organic electroluminescence element

Abstract

[Problem] The purpose of the present invention is to provide an organic electroluminescent element that has (1) a high absorption coefficient, (2) a high refractive index, (3) a thin film with good stability, (4) excellent durability, and (5) excellent light resistance, and (6) that is provided with a capping layer formed from a non-absorptive material in respective wavelength ranges of blue, green, and red. [Solution] An arylamine-based material having a specific structure in the present invention has excellent thin film stability and durability. Thus, this organic electroluminescence element exhibiting preferably element characteristics is obtained by selecting and using, as a material for forming a capping layer, a material having high absorbance at wavelengths of 400-410 nm in the absorption spectrum for a concentration of 10-5 mol / L of an amine compound having a specific benzazole ring structure and a high refractive index.

Description

[Technical Field]

[0001] The present invention relates to a compound and an element suitable for an organic electroluminescence element (hereinafter abbreviated as organic EL element), which is a self-luminous element suitable for various display devices, and more particularly to an amine compound having a benzoazole ring structure and an organic EL element using the compound. [Background technology]

[0002] Organic EL elements are self-luminous elements, and therefore are brighter and more visible than liquid crystal elements, enabling clearer displays, and therefore have been the subject of active research.

[0003] In 1987, C.W. Tang and his colleagues at Eastman Kodak Company made organic EL devices practical by developing a layered structure element in which various roles are assigned to each material. They layered a phosphor that can transport electrons and an organic material that can transport holes, and by injecting both charges into the phosphor layer to emit light, they achieved a brightness of 1000 cd / m at a voltage of 10 V or less. 2 Such high brightness has become possible (see, for example, Patent Documents 1 and 2).

[0004] To date, many improvements have been made to the practical application of organic EL devices, and the various roles of the laminated structure have been further subdivided. In electroluminescent devices in which an anode, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer, and a cathode are sequentially formed on a substrate, high efficiency and durability have been achieved by light-emitting devices with a bottom emission structure that emits light from the bottom (see, for example, Non-Patent Document 1). 。

[0005] In recent years, light-emitting devices with a top-emission structure that uses a metal with a high work function as the anode and emits light from the top have come into use. In a bottom-emission structure in which light is extracted from the bottom where the pixel circuit is located, the area of ​​the light-emitting section is limited, whereas a light-emitting device with a top-emission structure has the advantage of being able to extract light from the top and not be obstructed by the pixel circuit, allowing for a larger light-emitting section. Light-emitting devices with a top-emission structure use semi-transparent electrodes such as LiF / Al / Ag (see, for example, Non-Patent Document 2), Ca / Mg (see, for example, Non-Patent Document 3), or LiF / MgAg as the cathode.

[0006] In such light-emitting devices, when light emitted from the light-emitting layer is incident on another film at an angle greater than a certain level, it is totally reflected at the interface between the light-emitting layer and the other film. As a result, only a portion of the emitted light can be utilized. In recent years, light-emitting devices have been proposed that provide a high-refractive-index "capping layer" on the outside of a semi-transparent electrode with a low refractive index in order to improve light extraction efficiency (see, for example, Non-Patent Documents 2 and 3).

[0007] The effect of the capping layer on a top-emission light-emitting device using Ir(ppy)3 as the light-emitting material was such that, while the current efficiency was 38 cd / A without the capping layer, the efficiency was improved by approximately 1.7 times to 64 cd / A in a light-emitting device using a 60 nm-thick ZnSe capping layer. It has also been shown that the maximum transmittance of the semi-transparent electrode and capping layer does not necessarily coincide with the maximum efficiency, and that the maximum light extraction efficiency is determined by the interference effect (see, for example, Non-Patent Document 3).

[0008] Conventionally, the use of high-resolution metal masks has been proposed for forming capping layers, but there is a problem in that the metal masks can become distorted by heat when used under high-temperature conditions, resulting in reduced alignment accuracy. ZnSe has a high melting point of 1100°C or higher (see, for example, Non-Patent Document 3), making it impossible to deposit it in the correct position using a high-resolution metal mask, which may affect the light-emitting element itself. Furthermore, even when film formation is performed using the sputtering method, the light-emitting element is affected, so capping layers made of inorganic constituent materials are not suitable for use.

[0009] In addition, when tris(8-hydroxyquinoline)aluminum (hereinafter abbreviated as Alq3) is used as a capping layer to adjust the refractive index (see, for example, Non-Patent Document 2), Alq3 is known as an organic EL material that is generally used as a green emitting material or electron transport material, but because it has weak absorption in the vicinity of 450 nm, which is used as a blue emitting material, there are problems with blue light emitting devices in that it reduces color purity and light extraction efficiency.

[0010] Furthermore, elements made with conventional capping layers allow sunlight with wavelengths of 400 to 410 nm to pass through, affecting the materials inside the element and resulting in reduced color purity and reduced light extraction efficiency.

[0011] To improve the device characteristics of organic EL devices, particularly those that can absorb sunlight with wavelengths of 400 to 410 nm without affecting the materials inside the device, and to significantly improve light extraction efficiency, materials with high absorption coefficients, high refractive indices, and excellent thin-film stability and durability are required as capping layer materials. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Japanese Patent Application Publication No. 8-048656 [Patent Document 2] 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 Document 1] Proceedings of the 9th Seminar of the Japan Society of Applied Physics, pp. 55-61 (2001) [Non-patent document 2] Appl.Phys.Lett.,78,544(2001) [Non-patent document 3] Appl.Phys.Lett.,82,466(2003) [Non-patent document 4] J. Org. Chem., 71, 1802 (2006) [Non-patent document 5] J. Org. Chem., 60, 7508 (1995) [Non-patent document 6] Synth.Commun.,11,513(1981) [Non-Patent Document 7] Appl.Phys.Lett.,98,083302(2011) Summary of the Invention [Problem to be solved by the invention]

[0014] The object of the present invention is to provide an organic EL element having a capping layer made of a material that (1) has a high absorption coefficient for light with wavelengths of 400 nm to 410 nm, (2) a high refractive index, (3) good thin film stability, (4) excellent durability, (5) excellent light resistance, and (6) does not absorb light in the blue, green, and red wavelength regions, in order to improve the element characteristics of the organic EL element, particularly to prevent the absorption of sunlight light with wavelengths of 400 nm to 410 nm from affecting the materials inside the element, and to significantly improve the light extraction efficiency.

[0015] The physical properties of the capping layer material suitable for the present invention are: (1) a high absorption coefficient for light with a wavelength of 400 nm to 410 nm; (2) a high refractive index; (3) the ability to be vapor-deposited; (4) a stable thin film; and (5) a high glass transition temperature. 、 can be given. The physical properties of the organic EL element that are pursued in the present invention are: (1) absorption of sunlight with a wavelength of 400 nm to 410 nm; (2) high light extraction efficiency; (3) no decrease in color purity; (4) light transmission without change over time; and (5) long life. 、 can be given. [Means for solving the problem]

[0016] Therefore, the present inventors have conducted extensive research to achieve the above object. Focusing on the fact that arylamine-based materials have excellent thin film stability and durability, they have selected amine compounds having a specific benzoazole ring structure with a high refractive index, and have investigated the properties of arylamine-based materials with a concentration of 10 -5 Materials with high absorbance in the wavelength range of 400 nm to 410 nm in the absorption spectrum of 1 mol / L were selected, and organic EL devices were fabricated using these materials as materials for the capping layer. The characteristics of the devices were evaluated, leading to the completion of the present invention.

[0017] That is, according to the present invention, the following organic EL device is provided.

[0018] 1) An organic EL device comprising at least an anode electrode, a hole transport layer, an emitting layer, an electron transport layer, a cathode electrode, and a capping layer in this order, wherein the capping layer has a refractive index of 2.00 or more within the wavelength range of 400 nm or more to 500 nm or less of light that transmits through the capping layer, and a refractive index of 1.90 or more within the wavelength range of more than 500 nm to 570 nm or less of light that transmits through the capping layer, and the organic EL device comprises an amine compound having a benzoazole ring structure represented by the following general formula (1):

[0019] [ka] (1)

[0020] (wherein R1 to R8 may be the same or different and are each a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a nitro group, an optionally substituted linear or branched alkyl group of 1 to 6 carbon atoms, an optionally substituted cycloalkyl group of 5 to 10 carbon atoms, an optionally substituted linear or branched alkenyl group of 2 to 6 carbon atoms, an optionally substituted linear or branched alkyloxy group of 1 to 6 carbon atoms, an optionally substituted cycloalkyloxy group of 5 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted fused polycyclic aromatic group, or represents a substituted or unsubstituted aryloxy group, and each group may be bonded to the benzene ring to which it is bonded via a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring, and R1 to R4 or R5 to R8 bonded to the same benzene ring may be bonded to each other via a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring. X and Y may be the same or different and represent an oxygen atom or a sulfur atom. Ar1 to Ar3 may be the same or different and represent 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 fused polycyclic aromatic ring. A is 、 R9 to R represented by the following general formula (2) 15 represents a monovalent group having one of the following as a bonding site:

[0021] [ka] (2)

[0022] (In the formula, R9~R 15may be the same or different and represent a linking group as a binding site, a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a nitro group, a linear or branched alkyl group of 1 to 6 carbon atoms which may have a substituent, a cycloalkyl group of 5 to 10 carbon atoms which may have a substituent, a linear or branched alkenyl group of 2 to 6 carbon atoms which may have a substituent, a linear or branched alkyloxy group of 1 to 6 carbon atoms which may have a substituent, a cycloalkyloxy group of 5 to 10 carbon atoms which 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 fused polycyclic aromatic group, and each group may be bonded to the aromatic ring to which it is bonded via a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring; R 10 and R 11 or R 12 ~R 15 may be bonded to each other via a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring. Z represents an oxygen atom, a sulfur atom, or a nitrogen atom. However, when Z is an oxygen atom or a sulfur atom, Z does not have R9.

[0023] 2) The organic EL device according to 1) above, wherein the amine compound having a benzazole ring structure is represented by the following general formula (1a):

[0024] [ka] (1a)

[0025] (In the formula, R1 to R8, X, Y, and A are as defined in the general formula (1) above.)

[0026] 3) The organic EL device according to 1) or 2) above, wherein in the general formula (1) or (1a), all of R1 to R8 are hydrogen atoms.

[0027] 4) The organic EL device according to any one of 1) to 3) above, wherein the capping layer has an extinction coefficient of 0.40 or more within a wavelength range of 400 nm or more and 410 nm or less.

[0028] 5) The organic EL device according to 1) or 2) above, wherein in the general formula (1) or (1a), X and Y are oxygen atoms. 6) The organic EL device according to 1) or 2) above, wherein in the general formula (1) or (1a), X and Y are sulfur atoms. 7) The organic EL device according to 1) or 2) above, wherein in the general formula (2), Z is an oxygen atom. 8) The organic EL device according to 1) or 2) above, wherein in the general formula (2), Z is a sulfur atom. 9) The organic EL device according to 1) or 2) above, wherein in the general formula (2), Z is a nitrogen atom. 10) The organic EL device according to 1) or 2) above, wherein in the general formula (2), R9 is a linking group serving as a bonding site. 11) In the general formula (2), R 10 The organic EL device according to 1) or 2) above, wherein is a linking group serving as a bonding site. 12) In the general formula (2), R 13 The organic EL device according to 1) or 2) above, wherein is a linking group serving as a bonding site. 13) The organic EL device according to 9) above, wherein in the general formula (2), R9 is a linking group serving as a bonding site. 14) An amine compound having a benzazole ring structure represented by the general formula (1) or (1a), which has a refractive index of 2.00 or more in the light wavelength range of 400 nm or more and 500 nm or less, and a refractive index of 1.90 or more in the light wavelength range of more than 500 nm and 570 nm or less. 、 A method used for the capping layer of organic EL devices.

[0029] 15) A method for producing an organic EL element according to any one of 1) to 4) above, comprising forming a capping layer of the organic EL element using an amine compound having a benzazole ring structure represented by the following general formula (1) or general formula (1a):

[0030] [ka] (1)

[0031] (wherein R1 to R8 may be the same or different and are each a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a nitro group, an optionally substituted linear or branched alkyl group of 1 to 6 carbon atoms, an optionally substituted cycloalkyl group of 5 to 10 carbon atoms, an optionally substituted linear or branched alkenyl group of 2 to 6 carbon atoms, an optionally substituted linear or branched alkyloxy group of 1 to 6 carbon atoms, an optionally substituted cycloalkyloxy group of 5 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted fused polycyclic aromatic group, or represents a substituted or unsubstituted aryloxy group, and each group may be bonded to the benzene ring to which it is bonded via a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring, and R1 to R4 or R5 to R8 bonded to the same benzene ring may be bonded to each other via a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring. X and Y may be the same or different and represent an oxygen atom or a sulfur atom. Ar1 to Ar3 may be the same or different and represent 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 fused polycyclic aromatic ring. A is 、 R9 to R represented by the following general formula (2) 15 represents a monovalent group having one of the following as a bonding site:

[0032] [ka] (2)

[0033] (In the formula, R9~R 15 may be the same or different and represent a linking group as a binding site, a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a nitro group, a linear or branched alkyl group of 1 to 6 carbon atoms which may have a substituent, a cycloalkyl group of 5 to 10 carbon atoms which may have a substituent, a linear or branched alkenyl group of 2 to 6 carbon atoms which may have a substituent, a linear or branched alkyloxy group of 1 to 6 carbon atoms which may have a substituent, a cycloalkyloxy group of 5 to 10 carbon atoms which 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 fused polycyclic aromatic group, and each group may be bonded to the aromatic ring to which it is bonded via a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring; R 10 and R 11 or R 12 ~R 15 may be bonded to each other via a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring. Z represents an oxygen atom, a sulfur atom, or a nitrogen atom. However, when Z is an oxygen atom or a sulfur atom, Z does not have R9.

[0034] [ka] (1a)

[0035] (In the formula, R1 to R8, X, Y, and A are as defined in the general formula (1) above.)

[0036] R1 to R in general formula (1), general formula (2), or general formula (1a) 15Specific examples of the "aromatic hydrocarbon group", "aromatic heterocyclic group" or "condensed polycyclic aromatic group" in the "substituted or unsubstituted aromatic hydrocarbon group", "substituted or unsubstituted aromatic heterocyclic group" or "substituted or unsubstituted condensed polycyclic aromatic group" represented by the formula (I) include a phenyl group, a biphenylyl group, a terphenylyl group, a naphthyl group, an anthracenyl group, a phenanthrenyl group, a fluorenyl group, a spirobifluorenyl group, an indenyl group, a pyrenyl group, a perylenyl group, a fluoranthenyl group, a triphenylenyl group, a pyridyl group and a pyrimidinyl group. , triazinyl group, furyl group, pyrrolyl group, thienyl group, quinolyl group, isoquinolyl group, benzofuranyl group, benzothienyl group, indolyl group, carbazolyl group, benzoxazolyl group, benzothiazolyl group, quinoxalinyl group, benzimidazolyl group, pyrazolyl group, dibenzofuranyl group, dibenzothienyl group, naphthyridinyl group, phenanthrolinyl group, acridinyl group, and carbolinyl group, as well as an aryl group having 6 to 30 carbon atoms or a heteroaryl group having 2 to 20 carbon atoms. Furthermore, when a plurality of these groups are bonded to the same aromatic ring (a benzene ring or a five-membered heterocyclic ring), they may be bonded to each other via a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring, or each group may be bonded to the aromatic ring (a benzene ring or a five-membered heterocyclic ring) to which it is bonded via a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring.

[0037] R1 to R in general formula (1), general formula (2), or general formula (1a) 15and "C1-C6 linear or branched alkyl group", "C5-C10 cycloalkyl group", "C2-C6 linear or branched alkenyl group", "C2-C6 linear or branched alkyloxy group", "C5-C10 cycloalkyloxy group", or "substituted or unsubstituted aryloxy group" as represented by the above formula (I). Specific examples of the "linear or branched alkyloxy group having 5 to 6 carbon atoms," "cycloalkyloxy group having 5 to 10 carbon atoms," or "aryloxy group" include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, n-pentyl group, isopentyl group, neopentyl group, n-hexyl group, cyclopentyl group, cyclohexyl group, 1-adamantyl group, 2-adamantyl group, vinyl group, allyl group, isopropenyl group, 2-butenyl group, methyloxy group, ethyloxy group, n-propyloxy group, cyclopentyloxy group, cyclohexyloxy group, 1-adamantyloxy group, phenyloxy group, tolyloxy group, and biphenyloxy group. Furthermore, when a plurality of these groups are bonded to the same aromatic ring (a benzene ring or a five-membered heterocyclic ring), they may be bonded to each other via a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring, or each group may be bonded to the aromatic ring (a benzene ring or a five-membered heterocyclic ring) to which it is bonded via a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring.

[0038] R1 to R in general formula (1), general formula (2), or general formula (1a) 15Examples of the "substituent" in the "substituted aromatic hydrocarbon group," "substituted aromatic heterocyclic group," "substituted fused polycyclic aromatic group," "substituted C 1 to C 6 linear or branched alkyl group," "substituted C 5 to C cycloalkyl group," or "substituted C 2 to C 6 linear or branched alkenyl group," "substituted C 1 to C 6 linear or branched alkyloxy group," "substituted C 5 to C cycloalkyloxy group," or "substituted aryloxy group" include specifically deuterium atoms, cyano groups, nitro groups; halogen atoms such as fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms; silyl groups such as trimethylsilyl groups and triphenylsilyl groups; C 1 to C 6 linear or branched alkyl groups such as methyl groups, ethyl groups, and propyl groups; methyloxy groups, ethyloxy groups, propyl ... linear or branched alkyloxy groups having 1 to 6 carbon atoms, such as aryloxy; alkenyl groups, such as vinyl and allyl; aryloxy groups, such as phenyloxy and tolyloxy; arylalkyloxy groups, such as benzyloxy and phenethyloxy; phenyl, biphenylyl, terphenylyl, naphthyl, anthracenyl, phenanthrenyl, fluorenyl, spirobifluorenyl, indenyl, pyrenyl aromatic hydrocarbon groups or condensed polycyclic aromatic groups such as a pyridyl group, a thienyl group, a furyl group, a pyrrolyl group, a quinolyl group, an isoquinolyl group, a benzofuranyl group, a benzothienyl group, an indolyl group, a carbazolyl group, a benzoxazolyl group, a benzothiazolyl group, a quinoxalinyl group, a benzimidazolyl group, a pyrazolyl group, a dibenzofuranyl group, a dibenzothienyl group, a carbolinyl group, etc. Aromatic heterocyclic groups In addition to the above, examples include an aryl group having 6 to 30 carbon atoms and a heteroaryl group having 2 to 20 carbon atoms, and these substituents may be further substituted with the substituents exemplified above. Furthermore, these substituents may be bonded to each other via a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring.

[0039] In the "substituted or unsubstituted aromatic hydrocarbon divalent group," "substituted or unsubstituted aromatic heterocyclic group," or "substituted or unsubstituted fused polycyclic aromatic divalent group" represented by Ar1 to Ar3 in the general formula (1), the "aromatic hydrocarbon," "aromatic heterocyclic ring," or "fused polycyclic aromatic" in the "substituted or unsubstituted aromatic hydrocarbon," "substituted or unsubstituted aromatic heterocyclic ring," or "substituted or unsubstituted fused polycyclic aromatic" specifically includes benzene, biphenyl, terphenyl, tetrakisphenyl, styrene, styrene-2-phenyl ... Examples of the aromatic hydrocarbon include phenylene, naphthalene, anthracene, acenaphthalene, fluorene, phenanthrene, indane, pyrene, triphenylene, pyridine, pyrimidine, triazine, pyrrole, furan, thiophene, quinoline, isoquinoline, benzofuran, benzothiophene, indoline, carbazole, carboline, benzoxazole, benzothiazole, quinoxaline, benzimidazole, pyrazole, dibenzofuran, dibenzothiophene, naphthyridine, phenanthroline, and acridine.

[0040] The "divalent group of a substituted or unsubstituted aromatic hydrocarbon," "divalent group of a substituted or unsubstituted aromatic heterocycle," or "divalent group of a substituted or unsubstituted condensed polycyclic aromatic ring" represented by Ar1 to Ar3 in the general formula (1) "Divalent aromatic hydrocarbon radical," "divalent aromatic heterocyclic radical," or "divalent condensed polycyclic aromatic radical" in represents a divalent group obtained by removing two hydrogen atoms from the above-mentioned "aromatic hydrocarbon," "aromatic heterocycle," or "condensed polycyclic aromatic ring." These divalent groups may have a substituent, and the substituent may be any of R1 to R2 in general formula (1), general formula (2), or general formula (1a). 15and the like can be mentioned as the "substituent" in "substituted aromatic hydrocarbon group," "substituted aromatic heterocyclic group," "substituted fused polycyclic aromatic group," "substituted C linear or branched alkyl group," "substituted C cycloalkyl group," "substituted C 5 to C cycloalkyl group," "substituted C substituted linear or branched alkenyl group," "substituted C 2 to C linear or branched alkyloxy group," "substituted C cycloalkyloxy group," or "substituted aryloxy group," and these substituents may be bonded to each other via a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring.

[0041] In general formula (1), general formula (2), or general formula (1a), X, Y, and Z may be the same or different and represent an oxygen atom, a sulfur atom, or a nitrogen atom. However, when Z is an oxygen atom or a sulfur atom, Z does not have R9. X and Y are preferably oxygen atoms or sulfur atoms, and more preferably, all of X and Y are oxygen atoms or sulfur atoms. In general formula (2), R to R 15 is a linking group serving as a binding site, and R9 is preferably a linking group serving as a binding site, a linear or branched alkyl group of 1 to 6 carbon atoms which may have a substituent, a cycloalkyl group of 5 to 10 carbon atoms which may have a substituent, a linear or branched alkenyl group of 2 to 6 carbon atoms which may have a substituent, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted fused polycyclic aromatic group, more preferably a linking group serving as a binding site, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted fused polycyclic aromatic group, and even more preferably a linking group serving as a binding site, or a substituted or unsubstituted aromatic hydrocarbon group.

[0042] In general formula (1), Ar1 to Ar3 are preferably divalent groups of substituted or unsubstituted aromatic hydrocarbons, more preferably divalent groups (phenylene groups) obtained by removing two hydrogen atoms from substituted or unsubstituted benzene, and even more preferably divalent groups (phenylene groups) obtained by removing two hydrogen atoms from substituted or unsubstituted benzene.

[0043] In the organic EL device of the present invention, the thickness of the capping layer is preferably in the range of 30 nm to 120 nm, and more preferably in the range of 40 nm to 80 nm.

[0044] In the organic EL device of the present invention, the refractive index of the capping layer is preferably 1.90 or more, more preferably 1.95 or more, and even more preferably 2.00 or more, when the wavelength of light transmitted through the capping layer is in the range of more than 500 nm and not more than 570 nm.The refractive index of the capping layer is preferably 2.00 or more, more preferably 2.05 or more, when the wavelength of light transmitted through the capping layer is in the range of 400 nm or more and not more than 500 nm.

[0045] In the organic EL element of the present invention, the extinction coefficient of the capping layer is preferably 0.40 or more, and more preferably 0.50 or more, within the wavelength range of 400 nm or more and 410 nm or less of light transmitted through the capping layer.

[0046] In the organic EL device of the present invention, the capping layer may be formed by laminating or mixing two or more different constituent materials. [Effects of the Invention]

[0047] The organic EL device of the present invention uses, as the material for the capping layer, a material that has a high light absorption coefficient in the wavelength range of 400 nm to 410 nm, a high refractive index, and excellent thin film stability, durability, and light resistance. .Therefore,By providing a capping layer with a higher refractive index than the transparent or semitransparent electrode on the outside, it is possible to significantly improve the light extraction efficiency compared to conventional organic EL devices. Furthermore, the capping layer formed using the amine compound having a benzazole ring structure effectively absorbs sunlight with a wavelength of 400 to 410 nm, so the inside of the organic EL device is not affected by sunlight, making it possible to realize an organic EL device with high efficiency and long life. [Brief explanation of the drawings]

[0048] [Figure 1] FIG. 1 shows structures of compounds (1-1) to (1-12) as amine compounds having a benzazole ring structure represented by general formula (1) of the present invention. [Figure 2] FIG. 1 shows the structures of compounds (1-13) to (1-21), which are amine compounds having a benzazole ring structure represented by general formula (1) of the present invention. [Figure 3] FIG. 1 shows the structures of compounds (1-22) to (1-24), which are amine compounds having a benzazole ring structure represented by general formula (1) of the present invention. [Figure 4] FIG. 1 is a diagram showing the configurations of the organic EL devices of Examples 10 to 15 and Comparative Examples 1 to 4. DETAILED DESCRIPTION OF THE INVENTION

[0049] The benzazole derivative, which is the main skeleton of the amine compound having a benzazole ring structure represented by the general formula (1) or (1a) of the present invention, can be synthesized by a method known per se, for example, as follows: To do (For example, see Non-Patent Document 4.) Furthermore, by subjecting the synthesized halogenated benzazole derivative and arylamine to a coupling reaction using a copper catalyst, a palladium catalyst, or the like, the amine compound having a benzazole ring structure represented by the general formula (1) or (1a) of the present invention can be synthesized. In addition, the amine compound having a benzazole ring structure represented by the general formula (1) or (1a) of the present invention can be similarly synthesized by converting a halogenated benzazole derivative into a boronic acid derivative or a boronic acid ester derivative and then carrying out a coupling reaction with a halogenated arylamine (see, for example, Non-Patent Documents 5 and 6).

[0050] [ka]

[0051] Among the amine compounds having a benzoazole ring structure represented by the general formula (1) or (1a) that are suitably used in the organic EL device of the present invention, specific examples of preferred compounds are shown in Figures 1 to 3, but the compounds are not limited to these.

[0052] The amine compound having a benzoazole ring structure represented by the general formula (1) or (1a) and suitable for use in the organic EL device of the present invention was purified by column chromatography, adsorption purification using silica gel, activated carbon, activated clay, etc., recrystallization or crystallization using a solvent, and finally by sublimation purification. The compound was identified by NMR analysis. The physical properties measured were the melting point, glass transition point (Tg), refractive index, extinction coefficient, and absorbance. The melting point is an index of vapor deposition properties, the glass transition point (Tg) is an index of thin film stability, and the refractive index is an index of improved light extraction efficiency. The extinction coefficient is an index of light resistance. The absorbance is an index of light absorption ability.

[0053] The melting point and glass transition temperature (Tg) were measured using a high-sensitivity differential scanning calorimeter (DSC3100SA, manufactured by Bruker AXS) using powder.

[0054] The refractive index and extinction coefficient were measured by forming an 80 nm thin film on a silicon substrate and using a spectrophotometer (F10-RT-UV, manufactured by Filmetrics).

[0055] The absorbance is solution At a concentration of 10 -5 mol / L, and the extinction coefficient is 5.0 × 10 in toluene solution. -6 mol / L, 1.0 x 10 -5 mol / L, 1.5 x 10 -5 mol / L, and 2.0 × 10 -5 The solutions were prepared at four different concentrations (mol / L) and measured using an ultraviolet-visible-near infrared spectrophotometer (JASCO Corporation, V-650).

[0056] The organic EL device of the present invention may have a top-emission structure, for example, consisting of an anode, a hole-transport layer, an emitting layer, an electron-transport layer, a cathode, and a capping layer, arranged in this order on a glass substrate. It may also have a hole-injection layer between the anode and the hole-transport layer, an electron-blocking layer between the hole-transport layer and the emitting layer, a hole-blocking layer between the emitting layer and the electron-transport layer, or an electron-injection layer between the electron-transport layer and the cathode. In these multilayer structures, some organic layers may be omitted or may serve as both layers. For example, a layer may serve as both a hole-injection layer and a hole-transport layer, a layer may serve as both a hole-transport layer and an electron-blocking layer, a layer may serve as both a hole-blocking layer and an electron-transport layer, or a layer may serve as both an electron-transport layer and an electron-injection layer. It may also have a structure in which two or more organic layers having the same function are stacked, such as a layer with two hole-transport layers, a layer with two emitting layers, a layer with two electron-transport layers, or a layer with two capping layers.

[0057] The total thickness of each layer of the organic EL element is preferably about 200 nm to 750 nm, more preferably about 350 nm to 600 nm. The thicker the capping layer, the greater the absorbance. However, the thickness is not particularly limited as long as it does not interfere with thinning of the organic EL element. For example, the thickness is preferably 30 nm to 120 nm, more preferably 40 nm to 80 nm. In this case, good light extraction efficiency can be obtained. The thickness of the capping layer can be appropriately changed depending on the type of light-emitting material used in the light-emitting element, the thickness of the organic EL element other than the capping layer, etc.

[0058] For the anode of the organic EL device of the present invention, an electrode material with a large work function such as ITO or gold is used.

[0059] For the hole injection layer of the organic EL device of the present invention, preferred materials include arylamine compounds having a structure in which two or more triphenylamine structures are linked in the molecule by a single bond or a divalent group not containing a heteroatom, for example, arylamine compounds having a structure in which two triphenylamine structures are linked in the molecule by a single bond or a divalent group not containing a heteroatom, such as benzidine derivatives, starburst-type triphenylamine derivatives, and various triphenylamine tetramers. Also preferred are porphyrin compounds typified by copper phthalocyanine, and acceptor heterocyclic compounds such as hexacyanoazatriphenylene. 、 and coating-type polymer materials , etc. These may be used alone or in combination with other materials. of Materials and Both They may be used as a single layer formed by mixing them together, or as a laminate structure of layers formed by mixing them together, or a layer formed by mixing them together, or a layer formed by mixing them together. These materials can be used to form thin films by known methods such as vapor deposition, spin coating, and ink jet printing.

[0060] For the hole-transport layer of the organic EL device of the present invention, 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'-tetrabiphenylylbenzidine, 1,1-bis[4-(di-4-tolylamino)phenyl]cyclohexane (TAPC), and particularly arylamine compounds having two triphenylamine structures linked by a single bond or a divalent group not containing a heteroatom, such as N,N,N',N'-tetrabiphenylylbenzidine, and arylamine compounds having only one triphenylamine structure, are preferred. Furthermore, arylamine compounds having three or more triphenylamine structures linked by a single bond or a divalent group not containing a heteroatom, such as various triphenylamine trimers and tetramers, are also preferred. These may be formed as a film by themselves, or may be mixed with other materials and formed as a single layer. often Alternatively, the layer may be a laminate structure of layers formed independently, layers formed in a mixture, or layers formed in a mixture with layers formed independently. Furthermore, a coating-type polymer material such as poly(3,4-ethylenedioxythiophene) (PEDOT) / poly(styrene sulfonate) (PSS) can be used as the hole injection / transport layer. These materials can be formed into thin films by known methods such as vapor deposition, spin coating, and inkjet printing.

[0061] Furthermore, in the hole injection layer or hole transport layer, it is preferable to use a material that is normally used for the layer and is further doped with P, such as trisbromophenylaminehexachloroantimony or a radialene derivative (see, for example, Patent Document 3). Also, a polymer compound having a benzidine derivative structure such as TPD in its partial structure can be used.

[0062] For the electron blocking layer of the organic EL device of the present invention, compounds having an electron blocking effect can be used, such as carbazole derivatives such as 4,4',4''-tri(N-carbazolyl)triphenylamine (TCTA), 9,9-bis[4-(carbazol-9-yl)phenyl]fluorene, 1,3-bis(carbazol-9-yl)benzene (mCP), and 2,2-bis(4-carbazol-9-ylphenyl)adamantane (Ad-Cz), and compounds having a triphenylsilyl group and a triarylamine structure, typified by 9-[4-(carbazol-9-yl)phenyl]-9-[4-(triphenylsilyl)phenyl]-9H-fluorene. These compounds may be formed into a film alone or may be mixed with other materials to form a single layer. often The material may be a laminate of layers formed independently, layers formed as a mixture, or layers formed as a mixture with layers formed as a mixture. These materials can be used to form thin films by known methods such as vapor deposition, spin coating, and ink jet printing.

[0063] The light-emitting layer of the organic EL device of the present invention can be formed using metal complexes of quinolinol derivatives such as Alq3, as well as various metal complexes, anthracene derivatives, bisstyrylbenzene derivatives, pyrene derivatives, oxazole derivatives, polyparaphenylenevinylene derivatives, and the like. The light-emitting layer can also be formed using a host material and a dopant material. Anthracene derivatives are preferred as the host material. In addition to the light-emitting materials, heterocyclic compounds having an indole ring as a fused ring substructure, heterocyclic compounds having a carbazole ring as a fused ring substructure, carbazole derivatives, thiazole derivatives, benzimidazole derivatives, polydialkylfluorene derivatives, and the like can also be used. Furthermore, dopant materials can include quinacridone, coumarin, rubrene, perylene, and derivatives thereof, benzopyran derivatives, rhodamine derivatives, and aminostyryl derivatives, with green light-emitting materials being particularly preferred. These may be formed alone, or may be mixed with other materials to form a single layer, or may be stacked with other layers formed alone, other layers formed as a mixture, or a layer formed alone and a layer formed as a mixture.

[0064] Phosphorescent materials can also be used as light-emitting materials. preferable Phosphorescent emitters include metal complexes of iridium and platinum. Green phosphorescent emitters such as Ir(ppy)3, blue phosphorescent emitters such as FIrpic and FIr6, and red phosphorescent emitters such as Btp2Ir(acac) are commonly used, with green phosphorescent emitters being particularly preferred. Hole-injecting and transporting host materials include carbazole derivatives such as 4,4'-di(N-carbazolyl)biphenyl (CBP), TCTA, and mCP. Electron-transporting host materials include p-bis(triphenylsilyl)benzene (UGH2) and 2,2',2''-(1,3,5-phenylene)-tris(1-phenyl-1H-benzimidazole) (TPBI), enabling the fabrication of high-performance organic EL devices.

[0065] In order to avoid concentration quenching, the phosphorescent light-emitting material is preferably doped into the host material by co-evaporation in an amount ranging from 1 to 30 weight percent based on the entire light-emitting layer.

[0066] Furthermore, materials that emit delayed fluorescence, such as CDCB derivatives such as PIC-TRZ, CC2TA, PXZ-TRZ, and 4CzIPN, can also be used as light-emitting materials (see, for example, Non-Patent Document 7). These materials can be formed into thin films by known methods such as vapor deposition, spin coating, and inkjet printing.

[0067] For the hole-blocking layer of the organic EL device of the present invention, compounds having hole-blocking properties can be used, such as phenanthroline derivatives such as bathocuproine (BCP), metal complexes of quinolinol derivatives such as aluminum (III) bis(2-methyl-8-quinolinato)-4-phenylphenolate (BAlq), various rare earth complexes, triazole derivatives, triazine derivatives, pyrimidine derivatives, oxadiazole derivatives, and benzoazole derivatives. These materials may also serve as materials for the electron-transporting layer. These materials may be formed alone or as a single layer formed by mixing with other materials. often The material may be a laminate of layers formed independently, layers formed as a mixture, or layers formed as a mixture with layers formed as a mixture. These materials can be used to form thin films by known methods such as vapor deposition, spin coating, and ink jet printing.

[0068] For the electron transport layer of the organic EL device of the present invention, metal complexes of quinolinol derivatives such as Alq3 and BAlq, as well as various metal complexes, triazole derivatives, triazine derivatives, pyrimidine derivatives, oxadiazole derivatives, pyridine derivatives, benzimidazole derivatives, benzoazole derivatives, thiadiazole derivatives, anthracene derivatives, carbodiimide derivatives, quinoxaline derivatives, pyridoindole derivatives, phenanthroline derivatives, silole derivatives, etc. can be used. These may be formed into a film alone, or may be mixed with other materials to form a film as a single layer. often The material may be a laminate of layers formed independently, layers formed as a mixture, or layers formed as a mixture with layers formed as a mixture. These materials can be used to form thin films by known methods such as vapor deposition, spin coating, and ink jet printing.

[0069] The electron injection layer of the organic EL device of the present invention can be made of alkali metal salts such as lithium fluoride and cesium fluoride, alkaline earth metal salts such as magnesium fluoride, metal complexes of quinolinol derivatives such as lithium quinolinol, metal oxides such as aluminum oxide, or metals such as ytterbium (Yb), samarium (Sm), calcium (Ca), strontium (Sr), and cesium (Cs). However, in the preferred selection of the electron transport layer and the cathode, this can be omitted.

[0070] Furthermore, in the electron injection layer or electron transport layer, materials that are normally used for the layer can be further doped with N-doping of a metal such as cesium.

[0071] For the cathode of the organic EL element of the present invention, an electrode material having a low work function such as aluminum, an alloy having an even lower work function such as a magnesium-silver alloy, a magnesium-calcium alloy, a magnesium-indium alloy, or an aluminum-magnesium alloy, ITO, IZO, or the like is used as the electrode material.

[0072] As the capping layer of the organic EL device of the present invention, it is preferable to use an amine compound having a benzoazole ring structure represented by the general formula (1) or (1a). These compounds may be used alone to form a film, but they can also be used in combination with other materials. Both They may be used as a single layer formed by mixing them together, or as a laminate structure of layers formed by mixing them together, or a layer formed by mixing them together, or a layer formed by mixing them together. These materials can be used to form thin films by known methods such as vapor deposition, spin coating, and ink jet printing.

[0073] Although the organic EL element having a top emission structure has been described above, the present invention is not limited to this and can be similarly applied to an organic EL element having a bottom emission structure or an organic EL element having a dual emission structure that emits light from both the top and bottom. In these cases, the electrode in the direction in which light is extracted from the light-emitting element to the outside must be transparent or semi-transparent.

[0074] The refractive index of the material constituting the capping layer is preferably higher than that of the adjacent electrode. That is, the capping layer improves the light extraction efficiency of the organic EL element, but this effect is more effective when the reflectance at the interface between the capping layer and the material in contact with the capping layer is higher, due to the greater effect of light interference. Therefore, the refractive index of the material constituting the capping layer is preferably higher than that of the adjacent electrode. Within the wavelength range of more than 500 nm and not more than 570 nm, the refractive index should be 1.90 or higher, more preferably 1.95 or higher, and even more preferably 2.00 or higher. Furthermore, within the wavelength range of not less than 400 nm and not more than 500 nm, the refractive index should be 2.00 or higher, more preferably 2.05 or higher, and even more preferably 2.10 or higher.

[0075] Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention. [Example]

[0076] <Synthesis of Exemplary Compound (1-1)> A reaction vessel was charged with 7.4 g of 4-benzo[b]thien-2-yl-aniline, 19.8 g of 2-(4-bromophenyl)benzoxazole, 9.5 g of sodium tert-butoxide, and 70 ml of toluene, and nitrogen gas was passed through the vessel for 30 minutes. Ri(0.8 g of a 50% (w / v) toluene solution of tert-butylphosphine was added and stirred overnight under reflux. After cooling, the mixture was dispersed and washed at 80°C, and the insoluble matter was filtered off. The filtrate was concentrated to obtain a crude product. The crude product was purified by crystallization using a toluene solvent, and the precipitated solid was collected to obtain 7.5 g (yield 37.3%) of a yellow powder of exemplary compound (1-1).

[0077] [ka] (1-1)

[0078] The structure of the resulting yellow powder was identified using NMR. 1 The following 25 hydrogen signals were detected by H-NMR (CDCl3). δ(ppm)=8.23-8.19(4H), 7.87-7.84(1H), 7.82-7.77(3H), 7.75-7.71(2H), 7.62-7.57(2H), 7.56(1H), 7.41-7.27(12H). [Example]

[0079] <Synthesis of Exemplary Compound (1-2)> A reaction vessel was charged with 7.4 g of 4-benzo[b]thien-2-yl-aniline, 21.0 g of 2-(4-bromophenyl)benzothiazole, 9.5 g of sodium tert-butoxide, and 75 ml of toluene, and nitrogen gas was passed through the vessel for 30 minutes. Ri( 0.8 g of a 50% (w / v) toluene solution of tert-butylphosphine was added and stirred overnight under reflux. After cooling, the mixture was dispersed and washed at 80°C, and the insoluble matter was filtered off. The filtrate was concentrated to obtain a crude product. The crude product was purified by crystallization using a toluene solvent, and the precipitated solid was collected to obtain 3.8 g (yield 18.0%) of a yellow powder of exemplary compound (1-2).

[0080] [ka] (1-2)

[0081] The structure of the resulting yellow powder was identified using NMR. 1 The following 25 hydrogen signals were detected by H-NMR (CDCl3). δ(ppm)=8.09-8.04(6H), 7.94-7.91(2H), 7.8 7- 7.79(2H), 7.73-7.70(2H), 7.53-7.49(3H), 7.43-7.26(10H). [Example]

[0082] <Synthesis of exemplary compound (1-3)> A reaction vessel was charged with 5.0 g of 4-benzo[b]thien-5-yl-aniline, 13.4 g of 2-(4-bromophenyl)benzoxazole, 6.4 g of sodium tert-butoxide, and 50 ml of toluene, and nitrogen gas was passed through the vessel for 30 minutes. Ri( 0.5 g of a 50% (w / v) toluene solution of tert-butylphosphine was added and stirred overnight under reflux. After cooling, the mixture was dispersed and washed at 80°C, and the insoluble matter was filtered off. The filtrate was concentrated to obtain a crude product. The crude product was purified by crystallization using toluene and acetone solvents, and the precipitated solid was collected to obtain 8.8 g (yield 64.9%) of a yellow powder of exemplary compound (1-3).

[0083] [ka] (1-3)

[0084] The structure of the resulting yellow powder was identified using NMR. 1 The following 25 hydrogen signals were detected by H-NMR (CDCl3). δ(ppm)=8.22-8.19(4H), 8.08(1H), 7.99-7.97(1H), 7.80-7.77(2H), 7.71-7.58(5H), 7.53-7.51(1H), 7.44-7.32(11H). [Example]

[0085] <Synthesis of exemplary compound (1-4)> A reaction vessel was charged with 5.0 g of 4-benzo[b]thien-5-yl-aniline, 14.2 g of 2-(4-bromophenyl)benzothiazole, 6.4 g of sodium tert-butoxide, and 50 ml of toluene, and nitrogen gas was passed through for 30 minutes. Ri( 0.5 g of a 50% (w / v) toluene solution of tert-butylphosphine was added and stirred overnight under reflux. After cooling, the mixture was dispersed and washed at 80°C, and the insoluble matter was filtered off. The filtrate was concentrated to obtain a crude product. The crude product was purified by crystallization using toluene and acetone solvents, and the precipitated solid was collected to obtain 8.6 g (yield 59.83%) of yellow powder of exemplary compound (1-4).

[0086] [ka] (1-4)

[0087] The structure of the resulting yellow powder was identified using NMR. 1 The following 25 hydrogen signals were detected by H-NMR (CDCl3). δ(ppm)=8.09-8.02(7H), 7.99-7.90(3H), 7.69-7.62(3H), 7.54-7.49(3H), 7.46-7.37(3H), 7.34-7.29(6H). [Example]

[0088] <Synthesis of exemplary compound (1-23)> Add 4-(9H-carbazole-9 -6.0 g of 2-(4-bromophenyl)benzoxazole, 14.0 g of sodium tert-butoxide, and 60 ml of toluene were added, and nitrogen gas was passed through the mixture for 30 minutes. Ri( 0.6 g of a 50% (w / v) toluene solution of tert-butylphosphine was added and stirred overnight under reflux. After cooling, the mixture was dispersed and washed at 80°C, and the insoluble matter was filtered off. The filtrate was concentrated to obtain a crude product. The crude product was purified by crystallization using monochlorobenzene solvent, and the precipitated solid was collected to obtain 6.7 g (yield 44.77%) of yellow powder of exemplary compound (1-23).

[0089] [ka] (1-23)

[0090] The structure of the resulting yellow powder was identified using NMR. 1 The following 28 hydrogen signals were detected by H-NMR (CDCl3). δ(ppm)=8.27-8.17(6H), 7.81-7.78(2H), 7.63-7.59(4H), 7.55-7.31(16H). [Example]

[0091] <Synthesis of exemplary compound (1-24)> Add 4-(9H-carbazole-9 - 6.0 g of (4-bromophenyl)aniline, 14.8 g of 2-(4-bromophenyl)benzothiazole, 6.7 g of sodium tert-butoxide, and 60 ml of toluene were added, and nitrogen gas was passed through the mixture for 30 minutes. Ri(0.6 g of a 50% (w / v) toluene solution of tert-butylphosphine was added and stirred overnight under reflux. After cooling, the mixture was dispersed and washed at 80°C, and the insoluble matter was filtered off. The filtrate was concentrated to obtain a crude product. The crude product was purified by crystallization using monochlorobenzene solvent, and the precipitated solid was collected to obtain 7.6 g (yield 48.34%) of yellow powder of exemplary compound (1-24).

[0092] [ka] (1-24)

[0093] The structure of the resulting yellow powder was identified using NMR. 1 The following 28 hydrogen signals were detected by H-NMR (CDCl3). δ(ppm)=8.20-8.18(2H), 8.12-8.08(6H), 7.95-7.92(2H), 7.59-7.32(18H). [Example]

[0094] The melting point and glass transition temperature (Tg) of the amine compound having a benzoazole ring structure represented by general formula (1) or (1a) were measured using a high-sensitivity differential scanning calorimeter (DSC3100SA, manufactured by Bruker AXS). Melting point Glass transition point (Tg) Compound (1-1) of Example 1 276 °C 120 °C Compound (1-2) of Example 2 272 °C 118 °C Compound (1-3) of Example 3 259 ° C 116 ° C Compound (1-4) of Example 4 251 °C 113 °C Compound (1-23) of Example 5 252 °C 132 °C Compound (1-24) of Example 6 230 °C 130 °C

[0095] The amine compound having a benzazole ring structure represented by general formula (1) or (1a) of the present invention has a glass transition point (Tg) of 100° C. or higher, which indicates that the thin film state is stable. [Example]

[0096] An amine compound having a benzoazole ring structure represented by general formula (1) or (1a) was used to form an 80 nm thick vapor-deposited film on a silicon substrate, and the refractive index n at wavelengths of 400 nm, 410 nm, 500 nm, and 570 nm and the extinction coefficient k at wavelengths of 400 nm and 410 nm were measured using a spectrophotometer (Filmetrics, F10-RT-UV). For comparison, measurements were also made on comparative compounds (2-1), (2-2), (2-3), and (2-4) with the following structural formulas (see, for example, Patent Document 4). The measurement results are summarized in Table 1.

[0097] [ka] (2-1)

[0098] [ka] (2-2)

[0099] [ka] (2-3)

[0100] [ka] (2-4)

[0101] [Table 1]

[0102] Thus, the compounds of the present invention have a refractive index of 2.00 or more in the wavelength range of 400 nm or more to 500 nm or less, and a refractive index of 1.90 or more in the wavelength range of more than 500 nm to 570 nm or less, which is higher than that of the comparative compounds (2-1), (2-2), (2-3), and (2-4), indicating that an improvement in the light extraction efficiency of organic EL devices can be expected. Furthermore, the extinction coefficients in the wavelength range of 400 nm or more and 410 nm or less are 0.03 to 0.45 for the comparative compounds (2-1), (2-2), (2-3), and (2-4), whereas the compounds of the present invention have large values ​​of 0.47 to 1.17. This large extinction coefficient indicates that the capping layer formed using the compound of the present invention effectively absorbs sunlight with a wavelength of 400 nm to 410 nm and has little effect on the materials inside the device. [Example]

[0103] The compound of the present invention was used in a toluene solution at a concentration of 10 -5 The absorbance at wavelengths of 400 nm and 410 nm was measured using a UV-visible-near-infrared spectrophotometer (JASCO Corporation, V-650). The extinction coefficient was 5 × 10 in toluene solution. -6 mol / L, 1×10 -5 mol / L, 1.5 x 10 -5 mol / L, and 2.0 × 10 -5 The compounds were prepared at four different concentrations (mol / L) and measured using an ultraviolet-visible-near-infrared spectrophotometer (JASCO Corporation, V-650), and the extinction coefficients were calculated from the calibration curve. For comparison, the comparative compounds (2-1), (2-2), (2-3), and (2-4) with the above structural formulas were also measured. The measurement results are summarized in Table 2.

[0104] [Table 2]

[0105] Thus, the absorbance at a wavelength of 400 nm for the comparative compounds (2-1), (2-2), (2-3), and (2-4) was 0.02 to 0.60, whereas the compounds of the present invention had a high value of 0.85 to 1.77. Furthermore, the absorbance at a wavelength of 410 nm for the comparative compounds (2-1), (2-2), (2-3), and (2-4) was 0.00 to 0.21, whereas the compounds of the present invention had a high value of 0.24 to 1.27. This indicates that the compounds of the present invention absorb sunlight with wavelengths of 400 to 410 nm well. Furthermore, the extinction coefficients of the compounds of the present invention were greater than 130,000, indicating that they absorb light well under the same concentration conditions, and that they are materials with excellent light resistance. [Example]

[0106] As shown in Figure 4, the organic EL device was fabricated by depositing a hole injection layer 3, a first hole transport layer 4, a second hole transport layer 5, an emitting layer 6, an electron transport layer 7, an electron injection layer 8, a cathode 9, and a capping layer 10 in this order on a glass substrate 1 on which a reflective ITO electrode was previously formed as a metal anode 2.

[0107] Specifically, a metal anode 2 was formed on a glass substrate 1. The metal anode 2 consisted of a 50 nm thick ITO film, a 100 nm thick silver alloy reflective film, and a 5 nm thick ITO film were deposited in this order. This film was then ultrasonically cleaned in isopropyl alcohol for 20 minutes and then dried on a hot plate heated to 250°C for 10 minutes. This was then subjected to UV ozone treatment for 2 minutes. The ITO-coated glass substrate was then placed in a vacuum deposition chamber and the pressure was reduced to 0.001 Pa or less. Next, a hole injection layer 3 was formed covering the metal anode 2 by binary deposition of an electron acceptor (Acceptor-1) of the following structural formula and a compound (3-1) of the following structural formula at a deposition rate ratio of Acceptor-1:Compound (3-1) = 3:97, resulting in a thickness of 10 nm. On this hole injection layer 3, a first hole transport layer 4 was formed of a compound (3-1) of the following structural formula at a thickness of 70 nm. On the first hole transport layer 4, a second hole transport layer 5 was formed using a compound (3-2) of the following structural formula to a thickness of 10 nm. On the second hole transport layer 5, a light-emitting layer 6 was formed using a compound (3-3) of the following structural formula and a compound (3-4) of the following structural formula by binary deposition at a deposition rate ratio of compound (3-3):compound (3-4) = 5:95 to a thickness of 40 nm. On the light-emitting layer 6, a compound (3-5) of the following structural formula and a compound (3-6) of the following structural formula by binary deposition at a deposition rate ratio of compound (3-5):compound (3-6) = 50:50 to a thickness of 30 nm. On the electron transport layer 7, lithium fluoride was formed as an electron injection layer 8 to a thickness of 1 nm. On the electron injection layer 8, a cathode 9 was formed using a magnesium-silver alloy to a thickness of 12 nm. Finally, the compound (1-1) of Example 1 was formed to a thickness of 60 nm as a capping layer 10. The characteristics of the produced organic EL device were measured in the air at room temperature. The light-emitting characteristics of the fabricated organic EL devices were measured by applying a DC voltage, and the results are summarized in Table 3.

[0108] [ka] (Acceptor-1)

[0109] [ka] (3-1)

[0110] [ka] (3-2)

[0111] [ka] (3-3)

[0112] [ka] (3-4)

[0113] [ka] (3-5)

[0114] [ka] (3-6)

[0115] [ka] (1-1) [Example]

[0116] An organic EL device was fabricated under the same conditions as in Example 10, except that the compound (1-2) of Example 2 was used instead of the compound (1-1) of Example 1 as the material for the capping layer 10. The characteristics of the fabricated organic EL device were measured in the air at room temperature. Table 3 shows the results of measuring the light-emitting characteristics when a DC voltage was applied to the fabricated organic EL device.

[0117] [ka] (1-2) [Example]

[0118] An organic EL device was fabricated under the same conditions as in Example 10, except that the compound (1-3) of Example 3 was used as the material for the capping layer 10 instead of the compound (1-1) of Example 1. The characteristics of the fabricated organic EL device were measured in the air at room temperature. Table 3 shows the results of measuring the light-emitting characteristics when a DC voltage was applied to the fabricated organic EL device.

[0119] [ka] (1-3) [Example]

[0120] An organic EL device was fabricated under the same conditions as in Example 10, except that the compound (1-4) of Example 4 was used instead of the compound (1-1) of Example 1 as the material for the capping layer 10. The characteristics of the fabricated organic EL device were measured in the air at room temperature. Table 3 shows the results of measuring the light-emitting characteristics when a DC voltage was applied to the fabricated organic EL device.

[0121] [ka] (1-4) [Example]

[0122] An organic EL device was fabricated under the same conditions as in Example 10, except that the compound (1-23) of Example 5 was used instead of the compound (1-1) of Example 1 as the material for the capping layer 10. The characteristics of the fabricated organic EL device were measured in the air at room temperature. Table 3 shows the results of measuring the light-emitting characteristics when a DC voltage was applied to the fabricated organic EL device.

[0123] [ka] (1-23) [Example]

[0124] An organic EL device was fabricated under the same conditions as in Example 10, except that compound (1-24) of Example 6 was used instead of compound (1-1) of Example 1 as the material for the capping layer 10. The characteristics of the fabricated organic EL device were measured in the air at room temperature. Table 3 shows the results of measuring the light-emitting characteristics when a DC voltage was applied to the fabricated organic EL device.

[0125] [ka] (1-24)

[0126] [Comparative Example 1] For comparison, an organic EL device was fabricated under the same conditions as in Example 10, except that a comparative compound (2-1) having the following structural formula was used as the capping layer 10 instead of the compound (1-1) in Example 1. The characteristics of the fabricated organic EL device were measured in the air at room temperature. Table 3 shows the results of measuring the light-emitting characteristics when a DC voltage was applied to the fabricated organic EL device.

[0127] [ka] (2-1)

[0128] Comparative Example 2 For comparison, an organic EL device was fabricated under the same conditions as in Example 10, except that a comparative compound (2-2) having the following structural formula was used as the capping layer 10 instead of the compound (1-1) in Example 1. The characteristics of the fabricated organic EL device were measured in the air at room temperature. Table 3 shows the results of measuring the light-emitting characteristics when a DC voltage was applied to the fabricated organic EL device.

[0129] [ka] (2-2)

[0130] Comparative Example 3 For comparison, an organic EL device was fabricated under the same conditions as in Example 10, except that a comparative compound (2-3) having the following structural formula was used as the capping layer 10 instead of the compound (1-1) in Example 1. The characteristics of the fabricated organic EL device were measured in the air at room temperature. Table 3 shows the results of measuring the light-emitting characteristics when a DC voltage was applied to the fabricated organic EL device.

[0131] [ka] (2-3)

[0132] Comparative Example 4 For comparison, an organic EL device was fabricated under the same conditions as in Example 10, except that a comparative compound (2-4) having the following structural formula was used as the capping layer 10 instead of the compound (1-1) in Example 1. The characteristics of the fabricated organic EL device were measured in the air at room temperature. Table 3 shows the results of measuring the light-emitting characteristics when a DC voltage was applied to the fabricated organic EL device.

[0133] [ka] (2-4)

[0134] The organic EL elements fabricated in Examples 10 to 15 and Comparative Examples 1 to 4 were used to measure the element lifetime, and the results are summarized in Table 3. The element lifetime was 10 mA / cm 2 When the device was driven at a constant current of 100%, the time required for the initial luminance to decay to 95% (95% decay) was measured.

[0135] [Table 3]

[0136] As shown in Table 3, a current density of 10 mA / cm 2 The driving voltage at this time was almost the same for the devices of Comparative Examples 1 to 4 using the comparative compounds and the devices of Examples 10 to 15 using the compounds of the present invention, whereas the luminance, luminous efficiency, power efficiency, and device life were significantly improved for the devices of Examples 10 to 15 using the compounds of the present invention compared to the devices of Comparative Examples 1 to 4 using the comparative compounds. This shows that the light extraction efficiency can be significantly improved by including in the capping layer a material with a high refractive index that is suitable for use in the organic EL device of the present invention. [Industrial Applicability]

[0137] As described above, the amine compound having a benzoazole ring structure represented by general formula (1) of the present invention has a high absorption coefficient, a high refractive index, can significantly improve light extraction efficiency, and is stable in a thin film state, making it an excellent compound for use in the capping layer of an organic EL device. The organic EL device of the present invention fabricated using this compound can achieve high efficiency and can also improve durability and light resistance so as to absorb sunlight and not affect the materials inside the device. Furthermore, the use of this compound, which has no absorption in the blue, green, and red wavelength regions, is particularly suitable for displaying clear, bright images with good color purity. Furthermore, the present invention provides a method for producing a capping layer of an organic EL device.、 The amine compound having a benzazole ring structure represented by the general formula (1) can be formed into a film at a temperature of 400°C or less, which makes it possible to optimize the light extraction efficiency of each color using a high-resolution mask without damaging the light-emitting element, making it suitable for full-color displays, and enabling its application to, for example, home appliances and lighting.

[0138] [Explanation of symbols] 1. Glass substrate 2 metal anode 3. Hole injection layer 4 First hole transport layer 5 Second hole transport layer 6. Light-emitting layer 7 Electron transport layer 8 Electron injection layer 9 Cathode 10 Capping Layer

Claims

1. 1. An organic electroluminescence device comprising at least an anode electrode, a hole injection layer formed by P-doping a radialene derivative, a first hole transport layer, a second hole transport layer made of an arylamine compound having only one triphenylamine structure in the molecule, an emitting layer, an electron transport layer, a cathode electrode, and a capping layer, in this order, wherein the capping layer has a refractive index of 2.00 or more within the wavelength range of 400 nm or more to 500 nm or less of light transmitted through the capping layer, and a refractive index of 1.90 or more within the wavelength range of more than 500 nm to 570 nm or less of light transmitted through the capping layer, and the organic electroluminescence device comprises an amine compound having a benzoazole ring structure represented by the following general formula (1): 【Chemical 1】 （１） (In the formula, R １ ~R ８ may be the same or different and represent a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a nitro group, an optionally substituted linear or branched alkyl group of 1 to 6 carbon atoms, a optionally substituted cycloalkyl group of 5 to 10 carbon atoms, a optionally substituted linear or branched alkenyl group of 2 to 6 carbon atoms, an optionally substituted linear or branched alkyloxy group of 1 to 6 carbon atoms, a optionally substituted cycloalkyloxy group of 5 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted condensed polycyclic aromatic group, or a substituted or unsubstituted aryloxy group, and each of these groups may be bonded to the benzene ring to which they are bonded via a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring, and R １ ~R ４ or R ５ ~R ８ may be bonded to each other via a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring. X and Y may be the same or different and represent an oxygen atom or a sulfur atom. Ar １ ~Ar ３ may be the same or different and represent 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 ring. A represents R represented by the following general formula (2): ９ ~R １５ represents a monovalent group having one of the following as a bonding site: 【Chemistry 2】 （２） (In the formula, R ９ ~R １５ may be the same or different and represent a linking group as a binding site, a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a nitro group, a linear or branched alkyl group of 1 to 6 carbon atoms which may have a substituent, a cycloalkyl group of 5 to 10 carbon atoms which may have a substituent, a linear or branched alkenyl group of 2 to 6 carbon atoms which may have a substituent, a linear or branched alkyloxy group of 1 to 6 carbon atoms which may have a substituent, a cycloalkyloxy group of 5 to 10 carbon atoms which 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. １１ or R １２ ~R １５ are not bonded to each other to form a ring. Z represents an oxygen atom, a sulfur atom, or a nitrogen atom. However, when Z is an oxygen atom or a sulfur atom, Z is not R ９ (The following shall not be included in the above.)

2. 2. The organic electroluminescence device according to claim 1, wherein the amine compound having a benzazole ring structure is represented by the following general formula (1a): 【Chemistry 3】 (1a) (In the formula, R １ ~R ８ , X, Y, and A are as defined in the general formula (1).

3. In the general formula (1) or the general formula (1a), R １ ~R ８ 3. The organic electroluminescence device according to claim 1, wherein all of the following are hydrogen atoms.

4. 4. The organic electroluminescence device according to claim 1, wherein the capping layer has an extinction coefficient of 0.40 or more in a wavelength range of 400 nm or more and 410 nm or less.

5. A method for producing the organic electroluminescence element according to any one of claims 1 to 4, comprising forming a capping layer of the organic electroluminescence element using an amine compound having a benzazole ring structure represented by general formula (1) or general formula (1a).

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