Organic electroluminescent element

Abstract

To provide an organic EL element that has high efficiency, a low drive voltage and high durability, and provides phosphorescent light emission, where a light-emitting layer contains a host and a dopant and the dopant includes a phosphorescent light-emitting material.SOLUTION: There is provided an organic electroluminescent element by combining an organic compound which has superior properties of superior injection / transport performance for electron hole, electron blocking capability, high stability in a thin film state, and high light emission efficiency and various materials for organic EL elements with superior durability such that the respective materials can effectively exhibit their properties.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an organic electroluminescence element suitable for various display devices, and more particularly to an organic electroluminescence element (hereinafter abbreviated as organic EL element) using a specific arylamine compound. [Background technology]

[0002] Organic EL elements are self-luminous elements, and therefore are brighter than liquid crystal elements, have excellent visibility, and are capable of producing clearer displays, so they have been the subject of vigorous research.

[0003] In 1987, C.W. Tang and his colleagues at Eastman Kodak Company made organic EL devices practical by developing a layered structure element in which various roles are assigned to each material. They layered a phosphor, tris(8-hydroxyquinoline)aluminum (hereafter abbreviated as Alq3), which can transport electrons, and an aromatic amine compound, which can transport holes, and emitted light by injecting both charges into the phosphor layer, achieving an OLED with a brightness of 1000cd / m at a voltage of 10V or less. 2 The above high brightness was obtained (for example, see Patent Documents 1 and 2).

[0004] To date, many improvements have been made to the practical application of organic EL elements, and various roles have been further subdivided to achieve high efficiency and durability by using electroluminescent elements having an anode, hole injection layer, hole transport layer, light-emitting layer, electron transport layer, electron injection layer, and cathode provided in that order on a substrate (see, for example, Non-Patent Document 1).

[0005] In addition, in order to further improve the luminous efficiency, the use of triplet excitons has been attempted, and the use of phosphorescent emitters has been considered (see, for example, Non-Patent Document 2). A highly efficient blue phosphorescent organic EL element has been proposed using a platinum complex as a phosphorescent luminescent material (see, for example, Patent Document 3).

[0006] By using a compound having a nitrogen-containing heteroaromatic ring structure with high electron transporting ability and a compound having a carbazole structure with hole transporting ability as a host together, the transportability of electrons and holes is increased and the luminous efficiency is significantly improved compared to when they are used alone (see, for example, Patent Document 4 and Patent Document 5). Furthermore, by combining with a platinum complex, a highly efficient blue phosphorescent organic EL device has been realized (see, for example, Non-Patent Document 3).

[0007] As a second hole transport material and a host material having a hole transport ability that have been used in recent phosphorescent organic EL devices, carbazole derivatives (eg, SiCzCz) shown in Non-Patent Document 3 have been proposed.

[0008] [ka]

[0009] This compound has a high triplet excitation energy (hereafter referred to as T1 level), but the molecular design to increase the T1 level limits pi-conjugation, resulting in low hole mobility. Therefore, when combined with an emitting layer with improved electron transport ability, the supply of holes to the emitting layer becomes rate-limiting, and there is a concern that the emitting layer may become electron-excessive.

[0010] It is known that in devices using this compound in the second hole transport layer, the device life is insufficient due to the increase in the driving voltage of the device and the bias of the excess of electrons in the light emitting layer, so a second hole transport material with high hole mobility and excellent durability against electrons is required. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Publication No. 8-048656 [Patent Document 2] Patent No. 3194657 [Patent Document 3] International Publication No. 2012 / 116231 [Patent Document 4] International Publication No. 2015 / 034125 [Patent Document 5] International Publication No. 2016 / 013732 [Patent Document 6] Patent No. 6715781 [Patent Document 7] International Publication No. 2014 / 009310 [Non-patent literature]

[0012] [Non-Patent Document 1] Proceedings of the 9th Workshop of the Japan Society of Applied Physics, pp. 55-61 (2001) [Non-Patent Document 2] Proceedings of the 9th Seminar of the Japan Society of Applied Physics, pp. 23-31 (2001) [Non-Patent Document 3] Nature Photonics16,212-218(2022) [Non-Patent Document 4] Science Advances.,Vol8,Issue 41(2022) Summary of the Invention [Problem to be solved by the invention]

[0013] The object of the present invention is to provide an organic EL device that exhibits phosphorescent emission with high efficiency, low driving voltage and high durability by combining an organic compound having excellent properties such as excellent hole injection / transport performance, electron blocking ability, high stability in a thin film state, and high luminous efficiency with various materials for organic EL devices that have excellent hole and electron injection / transport performance, electron blocking ability, stability in a thin film state, and durability, so that the properties of each material can be effectively exhibited. [Means for solving the problem]

[0014] The physical properties that the organic compound used in the organic EL device of the present invention should have include (1) good hole injection properties, (2) high hole mobility, (3) excellent electron blocking ability, (4) a stable thin film state, and (5) excellent heat resistance. The physical properties that the organic EL device to be provided by the present invention should have include (1) a low light emission start voltage, (2) a low practical driving voltage, and (3) a long life.

[0015] In order to achieve the above object, the present inventors focused on the fact that arylamine compounds having a specific structure are excellent in hole injection / transport capability, thin film stability, and durability, selected various arylamine compounds, prepared organic EL devices, and diligently evaluated the characteristics of the devices. As a result, the present inventors found that when an arylamine compound having a specific structure is selected as a material for the hole transport layer, holes injected from the anode side can be efficiently transported. Furthermore, various organic EL devices were prepared by combining light-emitting materials having specific structures, and diligently evaluated the characteristics of the devices. As a result, the present invention was completed.

[0016] That is, according to the present invention, the following organic electroluminescence device is provided.

[0017] 1) An organic electroluminescence device having at least an anode, a hole transport layer, a light emitting layer, an electron transport layer and a cathode in this order, characterized in that the hole transport layer contains an arylamine compound represented by the following general formula (1), the light emitting layer contains a host and a dopant, and the dopant contains a phosphorescent light emitting material.

[0018] [ka]

[0019] (Wherein, A is a substituted or unsubstituted phenyl group; a substituted or unsubstituted naphthyl group, a substituted or unsubstituted dibenzofuranyl group, a substituted or unsubstituted dibenzothienyl group, a substituted or unsubstituted phenanthryl group, or represents a substituted or unsubstituted biphenylyl group, B and C may be the same or different from each other; represents a divalent or trivalent naphthalene group, Ar 1 and Ar 2 may be the same or different from each other, deuterium-substituted or unsubstituted aromatic hydrocarbon groups; a deuterium-substituted or unsubstituted heterocyclic group, or represents a deuterium-substituted or unsubstituted condensed polycyclic hydrocarbon group, L 1 , L 2 and L 3 may be the same or different from each other, Single bond, a deuterium-substituted or unsubstituted divalent aromatic hydrocarbon group; a deuterium-substituted or unsubstituted divalent heterocyclic group, or It represents a deuterium-substituted or unsubstituted divalent condensed polycyclic hydrocarbon group. k 1 , k 2 represents an integer of 1 or 2, k 1 When is 2, there are multiple structures in the brackets Ar 1 may be the same or different, k 2 When is 2, there are multiple structures in the brackets Ar 2 may be the same or different.)

[0020] 2) The organic electroluminescence element according to 1) above, wherein the hole transport layer is represented by an arylamine compound represented by the following general formula (2):

[0021] [ka]

[0022] (In the formula, A and Ar 1 , Ar 2、 L 3、 k 1 and k 2 is defined as the same as in general formula (1).

[0023] 3) The organic electroluminescence device according to 2) above, wherein the hole transport layer is represented by an arylamine compound represented by the following general formula (3):

[0024] [ka]

[0025] (Ar in the formula 1 , Ar 2 , k 1 and k 2 is defined as the same as in general formula (1).

[0026] 4) In the general formula (3), Ar 1 and Ar 2 may be the same or different, and are represented by a deuterium-substituted or unsubstituted phenyl group, a deuterium-substituted or unsubstituted biphenylyl group, or a deuterium-substituted or unsubstituted naphthyl group.

[0027] 5) The organic electroluminescence element according to any one of 1) to 4), wherein the hole transport layer has a two or more layer structure including a first hole transport layer and a second hole transport layer, and the second hole transport layer contains an arylamine compound represented by the general formula (1).

[0028] 6) The organic electroluminescence element according to 1) above, characterized in that the host contains a first host compound having an electron transporting ability and a second host compound having a hole transporting ability, and is a compound having a hole transporting carbazole structure.

[0029] 7) The organic electroluminescence element according to 1) above, wherein the phosphorescent material is a platinum complex.

[0030] 8) The organic electroluminescence element according to 7) above, characterized in that the platinum complex contains at least one polydentate ligand that forms a five-membered chelate ring with platinum, the at least one polydentate ligand is a tetradentate ligand, and the five-membered chelate ring contains a carbene bond.

[0031] 9) The organic electroluminescence element according to 8) above, wherein the platinum complex is represented by the following general formula (4):

[0032] [ka]

[0033] (In the formula, L 4 and L 5 may be the same or different, and each represents a single bond, NR 5 , an oxygen atom, and a sulfur atom. n 1 is 0 or 1, n 2 represents 0 or 1, Z 1 and Z 2 may be the same or different and represent a nitrogen atom or a carbon atom, R 1 ~R 5 may be the same or different and represent a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted heterocyclic group, or a substituted or unsubstituted condensed polycyclic hydrocarbon group. L 4 and L 5 At least one of the following is NR 5 If R 5 and R 2 , R 5 and R 3 and R 5 and R4 may be bonded to each other to form a ring.)

[0034] 10) The organic electroluminescence element according to any one of 7) to 9) above, wherein the dopant contains a platinum complex as a phosphorescent material and an organoboron compound as a thermally activated delayed fluorescence (TADF) material.

[0035] 11) The arylamine compound represented by the general formula (1) has a hole mobility of 1.0x10 at an electric field strength of 0.25 MV / cm. -5 cm 2 3. The organic electroluminescence element according to claim 1, wherein the Vref is 1.0 V or more. Effect of the Invention

[0036] The arylamine compound of the present invention represented by the general formula (1) has the following characteristics: (1) good hole injection properties, (2) high hole mobility, (3) excellent electron blocking ability, (4) a stable thin film state, and (5) excellent heat resistance.

[0037] Furthermore, according to the present invention, by using an arylamine compound represented by general formula (1), which has a larger hole mobility than conventional hole transport materials, an excellent electron blocking ability, an excellent amorphous property, and a stable thin film state, it is possible to realize an organic EL device that exhibits phosphorescent emission, has high power efficiency, a low driving voltage, and a long life. [Brief description of the drawings]

[0038] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of an organic EL element having a hole transport layer with a two-layer structure. [Diagram 2] FIG. 1 is a diagram showing an example of the configuration of an organic EL element having a hole transport layer with a three-layer structure. [Diagram 3] FIG. 1 shows specific examples of the compound represented by general formula (1). [Figure 4] FIG. 1 shows specific examples of the compound represented by general formula (1). [Diagram 5] FIG. 1 shows specific examples of the compound represented by general formula (1). [Figure 6] FIG. 1 shows specific examples of the compound represented by general formula (1). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] <Organic EL element> The organic EL device of the present invention has at least an anode, a hole transport layer, an emitting layer, an electron transport layer and a cathode in this order. In the present invention, the hole transport layer contains an arylamine compound represented by the above general formula (1), the emitting layer contains a host and a dopant, and the dopant contains a phosphorescent emitting material.

[0040] As shown in FIG. 1, an organic EL device according to an embodiment of the present invention has a structure in which an anode 2, a hole transport layer 4, an emitting layer 5, an electron transport layer 7, and a cathode 9 are laminated in this order on a substrate 1. The organic EL device of the present invention may have a hole injection layer 3 between the anode and the hole transport layer, a hole blocking layer 6 between the emitting layer and the electron transport layer, or an electron injection layer 8 between the electron transport layer and the cathode. In these multilayer structures, some organic layers may be omitted or may serve as both layers. For example, it may be configured to serve as both a hole injection layer and a hole transport layer, or to serve as both an electron injection layer and an electron transport layer. It is also possible to have a structure in which two or more organic layers having the same function are laminated. FIG. 1 shows an example of a structure in which two hole transport layers are laminated, and a first hole transport layer 4a and a second hole transport layer 4b are laminated. As shown in FIG. 2, a third hole transport layer 4c may be further laminated on the second hole transport layer 4b, resulting in a three-layer structure of hole transport layers. However, the organic EL element of the present invention is not limited to the embodiment shown in Figures 1 and 2. As long as the organic EL element of the present invention has at least an anode, a hole transport layer, a light-emitting layer, an electron transport layer, and a cathode in the above order, it does not exclude an embodiment in which other layers are present between the layers.

[0041] <Substrate> The substrate is not particularly limited, and may be a glass substrate, a plastic substrate, or the like, and may be transparent or opaque. Examples of the substrate include plastic substrates such as polyethylene terephthalate, polyethylene naphthalate, polyethylene, polypropylene, cellophane, cellulose diacetate, cellulose triacetate, cellulose acetate butyrate, cellulose acetate propionate, cellulose acetate phthalate, cellulose nitrate, polyvinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol, syndiotactic polystyrene, polycarbonate, norbornene resin, polymethylpentene, polyether ketone, polyimide, polyether sulfone, polyphenylene sulfide, polysulfones, polyether imide, polyether ketone imide, polyamide, fluororesin, nylon, polymethyl methacrylate, acrylic or polyarylates, and organic-inorganic hybrid resins; inorganic substrates such as glass, quartz, aluminum oxide, silicon, silicon oxide, tantalum dioxide, tantalum pentoxide, and indium tin oxide; and metal substrates such as gold, copper, chromium, titanium, and aluminum. Among these, from the viewpoint of forming a transistor, a glass substrate and a polyimide substrate having excellent heat resistance are preferred.

[0042] <Electrode (anode / cathode)> The anode and cathode are not particularly limited as long as they are conductive materials generally used as electrodes, and metals, metal oxides, metal nitrides, metal borides, organic conductive compounds, mixtures thereof, etc. Specific examples of electrodes include conductive metal oxides such as tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO), indium zinc oxide (IZO), indium gallium zinc oxide (IGZO), indium tungsten oxide (IWO), molybdenum oxide (MoO), and titanium oxide, metal nitrides such as titanium oxide nitride (TiNxOx) and titanium nitride (TiN), metals such as gold (Au), platinum (Pt), silver (Ag), chromium (Cr), nickel (Ni), and aluminum (Al), mixtures or laminates of these metals and conductive metal oxides, alloys such as magnesium silver alloy, magnesium indium alloy, and aluminum magnesium alloy, organic conductive compounds such as polyaniline, polythiophene, and polypyrrole, and laminates of these and ITO, etc. Among these, from the viewpoint of work function, ITO or IGZO is preferable for the anode, and aluminum, magnesium silver alloy is preferable for the cathode.

[0043] <Hole injection layer> The hole injection layer can be made of a triarylamine compound represented by the general formula (1). In addition, known compounds such as porphyrin compounds represented by copper phthalocyanine, starburst triphenylamine derivatives, and arylamine compounds having two or more structures selected from triphenylamine structures or carbazolyl structures in the molecule, each of which is linked by a single bond or a divalent group not containing a heteroatom, can be used, and acceptor heterocyclic compounds such as hexacyanoazatriphenylene and coating-type polymer materials such as poly(3,4-ethylenedioxythiophene) (hereinafter abbreviated as PEDOT) / poly(styrenesulfonate) (hereinafter abbreviated as PSS) can also be used.

[0044] These compounds and materials may be used alone for film formation, or may be used in combination of a plurality of types. In the case of using a plurality of types for film formation in combination, one of the compounds may be P-doped trisbromophenylamine hexachloroantimony, radialene derivatives (see, for example, Patent Document 6), or a polymer compound having a benzidine derivative structure such as N,N'-diphenyl-N,N'-di(m-tolyl)-benzidine (hereinafter abbreviated as TPD) in its partial structure.

[0045] These compounds and materials can be used to form thin films by known methods such as vapor deposition, spin coating, and ink jet printing.

[0046] <Hole transport layer> In the organic EL device of the present invention, the hole transport layer contains an arylamine compound represented by the general formula (1). a substituted or unsubstituted phenyl group; a substituted or unsubstituted naphthyl group, a substituted or unsubstituted dibenzofuranyl group, a substituted or unsubstituted dibenzothienyl group, a substituted or unsubstituted phenanthryl group, or It represents a substituted or unsubstituted biphenylyl group.

[0047] Specific examples of the "substituent" in the substituted or unsubstituted phenyl group, substituted or unsubstituted naphthyl group, substituted or unsubstituted dibenzofuranyl group, substituted or unsubstituted dibenzothienyl group, substituted or unsubstituted phenanthryl group, or substituted or unsubstituted biphenylyl group represented by A in the general formula (1) include a deuterium atom, a cyano group, a nitro group; a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom; a silyl group such as a trimethylsilyl group or a triphenylsilyl group; a linear or branched alkyl group having 1 to 6 carbon atoms such as a methyl group, an ethyl group, or a propyl group; a linear or branched alkyloxy group having 1 to 6 carbon atoms such as a methyloxy group, an ethyloxy group, or a propyloxy group; an alkenyl group such as a vinyl group or an allyl group; an aryloxy group such as a phenyloxy group or a tolyloxy group; a benzyl Examples of the substituent include arylalkyloxy groups such as an oxy group or a phenethyloxy group; aromatic hydrocarbon groups or condensed polycyclic hydrocarbon groups such as a phenyl group, a biphenylyl group, a terphenylyl group, a naphthyl group, an anthryl group, a phenanthryl group, a fluorenyl group, a spirobifluorenyl group, an indenyl group, a pyrenyl group, a perylenyl group, a fluoranthenyl group, or a triphenylenyl group; and heterocyclic groups such as a pyridyl group, a pyrimidinyl group, a triazinyl group, a thienyl group, a furyl group, a pyrrolyl group, a quinolyl group, an isoquinolyl group, a benzofuranyl group, a benzothienyl group, an indolyl group, a carbazolyl group, a benzoxazolyl group, a benzothiazolyl group, a quinoxalinyl group, a benzimidazolyl group, a pyrazolyl group, a dibenzofuranyl group, a dibenzothienyl group, or a carbolinyl group. These substituents may be further substituted with the substituents exemplified above. In addition, a benzene ring substituted with these substituents, or a plurality of substituents substituted on the same benzene ring, may be bonded to each other via a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring.

[0048] In the present invention, A in general formula (1) is preferably a substituted or unsubstituted phenyl group or a substituted or unsubstituted phenanthryl group, and more preferably a phenyl group or a 9-phenanthryl group.

[0049] In formula (1), B and C may be the same or different and each represent a divalent or trivalent naphthalene group. In the present invention, B and C in general formula (1) are preferably a 1,2-naphthylene group or a 1,3-naphthylene group.

[0050] In general formula (1), Ar 1 and Ar 2 may be the same or different from each other, deuterium-substituted or unsubstituted aromatic hydrocarbon groups; a deuterium-substituted or unsubstituted heterocyclic group, or It represents a deuterium-substituted or unsubstituted condensed polycyclic hydrocarbon group.

[0051] Ar in general formula (1) 1 and Ar 2 Specific examples of the "aromatic hydrocarbon group", "heterocyclic group", or "condensed polycyclic hydrocarbon group" of the "aromatic hydrocarbon group", "heterocyclic group", or "condensed polycyclic hydrocarbon group" represented by the above formula (1) include a phenyl group, a biphenylyl group, a terphenyl group, a naphthyl group, an anthryl group, a phenanthryl group, an indenyl group, a pyrenyl group, a perylenyl group, a fluoranthenyl group, a triphenylenyl group, a fluorenyl group, a spirobifluorenyl group, a pyridyl group, a pyrimidinyl group, a triazinyl group, a furyl group, a pyrrolyl group, , thienyl group, quinolyl group, isoquinolyl group, benzofuranyl group, benzothienyl group, indolyl group, carbazolyl group, benzoxazolyl group, benzothiazolyl group, azafluorenyl group, diazafluorenyl group, azaspirobifluorenyl group, diazaspirobifluorenyl group, quinoxalinyl group, benzimidazolyl group, pyrazolyl group, dibenzofuranyl group, dibenzothienyl group, naphthyridinyl group, phenanthrolinyl group, acridinyl group, and carbolinyl group. The number of carbon atoms can be selected from aromatic hydrocarbon groups having 6 to 30 carbon atoms, and heterocyclic groups having 2 to 20 carbon atoms.

[0052] In the present invention, Ar in general formula (1) 1and Ar 2 is preferably a deuterium-substituted or unsubstituted aromatic hydrocarbon group or a deuterium-substituted or unsubstituted condensed polycyclic hydrocarbon group, and more preferably a phenyl group or a naphthyl group. In the present specification, a hydrogen atom ( 1 H) and deuterium atoms ( 2 Since hydrogen atoms are defined separately as hydrogen (H) and deuterium (D), deuterium atoms are not included in hydrogen atoms.

[0053] In general formula (1), L 1 , L 2 and L 3 may be the same or different from each other, Single bond, a deuterium-substituted or unsubstituted divalent aromatic hydrocarbon group; a deuterium-substituted or unsubstituted divalent aromatic heterocyclic group, or It represents a deuterium-substituted or unsubstituted divalent condensed polycyclic hydrocarbon group.

[0054] L in general formula (1) 1 , L 2 and L 3 The "aromatic hydrocarbon group", "heterocyclic group", or "condensed polycyclic hydrocarbon group" of the "divalent aromatic hydrocarbon group", "divalent heterocyclic group", or "divalent condensed polycyclic hydrocarbon group" represented by the above formula (1) is an aromatic hydrocarbon group, a heterocyclic group, or a condensed polycyclic hydrocarbon group, 1 and Ar 2 The term "divalent" refers to a monovalent aromatic hydrocarbon group or heterocyclic group from which one hydrogen atom has been removed. The number of carbon atoms can be selected from aromatic hydrocarbon groups having 6 to 30 carbon atoms, or heteroaryl groups having 2 to 20 carbon atoms. In the present invention, L in general formula (1) 1 and L 2is preferably represented by a "divalent aromatic hydrocarbon group", more preferably a phenylene group (divalent phenyl group), and further preferably a 1,4-phenylene group. 3 is preferably a single bond or a phenylene group (particularly a 1,4-phenylene group), and more preferably a single bond.

[0055] k in general formula (1) 1 , k 2 is k 1 , k 2 represents an integer of 1 or 2, k 1 When is 2, there are multiple structures in the brackets Ar 1 may be the same or different, k 2 When is 2, there are multiple structures in the brackets Ar 2 may be the same or different. 1 and k 2 is preferably 1.

[0056] In the present invention, general formula (1) is preferably represented by the above general formula (2), and more preferably represented by the above general formula (3).

[0057] Each symbol A and L in the general formula (2) 3 , Ar 1 , Ar 2 , k 1 and k 2 Each symbol A, L in the general formula (1) 3 , Ar 1 , Ar 2 , k 1 and k 2 This is the same definition as

[0058] Each symbol Ar represented in general formula (3) 1 , Ar 2 , k 1 and k 2 represents each symbol Ar 1 , Ar 2 , k1 and k 2 This is the same definition as

[0059] Among the arylamine compounds represented by the above general formula (1), specific examples of preferred compounds are shown in Figs. 3 to 6, but the present invention is not limited to these compounds. The arylamine compound represented by the above general formula (1) can be synthesized according to known methods (see, for example, Patent Document 6).

[0060] The arylamine compound represented by the general formula (1) can be purified by column chromatography, adsorption purification using silica gel, activated carbon, activated clay, etc., recrystallization using a solvent, crystallization, etc. The compound can be identified by NMR analysis. It is preferable to measure the glass transition temperature (Tg), HOMO level, and hole mobility (μh) as the physical property values ​​of the compound. The glass transition temperature (Tg) is an index of the stability of the thin film state. The HOMO level is an index of smooth exchange of holes between the adjacent first hole transport layer and the light emitting layer when the compound is used in the second hole transport layer. The hole mobility is an index of hole transport ability.

[0061] The glass transition temperature (Tg) can be determined by a high-sensitivity differential scanning calorimeter (DSC3100SA, manufactured by Bruker AXS) using a powder. From the viewpoint of application to a manufacturing process having a heating step and improvement of storage stability, the glass transition temperature (Tg) is preferably 100°C or higher, more preferably 110°C or higher.

[0062] The HOMO level can be determined by forming a 100 nm organic film on an ITO substrate by vacuum deposition and using an ionization potential measuring device (PYS-202, manufactured by Sumitomo Heavy Industries, Ltd.) The absolute value of the HOMO level is preferably within the range of 5.0 eV to 7.0 eV, more preferably within the range of 5.2 to 5.8 eV, from the viewpoint of the energy difference between the HOMO levels of the adjacent light-emitting layer and the first hole transport layer.

[0063] The hole mobility can be measured by forming an organic film of 3 to 4 μm on an ITO substrate by vacuum deposition and using a time-of-flight measurement device (TOF-401, manufactured by Optel). From the viewpoint of efficiently transporting holes generated in the photoelectric conversion layer to the anode, the hole mobility at an electric field strength of 0.25 MV / cm is set to 1.0 × 10 -6 (cm 2 / Vs) or more, and 1.0×10 -5 (cm 2 / Vs) or more, and more preferably 1.0×10 -4 (cm 2 / Vs) or more is more preferable. It may have a function of suppressing the diffusion of electrons present in the light-emitting layer to the outside of the light-emitting layer (to the hole-transporting layer side).

[0064] In addition to the arylamine compound represented by the general formula (1), the hole transport layer may also use a known compound having hole transport properties. Examples of known compounds having hole transport properties include benzidine derivatives such as TPD, NPD, N,N,N',N'-tetrabiphenylylbenzidine, 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC), arylamine compounds having two or more triphenylamine structures or carbazolyl structures in the molecule, each of which is linked by a single bond or a divalent group not containing a hetero atom, and carbazole derivatives having hole transport properties such as the above-mentioned SiCzCz. Coating-type polymer materials such as the above-mentioned PEDOT and PSS may also be used. These may be formed into a film alone, or may be formed by mixing a plurality of types, and each may be used as a single layer. The above-mentioned compounds or materials may be laminated together in a single layer, a layer formed by mixing a plurality of kinds of the compounds or materials, or a layer formed by mixing a plurality of kinds of the compounds or materials with a layer formed by mixing a plurality of the compounds or materials. These compounds and materials can be formed into a film by known methods such as a vapor deposition method, a spin coating method, an inkjet method, etc.

[0065] In addition to the compounds and materials that are usually used for the hole transport layer, trisbromophenylaminehexachloroantimony, radialene derivatives (see, for example, Patent Document 7) doped with P, and polymer compounds having a benzidine derivative structure such as TPD in their partial structure can be used.

[0066] Furthermore, in the present invention, the hole transport layer can have a two-layer structure of a first hole transport layer and a second hole transport layer. In the case of a two-layer structure, it is preferable that the arylamine compound represented by the general formula (1) is located on the light-emitting layer side and serves as the second hole transport layer. By forming the second hole transport layer located on the light-emitting layer side with the arylamine compound represented by the general formula (1), the electron blocking performance of the arylamine compound can be maximized, and an organic EL device exhibiting phosphorescence emission with a lower driving voltage and a longer life can be realized. In addition, in the present invention, when the hole transport layer has a three-layer structure of a first hole transport layer, a second hole transport layer, and a third hole transport layer, it is preferable to use the arylamine compound represented by the general formula (1) as an intermediate layer in the second hole transport layer.

[0067] Between the hole transport layer and the light emitting layer, an electron blocking layer (not shown) having a function of suppressing the diffusion of electrons present in the light emitting layer to the outside of the light emitting layer (the hole transport layer side) may be provided. Alternatively, a material having such a function may be used in the hole transport layer. In this case, in a two-layer or three-layer hole transport layer, it is preferable to use a material having such a function in the hole transport layer (the second hole transport layer or the third hole transport layer) located on the light emitting layer side.

[0068] <Light-emitting layer> The light-emitting layer includes a host and a dopant.

[0069] (host) In the present invention, the light-emitting layer contains one or more hosts, but preferably contains two or more hosts. Specifically, the light-emitting layer preferably contains at least a first host compound having an electron transporting ability and a second host compound having a hole transporting ability. The first host compound and the second host compound may each be used in one or more kinds. The mass ratio of the first host compound to the second host compound may be, for example, 1:10 to 10:1.

[0070] The first host compound is preferably a compound having a nitrogen-containing heteroaromatic ring structure (e.g., see Patent Document 4 and Patent Document 5), and the second host compound is preferably a compound having a carbazole ring structure (e.g., see Non-Patent Document 3).

[0071] The light-emitting layer may further contain one or more host compounds in addition to the first host compound and the second host compound.

[0072] (Dopant) The light-emitting layer contains one or more dopants, and at least one of the dopants is a phosphorescent light-emitting material (hereinafter also referred to as "phosphorescent light-emitting dopant"). That is, in the present invention, the dopant includes a phosphorescent light-emitting material. As the phosphorescent light-emitting material, a platinum complex is more preferable, and an organometallic compound containing Pt, Os, Ti, Zr, Hf, Eu, Tb, Tm, Fe, Co, Ni, Ru, Rh, Pd, or a combination thereof can be used. The dopant may be a blue, green, or red phosphorescent light-emitting dopant, and a high-performance organic EL device can be prepared.

[0073] The platinum complex is preferably a platinum complex containing one or more polydentate ligands forming a five-membered chelate ring with platinum, at least one of the polydentate ligands being a tetradentate ligand, and the five-membered chelate ring containing a carbene bond, and more preferably a platinum complex represented by the general formula (4). Here, the carbene bond is a bond between a five-membered chelate ring carbene and a platinum atom, and can also be said to be a structure in which a five-membered chelate ring carbene is coordinated to a platinum atom.

[0074] In general formula (4), L 4 and L 5 may be the same or different, and each represents a single bond, NR 5 , oxygen atom, and sulfur atom. In addition, in the general formula (4), n 1 is 0 or 1, n 2 represents 0 or 1. Z 1 and Z 2 may be the same or different and represent a nitrogen atom or a carbon atom. R 1 ~R 5 may be the same or different and represent a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted heterocyclic group, or a substituted or unsubstituted condensed polycyclic hydrocarbon group. L 4 and L 5 At least one of the following is NR 5 If R 5 and R 2 , R 5 and R 3 and R 5 and R 4 may be bonded to each other to form a ring.

[0075] R represented by general formula (4) 1 ~R 5 Specific examples of the "alkyl group" and "alkenyl group" include a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, s-butyl group, t-butyl group, n-pentyl group, isopentyl group, n-hexyl group, 2-ethylhexyl group, heptyl group, octyl group, isooctyl group, nonyl group, decyl group, vinyl group, 1-propenyl group, allyl group, 1-butenyl group, 2-butenyl group, 1-pentenyl group, 1-hexenyl group, isopropenyl group, isobutenyl group, and the like.

[0076] R represented by general formula (4) 1~R 5 The "aromatic hydrocarbon group", "heterocyclic group", or "condensed polycyclic hydrocarbon group" of the general formula (1) is Ar 1 and Ar 2 Examples of the aromatic hydrocarbon group include those similar to the "aromatic hydrocarbon group", "heterocyclic group", and "condensed polycyclic hydrocarbon group" represented by the above formulas.

[0077] R represented by general formula (4) 1 ~R 5 Examples of the "substituent" of the "substituted alkyl group", "substituted alkenyl group", "substituted aromatic hydrocarbon group", "substituted heterocyclic group", or "substituted fused polycyclic hydrocarbon group" in the above formula (1) include the same as the "substituent" in the substituted or unsubstituted phenyl group, substituted or unsubstituted naphthyl group, substituted or unsubstituted dibenzofuranyl group, substituted or unsubstituted dibenzothienyl group, substituted or unsubstituted phenanthryl group, or substituted or unsubstituted biphenylyl group represented by A in the general formula (1).

[0078] In the present invention, L represented by the general formula (4) 4 and L 5 may be the same or different, and each represents a single bond, NR 5 , oxygen and sulfur atoms. 4 is preferably an oxygen atom or a sulfur atom, and L 5 is NR 5 It is preferable that: In addition, in the general formula (4), n 1 represents 0 or 1, and n 2 represents 0 or 1. Z 1 and Z 2 may be the same or different and represent a nitrogen atom or a carbon atom. 1 ~R 5 may be the same or different, and each represents a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group. 4 and L 5 At least one of the following is NR5 If R 5 and R 2 , R 5 and R 3 , and R 5 and R 4 may be bonded to each other via a single bond, an oxygen atom, a sulfur atom, or a nitrogen atom to form a ring. R 1 ~R 5 As the aromatic hydrocarbon group, aromatic heterocyclic group, and condensed polycyclic aromatic group represented by the formula (1), Ar 1 Examples of the substituent that these may have include the same ones as those exemplified for the "substituent" in A in the general formula (1).

[0079] In the present invention, R represented by the general formula (4) 1 is preferably a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted heterocyclic group, or a substituted or unsubstituted condensed polycyclic hydrocarbon group, R 2 ~R 4 may be the same or different, and are preferably represented by a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted heterocyclic group, or a substituted or unsubstituted condensed polycyclic hydrocarbon group; R 5 is preferably represented by a substituted or unsubstituted alkyl group, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted heterocyclic group, or a substituted or unsubstituted condensed polycyclic hydrocarbon group.

[0080] The phosphorescent light-emitting dopant is preferably doped into the host in an amount ranging from 1 to 30 mass percent based on the entire light-emitting layer in order to avoid concentration quenching, and is preferably doped by co-evaporation.

[0081] In addition, a thermally activated delayed fluorescent (TADF) material may be used as a dopant together with the phosphorescent material. That is, in the present invention, the dopant preferably includes a phosphorescent material and a TADF material. Examples of the TADF material include triazine derivatives such as the following PIC-TRZ, CC2TA, and PBICT, phenoxazine derivatives such as the following PXZ-TRZ, carbazolyldicyanobenzene derivatives (CDCB derivatives) such as the following 4CzIPN and 4CzTPN-Me, and organic boron compounds utilizing the multiple resonance effect. Among these, organic boron compounds are preferable as the TADF material.

[0082] [ka]

[0083] [ka]

[0084] The organic boron compound is preferably a triaryl boron compound, and specific examples thereof include compounds represented by the following general formula (5).

[0085] [ka]

[0086] In the general formula (5), R a1 ~R a3 may be the same or different and each represents a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted amino group, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted heterocyclic group, or a substituted or unsubstituted condensed polycyclic hydrocarbon group; R b represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, or a substituted or unsubstituted aromatic hydrocarbon group.

[0087] Ra1 ~R a3 The alkyl group and the alkenyl group represented by the formula (4) are 1 The same can be mentioned for the substituents that these groups may have. a1 ~R a3 The substituted or unsubstituted amino group represented by the formula (I) is an unsubstituted amino group (-NH 2 ), mono-substituted amino groups having a substituent with 2 to 20 carbon atoms (e.g., ethylamino, acetylamino, phenylamino, and pyridylamino), and di-substituted amino groups (e.g., diethylamino, diphenylamino, acetylphenylamino, phenylpyridylamino, and carbazolyl). a1 ~R a3 As the aromatic hydrocarbon group, heterocyclic group, and condensed polycyclic hydrocarbon group represented by the formula (1), Ar 1 Examples of the substituent that these groups may have include the same ones as those exemplified for the "substituent" in A in the general formula (1).

[0088] R a1 ~R a3 is preferably a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted amino group, a substituted or unsubstituted aromatic hydrocarbon group, or a substituted or unsubstituted condensed polycyclic hydrocarbon group, and more preferably a hydrogen atom, a substituted or unsubstituted amino group, or a substituted or unsubstituted aromatic hydrocarbon group. b is preferably a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aromatic hydrocarbon group, and more preferably a substituted or unsubstituted aromatic hydrocarbon group.

[0089] Examples of the compound represented by the general formula (5) include the following DABNA and TBE02 (see, for example, Non-Patent Document 2). In addition, boron compounds such as the following ν-DABNA can also be used.

[0090] [ka]

[0091] The doping of the TADF material into the host is preferably in the range of 0.1 to 10 mass % relative to the entire light-emitting layer in order to avoid concentration quenching, and is preferably done by co-evaporation. These materials can be formed into thin films by known methods such as evaporation, spin coating, and inkjet printing.

[0092] <Hole blocking layer> A hole blocking layer can be provided between the light emitting layer and the electron transport layer. The hole blocking layer can be made of a known compound having a hole blocking effect. Examples of known compounds having a hole blocking effect include phenanthroline derivatives such as bathocuproine (hereinafter abbreviated as BCP), metal complexes of quinolinol derivatives such as aluminum (III) bis(2-methyl-8-quinolinato)-4-phenylphenolate (hereinafter abbreviated as BAlq), various rare earth complexes, oxazole derivatives, triazole derivatives, triazine derivatives, pyrimidine derivatives, oxadiazole derivatives, and benzoazole derivatives. These compounds may also serve as materials for the electron transport layer. These may be formed as films alone, or may be formed as films by mixing a plurality of types, and each may be used as a single layer. A laminated structure of layers formed by forming a film of the above compound alone, a laminated structure of layers formed by mixing a plurality of types, or a laminated structure of a layer formed by forming a film of the above compound alone and a layer formed by mixing a plurality of types may be used. These materials can be used to form thin films by known methods such as vapor deposition, spin coating, and ink jet printing.

[0093] <Electron transport layer> A known compound having electron transport properties can be used for the electron transport layer. Examples of known compounds having electron transport properties include metal complexes of quinolinol derivatives such as Alq3 and BAlq, various metal complexes, triazole derivatives, triazine derivatives, pyrimidine derivatives, oxadiazole derivatives, pyridine derivatives, benzimidazole derivatives, benzoazole derivatives, thiadiazole derivatives, anthracene derivatives, carbodiimide derivatives, quinoxaline derivatives, pyridoindole derivatives, phenanthroline derivatives, and silole derivatives. These may be formed into a film alone, or may be formed by mixing a plurality of types, and each may be used as a single layer. A laminated structure of layers formed by the above compounds alone, a laminated structure of layers formed by mixing a plurality of types, or a laminated structure of a layer formed by the above compounds alone and a layer formed by mixing a plurality of types. These materials can be formed into a film by known methods such as vapor deposition, spin coating, and inkjet.

[0094] <Electron injection layer> The electron injection layer can be made of alkali metal salts such as lithium fluoride and cesium fluoride, alkaline earth metal salts such as magnesium fluoride, metal complexes of quinolinol derivatives such as lithium quinolinol, metal oxides such as aluminum oxide, or metals such as ytterbium (Yb), samarium (Sm), calcium (Ca), strontium (Sr), cesium (Cs), etc. By selecting a preferred combination of the electron transport layer and the cathode, the electron injection layer can be omitted.

[0095] Furthermore, for the electron injection layer and the electron transport layer, materials obtained by doping a metal such as cesium with a material normally used for the layers can be used. The thickness of each of the layers constituting the organic EL element is not limited and can be appropriately selected. EXAMPLES

[0096] Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited to the following examples.

[0097] [Synthesis Example 1] <Synthesis of compound (1-4)> In a nitrogen-substituted reaction vessel, 10.0 g of N-phenyl-4-(phenylnaphthalene-3-yl)aniline, 9.3 g of 3-(4-chlorophenyl)-1-phenylnaphthalene, 5.2 g of t-butoxy sodium, 0.3 g of bis[tri(t-butylphosphine)]palladium(0), and 100 ml of toluene were added, and the mixture was stirred overnight under heating and reflux. After confirming the completion of the reaction, the filtrate obtained by filtration was concentrated to obtain a crude product. The obtained crude product was purified by crystallization using a dichloromethane / acetone mixed solvent, to obtain 14.4 g of compound (1-4) (yield: 82.3%). The structure of the obtained white powder was identified by NMR. 1 H-NMR (CDCl 3 ) the following 35 hydrogen signals were detected: δ(ppm)=8.05(2H), 7.95(2H), 7.90(2H), 7.71(2H), 7.67(4H), 7.65-7.49(10H), 7.47-7.40(4H), 7.31(2H), 7.26-7.21(6H), 7.08(1H).

[0098] [ka]

[0099] [Example 1] <Measurement of glass transition temperature> The glass transition temperatures of the compound (1-4) of the present invention having the following structure and SiCzCz having the following structure disclosed in Non-Patent Document 3 as a comparative compound were measured using a high-sensitivity differential scanning calorimeter (DSC3100SA, manufactured by Bruker AXS). The results of the measured glass transition temperatures are summarized in Table 1.

[0100] [ka]

[0101]

Table 1

[0102] From Table 1, it is shown that the compounds (1-4) of the present invention have a high glass transition temperature of 110 °C or higher, indicating that the thin film state is stable. By using the compounds (1-4) in an organic EL element, an element excellent in thermal stability can be fabricated.

[0103] [Example 2] <Measurement of HOMO level> The compounds (1-4) of the present invention, a comparative compound (SiCzCz), and BCFN having the following structure generally used as a first hole transport layer material (see, for example, Non-Patent Document 3) were each formed into a vapor deposition film with a thickness of 100 nm on an ITO substrate. The results of measuring the work function (corresponding to the absolute value of the HOMO level) by an ionization potential measuring device (Sumitomo Heavy Industries, Ltd., PYS-202) are summarized in Table 2.

[0104]

Chemical formula

[0105]

Table 2

[0106] From Table 2, it can be seen that the compounds (1-4) of the present invention have a smaller energy difference in the HOMO level from BCFN compared to the comparative compound (SiCzCz), indicating that they have an appropriate HOMO level from the viewpoint of hole transport.

[0107] [Example 3] <Measurement of T1 level> 2-Methyltetrahydrofuran (10 containing the compounds (1-4) of the present invention, a comparative compound (SiCzCz), and BCFN having the above structure generally used as a first hole transport layer material, respectively -5M) solutions were prepared and their phosphorescence spectra were measured using a spectrofluorophotometer (JASCO Corporation, FP-8500) at 77 K. The results of the T1 levels calculated from the rise of the phosphorescence spectra are summarized in Table 3.

[0108] [Table 3]

[0109] As can be seen from Table 3, the T1 level of compound (1-4) is smaller than those of SiCzCz and BCFN. However, by using a carbazole compound as a hole-transporting host in the light-emitting layer, the recombination region can be separated from the interface between the hole-transporting layer and the light-emitting layer, and the decrease in efficiency due to the low T1 level can be suppressed.

[0110] [Example 4] <Measurement of hole mobility> Using the compound (1-4) of the present invention and the comparative compound (SiCzCz), a film of the organic compound to be measured was formed to a thickness of 3 to 4 μm on a glass substrate with ITO by vacuum deposition. Subsequently, an aluminum film was formed to a thickness of about 100 nm to prepare a device for measuring hole mobility. This device was sealed in a nitrogen atmosphere with a glass cap to which a moisture getter sheet for organic electroluminescence was attached to prevent deterioration due to adsorption of moisture and oxygen.

[0111] The element was measured under the following conditions using a transient photocurrent measuring device, and the measured values ​​are shown in Table 4. (Measurement conditions) Equipment: Time-of-flight measurement device TOF-401 (Optel) Excitation light source: Nitrogen laser (337.1 nm) Light pulse width: 1nsec or less Measurement area: 0.04cm 2 Sample temperature: 25℃ Load resistance: 50Ω Electric field strength: 0.25MV / cm

[0112] [Table 4]

[0113] From Table 4, the hole mobility of compound (1-4) was observed to be 100 times higher than that of the comparative compound (SiCzCz). By using compound (1-4) in the second hole transport layer of an organic electroluminescence device, holes supplied from the first hole transport layer can be effectively transported to the light emitting layer, and the driving voltage can be improved.

[0114] [Example 5] <Evaluation of organic electroluminescence (two-layered hole transport layer)> As shown in FIG. 1, an organic EL element having a two-layer hole transport layer structure was fabricated by depositing a hole injection layer 3, a first hole transport layer 4a, a second hole transport layer 4b, an emitting layer 5, a hole blocking layer 6, an electron transport layer 7, an electron injection layer 8, and a cathode 9 in this order on a glass substrate 1 on which an ITO electrode was previously formed as a transparent anode 2.

[0115] Specifically, a glass substrate 1 on which an ITO film having a thickness of 150 nm was formed was subjected to ultrasonic cleaning in isopropyl alcohol for 20 minutes, and then dried on a hot plate heated to 200°C for 10 minutes. After that, UV ozone treatment was performed for 15 minutes, and the glass substrate with ITO was attached in a vacuum deposition machine and the pressure was reduced to 0.001 Pa or less. Next, an electron acceptor (Acceptor-1) having the following structural formula and a compound (BCFN) having the above structural formula were subjected to binary deposition at a deposition rate such that the deposition rate ratio was Acceptor-1: compound (BCFN) = 3:97 so as to cover the transparent anode 2, and a hole injection layer 3 was formed to a thickness of 10 nm. A compound (BCFN) having the following structural formula was formed on the hole injection layer 3 as a first hole transport layer 4 to a thickness of 55 nm. A compound (1-4) of the present invention was deposited on the first hole transport layer 4a as a second hole transport layer 4b to a thickness of 10 nm. On the second hole transport layer 4b, a hole transport host (SiCzCz) and an electron transport host (SiTrzCz) having the following structural formula are formed as the light emitting layer 5. 2), and the blue phosphorescent dopant (PtON-TBBI) with the following structure were deposited at a deposition rate ratio of SiCzCz:SiTrzCz 2 A three-component deposition was performed at a deposition rate of compound (ETM-1):PtON-TBBI=60:27:13 to form a film having a thickness of 30 nm. On this light-emitting layer 5, a compound (mSiTrz) having the following structural formula was formed as a hole-blocking layer 6 to a thickness of 5 nm. On the hole-blocking layer 6, a compound (ETM-1) having the following structural formula and a compound (ETM-2) having the following structural formula were deposited by two-component deposition at a deposition rate ratio of compound (ETM-1):compound (ETM-2)=50:50 to form an electron-transporting layer 7 to a thickness of 30 nm. On this electron-transporting layer 7, ETM-2 was formed as an electron-injecting layer 8 to a thickness of 1 nm. Finally, aluminum was deposited to a thickness of 100 nm to form a cathode 9, and an organic EL device was produced.

[0116] [ka]

[0117] [ka]

[0118] [Comparative Example 1] For comparison, an organic EL device was prepared under the same conditions as in Example 5, except that SiCzCz was used instead of compound (1-4) as the material for the second hole transport layer 4b.

[0119] [Comparative Example 2] For comparison, an organic EL device was prepared under the same conditions as in Example 5, except that BCFN was used instead of compound (1-4) as the material of the second hole transport layer 4b.

[0120] The organic EL devices prepared in Example 5 and Comparative Examples 1 and 2 were driven by a direct current to emit light in the atmosphere at room temperature, and the luminance was 1000 cd / m 2The driving voltage, power efficiency, and the lifetime until the luminance decreases to 95% (100% when the light emission starts) were measured. The measurement results are summarized in Table 5.

[0121] [Table 5]

[0122] As shown in Table 5, the brightness is 1000cd / m 2 The driving voltage at this time was 4.10 to 4.25 V for the organic EL elements of Comparative Examples 1 and 2, while the organic EL element of Example 5 had a low driving voltage of 3.81 V. In addition, the power efficiency was 13.5 to 15.3 lm / W for the organic EL elements of Comparative Examples 1 and 2, while the organic EL element of Example 5 had a high power efficiency of 16.3 lm / W. Furthermore, it can be seen that the element life was 39 to 50 hours for the organic EL elements of Comparative Examples 1 and 2, while the organic EL element of Example 5 had a long life of 58 hours. This result shows that the driving voltage can be significantly improved by the appropriate HOMO level and high hole mobility of the compound having a structure represented by the general formula (1) of the present invention.

[0123] [Example 6] <Evaluation of organic electroluminescence (three-layered hole transport layer)> As shown in FIG. 2, an ITO electrode was formed in advance as a transparent anode 2 on a glass substrate 1, and a hole injection layer 3, a first hole transport layer 4a, a second hole transport layer 4b, a third hole transport layer 4c, a light-emitting layer 5, a hole blocking layer 6, an electron transport layer 7, an electron injection layer 8, and a cathode 9 were deposited in this order on the ITO electrode. Thus, an organic EL device having a hole transport layer with a three-layer structure was fabricated.

[0124] Specifically, a glass substrate 1 on which an ITO film having a thickness of 150 nm was formed was subjected to ultrasonic cleaning in isopropyl alcohol for 20 minutes, and then dried on a hot plate heated to 200°C for 10 minutes. After that, a UV ozone treatment was performed for 15 minutes, and the glass substrate with ITO was attached in a vacuum deposition machine, and the pressure was reduced to 0.001 Pa or less. Next, a hole injection layer 3 was formed so as to cover the transparent anode 2 by performing binary deposition of an electron acceptor (Acceptor-1) having the following structural formula and a compound (BCFN) having the above structural formula at a deposition rate of a deposition rate ratio of Acceptor-1: compound (BCFN) = 3:97, so as to have a thickness of 10 nm. On this hole injection layer 3, a compound (BCFN) having the following structural formula was formed as a first hole transport layer 4 to a thickness of 55 nm. On this first hole transport layer 4a, a compound (1-4) of the present invention was deposited as a second hole transport layer 4b to a thickness of 5 nm. On the second hole transport layer 4b, a third hole transport layer 4c was formed by depositing SiCzCz to a thickness of 5 nm. On the third hole transport layer 4c, a hole transport host (SiCzCz) and an electron transport host (SiTrzCz 2 ), and blue phosphorescent dopant (PtON-TBBI) were deposited at a deposition rate ratio of SiCzCz:SiTrzCz 2 A 30-nm-thick light-emitting layer 5 was formed by ternary deposition at a deposition rate of 100:100:100:PtON-TBBI=60:27:13. A 5-nm-thick hole-blocking layer 6 was formed by deposition of compound (mSiTrz) on the light-emitting layer 5. A 30-nm-thick electron-transporting layer 7 was formed on the hole-blocking layer 6 by binary deposition of compound (ETM-1) and compound (ETM-2) on the hole-blocking layer 6 at a deposition rate ratio of compound (ETM-1):compound (ETM-2)=50:50. A 1-nm-thick electron-injecting layer 8 was formed by deposition of ETM-2 on the electron-transporting layer 7. Finally, 100-nm-thick aluminum was deposited to form a cathode 9, and an organic EL device was produced.

[0125] [Comparative Example 3] For comparison, an organic EL device was prepared under the same conditions as in Example 6, except that SiCzCz was used instead of compound (1-4) as the material for the second hole transport layer 4b.

[0126] [Comparative Example 4] For comparison, an organic EL device was prepared under the same conditions as in Example 6, except that BCFN was used as the material of the second hole transport layer 5 instead of the compound (1-4).

[0127] The organic EL devices prepared in Example 6 and Comparative Examples 3 and 4 were driven by a direct current to emit light in the atmosphere at room temperature, and the luminance was 1000 cd / m 2 The driving voltage, power efficiency, and the lifetime until the luminance decreases to 95% (100% when the light emission starts) were measured. The measurement results are summarized in Table 6.

[0128] [Table 6]

[0129] As shown in Table 6, the brightness is 1000cd / m 2 The driving voltage at this time was 4.03 V for the organic EL element of Example 6, which was a low driving voltage, compared to 4.11 to 4.25 V for the organic EL elements of Comparative Examples 3 and 4. The power efficiency was also high, 17.0 m / W for the organic EL element of Example 6, which was 15.3 to 16.0 m / W for the organic EL elements of Comparative Examples 3 and 4. Furthermore, it can be seen that the element life was 49 to 50 hours for the organic EL elements of Comparative Examples 3 and 4, and was 63 hours for the organic EL element of Example 6, which was longer. This result shows that even when the compound represented by the general formula (1) is used in the intermediate layer (second hole transport layer) in the hole transport layer having a three-layer structure, the driving voltage of the organic EL element can be significantly improved due to the appropriate HOMO level and high hole mobility of the compound.

[0130] [Example 7] <Evaluation of organic EL (phosphorescent dopant + TADF dopant)> As shown in Figure 1, an ITO electrode was previously formed as a transparent anode 2 on a glass substrate 1, and a hole injection layer 3, a first hole transport layer 4a, a second hole transport layer 4b, an emitting layer 5, a hole blocking layer 6, an electron transport layer 7, an electron injection layer 8, and a cathode 9 were sequentially evaporated on the ITO electrode as a transparent anode 2 on a glass substrate 1 to fabricate an organic EL device combining a phosphorescent emitting material and a TADF material.

[0131] Specifically, a glass substrate 1 on which an ITO film having a thickness of 150 nm was formed was subjected to ultrasonic cleaning in isopropyl alcohol for 20 minutes, and then dried on a hot plate heated to 200°C for 10 minutes. After that, a UV ozone treatment was performed for 15 minutes, and the glass substrate with ITO was attached in a vacuum deposition machine, and the pressure was reduced to 0.001 Pa or less. Next, a hole injection layer 3 was formed so as to cover the transparent anode 2 by performing binary deposition of an electron acceptor (Acceptor-1) having the following structural formula and a compound (BCFN) having the above structural formula at a deposition rate of a deposition rate ratio of Acceptor-1: compound (BCFN) = 3:97, so as to have a thickness of 10 nm. On this hole injection layer 3, a compound (BCFN) having the above structural formula was deposited as a first hole transport layer 4a to a thickness of 55 nm. On this first hole transport layer 4a, a compound (1-4) of the present invention was formed as a second hole transport layer 4b to a thickness of 10 nm. On the second hole transport layer 4b, a hole transport host (SiCzCz) and an electron transport host (SiTrzCz) are formed as the light emitting layer 5. 2 ), a blue phosphorescent dopant (PtON-TBBI), and a TADF dopant (TBE02) having the following structure disclosed in Non-Patent Document 4 were deposited at a deposition rate ratio of SiCzCz:SiTrzCz 2A quaternary deposition was performed at a deposition rate of :PtON-TBBI:TBE02=60:27:12:1 to form an emitting layer 5 with a thickness of 30 nm. On this emitting layer 5, a compound (mSiTrz) was deposited as a hole blocking layer 6 to a thickness of 5 nm. On the hole blocking layer 6, a compound (ETM-1) and a compound (ETM-2) were deposited at a deposition rate ratio of compound (ETM-1):compound (ETM-2)=50:50 to form an electron transport layer 7 with a thickness of 30 nm. On this electron transport layer 7, ETM-2 was formed as an electron injection layer 8 with a thickness of 1 nm. Finally, aluminum was deposited to a thickness of 100 nm to form a cathode 9, and an organic EL device was produced.

[0132] [ka]

[0133] [Comparative Example 5] An organic EL device was produced under the same conditions as in Example 7, except that as the material of the second hole transport layer 5, SiCzCz was used instead of the compound (1-4).

[0134] [Comparative Example 6] An organic EL device was produced under the same conditions as in Example 7, except that BCFN was used as the material for the second hole transport layer 5 instead of the compound (1-4).

[0135] The organic EL devices prepared in Example 7 and Comparative Examples 5 and 6 were driven by a direct current to emit light in the atmosphere at room temperature, and the luminance was 1000 cd / m 2 The driving voltage, power efficiency, and lifetime until the luminance decreases to 95% at 1000 Hz were measured. The measurement results are summarized in Table 7.

[0136] [Table 7]

[0137] As shown in Table 7, the brightness is 1000cd / m 2The driving voltage at this time was 3.95 V, which was a low driving voltage, for the organic EL element of Example 7, compared to 4.10 to 4.35 V for the organic EL elements of Comparative Examples 5 and 6. In addition, the power efficiency was also high, at 15.5 m / W, compared to 13.6 to 14.6 m / W for the organic EL elements of Comparative Examples 5 and 6. Furthermore, it can be seen that the element lifetime was 53 hours for the organic EL element of Example 7, which was longer than the 29 to 49 hours for the organic EL elements of Comparative Examples 5 and 6. Therefore, in the organic EL device of the present invention, in which the compound represented by general formula (1) of the present invention is used in the second hole transport layer and which has an emitting layer containing a phosphorescent emitting dopant and a TADF dopant, due to the appropriate HOMO level and high hole mobility, the organic EL device of the present invention can significantly improve the driving voltage compared to devices using conventional compounds, and can become a device with high power efficiency and long life.

[0138] From the above results, an organic EL element using the compound represented by the general formula (1) of the present invention in the second hole transport layer has a HOMO level required for hole transfer from the first hole transport layer, high heat resistance, and high hole mobility, so that an organic EL element with low driving voltage and long life can be produced. It was found that, compared with an organic EL element using a conventional material, by adopting the structure represented by the general formula (1), an organic EL element exhibiting phosphorescent emission can be realized that has excellent three characteristics, namely, a lower driving voltage, improved power efficiency, and a longer life. [Industrial Applicability]

[0139] Organic EL devices using arylamine compounds having specific structures can reduce the driving voltage and improve durability, and can be used in, for example, home appliances and lighting. [Explanation of symbols]

[0140] 1 Board 2 Anode 3. Hole injection layer 4. Hole transport layer 4a First hole transport layer 4b Second hole transport layer 4c Third hole transport layer 5. Light-emitting layer 6 Hole Blocking Layer 7 Electron transport layer 8 Electron injection layer 9 Cathode

Claims

1. The organic electroluminescence element has at least an anode, a hole transport layer, an emitting layer, an electron transport layer and a cathode in this order, characterized in that the hole transport layer contains an arylamine compound represented by the following general formula (1), the emitting layer contains a host and a dopant, and the dopant contains a phosphorescent emitting material. 【Chemistry 1】 (Wherein, A is a substituted or unsubstituted phenyl group; a substituted or unsubstituted naphthyl group, a substituted or unsubstituted dibenzofuranyl group, a substituted or unsubstituted dibenzothienyl group, a substituted or unsubstituted phenanthryl group, or represents a substituted or unsubstituted biphenylyl group, B and C may be the same or different from each other; represents a divalent or trivalent naphthalene group, Ar １ and Ar ２ may be the same or different from each other, deuterium-substituted or unsubstituted aromatic hydrocarbon groups; a deuterium-substituted or unsubstituted heterocyclic group, or represents a deuterium-substituted or unsubstituted condensed polycyclic hydrocarbon group, L １ , L ２ and L ３ may be the same or different from each other, Single bond, a deuterium-substituted or unsubstituted divalent aromatic hydrocarbon group, a deuterium-substituted or unsubstituted divalent aromatic heterocyclic group, or It represents a deuterium-substituted or unsubstituted divalent condensed polycyclic hydrocarbon group. k １ , k ２ represents an integer of 1 or 2, k １ When is 2, the structure Ar １ may be the same or different, k ２ When is 2, the structure Ar ２ may be the same or different.)

2. 2. The organic electroluminescence device according to claim 1, wherein the hole transport layer is represented by an arylamine compound represented by the following general formula (2): 【Chemistry 2】 (In the formula, A and Ar １ , Ar ２、 L ３、 k １ and k ２ The definition is the same as in general formula (1).

3. The organic electroluminescence device according to claim 2 , wherein the hole transport layer is represented by an arylamine compound represented by the following general formula (3): 【Chemistry 3】 (In the formula, Ar １ , Ar ２、 k １ and k ２ The definition is the same as in general formula (1).

4. In the general formula (3), Ar １ and Ar ２ 4. The organic electroluminescence device according to claim 3, wherein: may be the same or different and are represented by a deuterium-substituted or unsubstituted phenyl group, a deuterium-substituted or unsubstituted biphenylyl group, or a deuterium-substituted or unsubstituted naphthyl group.

5. The organic electroluminescence device according to any one of claims 1 to 4, characterized in that the hole transport layer has a two or more layer structure including a first hole transport layer and a second hole transport layer, and the second hole transport layer contains an arylamine compound represented by the general formula (1).

6. 2. The organic electroluminescence device according to claim 1, wherein the host contains a first host compound having an electron transporting ability and a second host compound having a hole transporting ability, and is a compound having a carbazole structure having a hole transporting ability.

7. 2. The organic electroluminescence device according to claim 1, wherein the phosphorescent material is a platinum complex.

8. 8. The organic electroluminescence device according to claim 7, wherein the platinum complex comprises at least one polydentate ligand that forms a five-membered chelate ring with platinum, the at least one polydentate ligand being a tetradentate ligand, and the five-membered chelate ring comprises a carbene bond.

9. 9. The organic electroluminescence device according to claim 8, wherein the platinum complex is represented by the following general formula (4): 【Chemistry 4】 (In the formula, L ４ and L ５ may be the same or different, a single bond, NR ５ , an oxygen atom, and a sulfur atom. n １ is 0 or 1, n ２ represents 0 or 1, Z １ and Z ２ may be the same or different and represent a nitrogen atom or a carbon atom, R １ ~R ５ may be the same or different and represent a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted heterocyclic group, or a substituted or unsubstituted condensed polycyclic hydrocarbon group. L ４ and L ５ At least one of the following is NR ５ If R ５ and R ２ , R ５ and R ３ and R ５ and R ４ may be bonded to each other to form a ring.)

10. The organic electroluminescence device according to any one of claims 7 to 9, wherein the dopant comprises a platinum complex as a phosphorescent light-emitting material and an organoboron compound as a thermally activated delayed fluorescence (TADF) material.

11. The arylamine compound represented by the general formula (1) has a hole mobility of 1.0×10 -５ cm ２ 2. The organic electroluminescence device according to claim 1, wherein the Vref is 1. / Vs or more.

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