KR20140098497A - Novel flurocycloalkene Iridium complex group and organic electroluminescent devices using the same - Google Patents

Abstract

The present invention relates to a novel blue phosphorescent material and an organic electroluminescent device using the same and, more specifically, to a new form of a blue phosphorescent iridium complex compound applying fluorocycloalkene which is an electron pulling member to a main ligand of the iridium complex compound, and to an organic electroluminescent device using the same. The blue phosphorescent iridium complex compound according to the present invention can be a light emitting material of an organic electroluminescent device forming high color purity and having high light emitting efficiency, and can be used as an blue phosphorescent material for vacuum deposition and solution process.

Description

[0001] The present invention relates to an iridium complex containing a novel fluorinated cycloalkene and an organic electroluminescent device employing the iridium complex,

The present invention relates to a novel blue phosphorescent material and an organic electroluminescent device employing the same. More particularly, the present invention relates to a novel blue phosphorescent iridium complex which introduces a fluorinated cycloalkene as an electron withdrawing group into a main ligand of an iridium complex, To an organic electroluminescent device.

The blue phosphorescent iridium complex according to the present invention can be utilized as a light emitting material of organic electroluminescent devices having a high color purity and a high luminous efficiency and can be used as a blue phosphorescent material for vacuum vapor deposition and solution process.

Nowadays, as the development of the IT field has been progressed rapidly and rapidly, the display field has become necessary to enhance the ability to express information in accordance with the display field, and the display field has grown accordingly. Liquid Crystal Display (LCD), which has been mainly used as a display window for TVs, laptops and mobile phones until recently, is a backlight system that emits light from the back, so it is not visible from the side because of its low color purity, Point, and a residual image due to a slow reaction rate. As a solution to this problem, many companies actively studied organic light-emitting diodes (OLEDs). OLEDs are self-luminous and require no back-ride, and their response speed is faster than LCD, they are superior to LCD in almost all aspects such as low DC driving voltage, wide viewing angle, lightweight thin, And has recently been recognized as a display core technology as a product that has applied technology has been released. However, the problems of efficiency and color purity remain, and it is urgent to develop a blue organic light emitting material for easier practical use of OLED.

The structure of the organic EL device generally includes an anode, a hole injection layer (HIL), a hole transfer layer (HTL), an emission layer (EML), an electron transfer layer (ETL) ), An electron injection layer (EIL), and a cathode. The thin film layers are formed by thermal evaporation at a high vacuum (10 ^-6 to 10 ^-7 Torr) . In the luminescent mechanism, first, holes are injected from the anode and electrons are injected from the cathode, and they meet in the light emitting layer to form an unstable exciton. This unstable exciton becomes stable again and releases energy, which is emitted as light energy. Because OLED is driven by this principle, emitting material is also important, but it is also important that electrons and holes must meet in the light emitting layer, so it is also important to inject and transport electrons and holes.

The color of the light emitted from the OLED is determined by the energy level difference between the HOMO-LUMO of the light emitting material. When the energy difference becomes large, the short wavelength light and the energy difference emit light of a long wavelength. The energy gap between HOMO-LUMO can be controlled by varying the conjugation length of the molecule using LCAO (Linear Combination of Atomic Orbital) method. As a result, when the conjugation becomes longer, the band gap becomes smaller and the wavelength becomes longer. In order for OLED to display all the colors of nature, red, green, and blue colors are required, which are the three primary colors of light. However, the development of high efficiency blue light emission is the most problematic for the practical use of OLED, which causes a problem that the performance of the entire device is deteriorated due to low color purity and lifetime of the blue light emitting material compared with other materials.

Eastman Kodak Company, in 1987, developed an organic electroluminescent device using a low-molecular aromatic diamine and an aluminum complex as a light emitting layer forming material (Appl. Phys. Lett. 51, 913, 1987) A polymer such as poly (p-phenylenevinylene) (PPV) and poly (2-methoxy-5- (2'-ethylhexyloxy) -1,4-phenylene vinylene) (Nature, 347, 539, 1990 & Appl. Phys. Lett. 58, 1982, 1991). In 2000, Princeton University developed an electrophosphorescent device containing Ir as a light emitting layer forming material (Nature, 403, 750, 2000).

However, in the case of an iridium-based light emitting compound, blue light emission has many problems in terms of color purity and efficiency. Generally, the luminescent color of an iridium complex having a phenylpyridine ligand shifts to blue as the electron density to the phenyl group becomes smaller and the electron density to the pyridine group increases. However, except for F, CF ₃ , and CN, most of the electron withdrawing substances that reduce the electron density do not move to blue due to the expansion of the conjugate, but rather exhibit red migration.

Korean Patent Publication No. 10-2009-0010865 (Jan. 30, 2009) Korean Patent Laid-Open No. 10-2011-0125932 (Nov. Korean Patent Laid-Open No. 10-2009-0052095 (2009.05.25.)

 Appl. Phys. Lett. 51, 913, 1987  Nature, 347, 539, 1990  Appl. Phys. Lett. 58, 1982, 1991  Nature, 403, 750, 2000

It is an object of the present invention to provide a novel type of blue phosphorescent iridium complex which is easy to sublimate and purify by introducing a fluorinated cycloalkene as an electron withdrawing group into the main ligand of the iridium complex and has high color purity and high efficiency.

Another object of the present invention is to provide a display element employing the blue phosphorescent iridium complex as a coloring material.

It is still another object of the present invention to provide an organic electroluminescent device comprising the blue phosphorescent iridium complex in the light emitting layer.

The present invention relates to a novel blue phosphorescent material and an organic electroluminescent device employing the same. More particularly, the present invention relates to a novel blue phosphorescent material and a novel organic phosphorescent material employing the blue phosphorescent material, Phosphorescent iridium complexes, and organic electroluminescent devices employing the phosphorescent iridium complexes.

[Chemical Formula 1]

In Formula 1,

R is selected from C ₁ -C ₆ alkyl, C ₆ -C ₁₂ aryl, C ₆ -C ₁₂ aryloxy, di C ₁ -C ₆ alkylamino and SiR ₁ R ₂ R ₃ , wherein R ₁ to R ₃ are each Independently, C ₁ -C ₆ alkyl or C ₆ -C ₁₂ aryl, m is an integer from 1 to 4, L is an organic ligand, and n is an integer from 1 to 3.

Wherein R is selected from the group consisting of methyl, ethyl, propyl, butyl, pentyl, hexyl, phenyl, naphthyl, biphenyl, phenoxy, dimethylamino, methylethylamino, diethylamino, trimethylsilyl, Dimethylphenylsilyl.

In the above formula (1), L may be exemplified by organic ligands selected from the following structures, but is not limited thereto:

Each of R ₁₁ to R ₁₄ is independently hydrogen, C ₁ -C ₆ alkyl, halo C ₁ -C ₆ alkyl, C ₁ -C ₆ alkoxy or C ₆ -C ₁₂ aryl;

R ₁₅ is C _a F _{2a +1} ;

a is an integer of 1 to 10;

R ₁₆ and R ₁₇ are each independently C ₁ -C ₆ alkyl or C ₆ -C ₁₂ aryl;

A is O or N;

Preferably, L in the above formula (1) can be selected from the following structures:

Specifically, the iridium luminescent compound of Formula 1 according to the present invention may be represented by the following compounds, but is not limited thereto:

The present invention also relates to a display element employing the iridium luminescent compound of Formula 1 as a coloring material.

In addition, the present invention relates to an organic electroluminescent device comprising an anode, a cathode, and a light emitting layer between both electrodes, wherein the organic electroluminescent device includes an iridium luminescent compound of Formula 1 in the luminescent layer, Lt; / RTI >

The iridium luminescent compound of formula (1) according to the present invention, when used together with itself or a blue host, is excellent in luminescence efficiency as a blue luminescent material and useful as a coloring material for a display device.

Since the blue phosphorescent iridium complex according to the present invention introduces the fluorinated cycloalkene as the electron withdrawing group to the main ligand of the iridium complex in order to solve the problems of the sublimation purification phase, color purity and luminous efficiency of the conventional iridium organic complexes, And as a light emitting material of an organic electroluminescent device having a high luminous efficiency, and can be used as a blue phosphorescent material for vacuum vapor deposition and solution process.

The iridium luminescent compound of the formula (1) according to the present invention can be used as a blue luminescent material together with a blue host. Here, the blue host is not particularly limited, and specific examples thereof may be selected from the following structural formulas, but are not limited thereto.

Hereinafter, a method of manufacturing an organic electroluminescent device according to the present invention will be described.

First, an anode electrode material is coated on the substrate. As the substrate, a substrate used in a conventional organic EL device is used, and a glass substrate or a transparent plastic substrate having excellent transparency, surface smoothness, ease of handling, and waterproofness is preferable. As the material for the anode electrode, indium tin oxide (ITO), tin oxide (SnO ₂ ), zinc oxide (ZnO), indium zinc oxide (IZO), antimony tin oxide (ATO) and the like which are transparent and excellent in conductivity are used.

A hole transport layer is formed on the anode by vacuum deposition or spin coating. An iridium luminescent compound of Formula 1 is vacuum-deposited on the hole transport layer to form a light emitting layer.

The hole transporting layer material is not particularly limited, and may be selected from the group consisting of N, N'-bis (3-methylphenyl) -N, N'- diphenyl- [1,1'- biphenyl] -4,4'- diamine (TPD) NPN), 9,9-bis [4- (N, N-bis-biphenyl-4- (Phenyl) -9H-fluorene (BPAPF), N, N'-bis (phenanthrene-9-yl) -N, N'- (N, N-ditolyl-amino) -phenyl] cyclohexane (TAPC) and N, N, N ', N'-tetra-naphthalene-benzidine (α-TNB).

A metal for forming a cathode is vacuum-deposited on the light emitting layer to form a cathode, thereby completing the organic EL device. Here, the metal for cathode formation may be Li, Mg, Al, Al-Li, Ca-Al, LiF-Al ), Magnesium-indium (Mg-In), magnesium-silver (Ag-Ag), barium-aluminum (Ba-Al), gold (Au), silver (Ag) and copper (Cu)

A hole barrier layer or an electron transport layer may be formed on the emission layer before forming the cathode. The hole blocking layer and the electron transporting layer use a typical hole blocking layer electron transporting layer forming material.

The organic electroluminescent device of the present invention can further form an intermediate layer between the two selected from among the anode, the hole transporting layer, the light emitting layer, the electron transporting layer and the cathode. For example, a hole injection layer (HIL) may be further formed between the anode and the hole transport layer. When the hole injection layer is formed as described above, the hole transport layer (for example,? -NPD) and the anode Thereby improving adhesion and assisting injection of holes from the anode into the hole transport layer.

The material for forming the hole injection layer is not particularly limited, but CuPc, m-MTDATA, 1I-TNATA, 2T-NATA, NATA, NTNPB, NPNPB and MeO-TPD are used.

The organic electroluminescent device may be manufactured in the order as described above, that is, in the order of anode / hole transporting layer / light emitting layer / hole blocking layer / electron transporting layer / cathode, / Hole transporting layer / anode.

The present invention provides an iridium luminescent compound and an organic electroluminescent device employing the iridium luminescent compound as a coloring material. The organic electroluminescent device according to the present invention has remarkably improved color purity and luminescent efficiency characteristics and is useful for a display element employing it as a coloring material Can be used to make.

That is, since the blue phosphorescent iridium complex according to the present invention introduces the fluorinated cycloalkene as the electron withdrawing group into the main ligand of the iridium complex in order to solve the problem of the sublimation purification phase, color purity and luminous efficiency of the iridium organic complex, It can be used as a light emitting material of an organic electroluminescent device having color purity and high luminous efficiency and can be used as a blue phosphorescent material for vacuum vapor deposition and solution process.

1 - thermogravimetric analysis (TGA) of the iridium complex A prepared in Example 1,
2 - Differential calorimetric analysis (DSC) of the iridium complex A prepared in Example 1,
Figure 3 - UV absorption and PL spectra of the liquid state of the iridium complex A prepared in Example 1
4 - Cyclic Voltammetry Curve of Iridium Complex A prepared in Example 1
5 - PL spectra and color coordinates of liquid state of iridium complex A prepared in Example 1

The present invention can be more clearly understood by the following examples, and the following examples are merely illustrative of the present invention and are not intended to limit the scope of the invention.

[ Example  1] Preparation of iridium complex A

Preparation of compound a-1

Mg (0.85 g, 34.9 mmol), 2-bromo-4-methylpyridine (6 g, 34.9 mmol) and purified THF (100 mL) were added to a 250 mL three-necked flask and stirred at room temperature for 1 hour. Perfluorocyclopentene (7.4 g, 34.9 mmol) and Ni (dppp) Cl ₂ (0.32 g, 0.6 mmol) were added to a refluxed 500 mL three-necked flask containing 50 mL of THF and stirred slowly. An ice-bath was installed and the Grignard reagent made at 0 ° C was slowly added dropwise and stirred for 18 hours. After completion of the reaction, the reaction mixture was extracted with Et ₂ O (200 mL) and washed with water (100 mL × 3). The organic solution was dehydrated with MgSO ₄ and the solvent was removed using a rotary evaporator. The product was separated by column chromatography (n-hexane / ethyl acetate; 3/1 v / v) to obtain the compound a-1 (yield: 1.95 g (20%)).

¹ H NMR (300 MHz, DMSO-d ₆ )? 8.53 (d, 1H), 8.24 (s, 1H), 7.29 (d,

Preparation of compound a-2

Compound ( a-1) (1.95 g, 6.83 mmol) and purified THF (30 mL) were added to a 100 mL three-necked flask, and the mixture was cooled to -78 ° C and stirred for 20 minutes. Then, 0.2 M NaBH ₄ (17.1 mL, 3.42 mmol) was slowly added thereto, followed by stirring at -78 ° C for 3 hours. The reaction temperature was raised to 0 ° C and distilled water (50 mL) was added to terminate the reaction. Extracted with ethyl acetate (200 mL), and washed with water (100 mL). The organic solution was dehydrated with MgSO ₄ and the solvent was removed using a rotary evaporator. The product was separated by column chromatography (n-hexane / ethyl acetate; 5/1 v / v) to obtain the compound a-2 (yield: 0.96 g (53%)).

^{1 H NMR (300 MHz, DMSO} -d 6) δ 8.64 (d, 1H), 7.70 (s, 1H), 7.43 (d, 1H), 6.83 (s, 1H), 2.40 (s, 3H).

Preparation of compound a-3

100 mL 2-necked flask to _{IrCl 3 · 3H 2 O (0.67} g, 2.24 mmol) and the compound a-2 (1.5 g, 5.61 mmol), into the 2-EtO-EtOH (20 mL ), at 80 ℃ for 12 hours It was cold. After the temperature is lowered to room temperature, distilled water (50 mL) is added and stirred to form a precipitate. The precipitate was filtered, washed with water (50 mL x 3), dried and the next step was carried out without purification.

^{1 H NMR (300 MHz, DMSO} -d 6) δ 7.64 (s, 2H), 7.33 (m, 2H), 7.16 (m, 4H), 7.09 (d, 2H), 7.04 (d, 2H), 2.27 ( s, 6H), 2.24 (s, 6H).

Preparation of Compound A

Na ₂ CO ₃ (0.5 g) was added to a well-dried two-necked flask and water was removed by using a torch. Then, Compound a-3 (1.3 g, 0.86 mmol), 2,4-pentadione (0.19 g, 1.89 mmol) 2-ethoxyethanol (10 mL) was added thereto, and the mixture was refluxed at 60 DEG C for 24 hours. After the temperature was lowered to room temperature, distilled water (50 mL) was added and stirred to form a precipitate. The precipitate was filtered, washed several times with water, and then dried. The product was separated by column chromatography (dichloromethane) to obtain Compound A (yield: 0.13 g (9%)).

^{1 H NMR (300 MHz, CDCl} 3) δ 8.30 (d, 2H), 6.97 (d, 2H), 6.85 (s, 2H), 5.32 (s, 1H), 2.35 (s, 6H), 2.12 (s, 6H).

¹⁹ F NMR (300 MHz, CDCl ₃ )? -107.23, -111.59, -112.09, -114.72, -115.70, -115.74, -117.74, -117.78, -118.28, -118.32, -122.19, -122.69.

In order to examine the thermal properties of the iridium complex A prepared in Example 1, a thermogravimetric analysis (TGA) was carried out by heating to 10 ° C. per minute from 50 ° C. to 500 ° C. under a nitrogen atmosphere, Respectively.

The thermal stability of the iridium complex A prepared in Example 1 was measured by a thermal analyzer (DSC). The results are shown in FIG.

FIG. 3 shows UV absorption and PL spectra of the iridium complex A prepared in Example 1 in liquid state.

The electrochemical characteristics of the iridium complex A prepared in Example 1 were measured by a cyclic voltammetry. This was measured under the conditions of 100 mV / s in a solvent of ₄ NClO ₄ (0.1 molar concentration). In the measurement, a voltage was applied through the coating using a Pt electrode. The results are shown in Fig.

The PL spectra and the color coordinates of the liquid state of the iridium complex A prepared in Example 1 are shown in FIG.

The spectroscopic, thermal and electrochemical properties of the iridium complex A prepared in Example 1 are summarized in Table 1 below.

UV
(nm) PL
(nm) T _{5 % d}
( ^o C) T _g
( ^o C) T _m
( ^o C) HOMO
(eV) LUMO
(eV) E _g
(eV) CIE
(x, y) 249, 283, 334 401, 428 337 112.5 212 5.30 2.36 2.94 0.154, 0.036

Claims (8)

An iridium light-emitting compound represented by the following formula
[Chemical Formula 1]

In Formula 1,
R is selected from C ₁ -C ₆ alkyl, C ₆ -C ₁₂ aryl, C ₆ -C ₁₂ aryloxy, di C ₁ -C ₆ alkylamino and SiR ₁ R ₂ R ₃ , wherein R ₁ to R ₃ are each Independently, C ₁ -C ₆ alkyl or C ₆ -C ₁₂ aryl, m is an integer from 1 to 4, L is an organic ligand, and n is an integer from 1 to 3.
The method according to claim 1,
Wherein R is selected from methyl, ethyl, propyl, butyl, pentyl, hexyl, phenyl, naphthyl, biphenyl, phenoxy, dimethylamino, methylethylamino, diethylamino, trimethylsilyl, triphenylsilyl or dimethylphenylsilyl An iridium luminescent compound.
The method according to claim 1,
Wherein L is an organic ligand selected from the following structures:

Each of R ₁₁ to R ₁₄ is independently hydrogen, C ₁ -C ₆ alkyl, halo C ₁ -C ₆ alkyl, C ₁ -C ₆ alkoxy or C ₆ -C ₁₂ aryl;
R ₁₅ is C _a F _{2a +1} ;
a is an integer of 1 to 10;
R ₁₆ and R ₁₇ are each independently C ₁ -C ₆ alkyl or C ₆ -C ₁₂ aryl;
A is O or N;
The method of claim 3,
Wherein L is an organic ligand selected from the following structures:

The method according to claim 1,
An iridium luminescent compound which is an organic ligand selected from the following compounds.

A display element employing an iridium complex according to any one of claims 1 to 5 as a coloring material.
An organic electroluminescent device comprising an anode, a cathode, and a light emitting layer between both electrodes, wherein the organic electroluminescent element comprises an iridium complex according to any one of claims 1 to 5 in the light emitting layer.
8. The method of claim 7,
Wherein the iridium complex is used as a host material of the light emitting layer.

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