KR100407250B1 - Organic luminescent compound, and organic electroluminescence device using the same - Google Patents

Abstract

The present invention relates to an organic light emitting compound having high heat resistance and high quality blue light emission, and an organic electroluminescent device including the same, comprising: a first electrode having a low work function, a second electrode having a high work function, and a chemical formula Provided is an organic electroluminescent device comprising a novel organic light emitting compound represented by and comprising an organic light emitting layer positioned between the first and second electrodes.

Wherein M is Li, Na or K, X is N, O or S, R ₁ to R ₈ may be the same as or different from each other, hydrogen or substituted or unsubstituted alkyl having 1 to 10 carbon atoms, aryl, Heteroaryl or fused ring groups.

Description

Organic luminescent compound, and organic electroluminescence device using the same

The present invention relates to an organic light emitting compound having a novel structure, and more particularly, to an organic light emitting compound having high heat resistance, which can be used as a light emitting layer and / or an electron transport layer of an organic electroluminescent device, and an organic electroluminescent device using the same. Electroluminescence device (OELD).

Electroluminescence devices, commonly referred to as EL, 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 to reduce the thickness of the light emitting layer and to lower the resistance and driving voltage of the light emitting layer. Metal complex compounds such as ZnPBO and Balq that emit light at (460 nm), DPVBi which is a styrylarylene derivative, OXA-D which is an oxadiazole derivative and BczVBi as a single layer device, and red 4- (Dicyanomethylene) -2-methyl-6- (p-dimethylaminostyryl) -4H-pyran (4- (dicyanomethylene) -2-methyl-6- (p) that emits light in the region (590 nm) -dimethyl aminostyryl) -4H -pyran: DCM), DCJTB of the DCM series that emits light at 630nm is known. Recently, a color light emitting layer has been developed and used to improve the luminous efficiency and durability by forming a guest-host doping system by mixing a host material having sufficient electron, hole mobility, and luminescence with a dopant having various hues. have.

Among such 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 the DPVBi derivative is easy to deteriorate 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 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 exhibit high quality blue and an organic electroluminescent device using the same.

It is another object of the present invention to provide an organic light emitting compound that 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 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 a compound represented by the following Chemical Formula 2, wherein at least one organic material is disposed between the first and second electrodes. An organic electroluminescent device comprising a light emitting layer is provided.

Wherein M is Li, Na or K, X is N, O or S, R ₁ to R ₈ may be the same as or different from each other, hydrogen or substituted or unsubstituted alkyl having 1 to 10 carbon atoms, aryl, Heteroaryl or fused ring groups.

In the organic electroluminescent device, it is preferable that an electron transport layer including the compound of Formula 2 is further formed between the second electrode and the organic light emitting layer.

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

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

Wherein M is Li, Na or K, X is N, O or S, and R ₁ to R ₈ may be the same as or different from each other, and hydrogen or substituted or unsubstituted t-butyl and the like have 1 to 10 carbon atoms. Alkyl, aryl, heteroaryl, or fused ring groups.

Herein, M is Li, and X is more preferably O. The fused ring group is a group formed by conjugation of a ring compound to each other, and non-limiting examples of such a fused ring group include , , , , A compound in which two or more benzene rings are bonded; , , , , , , , And R ₁ and R ₂ , R ₂ and R ₃ , R ₃ and R ₄ , R ₅ and R ₆ , R ₆ and R ₇ , and / or R ₇ and R ₈ are joined to form a junction ring. It may form, and such a conjugated ring group may be a heterocyclic compound.

The organic light emitting compound according to the present invention exhibits excellent blue light emitting properties, and a preferred example of such an organic light emitting compound includes a compound represented by the following Chemical Formula 3.

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, exemplifying the method for preparing the compound of Formula 3, first, methanol, ethanol, isopropyl alcohol Excess 2- (2-hydroxybenz) oxazole and metal boron compounds such as LiBH ₄ , NaBH ₄ , KBH ₄ and the like are mixed in an alcohol solvent such as, and stirred at room temperature for 30 to 60 hours, or refluxed for reaction. Proceed. The solid product thus obtained can be washed with an alcohol solvent and dried in vacuo to yield a relatively pure boron complex. A very pure boron complex can be obtained by removing impurities through a purification process such as sublimation of the obtained boron complex under vacuum and elevated temperature conditions.

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 organic light emitting compound according to the present invention is formed on the first electrode 12. 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 hole injection from the hole injection electrode 12, to transport holes stably, and to block electrons, and to the hole injection layer 21. A non-limiting example may be a porphyrinic compound such as phthalocyanine copper disclosed in US Pat. No. 4,356,429, and the hole transport layer 22 may include a triphenyldiamine derivative, a styrylamine derivative, and N, N'-. An amine derivative having an aromatic condensed ring such as bis- (1-naphthyl) -N, N'-diphenylbenzidine can be used.

The electron injection and transport layers 25 and 26 are functions of facilitating injection of electrons from the electron injection electrode 16, stably transporting electrons, and blocking holes, and are not limited to chinoline. It is also possible to use derivatives, in particular tris (8-chinolinorate) aluminum (aluminaquinone, Alq3). These layers function to augment, confine, and combine holes and electrons injected into the light emitting layer 14, and to improve luminous efficiency. 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 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 having the structure shown in FIG. 1 or 2, but also to the organic electroluminescent device having various structures exhibiting light emission phenomenon by hole-electron coupling, and a blue light emitting host The organic light emitting layer 14 may be included as a material or a dopant, or may be included in the electron transport layer 26 to perform an electron transport function.

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

30 g (0.142 mol) of 2- (2-hydroxybenzoxazole) was added to 450 ml of isopropyl alcohol, and then 0.773 g (0.0355 mol) of LiBH ₄ was added thereto, followed by stirring at room temperature for 48 hours. The resulting reaction was filtered to obtain a solid sample, which was then added to 450 ml of isopropyl alcohol and stirred, filtered, and vacuum dried to give 21.43 g (yield: 70%) of a relatively pure boron complex. 1 g of the boron complex obtained by the above method was purified by sublimation, one of the conventional purification methods. Sublimation conditions were raised to 370 ° C. at 2 ° C./min under a vacuum of 4.2 × 10 ⁻³ torr, and the impurities were removed by sublimation of the boron complex. The yield of the sublimation process was 0.3 g (30%).

As described above, the organic light emitting compound according to the present invention is not only excellent and stable in heat resistance, but also emits high-quality blue light. The organic light emitting compound 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 transporting layer.

Claims (4)

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 M is Li, Na or K, X is N, O or S, R ₁ to R ₈ may be the same as or different from each other, hydrogen or substituted or unsubstituted alkyl having 1 to 10 carbon atoms, aryl, Heteroaryl or fused ring groups. The organic light emitting compound of claim 1, wherein the organic light emitting compound has the following formula. A first electrode having a high work function; A second electrode having a low work function; And An organic electroluminescent device comprising an organic light emitting compound represented by Formula 2 and comprising at least one organic light emitting layer positioned between the first and second electrodes. [Formula 2] Wherein M is Li, Na or K, X is N, O or S, R ₁ to R ₈ may be the same as or different from each other, hydrogen or substituted or unsubstituted alkyl having 1 to 10 carbon atoms, aryl, Heteroaryl or fused ring groups. The organic electroluminescent device according to claim 3, wherein an electron transport layer including the compound of Formula 2 is further formed between the second electrode and the organic light emitting layer.