JPH07310071A - Electroluminescent element - Google Patents

Abstract

PURPOSE:To obtain an electroluminescent element which has a layer containing a specific compound, thus is excellent in luminescent intensity and durability and useful as a planer light source and a flat display with practically adequate durability. CONSTITUTION:This element has a layer containing at least one selected from compounds of formulas I and II [R1-R4 are an alkoxy, an aralkyl, a dialkylamino, an alkyl of 1-6 carbon atoms, an aryl of 6-20 carbon atoms, a halogen, nitro, cyano, H; R1 and R2, R3 and R4 bond to each other to form an aromatic ring; X, Y are O, S, or NR5 (R5 is an alkyl of 1-6 carbon atoms, an.aryl of 6-20 carbon atoms, H)]. The element preferably is composed of a pair of opposite electrodes and said layer, and said compound is used as a luminescent substance and/or an electron injection compound.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescence device, and more particularly to an organic electroluminescence device used for flat light sources, flat displays and the like.

[0002]

2. Description of the Related Art Organic electroluminescent devices are
It is usually composed of a pair of counter electrodes and an organic light emitting layer sandwiched between them. The emitted light is recombined in the light emitting layer due to the electrons injected from one electrode and the holes injected from the other electrode, the light emitter is excited to a higher energy level, and the emitted light is excited. It is thought to be due to the fact that energy is emitted as light when the body returns to the ground state.
Since such a carrier injection type electroluminescence device has started to use an organic compound thin film, a device having a high light emission intensity has been obtained. For example, U.S. Pat. No. 3,530,325 uses a single crystal anthracene or the like as a light emitting body, and JP-A-59-194393 discloses a combination of a hole injection layer and an organic light emitting layer. No. 63-295695 is a combination of a hole injecting and transporting layer and an organic electron injecting and transporting layer, which is described in Jpn.
Physics, vol127, No.2, p269-271 describes the combination of a hole transfer layer, a light emitting layer, and an electron transfer layer, respectively, and these have improved the emission intensity.

However, these electroluminescent elements have a problem in durability and have not yet reached a practical level of emission intensity and durability.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to provide an organic electroluminescence device having a higher emission intensity and a higher durability and a practical level.

[0005]

The above object of the present invention is to provide an electroluminescence device having a layer containing at least one selected from the compounds represented by the general formulas [1] and [2]. , An electroluminescent device having a pair of counter electrodes and a layer sandwiched between them and containing at least one selected from compounds represented by the general formulas [1] and [2], the general formula [1] or [2] Using a compound represented by the formula
Alternatively, the compound represented by [2] is used as an electron injecting compound.

The present invention will be described in detail below.

R _{1 to} R ₄ in the general formulas [1] and [2]
The alkyl group having 1 to 6 carbon atoms represented by is a methyl group,
Substituted or unsubstituted ethyl group, propyl group, butyl group, trifluoromethyl group or the like, alkoxy group such as methoxy group, ethoxy group, propoxy group, butoxy group or the like, substituted or unsubstituted group, aralkyl group Substituted or unsubstituted such as benzyl group, substituted or unsubstituted such as phenyl group, naphthyl group, anthryl group, biphenyl group as aryl group having 6 to 20 carbon atoms, dimethylamino group as dialkylamino group , Diethylamino group and the like.

Specific examples of the compounds represented by the above general formula are shown below, but the present invention is not limited thereto.

[0009]

[Chemical 2]

[0010]

[Chemical 3]

[0011]

[Chemical 4]

[0012]

[Chemical 5]

[0013]

[Chemical 6]

[0014]

[Chemical 7]

[0015]

[Chemical 8]

[0016]

[Chemical 9]

[0017]

[Chemical 10]

[0018]

[Chemical 11]

[0019]

[Chemical 12]

[0020]

[Chemical 13]

The electroluminescence device of the present invention can take various modes, but basically it is composed of a light emitting layer and a pair of counter electrodes sandwiching the layer, and the substrate / anode / light emitting layer / cathode, substrate / Anode / hole injection layer / light emitting layer /
Examples include cathodes, substrates / anode / emission layers / electron injection layers / cathodes, substrates / anode / hole injection layers / emission layers / electron injection layers / cathodes, but the present invention is not limited to these. A plurality of light emitting layers, hole injection layers, and electron injection layers may be provided, or a combination of hole injection layers / light emitting layers, light emitting layers / electron injection layers, hole injection layers / light emitting layers may be repeatedly stacked, or light emitting layers and A mixed layer of an electron injecting material and a light emitting material is provided between the electron injecting layer, a mixed layer of a hole injecting material and a light emitting material is provided between the hole injecting layer and the light emitting layer, and other layers are provided. It may be provided.

The compound of the general formula of the present invention is preferably used in the electron injection layer or the light emitting layer.

The light emitting layer, the hole injection layer and the electron injection layer are formed by a vapor deposition method, a spin coating method, a casting method or the like, and the film thickness thereof is preferably 10 to 1000 nm, more preferably 20 to 200 n.
m.

The substrate is a glass plate such as soda glass, non-fluorescent glass, phosphoric acid glass, silicate glass, quartz, acrylic resin, styrene resin, polycarbonate resin, epoxy resin, polyethylene, polyester, silicone resin. A plastic plate made of resin or the like, a plastic film, a metal plate made of alumina or the like, a metal foil, or the like is used.

The anode preferably has a work function of more than 4 eV, such as carbon, aluminum, vanadium, iron, cobalt, nickel, chromium, copper, zinc, tungsten,
Metals such as silver, tin, platinum and gold and alloys thereof, oxides such as zinc oxide, indium oxide, ITO and NESA or complex compounds such as indium tin oxide, compounds such as copper iodide, ZnO: Al: SnO ₂ : A mixture of an oxide such as Sb and a metal, and a conductive polymer such as poly (3-methylthiophene), polypyrrole, polyaniline and the like are used. Film thickness is 10
-1000 nm is preferable, and 50-500 nm is more preferable.

The cathode preferably has a work function smaller than 4 eV, such as magnesium, calcium, sodium,
Metals such as potassium, titanium, indium, yttrium, lithium, gadolinium, ytterbium, ruthenium, manganese, aluminum, silver, tin and lead, alloys thereof, aluminum / aluminum oxide composites and the like are used. The film thickness is preferably 10 to 1000 nm, more preferably 50 to 500 nm.

When light is taken out from the electrode, at least one of the anode and the cathode is transparent or translucent with a transmittance of 10% or more, and the substrate is also transparent or transparent when only the anode has a transmittance of 10% or more. Translucency is desirable.

As the light-emitting substance used in the light-emitting layer, in addition to the compounds of the present invention, oxinoid compounds (JP-A-63-295).
No. 695, those described in JP-A Nos. 2-15595 and 2-66873, etc.), perylene compounds (“Soluble Perylen Fluorensce”).
nt Dyes with Photostability, vol.115, P2927 (198
2) '', `` Jpn. Journal of Applied Physics, vol.27, No.
2, L269 (1988) '', `` Bull.Chem.Soc.Jpn.vol.25, L411 (19
52) '', those described in European Patent No. 533,353A1, JP-A-55-36849, JP-A-2-66873, etc.), coumarin compounds (JP-A-57-51781, JP-A-2-66873, etc.) Listed in),
Azacoumarin compounds (described in JP-A-3-792, etc.), oxazole compounds (US Pat. No. 3,257,203,
JP-A-3-93763 etc.), oxadiazole compound (US Pat. No. 3,189,447, JP-A-2-216791 etc.), perinone compound (JP-A-2-88689,
2-289676, etc.), pyrrolopyrrole compounds (described in JP-A-2-296891, etc.), naphthalene compounds (described in JP-A-57-51781, JP-A-2-255789, etc.) ), Anthracene compound (JP-A-56-46234, JP-A-5-46234)
2-66873), fluorene compounds (described in JP-A-54-110837, JP-A-3-162485, etc.),
Pyrene compounds (described in JP-A-57-51781 and JP-A-3-162485), coronene compounds (described in JP-A-3-162485), quinolone compounds and azaquinolone compounds (US Pat. No. 3,180,729). No. 4,278,746, JP Sho
55-88064, JP-A-2-220394, JP-A 3-162486, etc.), stilbene compounds (US Pat. No. 4,356,429)
JP, 57-51781, 61-210363, 61-228451
No. 61, No. 61-14642, No. 61-72255, No. 62-47646, No. 62
-30255, 60-94462, 63-14965
2, those described in JP-A Nos. 1-173034 and 1-245087, etc.) and styryl compounds (JP-A 1-245087 and 2-222484).
No. 4, etc.), butadiene compounds (US Pat. No. 4,
356,429, those described in JP-A-57-51781), anthracene compounds (described in JP-A-3-178942), cyanine compounds (described in JP-A-2-66873), acridine compounds ( Those described in JP-A-57-51781), 8-
Hydroxyquinoline compound (JP-A Nos. 2-8287 and 2-8290)
No. etc.), complexes of Schiff salts with Group III metals (those described in JP-A 1-297490), oxine metal complexes (those described in JP-A 3-176993), rare earth complexes. Fluorescent substances such as those described in JP-A-1-256584 can be used.

Examples of the hole injection compound having a hole transporting ability used in the hole injection layer include triazole compounds (described in US Pat. No. 3,112,197) and oxadiazole derivatives (US Pat. No. 3,189,447). Listed)),
Imidazole derivatives (described in Japanese Examined Patent Publication No. 37-16096), polyarylalkane derivatives (US Pat. No. 3,615,40)
2, JP-B-45-555, JP-A-51-93224, 56-36656
Nos. Etc.), pyrazoline derivatives and pyrazolone derivatives (US Pat. No. 3,180,729, JP-A-55-88064,
57-45545), phenylenediamine derivatives (US Pat. No. 3,615,404, JP-B-51-10105, JP-A-54-53435, etc.), arylamine derivatives (US Pat. 4,175,961, JP-B-49-65702, JP-A-56-223437, West German Patent No. 1,110,518, etc.), oxazole derivatives (US Pat. No. 3,257,203, etc.), styrylanthracene derivatives (* Kaisho
56-46234, etc.), fluorene derivatives (described in JP-A-54-110837, etc.), hydrazone derivatives (US Pat. No. 3,717,462, JP-A-54-59143, JP-A-3).
-138654), stilbene derivatives (described in JP-A-61-210363, JP-A-1-200262, etc.),
Polyfin compound (JP-A-63-295695, JP-A-2-1295)
No. 4,127,412), aromatic tertiary amine compounds and styrylamine compounds (US Pat.
3-27033, 63-295695, JP-A-1-274154, 3-11
No. 1485 etc.), butadiene compounds (JP-A-3-
111484 etc.), polystyrene derivatives (described in JP-A-3-95291 etc.), hydrazone derivatives (described in JP-A-3-137187 etc.), triphenylmethane derivatives and tetraphenylbenzidine derivatives. (JP-A-3-
54289 etc.) etc. can be used.
Particularly preferred are porphyrin compounds, aromatic tertiary amine compounds and styrylamine compounds.

As the electron injecting compound having an electron transporting ability used in the electron injecting layer, in addition to the compound of the present invention, a nitro-substituted fluorene-derived thiopyrandioxide derivative and a diphenoquinone derivative (“Polymer Preprints, Japa”).
n, vol.37, No. 3, P681 (1988) ", those described in JP-A-3-152184, etc.), perylene tetracarboxyl derivatives (" Jp
n.Journal of Applied Physics, vol.27, No.2, L269 (198
8) ”,“ Bull. Chem. Soc. Jpn., Vol125, L411 (1952) ”and the like), anthraquinodimethane derivative (JP-A-57).
-149259, 63-104061 and the like), and a fluoronylidene methane derivative (JP-A-60-69657 and 61-14815).
No. 9, etc.), anthrone derivative (JP-A-61-22)
5151, 61-233750, etc.), oxadiazole derivatives (described in JP-A-3-79692, etc.), perinone derivatives (described in JP-A-2-289676, etc.), quinoline A compound such as a complex derivative can be used.

[0031]

The present invention will be described in detail below with reference to examples, but the embodiments of the present invention are not limited thereto.

Example 1 A substrate having a 150 nm ITO film formed on glass as an anode (N
After patterning to H-Techno Glass NA-45), ultrasonic cleaning was performed and hot air drying was performed at 120 ° C.

Next, the following compound (A-1) was added to this substrate by using a tungsten board (SF20 manufactured by Nippon Bucks Metal Co., Ltd.).
8), and a hole injection layer of about 80 nm was formed at a film formation rate of 0.2 nm / sec under a vacuum condition of 8.0 × 10 ⁻⁷ Torr.

[0034]

[Chemical 14]

Next, the exemplified compounds are maintained under the vacuum condition.
No. 58 is molybdenum board (S manufactured by Nippon Bucks Metal Co., Ltd.)
S-1-9), under vacuum condition of 8.0 × 10 ^-7 Torr, 0.2 nm / s
A light emitting layer of about 60 nm was formed at a film forming speed of ec.

On top of this, M
g: Ag (10: 1 atomic ratio alloy) was vacuum-deposited at 200 nm to form a cathode.

An external power source was connected to the obtained electroluminescent device, a DC voltage of 12 V was applied, and the maximum luminance at that time was measured. Further, continuous lighting was performed by applying a DC voltage of 12 V in a dry nitrogen gas atmosphere at a temperature of 23 ° C., and the time at which the brightness was reduced to half was measured. The results are shown in Table 1.

Examples 2 to 5 Electroluminescent devices were obtained in the same manner as in Example 1 except that the compounds shown in Table 1 were used in the light emitting layer. The characteristics are also shown in Table 1.

Comparative Example 1 Example 1 except that the following compound (B-1) was used in the light emitting layer.
Table 1 also shows the evaluation of the electroluminescence device obtained in the same manner as in.

[0040]

[Chemical 15]

[0041]

[Table 1]

Examples 6 to 10 Electroluminescent devices were prepared and evaluated in the same manner as in Example 1 except that the following compound (A-2) was used in the light emitting layer and the compounds shown in Table 2 were used in the electron injecting layer. . The results are shown in Table 2.

[0043]

[Chemical 16]

Comparative Example 2 Table 2 also shows the evaluation of the electroluminescent device obtained in the same manner as in Example 7 except that the following compound (B-2) was used in the electron injection layer.

[0045]

[Chemical 17]

[0046]

[Table 2]

Examples 11 to 15 A substrate on which ITO was formed in a thickness of 150 nm on a glass as an anode (N
After patterning to H-Techno Glass NA-45), ultrasonic cleaning was performed and hot air drying was performed at 120 ° C.

Next, the compound (A
-2) 0.03 g, and the compound shown in Table 3 as a luminescent substance.
A coating solution was prepared by dissolving 0.045 g of polymethacrylate, which had been purified twice by reprecipitation, as a binder resin, and dissolving them in 10 ml of 1,2-dichloroethane. Spin coater (1H-D3 type manufactured by Mikasa Co., Ltd.) on the above substrate with this coating solution
At 1000 rpm for 15 sec. To obtain a coating film of about 100 nm.

Further, under this vacuum condition of 8.0 × 10 ⁻⁷ Torr, Mg: Ag (alloy with 10: 1 atomic ratio) was vacuum-deposited with a thickness of 50 nm to form a cathode.

An external power supply was connected to the obtained electroluminescent device, a DC voltage of 12 V was applied, and the maximum luminance at that time was measured. In addition, continuous lighting was performed by applying a DC voltage of 12 V in a dry nitrogen gas atmosphere at a temperature of 23 ° C.
The time required for the luminance to halve was measured. The results are shown in Table 3.

[0051]

[Table 3]

[0052]

Industrial Applicability According to the present invention, an organic electroluminescence device which is excellent in light emission intensity and durability and can withstand practical use is obtained.

Claims (4)

[Claims] 1. An electroluminescent device having a layer containing at least one selected from compounds represented by the following general formulas [1] and [2]. [Chemical 1] [In the formula, R _{1 to} R ₄ are an alkoxy group, an aralkyl group, a dialkylamino group, an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 20 carbon atoms, a halogen atom, a nitro group, a cyano group or a hydrogen atom. Represents R ₁ and R ₂ , and R ₃ and R ₄ may combine to form an aromatic ring. X and Y are O, S or NR ₅
R ₅ represents an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 20 carbon atoms, or a hydrogen atom. ] 2. A pair of counter electrodes, and a layer containing at least one selected from the compounds represented by the general formulas [1] and [2] sandwiched between the pair of counter electrodes. Electroluminescent device. 3. The electroluminescent device according to claim 2, wherein the compound represented by the general formula [1] or [2] is used as a light emitting substance. 4. The electroluminescent device according to claim 2, wherein the compound represented by the general formula [1] or [2] is used as an electron injecting compound.