# Patent

## Title
Luminescent device

## Abstract

The present invention provides a luminescent device using a luminescent material which has high luminescence efficiency and high stability, and is available at a low cost. The luminescent device is characterized in that as a luminescent material is used a binuclear copper coordination compound having a partial structure represented by the general formula (1): Cu-A-Cu, wherein Cu is a copper ion and A is a bidentate ligand.

## Background
TECHNICAL FIELD
The present invention relates to a luminescent device using an organic compound, more particularly to a luminescent device exhibiting stability and high efficiency which is provided by using a metal coordination compound as a luminescent material.
BACKGROUND ART
Organic EL devices as luminescent devices with high-speed response and high efficiency have been intensively investigated for their application (see Macromol. Symp. 125, 1-48 (1997), for example).
A copper coordination compound can be produced at a relatively low cost due to inexpensive raw materials, and low-cost and high performance organic EL devices can be obtained when performance of the copper coordination compound is fully utilized.
Organic EL devices using copper coordination compounds are disclosed in Japanese Patent No. 2940514 and Advanced materials 1999 11 No. 10 p. 852 Y. Ma et al. However, these EL devices have remarkably low luminescence efficiency, and these documents have insufficient description of device efficiency. It is difficult to consider that the properties of the copper coordination compounds are fully exploited. Thus, these EL devices do not have enough performance to be used for displaying or lighting.
In addition, a luminescent material of a copper coordination compound used in Advanced materials 1999 11 No. 10 p. 852 Y. Ma et al. has a molecular weight of 1,600 or more, and its molecular weight is so large that the material has inferior sublimation, thus making the material unsuitable for vacuum evaporation.
Further, copper coordination compounds having the same structure as some of the compounds used in the present invention are disclosed in Journal of chemical Society Dalton Transaction 1991 p. 2859; Journal of Chemical Society Dalton Transaction 1983 p. 1419; and Journal of Chemical Society Dalton Transaction 2001 p. 3069, but there is no description concerning luminescence therein.
In Journal of American Chemical Society, 2003 125(40) p. 12072, there is a description of a trinuclear copper coordination compound different from the copper coordination compound of the present invention. The compound described therein has luminescence property, and application of the compound to an organic LED is suggested therein. The distance between copper atoms in the molecular of the compound is about 3.22 Å, and interaction between copper atoms is not strong. This trinuclear copper coordination compound can be vapor-deposited, but has inferior luminescence property (efficiency) and stability for a device.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide a luminescent device using a luminescent material, which has high luminescence efficiency and high stability, and is available at a low cost.
Namely, a luminescent device of the present invention uses as a luminescent material a binuclear copper coordination compound having a partial structure represented by the following general formula (1). Further, the above-described copper coordination compound preferably has a partial structure represented by the following general formulae (2) and (3).




wherein Cu is a monovalent copper ion; and each of A1 to A3 and A1′ to A3′ is selected from the group consisting of a nitrogen atom, a carbon atom, and a phosphorus atom.





wherein each of R1, R2, R1′ and R2′ is a branched or straight alkyl group in which a hydrogen atom is optionally substituted by a halogen and which has 10 or less carbon atoms, an aromatic ring group optionally having a substituent, a trimethylsilyl group, a dialkylamino group which is optionally substituted, or a diarylamino group; each of R1, R2, R1′ and R2′ may be the same or different; and N is an imine group on a heteroaromatic ring, and the heteroaromatic ring is selected from the group consisting of a pyridine ring, a pyridazine ring, a pyrazine ring, a pyrimidine ring, a quinoline ring, an isoquinoline ring, a pyrazole ring, an azaquinoline ring, and an azaisoquinoline ring, and these rings may have a substituent.





wherein each of R3 and R3′ is a branched or straight alkyl group in which a hydrogen atom is optionally substituted by a halogen and which has 10 or less carbon atoms, an aromatic ring group optionally having a substituent, and a trimethylsilyl group; each of R3 and R3′ may be the same or different; and N is an imine group in a heteroaromatic ring, and the heteroaromatic ring is selected from the group consisting of a pyridine ring, a pyridazine-ring, a pyrazine ring, a pyrimidine ring, a quinoline ring, an isoquinoline ring, a pyrazole ring, an azaquinoline ring, and an azaisoquinoline ring, and these rings may have a substituent.

Another luminescent device of the present invention uses as a luminescent material a trinuclear copper coordination compound having a partial structure represented by the following general formula (4). Further, the copper coordination compound preferably has a partial structure represented by the following general formula (5).




wherein Cu is a copper ion and A′ is a tridentate ligand.





wherein B′ is a tridentate ligand and may be the same as or different from A′.

In the above luminescent device of the present invention, the copper coordination compound preferably has a partial structure represented by the following general formula (6).




Further, it is preferable that the distance between copper atoms of the copper coordination compound is 3.2Ω or less.
Furthermore, it is preferable that the copper of copper coordination compound is a monovalent ion.
Moreover, it is preferable that a luminescent layer contains a part of 100% of the copper coordination compound.



BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1A, 1B, 1C, 1D and 1E are cross sectional views showing one example of a luminescent device of the present invention;
FIG. 2 is a graph showing a luminescence spectrum of an exemplary compound 1001;
FIG. 3 is a graph showing a luminescence spectrum of a compound in a solid state in the present Example;
FIG. 4 is a graph showing a luminescence spectrum of a compound in a solid state in the present Example; and
FIG. 5 is a graph showing a luminescence spectrum of a compound in a solid state in the present Example.



BEST MODE FOR CARRYING OUT THE INVENTION
A copper coordination compound used in the present invention not only has high luminescence efficiency but also is suitable for vacuum deposition process or spin coating process wherein the compound is applied in a solution, or application method using an ink jet nozzle, thereby enabling stable device fabrication with no damage such as decomposition in a device fabrication process. Therefore, the luminescent device of the present invention exhibits high luminescence efficiency and high stability, and at the same time can be fabricated at a low cost.
Now, the present invention will be described in detail.
First, features or a copper coordination compound are described which is a luminescent material of the present invention.
The copper coordination compound used in the present invention is a copper coordination compound having a partial structure represented by the above general formulae (1) to (4), that is a binuclear copper coordination compound wherein two copper atoms are coupled to one or a plurality of bidentate ligands, or a trinuclear copper coordination compound wherein three copper atoms are coupled to one or a plurality of tridentate ligands. The copper coordination compounds falling within this category exhibit thermal stability and high luminescence efficiency and are suitable for luminescent material. Particularly in a solid powder state, they are characterized by stronger luminescence exhibited compared with other compounds.
In general, even among compounds that exhibit strong luminescence in a dilute solution, many of them exhibit extremely weak luminescence in a solid powder state. These compounds form associations in the ground state by interaction between molecules of the luminescent material or form exciplexes, this phenomenon is known as “concentration quenching” wherein original luminescence characteristic cannot be obtained.
It can be said that a Cu coordination compound of the present invention is less susceptible to the concentration quenching. Therefore, when considering a luminescent layer in a luminescent device, the concentration quenching is generally prevented by adding a small amount of luminescent material as a guest material to a host material. However, since the copper coordination compound of the present invention has no constraint of the concentration quenching, a high concentration of the compound can be applied or a luminescent layer of 100% of the compound can be formed. As a result, luminescent devices which have high luminescence efficiency and good productivity can be fabricated. In addition, because of small concentration dependency of luminescence characteristic, variations in fabrication can be reduced. In this view, luminescent devices with high productivity can be fabricated.
Here, it is preferable to use a copper ion of a center metal that is a monovalent cation. Considering electron arrangement of a copper atom, a positive monovalent copper contains 10 d-electrons. In general, there are many cases wherein a transition metal having even number of d electrons exhibits excellent luminescence characteristic.
In addition, vacuum deposition method is commonly employed for fabricating an organic LED device in general since it enables the fabrication of a stable thin film with good quality. From our experiments, as the molecular weight of a compound becomes large, this deposition method cannot be employed. Accordingly, for vacuum deposition, the copper coordination compound of the present invention has a molecular weight of preferably 1,500 or less, more preferably 1,200 or less.
Chemical formulae of ligands that can be used for the present invention are shown below (it should be noted that the following basic structures optionally have a condensed ring group or a substituent group. The substituent group is a halogen atom, a straight, branched or cyclic alkyl group or an aromatic ring group optionally having a substituent. CH2 group of the alkyl group may be substituted with —O— or —NR— (R is an alkyl group or an aromatic ring group which may be substituted), and a hydrogen atom of the alkyl group may be substituted with an aromatic ring group or a halogen atom.).












































































Ligands shown in chemical formulae 6 to 15 may become a bidentate ligand with negative monovalence after a hydrogen atom is withdrawn from “CH” or “NH” in the formulae, so that the hydrogen atom-withdrawn nitrogen atom or carbon atom become a coordinating atom to a copper atom. Further, since ligands shown in chemical formula 16 are zerovalent, a coordination compound as a whole is positive divalent. In the case of these ionic coordination compounds, PF6−, ClO4−, BF4− and a halogen ion can be used as a counter anion. For example, quadridentate ligands in which two of bidentate ligands shown in chemical formulae 6 to 16 are coupled by a covalent bond can be used as a ligand of the present invention.
Next, specific examples of the copper coordination compound of the present invention are shown in Tables 1 to 7 and Chemical Formula 17. Reference characters in the columns of “A and B”, “A” and “B” of the Tables represent the above-described ligands. Tables 1 and 2 show coordination compounds in which ligands A and B have the same structure. Tables 3 to 7 show coordination compounds in which ligands A and B have different structures. Chemical Formula 17 shows trinuclear coordination compounds.









TABLE 1






Compound Number
A and B








1001
A01



1002
A02



1003
A03



1004
A04



1005
A05



1006
A06



1007
A07



1008
A08



1009
A09



1010
A10



1011
A11



1012
A12



1013
A13



1014
A14



1015
A15



1016
A16



1017
A17



1018
A18



1019
A19



1020
A20



1021
A21



1022
B01



1023
B02



1024
B03



1025
B04



1026
B05



1027
B06



1028
B07



1029
B08



1030
B09



1031
B10



1032
B11



1033
B12



1034
B13



1035
B14



1036
B15



1037
B16



1038
B17



1039
B18



1040
B19



1041
B20



1042
B21



1043
C01



1044
C02



1045
C03



1046
C04



1047
C05



1048
C06



1049
C07



1050
C08



1051
C09



1052
C10



1053
C11



1054
C12



1055
C13



1056
C14



1057
C15



1058
C16



1059
C17



1060
D01



1061
D02



1062
D03



1063
D04



1064
D05



1065
D06



1066
D07



1067
D08



1068
D09



1069
D10



1070
D11



1071
D12



1072
D13



1073
D14



1074
D15



1075
D16



1076
D17



1077
D18



1078
E01



1079
E02



1080
E03



1081
E04



1082
E05



1083
E06



1084
E07



1085
E08



1086
E09



1087
E10



1088
E11



1089
E12



1090
E13



1091
E14



1092
E15



1093
E16



1094
F01



1095
F02



1096
F03



1097
F04



1098
F05



1099
F06



1100
F07



1101
F08



1102
F09



1103
F10



1104
F11



1105
F12



1106
F13



1107
F14



1108
F15



1109
F16



1110
F17



1111
G01



1112
G02



1113
G03



1114
G04



1115
G05



1116
G06



1117
G07



1118
G08



1119
G09



1120
G10



1121
G11



1122
G12



1123
G13



1124
G14



1125
G15



1126
G16



1127
G17



1128
G18



1129
G19



1130
G20



1131
G21



1132
G22



1133
G23



1134
H01



1135
H02



1136
H03



1137
H04



1138
H05



1139
H06



1140
H07



1141
H08



1142
H09



1143
H10



1144
H11



1145
H12



1146
H13



1147
H14



1148
H15



1149
H16



1150
H17



















TABLE 2







Compound Number
A and B









1151
I1



1152
I2



1153
I3



1154
I4



1155
I5



1156
I6



1157
I7



1158
I8



1159
I9



1160
I10



1161
I11



1162
I12



1163
I13



1164
I14



1165
I15



1166
I16



1167
I17



1168
I18



1169
I19



1170
J01



1171
J02



1172
J03



1173
J04



1174
J05



1175
J06



1176
J07



1177
J08



1178
J09



1179
J10



1180
F18



1181
F19




















TABLE 3






Compound Number
A
B








2001
A01
A02



2002
A01
A04



2003
A01
A05



2004
A01
A06



2005
A01
A07



2006
A01
A09



2007
A01
A11



2008
A01
A12



2009
A01
A13



2010
A01
A14



2011
A01
A15



2012
A01
A21



2013
A01
B01



2014
A01
B02



2015
A01
B06



2016
A01
B11



2017
A01
B12



2018
A01
B20



2019
A01
C01



2020
A01
C02



2021
A01
C04



2022
A01
C05



2023
A01
C06



2024
A01
C07



2025
A01
C10



2026
A01
C11



2027
A01
C12



2028
A01
C13



2029
A01
C14



2030
A01
C16



2031
A01
C07



2032
A01
D01



2033
A01
D04



2034
A01
D06



2035
A01
D07



2036
A01
D08



2037
A01
D09



2038
A01
D15



2039
A01
D16



2040
A01
D17



2041
A01
D18



2042
A01
E03



2043
A01
E08



2044
A01
E11



2045
A01
E12



2046
A01
E13



2047
A01
E14



2048
A01
E15



2049
A01
E16



2050
A01
F01



2051
A01
F03



2052
A01
F04



2053
A01
F05



2054
A01
F11



2055
A01
F14



2056
A01
F17



2057
A01
G01



2058
A01
G02



2059
A01
G03



2060
A01
G06



2061
A01
G12



2062
A01
G13



2063
A01
G15



2064
A01
G20



2065
A01
G21



2066
A01
G23



2067
A01
H01



2068
A01
H04



2069
A01
H10



2070
A01
H12



2071
A01
H14



2072
A01
H17



2073
A01
I01



2074
A01
I03



2075
A01
I14



2076
A01
I15



2077
A01
J01



2078
A01
J07



2079
A01
J10



2080
A02
A04



2081
A02
A05



2082
A02
A06



2083
A02
A07



2084
A02
A09



2085
A02
A11



2086
A02
A12



2087
A02
A13



2088
A02
A14



2089
A02
A15



2090
A02
A21



2091
A02
B01



2092
A02
B02



2093
A02
B10



2094
A02
B11



2095
A02
B12



2096
A02
B20



2097
A02
C01



2098
A02
C02



2099
A02
C04



2100
A02
C05



2101
A02
C06



2102
A02
C07



2103
A02
C10



2104
A02
C11



2105
A02
C12



2106
A02
C13



2107
A02
C14



2108
A02
C16



2109
A02
C07



2110
A02
D01



2111
A02
D04



2112
A02
D06



2113
A02
D07



2114
A02
D08



2115
A02
D09



2116
A02
D15



2117
A02
D16



2118
A02
D17



2119
A02
D18



2120
A02
E03



2121
A02
E08



2122
A02
E11



2123
A02
E12



2124
A02
E13



2125
A02
E14



2126
A02
E15



2127
A02
E16



2128
A02
F01



2129
A02
F03



2130
A02
F04



2131
A02
F05



2132
A02
F11



2133
A02
F14



2134
A02
F17



2135
A02
G01



2136
A02
G02



2137
A02
G03



2138
A02
G06



2139
A02
G12



2140
A02
G13



2141
A02
G15



2142
A02
G20



2143
A02
G21



2144
A02
G23



2145
A02
H01



2146
A02
H04



2147
A02
H10



2148
A02
H12



2149
A02
H14



2150
A02
H17



















TABLE 4






Compound Number
A
B








2151
A02
I01



2152
A02
I03



2153
A02
I14



2154
A02
I15



2155
A02
J01



2156
A02
J07



2157
A02
J10



2158
A03
A09



2159
A03
A13



2160
A03
A18



2161
A03
A20



2162
A03
B01



2163
A03
B02



2164
A03
B10



2165
A03
B13



2166
A03
B19



2167
A03
C01



2168
A03
C06



2169
A03
C10



2170
A03
C14



2171
A03
C16



2172
A03
D04



2173
A03
D08



2174
A03
D09



2175
A03
D15



2176
A03
D16



2177
A03
D18



2178
A03
E02



2179
A03
E12



2180
A03
F03



2181
A03
F04



2182
A03
F14



2183
A03
F17



2184
A03
G01



2185
A03
G18



2186
A03
H01



2187
A03
H10



2188
A03
H14



2189
A03
I1



2190
A03
I15



2191
A03
J07



2192
A04
A05



2193
A04
A06



2194
A04
A07



2195
A04
A09



2196
A04
A11



2197
A04
A12



2198
A04
A13



2199
A04
A14



2200
A04
A15



2201
A04
A21



2202
A04
B01



2203
A04
B02



2204
A04
B10



2205
A04
B11



2206
A04
B12



2207
A04
B20



2208
A04
C01



2209
A04
C02



2210
A04
C04



2211
A04
C05



2212
A04
C06



2213
A04
C07



2214
A04
C10



2215
A04
C11



2216
A04
C12



2217
A04
C13



2218
A04
C14



2219
A04
C16



2220
A04
C07



2221
A04
D01



2222
A04
D04



2223
A04
D06



2224
A04
D07



2225
A04
D08



2226
A04
D09



2227
A04
D15



2228
A04
D16



2229
A04
D17



2230
A04
D18



2231
A04
E03



2232
A04
E08



2233
A04
E11



2234
A04
E12



2235
A04
E13



2236
A04
E14



2237
A04
E15



2238
A04
E16



2239
A04
F01



2240
A04
F03



2241
A04
F04



2242
A04
F05



2243
A04
F11



2244
A04
F14



2245
A04
F17



2246
A04
G01



2247
A04
G02



2248
A04
G03



2249
A04
G06



2250
A04
G12



2251
A04
G13



2252
A04
G15



2253
A04
G20



2254
A04
G21



2255
A04
G23



2256
A04
H01



2257
A04
H04



2258
A04
H10



2259
A04
H12



2260
A04
H14



2261
A04
H17



2262
A04
I01



2263
A04
I03



2264
A04
I14



2265
A04
I15



2266
A04
J01



2267
A04
J07



2268
A04
J10



2269
A05
A09



2270
A05
A13



2271
A05
A18



2272
A05
A20



2273
A05
B01



2274
A05
B02



2275
A05
B10



2276
A05
B13



2277
A05
B19



2278
A05
C01



2279
A05
C06



2280
A05
C10



2281
A05
C14



2282
A05
C16



2283
A05
D04



2284
A05
D08



2285
A05
D09



2286
A05
D15



2287
A05
D16



2288
A05
D18



2289
A05
E02



2290
A05
E12



2291
A05
F03



2292
A05
F04



2293
A05
F14



2294
A05
F17



2295
A05
G01



2296
A05
G18



2297
A05
H01



2298
A05
H10



2299
A05
H14



2300
A05
I1



















TABLE 5






Compound Number
A
B








2301
A05
I15



2302
A05
J07



2303
A06
A09



2304
A06
A13



2305
A06
A18



2306
A06
A20



2307
A06
B01



2308
A06
B02



2309
A06
B10



2310
A06
B13



2311
A06
B19



2312
A06
C01



2313
A06
C06



2314
A06
C10



2315
A06
C14



2316
A06
C16



2317
A06
D04



2318
A06
D08



2319
A06
D09



2320
A06
D15



2321
A06
D16



2322
A06
D18



2323
A06
E02



2324
A06
E12



2325
A06
F03



2326
A06
F04



2327
A06
F14



2328
A06
F17



2329
A06
G01



2330
A06
G18



2331
A06
H01



2332
A06
H10



2333
A06
H14



2334
A06
I1



2335
A06
I15



2336
A06
J07



2337
A07
A09



2338
A07
A12



2339
A07
B01



2340
A07
B05



2341
A07
B20



2342
A07
C14



2343
A07
C16



2344
A07
D04



2345
A07
D09



2346
A07
D15



2347
A07
E01



2348
A07
F04



2349
A07
G21



2350
A07
I15



2351
A08
A09



2352
A08
A12



2353
A08
B01



2354
A08
B05



2355
A08
B20



2356
A08
C14



2357
A08
C16



2358
A08
D04



2359
A08
D09



2360
A08
D15



2361
A08
E03



2362
A08
F04



2363
A08
G21



2364
A08
I15



2365
A09
A11



2366
A09
A12



2367
A09
A13



2368
A09
A14



2369
A09
A15



2370
A09
A21



2371
A09
B01



2372
A09
B02



2373
A09
B10



2374
A09
B11



2375
A09
B12



2376
A09
B20



2377
A09
C01



2378
A09
C02



2379
A09
C04



2380
A09
C05



2381
A09
C06



2382
A09
C07



2383
A09
C10



2384
A09
C11



2385
A09
C12



2386
A09
C13



2387
A09
C14



2388
A09
C16



2389
A09
C07



2390
A09
D01



2391
A09
D04



2392
A09
D06



2393
A09
D07



2394
A09
D08



2395
A09
D09



2396
A09
D15



2397
A09
D16



2398
A09
D17



2399
A09
D18



2400
A09
E03



2401
A09
E08



2402
A09
E11



2403
A09
E12



2404
A09
E13



2405
A09
E14



2406
A09
E15



2407
A09
E16



2408
A09
F01



2409
A09
F03



2410
A09
F04



2411
A09
F05



2412
A09
F11



2413
A09
F14



2414
A09
F17



2415
A09
G01



2416
A09
G02



2417
A09
G03



2418
A09
G06



2419
A09
G12



2420
A09
G13



2421
A09
G15



2422
A09
G20



2423
A09
G21



2424
A09
G23



2425
A09
H01



2426
A09
H04



2427
A09
H10



2428
A09
H12



2429
A09
H14



2430
A09
H17



2431
A09
I01



2432
A09
I03



2433
A09
I14



2434
A09
I15



2435
A09
J01



2436
A09
J07



2437
A09
J10



2438
A13
B01



2439
A13
B05



2440
A13
B20



2441
A13
C14



2442
A13
C16



2443
A13
D04



2444
A13
D09



2445
A13
D15



2446
A13
E03



2447
AI3
F04



2448
A13
G21



2449
A13
I15



2450
A13
J07



















TABLE 6






Compound Number
A
B








2451
B01
B05



2452
B01
B09



2453
B01
C14



2454
B01
C16



2455
B01
D04



2456
B01
D09



2457
B01
D15



2458
B01
E03



2459
B01
F04



2460
B01
G21



2461
B01
I15



2462
B01
J07



2463
B06
B09



2464
B06
C14



2465
B06
C16



2466
B06
D04



2467
B06
D09



2468
B06
D15



2469
B06
E03



2470
B06
F04



2471
B06
G21



2472
B06
I15



2473
B06
J07



2474
B13
C14



2475
B13
C16



2476
B13
D04



2477
B13
D09



2478
B13
D15



2479
B13
E03



2480
B13
F04



2481
B13
G21



2482
B13
I15



2483
B13
J07



2484
C01
C02



2485
C01
C04



2486
C01
C16



2487
C01
D04



2488
C01
D09



2489
C01
D15



2490
C01
E03



2491
C01
F04



2492
C01
G21



2493
C07
C09



2494
C07
C16



2495
C07
D04



2496
C07
D09



2497
C07
D15



2498
C07
E03



2499
C07
F04



2500
C07
G21



2501
C14
C16



2502
C14
D04



2503
C14
D06



2504
C14
D09



2505
C14
D16



2506
C14
E03



2507
C14
F04



2508
C14
G21



2509
C16
C17



2510
C16
D04



2511
C16
D06



2512
C16
D09



2513
C16
D16



2514
C16
E03



2515
C16
F04



2516
C17
D01



2517
C17
D04



2518
C17
D15



2519
D04
D07



2520
D04
D09



2521
D04
D15



2522
D04
D16



2523
D04
E03



2524
D04
E11



2525
D04
E12



2526
D04
F03



2527
D04
F05



2528
D04
F14



2529
D04
F17



2530
D04
G07



2531
D04
G11



2532
D04
G21



2533
D04
H05



2534
D04
H17



2535
D04
I14



2536
D09
D07



2537
D09
D09



2538
D09
D15



2539
D09
D16



2540
D09
E03



2541
D09
E11



2542
D09
E12



2543
D09
F03



2544
D09
F05



2545
D09
F14



2546
D09
F17



2547
D09
G07



2548
D09
G11



2549
D09
G21



2550
D09
H05



2551
D09
H17



2552
D09
I14



2553
D16
D16



2554
D16
E03



2555
D16
E11



2556
D16
E12



2557
D16
F03



2558
D16
F05



2559
D16
F14



2560
D16
F17



2561
D16
G07



2562
D16
G11



2563
D16
G21



2564
D16
H05



2565
D16
H17



2566
D16
I14



2567
E01
E03



2568
E01
A01



2569
E01
A02



2570
E01
A09



2571
E01
E11



2572
E01
E12



2573
E01
F03



2574
E01
F05



2575
E01
F14



2576
E01
F17



2577
E01
G07



2578
E01
G11



2579
E01
G21



2580
E01
H05



2581
E01
H17



2582
E01
I14



2583
E02
A01



2584
E02
A02



2585
E02
A09



2586
E03
E11



2587
E03
E12



2588
E03
F03



2589
E03
F05



2590
E03
F14



2591
E03
F17



2592
E03
G07



2593
E03
G11



2594
E03
G21



2595
E03
H05



2596
E03
H17



2597
E03
I14



2598
E05
A01



2599
E05
A02



2600
E05
A09



















TABLE 7






Compound Number
A
B








2601
E12
F03



2602
E12
F05



2603
E12
F14



2604
E12
F17



2605
E12
G07



2606
E12
G11



2607
E12
G21



2608
E12
H05



2609
E12
H17



2610
E12
I14



2611
E15
E01



2612
E15
E02



2613
E15
E03



2614
E15
E08



2615
E15
F03



2616
E15
F05



2617
E15
F14



2618
E15
F17



2619
F03
F05



2620
F03
F14



2621
F03
F17



2622
F03
G07



2623
F03
G11



2624
F03
G21



2625
F03
H05



2626
F03
H17



2627
F03
I14



2628
F04
F05



2629
F04
F14



2630
F04
F17



2631
F04
G07



2632
F04
G11



2633
F04
G21



2634
F04
H05



2635
F04
H17



2636
F04
I14



2637
F05
A01



2638
F05
A02



2639
F05
A09



2640
F05
F14



2641
F05
F17



2642
F05
G07



2643
F05
G11



2644
F05
G21



2645
F17
G07



2646
G21
H12



2647
I08
I14



2648
I10
I14



2649
I10
I15



2650
I14
I15



2651
J01
J02



2652
J01
J03



2653
J01
J07



2654
J02
J07



2655
J03
J04



2656
J07
J08



2657
J07
J10













Among the above examples, structural formulae of preferable copper coordination compounds are shown below.
























Many of these cooper coordination compounds have a copper-copper interatomic distance of 3.2 Å or less, and interaction between copper atoms exists to maintain the bond therebetween. The copper coordination compound having a partial structure represented by the above general formula (1), preferably the above general formula (2) has two bidentate ligands such that the ligands surround two copper atoms from both ends of the two copper atoms. Taking Exemplary compound 1001 as an example, two ligands A01 are used as this ligand, and a nitrogen atom in pyridine and a carbon atom adjacent to the pyridine ring are coordinating atoms. These ligands are rotationally symmetrically coordinated in the coordination compound so as to surround two copper atoms. It is considered that an extremely bulky trimethylsilyl group in the ligand has an effect of stabilizing the bond between copper and ligand. Since the ligand has a three-dimensionally bulky substituent group therein, thermal stability is improved and it is desired as a luminescent material. Exemplary compound 1001 has a copper interatomic distance of 2.41 Å in its molecule and has a strong interaction. A compound having a copper interatomic distance of 3.2 or less Å has relatively strong interaction between copper atoms, thereby obtaining excellent thermal stability and luminescence characteristic.
A copper coordination compound using ligands having aromatic substituent group shown in Chemical Formula 10 can have not only a luminescence capability as a luminescent material but also a charge transport property due to its aromatic substituent. For example, when these coordination compounds are used in a luminescent layer at a high concentration, charge transport becomes possible, so that the use of the compound is more advantageous. Further, as the compound has several stable conformations, its amorphous property is enhanced to inhibit crystallization. This is more desirable for improving the durability of an organic LED device. As another example, a structure having a trimethylsilyl group in one ligand but no trimethylsilyl group in the other ligand is possible like Exemplary compound 2051. This can destabilize a structural symmetry, decrease crystallizability, and improve an amorphous property. Furthermore, like Exemplary compound 2054, a difference in conjugation length can be provided to localize an excited state, in addition to the presence or absence of a trimethylsilyl group, thereby enhancing the stability of the device. The reason therefore is not clear, but it is possible to enhance the stability of the device by localizing an excited state of a luminescent material.
The luminescent material of the present invention exhibit good luminescence in a solid as mentioned above, and thus it can be used in a luminescent layer at a high concentration. However, when a coordination compound is constructed with the same ligands, such compound is relatively easily crystallized. When this compound is used as a luminescent device, problems may arise such as easy deterioration. Thus, crystallization can be inhibited by reducing the symmetry of its molecule. Examples of those compounds are shown in Tables 3 to 7. For example, Exemplary compound 2033 has a carbazole group in one ligand but no carbazole group in the other ligand. A compound having such molecular structure has high amorphousness and low crystallizability, and therefore it is more desired as a luminescent material for an organic LED device.
The extremely strong luminescence characteristics of the copper coordination compounds of the present invention were observed for the first time by the present inventors, and its application to a luminescent device is disclosed. Accordingly, its luminescence mechanism has not been revealed so far. The description at luminescence mentioned below provides one model for our luminescence mechanism.
As the lowest excited state in luminescence of the copper coordination compound of the present invention, the following 3 types are considered, or a mixed state of these 3 types are considered.

    (1) MLCT (metal-to-ligand-charge-transfer) excited state
    (2) metal-centered excited state
    (3) ligand-centered (π-π*) excited state


Since an excited state has a short life and is complicated, it is difficult to experimentally identify in detail an excited state for each coordination compound.
As mentioned above, many copper coordination compounds of the present invention has a short distance between copper atoms in its molecule and the distance is 3.2 Å or less. Twice the van der Waals' radius of copper atom is 2.8 Å, and it is considered that a new molecular orbital is formed due to interaction between copper atoms. The orbital formed by this interaction between copper atoms has a higher energy than an occupied orbital of a single copper atom, and thus it can be a HOMO orbital (the highest occupied molecular orbital).
Further, many of the coordination compounds of the present invention have an electron-deficiency heterocycle such as pyridine, pyrazine, pyrimidine, pyridazine, quinoline, isoquinoline, pyrazole, azaquinoline, and azaisoquinoline rings, directly coordinated with a copper atom through an N atom as shown by, for example, the above general formula (3). When the compound is in an excited state, an electron is transited to an upper orbital from the ground state but the above heterocycle easily accepts the electron due to electron-deficiency. Thus, there are many cases wherein the heterocycle accepts an electron from a copper atom at the time of excitation transition. A ligand having such heterocycle accepts an electron from a copper atom at the time of excitation transition. When an electron is charge-transferred from a metal to a ligand at the time of excitation transition, such excited state is referred to as MLCT excited state. The MLCT excited state of the Cu coordination compound of the present invention is considered as follows. That is, an orbital formed by interaction between two copper atoms becomes a HOMO orbital of the molecule, and charge transfer from the HOMO orbital to a ligand occurs. This is the MLCT exited state.
Also, when the coordination compound among those of the present invention has no heterocycle in its molecule or accepts no electron at the time of excitation transition, the excited state at the time of excitation transition becomes (2) metal-centered excited state. Also, it is considered that it becomes (3) ligand-centered (π-π*) excited state.
Luminescence is generally generated from the lowest excited state. Since various excited states are “mixed” in the lowest excited state, the luminescence characteristic is determined depending upon which excited state is main in the lowest excited state.
With respect to MLCT excited state, when luminescence energy is changed by changing ligands, these ligands are determined to be in main excited states. When the distance between copper atoms in the molecule is about 3.2 Å or less, a bonding orbital is formed due to metal interaction and thus such orbital is considered as MLCT transition. Molecular structural characteristics such as a distance between copper atoms can be determined by X-ray crystal structure analysis.
The luminescence wavelength of the copper coordination compound of the present invention can be controlled by changing a ligand. For example, the wavelength can be controlled by using an electron-withdrawing or electron-donating group on a pyridine ring, like a ligand shown in Chemical Formula 6. Further, the N atom number in a heterocycle or a ring structure of a heterocycle can be changed as shown in Chemical Formulae 8 and 9. Furthermore, the luminescence wavelength can be controlled by changing the conjugation length of an aromatic ring as shown in Chemical Formulae 10 and 11.
The copper coordination compound of the present invention has a luminescent lifetime of 0.1 to 100 μs in a solid state. The luminescence occurs through a triplet excited state, and composed of delayed fluorescence or phosphorescence. The photoluminescence yield is about 1 to 60%, and exhibits strong luminescence.
For high luminescence efficiency, it is important to allow a compound to have a ligand structure so that structure changes between the ground state and an excited state are inhibited. The copper coordination compound of the present invention inhibits the above structural changes more in a solid rather than in a solution, and thus strong luminescence can be obtained. This is one reason why the copper coordination compound exhibits good luminescence in a solid. Aluminum-quinolinol derivatives, coumarin derivatives, quinacridon derivatives, which have been used so far, allow for extremely strong luminescence in a solution, and that strong luminescence characteristic is maintained in a solid state as it is. This characteristic effectively works in the case of an organic EL device and high luminescence efficiency of the device can be obtained. However, the Cu coordination compound of the present invention exhibits stronger luminescence in a solid than in a solution. The present inventors have noticed this characteristic and found that this characteristic is useful for highly efficient and stable luminescence of an organic EL device.
The Cu coordination compound of the present invention is useful as a luminescent material of an organic EL device. The compound is suitable for vacuum-deposition process or spin coating process wherein the compound is applied in a solution, or application method using an ink jet nozzle, in addition to high luminescence efficiency of the compound. With no damage such as decomposition in a device fabrication process, stable device fabrication is possible.
Next, a luminescent device will be described. The luminescent device of the present invention preferably contains the above luminescent material in its luminescent layer.
FIGS. 1A to 1E show basic structures of organic EL devices of the present invention. Reference numerals in the figures are explained as follows. Reference numeral 11 denotes a metal electrode, 12 a luminescent layer, 13 a hole-transporting layer, 14 a transparent electrode, 15 a transparent substrate, 16 an electron-transporting layer, and 17 an exciton diffusion prevention layer.
As shown in FIGS. 1A to 1E, the organic EL device is generally composed of single or plural organic layers which are sandwiched by the transparent electrode 14 on the transparent substrate 15 and the metal electrode 11.
FIG. 1A shows a simplest structure of the device wherein an organic layer is composed of only a luminescent layer 12.
FIGS. 1B and 1C show the devices having two organic layers, which are a luminescent layer 12 and a hole-transporting layer 13; and a luminescent layer 12 and an electron-transporting layer 16, respectively.
FIG. 1D show the device having three organic layers, which are a hole-transporting layer 13, a luminescent layer 12 and an electron-transporting layer 16.
FIG. 1E show the device having four organic layers, which are a hole-transporting layer 13, a luminescent layer 12, an exciton diffusion prevention layer 17, and an electron-transporting layer 16.
For the luminescent layer 12, an aluminum-quinolinol complex or the like having electron transport property and luminescence characteristic (typical example is Alq as shown below) is used.
As the luminescent layer, it is possible to use a guest host type which contains a luminescent copper coordination compound of the present invention in a carrier-transporting material; only the luminescent copper coordination compound at 100% concentration; or the layer composed of the luminescent copper coordination compound as a main component with the addition of a small amount of additive (e.g. carrier-transporting material or crystallization-preventing material). Further, among guest host types, two carrier-transporting materials as guests, one having an electron-transporting property and the other having a hole-transporting property, are used, and the luminescent copper coordination compound can be added thereto. Therefore, the luminescent layer of the present invention can be composed of a material containing one or more components, considering performance improvement or productivity.
In addition, for the hole-transporting layer 13, triphenylamine derivatives (typical example is αNPD), for example, are mainly used. In the case of polymers, PVK is used. PVK has mainly hole-transporting property, and PVK itself exhibit blue EL luminescence.
As the electron-transporting layer 16, oxadiazole derivatives, for example, are used, or Alq, Bphen or BCP as shown below can be used.




Production Example 1
Production of Exemplary Compound 1001




Into a 1000-ml flask, 32.6 g of TMEDA (281 mmol) was charged with 150 ml of cyclohexane, and cooled to −30° C. To this solution, 345 ml of n-butyl lithium (2.4 M hexane solution) was dropwise added with a cannular, and 26.1 g (281 mmol) of 2-methyl pyridine was dropwise added to the resultant suspended solution with a dropping funnel. Thereafter, the reaction solution was heated and stirred at room temperature for 10 minutes. Then, the solution was again cooled down to −30° C., and 91.5 g (843 mmol) of trimethylsilyl chloride was dropwise added thereto with a dropping funnel. After stirring for 15 minutes, the resultant solution was heated to room temperature, and stirred for 2 hours. After the reaction, the resultant mixture was treated with water, and extraction was carried out with hexane (1 L×3). An organic layer thereof was washed with saturated saline and dried on magnesium sulfate. Then, the solvent thereof was evaporated and a crude product was obtained. The obtained product was purified with column chromatography (ethyl acetate/hexane=1/10), and distilled under reduced pressure to obtain 13.0 g of Compound A01 (yield 19%).




To a 100-ml two-necked flask, 952 mg of 2-(bis-trimethylsilanyl-methyl)-pyridine (Compound A01) was charged with 20 ml of completely degassed dehydrated tetrahydrofuran, and 2.5 ml of n-butyllithium (4 mmol, 1.6 M hexane solution) was dropwise added while stirring at −20° C. under nitrogen gas flow.
Thereafter, the resultant solution was heated gradually to room temperature. After the solution reached to room temperature, 496 mg (4 mmol) of copper chloride (I) was added thereto and the resultant mixture was stirred for 15 minutes. After the reaction was completed, the solvent thereof was evaporated in nitrogen atmosphere. 50 ml of dehydrated and degassed hexane was added to the reaction mixture and the mixture was stirred. Then, in nitrogen atmosphere insoluble matters were filtrated. The resultant filtrate was concentrated in nitrogen atmosphere, and the obtained solid product was purified by sublimation purification to obtain 350 mg (yield 29%) of Exemplary compound 1001.
Production Example 2
Production of Exemplary Compound 1002




To a 100-ml two-necked flask, 1006 g (4 mmol) of 2-(bis-trimethylsilanyl-methyl)-6-methyl-pyridine (Compound A02) was charged with 20 ml of completely degassed and dehydrated tetrahydrofuran, and 2.5 ml of n-butyllithium (4 mmol, 1.6 M hexane solution) was dropwise added while stirring at −20° C. under nitrogen gas flow.
Thereafter, the resultant solution was heated gradually to room temperature. After the solution reached to room temperature, 496 mg (4 mmol) of copper chloride (I) was added thereto and the resultant mixture was stirred for 15 minutes. After the reaction was completed, the solvent thereof was evaporated in nitrogen atmosphere. To the reaction mixture 50 ml of dehydrated and degassed hexane was added, and the mixture was stirred. Then, in nitrogen atmosphere, insoluble matters were filtrated. The resultant filtrate was concentrated in nitrogen atmosphere, and the obtained solid product was purified by sublimation purification to obtain 390 mg (yield 31%) of Exemplary compound 1002.
Production Example 3
Production of Exemplary Compound 1176




To a 100-ml two-necked flask, 186 mg (0.5 mmol) of tetrakis(acetonitrile)copper(I)hexafluorophosphate and 20 ml of dehydrated toluene were fed and 132 mg (0.5 mmol) of 2-diphenylphosphanyl-pyridine (Compound J07) was charged thereto under nitrogen gas flow. Thereafter, the mixture was stirred for 1 hour. After the reaction was completed, the solvent thereof was evaporated and recrystallization was carried out with chloroform/methanol to obtain 159 mg (yield 50%) of Exemplary compound 1176.
Luminescence Characteristics of Compounds
Luminescence characteristics of compounds produced by Production Examples 1 to 3 were measured when these compounds were powder. Results thereof are shown in Table 8. In addition, a luminescence spectrum of Exemplary compound 1001 is shown in FIG. 2 as a representative example.









TABLE 8





Exemplary




Compound
Luminescence wavelength (nm)
Half-value width (nm)







1001
519
67


1002
525
70


1176
514
91









Examples 1 and 2
In these examples, a device having a device structure including three organic layers as shown in FIG. 1D was used.
On a glass substrate (transparent substrate 15), 100 nm-thick ITO (transparent electrode 14) was patterned such that the resultant opposing electrodes had an area of 3 mm2. The organic layers and the electrode layers described below were vacuum-deposited on the ITO substrate by resistive heating in a vacuum chamber at 10−4 Pa for continuous deposition. Two kinds of luminescent layer 12 having 40 nm (Example 1) and 20 nm (Example 2) in thickness were prepared.
Hole-transporting layer 13 (thickness: 40 nm): compound FL1
Luminescent layer 12 (thickness: 40 nm, 20 nm): CBP/Exemplary compound 1001 (10% by weight based on CBP)
Electron-transporting layer 16 (thickness: 50 nm): BPhen
Metal electrode 1 (thickness: 1 nm): KF Metal electrode 2 (thickness: 100 nm): Al
The structural formula of Compound FL1 is shown below.




Example 3
In this Example, a device having the device structure including three organic layers shown in FIG. 1D was used.
On an ITO substrate as prepared in the same manner as in Example 1, PEDOT (for organic EL) available from Bayer Corporation was applied by spin coating at 1000 rpm (20 sec.) to a thickness of 40 nm as a hole-transporting layer 13, and dried for 1 hour in a vacuum chamber at 120° C.
On top of that layer, the following solution was used for spin-coating at 2000 rpm for 20 seconds in nitrogen atmosphere so that the luminescent layer 12 with a thickness of 50 nm was formed. The formed layer was dried in the same condition as in forming the hole-transporting layer 13.

    Dehydrated chlorobenzene: 10 g
    Polyvinyl carbazole (average molecular weight 9600): 92 mg
    Exemplary compound 1001: 8 mg


This substrate was installed in a vacuum deposition chamber, and Bphen was vacuum-deposited thereon to form an electron-transporting layer 16 with a thickness of 40 nm.
Then, a cathode electrode (metal electrode 11) having the following structure was formed.
Metal electrode layer 1 (thickness: 15 nm): AlLi alloy (Li content: 1.8% by weight)
Metal electrode layer 2 (thickness: 100 nm): Al
Characteristics of Devices
Characteristics of the device were evaluated by applying DC voltage to the metal electrode 11 as the negative side and the transparent electrode 14 as the positive side.
As for voltage-current characteristic, good rectification was exhibited. Luminescence spectrum and luminescence intensity were measured with spectrometers SR1 and BM7 manufactured by TOPCON Corporation. A current value at the time of voltage application was measured with 4140Bd manufactured by Hewlett-Packard Corporation. Luminescence efficiency cd/A was calculated based on luminescence intensity and the measured current value. The results are shown in Table 9.










TABLE 9








Luminescence





wavelength
300 cd
600 cd












Example
(nm)
cd/A
lm/w
cd/A
Lm/W















1
535
20.7
10.1
18.1
9.2


2
535
24.9
17.8
21.4
14.5


3
540
11.5
5.2
10.1
4.3









The device exhibited excellent luminescence at 300 and 600 cd/cm2.
In Example 1, the external quantum efficiency was 7.5% and highly efficient luminescent device was obtained taking advantage of luminescence through a triplet excited state. Further, the devices of Examples 1 and 2 were energized for 100 hours for luminescence. It was confirmed that stable luminescence was obtained at that time.
Example 4
Using the same synthesis method as shown in Production Example 1, Exemplary compound 1078 was synthesized based on the following synthesis scheme. After the reaction between a ligand and CuCl, sublimation purification was carried out to obtain a compound in a synthesis yield of 10%. To identify the compound, elemental analysis and X-ray crystal analysis were employed. FIG. 3 shows a luminescence spectrum of the compound of this example in a solid state. A strong orange luminescence was observed from the compound, which had a peak wavelength at 577 nm and a half-value width of 91 nm.




Example 5
Exemplary compound 1007 was synthesized based on the following synthesis scheme.
To a 300-ml reaction vessel, diisopropylamine (14 ml, 99 mmol) and diethylether (100 ml) were fed and cooled down to −40° C. To this mixture solution, n-butyllithium in 2.44 M hexane solution (41 ml, 99 mmol) was added dropwise. The mixture solution was warmed to 0° C. while stirring, and then cooled down to −78° C. Then, 2-fluoro-6-methyl pyridine (5.0 g, 45 mmol) was added thereto. After stirring for 15 minutes, trimethylsilyl chloride (12.6 ml, 99 mmol) was slowly added dropwise. Thereafter, the resultant solution was warmed and stirred at room temperature for 18 hours. To this mixture solution, water and further hexane (150 ml) were added, and the mixture was separated to an organic layer and an aqueous layer. Then, the aqueous layer was extracted with hexane for collecting the organic layer. The collected organic layer was washed with saturated saline and dried on MgSO4. This solution was concentrated to obtain a light brown liquid of ligand.
The synthesis method for obtaining a copper coordination compound is the same as in Production Example 1 of reaction between a ligand and CuCl. The reaction between the ligand and CuCl is followed by sublimation purification to obtain the compound in a synthesis yield of 20%. To identify the compound, elemental analysis and X-ray crystal analysis were employed.




FIG. 4 shows a luminescence spectrum of the compound of this example in a solid state. A strong green luminescence was observed from the compound, which had a peak wavelength at 504 nm and a half-value width of 55 nm.
Example 6
Exemplary compound 3002 as the metal coordination compound was synthesized based on the following synthesis scheme. A ligand was obtained by reaction between trimethylsilyl diphenylphosphine and 1-iodine-2-bromobenzene in the presence of palladium catalyst in a benzene solvent. The method for obtaining a copper coordination compound was the same as in Production Example 1 of reaction between a ligand and CuCl. The reaction between the ligand and CuCl was carried out to obtain the compound in a synthesis yield of 12%. To identify the compound, elemental analysis and X-ray crystal analysis were employed.




FIG. 5 shows a luminescence spectrum of the compound of this example in a solid state. A red luminescence was observed from the compound, which had a peak wavelength of 705 nm.
Examples 7 and 8
In Examples 7 and 8, the device having the same device structure as in Example 2 was produced except for a luminescent layer. These examples employed the same Exemplary compound 1001 as a luminescent dopant as in Example 2, but the concentration thereof was changed so that the device of Example 7 had a luminescent layer with 50% concentration of the Exemplary compound 1001 and 50% concentration of CBP and the device of Example 8 had a luminescent layer with 100% concentration of the Exemplary compound 1001. The thickness of the luminescent layer was 20 nm.
After the production of the devices, characteristics of the devices were evaluated. The results thereof are shown in the following table, which shows the efficiency at 60.0 cd/m2 of luminance.











TABLE 10







Luminescence wavelength (nm)
cd/A
1m/W



















Example 7
540
19.3
13.2


Example 8
550
19.0
12.0









As shown above, these Examples exhibited an efficiency comparable with Example 2 wherein the concentration of the Exemplary compound 1001 in the luminescent layer was 10%. Thus, it is understood that Exemplary compound 1001 is a luminescent material that prevents concentration quenching, that is no decrease of efficiency, even when the concentration thereof is high. Further, stable luminescence was exhibited even when continuous luminescence was performed at 300 cd/m2.
Examples 9, 10 and 11
In Examples 9 to 11, the devices having the same structure as in Examples 1 and 2 except that Exemplary compound 1007 was used as a luminescent dopant. In the luminescent layer, the Exemplary compound 1007 had a concentration of 10% by weight, and the thicknesses of the luminescent layer were 40 nm (Example 9) and 20 nm (Example 10). Further, the luminescent layer of Example 11 had a thickness of 20 nm and was composed of only Exemplary compound 1007 without CBP.











TABLE 11







Luminescence wavelength (nm)
cd/A
lm/W



















Example 9
505
10.2
6.8


Example 10
505
15.0
11.0


Example 11
515
12.0
8.2









As shown above, the device using the Exemplary compound 1007 exhibited high luminescence efficiency. It is understood that the Exemplary compound 1007 is an excellent luminescent dopant. Further, the device of Example 11 having the luminescent layer of 100% Exemplary compound 1007 exhibited good efficiency. It is thus understood that the Exemplary compound 1007 is a luminescent material that prevents concentration quenching. Stable luminescence was exhibited even when continuous luminescence was performed at 300 cd/m2.
Example 12
In Example 12, the device having the same device structure as in Example 3, except that Exemplary compound 1176 synthesized in Production Example 3 was used instead of Exemplary compound 1001.











TABLE 12







Luminescence wavelength (nm)
cd/A
lm/W



















Example 12
520
4.3
2.0









High luminescence efficiency was confirmed and also stable luminescence was exhibited even when continuous luminescence was performed at 300 cd/m2.
This application claims priority from Japanese Patent Application Nos. 2003-401821 filed on Dec. 1, 2003 and 2004-298501 filed on Oct. 13, 2004, which are hereby incorporated by reference herein.

## Claims

1. A luminescent device comprising:
a pair of electrodes consisting of a first electrode and a second electrode, a luminescent layer having an organic compound disposed between said pair of electrodes, a first organic compound layer between said first electrode and said luminescent layer and a second organic compound layer between said second electrode and said luminescent layer,
wherein said luminescent layer has a host material and a guest material, said guest material being a copper coordination compound represented by the following