WO2004050794A1

WO2004050794A1 - Orgnaic light emitting materials and organic electroluminescence devices using the same

Info

Publication number: WO2004050794A1
Application number: PCT/KR2003/002605
Authority: WO
Inventors: Dong-Myung Shin; Gwon-Young Ryu; Sung-Taek Lim
Original assignee: Dong-Myung Shin; Gwon-Young Ryu; Sung-Taek Lim
Priority date: 2002-11-30
Filing date: 2003-11-28
Publication date: 2004-06-17
Also published as: AU2003284783A1; KR100515516B1; KR20030004216A

Abstract

The present invention provides light-emitting compounds represented by the following formula 1 and organic electroluminescent devices comprising the light-emitting compounds, which can exhibit red light emission and high luminous efficiency.

Description

ORGANIC LIGHT EMITTING MATERIALS AND ORGANIC ELECTROLUMINESCENCE DEVICES USING THE SAME

FIELD OF THE INVENTION

The present invention relates to red light-emitting materials for organic electroluminescent devices and to organic electroluminescent devices using the same. More particularly, it relates to low-molecular red light-emitting materials, to be applicable for a luminescent layer, a hole-injecting and -transporting layer and an electron-injecting and -transporting layer of an organic electroluminescent device, and to organic electroluminescent devices with high efficiency using the same.

BACKGROUND OF THE INVENTION

In recent years, organic electroluminescent (EL) devices have attracted attentions to their possibility for flat panel displays, and have been rapidly developed. An organic EL device is a self-luminescent flat panel display and is characterized by high brightness, low-voltage operation, good portability and high impact resistance resulting from being a complete solid device. An organic EL device has advantages that the manufacturing process thereof is simpler than those of a liquid crystal display, a plasma display device or the like, and therefore has high productivity, and multicolored electroluminescence can be realized.

Light-emitting materials for organic EL devices can be classified as polymer type compounds and low-molecular type compounds. Using polymer type compounds, an organic EL device should be produced by a wet process, which has relatively more factors to increase the defects of a device, such as pin-holes. On the other hand, an organic EL device manufactured using low-molecular compounds can minimize the above defects.

In a development of organic EL devices using low-molecular compounds, it is very important to realize multicolored electroluminescence, a merit thereof. For multicolored electroluminescence, a lamination method has been studied to form a luminescent layer of an organic EL device by mixing two or more compounds. This method has been applied especially to red organic EL devices. Recently, this method has used a triplet state of organic compounds. Red organic EL devices using the triplet state exhibit improved luminous efficiency. This method requires a process for forming a thin film by uniformly mixing two or more compounds. However, the method of using a triplet state has difficulty in obtaining a uniformly mixed state of compounds in the process of forming the thin film. In addition, it has a problem that it is very sensitive to oxygen in the air.

Further, for multicolored electroluminescence, a novel method of laminating light-emitting materials on both sides of the interface between two organic compounds was developed. This method makes use of the characteristic that exciton due to a recombination of a hole and an electron can be formed on both sides of the interface between two organic compounds. However, this method has difficulty in obtaining a uniformly mixed state of compounds in the process of forming a thin film. In addition, it is also difficult to develop materials having both hole-injecting and -transporting abilities together with satisfactory electroluminescence characteristics.

SUMMARY OF THE INVENTION

Therefore, the present invention provides light-emitting compounds to be applicable for a hole- injecting and -transporting layer, an electron-injecting and -transporting layer and a luminescent layer of an organic electroluminescent device, which is represented by the following formula 1.

Further, the present invention, in consideration of the problems of the above methods, provides an organic electroluminescent device comprising a luminescent layer without mixing of materials.

Light-emitting compounds according to the present invention may be represented by the following formula 1 : [Formula 1]

wherein Dj and D₂ each independently represent an aromatic amine group, carbazole group or carbazole derivatives which is able to donate electrons by resonance; and Ai and A₂ each includes a double bond capable of conjugation with the central benzene ring, a cyano group capable of conjugation with the central benzene ring and the double bond, and a heteroaromatic or aromatic group capable of conjugation with the central benzene ring and the double bond without conjugation with the cyano group.

DETAILED DESCRIPTION OF THE INVENTION

Light-emitting compounds represented by the above formula 1 have a symmetrical structure in which aromatic amine groups, carbazole groups or carbazole derivatives, which is able to donate electrons by resonance, are symmetrically arranged; and for control of the light-emitting region, groups including both a cyano group bonded to a double bond capable of conjugation with the central benzene ring and a heteroaromatic or aromatic group capable of conjugation with the central benzene ring and the double bond, without conjugation with the cyano group, are symmetrically arranged and conjugate with D] and D₂ via the central benzene ring.

The aromatic amine groups, carbazole groups and carbazole derivatives induce an electron-donating ability in the molecule of the light-emitting compound, and the cyano group and the heteroaromatic or aromatic group accept electron to control the luminescent region. In addition, the electroluminesence characteristic of the light-emitting compound and the electric property of an electric device containing the light-emitting compound can be controlled by modifying or changing the electron-donating group and the position of the cyano group and heteroaromatic or aromatic group.

In the above formula 1, D] and D₂ may be the same or different from each other and represented by the following formulae 2 or 3:

wherein Ri and R₂ may be the same or different from each other and selected from the group consisting of hydrogen atom, aliphatic alkyl group having from 1 to 20 carbon atoms, branched alkyl group, cyclic alkyl group having from 5 to 24 carbon atoms and aromatic group having from 4 to 30 carbon atoms; aromatic group of the formula has at least one substituent selected from the group consisting of halogen atom comprising F, CI, Br and I, alkoxy group having from 1 to 12 carbon atoms, aliphatic amine and aromatic amine; and n is an integer from 0 to 3; [Formula 3]

w Xherein R₃ and R₄ may be the same or different from each other, each having at least one substituent selected from the group consisting of aliphatic alkyl group having from 1 to 20 carbon atoms and groups represented by the following formulae 4 to 6; and n is an integer from 1 to 5:

[Formula 4] — (CH₂)n-^^~^>

wherein n is an integer from 0 to 10;

[Formula 5]

wherein n is an integer from 0 to 10;

[Formula 6]

wherein R₅ and R₆ each independently represents hydrogen atom or alkyl group having from 1 to 6 carbon atoms; and n is an integer from 0 to 10.

Meanwhile, in the above formula 1, A_! and A₂ each includes a double bond capable of conjugation with the central benzene ring, a cyano group capable of conjugation with the central benzene ring and the double bond, and a heteroaromatic or aromatic group capable of conjugation with the central benzene ring and the double bond, without conjugation with the cyano group, and particularly may be represented by the following formulae 7 or 8:

[Formula 7]

wherein Y is hydrogen atom or cyano group; n is an integer from 1 to 6; and R is selected from groups represented by the above formulae 2 and 3 and the following formulae 9 to 19;

[Formula 8]

wherein Y is hydrogen atom or cyano group; n is an integer from 1 to 6; and R₈ is selected from groups represented by the above formulae 2 and 3 and the following formulae 9 to 20:

[Formula 9]

wherein R₉ is selected from the group consisting of alkyl group having from 1 to 5 carbon atoms, cyclic compound having from 5 to 20 carbon atoms and halogen atom comprising F, CI, Br and I;

[Formula 10]

wherein Rι₀ is selected from groups represented by the following formulae 12 to 20;

[Formula 11]

wherein R_u is selected from groups represented by the following formulae 12 to 20;

[Formula 12]

wherein n is an integer from 2 to 8;

[Formula 13]

wherein X is selected from the group consisting of oxygen, nitrogen and sulfur; and n is an integer from 2 to 8;

[Formula 14]

wherein X is selected from the group consisting of oxygen, nitrogen and sulfur; and n is an integer from 2 to 7;

[Formula 16]

[Formula 17]

wherein X is selected from the group consisting of oxygen, nitrogen and sulfur; and n is an integer from 2 to 7; [Formula 18]

wherein X is selected from the group consisting of oxygen, nitrogen and sulfur; and n is an integer from 2 to 4;

[Formula 19]

[Formula 20]

-CN

Meanwhile, in each functional group of the formulae, at least one hydrogen atom of the aryl group, aromatic group and heteroaromatic group may be substituted by a halogen atom selected from F, CI, Br and I, preferably F, CF₃ or CN.

The present invention provides an organic EL device comprising at least one layer containing the light-emitting compound represented by the above formula 1 , inserted between anode and cathode.

Further, the present invention provides an organic EL device having high luminous efficiency, which comprises a pure organic layer without mixing of other organic compounds as a luminescent layer. Light-emitting compounds for electric devices, particularly organic EL devices, are used for forming a luminescent layer (104, 204), as shown in Figs. 1 or 2. Such a luminescent layer can be composed of pure or doped organic compounds. In the prior art, this layer was composed of light-emitting compound capable of functioning as an electron-transporting layer.

Departing from known light-emitting compounds used in the prior art, the present invention suggests organic EL devices using the light-emitting compound as a hole-injecting and -transporting layer (103 of Fig. 1 or 203 of Fig. 2), without separate hole-injecting and transporting layer. In addition, the light-emitting compound of the present invention can be applied to a luminescent layer, electron-transporting layer and electron-injecting layer of organic an EL device. In all cases of organic EL devices using the present light-emitting compound as an electron-injecting and -transporting and luminescent layer (104, 204) of Figs. 1 or 2, light emission in the visible region was observed.

In prior organic EL devices, particularly red organic EL devices, it was known how to form a luminescent layer by mixing other kinds of light-emitting compounds or sensitizer, in order to maximize luminous efficiency.

However, the present invention provides light-emitting compounds satisfying the general structure of the above formula 1 which can maximize luminous efficiency in the pure form of the luminescent layer without mixing of other kinds of light-emitting compounds or sensitizer.

In the case that the light-emitting compound satisfying the general structure of the above formula 1 is used as an electron-injecting and -transporting and luminescent layer, an organic EL device may be manufactured by using a known hole-injecting and -transporting layer, as shown in Fig. 1. The hole

-injecting and -transporting layer may be composed of 4,4|-bis[N-(l-naphthyl)- N-phenylamino]biphenyl (hereinafter may be abbreviated to "NPD"), aryl amines, polycarbazole, polycyclic aromatic compounds, etc.

In the case that the light-emitting compound satisfying the general structure of the above formula 1 is used as a hole- injecting and -transporting and luminescent layer, an organic EL device may be manufactured by using a known electron-injecting and -transporting layer as shown in Fig. 2. The electron-injecting and -transporting layer may be composed of 8 -hydroxyquinoline aluminum salt (hereinafter may be abbreviated to "Alq"), l,l,4,4-tetraphenyl-l,3-butaniene (hereinafter may be abbreviated to "TPB"), oxadiazole derivatives, etc. In the case that the light-emitting compound satisfying the general structure of the above formula 1 is used only as a luminescent layer, an organic EL device may be manufactured by using a known electron-injecting and -transporting layer and hole-injecting and -transporting layer, as shown in Fig. 3. The electron-injecting and -transporting layer may be composed of Alq, TPB, or oxadiazole derivatives, etc., and the hole-injecting and -transporting layer may be composed of NPD, polycarbazole, or polycyclic aromatic compounds, etc.

The cathode electrodes shown in Figs 1 to 3 may be formed from materials capable of easily injecting electrons into an electron-injecting and -transporting layer. Specific examples thereof include lithium-aluminum alloys; magnesium-silver alloys; magnesium; calcium; or multi-layer structures such as lithium fluoride(LiF)/aluminum, lithium oxide(Li₂0)/aluminum, etc.

According to the present invention, the compounds represented by the following formulae 21a, 21b, 21c and 2 Id may typically exemplify the compounds of the above formula 1. [Formula 21a]

[Formula 21b]

[Formula 21c]

[Formula 2 Id]

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic cross-sectional view of an organic EL device manufactured by using the light-emitting compound of the present invention as an electron- injecting and -transporting and luminescent layer.

Fig. 2 is a schematic cross-sectional view of an organic EL device manufactured by using the light-emitting compound of the present invention as a hole-injecting and -transporting and luminescent layer.

Fig. 3 is a schematic cross-sectional view of an organic EL device manufactured by using the light-emitting compound of the present invention as a luminescent layer. Fig. 4 is a schematic cross-sectional view of an organic EL device comprising a single layer of the light-emitting compound of the present invention.

Fig. 5 is an electroluminescence spectrum of the organic EL device shown in Fig. 4, manufactured by using the light-emitting compound of the formula 21a satisfying the chemical structure of the formula 1 , in the example 1. Fig. 6 is an electroluminescence spectrum of the organic EL device shown in Fig. 4, manufactured by using the light-emitting compound of the formula 21b satisfying the chemical structure of the formula 1, in the example 2.

Fig. 7 is an electroluminescence spectrum of the organic EL device shown in Fig. 4, manufactured by using the light-emitting compound of the formula 21c satisfying the chemical structure of the formula 1, in the example 3.

Fig. 8 is an electroluminescence spectrum of the organic EL device shown in Fig. 4, manufactured by using the light-emitting compound of the formula 2 Id satisfying the chemical structure of the formula 1, in the example 4. Fig. 9 is an electroluminescence spectrum of the organic EL device shown in Fig. 1, manufactured by using the light- emitting compound of the formula 21c satisfying the chemical structure of the formula 1, in the example 5.

Fig. 10 is an electroluminescence spectrum of the organic EL device shown in Fig. 2, manufactured by using the light-emitting compound of the formula 21a satisfying the chemical structure of the formula 1, in the example 6.

Fig. 11 is an electroluminescence spectrum of the organic EL device shown in Fig. 3, manufactured by using the light-emitting compound of the formula 21b satisfying the chemical structure of the formula 1, in the example 7.

101, 201, 301, 401 : Glass substrate

102, 202, 302, 402 : Anode electrode 403 : Organic light-emitting layer

103 : Hole-injecting and -transporting layer 104 : Electron-injecting and -transporting and luminescent layer

203 : Hole-injecting and -transporting and luminescent layer

204 : Electron-injecting and -transporting layer, or Electron-injecting and -transporting and luminescent layer

303 : Hole-injecting and -transporting layer

304 : Luminescent layer

305 : Electron-injecting and -transporting layer, or Electron-injecting and -transporting and luminescent layer

105, 205, 306, 404 : Cathode electrode

PREFERRED EMBODIMENT OF THE INVENTION

The present invention will be described in more detail by way of the following synthesis examples and examples, which should not be considered to limit the scope of the present invention.

[Synthesis Examples] A method for synthesizing light-emitting compounds of the present invention may be schematized by the following reaction schemes la and lb.

[Reaction Scheme la]

(1)

(IV)

[Reaction Scheme lb]

(π) + (HI) ABCV-n

(II) + (IV) ABCV-IH

<Synthesis Example 1> Preparation of ( II );

4,4"-bis(di-methylamino - 1 , l':4'.1 "-terphenyl-2'.5'-dicarbaldehvde

0.5g of 2,5-dibromo-l,4-dicarbaldehyde, 0.69g of 4-(dimethylamino) phenylboronic acid and O. lg of tetrakis(triphenylphosphine) palladium(O) were added to a mixture of 20rn-6 of toluene, lOmϋ. of tetrahydrofiiran and 1.5m# of

1M Na₂CO₃ degassed by nitrogen gas. The obtained mixture was reacted for 24 hours while refluxing and stirring under a nitrogen atmosphere, at a temperature of 86^°C .

After reaction, the mixture was poured into water, extracted with methylene chloride, and dried over magnesium sulfate anhydride, then distillated under reduced pressure to remove solvent, to give light-brown solid. It was then subjected to chromatography using ethylacetate and n-hexane as eluant, to give

0.48g (75.2% of yield) of the title compound as light- yellow solid.

NMR analysis : Varian Unity INOVA 500 Η-NMR( δ , CDC1₃) : 10.10(2H, s), 8.06(2H, s, aromatic), 7.31(4H, d, aromatic),

6.82(4H, d, aromatic), 3.04(12H, s)

¹³C-NMR( δ , CDC1₃) : 192.85, 192.80, 150.45, 143.64, 136.36, 131.07, 129.88,

123.00, 112.15, 40.33

<Svnthesis Example 2> Preparation of (HI); l, -biphenyl-4-ylacetonitrile

2.00g of 4-bromophenylacetonitrile, 1.57g of phenylboronic acid and

0.59g of tetrakis(triphenylphosphine) palladium(O) were added to a mixture of

240m£ of toluene and 10ml of 1M Na₂C0₃ degassed by nitrogen gas. The obtained mixture was reacted for 24 hours while refluxing and stirring under a nitrogen atmosphere, at a temperature of 86 ^°C .

After reaction, the mixture was poured into water, extracted with methylene chloride, dried over magnesium sulfate anhydride, and distillated under reduced pressure to remove solvent, then subjected to chromatography using ethylacetate and n-hexane as eluant, to give 1.42g (72.0% of yield) of the title compound as white solid, mp ^°C (DSC): 97.3 ^°C NMR analysis : Varian Unity INOVA 500

Η-NMR( δ , CDC1₃) : 7.61~7.34(9H, aromatic), 3.79(2H, s)

¹³C-NMR( δ , CDCI₃) : 141.09, 140.17, 128.85, 128.33, 127.80, 127.61, 127.04,

23.28

<Synthesis Example 3> Preparation of (IV); (4-thien-2-yrphenyl) acetonitrile)

3.00g of 4-bromophenylacetonitrile, 2.35g of 2-thiopheneboronic acid and 0.88g of tetrakis(triphenylphosphine) palladium(O) were added to a mixture of 200ro£ of toluene, 40m£ of tetrahydrofiiran and 15m£ of 1M Na₂C0₃ degassed by nitrogen gas. The obtained mixture was reacted for 24 hours while refluxing and Stirling under a nitrogen atmosphere, at a temperature of 86 ^°C .

After reaction, the mixture was poured into water, extracted with methylene chloride, dried over magnesium sulfate anhydride, and distillated under reduced pressure to remove solvent, and then subjected to chromatography using methylene chloride and n-hexane as eluant, to give 0.89g (29.2% of yield) of the title compound as white solid. mp^°C (DSC): 106^°C

NMR analysis : Varian Unity INOVA 500

Η-NMR( δ , CDCI₃) : 7.61(2H, d, aromatic), 7.33~7.29(4H, aromatic) 7.08(1H, s, aromatic), 3.75(2H, s) 1³C-NMR( δ , CDCI₃) : 143.26, 134.28, 128.84, 128.43, 128.10, 126.49, 125.23, 123.49, 117.65, 23.28 <Synthesis Example 4> Preparation of ABCV- I ;

((2Z)-3-4,4"-bis(dimethylamino -5'-[(£^r)-2-cvano-2-phenylvinyl1- 1.1 ':4M"-terphenyl -2'-yl-2-phenylacrylonitrile

0.50g of 4,4"-bis(dimethylamino)-l,l':4',l^,,-te henyl-2^,,5^,-dicarbaldehyde and 0.40g of benzyl cyanide were added to \40mi of ethanol and thereto was added a solution of 0.15g of sodium in 10m# of absolute ethanol, under stirring. The mixture was then reacted for 40 hours at room temperature, to give red solid.

The red solid was filtrated then washed successively with distilled water, ethanol, n-hexane and a sufficient quantity of ethylacetate. Subsequently, it was recrystallized from methylene chloride/hexane and sublimated under 10-6 mmHg, to give 0.35g (45.5% of yield) of the title compound as red solid.

<Synthesis Example 5> Preparation of ABCV- II ; (2Z)-2-(l.l^,-biphenyl-4-yl)-3-r5'-r(E)-2-cvano-2-(l,l^,-biphenyl-4-vnvinvn-4,4"-bis (dimethylamino - 1 , l':4', 1 "-terphenyl-2'-yl] acryl onitrile

0.1 Og of 4,4"-bis(dimethylamino)- 1 , 1 ':4 1 "-teφhenyl-2',5^,-dicarbaldehyde and 0.12g of l,r-biphenyl-4-ylacetonitrile were added to 130m-£ of ethanol and thereto was added a solution of 0.15g of sodium in lOmt of absolute ethanol, under stirring. The mixture was then reacted for 40 hours at room temperature, to give red solid.

The red solid was filtrated then washed successively with distilled water, ethanol, n-hexane and a sufficient quantity of ethylacetate. Subsequently, it was recrystallized from methylene chloride/hexane and sublimated under 10-6 mmHg, to give 0.1 lg (55.6% of yield) of the title compound as red solid.

<Synthesis Example 6> Preparation of ABCV- HI; ((2Z)-3-4,4"-bis(dimethylamino)-5'-r(jg -2-cvano-2-(4-thien-2-vIphenyl vinyl]-l . :4'.l"-terphenyl-2'-yl-2-(^'4-thien-2-ylρhenyl acrylonitrile

0.50g of 4,4"-bis(dimethylamino)- 1 , 1 ':4', 1 "-teφhenyl-2',5'-dicarbaldehyde and 0.59g of (4-thien-2-ylphenyl)acetonitrile were added to \30ml of ethanol and lOm-β of tetrahydrofiiran, and thereto was added a solution of 0.1 g of sodium in 5ml of absolute ethanol, under stirring. The mixture was then reacted for 40 hours at room temperature, to give red solid.

The red solid was filtrated and then washed successively with distilled water, ethanol, n-hexane and a sufficient quantity of ethylacetate. Subsequently, it was recrystallized from methylene chloride/hexane, to give 0.57g (57.8% of yield) of the title compound as red solid.

<Synthesis Example 7> Preparation of ABCV- IV;

(^'2E)-3-4,4"-bis(dimethylamino)-5'-r(E)-2-cvano-2-thien-2-ylvinyll- 1.1 ':4'.1 "-teφhenyl -2'-yl-2-thien-2-ylacrylonitrile 0.50g of 4,4"-bis(dimethylamino)-l,l^,:4^,,l"-teφhenyl-2',5'-dicarbaldehyde and 0.40g of 2-thiopheneacetonitrile were added to \50ml of ethanol and thereto was added a solution of 0.15g of sodium in 5ml of absolute ethanol, under stirring. The mixture was then reacted for 40 hours at room temperature, to give red solid. The red solid was filtrated and then washed successively with distilled water, ethanol, n-hexane and a sufficient quantity of ethylacetate. Subsequently, it was recrystallized from methylene chloride/hexane and sublimated under 10-6 mmHg, to give 0.49g (62.6% of yield) of the title compound as red solid.

<Synthesis Example 8> Preparation of ABCV- V ; (2Z)-3-4,4"-bis(dimethylamino -5^l-[(E -2-cvano-2-(pentafluorophenyl vinyl]-l ,r :4M "-teφhenyl-2'-yl-2-ψentafluorophenyl acrylonitrile

0.50g of 4,4"-bis(dimethylamino)-l ,l':4',l"-teφhenyl-2^,,5^,-dicarbaldehyde and 0.70g of pentafluoroacetonitrile were added to 150m£ of ethanol and thereto was added a solution of 0.15g of sodium in 5ml of absolute ethanol, under stirring. The mixture was then reacted for 40 hours at room temperature, to give red solid.

The red solid was filtrated, and washed successively with distilled water, ethanol and n-hexane, then dissolved in ethylacetate. Subsequently, the obtained red solution was distillated under reduced pressure to remove solvent, to give red solid, which was recrystallized from methylene chloride/hexane, to give 0.41g of red solid. It was then sublimated under 10-6 mmHg, to give 0.35g (24.3%) of yield) of the title compound.

In order to confirm that the light-emitting compounds satisfying the chemical structure of the formula 1 may function as a hole-injecting and hole-transporting layer in an organic EL device, the following organic EL devices were manufactured by using the compounds of the formulae 21a to 2 Id satisfying the chemical structure of the formula 1 as hole-injecting material.

<Examρle 1>

An organic single layer was formed by thermal evaporation of the compound of the formula 21a satisfying the chemical structure of the above formula 1 at a thickness of lOOnm on an ITO transparent electrode as shown in Fig. 4. An aluminum electrode was formed thereon at a thickness of 200nm. In this process, deposition rates of the compound and of aluminum were O.lnm/sec and lnm/sec respectively. An electroluminescence spectrum of the obtained organic EL device is shown in Fig. 5. <Example 2>

An organic EL device having the same structure as that in example 1 was manufactured by using the compound of the formula 21b. An electroluminescence spectrum of the obtained organic EL device is shown in Fig. 6.

An organic EL device having the same structure as that in example 1 was manufactured by using the compound of the formula 21c. An electroluminescence spectrum of the obtained organic EL device is shown in Fig. 7.

An organic EL device having the same structure as that in example 1 was manufactured by using the compound of the formula 2 Id. An electroluminescence spectrum of the obtained organic EL device is shown in Fig. 8.

In order to demonstrate if electroluminescence may be observed in the case that the light-emitting compound of the formula 21c satisfying the chemical structure of the above formula 1 is used for an electron-injecting and -transporting and luminescent layer, an organic EL device having the structure shown in Fig. 1 was manufactured and electroluminescence characteristic thereof was measured. After thermal evaporation of NPD at a thickness of 50nm on an ITO transparent electrode as a hole-injecting and -transporting layer, an electron-injecting and transporting and luminescent layer was formed thereon by thermal evaporation of the compound of the formula 21c satisfying the chemical structure of the above formula 1 at a thickness of 50nm. Thereafter, the same procedure as that in example 1 was followed to form an aluminum electrode. A schematic cross-sectional view of the obtained organic EL device is shown in Fig. 1, and an electroluminescence spectrum of the obtained organic EL device in Fig. 9.

In order to demonstrate if electroluminescence may be observed in the case that the light-emitting compound of the formula 21a satisfying the chemical structure of the above formula 1 is used for a hole-injecting and -transporting and luminescent layer, an organic EL device having the structure shown in Fig. 2 was manufactured and the electroluminescence characteristic thereof was measured.

After thermal evaporation of the compound of the formula 21a satisfying the chemical structure of the above formula 1 at a thickness of 50nm on an ITO transparent electrode as a hole-injecting and -transporting and luminescent layer, an electron-injecting and transporting layer was formed thereon by thermal evaporation of 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-l,3,4-oxadiazole (hereinafter may be abbreviated to "PBD" ) at a thickness of 50nm. Thereafter, the same procedure as that in example 1 was followed to form an aluminum electrode. A schematic cross-sectional view of the obtained organic EL device is shown in Fig. 2, and an electroluminescence spectrum of the obtained organic EL device in Fig. 10.

In order to demonstrate if electroluminescence may be observed in the case that the light-emitting compound of the formula 21b satisfying the chemical structure of the above formula 1 is used for a luminescent layer, an organic EL device having the structure shown in Fig. 3 was manufactured and the electroluminescence characteristic thereof was measured.

After thermal evaporation of NPD at a thickness of 50nm on an ITO transparent electrode as a hole-injecting and -transporting layer, a luminescent layer was formed thereon by thermal evaporation of the compound of the formula 21b satisfying the chemical structure of the above formula 1 at a thickness of 20mn. An electron-injecting and -transporting layer was then formed by thermal evaporation of PBD at a thickness of 30nm. Thereafter, the same procedure as that in example 1 was followed to form an aluminum electrode. A schematic cross-sectional view of the obtained organic EL device is shown in Fig. 3, and an electroluminescence spectrum of the obtained organic EL device in Fig. 11.

Light-emitting compounds of the present invention have a symmetric structure of amine derivatives donating electrons and cyano group withdrawing electron. Therefore, they can be applied as hole-transporting layer, an electron-transporting layer and a luminescent layer, and all for them. In the case that the light-emitting compounds of the present invention may be used for organic EL devices, they can perform all the functions of a hole-transporting layer and an electron-transporting layer, as well as that of a luminescent layer. Multicolored electroluminescence can be realized by mixing other kinds of light-emitting compounds.

While the present invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various modifications and variations can be made therein and without departing from the spirit and scope thereof. Thus, it is intended that the present invention cover the modifications and variations thereof provided they come within the scope of the appended claims and their equivalents. INDUSTRIAL APPLICATION OF THE INVENTION

Light-emitting compounds of the present invention can be applied as a hole-transporting layer, an electron-transporting layer and a luminescent layer and thereby realize multicolored electroluminescence. Therefore, the present compounds can be applied to organic EL devices such as flat panel displays.

Claims

1. A light-emitting compound represented by the following formula 1 : [Formula 1]

wherein Dj and D₂ each independently represent an aromatic amine group, carbazole group or carbazole derivatives, able to donate electrons by resonance; and A) and A₂ each includes a double bond capable of conjugation with the central benzene ring, a cyano group capable of conjugation with the central benzene ring and the double bond, and a heteroaromatic or aromatic group capable of conjugation with the central benzene ring and the double bond, without conjugation with the cyano group.

2. The light-emitting compound according to Claim 1, wherein Dj and D₂ in the formula 1, are the same or different from each other and represented by the following formulae 2 or 3: [Formula 2] wherein _\ and R₂ are the same or different from each other and selected from the group consisting of hydrogen atom, aliphatic alkyl group having from 1 to 20 carbon atoms, branched alkyl group, cyclic alkyl group having from 5 to 24 carbon atoms, and aromatic group of the formula having from 4 to 30 carbon atoms; the aromatic group has at least one substituent selected from the group consisting of halogen atom including one or more of F, CI, Br and I, alkoxy group having from 1 to 12 carbon atoms, aliphatic amine and aromatic amine; and n is an integer from 0 to 3; [Formula 3]

wherein R₃ and R may be the same or different from each other each having at least one substituent selected from the group consisting of aliphatic alkyl group having from 1 to 20 carbon atoms and groups represented by the following formulae 4 to 6; and n is an integer from 1 to 5: [Formula 4]

-(CH₂)n- W / wherein n is an integer from 0 to 10; [Formula 5]

wherein n is an integer from 0 to 10; [Formula 6]

wherein R₅ and R₆ each independently represents hydrogen atom or alkyl group having from 1 to 6 carbon atoms; and n is an integer of from 0 to 10.

3. The light-emitting compound according to Claim 1, wherein A] and A₂ in the formula 1 are represented by the following formulae 7 or 8: [Formula 7]

wherein Y is hydrogen atom or cyano group; n is an integer from 1 to 6; and R₇ is selected from groups represented by the above formulae 2 and 3 and the following formulae 9 to 19;

[Formula 8]

wherein Y is hydrogen atom or cyano group; n is an integer from 1 to 6; and Rg is selected from groups represented by the above formulae 2 and 3 and the following formulae 9 to 20: [Formula 9]

wherein R₉ is selected from the group consisting of alkyl group having from 1 to 5 carbon atoms, cyclic compound having from 5 to 20 carbon atoms, and halogen atom comprising F, CI, Br and I; [Formula 10]

10

wherein R₁₀ is selected from groups represented by the following formulae 12 to

20;

[Formula 11]

wherein Rn is selected from groups represented by the following formulae 12 to

20;

[Formula 12]

wherein n is an integer from 2 to 8; [Formula 13]

wherein X is selected from the group consisting of oxygen, nitrogen and sulfur; and n is an integer from 2 to 8; [Formula 14]

wherein X is selected from the group consisting of oxygen, nitrogen and sulfur; and n is an integer from 2 to 7; [Formula 15]

wherein X is selected from the group consisting of oxygen, nitrogen and sulfur; and n is an integer from 2 to 7; [Formula 16]

wherein X is selected from the group consisting of oxygen, nitrogen and sulfur; and n is an integer from 2 to 7; [Formula 17]

[Formula 19]

[Formula 20]

-CN

4. The light-emitting compound according to any one of Claims 1 to 3, wherein in each functional group of the formulae 2 to 19, at least one hydrogen atom of the aryl group, aromatic group and heteroaromatic group is substituted by halogen atom selected from F, CI, Br and I, CF₃, or CN.

5. The light-emitting compound according to Claim 1, which is selected from the compounds represented by the following formulae 21a to 2 Id: [Formula 21a]

[Formula 21b]

[Formula 21c]

[Formula 2 Id]

6. An organic electroluminescent device comprising an organic layer inserted between a pair of electrodes, wherein the organic layer contains the light-emitting compound according to Claim 1, represented by the formula 1.

7. The organic electroluminescent device according to Claim 6, wherein the organic layer is both hole-injecting and -transporting layer and luminescent layer.

8. The organic electroluminescent device according to Claim 6, wherein the organic layer is both electron-injecting and -transporting layer and luminescent layer.

9. The organic electroluminescent device according to Claim 6, wherein the organic layer is formed adjacent to both hole-injecting and -transporting layer and electron-injecting and transporting layer.