Aromatic compound, organic electroluminescent element, and electronic apparatus

Abstract

An aromatic compound represented by general formula (a) or (b) has a low refractive index, and therefore, an organic electroluminescent (EL) element having improved light extraction efficiency can be achieved by laminating a low refractive index layer containing said aromatic compound and a high refractive index layer, and using the result as a capping layer. A1 and A2 represent an alkanediyl group, a cycloalkanediyl group, or a fluorenediyl group, L1 through L4 represent a single bond, -O-, -NH-, or an alkanediyl group, Cy1 through Cy4 represent an alkyl group, a cycloalkyl group, or a monovalent aromatic hydrocarbon group, and X1 through X4 represent -O- or -NH-.

Description

Aromatic compound, organic electroluminescent element and electronic device

[0001] The present invention relates to an aromatic compound suitable as a material for organic electroluminescence elements (hereinafter referred to as organic EL elements), which are self-luminous elements suitable for various display devices, and electronic devices. More specifically, the present invention relates to an aromatic compound having excellent low refractive index characteristics, and also to an organic EL element and electronic device using the aromatic compound.

[0002] In 1987, C. W. Tang et al. of Eastman Kodak Company made organic EL devices practical by developing a layered structure element in which various roles are assigned to each material. They layered a phosphor capable of transporting electrons and an organic material capable of transporting holes, and by injecting both charges into the phosphor layer to emit light, they achieved 1000 cd / m at a voltage of 10 V or less. ２ Such high brightness is obtained (see Patent Documents 1 and 2).

[0003] In recent years, light-emitting devices with a top-emission structure that uses a metal with a high work function as the anode and emits light from the top have come into use. In a bottom-emission structure in which light is extracted from the bottom where the pixel circuit is located, the area of ​​the light-emitting section is limited, whereas a light-emitting device with a top-emission structure has the advantage that the light is extracted from the top and is not blocked by the pixel circuit, allowing for a larger light-emitting section. In light-emitting devices with a top-emission structure, a semi-transparent electrode such as LiF / Al / Ag (see, for example, Non-Patent Document 1), Ca / Mg (see Non-Patent Document 2), or LiF / MgAg is used as the cathode.

[0004] In such light-emitting devices, when light emitted from the light-emitting layer is incident on another film at an angle greater than a certain value, it is totally reflected at the interface between the light-emitting layer and the other film. As a result, only a portion of the emitted light can be utilized. In recent years, light-emitting devices have been proposed that provide a high-refractive-index "capping layer" on the outside of a semi-transparent electrode with a low refractive index in order to improve light extraction efficiency (see, for example, Non-Patent Document 1 and Patent Documents 2, 4, and 5).

[0005] On the other hand, an organic optical device has also been proposed in which a low refractive index layer formed by co-evaporating an additive for adjusting the refractive index and an organic semiconductor material is stacked with a high refractive index layer, and the optical interference effect of this stacked film is utilized to effectively control light propagation (see Patent Document 3).

[0006] Japanese Patent Publication No. 8-048656 Japanese Patent No. 3194657 Japanese Patent No. 6210473 International Publication No. 2021 / 140896A1 International Publication No. 2015 / 001726A1

[0007] Appl. Phys. Let. , 78, 544 (2001) Appl. Phys. Let. , 82, 466 (2003)

[0008] As described above, a technique for controlling light propagation in organic EL devices by combining a low-refractive index layer and a high-refractive index layer has been proposed. However, the low-refractive index layer is formed by co-evaporation of an organic semiconductor material and an additive, which makes it difficult to control the amount of additive and the film-forming conditions. Therefore, there is a need for the development of a material that exhibits excellent low-refractive index characteristics even when vapor-deposited alone.

[0009] Therefore, in order to solve the problems of the conventional technology, the present inventors have conducted extensive research with the aim of providing a material with excellent low refractive index characteristics, and further with the aim of providing an organic EL device with high luminous efficiency.

[0010] As a result of intensive research conducted by the present inventors to achieve the above object, they found that an aromatic compound having a structure in which two phenylene groups having a substituent containing an amide structure or a substituent containing an ester structure are bonded to an alkanediyl, cycloalkanediyl, or fluorenediyl exhibits excellent low refractive index characteristics. They also found that by providing a capping layer in which a low refractive index layer containing this aromatic compound is laminated with a high refractive index layer, an organic EL device with improved light extraction efficiency can be realized. The present invention has been proposed based on these findings and specifically has the following configuration.

[0011] 1) An aromatic compound represented by the following general formula (a) or (b):

[0012]

[0013]

[0014] [In the general formula (a) and the general formula (b), A and A ２ each independently represents a substituted or unsubstituted alkanediyl group, a substituted or unsubstituted cycloalkanediyl group, or a substituted or unsubstituted fluorenediyl group; L １ ~L ４ each independently represents a single bond, —O—, —NH—, or a substituted or unsubstituted alkanediyl group; R １ ~R １６ each independently represents a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted monovalent aromatic hydrocarbon group, or a substituted or unsubstituted monovalent aromatic heterocyclic group; Cy １ ~Cy ４ each independently represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, or a substituted or unsubstituted monovalent aromatic hydrocarbon group; １ ~X ４ each independently represents —O— or —NH—.]

[0015] 2) R in the general formula (a) １ ~R ８ and R in the general formula (b) ９ ~R １６ are each independently a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted cycloalkyl group.

[0016] 3) A in the general formula (a) １ and A in the general formula (b) ２ are each independently a divalent group represented by the following formula (c), formula (d), formula (e), formula (f), or formula (g):

[0017]

[0018] [In formula (c), Ak １ and Ak２ each independently represents a hydrogen atom, an unsubstituted alkyl group, or an unsubstituted haloalkyl group, and the dashed line represents a bonding site.

[0019]

[0020] [In formula (d), the dashed line represents a binding site.]

[0021]

[0022] [In formula (e), the dashed line represents a binding site.]

[0023]

[0024] [In formula (f), the dashed line represents a binding site.]

[0025]

[0026] [In formula (g), the dashed line represents a binding site.]

[0027] 4) L in the general formula (a) １ and L ２ and L in the general formula (b). ３ and L ４ each independently represent a single bond, —O—, —NH—, a substituted or unsubstituted methylene group, a substituted or unsubstituted ethanediyl group, or a substituted or unsubstituted propanediyl group.

[0028] 5) Cy in the general formula (a) １ and Cy ２ and Cy of the general formula (b). ３ and Cy ４ each independently represent a substituted or unsubstituted methyl group, a substituted or unsubstituted cyclohexyl group, a substituted or unsubstituted norbornyl group, a substituted or unsubstituted adamantyl group, or a substituted or unsubstituted phenyl group.

[0029] 6) An organic EL device having at least an anode electrode, a hole transport layer, a light-emitting layer, an electron transport layer, a cathode electrode, and a capping layer in this order, wherein the capping layer contains the aromatic compound according to any one of 1) to 5).

[0030] 7) The organic EL element according to 6), wherein the aromatic compound exhibits a refractive index of 1.70 or less at room temperature (25±2°C) for light having a wavelength of 400 nm or more and 700 nm or less when vacuum-deposited to form a vapor-deposited film of 80 nm on a silicon substrate.

[0031] 8) The organic EL device according to 6) or 7), wherein the capping layer is a laminated or mixed layer made of two or more compounds, and at least one compound in the capping layer is the aromatic compound.

[0032] 9) An electronic element or electronic device having a pair of electrodes and at least one organic layer, wherein the organic layer contains the aromatic compound according to any one of 1) to 5).

[0033] The aromatic compound of the present invention has excellent low refractive index properties. Therefore, by combining a low refractive index layer formed using the compound with a high refractive index layer, an organic EL device with improved luminous efficiency can be realized due to the light interference effect. Furthermore, the aromatic compound of the present invention can be used not only in organic EL devices but also in electronic devices such as electrophotographic photoreceptors, image sensors, photoelectric conversion elements, and solar cells.

[0034] 1 is a diagram showing an example of the configuration of an organic EL element of the present invention.

[0035] The present invention will be described in detail below. The following description of the constituent elements may be based on typical embodiments or specific examples of the present invention, but the present invention is not limited to such embodiments or specific examples. In this specification, a numerical range expressed using "to" means a range including the numerical values ​​before and after "to" as the lower and upper limits. In addition, the isotopes of hydrogen atoms present in the molecules of the compound used in the present invention are not particularly limited, and for example, all hydrogen atoms in the molecule may be１ H, or part or all of ２ H (deuterium D). In this specification, the term "substituted or unsubstituted" means that the group to which the term is attached may be an unsubstituted group (a group in which a hydrogen atom is not substituted with a substituent), or at least one hydrogen atom of the group may be substituted with a substituent. In this specification, "transparent" means that the transmittance of visible light is 50% or more, for example, 80% or more, for example, 90% or more, for example, 99% or more. The transmittance of visible light can be measured using an ultraviolet-visible spectrophotometer.

[0036] <Aromatic Compound Represented by General Formula (a) or General Formula (b)> The compound of the present invention is an aromatic compound represented by the following general formula (a) or (b).

[0037]

[0038]

[0039] R in general formula (a) １ ~R ８ and R in general formula (b) ９ ~R １６ R each independently represents a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted monovalent aromatic hydrocarbon group, or a substituted or unsubstituted monovalent aromatic heterocyclic group. １ ~R １６ may be the same or different from each other. １ and Cy ２ and Cy of general formula (b) ３ and Cy ４ each independently represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, or a substituted or unsubstituted monovalent aromatic hydrocarbon group. １ ~Cy ４ may be the same or different from each other.

[0040] R in general formula (a) １ ~R ８ and R in general formula (b)９ ~R １６ The "halogen atom" represented by the formula (I) includes a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, with a fluorine atom and a chlorine atom being preferred, and a fluorine atom being particularly preferred.

[0041] R in general formula (a) １ ~R ８ , Cy １ and Cy ２ , R in general formula (b) ９ ~R １６ , Cy ３ and Cy ４ The "alkyl group" in the "substituted or unsubstituted alkyl group" represented by the formula (I) may be linear or branched. The number of carbon atoms in the alkyl group is, for example, 1 to 40, and may be 1 to 30, 1 to 20, 1 to 10, or 1 to 6. Specific examples of the "alkyl group" include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, and a t-butyl group. A methyl group, an isopropyl group, and a t-butyl group are preferred, and a t-butyl group is particularly preferred.

[0042] R in general formula (a) １ ~R ８ , Cy １ and Cy ２ , R in general formula (b) ９ ~R １６ , Cy ３ and Cy ４ The "cycloalkyl group" in the "substituted or unsubstituted cycloalkyl group" represented by the formula (I) may be a monocyclic cycloalkyl group or a polycyclic cycloalkyl group. Examples of polycyclic cycloalkyl groups include bicycloalkyl groups and tricycloalkyl groups. The cycloalkyl group has, for example, 3 to 40 carbon atoms, and may have 5 to 30, 5 to 20, or 5 to 10 carbon atoms. Specific examples of the "cycloalkyl group" include a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a norbornyl group, and an adamantyl group. The cyclohexyl group, the cyclooctyl group, the norbornyl group, and the adamantyl group are preferred, and the norbornyl group and the adamantyl group are particularly preferred.

[0043] R in general formula (a) １ ~R ８ , Cy １ and Cy ２ , R in general formula (b) ９ ~R １６ , Cy ３ and Cy ４ The "monovalent aromatic hydrocarbon group" in the "substituted or unsubstituted monovalent aromatic hydrocarbon group" represented by the formula (I) may be a monocyclic aromatic hydrocarbon group, or may be composed of a fused ring in which two or more rings are fused, or a linked ring in which two or more rings are linked by a single bond. Here, each of the rings constituting the fused ring constituting the monovalent aromatic hydrocarbon group may be an aromatic hydrocarbon ring (e.g., a benzene ring) or an aliphatic hydrocarbon ring, but the fused rings as a whole form an aromatic hydrocarbon ring. The number of carbon atoms in the monovalent aromatic hydrocarbon group is, for example, 6 to 40, or may be 6 to 30, 6 to 20, or 6 to 14. Specific examples of the "monovalent aromatic hydrocarbon group" include a phenyl group, a biphenylyl group, a 1-naphthyl group, a 2-naphthyl group, a 2-phenanthrenyl group, a 9-phenanthrenyl group, and a fluorenyl group. Of these, a phenyl group, a biphenylyl group, a 1-naphthyl group, a 2-naphthyl group, and a fluorenyl group are preferred, and a phenyl group is particularly preferred.

[0044] R in general formula (a) １ ~R ８ and R in general formula (b) ９ ~R １６The "monovalent aromatic heterocyclic group" in the "substituted or unsubstituted monovalent aromatic heterocyclic group" represented by may be a monocyclic aromatic heterocyclic group, or may be composed of a fused ring in which two or more rings are fused. Here, the multiple constituent rings of the fused ring constituting the monovalent aromatic heterocyclic group may all be heterocyclic, or may contain a heterocyclic ring and a hydrocarbon ring (e.g., a benzene ring). The constituent heterocyclic ring and hydrocarbon ring may be an aromatic ring or an aliphatic ring, but the fused rings as a whole form an aromatic heterocyclic ring. Examples of heteroatoms contained in the heteroaryl group include a nitrogen atom, a sulfur atom, and an oxygen atom. The monovalent aromatic heterocyclic group may contain one heteroatom or two or more heteroatoms. When the monovalent aromatic heterocyclic group contains two or more heteroatoms, these heteroatoms may be the same or different. The number of atoms constituting the ring skeleton of the monovalent aromatic heterocyclic group is, for example, 4 to 40, 5 to 20, 5 to 16, or 6 to 14. The number of carbon atoms in the heteroaryl group is, for example, 3 to 35, and may be 3 to 30 or 2 to 20. Specific examples of the "monovalent aromatic heterocyclic group" include a pyridyl group, a thienyl group, a furyl group, a pyrrolyl group, a quinolyl group, an isoquinolyl group, a benzofuranyl group, a benzothienyl group, an indolyl group, a carbazolyl group, a benzoxazolyl group, a benzothiazolyl group, a quinoxalinyl group, a benzimidazolyl group, a pyrazolyl group, a dibenzofuranyl group, a dibenzothienyl group, and a carbolinyl group, among which a pyridyl group, a benzofuranyl group, a dibenzofuranyl group, a benzothienyl group, and a dibenzothienyl group are preferred, and a pyridyl group and a benzofuranyl group are particularly preferred.

[0045] R in general formula (a) １ ~R ８ , Cy １ and Cy ２ , R in general formula (b) ９ ~R １６ , Cy ３ and Cy ４ The alkyl group, cycloalkyl group, and monovalent aromatic hydrocarbon group in the general formula (a) may be unsubstituted, or at least one hydrogen atom thereof may be substituted with a substituent. １ ~R ８and R in general formula (b) ９ ~R １６The monovalent aromatic heterocyclic group in the above formula (I) may be unsubstituted, or at least one hydrogen atom thereof may be substituted with a substituent. Specific examples of the "substituent" in the "substituted alkyl group," "substituted cycloalkyl group," "substituted aromatic hydrocarbon group," and "substituted aromatic heterocyclic group" include a cyano group, a nitro group; a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom; a silyl group such as a trimethylsilyl group or a triphenylsilyl group; a linear or branched alkyl group having 1 to 6 carbon atoms such as a methyl group, an ethyl group, or a propyl group; a linear or branched haloalkyl group having 1 to 6 carbon atoms such as a trifluoromethyl group, a pentafluoroethyl group, a perfluoro-n-propyl group, a perfluoroisopropyl group, a perfluoro-n-butyl group, a perfluoro-s-butyl group, or a perfluoro-t-butyl group; a linear or branched alkyloxy group having 1 to 6 carbon atoms such as a methyloxy group, an ethyloxy group, or a propyloxy group; an alkenyl group such as a vinyl group or an allyl group; aralkyloxy groups such as benzyloxy group and phenethyloxy group; aromatic hydrocarbon groups such as phenyl group, biphenylyl group, terphenylyl group, naphthyl group, anthracenyl group, phenanthrenyl group, indenyl group, pyrenyl group, perylenyl group, fluoranthenyl group, triphenylenyl group, fluorenyl group and spirobifluorenyl group; and aromatic heterocyclic groups such as pyridyl group, thienyl group, furyl group, pyrrolyl group, quinolyl group, isoquinolyl group, benzofuranyl group, benzothienyl group, indolyl group, carbazolyl group, benzoxazolyl group, benzothiazolyl group, quinoxalinyl group, benzimidazolyl group, pyrazolyl group, dibenzofuranyl group, dibenzothienyl group and carbolinyl group, and these substituents may be further substituted with the substituents exemplified above. Furthermore, when these substituents are substituents on a benzene ring (including a benzene ring that is a constituent ring of a fused ring), the benzene rings substituted with the substituents, or the plurality of substituents substituted on the same benzene ring, may be bonded to each other via a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring.For examples of the substituents of the methylene group, reference can be made to the description of the "substituents" in the above "substituted alkyl group" and the like.

[0046] A in general formula (a) １ and A in general formula (b) ２ A each independently represents a substituted or unsubstituted alkanediyl group, a substituted or unsubstituted cycloalkanediyl group, or a substituted or unsubstituted fluorenediyl group. １ and A ２ may be the same or different from each other. １ and L ２ and L in general formula (b) ３ and L ４ each independently represents a single bond, —O—, —NH—, or a substituted or unsubstituted alkanediyl group. １ ~L ４ may be the same or different from each other. １ and X ２ and X in general formula (b) ３ and X ４ Each of X independently represents —O— or —NH—. １ ~X ４ may be the same or different from each other. １ , L １ and L ２ , A in general formula (b) ２ , L ３ and L ４ The "alkanediyl group" in the "substituted or unsubstituted alkanediyl group" represented by is a divalent group obtained by removing one hydrogen atom from an alkyl group. １ ~R ８ The description of "alkyl group" in the above can be read as "alkanediyl group". Specific examples of "alkanediyl group" include the above R １ ~R ８ Examples of the "alkyl group" include divalent groups in which one hydrogen atom has been removed from the alkyl groups in the above.

[0047] A in general formula (a)１ and A in general formula (b) ２ The "cycloalkanediyl group" in the "substituted or unsubstituted cycloalkanediyl group" represented by is a divalent group obtained by removing one hydrogen atom from a "cycloalkyl group". For an explanation of the "cycloalkanediyl group", see the above R １ ~R ８ The description of "cycloalkyl group" in the above can be read by replacing "cycloalkyl group", "bicycloalkyl group", and "tricycloalkyl group" with "cycloalkanediyl group", "bicycloalkanediyl group", and "tricycloalkanediyl group". Specific examples of "cycloalkanediyl group" include the above R １ ~R ８ Examples of the "cycloalkanediyl group" include divalent groups in which one hydrogen atom has been removed from the specific examples of the "cycloalkanediyl group" in the above.

[0048] A in general formula (a) １ , L １ and L ２ , A in general formula (b) ２ , L ３ and L ４ The alkanediyl group in the general formula (a) may be unsubstituted, or at least one hydrogen atom of the alkanediyl group may be substituted with a substituent. １ and A in general formula (b) ２ The cycloalkanediyl group and fluorenediyl group in the above may be unsubstituted, or at least one hydrogen atom of the cycloalkanediyl group and fluorenediyl group may be substituted with a substituent. Examples of the "substituent" in the "substituted alkanediyl group", "substituted cycloalkanediyl group", and "substituted fluorenediyl group" are the same as those in the above R １ ~R ８ Reference can be made to the descriptions of the "substituents" in the "substituted alkyl group," "substituted cycloalkyl group," and "substituted aromatic hydrocarbon group" represented by the above.

[0049] A in general formula (a) １ and A in general formula (b) ２The "alkanediyl group" in the above formula (c) can be exemplified by a group represented by the following formula (c):

[0050]

[0051] A in formula (c) １ and Ak ２ each independently represents a hydrogen atom, an unsubstituted alkyl group, or an unsubstituted haloalkyl group, and the dashed line represents a bonding site (a single bond connecting the carbon atom at the base end of the dashed line to a carbon atom of the benzene ring). １ and Ak ２ A in formula (c) may be the same or different. １ and Ak ２ The "alkyl group" in the "unsubstituted alkyl group" represented by R １ ~R ８ etc. Specific examples of the "alkyl group" include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, a t-butyl group, etc., with a methyl group, an isopropyl group, and a t-butyl group being preferred, and a methyl group being particularly preferred.

[0052] A in formula (c) １ and Ak ２ The "haloalkyl group" in the "unsubstituted haloalkyl group" represented by is an alkyl group in which at least one hydrogen atom is substituted with a halogen atom. For details of the alkyl group and halogen atom that constitute the haloalkyl group, see the above R １ ~R ８ etc. Specific examples of the "haloalkyl group" include a trifluoromethyl group, a 2,2,2-trifluoroethyl group, a pentafluoroethyl group, a perfluoro-n-propyl group, a perfluoroisopropyl group, a perfluoro-n-butyl group, a perfluoro-t-butyl group, etc., with a trifluoromethyl group, a perfluoroisopropyl group, and a perfluoro-t-butyl group being preferred, and a trifluoromethyl group being particularly preferred.

[0053] A in general formula (a) １ and A in general formula (b) ２ Examples of the "cycloalkanediyl group" in the above formula (d) include groups represented by any of the following formulas (d) to (f).

[0054]

[0055]

[0056]

[0057] A in general formula (a) １ and A in general formula (b) ２ An example of the "fluorenediyl group" in the formula (g) is a group represented by the following formula (g):

[0058]

[0059] In formulas (d) to (g), the dashed line represents a bonding site (a single bond connecting the carbon atom at the base end of the dashed line to a carbon atom of the benzene ring).

[0060] In the aromatic compound represented by the general formula (a), Cy １ -L １ -X １ —C(═O)— and Cy ２ -L ２ -X ２ In a preferred embodiment of the present invention, the aromatic compound represented by general formula (a) has a structure represented by the following general formula (a1):

[0061]

[0062] R in general formula (a1) １ ~R ８ , Cy １ , Cy ２ , A １ , L １ and L ２ is R in general formula (a). １ ~R ８ , Cy １ , Cy ２ , A １ , L１ and L ２ R in general formula (a1) has the same meaning as １ ~R ８ , Cy １ , Cy ２ , A １ , L １ and L ２ For the explanation of formula (a), reference can be made to the corresponding description of formula (a).

[0063] In the aromatic compound represented by the general formula (b), Cy ３ -L ３ -C(=O)-X ３ - and Cy ４ -L ４ -C(=O)-X ４ The - may be bonded to any position of the benzene ring (the benzene ring constituting the ring skeleton) to which the bond is attached. In a preferred embodiment of the present invention, the aromatic compound represented by general formula (b) has a structure represented by the following general formula (b1):

[0064]

[0065] R in general formula (b1) １ ~R １６ , Cy ３ , Cy ４ , A ２ , L ３ and L ４ is R in general formula (b). １ ~R １６ , Cy ３ , Cy ４ , A ２ , L ３ and L ４ R in general formula (a1) has the same meaning as １ ~R １６ , Cy ３ , Cy ４ , A ２ , L ３ and L ４ For the explanation of formula (b), reference can be made to the corresponding description of formula (b).

[0066] In the general formula (a) and the general formula (a1), X １ and X ２ the same group, L１ and L ２ The group Cy １ and Cy ２ are the same, R １ ~R ４ and R ５ ~R ８ a group in which the groups are identical in order, R １ ~R ８ The group X １ and X ２ is the same and L １ and L ２ the same group, L １ and L ２ are the same and Cy １ and Cy ２ The group X １ and X ２ is the same and L １ and L ２ are the same and Cy １ and Cy ２ The group X １ and X ２ is the same and L １ and L ２ are the same and Cy １ and Cy ２ are the same and R １ ~R ４ and R ５ ~R ８ The group X １ and X ２ is the same and L １ and L ２ are the same and Cy １ and Cy ２ are the same and R １ ~R ８ The group X １ and X ２ groups with different １ and L ２ groups with different １ and X ２ is different １ and L ２ groups with different １ and X ２ O and L １ and L ２ is a single bond, X １ and X ２ NH and L １ and L２ is a single bond, X １ and X ２ O and L １ and L ２ a group in which X is an unsubstituted alkanediyl group; １ and X ２ NH and L １ and L ２ a group in which X is an unsubstituted alkanediyl group; １ and X ２ O and L １ and L ２ the group where X is NH １ and X ２ NH and L １ and L ２ The group X １ and X ２ NH and L １ and L ２ is NH, R １ ~R ８ is a hydrogen atom, R １ ~R ８ a group in which one or more of R １ ~R ８ a group in which one or more of R １ ~R ８ a group in which one or more of R is a substituted or unsubstituted cycloalkyl group; １ ~R ８ a group in which one or more of R are substituted or unsubstituted monovalent aromatic hydrocarbon groups; １ ~R ８ at least one of which is a substituted or unsubstituted monovalent aromatic heterocyclic group.

[0067] In the general formula (b) and the general formula (b1), X ３ and X ４ the same group, L ３ and L ４ The group Cy ３ and Cy ４ are the same, R ９ ~R １２ and R １３ ~R １６ a group in which the groups are identical in order, R ９ ~R １６ The group X ３ and X４ is the same and L ３ and L ４ the same group, L ３ and L ４ are the same and Cy ３ and Cy ４ The group X ３ and X ４ is the same and L ３ and L ４ are the same and Cy ３ and Cy ４ The group X ３ and X ４ is the same and L ３ and L ４ are the same and Cy ３ and Cy ４ are the same and R ９ ~R １２ and R １３ ~R １６ The group X ３ and X ４ is the same and L ３ and L ４ are the same and Cy ３ and Cy ４ are the same and R ９ ~R １６ The group X ３ and X ４ groups with different ３ and L ４ groups with different ３ and X ４ is different ３ and L ４ groups with different ３ and X ４ O and L ３ and L ４ is a single bond, X ３ and X ４ NH and L ３ and L ４ is a single bond, X ３ and X ４ O and L ３ and L ４ a group in which X is an unsubstituted alkanediyl group; ３ and X ４ NH and L ３ and L ４ a group in which X is an unsubstituted alkanediyl group; ３ and X４ O and L ３ and L ４ the group where X is NH ３ and X ４ O and L ３ and L ４ The group X ３ and X ４ NH and L ３ and L ４ The group X ３ and X ４ NH and L ３ and L ４ is NH, R ９ ~R １６ is a hydrogen atom, R ９ ~R １６ a group in which one or more of R ９ ~R １６ a group in which one or more of R ９ ~R １６ a group in which one or more of R is a substituted or unsubstituted cycloalkyl group; ９ ~R １６ a group in which one or more of R are substituted or unsubstituted monovalent aromatic hydrocarbon groups; ９ ~R １６ at least one of which is a substituted or unsubstituted monovalent aromatic heterocyclic group.

[0068] Compound group 1 represented by general formula (a) can be mentioned as a compound group of the present invention. Compound group 1 is A １ is a substituted or unsubstituted alkanediyl group, and Cy １ and Cy ２ Compound group 1a, A is a substituted or unsubstituted cycloalkyl group １ is a substituted or unsubstituted cycloalkanediyl group, and Cy １ and Cy ２ Compound group 1b, A is a substituted or unsubstituted cycloalkyl group; １ is a substituted or unsubstituted fluorenediyl group, and Cy １ and Cy ２ Compound group 1c, where A is a substituted or unsubstituted cycloalkyl group; １ is a substituted or unsubstituted alkanediyl group, and Cy１ and Cy ２ Compound group 1dA is a substituted or unsubstituted monovalent aromatic hydrocarbon group １ is a substituted or unsubstituted cycloalkanediyl group, and Cy １ and Cy ２ Compound group 1e, A is a substituted or unsubstituted monovalent aromatic hydrocarbon group; １ is a substituted or unsubstituted fluorenediyl group, and Cy １ and Cy ２ Compound group 1f, in which A is a substituted or unsubstituted monovalent aromatic hydrocarbon group; １ is a substituted or unsubstituted alkanediyl group, and Cy １ and Cy ２ Compound group 1g, A is a substituted or unsubstituted alkyl group; １ is a substituted or unsubstituted cycloalkanediyl group, and Cy １ and Cy ２ Compound group 1h, A is a substituted or unsubstituted alkyl group; １ is a substituted or unsubstituted fluorenediyl group, and Cy １ and Cy ２ Each of the compound groups 1a to 1i may further satisfy at least one of the following additional conditions. One of the additional conditions is that A １ is an unsubstituted alkanediyl group, an unsubstituted cycloalkanediyl group, or an unsubstituted fluorenediyl group. １ and Cy ２ is an unsubstituted cycloalkyl group, an unsubstituted monovalent aromatic hydrocarbon group, or an unsubstituted alkyl group. １ and Cy ２ are identical. One additional condition is a condition described in any one of the above groups listed as being included in general formula (a) and general formula (a1).

[0069] Compound group 2 represented by general formula (b) can be mentioned as a compound group of the present invention. Compound group 2 is A ２ is a substituted or unsubstituted alkanediyl group, and Cy ３and Cy ４ Compound group 2a, A is a substituted or unsubstituted cycloalkyl group ２ is a substituted or unsubstituted cycloalkanediyl group, and Cy ３ and Cy ４ Compound group 2b, A is a substituted or unsubstituted cycloalkyl group; ２ is a substituted or unsubstituted fluorenediyl group, and Cy ３ and Cy ４ Compound group 2c, where A is a substituted or unsubstituted cycloalkyl group; ２ is a substituted or unsubstituted alkanediyl group, and Cy ３ and Cy ４ Compound group 2d, in which A is a substituted or unsubstituted monovalent aromatic hydrocarbon group; ２ is a substituted or unsubstituted cycloalkanediyl group, and Cy ３ and Cy ４ Compound group 2e, A is a substituted or unsubstituted monovalent aromatic hydrocarbon group; ２ is a substituted or unsubstituted fluorenediyl group, and Cy ３ and Cy ４ Compound group 2f, in which A is a substituted or unsubstituted monovalent aromatic hydrocarbon group; ２ is a substituted or unsubstituted alkanediyl group, and Cy ３ and Cy ４ Compound group 2g, A is a substituted or unsubstituted alkyl group ２ is a substituted or unsubstituted cycloalkanediyl group, and Cy ３ and Cy ４ Compound group 2h, A is a substituted or unsubstituted alkyl group; ２ is a substituted or unsubstituted fluorenediyl group, and Cy ３ and Cy ４ Each of the compound groups 2a to 2i may further satisfy at least one of the following additional conditions. One of the additional conditions is that A ２ is an unsubstituted alkanediyl group, an unsubstituted cycloalkanediyl group, or an unsubstituted fluorenediyl group. ３ and Cy４ is an unsubstituted cycloalkyl group, an unsubstituted monovalent aromatic hydrocarbon group, or an unsubstituted alkyl group. ３ and Cy ４ are identical. One additional condition is a condition described in any one of the above groups listed as being included in general formula (b) and general formula (b1).

[0070] Specific examples of aromatic compounds represented by general formula (a) or (b) are given below, but the aromatic compounds represented by general formula (a) or (b) that can be used in the present invention should not be construed as being limited by these specific examples.

[0071]

[0072]

[0073]

[0074]

[0075]

[0076]

[0077]

[0078]

[0079]

[0080] <Method for synthesizing aromatic compounds represented by general formula (a) or general formula (b)> The aromatic compounds represented by general formula (a) or general formula (b) are novel compounds. The aromatic compounds represented by general formula (a) or general formula (b) can be synthesized using known reactions, such as the reaction of an acid chloride with an amine or the reaction of an acid chloride with a hydroxyl compound. For details of the synthesis method, please refer to the synthesis examples described below.

[0081] The method for producing the aromatic compound represented by general formula (a) or general formula (b) is not particularly limited. For example, the aromatic compound can be purified by a known method used for purifying organic compounds, such as purification by column chromatography, recrystallization or crystallization using a solvent, or sublimation purification. The compound can be identified by NMR analysis, mass spectrometry, or the like.

[0082] As physical property values ​​of the aromatic compound represented by general formula (a) or (b) of the present invention, it is preferable to measure the melting point, glass transition point (Tg), and refractive index. The melting point is an index of vapor deposition property, the glass transition point (Tg) is an index of stability of the thin film state, and the refractive index is an index of improvement in light extraction efficiency.

[0083] The melting point and glass transition point (Tg) of the aromatic compound of the present invention can be measured, for example, by using a powder with a high-sensitivity differential scanning calorimeter (DSC3100SA, manufactured by Bruker AXS).

[0084] The refractive index and extinction coefficient of the aromatic compound of the present invention can be measured by forming an 80 nm thin film on a silicon substrate and using a spectrophotometer (F10-RT-UV, manufactured by Filmetrics).

[0085] The aromatic compound represented by general formula (a) or (b) of the present invention is characterized by a low refractive index. Therefore, a capping layer formed by stacking a first capping layer (low refractive index layer) containing the aromatic compound and a second capping layer (high refractive index layer) having a higher refractive index than the first capping layer can be disposed on the outer side of the light-extraction electrode of an organic EL device (opposite the light-emitting layer side of the electrode) so that the first capping layer faces the electrode. This effectively improves light extraction efficiency through the light interference effect of the capping layer, thereby achieving high luminous efficiency. Furthermore, the aromatic compound represented by general formula (a) or (b) has a melting point suitable for vapor deposition and a high glass transition temperature, resulting in a stable thin film. Herein, the term "capping layer" refers to a layer disposed on the opposite side (outside) of at least one of the electrodes in an organic EL device having a light-emitting layer disposed between a pair of electrodes. The capping layer containing the aromatic compound represented by general formula (a) or (b) may be disposed on the outer side of only one of the pair of electrodes, or may be disposed on the outer side of both electrodes. An organic layer such as a charge transport layer may be disposed between the light-emitting layer and each electrode of the organic EL element to which the capping layer is applied.

[0086] <Organic Electroluminescence Element> Next, the organic electroluminescence element (organic EL element) of the present invention will be described. The organic EL element of the present invention has at least an anode electrode, a hole transport layer, an emitting layer, an electron transport layer, a cathode electrode, and a capping layer, in this order, and is characterized in that the capping layer contains an aromatic compound represented by general formula (a) or general formula (b). For an explanation of the aromatic compound represented by general formula (a) or general formula (b), please refer to the description in the above section "Aromatic Compound Represented by General Formula (a) or General Formula (b)." In a preferred embodiment of the present invention, the capping layer is formed by laminating a first capping layer (low refractive index layer) containing an aromatic compound represented by general formula (a) or general formula (b) and a second capping layer (high refractive index layer) having a refractive index higher than that of the first capping layer. In this configuration, the second capping layer has a high refractive index, which improves the light extraction efficiency of the organic EL element. Furthermore, the high reflectivity at the interface between the second capping layer and the first capping layer creates a light interference effect, further enhancing the light extraction efficiency improvement effect of the second capping layer. The capping layer is preferably arranged such that the first capping layer is on the electrode side (the second capping layer is on the outside) of the first capping layer and the second capping layer. In a more preferred embodiment of the present invention, the organic EL element has at least an anode electrode, a hole transport layer, an emitting layer, an electron transport layer, a cathode electrode, a first capping layer, and a second capping layer, in this order.

[0087] The organic EL device of the present invention may have a top-emission structure, for example, comprising an anode, a hole transport layer, an emitting layer, an electron transport layer, a cathode, and a capping layer, arranged in this order on a substrate made of glass or the like. It may also have a hole injection layer between the anode and the hole transport layer, an electron blocking layer between the hole transport layer and the emitting layer, a hole blocking layer between the emitting layer and the electron transport layer, or an electron injection layer between the electron transport layer and the cathode. In these multilayer structures, some organic layers may be omitted or may serve as both layers. For example, a layer may serve as both a hole injection layer and a hole transport layer, a layer may serve as both a hole transport layer and an electron blocking layer, a layer may serve as both a hole blocking layer and an electron transport layer, or a layer may serve as both an electron transport layer and an electron injection layer. It may also have a structure in which two or more organic layers having the same function are stacked, such as a layer with two hole transport layers, a layer with two emitting layers, a layer with two electron transport layers, or a layer with two capping layers.

[0088] The total thickness of each layer of the organic EL element is preferably about 200 nm to 750 nm, more preferably about 350 nm to 600 nm. The thickness of the capping layer is preferably, for example, 30 nm to 120 nm, more preferably 40 nm to 80 nm. In this case, good light extraction efficiency can be obtained. The thickness of the capping layer can be appropriately changed depending on the type of light-emitting material used in the light-emitting element, the thickness of the organic EL element other than the capping layer, and other factors. Each component and layer constituting the organic EL element will be described below.

[0089] [Anode] As the material for the anode of the organic EL element of the present invention, an electrode material having a large work function, such as ITO (indium tin oxide) or gold, is used.

[0090] [Hole Injection Layer] The hole injection layer of the organic EL device of the present invention can be an arylamine compound having three or more triphenylamine structures in the molecule, with these triphenylamine structures connected by a single bond or a divalent group not containing a heteroatom. Examples of arylamine compounds include starburst triphenylamine derivatives and various triphenylamine tetramers. Materials for the hole injection layer can also include porphyrin compounds such as copper phthalocyanine, acceptor heterocyclic compounds such as hexacyanoazatriphenylene, and coating-type polymeric materials. The hole injection layer can be composed of a single layer formed from one of these hole injection materials, or a mixed layer formed from a mixture of two or more materials. The hole injection layer can have a single layer structure, a laminate structure of layers formed from a single material or a mixture of layers, or a laminate structure of layers formed from a single material and a mixture of layers. These materials can be formed into thin films by known methods such as vapor deposition, spin coating, and inkjet printing.

[0091] [Hole Transport Layer] For the hole transport layer of the organic EL device of the present invention, benzidine derivatives such as N,N'-diphenyl-N,N'-di(m-tolyl)benzidine (hereinafter abbreviated as TPD), N,N'-diphenyl-N,N'-di(α-naphthyl)benzidine (hereinafter abbreviated as NPD), N,N,N',N'-tetrabiphenylylbenzidine, 1,1-bis[4-(di-4-tolylamino)phenyl]cyclohexane (hereinafter abbreviated as TAPC), etc. are usable. In particular, it is preferable to use an arylamine compound having two triphenylamine structures in the molecule, and having a structure in which these triphenylamine structures are linked by a single bond or a divalent group not containing a heteroatom, such as N,N,N',N'-tetrabiphenylylbenzidine. In addition, it is preferable to use arylamine compounds having three or more triphenylamine structures in the molecule, with these triphenylamine structures linked by single bonds or divalent groups containing no heteroatoms, such as various triphenylamine trimers and tetramers. The hole transport layer may be composed of a single layer formed from one of these hole transport materials alone, or a mixed layer formed from a mixture of two or more materials. The hole transport layer may also have a single layer structure, a laminate structure formed from layers formed from a single material or a mixture of layers, or a laminate structure formed from a layer formed from a single material and a mixture of layers. Furthermore, a coating-type polymer material such as poly(3,4-ethylenedioxythiophene) (hereinafter abbreviated as PEDOT) / poly(styrene sulfonate) (hereinafter abbreviated as PSS) can be used as the hole injection / transport layer. These materials can be formed into thin films by known methods such as vapor deposition, spin coating, and inkjet printing.

[0092] Furthermore, in the hole injection layer or the hole transport layer, a material that is further doped with a p-type dopant such as trisbromophenylaminehexachloroantimony or a radialene derivative, or a polymer compound that includes a structure of a benzidine derivative such as TPD as a partial structure, can be used in addition to a material that is normally used in these layers.

[0093] [Electron Blocking Layer] The organic EL device of the present invention may have an electron blocking layer between the light-emitting layer and the hole-transporting layer. Examples of materials that can be used for the electron blocking layer include carbazole derivatives such as 4,4',4''-tri(N-carbazolyl)triphenylamine (hereinafter abbreviated as TCTA), 9,9-bis[4-(carbazol-9-yl)phenyl]fluorene, 1,3-bis(carbazol-9-yl)benzene (hereinafter abbreviated as mCP), and 2,2-bis(4-carbazol-9-ylphenyl)adamantane (hereinafter abbreviated as Ad-Cz), and compounds having a triphenylsilyl group and a triarylamine structure, such as 9-[4-(carbazol-9-yl)phenyl]-9-[4-(triphenylsilyl)phenyl]-9H-fluorene. The electron blocking layer may be a single layer formed from one of these electron blocking materials, or a mixed layer formed from a mixture of two or more materials. The electron blocking layer may have a single layer structure, a laminated structure formed from layers formed from a single material or a mixed layer, or a laminated structure formed from a layer formed from a single material and a mixed layer. These materials can be formed into thin films by known methods such as vapor deposition, spin coating, or inkjet printing.

[0094] [Light-emitting layer] As a material for the light-emitting layer of the organic EL element of the present invention, tris(8-quinolinolato)aluminum (Alq ３In addition to metal complexes of quinolinol derivatives such as quinolinol derivatives (e.g., quinolinol derivatives), various metal complexes, anthracene derivatives, bisstyrylbenzene derivatives, pyrene derivatives, oxazole derivatives, polyparaphenylenevinylene derivatives, and other light-emitting materials can be used. The light-emitting layer may be composed of a host material and a dopant material. Anthracene derivatives are preferably used as the host material. In addition to the above light-emitting materials, heterocyclic compounds having an indole ring as a partial structure of a fused ring, heterocyclic compounds having a carbazole ring as a partial structure of a fused ring, carbazole derivatives, thiazole derivatives, benzimidazole derivatives, polydialkylfluorene derivatives, and the like can also be used. Furthermore, quinacridone, coumarin, rubrene, perylene, and derivatives thereof, benzopyran derivatives, rhodamine derivatives, aminostyryl derivatives, and the like can also be used as the dopant material. Green light-emitting materials are particularly preferred. The light-emitting layer may be composed of a single layer formed by solely using one of the above light-emitting materials, or may be composed of a mixed layer formed by mixing two or more materials (for example, two or more light-emitting materials, or one or more host materials and one or more dopant materials). The light-emitting layer may have a single-layer structure, a laminated structure in which layers formed by solely using the light-emitting materials or layers formed by mixing the light-emitting materials are laminated, or a laminated structure in which a layer formed by solely using the light-emitting materials and a layer formed by mixing the light-emitting materials are laminated.

[0095] It is also possible to use a phosphorescent emitter as the light-emitting material. As the phosphorescent emitter, a phosphorescent emitter of a metal complex such as iridium or platinum can be used. For example, Ir(ppy) ３ green phosphorescent emitters such as FIrpic (bis[2-(4,6-difluorophenyl)pyridinato-C2,N](picolinato)iridium(III)) and FIr6 (bis(2,4-difluorophenylpyridinato)tetrakis(1-pyrazolyl)borate iridium(III)); ２Red phosphorescent emitters such as Ir(acac) (bis(2-benzo[b]thiophen-2-yl-pyridine)(acetylacetonato)iridium(III)) are used, and green phosphorescent emitters are particularly preferred. The light-emitting layer may be composed of only these phosphorescent emitters, or may be composed of a host material and a phosphorescent emitter (for example, a co-deposited film of a host material and a phosphorescent emitter). Carbazole derivatives such as 4,4'-di(N-carbazolyl)biphenyl (hereinafter abbreviated as CBP), TCTA, and mCP can be used as hole-injecting / transporting host materials. As the electron-transporting host material, p-bis(triphenylsilyl)benzene (hereinafter abbreviated as UGH2) or 2,2′,2″-(1,3,5-phenylene)-tris(1-phenyl-1H-benzimidazole) (hereinafter abbreviated as TPBI) can be used, and a high-performance organic EL device can be fabricated.

[0096] The amount of phosphorescent material doped into the host material is preferably in the range of 1 to 30 weight percent based on the amount of the light-emitting layer in order to avoid concentration quenching.

[0097] Furthermore, a material that emits delayed fluorescence can also be used as the light-emitting material. These materials can be formed into thin films by known methods such as vapor deposition, spin coating, and ink-jet printing.

[0098] [Hole Blocking Layer] The organic EL device of the present invention may have a hole blocking layer between the light-emitting layer and the electron-transporting layer. Examples of materials that can be used for the hole blocking layer include phenanthroline derivatives such as bathocuproine (hereinafter abbreviated as BCP), metal complexes of quinolinol derivatives such as aluminum(III) bis(2-methyl-8-quinolinato)-4-phenylphenolate (hereinafter abbreviated as BAlq), various rare earth complexes, triazole derivatives, triazine derivatives, pyrimidine derivatives, oxadiazole derivatives, and benzoazole derivatives. These materials may also serve as materials for the electron-transporting layer. The hole blocking layer may be composed of a single layer formed from one of these electron-blocking materials, or a mixed layer formed from a mixture of two or more materials. The hole blocking layer may have a single layer structure, a laminate structure formed from layers formed from a single material or a mixture of layers formed from a single material, or a laminate structure formed from a layer formed from a mixture of layers formed from a single material and a layer formed from a mixture of layers. These materials can be used to form thin films by known methods such as vapor deposition, spin coating, and ink jet printing.

[0099] [Electron Transport Layer] As a material for the electron transport layer of the organic EL element of the present invention, Alq ３ In addition to metal complexes of quinolinol derivatives such as BAlq, various metal complexes, triazole derivatives, triazine derivatives, pyrimidine derivatives, oxadiazole derivatives, pyridine derivatives, benzimidazole derivatives, benzoazole derivatives, thiadiazole derivatives, anthracene derivatives, carbodiimide derivatives, quinoxaline derivatives, pyridoindole derivatives, phenanthroline derivatives, silole derivatives, etc. can be used. The electron transport layer may be composed of a single layer formed by depositing one of these electron transport materials alone, or a mixed layer formed by mixing two or more materials. The electron transport layer may also have a single layer structure, a laminate structure formed by laminating layers formed by depositing layers formed by a single material or a mixed material, or a laminate structure formed by laminating layers formed by a single material and a mixed material. These materials can be formed into thin films by known methods such as vapor deposition, spin coating, inkjet printing, etc.

[0100] [Electron Injection Layer] Materials that can be used for the electron injection layer of the organic EL element of the present invention include alkali metal salts such as lithium fluoride and cesium fluoride, alkaline earth metal salts such as magnesium fluoride, metal complexes of quinolinol derivatives such as lithium quinolinol, metal oxides such as aluminum oxide, and metals such as ytterbium (Yb), samarium (Sm), calcium (Ca), strontium (Sr), and cesium (Cs). However, in the preferred selection of the electron transport layer and the cathode, these may be omitted.

[0101] Furthermore, as the material for the electron injection layer or electron transport layer, a material that is doped with an n-type metal dopant such as cesium in addition to the materials that are normally used for these layers can be used.

[0102] [Cathode] The cathode material for the organic EL element of the present invention may be an electrode material with a low work function such as aluminum, an alloy with an even lower work function such as a magnesium-silver alloy, a magnesium-calcium alloy, a magnesium-indium alloy, or an aluminum-magnesium alloy, or a conductive transparent material such as ITO (indium tin oxide) or IZO (indium zinc oxide). The metal or alloy is formed to a thickness of about 10 to 200 nm to form a semitransparent cathode.

[0103] [Capping Layer] The organic EL device of the present invention includes a capping layer containing an aromatic compound represented by general formula (a) or (b). As described above, the capping layer preferably has a laminated structure including a first capping layer containing an aromatic compound represented by general formula (a) or (b) and a second capping layer having a higher refractive index than the first capping layer, and preferably has a two-layer structure including a first capping layer and a second capping layer. Furthermore, a capping layer having a laminated structure is preferably arranged so that the first capping layer is adjacent to the cathode electrode. The capping layer and the first capping layer may contain only one or more of the aromatic compounds represented by general formula (a). The capping layer and the first capping layer may contain only one or more of the aromatic compounds represented by general formula (b). Furthermore, the capping layer and the first capping layer may contain only one or both of the aromatic compounds represented by general formula (a) and the aromatic compounds represented by general formula (b). The second capping layer is made of a material having a refractive index higher than that of the aromatic compound used in the first capping layer, such as an arylamine compound (see, for example, Patent Documents 4 and 5).

[0104] The refractive index of the material constituting the second capping layer is preferably 0.15 or more higher than the refractive index of the adjacent first capping layer, more preferably 0.20 or more higher, and even more preferably 0.30 or more higher. The first capping layer and the second capping layer may each be composed of a single layer formed from one of the above-mentioned capping layer materials alone, or may be composed of a mixed layer formed from a mixture of two or more materials. These materials can be formed into thin films by known methods such as vapor deposition, spin coating, inkjet printing, etc.

[0105] The total thickness of the first capping layer and the second capping layer is, for example, preferably 30 nm to 120 nm, more preferably 40 nm to 80 nm. The thickness ratio of the first capping layer to the second capping layer is preferably 1:99 to 99:1, more preferably 90:10 to 90:10, and even more preferably 20:80 to 80:20. In this case, good light extraction efficiency can be obtained. The thicknesses of the first capping layer and the second capping layer can be appropriately changed depending on the type of light-emitting material used in the light-emitting element, the thickness of the organic EL element other than the capping layer, and the like.

[0106] While the present invention has been described above using an organic EL element with a top emission structure as an example, the organic EL element to which the present invention is applicable is not limited thereto and may also be a bottom emission organic EL element or a dual emission organic EL element that emits light from both the top and bottom. For descriptions of the components and layers constituting organic EL elements with bottom emission and dual emission structures, please refer to the descriptions of the organic EL elements described above. However, the electrode in the direction in which light is extracted from the light-emitting element must be transparent or translucent. That is, in a bottom emission structure, the electrode on the substrate side is preferably transparent or translucent, while in a dual emission structure, both electrodes are preferably transparent or translucent. Furthermore, in a bottom emission structure, a capping layer can be provided between the electrode on the substrate side and the substrate. In a dual emission structure, a capping layer can be provided between the electrode on the substrate side and the substrate, or on the outside of the electrode on the side opposite the substrate, or it can be provided on only one of them.

[0107] <Electronic Device and Electronic Element> The electronic device and electronic element of the present invention have a pair of electrodes and at least one organic layer, and at least one of the organic layers contains an aromatic compound represented by general formula (a) or general formula (b). For an explanation of the aromatic compound represented by general formula (a) or general formula (b), please refer to the description in the above section "Aromatic Compound Represented by General Formula (a) or General Formula (b)." Examples of the electronic device include display devices and light-emitting devices equipped with organic EL elements, as well as electrophotographic photoreceptors, image sensors, photoelectric conversion elements, solar cells, etc. Examples of the display device include display components such as organic EL panel modules, televisions, mobile phones, tablets, personal computers, etc. Examples of the light-emitting device include lighting or vehicle lamps, etc.

[0108] Hereinafter, the embodiments of the present invention will be described in detail with reference to examples. However, the present invention is not limited to the following examples as long as it does not depart from the gist of the present invention. In these examples, the light-emitting characteristics of the organic EL element were measured at a current density of 10 mA / cm. ２ First, in the following Examples 1 to 8, aromatic compounds represented by general formula (a) or general formula (b) were synthesized.

[0109] Example 1 Synthesis of Compound (1-7) 5.0 g of 2,2'-bis(4-aminophenyl)hexafluoropropane, 6.4 g of triethylamine, and 100 mL of tetrahydrofuran were added to a reaction vessel and stirred in an ice bath for 30 minutes. A mixture of 6.3 g of 1-adamantanecarbonyl chloride and 20 mL of tetrahydrofuran was added dropwise to the reaction vessel over 30 minutes and stirred for 3 hours. The mixture was warmed to room temperature and stirred overnight, after which 100 mL of water and 300 mL of dichloromethane were added and an extraction operation was carried out. The organic layer was concentrated, and the resulting solid was dispersed and washed sequentially with 200 mL of methanol and 50 mL of dichloromethane to obtain 8.2 g of a white powder of (1-7) (yield: 83.2%).

[0110]

[0111] The structure of the resulting white powder was identified using NMR.１ H-NMR (CDCl ３ The following 40 hydrogen signals were detected at δ (ppm) = 7.55 (4H), 7.36-7.31 (6H), 2.11 (6H), 1.96 (12H), 1.76 (12H).

[0112] Example 2 Synthesis of Compound (1-8) 7.0 g of 2,2'-bis(4-hydroxyphenyl)hexafluoropropane, 4.9 g of triethylamine, and 30 mL of dichloromethane were added to a reaction vessel and stirred in an ice bath for 30 minutes. A mixture of 8.7 g of 1-adamantanecarbonyl chloride and 20 mL of dichloromethane was added dropwise to the reaction vessel over 30 minutes and stirred for 3 hours. The mixture was warmed to room temperature and stirred overnight, after which 50 mL of water was added and the precipitated solid was collected by filtration. 60 mL of methanol and 60 mL of water were added, dispersed and washed, and then cooled to room temperature, after which the solid was collected by filtration. The obtained solid was washed with 130 mL of methanol to obtain 12.3 g of white powder of (1-8) (yield: 89.2%).

[0113]

[0114] The structure of the resulting white powder was identified using NMR. １ H-NMR (CDCl ３ The following 38 hydrogen signals were detected at δ (ppm): δ (ppm) = 7.39 (4H), 7.08 (4H), 2.09-2.06 (18H), 1.77 (12H).

[0115] Example 3 Synthesis of Compound (1-10) 5.1 g of 1-adamantamine hydrochloride, 5.5 g of triethylamine, and 100 mL of tetrahydrofuran were added to a reaction vessel and stirred in an ice bath for 30 minutes. A mixture of 5.5 g of 4,4'-[2,2,2-trifluoro-1-(trifluoromethyl)ethylidene]bis[benzoyl chloride] and 20 mL of tetrahydrofuran was added dropwise to the reaction vessel over 30 minutes and stirred for 3 hours. The mixture was warmed to room temperature and stirred overnight. Then, 120 mL of water and 300 mL of dichloromethane were added and an extraction operation was carried out. The organic layer was concentrated, and the resulting solid was dispersed and washed with 200 mL of methanol, yielding 6.6 g of white powder of (1-10) (yield: 78.2%).

[0116]

[0117] The structure of the resulting white powder was identified using NMR. １ H-NMR (CDCl ３ ) the following 40 hydrogen signals were detected: δ (ppm) = 7.71 (4H), 7.41 (4H), 5.79 (2H), 2.12 (18H), 1.72 (12H).

[0118] Example 4 Synthesis of Compound (1-19) 4.0 g of 1,1'-bis(4-aminophenyl)cyclohexane, 6.4 g of triethylamine, and 140 mL of tetrahydrofuran were added to a reaction vessel and stirred in an ice bath for 30 minutes. A mixture of 6.3 g of 1-adamantanecarbonyl chloride and 28 mL of tetrahydrofuran was added dropwise to the reaction vessel over 30 minutes and stirred for 2 hours. The temperature was raised to room temperature and stirred for 3 hours, after which water was added and the precipitated solid was collected by filtration. The obtained solid was dispersed and washed with methanol and then subjected to THF crystallization to obtain 6.6 g of white powder of (1-19) (yield: 74.4%).

[0119]

[0120] The structure of the resulting white powder was identified using NMR. １ H-NMR (CDCl ３The following 50 hydrogen signals were detected at δ (ppm): δ (ppm) = 7.43 (4H), 7.22-7.18 (6H), 2.20 (4H), 2.09 (6H), 1.94 (12H), 1.75 (12H), 1.53-1.47 (6H).

[0121] Example 5 Synthesis of Compound (1-2) 5.0 g of 2,2'-bis(4-hydroxyphenyl)propane, 4.9 g of triethylamine, and 20 mL of dichloromethane were added to a reaction vessel and stirred in an ice bath for 30 minutes. A mixture of 9.2 g of 1-adamantanecarbonyl chloride and 15 mL of dichloromethane was added dropwise to the reaction vessel over 30 minutes and stirred for 2 hours. The mixture was warmed to room temperature and stirred overnight, after which 0.6 g of triethylamine was added and stirred in an ice bath for 30 minutes. A mixture of 1.0 g of 1-adamantanecarbonyl chloride and 5 mL of dichloromethane was added dropwise to the reaction vessel over 30 minutes and stirred for 2 hours. The mixture was warmed to room temperature and stirred for 2 hours, after which 60 mL of water was added. After stirring for 1 hour, the precipitated solid was collected by filtration. 120 mL of methanol and 120 mL of water were added, dispersed and washed, and the solid was collected by filtration. The obtained crude product was crystallized using a mixed solvent of toluene and methanol to obtain 9.3 g (yield: 76.9%) of white powder of (1-2).

[0122]

[0123] The structure of the resulting white powder was identified using NMR. １ H-NMR (CDCl ３ The following 44 hydrogen signals were detected at δ (ppm) = 7.20 (4H), 6.93 (4H), 2.08 (6H), 2.04 (12H), 1.76 (12H), 1.65 (6H).

[0124] Example 6 Synthesis of Compound (1-20) 5.0 g of 1,1'-bis(4-hydroxyphenyl)cyclohexane, 4.1 g of triethylamine, and 20 mL of dichloromethane were added to a reaction vessel and stirred in an ice bath for 30 minutes. A mixture of 7.8 g of 1-adamantanecarbonyl chloride and 10 mL of dichloromethane was added dropwise to the reaction vessel over 30 minutes and stirred for 2 hours. The mixture was warmed to room temperature and stirred overnight, after which 100 mL of water and 200 mL of dichloromethane were added and an extraction operation was performed. The organic layer was concentrated, and the resulting crude product was crystallized using a dichloromethane / methanol mixed solvent to obtain 9.1 g of white powder (1-20) (yield: 82.4%).

[0125]

[0126] The structure of the resulting white powder was identified using NMR. １ H-NMR (CDCl ３ The following 48 hydrogen signals were detected at δ (ppm): δ (ppm) = 7.23 (4H), 6.94 (4H), 2.24 (4H), 2.07 (6H), 2.03 (12H), 1.76 (12H), 1.55-1.49 (6H).

[0127] Example 7 Synthesis of Compound (1-193) 4.4 g of 1-adamantanemethylamine, 5.4 g of triethylamine, and 120 mL of tetrahydrofuran were added to a reaction vessel and stirred in an ice bath for 30 minutes. A mixture of 5.8 g of 4,4'-[2,2,2-trifluoro-1-(trifluoromethyl)ethylidene]bis[benzoyl chloride] and 20 mL of tetrahydrofuran was added dropwise to the reaction vessel over 30 minutes and stirred for 3 hours. The mixture was warmed to room temperature and stirred overnight. 150 mL of water was added, dispersed and washed, and the solid was collected by filtration. The resulting crude product was crystallized using a tetrahydrofuran / methanol mixed solvent to obtain 5.5 g of white powder (1-193) (yield: 62.6%).

[0128]

[0129] The structure of the resulting white powder was identified using NMR. １ H-NMR (CDCl ３The following 44 hydrogen signals were detected at δ (ppm) = 7.77 (4H), 7.45 (4H), 6.16 (2H), 3.17 (4H), 2.00 (6H), 1.75-1.56 (24H).

[0130] Example 8 Synthesis of Compound (1-194) 5.8 g of 3,5-dimethyl-1-adamantamine hydrochloride, 5.4 g of triethylamine, and 120 mL of tetrahydrofuran were added to a reaction vessel and stirred in an ice bath for 30 minutes. A mixture of 5.9 g of 4,4'-[2,2,2-trifluoro-1-(trifluoromethyl)ethylidene]bis[benzoyl chloride] and 20 mL of tetrahydrofuran was added dropwise to the reaction vessel over 30 minutes and stirred for 3 hours. The mixture was warmed to room temperature and stirred overnight. 150 mL of water was added, dispersed and washed, and the solid was collected by filtration. The resulting crude product was crystallized using a tetrahydrofuran / methanol mixed solvent to obtain 4.0 g of white powder (1-194) (yield: 44.2%).

[0131]

[0132] The structure of the resulting white powder was identified using NMR. １ H-NMR (CDCl ３ The following 48 hydrogen signals were detected at δ (ppm) = 7.70 (4H), 7.40 (4H), 5.81 (2H), 2.20 (2H), 1.95 (4H), 1.76 (8H), 1.45-1.19 (12H), 0.88 (12H).

[0133] [Example 9] Measurement of glass transition point and melting point The glass transition points of the aromatic compounds obtained in Examples 1 to 8 were measured using a high-sensitivity differential scanning calorimeter (DSC3100SA, manufactured by Bruker AXS). The measurement results are summarized in Table 1.

[0134]

[0135] [Example 10] Measurement of refractive index Using the aromatic compounds obtained in Examples 1 to 8, a vapor-deposited film having a thickness of 80 nm was prepared on a silicon substrate, and the refractive index n was measured at room temperature using a spectrophotometer (F10-RT-UV, manufactured by Filmetrics). In addition, in the following examples of preparing organic EL devices, the compound (CPL-1) used as a high refractive index capping material and Alq ３ The refractive index n was also measured for each of the samples. The measurement results are shown in Table 2.

[0136]

[0137]

[0138] As shown in Table 2, the refractive index of the aromatic compound of the present invention is 1.70 or less in the wavelength range of 400 nm to 700 nm, and Alq ３ and has a refractive index smaller than that of the compound (CPL-1).

[0139] Example 11 Preparation of Organic EL Device Using Compound (1-7) As shown in FIG. 10 , a reflective ITO electrode was previously formed as a transparent anode 2 on a glass substrate 1, and a hole injection layer 3, a hole transport layer 4, an emitting layer 5, an electron transport layer 6, an electron injection layer 7, a cathode 8, a first capping layer 9, and a second capping layer 10 were deposited in this order by vapor deposition thereon to prepare an organic EL device.

[0140] Specifically, a glass substrate 1 on which a 50 nm thick ITO film, a 100 nm thick silver alloy reflective film, and a 5 nm thick ITO film were sequentially formed was subjected to ultrasonic cleaning in isopropyl alcohol for 20 minutes and then dried for 10 minutes on a hot plate heated to 250°C. After that, UV ozone treatment was performed for 2 minutes, and the ITO-coated glass substrate was mounted in a vacuum deposition machine and the pressure was reduced to 0.001 Pa or less. Subsequently, a hole injection layer 3 was formed covering the transparent anode 2 by binary deposition of an electron acceptor (Acceptor-1) of the following structural formula and a compound (3-1) of the following structural formula at a deposition rate ratio of (Acceptor-1):Compound (3-1) = 3:97, resulting in a thickness of 10 nm. On this hole injection layer 3, a hole transport layer 4 was formed of a compound (3-1) of the following structural formula to a thickness of 140 nm. On this hole transport layer 4, a light-emitting layer 5 was formed by binary deposition of a compound (EMD-1) having the following structural formula and a compound (EMH-1) having the following structural formula at a deposition rate ratio of (EMD-1):(EMH-1) = 5:95, to a thickness of 20 nm. On this light-emitting layer 5, a compound (4-1) having the following structural formula and a compound (ETM-1) having the following structural formula at a deposition rate ratio of (4-1):(ETM-1) = 50:50, to a thickness of 30 nm. On this electron transport layer 6, lithium fluoride was formed as an electron injection layer 7 to a thickness of 1 nm.

[0141] On this electron injection layer 7, a magnesium-silver alloy was formed as a cathode 8 to a thickness of 12 nm. On the cathode 8, a first capping layer 9 was formed of the compound (1-7) of Example 1 to a thickness of 30 nm, and finally, a second capping layer 10 was formed of the compound (CPL-1) to a thickness of 30 nm. The light-emitting characteristics of the produced organic EL device were measured by applying a DC voltage in the atmosphere at room temperature. The measurement results are summarized in Table 3.

[0142]

[0143] Example 12 Preparation of Organic EL Device Using Compound (1-8) An organic EL device was prepared under the same conditions as in Example 11, except that compound (1-8) was used instead of compound (1-7) as the material for first capping layer 9, and first capping layer 9 was formed to a thickness of 30 nm. The light-emitting characteristics of the prepared organic EL device were measured by applying a DC voltage in the atmosphere at room temperature. The measurement results are summarized in Table 3.

[0144] Example 13 Preparation of Organic EL Device Using Compound (1-10) An organic EL device was prepared under the same conditions as in Example 11, except that compound (1-10) was used instead of compound (1-7) as the material for first capping layer 9, and first capping layer 9 was formed to a thickness of 30 nm. The light-emitting characteristics of the prepared organic EL device were measured by applying a DC voltage in the atmosphere at room temperature. The measurement results are summarized in Table 3.

[0145] Example 14 Preparation of Organic EL Device Using Compound (1-19) An organic EL device was prepared under the same conditions as in Example 11, except that compound (1-19) was used instead of compound (1-7) as the material for first capping layer 9, and first capping layer 9 was formed to a thickness of 30 nm. The light-emitting characteristics of the prepared organic EL device were measured by applying a DC voltage in the atmosphere at room temperature. The measurement results are summarized in Table 3.

[0146] Example 15 Preparation of Organic EL Device Using Compound (1-2) An organic EL device was prepared under the same conditions as in Example 11, except that compound (1-2) was used instead of compound (1-7) as the material for first capping layer 9, and first capping layer 9 was formed to a thickness of 30 nm. The light-emitting characteristics of the prepared organic EL device were measured by applying a DC voltage in the atmosphere at room temperature. The measurement results are summarized in Table 3.

[0147] Example 16 Preparation of Organic EL Device Using Compound (1-20) An organic EL device was prepared under the same conditions as in Example 11, except that compound (1-20) was used instead of compound (1-7) as the material for first capping layer 9, and first capping layer 9 was formed to a thickness of 30 nm. The light-emitting characteristics of the prepared organic EL device were measured by applying a DC voltage in the atmosphere at room temperature. The measurement results are summarized in Table 3.

[0148] Example 17 Preparation of Organic EL Device Using Compound (1-193) An organic EL device was prepared under the same conditions as in Example 11, except that compound (1-193) was used instead of compound (1-7) as the material for first capping layer 9, and first capping layer 9 was formed to a thickness of 30 nm. The light-emitting characteristics of the prepared organic EL device were measured by applying a DC voltage in the atmosphere at room temperature. The measurement results are summarized in Table 3.

[0149] Example 18 An organic EL device was fabricated under the same conditions as in Example 11, except that compound (1-194) was used instead of compound (1-7) as the material for first capping layer 9, and first capping layer 9 was formed to a thickness of 30 nm. The light-emitting characteristics of the fabricated organic EL device were measured by applying a DC voltage in the atmosphere at room temperature. The measurement results are summarized in Table 3.

[0150] [Comparative Example 1] Alq ３ As the material for the first capping layer 9, Alq was used instead of the compound (1-13). ３ An organic EL device was fabricated under the same conditions as in Example 7, except that a first capping layer was formed using the compound (I) to a thickness of 30 nm. The light-emitting characteristics of the fabricated organic EL device were measured by applying a DC voltage in the atmosphere at room temperature. The measurement results are summarized in Table 3.

[0151] Comparative Example 2 Preparation of Organic EL Device Having a Single-Layer Capping Layer An organic EL device was prepared under the same conditions as in Example 7, except that instead of the capping layer consisting of first capping layer 9 and second capping layer 10, a single-layer capping layer was formed by depositing compound (CPL-1) to a thickness of 60 nm. The light-emitting characteristics of the prepared organic EL device were measured by applying a DC voltage in the atmosphere at room temperature. The measurement results are summarized in Table 3.

[0152] The device lifespans of the organic EL devices fabricated in Examples 11 to 18 and Comparative Examples 1 and 2 were measured and the results are shown in Table 3. The device lifespan was 10 mA / cm ２ The brightness was expressed as the time it took for the brightness to decay to 95% of the initial brightness when the device was driven at a constant current of 1000 kJ / s.

[0153]

[0154] As shown in Table 3, the current density was 10 mA / cm ２ The driving voltage at this time was almost the same for the elements of Comparative Examples 1 and 2 and the elements of Examples 11 to 18. In contrast, the luminance, luminous efficiency, power efficiency, and lifespan were all improved for the elements of Examples 11 to 18 compared to the elements of Comparative Examples 1 and 2. This shows that the light extraction efficiency can be significantly improved by providing a stacked structure of a first capping layer containing the aromatic compound of the present invention and a second capping layer having a high refractive index as a capping layer.

[0155] An organic EL device having a capping layer containing the aromatic compound of the present invention, particularly an organic EL device in which a second capping layer having a high refractive index is laminated on a first capping layer containing the aromatic compound of the present invention, can achieve high efficiency and can be effectively used in various devices using light-emitting elements. Therefore, the present invention has high industrial applicability.

[0156] REFERENCE SIGNS LIST 1 glass substrate 2 transparent anode 3 hole injection layer 4 hole transport layer 5 light emitting layer 6 electron transport layer 7 electron injection layer 8 cathode 9 first capping layer 10 second capping layer

Claims

1. An electronic element or electronic device having a pair of electrodes and at least one organic layer, wherein the organic layer contains an aromatic compound represented by the following general formula (a) or (b): 【Chemistry 1】 【Chemistry 2】 [In the general formula (a) and the general formula (b), A １ and A ２ each independently represents a substituted or unsubstituted alkanediyl group, a substituted or unsubstituted cycloalkanediyl group, or a substituted or unsubstituted fluorenediyl group, L １ ~L ４ each independently represents a single bond, —O—, —NH—, or a substituted or unsubstituted alkanediyl group, R １ ~R １６ each independently represents a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted monovalent aromatic hydrocarbon group, or a substituted or unsubstituted monovalent aromatic heterocyclic group; Cy １ ~Cy ４ each independently represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, or an unsubstituted monovalent aromatic hydrocarbon group, X １ ~X ４ each independently represents —O— or —NH—.]

2. 2. The electronic element or electronic device according to claim 1, wherein the organic EL element has at least an anode electrode, a hole transport layer, a light-emitting layer, an electron transport layer, a cathode electrode, and a capping layer in this order, and the capping layer contains an aromatic compound represented by the general formula (a) or the general formula (b).

3. 3. The electronic element or electronic device according to claim 2, wherein the aromatic compound exhibits a refractive index of 1.70 or less at room temperature for light having a wavelength of 400 nm or more and 700 nm or less when vacuum-deposited to form a vapor-deposited film having a thickness of 80 nm on a silicon substrate.

4. 3. The electronic device or electronic equipment according to claim 2, wherein the capping layer is a laminated or mixed layer made of two or more compounds, and at least one of the compounds in the capping layer is the aromatic compound.

5. An aromatic compound represented by the following general formula (a) or (b): 【Transformation 3】 【Chemistry 4】 [In general formula (a) and general formula (b), A 1 represents a substituted or unsubstituted alkanediyl group, or a substituted or unsubstituted cycloalkanediyl group; A 2 represents an alkanediyl group optionally substituted with a halogen atom, or a substituted or unsubstituted cycloalkanediyl group; L １ and L 2 each independently represent a single bond, —O—, —NH—, or a substituted or unsubstituted alkanediyl group; L 3 and L 4 each independently represent a single bond, —O—, or a substituted or unsubstituted alkanediyl group; R １ R 9 to R 16 each independently represent a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted monovalent aromatic hydrocarbon group, or a substituted or unsubstituted monovalent aromatic heterocyclic group; R 9 to R 16 each independently represent a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, an unsubstituted monovalent aromatic hydrocarbon group, or a substituted or unsubstituted monovalent aromatic heterocyclic group; Cy １ ~Cy ４ each independently represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, or a substituted or unsubstituted monovalent aromatic hydrocarbon group, and the cycloalkyl group of the substituted or unsubstituted cycloalkyl group represented by Cy 3 and Cy 4 is a monocyclic cycloalkyl group, a bicycloalkyl group, or a tricycloalkyl group; X １ ~X ４ each independently represents —O— or —NH—.]

6. R in the general formula (a) １ ~R ８ and R in the general formula (b) ９ ~R １６ and each independently represent a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted cycloalkyl group.

7. The aromatic compound according to claim 6, wherein A 1 in the general formula (a) is a divalent group represented by the following formula (c), formula (d), formula (e), formula (f), or formula (g), and A 2 in the general formula (b) is a divalent group represented by the following formula (c), formula (d), formula (e), or formula (f). 【Transformation 5】 [In formula (c), Ak １ and Ak ２ each independently represents a hydrogen atom, an unsubstituted alkyl group, or an unsubstituted haloalkyl group, and the dashed line represents a bonding site. 【Transformation 6】 [In formula (d), the dashed line represents a binding site.] 【Transformation 7】 [In formula (e), the dashed line represents a binding site.] 【Transformation 8】 [In formula (f), the dashed line represents a binding site.] 【Chemistry 9】 [In formula (g), the dashed line represents a binding site.]

8. L in the general formula (a) １ and L 2 represent a single bond, -O-, -NH-, a substituted or unsubstituted methylene group, a substituted or unsubstituted ethanediyl group, or a substituted or unsubstituted propanediyl group, and L 3 and L 4 in general formula (b) represent a single bond, -O-, a substituted or unsubstituted methylene group, a substituted or unsubstituted ethanediyl group, or a substituted or unsubstituted propanediyl group.

9. Cy in the general formula (a) １ and Cy ２ and Cy of the general formula (b). ３ and Cy ４ each independently represent a substituted or unsubstituted methyl group, a substituted or unsubstituted cyclohexyl group, a substituted or unsubstituted norbornyl group, a substituted or unsubstituted adamantyl group, or a substituted or unsubstituted phenyl group.

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