Benzoazole compound and organic electroluminescent element using said compound

Abstract

Provided is an organic electroluminescent (EL) element in which, in order to improve light extraction efficiency of the organic EL element, a compound having a high refractive index at a wavelength of 450-750 nm and a low extinction coefficient is used in a capping layer. Provided is an organic EL element having a positive electrode, a hole transport layer, a light-emitting layer, an electron transport layer, a negative electrode, and a capping layer in the stated order, wherein the capping layer contains a benzoazole compound represented by general formula (1). (In the formula: A represents a benzoxazolyl ring or the like; B and C represent a phenyl group, a naphthyl group, a phenanthrolinyl group, an oxazolopyridyl group, or the like; D represents a hydrogen atom or an aryl group or the like; and L1-L3 represents a single bond or a divalent aryl group or the like.)

Description

Benzazole compound and organic electroluminescent device using said compound

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

[0002] Organic EL devices have been the subject of active research because they are brighter, have better visibility, and are capable of producing clearer displays than liquid crystal devices. In 1987, C. W. Tang et al. of Eastman Kodak Company developed a layered structure element in which various roles are assigned to each material, making organic EL devices using organic materials practical. To date, many improvements have been made to commercialize organic EL devices, and the roles of each layer in the layered structure have been further subdivided. By sequentially providing 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 on a substrate, and designing a bottom-emission light-emitting device that emits light from the bottom, high efficiency and durability have been achieved (see Non-Patent Document 1).

[0003] In recent years, light-emitting devices with a top-emission structure, which use a metal with a high work function as the anode and emit light from the top, have become popular. While bottom-emission light-emitting devices, which extract light from the bottom where the pixel circuit is located, have a limited area of ​​the light-emitting section, top-emission light-emitting devices have the advantage of extracting light from the top, which does not block the pixel circuit and allows for a larger light-emitting section. On the other hand, top-emission light-emitting devices have a limitation in that when light emitted from the light-emitting layer is incident on other films at an angle greater than a certain value, it is totally reflected at the interface between the light-emitting layer and other films, resulting in only a portion of the emitted light being usable. Therefore, to improve light extraction efficiency, light-emitting devices have been proposed that include a high-refractive-index capping layer on the outer side of a semi-transparent electrode (cathode) such as LiF / Al / Ag, Ca / Mg, or LiF / MgAg (see Non-Patent Documents 2 and 3).

[0004] International Publication No. 2014 / 009310 International Publication No. 2018 / 008718 International Publication No. 2013 / 179536

[0005] Proceedings of the 9th Seminar of the Japan Society of Applied Physics, 2001, p. 55-61Appl. Phys. Let. , 2001, Volume 78, No. 4, p. 544-546Appl. Phys. Let. , 2003, Volume 82, No. 3, p. 466-468 Tetrahedron, 2002, Volume 58, p. 9633-9695J. Org. chem. , 2006, Volume 71, p. 1802-1808 Appl. Phys. Let. , 2011, Volume 98, No. 8, 083302

[0006] Conventionally, high-resolution metal masks have been used to form capping layers. However, when used under high-temperature conditions, the heat can cause distortion in the metal mask, resulting in reduced alignment accuracy. Therefore, ZnSe (melting point: 1100°C or higher), which is used for the capping layer in Non-Patent Document 3, cannot be deposited in the correct position using a high-resolution metal mask, which may adversely affect the light-emitting element. Furthermore, even when film formation is performed using a sputtering method, inorganic substances are not suitable as constituent materials for the capping layer because they adversely affect the light-emitting element.

[0007] In addition, Non-Patent Document 2 discloses that tris(8-hydroxyquinoline)aluminum (Alq) is used as a constituent material of a capping layer for adjusting the refractive index. ３ However, the use of Alq ３ is a common material used as a green light-emitting material or electron transport material, and exhibits weak absorption around 450 nm, which is close to the emission wavelength of blue light-emitting materials. ３ When used in a blue light-emitting device, there is a problem that color purity and light extraction efficiency are reduced.

[0008] As described above, in order to improve the device characteristics of organic EL devices and to improve the light extraction efficiency, there is a demand for a material that can be used for a capping layer and has a high refractive index, a low extinction coefficient, and excellent thin film stability, film formability, and durability.

[0009] 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 a capping layer of an organic EL device. Another object of the present invention is to provide an organic EL device that has improved light extraction efficiency compared to conventional devices.

[0010] In order to achieve the above object, the present inventors have focused on the advantage that benzoazole compounds have excellent thin film stability and durability, and have diligently optimized the molecular design. As a result, they 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, thereby completing the present invention. That is, the present invention includes the following features.

[0011] 1) An organic electroluminescence device having an anode, a hole transport layer, a light-emitting layer, an electron transport layer, a cathode, and a capping layer in this order, wherein the capping layer contains a benzazole compound represented by the following general formula (1):

[0012]

[0013] In the formula, A represents a benzoxazolyl ring or a benzothiazolyl ring; B and C each independently represent a substituted or unsubstituted phenyl group, naphthyl group, quinolyl group, quinoxalinyl group, quinazolinyl group, phenanthrolinyl group, benzoxazolyl group, benzothiazolyl group, benzofuryl group, benzothienyl group, or oxazolopyridyl group; D represents a hydrogen atom, or a substituted or unsubstituted aryl group or heteroaryl group; L １ ~L ３ represent each independently a single bond, or an unsubstituted divalent aryl group or divalent heteroaryl group.

[0014] 2) In the general formula (1), L ２ , L ３ , and L １are bonded to the 2-, 4-, and 6-positions of the benzoxazolyl ring or benzothiazolyl ring represented by A. 3) The organic electroluminescence device according to 1), wherein L １ ~L ３ are each independently a single bond, or an unsubstituted phenylene group, biphenylylene group, or naphthylene group. 4) The organic electroluminescence device according to any one of 1) to 3), wherein the aryl group or heteroaryl group represented by D in general formula (1) is selected from the group consisting of a phenyl group, a biphenylyl group, a naphthyl group, a furyl group, a quinolyl group, a benzoxazolyl group, a benzothiazolyl group, an oxazolopyridyl group, a quinoxalinyl group, a quinazolinyl group, and a phenanthrolinyl group. 5) The organic electroluminescence device according to any one of 1) to 4), wherein D in the general formula (1) is a hydrogen atom, a cyanophenyl group, or an unsubstituted phenyl group, biphenylyl group, naphthyl group, furyl group, quinolyl group, benzoxazolyl group, benzothiazolyl group, oxazolopyridyl group, quinoxalinyl group, quinazolinyl group, or phenanthrolinyl group. 6) The organic electroluminescence device according to any one of 1) to 5), wherein at least one of B and C in the general formula (1) is an unsubstituted group selected from the group consisting of a phenyl group, a naphthyl group, a quinolyl group, a quinazolinyl group, a phenanthrolinyl group, a benzoxazolyl group, a benzothiazolyl group, and an oxazolopyridyl group. 7) The organic electroluminescence device according to any one of 1) to 6), wherein the capping layer has a refractive index of 1.70 or more in a wavelength range of 450 nm to 750 nm when the capping layer is formed to a thickness of 30 nm to 120 nm. 8) The organic electroluminescence device according to any one of 1) to 7), wherein the capping layer is a laminated or mixed layer containing two or more compounds including the benzoazole compound represented by general formula (1).

[0015] 9) A benzazole compound represented by the following general formula (2):

[0016]

[0017] In the formula, A represents a benzoxazolyl ring or a benzothiazolyl ring; B and C each independently represent a substituted or unsubstituted phenyl group, naphthyl group, quinolyl group, quinoxalinyl group, quinazolinyl group, phenanthrolinyl group, benzoxazolyl group, benzothiazolyl group, benzofuryl group, benzothienyl group, or oxazolopyridyl group; D represents a hydrogen atom, or a substituted or unsubstituted phenyl group, biphenylyl group, naphthyl group, furyl group, quinolyl group, quinoxalinyl group, quinazolinyl group, phenanthrolinyl group, benzoxazolyl group, benzothiazolyl group, benzofuryl group, benzothienyl group, or oxazolopyridyl group; L １ ~L ３ each independently represents a single bond, or an unsubstituted phenylene group, biphenylylene group, or naphthylene group; L ２ , L ３ , and L １ are bonded to the 2-, 4-, and 6-positions of the benzoxazolyl ring or benzothiazolyl ring represented by A, respectively, and satisfy either of the following requirement 1 or 2: Requirement 1: At least one of B, C, and D contains a structure selected from the group consisting of quinazoline, phenanthroline, and oxazolopyridine, provided that, when one or two of B, C, and D is a substituted or unsubstituted phenanthrolinyl group, and when none of the one or two of B, C, and D that is not the phenanthrolinyl group is a group selected from a substituted or unsubstituted quinazolinyl group and an oxazolopyridyl group, L bonded to the phenanthrolinyl group １ , L ２ , and L ３ at least one selected from B, C, and D is an unsubstituted phenylene group, biphenylylene group, or naphthylene group, and when B, C, and D are all substituted or unsubstituted phenanthrolinyl groups, L bonded to the phenanthrolinyl group １ , L ２ , and L ３At least one selected from the group consisting of B, C, and D is an unsubstituted phenylene group, biphenylylene group, or naphthylene group; Requirement 2: None of B, C, and D contains a structure selected from the group consisting of quinazoline, phenanthroline, and oxazolopyridine, and L ３ is a single bond and D is a hydrogen atom.

[0018] 10) The benzoazole compound according to 9), wherein in the general formula (2), at least one of B and C is a substituted or unsubstituted group selected from the group consisting of a phenyl group, a naphthyl group, a quinolyl group, a quinazolinyl group, a phenanthrolinyl group, a benzoxazolyl group, a benzothiazolyl group, a benzofuryl group, and an oxazolopyridyl group. 11) An electronic device or an electronic element having a pair of electrodes and at least one organic layer, wherein the organic layer contains the benzoazole compound according to 9) or 10).

[0019] The benzoazole compound according to the present invention has a high refractive index in the wavelength range of 450 nm to 750 nm, a low extinction coefficient, can be vapor-deposited, is stable in a thin film state, and has high heat resistance. Therefore, by providing a capping layer containing the compound on the outer side of the electrode of an organic EL device, it is possible to improve the light extraction efficiency compared to conventional devices.

[0020] FIG. 1 is a diagram showing specific examples of benzoazole compounds represented by general formula (1). FIG. 2 is a diagram showing specific examples of benzoazole compounds represented by general formula (1). FIG. 3 is a diagram showing specific examples of benzoazole compounds represented by general formula (1). FIG. 4 is a diagram showing specific examples of benzoazole compounds represented by general formula (1). FIG. 5 is a diagram showing specific examples of benzoazole compounds represented by general formula (1). FIG. 6 is a diagram showing specific examples of benzoazole compounds represented by general formula (1). FIG. 7 is a diagram showing specific examples of benzoazole compounds represented by general formula (1). FIG. 8 is a diagram showing specific examples of benzoazole compounds represented by general formula (1). FIG. 9 is a diagram showing an example of the configuration of an organic EL element of the present invention.

[0021] <Organic EL Element> The organic EL element of the present invention has at least an anode, a hole transport layer, a light-emitting layer, an electron transport layer, a cathode, and a capping layer in this order.

[0022] As an example of the structure of an organic EL device, in the case of a top-emission light-emitting element, a structure in which an anode 2, a hole transport layer 4, an emitting layer 5, an electron transport layer 6, a cathode 8, and a capping layer 9 are sequentially stacked on a glass substrate 1, as shown in FIG. 10 , is also possible. Examples of the organic EL device include a hole injection layer 3 between the anode 2 and the hole transport layer 4, an electron blocking layer (not shown) between the hole transport layer 4 and the emitting layer 5, a hole blocking layer (not shown) between the emitting layer 5 and the electron transport layer 6, and an electron injection layer 7 between the electron transport layer 6 and the cathode 8. In other words, the organic EL device of the present invention does not exclude embodiments in which other layers are present between each layer, as long as the organic EL device has at least an anode, a hole transport layer, an emitting layer, an electron transport layer, a cathode, and a capping layer in this order. Furthermore, in these multilayer structures, one organic layer can serve multiple roles. For example, the organic EL element may have a structure that combines the functions of a hole injection layer and a hole transport layer, a structure that combines the functions of a hole transport layer and an electron blocking layer, a structure that combines the functions of a hole blocking layer and an electron transport layer, and / or a structure that combines the functions of an electron transport layer and an electron injection layer. Furthermore, the organic EL element may have a structure in which two or more organic layers having the same function are laminated. Specifically, the organic EL element may have 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, and / or a structure in which two capping layers are laminated. Each layer constituting the organic EL element will now be described.

[0023] [Capping Layer] In the organic EL element of the present invention, the capping layer contains at least a benzazole compound represented by the following general formula (1).

[0024]

[0025] In the general formula (1), A represents a benzoxazolyl ring or a benzothiazolyl ring, and L is １ , L ２ , and L ３For example, as in the compound (1) shown in FIG. 1, the benzoxazolyl ring or benzothiazolyl ring represented by A is bonded to L at the 2-position, 4-position, and 6-position, respectively. ２ , L ３ , and L １ is preferably bonded to A. Also, A is preferably a benzoxazolyl ring.

[0026] B and C each independently represent a substituted or unsubstituted group selected from the following groups: phenyl, naphthyl, quinolyl, quinoxalinyl, quinazolinyl, phenanthrolinyl, benzoxazolyl, benzothiazolyl, benzofuryl, benzothienyl, or oxazolopyridyl. The oxazolopyridyl group may be an oxazolo[4,5-b]pyridyl group or an oxazolo[5,4-b]pyridyl group.

[0027] Specific examples of the "substituent" that each of the above substituted or unsubstituted groups represented by B and C may have include the following atoms or groups: deuterium atom; halogen atoms such as fluorine atom, chlorine atom, bromine atom, and iodine atom; cyano group; nitro group; silyl groups such as trimethylsilyl group and triphenylsilyl group; linear or branched alkyl groups having 1 to 6 carbon atoms such as methyl group, ethyl group, and propyl group; linear or branched alkyloxy groups having 1 to 6 carbon atoms such as methyloxy group, ethyloxy group, and propyloxy group; alkenyl groups such as vinyl group and allyl group; aryloxy groups such as phenyloxy group and tolyloxy group; arylalkyloxy groups such as benzyloxy group and phenethyloxy group; phenyl group, biphenylyl group, terf an aryl group having 6 to 30 carbon atoms or a heteroaryl group having 2 to 20 carbon atoms, such as a phenylyl group, a naphthyl group, an anthryl group, a phenanthryl group, a fluorenyl group, a spirobifluorenyl group, an indenyl group, a pyrenyl group, a perylenyl group, a fluoranthenyl group, a triphenylenyl group, a pyridyl group, a thienyl group, a furyl group, a pyrrolyl group, a quinolyl group, an isoquinolyl group, a benzofuryl group, a benzothienyl group, an indolyl group, a carbazolyl group, a benzoxazolyl group, a benzothiazolyl group, a quinoxalinyl group, a quinazolinyl group, a benzimidazolyl group, a pyrazolyl group, a dibenzofuryl group, a dibenzothienyl group, a carbolinyl group, or a phenanthrolinyl group. These substituents may further have the substituents exemplified above. Furthermore, these substituents and the benzene ring on which they are substituted, or multiple substituents 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.

[0028] In the substituted or unsubstituted phenyl groups represented by B and C, the substituent that the phenyl group may have is preferably a cyano group among those exemplified above. That is, when B and / or C is a substituted phenyl group, the substituted phenyl group is preferably a cyanophenyl group, and more preferably a 3-cyanophenyl group or a 4-cyanophenyl group.

[0029] In the substituted or unsubstituted naphthyl group, the naphthyl group is preferably a 2-naphthyl group. That is, in the substituted or unsubstituted naphthyl group, the substituted or unsubstituted 2-naphthyl group is preferably a substituted or unsubstituted quinolyl group. In the substituted or unsubstituted quinoxalinyl group, the quinoxalinyl group is preferably a 2-quinoxalinyl group or a 6-quinoxalinyl group. In the substituted or unsubstituted quinazolinyl group, the quinazolinyl group is preferably a 2-quinazolinyl group or a 6-quinazolinyl group. In the substituted or unsubstituted phenanthrolinyl group, the phenanthrolinyl group is preferably a [1,10]phenanthrolinyl group, more preferably a 2-[1,10]phenanthrolinyl group. In the substituted or unsubstituted benzoxazolyl group, the benzoxazolyl group is preferably a 2-benzoxazolyl group or a 6-benzoxazolyl group, and more preferably a 2-benzoxazolyl group. In the substituted or unsubstituted benzothiazolyl group, the benzothiazolyl group is preferably a 2-benzothiazolyl group or a 6-benzothiazolyl group, and more preferably a 2-benzothiazolyl group. In the substituted or unsubstituted benzofuryl group, the benzofuryl group is preferably a 2-benzofuryl group. In the substituted or unsubstituted benzothienyl group, the benzothienyl group is preferably a 2-benzothienyl group. In the substituted or unsubstituted oxazolopyridyl group, the oxazolopyridyl group is preferably an oxazolo[5,4-b]pyridyl group, more preferably a 2-oxazolo[5,4-b]pyridyl group or a 5-oxazolo[5,4-b]pyridyl group, and even more preferably a 2-oxazolo[5,4-b]pyridyl group.

[0030] B and C are preferably selected from the following groups, each of which may be substituted or unsubstituted, independently of one another: a phenyl group, a 2-naphthyl group, a 2-quinolyl group, a 3-quinolyl group, a 2-quinoxalinyl group, a 6-quinoxalinyl group, a 2-quinazolinyl group, a 6-quinazolinyl group, a 2-[1,10]phenanthrolinyl group, a 2-benzoxazolyl group, a 6-benzoxazolyl group, a 2-benzothiazolyl group, a 6-benzothiazolyl group, a 2-benzofuryl group, a 2-benzothienyl group, a 2-oxazolo[5,4-b]pyridyl group, or a 5-oxazolo[5,4-b]pyridyl group. Furthermore, B and C are more preferably each independently selected from the following substituted or unsubstituted groups: a phenyl group, a 2-naphthyl group, a 2-quinolyl group, a 3-quinolyl group, a 2-quinoxalinyl group, a 6-quinoxalinyl group, a 2-quinazolinyl group, a 6-quinazolinyl group, a 2-[1,10]phenanthrolinyl group, a 2-benzoxazolyl group, a 2-benzothiazolyl group, a 2-benzofuryl group, a 2-benzothienyl group, or a 2-oxazolo[5,4-b]pyridyl group.

[0031] At least one of B and C is preferably selected from the following unsubstituted groups: a phenyl group, a naphthyl group, a quinolyl group, a quinazolinyl group, a phenanthrolinyl group, a benzoxazolyl group, a benzothiazolyl group, or an oxazolopyridyl group; more preferably selected from the following unsubstituted groups: a phenyl group, a naphthyl group, a quinolyl group, a quinazolinyl group, a phenanthrolinyl group, a benzothiazolyl group, or an oxazolopyridyl group; and even more preferably selected from the following unsubstituted groups: a phenyl group, a naphthyl group, a quinazolinyl group, a phenanthrolinyl group, or an oxazolopyridyl group.

[0032] In general formula (1), D represents a hydrogen atom, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group. Specific examples of the "aryl group" or "heteroaryl group" in the "substituted or unsubstituted aryl group" or "substituted or unsubstituted heteroaryl group" include a phenyl group, a biphenylyl group, a terphenylyl group, a naphthyl group, an anthryl group, a phenanthryl group, a fluorenyl group, a spirobifluorenyl group, an indenyl group, a pyrenyl group, a perylenyl group, a fluoranthenyl group, a triphenylenyl group, a pyridyl group, a pyrimidinyl group, a triazinyl group, a thienyl group, a furyl group, a pyrrolyl group, a quinolyl group, an isoxalyl group, a phenyl ...phenyl group, a phenyl group, a phenyl group, a phenyl group, a phenyl group, a phenyl group, a phenyl group, a phenyl group, a phenyl group, a phenyl group, a phenyl group, a phenyl group, a phenyl group, a phenyl group, a phenyl group, a phenyl group, a phenyl group, a phenyl group, a phenyl group, a phenyl group, a phenyl group, a phenyl group, a phenyl group, a phenyl group, a phenyl group, a phenyl group, a Examples of the aryl group include aryl groups having 6 to 30 carbon atoms and heteroaryl groups having 2 to 20 carbon atoms, such as a noryl group, a benzofuryl group, a benzothienyl group, an indolyl group, a carbazolyl group, a benzoxazolyl group, a benzothiazolyl group, an oxazolopyridyl group, an oxazolopyrazyl group, a quinoxalinyl group, a quinazolinyl group, a benzimidazolyl group, a pyrazolyl group, a dibenzofuryl group, a dibenzothienyl group, a naphthyridinyl group, a phenanthrolinyl group, an acridinyl group, and a carbolinyl group. The oxazolopyridyl group may be an oxazolo[4,5-b]pyridyl group or an oxazolo[5,4-b]pyridyl group.

[0033] Examples of the "substituents" that the "aryl group" or "heteroaryl group" in the substituted or unsubstituted aryl group or heteroaryl group represented by D may have include the same as those exemplified as the "substituents" that the groups represented by B and C above may have. The same applies to the embodiments that the substituents may take. The substituted or unsubstituted aryl group or heteroaryl group represented by D is preferably a cyanophenyl group (a phenyl group having a cyano group as a substituent) or an unsubstituted aryl group or heteroaryl group.

[0034] The substituted or unsubstituted aryl or heteroaryl group represented by D is preferably selected from the group consisting of a substituted or unsubstituted phenyl group, biphenylyl group, naphthyl group, furyl group, quinolyl group, benzoxazolyl group, benzothiazolyl group, oxazolopyridyl group, quinoxalinyl group, quinazolinyl group, and phenanthrolinyl group, and more preferably selected from the group consisting of a cyanophenyl group (a phenyl group having a cyano group as a substituent), and an unsubstituted phenyl group, biphenylyl group, naphthyl group, furyl group, quinolyl group, benzoxazolyl group, benzothiazolyl group, oxazolopyridyl group, quinoxalinyl group, quinazolinyl group, and phenanthrolinyl group. That is, D is preferably a hydrogen atom or a substituted or unsubstituted group selected from the following: a phenyl group, a biphenylyl group, a naphthyl group, a furyl group, a quinolyl group, a benzoxazolyl group, a benzothiazolyl group, an oxazolopyridyl group, a quinoxalinyl group, a quinazolinyl group, or a phenanthrolinyl group, and more preferably a hydrogen atom, a cyanophenyl group, or a unsubstituted group selected from the following: a phenyl group, a biphenylyl group, a naphthyl group, a furyl group, a quinolyl group, a benzoxazolyl group, a benzothiazolyl group, an oxazolopyridyl group, a quinoxalinyl group, a quinazolinyl group, or a phenanthrolinyl group.

[0035] L １ ~L ３ are each independently a single bond, or an unsubstituted divalent aryl group or an unsubstituted divalent heteroaryl group. The "divalent aryl group" or "divalent heteroaryl group" in the "unsubstituted divalent aryl group" or "unsubstituted divalent heteroaryl group" includes a divalent group obtained by removing one hydrogen atom from the "aryl group" or "heteroaryl group" represented by D above, for example, a divalent group obtained by removing one hydrogen atom from the specific groups exemplified above. The "divalent aryl group" is preferably a phenylene group, a biphenylylene group, or a naphthylene group.

[0036] L １ ~L ３are preferably each independently a single bond, an unsubstituted phenylene group, an unsubstituted biphenylylene group, or an unsubstituted naphthylene group, and more preferably a single bond, an unsubstituted 1,3-phenylene group or 1,4-phenylene group, an unsubstituted 4,4'-biphenylylene group, an unsubstituted 2,6-naphthylene group, or an unsubstituted 2,7-naphthylene group. １ and L ３ are preferably the same bond or group, and L １ and L ３ are each more preferably a single bond or a phenylene group (preferably a 1,3-phenylene group or a 1,4-phenylene group).

[0037] Among the benzoazole compounds represented by the general formula (1) that can be used in the capping layer of the organic EL element of the present invention, the benzoazole compound represented by the following general formula (2) is a novel compound and has a more characteristic structure. That is, the benzoazole compound represented by the general formula (1) may be a benzoazole compound represented by the following general formula (2):

[0038]

[0039] In the general formula (2), A represents a benzoxazolyl ring or a benzothiazolyl ring, and L is １ , L ２ , and L ３ is bonded to. A is preferably a benzoxazolyl ring. B and C each independently represent a substituted or unsubstituted group selected from the following groups: a phenyl group, a naphthyl group, a quinolyl group, a quinoxalinyl group, a quinazolinyl group, a phenanthrolinyl group, a benzoxazolyl group, a benzothiazolyl group, a benzofuryl group, a benzothienyl group, or an oxazolopyridyl group. D represents a hydrogen atom, or a substituted or unsubstituted group selected from the following groups: a phenyl group, a biphenylyl group, a naphthyl group, a furyl group, a quinolyl group, a quinoxalinyl group, a quinazolinyl group, a phenanthrolinyl group, a benzoxazolyl group, a benzothiazolyl group, a benzofuryl group, a benzothienyl group, or an oxazolopyridyl group. L １~L ３ each independently represents a single bond, or an unsubstituted phenylene group, biphenylylene group, or naphthylene group. ２ , L ３ , and L １ are bonded to the 2-, 4-, and 6-positions of the benzoxazolyl or benzothiazolyl ring represented by A, respectively.

[0040] In addition, general formula (2) satisfies either the following requirement 1 or 2. Requirement 1: At least one of B, C, and D contains a structure selected from the group consisting of quinazoline, phenanthroline, and oxazolopyridine. However, when one or two of B, C, and D is a substituted or unsubstituted phenanthrolinyl group, and when one or two of B, C, and D that are not the phenanthrolinyl group are not a group selected from a substituted or unsubstituted quinazolinyl group and an oxazolopyridyl group, L bonded to the phenanthrolinyl group １ , L ２ , and L ３ At least one selected from B, C, and D is an unsubstituted phenylene group, biphenylylene group, or naphthylene group (i.e., not a single bond), and when B, C, and D are all substituted or unsubstituted phenanthrolinyl groups, L bonded to the phenanthrolinyl group １ , L ２ , and L ３ At least one selected from B, C, and D is an unsubstituted phenylene group, biphenylylene group, or naphthylene group (i.e., not a single bond); Requirement 2: None of B, C, and D contains a structure selected from the group consisting of quinazoline, phenanthroline, and oxazolopyridine, and L ３ is a single bond and D is a hydrogen atom.

[0041] That is, in requirement 1, at least one of B, C, and D contains a structure selected from the group consisting of quinazoline, phenanthroline, and oxazolopyridine, and (1) at least one of B, C, and D is a phenanthrolinyl group, and any remaining B, C, and D is neither a quinazolinyl group nor an oxazolopyridyl group, and L bonded to the phenanthrolinyl group is １ , L ２ , and L ３ (2) When B, C, and D are all substituted or unsubstituted phenanthrolinyl groups, L １ -B, L ２ -C, and L ３ -D is a single bond-phenanthrolinyl group, １ , L ２ , and L ３ At least one of the groups must be a phenylene group, a biphenylylene group, or a naphthylene group other than a single bond.

[0042] wherein L is bonded to a structure selected from the group consisting of quinazoline and phenanthroline. １ , L ２ , and L ３ is preferably not a single bond. That is, when at least one of B, C, and D is a quinazoline or phenanthroline structure, L bonded to either of the structures is preferably not a single bond. １ , L ２ , and L ３ are preferably each independently an unsubstituted phenylene group, biphenylylene group, or naphthylene group. In addition, in general formula (2), it is particularly preferable that at least one of B, C, and D contains an oxazolopyridine structure. In this case, L bonded to the oxazolopyridine structure １ , L ２ , and L ３may be a single bond. The oxazolopyridine may be either oxazolo[4,5-b]pyridine or oxazolo[5,4-b]pyridine, but is preferably oxazolo[5,4-b]pyridine.

[0043] In general formula (2), it is preferable that at least one of B and C is a substituted or unsubstituted group selected from the group consisting of a phenyl group, a naphthyl group, a quinolyl group, a quinazolinyl group, a phenanthrolinyl group, a benzoxazolyl group, a benzothiazolyl group, a benzofuryl group, and an oxazolopyridyl group. It is more preferable that at least one of B and C is an unsubstituted group selected from the group consisting of phenyl, naphthyl (preferably 2-naphthyl), quinolyl (preferably 2-quinolyl or 3-quinolyl), quinazolinyl (preferably 2-quinazolinyl or 6-quinazolinyl), phenanthrolinyl (preferably 2-[1,10]phenanthrolinyl), benzoxazolyl (preferably 2-benzoxazolyl or 6-benzoxazolyl), benzothiazolyl (preferably 2-benzothiazolyl or 6-benzothiazolyl), benzofuryl (preferably 2-benzofuryl), and oxazolopyridyl (preferably 2-oxazolo[5,4-b]pyridyl or 5-oxazolo[5,4-b]pyridyl, more preferably 2-oxazolo[5,4-b]pyridyl). Furthermore, it is more preferable that at least one of B and C is an unsubstituted group selected from the group consisting of a phenyl group, a naphthyl group, a quinolyl group, a quinazolinyl group, a phenanthrolinyl group, a benzothiazolyl group, and an oxazolopyridyl group. １ ~L ３ For details of the above, the explanation of the general formula (1) can be referred to as appropriate.

[0044] The benzoazole compounds represented by the general formula (1) or (2) can be synthesized according to known methods, for example, as shown below. Alternatively, the compounds can be synthesized by known coupling reactions using a palladium catalyst or the like (see, for example, Patent Document 2 and Non-Patent Documents 4 and 5).

[0045]

[0046] Specific examples of preferred compounds among the benzazole compounds represented by general formula (1) or (2) are shown in FIGS. 1 to 9, but the present invention is not limited to these compounds.

[0047] The method for purifying the benzazole compound is not particularly limited, and the benzazole compound can be purified by a known method used for purifying organic compounds, such as purification by column chromatography, adsorption purification using silica gel, activated carbon, activated clay, etc., recrystallization purification or crystallization purification using a solvent, sublimation purification, etc. The compound can be identified by, for example, NMR analysis.

[0048] The physical properties of the benzoazole compound are preferably measured, including the melting point, glass transition point (Tg), refractive index, and extinction coefficient. The melting point is an index of vapor deposition property, and the glass transition point is an index of the stability of the thin film state. The refractive index and extinction coefficient are also indexes related to the improvement of light extraction efficiency.

[0049] The melting point and glass transition point can be measured for the powder using a high-sensitivity differential scanning calorimeter (e.g., manufactured by Bruker AXS, product name: DSC3100SA). The refractive index and extinction coefficient can be measured for an 80 nm thin film formed on a silicon substrate using a spectrophotometer (e.g., manufactured by Filmetrics, product name: F10-RT-UV).

[0050] In the present invention, the capping layer contains a benzoazole compound represented by the general formula (1). Among the benzoazole compounds represented by the general formula (1), the benzoazole compound represented by the general formula (2) is more preferred. The capping layer may also be a laminated or mixed layer containing two or more compounds, including the benzoazole compound represented by the general formula (1). Examples of compounds other than the benzoazole compound represented by the general formula (1) include phthalic acid derivatives (see Patent Document 3). Of course, two or more benzoazole compounds represented by the general formula (1) may also be included. These compounds may be formed alone or as a single layer formed by mixing with other materials. Alternatively, a laminate structure may be formed by layers formed alone, layers formed by mixing, or layers formed by mixing a layer formed alone and a layer formed by mixing. These materials can be formed into films by known methods such as vapor deposition, spin coating, and inkjet printing.

[0051] In the present invention, when a capping layer containing a benzazole compound represented by formula (1) or (2) is formed to a thickness of 30 nm to 120 nm, the refractive index of the resulting film is preferably 1.70 or more in the wavelength range of 450 nm to 700 nm, more preferably 1.85 or more, and even more preferably 1.90 or more.

[0052] [Other Layers] Known materials can be appropriately selected and used as the materials for the other layers. The substrate is not particularly limited, and a glass substrate, a plastic substrate, or the like can be used. The anode material is an electrode material with a large work function, such as ITO or gold.

[0053] Materials for the hole injection layer include arylamine compounds having a structure in which two or more triphenylamine structures are linked in the molecule by a single bond or a divalent group not containing a heteroatom, such as starburst triphenylamine derivatives, various triphenylamine tetramers, porphyrin compounds such as copper phthalocyanine, and acceptor heterocyclic compounds such as hexacyanoazatriphenylene, as well as coating-type polymeric materials. These materials may be formed alone or as a single layer formed by mixing with other materials. Alternatively, they may be formed into a laminate structure consisting of layers formed alone, layers formed by mixing, or layers formed by mixing. These materials can be formed into films by known methods such as vapor deposition, spin coating, and inkjet printing.

[0054] Examples of materials that can be used for the hole transport layer include benzidine derivatives such as N,N'-diphenyl-N,N'-di(m-tolyl)benzidine (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 linked in the molecule 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 linked in the molecule by a single bond or a divalent group not containing a heteroatom, such as various triphenylamine trimers and tetramers. These compounds may be used alone or in combination with other materials to form a single layer. Alternatively, a laminated structure may be used consisting of layers formed independently, layers formed as a mixture, or a layer formed as a mixture with a layer formed as a mixture. Furthermore, a coating-type polymer material such as poly(3,4-ethylenedioxythiophene) / poly(styrene sulfonate) can be used as the material for the hole injection layer and the hole transport layer. These materials can be formed into films by known methods such as vapor deposition, spin coating, and inkjet printing.

[0055] Furthermore, as materials for the hole injection layer and the hole transport layer, materials that are typically used for these layers can be doped with P dopants such as trisbromophenylaminehexachloroantimony and radialene derivatives (see, for example, Patent Document 1), as well as polymer compounds having a benzidine derivative structure such as TPD as a partial structure.

[0056] The organic EL device of the present invention may have an electron-blocking layer. Materials 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 (TCTA), 9,9-bis[4-(carbazol-9-yl)phenyl]fluorene, 1,3-bis(carbazol-9-yl)benzene (mCP), and 2,2-bis(4-carbazol-9-yl-phenyl)adamantane, and compounds having a triphenylsilyl group and a triarylamine structure, typified by 9-[4-(carbazol-9-yl)phenyl]-9-[4-(triphenylsilyl)phenyl]-9H-fluorene. These materials may be formed as films alone or as a single layer formed by mixing with other materials. Alternatively, a laminate structure may be formed of layers formed alone, layers formed as a mixture, or a layer formed as a mixture with a layer formed alone. These materials can be formed into films by known methods such as vapor deposition, spin coating, and ink jet printing.

[0057] The material for the light-emitting layer is Alq ３Examples of materials that can be used include metal complexes of quinolinol derivatives such as quinolinol derivatives, various metal complexes, anthracene derivatives, bisstyrylbenzene derivatives, pyrene derivatives, oxazole derivatives, and polyparaphenylenevinylene derivatives. The light-emitting layer may also contain a host material and a dopant material. Anthracene derivatives are preferred as the host material. Examples of materials that can be used as the host material include the materials of the light-emitting layer, 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, and polydialkylfluorene derivatives. Examples of dopant materials that can be used include quinacridone, coumarin, rubrene, perylene, pyrene, and their derivatives, benzopyran derivatives, rhodamine derivatives, and aminostyryl derivatives. A green light-emitting material is preferred as the dopant material. These materials may be used alone or in combination with other materials to form a single layer. Alternatively, a laminate structure of layers formed independently, layers formed as a mixture, or a layer formed independently and a layer formed as a mixture may be used.

[0058] Furthermore, a phosphorescent material can be used as the dopant material. As the phosphorescent material, a metal complex such as iridium or platinum can be used. Specifically, Ir(ppy) ３ green phosphorescent emitters such as FIrpic and FIr6, blue phosphorescent emitters such as Btp ２Examples of suitable phosphorescent emitters include red phosphorescent emitters such as Ir(acac). Of these, it is preferable to use a green phosphorescent emitter. When a phosphorescent emitter is used as the dopant material, the host material may be a hole-injecting or hole-transporting host material such as carbazole derivatives such as 4,4'-di(N-carbazolyl)biphenyl, TCTA, or mCP, or an electron-transporting host material such as p-bis(triphenylsilyl)benzene or 2,2',2''-(1,3,5-phenylene)-tris(1-phenyl-1H-benzimidazole). In order to avoid concentration quenching, the phosphorescent emitter is preferably doped into the host material by co-evaporation in a range of 1 to 30% by mass with respect to the entire light-emitting layer.

[0059] Furthermore, materials that emit delayed fluorescence, such as PIC-TRZ, CC2TA, PXZ-TRZ, and CDCB derivatives such as 4CzIPN, can also be used as dopant materials (see, for example, Non-Patent Document 6). These materials can be formed into films by known methods such as vapor deposition, spin coating, and inkjet printing.

[0060] The organic EL device of the present invention may have a hole-blocking layer. Examples of materials that can be used for the hole-blocking layer include compounds with hole-blocking properties, such as phenanthroline derivatives such as bathocuproine, metal complexes of quinolinol derivatives such as aluminum(III) bis(2-methyl-8-quinolinato)-4-phenylphenolate (BAlq), various rare earth complexes, triazole derivatives, triazine derivatives, pyrimidine derivatives, oxadiazole derivatives, and benzoazole derivatives. These materials may also be used as materials for the electron-transporting layer. These materials may be formed as films alone or as single layers formed by mixing with other materials. Alternatively, a laminate structure may be formed by layers formed alone, layers formed as a mixture, or layers formed as a mixture with a layer formed alone. These materials can be formed as films by known methods such as vapor deposition, spin coating, and inkjet printing.

[0061] The material for the electron transport layer is Alq ３Metal 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 can be used. These materials can be formed into films alone or as a single layer formed by mixing with other materials. Alternatively, they can be formed into a laminate structure of layers formed alone, layers formed by mixing, or layers formed by mixing. These materials can be formed into films by known methods such as vapor deposition, spin coating, and inkjet printing.

[0062] Materials that can be used for the electron injection layer 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.

[0063] Furthermore, as the material for the electron transport layer and the electron injection layer, materials that are normally used for these layers and are doped with N-type metals such as cesium can be used.

[0064] Materials used for the cathode 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, as well as ITO and IZO.

[0065] 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, for example, preferably 30 nm to 120 nm, more preferably 40 nm to 80 nm. When the thickness of the capping layer is within the above range, better 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 each layer other than the capping layer, and the like.

[0066] Although the organic EL element having a top emission structure has been described above, the present invention is not limited to this and can be similarly applied to an organic EL element having a bottom emission structure or an organic EL element having a dual emission structure that emits light from both the top and bottom. In either case, 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 semi-transparent.

[0067] The physical properties of a compound suitable for the capping layer of an organic EL device include (1) a high refractive index, (2) a low extinction coefficient, (3) vapor deposition capability, (4) a stable thin film state, and (5) a high glass transition temperature. The physical properties of the organic EL device include (1) a high light extraction efficiency, (2) suppression of a decrease in color purity, (3) light transmission without change over time, and (4) a long life. The benzoazole compound of the present invention represented by general formula (1) or (2) has the properties of a high refractive index, a low extinction coefficient, vapor deposition capability, a stable thin film state, and a high glass transition temperature. Therefore, by using such a benzoazole compound for the capping layer, an organic EL device can be provided that has a high light extraction efficiency, suppresses a decrease in color purity, is capable of transmitting light without change over time, and has a long life.

[0068] <Electronic Device or Electronic Element> The electronic device or electronic element of the present invention has a pair of electrodes and at least one organic layer, and the organic layer contains the benzoazole compound represented by the general formula (1) or (2). Preferably, at least one organic layer is provided on the outer side of one of the electrodes, and more preferably, the organic layer provided on the outer side of the electrode contains the benzoazole compound represented by the general formula (1) or (2).

[0069] 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.

[0070] Example 1 Synthesis of Compound (4) A reaction vessel was charged with 8.8 g of 2-(4-chlorophenyl)-4,6-di(naphthalen-2-yl)benzoxazole, 6.7 g of 3-[4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]quinoline, 0.5 g of tris(dibenzylideneacetone)dipalladium(0), 0.5 g of tricyclohexylphosphine, and 7.8 g of tripotassium phosphate, and the resulting mixture was diluted with 1,4-dioxane / H ２ The mixture was refluxed and stirred overnight in a 2,000 ml mixed solvent. After allowing the resulting mixture to cool, MeOH was added, and the precipitated solid was filtered to obtain a crude product. The resulting crude product was purified by recrystallization using monochlorobenzene to obtain 5.0 g (yield: 42.0%) of a pale yellow powder of 4,6-di(naphthalen-2-yl)-2-{4'-(quinolin-3-yl)[1,1'-biphenyl]-4-yl}-benzoxazole (compound (4)).

[0071]

[0072] The structure of the resulting pale yellow powder was identified using NMR. １ H-NMR (DMSO-d ６) the following 30 hydrogen signals were detected: δ (ppm) = 9.37 (1H), 8.83 (1H), 8.77 (1H), 8.52 (1H), 8.45 (1H), 8.42 (2H), 8.30 (2H), 8.19-7.99 (15H), 7.81 (1H), 7.68 (1H), 7.60 (4H).

[0073] Example 2 Synthesis of Compound (12) A reaction vessel was charged with 11.3 g of 2-(4-chlorophenyl)-4,6-di(quinolin-3-yl)benzoxazole, 6.4 g of 2-[4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]naphthalene, 0.6 g of tris(dibenzylideneacetone)dipalladium(0), 0.7 g of tricyclohexylphosphine, and 9.9 g of tripotassium phosphate, and the mixture was diluted with 1,4-dioxane / H ２ The mixture was refluxed and stirred overnight in a 2,000 ml mixed solvent. After allowing the mixture to cool, MeOH was added, and the precipitated solid was filtered to obtain a crude product. The crude product was purified by recrystallization using monochlorobenzene to obtain 6.3 g (yield: 41.3%) of a pale yellow powder of 2-{4'-(naphthalen-2-yl)[1,1'-biphenyl]-4-yl}-4,6-di(quinolin-3-yl)-benzoxazole (compound (12)).

[0074] The structure of the resulting pale yellow powder was identified using NMR. １ H-NMR (DMSO-d ６ ) the following 29 hydrogen signals were detected: δ (ppm) = 9.84 (1H), 9.54 (1H), 9.24 (1H), 8.96 (1H), 8.47 (2H), 8.42 (2H), 8.21 (1H), 8.23-7.92 (14H), 7.88 (1H), 7.83 (1H), 7.72 (2H), 7.57 (2H).

[0075] Example 3 Synthesis of Compound (32) A reaction vessel was charged with 8.0 g of 4,6-dibromo-2-(naphthalen-2-yl)-benzoxazole, 14.1 g of 2-[4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]benzothiazole, 0.9 g of tetrakis(triphenylphosphine)palladium(0), and 11.0 g of potassium carbonate, and the mixture was diluted with toluene / EtOH / H ２ The mixture was refluxed and stirred overnight in a 2000-methanol mixed solvent. After allowing the resulting mixture to cool, MeOH was added, and the precipitated solid was filtered to obtain a crude product. The resulting crude product was purified by recrystallization using monochlorobenzene to obtain 8.7 g (yield: 66.0%) of a pale yellow powder of 4,6-bis(4-benzothiazol-2-yl-phenyl)-2-(naphthalen-2-yl)-benzoxazole (compound (32)).

[0076] The structure of the resulting pale yellow powder was identified using NMR. １ H-NMR (DMSO-d ６ ) the following 25 hydrogen signals were detected: δ (ppm) = 8.93 (1H), 8.51 (2H), 8.39 (1H), 8.37 (1H), 8.34 (2H), 8.30-8.06 (12H), 7.70 (2H), 7.61 (2H), 7.52 (2H).

[0077] Example 4 Synthesis of Compound (33) A reaction vessel was charged with 4.3 g of 4,6-dibromo-2-(naphthalen-2-yl)-benzoxazole, 7.6 g of 2-[4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]oxazolo[5,4-b]pyridine, 0.5 g of tetrakis(triphenylphosphine)palladium(0), and 4.4 g of potassium carbonate, and the mixture was diluted with toluene / EtOH / H ２The mixture was refluxed and stirred overnight in a 2000-methanol mixed solvent. After allowing the mixture to cool, MeOH was added, and the precipitated solid was filtered to obtain a crude product. The crude product was purified by recrystallization using 1,2-dichlorobenzene to obtain 5.2 g (yield: 76.9%) of a pale yellow powder of 2-(naphthalen-2-yl)-4,6-bis(4-oxazolo[4,5-b]pyridin-2-yl-phenyl)-benzoxazole (compound (33)).

[0078] The structure of the resulting pale yellow powder was identified using NMR. １ H-NMR (THF-d ８ ) the following 23 hydrogen signals were detected: δ (ppm) = 8.96 (1H), 8.58 (4H), 8.49 (3H), 8.38 (2H), 8.24 (2H), 8.21-8.10 (6H), 8.02 (1H), 7.65 (2H), 7.45 (2H).

[0079] Example 5 Synthesis of Compound (58) A reaction vessel was charged with 5.0 g of 4,6-dibromo-2-([1,1′-biphenyl]-4-yl)-benzoxazole, 9.2 g of 2-[4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]benzothiazole, 0.9 g of tetrakis(triphenylphosphine)palladium(0), and 11.0 g of potassium carbonate, and the mixture was diluted with toluene / EtOH / H ２ The mixture was refluxed and stirred overnight in a 2,000 ml mixed solvent. After allowing the mixture to cool, MeOH was added, and the precipitated solid was filtered to obtain a crude product. The crude product was purified by recrystallization using monochlorobenzene to obtain 8.9 g (yield: 99.2%) of a pale yellow powder of 2-([1,1'-biphenyl]-4-yl)-4,6-bis(4-benzothiazol-2-yl-phenyl)-benzoxazole (compound (58)).

[0080] The structure of the resulting pale yellow powder was identified using NMR. １ H-NMR (DMSO-d ６) the following 27 hydrogen signals were detected: δ (ppm) = 8.50 (2H), 8.39 (2H), 8.33 (3H), 8.26 (2H), 8.23-8.10 (7H), 8.00 (2H), 7.83 (2H), 7.64-7.44 (7H).

[0081] Example 6 Synthesis of Compound (74) A reaction vessel was charged with 2.5 g of 4,6-dibromo-2-phenyl-benzoxazole, 4.9 g of 3-[4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]quinoline, 0.4 g of tetrakis(triphenylphosphine)palladium(0), and 2.9 g of potassium carbonate, and the mixture was diluted with toluene / EtOH / H ２ The resulting mixture was allowed to cool and then stirred under reflux overnight in a MeOH / H ２ O was added, and the precipitated solid was filtered to obtain a crude product. The obtained crude product was purified by recrystallization using monochlorobenzene to obtain 2.8 g (yield: 65.7%) of a white powder of 2-phenyl-4,6-bis(4-quinolin-3-yl-phenyl)-benzoxazole (compound (74)).

[0082] The structure of the resulting white powder was identified using NMR. １ H-NMR (CDCl ３ ) the following 27 hydrogen signals were detected: δ (ppm) = 9.30 (2H), 8.42 (2H), 8.38 (2H), 8.33 (2H), 8.18 (2H), 7.96-7.88 (10H), 7.76 (2H), 7.62 (2H), 7.58-7.57 (3H).

[0083] Example 7 Synthesis of Compound (86) A reaction vessel was charged with 5.0 g of 4,6-dibromo-2-phenyl-benzoxazole, 10.0 g of 2-[4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]oxazolo[5,4-b]pyridine, 0.8 g of tetrakis(triphenylphosphine)palladium(0), and 5.9 g of potassium carbonate, and the mixture was diluted with toluene / EtOH / H ２ The resulting mixture was stirred under reflux overnight in a mixed solvent of H. ２O was added, and the precipitated solid was filtered to obtain a crude product. The obtained crude product was purified by recrystallization using 1,2-dichlorobenzene to obtain 5.5 g (yield: 66.5%) of a white powder of 2-phenyl-4,6-bis(4-oxazolo[4,5-b]pyridin-2-yl-phenyl)-benzoxazole (compound (86)).

[0084] The structure of the resulting white powder was identified using NMR. １ H-NMR (CDCl ３ ) the following 21 hydrogen signals were detected: δ (ppm) = 8.50 (2H), 8.45 (2H), 8.40-8.36 (6H), 8.12 (2H), 7.95-7.92 (4H), 7.59-7.58 (3H), 7.41-7.37 (2H).

[0085] Example 8 Synthesis of Compound (119) A reaction vessel was charged with 9.0 g of 3'-(2-([1,1'-biphenyl]-4-yl)-6-chlorobenzo[b]oxazol-4-yl)-[1,1'-biphenyl]-4-carbonitrile, 6.6 g of 2-{4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl}oxazolo[5,4-b]pyridine, 0.5 g of tris(dibenzylideneacetone)dipalladium(0), 0.6 g of tricyclohexylphosphine, and 7.9 g of tripotassium phosphate, and the resulting mixture was diluted with 1,4-dioxane / H ２ The resulting mixture was stirred under reflux overnight in a mixed solvent of H. ２ O was added, and the precipitated solid was filtered to obtain a crude product. The obtained crude product was purified by recrystallization using 1,2-dichlorobenzene to obtain 7.1 g (yield: 59.3%) of a yellow powder of 3'-(2-([1,1'-biphenyl]-4-yl)-6-(4-(oxazolo[4,5-b]pyridin-2-yl)phenyl)benzo[b]oxazol-4-yl)-[1,1'-biphenyl]-4-carbonitrile (compound (119)).

[0086] The structure of the resulting yellow powder was identified using NMR. １ H-NMR (CDCl ３) the following 26 hydrogen signals were detected: δ (ppm) = 8.43 (2H), 8.39 (4H), 8.15 (1H), 8.10 (1H), 7.92-7.88 (4H), 7.85 (2H), 7.79 (4H), 7.70-7.68 (4H), 7.50 (2H), 7.44-7.37 (2H).

[0087] The melting points and glass transition points (Tg) of the compounds obtained in Examples 1 to 8 were measured using a high-sensitivity differential scanning calorimeter (manufactured by Bruker AXS, trade name: DSC3100SA). The measurement results are shown in Table 1.

[0088]

[0089] As shown in Table 1, the benzoazole compounds of the present invention can be vapor deposited even though they have a high melting point, and either have no glass transition point or have a glass transition point of 100° C. or higher. These results indicate that the benzoazole compounds of the present invention have a stable thin film state and excellent durability.

[0090] The compounds obtained in Examples 1 to 8, and Alq as a comparative compound, ３ and a compound (CPL-1) having the following structure (see, for example, Patent Document 2), were used to prepare vapor-deposited films with a thickness of 80 nm on silicon substrates. The refractive index n and extinction coefficient k of the prepared vapor-deposited films at wavelengths of 450 nm and 750 nm were measured using a spectrophotometer (manufactured by Filmetrics, Inc., product name: F10-RT-UV). The measurement results are summarized in Table 2.

[0091]

[0092]

[0093] As shown in Table 2, the benzazole compound of the present invention exhibited a high optical density compared to the comparative compound Alq ３ and has a refractive index and an extinction coefficient equal to or greater than those of compound (CPL-1). That is, by using the benzazole compound of the present invention as a constituent material of the capping layer, an improvement in the light extraction efficiency of an organic EL device can be expected.

[0094] Example 9 An organic EL device having the configuration shown in FIG. 10 was fabricated by sequentially depositing 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 on a glass substrate 1 on which a reflective ITO electrode was previously formed as a transparent anode 2.

[0095] 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 on a hot plate heated to 250°C for 10 minutes. This was then subjected to UV ozone treatment for 2 minutes, and the resulting ITO-coated glass substrate was placed in a vacuum deposition machine and the pressure was reduced to 0.001 Pa or less. Subsequently, an electron acceptor (Acceptor-1) and a compound (HTM-1) having the following structure were binary-evaporated at a deposition rate ratio of Acceptor-1:(HTM-1) = 3:97, covering the transparent anode 2, to form a 10 nm thick hole injection layer 3. The compound (HTM-1) was vapor-deposited on the hole injection layer 3 to form a hole transport layer 4 with a thickness of 140 nm. A 20-nm-thick light-emitting layer 5 was formed on the hole-transporting layer 4 by binary deposition of a compound (EMD-1) and a compound (EMH-1) having the following structure at a deposition rate ratio of (EMD-1):(EMH-1) = 5:95. A 30-nm-thick electron-transporting layer 6 was formed on the light-emitting layer 5 by binary deposition of a compound (ETM-1) and a compound (ETM-2) having the following structure at a deposition rate ratio of (ETM-1):(ETM-2) = 50:50. Lithium fluoride was deposited on the electron-transporting layer 6 to a thickness of 1 nm as the electron-injecting layer 7. A 12-nm-thick magnesium-silver alloy was deposited on the electron-injecting layer 7 as the cathode 8. Finally, the compound (4) obtained in Example 1 was deposited on the capping layer 9 to a thickness of 60 nm.

[0096]

[0097]

[0098] [Examples 10 to 16] Organic EL devices according to Examples 10 to 16 were produced in the same manner as in Example 9, except that the compounds obtained in Examples 2 to 8 were used as the capping layer 9 instead of Compound (4).

[0099] Comparative Example 1 As the capping layer 9, Alq was used instead of the compound (4). ３ An organic EL device was fabricated in the same manner as in Example 9, except that the organic EL element was used.

[0100] Comparative Example 2 An organic EL device was produced in the same manner as in Example 9, except that compound (CPL-1) was used in place of compound (4) for the capping layer 9.

[0101] The organic EL devices fabricated in the examples and comparative examples were evaluated for their light-emitting properties by applying a DC voltage in the atmosphere at room temperature (current density: 10 mA / cm ２ The organic EL elements fabricated in the examples and comparative examples were also used to measure their element lifespans. The results are summarized in Table 3. In the present invention, the element lifespan is measured at a current density of 10 mA / cm ２ The time required for the luminance to decay to 95% of the initial luminance (100%) when the device is driven at a constant current of 100% is shown.

[0102]

[0103] As shown in Table 3, the current density was 10 mA / cm ２ The driving voltage at 1000 kJ / s was almost the same for the devices according to Comparative Examples 1 and 2 and the devices according to Examples 9 to 16. On the other hand, the devices according to all Examples showed significant improvements in brightness, luminous efficiency, power efficiency, and device life compared to the devices according to Comparative Examples. These results indicate that the benzoazole compound of the present invention is a material suitable for use in a capping layer, and that increasing the refractive index of the material used in the capping layer can significantly improve the light extraction efficiency of an organic EL device.

[0104] While certain preferred embodiments of the present invention have been shown and described in detail above, it should be understood that the present invention is not limited to the above-described embodiments, but that various changes and modifications are possible without departing from the spirit or scope of the appended claims.

[0105] The benzoazole 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 suitable for use as a compound for the capping layer of an organic EL device. Furthermore, an organic EL device prepared using the benzoazole compound of the present invention can achieve high efficiency. Furthermore, the benzoazole compound of the present invention, which does not exhibit absorption in the blue, green, and red wavelength regions, is particularly suitable for displaying clear, bright images with good color purity. The benzoazole compound of the present invention is expected to be used in, for example, home appliances and lighting.

[0106] REFERENCE SIGNS LIST 1 glass substrate 2 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. An organic electroluminescence device having an anode, a hole transport layer, a light emitting layer, an electron transport layer, a cathode, and a capping layer in this order, wherein the capping layer contains a benzoazole compound represented by the following general formula (1): In the formula, A represents a benzoxazolyl ring or a benzothiazolyl ring; B and C each independently represent a substituted or unsubstituted phenyl group, naphthyl group, quinolyl group, quinoxalinyl group, quinazolinyl group, phenanthrolinyl group, benzoxazolyl group, benzothiazolyl group, benzofuryl group, benzothienyl group, or oxazolopyridyl group; D represents a hydrogen atom, or a substituted or unsubstituted aryl group or heteroaryl group; L １ ~L ３ each independently represents a single bond, or an unsubstituted divalent aryl group or divalent heteroaryl group.

2. In the general formula (1), L ２ , L ３ , and L １ 2. The organic electroluminescence device according to claim 1, wherein each of the groups represented by A is bonded to the 2-, 4- and 6-positions of the benzoxazolyl or benzothiazolyl ring represented by A.

3. L in the general formula (1) １ ~L ３ The organic electroluminescence device according to claim 1 , wherein each of the groups independently represents a single bond, or an unsubstituted phenylene group, biphenylylene group, or naphthylene group.

4. The organic electroluminescence device according to claim 1, wherein the aryl group or heteroaryl group represented by D in the general formula (1) is selected from the group consisting of a phenyl group, a biphenylyl group, a naphthyl group, a furyl group, a quinolyl group, a benzoxazolyl group, a benzothiazolyl group, an oxazolopyridyl group, a quinoxalinyl group, a quinazolinyl group, and a phenanthrolinyl group.

5. The organic electroluminescence element according to claim 4, wherein D in the general formula (1) is a hydrogen atom, a cyanophenyl group, or an unsubstituted phenyl group, biphenylyl group, naphthyl group, furyl group, quinolyl group, benzoxazolyl group, benzothiazolyl group, oxazolopyridyl group, quinoxalinyl group, quinazolinyl group, or phenanthrolinyl group.

6. The organic electroluminescence device according to claim 1, wherein in said general formula (1), at least one of B and C is an unsubstituted group selected from the group consisting of a phenyl group, a naphthyl group, a quinolyl group, a quinazolinyl group, a phenanthrolinyl group, a benzoxazolyl group, a benzothiazolyl group, and an oxazolopyridyl group.

7. The organic electroluminescence device according to claim 1, wherein when the capping layer is formed to a thickness of 30 nm to 120 nm, the refractive index of the film formed is 1.70 or more in the wavelength range of 450 nm to 750 nm.

8. The organic electroluminescence device according to any one of claims 1 to 7, wherein the capping layer is a laminate or mixed layer containing two or more compounds including the benzoazole compound represented by general formula (1).

9. A benzoazole compound represented by the following general formula (2): In the formula, A represents a benzoxazolyl ring or a benzothiazolyl ring; B and C each independently represent a substituted or unsubstituted phenyl group, naphthyl group, quinolyl group, quinoxalinyl group, quinazolinyl group, phenanthrolinyl group, benzoxazolyl group, benzothiazolyl group, benzofuryl group, benzothienyl group, or oxazolopyridyl group; D represents a hydrogen atom, or a substituted or unsubstituted phenyl group, biphenylyl group, naphthyl group, furyl group, quinolyl group, quinoxalinyl group, quinazolinyl group, phenanthrolinyl group, benzoxazolyl group, benzothiazolyl group, benzofuryl group, benzothienyl group, or oxazolopyridyl group; L １ ~L ３ each independently represents a single bond or an unsubstituted phenylene group, biphenylylene group, or naphthylene group; L ２ , L ３ , and L １ are bonded to the 2-, 4-, and 6-positions of the benzoxazolyl ring or benzothiazolyl ring represented by A, respectively, and either of the following requirements 1 or 2 is satisfied: Requirement 1: At least one of B, C, and D contains a structure selected from the group consisting of quinazoline, phenanthroline, and oxazolopyridine, with the proviso that, when one or two of B, C, and D that are not the phenanthrolinyl group are not all groups selected from a substituted or unsubstituted quinazolinyl group and an oxazolopyridyl group, L bonded to the phenanthrolinyl group １ , L ２ , and L ３ At least one selected from B, C, and D is an unsubstituted phenylene group, biphenylylene group, or naphthylene group, and when B, C, and D are all substituted or unsubstituted phenanthrolinyl groups, L bonded to the phenanthrolinyl group １ , L ２ , and L ３ At least one selected from the group consisting of B, C, and D is an unsubstituted phenylene group, a biphenylylene group, or a naphthylene group; Requirement 2: None of B, C, and D contains a structure selected from the group consisting of quinazoline, phenanthroline, and oxazolopyridine, and L ３ is a single bond, and D is a hydrogen atom.

10. The benzoazole compound according to claim 9, wherein in said general formula (2), at least one of B and C is a substituted or unsubstituted group selected from the group consisting of a phenyl group, a naphthyl group, a quinolyl group, a quinazolinyl group, a phenanthrolinyl group, a benzoxazolyl group, a benzothiazolyl group, a benzofuryl group, and an oxazolopyridyl group.

11. An electronic device or element having a pair of electrodes and at least one organic layer, wherein the organic layer contains the benzazole compound according to claim 9 or 10.

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