Crystal of phenanthroline derivative, method for producing the same, and light-emitting device using the same

Abstract

The purpose of the present invention is to provide: a crystal of a phenanthroline derivative, said crystal having high chemical purity and low residual solvent content, thereby being suitable for use as a light emitting element material; and a method for producing this crystal of a phenanthroline derivative. The present invention provides: a crystal of a phenanthroline derivative, said crystal having a structure represented by general formula (1), while respectively having peaks at diffraction angles 2θ (°) of 6.7 ± 0.2, 8.2 ± 0.2, 13.7 ± 0.2, 17.7 ± 0.2 and 22.2 ± 0.2 in the powder X-ray diffraction pattern (said crystal being referred to as a B-form crystal); and crystal of a phenanthroline derivative, said crystal having a structure represented by general formula (1), while respectively having peaks at diffraction angles 2θ (°) of 5.0 ± 0.2, 7.5 ± 0.2, 8.7 ± 0.2, 12.5 ± 0.2 and 17.3 ± 0.2 in the powder X-ray diffraction pattern (said crystal being referred to as a C-form crystal). In addition, the present invention provides a crystal of a phenanthroline derivative, said crystal having a structure represented by general formula (1), while respectively having peaks at diffraction angles 2θ (°) of 5.2 ± 0.2, 7.0 ± 0.2, 16.4 ± 0.2, 20.0 ± 0.2 and 23.6 ± 0.2 in the powder X-ray diffraction pattern, said crystal being suitable for the achievement of a C-form crystal. (In the formula, X represents a phenylene group or a naphthylene group.)

Description

[Technical Field]

[0001] The present invention relates to a crystal of a phenanthroline derivative and a method for producing the same. Phenanthroline derivatives are useful compounds as light-emitting device materials that can be used in fields such as display elements, flat panel displays, backlights, lighting, interiors, signs, billboards, electrophotographic machines, and optical signal generators. [Background technology]

[0002] With regard to phenanthroline derivatives, materials for light-emitting elements containing phenanthroline derivatives represented by the general formula (1) described below have been disclosed, and as manufacturing methods thereof, a method of reacting 1,3-di(1,10-phenanthroline-2-yl)benzene with phenyllithium and then oxidizing the same, and a method of reacting 1,3-dibromobenzene with t-butyllithium, then reacting the same with 2-phenyl-1,10-phenanthroline, and then oxidizing the same have been disclosed (see, for example, Patent Document 1).

[0003] Furthermore, as a method for producing nitrogen-containing aromatic ring derivatives, including phenanthroline derivatives represented by the general formula (1) described later, a method has been proposed in which a dibromoaromatic compound is dilithiated with n-butyllithium or sec-butyllithium, followed by addition of a nitrogen-containing aromatic ring derivative, and then oxidation (see, for example, Patent Document 2).

[0004] Furthermore, with regard to a polymer electrolyte composition containing an ionic group-containing polymer, an organic phosphorus-based additive, and a nitrogen-containing heteroaromatic ring additive, a method for producing the nitrogen-containing heteroaromatic ring additive has been disclosed in which 8-amino-7-quinolinecarbaldehyde is reacted with 1,3-diacetylbenzene and potassium hydroxide, and then reacted with phenyllithium, followed by oxidation and recrystallization for purification (see, for example, Patent Document 3). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-281390 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-189660 [Patent Document 3] International Publication No. 2015 / 156228 Summary of the Invention [Problem to be solved by the invention]

[0006] Organic compounds generally have multiple solid states, such as amorphous and crystalline. Phenanthroline derivatives also exhibit polymorphism. Even if the crystal structure of a phenanthroline derivative is identical at the molecular level, the molecular packing pattern differs, affecting its chemical and physical properties and ease of handling. For example, when using the aforementioned phenanthroline compound as a light-emitting device material, it is common to purify it by sublimation. However, Patent Document 1 does not disclose any method for identifying the solid state. Furthermore, the phenanthroline derivatives obtained by conventional manufacturing methods, such as those described in Patent Document 2, have low chemical purity, resulting in insufficient chemical purity for use as a light-emitting device material even after sublimation purification. Furthermore, while the manufacturing method disclosed in Patent Document 3 does not allow for the identification of the crystal form, some crystal forms form solvate crystals, resulting in a large amount of residual solvent, which can cause bumping during sublimation purification.

[0007] Therefore, an object of the present invention is to provide crystals of phenanthroline derivatives having high chemical purity and a small amount of residual solvent, and a method for producing the same. [Means for solving the problem]

[0008] That is, the present invention relates to a crystal of a phenanthroline derivative having a structure represented by general formula (1) and having peaks at diffraction angles 2θ (°) of 6.7±0.2, 8.2±0.2, 13.7±0.2, 17.7±0.2, and 22.2±0.2 in powder X-ray diffraction. Another aspect of the present invention relates to a crystal of a phenanthroline derivative having a structure represented by general formula (1) and having peaks at diffraction angles 2θ (°) of 5.0±0.2, 7.5±0.2, 8.7±0.2, 12.5±0.2, and 17.3±0.2 in powder X-ray diffraction. Another aspect of the present invention is a crystal of a phenanthroline derivative having a structure represented by general formula (1) and exhibiting peaks in powder X-ray diffraction at diffraction angles 2θ (°) of 5.2±0.2, 7.0±0.2, 16.4±0.2, 20.0±0.2, and 23.6±0.2, respectively. This crystal is highly suitable as a crystal for obtaining the C-type crystal described below.

[0009] [ka]

[0010] (In general formula (1), X represents a phenylene group or a naphthylene group.) [Effects of the Invention]

[0011] The crystals of the phenanthroline derivatives of the present invention have high chemical purity and a small amount of residual solvent. Therefore, bumping during sublimation purification can be suppressed. Furthermore, by taking advantage of the high chemical purity, the crystals can be suitably used as a material for a light-emitting device after sublimation purification. Furthermore, when a specific pyrromethene compound is used in combination with the phenanthroline derivatives, the light-emitting device can be driven at a low voltage. [Brief explanation of the drawings]

[0012] [Figure 1] Reference example 1 1 is a powder X-ray diffraction pattern of type B crystals of the phenanthroline derivative represented by general formula (1) obtained by [Figure 2] Reference example 11 is a diagram showing a differential thermal analysis curve obtained by simultaneous differential thermal and thermogravimetric measurements of type B crystals of the phenanthroline derivative represented by general formula (1) obtained by the above procedure. FIG. 3 is a powder X-ray diffraction pattern of the C-type crystals of the phenanthroline derivative represented by the general formula (1) obtained in Example 3. 4 is a diagram showing a differential thermal analysis curve obtained by simultaneous differential thermal and thermogravimetric measurements of the C-type crystals of the phenanthroline derivative represented by general formula (1) obtained in Example 3.

[0023] FIG. FIG. 5 is a powder X-ray diffraction pattern of the E-form crystals of the phenanthroline derivative represented by the general formula (1) obtained in Example 6. 6 is a diagram showing a differential thermal analysis curve obtained by simultaneous differential thermal and thermogravimetric measurements of E-type crystals of the phenanthroline derivative represented by general formula (1) obtained in Example 6.

[0033] FIG. 7 is a powder X-ray diffraction pattern of the D-form crystals of the phenanthroline derivative represented by the general formula (1) obtained in Comparative Example 1.

[0033] FIG. 8 is a diagram showing a differential thermal analysis curve obtained by simultaneous differential thermal and thermogravimetric measurements of the D-type crystals of the phenanthroline derivative represented by the general formula (1) obtained in Comparative Example 1.

[0033] FIG. FIG. 9 is a powder X-ray diffraction pattern of the amorphous phenanthroline derivative represented by general formula (1) obtained in Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will be described in detail below. The inventions described in claims 1 to 3 relate to type C crystals of a phenanthroline derivative. Meanwhile, the invention described in claim 16 relates to type E crystals of a phenanthroline derivative. Furthermore, the inventions described in claims 17 to 19 relate to type B crystals of a phenanthroline derivative. And the inventions described in claims 12 to 15 relate to a manufacturing method for producing type C crystals from type E crystals. And the invention described in claim 20 relates to a manufacturing method for producing type B crystals.

[0014] The crystal of the phenanthroline derivative according to the first aspect of the present invention has a structure represented by general formula (1) and has a specific crystalline form in which, in powder X-ray diffraction, the peaks are at diffraction angles 2θ (°) of 6.7±0.2, 8.2±0.2, 13.7±0.2, 17.7±0.2, and 22.2±0.2, respectively, and is referred to as type B crystal in this specification.

[0015] Furthermore, the crystal of the phenanthroline derivative according to the second aspect of the present invention has a structure represented by general formula (1) and has a specific crystalline form in which, in powder X-ray diffraction, it exhibits peaks at diffraction angles 2θ (°) of 5.0±0.2, 7.5±0.2, 8.7±0.2, 12.5±0.2, and 17.3±0.2, respectively, and is referred to as C-type crystal in this specification.

[0016] The B-type and C-type crystals of the phenanthroline derivative have high chemical purity and little residual solvent, which can prevent bumping during sublimation purification. Furthermore, taking advantage of their high chemical purity, they can be suitably used as light-emitting device materials after sublimation purification.

[0017] [ka]

[0018] In the above general formula (1), X represents a phenylene group or a naphthylene group, of which the phenylene group is preferred from the viewpoints of molecular weight and sublimation purification temperature.

[0019] Examples of the phenanthroline derivative represented by the general formula (1) include those having the following structures:

[0020] [ka]

[0021] Among these, 1,3-bis(9-phenyl-1,10-phenanthrolin-2-yl)benzene is preferred from the standpoints of ease of synthesis and thin film stability.

[0022] Among the crystals of the phenanthroline derivative of the present invention, the crystals designated as type B crystals are crystals having peaks at diffraction angles 2θ (°) of 6.7±0.2, 8.2±0.2, 13.7±0.2, 17.7±0.2, and 22.2±0.2 in powder X-ray diffraction, and the crystals designated as type C crystals are crystals having peaks at diffraction angles 2θ (°) of 5.0±0.2, 7.5±0.2, 8.7±0.2, 12.5±0.2, and 17.3±0.2.

[0023] Here, powder X-ray diffraction can be measured using a powder X-ray diffractometer under the following conditions: The measurement sample is prepared by filling a sample plate (material: silicon; depth: 0.2 mm) with the sample and smoothing the sample surface. X-ray source: CuKα ray *Uses a curved crystal monochromator (graphite) Output: 40kV / 50mA Divergence slit: 1 / 2° Divergence vertical limit slit: 5mm Scattering slit: 1 / 2° Receiving slit: 0.15 mm Detector: Scintillation counter Scan method: 2θ / θ scan, continuous scan Measurement range (2θ): 2 to 30° Scan speed (2θ): 20° / min Counting step (2θ): 0.04°.

[0024] The type B crystals of the phenanthroline derivative of the present invention preferably have an endothermic peak in the range of 180 to 184°C in simultaneous thermogravimetry and differential thermal analysis (hereinafter sometimes abbreviated as "TG-DTA"). Such an endothermic peak is one of the characteristics that identify the crystalline form, and the presence of an endothermic peak in the range of 180 to 184°C means that the crystals are the type B crystals described above. Furthermore, the type C crystals of the phenanthroline derivative of the present invention preferably have an endothermic peak in the range of 243 to 247°C in simultaneous thermogravimetry and differential thermal analysis. The presence of an endothermic peak in the range of 243 to 247°C means that the crystals are the type C crystals described above.

[0025] Here, TG-DTA can be measured using a TG-DTA device under the following conditions, and the peak top temperature shown in the DTA curve is taken as the endothermic peak. Heating rate: 5°C / min Atmosphere: dry nitrogen (flow rate: 100 mL / min) Sample cell: Aluminum open cell Sample size: 5 to 15 mg.

[0026] The phenanthroline derivative represented by general formula (1) can be produced, for example, by the method described in JP 2008-189660 A. That is, a dibromobenzene derivative is dilithiated with an alkyllithium, and then reacted with 2-phenyl-1,10-phenanthroline, followed by oxidation to obtain the desired phenanthroline derivative.

[0027] The type B crystals of the phenanthroline derivative represented by general formula (1) according to the first aspect of the present invention can be obtained, for example, by a method comprising the steps of: (I) dissolving any form of the phenanthroline derivative represented by general formula (1) in a mixed solvent containing an aprotic polar solvent and an aromatic solvent, followed by crystallization; and (II) dissolving the crystals obtained in step (I) in an ether-based solvent, followed by crystallization.

[0028] Examples of aprotic polar solvents include amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; sulfoxide solvents such as dimethyl sulfoxide; sulfone solvents such as sulfolane; urea solvents such as 1,3-dimethyl-2-imidazolidinone and N,N-dimethylpropyleneurea; nitrile solvents such as acetonitrile and propionitrile; and pyridine solvents such as pyridine and 2-methylpyridine. Two or more of these may be used. Among these, amide solvents, sulfoxide solvents, and urea solvents are preferred, and 1,3-dimethyl-2-imidazolidinone is more preferred from the viewpoint of improving the recovery rate of type B crystals.

[0029] Examples of aromatic solvents include benzene, chlorobenzene, anisole, toluene, xylene, cumene, and mesitylene. Two or more of these may be used. Among these, anisole, toluene, and xylene are preferred, and toluene is more preferred from the viewpoint of improving the recovery rate of type B crystals.

[0030] In the mixed solvent containing an aprotic polar solvent and an aromatic solvent, the content of the aromatic solvent is preferably 50 to 500 parts by weight, more preferably 100 to 300 parts by weight, per 100 parts by weight of the aprotic polar solvent, from the viewpoint of improving the recovery rate of the B-type crystals.

[0031] Furthermore, in a mixed solvent containing an aprotic polar solvent and an aromatic solvent, solvents other than the aprotic polar solvent and the aromatic solvent may be contained in the mixed solvent as long as the solvent can provide crystals of the phenanthroline derivative having the desired diffraction angle.

[0032] The amount of the mixed solvent used is preferably 300 parts by weight or more, more preferably 500 parts by weight or more, per 100 parts by weight of the phenanthroline derivative represented by general formula (1) from the viewpoint of facilitating stirring, while the amount of the mixed solvent used is preferably 10,000 parts by weight or less, more preferably 3,000 parts by weight or less, per 100 parts by weight of the phenanthroline derivative represented by general formula (1) from the viewpoint of improving production efficiency per unit volume.

[0033] The order of adding the solvents in step (I) is not particularly limited. For example, an aprotic polar solvent may be added to the phenanthroline derivative represented by general formula (1), and the mixture may be heated to dissolve the phenanthroline derivative, and then an aromatic solvent may be added.

[0034] In step (I), the phenanthroline derivative represented by general formula (1) is preferably dissolved in the mixed solvent by heating. The heating temperature is preferably 50°C or higher, more preferably 80°C or higher, from the viewpoint of quickly dissolving the phenanthroline derivative represented by general formula (1). On the other hand, from an industrial viewpoint, the heating temperature is preferably 150°C or lower, more preferably 130°C or lower. It is not necessary to completely dissolve the phenanthroline derivative, but if it does not completely dissolve, it is preferable to set the heating time according to the solubility. In this case, the heating time is preferably 0.5 to 100 hours, more preferably 1 to 50 hours.

[0035] When dissolving by heating in step (I), it is preferable to cool in the crystallization step. The cooling temperature is preferably -20 to 30°C, more preferably -10 to 10°C, from the viewpoint of improving the recovery rate of type B crystals. The cooling rate is preferably 0.1 to 50 hours, more preferably 0.5 to 20 hours. During cooling, the mixture may be stirred or left to stand.

[0036] Examples of ether solvents include acyclic ethers such as diethyl ether, diisopropyl ether, cyclopentyl methyl ether, tert-butyl methyl ether, dimethoxyethane, and diethylene glycol dimethyl ether; and cyclic ethers such as tetrahydrofuran, 2-methyltetrahydrofuran, and 1,4-dioxane. Two or more of these may be used. Among these, cyclic ethers are preferred, and from the viewpoint of improving the recovery rate of type B crystals, tetrahydrofuran is more preferred.

[0037] The amount of the ether solvent used is preferably 300 parts by weight or more, more preferably 500 parts by weight or more, per 100 parts by weight of the phenanthroline derivative represented by general formula (1) from the viewpoint of facilitating stirring, while the amount of the ether solvent used is preferably 10,000 parts by weight or less, more preferably 3,000 parts by weight or less, per 100 parts by weight of the phenanthroline derivative represented by general formula (1) from the viewpoint of improving production efficiency per unit volume.

[0038] In step (II), the phenanthroline derivative represented by general formula (1) is preferably dissolved in an ether-based solvent by heating. The heating temperature is preferably 40°C or higher, more preferably 60°C or higher, from the viewpoint of quickly dissolving the phenanthroline derivative represented by general formula (1). On the other hand, from an industrial viewpoint, the heating temperature is preferably 150°C or lower, more preferably 130°C or lower. It is not necessary to completely dissolve the phenanthroline derivative, but if it does not completely dissolve, it is preferable to set the heating time according to the solubility. In this case, the heating time is preferably 0.5 to 100 hours, more preferably 1 to 50 hours.

[0039] When the solution is dissolved by heating in step (II), it is preferable to cool it in the crystallization step. The preferred ranges of the cooling temperature and cooling rate are the same as those in step (I).

[0040] In the crystallization step in step (II), previously obtained B-type crystals of the phenanthroline derivative may be added as seed crystals, and the method may further include a step of drying the obtained crystals.

[0041] The C-type crystals of the phenanthroline derivative represented by general formula (1) according to the second aspect of the present invention can be obtained, for example, by a method comprising the steps of: dissolving any form of the phenanthroline derivative represented by general formula (1) in a mixed solvent containing an aprotic polar solvent and an aromatic solvent, followed by crystallization; and then drying the crystals obtained in step (I) at 50°C or higher; and then drying the crystals obtained in step (I) at 50°C or higher.

[0042] Examples of the aprotic polar solvent include those exemplified in the method for producing the B-type crystal of the first embodiment. Among these, amide-based solvents, sulfoxide-based solvents, and urea-based solvents are preferred, and from the viewpoint of improving the recovery rate of the C-type crystal, 1,3-dimethyl-2-imidazolidinone, N-methylpyrrolidone, and N,N-dimethylacetamide are more preferred.

[0043] Examples of aromatic solvents include those exemplified in the method for producing the B-type crystals of the first embodiment. Among these, anisole, toluene, and xylene are preferred, and anisole is more preferred from the viewpoint of improving the recovery rate of the C-type crystals.

[0044] In a mixed solvent containing an aprotic polar solvent and an aromatic solvent, the content of the aromatic solvent is preferably 50 to 210 parts by weight, more preferably 100 to 205 parts by weight, per 100 parts by weight of the aprotic polar solvent, from the viewpoint of improving the recovery rate of C-type crystals.

[0045] Furthermore, in the mixed solvent containing an aprotic polar solvent and an aromatic solvent used here, solvents other than the aprotic polar solvent and the aromatic solvent may be contained in the mixed solvent as long as crystals of the phenanthroline derivative having the desired diffraction angle can be obtained.

[0046] The amount of the mixed solvent used is preferably 300 parts by weight or more, more preferably 500 parts by weight or more, per 100 parts by weight of the phenanthroline derivative represented by general formula (1) from the viewpoint of facilitating stirring, while the amount of the mixed solvent used is preferably 10,000 parts by weight or less, more preferably 3,000 parts by weight or less, per 100 parts by weight of the phenanthroline derivative represented by general formula (1) from the viewpoint of improving production efficiency per unit volume.

[0047] The order of adding the solvents in step (I) is not particularly limited. For example, an aprotic polar solvent may be added to the phenanthroline derivative represented by general formula (1), and the mixture may be heated to dissolve the phenanthroline derivative, and then an aromatic solvent may be added.

[0048] In step (I), the phenanthroline derivative represented by general formula (1) is preferably dissolved in the mixed solvent by heating. The preferred ranges of the heating temperature and heating time are the same as those in step (I) in the method for producing the B-type crystal of the first embodiment.

[0049] When the dissolution is carried out by heating in step (I), it is preferable to carry out cooling in the crystallization step. The preferred ranges of the cooling temperature and cooling rate are the same as those in step (I) in the production method of the B-type crystal of the first embodiment.

[0050] The drying temperature in step (III) is preferably 50°C or higher, more preferably 80°C or higher, from the viewpoint of efficient polymorphic transformation. On the other hand, from an industrial viewpoint, the drying temperature is preferably 150°C or lower, more preferably 130°C or lower. Furthermore, drying in step (III) is preferably performed under reduced pressure. The degree of vacuum for the reduced pressure drying is preferably 666.6 Pa (5 mmHg) or lower, from the viewpoint of rapid removal of residual solvent.

[0051] Furthermore, the C-type crystal of the phenanthroline derivative represented by general formula (1) can also be obtained by polymorphic transformation of a crystal of the phenanthroline derivative (referred to herein as E-type crystal) having the structure represented by general formula (1) and exhibiting peaks at diffraction angles 2θ (°) of 5.2±0.2, 7.0±0.2, 16.4±0.2, 20.0±0.2, and 23.6±0.2 in powder X-ray diffraction. The C-type crystal of the phenanthroline derivative represented by general formula (1) can also be obtained by heating and drying a crystal other than the C-type crystal to promote polymorphic transformation, although the temperature varies significantly depending on the crystal form. Among the crystal forms, the E-type crystal is preferred from an industrial perspective because the polymorphic transformation proceeds at a relatively low temperature, allowing the C-type crystal to be obtained. In this case, it is preferable to obtain the E-type crystal in the aforementioned step (I) and then obtain the C-type crystal by polymorphic transformation in the aforementioned step (III).

[0052] Since E-type crystals of the phenanthroline derivative easily transform into C-type crystals by heating and drying, they are effective as precursors of C-type crystals. The E-type crystals of the phenanthroline derivative preferably have an endothermic peak in the range of 94 to 98°C in simultaneous differential thermal and thermogravimetry measurements, and the presence of an endothermic peak in this temperature range indicates that they are E-type crystals. Powder X-ray diffraction measurements and simultaneous differential thermal and thermogravimetry measurements can be performed in the same manner as described for the B-type crystals and C-type crystals.

[0053] The E-type crystals of the phenanthroline derivative represented by the general formula (1) can be obtained, for example, by a method including the steps of: dissolving any form of the phenanthroline derivative represented by the general formula (1) in a mixed solvent containing an aprotic polar solvent and an aromatic solvent, followed by crystallization (I); and then drying the crystals obtained by the step (I) at a temperature lower than 50°C (IV).

[0054] Examples of the aprotic polar solvent include those exemplified in the method for producing the B-type crystal of the first embodiment. Among these, amide-based solvents, sulfoxide-based solvents, and urea-based solvents are preferred, and from the viewpoint of improving the recovery rate of the C-type crystal, 1,3-dimethyl-2-imidazolidinone, N-methylpyrrolidone, and N,N-dimethylacetamide are more preferred.

[0055] Examples of aromatic solvents include those exemplified in the method for producing the B-type crystals of the first embodiment. Among these, anisole, toluene, and xylene are preferred, and anisole is more preferred from the viewpoint of improving the recovery rate of the C-type crystals.

[0056] In a mixed solvent containing an aprotic polar solvent and an aromatic solvent, the content of the aromatic solvent is preferably 50 to 210 parts by weight, more preferably 100 to 205 parts by weight, per 100 parts by weight of the aprotic polar solvent, from the viewpoint of improving the recovery rate of C-type crystals.

[0057] Furthermore, in the mixed solvent containing an aprotic polar solvent and an aromatic solvent used here, solvents other than the aprotic polar solvent and the aromatic solvent may be contained in the mixed solvent as long as crystals of the phenanthroline derivative having the desired diffraction angle can be obtained.

[0058] The amount of the mixed solvent used is preferably 300 parts by weight or more, more preferably 500 parts by weight or more, per 100 parts by weight of the phenanthroline derivative represented by general formula (1) from the viewpoint of facilitating stirring, while the amount of the mixed solvent used is preferably 10,000 parts by weight or less, more preferably 3,000 parts by weight or less, per 100 parts by weight of the phenanthroline derivative represented by general formula (1) from the viewpoint of improving production efficiency per unit volume.

[0059] The order of adding the solvents in step (I) is not particularly limited. For example, an aprotic polar solvent may be added to the phenanthroline derivative represented by general formula (1), and the mixture may be heated to dissolve the phenanthroline derivative, and then an aromatic solvent may be added.

[0060] In step (I), the phenanthroline derivative represented by general formula (1) is preferably dissolved in the mixed solvent by heating. The preferred ranges of the heating temperature and heating time are the same as those in step (I) in the method for producing the B-type crystal of the first embodiment.

[0061] When the dissolution is carried out by heating in step (I), it is preferable to carry out cooling in the crystallization step. The preferred ranges of the cooling temperature and cooling rate are the same as those in step (I) in the production method of the B-type crystal of the first embodiment.

[0062] The drying temperature in step (IV) is preferably 10° C. or higher, more preferably 20° C. or higher, from the viewpoint of rapidly removing the residual solvent, while the drying temperature is preferably less than 50° C., more preferably 30° C. or lower, from the viewpoint of maintaining the crystalline form.

[0063] The E-type crystals of the phenanthroline derivative represented by general formula (1) obtained by the above method can be efficiently converted to C-type crystals by polymorphic transformation. The polymorphic transformation step is preferably carried out at 50°C or higher, more preferably at 80°C or higher. On the other hand, since the E-type crystals undergo polymorphic transformation at relatively low temperatures, from an industrial viewpoint, the temperature is preferably 150°C or lower, more preferably 130°C or lower.

[0064] The B-type or C-type crystals of the phenanthroline derivative represented by general formula (1) of the present invention have a low residual solvent content and extremely high chemical purity, making them suitable for use as light-emitting device materials. The B-type or C-type crystals of the phenanthroline derivative of the present invention have high electron transport and injection properties, making them particularly suitable for use in the electron transport layer, electron injection layer, and charge generation layer of light-emitting devices. Furthermore, light-emitting devices of the present invention containing a phenanthroline derivative derived from the B-type or C-type crystals of the phenanthroline derivative in the electron transport layer, electron injection layer, or charge generation layer have a layer with an extremely high chemical purity of 99.7% or more, as achieved by the B-type or C-type crystals of the phenanthroline derivative. Therefore, the electron transport layer, electron injection layer, or charge generation layer can be a stable layer with little change in film quality over time. Furthermore, even when a thermally activated delayed fluorescent material is used in the light-emitting layer, the light-emitting device can exhibit an external quantum efficiency of 7.0% or more.

[0065] Furthermore, the B-type or C-type crystal of the phenanthroline derivative of the present invention has a small amount of residual solvent and extremely high chemical purity, so that the amount of degassing is small when fabricating a light-emitting device, making it possible to form a high-purity film and obtain a light-emitting device with high luminous efficiency. In particular, since it can reduce the driving voltage and obtain highly efficient luminescence, it is suitable for use in a light-emitting device containing a thermally activated delayed fluorescence material (sometimes referred to as a "TADF material") in the luminescent layer.

[0066] Next, a light-emitting device using the B-type crystal or C-type crystal of the phenanthroline derivative represented by the general formula (1) of the present invention will be described in detail.

[0067] The light-emitting device of the present invention has the function of converting electrical energy into light. While direct current is primarily used as the electrical energy, pulsed current or alternating current can also be used. There are no particular limitations on the current and voltage values, and the required characteristics vary depending on the purpose of the device. However, from the perspective of device power consumption and lifespan, it is preferable to achieve high brightness at a low voltage. Furthermore, from the perspective of improving color purity, the half-width of the emission spectrum upon application of current is preferably 60 nm or less, more preferably 50 nm or less, even more preferably 45 nm or less, and particularly preferably 30 nm or less. Because the light-emitting device of the present invention has a narrow half-width of the emission spectrum, it is more preferable to use it as a top-emission light-emitting device. Due to the resonance effect of the microcavity, the narrower the half-width, the higher the luminous efficiency of a top-emission light-emitting device. Therefore, it is possible to achieve both high color purity and high luminous efficiency.

[0068] The light-emitting element of the present invention is preferably used in display devices such as displays using a matrix system, a segment system, or a combination of both systems. It is also preferably used as a backlight for various devices. Backlights are primarily used to improve the visibility of non-self-luminous displays and other display devices, and are used in display devices such as liquid crystal displays, clocks, audio equipment, automotive panels, display boards, and signs. In particular, the light-emitting element of the present invention is preferably used as a backlight for liquid crystal displays, especially for personal computers, which are being considered for thinning, and can provide backlights that are thinner and lighter than conventional ones. The light-emitting element of the present invention is also preferably used in various lighting devices. Since it is possible to achieve both high luminous efficiency and high color purity and further to reduce the thickness and weight, it is possible to realize lighting devices that combine low power consumption, vivid luminous color, and high design flexibility.

[0069] The light-emitting device of the present invention has, for example, a structure including an anode, a cathode, and an organic layer between the anode and the cathode. The organic layer preferably includes at least a light-emitting layer, and the light-emitting layer is an organic electroluminescent device that emits light by electrical energy. The light-emitting device may be either a bottom-emission type or a top-emission type. The layer configuration of the organic layer between the anode and cathode in such a light-emitting element may be a configuration consisting of only the light-emitting layer, or may be a stacked configuration such as 1) light-emitting layer / electron transport layer, 2) hole transport layer / light-emitting layer, 3) hole transport layer / light-emitting layer / electron transport layer, 4) hole injection layer / hole transport layer / light-emitting layer / electron transport layer, 5) hole transport layer / light-emitting layer / electron transport layer / electron injection layer, 6) hole injection layer / hole transport layer / light-emitting layer / electron transport layer / electron injection layer, 7) hole injection layer / hole transport layer / light-emitting layer / hole blocking layer / electron transport layer / electron injection layer, or 8) hole injection layer / hole transport layer / electron blocking layer / light-emitting layer / hole blocking layer / electron transport layer / electron injection layer.

[0070] Furthermore, the light-emitting device may be a tandem-type light-emitting device in which a plurality of the above-described laminated structures are laminated via an intermediate layer. Examples of the intermediate layer include an intermediate electrode, an intermediate conductive layer, a charge-generating layer, an electron-extracting layer, a connecting layer, and an intermediate insulating layer, and known material structures can be used. A preferred example of a tandem-type light-emitting device is a laminated structure such as 9) hole injection layer / hole transport layer / light-emitting layer / electron transport layer / electron injection layer / charge generation layer / hole injection layer / hole transport layer / light-emitting layer / electron transport layer / electron injection layer. Each of the above layers may be a single layer or multiple layers, and may be doped. Further examples of the light-emitting device include a layer using a capping material to improve luminous efficiency due to the optical interference effect.

[0071] The electron transport layer is a layer that receives electrons injected from the cathode and transports them. The electron transport material used in the electron transport layer is required to have high electron affinity, high electron mobility, excellent stability, and a low tendency to generate impurities that trap electrons. Furthermore, low-molecular-weight compounds tend to crystallize and deteriorate film quality, so compounds with a molecular weight of 400 or more are preferred. The electron transport layer of the present invention also includes a hole-blocking layer that can efficiently block the movement of holes. The hole-blocking layer and electron transport layer may be composed of a single material or a laminate of multiple materials. Examples of electron transport materials include polycyclic aromatic derivatives, styryl aromatic ring derivatives, quinone derivatives, phosphorus oxide derivatives, and various metal complexes such as quinolinol complexes of tris(8-quinolinolato)aluminum(III), benzoquinolinol complexes, hydroxyazole complexes, azomethine complexes, tropolone metal complexes, and flavonol metal complexes.

[0072] Compounds having a heteroaryl group containing electron-accepting nitrogen are preferred because they reduce driving voltage and achieve highly efficient light emission. Here, electron-accepting nitrogen refers to a nitrogen atom that forms a multiple bond with an adjacent atom. Heteroaryl groups containing electron-accepting nitrogen have a high electron affinity, facilitating electron injection from the cathode and enabling lower-voltage driving. Furthermore, they increase the supply of electrons to the light-emitting layer, increasing the recombination probability and improving light-emitting efficiency. Preferred examples of compounds having a heteroaryl group structure containing electron-accepting nitrogen include pyridine derivatives, triazine derivatives, pyrazine derivatives, pyrimidine derivatives, quinoline derivatives, quinoxaline derivatives, quinazoline derivatives, naphthyridine derivatives, benzoquinoline derivatives, phenanthroline derivatives, imidazole derivatives, oxazole derivatives, thiazole derivatives, triazole derivatives, oxadiazole derivatives, thiadiazole derivatives, benzimidazole derivatives, benzoxazole derivatives, benzthiazole derivatives, phenanthroimidazole derivatives, and oligopyridine derivatives such as bipyridine and terpyridine.

[0073] Among these, imidazole derivatives such as tris(N-phenylbenzimidazol-2-yl)benzene, oxadiazole derivatives such as 1,3-bis[(4-tert-butylphenyl)-1,3,4-oxadiazolyl]phenylene, triazole derivatives such as N-naphthyl-2,5-diphenyl-1,3,4-triazole, phenanthroline derivatives such as bathocuproine and 1,3-bis(1,10-phenanthroline-9-yl)benzene, and 2,2'-bis(benzo[h]quinolin-2-yl) Benzoquinoline derivatives such as 9,9'-spirobifluorene; bipyridine derivatives such as 2,5-bis(6'-(2',2"-bipyridyl))-1,1-dimethyl-3,4-diphenylsilole; terpyridine derivatives such as 1,3-bis(4'-(2,2':6'2"-terpyridinyl))benzene; naphthyridine derivatives such as bis(1-naphthyl)-4-(1,8-naphthyridin-2-yl)phenylphosphine oxide, and triazine derivatives are preferably used from the viewpoint of electron transport ability. Furthermore, electron transport materials having a condensed polycyclic aromatic skeleton are more preferred because they have an improved glass transition temperature and high electron mobility, enabling lower voltages.

[0074] Such fused polycyclic aromatic skeletons are preferably fluoranthene, anthracene, pyrene, or phenanthroline, with fluoranthene or phenanthroline being particularly preferred. The electron transport material may be used alone or in combination. The electron transport layer may also contain a donor material. Here, a donor material is a compound that improves the electron injection barrier, thereby facilitating electron injection from the cathode or electron injection layer into the electron transport layer and further improving the electrical conductivity of the electron transport layer. Preferred examples of donor materials include alkali metals such as lithium, inorganic salts containing alkali metals such as lithium fluoride, complexes of alkali metals and organic substances such as lithium quinolinol, alkaline earth metals, inorganic salts containing alkaline earth metals, complexes of alkaline earth metals and organic substances, rare earth metals such as europium and ytterbium, inorganic salts containing rare earth metals, and complexes of rare earth metals and organic substances. Metallic lithium, rare earth metals, or lithium quinolinol (Liq) are particularly preferred as donor materials.

[0075] The electron injection layer is formed to facilitate the injection of electrons from the cathode to the electron transport layer and is composed of a compound having a heteroaryl ring structure containing electron-accepting nitrogen or the above-mentioned donor material. In addition, inorganic insulating or semiconducting materials can also be used for the electron injection layer. The use of these materials is preferable because it can prevent short-circuiting of the light-emitting device and improve electron injection properties. As such an insulator, it is preferable to use at least one metal compound selected from the group consisting of alkali metal chalcogenides, alkaline earth metal chalcogenides, alkali metal halides, and alkaline earth metal halides.

[0076] A charge generation layer generates or separates charges upon application of a voltage and injects the charges into adjacent layers. The charge generation layer may be formed as a single layer or as a laminate of multiple layers. Generally, layers that readily generate electrons as charges are called n-type charge generation layers, while layers that readily generate holes are called p-type charge generation layers. The charge generation layer preferably consists of a double layer, and a p-n junction charge generation layer consisting of an n-type charge generation layer and a p-type charge generation layer is more preferred. In a light-emitting device, a p-n junction charge generation layer generates charges upon application of a voltage or separates charges into holes and electrons, and injects these holes and electrons into the light-emitting layer via a hole transport layer and an electron transport layer. Specifically, in a light-emitting device including multiple light-emitting layers, when a charge generation layer is used as an intermediate layer, the n-type charge generation layer supplies electrons to the first light-emitting layer located on the anode side, and the p-type charge generation layer supplies holes to the second light-emitting layer located on the cathode side.

[0077] Therefore, in a light-emitting device having two or more light-emitting layers, by providing one or more charge-generating layers between the light-emitting layers, the device efficiency can be further improved, the driving voltage can be reduced, and the durability of the device can be further improved. The n-type charge-generating layer comprises an n-type dopant and an n-type host, and conventional materials can be used for these. For example, the donor materials exemplified as materials for the electron transport layer are preferably used as the n-type dopant. Among these, alkali metals or their salts and rare earth metals are preferred, and materials selected from metallic lithium, lithium fluoride (LiF), lithium quinolinol (Liq), and metallic ytterbium are more preferred. Furthermore, as the n-type host, those exemplified as electron transport materials are preferably used. Among these, materials selected from triazine derivatives, phenanthroline derivatives, and oligopyridine derivatives are preferred, and phenanthroline derivatives or terpyridine derivatives are more preferred.

[0078] The p-type charge generation layer comprises a p-type dopant and a p-type host, and conventional materials can be used for these. For example, the acceptor materials exemplified for the hole injection layer, as well as iodine, FeCl3, FeF3, SbCl5, and the like are suitable for use as p-type dopants. Specific examples include HAT-CN6, F4-TCNQ, tetracyanoquinodimethane derivatives, radialene derivatives, iodine, FeCl3, FeF3, and SbCl5. Among these, HAT-CN6 and radialene derivatives such as (2E,2'E,2''E)-2,2',2''-(cyclopropane-1,2,3-triylidene)tris(2-(perfluorophenyl)-acetonitrile) and (2E,2'E,2''E)-2,2',2''-(cyclopropane-1,2,3-triylidene)tris(2-(4-cyanoperfluorophenyl)-acetonitrile) are more preferred. A thin film of a p-type dopant may be formed, and the thickness thereof is preferably 10 nm or less. Also, an arylamine derivative is preferred as the p-type host.

[0079] The crystals of the phenanthroline derivatives of the present invention can be used in electron transport layers, electron injection layers, and charge generation layers. When used in electron transport layers, for example, they are preferably used as a vapor-deposited film having a thickness of several tens of nanometers formed on an emitting layer having a thickness of several tens of nanometers, which is composed of a host material, a dopant material, and a TADF material. The light-emitting device thus fabricated exhibits extremely high external quantum efficiency.

[0080] Furthermore, when the crystal of the phenanthroline derivative of the present invention is used in an electron injection layer, it is preferable to use it as a co-deposited film of a few nanometers thick containing an alkali metal donor material, and to form a layer on the electron transport layer after sequentially forming a light-emitting layer and an electron transport layer similar to those described above. The light-emitting device thus fabricated also exhibits very high external quantum efficiency.

[0081] Furthermore, when the crystal of the phenanthroline derivative of the present invention is used in a charge generating layer, it is suitable to use it as an n-type host material in the n-type charge generating layer of a tandem fluorescent light emitting device containing an alkali metal as an n-type dopant, for example, by laminating an emitting layer and an electron transport layer in this order as described above, and then laminating the crystal on the electron transport layer. The light emitting device thus fabricated also exhibits very high external quantum efficiency.

[0082] The anode is an electrode formed on a substrate and is not particularly limited as long as it is made of a material that can efficiently inject holes into the organic layer. However, a transparent or semitransparent electrode is preferred for bottom-emission devices, and a reflective electrode is preferred for top-emission devices. Examples of materials for the transparent or semitransparent electrode include conductive metal oxides such as zinc oxide, tin oxide, indium oxide, indium tin oxide (ITO), and indium zinc oxide (IZO); metals such as gold, silver, aluminum, and chromium; and conductive polymers such as polythiophene, polypyrrole, and polyaniline. However, when using a metal, it is preferable to make the film thickness thin so that light can be semitransmitted.

[0083] Among these, indium tin oxide (ITO) is more preferable from the viewpoint of transparency and stability. A material for the reflective electrode that does not absorb any light and has high reflectivity is preferred. Specific examples include metals such as aluminum, silver, and platinum. The anode can be formed by an optimal method depending on the material, and examples include sputtering, vapor deposition, and inkjet printing. For example, sputtering is used when the anode is formed from a metal oxide, and vapor deposition is used when the anode is formed from a metal. The thickness of the anode is not particularly limited, but is preferably several nanometers to several hundred nanometers. These electrode materials may be used alone, or multiple materials may be stacked or mixed. Various wirings, circuits, and switching elements may be interposed between the substrate and the anode.

[0084] The cathode is an electrode formed on the surface opposite to the anode with an organic layer sandwiched therebetween, and is preferably formed on the electron transport layer or the electron injection layer. The material used for the cathode is not particularly limited as long as it can efficiently inject electrons into the light-emitting layer, but is preferably a reflective electrode in a bottom-emission device and a semi-transparent electrode in a top-emission device.

[0085] Generally, preferred cathode materials include metals such as platinum, gold, silver, copper, iron, tin, aluminum, and indium; alloys or multilayer laminates of these metals with low-work-function metals such as lithium, sodium, potassium, calcium, and magnesium; and conductive metal oxides such as zinc oxide, indium tin oxide (ITO), and indium zinc oxide (IZO). Among these, metals selected from aluminum, silver, and magnesium as the main component are preferred in terms of electrical resistance, ease of film formation, film stability, and luminous efficiency.

[0086] Furthermore, a cathode made of magnesium and silver is preferred because it facilitates electron injection into the electron transport layer and electron injection layer in the present invention and enables low-voltage operation. A protective layer (cap layer) may be laminated on the cathode to protect the cathode. Materials constituting the protective layer are not particularly limited, but examples include metals such as platinum, gold, silver, copper, iron, tin, aluminum, and indium; alloys using these metals; inorganic materials such as silica, titania, and silicon nitride; and organic polymer compounds such as polyvinyl alcohol, polyvinyl chloride, and hydrocarbon-based polymer compounds. However, when the light-emitting device has a device structure in which light is extracted from the cathode side (top-emission structure), the material used for the protective layer is selected from materials that are optically transparent in the visible light region.

[0087] The emitting layer emits light due to excitation energy generated by the recombination of holes and electrons. While the emitting layer may be composed of a single material, it is preferably composed of two or more materials, namely, a host compound (hereinafter sometimes referred to as the "first compound") and a dopant compound (hereinafter sometimes referred to as the "second compound"), from the viewpoint of color purity and luminescence intensity. A suitable example of the first compound is a thermally activated delayed fluorescent material, i.e., a thermally activated delayed fluorescent compound. Thermally activated delayed fluorescent compounds, commonly referred to as TADF materials, are materials that promote reverse intersystem crossing from the triplet excited state to the singlet excited state by reducing the energy gap between the singlet excited state and the triplet excited state, thereby improving the probability of singlet exciton generation. In TADF materials, the difference between the lowest excited singlet energy level and the lowest excited triplet energy level (referred to as ΔEST) is preferably 0.3 eV or less. By utilizing delayed fluorescence due to this thermally activated delayed fluorescent mechanism, the theoretical internal efficiency can be increased to 100%.

[0088] Furthermore, when Förster-type energy transfer occurs from the singlet exciton of a first compound having thermally activated delayed fluorescence to the singlet exciton of a second compound, fluorescence emission from the singlet exciton of the second compound is observed. For such energy transfer to occur, the lowest excited singlet energy level of the first compound is preferably higher than the lowest excited singlet energy level of the second compound. Here, when the second compound is a fluorescent material having a sharp emission spectrum, a light-emitting device with high efficiency and high color purity can be obtained. Thus, when the light-emitting layer contains a thermally activated delayed fluorescence compound, high-efficiency emission is possible, contributing to reduced power consumption of displays. The thermally activated delayed fluorescence compound may be a compound that exhibits thermally activated delayed fluorescence as a single material, or may be a compound that exhibits thermally activated delayed fluorescence as a combination of multiple compounds, such as when an exciplex complex is formed.

[0089] The thermally activated delayed fluorescent compound may be a single compound or a mixture of multiple compounds, and known materials can be used. Specific examples include benzonitrile derivatives, triazine derivatives, disulfoxide derivatives, carbazole derivatives, indolocarbazole derivatives, dihydrophenazine derivatives, thiazole derivatives, and oxadiazole derivatives. Compounds having an electron-donating moiety (donor moiety) and an electron-withdrawing moiety (acceptor moiety) in the same molecule are particularly preferred.

[0090] The light-emitting layer of the light-emitting device may contain a pyrromethene boron complex represented by the following general formula (2). In particular, when the first compound is a thermally activated delayed fluorescent compound, it is preferable that the second compound is a pyrromethene boron complex. Although pyrromethene boron complexes are useful light-emitting materials that can produce a sharp emission spectrum when used as a dopant, it has been difficult to achieve a light-emitting device that has high luminous efficiency and high durability while maintaining a sharp emission spectrum. However, the pyrromethene boron complex represented by the following general formula (2) can provide a light-emitting material with a high fluorescence quantum yield and a sharp emission spectrum, as well as a light-emitting device with high luminous efficiency, color purity, and durability.

[0091] [ka]

[0092] Here, in the general formula (2), X 1is a nitrogen atom or a carbon atom, with the proviso that the carbon atom is bonded to one atom or monovalent group selected from the group consisting of a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted alkylthio group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted arylthio group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted heteroaryl group, a halogen atom, a carboxy group, a substituted or unsubstituted alkoxycarbonyl group, a substituted or unsubstituted carbamoyl group, a substituted or unsubstituted amino group, a nitro group, a cyano group, a substituted or unsubstituted silyl group, and a substituted or unsubstituted siloxanyl group.

[0093] R 1 ~R 6 are each independently an atom or group selected from the group consisting of a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aryl group, an alkoxy group, a substituted or unsubstituted alkylthio group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted arylthio group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted heteroaryl group, a halogen atom, a carboxy group, a substituted or unsubstituted alkoxycarbonyl group, a substituted or unsubstituted carbamoyl group, a substituted or unsubstituted amino group, a nitro group, a cyano group, a substituted or unsubstituted silyl group, and a substituted or unsubstituted siloxanyl group, with the proviso that R 1 and R 2 Group R 2 and R 3 Group R 4 and R 5 Group R 5 and R 6 In one or more of the groups, a bond may be formed between the groups constituting the group to form a ring. 1 and Z 2are each independently an atom or group selected from the group consisting of a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkoxy group, a cyano group, and a substituted or unsubstituted aryloxy group, provided that Z 1 and Z 2 A bond may be formed between the groups to form a ring.

[0094] In all of the above groups, hydrogen may be replaced with deuterium, as in the compounds or partial structures thereof described below.

[0095] In addition, in all of the above groups, when substituted, the substituent is preferably a group selected from the group consisting of alkyl groups, cycloalkyl groups, heterocyclic groups, alkenyl groups, cycloalkenyl groups, alkynyl groups, aryl groups, heteroaryl groups, hydroxyl groups, thiol groups, alkoxy groups, alkylthio groups, aryloxy groups, arylthio groups, aralkyl groups, halogen, cyano groups, formyl groups, acyl groups, carboxy groups, alkoxycarbonyl groups, carbamoyl groups, acyl groups, alkylsulfonyl groups, arylsulfonyl groups, alkoxysulfonyl groups, aminosulfonyl groups, amino groups, nitro groups, silyl groups, siloxanyl groups, boryl groups, phosphine oxide groups and oxo groups.Moreover, the specific substituents that are preferred in the description of each substituent below are more preferred.In addition, these substituents may be further substituted with the above-mentioned substituents.

[0096] In this description, "unsubstituted" means that the atoms bonded to the target basic skeleton or group are only hydrogen atoms or deuterium atoms. The same applies to "substituted or unsubstituted" in the compounds or partial structures described below.

[0097] The alkyl group refers to a saturated aliphatic hydrocarbon group such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, or a tert-butyl group, and may be substituted or unsubstituted. When substituted, the additional substituent is not particularly limited, and examples thereof include an alkyl group, a halogen, an aryl group, and a heteroaryl group, and this point is also applicable to the following description. The number of carbon atoms in the alkyl group is not particularly limited, but is preferably in the range of 1 to 20, more preferably 1 to 8, in terms of availability and cost.

[0098] The cycloalkyl group refers to a saturated alicyclic hydrocarbon group, such as a cyclopropyl group, a cyclohexyl group, a norbornyl group, an adamantyl group, or the like, which may be substituted or unsubstituted. The number of carbon atoms in the alkyl group is not particularly limited, but is preferably in the range of 3 to 20.

[0099] The heterocyclic group refers to an aliphatic ring having atoms other than carbon atoms in the ring, such as a pyran ring, a piperidine ring, or a cyclic amide, which may be substituted or unsubstituted. The number of carbon atoms in the heterocyclic group is not particularly limited, but is preferably in the range of 2 to 20.

[0100] The alkenyl group refers to an unsaturated aliphatic hydrocarbon group containing a double bond, such as a vinyl group, an allyl group, or a butadienyl group, which may be substituted or unsubstituted. The number of carbon atoms in the alkenyl group is not particularly limited, but is preferably in the range of 2 to 20.

[0101] The cycloalkenyl group refers to an unsaturated alicyclic hydrocarbon group containing a double bond, such as a cyclopentenyl group, a cyclopentadienyl group, or a cyclohexenyl group, which may be substituted or unsubstituted. The number of carbon atoms in the cycloalkenyl group is not particularly limited, but is preferably in the range of 3 to 20.

[0102] The alkynyl group refers to an unsaturated aliphatic hydrocarbon group containing a triple bond, such as an ethynyl group, which may be substituted or unsubstituted. The number of carbon atoms in the alkynyl group is not particularly limited, but is preferably in the range of 2 to 20.

[0103] The alkoxy group refers to a functional group in which an aliphatic hydrocarbon group is bonded via an ether bond, such as a methoxy group, an ethoxy group, or a propoxy group, and this aliphatic hydrocarbon group may be substituted or unsubstituted. The number of carbon atoms in the alkoxy group is not particularly limited, but is preferably in the range of 1 to 20.

[0104] An alkylthio group is an alkoxy group in which the oxygen atom of the ether bond is replaced with a sulfur atom. The hydrocarbon group of the alkylthio group may be substituted or unsubstituted. The number of carbon atoms in the alkylthio group is not particularly limited, but is preferably in the range of 1 to 20.

[0105] The aryloxy group refers to a functional group, such as a phenoxy group, to which an aromatic hydrocarbon group is bonded via an ether bond, and the aromatic hydrocarbon group may be substituted or unsubstituted. The number of carbon atoms in the aryloxy group is not particularly limited, but is preferably in the range of 6 to 40.

[0106] An arylthio group is an aryloxy group in which the oxygen atom of the ether bond is replaced with a sulfur atom. The aromatic hydrocarbon group in the arylthio group may be substituted or unsubstituted. The number of carbon atoms in the arylthio group is not particularly limited, but is preferably in the range of 6 to 40.

[0107] An aralkyl group is an alkyl group in which one of the hydrogen atoms of the alkyl group is substituted with an aryl group, such as a phenylmethyl group or a phenylethyl group. The number of carbon atoms in the aralkyl group is not particularly limited, but is preferably in the range of 6 to 40.

[0108] The aryl group may be either a single ring or a condensed ring, and may be, for example, an aromatic hydrocarbon group such as a phenyl group, a naphthyl group, a fluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenanthryl group, an anthracenyl group, a benzophenanthryl group, a benzanthracenyl group, a chrysenyl group, a pyrenyl group, a fluoranthenyl group, a triphenylenyl group, a benzofluoranthenyl group, a dibenzoanthracenyl group, a perylenyl group, or a helicenyl group. Among these, a group selected from the group consisting of a phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, a fluorenyl group, a phenanthryl group, an anthracenyl group, a pyrenyl group, a fluoranthenyl group, and a triphenylenyl group is preferred. The aryl group may be substituted or unsubstituted. In the present invention, a group in which multiple phenyl groups are bonded via single bonds, such as a biphenyl group or a terphenyl group, is considered to be a phenyl group having an aryl group as a substituent. The number of carbon atoms in the aryl group is not particularly limited, but is preferably in the range of from 6 to 40, more preferably from 6 to 30. In addition, in the case of a phenyl group, when two adjacent carbon atoms in the phenyl group each have a substituent, the substituents may together form a ring structure.

[0109] The heteroaryl group may be either a single ring or a condensed ring, and examples thereof include a pyridyl group, a furanyl group, a thiophenyl group, a quinolinyl group, an isoquinolinyl group, a pyrazinyl group, a pyrimidyl group, a pyridazinyl group, a triazinyl group, a naphthyridinyl group, a cinnolinyl group, a phthalazinyl group, a quinoxalinyl group, a quinazolinyl group, a benzofuranyl group, a benzothiophenyl group, an indolyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a carbazolyl group, a benzocarboxyl group, a benzocarbazin ... The term "aryl" refers to a cyclic aromatic group having one or more atoms other than carbon and hydrogen, i.e., heteroatoms, in the ring, such as a benzocarbazolyl group, a carbolinyl group, an indolocarbazolyl group, a benzofurocarbazolyl group, a benzothienocarbazolyl group, a dihydroindenocarbazolyl group, a benzoquinolinyl group, an acridinyl group, a dibenzoacridinyl group, a benzimidazolyl group, an imidazopyridyl group, a benzoxazolyl group, a benzothiazolyl group, or a phenanthrolinyl group. The heteroatom is preferably a nitrogen atom, an oxygen atom, or a sulfur atom. The heteroaryl group may be substituted or unsubstituted. The number of carbon atoms in the heteroaryl group is not particularly limited, but is preferably 2 to 40, more preferably 2 to 30.

[0110] Halogen refers to an atom selected from fluorine, chlorine, bromine and iodine.

[0111] A cyano group is a functional group with the structure -CN, where the carbon atom is the bond to other groups.

[0112] A formyl group is a functional group with the structure -C(=O)H, where the carbon atom is the bond to other groups.

[0113] The acyl group refers to a functional group in which an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, or a heteroaryl group is bonded via a carbonyl group, such as an acetyl group, a propionyl group, a benzoyl group, or an acrylyl group. These substituents may be further substituted. The number of carbon atoms in the acyl group is not particularly limited, but is preferably 2 to 40, more preferably 2 to 30.

[0114] An alkoxycarbonyl group refers to a functional group in which, for example, an alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, or the like is bonded via an ester bond. These substituents may be further substituted. The number of carbon atoms in the alkoxycarbonyl group is not particularly limited, but is preferably in the range of 1 to 20. More specific examples include a methoxycarbonyl group, an ethoxycarbonyl group, a propoxycarbonyl group, a butoxycarbonyl group, an isopropoxymethoxycarbonyl group, a hexyloxycarbonyl group, and a phenoxycarbonyl group.

[0115] A carbamoyl group refers to a functional group in which, for example, an alkyl group, a cycloalkyl group, an aryl group, or a heteroaryl group is bonded via an amide bond. These substituents may be further substituted. The number of carbon atoms in the amide group is not particularly limited, but is preferably in the range of 1 to 20. More specific examples include a methylamide group, an ethylamide group, a propylamide group, a butylamide group, an isopropylamide group, a hexylamide group, and a phenylamide group.

[0116] The alkylsulfonyl group and arylsulfonyl group refer to functional groups in which, for example, an alkyl group, a cycloalkyl group, an aryl group, or a heteroaryl group is bonded via an -S(=O)2- bond. These substituents may be further substituted. The number of carbon atoms in the alkylsulfonyl group and arylsulfonyl group is not particularly limited, but is preferably in the range of 1 to 20.

[0117] An alkoxysulfonyl group refers to a functional group in which, for example, an alkyl group, a cycloalkyl group, an aryl group, or a heteroaryl group is bonded via a sulfonate ester bond. Here, the sulfonate ester bond refers to a group in which the carbonyl portion of the ester bond, i.e., -C(=O)-, is replaced with a sulfonyl portion, i.e., -S(=O)2-. These substituents may be further substituted. The number of carbon atoms in the alkoxysulfonyl group is not particularly limited, but is preferably in the range of 1 to 20.

[0118] An aminosulfonyl group refers to a functional group in which, for example, an alkyl group, a cycloalkyl group, an aryl group, or a heteroaryl group is bonded via a sulfonamide bond. Here, the sulfonamide bond refers to an ester bond in which the carbonyl moiety, i.e., -C(=O)-, is replaced with a sulfonyl moiety, i.e., -S(=O)2-. These substituents may be further substituted. The number of carbon atoms in the aminosulfonyl group is not particularly limited, but is preferably in the range of 1 to 20.

[0119] The amino group is a substituted or unsubstituted amino group. In the case of substitution, examples of the substituent include an aryl group, a heteroaryl group, a linear alkyl group, and a branched alkyl group. Preferred aryl and heteroaryl groups are a phenyl group, a naphthyl group, a pyridyl group, and a quinolinyl group. These substituents may be further substituted. The number of carbon atoms is not particularly limited, but is preferably in the range of 2 to 50, more preferably 6 to 40, and particularly preferably 6 to 30.

[0120] The silyl group refers to a functional group to which a substituted or unsubstituted silicon atom is bonded, such as an alkylsilyl group such as a trimethylsilyl group, a triethylsilyl group, a tert-butyldimethylsilyl group, a propyldimethylsilyl group, or a vinyldimethylsilyl group, or an arylsilyl group such as a phenyldimethylsilyl group, a tert-butyldiphenylsilyl group, a triphenylsilyl group, or a trinaphthylsilyl group. The substituent on the silicon may be further substituted. The number of carbon atoms in the silyl group is not particularly limited, but is preferably in the range of 1 to 30.

[0121] The siloxanyl group refers to a silicon compound group bonded via an ether bond, such as a trimethylsiloxanyl group, etc. The substituent on the silicon may be further substituted.

[0122] The boryl group is a substituted or unsubstituted boryl group. When substituted, examples of the substituent include an aryl group, a heteroaryl group, a linear alkyl group, a branched alkyl group, an aryl ether group, an alkoxy group, and a hydroxyl group, and among these, an aryl group and an aryl ether group are preferred.

[0123] The phosphine oxide group is -P(=O)R 16 R 17 R is a group represented by 16 and R 17 are each independently R 1 ~R 6 is selected from the same group as

[0124] The range of substituents that can be substituted in the description of each group above, such as "may be substituted or unsubstituted" and "may be further substituted," is the range of substituents that can be substituted when compared with the compound before substitution, and are evaluated as being chemically equivalent or having almost no effect on the performance when used in a light-emitting device. From another perspective, it means including a range that can be evaluated as equivalent from the perspective of use in a light-emitting device. In addition, the explanation of each group in general formula (3) and general formula (4) below will refer to the explanation of each group above, and R 7 ~R 15 and Ar 1 The range of substituents in the case of substitution in the description of "substituted or unsubstituted" in the explanation of the above has the same meaning as the range of substitutable substituents in the case of substitution in the description of "may be substituted or unsubstituted" and the description of "the substituent may be further substituted."

[0125] Pyrromethene boron complexes have a strong and highly planar skeleton, and therefore exhibit high fluorescence quantum yield. Furthermore, because the peak half-width of the emission spectrum is small, efficient light emission and high color purity can be achieved in light-emitting devices. To further improve the emission efficiency, it is effective to suppress the rotation and vibration of the substituents of the pyrromethene boron complex, thereby reducing energy loss and improving the fluorescence quantum yield. Furthermore, to improve color purity, it is effective to reduce vibrational relaxation in the excited state of the pyrromethene boron complex and thereby reduce the half-width of the emission spectrum. From this perspective, in the structure represented by the general formula (2), X 1 is a carbon atom, and is preferably one to which the above-mentioned atom or monovalent group is bonded.

[0126] X 1 is a carbon atom, and by using a compound having one of the above-mentioned atoms or monovalent groups bonded to the carbon atom, a pyrromethene boron complex with a high fluorescence quantum yield and a narrow half-width can be provided. Furthermore, if the group bonded to the bridgehead position is prevented from intramolecular rotation with respect to the pyrromethene skeleton, energy deactivation can be suppressed, which is advantageous for improving luminous efficiency. In addition, the stability of the pyrromethene boron complex affects the durability of the light-emitting device. To further improve the stability, it is preferable to introduce a bulky substituent into the bridgehead position. By introducing a bulky substituent, the pyrromethene skeleton can be protected from interaction with other surrounding molecules.

[0127] X 1 When is a carbon atom, particularly preferred monovalent groups bonded to the carbon atom are groups represented by the following general formula (3) or (4), from the viewpoint of suppressing energy deactivation.

[0128] [ka]

[0129] (where R 9 ~R 11each independently represents an atom or group selected from the group consisting of a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted heterocyclic group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted cycloalkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, a hydroxyl group, a thiol group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted alkylthio group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted arylthio group, a halogen atom, a cyano group, a formyl group, an acyl group, a carboxy group, a substituted or unsubstituted alkoxycarbonyl group, a substituted or unsubstituted carbamoyl group, a substituted or unsubstituted alkylsulfonyl group, a substituted or unsubstituted arylsulfonyl group, a substituted or unsubstituted aminosulfonyl group, a substituted or unsubstituted amino group, a nitro group, a substituted or unsubstituted silyl group, and a ring structure formed between an adjacent group, R 7 and R 8 are each independently a group selected from the group consisting of a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, and a substituted or unsubstituted heteroaryl group.

[0130] [ka]

[0131] (where R 12 ~R 14are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted heterocyclic group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted cycloalkenyl group, a substituted or unsubstituted alkynyl group, a hydroxyl group, a thiol group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted alkylthio group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted arylthio group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, a halogen atom, a cyano group, a hydroxyl ... an atom or group selected from the group consisting of a methyl group, an acyl group, a carboxy group, a substituted or unsubstituted alkoxycarbonyl group, a substituted or unsubstituted carbamoyl group, a substituted or unsubstituted alkylsulfonyl group, a substituted or unsubstituted arylsulfonyl group, a substituted or unsubstituted alkoxysulfonyl group, a substituted or unsubstituted aminosulfonyl group, a substituted or unsubstituted amino group, a nitro group, a substituted or unsubstituted silyl group, a substituted or unsubstituted siloxanyl group, a substituted or unsubstituted boryl group, and a substituted or unsubstituted phosphine oxide group; R 15represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted heterocyclic group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted cycloalkenyl group, a substituted or unsubstituted alkynyl group, a hydroxyl group, a thiol group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted alkylthio group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted arylthio group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, a halogen atom, a cyano group, a formyl group, a group selected from the group consisting of an acyl group, a carboxy group, a substituted or unsubstituted alkoxycarbonyl group, a substituted or unsubstituted carbamoyl group, a substituted or unsubstituted alkylsulfonyl group, a substituted or unsubstituted arylsulfonyl group, a substituted or unsubstituted alkoxysulfonyl group, a substituted or unsubstituted aminosulfonyl group, a substituted or unsubstituted amino group, a nitro group, a substituted or unsubstituted silyl group, a substituted or unsubstituted siloxanyl group, a substituted or unsubstituted boryl group, and a substituted or unsubstituted phosphine oxide group; Ar 1 is a group selected from the group consisting of a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group. In addition, when the group represented by the general formula (3) is contained, the pyrromethene boron compound represented by the general formula (2) is Z 1 and Z 2 are each independently a group selected from the group consisting of a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted aryl group, a halogen atom, and a cyano group, and R 1 , R 3 , R 4 and R 6 are each independently a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group (wherein these aryl groups and heteroaryl groups may be monocyclic or fused rings, provided that R 1 and R 6When one or both of R are monocyclic aryl and heteroaryl groups, the monocyclic aryl and heteroaryl groups have one or more secondary alkyl groups, one or more tertiary alkyl groups, one or more aryl groups, or one or more heteroaryl groups as substituents, or have a total of two or more methyl groups and primary alkyl groups as substituents. 2 and R 5 are each independently preferably an atom or group selected from the group consisting of a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted alkylthio group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted arylthio group, a halogen atom, a cyano group, a carboxy group, a substituted or unsubstituted alkoxycarbonyl group, a substituted or unsubstituted carbamoyl group, a substituted or unsubstituted amino group, a nitro group, and a substituted or unsubstituted silyl group. 4 and R 5 Between and R 2 and R 3 One or both of the groups may be bonded via one or two atoms between the groups.

[0132] The greater the number of carbon atoms in the primary alkyl group, secondary alkyl group, and tertiary alkyl group, the greater the steric hindrance, and therefore the more preferable. However, from the viewpoint of ease of synthesis as a compound, the number of carbon atoms is preferably about 2 to 10, and more preferably 4 to 10.

[0133] Furthermore, Z 1 and Z 2 From the viewpoints of luminescence properties and thermal stability, Z is preferably an alkyl group, an alkoxy group, an aryl ether group, a halogen, or a cyano group. From the viewpoints of stabilizing the excited state and obtaining a higher fluorescence quantum yield, and of improving durability, Z 1 and Z 2is more preferably an electron-withdrawing group, specifically, more preferably a fluorine atom, a fluorine-containing alkyl group, a fluorine-containing alkoxy group, a fluorine-containing aryl ether group or a cyano group, further preferably a fluorine atom or a cyano group, and most preferably a fluorine atom.

[0134] R 1 and R 6 is a group that contributes to the stability and luminous efficiency of pyrromethene boron complex compounds. Stability refers to electrical stability and thermal stability. Electrical stability means that the compound is less likely to decompose or otherwise change in quality when electricity is continuously applied to the light-emitting device. Thermal stability means that the compound is less likely to change in quality due to heating processes such as sublimation purification and vapor deposition during manufacturing, or the environmental temperature around the light-emitting device. Since the luminous efficiency decreases when the compound changes quality, the stability of the compound is important for improving the durability of the light-emitting device. R 1 and R 6 From the viewpoint of the stability and luminous efficiency of the compound, R is preferably a substituted or unsubstituted aryl group. 1 and R 6 is preferably a group with the greatest steric hindrance among the above groups in order to prevent aggregation of pyrromethene boron complexes and avoid concentration quenching. 1 and R 6 is preferably selected from the group consisting of a phenyl group having one or more tertiary alkyl groups as a substituent, a phenyl group having one or more aryl groups as a substituent, a phenyl group having one or more heteroaryl groups as a substituent, a phenyl group having a total of two or more methyl groups and primary alkyl groups as substituents, at least one of which is substituted at the 2-position relative to the bonding site to the pyrrole ring, and a fused-ring aromatic hydrocarbon group. In addition, the smaller the degree of freedom of rotation or vibration, the more effectively the efficiency reduction due to thermal deactivation can be suppressed, so R 1 and R 6 is preferably a functional group having a rigid structure or a highly symmetric structure. 1 and R 6is more preferably a phenyl group having one or more tert-butyl groups as substituents, a phenyl group having one or more phenyl groups as substituents, or a phenyl group substituted with methyl groups at least at the 2- and 6-positions relative to the bonding site to the pyrrole ring, and having substituents in line symmetry with respect to the bond to the pyrrole as the axis of symmetry, or an unsubstituted fused-ring aromatic hydrocarbon group.Furthermore, from the viewpoint of ease of production, it is even more preferably a 2,6-dimethylphenyl group, a mesityl group, a 4-tert-butylphenyl group, a 3,5-di-tert-butylphenyl group, a 4-biphenyl group, or a 1-naphthyl group.

[0135] R 3 and R 4 is a group that contributes to controlling the emission wavelength. To make a pyrromethene boron complex emit red light, an aryl or heteroaryl group can be directly bonded to the pyrromethene metal complex skeleton to extend the conjugation and shift the emission wavelength to longer wavelengths. For this reason, R 3 and R 4 is a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group, but from the viewpoint of the stability of the compound, a substituted or unsubstituted aryl group is more preferred.

[0136] R 2 and R 5 mainly affects the peak wavelength, the half-width of the emission spectrum, stability, or crystallinity. From the viewpoints of narrowing the half-width of the emission spectrum, stability that affects the durability of the device, and ease of manufacturing including recrystallization and purification, R 2 and R 5 At least one of, and more preferably both of, is preferably a hydrogen atom or a substituted or unsubstituted alkyl group.

[0137] In addition, in the compound represented by general formula (2), R 1 and R 2 Group R 2 and R 3 Group R 4 and R 5 Group R5 and R 6 In any one or more of the groups, a bond may be formed between the groups constituting the group to form a ring, and Z 1 and Z 2 A bond may be formed between R to form a ring. 1 Or R 6 means that a condensed ring with a pyrromethene ring can be formed, preferably a condensed ring, i.e., a five- to seven-membered ring containing two carbon atoms of the pyrromethene ring; and Z 1 and Z 2 In the above, it is possible to have a heterocycle containing boron as a partial structure.

[0138] In order to improve the luminescence efficiency, it is effective to suppress the rotation and vibration of the group represented by general formula (3), thereby reducing the energy loss and improving the fluorescence quantum yield. 7 and R 8 is selected from a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group. Among these, it is preferable that at least one of R is a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group. On the other hand, from the viewpoint of ease of production, R 7 and R 8 Preferably, one of R is a substituted or unsubstituted alkyl group, more preferably a methyl group. 9 ~R 11 is used to adjust the peak wavelength, crystallinity, sublimation temperature, etc. The substituent at the 4-position relative to the bond with the pyrromethene skeleton, namely R 10 R 10 If R is an electron-donating group, the emission peak wavelength shifts to the shorter wavelength side. Specific examples of electron-donating groups include methyl, ethyl, tert-butyl, cyclohexyl, methoxy, ethoxy, phenyl, tolyl, naphthyl, furanyl, and dibenzofuranyl groups. 10When R is an alkoxy group such as a methoxy group or an ethoxy group, which has strong electron donating properties, the wavelength shift is large and it is useful for wavelength tuning. 10 If R is an electron-withdrawing group, the emission peak shifts to the longer wavelength side. Specific examples of electron-withdrawing groups include a fluorine atom, a trifluoromethyl group, a cyano group, a pyridyl group, and a pyrimidyl group. In particular, R 10 When is a group selected from a fluorine atom, a trifluoromethyl group, and a cyano group, which have strong electron-withdrawing properties, the long wavelength shift is large and is useful for wavelength tuning. However, the electron-donating group and the electron-withdrawing group are not limited to these.

[0139] In addition, when the group represented by the general formula (4) is contained, the pyrromethene boron compound represented by the general formula (2) is Z 1 and Z 2 are each independently an atom or group selected from the group consisting of a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted aryl group, a halogen atom, and a cyano group, and R 1 ~R 6 are each independently a group selected from the group consisting of a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted alkylthio group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, a substituted or unsubstituted amino group, a substituted or unsubstituted silyl group, and a substituted or unsubstituted siloxanyl group, with the proviso that R 1 , R 3 , R 4 , R 6 At least one of the groups is preferably a hydrogen atom or a substituted or unsubstituted alkyl group.

[0140] Furthermore, Z 1 and Z 2From the viewpoints of luminescence properties and thermal stability, Z is preferably an alkyl group, an alkoxy group, an aryl ether group, a halogen, or a cyano group. From the viewpoints of stabilizing the excited state and obtaining a higher fluorescence quantum yield, and of improving durability, Z 1 and Z 2 is more preferably an electron-withdrawing group, specifically, more preferably a fluorine atom, a fluorine-containing alkyl group, a fluorine-containing alkoxy group, a fluorine-containing aryl ether group or a cyano group, further preferably a fluorine atom or a cyano group, and most preferably a fluorine atom.

[0141] R 1 and R 6 affects the emission peak wavelength, crystallinity, sublimation temperature, etc. of the pyrromethene boron complex. From the viewpoint of narrowing the half-width of the emission spectrum, R 1 and R 6 is preferably a hydrogen atom or an alkyl group. Furthermore, from the viewpoint of further improving the fluorescence quantum yield, R 1 and R 6 is more preferably an alkyl group, and from the viewpoint of ease of production, is even more preferably a methyl group.

[0142] R 3 and R 4 The R mainly affects the emission peak wavelength, half-width of the emission spectrum, stability, or crystallinity of the pyrromethene boron complex. From the viewpoint of narrowing the half-width of the emission spectrum, improving stability, and facilitating synthesis including recrystallization, R 3 and R 4 Preferably, at least one of, and preferably both of, R are groups selected from the group consisting of a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, and a substituted or unsubstituted heteroaryl group. 3 and R 4 is more preferably an alkyl group, and from the viewpoint of ease of production, is even more preferably a methyl group.

[0143] R 2 and R 5 The R mainly affects the emission peak wavelength, half-width of the emission spectrum, stability, or crystallinity of the pyrromethene boron complex. From the viewpoint of narrowing the half-width of the emission spectrum, improving stability, and facilitating synthesis including recrystallization and purification, R 2 and R 5 At least one of, and preferably both of, the groups are preferably a hydrogen atom or a substituted or unsubstituted alkyl group, and from the viewpoint of ease of production, it is more preferable that both of them are hydrogen atoms.

[0144] In order to improve the luminescence efficiency, it is effective to suppress the rotation and vibration of the group represented by general formula (4), thereby reducing the energy loss and improving the fluorescence quantum yield. 11 and Ar 1 is more preferably a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group, and from the viewpoint of ease of production, is still more preferably a phenyl group, a 2,6-dimethylphenyl group, a mesityl group, a 4-tert-butylphenyl group, a 3,5-di-tert-butylphenyl group, a 4-methoxyphenyl group, a 4-biphenyl group, or a 1-naphthyl group.

[0145] Examples of methods for introducing an aryl group or a heteroaryl group into the pyrromethene skeleton include, but are not limited to, a method in which a carbon-carbon bond is generated by a coupling reaction between a halogenated derivative of a pyrromethene boron complex and a boronic acid or a boronate ester derivative in the presence of a metal catalyst such as palladium.Similarly, examples of methods for introducing an amino group or a carbazolyl group into the pyrromethene skeleton include, but are not limited to, a method in which a carbon-nitrogen bond is generated by a coupling reaction between a halogenated derivative of a pyrromethene boron complex and an amine or a carbazole derivative in the presence of a metal catalyst such as palladium.

[0146] The obtained pyrromethene boron complex is preferably purified by organic synthesis techniques such as recrystallization or column chromatography, and then further purified by heating under reduced pressure, commonly known as sublimation purification, to remove low-boiling components and improve purity. The heating temperature in sublimation purification is not particularly limited, but is preferably 330°C or lower, more preferably 300°C or lower, from the viewpoint of preventing thermal decomposition of the pyrromethene boron complex. The purity of the pyrromethene boron complex produced in this manner is preferably 99% by weight or higher, from the viewpoint of enabling a light-emitting device to exhibit stable characteristics.

[0147] The optical properties of the pyrromethene boron complex can be obtained by measuring the absorption and emission spectra of the diluted solution. The solvent is not particularly limited as long as it dissolves the pyrromethene boron complex and is transparent so that the absorption spectrum of the solvent does not overlap with the absorption spectrum of the pyrromethene boron complex. Specific examples include toluene. The concentration of the solution is not particularly limited as long as it has sufficient absorbance and does not cause concentration quenching. However, it is preferable to use a solution containing 1×10 -4 mol / L~1×10 -7 mol / L, preferably in the range of 1×10 -5 mol / L~1×10 -6 It is more preferable that the concentration is in the range of 100 mol / L.

[0148] The absorption spectrum can be measured using a general ultraviolet-visible spectrophotometer. The emission spectrum can be measured using a general fluorescence spectrophotometer. Furthermore, it is preferable to use an absolute quantum yield measurement device with an integrating sphere to measure the fluorescence quantum yield. In order to achieve high color purity, it is preferable that the emission spectrum of the light emitted by the pyrromethene boron complex when irradiated with excitation light is sharp.

[0149] Furthermore, top-emission elements, which are mainstream in display devices and lighting devices, can achieve high brightness and high color purity due to the resonance effect of their microcavity structure, and a sharp emission spectrum enhances this resonance effect, which is advantageous for achieving high efficiency. From this perspective, the half-width of the emission spectrum is preferably 60 nm or less, more preferably 50 nm or less, even more preferably 45 nm or less, and particularly preferably 28 nm or less.

[0150] The luminous efficiency of a light-emitting device depends on the fluorescence quantum yield of the luminescent material itself. Therefore, it is desirable that the fluorescence quantum yield of the luminescent material be as close to 100% as possible. The pyrromethene boron complex represented by general formula (2) can achieve a high fluorescence quantum yield by suppressing the rotation and vibration of the bridgehead position and reducing thermal deactivation. From the above perspective, the fluorescence quantum yield of the pyrromethene boron complex is preferably 90% or higher, and more preferably 95% or higher. However, the fluorescence quantum yield shown here was measured using a diluted solution using toluene as the solvent using an absolute quantum yield measurement device.

[0151] When the first compound is a thermally activated delayed fluorescent compound, the light-emitting layer may further contain a compound (hereinafter, such a compound may be referred to as a "third compound") whose singlet energy (referring to the energy difference between the lowest excited singlet state and the ground state; the same applies hereinafter) is greater than that of the first compound. This allows the third compound to have the function of confining the energy of the light-emitting material within the light-emitting layer, enabling efficient light emission. Furthermore, it is preferable that the third compound has a lowest excited triplet energy (referring to the energy difference between the lowest excited triplet state and the ground state; the same applies hereinafter) greater than that of the first compound. Such a third compound is preferably an organic compound with high charge transport capability and a high glass transition temperature.

[0152] The third compound may be composed of a single material or two or more materials. When two or more materials are used as the third compound, a combination of an electron-transporting third compound and a hole-transporting third compound is preferable. By combining the electron-transporting third compound and the hole-transporting third compound in an appropriate mixing ratio, the charge balance in the light-emitting layer can be adjusted and the unevenness of the light-emitting region can be suppressed, thereby improving the reliability and durability of the light-emitting device. In addition, an exciplex may be formed between the electron-transporting third compound and the hole-transporting third compound.

[0153] From the above viewpoints, it is preferable that the first compound and the third compound respectively satisfy the following relational formulas 1 to 4. It is more preferable that they satisfy formulas 1 and 2, and even more preferable that they satisfy formulas 3 and 4. It is even more preferable that they satisfy all of formulas 1 to 4. S1 (third electron-transporting compound)>S1 (first compound) (Formula 1) S1 (third compound having hole transporting properties)>S1 (first compound) (Equation 2) T1 (electron-transporting third compound)>T1 (first compound) (Equation 3) T1 (third compound having hole transporting properties)>T1 (first compound) (Equation 4) Here, S1 represents the energy level of the lowest excited singlet state of each compound, and T1 represents the energy level of the lowest excited triplet state of each compound.

[0154] Examples of the electron-transporting third compound include compounds containing a π-electron-deficient heteroaromatic ring. Specific examples include heterocyclic compounds having a polyazole skeleton, heterocyclic compounds having a quinoxaline skeleton or a dibenzoquinoxaline skeleton, heterocyclic compounds having a diazine skeleton (pyrimidine skeleton or pyrazine skeleton), and heterocyclic compounds having a pyridine skeleton. Examples of the hole-transporting third compound include compounds containing a π-electron-rich heteroaromatic ring. Specific examples include compounds having a carbazole skeleton.

[0155] The method for forming each of the layers constituting the light-emitting device of the present invention described above may be either a dry process or a wet process, including resistance heating evaporation, electron beam evaporation, sputtering, molecular lamination, coating, inkjet printing, and other methods, but is not particularly limited. Resistance heating evaporation is usually preferred from the viewpoint of device characteristics. The thickness of the organic layer is not particularly limited because it depends on the resistance value of the light-emitting material, but is preferably 1 to 1000 nm. The film thickness of the light-emitting layer, electron transport layer, and hole transport layer is preferably 1 nm to 200 nm, and more preferably 5 nm to 100 nm. [Example]

[0156] The present invention will be specifically described below with reference to examples, but the present invention should not be construed as being limited to these. First, the evaluation method will be described.

[0157] (1) Nuclear magnetic resonance analysis (NMR) The 400 MHz NMR spectrum of the white solid obtained in Synthesis Example 2 was measured using a JNM-AL400 nuclear magnetic resonance spectrometer (manufactured by JEOL Ltd.). Chemical shifts are expressed as δ (unit: ppm) relative to tetramethylsilane, and signals are represented as s (singlet), d (doublet), t (triplet), q (quartet), m (multiplet), br (broad), dd (double doublet), and dt (double triplet). The solvent names shown in the NMR data indicate the solvents used in the measurements.

[0158] (2) Powder X-ray Diffraction The white solid obtained in each of the Examples and Comparative Examples was packed into a sample plate (material: silicon; depth: 0.2 mm) of a powder X-ray diffractometer (Rigaku Corporation; 2200 / RINT ultima+PC), and the surface was flattened to prepare a measurement sample. Powder X-ray diffraction was measured under the following conditions. X-ray source: CuKα ray *Uses a curved crystal monochromator (graphite) Output: 40kV / 50mA Divergence slit: 1 / 2° Divergence vertical limit slit: 5mm Scattering slit: 1 / 2° Receiving slit: 0.15 mm Detector: Scintillation counter Scan method: 2θ / θ scan, continuous scan Measurement range (2θ): 2 to 30° Scan speed (2θ): 20° / min Counting step (2θ): 0.04°.

[0159] (3) Endothermic peak The white solids obtained in each of the Examples and Comparative Examples were subjected to simultaneous differential thermal and thermogravimetric measurements using a TG-DTA apparatus (TG8120 Smart Loader, manufactured by Rigaku Corporation), and the peak top temperature of the DTA curve was taken as the endothermic peak. Heating rate: 5°C / min Atmosphere: dry nitrogen (flow rate: 100 mL / min) Sample cell: Aluminum open cell Sample size: 5 to 15 mg.

[0160] (4) Chemical purity The chemical purity of the white solid obtained in each Example and Comparative Example was measured using high performance liquid chromatography (hereinafter referred to as HPLC), and the area percentage of the peak to be measured relative to all peaks excluding the blank peak and residual solvent peak was defined as the chemical purity. The HPLC analysis sample was prepared by dissolving 4 mg of the white solid obtained in each Example and Comparative Example in 40 mL of tetrahydrofuran. HPLC: LC-2010CHT (Shimadzu Corporation) Detection: UV (254 nm) Column: Mightysil RP-8GP (Kanto Chemical Co., Ltd.) Column size: 250 x 4.6 mm (5 μm) Column temperature: 45℃ Mobile phase: Solution A 0.1% phosphoric acid aqueous solution (weight ratio) Solution B: Acetonitrile / tetrahydrofuran = 80 / 20 (volume ratio) Development conditions: A / B = 55 / 45 → 0 / 100 (volume ratio); 0 → 25 min, linear gradient A / B = 0 / 100 (volume ratio); 25 → 30 min, constant A / B = 0 / 100 → 55 / 45 (volume ratio); 30 → 31 min, linear gradient A / B=55 / 45 (volume ratio), 31→35 minutes, constant Flow rate: 1.0mL / min Injection volume: 10μL.

[0161] (5) Residual solvent amount NMR measurement was performed on the white solid obtained in each Example and Comparative Example, and the molar ratio was calculated from the integrated peak values ​​of the target compound and the residual solvent, respectively, and the amount of residual solvent was calculated from the weight and molar ratio of the white solid obtained in each Example and Comparative Example. When multiple residual solvents were found, the total amount was calculated.

[0162] Next, examples of synthesis of precursors of the crystals of the present invention, examples and comparative examples of producing the crystals of the present invention, and the evaluation results thereof will be described.

[0163] (Synthesis Example 1) Synthesis of 2-phenyl-1,10-phenanthroline: Under an argon atmosphere, a phenyllithium solution (1.07 M, 100 mL) was added to a solution of 1,10-phenanthroline (9.64 g) in toluene (250 mL) and stirred at 0°C for 1.5 hours. Water (150 mL) was then added to the reaction mixture, which was then extracted three times with dichloromethane (200 mL). The organic layer was then washed with saturated brine (150 mL) and concentrated. Manganese dioxide (93 g) was added to a solution of the resulting concentrate in dichloromethane (300 mL) and stirred at room temperature for 56 hours. The reaction mixture was then filtered, and the residue was washed with dichloromethane (500 mL). The filtrate and washings were combined and concentrated. The resulting concentrate was suspended in ethyl acetate (30 mL) and stirred at 0°C. The precipitate was filtered and dried under reduced pressure at 80°C to obtain 9.44 g of 2-phenyl-1,10-phenanthroline as a white solid.

[0164] (Synthesis Example 2) Synthesis of 1,3-bis(9-phenyl-1,10-phenanthrolin-2-yl)benzene: Under an argon atmosphere, n-butyllithium (1.52 M, 17 mL) was added to a solution of 1,3-dibromobenzene (1.2 mL) in n-hexane (35 mL) and stirred under reflux for 1 hour. The reaction mixture was then cooled to 0°C, and a solution of 2-phenyl-1,10-phenanthroline (5.10 g) in tetrahydrofuran (100 mL) was added and stirred at 0°C for 2 hours. Water (100 mL) was then added to the reaction mixture, which was then extracted three times with dichloromethane (150 mL). The organic layer was washed with saturated brine (150 mL) and concentrated. Manganese dioxide (34.8 g) was added to a solution of the resulting concentrate in dichloromethane (180 mL) and stirred at room temperature for 12 hours. The reaction mixture was then filtered, and the residue was washed with dichloromethane (750 mL). The filtrate and washings were combined and concentrated.

[0165] The resulting concentrate was suspended in a dichloromethane / chloroform mixture (volume ratio 1 / 10, 85 mL) and stirred at 0°C. The precipitate was filtered and dried under reduced pressure at 100°C to obtain 3.25 g of 1,3-bis(9-phenyl-1,10-phenanthrolin-2-yl)benzene as a white solid. The NMR chemical shifts of the resulting compound are shown below. 1H-NMR (CDCl3, ppm): 9.75 (s, 1H), 8.72 (dd, 2H), 8.57-8.17 (m, 12H), 7.90-7.82 (m, 5H), 7.61-7.48 (m, 6H).

[0166] ( Reference example 1 ) Under an argon atmosphere, 1,3-dimethyl-2-imidazolidinone (4.9 mL, specific gravity 1.05) and toluene (8.7 mL, specific gravity 0.86) were added to 1,3-bis(9-phenyl-1,10-phenanthrolin-2-yl)benzene (1.28 g) obtained in Synthesis Example 2, and the mixture was stirred at 110°C for 0.5 hours. The mixture was then cooled to 0°C over 1 hour and stirred at 0°C for 1 hour. The precipitate was filtered and dried under reduced pressure at 20°C. Tetrahydrofuran (16.7 mL, specific gravity 0.89) was added to the resulting precipitate, and the mixture was heated under reflux and stirred for 2 hours. The mixture was then cooled to 0°C over 1 hour and stirred at 0°C for 1 hour. The precipitate was filtered and dried under reduced pressure at 100°C to obtain a white solid (yield 0.71 g, recovery rate 55%).

[0167] The obtained white solid was subjected to powder X-ray diffraction and endothermic peak measurement by the above-mentioned methods, and the measurement results are as follows, confirming that it was type B crystal. The powder X-ray diffraction pattern is shown in Figure 1, and the differential thermal analysis curve is shown in Figure 2. Diffraction angle 2θ(°): 6.7, 8.2, 13.7, 17.7, 22.2 Endothermic peak: 182℃ The chemical purity and residual solvent amount were evaluated by the above-mentioned methods and the results are shown in Table 1.

[0168] ( Reference example 2 ) Under an argon atmosphere, 1,3-dimethyl-2-imidazolidinone (2.2 mL, specific gravity 1.05) and toluene (6.6 mL, specific gravity 0.86) were added to 1,3-bis(9-phenyl-1,10-phenanthrolin-2-yl)benzene (0.97 g) obtained in Synthesis Example 2, and the mixture was stirred at 120°C for 0.5 hours. The mixture was then cooled to 0°C over 3 hours and stirred at 0°C for 2 hours. The precipitate was filtered and dried under reduced pressure at 100°C. Tetrahydrofuran (7.7 mL, specific gravity 0.89) was added to the resulting precipitate, and the mixture was heated under reflux and stirred for 2 hours. The mixture was then cooled to 0°C over 3 hours and stirred at 0°C for 2 hours. The precipitate was filtered and dried under reduced pressure at 100°C to obtain a white solid (yield 0.70 g, recovery rate 72%).

[0169] The obtained white solid was subjected to powder X-ray diffraction and endothermic peak measurement by the above-mentioned methods. The measurement results are shown below, and it was confirmed that the solid was type B crystals. Diffraction angle 2θ(°): 6.7, 8.2, 13.7, 17.7, 22.2 Endothermic peak: 182℃ The chemical purity and residual solvent amount were evaluated by the above-mentioned methods and the results are shown in Table 1.

[0170] Example 3 Under an argon atmosphere, 1,3-dimethyl-2-imidazolidinone (1.1 mL, specific gravity 1.05) and anisole (2.1 mL, specific gravity 0.99) were added to 1,3-bis(9-phenyl-1,10-phenanthrolin-2-yl)benzene (0.30 g) obtained in Synthesis Example 2, and the mixture was stirred at 100°C for 0.5 hours. The mixture was then cooled to 0°C over 1 hour and stirred at 0°C for 2 hours. The precipitate was filtered and dried under reduced pressure at 100°C to obtain a white solid (yield 0.24 g, recovery rate 80%).

[0171] The obtained white solid was subjected to powder X-ray diffraction and endothermic peak measurement by the above-mentioned method, and the measurement results are as follows, confirming that it was type C crystal. The powder X-ray diffraction pattern is shown in Figure 3, and the differential thermal analysis curve is shown in Figure 4. Diffraction angle 2θ(°): 5.0, 7.5, 8.7, 12.5, 17.3 Endothermic peak: 245℃ The chemical purity and residual solvent amount were evaluated by the above-mentioned methods and the results are shown in Table 1.

[0172] Example 4 Under an argon atmosphere, N-methylpyrrolidone (1.1 mL, specific gravity 1.03) and anisole (2.1 mL, specific gravity 0.99) were added to 1,3-bis(9-phenyl-1,10-phenanthrolin-2-yl)benzene (0.30 g) obtained in Synthesis Example 2, and the mixture was stirred at 100°C for 0.5 hours. The mixture was then cooled to 0°C over 1 hour and stirred at 0°C for 2 hours. The precipitate was filtered and dried under reduced pressure at 100°C to obtain a white solid (yield 0.23 g, recovery rate 77%).

[0173] The obtained white solid was subjected to powder X-ray diffraction and endothermic peak measurement by the above-mentioned methods, and the measurement results were as follows, confirming that it was C-type crystals. Diffraction angle 2θ(°): 5.0, 7.5, 8.7, 12.5, 17.3 Endothermic peak: 245℃ The chemical purity and residual solvent amount were evaluated by the above-mentioned methods and the results are shown in Table 1.

[0174] Example 5 Under an argon atmosphere, N,N-dimethylacetamide (1.1 mL, specific gravity 0.94) and anisole (2.1 mL, specific gravity 0.99) were added to 1,3-bis(9-phenyl-1,10-phenanthrolin-2-yl)benzene (0.30 g) obtained in Synthesis Example 2, and the mixture was stirred at 100°C for 0.5 hours. The mixture was then cooled to 0°C over 1 hour and stirred at 0°C for 2 hours. The precipitate was filtered and dried under reduced pressure at 100°C to obtain a white solid (yield 0.25 g, recovery rate 83%).

[0175] The obtained white solid was subjected to powder X-ray diffraction and endothermic peak measurement by the above-mentioned methods, and the measurement results were as follows, confirming that it was C-type crystals. Diffraction angle 2θ(°): 5.0, 7.5, 8.7, 12.5, 17.3 Endothermic peak: 245℃ The chemical purity and residual solvent amount were evaluated by the above-mentioned methods and the results are shown in Table 1.

[0176] Example 6 Under an argon atmosphere, 1,3-dimethyl-2-imidazolidinone (1.1 mL, specific gravity 1.05) and anisole (2.1 mL, specific gravity 0.99) were added to 1,3-bis(9-phenyl-1,10-phenanthrolin-2-yl)benzene (0.30 g) obtained in Synthesis Example 2, and the mixture was stirred at 100°C for 0.5 hours. The mixture was then cooled to 0°C over 4 hours and stirred at 0°C for 2 hours. The precipitate was filtered and dried under reduced pressure at 25°C to obtain a white solid (yield 0.30 g, recovery rate 100%).

[0177] The obtained white solid was subjected to powder X-ray diffraction and endothermic peak measurement by the above-mentioned method, and the measurement results are as follows, confirming that it was E-type crystals. The powder X-ray diffraction pattern is shown in Figure 5, and the differential thermal analysis curve is shown in Figure 6. Diffraction angle 2θ (°): 5.2, 7.0, 16.4, 20.0, 23.6 Endothermic peak: 96℃ Under an argon atmosphere, 1,3-bis(9-phenyl-1,10-phenanthrolin-2-yl)benzene (0.15 g) obtained from the above information was dried under reduced pressure at 100° C. to obtain a white solid (yield 0.12 g, recovery rate 80%).

[0178] The obtained white solid was subjected to powder X-ray diffraction and endothermic peak measurement by the above-mentioned methods, and the measurement results were as follows, confirming that it was C-type crystals. Diffraction angle 2θ(°): 5.0, 7.5, 8.7, 12.5, 17.3 Endothermic peak: 245℃ Furthermore, the chemical purity and residual solvent amount were evaluated by the above-mentioned methods and the results are shown in Table 2.

[0179] (Comparative Example 1) Under an argon atmosphere, 1,3-dimethyl-2-imidazolidinone (0.9 mL, specific gravity 1.05) and anisole (2.1 mL, specific gravity 0.99) were added to 1,3-bis(9-phenyl-1,10-phenanthrolin-2-yl)benzene (0.30 g) obtained in Synthesis Example 2, and the mixture was stirred at 100°C for 0.5 hours. The mixture was then cooled to 0°C over 1 hour and stirred at 0°C for 2 hours. The precipitate was filtered and dried under reduced pressure at 100°C to obtain a white solid (yield 0.27 g, recovery rate 90%).

[0180] The obtained white solid was subjected to powder X-ray diffraction and endothermic peak measurement by the above-mentioned methods. The measurement results are as follows, and it was confirmed that the crystal form (referred to as "D-type crystal") was different from the B-type crystal and the C-type crystal. The powder X-ray diffraction pattern is shown in Figure 7, and the differential thermal analysis curve is shown in Figure 8. Diffraction angle 2θ(°): 4.8, 7.2, 9.5, 22.9, 27.6 Endothermic peak: 173℃ Furthermore, the chemical purity and residual solvent amount were evaluated by the above-mentioned methods and the results are shown in Table 2.

[0181] (Comparative Example 2) Methanol (18 mL, specific gravity 0.79) was added to 1,3-bis(9-phenyl-1,10-phenanthrolin-2-yl)benzene (0.70 g) obtained in Synthesis Example 2 under an argon atmosphere, and the mixture was stirred at 20°C for 2 hours. The precipitate was filtered and then dried under reduced pressure at 100°C to obtain a white solid (yield 0.67 g, recovery rate 96%). The obtained white solid was subjected to powder X-ray diffraction measurement using the method described above. The measurement results are shown in Figure 9. As shown in Figure 9, no characteristic diffraction peaks were observed, indicating that the solid was amorphous. The chemical purity and residual solvent content were evaluated using the methods described above, and the results are shown in Table 2.

[0182] (Comparative Example 3) The 1,3-bis(9-phenyl-1,10-phenanthrolin-2-yl)benzene obtained in Synthesis Example 2 was subjected to powder X-ray diffraction measurement by the method described above. As in Comparative Example 2, no characteristic diffraction peaks were observed, and the product was amorphous. The results of evaluating the chemical purity and the amount of residual solvent by the methods described above are shown in Table 2. Reference Examples 1 and 2, Example 3 ~ 6 The main production methods and evaluation results of Comparative Examples 1 to 3 are shown in Tables 1 and 2.

[0183] [Table 1]

[0184] [Table 2]

[0185] As shown in Tables 1 and 2, the phenanthroline derivatives synthesized by conventional methods and those washed with methanol solvent were amorphous and had low residual solvent content, but low chemical purity. On the other hand, the D-type crystals of Comparative Example 1 had high chemical purity but a large amount of residual solvent. This indicates that crystallization of the amorphous phase alone is insufficient to obtain a phenanthroline derivative with high chemical purity and low residual solvent content; it is necessary to select B-type or C-type crystals with low residual solvent content. Furthermore, in Example 6, the E-type crystals readily underwent polymorphic transformation under reduced pressure drying conditions at 100°C, indicating that the E-type crystals are useful as precursors for obtaining C-type crystals by low-temperature drying.

[0186] Next, examples and comparative examples of light-emitting devices in which an electron transport layer is formed using the above-mentioned B-type crystal or C-type crystal and a thermally activated delayed fluorescent material is used as the light-emitting layer will be described.

[0187] The pyrromethene boron complex compounds used in the following examples and comparative examples are shown below, and their properties are shown in Table 3.

[0188] [ka]

[0189] [ka]

[0190] [Table 3]

[0191] Example 7 A glass substrate (manufactured by Geomatec Co., Ltd., 11 Ω / □, sputtered product) on which a 165 nm ITO transparent conductive film had been deposited was cut into 38 × 46 mm and etched. The resulting substrate was ultrasonically cleaned with "Semicoclean 56" (trade name, manufactured by Furuuchi Chemical Co., Ltd.) for 15 minutes, and then washed with ultrapure water. This substrate was subjected to ultraviolet light-ozone treatment for 1 hour immediately before fabricating the device, and then placed in a vacuum deposition apparatus, and the degree of vacuum in the apparatus was reduced to 5 × 10. -4 The chamber was evacuated to a pressure of 100 Pa or less. Using resistance heating, a 10-nm hole-injection layer (HAT-CN6) and a 180-nm hole-transport layer (HT-1) were deposited. Next, a 40-nm thick light-emitting layer was formed by depositing a host material (H-1), a dopant compound (D-1), and a TADF material (H-2) in a weight ratio of 80:1:19. A 35-nm thick electron-transport layer was then formed by depositing crystals (C-type crystals) of the phenanthroline derivative (ET-1). Next, a 0.5-nm thick electron-injection layer (2E-1) was deposited, followed by co-deposition of 1000 nm of magnesium and silver to form the cathode. A 5 x 5 mm square device was fabricated.

[0192] This light-emitting element is 1000cd / m 2 The external quantum efficiency when emitting light was 11.4%. The structures of HAT-CN6, HT-1, H-1, H-2, ET-1, and 2E-1 are shown below.

[0193] [ka]

[0194] ( Reference Example 3, Example 9, Reference Example 4 ) Light-emitting devices were fabricated and evaluated in the same manner as in Example 7, except that the crystals of the phenanthroline derivative ET-1 shown in Table 1 were used as the crystal form, and the compounds shown in Table 3 were used as the dopant materials for the light-emitting layer. The results are shown in Table 4.

[0195] Example 11 A glass substrate (manufactured by Geomatec Co., Ltd., 11 Ω / □, sputtered product) on which a 165 nm ITO transparent conductive film had been deposited was cut into 38 × 46 mm and etched. The resulting substrate was ultrasonically cleaned with "Semicoclean 56" (trade name, manufactured by Furuuchi Chemical Co., Ltd.) for 15 minutes, and then washed with ultrapure water. This substrate was subjected to ultraviolet light-ozone treatment for 1 hour immediately before fabricating the device, and then placed in a vacuum deposition apparatus, and the degree of vacuum in the apparatus was reduced to 5 × 10. -4 The chamber was evacuated to a pressure of 0.1 Pa or less. Using resistance heating, a 10-nm hole-injection layer (HAT-CN6) and a 40-nm hole-transport layer (HT-1) were deposited. Next, a 30-nm thick light-emitting layer was formed by depositing a host material, H-1, a dopant compound, and a TADF material, H-3, in a weight ratio of 80:1:19. A 50-nm thick electron-transport layer was then formed by depositing crystals (C-type crystals) of the phenanthroline derivative, ET-1. Next, a 0.5-nm thick electron-injection layer (2E-1), followed by co-deposition of 1000 nm of magnesium and silver, was used to fabricate a 5 x 5 mm square device.

[0196] This light-emitting element is 1000cd / m 2 The external quantum efficiency when emitting light was 9.2%. The structure of H-3 is shown below.

[0197] [ka]

[0198] ( Reference Example 5, Example 13, Reference Example 6 ) Light-emitting devices were fabricated and evaluated in the same manner as in Example 11, except that the crystals of the phenanthroline derivative ET-1 shown in Table 1 were used as the crystal form, and the compounds shown in Table 3 were used as the dopant materials for the light-emitting layer. The results are shown in Table 4.

[0199] (Comparative Examples 4 and 5) Light-emitting devices were fabricated and evaluated in the same manner as in Example 7, except that the phenanthroline derivative ET-1 had a crystal form shown in Table 2 and the dopant material for the light-emitting layer was a compound shown in Table 3. The results are shown in Table 4.

[0200] (Comparative Examples 6 and 7) Light-emitting devices were fabricated and evaluated in the same manner as in Example 11, except that the phenanthroline derivative ET-1 had a crystal form shown in Table 2 and the dopant material for the light-emitting layer was a compound shown in Table 3. The results are shown in Table 4.

[0201] [Table 2]

[0202] From Table 4, Example 7 , 9, 11 and 13, Reference Examples 3 to 6 It can be seen that the external quantum efficiency of each of the examples is higher than that of Comparative Examples 4 to 7, which use the same light-emitting layer. That is, as can be seen from Table 4, Example 7, which uses the B-type crystal or C-type crystal of compound ET-1 as the electron transport material, , 9, 11 and 13, Reference Examples 3 to 6 It was found that when any of the thermally activated delayed fluorescent materials was used in the light-emitting layer, a light-emitting device with significantly improved external quantum efficiency could be obtained, compared to Comparative Examples 4 to 7, in which the D-type crystal or amorphous form of compound ET-1 was used as the electron-transporting material.

[0203] Next, examples and comparative examples of light-emitting devices in which an electron injection layer is formed using the above-mentioned B-type crystal or C-type crystal and a thermally activated delayed fluorescent material is used as the light-emitting layer will be described.

[0204] Example 15 A glass substrate (manufactured by Geomatec Co., Ltd., 11 Ω / □, sputtered product) on which a 165 nm ITO transparent conductive film had been deposited was cut into 38 × 46 mm and etched. The resulting substrate was ultrasonically cleaned with "Semicoclean 56" (trade name, manufactured by Furuuchi Chemical Co., Ltd.) for 15 minutes, and then washed with ultrapure water. This substrate was subjected to ultraviolet light-ozone treatment for 1 hour immediately before fabricating the device, and then placed in a vacuum deposition apparatus, and the degree of vacuum in the apparatus was reduced to 5 × 10. -4 The chamber was evacuated to a pressure of 100 Pa or less. Using resistance heating, a 10-nm hole-injection layer (HAT-CN6) and a 180-nm hole-transport layer (HT-1) were deposited by resistive heating. Next, a 40-nm thick light-emitting layer was formed by depositing a host material (H-1), a dopant compound (D-1), and a TADF material (H-2) in a weight ratio of 80:1:19. A 35-nm thick electron-transport layer was formed by depositing compound ET-2 as the electron-transport material and 2E-1 as the donor material at a deposition rate ratio of 1:1. Next, a 5-nm thick electron-injection layer was formed using crystals (C-form crystals) of the phenanthroline derivative compound ET-1 and metallic lithium as the donor material at a deposition rate ratio of 99:1. Finally, a 1000-nm thick cathode was co-deposited with magnesium and silver to fabricate a 5 x 5 mm square device.

[0205] This light-emitting element is 1000cd / m 2 The external quantum efficiency when emitting light was 14.4%. The structure of ET-2 is shown below.

[0206] [ka]

[0207] ( Reference Example 7, Example 17, Reference Example 8 ) Light-emitting devices were fabricated and evaluated in the same manner as in Example 15, except that the crystals of the phenanthroline derivative ET-1 shown in Table 1 were used as the crystal form, and the compounds shown in Table 3 were used as the dopant materials for the light-emitting layer. The results are shown in Table 5.

[0208] Example 19 A glass substrate (manufactured by Geomatec Co., Ltd., 11 Ω / □, sputtered product) on which a 165 nm ITO transparent conductive film had been deposited was cut into 38 × 46 mm and etched. The resulting substrate was ultrasonically cleaned with "Semicoclean 56" (trade name, manufactured by Furuuchi Chemical Co., Ltd.) for 15 minutes, and then washed with ultrapure water. This substrate was subjected to ultraviolet light-ozone treatment for 1 hour immediately before fabricating the device, and then placed in a vacuum deposition apparatus, and the degree of vacuum in the apparatus was reduced to 5 × 10. -4 The chamber was evacuated to a pressure of 100 Pa or less. Using resistance heating, a 10-nm hole-injection layer (HAT-CN6) and a 40-nm hole-transport layer (HT-1) were deposited. Next, a 30-nm thick light-emitting layer was formed by depositing a host material (H-1), a dopant compound (D-6), and a TADF material (H-3) in a weight ratio of 80:1:19. A 50-nm thick electron-transport layer was formed by depositing a 50-nm thick electron-transport layer using compound ET-2 as the electron-transport material and 2E-1 as the donor material at a deposition rate ratio of 1:1. Next, a 5-nm thick crystal of the phenanthroline derivative ET-1 (C-form crystal) was deposited as an electron-injection layer using metallic lithium as the donor material at a deposition rate ratio of 99:1. Magnesium and silver were then co-deposited to a thickness of 1000 nm to form a cathode. A 5 × 5 mm square device was fabricated.

[0209] This light-emitting element is 1000cd / m 2 The external quantum efficiency when emitting light was 12.2%.

[0210] ( Reference Example 9, Example 21, Reference Example 10 ) Light-emitting devices were fabricated and evaluated in the same manner as in Example 19, except that the crystals of the phenanthroline derivative ET-1 shown in Table 1 were used as the crystal form, and the compounds shown in Table 3 were used as the dopant materials for the light-emitting layer. The results are shown in Table 5.

[0211] (Comparative Examples 8 and 9) Light-emitting devices were fabricated and evaluated in the same manner as in Example 15, except that the crystal form of ET-1 shown in Table 2 was used and the compound shown in Table 3 was used as the dopant material for the light-emitting layer. The results are shown in Table 5.

[0212] (Comparative Examples 10 and 11) Light-emitting devices were fabricated and evaluated in the same manner as in Example 19, except that the crystal form of ET-1 shown in Table 2 was used and the compound shown in Table 3 was used as the dopant material for the light-emitting layer. The results are shown in Table 5.

[0213] [Table 3]

[0214] From Table 5, Example 15 , 17, 19 and 21, Reference Examples 7 to 10 It can be seen that the external quantum efficiency of each of Example 15, which uses the B-type crystal or C-type crystal of compound ET-1 as the electron injection material, is higher than that of Comparative Examples 8 and 9, which use the same light-emitting layer. , 17, 19 and 21, Reference Examples 7 to 10 It was found that when any of the thermally activated delayed fluorescence materials was used in the light-emitting layer, a light-emitting device with significantly improved external quantum efficiency could be obtained, compared to Comparative Examples 8 to 11, in which the D-type crystal or amorphous form of compound ET-1 was used as the electron injection material.

[0215] Next, an example of a light-emitting device in which the charge generation layer of a tandem fluorescent light-emitting device is formed using the above-mentioned B-type crystal or C-type crystal and a thermally activated delayed fluorescent material is used as the light-emitting layer will be described.

[0216] Example 23 A glass substrate (manufactured by Geomatec Co., Ltd., 11 Ω / □, sputtered product) on which a 165 nm ITO transparent conductive film had been deposited was cut into 38 × 46 mm and etched. The resulting substrate was ultrasonically cleaned with "Semicoclean 56" (trade name, manufactured by Furuuchi Chemical Co., Ltd.) for 15 minutes, and then washed with ultrapure water. This substrate was subjected to ultraviolet light-ozone treatment for 1 hour immediately before fabricating the device, and then placed in a vacuum deposition apparatus, and the degree of vacuum in the apparatus was reduced to 5 × 10. -4The chamber was evacuated to a pressure of 100 Pa or less. Using a resistance heating method, 5 nm of HAT-CN6 was first deposited as a hole injection layer, followed by 50 nm of HT-1 as a hole transport layer. Next, a 20 nm thick light-emitting layer was formed by depositing a host material, H-1, a dopant compound, and a TADF material, compound H-2, in a weight ratio of 80:1:19. Furthermore, a 35 nm thick electron transport layer was formed using compound ET-2 as the electron transport material and 2E-1 as the donor material, with the deposition rate ratio of compounds ET-2 and 2E-1 being 1:1. Subsequently, a 10 nm thick n-type charge generation layer was formed using a crystal of the phenanthroline derivative ET-1 (C-type crystal: Example 6) as the n-type host and metallic lithium as the n-type dopant, with the deposition rate ratio of compound ET-1 to metallic lithium being 99:1. Finally, a 10 nm thick p-type charge emission layer was formed using HAT-CN6. A 50 nm hole transport layer, a 20 nm light emitting layer, and a 35 nm electron transport layer were deposited on top of the layer in this order, as described above. Next, 0.5 nm of 2E-1 was deposited as an electron injection layer, and then 1000 nm of magnesium and silver were co-deposited as a cathode to produce a 5 × 5 mm square tandem fluorescent light emitting device.

[0217] This light-emitting element is 1000cd / m 2 The external quantum efficiency when light was emitted at 1000 kJ / cm2 was 16.2%. It was confirmed that the external quantum efficiency was improved compared to Example 15 which had only one light-emitting layer.

[0218] Example 24 A glass substrate (manufactured by Geomatec Co., Ltd., 11 Ω / □, sputtered product) on which a 165 nm ITO transparent conductive film had been deposited was cut into 38 × 46 mm and etched. The resulting substrate was ultrasonically cleaned with "Semicoclean 56" (trade name, manufactured by Furuuchi Chemical Co., Ltd.) for 15 minutes, and then washed with ultrapure water. This substrate was subjected to ultraviolet light-ozone treatment for 1 hour immediately before fabricating the device, and then placed in a vacuum deposition apparatus, and the degree of vacuum in the apparatus was reduced to 5 × 10. -4The chamber was evacuated until the pressure reached 0.1 Pa or less. Using a resistance heating method, first, 5 nm of HAT-CN6 was deposited as a hole injection layer, followed by 50 nm of HT-1 as a hole transport layer. Next, as an emitting layer, a host material, H-1, a dopant material, compound D-6, and a TADF material, compound H-3, were deposited in a weight ratio of 80:1:19 to a thickness of 30 nm. As an electron transport layer, a crystal (C-type crystal) of the phenanthroline derivative ET-1 was layered to a thickness of 35 nm. Next, as an n-type charge generation layer, a crystal (C-type crystal) of the phenanthroline derivative ET-1, which is an n-type host, was layered. 10 nm of the film (Example 6) and metallic lithium, an n-type dopant, were laminated at a deposition rate ratio of 99:1. Furthermore, 10 nm of HAT-CN6 was laminated as a p-type charge generation layer. As described above, a 50 nm hole transport layer, a 30 nm light emitting layer, and 35 nm of ET-1 (C-type crystal) as an electron transport layer were sequentially vapor-deposited on top of this. Next, 0.5 nm of 2E-1 was vapor-deposited as an electron injection layer, and then 1000 nm of magnesium and silver were co-deposited to form a cathode, producing a 5 mm x 5 mm square tandem light-emitting device.

[0219] This light-emitting element is 1000cd / m 2 The external quantum efficiency when light was emitted at 1000 kJ / cm 2 was 11.3%. It was confirmed that the external quantum efficiency was improved compared to Example 11 which had only one light-emitting layer. [Industrial Applicability]

[0220] The crystals of the phenanthroline derivatives of the present invention exhibit extremely high chemical purity compared with phenanthroline derivatives obtained by conventional methods, and since the amount of residual solvent is small, bumping during sublimation purification can be suppressed, making them suitable for industrial production.Furthermore, the phenanthroline derivatives obtained by sublimation purification of the crystals of the phenanthroline derivatives of the present invention have high chemical purity and can be suitably used as light-emitting element materials in fields such as display elements, flat panel displays, backlights, lighting, interior decoration, signs, billboards, electrophotographic machines, and optical signal generators.

Claims

1. A C-type crystal of 1,3-bis(9-phenyl-1,10-phenanthrolin-2-yl)benzene having peaks at diffraction angles 2θ (°) of 5.0±0.2, 7.5±0.2, 8.7±0.2, 12.5±0.2, and 17.3±0.2, respectively, in powder X-ray diffraction.

2. The C-type crystal of 1,3-bis(9-phenyl-1,10-phenanthrolin-2-yl)benzene according to claim 1, which has an endothermic peak in the range of 243 to 247°C in simultaneous differential scanning calorimetry and thermogravimetry.

3. 3. A light-emitting device that emits light using electrical energy, comprising an anode and a cathode, and, between the cathode and the anode, a light-emitting layer containing a thermally activated delayed fluorescent material, and at least one layer selected from the group consisting of an electron transport layer, an electron injection layer, and a charge generation layer, and containing the C-type crystal according to claim 1 or 2.

4. 4. The light-emitting device according to claim 3, wherein the light-emitting layer further contains a pyrromethene boron complex represented by the following general formula (2): 【Chemical 1】 (wherein, in the above general formula (2), X １ is a nitrogen atom or a carbon atom, with the proviso that the carbon atom is bonded to one atom or monovalent group selected from the group consisting of a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted alkylthio group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted arylthio group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted heteroaryl group, a halogen atom, a carboxy group, a substituted or unsubstituted alkoxycarbonyl group, a substituted or unsubstituted carbamoyl group, a substituted or unsubstituted amino group, a nitro group, a cyano group, a substituted or unsubstituted silyl group, and a substituted or unsubstituted siloxanyl group. R １ ~R ６ are each independently an atom or group selected from the group consisting of a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aryl group, an alkoxy group, a substituted or unsubstituted alkylthio group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted arylthio group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted heteroaryl group, a halogen atom, a carboxy group, a substituted or unsubstituted alkoxycarbonyl group, a substituted or unsubstituted carbamoyl group, a substituted or unsubstituted amino group, a nitro group, a cyano group, a substituted or unsubstituted silyl group, and a substituted or unsubstituted siloxanyl group, with the proviso that R １ and R ２ Group R ２ and R ３ Group R ４ and R ５ Group R ５ and R ６ In any one or more of the groups, a bond may be formed between the groups constituting the group to form a ring. Z １ and Z ２ are each independently an atom or group selected from the group consisting of a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkoxy group, a cyano group, and a substituted or unsubstituted aryloxy group, provided that Z １ and Z ２ A bond may be formed between the groups to form a ring.)

5. In the general formula (2), X １ is a carbon atom, the group bonded to the carbon atom is a group represented by the following general formula (3): 【Chemistry 2】 (where R ９ ~R １１ each independently represents an atom or group selected from the group consisting of a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted heterocyclic group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted cycloalkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, a hydroxyl group, a thiol group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted alkylthio group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted arylthio group, a halogen atom, a cyano group, a formyl group, an acyl group, a carboxy group, a substituted or unsubstituted alkoxycarbonyl group, a substituted or unsubstituted carbamoyl group, a substituted or unsubstituted alkylsulfonyl group, a substituted or unsubstituted arylsulfonyl group, a substituted or unsubstituted aminosulfonyl group, a substituted or unsubstituted amino group, a nitro group, a substituted or unsubstituted silyl group, and a ring structure formed between an adjacent group, R ７ and R ８ are each independently a group selected from the group consisting of a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, and a substituted or unsubstituted heteroaryl group. Z １ and Z ２ are each independently a group selected from the group consisting of a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted aryl group, a halogen atom, and a cyano group; R １ , R ３ , R ４ and R ６ are each independently a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group, (Here, these aryl and heteroaryl groups may be monocyclic or condensed rings. However, R １ and R ６ When one or both of the groups are monocyclic aryl and heteroaryl groups, the monocyclic aryl and heteroaryl groups have one or more secondary alkyl groups, one or more tertiary alkyl groups, one or more aryl groups, or one or more heteroaryl groups as substituents, or have a total of two or more methyl groups and primary alkyl groups as substituents. R ２ and R ５ are each independently an atom or group selected from the group consisting of a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted alkylthio group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted arylthio group, a halogen atom, a cyano group, a carboxy group, a substituted or unsubstituted alkoxycarbonyl group, a substituted or unsubstituted carbamoyl group, a substituted or unsubstituted amino group, a nitro group, and a substituted or unsubstituted silyl group; (where R ４ and R ５ and R ２ and R ３ One or both of the groups may be a group in which a bond is formed between the groups constituting the group to form a five- or greater-membered ring.) The light-emitting device according to claim 4 .

6. In the general formula (2), X １ is a carbon atom, the group bonded to the carbon atom is a group represented by the following general formula (4): 【Chemistry 3】 (where R １２ ~R １４ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted heterocyclic group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted cycloalkenyl group, a substituted or unsubstituted alkynyl group, a hydroxyl group, a thiol group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted alkylthio group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted arylthio group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, a halogen atom, a cyano group, a hydroxyl ... an atom or group selected from the group consisting of a methyl group, an acyl group, a carboxy group, a substituted or unsubstituted alkoxycarbonyl group, a substituted or unsubstituted carbamoyl group, a substituted or unsubstituted alkylsulfonyl group, a substituted or unsubstituted arylsulfonyl group, a substituted or unsubstituted alkoxysulfonyl group, a substituted or unsubstituted aminosulfonyl group, a substituted or unsubstituted amino group, a nitro group, a substituted or unsubstituted silyl group, a substituted or unsubstituted siloxanyl group, a substituted or unsubstituted boryl group, and a substituted or unsubstituted phosphine oxide group; R １５ represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted heterocyclic group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted cycloalkenyl group, a substituted or unsubstituted alkynyl group, a hydroxyl group, a thiol group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted alkylthio group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted arylthio group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, a halogen atom, a cyano group, a formyl group, a group selected from the group consisting of an acyl group, a carboxy group, a substituted or unsubstituted alkoxycarbonyl group, a substituted or unsubstituted carbamoyl group, a substituted or unsubstituted alkylsulfonyl group, a substituted or unsubstituted arylsulfonyl group, a substituted or unsubstituted alkoxysulfonyl group, a substituted or unsubstituted aminosulfonyl group, a substituted or unsubstituted amino group, a nitro group, a substituted or unsubstituted silyl group, a substituted or unsubstituted siloxanyl group, a substituted or unsubstituted boryl group, and a substituted or unsubstituted phosphine oxide group; Ar １ is a group selected from the group consisting of a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group. Z １ and Z ２ are each independently an atom or group selected from the group consisting of a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted aryl group, a halogen atom, and a cyano group; R １ ~R ６ are each independently a group selected from the group consisting of a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted alkylthio group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, a substituted or unsubstituted amino group, a substituted or unsubstituted silyl group, and a substituted or unsubstituted siloxanyl group, with the proviso that R １ , R ３ , R ４ , R ６ At least one of the groups is a hydrogen atom or a substituted or unsubstituted alkyl group. The light-emitting device according to claim 4 .

7. 7. The light-emitting device according to claim 3, which has a charge-generating layer, and the charge-generating layer further contains an alkali metal or an alkali metal compound.

8. 8. The light-emitting device according to claim 7, wherein the alkali metal or alkali metal element constituting the alkali metal compound is lithium.

9. A display device comprising the light-emitting device according to any one of claims 3 to 8.

10. A lighting device comprising the light-emitting element according to any one of claims 3 to 8.

11. 3. A method for producing C-type crystals of 1,3-bis(9-phenyl-1,10-phenanthrolin-2-yl)benzene according to claim 1 or 2, comprising: a step (I) of dissolving 1,3-bis(9-phenyl-1,10-phenanthrolin-2-yl)benzene in a mixed solvent containing an aprotic polar solvent and an aromatic solvent, followed by crystallization; and a step (III) of drying the crystals obtained in step (I) at 50°C or higher.

12. 3. A method for producing a C-type crystal of 1,3-bis(9-phenyl-1,10-phenanthrolin-2-yl)benzene according to claim 1 or 2, comprising a step of subjecting a crystal of 1,3-bis(9-phenyl-1,10-phenanthrolin-2-yl)benzene having peaks at diffraction angles 2θ (°) of 5.2±0.2, 7.0±0.2, 16.4±0.2, 20.0±0.2, and 23.6±0.2 in powder X-ray diffraction.

13. The method for producing type C crystals of a phenanthroline derivative according to claim 12, wherein the crystals of 1,3-bis(9-phenyl-1,10-phenanthrolin-2-yl)benzene have peaks at diffraction angles 2θ (°) of 5.2±0.2, 7.0±0.2, 16.4±0.2, 20.0±0.2, and 23.6±0.2 in powder X-ray diffraction, and have an endothermic peak in the range of 94 to 98°C in simultaneous differential thermal and thermogravimetric analysis.

14. 14. The method for producing a C-type crystal of 1,3-bis(9-phenyl-1,10-phenanthrolin-2-yl)benzene according to claim 12 or 13, wherein the crystal has peaks at diffraction angles 2θ (°) of 5.2±0.2, 7.0±0.2, 16.4±0.2, 20.0±0.2, and 23.6±0.2 in powder X-ray diffraction, by the steps of: (I) dissolving 1,3-bis(9-phenyl-1,10-phenanthrolin-2-yl)benzene in a mixed solvent containing an aprotic polar solvent and an aromatic solvent, and crystallizing the 1,3-bis(9-phenyl-1,10-phenanthrolin-2-yl)benzene; and (IV) drying the crystal obtained by the step (I) at less than 50°C.