Organic electroluminescent element

Abstract

The present invention provides an organic electroluminescent element which sequentially comprises at least a positive electrode, a first hole transport layer, a second hole transport layer, a blue light emitting layer, an electron transport layer and a negative electrode in this order, wherein the second hole transport layer contains an arylamine compound that is represented by general formula (1).

Description

[Technical Field]

[0001] The present invention relates to an organic electroluminescent element, which is a self-light-emitting element suitable for various display devices, and more specifically to an organic electroluminescent element (hereinafter abbreviated as organic EL element) using a specific arylamine compound. [Background technology]

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

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

[0004] To date, many improvements have been made to commercialize organic EL elements, and the various roles of the stacked structure have been further subdivided. High efficiency and high durability have now been achieved with field-emitting elements that sequentially arrange an anode, hole injection layer, hole transport layer, light-emitting layer, electron transport layer, electron injection layer, and cathode on a substrate (see, for example, Non-Patent Document 1).

[0005] Furthermore, attempts have been made to utilize triplet excitons to further improve luminescence efficiency, and the use of phosphorescent compounds is being considered (see, for example, Non-Patent Document 2). Furthermore, devices utilizing luminescence by thermally activated delayed fluorescence (TADF) have also been developed. In 2011, Adachi et al. at Kyushu University achieved an external quantum efficiency of 5.3% using a device with thermally activated delayed fluorescence material (see, for example, Non-Patent Document 3).

[0006] The light-emitting layer can also be fabricated by doping a charge-transporting compound, generally referred to as a host material, with a fluorescent compound, a phosphorescent compound, or a material that emits delayed fluorescence. As described in the aforementioned non-patent literature, the selection of organic materials in an organic EL device greatly affects various properties such as the efficiency and durability of the device (see, for example, non-patent literature 1 to 3).

[0007] In organic light-emitting diodes (OLEDs), light emission is obtained when charges injected from both electrodes recombine in the light-emitting layer. However, efficiently transferring both holes and electrons to the light-emitting layer is crucial, requiring a device with excellent carrier balance. Furthermore, increasing hole injection capacity and electron blocking (blocking electrons injected from the cathode) improves the probability of hole-electron recombination. Additionally, confining excitons generated within the light-emitting layer allows for high luminescence efficiency. Therefore, hole transport materials play a vital role, and there is a demand for hole transport materials with high hole injection capacity, high hole mobility, high electron blocking, and high electron resistance.

[0008] Furthermore, the heat resistance and amorphous properties of the material are also important for the lifespan of the device. Materials with low heat resistance will decompose even at low temperatures due to the heat generated during device operation, leading to material degradation. Materials with low amorphous properties will crystallize even in a short time, causing the device to degrade. Therefore, the materials used must have high heat resistance and good amorphous properties.

[0009] Until now, N,N'-diphenyl-N,N'-di(α-naphthyl)benzidine (NPD) and various aromatic amine derivatives have been known as hole transport materials used in organic EL devices (see, for example, Patent Documents 1 and 2). Although NPD has good hole transport capability, its glass transition temperature (Tg), which is an indicator of heat resistance, is low at 96°C, and under high-temperature conditions, crystallization occurs, leading to a decrease in device properties (see, for example, Non-Patent Document 4). In addition, among the aromatic amine derivatives described in the aforementioned patent documents, the hole mobility is 10 -3 cm2 Although compounds with excellent mobility of 1 / Vs or higher are known (see, for example, Patent Documents 1 and 2), their electron blocking properties are insufficient, allowing some electrons to pass through the light-emitting layer, thus preventing improvements in luminous efficiency. Therefore, there has been a need for materials with higher electron blocking properties, more stable thin films, and greater heat resistance for further efficiency improvements. In addition, there have been reports of highly durable aromatic amine derivatives (see, for example, Patent Document 3), but these have been used as charge transport materials in electrophotographic photoreceptors, and there have been no examples of their use in organic EL elements.

[0010] While arylamine compounds having a substituted carbazole structure have been proposed as compounds with improved properties such as heat resistance and hole injection capabilities (see, for example, Patent Documents 4 and 5), devices using these compounds in the hole injection layer or hole transport layer, although improvements in heat resistance and luminous efficiency have been made, are still not sufficient, and further reductions in driving voltage and further increases in luminous efficiency are required.

[0011] To improve the characteristics of organic EL elements and increase the yield of element fabrication, there is a need for elements that combine materials with excellent hole and electron injection and transport performance, as well as thin film stability and durability, to enable highly efficient recombination of holes and electrons, resulting in elements with high luminous efficiency, low driving voltage, and long lifespan.

[0012] Furthermore, in order to improve the device characteristics of organic EL elements, there is a need for high-efficiency, low-drive-voltage, and long-life elements with a balanced carrier architecture by combining materials that have excellent hole and electron injection and transport performance, as well as thin film stability and durability. [Prior art documents] [Patent Documents]

[0013] [Patent Document 1] Japanese Patent Publication No. 8-048656 [Patent Document 2] Japanese Patent No. 3194657 [Patent Document 3] Japanese Patent No. 4943840 [Patent Document 4] Japanese Unexamined Patent Application Publication No. 2006 - 151979 [Patent Document 5] International Publication No. 2008 / 62636 [Patent Document 6] International Publication No. 2014 / 009310 [Non - Patent Document]

[0014] [Non - Patent Document 1] Proceedings of the 9th Symposium of the Japan Society of Applied Physics, pp. 55 - 61 (2001) [Non - Patent Document 2] Proceedings of the 9th Symposium of the Japan Society of Applied Physics, pp. 23 - 31 (2001) [Non - Patent Document 3] Appl. Phys. Let., 98, 083302 (2011) [Non - Patent Document 4] Proceedings of the 3rd Regular Meeting of the Organic EL Symposium, pp. 13 - 14 (2006) [Summary of the Invention] [Problems to be Solved by the Invention]

[0015] An object of the present invention is to provide a hole - transporting material for an organic EL device that is excellent in hole injection / transport performance, electron blocking ability, stability in a thin - film state, and durability as a material for a highly efficient and highly durable organic EL device. Furthermore, by combining the hole - transporting material and various materials for an organic EL device that are excellent in hole and electron injection / transport performance, electron blocking ability, light - emitting efficiency, stability in a thin - film state, and durability, such as a blue - light - emitting material, so that the characteristics of each material can be effectively exerted, to provide a highly efficient, low - driving - voltage, and long - life organic EL device.

[0016] Physical properties that the organic compound to be used as the hole transport material provided by the present invention should possess include: (1) good hole injection properties, (2) high hole mobility, (3) excellent electron blocking ability, (4) stable thin film state, and (5) excellent heat resistance. Further, physical properties that the organic compound to be used as the blue light emitting material provided by the present invention should possess include: (1) high luminescence quantum yield in the blue wavelength region (430 - 490 nm), (2) excellent stability against oxidation-reduction, (3) stable thin film state, and (4) excellent heat resistance. By combining the properties of the hole transport material and the blue light emitting material provided by the present invention so that they can be effectively exerted, physical properties that the organic EL device to be provided should possess include: (1) high luminous efficiency and power efficiency, (2) low emission start voltage, (3) low practical driving voltage, and (4) long lifespan.

Means for Solving the Problems

[0017] Therefore, in order to achieve the above object, the present inventors focused on the fact that an arylamine compound having a specific structure is excellent in hole injection / transport ability, thin film stability, and durability, selected various arylamine compounds, fabricated organic EL devices, and intensively evaluated the properties of the devices. As a result, the present inventors obtained the finding that when an arylamine compound having a triphenylsilyl group is selected as the material for the second hole transport layer, holes injected from the anode side can be efficiently transported and the electron blocking ability is improved. Further, various organic EL devices combined with a blue light emitting material having a specific structure and the like were fabricated, and the properties of the devices were intensively evaluated. As a result, a combination of a specific arylamine compound and a blue light emitting material was found.

[0018] The organic electroluminescence device according to one aspect of the present invention capable of solving the above problems is An organic electroluminescent element having at least an anode, a first hole transport layer, a second hole transport layer, a blue light-emitting layer, an electron transport layer, and a cathode in this order, wherein the second hole transport layer contains an arylamine compound represented by the following general formula (1). [ka] (In the formula, Ar1 and Ar2 may be the same or different from each other, and represent a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group.) Ar1 and Ar2 may be bonded to each other via single bonds, substituted or unsubstituted methylene groups, substituted or unsubstituted amino groups, oxygen atoms, or sulfur atoms to form a ring. L1 and L2 may be the same or different from each other, and represent a divalent group of a substituted or unsubstituted aromatic hydrocarbon or a divalent group of a substituted or unsubstituted condensed polycyclic aromatic hydrocarbon. R1 represents a fluorine atom, a chlorine atom, a trifluoromethyl group, a linear or branched alkyl group having 1 to 6 carbon atoms which may have substituents, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group. m represents an integer between 0 and 4, and n represents an integer between 0 and 2. Note that when m is an integer greater than or equal to 2, multiple R1 atoms may be identical or different from each other, and when n is 2, multiple R1 atoms bonded to the same benzene ring may be identical or different from each other.

[0019] An organic electroluminescent element according to one aspect of the present invention, which can solve the above problems, In the aforementioned organic electroluminescent element, the blue light-emitting layer contains a compound represented by the following general formula (2) or (3) as a blue light-emitting dopant. [ka] [ka] (In general formulas (2) and (3), Q1 to Q3 may be the same or different from each other, and represent a substituted or unsubstituted aromatic hydrocarbon, a substituted or unsubstituted condensed polycyclic aromatic, or a substituted or unsubstituted aromatic heterocycle. X represents B, P, P=O, or P=S. Y1 to Y3 may be the same or different from each other, and are selected from one of the following: N-R2, C-R3R4, O, S, Se, or Si-R5R6. R2 to R6 may be the same or different from each other, and represent a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a nitro group, a linear or branched alkyl group having 1 to 6 carbon atoms which may be substituted, a cycloalkyl group having 5 to 10 carbon atoms which may be substituted, a linear or branched alkenyl group having 2 to 6 carbon atoms which may be substituted, a linear or branched alkyloxy group having 1 to 6 carbon atoms which may be substituted, a cycloalkyloxy group having 5 to 10 carbon atoms which may be substituted, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted condensed polycyclic aromatic group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted aryloxy group. Furthermore, R3 and R4, and R5 and R6 may be bonded to each other via single bonds, substituted or unsubstituted methylene groups, oxygen or sulfur atoms, or monosubstituted amino groups to form rings. However, if Y1-Y3 are N-R2, C-R3R4, or Si-R5R6, R2-R6 may each bond to adjacent Q1-Q3 via single bonds, substituted or unsubstituted methylene groups, oxygen atoms, sulfur atoms, monosubstituted amino groups, or other linking groups to form rings. [Effects of the Invention]

[0020] The arylamine compound represented by general formula (1) according to the present invention has a higher hole mobility than conventional hole transport materials, possesses excellent electron blocking ability and amorphous properties, and constitutes a stable thin film state. Therefore, in the present invention, the hole transport layer has a two-layer structure consisting of a first hole transport layer and a second hole transport layer, and the second hole transport layer located adjacent to the light-emitting layer is formed from the arylamine compound of general formula (1), thereby maximizing the electron blocking performance of the arylamine compound.

[0021] Furthermore, in the present invention, by including a compound represented by general formula (2) or (3) as a blue light-emitting dopant in the blue light-emitting layer of the organic EL element, a more efficient and longer-life organic EL element can be realized. [Brief explanation of the drawing]

[0022] [Figure 1] This figure shows the structural formulas of compounds 1-1 to 1-10, which are arylamine compounds represented by general formula (1). [Figure 2] This figure shows the structural formulas of compounds 1-11 to 1-18, which are arylamine compounds represented by general formula (1). [Figure 3] This figure shows the structural formulas of compounds 1-19 to 1-28, which are arylamine compounds represented by general formula (1). [Figure 4] This figure shows the structural formulas of compounds 1-29 to 1-38, which are arylamine compounds represented by general formula (1). [Figure 5] This figure shows the structural formulas of compounds 2-1 to 2-11, which are compounds represented by general formula (2). [Figure 6] This figure shows the structural formulas of compounds 2-12 to 2-26, which are represented by general formula (2). [Figure 7] This figure shows the structural formulas of compounds 3-1 to 3-12, which are represented by general formula (3). [Figure 8] This figure shows the organic EL element configurations of Examples 6 and 7 and Comparative Examples 1 and 2. [Modes for carrying out the invention]

[0023] The embodiments of the present invention will now be described in detail. First, the aspects of this embodiment will be described by listing them.

[0024] 1) An organic electroluminescent element having at least an anode, a first hole transport layer, a second hole transport layer, a blue light-emitting layer, an electron transport layer, and a cathode in this order, wherein the second hole transport layer contains an arylamine compound represented by the following general formula (1).

[0025] [ka]

[0026] In the formula, Ar1 and Ar2 may be the same or different from each other, and represent a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group. Ar1 and Ar2 may be bonded to each other via single bonds, substituted or unsubstituted methylene groups, substituted or unsubstituted amino groups, oxygen atoms, or sulfur atoms to form a ring. L1 and L2 may be the same or different from each other, and represent a divalent group of a substituted or unsubstituted aromatic hydrocarbon or a divalent group of a substituted or unsubstituted condensed polycyclic aromatic hydrocarbon. R1 represents a fluorine atom, a chlorine atom, a trifluoromethyl group, a linear or branched alkyl group having 1 to 6 carbon atoms which may have substituents, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group. m represents an integer between 0 and 4, and n represents an integer between 0 and 2. Furthermore, if m is an integer greater than or equal to 2, multiple R1 atoms may be identical or different from one another, and if n is 2, multiple R1 atoms bonded to the same benzene ring may be identical or different from one another.

[0027] 2) The organic EL element according to 1), wherein L1 and L2 in the general formula (1) are substituted or unsubstituted phenylene groups.

[0028] 3) The organic EL element according to 1), wherein L1 and L2 in the general formula (1) are substituted or unsubstituted 1,4-phenylene groups, or substituted or unsubstituted 1,3-phenylene groups.

[0029] 4) An organic EL element according to any of 1) to 3) above, wherein m in the general formula (1) is 0.

[0030] 5) The organic EL element according to any one of 1) to 4), wherein the blue light-emitting layer contains a pyrene derivative having a pyrene skeleton in its molecule as a blue light-emitting dopant.

[0031] 6) The organic EL element according to any one of 1) to 4), wherein the blue light-emitting layer contains a compound represented by the following general formula (2) or (3) as a blue light-emitting dopant.

[0032] [ka]

[0033] [ka]

[0034] In general formulas (2) and (3), Q1 to Q3 may be the same or different from each other, and represent a substituted or unsubstituted aromatic hydrocarbon, a substituted or unsubstituted condensed polycyclic aromatic compound, or a substituted or unsubstituted aromatic heterocycle. X represents B, P, P=O, or P=S. Y1 to Y3 may be the same or different from each other, and are selected from one of the following: N-R2, C-R3R4, O, S, Se, or Si-R5R6. R2 to R6 may be the same or different from each other, and represent a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a nitro group, a linear or branched alkyl group having 1 to 6 carbon atoms which may be substituted, a cycloalkyl group having 5 to 10 carbon atoms which may be substituted, a linear or branched alkenyl group having 2 to 6 carbon atoms which may be substituted, a linear or branched alkyloxy group having 1 to 6 carbon atoms which may be substituted, a cycloalkyloxy group having 5 to 10 carbon atoms which may be substituted, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted condensed polycyclic aromatic group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted aryloxy group. Furthermore, R3 and R4, and R5 and R6 may be bonded to each other via single bonds, substituted or unsubstituted methylene groups, oxygen or sulfur atoms, or monosubstituted amino groups to form rings. However, if Y1~Y3 are N-R2, C-R3R4, or Si-R5R6, R2~R6 may each bond to adjacent Q1~Q3 via single bonds, substituted or unsubstituted methylene groups, oxygen atoms, sulfur atoms, monosubstituted amino groups, or other linking groups to form rings.

[0035] 7) The organic EL element according to 6), wherein the compound represented by general formula (2) or (3) is a compound represented by any of the following general formulas (4) to (7).

[0036] [ka]

[0037] [ka]

[0038] [ka]

[0039] [ka]

[0040] In general formulas (4) to (7), X, Y 1、 Y 2、 Y3 is defined in the same way as in the general formulas (2) and (3) above. Y4 is one of the following selected from N-R2, C-R3R4, O, S, Se, or Si-R5R6. R2 to R6 are defined in the same way as those in general formulas (2) and (3) above. Z may be the same or different from each other, and is either CR7 or N. R7 may be the same or different from each other and represents a hydrogen atom, a deuterium atom, a halogen group, a cyano group, a nitro group, a linear or branched alkyl group having 1 to 6 carbon atoms which may be substituted, a cycloalkyl group having 5 to 10 carbon atoms which may be substituted, a linear or branched alkyloxy group having 1 to 6 carbon atoms which may be substituted, a linear or branched alkylthiooxy group having 1 to 6 carbon atoms which may be substituted, a linear or branched alkylamine group having 1 to 6 carbon atoms which may be substituted, a linear or branched alkylsilyl group having 3 to 10 carbon atoms which may be substituted, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted arylthiooxy group, a substituted or unsubstituted arylamine group, or a substituted or unsubstituted arylsilyl group. R7 groups can bond to each other or to adjacent substituents to form aliphatic or aromatic single or polycyclic rings, and the carbon atoms of the aliphatic or aromatic single or polycyclic rings can be substituted with one or more heteroatoms selected from N, S, and O.

[0041] In the general formula (1) above, the "linear or branched alkyl group having 1 to 6 carbon atoms that may have substituents" represented by R1 can specifically include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, n-pentyl group, isopentyl group, neopentyl group, n-hexyl group, and the like.

[0042] In general formula (1), the "substituents" in the "linear or branched alkyl group having 1 to 6 carbon atoms that may have substituents" represented by R1 include, specifically, deuterium atoms; cyano groups; nitro groups; halogen atoms such as fluorine, chlorine, bromine, and iodine atoms; linear or branched alkyloxy groups having 1 to 6 carbon atoms such as methyloxy, ethyloxy, and propyloxy groups; alkenyl groups such as vinyl and allyl groups; aryloxy groups such as phenyloxy and tolyloxy groups; arylalkyloxy groups such as benzyloxy and phenethyloxy groups; and aromatic groups such as phenyl, biphenylyl, terphenylyl, naphthyl, anthracenyl, phenantrenyl, fluorenyl, indenyl, pyrenyl, perilenyl, fluoranthenyl, and triphenylenyl groups. Examples include cyclic hydrocarbon groups or condensed polycyclic aromatic groups; aromatic heterocyclic groups such as pyridyl, pyrimidinyl, triazinyl, thienyl, furyl, pyrrolyl, quinolyl, isoquinolyl, benzofuranyl, benzothienyl, indolyl, carbazolyl, benzoxazolyl, benzothiazolyl, quinoxalinyl, benzimidazolyl, pyrazolyl, dibenzofuranyl, dibenzothienyl, and carbonyl groups; disubstituted amino groups substituted with aromatic hydrocarbon groups or condensed polycyclic aromatic groups such as diphenylamino and dinaphthylamino groups; disubstituted amino groups substituted with aromatic heterocyclic groups such as dipyridylamino and dithienylamino groups; and disubstituted amino groups substituted with substituents selected from aromatic hydrocarbon groups, condensed polycyclic aromatic groups, or aromatic heterocyclic groups. These substituents may further be substituted with the substituents exemplified above.

[0043] In general formula (1), the "substituted or unsubstituted aromatic hydrocarbon group," "substituted or unsubstituted aromatic heterocyclic group," or "substituted or unsubstituted condensed polycyclic aromatic group" represented by Ar1, Ar2, and R1 include, specifically, phenyl group, biphenylyl group, terphenylyl group, naphthyl group, anthracenyl group, phenantrenyl group, fluorenyl group, indenyl group, pyrenyl group, perilenyl group, and fluoranthenyl group. Examples of these groups include triphenylenyl group, pyridyl group, pyrimidinyl group, triazinyl group, furyl group, pyrrolyl group, thienyl group, quinolyl group, isoquinolyl group, benzofuranyl group, benzothienyl group, indolyl group, carbazolyl group, benzoxazolyl group, benzothiazolyl group, quinoxalinyl group, benzimidazolyl group, pyrazolyl group, dibenzofuranyl group, dibenzothienyl group, naphthylidinyl group, phenanthrolinyl group, acridinyl group, and carbonyl group.

[0044] Furthermore, these groups may have substituents, and examples of substituents include those similar to those shown for the "substituents" in the "linear or branched alkyl group having 1 to 6 carbon atoms that may have substituents" represented by R1 in the general formula (1).

[0045] In the "divalent group of a substituted or unsubstituted aromatic hydrocarbon" or "divalent group of a substituted or unsubstituted condensed polycyclic aromatic" represented by L1 and L2 in the general formula (1) above, specific examples of "aromatic hydrocarbons" or "condensed polycyclic aromatics" include benzene, biphenyl, terphenyl, naphthalene, anthracene, acenaphthalene, fluorene, phenanthrene, indan, pyrene, and triphenylene.

[0046] Furthermore, the "divalent group of a substituted or unsubstituted aromatic hydrocarbon" or "divalent group of a substituted or unsubstituted condensed polycyclic aromatic compound" represented by L1 and L2 in general formula (1) represent a divalent group obtained by removing two hydrogen atoms from the above-mentioned "aromatic hydrocarbon" or "condensed polycyclic aromatic compound." These divalent groups may have substituents, and examples of substituents are the same as those shown for the "substituents" in the "linear or branched alkyl group having 1 to 6 carbon atoms that may have substituents" represented by R1 in general formula (1).

[0047] In general formula (1), Ar1 and Ar2 are preferably "substituted or unsubstituted aromatic hydrocarbon groups" or "substituted or unsubstituted condensed polycyclic aromatic groups," more preferably substituted or unsubstituted phenyl groups, biphenylyl groups, terphenylyl groups, naphthyl groups, phenanthrasennyl groups, anthracennyl groups, or fluorenyl groups, and particularly preferably substituted or unsubstituted phenyl groups, biphenylyl groups, naphthyl groups, or phenanthrasennyl groups.

[0048] In general formula (1), L1 and L2 are preferably "divalent groups of substituted or unsubstituted aromatic hydrocarbons," more preferably substituted or unsubstituted phenylene groups, and particularly preferably substituted or unsubstituted 1,4-phenylene groups or substituted or unsubstituted 1,3-phenylene groups.

[0049] In general formula (1), m represents an integer from 0 to 4, but is preferably 0 or 1, and particularly preferably 0.

[0050] In the general formulas (2) and (3) above, the "substituted or unsubstituted aromatic hydrocarbons," "substituted or unsubstituted condensed polycyclic aromatics," or "substituted or unsubstituted aromatic heterocycles" represented by Q1 to Q3 include, specifically, benzene, naphthalene, anthracene, fluorene, phenanthrene, pyridine, pyrimidine, triazine, pyrrole, furan, thiophene, quinoline, isoquinoline, indene, benzofuran, benzothiophene, indole, indoline, carbazole, carbolin, benzoxazole, benzothiazole, quinoxaline, benzimidazole, pyrazole, dibenzofuran, dibenzothiophene, naphthyridine, phenanthroline, acridine, and others.

[0051] Furthermore, these elements may have substituents, and examples of substituents include those similar to those shown for the "substituents" in the "linear or branched alkyl group having 1 to 6 carbon atoms that may have substituents" represented by R1 in the general formula (1). In addition, these substituents may be bonded to each other via single bonds, substituted or unsubstituted methylene groups, oxygen atoms, or sulfur atoms to form a ring.

[0052] In the general formulas (2) and (3) above, X represents B, P, P=O, or P=S. B is defined as a boron atom, P as a phosphorus atom, P=O as a phosphorus atom bonded to an oxygen atom by a double bond, or P=S as a phosphorus atom bonded to a sulfur atom by a double bond. When X is P=O or P=S, the phosphorus atom becomes the bonding site with the other atoms in general formulas (2) and (3).

[0053] In the general formulas (2) and (3) above, Y1 to Y3 may be the same or different from each other, and are selected from N-R2, C-R3R4, O, S, Se, or Si-R5R6. N-R2 is defined as a nitrogen atom with R2 as a substituent, C-R3R4 as a carbon atom with R3 and R4 as substituents, O as an oxygen atom, S as a sulfur atom, Se as a selenium atom, and Si-R5R6 as a silicon atom with R5 and R6 as substituents. When Y1 to Y3 are N-R2, C-R3R4, or Si-R5R6, the nitrogen atom, carbon atom, or silicon atom, respectively, becomes the bonding site with the other atoms in general formulas (2) and (3). The definitions of R2 to R6 will be explained in more detail below.

[0054] In the case where Y1 to Y3 in the general formulas (2) and (3) above are N-R2, C-R3R4, or Si-R5R6, the R2 to R6 represent "a linear or branched alkyl group having 1 to 6 carbon atoms which may have substituents", "a cycloalkyl group having 5 to 10 carbon atoms which may have substituents", or "a linear or branched alkenyl group having 2 to 6 carbon atoms which may have substituents", and "a linear or branched alkyl group having 1 to 6 carbon atoms which may have substituents", the R2 to R6 represent "a linear or branched alkyl group having 1 to 6 carbon atoms", "a cycloalkyl group having 5 to 10 carbon atoms which may have substituents", or "a linear or branched alkenyl group having 5 to 6 carbon atoms which may have substituents". Examples of the "10 cycloalkyl groups" or "linear or branched alkenyl groups having 2 to 6 carbon atoms" include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, n-hexyl, cyclopentyl, cyclohexyl, 1-adamantyl, 2-adamantyl, vinyl, allyl, isopropenyl, and 2-butenyl groups. These groups may also have substituents, and examples of substituents are the same as those shown for the "substituents" in the "linear or branched alkyl group having 1 to 6 carbon atoms that may have substituents" represented by R1 in the general formula (1).

[0055] In the cases where Y1 to Y3 in the general formulas (2) and (3) are N-R2, C-R3R4, or Si-R5R6, the "linear or branched alkyloxy group having 1 to 6 carbon atoms that may have substituents" or "cycloalkyloxy group having 5 to 10 carbon atoms that may have substituents" represented by R2 to R6 can specifically include methyloxy group, ethyloxy group, n-propyloxy group, isopropyloxy group, n-butyloxy group, tert-butyloxy group, n-pentyloxy group, n-hexyloxy group, cyclopentyloxy group, cyclohexyloxy group, cycloheptyloxy group, cyclooctyloxy group, 1-adamantyloxy group, 2-adamantyloxy group, and the like.

[0056] Furthermore, these groups may have substituents, and examples of substituents include those similar to those shown for the "substituents" in the "linear or branched alkyl group having 1 to 6 carbon atoms that may have substituents" represented by R1 in the general formula (1).

[0057] In general formulas (2) and (3), when Y1 to Y3 are N-R2, C-R3R4, or Si-R5R6, the "substituted or unsubstituted aromatic hydrocarbon group," "substituted or unsubstituted condensed polycyclic aromatic group," or "substituted or unsubstituted aromatic heterocyclic group" represented by R2 to R6 can specifically include phenyl group, biphenylyl group, terphenylyl group, naphthyl group, anthracenyl group, phenantrenyl group, pyridyl group, pyrimidinyl group, triazinyl group, furyl group, pyrrolyl group, thienyl group, and the like. These groups may also have substituents, and the substituents can be the same as those shown for the "substituents" in the "linear or branched alkyl group having 1 to 6 carbon atoms that may have substituents" represented by R1 in general formula (1).

[0058] When Y1 to Y3 in the general formulas (2) and (3) are N-R2, C-R3R4, or Si-R5R6, the "aryloxy group" in the "substituted or unsubstituted aryloxy group" represented by R2 to R6 can specifically be a phenyloxy group, biphenylyloxy group, terphenylyloxy group, naphthyloxy group, anthracenyloxy group, phenantrenyloxy group, fluorenyloxy group, indenyloxy group, pyrenyloxy group, perilennyloxy group, etc. Furthermore, these groups may have substituents, and the substituents can be the same as those shown for the "substituents" in the "linear or branched alkyl group having 1 to 6 carbon atoms that may have substituents" represented by R1 in the general formula (1).

[0059] In the general formulas (2) and (3) above, the "aromatic hydrocarbon" or "aromatic heterocycle" in the "substituted or unsubstituted aromatic hydrocarbon" or "substituted or unsubstituted aromatic heterocycle" of Q1 to Q3 is preferably benzene, naphthalene, phenanthrene, pyridine, pyrimidine, indene, benzofuran, benzothiophene, or indole, with benzene and naphthalene being more preferred.

[0060] In the general formulas (2) and (3) above, Y1 is preferably N-R2, O, or S, and more preferably O or S. Also, in the general formulas (2) and (3) above, at least one of Y2 and Y3 is preferably N-R2, and more preferably both are N-R2. R2 is preferably a "substituted or unsubstituted aromatic hydrocarbon group" or a "substituted or unsubstituted condensed polycyclic aromatic group," and more preferably a substituted or unsubstituted phenyl group, biphenylyl group, terphenylyl group, or naphthyl group. X in the general formulas (2) and (3) above may be B.

[0061] The compounds represented by the general formulas (2) and (3) above may also be compounds having a skeletal structure shown in any of the following general formulas (4) to (7).

[0062] [ka]

[0063] [ka]

[0064] [ka]

[0065] [ka]

[0066] In general formulas (4) to (7), X, Y 1、 Y 2、 Y3 is defined in the same way as in the general formulas (2) and (3) above. Y4 is one of the following selected from N-R2, C-R3R4, O, S, Se, or Si-R5R6. R2 to R6 are defined in the same way as those in general formulas (2) and (3) above. Z may be the same or different from each other, and is either CR7 or N. R7 may be the same or different from each other and represents a hydrogen atom, a deuterium atom, a halogen group, a cyano group, a nitro group, a linear or branched alkyl group having 1 to 6 carbon atoms which may be substituted, a cycloalkyl group having 5 to 10 carbon atoms which may be substituted, a linear or branched alkyloxy group having 1 to 6 carbon atoms which may be substituted, a linear or branched alkylthiooxy group having 1 to 6 carbon atoms which may be substituted, a linear or branched alkylamine group having 1 to 6 carbon atoms which may be substituted, a linear or branched alkylsilyl group having 3 to 10 carbon atoms which may be substituted, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted arylthiooxy group, a substituted or unsubstituted arylamine group, or a substituted or unsubstituted arylsilyl group. Furthermore, R7 groups can bond to each other or to adjacent substituents to form aliphatic or aromatic single or polycyclic rings, and the carbon atoms of the aliphatic or aromatic single or polycyclic rings can be substituted with one or more heteroatoms selected from N, S, and O.

[0067] In general formulas (4) to (7), R7 represents a "linear or branched alkyl group having 1 to 6 carbon atoms that may have substituents" or a "cycloalkyl group having 5 to 10 carbon atoms that may have substituents." Specifically, examples of the "linear or branched alkyl group having 1 to 6 carbon atoms" or "cycloalkyl group having 5 to 10 carbon atoms" include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, n-hexyl, cyclopentyl, cyclohexyl, 1-adamantyl, and 2-adamantyl groups. These groups may also have substituents, and examples of substituents are the same as those shown for the "substituents" in the "linear or branched alkyl group having 1 to 6 carbon atoms that may have substituents" represented by R1 in general formula (1).

[0068] In general formulas (4) to (7), the "linear or branched alkyloxy group having 1 to 6 carbon atoms that may have substituents" represented by R7 specifically includes methyloxy group, ethyloxy group, n-propyloxy group, isopropyloxy group, n-butyloxy group, tert-butyloxy group, n-pentyloxy group, n-hexyloxy group, and the like. These groups may also have substituents, and the substituents are the same as those shown for the "substituents" in the "linear or branched alkyl group having 1 to 6 carbon atoms that may have substituents" represented by R1 in general formula (1).

[0069] In general formulas (4) to (7), the "linear or branched alkyl thioxy group having 1 to 6 carbon atoms that may have substituents" represented by R7 specifically includes methyl thioxy group, ethyl thioxy group, n-propyl thioxy group, isopropyl thioxy group, n-butyl thioxy group, isobutyl thioxy group, tert-butyl thioxy group, n-pentyl thioxy group, isopentyl thioxy group, neopentyl thioxy group, n-hexyl thioxy group, and the like. These groups may also have substituents, and the substituents are the same as those shown for the "substituents" in the "linear or branched alkyl group having 1 to 6 carbon atoms that may have substituents" represented by R1 in general formula (1).

[0070] In general formulas (4) to (7), the "linear or branched alkylamine group having 1 to 6 carbon atoms that may have substituents" represented by R7 specifically includes methylamine group, ethylamine group, n-propylamine group, isopropylamine group, n-butylamine group, isobutylamine group, tert-butylamine group, n-pentylamine group, isopentylamine group, neopentylamine group, n-hexylamine group, and the like. These groups may also have substituents, and the substituents are the same as those shown for the "substituents" in the "linear or branched alkyl group having 1 to 6 carbon atoms that may have substituents" represented by R1 in general formula (1).

[0071] In general formulas (4) to (7), the "linear or branched alkylsilyl group having 3 to 10 carbon atoms that may have substituents" represented by R7 specifically includes trimethylsilyl, triethylsilyl, tri-n-propylsilyl, triisopropylsilyl, n-butyldimethylsilyl, isobutyldimethylsilyl, and tert-butyldimethylsilyl groups. These groups may also have substituents, and the substituents are the same as those shown for the "substituents" in the "linear or branched alkyl group having 1 to 6 carbon atoms that may have substituents" represented by R1 in general formula (1).

[0072] In general formulas (4) to (7), the "substituted or unsubstituted aromatic hydrocarbon group" or "substituted or unsubstituted aromatic heterocyclic group" represented by R7 can specifically refer to the "aromatic hydrocarbon group" or "aromatic heterocyclic group," such as the phenyl group, biphenylyl group, terphenylyl group, naphthyl group, anthracenyl group, phenantrenyl group, pyridyl group, pyrimidinyl group, triazinyl group, furyl group, pyrrolyl group, and thienyl group. These groups may also have substituents, and the substituents can be the same as those shown for the "substituents" in the "linear or branched alkyl group having 1 to 6 carbon atoms that may have substituents" represented by R1 in general formula (1).

[0073] In general formulas (4) to (7), the "substituted or unsubstituted aryloxy group" represented by R7 can be specifically phenyloxy group, biphenylyloxy group, terphenylyloxy group, naphthyloxy group, anthracenyloxy group, phenantrenyloxy group, fluorenyloxy group, indenyloxy group, pyrenyloxy group, perilenyloxy group, and the like. These groups may also have substituents, and the substituents can be the same as those shown for the "substituents" in the "linear or branched alkyl group having 1 to 6 carbon atoms that may have substituents" represented by R1 in general formula (1).

[0074] In general formulas (4) to (7), the "substituted or unsubstituted aryl thiooxy group" represented by R7 can specifically refer to phenyl thiooxy group, biphenylyl thiooxy group, terphenylyl thiooxy group, naphthyl thiooxy group, anthracenyl thiooxy group, phenantrenyl thiooxy group, fluorenyl thiooxy group, indenyl thiooxy group, pyrenyl thiooxy group, and perilenyl thiooxy group. These groups may also have substituents, and the substituents can be the same as those shown for the "substituents" in the "linear or branched alkyl group having 1 to 6 carbon atoms that may have substituents" represented by R1 in general formula (1).

[0075] In general formulas (4) to (7), the "substituted or unsubstituted arylamine group" represented by R7 can specifically refer to phenylamine, biphenylylamine, terphenylylamine, naphthylamine, anthracenylamine, phenantrenylamine, fluorenylamine, indenylamine, pyrenylamine, and perilennylamine groups. These groups may also have substituents, and the substituents are the same as those shown for the "substituents" in the "linear or branched alkyl group having 1 to 6 carbon atoms that may have substituents" represented by R1 in general formula (1).

[0076] In general formulas (4) to (7), the "substituted or unsubstituted arylsilyl group" represented by R7 can specifically refer to the "arylsilyl group," such as the triphenylsilyl group, trinaphthylsilyl group, and terphenylylsilyl group. These groups may also have substituents, and the substituents can be the same as those shown for the "substituents" in the "linear or branched alkyl group having 1 to 6 carbon atoms that may have substituents" represented by R1 in general formula (1).

[0077] Specific examples of preferred compounds among the arylamine compounds represented by the general formula (1) that are suitably used in the organic EL elements of this embodiment are shown in Figures 1 to 4, but the invention is not limited to these compounds.

[0078] Figures 5 and 6 show specific examples of preferred compounds among those represented by the general formula (2) that are suitably used in the organic EL elements of this embodiment, but the present invention is not limited to these compounds.

[0079] Figure 7 shows specific examples of preferred compounds among those represented by the general formula (3) that are suitably used in the organic EL elements of this embodiment, but the present invention is not limited to these compounds.

[0080] The arylamine compound represented by general formula (1) may be purified by column chromatography, adsorption using silica gel, activated carbon, activated clay, etc., recrystallization or crystallization with a solvent, or sublimation. Compound identification may be performed by NMR analysis. Physical properties such as melting point, glass transition temperature (Tg), and work function may be measured. The melting point is an indicator of vapor deposition properties, the glass transition temperature (Tg) is an indicator of the stability of the thin film state, and the work function is an indicator of hole transport and hole blocking properties. In addition, the compound used in the organic EL element of this embodiment may be purified by column chromatography, adsorption using silica gel, activated carbon, activated clay, etc., recrystallization or crystallization with a solvent, sublimation, etc., and finally purified by sublimation.

[0081] The melting point and glass transition temperature (Tg) are measured using a powder with a high-sensitivity differential scanning calorimeter (Bruker AXS, DSC3100SA). The glass transition temperature of the compound represented by general formula (1) is not particularly limited, but from the viewpoint of the stability of the formed thin film, it is preferably 80°C or higher, more preferably 100°C or higher, and particularly preferably 110°C or higher. The upper limit of the glass transition temperature is not particularly limited, but for example, compounds with a glass transition temperature of 250°C or lower can be used.

[0082] The work function is determined by fabricating a 100 nm thin film on an ITO substrate and using an ionization potential measuring device (Sumitomo Heavy Industries, Ltd., PYS-202). The work function of a 100 nm thick deposited film fabricated on an ITO substrate using the compound represented by general formula (1) is not particularly limited, but it is preferable to have a work function greater than 5.4 eV. The upper limit of the work function of this deposited film is not particularly limited, but for example, it can be a deposited film with a work function of 7.0 eV or less.

[0083] The structure of the organic EL element in this embodiment includes a substrate in which an anode, hole transport layer, light-emitting layer, electron transport layer, and cathode are arranged sequentially. Other examples include a hole injection layer between the anode and the hole transport layer, a hole blocking layer between the light-emitting layer and the electron transport layer, and an electron injection layer between the electron transport layer and the cathode. In these multilayer structures, some organic layers can be omitted or combined. For example, a configuration in which the hole injection layer and hole transport layer are combined, or a configuration in which the electron injection layer and electron transport layer are combined, is possible. Furthermore, it is possible to have a configuration in which two or more organic layers having the same function are stacked. For example, a configuration in which two hole transport layers are stacked, a configuration in which two light-emitting layers are stacked, or a configuration in which two electron transport layers are stacked is possible. In the structure of the organic EL element in this embodiment, the hole transport layer has a two-layer structure consisting of a first hole transport layer and a second hole transport layer. In this case, the second hole transport layer is adjacent to the light-emitting layer and functions as an electron blocking layer.

[0084] In this embodiment, electrode materials with a large work function, such as ITO or gold, are used as the anode of the organic EL element. For the hole injection layer of the organic EL element in this embodiment, materials such as starburst-type triphenylamine derivatives, various triphenylamine tetramers, porphyrin compounds represented by copper phthalocyanine, acceptor-type heterocyclic compounds such as hexacyanoazatriphenylene, and coated polymer materials can be used. These materials can be formed into thin films by known methods such as vapor deposition, spin coating, and inkjet printing.

[0085] As hole-transporting materials that can be used as the first hole transport layer of the organic EL element of this embodiment, various organic amine compounds such as benzidine derivatives such as N,N'-diphenyl-N,N'-di(m-tolyl)benzidine (TPD), N,N'-diphenyl-N,N'-di(α-naphthyl)benzidine (NPD), and N,N,N',N'-tetrabiphenylylbenzidine, as well as 1,1-bis[4-(di-4-tolylamino)phenyl]cyclohexane (TAPC), and arylamine compounds having a structure in which four triphenylamine structures are linked by single bonds or divalent groups that do not contain heteroatoms, or arylamine compounds having a structure in which two triphenylamine structures are linked by single bonds or divalent groups that do not contain heteroatoms, can be used. These materials may be deposited individually, or used as single layers formed by mixing them with other materials. They may also be used in laminated structures, such as layers deposited individually, layers deposited by mixing, or layers deposited individually and layers deposited by mixing. These materials can be used to form thin films using known methods such as vapor deposition, spin coating, and inkjet printing.

[0086] Furthermore, in the hole injection layer or the first hole transport layer, materials that are P-doped with trisbromophenylamine hexachloroantimony, radialene derivatives (see, for example, Patent Document 6), or polymer compounds having the structure of a benzidine derivative such as TPD as a substructure can be used in addition to the materials normally used in the layer.

[0087] In the organic EL element of this embodiment, the second hole transport layer located on the light-emitting layer side is an arylamine compound represented by the general formula (1). Examples of hole-transporting materials that can be mixed with or used simultaneously with the arylamine compound represented by the general formula (1) include carbazole derivatives such as 4,4',4''-tri(N-carbazolyl)triphenylamine (TCTA), 9,9-bis[4-(carbazole-9-yl)phenyl]fluorene, 1,3-bis(carbazole-9-yl)benzene (mCP), and 2,2-bis(4-carbazole-9-ylphenyl)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-(carbazole-9-yl)phenyl]-9-[4-(triphenylsilyl)phenyl]-9H-fluorene.

[0088] These materials may be deposited individually, or used as single layers formed by mixing them with other materials. They may also be used in laminated structures, such as layers deposited individually, layers deposited by mixing, or layers deposited individually and layers deposited by mixing. These materials can be used to form thin films using known methods such as vapor deposition, spin coating, and inkjet printing.

[0089] As the blue light-emitting layer of the organic EL element of this embodiment, pyrene derivatives having a pyrene skeleton in the molecule, or compounds represented by the general formula (2) or (3) above, are preferably used. In addition, various metal complexes, anthracene derivatives, bis-styrylbenzene derivatives, oxazole derivatives, etc., can be used. The light-emitting layer may also be composed of a host material and a dopant material, in which case, an anthracene derivative having an anthracene skeleton in the molecule is preferably used as the host material. As the dopant material, pyrene derivatives having a pyrene skeleton in the molecule, or compounds represented by the general formula (2) or (3) above, are preferably used, but in addition, heterocyclic compounds having an indole ring as a substructure of the fused ring, heterocyclic compounds having a carbazole ring as a substructure of the fused ring, carbazole derivatives, benzimidazole derivatives, polydialkylfluorene derivatives, perylene derivatives, indenophenanthrene derivatives, etc., can be used. These materials may be deposited individually, or they may be used as single layers deposited by mixing them with other materials. They may also be used in laminated structures, such as layers deposited individually, layers deposited by mixing, or layers deposited individually and layers deposited by mixing.

[0090] Furthermore, phosphorescent materials can be used as light-emitting materials. As phosphorescent materials, metal complex phosphorescent materials such as iridium and platinum can be used. Blue phosphorescent materials such as FIrpic and FIr6 are used, and in this case, anthracene derivatives having an anthracene skeleton in the molecule are preferably used as the host material. In addition, carbazole derivatives such as 4,4'-di(N-carbazolyl)biphenyl (CBP), TCTA, and mCP can be used as hole-injection and transport host materials. As electron-transport host materials, p-bis(triphenylsilyl)benzene (UGH2) and 2,2',2''-(1,3,5-phenylene)-tris(1-phenyl-1H-benzimidazole) (TPBI) can be used, and high-performance organic EL devices can be fabricated.

[0091] To avoid concentration quenching, it is preferable to dope the phosphorescent luminescent material onto the host material by co-deposition in an amount ranging from 1 to 30 weight percent of the entire luminescent layer.

[0092] These materials can be formed into thin films using known methods such as vapor deposition, spin coating, and inkjet printing.

[0093] As the hole-blocking layer of the organic EL element in this embodiment, metal complexes of phenanthroline derivatives such as bathocuproine (BCP) and quinolinol derivatives such as aluminum(III) bis(2-methyl-8-quinolinate)-4-phenylphenolate (hereinafter abbreviated as BAlq), as well as various rare earth complexes, triazole derivatives, triazine derivatives, oxadiazole derivatives, and other compounds having hole-blocking properties can be used. These materials may also serve as the electron transport layer material. These may be deposited individually, or used as a single layer by mixing them with other materials. They may also be used in a laminated structure of layers deposited individually, layers deposited by mixing, or layers deposited individually and layers deposited by mixing. These materials can be used to form thin films by known methods such as vapor deposition, spin coating, and inkjet printing.

[0094] As the electron transport layer of the organic EL element in this embodiment, metal complexes of quinolinol derivatives such as Alq3 and BAlq, various metal complexes, triazole derivatives, triazine derivatives, oxadiazole derivatives, pyridine derivatives, pyrimidine derivatives, benzimidazole derivatives, thiadiazole derivatives, anthracene derivatives, carbodiimide derivatives, quinoxaline derivatives, pyridoindole derivatives, phenanthroline derivatives, silole derivatives, etc., can be used. These may be deposited as films on their own, or as monolayers formed by mixing them with other materials. They may also be used in laminated structures of layers deposited individually, layers deposited by mixing, or layers deposited individually and layers deposited by mixing. These materials can be used to form thin films by known methods such as vapor deposition, spin coating, and inkjet printing.

[0095] As the electron injection layer of the organic EL element of this embodiment, alkali metal salts such as lithium fluoride and cesium fluoride, alkaline earth metal salts such as magnesium fluoride, metal complexes of quinoline derivatives such as lithium quinolinol, metal oxides such as aluminum oxide, or metals such as ytterbium (Yb), samarium (Sm), calcium (Ca), strontium (Sr), cesium (Cs), etc. can be used. However, in a preferred selection of the electron transport layer and the cathode, this can be omitted.

[0096] Furthermore, in the electron injection layer or the electron transport layer, a material obtained by N-doping a metal such as cesium into the material usually used for the layer can be used.

[0097] As the cathode of the organic EL element of this embodiment, electrode materials with a low work function such as aluminum, or alloys with an even lower work function such as magnesium-silver alloy, magnesium-indium alloy, and aluminum-magnesium alloy are used as the electrode material.

Example

[0098] Hereinafter, the embodiments of the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples.

[0099] [Example 1] <Synthesis of N-([1,1'-biphenyl]-4-yl)-N-phenyl-4''-(triphenylsilyl)-[1,1':4',1''-terphenyl]-4-amine (1-11)> In a nitrogen-purged reaction vessel, an aqueous solution of 30.0 g of 4'-bromo-N-phenyl-[1,1'-biphenyl]-4-amine, 36.9 g of 1-bromo-4-(triphenylsilyl)benzene, 240 mL of toluene, 120 mL of ethanol, and 22.3 g of potassium carbonate dissolved in 90 mL of purified water was added, and nitrogen gas was passed through while irradiating with sonication for 30 minutes. 3.7 g of tetrakistriphenylphosphine palladium was added, and the mixture was stirred under reflux for 18 hours. After cooling, the mixture was separated, and the organic layer was sequentially washed with 200 mL of tap water and 200 mL of saturated saline solution. The organic layer was dried over anhydrous magnesium sulfate, and the drying agent was removed by filtration. The filtrate was concentrated, and 450 mL of chlorobenzene was added to the residue, and the mixture was heated and stirred. 24 g of silica gel was added at 80°C, the mixture was stirred for 1 hour, and the solid was removed by thermal filtration. The filtrate was concentrated, and the residue was recrystallized with chlorobenzene to obtain 38.0 g (81% yield) of a pale yellow powder of N-phenyl-4''-(triphenylsilyl)-[1,1':4',1''-terphenyl]-4-amine.

[0100] 8.5 g of N-phenyl-4''-(triphenylsilyl)-[1,1':4',1''-terphenyl]-4-amine, 3.9 g of 4-bromoviphenyl, 2.1 g of t-butoxysodium, and 125 mL of toluene were added to a nitrogen-purged reaction vessel, and nitrogen gas was passed through while irradiating with sonication for 30 minutes. 0.1 g of palladium acetate and 0.2 g of a 50% toluene solution of t-butylphosphine were added, and the mixture was heated and stirred under reflux for 3 hours. The mixture was cooled to 80°C, and inorganic substances were removed by thermal filtration. The filtrate was heated and stirred, 10 g of silica gel was added at 80°C, and the mixture was stirred for 1 hour. The solid was removed by thermal filtration. The filtrate was concentrated, and the residue was purified by column chromatography to obtain 7.2 g (67% yield) of N-([1,1'-biphenyl]-4-yl)-N-phenyl-4''-(triphenylsilyl)-[1,1':4',1''-terphenyl]-4-amine(1-11) as a white solid.

[0101] [ka]

[0102] The structure of the obtained white powder was identified using NMR. 1 The following 41 hydrogen signals were detected by 1H-NMR (CDCl3). δ (ppm) = 7.49 - 7.70 (20H), 7.35 - 7.46 (11H), 7.27 - 7.32 (3H), 7.18 - 7.21 (6H), 7.04 - 7.08 (1H).

[0103] [Example 2] <Synthesis of N-Phenyl-N-(4''-(Triphenylsilyl)-[1,1':4',1''-Terphenyl]-4-yl)Phenanthrene-9-amine (1-27)> 8.5 g of N-Phenyl-4''-(triphenylsilyl)-[1,1':4',1''-terphenyl]-4-amine, 4.3 g of 9-bromophenanthrene, 2.1 g of sodium t-butoxide, and 130 mL of toluene were added to a nitrogen-substituted reaction vessel, and nitrogen gas was bubbled while irradiating with ultrasonic waves for 30 minutes. 0.1 g of palladium acetate and 0.2 g of a 50% toluene solution of t-butylphosphine were added and heated, and refluxed with stirring for 3 hours. It was cooled to 80 °C, and inorganic substances were removed by hot filtration. The filtrate was heated and stirred, 10 g of silica gel was added at 80 °C, stirred for 1 hour, and the solid was removed by hot filtration. The filtrate was concentrated, and the residue was purified by column chromatography to obtain 6.7 g (yield 60%) of a white solid of N-Phenyl-N-(4''-(triphenylsilyl)-[1,1':4',1''-terphenyl]-4-yl)phenanthrene-9-amine.

[0104] [Chemical formula]

[0105] The structure of the obtained white powder was identified using NMR. The structure of the obtained white powder was identified using NMR. 1 The following 41 hydrogen signals were detected by 1H-NMR (CDCl3). δ(ppm)=8.69-8.75(2H), 8.06-8.08(1H), 7.75-7.77(1H), 7.36-7.65(30H), 7.13-7.25(6H), 6.96-6.99(1H).

[0106] [Example 3] <Synthesis of compounds (2-11)> 45.0 g of 1-bromobenzene (D-substituted), 58.0 g of 4-tert-butylaniline, 1.0 g of palladium(II) acetate, 30.0 g of tert-butoxysodium, 2.0 g of bis(diphenylphosphin)-1,1'-binaphthyl, and 450 mL of toluene were added to a reaction vessel and stirred under reflux for 24 hours. After cooling, the mixture was concentrated and purified by column chromatography to obtain 49.9 g (78% yield) of the following compound (2-11a) in powder form.

[0107] [ka]

[0108] 20.0 g of the above compound (2-11a), 18.4 g of the following compound (2-11b), 0.5 g of palladium(II) acetate, 18.9 g of tert-butoxysodium, 0.8 g of tri(tert-butyl)phosphine, and 200 mL of toluene were added to a reaction vessel and stirred under reflux for 24 hours. After cooling, the mixture was concentrated and purified by column chromatography to obtain 21.5 g of the following compound (2-11c) in powder form (84% yield).

[0109] [ka]

[0110] [ka]

[0111] 12.0 g of the above compound (2-11c) and 120 ml of tert-butylbenzene were added to a reaction vessel, and 42.5 ml of n-butyllithium was added dropwise at -78°C. Nitrogen gas was then passed through while stirring at 60°C for 3 hours. Next, 11.3 g of boron tripromide was added dropwise at -78°C, and the mixture was stirred at room temperature for 1 hour. Then, 5.9 g of N,N-diisopropylethylamine was added dropwise at 0°C, and the mixture was stirred at 120°C for 2 hours. After cooling, an aqueous sodium acetate solution was added and the mixture was stirred. The mixture was extracted with ethyl acetate, and the organic layer was concentrated. Purification by column chromatography yielded 1.7 g (yield 11%) of the following compound (2-11) in powder form.

[0112] [ka]

[0113] [Example 4] The glass transition temperature of arylamine compounds represented by general formula (1) was measured using a high-sensitivity differential scanning calorimeter (Bruker AXS, DSC3100SA). glass transition Compounds from Example 1 (1-11) 107℃ Compounds of Example 2 (1-27) 128℃

[0114] The arylamine compounds represented by general formula (1) in Examples 1 and 2 have a glass transition temperature of 100°C or higher, indicating that the thin film state is stable.

[0115] [Example 5] Using the arylamine compounds represented by general formula (1) in Examples 1 and 2, a 100 nm thick vapor-deposited film was fabricated on an ITO substrate, and the work function was measured using an ionization potential analyzer (Sumitomo Heavy Industries, Ltd., PYS-202). Work function Compounds from Example 1 (1-11) 5.78 eV Compound (1-27) of Example 2: 5.82 eV

[0116] The arylamine compounds represented by general formula (1) in Examples 1 and 2 exhibit favorable energy levels compared to the work function of 5.4 eV of common hole transport materials such as NPDs and TPDs, indicating that they possess good hole transport capabilities.

[0117] [Example 6] As shown in Figure 8, the organic EL element was prepared by first forming a reflective ITO electrode as a transparent anode 2 on a glass substrate 1, and then depositing a hole injection layer 3, a first hole transport layer 4, a second hole transport layer 5, an emissive layer 6, an electron transport layer 7, an electron injection layer 8, a cathode 9, and a capping layer 10 in that order.

[0118] Specifically, a glass substrate 1, on which a 50 nm thick ITO film, a 100 nm thick silver alloy reflective film, and a 5 nm thick ITO film were sequentially deposited, was ultrasonically cleaned in isopropyl alcohol for 20 minutes, and then dried on a hot plate heated to 250°C for 10 minutes. After that, UV ozone treatment was performed for 15 minutes, and then this ITO-coated glass substrate was placed in a vacuum deposition machine and the pressure was reduced to 0.001 Pa or less. Subsequently, an electron acceptor (Acceptor-1) with the following structural formula and a compound (HTM-1) with the following structural formula were binary deposited on a transparent anode 2 at a deposition rate ratio of Acceptor-1:compound (HTM-1) = 3:97, forming a hole injection layer 3 with a thickness of 10 nm so as to cover the transparent anode 2. On this hole injection layer 3, a first hole transport layer 4 was formed with the compound (HTM-1) with the following structural formula to a thickness of 140 nm. On this first hole transport layer 4, a second hole transport layer 5 was formed with compound (1-11) from Example 1 to a thickness of 5 nm. On this second hole transport layer 5, compound (2-11) from Example 3 and compound (EMH-1) with the following structural formula were deposited by binary deposition at a deposition rate ratio of compound (2-11):compound (EMH-1)=5:95 to form an emissive layer 6 to a thickness of 20 nm. On this emissive layer 6, compound (ETM-1) and compound (ETM-2) with the following structural formula were deposited by binary deposition at a deposition rate ratio of compound (ETM-1):compound (ETM-2)=50:50 to form an electron transport layer 7 to a thickness of 30 nm. On this electron transport layer 7, an electron injection layer 8 was formed with lithium fluoride to a thickness of 1 nm. On this electron injection layer 8, a cathode 9 was formed with a magnesium-silver alloy to a thickness of 12 nm. Finally, a capping layer 10 was formed with a compound (CPL-1) of the following structural formula to a thickness of 60 nm. The luminescence characteristics of the fabricated organic EL device were measured by applying a DC voltage in air at room temperature. The results are summarized in Table 1.

[0119] [ka]

[0120] [ka]

[0121] [ka]

[0122] [ka]

[0123] [ka]

[0124] [ka]

[0125] [ka]

[0126] [ka]

[0127] [Example 7] In Example 6, an organic EL element was fabricated under the same conditions as in Example 1, except that the compound (1-27) from Example 2 was used as the material for the second hole transport layer 5 instead of the compound (1-11) from Example 1. The fabricated organic EL element was subjected to characteristic measurements in air at room temperature. The measurement results of the luminescence characteristics when a DC voltage was applied to the fabricated organic EL element are summarized in Table 1.

[0128] [ka]

[0129] [Comparative Example 1] For comparison, in Example 6, an organic EL element was fabricated under the same conditions as in Example 1, except that the compound with the following structural formula (HTM-2) was used as the material for the second hole transport layer 5, instead of the compound (1-11) from Example 1. The fabricated organic EL element was subjected to characteristic measurements in air at room temperature. The measurement results of the luminescence characteristics when a DC voltage was applied to the fabricated organic EL element are summarized in Table 1.

[0130] [ka]

[0131] [Comparative Example 2] For comparison, in Example 6, an organic EL element was fabricated under the same conditions as in Example 1, except that the compound with the following structural formula (HTM-3) was used as the material for the second hole transport layer 5, instead of the compound (1-11) from Example 1. The fabricated organic EL element was subjected to characteristic measurements in air at room temperature. The measurement results of the luminescence characteristics when a DC voltage was applied to the fabricated organic EL element are summarized in Table 1.

[0132] [ka]

[0133] Table 1 summarizes the results of measuring the device lifetime using the organic EL elements fabricated in Examples 6-7 and Comparative Examples 1-2. The device lifetime is calculated using an initial luminescence of 2000 cd / m². 2 When driven with a constant current, the luminescence brightness is 1900 cd / m². 2 The time taken for the brightness to decay to 95% (equivalent to 95% of the initial brightness, which is set to 100%) was measured.

[0134] [Table 1]

[0135] As shown in Table 1, the current density is 10 mA / cm². 2When a current was applied, the luminous efficiency of the organic EL elements in Examples 6 and 7 was 10.34 to 10.49 cd / A, which was higher than that of the organic EL elements in Comparative Examples 1 and 2 (9.69 to 9.93 cd / A). In terms of power efficiency, the organic EL elements in Examples 6 and 7 were also more efficient, at 9.72 to 9.87 lm / W, compared to 8.96 to 9.18 lm / W for the organic EL elements in Comparative Examples 1 and 2. Furthermore, the element lifespan (95% decay) was significantly longer for the organic EL elements in Examples 6 and 7, at 383 to 456 hours, compared to 301 to 336 hours for the organic EL elements in Comparative Examples 1 and 2.

[0136] As is clear from the above results, arylamine compounds having a specific structure represented by general formula (1) exhibit greater hole mobility and superior electron blocking ability compared to conventional arylamine compounds used as hole transport materials. Furthermore, it was found that organic EL devices using both a second hole transport layer made of the arylamine compound and a blue light-emitting layer with a compound represented by general formula (2) or general formula (3) as a blue light-emitting dopant can realize organic EL devices with higher luminous efficiency and longer lifespan compared to conventional organic EL devices.

[0137] Although the present invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications are possible without departing from the spirit and scope of the invention. This application is based on a Japanese patent application (Patent Application No. 2020-185577) filed on November 6, 2020, which is incorporated by reference in its entirety. All references cited herein are incorporated as a whole. [Industrial applicability]

[0138] The organic EL element using an arylamine compound having a specific structure according to the present invention has improved luminous efficiency and durability, making it possible to apply it to applications such as home appliances and lighting. [Explanation of symbols]

[0139] 1. Glass substrate 2 transparent anode 3. Hole injection layer 4 First hole transport layer 5 Second hole transport layer 6. Emitting layer 7 Electron transport layer 8 Electron injection layer 9 Cathode 10 Capping Layers

Claims

1. An organic electroluminescent element having at least an anode, a first hole transport layer, a second hole transport layer, a blue light-emitting layer, an electron transport layer, and a cathode in this order, wherein the second hole transport layer contains an arylamine compound represented by the following general formula (1). 【Chemistry 1】 (In the formula, Ar １ and Ar ２ These may be identical or different from each other, and represent an aromatic hydrocarbon group substituted with or unsubstituted with an aromatic hydrocarbon group having 6 to 10 carbon atoms, or a condensed polycyclic aromatic group substituted with or unsubstituted with an aromatic hydrocarbon group having 6 to 10 carbon atoms. L １ and L ２ (This represents an unsubstituted 1,4-phenylene group.)

2. The organic electroluminescent element according to claim 1, wherein the blue light-emitting layer contains a pyrene derivative having a pyrene skeleton in its molecule as a blue light-emitting dopant.

3. An organic electroluminescent element having at least an anode, a first hole transport layer, a second hole transport layer, a blue light-emitting layer, an electron transport layer, and a cathode in this order, wherein the second hole transport layer contains an arylamine compound represented by the following general formula (1), 【Chemistry 2】 (In the formula, Ar １ and Ar ２ These may be identical or different from each other, and represent an aromatic hydrocarbon group substituted with or unsubstituted with an aromatic hydrocarbon group having 6 to 10 carbon atoms, or a condensed polycyclic aromatic group substituted with or unsubstituted with an aromatic hydrocarbon group having 6 to 10 carbon atoms. L １ and L ２ (This represents an unsubstituted 1,4-phenylene group.) An organic electroluminescent element wherein the blue light-emitting layer contains a compound represented by any of the following general formulas (4) to (7) as a blue light-emitting dopant. 【Transformation 5】 【Transformation 6】 【Transformation 7】 【Transformation 8】 (In general formulas (4) to (7), X represents B.) Y １ ~Y ４ may be the same as or different from each other, N-R ２ C-R ３ R ４ O, S, Se or Si-R ５ R ６ and is any one selected from among them, R ２ ~R ６ These may be identical or different from each other and represent a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a nitro group, a linear or branched alkyl group having 1 to 6 carbon atoms which may have substituents, a cycloalkyl group having 5 to 10 carbon atoms which may have substituents, a linear or branched alkenyl group having 2 to 6 carbon atoms which may have substituents, a linear or branched alkyloxy group having 1 to 6 carbon atoms which may have substituents, a cycloalkyloxy group having 5 to 10 carbon atoms which may have substituents, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted condensed polycyclic aromatic group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted aryloxy group. The substituents are selected from: deuterium atoms; cyano groups; nitro groups; halogen atoms; alkyl groups having 1 to 4 carbon atoms; linear or branched alkyloxy groups having 1 to 6 carbon atoms; alkenyl groups; aryloxy groups; arylalkyloxy groups; aromatic hydrocarbon groups or fused polycyclic aromatic groups; aromatic heterocyclic groups; disubstituted amino groups substituted with aromatic hydrocarbon groups or fused polycyclic aromatic groups; and disubstituted amino groups substituted with aromatic heterocyclic groups. Also, R ３ and R ４ , R ５ and R ６ These groups may be bonded to each other by single bonds, or via substituted or unsubstituted methylene groups, oxygen atoms or sulfur atoms, or monosubstituted amino groups to form a ring. However, Y １ ~Y ４ N-R ２ , C-R ３ R ４ , or Si-R ５ R ６ In the case of R ２ ~R ６ Each is an adjacent Q １ ~Q ３ They may also be bonded to each other via single bonds, substituted or unsubstituted methylene groups, oxygen atoms, sulfur atoms, or monosubstituted amino groups to form a ring. Z may be the same or different from each other, CR ７ or N, R ７ These may be the same or different from each other and represent a hydrogen atom, a deuterium atom, a halogen group, a cyano group, a nitro group, a linear or branched alkyl group having 1 to 6 carbon atoms which may have the substituent, a cycloalkyl group having 5 to 10 carbon atoms which may have the substituent, a linear or branched alkyloxy group having 1 to 6 carbon atoms which may have the substituent, a linear or branched alkylthiooxy group having 1 to 6 carbon atoms which may have the substituent, a linear or branched alkylamine group having 1 to 6 carbon atoms which may have the substituent, a linear or branched alkylsilyl group having 3 to 10 carbon atoms which may have the substituent, an aromatic hydrocarbon group substituted or unsubstituted with the substituent, an aromatic heterocyclic group substituted or unsubstituted with the substituent, an aryloxy group substituted or unsubstituted with the substituent, an arylthiooxy group substituted or unsubstituted with the substituent, an arylamine group substituted or unsubstituted with the substituent, or an arylsilyl group substituted or unsubstituted with the substituent. Also, R ７ These groups can bond to each other or to adjacent substituents to form aliphatic or aromatic single or polycyclic rings, and the carbon atoms of the aliphatic or aromatic single or polycyclic rings can be substituted with one or more heteroatoms selected from N, S, and O.

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