Nitrogen-containing condensed fluorene compound, material for organic electroluminescent element, and organic electroluminescent element

Abstract

To provide a novel nitrogen-containing condensed fluorene compound which contribute to the fabrication of an organic electroluminescent element capable of lowering driving voltage; a material for an organic electroluminescent element comprising the nitrogen-containing condensed fluorene compound; and an organic electroluminescent element comprising the nitrogen-containing condensed fluorene compound.SOLUTION: The present invention provides a nitrogen-containing condensed fluorene compound having a specific structure represented by formula (1); a material for an organic electroluminescent element comprising the nitrogen-containing condensed fluorene compound; and an organic electroluminescent element comprising the nitrogen-containing condensed fluorene compound.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a nitrogen-containing condensed fluorene compound, a material for an organic electroluminescent device containing the nitrogen-containing condensed fluorene compound, and an organic electroluminescent device.

Background Art

[0002] Organic electroluminescent devices have begun to be put into practical use mainly for small mobile applications. However, for further expansion of applications, performance improvement is essential, and materials having high current efficiency, low driving voltage, high luminous efficiency characteristics, and long life characteristics are required. Patent Documents 1 and 2 disclose fluorene compounds which are materials for organic electroluminescent devices.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, it cannot be said that the organic electroluminescent devices using the fluorene compounds according to Patent Documents 1 and 2 sufficiently satisfy the driving voltage characteristics.

[0005] Therefore, one aspect of the present invention is directed to providing a new nitrogen-containing condensed fluorene compound that contributes to the formation of an organic electroluminescent device capable of reducing the driving voltage.

[0006] Furthermore, another aspect of the present invention is directed to providing an organic electroluminescent device with a reduced driving voltage.

Means for Solving the Problems

[0007] The nitrogen-containing condensed fluorene compound according to one aspect of the present invention is a nitrogen-containing condensed fluorene compound represented by formula (1):

[0008] The nitrogen-containing condensed fluorene compound represented by formula (1):

[0009] [Chemical formula]

[0010] In formula (1), Ring A represents a fluoranthene ring represented by formula (A-1) or an optionally substituted benzofluoranthene ring;

[0011] [Chemical formula]

[0012] R is each independently an optionally substituted alkyl group having 1 to 10 carbon atoms, or an optionally substituted monocyclic ring which may be linked, an optionally condensed ring which may be linked, or a structure in which these are linked, (i) an aromatic hydrocarbon group having 6 to 60 carbon atoms, (ii) a heteroaromatic group having 3 to 60 carbon atoms, (iii) an arylamino group having 6 to 60 carbon atoms, or (iv) a group composed of any combination of two or more selected from the above (i) to (iii); X each independently represents CH or a nitrogen atom; In formula (1), the number of nitrogen atoms represented by X is 2 to 4 *1 represents a condensation site; n is an integer from 0 to 6; Ring B is an optionally substituted monocyclic ring which may be linked, an optionally condensed ring which may be linked, or a structure in which these are linked, (i) an aromatic hydrocarbon group having 6 to 20 carbon atoms, or (ii) It represents a heteroaromatic group having 3 to 20 carbon atoms.

[0013] The organic electroluminescent device according to another aspect of the present invention is an anode, a cathode, and one or more organic thin film layers including at least a light emitting layer. At least one of the organic thin film layers contains the above nitrogen-containing condensed ring fluorene compound.

Advantages of the Invention

[0014] According to one aspect of the present invention, it is possible to provide a new nitrogen-containing condensed ring fluorene compound contributing to the formation of an organic electroluminescent device capable of reducing the driving voltage.

[0015] Also, according to another aspect of the present invention, it is possible to provide a material for an organic electroluminescent device containing the above nitrogen-containing condensed ring fluorene compound and an electron transport material for an organic electroluminescent device. Furthermore, according to another aspect of the present invention, it is possible to provide an organic electroluminescent device with a reduced driving voltage.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0017] Hereinafter, each aspect of the present invention will be described in detail. In this specification, the numerical range indicated by using "~" indicates a range including the numerical values described before and after "~" as the minimum value and the maximum value, respectively. Also, unless specifically specified, the units of the numerical values described before and after "~" are the same.

[0018] The nitrogen-containing condensed fluorene compound according to one aspect of the present invention is a nitrogen-containing condensed fluorene compound represented by the formula (1).

[0019] Nitrogen-containing condensed fluorene compound represented by the formula (1):

[0020] [Chemical formula]

[0021] In the formula (1), ring A represents a fluoranthene ring represented by the formula (A-1) or an optionally substituted benzofluoranthene ring;

[0022] [Chemical formula]

[0023] R is each independently an optionally substituted alkyl group having 1 to 10 carbon atoms, or an optionally substituted (i) aromatic hydrocarbon group having 6 to 60 carbon atoms, (ii) heteroaromatic group having 3 to 60 carbon atoms, (iii) arylamino group having 6 to 60 carbon atoms, or (iv) a group composed of any combination of two or more selected from the above (i) to (iii), X each independently represents CH or a nitrogen atom; In the formula (1), the number of nitrogen atoms represented by X is 2 to 4 *1 represents a condensation site; n is an integer of 0 to 6; Ring B is an optionally substituted (i) aromatic hydrocarbon group having 6 to 20 carbon atoms, or (ii) heteroaromatic group having 3 to 20 carbon atoms. [Regarding Ring A] Ring A represents a fluoranthene ring represented by formula (A-1) or an optionally substituted benzofluoranthene ring.

[0024] [Chemical formula]

[0025] The optionally substituted benzofluoranthene ring, which is one embodiment of Ring A, is preferably represented by formula (A-2).

[0026] [Chemical formula]

[0027] In formula (A-2), any two adjacent carbon atoms among the carbon atoms constituting the benzofluoranthene ring that do not have a substituent serve as the condensation sites.

[0028] In terms of increasing the glass transition temperature, Ring A is preferably represented by formula (A-2). [Regarding R] R is each independently an optionally substituted alkyl group having 1 to 10 carbon atoms, or an optionally substituted (i) aromatic hydrocarbon group having 6 to 60 carbon atoms, (ii) heteroaromatic group having 3 to 60 carbon atoms, (iii) arylamino group having 6 to 60 carbon atoms, or (iv) a group composed of any combination of two or more selected from the above (i) to (iii).

[0029] Specific examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, or a branched or cyclic Examples include a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an adamantyl group, and the like.

[0030] Specific examples of the aryl group having 6 to 60 carbon atoms include a phenyl group, a naphthyl group, a phenanthryl group, an anthryl group, a pyrenyl group, a perylenyl group, a fluorenyl group, a dimethylfluorenyl group, a diphenylfluorenyl group, a triphenylenyl group, a fluoranthenyl group, a benzofluoranthenyl group, a chrysenyl group, a dibenzochrysenyl group, a dinaphthochrysenyl group, and the like.

[0031] Specific examples of the heteroaryl group having 3 to 60 carbon atoms include a pyridyl group, a pyrimidyl group, a pyrazyl group, a triazinyl group, a quinolyl group, an isoquinolyl group, a naphthyridinyl group, an acridinyl group, a phenanthrolinyl group, a phenanthridinyl group, a pyrrolyl group, an indolyl group, an indolizinyl group, a carbazolyl group, a carbolinyl group, a benzocarbazolyl group, a benzocarbolinyl group, a furanyl group, a benzofuranyl group, a dibenzofuranyl group, a xanthenyl group, a spiroxanthenyl group, a benzoxanthenyl group, a thienyl group, a benzothienyl group, a dibenzothienyl group, an oxazolyl group, a benzoxazolyl group, a thiazolyl group, a benzothiazolyl group, and the like.

[0032] Specific examples of the arylamino group having 6 to 60 carbon atoms include a phenylamino group, a diphenylamino group, a biphenylylamino group, a dibiphenylylamino group, a naphthylamino group, a dinaphthylamino group, and the like. [Regarding Ring B] Ring B is an optionally substituted monocyclic ring which may be linked, a condensed ring which may be linked, or a structure in which these are linked. (i) an aromatic hydrocarbon group having 6 to 20 carbon atoms, or (ii) a heteroaromatic group having 3 to 20 carbon atoms.

[0033] Specific examples of the aromatic hydrocarbon group having 6 to 20 carbon atoms include a phenyl group, a naphthyl group, a phenanthryl group, an anthryl group, a pyrenyl group, a perylenyl group, a fluorenyl group, a dimethylfluorenyl group, a diphenylfluorenyl group, a triphenylenyl group, a fluoranthenyl group, and the like.

[0034] Specific examples of the heteroaromatic group having 3 to 20 carbon atoms include a pyridyl group, a pyrimidyl group, a pyrazyl group, a triazinyl group, a quinolyl group, an isoquinolyl group, a naphthyridinyl group, an acridinyl group, a phenanthrolinyl group, a phenanthridinyl group, a pyrrolyl group, an indolyl group, an indolizinyl group, a carbazolyl group, a carbolinyl group, a benzocarbazolyl group, a benzocarbolinyl group, a furanyl group, a benzofuranyl group, a dibenzofuranyl group, a xanthenyl group, a spiroxanthenyl group, a benzoxanthenyl group, a thienyl group, a benzothienyl group, a dibenzothienyl group, an oxazolyl group, a benzoxazolyl group, a thiazolyl group, a benzothiazolyl group, and the like.

[0035] Ring B is preferably a phenyl group, a naphthyl group, a fluorenyl group, a triphenylenyl group, a pyridyl group, a pyrimidyl group, a pyrazyl group, a triazinyl group, a quinolyl group, or an isoquinolyl group in terms of improving the driving voltage characteristics, and more preferably a phenyl group, a naphthyl group, a pyridyl group, a triazinyl group, a quinolyl group, or an isoquinolyl group. [Regarding substituents] Each group represented by Ring A, Ring B, and R may be substituted with one or more substituents selected from the group consisting of deuterium, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a formyl group, a cyano group, a nitro group, an alkyl group having 1 to 20 carbon atoms which may be branched or cyclized, an alkenyl group having 2 to 20 carbon atoms which may be branched or cyclized, an alkynyl group which may be branched or cyclized, an alkoxy group having 1 to 20 carbon atoms, an aromatic hydrocarbon group having 6 to 20 carbon atoms which may be monocyclic or linked, a heteroaromatic group having 3 to 20 carbon atoms which may be monocyclic or linked, P(=O)(R')2, C(=O)R', B(R')2, B(OR')2, OSO2R', and Si(R')4.

[0036] R' is the same or different each time it appears and is composed of a group consisting of an alkyl group having 1 to 10 carbon atoms, an aromatic hydrocarbon group having 6 to 60 carbon atoms, and a heteroaromatic group having 3 to 60 carbon atoms.

[0037] Hereinafter, specific examples of the nitrogen-containing condensed-ring fluorene compound will be shown. Note that the present invention is not limited thereto.

[0038]

Chemical formula

[0039]

Chemical formula

[0040] The nitrogen-containing condensed-ring fluorene compound can be used, for example, in applications of organic electronic devices such as organic electroluminescent devices and optoelectronic devices. <Material for organic electroluminescent device> The material for an organic electroluminescent device according to one aspect of the present invention contains a nitrogen-containing condensed-ring fluorene compound.

[0041] The nitrogen-containing condensed-ring fluorene compound can be used, for example, as an electron transport material for an organic electroluminescent device. <Organic electroluminescent device> Hereinafter, an organic electroluminescent device according to one aspect of the present invention (hereinafter, may be simply referred to as an organic electroluminescent device) will be described.

[0042] The organic electroluminescent device according to one aspect of the present invention contains a nitrogen-containing condensed-ring fluorene compound.

[0043] The configuration of the organic electroluminescent device is not particularly limited, and examples thereof include the configurations of (i) to (vii) shown below.

[0044] (i): Anode / Light-emitting layer / Cathode (ii): Anode / Hole transport layer / Light-emitting layer / Cathode (iii): Anode / Light-emitting layer / Electron transport layer / Cathode (iv): Anode / Hole Transport Layer / Light Emitting Layer / Electron Transport Layer / Cathode (v): Anode / Hole Injection Layer / Hole Transport Layer / Light Emitting Layer / Electron Transport Layer / Electron Injection Layer / Cathode (vi): Anode / Hole Injection Layer / Hole Transport Layer / Electron Blocking Layer / Light Emitting Layer / Hole Blocking Layer / Electron Transport Layer / Electron Injection Layer / Cathode (vii): Anode / Hole Injection Layer / First Hole Transport Layer / Second Hole Transport Layer / Light Emitting Layer / First Electron Transport / Second Electron Transport Layer / Cathode The nitrogen-containing condensed ring fluorene compound may be contained in any of the above layers, but is preferably contained in at least one layer selected from the group consisting of the light emitting layer and the layers between the light emitting layer and the cathode in terms of excellent light emitting characteristics of the organic electroluminescent device. Therefore, in the case of the configurations shown in the above (i) to (vi), the pyrimidine compound is preferably contained in at least one layer selected from the group consisting of the light emitting layer, the electron transport layer, and the electron injection layer.

[0045] Hereinafter, the organic electroluminescent device according to one embodiment of the present invention will be described in more detail with reference to FIG. 1 by taking the configuration of the above (v) as an example.

[0046] Note that the organic electroluminescent device shown in FIG. 1 has a so-called bottom emission type device configuration, but the organic electroluminescent device according to one embodiment of the present invention is not limited to the bottom emission type device configuration. That is, the organic electroluminescent device according to one embodiment of the present invention may have another known device configuration such as a top emission type.

[0047] FIG. 1 is a schematic cross-sectional view showing an example of the stacked structure of the organic electroluminescent device according to one embodiment of the present invention.

[0048] The organic electroluminescent element 100 includes a substrate 1, an anode 2, a hole injection layer 3, a hole transport layer 4, a light-emitting layer 5, an electron transport layer 6, an electron injection layer 7, and a cathode 8 in this order. However, some of these layers may be omitted, and conversely, other layers may be added. For example, a hole blocking layer may be provided between the light-emitting layer 5 and the electron transport layer 6, the hole injection layer 3 may be omitted, and the hole transport layer 4 may be directly provided on the anode 2.

[0049] Also, for example, a single layer having functions of a plurality of layers, such as an electron injection / transport layer having functions of an electron injection layer and an electron transport layer in a single layer, may be provided instead of the plurality of layers. Further, for example, a single-layer hole transport layer 4 and a single-layer electron transport layer 6 may each be composed of a plurality of layers. <Layer containing a nitrogen-containing condensed-ring fluorene compound> In the configuration example shown in FIG. 1, the organic electroluminescent element 100 contains the above nitrogen-containing condensed-ring fluorene compound in at least one layer selected from the group consisting of the light-emitting layer 5, the electron transport layer 6, and the electron injection layer 7. In particular, it is preferable that the electron transport layer 6 contains a nitrogen-containing condensed-ring fluorene compound. The nitrogen-containing condensed-ring fluorene compound may be contained in a plurality of layers included in the organic electroluminescent element.

[0050] Hereinafter, the organic electroluminescent element 100 in which the electron transport layer 6 contains a nitrogen-containing condensed-ring fluorene compound will be described. [Substrate 1] The substrate 1 is not particularly limited, and a substrate that can be used for a normal organic electroluminescent element can be used. For example, a glass plate, a quartz plate, a plastic plate, etc. may be mentioned. [Anode 2] The anode 2 is provided on the substrate 1 (on the hole injection layer 3 side).

[0051] As the material of the anode, compounds that can be used in ordinary organic electroluminescent elements can be used. For example, metals, alloys, electrically conductive compounds, and mixtures thereof having a large work function (e.g., 4 eV or more) can be mentioned. Specific examples of the anode material include metals such as Au; and conductive transparent materials such as CuI, indium tin oxide (ITO), SnO2, and ZnO. [Hole injection layer 3, hole transport layer 4] Between the anode 2 and the light-emitting layer 5 described later, a hole injection layer 3 and a hole transport layer 4 are provided in this order from the anode 2 side.

[0052] As the materials of the hole injection layer and the hole transport layer, those having at least any one of hole injection property, hole transport property, and electron barrier property are used. The materials of the hole injection layer and the hole transport layer may be either organic or inorganic, and compounds that can be used in ordinary organic electroluminescent elements can be used.

[0053] The hole injection layer and the hole transport layer may have a single structure composed of one or more materials, or may have a laminated structure composed of a plurality of layers of the same composition or different compositions.

[0054] The hole transport layer 4 may have a laminated structure of two or more layers, and is provided in the order of the first hole transport layer 41 and the second hole transport layer 42 from the anode 2 side, and this second hole transport layer 42 can be used as the electron blocking layer in the above configuration (vi). [Light-emitting layer 5] A light-emitting layer 5 is provided between the hole transport layer 4 and the electron transport layer 6 described later.

[0055] As the material of the light-emitting layer, light-emitting materials that can be used in ordinary organic electroluminescent elements can be used. For example, phosphorescent materials, fluorescent materials, and thermally activated delayed fluorescent materials can be mentioned.

[0056] The light-emitting layer may be composed of a single low-molecular material or a single polymer material, but more commonly, it is composed of a host material doped with a guest compound. The light emission mainly occurs from the dopant and can have any color.

[0057] Also, the light-emitting material is not limited to being contained only in the light-emitting layer. For example, the light-emitting material may be contained in a layer adjacent to the light-emitting layer (the hole transport layer 4 or the electron transport layer 6). This can further improve the light emission efficiency of the organic electroluminescent element.

[0058] The light-emitting layer may have a single-layer structure composed of one or more materials, or may have a laminated structure composed of a plurality of layers of the same composition or different compositions. [Electron transport layer 6] An electron transport layer 6 is provided between the light-emitting layer 5 and the electron injection layer 7 described later.

[0059] The electron transport layer preferably contains a nitrogen-containing condensed-ring fluorene compound. Also, the electron transport layer may contain one or more selected from conventionally known electron transport materials in addition to the pyrimidine compound.

[0060] In addition, when the nitrogen-containing condensed-ring fluorene compound is not contained in the electron transport layer but is contained in other layers, one or more selected from conventionally known electron transport materials can be used as the electron transport material constituting the electron transport layer.

[0061] Examples of conventionally known electron transporting materials include alkali metal complexes, alkaline earth metal complexes, and rare earth metal complexes. Examples of alkali metal complexes, alkaline earth metal complexes, and rare earth metal complexes include lithium 8-hydroxyquinolinate (Liq), zinc bis(8-hydroxyquinolinate), copper bis(8-hydroxyquinolinate), manganese bis(8-hydroxyquinolinate), aluminum tris(8-hydroxyquinolinate), aluminum tris(2-methyl-8-hydroxyquinolinate), gallium tris(8-hydroxyquinolinate), beryllium bis(10-hydroxybenzo[h]quinolinate), zinc bis(10-hydroxybenzo[h]quinolinate), gallium bis(2-methyl-8-quinolinato)chloride, gallium bis(2-methyl-8-quinolinato)(o-cresolato), aluminum bis(2-methyl-8-quinolinato)-1-naphtholate, gallium bis(2-methyl-8-quinolinato)-2-naphtholate, and the like.

[0062] The electron transport layer may have a single-layer structure composed of one or more materials, or may have a laminated structure composed of a plurality of layers of the same composition or different compositions.

[0063] In the organic electroluminescent device according to this aspect, an electron injection layer may be provided for the purpose of improving electron injectability and improving device characteristics (for example, luminous efficiency, low voltage driving, or high durability).

[0064] The electron transport layer 6 may have a laminated structure of two or more layers, and may be provided in the order of the first electron transport layer 61 and the second electron transport layer 62 from the light-emitting layer 5 side, and this first electron transport layer 61 can be used as a hole blocking layer in the above configuration (vi).

[0065] The nitrogen-containing condensed ring fluorene compound according to one aspect of the present invention can be used in both or either of the first electron transport layer and the second electron transport layer. [Electron injection layer 7] An electron injection layer 7 is provided between the electron transport layer 6 and the cathode 8 described later.

[0066] As the material of the electron injection layer, compounds that can be used in ordinary organic electroluminescent elements can be used. For example, organic compounds such as fluorenone, anthraquinodimethane, diphenoquinone, thiopyrandioxide, oxazole, oxadiazole, triazole, imidazole, perylenetetracarboxylic acid, fluorenylidenemethane, anthraquinodimethane, and anthrone can be mentioned.

[0067] In addition, as the material of the electron injection layer, various inorganic compounds such as oxides, fluorides, nitrides, and oxynitrides such as SiO2, AlO, SiN, SiON, AlON, GeO, LiO, LiON, TiO, TiON, TaO, TaON, TaN, LiF, C, and Yb can also be mentioned. The nitrogen-containing condensed ring fluorene compound of the present invention can also be used. [Cathode 8] A cathode 8 is provided on the electron injection layer 7.

[0068] As the material of the cathode, compounds that can be used in ordinary organic electroluminescent elements can be used. For example, metals with a small work function (hereinafter also referred to as electron injection metals), alloys, electrically conductive compounds, and mixtures thereof can be mentioned. Here, the metal with a small work function is, for example, a metal of 4 eV or less.

[0069] Mixtures of an electron injection metal and a second metal that is a metal with a larger and more stable work function value than this, such as a magnesium / silver mixture, a magnesium / aluminum mixture, a magnesium / indium mixture, an aluminum / aluminum oxide (Al2O3) mixture, a lithium / aluminum mixture, etc. are preferable. [Method for forming each layer] Each layer other than the electrodes (anode, cathode) described above can be formed by thinning it by a known method such as a vacuum evaporation method, a spin coating method, a casting method, or an LB (Langmuir-Blodgett method). The material of each layer may be used alone, or may be used together with a material such as a binder resin and a solvent as necessary.

[0070] There is no particular limitation on the film thickness of each layer formed in this way, and it can be appropriately selected according to the situation. Usually, it is in the range of 5 nm to 5 μm.

[0071] The anode and the cathode can be formed by thinning the electrode material by methods such as vapor deposition or sputtering. A pattern may be formed through a mask of a desired shape during vapor deposition or sputtering, or after forming a thin film by vapor deposition, sputtering, etc., a pattern of a desired shape may be formed by photolithography.

[0072] The film thickness of the anode and the cathode is preferably 1 μm or less, and more preferably 10 nm or more and 200 nm or less.

[0073] In addition, when forming a layer containing a nitrogen-containing condensed ring fluorene compound, it may be used in combination with the above-mentioned conventionally known electron transporting material. Therefore, for example, a nitrogen-containing condensed ring fluorene compound and a conventionally known electron transporting material may be co-evaporated, or a layer of a conventionally known electron transporting material may be laminated on the layer of the nitrogen-containing condensed ring fluorene compound.

[0074] The organic electroluminescent element may be used as a kind of lamp such as for lighting or an exposure light source, or as a projection device of a type that projects an image onto a screen or the like, or a display device (display) of a type that directly visually recognizes a still image or a moving image.

[0075] When using an organic electroluminescent element as a display device for video playback, the driving method may be a simple matrix (passive matrix) method or an active matrix method. In addition, by using two or more organic electroluminescent elements having different emission colors, it is possible to fabricate a full-color display device.

Examples

[0076] Hereinafter, the present disclosure will be described in more detail based on examples, but the present disclosure is not to be construed as being limited in any way by these examples.

[0077] 1 The measurement of the 1H-NMR spectrum was carried out using Gemini 200 (manufactured by Varian) or Bruker ASCEND 400 (400 MHz; manufactured by BRUKER).

[0078] The measurement of the glass transition temperature, crystallization temperature and melting point was carried out using DSC7020 (manufactured by Hitachi High-Tech Sciences Corporation, product name).

[0079] The measurement conditions of DSC are as follows. The measurement was carried out under a nitrogen atmosphere (flow rate: 50 mL / min). Also, the measurements were performed in the order of first heating, first cooling, and second heating, and the glass transition temperature, crystallization temperature and melting point during the second heating were taken as the glass transition temperature, crystallization temperature and melting point of the sample, respectively.

[0080] Sample amount: 5 - 10 mg Measurement conditions: <First heating> Heating rate: 15°C / min Measurement temperature range: 30°C to 360°C <First cooling> Quick cooling with dry ice <Second heating> Heating rate: 5°C / min Measurement temperature range: 30°C to 360°C The light-emitting characteristics of the organic electroluminescent device were evaluated at room temperature by applying a direct current to the fabricated device and using a luminance meter (product name: BM-9, manufactured by Topcon Techno House Co., Ltd.). Synthesis Example - 1 (Synthesis of E13)

[0081] [Chemical formula]

[0082] Under an argon atmosphere, 5-[2-(benzo[b]fluoranthen-7-yl)phenyl],5-hydroxy-5H-cyclopenta[2,1-b:3,4-b]dipyridine (3.30 g, 6.07 mmol) was suspended in ortho-dichlorobenzene (120 mL) and methanesulfonic acid (60 mL), and stirred at 120 °C for 1 hour. After cooling to 0 °C, water and toluene were added, and the organic layer was separated by liquid extraction. The obtained organic layer was concentrated and purified by column chromatography to obtain the target compound (yield 1.12 g, yield 37%). The glass transition temperature was 155 °C. 1H-NMR(400MHz,CDCl3):9.05(s,1H),8.85(d,J=8.0Hz,1H),8.78(dd,J=1.6Hz,4.4Hz,1H),8.74(d,J=16.8Hz,1H),8.56(d,J=8.4Hz,1H),8.28(brd,J=8.0Hz,1H),8.01(d,J=7.6Hz,1H),7.73-7.83(m,4H),7.66(ddd,J=14.8Hz,14.8Hz,0.8Hz,1H),7.29(ddd,J=14.8Hz,14.8Hz,2.0Hz,1H),7.22-7.24(m,2H),7.14-7.17(m,2H),6.86(d,J=7.6Hz,1H).6.79(d,J=7.6Hz,1H). The structural formulas and their abbreviations of the compounds used for the fabrication and performance evaluation of the organic electroluminescent device are shown below.

[0083]

Chemical formula

[0084] Device Example-1 (see Figure 2) (Preparation of Substrate 101 and Anode 102) As a substrate having an anode on its surface, a glass substrate with an indium tin oxide (ITO) transparent electrode patterned in a stripe shape with a 2 mm-wide ITO film (film thickness 110 nm) was prepared. Then, this substrate was washed with isopropyl alcohol and surface-treated by ozone ultraviolet cleaning. (Preparation for Vacuum Deposition) On the substrate with surface treatment after cleaning, vacuum evaporation of each layer was performed by the vacuum evaporation method, and each layer was laminated and formed.

[0085] First, the glass substrate was introduced into the vacuum evaporation chamber and the pressure was reduced to 1.0×10-4 Pa. Then, they were respectively fabricated according to the film formation conditions of each layer in the following order. (Fabrication of the hole injection layer 103) The sublimated and purified HTL and NDP-9 were formed into a film with a thickness of 10 nm at a speed of 0.15 nm / second to fabricate the hole injection layer 103. (Fabrication of the first hole transport layer 1051) The sublimated and purified HTL was formed into a film with a thickness of 85 nm at a speed of 0.15 nm / second to fabricate the first hole transport layer 1051. (Fabrication of the second hole transport layer 1052) The sublimated and purified EBL-1 was formed into a film with a thickness of 5 nm at a speed of 0.15 nm / second to fabricate the second hole transport layer 1052. (Fabrication of the light-emitting layer 106) The sublimated and purified BH-1 and BD-1 were formed into a film with a thickness of 20 nm at a ratio of 95:5 (mass ratio) to fabricate the light-emitting layer 106. The film formation speed was 0.18 nm / second. (Fabrication of the first electron transport layer 1071) The sublimated and purified HBL-1 was formed into a film with a thickness of 6 nm at a speed of 0.05 nm / second to fabricate the first electron transport layer 1071. (Fabrication of the second electron transport layer 1072) Compound E13 and Liq were formed into a film with a thickness of 25 nm at a ratio of 50:50 (mass ratio) to fabricate the second electron transport layer 1072. The film formation speed was 0.15 nm / second. (Fabrication of the cathode 108) Finally, a metal mask was arranged so as to be orthogonal to the ITO stripe on the substrate, and the cathode 108 was formed. The cathode was formed of ytterbium, silver / magnesium (mass ratio 9 / 1) and silver in this order, with thicknesses of 2 nm, 12 nm and 90 nm respectively, to form a three-layer structure. The film formation speed of ytterbium was 0.02 nm / second, the film formation speed of silver / magnesium was 0.5 nm / second, and the film formation speed of silver was 0.2 nm / second.

[0086] As described above, an organic electroluminescent element 100 having a light-emitting area of 4 mm2 as shown in FIG. 2 was fabricated. The film thickness of each layer was measured with a stylus profilometer (DEKTAK, manufactured by Bruker).

[0087] Furthermore, this element was sealed in a nitrogen atmosphere glove box with an oxygen and moisture concentration of 1 ppm or less. The sealing was performed using a glass sealing cap and a film-forming substrate (element) with a bisphenol F type epoxy resin (manufactured by Nagase ChemteX).

[0088] A direct current was applied to the organic electroluminescent element fabricated as described above, and the driving voltage (V) when a current density of 10 mA / cm2 was passed was measured. The current efficiency is a relative value based on the result in Element Comparative Example-1 described later as a reference value (100). The obtained measurement results are shown in Table 1. Element Comparative Example-1 An organic electroluminescent element was fabricated and evaluated in the same manner as in Element Example-1, except that ETL-1 was used instead of Compound E1 in Element Example-1. The obtained measurement results are shown in Table 1.

[0089]

Table 1

Explanation of Symbols

[0090] 100 Organic electroluminescent element 1 Substrate 2 Anode 3 Hole injection layer 4 Hole transport layer 41 First hole transport layer 42 Second hole transport layer 5 Light-emitting layer 6 Electron transport layer 7 Electron injection layer 8 Cathode 101 Substrate 102 Anode 103 Hole injection layer 1051 First hole transport layer 1052 Second hole transport layer 106 Light-emitting layer 1071 First electron transport layer 1072 Second electron transport layer 108 Cathode

Claims

1. A nitrogen-containing condensed-ring fluorene compound represented by formula (1): 【Chemical 1】 In formula (1), ring A represents a fluoranthene ring represented by formula (A-1) or an optionally substituted benzofluoranthene ring; 【Chemical 2】 R each independently represents an optionally substituted alkyl group having 1 to 10 carbon atoms, or an optionally substituted (i) aromatic hydrocarbon group having 6 to 60 carbon atoms, (ii) heteroaromatic group having 3 to 60 carbon atoms, (iii) arylamino group having 6 to 60 carbon atoms, or (iv) a group composed of any combination of two or more selected from the above (i) to (iii); X each independently represents CH or a nitrogen atom; In formula (1), the number of nitrogen atoms represented by X is 2 to 4; *1 represents a condensation site; n is an integer from 0 to 6; Ring B is an optionally substituted (i) aromatic hydrocarbon group having 6 to 20 carbon atoms, or (ii) heteroaromatic group having 3 to 20 carbon atoms, which may be a single ring that may be linked, a condensed ring that may be linked, or a structure in which these are linked.

2. The nitrogen-containing condensed-ring fluorene compound according to claim 1, wherein ring A is (A-2): 【Chemical Formula 3】 In formula (A-2), R and n have the same meanings as in claim 1; m is an integer from 0 to 4; Of the carbon atoms constituting the benzofluoranthene ring, any two adjacent carbon atoms without substituents represent a condensation site.

3. The nitrogen-containing condensed-ring fluorene compound according to claim 1, wherein ring A is represented by formula (A-2):

4. The nitrogen-containing condensed-ring fluorene compound according to claim 1, wherein the number of nitrogen atoms represented by X in formula (1) is 2:

5. An organic electroluminescent device comprising an anode, a cathode, and one or more organic thin film layers including at least a light-emitting layer, wherein at least one layer of the organic thin film layers contains the nitrogen-containing condensed-ring fluorene compound according to any one of claims 1 to 4.

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