] International Publication No. 2014 / 009310 [Patent Document 4] International Publication No. 2013 / 038627 [Non-patent literature]

[0013] [Non-Patent Literature 1] Proceedings of the 9th Workshop of the Chinese Society of Applied Physics, pp. 55-61 (2001) [Non-Patent Literature 2] Appl. Phys. Let., 78, 544 (2001) [Non-Patent Literature 3] Appl. Phys. Let., 82, 466 (2003) [Non-Patent Literature 4] SYNLETT., 7, 1172 (2009) [Non-Patent Literature 5] J.Org.Chcm., 60, 7508 (1995) [Non-Patent Literature 6] Synth. Commun., 11, 513 (1981) [Non-Patent Literature 7] Appl. Phys. Lett., 98, 083302 (2011) Summary of the Invention

[0014] (The problem the invention aims to solve)

[0015] The purpose of this invention is to improve the characteristics of organic EL devices, particularly in absorbing sunlight with wavelengths from 400 nm to 410 nm without affecting the internal materials of the device. This invention provides a compound with a high refractive index in the wavelength range of 450 nm to 750 nm, and provides an organic EL device using this compound as a cover layer material for the organic EL device, thereby preventing internal degradation of the device and significantly improving light extraction efficiency.

[0016] In other words, regarding the physical properties of the material suitable for the cover layer of organic EL elements, the following can be listed: (1) high light absorption coefficient, (2) high refractive index, (3) vapor deposition capability, (4) stable thin film state, and (5) high glass transition temperature. Furthermore, the characteristics of the organic EL element provided by the present invention can be listed as: (1) absorption of light with wavelengths from 400 nm to 410 nm, (2) high light extraction efficiency, (3) no decrease in color purity, (4) light transmission without changes over time, and (5) long lifespan. (Methods for solving problems)

[0017] In order to achieve the above objectives, the inventors of this case focused on the excellent thin film stability and durability of aromatic amine materials. They designed a material with high absorbance in the wavelength range of 400 nm to 410 nm in the absorption spectrum of a diamine compound with a high refractive index and a specific benzoazole ring structure at a concentration of 10⁻⁵ mol / L. They then fabricated an organic EL element that used it as a material constituting a capping layer and diligently evaluated the characteristics of the element, resulting in the completion of this invention.

[0018] That is, according to the present invention, the following diamine compounds having an azabenzothazole ring structure can be provided, as well as organic EL elements, electronic devices or electronic components using such compounds.

[0019] 1) A diamine compound having an azirconazole ring structure, having the azirconazole ring structure represented by the following general formula (a-1),

[0020] [Chemistry 1] (a-1)

[0021] In the aforementioned general formula (a-1), A, B, C, and D may be the same or different from each other, representing a monovalent group with an azirconazole group, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group as represented by the following structural formula (b-1). However, at least one of A, B, C, or D is a monovalent group with an azirconazole group as represented by the following structural formula (b-1). L represents a divalent group with an substituted or unsubstituted aromatic hydrocarbon group, a divalent group with a substituted or unsubstituted aromatic heterocyclic group, or a divalent group with a substituted or unsubstituted condensed polycyclic aromatic group, and may also bond to A, B, C, or D through a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring. m represents an integer from 1 to 3. When m is an integer of 2 or more, multiple Ls may be the same or different from each other.

[0022] [Chemistry 2] (b-1)

[0023] In the aforementioned structural formula (b-1), each Y can be the same or different, representing CR or a nitrogen atom. However, among the multiple Ys, at least one Y is a nitrogen atom. R can be the same as or different from each other. Among the multiple R, any one of them is a linking group to the bonding site of the aforementioned general formula (a-1) and represents a hydrogen atom, a deuterium atom, a chlorine atom, a cyano group, a nitro group, a trimethylsilyl group, a triphenylsilyl group, a straight-chain or branched alkyl group with 1 to 6 carbon atoms that may have a substituent, a cycloalkyl group with 5 to 10 carbon atoms that may have a substituent, a straight-chain or branched alkenyl group with 2 to 6 carbon atoms that may have a substituent, a straight-chain or branched alkoxy group with 1 to 6 carbon atoms that may have a substituent, a cycloalkoxy group with 5 to 10 carbon atoms that may have a substituent, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group.

[0024] 2) A diamine compound having an azabenzothiazolium ring structure as described in 1) above, wherein A, B, C, and D in the aforementioned general formula (a-1) are, as represented by the aforementioned structural formula (b-1), a monovalent group having an azabenzothiazolium group, a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted naphthyl group, a substituted or unsubstituted phenanthyl group, a substituted or unsubstituted carbazolyl group, a substituted or unsubstituted benzofuranyl group, a substituted or unsubstituted benzothiophene group, a substituted or unsubstituted indolyl group, a substituted or unsubstituted benzimidazolyl group, a substituted or unsubstituted imidazopyridyl group, a substituted or unsubstituted benzobenzothiazolyl group, a substituted or unsubstituted dibenzofuranyl group, or a substituted or unsubstituted dibenzothiophene group.

[0025] 3) A diamine compound having an azabenzothazole ring structure as described in 1) or 2) above, wherein the structural formula (b-1) is the following structural formula (b-2) or structural formula (b-3).

[0026] [Chemistry 3] (b-2)

[0027] [Chemistry 4] (b-3)

[0028] In the aforementioned structural formula (b-2) or structural formula (b-3), R is defined as in the aforementioned structural formula (b-1).

[0029] 4) A diamine compound having an azabenzothazole ring structure as described in any of 1) to 3) above, wherein L in the aforementioned general formula (a-1) is a substituted or unsubstituted pentenylphenyl, a substituted or unsubstituted pentenylbiphenyl, or a substituted or unsubstituted pentenylnaphthyl.

[0030] 5) A diamine compound having an azabenzothazole ring structure as described in any of 1) to 4) above, wherein m in the aforementioned general formula (a-1) is 1 or 2.

[0031] 6) A diamine compound having an azabenzothazole ring structure as described in any of 1) to 5) above, wherein the aforementioned structural formula (b-1) is either structural formula (b-4) or structural formula (b-5).

[0032] [Chemistry 5] (b-4)

[0033] [Chemistry 6] (b-5)

[0034] In the aforementioned structural formula (b-4) or structural formula (b-5), R is defined as in the aforementioned structural formula (b-1).

[0035] 7) A diamine compound having an azabenzothazole ring structure as described in any of 1) to 6) above, wherein only one of A, B, C, or D in the aforementioned general formula (a-1) is the aforementioned structural formula (b-4) or the aforementioned structural formula (b-5).

[0036] 8) A diamine compound having an azabenzothazole ring structure as described in any of 1) to 6) above, wherein any two of A, B, C or D in the aforementioned general formula (a-1) are the aforementioned structural formula (b-4) or the aforementioned structural formula (b-5).

[0037] 9) A diamine compound having an azabenzothazole ring structure as described in any of 1) to 6) above, wherein A and B in the aforementioned general formula (a-1) are the aforementioned structural formula (b-4) or the aforementioned structural formula (b-5).

[0038] 10) A diamine compound having an azabenzothazole ring structure as described in any of 1) to 6) above, wherein A and C in the aforementioned general formula (a-1) are the aforementioned structural formula (b-4) or the aforementioned structural formula (b-5).

[0039] 11) An organic electroluminescent element, comprising at least an anode electrode, a hole transport layer, a light-emitting layer, an electron transport layer, a cathode electrode, and a capping layer in sequence, characterized in that: The capping layer contains a diamine compound having an azabenzothazole ring structure, as described in any one of 1) to 10) above.

[0040] 12) The organic electroluminescent element as described in 11) above, wherein the attenuation coefficient of the aforementioned cover layer is 0.2 or more in the wavelength range of 400 nm to 410 nm, and the absorbance in the wavelength range of 400 nm to 410 nm in the absorption spectrum of the aforementioned diamine compound having a benzo[a]azole ring structure at a concentration of 10⁻⁵ mol / L is 0.2 or more.

[0041] 13) An organic electroluminescent element as described in 11) or 12) above, wherein the refractive index of the cover layer is 1.85 or higher in the range of 450 nm to 750 nm for the wavelength of light transmitted through the cover layer.

[0042] 14) An organic electroluminescent element as described in any one of 11) to 13) above, wherein when the cover layer is composed of a stack or mixed layer containing two or more compounds, at least one of the compounds is the aforementioned diamine compound having an azabenzothazole ring structure.

[0043] 15) An electronic device or electronic component having a pair of electrodes and at least one organic layer sandwiched therebetween. Its characteristics are: The aforementioned organic layer contains a diamine compound having an azabenzothazole ring structure as described in any one of 1) to 10) above.

[0044] In general formula (a-1) and structural formula (b-1), A, B, C, D, and R represent "substituted or unsubstituted aromatic hydrocarbon groups," "substituted or unsubstituted aromatic heterocyclic groups," or "substituted or unsubstituted condensed polycyclic aromatic groups." Specifically, these can be derived from phenyl, biphenyl, triphenyl, naphthyl, anthracene, phenanthrene, fumonisinyl, spirofumonisinyl, indole, pyrene, perylene, propylene, etc. Dienyl, triphenylene, pyridyl, pyrimidinyl, triterpenoid, furanyl, pyrrolithyl, thiophene, quinolinyl, isoquinolinyl, benzofuranyl, benzothiophene, indolyl, carbazolyl, imidazopyridyl, benzoxazolyl, benzothiazolyl, quinolinel, benzoimidazolyl, pyrazolyl, dibenzofuranyl, dibenzothiophene, acetylinyl, phenazinyl, acridinel, and carbazolyl are all acceptable choices. In addition, aryl groups with 6 to 30 carbon atoms or heteroaryl groups with 2 to 20 carbon atoms can be selected.

[0045] In general formula (a-1), L represents "a divalent group of a substituted or unsubstituted aromatic hydrocarbon", "a divalent group of a substituted or unsubstituted aromatic heterocycle", or "a divalent group of a substituted or unsubstituted condensed polycyclic aromatic hydrocarbon". Specifically, examples include benzene, biphenyl, terphenyl, naphthalene, anthracene, phenanthrene, fentanyl, pyridine, pyrimidine, quinoline, benzofuran, benzothiophene, benzo[a]azole, benzo[a]thiazole, dibenzofuran, dibenzothiophene, phenanthrene, pyridine, pyrimidine, quinoline, benzo[a]furan, benzo[a]thiophene, benzo[a]azole, dibenzo[a]thiazole, dibenzo[a]furan, dibenzo[a]thiphene, phenanthrene, etc. Furthermore, in the general formula (a-1), L represents "a divalent group of a substituted or unsubstituted aromatic hydrocarbon", "a divalent group of a substituted or unsubstituted aromatic heterocycle", or "a divalent group of a substituted or unsubstituted condensed polycyclic aromatic hydrocarbon". The divalent group of "aromatic hydrocarbon", "a divalent group of an aromatic heterocycle", or "a divalent group of a condensed polycyclic aromatic hydrocarbon" represents a divalent group formed by removing two hydrogen atoms from the aforementioned "aromatic hydrocarbon", "aromatic heterocycle", or "condensed polycyclic aromatic hydrocarbon".

[0046] In structural formula (b-1), R represents "a straight-chain or branched alkyl group having 1 to 6 carbon atoms that may also have substituents", "a cycloalkyl group having 5 to 10 carbon atoms that may also have substituents", "a straight-chain or branched alkenyl group having 2 to 6 carbon atoms that may also have substituents", "a straight-chain or branched alkoxy group having 1 to 6 carbon atoms that may also have substituents", "a cycloalkoxy group having 5 to 10 carbon atoms that may also have substituents", or "a substituted or unsubstituted aryloxy group", specifically "a straight-chain or branched alkyl group having 1 to 6 carbon atoms", "a cycloalkyl group having 5 to 10 carbon atoms", etc. "Alkenyl groups with 2 to 6 carbon atoms in a straight-chain or branched manner", "alkoxy groups with 1 to 6 carbon atoms in a straight-chain or branched manner", "cycloalkoxy groups with 5 to 10 carbon atoms", or "aryloxy groups", specifically including methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tributyl, n-pentyl, isopentyl, neopentyl, n-hexyl, cyclopentyl, cyclohexyl, 1-adamantyl, 2-adamantyl, vinyl, allyl, isopropenyl, 2-butenyl, methoxy, ethoxy, n-propoxy, cyclopentoxy, cyclohexyloxy, 1-adamantyloxy, phenoxy, tolyloxy, and biphenoxy, etc.

[0047] The A, B, C, D, L, and R in general formula (a-1) and structural formula (b-1) represent: "substituted aromatic hydrocarbon group", "substituted aromatic heterocyclic group", "substituted condensed polycyclic aromatic group", "divalent group of an aromatic hydrocarbon with a substituent", "divalent group of an aromatic heterocyclic group with a substituent", "divalent group of a condensed polycyclic aromatic group with a substituent", "linear or branched alkyl group with 1 to 6 carbon atoms with a substituent", and "carbon group with a substituent". The "substituents" in the following categories include "cycloalkyl group with 5 to 10 atoms", "alkenyl group with 2 to 6 carbon atoms in a straight-chain or branched manner having a substituent", "alkoxy group with 1 to 6 carbon atoms in a straight-chain or branched manner having a substituent", "cycloalkoxy group with 5 to 10 carbon atoms having a substituent", or "substituted aryloxy group". Specifically, examples include deuterium, cyano, nitro; halogen atoms such as fluorine, chlorine, bromine, and iodine; and silyl groups such as trimethylsilyl and triphenylsilyl. Alkyl groups with 1-6 carbon atoms, such as methyl, ethyl, and propyl; alkoxy groups with 1-6 carbon atoms, such as methoxy, ethoxy, and propoxy; alkenyl groups, such as vinyl and allyl; aryloxy groups, such as phenoxy and tolyloxy; arylalkoxy groups, such as benzyloxy and phenethoxy; aromatic hydrocarbon groups or condensed groups, such as phenyl, biphenyl, triphenyl, naphthyl, anthracene, phenanthrene, piracene, spiropiracene, indole, pyrene, perylene, propadienylpiracene, and triphenylene. Polycyclic aromatic groups include pyridyl, thiophene, furanyl, pyrroleyl, quinolinyl, isoquinolinyl, benzofuranyl, benzothiophene, indolyl, carbazoyl, imidazopyridyl, benzoxazoyl, benzothiazoyl, quinophene, benzimidazolyl, pyrazolyl, dibenzofuranyl, dibenzothiophene, carbazoyl, etc. Other examples include aryl groups with 6 to 30 carbon atoms or heteroaryl groups with 2 to 20 carbon atoms. These substituents can be further substituted with the substituents exemplified above. Furthermore, these substituents and substituted aromatic rings, or multiple substituents on the same aromatic ring, can be bonded to each other through single bonds, substituted or unsubstituted methylene groups, oxygen atoms, or sulfur atoms to form a ring.

[0048] In the amine compound having an azabenzothazole ring structure represented by the general formula (a-1) of the present invention, L is preferably a divalent group (extrinyl) formed by removing two hydrogen atoms from substituted or unsubstituted benzene, a divalent group (extrinyl-biphenyl) formed by removing two hydrogen atoms from substituted or unsubstituted biphenyl, or a divalent group (extrinyl-naphthyl) formed by removing two hydrogen atoms from substituted or unsubstituted naphthalene. It is even more ideal to have a divalent group (extrinyl) formed by removing two hydrogen atoms from unsubstituted benzene, a divalent group (extrinyl-biphenyl) formed by removing two hydrogen atoms from unsubstituted biphenyl, or a divalent group (extrinyl-naphthyl) formed by removing two hydrogen atoms from unsubstituted naphthalene.

[0049] In the amine compound having an azabenzothazole ring structure represented by the general formula (a-1) of this invention, L and A, B, C, or D can also be bonded to each other and form a ring through a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom. In the amine compound having an azabenzothazole ring structure represented by the general formula (a-1) of this invention, the number m of L represents an integer from 1 to 3, but m being 1 or 2 is preferred. Furthermore, when m is an integer greater than 2, the multiple Ls may be the same or different from each other. In the amine compounds having an azabenzothiazolium ring structure represented by the general formula (a-1) of the present invention, the "aromatic hydrocarbon group," "aromatic heterocyclic group," or "condensed polycyclic aromatic group" represented by A, B, C, and D as "substituted or unsubstituted aromatic hydrocarbon group," "substituted or unsubstituted aromatic heterocyclic group," or "substituted or unsubstituted condensed polycyclic aromatic group" is preferably phenyl, biphenyl, naphthyl, phenanthryl, carbazolyl, benzofuranyl, benzothiophene, indolyl, benzoimidazolyl, imidazopyridyl, benzothiazolyl, benzothiazolyl, dibenzofuranyl, or dibenzothiophene.

[0050] In the amine compound having an azabenzothazole ring structure represented by the general formula (a-1) of this invention, the Y atoms in the aforementioned structural formula (b-1) may be the same or different, representing CR or a nitrogen atom. However, among the plurality of Y atoms, at least one is a nitrogen atom. In the amine compound having an azabenzothazole ring structure represented by the general formula (a-1) of the present invention, at least one of A, B, C, and D is the aforementioned structural formula (b-1), but it is preferable that only one or any two of A, B, C, and D (e.g., A and B, or A and C) are structural formula (b-1). In the amine compound having an azabenzothazole ring structure represented by the general formula (a-1) of the present invention, the aforementioned structural formula (b-1) is preferably (b-2), (b-3), (b-4), or (b-5), with (b-4) or (b-5) being more preferred.

[0051] In the organic EL element of the present invention, the thickness of the aforementioned cover layer is preferably in the range of 30nm to 120nm, and more preferably in the range of 40nm to 80nm.

[0052] In the organic EL element of the present invention, in the range of 450nm to 750nm for the wavelength of light transmitted through the aforementioned cover layer, the refractive index of the aforementioned cover layer is preferably 1.85 or higher, more preferably 1.88 or higher, and even more preferably 1.90 or higher. In the organic EL element of the present invention, in the wavelength range of light from 400 nm to 410 nm, it is preferable that the attenuation coefficient of the aforementioned cover layer is 0.2 or higher, more preferably 0.4 or higher, and even more preferably 0.8 or higher.

[0053] In the organic EL element of the present invention, for the diamine compound having an azabenzothazole ring structure represented by the aforementioned general formula (a-1) that is suitable for use, the absorbance in the wavelength range of 400 nm to 410 nm of the absorption spectrum at a concentration of 10⁻⁵ mol / L is preferably 0.2 or more, more preferably 0.3 or more, and even more preferably 0.4 or more.

[0054] In the organic EL element of the present invention, the aforementioned cover layer can be made by laminating or mixing two or more different constituent materials. In this case, at least one of the constituent materials is preferably a diamine compound having an azabenzothazole ring structure represented by the general formula (a-1) of the present invention. (Effects of the invention)

[0055] The diamine compound with a benzoxazole ring structure represented by the general formula (a-1) of this invention has (1) a high light absorption coefficient, (2) a high refractive index in the wavelength range of 450nm to 750nm, (3) can be vapor-deposited, (4) has a stable thin film state, and (5) has high heat resistance. Therefore, when it is used as a cover layer on the outside of the transparent or semi-transparent electrode of the organic EL element, by using it as a cover layer with a refractive index higher than that of the electrode, the light extraction efficiency can be greatly improved, the material inside the element can be prevented from deteriorating, and an organic EL element with better brightness, luminous efficiency, power efficiency and lifespan can be obtained. Simple Explanation of the Diagram

[0056] [Figure 1] shows the structures of compounds (1-1) to (1-12) that are diamine compounds having an azabenzothazole ring structure, represented by the general formula (a-1) of the present invention. [Figure 2] shows the structures of compounds (1-13) to (1-23) that are diamine compounds having an azabenzothazole ring structure, represented by the general formula (a-1) of the present invention. [Figure 3] shows the structures of compounds (1-24) to (1-35) that are diamine compounds having an azabenzothazole ring structure, represented by the general formula (a-1) of the present invention. [Figure 4] shows the structures of compounds (1-36) to (1-47) that are diamine compounds having an azabenzothazole ring structure, represented by the general formula (a-1) of the present invention. [Figure 5] shows the structures of compounds (1-48) to (1-57) that are diamine compounds having an azabenzothazole ring structure, represented by the general formula (a-1) of the present invention. [Figure 6] shows the structures of compounds (1-58) to (1-69) that are diamine compounds having an azabenzothazole ring structure, represented by the general formula (a-1) of the present invention. [Figure 7] shows the configuration of the organic EL elements in Examples 10-15 and Comparative Examples 1-2. Implementation

[0057] The diamine compounds having an azirconazole ring structure represented by the general formula (a-1) of this invention are novel compounds. The azirconazole derivatives serving as the main skeleton of these compounds can be synthesized using methods known to the public (e.g., see Non-Patent Document 4). Furthermore, the diamine compounds having an azirconazole ring structure represented by the general formula (a-1) of this invention can be synthesized by performing a coupling reaction between the synthesized azirconazole halide derivative and an aromatic amine using a copper catalyst, palladium catalyst, or the like. Additionally, the diamine compounds having an azirconazole ring structure represented by the general formula (a-1) of this invention can also be synthesized by performing a coupling reaction between the azirconazole halide derivative and a borate ester derivative (e.g., see Non-Patent Documents 5 and 6).

[0058] [Chemistry 7]

[0059] The general formula (a-1) of this invention represents diamine compounds having an azabenzothiazolium ring structure. Specific examples of ideal compounds are shown in Figures 1 to 6, but are not limited to these compounds.

[0060] The purification of diamine compounds with an azabenzothazole ring structure, represented by the general formula (a-1) of this invention, is not particularly limited and can be carried out using known methods used in the purification of organic compounds, such as column chromatography, adsorption purification using silica gel, activated carbon, activated clay, etc., recrystallization purification using solvents, and crystallization purification. Finally, purification can be performed using methods such as sublimation purification. The compounds are identified using NMR analysis. Physical properties are determined by measuring melting point and glass transition point (Tg), refractive index and attenuation coefficient, and absorbance. Melting point is an indicator of vapor deposition properties, glass transition point (Tg) is an indicator of thin film stability, refractive index and attenuation coefficient are indicators related to improved light extraction efficiency, and absorbance is an indicator of color purity and lightfastness.

[0061] Melting point and glass transition point (Tg) can be determined, for example, using a powder with a high-sensitivity differential scanning calorimeter (BRUKER AXS, DSC3100SA).

[0062] The refractive index and attenuation coefficient were measured using a spectrophotometer (FILMETRICS F10-RT-UV) on an 80 nm thin film fabricated on a silicon substrate.

[0063] The absorbance was prepared with toluene solvent at a concentration of 10⁻⁵ mol / L. The absorbance coefficient was prepared with toluene solution at four concentrations: 5.0 × 10⁻⁶ mol / L, 1.0 × 10⁻⁵ mol / L, 1.5 × 10⁻⁵ mol / L, and 2.0 × 10⁻⁵ mol / L. The absorbance was measured using a UV-Vis-NIR spectrophotometer (Japanese Spectrophotometer, V-650).

[0064] The structure of the organic EL element of the present invention, for example, in the case of a top-emitting structure light-emitting element, can be exemplified by: a structure consisting of an anode, a hole transport layer, a light-emitting layer, an electron transport layer, a cathode, and a capping layer in sequence on a glass substrate; a structure with a hole injection layer between the anode and the hole transport layer; a structure with an electron blocking layer between the hole transport layer and the light-emitting layer; a structure with a hole blocking layer between the light-emitting layer and the electron transport layer; and a structure with an electron injection layer between the electron transport layer and the cathode. In such multilayer structures, several organic layers may be omitted or combined, for example, a structure that serves as both a hole injection layer and a hole transport layer, a structure that serves as both a hole transport layer and an electron blocking layer, a structure that serves as both a hole blocking layer and an electron transport layer, or a structure that serves as both an electron transport layer and an electron injection layer, etc. Alternatively, it can be a structure consisting of two or more organic layers with the same function, or a structure consisting of two stacked hole transport layers, two stacked light-emitting layers, two stacked electron transport layers, two stacked cover layers, etc.

[0065] The total thickness of all layers in an organic EL element should ideally be between 200 nm and 750 nm, with approximately 350 nm to 600 nm being more desirable. Furthermore, the thickness of the capping layer is ideally between 30 nm and 120 nm, and even more so between 40 nm and 80 nm. Under these conditions, good light extraction efficiency can be achieved. Moreover, the thickness of the capping layer can be appropriately varied depending on the type of light-emitting material used in the light-emitting element and the thickness of each layer of the organic EL element outside the capping layer.

[0066] The anode of the organic EL element of the present invention can be an electrode material with a high work function, such as ITO or gold.

[0067] For the hole injection layer of the organic EL element of this invention, aromatic amine compounds with two or more triphenylamine structures linked by single bonds or divalent groups without heteroatoms can be used, such as benzidine derivatives and other aromatic amine compounds with two triphenylamine structures linked by single bonds or divalent groups without heteroatoms; luminescent triphenylamine derivatives; and various triphenylamine tetrapolymers are preferred materials. Porphyrin compounds represented by copper phthalocyanine; acceptor heterocyclic compounds such as hexacyanoazines; and coating-type polymer materials can also be used. These materials can be used individually as films, or mixed with other materials to form monolayer films, or in a stacked structure of individually formed layers, mixed layers, or individually formed layers and mixed layers. These materials can be formed into thin films using known methods such as spin coating and inkjet printing, in addition to vapor deposition.

[0068] The hole transport layer of the organic EL element of this invention preferably uses benzidine derivatives such as N,N'-diphenyl-N,N'-di(m-tolyl)benzidine (TPD), N,N'-diphenyl-N,N'-di(α-naphthyl)benzidine (NPD), and N,N,N',N'-tetraphenylbenzidine, or aromatic amine compounds with two triphenylamine structures linked by single bonds or divalent groups without heteroatoms, such as 1,1-bis[4-(di-4-tolyl)phenyl]cyclohexane (TAPC). Aromatic amine compounds with only one triphenylamine structure are also preferred. Furthermore, aromatic amine compounds with three or more triphenylamine structures linked by single bonds or divalent groups without heteroatoms, such as various triphenylamine trimers and tetramers, are preferred. They can be used individually as films, or as monolayers mixed with other materials. They can also be used in stacked structures of individually formed layers, mixed layers, or a combination of individually formed layers and mixed layers. Furthermore, the hole injection and transport layers can use coating-type polymers such as poly(3,4-ethyldioxythiophene) (PEDOT) / poly(styrene sulfonate) (PSS). These materials can be formed into thin films using known methods such as spin coating and inkjet printing, in addition to vapor deposition.

[0069] Furthermore, in the hole injection layer or hole transport layer, it is preferable to further p-dopantize the material commonly used in this layer with bromoaniline hexachloroantimony, axial alkene derivatives (for example, see Patent Document 3). Also, polymeric compounds with structures containing benzidine derivatives such as TPD in the substructure can be used.

[0070] The electron blocking layer of the organic EL element of this invention can use carbazole derivatives such as 4,4',4''-tris(N-carbazole)triphenylamine (TCTA), 9,9-bis[4-(carbazole-9-yl)phenyl]furan, 1,3-bis(carbazole-9-yl)phenyl (mCP), and 2,2-bis(4-carbazole-9-yl-phenyl)adamantane (Ad-Cz); compounds with electron blocking effects, such as 9-[4-(carbazole-9-yl)phenyl]-9-[4-(triphenylsilyl)phenyl]-9H-furan, which have triphenylsilyl and triarylamine structures. They can be used alone as films, or as monolayers mixed with other materials, or in a stacked structure of individual layers, mixed layers, or individual and mixed layers. In addition to vapor deposition, these materials can also be formed into thin films using known methods such as spin coating and inkjet printing.

[0071] The light-emitting layer of the organic EL element of this invention can use metal complexes of quinoline phenol derivatives, primarily Alq 3. In addition, various metal complexes, anthracene derivatives, bis(styrene)benzene derivatives, pyrene derivatives, acetazole derivatives, and poly(p-phenylene)ethylene derivatives can be used. Furthermore, the light-emitting layer can also be composed of a host material and dopant materials. Anthracene derivatives are ideally preferred as the host material. However, besides the aforementioned light-emitting materials, heterocyclic compounds with an indole ring as a condensation ring secondary structure, heterocyclic compounds with a carbazole ring as a condensation ring secondary structure, carbazole derivatives, thiazole derivatives, benzimidazole derivatives, and polydialkylbenzene derivatives can also be used. Furthermore, dopant materials can include quinacridone, coumarin, fluorene, perylene and their derivatives, benzo[a]piperanone derivatives, rhodamine derivatives, and aminostyrene derivatives. They can be used as individual films, or as single-layer films mixed with other materials. They can also be used in a stacked structure of individual film layers, mixed film layers, or individual film layers and mixed film layers.

[0072] Alternatively, phosphorescent materials can be used as luminescent materials. For phosphorescent materials, metal complexes such as iridium and platinum can be used. Green phosphorescent materials such as Ir(ppy)3, blue phosphorescent materials such as Firpic and Fir6, and red phosphorescent materials such as Btp2Ir(acac) can be used. For the host material, for materials with good hole injection and transport properties, carbazole derivatives such as 4,4'-bis(N-carbazolyl)biphenyl (CBP), TCTA, and mCP can be used. For materials with good electron transport properties, p-bis(triphenylsilyl)benzene (UGH2) and 2,2',2''-(1,3,5-epenylphenyl)-tris(1-phenyl-1H-benzimidazole) (TPBI) can be used to fabricate high-performance organic EL devices.

[0073] To avoid concentration extinction, co-evaporation is preferred for doping the host material of phosphorescent luminescent materials in the range of 1 to 30% by weight relative to the total luminescent layer.

[0074] Furthermore, materials that emit delayed fluorescence, such as PIC-TRZ, CC2TA, PXZ-TRZ, and 4CzIPN, can also be used as luminescent materials (see, for example, Non-Patent Literature 7). In addition to vapor deposition, these materials can also be formed into thin films using known methods such as spin coating and inkjet printing.

[0075] For the hole-blocking layer of the organic EL element of the present invention, compounds with hole-blocking properties such as bathocuproine (BCP) and other phenocyanate derivatives, metal complexes of quinolinephenol derivatives such as bis(2-methyl-8-quinolinephenol)-4-phenylphenolate aluminum(III) (BAlq), various rare earth complexes, triazole derivatives, triazine derivatives, pyrimidine derivatives, diazole derivatives, and benzo[a]azole derivatives can be used. These materials can also be used as electron transport layer materials. They can be formed into films individually, or in the form of monolayers mixed with other materials, or in a stacked structure of individually formed layers, mixed layers, or individually formed layers and mixed layers. In addition to vapor deposition, these materials can also be formed into thin films using known methods such as spin coating and inkjet printing.

[0076] For the electron transport layer of the organic EL element of this invention, metal complexes of quinoline phenol derivatives, primarily Alq 3 and BAlq, can be used. In addition, various metal complexes, triazole derivatives, triazine derivatives, pyrimidine derivatives, diazole derivatives, pyridine derivatives, benzimidazole derivatives, benzoxazole derivatives, thiadiazole derivatives, anthracene derivatives, carbodiimide derivatives, quinoline derivatives, pyridoindole derivatives, phenoline derivatives, silole derivatives, etc., can also be used. These materials can be used individually as films, or as monolayers mixed with other materials. They can also be used in stacked structures of individually formed layers, mixed layers, or individually formed layers and mixed layers. Besides vapor deposition, these materials can also be used to form thin films using known methods such as spin coating and inkjet printing.

[0077] For the electron injection layer of the organic EL element of the present invention, alkali metal salts such as lithium fluoride and cesium fluoride, alkaline earth metal salts such as magnesium fluoride, metal complexes of quinoline phenol derivatives such as lithium quinoline phenol, metal oxides such as alumina, or metals such as ytterbium (Yb), samarium (Sm), calcium (Ca), strontium (Sr), and cesium (Cs) can be used. However, in the ideal selection of the electron transport layer and the cathode, these can be omitted.

[0078] Furthermore, in the electron injection layer or electron transport layer, materials commonly used in this layer may be further N-doped with metals such as cesium.

[0079] For the cathode of the organic EL element of the present invention, electrode materials with low work function, such as aluminum, such as magnesium-silver alloys, magnesium-calcium alloys, magnesium-indium alloys, and aluminum-magnesium alloys with even lower work functions, as well as ITO and IZO, can be used as electrode materials. In the top-emitting organic EL element of the present invention, the cathode located in the direction from which light is extracted from the light-emitting element to the outside is preferably transparent or semi-transparent.

[0080] As the capping layer for the organic EL element of the present invention, it is preferable to use an amine compound having an azabenzozazole ring structure represented by the aforementioned general formula (a-1). In the wavelength range of 450 nm to 750 nm for light transmitted through the capping layer, the refractive index of the capping layer using the amine compound having an azabenzozazole ring structure represented by the aforementioned general formula (a-1) as the constituent material is preferably 1.85 or higher, more preferably 1.88 or higher, and even more preferably 1.90 or higher.

[0081] When the amine compound with an azabenzozazole ring structure represented by the general formula (a-1) of the present invention is used as a cover layer for organic EL elements, it can be formed into a film alone, or it can be used as a single layer mixed with other materials to form a film. It can also be used in a stacked structure of layers formed alone, layers mixed together, or layers formed alone and layers mixed together.

[0082] When the capping layer of the organic EL element of the present invention is a stack or a mixture of two or more compounds, it is preferable that the organic EL element, for which at least one compound is a diamine compound having an azabenzothiazolium ring structure represented by the aforementioned general formula (a-1), is also preferred. These materials can be formed individually, or used as a monolayer mixed with other materials, or in a stacked structure of individually formed layers, mixed layers, or a combination of individually formed layers and mixed layers. These materials can be formed into thin films using known methods such as spin coating and inkjet printing, in addition to vapor deposition.

[0083] The refractive index of the capping layer should ideally be higher than that of the adjacent electrodes. That is, the light extraction efficiency of the organic EL element is improved through the capping layer. However, in terms of effectiveness, a higher reflectivity at the interface between the capping layer and the contact material of the capping layer results in greater light interference, thus being more effective. Therefore, it is ideal for the refractive index of the capping layer to be higher than that of the adjacent electrodes; a refractive index of 1.70 or higher is sufficient, but 1.85 or higher is better, 1.88 or higher is even better, and 1.90 or higher is still the best.

[0084] Furthermore, the above description pertains to organic EL elements with a top-emitting structure, but the invention is not limited thereto. It is also applicable to organic EL elements with a bottom-emitting structure and organic EL elements with a dual-emitting structure that emits light from both the top and bottom. In these cases, the electrode located in the direction in which light is extracted from the light-emitting element and directed to the outside should preferably be transparent or semi-transparent. [Example]

[0085] The following describes the embodiments of the present invention in more detail with reference to examples, but the present invention is not limited to the following embodiments as long as it does not depart from this spirit. [Example 1]

[0086] Synthesis of Compound (1-1) Diphenylbenzidine: 6.2 g, 2-(4-bromophenyl)azolo[5,4-b]pyridine: 11.15 g, sodium tributoxide: 3.9 g, palladium(II) acetate: 0.17 g, and tritert-tert-butylphosphine (50% toluene solution): 0.3 g were added to a reaction vessel and refluxed in toluene solution with stirring for one night. After the reaction was completed, the mixture was dispersed and washed, and insoluble matter was removed by filtration. The filtrate was concentrated to obtain a crude product. The crude product was purified by crystallization using a mixed solvent of monochlorobenzene / acetone to obtain a yellow powder of compound (1-1): 5.5 g (yield 41.2%).

[0087] [Chemistry 8] (1-1)

[0088] The structure of the obtained yellow powder was identified using NMR. 1H-NMR (CDCl3) detected the signals of the following 32 hydrogen atoms. δ(ppm)=8.30-8.28(2H), 8.13-8.11(4H), 8.01-7.99(2H), 7.56-7.54(4H), 7.38-7.30(6H), 7.26-7.22(8H), 7.19-7.15(6H). [Example 2]

[0089] Synthesis of Compounds (1-24) Phenyl-(4'-bromobiphenyl-4-yl)-4-(2-benzo(benzo(azo)aniline): 8.0 g, phenyl-4-(azo[5,4-b]pyridin-2-yl)aniline: 4.9 g, sodium tributoxide: 2.2 g, tris(dibenzyl)acetonepalladium(O): 0.4 g, and tritert-tert-butylphosphine (50% toluene solution): 0.4 g were added to a reaction vessel and stirred under reflux in toluene solution for one night. After the reaction was completed, insoluble matter was removed by filtration, and the filtrate was concentrated to obtain a crude product. The crude product was purified by column chromatography (using a mixed solvent of dichloromethane and ethyl acetate) to obtain a yellow powder of compound (1-24): 5.6 g (yield 49.6%).

[0090] [Chemistry 9] (1-24)

[0091] The structure of the obtained yellow powder was identified using NMR. 1H-NMR (CDCl3) detected the signals of the following 33 hydrogen atoms. δ(ppm)=8.29(1H), 8.11(4H), 8.00(1H), 7.73(1H), 7.57-7.54(5H), 7.38-7.30(7H), 7.26-7.21(8H), 7.19-7.16(6H). [Example 3]

[0092] Synthesis of Compounds (1-52) 7.0 g of 1-bromo-4-iodobenzene, 15.6 g of phenyl-(4-azolo[5,4-b]pyridin-2-yl)aniline, 7.1 g of sodium tributoxide, 0.9 g of tris(dibenzyl)acetonepalladium(O), and 0.4 g of tritert-butylphosphine were added to a reaction vessel and refluxed in toluene solution with stirring for one night. After the reaction was completed, the mixture was dispersed and washed to obtain a crude product. The crude product was purified by crystallization using a mixed solvent of monochlorobenzene and acetone to obtain 8.8 g of a yellow powder of compound (1-52) (yield 55.1%).

[0093] [Chemistry 10] (1-52)

[0094] The structure of the obtained yellow powder was identified using NMR. 1H-NMR (CDCl3) detected signals of the following 28 hydrogen atoms. δ(ppm)=8.29(2H), 8.12(4H), 8.00(2H), 7.38(4H), 7.32(2H), 7.23(4H), 7.20-7.13(10H). [Example 4]

[0095] Synthesis of Compounds (1-55) 2,6-Dibromonaphthalene: 5.0 g, phenyl-(4-azolo[5,4-b]pyridin-2-yl)aniline: 11.1 g, sodium tributoxide: 5.1 g, tris(dibenzyl)acetone palladium(O): 0.6 g, and tritert-butylphosphine: 0.3 g were added to a reaction vessel and refluxed in toluene solution with stirring for one night. After the reaction was completed, the mixture was dispersed and washed to obtain a crude product. The crude product was purified by crystallization using a mixed solvent of monochlorobenzene / acetone to obtain a yellow powder of compound (1-55): 7.9 g (yield 53.1%).

[0096] [Chemistry 11] (1-55)

[0097] The structure of the obtained yellow powder was identified using NMR. 1H-NMR (CDCl3) detected signals of the following 30 hydrogen atoms. δ(ppm)=8.30(2H), 8.12(4H), 8.01(2H), 7.64(2H), 7.54(2H), 7.38-7.29(8H), 8.24(4H), 7.19(6H). [Example 5]

[0098] Synthesis of Compounds (1-56) 2,7-Dibromonaphthalene: 6.0 g, phenyl-(4-azolo[5,4-b]pyridin-2-yl)aniline: 13.3 g, sodium tributoxide: 6.1 g, tris(dibenzyl)acetone palladium(O): 0.8 g, tritert-butylphosphine: 0.3 g were added to a reaction vessel and refluxed in toluene solution with stirring for one night. After the reaction was completed, the mixture was dispersed and washed to obtain a crude product. The crude product was purified by crystallization using a mixed solvent of monochlorobenzene / acetone to obtain 8.1 g (yield 55.1%) of a yellow powder of compound (1-56).

[0099] [Chemistry 12] (1-56)

[0100] The structure of the obtained yellow powder was identified using NMR. 1H-NMR (CDCl3) detected signals of the following 30 hydrogen atoms. δ(ppm)=8.29(2H), 8.10(4H), 7.99(2H), 7.75(2H), 7.36-7.26(10H), 7.21(4H), 7.16(6H). [Example 6]

[0101] Synthesis of Compounds (1-57) 7.1 g of 4,4''-diiodo-p-terphenyl, 9.2 g of phenyl-(4-azolo[5,4-b]pyridin-2-yl)aniline, 4.2 g of sodium tert-butoxide, 0.4 g of tris(dibenzyl)acetonepalladium(O), and 0.3 g of tritert-tert-butylphosphine (50% toluene solution) were added to a reaction vessel and stirred under reflux in toluene solution for one night. After the reaction was completed, the mixture was dispersed and washed, and insoluble matter was removed by filtration. The filtrate was concentrated to obtain a crude product. The crude product was purified by column chromatography (using a mixed solvent of dichloromethane and ethyl acetate) to obtain 6.8 g of a yellow powder of compound (1-57) (yield 58.6%).

[0102] [Chemistry 13] (1-57)

[0103] The structure of the obtained yellow powder was identified using NMR. 1H-NMR (CDCl3) detected the signals of the following 36 hydrogen atoms. δ(ppm)=8.30(2H), 8.13(4H), 8.00(2H), 7.68(4H), 7.61(4H), 7.37(4H), 7.32(2H), 7.27-7.22(8H), 7.20-7.17(6H). [Example 7]

[0104] For diamine compounds with an azabenzothiazolium ring structure represented by general formula (a-1), the melting point and glass transition point (Tg) were determined using a high-sensitivity differential scanning calorimeter (BRUKER AXS, DSC3100SA). The results are shown below.

[0105] Melting point glass transfer point (Tg) Compound (1-1) 279.6℃ 136.7℃ Compounds (1-24) did not show a temperature of 131.5℃. Compounds (1-52) 280.6℃ 120.4℃ Compounds (1-55) 301.0℃ 143.1℃ Compounds (1-56) 251.1℃ 141.6℃ Compound (1-57) 300.2℃ 144.3℃

[0106] As shown above, the diamine compound with an azabenzothazole ring structure represented by general formula (a-1) has a glass transition point above 100°C, indicating that the thin film is stable. [Example 8]

[0107] A diamine compound with an azabenzothiazolium ring structure, represented by general formula (a-1), was deposited on a silicon substrate with a film thickness of 80 nm. The refractive index n at wavelengths of 450 nm and 750 nm, and the attenuation coefficient k at wavelengths of 400 nm and 410 nm were measured using a spectrophotometer (FILMETRICS, F10-RT-UV). For comparison, measurements were also performed on the following comparative compound (2-1) and Alq 3 (see, for example, Patent Document 4). The measurement results are summarized in Table 1.

[0108] [Chemistry 14] (2-1)

[0109] [Table 1]

[0110] Thus, for a wavelength of 450 nm, the refractive index of the conventional material Alq 3 and the comparative compound (2-1) is 1.88 and 1.93, respectively, while the diamine compound with an azirconazole ring structure represented by the general formula (a-1) of the present invention exhibits a high value of 2.35 to 2.58. Furthermore, for a wavelength of 750 nm, the refractive index of the conventional material Alq 3 and the comparative compound (2-1) is 1.73 and 1.78, respectively, while the diamine compound with an azirconazole ring structure represented by the general formula (a-1) of the present invention exhibits high values ​​of 1.88 to 1.92 and 1.85 or higher. This demonstrates that by using the diamine compound with an azirconazole ring structure represented by the general formula (a-1) suitable for use in the organic EL element of the present invention as a constituent material of the capping layer, an improvement in the light extraction efficiency of the organic EL element can be expected. Furthermore, regarding the attenuation coefficient for wavelengths of 400nm to 410nm, the known material Alq 3 and comparative compound (2-1) have a coefficient of 0.06 to 0.16, while the diamine compound with an azabenzo[a]azole ring structure represented by the general formula (a-1) of this invention exhibits high values ​​of 0.80 to 1.09 and above 0.2. This demonstrates that a capping layer formed by a diamine compound with an azabenzo[a]azole ring structure represented by the general formula (a-1) suitable for use with the organic EL element of this invention will fully absorb sunlight with wavelengths of 400nm to 410nm without affecting the materials inside the element. [Example 9]

[0111] Diamine compounds with an azabenzothiazolium ring structure, represented by general formula (a-1), were prepared in toluene solution at a concentration of 10⁻⁵ mol / L. The absorbance at wavelengths of 400 nm and 410 nm was measured using a UV-Vis-NIR spectrophotometer (Japanese Spectrophotometer, V-650). For the absorbance coefficient, four concentrations of 5 × 10⁻⁶ mol / L, 1 × 10⁻⁵ mol / L, 1.5 × 10⁻⁵ mol / L, and 2.0 × 10⁻⁵ mol / L were prepared in toluene solution and measured using the same UV-Vis-NIR spectrophotometer (Japanese Spectrophotometer, V-650). The absorbance coefficient was calculated from the calibration curve. For comparison, the absorbance of the comparative compound (2-1) and Alq 3 with the above structural formula was also measured in the same manner. The results are summarized in Table 2.

[0112] [Table 2]

[0113] As mentioned above, for absorbance at wavelengths of 400 nm and 410 nm, the absorbance of conventional material Alq 3 and comparative compound (2-1) is 0.02~0.07, while the diamine compound with an azabenzo[a]azole ring structure represented by the general formula (a-1) of this invention exhibits high values ​​of 0.49~1.42 and above 0.2. This shows that the diamine compound with an azabenzo[a]azole ring structure represented by the general formula (a-1) of this invention can fully absorb sunlight with wavelengths of 400 nm~410 nm. Furthermore, regarding the absorbance coefficient, the diamine compound with an azabenzo[a-1] ring structure represented by the general formula of the present invention has a value of 100,000 or higher, which is more than one digit higher than the absorbance coefficient of the comparative compound. That is, the diamine compound with an azabenzo[a-1] ring structure represented by the general formula of the present invention can absorb sufficient light under the same concentration conditions, and the thicker the film, the more sufficient the light absorption, making it a material with excellent lightfastness. [Example 10]

[0114] As shown in Figure 7, the organic EL element is fabricated by depositing a hole injection layer 3, a hole transport layer 4, a light-emitting layer 5, an electron transport layer 6, an electron injection layer 7, a cathode 8, and a capping layer 9 on a glass substrate 1 after a reflective ITO electrode serving as a transparent anode 2 has been pre-formed on the substrate 1.

[0115] Specifically, on a glass substrate 1, a 50 nm thick ITO film, a 100 nm thick silver alloy reflective film, and a 5 nm thick ITO film are sequentially formed as the metal anode 2. The substrate is then ultrasonically cleaned in isopropanol for 20 minutes, followed by drying on a hot plate heated to 250°C for 10 minutes. After UV ozone treatment for 2 minutes, the ITO-coated glass substrate is mounted in a vacuum evaporation machine, and the pressure is reduced to below 0.001 Pa. Then, using a transparent anode 2 as a coating, an electron acceptor (Acceptor-1) of the following structural formula and a compound (3-1) of the following structural formula are binary deposited at a deposition rate ratio of Acceptor-1:compound (3-1) = 3:97 to form a 10 nm thick film, serving as the hole injection layer 3. On top of this hole injection layer 3, a compound (3-1) of the following structural formula is deposited to a thickness of 140 nm to serve as the hole transport layer 4. On top of the hole transport layer 4, compound (3-2) and compound (3-3) of the following structural formulas are deposited in a binary vapor deposition ratio of 5:95 to form a film with a thickness of 20 nm, serving as the light-emitting layer 5. On top of the light-emitting layer 5, compound (3-4) and compound (3-5) of the following structural formulas are deposited in a binary vapor deposition ratio of 50:50 to form a film with a thickness of 30 nm, serving as the electron transport layer 6. On top of the electron transport layer 6, lithium fluoride is deposited to form a film with a thickness of 1 nm, serving as the electron injection layer 7. On top of the electron injection layer 7, a magnesium-silver alloy is deposited to form a film with a thickness of 12 nm, serving as the cathode 8. Finally, compound (1-1) of Example 1 is deposited to form a film with a thickness of 60 nm, serving as the capping layer 9. The characteristics of the fabricated organic EL element were measured in the atmosphere at room temperature. The results of measuring the light emission characteristics of the fabricated organic EL element after applying a DC voltage are summarized in Table 3.

[0116] [Chemistry 15]

[0117] [Example 11] The compound (1-1) of Example 1, which served as the material for the capping layer 9 in Example 10, was replaced with the compound (1-24) of Example 2, and the organic EL element was fabricated under the same conditions. The characteristics of the fabricated organic EL element were measured at room temperature in atmospheric conditions. The results of measuring the light emission characteristics of the fabricated organic EL element after applying a DC voltage are summarized in Table 3.

[0118] [Example 12] The compound (1-1) of Example 1, which served as the material for the capping layer 9 in Example 10, was replaced with the compound (1-52) of Example 3, and the organic EL element was fabricated under the same conditions. The characteristics of the fabricated organic EL element were measured at room temperature in atmospheric conditions. The results of measuring the light emission characteristics of the fabricated organic EL element after applying a DC voltage are summarized in Table 3.

[0119] [Example 13] The compound (1-1) of Example 1, which served as the material for the capping layer 9 in Example 10, was replaced with the compound (1-55) of Example 4, and the organic EL element was fabricated under the same conditions. The characteristics of the fabricated organic EL element were measured in air at room temperature. The results of measuring the light emission characteristics of the fabricated organic EL element after applying a DC voltage are summarized in Table 3.

[0120] [Example 14] The compound (1-1) of Example 1, which served as the material for the capping layer 9 in Example 10, was replaced with the compound (1-56) of Example 5, and the organic EL element was fabricated under the same conditions. The characteristics of the fabricated organic EL element were measured in air at room temperature. The results of measuring the light emission characteristics of the fabricated organic EL element after applying a DC voltage are summarized in Table 3.

[0121] [Example 15] The compound (1-1) of Example 1, which served as the material for the capping layer 9 in Example 10, was replaced with the compound (1-57) of Example 6, and the organic EL element was fabricated under the same conditions. The characteristics of the fabricated organic EL element were measured in air at room temperature. The results of measuring the light emission characteristics of the fabricated organic EL element after applying a DC voltage are summarized in Table 3.

[0122] [Comparative Example 1] For comparison, the compound (1-1) of Example 1, which served as the material for the capping layer 9 in Example 10, was replaced with Alq 3, and the organic EL element was fabricated under the same conditions. The characteristics of the fabricated organic EL element were measured at room temperature in atmospheric conditions. The results of measuring the light emission characteristics of the fabricated organic EL element after applying a DC voltage are summarized in Table 3.

[0123] [Comparative Example 2] For comparison, the compound (1-1) of Example 1, which served as the material for the capping layer 9 in Example 10, was replaced with the comparative compound (2-1) using the above-described structural formula. Otherwise, organic EL elements were fabricated under the same conditions. The characteristics of the fabricated organic EL elements were measured at room temperature in atmospheric conditions. The results of measuring the luminescence characteristics of the fabricated organic EL elements under a DC voltage are summarized in Table 3.

[0124] The device lifetime was measured using organic EL devices fabricated using Examples 10-15 and Comparative Examples 1-2, and the results are summarized in Table 3. The device lifetime was measured as the time until it decayed to 95% of the initial brightness when driven by a constant current of 10 mA / cm² (95% decay).

[0125] [Table 3]

[0126] As shown in Table 3, for the driving voltage at a current density of 10 mA / cm², the devices using Comparative Examples 1-2 with the comparative compounds were substantially equivalent to those using Examples 10-15 with the compounds of the present invention. However, in terms of brightness, luminous efficiency, power efficiency, and device lifetime, the devices using the compounds of the present invention showed significant improvements compared to those using Comparative Examples 1-2 with the comparative compounds. This result demonstrates that by including a diamine compound with a high refractive index, represented by the general formula (a-1) of the present invention, having a benzoxazole ring structure, in the capping layer, the light extraction efficiency of organic EL devices can be significantly improved. [Industrial Utilization]

[0127] As described above, the diamine compound with an azabenzozazole ring structure represented by the general formula (a-1) of this invention has a high absorption coefficient, high refractive index, and significantly improved light extraction efficiency, and exhibits stable film properties. Therefore, it is an excellent compound suitable for use as a cover layer in organic EL devices. Organic EL devices fabricated using this compound can achieve high efficiency, absorb sunlight without affecting the internal materials of the device, thus improving durability and lightfastness. Furthermore, the use of this compound, which does not absorb in the blue, green, and red wavelength regions, is particularly suitable when displaying images with good color purity, vividness, and brightness. For example, it can be applied to household appliances and lighting.

[0128] 1: Glass substrate 2: Transparent anode 3: Hole Injection Layer 4: Electricity transport layer 5: Emissive layer 6: Electron transport layer 7: Electron Injection Layer 8: Cathode 9: Cover layer

Claims

1. A diamine compound having an azirconazole ring structure, having the azirconazole ring structure represented by the following general formula (a-1), (a-1) In the formula, A, B, C, and D may be the same or different from each other, representing a monovalent group with an azirconazole group, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group as represented by the following structural formula (b-2), provided that at least one of A, B, C, or D is a monovalent group with an azirconazole group as represented by the following structural formula (b-2); L represents a divalent group with an substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group, and may also be bonded to A, B, C, or D through a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring; m represents an integer from 1 to 3. When m is an integer greater than 2, multiple Ls may be the same or different from each other, (b-2) In the formula, R can be the same or different from each other. Among the multiple R, any one of them is a linking group to the bonding site of the general formula (a-1) and represents a hydrogen atom, a deuterium atom, a chlorine atom, a cyano group, a nitro group, a trimethylsilyl group, a triphenylsilyl group, a straight-chain or branched alkyl group with 1 to 6 carbon atoms that may have a substituent, a cycloalkyl group with 5 to 10 carbon atoms that may have a substituent, a straight-chain or branched alkenyl group with 2 to 6 carbon atoms that may have a substituent, a straight-chain or branched alkoxy group with 1 to 6 carbon atoms that may have a substituent, a cycloalkoxy group with 5 to 10 carbon atoms that may have a substituent, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group.

2. A diamine compound having an azirconazole ring structure, as claimed in claim 1, wherein, In the general formula (a-1), A, B, C, and D are the monovalent group with an azabenzo-azolyl group, a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted naphthyl group, a substituted or unsubstituted phenanthyl group, a substituted or unsubstituted carbazole group, a substituted or unsubstituted benzofuranyl group, a substituted or unsubstituted benzothiophenyl group, a substituted or unsubstituted indolyl group, a substituted or unsubstituted benzoimidazolyl group, a substituted or unsubstituted imidazopyridyl group, a substituted or unsubstituted benzobenzo-azolyl group, a substituted or unsubstituted benzothiazolyl group, a substituted or unsubstituted dibenzofuranyl group, or a substituted or unsubstituted dibenzothiaphenyl group, as represented by the structural formula (b-2).

3. A diamine compound having an azirconazole ring structure, as claimed in claim 1 or 2, wherein, In the general formula (a-1), L is a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, or a substituted or unsubstituted naphthyl group.

4. A diamine compound having an azirconazole ring structure, as claimed in claim 1 or 2, wherein, In the general formula (a-1), m is either 1 or 2.

5. A diamine compound having an azirconazole ring structure, as claimed in claim 1 or 2, wherein, The structure (b-2) is the following structure (b-4), where R is defined as in the structure (b-2).

6. A diamine compound having an azirconazole ring structure, as claimed in claim 5, wherein, In the general formula (a-1), only one of A, B, C, or D is a structural formula (b-4).

7. A diamine compound having an azirconazole ring structure, as claimed in claim 5, wherein, Any two of A, B, C, or D in the general formula (a-1) constitute the structural formula (b-4).

8. A diamine compound having an azirconazole ring structure, as claimed in claim 5, wherein, In the general formula (a-1), A and B are structural formulas (b-4).

9. A diamine compound having an azirconazole ring structure as claimed in claim 5, wherein, In the general formula (a-1), A and C are structural formulas (b-4).

10. An organic electroluminescent element having, in sequence, at least an anode electrode, a hole transport layer, a light-emitting layer, an electron transport layer, a cathode electrode, and a capping layer, characterized in that: the capping layer contains a diamine compound having an azabenzothazole ring structure as claimed in any one of claims 1 to 9.

11. The organic electroluminescent element as claimed in claim 10, wherein, The attenuation coefficient of the cover layer is greater than 0.2 in the wavelength range of 400 nm to 410 nm, and the absorbance of the diamine compound having the azabenzothiazolium ring structure in the absorption spectrum at a concentration of 10⁻⁵ mol / L is greater than 0.2 in the wavelength range of 400 nm to 410 nm.

12. The organic electroluminescent element as claimed in claim 10, wherein, The refractive index of the cover layer is greater than 1.85 in the range of 450nm to 750nm for the wavelength of light transmitted through the cover layer.

13. The organic electroluminescent element as claimed in claim 10, wherein, When the capping layer is composed of a stack or mixed layer containing two or more compounds, at least one of the compounds is a diamine compound having an azabenzothazole ring structure.

14. An electronic device having a pair of electrodes and at least one organic layer sandwiched therebetween, characterized in that: the organic layer contains a diamine compound having an azabenzothazole ring structure as claimed in any one of claims 1 to 9.

15. An electronic component having a pair of electrodes and at least one organic layer sandwiched therebetween, characterized in that: the organic layer contains a diamine compound having an azabenzothazole ring structure as claimed in any one of claims 1 to 9.

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