KR20080038957A - Electroluminescent compounds and organic electroluminescent device using the same - Google Patents

Abstract

An organic electroluminescent compound is provided to improve luminous efficiency characteristics and to produce an organic electroluminescent device having wide viewing angle, excellent contrast, and fast response time. An organic electroluminescent compound has a structure represented by the following formula 1, wherein R1 and R2 are selected from substituted or unsubstituted phenyl groups, substituted or unsubstituted C10-20 fused polycyclic aromatic groups, or substituted or unsubstituted heterocycles. An organic electroluminescent device comprises the organic electroluminescent compound as an electroluminescent material. The organic electroluminescent compound is used as an electroluminescent host or electroluminescent guest.

Description

9,10-diphenylanthracene light emitting compound having a 2,6-substituent and a light emitting device employing the same as a light emitting material {Electroluminescent compounds and organic electroluminescent device using the same}

1 is a cross-sectional structure of a typical OLED,

Figure 2 shows the ¹ H-NMR spectrum of the organic light emitting compound according to the present invention,

3 is a graph showing the UV absorption spectrum and the PL spectrum in the liquid state of the organic light emitting compound according to the present invention,

4 is a light emission efficiency graph of the organic light emitting device according to the present invention.

<Explanation of symbols for the main parts of the drawings>

11: Substrate 12: Anode

13: hole transport layer 14: light emitting layer

15: electron transport layer 16: electron injection layer

17: cathode

The present invention relates to a light emitting compound containing 9,10-diphenyl anthracene having aryl substituents at the 2,6 position having excellent luminous efficiency characteristics, and an organic light emitting device employing the light emitting compound as a light emitting material.

Light emitting devices (LEDs) are classified into inorganic light emitting devices and organic light emitting devices (OLEDs) according to materials for forming an emitter layer. Herein, the organic light emitting diode has an advantage of excellent luminance, driving voltage, and response speed, and multicoloring, compared to the inorganic light emitting diode.

1 is a cross-sectional view showing the structure of a general organic light emitting device. Referring to the structure of the organic light emitting device, an anode is formed on the substrate, and the hole transport layer (HTL), the light emitting layer (EML), the electron transport layer (ETL), and the cathode (Cathode) are sequentially formed on the anode. Is formed. Here, the hole transport layer, the light emitting layer, and the electron transport layer are organic thin films made of an organic compound.

The driving principle of the organic light emitting device having the structure as described above is as follows.

When a voltage is applied between the anode and the cathode, holes injected from the anode are moved to the light emitting layer via the hole transport layer. On the other hand, electrons are injected from the cathode into the light emitting layer via the electron transport layer, and carriers recombine in the light emitting layer to generate excitons. The excitons change from the excited state to the ground state, whereby the fluorescent molecules in the light emitting layer emit light to form an image.

In 1987, Eastman Kodak Inc. developed for the first time an organic electroluminescent device using a low molecular aromatic diamine and an aluminum complex as a material for forming a light emitting layer (Appl. Physc. Lett. 51, 913, 1987). On the other hand, as a blue light emitting material, compounds such as diphenylanthracene, tetraphenylbutadiene, and distriylbenzene derivatives have been developed, but are known to have a tendency to crystallize easily due to poor film stability. Idemitz Co., Ltd. has developed a diphenyl stryl based material with improved phenyl stability by hindering crystallization of bran groups [H, Tokailin, H. Higashi, C. Hosokawa, EP 388, 768 (1990)], Kuju University Has developed a distriyl anthracene derivative with improved electron beam stability and thin film stability [Pro. SPIE, 1910, 180 (1993)].

The blue light emitting compound known to date has lower luminous efficiency than other light emitting compounds and the thin film stability should be further improved. Therefore, the development of a new blue light emitting compound is an urgent problem to develop a blue light emitting device or a total color light emitting device. In addition, the blue light emitting material currently used is very expensive at a price of about 200,000 won / g. Therefore, the development of a low-cost high-efficiency blue light emitting material is urgently required for the development of a large-area total color device. The need for development is increasing.

Accordingly, an object of the present invention is to provide a blue light emitting compound containing 9,10-diphenyl anthracene having aryl substituents in the 2,6 position with improved luminous efficiency characteristics, and another object of the present invention The present invention provides an organic light emitting device using the blue light emitting compound as a light emitting material.

In addition, another object of the present invention is to provide an organic light emitting device having a wide viewing angle, excellent contrast, and fast response time as a spontaneous light emitting display device.

The present invention is characterized by providing an organic light emitting compound represented by the following formula (1).

[Formula 1]

[R ₁ and R ₂ in Formula 1 are independently selected from a substituted or unsubstituted phenyl group, or a substituted or unsubstituted C10-C20 conjugated polycyclic aromatic group, or a substituted or unsubstituted heterocycle.]

In another aspect, the present invention is characterized by an organic light emitting device comprising the organic light emitting compound of Formula 1 as a light emitting material.

Substituents of the phenyl group substituted in R ₁ and R ₂ of the compound of Formula 1 are phenyl, diarylamine, triarylsilyl, naphthyl or anthracenyl, and the conjugated polycyclic aromatic group is naphthyl, anthracenyl, unsubstituted or 9 And fluorenyl substituted with a C1-C12 alkyl group at position 9, and the heterocycle is selected from oxazolyl, pyrazinyl, imidazolyl, pyridyl, and the diarylamine and triarylsilyl. Aryl is selected from phenyl, naphthyl or anthracenyl.

In particular, the organic light emitting compound according to the invention is characterized in that it is selected from the formula (2) or (3) of the structure.

[Formula 2]

[Formula 3]

[In Formula 2 and Formula 3, R ₃ to R ₆ are independently of each other alkyl of C1-C7, and R ₇ to R ₁₀ are independently of each other phenyl, naphthyl or anthracenyl.]

In particular, the organic light emitting compound according to the present invention is selected from the following compounds.

The present invention includes an organic light emitting device employing the organic light emitting compound as a light emitting material, in particular the organic light emitting compound can be used as a light emitting host or a light emitting guest.

The organic light emitting compound of Formula 1 according to the present invention has steric hindrance due to substituents R ₁ and R ₂ introduced at the 2,6 position of the anthracene ring, thereby inducing pi stacking between molecules. This is suppressed. As such, introducing a bulky substituent into the molecule prevents two-dimensional and three-dimensional interactions between the molecules and prevents incidence of excitons by preventing intermolecular interactions. Examples of the substituent include phenyl, naphthyl, anthracenyl, fluorenyl, oxazolyl, pyrazinyl, imidazolyl, pyridyl, and the like. These substituents may further have substituents such as alkyl and aryl. Substituents introduced at positions 2 and 6 of the anthracene ring may also improve luminous efficiency through intramolecular energy transfer from substituents to anthracene. Herein, the organic light emitting device employing the low molecular weight as a coloring material can realize high luminous efficiency.

Hereinafter, the manufacturing of the organic light emitting diode according to the present invention will be described in detail.

First, an anode electrode material is coated on the substrate. As the substrate, a substrate used in a conventional organic light emitting device is used, and a glass substrate or a transparent plastic substrate excellent in 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) and the like which are transparent and have excellent conductivity are used.

The OLED is completed by forming a light emitting layer including an organic light emitting compound on the anode electrode, and forming a cathode by vacuum deposition or sputtering on the light emitting layer. Here, lithium, magnesium, aluminum or the like is used as the metal for forming the cathode.

Preferably, the hole transport layer (HTL), the light emitting layer (EML), the electron transport layer (ETL) and the cathode (Cathode) are generally formed sequentially between the anode and the cathode, and the electron transport layer is vacuum deposited on a conventional electron transport layer forming material. Can be used.

The hole transport layer and the electron transport layer material is not particularly limited, and N.N'-bis (3-methylphenyl) -N, N-diphenyl- [1,1'-biphenyl] -4,4'-diamine ( TPD), PBD (2- (4-biphenyl) -5-phenyl-1,3,4--oxadiazole) which is a 1,3,4, -oxadiazole derivative, Alq3, tris (quinolinato) Aluminum etc. are illustrated.

The organic light emitting device may be manufactured in the order described above, that is, in the order of substrate / anode / hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode and vice versa, namely, substrate / cathode / electron injection layer / electron transport layer. It may also be prepared in the order of / light emitting layer / hole transport layer / anode.

The organic light emitting compound according to the present invention can be prepared by the method as shown in Schemes 1 and 2. However, the preparation of the compound according to the present invention is not limited to the reaction schemes exemplified in the present invention, and can be variously prepared using a known organic synthesis method. As in Scheme 1, a compound having the same substituent at 2,6 position can be prepared from 2,6-dibromo-9,10-diphenylanthracene (compound 3 ), and as shown in Scheme 2 below, Through the reaction of the step can be prepared a light emitting compound having different substituents at positions 2,6.

Scheme 1

Scheme 2

For example, the organic light emitting compound of Compound 6 and Compound 7 may be prepared from Compound 3 and boronic acid compound (Compound 4 , Compound 5 ), as shown in Scheme 3 and Scheme 4 below. can do.

Scheme 3

Scheme 4

On the other hand, the 2,6-dibromo-9,10-diphenylanthracene (Compound 3 ) can be prepared by the preparation method shown in Scheme 5. Namely, 2,6-dibromoanthraquinone (Compound 1 ) was prepared from 2,6-diaminoanthraquinone and then reacted with 2,6-dibro by reaction with a Grignard reagent of bromobenzene (C6H5MgBr). Prepares parent-9,10-dihydro-9,10-diphenylanthracene (Compound 2 ), and 2,6-dibromo-9,10-dihydro-9,10-diphenylanthracene (Compound 2 ) The 2,6-dibromo-9,10-diphenylanthracene (Compound 3 ) was prepared by a reduction reaction to remove the hydroxyl group.

Scheme 5

Hereinafter, the light emission characteristics of the compound according to the present invention, a method for preparing the same, and a device for the present invention will be described for the detailed understanding of the present invention, which is merely to exemplify the embodiments and the scope of the present invention. It is not intended to be limiting.

Preparation Example 1 Preparation of 2,6-dibromoanthraquinone (Compound 1 )

A two-necked flask was refluxed, acetonitrile was added as a solvent, and 0.202 mol of CuBr ₂ and 0.202 mol of t-butylite were stirred on a hot plate. Light (t-butyl-nitrite) is added to the reaction vessel. Here, 0.084 mol of 2,6-diaminoanthraquinone was added dropwise little by little, followed by reflux for 2 hours. When the reaction is complete, lower the temperature and work up with 6M HCl. The product is washed several times with water and ethanol and filtered. To obtain pure 2,6-dibromoanthraquinone (2,6-dibromoanthraquinone) was dissolved in hot chloroform (chloroform) to prepare a compound 1 by hot filtration using a Buchner funnel (yield: 85% ).

¹ H-NMR (500 MHz, CDCl ₃ ) [ppm] δ 8.09 (m, 2H), 7.30 (m, 4H), 7.20 (m, 4H), 7.10 (m, 4H) FT-IR (KBr, cm ^{− 1} ): 3030 (aromatic CH str), 1710 (C = O str), 1300 (C-Br str)

Preparation Example 2 Preparation of 2,6-dibromo-9,10-dihydro-9,10-diphenylanthracene (Compound 2 )

A solution of Compound 1 (2.734 mmol) in which 13.67 mmol of phenyl magnesium bromide was dissolved in a solvent in diethylether, adjusted to -10 ° C, in a two neck flask using a cannula. Drop by. After dropping, the solution is stirred for about 30 minutes and then worked up using HCl solution. The product is extracted with diethyl ether, dried over MgSO ₄ and blown off to obtain the product. Ethyl acetate to obtain pure 2,6-dibromo-9,10-dihydro-9,10-diphenylanthracene (2,6-dibromo-9,10-dihydro-9,10-dipenylanthracene) ) Was separated by column chromatography using an eluent (yield: 45%).

¹ H-NMR (500 MHz, CDCl ₃ ) [ppm] δ 7.50 (m, 2H), 7.39 (m, 1H), 7.35 (m, 5H), 7.30 (m, 1H), 7.29 (m, 4H), 7.25 (m, 2H), 7.20 (m, 1H) FT-IR (KBr, cm ^-1 ): 3030 (aromatic CH str), 3600 (broad OH str), 1310 (C-Br str)

Preparation Example 3 Preparation of 2,6-Dibromo-9,10-diphenylanthracene (Compound 3 )

1.915 × 10 ^-4 mol and 2.809 × 10 ^-3 mol of NaH in 2,6-dibromo-9,10-dihydro-9,10-diphenylanthracene (Compound 2 ) in a two neck flask ₂ PO ₂ was added and acetic acid was refluxed with a solvent to perform a reduction reaction. As it is reduced, insoluble white solids start to form on the wall. After refluxing for about 10 hours, the temperature is lowered, filtered, and washed several times with water. The product was separated by column chromatography to give pure compound 3 (yield: 70%).

mp: 307.7 ° C. ¹ H-NMR (500 MHz, CDCl ₃ ) [ppm] δ 7.41 (m, 8H), 7.62 (m, 6H), 7.82 (m, 2H) FT-IR (KBr, cm ⁻¹ ): 3030 (aromatic CH str), 1640 (CC)

Preparation Example 4 Preparation of 9,9-diethylfluorene-2-boronic acid (Compound 4 )

Mg (1.2 mmol) and 1,2-dibromoethane (1,2-dibromoethane) were added as an activator in a two neck flask and 2-bromo-9, Grignard reagent is prepared by dropwise addition of 9-diethylfluorene (2-bromo-9,9-diethylfluorene) (1 mmol). After all the Mg is gone and the Grignard reagent is made, triethylborate (1 mmol) is added and reacted. Upon completion of the reaction, work-up with 1M HCl yields 9,9-diethylfluorene-2-boronic acid (Compound 4 ).

Preparation Example 5 Preparation of 4- (N, N-diphenylamino) benzeneboronic acid (Compound 5 )

1-bromo-4- (N, N-diphenylamino) benzene (1-bromo-4- instead of 2-bromo-9,9-diethylfluorene) Except for using (N, N-diphenylamino) benzene) 4- (N, N-diphenylamino) benzene boronic acid (4- (N, N-diphenylamino) Benzene boronic acid) (Compound 5 ) is prepared.

Synthesis Example 1 Preparation of Organic Light Emitting Compound (Compound 6 )

2M K ₂ CO ₃ in a three-necked flask containing Compound 3 (0.4 mmol) and Compound 4 (0.94 mmol). Add 10 mL of THF and 50 mL of THF, purge with nitrogen, and add Pd (PPh ₃ ) ₄ (tetrakis (triphenylphosphine) palladium) (0.2 mmol) as a catalyst. After reacting for approximately 24 hours, work up in 2N HCl. The product is extracted using ethyl acetate, dried using MgSO ₄ and blown off to obtain the product. To obtain the pure compound 6 was separated by column chromatography using a mixture of hexane: ethyl acetate = 10: 1 solution (yield: 50%). ¹ H NMR data of the prepared compound 6 is shown in FIG. 2A, and the UV absorption and PL spectrum of the liquid state are shown in FIG. 3A. Maximum UV absorption is 320, 370, 400, 415, showing the characteristic absorption of anthracene. In the PL spectrum, the maximum light emission was around 470 nm.

¹ H-NMR (500 MHz, CDCl ₃ ) [ppm] δ 7.9-7.0 (m, 30H), 2.1 (q, 8H), 1.5 (t, 12H)

Synthesis Example 2 Preparation of Organic Light Emitting Compound (Compound 7 )

4- (N, N-diphenylamino) benzene boronic acid (4- (N) instead of 9,9-diethylfluorene-2-boronic acid (compound 4 ) An organic light emitting compound of Compound 7 was prepared in the same manner as in Synthesis Example 1 except for using, N-diphenylamino) benzene boronic acid) (compound 5 ) (yield: 50%).

¹ H NMR data of the prepared compound 7 is shown in FIG. 2B, and the UV absorption and PL spectrum of the liquid state are shown in FIG. 3B. UV maximum absorption was 320, 370, 420 nm and PL maximum emission was around 505 nm.

¹ H-NMR (500 MHz, CDCl ₃ ) [ppm] δ 7.9-7.0 (m, 44H)

Example 1 Fabrication of Organic Light Emitting Diode

After the ITO electrode was formed on the glass substrate, Compound 6 prepared in Synthesis Example 1 was vacuum deposited on the glass substrate to form a light emitting layer having a thickness of 600 kHz. Compound (Alq) of the following formula (4) was vacuum deposited on the emission layer to form an electron transport layer having a thickness of 600 mV, and a LiF electron injection layer was formed on the electron transport layer at a thickness of 10 mV. OLED was fabricated by vacuum depositing Al-Li on the electron injection layer to form an aluminum lithium electrode having a thickness of 1200 kHz.

[Formula 4]

As shown in FIG. 4, the luminous efficiency of the organic light emitting diode according to the present exemplary embodiment was 5.3 cd / A.

Example 2 Fabrication of Organic Light Emitting Diode

Compound 6 used in Example 1 was used as a dopant, and the host material was MADN (2-methyl-9,10-di (2-naphthyl) anthracene), except that the light emitting layer was prepared such that the dopant material contained 2% by weight. An organic light emitting device was manufactured in the same manner as in Example 1.

As a result of evaluating the luminescence properties of the manufactured organic light emitting device, the maximum was 8.37 cd / A and the color purity was CIE standard (0.16, 0.12).

The blue light emitting compound for OLEDs of the present invention is a diphenylanthracene derivative having an aryl substituent at the 2,6 position, which can be easily synthesized in a low cost process, has excellent color purity, and is useful as a coloring material of a display device. In addition, the OLED according to the present invention not only solves the problem of deterioration due to the driving heat generated when driving the OLED device using the blue light emitting compound of the present invention and the problem of deterioration of the light emission characteristics due to π-stacking of the organic film-forming material. The energy transfer further improves the luminous efficiency, thereby greatly improving the luminous efficiency and at the same time improving the stability of the device.

Claims (6)

An organic light emitting compound represented by Formula 1 below. [Formula 1]

R ₁ and R ₂ in Formula 1 are independently selected from a substituted or unsubstituted phenyl group, or a substituted or unsubstituted C10-C20 conjugated polycyclic aromatic group, or a substituted or unsubstituted heterocycle. The method of claim 1, In the substituted phenyl group, the substituent is phenyl, diarylamine, triarylsilyl, naphthyl or anthracenyl, and the conjugated polycyclic aromatic group has a naphthyl, anthracenyl, unsubstituted or substituted C1-C12 alkyl group at 9,9 position. Fluorenyl, and the heterocycle is selected from oxazolyl, pyrazinyl, imidazolyl or pyridyl. The method of claim 2, An organic light emitting compound, characterized in that selected from compounds of the following structure. [Formula 2]

[Formula 3]

In Chemical Formulas 2 and 3, R ₃ to R ₆ are each independently C1-C7 alkyl, and R ₇ to R ₁₀ are independently selected from phenyl, naphthyl or anthracenyl. The method of claim 3, An organic light emitting compound, characterized in that selected from the following compounds.

An organic light emitting device comprising the organic light emitting compound according to any one of claims 1 to 4 as a light emitting material. The method of claim 5, The organic light emitting device according to any one of claims 1 to 4, wherein the organic light emitting compound is used as a light emitting host or a light emitting guest.

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