KR100462050B1 - Novel organometallic compound including oxa- or thiadiazole moiety and organic electroluminescence device using the same - Google Patents

Abstract

The present invention relates to an organometallic complex exhibiting high-quality blue color and high stability and heat resistance, and an organic electroluminescent device using the same, which provides a novel organometallic complex having a structure of any one of Chemical Formulas 2 to 5. The present invention also includes a first electrode having a high work function, a second electrode having a low work function, and the organometallic complex, and including at least one organic compound layer positioned between the first and second electrodes. It provides an organic electroluminescent device.

[Formula 2]

[Formula 3]

[Formula 4]

[Formula 5]

Wherein M ₁ is Li, Na or K, M ₂ is the same or different divalent metal, R ₁ to R ₉ may be the same or different, hydrogen or substituted or unsubstituted carbon of 1 to 10 Alkyl, aryl, heteroaryl or fused ring group, X is O or S.

Description

Novel organometallic compounds including oxa- or thiadiazole moiety and organic electroluminescence device using the same

The present invention relates to a novel organometallic complex comprising an oxa- or thiadiazole moiety. More specifically, the present invention relates to a novel organometallic complex comprising, in particular, high heat resistance, high quality blue light emission, and use as an emission layer and / or electron transport layer of an organic electroluminescent device. The present invention relates to an organometallic complex and an organic electroluminescence device (OELD) using the same.

Electroluminescence devices, commonly referred to as ELs, are representative flat panel displays such as liquid crystal displays (LCDs), plasma display panels (PDPs), field emission displays (FEDs), and the like. As one of the devices, there is no need for a backlight as in an LCD, a fast response speed, and a spontaneous light emitting device, which has excellent brightness and viewing angle characteristics. In particular, the organic electroluminescent device forms an organic light emitting layer that exhibits strong light emission between a transparent electrode such as ITO having a large work function and an electrode such as Mg having a small work function, and applies a voltage to the electrode to generate holes generated at each electrode. And when the electrons are combined in the organic light emitting layer, the organic light emitting layer generates light, and the device can be manufactured in a thin film and a bendable form, and the pattern formation and mass production by the film fabrication technology are easy. Rather, the driving voltage is low, and theoretically, all colors can be emitted in the visible region.

Conductive, non-conductive or semiconducting organic monomolecules, oligomers, or polymers may be used as the material capable of forming the organic light emitting layer, and the organic monomolecule having luminescence may be conjugated with a plurality of benzene rings. Conjugated organic host materials and conjugated organic activators are known. Typical examples of the organic host material include naphthalene, anthracene, phenanthrene, pyrene, benzopyrene, chrisene, picene, carbazole (carbazole), fluorene, biphenyl, terphenyl, qurterphenyl, triphenylene oxide, dihalobiphenyl, transstilbene ), 1,4-diphenyl butadiene, and the like, anthracene, tetracene, pentacene, and the like are known. 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 5,150,006), BeBq2 (10-benzo [h] quinolinol- beryllium complex. Chemistry Letters (1993), 905-906), Almq (tris (4-methyl-8 -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) And the like, and the red region ( 590 nm), 4- (dicyanomethylene) -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 the organic light emitting compounds, a compound typically used as a blue light emitter is a DPVBi derivative represented by Chemical Formula 1 (see US Pat. Nos. 5,503,910 and 5,536,949). However, since such DPVBi derivatives are easily deteriorated due to low heat resistance, the DPVBi derivative not only reduces the lifespan of the organic electroluminescent device, but also has a disadvantage in that it does not emit high-quality blue color on a color coordinate.

In addition, US Patent No. 5,336,546 discloses an organic light emitting compound comprising an oxadiazole or thiadiazole moiety, US Patent No. 5,486,406 an organometallic including a benzotriazole derivative Complex luminescent materials are disclosed, and European Patent No. 700,917 discloses organometallic complex luminescent materials comprising benzoxazole derivatives.

It is therefore an object of the present invention to provide an organometallic complex having an oxa- or thiadiazole moiety and a organic electroluminescent device using the same, which have a novel structure that is not known in the prior art.

Another object of the present invention is to provide an organometallic complex and an organic electroluminescent device using the same, which are excellent in heat resistance and stable, and can exhibit high quality blue.

Still another object of the present invention is to provide an organic metal complex which can be used as a host material or a blue dopant of an organic light emitting layer, and can also be used as an electron transport 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 novel organometallic complex having a structure of any one of the following formulas 2 to 5 as a compound which emits light by receiving energy generated by the recombination of electron-holes. The present invention also includes a first electrode having a high work function, a second electrode having a low work function, and the organometallic complex, and including at least one organic compound layer positioned between the first and second electrodes. It provides an organic electroluminescent device.

Wherein M ₁ is Li, Na or K, M ₂ is the same or different divalent metal, R ₁ to R ₉ may be the same or different, hydrogen or substituted or unsubstituted carbon of 1 to 10 Alkyl, aryl, heteroaryl or fused ring group, X is O or S. In the organic electroluminescent device, the organic compound layer including any one of Formulas 2 to 5 may be an organic emission layer or an electron transport layer formed between the second electrode and the organic emission layer.

Hereinafter, the present invention will be described in more detail.

The organometallic complex according to the present invention has a structure of any one of the following Chemical Formulas 2 to 5 as a compound which emits light by receiving energy generated by recombination of electron-holes.

[Formula 2]

[Formula 3]

[Formula 4]

[Formula 5]

Wherein M ₁ is Li, Na or K, preferably Li, M ₂ is the same or different divalent metal, preferably Mg ⁺² , Zn ⁺² , or Be ⁺² , R ₁ R ₉ may be the same as or different from each other, and hydrogen or a substituted or unsubstituted alkyl, aryl, heteroaryl, or fused ring group having 1 to 10 carbon atoms, and X is O or S. A fused ring group is a group formed by conjugation of ring compounds to each other. , , , , A compound in which two or more benzene rings are conjugated may be exemplified, and R ₁ to R ₉ may form a conjugated conjugated ring together with a benzene ring forming the structure of Chemical Formulas 2 to 5. .

The organometallic complex according to the present invention uses an oxadiazole or thiadiazole derivative which emits light from blue to green depending on a substituent, and uses the ligand and Li, Na, K, B, and divalent. Metal salts and the like form an organometallic complex. Therefore, the organometallic complex according to the present invention can emit high quality blue according to the type of ligand, has high efficiency and heat resistance, and can be used as an emission layer and an electron transfer layer of an organic electroluminescent device.

The organic light emitting compound according to the present invention can be prepared by a variety of known organic synthesis method, and the manufacturing method is not particularly limited, but exemplifying a method for producing a compound having the structure of Formula 2 or 3. First, as shown in Scheme 1 below, methyl-2-methoxybenzoate and hydrazine monohydrate are reacted, and then, as shown in Scheme 2, the compound obtained in Scheme 1 and benzoyl chloride are reacted, and a cyclization reaction is carried out. To form an oxadiazole ring (see Scheme 3), followed by a hydrolysis reaction (Scheme 4). When the compound obtained in Scheme 4 is refluxed and stirred together with a metal salt such as lithium salt or zinc salt, a compound having the structure of Chemical Formula 2 or 3 may be prepared.

In addition, the compound having the structure of Formula 4 or 5, first reacted with methyl-2-methoxybenzoate and hydrazine monohydrate, as shown in Scheme 1, then, as shown in Scheme 5 below, obtained in Scheme 1 The compound is reacted with 2-methoxybenzoyl chloride, an oxadiazole ring is formed using a cyclization reaction (see Scheme 6), and then a hydrolysis reaction is performed (Scheme 7). When the compound obtained in Scheme 7 is refluxed and stirred together with a metal salt such as lithium salt or zinc salt, a compound having Chemical Formula 4 or 5 may be prepared.

1 is a cross-sectional view of an organic EL device according to an embodiment of the present invention. As shown in FIG. 1, an organic EL device includes a first electrode having a high work function on an upper surface of a substrate 10. 12 is formed as a hole injection layer (anode), and at least one light emitting layer 14 including the organometallic complex according to the present invention is formed on the first electrode 12. In addition, the light emitting layer 14 may include a conventional organic light emitting compound, a conventional fluorescent dye, and / or a dopant together with the organometallic complex according to the present invention. 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 functions as a hole injection layer (anode), and is made of indium tin oxide (ITO), polyaniline, silver (Ag), or the like having a high work function without limitation. The second electrode 16 may be formed of a metal alloy, such as Al, Mg, Ca, or LiAl, Mg-Ag, which functions as an electron injection layer and has a low work function. Can be.

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 is different from the organic electroluminescent element shown in FIG. 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 formed of a triphenyldiamine derivative, a styrylamine derivative, α-NPD (N, N′-diphenyl-N, N′-bis (α-naphthyl)-[1, And a conventional amine derivative having an aromatic condensed ring such as 1'-biphenyl] 4,4'-diamine) The electron injection and transport layers 25 and 26 are formed from the electron injection electrode 16. Functions to facilitate the injection of electrons, to transport electrons stably, and to prevent holes As the compound according to the present invention, alone or without limitation, the electron transport layer 26 together with conventional compounds such as, but not limited to, chinoline derivatives, especially tris (8-kinolinorate) aluminum (aluminaquinone, Alq3). These layers serve to augment, confine, and combine the holes and electrons injected into the light emitting layer 14. The light emitting layer 14, the hole injection and transport layer 21, respectively. , And the thickness of the electron injection and transport layers 25 and 26 is not particularly limited and may vary depending on the formation method, but usually has a thickness of about 5 to 500 nm.

The organic light emitting compound according to the present invention may be included in the hole injection and transport layers 21 and 22 and / or the electron injection and transport layers 25 and 26, and the organic layers may be vacuum used for fabricating an organic electroluminescent device. It may be formed by a vapor deposition method or spin coating method. 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 are intended to illustrate the invention, not to limit the invention.

Preparation Example 1 Synthesis of Oxadiazole Derivative

To 9.7 ml of hydrazine monohydrate, 5 ml of methanol was added and refluxed, and 14.3 ml of methyl-2-methoxybenzoate was added dropwise for 1 hour. After further refluxing for 5 minutes, the mixture was cooled and decompressed to remove the solvent and excess hydrazine, and 70 ml of N-methylpyrrolidinone was added to the composite, followed by benzoyl chloride at room temperature. 11.64 ml was added dropwise, stirred at room temperature for 1 hour, and 100 ml of ice water was added to obtain a white solid.

The white solid obtained was filtered, washed with water, 1.54 g of phosphorus pentoxide and 18.5 g of methanesulfonic acid were added to 0.86 g of a dry white solid, followed by stirring at 120 ° C. for 3 hours. Then cooled. Next, 100 ml of ice water was added thereto, and the reaction solution was extracted with methylene chloride. After the solvent was blown, 15 ml of methylene chloride was further added to the compound, and the mixture was cooled to 0 ° C. Next, a solution of 1.3 ml of boron tribromide diluted in 5 ml of methylene chloride was added dropwise to the compound at 0 ° C. for 15 minutes, and then stirred at room temperature for 2 hours. Then, the reactant was added to 100 ml of ice water, Extraction, the obtained extract was crystallized with ethanol, filtered and washed with ethanol to 2- (5-phenyl- [1,3,4] oxadiazol-2-yl) -phenol of formula 6 0.4 g of 2- (5-Phenyl- [1,3,4] oxadiazol-2-yl) -phenol) was obtained.

Preparation Example 2 Synthesis of Oxadiazole Derivative

4.27 g of o-anisoyl chloride was added dropwise instead of 11.64 ml of benzoyl chloride, and 0.96 g was used instead of 0.86 g of the white solid. 2- (5- (2-hydroxyphenyl)-[1,3,4] oxadiazol-2-yl) -phenol (2- (5- (2-hydroxyphenyl)-[1,3,4] oxadiazol -2-yl) -phenol) 0.4g was obtained.

Example 1 Synthesis of Lithium Salt

1.19 g of the compound synthesized in Preparation Example 1 was added to 70 ml of ethanol and refluxed until completely dissolved. Then, 0.22 g of lithium hydroxide monohydrate was added, and refluxed and stirred for 6 hours. The resulting solid was filtered and washed with ethanol to obtain 1.16 g of the target compound of the formula (8).

Example 2 Synthesis of Lithium Salt

1.00 g of the compound synthesized in Preparation Example 2 was added to 150 ml of ethanol, and refluxed until completely dissolved. Then, 0.36 g of lithium hydroxide monohydrate was added, and refluxed and stirred for 6 hours. The resulting solid was filtered and washed with ethanol to obtain 0.86 g of the target compound of formula (9).

Example 3 Synthesis of Boron Salt

1.19 g of the compound synthesized in Preparation Example 1 was added to 70 ml of isopropyl alcohol, and stirred at room temperature for 1 hour. Then, 0.027 g of lithium borohydride was added and stirred for 24 hours. The resulting solid was filtered and washed with isopropyl alcohol to obtain 0.86 g of the target compound of Formula 10.

Example 4 Synthesis of Zinc Salt

NaOH 1.59 mmol and 1.59 mmol of the compound synthesized in Preparation Example 2 were added to 20 ml of methanol, and refluxed and stirred. When the solution became transparent, 1.59 mmol of zinc acetate and dihydrate was added thereto, and the mixture was refluxed and stirred for 16 hours. After cooling, the solid was filtered and washed with water and methanol to obtain the target compound of formula 11 in 85% yield.

Example 5 Fabrication of Organic Electroluminescent Device

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 metal complex synthesized in Example 1 was deposited on the hole transport layer to a thickness of 600 kPa to form an organic light emitting layer, and then Alq3 was deposited on the organic light emitting layer to a thickness of 300 kW 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 luminous efficiency of the manufactured organic electroluminescent device was 2.1 lm / w, and showed a maximum light emission intensity of 6000 cd / m ² and a maximum light emission wavelength of 465 nm at 15V.

Example 6 Fabrication of Organic Electroluminescent Device

An organic electroluminescent device was manufactured in the same manner as in Example 5, except that the organometallic complex obtained in Example 4 was used. The luminous efficiency of the manufactured organic electroluminescent device was 1.81 lm / w, and showed a maximum emission intensity of 5500 cd / m ² and a maximum emission wavelength of 450 nm at 15V.

As described above, the novel organometallic complex containing the oxa- or thiadiazole moiety according to the present invention is not only excellent in heat resistance and stable, but also emits blue light of high quality and various wavelengths depending on the substituent. The organometallic complex may not only be used as a host material or a blue dopant of the organic light emitting layer, but may also be used as an electron transport layer.

Claims (4)

An organometallic complex having a structure of Formula 3 below, which emits light by receiving energy generated by electron-hole recombination. [Formula 3] Wherein M ₁ is Li, Na or K, R ₁ to R ₉ may be the same or different from each other, hydrogen or substituted or unsubstituted alkyl, aryl, heteroaryl or fused ring of 1 to 10 carbon atoms ) And X is O or S. delete A first electrode having a high work function; A second electrode having a low work function; And An organic electroluminescent device comprising an organometallic complex of Formula 3 and comprising at least one organic compound layer positioned between the first and second electrodes. [Formula 3] Wherein M ₁ is Li, Na or K, R ₁ to R ₉ may be the same or different from each other, hydrogen or substituted or unsubstituted alkyl, aryl, heteroaryl or fused ring of 1 to 10 carbon atoms ) And X is O or S. The organic electroluminescent device according to claim 3, wherein the organic compound layer including the organometallic complex is an organic light emitting layer or an electron transport layer formed between the second electrode and the organic light emitting layer.