Organic electroluminescent elements and their compounds

Abstract

[Problem] The purpose of the present invention is to provide a compound which absorbs sunlight having a wavelength of 400 nm to 410 nm, does not affect a material inside an organic electroluminescent element, and has a high refractive index in the wavelength range from 450 nm to 750 nm, in order to prevent deterioration inside the organic electroluminescent element and to considerably improve the light extraction efficiency. [Solution] The present invention focused attention on excellent stability and durability of an arylamine material in the form of a thin film, and has achieved an organic electroluminescent element that has excellent luminous efficiency by designing a diamine compound that has a specific benzazole ring structure and a high refractive index and using this diamine compound as a material that constitutes a capping layer.

Description

[Technical Field]

[0001] The present invention relates to compounds suitable for self-emissive electronic elements suitable for various display devices, particularly compounds suitable for organic electroluminescent elements (hereinafter abbreviated as organic EL elements), and organic EL elements, electronic devices, or electronic elements using said compounds. [Background technology]

[0002] Because organic EL elements are self-emissive elements, they are brighter, more visible, and capable of sharper displays compared to liquid crystal elements, which has led to active research into them.

[0003] In 1987, CWTang et al. at Eastman Kodak made organic light-emitting diodes (OLEDs) practical by developing a multilayer structure in which various roles were assigned to different materials. They layered a phosphor capable of transporting electrons with an organic material capable of transporting holes, and injected the charges of both into the phosphor layer to cause light emission, achieving an emission of 1000 cd / m² at a voltage of 10V or less. 2 The above high brightness levels can now be achieved (see, for example, Patent Documents 1 and 2).

[0004] To date, many improvements have been made to commercialize organic EL elements, and the various roles of the stacked structure have been further subdivided. In electroluminescent elements where an anode, hole injection layer, hole transport layer, light-emitting layer, electron transport layer, electron injection layer, and cathode are sequentially arranged on a substrate, high efficiency and durability have been achieved by light-emitting elements 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, which use a metal with a high work function as the anode and emit light from the top, have come into use. In bottom-emission structures, where light is extracted from the bottom where the pixel circuit is located, the area of ​​the light-emitting part is limited. In contrast, light-emitting devices with a top-emission structure have the advantage of being able to emit light from a wider area because the light is extracted from the top and does not obstruct the pixel circuit. In light-emitting devices with a top-emission structure, translucent electrodes such as LiF / Al / Ag (see, for example, Non-Patent Document 2), Ca / Mg (see, for example, Non-Patent Document 3), and LiF / MgAg are used as cathodes.

[0006] In such light-emitting devices, when light emitted from the light-emitting layer is incident on another film, if it is incident at an angle greater than a certain degree, it undergoes total internal reflection 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, in order to improve the light extraction efficiency, light-emitting devices have been proposed in which a high refractive index "capping layer" is provided on the outside of a low refractive index semi-transparent electrode (see, for example, Non-Patent Documents 2 and 3).

[0007] In light-emitting devices with a top-emission structure, the effect of the capping layer was observed in a light-emitting device using Ir(ppy)3 as the light-emitting material. While the current efficiency was 38 cd / A without a capping layer, a light-emitting device using ZnSe with a 60 nm film thickness as a capping layer achieved an efficiency improvement of approximately 1.7 times, reaching 64 cd / A. Furthermore, it has been shown that the maximum transmittance points of the translucent electrode and capping layer do not necessarily coincide with the maximum efficiency points, indicating that the point of maximum light extraction efficiency is determined by interference effects (see, for example, Non-Patent Document 3).

[0008] Conventionally, the use of a highly detailed metal mask has been proposed for forming the capping layer. However, when used under high-temperature conditions, the metal mask becomes distorted by heat, resulting in a decrease in alignment accuracy. Therefore, since ZnSe has a high melting point of over 1100°C (see, for example, Non-Patent Document 3), it cannot be deposited in the correct position using a highly detailed metal mask, potentially affecting the light-emitting element itself. Furthermore, even with film deposition by sputtering, it can affect the light-emitting element, making capping layers composed of inorganic materials unsuitable for use.

[0009] Furthermore, when using tris(8-hydroxyquinoline)aluminum (Alq3) as a capping layer to adjust the refractive index (see, for example, Non-Patent Document 2), Alq3 is known as an organic EL material commonly used as a green light-emitting material or electron transport material. However, because it has weak absorption around 450 nm, which is used for blue light-emitting materials, there were problems such as a decrease in color purity and a decrease in light extraction efficiency in the case of blue light-emitting elements.

[0010] Furthermore, devices fabricated with conventional capping layers allowed sunlight with wavelengths of 400nm to 410nm to pass through, affecting the internal materials of the device and resulting in problems such as a decrease in color purity and reduced light extraction efficiency.

[0011] To improve the characteristics of organic EL elements, and in particular to absorb light with wavelengths of 400nm to 410nm from sunlight without affecting the internal materials of the element, and to significantly improve light extraction efficiency, there is a need for a capping layer material with a high absorption coefficient, a high refractive index, and excellent thin-film stability and durability. [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

Patent Document 4

Non-Patent Document

[0013]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Non-Patent Document 4

Non-Patent Document 5

Non-Patent Document 6

Non-Patent Document 7

Summary of the Invention

Problems to be Solved by the Invention

[0014] An object of the present invention is to provide a compound that absorbs light with wavelengths from 400 nm to 410 nm of sunlight, does not affect the materials inside the device, and has a high refractive index in the range of wavelengths from 450 nm to 750 nm, in order to improve the device characteristics of an organic EL device. By using the compound as a capping layer material for the organic EL device, an organic EL device is provided that can prevent deterioration inside the device and significantly improve the light extraction efficiency.

[0015] Specifically, the physical properties of a capping layer material suitable for an organic EL element include (1) a high absorption coefficient, (2) a high refractive index, (3) the ability to be deposited, (4) a stable thin film state, and (5) a high glass transition temperature. Furthermore, the properties of the organic EL element provided by the present invention include (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 change over time, and (5) a long lifespan. [Means for solving the problem]

[0016] Therefore, in order to achieve the above objective, the present inventors focused on the fact that arylamine-based materials have excellent stability and durability in thin films, and selected a diamine compound having a specific benzoazole ring structure with a high refractive index, and a concentration of 10 -5 By designing a material with high absorbance in the wavelength range of 400 nm to 410 nm in its mol / L absorption spectrum, fabricating an organic EL device using this material as the capping layer, and diligently evaluating the characteristics of the device, we have completed this invention.

[0017] In other words, the present invention provides a diamine compound having the following azabenzoxazole ring structure, and an organic EL element and an electronic device or electronic element using the same.

[0018] 1) A diamine compound having an azabenzoxazole ring structure represented by the following general formula (a-1).

[0019] [ka] (a-1)

[0020] In the general formula (a-1) above, A, B, C, and D may be the same or different from each other, and represent a monovalent group having an azabenzoxazole group represented by the following structural formula (b-1), a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group. However, at least one of A, B, C, or D is a monovalent group having an azabenzoxazole group represented by the following structural formula (b-1). L represents a divalent group of a substituted or unsubstituted aromatic hydrocarbon, a divalent group of a substituted or unsubstituted aromatic heterocyclic group, or a divalent group of a substituted or unsubstituted condensed polycyclic aromatic group, and may be bonded to A, B, C, or D via 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, and if m is an integer of 2 or more, multiple Ls may be the same or different from each other.

[0021] [ka] (b-1)

[0022] In the above structural formula (b-1), each Y may be the same or different from each other and represents a CR or nitrogen atom. However, at least one of the Ys shall be a nitrogen atom. Each R may be the same or different from each other and any one of the Rs shall be a linking group that serves as a bonding site with the above 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 linear or branched alkyl group having 1 to 6 carbon atoms which may be substituted, a cycloalkyl group having 5 to 10 carbon atoms which may be substituted, a linear or branched alkenyl group having 2 to 6 carbon atoms which may be substituted, a linear or branched alkyloxy group having 1 to 6 carbon atoms which may be substituted, a cycloalkyloxy group having 5 to 10 carbon atoms which may be substituted, 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.

[0023] 2) A diamine compound having the azabenzoxazole ring structure as described in 1), characterized in that A, B, C, and D in the general formula (a-1) are a monovalent group having an azabenzoxazole group represented by the structural formula (b-1), a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted naphthyl group, a substituted or unsubstituted phenantrenyl group, a substituted or unsubstituted carbazolyl group, a substituted or unsubstituted benzofuranyl group, a substituted or unsubstituted benzothienyl group, a substituted or unsubstituted indolyl group, a substituted or unsubstituted benzimidazolyl group, a substituted or unsubstituted imidazopyridyl group, a substituted or unsubstituted benzoxazolyl group, a substituted or unsubstituted benzothiazolyl group, a substituted or unsubstituted dibenzofuranyl group, or a substituted or unsubstituted dibenzothienyl group.

[0024] 3) A diamine compound having the azabenzoxazole ring structure described in 1) or 2) above, characterized in that the structural formula (b-1) is the following structural formula (b-2) or structural formula (b-3).

[0025] [ka] (b-2)

[0026] [ka] (b-3)

[0027] In the aforementioned structural formula (b-2) or structural formula (b-3), R is defined as in the aforementioned structural formula (b-1).

[0028] 4) A diamine compound having the azabenzoxazole ring structure according to any one of 1) to 3) above, characterized in that L in the general formula (a-1) is a substituted or unsubstituted phenylene group, a substituted or unsubstituted biphenylene group, or a substituted or unsubstituted naphthylene group.

[0029] 5) A diamine compound having the azabenzoxazole ring structure described in any of 1) to 4) above, characterized in that m in the general formula (a-1) is 1 or 2.

[0030] 6) A diamine compound having an azabenzoxazole ring structure as described in any of 1) to 5) above, characterized in that the structural formula (b-1) is the following structural formula (b-4) or structural formula (b-5).

[0031] [ka] (b-4)

[0032] [ka] (b-5)

[0033] In the aforementioned structural formula (b-4) or structural formula (b-5), R is defined as in the aforementioned structural formula (b-1).

[0034] 7) A diamine compound having the azabenzoxazole ring structure described in any of 1) to 6) above, characterized in that only one of A, B, C, or D in the general formula (a-1) is the structural formula (b-4) or the structural formula (b-5).

[0035] 8) A diamine compound having an azabenzoxazole ring structure as described in any of 1) to 6) above, characterized in that any two of A, B, C, or D in the general formula (a-1) are the structural formula (b-4) or the structural formula (b-5).

[0036] 9) A diamine compound having the azabenzoxazole ring structure according to any one of 1) to 6) above, characterized in that A and B in the general formula (a-1) are the structural formula (b-4) or the structural formula (b-5).

[0037] 10) A diamine compound having the azabenzoxazole ring structure described in any of 1) to 6) above, characterized in that A and C in the general formula (a-1) are the structural formula (b-4) or the structural formula (b-5).

[0038] 11) An organic EL element having 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 this order, characterized in that the capping layer contains a diamine compound having an azabenzoxazole ring structure as described in any of 1) to 10) above.

[0039] 12) The extinction coefficient of the capping layer in the wavelength range of 400 nm to 410 nm is 0.2 or more, and the concentration of the diamine compound having the azabenzoxazole ring structure is 10 -5 The organic EL element according to 11) above, characterized in that the absorbance in the wavelength range of 400 nm to 410 nm in the mol / L absorption spectrum is 0.2 or more.

[0040] 13) The organic EL element according to 11) or 12) above, characterized in that the refractive index of the capping layer is 1.85 or more when the wavelength of light transmitted through the capping layer is in the range of 450 nm to 750 nm.

[0041] 14) The organic EL element according to any one of 11) to 13) above, characterized in that, when the capping layer consists of a laminated or mixed layer containing two or more compounds, at least one of the compounds is a diamine compound having the azabenzoxazole ring structure.

[0042] 15) An electronic device or electronic element having a pair of electrodes and at least one organic layer sandwiched between them, characterized in that the organic layer contains a diamine compound having an azabenzoxazole ring structure as described in any of 1) to 10) above.

[0043] In general formula (a-1) and structural formula (b-1), the "substituted or unsubstituted aromatic hydrocarbon group," "substituted or unsubstituted aromatic heterocyclic group," or "substituted or unsubstituted condensed polycyclic aromatic group" represented by A, B, C, D, and R are specifically the "aromatic hydrocarbon group," "aromatic heterocyclic group," or "condensed polycyclic aromatic group," which include phenyl group, biphenylyl group, terphenylyl group, naphthyl group, anthracenyl group, phenantrenyl group, fluorenyl group, spirobifluorenyl group, indenyl group, pyrenyl group, perilenyl group, fluoranthenyl group, triphenylenyl group, and pylenyl group. In addition to lysyl groups, pyrimidinyl groups, triazinyl groups, furyl groups, pyrrolyl groups, thienyl groups, quinolyl groups, isoquinolyl groups, benzofuranyl groups, benzothienyl groups, indolyl groups, carbazolyl groups, imidazopyridyl groups, benzoxazolyl groups, benzothiazolyl groups, quinoxalinyl groups, benzimidazolyl groups, pyrazolyl groups, dibenzofuranyl groups, dibenzothienyl groups, naphthilidinyl groups, phenanthrolinyl groups, acridinyl groups, and carbonyl groups, the following can be selected: aryl groups consisting of 6 to 30 carbon atoms, or heteroaryl groups consisting of 2 to 20 carbon atoms.

[0044] In general formula (a-1), the "divalent group of a substituted or unsubstituted aromatic hydrocarbon," the "divalent group of a substituted or unsubstituted aromatic heterocycle," or the "divalent group of a substituted or unsubstituted condensed polycyclic aromatic" represented by L can be specifically benzene, biphenyl, terphenyl, naphthalene, anthracene, phenanthrene, fluorene, pyridine, pyrimidine, quinoline, benzofuran, benzothiophene, benzoxazole, benzothiazole, dibenzofuran, dibenzothiophene, phenanthroline, and others. Furthermore, 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" represented by L in general formula (a-1) represent a divalent group formed by removing two hydrogen atoms from the above-mentioned "aromatic hydrocarbon," "aromatic heterocycle," or "condensed polycyclic aromatic."

[0045] In structural formula (b-1), R represents "a linear or branched alkyl group having 1 to 6 carbon atoms which may have substituents," "a cycloalkyl group having 5 to 10 carbon atoms which may have substituents," "a linear or branched alkenyl group having 2 to 6 carbon atoms which may have substituents," "a linear or branched alkyloxy group having 1 to 6 carbon atoms which may have substituents," "a cycloalkyloxy group having 5 to 10 carbon atoms which may have substituents," or "a substituted or unsubstituted aryloxy group," and in these cases, "a linear or branched alkyl group having 1 to 6 carbon atoms," "a cycloalkyl group having 5 to 10 carbon atoms which may have substituents," "a linear or branched alkenyl group having 2 to 6 carbon atoms," "a linear or branched alkenyl group having 1 to 6 carbon atoms," "a cycloalkyl group having 5 to 10 carbon atoms which may have substituents," or "a substituted or unsubstituted aryloxy group." Examples of "linear or branched alkyloxy groups of 6," "cycloalkyloxy groups having 5 to 10 carbon atoms," or "aryloxy groups" include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, n-hexyl, cyclopentyl, cyclohexyl, 1-adamantyl, 2-adamantyl, vinyl, allyl, isopropenyl, 2-butenyl, methyloxy, ethyloxy, n-propyloxy, cyclopentyloxy, cyclohexyloxy, 1-adamantyloxy, phenyloxy, tolyloxy, and biphenyloxy groups.

[0046] In general formula (a-1) and structural formula (b-1), A, B, C, D, L, and R represent "substituted aromatic hydrocarbon groups," "substituted aromatic heterocyclic groups," "substituted condensed polycyclic aromatic groups," "substituted aromatic hydrocarbon divalent groups," "substituted aromatic heterocyclic divalent groups," "substituted condensed polycyclic aromatic divalent groups," "substituted linear or branched alkyl groups having 1 to 6 carbon atoms," "substituted cycloalkyl groups having 5 to 10 carbon atoms," "substituted linear or branched alkenyl groups having 2 to 6 carbon atoms," "substituted linear or branched alkyloxy groups having 1 to 6 carbon atoms," "substituted cycloalkyloxy groups having 5 to 10 carbon atoms," or "substituted aryloxy groups," the "substituents" specifically include 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; and linear groups having 1 to 6 carbon atoms such as methyl groups, ethyl groups, and propyl groups. Linear or branched alkyl groups; linear or branched alkyl groups with 1 to 6 carbon atoms such as methyloxy, ethyloxy, and propyloxy groups; alkenyl groups such as vinyl and allyl groups; aryloxy groups such as phenyloxy and tolyloxy groups; arylalkyloxy groups such as benzyloxy and phenethyloxy groups; phenyl, biphenylyl, terphenylyl, naphthyl, anthracenyl, phenantrenyl, fluorenyl, and spirobifluorenyl groups. Aromatic hydrocarbon groups or condensed polycyclic aromatic groups such as indenyl, pyrenyl, perilenyl, fluoranthenyl, and triphenylenyl groups; pyridyl, thienyl, furyl, pyrrolyl, quinolyl, isoquinolyl, benzofuranyl, benzothienyl, indolyl, carbazolyl, imidazopyridyl, benzooxazolyl, benzothiazolyl, quinoxalinyl, benzimidazolyl, pyrazolyl, dibenzofuranyl, dibenzothienyl, and carbolinyl groups. Aromatic heterocyclic groupsOther examples include aryl groups having 6 to 30 carbon atoms, or heteroaryl groups having 2 to 20 carbon atoms, and these substituents may further be substituted with the substituents exemplified above. Furthermore, aromatic rings substituted with these substituents, or substituents multiple times substituted on the same aromatic ring, may be bonded to each other via single bonds, substituted or unsubstituted methylene groups, oxygen atoms, or sulfur atoms to form a ring.

[0047] The present invention has an azabenzoxazole ring structure represented by the general formula (a-1). Ji In amine compounds, L is preferably a divalent group (phenylene group) obtained by removing two hydrogen atoms from substituted or unsubstituted benzene, a divalent group (biphenylene group) obtained by removing two hydrogen atoms from substituted or unsubstituted biphenyl, or a divalent group (naphthylene group) obtained by removing two hydrogen atoms from substituted or unsubstituted naphthalene. More preferably, L is a divalent group (phenylene group) obtained by removing two hydrogen atoms from unsubstituted benzene, a divalent group (biphenylene group) obtained by removing two hydrogen atoms from unsubstituted biphenyl, or a divalent group (naphthylene group) obtained by removing two hydrogen atoms from unsubstituted naphthalene.

[0048] The present invention has an azabenzoxazole ring structure represented by the general formula (a-1). Ji In amine compounds, L may be bonded to A, B, C, or D via single bonds, substituted or unsubstituted methylene groups, oxygen atoms, or sulfur atoms to form a ring. The present invention has an azabenzoxazole ring structure represented by the general formula (a-1). Ji In amine compounds, the number of L atoms m represents an integer from 1 to 3, but m is preferably 1 or 2. Furthermore, when m is an integer of 2 or more, multiple L atoms may be identical or different from one another. The present invention has an azabenzoxazole ring structure represented by the general formula (a-1). JiIn amine compounds, the "substituted or unsubstituted aromatic hydrocarbon group," "substituted or unsubstituted aromatic heterocyclic group," or "substituted or unsubstituted condensed polycyclic aromatic group" represented by A, B, C, and D are preferably a phenyl group, biphenyl group, naphthyl group, phenantrenyl group, carbazolyl group, benzofuranyl group, benzothienyl group, indolyl group, benzimidazolyl group, imidazopyridyl group, benzoxazolyl group, benzothiazolyl group, dibenzofuranyl group, or dibenzothienyl group.

[0049] The present invention has an azabenzoxazole ring structure represented by the general formula (a-1). Ji In amine compounds, the Y atoms in the structural formula (b-1) may be the same or different from each other, and represent either CR or a nitrogen atom. However, at least one of the multiple Y atoms must be a nitrogen atom. The present invention has an azabenzoxazole ring structure represented by the general formula (a-1). Ji In the amine compound, at least one of A, B, C, and D has the structural formula (b-1), but it is preferable that only one of A, B, C, and D, or any two of them (for example, A and B, or A and C), has the structural formula (b-1). The present invention has an azabenzoxazole ring structure represented by the general formula (a-1). Ji In the amine compound, the structural formula (b-1) is preferably (b-2), (b-3), (b-4), or (b-5), and more preferably (b-4) or (b-5).

[0050] In the organic EL element 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.

[0051] In the organic EL element of the present invention, the refractive index of the capping layer is preferably 1.85 or higher, more preferably 1.88 or higher, and even more preferably 1.90 or higher, for light transmitted through the capping layer in the range of 450 nm to 750 nm. In the organic EL element of the present invention, the extinction coefficient of the capping layer in the range of 400 nm to 410 nm wavelength of light is preferably 0.2 or higher, more preferably 0.4 or higher, and even more preferably 0.8 or higher.

[0052] In the organic EL element of the present invention, the diamine compound having an azabenzoxazole ring structure represented by the general formula (a-1) that is preferably used is one with a concentration of 10 -5 The absorbance in the mol / L absorption spectrum within the wavelength range of 400 nm to 410 nm is preferably 0.2 or higher, more preferably 0.3 or higher, and even more preferably 0.4 or higher.

[0053] In the organic EL element of the present invention, the capping layer may be made by stacking or mixing two or more different constituent materials, and in that case, it is preferable that at least one of the constituent materials is a diamine compound having an azabenzoxazole ring structure represented by the general formula (a-1) of the present invention. [Effects of the Invention]

[0054] The diamine compound having an azabenzoxazole ring structure represented by the general formula (a-1) of the present invention has (1) a high extinction coefficient and (2) a wavelength range of 450 nm to 750 nm. Inside to OkeruBecause it has a high refractive index, (3) can be deposited, (4) is stable in thin film state, and (5) has high heat resistance, when used as a capping layer on the outside of the transparent or translucent electrodes of an organic EL element, using a capping layer with a refractive index higher than that of the electrodes can significantly improve the light extraction efficiency, prevent material degradation inside the element, and make it possible to obtain an organic EL element that can improve brightness, luminous efficiency, power efficiency, and lifespan. [Brief explanation of the drawing]

[0055] [Figure 1] This figure shows the structures of compounds (1-1) to (1-12) as diamine compounds having an azabenzoxazole ring structure represented by the general formula (a-1) of the present invention. [Figure 2] This figure shows the structures of compounds (1-13) to (1-23), which are diamine compounds having an azabenzoxazole ring structure represented by the general formula (a-1) of the present invention. [Figure 3] This figure shows the structures of compounds (1-24) to (1-35), which are diamine compounds having an azabenzoxazole ring structure represented by the general formula (a-1) of the present invention. [Figure 4] This figure shows the structures of compounds (1-36) to (1-47), which are diamine compounds having an azabenzoxazole ring structure represented by the general formula (a-1) of the present invention. [Figure 5] This figure shows the structures of compounds (1-48) to (1-57), which are diamine compounds having an azabenzoxazole ring structure represented by the general formula (a-1) of the present invention. [Figure 6] This figure shows the structures of compounds (1-58) to (1-69), which are diamine compounds having an azabenzoxazole ring structure represented by the general formula (a-1) of the present invention. [Figure 7] This figure shows the organic EL element configurations of Examples 10-15 and Comparative Examples 1-2. [Modes for carrying out the invention]

[0056] The diamine compounds having an azabenzoxazole ring structure represented by general formula (a-1) of the present invention are novel compounds. However, the azabenzoxazole derivatives that form the main skeleton of these compounds can be synthesized by known methods, as described below (see, for example, Non-Patent Document 4). Furthermore, by performing a coupling reaction between the synthesized halogenated azabenzoxazole derivative and an arylamine using a copper catalyst or a palladium catalyst, the diamine compounds having an azabenzoxazole ring structure represented by general formula (a-1) of the present invention can be synthesized. In addition, by first converting the halogenated azabenzoxazole derivative to a boronic acid ester derivative and then performing a coupling reaction with a halogenated arylamine, the diamine compounds having an azabenzoxazole ring structure represented by general formula (a-1) of the present invention can be synthesized in a similar manner (see, for example, Non-Patent Documents 5 and 6).

[0057] [ka]

[0058] Specific examples of preferred diamine compounds having an azabenzoxazole ring structure represented by the general formula (a-1) of the present invention are shown in Figures 1 to 6, but the invention is not limited to these compounds.

[0059] The purification of the diamine compound having an azabenzoxazole ring structure represented by the general formula (a-1) of the present invention is not particularly limited, but can be carried out by known methods used for the purification of organic compounds, such as purification by column chromatography, adsorption purification using silica gel, activated carbon, activated clay, etc., recrystallization purification or crystallization purification using solvents, and finally purification by sublimation purification. Compound identification was performed by NMR analysis. As physical properties, the melting point, glass transition temperature (Tg), refractive index, extinction coefficient, and absorbance were measured. The melting point is an indicator of vapor deposition properties, the glass transition temperature (Tg) is an indicator of the stability of the thin film state, the refractive index and extinction coefficient are indicators related to the improvement of light extraction efficiency, and absorbance is an indicator related to color purity and lightfastness.

[0060] The melting point and glass transition temperature (Tg) were measured using a high-sensitivity differential scanning calorimeter (manufactured by Bruker AXS, DSC3100SA) with the powder.

[0061] The refractive index and extinction coefficient were measured using a spectroscopic measurement device (manufactured by Filmetrics, F10-RT-UV) by forming an 80-nm thin film on a silicon substrate.

[0062] The absorbance was adjusted to a concentration of 10 -5 mol / L in a toluene solvent, and the absorption coefficient was adjusted to concentrations of 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 in four types of toluene solutions, and measured using an ultraviolet-visible near-infrared spectrophotometer (manufactured by JASCO, V-650).

[0063] As the structure of the organic EL device of the present invention, for example, in the case of a top emission structure light-emitting device, it is composed of an anode, a hole transport layer, a light-emitting layer, an electron transport layer, a cathode, and a capping layer sequentially on a glass substrate, and also those having a hole injection layer between the anode and the hole transport layer, those having an electron blocking layer between the hole transport layer and the light-emitting layer, those having a hole blocking layer between the light-emitting layer and the electron transport layer, and those having an electron injection layer between the electron transport layer and the cathode. In these multilayer structures, it is possible to omit or combine several organic layers. For example, a structure that combines a hole injection layer and a hole transport layer, a structure that combines a hole transport layer and an electron blocking layer, a structure that combines a hole blocking layer and an electron transport layer, a structure that combines an electron transport layer and an electron injection layer, etc. can also be made. Also, it is possible to form a structure in which two or more organic layers having the same function are laminated, such as a structure in which two hole transport layers are laminated, a structure in which two light-emitting layers are laminated, a structure in which two electron transport layers are laminated, a structure in which two capping layers are laminated, etc.

[0064] The total thickness of each layer of the organic EL element is preferably around 200 nm to 750 nm, and more preferably around 350 nm to 600 nm. The thickness of the capping layer is preferably, for example, 30 nm to 120 nm, and 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 for the light-emitting element, the thickness of the organic EL element other than the capping layer, etc.

[0065] As the anode for the organic EL element of the present invention, a transparent electrode material with a large work function, such as ITO or gold, is used.

[0066] As the hole injection layer of the organic EL element of the present invention, arylamine compounds having a structure in which two or more triphenylamine structures are linked in the molecule by single bonds or divalent groups that do not contain heteroatoms, such as benzidine derivatives; starburst-type triphenylamine derivatives; and various triphenylamine tetramers are preferred materials. In addition, porphyrin compounds represented by copper phthalocyanine; acceptor-type heterocyclic compounds such as hexacyanoazatriphenylene; and coating-type polymer materials can be used. These may be deposited individually, or used as monolayers deposited by mixing with other materials. They may also be used in a laminated structure of layers deposited individually, layers deposited by mixing, or layers deposited individually and layers deposited by mixing. These materials can be used to form thin films by known methods such as vapor deposition, spin coating, and inkjet.

[0067] As the hole transport layer of the organic EL device of the present invention, it is preferable to use arylamine compounds having a structure in which two triphenylamine structures are linked in the molecule by single bonds or divalent groups that do not contain heteroatoms, such as 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; or arylamine compounds having only one triphenylamine structure in the molecule, such as 1,1-bis[4-(di-4-tolylamino)phenyl]cyclohexane (TAPC). Furthermore, it is preferable to use arylamine compounds having a structure in which three or more triphenylamine structures are linked in the molecule by single bonds or divalent groups that do not contain heteroatoms, such as various triphenylamine trimers and tetramers. These materials may be deposited individually, or they may be used as single layers formed by mixing them with other materials. They may also be used in laminated structures, such as layers deposited individually, layers deposited by mixing, or layers deposited individually and layers deposited by mixing. 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 used to form thin films by known methods such as vapor deposition, spin coating, and inkjet printing.

[0068] Furthermore, in the hole injection layer or hole transport layer, it is preferable to further dope the material commonly used in the layer with trisbromophenylamine hexachloroantimony, radialene derivatives (see, for example, Patent Document 3), etc. Also, polymer compounds having the structure of a benzidine derivative such as TPD as a substructure can be used.

[0069] As the electron blocking layer of the organic EL device of the present invention, compounds having electron blocking properties can be used, such as carbazole derivatives such as 4,4',4''-tri(N-carbazolyl)triphenylamine (TCTA), 9,9-bis[4-(carbazole-9-yl)phenyl]fluorene, 1,3-bis(carbazole-9-yl)benzene (mCP), and 2,2-bis(4-carbazole-9-yl-phenyl)adamantane (Ad-Cz); and compounds having a triphenylsilyl group and a triarylamine structure, such as 9-[4-(carbazole-9-yl)phenyl]-9-[4-(triphenylsilyl)phenyl]-9H-fluorene. These may be deposited individually, or used as a single layer by mixing them with other materials. They may also be used in a laminated structure of layers deposited individually, layers deposited by mixing them, or layers deposited individually and layers deposited by mixing them. These materials can be formed into thin films using known methods such as vapor deposition, spin coating, and inkjet printing.

[0070] As the light-emitting layer of the organic EL element of the present invention, in addition to metal complexes of quinolinol derivatives such as Alq3, various metal complexes, anthracene derivatives, bis-styrylbenzene derivatives, pyrene derivatives, oxazole derivatives, poly(p-phenylenevinylene) derivatives, etc., can be used. The light-emitting layer may also be composed of a host material and a dopant material. Anthracene derivatives are preferably used as the host material, but in addition to the above-mentioned light-emitting materials, heterocyclic compounds having an indole ring as a substructure of the fused ring, heterocyclic compounds having a carbazole ring as a substructure of the fused ring, carbazole derivatives, thiazole derivatives, benzimidazole derivatives, polydialkylfluorene derivatives, etc., can be used. As the dopant material, quinacridone, coumarin, rubrene, perylene and their derivatives, benzopyran derivatives, rhodamine derivatives, aminostyryl derivatives, etc., can be used. These materials may be deposited individually, or they may be used as single layers deposited by mixing them with other materials. They may also be used in laminated structures, such as layers deposited individually, layers deposited by mixing, or layers deposited individually and layers deposited by mixing.

[0071] Furthermore, phosphorescent materials can be used as light-emitting materials. As phosphorescent materials, metal complex phosphorescent materials 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. As the host material in this case, hole-injection and transport-enabled host materials such as 4,4'-di(N-carbazolyl)biphenyl (CBP), TCTA, and mCP, which are carbazole derivatives, can be used. As electron-transport-enabled host materials, p-bis(triphenylsilyl)benzene (UGH2) and 2,2',2''-(1,3,5-phenylene)-tris(1-phenyl-1H-benzimidazole) (TPBI) can be used, and high-performance organic EL devices can be fabricated.

[0072] To avoid concentration quenching, it is preferable to dope the phosphorescent luminescent material onto the host material by co-deposition in an amount ranging from 1 to 30 weight percent of the entire luminescent layer.

[0073] Furthermore, materials that emit delayed fluorescence, such as PIC-TRZ, CC2TA, PXZ-TRZ, and CDCB derivatives like 4CzIPN, can also be used as light-emitting materials (see, for example, Non-Patent Document 7). These materials can be used to form thin films using known methods such as vapor deposition, spin coating, and inkjet printing.

[0074] As 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 like bathocuproine (BCP), metal complexes of quinolinol derivatives like aluminum(III) bis(2-methyl-8-quinolinate)-4-phenylphenolate (BAlq), various rare earth complexes, triazole derivatives, triazine derivatives, pyrimidine derivatives, oxadiazole derivatives, and benzoazole derivatives. These materials may also serve as the electron transport layer material. These materials may be deposited individually, or used as monolayers formed by mixing them with other materials. They may also be used in laminated structures, such as layers deposited individually, layers deposited by mixing, or layers deposited individually and layers deposited by mixing. These materials can be used to form thin films by known methods such as vapor deposition, spin coating, and inkjet printing.

[0075] As 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 deposited as films on their own, or as monolayers deposited by mixing them with other materials. They may also be used in laminated structures of layers deposited individually, layers deposited by mixing, or layers deposited individually and layers deposited by mixing. These materials can be used to form thin films by known methods such as vapor deposition, spin coating, and inkjet printing.

[0076] As 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 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) can be used, but these can be omitted in the preferred selection of the electron transport layer and cathode.

[0077] Furthermore, in the electron injection layer or electron transport layer, a material that is N-doped with a metal such as cesium can be used in addition to the material normally used in the layer.

[0078] As the cathode of the organic EL element of the present invention, electrode materials with a low work function such as aluminum, or alloys with an even lower work function such as magnesium-silver alloy, magnesium-calcium alloy, magnesium-indium alloy, or aluminum-magnesium alloy, as well as ITO and IZO, can be used as electrode materials. In an organic EL element with a top-emission structure, which is an example of the present invention, the cathode in the direction in which light is extracted from the light-emitting element to the outside is preferably transparent or semi-transparent.

[0079] As the capping layer of the organic EL element of the present invention, azabenzo represented by the general formula (a-1) is used. Oxa Having a zole ring structure Ji It is preferable to use an amine compound. The azabenzo represented by the general formula (a-1) is used, wherein the wavelength of light transmitted through the capping layer is in the range of 450 nm to 750 nm. Oxa Having a zole ring structure Ji The refractive index of the capping layer, which is composed of an amine compound, is preferably 1.85 or higher, more preferably 1.88 or higher, and even more preferably 1.90 or higher.

[0080] Azabenzo represented by the general formula (a-1) of the present invention Oxa Having a zole ring structure JiWhen using amine compounds as the capping layer of an organic EL element, they may be deposited individually, or they may be used as a single layer formed by mixing two or more compounds. They may also be used in a stacked structure consisting of layers deposited individually, layers deposited by mixing, or layers deposited individually and layers deposited by mixing.

[0081] In the case where the capping layer of the organic EL element of the present invention is a stacked or mixed layer composed of two or more compounds, it is preferable that at least one of the constituent materials is a diamine compound having an azabenzoxazole ring structure represented by the general formula (a-1). These may be deposited individually, or used as a single layer by mixing with other materials, or as a stacked structure of layers deposited individually, layers deposited by mixing, or layers deposited individually and layers deposited by mixing. These materials can be formed into thin films by known methods such as vapor deposition, spin coating, and inkjet printing.

[0082] The refractive index of the capping layer is preferably greater than that of the adjacent electrodes. That is, the capping layer improves the light extraction efficiency in the organic EL element, and this effect is more effective when the reflectivity at the interface between the capping layer and the material in contact with the capping layer is high, because the effect of optical interference is greater. For this reason, the refractive index of the capping layer is preferably greater than that of the adjacent electrodes, and a refractive index of 1.70 or higher is sufficient, but 1.85 or higher is preferable, 1.88 or higher is more preferable, and 1.90 or higher is even preferable.

[0083] Although the above describes an organic EL element with a top emission structure, the present invention is not limited thereto, and can be similarly applied to organic EL elements with a bottom emission structure, and organic EL elements with a dual emission structure that emit light from both the top and bottom. In these cases, the electrodes in the direction from which light is extracted from the light-emitting element are preferably transparent or semi-transparent. [Examples]

[0084] The embodiments of the present invention will be described in detail below with reference to examples, but the present invention is not limited to the following embodiments unless it exceeds the gist of the invention. [Examples]

[0085] <Synthesis of compound (1-1)> In a reaction vessel, 6.2 g of diphenylbenzidine, 11.15 g of 2-(4-bromophenyl)oxazolo[5,4-b]pyridine, 3.9 g of sodium tert-butoxide, 0.17 g of palladium(II) acetate, and 0.3 g of tri-tert-butylphosphine (50% toluene solution) were added, and the mixture was stirred under reflux overnight in toluene solution. After the reaction was complete, the mixture was washed to remove dispersions, insoluble matter was removed by filtration, and the filtrate was concentrated to obtain the crude product. The crude product was purified by crystallization using a monochlorobenzene / acetone mixed solvent to obtain 5.5 g of compound (1-1) as a yellow powder (yield 41.2%).

[0086] [ka] (1-1)

[0087] The structure of the obtained yellow powder was identified using NMR. 1 The following 32 hydrogen signals were detected by 1H-NMR (CDCl3). 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). [Examples]

[0088] <Synthesis of compounds (1-24)> In a reaction vessel, 8.0 g of phenyl-(4'-bromoviphenyl-4-yl)-4-(2-benzoxazolyl)phenylamine, 4.9 g of phenyl-4-(oxazolo[5,4-b]pyridine-2-yl)phenylamine, 2.2 g of sodium tert-butoxide, 0.4 g of tridibenzylideneacetone palladium(0), and 0.4 g of tri-tert-butylphosphine (50% toluene solution) were added, and the mixture was stirred under reflux overnight in toluene solution. After the reaction was complete, insoluble matter was removed by filtration, and the filtrate was concentrated to obtain the crude product. The crude product was then subjected to column chromatography. Fu Purification was carried out using a mixed solvent of dichloromethane and ethyl acetate to obtain 5.6 g of the yellow powder compound (1-24) (yield 49.6%).

[0089] [ka] (1-24)

[0090] The structure of the obtained yellow powder was identified using NMR. 1 The following 33 hydrogen signals were detected by 1H-NMR (CDCl3). 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). [Examples]

[0091] <Synthesis of compounds (1-52)> In the reaction vessel, add 7.0g of 1-bromo-4-iodobenzene and phenyl -4 - (15.6 g of oxazolo[5,4-b]pyridine-2-yl)phenylamine, 7.1 g of sodium tert-butoxide, 0.9 g of tridibenzylideneacetone palladium (0), and 0.4 g of tri-tert-butylphosphine were added and stirred under reflux overnight in toluene solution. After the reaction was complete, the mixture was washed to obtain the crude product. The crude product was purified by crystallization using a monochlorobenzene / acetone mixed solvent to obtain 8.8 g of compound (1-52) as a yellow powder (yield 55.1%).

[0092] [ka] (1-52)

[0093] The structure of the obtained yellow powder was identified using NMR. 1 The following 28 hydrogen signals were detected by 1H-NMR (CDCl3). 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). [Examples]

[0094] <Synthesis of compounds (1-55)> In the reaction vessel, add 5.0 g of 2,6-dibromonaphthalene and phenyl -4 - ( 11.1 g of oxazolo[5,4-b]pyridine-2-yl)phenylamine, 5.1 g of sodium tert-butoxide, 0.6 g of tridibenzylideneacetone palladium(0), and 0.3 g of tri-tert-butylphosphine were added and stirred under reflux overnight in toluene solution. After the reaction was complete, the mixture was washed to obtain the crude product. The crude product was purified by crystallization using a monochlorobenzene / acetone mixed solvent to obtain 7.9 g of compound (1-55) as a yellow powder (yield 53.1%).

[0095] [ka] (1-55)

[0096] The structure of the obtained yellow powder was identified using NMR. 1 The following 30 hydrogen signals were detected by 1H-NMR (CDCl3). 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). [Examples]

[0097] <Synthesis of compounds (1-56)> In the reaction vessel, add 6.0 g of 2,7-dibromonaphthalene and phenyl -4 - ( 13.3 g of oxazolo[5,4-b]pyridine-2-yl)phenylamine, 6.1 g of sodium tert-butoxide, 0.8 g of tridibenzylideneacetone palladium (0), and 0.3 g of tri-tert-butylphosphine were added and stirred under reflux overnight in toluene solution. After the reaction was complete, the mixture was washed to obtain the crude product. The crude product was purified by crystallization using a monochlorobenzene / acetone mixed solvent to obtain 8.1 g of the yellow powder compound (1-56) (yield 55.1%).

[0098] [ka] (1-56)

[0099] The structure of the obtained yellow powder was identified using NMR. 1 The following 30 hydrogen signals were detected by 1H-NMR (CDCl3). 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). [Examples]

[0100] <Synthesis of compounds (1-57)> In the reaction vessel, add 7.1g of 4,4''-diiodo-p-terphenyl and phenyl -4 - ( 9.2 g of oxazolo[5,4-b]pyridine-2-yl)phenylamine, 4.2 g of sodium tert-butoxide, 0.4 g of tridibenzylideneacetone palladium(0), and 0.3 g of tri-tert-butylphosphine (50% toluene solution) were added, and the mixture was stirred under reflux overnight in toluene solution. After the reaction was complete, dispersion washing was performed, insoluble matter was removed by filtration, and the filtrate was concentrated to obtain the crude product. The crude product was then subjected to column chromatography. Fu Purification was carried out using a mixed solvent of dichloromethane and ethyl acetate to obtain 6.8 g of the yellow powder compound (1-57) (yield 58.6%).

[0101] [ka] (1-57)

[0102] The structure of the obtained yellow powder was identified using NMR. 1 The following 36 hydrogen signals were detected by 1H-NMR (CDCl3). 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). [Examples]

[0103] The melting point and glass transition temperature (Tg) of a diamine compound having an azabenzoxazole ring structure represented by general formula (a-1) were measured using a high-sensitivity differential scanning calorimeter (Bruker AXS, DSC3100SA). The measurement results are shown below.

[0104] Melting point, glass transition temperature (Tg) Compound (1-1) 279.6℃ 136.7℃ Compound (1-24): Not observed at 131.5°C Compound (1-52) 280.6℃ 120.4℃ Compound (1-55) 301.0℃ 143.1℃ Compound (1-56) 251.1℃ 141 . 6℃ Compound (1-57) 300.2℃ 144.3℃

[0105] Thus, diamine compounds having an azabenzoxazole ring structure represented by general formula (a-1) have a glass transition temperature of 100°C or higher, indicating that the thin film state is stable. [Examples]

[0106] A diamine compound having an azabenzoxazole ring structure represented by general formula (a-1) was used to fabricate a vapor-deposited film with a thickness of 80 nm on a silicon substrate. The refractive index n at wavelengths of 450 nm and 750 nm, and the extinction coefficient k at wavelengths of 400 nm and 410 nm were measured using a spectroscopic measuring device (Filmetrics, F10-RT-UV). For comparison, the comparative compound (2-1) with the following structural formula and Alq3 were also measured (see, for example, Patent Document 4). The measurement results are summarized in Table 1.

[0107] [ka] (2-1)

[0108] [Table 1]

[0109] Thus, the refractive index at a wavelength of 450 nm is 1.88 and 1.93 for the conventional material Alq3 and comparative compound (2-1), respectively, while the diamine compound having an azabenzoxazole ring structure represented by the general formula (a-1) of the present invention shows a large value of 2.35 to 2.58. Furthermore, the refractive index at a wavelength of 750 nm is 1.73 and 1.78 for the conventional material Alq3 and comparative compound (2-1), respectively, while the diamine compound having an azabenzoxazole ring structure represented by the general formula (a-1) of the present invention shows a large value of 1.88 to 1.92, which is above 1.85. This indicates that by using the diamine compound having an azabenzoxazole ring structure represented by the general formula (a-1), which is suitably used in the organic EL element of the present invention, as a constituent material for the capping layer, an improvement in the light extraction efficiency of the organic EL element can be expected. Furthermore, the extinction coefficient at wavelengths of 400 nm to 410 nm is 0.06 to 0.16 for conventional materials such as Alq3 and comparative compound (2-1), while the diamine compound having an azabenzoxazole ring structure represented by the general formula (a-1) of the present invention shows a much larger value of 0.80 to 1.09, which is greater than 0.2. This indicates that the capping layer formed using the diamine compound having an azabenzoxazole ring structure represented by the general formula (a-1), which is suitably used in the organic EL element of the present invention, absorbs sunlight light at wavelengths of 400 nm to 410 nm well and has less impact on the materials inside the element. [Examples]

[0110] Using a diamine compound having an azabenzoxazole ring structure represented by general formula (a-1), a concentration of 10°C was obtained using a toluene solution. -5 The absorbance at wavelengths of 400 nm and 410 nm was measured using a UV-Vis-Near-Infrared spectrophotometer (JASCO, V-650) after preparing the solution to mol / L. The extinction coefficient was measured using a toluene solution at a concentration of 5 × 10⁻⁶. -6 mol / L, 1 × 10 -5 mol / L, 1.5 × 10 -5 mol / L, and 2.0 × 10⁻⁶ -5The solution was prepared at four different concentrations in mol / L and measured using a UV-Vis-Near-Infrared spectrophotometer (JASCO, V-650). The extinction coefficient was calculated from the calibration curve. For comparison, the same measurements were performed on the comparative compound (2-1) and Alq3, which have the same structural formula as described above. The measurement results are summarized in Table 2.

[0111] [Table 2]

[0112] Thus, the absorbance at wavelengths of 400 nm and 410 nm is 0.02 to 0.07 for conventional materials such as Alq3 and comparative compound (2-1), while the diamine compound having an azabenzoxazole ring structure represented by the general formula (a-1) of the present invention shows a much larger value of 0.49 to 1.42, which is more than 0.2. This indicates that the diamine compound having an azabenzoxazole ring structure represented by the general formula (a-1) of the present invention absorbs sunlight light at wavelengths of 400 nm to 410 nm very well. Furthermore, regarding the absorption coefficient, the present invention one The diamine compound having an azabenzoxazole ring structure represented by general formula (a-1) has an extinction coefficient of 100,000 or more, which is more than an order of magnitude larger than that of the comparative compound. In other words, the diamine compound having an azabenzoxazole ring structure represented by general formula (a-1) of the present invention absorbs light well under the same concentration conditions, and absorbs light better as the film thickness increases in thin films, indicating that it is a material with excellent light resistance. [Examples]

[0113] As shown in Figure 7, the organic EL element was fabricated by pre-forming a reflective ITO electrode as a transparent anode 2 on a glass substrate 1, and then depositing the following layers in that order: hole injection layer 3, hole transport layer 4, light-emitting layer 5, electron transport layer 6, electron injection layer 7, cathode 8, and capping layer 9.

[0114] Specifically, a metal anode 2 was formed on a glass substrate 1 by sequentially depositing ITO with a thickness of 50 nm, a reflective silver alloy with a thickness of 100 nm, and ITO with a thickness of 5 nm. This was then ultrasonically cleaned in isopropyl alcohol for 20 minutes, and dried on a hot plate heated to 250°C for 10 minutes. After that, UV ozone treatment was performed for 2 minutes, and then this ITO-coated glass substrate was placed in a vacuum deposition machine and the pressure was reduced to below 0.001 Pa. Subsequently, a hole injection layer 3 was formed covering the transparent anode 2 by binary deposition of an electron acceptor (Acceptor-1) with the following structural formula and a compound (3-1) with the following structural formula, at a deposition rate ratio of Acceptor-1:compound (3-1) = 3:97, to a thickness of 10 nm. On this hole injection layer 3, a hole transport layer 4 was formed using the compound (3-1) with the following structural formula to a thickness of 140 nm. On this hole transport layer 4, two compounds with the following structural formulas (3-2) and (3-3) were deposited as an emissive layer 5 using a binary deposition method with a deposition rate ratio of compound (3-2):compound (3-3)=5:95, resulting in a film thickness of 20 nm. On this emissive layer 5, two compounds with the following structural formulas (3-4) and (3-5) were deposited as an electron transport layer 6 using a binary deposition method with a deposition rate ratio of compound (3-4):compound (3-5)=50:50, resulting in a film thickness of 30 nm. On this electron transport layer 6, lithium fluoride was deposited as an electron injection layer 7 to a film thickness of 1 nm. On this electron injection layer 7, a magnesium-silver alloy was deposited as a cathode 8 to a film thickness of 12 nm. Finally, compound (1-1) from Example 1 was deposited as a capping layer 9 to a film thickness of 60 nm. The fabricated organic EL element was subjected to characteristic measurements in air at room temperature. Table 3 summarizes the measurement results of the light emission characteristics when a DC voltage was applied to the fabricated organic EL element.

[0115] [ka]

[0116] [Example 11] In Example 10, an organic EL element was fabricated under the same conditions as in Example 10, except that the compound (1-24) from Example 2 was used as the material for the capping layer 9 instead of the compound (1-1) from Example 1. The fabricated organic EL element was subjected to characteristic measurements in air at room temperature. Table 3 summarizes the measurement results of the light emission characteristics when a DC voltage was applied to the fabricated organic EL element.

[0117] [Example 12] In Example 10, the compound (1-1) from Example 1 was used as the material for the capping layer 9, 3 Organic EL elements were fabricated under the same conditions, except for the use of compound (1-52). The fabricated organic EL elements were subjected to characteristic measurements in air at room temperature. Table 3 summarizes the measurement results of the light emission characteristics when a DC voltage was applied to the fabricated organic EL element.

[0118] [Example 13] In Example 10, the compound (1-1) from Example 1 was used as the material for the capping layer 9, 4 Organic EL elements were fabricated under the same conditions, except for the use of compound (1-55). The fabricated organic EL elements were subjected to characteristic measurements in air at room temperature. Table 3 summarizes the measurement results of the light emission characteristics when a DC voltage was applied to the fabricated organic EL element.

[0119] [Example 14] In Example 10, the compound (1-1) from Example 1 was used as the material for the capping layer 9, 5 Organic EL elements were fabricated under the same conditions, except for the use of compound (1-56). The fabricated organic EL elements were subjected to characteristic measurements in air at room temperature. Table 3 summarizes the measurement results of the light emission characteristics when a DC voltage was applied to the fabricated organic EL element.

[0120] [Example 15] In Example 10, the compound (1-1) from Example 1 was used as the material for the capping layer 9, 6Organic EL elements were fabricated under the same conditions, except for the use of compound (1-57). The fabricated organic EL elements were subjected to characteristic measurements in air at room temperature. Table 3 summarizes the measurement results of the light emission characteristics when a DC voltage was applied to the fabricated organic EL element.

[0121] [Comparative Example 1] For comparison, in Example 10, an organic EL element was fabricated under the same conditions as in Example 1, except that Alq3 was used as the material for the capping layer 9 instead of compound (1-1) from Example 1. The fabricated organic EL element was subjected to characteristic measurements in air at room temperature. Table 3 summarizes the measurement results of the light emission characteristics when a DC voltage was applied to the fabricated organic EL element.

[0122] [Comparative Example 2] For comparison ,fruit In Example 10, an organic EL element was fabricated under the same conditions as in Example 1, except that the comparative compound (2-1) with the above structural formula was used as the material for the capping layer 9 instead of the compound (1-1) from Example 1. The fabricated organic EL element was subjected to characteristic measurements in air at room temperature. The measurement results of the luminescence characteristics when a DC voltage was applied to the fabricated organic EL element are summarized in Table 3.

[0123] Table 3 summarizes the results of measuring the device lifetime using the organic EL devices fabricated in Examples 10-15 and Comparative Examples 1-2. The device lifetime was 10 mA / cm². 2 When driven with a constant current, the time it took for the initial brightness to decay to 95% (95% decay) was measured.

[0124] [Table 3]

[0125] As shown in Table 3, the current density is 10 mA / cm². 2While the driving voltage at time was almost the same for the elements of Comparative Examples 1-2 using the comparative compound and the elements of Examples 10-15 using the compound of the present invention, the brightness, luminous efficiency, power efficiency, and element life were significantly improved in the elements of Examples 10-15 using the compound of the present invention compared to the elements of Comparative Examples 1-2 using the comparative compound. This is because the capping layer contains azabenzo represented by the general formula (a-1) of the present invention, which has a high refractive index. Oxa This study demonstrates that including a diamine compound having a zole ring structure can significantly improve the light extraction efficiency in organic EL devices. [Industrial applicability]

[0126] As described above, the azabenzo represented by the general formula (a-1) of the present invention Oxa Diamine compounds having a zole ring structure exhibit high absorption coefficients and refractive indices, significantly improving light extraction efficiency, and maintaining a stable thin film state. Therefore, they are excellent compounds for use in the capping layer of organic EL devices. By fabricating organic EL devices using these compounds, high efficiency can be achieved, and because they absorb sunlight without affecting the internal materials of the device, durability and light resistance can be improved. Furthermore, by using compounds that do not absorb in the blue, green, and red wavelength regions, they are particularly suitable for applications where high color purity, clarity, and brightness are desired. For example, this opens up possibilities for applications in home appliances and lighting. [Explanation of symbols]

[0127] 1. Glass substrate 2 transparent anode 3. Hole injection layer 4. Hole transport layer 5. Emitting layer 6 Electron transport layer 7 Electron injection layer 8 cathode 9. Capping layer

Claims

1. A diamine compound having an azabenzoxazole ring structure represented by the following general formula (a-1). 【Chemistry 1】 (a-1) In the formula, A, B, C, and D may be the same or different from each other, and represent a monovalent group having an azabenzoxazole group represented by the following structural formula (b-2), a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group. However, at least one of A, B, C, or D is a monovalent group having an azabenzoxazole group represented by the following structural formula (b-2), and when a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group represented by A, B, C, or D has substituents, the substituents are deuterium, cyano, nitro, fluorine, chlorine, bromine, iodine, trimethylsilyl, triphenylsilyl, methyl, ethyl, propyl, methyloxy, ethyloxy, propyloxy, vinyl, allyl, phenyloxy, tolyloxy, benzyloxy, and phenyloxy groups. The group shall be selected from netyloxy group, phenyl group, biphenylyl group, terphenylyl group, naphthyl group, anthracenyl group, phenantrenyl group, fluorenyl group, spirobifluorenyl group, indenyl group, pyrenyl group, perilenyl group, fluoranthenyl group, triphenylenyl group, pyridyl group, thienyl group, furyl group, pyrrolyl group, quinolyl group, isoquinolyl group, benzofuranyl group, benzothienyl group, indolyl group, carbazolyl group, imidazopyridyl group, benzoxazolyl group, benzothiazolyl group, quinoxalinyl group, benzimidazolyl group, pyrazolyl group, dibenzofuranyl group, dibenzothienyl group, or carboninyl group. L represents a divalent group of a substituted or unsubstituted aromatic hydrocarbon, a divalent group of a substituted or unsubstituted aromatic heterocyclic, or a divalent group of a substituted or unsubstituted condensed polycyclic aromatic.However, L does not bond with A, B, C, or D to form a ring, and when a divalent group of a substituted or unsubstituted aromatic hydrocarbon represented by L, a divalent group of a substituted or unsubstituted aromatic heterocycle, or a divalent group of a substituted or unsubstituted condensed polycyclic aromatic has substituents, the substituents are deuterium, cyano, nitro, fluorine, chlorine, bromine, iodine, trimethylsilyl, triphenylsilyl, methyl, ethyl, propyl, methyloxy, ethyloxy, propyloxy, vinyl, allyl, phenyloxy, tolyloxy, benzyloxy, phenethyloxy, and phenyloxy. The L group shall be selected from the following: nyl group, biphenylyl group, terphenylyl group, naphthyl group, anthracenyl group, phenantrenyl group, fluorenyl group, spirobifluorenyl group, indenyl group, pyrenyl group, perilenyl group, fluoranthenyl group, triphenylenyl group, pyridyl group, thienyl group, furyl group, pyrrolyl group, quinolyl group, isoquinolyl group, benzofuranyl group, benzothienyl group, indolyl group, carbazolyl group, imidazopyridyl group, benzoxazolyl group, benzothiazolyl group, quinoxalinyl group, benzimidazolyl group, pyrazolyl group, dibenzofuranyl group, dibenzothienyl group, or carboninyl group. m represents an integer from 1 to 3, and if m is an integer of 2 or more, multiple L groups may be the same or different from each other. 【Chemistry 2】 (b-2) In the formula, each R may be the same or different from each other, and any one of the Rs is a linking group that serves as a bonding site with 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 linear or branched alkyl group having 1 to 6 carbon atoms which may be substituted, a cyclopentyl group which may be substituted, a cyclohexyl group which may be substituted, a linear or branched alkenyl group having 2 to 6 carbon atoms which may be substituted, a linear or branched alkyloxy group having 1 to 6 carbon atoms which may be substituted, a cyclopentyloxy group which may be substituted, a cyclohexyloxy group which may be substituted, 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.However, if a linear or branched alkyl group having 1 to 6 carbon atoms that may have substituents represented by R, a substituted or substituted cyclopentyl group, a substituted or substituted cyclohexyl group, a linear or branched alkenyl group having 2 to 6 carbon atoms that may have substituents, a linear or branched alkyloxy group having 1 to 6 carbon atoms that may have substituents, a substituted or substituted cyclopentyloxy group, a substituted or substituted cyclohexyloxy group, 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 has substituents, the substituents are deuterium, cyano, nitro, fluorine, chlorine, bromine, iodine, trimethylsilyl, and triphenylsilyl. The group shall be selected from the following: methyl group, ethyl group, propyl group, methyloxy group, ethyloxy group, propyloxy group, vinyl group, allyl group, phenyloxy group, tolyloxy group, benzyloxy group, phenethyloxy group, phenyl group, biphenylyl group, terphenylyl group, naphthyl group, anthracenyl group, phenantrenyl group, fluorenyl group, spirobifluorenyl group, indenyl group, pyrenyl group, perilenyl group, fluoranthenyl group, triphenylenyl group, pyridyl group, thienyl group, furyl group, pyrrolyl group, quinolyl group, isoquinolyl group, benzofuranyl group, benzothienyl group, indolyl group, carbazolyl group, imidazopyridyl group, benzoxazolyl group, benzothiazolyl group, quinoxalinyl group, benzimidazolyl group, pyrazolyl group, dibenzofuranyl group, dibenzothienyl group, or carboninyl group.

2. A diamine compound having an azabenzoxazole ring structure according to claim 1, characterized in that A, B, C, and D in the general formula (a-1) are a monovalent group having an azabenzoxazole group represented by the structural formula (b-2), a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted naphthyl group, a substituted or unsubstituted phenantrenyl group, a substituted or unsubstituted carbazolyl group, a substituted or unsubstituted benzofuranyl group, a substituted or unsubstituted benzothienyl group, a substituted or unsubstituted indolyl group, a substituted or unsubstituted benzimidazolyl group, a substituted or unsubstituted imidazopyridyl group, a substituted or unsubstituted benzoxazolyl group, a substituted or unsubstituted benzothiazolyl group, a substituted or unsubstituted dibenzofuranyl group, or a substituted or unsubstituted dibenzothienyl group.

3. A diamine compound having an azabenzoxazole ring structure according to claim 1 or claim 2, characterized in that L in the general formula (a-1) is a substituted or unsubstituted phenylene group, a substituted or unsubstituted biphenylene group, or a substituted or unsubstituted naphthylene group.

4. A diamine compound having an azabenzoxazole ring structure according to claim 1 or claim 2, characterized in that m in the general formula (a-1) is 1 or 2.

5. A diamine compound having an azabenzoxazole ring structure according to claim 1 or claim 2, characterized in that the structural formula (b-2) is the following structural formula (b-4). 【Transformation 3】 (b-4) In the formula, R is defined as in the structural formula (b-2) above.

6. The diamine compound having an azabenzoxazole ring structure according to claim 5, characterized in that only one of A, B, C, or D in the general formula (a-1) is structural formula (b-4).

7. The diamine compound having an azabenzoxazole ring structure according to claim 5, characterized in that any two of A, B, C, or D in the general formula (a-1) are structural formula (b-4).

8. The diamine compound having an azabenzoxazole ring structure according to claim 5, characterized in that A and B in the general formula (a-1) are structural formula (b-4).

9. The diamine compound having an azabenzoxazole ring structure according to claim 5, characterized in that A and C in the general formula (a-1) are structural formula (b-4).

10. An organic electroluminescent element having 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 this order, characterized in that the capping layer contains a diamine compound having an azabenzoxazole ring structure as described in claim 1 or claim 2.

11. The extinction coefficient of the capping layer in the wavelength range of 400 nm to 410 nm is 0.2 or more, and the concentration of the diamine compound having the azabenzoxazole ring structure is 10 －５ The organic electroluminescent element according to claim 10, characterized in that the absorbance in the wavelength range of 400 nm to 410 nm in the mol / L absorption spectrum is 0.2 or more.

12. The organic electroluminescent element according to claim 10, characterized in that the refractive index of the capping layer is 1.85 or more when the wavelength of light transmitted through the capping layer is in the range of 450 nm to 750 nm.

13. The organic electroluminescent element according to claim 10, characterized in that, when the capping layer consists of a laminated or mixed layer containing two or more compounds, at least one of the compounds is a diamine compound having the azabenzoxazole ring structure.

14. An electronic device or electronic element having a pair of electrodes and at least one organic layer sandwiched between them, characterized in that the organic layer contains a diamine compound having an azabenzoxazole ring structure as described in claim 1 or claim 2.

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