Carbazole compounds and organic electroluminescent elements

Abstract

The object of the present invention is to provide a compound with a high refractive index in the 450nm to 750nm range and a low extinction coefficient in the capping layer, in order to improve the light extraction efficiency of organic EL elements. [Solution] This invention focuses on the fact that certain carbazole compounds exhibit excellent thin-film stability and durability, and that the refractive index can be improved by adjusting the molecular structure. By designing the molecules and using them as materials to constitute the capping layer, an organic EL element with excellent luminescence efficiency was obtained.

Description

[Technical Field]

[0001] The present invention relates to compounds suitable for self-emissive electronic elements suitable for various display devices, particularly carbazole compounds suitable for organic electroluminescent elements (hereinafter abbreviated as organic EL elements), and organic EL elements, electronic elements, and electronic devices 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 is achieved (see, for example, Patent Documents 1 and 2).

[0004] To date, many improvements have been made to commercialize organic EL elements. By further subdividing the roles of each layer in the stacked structure and sequentially arranging the anode, hole injection layer, hole transport layer, light-emitting layer, electron transport layer, electron injection layer, and cathode on the substrate, high efficiency and durability can be achieved by creating a bottom-emission light-emitting element 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, top-emission light-emitting devices have the advantage of a wider light-emitting part because the pixel circuit does not obstruct the light as it is extracted from the top. In top-emission light-emitting devices, 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 efficiency of light extraction, light-emitting devices have been proposed in which a high-refractive-index "capping layer" is provided on the outside of a low-refractive-index translucent electrode (see, for example, Non-Patent Documents 2 and 3).

[0007] As an effect of the capping layer in a top-emission light-emitting element, in a light-emitting element using Ir(ppy)3 as the light-emitting material, the current efficiency was 38 cd / A without a capping layer, while in a light-emitting element using ZnSe with a film thickness of 60 nm as a capping layer, an efficiency improvement of approximately 1.7 times was observed, reaching 64 cd / A. Furthermore, it has been shown that the maximum transmittance point of the translucent electrode and the capping layer do not necessarily coincide with the maximum efficiency point, and 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 fine metal mask has been proposed for forming the capping layer. However, when used under high-temperature conditions, the metal mask becomes distorted due to heat, resulting in a decrease in alignment accuracy. Therefore, ZnSe, which has a high melting point of over 1100°C, cannot be deposited in the correct position using a highly fine metal mask, potentially adversely affecting the light-emitting element (see, for example, Non-Patent Document 3). Furthermore, even with film deposition by sputtering, it adversely affects the light-emitting element, making capping layers composed of inorganic materials unsuitable for use.

[0009] In addition, it has been proposed to use tris(8-hydroxyquinoline)aluminum (hereinafter abbreviated as Alq3) as a capping layer to adjust the refractive index (see, for example, Non-Patent Document 2). However, Alq3 is known as an organic EL material commonly used as a green light-emitting material or electron transport material, and it has weak absorption around 450 nm, which is close to the emission wavelength of blue light-emitting materials. Therefore, in the case of blue light-emitting elements, there have been problems such as a decrease in color purity and a decrease in light extraction efficiency.

[0010] To improve the characteristics of organic EL elements and to significantly improve light extraction efficiency, there is a need for capping layer materials that have a high refractive index, a low extinction coefficient, and excellent thin-film stability and durability. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] No. US5792557 [Patent Document 2] No. US5639914 [Patent Document 3] International Publication No. 2014 / 009310 [Patent Document 4] No. KR2164767 [Non-patent literature]

[0012] [Non-Patent Document 1] Proceedings of the 9th Workshop of the Japan Society of Applied Physics, pp. 55-61 (2001) [Non-Patent Document 2] Appl.Phys.Let.,78,544(2001) [Non-Patent Document 3] Appl.Phys.Let.,82,466(2003) [Non-Patent Document 4] Tetrahedron, 58, 9633 (2002) [Non-Patent Document 5] Appl.Phys.Let.,98,083302(2011) [Overview of the project]

[0013] The object of the present invention is to provide a compound suitable as a capping layer material for an organic EL element, which has a high refractive index in the wavelength range of 450 nm to 750 nm and a low extinction coefficient. Furthermore, the object is to provide an organic EL element with improved light extraction efficiency by using the above compound.

[0014] The physical properties of compounds suitable for the capping layer of organic EL elements include (1) a high refractive index, (2) a low extinction coefficient, (3) the ability to be deposited, (4) a stable thin film state, and (5) a high glass transition temperature. Furthermore, the physical properties of the organic EL element to be provided in this invention include (1) high light extraction efficiency, (2) no decrease in color purity, (3) light transmission without change over time, and (4) a long lifespan.

[0015] Therefore, in order to achieve the above objectives, the inventors focused on the fact that carbazole compounds have excellent stability and durability in thin films, and by optimizing the molecular design, developed a material with a high refractive index in the wavelength range of 450 nm to 750 nm and a low extinction coefficient. Furthermore, by fabricating an organic EL device using this compound and diligently evaluating the characteristics of the device, the inventors were able to solve the conventional problems, thus completing the present invention.

[0016] That is, according to the present invention, there are provided a carbazole compound represented by the following general formula (A) or (B) and an organic EL device.

[0017] 1) A carbazole compound represented by the following general formula (A) or (B).

[0018]

Chemical formula

[0019]

Chemical formula

[0020] In formulas (A) and (B), Ar, A, and B each represent a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group, provided that at least one of A and B is a substituted or unsubstituted oxazolopyridyl group or a substituted or unsubstituted oxazolopyrazyl group. L1 to L3 each represent a single bond, an unsubstituted divalent aromatic hydrocarbon group, an unsubstituted divalent aromatic heterocyclic group, or an unsubstituted divalent condensed polycyclic aromatic group.

[0021] 2) The carbazole compound according to 1) is represented by the following general formula (C) or (D).

[0022]

Chemical formula

[0023]

Chemical formula

[0024] In formula (C) or (D), Ar, A, B, and L1 to L3 are as defined in the general formula (A) or (B) above.

[0025] 3) The carbazole compound according to 2), wherein L1 to L3 in the general formula (C) or (D) are single bonds, unsubstituted phenylene groups, or unsubstituted naphthylene groups.

[0026] 4) The carbazole compound according to 3), wherein L1 to L3 in the general formula (C) or (D) above are single bonds, unsubstituted 1,4-phenylene groups, or unsubstituted 2,6-naphthylene groups.

[0027] 5) The carbazole compound according to 4), wherein Ar, A, and B in the general formula (C) or (D) are a substituted or unsubstituted phenyl group, a substituted or unsubstituted naphthyl group, a substituted or unsubstituted quinolyl group, a substituted or unsubstituted isoquinolyl group, a substituted or unsubstituted quinoxalyl group, a substituted or unsubstituted phenantrenyl group, a substituted or unsubstituted phenantronyl group, a substituted or unsubstituted dibenzofuranyl group, a substituted or unsubstituted dibenzothienyl group, a substituted or unsubstituted benzoxazolyl group, a substituted or unsubstituted benzothiazolyl group, a substituted or unsubstituted benzofuranyl group, a substituted or unsubstituted benzothienyl group, a substituted or unsubstituted oxazolopyridyl group, or a substituted or unsubstituted oxazolopyradyl group.

[0028] 6) The carbazole compound according to 5), wherein Ar in the general formula (C) or (D) is an unsubstituted phenyl group, an unsubstituted naphthyl group, an unsubstituted quinolyl group, an unsubstituted isoquinolyl group, an unsubstituted quinoxalyl group, an unsubstituted phenantrenyl group, an unsubstituted phenantronyl group, an unsubstituted dibenzofuranyl group, an unsubstituted dibenzothienyl group, an unsubstituted benzoxazolyl group, an unsubstituted benzothiazolyl group, an unsubstituted benzofuranyl group, an unsubstituted benzothienyl group, an unsubstituted oxazolopyridyl group, or an unsubstituted oxazolopyradyl group.

[0029] 7) The carbazole compound according to 6), wherein at least one of A and B in the general formula (C) or (D) is a substituted or unsubstituted 2-oxazolopyridyl group, a substituted or unsubstituted 5-oxazolopyridyl group, or a substituted or unsubstituted 2-oxazolopyridyl group.

[0030] 8) The carbazole compound according to 7), wherein A and B in the general formula (C) or (D) are a substituted or unsubstituted 2-oxazolopyridyl group, a substituted or unsubstituted 5-oxazolopyridyl group, or a substituted or unsubstituted 2-oxazolopyridyl group.

[0031] 9) 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, wherein the capping layer contains a carbazole compound represented by the general formula (A) or (B) described in 1).

[0032] The organic EL element according to 9), characterized in that when the capping layer described in 10)9) is deposited to a thickness of 30 nm to 120 nm, the refractive index of the capping layer is 1.70 or higher when the wavelength of transmitted light is in the range of 450 nm to 750 nm.

[0033] 11) The organic EL element according to 9), wherein the capping layer is a laminated or mixed layer consisting of two or more compounds, and at least one of the compounds is a carbazole compound represented by the general formula (A) or (B).

[0034] 12) An electronic device or electronic element having a pair of electrodes and at least one organic layer sandwiched between them, wherein the organic layer contains a carbazole compound represented by the general formula (A) or (B) described in 1).

[0035] In general formulas (A) or (B), the "substituted or unsubstituted aromatic hydrocarbon group," "substituted or unsubstituted aromatic heterocyclic group," or "substituted or unsubstituted condensed polycyclic aromatic group" represented by Ar, A, or B specifically 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, pyridyl group, pyrimidinyl group, and triazinyl group. Examples of groups that can be selected from aryl groups having 6 to 30 carbon atoms or heteroaryl groups having 2 to 20 carbon atoms include aryl groups having 6 to 30 carbon atoms, such as aryl groups, furyl groups, pyrrolyl groups, thienyl groups, quinolyl groups, isoquinolyl groups, benzofuranyl groups, benzothienyl groups, indolyl groups, carbazolyl groups, benzoxazolyl groups, benzothiazolyl groups, oxazolopyridyl groups, oxazolopyridyl groups, quinoxalinyl groups, quinazolinyl groups, benzimidazolyl groups, pyrazolyl groups, dibenzofuranyl groups, dibenzothienyl groups, naphthilidinyl groups, phenanthronyl groups, acridinyl groups, and carbonyl groups.

[0036] In the "substituted or unsubstituted divalent aromatic hydrocarbon group," "substituted or unsubstituted divalent aromatic heterocyclic group," or "substituted or unsubstituted divalent condensed polycyclic aromatic group" represented by L1 to L3 in general formula (A) or (B), the "divalent aromatic hydrocarbon group," "divalent aromatic heterocyclic group," or "divalent condensed polycyclic aromatic group" can be a divalent group obtained by removing one hydrogen atom from the "aromatic hydrocarbon group," "aromatic heterocyclic group," or "condensed polycyclic aromatic group" represented by Ar, A, and B in general formula (A). For example, a divalent group obtained by removing one hydrogen atom from the specific groups listed above can be given.

[0037] In general formulas (A) or (B), the "substituted aromatic hydrocarbon group," "substituted aromatic heterocyclic group," or "substituted condensed polycyclic aromatic group" represented by Ar, A, and B include, specifically, deuterium atoms, cyano groups, nitro groups; halogen atoms such as fluorine, chlorine, bromine, and iodine atoms; silyl groups such as trimethylsilyl and triphenylsilyl groups; linear or branched alkyl groups having 1 to 6 carbon atoms such as methyl, ethyl, and propyl groups; linear or branched alkyloxy groups having 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, and terphenylyl groups. Aromatic hydrocarbon groups or condensed polycyclic aromatic groups such as the group, naphthyl group, anthracenyl group, phenanthrenyl 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, benzoxazolyl group, benzothiazolyl group, quinoxalinyl group, quinazolinyl group, benzimidazolyl group, pyrazolyl group, dibenzofuranyl group, dibenzothienyl group, carbonyl group, phenanthronyl group, etc., as well as 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, the benzene rings substituted with these substituents, or multiple substituents substituted on the same benzene ring, may be bonded to each other via single bonds, substituted or unsubstituted methylene groups, oxygen atoms, or sulfur atoms to form a ring.

[0038] In general formula (A) or (B), L1 to L3 are preferably single bonds or unsubstituted 1,4-phenylene groups, and it is particularly preferable that L1 is a single bond.

[0039] In general formula (A) or (B), Ar is preferably an unsubstituted phenyl group or an unsubstituted naphthyl group, and is particularly preferably an unsubstituted naphthyl group.

[0040] In general formula (A) or (B), A and B are preferably substituted or unsubstituted oxazolopyridyl groups, and are particularly preferably substituted or unsubstituted 2-oxazolopyridyl groups and substituted or unsubstituted 5-oxazolopyridyl groups.

[0041] In the carbazole compound of the present invention represented by general formula (C) or (D), Ar, A, B, and L1-L3 are as defined in general formula (A) or (B), and specific examples and preferred examples of the substituents represented by each are as described above.

[0042] In an organic EL element, the thickness of the capping layer is preferably in the range of 30 nm to 120 nm, and particularly preferably in the range of 40 nm to 80 nm.

[0043] The carbazole compound of the present invention has (1) a high refractive index in the wavelength range of 450 nm to 750 nm, (2) a low extinction coefficient, (3) is suitable for deposition, (4) maintains a stable thin film state, and (5) has high heat resistance. Therefore, by providing it as a capping layer on the outside of the transparent or translucent electrodes of an organic EL element, the light extraction efficiency can be significantly improved. [Brief explanation of the drawing]

[0044] [Figure 1] This figure shows the structures of compounds 1 to 12, which are examples of the carbazole compounds of the present invention. [Figure 2] This figure shows the structures of compounds 13 to 27, which are examples of carbazole compounds of the present invention. [Figure 3] This figure shows the structures of compounds 28-38, which are examples of carbazole compounds of the present invention. [Figure 4] This figure shows the structures of compounds 39 to 50, which are examples of carbazole compounds of the present invention. [Figure 5] This figure shows the structures of compounds 51 to 65, which are examples of carbazole compounds of the present invention. [Figure 6] This figure shows the structures of compounds 66 to 79, which are examples of carbazole compounds of the present invention. [Figure 7] This figure shows the structures of compounds 80-89, which are examples of carbazole compounds of the present invention. [Figure 8] This figure shows the structures of compounds 90 to 100, which are examples of carbazole compounds of the present invention. [Figure 9] This figure shows the structures of compounds 101 to 111, which are examples of carbazole compounds of the present invention. [Figure 10] This figure shows the structures of compounds 112 to 121, which are examples of carbazole compounds of the present invention. [Figure 11] This figure shows the structures of compounds 122 to 135, which are examples of carbazole compounds of the present invention. [Figure 12] This figure shows the structures of compounds 136-148, which are examples of carbazole compounds of the present invention. [Figure 13] This figure shows the structures of compounds 149 to 160, which are examples of carbazole compounds of the present invention. [Figure 14] This figure shows the structures of compounds 161 to 171, which are examples of the carbazole compounds of the present invention. [Figure 15] This figure shows an example of the configuration of the organic EL element of the present invention. [Modes for carrying out the invention]

[0045] Although the carbazole compound of the present invention is a novel compound, it can be synthesized, for example, by a coupling reaction using a known palladium catalyst (see, for example, Non-Patent Document 4).

[0046] Specific examples of preferred compounds among the carbazole compounds of the present invention are shown in Figures 1 to 14, but the invention is not limited to these compounds.

[0047] The purification of the carbazole compound of the present invention is not particularly limited and 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, or sublimation purification. The compound can be identified by NMR analysis.

[0048] In the present invention, it is preferable to measure the melting point, glass transition temperature (Tg), refractive index, and extinction coefficient as physical properties of the carbazole compound. 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, and the refractive index and extinction coefficient are indicators related to the improvement of light extraction efficiency.

[0049] The melting point and glass transition temperature (Tg) can be measured using a powder with a high-sensitivity differential scanning calorimeter (Bruker AXS, DSC3100SA).

[0050] The refractive index and extinction coefficient can be measured by fabricating an 80 nm thin film on a silicon substrate and using a spectroscopic measurement device (F10-RT-UV, manufactured by Filmetrics).

[0051] Examples of organic EL element structures include, for example, a top-emission light-emitting element consisting of an anode, hole transport layer, light-emitting layer, electron transport layer, cathode, and capping layer arranged sequentially on a glass substrate. Other examples include those having a hole injection layer between the anode and the hole transport layer, an electron blocking layer between the hole transport layer and the light-emitting layer, a hole blocking layer between the light-emitting layer and the electron transport layer, and an electron injection layer between the electron transport layer and the cathode. In these multilayer structures, one organic layer can perform multiple roles; for example, a configuration combining the hole injection layer and hole transport layer, a configuration combining the hole transport layer and electron blocking layer, a configuration combining the hole blocking layer and electron transport layer, or a configuration combining the electron transport layer and electron injection layer. Furthermore, it is possible to construct a configuration in which two or more organic layers having the same function are stacked, such as a configuration with two layers of hole transport layers, a configuration with two layers of light-emitting layers, a configuration with two layers of electron transport layers, or a configuration with two layers of capping layers.

[0052] The total thickness of each layer of the organic EL element is preferably 200 nm to 750 nm, and more preferably 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 elements other than the capping layer, etc.

[0053] For the anode of an organic EL device, electrode materials with a high work function, such as ITO and gold, are used.

[0054] As materials for the hole injection layer of an organic EL device, arylamine compounds having a structure in which three or more triphenylamine structures are linked by single bonds or divalent groups that do not contain heteroatoms, such as starburst-type triphenylamine derivatives and various triphenylamine tetramers; porphyrin compounds represented by copper phthalocyanine; acceptor-type heterocyclic compounds such as hexacyanoazatriphenylene; and coated polymer materials 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.

[0055] As a material for the hole transport layer of an organic EL device, benzidine derivatives such as N,N'-diphenyl-N,N'-di(m-tolyl)benzidine (hereinafter abbreviated as TPD), N,N'-diphenyl-N,N'-di(α-naphthyl)benzidine, and N,N,N',N'-tetrabiphenylylbenzidine, as well as 1,1-bis[4-(di-4-tolylamino)phenyl]cyclohexane can be used. Particularly preferred is the use of arylamine compounds having a structure in which two triphenylamine structures are linked in the molecule by single bonds or by divalent groups that do not contain heteroatoms, such as N,N,N',N'-tetrabiphenylylbenzidine. It is also preferred to use arylamine compounds having a structure in which three or more triphenylamine structures are linked in the molecule by single bonds or by divalent groups that do not contain heteroatoms, such as various triphenylamine trimers and tetramers. These materials may be deposited individually, or 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) / poly(styrene sulfonate) 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.

[0056] Furthermore, as materials for the hole injection layer and hole transport layer, materials that are P-doped with dopants such as trisbromophenylamine hexachloroantimony and radialene derivatives (see, for example, Patent Document 3) compared to materials commonly used in these layers, as well as polymer compounds having the structure of benzidine derivatives such as TPD as a substructure, can be used.

[0057] Furthermore, it is also possible to laminate an electron blocking layer on an organic EL element. As materials for the electron blocking layer, carbazole derivatives such as 4,4',4''-tri(N-carbazolyl)triphenylamine (hereinafter abbreviated as TCTA), 9,9-bis[4-(carbazole-9-yl)phenyl]fluorene, 1,3-bis(carbazole-9-yl)benzene (hereinafter abbreviated as mCP), and 2,2-bis(4-carbazole-9-yl-phenyl)adamantane, as well as compounds having electron blocking properties such as compounds having a triphenylsilyl group and a triarylamine structure, represented by 9-[4-(carbazole-9-yl)phenyl]-9-[4-(triphenylsilyl)phenyl]-9H-fluorene, can be used. These may be deposited individually, or used as a single layer 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 formed into thin films using known methods such as vapor deposition, spin coating, and inkjet printing.

[0058] As the material for the light-emitting layer of an organic EL device, metal complexes of quinolinol derivatives such as Alq3, various metal complexes, anthracene derivatives, bis-styrylbenzene derivatives, pyrene derivatives, oxazole derivatives, and poly(p-phenylenevinylene) derivatives 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 other materials that can be used include the aforementioned 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, and polydialkylfluorene derivatives. As the dopant material, quinacridone, coumarin, rubrene, perylene and their derivatives, benzopyran derivatives, rhodamine derivatives, and aminostyryl derivatives can be used, and the use of a green light-emitting material is particularly preferred. 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 a laminated structure consisting of layers deposited individually, layers deposited by mixing, or layers deposited individually and layers deposited by mixing.

[0059] Furthermore, phosphorescent materials can be used as luminescent materials. As phosphorescent materials, phosphorescent materials of metal complexes such as iridium and platinum can be used. For example, 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, with the use of green phosphorescent materials being particularly preferred. As the host material in this case, carbazole derivatives such as 4,4'-di(N-carbazolyl)biphenyl, TCTA, and mCP can be used as hole-injection and transport host materials, and p-bis(triphenylsilyl)benzene and 2,2',2''-(1,3,5-phenylene)-tris(1-phenyl-1H-benzimidazole) can be used as electron-transport host materials.

[0060] To avoid concentration quenching, doping of the phosphorescent luminescent material into the host material is preferably carried out by co-deposition in an amount ranging from 1 to 30 weight percent of the entire luminescent layer.

[0061] Furthermore, materials that emit delayed fluorescence, such as PIC-TRZ, CC2TA, PXZ-TRZ, and CDCB derivatives like 4CzIPN, can also be used as luminescent materials (see, for example, Non-Patent Document 5). These materials can be formed into thin films by known methods such as vapor deposition, spin coating, and inkjet printing.

[0062] Furthermore, it is possible to laminate a hole-blocking layer onto an organic EL element. As materials for the hole-blocking layer, metal complexes of phenanthroline derivatives such as bathocuproine, quinolinol derivatives such as aluminum(III) bis(2-methyl-8-quinolinate)-4-phenylphenolate (hereinafter abbreviated as BAlq), various rare earth complexes, triazole derivatives, triazine derivatives, pyrimidine derivatives, oxadiazole derivatives, and benzoazole derivatives, which have hole-blocking properties, can be used. These materials may also be used as materials for the electron transport layer. 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.

[0063] As electron transport layers for organic EL devices, metal complexes of quinolinol derivatives such as Alq3 and BAlq, 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, and silole derivatives can be used. These may be deposited individually, or used as monolayers formed by mixing 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 formed into thin films by known methods such as vapor deposition, spin coating, and inkjet printing.

[0064] As the electron injection layer of the organic EL device, 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, and metals such as ytterbium (Yb), samarium (Sm), calcium (Ca), strontium (Sr), and cesium (Cs) can be used. The electron injection layer can be omitted by preferred selection of the electron transport layer and cathode.

[0065] Furthermore, as materials for the electron injection layer and electron transport layer, materials that are N-doped with metals such as cesium can be used in addition to the materials normally used for these layers.

[0066] Materials used for the cathode of organic EL elements include metals with low work functions such as aluminum, alloys with even lower work functions such as magnesium-silver alloys, magnesium-calcium alloys, magnesium-indium alloys, and aluminum-magnesium alloys, as well as ITO and IZO.

[0067] It is preferable to use the carbazole compound of the present invention as the capping layer for an organic EL element. These compounds may be deposited individually, or they may be used as a single layer deposited by mixing them 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 printing.

[0068] When the carbazole compound of the present invention is formed into a film, the wavelength of light transmitted through the film is in the range of 450 nm to 700 nm, and the refractive index of the film is preferably 1.70 or higher, and particularly preferably 1.85 or higher.

[0069] 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]

[0070] 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.

[0071] [Example 1] <Synthesis of 3,6-bis{4-(oxazolo[5,4-b]pyridine-2-yl)phenyl}-9-phenyl-9H-carbazole (compound (33))> In a reaction vessel, 10.5 g of 3,6-dibromo-9-phenyl-9H-carbazole, 17.7 g of 2-{4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl}oxazolo[5,4-b]pyridine, 0.6 g of tetrakis(triphenylphosphine)palladium(0), and 10.9 g of potassium carbonate were charged, and the mixture was stirred under reflux overnight in a toluene / EtOH / H2O mixed solvent. After cooling, MeOH was added, and the precipitated solid was filtered to obtain the crude product. The obtained crude product was recrystallized and purified using monochlorobenzene solvent to obtain 7.2 g (yield: 43.5%) of pale yellow powder 3,6-bis{4-(oxazolo[5,4-b]pyridine-2-yl)phenyl}-9-phenyl-9H-carbazole (compound 33).

[0072] [ka]

[0073] The structure of the obtained pale yellow powder was identified using NMR. 1 The following 25 hydrogen signals were detected by 1H-NMR (CDCl3), confirming that it was compound 33. δ(ppm)=8.55(2H), 8.42(4H), 8.38(2H), 8.10(2H), 7.96(4H), 7.79(2H), 7.68(2H), 7.66(2H), 7.54(3H), 7.38(2H).

[0074] [Example 2] <Synthesis of 3,6-bis{4-(oxazolo[5,4-b]pyridine-2-yl)phenyl}-9-(naphthalene-2-yl)-9H-carbazole (compound (47))> In a reaction vessel, 10.0 g of 3,6-dibromo-9-(naphthalene-2-yl)-9H-carbazole, 15.7 g of 2-{4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl}oxazolo[5,4-b]pyridine, 0.8 g of tetrakis(triphenylphosphine)palladium(0), and 9.2 g of potassium carbonate were charged, and the mixture was stirred under reflux overnight in a toluene / EtOH / H2O mixed solvent. After cooling, MeOH was added, and the precipitated solid was filtered to obtain the crude product. The obtained crude product was recrystallized and purified using monochlorobenzene solvent to obtain 8.3 g (yield: 54.9%) of a pale yellow powder of 3,6-bis{4-(oxazolo[5,4-b]pyridine-2-yl)phenyl}-9-(naphthalene-2-yl)-9H-carbazole (compound 47).

[0075] [ka]

[0076] The structure of the obtained pale yellow powder was identified using NMR. 1 The following 27 hydrogen signals were detected by 1H-NMR (CDCl3), confirming that it was compound 47. δ(ppm)=8.57(2H), 8.42(4H), 8.37(2H), 8.14(1H), 8.12(1H), 8.10(2H), 8 .02(1H), 7.96(5H), 7.79(2H), 7.73(1H), 7.64(2H), 7.58(2H), 7.38(2H). [Example 3]

[0077] <Synthesis of 3,6-bis{4-(oxazolo[5,4-b]pyridine-2-yl)phenyl}-9-(3,5-dimethylphenyl)-9H-carbazole (compound 164)> In a nitrogen-purged reaction vessel, 8.0 g of 3,6-dibromo-9-(3,5-dimethylphenyl)-9H-carbazole, 13.2 g of 2-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)oxazolo[5,4-b]pyridine, 7.7 g of potassium carbonate, 0.9 g of tetrakis(triphenylphosphine)palladium(0), 65 ml of toluene, 40 ml of ethanol, and 26 ml of tap water were added, and the mixture was stirred overnight under reflux. After confirming the completion of the reaction, methanol was added, and the resulting precipitate was filtered to obtain the crude product. The obtained solid was dissolved in heated monochlorobenzene, silica gel was added and stirred, and then Celite filtration was performed. The filtrate was concentrated, and the obtained crude product was purified by crystallization in monochlorobenzene solvent to obtain 3,6-bis{4-(oxazolo[5,4-b]pyridine-2-yl)phenyl}-9-(3,5-dimethylphenyl)-9H-carbazole (compound 164): 6.5 g (yield: 52.8%).

[0078] [ka]

[0079] The structure of the obtained yellow powder was identified using NMR. 1 The following 31 hydrogen signals were detected by 1H-NMR (CDCl3). δ(ppm)=8.56(2H), 8.44(4H), 8.40(2H), 8.13(2H), 7.98(4H), 7.80(2H), 7.55(2H), 7.42-7.39(2H), 7.28-7.26(4H), 7.20(1H), 2.50(6H). [Example 4]

[0080] <Synthesis of 3,6-bis{4-(oxazolo[5,4-b]pyridine-2-yl)phenyl}-9-(4-methylphenyl)-9H-carbazole (compound 165)> In a nitrogen-purged reaction vessel, 8.0 g of 3,6-dibromo-9-(4-methylphenyl)-9H-carbazole, 13.7 g of 2-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)oxazolo[5,4-b]pyridine, 8.0 g of potassium carbonate, 0.9 g of tetrakis(triphenylphosphine)palladium(0), 70 ml of toluene, 42 ml of ethanol, and 28 ml of tap water were added, and the mixture was stirred overnight under reflux. After confirming the completion of the reaction, methanol was added, and the resulting precipitate was filtered to obtain the crude product. The obtained solid was dissolved in heated monochlorobenzene, silica gel was added and stirred, and then Celite filtration was performed. The filtrate was concentrated, and the obtained crude product was purified by crystallization in a monochlorobenzene / acetone mixed solvent to obtain 3,6-bis{4-(oxazolo[5,4-b]pyridine-2-yl)phenyl}-9-(4-methylphenyl)-9H-carbazole (compound 165): 6.8 g (yield: 54.8%).

[0081] [ka]

[0082] The structure of the obtained pale yellow powder was identified using NMR. 1 The following 27 hydrogen signals were detected by 1H-NMR (CDCl3). δ(ppm)=8.54(2H), 8.43(4H), 8.39(2H), 8.11(2H), 7.96(4H), 7.79(2H), 7.53-7.47(6H), 7.41-7.38(2H), 2.55(3H). [Example 5]

[0083] <Synthesis of 3,6-bis{4-(6-methyloxazolo[5,4-b]pyridine-2-yl)phenyl}-9-phenyl-9H-carbazole (compound 166)> In a nitrogen-purged reaction vessel, 5.0 g of 3,6-dibromo-9-phenyl-9H-carbazole, 8.8 g of 6-methyl-2-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)oxazolo[5,4-b]pyridine, 5.2 g of potassium carbonate, 0.6 g of tetrakis(triphenylphosphine)palladium(0), 35 ml of toluene, 15 ml of ethanol, and 10 ml of tap water were added, and the mixture was stirred overnight under reflux. After confirming the completion of the reaction, methanol and tap water were added, and the resulting precipitate was filtered to obtain a solid. The obtained solid was dissolved in heated dichlorobenzene, silica gel was added and stirred, and then Celite filtration was performed. The filtrate was concentrated, and the resulting crude product was purified by crystallization in dichlorobenzene solvent to obtain 3,6-bis{4-(6-methyloxazolo[5,4-b]pyridine-2-yl)phenyl}-9-phenyl-9H-carbazole (compound 166): 5.0 g (yield: 60.8%).

[0084] [ka]

[0085] The structure of the obtained yellow powder was identified using NMR. 1 The following 29 hydrogen signals were detected by 1H-NMR (CDCl3). δ(ppm)=8.55(2H), 8.42(4H), 8.21(2H), 7.97-7.91(6H), 7.80(2H), 7.72-7.54(7H), 2.53(6H). [Example 6]

[0086] <Synthesis of 3,6-bis{4-(6-methyloxazolo[5,4-b]pyridine-2-yl)phenyl}-9-(4-ethylphenyl)-9H-carbazole (compound 167)> In a nitrogen-purged reaction vessel, 7.0 g of 3,6-dibromo-9-(4-ethylphenyl)-9H-carbazole, 12.1 g of 6-methyl-2-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)oxazolo[5,4-b]pyridine, 6.8 g of potassium carbonate, 0.8 g of tetrakis(triphenylphosphine)palladium(0), 35 ml of toluene, 21 ml of ethanol, and 14 ml of tap water were added, and the mixture was stirred overnight under reflux. After confirming the completion of the reaction, methanol and tap water were added, and the resulting precipitate was filtered to obtain a solid. The obtained solid was dissolved in heated dichlorobenzene, silica gel was added and stirred, and then Celite filtration was performed. The filtrate was concentrated, and the resulting crude product was purified by crystallization in dichlorobenzene solvent to obtain 3,6-bis{4-(6-methyloxazolo[5,4-b]pyridine-2-yl)phenyl}-9-(4-ethylphenyl)-9H-carbazole (compound 167): 6.0 g (yield: 53.8%).

[0087] [ka]

[0088] The structure of the obtained white powder was identified using NMR. 1 The following 33 hydrogen signals were detected by 1H-NMR (CDCl3). δ(ppm)=8.55(2H), 8.42(4H), 8.21(2H), 7.96(4H), 7.92(2H), 7.80(2H), 7.57-7.50(6H), 2.86(2H), 2.54(6H), 1.40(3H). [Example 7]

[0089] <Synthesis of 3,6-bis{4-(6-methyloxazolo[5,4-b]pyridine-2-yl)phenyl}-9-(4-methylphenyl)-9H-carbazole (compound 168)> In a nitrogen-purged reaction vessel, add 8.0 g of 3,6-dibromo-9-(4-methylphenyl)-9H-carbazole. 6-Methyl-2-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)oxazolo[5,4-b]pyridine: 13.6g, 8.0 g of potassium carbonate, 0.7 g of tetrakis(triphenylphosphine)palladium (0), 56 ml of toluene, 24 ml of ethanol, and 16 ml of tap water were added, and the mixture was stirred overnight under reflux. After confirming the completion of the reaction, methanol and tap water were added, and the resulting precipitate was filtered to obtain a solid. The obtained solid was dissolved in heated dichlorobenzene, silica gel was added and stirred, and then Celite filtration was performed. The filtrate was concentrated, and the resulting crude product was purified by crystallization in dichlorobenzene solvent to obtain 3,6-bis{4-(6-methyloxazolo[5,4-b]pyridine-2-yl)phenyl}-9-(4-methylphenyl)-9H-carbazole (compound 168): 7.8 g (yield: 60.1%).

[0090] [ka]

[0091] The structure of the obtained yellow powder was identified using NMR. 1 The following 31 hydrogen signals were detected by 1H-NMR (CDCl3). δ(ppm)=8.57(2H), 8.42(4H), 8.22(2H), 7.98-7.92(6H), 7.80(2H), 7.54-7.42(6H), 2.56(3H), 2.54(6H). [Example 8]

[0092] <Synthesis of 3,6-bis{4-(6-methyloxazolo[5,4-b]pyridine-2-yl)phenyl}-9-(naphthalene-2-yl)-9H-carbazole (compound 169)> Into a nitrogen-substituted reaction vessel, 7.5 g of 3,6-dibromo-9-(naphthalen-2-yl)-9H-carbazole, 12.3 g of 6-methyl-2-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)oxazolo[5,4-b]pyridine, 6.9 g of potassium carbonate, 0.8 g of tetrakis(triphenylphosphine)palladium(0), 38 ml of toluene, 23 ml of ethanol, and 15 ml of city water were added, and the mixture was stirred overnight under heating and reflux. After confirming the completion of the reaction, methanol was added, and the resulting precipitate was collected by filtration to obtain a solid. The obtained solid was dissolved in heated dichlorobenzene, silica gel was added and stirred, and then celite filtration was performed. The filtrate was concentrated, and the crude product obtained was subjected to crystallization purification with a dichlorobenzene solvent to obtain 7.2 g (yield: 61.4%) of 3,6-bis{4-(6-methyloxazolo[5,4-b]pyridin-2-yl)phenyl}-9-(naphthalen-2-yl)-9H-carbazole (Compound 169).

[0093]

Chemical formula

[0094] The structure of the obtained pale yellow powder was identified using NMR. 1 31 hydrogen signals were detected by 1H-NMR (CDCl3) as follows. δ (ppm) = 8.56 (2H), 8.43 (4H), 8.22 - 8.14 (4H), 8.05 (1H), 7.98 (5H), 7.92 (2H), 7.82 (2H), 7.75 (1H), 7.66 (2H), 7.61 (2H), 2.54 (6H). [Example 9]

[0095] [Synthesis of 3,6-bis{4-(oxazolo[5,4-b]pyridin-2-yl)phenyl}-9-(pyridin-3-yl)-9H-carbazole (Compound 170)] 14.0 g of 3,6-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9-(pyridine-3-yl)-9H-carbazole, 16.3 g of 2-(4-bromophenyl)oxazolo[5,4-b]pyridine, 19.5 g of potassium carbonate, 3.3 g of tetrakis(triphenylphosphine)palladium(0), 150 ml of toluene, 100 ml of ethanol, and 150 ml of tap water were added to a nitrogen-purged reaction vessel and stirred overnight under reflux. After confirming the completion of the reaction, the resulting precipitate was filtered to obtain a solid. The obtained solid was dissolved in heated monochlorobenzene, silica gel was added and stirred, and then Celite filtration was performed. The filtrate was concentrated and the resulting crude product was purified by crystallization in monochlorobenzene solvent to obtain 3,6-bis{4-(oxazolo[5,4-b]pyridine-2-yl)phenyl}-9-(pyridine-3-yl)-9H-carbazole (compound 170): 2.2 g (yield: 12.4%).

[0096] [ka]

[0097] The structure of the obtained yellow powder was identified using NMR. 1 The following 24 hydrogen signals were detected by 1H-NMR (CDCl3). δ(ppm)=9.02(1H), 8.84(1H), 8.56(2H), 8.44(4H), 8.40(2H), 8.12(3H), 7.97(4H), 7.81(2H), 7.73(1H), 7.54(2H), 7.42-7.38(2H).

[0098] [Example 10] The melting point and glass transition temperature (Tg) of the compounds obtained in Examples 1 to 9 were measured using a high-sensitivity differential scanning calorimeter (Bruker AXS, DSC3100SA). The measurement results are shown in Table 1.

[0099] [Table 1]

[0100] From the above results, it can be seen that the carbazole compounds of the present invention obtained in Examples 1 to 9 have high melting points and either do not have a glass transition temperature or have a glass transition temperature of 100°C or higher. This indicates that the thin film state is stable.

[0101] [Example 11] Using the compounds obtained in Examples 1 to 9, 80 nm thick vapor-deposited films were fabricated on a silicon substrate, and the refractive index n and extinction coefficient k at wavelengths of 450 nm and 750 nm were measured using a spectroscopic measuring device (F10-RT-UV, Filmetrics). For comparison, Alq3 and a comparative compound with the following structural formula (CPL-1) were also measured (see, for example, Patent Document 4). The measurement results are summarized in Table 2.

[0102] [ka]

[0103] [Table 2]

[0104] As shown in Table 2, the carbazole compound of the present invention has extinction coefficients and refractive indices equal to or greater than those of Alq3 and the comparative compound (CPL-1) in the wavelength range of 450 nm to 750 nm. By using the carbazole compound of the present invention as a constituent material for the capping layer, it is expected that the light extraction efficiency in organic EL devices will be improved.

[0105] [Example 12] As an example, as shown in Figure 15, the organic EL element of the present invention was fabricated by depositing a hole injection layer 3, a hole transport layer 4, an emissive layer 5, an electron transport layer 6, an electron injection layer 7, a cathode 8, and a capping layer 9 in the order shown on a glass substrate 1 on which a reflective ITO electrode as a transparent anode 2 was pre-formed.

[0106] Specifically, a glass substrate 1, on which a 50 nm thick ITO film, a 100 nm thick silver alloy reflective film, and a 5 nm thick ITO film were sequentially deposited, was ultrasonically cleaned in isopropyl alcohol for 20 minutes, and then 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 0.001 Pa or less. 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 (HTM-1) with the following structural formula, at a deposition rate ratio of Acceptor-1:compound (HTM-1) = 3:97, to a thickness of 10 nm.

[0107] On top of the hole injection layer 3 described above, a hole transport layer 4 was formed using a compound with the following structural formula (HTM-1) to a thickness of 140 nm. On top of this hole transport layer 4, a light-emitting layer 5 was formed using a binary deposition method with a deposition rate ratio of (EMD-1):(EMH-1)=5:95, using a compound with the following structural formula (EMD-1) and a compound with the following structural formula (EMH-1) to a thickness of 20 nm. On top of this light-emitting layer 5, an electron transport layer 6 was formed using a binary deposition method with a deposition rate ratio of (ETM-1):(ETM-2)=50:50, using a compound with the following structural formula (ETM-1) and a compound with the following structural formula (ETM-2) to a thickness of 30 nm. On top of this electron transport layer 6, a lithium fluoride layer was formed as an electron injection layer 7 to a thickness of 1 nm. On top of this electron injection layer 7, a magnesium-silver alloy layer was formed as a cathode 8 to a thickness of 12 nm.

[0108] Finally, the compound (33) from Example 1 was formed as the capping layer 9 to a thickness of 60 nm. The fabricated organic EL elements were subjected to characteristic measurements in air at room temperature, and the results of the luminescence characteristics measured with a DC voltage applied are summarized in Table 3.

[0109] [ka]

[0110] [Example 13] In Example 12, an organic EL element was fabricated under the same conditions as in Example 12, except that the compound obtained in Example 2 (47) was used as the capping layer 9 instead of the compound (33) from Example 1. The fabricated organic EL element was subjected to characteristic measurements in air at room temperature, and the results of the luminescence characteristics measured with a DC voltage applied are summarized in Table 3.

[0111] [Example 14] In Example 12, an organic EL element was fabricated under the same conditions as in Example 12, except that the compound obtained in Example 3 (164) was used as the capping layer 9 instead of the compound (33) from Example 1. The fabricated organic EL element was subjected to characteristic measurements in air at room temperature, and the results of the luminescence characteristics measured with a DC voltage applied are summarized in Table 3.

[0112] [Example 15] In Example 12, an organic EL element was fabricated under the same conditions as in Example 12, except that the compound obtained in Example 4 (165) was used as the capping layer 9 instead of the compound (33) from Example 1. The fabricated organic EL element was subjected to characteristic measurements in air at room temperature, and the results of the luminescence characteristics measured with a DC voltage applied are summarized in Table 3.

[0113] [Example 16] In Example 12, an organic EL element was fabricated under the same conditions as in Example 12, except that the compound obtained in Example 5 (166) was used as the capping layer 9 instead of the compound (33) from Example 1. The fabricated organic EL element was subjected to characteristic measurements in air at room temperature, and the results of the luminescence characteristics measured with a DC voltage applied are summarized in Table 3.

[0114] [Example 17] In Example 12, an organic EL element was fabricated under the same conditions as in Example 12, except that the compound obtained in Example 6 (167) was used as the capping layer 9 instead of the compound (33) from Example 1. The fabricated organic EL element was subjected to characteristic measurements in air at room temperature, and the results of the luminescence characteristics measured with a DC voltage applied are summarized in Table 3.

[0115] [Example 18] In Example 12, an organic EL element was fabricated under the same conditions as in Example 12, except that the compound obtained in Example 7 (168) was used as the capping layer 9 instead of the compound (33) from Example 1. The fabricated organic EL element was subjected to characteristic measurements in air at room temperature, and the results of the luminescence characteristics measured with a DC voltage applied are summarized in Table 3.

[0116] [Example 19] In Example 12, an organic EL element was fabricated under the same conditions as in Example 12, except that the compound obtained in Example 8 (169) was used as the capping layer 9 instead of the compound (33) from Example 1. The fabricated organic EL element was subjected to characteristic measurements in air at room temperature, and the results of the luminescence characteristics measured with a DC voltage applied are summarized in Table 3.

[0117] [Example 20] In Example 12, an organic EL element was fabricated under the same conditions as in Example 12, except that the compound obtained in Example 9 (170) was used as the capping layer 9 instead of the compound (33) from Example 1. The fabricated organic EL element was subjected to characteristic measurements in air at room temperature, and the results of the luminescence characteristics measured with a DC voltage applied are summarized in Table 3.

[0118] [Comparative Example 1] For comparison, in Example 12, an organic EL element was fabricated under the same conditions as in Example 1, except that Alq3 was used as the capping layer 9 instead of the compound (33) from Example 1. The fabricated organic EL elements were subjected to characteristic measurements in air at room temperature, and the results of the luminescence characteristics measured with a DC voltage applied are summarized in Table 3.

[0119] [Comparative Example 2] For comparison, in Example 12, an organic EL element was fabricated under the same conditions as in Example 1, except that compound (CPL-1) was used as the capping layer 9 instead of compound (33) from Example 1. The fabricated organic EL elements were subjected to characteristic measurements in air at room temperature, and the results of the luminescence characteristics measured with a DC voltage applied are summarized in Table 3.

[0120] Table 3 summarizes the results of measuring the device lifetime using the organic EL elements fabricated in the above examples and comparative examples. The device lifetime measured in this invention is 10 mA / cm². 2 When driven with a constant current, the time it took for the brightness to decay to 95% of its initial brightness (with the initial brightness set to 100%) was measured.

[0121] [Table 3]

[0122] As shown in Table 3, the current density is 10 mA / cm². 2 While the driving voltage at time was almost the same for the elements of Comparative Examples 1 and 2 and the elements of Examples 12 to 20, the elements of the Examples showed significant improvements in brightness, luminous efficiency, power efficiency, and element lifespan compared to the comparative examples. This indicates that the carbazole compound of the present invention is a suitable material for use in the capping layer, and that the light extraction efficiency of the organic EL element can be greatly improved by increasing the refractive index of the capping layer. [Industrial applicability]

[0123] The carbazole compound of the present invention has a high refractive index, significantly improves light extraction efficiency, and maintains a stable thin film state, making it an excellent compound for use in the capping layer of organic EL elements. Furthermore, organic EL elements fabricated using the carbazole compound of the present invention as a constituent material for the capping layer can achieve high efficiency. Moreover, using the compound of the present invention, which does not absorb in the blue, green, and red wavelength regions, is particularly suitable when it is desired to display images with high color purity, clarity, and brightness. For example, it is expected to be used in applications such as home appliances and lighting. [Explanation of Symbols]

[0124] 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 9th Cabin Floor

Claims

1. A carbazole compound represented by the following general formula (A) or (B). 【Chemistry 1】 【Chemistry 2】 (In the formula, Ar, A, and B each represent a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group, provided that at least one of A and B is a substituted or unsubstituted oxazolopyridyl group or a substituted or unsubstituted oxazolopyradyl group.) L １ ~L ３ This represents a single-bonded, unsubstituted, divalent aromatic hydrocarbon group, an unsubstituted, divalent aromatic heterocyclic group, or an unsubstituted, divalent condensed polycyclic aromatic group.

2. The carbazole compound described in claim 1 is represented by the following general formula (C) or (D). 【Transformation 3】 【Chemistry 4】 (In formula (C) or (D), Ar, A, B and L １ ~L ３ This is defined as in the general formula (A) or (B) above.

3. In the above general formula (C) or (D), L １ ~L ３ The carbazole compound according to claim 2, wherein is a single bond, an unsubstituted phenylene group, or an unsubstituted naphthylene group.

4. In the above general formula (C) or (D), L １ ~L ３ The carbazole compound according to claim 3, wherein is a single bond, an unsubstituted 1,4-phenylene group, or an unsubstituted 2,6-naphthylene group.

5. The carbazole compound according to claim 4, wherein Ar, A, and B in the general formula (C) or (D) are a substituted or unsubstituted phenyl group, a substituted or unsubstituted naphthyl group, a substituted or unsubstituted quinolyl group, a substituted or unsubstituted isoquinolyl group, a substituted or unsubstituted quinoxalyl group, a substituted or unsubstituted phenantrenyl group, a substituted or unsubstituted phenantronyl group, a substituted or unsubstituted dibenzofuranyl group, a substituted or unsubstituted dibenzothienyl group, a substituted or unsubstituted benzoxazolyl group, a substituted or unsubstituted benzothiazolyl group, a substituted or unsubstituted benzofuranyl group, a substituted or unsubstituted benzothienyl group, a substituted or unsubstituted oxazolopyridyl group, or a substituted or unsubstituted oxazolopyridyl group.

6. The carbazole compound according to claim 5, wherein Ar in the general formula (C) or (D) represents an unsubstituted phenyl group, an unsubstituted naphthyl group, an unsubstituted quinolyl group, an unsubstituted isoquinolyl group, an unsubstituted quinoxalyl group, an unsubstituted phenantrenyl group, an unsubstituted phenantronyl group, an unsubstituted dibenzofuranyl group, an unsubstituted dibenzothienyl group, an unsubstituted benzoxazolyl group, an unsubstituted benzothiazolyl group, an unsubstituted benzofuranyl group, an unsubstituted benzothienyl group, an unsubstituted oxazolopyridyl group, or an unsubstituted oxazolopyridyl group.

7. The carbazole compound according to claim 6, wherein at least one of A and B in the general formula (C) or (D) is a substituted or unsubstituted 2-oxazolopyridyl group, a substituted or unsubstituted 5-oxazolopyridyl group, or a substituted or unsubstituted 2-oxazolopyridyl group.

8. The carbazole compound according to claim 7, wherein A and B in the general formula (C) or (D) are a substituted or unsubstituted 2-oxazolopyridyl group, a substituted or unsubstituted 5-oxazolopyridyl group, or a substituted or unsubstituted 2-oxazolopyridyl group.

9. 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, wherein the capping layer contains a carbazole compound represented by the general formula (A) or (B) described in claim 1.

10. An organic EL element characterized in that, when the capping layer described in claim 9 is deposited to a thickness of 30 nm to 120 nm, the refractive index of the capping layer is 1.70 or higher when the wavelength of transmitted light is in the range of 450 nm to 750 nm.

11. An organic EL element in which the capping layer according to claim 9 is a laminated or mixed layer consisting of two or more compounds, wherein at least one of the compounds is a carbazole compound represented by the general formula (A) or (B).

12. An electronic device or electronic element having a pair of electrodes and at least one organic layer sandwiched between them, wherein the organic layer contains a carbazole compound represented by the general formula (A) or (B) described in claim 1.

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