Organic electroluminescence device

Abstract

An organic EL device is provided, including at least an anode, a hole transport layer, a light-emitting layer, an electron transport layer, and a cathode in this order, wherein the hole transport layer contains an arylamine compound represented by the following formula (1), wherein Ar.sub.1 to Ar.sub.8 and n1 are defined in the specification, and the electron transport layer contains a compound having a benzoazole ring structure represented by the following formula (2), wherein Ar.sub.9, Ar.sub.10, X, Y.sub.1, Z.sub.1 and Z.sub.2 are defined in the specification. ##STR00001## ##STR00002##

Claims

1. An organic electroluminescence device including at least an anode, a hole transport layer, a light-emitting layer, an electron transport layer, and a cathode in this order, wherein the hole transport layer contains an arylamine compound represented by the following general formula (1), and the electron transport layer contains a compound having a benzoazole ring structure represented by the following general formula (2), ##STR00022## in the formula (1), Ar.sub.1 to Ar.sub.5 may be the same or different from each other, and represent a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted fused polycyclic aromatic group, Ar.sub.6 to Ar.sub.8 may be the same or different from each other, and represent a hydrogen atom, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted fused polycyclic aromatic group, n1 represents 0, 1, or 2, or Ar.sub.3 and Ar.sub.4 may join to form a ring, wherein Ar.sub.3 and Ar.sub.4 are 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, or Ar.sub.3 or Ar.sub.4 may join to form a ring with a benzene ring to which an Ar.sub.3Ar.sub.4—N group is bonded, wherein Ar.sub.3 and the benzene ring or Ar.sub.4 and the benzene ring are 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, ##STR00023## in the formula (2), Ar.sub.9 and Ar.sub.10 may be the same or different from each other, and represent a hydrogen atom, a deuterium atom, 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 alkyl group, Y.sub.1 represents 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 alkyl 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 represent a carbon atom or a nitrogen atom.

2. The organic electroluminescence device according to claim 1, wherein the arylamine compound is represented by the following general formula (1a), ##STR00024## in the formula (1a), Ar.sub.1 to Ar.sub.5 may be the same or different from each other, and represent a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted fused polycyclic aromatic group, Ar.sub.6 to Ar.sub.8 may be the same or different from each other, and represent a hydrogen atom, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted fused polycyclic aromatic group, n1 represents 0, 1, or 2, or Ar.sub.3 and Ar.sub.4 may join to form a ring, wherein Ar.sub.3 and Ar.sub.4 are 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, or Ar.sub.3 or Ar.sub.4 may join to form a ring with a benzene ring to which an Ar.sub.3Ar.sub.4—N group is bonded, wherein Ar.sub.3 and the benzene ring or Ar.sub.4 and the benzene ring are 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.

3. The organic electroluminescence device according to claim 1, wherein the compound having a benzoazole ring structure is represented by the following general formula (3), ##STR00025## in the formula (3), Ar.sub.11 and Ar.sub.12 may be the same or different from each other, and represent a hydrogen atom, a deuterium atom, 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 alkyl group, Y.sub.2 represents 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 alkyl group, X represents an oxygen atom or a sulfur atom.

4. The organic electroluminescence device according to claim 1, wherein the organic electroluminescence device further includes an electron blocking layer between the hole transport layer and the light-emitting layer.

5. The organic electroluminescence device according to claim 4, wherein the electron blocking layer contains an arylamine compound represented by the following general formula (4), ##STR00026## in the formula (4), Ar.sub.13 to Ar.sub.16 may be the same or different from each other, and represent a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted fused polycyclic aromatic group.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a diagram showing the structural formulae of Compounds 1-1 to 1-15 as arylamine compounds represented by the general formula (1).

(2) FIG. 2 is a diagram showing the structural formulae of Compounds 1-16 to 1-30 as arylamine compounds represented by the general formula (1).

(3) FIG. 3 is a diagram showing the structural formulae of Compounds 1-31 to 1-44 as arylamine compounds represented by the general formula (1).

(4) FIG. 4 is a diagram showing the structural formulae of Compounds 2-1 to 2-10 as benzoxazole compounds represented by the general formula (2).

(5) FIG. 5 is a diagram showing the structural formulae of Compounds 2-11 to 2-20 as benzoxazole compounds represented by the general formula (2).

(6) FIG. 6 is a diagram showing the structural formulae of Compounds 2-21 to 2-30 as benzoxazole compounds represented by the general formula (2).

(7) FIG. 7 is a diagram showing the structural formulae of Compounds 2-31 to 2-42 as benzoxazole compounds represented by the general formula (2).

(8) FIG. 8 is a diagram showing the structural formulae of Compounds 2-43 to 2-54 as benzoxazole compounds represented by the general formula (2).

(9) FIG. 9 is a diagram showing the structural formulae of Compounds 2-55 to 2-68 as benzoxazole compounds represented by the general formula (2).

(10) FIG. 10 is a diagram showing the structural formulae of Compounds 2-69 to 2-80 as benzoxazole compounds represented by the general formula (2).

(11) FIG. 11 is a diagram showing the structural formulae of Compounds 2-81 to 2-92 as benzoxazole compounds represented by the general formula (2).

(12) FIG. 12 is a diagram showing the structural formulae of Compounds 2-93 to 2-102 as benzoxazole compounds represented by the general formula (2).

(13) FIG. 13 is a diagram showing the structural formulae of Compounds 2-103 to 2-113 as benzoxazole compounds represented by the general formula (2).

(14) FIG. 14 is a diagram showing the structural formulae of Compounds 2-114 to 2-125 as benzoxazole compounds represented by the general formula (2).

(15) FIG. 15 is a diagram showing the structural formulae of Compounds 2-126 to 2-133 as benzoxazole compounds represented by the general formula (2).

(16) FIG. 16 is a diagram showing the structural formulae of Compounds 3-1 to 3-10 as benzothiazole compounds represented by the general formula (3).

(17) FIG. 17 is a diagram showing the structural formulae of Compounds 3-11 to 3-20 as benzothiazole compounds represented by the general formula (3).

(18) FIG. 18 is a diagram showing the structural formulae of Compounds 3-21 to 3-30 as benzothiazole compounds represented by the general formula (3).

(19) FIG. 19 is a diagram showing the structural formulae of Compounds 3-31 to 3-42 as benzothiazole compounds represented by the general formula (3).

(20) FIG. 20 is a diagram showing the structural formulae of Compounds 3-43 to 3-53 as benzothiazole compounds represented by the general formula (3).

(21) FIG. 21 is a diagram showing the structural formulae of Compounds 3-54 to 3-63 as benzothiazole compounds represented by the general formula (3).

(22) FIG. 22 is a diagram showing the structural formulae of Compounds 4-1 to 4-15 as arylamine compounds represented by the general formula (4).

(23) FIG. 23 is a diagram showing the structural formulae of Compounds 4-16 to 4-30 as arylamine compounds represented by the general formula (4).

(24) FIG. 24 is a diagram showing the structural formulae of Compounds 4-31 to 4-45 as arylamine compounds represented by the general formula (4).

(25) FIG. 25 is a diagram showing the structural formulae of Compounds 4-46 to 4-60 as arylamine compounds represented by the general formula (4).

(26) FIG. 26 is a diagram showing the structural formulae of Compounds 4-61 to 4-75 as arylamine compounds represented by the general formula (4).

(27) FIG. 27 is a diagram showing the structural formulae of Compounds 4-76 to 4-90 as arylamine compounds represented by the general formula (4).

(28) FIG. 28 is a diagram showing the structural formulae of Compounds 4-91 to 4-105 as arylamine compounds represented by the general formula (4).

(29) FIG. 29 is a diagram showing the structural formulae of Compounds 4-106 to 4-118 as arylamine compounds represented by the general formula (4).

(30) FIG. 30 is a diagram showing the structural formulae of Compounds 4-119 to 4-133 as arylamine compounds represented by the general formula (4).

(31) FIG. 31 is a diagram showing the structural formulae of Compounds 4-134 to 4-148 as arylamine compounds represented by the general formula (4).

(32) FIG. 32 is a diagram showing the structural formulae of Compounds 4-149 to 4-163 as arylamine compounds represented by the general formula (4).

(33) FIG. 33 is a diagram showing the structural formulae of Compounds 4-164 to 4-178 as arylamine compounds represented by the general formula (4).

(34) FIG. 34 is a diagram showing the structural formulae of Compounds 4-179 to 4-193 as arylamine compounds represented by the general formula (4).

(35) FIG. 35 is a diagram showing the structural formulae of Compounds 4-194 to 4-201 as arylamine compounds represented by the general formula (4).

(36) FIG. 36 is a diagram showing a configuration of organic EL devices according to Examples 10 to 15 and Comparative Examples 1 to 7.

MODE(S) FOR CARRYING OUT THE INVENTION

(37) Compounds 1-1 to 1-44 are shown in FIG. 1 to FIG. 3 as specific examples of favorable compounds among the arylamine compounds represented by the general formula (1), which are favorably used for the organic EL element according to the present invention. However, the present invention is not limited to these compounds.

(38) Compounds 2-1 to 2-133 are shown in FIG. 4 to FIG. 15 as specific examples of favorable compounds among the benzoxazole compounds represented by the general formula (2), which are favorably used for the organic EL element according to the present invention. However, the present invention is not limited to these compounds.

(39) Compounds 3-1 to 3-63 are shown in FIG. 16 to FIG. 21 as specific examples of favorable compounds among the benzothiazole compounds represented by the general formula (2), which are favorably used for the organic EL element according to the present invention. However, the present invention is not limited to these compounds.

(40) Compounds 4-1 to 4-201 are shown in FIG. 22 to FIG. 35 as specific examples of favorable compounds among the arylamine compounds represented by the general formula (4), which are favorably used for the organic EL element according to the present invention. However, the present invention is not limited to these compounds.

(41) Purification of compounds represented by the general formulae (1) to (4) 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, or the like, and finally purification by sublimation purification or the like was performed. Identification of the compounds was performed by NMR analysis. As physical property values, a glass transition point (Tg) and a work function were measured. 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.

(42) 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).

(43) 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.).

(44) 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.

(45) For 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 starburst type triphenylamine derivative, materials such as various triphenylamine tetramers; a porphyrin compound typified by copper phthalocyanine; an acceptor heterocyclic compound such as hexacyanoazatriphenylene, a coating type polymer material, or the like in addition to the arylamine compounds represented by the general formulae (1) and (1a) 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.

(46) For the hole transport layer of the organic EL device according to the present invention, the arylamine compounds represented by the general formulae (1) and (1a) are 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 of layers deposited alone, layers mixed and deposited, or at least one layer deposited alone and at least one layer mixed and deposited 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.

(47) Further, in the hole injection layer or the hole transport layer, those obtained by P-doping a material typically used for the layer with trisbromophenylamine hexachloroantimony, a radialene derivative (see, for example, Patent Literature 6), or the like, a polymer compound having, as a partial structure, the structure of a benzidine derivative such as TPD, or the like can be used.

(48) For the hole transport layer of the organic EL device according to the present invention, a benzidine derivative such as N,N′-diphenyl-N,N′-di(m-tolyl)benzidine (TPD), N,N′-diphenyl-N,N′-di(α-naphthyl)benzidine (NPD), and N,N,N′,N′-tetrabiphenylylbenzidine, an arylamine compound having two triphenylamine structures in the molecule, each of which is bonded via a single bond or a divalent group containing no hetero atom, such as 1,1-bis[4-(di-4-tolylamino)phenyl]cyclohexane (TAPC), an arylamine compound having four triphenylamine structures in the molecule, each of which is bonded via a single bond or a divalent group containing no hetero atom, various triphenylamine trimers, or the like, in addition to the arylamine compounds represented by the general formulae (1) and (1a), 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 of layers deposited alone, layers mixed and deposited, or at least one layer deposited alone and at least one layer mixed and deposited may be achieved. Further, for the hole injection/transport layer, a coating polymer material such as poly(3,4-ethylenedioxythiophene) (PEDOT)/poly(styrene sulfonate) (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.

(49) For the electron blocking layer of the organic EL device according to the present invention, an arylamine compound having four triphenylamine structures in the molecule, each of which is bonded via a single bond or a divalent group containing no hetero atom, an arylamine compound having two triphenylamine structures in the molecule, each of which is bonded via a single bond or a divalent group containing no hetero atom, a compound having an electron blocking property, such as a carbazol derivative 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-ylphenyl)adamantane (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 compound represented by the general formula (4), 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 of layers deposited alone, layers mixed and deposited, or at least one layer deposited alone and at least one layer mixed and deposited 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.

(50) 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 polyparaphenylene 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, a pyrene derivative and an amine derivative having a fluorene ring as a partial structure of the fused ring are favorably used. In addition, quinacridone, coumarin, rubrene, perylene, and derivatives thereof, a benzopyran derivative, an indenophenanthrene 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 of layers deposited alone, layers mixed and deposited, or at least one layer deposited alone and at least one layer mixed and deposited may be achieved.

(51) 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 FIr6, 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, a carbazol derivative such as 4,4′-di(N-carbazolyl) biphenyl (CBP), TCTA, and mCP can be used. As a host material having an electron transportability, p-bis(triphenylsilyl)benzene (UGH2), 2,2′,2″-(1,3,5-phenylene)-tris(1-phenyl-1H-benzimidazole) (TPBI), or the like can be used, and an organic EL device having high performance can be prepared.

(52) 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.

(53) 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).

(54) 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.

(55) For the hole blocking layer of the organic EL device according to the present invention, a compound having a hole blocking effect, such as various rare earth complexes, a triazole derivative, a triazine derivative, and an oxadiazole derivative, in addition to a phenanthroline derivative such as bathocuproin (BCP) and metal complex of a quinolinol derivative such as aluminum (III) bis (2-methyl-8-quinolinate)-4-phenylphenolate (BAlq), can be used. These materials 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 of layers deposited alone, layers mixed and deposited, or at least one layer deposited alone and at least one layer mixed and deposited 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.

(56) For the electron transport layer of the organic EL device according to the present invention, a compound having a benzoazole ring structure, which is represented by the general formula (2) or (3), is 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 of layers deposited alone, layers mixed and deposited, or at least one layer deposited alone and at least one layer mixed and deposited 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.

(57) For the electron transport layer of the organic EL device according to the present invention, a metal complex of a quinolinol derivative including Alq.sub.3 and BAlq, various metal complexes, a triazole derivative, a triazine derivative, an oxadiazole derivative, a pyridine derivative, a pyrimidine 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 the compounds having a benzoazole ring structure, which are represented by the general formulae (2) and (3), 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 of layers deposited alone, layers mixed and deposited, or at least one layer deposited alone and at least one layer mixed and deposited 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.

(58) 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 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.

(59) 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.

(60) Hereinafter, the embodiment of the present invention will be specifically described by way of Examples. However, the present invention is not limited to the following Examples.

EXAMPLE 1

Synthesis of 4-{(9,9-dimethylfluoren-2-yl)-(biphenyl-4-yl)amino}-4′-(biphenyl-4-yl-phenylamino)-2-phenyl-biphenyl (Compound 1-7)

(61) (9,9-dimethylfluoren-2-yl)-(biphenyl-4-yl)-(6-brombiphenyl-3-yl)amine: 10.0 g, 4-{(biphenyl-4-yl)-phenylamino} phenylboronic acid: 7.9 g, tetrakistriphenylphosphine palladium (0): 0.60 g, potassium carbonate: 5.0 g, toluene: 80 ml, ethanol: 40 ml, and water: 30 ml were added to a reaction vessel purged with nitrogen, and the mixture was heated and stirred at 100° C. overnight. After the mixture was cooled, an organic layer was extracted by liquid separation and then the extract was concentrated and purified by column chromatography (carrier: silica gel, eluent: dichloromethane/heptane). Thus, a white powder of 4-{(9,9-dimethylfluoren-2-yl)-(biphenyl-4-yl)amino}-4′-(biphenyl-4-yl-phenylamino)-2-phenyl-biphenyl (Compound 1-7): 8.30 g (yield of 49%) was obtained.

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

(63) The following 48 hydrogen signals were detected by .sup.1H-NMR (CDCl.sub.3).

(64) δ (ppm)=7.72-7.60 (2H), 7.59-7.52 (2H), 7.51-7.10 (35), 7.09-6.90 (3H), 1.56 (6H).

(65) ##STR00008##

EXAMPLE 2

Synthesis of 4-{(9,9-dimethylfluoren-2-yl)-(biphenyl-4-yl)amino}-4′-(diphenylamino)-2-phenyl-biphenyl (Compound 1-11)

(66) By using 4-(diphenylamino) phenylboronic acid instead of 4-{(biphenyl-4-yl)-phenylamino} phenylboronic acid in Example 1 and performing the reaction under similar conditions, a white powder of 4-{(9,9-dimethylfluoren-2-yl)-(biphenyl-4-yl)amino}-4′-(diphenylamino)-2-phenyl-biphenyl (Compound 1-11): 11.5 g (yield of 75%) was obtained.

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

(68) The following 44 hydrogen signals were detected by .sup.1H-NMR (CDCl.sub.3).

(69) δ(ppm)=7.71-7.64 (4H), 7.58-7.56 (2H), 7.49-6.94 (32), 1.51 (6H).

(70) ##STR00009##

EXAMPLE 3

Synthesis of 4-{(9,9-dimethylfluoren-2-yl)-phenylamino}-4′-(biphenyl-4-yl-phenylamino)-2-phenyl-biphenyl (Compound 1-14)

(71) By using (9,9-dimethylfluoren-2-yl)-phenyl-(6-brombiphenyl-3-yl) amine instead of (9,9-dimethylfluoren-2-yl)-(biphenyl-4-yl)-(6-brombiphenyl-3-yl) amine in Example 1 and performing the reaction under similar conditions, a white powder of 4-{(9,9-dimethylfluoren-2-yl)-phenylamino}-4′-(biphenyl-4-yl-phenylamino)-2-phenyl-biphenyl (Compound 1-14): 10.2 g (yield of 69%) was obtained.

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

(73) The following 44 hydrogen signals were detected by .sup.1H-NMR (CDCl.sub.3).

(74) δ (ppm)=7.69-7.59 (4H), 7.48-7.42 (4H), 7.37-6.98 (30), 1.49 (6H).

(75) ##STR00010##

EXAMPLE 4

(76) The melting point and the glass transition point of the arylamine compound represented by the general formula (1) were measured using a high sensitivity differential scanning calorimeter (DSC3100S manufactured by Bruker AXS GmbH).

(77) Melting Point Glass Transition Point

(78) Compound of Example 1 Not observed 125° C.

(79) Compound of Example 2 Not observed 117° C.

(80) Compound of Example 3 Not observed 114° C.

(81) The arylamine compound represented by the general formula (1) has the glass transition point of 100° C. or more, which indicates that it is stable in a thin film state.

EXAMPLE 5

(82) The arylamine compound 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.).

Work Function

(83) Compound of Example 1 5.57 eV

(84) Compound of Example 2 5.62 eV

(85) Compound of Example 3 5.59 eV

(86) It can be seen that the arylamine compound represented by the general formula (1) has favorable hole transport performance because it has a more favorable energy level than the work function that a general hole transport material such as NPD and TPD has, which is 5.4 eV.

EXAMPLE 6

4,6-bis(naphthalen-1-yl-phenyl)-2-{4-(pyridin-3-yl)-phenyl}-benzoxazole (Compound 2-1)

(87) 2-(4-chloro-phenyl)-4,6-bis (naphthalen-1-yl-phenyl)-benzoxazole: 4.5 g, 3-pyridylboronic acid: 1.0 g, bis(dibenzylideneacetone) palladium (0): 0.32 g, tricyclohexylphosphine: 0.4 g, and tripotassium phosphate were charged into a reaction vessel and

(88) ##STR00011##
stirred under reflux overnight. 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 dichloromethane/methanol. Thus, a white powder of 4,6-bis(naphthalen-1-yl-phenyl)-2-{4-(pyridin-3-yl)-phenyl}-benzoxazole (Compound 2-1): 1.8 g (yield of 38%) was obtained.

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

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

(91) δ(ppm)=8.98 (1H), 8.68 (1H), 8.52 (2H), 8.34 (2H), 8.12 (1H), 8.07-7.89 (10H), 7.82 (2H), 7.76 (2H), 7.69 (2H), 7.64 (9H).

EXAMPLE 7

Synthesis of 2-(biphenyl-4-yl)-6-(phenanthren-9-yl)-4-{4-(pyridin-3-yl)-phenyl}-benzoxazole (Compound 2-118)

(92) By using 2-(4-chloro-phenyl)-6-(phenanthren-9-yl)-4-{4-(pyridin-3-yl)-phenyl}-benzoxazole, 3-pyridylboronic acid, and bis(dibenzylideneacetone) palladium (0) instead of 2-(4-chlorophenyl)-4,6-bis(naphthalen-1-ylphenyl)-benzoxazole, phenylboronic acid, and tris (dibenzylideneacetone) palladium (0) in Example 6, respectively, and performing the reaction under similar conditions, a white powder of 2-(biphenyl-4-yl)-6-(phenanthren-9-yl)-4-{4-(pyridin-3-yl)-phenyl}-benzoxazole (Compound 1-118): 4.3 g (yield of 67%) was obtained.

(93) ##STR00012##

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

(95) The following 28 hydrogen signals were detected by .sup.1H-NMR (CDCl.sub.3).

(96) δ(ppm)=8.98 (1H), 8.86 (1H), 8.80 (1H), 8.64 (1H), 8.46 (2H), 8.32 (2H), 8.07 (1H), 7.98 (2H), 7.88-7.57 (13H), 7.52 (2H), 7.44 (2H).

EXAMPLE 8

(97) The melting point and the glass transition point of the benzoazole compound represented by the general formula (2) were measured using a high sensitivity differential scanning calorimeter (DSC3100SA manufactured by Bruker AXS GmbH).

(98) Melting Point Glass Transition Point

(99) Compound of Example 6 Not observed 128° C.

(100) Compound of Example 7 Not observed 132° C.

(101) The benzoazole compound represented by the general formula (2) has the glass transition point of 100° C. or more, which indicates that it is stable in a thin film state.

EXAMPLE 9

(102) The benzoazole compound represented by the general formula (2) 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.).

(103) Work Function

(104) Compound of Example 6 6.34 eV

(105) Compound of Example 7 6.43 eV

(106) The compound having a benzoazole ring structure represented by the general formula (2) has a value of work function larger than 5.4 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 10

(107) The organic EL device was prepared by depositing a hole injection layer 3, a hole transport layer 4, an electron blocking layer 5, a light-emitting 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. 36.

(108) Specifically, after performing, in isopropyl alcohol for 20 minutes, ultrasonic cleaning on the glass substrate 1 on which ITO having a film thickness of 50 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 0.001 Pa or less. Subsequently, a film of an electron acceptor (Acceptor-1) having the following structural formula and the Compound (1-7) according to Example 1 was 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 (1-7) was 3:97. As the hole transport layer 4, a film of the Compound (1-7) according to the Example 1 was formed on the hole injection layer 3 to have a film thickness of 50 nm. A film of the Compound (4-158) having the following structural formula was formed, as the electron blocking layer 5, on the hole transport layer 4 to have a film thickness of 5 nm. A film of a Compound (EMD-1) having the following structural formula and a Compound (EMH-1) having the following structural formula was formed, as the light-emitting layer 6, on the electron blocking layer 5 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 (2-1) according to Example 6 and a Compound (ETM-1) having the following structural formula was formed on the light-emitting layer 6, as the electron transport layer 7 to have a film thickness of 30 nm by binary deposition at a deposition rate in which the ratio of the deposition rates of Compound (2-1) and the Compound (ETM-1) 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.

(109) ##STR00013## ##STR00014## ##STR00015##

EXAMPLE 11

(110) An organic EL device was prepared in similar conditions to Example 10 except that the Compound (1-11) according to Example 2 was used for the material of the hole injection layer 3 and the hole transport layer 4 instead of the Compound (1-7) according to Example 1. 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.

(111) ##STR00016##

EXAMPLE 12

(112) An organic EL device was prepared in similar conditions to Example 10 except that the Compound (1-14) according to Example 3 was used for the material of the hole injection layer 3 and the hole transport layer 4 instead of the Compound (1-7) according to Example 1. 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.

(113) ##STR00017##

EXAMPLE 13

(114) An organic EL device was prepared in similar conditions to Example 10 except that the Compound (2-118) according to Example 7 was used for the material of the electron transport layer 7 instead of the Compound (2-1) according to Example 6. 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.

(115) ##STR00018##

EXAMPLE 14

(116) An organic EL device was prepared in similar conditions to Example 10 except that the Compound (1-11) according to Example 2 was used for the material of the hole injection layer 3 and the hole transport layer 4 instead of the Compound (1-7) according to Example 1 and the Compound (2-118) according to Example 7 was used for the material of the electron transport layer 7 instead of the Compound (2-1) according to Example 6. 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.

EXAMPLE 15

(117) An organic EL device was prepared in similar conditions to Example 10 except that the Compound (1-14) according to Example 3 was used for the material of the hole injection layer 3 and the hole transport layer 4 instead of the Compound (1-7) according to Example 1 and the Compound (2-118) according to Example 7 was used for the material of the electron transport layer 7 instead of the Compound (2-1) according to Example 6. 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.

COMPARATIVE EXAMPLE 1

(118) For comparison, an organic EL device was prepared in similar conditions to Example 10 except that the Compound (HTM-1) having the following structure was used for the material of the hole injection layer 3 and the hole transport layer 4 instead of the Compound (1-7) according to Example 1. 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.

(119) ##STR00019##

COMPARATIVE EXAMPLE 2

(120) For comparison, an organic EL device was prepared in similar conditions to Example 10 except that the Compound (HTM-1) having the following structure was used for the material of the hole injection layer 3 and the hole transport layer 4 instead of the Compound (1-7) according to Example 1 and the Compound (2-118) according to Example 7 was used for the material of the electron transport layer 7 instead of the Compound (2-1) according to Example 6. 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.

COMPARATIVE EXAMPLE 3

(121) For comparison, an organic EL device was prepared in similar conditions to Example 10 except that the Compound (HTM-2) having the following structural formula was used for the material of the hole injection layer 3 and the hole transport layer 4 instead of the Compound (1-7) according to Example 1. 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.

(122) ##STR00020##

COMPARATIVE EXAMPLE 4

(123) For comparison, an organic EL device was prepared in similar conditions to Example 10 except that the Compound (HTM-2) having the following structural formula was used for the material of the hole injection layer 3 and the hole transport layer 4 instead of the Compound (1-7) according to Example 1 and the Compound (2-118) according to Example 7 was used for the material of the electron transport layer 7 instead of the Compound (2-1) according to Example 6. 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.

COMPARATIVE EXAMPLE 5

(124) For comparison, an organic EL device was prepared in similar conditions to Example 10 except that the Compound (HTM-2) having the following structural formula was used for the material of the electron transport layer 7 instead of the Compound (2-1) according to Example 6. 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.

(125) ##STR00021##

COMPARATIVE EXAMPLE 6

(126) For comparison, an organic EL device was prepared in similar conditions to Example 10 except that the Compound (1-11) according to Example 2 was used for the material of the hole transport layer 4 instead of the Compound (1-7) according to Example 1 and the Compound (HTM-2) having the following structural formula was used for the material of the electron transport layer 7 instead of the Compound (2-1) according to Example 6. 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.

COMPARATIVE EXAMPLE 7

(127) For comparison, an organic EL device was prepared in similar conditions to Example 10 except that the Compound (1-14) according to Example 3 was used for the material of the hole transport layer 4 instead of the Compound (1-7) according to Example 1 and the Compound (HTM-2) having the following structural formula was used for the material of the electron transport layer 7 instead of the Compound (2-1) according to Example 6. 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.

(128) The device lifetime was measured using each of the organic EL devices prepared in Examples 10 to 15 and Comparative Examples 1 to 7, 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.

(129) TABLE-US-00001 TABLE 1 Light emission Element Hole Electron Light- Electron Lumi- effi- Power effi- lifetime transport blocking emitting transport Voltage[V] nance[cd/m2] ciency[cd/A] ciency[lm/W] 95% layer layer layer layer (@10 mA/cm2) (@10 mA/cm2) (@10 mA/cm2) (@10 mA/cm2) attenuated Example Compound Compound EMD-1/ Compound 2-1/ 3.89 953 9.53 8.34 211 hours 10 1-7 4-158 EMH-1 ETM-1 Example Compound Compound EMD-1/ Compound 2-1/ 3.57 1034 10.34 9.08 230 hours 11 1-11 4-158 EMH-1 ETM-1 Example Compound Compound EMD-1/ Compound 2-1/ 3.56 988 9.86 8.71 213 hours 12 1-14 4-158 EMH-1 ETM-1 Example Compound Compound EMD-1/ Compound 2-118/ 3.57 941 9.41 8.27 262 hours 13 1-7 4-158 EMH-1 ETM-1 Example Compound Compound EMD-1/ Compound 2-118/ 3.54 1042 10.42 9.25 301 hours 14 1-11 4-158 EMH-1 ETM-1 Example Compound Compound EMD-1/ Compound 2-118/ 3.55 998 9.98 8.85 286 hours 15 1-14 4-158 EMH-1 ETM-1 Comparative HTM-1 Compound EMD-1/ Compound 2-1/ 3.69 893 8.93 7.61 141 hours Example 1 4-158 EMH-1 ETM-1 Comparative HTM-1 Compound EMD-1/ Compound 2-118/ 3.64 894 8.94 7.72 176 hours Example 2 4-158 EMH-1 ETM-1 Comparative HTM-2 Compound EMD-1/ Compound 2-1/ 3.71 875 8.75 7.42 122 hours Example 3 4-158 EMH-1 ETM-1 Comparative HTM-2 Compound EMD-1/ Compound 2-118/ 3.64 857 8.57 7.40 157 hours Example 4 4-158 EMH-1 ETM-1 Comparative Compound Compound EMD-1/ ETM-2/ 4.01 859 6.59 5.18 137 hours Example 5 1-7 4-158 EMH-1 ETM-1 Comparative Compound Compound EMD-1/ ETM-2/ 4.10 770 7.70 5.90 165 hours Example 6 1-11 4-158 EMH-1 ETM-1 Comparative Compound Compound EMD-1/ ETM-2/ 4.00 736 7.36 5.79 152 hours Example 7 1-14 4-158 EMH-1 ETM-1

(130) As shown in Table 1, the light emission efficiency when a current having a current density of 10 mA/cm.sup.2 was caused to flow was high in any of the organic EL devices according to Examples 10 to 15, i.e., 9.41 to 10.42 cd/A, as compared with those of the organic EL devices according to Comparative Examples 1 to 7, i.e., 6.59 to 8.94 cd/A. Further, also the power efficiency was high in any of the organic EL devices according to Examples 10 to 15, i.e., 8.27 to 9.25 lm/W, as compared with those of the organic EL devices according to Comparative Examples 1 to 7, i.e., 5.16 to 7.72 lm/W. Meanwhile, it can be seen that the device lifetime (95% attenuation) was largely extended to 211 to 301 hours in the organic EL devices according to Examples 10 to 15 as compared with 122 to 176 hours of the organic EL devices according to Comparative Examples 1 to 7.

(131) It has been found that the organic EL device according to the present invention is capable of realizing an organic EL device that has higher light emission efficiency and a longer lifetime than the existing organic EL device because the carrier balance inside the organic EL device is improved by combining a specific arylamine compound and a specific compound having a benzoazole ring structure and the combination is made so that the carrier balance matches the characteristics of the light-emitting material.

INDUSTRIAL APPLICABILITY

(132) The organic EL device according to the present invention, which is obtained by combining a specific arylamine compound and a specific compound having a benzoazole ring structure is capable of improving the light emission efficiency and the durability of the organic EL device. For example, it has become possible to expand to home appliances and lighting applications.

REFERENCE SIGNS LIST

(133) 1 glass substrate 2 transparent anode 3 hole injection layer 4 hole transport layer 5 electron blocking layer 6 light-emitting layer 7 electron transport layer 8 electron injection layer 9 cathode