JP2023011486A - Compound, and luminous element and color conversion composition that are based thereon - Google Patents

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

The present invention relates to novel compounds and light-emitting device materials, light-emitting devices, color-converting compositions, color-converting sheets, light source units, display devices, and lighting devices using the same.

An organic thin film light-emitting device that emits light by recombination of electrons injected from the cathode and holes injected from the anode in the light-emitting layer sandwiched between the two electrodes can be made thinner and has a low driving voltage. , high luminance, and the ability to emit light in multiple colors.

In order to further increase the color gamut of display devices using organic light-emitting devices, materials with narrow half widths of emission spectra have been actively developed. As such a technique, for example, polycyclic aromatic compounds in which a plurality of aromatic rings are linked by boron atoms and nitrogen atoms (see, for example, Patent Documents 1 to 5 and Non-Patent Document 1) have been proposed.

WO2015/102118 WO2018/186670 WO2019/240080 Japanese Patent Application Laid-Open No. 2020-132636 WO2021/013993

"Advanced. Materials", 2016, vol. 28, p. 2777-2781

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 light-emitting materials, but their emission wavelengths are insufficient as green light-emitting materials. In addition, although the compound described in Patent Document 5 emits green light, its luminous efficiency and durability are insufficient. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a compound having green light emission characteristics, which has high luminous efficiency and excellent durability.

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

In the above general formula (3), R ¹⁰¹ to R ¹²⁴ are each independently hydrogen, halogen, cyano group, alkyl group, cycloalkyl group, heterocyclic group, alkenyl group, cycloalkenyl group, alkynyl group, alkoxy group , an alkylthio group, an arylether group, an arylthioether group, an aryl group, a heteroaryl group, an oxycarbonyl group, a carbamoyl group, an amino group, a nitro group, a silyl group or an adjacent substituent among R ¹⁰¹ to R ¹²⁴ It is the saturated or unsaturated ring that is formed. These groups may further have a substituent.

L3 and L4 ^{are each} independently a single bond, O, S, ^{CR125R126 or SiR127R128 .} R ¹²⁵ to R ¹²⁸ are each independently hydrogen, halogen, alkyl group, cycloalkyl group, aryl group or heteroaryl group, and these groups may further have a substituent. R ¹²⁵ and R ¹²⁶ or R ¹²⁷ and R ¹²⁸ may be bonded via a single bond or a linking group. However, L ³ and L ⁴ are necessarily different groups.

The compound of the present invention has green emission characteristics with high luminous efficiency and excellent durability. The compound of the present invention can provide a light-emitting device material, a light-emitting device, a color conversion composition, and a color conversion sheet having green emission characteristics with high luminous efficiency and excellent durability.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic cross section showing one aspect|mode of the color conversion sheet of this invention. FIG. 3 is a schematic cross-sectional view showing another aspect of the color conversion sheet of the present invention; FIG. 3 is a schematic cross-sectional view showing another aspect of the color conversion sheet of the present invention; FIG. 3 is a schematic cross-sectional view showing another aspect of the color conversion sheet of the present invention;

The contents of the present invention will be described in detail below. The present invention is not limited to the embodiments and specific examples described below.

The compound of the present invention has a structure represented by the following general formula (3). A compound having a structure represented by the following general formula (3) has an asymmetric crosslinked structure represented by L ³ or L ⁴ at a specific position, has a strong and highly planar skeleton, and has a high Fluorescence quantum yield is shown. The fluorescence quantum yield is an index of luminous efficiency, and the higher the fluorescence quantum yield, the higher the luminous efficiency. Furthermore, the presence of the crosslinked structures L3 and L4 ^expands the π ^- conjugated system and lengthens the emission wavelength. Therefore, the compound having the structure represented by general formula (3) has excellent green light emission properties. In addition, since the molecular structure is asymmetric due to the difference in the cross ^- linking structures L3 and L4 ^, intermolecular interactions can be suppressed, suppressing deterioration in luminous efficiency and durability caused by intermolecular interactions. , the luminous efficiency and durability can be improved.

In the above general formula (3), R ¹⁰¹ to R ¹²⁴ are each independently hydrogen, halogen, cyano group, alkyl group, cycloalkyl group, heterocyclic group, alkenyl group, cycloalkenyl group, alkynyl group, alkoxy group , an alkylthio group, an arylether group, an arylthioether group, an aryl group, a heteroaryl group, an oxycarbonyl group, a carbamoyl group, an amino group, a nitro group, a silyl group or an adjacent substituent among R ¹⁰¹ to R ¹²⁴ It is the saturated or unsaturated ring that is formed. These groups may further have a substituent.

L3 and L4 ^{are each} independently a single bond, O, S, ^{CR125R126 or SiR127R128 .} R ¹²⁵ to R ¹²⁸ are each independently hydrogen, halogen, alkyl group, cycloalkyl group, aryl group or heteroaryl group, and these groups may further have a substituent. R ¹²⁵ and R ¹²⁶ or R ¹²⁷ and R ¹²⁸ may be bonded via a single bond or a linking group. However, L ³ and L ⁴ are necessarily different groups.

In ^all of the following descriptions of this specification, the isotopic species of hydrogen atoms present in the molecule of the compound is not particularly limited. Or all may be ² H (deuterium D).

In all of the descriptions herein below, "unsubstituted" when referring to "substituted or unsubstituted" means that a hydrogen atom or deuterium atom is attached.

Descriptions of halogens and each group described below are common to all of the descriptions below in this specification.

Halogen denotes fluorine, chlorine, bromine or iodine.

A cyano group is a group whose structure is represented by -C≡N. It is the carbon atom that is bonded to the other group here.

The alkyl group is, for example, a saturated aliphatic hydrocarbon group such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, which is a substituent may or may not have The number of carbon atoms in the alkyl group is not particularly limited, but is preferably from 1 to 20, more preferably from 1 to 8, from the viewpoint of availability and cost. The number of carbon atoms as used herein includes the number of carbon atoms contained in the substituents bonded to the alkyl group, and the same applies to other substituents defining the number of carbon atoms.

A cycloalkyl group is, for example, a saturated alicyclic hydrocarbon group such as a cyclopropyl group, a cyclohexyl group, a norbornyl group, and an adamantyl group, which may or may not have a substituent. The number of ring-forming carbon atoms is not particularly limited, but is preferably in the range of 3 or more and 20 or less.

A heterocyclic group is, for example, a pyran ring, a piperidine ring, an aliphatic ring having a non-carbon atom in the ring such as a cyclic amide, which may or may not have a substituent. . Although the number of ring-forming atoms is not particularly limited, it is preferably in the range of 3 or more and 20 or less.

The alkenyl group is, for example, an unsaturated aliphatic hydrocarbon group containing a double bond such as a vinyl group, an allyl group, a butadienyl group, etc., which may or may not have a substituent. Although the number of carbon atoms in the alkenyl group is not particularly limited, it is preferably in the range of 2 or more and 20 or less.

A cycloalkenyl group is an unsaturated alicyclic hydrocarbon group containing a double bond such as, for example, a cyclopentenyl group, a cyclopentadienyl group, a cyclohexenyl group, which may or may not have a substituent. You don't have to. The number of ring-forming carbon atoms is not particularly limited, but is preferably in the range of 3 or more and 20 or less.

An alkynyl group is, for example, an unsaturated aliphatic hydrocarbon group containing a triple bond such as an ethynyl group, which may or may not have a substituent. Although the number of carbon atoms in the alkynyl group is not particularly limited, it is preferably in the range of 2 or more and 20 or less.

An alkoxy group is, for example, 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, which may or may not have a substituent. good too. Although the number of carbon atoms in the alkoxy group is not particularly limited, it is preferably in the range of 1 or more and 20 or less.

An alkylthio group is an alkoxy group in which the oxygen atom of the ether bond is substituted with a sulfur atom. The hydrocarbon group of the alkylthio group may or may not have a substituent. Although the number of carbon atoms in the alkylthio group is not particularly limited, it is preferably in the range of 1 or more and 20 or less.

An aryl ether group is, for example, a group in which an aromatic hydrocarbon group is bonded via an ether bond, such as a phenoxy group, which may or may not have a substituent. Although the number of ring-forming carbon atoms in the aryl ether group is not particularly limited, it is preferably in the range of 6 or more and 40 or less.

An arylthioether group is an arylether group in which the oxygen atom of the ether bond is substituted with a sulfur atom. It may or may not have a substituent. Although the number of ring-forming carbon atoms in the arylthioether group is not particularly limited, it is preferably in the range of 6 or more and 40 or less.

An aryl group includes, for example, a phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, a fluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenanthryl group, anthracenyl group, a benzophenanthryl group, and a benzoanthracene. It represents an aromatic hydrocarbon group such as a nyl group, a chrysenyl group, a pyrenyl group, a fluoranthenyl group, a triphenylenyl group, a benzofluoranthenyl group, a dibenzoanthracenyl group, a perylenyl group, and a helicenyl group. It 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 and triphenylenyl group are preferred. The number of ring-forming carbon atoms is not particularly limited, but is preferably 6 or more and 40 or less, more preferably 6 or more and 30 or less.

Moreover, in the substituted phenyl group, when there are substituents on two adjacent carbon atoms in the phenyl group, the substituents may form a ring structure. The resulting group, depending on its structure, is a "substituted phenyl group", an "aryl group having a structure in which two or more rings are condensed", or a "structure in which two or more rings are condensed." any one or more of "heteroaryl group having".

The heteroaryl group includes, for example, pyridyl group, furanyl group, thiophenyl group, quinolinyl group, isoquinolinyl group, pyrazinyl group, pyrimidyl group, pyridazinyl group, triazinyl group, napthyridinyl group, cinnolinyl group, phthalazinyl group, quinoxalinyl group, quinazolinyl group, benzofuranyl group, benzothiophenyl group, indolyl group, dibenzofuranyl group, dibenzothiophenyl group, carbazolyl group, benzocarbazolyl group, carbolinyl group, indolocarbazolyl group, benzoflocarbazolyl group, benzothienocarba non-carbon groups such as zolyl, dihydroindenocarbazolyl, benzoquinolinyl, acridinyl, dibenzoacridinyl, benzimidazolyl, imidazopyridyl, benzoxazolyl, benzothiazolyl, phenanthrolinyl represents a cyclic aromatic group having one or more atoms in the ring. However, the naphthyridinyl group is 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. or A heteroaryl group may or may not have a substituent. The number of ring-forming atoms is not particularly limited, but is preferably 3 or more and 40 or less, more preferably 3 or more and 30 or less.

An 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 2 or more and 50 or less, more preferably 6 or more and 40 or less, and particularly preferably 6 or more and 30 or less.

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

Moreover, an oxycarbonyl group and a carbamoyl group may or may not have a substituent. Here, examples of substituents include alkyl groups, cycloalkyl groups, aryl groups, heteroaryl groups, and the like, and these substituents may be further substituted.

In all 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 , arylthioether group, aryl group, heterocyclic group, heteroaryl group, oxycarbonyl group, carbamoyl group, amino group, nitro group, silyl group and the like. Furthermore, specific substituents that are preferred in the description of each substituent are preferred. In addition, these substituents may be further substituted with the above substituents.

When R ¹⁰¹ to R ¹²⁴ are other than hydrogen, fluorine, a cyano group, an aryl group, a heteroaryl group, and an amino group are preferable from the viewpoint of fine adjustment of the emission wavelength. An alkyl group and a cycloalkyl group are preferable from the viewpoint of suppressing intermolecular interaction due to moderate steric hindrance and suppressing a decrease in fluorescence quantum yield. Among these, an alkyl group and an aryl group are more preferable. The alkyl group is preferably a methyl group, an ethyl group, an isopropyl group or a tert-butyl group, more preferably a methyl group or a tert-butyl group. The aryl group is preferably a phenyl group, a naphthyl group, a biphenyl group, a terphenyl group, a fluorenyl group, 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 a phenyl group. More preferred.

A compound having a structure represented by the general formula ( ³ ) has a higher fluorescence quantum yield than a compound having no crosslinked structures L3 and L4 ^, and is an assist dopant material for a green organic EL light-emitting device or a green It is a compound useful as a dopant material. This can be explained as follows. The compound represented by the following formula (3-1) is known to emit blue light. Ring h and ring i, which are substituents of , are not coplanar and have a twist. Therefore, HOMO orbitals and LUMO orbitals are hardly extended to ring h and ring i. On the other hand, when having the crosslinked structures L ³ and L ⁴ , the surface of the partial structure composed of ring e, ring f, ring g, boron atoms, and nitrogen atoms as shown in the following formula (3-2) Then, ring h and ring i, which are substituents of nitrogen, are almost coplanar, so the HOMO orbital and LUMO orbital are extended to ring h and ring i. That is, since the conjugated system is extended, the energy gap between the HOMO level and the LUMO level becomes smaller, and the emission wavelength becomes longer. In addition, the introduction of the crosslinked structures L ³ and L ⁴ can suppress the vibration and rotational motion of the rings h and i, which are the substituents of the nitrogen atoms in the compound represented by the formula (3-1). Quantum yield is improved. Such effects of the crosslinked structures L3 and ^{L4 are} more pronounced for compounds having only ^L3 and compounds having only ^L4 .

In addition, the compound represented by formula (3-1) has a small energy difference (ΔEST) between the lowest singlet excited state (S1 state) and the lowest triplet excited state (T1 state), and emits delayed fluorescence. It has been known. Generally, the T1 state of common organic compounds is deactivated at room temperature without radiation, that is, without emitting light. However, a compound with a small ΔEST is converted from the T1 state generated by excitation to the S1 state even with thermal energy of about room temperature, and emits delayed fluorescence. In general organic compounds, the T1 state is thermally deactivated at room temperature and does not contribute to light emission, so this property is very important in improving the efficiency of organic EL devices. In an organic EL device, current excitation generates the S1 state and the T1 state of the light-emitting material in proportions of 25% and 75%, respectively. A compound that emits only simple fluorescence would have only 25% S1 states available. On the other hand, a compound with a small ΔEST can convert 75% of the T1 state generated by current excitation to the S1 state, and almost 100% of the fluorescence emission from the S1 state, including the converted S1 state, can be used. , the luminous efficiency is dramatically improved compared to the case of using a simple fluorescent light-emitting material.

The compound having the structure represented by general formula (3) is characterized in that L ³ and L ⁴ are different groups. If the crosslinked structures L ³ and L ⁴ are different groups, the symmetry can be suppressed, the intermolecular force can be weakened, and the crystallinity can be reduced compared to the case where L ³ and L ⁴ are the same group. As a result, the solubility in solvents is improved, high purity can be easily achieved by column purification and recrystallization purification, and the deposition temperature can be lowered, so it has heat resistance that can withstand long-term vacuum deposition processes. can get. In addition, since the symmetry can be suppressed and the intermolecular interaction can be weakened, the decrease in fluorescence quantum yield and durability due to the intermolecular interaction can be suppressed, and the luminous efficiency and durability can be improved.

Here, when L ³ and L ⁴ are CR ¹²⁵ R ¹²⁶ , that is, even if both L ³ and L ⁴ are bridged by methylene groups, the combination of R ¹²⁵ and R ¹²⁶ in L ³ and L ⁴ If the combinations of R ¹²⁵ and R ¹²⁶ in are different, L ³ and L ⁴ are regarded as different linking groups. For example, when both R ¹²⁵ and R ¹²⁶ in L ³ are methyl groups and both R ¹²⁵ and R ¹²⁶ in L ⁴ are phenyl groups, L ³ and L ⁴ are different linking groups. The same applies when L ³ and L ⁴ are SiR ¹²⁷ R ¹²⁸ , ie both are silicon bridges.

As described above, the compound having the structure represented by the general formula ( ³ ) can improve the fluorescence quantum yield and durability of the compound itself by introducing different cross ^- linking structures L3 and L4. It is possible to improve the luminous efficiency and durability of the color conversion sheet.

From the viewpoint of further lowering the vapor deposition temperature and further improving the heat resistance, from the viewpoint of further improving the fluorescence quantum yield and durability, L ³ and / or L ⁴ is CR ¹²⁵ R ¹²⁶ , that is, a methylene group A crosslinked structure is preferred. When the bridge structure L ³ and/or L ⁴ is a methylene group, it is composed of ring e, ring f, ring g, ring h, ring i, boron atom and nitrogen atom described in formula (3-2). The methylene group substituents R ¹²⁵ and R ¹²⁶ protrude sterically from the surface of the partial structure, resulting in a sterically bulky structure, so the compound having the structure represented by the general formula (3) high flatness can be relaxed. This effect weakens the intermolecular force acting between the molecules of the compound having the structure represented by the general formula (3), thereby reducing the crystallinity. As described above, the solubility in a solvent can be further increased, and the heat resistance can be further improved. In addition, quenching due to intermolecular interactions caused by intermolecular forces can be suppressed, and the fluorescence quantum yield can be further improved. ^More preferably, ^L3 and ^L4 are ^CR125R126 .

From the viewpoint of the sterically bulky structure described 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 more preferably an aryl group. preferable. It is most preferred that R ¹²⁵ and R ¹²⁶ are aryl groups as this results in a more sterically bulky structure. The aryl group is preferably a phenyl group, a naphthyl group, a biphenyl group, a terphenyl group, a fluorenyl group, 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 a phenyl group. More preferred. Also, R ¹²⁵ and R ¹²⁶ are aryl groups, and these aryl groups may be further bonded via a single bond or a linking group. This linking group is preferably a single bond, -O- or -S-, more preferably a single bond.

A compound having a structure represented by formula (3) is useful as an assist dopant material or a green dopant material for a green organic EL light-emitting device. As the green dopant material, in the fluorescence spectrum of the compound having the structure represented by the general formula (3), the peak wavelength is preferably 500 nm or more and 550 nm or less, and 510 nm or more and 540 nm or less, from the viewpoint of further improving the color purity of the green emission. is more preferred. Here, the fluorescence spectrum of the compound having the structure represented by the general formula (3) is measured using a fluorescence spectrophotometer using a diluted solution with a concentration of 10 ⁻⁵ mol/L in toluene as a solvent. can be done.

In order to make the emission wavelength within the above range, for example, at least one of R ¹⁰¹ to R ¹²⁴ is a group having a positive substituent constant σp value in Hammett's rule or an electron-donating substituted amino group. Preferably. Here, the "substituent constant σp value in Hammett's rule" (hereinafter sometimes simply referred to as "σp value") is defined by L. P. It was proposed by Hammett and represents a per-substituent reaction constant that quantifies the effect of a substituent on the reaction rate or equilibrium of para-substituted benzene derivatives. The "σp value" in the present invention is Hansch, C.; et. al. , "Chemical Reviews", 1991, vol. 91, p. 165-195. A group with a positive σp value tends to exhibit electron-withdrawing properties (acceptor properties).

When at least one of R ¹⁰¹ to R ¹²⁴ is an electron withdrawing group or a substituted amino group, the HOMO level and LUMO level can be shifted, resulting in an energy gap between the HOMO level and the LUMO level. can be adjusted, and the emission wavelength can be easily adjusted.

In particular, R ¹⁰³ , R ¹¹¹ and/or R ¹²² at the para-position of the boron atom in general formula (3) are preferably groups with a positive σp value, that is, electron-withdrawing groups. By introducing an electron-withdrawing group into these positions, the LUMO level can be greatly stabilized without significantly shifting the HOMO level. That is, it is possible to deepen the LUMO level while roughly maintaining the HOMO level. A pure green emission is obtained. Regarding the emission wavelength, considering the effect of lengthening the wavelength by introducing the crosslinked structures L3 and L4 ^, the desired green light emission can be obtained by adjusting the electron withdrawing property of the electron withdrawing group introduced at the para ^- position of the boron atom. can be obtained. That is, the greater the electron-withdrawing property of the electron-withdrawing group introduced at at least one position of R ¹⁰³ , R ¹¹¹ and/or R ¹²² , the greater the degree of stabilization of the LUMO level, and the more LUMO It becomes possible to deepen the level. 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, ^ΔEST is one of the ^factors that affect the conversion efficiency from the T1 state to the S1 state. /or At least one of R ¹²² is an electron withdrawing group, resulting in a smaller ΔEST. Therefore, the conversion efficiency from the T1 state to the S1 state is further improved, 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, organic light-emitting materials have a longer lifetime in the T1 state than in the S1 state, so there is a process of direct decomposition and deterioration from the T1 state. By improving the conversion efficiency of , the process of direct decomposition from the T1 state can be suppressed, so that the durability of the compound is further improved. As the introduction position of the electron-withdrawing group, R ¹¹¹ is preferable because it is highly effective in reducing ΔEST.

Groups with a positive substituent constant σp value in Hammett's rule include fluorine, fluorine-substituted alkyl groups, fluorine-substituted cycloalkyl groups, fluorine-substituted aryl groups, fluorine-substituted heteroaryl groups, cyano groups, 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, fluorine-substituted alkyl groups, fluorine-substituted cycloalkyl groups, fluorine-substituted aryl groups, fluorine-substituted heteroaryl groups, cyano-substituted aryl groups, cyano-substituted hetero More preferably an aryl group or an electron-accepting nitrogen-containing heteroaryl group, more preferably a fluorine-substituted alkyl group, a fluorine-substituted aryl group, a cyano-substituted aryl group, or an electron-accepting nitrogen-containing heteroaryl group, Electron-accepting nitrogen-containing heteroaryl groups are particularly preferred. By selecting an electron-accepting nitrogen-containing heteroaryl group, ΔEST becomes smaller, and the fluorescence quantum yield of the compound and the luminous efficiency and durability of the light-emitting device and color conversion sheet can be further improved.

Among the fluorine-substituted alkyl groups, a perfluoroalkyl group is preferable, and a trifluoromethyl group is more preferable, since it has a strong electron-withdrawing property and can be expected to have an effect of greatly lengthening the wavelength.

A fluorine-substituted aryl group is, for example, an aryl group having one or more fluorine atoms as substituents on the above-mentioned aryl group, but also an aryl group substituted with one or more perfluoroalkyl groups. include. Alternatively, an aryl group having both fluorine and a perfluoroalkyl group as substituents may be used. Among fluorine-substituted aryl groups, fluorophenyl group, difluorophenyl group, trifluorophenyl group, tetrafluorophenyl group, pentafluorophenyl group, trifluoromethylphenyl group, bis(trifluoromethyl)phenyl group, tris(tri A fluoromethyl)phenyl group is more preferably used. The number and substitution positions of fluorine or trifluoromethyl groups as substituents may be selected in consideration of electron-withdrawing properties so as to obtain desired green light emission. The fluorine-substituted aryl group may further have a substituent, and in the case of having a substituent, the substituent may be a cyano group or an alkyl group from the viewpoint of adjusting the electron-withdrawing property. An aryl group or a heteroaryl group is preferable from the viewpoint of lengthening the emission wavelength by extending the conjugated system.

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

The aryl group substituted with a cyano group is, for example, an aryl group having one or more cyano groups as substituents on the above-mentioned aryl group. The aryl group having a cyano group as a substituent includes 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, 2,6-dicyanophenyl group, 3,4-dicyanophenyl group, 3,5-dicyanophenyl group and the like. The number and substitution position of cyano groups as substituents may be selected in consideration of electron-withdrawing properties so that desired green light emission can be obtained. The aryl group substituted with a cyano group may further have a substituent, and in the case of having a substituent, the substituent may be fluorine, perfluoro An alkyl group and an alkyl group are preferred, and an aryl group and a heteroaryl group are preferred from the viewpoint of lengthening the emission wavelength by extending the conjugated system.

A heteroaryl group substituted with a cyano group is, for example, a heteroaryl group further having one or more cyano groups as substituents on the aforementioned heteroaryl group. The number and substitution positions of cyano groups as substituents may be selected in consideration of electron-withdrawing properties so as to obtain 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 those of the aryl group substituted with a cyano group. groups.

An electron-accepting nitrogen-containing heteroaryl group is a heteroaryl group containing a multiple-bonded nitrogen atom as a heteroatom. Specifically, imidazolyl group, oxazolyl group, thiazole group, benzimidazolyl group, benzoxazolyl group, benzothiazolyl group, pyridyl group, pyrimidyl group, pyrazinyl group, pyridazinyl group, triazinyl group, quinolinyl group, isoquinolinyl group, quinoxalinyl group, A quinazolyl group, naphthyridinyl group, phenanthrolinyl group and the like can be preferably used. Among them, pyridyl group, pyrimidyl group, pyrazinyl group, pyridazinyl group, triazinyl group, quinolinyl group, isoquinolinyl group, quinoxalinyl group, quinazolyl group and naphthyridinyl group are , and a phenanthrolinyl group are more preferable, and from the viewpoint 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 more preferable. The number and positions of electron-accepting nitrogen atoms as heteroatoms 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 when it has a substituent, the substituent is fluorine, a perfluoroalkyl group, from the viewpoint of adjusting electron-withdrawing properties. , a cyano group, an electron-accepting nitrogen-containing heteroaryl group, and an alkyl group are preferable, and from the viewpoint of lengthening the wavelength by extending the conjugated system, a heteroaryl group and an aryl group are preferable.

It is also preferred that R ¹⁰² , R ¹⁰⁷ , R ¹¹⁰ , R ¹¹² , R ¹²⁰ and/or R ¹²³ at the para-position of the nitrogen atom in formula (3) is 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 shallow without significantly shifting the LUMO level. That is, it is possible to reduce the energy gap, and by lengthening the wavelength of light emission, green light emission with high color purity can be obtained. Regarding the emission wavelength, considering the effect of lengthening the wavelength by introducing the crosslinked structures L3 and L4 ^, the desired green emission is obtained by adjusting the electron ^- donating property of the substituted amino group introduced at the para-position of the nitrogen atom. be able to. That is, the greater the electron-donating ability of the substituted amino group introduced into at least one position of R ¹⁰² , R ¹⁰⁷ , R ¹¹⁰ , R ¹¹² , R ¹²⁰ or R ¹²³ , the shallower the HOMO level and the energy gap. become smaller. As a result, the emission wavelength becomes longer. This property can be used to adjust the emission wavelength. Furthermore, ΔEST becomes smaller when at least one of R ¹⁰² , R ¹⁰⁷ , R ¹¹⁰ , R ¹¹² , R ¹²⁰ or R ¹²³ is a substituted amino group. Thereby, the fluorescence quantum yield and durability of the compound having the structure represented by the general formula (3) can be further improved.

Of R ¹⁰³ , R ¹¹¹ or R ¹²² at the para position of boron in the general formula (3), introduction of an electron-withdrawing group to R ¹¹¹ allows the HOMO orbital and LUMO orbital to be separated more clearly, and ΔEST is smaller. As a result, the luminous efficiency and durability of the light-emitting element can be expected to be improved, which is preferable. Also, a substituted amino group is preferably introduced into R ¹¹⁰ or R ¹¹² for the same reason.

As the substituted amino group, a structure represented by the following general formula (4) is preferable.

In general formula (4) above, Ar ¹ and Ar ² are each independently an aryl group or a heteroaryl group. These groups may further have a substituent. Ar ¹ and Ar ² may be linked via a single bond or a linking group, in which 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 hydrogen, halogen, alkyl group, cycloalkyl group, aryl group or heteroaryl group. These groups may further have a substituent.

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 and a pyrenyl group, preferably a phenyl group, a naphthyl group, a biphenyl group and a fluorenyl group, and a phenyl group and a biphenyl group. , more preferably a fluorenyl group.

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. Nyl group, dibenzothiophenyl group and carbazolyl group are more preferred.

When Ar ¹ and Ar ² are bound, they are preferably bound through a single bond.

Examples of compounds having a structure represented by general formula (3) are shown below, but are not limited thereto.

A compound having a structure represented by general formula (3) is described in, for example, "Advanced. Materials", 2016, vol. 28, p. 2777-2781, and "Angew. Chem. Int. Ed.", 2019, vol.58, p. 16912-16917 can be referred to.

The obtained compound having the structure represented by the general formula (3) is purified by organic synthesis such as recrystallization and column chromatography, and then further purified by heating under reduced pressure, which is generally called sublimation purification. It is preferable to remove low boiling point components to improve purity.

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.

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

The desired final products can be obtained from intermediate 9 by Suzuki-Miyaura coupling reaction with desired arylboronic acid, heteroarylboronic acid and heteroarylboronic acid. Further, if intermediate 10 is synthesized, the desired final aryl chloro, heteroaryl chloro, aryl bromo, heteroaryl bromo, aryl iodine, or heteroaryl iodine, etc., and Suzuki-Miyaura coupling reaction A product can be obtained.

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

The light-emitting device material may contain other components together with the compound having the structure represented by general formula (3). Other components include, for example, those exemplified as materials constituting the hole injection layer, hole transport layer, light emitting layer, electron transport layer and/or electrode protective film (cap layer) described later.

<Light emitting element>
Next, embodiments 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 by electrical energy.

The light emitting device of the present invention may be of either bottom emission type or top emission type. A top-emission type light-emitting device has a higher luminous efficiency with a narrower half width due to the resonance effect of the microcavity. Therefore, it is preferable because both color purity and luminous efficiency can be achieved at a higher level.

The layer structure between the anode and the cathode in such a light-emitting element includes, in addition to the structure consisting only of the light-emitting layer, 1) light-emitting layer/electron transport layer, 2) hole transport layer/light-emitting layer, and 3) hole transport layer. layer/emissive layer/electron transport layer, 4) hole injection layer/hole transport layer/emissive layer/electron transport layer, 5) hole transport layer/emissive 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, 8) positive Layered structures such as hole-injection layer/hole-transport layer/electron-blocking layer/light-emitting layer/hole-blocking layer/electron-transporting layer/electron-injecting layer can be mentioned.

Furthermore, a tandem type in which a plurality of the above laminated structures are laminated via an intermediate layer may be used. The intermediate layer generally includes an intermediate electrode, an intermediate conductive layer, a charge generation layer, an electron extraction layer, a connection layer, an intermediate insulating layer, and the like, and known material configurations can be used. As a preferred specific example of the tandem type, 9) hole injection layer/hole transport layer/light emitting layer/electron transport layer/electron injection layer/charge generation layer/hole injection layer/hole transport layer/light emitting layer/electron transport Laminate constructions such as layer/electron injection layer are included.

Further, each of the above layers may be either a single layer or multiple layers, and may be doped. Moreover, in addition to the above layers, a protective layer (cap layer) may be further provided, and the light emission efficiency can be further improved by the optical interference effect.

Specific examples of the structure of the light-emitting element are given below, but the structure of the present invention is not limited thereto.

(substrate)
It is preferable to form the light-emitting element over a substrate in order to maintain the mechanical strength of the light-emitting element, reduce thermal deformation, and have barrier properties to prevent water vapor and oxygen from entering the light-emitting layer. Examples of the substrate include, but are not limited to, a glass plate, a ceramic plate, a resin film, a resin thin film, a metal thin plate, and the like. Among these substrates, a glass substrate is preferably used because it is transparent and easy to process. In particular, in the case of a bottom-emission type light-emitting device in which light is extracted through a substrate, a glass substrate having high transparency is preferable. In addition, flexible displays and foldable displays are increasing mainly in mobile devices such as smartphones, and resin films and resin thin films obtained by curing varnish are suitably used for these applications. A heat-resistant film is used as the resin film, and specific examples thereof include a polyimide film and a polyethylene naphthalate film.

Various wirings, circuits, and TFT switching elements for driving the organic EL may be provided on the surface of the substrate.

(anode)
An anode is preferably formed on the substrate. Various wiring, 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 is a material that can efficiently inject holes into the organic layer. In this case, it is preferably a reflective electrode.

Examples of materials for the transparent or translucent electrode include conductive metal oxides such as zinc oxide, tin oxide, indium oxide, indium tin oxide (ITO), and indium zinc oxide (IZO), gold, silver, aluminum, chromium, and the like. and conductive polymers such as polythiophene, polypyrrole and polyaniline. However, when a metal is used, it is preferable to make the film thickness thin so that light can be semi-transmitted. Among these, indium tin oxide (ITO) is more preferable from the viewpoint of transparency and stability.

As a material for the reflective electrode, it is preferable to use a material that does not absorb all light and has a high reflectance. Examples thereof include metals such as aluminum, silver, and platinum.

Two or more kinds of these electrode materials may be used, and a plurality of materials may be laminated.

Although the film thickness of the anode is not particularly limited, it is preferably several nanometers to several hundreds of nanometers.

As for the method of forming the anode, an optimum method can be selected according to the material for forming the anode, and examples thereof include a sputtering method, a vapor deposition method, an inkjet method, and the like. For example, a sputtering method is preferably used when forming an anode from a metal oxide, and a vapor deposition method is preferably used when forming an anode from a metal. Although the film thickness of the anode is not particularly limited, it is preferably several nanometers to several hundreds of nanometers.

(cathode)
The cathode is formed on the surface opposite to the anode with the organic layer interposed therebetween, and is particularly 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 is a material that can efficiently inject electrons into the light-emitting layer. It is preferably an electrode.

In general, metals such as platinum, gold, silver, copper, iron, tin, aluminum, and indium, alloys of these metals with low work function metals such as lithium, sodium, potassium, calcium, and magnesium, and multi-layer laminated films , zinc oxide, indium tin oxide (ITO), and conductive metal oxides such as indium zinc oxide (IZO) are preferred. Among these, aluminum, silver, and magnesium are preferable as the main component from the viewpoints of electrical resistance, ease of film formation, film stability, luminous efficiency, and the like. Moreover, when it is composed of magnesium and silver, electron injection into the electron transport layer and the electron injection layer is facilitated, and the driving voltage can be reduced, which is preferable.

(protective layer)
For cathodic protection, it is preferred to laminate a protective layer (cap layer) on the cathode. The material constituting the protective layer is not particularly limited, but examples include metals such as platinum, gold, silver, copper, iron, tin, aluminum and indium, alloys using these metals, silica, titania and silicon nitride. Examples include inorganic substances, polyvinyl alcohol, polyvinyl chloride, and organic polymer compounds such as hydrocarbon polymer compounds. However, in the case of a top emission type light emitting device, the material used for the protective layer is preferably selected from materials that transmit light in the visible light region. In particular, arylamine derivatives, which are commonly used in hole-transporting layers, have good optical transparency in the visible light region and, at wavelengths in the visible light region, have a higher refractive index than conventional organic materials. In particular, it can promote the resonance effect due to the microcavity effect in a top emission type light emitting device, so it is also suitably used as a material for a protective layer.

(hole injection layer)
The hole injection layer is a layer that 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 a plurality of layers. The presence of a hole injection layer between the hole transport layer and the anode is preferable because it not only enables the device to be driven at a lower voltage and extends the durability life, but also improves the carrier balance of the device and the luminous efficiency.

A preferred example of the hole injection material is an electron-donating hole injection material (donor material). These materials have a HOMO level shallower than that of the hole transport layer and are close to the work function of the anode, so that the energy barrier with the anode can be reduced. Specifically, benzidine derivatives, 4,4′,4″-tris(3-methylphenyl(phenyl)amino)triphenylamine (m-MTDATA), 4,4′,4″-tris(1-naphthyl ( Aromatic amine materials such as starburst arylamines such as phenyl)amino)triphenylamine (1-TNATA), carbazole derivatives, pyrazoline derivatives, stilbene compounds, hydrazone compounds, benzofuran derivatives, thiophene derivatives, oxadiazole Derivatives, phthalocyanine derivatives, heterocyclic compounds such as porphyrin derivatives, polymer systems such as polycarbonates and styrene derivatives having the aforementioned monomers in side chains, polythiophenes such as PEDOT/PSS, polyanilines, polyfluorenes, polyvinylcarbazoles, and polysilanes. be. You may use 2 or more types of these. Alternatively, a hole injection layer may be formed by laminating a plurality of materials.

Another preferred example of the hole injection material is an electron-accepting hole injection material (acceptor material). Here, the hole injection layer may be composed of the acceptor material alone, or may be used by doping the acceptor material into the donor 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 doped with the donor material. The use of such a material is more preferable because it contributes to the improvement of the conductivity of the hole injection layer and the reduction of the driving voltage of the device, and the effects such as the improvement of the luminous efficiency and the durability of the device can be obtained. 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), 1,4,5, 8,9,11-hexaazatriphenylene-hexacarbonitrile (HAT-CN6), 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ), fluorine Examples include n-type organic semiconductor compounds such as copper phthalocyanine, fullerenes, and the like. When the hole injection layer contains the acceptor compound, the hole injection layer may consist of one layer or may be formed by laminating a plurality of layers.

(Hole transport layer)
The hole-transporting layer is a layer that transports holes injected from the anode to the light-emitting layer. The hole transport layer may be either a single layer or a laminate of a plurality of layers.

The hole-transporting layer is formed using one type of hole-transporting material alone, or by laminating or mixing two or more types of hole-transporting materials. Further, the hole transport material preferably has a high hole injection efficiency and efficiently transports the injected holes. For this purpose, it is required that the material has an appropriate ionization potential, high hole mobility, excellent stability, and does not easily generate trapping impurities.

Substances that satisfy these conditions are not particularly limited, but examples include benzidine derivatives, a group of aromatic amine materials called starburst arylamines, carbazole derivatives, pyrazoline derivatives, stilbene compounds, hydrazone compounds, Heterocyclic compounds such as benzofuran derivatives, dibenzofuran derivatives, thiophene derivatives, benzothiophene derivatives, dibenzothiophene derivatives, fluorene derivatives, spirofluorene derivatives, oxadiazole derivatives, phthalocyanine derivatives, and porphyrin derivatives; Polycarbonate, styrene derivative, polythiophene, polyaniline, polyfluorene, polyvinylcarbazole, polysilane, etc.

(Light emitting layer)
The light-emitting layer is a layer that emits light by excitation energy generated by recombination of holes and electrons. The light-emitting layer may be composed of a single material, but from the viewpoint of color purity, it preferably contains a first compound and a second compound, which are dopants that emit light with a narrow half-value width. Suitable examples of the second compound include a host material responsible for charge transfer and a thermally activated delayed fluorescent compound.

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

Examples of the host material include, but are not limited to, compounds having condensed aryl rings such as naphthacene, pyrene, anthracene, fluoranthene, derivatives thereof, N,N'-dinaphthyl-N,N'-diphenyl-4,4'- Aromatic amine derivatives such as 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; paraphenylene derivatives, polyfluorene derivatives, polyvinylcarbazole derivatives, polythiophene derivatives and the like. Two or more of these may be used, or two or more host materials may be laminated. Among these, carbazole derivatives, anthracene derivatives, and naphthacene derivatives are preferred.

As a dopant material, a fluorescence-emitting material other than the compound having the structure represented by general formula (3) may be contained. Specifically, compounds having a condensed aryl ring such as naphthacene, pyrene, anthracene, and fluoranthene and their derivatives, compounds having a heteroaryl ring and their derivatives, distyrylbenzene derivatives, aminostyryl derivatives, tetraphenylbutadiene derivatives, and stilbene derivatives. , aldazine derivatives, pyrromethene derivatives, diketopyrrolo[3,4-c]pyrrole derivatives, coumarin derivatives, azole derivatives and their metal complexes, and aromatic amine derivatives. You may use 2 or more types of these.

Moreover, you may contain a phosphorescence-emitting material as a dopant material. The phosphorescent material contains at least one metal selected from the group consisting of iridium (Ir), ruthenium (Ru), palladium (Pd), platinum (Pt), osmium (Os), and rhenium (Re). A metal complex compound is preferable, and an iridium complex or a platinum complex is more preferable from the viewpoint of high-efficiency light emission. The ligand preferably has a nitrogen-containing heteroaryl group such as a phenylpyridine skeleton, a phenylquinoline skeleton, and a carbene skeleton, but is not limited to these.

However, from the viewpoint of further improving color purity, the dopant material is preferably only a compound having a structure represented by general formula (3).

It is also preferable that the light-emitting layer contains an assist dopant in addition to the dopant. The assist dopant is preferably a compound that emits delayed fluorescence. Delayed fluorescence materials are also generally called TADF (Thermally Activated Delayed Fluorescence) materials, and by reducing the energy gap between the S1 state and the T1 excited state, that is, ΔEST, the reverse intersystem from the T1 state to the S1 state It is a material that promotes crossover and improves conversion efficiency from the T1 state to the S1 state. By utilizing delayed fluorescence by this TADF mechanism, the theoretical internal quantum efficiency of the light-emitting device can be increased to 100%. Furthermore, when Förster-type energy transfer occurs from the S1 state of the assist dopant having thermally activated delayed fluorescence to the S1 state of the dopant material, fluorescence emission from the S1 state of the dopant material is observed. Here, when the dopant material is a fluorescent light-emitting material having a sharp fluorescence spectrum, a light-emitting device with superior luminous efficiency and color purity can be obtained. Thus, 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 fluorescence material as an assist dopant may be a material that exhibits delayed fluorescence with a single material, or a material that exhibits delayed fluorescence with a plurality of materials as in the case of forming an exciplex complex. .

The compound having the structure represented by the general formula (3) is a compound that emits delayed fluorescence with high conversion efficiency from the T1 state to the S1 state by reducing ΔEST in addition to having a high fluorescence quantum yield. It can also be suitably used as an assist dopant.

As the delayed fluorescence compound as the assist dopant, a single material or a plurality of materials may be used, and known materials can be used in addition to the compound having the structure represented by the general formula (3). Specific examples include benzonitrile derivatives, triazine derivatives, disulfoxide derivatives, carbazole derivatives, indolocarbazole derivatives, dihydrophenazine derivatives, thiazole derivatives, oxadiazole derivatives and the like. Examples of such a heat-activated delayed fluorescent compound include, but are not limited to, the following examples.

The light-emitting layer may further contain a matrix material for adjusting carrier balance in the light-emitting layer and stabilizing the layer structure of the light-emitting layer, in addition to the assist dopant material and the dopant material. However, as the matrix material, it is preferable to select a material that does not interact with the assist dopant material or the dopant material. When the light emitting layer contains a matrix material, the excited singlet energy of the dopant material is S ₁ (1), the excited singlet energy of the assist dopant material is S ₁ (2), and the excited singlet energy of the matrix material is S ₁ ( 3), it is preferable that the relationship of Equation 1 is satisfied.
S ₁ (3)>S ₁ (2)>S ₁ (1) (Formula 1)
If Formula 1 can be 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.

The excited singlet energy S ₁ (1) of the dopant material in the present invention can be obtained by the following method. A toluene solution (concentration 1×10 ⁻⁵ mol/L) of a dopant material, which is a substance to be measured, is prepared, and its emission spectrum is measured at room temperature. In the emission spectrum, the vertical axis is the emission intensity, and the horizontal axis is the wavelength. A tangent line is drawn to the rise on the short wavelength side of the emission spectrum, and the wavelength λ _edge (nm) at the intersection with the horizontal axis is obtained. This λ _edge is converted into an energy value by the following conversion formula, and this is defined as the excited singlet energy S ₁ (1) of the dopant material.
Conversion formula: S ₁ (1) = 1239.85/λ _edge
By a similar method, the lowest singlet excitation energy S ₁ (2) of the assist dopant material and the lowest singlet excitation energy S ₁ (3) of the matrix material can be obtained.

The matrix material is preferably an organic compound having a high charge transport ability such as holes and electrons and a high glass transition temperature. Examples of the matrix material include, but are not limited to, the following.

(Electron transport layer)
The electron transport layer is a layer into which electrons are injected from the cathode and which transports the electrons. The electron-transporting material used in the electron-transporting layer is required to have a high electron affinity, a high electron mobility, excellent stability, and a substance that does not easily generate trapping impurities. From the viewpoint of suppressing film quality deterioration due to crystallization, a compound having a molecular weight of 400 or more is preferable.

The electron-transporting 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-transporting layer may be composed of a single material or a laminate of multiple materials.

Examples of electron transport materials include polycyclic aromatic derivatives, styryl aromatic ring derivatives, quinone derivatives, phosphorus oxide derivatives, quinolinol complexes such as tris(8-quinolinolate) aluminum (III), benzoquinolinol complexes, hydroxyazole complexes, and azomethine complexes. , tropolone metal complexes and flavonol metal complexes. From the viewpoint of reducing driving voltage and further improving device efficiency, it is preferable to use a compound having a heteroaryl group containing electron-accepting nitrogen. Here, electron-accepting nitrogen represents a nitrogen atom forming a multiple bond with an adjacent atom. A heteroaryl group containing an electron-accepting nitrogen has a high electron affinity, so that electrons can be easily injected from the cathode, enabling lower voltage driving. In addition, more electrons are supplied to the light-emitting layer, and the recombination probability increases, so that the device efficiency is further improved. Examples of compounds having a heteroaryl group structure containing an electron-accepting nitrogen include pyridine derivatives, triazine derivatives, pyrazine derivatives, pyrimidine derivatives, quinoline derivatives, quinoxaline derivatives, quinazoline derivatives, naphthyridine derivatives, benzoquinoline derivatives, phenanthroline derivatives, and 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. You may use 2 or more types of these.

Further, it is more preferable that the electron transporting material has a condensed polycyclic aromatic skeleton, because the glass transition temperature is improved, the electron mobility is high, and the driving voltage can be reduced. As such a condensed polycyclic aromatic skeleton, a quinolinol skeleton, triazine skeleton, fluoranthene skeleton, anthracene skeleton, pyrene skeleton or phenanthroline skeleton is preferable.

The electron transport layer may contain a donor material. Here, the donor material is a compound that facilitates injection of electrons from the cathode or the electron injection layer into the electron transport layer by improving the electron injection barrier, and further improves the electrical conductivity of the electron transport layer.

Preferred examples of the donor material 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, and alkali earth metals. Examples include inorganic salts, 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. You may use 2 or more types of these. Among these, metallic lithium, rare earth metals, and lithium quinolinol (Liq) are preferred.

(Electron injection layer)
In the present invention, an electron injection layer may be provided between the cathode and the electron transport layer. In general, the electron injection layer is formed for the purpose of assisting 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-described donor material. . Moreover, you may contain 2 or more types of these. Among these, triazine derivatives, phenanthroline derivatives and oligopyridine derivatives are preferred, phenanthroline derivatives and terpyridine derivatives are more preferred, and phenanthroline derivatives represented by the following general formula (7) are even more preferred. That is, the light-emitting device of the present invention preferably contains the phenanthroline derivative represented by the general formula (7) in the electron injection layer.

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. p is a natural number from 1 to 3; R ³⁰¹ to 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. Ar ⁵ can be substituted with p phenanthrolyl groups at any position.

Examples of aromatic hydrocarbon groups that are monovalent include phenyl, biphenyl, terphenyl, naphthyl, fluorenyl, benzofluorenyl, dibenzofluorenyl, phenanthryl, anthracenyl, benzo phenanthryl group, benzoanthracenyl group, chrysenyl group, pyrenyl group, fluoranthenyl group, triphenylenyl group, benzofluoranthenyl group, dibenzoanthracenyl group, perylenyl group, helicenyl group and the like. Among them, from the viewpoint of ease of synthesis and sublimation, phenyl group, biphenyl group, terphenyl group, naphthyl group, fluorenyl group, phenanthryl group, anthracenyl group, pyrenyl group, fluoranthenyl group, triphenylenyl group, and hydrogen atoms thereof A group excluding at least a part of is preferred. The aromatic hydrocarbon group may or may not have a substituent. The number of ring-forming carbon atoms is not particularly limited, but is preferably 6 or more and 40 or less, more preferably 6 or more and 30 or less. Also, when there are substituents on two adjacent carbon atoms, the substituents may form a ring structure.

The aromatic heterocyclic group refers to a cyclic aromatic group having one or more atoms other than carbon in the ring. For example, monovalent pyridyl, furanyl, thiophenyl, quinolinyl, isoquinolinyl, pyrazinyl group, pyrimidyl group, pyridazinyl group, triazinyl group, naphthyridinyl group, cinnolinyl group, phthalazinyl group, quinoxalinyl group, quinazolinyl group, benzofuranyl group, benzothiophenyl group, indolyl group, dibenzofuranyl group, dibenzothiophenyl group, carbazolyl group, benzocarbazolyl group, carbolinyl group, indolocarbazolyl group, benzofurocarbazolyl group, benzothienocarbazolyl group, dihydroindenocarbazolyl group, benzoquinolinyl group, acridinyl group, dibenzoacridinyl group, benzimidazolyl group, imidazopyridyl group, benzoxazolyl group, benzothiazolyl group, phenanthrolinyl group and the like. However, the naphthyridinyl group is 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. or The aromatic heterocyclic group may or may not have a substituent. The number of ring-forming carbon atoms in the aromatic heterocyclic group is not particularly limited, but is preferably in the range of 2 to 40, more preferably in the range of 2 to 30.

The aromatic hydrocarbon group or aromatic heterocyclic group may have a substituent other than the phenanthryl group.

From the viewpoint of sublimability and thin film formability, p is preferably 2.

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

Inorganic substances such as insulators and semiconductors can also be used for the electron injection layer. By using these materials, it is possible to suppress the short circuit of the light-emitting element and improve the electron injection property, which is preferable.

As such an insulator, metal compounds such as alkali metal chalcogenides, alkaline earth metal chalcogenides, alkali metal halides, and alkaline earth metal halides are preferable. You may use 2 or more types of these.

(Charge generating layer)
The charge generation layer in the present invention generally consists of a double layer, and specifically can be used as a pn junction type charge generation layer consisting of an n-type charge generation layer and a p-type charge generation layer. The pn junction charge generation layer generates charges or separates the charges into holes and electrons when a voltage is applied in the light emitting device, and transfers these holes and electrons to the hole transport layer and the electron transport layer. injected into the light-emitting layer through the layer. Specifically, it functions as an intermediate charge-generating layer in a light-emitting element in which light-emitting layers are stacked. The n-type charge-generating layer supplies electrons to the first light-emitting layer on the anode side, and the p-type charge-generating layer supplies holes to the second light-emitting layer on the cathode side. Therefore, it is possible to improve the luminous efficiency of a light-emitting element in which a plurality of light-emitting layers are stacked, reduce the driving voltage, and improve the durability of the light-emitting element.

The n-type charge generation layer consists of an n-type dopant and a host, which can be conventional materials. Examples of n-type dopants include alkali metals, alkaline earth metals, and rare earth metals. You may use 2 or more types of these. Among these, alkali metals or salts thereof, and rare earth metals are preferable, and metallic lithium, lithium fluoride (LiF), lithium quinolinol (Liq), and metallic ytterbium are more preferable. Examples of hosts include triazine derivatives, phenanthroline derivatives, oligopyridine derivatives and the like. You may use 2 or more types of these. Among these, triazine derivatives, phenanthroline derivatives and oligopyridine derivatives are preferred, phenanthroline derivatives and terpyridine derivatives are more preferred, and phenanthroline derivatives represented by the general formula (7) are even more preferred. That is, the light emitting device of the present invention preferably contains the phenanthroline derivative represented by the general formula (7) in the charge generation layer.

The p-type charge generation layer consists of a p-type dopant and a host, which can be conventional materials. For example, p-type dopants include tetrafluor-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ), tetracyanoquinodimethane derivatives, radialene derivatives, iodine, FeCl ₃ , FeF ₃ , SbCl ₅ etc. You may use 2 or more types of these. Among these, arylamine derivatives are preferred.

(Method for manufacturing light-emitting device)
A method for forming each layer constituting the light-emitting element may be either a dry process or a wet process, and examples thereof include resistance heating deposition, electron beam deposition, sputtering, molecular lamination, coating, inkjet, and printing. . Among these, resistance heating vapor deposition is preferable from the viewpoint of device characteristics.

The thickness of the organic layer depends on the resistance value of the light-emitting substance and cannot be limited, but is preferably 1 to 1000 nm. Each of the light-emitting layer, the electron transport layer, and the hole transport layer preferably has a film thickness of 1 nm or more and 200 nm or less, more preferably 5 nm or more and 100 nm or less.

(Characteristics of light-emitting element)
A light emitting device according to an embodiment of the present invention has a function of converting electrical energy into light. Here, direct current is mainly used as electric energy, but pulse current and alternating current can also be used. The current value and voltage value are not particularly limited, and the required characteristic values differ depending on the purpose of the device. However, from the viewpoint of power consumption and life of the device, it is preferable to obtain high luminance at a low voltage.

In the light-emitting device according to the embodiment of the present invention, from the viewpoint of improving color purity, the half-value width is preferably 45 nm or less, more preferably 35 nm or less, and 30 nm from the viewpoint of further improving color purity in the fluorescence spectrum by energization. More preferred are:

<Color conversion composition>
The color conversion composition in the present invention represents a composition that converts incident light into light with a wavelength different from that of the incident light. It is preferable to convert the incident light to light of a longer wavelength. The color conversion composition of the present invention contains a compound having a structure represented by general formula (3) and a binder resin. A compound having a structure represented by general formula (3) can also be suitably used in a color conversion composition that converts incident light into light with a wavelength different from that of the incident light.

(binder resin)
Suitable specific examples of the binder resin include, for example, International Publication No. 2016/190283, International Publication No. 2017/61337, International Publication No. 2018/43237, International Publication No. 2019/21813 and International Publication No. 2019/188019. and the like.

(solvent)
The color conversion composition of the present invention may contain a solvent to 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, propylene glycol monomethyl ether acetate and the like. You may contain 2 or more types of these. Among these, toluene and ethyl acetate are particularly preferred because they maintain the durability of the compound having the structure represented by the general formula (3) and leave little residual solvent after drying.

(other ingredients)
The color conversion composition of the present invention contains, if necessary, a light stabilizer, an antioxidant, a processing and heat stabilizer, a light stabilizer such as an ultraviolet absorber, scattering particles, silicone fine particles, and a silane coupling agent. It may contain other components (additives) such as agents.

Examples of light stabilizers include tertiary amines, catechol derivatives, nickel compounds, and at least one selected from the group consisting of Sc, V, Mn, Fe, Co, Cu, Y, Zr, Mo, Ag, and lanthanoids. including transition metal complexes and salts with organic acids. You may contain 2 or more types of these.

Examples of antioxidants include phenolic antioxidants such as 2,6-di-tert-butyl-p-cresol and 2,6-di-tert-butyl-4-ethylphenol. You may contain 2 or more types of these.

Processing and thermal stabilizers include, for example, phosphorus-based stabilizers such as tributylphosphite, tricyclohexylphosphite, triethylphosphine, diphenylbutylphosphine, and the like. You may contain 2 or more types of these.

Examples of light stabilizers include 2-(5-methyl-2-hydroxyphenyl)benzotriazole, 2-[2-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]-2H- Examples include benzotriazoles such as benzotriazole. You may contain 2 or more types of these.

As the scattering particles, inorganic particles having a refractive index of 1.7 to 2.8 are preferable, such as titania, zirconia, alumina, ceria, tin oxide, indium oxide, iron oxide, zinc oxide, aluminum nitride, aluminum, and tin. , particles of titanium or zirconium sulfide, titanium or zirconium hydroxide, and the like. You may contain 2 or more types of these.

In the color conversion composition of the present invention, the content of these additives is appropriately selected depending on the molar absorption coefficient of the compound, the emission quantum yield, the absorption intensity at the excitation wavelength, and the thickness and transmittance of the color conversion sheet to be produced. can do. It is preferably 1.0×10 ⁻¹ parts by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the binder resin.

<Method for producing color conversion composition>
The color conversion composition of the present invention is prepared by mixing, for example, a binder resin, a compound having a structure represented by general formula (3), and, if necessary, additives and solvents so as to obtain a predetermined composition, followed by stirring and mixing. It can be obtained by homogeneously mixing or kneading using a kneader. The stirring/kneading machine includes, for example, a homogenizer, a rotation-revolution stirrer, a three-roller, a ball mill, a planetary ball mill, and a bead mill. After mixing or dispersing, or during the process of mixing or dispersing, defoaming under vacuum or reduced pressure conditions is also preferably performed. In addition, it may be possible to mix certain specific components in advance or to perform processing such as aging. It is also possible to remove the solvent by an evaporator to achieve the desired solids concentration.

<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 having a wavelength different from that of the incident light, and contains the aforementioned color conversion composition of the present invention. It is preferable to convert the incident light to light of a longer wavelength.

The color conversion sheet of the present invention preferably includes a color conversion layer which is a layer formed from the color conversion composition described above. The amount of residual solvent in the color conversion layer is preferably 0.5% by weight or less from the viewpoint of further improving 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 from the viewpoint of further improving the luminous efficiency of the color conversion sheet.

As representative structural examples of the color conversion sheet, there are, for example, the following four types.

FIG. 1 shows a schematic cross-sectional view of one embodiment of the color conversion sheet of the present invention. The color conversion sheet 1A is a single-layer sheet composed of a color conversion layer 11. As shown in FIG. The color conversion layer 11 is a layer made of a cured product of the color conversion composition described above.

FIG. 2 shows a schematic cross-sectional view of another embodiment of the color conversion sheet of the present invention. The color conversion sheet 1B is a laminate of a base layer 10 and a color conversion layer 11, and the color conversion layer 11 is laminated on the base layer 10. As shown in FIG.

FIG. 3 shows a schematic cross-sectional view of another embodiment of the color conversion sheet of the present invention. The color conversion sheet 1</b>C is a laminate of a plurality of base layers 10 and a color conversion layer 11 , with the color conversion layer 11 sandwiched between the base layers 10 .

FIG. 4 shows a schematic cross-sectional view of another embodiment of the color conversion sheet of the present invention. The color conversion sheet 1D is a laminate of a plurality of base layers 10, a color conversion layer 11, and a plurality of barrier films 12. The color conversion layer 11 is sandwiched between the plurality of barrier films 12, and these A laminate of a color conversion layer 11 and a plurality of barrier films 12 is sandwiched between a plurality of base layers 10 . That is, the color conversion sheet 1D preferably has a barrier film 12 as shown in FIG. 4 in order to prevent deterioration of the color conversion layer 11 due to oxygen, moisture and heat.

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

The color conversion sheet of the present invention preferably contains a luminescent material (a) having a peak emission wavelength of 500 nm or more and less than 580 nm and/or a luminescent material (b) having a peak emission wavelength of 580 nm or more and 750 nm or less. Further, the compound having the structure represented by general formula (3) is preferably the luminescent material (a) and/or the luminescent material (b). In particular, it is more preferable that the color conversion sheet contains the luminescent material (a) and the luminescent material (b), and the compound having the structure represented by the general formula (3) is the luminescent material (a).

In the color conversion sheet of the present invention, the emission spectrum of the luminescent material (a) and the absorption spectrum of the luminescent material (b) are overlapped so that the luminescent material (b) efficiently absorbs the light emitted by the luminescent material (a). is preferred. Therefore, the half-value width of the emission spectrum at the emission peak wavelength of the light-emitting material (a) (hereinafter referred to as "peak half-value width") is preferably 30 nm or more. Here, by increasing the overlap between the emission spectrum of the light-emitting material (a) and the absorption spectrum of the light-emitting material (b), it becomes easier to maintain the emission intensity of the light-emitting material (b). Durability can be further improved.

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

One example of the color conversion sheet of the present invention is a color conversion sheet containing one or more color conversion layers and containing the luminescent material (a) and the luminescent material (b) in the same layer. In the color conversion sheet according to this embodiment, the excitation energy of the luminescent material (a) in the excited state does not become electromagnetic waves, but directly moves to the luminescent material (b) due to electron resonance. This is called fluorescence resonance energy transfer or Förster resonance energy transfer, and the energy transfer efficiency is higher than when the excitation energy of the luminescent material (a) is emitted as light and absorbed by the luminescent material (b). is a very high phenomenon. Therefore, the molar ratio of the content of the luminescent material (a) and the content of the luminescent material (b) contained in the same layer is 50:1 to 500:1. preferable.

Another example of the color conversion sheet of the present invention is a color conversion sheet comprising two or more color conversion layers, in which the luminescent material (a) and the luminescent material (b) are contained in different layers. A specific example of such a color conversion layer is a color conversion sheet including at least the following (A) layer and (B) layer.
(A) layer: a layer containing at least a light-emitting material (a) and a binder resin.
(B) layer: a layer containing at least the luminescent material (b) and a binder resin.
In the color conversion sheet according to this embodiment, Förster resonance energy transfer does not occur. The ratio of luminescent material (a):luminescent material (b) is preferably 5:1 to 100:1.

As the light-emitting material (b), a light-emitting material having an emission peak wavelength of 580 nm or more and 750 nm or less, that is, a material exhibiting red light emission is preferable, and a light-emitting material such as an organic light-emitting material, an inorganic phosphor, or an inorganic quantum dot can be used. can be done. A light-emitting material having a pyrromethene skeleton can be suitably used as the organic light-emitting material. This is because the half-value width of the emission spectrum is narrower than that of conventional organic red light-emitting materials, and red light emission with high color purity is exhibited. This can contribute to improving the color reproducibility of the display device.

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

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

The color conversion layer can be formed, for example, by applying the color conversion composition prepared by the method described above onto a substrate such as a base material layer or a barrier film and drying the composition.

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

(barrier layer)
As the barrier layer, one that suppresses the entry of oxygen, moisture, heat, etc. into the color conversion layer is preferable, and two or more barrier layers may be provided. Both sides of the color conversion layer may have barrier layers, or one side may have a barrier layer.

Examples of films having 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 titanium and silicon carbide nitride, metal oxide thin films and metal nitride thin films added with other elements, polyvinylidene chloride, acrylic resins, silicone resins, melamine resins, urethane resins, Films containing various resins such as fluorine-based resins, polyvinyl alcohol-based resins such as saponified products of vinyl acetate, and the like are included. Two or more of these may be included. Examples of films having a barrier function against moisture include polyethylene, polypropylene, nylon, polyvinylidene chloride, copolymers of vinylidene chloride and vinyl chloride, vinylidene chloride and acrylonitrile copolymers, fluororesins, and saponified vinyl acetate. Examples include films containing various resins such as polyvinyl alcohol-based resins.

The color conversion sheet of the present invention has a light diffusion layer, an adhesive layer, an antireflection function, an antiglare function, an antireflection antiglare function, a hard coat function (friction resistance function), an antistatic function, an antistatic function, and an antiglare function. An auxiliary layer having an antifouling function, an electromagnetic shielding function, an infrared ray cutting function, an ultraviolet ray cutting function, a polarizing function, and a toning function may be further provided.

(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, and the like. Preferred specific examples of the wavelength-selective reflective film include those described in International Publication No. 2017/164155 and Japanese Patent Application Laid-Open No. 2018-81250.

<Manufacturing method of color conversion sheet>
Next, an example of the method for manufacturing the color conversion sheet of the present invention will be described. A color conversion layer is formed by applying the color conversion composition prepared by the method described above onto a substrate and drying it. When the binder resin is a thermosetting resin, the color conversion composition may be coated on the substrate and then cured by heating to form a color conversion layer. The material may be coated on a substrate and then photocured to form a color conversion layer.

Coating includes 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, An applicator, dip coater, curtain coater, spin coater, knife coater, or the like can be used. In order to obtain uniform film thickness of the color conversion layer, it is preferable to apply with a slit die coater, a comma coater, or a dip coater.

Drying of the color conversion layer can be performed using a general 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 harden in stages by a method such as step curing.

After producing the color conversion layer, it is also possible to change the base material if necessary. In this case, as a simple method, there are a method of re-sticking using a hot plate, a method using a vacuum laminator or a dry film laminator, and the like.

<Light source unit>
A light source unit of the present invention includes at least a light source and the aforementioned color conversion sheet of the present invention. The light source included in the light source unit of the present invention is the source of the excitation light described above. The method of arranging the light source and the color conversion sheet is not particularly limited, and a configuration in which the light source and the color conversion sheet are in close contact with each other may be adopted, or a remote phosphor type in which the light source and the color conversion sheet are separated from each other may be adopted. good too. In addition, the light source unit may further include a color filter for the purpose of increasing color purity.

<Light source>
Any light source can be used as long as it emits light in a wavelength region that can be absorbed by the light emitting material (a) and the light emitting material (b). For example, any light source 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 can be used in principle. Among these, LEDs are preferable light sources, and blue LEDs having a light source in the range of 430 to 500 nm are more preferable light sources in terms of increasing the color purity of blue light for displays (display devices) and lighting applications. be.

The light source may have one type of emission peak, or may have two or more types of emission peaks, but preferably has one type of emission peak in order to increase color purity. It is also possible to arbitrarily combine and use a plurality of light sources having different types of emission peaks.

The light source unit in the present invention is useful for various light sources such as space illumination and backlight, and specifically, it can be used for applications such as display devices, lighting, interiors, signs, signboards, etc., but it is particularly useful for display devices and lighting applications. is particularly preferably used for

<Display device, lighting device>
A display device of the present invention includes at least the light-emitting element of the present invention described above and/or the color conversion sheet described above. For example, the light source unit of the present invention described above is preferably used as a backlight unit in a display device such as a liquid crystal display. Further, by using the above-described light-emitting element, for example, a display device such as an organic EL display having high luminous efficiency and excellent durability, which displays in a matrix and/or a segment system, can be manufactured.

Further, a lighting device of the present invention includes at least the light-emitting element of the present invention described above and/or the color conversion sheet of the present invention described above. For example, this illumination device combines a blue LED light source as a light source unit and a color conversion sheet that converts the blue light from the blue LED light source into light with a longer wavelength to emit white light. Configured. A lighting device can also be obtained using the above-described light-emitting element of the present invention. These lighting devices include, for example, medical lighting, interior lighting, and the like, and can achieve both bright emission colors, high durability, and high designability.

Any light source can be used as long as it emits light in a wavelength region that can be absorbed by the light emitting material (a) and the light emitting material (b). For example, any light source 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 can be used in principle. Among these, an LED is a preferred light source, and a blue LED having a light source in the range of 430 to 500 nm is a more preferred light source in terms of increasing the color purity of blue light for use in display devices and lighting devices. .

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

Evaluation methods in each example and comparative example are described below.

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

(Emission Peak Wavelength and External Quantum Efficiency of Light Emitting Element)
A voltage was applied to the light emitting devices obtained in Examples 6 to 10 and Comparative Examples 4 to 6 so that the current density was 10 mA/cm ² , and a spectral radiance meter CS-1000 manufactured by Konica Minolta Co., Ltd. was used. , the emission spectrum was measured and the peak wavelength of emission was read. Assuming that the obtained light emission is Lambassian radiation, the external quantum efficiency (EQE) was calculated from the obtained emission spectrum and used as an index of the light emission efficiency of the light emitting device.

(Durability of compound and light-emitting element)
In the light-emitting element for which the external quantum efficiency was measured, the luminance when a current density of 10 mA/cm ² was applied was measured and defined as the initial luminance. Furthermore, a voltage was continuously applied so that the current density was 10 mA/cm ² , and a photodiode was used to measure the time (LT90) when the luminance reached 90% of the initial luminance, and the durability of the compound and the light-emitting element was measured. used as an index.

(Emission peak wavelength of color conversion sheet)
A backlight unit having a blue LED element (emission peak wavelength: 445 nm) and a light guide plate was provided with the color conversion sheets obtained in Examples 11 to 14 and Comparative Examples 7 to 9 on one surface of the light guide plate, Furthermore, a prism sheet was placed on the color conversion sheet. An electric current was passed through the blue LED element to light the blue LED element, and the initial value was set so that the brightness of the light from the blue LED element was 800 cd/m ² . A current is passed through the blue LED element at the set initial value to light the blue LED element, and the emission spectrum is measured in the wavelength range of 400 to 700 nm using a spectral radiance meter (CS-1000, manufactured by Konica Minolta). , the emission peak wavelength in the green emission region was read.

(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 measured using an absolute PL quantum yield measurement device (Quantaurus-QY, manufactured by Hamamatsu Photonics). was measured and used as an indicator of the luminous efficiency of the color conversion sheet.

(Durability of compound and color conversion sheet)
Using the same evaluation system as the emission peak wavelength of the color conversion sheet described above, the brightness of the light from the blue LED element (emission peak wavelength: 445 nm) was adjusted to 10,000 cd/m ² , and then 85 C. environment, and the time required for the brightness to decrease by 5% was measured, which was used as an index of the durability of the compound and the color conversion sheet.

(Example 1)
[Synthesis of Intermediate 6]

1-bromo-2,5-dichloro-3-fluorobenzene 10.0 g (molecular weight 243.89 41 mmol), 9,9-diphenyl-9,10-dihydroacridine 15.04 g (molecular weight 333.43 45.1 mmol), A flask containing 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 completion of the reaction, the reaction mixture was cooled to room temperature, and water and toluene were added to separate the layers. After concentrating the organic layer with an evaporator, it was purified with a silica gel column to obtain 16.99 g of intermediate 6 (molecular weight: 557.31) (yield: 70%).

[Synthesis of Intermediate 11]

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

[Synthesis of Intermediate 12]

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

[Synthesis of Intermediate 13]

5 g (6.43 mmol) of intermediate 12, 8.57 g of aluminum chloride (molecular weight 133.33 64.3 mmol), N,N-diisopropylethylamine 12.47 g (molecular weight 129.25 96.5 mmol), and chlorobenzene 70 ml were placed in a flask. , heated to 120° C. in a nitrogen atmosphere, and stirred for 3 hours. After completion of the reaction, the mixture was cooled to room temperature and water was slowly added dropwise to quench the aluminum chloride. Further, after adding dichloromethane, the organic layer was separated and washed, and after concentrating the organic layer with an evaporator, the concentrate was recrystallized twice with toluene to obtain 2.20 g of intermediate 13 (molecular weight: 659.04) (yield: 52%). )Obtained.

[Synthesis of Intermediate 14]

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

[Synthesis of G-1]

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), bis(dibenzylideneacetone)palladium7. 48 mg (molecular weight 575.02 0.013 mmol), 2-dicyclohexylphosphino-2'-4'-6'-triisopropylbiphenyl 24.8 mg (molecular weight 476.72 0.052 mmol), potassium phosphate 847 mg (molecular weight 212. 27 3.99 mmol), 1,4-dioxane 30 ml, and water 15 ml were put into 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 after liquid separation and washing, the organic layer was concentrated by an evaporator. The concentrate was recrystallized three times with toluene to obtain 512 mg (45% yield) of G-1 (molecular weight: 855.85). The resulting G-1 was purified by sublimation and used for evaluation.

(Examples 2-4)
[Synthesis of G-2 to G-4]
G-2 to G-4 were synthesized and evaluated in the same manner as in Example 1 by changing the raw material as appropriate and performing the same operation as in the synthesis of G-1 from intermediate 14. The structures of G-2 to G-4 are shown below.

(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.

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

[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.

[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 resulting G-5 was purified by sublimation and used for evaluation.

(Comparative Examples 1 to 3)
Fluorescence quantum yields were measured using ref-1 to ref-3 having the following structures.

Table 1 summarizes the measurement results of fluorescence quantum yields of Examples and Comparative Examples.

Comparing G-1 to G-5 with Ref-1, both emitted green, but G-1 to G-5 had a higher fluorescence quantum yield. This is because G-1 to G-5 have crosslinked structures on both sides, and in addition to the effect of increasing the overlap between the HOMO orbital and the LUMO orbital, the vibration and rotation of the phenyl group, which is the substituent of N, are suppressed. , the result that the heat deactivation from the S1 state could be suppressed. In addition, when G-1 to G-5 and Ref-2 to Ref-3 are compared, although both of the emission colors are green, the fluorescence quantum yield of G-1 to G-5 is higher. . All of these are compounds having a crosslinked structure on both sides, but due to the different crosslinked structures of G-1 to G-5, the symmetry of the compound is reduced, and as a result, the intermolecular interaction can be suppressed. It is considered that the fluorescence quantum yield is improved.

(Example 6)
A glass substrate (manufactured by Geomatec Co., Ltd., 11Ω/□, sputtered product) on which an ITO transparent conductive film was deposited to a thickness of 165 nm was cut into a size of 38 mm×46 mm and etched. The obtained substrate was ultrasonically cleaned for 15 minutes using "Semico Clean" (registered trademark) 56 (trade name, manufactured by Furuuchi Chemical Co., Ltd.) and then cleaned with ultrapure water. This substrate was treated with UV-ozone for 1 hour immediately before manufacturing the device, placed in a vacuum deposition apparatus, and evacuated until the degree of vacuum in the apparatus reached 5×10 ⁻⁴ Pa or less. By resistance heating, HAT-CN6 was deposited to a thickness of 10 nm as a hole injection layer, then HT-1 was deposited to a thickness of 20 nm as a hole transport layer, and HT-2 was deposited to a thickness of 10 nm as an electron blocking layer. Next, as a light-emitting layer, a compound M-1 as a matrix material, a compound A-1 that emits delayed fluorescence as an assist dopant, and a compound G-1 as a dopant material were mixed at a weight ratio of 79.0:20:1. It was vapor-deposited to a thickness of 30 nm. Subsequently, ET-1 was laminated with a thickness of 10 nm as a hole blocking layer, and ET-2 and 2E-1 were laminated with a thickness of 30 nm as an electron transport layer so that the weight ratio was 1:1. Next, after vapor-depositing 2E-1 with a thickness of 2 nm as an electron injection layer, magnesium and silver were co-deposited with a thickness of 100 nm in a weight ratio of 9:1 to form a cathode, thereby fabricating a light-emitting device of 5 mm×5 mm square. The obtained light-emitting device was evaluated by the method described above.

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 light emitting devices are shown below.

(Examples 7-10)
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 instead of compound G-1 as dopant materials.

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

The results of Examples 6-10 and Comparative Examples 4-6 are summarized in Table 2.

Comparing G-1 to G-5 with ref-1 to ref-3, the emission color is green, but the external quantum efficiency, which is an index of luminous efficiency, is higher for G-1 to G-5. Met. This result reflects the high fluorescence quantum yield of Examples 1-5. Furthermore, focusing on LT90, which is an index of durability, all of G-1 to G-4 exceeded ref-1 to ref-2. This is due to the effect of suppressing intermolecular interactions by introducing an asymmetric cross-linking structure and improving durability, and the introduction of an electron-withdrawing group to the para-position of boron to reduce ΔEST. This reflects both effects of being able to suppress the process of direct decomposition of . In addition, even in the comparison of LT90 of G-5 and ref-3, which do not have an electron-withdrawing group, the result of G-5 is higher than that of ref-3. It is possible to suppress the action and suppress the deterioration of durability caused by intermolecular interaction.

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

100 parts by weight of a polyester resin as a binder resin is mixed with 300 parts by weight of toluene as a solvent, and the mixture is stirred at 300 rpm for 20 minutes using a planetary stirring/defoaming device "Mazerustar" KK-400 (manufactured by Kurabo Industries). After defoaming, an adhesive composition was obtained.

Next, the obtained color conversion composition is applied onto the first substrate layer “Lumirror” (registered trademark) U48 (manufactured by Toray Industries, Inc., thickness 50 μm) using a slit die coater. and dried at 100° C. for 20 minutes to form a color conversion layer having an average thickness of 16 μm.

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

Next, these laminates are heat-laminated so that the color conversion layer and the adhesive layer are directly laminated, and the first substrate layer/color conversion layer/adhesive layer/second substrate layer/light A color conversion sheet having a laminated structure of diffusion layers was produced.

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

(Comparative Examples 7-9)
Color conversion films were prepared and evaluated in the same manner as in Example 11, except that Ref-1 to Ref-3 were used instead of compound G-1 as the luminescent material.

The results of Examples 11-14 and Comparative Examples 7-9 are summarized in Table 3.

Comparing G-1 to G-4 with ref-1 to Ref-3, although the emission color is green, G-1 to G-4 have higher absolute luminous quantum efficiency, which is an index of luminous efficiency. was the result. This result reflects the high fluorescence quantum yields of Examples 1-4. Furthermore, focusing on durability, all of G-1 to G-4 were superior to ref-1 to ref-3. This is due to the effect of suppressing intermolecular interactions by introducing an asymmetric cross-linking structure and improving durability, and the introduction of an electron-withdrawing group to the para-position of boron to reduce ΔEST. This reflects both effects of being able to suppress the process of direct decomposition of .

1A, 1B, 1C, 1D Color Conversion Sheet 10 Base Layer 11 Color Conversion Layer 12 Barrier Film

Claims (18)

A compound having a structure represented by the following general formula (3).

(In general formula (3) above, R ¹⁰¹ to R ¹²⁴ each independently represent hydrogen, halogen, cyano group, alkyl group, cycloalkyl group, heterocyclic group, alkenyl group, cycloalkenyl group, alkynyl group, alkoxy group, alkylthio group, arylether group, arylthioether group, aryl group, heteroaryl group, oxycarbonyl group, carbamoyl group, amino group, nitro group, silyl group or adjacent substituents among R ¹⁰¹ to R ¹²⁴ A saturated or unsaturated ring formed in These groups may further have a substituent.
L3 and L4 ^{are each} independently a single bond, O, S, ^{CR125R126 or SiR127R128 .} R ¹²⁵ to R ¹²⁸ are each independently hydrogen, halogen, alkyl group, cycloalkyl group, aryl group or heteroaryl group, and these groups may further have a substituent. R ¹²⁵ and R ¹²⁶ or R ¹²⁷ and R ¹²⁸ may be bonded via a single bond or a linking group. However, L ³ and L ⁴ are necessarily different groups. ) 2. The compound according to claim 1, wherein L3 and/or ^L4 in general formula ( ^{3 )} are ^CR125R126 . 3. The compound of claim 2, wherein ^{R125 and/or R126 is} an aryl group. In the general formula (3), R ¹⁰³ , R ¹¹¹ and/or R ¹²² are groups having a positive substituent constant σp value in Hammett's rule, or R ¹⁰² , R ¹⁰⁷ , R ¹¹⁰ , R ¹¹² , A compound according to any one of claims 1 to 3, wherein R ¹²⁰ and/or R ¹²³ are substituted amino groups. A 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, 5. The compound according to claim 4, which is a cyano-substituted aryl group, a cyano-substituted heteroaryl group or an electron-accepting nitrogen-containing heteroaryl group. 6. The compound according to claim 5, wherein the group having a positive substituent constant σp value in Hammett's rule is an electron-accepting nitrogen-containing heteroaryl group. 5. The compound according to claim 4, wherein R ¹⁰² , R ¹⁰⁷ , R ¹¹⁰ , R ¹¹² , R ¹²⁰ and/or R ¹²³ in general formula (3) have a structure represented by general formula (4) below.

(In general formula (4) above, Ar ¹ and Ar ² are each independently an aryl group or a heteroaryl group. These groups may further have a substituent. Ar ¹ and Ar ² may be linked via a single bond or a linking group, in which case the linking group is —O—, —S—, >CR ¹³³ R ¹³⁴ , >SiR ¹³⁵ R ¹³⁶ or >C=O , R ¹³³ to R ¹³⁶ are each independently hydrogen, halogen, an alkyl group, a cycloalkyl group, an aryl group or a heteroaryl group.These groups may further have a substituent.) 8. The compound according to any one of claims 1 to 7, which is a material for a light-emitting device. A light emitting device comprising a cathode, an anode, and at least one organic layer disposed between the cathode and the anode, wherein the compound according to any one of claims 1 to 8 is contained in the at least one organic layer. element. 10. The light-emitting device according to claim 9, wherein said at least one organic layer is a light-emitting layer. 11. The light emitting device according to claim 10, wherein the light emitting layer has 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 8. 12. The light-emitting device according to claim 11, wherein the assist dopant material is a compound that emits delayed fluorescence. The light emitting device according to claim 10 or 11, wherein the light emitting layer has 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 8. A color conversion composition for converting incident light into light having a wavelength different from that of the incident light, the color conversion composition comprising the compound according to any one of claims 1 to 7 and a binder resin. A color conversion sheet comprising a color conversion layer formed from the color conversion composition according to claim 14. A light source unit comprising a light source and the color conversion sheet according to claim 15 . A display device comprising the light emitting device according to any one of claims 9 to 13 and/or the light source unit according to claim 16. A lighting device comprising the light emitting element according to any one of claims 9 to 13 and/or the light source unit according to claim 16.

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