Adamantane compounds, organic electroluminescent elements, and electronic devices

Abstract

[Problem] The purpose of the present invention is to provide a compound which is suitable for a low refractive index layer in a capping layer in order to improve the light extraction efficiency of an organic EL element. [Solution] The present invention is achieved by focusing on the fact that a thin film of an adamantane compound has excellent stability and founding out that an amide compound, ester compound, amine compound or ether compound, in the center of which adamantane is arranged, exhibits low refractive index characteristics; and an organic EL element having excellent luminous efficiency is achieved by using this compound as a material which constitutes a capping layer that has a low refractive index.

Description

[Technical Field]

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

[0002] In 1987, C.W. Tang and his colleagues at Eastman Kodak Company made organic EL devices practical by developing a layered structure element in which various roles are assigned to each material. They layered a phosphor that can transport electrons and an organic material that can transport holes, and by injecting both charges into the phosphor layer to emit light, they achieved a brightness of 1000 cd / m at a voltage of 10 V or less. 2 Such high brightness has become possible (see Patent Documents 1 and 2).

[0003] In recent years, light-emitting devices with a top-emission structure that uses a metal with a high work function as the anode and emits light from the top have come into use. In a bottom-emission structure in which light is extracted from the bottom where the pixel circuit is located, the area of ​​the light-emitting section is limited, whereas a light-emitting device with a top-emission structure has the advantage that the light is extracted from the top and is not blocked by the pixel circuit, allowing for a larger light-emitting section. In light-emitting devices with a top-emission structure, a semi-transparent electrode such as LiF / Al / Ag (see, for example, Non-Patent Document 1), Ca / Mg (see Non-Patent Document 2), or LiF / MgAg is used as the cathode.

[0004] In such light-emitting devices, when light emitted from the light-emitting layer is incident on another film at an angle greater than a certain level, it is totally reflected at the interface between the light-emitting layer and the other film. As a result, only a portion of the emitted light can be utilized. In recent years, light-emitting devices have been proposed in which a "capping layer" with a high refractive index is provided on the outside of a semi-transparent electrode with a low refractive index in order to improve light extraction efficiency (see, for example, Non-Patent Documents 1 and 2).

[0005] On the other hand, an organic optical device has been shown in which a low refractive index layer is formed by co-evaporating an additive, and then laminated with a high refractive index layer to utilize the effect of optical interference, thereby forming a multilayer film that effectively controls light propagation (see Patent Document 3).

[0006] It is known that the light extraction efficiency of organic EL elements can be improved by forming a capping layer with a high refractive index. However, to form a low refractive index layer, co-deposition with an additive is performed as described in Patent Document 3, and therefore a compound that can be vapor-deposited alone at low temperatures is required. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 8-048656 [Patent Document 2] Patent No. 3194657 [Patent Document 3] Patent No. 6210473

[0008] [Non-Patent Document 1] Appl.Phys.Lett.,78,544(2001) [Non-patent document 2] Appl.Phys.Lett.,82,466(2003) Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide a compound suitable for a low refractive index layer in a capping layer in order to improve the light extraction efficiency of an organic EL device.

[0010] The physical properties of the material for the low refractive index layer suitable for the present invention include (1) vapor deposition and no thermal decomposition, (2) a stable thin film state, and (3) a low refractive index. The physical properties of the element suitable for the present invention include (1) high light extraction efficiency, (2) no reduction in color purity, (3) light transmission without change over time, and (4) a long life. [Means for solving the problem]

[0011] In order to achieve the above object, the present inventors have focused on the excellent stability of adamantane compounds when formed into thin films, and have found that amide compounds, ester compounds, amine compounds, or ether compounds having adamantane at the center exhibit low refractive index properties. They have fabricated organic EL devices using such compounds as materials for constituting a low refractive index capping layer, and have diligently evaluated the properties of the devices, which has resulted in the completion of the present invention.

[0012] That is, according to the present invention, the following adamantane compound and organic EL device are provided.

[0013] 1) An adamantane compound represented by the following general formula (1):

[0014] [ka] (1)

[0015] (In the formula, X represents an oxygen atom or an NH group, L represents a linear or branched alkylene group or a carbonyl group having 1 to 3 carbon atoms, and R1 and R2 may be the same or different and represent a substituted or unsubstituted aromatic hydrocarbon group.)

[0016] 2) The adamantane compound according to 1) above, which is represented by the following general formula (1-A):

[0017] [ka] (1-A)

[0018] (In the formula, X and L are as defined in the general formula (1). R3 to R 12 may be the same or different and represent a hydrogen atom, a halogen atom, a cyano group, a substituted or unsubstituted linear or branched alkyl group having 1 to 3 carbon atoms, a substituted or unsubstituted linear or branched alkyloxy group having 1 to 3 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group.

[0019] 3) The adamantane compound according to 1) or 2) above, which is represented by the following general formula (1-B):

[0020] [ka] (1-B)

[0021] (In the formula, R3~R 12 is as defined in the general formula (1-A) above.

[0022] 4) The adamantane compound according to 1) or 2) above, wherein the adamantane compound is represented by the following general formula (1-C):

[0023] [ka] (1-C)

[0024] (In the formula, R3~R 12 is as defined in the general formula (1-A) above.

[0025] 5) The adamantane compound according to 1) or 2) above, which is represented by the following general formula (1-D):

[0026] [ka] (1-D)

[0027] (In the formula, R3~R 12 is as defined in the general formula (1-A) above.

[0028] 6) The adamantane compound according to 1) or 2) above, which is represented by the following general formula (1-E):

[0029] [ka] (1-E)

[0030] (In the formula, R3~R 12 is as defined in the general formula (1-A) above.

[0031] 7) An organic thin film comprising the adamantane compound according to any one of 1) to 6) above, characterized in that the refractive index in the wavelength range of 400 nm to 700 nm is 1.60 or less.

[0032] 8) An organic EL device having at least an anode electrode, a hole transport layer, an emitting layer, an electron transport layer, a cathode electrode, and a capping layer in this order, wherein the capping layer is the organic thin film described in 7) above.

[0033] 9) An organic EL device having at least an anode electrode, a hole transport layer, an emitting layer, an electron transport layer, a cathode electrode, and a capping layer in this order, characterized in that the capping layer has a two-layer structure consisting of a first capping layer and a second capping layer, and the first capping layer is the organic thin film described in 7) above.

[0034] 10) The organic EL element according to 9) above, characterized in that the difference between the refractive index of the first capping layer and the refractive index of the second capping layer ([refractive index of the second capping layer] - [refractive index of the first capping layer]) is 0.2 or more.

[0035] 11) An electronic device or an electronic element having a pair of electrodes and at least one organic layer sandwiched between them, characterized in that the organic layer contains the adamantane compound described in any one of 1) to 6) above as a constituent material.

[0036] In the present specification, "unsubstituted" in the context of "substituted or unsubstituted" means that a hydrogen atom is not substituted with a substituent.

[0037] In this specification, the term "hydrogen atom" is used to mean isotopes with different numbers of neutrons, namely protium and deuterium.

[0038] Specific examples of the "alkylene group" in the "linear or branched alkylene group having 1 to 3 carbon atoms" represented by L in general formula (1) include a methylene group, a 1,2-ethylene group, and a 1,3-propylene group, with a methylene group and a 1,2-ethylene group being preferred, and a methylene group being more preferred. Furthermore, these divalent groups are preferably unsubstituted, but may have a substituent. In this case, specific examples of the substituent include a cyano group; a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom; and a linear or branched alkyloxy group having 1 to 3 carbon atoms such as a methyloxy group, an ethyloxy group, or a propyloxy group.

[0039] In the general formula (1), X represents an oxygen atom or an NH group. Specifically, when X in general formula (1) is an oxygen atom and L is an alkylene group, (-LX-) in the general formula (1) is an ether group, and when X in general formula (1) is an oxygen atom and L is a carbonyl group, (-LX-) in the general formula (1) is an ester group. When X in general formula (1) is an NH group and L is an alkylene group, (-LX-) in the general formula (1) is an amino group, and when X in general formula (1) is an NH group and L is a carbonyl group, (-LX-) in the general formula (1) is an amide group.

[0040] Specific examples of the "aromatic hydrocarbon group" in the "substituted or unsubstituted aromatic hydrocarbon group" represented by R1 and R2 in general formula (1) include a phenyl group, a biphenyl group, a 1-naphthyl group, a 2-naphthyl group, a 2-phenanthrenyl group, a 9-phenanthrenyl group, and a fluorenyl group, with a phenyl group, a biphenyl group, a 1-naphthyl group, a 2-naphthyl group, and a fluorenyl group being preferred, and a phenyl group and a fluorenyl group being more preferred. Furthermore, these groups may have a substituent, and in this case, specific examples of the substituent include a cyano group; a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom; a linear or branched alkyl group having 1 to 3 carbon atoms such as a methyl group, an ethyl group, or a propyl group; a linear or branched alkyloxy group having 1 to 3 carbon atoms such as a methyloxy group, an ethyloxy group, or a propyloxy group; and an aromatic hydrocarbon group such as a phenyl group, a biphenyl group, a 1-naphthyl group, a 2-naphthyl group, or a fluorenyl group.

[0041] R to R in general formula (1-A) 12 Examples of the "halogen atom" represented by the formula (I) include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, with a fluorine atom and a chlorine atom being preferred, and a fluorine atom being more preferred.

[0042] R to R in general formula (1-A) 12 Examples of the "alkyl group" in the "substituted or unsubstituted, linear or branched alkyl group having 1 to 3 carbon atoms" represented by the formula (1) include a methyl group, an ethyl group, and a propyl group, with a methyl group and an ethyl group being preferred, and a methyl group being more preferred.

[0043] R to R in general formula (1-A) 12The "alkyloxy group" in the "substituted or unsubstituted linear or branched alkyloxy group having 1 to 3 carbon atoms" represented by the following formula is: methyloxy group , Ethyloxy group and propyloxy groups, methyloxy group , Ethyloxy group is preferred, methyloxy group is more preferred.

[0044] R to R in general formula (1-A) 12 Specific examples of the "aromatic hydrocarbon group" in the "substituted or unsubstituted aromatic hydrocarbon group" represented by the formula (I) include a phenyl group, a biphenyl group, a 1-naphthyl group, a 2-naphthyl group, a 2-phenanthrenyl group, a 9-phenanthrenyl group, and a fluorenyl group, of which a phenyl group, a biphenyl group, a 1-naphthyl group, a 2-naphthyl group, and a fluorenyl group are preferred, a phenyl group and a fluorenyl group are more preferred, and a phenyl group is even more preferred. These groups may have a substituent, and specific examples of the substituent in this case include a cyano group; a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom; a linear or branched alkyl group having 1 to 3 carbon atoms such as a methyl group, an ethyl group, or a propyl group; and a linear or branched alkyloxy group having 1 to 3 carbon atoms such as a methyloxy group, an ethyloxy group, or a propyloxy group.

[0045] R to R in general formula (1-A) 12 The "linear or branched alkyl group having 1 to 3 carbon atoms" and the "linear or branched alkyloxy group having 1 to 3 carbon atoms" represented by the following formula (I) may have a substituent, and in this case, the "substituent" is preferably a halogen atom, and more preferably a fluorine atom.

[0046] The adamantane compound represented by general formula (1) of the present invention is preferably an adamantane compound represented by any one of the following general formulae (1-A) to (1-E), and more preferably an adamantane compound represented by any one of the following general formulae (1-B) to (1-E). The two Ls in general formula (1) are preferably the same group, but may be different groups. Furthermore, the two Xs in general formula (1) are preferably the same group, but may be different groups. In addition, in general formula (1), R1 and R2 may be the same or different from each other, but are preferably the same.

[0047] [ka] (1-A)

[0048] [ka] (1-B)

[0049] [ka] (1-C)

[0050] [ka] (1-D)

[0051] [ka] (1-E)

[0052] In the general formulae (1-A) to (1-E), X represents an oxygen atom or an NH group, and L represents a linear or branched alkylene group having 1 to 3 carbon atoms or a carbonyl group. R3~R 12 may be the same or different and are a hydrogen atom, a halogen atom, a cyano group, a substituted or unsubstituted linear or branched alkyl group having 1 to 3 carbon atoms, a substituted or unsubstituted linear or branched alkyloxy group having 1 to 3 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group. Details of the linear or branched alkylene group having 1 to 3 carbon atoms, the aromatic hydrocarbon group, the halogen atom, the linear or branched alkyl group having 1 to 3 carbon atoms, the linear or branched alkyloxy group having 1 to 3 carbon atoms, and the substituents thereof are as described above. [Effects of the Invention]

[0053] The adamantane compound of the present invention represented by general formula (1) has excellent low refractive index characteristics. Therefore, by forming a low refractive index layer (organic thin film) using this compound and combining it with a high refractive index layer (organic thin film), an organic EL device with improved light extraction efficiency can be realized due to the optical interference effect.

[0054] In addition, the adamantane compound of the present invention can be used not only in organic EL devices but also in the field of electronic devices such as electrophotographic photoreceptors, image sensors, photoelectric conversion elements, and solar cells. [Brief explanation of the drawings]

[0055] [Figure 1] FIG. 1 shows the structures of compounds (1-1) to (1-16) as adamantane compounds represented by general formula (1) of the present invention. [Figure 2] FIG. 1 shows the structures of compounds (1-17) to (1-32) as adamantane compounds represented by general formula (1) of the present invention. [Figure 3] FIG. 1 shows the structures of compounds (1-33) to (1-50) as adamantane compounds represented by general formula (1) of the present invention. [Figure 4] FIG. 1 shows the structures of compounds (1-51) to (1-68) as adamantane compounds represented by general formula (1) of the present invention. [Figure 5] FIG. 1 shows the structures of compounds (1-69) to (1-86), which are adamantane compounds represented by general formula (1) of the present invention. [Figure 6]FIG. 1 shows the structures of compounds (1-87) to (1-104), which are adamantane compounds represented by general formula (1) of the present invention. [Figure 7] FIG. 1 shows the structures of compounds (1-105) to (1-122) as adamantane compounds represented by general formula (1) of the present invention. [Figure 8] FIG. 1 shows the structures of compounds (1-123) to (1-140) as adamantane compounds represented by general formula (1) of the present invention. [Figure 9] FIG. 2 shows the structures of compounds (2-1) to (2-10) as specific examples of high refractive index arylamine compounds that can be suitably used in the organic EL device of the present invention. [Figure 10] FIG. 2 shows the structures of compounds (2-11) to (2-18) as specific examples of high refractive index arylamine compounds that can be suitably used in the organic EL device of the present invention. [Figure 11] FIG. 1 is a diagram showing the configurations of organic EL devices according to Examples 6 to 8 and Comparative Examples 1 and 2. DETAILED DESCRIPTION OF THE INVENTION

[0056] The adamantane compounds of the present invention represented by the general formula (1) are novel compounds, but these compounds themselves can be synthesized according to known methods.

[0057] Specific examples of the adamantane compound represented by general formula (1) of the present invention are shown in FIGS. 1 to 8, but the present invention is not limited to these compounds.

[0058] Specific examples of high refractive index arylamine compounds that can be suitably used in the organic EL device of the present invention are shown in FIGS. 9 and 10, but the present invention is not limited to these compounds.

[0059] The method for producing the adamantane compound represented by general formula (1) of the present invention is not particularly limited, but the compound can be purified by known methods used for purifying organic compounds, such as purification by column chromatography, adsorption purification using silica gel, activated carbon, activated clay, etc., recrystallization or crystallization using a solvent, and finally, purification by sublimation purification, etc. The compound can be identified by NMR analysis, mass spectrometry analysis, etc. It is preferable to measure the melting point, glass transition temperature (Tg), refractive index, and absorbance as physical property values.

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

[0061] The refractive index was measured by forming an 80 nm thin film on a silicon substrate and using a spectrophotometer (F10-RT-UV, manufactured by Filmetrics).

[0062] The organic EL device of the present invention may have a top-emission structure, in which an anode, a hole transport layer, an emitting layer, an electron transport layer, a cathode, and a capping layer are sequentially arranged on a glass substrate. It may also have a hole injection layer between the anode and the hole transport layer, an electron blocking layer between the hole transport layer and the emitting layer, a hole blocking layer between the emitting layer and the electron transport layer, or an electron injection layer between the electron transport layer and the cathode. In these multilayer structures, some organic layers may be omitted or may serve as multiple layers. For example, a layer may serve as both a hole injection layer and a hole transport layer, a layer may serve as both a hole transport layer and an electron blocking layer, a layer may serve as both a hole blocking layer and an electron transport layer, or a layer may serve as both an electron transport layer and an electron injection layer. It may also have a structure in which two or more organic layers having the same function are stacked, such as a layer with two hole transport layers, a layer with two emitting layers, a layer with two electron transport layers, or a layer with two capping layers.

[0063] The total thickness of each layer of the organic EL element is preferably about 200 nm to 750 nm, more preferably about 350 nm to 600 nm. The thickness of the capping layer is preferably, for example, 30 nm to 120 nm, more preferably 40 nm to 80 nm. In this case, good light extraction efficiency can be obtained. The thickness of the capping layer can be appropriately changed depending on the type of light-emitting material used in the light-emitting element, the thickness of each layer of the organic EL element other than the capping layer, and the like.

[0064] For the anode of the organic EL device of the present invention, an electrode material with a large work function such as ITO or gold is used.

[0065] For the hole injection layer of the organic EL device of the present invention, preferred materials include arylamine compounds having two or more triphenylamine structures in a molecule linked by a single bond or a divalent group containing no heteroatoms, such as benzidine derivatives, starburst triphenylamine derivatives, and various triphenylamine tetramers. Porphyrin compounds, such as copper phthalocyanine, acceptor heterocyclic compounds such as hexacyanoazatriphenylene, and polymeric coating materials can also be used. These materials can be used alone or in combination with other materials to form a single layer, or in a laminate structure of layers formed by mixing layers formed by themselves, layers formed by mixing layers formed by themselves, or layers formed by mixing layers formed by mixing layers formed by themselves. These materials can be used to form thin films by known methods, such as vapor deposition, spin coating, or inkjet printing.

[0066] For the hole-transport layer of the organic EL device of the present invention, benzidine derivatives such as N,N'-diphenyl-N,N'-di(m-tolyl)benzidine (TPD), N,N'-diphenyl-N,N'-di(α-naphthyl)benzidine (NPD), and N,N,N',N'-tetrabiphenylylbenzidine, 1,1-bis[4-(di-4-tolylamino)phenyl]cyclohexane (TAPC), and particularly arylamine compounds having two triphenylamine structures linked by a single bond or a divalent group not containing a heteroatom, such as N,N,N',N'-tetrabiphenylylbenzidine, are preferred. Also preferred are arylamine compounds having only one triphenylamine structure per molecule, and arylamine compounds having three or more triphenylamine structures linked by a single bond or a divalent group not containing a heteroatom, such as various triphenylamine trimers and tetramers. These materials can be formed as films by themselves, or as single layers formed by mixing with other materials. They can also be used as laminated structures of layers formed by themselves, layers formed by mixing, or layers formed by mixing with other materials. Furthermore, coating-type polymer materials such as poly(3,4-ethylenedioxythiophene) (PEDOT) / poly(styrene sulfonate) (PSS) can be used as hole injection / transport layers. These materials can be formed into thin films by known methods such as vapor deposition, spin coating, and inkjet printing.

[0067] Furthermore, in the hole injection layer or hole transport layer, it is preferable to use a material that is p-doped with trisbromophenylaminehexachloroantimony, a radialene derivative, etc., in addition to the materials normally used in the layer. Also, a polymer compound having a benzidine derivative structure such as TPD in its partial structure can be used.

[0068] The electron-blocking layer of the organic EL device of the present invention can be formed using compounds having electron-blocking properties, such as carbazole derivatives such as 4,4',4"-tri(N-carbazolyl)triphenylamine (TCTA), 9,9-bis[4-(carbazol-9-yl)phenyl]fluorene, 1,3-bis(carbazol-9-yl)benzene (mCP), and 2,2-bis(4-carbazol-9-ylphenyl)adamantane (Ad-Cz), and compounds having a triphenylsilyl group and a triarylamine structure, such as 9-[4-(carbazol-9-yl)phenyl]-9-[4-(triphenylsilyl)phenyl]-9H-fluorene. These compounds may be formed as a film alone or as a single layer formed by mixing with other materials. Alternatively, they may be formed as a laminate structure of layers formed alone, layers formed as a mixture, or layers formed as a mixture with layers formed alone. These materials can be used to form thin films by known methods such as vapor deposition, spin coating, and ink jet printing.

[0069] The light-emitting layer of the organic EL device of the present invention can be formed using metal complexes of quinolinol derivatives such as Alq3, as well as various metal complexes, anthracene derivatives, bisstyrylbenzene derivatives, pyrene derivatives, oxazole derivatives, polyparaphenylenevinylene derivatives, and the like. The light-emitting layer can also be formed using a host material and a dopant material. Anthracene derivatives are preferred as the host material. In addition to the light-emitting materials, heterocyclic compounds having an indole ring as a fused ring substructure, heterocyclic compounds having a carbazole ring as a fused ring substructure, carbazole derivatives, thiazole derivatives, benzimidazole derivatives, polydialkylfluorene derivatives, and the like can also be used. The dopant material can be quinacridone, coumarin, rubrene, perylene, and derivatives thereof, benzopyran derivatives, rhodamine derivatives, aminostyryl derivatives, and the like, with green light-emitting materials being more preferred. These may be formed alone, or may be mixed with other materials to form a single layer, or may be stacked with other layers formed alone, other layers formed as a mixture, or a layer formed alone and a layer formed as a mixture.

[0070] Phosphorescent emitters can also be used as light-emitting materials. Examples of phosphorescent emitters include metal complexes of iridium and platinum. Green emitters such as Ir(ppy)3, blue emitters such as FIrpic and FIr6, and red emitters such as Btp2Ir(acac) are commonly used, with green emitters being preferred. In this case, hole-injecting and transporting host materials include carbazole derivatives such as 4,4'-di(N-carbazolyl)biphenyl (CBP), TCTA, and mCP. Electron-transporting host materials such as p-bis(triphenylsilyl)benzene (UGH2) and 2,2',2''-(1,3,5-phenylene)-tris(1-phenyl-1H-benzimidazole) (TPBI) can be used, enabling the fabrication of high-performance organic EL devices.

[0071] In order to avoid concentration quenching, the phosphorescent light-emitting material is preferably doped into the host material by co-evaporation in an amount ranging from 1 to 30 weight percent based on the entire light-emitting layer.

[0072] Furthermore, a material that emits delayed fluorescence can also be used as the light-emitting material. These materials can be formed into thin films by known methods such as vapor deposition, spin coating, and ink-jet printing.

[0073] The hole-blocking layer of the organic EL device of the present invention can be formed using compounds with hole-blocking properties, such as phenanthroline derivatives such as bathocuproine (BCP), metal complexes of quinolinol derivatives such as aluminum(III) bis(2-methyl-8-quinolinato)-4-phenylphenolate (BAlq), various rare earth complexes, triazole derivatives, triazine derivatives, pyrimidine derivatives, oxadiazole derivatives, and benzoazole derivatives. These materials may also serve as materials for the electron-transporting layer. These materials may be formed alone or mixed with other materials to form a single layer, or may be stacked together with other layers, or with other layers, or with other layers. These materials can be formed into thin films by known methods such as vapor deposition, spin coating, and inkjet printing.

[0074] The electron transport layer of the organic EL device of the present invention can be formed using 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, and silole derivatives. These materials can be formed into thin films by vapor deposition or known methods such as spin coating and inkjet printing. These materials can be used alone or mixed with other materials to form a single layer. They can also be used as a laminate structure consisting of layers formed alone, layers formed in a mixture, or layers formed in a mixture with other layers. These materials can be used to form thin films by known methods such as vapor deposition, spin coating, and inkjet printing.

[0075] The electron injection layer of the organic EL device of the present invention can be made of alkali metal salts such as lithium fluoride and cesium fluoride, alkaline earth metal salts such as magnesium fluoride, metal complexes of quinolinol derivatives such as lithium quinolinol, metal oxides such as aluminum oxide, or metals such as ytterbium (Yb), samarium (Sm), calcium (Ca), strontium (Sr), and cesium (Cs). However, in the preferred selection of the electron transport layer and the cathode, this can be omitted.

[0076] 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 materials that are normally used in the layer.

[0077] For the cathode of the organic EL element of the present invention, an electrode material having a low work function such as aluminum, an alloy having an even lower work function such as a magnesium-silver alloy, a magnesium-calcium alloy, a magnesium-indium alloy, or an aluminum-magnesium alloy, ITO, IZO, or the like is used as the electrode material.

[0078] The capping layer of the organic EL element of the present invention preferably has a two-layer structure consisting of a first capping layer and a second capping layer. In this case, it is preferable to use the adamantane compound of the present invention represented by the general formula (1) as the first capping layer adjacent to the cathode electrode. These materials may be used to form a film by themselves or may be used as a single layer by mixing with other materials. These materials can be used to form a thin film by known methods such as vapor deposition, spin coating, and ink jet printing.

[0079] The adamantane compound of the present invention represented by the general formula (1) preferably has a refractive index of 1.6 or less, more preferably 1.5 or less, in the wavelength range of 400 nm to 700 nm.

[0080] In the organic EL device of the present invention, a high refractive index arylamine compound is preferably used as the second capping layer laminated on the first capping layer. The high refractive index arylamine compound preferably has a refractive index of 1.6 or more, more preferably 1.8 or more, and even more preferably 1.9 or more in the wavelength range of 450 nm to 700 nm. As the high refractive index arylamine compound, those having a structure in which two triphenylamine structures are linked by a single bond or a phenylene group in the molecule and having two benzoazole or benzotriazole groups as substituents, or those having only one triphenylamine structure in the molecule and two or three benzoazole, benzotriazole, or benzothienyl groups as substituents, as exemplified in Figures 9 and 10, are preferably used. These compounds have no absorption in the blue, green and red wavelength regions, and are therefore particularly suitable for displaying clear, bright images with good color purity. These materials may be used to form a film by themselves or may be used as a single layer by mixing with other materials. These materials can be used to form a thin film by known methods such as vapor deposition, spin coating, and ink jet printing.

[0081] The refractive index of the material forming the second capping layer is preferably 0.2 or more greater than the refractive index of the adjacent first capping layer ([refractive index of the second capping layer] - [refractive index of the first capping layer] ≥ 0.2). That is, the second capping layer improves the light extraction efficiency in the organic EL device, but the effect is more effective because the greater the reflectance at the interface between the second capping layer and the first capping layer, the greater the effect of light interference. Therefore, the refractive index of the material forming the second capping layer is preferably 0.2 or more greater than the refractive index of the adjacent first capping layer.

[0082] In the above description, the organic EL device with a top emission structure has been described, but the present invention is not limited to this, and the present invention can be similarly applied to an organic EL device with a bottom emission structure and an organic EL device with a dual emission structure that emits light from both the top and the bottom. In these cases, the electrode in the direction in which light is extracted from the light emitting element to the outside needs to be transparent or semi-transparent.

[0083] Hereinafter, embodiments of the present invention will be specifically described by way of examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

Examples

[0084] <Synthesis of N,N'-adamantane-1,3-diylbis(4-fluorobenzamide) (1-13)> 5.0 g of adamantane-1,3-diamine, 120 mL of tetrahydrofuran, and 10.4 g of potassium carbonate were added to a nitrogen-substituted reaction vessel, 10.5 g of 4-fluorobenzoyl chloride was added dropwise over 10 minutes, and the mixture was further stirred at 25°C for 4 hours. 100 mL of water was added, tetrahydrofuran was distilled off under reduced pressure, and the precipitated solid was collected by filtration. 60 mL of methanol and 60 mL of water were added, and the mixture was refluxed and dispersed for washing for 1 hour. After cooling to room temperature, the solid was collected by filtration. It was dissolved in 180 mL of dichloromethane, 6 g of silica gel was added and 、2After stirring at 5 °C for 1 hour, the silica gel was removed by filtration. The filtrate was concentrated, and the residue was washed with methanol to obtain 8.4 g (yield 68%) of a white powder of N,N'-adamantane-1,3-diylbis(4-fluorobenzeneamide) (1-13).

[0085]

Chemical formula

[0086] [[ID=​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​δ (ppm) = 7.22 - 7.29 (4H), 6.92 - 6.97 (2H), 5.88 (2H), 2.57 (2H), 2.37 (2H), 2.07 - 2.18 (8H), 1.73 (2H).

Example

[0090] <Synthesis of N,N'-Adamantane-1,3-diylbis(pentafluorobenzene amide) (1-23)> In Example 1, 4-fluorobenzoyl chloride was replaced with pentafluorobenzoyl chloride, and the same operation was carried out to obtain 9.0 g (yield 54%) of white powder of N,N'-adamantane-1,3-diylbis(pentafluorobenzene amide) (1-23).

[0091]

Chemical formula

[0092] The structure of the obtained white powder was identified using NMR and mass spectrum analysis. 1 The following 16 hydrogen signals were detected by 1H-NMR (DMSO-d6). δ (ppm) = 8.64 (2H), 2.36 (2H), 2.23 (2H), 1.93 - 2.04 (8H), 1.61 (2H). 13 The following 13 C signals were detected by 13C-NMR (DMSO-d6). δ (ppm) = 157.0, 144.6, 142.5, 142.2, 140.0, 138.5, 138.4, 136.2, 136.0, 114.1, 113.9, 113.6, 67.5, 54.1, 54.0, 44.4, 39.4, 35.1, 29.6, 25.6. m / z (M+1) = 555

Example

[0093] The glass transition temperature (Tg) and melting point of the adamantane compound represented by general formula (1) were measured using a high-sensitivity differential scanning calorimeter (DSC3100SA, manufactured by Bruker AXS). Glass transition temperature (Tg) Melting point Compound (1-13) of Example 1 71°C 222°C Compound (1-18) of Example 2 (not observed) 256°C Compound (1-23) of Example 3 (not observed) 322°C [Example]

[0094] An 80 nm thick film was prepared by vapor deposition on a silicon substrate using the adamantane compound represented by general formula (1). The refractive index n was measured at wavelengths of 400 nm, 450 nm, and 700 nm using a spectrophotometer (Filmetrics, F10-RT-UV). For comparison, measurements were also performed on the high-refractive-index arylamine compound (2-8) and Alq3. The measurement results are summarized in Table 1.

[0095] [ka] (2-8)

[0096] [Table 1]

[0097] As described above, the refractive index of the adamantane compound represented by the general formula (1) of the present invention is 1.60 or less in the wavelength range of 400 nm to 700 nm, and is smaller by 0.2 or more than the refractive index of the arylamine compound (2-8) having a high refractive index. [Example]

[0098] As shown in Figure 11, the organic EL device was fabricated by depositing a hole injection layer 3, a hole transport layer 4, an emitting layer 5, an electron transport layer 6, an electron injection layer 7, a cathode 8, a first capping layer 9, and a second capping layer 10 in this order on a glass substrate 1 on which a reflective ITO electrode was previously formed as a metal anode 2.

[0099] Specifically, a metal anode 2 was formed on a glass substrate 1. The metal anode 2 was formed by depositing a 50 nm thick ITO film, a 100 nm thick silver alloy reflective film, and a 5 nm thick ITO film in that order. This film was then ultrasonically cleaned in isopropyl alcohol for 20 minutes and then dried on a hot plate heated to 250°C for 10 minutes. After 2 minutes of UV ozone treatment, the ITO-attached glass substrate was placed in a vacuum deposition chamber and the pressure was reduced to 0.001 Pa or less. Next, a hole-injection layer 3 was formed covering the metal anode 2 by binary deposition of an electron acceptor (Acceptor-1) of the following structural formula and a compound (3-1) of the following structural formula at a deposition rate ratio of (Acceptor-1):compound (3-1) = 3:97, resulting in a thickness of 10 nm. On top of this hole-injection layer 3, a hole-transport layer 4 was formed by depositing a compound (3-1) of the following structural formula to a thickness of 140 nm. On the hole transport layer 4, a compound (EMD-1) having the following structural formula and a compound (EMH-1) having the following structural formula were binary-evaporated at a deposition rate ratio of compound (EMD-1) to compound (EMH-1) of 5:95 to form a 20 nm thick light-emitting layer 5. On the light-emitting layer 5, a compound (4-1) having the following structural formula and a compound (ETM-1) having the following structural formula were binary-evaporated at a deposition rate ratio of compound (4-1) to compound (ETM-1) of 50:50 to form a 30 nm thick electron transport layer 6. On the electron transport layer 6, lithium fluoride was formed as an electron injection layer 7 to a thickness of 1 nm. On the electron injection layer 7, a magnesium-silver alloy was formed as a cathode 8 to a thickness of 12 nm. On the cathode 8, the compound (1-13) of Example 1 was formed as a first capping layer 9 to a thickness of 30 nm, and finally, the arylamine compound (2-8) having a high refractive index was formed as a second capping layer 10 to a thickness of 30 nm. The characteristics of the produced organic EL device were measured in the air at room temperature. The light-emitting characteristics of the fabricated organic EL device were measured by applying a DC voltage, and the results are summarized in Table 2.

[0100] [ka] [Example]

[0101] An organic EL device was fabricated under the same conditions as in Example 6, except that the compound (1-18) of Example 2 was used instead of the compound (1-13) of Example 1 for the first capping layer 9. The characteristics of the fabricated organic EL device were measured in the air at room temperature. The light-emitting characteristics of the fabricated organic EL device were measured by applying a DC voltage, and the results are summarized in Table 2. [Example]

[0102] An organic EL device was fabricated under the same conditions as in Example 6, except that the compound (1-23) of Example 3 was used as the first capping layer 9 instead of the compound (1-13) of Example 1. The characteristics of the fabricated organic EL device were measured in the air at room temperature. The light-emitting characteristics of the fabricated organic EL device were measured by applying a DC voltage, and the results are summarized in Table 2.

[0103] [Comparative Example 1] For comparison, an organic EL device was fabricated under the same conditions as in Example 6, except that Alq3 was used as the first capping layer 9 instead of the compound (1-13) in Example 1. The characteristics of the fabricated organic EL device were measured in the air at room temperature. The light-emitting characteristics of the fabricated organic EL device were measured by applying a DC voltage, and the results are summarized in Table 2.

[0104] Comparative Example 2 For comparison, an organic EL device was fabricated in Example 6 by forming a second capping layer 10 of a high refractive index arylamine compound (2-8) to a thickness of 60 nm, which is twice as thick, and not including a first capping layer 9. The characteristics of the fabricated organic EL device were measured in the air at room temperature. The light-emitting characteristics of the fabricated organic EL device were measured by applying a DC voltage, and the results are summarized in Table 2.

[0105] The organic EL elements fabricated in Examples 6 to 8 and Comparative Examples 1 and 2 were used to measure the element lifetime, and the results are summarized in Table 2. The element lifetime was 10 mA / cm 2 When the device was driven at a constant current of 100%, the time required for the initial luminance to decay to 95% (95% decay) was measured.

[0106] [Table 2]

[0107] As shown in Table 2, a current density of 10 mA / cm 2 The driving voltage at this time was almost the same for the devices of Comparative Examples 1 and 2 and the devices of Examples 6 to 8, which used the adamantane compound represented by general formula (1) of the present invention as the first capping layer, whereas the brightness, luminous efficiency, power efficiency, and device life of the devices of Examples 6 to 8 were all significantly improved compared to the devices of Comparative Examples 1 and 2. This shows that the light extraction efficiency can be significantly improved by using a laminated structure in which a second capping layer is laminated on a first capping layer containing an adamantane compound represented by general formula (1) of the present invention, and by combining materials for the second capping layer so that the difference in refractive index between the first capping layer and the second capping layer is large. [Industrial Applicability]

[0108] Organic EL devices containing a capping layer containing the adamantane compound represented by general formula (1) of the present invention, particularly organic EL devices in which a material with a large refractive index difference is laminated as a second capping layer on a first capping layer containing the adamantane compound represented by general formula (1) of the present invention, can achieve high light extraction efficiency. Furthermore, the use of this compound, which has no absorption in the blue, green, and red wavelength regions, is particularly suitable for displaying clear, bright images with good color purity. For example, this compound can be used in home appliances and lighting applications. [Explanation of symbols]

[0109] 1. Glass substrate 2 metal anode 3. Hole injection layer 4. Hole transport layer 5. Light-emitting layer 6 Electron transport layer 7 Electron injection layer 8 cathode 9 First capping layer 10 Second capping layer

Claims

1. An organic thin film containing an adamantane compound represented by the following general formula (1-B) or compound (1-13), characterized in that the refractive index in the wavelength range of 400 nm to 700 nm is 1.60 or less. 【Chemical 1】 (1-B) (In the formula, R ３ ~R １２ may be the same or different and represent a hydrogen atom, a halogen atom, a cyano group, a substituted or unsubstituted linear or branched alkyl group having 1 to 3 carbon atoms, a substituted or unsubstituted linear or branched alkyloxy group having 1 to 3 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group, provided that any two of R 3 to R 7 and any two of R 8 to R 12 are not hydrogen atoms. 【Chemistry 2】 （１－１３）

2. 10. An organic electroluminescence device comprising at least an anode electrode, a hole transport layer, a light-emitting layer, an electron transport layer, a cathode electrode, and a capping layer in this order, wherein the capping layer is the organic thin film according to claim 1.

3. 10. An organic electroluminescent device comprising at least an anode electrode, a hole transport layer, an emitting layer, an electron transport layer, a cathode electrode, and a capping layer in this order, wherein the capping layer has a two-layer structure of a first capping layer and a second capping layer, and the first capping layer is the organic thin film according to claim 1.

4. The organic electroluminescent element according to claim 3, characterized in that the difference between the refractive index of the first capping layer and the refractive index of the second capping layer ([refractive index of the second capping layer] - [refractive index of the first capping layer]) is 0.2 or more.

5. An electronic device or an electronic element having a pair of electrodes and at least one organic layer sandwiched between them, characterized in that the organic layer contains an adamantane compound represented by the following general formula (1-B) or compound (1-13) as a constituent material: 【Chemistry 3】 (1-B) (In the formula, R ３ ~R １２ may be the same or different and represent a hydrogen atom, a halogen atom, a cyano group, a substituted or unsubstituted linear or branched alkyl group having 1 to 3 carbon atoms, a substituted or unsubstituted linear or branched alkyloxy group having 1 to 3 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group, provided that any two of R 3 to R 7 and any two of R 8 to R 12 are not hydrogen atoms. 【Chemistry 4】 （１－１３）

6. An adamantane compound represented by the following general formula (1-B) or compound (1-13): 【Chemistry 5】 (1-B) (In the formula, R 3 to R 12 may be the same or different and represent a hydrogen atom, a halogen atom, a cyano group, a substituted or unsubstituted linear or branched alkyl group having 1 to 3 carbon atoms, a substituted or unsubstituted linear or branched alkyloxy group having 1 to 3 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group, provided that any two of R 3 to R 7 and any two of R 8 to R 12 are not hydrogen atoms.) 【Chemistry 6】 （１－１３）

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