KR20030058458A - Blue lay emitting organic compound, and organic electroluminescence device using the same - Google Patents

Abstract

PURPOSE: A blue light emitting organic compound and an organic electroluminescence device using the compound are provided, wherein the compound comprises a pyrazoline dimer and shows high efficiency and heat resistance. CONSTITUTION: The blue light emitting organic compound is represented by the formula 2, wherein R1 is an alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group or a their combined group; and R2 to R15 are identical or different one another and are H, an alkyl group, an alkoxy group, a t-butyl group, an aryl group, a heteroaryl group or a fused ring. The organic electroluminescence device comprises a first electrode having a high work function; a second electrode having a low work function; and at least one organic compound layer which is placed between the first and second electrodes and comprises the organic compound of the formula 2. Preferably the organic compound layer is an organic light emitting layer and/or a hole transport layer.

Description

Blue lay emitting organic compound, and organic electroluminescence device using the same

The present invention relates to a blue light emitting organic compound, and more particularly, to a blue light emitting organic compound having high heat resistance and high luminous efficiency, and an organic electroluminescence device (OELD) using the same.

An organic electroluminescent device is an image display device having a structure in which a low molecular or polymer organic light emitting compound is inserted between a transparent electrode (anode) and a metal electrode (cathode) and generates light by applying power to an opposite electrode. As such, the backlight is unnecessary, the response speed is not only fast, and the spontaneous light emitting device has excellent brightness and viewing angle characteristics. In particular, the organic electroluminescent device can be manufactured in a thin film and bendable form, it is easy to form and mass-produce the pattern by the film fabrication technology, low driving voltage, light emission of all colors in the visible region There are possible advantages.

The organic light emitting compound may be a light emitting conductive, nonconductive or semiconducting organic monomolecule, oligomer, or polymer, and the light emitting organic monomolecule is a conjugated organic host in which a plurality of benzene rings are combined. (host) substances and conjugated organic activators are known. Typical examples of the organic host material include naphthalene, anthracene, phenanthrene, pyrene, benzopyrene, chrisene, picene, carbazole, and florene. (fluorene), biphenyl, terphenyl, qurterphenyl, triphenylene oxide, dihalobiphenyl, transstilbene, 1,4- Diphenyl butadiene and the like, and anthracene, tetracene, pentacene and the like are known as the conjugated organic activator. However, the light emitting layer formed by using such a typical light emitting organic single molecule has a disadvantage that the thickness of the light emitting layer is 1 μm or more, and the light emitting layer has a high resistance and a high driving voltage.

Therefore, various types of organic monomolecules have been developed that can reduce the thickness of the light emitting layer and lower the resistance and driving voltage of the light emitting layer. Typically, alumina quinone (Alq3: aluminum-tris (8)) emits light in the green region (550 nm). -hydroxyquinolinate), see US Pat. Nos. 4,539,507 and US Pat. No. 5,150,006), BeBq2 (10-benzo [h] quinolinol- beryllium complex. -quinolinolate) aluminum), Zn (BTZ) ₂ , Zn (NBTZ) ₂ , An (Oc-BTAZ) ₂ (Jpn, J. Appl. Phys. Vol. 35 (1996), 1339-1341), and the like. Examples of materials emitting light in the blue region (460 nm) include organic metals such as ZnPBOX (Chemistry Letters (1994), 1741-1742) and Balq (Bis (2-methyl-8-quinolinolato) (para-phenyl-phenolato) aluminum) Complex compounds, styrylarylene derivatives DPVBi (1,4-bis (2,2-diphenyl-vinyl) biphenyl) and BczVBi (4,4'-Bis ((2-carbazole) vinylene) biphenyl) The back is known, red Examples of the material that emits light in the region (590 nm) include 4- (dicinomethylene) -2-methyl-6- (p-dimethylaminostyryl) -4H-pyran (4- (dicyanomethylene) -2-methyl-6 -(p-dimethyl aminostyryl) -4H-pyran: DCM) and the like are known. In addition, a color light emitting layer is used in which a guest-host doping system is formed by mixing a host material having sufficient electron, hole mobility, and luminescence with a dopant exhibiting various color tones to improve luminous efficiency and durability.

Among such luminescent organic compounds, the compounds currently used as blue light emitters are DPVBi derivatives of the general formula (1) (see US Pat. Nos. 5,503,910 and 5,536,949).

However, since the DPVBi derivative is easy to deteriorate due to low heat resistance, the organic electroluminescent device using the same has a short lifespan, and has a disadvantage in that high-quality blue light cannot be emitted on color coordinates. In addition, blue light-emitting compounds comprising pyrazoline derivatives are described in Jpn, J, appl. Phys. Vol 34 (1995) pp 3124-3127 and Synthetic Metal 105 (1999) 141-144, but these compounds also have the disadvantages of lack of thermal stability and high quality blue light emission.

Accordingly, an object of the present invention is to provide an organic light emitting compound having excellent heat resistance and stability and an organic electroluminescent device using the same.

Another object of the present invention is to provide an organic light emitting compound which can not only display high-quality blue color but also have excellent luminous efficiency and have a long service life, and an organic electroluminescent device using the same.

Still another object of the present invention is to provide an organic light emitting compound capable of simultaneously performing functions of a light emitting layer and a hole transporting layer, and an organic electroluminescent device using the same.

1 is a cross-sectional view of an organic electroluminescent device according to an embodiment of the present invention.

Figure 2 is a cross-sectional view of the organic electroluminescent device according to another embodiment of the present invention.

In order to achieve the above object, the present invention provides a blue organic light emitting compound having a novel structure represented by the following formula (2). The present invention also includes a first electrode having a high work function, a second electrode having a low work function, and an organic compound represented by the following Chemical Formula 1, wherein at least one of the first and second electrodes is disposed between the first electrode and the second electrode. An organic electroluminescent device comprising an organic compound layer is provided.

Wherein R ₁ is alkyl, cycloalkyl, aryl, heteroaryl group or a combination thereof, R ₂ to R ₁₅ may be the same or different from each other, hydrogen, alkyl group, alkoxy group, t-butyl group, aryl group, Heteroaryl group or fused ring.

In the organic electroluminescent device, the organic compound layer is preferably an organic light emitting layer and / or a hole transport layer.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The organic light emitting compound according to the present invention is a compound which emits light by receiving energy generated by recombination of electron-holes, and includes a pyrazoline dimer and has the following formula.

[Formula 2]

In the above formula, R ₁ is alkyl, cycloalkyl, aryl, heteroaryl group or a combination thereof, the alkyl group is an alkyl group having 1 to 5 carbon atoms, the cycloalkyl group is preferably a cycloalkyl group having 3 to 8 carbon atoms, Most preferably, R ₁ is a 4,4'-bismethylenebiphenyl group. R ₂ to R ₁₅ may be the same as or different from each other, and are hydrogen, an alkyl group, an alkoxy group, a t-butyl group, an aryl group, a heteroaryl group, or a fused ring, wherein the alkyl group has 1 to 10 carbon atoms. It is an alkyl group, and it is preferable that the said alkoxy group is a C1-C5 alkoxy group.

In general, a compound containing a pyrazoline derivative has excellent fluorescence efficiency but low thermal stability. However, the organic light emitting compound of the present invention combines a pyrazoline derivative in the form of a dimer, which is 230 ° C. Since it has the above melting point, it is excellent in thermal stability. In addition, since the fluorescence wavelength varies from 400 nm to 480 nm depending on the type of the substituent, it can be used as a high quality blue light emitting compound, and the luminous efficiency is high.

The organic light emitting compound according to the present invention can be prepared by various known organic synthesis methods. For example, in the presence of a polar solvent such as N, N-dimethylformamide (DMF) and a base such as sodium hydroxide, 2- (1,5-diphenyl-4,5-dihydro-1H-pyrazole- When a compound comprising a pyrazoline monomer such as 3-yl) -phenol is reacted with an R ₁ compound having two reactive functional groups such as halogen, for example, 4,4'-bischloromethylbiphenyl, the organic The light emitting compound can be easily obtained.

1 is a cross-sectional view of an organic electroluminescent device according to an embodiment of the present invention. As shown in FIG. 1, an organic electroluminescent device according to an embodiment of the present invention has a high height on a substrate 10. A first electrode 12 having a work function is formed as a hole injection layer (anode), and at least one light emitting layer 14 including an organic light emitting compound according to the present invention on the first electrode 12. ) Is formed. A second electrode 16 having a low work function is formed on the emission layer 14 to face the first electrode 12 as an electron injection layer (cathode). When a voltage is applied to the first and second electrodes 12 and 16 of the organic electroluminescent device, holes and electrons generated in the first and second electrodes 12 and 16 are injected into the light emitting layer 14, In the molecular structure of the emission layer 14, electrons and holes are combined to emit light, and the emitted light passes through the first electrode 12 and the substrate 10 made of a transparent material to display an image.

The substrate 10 of the organic electroluminescent device is electrically insulative, and in particular, when fabricating a device emitting light toward the first electrode 12, the substrate 10 is made of a transparent material, preferably made of glass or transparent plastic film. The first electrode 12 may be formed of, but not limited to, indium tin oxide (ITO), polyaniline, silver (Ag), and the like, and the second electrode 16 may be formed of Al, Mg, Ca, or Li—. It may be made of a metal alloy such as Al, Mg-Ag.

FIG. 2 is a cross-sectional view of an organic electroluminescent device according to another exemplary embodiment of the present invention. In the organic electroluminescent device shown in FIG. 2, holes and electrons generated in the first and second electrodes 12 and 16, respectively, may be formed. Further, hole injection and transport layers 21 and 22 and electron injection and transport layers 25 and 26 are further formed between the first and second electrodes 12 and 16 and the light emitting layer 14 so as to be easily injected into the 14. This point is different from the organic electroluminescent device shown in FIG. 1. The hole injection and transport layers 21 and 22 serve to facilitate the injection of holes from the hole injection electrode 12, to transport holes stably, and to block electrons. Porphyrinic compounds, such as but not limited to phthalocyanine copper disclosed in US Pat. No. 4,356,429, for example m-MTDATA (4,4 ', 4 "-tris (3-methylphenylphenylamino) triphenylamine) The hole transport layer 22 may be made of an organic light emitting compound according to the present invention alone, or triphenyldiamine derivative, styrylamine derivative, α-NPD (N, N) together with the organic light emitting compound according to the present invention. Can be formed using a conventional amine derivative having an aromatic condensed ring such as' -diphenyl-N, N'-bis (α-naphthyl)-[1,1'-biphenyl] 4,4'-diamine) The electron injection and transport layers 25 and 26 may be formed from the electron injection electrode 16. Functions that facilitate the injection of electrons, functions to transport electrons stably, and to prevent holes, including but not limited to quinoline derivatives, especially tris (8-kinolinorate) aluminum (aluminaquinone, Alq3 The thickness of the light emitting layer 14, the hole injection and transport layers 21 and 22, and the electron injection and transport layers 25 and 26 is not particularly limited and may vary depending on the formation method, but is usually 5 to 500 nm. It has a thickness of about.

The organic light emitting compound according to the present invention forms a layer between the first and second electrodes 12, 16 alone or together with a conventional organic compound to be used as the organic light emitting layer 14 and / or hole transport layer 22. The organic light emitting layer 14 and / or the hole transport layer 22 may be formed by a vacuum deposition method, a spin coating method, or the like, which is commonly used for fabricating an organic electroluminescent device. The organic light emitting compound of the present invention can be applied not only to the organic electroluminescent device of the structure shown in FIG. 1 or 2, but also to the organic electroluminescent device of various structures exhibiting light emission phenomenon by hole-electron coupling.

Next, preferred examples are provided to help understanding of the present invention. However, the following examples illustrate the present invention and do not limit the present invention.

Example 1

Into 90 ml of N, N-dimethylformamide (DMF) was added 5.97 g (19 mmol) of 2- (1,5-diphenyl-4,5-dihydro-1H-pyrazol-3-yl) -phenol. 0.83 g of sodium hydroxide (NaOH) was added thereto, and 2.39 g (9.5 mmol) of 4,4'-bischloromethylbiphenyl dissolved in 30 ml of DMF was added dropwise to the reaction solution (see Scheme 1 below). After completion of the dropwise addition, the reaction solution was heated to 50 ° C., stirred for about 2 hours, cooled, and distilled water was added to the cooled reaction solution. The reaction solution was filtered, and the obtained solid was washed with distilled water and dried. The obtained solid was purified by column to give 5.5 g of the target compound (yield 71%). The maximum emission wavelength ?? max of the obtained organic light emitting compound was 450 nm, and the melting point T _m was 234 ° C.

Example 2

2- (1,5-diphenyl-4,5-dihydro-1H-pyrazol-3-yl) -phenol instead of 5.97 g (19 mmol) of 1- (1,5-diphenyl-4,5-di 5.5 g of the target compound was obtained by the same method as Example 1 except for using 6.92 g (19 mmol) of hydro-1H-pyrazol-3-yl) -naphthalene-2-ol (yield 61%, see Scheme 2 below). ). The maximum light emission wavelength [lambda] max of the obtained organic light emitting compound was 470 nm, and the melting point T _m was 265 占 폚.

Example 3

The glass substrate coated with indium tin oxide (ITO) was ultrasonically cleaned, and again washed with deionized water, then degreased with toluene gas and dried. Next, a hole injection layer was formed by vacuum deposition of 150 m thick m-MTDATA on the ITO electrode, and a hole transport layer was formed by vacuum deposition of α-NPD on the hole injection layer to 500 mm thick. The organic light emitting compound synthesized in Example 1 was deposited on the hole transport layer to a thickness of 600 kV to form an organic light emitting layer, and Alq3 was vacuum deposited to a thickness of 300 kW on the organic light emitting layer to form an electron transport layer. Finally, the organic electroluminescent device was manufactured by forming a cathode by depositing Mg-Ag at a thickness of 2000 kPa on the electron transport layer. The prepared organic electroluminescent device exhibited a maximum emission intensity of 3500 cd / m ² and a maximum emission wavelength of 450 nm at 18V voltage and a luminous efficiency of 1.5 lm / w.

As described above, the organic light emitting compound including the pyrazoline dimer according to the present invention is not only more stable than the conventional organic light emitting compound but also has excellent efficiency and can change the color purity of blue according to the substituent. It is useful as a high quality blue light emitting material.

Claims (5)

An organic light emitting compound represented by Chemical Formula 2, which emits light by receiving energy generated by recombination of electrons and holes. [Formula 2] Wherein R ₁ is alkyl, cycloalkyl, aryl, heteroaryl group or a combination thereof, R ₂ to R ₁₅ may be the same or different from each other, hydrogen, alkyl group, alkoxy group, t-butyl group, aryl group, Heteroaryl group or fused ring. The organic light emitting compound according to claim 1, wherein R ₁ is an alkyl group having 1 to 5 carbon atoms or a cycloalkyl group having 3 to 8 carbon atoms. The organic light emitting compound according to claim 1, wherein R ₁ is a 4,4'-bismethylenebiphenyl group. A first electrode having a high work function; A second electrode having a low work function; And An organic electroluminescent device comprising an organic compound represented by Formula 2 and comprising at least one organic compound layer positioned between the first and second electrodes. [Formula 2] Wherein R ₁ is alkyl, cycloalkyl, aryl, heteroaryl group or a combination thereof, R ₂ to R ₁₅ may be the same or different from each other, hydrogen, alkyl group, alkoxy group, t-butyl group, aryl group, Heteroaryl group or fused ring. The organic electroluminescent device according to claim 4, wherein the organic compound layer is an organic light emitting layer and / or a hole transport layer.