KR100425360B1 - Organic luminescent compound including pyrazoline group, and organic electroluminescence device using the same - Google Patents

Abstract

The present invention relates to an organic light emitting compound having a high heat resistance and comprising a pyrazoline group that can be used as a light emitting layer and / or a hole transporting layer of an organic electroluminescent device, and provides an organic light emitting compound having a novel structure represented by the following formula. 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 X is one or more aryl groups bonded with nitrogen, wherein the total number of carbon atoms of the aryl group is 18 to 50, and n is an integer of 2 to 4. In addition, R ₁ , R ₂ may be the same or different from each other, hydrogen, SO ₂ R, CO ₂ R, SR, OR, NR ₂ , CN, halogen or Wherein R ₃ is hydrogen, SO ₂ R, CO ₂ R, SR, OR or NR ₂ , and R is an alkyl group having 1 to 10 carbon atoms.

Description

Organic luminescent compound including pyrazoline group, and organic electroluminescence device using the same

The present invention relates to an organic light emitting compound comprising a pyrazoline group, and more particularly, to an organic light emitting compound having a high heat resistance and comprising a pyrazoline group which can be used as a light emitting layer and / or a hole transport layer of an organic electroluminescent device. An electroluminescent device (OELD) relates.

An organic electroluminescent device is an image display device having a structure of generating light by inserting a low molecular or polymer organic light emitting compound between a transparent electrode (anode) and a metal electrode (cathode) and applying electric 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, compounds which are 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.

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 the functions of the light emitting layer and the 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 an 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 X is one or more aryl groups bonded with nitrogen, wherein the total number of carbon atoms of the aryl group is 18 to 50, and n is an integer of 2 to 4. In addition, R ₁ , R ₂ may be the same or different from each other, hydrogen, SO ₂ R, CO ₂ R, SR, OR, NR ₂ , CN, halogen or Wherein R ₃ is hydrogen, SO ₂ R, CO ₂ R, SR, OR or NR ₂ , and R is an alkyl group having 1 to 10 carbon atoms.

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 group, and has the following formula.

[Formula 2]

In the above formula, X is one or more aryl groups bonded to nitrogen, the total carbon number of the aryl group is 18 to 50, preferably an aryl group having 6 to 14 carbon atoms bonded via nitrogen to have a tertiary amine form It may be, or two or more such tertiary amines are bonded. The aryl group bonded to the nitrogen is preferably a phenyl group having 6 carbon atoms or a naphthyl group having 10 carbon atoms, and exemplifying a particularly preferable group as X is as follows.

, , , , ,

, , or

In Chemical Formula 2, n is the number of pyrazoline groups to be bonded, which is determined according to the type of X, but is usually an integer of 2 to 4. In addition, in Formula 2, R ₁ , R ₂ may be the same or different from each other, hydrogen, SO ₂ R, CO ₂ R, SR, OR, NR ₂ , CN, halogen (F, Cl, Br, I) or Wherein R ₃ is hydrogen, SO ₂ R, CO ₂ R, SR, OR or NR ₂ , and R is an alkyl group having 1 to 10 carbon atoms.

In general, compounds containing pyrazoline derivatives have excellent fluorescence efficiency but low thermal stability, but the organic light emitting compound of the present invention uses a linkage containing nitrogen to dimerize the pyrazoline derivatives. The organic light emitting compound according to the present invention is not only excellent in thermal stability, but also easy to transport holes by using an amine group as a linker. The luminous efficiency rises. Pyrazoline dimers, trimers or tetramers have a melting point (mp) of about 60 to 180 ° C. compared to pyrazoline monomers, and the monomers exhibit a glass transition temperature of 100 ° C. or more, compared to almost no glass transition temperature (Tg). Excellent heat resistance. 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.

The organic light emitting compound according to the present invention can be prepared by various known organic synthesis methods. For example, first reacting a tertiary amine compound or a combination of tertiary amine compounds corresponding to X in Formula 2 with dimethylformamide (DMF) and POCl ₃ , an aldehyde group is introduced into the tertiary amine compound (vilsmeier reagent). In this case, the number of aldehydes to be introduced is determined according to the equivalent of DMF and POCl ₃ . The number of aldehyde groups bonded is controlled according to the number n of pyrazoline groups bonded to the target compound, and the aldehyde reaction product can be separated by column chromatography to obtain a compound in which a desired number of aldehydes are bound. The combined aldehyde group and acetophenone can be reacted in an alcohol solvent to synthesize α, β unsaturated ketones, and then reacted with the obtained compound and phenylhydrazine in an alcohol solvent.

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 voltage is applied to the first and second electrodes 12 and 16 of the organic electroluminescent device, holes and electrons generated by 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 1-10

10 g of triphenylamine and 80 mL of N, N-dimethylformamide (DMF) were mixed, stirred at room temperature for 10 minutes, cooled to 0 ° C., and then 69 g (POCl ₃ ) of phosphorus oxychloride (POCl ₃ ) at 0 to 5 ° C. Drop it off. When the dropwise addition is completed, the temperature is raised to 90 ° C and reacted for 24 hours. After the reaction was completed, the mixture was cooled to room temperature, and slowly added dropwise the reaction solution to 1000 mL of ice water, followed by extraction with ethyl acetate. The solvent was distilled off under reduced pressure, and the compound with one and three aldehyde groups was separated and removed by column chromatography to obtain a yellow solid of the following Chemical Formula 3 in a yield of 70%. (H NMR data (400 MHz, CDCl ₃ ) δ9.9 (s, 2H, CHO), δ 7.8 (d, 4H), δ 7.4 (t, 2H), δ7.3 (t, 1H), 7.2 ( multi, 6H))

3 g of the obtained compound of Chemical Formula 3 and 30 mL of ethanol were mixed, 2.5 g of acetophenone substituted with 4-position of R ₅ was stirred, and then 1.67 g of potassium hydroxide was added thereto, followed by further stirring for 24 hours. When the reaction was completed, the reaction was filtered, washed with ethanol, and dried to give 4.5g (yield 90%) of a yellow solid of the formula (4). (H NMRdata (400 MHz, CDCl ₃ ) δ8.0 (d, 4H), δ7.7 (d, 2H), δ7.5 (m, 12H), δ7.3 (t, 2H), δ7.15 (t , 6H), δ 7.1 (d, 4H))

6 g of the α, β-unsaturated ketone obtained in Chemical Formula 4 and 5.2 g (4eq) of _4- phenyl substituted with R ₄ are suspended in 100 mL of ethanol and refluxed for 12 hours. When the reaction is complete, the reaction is cooled, filtered and washed with ethanol. The obtained yellow solid was separated by column chromatography to obtain 1.6 g of a white solid represented by the following Chemical Formula 5. (H NMR data (400MHz, CDCl ₃ ) δ7.7 (d, 4H), δ7.3 (m, 7H), δ7.2 (m, 8H), δ7.1 (d, 4H), δ7.05 ( d, 2H), δ7.0 (d, 4H), δ6.8 (t, 3H), DSC data: mp = 230 ° C, Tg = 110 ° C)

The compound of Formula 5 was synthesized by changing the substituent R ₅ of acetophenone and the substituent R ₄ of phenylhydrazine used in the reaction as shown in Table 1 below, and the PL (photoluminescence) data of the target compound according to the substituent were cyclohexane solvent. Measured using, the results are shown in Table 1 (Me represents a methyl group).

No R ₄ R ₅ absorption (λ _max ) Fluorescence (λ _max ) Example 1 H H 356 nm 430 nm Example 2 NH ₂ H 375 nm 484 nm Example 3 OMe H 366 nm 450 nm Example 4 SMe H 366 nm 465 nm Example 5 CO ₂ Me H 364 nm 405 nm Example 6 SO ₂ Me H 355 nm 410 nm Example 7 H NH ₂ 350 nm 430 nm Example 8 H OMe 360 nm 465 nm Example 9 H CO ₂ Me 355 nm 465 nm Example 10 H SO ₂ Me 390 nm 460 nm

As can be seen from the table, the organic light emitting compound according to the present invention emits blue light in various regions according to the type of substituents, and also in the case of the organic light emitting compound according to the present invention having the form of a trimer or tetramer. Results similar to Table 1 are shown.

Example 11

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 3 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 5230 cd / m ² and a maximum emission wavelength of 465 nm and a luminous efficiency (lumen / watt) of 2.7 lm / w.

As described above, the organic light emitting compound including the pyrazoline group according to the present invention not only is more stable than the existing organic light emitting compound, but also includes an amine group that can serve as a hole transport layer, and thus has excellent efficiency. Since the color purity of blue can be changed depending on 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 X is one or more aryl groups bonded with nitrogen, wherein the total number of carbon atoms of the aryl group is 18 to 50, and n is an integer of 2 to 4. In addition, R ₁ , R ₂ may be the same or different from each other, hydrogen, SO ₂ R, CO ₂ R, SR, OR, NR ₂ , CN, halogen or Wherein R ₃ is hydrogen, SO ₂ R, CO ₂ R, SR, OR or NR ₂ , and R is an alkyl group having 1 to 10 carbon atoms. The organic light emitting compound according to claim 1, wherein X is an aryl group having 6 to 14 carbon atoms bonded through nitrogen to form a tertiary amine, or two or more tertiary amines are bonded to each other. . The method of claim 1, wherein X is , , , , , , And An organic light emitting compound, characterized in that selected from the group consisting of. 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 X is one or more aryl groups bonded with nitrogen, wherein the total number of carbon atoms of the aryl group is 18 to 50, and n is an integer of 2 to 4. In addition, R ₁ , R ₂ may be the same or different from each other, hydrogen, SO ₂ R, CO ₂ R, SR, OR, NR ₂ , CN, halogen or Wherein R ₃ is hydrogen, SO ₂ R, CO ₂ R, SR, OR or NR ₂ , and R is an alkyl group having 1 to 10 carbon atoms. 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.