KR101794796B1 - Electron transporting material and Organic electroluminescent display device using the same - Google Patents

Abstract

The present invention relates to a compound represented by the following formula: wherein R1 is selected from substituted or unsubstituted alicyclic compounds, and each of R2 and R3 is selected from a substituted or unsubstituted aromatic compound or a substituted or unsubstituted aliphatic ring compound Thereby providing an electron transporting material.

Description

TECHNICAL FIELD The present invention relates to an electron transport material and an organic electroluminescent display device using the same.

The present invention relates to an electron transport material and an organic electroluminescent device using the same. More particularly, the present invention relates to an electron transporting material capable of enhancing the luminous efficiency by having an excellent electron transporting ability, and an organic electroluminescent device driven by a low voltage by including the electron transporting material.

In recent years, the demand for a flat display device having a small space occupancy has been increased due to the enlargement of the display device. The technology of the organic electroluminescent device, which is also called an organic light emitting diode (OLED) And several prototypes have already been announced.

An organic electroluminescent device is a device that injects electric charge into a light emitting material layer formed between an electron injecting electrode (cathode) and a hole injecting electrode (anode) to form an electron and a hole. The device can be formed on a flexible transparent substrate such as a plastic substrate and can be driven at a lower voltage (10 V or less) than a plasma display panel or an inorganic electroluminescence (EL) It also has the advantage of low power consumption and excellent color. In addition, organic electroluminescence (EL) devices can display three colors of green, blue, and red, making them a next-generation rich color display device and attracting a lot of interest from many people. Here, the process of fabricating the organic electroluminescent device will be briefly described.

(1) First, a material such as indium tin oxide (ITO) is deposited on a transparent substrate to form an anode.

(2) A hole injecting layer (HIL) is formed on the anode. The hole injection layer is mainly formed by depositing copper phthalocyanine (CuPc) represented by the following formula 1-1 to a thickness of 10 nm to 30 nm.

(3) Next, a hole transport layer (HTL) is formed on the hole injection layer. This hole transport layer is formed by depositing 4,4'-bis [N- (1-naphtyl) -N-phenylamino] -biphenyl (NPD)

(4) Next, an emitting material layer (EML) is formed on the hole transport layer. At this time, a dopant is added as needed.

For example, DPBVi represented by the following Formula 1-3 is used as a host, and about 1 to 10% of a substance represented by Formula 1-4 below (hereinafter abbreviated as "BD-A") is added as a dopant.

(5) Next, an electron transport layer (ETL) and an electron injecting layer (EIL) are successively formed on the light emitting material layer. At this time, the electron transport layer is composed of tris (8-quinolate) aluminum (III) (Alq3) represented by the following Formula 1-5 and the electron injection layer is made of LiF.

(6) Next, a cathode is formed on the electron injection layer, and finally, a protective film is formed on the cathode.

Formula 1 -One

Formula 1 -2

Formula 1 -3

Formula 1 -4

Formula 1 -5

However, in the case of Alq3 used in the electron transporting layer, there is a problem that the energy level difference between the electron injection layer and the cathode is large, thereby lowering the luminous efficiency and increasing the driving voltage of the organic electroluminescent device. That is, there is a problem that the electron transporting speed of the electron transporting layer made of Alq3 is slow, and the efficiency of the organic EL device is reduced.

The present invention aims to improve the electron transport ability of the electron transport layer by lowering the LUMO energy level of the electron transport layer material.

Also, an organic electroluminescent device which is excellent in luminous efficiency and can be driven at a low voltage by using an electron transporting layer material having an excellent electron transporting ability is provided.

In order to solve the above problems, the present invention is represented by the following formula: wherein R1 is selected from substituted or unsubstituted alicyclic compounds, and each of R2 and R3 is a substituted or unsubstituted aromatic compound or a substituted or unsubstituted And a ring compound.

Wherein R1 is any of substituted or unsubstituted pyridine, quinoline, and benzothiazole.

The substituent of R1 is selected from C1-C20 aryl, C1-C20 alkyl, C1-C20 alkoxy, halogen, cyano, silyl .

Each of R 2 and R 3 is independently selected from the group consisting of phenyl, biphenyl, naphthyl, phenanthrene, anthracene, terphenyl, pyrene, pyridine, Quinoline, or benzothiazole. The term " quinoline "

Each of R2 and R3 is independently selected from the group consisting of methyl, ethyl, propyl, isopropyl, octyl, t-butyl, methoxy, ethoxy, , Butoxy, trimethylsilyl, fluorine, and chlorine.

In another aspect, the present invention provides a liquid crystal display comprising: a first electrode; A second electrode facing the first electrode; And a light emitting material layer disposed between the first and second electrodes and including a hole injecting layer, a hole transporting layer, a light emitting material layer, an electron transporting layer, and an electron injecting layer, wherein the electron injecting layer is represented by the following formula: R1 is selected from substituted or unsubstituted alicyclic compounds, and each of R2 and R3 is selected from a substituted or unsubstituted aromatic compound or a substituted or unsubstituted aliphatic cyclic compound.

The R1 is any one of pyridine, quinoline, and benzothiazole.

Wherein R1 is substituted with any one of C1-C20 aryl, C1-C20 alkyl, C1-C20 alkoxy, halogen, cyano and silyl Feature.

Each of R 2 and R 3 is independently selected from the group consisting of phenyl, biphenyl, naphthyl, phenanthrene, anthracene, terphenyl, pyrene, pyridine, Quinoline, or benzothiazole. The term " quinoline "

Each of R2 and R3 is independently selected from the group consisting of methyl, ethyl, propyl, isopropyl, octyl, t-butyl, methoxy, ethoxy, , Butoxy, trimethylsilyl, fluorine, and chlorine.

The electron transporting material of the present invention has improved electron transporting ability and improved luminous efficiency.

In addition, by using an electron transporting layer material having an excellent electron transporting ability, the light emitting efficiency of the organic electroluminescent device is improved and low voltage driving is possible.

1 is a schematic cross-sectional view of an organic electroluminescent device according to an embodiment of the present invention.

Hereinafter, the structure of the electron transport material according to the present invention, its synthesis example, and the organic electroluminescent device using the same will be described.

The electron transporting material of the present invention is characterized in that an aromatic ring compound is substituted at positions 4 and 7 of phenanthroline and an aromatic compound or a heterocyclic ring compound is substituted at positions 2 and 9, And is represented by the following formula (2).

(2)

That is, in Formula 2, R 1 is selected from substituted or unsubstituted dicyclic compounds, and each of R 2 and R 3 is selected from a substituted or unsubstituted aromatic compound or a substituted or unsubstituted aliphatic ring compound.

For example, R1 may be an alicyclic ring compound comprising nitrogen and / or sulfur, such as pyridine, quinoline, benzothiazole, and the like.

Each of R 2 and R 3 is independently selected from the group consisting of C6 to C22 such as phenyl, biphenyl, naphthyl, phenanthrene, anthracene, terphenyl, pyrene, Or an alicyclic compound containing nitrogen or / and sulfur such as pyridine, quinoline, benzothiazole or the like.

The substituent of the aliphatic cyclic compound or aromatic compound is selected from aryl, C1 to C20 alkyl, C1 to C20 alkoxy, halogen, cyano, silyl . For example, the substituent may be selected from the group consisting of methyl, ethyl, propyl, isopropyl, octyl, t-butyl, methoxy, ethoxy, ), Butoxy, trimethylsilyl, fluorine, and chlorine.

Such an electron transporting material is characterized in that it has an excellent electron transporting ability by substituting a hetero ring compound at positions 4 and 7 of phenanthroline and substituting an aromatic compound or a heterocyclic ring compound at positions 2 and 9 to be. For example, the electron transport material of the present invention is represented by the following formula (2-1) and R is phenyl, biphenyl, naphthyl, phenanthrenyl, acrydinyl And when R is phenyl, R is substituted and the substituent may be selected from alkyl, alkoxy, florine, naphthyl, phenanthrenyl, pyridyl, quinolinyl, benzimidazoyl, benzothiazoyl .
2-1

For example, the electron transport material of Formula 2 may be any of a number of materials represented by Formula 3 below. For convenience of explanation, symbols ET 1 to ET 120 are assigned to the bottom of each material.

(3)

Hereinafter, among the electron transport materials for an organic electroluminescence device according to the present invention, 2- (3- (phenanthren-10-yl) phenyl) -9-phenyl-4,7-di pyridin-3-yl) -1,10-phenanthroline as an example, a synthesis example of the electron transport material of the present invention will be described.

Synthetic example

1. Synthesis of 4,7-di (pyridin3-yl) -1,10-phenanthroline

4,7-di (pyridin3-yl) -1,10-phenanthroline is synthesized by the following Reaction 1.

Scheme 1

Specifically, 4,7-dibromo-1,10-phenanthroline (2 g, 5.95 mmol) and 3-pyridine boronic acid (1.61 g, 13.10 mmol) were added to 80 mL of anhydrous tetrahydrofuran and stirred. Tetrakis (triphenylphosphine) palladium (0.21 g, 5 mol%), potassium carbonate (K2CO3, 20 g) and distilled water (80 mL) were added and refluxed at 100 ° C for 24 hours. At the end of the reaction, tetrahydrofuran is removed and the resulting solid is filtered. Recrystallization was performed using dichloromethane and methanol to obtain 4,7-di (pyridin3-yl) -1,10-phenanthroline (1.11 g, 56%).

Synthesis of 2-phenyl-4,7-di (pyridin-3-yl) -1,10-phenanthroline

2-phenyl-4,7-di (pyridin-3-yl) -1,10-phenanthroline is synthesized by the following reaction formula 2.

Scheme 2

Specifically, 4,7-di (pyridin3-yl) -1,10-phenanthroline, bromobenzene (2 g, 12.74 mmol) and 50 mL of THF are added to a three-necked round bottom flask and stirred. 5.1 ml n-butyllithium (2.5 M in hexane solution) was slowly added dropwise at -78 ° C for 30 minutes and then stirred at the same temperature for 1 hour, then 4,7-di (pyridin- yl) -1,10-phenanthroline (4.69 g, 14.01 mmol) was slowly added dropwise at -78 ° C and further stirred at room temperature. When the reaction is complete, add 100 mL of distilled water and extract with dichloromethane. 2-phenyl-4,7-di (pyridin-3-yl) -1,10-phenanthroline (2.59 g, 45%) was obtained by column chromatography using dichloromethane / hexane.

Synthesis of 2- (3- (phenanthren-10-yl) phenyl) -9-phenyl-4,7-di (pyridin-3-yl) -1,10-phenanthroline

2- (3- (phenanthren-10-yl) phenyl) -9-phenyl-4,7-di (pyridin-3-yl) -1,10-phenanthroline is synthesized by the following reaction formula 3.

Scheme 3

Specifically, 9- (3-bromophenyl) phenanthrene (4.46 g, 13.40 mmol) and 50 mL of THF are added to a three-neck round bottom flask and stirred. 5.5 ml of n-butyllithium (2.5 M in hexane solution) was slowly added dropwise at -78 ° C for 30 minutes and then stirred at the same temperature for 1 hour. Then, 2-phenyl-4,7- di (pyridin-3-yl) -1,10-phenanthroline (5 g, 12.18 mmol) was slowly added dropwise at -78 ° C and stirred at room temperature. When the reaction is complete, add 100 mL of distilled water and extract with dichloromethane. 3- (phenanthren-10-yl) phenyl) -9-phenyl-4,7-di (pyridin-3-yl) -1,10-phenanthroline (2.58 g , 32%).

Hereinafter, the performance of the electron transport material of the present invention and the organic electroluminescent device using the electron transport material of the present invention will be compared with each other through an experiment to fabricate the organic electroluminescent device using the electron transport material of the present invention.

Experimental Example

The ITO layer was patterned to have a light emitting area of 3 mm x 3 mm on the substrate and then cleaned. (200 Å), NPD (400 Å), DPBVi (200 Å) and BD-A (3%), the electron transport material (350 Å), LiF (5 Å) and Al Respectively.

(0.18 cd / m ² (5.18 V) at 0.9 mA, where CIE x = 0.130 and y = 0.160.

Comparative Example

The ITO layer was patterned to have a light emitting area of 3 mm x 3 mm on the substrate and then cleaned. The ITO layer was formed in the order of CuPC (200 Å), NPD (400 Å), DPBVi (200 Å) + BD-A (3%), Alq3 (350 Å), LiF (5 Å) and Al (1000 Å).

At 0.9 mA exhibited a ^{619.6 cd / m 2 (6.79 V} ) In this case exhibited a CIE x = 0.135, y = 0.190 .

The comparison results of the above-described experimental examples and comparative examples are shown in Table 1 below. Here, the unit of voltage is V, the unit of current is mA, and the unit of luminance is cd / m ² .

Voltage electric current Luminance CIE (X) CIE (Y) Experimental Example 5.18 0.9 1008 0.130 0.160 Comparative Example 6.79 0.9 619.6 0.135 0.190

As can be seen from Table 1, the organic electroluminescent device using the electron transport material of the experimental example can be driven at a low voltage and has high luminance as compared with the conventional organic electroluminescent device using Alq3.

An embodiment of an organic electroluminescent device including the above-mentioned electron transporting material is shown in FIG.

As shown, the organic electroluminescent device includes first and second substrates (not shown) facing each other, and an organic light emitting diode (E) formed between the first and second substrates (not shown) .

The organic light emitting diode E includes a first electrode 110 serving as an anode, a second electrode 130 serving as a cathode, and an organic emission layer 120 formed between the first and second electrodes 110 and 130. [ ).

The first electrode 110 is made of a relatively high work function material such as indium-tin-oxide (ITO), and the second electrode 130 is made of a material having a relatively low work function value, For example, aluminum (Al) or an aluminum alloy (AlNd). In addition, the organic light emitting layer 120 has red, green, and blue organic light emission patterns.

The organic light emitting layer 120 may include a hole injection layer (HTL) 121, a hole transporting layer (HIL) 121, and a hole transporting layer (HIL) 121 sequentially from the first electrode 110 in order to maximize luminous efficiency. An emission layer 122, an emitting material layer (EML) 123, an electron transporting layer 124, and an electron injection layer 125.

Here, the electron transporting layer 124 includes the electron transporting material represented by Formula 2. That is, an aromatic ring compound is substituted at positions 4 and 7 of phenanthroline, and an aromatic compound or a heterocyclic ring compound is substituted at positions 2 and 9, thereby using an electron transporting material having excellent electron transporting ability Thereby lowering the driving voltage of the organic electroluminescent device and increasing the luminous efficiency.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the appended claims. It can be understood that

110: first electrode
120: organic light emitting layer
124: electron transport layer
130: second electrode

Claims (10)

Is represented by the following formula,
R is selected from phenyl, biphenyl, naphthyl, phenanthrenyl, acrydinyl, and when R is phenyl, R is substituted and the substituent is alkyl, Lt; RTI ID = 0.0 > phenanthrenyl. ≪ / RTI >

delete delete delete delete A first electrode;
A second electrode facing the first electrode;
And a light emitting layer which is located between the first and second electrodes and is composed of a hole injecting layer, a hole transporting layer, a light emitting material layer, an electron transporting layer and an electron injecting layer,
Wherein the electron injection layer is represented by the following formula,
R is selected from phenyl, biphenyl, naphthyl, phenanthrenyl, acrydinyl, and when R is phenyl, R is substituted and the substituent is alkyl, Phenanthrenyl. ≪ / RTI >

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