Adamantane Compound, Organic Electroluminescent Element, and Electronic Device

Abstract

An object of the present invention is to provide a compound suitable for a low refractive index layer in a cover layer in order to improve the light extraction efficiency of an organic EL element. The present invention focuses on the excellent thin film stability of adamantane compounds, and has found that an amide compound, an ester compound, an amine compound, or an ether compound having an adamantane at the center exhibits a low refractive index property, and by using it as a material constituting a low refractive index cover layer, an organic EL element excellent in luminous efficiency can be obtained.

Description

Technical Field

[0001] The present invention relates to a self-luminous element suitable for various display devices, namely an organic electroluminescent element (hereinafter simply referred to as an organic EL element), or a compound and an element suitable for an electronic device. Specifically, the present invention relates to an adamantane compound and an organic EL element or an electronic device obtained by using the compound. Background Art

[0002] In 1987, C.W. Tang et al. of Eastman Kodak Company developed a laminated structure element in which various functions are shared among various materials, thereby putting an organic EL element using an organic material into practical use. They obtained a luminance of 1000 cd / m 2 or more at a voltage of 10 V or less by laminating a phosphor capable of transporting electrons and an organic substance capable of transporting holes, and injecting two kinds of charges into the layer of the phosphor to cause it to emit light (see Patent Document 1 and Patent Document 2).

[0003] In recent years, a light-emitting element having a top-emission structure in which a metal having a high work function is used for an anode and light is emitted from above has been gradually used. In a bottom-emission structure in which light is taken out from the bottom having a pixel circuit, the area of the light-emitting portion is limited. On the other hand, in a light-emitting element having a top-emission structure, since light is taken out from above, the pixel circuit is not blocked, and thus there is an advantage that the light-emitting portion can be enlarged. In a light-emitting element having a top-emission structure, a semi-transparent electrode such as LiF / Al / Ag (see Non-Patent Document 1, for example), Ca / Mg (see Non-Patent Document 2), or LiF / MgAg is used for the cathode.

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

[0005] On the other hand, an organic optical device is shown in which a low refractive index layer is formed by co-evaporating an additive, and the effect of light interference is utilized by laminating with a high refractive index layer to form a multilayer film in which effective light propagation control is performed (see Patent Document 3).

[0006] It is known that the light extraction efficiency of an organic EL element is improved by forming a cover layer having a high refractive index. However, in order to form a low refractive index layer, co-evaporation with an additive is performed as described in Patent Document 3, and a compound capable of performing low-temperature evaporation alone is sought.

[0007] Prior Art Documents

[0008] Patent Document

[0009] Patent Document 1: Japanese Patent Laid-Open No. 8-048656

[0010] Patent Document 2: Japanese Patent No. 3194657

[0011] Patent Document 3: Japanese Patent No. 6210473

[0012] Non-Patent Document 1: Appl. Phys. Let., 78, 544 (2001)

[0013] Non-Patent Document 2: Appl. Phys. Let., 82, 466 (2003) Summary of the Invention

[0014] Problems to be Solved by the Invention

[0015] An object of the present invention is to provide a compound suitable for a low refractive index layer in a cover layer in order to improve the light extraction efficiency of an organic EL element.

[0016] As the physical properties of the material suitable for the low refractive index layer of the present invention, the following can be cited: (1) It can be vapor-deposited without thermal decomposition; (2) The thin film state is stable; (3) The refractive index is low. In addition, as the physical properties of the element suitable for the present invention, the following can be cited: (1) High light extraction efficiency; (2) Color purity is not reduced; (3) It is transparent without change over time; (4) Long life.

[0017] Solutions to the Problems

[0018] The inventors of the present invention focused on the excellent thin film stability of adamantane compounds in order to achieve the above object, and found that: an amide compound, an ester compound, an amine compound or an ether compound having adamantane at the center exhibits a low refractive index property, and it is used as a material for forming a low refractive index cover layer to fabricate an organic EL element, and as a result of in-depth evaluation of the characteristics of the element, the present invention has been completed.

[0019] That is, according to the present invention, the following adamantane compounds and organic EL elements are provided.

[0020] 1) An adamantane compound represented by the following general formula (1).

[0021]

[0022] (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; R1 and R2 are optionally the same or different and represent a substituted or unsubstituted aromatic hydrocarbon group.)

[0023] 2) The adamantane compound according to 1) above, wherein the adamantane compound is represented by the following general formula (1-A).

[0024]

[0025] (In the formula, X and L are as defined in the general formula (1) above. R3 to R 12 Optionally the same as or different from each other, 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 alkoxy group having 1 to 3 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group.)

[0026] 3) The adamantane compound according to 1) or 2) above, wherein the adamantane compound is represented by the following general formula (1-B).

[0027]

[0028] (In the formula, R3 to R 12 Are as defined in the general formula (1-A) above.)

[0029] 4) The adamantane compound according to 1) or 2) above, wherein the adamantane compound is represented by the following general formula (1-C).

[0030]

[0031] (In the formula, R3 to R 12 Are as defined in the general formula (1-A) above.)

[0032] 5) The adamantane compound according to 1) or 2) above, wherein the adamantane compound is represented by the following general formula (1-D).

[0033]

[0034] (In the formula, R3 to R 12 Are as defined in the general formula (1-A) above.)

[0035] 6) The adamantane compound according to 1) or 2) above, wherein the adamantane compound is represented by the following general formula (1-E).

[0036]

[0037] (In the formula, R3 to R 12 Are as defined in the general formula (1-A) above.)

[0038] 7) An organic thin film, characterized in that it contains the adamantane compound according to any one of the above 1) to 6), and the refractive index of the organic thin film in the wavelength range of 400 nm to 700 nm is 1.60 or less.

[0039] 8) An organic EL element, characterized in that it has at least an anode electrode, a hole transport layer, a light-emitting layer, an electron transport layer, a cathode electrode, and a covering layer in this order, and the aforementioned covering layer is the organic thin film according to 7) above.

[0040] 9) An organic EL element, characterized in that it has at least an anode electrode, a hole transport layer, a light-emitting layer, an electron transport layer, a cathode electrode, and a covering layer in this order, and the aforementioned covering layer is a two-layer structure of a first covering layer and a second covering layer, and the first covering layer is the organic thin film according to 7) above.

[0041] 10) The organic EL element according to 9) above, characterized in that the difference in refractive index between the aforementioned first covering layer and the second covering layer ([refractive index of the second covering layer] - [refractive index of the first covering layer]) is 0.2 or more.

[0042] 11) An electronic device or electronic component, characterized in that it has a pair of electrodes and at least one organic layer sandwiched therebetween, and the aforementioned organic layer uses the adamantane compound according to any one of the above 1) to 6) as its constituent material.

[0043] In this specification, when it is noted as "substituted or unsubstituted", "unsubstituted" means that the hydrogen atom is not substituted by a substituent.

[0044] In this specification, "hydrogen atom" means isotopes with different numbers of neutrons, that is, it is used in the meaning including protium and deuterium.

[0045] As the "alkylene group" in the "linear or branched alkylene group having 1 to 3 carbon atoms" represented by L in the general formula (1), specifically, methylene, 1,2-ethylene, and 1,3-propylene can be mentioned. Preferred are methylene and 1,2-ethylene, and more preferred is methylene.

[0046] In addition, these divalent groups are preferably unsubstituted, and may also have a substituent. As the substituent at this time, specifically, cyano group; halogen atoms such as fluorine atom, chlorine atom, bromine atom, and iodine atom; linear or branched alkoxy groups having 1 to 3 carbon atoms such as methoxy group, ethoxy group, and propoxy group, etc. can be mentioned.

[0047] X in the general formula (1) represents an oxygen atom or an NH group.

[0048] Specifically, when X in the general formula (1) is an oxygen atom and L is an alkylene group, (-L-X-) in the aforementioned general formula (1) is an ether group; when X in the general formula (1) is an oxygen atom and L is a carbonyl group, (-L-X-) in the aforementioned general formula (1) is an ester group.

[0049] Moreover, when X in the general formula (1) is an NH group and L is an alkylene group, (-L-X-) in the aforementioned general formula (1) is an amino group; when X in the general formula (1) is an NH group and L is a carbonyl group, (-L-X-) in the aforementioned general formula (1) is an amide group.

[0050] Specific examples of the "aromatic hydrocarbon group" in the "substituted or unsubstituted aromatic hydrocarbon group" represented by R1 and R2 in the general formula (1) include phenyl, biphenyl, 1-naphthyl, 2-naphthyl, 2-phenanthryl, 9-phenanthryl, and fluorenyl. Preferred are phenyl, biphenyl, 1-naphthyl, 2-naphthyl, and fluorenyl, and more preferred are phenyl and fluorenyl.

[0051] In addition, these groups may have substituents. Specific examples of the substituents in this case include a cyano group; halogen atoms such as fluorine atom, chlorine atom, bromine atom, and iodine atom; linear or branched alkyl groups having 1 to 3 carbon atoms such as methyl, ethyl, and propyl; linear or branched alkoxy groups having 1 to 3 carbon atoms such as methoxy, ethoxy, and propoxy; and aromatic hydrocarbon groups such as phenyl, biphenyl, 1-naphthyl, 2-naphthyl, and fluorenyl.

[0052] As the "halogen atom" represented by R3 to R 12 in the general formula (1-A), examples include fluorine atom, chlorine atom, bromine atom, and iodine atom. Preferred are fluorine atom and chlorine atom, and more preferred is fluorine atom.

[0053] As the "alkyl group" in the "substituted or unsubstituted linear or branched alkyl group having 1 to 3 carbon atoms" represented by R3 to R 12 in the general formula (1-A), examples include methyl, ethyl, and propyl. Preferred are methyl and ethyl, and more preferred is methyl.

[0054] As the "alkoxy group" in the "substituted or unsubstituted linear or branched alkoxy group having 1 to 3 carbon atoms" represented by R3 to R 12 in the general formula (1-A), examples include methoxy, ethoxy, and propoxy. Preferred are methoxy and ethoxy, and more preferred is methoxy.

[0055] As the R3 to R in the general formula (1-A) 12The "aromatic hydrocarbon group" in the "substituted or unsubstituted aromatic hydrocarbon group" shown specifically includes phenyl, biphenyl, 1-naphthyl, 2-naphthyl, 2-phenanthryl, 9-phenanthryl, fluorenyl, preferably phenyl, biphenyl, 1-naphthyl, 2-naphthyl, fluorenyl, more preferably phenyl, fluorenyl, and still more preferably phenyl.

[0056] In addition, these groups may have substituents. As the substituents at this time, specifically, cyano group; halogen atoms such as fluorine atom, chlorine atom, bromine atom, iodine atom; linear or branched alkyl groups having 1 to 3 carbon atoms such as methyl group, ethyl group, propyl group; linear or branched alkoxy groups having 1 to 3 carbon atoms such as methoxy group, ethoxy group, propoxy group, etc. can be cited.

[0057] R3 to R in the general formula (1-A) 12 The "linear or branched alkyl group having 1 to 3 carbon atoms" and the "linear or branched alkoxy group having 1 to 3 carbon atoms" shown may have substituents. As the "substituents" at this time, preferably halogen atoms, and more preferably fluorine atom.

[0058] The adamantane compound represented by the general formula (1) of the present invention is preferably an adamantane compound represented by any one of the following general formulas (1-A) to (1-E), and more preferably an adamantane compound represented by any one of the following general formulas (1-B) to (1-E).

[0059] Two Ls in the general formula (1) are preferably the same group, and may also be different groups.

[0060] In addition, two Xs in the general formula (1) are preferably the same group, and may also be different groups.

[0061] In addition, in the general formula (1), R1 and R2 may be the same or different from each other, and are preferably the same.

[0062]

[0063]

[0064] In the general formulas (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.

[0065] R3 to R 12 Optionally the same as or different from each other, 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 alkoxy group having 1 to 3 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group.

[0066] Details of a linear or branched alkylene group having 1 to 3 carbon atoms, an aromatic hydrocarbon group, a halogen atom, a linear or branched alkyl group having 1 to 3 carbon atoms, a linear or branched alkoxy group having 1 to 3 carbon atoms, and their substituents are as described above.

[0067] Effects of the Invention

[0068] The adamantane compound represented by the general formula (1) of the present invention has excellent low refractive index characteristics. Therefore, by using this compound to form a low refractive index layer (organic thin film) and combining it with a high refractive index layer (organic thin film), an organic EL element that further improves the light extraction efficiency by utilizing the optical interference effect can be realized.

[0069] In addition, the adamantane compound of the present invention can be used not only for organic EL elements but also in the fields of electronic devices such as electrophotographic photoreceptors, image sensors, photoelectric conversion elements, and solar cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 FIGS. show the structures of Compounds (1-1) to (1-16) as the adamantane compounds represented by the general formula (1) of the present invention.

[0071] Figure 2 FIGS. show the structures of Compounds (1-17) to (1-32) as the adamantane compounds represented by the general formula (1) of the present invention.

[0072] Figure 3 FIGS. show the structures of Compounds (1-33) to (1-50) as the adamantane compounds represented by the general formula (1) of the present invention.

[0073] Figure 4 FIGS. show the structures of Compounds (1-51) to (1-68) as the adamantane compounds represented by the general formula (1) of the present invention.

[0074] Figure 5 FIGS. show the structures of Compounds (1-69) to (1-86) as the adamantane compounds represented by the general formula (1) of the present invention.

[0075] Figure 6 FIGS. show the structures of Compounds (1-87) to (1-104) as the adamantane compounds represented by the general formula (1) of the present invention.

[0076] Figure 7 FIGS. show the structures of Compounds (1-105) to (1-122) as the adamantane compounds represented by the general formula (1) of the present invention.

[0077] Figure 8It is a diagram showing the structures of compounds (1-123) to (1-140) as adamantane compounds represented by the general formula (1) of the present invention.

[0078] Figure 9 It is a diagram showing the structures of compounds (2-1) to (2-10) as specific examples of arylamine compounds with a high refractive index suitable for use in the organic EL element of the present invention.

[0079] Figure 10 It is a diagram showing the structures of compounds (2-11) to (2-18) as specific examples of arylamine compounds with a high refractive index suitable for use in the organic EL element of the present invention.

[0080] Figure 11 It is a diagram showing the configurations of the organic EL elements of Examples 6 to 8 and Comparative Examples 1 to 2. Detailed Description

[0081] The adamantane compounds represented by the general formula (1) of the present invention are novel compounds, but these compounds themselves can be synthesized according to known methods.

[0082] Specific examples of the adamantane compounds represented by the general formula (1) of the present invention are shown in Figures 1 to 8 , but are not limited to these compounds.

[0083] Specific examples of the arylamine compounds with a high refractive index suitable for use in the organic EL element of the present invention are shown in Figures 9 to 10 , but are not limited to these compounds.

[0084] The method for producing the adamantane compounds represented by the general formula (1) of the present invention is not particularly limited. The purification of the compounds can be carried out by known methods used in the purification of organic compounds, such as purification based on column chromatography, adsorption purification based on silica gel, activated carbon, activated clay, etc., recrystallization based on solvents, crystallization, etc., and finally purification is carried out using a sublimation purification method, etc. The identification of the compounds can be carried out by NMR analysis, mass spectrometry, etc. As physical property values, it is preferable to measure the melting point, glass transition temperature (Tg), refractive index, and absorbance.

[0085] The melting point and glass transition temperature (Tg) are measured by, for example, using a powder and a high-sensitivity differential scanning calorimeter (manufactured by BRUKER-AXS, DSC3100SA).

[0086] The refractive index is measured by forming an 80-nm thin film on a silicon substrate and using a spectroscopic measurement device (manufactured by FILMETRICS, F10-RT-UV).

[0087] As the structure of the organic EL element of the present invention, for example, in the case of a top-emitting structure light-emitting element, the following structures can be cited: a structure including an anode, a hole transport layer, a light-emitting layer, an electron transport layer, a cathode, and a cover layer in this order on a glass substrate; in addition, a structure having a hole injection layer between the anode and the hole transport layer; a structure having an electron blocking layer between the hole transport layer and the light-emitting layer; a structure having a hole blocking layer between the light-emitting layer and the electron transport layer; a structure having an electron injection layer between the electron transport layer and the cathode. In these multilayer structures, several organic layers can be omitted or several layers can be combined. For example, it can also be made into a configuration that serves as both a hole injection layer and a hole transport layer, a configuration that serves as both a hole transport layer and an electron blocking layer, a configuration that serves as both a hole blocking layer and an electron transport layer, a configuration that serves as both an electron transport layer and an electron injection layer, etc. In addition, it can be made into a configuration obtained by laminating two or more organic layers having the same function, or a configuration obtained by laminating two hole transport layers, a configuration obtained by laminating two light-emitting layers, a configuration obtained by laminating two electron transport layers, a configuration obtained by laminating two cover layers, etc.

[0088] The total film 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. In addition, the film thickness of the cover 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. It should be noted that the film thickness of the cover layer can be appropriately changed according to 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 cover layer, etc.

[0089] As the anode of the organic EL element of the present invention, electrode materials having a large work function such as ITO and gold can be used.

[0090] As the hole injection layer of the organic EL element of the present invention, an arylamine compound having a structure in which two or more triphenylamine structures are connected by a single bond or a divalent group containing no heteroatom in the molecule is preferred; for example, a biphenylamine derivative and other arylamine compounds having a structure in which two triphenylamine structures are connected by a single bond or a divalent group containing no heteroatom in the molecule; star-shaped triphenylamine derivatives; various triphenylamine tetramers and other materials. In addition, porphyrin compounds represented by copper phthalocyanine, acceptor heterocyclic compounds such as hexacyanoazaphenanthrene, and coating-type polymer materials can be used. They can be formed into a film alone, or used in the form of a single layer obtained by mixing and forming a film with other materials, and can also be made into a laminated structure of layers formed into a film alone, a laminated structure of layers formed by mixing and forming a film, or a laminated structure of a layer formed into a film alone and a layer formed by mixing and forming a film. For these materials, in addition to the evaporation method, known methods such as spin coating and inkjet printing can also be used to form a thin film.

[0091] As the hole transport layer of the organic EL element of the present invention, it is preferable to use benzidine derivatives such as N,N'-diphenyl-N,N'-bis(m-tolyl)benzidine (TPD), N,N'-diphenyl-N,N'-bis(α-naphthyl)benzidine (NPD), and N,N,N',N'-tetraphenylbenzidine; 1,1-bis[4-(di-p-tolylamino)phenyl]cyclohexane (TAPC). Particularly preferably, an arylamine compound having a structure in which two triphenylamine structures are connected by a single bond or a divalent group containing no heteroatom in the molecule is used, such as N,N,N',N'-tetraphenylbenzidine. In addition, an arylamine compound having only one triphenylamine structure in the molecule, an arylamine compound having a structure in which three or more triphenylamine structures are connected by a single bond or a divalent group containing no heteroatom in the molecule, such as various triphenylamine trimers and tetramers, etc. are preferably used. They can be formed into a film alone, or used in the form of a single layer obtained by forming a film by mixing with other materials. They can also be made into a stacked structure of layers formed into a film alone, a stacked structure of layers formed by mixing into a film, or a stacked structure of a layer formed into a film alone and a layer formed by mixing into a film. In addition, as the hole injection / transport layer, a coating type polymer material such as poly(3,4-ethylenedioxythiophene) (PEDOT) / poly(styrenesulfonate) (PSS) can be used. These materials can be formed into a thin film by known methods such as spin coating method and inkjet method in addition to the evaporation method.

[0092] In addition, in the hole injection layer or the hole transport layer, it is preferable to further p-dope tribromophenylamine hexachloroantimonate, axisene derivatives, etc. into the materials usually used in this layer. In addition, a polymer compound having a structure of a benzidine derivative such as TPD in a part of its structure can be used.

[0093] As the electron blocking layer of the organic EL element of the present invention, carbazole derivatives such as 4,4',4''-tris(N-carbazolyl)triphenylamine (TCTA), 9,9-bis[4-(carbazol-9-yl)phenyl]fluorene, 1,3-bis(carbazol-9-yl)benzene (mCP), 2,2-bis(4-carbazol-9-yl-phenyl)adamantane (Ad-Cz), and compounds having an electron blocking effect such as compounds having a triphenylsilyl group and a triarylamine structure represented by 9-[4-(carbazol-9-yl)phenyl]-9-[4-(triphenylsilyl)phenyl]-9H-fluorene can be used. They can be formed into a film alone, or used in the form of a single layer obtained by forming a film by mixing with other materials. They can also be made into a stacked structure of layers formed into a film alone, a stacked structure of layers formed by mixing into a film, or a stacked structure of a layer formed into a film alone and a layer formed by mixing into a film. These materials can be formed into a thin film by known methods such as spin coating method and inkjet method in addition to the evaporation method.

[0094] As the light-emitting layer of the organic EL element of the present invention, in addition to metal complexes of hydroxyquinoline derivatives such as Alq3, various metal complexes, anthracene derivatives, bisstyrylbenzene derivatives, pyrene derivatives, oxazole derivatives, poly(phenylene vinylene) derivatives, etc. can also be used. In addition, the light-emitting layer may be composed of a host material and a dopant material. As the host material, anthracene derivatives are preferably used. In addition, on the basis of using the aforementioned light-emitting materials, heterocyclic compounds having an indole ring as a partial structure of a condensed ring, heterocyclic compounds having a carbazole ring as a partial structure of a condensed ring, carbazole derivatives, thiazole derivatives, benzimidazole derivatives, polydialkylfluorene derivatives, etc. can also be used. In addition, as the dopant material, quinacridone, coumarin, rubrene, perylene and their derivatives, benzopyran derivatives, rhodamine derivatives, aminostyryl derivatives, etc. can be used, and green light-emitting materials are more preferably used. They can be formed into a film alone, or used in the form of a single layer obtained by forming a film by mixing with other materials, and can also be made into a stacked structure of layers formed into a film alone, a stacked structure of layers formed by mixing into a film, or a stacked structure of a layer formed into a film alone and a layer formed by mixing into a film.

[0095] In addition, as the light-emitting material, phosphorescent emitters can also be used. As the phosphorescent emitter, phosphorescent emitters of metal complexes such as iridium and platinum can be used. Green phosphorescent emitters such as Ir(ppy)3, blue phosphorescent emitters such as FIrpic and FIr6, red phosphorescent emitters such as Btp2Ir(acac), etc. can be used, and green phosphorescent emitters are more preferably used. Regarding the host material at this time, as the hole injection / transporting host material, carbazole derivatives such as 4,4'-bis(N-carbazolyl)biphenyl (CBP), TCTA, and mCP can be used. As the electron transporting host material, bis(triphenylsilyl)benzene (UGH2), 2,2',2''-(1,3,5-phenylene)-tris(1-phenyl-1H-benzimidazole) (TPBI), etc. can be used, and high-performance organic EL elements can be fabricated.

[0096] Regarding the doping of the phosphorescent light-emitting material in the host material, in order to avoid concentration quenching, it is preferably doped by co-evaporation in the range of 1 to 30% by weight relative to the whole light-emitting layer.

[0097] In addition, as the light-emitting material, materials that emit delayed fluorescence can also be used. These materials can be formed into a thin film by known methods such as spin coating and inkjet printing in addition to the evaporation method.

[0098] As the hole blocking layer of the organic EL element of the present invention, phenanthroline derivatives such as bathocuproine (BCP), metal complexes of hydroxyquinoline derivatives such as aluminum(III) bis(2-methyl-8-hydroxyquinolinato)-4-phenylphenolate (BAlq), various rare earth complexes, triazole derivatives, triazine derivatives, pyrimidine derivatives, oxadiazole derivatives, benzoxazole derivatives and other compounds having a hole blocking effect can be used. These materials can also serve as materials for the electron transport layer. They can be formed into a film alone, or used in the form of a single layer obtained by forming a film by mixing with other materials. They can also be formed into a stacked structure of layers formed into a film alone, a stacked structure of layers formed by mixing into a film, or a stacked structure of a layer formed into a film alone and a layer formed by mixing into a film. In addition to the evaporation method, these materials can also be formed into a thin film by using known methods such as spin coating method and inkjet method.

[0099] As the electron transport layer of the organic EL element of the present invention, in addition to using metal complexes of hydroxyquinoline derivatives such as Alq3 and Balq, various metal complexes, triazole derivatives, triazine derivatives, pyrimidine derivatives, oxadiazole derivatives, pyridine derivatives, benzimidazole derivatives, benzoxazole derivatives, thiadiazole derivatives, anthracene derivatives, carbodiimide derivatives, quinoxaline derivatives, pyridoindole derivatives, phenanthroline derivatives, silole derivatives, etc. can also be used. They can be formed into a film alone, or used in the form of a single layer obtained by forming a film by mixing with other materials. They can also be formed into a stacked structure of layers formed into a film alone, a stacked structure of layers formed by mixing into a film, or a stacked structure of a layer formed into a film alone and a layer formed by mixing into a film. In addition to the evaporation method, these materials can also be formed into a thin film by using known methods such as spin coating method and inkjet method.

[0100] As the electron injection layer of the organic EL element of the present invention, alkali metal salts such as lithium fluoride and cesium fluoride; alkaline earth metal salts such as magnesium fluoride; metal complexes of hydroxyquinoline derivatives such as lithium hydroxyquinolate; metal oxides such as aluminum oxide; or metals such as ytterbium (Yb), samarium (Sm), calcium (Ca), strontium (Sr), cesium (Cs), etc. can be used, and it can be omitted in the preferred selection of the electron transport layer and the cathode.

[0101] Furthermore, in the electron injection layer or the electron transport layer, substances obtained by further n-doping metals such as cesium into the materials commonly used in this layer can be used.

[0102] As the cathode of the organic EL element of the present invention, electrode materials with a low work function such as aluminum, alloys with an even lower work function such as magnesium-silver alloy, magnesium-calcium alloy, magnesium-indium alloy, aluminum-magnesium alloy, ITO, IZO, etc. can be used as electrode materials.

[0103] As the covering layer of the organic EL element of the present invention, a two-layer structure of a first covering layer and a second covering layer is preferred. In this case, as the first covering layer adjacent to the cathode electrode, the adamantane compound represented by the aforementioned general formula (1) of the present invention is preferably used.

[0104] They can be formed into a film alone or used in the form of a single layer obtained by mixing and forming a film together with other materials. In addition to the evaporation method, these materials can also be formed into a thin film by known methods such as spin coating method and inkjet method.

[0105] As the adamantane compound represented by the aforementioned general formula (1) of the present invention, the refractive index in the wavelength range of 400 nm to 700 nm is preferably 1.6 or less, more preferably 1.5 or less.

[0106] In the organic EL element of the present invention, as the second covering layer laminated on the first covering layer, an arylamine compound with a high refractive index is preferably used. As the arylamine compound with a high refractive index, the refractive index in the wavelength range of 450 nm to 700 nm is preferably 1.6 or more, more preferably 1.8 or more, and further preferably 1.9 or more. As these arylamine compounds with a high refractive index, preferably used are Figures 9 to 10 compounds exemplified in [ ], having a structure in which two triphenylamine structures are connected by a single bond or a phenylene group in the molecule and having two benzoxazolyl groups or benzotriazolyl groups as substituents; or compounds having only one triphenylamine structure in the molecule and having two or three benzoxazolyl groups, benzotriazolyl groups or benzothiophenyl groups as substituents.

[0107] These compounds do not have absorption in the respective wavelength regions of blue, green and red, so they are particularly suitable when a color-pure, clear and bright image is desired to be displayed.

[0108] They can be formed into a film alone or used in the form of a single layer obtained by mixing and forming a film together with other materials. In addition to the evaporation method, these materials can also be formed into a thin film by known methods such as spin coating method and inkjet method.

[0109] The refractive index of the material constituting the second covering layer is preferably 0.2 or more greater than the refractive index of the adjacent first covering layer ([refractive index of the second covering layer] - [refractive index of the first covering layer] ≥ 0.2). That is, the light extraction efficiency in the organic EL element is improved by the second covering layer, but its effect is more effective because the light interference effect is greater when the reflectivity at the interface between the second covering layer and the first covering layer is large. Therefore, the refractive index of the material constituting the second covering layer is preferably 0.2 or more greater than the refractive index of the adjacent first covering layer.

[0110] Note that the above description is for the top-emitting organic EL element, but the present invention is not limited thereto, and the bottom-emitting organic EL element and the double-emitting organic EL element that emits light from both the upper and bottom can be similarly applied. In these cases, the electrode in the direction of extracting light from the light-emitting element needs to be transparent or semi-transparent.

[0111] 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 it does not exceed its gist.

[0112] [Example 1]

[0113] [Synthesis of N,N'-adamantane-1,3-diylbis(4-fluorobenzamide) (1-13)]

[0114] Add 5.0 g of adamantane-1,3-diamine, 120 mL of tetrahydrofuran, and 10.4 g of potassium carbonate to a reaction vessel purged with nitrogen. Dropwise add 10.5 g of 4-fluorobenzoyl chloride over 10 minutes, and then stir at 25 °C for 4 hours. Add 100 mL of water and distill off tetrahydrofuran under reduced pressure. Collect the precipitated solid by filtration. Add 60 mL of methanol and 60 mL of water, reflux and disperse for washing for 1 hour. After cooling to room temperature, collect the solid by filtration. Dissolve in 180 mL of dichloromethane, add 6 g of silica gel, stir at 25 °C for 1 hour, and then remove the silica gel by filtration. Concentrate the filtrate and wash the residue with methanol to obtain 8.4 g (yield 68%) of white powder of N,N'-adamantane-1,3-diylbis(4-fluorobenzamide) (1-13).

[0115]

[0116] The structure of the obtained white powder was identified using NMR.

[0117] Using 1 1H-NMR (CDCl3), signals of the following 24 hydrogens were detected.

[0118] δ (ppm) = 7.71 - 7.74 (4H), 7.06 - 7.11 (4H), 5.31 (2H), 2.57 (2H), 2.33 (2H), 2.07 - 2.19 (8H), 1.71 (2H).

[0119] [Example 2]

[0120] [Synthesis of N,N'-adamantane-1,3-diylbis(3,5-difluorobenzamide) (1-18)]

[0121] In Example 1, 4-fluorobenzoyl chloride was replaced with 3,5-difluorobenzoyl chloride, and the same operation was carried out to obtain 11.4 g of white powder of N,N'-adamantane-1,3-diylbis(3,5-difluorobenzamide) (1-18) (yield: 80.9%).

[0122]

[0123] For the obtained white powder, NMR was used to identify the structure.

[0124] Using 1 1H-NMR (CDCl3), signals of the following 22 hydrogens were detected.

[0125] 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).

[0126] [Example 3]

[0127] [Synthesis of N,N'-adamantane-1,3-diylbis(pentafluorobenzamide) (1-23)]

[0128] In Example 1, 4-fluorobenzoyl chloride was replaced with pentafluorobenzoyl chloride, and the same operation was carried out to obtain 9.0 g of white powder of N,N'-adamantane-1,3-diylbis(pentafluorobenzamide) (1-23) (yield: 54%).

[0129]

[0130] For the obtained white powder, NMR and mass spectrometry were used to identify the structure.

[0131] Using 1 1H-NMR (DMSO-d6), signals of the following 16 hydrogens were detected.

[0132] δ (ppm) = 8.64 (2H), 2.36 (2H), 2.23 (2H), 1.93 - 2.04 (8H), 1.61 (2H).

[0133] Using 13 13C-NMR (DMSO-d6), the following 13 13C signals were detected.

[0134] 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.

[0135] m / z (M+1) = 555

[0136] [Example 4]

[0137] For the adamantane compound represented by the general formula (1), the glass transition temperature (Tg) and melting point were measured using a high-sensitivity differential scanning calorimeter (manufactured by BRUKER AXS, DSC3100SA).

[0138] Glass transition temperature (Tg) Melting point

[0139] Compound (1-13) of Example 1 71 °C 222 °C

[0140] Compound (1-18) of Example 2 (not observed) 256 °C

[0141] Compound (1-23) of Example 3 (not observed) 322 °C

[0142] [Example 5]

[0143] Using the adamantane compound represented by the general formula (1), a vapor deposition film with a thickness of 80 nm was formed on a silicon substrate, and the refractive index n at wavelengths of 400 nm, 450 nm, and 700 nm was measured using a spectroscopic measurement device (manufactured by FILMETRICS, F10-RT-UV). In addition, for comparison, a high-refractive-index arylamine compound (2-8) and Alq3 were also measured. The measurement results are summarized in Table 1.

[0144]

[0145] [Table 1]

[0146]

[0147] Thus, 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 has a value that is 0.2 or more smaller than the refractive index of the high-refractive-index arylamine compound (2-8).

[0148] [Example 6]

[0149] The organic EL element is as Figure 11As shown, a metal anode 2 is formed by pre-forming a reflective ITO electrode on a glass substrate 1, and a hole injection layer 3, a hole transport layer 4, a light-emitting layer 5, an electron transport layer 6, an electron injection layer 7, a cathode 8, a first cover layer 9, and a second cover layer 10 are sequentially vapor-deposited on the resulting object to fabricate it.

[0150] Specifically, ITO with a film thickness of 50 nm, a reflective film of a silver alloy with a film thickness of 100 nm, and ITO with a film thickness of 5 nm are sequentially formed on the glass substrate 1 as the metal anode 2. After ultrasonic cleaning in isopropyl alcohol for 20 minutes, it is dried on a heating plate heated to 250 °C for 10 minutes. Thereafter, after performing a 2-minute UV ozone treatment, the glass substrate with ITO is placed in a vacuum vapor deposition machine and the pressure is reduced to 0.001 Pa or less. Next, a binary vapor deposition is performed at a vapor deposition rate ratio of an electron acceptor (Acceptor-1) of the following structural formula and a compound (3-1) of the following structural formula such that (Acceptor-1):Compound (3-1) = 3:97 to form a hole injection layer 3 with a film thickness of 10 nm. On this hole injection layer 3, the compound (3-1) of the following structural formula is formed into a hole transport layer 4 with a film thickness of 140 nm. On this hole transport layer 4, a binary vapor deposition is performed at a vapor deposition rate ratio of a compound (EMD-1) of the following structural formula and a compound (EMH-1) of the following structural formula such that Compound (EMD-1):Compound (EMH-1) = 5:95 to form a light-emitting layer 5 with a film thickness of 20 nm. On this light-emitting layer 5, a binary vapor deposition is performed at a vapor deposition rate ratio of a compound (4-1) of the following structural formula and a compound (ETM-1) of the following structural formula such that Compound (4-1):Compound (ETM-1) = 50:50 to form an electron transport layer 6 with a film thickness of 30 nm. On this electron transport layer 6, lithium fluoride is formed into an electron injection layer 7 with a film thickness of 1 nm. On this electron injection layer 7, a magnesium-silver alloy is formed into a cathode 8 with a film thickness of 12 nm. On the cathode 8, the compound (1-13) of Example 1 is formed into a first cover layer 9 with a film thickness of 30 nm, and finally, a high refractive index arylamine compound (2-8) is formed into a second cover layer 10 with a film thickness of 30 nm. For the fabricated organic EL element, the characteristics are measured in the atmosphere at room temperature.

[0151] The measurement results of the light-emitting characteristics obtained by applying a DC voltage to the fabricated organic EL element are summarized in Table 2.

[0152]

[0153] [Example 7]

[0154] In Example 6, as the first covering layer 9, Compound (1-18) of Example 2 was used instead of Compound (1-13) of Example 1. Otherwise, an organic EL element was fabricated under the same conditions. For the fabricated organic EL element, characteristic measurements were carried out in the atmosphere at room temperature.

[0155] The measurement results of the light-emitting characteristics obtained by applying a DC voltage to the fabricated organic EL element are summarized in Table 2.

[0156] [Example 8]

[0157] In Example 6, as the first covering layer 9, Compound (1-23) of Example 3 was used instead of Compound (1-13) of Example 1. Otherwise, an organic EL element was fabricated under the same conditions. For the fabricated organic EL element, characteristic measurements were carried out in the atmosphere at room temperature.

[0158] The measurement results of the light-emitting characteristics obtained by applying a DC voltage to the fabricated organic EL element are summarized in Table 2.

[0159] [Comparative Example 1]

[0160] For comparison, in Example 6, as the first covering layer 9, Alq3 was used instead of Compound (1-13) of Example 1. Otherwise, an organic EL element was fabricated under the same conditions. For the fabricated organic EL element, characteristic measurements were carried out in the atmosphere at room temperature.

[0161] The measurement results of the light-emitting characteristics obtained by applying a DC voltage to the fabricated organic EL element are summarized in Table 2.

[0162] [Comparative Example 2]

[0163] For comparison, in Example 6, as the second covering layer 10, a high refractive index arylamine compound (2-8) was formed to have a double film thickness of 60 nm, and an organic EL element without the first covering layer 9 was fabricated. For the fabricated organic EL element, characteristic measurements were carried out in the atmosphere at room temperature.

[0164] The measurement results of the light-emitting characteristics obtained by applying a DC voltage to the fabricated organic EL element are summarized in Table 2.

[0165] Using the organic EL elements fabricated in Examples 6 to 8 and Comparative Examples 1 and 2, the element lifetimes were measured, and the results are summarized in Table 2. Regarding the element lifetime, during constant current driving at 10 mA / cm 2 it was measured as the time (95% decay) until the initial luminance decayed to 95% when the initial luminance was set to 100%.

[0166] [Table 2]

[0167]

[0168] As shown in Table 2, regarding the driving voltage at a current density of 10 mA / cm 2 , the elements of Comparative Example 1 and Comparative Example 2 are substantially equivalent to the elements of Examples 6 to 8 using the adamantane compound represented by the general formula (1) of the present invention as the first cover layer. In contrast, regarding brightness, luminous efficiency, power efficiency, and element lifetime, the elements of Examples 6 to 8 are significantly improved compared to the elements of Comparative Example 1 and Comparative Example 2. This indicates that by forming a laminated structure in which a second cover layer is laminated on the first cover layer containing the adamantane compound represented by the general formula (1) of the present invention, and further, by combining with the material of the second cover layer so that the difference in refractive index between the first cover layer and the second cover layer becomes larger, the light extraction efficiency can be greatly improved.

[0169] Industrial Applicability

[0170] An organic EL element containing the adamantane compound represented by the general formula (1) of the present invention in the cover layer, particularly an organic EL element in which a material having a larger difference in refractive index is laminated as the second cover layer on the first cover layer containing the adamantane compound represented by the general formula (1) of the present invention can obtain high light extraction efficiency. In addition, by using this compound that does not have absorption in the respective wavelength regions of blue, green, and red, it is particularly suitable when a highly pure, clear, and bright image is desired. It can be applied, for example, to home appliances and lighting applications.

[0171] Explanation of Reference Numerals

[0172] 1 Glass substrate

[0173] 2 Metal anode

[0174] 3 Hole injection layer

[0175] 4 Hole transport layer

[0176] 5 Light-emitting layer

[0177] 6 Electron transport layer

[0178] 7 Electron injection layer

[0179] 8 Cathode

[0180] 9 First cover layer

[0181] 10 Second cover layer

Claims

1. An adamantane compound represented by the following general formula (1), general formula (1-A), general formula (1-B), general formula (1-C), chemical formula (1-13), chemical formula (1-18), or chemical formula (1-23): In formula (1), 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; R1 and R2 are optionally the same or different from each other and represent a substituted or unsubstituted aromatic hydrocarbon group selected from biphenyl, 1-naphthyl, 2-naphthyl, 2-phenanthryl, 9-phenanthryl, and fluorenyl, and the substituted or unsubstituted aromatic hydrocarbon group optionally has a substituent selected from a cyano group, a halogen atom, a linear or branched alkyl group having 1 to 3 carbon atoms, a linear or branched alkoxy group having 1 to 3 carbon atoms, a phenyl group, a biphenyl group, 1-naphthyl, 2-naphthyl, and fluorenyl. In formula (1-A), X is defined as in the above general formula (1); L represents a linear or branched alkylene group having 1 to 3 carbon atoms; R3 to R 12 are optionally the same or different from each other 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 alkoxy group having 1 to 3 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group. The substituted or unsubstituted linear or branched alkyl group having 1 to 3 carbon atoms optionally has a halogen atom as a substituent, and the substituted or unsubstituted linear or branched alkoxy group having 1 to 3 carbon atoms optionally has a halogen atom as a substituent; the aromatic hydrocarbon group is selected from a phenyl group, a biphenyl group, 1-naphthyl, 2-naphthyl, 2-phenanthryl, 9-phenanthryl, and fluorenyl, and the substituted or unsubstituted aromatic hydrocarbon group optionally has a substituent selected from a cyano group, a halogen atom, a linear or branched alkyl group having 1 to 3 carbon atoms, and a linear or branched alkoxy group having 1 to 3 carbon atoms. In formula (1-B), R3 to R 12 are optionally the same or different from each other and represent a hydrogen atom, a bromine atom, an ethyl group, a propyl group, a propoxy group, a phenyl group, a biphenyl group, 1-naphthyl, 2-naphthyl, or fluorenyl. In formula (1-C), R3 to R 12 are optionally the same or different from each other and represent a halogen atom, a cyano group, a linear or branched alkyl group having 1 to 3 carbon atoms, a linear or branched alkoxy group having 1 to 3 carbon atoms, a phenyl group, a biphenyl group, 1-naphthyl, 2-naphthyl, or fluorenyl.

2. The adamantane compound according to claim 1, wherein,The adamantane compound is represented by the following general formula (1-D). In formula (1-D), R3 to R 12 As defined in the general formula (1-A) above.

3. The adamantane compound according to claim 1, wherein, The adamantane compound is represented by the following general formula (1-E). In formula (1-E), R3 to R 12 As defined in the above general formula (1-A).

4. An organic thin film, characterized in that, It contains the adamantane compound according to any one of claims 1 to 3, and the refractive index of the organic thin film in the wavelength range of 400 nm to 700 nm is 1.60 or less.

5. An organic electroluminescent element, characterized in that, It at least sequentially has an anode electrode, a hole transport layer, a light-emitting layer, an electron transport layer, a cathode electrode, and a covering layer, and the covering layer is the organic thin film according to claim 4.

6. An organic electroluminescent element, characterized in that, It at least sequentially has an anode electrode, a hole transport layer, a light-emitting layer, an electron transport layer, a cathode electrode, and a covering layer, and the covering layer has a two-layer structure of a first covering layer and a second covering layer, and the first covering layer is the organic thin film according to claim 4.

7. The organic electroluminescent element according to claim 6, characterized in that, The difference in refractive index between the first covering layer and the second covering layer ([refractive index of the second covering layer] - [refractive index of the first covering layer]) is 0.2 or more.

8. An electronic device or electronic component, characterized in that, It has a pair of electrodes and at least one organic layer sandwiched therebetween, and the organic layer uses the adamantane compound according to any one of claims 1 to 3 as a constituent material.

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