Organic electroluminescence device that includes compound having benzoazole structure

Abstract

It is an object of the present invention to provide an organic EL device in which, as a highly efficient and highly durable organic EL material, various materials excelling in electron injection/transport performance, hole blocking performance, hole resistance performance, exciton confinement performance, stability in a film state, and durability, are combined so that properties of each material can be effectively demonstrated, thereby achieving (1) high light emission efficiency and power efficiency, (2) low luminescence starting voltage, (3) low practical driving voltage, and (4) particularly long lifetime. An organic EL device including at least a anode, a hole transport layer, a light-emitting layer, a hole blocking layer, an electron transport layer, and a cathode in this order, characterized in that the hole blocking layer includes a compound having a benzoazole structure represented by the following general formula (1). ##STR00001##
(In the formula, Ar.sup.1 and Ar.sup.2 may be the same or different from each other and each represent a hydrogen atom, a deuterium atom, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted fused polycyclic aromatic group, or a substituted or unsubstituted aromatic heterocyclic group. Y.sub.1 represents a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted fused polycyclic aromatic group, a substituted or unsubstituted aromatic heterocyclic group, a straight-chained or branched alkyl group that has 1 to 6 carbon atoms and may have a substituent group, a cycloalkyl group that has 5 to 10 carbon atoms and may have a substituent group, or a straight-chained or branched alkenyl group that has 2 to 6 carbon atoms and may have a substituent group. X represents an oxygen atom or a sulfur atom. Z.sub.1 and Z.sub.2 may be the same or different from each other and each represent a carbon atom or a nitrogen atom).

Claims

1. An organic electroluminescence device (hereinafter, abbreviated as organic EL device) including at least an anode, a hole transport layer, a light-emitting layer, a hole blocking layer, an electron transport layer, and a cathode in this order, characterized in that the hole blocking layer includes a compound having a benzoazole structure represented by the following general formula (1); ##STR00044## In the formula, Ar.sup.1 and Ar.sup.2 may be the same or different from each other and each represent a hydrogen atom, a deuterium atom, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted fused polycyclic aromatic group, or a substituted or unsubstituted aromatic heterocyclic group, Y.sub.1 represents a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted fused polycyclic aromatic group, a substituted or unsubstituted aromatic heterocyclic group, a straight-chained or branched alkyl group that has 1 to 6 carbon atoms and may have a substituent group, a cycloalkyl group that has 5 to 10 carbon atoms and may have a substituent group, or a straight-chained or branched alkenyl group that has 2 to 6 carbon atoms and may have a substituent group, X represents an oxygen atom or a sulfur atom, and Z.sub.1 and Z.sub.2 may be the same or different from each other and each represent a carbon atom or a nitrogen atom; and wherein the aromatic heterocyclic group of Y.sub.1 is other than a carbazolyl group.

2. The organic EL device according to claim 1, characterized in that the general formula (1) includes a compound having a benzoazole structure represented by the following general formula (2); ##STR00045## In the formula, Ar.sup.3 and Ar.sup.4 may be the same or different from each other and each represent a hydrogen atom, a deuterium atom, a substituted or unsubstituted aromatic hydrocarbon group, or a substituted or unsubstituted aromatic heterocyclic group, Y.sub.2 represents a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, a straight-chained or branched alkyl group that has 1 to 6 carbon atoms and may have a substituent group, a cycloalkyl group that has 5 to 10 carbon atoms and may have a substituent group, or a straight-chained or branched alkenyl group that has 2 to 6 carbon atoms and may have a substituent group, X represents an oxygen atom or a sulfur atom, and Z.sub.3 and Z.sub.4 may be the same or different from each other and each represent a carbon atom or a nitrogen atom; and wherein the aromatic heterocyclic group of each of Ar.sup.3, Ar.sup.4, and Y.sub.2 is other than an azine ring, the aromatic heterocyclic group of Y.sub.2 is also other than a carbazolyl group, and the substituent group of each of Ar.sup.3, Ar.sup.4, and Y.sub.2 is other than a fused polycyclic aromatic group and an azine ring.

3. The organic EL device according to claim 2, characterized in that the general formula (2) includes a compound having a benzoazole structure represented by the following general formula (3); ##STR00046## In the formula, Ar.sup.5 and Ar.sup.6 may be the same or different from each other and each represent a hydrogen atom, a deuterium atom, a substituted or unsubstituted aromatic hydrocarbon group, or a substituted or unsubstituted aromatic heterocyclic group, Y.sub.3 represents a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, a straight-chained or branched alkyl group that has 1 to 6 carbon atoms and may have a substituent group, a cycloalkyl group that has 5 to 10 carbon atoms and may have a substituent group, or a straight-chained or branched alkenyl group that has 2 to 6 carbon atoms and may have a substituent group, and X represents an oxygen atom or a sulfur atom; and wherein the aromatic heterocyclic group of each of Ar.sup.5 and Ar.sup.6 is other than an azine ring, the aromatic heterocyclic group of Y.sub.3 is other than a carbazolyl group and an azine ring, and the substituent group of Ar.sup.5, Ar.sup.6, and Y.sub.3 is other than a fused polycyclic aromatic group and an azine ring.

4. The organic EL device according to claim 3, characterized in that the general formula (3) includes a compound having a benzoazole structure represented by the following general formula (4); ##STR00047## In the formula, Ar.sup.7 to Ar.sup.8 may be the same or different from each other and each represent a hydrogen atom, a deuterium atom, a substituted or unsubstituted aromatic hydrocarbon group, or a substituted or unsubstituted aromatic heterocyclic group, Ar.sup.9 represents a substituted or unsubstituted aromatic hydrocarbon group, or a substituted or unsubstituted aromatic heterocyclic group, and X represents an oxygen atom or a sulfur atom; and wherein the aromatic heterocyclic group of each of Ar.sup.7 to Ar.sup.9 is other than an azine ring, the aromatic heterocyclic group of Ar.sup.9 is also other than a carbazolyl group, and the substituent group of each of Ar.sup.7 to Ar.sup.9 is other than a fused polycyclic aromatic group and an azine ring.

5. The organic EL device according to claim 4, characterized in that the general formula (4) includes a compound having a benzoazole structure represented by the following general formula (5); ##STR00048## In the formula, Ar.sup.10 to Ar.sup.11 may be the same or different from each other and each represent a hydrogen atom, a deuterium atom, a substituted or unsubstituted aromatic hydrocarbon group, or a substituted or unsubstituted aromatic heterocyclic group; Ar.sup.12 represents a substituted or unsubstituted aromatic hydrocarbon group, or a substituted or unsubstituted aromatic heterocyclic group; and wherein the aromatic heterocyclic group of each of Ar.sup.10 to Ar.sup.12 is other than an azine ring, the aromatic heterocyclic group of Ar.sup.12 is also other than a carbazolyl group, and the substituent group Ar.sup.10 to Ar.sup.12 is other than a fused polycyclic aromatic group and an azine ring.

6. The organic EL device according to claim 5, characterized in that the general formula (5) includes a compound having a benzoazole structure represented by the following general formula (6); ##STR00049## In the formula, Ar.sup.13 to Ar.sup.14 may be the same or different from each other and each represent a hydrogen atom, a deuterium atom, a substituted or unsubstituted aromatic hydrocarbon group, or a substituted or unsubstituted aromatic heterocyclic group; Ar.sup.15 represents a substituted or unsubstituted aromatic hydrocarbon group, or a substituted or unsubstituted aromatic heterocyclic group; and wherein the aromatic heterocyclic group of each of Ar.sup.13 to Ar.sup.15 is other than an azine ring, the aromatic heterocyclic group of Ar.sup.15 is also other than a carbazolyl group, the substituent group of each of each of Ar.sup.13 to Ar.sup.15 is other than a fused polycyclic aromatic group and an azine ring, and at least one monovalent group represented by the following structural formula (A-1) or (A-2) is included as the aromatic heterocyclic group of each of Ar.sup.13 to Ar.sup.15 or the substituent group of each of Ar.sup.13 to Ar.sup.15; ##STR00050## In the formula, a broken line represents a binding site, each of R.sub.1 to R.sub.5 is a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a nitro group, a straight-chained or branched alkyl group that has 1 to 6 carbon atoms and may have a substituent group, a cycloalkyl group that has 5 to 10 carbon atoms and may have a substituent group, a straight-chained or branched alkenyl group that has 2 to 6 carbon atoms and may have a substituent group, a straight-chained or branched alkyloxy group that has 1 to 6 carbon atoms and may have a substituent group, a cycloalkyloxy group that has 5 to 10 carbon atoms and may have a substituent group, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted aryloxy group, r.sub.1 to r.sub.5 may be the same or different from each other, r.sub.1 to r.sub.3 each represent an integer of 0 to 4, r.sub.4 represents an integer of 0 to 5, and r.sub.5 represents an integer of 0 to 3; In a case where any of r.sub.1 to r.sub.5 is an integer of two or more, a plurality of R.sub.1, a plurality of R.sub.2, a plurality of R.sub.3, a plurality of R.sub.4, or a plurality of R.sub.5 bonded to the same benzene ring may be the same as or different from each other and the plurality of R.sub.1, the plurality of R.sub.2, the plurality of R.sub.3, and the plurality of R.sub.5 may be bonded to the same substituted benzene ring via a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring.

7. The organic EL device according to claim 1, characterized in that the electron transport layer includes a compound having a benzoazole structure represented by the following general formula (ETM-1) or a compound having a pyrimidine ring structure represented by the following general formula (ETM-2); ##STR00051## In the formula, Ar.sup.16 and Ar.sup.17′ may be the same or different from each other and each represent a hydrogen atom, a deuterium atom, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted fused polycyclic aromatic group, Y.sub.4 represents a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted fused polycyclic aromatic group, a straight-chained or branched alkyl group that has 1 to 6 carbon atoms and may have a substituent group, a cycloalkyl group that has 5 to 10 carbon atoms and may have a substituent group, or a straight-chained or branched alkenyl group that has 2 to 6 carbon atoms and may have a substituent group, X represents an oxygen atom or a sulfur atom, and Z.sub.5 and Z.sub.6 may be the same or different from each other and each represent a carbon atom or a nitrogen atom; and wherein the aromatic heterocyclic group of Y.sub.4 is other than a carbazolyl group; ##STR00052## In the formula, Ar.sup.18 represents a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted fused polycyclic aromatic group, Ar.sup.19 and Ar.sup.20 each represent a hydrogen atom, a deuterium atom, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted fused polycyclic aromatic group, both Ar.sup.19 and Ar.sup.20 do not represent any of a hydrogen atom and a deuterium atom, and A represents a monovalent group represented by the following structural formula (ETM-A); ##STR00053## In the formula, a broken line represents a binding site, Ar.sup.21 represents a substituted or unsubstituted aromatic heterocyclic group, R.sub.6 represents a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a trifluoromethyl group, a straight-chained or branched alkyl group that has 1 to 6 carbon atoms and may have a substituent group, a cycloalkyl group that has 5 to 10 carbon atoms and may have a substituent group, a straight-chained or branched alkenyl group that has 2 to 6 carbon atoms and may have a substituent group, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted fused polycyclic aromatic group, and r.sub.6 represents an integer of 0 to 4; In a case where r.sub.6 is an integer of two or more, a plurality of R.sub.6 bonded to the same benzene ring may be the same or different from each other and R.sub.6 and Ar.sup.21 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.

8. The organic EL device according to claim 7, characterized in that the hole transport layer has a two-layer structure of a first hole transport layer and a second hole transport layer, and the first hole transport layer is a triphenylamine derivative represented by the following general formula (HTM-1) or (HTM-2); ##STR00054## In the formula, each of R.sub.7 to R.sub.12 represents a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a nitro group, a straight-chained or branched alkyl group that has 1 to 6 carbon atoms and may have a substituent group, a cycloalkyl group that has 5 to 10 carbon atoms and may have a substituent group, a straight-chained or branched alkenyl group that has 2 to 6 carbon atoms and may have a substituent group, a straight-chained or branched alkyloxy group that has 1 to 6 carbon atoms and may have a substituent group, a cycloalkyloxy group that has 5 to 10 carbon atoms and may have a substituent group, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted fused polycyclic aromatic group, or a substituted or unsubstituted aryloxy group r.sub.7 to r.sub.12 may be the same or different from each other, r.sub.7 to r.sub.10 each represent an integer of 0 to 5, and r.sub.11 and r.sub.12 each represent an integer of 0 to 4; In a case where any of r.sub.7 to r.sub.12 is an integer of two or more, a plurality of R.sub.7, a plurality of R.sub.8, a plurality of R.sub.9, a plurality of R.sub.10 a plurality of R.sub.11, or a plurality of R.sub.12 bonded to the same benzene ring may be the same or different from each other; Further, a benzene ring and a substituent group substituted with a benzene ring, a plurality of substituent groups substituted with the same benzene ring, or benzene rings adjacent to each other via a nitrogen atom 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; L.sub.1 represents a bivalent group represented by the following structural formulae (HTM-A) to (HTM-F) or a single bond; ##STR00055## In the formula, n represents an integer of 1 to 3; ##STR00056## In the formula, R.sub.13 to R.sub.24 each represent a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a nitro group, a straight-chained or branched alkyl group that has 1 to 6 carbon atoms and may have a substituent group, a cycloalkyl group that has 5 to 10 carbon atoms and may have a substituent group, a straight-chained or branched alkenyl group that has 2 to 6 carbon atoms and may have a substituent group, a straight-chained or branched alkyloxy group that has 1 to 6 carbon atoms and may have a substituent group, a cycloalkyloxy group that has 5 to 10 carbon atoms and may have a substituent group, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted fused polycyclic aromatic group, or a substituted or unsubstituted aryloxy group; r.sub.13 to r.sub.24 may be the same or different from each other, r.sub.13 to r.sub.18 each represent an integer of 0 to 5, and r.sub.19 to r.sub.24 each represent an integer of 0 to 4; In a case where any of r.sub.13 to r.sub.24 is an integer of two or more, a plurality of R.sub.13, a plurality of R.sub.14, a plurality of R.sub.15, a plurality of R.sub.16, a plurality of R.sub.17, a plurality of R.sub.18, a plurality of R.sub.19, a plurality of R.sub.20, a plurality of R.sub.21, a plurality of R.sub.22, a plurality of R.sub.23, or a plurality of R.sub.24 bonded to the same benzene ring may be the same or different from each other; Further, a benzene ring and a substituent group substituted with a benzene ring, a plurality of substituent groups substituted with the same benzene ring, or benzene rings adjacent to each other via a nitrogen atom 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; L.sub.2 to L.sub.4 may be the same or different from each other, and each represent a bivalent group represented by the following structural formulae (HTM-A) to (HTM-F) or a single bond.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a diagram showing structural formulae of compounds 1 to 15 that are benzoxazole compounds.

(2) FIG. 2 is a diagram showing structural formulae of compounds 16 to 30 that are benzoxazole compounds.

(3) FIG. 3 is a diagram showing structural formulae of compounds 31 to 45 that are benzoxazole compounds.

(4) FIG. 4 is a diagram showing structural formulae of compounds 46 to 60 that are benzoxazole compounds.

(5) FIG. 5 is a diagram showing structural formulae of compounds 61 to 75 that are benzoxazole compounds.

(6) FIG. 6 is a diagram showing structural formulae of compounds 76 to 90 that are benzoxazole compounds.

(7) FIG. 7 is a diagram showing structural formulae of compounds 91 to 100 that are benzoxazole compounds.

(8) FIG. 8 is a diagram showing structural formulae (ETM-1-1) to (ETM-1-15) that are compounds each having a benzoazole structure.

(9) FIG. 9 is a diagram showing structural formulae (ETM-1-16) to (ETM-1-30) that are compounds each having a benzoazole structure.

(10) FIG. 10 is a diagram showing structural formulae (ETM-1-31) to (ETM-1-45) that are compounds each having a benzoazole structure.

(11) FIG. 11 is a diagram showing structural formulae (ETM-1-46) to (ETM-1-60) that are compounds each having a benzoazole structure.

(12) FIG. 12 is a diagram showing structural formulae (ETM-1-61) to (ETM-1-75) that are compounds each having a benzoazole structure.

(13) FIG. 13 is a diagram showing structural formulae (ETM-1-76) to (ETM-1-90) that are compounds each having a benzoazole structure.

(14) FIG. 14 is a diagram showing structural formulae (ETM-1-91) to (ETM-1-99) that are compounds each having a benzoazole structure.

(15) FIG. 15 is a diagram showing structural formulae (ETM-2-1) to (ETM-2-15) that are compounds each having a pyrimidine ring structure.

(16) FIG. 16 is a diagram showing structural formulae (ETM-2-16) to (ETM-2-30) that are compounds each having a pyrimidine ring structure.

(17) FIG. 17 is a diagram showing structural formulae (ETM-2-31) to (ETM-2-45) that are compounds each having a pyrimidine ring structure.

(18) FIG. 18 is a diagram showing structural formulae (ETM-2-46) to (ETM-2-60) that are compounds each having a pyrimidine ring structure.

(19) FIG. 19 is a diagram showing structural formulae (ETM-2-61) to (ETM-2-72) that are compounds each having a pyrimidine ring structure.

(20) FIG. 20 is a diagram showing structural formulae (ETM-2-73) to (ETM-2-84) that are compounds each having a pyrimidine ring structure.

(21) FIG. 21 is a diagram showing structural formulae (ETM-2-85) to (ETM-2-87) that are compounds each having a pyrimidine ring structure.

(22) FIG. 22 is a diagram showing structural formulae (HTM-1-1) to (HTM-1-15) that are triphenylamine derivatives.

(23) FIG. 23 is a diagram showing structural formulae (HTM-1-16) to (HTM-1-32) that are triphenylamine derivatives.

(24) FIG. 24 is a diagram showing structural formulae (HTM-2-1) to (HTM-2-10) that are triphenylamine derivatives.

(25) FIG. 25 is a diagram showing structural formulae (HTM-2-11) to (HTM-2-16) that are triphenylamine derivatives.

(26) FIG. 26 is a diagram showing a configuration of each of organic EL devices according to Examples 18 to 26 and Comparative Examples 1 and 2.

MODE(S) FOR CARRYING OUT THE INVENTION

(27) Compounds 1 to 100 are shown in FIGS. 1 to 7 as specific examples of favorable compounds among the benzoxazole compounds represented by the above-mentioned general formula (1), which are favorably used for the organic EL device according to the present invention. However, the present invention is not limited to these compounds.

(28) Structural formulae (ETM-1-1) to (ETM-1-99) are shown in FIGS. 8 to 14 as specific examples of favorable compounds among compounds each having a benzoazole structure represented by the above-mentioned general formula (ETM-1), which are favorably used for the organic EL device according to the present invention. However, the present invention is not limited to these compounds.

(29) Note that the above-mentioned compound having a benzoazole structure can be synthesized in accordance with a method well-known per se (see, for example, patent Literatures 5 and 6, and Non-Patent Literatures 6 and 7).

(30) Structural formulae (ETM-2-1) to (ETM-2-87) are shown in FIGS. 15 to 21 as specific examples of favorable compounds among compounds each having a pyrimidine ring structure represented by the above-mentioned general formula (ETM-2), which are favorably used for the organic EL device according to the present invention. However, the present invention is not limited to these compounds.

(31) Note that the above-mentioned compound having a pyrimidine ring structure can be synthesized by a method well-known per se (see, for example, patent Literatures 7 and 8).

(32) Structural formulae (HTM-1-1) to (HTM-1-32) are shown in FIGS. 22 and 23 as specific examples of favorable compounds among triphenylamine derivatives represented by the above-mentioned general formula (HTM-1), which are favorably used for the organic EL device according to the present invention. However, the present invention is not limited to these compounds.

(33) Structural formulae (HTM-2-1) to (HTM-2-16) are shown in FIGS. 24 and 25 as specific examples of favorable compounds among triphenylamine derivatives represented by the above-mentioned general formula (HTM-2), which are favorably used for the organic EL device according to the present invention. However, the present invention is not limited to these compounds.

(34) Note that the above-mentioned compound having a triarylamine structure can be synthesized in accordance with a method well-known per se (see, for example, Patent Literatures 9 to 11).

(35) Purification of compounds represented by the general formulae (1) to (6), (ETM-1), (ETM-2), (HTM-1), and (HTM-2) was carried out by purification by column chromatography, adsorption purification with silica gel, activated carbon, activated clay, or the like, recrystallization with a solvent, a crystallization method, a sublimation purification method, or the like. Identification of the compounds was performed by NMR analysis. As physical property values, a melting point, a glass transition point (Tg), and a work function were measured. The melting point is an index of vapor deposition property. The glass transition point (Tg) is an index of stability in a thin film state. The work function is an index of a hole transport property and a hole blocking property.

(36) The melting point and the glass transition point (Tg) were measured with a powder using a high sensitivity differential scanning calorimeter (DSC3100SA manufactured by Bruker AXS GmbH).

(37) The work function was obtained by preparing a thin film of 100 nm on an ITO substrate and using an ionization potential measuring apparatus (PYS-202 manufactured by Sumitomo Heavy Industries, Ltd.).

(38) Examples of the structure of the organic EL device according to the present invention include those including 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 in the stated order on a substrate, those including an electron blocking layer between the hole transport layer and the light-emitting layer, and those including a hole blocking layer between the light-emitting layer and the electron transport layer. In the multilayer structures, several organic layers can be omitted or combined. For example, the hole injection layer and the hole transport layer may be combined or the electron injection layer and the electron transport layer may be combined. Further, two or more organic layers having the same function can be stacked. For example, two hole transport layers may be stacked, two light-emitting layers may be stacked, or two electron transport layers may be stacked.

(39) As the anode of the organic EL device according to the present invention, an electrode material having a large work function such as ITO and gold is used. As the hole injection layer of the organic EL device according to the present invention, a porphyrin compound typified by copper phthalocyanine, a starburst type triphenylamine derivative, an acceptor heterocyclic compound such as hexacyanoazatriphenylene, a coating type polymer material, or the like in addition to the arylamine compounds represented by the above-mentioned general formulae (HTM-1) and (HTM-2) can be used. These materials can be formed into a thin film by a known method such as a spin coat method and an ink jet method in addition to a vapor deposition method.

(40) As the hole transport layer of the organic EL device according to the present invention, the arylamine compounds represented by the above-mentioned general formulae (HTM-1) and (HTM-2) are more favorable, but also a benzidine derivative such as N,N′-diphenyl-N,N′-di(m-tolyl)-benzidine (hereinafter, referred to as TPD), N,N′-diphenyl-N,N′-di(α-naphthyl)-benzidine (hereinafter, referred to as NPD), and N,N,N′,N′-tetrabiphenylylbenzidine, 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (hereinafter, referred to as TAPC), or the like can be used. These materials may be deposited alone. However, any of the materials may be mixed with another material and used as a single deposited layer. Further, a stacked structure may be achieved by depositing layers of the plurality of materials alone, or mixing the plurality of materials and depositing layers thereof. Alternatively, a stacked structure of at least one layer of any of the plurality of materials deposited alone and at least one layer obtained by mixing the plurality of materials and depositing at least one layer thereof may be achieved. Further, as a hole injection/transport layer, a coating polymer material such as poly(3,4-ethylenedioxythiophene) (hereinafter, referred to as PEDOT)/poly(styrene sulfonate) (hereinafter, referred to as PSS) can be used. These materials can be formed into a thin film by a known method such as a spin coat method and an ink jet method in addition to a vapor deposition method.

(41) Further, for the hole injection layer or hole transport layer, those obtained by P-doping the material typically used for the layer with trisbromophenylamine hexachloroantimony or a radialene derivative (see, for example, Patent Literature 12), a polymer compound having, as a partial structure, the structure of a benzidine derivative such as TPD, or the like can be used.

(42) For the electron blocking layer of the organic EL device according to the present invention, a compound having an electron blocking property, such as a carbazol derivative such as 4,4′,4″-tri(N-carbazolyl) triphenylamine (hereinafter, referred to as TCTA), 9,9-bis[4-(carbazol-9-yl)phenyl]fluorene, 1,3-bis(carbazol-9-yl)benzene (hereinafter, referred to as mCP), and 2,2-bis(4-carbazol-9-ylphenyl)adamantane (hereinafter, referred to as Ad-Cz), and a compound having a triphenylsilyl group and a triarylamine structure typified by 9-[4-(carbazol-9-yl)phenyl]-9-[4-(triphenylsilyl)phenyl]-9H-fluorene in addition to the arylamine compounds represented by the above-mentioned general formulae (HTM-1) and (HTM-2) can be used. These materials may be deposited alone. However, any of the materials may be mixed with another material and used as a single deposited layer. Further, a stacked structure may be achieved by depositing layers of the plurality of materials alone, or mixing the plurality of materials and depositing layers thereof. Alternatively, a stacked structure of at least one layer of any of the plurality of materials deposited alone and at least one layer obtained by mixing the plurality of materials and depositing at least one layer thereof may be achieved. These materials can be formed into a thin film by a known method such as a spin coat method and an ink jet method in addition to a vapor deposition method.

(43) For the light-emitting layer of the organic EL device according to the present invention, various metal complexes, an anthracene derivative a bis-styryl benzene derivative, a pyrene derivative, an oxazole derivative, a poly(p-phenylene vinylene) derivative, or the like in addition to a metal complex of a quinolinol derivative including Alq.sub.3 can be used. Further, the light-emitting layer may be formed of a host material and a dopant material. As the host material, an anthracene derivative is favorably used. In addition, not only the above-mentioned light-emitting material but also a heterocyclic compound having an indole ring as a partial structure of the fused ring, a heterocyclic compound having a carbazol ring as a partial structure of the fused ring, a carbazol derivative, a thiazole derivative, a benzimidazole derivative, a polydialkylfluorene derivative, or the like can be used. Further, as the dopant material, quinacridone, coumarin, rubrene, perylene, and derivatives thereof, a benzopyran derivative, a rhodamine derivative, an aminostyryl derivative, or the like can be used. These materials may be deposited alone. However, any of the materials may be mixed with another material and used as a single deposited layer. Further, a stacked structure may be achieved by depositing layers of the plurality of materials alone, or mixing the plurality of materials and depositing layers thereof. Alternatively, a stacked structure of at least one layer of any of the plurality of materials deposited alone and at least one layer obtained by mixing the plurality of materials and depositing at least one layer thereof may be achieved.

(44) Further, as the light-emitting material, a phosphorescent material can be used. As the phosphorescent material, a phosphorescent material of a metal complex such as iridium and platinum can be used. A green phosphorescent material such as Ir(ppy).sub.3, a blue phosphorescent material such as FIrpic and FIr.sub.6, a red phosphorescent material such as Btp.sub.2Ir (acac), or the like is used. As the host material (having a hole injection/transporting property) at this time, 4,4′-di(N-carbazolyl) biphenyl (hereinafter, referred to as CEP) and a carbazol derivative such as TCTA and mCP can be used. As a host material having an electron transportability, p-bis(triphenylsilyl)benzene (hereinafter, referred to as UGH.sub.2), 2,2′,2″-(1,3,5-phenylene)-tris(1-phenyl-1H-benzimidazole) (hereinafter, referred to as, TPBI), or the like can be used, and an organic EL device having high performance can be prepared.

(45) In order to avoid concentration quenching, it is favorable to dope the host material with the phosphorescent material by co-deposition in the range of 1 to 30 weight percent with respect to the entire light-emitting layer.

(46) Further, as the light-emitting material, a material emitting delayed fluorescence such as a CDCB derivative including PIC-TRZ, CC2TA, PXZ-TRZ, and 4CzIPN can be used (see, for example, Non-Patent Literature 3). These materials can be formed into a thin film by a known method such as a spin coat method and an ink jet method in addition to a vapor deposition method.

(47) For the hole blocking layer of the organic EL device according to the present invention, the benzoazole compounds represented by the above-mentioned general formula (1) to (6) can be used. These compounds may double as the material of the electron transport layer. These materials may be deposited alone. However, any of the materials may be mixed with another material and used as a single deposited layer. Further, a stacked structure may be achieved by depositing layers of the plurality of materials alone, or mixing the plurality of materials and depositing layers thereof. Alternatively, a stacked structure of at least one layer of any of the plurality of materials deposited alone and at least one layer obtained by mixing the plurality of materials and depositing at least one layer thereof may be achieved. These materials can be formed into a thin film by a known method such as a spin coat method and an ink jet method in addition to a vapor deposition method.

(48) As the electron transport layer of the organic EL device according to the present invention, the benzoazole compound and the pyrimidine compound respectively represented by the above-mentioned general formulae (ETM-1) and (ETM-2) are more favorable, but also various metal complexes, a triazole derivative, triazine derivative, an oxadiazole derivative, a pyridine derivative, a benzimidazole derivative, a thiadiazole derivative, an anthracene derivative, a carbodiimide derivative, a quinoxaline derivative, a pyridoindole derivative, a phenanthroline derivative, a silole derivative, or the like in addition to a metal complex of a quinolinol derivative including Alq.sub.3 and BAlq can be used. These materials may be deposited alone. However, any of the materials may be mixed with another material and used as a single deposited layer. Further, a stacked structure may be achieved by depositing layers of the plurality of materials alone, or mixing the plurality of materials and depositing layers thereof. Alternatively, a stacked structure of at least one layer of any of the plurality of materials deposited alone and at least one layer obtained by mixing the plurality of materials and depositing at least one layer thereof may be achieved. These materials can be formed into a thin film by a known method such as a spin coat method and an ink jet method in addition to a vapor deposition method.

(49) For the electron injection layer of the organic EL device according to the present invention, an alkali metal salt such as lithium fluoride and cesium fluoride, an alkaline earth metal salt such as magnesium fluoride, a metal complex of a quinolinol derivative such as lithiumquinolinol, a metal oxide such as an aluminum oxide, a metal such as ytterbium (Yb), samarium (Sm), calcium (Ca), strontium (Sr), and cesium (Cs), or the like can be used. However, this can be omitted in the favorable selection of the electron transport layer and the cathode.

(50) Further, for the electron injection layer or electron transport layer, those obtained by N-doping the material typically used for the layer with a metal such as cesium can be used.

(51) In the cathode of the organic EL device according to the present invention, an electrode material having a low work function, such as aluminum, an alloy having a lower work function, such as a magnesium silver alloy, a magnesium indium alloy, and an aluminum magnesium alloy, or the like is used as the electrode material.

(52) Hereinafter, the embodiment of the present invention will be specifically described by way of Examples. However, the present technology is not limited to the following Examples as long as the essence of the present invention is not exceeded.

Example 1

Synthesis of 4,6-bis (biphenyl-3-yl)-2-([1,1′,3′,1″] terphenyl-4-yl)-benzoxazole (Compound 6)

(53) 4,6-bis(biphenyl-3-yl)-2-(4-chloro-phenyl)-benzoxazole: 10.0 g, 3-biphenylboronic acid: 7.5 g, bis(dibenzylideneacetone) palladium (0): 0.5 g, tricyclohexylphosphine: 1.1 g, and tripotassium phosphate: 12.1 g were charged into a reaction vessel, and stirred under reflux overnight in a 1,4-dioxane/H.sub.2O mixed solvent. The mixture was allowed to cool and then separated. Extraction was performed with ethyl acetate from the aqueous layer, and then, the extract was concentrated. The crude product thus obtained was purified by column chromatography (carrier: silica gel, eluent: dichloromethane/ethyl acetate), and then crystallized with acetone. In this way, 8.3 g (yield of 68.0%) of white powder of 4,6-bis (biphenyl-3-yl)-2-([1,1′,3′, 1″] terphenyl-4-yl)-benzoxazole (Compound 6) was obtained.

(54) ##STR00016##

(55) The structure of the obtained white powder was identified using NMR.

(56) The following 33 hydrogen signals were detected by .sup.1H-NMR (CDCl.sub.3).

(57) δ (ppm)=8.44 (2H), 8.35 (1H), 8.14 (1H), 8.00-7.82 (6H), 7.80-7.47 (20H), 7.46-7.37 (3H).

Example 2

Synthesis of 2-{3,5-di([9H]-carbazol-9-yl)-phenyl}-4,6-diphenyl-benzoxazole (Compound 22)

(58) By using 2-(3,5-dichloro-phenyl)-4,6-diphenyl-benzoxazole and carbazole instead of 4,6-bis(biphenyl-3-yl)-2-(4-chloro-phenyl)-benzoxazole and 3-biphenylboronic acid in Example 1, respectively, and performing the reaction under similar conditions, 4.8 g (yield of 30%) of a white powder of 2-{3,5-di([9H]-carbazol-9-yl)-phenyl}-4,6-diphenyl-benzoxazole (Compound 22) was obtained.

(59) ##STR00017##

(60) The structure of the obtained white powder was identified using NMR.

(61) The following 31 hydrogen signals were detected by .sup.1H-NMR (CDCl.sub.3).

(62) δ (ppm)=8.67 (2H), 8.21 (4H), 8.10 (2H), 8.01 (1H), 7.85 (1H), 7.79 (1H), 7.73 (2H), 7.63 (4H), 7.57-7.46 (8H), 7.46-7.33 (6H).

Example 3

Synthesis of 2-{2,5-di([9H]-carbazol-9-yl)-phenyl}-4,6-diphenyl-benzoxazole (Compound 24)

(63) 2-{2,5-difluoro-phenyl}-4,6-diphenyl-benzoxazole: 3.7 g, carbazole: 3.4 g, and cesium carbonate: 12.9 g were charged into a reaction vessel, and heated and stirred overnight at 120° C. in a DMF solvent. The mixture was allowed to cool, and then H.sub.2O was added thereto. Then, the precipitated solid was collected to obtain a crude product. The crude product was crystallized and purified with a monochlorobenzene/acetone mixed solvent, and thus, 4.3 g (yield of 64%) of white powder of 2-{2,5-di([9H]-carbazol-9-yl)-phenyl}-4,6-diphenyl-benzoxazole (Compound 24) was obtained.

(64) ##STR00018##

(65) The structure of the obtained white powder was identified using NMR.

(66) The following 31 hydrogen signals were detected by .sup.1H-NMR (CDCl.sub.3).

(67) δ (ppm)=8.81 (1H), 8.25 (4H), 8.02 (1H), 7.94 (1H), 7.69 (2H), 7.63 (1H), 7.56 (2H), 7.55 (2H), 7.48-7.29 (17H).

Example 4

Synthesis of 4,6-bis(biphenyl-3-yl)-2-{([9H]-carbazol-9-yl)-phenyl}-benzoxazole (Compound 45)

(68) By using carbazole instead of 3-biphenylboronic acid in Example 1 and performing the reaction under similar conditions, 4.2 g (yield of 34%) of white powder of 4,6-bis(biphenyl-3-yl)-2-{([9H]-carbazol-9-yl)-phenyl}-benzoxazole (Compound 45) was obtained.

(69) ##STR00019##

(70) The structure of the obtained white powder was identified using NMR.

(71) The following 32 hydrogen signals were detected by .sup.1H-NMR (CDCl.sub.3).

(72) δ (ppm)=8.59 (2H), 8.36 (1H), 8.19 (2H), 8.15 (1H), 7.97 (1H), 7.92 (1H), 7.94-7.32 (23H).

Example 5

Synthesis of 4,6-bis(biphenyl-3-yl)-2-{4-(9-phenyl-[9H]-carbazol-3-yl)-phenyl}-benzoxazole (Compound 47)

(73) By using 3-(9-phenyl-[9H]-carbazole)-boronic acid instead of 3-biphenylboronic acid in Example 1 and performing the reaction under similar conditions, 3.8 g (yield of 27%) of pale yellow powder of 4,6-bis(biphenyl-3-yl)-2-{4-(9-phenyl-[9H]-carbazol-3-yl)-phenyl}-benzoxazole (Compound 47) was obtained.

(74) ##STR00020##

(75) The structure of the obtained pale yellow powder was identified using NMR.

(76) The following 36 hydrogen signals were detected by .sup.1H-NMR (CDCl.sub.3).

(77) δ (ppm)=8.47 (1H), 8.45 (2H), 8.37 (1H), 8.25 (1H), 8.15 (1H), 7.92 (5H), 7.82-7.59 (14H), 7.58-7.33 (11H).

Example 6

Synthesis of 2,6-diphenyl-4-(9,9′-spirobi[9H]fluoren-2-yl)-benzoxazole (Compound 57)

(78) By using 6-Chloro-2-phenyl-4-(9,9′-spirobi[9H]fluoren-2-yl)-benzoxazole and phenylboronic acid instead of 4,6-bis(biphenyl-3-yl)-2-(4-chloro-phenyl)-benzoxazole and 3-biphenylboronic acid in Example 1, respectively, and performing the reaction under similar conditions, 4.5 g (yield of 41%) of white powder of 2,6-diphenyl-4-(9,9′-spirobi[9H]fluoren-2-yl)-benzoxazole (Compound 57) was obtained.

(79) ##STR00021##

(80) The structure of the obtained white powder was identified using NMR.

(81) The following 27 hydrogen signals were detected by .sup.1H-NMR (CDCl.sub.3).

(82) δ (ppm)=8.15-7.98 (6H) 7.97-7.85 (4H), 7.60-7.36 (9H), 7.17 (4H), 6.90-6.80 (4H).

Example 7

<Synthesis of <6-(Biphenyl-3-yl)-2-(biphenyl-4-yl)-4-(9-phenyl-[9H]-carbazol-3-yl)-benzoxazole (Compound 60)>

(83) By using 6-(biphenyl-3-yl)-2-(4-chlorophenyl)-4-(9-phenyl-[9H]-carbazol-3-yl)-benzoxazole and phenylboronic acid instead of 4,6-bis(biphenyl-3-yl)-2-(4-chloro-phenyl)-benzoxazole and 3-biphenylboronic acid in Example 1, respectively, and performing the reaction under similar conditions, 3.0 g (yield of 44%) of white powder of 6-(Biphenyl-3-yl)-2-(biphenyl-4-yl)-4-(9-phenyl-[9H]-carbazol-3-yl)-benzoxazole (Compound 60) was obtained.

(84) ##STR00022##

(85) The structure of the obtained white powder was identified using NMR.

(86) The following 32 hydrogen signals were detected by .sup.1H-NMR (CDCl.sub.3).

(87) δ (ppm)=8.90 (1H), 8.45 (2H), 8.30 (1H), 8.26 (1H), 7.94 (1H), 7.91 (1H), 7.85 (2H), 7.80 (3H), 7.74-7.32 (20H).

Example 8

Synthesis of 4-{3,5-di([9H]-carbazol-9-yl)-phenyl}-2,6-diphenyl-benzoxazole (Compound 62)

(88) By using 6-chloro-4-{3,5-di([9H]-carbazol-9-yl)-phenyl}-2-phenyl-benzoxazole and phenylboronic acid instead of 4,6-bis(biphenyl-3-yl)-2-(4-chloro-phenyl)-benzoxazole and 3-biphenylboronic acid in Example 1, respectively, and performing the reaction under similar conditions, 8.0 g (yield of 60%) of white powder of 4-{3,5-di([9H]-carbazol-9-yl)-phenyl}-2,6-diphenyl-benzoxazole (Compound 62) was obtained.

(89) ##STR00023##

(90) The structure of the obtained white powder was identified using NMR.

(91) The following 31 hydrogen signals were detected by .sup.1H-NMR (CDCl.sub.3).

(92) δ (ppm)=8.52 (2H), 8.42 (2H), 8.21 (4H), 7.91 (1H), 7.90 (1H), 7.87 (1H), 7.85 (4H), 7.71 (2H), 7.65-7.46 (9H), 7.45-7.34 (5H).

Example 9

Synthesis of 6-{3,5-di([9H]-carbazol-9-yl)-phenyl}-2,4-diphenyl-benzoxazole (Compound 69)

(93) By using 6-chloro-2,4-diphenyl-benzoxazole and 3,5-di([9H]-carbazol-9-yl)-phenylboronic acid instead of 4,6-bis(biphenyl-3-yl)-2-(4-chloro-phenyl)-benzoxazole and 3-biphenylboronic acid in Example 1, respectively, and performing the reaction under similar conditions, 6.8 g (yield of 61%) of white powder of 6-{3,5-di([9H]-carbazol-9-yl)-phenyl}-2,4-diphenyl-benzoxazole (Compound 69) was obtained.

(94) ##STR00024##

(95) The structure of the obtained white powder was identified using NMR.

(96) The following 31 hydrogen signals were detected by .sup.1H-NMR (CDCl.sub.3).

(97) δ (ppm)=8.35 (2H), 8.21 (4H), 8.11 (2H), 8.07 (2H), 7.91 (2H), 7.88 (1H), 7.66 (4H), 7.59-7.42 (10H), 7.36 (4H).

Example 10

Synthesis of 2-Phenyl-6-(9-phenyl-[9H]-carbazol-3-yl)-4-(5-phenyl-[5H]-pyrido[4,3,b]indol-8-yl)-benzoxazole (Compound 82)

(98) By using 6-chloro-2-phenyl-4-(5-phenyl-[5H]-pyrido[4,3,b]indol-8-yl)-benzoxazole and 9-phenyl-[9H]-carbazol-3-yl-boronic acid instead of 4,6-bis(biphenyl-3-yl)-2-(4-chloro-phenyl)-benzoxazole and 3-biphenylboronic acid in Example 1, respectively, and performing the reaction under similar conditions, 2.9 g (yield of 50%) of yellow powder of 2-Phenyl-6-(9-phenyl-[9H]-carbazol-3-yl)-4-(5-phenyl-[5H]-pyrido[4,3,b]indol-8-yl)-benzoxazole (Compound 82) was obtained.

(99) ##STR00025##

(100) The structure of the obtained yellow powder was identified using NMR.

(101) The following 30 hydrogen signals were detected by .sup.1H-NMR (CDCl.sub.3).

(102) δ (ppm)=9.56 (1H), 9.04 (1H), 8.59 (1H), 8.53 (1H), 8.48 (1H), 8.45 (1H), 8.36 (1H), 8.26 (2H), 8.05 (1H), 7.93 (2H), 7.88-7.43 (16H), 7.36 (2H).

Example 11

Synthesis of 2-{3,5-di([9H]-carbazol-9-yl)-phenyl}-benzoxazole (Compound 96)

(103) By using 2-(3,5-dichloro-phenyl)-benzoxazole and carbazole instead of 4,6-bis(biphenyl-3-yl)-2-(4-chloro-phenyl)-benzoxazole and 3-biphenylboronic acid in Example 1, respectively, and performing the reaction under similar conditions, 10.6 g (yield of 67%) of white powder of 2-{3,5-di([9H]-carbazol-9-yl)-phenyl}-benzoxazole (Compound 96) was obtained.

(104) ##STR00026##

(105) The structure of the obtained white powder was identified using NMR.

(106) The following 23 hydrogen signals were detected by .sup.1H-NMR (CDCl.sub.3).

(107) δ (ppm)=8.64 (2H), 8.21 (4H), 8.03 (1H), 7.87 (1H), 7.64 (5H), 7.51 (4H), 7.47-7.32 (6H).

Example 12

Synthesis of 2-{3,5-di([9H]-carbazol-9-yl)-biphenyl-4′-yl}-benzoxazole (Compound 97)

(108) 2-(4-bromophenyl)-benzoxazole: 4.0 g, and 3,5-di([9H]-carbazol-9-yl)-phenylboronic acid: 7.3 g were charged into a reaction vessel, toluene: 80 mL, ethanol: 20 mL, and then an aqueous solution prepared by dissolving potassium carbonate; 2.4 g in H.sub.2O: 20 mL in advance were added thereto, and nitrogen gas was aerated while applying ultrasonic waves for 30 minutes. Tetrakis (triphenylphosphine) palladium (0): 0.3 g was added thereto, and the mixture was stirred overnight with heating under reflux. The mixture was allowed to cool and then, an organic layer was separated by a liquid separation operation and concentrated to obtain a crude product. The crude product was crystallized and purified with a toluene/acetone mixed solvent, and thus, 4.4 g (yield of 50%) of white powder of 2-{3,5-di([9H]-carbazol-9-yl)-biphenyl-4′-yl}-benzoxazole (Compound 97) was obtained.

(109) ##STR00027##

(110) The structure of the obtained white powder was identified using NMR.

(111) The following 27 hydrogen signals were detected by .sup.1H-NMR (CDCl.sub.3).

(112) δ (ppm)=8.42 (2H), 8.21 (4H), 8.04 (2H), 7.91 (3H), 7.82 (1H), 7.64 (5H), 7.51 (4H), 7.45-7.32 (6H).

Example 13

Synthesis of 2-{3,5-di([9H]-carbazol-9-yl)-phenyl}-6-(biphenyl-4-yl)-4-phenyl-benzoxazole (Compound 98)

(113) By using 2-(3,5-dichloro-phenyl)-6-(biphenyl-4-yl)-4-phenyl-benzoxazole and carbazole instead of 4,6-bis(biphenyl-3-yl)-2-(4-chloro-phenyl)-benzoxazole and 3-biphenylboronic acid in Example 1, respectively, and performing the reaction under similar conditions, 7.9 g (yield of 57%) of white powder of 2-{3,5-di([9H]-carbazol-9-yl)-phenyl}-6-(biphenyl-4-yl)-4-phenyl-benzoxazole (Compound 98) was obtained.

(114) ##STR00028##

(115) The structure of the obtained white powder was identified using NMR.

(116) The following 35 hydrogen signals were detected by .sup.1H-NMR (CDCl.sub.3).

(117) δ (ppm)=8.68 (2H), 8.22 (4H), 8.11 (2H), 8.01 (1H), 7.87 (2H), 7.79 (4H), 7.69 (2H), 7.64 (4H), 7.57-7.47 (8H), 7.42 (2H), 7.38 (4H).

Example 14

Synthesis of 2-{3,4-di([9H]-carbazol-9-yl)-phenyl}-4,6-diphenyl-benzoxazole (Compound 99)

(118) By using 2-{3,4-difluoro-phenyl}-4,6-diphenyl-benzoxazole instead of 2-{2,5-difluoro-phenyl}-4,6-diphenyl-benzoxazole in Example 3 and performing the reaction under similar conditions, 3.1 g (yield of 60%) of white powder of 2-{3,4-di([9H]-carbazol-9-yl)-phenyl}-4,6-diphenyl-benzoxazole (Compound 99) was obtained.

(119) ##STR00029##

(120) The structure of the obtained white powder was identified using NMR.

(121) The following 31 hydrogen signals were detected by .sup.1H-NMR (CDCl.sub.3).

(122) δ (ppm)=8.79 (1H), 8.67 (1H), 8.14 (2H), 8.04 (1H), 7.89-7.79 (6H), 7.75 (2H), 7.56 (4H), 7.45 (2H), 7.24 (4H), 7.15-7.06 (8H).

Example 15

Synthesis of 4-(biphenyl-3-yl)-2-(biphenyl-4-yl)-6-(9-phenyl-[9H]-carbazol-3-yl)-benzoxazole (Compound 100)

(123) By using 4-(biphenyl-3-yl)-2-(4-chlorophenyl)-6-(9-phenyl-[9H]-carbazol-3-yl)-benzoxazole and phenylboronic acid instead of 4,6-bis(biphenyl-3-yl)-2-(4-chloro-phenyl)-benzoxazole and 3-biphenylboronic acid in Example 1, respectively, and performing the reaction under similar conditions, 2.1 g (yield of 31%) of white powder of 4-(biphenyl-3-yl)-2-(biphenyl-4-yl)-6-(9-phenyl-[9H]-carbazol-3-yl)-benzoxazole (Compound 100) was obtained.

(124) ##STR00030##

(125) The structure of the obtained white powder was identified using NMR.

(126) The following 32 hydrogen signals were detected by .sup.1H-NMR (CDCl.sub.3).

(127) δ (ppm)=8.47 (1H), 8.50 (2H), 8.36 (1H), 8.25 (1H), 8.16 (1H), 7.92 (2H), 7.85 (2H), 7.77 (5H), 7.72-7.59 (6H), 7.57-7.33 (11H).

Example 16

(128) The melting point and the glass transition point of the benzoazole compound represented by the general formula (1) were measured using a high sensitivity differential scanning calorimeter (DSC3100SA manufactured by Bruker AXS GmbH).

(129) TABLE-US-00001 transition point Melting point Glass Compound of Example 1 Not observed  82° C. Compound of Example 2 273° C. 144° C. Compound of Example 3 256° C. 136° C. Compound of Example 4 Not observed 107° C. Compound of Example 5 220° C. 112° C. Compound of Example 6 242° C. 121° C. Compound of Example 7 236° C. 113° C. Compound of Example 8 313° C. 144° C. Compound of Example 9 277° C. 145° C. Compound of Example 10 Not observed 180° C. Compound of Example 11 261° C. 117° C. Compound of Example 12 243° C. 135° C. Compound of Example 13 315° C. 162° C. Compound of Example 14 270° C. 144° C. Compound of Example 15 Not observed 111° C.

(130) The compound having a benzoazole structure represented by the general formula (1) has the glass transition point of not less than 100° C., which shows that the thin film state is stable.

Example 17

(131) The compound having a benzoazole structure represented by the general formula (1) was used to prepare a vapor deposition film having a film thickness of 100 nm on an ITO substrate, and the work function thereof was measured by an ionization potential measuring apparatus (PYS-202 manufactured by Sumitomo Heavy Industries, Ltd.).

(132) TABLE-US-00002 Work function Compound of Example 1 6.34 eV Compound of Example 2 6.28 eV Compound of Example 3 6.12 eV Compound of Example 4 6.20 eV Compound of Example 5 6.00 eV Compound of Example 6 6.46 eV Compound of Example 7 5.98 eV Compound of Example 8 6.18 eV Compound of Example 9 6.21 eV Compound of Example 10 5.94 eV Compound of Example 11 6.24 eV Compound of Example 12 6.24 eV Compound of Example 13 6.32 eV Compound of Example 14 6.18 eV Compound of Example 15 6.02 eV

(133) The compound having a benzoazole structure represented by the general formula (1) has a value of work function larger than 5.5 eV that is a value of work function of a general hole transport material such as NPD and TPD and has large hole blocking performance.

Example 18

(134) The organic EL device was prepared by depositing a hole injection layer 3, a hole transport layer 4, a light-emitting layer 5, a hole blocking layer 6, an electron transport layer 7, an electron injection layer 8, and a cathode (aluminum electrode) 9 in the stated order on a transparent anode 2, which has been formed on a glass substrate 1 as an ITO electrode in advance, as shown in FIG. 26.

(135) Specifically, after performing, in isopropyl alcohol for 20 minutes, ultrasonic cleaning on the glass substrate 1 on which ITO having a film thickness of 150 nm was formed, the glass substrate 1 was dried for 10 minutes on a hot plate heated to 200° C. After that, UV ozone treatment was performed for 15 minutes, and then, the ITO-attached glass substrate was mounted in a vacuum deposition machine. The pressure in the vacuum deposition machine was reduced to not more than 0.001 Pa. Subsequently, a film of an electron acceptor (Acceptor-1) having the following structural formula and a compound (HTM-1-1) having the following structural formula were formed, as the hole injection layer 3, to have a film thickness of 10 nm and cover the transparent anode 2 by binary deposition at a deposition rate in which the ratio of the deposition rates of Acceptor-1 and the compound (HTM-1-1) was 3:97. As the hole transport layer 4, a film of the compound (HTM-1-1) having the following structural formula was formed on the hole injection layer 3 to have a film thickness of 60 nm. A film of a compound EMD-1 having the following structural formula and a compound EMH-1 having the following structural formula were formed, as the light-emitting layer 5, on the hole transport layer 4 to have a film thickness of 20 nm by binary deposition at a deposition rate in which the ratio of the deposition rates of EMD-1 and EMH-1 was 5:95. A film of the compound (Compound 22) according to Example 2 was formed on the light-emitting layer 5, as the hole blocking layer 6 to have a film thickness of 5 nm. A film of a compound (ETM-2-87) having the following structural formula and a compound (ETM-3) having the following structural formula were formed, as the electron transport layer 7, on the hole blocking layer 6 to have a film thickness of 25 nm by binary deposition at a deposition rate in which the ratio of the deposition rates of the compound (ETM-2-87) and the compound ETM-3 was 50:50. A film of lithium fluoride was formed, as the electron injection layer 8, on the electron transport layer 7 to have a film thickness of 1 nm. Finally, aluminum was deposited to have a thickness of 100 nm to form the cathode 9. The characteristics of the prepared organic EL device were measured at room temperature in the atmosphere. The measurement results of the light-emitting characteristics when a direct current voltage was applied to the prepared organic EL device were collectively shown in Table 1.

(136) ##STR00031## ##STR00032## ##STR00033##

Example 19

(137) An organic EL device was prepared in similar conditions to Example 18 except that the compound (Compound 24) according to Example 3 of the present invention was used as the material of the hole blocking layer 6 instead of the compound (Compound 22) according to Example 2 of the present invention. The characteristics of the prepared organic EL device were measured at room temperature in the atmosphere. The measurement results of the light-emitting characteristics when a direct current voltage was applied to the prepared organic EL device were collectively shown in Table 1.

(138) ##STR00034##

Example 20

(139) An organic EL device was prepared in similar conditions to Example 18 except that the compound (Compound 60) according to Example 7 of the present invention was used as the material of the hole blocking layer 6 instead of the compound (Compound 22) according to Example 2 of the present invention. The characteristics of the prepared organic EL device were measured at room temperature in the atmosphere. The measurement results of the light-emitting characteristics when a direct current voltage was applied to the prepared organic EL device were collectively shown in Table 1.

(140) ##STR00035##

Example 21

(141) An organic EL device was prepared in similar conditions to Example 18 except that the compound (Compound 62) according to Example 8 of the present invention was used as the material of the hole blocking layer 6 instead of the compound (Compound 22) according to Example 2 of the present invention. The characteristics of the prepared organic EL device were measured at room temperature in the atmosphere. The measurement results of the light-emitting characteristics when a direct current voltage was applied to the prepared organic EL device were collectively shown in Table 1.

(142) ##STR00036##

Example 22

(143) An organic EL device was prepared in similar conditions to Example 18 except for the compound (Compound 69) according to Example 9 of the present invention was used as the material of the hole blocking layer 6 instead of the compound (Compound 22) according to Example 2 of the present invention. The characteristics of the prepared organic EL device were measured at room temperature in the atmosphere. The measurement results of the light-emitting characteristics when a direct current voltage was applied to the prepared organic EL device were collectively shown in Table 1.

(144) ##STR00037##

Example 23

(145) An organic EL device was prepared in similar conditions to Example 18 except that the compound (Compound 96) according to Example 11 of the present invention was used as the material of the hole blocking layer 6 instead of the compound (Compound 22) according to Example 2 of the present invention. The characteristics of the prepared organic EL device were measured at room temperature in the atmosphere. The measurement results of the light-emitting characteristics when a direct current voltage was applied to the prepared organic EL device were collectively shown in Table 1.

(146) ##STR00038##

Example 24

(147) An organic EL device was prepared in similar conditions to Example 18 except that the compound (Compound 97) according to Example 12 of the present invention was used as the material of the hole blocking layer 6 instead of the compound (Compound 22) according to Example 2 of the present invention. The characteristics of the prepared organic EL device were measured at room temperature in the atmosphere. The measurement results of the light-emitting characteristics when a direct current voltage was applied to the prepared organic EL device were collectively shown in Table 1.

(148) ##STR00039##

Example 25

(149) An organic EL device was prepared in similar conditions to Example 18 except that the compound (Compound 98) according to Example 13 of the present invention was used as the material of the hole blocking layer 6 instead of the compound (Compound 22) according to Example 2 of the present invention. The characteristics of the prepared organic EL device were measured at room temperature in the atmosphere. The measurement results of the light-emitting characteristics when a direct current voltage was applied to the prepared organic EL device were collectively shown in Table 1.

(150) ##STR00040##

Example 26

(151) An organic EL device was prepared in similar conditions to Example 18 except that the compound (Compound 99) according to Example 14 of the present invention was used as the material of the hole blocking layer 6 instead of the compound (Compound 22) according to Example 2 of the present invention. The characteristics of the prepared organic EL device were measured at room temperature in the atmosphere. The measurement results of the light-emitting characteristics when a direct current voltage was applied to the prepared organic EL device were collectively shown in Table 1.

(152) ##STR00041##

Comparative Example 1

(153) For comparison, an organic EL device was prepared in similar conditions to Example 18 except that a compound ETM-4 having the following structural formula was used as the material of the hole blocking layer 6 instead of the compound (Compound 22) according to Example 2 of the present invention. The characteristics of the prepared organic EL device were measured at room temperature in the atmosphere. The measurement results of the light-emitting characteristics when a direct current voltage was applied to the prepared organic EL device were collectively shown in Table 1.

(154) ##STR00042##

Comparative Example 2

(155) For comparison, an organic EL device was prepared in similar conditions to Example 18 except that the above-mentioned compound (ETM-2-87) was used as the material of the hole blocking layer 6 instead of the compound (Compound 22) according to Example 2 of the present invention. The characteristics of the prepared organic EL device were measured at room temperature in the atmosphere. The measurement results of the light-emitting characteristics when a direct current voltage was applied to the prepared organic EL device were collectively shown in Table 1.

(156) ##STR00043##

(157) The device lifetime was measured using each of the organic EL devices prepared in Examples 18 and 26 and Comparative Examples 1 and 2, and the results were collectively shown in Table 1. The device lifetime was measured as the time until the light emission luminance attenuated to 1900 cd/m.sup.2 (corresponding to 95% in the case where the initial luminance was 100%: 95% attenuation) when constant current driving was performed with the light emission luminance (initial luminance) at the start of light emission set to 2000 cd/m.sup.2.

(158) TABLE-US-00003 TABLE 1 Light emission Power Device Luminance efficiency efficiency lifetime Hole blocking Voltage [V] [cd/m.sup.2] [cd/A] [lm/W] 95% layer (@ 10 mA/cm.sup.2) (@ 10 mA/cm.sup.2) (@ 10 mA/cm.sup.2) (@ 10 mA/cm.sup.2) attenuated Example 18 Compound 22 3.48 1008 10.08 9.11 235 hours Example 19 Compound 24 3.52 1004 10.04 8.97 212 hours Example 20 Compound 60 3.49 1009 10.09 9.10 151 hours Example 21 Compound 62 3.50  980  9.80 8.81 204 hours Example 22 Compound 69 3.52  985  9.85 8.80 272 hours Example 23 Compound 96 3.51  999  9.99 8.95 217 hours Example 24 Compound 97 3.47 1010 10.10 9.16 195 hours Example 25 Compound 98 3.52  985  9.85 8.81 256 hours Example 26 Compound 99 3.52 1007 10.07 8.99 227 hours Comparative ETM-4 3.53  966  9.66 8.60 117 hours Example 1 Comparative ETM-2-87 3.66  900  9.00 7.74 137 hours Example 2

(159) As shown in Table 1, the drive voltage when a current having a current density of 10 mA/cm.sup.2 was caused to flow was lowered to 3.47 to 3.52 V in the organic EL devices according to Examples 18 to 26 as compared with the 3.53 to 3.66 V of the organic EL devices according to Comparative Examples 1 and 2. Further, the light emission efficiency was improved to 9.80 to 10.10 cd/A in the organic EL devices according to Examples 18 to 26 as compared with 9.00˜9.66 cd/A of the organic EL devices according to Comparative Examples 1 and 2. Also the power efficiency of the organic EL devices according to Examples 18 to 26 was largely improved to 8.80 to 9.16 lm/W as compared with 7.74 to 8.60 lm/W of the organic EL devices according to Comparative Examples 1 and 2. In particular, the device lifetime (95% attenuation) was largely extended to 151 to 272 hours in the organic EL devices according to Examples 18 to 26 as compared with 117 to 137 hours of the organic EL devices according to Comparative Examples 1 and 2.

(160) As described above, the organic EL device according to the present invention is excellent in the light emission efficiency and power efficiency as compared with the existing organic EL devices because hole blocking performance, hole resistance performance, and exciton confinement performance are improved by selecting a specific benzoazole-based compound as the material of a hole blocking layer. Thus, it has been found that it is possible to realize an organic EL device having a long lifetime.

INDUSTRIAL APPLICABILITY

(161) The compound having a specific benzoazole structure according to the present invention is excellent in electron injection property and hole blocking performance and is stable in a thin film state, and thus is suitably used as a compound for organic EL device. By preparing an organic EL device using the compound, it is possible to achieve high efficiency, reduce the drive voltage, and improve the durability. For example, it has become possible to expand to home appliances and lighting applications.

REFERENCE SIGNS LIST

(162) 1 glass substrate 2 transparent anode 3 hole injection layer 4 hole transport layer 5 light-emitting layer 6 hole blocking layer 7 electron transport layer 8 electron injection layer 9 cathode 20