KR20090036441A - Host material and organic light emitting device comprising the same - Google Patents

Abstract

A host material is provided to show excellent blue light-emitting property because a color coordinate and emission spectrum is more near to deep blue, and to ensure excellent color and efficiency. A host material has a structure represented by the chemical formula 1. In the chemical formula 1, R1 is hydrogen, C1-C12 alkyl, or C4-C30 aromatic ring(heteroaromatic ring) where a hydrogen position is substituted or is not substituted; and R2 and R3 is selected from C4-C30 aromatic ring(heteroaromatic ring) where a hydrogen position is substituted or is not substituted.

Description

Host material and organic light emitting device comprising the same

The present invention relates to a host material and an organic electroluminescent device using the compound as a host material in the light emitting layer.

Organic light emitting diodes (OLEDs) emit light by injecting charges into the organic light emitting layer formed between the electron injection electrode (cathode) and the hole injection electrode (anode) and then disappear after pairing electrons and holes. to be.

Organic electroluminescent devices not only form devices on flexible transparent substrates such as plastics, but also operate at lower voltages of 10V or less than plasma display panels or inorganic electroluminescent (EL) displays. This is possible, the power consumption is relatively low, the color is excellent. In addition, the organic electroluminescent device can display three colors of green, blue, and red, and thus, has become a subject of much interest as a next generation rich color display device.

Here, the process of manufacturing the organic EL device is briefly described as follows.

(1) First, an anode material is coated on the transparent substrate. Indium tin oxide (ITO) is commonly used as the anode material.

(2) Apply a hole injecting layer (HIL) on it. As the hole injection layer, copper phthalocyanine (CuPc) is mainly coated with a thickness of 10 nm to 30 nm.

(3) Then introduce the hole transport layer (HTL). Such a hole transport layer is 4,4'-bis [N- (1-naphthyl) -N-pentylamino] biphenyl (4,4'-bis [N- (1-naphthyl) -N-phenthylamino]- biphenyl, NPB) is coated by depositing about 30nm to 60nm.

(4) An organic emitting layer is formed thereon. At this time, a dopant is added as necessary. In the organic light emitting layer, the red light emitting layer, the green light emitting layer, and the blue light emitting layer form one pixel to express various gray scales.

(5) An electron transport layer (ETL) and an electron injecting layer (EI L) are continuously coated thereon or an electron injection transport layer is formed thereon.

(6) Next, a cathode is coated, and finally a protective film is laminated.

In the above structure, the efficiency and performance of the light emitting device varies depending on which host material is used for the light emitting layer. In the conventional blue host, it is difficult to implement deep blue light emission due to the high HOMO level. There was also a problem of low efficiency.

The present invention has a heteroaromatic ring structure containing nitrogen, and thus, HOMO level is lower than that of the conventional host, so that light emission of deep blue can be realized more efficiently and the host material having high efficiency and organic electroluminescence using the same It is an object to provide an element.

As a means for achieving the above object,

The present invention provides a host material represented by the following Chemical Formula 1, and the following host material is particularly used in a blue light emitting layer to enable deep blue light emission.

[Formula 1]

The present invention also provides an organic electroluminescent device having a light emitting layer comprising the host material.

Hereinafter, the present invention will be described in detail.

The host material of the present invention is characterized by the following formula (1). As described below, by having a heteroaromatic ring structure in which nitrogen is located at a carbon position in the phenanthrene structure, the HOMO level can be lowered to cause deep blue light emission. Synthesis method of the host material represented by the following formula (1) is not limited, as a specific example can be synthesized without difficulty by referring to the reaction scheme of the synthesis examples described later.

[Formula 1]

In Chemical Formula 1, R ₁ is selected from hydrogen, alkyl of C ₁ to C ₁₂ , or an aromatic group of C ₄ to C _{30 with} or without substituted hydrogen, and R ₂ and R ₃ are each independently hydrogen Is selected from substituted or unsubstituted aromatic groups of C ₄ to C ₃₀ . The aromatic group may be free of heteroaromatic rings, all heteroaromatic rings, or part of heteroaromatic rings. A heteroaromatic ring is a vent containing N, O, S, etc. which are hetero elements, and means having aromaticity. As an example, pyridine, pyrrole, furan, thiophene, pyrazole, imidazole, oxazole, isoxazole, thiazole, isothiazole, and aromatic group couple | bonded with these, etc. are mentioned. R ₂ , R ₃ may be the same or different.

The R ₁ , R ₂ , R ₃ may be substituted part or all of hydrogen, and is not limited to a substituent, aryl (alkyl), alkyl (alkoxy), alkoxy (halkoxy), halogen (halogen), cyano (cyano), silyl (silyl) can be selected from the group consisting of. Specifically, methyl, ethyl, propyl, isopropyl, butyl, t-butyl, methoxy, ethoxy and butoxy , Trimethylsilyl, fluorine and chlorine.

Specific examples of the R ₁ , R ₂ , R ₃ may be selected from those represented by the following formula (2). However, the present invention is not limited thereto, and those known to the aryl group of the light emitting material structure in the art may be selected as long as they can achieve the object of the present invention and are included in the present invention.

[Formula 2]

The host material represented by Chemical Formula 1 may form a compound of various forms by combining the above-described R ₁ , R ₂ , and R ₃ , and typically, the compounds described in Chemical Formula 3 may be exemplified.

[Formula 3]

The present invention also provides an organic electroluminescent device having a light emitting layer comprising the above-described host material. As long as the above-mentioned host material is an organic electroluminescent element included as a light emitting layer material, all of them are included in the present invention without being limited to the structure. Specific examples of the structure include (1) anode / light emitting layer / cathode, (2) anode / hole transporting layer / light emitting layer / cathode, (3) anode / hole transporting layer / electron transporting layer / cathode, (4) anode / hole injection Layer / hole transport layer / light emitting layer / cathode, (5) anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / cathode, (6) anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode And (7) anode / hole injection layer / light emitting layer / electron injection layer / cathode.

1 is a cross-sectional view of an organic electroluminescent device according to an embodiment of the present invention. Briefly described as follows. First, the anode 2 is formed on the transparent substrate 1 by a method such as sputtering, and the hole injection layer 3 and the hole transport layer 4 are sequentially vacuum deposited on the anode. After forming the organic light emitting layer 5 and the electron transport layer 6 on the hole transport layer 4 again by vacuum deposition, an electron injection layer 7 and a cathode 8 are formed on the electron transport layer 6.

The light emitting layer 5 is formed by using the above-described host material alone or in combination with a dopant. The light emitting layer may be manufactured in a multi-layered structure in which red and green light emitting layers are further provided for white light emission.

The substrate 1 is not particularly limited, and those commonly used in organic electroluminescent devices, for example, glass, transparent plastic, quartz, and the like may be used.

As the material of the positive electrode 2 mentioned above, ITO or IZO can be generally used, and as the material of the hole injection layer 3, copper (II) phthalocyanine is usually used. The hole transport layer 4 may be a triphenylamine or diphenylamine derivative such as NPD (N, N-di (naphthalen-1-yl) -N, N'-diphenylbenzidine), and may be used as a dopant of the light emitting layer 5. The general blue dopant may be used, and for example, CBP (4,4'-N, N-dicarbazole-biphenyl) may be used. In addition, Alq3 can be used as the electron transport layer 6 because of its excellent electron transport properties, and another material that can be used as the electron transport layer 6 is 2- (4-non-phenyl) -5- (4-tert. Oxadiazole and triazole derivatives such as -butylphenyl) -1,3,4-oxadiazole. Alkali metal (Cs, Rb, K, Na, Li) derivatives (Li ₂ O, etc.) may be used as the material of the electron injection layer, and Mg / Ag, Al, Al / Li, Al / Nd as the cathode material. Etc. are possible.

Each layer constituting the organic electroluminescent element of the present invention can be formed by applying a known method, such as a vapor deposition method, a spin coating method, a cast method, or the like, to a material which should constitute each layer, to form a thin film. The film thickness of each of the layers thus formed, for example, the light emitting layer, is not particularly limited and can be appropriately selected depending on the situation.

Since the host material of the present invention has a heteroaromatic ring structure containing nitrogen, the HOMO level is low, and the color coordinates and emission spectrum are closer to Deep Blue than the conventional blue host, resulting in excellent blue light emission characteristics. It is possible to provide an organic EL device having excellent efficiency.

Hereinafter, the present invention will be described in more detail with reference to Examples. The following examples are specific examples of the present invention, but the present invention is not limited thereto even though there is a certain or definite expression.

Synthesis Example Synthesis of Compound 1

<Scheme>

                                             Compound 1

The synthesis method of compound 1 is according to the above scheme.

Copper (II) bromide (9.8g), t-BuNO ₂ (9.4g) and acetonitrile were added to a three-necked round flask and heated to 65 ° C.

After stirring for 10 minutes, 3,8-diamino-6-phenylphenanthridine (5.0 g) is slowly added dropwise. After completion of the dropwise addition, the mixture was stirred for about 1 hour and then added with 20% hydrochloric acid solution and water to form a solid. The solid obtained by filtration can be recrystallized with toluene to obtain 3,8-dibromo-6-phenylphenanthridine (3.1 g, 42.8%).

In a dried two-necked flask, 3,8-dibromo-6-phenylphenanthridine (3.1 g), phenanthrene-9-boronic acid (4.2 g), and Pd (PPh ₃ ) ₄ (0.3 g), K ₂ CO ₃ (7.8 g), THF, and H ₂ O are added and stirred.

After refluxing in a heating mantle at 100 ° C. for 24 hours, when the reaction was completed, the THF was removed, extracted with dichloromethane and water, distilled under reduced pressure, and then the solvent was distilled off under reduced pressure, followed by distillation of the solvent under reduced pressure. Filter through recrystallization to obtain the final product (2.2 g, 48%).

 NMR analysis: δ 8.93 (s, 4H) 7.88 (s, 4H) 7.82 (m, 4H) 8.12 (s, 4H) 7.93 (s, 2H) 8.31 (d, 2H) 7.55 (m, 3H) 8.27 (m, 1H) 7.65 (d, 1H) 8.09 (s, 1H) 7.77 (m, 3H)

In the synthesis example, the synthesis of Compound 1 has been described as an example, but other host materials may be easily synthesized by those skilled in the art in a similar manner to the above synthesis example, and thus a detailed description thereof will be omitted.

EXAMPLE

The light emitting area of the ITO gliss was patterned to have a size of 3 mm × 3 mm and then washed. After mounting the substrate in the vacuum chamber, the basic pressure was 1 X 10 ^-6 torr, and the organic material was placed on ITO CuPc (650Å) / NPD (400Å) / Compound 1 + CBP (3%) (250Å) ) / LiF (5 kV) / Al (1,000 kV) in this order. That is, Compound 1 was used as a host material of the emission layer, and CBP was used as the dopant.

[Comparative Example]

The host material of the light emitting layer was the same as in Example, except that ADN was used instead of Compound 1.

Efficiency characteristics and color coordinates of the organic electroluminescent devices manufactured according to Examples and Comparative Examples are shown in Table 1, and the EL spectrum is shown in FIG. As can be seen, it can be seen that the organic electroluminescent device of the example is superior to the comparative example, and the color coordinates and the EL spectrum are close to deep blue.

TABLE 1

Voltage (V) Efficiency (cd / A) @ 20mA / ㎠ Color coordinates (CIE, x, y) @ 20mA / ㎠ Example 6.6 5.4 0.135, 0.193 Comparative example 6.5 6 0.129, 0.179

1 is a cross-sectional view of an organic light emitting display device according to an embodiment of the present invention;

2 shows EL spectra of Examples and Comparative Examples of the present invention.

** Description of the main symbols in the drawings **

1: substrate 2: anode

3: hole injection layer 4: hole transport layer

5: light emitting layer 6: electron transport layer

7: electron injection layer 8: cathode

Claims (6)

A host material represented by the following formula (1). [Formula 1]

Wherein R ₁ is selected from hydrogen, alkyl of C ₁ to C ₁₂ , or an aromatic group of C ₄ to C _{30 with} or without a substituted hydrogen position (which may include a heteroaromatic ring), R ₂ , Each R ₃ is independently selected from a C ₄ to C ₃₀ aromatic group, which may be substituted or unsubstituted with a hydrogen position, which may include a heteroaromatic ring.) The method of claim 1, wherein when the hydrogen positions of R ₁ , R ₂ , and R ₃ are substituted, the substituent is aryl, alkyl, alkoxy, halogen, cyano. And a host material selected from the group consisting of silyl. The host material of claim 1, wherein R ₁ , R ₂ , and R ₃ are each independently any one of Formula 2 below. [Formula 2]

The host material of claim 1, wherein the host material is any one of an organic compound represented by Formula 3 below. [Formula 3]

The host material of claim 1, wherein the host material is used in a blue light emitting layer. An organic electroluminescent device having a light emitting layer comprising the host material of any one of claims 1 to 4.

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