Pyrromethene boron complex, light-emitting element, display device, and lighting device containing the same

Abstract

By means of a pyrromethene boron complex represented by general formula (1), provided are: a light-emitting material having a high fluorescence quantum yield and a sharp light-emitting spectrum; and a light-emitting element having a high light-emitting efficiency, color purity, and a durability. (R1-R6 are each independently selected from the group consisting of a hydrogen atom, an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a hydroxyl group, a thiol group, an alkoxy group, an alkylthio group, an aryl ether group, an aryl thioether group, an aryl group, a heteroaryl group, an amino group, a silyl group, a siloxanyl group, and a boryl group. Said groups may also be substituents. Here, at least one among R1 to R4 is a hydrogen atom or an alkyl group. X1 and X2 are each independently selected from the group consisting of a hydrogen atom, an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a hydroxyl group, a thiol group, an alkoxy group, an alkylthio group, an aryl ether group, an aryl thioether group, an aryl group, a heteroaryl group, halogen, a cyano group, an aldehyde group, an acyl group, a carboxyl group, an ester group, an amide group, a sulfonyl group, a sulfonic acid ester group, a sulfonamide group, an amino group, a nitro group, a silyl group, a siloxanyl group, a boryl group, and a phosphine oxide group. Said groups may also be substituents. R7 is represented by general formula (2).) (R8-R10 are each independently selected from the group consisting of a hydrogen atom, an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a hydroxyl group, a thiol group, an alkoxy group, an alkylthio group, an arylether group, an arylthioether group, an aryl group, a heteroaryl group, halogen, a cyano group, an aldehyde group, an acyl group, a carboxyl group, an ester group, an amide group, a sulfonyl group, a sulfonic acid ester group, a sulfonamide group, an amino group, a nitro group, a silyl group, a siloxanyl group, a boryl group, and a phosphine oxide group. Said groups may also be substituents. R11 is selected from the group consisting of an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a hydroxyl group, a thiol group, an alkoxy group, an alkylthio group, an arylether group, an arylthioether group, an aryl group, a heteroaryl group, halogen, a cyano group, an aldehyde group, an acyl group, a carboxyl group, an ester group, an amide group, a sulfonyl group, a sulfonic acid ester group, a sulfonamide group, an amino group, a nitro group, a silyl group, a siloxanyl group, a boryl group, and a phosphine oxide group. Said groups may also be substituents. Ar1 is a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group.)

Description

[Technical field]

[0001] The present invention relates to a pyrromethene boron complex, and a light-emitting device, a display device, and a lighting device each containing the same. [Background technology]

[0002] Organic thin-film light-emitting devices, which emit light by recombining electrons injected from a cathode and holes injected from an anode in a light-emitting layer sandwiched between the two electrodes, are characterized by being thin, capable of emitting light with a low driving voltage and high luminance, and further capable of emitting light in multiple colors by selecting the light-emitting material. In particular, by using a combination of a host material and a dopant material in the light-emitting layer, a light-emitting device that emits light in the three primary colors of blue, green, and red with high efficiency can be obtained.

[0003] As a dopant, a dye with a high fluorescence quantum yield is usually used. For example, a complex having a pyrromethene skeleton is a compound that satisfies the requirements for obtaining high efficiency as a dopant, such as a high fluorescence quantum yield, a small Stokes shift, and a small half-width of the peak of the emission spectrum, and it is known that a light-emitting device using a pyrromethene complex as a dopant exhibits good device characteristics (see, for example, Patent Document 1). Furthermore, in recent years, aiming for high emission efficiency, a light-emitting device containing a TADF (Thermally Activated Delayed Fluorescence) material and a pyrromethene boron complex has been studied (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2003-12676 A [Patent Document 2] International Publication No. 2016 / 056559 Summary of the Invention [Problem to be solved by the invention]

[0005] When organic thin-film light-emitting elements are used as display devices or lighting devices, it is required to widen the color gamut. The color gamut is expressed by a triangle formed by determining the vertex coordinates that indicate the emission of red, green, and blue on an xy chromaticity diagram. In order to widen the color gamut, it is necessary to set the vertex coordinates of red, green, and blue to appropriate chromaticity so that the area of ​​the triangle becomes large, and various color designs are carried out for this purpose.

[0006] Chromaticity is determined by the combination of the emission peak wavelength and color purity. Color purity is determined by the width of the emission spectrum, and the narrower the emission spectrum and the closer it is to monochromatic light, the higher the color purity. In order to widen the color gamut, it is particularly important to increase color purity, and there is a strong demand for luminescent materials with sharp emission spectra.

[0007] Furthermore, when organic thin-film light-emitting elements are used as display devices or lighting devices, there is a demand for improving the durability of the light-emitting elements, which in turn requires increasing the stability of the light-emitting material.

[0008] On the other hand, organic thin-film light-emitting devices are desired to have high luminous efficiency from the viewpoints of improving brightness and saving power. Particularly in the case of mobile display devices, the use of which has expanded in recent years, power saving has become a particularly important issue.

[0009] In this situation, although pyrromethene boron complexes are useful luminescent materials that can obtain a sharp emission spectrum when used as a dopant, light-emitting devices are required to have higher luminous efficiency and higher durability, but it has been difficult to achieve a light-emitting device that has high luminous efficiency and high durability while maintaining a sharp emission spectrum.

[0010] An object of the present invention is to solve the problems of the conventional techniques and to provide a light-emitting material having a high fluorescence quantum yield and a sharp emission spectrum, and a light-emitting device having high luminous efficiency, color purity and durability. [Means for solving the problem]

[0011] The present invention is a pyrromethene boron complex represented by general formula (1).

[0012] [ka]

[0013] R 1 ~R 6 are each independently selected from the group consisting of a hydrogen atom, an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a hydroxyl group, a thiol group, an alkoxy group, an alkylthio group, an aryl ether group, an aryl thioether group, an aryl group, a heteroaryl group, an amino group, a silyl group, a siloxanyl group, and a boryl group. These groups may further have a substituent. However, R 1 ~R 4 At least one of the groups is a hydrogen atom or an alkyl group. X 1 and X 2 are each independently selected from the group consisting of an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a hydroxyl group, a thiol group, an alkoxy group, an alkylthio group, an aryl ether group, an aryl thioether group, an aryl group, a heteroaryl group, a halogen, and a cyano group. These groups may further have a substituent. R 7 is represented by the following general formula (2).

[0014] [ka]

[0015] R 8 ~R 10are each independently selected from the group consisting of a hydrogen atom, an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a hydroxyl group, a thiol group, an alkoxy group, an alkylthio group, an aryl ether group, an aryl thioether group, an aryl group, a heteroaryl group, a halogen atom, a cyano group, an aldehyde group, an acyl group, a carboxyl group, an ester group, an amide group, a sulfonyl group, a sulfonate ester group, a sulfonamide group, an amino group, a nitro group, a silyl group, a siloxanyl group, a boryl group, and a phosphine oxide group. These groups may further have a substituent. R 11 is selected from the group consisting of an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a hydroxyl group, a thiol group, an alkoxy group, an alkylthio group, an aryl ether group, an aryl thioether group, an aryl group, a heteroaryl group, a halogen, a cyano group, an aldehyde group, an acyl group, a carboxyl group, an ester group, an amide group, a sulfonyl group, a sulfonate ester group, a sulfonamide group, an amino group, a nitro group, a silyl group, a siloxanyl group, a boryl group, and a phosphine oxide group. These groups may further have a substituent. Ar 1 is a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group.

[0016] Another embodiment of the present invention is a light-emitting element having an anode, a cathode, and a light-emitting layer present between the anode and the cathode, the light-emitting layer emitting light in response to electric energy, the light-emitting layer containing the above-mentioned pyrromethene boron complex. Effect of the Invention

[0017] According to the present invention, it is possible to provide a light-emitting material having a high fluorescence quantum yield and a sharp emission spectrum, and a light-emitting device having high luminous efficiency, color purity and durability. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, preferred embodiments of the pyrromethene boron complex according to the present invention, and the light-emitting device, display device, and lighting device containing the same will be described in detail. However, the present invention is not limited to the following embodiments, and can be modified in various ways depending on the purpose and application.

[0019] <Pyrromethene boron complex> The pyrromethene boron complex according to the present invention is represented by the general formula (1).

[0020] [ka]

[0021] R 1 ~R 6 are each independently selected from the group consisting of a hydrogen atom, an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a hydroxyl group, a thiol group, an alkoxy group, an alkylthio group, an aryl ether group, an aryl thioether group, an aryl group, a heteroaryl group, an amino group, a silyl group, a siloxanyl group, and a boryl group. These groups may further have a substituent. However, R 1 ~R 4 At least one of the groups is a hydrogen atom or an alkyl group.

[0022] X 1 and X 2 are each independently selected from the group consisting of an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a hydroxyl group, a thiol group, an alkoxy group, an alkylthio group, an aryl ether group, an aryl thioether group, an aryl group, a heteroaryl group, a halogen, and a cyano group. These groups may further have a substituent.

[0023] R 7 is represented by the following general formula (2).

[0024] [ka]

[0025] R 8 ~R 10 are each independently selected from the group consisting of a hydrogen atom, an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a hydroxyl group, a thiol group, an alkoxy group, an alkylthio group, an aryl ether group, an aryl thioether group, an aryl group, a heteroaryl group, a halogen atom, a cyano group, an aldehyde group, an acyl group, a carboxyl group, an ester group, an amide group, a sulfonyl group, a sulfonate ester group, a sulfonamide group, an amino group, a nitro group, a silyl group, a siloxanyl group, a boryl group, and a phosphine oxide group. These groups may further have a substituent.

[0026] R 11 is selected from the group consisting of an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a hydroxyl group, a thiol group, an alkoxy group, an alkylthio group, an aryl ether group, an aryl thioether group, an aryl group, a heteroaryl group, a halogen, a cyano group, an aldehyde group, an acyl group, a carboxyl group, an ester group, an amide group, a sulfonyl group, a sulfonate ester group, a sulfonamide group, an amino group, a nitro group, a silyl group, a siloxanyl group, a boryl group, and a phosphine oxide group. These groups may further have a substituent.

[0027] Ar 1 is a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group.

[0028] In the pyrromethene skeleton, R 7 Hereinafter, the site substituted with may be referred to as "bridgehead position".

[0029] In the present invention, those having a pyrromethene skeleton represented by the following formula and those having a condensed ring structure in a part of the pyrromethene skeleton and an expanded ring structure are collectively referred to as "pyrromethene".

[0030] [ka]

[0031] In all of the above groups, hydrogen may be deuterium. The same applies to the compounds or partial structures thereof described below.

[0032] In addition, in all the above groups, the substituent in the case of substitution is preferably a group selected from the group consisting of an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, an aryl group, a heteroaryl group, a hydroxyl group, a thiol group, an alkoxy group, an alkylthio group, an aryl ether group, an aryl thioether group, a halogen, a cyano group, an aldehyde group, an acyl group, a carboxyl group, an ester group, an amide group, an acyl group, a sulfonyl group, a sulfonate ester group, a sulfonamide group, an amino group, a nitro group, a silyl group, a siloxanyl group, a boryl group, a phosphine oxide group and an oxo group.Moreover, the specific substituents that are preferred in the description of each substituent below are more preferable.In addition, these substituents may be further substituted with the above-mentioned substituents.

[0033] In this description, "unsubstituted" means that the atoms bonded to the target basic skeleton or group are only hydrogen atoms or deuterium atoms. The same applies to "substituted or unsubstituted" in the compounds or partial structures described below.

[0034] The alkyl group refers to a saturated aliphatic hydrocarbon group such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, or a tert-butyl group, which may be substituted or unsubstituted. If substituted, the additional substituent is not particularly limited, and may be, for example, an alkyl group, a halogen, an aryl group, or a heteroaryl group, which is also common to the following description. The number of carbon atoms in the alkyl group is not particularly limited, but is preferably 1 to 20, more preferably 1 to 8, in terms of availability and cost.

[0035] The cycloalkyl group refers to a saturated alicyclic hydrocarbon group, such as a cyclopropyl group, a cyclohexyl group, a norbornyl group, an adamantyl group, etc., which may be substituted or unsubstituted. The number of carbon atoms in the alkyl group portion is not particularly limited, but is preferably in the range of 3 to 20.

[0036] The heterocyclic group refers to an aliphatic ring having an atom other than carbon in the ring, such as a pyran ring, a piperidine ring, or a cyclic amide, which may be substituted or unsubstituted. The number of carbon atoms in the heterocyclic group is not particularly limited, but is preferably in the range of 2 to 20.

[0037] The alkenyl group refers to an unsaturated aliphatic hydrocarbon group containing a double bond, such as a vinyl group, an allyl group, or a butadienyl group, which may be substituted or unsubstituted. The number of carbon atoms in the alkenyl group is not particularly limited, but is preferably in the range of 2 to 20.

[0038] The cycloalkenyl group refers to an unsaturated alicyclic hydrocarbon group containing a double bond, such as a cyclopentenyl group, a cyclopentadienyl group, a cyclohexenyl group, etc., which may be substituted or unsubstituted. The number of carbon atoms in the cycloalkenyl group is not particularly limited, but is preferably in the range of 3 to 20.

[0039] The alkynyl group refers to an unsaturated aliphatic hydrocarbon group containing a triple bond, such as an ethynyl group, which may be substituted or unsubstituted. The number of carbon atoms in the alkynyl group is not particularly limited, but is preferably in the range of 2 to 20.

[0040] The alkoxy group refers to a functional group in which an aliphatic hydrocarbon group is bonded via an ether bond, such as a methoxy group, an ethoxy group, or a propoxy group, and this aliphatic hydrocarbon group may be substituted or unsubstituted. The number of carbon atoms in the alkoxy group is not particularly limited, but is preferably in the range of 1 to 20.

[0041] An alkylthio group is an alkoxy group in which the oxygen atom of the ether bond is replaced with a sulfur atom. The hydrocarbon group of the alkylthio group may be substituted or unsubstituted. The number of carbon atoms in the alkylthio group is not particularly limited, but is preferably in the range of 1 to 20.

[0042] The aryl ether group refers to a functional group in which an aromatic hydrocarbon group is bonded via an ether bond, such as a phenoxy group, and the aromatic hydrocarbon group may be substituted or unsubstituted. The number of carbon atoms in the aryl ether group is not particularly limited, but is preferably in the range of 6 to 40.

[0043] The aryl thioether group is an aryl ether group in which the oxygen atom of the ether bond is replaced with a sulfur atom. The aromatic hydrocarbon group in the aryl thioether group may be substituted or unsubstituted. The number of carbon atoms in the aryl thioether group is not particularly limited, but is preferably in the range of 6 to 40.

[0044] The aryl group may be either a single ring or a condensed ring, and may be, for example, an aromatic hydrocarbon group such as a phenyl group, a naphthyl group, a fluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenanthryl group, an anthracenyl group, a benzophenanthryl group, a benzoanthracenyl group, a chrysenyl group, a pyrenyl group, a fluoranthenyl group, a triphenylenyl group, a benzofluoranthenyl group, a dibenzoanthracenyl group, a perylenyl group, or a helicenyl group. Among them, a group selected from the group consisting of a phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, a fluorenyl group, a phenanthryl group, an anthracenyl group, a pyrenyl group, a fluoranthenyl group, and a triphenylenyl group is preferred. The aryl group may be substituted or unsubstituted. In the present invention, a group in which a plurality of phenyl groups are bonded via a single bond, such as a biphenyl group or a terphenyl group, is treated as a phenyl group having an aryl group as a substituent. The number of carbon atoms in the aryl group is not particularly limited, but is preferably in the range of 6 to 40, more preferably 6 to 30. In addition, in a phenyl group, when two adjacent carbon atoms in the phenyl group each have a substituent, the substituents may form a ring structure together.

[0045] The heteroaryl group may be a single ring or a condensed ring, and examples of the heteroaryl group include a pyridyl group, a furanyl group, a thiophenyl group, a quinolinyl group, an isoquinolinyl group, a pyrazinyl group, a pyrimidyl group, a pyridazinyl group, a triazinyl group, a naphthyridinyl group, a cinnolinyl group, a phthalazinyl group, a quinoxalinyl group, a quinazolinyl group, a benzofuranyl group, a benzothiophenyl group, an indolyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a carbazolyl group, a benzocarboxyl group, a benzocarbazolyl group, and the like. It refers to a cyclic aromatic group having one or more atoms other than carbon and hydrogen, i.e., heteroatoms, in the ring, such as a bazolyl group, a carbolinyl group, an indolocarbazolyl group, a benzofurocarbazolyl group, a benzothienocarbazolyl group, a dihydroindenocarbazolyl group, a benzoquinolinyl group, an acridinyl group, a dibenzoacridinyl group, a benzimidazolyl group, an imidazopyridyl group, a benzoxazolyl group, a benzothiazolyl group, and a phenanthrolinyl group. The heteroatom is preferably a nitrogen atom, an oxygen atom, or a sulfur atom. The heteroaryl group may be substituted or unsubstituted. The number of carbon atoms in the heteroaryl group is not particularly limited, but is preferably 2 to 40, more preferably 2 to 30.

[0046] The term "halogen" refers to an atom selected from fluorine, chlorine, bromine and iodine.

[0047] A cyano group is a functional group with the structure -CN, where it is the carbon atom that is attached to other groups.

[0048] An aldehyde group is a functional group with the structure -C(=O)H, where it is the carbon atom that bonds to other groups.

[0049] The acyl group refers to a functional group in which an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, or a heteroaryl group is bonded via a carbonyl group, such as an acetyl group, a propionyl group, a benzoyl group, or an acrylyl group. These substituents may be further substituted. The number of carbon atoms in the acyl group is not particularly limited, but is preferably 2 to 40, more preferably 2 to 30.

[0050] The ester group refers to a functional group in which, for example, an alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, or the like is bonded via an ester bond. These substituents may be further substituted. The number of carbon atoms in the ester group is not particularly limited, but is preferably in the range of 1 to 20. More specifically, examples of the ester group include methyl ester groups such as a methoxycarbonyl group, ethyl ester groups such as an ethoxycarbonyl group, propyl ester groups such as a propoxycarbonyl group, butyl ester groups such as a butoxycarbonyl group, isopropyl ester groups such as an isopropoxymethoxycarbonyl group, hexyl ester groups such as a hexyloxycarbonyl group, and phenyl ester groups such as a phenoxycarbonyl group.

[0051] The amide group refers to a functional group in which, for example, an alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, or the like is bonded via an amide bond. These substituents may be further substituted. The number of carbon atoms in the amide group is not particularly limited, but is preferably in the range of 1 to 20. More specifically, examples of the amide group include a methylamide group, an ethylamide group, a propylamide group, a butylamide group, an isopropylamide group, a hexylamide group, and a phenylamide group.

[0052] The sulfonyl group is, for example, an alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, etc., which is -S(=O). 2 It represents a functional group bonded via a - bond. These substituents may be further substituted. The number of carbon atoms of the sulfonyl group is not particularly limited, but is preferably in the range of 1 to 20.

[0053] The sulfonate ester group refers to a functional group in which, for example, an alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, etc. are bonded via a sulfonate ester bond. Here, the sulfonate ester bond refers to a bond in which the carbonyl part of the ester bond, i.e. -C(=O)-, is bonded to the sulfonyl part, i.e. -S(=O). 2The sulfonate ester group refers to a group substituted with -. These substituents may be further substituted. The number of carbon atoms in the sulfonate ester group is not particularly limited, but is preferably in the range of 1 to 20.

[0054] The sulfonamide group refers to a functional group in which, for example, an alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, etc. are bonded via a sulfonamide bond. Here, the sulfonamide bond refers to a bond in which the carbonyl part of an ester bond, i.e., -C(=O)-, is replaced by the sulfonyl part, i.e., -S(=O). 2 The sulfonamide group refers to a group substituted with -. These substituents may be further substituted. The number of carbon atoms in the sulfonamide group is not particularly limited, but is preferably in the range of 1 to 20.

[0055] The amino group is a substituted or unsubstituted amino group. In the case of substitution, examples of the substituent include an aryl group, a heteroaryl group, a linear alkyl group, and a branched alkyl group. As the aryl group and the heteroaryl group, a phenyl group, a naphthyl group, a pyridyl group, and a quinolinyl group are preferable. These substituents may be further substituted. The number of carbon atoms is not particularly limited, but is preferably 2 to 50, more preferably 6 to 40, and particularly preferably 6 to 30.

[0056] The silyl group refers to a functional group to which a substituted or unsubstituted silicon atom is bonded, and examples thereof include alkylsilyl groups such as trimethylsilyl, triethylsilyl, tert-butyldimethylsilyl, propyldimethylsilyl, and vinyldimethylsilyl, and arylsilyl groups such as phenyldimethylsilyl, tert-butyldiphenylsilyl, triphenylsilyl, and trinaphthylsilyl. The substituent on silicon may be further substituted. The number of carbon atoms in the silyl group is not particularly limited, but is preferably in the range of 1 to 30.

[0057] The siloxanyl group refers to a silicon compound group bonded via an ether bond, such as a trimethylsiloxanyl group, etc. The substituent on the silicon may be further substituted.

[0058] The boryl group is a substituted or unsubstituted boryl group. In the case of substitution, examples of the substituent include an aryl group, a heteroaryl group, a linear alkyl group, a branched alkyl group, an aryl ether group, an alkoxy group, and a hydroxyl group, and among these, an aryl group and an aryl ether group are preferred.

[0059] The phosphine oxide group is -P(=O)R 50 R 51 R is a group represented by the formula: 50 and R 51 are each independently R 1 ~R 6 is selected from the same group as above.

[0060] The pyrromethene boron complex has a strong and highly planar skeleton, which allows it to exhibit high fluorescence quantum yields and a narrow half-width peak in the emission spectrum, enabling efficient emission and high color purity in light-emitting devices.

[0061] In order to further improve the emission efficiency, it is effective to suppress the rotation and vibration of the substituents of the pyrromethene boron complex, thereby reducing the energy loss and improving the fluorescence quantum yield. In addition, in order to improve the color purity, it is effective to reduce the vibrational relaxation in the excited state of the pyrromethene boron complex and thereby reduce the half-width of the emission spectrum.

[0062] From this viewpoint, the bridgehead position of the pyrromethene skeleton is provided with a substituent R 7 R has been introduced. 7 By introducing the substituent R, it is possible to provide a pyrromethene boron complex having a high fluorescence quantum yield and a small half-width. 7 Middle, Ar 1 and R 11 When each of the groups is the above, it is possible to suppress the bridgehead position from rotating intramolecularly with respect to the pyrromethene skeleton and causing energy deactivation, which is advantageous for improving the luminous efficiency.

[0063] Also, R 1 ~R 4When at least one of the groups is a hydrogen atom or an alkyl group, vibrational relaxation in the excited state is reduced, and the half-width of the emission spectrum can be reduced.

[0064] In addition, the stability of the pyrromethene boron complex affects the durability of the light-emitting device. In order to further improve the stability, it is preferable to introduce a bulky substituent into the bridgehead position. By introducing a bulky substituent, the pyrromethene skeleton can be protected from interactions with other surrounding molecules. Substituent R 7 Middle, Ar 1 and R 11 By each of R being the above group, the stability of the pyrromethene boron complex can be improved, and the durability of the light-emitting device can be improved. 11 is preferably a bulkier substituent, and is preferably a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group.

[0065] R 1 and R 4 is selected from the above group and affects the emission peak wavelength, crystallinity, sublimation temperature, etc. of the pyrromethene boron complex. From the viewpoint of narrowing the half-width of the emission spectrum, R 1 and R 4 is preferably a hydrogen atom or an alkyl group. 1 and R 4 More preferably, is an alkyl group.

[0066] R 2 and R 3 is selected from the above group and mainly affects the emission peak wavelength, the half-width of the emission spectrum, the stability, or the crystallinity of the pyrromethene boron complex. From the viewpoint of making the half-width of the emission spectrum smaller, improving the stability, and easiness of synthesis including recrystallization, R 2 and R 3At least one of, and preferably both of, R 2 and R 3 More preferably, is an alkyl group.

[0067] R 5 and R 6 is selected from the above group and mainly affects the emission peak wavelength, the half-width of the emission spectrum, the stability, or the crystallinity of the pyrromethene boron complex. From the viewpoint of making the half-width of the emission spectrum smaller, improving the stability, and easiness of synthesis including recrystallization purification, R 5 and R 6 At least one of, and preferably both of, is a hydrogen atom or a substituted or unsubstituted alkyl group.

[0068] X 1 and X 2 is selected from the above. From the viewpoint of luminescence properties and thermal stability, X 1 and X 2 is preferably a group selected from the group consisting of an alkoxy group, a haloalkyl group, a haloalkoxy group, an aryl ether group, a haloaryl ether group, a haloaryl group, a halogen atom, and a cyano group. Here, the haloalkyl group is an alkyl group substituted with at least one halogen. The haloaryl group is an aryl group substituted with at least one halogen.

[0069] In addition, from the viewpoint of obtaining a stable excited state and a higher fluorescence quantum yield, and from the viewpoint of improving durability, X 1 and X 2is more preferably a group selected from the group consisting of a fluorine atom, a fluorine-containing alkyl group, a fluorine-containing alkoxy group, a fluorine-containing aryl group and a cyano group, further preferably a fluorine atom or a cyano group, and most preferably a fluorine atom. These are electron-withdrawing groups that can reduce the electron density of the pyrromethene skeleton and increase the stability of the compound.

[0070] Examples of the pyrromethene boron complex represented by the general formula (1) are shown below, but the invention is not limited thereto.

[0071] [ka]

[0072] [ka]

[0073] [ka]

[0074] [ka]

[0075] [ka]

[0076] [ka]

[0077] [ka]

[0078] [ka]

[0079] [ka]

[0080] [ka]

[0081] [ka]

[0082] [ka]

[0083] [ka]

[0084] [ka]

[0085] [ka]

[0086] [ka]

[0087] The pyrromethene boron complex represented by the general formula (1) can be produced by referring to the methods described in J. Org. Chem., vol. 64, No. 21, pp. 7813-7819 (1999), Angew. Chem., Int. Ed. Engl., vol. 36, pp. 1333-1335 (1997), Org. Lett., vol. 12, pp. 296 (2010), and the like.

[0088] Furthermore, in order to introduce an aryl group or a heteroaryl group into the pyrromethene skeleton, for example, a method of generating a carbon-carbon bond by using a coupling reaction between a halogenated derivative of a pyrromethene boron complex and a boronic acid or a boronic acid ester derivative in the presence of a metal catalyst such as palladium, but this is not limited thereto. Similarly, in order to introduce an amino group or a carbazolyl group into the pyrromethene skeleton, for example, a method of generating a carbon-nitrogen bond by using a coupling reaction between a halogenated derivative of a pyrromethene boron complex and an amine or a carbazole derivative in the presence of a metal catalyst such as palladium, but this is not limited thereto.

[0089] The obtained pyrromethene boron complex is preferably purified by organic synthesis methods such as recrystallization or column chromatography, and then further purified by heating under reduced pressure, generally called sublimation purification, to remove low boiling point components and improve the purity. The heating temperature in the sublimation purification is not particularly limited, but is preferably 330° C. or lower, more preferably 300° C. or lower, from the viewpoint of preventing thermal decomposition of the pyrromethene boron complex.

[0090] The purity of the pyrromethene boron complex thus produced is preferably 99% by weight or more, from the viewpoint of enabling the light-emitting device to exhibit stable characteristics.

[0091] The optical properties of the pyrromethene boron complex represented by general formula (1) can be obtained by measuring the absorption spectrum and emission spectrum of a diluted solution. The solvent is not particularly limited as long as it dissolves the pyrromethene boron complex and is transparent so that the absorption spectrum of the solvent does not overlap with the absorption spectrum of the pyrromethene boron complex. A specific example is toluene. The concentration of the solution is not particularly limited as long as it has sufficient absorbance and is in a concentration range in which concentration quenching does not occur, but is preferably 1×10 -4 mol / L~1×10 -7 mol / L, preferably in the range of 1×10 -5 mol / L~1×10 -6It is more preferable that the concentration is in the range of mol / L. The absorption spectrum can be measured by a general ultraviolet-visible spectrophotometer. The emission spectrum can be measured by a general fluorescence spectrophotometer. Furthermore, it is preferable to use an absolute quantum yield measurement device using an integrating sphere for measuring the fluorescence quantum yield.

[0092] In order to achieve high color purity, it is preferable that the emission spectrum of the light emitted by the pyrromethene boron complex represented by the general formula (1) upon irradiation with excitation light is sharp. In addition, in top emission elements, which are mainstream in display devices and lighting devices, high brightness and high color purity can be achieved due to the resonance effect of the microcavity structure, and if the emission spectrum is sharp, this resonance effect is more pronounced, which is advantageous for high efficiency. From this viewpoint, the half-width of the emission spectrum is preferably 60 nm or less, more preferably 50 nm or less, even more preferably 45 nm or less, and particularly preferably 28 nm or less.

[0093] The luminous efficiency of a light-emitting element depends on the fluorescence quantum yield of the light-emitting material itself. Therefore, it is desirable for the fluorescence quantum yield of the light-emitting material to be as close to 100% as possible. The pyrromethene boron complex represented by the general formula (1) is 11 and Ar 1 As described above, the rotation and vibration of the bridgehead position are suppressed, and thermal deactivation is reduced, resulting in a high fluorescence quantum yield. From the above viewpoints, the fluorescence quantum yield of the pyrromethene boron complex is preferably 90% or more, and more preferably 95% or more. However, the fluorescence quantum yield shown here is measured using a dilute solution using toluene as the solvent, using an absolute quantum yield measurement device.

[0094] <Light emitting device materials> The pyrromethene boron complex represented by the general formula (1) can achieve high luminous efficiency, and is therefore used as a light-emitting device material in a light-emitting device. Here, the light-emitting device material in the present invention refers to a material used in any layer of the light-emitting device, and includes a material used in a layer selected from a hole injection layer, a hole transport layer, a light-emitting layer, and an electron transport layer, as described below, as well as a material used in a protective film (cap layer) of an electrode.

[0095] The pyrromethene boron complex represented by the general formula (1) has high light-emitting performance, and is therefore preferably used as a material for the light-emitting layer.

[0096] <Light emitting element> Next, an embodiment of the light-emitting device of the present invention will be described. The light-emitting device of the present invention has an anode, a cathode, and an organic layer present between the anode and the cathode. The organic layer preferably includes at least a light-emitting layer, and the light-emitting layer is an organic electroluminescent device that emits light by electrical energy.

[0097] The light-emitting device of the present invention may be either a bottom emission type or a top emission type.

[0098] The layer configuration of the organic layer between the anode and cathode in such light-emitting elements may be a configuration consisting of only a light-emitting layer, or may be a stacked configuration such as 1) light-emitting layer / electron transport layer, 2) hole transport layer / light-emitting layer, 3) hole transport layer / light-emitting layer / electron transport layer, 4) hole injection layer / hole transport layer / light-emitting layer / electron transport layer, 5) hole transport layer / light-emitting layer / electron transport layer / electron injection layer, 6) hole injection layer / hole transport layer / light-emitting layer / electron transport layer / electron injection layer, 7) hole injection layer / hole transport layer / light-emitting layer / hole blocking layer / electron transport layer / electron injection layer, or 8) hole injection layer / hole transport layer / electron blocking layer / light-emitting layer / hole blocking layer / electron transport layer / electron injection layer.

[0099] Furthermore, the above-mentioned laminated structure may be laminated in a plurality of layers via an intermediate layer to form a tandem-type light-emitting element. The intermediate layer generally includes an intermediate electrode, an intermediate conductive layer, a charge generating layer, an electron extracting layer, a connection layer, an intermediate insulating layer, and the like, and may be made of a known material. A preferred specific example of the tandem-type light-emitting element includes a laminated structure such as 9) hole injection layer / hole transport layer / light-emitting layer / electron transport layer / electron injection layer / charge generating layer / hole injection layer / hole transport layer / light-emitting layer / electron transport layer / electron injection layer.

[0100] Each of the above layers may be a single layer or multiple layers, and may be doped.Furthermore, the device may have a configuration including a layer using a capping material for improving the luminous efficiency due to the optical interference effect.

[0101] The pyrromethene boron complex represented by the general formula (1) may be used in any layer in the above-mentioned device configuration, but is preferably used in the light-emitting layer because of its high fluorescent quantum yield and thin film stability.

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

[0103] (substrate) In order to maintain the mechanical strength of the light-emitting element, to reduce thermal deformation, and to have a barrier property that prevents water vapor and oxygen from penetrating into the light-emitting layer, it is preferable to form the light-emitting element on a substrate. The substrate is not particularly limited, but examples thereof include a glass plate, a ceramic plate, a resin film, a resin thin film, and a metal thin plate. Among these, a glass substrate is preferably used from the viewpoint of transparency and ease of processing. In particular, a glass substrate having high transparency is preferable for a bottom emission element that extracts light through a substrate. In addition, flexible displays and foldable displays are increasing in mobile devices such as smartphones, and resin films and resin thin films obtained by curing varnish are preferably used for this purpose. As the resin film, a heat-resistant film is used, and specific examples thereof include a polyimide film and a polyethylene naphthalate film.

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

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

[0106] Examples of materials for transparent or semi-transparent electrodes include conductive metal oxides such as zinc oxide, tin oxide, indium oxide, indium tin oxide (ITO), and indium zinc oxide (IZO); metals such as gold, silver, aluminum, and chromium; and conductive polymers such as polythiophene, polypyrrole, and polyaniline. However, when using metals, it is preferable to make the film thin so that light can be semi-transmitted. Of the above, indium tin oxide (ITO) is more preferable from the viewpoints of transparency and stability.

[0107] The material of the reflective electrode is preferably one that has no absorption and high reflectance for all light, and specific examples thereof include metals such as aluminum, silver, and platinum.

[0108] The method of forming the anode can be an optimal method depending on the material, and examples of the method include sputtering, vapor deposition, and inkjet. For example, when the anode is formed from a metal oxide, the sputtering method is used, and when the anode is formed from a metal, the vapor deposition method is used. The thickness of the anode is not particularly limited, but is preferably several nm to several hundred nm.

[0109] Furthermore, these electrode materials may be used alone, or a plurality of materials may be laminated or mixed for use.

[0110] (cathode) The cathode is formed on the surface opposite to the anode with the organic layer sandwiched therebetween, and is preferably formed on the electron transport layer or the electron injection layer. The material used for the cathode is not particularly limited as long as it can efficiently inject electrons into the light emitting layer, but is preferably a reflective electrode in a bottom emission type element and is preferably a semi-transparent electrode in a top emission type element.

[0111] As the material of the cathode, generally, metals such as platinum, gold, silver, copper, iron, tin, aluminum, indium, etc.; alloys or multilayer laminated films of these metals and low work function metals such as lithium, sodium, potassium, calcium, magnesium, etc.; or conductive metal oxides such as zinc oxide, indium tin oxide (ITO), indium zinc oxide (IZO), etc. are preferable. Among them, metals selected from aluminum, silver, and magnesium as the main component are preferable in terms of electrical resistance value, ease of film formation, film stability, luminous efficiency, etc. In addition, when the cathode is composed of magnesium and silver, it is preferable because it facilitates electron injection into the electron transport layer and electron injection layer in the present invention and enables low-voltage driving.

[0112] (protective layer) For cathode protection, it is preferable to laminate a protective layer (cap layer) on the cathode. The material constituting the protective layer is not particularly limited, but examples thereof include metals such as platinum, gold, silver, copper, iron, tin, aluminum, and indium; alloys using these metals; inorganic substances such as silica, titania, and silicon nitride; and organic polymer compounds such as polyvinyl alcohol, polyvinyl chloride, and hydrocarbon polymer compounds. However, when the light-emitting element has an element structure (top emission structure) in which light is extracted from the cathode side, the material used for the protective layer is selected from materials that are optically transparent in the visible light region.

[0113] (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 multi-layer laminate. The hole injection layer between the hole transport layer and the anode is preferable because it allows lower voltage driving and improves the durability and life of the device, and also improves the carrier balance of the device and the luminous efficiency.

[0114] A preferred example of the hole injection material is an electron-donating hole injection material (donor material). These materials have a shallower HOMO level than the hole transport layer and are close to the work function of the anode, so that the energy barrier with the anode can be reduced. Specific examples include aromatic amine-based materials such as starburst arylamines such as benzidine derivatives, 4,4',4"-tris(3-methylphenyl(phenyl)amino)triphenylamine (m-MTDATA), and 4,4',4"-tris(1-naphthyl(phenyl)amino)triphenylamine (1-TNATA); heterocyclic compounds such as carbazole derivatives, pyrazoline derivatives, stilbene-based compounds, hydrazone-based compounds, benzofuran derivatives, thiophene derivatives, oxadiazole derivatives, phthalocyanine derivatives, and porphyrin derivatives; and polymer-based materials such as polycarbonates and styrene derivatives having the above-mentioned monomers in the side chains, polythiophenes such as PEDOT / PSS, polyanilines, polyfluorenes, polyvinylcarbazoles, and polysilanes. These materials may be used alone or in combination of two or more materials. A hole injection layer may be formed by laminating a plurality of materials.

[0115] 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 an acceptor material alone, or the donor material may be doped with the acceptor material. The acceptor material is a material that forms a charge transfer complex between the adjacent hole transport layer when used alone, and between the donor material when used doped with the donor material. The use of such a material is more preferred because it contributes to improving the conductivity of the hole injection layer and reducing the driving voltage of the device, and provides effects such as improving the luminous efficiency and improving the durability and life. Examples of the acceptor material include metal oxides such as molybdenum oxide, vanadium oxide, tungsten oxide, and ruthenium oxide; charge transfer complexes such as tris(4-bromophenyl)aminium hexachloroantimonate (TBPAH); n-type organic semiconductor compounds such as 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile (HAT-CN6), 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ), and fluorinated copper phthalocyanine; and fullerene. When the hole injection layer contains an acceptor material, the hole injection layer may be a single layer or may be configured by laminating multiple layers.

[0116] (Hole transport layer) The hole transport layer is a layer that transports holes injected from the anode to the light emitting layer. The hole transport layer may be a single layer or a laminate of multiple layers.

[0117] The hole transport layer is formed by laminating or mixing one type of hole transport material alone or two or more types of hole transport materials. It is preferable that the hole transport material has high hole injection efficiency and efficiently transports the injected holes. For this purpose, it is required that the material has an appropriate ionization potential, a large hole mobility, excellent stability, and is unlikely to generate impurities that become traps.

[0118] Substances that satisfy such conditions include, but are not limited to, benzidine derivatives, aromatic amine-based materials called starburst arylamines, for example; heterocyclic compounds such as carbazole derivatives, pyrazoline derivatives, stilbene compounds, hydrazone compounds, benzofuran derivatives, dibenzofuran derivatives, thiophene derivatives, benzothiophene derivatives, dibenzothiophene derivatives, fluorene derivatives, spirofluorene derivatives, oxadiazole derivatives, phthalocyanine derivatives, and porphyrin derivatives; and polymer-based compounds such as polycarbonates and styrene derivatives having the above-mentioned monomers in their side chains, polythiophenes, polyanilines, polyfluorenes, polyvinylcarbazoles, and polysilanes.

[0119] (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 is preferable to have a first compound and a second compound that is a dopant that exhibits strong light emission. Suitable examples of the first compound include, for example, a host material that is responsible for charge transfer and a thermally activated delayed fluorescent compound.

[0120] The pyrromethene boron complex represented by the general formula (1) has a particularly excellent fluorescence quantum yield, and has a narrow half-width of the emission spectrum, so that it can achieve high color purity, and is therefore preferably used as the second compound, which is a dopant for the light-emitting layer. If the doping amount of the second compound is too large, concentration quenching occurs, so it is preferably 20% by weight or less, more preferably 10% by weight or less, even more preferably 5% by weight or less, and most preferably 2% by weight or less, based on the weight of the entire light-emitting layer. If the doping concentration is too low, sufficient energy transfer is difficult to occur, so it is preferably 0.1% by weight or more, more preferably 0.5% by weight or more, based on the weight of the entire light-emitting layer.

[0121] The host material is not limited to a single type of compound, and may be a mixture of two or more types, or may be laminated. The host material is not particularly limited, but may be a compound having a condensed aryl ring such as naphthacene, pyrene, anthracene, or fluoranthene, or a derivative thereof; an aromatic amine derivative such as N,N'-dinaphthyl-N,N'-diphenyl-4,4'-diphenyl-1,1'-diamine; a metal chelated oxinoid compound such as tris(8-quinolinato)aluminum(III); a bisstyryl derivative such as a distyrylbenzene derivative; a tetraphenylbutadiene derivative, an indene derivative, a coumarin derivative, an oxadiazole derivative, a pyrrolopyridine derivative, a perinone derivative, a pyrrolopyrrole derivative, a thiadiazolopyridine derivative, a dibenzofuran derivative, a carbazole derivative, an indolocarbazole derivative, or a triazine derivative; or a polymer-based compound such as a polyphenylenevinylene derivative, a polyparaphenylene derivative, a polyfluorene derivative, a polyvinylcarbazole derivative, or a polythiophene derivative. An anthracene derivative or a naphthacene derivative is particularly preferred as the host material.

[0122] The dopant material is not particularly limited, but may contain a fluorescent material other than the pyrromethene boron complex represented by the general formula (1). Specific examples include compounds having condensed aryl rings such as naphthacene, pyrene, anthracene, and fluoranthene, and derivatives thereof; compounds having heteroaryl rings and derivatives thereof; distyrylbenzene derivatives, aminostyryl derivatives, tetraphenylbutadiene derivatives, stilbene derivatives, aldazine derivatives, pyrromethene derivatives, diketopyrrolo[3,4-c]pyrrole derivatives, coumarin derivatives, azole derivatives and metal complexes thereof, and aromatic amine derivatives.

[0123] The dopant material may contain a phosphorescent material. The phosphorescent dopant is preferably a metal complex compound containing at least one metal selected from the group consisting of iridium (Ir), ruthenium (Ru), palladium (Pd), platinum (Pt), osmium (Os), and rhenium (Re), and is more preferably an iridium complex or a platinum complex from the viewpoint of highly efficient light emission. The ligand preferably has a nitrogen-containing heteroaryl group such as a phenylpyridine skeleton, a phenylquinoline skeleton, or a carbene skeleton, but is not limited thereto.

[0124] However, from the viewpoint of increasing color purity, the dopant material is preferably one kind of pyrromethene boron complex represented by the general formula (1).

[0125] In addition to the above host material or dopant material, the light-emitting layer may further contain a third component for adjusting the carrier balance in the light-emitting layer or for stabilizing the layer structure of the light-emitting layer. However, as the third component, a material that does not cause an interaction between the host material and the dopant material is selected.

[0126] Thermally activated delayed fluorescent compounds are generally also called TADF materials, and are materials that promote reverse intersystem crossing from a triplet excited state to a singlet excited state by reducing the energy gap between the energy levels of the singlet excited state and the triplet excited state, thereby improving the probability of generating singlet excitons. The difference between the lowest excited singlet energy level and the lowest excited triplet energy level in a TADF material (ΔEST) is preferably 0.3 eV or less. By utilizing delayed fluorescence due to this TADF mechanism, the theoretical internal efficiency can be increased to 100%. Furthermore, when Förster-type energy transfer occurs from the singlet exciton of a first compound having thermally activated delayed fluorescence to the singlet exciton of a second compound, fluorescence emission from the singlet exciton of the second compound is observed. For such energy transfer to occur, it is preferable that the lowest excited singlet energy level of the first compound is higher than the lowest excited singlet energy level of the second compound. Here, when the second compound is a fluorescent material having a sharp emission spectrum, a light-emitting device with high efficiency and high color purity can be obtained. In this way, when the light-emitting layer contains a thermally activated delayed fluorescent compound, it is possible to achieve high-efficiency light emission, which contributes to reducing the power consumption of the display. The thermally activated delayed fluorescent compound may be a compound that exhibits thermally activated delayed fluorescence with a single material, or may be a compound that exhibits thermally activated delayed fluorescence with multiple compounds, such as when forming an exciplex complex.

[0127] The thermally activated delayed fluorescent compound may be a single compound or a mixture of multiple compounds, and known materials may be used. Specific examples include benzonitrile derivatives, triazine derivatives, disulfoxide derivatives, carbazole derivatives, indolocarbazole derivatives, dihydrophenazine derivatives, thiazole derivatives, and oxadiazole derivatives. In particular, a compound having an electron donor portion (donor portion) and an electron withdrawing portion (acceptor portion) in the same molecule is preferable. The electron donor portion (donor portion) and the electron withdrawing portion may be directly bonded via a single bond or a spiro bond, or may be bonded via a linking group. Examples of such compounds include compounds having a structure represented by the following general formula (3).

[0128] [ka]

[0129] In the general formula (3), A is an electron-withdrawing moiety, B is an electron-donating moiety, and L is a linking group. When a plurality of As are present, the plurality of As may be the same or different from one another, and may be bonded to each other to form a ring structure. When a plurality of Bs are present, the plurality of Bs may be the same or different from one another, and may be bonded to each other to form a ring structure.

[0130] L is a direct bond or a group selected from the group consisting of a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 ring carbon atoms, a substituted or unsubstituted heteroaromatic ring group having 5 to 30 ring atoms, a group in which 2 to 5 of these groups are linked together, and a methylene group having a fluorinated alkyl group. Here, the direct bond includes a single bond and a spiro bond. However, the heteroaromatic ring group does not include an aromatic amino group having electron donating properties or a π-electron-rich heterocyclic functional group.

[0131] a and b each independently represents an integer of 1 to 5.

[0132] A plurality of L's may be present in the same molecule. When a plurality of L's are present, the plurality of L's may be the same or different, and the L's may be bonded to each other to form a saturated or unsaturated ring. In addition, a plurality of L's may be bonded via A and / or B. When a plurality of A's and / or B's and a plurality of L's are present, a plurality of A's and / or B's may be bonded to the same L or to different L's.

[0133] Here, the electron-donating portion (donor portion) refers to a portion that is relatively electron-rich with respect to the adjacent portion. For example, aromatic amino groups and π-electron-rich heterocyclic functional groups can be mentioned. Specific examples include diarylamino groups, carbazolyl groups, benzocarbazolyl groups, dibenzocarbazolyl groups, indolocarbazolyl groups, dihydroacridinyl groups, phenoxazinyl groups, dihydrophenazinyl groups, and groups in which a plurality of these groups are linked together. These groups may be further substituted or unsubstituted. In the case of substitution, examples of the substituent include the above-mentioned preferred examples of the substituent.

[0134] The electron-withdrawing portion (acceptor portion) refers to a portion that is relatively electron-deficient with respect to the adjacent portion. For example, an electron-withdrawing group, a phenyl group having an electron-withdrawing group as a substituent, or a π-electron-deficient heterocyclic functional group can be mentioned. Specific examples include an electron-withdrawing group selected from a carbonyl group, a sulfonyl group, a cyano group, and a fluorine atom, a phenyl group having an electron-withdrawing group as a substituent, a pyrimidinyl group, and a triazinyl group. These groups may be further substituted or unsubstituted. In the case of substitution, examples of the substituent include the above-mentioned preferred examples of the substituent.

[0135] Examples of the aromatic hydrocarbon group having 6 to 30 ring carbon atoms used as the linking group L include (a+b)-valent groups obtained by removing some hydrogen atoms from an aryl group, such as a phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, a fluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenanthryl group, an anthracenyl group, a benzophenanthryl group, a benzoanthracenyl group, a chrysenyl group, a pyrenyl group, a fluoranthenyl group, a triphenylenyl group, a benzofluoranthenyl group, a dibenzoanthracenyl group, a perylenyl group, or a helicenyl group.

[0136] Examples of the heteroaromatic ring group having 5 to 30 ring atoms used as the linking group L include (a+b)-valent cyclic aromatic groups obtained by removing some hydrogen from a heteroaryl group having one or more atoms other than carbon and hydrogen, i.e., a heteroatom, in the ring, such as a pyridyl group, a furanyl group, a thiophenyl group, a quinolinyl group, an isoquinolinyl group, a pyrazinyl group, a pyrimidyl group, a pyridazinyl group, a triazinyl group, a naphthyridinyl group, a cinnolinyl group, a phthalazinyl group, a quinoxalinyl group, a quinazolinyl group, a benzofuranyl group, a benzothiophenyl group, an indolyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzoquinolinyl group, a benzimidazolyl group, an imidazopyridyl group, a benzoxazolyl group, a benzothiazolyl group, and a phenanthrolinyl group. The heteroatom is preferably a nitrogen atom, an oxygen atom, or a sulfur atom. The heteroaromatic ring group may be substituted or unsubstituted.

[0137] Such a thermally activated delayed fluorescent compound is not particularly limited, but examples thereof include the following.

[0138] [ka]

[0139] [ka]

[0140]

change

[0141]

change

[0142]

change

[0143]

change

[0144]

change

[0145]

change

[0146]

change

[0147]

change

[0148]

change

[0149]

change

[0150]

change

[0151] [ka]

[0152] It is preferable that the first compound is a thermally activated delayed fluorescent compound, and the second compound is a pyrromethene boron complex represented by the general formula (1). In addition, when the first compound is a thermally activated delayed fluorescent compound, it is preferable that the light-emitting layer further contains a third compound whose singlet energy is larger than that of the first compound. This allows the third compound to have a function of trapping the energy of the light-emitting material in the light-emitting layer, making it possible to emit light efficiently. It is also preferable that the lowest excited triplet energy of the third compound is larger than the lowest excited triplet energy of the first compound.

[0153] Such a third compound is preferably an organic compound having high charge transport ability and high glass transition temperature. The third compound is not particularly limited, but examples thereof include the following.

[0154] [ka]

[0155] [ka]

[0156] [ka]

[0157] [ka]

[0158] [ka]

[0159] [ka]

[0160] [ka]

[0161] [ka]

[0162] [ka]

[0163] [ka]

[0164] [ka]

[0165] The third compound may be composed of a single material or two or more materials. When two or more materials are used as the third compound, it is preferable that the third compound is a combination of an electron-transporting third compound and a hole-transporting third compound. By combining the third compound with an electron-transporting third compound and the third compound with a hole-transporting third compound at an appropriate mixing ratio, the charge balance in the light-emitting layer can be adjusted, and the light-emitting region can be suppressed from being biased, thereby improving the reliability of the light-emitting device and increasing its durability. In addition, an exciplex may be formed between the third compound with an electron-transporting third compound and the third compound with a hole-transporting third compound. From the above viewpoint, it is preferable that the first compound and the third compound satisfy the following relational formulas 1 to 4, respectively. It is more preferable that the first compound and the third compound satisfy the following relational formulas 1 and 2, and it is even .... It is even more preferable that the first compound and the third compound satisfy all of the formulas 1 to 4. S1 (third electron transporting compound)>S1 (first compound) (Formula 1) S1 (third compound having hole transporting properties)>S1 (first compound) (Formula 2) T1 (third electron transporting compound)>T1 (first compound) (Formula 3) T1 (third compound having hole transporting properties)>T1 (first compound) (Formula 4) Here, S1 represents the energy level of the lowest excited singlet state of each compound, and T1 represents the energy level of the lowest excited triplet state of each compound.

[0166] Examples of the third electron transporting compound include compounds containing a π-electron deficient heteroaromatic ring. Specifically, 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (TAZ), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene (OXD-7), 9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole (CO11), 2,2',2' Heterocyclic compounds with polyazole skeletons such as '-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole) (TPBI) and 2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole (mDBTBIm-II); 2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (2mDBTPDBq-II), 2-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline ( 2mDBTBPDBq-II), 2-[4-(3,6-diphenyl-9H-carbazol-9-yl)phenyl]dibenzo[f,h]quinoxaline (2CzPDBq-III), 7-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (7mDBTPDBq-II), and 6-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (6mDBTPDBq-II), 2-[3'-(9H-carbazol-9-yl)biphenyl-3-yl]dibenzo[f ,h]quinoxaline (2mCzBPDBq) and other heterocyclic compounds having a quinoxaline or dibenzoquinoxaline skeleton; 4,6-bis[3-(phenanthren-9-yl)phenyl]pyrimidine (4,6mPnP2Pm), 4,6-bis[3-(9H-carbazol-9-yl)phenyl]pyrimidine (4,6mCzP2Pm), 4,6-bis[3-(4-dibenzothienyl)phenyl]pyrimidine (4,6mDBTP2Pm-II) and other heterocyclic compounds having a diazine skeleton (pyrimidine skeleton or pyrazine skeleton);Examples of heterocyclic compounds having a pyridine skeleton include 3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine (3,5DCzPPy), 1,3,5-tri[3-(3-pyridyl)phenyl]benzene (TmPyPB), and 3,3',5,5'-tetra[(m-pyridyl)-phen-3-yl]biphenyl (BP4mPy).

[0167] Examples of the third hole transporting compound include compounds containing a π-electron rich heteroaromatic ring.Specific examples of the third hole transporting compound include 1,3-bis(N-carbazolyl)benzene, 4,4'-di(N-carbazolyl)biphenyl (CBP), 3,3'-di(N-carbazolyl)biphenyl (mCBP), 1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (TCPB), 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (CzPA), 1,4-bis[4-(N-carbazolyl)phenyl]-2,3,5,6-tetraphenylbenzene, 9-phenyl-9H-3-(9-phenyl-9H-carbazol-3-yl)carbazole, and 3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino] Examples of compounds having a carbazole skeleton include 1,1-biphenyl-4-yl)-9'-([1,1':4',1"-terphenyl]-4-yl)-9H,9'H-3,3'-bicarbazole, 9-([1,1':4',1"-terphenyl]-4-yl)-9'-(naphthalen-2-yl)-9H,9'H-3,3'-bicarbazole, and 9,9',9"-triphenyl-9H,9'H,9"H-3,3':6',3"-tricarbazole.

[0168] (electron transport layer) The electron transport layer is a layer into which electrons are injected from the cathode and further transports the electrons. The electron transport material used in the electron transport layer is required to have a large electron affinity, a large electron mobility, excellent stability, and to be a substance that is unlikely to generate impurities that become traps. In addition, compounds with low molecular weights are prone to crystallization and deterioration of film quality, so compounds with a molecular weight of 400 or more are preferred.

[0169] The electron transport layer in the present invention also includes a hole blocking layer capable of efficiently blocking the movement of holes. The hole blocking layer and the electron transport layer may be formed of a single material or a laminate of a plurality of materials.

[0170] Examples of electron transport materials include polycyclic aromatic derivatives, styryl aromatic ring derivatives, quinone derivatives, phosphorus oxide derivatives, quinolinol complexes such as tris(8-quinolinolato)aluminum(III), benzoquinolinol complexes, hydroxyazole complexes, azomethine complexes, tropolone metal complexes, and flavonol metal complexes. It is preferable to use a compound having a heteroaryl group containing electron-accepting nitrogen, since it reduces the driving voltage and provides highly efficient light emission. Here, electron-accepting nitrogen refers to a nitrogen atom that forms multiple bonds with adjacent atoms. Heteroaryl groups containing electron-accepting nitrogen have a large electron affinity, making it easier for electrons to be injected from the cathode, and enabling lower voltage driving. In addition, the supply of electrons to the light-emitting layer increases, increasing the probability of recombination, thereby improving the light-emitting efficiency. Preferred examples of the compound 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, imidazole derivatives, oxazole derivatives, thiazole derivatives, triazole derivatives, oxadiazole derivatives, thiadiazole derivatives, benzimidazole derivatives, benzoxazole derivatives, benzthiazole derivatives, phenanthroimidazole derivatives, and oligopyridine derivatives such as bipyridine and terpyridine.Among them, imidazole derivatives such as tris(N-phenylbenzimidazol-2-yl)benzene, oxadiazole derivatives such as 1,3-bis[(4-tert-butylphenyl)-1,3,4-oxadiazolyl]phenylene; triazole derivatives such as N-naphthyl-2,5-diphenyl-1,3,4-triazole; phenanthroline derivatives such as bathocuproine and 1,3-bis(1,10-phenanthroline-9-yl)benzene; 2,2'-bis(benzo[h]quinolin-2-yl) Benzoquinoline derivatives such as 9,9'-spirobifluorene; bipyridine derivatives such as 2,5-bis(6'-(2',2"-bipyridyl))-1,1-dimethyl-3,4-diphenylsilole; terpyridine derivatives such as 1,3-bis(4'-(2,2':6'2"-terpyridinyl))benzene; naphthyridine derivatives such as bis(1-naphthyl)-4-(1,8-naphthyridin-2-yl)phenylphosphine oxide, and triazine derivatives are preferably used from the viewpoint of electron transport ability.

[0171] In addition, when the electron transport material has a condensed polycyclic aromatic skeleton, the glass transition temperature is improved, and the electron mobility is large, so that a lower voltage can be achieved, which is more preferable. As such a condensed polycyclic aromatic skeleton, a fluoranthene skeleton, an anthracene skeleton, a pyrene skeleton, or a phenanthroline skeleton is preferable, and a fluoranthene skeleton or a phenanthroline skeleton is particularly preferable.

[0172] The electron transport material may be used alone or in combination of two or more kinds. The electron transport layer may contain a donor material. Here, the donor material is a compound that improves the electron injection barrier, facilitates electron injection from the cathode or the electron injection layer to the electron transport layer, and further improves the electrical conductivity of the electron transport layer.

[0173] Preferable 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, inorganic salts containing alkaline earth metals, complexes of alkaline earth metals and organic substances, rare earth metals such as Eu and Yb, inorganic salts containing rare earth metals, complexes of rare earth metals and organic substances, etc. As the donor material, metallic lithium, rare earth metals, or lithium quinolinol (Liq) are particularly preferable.

[0174] (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 helping the injection of electrons from the cathode to the electron transport layer, and is composed of a compound having a heteroaryl ring structure containing electron-accepting nitrogen or the above-mentioned donor material. For example, a phenanthroline derivative represented by the general formula (4) described later is preferable.

[0175] Furthermore, inorganic insulators or semiconductors can also be used for the electron injection layer, which is preferable because the use of these materials can prevent short circuits in the light emitting device and improve the electron injection properties.

[0176] As such an insulator, it is preferable to use at least one metal compound selected from the group consisting of alkali metal chalcogenides, alkaline earth metal chalcogenides, alkali metal halides, and alkaline earth metal halides.

[0177] (Charge generation layer) The charge generation layer in the present invention is a layer that generates or separates charges by application of a voltage and injects charges into adjacent layers. The charge generation layer may be formed of one layer, or multiple layers may be laminated. In general, a layer that easily generates electrons as charges is called an n-type charge generation layer, and a layer that easily generates holes is called a p-type charge generation layer. The charge generation layer is preferably made of a double layer, and a pn junction type charge generation layer made of an n-type charge generation layer and a p-type charge generation layer is more preferable. In a light-emitting device, a pn junction type charge generation layer generates charges or separates charges into holes and electrons by application of a voltage, and injects these holes and electrons into the light-emitting layer via a hole transport layer and an electron transport layer. Specifically, in a light-emitting device including multiple light-emitting layers, when a charge generation layer is used as an intermediate layer, the n-type charge generation layer supplies electrons to the first light-emitting layer present on the anode side, and the p-type charge generation layer supplies holes to the second light-emitting layer present on the cathode side. Therefore, in a light-emitting element having two or more light-emitting layers, by having one or more charge generating layers between the light-emitting layers, the efficiency of the element can be further improved, the driving voltage can be reduced, and the durability of the element can be further improved.

[0178] The n-type charge generating layer is composed of an n-type dopant and an n-type host, and these may be conventional materials. For example, the donor material exemplified as the material of the electron transport layer is preferably used as the n-type dopant. Among these, alkali metals or their salts, and rare earth metals are preferred, and materials selected from metallic lithium, lithium fluoride (LiF), lithium quinolinol (Liq) and metallic ytterbium are more preferred. In addition, as the n-type host, those exemplified as the electron transport material are preferably used. Among these, materials selected from triazine derivatives, phenanthroline derivatives and oligopyridine derivatives are preferred, phenanthroline derivatives or terpyridine derivatives are more preferred, and phenanthroline derivatives represented by the following general formula (4) are even more preferred. That is, it is preferred that the charge generating layer contains a phenanthroline derivative represented by general formula (4).

[0179] [ka]

[0180] In the above general formula (4), Ar 2 is selected from the group consisting of p-valent aromatic hydrocarbon groups and p-valent heteroaromatic ring groups. p is a natural number from 1 to 3. 15 ~R 22 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. 2 In the above, the substitution positions of the p phenanthrolyl groups are arbitrary positions.

[0181] Examples of the aromatic hydrocarbon group and the heteroaromatic ring group include, but are not limited to, those described above as examples of the aryl group and the heteroaryl group. The aromatic hydrocarbon group or the heteroaromatic ring group may further have a substituent other than the phenanthryl group.

[0182] From the viewpoint of sublimability and thin film formability, p is preferably 2.

[0183] An example of the phenanthroline derivative represented by the general formula (4) is shown below.

[0184] [ka]

[0185] The p-type charge generating layer is composed of a p-type dopant and a p-type host, and these may be conventional materials. For example, the p-type dopant may be an acceptor material exemplified as the material for the hole injection layer, or iodine or FeCl 3 , FeF 3 , SbCl 5 Specifically, HAT-CN6, F4-TCNQ, tetracyanoquinodimethane derivatives, radialene derivatives, iodine, FeCl 3 , FeF 3 , SbCl 5Among these, radialene derivatives such as HAT-CN6, (2E,2'E,2''E)-2,2',2''-(cyclopropane-1,2,3-triylidene)tris(2-(perfluorophenyl)-acetonitrile), and (2E,2'E,2''E)-2,2',2''-(cyclopropane-1,2,3-triylidene)tris(2-(4-cyanoperfluorophenyl)-acetonitrile) are more preferred. A thin film of a p-type dopant may be formed, and the thickness of the thin film is preferably 10 nm or less. As a p-type host, an arylamine derivative is preferred.

[0186] (Method of forming light-emitting element) The method for forming each of the above layers constituting the light-emitting element may be any of a dry process or a wet process, and may be, but is not limited to, resistance heating deposition, electron beam deposition, sputtering, molecular lamination, coating, inkjet, printing, etc., but resistance heating deposition is usually preferred in terms of element characteristics.

[0187] The thickness of the organic layer is not limited because it depends on the resistance value of the light-emitting material, but is preferably 1 to 1000 nm. The thickness of each of the light-emitting layer, the electron transport layer, and the hole transport layer is preferably 1 nm or more and 200 nm or less, and more preferably 5 nm or more and 100 nm or less.

[0188] (Light Emitting Element Characteristics) The light-emitting element according to the embodiment of the present invention has a function of converting electric energy into light. Here, a direct current is mainly used as the electric energy, but a pulse current or an alternating current can also be used. There are no particular limitations on the current value and voltage value, and the characteristic values ​​required for the element differ depending on the purpose of the element. However, it is preferable that a high brightness can be obtained at a low voltage from the viewpoint of the power consumption and life of the element.

[0189] From the viewpoint of enhancing color purity, the light-emitting element according to the embodiment of the present invention preferably has a half-width of the emission spectrum when a current is passed therethrough of 60 nm or less, more preferably 50 nm or less, even more preferably 45 nm or less, and particularly preferably 30 nm or less.

[0190] Since the light-emitting element of the present invention has a narrow half-width of the emission spectrum, it is more preferable to use it as a top-emission type light-emitting element. Due to the resonance effect of the microcavity, the narrower the half-width of the top-emission type light-emitting element, the higher the luminous efficiency. Therefore, it is possible to achieve both high color purity and high luminous efficiency.

[0191] (Application of light-emitting element) The light emitting device according to the embodiment of the present invention is suitably used as a display device such as a display that displays in a matrix and / or segment mode.

[0192] The light-emitting element according to the embodiment of the present invention is also preferably used as a backlight for various devices. Backlights are mainly used for the purpose of improving the visibility of display devices such as non-self-luminous displays, and are used in display devices such as liquid crystal displays, clocks, audio devices, automobile panels, display boards, and signs. In particular, the light-emitting element of the present invention is preferably used as a backlight for liquid crystal displays, especially for personal computers, which are being considered for thinning, and can provide a backlight that is thinner and lighter than conventional ones.

[0193] The light-emitting element according to the embodiment of the present invention is also preferably used as various lighting devices. The light-emitting element according to the embodiment of the present invention can achieve both high luminous efficiency and high color purity, and can also be made thin and lightweight, so that a lighting device that combines low power consumption, vivid luminous color, and high designability can be realized. EXAMPLES

[0194] The present invention will be described below with reference to examples, but the present invention is not limited to these examples. It should be noted that Examples 3-5, 11, 13, 14, 17, and 20 are currently reference examples, and Examples 1, 2, 6-10, 12, 15, 16, 18, and 19 are examples of the present invention.

[0195] Synthesis Example 1 Method for synthesizing compound D-1 Compound D-1 was synthesized according to the following reaction scheme.

[0196] [ka]

[0197] 5.35g of 2,6-dibromobenzaldehyde, 7.40g of 4-t-butylphenylboronic acid, 5.38g of sodium carbonate, 100mL of dimethoxyethane, and 20mL of water were placed in a flask and substituted with nitrogen. 142mg of bis(triphenylphosphine)palladium(II) dichloride was added thereto and refluxed for 4 hours. The reaction solution was cooled to room temperature, and the organic layer was separated, dried over magnesium sulfate, filtered, and the solvent was distilled off. Methanol was added to the resulting reaction product, and 4.03g of 2,6-bis(pt-butylphenyl)benzaldehyde was obtained as a white solid by filtering.

[0198] 4.03 g of 2,6-bis(pt-butylphenyl)benzaldehyde and 2.17 g of 2,4-dimethylpyrrole thus obtained were placed in a reaction vessel, and 360 mL of dichloromethane and 5 drops of trifluoroacetic acid were added and stirred at room temperature for one week. 2.70 g of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) was further added and stirred at room temperature for four days. Then, the mixture was filtered and the solvent was distilled off. 360 mL of dichloromethane and 5.90 mL of diisopropylethylamine were added to the reaction product obtained and stirred at room temperature for 30 minutes, and 4.10 mL of boron trifluoride diethyl ether complex was added and stirred at room temperature for four hours, after which the solvent was distilled off, water was added and stirred. The organic layer was separated and washed with saturated saline. This organic layer was dried over magnesium sulfate, filtered and the solvent was distilled off. The reaction product obtained was purified by silica gel chromatography to obtain 580 mg of a red powder. The obtained powder was 1Analysis by 1 H-NMR and LC-MS confirmed that the red powder was a pyrromethene boron complex, compound D-1. 1 H-NMR (CDCl 3 (d=ppm)):7.52(d,1H),7.43(d,2H),7.23-7.17(m,4H),7.10(d,4H),5.79(s,2H),2.38(s,6H),1.52(s,6H),1.22(s,18H) MS(m / z) Molecular weight: 589.

[0199] The luminescence characteristics of compound D-1 in solution are shown below. Absorption spectrum (solvent: toluene): λmax 513nm Fluorescence spectrum (solvent: toluene): λmax 526nm, half width 23nm Fluorescence quantum yield (solvent: toluene, excitation light: 460 nm): 100%.

[0200] To further increase the purity, sublimation purification was performed. The metal container containing compound D-1 was placed in a glass tube, and this was diluted with 1×10 -3 Compound D-1 was sublimated by heating at 190° C. under a pressure of 100 Pa. The solid adhering to the wall of the glass tube was collected, and the purity was confirmed to be 99% by LC-MS analysis.

[0201] Synthesis Example 2 Method for synthesizing compound D-2 Compound D-2 was synthesized according to the following reaction scheme.

[0202] [ka]

[0203] 4.16g of 2,4,6-trichlorobenzaldehyde, 11.0g of 4-t-butylphenylboronic acid, 21.12g of potassium phosphate, 100mL of dioxane, and 20mL of water were placed in a flask and substituted with nitrogen. 229mg of bis(dibenzylideneacetone)palladium(0) and 379mg of XPhos were added thereto and refluxed for 2 hours. The reaction solution was cooled to room temperature, and the organic layer was separated, dried over magnesium sulfate, filtered, and the solvent was distilled off. The resulting reaction product was purified by silica gel chromatography to obtain 9.76g of 2,4,6-tri(pt-butylphenyl)benzaldehyde as a white solid.

[0204] 9.76 g of 2,4,6-tri(pt-butylphenyl)benzaldehyde and 5.54 g of 2,4-dimethylpyrrole thus obtained were placed in a reaction vessel, 200 mL of toluene and 5 drops of trifluoroacetic acid were added, and the mixture was stirred at 40°C for 30 minutes. Water was then added and stirred, and the organic layer was separated and washed with saturated saline. This organic layer was dried over magnesium sulfate, filtered, and the solvent was distilled off. The reaction product thus obtained, 8.81 g of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), and 200 mL of toluene were placed in a flask and stirred at 40°C for 30 minutes. Then, 17.2 mL of diisopropylethylamine and 12.2 mL of boron trifluoride diethyl ether complex were added, and the mixture was stirred at room temperature for 30 minutes. Water was then added and stirred. The organic layer was separated and washed with saturated saline. This organic layer was dried over magnesium sulfate, filtered, and the solvent was distilled off. The reaction product thus obtained was purified by silica gel chromatography, and 3.63 g of red powder was obtained. The resulting powder 1 Analysis by 1 H-NMR and LC-MS confirmed that the red powder was a pyrromethene boron complex, compound D-2. 1 H-NMR (CDCl 3 (d=ppm)):7.72-7.63(m,4H),7.47(d,2H),7.23-7.12(m,8H),5.81(s,2H),2.38(s,6H),1.57(s,6H),1.32(s,9H),1.22(s,18H) MS(m / z) Molecular weight: 721.

[0205] The luminescence characteristics of compound D-2 in solution are shown below. Absorption spectrum (solvent: toluene): λmax 513nm Fluorescence spectrum (solvent: toluene): λmax 527nm, half width 22nm Fluorescence quantum yield (solvent: toluene, excitation light: 460 nm): 100%.

[0206] To further increase the purity, sublimation purification was performed. The metal container containing compound D-2 was placed in a glass tube, and this was diluted with 1×10 -3 Compound D-2 was sublimated by heating at 240° C. under a pressure of 100 Pa. The solid adhering to the wall of the glass tube was collected, and the purity was confirmed to be 99% by LC-MS analysis.

[0207] The pyrromethene boron complexes used in the following examples and comparative examples are the compounds shown below. The molecular weights and luminescence properties of these pyrromethene boron complexes measured in toluene solutions are shown in Table 1.

[0208] [ka]

[0209] [ka]

[0210] [Table 1]

[0211] Example 1 (Fluorescent light emitting device evaluation) A glass substrate (Geomatec Co., Ltd., 11 Ω / □, sputtered product) on which an ITO transparent conductive film was deposited to 165 nm as an anode was cut into a size of 38 × 46 mm and etched. The resulting substrate was ultrasonically cleaned with "Semicoclean 56" (trade name, Furuuchi Chemical Co., Ltd.) for 15 minutes, then washed with ultrapure water and dried.

[0212] This substrate was treated with UV-ozone for 1 hour immediately before the element fabrication, and then placed in a vacuum deposition apparatus. The pressure in the apparatus was adjusted to 5×10 -4 The vacuum was evacuated until the pressure was below 1 Pa. First, 10 nm of HAT-CN6 was deposited as a hole injection layer, and 50 nm of HT-1 was deposited as a hole transport layer by resistance heating. Next, H-1 was deposited as a host material and compound D-1 was deposited as a dopant material to a thickness of 20 nm so that the doping concentration was 1.0 wt%. Furthermore, ET-1 was deposited as an electron transport layer, and 2E-1 was deposited as a donor material to a thickness of 30 nm so that the deposition rate ratio of ET-1 and 2E-1 was 1:1. Next, 0.5 nm of 2E-1 was deposited as an electron injection layer, and then 1000 nm of magnesium and silver were co-deposited to form a cathode, and a 5 x 5 mm square device was fabricated.

[0213] This light-emitting element is 1000cd / m 2 The emission characteristics when it was emitted at 1000 cd / m2 were a peak emission wavelength of 529 nm, a half-width of 26 nm, and an external quantum efficiency of 4.0%. 2 The device was continuously energized at a current of 0.01 V, and the time required for the device to reach 90% of the initial luminance (hereinafter referred to as LT90) was evaluated. As a result, the LT90 of this light-emitting device was 99 hours. In the above, HAT-CN6, HT-1, H-1, ET-1, and 2E-1 are the compounds shown below.

[0214] [ka]

[0215] Examples 2 to 15, Comparative Examples 1 to 3 A light-emitting device was fabricated and evaluated in the same manner as in Example 1, except that, as the dopant material, the compounds shown in Table 2 were used instead of Compound D-1. The results are shown in Table 2.

[0216] [Table 2]

[0217] As can be seen by referring to Table 2, in Examples 1 to 15, the external quantum efficiency and device durability (LT90) were significantly improved while maintaining a small full width at half maximum, compared to Comparative Examples 1 to 3. This shows that the present invention can provide a light-emitting device having high color purity, high luminous efficiency, and high device durability.

[0218] (Thermal activation delayed fluorescence element evaluation) Example 16 A glass substrate (Geomatec Co., Ltd., 11 Ω / □, sputtered product) with 100 nm of ITO transparent conductive film deposited as an anode was cut into 38 × 46 mm and etched. The obtained substrate was ultrasonically cleaned with "Semicoclean 56" (trade name, Furuuchi Chemical Co., Ltd.) for 15 minutes, and then washed with ultrapure water.

[0219] This substrate was subjected to UV-ozone treatment for 1 hour immediately before fabricating the element, and then placed in a vacuum deposition apparatus. The degree of vacuum in the apparatus was adjusted to 5×10 -4 The vacuum was evacuated until the pressure was below 10 Pa. First, 10 nm of HAT-CN6 was deposited as a hole injection layer, and 40 nm of HT-1 was deposited as a hole transport layer by resistance heating. Next, a host material H-2, a compound D-1, and a compound H-3, which is a TADF material, were deposited as an emission layer to a thickness of 30 nm in a weight ratio of 79.5:0.5:20. Furthermore, as an electron transport layer, a compound ET-1 was used as an electron transport material, and a compound 2E-1 was used as a donor material, and the deposition rate ratio of the compounds ET-1 and 2E-1 was 1:1 to a thickness of 50 nm. Next, 0.5 nm of 2E-1 was deposited as an electron injection layer, and then 1000 nm of magnesium and silver were co-deposited to form a cathode, and a 5 x 5 mm square element was fabricated.

[0220] This light-emitting element is 1000cd / m 2 The emission characteristics when the compound was made to emit light at 1000 nm were an emission peak wavelength of 529 nm, a half-width of 28 nm, an external quantum efficiency of 14.2%, and a LT90 of 80 hours. In the above, H-2 and H-3 are the compounds shown below.

[0221] [ka]

[0222] Examples 17 to 20, Comparative Examples 4 to 6 A light-emitting device was fabricated and evaluated in the same manner as in Example 16, except that the compounds shown in Table 3 were used as dopant materials. The results are shown in Table 3.

[0223] [Table 3]

[0224] As can be seen by referring to Table 3, in Examples 16 to 20, the external quantum efficiency and device durability (LT90) were significantly improved while maintaining a small full width at half maximum, compared to Comparative Examples 4 to 6. This shows that the present invention can provide a light-emitting device having high color purity, high luminous efficiency, and high device durability.

[0225] As described above, it has been demonstrated that the present invention can fabricate a light-emitting device having high color purity, luminous efficiency, and element durability. This shows that the luminous efficiency can be increased in the manufacture of display devices such as displays and lighting devices.

[0226] (Tandem-type fluorescent light-emitting device evaluation) Example 21 A glass substrate (Geomatec Co., Ltd., 11 Ω / □, sputtered product) on which an ITO transparent conductive film was deposited to 165 nm as an anode was cut into 38 mm x 46 mm and etched. The resulting substrate was ultrasonically cleaned for 15 minutes using "Semicoclean" 56 (trade name, Furuuchi Chemical Co., Ltd.), and then washed with ultrapure water.

[0227] This substrate was subjected to UV-ozone treatment for 1 hour immediately before fabricating the element, and then placed in a vacuum deposition apparatus. The degree of vacuum in the apparatus was adjusted to 5×10 -4 The vacuum was evacuated until the pressure was below 10 Pa. First, HAT-CN6 was evaporated as a hole injection layer to 5 nm, followed by HT-1 to 50 nm as a hole transport layer by resistance heating. Next, H-1 was evaporated as a hole blocking layer to 10 nm, and the host material H-1 and the dopant compound D-1 were evaporated as a light emitting layer to a thickness of 20 nm at a weight ratio of 99.5:0.5. Furthermore, ET-1 was laminated as an electron blocking layer to a thickness of 10 nm, and compound ET-3 was laminated as an electron transport layer to a thickness of 35 nm. Next, compound ET-3, which is an n-type host, and metallic lithium, which is an n-type dopant, were laminated as an n-type charge generating layer to a thickness of 10 nm at a deposition rate ratio of 99:1. Furthermore, HAT-CN6 was laminated as a p-type charge generating layer to 10 nm. On top of that, a hole transport layer of 50 nm, a hole blocking layer of 10 nm, and a light emitting layer of 20 nm were formed in the same manner as above. Furthermore, ET-2 was evaporated to a thickness of 10 nm as an electron blocking layer, and ET-3 was evaporated to a thickness of 35 nm as an electron transport layer, in that order. Next, 2E-1 was evaporated to a thickness of 0.5 nm as an electron injection layer, and then magnesium and silver were co-evaporated to a thickness of 1000 nm as a cathode to fabricate a tandem-type light-emitting device measuring 5 mm x 5 mm.

[0228] This light-emitting element is 1000cd / m 2 The emission characteristics when the material was made to emit light at 200° C. were an emission peak wavelength of 530 nm, a half-width of 25 nm, an external quantum efficiency of 4.3%, and a LT90 of 110 hours. It was confirmed that the durability was improved compared to Example 1, which had only one light-emitting layer. In the above, ET-2 and ET-3 are the compounds shown below.

[0229] [ka]

Claims

1. Pyrromethene boron complex represented by general formula (1): 【Chemistry 1】 R 1 to R 4 each independently represent an alkyl group; Both R 5 and R 6 are a hydrogen atom or a substituted or unsubstituted alkyl group; X １ and X ２ are each independently selected from the group consisting of an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a hydroxyl group, a thiol group, an alkoxy group, an alkylthio group, an aryl ether group, an aryl thioether group, an aryl group, a heteroaryl group, a halogen, and a cyano group; these groups may further have a substituent; R ７ is represented by the following general formula (2): 【Chemistry 2】 R ８ ~R １０ are each independently selected from the group consisting of a hydrogen atom, an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a hydroxyl group, a thiol group, an alkoxy group, an alkylthio group, an aryl ether group, an aryl thioether group, an aryl group, a heteroaryl group, a halogen, a cyano group, an aldehyde group, an acyl group, a carboxyl group, an ester group, an amide group, a sulfonyl group, a sulfonate ester group, a sulfonamide group, an amino group, a nitro group, a silyl group, a siloxanyl group, a boryl group, and a phosphine oxide group; these groups may further have a substituent; R １１ represents an aryl group which may further have a substituent; Ar １ is a substituted or unsubstituted aryl group.

2. 13. A light-emitting device comprising an anode, a cathode, and a light-emitting layer present between the anode and the cathode, the light-emitting layer emitting light in response to electrical energy, the light-emitting layer comprising the pyrromethene boron complex according to claim 1.

3. 3. The light-emitting element according to claim 2, wherein the light-emitting layer comprises a first compound and a second compound, the first compound is a thermally activated delayed fluorescent compound, and the second compound is a pyrromethene boron complex represented by the general formula (1).

4. 4. The light-emitting device according to claim 2, wherein the thermally activated delayed fluorescent compound according to claim 3 is a compound having an electron-donating moiety and an electron-withdrawing moiety in the same molecule.

5. 5. The light-emitting device according to claim 2, further comprising at least two light-emitting layers between an anode and a cathode, and at least one charge-generating layer between each of the light-emitting layers.

6. The light-emitting device according to claim 5, wherein the charge generating layer contains a phenanthroline derivative represented by general formula (4): 【Chemistry 3】 In the above general formula (4), Ar ２ is selected from the group consisting of p-valent aromatic hydrocarbon groups and p-valent heteroaromatic ring groups; p is a natural number from 1 to 3; R １５ ~R ２２ 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 ２ In the above, the substitution positions of the p phenanthrolyl groups are arbitrary positions.

7. A display device comprising the light-emitting device according to any one of claims 2 to 6.

8. A lighting device comprising the light-emitting element according to any one of claims 2 to 6.

Images