KR100274872B1 - Photoluminescence compound and display device adopting photoluminescence compound as color-developing substance - Google Patents

Abstract

The present invention discloses a light emitting compound represented by the formula (1) and an organic electroluminescent device employing the light emitting compound as a coloring material.

Wherein A is hydrogen or -Si (R ₄ ) (R ₅ ) (R ₆ ) and R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are independently of each other hydrogen, aryl ( aryl) group and an alkyl group having 1 to 20 carbon atoms, and n is an integer of 10 to 200. The compound of Formula 1 according to the present invention is an amorphous and soluble PPV-based polymer and is a blue light emitting material having excellent luminous efficiency. Such a compound can be usefully used as a coloring material of a display element. In addition, the organic electroluminescent device according to the present invention may implement blue by forming an organic layer such as a light emitting layer, a hole transport layer, etc. using the compound of Formula 1.

Description

Light-Emitting Compound and Display Device Adopting It as Coloring Material

The present invention relates to a blue light emitting compound and a display element employing the light emitting compound as a color developing material.

As the development of the information and communication industry accelerates, there is a demand for display devices having high performance. Display devices are generally classified into light emitting display devices and non-light emitting display devices. The light emitting display device includes a cathode ray tube, an electro-luminescence display (ELD), a light emitting diode (LED), and the like, and a non-light emitting display device includes a liquid crystal display device.

Indicators indicating the basic performance of the display device include an operating voltage, power consumption, brightness, contrast, response time, lifetime, and display color.

Liquid crystal display devices, which are one of the non-light emitting display devices, have the advantage of being light and low power consumption, and are currently being used most widely. However, the characteristics such as response time, contrast, and viewing angle have not reached satisfactory levels, and there is still much room for improvement. Accordingly, an electron light emitting device is attracting attention as a next generation display device that can solve such a problem.

An electroluminescence device (EL device) is a spontaneous light emitting display device having advantages of wide viewing angle, excellent contrast, and fast response speed.

EL devices are classified into inorganic EL devices and organic EL devices according to materials for forming an emitter layer. Herein, the organic EL device has an advantage of excellent luminance, driving voltage, and response speed, and multicoloring, compared to the inorganic EL device.

1 is a cross-sectional view showing the structure of a general organic EL device. Referring to this, an anode 12 is formed on the substrate 11. On the anode 12, a hole transport layer 13, a light emitting layer 14, an electron transport layer 15, and a cathode 16 are sequentially formed. Here, the hole transport layer 13, the light emitting layer 14, and the electron transport layer 15 are organic thin films made of an organic compound.

The driving principle of the organic EL element having the above structure is as follows.

When a voltage is applied between the anode 12 and the cathode 16, holes injected from the anode 12 are moved to the light emitting layer 14 via the hole transport layer 13. On the other hand, electrons are injected from the cathode 16 into the light emitting layer 14 via the electron transport layer 15, and carriers recombine in the light emitting layer 14 region to generate excitons. This exciton is changed from an excited state to a ground state, whereby an image is formed by the fluorescent molecules of the light emitting layer emitting light.

Meanwhile, in 1987, kodak Corp. developed an organic electroluminescent device using a low molecular weight aromatic diamine and an aluminum complex as a light emitting layer forming material (Appl. Phys. Lett. 51 , 913, 1987).

In addition, as a light emitting layer forming material, a polymer such as poly (p-phenylenevinylene) (PPV), poly (2-methoxy-5- (2'-ethylhexyloxy) -1,4-phenylenevinylene) or the like Has been published (Nature, 347 , 539, 1990 & Appl. Phys. Lett. 58 , 1982, 1991).

However, PPV in the polymer has a great difficulty in forming a film by spin coating because of poor solubility in organic solvents. In order to solve this problem, a soluble PPV has been developed incorporating a functional group capable of improving the solubility characteristics of the organic solvent in the PPV. Typically, an organic electroluminescent device having a light emitting layer made of PPV or derivatives thereof realizes a color from green to orange.

On the other hand, the blue light emitting compound known to date has a problem that the luminous efficiency and stability is lowered compared to the light emitting compound of other colors, and thus the need for the development of a new blue light emitting compound is gradually increasing.

The technical problem to be achieved by the present invention is to provide a new blue light emitting compound with improved luminous efficiency and stability in order to solve the above problems.

Another technical problem to be achieved by the present invention is to provide a display device employing the compound as a coloring material.

1 is a view showing the structure of a general organic electroluminescent device,

2 is a view showing a synthetic route of the compound represented by the formula (2) of the present invention.

<Explanation of code for main part of drawing>

11 ... substrate 12 ... anode

13 ... hole transport layer 14 ... light emitting layer

15 ... electron transport layer 16 ... cathode

In order to achieve the above object, the present invention provides a light emitting compound represented by the formula (1).

<Formula 1>

Wherein A is hydrogen or -Si (R ₄ ) (R ₅ ) (R ₆ ),

R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are independently selected from the group consisting of hydrogen, an aryl group and an alkyl group having 1 to 20 carbon atoms,

n is an integer of 10-20.

A is a triphenylsilyl group, and at least one of R ₁ , R ₂ and R ₃ is preferably a phenyl group or a t-butyl group. Or A is hydrogen, and at least one of R ₁ , R ₂ , and R ₃ is a phenyl group or a t-butyl group.

Another object of the present invention is achieved by a display element, wherein the light emitting compound is employed as a color developing material. As a preferable aspect of this invention, the organic electroluminescent element which employ | adopts the said light emitting compound as a coloring material is mentioned.

That is, another object of the present invention is also an organic electroluminescent device comprising an organic film provided between a pair of electrodes,

It provides an organic electroluminescent device characterized in that the organic film comprises a light emitting compound of formula (1).

<Formula 1>

Wherein A is hydrogen or -Si (R ₄ ) (R ₅ ) (R ₆ ),

R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are independently selected from the group consisting of hydrogen, an aryl group and an alkyl group having 1 to 20 carbon atoms,

n is an integer of 10-20.

The polymer of Formula 1 according to the present invention is a soluble PPV-based compound. It has a substituent which may give steric hindrance, and thus, π-stacking between polymer chains is suppressed. In this way, the introduction of bulky substituents in the molecule prevents two-dimensional and three-dimensional interactions between the polymer chains and suppresses the quenching of excitons due to intermolecular interactions. As a result, the organic electroluminescent device employing such a polymer as a light emitting material has a very high luminous efficiency. In addition, since the polymer of Chemical Formula 1 is in an amorphous state, forming an organic film using the same may produce an organic electroluminescent device having improved stability. Herein, the organic electroluminescent device employing the polymer as a coloring material may realize blue color.

As a specific example of the polymer represented by Formula 1, A is hydrogen, and R ₁ , R ₂ , and R ₃ are all phenyl groups, and A is triphenylsilyl group, R ₁ , R ₂ , There is a polymer of formula (3) wherein R ₃ is all a phenyl group.

In the formula, n ₁ is an integer of 10 to 200.

In said formula, n <_2> is an integer of 10-200.

The compound of Formula 1 according to the present invention may be used as a material for forming an emission layer or an electron transport layer of an organic electroluminescent device.

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. Here, a substrate used in a conventional organic EL device is used, and a glass substrate or a transparent plastic substrate excellent in transparency, surface smoothness, ease of handling, and waterproofness is preferable. In addition, transparent and excellent indium tin oxide (ITO), tin oxide (SnO ₂ ), and zinc oxide (ZnO) are used as the anode electrode material.

A hole transport layer is formed on the anode by using a material for forming a hole transport layer. The light emitting layer is formed by spin coating the compound of Chemical Formula 1 on the hole transport layer. The organic EL device is completed by forming a cathode by vacuum depositing a metal for forming a cathode on the light emitting layer as a whole. The metal for forming the cathode may be lithium (Li), magnesium (Mg), aluminum (Al), aluminum (Al-Li), calcium (Ca), magnesium-indium (Mg-In), magnesium-silver (Mg- Ag) and the like.

The electron transport layer may be formed on the emission layer before forming the cathode. This electron transport layer is formed using a conventional material for forming an electron transport layer.

The hole transport layer material is not particularly limited, and a conventional hole transport layer forming material such as polyvinylcarbazole (PVK), PDPMA having the following structural formula, or the compound of Formula 1 may be used.

The organic electroluminescent device of the present invention can further form an intermediate layer for improving properties between two layers selected from an anode, a hole transport layer, a light emitting layer, an electron transport layer and a cathode. For example, a buffer layer may be further formed between the anode and the hole transport layer. The formation of the buffer layer reduces the contact resistance between the anode and the hole transport layer and improves the hole transport ability of the anode to the light emitting layer. It is possible to obtain an effect of improving the characteristics of the device as a whole.

The buffer layer forming material is not particularly limited, but polyethylene dioxythiophene (PEDT), polyaniline, or the like is used.

The organic EL device may be manufactured in the order described above, that is, in the order of anode / hole transport layer / light emitting layer / electron transport layer / cathode, or in the reverse order, that is, cathode / electron transport layer / light emitting layer / hole transport layer / anode order. You may manufacture.

2 is a view showing a synthetic route of the polymer represented by the formula (2). Although the present invention will be described in detail with reference to the drawings, the present invention is not limited only to the following examples.

Synthesis Example 1 Polymer of Formula 2

Carbon tetrachloride was added to p-xylene, and bromine was then added to bromine to obtain 2-bromo-p-xylene (A).

The 2-bromo-p-xylene (A) was dissolved in diethyl ether and then the temperature of the reaction mixture was lowered to (-40) ° C. N-butyllithium was slowly added thereto and stirred at room temperature for 2 hours. The temperature of the reaction mixture was then adjusted to -78 ° C and then triphenylchlorosilane was added dropwise. The reaction mixture was stirred at room temperature for 3 hours to afford 2-triphenylsilyl-p-xylene (B) (yield: 25%).

Carbon tetrachloride was added to 2-triphenylsilyl-p-xylene (B), followed by N-bromosuccinimide and 2- (4-biphenylyl) -5-phenyloxazole (2- (4 -biphenylyl) -5-phenyloxazole: BPO) was added. The reaction mixture was refluxed at room temperature for 1 hour to obtain compound (C) (yield: 60%).

The compound (C) was dissolved in THF, and then potassium t-butoxide was added thereto. The reaction mixture was reacted to obtain a polymer represented by Chemical Formula 2 (yield: 40%). N ₁ here was 10-200.

Synthesis Example 2 Polymer of Formula 3

Carbon tetrachloride was added to p-xylene, and bromine was then added to bromine to obtain 2,5-bromo p-xylene (A).

The 2,5-bromo p-xylene (A) was dissolved in diethyl ether and then the temperature of the reaction mixture was lowered to -40 ° C. Subsequently, n-butyl lithium was added dropwise to the reaction mixture, followed by stirring at room temperature for 2 hours.

Thereafter, the temperature of the reaction mixture was adjusted to -78 ° C, and then triphenylsilane was added dropwise. Subsequently, the reaction mixture was stirred at room temperature for 3 hours, and then the temperature of the reaction mixture was lowered to -40 ° C, and n-butyllithium was added dropwise and stirred at room temperature for 2 hours.

Subsequently, the temperature of the reaction mixture was adjusted to −78 ° C., and then triphenylsilane was added dropwise to stir the reaction mixture for 3 hours to obtain 2,5-bistriphenylsilyl-p-xylene (B) (yield: 25%).

Carbon tetrachloride was added to the 2,5-bistriphenylsilyl-p-xylene (B), and then N-bromosuccinimide and benzoyl peroxide were added thereto. The reaction mixture was refluxed at room temperature for 1 hour to obtain compound (C) (yield: 60%).

The compound (C) was dissolved in THF, and then potassium t-butoxide was added thereto. The reaction mixture was reacted to obtain a polymer represented by Chemical Formula 3 (yield: 40%). N ₂ here was 10-200.

Example 1

After forming an ITO electrode on the glass substrate, the light emitting layer formation composition was spin-coated on the upper part, and the light emitting layer of 1000 micrometers thickness was formed. The light emitting layer-forming composition was prepared by dissolving 0.1 g of the compound of Formula 2 in 5 g of chlorobenzene.

Thereafter, Al: Li was vacuum-deposited on the emission layer to form an aluminum lithium electrode having a thickness of 1200 Å, thereby manufacturing an organic EL device.

Example 2

An organic electroluminescent device was manufactured in the same manner as in Example 1, except that the compound of Formula 3 was used instead of the compound of Formula 2 to form an emission layer.

Example 3

After forming an ITO electrode on the glass substrate, the buffer layer was formed by spin-coating a composition for buffer filling in which 0.1 g of polyethylene dioxythiophene (PEDT) was dissolved in 10 g of isopropyl alcohol.

Subsequently, a light emitting layer having a thickness of 600 에 was formed by spin coating the light emitting layer forming composition on the buffer layer. The light emitting layer-forming composition was prepared by dissolving 0.1 g of the compound of Formula 2 in 5 g of chlorobenzene.

Thereafter, Al: Li was vacuum-deposited on the emission layer to form an aluminum lithium electrode having a thickness of 1200 Å, thereby manufacturing an organic EL device.

Example 4

After forming an ITO electrode on the glass substrate, the buffer layer was formed by spin-coating a composition for buffer filling in which 0.1 g of polyethylene dioxythiophene (PEDT) was dissolved in 10 g of isopropyl alcohol.

Subsequently, a light emitting layer having a thickness of 600 층 was formed by spin coating the light emitting layer forming composition on the hole transport layer. The light emitting layer-forming composition was prepared by dissolving 0.1 g of the compound of Formula 2 in 5 g of chlorobenzene.

Thereafter, Alq of Chemical Formula 4 was vacuum deposited on the emission layer to form an electron transport layer having a thickness of 400 kHz.

Thereafter, Al: Li was vacuum-deposited on the electron transport layer to form an aluminum lithium electrode having a thickness of 1200 Å, thereby manufacturing an organic EL device.

Example 5

After forming an ITO electrode on the glass substrate, the 600-thick hole transport layer was spin-coated with a composition for forming a hole transport layer in which 0.7 g of polyvinylcarbazole and 0.3 g of a compound of Formula 2 were dissolved in 50 g of chlorobenzene. Formed.

Subsequently, Alq of Chemical Formula 4 was vacuum deposited on the hole transport layer to form a light emitting layer having a thickness of 600 Å.

Thereafter, Al: Li was vacuum-deposited on the emission layer to form an aluminum lithium electrode having a thickness of 1200 Å, thereby manufacturing an organic EL device.

In the organic electroluminescent device manufactured according to Example 1-5, the current-voltage, luminance-voltage and color characteristics were evaluated and shown in Table 1 below.

division Drive start voltage (V) (Turn-on voltage) Luminance (@ 18V) (cd / ㎡) color Example 1 8 300 blue Example 2 9.5 250 blue Example 3 6 700 (@ 15 V) blue Example 4 6.5 800 (@ 15 V) blue Example 5 10 1000 blue

From Table 1, it can be seen that the organic electroluminescent device manufactured according to Example 1-5 can implement blue. In addition, the driving voltage is lower than that of the conventional blue light emitting material (driving voltage: 12-15V). In particular, the use of a buffer layer or blending with polyvinylcarbazole greatly improves the brightness and device stability.

The compound of Formula 1 according to the present invention is an amorphous and soluble PPV-based polymer and is a blue light emitting material having excellent luminous efficiency. Such a compound can be usefully used as a coloring material of a display element.

In addition, the organic electroluminescent device according to the present invention may be implemented by forming an organic film such as a light emitting layer, a hole transport layer, etc. using the compound of Formula 1, and the luminous efficiency and stability is improved.

Claims (10)

Compound represented by Formula 1: <Formula 1> Wherein A is hydrogen, -Si (R ₄ ) (R ₅ ) (R ₆ ), R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are independently selected from the group consisting of hydrogen, an aryl group and an alkyl group having 1 to 20 carbon atoms, n is an integer from 10 to 200. The light emitting compound according to claim 1, wherein A is a triphenylsilyl group, and at least one of R ₁ , R ₂ , and R ₃ is a phenyl group or a t-butyl group. The light emitting compound according to claim 2, wherein A is a triphenylsilyl group, and R ₁ , R ₂ , and R ₃ are all phenyl groups. The light emitting compound of claim 1, wherein A is hydrogen and at least one of R ₁ , R ₂ , and R ₃ is a phenyl group or a t-butyl group. The light emitting compound according to claim 4, wherein A is hydrogen and R ₁ , R ₂ , and R ₃ are all phenyl groups. In an organic electroluminescent device comprising an organic film provided between a pair of electrodes, An organic electroluminescent device, characterized in that the organic film comprises a light emitting compound of Formula 1: <Formula 1> Wherein A is hydrogen, -Si (R ₄ ) (R ₅ ) (R ₆ ), R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are independently selected from the group consisting of hydrogen, an aryl group and an alkyl group having 1 to 20 carbon atoms, n is an integer from 10 to 200. The organic electroluminescent device according to claim 6, wherein A is a triphenylsilyl group, and at least one of R ₁ , R ₂ , and R ₃ is a phenyl group or a t-butyl group. The organic electroluminescent device according to claim 6, wherein A is hydrogen and at least one of R ₁ , R ₂ , and R ₃ is a phenyl group or a t-butyl group. The organic electroluminescent device according to claim 6, wherein the organic film is a light emitting layer or a hole transporting layer. A display element comprising the light emitting compound according to any one of claims 1 to 5 as a color developing material.