Organic electric field light emitting element and method for manufacturing the same

Abstract

An organic EL element and a method for manufacturing an organic electric field luminescent element, wherein the organic EL element is an organic electric field luminescent element comprising a light-emitting layer between an anode and a cathode facing each other, wherein the light-emitting layer comprises a first host, a second host and a light-emitting dopant, and comprises an indolecarbazole compound represented by the following general formula (1) as the first host, and comprises a biscarbazole compound or a dibenzofuran compound having a dibenzofuran or dibenzothiophene ring as the second host. The organic EL element has a low driving voltage and high efficiency, and has high driving stability.

Description

Technical Field

[0001] The present invention relates to an organic electroluminescent device (hereinafter referred to as an organic EL device), and more particularly to an organic EL device using an organic electroluminescent device material containing an indolocarbazole compound and a method for producing the organic electroluminescent device. Background Art

[0002] By applying voltage to the organic EL element, holes are injected into the light-emitting layer from the anode, and electrons are injected into the light-emitting layer from the cathode. Moreover, in the light-emitting layer, the injected holes recombine with the electrons to generate excitons. At this time, according to the statistical law of electron spin, singlet excitons and triplet excitons are generated in a ratio of 1:3. It can be said that the limit of the internal quantum efficiency of the fluorescent organic EL element using the light emission of singlet excitons is 25%. On the other hand, it is known that the internal quantum efficiency of the phosphorescent organic EL element using the light emission of triplet excitons can be increased to 100% when the intersystem crossing (intersystem crossing) is efficiently performed from the singlet excitons.

[0003] However, regarding phosphorescent organic EL elements, extending their lifespan has become a technical challenge.

[0004] Recently, highly efficient organic EL elements utilizing delayed fluorescence are being developed. For example, Patent Document 1 discloses an organic EL element that utilizes a triplet-triplet fusion (TTF) mechanism, which is one of the mechanisms of delayed fluorescence. The TTF mechanism utilizes the phenomenon of generating singlet excitons by the collision of two triplet excitons, and it is believed that the internal quantum efficiency can be increased to 40% in theory. However, compared with phosphorescent organic EL elements, the efficiency is low, and therefore more efficient improvements are required.

[0005] Patent document 2 discloses an organic EL element using a thermally activated delayed fluorescence (TADF) mechanism. The TADF mechanism utilizes the following phenomenon: in a material with a small energy difference between the singlet energy level and the triplet energy level, an inverse intersystem crossing from a triplet exciton to a singlet exciton occurs; it is believed that the internal quantum efficiency can be increased to 100% in theory. However, as with phosphorescent light-emitting elements, further improvement in life characteristics is required.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: WO2010 / 134350A

[0009] Patent Document 2: WO2011 / 070963A

[0010] Patent Document 3: WO2008 / 056746A

[0011] Patent Document 4: Japanese Patent Application Publication No. 2003-133075

[0012] Patent Document 5: WO2013 / 062075A

[0013] Patent Document 6: US2014 / 0374728A

[0014] Patent Document 7: US2014 / 0197386A

[0015] Patent Document 8: US2015 / 0001488A

[0016] Patent Document 9: US2015 / 0236262A

[0017] Patent Document 10: WO2016 / 194604A

[0018] Patent Document 11: WO2011 / 136755A

[0019] Patent Document 3 discloses the use of an indolocarbazole compound as a host material. Patent Document 4 discloses the use of a biscarbazole compound as a host material.

[0020] Patent Documents 5 and 6 disclose the use of a biscarbazole compound as a mixed host. Patent Documents 7, 8, 9, and 10 disclose the use of an indolocarbazole compound and a biscarbazole compound as a mixed host.

[0021] Patent Document 11 discloses the use of a host material in which a plurality of hosts including an indolocarbazole compound are mixed in advance.

[0022] However, none of the above can be said to be sufficient, and further improvements are desired. Summary of the invention

[0023] In order to apply organic EL elements to display elements such as flat panel displays or light sources, it is necessary to improve the luminous efficiency of the elements while fully ensuring the stability during driving. The object of the present invention is to provide an organic EL element with low driving voltage, high efficiency and high driving stability.

[0024] The present inventors have conducted intensive studies and, as a result, have found that an organic EL device having excellent characteristics can be obtained by using a specific indolocarbazole compound as a first host, thereby completing the present invention.

[0025] The present invention is an organic EL element, which is an organic electric field light-emitting element comprising one or more light-emitting layers between opposing anodes and cathodes, wherein at least one light-emitting layer contains a first main body selected from compounds represented by the following general formula (1) and a second main body selected from compounds represented by the following general formula (2) or general formula (3).

[0026] [Chemistry 1]

[0027]

[0028] Here, ring A is a heterocyclic ring represented by formula (1a), and ring A is condensed with an adjacent ring at an arbitrary position.

[0029] R is independently hydrogen, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, an aromatic hydrocarbon group having 6 to 10 carbon atoms, or an aromatic heterocyclic group having 3 to 12 carbon atoms, and L 1 ~L 3 They are independently a direct bond, an aromatic hydrocarbon group having 6 to 10 carbon atoms, or an aromatic heterocyclic group having 3 to 12 carbon atoms.

[0030] B 1 ~B 3 independently represents a direct bond or a biphenyldiyl group represented by formula (1b), 1 ~B 3 Among them, at least one is the biphenyl diyl group.

[0031] a, b, c, d, and e each independently represent an integer of 0 to 3, and s, t, and u each independently represent an integer of 1 to 2.

[0032] [Chemistry 2]

[0033]

[0034] Here, R independently represents hydrogen, an alkyl group having 1 to 20 carbon atoms, an acyl group having 2 to 20 carbon atoms, an alkoxy group having 2 to 20 carbon atoms, an aromatic hydrocarbon group having 6 to 24 carbon atoms, or an aromatic heterocyclic group having 3 to 16 carbon atoms, but will not be a carbazole ring group.

[0035] B 4 Each of them independently represents hydrogen, an aromatic hydrocarbon group having 6 to 24 carbon atoms, or an aromatic heterocyclic group having 3 to 16 carbon atoms, and the aromatic hydrocarbon group or the aromatic heterocyclic group may have a substituent.

[0036] j represents an integer of 1 to 6, X independently represents N, C-R' or C-, R' independently represents hydrogen, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms or a diarylamino group having 12 to 44 carbon atoms. f, g, h and i independently represent an integer of 1 to 3.

[0037] [Chemistry 3]

[0038]

[0039] Here, ring C is a heterocyclic group represented by formula (3a), and L 4 , L 5 are independently a direct bond, an aromatic hydrocarbon group having 6 to 10 carbon atoms, or an aromatic heterocyclic group having 3 to 16 carbon atoms, 5 , B 6 represents a direct bond or an aromatic hydrocarbon group having 6 to 22 carbon atoms, R independently represents hydrogen, an aromatic hydrocarbon group having 6 to 10 carbon atoms or an aromatic heterocyclic group having 3 to 16 carbon atoms, an alkyl group having 1 to 10 carbon atoms or a cycloalkyl group having 3 to 11 carbon atoms, and Y independently represents O or S.

[0040] m and n are substitution numbers, and represent integers of 1 to 3. p and q are repetition numbers, and represent integers of 1 to 4, respectively and independently.

[0041] Preferred embodiments of the general formulae (1) to (3) are shown below.

[0042] In the general formula (1), B 3 It is a biphenyldiyl group represented by the formula (1b), or a, b and c are 0.

[0043] In the general formula (2), j is an integer of 1 to 3, or X is N or CH.

[0044] Formula (3a) is the following formula (4) or formula (5).

[0045] In the general formula (3), L 4 and B 5 For direct key, or B 6 is an aromatic hydrocarbon group represented by the following formula (6), or L 5 It is an aromatic heterocyclic group represented by the following formula (7).

[0046] [Chemistry 4]

[0047]

[0048] (Here, Y is O or S)

[0049] [Chemistry 5]

[0050]

[0051] [Chemistry 6]

[0052]

[0053] The general formula (1) is any one of the following formulas (8) to (11).

[0054] [Chemistry 7]

[0055]

[0056] (Here, B 1 ~B 3 , L 1 ~L 3 , R, a~f and s~u have the same meanings as in general formula (1)

[0057] The organic electroluminescent element is preferably configured such that the ratio of the first host to the total of the first host and the second host is more than 20 wt % and less than 55 wt %.

[0058] The organic electroluminescent element preferably includes a host and a light-emitting dopant material in a light-emitting layer.

[0059] The luminescent dopant material may be an organic metal complex containing at least one metal selected from the group consisting of ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum and gold, or a thermally activated delayed fluorescence luminescent dopant material.

[0060] The organic electroluminescent element may include a hole blocking layer provided adjacent to the light-emitting layer, and the hole blocking layer may contain the compound represented by the general formula (1).

[0061] Furthermore, the present invention is a method for manufacturing an organic electroluminescent element, which comprises the steps of mixing a first host and a second host to form a premix, and then vapor-depositing a host material containing the premix to form a light-emitting layer.

[0062] At this time, the difference between the 50% weight reduction temperatures of the first body and the second body may be within 20°C.

[0063] In order to improve the device characteristics, the materials used in the organic layer need to have high durability against charges. In particular, in the light-emitting layer, it is important to suppress the leakage of excitons and charges to the peripheral layer. For the leakage suppression of the charges / excitons, it is effective to improve the deviation of the light-emitting area in the light-emitting layer. For this purpose, it is necessary to control the injection amount of the two charges (electrons / holes) into the light-emitting layer or the two charge transfer amount in the light-emitting layer to a preferred range.

[0064] Here, the indolecarbazole compound bonded with a specific aromatic heterocycle used in the present invention has an ortho-linked biphenyl diyl represented by formula (1b). The two-charge injection transport energy of the material used in the organic layer is greatly affected by the energy level of the molecular orbital of the material and the size of the intermolecular interaction. The indolecarbazole compound bonded with a specific aromatic heterocycle has a particularly high electron injection transport energy, but the biphenyl diyl can inhibit the indolecarbazole molecules from approaching each other due to its steric hindrance effect. In addition, by changing the substituent species or bonding position of the biphenyl diyl, it is possible to control the intermolecular interaction of the molecular orbitals that have a large influence on the electron injection transport of the light-emitting layer at a high level.

[0065] On the other hand, the carbazole compounds and dibenzofuran / dibenzothiophene compounds represented by general formula (2) to general formula (3) have high hole injection transport energy in particular, and the hole injection transport property can be controlled at a high level by changing the bonding pattern of the carbazole ring or the type / number of substituents for the skeleton. Therefore, by mixing the indole carbazole compound and the dicarbazole compound for use, the injection amount of the two charges into the organic layer can be adjusted to a preferred range, so that better device characteristics can be expected. In particular, in the case of a delayed fluorescent EL element or a phosphorescent EL element, since it has a minimum excited triplet energy level that is high enough for the excitation energy generated in the enclosed light-emitting layer, there is no energy outflow from the light-emitting layer, the voltage is low, the efficiency is high, and a long life can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 It is a schematic cross-sectional view showing an example of an organic EL element.

[0067] [Explanation of Symbols]

[0068] 1: Substrate

[0069] 2: Anode

[0070] 3: Hole injection layer

[0071] 4: Hole transport layer

[0072] 5: Luminous layer

[0073] 6: Electron transport layer

[0074] 7: Cathode DETAILED DESCRIPTION

[0075] There is one or more light-emitting layers between the anode and cathode facing each other, and at least one light-emitting layer contains a first main body and a second main body. Preferably, the light-emitting layer includes a vapor-deposited layer containing the first main body, the second main body and a light-emitting doping material. The vapor-deposited layer can be made by vacuum evaporation. The organic EL element of the present invention has a plurality of organic layers between the anode and cathode facing each other, at least one of the plurality of layers is a light-emitting layer, and the light-emitting layer can also be a plurality of layers.

[0076] The first host is a compound represented by the general formula (1), and the second host is a compound represented by the general formula (2) or (3).

[0077] The general formula (1) will be described.

[0078] Ring A is a heterocyclic ring represented by formula (1a), and is condensed with an adjacent ring at an arbitrary position.

[0079] R independently represents hydrogen, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, an aromatic hydrocarbon group having 6 to 10 carbon atoms, or an aromatic heterocyclic group having 3 to 12 carbon atoms. Preferably, it is an aliphatic hydrocarbon group having 1 to 8 carbon atoms, a phenyl group, or an aromatic heterocyclic group having 3 to 9 carbon atoms. More preferably, it is an aliphatic hydrocarbon group having 1 to 6 carbon atoms, a phenyl group, or an aromatic heterocyclic group having 3 to 6 carbon atoms.

[0080] Specific examples of the aliphatic hydrocarbon group having 1 to 10 carbon atoms include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, and decyl. An alkyl group having 1 to 4 carbon atoms is preferred.

[0081] Specific examples of the aromatic hydrocarbon group having 6 to 10 carbon atoms or the aromatic heterocyclic group having 3 to 12 carbon atoms include aromatic groups generated by removing one H from benzene, naphthalene, pyridine, pyrimidine, triazine, thiophene, isothiazole, thiazole, pyridazine, pyrrole, pyrazole, imidazole, triazole, thiadiazole, pyrazine, furan, isoxazole, oxazole, oxadiazole, quinoline, isoquinoline, quinoxaline, quinazoline, oxadiazole, thiadiazole, benzotriazine, phthalazine, tetrazole, indole, benzofuran, benzothiophene, benzoxazole, benzothiazole, indazole, benzimidazole, benzotriazole, benzisothiazole, benzothiadiazole, dibenzofuran, dibenzothiophene, dibenzoselenophene, or carbazole. Preferred are aromatic groups derived from benzene, pyridine, pyrimidine, triazine, thiophene, isothiazole, thiazole, pyridazine, pyrrole, pyrazole, imidazole, triazole, thiadiazole, pyrazine, furan, isoxazole, oxazole, oxadiazole, quinoline, isoquinoline, quinoxaline, quinazoline, oxadiazole, thiadiazole, benzotriazine, phthalazine, tetrazole, indole, benzofuran, benzothiophene, benzoxazole, benzothiazole, indazole, benzimidazole, benzotriazole, benzisothiazole, or benzothiadiazole. More preferred are aromatic groups derived from benzene, pyridine, pyrimidine, triazine, thiophene, isothiazole, thiazole, pyridazine, pyrrole, pyrazole, imidazole, triazole, thiadiazole, pyrazine, furan, isoxazole, oxazole, or oxadiazole.

[0082] L 1 , L 2 , L 3 They are independently a direct bond, an aromatic hydrocarbon group having 6 to 10 carbon atoms, or an aromatic heterocyclic group having 3 to 12 carbon atoms. Preferred examples of the aromatic hydrocarbon group or aromatic heterocyclic group are the same as those when R is these groups, except that these groups are divalent groups.

[0083] B 1 , B 2 , B 3 independently represents a direct bond or a group represented by formula (1b), B 1 ~B 3 At least one of them is a group represented by formula (1b). Preferably, B 3 It is a group represented by formula (1b).

[0084] a, b, c, d, and e represent the number of substitutions, and each independently represents an integer of 0 to 3, and preferably an integer of 0 or 1. Preferably, a, b, and c are 0.

[0085] s, t, and u represent the number of repetitions and each independently represents an integer of 1 to 2. Preferably, s, t, and u are 1.

[0086] A preferred embodiment of the compound represented by the general formula (1) is a compound represented by any one of the general formulas (8) to (11). In the general formulas (8) to (11), the symbols common to the general formula (1) have the same meanings.

[0087] Specific examples of the compound represented by the general formula (1) are shown below, but the compound is not limited to these exemplified compounds.

[0088] [Chemistry 8]

[0089]

[0090] [Chemistry 9]

[0091]

[0092] [Chemistry 10]

[0093]

[0094] [Chemistry 11]

[0095]

[0096] [Chemistry 12]

[0097]

[0098] The general formula (2) serving as the second host will be described.

[0099] In the general formula (2), B 4 Each independently represents hydrogen, an aromatic hydrocarbon group having 6 to 24 carbon atoms, or an aromatic heterocyclic group having 3 to 16 carbon atoms. Preferably, it is hydrogen, an aromatic hydrocarbon group having 6 to 12 carbon atoms, or an aromatic heterocyclic group having 4 to 14 carbon atoms, and more preferably, it is an aromatic hydrocarbon group having 6 to 10 carbon atoms.

[0100] Specific examples of the aromatic hydrocarbon group having 6 to 24 carbon atoms or the aromatic heterocyclic group having 3 to 16 carbon atoms include aromatic groups generated by removing one H from benzene, naphthalene, pyridine, pyrimidine, triazine, thiophene, isothiazole, thiazole, pyridazine, pyrrole, pyrazole, imidazole, triazole, thiadiazole, pyrazine, furan, isoxazole, oxazole, oxadiazole, quinoline, isoquinoline, quinoxaline, quinazoline, oxadiazole, thiadiazole, benzotriazine, phthalazine, tetrazole, indole, benzofuran, benzothiophene, benzoxazole, benzothiazole, indazole, benzimidazole, benzotriazole, benzisothiazole, benzothiadiazole, dibenzofuran, dibenzothiophene, dibenzoselenophene, or carbazole. Preferred are aromatic groups derived from benzene, pyridine, pyrimidine, triazine, thiophene, isothiazole, thiazole, pyridazine, pyrrole, pyrazole, imidazole, triazole, thiadiazole, pyrazine, furan, isoxazole, oxazole, oxadiazole, quinoline, isoquinoline, quinoxaline, quinazoline, oxadiazole, thiadiazole, benzotriazine, phthalazine, tetrazole, indole, benzofuran, benzothiophene, benzoxazole, benzothiazole, indazole, benzimidazole, benzotriazole, benzisothiazole, or benzothiadiazole. More preferred are aromatic groups derived from benzene, pyridine, pyrimidine, triazine, thiophene, isothiazole, thiazole, pyridazine, pyrrole, pyrazole, imidazole, triazole, thiadiazole, pyrazine, furan, isoxazole, oxazole, or oxadiazole.

[0101] j represents the number of repetitions, and is an integer of 1-6, preferably an integer of 1-3.

[0102] In the present specification, when the number of repetitions is 2 or more, the repeating units may be the same or different.

[0103] R independently represents hydrogen, an alkyl group having 1 to 20 carbon atoms, an acyl group having 2 to 20 carbon atoms, an alkoxy group having 2 to 20 carbon atoms, an aromatic hydrocarbon group having 6 to 24 carbon atoms, or an aromatic heterocyclic group having 3 to 16 carbon atoms, but is not a carbazole ring group. Preferably, it represents hydrogen, an aromatic hydrocarbon group having 6 to 24 carbon atoms, or an aromatic heterocyclic group having 3 to 16 carbon atoms.

[0104] f, g, h, and i represent the number of substitutions, and each independently represents an integer of 1 to 3, and preferably an integer of 1 to 2.

[0105] X independently represents N, C-R' or C-, preferably N or CH. More preferably, all Cs are CH or CH and N. R' represents hydrogen, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms or a diarylamino group having 12 to 44 carbon atoms.

[0106] Preferred specific examples of the compound represented by the general formula (2) are shown below, but the compound is not limited to these.

[0107] [Chemistry 13]

[0108]

[0109] [Chemistry 14]

[0110]

[0111] [Chemistry 15]

[0112]

[0113] Next, the general formula (3) will be described.

[0114] In the general formula (3), ring C is a heterocyclic group represented by the formula (3a), preferably a heterocyclic group represented by the formula (4) or (5).

[0115] Y represents O or S.

[0116] L 4 , L 5 They are independently a direct bond, an aromatic hydrocarbon group having 6 to 10 carbon atoms, or an aromatic heterocyclic group having 3 to 16 carbon atoms. Preferably, they are an aromatic hydrocarbon group having 6 to 10 carbon atoms or an aromatic heterocyclic group represented by formula (7).

[0117] B 5 , B 6 represents a direct bond or an aromatic hydrocarbon group having 6 to 22 carbon atoms. An aromatic hydrocarbon group represented by formula (6) is preferred.

[0118] R is each independently hydrogen, an aromatic hydrocarbon group having 6 to 10 carbon atoms, an aromatic heterocyclic group having 3 to 16 carbon atoms, an alkyl group having 1 to 10 carbon atoms, or a cycloalkyl group having 3 to 11 carbon atoms.

[0119] In the present specification, unless otherwise specified, an aromatic hydrocarbon group, an aromatic heterocyclic group, etc. may have a substituent. m and n are the number of substitutions, and represent an integer of 1 to 3, and preferably an integer of 1 to 2.

[0120] p and q are repeating numbers, and are each independently an integer of 1 to 4, preferably an integer of 1 to 2.

[0121] Specific examples of the compound represented by the general formula (3) are shown below, but the compound is not limited to these.

[0122] [Chemistry 16]

[0123]

[0124] [Chemistry 17]

[0125]

[0126] [Chemistry 18]

[0127]

[0128] [Chemistry 19]

[0129]

[0130] By using a first host selected from the compounds represented by the general formula (1) and a second host selected from the compounds represented by the general formula (2) and the general formula (3) as host materials for the light-emitting layer, an excellent organic EL device can be provided.

[0131] The first host and the second host may be used by being evaporated from different evaporation sources, but preferably they are premixed before evaporation to form a premix, and the premix is ​​simultaneously evaporated from one evaporation source to form a light-emitting layer. In this case, the light-emitting doping material required for forming the light-emitting layer or other hosts used as needed may be mixed in the premix, but if there is a large difference in the temperature at which the desired vapor pressure is achieved, evaporation may be performed from another evaporation source.

[0132] Furthermore, regarding the mixing ratio (weight ratio) of the first body to the second body, the proportion of the first body relative to the total of the first body and the second body can be 20% to 60%, preferably more than 20% and less than 55%, and more preferably 40% to 50%.

[0133] Next, the structure of the organic EL element of the present invention will be described with reference to the drawings, but the structure of the organic EL element of the present invention is not limited thereto.

[0134] Figure 1 It is a cross-sectional view showing a structural example of a general organic EL element used in the present invention, wherein 1 represents a substrate, 2 represents an anode, 3 represents a hole injection layer, 4 represents a hole transport layer, 5 represents a light-emitting layer, 6 represents an electron transport layer, and 7 represents a cathode. The organic EL element of the present invention may also have an exciton blocking layer adjacent to the light-emitting layer, and may also have an electron blocking layer between the light-emitting layer and the hole injection layer. The exciton blocking layer may also be inserted into either the anode side or the cathode side of the light-emitting layer, or may be inserted into both sides at the same time. In the organic EL element of the present invention, an anode, a light-emitting layer, and a cathode are provided as necessary layers, but in addition to the necessary layers, a hole injection transport layer and an electron injection transport layer may also be provided, and a hole blocking layer may further be provided between the light-emitting layer and the electron injection transport layer. In addition, the hole injection transport layer represents either or both of the hole injection layer and the hole transport layer, and the electron injection transport layer represents either or both of the electron injection layer and the electron transport layer.

[0135] Can also be Figure 1 The opposite structure is that the cathode 7, the electron transport layer 6, the light-emitting layer 5, the hole transport layer 4, and the anode 2 are sequentially stacked on the substrate 1. At this time, the layers can be added or omitted as needed.

[0136] -Substrate-

[0137] The organic EL element of the present invention is preferably supported on a substrate. The substrate is not particularly limited as long as it is a substrate conventionally used in organic EL elements, and for example, a substrate made of glass, transparent plastic, quartz, etc. can be used.

[0138] -anode-

[0139] As the anode material in the organic EL element, a material containing a metal, alloy, conductive compound or a mixture of these with a large work function (above 4 eV) can be preferably used. As specific examples of such electrode materials, metals such as Au, conductive transparent materials such as CuI, indium tin oxide (ITO), SnO2, and ZnO can be listed. In addition, amorphous materials such as IDIXO (In2O3-ZnO) that can be made into transparent conductive films can also be used. The anode can be formed into a thin film by methods such as evaporation or sputtering, and a pattern of the desired shape can be formed by photolithography, or when the pattern accuracy is not very required (about 100 μm or more), the pattern can be formed through a mask of the desired shape during the evaporation or sputtering of the electrode material. Or when using a coatable substance such as an organic conductive compound, a wet film forming method such as printing or coating can also be used. In the case of extracting light from the anode, it is ideal to make the transmittance greater than 10%, and the sheet resistance of the anode is preferably less than hundreds of Ω / Y. The film thickness also depends on the material, and is usually selected within the range of 10 nm to 1000 nm, preferably 10 nm to 200 nm.

[0140] -cathode-

[0141] On the other hand, as a cathode material, a material containing a metal ("electron injecting metal") with a small work function (less than 4 eV), an alloy, a conductive compound or a mixture thereof can be used. Specific examples of such electrode materials include sodium, sodium-potassium alloys, magnesium, lithium, magnesium / copper mixtures, magnesium / silver mixtures, magnesium / aluminum mixtures, magnesium / indium mixtures, aluminum / aluminum oxide mixtures, indium, lithium / aluminum mixtures, rare earth metals, etc. From the perspective of electron injectability and durability to oxidation, etc., a mixture of an electron injecting metal and a second metal having a work function value greater than that of the metal and being stable is suitable, such as a magnesium / silver mixture, a magnesium / aluminum mixture, a magnesium / indium mixture, an aluminum / aluminum oxide (Al2O3) mixture, a lithium / aluminum mixture, aluminum, etc. The cathode can be made as follows: these cathode materials are formed into a thin film by methods such as evaporation or sputtering. Moreover, as a cathode, the sheet resistance is preferably less than several hundred Ω / Υ, and the film thickness is usually selected in the range of 10nm to 5μm, preferably 50nm to 200nm. Furthermore, in order to allow the emitted light to pass through, if either the anode or cathode of the organic EL element is transparent or semi-transparent, then the emission brightness is improved, which is advantageous.

[0142] Moreover, after the metal is formed in the cathode with a film thickness of 1nm to 20nm, the conductive transparent material listed in the description of the anode is formed thereon, thereby making a transparent or translucent cathode. By applying this method, an element in which both the anode and the cathode are transparent can be made.

[0143] -Luminous layer-

[0144] The light-emitting layer is a layer that emits light after holes and electrons injected from the anode and the cathode are recombined to generate excitons, and contains an organic light-emitting dopant material and a host material.

[0145] As the host material in the light-emitting layer, a first host represented by the general formula (1) and a second host represented by the general formula (2) or the general formula (3) are used. Furthermore, one known host material can be used or a plurality of them can be used in combination, and the amount used can be 50 wt% or less, preferably 25 wt% or less relative to the total of the host materials. Moreover, the first host represented by the general formula (1) and the second host represented by the general formula (2) or the general formula (3) can be used in one type each, or in two or more types.

[0146] The first main body and the second main body may be deposited from different deposition sources, or may be pre-mixed before deposition to form a pre-mixed mixture, thereby simultaneously depositing the first main body and the second main body from one deposition source.

[0147] When the first host and the second host are premixed and used, in order to produce an organic EL element having good characteristics with good reproducibility, it is desirable that the 50% weight loss temperature (T 50 ) is small. The 50% weight loss temperature refers to the temperature at which the weight is reduced by 50% when the temperature is increased from room temperature to 550°C at a rate of 10°C per minute in a thermogravimetric / differential thermal analysis (TG-DTA) measurement under a nitrogen flow reduced pressure (50 Pa). It is believed that gasification due to evaporation or sublimation occurs most strongly near this temperature.

[0148] The difference between the 50% weight loss temperature of the first body and the second body is preferably within 20° C., more preferably within 15° C. As the premixing method, a known method such as pulverization mixing can be used, and it is ideal to mix as uniformly as possible.

[0149] When a phosphorescent dopant is used as a luminescent dopant material, the phosphorescent dopant may be a phosphorescent dopant containing an organic metal complex, wherein the organic metal complex comprises at least one metal selected from ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum and gold. Specifically, the iridium complex described in Journal of the American Chemical Society, J. Am. Chem. Soc. 2001, 123, 4304 or Japanese Patent Table 2013-53051 may be suitably used, but is not limited to these.

[0150] The phosphorescent dopant material may be contained in the light emitting layer in one kind or in two or more kinds. The content of the phosphorescent dopant material is preferably 0.1 wt% to 30 wt%, more preferably 1 wt% to 20 wt%, relative to the host material.

[0151] The phosphorescent dopant material is not particularly limited, and specific examples thereof include the following.

[0152] [Chemistry 20]

[0153]

[0154] [Chemistry 21]

[0155]

[0156] When a fluorescent dopant is used as the luminescent dopant material, the fluorescent dopant is not particularly limited, and examples thereof include benzoxazole derivatives, benzothiazole derivatives, benzimidazole derivatives, styrylbenzene derivatives, polyphenyl derivatives, diphenylbutadiene derivatives, tetraphenylbutadiene derivatives, naphthalimide derivatives, coumarin derivatives, condensed aromatic compounds, perinone derivatives, oxadiazole derivatives, oxazine derivatives, aldazine derivatives, pyrrolidine derivatives, cyclopentadiene derivatives, distyrylanthracene derivatives, quinacridone derivatives, pyrrolopyridine derivatives, thiadiazolopyridine derivatives, styrylamine derivatives, diketopyrrolopyrrole derivatives, aromatic dimethyl compounds, metal complexes of 8-hydroxyquinoline derivatives or metal complexes of pyrromethene derivatives, rare earth complexes, various metal complexes represented by transition metal complexes, polymer compounds such as polythiophene, polyphenylene, polyphenylene vinylene, and organic silane derivatives. Preferred are condensed aromatic derivatives, styryl derivatives, diketopyrrolopyrrole derivatives, oxazine derivatives, pyrromethene metal complexes, transition metal complexes, or lanthanide complexes, and more preferred are naphthalene, pyrene, Triphenylene, benzo[c]phenanthrene, benzo[a]anthracene, fused pentacene, perylene, fluoranthene, acenaphthenefluoranthene, dibenzo[a,j]anthracene, dibenzo[a,h]anthracene, benzo[a]naphthalene, fused hexaphenylene, naphtho[2,1-f]isoquinoline, α-naphthophenanthridine, phenanthroxazole, quinolino[6,5-f]quinoline, benzonaphthothiophene, etc. These may have an alkyl group, an aryl group, an aromatic heterocyclic group, or a diarylamino group as a substituent.

[0157] The light-emitting layer may contain only one type of fluorescent dopant material or two or more types of fluorescent dopant material. The content of the fluorescent dopant material is preferably 0.1% to 20%, more preferably 1% to 10%, relative to the host material.

[0158] When a thermally activated delayed fluorescence dopant is used as a luminescent dopant material, the thermally activated delayed fluorescence dopant is not particularly limited, and examples thereof include metal complexes such as tin complexes or copper complexes, or indolecarbazole derivatives described in WO2011 / 070963, cyanobenzene derivatives and carbazole derivatives described in Nature 2012, 492, 234, phenazine derivatives, oxadiazole derivatives, triazole derivatives, sulfone derivatives, phenoxazine derivatives, and acridine derivatives described in Nature Photonics 2014, 8, 326.

[0159] The thermally activated delayed fluorescence dopant material is not particularly limited, and specific examples thereof include the following.

[0160] [Chemistry 22]

[0161]

[0162] The thermally activated delayed fluorescent luminescent dopant material may contain only one kind or more than two kinds in the luminescent layer. Moreover, the thermally activated delayed fluorescent luminescent dopant may be mixed with a phosphorescent luminescent dopant or a fluorescent luminescent dopant for use. The content of the thermally activated delayed fluorescent luminescent dopant material is preferably 0.1% to 50% relative to the host material, and more preferably 1% to 30%.

[0163] -Injection layer-

[0164] The so-called injection layer is a layer provided between the electrode and the organic layer in order to reduce the driving voltage or to increase the luminous brightness. There are hole injection layers and electron injection layers, and they may also exist between the anode and the light-emitting layer or the hole transport layer, and between the cathode and the light-emitting layer or the electron transport layer. The injection layer can be provided as needed.

[0165] -Hole blocking layer-

[0166] The so-called hole blocking layer, in a broad sense, has the function of an electron transport layer and includes a hole blocking material that has the function of transporting electrons but has a significantly lower ability to transport holes. It can increase the probability of recombination between electrons and holes in the light-emitting layer by transporting electrons and blocking holes.

[0167] A known hole-blocking layer material can be used for the hole-blocking layer, but it is preferable to contain a compound represented by the general formula (1).

[0168] -Electron blocking layer-

[0169] The electron blocking layer, in a broad sense, has the function of a hole transporting layer, and can increase the probability of recombination between electrons and holes in the light-emitting layer by transporting holes and blocking electrons.

[0170] As the material of the electron blocking layer, a known electron blocking layer material can be used, and the material of the hole transport layer described later can be used as necessary. The film thickness of the electron blocking layer is preferably 3 nm to 100 nm, more preferably 5 nm to 30 nm.

[0171] - Exciton blocking layer -

[0172] The so-called exciton blocking layer is a layer used to block the excitons generated by the recombination of holes and electrons in the light-emitting layer from diffusing to the charge transport layer. By inserting this layer, the excitons can be efficiently enclosed in the light-emitting layer, which can improve the luminous efficiency of the element. The exciton blocking layer can be inserted between two adjacent light-emitting layers in an element with two or more adjacent light-emitting layers.

[0173] As the material of the exciton-blocking layer, a known exciton-blocking layer material can be used, for example, 1,3-dicarbazolylbenzene (mCP) or bis(2-methyl-8-hydroxyquinolinolato)-4-phenylphenol aluminum (III) (BAlq) can be mentioned.

[0174] -Hole transport layer-

[0175] The hole transport layer includes a hole transport material having the function of transporting holes, and the hole transport layer may be provided as a single layer or multiple layers.

[0176] The hole transport material is a material having any of the injection or transport of holes and the barrier property of electrons, and can be any of organic and inorganic substances. In the hole transport layer, any one can be selected from existing known compounds and used. The hole transport material can be, for example, porphyrin derivatives, arylamine derivatives, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives and pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline copolymers, and conductive polymer oligomers, especially thiophene oligomers, etc., preferably using porphyrin derivatives, arylamine derivatives and styrylamine derivatives, more preferably using arylamine compounds.

[0177] -Electron transport layer-

[0178] The electron transport layer includes a material having a function of transporting electrons, and the electron transport layer may be provided as a single layer or multiple layers.

[0179] Electron transport materials (also serving as hole blocking materials) can be used as long as they have the function of transmitting electrons injected from the cathode to the light-emitting layer. The electron transport layer can be selected from any of the existing known compounds, for example, polycyclic aromatic derivatives such as naphthalene, anthracene, and phenanthroline, tris (8-hydroxyquinoline) aluminum (III) derivatives, phosphine oxide derivatives, nitro-substituted fluorene derivatives, diphenylquinone derivatives, dioxythiopyran derivatives, carbodiimides, fluorenyl methane derivatives, anthraquinone dimethane and anthrone derivatives, bipyridine derivatives, quinoline derivatives, oxadiazole derivatives, benzimidazole derivatives, benzothiazole derivatives, indole and carbazole derivatives, etc. In addition, polymer materials that introduce these materials into polymer chains or use these materials as the main chain of polymers can also be used.

[0180] Example

[0181] Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples and can be implemented in various forms without departing from the gist of the present invention.

[0182] Example 1

[0183] On a glass substrate on which an anode made of ITO with a film thickness of 110 nm was formed, a vacuum deposition method was performed at a vacuum degree of 4.0×10 -5 Pa and stack each thin film. First, HAT-CN is formed to a thickness of 25nm on ITO as a hole injection layer, and then NPD is formed to a thickness of 30nm as a hole transport layer. Next, HT-1 is formed to a thickness of 10nm as an electron blocking layer. Next, compound 1-4 as the first main body, compound 2-4 as the second main body, and Ir(ppy)3 as a light-emitting dopant are co-deposited from different evaporation sources to form a light-emitting layer with a thickness of 40nm. At this time, co-evaporation is performed under evaporation conditions in which the concentration of Ir(ppy)3 is 10wt% and the weight ratio of the first main body to the second main body is 30:70. Next, ET-1 is formed to a thickness of 20nm as an electron transport layer. Further, LiF is formed to a thickness of 1nm on the electron transport layer as an electron injection layer. Finally, Al is formed to a thickness of 70nm on the electron injection layer as a cathode to produce an organic EL element.

[0184] Embodiment 2 to Embodiment 46

[0185] In Example 1, an organic EL device was produced in the same manner as in Example 1, except that the compounds shown in Table 1 and Table 2 were used as the first host and the second host.

[0186] Example 47 to Example 51

[0187] The first main body and the second main body are mixed in advance to form a premix, and then co-evaporated from one evaporation source.

[0188] In Example 1, an organic EL device was produced in the same manner as in Example 1 except that a premix obtained by weighing the first main body (0.30 g) and the second main body (0.70 g) and mixing them in a mortar was used.

[0189] Tables 1 and 2 show the evaluation results of the produced organic EL devices.

[0190] In the table, the brightness, driving voltage and luminous efficiency are based on the driving current of 20mA / cm 2 The value at , is the initial characteristic. LT70 is the time it takes for the initial brightness to decay to 70%, indicating the lifespan characteristic.

[0191] [Table 1]

[0192]

[0193] [Table 2]

[0194]

[0195] Comparative Example 1

[0196] An organic EL device was prepared in the same manner as in Example 1 except that Compound 1-1 was used alone as a host. The thickness of the light-emitting layer and the concentration of the light-emitting dopant were the same as those in Example 1.

[0197] Comparative Example 2 to Comparative Example 15

[0198] An organic EL device was prepared in the same manner as in Comparative Example 1 except that the compound shown in Table 3 was used alone as a host.

[0199] Comparative Examples 16 to 19

[0200] In Example 1, an organic EL device was prepared in the same manner as in Example 1 except that Compound A was used as the first host and Compound 2-5, Compound 2-48, Compound 3-8, or Compound 3-49 was used as the second host.

[0201] Comparative Examples 20 to 23

[0202] In Comparative Examples 16 to 19, organic EL devices were produced in the same manner as in Comparative Examples 16 to 19 except that Compound B was used as the first host.

[0203] Comparative Examples 24 to 27

[0204] In Comparative Examples 16 to 19, organic EL devices were produced in the same manner as in Comparative Examples 16 to 19 except that Compound C was used as the first host.

[0205] Table 3 shows the evaluation results of the produced organic EL devices.

[0206] [Table 3]

[0207]

[0208] According to Table 1 and Table 2, in Examples 1 to 51, the power efficiency and life characteristics are improved, showing good characteristics.

[0209] Embodiment 52

[0210] On a glass substrate on which an anode made of ITO with a film thickness of 110 nm was formed, a vacuum deposition method was performed at a vacuum degree of 4.0×10 -5Pa and stack each thin film. First, HAT-CN is formed to a thickness of 25nm on ITO as a hole injection layer, and then NPD is formed to a thickness of 45nm as a hole transport layer. Secondly, HT-1 is formed to a thickness of 10nm as an electron blocking layer. Secondly, compound 1-4 as the first main body, compound 2-4 as the second main body, and Ir(piq)2acac as a light-emitting dopant are co-deposited from different evaporation sources to form a light-emitting layer with a thickness of 40nm. At this time, co-evaporation is performed under evaporation conditions in which the concentration of Ir(piq)2acac becomes 6.0wt%. Secondly, ET-1 is formed to a thickness of 37.5nm as an electron transport layer. Subsequently, LiF is formed to a thickness of 1nm on the electron transport layer as an electron injection layer. Finally, Al is formed to a thickness of 70nm on the electron injection layer as a cathode to produce an organic EL element.

[0211] Embodiment 53 to Embodiment 73

[0212] In Example 52, an organic EL device was produced in the same manner as in Example 52, except that the compounds shown in Table 4 were used as the first host and the second host.

[0213] The evaluation results of the produced organic EL elements are shown in Table 4. Here, LT95 is the time taken for the initial luminance to decay to 95%, and indicates the life characteristics.

[0214] [Table 4]

[0215]

[0216] Comparative Example 28

[0217] In Example 52, an organic EL device was produced in the same manner as in Example 52 except that Compound 1-1 was used alone as a host. The thickness of the light-emitting layer and the concentration of the light-emitting dopant were the same as those in Example 52.

[0218] Comparative Examples 29 to 41

[0219] An organic EL device was prepared in the same manner as in Comparative Example 28 except that the compound shown in Table 5 was used alone as a host.

[0220] Comparative Example 42 to Comparative Example 45

[0221] In Example 52, an organic EL device was prepared in the same manner as in Example 52 except that Compound A was used as the first host and Compound 2-5, Compound 2-48, Compound 3-8, and Compound 3-49 were used as the second host.

[0222] Comparative Examples 46 to 49

[0223] In Comparative Examples 42 to 45, organic EL devices were produced in the same manner as in Comparative Examples 42 to 45 except that Compound B was used as the first host.

[0224] Comparative Examples 50 to 53

[0225] In Comparative Examples 42 to 45, organic EL devices were produced in the same manner as in Comparative Examples 42 to 45 except that Compound C was used as the first host.

[0226] Table 5 shows the evaluation results of the produced organic EL elements.

[0227] [Table 5]

[0228]

[0229] According to Table 4, in Examples 52 to 73, the power efficiency and life characteristics are improved, showing good characteristics.

[0230] The compounds used in the Examples are shown below.

[0231] [Chemistry 23]

[0232]

[0233] Industrial Applicability

[0234] The organic EL element of the present invention has a low driving voltage and high efficiency at the same time, and has high driving stability.

Claims

1. An organic electroluminescent element, comprising one or more luminescent layers between an anode and a cathode facing each other, characterized in that: At least one light-emitting layer contains a first host selected from the compounds represented by the following general formula (1) and a second host selected from the compounds represented by the following general formula (2) or (3); Here, ring A is a heterocyclic ring represented by formula (1a), and ring A is condensed with an adjacent ring at any position. R is independently hydrogen, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, an aromatic hydrocarbon group having 6 to 10 carbon atoms, or an aromatic heterocyclic group having 3 to 12 carbon atoms, L 1 ~L 3 are independently a direct bond, an aromatic hydrocarbon group having 6 to 10 carbon atoms, or an aromatic heterocyclic group having 3 to 12 carbon atoms, B 1 ~B 2 independently represents a direct bond or a biphenyldiyl group represented by formula (1b), 3 is the biphenyl diyl group; a and b are 0, c, d, and e each independently represent an integer of 0 to 3, and s, t, and u each independently represent an integer of 1 to 2; Here, R independently represents hydrogen, an alkyl group having 1 to 20 carbon atoms, an acyl group having 2 to 20 carbon atoms, an alkoxy group having 2 to 20 carbon atoms, an aromatic hydrocarbon group having 6 to 24 carbon atoms, or an aromatic heterocyclic group having 3 to 16 carbon atoms, but will not be a carbazole ring group; B 4 independently represents hydrogen, an aromatic hydrocarbon group having 6 to 24 carbon atoms, or an aromatic heterocyclic group having 3 to 16 carbon atoms, the aromatic hydrocarbon group or the aromatic heterocyclic group may have a substituent; j represents an integer of 1 to 6, X independently represents N, C-R' or C-, R' independently represents hydrogen, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, or a diarylamino group having 12 to 44 carbon atoms; f, g, h, i independently represent an integer of 1 to 3; Here, ring C is a heterocyclic group represented by formula (3a), and L 4 , L 5 are independently a direct bond, an aromatic hydrocarbon group having 6 to 10 carbon atoms, or an aromatic heterocyclic group having 3 to 16 carbon atoms, 5 , B 6 represents a direct bond, an aromatic hydrocarbon group having 6 to 22 carbon atoms, R independently represents hydrogen, an aromatic hydrocarbon group having 6 to 10 carbon atoms, an aromatic heterocyclic group having 3 to 16 carbon atoms, an alkyl group having 1 to 10 carbon atoms, or a cycloalkyl group having 3 to 11 carbon atoms, and Y independently represents O or S; m and n are substitution numbers, which represent integers of 1 to 3; p and q are repetition numbers, which represent integers of 1 to 4 respectively and independently. 2 . The organic electroluminescent element according to claim 1 , wherein in the general formula (2), j is an integer of 1 to 3. 3 . The organic electroluminescent element according to claim 1 , wherein in the general formula (2), X is N or CH.

4. The organic electroluminescent element according to claim 1 or 2, characterized in that: Formula (3a) is the following formula (4) or formula (5); Here, Y is O or S.

5. The organic electroluminescent element according to claim 1 or 2, wherein in the general formula (3), L 4 and B 5 For direct keys.

6. The organic electroluminescent element according to claim 1 or 2, characterized in that: In the general formula (3), B 6 is an aromatic hydrocarbon group represented by the following formula (6); 7. The organic electroluminescent element according to claim 1 or 2, characterized in that: In the general formula (3), L 5 is an aromatic heterocyclic group represented by the following formula (7); 8. The organic electroluminescent element according to claim 1 or 2, characterized in that: The compound represented by the general formula (1) is a compound represented by any one of the following formulas (8) to (11); Here, B 1 ~B 3 , L 1 ~L 3 , R, a to b and s to u have the same meanings as in the general formula (1), c is 0, and d, e, and f each independently represent an integer of 0 to 3.

9. The organic electroluminescent element according to claim 1 or 2, characterized in that: The ratio of the first body to the total of the first body and the second body is more than 20 wt % and less than 55 wt %.

10. The organic electroluminescent element according to claim 1 or 2, characterized in that: The light-emitting layer contains a light-emitting dopant material, which is an organic metal complex containing at least one metal selected from the group consisting of ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum and gold.

11. The organic electroluminescent element according to claim 1 or 2, characterized in that: The light-emitting layer contains a light-emitting dopant material, and the light-emitting dopant material is a thermally activated delayed fluorescence light-emitting dopant material.

12. The organic electroluminescent element according to claim 1 or 2, characterized in that: A hole blocking layer is provided adjacent to the light-emitting layer, and the hole blocking layer contains a compound represented by the general formula (1).

13. A method for manufacturing an organic electroluminescent element, characterized in that: The method comprises the steps of mixing a first host and a second host to prepare a premix, and then evaporating a host material containing the premix to form a light-emitting layer when manufacturing the organic electroluminescent element according to any one of claims 1 to 12.

14. The method for manufacturing an organic electroluminescent element according to claim 13, characterized in that: The difference in 50% weight reduction temperature between the first body and the second body is within 20°C.

Images