Compound, light-emitting element using the same, and color-converting composition

Abstract

To provide a compound with green emission characteristics having high luminous efficacy and excellent durability.SOLUTION: A compound has a structure represented by the general formula (3) in the figure.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a novel compound, and to a light-emitting device material, a light-emitting device, a color-converting composition, a color-converting sheet, a light source unit, a display device, and a lighting device, all of which use the compound. [Background technology]

[0002] Organic thin-film light-emitting devices emit light when electrons injected from a cathode and holes injected from an anode recombine in the light-emitting layer sandwiched between the two electrodes. These devices have the following characteristics: they can be made thin, their driving voltage is low, their brightness is high, and they are capable of emitting multicolor light.

[0003] To further widen the color gamut of display devices using organic light-emitting elements, active development is being conducted on materials with narrow half-width emission spectra. As such technology, for example, polycyclic aromatic compounds in which multiple aromatic rings are linked by boron atoms, nitrogen atoms, etc. (see, for example, Patent Documents 1 to 5 and Non-Patent Document 1) have been proposed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2015 / 102118 [Patent Document 2] International Publication No. 2018 / 186670 [Patent Document 3] International Publication No. 2019 / 240080 [Patent Document 4] Japanese Patent Publication No. 2020-132636 [Patent Document 5] International Publication No. 2021 / 013993 [Non-patent literature]

[0005] [Non-Patent Document 1] "Advanced.Materials", 2016, vol.28, p.2777-2781 Summary of the Invention [Problem to be solved by the invention]

[0006] The polycyclic aromatic compounds described in Patent Documents 1 to 4 and Non-Patent Document 1 have relatively high luminance as blue to light blue emitting materials, but their emission wavelengths are insufficient as green emitting materials. Furthermore, the compound described in Patent Document 5 emits green light, but its luminous efficiency and durability are insufficient. Therefore, an object of the present invention is to provide a compound having green emitting properties with high luminous efficiency and excellent durability. [Means for solving the problem]

[0007] The present invention is a compound having a structure represented by the following general formula (3).

[0008] [ka]

[0009] In the above general formula (3), R 101 ~R 124 are each independently a hydrogen atom, a halogen atom, a cyano group, an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, an alkoxy group, an alkylthio group, an aryl ether group, an aryl thioether group, an aryl group, a heteroaryl group, an oxycarbonyl group, a carbamoyl group, an amino group, a nitro group, a silyl group, or R 101 ~R 124 These groups may further have a substituent.

[0010] L 3 and L 4 are each independently a single bond, O, S, or CR 125 R 126 or SiR 127 R 128 R 125 ~R 128are each independently hydrogen, halogen, an alkyl group, a cycloalkyl group, an aryl group, or a heteroaryl group, and these groups may further have a substituent. 125 and R 126 or R 127 and R 128 may be bonded via a single bond or a linking group. 3 and L 4 are always different groups. [Effects of the Invention]

[0011] The compound of the present invention has high luminous efficiency and excellent durability, and has green luminous properties. The compound of the present invention can provide a light-emitting element material, a light-emitting element, a color-converting composition, and a color-converting sheet, which have high luminous efficiency and excellent durability, and have green luminous properties. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic cross-sectional view illustrating one embodiment of the color conversion sheet of the present invention. [Figure 2] FIG. 2 is a schematic cross-sectional view showing another embodiment of the color conversion sheet of the present invention. [Figure 3] FIG. 2 is a schematic cross-sectional view showing another embodiment of the color conversion sheet of the present invention. [Figure 4] FIG. 2 is a schematic cross-sectional view showing another embodiment of the color conversion sheet of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will be described in detail below, but the present invention is not limited to the embodiments and specific examples described below.

[0014] The compound of the present invention has a structure represented by the following general formula (3): 3 or L 4The crosslinked structure represented by the formula (I) has a strong and highly planar skeleton and exhibits a high fluorescence quantum yield. The fluorescence quantum yield is an index of luminescence efficiency, and the higher the fluorescence quantum yield, the higher the luminescence efficiency. Furthermore, the crosslinked structure L 3 and L 4 By having the bridged structure L, the π-conjugated system is expanded, and the emission wavelength becomes longer. Therefore, the compound having the structure represented by general formula (3) has excellent green emission properties. 3 and L 4 Since the molecular structure becomes asymmetric due to the difference in the molecular structure, it is possible to suppress intermolecular interactions, and to suppress the decrease in luminous efficiency and durability caused by the intermolecular interactions, thereby improving the luminous efficiency and durability.

[0015] [ka]

[0016] In the above general formula (3), R 101 ~R 124 are each independently a hydrogen atom, a halogen atom, a cyano group, an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, an alkoxy group, an alkylthio group, an aryl ether group, an aryl thioether group, an aryl group, a heteroaryl group, an oxycarbonyl group, a carbamoyl group, an amino group, a nitro group, a silyl group, or R 101 ~R 124 These groups may further have a substituent.

[0017] L 3 and L 4 are each independently a single bond, O, S, or CR 125 R 126 or SiR 127 R 128 R 125 ~R 128 are each independently hydrogen, halogen, an alkyl group, a cycloalkyl group, an aryl group, or a heteroaryl group, and these groups may further have a substituent.125 and R 126 or R 127 and R 128 may be bonded via a single bond or a linking group. 3 and L 4 are always different groups.

[0018] In all of the following descriptions in this specification, the isotopes of hydrogen atoms present in the molecule of a compound are not particularly limited. For example, it is possible to use an isotope of hydrogen atoms present in a molecule of a compound. 1 H, or part or all of 2 It may also be H (deuterium D).

[0019] In all of the following descriptions in this specification, "unsubstituted" in the context of "substituted or unsubstituted" means that a hydrogen atom or a deuterium atom is bonded.

[0020] The following explanations of halogens and each group are common to all subsequent explanations in this specification.

[0021] Halogen refers to fluorine, chlorine, bromine or iodine.

[0022] A cyano group is a group with the structure -C≡N, where the carbon atom is the bond to the other group.

[0023] 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, which may or may not have a substituent. The number of carbon atoms in the alkyl group is not particularly limited, but from the standpoints of availability and cost, it is preferably in the range of 1 to 20, more preferably 1 to 8. The number of carbon atoms referred to here includes the number of carbon atoms contained in a substituent bonded to the alkyl group, and the same applies to other substituents that specify the number of carbon atoms.

[0024] 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 or may not have a substituent. The number of ring carbon atoms is not particularly limited, but is preferably in the range of 3 to 20.

[0025] 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 or may not have a substituent. The number of ring atoms is not particularly limited, but is preferably in the range of 3 to 20.

[0026] 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 or may not have a substituent. The number of carbon atoms in the alkenyl group is not particularly limited, but is preferably in the range of 2 to 20.

[0027] 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 or may not have a substituent. The number of ring carbon atoms is not particularly limited, but is preferably in the range of 3 to 20.

[0028] The alkynyl group refers to an unsaturated aliphatic hydrocarbon group containing a triple bond, such as an ethynyl group, which may or may not have a substituent. The number of carbon atoms in the alkynyl group is not particularly limited, but is preferably in the range of 2 to 20.

[0029] 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 may or may not have a substituent. The number of carbon atoms in the alkoxy group is not particularly limited, but is preferably in the range of 1 to 20.

[0030] 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 or may not have a substituent. The number of carbon atoms in the alkylthio group is not particularly limited, but is preferably in the range of 1 to 20.

[0031] The aryl ether group refers to a group in which an aromatic hydrocarbon group is bonded via an ether bond, such as a phenoxy group, and may or may not have a substituent. The number of ring carbon atoms of the aryl ether group is not particularly limited, but is preferably in the range of 6 to 40.

[0032] An aryl thioether group is an aryl ether group in which the oxygen atom of the ether bond is replaced with a sulfur atom. This group may or may not have a substituent. The number of ring carbon atoms of the aryl thioether group is not particularly limited, but is preferably in the range of 6 to 40.

[0033] The aryl group refers to an aromatic hydrocarbon group such as a phenyl group, biphenyl group, terphenyl group, naphthyl group, fluorenyl group, benzofluorenyl group, dibenzofluorenyl group, phenanthryl group, anthracenyl group, benzophenanthryl group, benzanthracenyl group, chrysenyl group, pyrenyl group, fluoranthenyl group, triphenylenyl group, benzofluoranthenyl group, dibenzoanthracenyl group, perylenyl group, or helicenyl group. These groups may or may not have a substituent. Among these, phenyl group, biphenyl group, terphenyl group, naphthyl group, fluorenyl group, phenanthryl group, anthracenyl group, pyrenyl group, fluoranthenyl group, or triphenylenyl group is preferred. The number of ring carbon atoms is not particularly limited, but is preferably 6 to 40, more preferably 6 to 30.

[0034] Furthermore, in a substituted phenyl group, when two adjacent carbon atoms in the phenyl group each have a substituent, the substituents may join together to form a ring structure. Depending on the structure, the resulting group may fall into one or more of the following categories: a "substituted phenyl group," an "aryl group having a structure in which two or more rings are fused," and a "heteroaryl group having a structure in which two or more rings are fused."

[0035] The heteroaryl group refers to a cyclic aromatic group having one or more atoms other than carbon in the ring, such as 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 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. Here, the naphthyridinyl group refers to any of a 1,5-naphthyridinyl group, a 1,6-naphthyridinyl group, a 1,7-naphthyridinyl group, a 1,8-naphthyridinyl group, a 2,6-naphthyridinyl group, and a 2,7-naphthyridinyl group. The heteroaryl group may or may not have a substituent. The number of ring atoms is not particularly limited, but is preferably 3 to 40, more preferably 3 to 30.

[0036] The amino group is a substituted or unsubstituted amino group. The number of carbon atoms in the amino group 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.

[0037] The silyl group refers to a functional group to which a substituted or unsubstituted silicon atom is bonded, and examples thereof include alkylsilyl groups such as trimethylsilyl, triethylsilyl, tert-butyldimethylsilyl, propyldimethylsilyl, and vinyldimethylsilyl, and arylsilyl groups such as phenyldimethylsilyl, tert-butyldiphenylsilyl, triphenylsilyl, and trinaphthylsilyl. The number of carbon atoms in the silyl group is not particularly limited, but is preferably in the range of 1 to 30.

[0038] The oxycarbonyl group and carbamoyl group may or may not have a substituent. Examples of the substituent include an alkyl group, a cycloalkyl group, an aryl group, and a heteroaryl group, and these substituents may be further substituted.

[0039] In addition, in all of the above groups, the substituents when substituted include halogen, cyano group, alkyl group, cycloalkyl group, alkenyl group, cycloalkenyl group, alkynyl group, alkoxy group, alkylthio group, aryl ether group, aryl thioether group, aryl group, heterocyclic group, heteroaryl group, oxycarbonyl group, carbamoyl group, amino group, nitro group, silyl group, etc. Furthermore, specific substituents that are preferred in the description of each substituent are preferred. Furthermore, these substituents may be further substituted with the above-mentioned substituents.

[0040] R 101 ~R 124When is other than hydrogen, from the viewpoint of enabling fine adjustment of the emission wavelength, fluorine, cyano group, aryl group, heteroaryl group, and amino group are preferred. From the viewpoint of suppressing intermolecular interactions through moderate steric hindrance and suppressing a decrease in fluorescence quantum yield, alkyl groups and cycloalkyl groups are preferred. Among these, alkyl groups and aryl groups are more preferred. As the alkyl group, methyl group, ethyl group, isopropyl group, and tert-butyl group are preferred, and methyl group and tert-butyl group are more preferred. As the aryl group, phenyl group, naphthyl group, biphenyl group, terphenyl group, fluorenyl group, anthracenyl group, phenanthryl group, and pyrenyl group are preferred, and phenyl group, naphthyl group, biphenyl group, and fluorenyl group are more preferred, and phenyl group is even more preferred.

[0041] The compound having the structure represented by general formula (3) has a crosslinked structure L 3 and L 4 Compared with compounds that do not have this structure, these compounds have a high fluorescence quantum yield and are useful as assist dopant materials or green dopant materials for green organic EL light-emitting devices. This can be explained as follows. The compound represented by the following formula (3-1) is known to emit blue light, but the rings h and i, which are nitrogen substituents, are not on the same plane as the plane of the partial structure consisting of rings e, f, g, boron atoms, and nitrogen atoms, and have a twist. For this reason, the HOMO orbital and LUMO orbital hardly extend to rings h and i. In contrast, the bridged structure L 3 and L 4 In the case of the compound having the formula (3-2), the plane of the partial structure consisting of rings e, f, g, boron atoms, and nitrogen atoms and the rings h and i, which are nitrogen substituents, are almost on the same plane, so the HOMO orbital and LUMO orbital are extended to rings h and i. In other words, the conjugated system is extended, so the energy gap between the HOMO level and the LUMO level becomes smaller, and the emission wavelength becomes longer. In addition, the crosslinked structure L 3 and L 4By introducing the bridged structure L, the vibration and rotation of the rings h and i, which are the substituents of the nitrogen atom in the compound represented by formula (3-1), can be suppressed, thereby improving the fluorescence quantum yield. 3 and L 4 The effect of L 3 Compounds with only L 4 The effect is even more remarkable since it is greater than that of a compound having only

[0042] [ka]

[0043] [ka]

[0044] Furthermore, compounds represented by formula (3-1) are known to emit delayed fluorescence due to the small energy difference (ΔEST) between the lowest singlet excited state (S1 state) and the lowest triplet excited state (T1 state). Typically, the T1 state of common organic compounds is non-radiative at room temperature, i.e., it deactivates without emitting light. However, compounds with small ΔEST can convert from the T1 state generated by excitation to the S1 state even with thermal energy at room temperature, emitting delayed fluorescence. In common organic compounds, the T1 state is thermally deactivated at room temperature and does not contribute to light emission, making this property extremely important for improving the efficiency of organic electroluminescence (EL) devices. In organic EL devices, current excitation generates the S1 and T1 states of the emitting material at rates of 25% and 75%, respectively. For compounds that emit only simple fluorescence, only 25% of the S1 state is available. On the other hand, compounds with a small ΔEST can convert 75% of the T1 state generated by current excitation to the S1 state, and since the fluorescence emission from the S1 state, including the converted S1 state, is almost 100%, the luminescence efficiency is dramatically improved compared to when using simple fluorescent materials.

[0045] The compound having the structure represented by general formula (3) is L 3 and L4 The crosslinked structure L 3 and L 4 If are different groups, L 3 and L 4 Compared to when the groups are the same, this suppresses symmetry, weakens intermolecular forces, and reduces crystallinity. As a result, solubility in solvents improves, high purity can be easily achieved by column purification or recrystallization purification, and the deposition temperature can be lowered, resulting in heat resistance that can withstand long vacuum deposition processes. Furthermore, suppressing symmetry and weakening intermolecular interactions can suppress the decline in fluorescence quantum yield and durability due to intermolecular interactions, thereby improving luminescence efficiency and durability.

[0046] where L 3 and L 4 is CR 125 R 126 That is, if L 3 and L 4 Even if both are bridged by methylene groups, L 3 R in 125 and R 126 The combination of 4 R in 125 and R 126 If the combination of 3 and L 4 are considered to be different linking groups. For example, L 3 R in 125 and R 126 are both methyl groups, and L 4 R in 125 and R 126 are both phenyl groups, L 3 and L 4 are different linking groups. 3 and L 4 SiR 127 R 128 The same applies when both are silicon-bridged.

[0047] As described above, the compound having the structure represented by the general formula (3) can be formed by using different crosslinking structures L 3 and L4 By introducing the compound, it is possible to improve the fluorescence quantum yield and durability of the compound itself, and to improve the luminous efficiency and durability of the light-emitting element and color conversion sheet.

[0048] From the viewpoint of further reducing the deposition temperature and further improving heat resistance, and further improving the fluorescence quantum yield and durability, L 3 and / or L 4 is CR 125 R 126 That is, a crosslinked structure formed by a methylene group is preferred. 3 and / or L 4 is a methylene group, R which is a substituent of the methylene group, is positioned on the surface of the partial structure consisting of ring e, ring f, ring g, ring h, ring i, a boron atom, and a nitrogen atom described in formula (3-2). 125 and R 126 Since the L has a three-dimensionally protruding shape and a three-dimensionally bulky structure, the high planarity of the compound having the structure represented by general formula (3) can be alleviated. This effect weakens the intermolecular forces acting between the molecules of the compound having the structure represented by general formula (3), thereby reducing the crystallinity. As a result, it is possible to further increase the solubility in solvents and improve the heat resistance. In addition, it is possible to suppress quenching due to intermolecular interactions caused by intermolecular forces, thereby further improving the fluorescence quantum yield. 3 and L 4 is CR 125 R 126 It is more preferable that:

[0049] In terms of the three-dimensional bulky structure mentioned above, R 125 and / or R 126 is preferably an alkyl group, a cycloalkyl group, an aryl group, or a heteroaryl group, more preferably an alkyl group or an aryl group, and even more preferably an aryl group. 125 and R 126is most preferably an aryl group. The aryl group is preferably a phenyl group, a naphthyl group, a biphenyl group, a terphenyl group, a fluorenyl group, an anthracenyl group, a phenanthryl group, or a pyrenyl group, more preferably a phenyl group, a naphthyl group, a biphenyl group, or a fluorenyl group, and even more preferably a phenyl group. 125 and R 126 is an aryl group, and these aryl groups may be further bonded via a single bond or a linking group. As the linking group, a single bond, -O-, or -S- is preferred, and a single bond is more preferred.

[0050] The compound having the structure represented by general formula (3) is a useful compound as an assist dopant material or a green dopant material for a green organic EL light-emitting device. As a green dopant material, the peak wavelength in the fluorescence spectrum of the compound having the structure represented by general formula (3) is preferably 500 nm or more and 550 nm or less, more preferably 510 nm or more and 540 nm or less, from the viewpoint of further improving the color purity of green light emission. Here, the fluorescence spectrum of the compound having the structure represented by general formula (3) is -5 It can be measured using a fluorescence spectrophotometer using a diluted solution of 100 mol / L.

[0051] In order to set the emission wavelength within the above range, for example, R 101 ~R 124 Preferably, at least one of the groups is a group having a positive substituent constant σp value in Hammett's rule or a substituted amino group having electron-donating properties. Here, the "substituent constant σp value in Hammett's rule" (hereinafter sometimes simply referred to as "σp value") is a term proposed by L.P. Hammett and represents a reaction constant determined for each substituent that quantifies the effect of the substituent on the reaction rate or equilibrium of a para-substituted benzene derivative. In the present invention, the "σp value" refers to the σp value described in Hansch, C. et al., "Chemical Reviews," vol. 91, pp. 165-195, 1991. Groups with a positive σp value tend to exhibit electron-withdrawing (acceptor) properties.

[0052] R 101 ~R 124 When at least one of the groups is an electron-withdrawing group or a substituted amino group, the HOMO level or LUMO level can be shifted, and as a result, the energy gap between the HOMO level and the LUMO level can be adjusted, making it easy to adjust the emission wavelength.

[0053] In particular, R, which is the para position of the boron atom in general formula (3), 103 , R 111 and / or R 122 However, it is preferable that the σp value is a positive group, i.e., an electron-withdrawing group. By introducing an electron-withdrawing group into these positions, the LUMO level can be greatly stabilized without significantly shifting the HOMO level. In other words, it is possible to deepen the LUMO level while roughly maintaining the HOMO level, which results in a smaller energy gap between the HOMO level and the LUMO level, and the emission wavelength becomes longer, resulting in green emission with high color purity. The emission wavelength can be determined by the crosslinked structure L 3 and L 4 Taking into account the effect of introducing an electron-withdrawing group into the para-position of the boron atom, the desired green emission can be obtained by adjusting the electron-withdrawing property of the group. 103 , R 111 and / or R 122 The greater the electron-withdrawing property of the electron-withdrawing group introduced into at least one of the positions, the greater the degree of stabilization of the LUMO level, making it possible to make the LUMO level deeper. Therefore, the energy gap can be made smaller and the emission wavelength can be made longer. This property can be used to adjust the emission wavelength. Also, one of the factors that influences the conversion efficiency from the T1 state to the S1 state is ΔEST, and the smaller this ΔEST is, the more the conversion efficiency from the T1 state to the S1 state improves. 103 , R 111 and / or R 122By having at least one of these be an electron-withdrawing group, ΔEST becomes smaller. This further improves the conversion efficiency from the T1 state to the S1 state, and as a result, the fluorescence quantum yield of the compound having the structure represented by general formula (3) can be further improved. Furthermore, in general, in organic light-emitting materials, the life of the T1 state is longer than that of the S1 state, so there is a process of direct decomposition and deterioration from the T1 state. However, by reducing ΔEST and improving the conversion efficiency from the T1 state to the S1 state, the process of direct decomposition from the T1 state can be suppressed, and the durability of the compound is further improved. As for the position for introducing the electron-withdrawing group, since it has a large effect on reducing ΔEST, it is preferable to introduce it at the R 111 is preferred.

[0054] As a group having a positive substituent constant σp value in Hammett's rule, fluorine, a fluorine-substituted alkyl group, a fluorine-substituted cycloalkyl group, a fluorine-substituted aryl group, a fluorine-substituted heteroaryl group, a cyano group, an aryl group substituted with a cyano group, a heteroaryl group substituted with a cyano group, or an electron-accepting nitrogen-containing heteroaryl group is preferred. Among these, a fluorine-substituted alkyl group, a fluorine-substituted cycloalkyl group, a fluorine-substituted aryl group, a fluorine-substituted heteroaryl group, an aryl group substituted with a cyano group, a heteroaryl group substituted with a cyano group, or an electron-accepting nitrogen-containing heteroaryl group is more preferred, a fluorine-substituted alkyl group, a fluorine-substituted aryl group, an aryl group substituted with a cyano group, or an electron-accepting nitrogen-containing heteroaryl group is even more preferred, and an electron-accepting nitrogen-containing heteroaryl group is particularly preferred. By selecting an electron-accepting nitrogen-containing heteroaryl group, ΔEST can be made smaller, thereby further improving the fluorescence quantum yield of the compound and the luminous efficiency and durability of the light-emitting device and color conversion sheet.

[0055] Among the fluorine-substituted alkyl groups, perfluoroalkyl groups are preferred because they have strong electron-withdrawing properties and are expected to have the effect of significantly lengthening the wavelength, and trifluoromethyl groups are more preferred.

[0056] The fluorine-substituted aryl group refers to, for example, an aryl group having one or more fluorine atoms as a substituent on the aforementioned aryl group, but also includes an aryl group substituted with one or more perfluoroalkyl groups. An aryl group having both fluorine and perfluoroalkyl groups as substituents may also be used. Among fluorine-substituted aryl groups, fluorophenyl, difluorophenyl, trifluorophenyl, tetrafluorophenyl, pentafluorophenyl, trifluoromethylphenyl, bis(trifluoromethyl)phenyl, and tris(trifluoromethyl)phenyl groups are more preferably used. The number and substitution positions of fluorine or trifluoromethyl groups as substituents may be selected to obtain the desired green emission, taking into account electron-withdrawing properties. The fluorine-substituted aryl group may further have a substituent. When the substituent has a substituent, a cyano group or an alkyl group is preferred from the viewpoint of adjusting the electron-withdrawing properties, and an aryl group or a heteroaryl group is preferred from the viewpoint of extending the conjugated system to lengthen the emission wavelength.

[0057] The fluorine-substituted heteroaryl group is, for example, a heteroaryl group having one or more fluorine atoms, perfluoroalkyl groups, or both as substituents on the aforementioned heteroaryl group. The number and substitution positions of the fluorine atoms or perfluoroalkyl groups as substituents may be selected in consideration of electron-withdrawing properties so as to obtain the desired green light emission. The fluorine-substituted heteroaryl group may further have a substituent, and when it has a substituent, examples of the substituent include the groups exemplified as the substituents for the fluorine-substituted aryl group.

[0058] An aryl group substituted with a cyano group is, for example, an aryl group having one or more cyano groups as substituents on the aforementioned aryl group. Examples of aryl groups having a cyano group as a substituent include a 2-cyanophenyl group, a 3-cyanophenyl group, a 4-cyanophenyl group, a 2,3-dicyanophenyl group, a 2,4-dicyanophenyl group, a 2,5-dicyanophenyl group, a 2,6-dicyanophenyl group, a 3,4-dicyanophenyl group, and a 3,5-dicyanophenyl group. The number and substitution positions of the cyano groups as substituents may be selected to obtain the desired green emission, taking into account the electron-withdrawing properties. The aryl group substituted with a cyano group may further have a substituent. In the case where a substituent is present, the substituent is preferably a fluorine group, a perfluoroalkyl group, or an alkyl group from the viewpoint of adjusting the electron-withdrawing properties. In the case where a substituent is present, an aryl group or a heteroaryl group from the viewpoint of extending the conjugated system to increase the emission wavelength.

[0059] A heteroaryl group substituted with a cyano group is, for example, a heteroaryl group having one or more cyano groups as substituents on the aforementioned heteroaryl group. The number and substitution positions of the cyano groups as substituents may be selected in consideration of electron-withdrawing properties so as to obtain the desired green light emission. The heteroaryl group substituted with a cyano group may further have a substituent, and when it has a substituent, examples of the substituent include the groups exemplified as the substituents for the aryl group substituted with a cyano group.

[0060] The electron-accepting nitrogen-containing heteroaryl group is a heteroaryl group containing a nitrogen atom having a multiple bond as a heteroatom.Specific examples thereof include an imidazolyl group, an oxazolyl group, a thiazole group, a benzimidazolyl group, a benzoxazolyl group, a benzothiazolyl group, a pyridyl group, a pyrimidyl group, a pyrazinyl group, a pyridazinyl group, a triazinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolyl group, a naphthyridinyl group, and a phenanthrolinyl group. Among these, in consideration of appropriate electron-withdrawing properties and stability as a substituent, a pyridyl group, a pyrimidyl group, a pyrazinyl group, a pyridazinyl group, a triazinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolyl group, a naphthyridinyl group, and a phenanthrolinyl group are more preferred, and further in consideration of heat resistance, a pyridyl group, a pyrimidyl group, a triazinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, and a quinazolyl group are even more preferred. The number and position of the electron-accepting nitrogen atom as a heteroatom may be selected in consideration of electron-withdrawing properties so as to obtain a desired emission wavelength. The electron-accepting nitrogen-containing heteroaryl group may further have a substituent, and in the case where the substituent has a substituent, from the viewpoint of adjusting the electron-withdrawing properties, fluorine, a perfluoroalkyl group, a cyano group, an electron-accepting nitrogen-containing heteroaryl group, or an alkyl group is preferred. Furthermore, from the viewpoint of extending the conjugated system to increase the wavelength, a heteroaryl group or an aryl group is preferred.

[0061] In addition, R which is the para position of the nitrogen atom in general formula (3) 102 , R 107 , R 110 , R 112 , R 120 and / or R 123 is also preferably a substituted amino group. By introducing an electron-donating substituted amino group into at least one of these positions, the HOMO level can be made shallower without significantly shifting the LUMO level. In other words, it is possible to reduce the energy gap, and the emission wavelength is shifted to a longer wavelength, thereby obtaining green emission with high color purity. The emission wavelength is determined by the crosslinked structure L 3 and L 4Taking into account the effect of introducing a longer wavelength, the desired green emission can be obtained by adjusting the electron donating property of the substituted amino group introduced at the para position of the nitrogen atom. 102 , R 107 , R 110 , R 112 , R 120 or R 123 The greater the electron donating ability of the substituted amino group introduced into at least one position of R, the shallower the HOMO level becomes and the smaller the energy gap becomes. This results in a longer emission wavelength. This property can be utilized to adjust the emission wavelength. 102 , R 107 , R 110 , R 112 , R 120 or R 123 When at least one of the groups is a substituted amino group, ΔEST becomes smaller, which can further improve the fluorescence quantum yield and durability of the compound having the structure represented by general formula (3).

[0062] R, which is the para position of boron in general formula (3), 103 , R 111 or R 122 Among them, R 111 By introducing an electron-withdrawing group into R, it is expected that the HOMO orbital and the LUMO orbital can be more clearly separated, and ΔEST can be made smaller, which is preferable because it is expected that the luminous efficiency and durability of the light-emitting device can be improved as a result. 110 or R 112 It is preferable to introduce it into

[0063] The substituted amino group preferably has a structure represented by the following general formula (4).

[0064] [ka]

[0065] In the above general formula (4), Ar 1 and Ar 2are each independently an aryl group or a heteroaryl group. These groups may further have a substituent. 1 and Ar 2 may be bonded via a single bond or a linking group, and in this case, the linking group is -O-, -S-, >CR 133 R 134 , >SiR 135 R 136 or >C=O and R 133 ~R 136 are each independently a hydrogen atom, a halogen atom, an alkyl group, a cycloalkyl group, an aryl group, or a heteroaryl group. These groups may further have a substituent.

[0066] The aryl group is preferably a phenyl group, a naphthyl group, a biphenyl group, a terphenyl group, a fluorenyl group, an anthracenyl group, a phenanthryl group, or a pyrenyl group, more preferably a phenyl group, a naphthyl group, a biphenyl group, or a fluorenyl group, and more preferably a phenyl group, a biphenyl group, or a fluorenyl group.

[0067] The heteroaryl group is preferably a pyridyl group, a quinolinyl group, an isoquinolinyl group, a pyrazinyl group, a pyrimidyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a carbazolyl group, or a benzocarbazolyl group, and more preferably a pyridyl group, a quinolinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, or a carbazolyl group.

[0068] Ar 1 and Ar 2 When is bonded, it is preferably bonded via a single bond.

[0069] Examples of compounds having a structure represented by general formula (3) are shown below, but the invention is not limited to these.

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[0089] The compound having the structure represented by general formula (3) can be produced by referring to, for example, the synthesis method described in "Advanced Materials", 2016, vol. 28, pp. 2777-2781, or the synthesis method described in "Angew. Chem. Int. Ed.", 2019, vol. 58, pp. 16912-16917.

[0090] The obtained compound having a structure represented by general formula (3) is preferably purified by organic synthesis techniques such as recrystallization or column chromatography, and then further purified by heating under reduced pressure, generally known as sublimation purification, to remove low-boiling components and improve the purity.

[0091] The purity of the compound having the structure represented by general formula (3) is preferably 99% by weight or more from the viewpoint of stabilizing the characteristics of the light-emitting device and the color conversion sheet.

[0092] An example of a method for synthesizing an intermediate for a compound having a structure represented by general formula (3) is shown below.

[0093] [ka]

[0094] The desired final product can be obtained from intermediate 9 by Suzuki-Miyaura coupling reaction with a desired arylboronic acid or heteroarylboronic acid. Furthermore, once intermediate 10 is synthesized, the desired final product can be obtained by Suzuki-Miyaura coupling reaction with a desired aryl chloro compound, heteroaryl chloro compound, aryl bromo compound, heteroaryl bromo compound, aryl iodo compound, or heteroaryl iodo compound.

[0095] <Light-emitting device materials> The light-emitting device material in the present invention refers to a material that includes a compound having a structure represented by general formula (3) and is used in any layer of a light-emitting device. Examples include materials used in the hole injection layer, hole transport layer, light-emitting layer, electron transport layer, and / or protective film (cap layer) of an electrode, which will be described later. Among these, the light-emitting device material is preferably used in the light-emitting layer because it has high device luminous efficiency and high color purity due to high fluorescence quantum yield.

[0096] The light-emitting device material may contain other components in addition to the compound having the structure represented by general formula (3), such as those exemplified as materials for forming the hole injection layer, hole transport layer, light-emitting layer, electron transport layer, and / or protective film (cap layer) of the electrode, which will be described later.

[0097] <Light-emitting element> Next, an embodiment of the light-emitting device of the present invention will be described. The light-emitting device of the present invention has a light-emitting layer containing the light-emitting device material described above between an anode and a cathode, and emits light when exposed to electrical energy.

[0098] The light-emitting device of the present invention may be either a bottom-emission type or a top-emission type. The narrower the half-width of a top-emission light-emitting device, the higher the luminous efficiency due to the resonance effect of the microcavity. Therefore, it is preferable because it can achieve both high levels of color purity and luminous efficiency.

[0099] The layer configuration 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.

[0100] Furthermore, a tandem type may be used 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 is a laminated structure such as 9) hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer / charge generating layer / hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer.

[0101] Each of the above layers may be a single layer or multiple layers, and may be doped. In addition to the above layers, a protective layer (cap layer) may be further provided, which can further improve the luminous efficiency by optical interference effect.

[0102] Specific examples of the configuration of the light-emitting element are given below, but the configuration of the present invention is not limited to these.

[0103] (substrate) It is preferable to form the light-emitting element on a substrate in order to maintain the mechanical strength of the light-emitting element, minimize thermal deformation, and provide barrier properties that prevent water vapor and oxygen from penetrating the light-emitting layer. The substrate is not particularly limited, but examples include glass plates, ceramic plates, resin films, thin resin films, and thin metal plates. Among these, glass substrates are preferably used because of their transparency and ease of processing. In particular, for bottom-emission light-emitting elements that extract light through the substrate, highly transparent glass substrates are preferred. Furthermore, flexible displays and foldable displays are becoming increasingly common, primarily in mobile devices such as smartphones, and for these applications, resin films and thin resin films obtained by curing varnish are preferably used. Heat-resistant films are used as resin films, and specific examples include polyimide films and polyethylene naphthalate films.

[0104] In addition, various wirings and circuits for driving the organic EL, and switching elements using TFTs may be provided on the surface of the substrate.

[0105] (anode) The anode is preferably formed on the substrate. Various wirings, circuits, and switching elements may be interposed between the substrate and the anode. The material used for the anode is not particularly limited as long as it can efficiently inject holes into the organic layer. In the case of a bottom-emission light-emitting element, it is preferably a transparent or semi-transparent electrode, and in the case of a top-emission light-emitting element, it is preferably a reflective electrode.

[0106] Examples of materials for transparent or translucent electrodes 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 metals, it is preferable to make the film thin so that light can be semi-transmitted. Among these, indium tin oxide (ITO) is more preferred from the viewpoints of transparency and stability.

[0107] The material of the reflective electrode is preferably one that does not absorb any light and has high reflectivity, and examples thereof include metals such as aluminum, silver, and platinum.

[0108] Two or more of these electrode materials may be used, or a plurality of materials may be laminated.

[0109] The thickness of the anode is not particularly limited, but is preferably several nm to several hundred nm.

[0110] The anode formation method can be selected optimally depending on the material used, and examples include sputtering, vapor deposition, and inkjet printing. For example, sputtering is preferably used when the anode is made of metal oxide, and vapor deposition is preferably used when the anode is made of metal. The thickness of the anode is not particularly limited, but is preferably several nm to several hundred nm.

[0111] (cathode) The cathode is formed on the surface opposite to the anode with the organic layer sandwiched therebetween, and is preferably formed on the surface of 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 in the case of a bottom emission type light emitting element, it is preferably a reflective electrode, and in the case of a top emission type light emitting element, it is preferably a semi-transparent electrode.

[0112] Generally, 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) are preferred. Among these, aluminum, silver, and magnesium are preferred as the main component from the viewpoints of electrical resistance, ease of film formation, film stability, and luminous efficiency. Furthermore, a combination of magnesium and silver is preferred because it facilitates electron injection into the electron transport layer and electron injection layer, thereby enabling a reduction in driving voltage.

[0113] (protective layer) For cathode protection, it is preferable to laminate a protective layer (cap layer) on 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 substances such as silica, titania, and silicon nitride, and organic polymer compounds such as polyvinyl alcohol, polyvinyl chloride, and hydrocarbon-based polymer compounds. However, in the case of top-emission light-emitting devices, the material used for the protective layer is preferably selected from materials that are optically transparent in the visible light region. In particular, arylamine derivatives, which are typically used in hole transport layers, have good optical transparency in the visible light region and a higher refractive index than conventional organic materials at wavelengths in the visible light region. This can promote the resonance effect due to the microcavity effect, particularly in top-emission light-emitting devices, and are therefore suitable for use as protective layer materials.

[0114] (hole injection layer) The hole injection layer is inserted between the anode and the hole transport layer to facilitate hole injection. The hole injection layer may be a single layer or a laminate of multiple layers. The presence of a hole injection layer between the hole transport layer and the anode is preferable because it not only enables lower voltage operation and improves durability and lifespan, but also improves the carrier balance of the device and the luminous efficiency.

[0115] A preferred example of the hole injection material is an electron-donating hole injection material (donor material). These materials have a shallower HOMO level than the hole transport layer and are close to the work function of the anode, thereby reducing the energy barrier with the anode. Specific examples include aromatic amine-based materials such as benzidine derivatives, starburst arylamines such as 4,4',4"-tris(3-methylphenyl(phenyl)amino)triphenylamine (m-MTDATA) and 4,4',4"-tris(1-naphthyl(phenyl)amino)triphenylamine (1-TNATA), and other starburst arylamines; heterocyclic compounds such as carbazole derivatives, pyrazoline derivatives, stilbene compounds, hydrazone compounds, benzofuran derivatives, thiophene derivatives, oxadiazole derivatives, phthalocyanine derivatives, and porphyrin derivatives; and polymer-based materials such as polycarbonates and styrene derivatives having the above-mentioned monomers in their side chains, polythiophenes such as PEDOT / PSS, polyaniline, polyfluorene, polyvinylcarbazole, and polysilane. Two or more of these may be used together. Also, a plurality of materials may be laminated to form the hole injection layer.

[0116] Another preferred example of the hole injection material is an electron-accepting hole injection material (acceptor material). The hole injection layer may be composed of an acceptor material alone, or may be composed of the donor material doped with the acceptor material. The acceptor material is a material that forms a charge-transfer complex with the adjacent hole transport layer when used alone, or with the donor material when used as a dopant. The use of such a material is more preferred because it contributes to improving the conductivity of the hole injection layer and reducing the driving voltage of the device, thereby improving the luminous efficiency and enhancing the durability and lifespan. Examples of acceptor materials include metal oxides such as molybdenum oxide, vanadium oxide, tungsten oxide, and ruthenium oxide, charge-transfer complexes such as tris(4-bromophenyl)aminium hexachloroantimonate (TBPAH), n-type organic semiconductor compounds such as 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile (HAT-CN6), 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ), and fluorinated copper phthalocyanine, and fullerenes. When the hole-injection layer contains an acceptor compound, the hole-injection layer may be a single layer or may be configured by laminating multiple layers.

[0117] (Hole transport layer) The hole transport layer is a layer that transports holes injected from the anode to the light emitting layer, and may be a single layer or a laminate of multiple layers.

[0118] The hole transport layer is formed by using one hole transport material alone or by laminating or mixing two or more hole transport materials. It is preferable that the hole transport material has high hole injection efficiency and efficiently transports the injected holes. To this end, the material must have an appropriate ionization potential, high hole mobility, excellent stability, and be less likely to generate impurities that act as traps.

[0119] Substances that satisfy these conditions are not particularly limited, but examples include heterocyclic compounds such as benzidine derivatives, aromatic amine materials called starburst arylamines, carbazole derivatives, pyrazoline derivatives, stilbene compounds, hydrazone compounds, benzofuran derivatives, dibenzofuran derivatives, thiophene derivatives, benzothiophene derivatives, dibenzothiophene derivatives, fluorene derivatives, spirofluorene derivatives, oxadiazole derivatives, phthalocyanine derivatives, and porphyrin derivatives, and polymers such as polycarbonates and styrene derivatives having the above-mentioned monomers in their side chains, polythiophenes, polyanilines, polyfluorenes, polyvinylcarbazoles, and polysilanes.

[0120] (Emitting layer) The light-emitting layer is a layer that emits light by excitation energy generated by the recombination of holes and electrons. The light-emitting layer may be composed of a single material, but from the viewpoint of color purity, it is preferable to have a first compound that is a dopant exhibiting emission with a narrow half-width, and a second compound. Suitable examples of the second compound include a host material responsible for charge transfer and a thermally activated delayed fluorescent compound.

[0121] A compound having a structure represented by general formula (3) is preferably used as the first compound, which is a dopant in the light-emitting layer, because it has particularly excellent fluorescence quantum yield, a peak wavelength of the fluorescence spectrum suitable for green emission, a narrow half-width, excellent color purity, and high durability. The content of the first compound in the light-emitting layer is preferably 5 wt % or less, more preferably 2 wt % or less, from the viewpoint of further suppressing concentration quenching. On the other hand, the content of the first compound in the light-emitting layer is preferably 0.1 wt % or more, more preferably 0.5 wt % or more, from the viewpoint of more efficient energy transfer.

[0122] The host material is not particularly limited, but examples thereof include compounds having fused aryl rings such as naphthacene, pyrene, anthracene, and fluoranthene, and derivatives thereof, aromatic amine derivatives such as N,N'-dinaphthyl-N,N'-diphenyl-4,4'-diphenyl-1,1'-diamine, metal chelated oxinoid compounds such as tris(8-quinolinato)aluminum(III), bisstyryl derivatives such as distyrylbenzene derivatives, tetraphenylbutadiene derivatives, indene derivatives, coumarin derivatives, oxadiazole derivatives, pyrrolopyridine derivatives, perinone derivatives, pyrrolopyrrole derivatives, thiadiazolopyridine derivatives, dibenzofuran derivatives, carbazole derivatives, indolocarbazole derivatives, triazine derivatives, and polymer-based materials such as polyphenylenevinylene derivatives, polyparaphenylene derivatives, polyfluorene derivatives, polyvinylcarbazole derivatives, and polythiophene derivatives. Two or more of these host materials may be used, or two or more host materials may be laminated. Among these, carbazole derivatives, anthracene derivatives, and naphthacene derivatives are preferred.

[0123] The dopant material may contain a fluorescent material other than the compound having the structure represented by general formula (3). Specific examples include compounds having fused aryl rings such as naphthacene, pyrene, anthracene, and fluoranthene, and derivatives thereof; compounds having heteroaryl rings and derivatives thereof; distyrylbenzene derivatives; aminostyryl derivatives; tetraphenylbutadiene derivatives; stilbene derivatives; aldazine derivatives; pyrromethene derivatives; diketopyrrolo[3,4-c]pyrrole derivatives; coumarin derivatives; azole derivatives and metal complexes thereof; and aromatic amine derivatives. Two or more of these may be used.

[0124] The dopant material may contain a phosphorescent material. The phosphorescent material is preferably a metal complex compound containing at least one metal selected from the group consisting of iridium (Ir), ruthenium (Ru), palladium (Pd), platinum (Pt), osmium (Os), and rhenium (Re). From the viewpoint of highly efficient luminescence, an iridium complex or a platinum complex is more preferable. The ligand preferably has a nitrogen-containing heteroaryl group such as a phenylpyridine skeleton, a phenylquinoline skeleton, or a carbene skeleton, but is not limited thereto.

[0125] However, from the viewpoint of further improving color purity, it is preferable that the dopant material is only a compound having a structure represented by general formula (3).

[0126] The emitting layer preferably contains an assist dopant in addition to the dopant. The assist dopant is preferably a compound that emits delayed fluorescence. Delayed fluorescent materials, commonly referred to as TADF (Thermally Activated Delayed Fluorescence) materials, promote reverse intersystem crossing from the T1 state to the S1 state by reducing the energy gap between the S1 state and the T1 excited state, i.e., ΔEST, thereby improving the conversion efficiency from the T1 state to the S1 state. By utilizing delayed fluorescence via this TADF mechanism, the theoretical internal quantum efficiency of light-emitting devices can be increased to 100%. Furthermore, when Förster-type energy transfer occurs from the S1 state of the thermally activated delayed fluorescent assist dopant to the S1 state of the dopant material, fluorescence emission from the S1 state of the dopant material is observed. Here, if the dopant material is a fluorescent material with a sharp fluorescence spectrum, light-emitting devices with superior luminous efficiency and color purity can be obtained. In this way, when the light-emitting layer contains an assist dopant that emits a thermally activated delayed fluorescent material, the luminous efficiency of the device is further improved, contributing to lower power consumption of the display. The delayed fluorescent material as an assist dopant may be a material that exhibits delayed fluorescence with a single material, or may be a material that exhibits delayed fluorescence with multiple materials, such as when forming an exciplex complex.

[0127] The compound having the structure represented by general formula (3) has a high fluorescence quantum yield and also has a high conversion efficiency from the T1 state to the S1 state due to a reduction in ΔEST, and thus emits delayed fluorescence. Therefore, it can be suitably used as an assist dopant.

[0128] The delayed fluorescent compound as the assist dopant may be a single material or multiple materials, and known materials can be used in addition to the compound having the structure represented by general formula (3). Specific examples include benzonitrile derivatives, triazine derivatives, disulfoxide derivatives, carbazole derivatives, indolocarbazole derivatives, dihydrophenazine derivatives, thiazole derivatives, and oxadiazole derivatives. Examples of such thermally activated delayed fluorescent compounds include, but are not limited to, the following:

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[0136] In addition to the above-mentioned assist dopant material and dopant material, the light-emitting layer may further contain a matrix material for adjusting the carrier balance within the light-emitting layer or for stabilizing the layer structure of the light-emitting layer. However, it is preferable to select a matrix material that does not interact with the assist dopant material or the dopant material. When the light-emitting layer contains a matrix material, it is preferable that the relationship of Equation 1 be satisfied, where S1(1) is the excited singlet energy of the dopant material, S1(2) is the excited singlet energy of the assist dopant material, and S1(3) is the excited singlet energy of the matrix material. S1(3)>S1(2)>S1(1) (Equation 1) If formula 1 is satisfied, the matrix material can have the function of confining the excitation energy of the light-emitting material within the light-emitting layer, making it possible to emit light efficiently.

[0137] The excited singlet energy S1(1) of the dopant material in the present invention can be determined by the following method. -5 A solution of 1000 mol / L is prepared and its emission spectrum is measured at room temperature. The vertical axis of the emission spectrum is the emission intensity, and the horizontal axis is the wavelength. A tangent line is drawn to the rising edge of the emission spectrum on the short wavelength side, and the wavelength λ at the intersection with the horizontal axis is edge (nm) is calculated. edge is converted into an energy value using the following conversion formula, and this is taken as the excited singlet energy S1(1) of the dopant material. Conversion formula: S1(1)=1239.85 / λ edge By a similar method, the lowest excited singlet energy S1(2) of the assist dopant material and the lowest excited singlet excitation energy S1(3) of the matrix material can be determined.

[0138] The matrix material is preferably an organic compound having a high transport ability of charges such as holes and electrons and a high glass transition temperature. The matrix material is not particularly limited, but examples include the following:

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[0150] (electron transport layer) The electron transport layer is a layer that receives electrons 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 be a substance that is unlikely to generate impurities that become traps. Furthermore, from the viewpoint of suppressing film quality deterioration due to crystallization, compounds with a molecular weight of 400 or more are preferred.

[0151] The electron transport layer in the present invention also includes a hole blocking layer capable of efficiently blocking the movement of holes. The hole blocking layer and the electron transport layer may be formed of a single material or a laminate of multiple materials.

[0152] Examples of electron-transporting 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. To reduce driving voltage and further improve device efficiency, it is preferable to use a compound having a heteroaryl group containing electron-accepting nitrogen. Here, electron-accepting nitrogen refers to a nitrogen atom that forms multiple bonds with adjacent atoms. Heteroaryl groups containing electron-accepting nitrogen have a high electron affinity, which facilitates electron injection from the cathode and enables lower-voltage operation. Furthermore, the increased supply of electrons to the light-emitting layer increases the recombination probability, further improving device efficiency. 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, oligopyridine derivatives such as bipyridine and terpyridine, etc. Two or more of these may be used.

[0153] Furthermore, it is more preferable that the electron transport material has a condensed polycyclic aromatic skeleton, since the glass transition temperature is improved, the electron mobility is large, and the driving voltage can be reduced. As such a condensed polycyclic aromatic skeleton, a quinolinol skeleton, a triazine skeleton, a fluoranthene skeleton, an anthracene skeleton, a pyrene skeleton, or a phenanthroline skeleton is preferable.

[0154] The electron transport layer may contain a donor material. Here, the donor material is a compound that improves the electron injection barrier, thereby facilitating electron injection from the cathode or the electron injection layer into the electron transport layer, and further improving the electrical conductivity of the electron transport layer.

[0155] Preferred examples of donor materials include alkali metals such as Li, inorganic salts containing alkali metals such as LiF, 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 Eu and Yb, inorganic salts containing rare earth metals, and complexes of rare earth metals and organic substances. Two or more of these may be used. Among these, metallic lithium, rare earth metals, and lithium quinolinol (Liq) are preferred.

[0156] (electron injection layer) In the present invention, an electron injection layer may be provided between the cathode and the electron transport layer. Generally, the electron injection layer is formed to assist 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. Two or more of these may be contained. Among these, triazine derivatives, phenanthroline derivatives, and oligopyridine derivatives are preferred, with phenanthroline derivatives and terpyridine derivatives being more preferred, and phenanthroline derivatives represented by the following general formula (7) being even more preferred. That is, the light-emitting element of the present invention preferably contains a phenanthroline derivative represented by general formula (7) in the electron injection layer.

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[0158] In the above general formula (7), Ar 5 is selected from the group consisting of p-valent aromatic hydrocarbon groups and p-valent aromatic heterocyclic groups, where p is a natural number from 1 to 3. 301 ~R 308 may be the same or different and are selected from the group consisting of a hydrogen atom, an alkyl group, a cycloalkyl group, a heterocyclic group, an aryl group, and a heteroaryl group. 5 In the above, the substitution positions of the p phenanthrolyl groups are arbitrary positions.

[0159] Examples of monovalent aromatic hydrocarbon groups include phenyl, biphenyl, terphenyl, naphthyl, fluorenyl, benzofluorenyl, dibenzofluorenyl, phenanthryl, anthracenyl, benzophenanthryl, benzanthracenyl, chrysenyl, pyrenyl, fluoranthenyl, triphenylenyl, benzofluoranthenyl, dibenzoanthracenyl, perylenyl, and helicenyl groups. Among these, from the viewpoints of ease of synthesis and sublimation, phenyl, biphenyl, terphenyl, naphthyl, fluorenyl, phenanthryl, anthracenyl, pyrenyl, fluoranthenyl, and triphenylenyl groups, as well as groups obtained by removing at least some of the hydrogen atoms from these groups, are preferred. The aromatic hydrocarbon group may or may not have a substituent. The number of ring carbon atoms is not particularly limited, but is preferably 6 to 40, more preferably 6 to 30. In addition, when two adjacent carbon atoms each have a substituent, the substituents may be bonded together to form a ring structure.

[0160] The aromatic heterocyclic group refers to a cyclic aromatic group having one or more atoms other than carbon in the ring, and examples of such a monovalent group 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 Examples of aromatic heterocyclic groups include a phenyl group, a dibenzothiophenyl group, a carbazolyl group, 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, and a phenanthrolinyl group. The naphthyridinyl group refers to a 1,5-naphthyridinyl group, a 1,6-naphthyridinyl group, a 1,7-naphthyridinyl group, a 1,8-naphthyridinyl group, a 2,6-naphthyridinyl group, or a 2,7-naphthyridinyl group. The aromatic heterocyclic group may or may not have a substituent. The number of ring carbon atoms of the aromatic heterocyclic group is not particularly limited, but is preferably in the range of 2 or more and 40 or less, more preferably 2 or more and 30 or less.

[0161] The aromatic hydrocarbon group or aromatic heterocyclic group may further have a substituent other than the phenanthryl group.

[0162] From the viewpoint of sublimation property and thin film formability, p is preferably 2.

[0163] An example of the phenanthroline derivative represented by the general formula (7) is shown below.

[0164] [ka]

[0165] Furthermore, inorganic insulating or semiconducting materials can also be used for the electron injection layer, which is preferable because the use of these materials can prevent short circuits in the light emitting element and improve the electron injection properties.

[0166] Such an insulator is preferably a metal compound such as an alkali metal chalcogenide, an alkaline earth metal chalcogenide, an alkali metal halide, an alkaline earth metal halide, etc. Two or more of these may be used.

[0167] (charge generation layer) The charge generation layer in the present invention generally comprises a double layer, specifically, a pn junction type charge generation layer consisting of an n-type charge generation layer and a p-type charge generation layer. When a voltage is applied to the light-emitting device, the pn junction type charge generation layer generates charges or separates the charges into holes and electrons, and injects the holes and electrons into the light-emitting layer via the hole transport layer and electron transport layer. Specifically, it functions as an intermediate charge generation layer in a light-emitting device in which light-emitting layers are stacked. 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. Therefore, the luminous efficiency of a light-emitting device in which multiple light-emitting layers are stacked can be improved, the driving voltage can be reduced, and the durability of the light-emitting device can also be improved.

[0168] The n-type charge generating layer comprises an n-type dopant and a host, and conventional materials can be used for these. Examples of n-type dopants include alkali metals, alkaline earth metals, and rare earth metals. Two or more of these may be used. Among these, alkali metals or their salts and rare earth metals are preferred, with metallic lithium, lithium fluoride (LiF), lithium quinolinol (Liq), and metallic ytterbium being more preferred. Furthermore, examples of hosts include triazine derivatives, phenanthroline derivatives, and oligopyridine derivatives. Two or more of these may be used. Among these, triazine derivatives, phenanthroline derivatives, and oligopyridine derivatives are preferred, with phenanthroline derivatives and terpyridine derivatives being more preferred, and the phenanthroline derivative represented by the general formula (7) being even more preferred. That is, the light-emitting element of the present invention preferably contains a phenanthroline derivative represented by the general formula (7) in the charge generating layer.

[0169] The p-type charge generating layer comprises a p-type dopant and a host, and conventional materials can be used for these. Examples of p-type dopants include tetrafluorene-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ), tetracyanoquinodimethane derivatives, radialene derivatives, iodine, FeCl3, FeF3, and SbCl5. Two or more of these may be used. Among these, arylamine derivatives are preferred.

[0170] (Method of manufacturing light-emitting element) The method for forming each of the layers constituting the light-emitting device may be either a dry process or a wet process, such as resistance heating evaporation, electron beam evaporation, sputtering, molecular lamination, coating, inkjet printing, etc. Among these, resistance heating evaporation is preferred from the viewpoint of device characteristics.

[0171] The thickness of the organic layer is not limited because it depends on the resistance value of the light-emitting substance, but is preferably 1 to 1,000 nm. The thickness of each of the light-emitting layer, electron transport layer, and hole transport layer is preferably 1 nm to 200 nm, more preferably 5 nm to 100 nm.

[0172] (Light-emitting element characteristics) The light-emitting device according to the embodiment of the present invention has a 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 characteristic values ​​vary depending on the purpose of the device. However, from the viewpoint of the power consumption and lifespan of the device, it is preferable to obtain high brightness at a low voltage.

[0173] In the light-emitting element according to the embodiment of the present invention, from the viewpoint of increasing color purity, in terms of further improving color purity in the fluorescent spectrum upon application of current, the half-value width is preferably 45 nm or less, more preferably 35 nm or less, and even more preferably 30 nm or less.

[0174] <Color-changing composition> The color-converting composition of the present invention refers to a composition that converts incident light into light with a wavelength different from that of the incident light. Preferably, the conversion is to light with a wavelength longer than that of the incident light. The color-converting composition of the present invention contains a compound having a structure represented by general formula (3) and a binder resin. The compound having a structure represented by general formula (3) can also be suitably used in a color-converting composition that converts incident light into light with a wavelength different from that of the incident light.

[0175] (binder resin) Suitable specific examples of binder resins include those described in, for example, WO 2016 / 190283, WO 2017 / 61337, WO 2018 / 43237, WO 2019 / 21813, and WO 2019 / 188019.

[0176] (solvent) The color-changing composition of the present invention may contain a solvent, which can adjust the viscosity of the resin in a fluid state. Examples of solvents include toluene, methyl ethyl ketone, methyl isobutyl ketone, hexane, acetone, terpineol, Texanol, ethyl acetate, tetrahydrofuran, methyl cellosolve, butyl carbitol, butyl carbitol acetate, and propylene glycol monomethyl ether acetate. Two or more of these may be contained. Among these, toluene and ethyl acetate are particularly preferred because they maintain the durability of the compound having the structure represented by general formula (3) and leave little residual solvent after drying.

[0177] (Other ingredients) The color-changing composition of the present invention may contain other components (additives) as needed, such as light stabilizers, antioxidants, processing and heat stabilizers, light resistance stabilizers such as ultraviolet absorbers, scattering particles, silicone microparticles, silane coupling agents, etc.

[0178] Examples of light stabilizers include tertiary amines, catechol derivatives, nickel compounds, and complexes or salts with organic acids containing at least one transition metal selected from the group consisting of Sc, V, Mn, Fe, Co, Cu, Y, Zr, Mo, Ag, and lanthanoids. Two or more of these may be contained.

[0179] Examples of the antioxidant include phenolic antioxidants such as 2,6-di-tert-butyl-p-cresol, 2,6-di-tert-butyl-4-ethylphenol, etc. Two or more of these may be contained.

[0180] Examples of processing and heat stabilizers include phosphorus-based stabilizers such as tributyl phosphite, tricyclohexyl phosphite, triethyl phosphine, diphenylbutyl phosphine, etc. Two or more of these may be contained.

[0181] Examples of light resistance stabilizers include benzotriazoles such as 2-(5-methyl-2-hydroxyphenyl)benzotriazole and 2-[2-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole, etc. Two or more of these may be contained.

[0182] The scattering particles are preferably inorganic particles having a refractive index of 1.7 to 2.8, such as particles of titania, zirconia, alumina, ceria, tin oxide, indium oxide, iron oxide, zinc oxide, aluminum nitride, aluminum, tin, titanium or zirconium sulfide, titanium or zirconium hydroxide, etc. Two or more of these may be contained.

[0183] In the color-changing composition of the present invention, the content of these additives can be appropriately selected depending on the molar absorption coefficient, luminescence quantum yield, and absorption intensity at the excitation wavelength of the compound, as well as the thickness and transmittance of the color-changing sheet to be produced. -1 Parts by weight or more and 10 parts by weight or less are preferred.

[0184] <Method of manufacturing color-changing composition> The color-changing composition of the present invention can be obtained, for example, by mixing a binder resin, a compound having a structure represented by general formula (3), and, if necessary, additives and solvents to a predetermined composition, followed by homogeneous mixing or kneading using a stirrer / kneader. Examples of stirrers / kneaders include homogenizers, planetary mixers, three-roller mixers, ball mills, planetary ball mills, and bead mills. After mixing or dispersing, or during the mixing or dispersing process, degassing under vacuum or reduced pressure conditions is also preferred. It is also acceptable to premix certain components or to perform aging or other treatments. The desired solids concentration can also be achieved by removing the solvent using an evaporator.

[0185] <Color conversion sheet> The color conversion sheet of the present invention is a sheet that converts incident light from a light emitting body such as a light source into light with a wavelength different from that of the incident light, and contains the color conversion composition of the present invention described above. It is preferable that the color conversion sheet converts incident light into light with a wavelength longer than that of the incident light.

[0186] The color conversion sheet of the present invention preferably includes a color conversion layer formed from the color conversion composition. The amount of residual solvent in the color conversion layer is preferably 0.5% by weight or less in order to further improve the durability of the color conversion sheet. On the other hand, the amount of residual solvent in the color conversion layer is preferably 0.1% by weight or more in order to further improve the luminous efficiency of the color conversion sheet.

[0187] Typical examples of the structure of the color conversion sheet include the following four types.

[0188] Figure 1 shows a schematic cross-sectional view of one embodiment of the color conversion sheet of the present invention. Color conversion sheet 1A is a single-layer sheet composed of a color conversion layer 11. Color conversion layer 11 is a layer made of a cured product of the color conversion composition described above.

[0189] A schematic cross-sectional view of another embodiment of the color conversion sheet of the present invention is shown in Figure 2. Color conversion sheet 1B is a laminate of base layer 10 and color conversion layer 11, with color conversion layer 11 laminated on base layer 10.

[0190] A schematic cross-sectional view of another embodiment of the color conversion sheet of the present invention is shown in Figure 3. The color conversion sheet 1C is a laminate of multiple base layers 10 and color conversion layers 11, with the color conversion layer 11 sandwiched between the multiple base layers 10.

[0191] Figure 4 shows a schematic cross-sectional view of another embodiment of the color conversion sheet of the present invention. Color conversion sheet 1D is a laminate of multiple base layers 10, color conversion layers 11, and multiple barrier films 12, with color conversion layer 11 sandwiched between multiple barrier films 12, and this laminate of color conversion layer 11 and multiple barrier films 12 sandwiched between multiple base layers 10. That is, color conversion sheet 1D preferably also has barrier films 12 as shown in Figure 4 to prevent deterioration of color conversion layer 11 due to oxygen, moisture, or heat.

[0192] The thickness of the color conversion sheet is preferably 30 to 300 μm. Here, the thickness of the color conversion sheet refers to the combined thickness of all layers included in the color conversion sheet, and refers to the film thickness (average film thickness) measured based on Method A of the thickness measurement by mechanical scanning in JIS K7130 (1999) Plastics - Films and Sheets - Thickness Measurement Methods. By making the thickness of the color conversion sheet 30 μm or more, the toughness of the sheet can be improved, and by making it 300 μm or less, cracking can be suppressed.

[0193] The color conversion sheet of the present invention preferably contains a light-emitting material (a) having an emission peak wavelength of 500 nm or more and less than 580 nm and / or a light-emitting material (b) having an emission peak wavelength of 580 nm or more and 750 nm or less. Furthermore, the compound having a structure represented by general formula (3) is preferably the light-emitting material (a) and / or the light-emitting material (b). It is particularly preferred that the color conversion sheet contains the light-emitting material (a) and the light-emitting material (b), and that the compound having a structure represented by general formula (3) is the light-emitting material (a).

[0194] In the color conversion sheet of the present invention, it is preferable to increase the overlap between the emission spectrum of the luminescent material (a) and the absorption spectrum of the luminescent material (b) so that the luminescent material (b) efficiently absorbs the luminescence emitted by the luminescent material (a). Therefore, the half-width of the emission spectrum at the emission peak wavelength of the luminescent material (a) (hereinafter referred to as the "peak half-width") is preferably 30 nm or more. Here, by increasing the overlap between the emission spectrum of the luminescent material (a) and the absorption spectrum of the luminescent material (b), it becomes easier to maintain the luminescent intensity of the luminescent material (b), and as a result, the durability of the luminescent material (b) can be further improved.

[0195] In order to obtain light emission with high color purity when used in a display device, the light-emitting material (a) preferably has a peak half-width of 50 nm or less, more preferably 40 nm or less.

[0196] One example of the color conversion sheet of the present invention is a color conversion sheet that includes one or more color conversion layers, in which luminescent material (a) and luminescent material (b) are contained in the same layer. In the color conversion sheet according to this embodiment, the excitation energy of excited luminescent material (a) is not converted into electromagnetic waves but is transferred directly to luminescent material (b) through electron resonance. This is called fluorescence resonance energy transfer or Förster resonance energy transfer, and is a phenomenon with significantly higher energy transfer efficiency than when the excitation energy of luminescent material (a) is emitted as light and absorbed by luminescent material (b). Therefore, the molar ratio of the content of luminescent material (a) to the content of luminescent material (b) contained in the same layer is preferably luminescent material (a):luminescent material (b) = 50:1 to 500:1.

[0197] Another example of the color conversion sheet of the present invention is a color conversion sheet that includes two or more color conversion layers, in which the luminescent material (a) and the luminescent material (b) are included in different layers. A specific example of such a color conversion layer is a color conversion sheet that includes at least the following layer (A) and layer (B): Layer (A): A layer containing at least a light-emitting material (a) and a binder resin. Layer (B): A layer containing at least a light-emitting material (b) and a binder resin. In the color conversion sheet according to this embodiment, since Förster resonance energy transfer does not occur, it is preferable that the molar ratio of the luminescent material (a) contained in the layer (A) to the luminescent material (b) contained in the layer (B) is luminescent material (a):luminescent material (b) = 5:1 to 100:1.

[0198] The light-emitting material (b) is preferably a light-emitting material whose emission peak wavelength is 580 nm or more and 750 nm or less, i.e., a material that emits red light. Light-emitting materials such as organic light-emitting materials, inorganic phosphors, and inorganic quantum dots can be used. Light-emitting materials having a pyrromethene skeleton are preferably used as organic light-emitting materials. This is because they have a narrower half-width of the emission spectrum and emit red light with high color purity compared to conventional organic red light-emitting materials. This contributes to improving the color reproducibility of display devices.

[0199] (base material layer) Examples of the substrate layer include glass and resin films. The resin film is preferably a plastic film such as polyethylene terephthalate (PET), polyphenylene sulfide, polycarbonate, polypropylene, or polyimide. To facilitate easy peeling of the film, the surface of the substrate layer may be subjected to a release treatment in advance. The thickness of the substrate layer is preferably 38 μm or more and 3000 μm or less.

[0200] (color conversion layer) The thickness of the color conversion layer is preferably 10 μm to 50 μm.

[0201] The color conversion layer can be formed, for example, by applying the color conversion composition prepared by the method described above onto an underlayer such as a substrate layer or a barrier film, and then drying it.

[0202] The color conversion layer may be one layer or two or more layers. When the color conversion layer is two or more layers, it is preferable that at least one layer contains a compound having a structure represented by general formula (3).

[0203] (barrier layer) The barrier layer is preferably one that prevents oxygen, moisture, heat, etc. from penetrating into the color conversion layer, and two or more barrier layers may be provided. The barrier layer may be provided on both sides of the color conversion layer, or on one side.

[0204] Examples of films with gas barrier properties include inorganic oxides such as silicon oxide, aluminum oxide, titanium oxide, tantalum oxide, zinc oxide, tin oxide, indium oxide, yttrium oxide, and magnesium oxide; inorganic nitrides such as silicon nitride, aluminum nitride, titanium nitride, and silicon carbonitride; metal oxide thin films or metal nitride thin films containing these with added elements; and films containing various resins such as polyvinylidene chloride, acrylic resins, silicone resins, melamine resins, urethane resins, fluorine-containing resins, and polyvinyl alcohol resins such as saponified vinyl acetate. Two or more of these may be included. Examples of films with moisture barrier properties include films containing various resins such as polyethylene, polypropylene, nylon, polyvinylidene chloride, copolymers of vinylidene chloride and vinyl chloride, copolymers of vinylidene chloride and acrylonitrile, fluorine-containing resins, and polyvinyl alcohol resins such as saponified vinyl acetate.

[0205] The color conversion sheet of the present invention may further have an auxiliary layer having a light diffusion layer, an adhesive layer, an anti-reflection function, an anti-glare function, an anti-reflection and anti-glare function, a hard coat function (abrasion resistance function), an anti-static function, an anti-fouling function, an electromagnetic wave shielding function, an infrared ray blocking function, an ultraviolet ray blocking function, a polarizing function, or a color-tuning function, depending on the required functions.

[0206] (Other films) The color conversion sheet according to the embodiment of the present invention may further include a polarizing reflective film, a diffusion sheet, a prism sheet, a wavelength-selective reflective film, etc. Suitable specific examples of wavelength-selective reflective films include those described in WO 2017 / 164155 and JP 2018-81250 A.

[0207] <Manufacturing method of color conversion sheet> Next, an example of a method for producing the color conversion sheet of the present invention will be described. The color conversion composition prepared by the above-mentioned method is applied to a substrate and dried to form a color conversion layer. If the binder resin is a thermosetting resin, the color conversion composition may be applied to the substrate and then heat-cured to form the color conversion layer. If the binder resin is a photocurable resin, the color conversion composition may be applied to the substrate and then photocured to form the color conversion layer.

[0208] Coating can be carried out using a reverse roll coater, blade coater, comma coater, slit die coater, direct gravure coater, offset gravure coater, kiss coater, natural roll coater, air knife coater, roll blade coater, two-stream coater, rod coater, wire bar coater, applicator, dip coater, curtain coater, spin coater, knife coater, etc. In order to obtain a uniform thickness of the color conversion layer, coating with a slit die coater, comma coater or dip coater is preferred.

[0209] The color conversion layer can be dried using a common heating device such as a hot air dryer or an infrared dryer. In this case, the heating temperature is preferably 60 to 200°C, and the heating time is preferably 2 minutes to 4 hours. It is also possible to heat and cure the layer in stages using a method such as step curing.

[0210] After the color conversion layer is produced, the substrate can be changed as needed. In this case, simple methods include a method of replacing the substrate using a hot plate, or a method using a vacuum laminator or a dry film laminator.

[0211] <Light source unit> The light source unit of the present invention includes at least a light source and the color conversion sheet of the present invention. The light source included in the light source unit of the present invention is a source of the excitation light. The arrangement of the light source and the color conversion sheet is not particularly limited, and the light source and the color conversion sheet may be closely attached to each other, or a remote phosphor type in which the light source and the color conversion sheet are separated from each other may be used. Furthermore, the light source unit may further include a color filter for the purpose of increasing color purity.

[0212] <Light source> Any light source can be used as long as it emits light in the wavelength range that can be absorbed by the luminescent material (a) and the luminescent material (b). For example, any light source can be used, such as a hot cathode tube, a cold cathode tube, a fluorescent light source such as an inorganic EL, an organic electroluminescence element light source, an LED light source, an incandescent light source, or sunlight. Among these, an LED is a preferred light source, and for display (display device) and lighting applications, a blue LED with a light source in the range of 430 to 500 nm is even more preferred, as it can enhance the color purity of blue light.

[0213] The light source may have one emission peak or two or more emission peaks, but in order to improve color purity, it is preferable to have one emission peak. It is also possible to use any combination of multiple light sources with different emission peaks.

[0214] The light source unit of the present invention is useful for various light sources such as spatial lighting and backlighting, and specifically can be used for applications such as display devices, lighting, interior design, signs, and billboards, but is particularly suitable for use in display devices and lighting.

[0215] <Display device, lighting device> The display device of the present invention includes at least the light-emitting element of the present invention and / or the color conversion sheet. For example, the light source unit of the present invention is preferably used as a backlight unit in a display device such as a liquid crystal display. Furthermore, by using the light-emitting element, a display device such as an organic EL display that displays in a matrix and / or segment format and has high luminous efficiency and excellent durability can be produced.

[0216] Furthermore, the lighting device of the present invention includes at least the light-emitting element of the present invention and / or the color conversion sheet of the present invention. For example, this lighting device is configured to emit white light by combining a blue LED light source as a light source unit with a color conversion sheet that converts the blue light from the blue LED light source into light with a longer wavelength. Furthermore, lighting devices can also be obtained using the light-emitting element of the present invention. Examples of such lighting devices include medical lighting and interior lighting, and they can combine vivid light emission colors, high durability, and excellent design.

[0217] Any light source can be used as long as it emits light in the wavelength range that can be absorbed by the luminescent material (a) and the luminescent material (b). For example, any light source can be used, such as a hot cathode tube, a cold cathode tube, a fluorescent light source such as an inorganic EL, an organic electroluminescence element light source, an LED light source, an incandescent light source, or sunlight. Among these, an LED is a preferred light source, and for display devices and lighting devices, a blue LED with a light source in the range of 430 to 500 nm is even more preferred, as it can enhance the color purity of blue light. [Example]

[0218] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0219] The evaluation methods used in each of the examples and comparative examples are described below.

[0220] (Emission color and fluorescence quantum yield of the compound) The compounds obtained in Examples 1 to 5 and Comparative Examples 1 to 3 were dissolved in toluene, and 10 -5 The concentration was adjusted to 100 mol / L. This toluene solution was irradiated with ultraviolet light having a peak at a wavelength of 360 nm, and the emitted light color was visually confirmed. Furthermore, the fluorescence quantum yield was measured using an absolute PL quantum yield measurement device manufactured by Hamamatsu Photonics, and this was used as an index of the luminescence efficiency of the compound.

[0221] (Emission Peak Wavelength and External Quantum Efficiency of Light-Emitting Device) The light-emitting devices obtained in Examples 6 to 10 and Comparative Examples 4 to 6 were subjected to a current density of 10 mA / cm 2 The emission spectrum was measured and the peak wavelength of the emission was read using a spectroradiometer CS-1000 manufactured by Konica Minolta, Inc. The obtained emission was assumed to be Lambertian radiation, and the external quantum efficiency (EQE) was calculated from the obtained emission spectrum and used as an index of the luminous efficiency of the light-emitting element.

[0222] (Durability of Compound and Light-Emitting Element) The external quantum efficiency of the light-emitting device measured was 10 mA / cm 2 The luminance was measured when a current density of 10 mA / cm was applied, and this was taken as the initial luminance. 2 A voltage was continuously applied so that the luminance reached 90% of the initial luminance (LT90), and the time required for the luminance to reach 90% of the initial luminance was measured using a photodiode, and this was used as an index of the durability of the compound and the light-emitting element.

[0223] (Peak emission wavelength of color conversion sheet) A backlight unit equipped with a blue LED element (emission peak wavelength: 445 nm) and a light guide plate was used. The color conversion sheet obtained in Examples 11 to 14 and Comparative Examples 7 to 9 was placed on one side of the light guide plate, and a prism sheet was further placed on the color conversion sheet. An electric current was passed through the blue LED element to light it up, and the brightness of the light from the blue LED element was 800 cd / m 2An initial value was set so that a current was passed through the blue LED element at the set initial value to light up the blue LED element, and the emission spectrum was measured in the wavelength region of 400 to 700 nm using a spectroradiometer (CS-1000, manufactured by Konica Minolta), and the emission peak wavelength in the green emission region was read.

[0224] (Absolute luminescence quantum yield of color conversion sheet) The color conversion sheets obtained in Examples 11 to 14 and Comparative Examples 7 to 9 were cut into 1 cm squares, and the absolute luminescence quantum yield was measured using an absolute PL quantum yield measurement device (Quantaurus-QY, manufactured by Hamamatsu Photonics KK) and used as an index of the luminous efficiency of the color conversion sheet.

[0225] (Durability of the compound and color conversion sheet) Using the same evaluation system as the peak emission wavelength of the color conversion sheet mentioned above, the brightness of light from a blue LED element (peak emission wavelength: 445 nm) was measured to be 10,000 cd / m 2 After adjusting the temperature so that the compound and the color-conversion sheet were in a state where the compound was irradiated continuously in an environment at 85°C, the time until the brightness decreased by 5% was measured and used as an index of the durability of the compound and the color-conversion sheet.

[0226] Example 1 [Synthesis of Intermediate 6]

[0227] [ka]

[0228] A flask containing 10.0 g of 1-bromo-2,5-dichloro-3-fluorobenzene (molecular weight 243.89, 41 mmol), 15.04 g of 9,9-diphenyl-9,10-dihydroacridine (molecular weight 333.43, 45.1 mmol), potassium carbonate (molecular weight 138.20, 67.7 mmol), and 250 mL of NMP was heated and stirred at 170°C for 10 hours in a nitrogen atmosphere. After the reaction was completed, the mixture was cooled to room temperature, and water and toluene were added and the mixture was separated. The organic layer was concentrated using an evaporator and then purified using a silica gel column, yielding 16.99 g of intermediate 6 (molecular weight 557.31) (70% yield).

[0229] [Synthesis of Intermediate 11]

[0230] [ka]

[0231] 15 g of intermediate 6 (molecular weight 557.31, 26.9 mmol), 6.76 g of 9,9-dimethyl-9,10-dihydroacridine (molecular weight 209.29, 32.28 mmol), 60.4 mg of palladium acetate (molecular weight 224.51, 0.269 mmol), 217.7 mg of tri-tert-butylphosphine (molecular weight 202.32, 1.08 mmol), 3.62 g of sodium tert-butoxide (molecular weight 96.10, 37.66 mmol), and 200 mL of o-xylene were placed in a flask and heated with stirring at 130 °C for 3 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled to room temperature, filtered, and the solvent was removed using an evaporator. The concentrate was purified using a silica gel column to obtain 14.76 g of intermediate 11 (molecular weight 685.69) (80% yield).

[0232] [Synthesis of Intermediate 12]

[0233] [ka]

[0234] 14 g (20.4 mmol) of intermediate 11 and 150 ml of tert-butylbenzene were placed in a flask. After purging with nitrogen, the flask was cooled to -40°C, and 12 ml of 1.7 M tert-butyllithium pentane solution was added dropwise using a syringe. After the addition, the mixture was warmed to room temperature and stirred for 2 hours. The mixture was then cooled to -40°C again, and 3.80 g of 2-isopropoxy-4,4,5,5-tetramethyldioxaborolane (molecular weight 186.06, 20.4 mmol) was added dropwise using a syringe. After the addition, the reaction mixture was heated to 100°C and stirred for 5 hours. After the reaction was completed, the mixture was cooled to room temperature, and ethyl acetate and water were added. The mixture was separated and washed, and the organic layer was concentrated using an evaporator. The resulting concentrate was recrystallized from toluene to obtain 5.23 g (33% yield) of intermediate 12 (molecular weight 777.21).

[0235] [Synthesis of intermediate 13]

[0236] [ka]

[0237] 5 g (6.43 mmol) of intermediate 12, 8.57 g of aluminum chloride (molecular weight 133.33, 64.3 mmol), 12.47 g of N,N-diisopropylethylamine (molecular weight 129.25, 96.5 mmol), and 70 mL of chlorobenzene were placed in a flask, heated to 120 °C in a nitrogen atmosphere, and stirred for 3 hours. After the reaction was complete, the mixture was cooled to room temperature, and water was slowly added dropwise to quench the aluminum chloride. Further addition of dichloromethane followed by separation and washing was performed. The organic layer was concentrated using an evaporator, and the concentrate was recrystallized twice with toluene to obtain 2.20 g (52% yield) of intermediate 13 (molecular weight 659.04).

[0238] [Synthesis of intermediate 14]

[0239] [ka]

[0240] 2 g (3.03 mmol) of intermediate 13, 1.15 g (molecular weight 253.94, 4.55 mmol) of bis(pinacolato)diboron, 17.4 mg (molecular weight 575.02, 0.03 mmol) of bis(dibenzylideneacetone)palladium, 57.2 mg (molecular weight 476.72, 0.12 mmol) of 2-dicyclohexylphosphino-2'-4'-6'-triisopropylbiphenyl, 446 mg (molecular weight 98.15, 4.55 mmol) of potassium acetate, and 50 mL of 1,4-dioxane were placed in a flask, heated to 87 °C in a nitrogen atmosphere, and stirred for 3 hours. After completion of the reaction, the mixture was cooled to room temperature and filtered. Ethyl acetate and water were added to the filtrate for separation and washing, and the organic layer was concentrated using an evaporator. The concentrate was purified by a silica gel column to obtain 1.36 g (yield 60%) of intermediate 14 (molecular weight 750.56).

[0241] [Synthesis of G-1]

[0242] [ka]

[0243] 1.0 g (1.33 mmol) of intermediate 14, 392 mg of 2-chloro-4,6-diphenyl-1,3,5-triazine (molecular weight 267.72, 1.46 mmol), 7.48 mg of bis(dibenzylideneacetone)palladium (molecular weight 575.02, 0.013 mmol), 24.8 mg of 2-dicyclohexylphosphino-2'-4'-6'-triisopropylbiphenyl (molecular weight 476.72, 0.052 mmol), 847 mg of potassium phosphate (molecular weight 212.27, 3.99 mmol), 30 ml of 1,4-dioxane, and 15 ml of water were placed in a flask, heated to 87°C in a nitrogen atmosphere, and stirred for 3 hours. After completion of the reaction, toluene and water were added, and the mixture was separated and washed. The organic layer was then concentrated using an evaporator. The concentrate was recrystallized three times with toluene to obtain 512 mg (45% yield) of G-1 (molecular weight: 855.85). The obtained G-1 was purified by sublimation and used for evaluation.

[0244] Examples 2 to 4 [Synthesis of G-2 to G-4] By appropriately changing the raw materials, G-2 to G-4 were synthesized from Intermediate 14 in the same manner as in the synthesis of G-1, and evaluated in the same manner as in Example 1. The structures of G-2 to G-4 are shown below.

[0245] [ka]

[0246] Example 5 [Synthesis of Intermediate 15] Intermediate 15 was synthesized in the same manner as in the synthesis of Intermediate 6, except that the starting material was changed to 1-bromo-2-chloro-3-fluorobenzene.

[0247] [ka]

[0248] [Synthesis of intermediate 16] Intermediate 16 was synthesized in the same manner as in the synthesis of Intermediate 11, except that the starting material was Intermediate 15 and 9,9-diphenyl-9,10-dihydroacridine was changed to phenoxazine.

[0249] [ka]

[0250] [Synthesis of intermediate 17] Intermediate 17 was synthesized in the same manner as in the synthesis of Intermediate 12, except that the starting material was changed to Intermediate 16.

[0251] [ka]

[0252] [Synthesis of G-5] G-5 was synthesized in the same manner as in the synthesis of intermediate 13, except that the starting material was changed to intermediate 17. The obtained G-5 was purified by sublimation and used for evaluation.

[0253] [ka]

[0254] (Comparative Examples 1 to 3) The fluorescence quantum yield was measured using ref-1 to ref-3 having the following structures.

[0255] [ka]

[0256] The measurement results of the fluorescence quantum yields of the examples and comparative examples are summarized in Table 1.

[0257] [Table 1]

[0258] Comparing G-1 to G-5 with Ref-1, both compounds emitted green light, but the fluorescence quantum yields of G-1 to G-5 were higher. This is due to the bridged structures on both sides of G-1 to G-5, which increased the overlap between the HOMO and LUMO orbitals. This also reflects the suppression of the vibration and rotation of the phenyl group, which is the N substituent, thereby suppressing thermal deactivation from the S1 state. Comparing G-1 to G-5 with Ref-2 and Ref-3, both compounds emitted green light, but the fluorescence quantum yields of G-1 to G-5 were higher. While all of these compounds have bridged structures on both sides, the difference in the bridged structures of G-1 to G-5 reduces the symmetry of the compounds, suppressing intermolecular interactions and improving the fluorescence quantum yield.

[0259] Example 6 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 mm × 46 mm and etched. The resulting substrate was ultrasonically cleaned for 15 minutes using "Semicoclean" (registered trademark) 56 (trade name, manufactured by Furuuchi Chemical Co., Ltd.) and then washed with ultrapure water. This substrate was UV-ozone treated 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 adjusted to 5 × 10. -4 The chamber was evacuated to a pressure of 100 Pa or less. Using a resistance heating method, 10 nm of HAT-CN6 was first deposited as a hole injection layer, followed by 20 nm of HT-1 as a hole transport layer, and 10 nm of HT-2 as an electron blocking layer. Next, a 30 nm thick light-emitting layer was formed by depositing compound M-1 as a matrix material, compound A-1, which emits delayed fluorescence as an assist dopant, and compound G-1 as a dopant in a weight ratio of 79.0:20:1. Next, a 10 nm thick hole blocking layer was formed by depositing ET-1, and a 30 nm thick electron transport layer was formed by depositing ET-2 and 2E-1 in a weight ratio of 1:1. Next, 2 nm of 2E-1 was deposited as an electron injection layer, followed by co-deposition of 100 nm of magnesium and silver in a weight ratio of 9:1 to form a cathode. A 5 mm x 5 mm square light-emitting device was fabricated using the method described above. The resulting light-emitting device was evaluated.

[0260] The structures of HAT-CN6, HT-1, HT-2, M-1, A-1, ET-1, ET-2 and 2E-1 used in the fabrication of the light-emitting device are shown below.

[0261] [ka]

[0262] Examples 7 to 10 Light-emitting devices were fabricated and evaluated in the same manner as in Example 6, except that compounds G-2 to G-5 were used as the dopant material instead of compound G-1.

[0263] (Comparative Examples 4 to 6) Light-emitting devices were fabricated and evaluated in the same manner as in Example 6, except that Ref-1 to Ref-3 were used as the dopant material instead of Compound G-1.

[0264] The results of Examples 6 to 10 and Comparative Examples 4 to 6 are summarized in Table 2.

[0265] [Table 2]

[0266] Comparing G-1 to G-5 with ref-1 to ref-3, although the emission color was all green, the external quantum efficiency, an indicator of luminous efficiency, of G-1 to G-5 was higher. This reflects the high fluorescence quantum yield of Examples 1 to 5. Furthermore, when focusing on the LT90, an indicator of durability, G-1 to G-4 all exceeded ref-1 to ref-2. This reflects both the effect of suppressing intermolecular interactions and improving durability by introducing an asymmetric crosslinking structure, and the effect of suppressing the direct decomposition process from T1 due to the reduction in ΔEST caused by the introduction of an electron-withdrawing group at the para-position of boron. Furthermore, when comparing the LT90 of G-5, which does not have an electron-withdrawing group, with ref-3, G-5 also exceeded ref-3. This indicates that the asymmetric crosslinking structure suppresses intermolecular interactions and thus reduces the decrease in durability caused by intermolecular interactions.

[0267] Example 11 100 parts by weight of acrylic resin as a binder resin was mixed with 0.25 parts by weight of compound G-1 as a light-emitting material and 400 parts by weight of toluene as a solvent. The resulting mixture was stirred and degassed at 300 rpm for 20 minutes using a planetary stirring and degassing device "Mazerustar" (registered trademark) KK-400 (manufactured by Kurabo Industries, Ltd.) to obtain a color-changing composition.

[0268] 100 parts by weight of polyester resin as a binder resin was mixed with 300 parts by weight of toluene as a solvent, and the mixture was stirred and degassed at 300 rpm for 20 minutes using a planetary stirring and degassing device "Mazerustar" KK-400 (manufactured by Kurabo Industries, Ltd.) to obtain an adhesive composition.

[0269] Next, the obtained color-changing composition was applied to a first substrate layer, "Lumirror" (registered trademark) U48 (manufactured by Toray Industries, Inc., thickness 50 μm), using a slit die coater, and dried by heating at 100°C for 20 minutes to form a color-changing layer with an average thickness of 16 μm.

[0270] In addition, the obtained adhesive composition was applied using a slit die coater to the second substrate layer side of a light diffusion film "Chemical Mat 125PW" (manufactured by Kimoto Co., Ltd., thickness 138 μm) having a light diffusion layer on one side of the second substrate layer (PET), and heated and dried at 100°C for 20 minutes to obtain a laminate of adhesive layer / second substrate layer / light diffusion layer.

[0271] Next, these laminates were heated and laminated so that the color conversion layer and the adhesive layer were directly laminated to produce a color conversion sheet with a laminated structure of first base layer / color conversion layer / adhesive layer / second base layer / light diffusion layer.

[0272] (Examples 12 to 14) Color conversion films were produced and evaluated in the same manner as in Example 11, except that compounds G-2 to G-4 were used as the light-emitting material instead of compound G-1.

[0273] (Comparative Examples 7 to 9) Color-changing films were produced and evaluated in the same manner as in Example 11, except that Ref-1 to Ref-3 were used as the light-emitting material instead of compound G-1.

[0274] The results of Examples 11 to 14 and Comparative Examples 7 to 9 are summarized in Table 3.

[0275] [Table 3]

[0276] Comparing G-1 to G-4 with ref-1 to Ref-3, although the emission color was all green, G-1 to G-4 had higher absolute luminescence quantum efficiency, which is an index of luminescence efficiency. This reflects the high fluorescence quantum yield of Examples 1 to 4. Furthermore, in terms of durability, G-1 to G-4 all had results that exceeded ref-1 to ref-3. This reflects both the effect of suppressing intermolecular interactions and improving durability by introducing an asymmetric crosslinked structure, and the effect of suppressing the direct decomposition process from T1 due to the reduction in ΔEST by introducing an electron-withdrawing group to the para-position of boron. [Explanation of symbols]

[0277] 1A, 1B, 1C, 1D color conversion sheet 10 Base material layer 11 Color conversion layer 12 Barrier film

Claims

1. A compound having a structure represented by the following general formula (3): 【Chemistry 1】 (In the above general formula (3), R １０１ ~R １２４ are each independently a hydrogen atom, an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, an aryl group, a heteroaryl group, an amino group, or R １０１ ~R １２４ These groups may further have a substituent. L 3 is a single bond, O, S, or CR. １２５ R １２６ or SiR １２７ R １２８ It is. １２５ ~R １２８ are each independently hydrogen, halogen, an alkyl group, a cycloalkyl group, an aryl group, or a heteroaryl group, and these groups may further have a substituent. １２５ and R １２６ or R １２７ and R １２８ may be bonded via a single bond or a linking group. L 4 is CR 125 R 126 . R 125 and R 126 in L 4 are aryl groups. ３ and L ４ are always different groups.)

2. In the general formula (3), R １０３ , R １１１ and / or R １２２ is a group having a positive substituent constant σp value in Hammett's rule, or R １０２ , R １０７ , R １１０ , R １１２ , R １２０ and / or R １２３ The compound of claim 1 , wherein is a substituted amino group.

3. The compound according to claim 2, wherein the group having a positive substituent constant σp value in Hammett's rule is fluorine, a fluorine-substituted alkyl group, a fluorine-substituted cycloalkyl group, a fluorine-substituted aryl group, a fluorine-substituted heteroaryl group, a cyano group, an aryl group substituted with a cyano group, a heteroaryl group substituted with a cyano group, or an electron-accepting nitrogen-containing heteroaryl group.

4. The compound according to claim 3, wherein the group having a positive substituent constant σp value in Hammett's rule is an electron-accepting nitrogen-containing heteroaryl group.

5. In the general formula (3), R １０２ , R １０７ , R １１０ , R １１２ , R １２０ and / or R １２３ The compound according to claim 2, wherein the compound has a structure represented by the following general formula (4): 【Chemistry 2】 (In the above general formula (4), Ar １ and Ar ２ are each independently an aryl group or a heteroaryl group. These groups may further have a substituent. １ and Ar ２ may be bonded via a single bond or a linking group, and in this case, the linking group is -O-, -S-, >CR １３３ R １３４ , >SiR １３５ R １３６ or >C=O, and R １３３ ~R １３６ are each independently a hydrogen atom, a halogen atom, an alkyl group, a cycloalkyl group, an aryl group, or a heteroaryl group. These groups may further have a substituent.

6. The compound according to any one of claims 1 to 5, which is a material for a light-emitting device.

7. A light-emitting device comprising a cathode, an anode, and at least one organic layer disposed between the cathode and the anode, wherein the at least one organic layer contains the compound according to any one of claims 1 to 6.

8. The light-emitting device according to claim 7 , wherein the at least one organic layer is a light-emitting layer.

9. 9. The light-emitting device according to claim 8, wherein the light-emitting layer comprises at least a dopant material and an assist dopant material, and the dopant material contains the compound according to any one of claims 1 to 6.

10. The light-emitting device according to claim 9 , wherein the assist dopant material is a compound that emits delayed fluorescence.

11. 10. The light-emitting device according to claim 8, wherein the light-emitting layer comprises at least a dopant material and an assist dopant material, and the assist dopant material contains the compound according to any one of claims 1 to 6.

12. A color-changing composition that converts incident light into light of a wavelength different from that of the incident light, the color-changing composition comprising the compound according to any one of claims 1 to 5 and a binder resin.

13. A color conversion sheet comprising a color conversion layer formed from the color conversion composition according to claim 12.

14. A light source unit comprising a light source and the color conversion sheet according to claim 13.

15. A display device comprising the light emitting device according to any one of claims 7 to 11 and / or the light source unit according to claim 14.

16. A lighting device comprising the light emitting element according to any one of claims 7 to 11 and / or the light source unit according to claim 14.

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