Carbazole compound and organic electroluminescent element

Abstract

This carbazole compound represented by general formula (I) has a high refractive index and a low extinction coefficient with respect to wavelengths of 450-750 nm. Therefore, an organic EL element having excellent luminous efficiency can be provided by using the carbazole compound as a material for a capping layer. A to C each represent an aryl group or a heteroaryl group, and at least one of them is a pyrimidinyl group, a pyrazinyl group, a pyridazinyl group, or a cyanopyridyl group. L1 to L3 each represent a single bond, an arylene group, or a heteroarylene group.

Description

Carbazole compound and organic electroluminescent device

[0001] The present invention relates to a compound suitable for a self-luminous electronic element suitable for various display devices, particularly a carbazole compound suitable for an organic electroluminescence element (hereinafter abbreviated as organic EL element), and to an organic EL element, an electronic element and an electronic device using the compound.

[0002] Organic EL elements are self-luminous elements, and therefore are brighter and more visible than liquid crystal elements, and are capable of producing clearer displays, and therefore have been the subject of vigorous research.

[0003] 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 achieved (see, for example, Patent Documents 1 and 2).

[0004] To date, many improvements have been made to the practical application of organic EL elements, and the role of each layer in the laminated structure has been further subdivided. An anode, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer, and a cathode are sequentially provided on a substrate to form a light-emitting element with a bottom emission structure that emits light from the bottom, thereby achieving high efficiency and durability (see, for example, Non-Patent Document 1).

[0005] 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 2), Ca / Mg (see, for example, Non-Patent Document 3), or LiF / MgAg is used as the cathode.

[0006] 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, in order to improve the light extraction efficiency, light-emitting devices have been proposed in which a "capping layer" with a high refractive index is provided on the outside of a semi-transparent electrode with a low refractive index (see, for example, Non-Patent Documents 2 and 3).

[0007] As an effect of the capping layer in a top-emission light-emitting device, Ir(ppy) ３ In a light-emitting device using ZnSe as the light-emitting material, the current efficiency was 38 cd / A when there was no capping layer, whereas in a light-emitting device using ZnSe with a thickness of 60 nm as the capping layer, the efficiency was improved by approximately 1.7 times to 64 cd / A. Furthermore, it has been shown that the maximum points of the transmittance of the semi-transparent electrode and the capping layer do not necessarily coincide with the maximum points of the efficiency, and that the maximum point of the light extraction efficiency is determined by the interference effect (see, for example, Non-Patent Document 3).

[0008] Conventionally, the use of a high-resolution metal mask has been proposed for forming a capping layer, but when used under high-temperature conditions, the metal mask can become distorted due to heat, resulting in a problem of reduced alignment accuracy. Therefore, ZnSe, which has a high melting point of 1100°C or higher, cannot be deposited in the correct position using a high-resolution metal mask, which may adversely affect the light-emitting element (see, for example, Non-Patent Document 3). Furthermore, even when deposited by sputtering, the capping layer, which is made of an inorganic material, is not suitable for use, since it adversely affects the light-emitting element.

[0009] In addition, tris(8-hydroxyquinoline)aluminum (hereinafter referred to as Alq) is used as a capping layer for adjusting the refractive index. ３ It has also been proposed to use Alq ３is known as an organic EL material that is generally used as a green light-emitting material or an electron transport material, and has weak absorption around 450 nm, which is close to the emission wavelength of blue light-emitting materials. Therefore, in the case of blue light-emitting devices, it has also had problems such as a decrease in color purity and a decrease in light extraction efficiency.

[0010] US Patent No. 5,792,557 US Patent No. 5,639,914 International Publication No. 2014 / 009310 Korean Patent No. 10-2164767

[0011] Proceedings of the 9th Seminar of the Japan Society of Applied Physics, 2001, p. 55-61Appl. Phys. Lett. , (USA), 2001, Vol. 78, p. 544-546Appl. Phys. Lett. , (USA), 2003, Vol. 82, p. 466-468 Tetrahedron, (Netherlands), 2002, Vol. 58, 9633-9695Chem. Rev. , (US), 2016, 116, 12564-12649Appl. Phys. Lett. , (US), 2011, Vol. 98, p. 083302

[0012] As described above, the characteristics of an organic EL element can be controlled by providing a capping layer, but conventional capping layer materials cannot sufficiently improve the element characteristics and light extraction efficiency of an organic EL element. Therefore, in order to improve the element characteristics of an organic EL element and significantly improve the light extraction efficiency, a material for the capping layer that has a high refractive index, a low extinction coefficient, and excellent thin film stability and durability is required.

[0013] An object of the present invention is to provide a compound that has a high refractive index and a low extinction coefficient in the wavelength range of 450 nm to 750 nm, and is suitable as a material for the capping layer of an organic EL device, and to provide an organic EL device that uses such a compound and thereby improves light extraction efficiency.

[0014] To achieve the above object, the present inventors have focused on the excellent stability and durability of thin films of carbazole compounds and have developed a material that has a high refractive index and a low extinction coefficient in the wavelength range of 450 nm to 750 nm by optimizing the molecular design. Furthermore, they have fabricated organic EL devices using the compound and diligently evaluated the device's characteristics, which have led to the completion of the present invention, as they have been able to solve the conventional problems.

[0015] That is, according to the present invention, there are provided a carbazole compound represented by the following general formula (I) and an organic EL device.

[0016] 1) A carbazole compound represented by the following general formula (I): In general formula (I), A, B, and C may be the same or different and represent a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group, and at least one of A, B, and C represents a substituted or unsubstituted pyrimidinyl group, a substituted or unsubstituted pyrazinyl group, a substituted or unsubstituted pyridazinyl group, or a substituted or unsubstituted cyanopyridyl group. １ ~L ３ and may be the same or different and represent a single bond, an unsubstituted arylene group, or an unsubstituted heteroarylene group.

[0017] 2) The carbazole compound according to 1), which is represented by the following general formula (II): A, B, C, and L in general formula (II) １ ~L ３ are as defined in the general formula (I). However, when the definition of either the general formula (I) or the general formula (II) is changed in the claims, the definition of the other does not necessarily change accordingly. １ ~L ３ The definitions of may differ from each other within the claims.

[0018] 3) The carbazole compound according to 1) or 2), wherein at least two of A, B, and C in general formula (I) or (II) may be the same or different and are a substituted or unsubstituted pyrimidinyl group, a substituted or unsubstituted pyrazinyl group, a substituted or unsubstituted pyridazinyl group, or a substituted or unsubstituted cyanopyridyl group.

[0019] 4) The carbazole compound according to any one of 1) to 3), wherein A and B in the general formula (I) or (II) may be the same or different and are a substituted or unsubstituted pyrimidinyl group, a substituted or unsubstituted pyrazinyl group, a substituted or unsubstituted pyridazinyl group, or a substituted or unsubstituted cyanopyridyl group.

[0020] 5) The carbazole compound according to any one of 1) to 4), wherein A and B in the general formula (I) or (II) may be the same or different and are a substituted or unsubstituted pyrimidinyl group, or a substituted or unsubstituted cyanopyridyl group.

[0021] 6) The carbazole compound according to any one of 1) to 5), wherein A and B in the general formula (I) or (II) may be the same or different and represent any one of the following formulas (III-1) to (III-4): In formulas (III-1) and (III-2), R represents a hydrogen atom, a cyano group, an unsubstituted aryl group, or an unsubstituted heteroaryl group. In formulas (III-1) to (III-4), the dashed lines represent L １ , or L ２ Represents the connection part with.

[0022] 7) The carbazole compound according to any one of 1) to 6), wherein A and B in the general formula (I) or (II) are the same.

[0023] 8) In the general formula (I) or (II), L １ ~L ３and may be the same or different and are a single bond, an unsubstituted phenylene group, an unsubstituted biphenylylene group, an unsubstituted naphthylene group, or an unsubstituted pyridinediyl group.

[0024] 9) The carbazole compound according to any one of 1) to 8), wherein C in general formula (I) or (II) is a substituted or unsubstituted phenyl group (for example, a substituted or unsubstituted cyanophenyl group), a substituted or unsubstituted naphthyl group, a substituted or unsubstituted benzoxazolyl group, a substituted or unsubstituted benzothiazolyl group, a substituted or unsubstituted benzofuranyl group, a substituted or unsubstituted benzothienyl group, a substituted or unsubstituted benzotriazolyl group, a substituted or unsubstituted oxazolopyridyl group, a substituted or unsubstituted pyridyl group, a substituted or unsubstituted quinolyl group, or a substituted or unsubstituted quinoxalyl group.

[0025] 10) 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 carbazole compound represented by general formula (I).

[0026] 11) The organic EL element according to 10) above, wherein a vapor-deposited film of the carbazole compound represented by general formula (I) vacuum-deposited on a silicon substrate to a thickness of 80 nm has a refractive index of 1.70 or more in a wavelength range of 450 nm to 750 nm, measured at room temperature (25±2°C).

[0027] 12) The organic EL element according to 10) or 11), wherein the capping layer is a laminated or mixed layer made of two or more compounds, and the capping layer contains at least one carbazole compound represented by general formula (I).

[0028] 13) An electronic device or electronic element having a pair of electrodes and at least one organic layer sandwiched between them, wherein the organic layer contains a carbazole compound represented by general formula (I).

[0029] The carbazole compound of the present invention represented by general formula (I) has a high refractive index and a low extinction coefficient in the wavelength range of 450 nm to 750 nm, and therefore, by providing a capping layer containing the carbazole compound of the present invention on the outer side of a transparent or semitransparent electrode of an organic EL device, the light extraction efficiency can be significantly improved.

[0030] 1 is a diagram showing an example of the configuration of an organic EL element of the present invention.

[0031] 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 be １ H, or part or all of ２ H (heavy hydrogen atom, 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. All hydrogen atoms present in an unsubstituted group １ H, or part or all of ２ H (heavy hydrogen atom, deuterium D). All hydrogen atoms present in the substituent may also be １ H, or part or all of ２ It may also be H (heavy hydrogen atom, deuterium D).

[0032] As used herein, "organic layer" refers to a layer containing 70% by weight or more of an organic compound, and "organic compound" refers to a compound containing one or more carbon atoms. The organic compound may be composed solely of atoms selected from the group consisting of carbon atoms, hydrogen atoms, nitrogen atoms, oxygen atoms, sulfur atoms, boron atoms, and halogen atoms. As used herein, "transparent" refers to a visible light transmittance of 50% or more, for example, 80% or more, for example, 90% or more, or for example, 99% or more. Visible light transmittance can be measured using an ultraviolet-visible spectrophotometer.

[0033] <Carbazole Compound Represented by General Formula (I)> The carbazole compound of the present invention is a compound represented by the following general formula (I).

[0034]

[0035] In general formula (I), A, B, and C each independently represent a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group, and at least one of A, B, and C represents a substituted or unsubstituted pyrimidinyl group, a substituted or unsubstituted pyrazinyl group, a substituted or unsubstituted pyridazinyl group, or a substituted or unsubstituted cyanopyridyl group. A, B, and C may be the same or different from each other, but from the viewpoint of molecular design, it is preferable that A and B are the same. L １ ~L ３ each independently represents a single bond, an unsubstituted arylene group, or an unsubstituted heteroarylene group. １ ~L ３ may be the same or different from each other.

[0036] In general formula (I), A-L1-, B-L ２ - and C-L ３ A to C and L in - １ ~L ３ The distinction will be made according to the following rules (a) to (c). Specifically, the target compound A-L1-, B-L ２ - or C-L ３ If the partial structure corresponding to - corresponds to (a), A to C and L according to (a)１ ~L ３ If it does not fall under (a), A to C and L are classified according to (b). １ ~L ３ Furthermore, if neither (a) nor (b) applies, A to C and L are classified in accordance with (c). １ ~L ３ (a) If there is a group that corresponds to "a substituted or unsubstituted pyrimidinyl group, a substituted or unsubstituted pyrazinyl group, a substituted or unsubstituted pyridazinyl group, or a substituted or unsubstituted cyanopyridyl group," then it will be classified as A to C, and the rest will be classified as L. １ ~L ３ A-L1-, B-L ２ - or C-L ３ When - includes a structure in which a plurality of pyrimidine rings, pyrazine rings, pyridazine rings, or pyridine rings to which a cyano group is bonded are linked, the groups constituting the rings from the most terminal to the terminal among the plurality of rings are A to C, and the remaining groups are L １ ~L ３ (b) If there are any "substituted or unsubstituted heteroaryl groups" other than "substituted or unsubstituted pyrimidinyl groups, substituted or unsubstituted pyrazinyl groups, substituted or unsubstituted pyridazinyl groups, or substituted or unsubstituted cyanopyridyl groups," they are designated as A to C, and the rest are designated as L. １ ~L ３ A-L1-, B-L ２ - or C-L ３ When - includes a structure in which multiple heteroaryl rings are linked, the groups (substituted or unsubstituted heteroaryl groups) constituting the heteroaryl ring from the most terminal to the terminal are designated as A to C, and the remaining groups are designated as L. １ ~L ３ (c) When there is no heteroaryl ring, the groups (substituted or unsubstituted aryl groups) constituting the terminal aryl ring and the group from the most terminal aryl ring to the terminal are designated as A to C, and the remaining groups are designated as L １ ~L ３ Let's say.

[0037] According to the above rules, for example, in the following compound (46), A-L1- and B-L ２ - corresponds to (a), so A and B are 2-phenyl-5-pyrimidinyl groups, L１ and L ２ becomes a single bond, and C-L ３ - corresponds to (c), so C is a 2-naphthyl group, L ３ becomes a phenylene group.

[0038] The aromatic ring constituting the "aryl group" of the "substituted or unsubstituted aryl group" represented by A, B, and C in general formula (I) may be a monocyclic ring, a fused ring in which two or more rings are fused, or a spiro ring in which two or more rings are linked by a spiro bond. In the case of a fused ring, the number of fused rings is preferably 2 to 6, for example, 2 to 4. The number of carbon atoms in the aromatic ring is, for example, 6 to 30, for example, 6 to 22, for example, 6 to 18, for example, 6 to 14, for example, 6 to 10. Specific examples of the "aryl group" in A, B, and C include aryl groups having 6 to 30 carbon atoms, such as a phenyl group, a naphthyl group, an anthryl group, a phenanthryl group, an indenyl group, a pyrenyl group, a perylenyl group, a fluoranthenyl group, a triphenylenyl group, a fluorenyl group, and a spirobifluorenyl group.

[0039] The aromatic heterocycle constituting the "heteroaryl group" in the "substituted or unsubstituted heteroaryl group" represented by A, B, and C in general formula (I) may be a monocycle or a fused ring in which two or more rings are fused. In the case of a fused ring, the number of fused rings is preferably 2 to 6, for example, 2 to 4. Examples of heteroatoms constituting the aromatic heterocycle include a nitrogen atom, an oxygen atom, and a sulfur atom. The number of carbon atoms in the aromatic heterocycle is, for example, 2 to 40, for example, 2 to 30, for example, 2 to 18. Specific examples of the "heteroaryl group" for A, B, and C include heteroaryl groups having 2 to 20 carbon atoms, such as a pyridyl group, a pyrimidinyl group, a triazinyl group, a furyl group, a pyrrolyl group, a thienyl 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, an imidazopyridyl group, an oxazolopyridyl group, an oxazolopyrazinyl group, a quinoxalinyl group, a quinazolyl group, a benzimidazolyl group, a pyrazolyl group, a dibenzofuranyl group, a dibenzothienyl group, a naphthyridinyl group, a phenanthrolinyl group, an acridinyl group, and a carbolinyl group.

[0040] The heteroaryl group is preferably a monocyclic or bicyclic heteroaryl group, specifically, a pyridyl group, a pyrimidinyl group, a pyrazinyl group, a pyridazinyl group, a benzoxazolyl group, a benzothiazolyl group, a benzofuranyl group, a benzothienyl group, a benzotriazolyl group, an oxazolopyridyl group, a quinolyl group, or a quinoxalyl group is preferred, a pyridyl group, a pyrimidinyl group, a pyrazinyl group, a pyridazinyl group, or a benzoxazolyl group is more preferred, and a 2-pyridyl group, a 3-pyridyl group, a 2-pyrimidinyl group, or a 5-pyrimidinyl group is particularly preferred. At least one of A, B, and C is preferably a 2-pyridyl group, a 3-pyridyl group, a 2-pyrimidinyl group, or a 5-pyrimidinyl group, and more preferably a 5-cyano-2-pyridyl group, a 6-cyano-3-pyridyl group, an unsubstituted 2-pyrimidinyl group, or a substituted 5-pyrimidinyl group.

[0041] In the general formula (I) of the present invention, at least one of A, B, and C is a substituted or unsubstituted pyrimidinyl group, a substituted or unsubstituted pyrazinyl group, a substituted or unsubstituted pyridazinyl group, or a substituted or unsubstituted cyanopyridyl group.

[0042] The "pyrimidinyl group" in the "substituted or unsubstituted pyrimidinyl group" may be any of a 2-pyrimidinyl group, a 4-pyrimidinyl group, and a 5-pyrimidinyl group, but is preferably a 2-pyrimidinyl group or a 5-pyrimidinyl group. Here, the pyrimidine ring constituting the "pyrimidinyl group" is a monocyclic aromatic heterocycle, but the pyrimidine ring may be fused with another ring to form a bicyclic or polycyclic (preferably bicyclic) ring. Examples of rings that can be fused to the pyrimidine ring include aromatic rings and aromatic heterocycles. For an explanation of aromatic rings and aromatic heterocycles, please refer to the descriptions of the aromatic rings constituting the "aryl group" and the aromatic heterocycles constituting the "heteroaryl group" in A, B, and C above. The ring fused to the pyrimidine ring is preferably a benzene ring. In some preferred embodiments of the present invention, at least one of A, B, and C is a substituted or unsubstituted 2-pyrimidinyl group or a substituted or unsubstituted 5-pyrimidinyl group, more preferably an unsubstituted 2-pyrimidinyl group or a substituted 5-pyrimidinyl group.

[0043] The pyrazine ring constituting the "pyrazinyl group" of the "substituted or unsubstituted pyrazinyl group" is a monocyclic aromatic heterocycle, but another ring may be fused to the pyrazine ring to form a bicyclic or polycyclic (preferably bicyclic) ring. Examples of rings that can be fused to the pyrazine ring include aromatic rings and aromatic heterocycles. For an explanation of aromatic rings and aromatic heterocycles, please refer to the descriptions of the aromatic rings constituting the "aryl group" and the aromatic heterocycles constituting the "heteroaryl group" in A, B, and C above. The ring fused to the pyrazine ring is preferably a benzene ring. An example of a substituted or unsubstituted bicyclic pyrazinyl group is a substituted or unsubstituted quinoxalyl group.

[0044] The "pyridazinyl group" in the "substituted or unsubstituted pyridazinyl group" may be a 3-pyridazinyl group or a 4-pyridazinyl group. The pyridazine ring constituting the "pyridazinyl group" is a monocyclic aromatic heterocycle, but the pyridazine ring may be fused with another ring to form a bicyclic or polycyclic (preferably bicyclic) ring. Examples of rings that can be fused to the pyridazine ring include aromatic rings and aromatic heterocycles. For an explanation of aromatic rings and aromatic heterocycles, please refer to the descriptions of the aromatic rings constituting the "aryl group" and the aromatic heterocycles constituting the "heteroaryl group" in A, B, and C above. The ring fused to the pyridazinyl ring is preferably a benzene ring.

[0045] The "pyridyl group" in the "substituted or unsubstituted cyanopyridyl group" may be any of a 2-pyridyl group, a 3-pyridyl group, and a 4-pyridyl group, and the substitution position of the cyano group is not particularly limited. The "cyanopyridyl group" is preferably a 5-cyano-2-pyridyl group or a 6-cyano-3-pyridyl group. The pyridine ring constituting the "cyanopyridyl group" is a monocyclic aromatic heterocycle, but the pyridine ring may be fused with another ring to form a bicyclic or polycyclic (preferably bicyclic) ring. Examples of rings that can be fused to the pyridine ring include aromatic rings and aromatic heterocycles. For an explanation of aromatic rings and aromatic heterocycles, please refer to the descriptions of the aromatic rings constituting the "aryl group" and the aromatic heterocycles constituting the "heteroaryl group" in A, B, and C above. The ring fused to the pyridine ring is preferably a benzene ring, an oxazole ring, or a thiazole ring. Examples of the substituted or unsubstituted bicyclic cyanopyridyl group include an oxazolopyridyl group substituted with a cyano group and a quinolyl group substituted with a cyano group. In some preferred embodiments of the present invention, at least one of A, B, and C is a substituted or unsubstituted 5-cyano-2-pyridyl group or a substituted or unsubstituted 6-cyano-3-pyridyl group.

[0046] Examples of the substituted or unsubstituted pyrimidyl group include groups represented by the following formula (III-1) or (III-2), and examples of the unsubstituted cyanopyridyl group include groups represented by the following formula (III-3) or (III-4). In the carbazole compound represented by general formula (I), it is preferable that at least one of A, B, and C is a group represented by any one of the following formulas (III-1) to (III-4), and it is more preferable that A and B are groups represented by any one of the following formulas (III-1) to (III-4).

[0047]

[0048] In formulas (III-1) and (III-2), R represents a hydrogen atom, a cyano group, an unsubstituted aryl group, or an unsubstituted heteroaryl group. For an explanation of the "aryl group" and "heteroaryl group" in R, please refer to the descriptions of the "aryl group" in the "substituted or unsubstituted aryl group" and the "heteroaryl group" in the "substituted or unsubstituted heteroaryl group" represented by A, B, and C above. In formulas (III-1) to (III-4), the dashed line represents L １ , or L ２ represents the bond with L １ , or L ２ A single bond is formed between

[0049] Of A, B, and C, those that are substituted or unsubstituted pyrimidinyl groups, substituted or unsubstituted pyrazinyl groups, substituted or unsubstituted pyridazinyl groups, or substituted or unsubstituted cyanopyridyl groups may be all of A, B, and C, or two or one of A, B, and C. In some preferred aspects of the present invention, at least two of A, B, and C are substituted or unsubstituted pyrimidinyl groups, substituted or unsubstituted pyrazinyl groups, substituted or unsubstituted pyridazinyl groups, or substituted or unsubstituted cyanopyridyl groups, and more preferably, A and B are substituted or unsubstituted pyrimidinyl groups, substituted or unsubstituted pyrazinyl groups, substituted or unsubstituted pyridazinyl groups, or substituted or unsubstituted cyanopyridyl groups. A and B are preferably a substituted or unsubstituted pyrimidinyl group or a substituted or unsubstituted cyanopyridyl group, more preferably a 5-cyano-2-pyridyl group, a 6-cyano-3-pyridyl group, an unsubstituted 2-pyrimidinyl group or a substituted 5-pyrimidinyl group, and also preferably a group represented by any one of the above formulas (III-1) to (III-4).

[0050] C is preferably a monocyclic or bicyclic aryl group or a monocyclic or bicyclic heteroaryl group. Specifically, C is preferably a phenyl group, a naphthyl group, a cyanophenyl group, a pyridyl group, a quinoxalyl group, a benzoxazolyl group, a benzothiazolyl group, a benzofuranyl group, a benzothienyl group, or an oxazolopyrimidinyl group, and more preferably a 4-cyanophenyl group, a 2-naphthyl group, a 3-pyridyl group, a 2-quinoxalyl group, a 2-benzoxazolyl group, a 2-benzothiazolyl group, a 2-benzofuranyl group, a 2-benzothiothienyl group, or a 2-oxazolopyrimidinyl group. Furthermore, C in general formula (I) can also be selected from the group consisting of a substituted or unsubstituted phenyl group (for example, a substituted or unsubstituted cyanophenyl group), a substituted or unsubstituted naphthyl group, a substituted or unsubstituted benzoxazolyl group, a substituted or unsubstituted benzothiazolyl group, a substituted or unsubstituted benzofuranyl group, a substituted or unsubstituted benzothienyl group, a substituted or unsubstituted benzotriazolyl group, a substituted or unsubstituted oxazolopyridyl group, a substituted or unsubstituted pyridyl group, a substituted or unsubstituted quinolyl group, and a substituted or unsubstituted quinoxalyl group.

[0051] In general formula (I), L １ ~L ３ Each of the groups independently represents a single bond, an unsubstituted arylene group, or an unsubstituted heteroarylene group. For an explanation of the aromatic ring constituting the "arylene group" of the "unsubstituted arylene group", the description of the aromatic ring constituting the "aryl group" in A, B, and C above can be referred to. １ ~L ３The aromatic ring constituting the "arylene group" in the above may be a linked ring in which two or more rings are linked by a single bond. Specific examples of the arylene group include divalent groups obtained by removing one hydrogen atom from the specific examples of the "aryl group" in the above A, B, and C, and further include a biphenylylene group and a terphenylene group. For an explanation of the aromatic heterocycle constituting the "heteroarylene group" of the "unsubstituted heteroarylene group," please refer to the description of the aromatic heterocycle constituting the "heteroaryl group" in the above A, B, and C. Specific examples of the heteroarylene group include divalent groups obtained by removing one hydrogen atom from the specific examples of the "heteroaryl group" in the above A, B, and C. Note that the term "arylene group" refers to a divalent group obtained by removing one hydrogen atom from an aryl group (monovalent aryl group), and the term "heteroarylene group" refers to a divalent group obtained by removing a hydrogen atom from a heteroaryl group (monovalent heteroaryl group).

[0052] In general formula (I), L １ ~L ３ is preferably a single bond, a monocyclic or bicyclic unsubstituted arylene group, or a monocyclic or bicyclic heteroarylene group. Specific examples of the monocyclic or bicyclic unsubstituted arylene group or the monocyclic or bicyclic unsubstituted heteroarylene group include preferably a phenylene group, a biphenylylene group, a naphthylene group, and a pyridinediyl group, and more preferably a 1,4-phenylene group or a 4,4'-biphenylylene group.

[0053] Specific examples of the "substituents" in the "substituted aryl group" of the "substituted or unsubstituted aryl group" and the "substituted heteroaryl group" of the "substituted or unsubstituted heteroaryl group" represented by A, B, and C in general formula (I) are listed below. However, among the substituents listed below, those that fall under the category of "substituted or unsubstituted aryl groups" do not constitute "substituents" in the "substituted aryl group" represented by A, B, and C. Specific examples of the substituent include cyano and nitro groups; halogen atoms such as fluorine, chlorine, bromine, and iodine; silyl groups such as trimethylsilyl and triphenylsilyl; linear or branched alkyl groups having 1 to 6 carbon atoms such as methyl, ethyl, and propyl; linear or branched alkyloxy groups having 1 to 6 carbon atoms such as methoxy, ethoxy, and propoxy; alkenyl groups such as vinyl and allyl; aryl groups having 6 to 30 carbon atoms such as phenyl, biphenylyl, terphenylyl, naphthyl, anthryl, phenanthryl, fluorenyl, spirobifluorenyl, indenyl, pyrenyl, perylenyl, fluoranthenyl, and triphenylenyl; Examples of the heteroaryl group include a heteroaryl group having 2 to 20 carbon atoms, such as a pyridyl group, a pyrimidinyl group, a triazinyl 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, an imidazopyridyl group, an oxazolopyridyl group, an oxazolopyrazinyl group, a quinoxalinyl group, a quinazolyl group, a benzimidazolyl group, a pyrazolyl group, a dibenzofuranyl group, a dibenzothienyl group, a naphthyridinyl group, an acridinyl group, a carbolinyl group, and a phenanthrolinyl group; an aryloxy group, such as a phenyloxy group, a tolyloxy group, a biphenylyloxy group, and a naphthyloxy group; and an aralkyloxy group, such as a benzyloxy group and a phenethyloxy group. The hydrogen atoms of these substituents may be further substituted with the substituents exemplified herein. Preferred substituents include a linear or branched alkyl group having 1 to 6 carbon atoms and a monovalent aromatic hydrocarbon group having 6 to 20 ring atoms.Regarding substituents substituted with substituents, the substituent directly substituted on the parent skeleton (aromatic hydrocarbon group, aromatic heterocyclic group) may be referred to as the "first substituent," and the substituent substituted on the first substituent may be referred to as the "second substituent." Here, when the first substituent contains a benzene ring, the benzene ring may be bonded to the parent skeleton to form a cyclic structure. Furthermore, when two or more substituents are substituted on the benzene ring of the first substituent, adjacent substituents may be bonded to each other to form a cyclic structure. Here, the bond between the benzene ring and the parent skeleton in the first substituent, and the bond between the second substituents may be a single bond or a bond via a linking group. Examples of the linking group include a substituted or unsubstituted methylene group, an ether group (bonded via an oxygen atom), and a thioether group (bonded via a sulfur atom).

[0054] In general formula (I), when at least two of A, B, and C are substituted or unsubstituted 2-pyrimidinyl groups, they are preferably unsubstituted 2-pyrimidinyl groups, and it is more preferable that A and B are unsubstituted 2-pyrimidinyl groups. When A and B are substituted or unsubstituted 2-pyrimidinyl groups, L １ and L ２ is preferably a single bond or an arylene group, more preferably a single bond or a phenylene group, and more preferably a single bond or a 1,4-phenylene group. When A and B are substituted or unsubstituted 2-pyrimidinyl groups, C is preferably a monocyclic or bicyclic aryl group or a monocyclic or bicyclic heteroaryl group, and more preferably a phenyl group, a naphthyl group, a pyridyl group, a pyrimidinyl group, a quinolyl group, or a benzothiazolyl group. Similarly, L ３ is preferably a single bond or a monocyclic or bicyclic arylene group, more preferably a single bond, a phenylene group, a biphenylylene group, a naphthylene group or a pyridinediyl group, and particularly preferably a single bond or a biphenylylene group.

[0055] In general formula (I), when at least two of A, B, and C are substituted or unsubstituted 5-pyrimidinyl groups, it is preferable that they are substituted 5-pyrimidinyl groups, and it is more preferable that A and B are substituted 5-pyrimidinyl groups. As the "substituent", a monocyclic or bicyclic aryl group is preferable, a phenyl group or a naphthyl group is more preferable, and an unsubstituted phenyl group or an unsubstituted 2-naphthyl group is particularly preferable. When A and B are substituted or unsubstituted 5-pyrimidinyl groups, L １ ~L ３ Similarly, C is preferably a monocyclic or bicyclic aryl group, more preferably a phenyl group or a naphthyl group.

[0056] In general formula (I), when at least two of A, B, and C are substituted or unsubstituted cyanopyridyl groups, it is preferable that A and B are substituted or unsubstituted cyanopyridyl groups. As the substituted or unsubstituted cyanopyridyl group, a substituted or unsubstituted 5-cyano-2-pyridyl group or a substituted or unsubstituted 6-cyano-3-pyridyl group is preferable, and an unsubstituted 5-cyano-2-pyridyl group or an unsubstituted 6-cyano-3-pyridyl group is more preferable. When A and B are substituted or unsubstituted cyanopyridyl groups, L １ and L ２ is preferably a single bond or a phenylene group, more preferably a single bond or a 1,4-phenylene group. When A and B are substituted or unsubstituted cyanopyridyl groups, C is preferably a monocyclic or bicyclic aryl group or a monocyclic or bicyclic heteroaryl group, more preferably a phenyl group, a naphthyl group, a pyridyl group or a quinolyl group. Similarly, L ３ is preferably a single bond or a monocyclic or bicyclic arylene group, and more preferably a single bond, a phenylene group, a biphenylylene group, a naphthylene group or a pyridinediyl group.

[0057] In the general formula (1), A-L1- and B-L ２The bonding positions of - in the carbazole ring are not particularly limited, but are preferably the 2- and 7-positions or the 3- and 6-positions, and more preferably the 3- and 6-positions. That is, the carbazole compound represented by general formula (I) is preferably a carbazole compound represented by the following general formula (II):

[0058] A, B, C, and L in general formula (II) １ ~L ３ are A, B, C, and L of general formula (I). １ ~L ３ A, B, C, and L in general formula (II) are synonymous with each other. １ ~L ３ For the explanation of A, B, C, and L of general formula (I), １ ~L ３ In some embodiments of the present invention, the carbazole compound represented by general formula (I) is represented by general formula (II), １ ~L ３ are each independently selected from the group consisting of a single bond, an unsubstituted phenylene group, an unsubstituted biphenylylene group, an unsubstituted naphthylene group, and an unsubstituted pyridinediyl group. １ ~L ３ may be the same or different. In some embodiments of the present invention, the carbazole compound represented by general formula (I) is represented by general formula (II), in which C is selected from the group consisting of a substituted or unsubstituted phenyl group (e.g., a substituted or unsubstituted cyanophenyl group), a substituted or unsubstituted naphthyl group, a substituted or unsubstituted benzoxazolyl group, a substituted or unsubstituted benzothiazolyl group, a substituted or unsubstituted benzofuranyl group, a substituted or unsubstituted benzothienyl group, a substituted or unsubstituted benzotriazolyl group, a substituted or unsubstituted oxazolopyridyl group, a substituted or unsubstituted pyridyl group, a substituted or unsubstituted quinolyl group, and a substituted or unsubstituted quinoxalyl group. For explanations and specific examples of substituents that may be substituted on these groups, please refer to the descriptions of the "substituents" in the "substituted aryl group" and "substituted heteroaryl group" in the above A, B, and C.

[0059] Specific examples of the carbazole compound represented by general formula (I) are shown below, but the carbazole compound represented by general formula (1) that can be used in the present invention should not be construed as being limited by these specific examples.

[0060]

[0061] <Method for synthesizing carbazole compounds represented by general formula (I)> The carbazole compounds represented by general formula (I) are novel compounds. The carbazole compounds represented by general formula (I) can be synthesized, for example, by a known coupling reaction using a palladium catalyst or the like (see, for example, Non-Patent Documents 4 and 5).

[0062] The purification of the carbazole compound represented by general formula (I) is not particularly limited, and can be performed by a known method used for purifying organic compounds, such as purification by column chromatography, adsorption purification using silica gel, activated carbon, activated clay, or the like, recrystallization purification method or crystallization purification method using a solvent, or sublimation purification method, and the compound can be identified by NMR analysis.

[0063] As the physical property values ​​of the carbazole compound represented by general formula (I), it is preferable to measure the melting point, glass transition point (Tg), sublimation temperature, refractive index, and extinction coefficient. The melting point and sublimation temperature are indicators of vapor deposition property, the glass transition point (Tg) is an indicator of stability of the thin film state, and the refractive index and extinction coefficient are indicators of improvement of light extraction efficiency.

[0064] The melting point and glass transition point (Tg) can be measured using a powder with a high-sensitivity differential scanning calorimeter (DSC3100SA, manufactured by Bruker AXS).

[0065] The refractive index and extinction coefficient can be measured by forming an 80 nm thin film on a silicon substrate and using a spectrophotometer (F10-RT-UV, manufactured by Filmetrics) at room temperature (25±2° C.).

[0066] The carbazole compound represented by general formula (I) of the present invention includes compounds that (1) have a high refractive index in the wavelength range of 450 nm to 750 nm, (2) a low extinction coefficient, (3) are vapor-depositable, (4) are stable in thin film state, and (5) have high heat resistance. Therefore, the carbazole compound represented by general formula (I) is useful as a material for the capping layer of an organic EL device. That is, by providing a capping layer containing the carbazole compound represented by general formula (I) on the outer side of the transparent or semitransparent electrode of an organic EL device, the light extraction efficiency is significantly improved, resulting in an organic EL device with high luminous efficiency and long life. Herein, the term "capping layer" refers to a layer disposed on the electrode side (i.e., the outer side) that does not include the luminescent layer in an organic EL device having a pair of electrodes between which the luminescent layer is disposed. The capping layer containing the compound represented by general formula (I) may be disposed on the outer side of only one electrode or on the outer sides 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.

[0067] <Organic Electroluminescence Device> Next, the organic electroluminescence device (organic EL device) of the present invention will be described. The organic EL device 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 a carbazole compound represented by general formula (I). For an explanation of the carbazole compound represented by general formula (I), please refer to the description in the above section "Carbazole Compound Represented by General Formula (I)." Examples of the structure of the organic EL device include, in the case of a top-emission light-emitting device, 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 glass substrate. Other examples include a device having a hole injection layer between the anode and the hole transport layer, a device having an electron blocking layer between the hole transport layer and the emitting layer, a device having a hole blocking layer between the emitting layer and the electron transport layer, and a device having an electron injection layer between the electron transport layer and the cathode. In these multilayer structures, one organic layer can serve multiple roles, such as a structure that serves both as a hole injection layer and a hole transport layer, a structure that serves both as a hole transport layer and an electron blocking layer, a structure that serves both as a hole blocking layer and an electron transport layer, a structure that serves both as an electron transport layer and an electron injection layer, etc. Also, a structure in which two or more organic layers having the same function are laminated is possible, such as a structure in which two hole transport layers are laminated, a structure in which two light-emitting layers are laminated, a structure in which two electron transport layers are laminated, a structure in which two capping layers are laminated, etc.

[0068] The total thickness of each layer of the organic EL element is preferably 200 nm to 750 nm, more preferably 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.

[0069] [Anode] For the anode of an organic EL element, an electrode material with a large work function, such as ITO (indium tin oxide) or gold, is used.

[0070] Examples of materials for the hole injection layer of organic EL devices include arylamine compounds having three or more triphenylamine structures in the molecule, with these triphenylamine structures linked by single bonds or divalent groups not containing heteroatoms. Examples of arylamine compounds include starburst triphenylamine derivatives and various triphenylamine tetramers. Materials for the hole injection layer include porphyrin compounds such as copper phthalocyanine, acceptor heterocyclic compounds such as hexacyanoazatriphenylene, and coating-type polymeric materials. The hole injection layer may 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 may 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.

[0071] [Hole Transport Layer] Materials that can be used for the hole transport layer of an organic EL device include 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, and N,N,N',N'-tetrabiphenylylbenzidine, as well as 1,1-bis[4-(di-4-tolylamino)phenyl]cyclohexane. In particular, it is preferable to use an arylamine compound having two triphenylamine structures in the molecule, where these triphenylamine structures are linked by a single bond or a divalent group not containing a heteroatom, such as N,N,N',N'-tetrabiphenylylbenzidine. It is also preferable to use an arylamine compound having three or more triphenylamine structures in the molecule, where these triphenylamine structures are linked by a single bond or a divalent group not containing a heteroatom, 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 have a single layer structure, a laminated structure of layers formed from a single material or a mixture of layers, or a laminated structure of a layer formed from a single material and a layer formed from a mixture of layers. Furthermore, a coating-type polymer material such as poly(3,4-ethylenedioxythiophene) / poly(styrene sulfonate) 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.

[0072] Furthermore, as materials for the hole injection layer and the hole transport layer, materials that are typically used for these layers doped with a p-type dopant such as trisbromophenylaminehexachloroantimony or a radialene derivative (see, for example, Patent Document 3), and polymer compounds containing the structure of a benzidine derivative such as TPD as a partial structure can be used.

[0073] [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. Materials that can be used for the electron blocking layer include compounds having an electron blocking effect, such as 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, 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 formed as a single layer using one of these electron blocking layer materials alone, or as a mixed layer using a mixture of two or more materials. The electron blocking layer may have a single layer structure, a laminate structure of layers formed independently or in a mixture, or a laminate structure of layers formed independently and in a mixture. These materials can be formed into thin films by known methods such as vapor deposition, spin coating, and ink jet printing.

[0074] [Light-emitting layer] As a material for the light-emitting layer of the organic EL element, tris(8-quinolinolato)aluminum (Alq ３Light-emitting materials that can be used include metal complexes of quinolinol derivatives such as quinolinol derivatives (e.g., quinolinol derivatives), various metal complexes, anthracene derivatives, bisstyrylbenzene derivatives, pyrene derivatives, oxazole derivatives, and polyparaphenylenevinylene derivatives. The light-emitting layer may also be composed of a host material and a dopant material. Anthracene derivatives are preferably used as the host material, but other examples include the above-mentioned light-emitting materials, heterocyclic compounds having an indole ring as a fused ring substructure, heterocyclic compounds having a carbazole ring as a fused ring substructure, carbazole derivatives, thiazole derivatives, benzimidazole derivatives, and polydialkylfluorene derivatives. Dopant materials that can be used include quinacridone, coumarin, rubrene, perylene, and their derivatives, benzopyran derivatives, rhodamine derivatives, and aminostyryl derivatives, with green light-emitting materials being particularly preferred. The light-emitting layer may be composed of a single layer formed using one of these light-emitting materials alone, or a mixed layer formed using a mixture of two or more materials. The light-emitting layer may have a single layer structure, a laminated structure of layers formed independently or layers formed in a mixture, or a laminated structure of layers formed independently and layers formed in a mixture.

[0075] 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)) can be used, and green phosphorescent emitters are particularly preferred. The light-emitting layer may be composed solely of these phosphorescent emitters, or may be composed of a host material and a phosphorescent emitter (e.g., a co-deposited film of a host material and a phosphorescent emitter). Carbazole derivatives such as 4,4'-di(N-carbazolyl)biphenyl, TCTA, and mCP can be used as hole-injecting / transporting host materials, and p-bis(triphenylsilyl)benzene and 2,2',2''-(1,3,5-phenylene)-tris(1-phenyl-1H-benzimidazole) can be used as electron-transporting host materials.

[0076] The amount of phosphorescent material doped into the host material is preferably in the range of 1 to 30 weight percent based on the total weight of the light-emitting layer in order to avoid concentration quenching.

[0077] Furthermore, as the light-emitting material, it is also possible to use materials that emit delayed fluorescence, such as carbazolyldicyanobenzene (CDCB) derivatives such as PIC-TRZ, CC2TA, PXZ-TRZ, and 4CzIPN (see, for example, Non-Patent Document 6). These materials can be formed into thin films by known methods such as vapor deposition, spin coating, and inkjet printing.

[0078] [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 for the hole blocking layer include phenanthroline derivatives such as bathocuproine, 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, all of which have hole-blocking properties. These materials may also be used as materials for the electron-transporting layer. The hole blocking layer may be composed of a single layer formed from one of these hole-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 of layers formed from a single material or a mixture of layers, or a laminate structure of a layer formed from a single material and 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.

[0079] [Electron Transport Layer] Alq was used as a material for the electron transport layer of the organic EL element. ３ Examples of materials that can be used include 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, and silole derivatives. The electron transport layer may be composed of a single layer formed from one of these electron transport materials, or a mixed layer formed from a mixture of two or more materials. The electron transport layer may 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 a layer formed from a single material and a layer formed from a mixture of layers. These materials can be formed into thin films by known methods such as vapor deposition, spin coating, and inkjet printing.

[0080] [Electron injection layer] Materials that can be used for the electron injection layer of an organic EL device 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). The electron injection layer can be omitted by selecting the electron transport layer and the cathode appropriately.

[0081] Furthermore, materials that are normally used for the electron injection layer and the electron transport layer can be doped with an n-type metal dopant such as cesium.

[0082] [Cathode] Materials used for the cathode of an organic EL element include metals with low work functions such as aluminum, alloys with even lower work functions such as magnesium-silver alloys, magnesium-calcium alloys, magnesium-indium alloys, and aluminum-magnesium alloys, and conductive transparent materials such as ITO (indium tin oxide) and IZO (indium zinc oxide). Metals and alloys are formed to a thin thickness of about 10 to 200 nm to form a semitransparent cathode electrode.

[0083] [Capping Layer] The organic EL device of the present invention contains a carbazole compound represented by general formula (I) in the capping layer. The capping layer may be composed of a single layer formed from a single carbazole compound selected from the group of compounds represented by general formula (I), or a mixed layer formed from a mixture of two or more materials. The capping layer may have a single layer structure, a laminated structure of layers formed from a single compound or a mixture of layers, or a laminated structure of a layer formed from a single compound and a layer formed from a mixture of layers. These materials can be formed into thin films by known methods such as vapor deposition, spin coating, and inkjet printing.

[0084] In the organic EL device, the thickness of the capping layer is preferably in the range of 30 nm to 120 nm, and particularly preferably in the range of 40 nm to 80 nm.

[0085] Furthermore, the carbazole compound represented by general formula (I) contained in the capping layer preferably has a refractive index of 1.70 or more, particularly preferably 1.85 or more, in a wavelength range of 450 nm to 700 nm at room temperature (25±2°C) when the carbazole compound is vacuum-deposited to form a vapor-deposited film with a thickness of 80 nm.

[0086] 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 to this, and may also be an organic EL element with a bottom emission structure or an organic EL element with a dual emission structure that emits light from both the top and bottom. For descriptions of the components and layers constituting organic EL elements with a bottom emission structure and a dual emission structure, please refer to the description of the organic EL element above. However, it is preferable that the electrode in the direction in which light is extracted from the light-emitting element to the outside be transparent or semitransparent. That is, in a bottom emission structure, the electrode on the substrate side is preferably transparent or semitransparent, and in a dual emission structure, it is preferable that both electrodes are transparent or semitransparent.

[0087] <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 disposed between the pair of electrodes, and at least one of the organic layers contains a compound represented by general formula (I). For an explanation of the compound represented by general formula (I), please refer to the description in the above section <Compound represented by general formula (I)>. 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.

[0088] Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention.

[0089] The reagents used in the synthesis examples were manufactured by Tokyo Chemical Industry Co., Ltd., Sigma-Aldrich, Alfa Aesar, etc. All reactions in the synthesis examples were carried out using reaction vessels equipped with a condenser, a stirrer, and a thermometer. The compounds in the synthesis examples below were identified using the following methods: １ H-NMR analysis (Bruker nuclear magnetic resonance apparatus, model: Ascend ＴＭ The measurement was performed using a frequency of 400 MHz.

[0090] Synthesis Example 1 Synthesis of Compound (23) 9.0 g of 3,6-di-(pyrimidin-2-yl)-9H-carbazole, 9.9 g of 2-(4'-chloro[1,1'-biphenyl]-4-yl)benzothiazole, 4.0 g of t-butoxysodium, 0.5 g of tris(dibenzylideneacetone)palladium(0), 0.5 g of 2-dicyclohexylphosphino-2',6'-dimethoxybiphenyl, and 90 ml of xylene were added to a reaction vessel and stirred overnight under reflux. After confirming the completion of the reaction, tap water and methanol were added, and the resulting precipitate was collected by filtration to obtain a crude product. The resulting crude product was dissolved in heated dichlorobenzene, silica gel was added, and the mixture was stirred for 30 minutes, followed by filtration through Celite at 90°C. The solvent was distilled off under reduced pressure, and the resulting mixture was purified by crystallization using dichlorobenzene to obtain 9.2 g of Compound (23) (yield: 54.5%).

[0091]

[0092] The structure of the resulting yellow powder was identified using NMR. １ H-NMR (DMSO-d ６ ) the following 24 hydrogen signals were detected, and it was confirmed to be compound (23): δ (ppm) = 9.40 (2H), 8.96 (4H), 8.63 (2H), 8.29 (2H), 8.22-8.07 (6H), 7.92 (2H), 7.66-7.44 (6H).

[0093] Synthesis Example 2 Synthesis of Compound (58) 9.0 g of 9-(naphthalen-2-yl)-3,6-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)9H-carbazole, 8.3 g of 5-chloro-2-(naphthalen-2-yl)pyrimidine, 10.5 g of tripotassium phosphate, 0.8 g of tris(dibenzylideneacetone)palladium(0), 0.9 g of tricyclohexylphosphine, 63 ml of dioxane, and 27 ml of city water were added to a reaction vessel and stirred overnight under reflux. After confirming the completion of the reaction, city water and methanol were added, and the resulting precipitate was collected by filtration to obtain a crude product. The resulting crude product was dissolved in heated monochlorobenzene, silica gel was added, and the mixture was stirred for 30 minutes, followed by filtration through Celite at 90°C. The solvent was evaporated under reduced pressure, and the resulting mixture was washed with acetone dispersion to obtain 9.7 g of compound (58) (yield: 83.7%).

[0094]

[0095] The structure of the resulting yellow powder was identified using NMR. １ H-NMR (DMSO-d ６ ), the following 31 hydrogen signals were detected, and the compound was identified as compound (58): δ (ppm) = 9.48 (4H), 9.08 (4H), 8.61 (2H), 8.37 (1H), 8.31 (1H), 8.19-8.01 (10H), 7.87 (1H), 7.71-7.62 (8H).

[0096] Synthesis Example 3 Synthesis of Compound (60) 9.0 g of 9-(4-cyanophenyl)-3,6-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)9H-carbazole, 8.7 g of 5-chloro-2-(naphthalen-2-yl)pyrimidine, 11.0 g of tripotassium phosphate, 0.8 g of tris(dibenzylideneacetone)palladium(0), 1.0 g of tricyclohexylphosphine, 63 ml of dioxane, and 27 ml of city water were added to a reaction vessel and stirred overnight under reflux. After confirming the completion of the reaction, city water and methanol were added, and the resulting precipitate was collected by filtration to obtain a crude product. The resulting crude product was dissolved in heated monochlorobenzene, silica gel was added, and the mixture was stirred for 30 minutes, followed by filtration through Celite at 90°C. The solvent was distilled off under reduced pressure, and the resulting mixture was purified by crystallization using a monochlorobenzene / acetone mixed solvent to obtain 9.7 g of compound (xx) (yield: 83.7%).

[0097]

[0098] The structure of the resulting yellow powder was identified using NMR. １ H-NMR (DMSO-d ６ ), the following 28 hydrogen signals were detected, and it was confirmed to be compound (60): δ (ppm) = 9.48 (4H), 9.08 (4H), 8.61 (2H), 8.25-8.02 (12H), 7.73 (2H), 7.63 (4H).

[0099] Synthesis Example 4 Synthesis of Compound (41) 15.0 g of 9-(naphthalen-2-yl)-3,6-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)9H-carbazole, 11.0 g of 2-(4-chlorophenyl)pyrimidine, 17.5 g of tripotassium phosphate, 1.3 g of tris(dibenzylideneacetone)palladium(0), 1.5 g of tricyclohexylphosphine, 105 ml of dioxane, and 45 ml of city water were added to a reaction vessel and stirred overnight under reflux. After confirming the completion of the reaction, city water and methanol were added, and the resulting precipitate was collected by filtration to obtain a crude product. The resulting crude product was dissolved in heated monochlorobenzene, silica gel was added, and the mixture was stirred for 30 minutes, followed by filtration through Celite at 90°C. The solvent was distilled off under reduced pressure, and the resulting mixture was purified by crystallization using a monochlorobenzene / acetone mixed solvent to obtain 10.4 g (yield: 62.8%) of compound (41).

[0100]

[0101] The structure of the resulting yellow powder was identified using NMR. １ H-NMR (DMSO-d ６ ), the following 27 hydrogen signals were detected, and the compound was identified as compound (41). δ (ppm) = 8.95 (6H), 8.54 (4H), 8.30 (1H), 8.26 (1H), 8.12 (2H), 8.04 (4H), 7.91 (2H), 7.81 (1H), 7.68-7.66 (2H), 7.57 (2H), 7.46 (2H).

[0102] Synthesis Example 5 Synthesis of Compound (57) 11.0 g of 9-(pyridin-3-yl)-3,6-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9H-carbazole, 11.7 g of 5-chloro-2-(naphthalen-2-yl)pyrimidine, 14.1 g of tripotassium phosphate, 1.0 g of tris(dibenzylideneacetone)palladium(0), 1.2 g of tricyclohexylphosphine, 77 ml of dioxane, and 33 ml of city water were added to a reaction vessel and stirred overnight under reflux. After confirming the completion of the reaction, city water and methanol were added, and the resulting precipitate was collected by filtration to obtain a crude product. The resulting crude product was dissolved in heated dichlorobenzene, silica gel was added, and the mixture was stirred for 30 minutes, followed by filtration through Celite. The solvent was distilled off under reduced pressure, and the resulting mixture was purified by crystallization using a dichlorobenzene / acetone mixed solvent to obtain 9.6 g of compound (57) (yield: 66.3%).

[0103]

[0104] The structure of the resulting pale yellow powder was identified using NMR. １ H-NMR (DMSO-d ６ ), the following 28 hydrogen signals were detected, confirming that the compound was compound (57): δ (ppm) = 9.46 (4H), 9.09 (2H), 9.02-9.00 (3H), 8.83 (1H), 8.60 (2H), 8.27-8.00 (9H), 7.81 (1H), 7.64-7.60 (6H).

[0105] Synthesis Example 6 Synthesis of Compound (65) 11.5 g of 9-(naphthalen-2-yl)-3,6-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9H-carbazole, 6.4 g of 6-chloronicotinonitrile, 13.4 g of tripotassium phosphate, 0.8 g of tris(dibenzylideneacetone)palladium(0), 1.2 g of tricyclohexylphosphine, 81 ml of dioxane, and 35 ml of city water were added to a reaction vessel and stirred overnight under reflux. After confirming the completion of the reaction, city water and methanol were added, and the resulting precipitate was collected by filtration to obtain a crude product. The resulting crude product was dissolved in heated dichlorobenzene, silica gel was added, and the mixture was stirred for 30 minutes, followed by filtration through Celite. The solvent was distilled off under reduced pressure, and the resulting mixture was purified by crystallization using dichlorobenzene to obtain 8.2 g of compound (65) (yield: 78.1%).

[0106]

[0107] The structure of the resulting yellow powder was identified using NMR. １ H-NMR (DMSO-d ６ ), the following 19 hydrogen signals were detected, and it was confirmed to be compound (65): δ (ppm) = 9.36 (2H), 9.12 (2H), 8.45-8.27 (8H), 8.13 (2H), 7.83 (1H), 7.68 (2H), 7.60 (2H).

[0108] Synthesis Example 7 Synthesis of Compound (66) 18.0 g of 9-(quinolin-3-yl)-3,6-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9H-carbazole, 10.0 g of 6-chloronicotinonitrile, 21.0 g of tripotassium phosphate, 1.2 g of tris(dibenzylideneacetone)palladium(0), 1.9 g of tricyclohexylphosphine, 126 ml of dioxane, and 54 ml of city water were added to a reaction vessel and stirred overnight under reflux. After confirming the completion of the reaction, city water and methanol were added, and the resulting precipitate was collected by filtration to obtain a crude product. The resulting crude product was dissolved in heated dichlorobenzene, silica gel was added, and the mixture was stirred for 30 minutes, followed by filtration through Celite. The solvent was distilled off under reduced pressure, and the resulting mixture was purified by crystallization using dichlorobenzene to obtain 11.2 g of compound (66) (yield: 68.2%).

[0109]

[0110] The structure of the resulting yellow powder was identified using NMR. １ H-NMR (DMSO-d ６ ), the following 18 hydrogen signals were detected, and the compound was identified as compound (66). δ (ppm) = 9.36 (2H), 9.23 (1H), 9.12 (2H), 8.88 (1H), 8.45-8.39 (6H), 8.24-8.18 (2H), 7.94 (1H), 7.79 (1H), 7.64 (2H).

[0111] Synthesis Example 8 Synthesis of Compound (84) 13.0 g of 9-(naphthalen-2-yl)-3,6-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9H-carbazole, 9.2 g of 5-bromopicolinonitrile, 9.9 g of potassium carbonate, 1.1 g of tetrakis(triphenylphosphine)palladium(0), 91 ml of toluene, 26 ml of ethanol, and 39 ml of city water were added to a reaction vessel and stirred overnight under reflux. After confirming the completion of the reaction, city water and methanol were added, and the resulting precipitate was filtered to obtain a crude product. The resulting crude product was dissolved in heated dichlorobenzene, silica gel was added, and the mixture was stirred for 30 minutes, followed by filtration through Celite. The solvent was evaporated under reduced pressure, and the resulting mixture was purified by crystallization using dichlorobenzene to obtain 7.5 g of compound (84) (yield: 63.2%).

[0112]

[0113] The structure of the resulting yellow powder was identified using NMR. １ H-NMR (DMSO-d ６ ), the following 19 hydrogen signals were detected, and it was confirmed to be compound (41). δ (ppm) = 9.29 (2H), 9.03 (2H), 8.50 (2H), 8.33 (1H), 8.28 (1H), 8.20 (2H), 8.13 (2H), 8.02 (2H), 7.82 (1H), 7.69-7.62 (4H).

[0114] Synthesis Example 9 Synthesis of Compound (85) 13.0 g of 9-(quinolin-3-yl)-3,6-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9H-carbazole, 9.1 g of 5-bromopicolinonitrile, 9.9 g of potassium carbonate, 1.1 g of tetrakis(triphenylphosphine)palladium(0), 91 ml of toluene, 26 ml of ethanol, and 39 ml of city water were added to a reaction vessel and stirred overnight under reflux. After confirming the completion of the reaction, city water and methanol were added, and the resulting precipitate was filtered to obtain a crude product. The resulting crude product was dissolved in heated dichlorobenzene, silica gel was added, and the mixture was stirred for 30 minutes, followed by filtration through Celite. The solvent was distilled off under reduced pressure, and the resulting mixture was purified by crystallization using dichlorobenzene to obtain 7.1 g of compound (85) (yield: 59.5%).

[0115]

[0116] The structure of the resulting pale yellow powder was identified using NMR. １ H-NMR (DMSO-d ６ ), the following 18 hydrogen signals were detected, and the compound was identified as compound (85). δ (ppm) = 9.29 (2H), 9.23 (1H), 9.04 (2H), 9.86 (1H), 8.50 (2H), 8.24-8.19 (4H), 8.02 (2H), 7.94 (1H), 7.79 (1H), 7.66 (2H).

[0117] Synthesis Example 10 Synthesis of Compound (103) 10.0 g of 9-(naphthalen-2-yl)-3-(quinoxalin-2-yl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9H-carbazole, 2.8 g of 6-chloronicotinonitrile, 3.3 g of potassium carbonate, 0.6 g of tetrakis(triphenylphosphine)palladium(0), 100 ml of toluene, 10 ml of ethanol, and 20 ml of tap water were added to a reaction vessel and stirred overnight under reflux. After confirming the completion of the reaction, tap water and methanol were added, and the resulting precipitate was collected by filtration to obtain a crude product. The resulting crude product was dissolved in heated monochlorobenzene, silica gel was added, and the mixture was stirred for 30 minutes, followed by filtration through Celite. The solvent was evaporated under reduced pressure, and the resulting mixture was subjected to acetone dispersion washing to obtain 7.9 g of Compound (103) (yield: 82.3%).

[0118]

[0119] The structure of the resulting yellow powder was identified using NMR. １ H-NMR (CDCl ３ ), the following 21 hydrogen signals were detected, confirming that the compound was compound (103). δ (ppm) = 9.51 (1H), 9.16 (1H), 9.07 (1H), 9.00 (1H), 8.35 (1H), 8.18-8.22 (2H), 8.12-8.16 (3H), 8.02-8.04 (3H), 7.97 (1H), 7.81-7.82 (1H), 7.76 (1H), 7.72 (1H), 7.62-7.66 (3H), 7.58 (1H).

[0120] Synthesis Example 11 Synthesis of Compound (104) 10.0 g of 9-(naphthalen-2-yl)-3-(quinoxalin-2-yl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9H-carbazole, 3.7 g of 5-bromopicolinonitrile, 3.3 g of potassium carbonate, 0.6 g of tetrakis(triphenylphosphine)palladium(0), 100 ml of toluene, 10 ml of ethanol, and 20 ml of tap water were added to a reaction vessel and stirred overnight under reflux. After confirming the completion of the reaction, tap water and methanol were added, and the resulting precipitate was collected by filtration to obtain a crude product. The resulting crude product was dissolved in heated dichlorobenzene, silica gel was added, and the mixture was stirred for 30 minutes, followed by filtration through Celite. The solvent was evaporated under reduced pressure, and the resulting mixture was subjected to acetone dispersion washing to obtain 7.0 g of Compound (104) (yield: 72.9%).

[0121]

[0122] The structure of the resulting yellow powder was identified using NMR. １ H-NMR (CDCl ３ ), the following 21 hydrogen signals were detected, and the compound was identified as compound (104). δ (ppm) = 9.50 (1H), 9.13 (2H), 8.57 (1H), 8.34 (1H), 8.21 (1H), 8.11-8.19 (4H), 8.02-8.05 (1H), 7.96-7.98 (1H), 7.70-7.84 (5H), 7.60-7.67 (4H).

[0123] [Evaluation of Physical Properties of Compounds] (Measurement of Melting Point and Glass Transition Point) The melting point and glass transition point (Tg) of the compounds obtained in Synthesis Examples 1 to 11 were measured using a high-sensitivity differential scanning calorimeter (DSC3100SA, manufactured by Bruker AXS). The measurement results are shown in Table 1.

[0124]

[0125] From the results shown in Table 1, it can be seen that the compounds obtained in Synthesis Examples 1 to 11 have high melting points and either no glass transition point or a glass transition point of 100° C. or higher. This indicates that the thin film state is stable and has excellent durability.

[0126] (Measurement of refractive index and extinction coefficient) Using the compounds obtained in Synthesis Examples 1 to 11, vapor-deposited films with a thickness of 80 nm were prepared on silicon substrates, and the refractive index n and extinction coefficient k at wavelengths of 450 nm and 750 nm were measured using a spectrophotometer (F10-RT-UV, manufactured by Filmetrics) at room temperature (25±2°C). For comparison, similar measurements were also performed on Alq3 and a comparative compound (CPL-1) having the following structural formula. The measurement results, along with the vapor deposition temperatures, are shown in Table 2.

[0127]

[0128]

[0129] As shown in Table 2, the carbazole compound of the present invention exhibits excellent luminescence properties in the wavelength range of 450 nm to 750 nm, and exhibits excellent luminescence properties in the wavelength range of Alq ３ and a higher refractive index than that of the comparative compound (CPL-1). These results demonstrate that the use of the carbazole compound of the present invention as a constituent material of the capping layer can be expected to improve the light extraction efficiency of an organic EL device.

[0130] [Fabrication and Evaluation of Organic EL Device] (Example 1) As shown in Figure 1, 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, a light-emitting layer 5, an electron transport layer 6, an electron injection layer 7, a cathode 8, and a capping layer 9 were deposited in this order by vapor deposition on the substrate to fabricate an organic EL device.

[0131] 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. This was then subjected to UV ozone treatment for 2 minutes, after which 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 (HTM-1) of the following structural formula at a deposition rate ratio of Acceptor-1:compound (HTM-1) = 3:97, to a thickness of 10 nm.

[0132] On the hole injection layer 3, a compound (HTM-1) having the following structural formula was formed as a hole transport layer 4 to a thickness of 140 nm. On this hole transport layer 4, a compound (EMD-1) having the following structural formula and a compound (EMH-1) having the following structural formula were formed as a light-emitting layer 5 by binary deposition at a deposition rate ratio of (EMD-1):(EMH-1) = 5:95 to form a layer of 20 nm. On this light-emitting layer 5, a compound (ETM-1) having the following structural formula and a compound (ETM-2) having the following structural formula were formed as an electron transport layer 6 by binary deposition at a deposition rate ratio of (ETM-1):(ETM-2) = 50:50 to form a layer 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. On this electron injection layer 7, a magnesium-silver alloy was formed as a cathode 8 to a thickness of 12 nm.

[0133] Finally, the compound (23) of Synthesis Example 1 was formed as a capping layer 9 to a thickness of 60 nm, thereby obtaining an organic EL device.

[0134]

[0135] Examples 2 to 11, Comparative Examples 1 and 2 Organic EL devices were prepared under the same conditions as in Example 1, except that the compounds shown in Table 3 were used as the capping layer 9 instead of the compound (23) in Synthesis Example 1.

[0136] The organic EL elements fabricated in Examples 2 to 11 and Comparative Examples 1 and 2 were subjected to application of a DC voltage in the atmosphere at room temperature to measure the light-emitting properties. The results are summarized in Table 3. The element life was measured using the fabricated organic EL elements. The element life was 10 mA / cm ２ The device was driven at a constant current of 100%, and the time required for the brightness to decay to 95% of the initial brightness was measured and evaluated.

[0137]

[0138] 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 organic EL elements of Comparative Examples 1 and 2 and the organic EL elements of Examples 1 to 11, whereas the brightness, luminous efficiency, and power efficiency were significantly improved in the organic EL elements of all Examples compared to the organic EL element of Comparative Examples. This indicates that the carbazole compound of the present invention represented by general formula (I) is a material that can be suitably used for the capping layer, and that increasing the refractive index of the capping layer can significantly improve the light extraction efficiency of the organic EL element.

[0139] The carbazole compound of the present invention has a high refractive index, can significantly improve light extraction efficiency, and is stable in a thin film state, making it an excellent compound suitable for use in organic EL devices. Furthermore, organic EL devices fabricated using the carbazole compound of the present invention can achieve high efficiency. Furthermore, the use of the compound of the present invention, which has no absorption in the blue, green, and red wavelength regions, is particularly suitable for displaying clear, bright images with good color purity. For example, the compound is expected to be used in home appliances and lighting.

[0140] 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 Capping layer

Claims

1. A carbazole compound represented by the following general formula (I): (In general formula (I), A, B, and C may be the same or different and represent a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group, and at least one of A, B, and C represents a substituted or unsubstituted pyrimidinyl group, a substituted or unsubstituted pyrazinyl group, a substituted or unsubstituted pyridazinyl group, or a substituted or unsubstituted cyanopyridyl group. L １ ~L ３ may be the same or different, and represent a single bond, an unsubstituted arylene group, or an unsubstituted heteroarylene group.

2. The carbazole compound according to claim 1, which is represented by the following general formula (II): (In general formula (II), A, B, and C may be the same or different and represent a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group, and at least one of A, B, and C represents a substituted or unsubstituted pyrimidinyl group, a substituted or unsubstituted pyrazinyl group, a substituted or unsubstituted pyridazinyl group, or a substituted or unsubstituted cyanopyridyl group. L １ ~L ３ may be the same or different, and represent a single bond, an unsubstituted arylene group, or an unsubstituted heteroarylene group.

3. The carbazole compound according to claim 2, wherein at least two of A, B, and C in said general formula (II) may be the same or different and are a substituted or unsubstituted pyrimidinyl group, a substituted or unsubstituted pyrazinyl group, a substituted or unsubstituted pyridazinyl group, or a substituted or unsubstituted cyanopyridyl group.

4. The carbazole compound according to claim 3, wherein A and B in said general formula (II) may be the same or different and are a substituted or unsubstituted pyrimidinyl group, a substituted or unsubstituted pyrazinyl group, a substituted or unsubstituted pyridazinyl group, or a substituted or unsubstituted cyanopyridyl group.

5. The carbazole compound according to claim 4, wherein A and B in said general formula (II) may be the same or different and each represent a substituted or unsubstituted pyrimidinyl group or a substituted or unsubstituted cyanopyridyl group.

6. The carbazole compound according to claim 5, wherein A and B in the general formula (II) may be the same or different and represent any one of the following formulas (III-1) to (III-4): In formula (III-1), R represents a hydrogen atom, a cyano group, an unsubstituted aryl group, or an unsubstituted heteroaryl group, and the dashed line represents L. １ , or L ２ represents the bond with In formula (III-2), R represents a hydrogen atom, a cyano group, an unsubstituted aryl group, or an unsubstituted heteroaryl group, and the dashed line represents L. １ , or L ２ represents the bond with (In formula (III-3), the dashed line represents L １ , or L ２ represents the bond with (In formula (III-4), the dashed line represents L １ , or L ２ represents the bond with 7. The carbazole compound according to claim 6, wherein A and B in the general formula (II) are the same.

8. In the general formula (II), L １ ~L ３ The carbazole compound according to claim 2 , wherein may be the same or different and are a single bond, an unsubstituted phenylene group, an unsubstituted biphenylylene group, an unsubstituted naphthylene group, or an unsubstituted pyridinediyl group.

9. The carbazole compound according to claim 2, wherein C in said general formula (II) is a substituted or unsubstituted phenyl group, a substituted or unsubstituted naphthyl group, a substituted or unsubstituted benzoxazolyl group, a substituted or unsubstituted benzothiazolyl group, a substituted or unsubstituted benzofuranyl group, a substituted or unsubstituted benzothienyl group, a substituted or unsubstituted benzotriazolyl group, a substituted or unsubstituted oxazolopyridyl group, a substituted or unsubstituted pyridyl group, a substituted or unsubstituted quinolyl group, or a substituted or unsubstituted quinoxalyl group.

10. An organic electroluminescence 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 a carbazole compound represented by the following general formula (I): (In general formula (I), A, B, and C may be the same or different and represent a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group, and at least one of A, B, and C represents a substituted or unsubstituted pyrimidinyl group, a substituted or unsubstituted pyrazinyl group, a substituted or unsubstituted pyridazinyl group, or a substituted or unsubstituted cyanopyridyl group. L １ ~L ３ may be the same or different, and represent a single bond, an unsubstituted arylene group, or an unsubstituted heteroarylene group.

11. The organic electroluminescence device according to claim 10, wherein the carbazole compound represented by general formula (I) is vacuum-deposited onto a silicon substrate to a thickness of 80 nm, and the refractive index of the deposited film measured at room temperature (25±2°C) in the wavelength range of 450 nm to 750 nm is 1.70 or higher.

12. An organic electroluminescent device according to claim 10, wherein the capping layer is a laminated or mixed layer made of two or more compounds, and the capping layer contains at least one carbazole compound represented by general formula (I).

13. An electronic device or electronic element having a pair of electrodes and at least one organic layer sandwiched between them, wherein the organic layer contains a carbazole compound represented by the following general formula (I): (In general formula (I), A, B, and C may be the same or different and represent a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group, and at least one of A, B, and C represents a substituted or unsubstituted pyrimidinyl group, a substituted or unsubstituted pyrazinyl group, a substituted or unsubstituted pyridazinyl group, or a substituted or unsubstituted cyanopyridyl group. L １ ~L ３ may be the same or different, and represent a single bond, an unsubstituted arylene group, or an unsubstituted heteroarylene group.

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