Luminescent device with a triarylamine compound

Abstract

A luminescent device having a pair of electrodes and a luminescent layer disposed between the electrodes. The luminescent layer comprises a compound represented by the following general formula: 1

Description

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a novel triarylamine compound and to a charge-injection-type luminescent device using the same. In particular, the present invention relates to a triarylamine compound applicable to a charge-injection-type luminescent device which directly converts injected charges into optical energy by an applied electric field, and relates to a luminescent device using the same.

[0004] 2. Description of the Related Art

[0005] Pope et al., first discovered electroluminescence (EL) in an organic material, that is, single-crystal anthracene in 1963 (J. Chem. Phys., 38, 2042 (1963)). Subsequently, Helfinch and Schneider observed relatively strong EL in an injection EL material containing a solution system having a high injection efficiency in 1965 (Phys. Rev. Lett., 14, 229 (1965)).

[0006] Many studies of organic luminescent materials containing conjugated organic hosts and conjugated organic activators having condensed benzene rings have been disclosed in U.S. Pat. Nos. 3,172,862, 3,173,050, and 3,710,167; J. Chem. Phys., 44, 2902 (1966); J. Chem. Phys., 58, 1542 (1973); and Chem. Phys. Lett., 36, 345 (1975). Examples of disclosed organic hosts include naphthalene, anthracene, phenanthrene, tetracene, pyrene, benzpyrene, chrysene, picene, carbazole, fluorene, biphenyl, terphenyl, triphenylene oxide, dihalobiphenyl, trans-stilbene, and 1,4-diphenylbutadiene. Examples of disclosed activators include anthracene, tetracene and pentacene. Since these organic luminescent materials are provided as single layers having a thickness of more than 1 μm, a high electric field is required for luminescence. Under these circumstances, thin film devices formed by a vacuum deposition process have been proposed (for example, “Thin Solid Films” p. 94 (1982); Polymer, 24, 748 (1983); and J. Appl. Phys., 25, L773 (1986)). Although the thin film devices are effective for reducing the driving voltage, their luminance is far from levels for practical use.

[0007] In recent years, Tang, et al., have developed an EL device having a high luminance at a low driving voltage (Appl. Phys. Lett., 51, 913 (1987) and U.S. Pat. No. 4,356,429). The EL device is fabricated by depositing two significantly thin layers, that is, a charge transport layer and a luminescent layer, between the anode and the cathode by a vacuum deposition process. Such layered organic EL devices are disclosed in, for example, Japanese Patent Application Laid-Open Nos. 59-194393, 59-194393, 63-264692, and 3-163188, U.S. Pat. Nos. 4,539,507 and 4,720,432, and Appl. Phys. Lett., 55, 1467 (1989).

[0008] Also, an EL device of a triple-layered structure having independently a carrier transport function and a luminescent ability was disclosed in Jpn. J. Apply. Phys., 27, L269 and L713 (1988). Since the carrier transportability is improved in such an EL device, the versatility of possible dyes in the luminescent layer is considerably increased. Further, the device configuration suggests feasibility of improved luminescence by effectively trapping holes and electrons (or excimers) in the central luminescent layer.

[0009] Layered organic EL devices are generally formed by vacuum deposition processes. EL devices having considerable luminance are also formed by casting processes (as described in, for example, Extended Abstracts (The 50th Autumn Meeting (1989), p. 1006 and The 51st Autumn Meeting (1990), p. 1041; The Japan Society of Applied Physics). Considerably high luminance is also achieved by a single-layered mixture-type EL device, in which the layer is formed by immersion-coating a solution containing polyvinyl carbazole as a hole transport compound, an oxadiazole derivative as an electron transport compound and coumarin-6 as a luminescent material, as described in Extended Abstracts of the 38th Spring Meeting 1991, p. 1086; The Japan Society of Applied Physics and Related Societies.

[0010] As described above, the organic EL devices have been significantly improved and have suggested the feasibility of a wide variety of applications; however, these EL devices have some problems in practical use, for example, insufficient luminance, changes in luminance during prolonged use, and deterioration by atmospheric gas containing oxygen and humidity. Further, the EL devices do not sufficiently satisfy needs for diverse wavelengths of luminescent light for precisely determining luminescent hues of blue, green and red colors in full-color displays, etc.

SUMMARY OF THE INVENTION

[0011] It is an object of the present invention to provide an organic compound applicable to a luminescent device having an optical output with significantly high efficiency and luminance.

[0012] It is another object of the present invention to provide an organic compound applicable to a luminescent device, which has diverse luminescent wavelengths, a variety of luminescent hues, and significantly high durability.

[0013] It is a further object of the present invention to provide a luminescent device easily produced at relatively low production cost and is highly safe.

[0014] An aspect of the present invention is a triarylamine compound represented by the following general formula [1]: 2

[0015] wherein R1 and R2 are each independently a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, or a substituted or unsubstituted aryl group; Ar1, Ar2, Ar3, and Ar4 are each a substituted or unsubstituted aryl or heterocyclic group, which may be the same or different from each other; and at least one of Ar1, Ar2, Ar3, and Ar4 is a fused aromatic ring.

[0016] Another aspect of the present invention is a triarylamine compound represented by the following general formula [2]: 3

[0017] wherein R3 and R4 are each independently a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, or a substituted or unsubstituted aryl group; Ar5, Ar6, Ar7, and Ar8 are each a substituted or unsubstituted aryl or heterocyclic group, which may be the same or different from each other; and at least one of Ar5, Ar6, Ar7, and Ar8 is a π-conjugated aromatic hydrocarbon having 12 or more carbon atoms.

[0018] A further aspect of the present invention is a luminescent device comprising a pair of electrodes, and at least one compound among the compounds represented by the general formulae [1] or [2] disposed therebetween.

[0019] The organic luminescent device in accordance with the present invention is a thin lightweight solid device having a large area and high resolution and capable of high-speed operation, unlike conventional incandescent lamps, fluorescent lamps, and inorganic luminescent diodes, and thus satisfies advanced requirements.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG. 1 is a cross-sectional view of an embodiment of a luminescent device in accordance with the present invention;

[0021] FIG. 2 is a cross-sectional view of another embodiment of a luminescent device in accordance with the present invention;

[0022] FIG. 3 is a cross-sectional view of a further embodiment of a luminescent device in accordance with the present invention;

[0023] FIG. 4 is a cross-sectional view of a luminescent device in accordance with Example 7 of the present invention; and

[0024] FIG. 5 is an infrared spectrum of an organic compound in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0025] The present invention is characterized by a novel triarylamine compound represented by the general formula [1] or [2]: 4

[0026] In the general formula [1], R1 and R2 are each independently a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, or a substituted or unsubstituted aryl group.

[0027] Examples of alkyl groups include methyl, ethyl, n-propyl, and isopropyl groups; examples of alkoxy groups include methoxy, ethoxy, and phenoxy groups; and examples of aryl groups include phenyl, biphenyl, and naphthyl groups.

[0028] Examples of the substituent groups include halogen atoms, e.g., fluorine, chlorine, bromine, and iodine; alkyl groups, e.g., methyl, ethyl, n-propyl, and iso-propyl groups; alkoxy groups, e.g., methoxy, ethoxy, and phenoxy groups; aralkyl groups, e.g., benzyl, phenetyl, and propylphenyl group; a nitro group; a cyano group; substituted amino groups, e.g., dimethyl amino, dibenzylamino, diphenylamino, and morpholino groups; aryl groups, e.g., phenyl, tolyl, biphenyl, naphthyl, anthryl, and pyrenyl groups; and heterocyclic groups, e.g., pyridyl, thienyl, furyl, quinolyl, and carbazolyl groups.

[0029] In the general formula [1], Ar1, Ar2, Ar3, and Ar4 are each a substituted or unsubstituted aryl or heterocyclic group, which may be the same or different from each other. Examples of the substituted or unsubstituted aryl groups include phenyl, biphenyl, terphenyl, naphthyl, anthryl, and fluorenyl. Examples of the substituted or unsubstituted heterocyclic groups include pyridyl, furyl, thienyl, and carbazolyl groups.

[0030] At least one of Ar1, Ar2, Ar3, and Ar4 is a fused aromatic ring. Examples of the fused aromatic rings include naphthyl, anthryl, acenaphthyl, phenanthryl, naphthanyl, and fluoranthenyl rings. These fused aromatic rings may have substituent groups. Examples of the substituent groups include halogen atoms, e.g., fluorine, chlorine, bromine, and iodine; alkyl groups, e.g. methyl, ethyl, n-propyl, and iso-propyl groups; alkoxy groups, e.g., methoxy, ethoxy, and phenoxy groups; aralkyl groups, e.g., benzyl, phenetyl, and propylphenyl group; a nitro group; a cyano group; substituted amino groups, e.g., dimethyl amino, dibenzylamino, diphenylamino, and morpholino groups; aryl groups, e.g., phenyl, tolyl, biphenyl, naphthyl, anthryl, and pyrenyl groups; and heterocyclic groups, e.g., pyridyl, thienyl, furyl, quinolyl, and carbazolyl groups. 5

[0031] In the general formula [2], R3 and R4 are the same as R and R2, respectively, in the general formula [1], and Ar5, Ar6, Ar7, and Ar8 are the same as Ar1, Ar2, Ar3, and Ar4, respectively, in the general formula [1]. At least one of Ar5, Ar6, Ar7, and Ar8 is a π-conjugated aromatic hydrocarbon having 12 or more carbon atoms. Examples of the π-conjugated aromatic hydrocarbon having 12 or more carbon atoms include polyphenyls, i.e., biphenyl, p-terphenyl, and quaterphenyl; and stilbene derivatives, i.e., styryl and phenylstyryl.

[0032] The following are typical non-limiting examples of the compounds represented by the general formula [1] or [2].

[0033] Compounds represented by the general formula [1]

Compound			Ar1	Ar2
No.	R1	R2	Ar3	Ar4
1	—H	—H	6	7
			8	9
2	—H	—H	10	11
			12	13
3	—H	—H	14	15
			16	17
4	—H	—H	18	19
			20	21
5	—H	—H	22	23
			24	25
6	—H	—H	26	27
			28	29
7	—H	—H	30	31
			32	33
8	—H	—CH3	34	35
			36	37
9	—H	38	39	40
			41	42
10	—H	—Br	43	44
			45	46
11	—CH3	—CH3	47	48
			49	50
12	—CH3	—CH3	51	52
			53	54
13	—CH3	—CH3	55	56
			57	58
14	—CH3	—CH3	59	60
			61	62
15	—CH3	—CH3	63	64
			65	66
16	—CH3	—CH3	67	68
			69	70
17	—CH3	—CH3	71	72
			73	74
18	—CH3	—CH3	75	76
			77	78
19	—CH3	—CH3	79	80
			81	82
20	—CH3	—CH3	83	84
			85	86
21	—CH3	—CH3	87	88
			89	90
22	—CH3	—CH3	91	92
			93	94
23	—CH3	—CH3	95	96
			97	98
24	—CH3	—CH3	99	100
			101	102
25	—CH3	—CH3	103	104
			105	106
26	—CH3	—CH3	107	108
			109	110
27	—CH3	—CH3	111	112
			113	114
28	—CH3	—CH3	115	116
			117	118
29	—CH3	—CH3	119	120
			121	122
30	—CH3	—CH3	123	124
			125	126
31	—C2H5	—C2H5	127	128
			129	130
32	—C2H5	—C2H5	131	132
			133	134
33	—C2H5	—C2H5	135	136
			137	138
34	—C2H5	—C2H5	139	140
			141	142
35	—C2H5	—C2H5	143	144
			145	146
36	—C2H5	—C2H5	147	148
			149	150
37	—C3H7	—CH3	151	152
			153	154
38	—C3H7	155	156	157
			158	159
39	—C4H9	—C4H9	160	161
			162	163
40	—C4H9	—C4H9	164	165
			166	167
41	—C4H8	—C4H8	168	169
	OCH3	OCH3	170	171
42	—C8H17	—C8H17	172	173
			174	175
43	—C8H17	—C8H17	176	177
			178	179
44	—C8H17	—C8H17	180	181
			182	183
45	—C18H37	—C18H37	184	185
			186	187

[0034] Compounds represented by the general formula [2]

Com-
pound			Ar5	Ar6
No.	R3	R4	Ar7	Ar8
46	—C2H5	—C2H5	188	189
			190	191
47	—C2H5	—C2H5	192	193
			194	195
48	—C2H5	—C2H5	196	197
			198	199
49	—C2H5	—C2H5	200	201
			202	203
50	—C2H5	—C2H5	204	205
			206	207
51	—C3H7	—C3H7	208	209
			210	211
52	—CH3	—C3H7	212	213
			214	215
53	—C3H7	216	217	218
			219	220
54	—C4H9	—C4H9	221	222
			223	224
55	—C4H9	—C4H9	225	226
			227	228
56	229	230	231	232
			233	234
57	—C8H17	—C8H17	235	236
			237	238
58	—C8H17	—C8H17	239	240
			241	242
59	—C8H17	—C8H17	243	244
			245	246
60	—C18H37	—C18H37	247	248
			249	250
61	—CH3	—CH3	251	252
			253	254
62	—CH3	—CH3	255	256
			257	258
63	—CH3	—CH3	259	260
			261	262
64	—CH3	—CH3	263	264
			265	266
65	—CH3	—CH3	267	268
			269	270
66	—CH3	—CH3	271	272
			273	274
67	—CH3	—CH3	275	276
			277	278
68	—CH3	—CH3	279	280
			281	282
69	—CH3	—CH3	283	284
			285	286
70	—CH3	—CH3	287	288
			289	290
71	—CH3	—CH3	291	292
			293	294
72	—CH3	—CH3	295	296
			297	298
73	—CH3	—CH3	299	300
			301	302
74	—CH3	—CH3	303	304
			305	306
75	—CH3	—CH3	307	308
			309	310
76	—H	—H	311	312
			313	314
77	—H	—H	315	316
			317	318
78	—H	—H	319	320
			321	322
79	—H	—H	323	324
			325	326
80	—H	—H	327	328
			329	330
81	—H	—H	331	332
			333	334
82	—H	—CH3	335	336
			337	338
83	—H	—C3H7	339	340
			341	342
84	—H	343	344	345
			346	347
85	—H	—Br	348	349
			350	351
86	—CH3	—CH3	352	353
			354	355
87	—CH3	—CH3	356	357
			358	359
88	—CH3	—CH3	360	361
			362	363
89	—CH3	—C3H7	364	365
			366	367
90	—CH3	—C3H7	368	369
			370	371

[0035] The luminescent device in accordance with the present invention has a layer or a plurality of layers composed of an organic compound disposed between an anode and a cathode, and at least one layer among the above organic layers contains a compound represented by the general formula [1] or [2].

[0036] The layer of the organic compound represented by the general formula [1] or [2] is formed between the anode and the cathode by a vacuum deposition process or a solution coating process. The thickness of the organic layer is preferably 2 μm or less, and more preferably 0.5 μm or less, and most preferably 0.05 to 0.5 μm.

[0037] The present invention will now be described in further detail with reference to the drawings.

[0038] FIG. 1 is a schematic cross-sectional view of an embodiment of the luminescent device in accordance with the present invention. An anode 2, a luminescent layer 3 and a cathode 4 are formed on a substrate 1, in that order. In such a configuration, a usable luminescent layer 3 is generally composed of a single compound having hole transportability, electron transportability and luminescence, or a mixture of compounds each having one of these properties.

[0039] FIG. 2 is a schematic cross-sectional view of another embodiment of the luminescent device in accordance with the present invention. An anode 2, a hole transport layer 5, an electron transport layer 6 and a cathode 4 are formed on a substrate 1, in that order. The hole transport layer 5 and the electron transport layer 6 function as a luminescent layer 3. In such a configuration, a usable hole transport layer 5 is generally composed of a luminescent material having hole transportability or a mixture including such a material and a non-luminescent material having hole transportability. The luminescent and non-luminescent materials may also have electron transportability. The electron transport layer 6 may be composed of a luminescent material having electron transportability or a mixture including such a material and a non-luminescent material having electron transportability. The luminescent and non-luminescent materials may also have hole transportability.

[0040] FIG. 3 is a schematic cross-sectional view of a further embodiment of the luminescent device in accordance with the present invention. An anode 2, a hole transport layer 5, a luminescent layer 3, an electron transport layer 6 and a cathode 4 are formed on a substrate 1 in that order. In this configuration, carrier transport and luminescence are performed in the individual layers. Such a configuration permits a wide variety of combinations of a material having excellent hole transportability, a material having excellent electron transportability and a material having excellent luminescence. Further, the configuration permits the use of various compounds emitting light at different wavelengths; hence the hue of the luminescent light can be controlled over a wide range. Effective trap of holes and electrons (or excimers) in the central luminescent layer will increase the luminescent efficiency.

[0041] FIG. 4 is a cross-sectional view of another luminescent device in accordance with the present invention. An anode 2, a hole injection-transport layer 7, a hole transport layer 5, an electron transport layer 6, and a cathode 4 are formed on a substrate 1, in that order. The hole injection-transport layer 7 facilitates hole injection from the anode 2. Thus, the luminescent device can maintain high efficiency for long driving times. In such a configuration, the hole transport layer 5 and/or the electron transport layer 6 function as a luminescent layer.

[0042] The compounds represented by the general formulae [1] and [2] have significantly superior luminescent characteristics to conventional compounds and can be used in all the electric field luminescent devices shown in FIGS. 1 to 4.

[0043] The compounds represented by the general formulae [1] and [2] have hole transportability and/or electron transportability depending on the structures thereof. In all the embodiments shown in FIGS. 1 to 4, the compounds represented by the general formula [1] may be used alone or in combination, and the compounds represented by the general formula [2] may also be used alone or in combination. Alternatively, the compounds represented by the general formulae [1] and [2] may be used in combination.

[0044] As components of the luminescent layer in the luminescent device in accordance with the present invention, hole transport materials studied in the field of electrophotographic photosensitive members and known luminescent hole transport compounds as shown in Tables 1 to 5 or electron transport compounds and known luminescent electron transport materials as shown in Table 6 to 9 can be used with the compounds represented by the general formulae [1] and [2]. These compounds are used alone or in combination.

[0045] Table 10 illustrates examples of dopant dyes. The addition of a trace amount of dopant dye in the luminescent layer will significantly increase the luminescent efficiency or will change the luminescent color.

TABLE 1
Hole Transport Compounds
372
373
374
375
376
377

[0046]

TABLE 2
Hole Transport Compounds
378
379
380
381
382

[0047]

TABLE 3
Hole Transport Compounds
383

[0048]

TABLE 4
Hole Transport Compounds
384
385
386
387
388
389
390

[0049]

TABLE 5
Hole Transport Compounds
391
392

[0050]

TABLE 6
Electron Transport Compounds
393           394
M: Al, Ga     M: Zn, Mg, Be
395           396
M: Zn, Mg, Be M: Zn, Mg, Be

[0051]

TABLE 7
Electron Transport Compounds
397
398
399
400

[0052]

TABLE 8
Electron Transport Compounds
401
402
403
404

[0053]

TABLE 9
Electron Transport Compounds
405
406
407
408
409
410

[0054]

TABLE 10
Dopant Dyes
411 412
413 414
415 416
417

[0055] In the luminescent device in accordance with the present invention, the luminescent layer containing the compounds represented by the general formulae [1] and [2] and the other organic layer are generally formed by a vacuum deposition process or using a binding resin.

[0056] Non-limiting examples of the binding resins include polyvinyl carbazole resins, polycarbonate resins, polyester resins, polyarylate resins, butyral resins, polystyrene resins, polyvinyl acetal resins, diallyl phthalate resins, acrylic resins, methacrylic resins, phenol resins, epoxy resins, silicon resins, polysulfone resins, and urea resins. These binding resins can be used alone or in combination.

[0057] Preferable anode materials have large work functions. Examples of such materials include nickel, gold, platinum, palladium, selenium, rhenium, and iridium; alloys thereof; and tin oxide, indium tin oxide, and copper iodide. Conductive polymers, such as poly(3-methylthiophene), polyphenylene sulfide and polypyrrole are also usable.

[0058] In contrast, preferable cathode materials have small work functions. Examples of such materials include silver, lead, tin, magnesium, aluminum, calcium, manganese, indium and chromium, and alloys thereof.

[0059] It is preferable that at least one electrode of the anode and cathode transmits 50% or more of incident light over the wavelength region of the luminescent light.

[0060] As the transparent substrate, glass and plastic films are used in the present invention.

EXAMPLES

[0061] The present invention is described in further detail with reference to the following examples.

[0062] Synthesis of N,N,N′,N′-tetra-(1-naphthyl)-2,7-diamino-9,9-dimethylfluorene (Compound 13)

[0063] Into a 100-ml egg-plant type flask, 2.24 g (10 mmol) of 2,7-diamino-9,9-dimethylfluorene, 15.22 g (160 mmol) of 1-iodonaphthalene, 6.91 g(50 mmol) of potassium carbonate, 12.71 g (200 mmol) of powdered copper, and 50 ml of o-dichlorobenzene were fed, and the mixture was refluxed with stirring for 24 hours.

[0064] The reactant solution was cooled and then filtered, and the filtrate was concentrated under reduced pressure. Into the concentrated solution, 35 ml of acetone was added and then filtered to collect precipitated crude crystal. The crude crystal was purified through a silica gel column using a toluene-hexane mixture, and 6.13 g (yield: 84.1%) of pale yellow fine crystal N,N,N′,N′-tetra-(1-naphthyl)-2,7-diamino-9,9-dimethylfluorene (Compound 13) was prepared.

[0065] The melting point (Tm) and the glass transition temperature (Tg) of the resulting compound were 331.0 to 332.7° C. and 169° C., respectively, according to differential scanning calorimetry using Pyris 1 by Perkin Elmer Corporation. FIG. 5 is an IR spectrum of the compound by a KBr tablet method using an FT-IR spectrophotometer (FT-IR-420) by JASCO.

Example 1

[0066] An indium tin oxide (ITO) film with a thickness of 100 nm was formed on a glass substrate by a sputtering process. After the transparent substrate was cleaned, a layer of Compound 12 with a thickness of 65 nm was deposited thereon at a deposition rate of 0.2 to 0.3 nm/sec. Then, a 65 nm thick aluminum quinolinol film was formed. Thereafter, a Mg—Ag metallic electrode having an atomic ratio of Mg:Ag=10:1 was formed by a vacuum deposition process at a deposition rate of 2.0 nm/sec under a vacuum pressure of 3 to 4×10−6 torr. A luminescent device was thereby formed.

[0067] A direct current of 10 V was applied between the ITO anode and the Mg—Ag cathode of the luminescent device. A current flow of 175 mA/cm2 and a green luminescence with a luminance of 5,300 cd/m2 were observed. A voltage with a current density of 3.0 mA/cm2 was applied to the sample for 100 hours. The luminance was 160 cd/m2 at the start and changed to 140 cd/m2 at the end.

Examples 2 to 6

[0068] Luminescent devices were prepared as in EXAMPLE 1 using Compounds 21, 36, 47, 72 and 88 instead of Compound 12. Table 11 shows the characteristics of these luminescent devices.

	TABLE 11
	Initial	After 100 hours
		Applied		Applied
	Com-	Voltage	Luminance	Voltage	Luminance
EXAMPLE	pound	(V)	(cd/m2)	(V)	(cd/m2)
2	21	5.3	350	5.9	345
3	36	6.7	275	7.8	280
4	47	4.8	345	5.7	330
5	72	4.9	550	5.5	530
6	88	5.7	450	3.8	450

Comparative Example 1

[0069] A luminescent device was prepared as in EXAMPLE 1 using the following compound instead of Compound 12. 418

[0070] A direct current of 15 V was applied between the ITO anode and the Mg—Ag cathode of the luminescent device. A current flow of 15 mA/cm2 and a green luminescence with a luminance of 35 cd/m2 were observed. A voltage with a current density of 27 mA/cm2 was applied to the sample for 100 hours. The luminance was 100 cd/m2 at the start and decreased to 8 cd/m2 at the end.

[0071] The results of EXAMPLES 1 to 6 and COMPARATIVE EXAMPLE 1 show that the compounds in accordance with the present invention have high luminance and prolonged life compared to the comparative amine compound.

Example 7

[0072] A luminescent device shown in FIG. 4 was prepared as follows. An indium tin oxide (ITO) anode 2 with a thickness of 100 nm was formed on a glass substrate by a sputtering process. After the transparent substrate was cleaned, a m-MTDATA hole injection-transport layer 7 with a thickness of 20 nm was formed thereon, and a layer of Compound 32 with a thickness of 50 nm was deposited thereon as a hole transport layer 5. Furthermore, an electron transport layer of an electron transport compound (Alq3) with a thickness of 65 nm was formed thereon, and then an aluminum cathode 4 with a thickness of 140 nm was formed thereon. 419

[0073] A direct current of 5 V was applied between the ITO anode and the aluminum cathode of the luminescent device. A current flow of 10 mA/cm2 and a green luminescence with a luminance of 576 cd/m2 were observed. A voltage with a current density of 3.0 mA/cm2 was applied to the sample for 100 hours. The luminance was 265 cd/m2 at the start and slightly changed to 250 cd/m2 at the end.

[0074] As described above, luminescent devices using compounds represented by the general formulae [1] and [2] in accordance with the present invention have significantly high luminance for a low applied-voltage, and high durability. A large device can be readily formed by a vacuum deposition process or a casting process with relatively low production costs.

[0075] While the present invention has been described with reference to what are presently considered to be the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. On the contrary, the invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

1. A luminescent device comprising a pair of electrodes and a luminescent layer disposed therebetween, the luminescent layer comprising a compound represented by the following general formula (1):

2. The luminescent device according to claim 1, wherein at least one of Ar1, Ar2, Ar3, and Ar4 is selected from the group of a naphthyl group and an anthryl group.

3. The luminescent device according to claim 1, wherein the thickness of the luminescent layer is less than 2 μm.

4. The luminescent device according to claim 3, wherein the thickness of the luminescent layer is in a range of 0.05 to 0.5 μm.

5. The luminescent device according to claim 1, wherein neither R1 nor R2 is a hydrogen.

6. The luminescent device according to claim 1, wherein the luminescent layer comprises a compound of formula (12):

6. The luminescent device according to claim 1, wherein the luminescent layer comprises a compound of formula (13):

7. A luminescent device comprising a pair of electrodes and a luminescent layer disposed therebetween, the luminescent layer comprises a compound represented by the following general formula (1) and a compound represented by the following general formula (2):