Organic electroluminescent device

Abstract

A material for an organic electroluminescent device that is excellent in hole injection and transport abilities, electron blocking ability, stability in a thin film state, and durability is provided as a material for an organic electroluminescent device having high efficiency and high durability. Further, an organic electroluminescent device having low driving voltage, high efficiency, and a long lifetime is provided by combining the material with various materials for an organic EL device that is excellent in hole and electron injection and transport abilities, electron blocking ability, thin film stability, and durability, in such a manner that the characteristics of the materials can be effectively exhibited. An organic electroluminescent device comprising 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 comprises an arylamine compound of the following general formula (1). ##STR00001##

Claims

1. An organic electroluminescent device comprising 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 comprises an arylamine compound of the formula ##STR00115## ##STR00116## ##STR00117## ##STR00118## ##STR00119## ##STR00120## ##STR00121## ##STR00122## ##STR00123## ##STR00124## ##STR00125## ##STR00126## and wherein the hole transport layer has a two-layer structure of a first hole transport layer on the anode side and a second hole transport layer, and the second hole transport layer includes the arylamine compound of the formula (1-1) through (1-43).

2. The organic electroluminescent device according to claim 1, wherein the electron transport layer includes a compound of the following general formula (2) having a pyrimidine ring structure: ##STR00127## wherein, Ar.sub.9 represents a substituted or unsubstituted aromatic hydrocarbon group or a substituted or unsubstituted condensed polycyclic aromatic group, and Ar.sub.10 to Ar.sub.11 may be the same or different, and represent a hydrogen atom, a substituted or unsubstituted aromatic hydrocarbon group or a substituted or unsubstituted condensed polycyclic aromatic group, and Ar.sub.12 represents a substituted or unsubstituted aromatic heterocyclic group, and R.sub.1 to R.sub.4 may be the same or different, and represent a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, cyano, trifluoromethyl, linear or branched alkyl of 1 to 6 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group, and Ar.sub.10 and Ar.sub.11 are not simultaneously a hydrogen atom.

3. The organic electroluminescent device according to claim 1, wherein the first hole transport layer includes a triphenylamine derivative different from the arylamine compound included in the second hole transport layer, and the triphenylamine derivative is a compound having a molecular structure containing two triphenylamine skeletons bonded to each other via a single bond or a divalent hydrocarbon group, and having 2 to 6 triphenylamine skeletons as a whole molecule.

4. The organic electroluminescent device according to claim 3, wherein the triphenylamine derivative contained in the first hole transport layer is a derivative of the following general formula (3): ##STR00128## wherein, R.sub.5 to R.sub.10 represent a deuterium atom, a fluorine atom, a chlorine atom, cyano, nitro, linear or branched alkyl of 1 to 6 carbon atoms that may have a substituent, cycloalkyl of 5 to 10 carbon atoms that may have a substituent, linear or branched alkenyl of 2 to 6 carbon atoms that may have a substituent, linear or branched alkyloxy of 1 to 6 carbon atoms that may have a substituent, cycloalkyloxy of 5 to 10 carbon atoms that may have a substituent, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted condensed polycyclic aromatic group, or substituted or unsubstituted aryloxy, and r.sub.5 to r.sub.10 may be the same or different, r.sub.5, r.sub.6, r.sub.9 and r.sub.10 representing 0 to 5, and r.sub.7 and r.sub.8 representing 0 to 4, and when r.sub.5, r.sub.6, r.sub.9 and r.sub.10 are 2 to 5, or when r.sub.7 and r.sub.8 are 2 to 4, R.sub.5 to R.sub.10, a plurality of which bind to the same benzene ring, may be the same or different and may bind to each other via a single bond, substituted or unsubstituted methylene, an oxygen atom, or a sulfur atom to form a ring, and L.sub.1 represents a divalent group of the following structural formulas (C) to (G), or a single bond ##STR00129##

5. The organic electroluminescent device according to claim 3, wherein the triphenylamine derivative contained in the first hole transport layer is a derivative of the following general formula (4): ##STR00130## wherein, R.sub.11 to R.sub.22 represent a deuterium atom, a fluorine atom, a chlorine atom, cyano, nitro, linear or branched alkyl of 1 to 6 carbon atoms that may have a substituent, cycloalkyl of 5 to 10 carbon atoms that may have a substituent, linear or branched alkenyl of 2 to 6 carbon atoms that may have a substituent, linear or branched alkyloxy of 1 to 6 carbon atoms that may have a substituent, cycloalkyloxy of 5 to 10 carbon atoms that may have a substituent, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted condensed polycyclic aromatic group, or substituted or unsubstituted aryloxy, and r.sub.11 to r.sub.22 may be the same or different, r.sub.11, r.sub.12, r.sub.15, r.sub.18, r.sub.21 and r.sub.22 representing 0 to 5, and r.sub.13, r.sub.14, r.sub.16, r.sub.17, r.sub.19 and r.sub.20 representing 0 to 4, and when r.sub.11, r.sub.12, r.sub.15, r.sub.18, r.sub.21 and r.sub.22 are 2 to 5, or when r.sub.13, r.sub.14, r.sub.16, r.sub.17, r.sub.19 and r.sub.20 are 2 to 4, R.sub.11 to R.sub.22, a plurality of which bind to the same benzene ring, may be the same or different and may bind to each other via a single bond, substituted or unsubstituted methylene, an oxygen atom, or a sulfur atom to form a ring, and L.sub.2, L.sub.3 and L.sub.4 may be the same or different, and represent a divalent group of the following structural formulas (B) to (G), or a single bond ##STR00131## (In the formula, n2 represents 1 to 3) ##STR00132##

6. The organic electroluminescent device according to claim 1, wherein the light emitting layer includes a blue light emitting dopant.

7. The organic electroluminescent device according to claim 6, wherein the light emitting layer includes a blue light emitting dopant, which is a pyrene derivative.

8. The organic electroluminescent device according to claim 1, wherein the light emitting layer includes an anthracene derivative.

9. The organic electroluminescent device according to claim 8, wherein the light emitting layer includes a host material which is the anthracene derivative.

10. The organic electroluminescent device according to claim 2, wherein the light emitting layer includes a blue light emitting dopant.

11. The organic electroluminescent device according to claim 2, wherein the light emitting layer includes an anthracene derivative.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a diagram illustrating the configuration of the organic EL devices of Examples 12 to 17 and Comparative Examples 1 to 2.

DESCRIPTION OF EMBODIMENTS

(2) The following presents specific examples of preferred compounds among the arylamine compounds of the general formula (1) preferably used in the organic EL device of the present invention. The present invention, however, is not restricted to these compounds.

(3) ##STR00018## ##STR00019## ##STR00020## ##STR00021## ##STR00022## ##STR00023## ##STR00024## ##STR00025## ##STR00026## ##STR00027## ##STR00028## ##STR00029##

(4) The following presents specific examples of preferred compounds among the compounds of the general formula (2) preferably used in the organic EL device of the present invention and having a pyrimidine ring structure. The present invention, however, is not restricted to these compounds.

(5) ##STR00030## ##STR00031## ##STR00032## ##STR00033## ##STR00034## ##STR00035## ##STR00036## ##STR00037## ##STR00038## ##STR00039## ##STR00040## ##STR00041## ##STR00042## ##STR00043## ##STR00044## ##STR00045## ##STR00046## ##STR00047## ##STR00048## ##STR00049## ##STR00050## ##STR00051## ##STR00052## ##STR00053## ##STR00054## ##STR00055## ##STR00056## ##STR00057## ##STR00058## ##STR00059## ##STR00060## ##STR00061## ##STR00062## ##STR00063## ##STR00064## ##STR00065## ##STR00066## ##STR00067## ##STR00068## ##STR00069## ##STR00070## ##STR00071## ##STR00072## ##STR00073## ##STR00074## ##STR00075## ##STR00076## ##STR00077## ##STR00078## ##STR00079##

(6) The compounds having a pyrimidine ring structure described above can be synthesized by a known method (refer to PTLs 6 to 7, for example).

(7) In the organic EL device of the present invention, the following presents specific examples of preferred compounds among the triphenylamine derivatives of the general formula (3) having two triphenylamine skeletons as a whole molecule and preferably used in the first hole transport layer in the case where the hole transport layer has a two-layer structure of the first hole transport layer and the second hole transport layer. The present invention, however, is not restricted to these compounds.

(8) ##STR00080## ##STR00081## ##STR00082## ##STR00083## ##STR00084## ##STR00085## ##STR00086## ##STR00087##

(9) In the organic EL device of the present invention, the following presents specific examples of preferred compounds among the triphenylamine derivatives of the general formula (4) having four triphenylamine skeletons as a whole molecule and preferably used in the first hole transport layer in the case where the hole transport layer has a two-layer structure of the first hole transport layer and the second hole transport layer. The present invention, however, is not restricted to these compounds.

(10) ##STR00088## ##STR00089## ##STR00090## ##STR00091## ##STR00092## ##STR00093## ##STR00094## ##STR00095## ##STR00096##

(11) The triphenylamine derivatives of the general formula (3) having two triphenylamine skeletons as a whole molecule, and the triphenylamine derivatives of the general formula (4) having four triphenylamine skeletons as a whole molecule can be synthesized by a known method (refer to PTLs 1 and 8 to 9, for example).

(12) The arylamine compounds of the general formula (1) and the general formula (1a) were purified by methods such as column chromatography, adsorption using, for example, a silica gel, activated carbon, or activated clay, recrystallization or crystallization using a solvent, and a sublimation purification method. The compounds were identified by an NMR analysis. A melting point, a glass transition point (Tg), and a work function were measured as material property values. The melting point can be used as an index of vapor deposition, the glass transition point (Tg) as an index of stability in a thin-film state, and the work function as an index of hole transportability and hole blocking performance.

(13) Other compounds used for the organic EL device of the present invention were purified by methods such as column chromatography, adsorption using, for example, a silica gel, activated carbon, or activated clay, recrystallization or crystallization using a solvent, and a sublimation purification method, and finally purified by a sublimation purification method.

(14) The melting point and the glass transition point (Tg) were measured by a high-sensitive differential scanning calorimeter (DSC3100SA produced by Bruker AXS) using powder.

(15) For the measurement of the work function, a 100 nm-thick thin film was fabricated on an ITO substrate, and an ionization potential measuring device (PYS-202 produced by Sumitomo Heavy Industries, Ltd.) was used.

(16) The organic EL device of the present invention may have a structure including an anode, a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and a cathode successively formed on a substrate, optionally with an electron blocking layer between the hole transport layer and the light emitting layer, a hole blocking layer between the light emitting layer and the electron transport layer, and an electron injection layer between the electron transport layer and the cathode. Some of the organic layers in the multilayer structure may be omitted, or may serve more than one function. For example, a single organic layer may serve as the hole injection layer and the hole transport layer, or as the electron injection layer and the electron transport layer, and so on. Further, any of the layers may be configured to laminate two or more organic layers having the same function, and the hole transport layer may have a two-layer laminated structure, the light emitting layer may have a two-layer laminated structure, the electron transport layer may have a two-layer laminated structure, and so on. The organic EL device of the present invention is preferably configured such that the hole transport layer has a two-layer laminated structure of a first hole transport layer and a second hole transport layer.

(17) Electrode materials with high work functions such as ITO and gold are used as the anode of the organic EL device of the present invention. The hole injection layer of the organic EL device of the present invention may be made of, for example, material such as starburst-type triphenylamine derivatives and various triphenylamine tetramers; porphyrin compounds as represented by copper phthalocyanine; accepting heterocyclic compounds such as hexacyano azatriphenylene; and coating-type polymer materials, in addition to the arylamine compounds of the general formula (1). These materials may be formed into a thin film by a vapor deposition method or other known methods such as a spin coating method and an inkjet method.

(18) The arylamine compounds of the general formula (1) are used as the hole transport layer of the organic EL device of the present invention. These may be individually deposited for film forming, may be used as a single layer deposited mixed with other hole transporting materials, or may be formed as a laminate of individually deposited layers, a laminate of mixedly deposited layers, or a laminate of the individually deposited layer and the mixedly deposited layer. These materials may be formed into a thin-film by a vapor deposition method or other known methods such as a spin coating method and an inkjet method.

(19) Examples of a hole transporting material that can be mixed or can be used at the same time with the arylamine compounds of the general formula (1) can be benzidine derivatives 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; 1,1-bis[4-(di-4-tolylamino)phenyl]cyclohexane (TAPC); triphenylamine derivatives of the general formula (3) having two triphenylamine skeletons as a whole molecule; triphenylamine derivatives of the general formula (4) having four triphenylamine skeletons as a whole molecule; and various triphenylamine derivatives having three triphenylamine skeletons as a whole molecule.

(20) The material used for the hole injection layer or the hole transport layer may be obtained by p-doping materials such as trisbromophenylamine hexachloroantimony, and radialene derivatives (refer to WO2014/009310, for example) into a material commonly used for these layers, or may be, for example, polymer compounds each having, as a part of the compound structure, a structure of a benzidine derivative such as TPD.

(21) In the case where the hole transport layer of the organic EL device of the present invention has a two-layer structure, examples of material used for the first hole transport layer on the anode side can be preferably triphenylamine derivatives of the general formula (3) having two triphenylamine skeletons as a whole molecule and triphenylamine derivatives of the general formula (4) having four triphenylamine skeletons as a whole molecule. Other examples of material used for the first hole transport layer on the anode side can be the above hole transporting materials.

(22) Further, examples of material used for the second hole transport layer can be preferably the arylamine compounds of the general formula (1). Other examples of material used for the second hole transport layer can be the above hole transporting materials.

(23) Examples of material used for the electron blocking layer of the organic EL device of the present invention can be compounds having an electron blocking effect, including, for example, carbazole derivatives such as 4,4′,4″-tri(N-carbazolyl)triphenylamine (TCTA), 9,9-bis[4-(carbazol-9-yl)phenyl]fluorene, 1,3-bis(carbazol-9-yl)benzene (mCP), and 2,2-bis(4-carbazol-9-ylphenyl)adamantane (Ad-Cz); and compounds having a triphenylsilyl group and a triarylamine structure, as represented by 9-[4-(carbazol-9-yl)phenyl]-9-[4-(triphenylsilyl)phenyl]-9H-fluorene, in addition to the arylamine compounds of the general formula (1). These may be individually deposited for film forming, may be used as a single layer deposited mixed with other materials, or may be formed as a laminate of individually deposited layers, a laminate of mixedly deposited layers, or a laminate of the individually deposited layer and the mixedly deposited layer. These materials may be formed into a thin-film by using a vapor deposition method or other known methods such as a spin coating method and an inkjet method.

(24) Examples of material used for the light emitting layer of the organic EL device of the present invention can be various metal complexes, anthracene derivatives, bis(styryl)benzene derivatives, pyrene derivatives, oxazole derivatives, and polyparaphenylene vinylene derivatives, in addition to quinolinol derivative metal complexes such as Alq3. Further, the light emitting layer may be made of a host material and a dopant material. Examples of the host material can be preferably anthracene derivatives. Other examples of the host material can be heterocyclic compounds having indole ring as a part of a condensed ring, heterocyclic compounds having carbazole ring as a part of a condensed ring, carbazole derivatives, thiazole derivatives, benzimidazole derivatives, and polydialkyl fluorene derivatives, in addition to the above light-emitting materials. Examples of the dopant material can be preferably pyrene derivatives. Other examples of the dopant material can be amine derivatives having fluorene ring as a part of a condensed ring, quinacridone, coumarin, rubrene, perylene, pyrene, derivatives thereof, benzopyran derivatives, indenophenanthrene derivatives, rhodamine derivatives, and aminostyryl derivatives. These may be individually deposited for film forming, may be used as a single layer deposited mixed with other materials, or may be formed as a laminate of individually deposited layers, a laminate of mixedly deposited layers, or a laminate of the individually deposited layer and the mixedly deposited layer.

(25) Further, the light-emitting material may be a phosphorescent material. Phosphorescent materials as metal complexes of metals such as iridium and platinum may be used. Examples of the phosphorescent materials include green phosphorescent materials such as Ir(ppy).sub.3, blue phosphorescent materials such as Flrpic and FIr6, and red phosphorescent materials such as Btp.sub.2Ir(acac). Here, carbazole derivatives such as 4,4′-di(N-carbazolyl)biphenyl (CBP), TCTA, and mCP may be used as the hole injecting and transporting host material. Compounds such as p-bis(triphenylsilyl)benzene (UGH2) and 2,2′,2″-(1,3,5-phenylene)-tris(1-phenyl-1H-benzimidazole) (TPBI) may be used as the electron transporting host material. In this way, a high-performance organic EL device can be produced.

(26) In order to avoid concentration quenching, the doping of the host material with the phosphorescent light-emitting material should preferably be made by co-evaporation in a range of 1 to 30 weight percent with respect to the whole light emitting layer.

(27) Further, Examples of the light-emitting material may be delayed fluorescent-emitting material such as a CDCB derivative of PIC-TRZ, CC2TA, PXZ-TRZ, 4CzIPN or the like (refer to NPL 3, for example).

(28) These materials may be formed into a thin-film by using a vapor deposition method or other known methods such as a spin coating method and an inkjet method.

(29) The hole blocking layer of the organic EL device of the present invention may be formed by using hole blocking compounds such as various rare earth complexes, triazole derivatives, triazine derivatives, and oxadiazole derivatives, in addition to the metal complexes of phenanthroline derivatives such as bathocuproin (BCP), and the metal complexes of quinolinol derivatives such as aluminum(III) bis(2-methyl-8-quinolinate)-4-phenylphenolate (hereinafter referred to as BAlq). These materials may also serve as the material of the electron transport layer. These may be individually deposited for film forming, may be used as a single layer deposited mixed with other materials, or may be formed as a laminate of individually deposited layers, a laminate of mixedly deposited layers, or a laminate of the individually deposited layer and the mixedly deposited layer. These materials may be formed into a thin-film by using a vapor deposition method or other known methods such as a spin coating method and an inkjet method.

(30) A material preferably used for the electron transport layer of the organic EL device of the present invention can be the compounds of the general formula (2) having a pyrimidine ring structure. These may be individually deposited for film forming, may be used as a single layer deposited mixed with other electron transporting materials, or may be formed as a laminate of individually deposited layers, a laminate of mixedly deposited layers, or a laminate of the individually deposited layer and the mixedly deposited layer. These materials may be formed into a thin film by a vapor deposition method or other known methods such as a spin coating method and an inkjet method.

(31) Examples of the electron transporting material that can be mixed or can be used at the same time with the compound represented by the general formula (2) having a pyrimidine ring structure can be metal complexes of quinolinol derivatives such as Alq.sub.3 and BAlq, various metal complexes, triazole derivatives, triazine derivatives, oxadiazole derivatives, pyridine derivatives, pyrimidine derivatives, benzimidazole derivatives, thiadiazole derivatives, anthracene derivatives, carbodiimide derivatives, quinoxaline derivatives, pyridoindole derivatives, phenanthroline derivatives, and silole derivatives.

(32) Examples of material used for the electron injection layer of the organic EL device of the present invention can be alkali metal salts such as lithium fluoride and cesium fluoride; alkaline earth metal salts such as magnesium fluoride; and metal oxides such as aluminum oxide. However, the electron injection layer may be omitted in the preferred selection of the electron transport layer and the cathode.

(33) The cathode of the organic EL device of the present invention may be made of an electrode material with a low work function such as aluminum, or an alloy of an electrode material with an even lower work function such as a magnesium-silver alloy, a magnesium-indium alloy, or an aluminum-magnesium alloy.

(34) The following describes an embodiment of the present invention in more detail based on Examples. The present invention, however, is not restricted to the following Examples.

Example 1

Synthesis of 4,4″-bis{(biphenyl-4-yl)-phenylamino}-3-phenyl-1,1′:3′,1″-terphenyl (Compound 1-12)

(35) 4-{(biphenyl-4-yl)-phenylamino}-4″-{(biphenyl-4-yl)-amino}-3-phenyl-1,1′:3′,1″-terphenyl (17.0 g), bromobenzene (4.12 g), palladium acetate (0.13 g), a toluene solution (0.33 mL) containing 50% (w/v) tri-tert-butylphosphine, sodium tert-butoxide (2.73 g), and toluene (190 mL) were added into a nitrogen-substituted reaction vessel. The mixture was heated and stirred at 80° C. for 3 hours. After cooling, the insoluble matter was removed by filtration, and the filtrate was concentrated. The crude product was purified by column chromatography (support: silica gel, eluent:toluene/n-hexane), a solid precipitated by adding acetone was collected, whereby a white powder of 4,4″-bis{(biphenyl-4-yl)-phenylamino}-3-phenyl-1,1′:3′,1″-terphenyl (Compound 1-12; 13.29 g; yield: 71%) was obtained.

(36) The structure of the obtained white powder was identified by NMR.

(37) .sup.1H-NMR (CDCl.sub.3) detected 44 hydrogen signals, as follows.

(38) δ (ppm)=7.62-7.58 (4H), 7.55-7.49 (4H), 7.48-7.38 (6H), 7.37-7.05 (30H).

(39) ##STR00097##

Example 2

Synthesis of 4,4″-bis{(biphenyl-4-yl)-phenylamino}-3,3″-diphenyl-1,1′:4′,1″-terphenyl (Compound 1-9)

(40) 4,4″-bis{(biphenyl-4-yl)-amino}-3,3″-diphenyl-1,1′:4′,1″-terphenyl (16.3 g), iodobenzene (18.6 g), copper powder (0.29 g), potassium carbonate (9.61 g), 3,5-di-tert-butylsalicylicacid (1.85 g), sodium hydrogensulfite (0.47 g), dodecylbenzene (20 mL) were added into a nitrogen-substituted reaction vessel. The mixture was heated and stirred at 190 to 200° C. for 17 hours. The mixture was cooled, toluene (1500 mL), a silica gel (40 g), and activated clay (20 g) was added thereto, and stirred. After the insoluble matter was removed by filtration, the filtrate was concentrated. The crude product was purified by recrystallization with chlorobenzene, the recrystallization procedure was repeated to obtain a white powder of 4,4″-bis{(biphenyl-4-yl)-phenylamino}-3,3″-diphenyl-1,1′:4′,1″-terphenyl (Compound 1-9; 9.65 g; yield 49%).

(41) The structure of the obtained white powder was identified by NMR.

(42) .sup.1H-NMR (CDCl.sub.3) detected 48 hydrogen signals, as follows.

(43) δ (ppm)=7.62 (4H), 7.52 (4H), 7.45 (4H), 7.36-7.04 (32H), 6.99 (4H).

(44) ##STR00098##

Example 3

Synthesis of 4-bis(biphenyl-4-yl)amino-4′-{(biphenyl-4-yl)-phenylamino}-2,6-diphenyl-biphenyl (Compound 1-23)

(45) 4-bis(biphenyl-4-yl)amino-2,6-diphenyl-bromobenzene (16.0 g), 4-{N-(biphenyl-4-yl)-N-phenylamino} phenylboronicacid (10.2 g), tetrakistriphenylphosphine palladium (0.60 g), potassium carbonate (4.62 g), water (60 mL), toluene (320 mL), and ethanol (60 mL) were added into a nitrogen-substituted reaction vessel. The mixture was heated, and stirred for 18 hours under reflux. After cooling, water (200 mL) was added thereto, and then an organic layer was collected by liquid separation. The organic layer was dried over anhydrous magnesium sulfate and purified by adsorption with a silica gel (40 g). The organic layer was then concentrated and dispersed and washed using methanol to obtain a crude product.

(46) The crude product was purified by recrystallization with a toluene/ethanol mixed solvent, and then with ethyl acetate. The recrystallization procedure was repeated to obtain a white powder of 4-bis(biphenyl-4-yl)amino-4′-{(biphenyl-4-yl)-phenylamino}-2,6-diphenyl-biphenyl (Compound 1-23; 12.7 g; yield 57%).

(47) The structure of the obtained white powder was identified by NMR.

(48) .sup.1H-NMR (CDCl.sub.3) detected 48 hydrogen signals, as follows.

(49) δ (ppm)=7.65-7.53 (8H), 7.48-6.97 (36H), 6.79-6.73 (4H).

(50) ##STR00099##

Example 4

Synthesis of 4,4″-bis{(biphenyl-4-yl)-phenylamino}-2-phenyl-1,1′:4′,1″-terphenyl (Compound 1-1)

(51) (6-bromo-1,1′-biphenyl-3-yl)-(1,1′-biphenyl-4-yl)phenylamine (18.0 g), 4-{N-(biphenyl-4-yl)-N-phenylamino} phenylboronicacid (10.2 g), (1,1′-biphenyl-4-yl)phenylamino(1,1′-biphenyl-4′-yl)boronic acid pinacolato ester (21.8 g), tetrakistriphenylphosphine palladium (0.87 g), potassium carbonate (6.3 g), water (46 mL), toluene (144 mL), and ethanol (36 mL) were added into a nitrogen-substituted reaction vessel. The mixture was heated, and stirred for 18 hours under reflux. After cooling, water (100 mL) was added thereto, and then an organic layer was collected by liquid separation. The organic layer was dried over anhydrous magnesium sulfate, and then concentrated. The residue was purified by column chromatography to obtain a white powder of 4,4″-bis{(biphenyl-4-yl)-phenylamino}-2-phenyl-1,1′:4′,1″-terphenyl (Compound 1-1; 12.9 g; yield 43%).

(52) The structure of the obtained white powder was identified by NMR.

(53) .sup.1H-NMR (CDCl.sub.3) detected 44 hydrogen signals, as follows.

(54) δ (ppm)=7.65-7.61 (4H), 7.57-7.07 (40H).

(55) ##STR00100##

Example 5

Synthesis of 4-bis(biphenyl-4-yl)amino-4′-{(biphenyl-4-yl)-phenylamino}-2-phenyl-1,1′-biphenyl (Compound 1-24)

(56) (6-bromo-1,1′-biphenyl-3-yl)-bis(biphenyl-4-yl)amine (10.0 g), 4-{N-(biphenyl-4-yl)-N-phenylamino} phenylboronicacid (7.9 g), tetrakistriphenylphosphine palladium (0.60 g), potassium carbonate (5.0 g), water (30 mL), toluene (80 mL), and ethanol (40 mL) were added into a nitrogen-substituted reaction vessel. The mixture was heated, and stirred for 16 hours under reflux. After cooling, water (100 mL) was added thereto, and then an organic layer was collected by liquid separation. The organic layer was dried over anhydrous magnesium sulfate, and then concentrated. The residue was purified by column chromatography to obtain a white powder of 4-bis(biphenyl-4-yl)amino-4′-{(biphenyl-4-yl)-phenylamino}-2-phenyl-1,1′-biphenyl (Compound 1-24; 5.3 g; yield 37%).

(57) The structure of the obtained white powder was identified by NMR.

(58) .sup.1H-NMR (CDCl.sub.3) detected 44 hydrogen signals, as follows.

(59) δ (ppm)=7.65-7.56 (8H), 7.52-7.14 (28H), 7.08-6.99 (8H).

(60) ##STR00101##

Example 6

Synthesis of 4-{(naphthalene-1-yl)phenyl-4-yl}(biphenyl-4-yl)amino-4′-{(biphenyl-4-yl)-phenylamino}-2-phenyl-1,1′-biphenyl (Compound 1-26)

(61) (6-bromo-1,1′-biphenyl-3-yl)-{(naphthalene-1-yl)phenyl-4-yl}(biphenyl-4-yl)amine (10.0 g), 4-{N-(biphenyl-4-yl)-N-phenylamino} phenylboronicacid (7.3 g), tetrakistriphenylphosphine palladium (0.60 g), potassium carbonate (4.6 g), water (30 mL), toluene (80 mL), and ethanol (40 mL) were added into a nitrogen-substituted reaction vessel. The mixture was heated, and stirred for 16 hours under reflux. After cooling, water (100 mL) was added thereto, and then an organic layer was collected by liquid separation. The organic layer was dried over anhydrous magnesium sulfate, and then concentrated. The residue was purified by column chromatography to obtain a white powder of 4-{(naphthalene-1-yl)phenyl-4-yl}(biphenyl-4-yl)amino-4′-{(biphenyl-4-yl)-phenylamino}-2-phenyl-1,1′-biphenyl (Compound 1-26; 9.7 g; yield 69%).

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

(63) .sup.1H-NMR (CDCl.sub.3) detected 46 hydrogen signals, as follows.

(64) δ (ppm)=8.08-8.07 (1H), 7.95-7.87 (2H), 7.66-6.99 (43H).

(65) ##STR00102##

Example 7

Synthesis of 4-{(naphthalene-2-yl)phenyl-4-yl}(biphenyl-4-yl)amino-4′-{(biphenyl-4-yl)-phenylamino}-2-phenyl-1,1′-biphenyl (Compound 1-27)

(66) (6-bromo-1,1′-biphenyl-3-yl)-{(naphthalene-2-yl)phenyl-4-yl}(biphenyl-4-yl)amine (7.5 g), 4-{N-(biphenyl-4-yl)-N-phenylamino}phenylboronicacid (5.5 g), tetrakistriphenylphosphine palladium (0.40 g), potassium carbonate (3.4 g), water (23 mL), toluene (60 mL), and ethanol (30 mL) were added into a nitrogen-substituted reaction vessel. The mixture was heated, and stirred for 16 hours under reflux. After cooling, water (100 mL) was added thereto, and then an organic layer was collected by liquid separation. The organic layer was dried over anhydrous magnesium sulfate, and then concentrated. The residue was purified by column chromatography to obtain a white powder of 4-{(naphthalene-2-yl)phenyl-4-yl}(biphenyl-4-yl)amino-4′-{(biphenyl-4-yl)-phenylamino}-2-phenyl-1,1′-biphenyl (Compound 1-27; 6.1 g; yield 58%).

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

(68) .sup.1H-NMR (CDCl.sub.3) detected 46 hydrogen signals, as follows.

(69) δ (ppm)=8.07 (1H), 7.95-7.76 (4H), 7.68-6.98 (41H).

(70) ##STR00103##

Example 8

Synthesis of 4-bis{(naphthalene-1-yl)phenyl-4-yl}amino-4′-{(biphenyl-4-yl)-phenylamino}-2-phenyl-biphenyl (Compound 1-29)

(71) (6-bromo-1,1′-biphenyl-3-yl)-bis{(naphthalene-1-yl)phenyl-4-yl}amine (10.0 g), 4-{N-(biphenyl-4-yl)-N-phenylamino}phenylboronicacid (6.7 g), tetrakistriphenylphosphine palladium (0.50 g), potassium carbonate (4.2 g), water (30 mL), toluene (80 mL), and ethanol (40 mL) were added into a nitrogen-substituted reaction vessel. The mixture was heated, and stirred for 16 hours under reflux. After cooling, water (100 mL) was added thereto, and then an organic layer was collected by liquid separation. The organic layer was dried over anhydrous magnesium sulfate, and then concentrated. The residue was purified by column chromatography to obtain a white powder of 4-bis{(naphthalene-1-yl)phenyl-4-yl}amino-4′-{(biphenyl-4-yl)-phenylamino}-2-phenyl-biphenyl (Compound 1-29; 10 g; yield 73%).

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

(73) .sup.1H-NMR (CDCl.sub.3) detected 48 hydrogen signals, as follows.

(74) δ (ppm)=8.12-8.10 (2H), 7.97-7.88 (4H), 7.63-7.01 (42H).

(75) ##STR00104##

Example 9

Synthesis of 4-{(9,9-dimethylfluorene-2-yl)phenyl-4-yl}(biphenyl-4-yl)amino-4′-{(biphenyl-4-yl)-phenylamino}-3-phenyl-1,1′-biphenyl (Compound 1-30)

(76) (6-bromo-1,1′-biphenyl-3-yl)-{(9,9-dimethylfluorene-2-yl)phenyl-4-yl}(biphenyl-4-yl)amine (12.1 g), 4-{N-(biphenyl-4-yl)-N-phenylamino}phenylboronicacid (8.9 g), tetrakistriphenylphosphine palladium (0.70 g), potassium carbonate (5.6 g), water (40 mL), toluene (100 mL), and ethanol (50 mL) were added into a nitrogen-substituted reaction vessel. The mixture was heated, and stirred for 16 hours under reflux. After cooling, water (100 mL) was added thereto, and then an organic layer was collected by liquid separation. The organic layer was dried over anhydrous magnesium sulfate, and then concentrated. The residue was purified by column chromatography to obtain a white powder of 4-{(9,9-dimethylfluorene-2-yl)phenyl-4-yl}(biphenyl-4-yl)amino-4′-{(biphenyl-4-yl)-phenylamino}-3-phenyl-1,1′-biphenyl (Compound 1-30; 8.3 g; yield 49%).

(77) The structure of the obtained white powder was identified by NMR.

(78) .sup.1H-NMR (CDCl.sub.3) detected 48 hydrogen signals, as follows.

(79) δ (ppm)=7.71-7.15 (34H), 7.09-6.99 (8H), 1.51 (6H).

(80) ##STR00105##

Example 10

(81) The melting points and the glass transition points of the arylamine compounds of the general formula (1) were measured using a high-sensitive differential scanning calorimeter (DSC3100SA produced by Bruker AXS).

(82) TABLE-US-00001 Glass transition Melting point point Compound of Example 1 No melting 116° C. point observed Compound of Example 2 263° C. 124° C. Compound of Example 3 238° C. 126° C. Compound of Example 4 No melting 120° C. point observed Compound of Example 5 No melting 118° C. point observed Compound of Example 6 No melting 121° C. point observed Compound of Example 7 No melting 121° C. point observed Compound of Example 8 No melting 125° C. point observed Compound of Example 9 No melting 125° C. point observed

(83) The arylamine compounds of the general formula (1) have glass transition points of 100° C. or higher, demonstrating that the compounds have a stable thin-film state.

Example 11

(84) A 100 nm-thick vapor-deposited film was fabricated on an ITO substrate using the arylamine compounds of the general formula (1), and a work function was measured using an ionization potential measuring device (PYS-202 produced by Sumitomo Heavy Industries, Ltd.).

(85) TABLE-US-00002 Work function Compound of Example 1 5.79 eV Compound of Example 2 5.74 eV Compound of Example 3 5.67 eV Compound of Example 4 5.70 eV Compound of Example 5 5.62 eV Compound of Example 6 5.60 eV Compound of Example 7 5.65 eV Compound of Example 8 5.63 eV Compound of Example 9 5.57 eV

(86) As the results show, the arylamine compounds of the general formula (1) have desirable energy levels compared to the work function 5.4 eV of common hole transport materials such as NPD and TPD, and thus possess desirable hole transportability.

Example 12

(87) The organic EL device, as shown in FIG. 1, was fabricated by vapor-depositing a hole injection layer 3, a first hole transport layer 4, a second hole transport layer 5, a light emitting layer 6, an electron transport layer 7, an electron injection layer 8, and a cathode (aluminum electrode) 9 in this order on a glass substrate 1 on which an ITO electrode was formed as a transparent anode 2 beforehand.

(88) Specifically, the glass substrate 1 having ITO having a film thickness of 150 nm formed thereon was subjected to ultrasonic washing in isopropyl alcohol for 20 minutes and then dried for 10 minutes on a hot plate heated to 200° C. Thereafter, after performing a UV ozone treatment for 15 minutes, the glass substrate with ITO was installed in a vacuum vapor deposition apparatus, and the pressure was reduced to 0.001 Pa or lower. Subsequently, as the hole injection layer 3 covering the transparent anode 2, Compound (HIM-1) of the structural formula below were formed in a film thickness of 5 nm. As the first hole transport layer 4 on the hole injection layer 3, the triphenylamine derivative (3-1) having two triphenylamine skeletons as a whole molecule was formed in a film thickness of 60 nm. As the second hole transport layer 5 on the first hole transport layer 4, Compound (1-12) of Example 1 was formed in a film thickness of 5 nm. As the light emitting layer 6 on the second hole transport layer 5, the pyrene derivative (EMD-1) of the structural formula below and the anthracene derivative (EMH-1) were formed in a film thickness of 20 nm by dual vapor deposition at a vapor deposition rate that satisfies a vapor deposition rate ratio of EMD-1/EMH-1=5/95. As the electron transport layer 7 on the light emitting layer 6, Compound (2-125) having the pyrimidine ring structure of the structural formula below and Compound (ETM-1) of the structural formula below were formed in a film thickness of 30 nm by dual vapor deposition at a vapor deposition rate that satisfies a vapor deposition rate ratio of Compound (2-125)/ETM-1=50/50. As the electron injection layer 8 on the electron transport layer 7, lithium fluoride was formed in a film thickness of 1 nm. Finally, aluminum was vapor-deposited in a thickness of 100 nm to form the cathode 9. The characteristics of the organic EL device were measured in the atmosphere at ordinary temperature. Table 1 summarizes the results of measurement of emission characteristics when applying a DC voltage to the fabricated organic EL device.

(89) ##STR00106## ##STR00107## ##STR00108##

Example 13

(90) An organic EL device was fabricated under the same conditions used in Example 12, except that the second hole transport layer 5 was formed by forming the compound (1-9) of Example 2 in a film thickness of 5 nm, instead of using the compound (1-12) of Example 1. The characteristics of the organic EL device thus fabricated were measured in the atmosphere at an ordinary temperature. Table 1 summarizes the results of emission characteristics measurements performed by applying a DC voltage to the fabricated organic EL device.

(91) ##STR00109##

Example 14

(92) An organic EL device was fabricated under the same conditions used in Example 10, except that the second hole transport layer 5 was formed by forming the compound (1-1) of Example 4 in a film thickness of 5 nm, instead of using the compound (1-12) of Example 1. The characteristics of the organic EL device thus fabricated were measured in the atmosphere at an ordinary temperature. Table 1 summarizes the results of emission characteristics measurements performed by applying a DC voltage to the fabricated organic EL device.

(93) ##STR00110##

Example 15

(94) An organic EL device was fabricated under the same conditions used in Example 12, except that the second hole transport layer 5 was formed by forming the compound (1-26) of Example 6 in a film thickness of 5 nm, instead of using the compound (1-12) of Example 1. The characteristics of the organic EL device thus fabricated were measured in the atmosphere at an ordinary temperature. Table 1 summarizes the results of emission characteristics measurements performed by applying a DC voltage to the fabricated organic EL device.

(95) ##STR00111##

Example 16

(96) An organic EL device was fabricated under the same conditions used in Example 12, except that the second hole transport layer 5 was formed by forming the compound (1-27) of Example 7 in a film thickness of 5 nm, instead of using the compound (1-12) of Example 1. The characteristics of the organic EL device thus fabricated were measured in the atmosphere at an ordinary temperature. Table 1 summarizes the results of emission characteristics measurements performed by applying a DC voltage to the fabricated organic EL device.

(97) ##STR00112##

Example 17

(98) An organic EL device was fabricated under the same conditions used in Example 12, except that the second hole transport layer 5 was formed by forming the compound (1-29) of Example 8 in a film thickness of 5 nm, instead of using the compound (1-12) of Example 1. The characteristics of the organic EL device thus fabricated were measured in the atmosphere at an ordinary temperature. Table 1 summarizes the results of emission characteristics measurements performed by applying a DC voltage to the fabricated organic EL device.

(99) ##STR00113##

Comparative Example 1

(100) For comparison, an organic EL device was fabricated under the same conditions used in Example 12, except that the second hole transport layer 5 was formed by forming the triphenylamine derivative (3-1) of the structural formula having two triphenylamine skeletons as a whole molecule in a film thickness of 5 nm, instead of using the compound (1-12) of Example 1. The characteristics of the organic EL device thus fabricated were measured in the atmosphere at an ordinary temperature. Table 1 summarizes the results of emission characteristics measurements performed by applying a DC voltage to the fabricated organic EL device.

Comparative Example 2

(101) For comparison, an organic EL device was fabricated under the same conditions used in Example 12, except that the second hole transport layer 5 was formed by forming the arylamine compound (HTM-1) of the structural formula below in which the 3-position was unsubstituted with a phenyl group in the compound (1-12) of Example 1 in a film thickness of 5 nm, instead of using the compound (1-12) of Example 1. The characteristics of the organic EL device thus fabricated were measured in the atmosphere at an ordinary temperature. Table 1 summarizes the results of emission characteristics measurements performed by applying a DC voltage to the fabricated organic EL device.

(102) ##STR00114##

(103) Table 1 summarizes the results of measurement of a device lifetime using the organic EL devices fabricated in Examples 12 to 17 and Comparative Examples 1 to 2. The device lifetime was measured as a time elapsed until the emission luminance of 2,000 cd/m.sup.2 (initial luminance) at the start of emission was attenuated to 1,900 cd/m.sup.2 (corresponding to 95% when taking the initial luminance as 100%: Attenuation to 95%) when carrying out constant current driving.

(104) TABLE-US-00003 TABLE 1 Luminous Power Lifetime of First hole Second hole Electron Voltage Luminance efficiency efficiency device, transport transport transport [V] [cd/m.sup.2] [cd/A] [lm/W] attenulation layer layer layer (@10 mA/cm.sup.2) (@10 mA/cm.sup.2) (@10 mA/cm.sup.2) (@10 mA/cm.sup.2) to 95% Example 12 3-1 1-12 2-125/ 3.81 905 9.05 7.54 213 hours ETM-1 Example 13 3-1 1-9  2-125/ 3.78 891 8.92 7.49 198 hours ETM-1 Example 14 3-1 1-1  2-125/ 3.85 880 8.82 7.21 228 hours ETM-1 Example 15 3-1 1-26 2-125/ 3.80 865 8.65 7.21 208 hours ETM-1 Example 16 3-1 1-27 2-125/ 3.76 862 8.64 7.29 211 hours ETM-1 Example 17 3-1 1-29 2-125/ 3.75 875 8.77 7.41 171 hours ETM-1 Comparative 3-1 3-1  2-125/ 3.76 781 7.82 6.54 162 hours Example 1 ETM-1 Comparative 3-1 HTM-1 2-125/ 3.83 868 8.69 7.13 136 hours Example 2 ETM-1

(105) As shown in Table 1, the luminous efficiency upon passing a current with a current density of 10 mA/cm.sup.2 was 8.64 to 9.05 cd/A for the organic EL devices in Examples 12 to 17, which was higher than 7.82 to 8.69 cd/A for the organic EL devices in Comparative Examples 1 to 2. Further, the power efficiency was 7.21 to 7.54 lm/W for the organic EL devices in Examples 12 to 17, which was higher than 6.54 to 7.13 lm/W for the organic EL devices in Comparative Examples 1 to 2.

(106) Table 1 also shows that the device lifetime (attenuation to 95%) was 171 to 228 hours for the organic EL devices in Examples 12 to 17, showing achievement of a far longer lifetime than 136 to 162 hours for the organic EL devices in Comparative Examples 1 to 2.

(107) It was found that the organic EL device of the present invention can achieve an organic EL device having high luminous efficiency and a long lifetime compared to the conventional organic EL devices by combining the arylamine compounds in which a specific position was substituted with an aryl group in the hole transport layer so that carrier balance inside the organic EL device is improved.

INDUSTRIAL APPLICABILITY

(108) The organic EL device of the present invention in which the hole transport layer combined the arylamine compounds in which a specific position was substituted with an aryl group improves the luminous efficiency, and also the durability of the organic EL device can be improved to attain potential applications for, for example, home electric appliances and illuminations. 1 Glass substrate 2 Transparent anode 3 Hole injection layer 4 First hole transport layer 5 Second hole transport layer 6 Light emitting layer 7 Electron transport layer 8 Electron injection layer 9 Cathode