Triarylboron compounds, organic electroluminescent devices, display devices and lighting devices

Abstract

A problem addressed by the present invention is to provide: a triarylboron compound that has the property of emitting light by thermally activated delayed fluorescence and has excellent thermal stability and chemical stability; and an organic electroluminescent element, a display device, and a lighting device having high luminous efficiency and long life.　The triarylboron compound of the present invention is characterized by having a structure represented by general formula (1).

Description

[Technical Field]

[0001] The present invention relates to a triarylboron compound, an organic electroluminescent device, a display device, and a lighting device. More specifically, the present invention relates to a triarylboron compound that emits light via a thermally activated delayed fluorescence process and has excellent thermal and chemical stability. The present invention also relates to an organic electroluminescent device, a display device, and a lighting device that have high luminous efficiency and long life. [Background technology]

[0002] In recent years, there has been growing interest in display devices and lighting devices that use organic electroluminescence (OLED) elements, which utilize the phenomenon in which organic materials emit light when a voltage is applied, due to their thinness, light weight, high contrast, and fast response.

[0003] For example, triarylboron compounds can be used as materials in organic electroluminescent devices due to the high electron-accepting property of boron. For example, due to their high electron-accepting property, electrons can easily hop and move, making them suitable for use as electron-transporting materials. Furthermore, by substituting the aryl group with a hole-transporting substituent, they can be made bipolar, allowing them to be used as host compounds. However, triarylboron compounds are unstable because the boron has an empty p-orbital, making them susceptible to attack by Lewis bases and nucleophiles.

[0004] Therefore, a two-bridged triarylboron compound has been developed in which the aryl groups are fixed to a plane by having two crosslinking sites (see Non-Patent Document 2). The two-bridged triarylboron compound has high performance as an emitting material, a host material, a thermally activated delayed fluorescent material, an electron transport material, a hole transport material, and the like. For example, nitrogen-bridged boron compounds can be used as emitting materials because they can be designed to have luminescence or thermally activated delayed fluorescent properties with high color purity and high quantum efficiency. Furthermore, oxygen-bridged boron compounds can be used as host materials because they have charge transport properties and the ability to act as a dispersion medium for dopants.

[0005] However, since di-bridged triarylborane compounds have only two cross-linking sites and the molecular structure is not completely fixed to a plane, they have a degree of steric freedom, and there is room for further improvement in their stability against heat and light.

[0006] In response to this, development of three-bridged triarylboron compounds having three crosslinking moieties has been progressing (see Non-Patent Documents 1, 2, and 3). By adding one more crosslinking moiety, the molecular structure is further fixed to a plane, improving thermal stability and device life. However, this also causes changes in physical properties such as a decrease in luminescence, loss of thermally activated delayed fluorescence properties, and changes in energy levels, resulting in a decrease in functionality as a light-emitting material or host material. Therefore, extensive research has been conducted into crosslinking structures that can fix the molecular structure to a plane without changing the physical properties. [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] Hirai, H.; Nakajima, K.; Nakatsuka, S.; Shiren, K.; Ni, J.; Nomura, S.; Ikuta, T.; Hatakeyama, T. One-Step Borylation of 1,3-Diaryloxybenzenes Towards Efficient Materials for Organic Light-Emitting Diodes. Angew. Chem. Int. Ed. 2015, 54, 13581 -13585. [Non-patent document 2] Hatakeyama, T.; Shiren, K.; Nakajima, K.; Nomura, S.; Nakatsuka, S.; Kinoshita, K.; Ni, J.; Ono, Y.; Ikuta, T. Ultrapure Blue Thermally Activated Delayed Fluorescence Molecules: Efficient HOMO-LUMO Separation by the Multiple Resonance Effect. Adv. Mater. 2016, 28, 2777-2781. [Non-patent document 3] Nakatsuka, S.; Gotoh, H.; Kinoshita, K.; Yasuda, N.; Hatakeyama, T. Divergent Synthesis of Heteroatom-Centered 4,8,12-Triazatriangulenes. Angew. Chem. Int. Ed. 2017, 56, 5087-5090. Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made in view of the above problems and circumstances, and an object of the present invention is to provide a triarylboron compound that has the property of emitting light via a thermally activated delayed fluorescence process and has excellent thermal and chemical stability, as well as an organic electroluminescence device, a display device, and a lighting device that have high luminous efficiency and a long lifetime. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems, the present inventors have investigated the causes of the above-mentioned problems and have found that, in a doubly-bridged triarylboron compound having thermally activated delayed fluorescence properties, providing an additional crosslinking moiety to fix an aryl group therein can fix the molecular structure to a plane, thereby achieving thermal stability and chemical stability. Furthermore, by forming the main chain of the crosslinking moiety with multiple atoms, the electronic state at the time of doubly crosslinking can be maintained, and thus physical properties such as luminescence, thermally activated delayed fluorescence properties, and energy levels do not change, leading to the present invention. That is, the above-mentioned problems of the present invention are solved by the following means.

[0010] 1. A structure represented by the following general formula (1) is A triarylboron compound characterized by:

[0011] [ka]

[0012] (Wherein, X1 and X2 is expressed as atom teeth , each independently 、S X1 and X2 may have a substituent Z1, and Z1 represents a hydrogen atom, an alkyl group, an aromatic hydrocarbon ring group, or an aromatic heterocyclic group. When there are a plurality of Z1, they may be the same or different. R1 to R9 each independently represent a hydrogen atom or a substituent. Y is represented by the following general formula (2): do. )

[0013] [ka]

[0014] (In the ceremony 、A The atoms represented by 1 and A2 are Each independently, S or O. The atomic group represented by B1 is NH 、C (Z2)2, B-Z2, P-Z2, Si(Z2)2, or Ge(Z2)2. n is 0 or 1Z2 represents a hydrogen atom, an alkyl group, an aromatic hydrocarbon ring group, or an aromatic heterocyclic group. When there are multiple Z2, they may be the same or different.

[0015] 2. In the general formula (1), represented by X1 and X2 Ruhara 2. The triarylboron compound according to claim 1, wherein each of the atoms is independently C, O, S, N, P, or Si.

[0017] 3 Item 1, characterized in that n is 1 in the general formula (2). or No. In item 2 The triarylboron compound described above.

[0018] 4 In the general formula (2), the atoms represented by A1 and A2 are O. 3 The triarylboron compound according to any one of the preceding claims.

[0019] 5 In the general formula (2), the atomic group represented by B1 is 、C (Z2)2, B-Z2, P-Z2, Si(Z2)2 or Ge(Z2)2. 4 The triarylboron compound according to any one of the preceding claims.

[0020] 6 In the general formula (1), X1 and X2 represent Ruhara Each of the first to third elements is independently either O or N. 5 The triarylboron compound according to any one of the preceding claims.

[0021] 7 In the general formula (1), X1 and X2 represent Ruhara The first to second terms are characterized by the fact that both children are N. 6 The triarylboron compound according to any one of the preceding claims.

[0022] 8 In the general formula (1), Z1 and R1 to R9 each independently represent an azine skeleton, a dibenzofuran skeleton, an azadibenzofuran skeleton, a diazadibenzofuran skeleton, a carboline skeleton, a diazacarbazole skeleton, or an aryl group having an electron-withdrawing group. 7 The triarylboron compound according to any one of the preceding claims.

[0023] 9 In the general formula (1), Z1 and R1 to R9 are each independently either a carbazole skeleton or an aryl group having an electron-donating group. 7 The triarylboron compound according to any one of the preceding claims. 10. Triarylboron compounds represented by the following structural formulas Tab-1 to Tab-8 or 12 to Tab-26. [ka] [ka] [ka] [ka]

[0024] 11. An organic electroluminescence element having an organic layer sandwiched between an anode and a cathode, wherein the organic layer contains the triaryl boron compound described in any one of items 1 to 10.

[0025] 12. A display device comprising the organic electroluminescence element according to item 11.

[0026] 13. A lighting device comprising the organic electroluminescence element according to item 11. [Effects of the Invention]

[0027] The above-described means of the present invention can provide a triarylboron compound that has the property of emitting light through a thermally activated delayed fluorescence process and has excellent thermal and chemical stability, as well as an organic electroluminescence device, a display device, and a lighting device that have high luminous efficiency and a long life.

[0028] The mechanism by which the effects of the present invention are manifested or the mechanism of action is not clear, but is speculated as follows.

[0029] Boron-containing π-electron compounds are unstable because boron has an empty p-orbital and excellent electron-accepting properties, making them susceptible to attack by Lewis bases and nucleophiles. One method for stabilizing these compounds is to make the area around the boron sterically bulky, making them less susceptible to attack by Lewis bases and nucleophiles. However, creating a molecular structure with significant steric hindrance prevents efficient charge transport in the solid state. Therefore, there is a need for a structural design of boron compounds with minimal steric hindrance and where the boron is less susceptible to nucleophilic attack.

[0030] Let's take triphenylborane, a type of triarylboron compound, as an example. Triphenylborane is a compound in which the boron atom and three phenyl groups are sp 2 The three bonds are on the same plane. However, the phenyl group is not fixed on this plane, so when the boron is attacked by a nucleophile such as a Lewis base, it easily undergoes sp 3 The phenyl group is rigidly fixed in the same plane as the three bonds to prevent nucleophilic attack.

[0031] The triarylboron compound of the present invention is characterized in that it is fixed to a plane by three bridging moieties between aryl groups, one of which is a bridging moiety Y. The presence of three bridging moieties allows the boron atom and the three aryl groups to be fixed to the same plane. Furthermore, since one of the three bridging moieties is a bridging moiety Y, changes in physical properties such as a decrease in luminescence, a loss of thermally activated delayed fluorescence properties, and a change in energy level do not occur.

[0032] Although the details of the mechanism by which this function is expressed are still unclear, the following possibilities are speculated.

[0033] It is believed that the triarylboron compound of the present invention has a planar structure fixed by the three bridges, which increases the rigidity of the ring and improves its thermal and electrical stability. Furthermore, electrons on the bridge atoms flow into the electron-deficient boron atom, thereby mitigating the electrophilicity and nucleophilicity of the entire molecule, resulting in stabilization. Furthermore, since the bridge Y is a bridge moiety whose main chain is composed of multiple atoms, nucleophilic attack from the direction of the bridge Y is less likely than in existing three-bridged triarylboron compounds, resulting in improved chemical stability against nucleophiles.

[0034] In existing tri-bridged triarylboron compounds, conjugation extends throughout the entire molecule via three bridging atoms, but in the triarylboron compound of the present invention, the crosslinking moiety Y is a non-conjugated crosslinking moiety whose main chain is composed of multiple atoms, and thus the conjugation throughout the molecule is severable at the crosslinking moiety Y. Therefore, the crosslinking moiety Y increases the rigidity of the molecule, improving stability, and also allows the compound to maintain an electronic state similar to that of a di-bridged triarylboron compound, without causing any change in physical properties. [Brief explanation of the drawings]

[0035] [Figure 1] Schematic diagram showing an example of the configuration of an organic EL element [Figure 2] Schematic diagram showing the mechanism of charge flow and light emission in an organic EL element [Figure 3] An example of a cross-sectional view showing a solar cell made of a bulk heterojunction type organic photoelectric conversion element [Figure 4] Analysis results of the exemplary compound Tab-9 in Example 1 by LC column measurement DETAILED DESCRIPTION OF THE INVENTION

[0036] The triarylboron compound of the present invention is characterized by having a structure represented by the general formula (1) above. This feature is a technical feature common to or corresponding to the following embodiments.

[0037] As an embodiment of the present invention, from the viewpoint of exerting the effects of the present invention, it is preferred that the main chain atoms in the crosslinking moieties represented by X1 and X2 in the general formula (1) are each independently any of C, O, S, N, P, and Si, in terms of thermal stability, chemical stability, luminescence property, and thermally activated delayed fluorescence properties.

[0038] In the general formula (2), n is preferably any one of 1 to 5 from the viewpoints of thermal stability, chemical stability, luminescence property, and thermally activated delayed fluorescence properties, and n is more preferably 1 from the viewpoints of thermal and chemical stability.

[0039] In the general formula (2), it is preferable that the main chain atom in the atoms or atomic groups represented by A1 and A2 is any one of C, O, or N from the viewpoints of thermal stability, chemical stability, luminescence properties, and thermally activated delayed fluorescence properties.

[0040] In the general formula (2), it is preferable that the atomic group represented by B1 is any one of SO2, C(Z2)2, B-Z2, P-Z2, Si(Z2)2, and Ge(Z2)2, from the viewpoints of thermal stability, chemical stability, luminescence, and thermally activated delayed fluorescence properties.

[0041] In the general formula (1), it is preferable that the main chain atoms in the crosslinking moieties represented by X1 and X2 are each independently either O or N, from the viewpoints of thermal stability, chemical stability, luminescence property, and thermally activated delayed fluorescence properties, and it is more preferable that both are N, from the viewpoints of luminescence property and thermally activated delayed fluorescence properties.

[0042] In the general formula (1), it is preferable that Z1 and R1 to R9 each independently represent any one of an azine skeleton, a dibenzofuran skeleton, an azadibenzofuran skeleton, a diazadibenzofuran skeleton, a carboline skeleton, a diazacarbazole skeleton, or an aryl group having an electron-withdrawing group, from the viewpoints of thermal stability, chemical stability, luminescence property, and thermally activated delayed fluorescence properties.

[0043] Alternatively, in the general formula (1), it is preferable that Z1 and R1 to R9 are each independently either a carbazole skeleton or an aryl group having an electron-donating group, from the viewpoints of thermal stability, chemical stability, luminescence, and thermally activated delayed fluorescence properties.

[0044] As an embodiment of the present invention, an organic electroluminescence element in which an organic layer contains the triarylboron compound is preferred, and a display device and a lighting device including the same are preferred.

[0045] The present invention, its components, and embodiments for carrying out the present invention will be described in detail below. In this application, the symbol "to" is used to mean that the numerical values ​​before and after it are included as lower and upper limits.

[0046] [Summary of the Triarylboron Compound of the Present Invention] The triarylboron compound of the present invention is characterized by having a structure represented by the general formula (1) above.

[0047] The triarylboron compound having such a structure can be fixed to a planar molecular structure by providing an additional cross-linking site at one position on the doubly bridged triarylboron compound to fix the aryl group, thereby achieving stability against heat and light. Furthermore, by forming the main chain of the cross-linking site with multiple atoms, the electronic state at the time of doubly bridged can be maintained, so that physical properties such as luminescence, thermally activated delayed fluorescence, and energy level do not change.

[0048] Among existing triarylboron compounds, di-bridged triarylboron compounds are known to have high performance as light-emitting materials, host materials, thermally activated delayed fluorescent materials, electron transport materials, hole transport materials, etc., but there is still room for improvement in terms of their stability against heat and light.

[0049] Therefore, in order to improve stability against heat and light, a tri-bridged triarylboron compound has been known in which an additional cross-linking site has been added to a di-bridged triarylboron compound with the aim of fixing the molecular structure more flat, but this changes the physical properties of the di-bridged triarylboron compound, such as its luminescence, thermally activated delayed fluorescence properties, and energy levels, leaving room for improvement.

[0050] <Triarylboron compound of the present invention> The triarylboron compound of the present invention is a compound in which the molecular structure is fixed to a plane by forming the main chain at the third crosslinking site with a plurality of atoms, and the physical properties of a di-bridged triarylboron compound are retained.

[0051] The triarylboron compound of the present invention is characterized by having a structure represented by the following general formula (1).

[0052] [ka]

[0053] (In the formula, X1 and X2 each independently represent a crosslinking moiety in which a main chain atom is a divalent, trivalent, or tetravalent element. X1 and X2 may have a substituent Z1, and Z1 represents a hydrogen atom, an alkyl group, an aromatic hydrocarbon ring group, or an aromatic heterocyclic group. When there are multiple Z1s, they may be the same or different. R1 to R9 each independently represent a hydrogen atom or a substituent. Y is a crosslinking moiety in which the main chain is composed of multiple atoms, as represented by the following general formula (2).)

[0054] [ka]

[0055] (In the formula, A1, A2, and B1 represent atoms or atomic groups. The types of atoms are not limited and may be the same or different. n is an integer of 0 or greater, and when n is 2 or greater, B1 may be the same or different. Furthermore, A1, A2, and B1 may have a substituent Z2, and Z2 represents a hydrogen atom, an alkyl group, an aromatic hydrocarbon ring group, or an aromatic heterocyclic group. When there are multiple Z2, they may be the same or different.)

[0056] <Crosslinking site X1, X2> X1 and X2 each independently represent a crosslinking moiety in which the main chain atom is a divalent, trivalent, or tetravalent element. X1 and X2 may have a substituent Z1, where Z1 represents a hydrogen atom, an alkyl group, an aromatic hydrocarbon ring group, or an aromatic heterocyclic group. When there are multiple Z1s, they may be the same or different. The main chain atom refers to an atom contained in the main chain.

[0057] The main chain atoms may be divalent, trivalent, or tetravalent elements, such as C, O, S, N, P, Si, Al, B, Ge, Sn, Pb, Se, and Te. C, O, S, N, P, or Si is more preferred from the viewpoints of thermal stability, chemical stability, luminescence, and thermally activated delayed fluorescence properties. It is more preferred that the main chain atoms are either O or N, and it is particularly preferred that both atoms are N.

[0058] The substituent represented by Z1 may be a hydrogen atom, an alkyl group, an aromatic hydrocarbon ring group or an aromatic heterocyclic group, and when there are a plurality of Z1, they may be the same or different.

[0059] The alkyl group represented by Z1 is not particularly limited, and examples thereof include the same alkyl groups as those represented by R1 to R9 described below.

[0060] The aromatic hydrocarbon ring group and aromatic heterocyclic group represented by Z1 are not particularly limited, and examples thereof include those having the same meanings as the aromatic hydrocarbon ring groups and aromatic heterocyclic groups represented by R1 to R9 described below.

[0061] <R1~R9> The substituents represented by R1 to R9 are not particularly limited, but are preferably, for example, an alkyl group, an alkoxy group, an amino group, an aromatic hydrocarbon ring group, an aromatic heterocyclic group, etc. These substituents may also have other substituents as part of their structures.

[0062] The alkyl group represented by R1 to R9 may have any of a linear, branched, and cyclic structure, and includes, for example, a linear, branched, or cyclic alkyl group having 1 to 20 carbon atoms. Specific examples include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an s-butyl group, a t-butyl group, an n-pentyl group, a neopentyl group, an n-hexyl group, a cyclohexyl group, a 2-ethylhexyl group, an n-heptyl group, an n-octyl group, a 2-hexyloctyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group, an n-tridecyl group, an n-tetradecyl group, an n-pentadecyl group, an n-hexadecyl group, an n-heptadecyl group, an n-octadecyl group, an n-nonadecyl group, and an n-icosyl group. Preferred examples of the alkyl group include a methyl group, an ethyl group, an isopropyl group, a t-butyl group, a cyclohexyl group, a 2-ethylhexyl group, and a 2-hexyloctyl group. Substituents on these alkyl groups include a halogen atom, an aromatic hydrocarbon ring group described below, an aromatic heterocyclic group described below, and an amino group described below.

[0063] The alkoxy groups represented by R1 to R9 may have a linear, branched, or cyclic structure. Examples of the alkoxy groups include linear, branched, or cyclic alkoxy groups having 1 to 20 carbon atoms. Specific examples include a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, an isobutoxy group, a t-butoxy group, an n-pentyloxy group, a neopentyloxy group, an n-hexyloxy group, a cyclohexyloxy group, an n-heptyloxy group, an n-octyloxy group, a 2-ethylhexyloxy group, a nonyloxy group, a decyloxy group, a 3,7-dimethyloctyloxy group, an n-undecyloxy group, an n-dodecyloxy group, an n-tridecyloxy group, an n-tetradecyloxy group, a 2-n-hexyl-n-octyloxy group, an n-pentadecyloxy group, an n-hexadecyloxy group, an n-heptadecyloxy group, an n-octadecyloxy group, an n-nonadecyloxy group, and an n-icosyloxy group. Among these, methoxy, ethoxy, isopropoxy, t-butoxy, cyclohexyloxy, 2-ethylhexyloxy, and 2-hexyloctyloxy are preferred. Substituents on these alkoxy groups include halogen atoms, aromatic hydrocarbon ring groups (described later), aromatic heterocyclic groups (described later), and amino groups (described later).

[0064] Examples of aromatic hydrocarbon ring groups represented by R1 to R9 include a benzene ring, an indene ring, a naphthalene ring, an azulene ring, a fluorene ring, a phenanthrene ring, an anthracene ring, an acenaphthylene ring, a biphenylene ring, a chrysene ring, a naphthacene ring, a pyrene ring, a pentalene ring, an aceanthrylene ring, a heptalene ring, a triphenylene ring, an as-indacene ring, a chrysene ring, an s-indacene ring, a pleiadene ring, a phenalene ring, a fluoranthene ring, a perylene ring, an acephenanthrylene ring, a biphenyl ring, a terphenyl ring, and a tetraphenyl ring. Substituents on these aromatic hydrocarbon ring groups include a halogen atom, the alkyl group described above, the alkoxy group described above, the aromatic heterocyclic group described below, and the amino group described below.

[0065] Examples of aromatic heterocyclic groups represented by R1 to R9 include a carbazole ring, an indoloindole ring, a 9,10-dihydroacridine ring, a phenoxazine ring, a phenothiazine ring, a dibenzothiophene ring, a benzofurylindole ring, a benzothienoindole ring, an indolocarbazole ring, a benzofurylcarbazole ring, a benzothienocarbazole ring, a benzothienobenzothiophene ring, a benzocarbazole ring, a dibenzocarbazole ring, a dibenzofuran ring, an azadibenzofuran ring, a diazadibenzofuran ring, a carboline ring, a diazacarbazole ring, a benzofurylbenzofuran ring, a dibenzosilole ring, etc. Substituents possessed by these aromatic heterocyclic groups include a halogen atom, the above-mentioned alkyl group, the above-mentioned alkoxy group, the above-mentioned aromatic hydrocarbon ring group, and the below-mentioned amino group, etc.

[0066] The amino groups represented by R1 to R9 may be substituted amino groups having a substituent, such as a halogen atom, the alkyl group described above, the aromatic hydrocarbon ring group described above, and the aromatic heterocyclic group described above.

[0067] It is particularly preferred that R1 to R9 each independently represent an azine skeleton, a dibenzofuran skeleton, an azadibenzofuran skeleton, a diazadibenzofuran skeleton, a carboline skeleton, a diazacarbazole skeleton, or an aryl group having an electron-withdrawing group. The electron-withdrawing group here refers to a substituent that exhibits electron-withdrawing properties when substituted on a benzene ring. Examples of the aryl group having an electron-withdrawing group include a nitrophenyl group, a trifluoromethylphenyl group, and a sulfonylphenyl group.

[0068] Alternatively, it is particularly preferable that R1 to R9 each independently represent an aryl group having a carbazole skeleton or an electron-donating group. The electron-donating group here refers to a substituent that exhibits electron-donating properties when substituted on a benzene ring. Examples of the aryl group having an electron-donating group include a 4-methoxyphenyl group, an N,N-dimethylaminophenyl group, a tolyl group, a 2-(5-octyl)thienyl group, and a trimethylsilylphenyl group.

[0069] The "electron-withdrawing group" refers to a substituent whose substituent constant σ value of the Hammett Rule is a positive value, while the "electron-donating group" refers to a substituent whose substitution constant σ value is a negative value.

[0070] <Crosslinking site Y> The triarylboron compound of the present invention is most characterized by having a crosslinking moiety Y represented by the general formula (2) above.

[0071] The atoms or atomic groups represented by A1 and A2 are not particularly limited in type, and examples thereof include C, O, S, N, P, Si, Al, B, Ge, Sn, Pb, Se, Te, etc. In the crosslinking moiety Y, A1 and A2 may be the same or different.

[0072] The atoms represented by A1 and A2 are more preferably any of C, O, and N.

[0073] The atom or atomic group represented by B1 is not particularly limited in type, and examples thereof include C, O, S, N, P, Si, Si, Al, B, Ge, Sn, Pb, Se, and Te. A1, A2, and B1 may be the same or different. Furthermore, n is an integer of 0 or greater, and when n is 2 or greater, B1 may be the same or different. n is more preferably an integer of 1 to 5, and particularly preferably 1.

[0074] A1, A2, and B1 may each have a substituent Z2, which represents a hydrogen atom, an alkyl group, an aromatic hydrocarbon ring group, or an aromatic heterocyclic group. Examples of the alkyl group represented by Z2 include the same alkyl groups as those represented by R1 to R9 above.

[0075] Examples of the aromatic hydrocarbon ring group represented by Z2 include the same as the examples of the aromatic hydrocarbon ring groups represented by R1 to R9.

[0076] Examples of the aromatic heterocyclic group represented by Z2 include the same as the examples of the aromatic heterocyclic groups represented by R1 to R9.

[0077] The atom or atomic group represented by B1 is preferably SO2, C(Z2)2, B-Z2, P-Z2, Si(Z2)2, or Ge(Z2)2, examples of which include CH2, C(CH3)2, B(CH3), PH, SiH2, Si(CH3)2, and GeH2.

[0078] <Exemplary Compounds of the Present Invention> Examples of the compound according to the present invention are shown below, but the present invention is not limited to these. [ka]

[0079] [ka]

[0080] [ka]

[0081] [ka]

[0082] [ka]

[0083] [ka]

[0084] [ka]

[0085] [ka]

[0086] [ka]

[0087] [ka]

[0088] [ka]

[0089] <<Method for synthesizing the compound of the present invention>> The exemplary compound represented by Tab-9, which is an example of the triarylboron compound of the present invention, can be synthesized by the following method.

[0090] <Synthesis of exemplary compound Tab-9> [Synthesis of 1-hydroxy-5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracen-13-yl 1,1,2,2,3,3,4,4,4-nonafluorobutane-1-sulfonic acid ester (compound (2))] [ka]

[0091] 979 mg (3.24 mmol) of compound (1) was placed in a 300 mL two-necked recovery flask and heated with a heat gun while purging with nitrogen. 668 μL of distilled N,N-diisopropylethylamine (Hunig's base) and 160 mL of a dry dichloromethane-trichloromethane mixed solvent (1:1 vol / vol) were added and cooled to −78°C with stirring. 1.02 mL (1.03 equiv.) of anhydrous nonafluorobutanesulfonic acid was added dropwise to this solution over 30 minutes. After the dropwise addition, the temperature was slowly raised to room temperature (20°C) and the reaction was allowed to proceed overnight (to completion). After the reaction, the mixture was washed with aqueous ammonium chloride and brine, the organic layer was dried over magnesium sulfate, and the solvent was removed under reduced pressure. The residue was passed through a short silica gel column (eluent: trichloromethane), and the solvent was removed under reduced pressure. The residue was dissolved in dichloromethane, and hexane was added as a poor solvent for recrystallization. Kiriyama filtration was performed to obtain 1.534 g (81% yield) of compound (2) as a yellowish white powder.

[0092] Compound (1) can be synthesized by the method described in Yuichi Kitamoto, Takatsugu Suzuki, Yasuo Miyata, Hiroshi Kita, Kenji Funaki, Shuichi Oi: The first synthesis and X-ray crystallographic analysis of an oxygen-bridged planarized triphenylborane (2016).

[0093] [Synthesis of 5,7,11,16-tetraoxa-6-thia-15b-bora-1,15-methanobenzo[4,5]cycloocta[1,2,3-de]anthracene 6,6-dioxide (compound (3))] [ka]

[0094] 583 mg (1.00 mmol) of compound (2) was placed in a 50 mL two-necked recovery flask and heated with a heat gun while replacing the atmosphere with nitrogen. 454 μL (3.0 equiv.) of distilled 1,8-diazabicyclo[5,4,0]undecene-7 (trade name "DBU", San-Apro Co., Ltd.) and 10 mL of dry N,N-dimethylformamide (DMF) were added and reacted at 120 °C for 20 hours. After the reaction, the solvent was removed by distillation using a Kugelrohr funnel, and the residue was dissolved in tetrahydrofuran (TDF). This tetrahydrofuran solution was slowly added dropwise to 130 mL (2.0 mol / L) of aqueous hydrochloric acid solution and vigorously stirred for 2 hours. The precipitate was then separated by Kiriyama filtration, dissolved in tetrahydrofuran, and recrystallized by adding dichloromethane as a semi-poor solvent. 351 mg (96% yield) of compound (3) was obtained as a white powder by Kiriyama filtration.

[0095] <Application of triarylboron compounds to electronic devices> The triarylboron compounds of the present invention are essentially electron-deficient compounds and inherently prone to electron hopping using the lowest unoccupied molecular orbital (hereinafter also referred to as "LUMO") level. However, by selecting the substituents and linking groups, they can also be made into bipolar compounds. Because they can accommodate various energy levels, they can be used not only as fluorescent compounds, host compounds, and assist dopants, but also as compounds suitable for hole transport and electron transport. Therefore, the triarylboron compounds of the present invention can be used in organic functional layers such as the light-emitting layer, hole injection layer, hole transport layer, electron blocking layer, hole blocking layer, electron transport layer, electron injection layer, and intermediate layer of organic electroluminescent devices (also referred to as "organic EL devices"), and can be used in various electron transport layer devices. Furthermore, the compounds of the present invention are characterized by the presence of an empty p orbital on the boron atom, which facilitates interaction and coordination with other molecules. Therefore, they can also be used as doping materials that exhibit various functions.

[0096] [Organic electroluminescence element] The organic EL device of the present invention is an organic EL device having organic functional layers including at least an emitting layer between an anode and a cathode, and at least one layer of the organic functional layers contains the triarylboron compound of the present invention. The organic EL device of the present invention can be suitably included in lighting devices and display devices.

[0097] Typical device configurations of the organic EL device of the present invention include, but are not limited to, the following configurations. (1) Anode / Emitting layer / / Cathode (2) Anode / Emitting layer / Electron transport layer / Cathode (3) Anode / hole transport layer / light-emitting layer / cathode (4) Anode / hole transport layer / light-emitting layer / electron transport layer / cathode (5) Anode / hole transport layer / light-emitting layer / electron transport layer / electron injection layer / cathode (6) Anode / hole injection layer / hole transport layer / light-emitting layer / electron transport layer / cathode (7) Anode / hole injection layer / hole transport layer / (electron blocking layer / ) light-emitting layer / (hole blocking layer / ) electron transport layer / electron injection layer / cathode Among the above, the configuration (7) is preferably used, but is not limited to this.

[0098] The light-emitting layer used in the present invention is composed of a single layer or multiple layers, and when multiple light-emitting layers are used, non-light-emitting intermediate layers may be provided between the light-emitting layers.

[0099] If necessary, a hole-blocking layer (also referred to as a hole-blocking layer) or an electron-injecting layer (also referred to as a cathode buffer layer) may be provided between the light-emitting layer and the cathode, and an electron-blocking layer (also referred to as an electron-blocking layer) or a hole-injecting layer (also referred to as an anode buffer layer) may be provided between the light-emitting layer and the anode.

[0100] The electron transport layer used in the present invention is a layer having a function of transporting electrons, and in a broad sense, includes an electron injection layer and a hole blocking layer. The electron transport layer may be composed of multiple layers.

[0101] The hole transport layer used in the present invention is a layer having a function of transporting holes, and in a broad sense, hole injection layers and electron blocking layers are also included in the hole transport layer. Also, the hole transport layer may be composed of multiple layers.

[0102] The organic functional layer refers to the layers excluding the anode and cathode in the above-mentioned typical device configuration.

[0103] 1 is a schematic diagram showing an example of the configuration of an organic EL element, which corresponds to the configuration (4) above. In FIG. 1, the hole transport layer 5, the light emitting layer 6, and the electron transport layer 7 are the organic functional layer F.

[0104] FIG. 2 is a schematic diagram showing the mechanism of charge flow and light emission in an organic EL element. When a voltage is applied to the organic EL element 1, electrons (e - ) from the anode 3 to the hole injection layer 4 + ) is injected.

[0105] The electrons and holes are then transported to the adjacent organic layers on the opposite side of the electrode, the electron transport layer 7 and the hole transport layer 5, respectively.

[0106] Finally, the electrons and holes that meet in the light-emitting layer 6 recombine R to generate excitons, and when these return from the excited state to the ground state, light (fluorescence or phosphorescence) L is emitted, making up the light-emitting element known as an organic EL element. In Figure 2, the layers from the hole injection layer to the electron injection layer are organic functional layers.

[0107] <Electron transport material> The first step in passing electrons through an organic compound is to inject charge from the electrode into the organic functional layer. Two injection mechanisms are known: Schottky thermal emission and tunnel injection. The charge injected into the organic functional layer causes hopping conduction, with the external electric field applied between the two electrodes acting as the driving force, resulting in the flow of current. The current at this time is space charge limited current (SCLC), which follows Child's law rather than Ohm's law, and since this is inversely proportional to the cube of the film thickness as shown in the following equation, the organic functional layer must be extremely thin.

[0108] Space charge limiting current ∝ (voltage) 2 / (thickness) 3 In actual electronic displays and lighting devices, the current is several tens of A / m at a voltage of several volts. 2 Because a large current needs to flow, the thickness of each layer must be approximately 50 nm or less.

[0109] In this case, the flow of electrons in the organic functional layer basically involves injecting electrons into the LUMO level of the compound and transferring them to the adjacent molecule. Therefore, it is important that the electron transport compound (hereinafter also referred to as the electron transport material) itself has the LUMO sites close to each other between adjacent molecules, and it is no exaggeration to say that the way in which the electrons flow changes depending on the way this overlaps.

[0110] In other words, it is preferable that there is no steric hindrance at the site of electron acceptance and that the site is planar. However, in triarylboron compounds, due to the strong electron acceptance of the boron atom, the position where the LUMO is located is almost always the boron atom, and the three bonds coming out of the boron atom are sp 2 Because the bond is formed by hybrid orbitals, it has a planar structure with a bond angle of 120°, and has the best properties of all organic compounds in terms of electron hopping movement.

[0111] This is easily predicted, and is supported by the fact that there have been many research examples of triarylboron compounds as electron transport materials for organic electroluminescence (EL). However, although the packing between compounds and the accompanying electron hopping are good, as mentioned above, the boron atom itself is highly susceptible to attack by nucleophiles and Lewis bases, and when attacked, the sp 2 Hybrid orbitals break down into sp 3 It is also true that the pyramidal structure of the hybrid orbitals results in a problem in that the electron mobility drops significantly over time when a current is applied.

[0112] On the other hand, the triarylboron compound of the present invention is a three-bridged triarylboron compound, and since the molecular structure is fixed to a plane, the bond between the boron atom and the aryl group is sp 2 The hybrid orbital bonds are easily maintained, preventing attack by nucleophiles and Lewis bases. Therefore, while maintaining the high electron hopping properties of conventional triarylboron compounds, the decrease in electron current flow over time is effectively suppressed, making this an extremely promising electron transport material.

[0113] <Light-emitting materials> As described above, the triarylboron compound of the present invention has a sp 2 It is a compound that can maintain hybrid orbitals at a high level. Therefore, no matter what aryl group is bonded to the boron atom, and whether the three substituents are the same or different, the LUMO is basically located on the boron atom, and the highest occupied molecular orbital (hereinafter also referred to as "HOMO") is located in the aryl moiety that is substituted, so all molecules become intramolecular CT-type dyes, although the strength may be greater or less. In addition, the sp 2 Because hybrid orbitals can be maintained at a high level, the oscillator strength is strong, and fluorescence occurs in almost all molecules (although they will no longer emit light if heavy atoms such as bromine or iodine are substituted to hasten the intersystem crossing to the triplet state).

[0114] Furthermore, as mentioned above, electrons hop on the boron atom, so when the compound is made into an organic EL device, a current always flows, and since the compound itself is a fluorescent substance, it can be used as a light-emitting material.

[0115] Furthermore, by changing the three aryl groups to hole-transporting substituents, it is possible to easily create bipolar substances, and this is also a group of compounds that are easy to design molecularly as light-emitting materials for organic electroluminescence (EL).

[0116] In fact, the following non-patent literature introduces examples of research into the application of triarylboron compounds as light-emitting materials for organic electroluminescence (EL).

[0117] http: / / onlinelibrary.wiley.com / doi / 10.1002 / adfm.200290007 / full J.Mater.Chem.C,2015,3,9122-9130. Chem.Comm.,51,9443,2015. Angew Chem Int Ed Engl 2015 Nov 13.Epub 2015 Nov 13.

[0118] Furthermore, in the following non-patent literature, a triarylboron compound is positioned as a LUMO localized portion, and by further introducing electron-donating groups such as carbazole or diphenylamino groups into the molecule, it has been successful in producing thermally excited delayed fluorescence (TADF). In both literatures, an extremely high luminous efficiency of 15% or more, with an external extraction quantum efficiency (the theoretical limit for normal fluorescent emission is 5%), has been achieved in actual organic EL devices. However, none of the research examples mentions the luminous lifetime, and this is probably due to the inherent fragility of the molecules specific to conventional triarylboron compounds, so although they may be acceptable at the research level, they are thought to be impossible to put into practical use as industrial products.

[0119] J.Mater.Chem.C,2015,3,9122-9130. Chem.Comm.,51,9443,2015. Angew Chem Int Ed Engl 2015 Nov 13.Epub 2015 Nov 13.

[0120] Thermally activated delayed fluorescence (TADF) compounds In organic EL devices, excitons are generated by the recombination of injected holes and electrons, and the light emitted when these excitons deactivate and return to the ground state is utilized. There are two types of excitons: singlet excitons and triplet excitons, which are typically generated in a ratio of 25:75. Light emission from fluorescent materials is due to singlet excitons, which are relatively difficult to generate, and therefore has low luminous efficiency, leading to a demand for the development of light-emitting technology that utilizes triplet excitons.

[0121] Thermally activated delayed fluorescence (TADF) compounds are light-emitting materials that utilize triplet excitons. TADF compounds are unique in that the energy level difference between the triplet excited state and the singlet excited state is extremely close, allowing reverse intersystem crossing from the triplet excited state to the singlet excited state, which would not normally occur. Furthermore, because the rate constant for decay from the singlet excited state to the ground state (i.e., fluorescence emission) is extremely large, it is kinetically advantageous for triplet excitons to return to the ground state while emitting fluorescence via the singlet excited state, rather than thermally decaying (non-radiatively decaying) to the ground state themselves. Therefore, TADF compounds theoretically enable 100% fluorescence emission.

[0122] The triarylboron compound of the present invention can be molecularly designed as a TADF compound and can be suitably used as a blue light-emitting material in an organic EL device.

[0123] <Light-emitting auxiliary material (host compound)> The host compound used in the light-emitting layer as a diluent for the dopant and as an energy transfer agent is preferably a bipolar compound that conducts both electrons and holes. In this regard, it is also possible to use bipolar compounds or TADF compounds designed as the light-emitting material. However, since one of the roles of the host compound is to maintain a uniform electric field strength, localized microcrystallization is not permitted. Furthermore, compounds that stabilize in an aggregated state (low T1) even if they do not reach the crystallization stage, or compounds that form excimers or exciplexes upon electric field excitation, cannot be used as host compounds.

[0124] In such cases, the cause is often the strong stacking phenomenon of the molecules, which can be alleviated by introducing a substituent with high steric hindrance at any position of the molecule, and such molecules can be suitably used as host compounds.

[0125] Semiconductor materials Although thin films and structures made of organic compounds are generally insulators, many π-conjugated compounds are known to exhibit semiconducting properties due to the close intermolecular distance that facilitates carrier hopping. Typical examples include pentacene and polythiophene. The triarylboron compounds of the present invention may also exhibit semiconducting properties due to electronic conduction using the vacant p orbital of the boron atom. Conventional triarylboron compounds have been stabilized by incorporating substituents with large steric hindrance into the aryl group. However, the triarylboron compounds of the present invention are stable despite their planar structure. Therefore, in thin films or structures formed from these compounds, the distance between boron atoms where the LUMO exists is shortened, making them suitable for use as n-type semiconductor materials.

[0126] Display and lighting devices The organic EL element of the present invention is capable of surface emission and dot emission, can reproduce patterns and characters, and can be suitably used in organic EL display devices that emit multicolor light and display high-quality color images with improved color mixing. Furthermore, the organic EL element of the present invention is capable of surface emission and dot emission, and therefore can be suitably used as a lighting device or various light sources, such as for home lighting, vehicle interior lighting, backlights for clocks and liquid crystal displays, billboard advertisements, traffic lights, light sources for optical storage media, electrophotographic copiers, optical communication processors, and light sources for optical sensors.

[0127] Other: Industrial applications <Solar Cells> The triarylboron compound of the present invention can also be used in various types of conventionally known organic thin film solar cells (OPV). For example, a bulk heterojunction type organic photoelectric conversion element can be used, which has a basic structure in which an anode which is a transparent electrode, a hole transport layer, a bulk heterojunction layer photoelectric conversion layer, an electron transport layer, and a cathode are sequentially stacked on one side of a substrate. The layer may also have other layers such as a hole blocking layer, an electron blocking layer, an electron injection layer, a hole injection layer, or a smoothing layer.

[0128] The photoelectric conversion layer is a layer that converts light energy into electrical energy, and is configured to have a bulk heterojunction layer in which p-type semiconductor material and n-type semiconductor material are uniformly mixed.

[0129] Furthermore, for the purpose of further improving the sunlight utilization rate (photoelectric conversion efficiency), such photoelectric conversion elements may be stacked to form a tandem structure (a structure having a plurality of bulk heterojunction layers).

[0130] Fig. 3 is a cross-sectional view showing an example of a solar cell having a single structure (a single bulk heterojunction layer) made of a bulk heterojunction organic photoelectric conversion element. In Fig. 3, a bulk heterojunction organic photoelectric conversion element 10 has a transparent electrode (anode) 12, a hole transport layer 17, a bulk heterojunction layer photoelectric conversion section 14, an electron transport layer (also referred to as a buffer layer) 18, and a counter electrode (cathode) 13 sequentially stacked on one surface of a substrate 11.

[0131] The substrate 11 is a member that holds the transparent electrode 12, the photoelectric conversion section 14, and the counter electrode 13, which are sequentially stacked. Since light to be photoelectrically converted is incident from the substrate 11 side, the substrate 11 is preferably a member that can transmit the light to be photoelectrically converted, that is, a member that is transparent to the wavelength of the light to be photoelectrically converted. For example, a glass substrate or a resin substrate is used as the substrate 11.

[0132] The photoelectric conversion section 14 is a layer that converts light energy into electrical energy, and is configured with a bulk heterojunction layer in which p-type and n-type semiconductor materials are uniformly mixed. The p-type semiconductor material functions relatively as an electron donor, and the n-type semiconductor material functions relatively as an electron acceptor. Here, the electron donor and electron acceptor are "electron donors and electron acceptors that, upon absorbing light, transfer electrons from the electron donor to the electron acceptor, forming a hole-electron pair (charge-separated state)," and do not simply donate or accept electrons like an electrode, but donate or accept electrons through a photoreaction.

[0133] In FIG. 3, light incident through the transparent electrode 12 via the substrate 11 is absorbed by the electron acceptor or electron donor in the bulk heterojunction layer of the photoelectric conversion section 14. Electrons then transfer from the electron donor to the electron acceptor, forming a hole-electron pair (charge-separated state). The generated charges are transported to different electrodes by an internal electric field—for example, when the work functions of the transparent electrode 12 and the counter electrode 13 are different, the electrons pass between the electron acceptors and the holes pass between the electron donors—due to the potential difference between the transparent electrode 12 and the counter electrode 13, and a photocurrent is detected. For example, when the work function of the transparent electrode 12 is greater than that of the counter electrode 13, the electrons are transported to the transparent electrode 12 and the holes are transported to the counter electrode 13. Note that if the work functions are reversed, the electrons and holes are transported in the opposite directions. Furthermore, the direction of electron and hole transport can be controlled by applying a potential between the transparent electrode 12 and the counter electrode 13.

[0134] The triarylboron compound of the present invention is a three-bridged triarylboron compound with a fixed molecular structure in a plane, which makes it suitable for use as an n-type heterojunction material in solar cells, particularly organic solar cells.

[0135] For example, it can be used in heterojunction solar cells, which are formed by stacking n-type and p-type layers, such as organic EL, and in bulk heterojunction solar cells, in which n-type and p-type compounds coexist in the photoelectric conversion section 14 and the area of ​​the p / n interface is increased by the sea-island structure.The bulk heterojunction solar cells can be applied whether the p-type and n-type materials are both made of low molecular weight materials or whether either one is made of a polymer material.

[0136] Transistor For the same reasons as those for solar cells, the compound of the present invention is suitable for use as an n-channel transistor material. The compound of the present invention is characterized by its thermal stability and can be handled without having a substituent with large steric hindrance around the boron atom, making it a more stable electronic device material. From this perspective, when applied to transistors, the compound of the present invention is preferably a small molecule, particularly a symmetrical small molecule, rather than a polymer.

[0137] <Electrode / charge mobility thin film> The compound of the present invention is a compound in which electron hopping conduction due to the electron deficiency of boron atoms is likely to occur, and when formed into a thin film by itself, the thin film basically conducts electrons.

[0138] In addition, the triarylboron compound of the present invention is sp 2Although the feature of this material is that hybrid orbitals can be maintained at a high level and that it has a planar structure, the presence of electron-deficient boron atoms on the plane also gives rise to a high affinity for Lewis basic substances. Some of these materials become conductive when added to or coexist with alkali metals and alkaline earth metals that readily release electrons, or other metals such as silver, copper, nickel, iron, and cobalt. These materials can be used as reflective electrodes, transparent electrodes, semi-transparent electrodes, and the like, by laminating them with or coexisting with such metals, or by laminating the metal on a film in which they coexist. [Example]

[0139] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these. In the examples, the terms "parts" and "%" are used, but unless otherwise specified, they represent "parts by mass" or "% by mass."

[0140] The triarylboron compounds used in the present invention are the above-described exemplary compounds Tab-1 to Tab-26. The structural formulae of comparative compounds a to c are shown below.

[0141] [ka]

[0142] [Example 1 (Comparison of chemical stability)] The exemplary compound Tab-9 of the present invention and the comparative compound a were placed in separate microwave reaction tubes, and diisopropylethylamine and toluene were added thereto to dissolve them. Then, the mixture was heated at 100°C for 1 hour under microwave irradiation.

[0143] Example Compound Tab-9 was reacted at 100° C. for 1 hour, and then subjected to LC column measurement, which confirmed that it was not decomposed. On the other hand, when comparative compound a was subjected to a similar reaction and then subjected to LC column measurement, a peak (2% of the total) that was not observed before the reaction was confirmed, as shown in FIG.

[0144] Similar measurements were also carried out on the other exemplary compounds (Tab-1 to Tab-8 and Tab-10 to Tab-26), confirming that they were not decomposed. These results demonstrate that the triarylboron compounds of the present invention are more stable against nucleophiles than known triarylboron compounds.

[0145] [Example 2 (Comparison of thermal stability)] Example compound Tab-9 and comparative compounds b and c were each packed into different sealed glass tubes and subjected to thermogravimetric differential calorimetry (TG measurement). The 5% decomposition temperatures were found to be 276°C, 264°C, and 269°C, respectively.

[0146] Similar measurements were also carried out on the other exemplary compounds Tab-1 to Tab-8 and Tab-10 to Tab-26, and it was confirmed that all of them exceeded 269° C. From the above results, it was found that the triarylboron compound of the present invention has sufficient thermal stability (heat resistance) compared to known triarylboron compounds.

[0147] [Example 3 (Use as a light-emitting material in an organic EL device)] Organic EL devices were fabricated using the exemplary compounds Tab-1 to Tab-26 of the present invention as light-emitting materials.

[0148] (Fabrication of organic EL elements 101 to 131) A glass substrate on which a 100 nm ITO (Indium Tin Oxide) film was formed as an anode was ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and cleaned with UV ozone, and then fixed to a substrate holder in a vacuum deposition apparatus.

[0149] The vacuum level in the vacuum deposition device was 1 x 10 -4 After reducing the pressure to 100 Pa, a hole injection layer of hexacyanohexaazatriphenylene (12 nm) and a hole transport layer of α-NPD (4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl) (40 nm) were formed in this order on the anode.

[0150] Next, 1,3-bis(N-carbazolyl)benzene (mCP) as a host material and exemplary compound Tab-1 as an emitting material were co-deposited on the emitting layer in a ratio of host material (mCP):emitting material (exemplary compound Tab-1) = 100:5 to form an emitting layer with a thickness of 40 nm.

[0151] Next, BPhen (4,7-diphenyl-1,10-phenanthroline) (30 nm) as an electron transport layer, lithium fluoride (1.0 nm) as an electron injection layer, and aluminum (100 nm) as a cathode were deposited in this order to prepare an organic EL device 101.

[0152] Organic EL devices 102 to 131 were prepared in the same manner except that the host material and the light-emitting material were changed to those shown in the table, where DPEPO in Table I refers to bis[2-(diphenylphosphino)phenyl]ether oxide.

[0153] <Evaluation> (1) Measurement of relative luminous efficiency (relative luminous brightness) The obtained organic EL devices 101 to 131 were subjected to a current flow of 2.5 mA / cm at room temperature (about 25°C). 2 The organic EL element was allowed to emit light under a constant current condition of 100. The luminance of the organic EL element immediately after the start of light emission was measured using a spectroradiometer CS-2000 (manufactured by Konica Minolta), and the obtained luminance was applied to the following equation to calculate the relative luminance efficiency (relative luminance) with respect to the luminance of the organic EL element 101. Relative luminous efficiency = (luminance of each organic EL element / luminance of organic EL element 101) × 100 The larger the obtained value, the more preferable the result.

[0154] (2) Measurement of relative drive life The obtained organic EL devices 101 to 131 were subjected to a luminescence test at room temperature (about 25°C) and 100 cd / m 2The luminance of the organic EL element immediately after the start of light emission was measured using a spectroradiometer CS-2000 (manufactured by Konica Minolta), and the driving life from the start of lighting until the luminance was reduced by half was applied to the following formula to calculate the relative driving life with respect to the driving life of the organic EL element 101. Relative driving life = (driving life of each organic EL element / driving life of organic EL element 101) × 100 The larger the obtained value, the more preferable the result.

[0155] The emitting and host materials used and the results obtained are shown in Table I.

[0156] [Table 1]

[0157] As can be seen from Table I, organic EL devices using the triarylboron compounds of the present invention as emitting materials have superior relative operating lifetimes compared to organic EL devices using comparative compounds a and b, which are known triarylboron compounds, as emitting materials, confirming the improved chemical stability of the triarylboron compounds of the present invention. Furthermore, the organic EL devices have superior relative luminous efficiency compared to organic EL devices using comparative compound c, a known triarylboron compound, as emitting materials, confirming the luminescent properties and thermally activated delayed fluorescence characteristics of the triarylboron compounds of the present invention.

[0158] [Example 4 (Use as a host material in an organic EL device)] Organic EL devices were fabricated using the exemplary compounds of the present invention (Tab-1 to Tab-26) as host materials.

[0159] (Fabrication of organic EL elements 201 to 231) Organic EL elements 201 to 231 were prepared in the same manner as in the preparation of the light-emitting layer of the above organic EL element, except that the host material and light-emitting material were changed to those shown in Table II and co-deposited at a ratio of host material:light-emitting material = 100:5.

[0160] Here, FIrpic in Table II refers to bis(3,5-difluoro-2-(2-pyridylphenyl-(2-carboxypyridyl))iridium(III). Additionally, Dopant-1 refers to a compound represented by the following structural formula:

[0161] [ka]

[0162] The obtained organic EL device was evaluated in the same manner as in Example 4. The results obtained are shown in Table II.

[0163] [Table 2]

[0164] From Table II, it can be seen that the organic EL devices using the triarylboron compounds of the present invention as host materials have a superior relative operating life compared to organic EL devices using comparative compounds a and b, which are known triarylboron compounds, as host materials, confirming the improved chemical stability of the triarylboron compounds of the present invention. Furthermore, the organic EL devices have a superior relative luminous efficiency compared to organic EL devices using comparative compound c, which is a known triarylboron compound, as host material, confirming that the triarylboron compounds of the present invention do not experience significant variations in energy levels.

[0165] The above results indicate that the triarylboron compounds of the present invention have higher thermal and chemical stability (stability against nucleophiles) than known triarylboron compounds. Therefore, by using the compounds as a light-emitting material or host material, it is possible to provide organic EL devices with high luminous efficiency and long life. [Industrial Applicability]

[0166] The triarylboron compound of the present invention has the property of emitting light through a thermally activated delayed fluorescence process and has excellent thermal and chemical stability. Therefore, by using the compound as a light-emitting material or a host material, an organic electroluminescence device having high luminous efficiency and a long life can be provided. Furthermore, by including the organic electroluminescence element, it is possible to provide a display device and a lighting device that have high luminous efficiency and a long life. [Explanation of symbols]

[0167] 1. Organic EL element 2 Transparent substrate 3 Anode 4. Hole injection layer 5. Hole transport layer 6. Light-emitting layer 7 Electron transport layer 8 Electron injection layer 9 Cathode F Organic functional layer R recombination L light 10. Bulk heterojunction organic photovoltaic cell 11 Circuit Board 12 Transparent electrode (anode) 13 Counter electrode (cathode) 14 Photoelectric conversion section (bulk heterojunction layer) 17 Hole transport layer 18 Electron transport layer

Claims

1. It is a structure represented by the following general formula (1): A triarylboron compound characterized by: 【Chemistry 1】 (In the formula, X 1 and X 2 The atoms represented by X are each independently Se, C, O, S, N, P, or Si. 1 and X 2 is a substituent Z １ and Z １ represents a hydrogen atom, an alkyl group, an aromatic hydrocarbon ring group, or an aromatic heterocyclic group. １ When there are a plurality of R, they may be the same or different. 1 ~R 9 each independently represents a hydrogen atom or a substituent, and Y is represented by the following general formula (2): 【Chemistry 2】 (In the formula, A 1 and A 2 The atoms represented by are each independently S or O. 1 The atomic group represented by is NH, C(Z ２ ) 2 , B-Z ２ , P-Z ２ , Si(Z ２ ) 2 , or Ge(Z ２ ) 2 n is 0 or 1. ２ represents a hydrogen atom, an alkyl group, an aromatic hydrocarbon ring group, or an aromatic heterocyclic group. ２ If there are multiple, they may be the same or different.)

2. In the general formula (1), X 1 and X 2 are each independently any of C, O, S, N, P, and Si. The triarylboron compound according to claim 1 .

3. In the general formula (2), n is 1. The triarylboron compound according to claim 1 or 2.

4. In the general formula (2), A 1 and A 2 is O The triarylboron compound according to any one of claims 1 to 3.

5. In the general formula (2), B 1 The atomic group represented by C(Z ２ ) 2 , B-Z ２ , P-Z ２ , Si(Z ２ ) 2 or Ge(Z ２ ) 2 Either The triarylboron compound according to any one of claims 1 to 4.

6. In the general formula (1), X 1 and X 2 are each independently either O or N. The triarylboron compound according to any one of claims 1 to 5.

7. In the general formula (1), X 1 and X 2 Both atoms represented by are N The triarylboron compound according to any one of claims 1 to 6.

8. In the general formula (1), Z １ and R 1 ~R 9 are each independently an azine skeleton, a dibenzofuran skeleton, an azadibenzofuran skeleton, a diazadibenzofuran skeleton, a carboline skeleton, a diazacarbazole skeleton, or an aryl group having an electron-withdrawing group; The triarylboron compound according to any one of claims 1 to 7.

9. In the general formula (1), Z １ and R 1 ~R 9 are each independently either a carbazole skeleton or an aryl group having an electron-donating group; The triarylboron compound according to any one of claims 1 to 7.

10. A compound represented by the following structural formula Tab-1 to Tab-8 or 12 to 26: A triarylboron compound characterized by: 【Transformation 3】 【Chemistry 4】 【Transformation 5】 【Transformation 6】

11. An organic electroluminescent device having an organic layer sandwiched between an anode and a cathode, The organic layer contains the triarylboron compound according to any one of claims 1 to 10. An organic electroluminescence element characterized by:

12. The organic electroluminescence device according to claim 11 is provided. A display device characterized by:

13. The organic electroluminescence device according to claim 11 is provided. A lighting device characterized by:

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