KR100440901B1 - Poly(aceanthrylene)-based Light Emitting Polymers and Electroluminescent Device Prepared Using the Same - Google Patents

Abstract

The present invention relates to an organic electroluminescent polymer having the following structural formula and an electroluminescent device using the same.

[Wherein l is 1 or more and m is an integer of 0 or more.]

The compound is prepared by polymerizing poly (acean ylene) or poly (acean ylene-vinylcarbazole) with a transition metal catalyst and various vinyl polymerization initiators, and has a cyclic condensation structure, which is hard and has a low vibration mode, thereby increasing fluorescence efficiency. Therefore, the luminous efficiency of the light emitting device emitting the polymer increases. In addition, acetonitrile and vinyl carbazole known as a hole transport material facilitate the exciton transfer, thereby improving the luminous efficiency, and there is an advantage that the light emitting device can be simplified because no hole transport layer is required.

Description

Poly (aceanthrylene) -based Light Emitting Polymers and Electroluminescent Device Prepared Using the Same}

The present invention relates to an organic electroluminescence device (EL device). More specifically, the present invention relates to poly (acerylylene-vinyl), which is a polyacean ylene having a rigid structure which is pericondenced, or a copolymer of vinyl carbazole which is known as a hole transfer material with an aceylene styrene having a rigid structure. REN) is synthesized using a transition metal catalyst and various vinyl polymerization initiators, and a novel organic electroluminescent polymer having high luminous efficiency and an electroluminescent device using these organic electroluminescent polymers.

Recently, due to the rapid growth of the optical communication and multimedia fields, the development into a highly information society has been accelerated. Accordingly, photoelectronic devices using the conversion of photons to electrons or the conversion of electrons to photons have become the core of the modern information electronics industry. Such semiconductor optoelectronic devices can be broadly classified into electroluminescent devices, light receiving devices, and devices in which they are combined. Until now, most displays are light-receiving types, whereas self-emissive electroluminescence displays are fast response and self-emissive, so they do not require backlighting and have excellent brightness. It is attracting attention as an element.

Electroluminescent devices are classified into inorganic and organic light emitting devices according to the material for forming the light emitting layer. In general, inorganic electroluminescent devices made of pn junctions of inorganic semiconductors such as GaN, ZnS, and SiC have a small area display and light emitting diode due to advantages of high efficiency, small size, long life, and low power consumption. It is used for lamps, semiconductor lasers and the like. However, in the case of an electroluminescent (EL) device made of an inorganic material, a driving voltage is required to be 200 V or more, and the manufacturing method of the device is made by vacuum deposition, which makes it difficult to enlarge the size and to obtain high efficiency blue color. In order to overcome this problem, a method of manufacturing an electroluminescent device using an organic electroluminescent phenomenon has been reported (Appl. Phys. Letter., 51, p913 (1987); Nature, 347, p539 (1990)).

An organic electroluminescence phenomenon is a phenomenon in which electrons and holes are transferred from a cathode and an anode, respectively, to be bonded within a material when an electric field is applied to an organic material, and energy generated at this time is emitted as light. The electroluminescence of these organic materials was reported by Pope et al in 1963, and in 1987 by Tang et al at Eastmann Kodak, the alumina-quinone π- Many studies have been conducted since a light emitting device having a multilayer structure having a quantum efficiency of 1% and a luminance of 1000 cd / m 2 at 10 V or less as a device manufactured from a dye having a conjugated structure has been reported. They have the advantage of easy synthesis and synthesis of various types of materials and simple color tuning. However, when the processability and thermal stability are low and the voltage is applied, Joule heat is generated in the light emitting layer, and as the molecules are rearranged, the device is destroyed and causes problems in luminous efficiency or life of the device. Substitution with organic electroluminescent devices having

1 is a cross-sectional view showing a structure of a general organic electroluminescent device manufactured from a substrate / anode / hole transport layer / light emitting layer / electron transport layer / cathode. In the figure, an anode 12 is formed on the substrate 11. The hole transport layer 13, the light emitting layer 14, the electron transport layer 15, and the cathode 16 are sequentially formed on the anode 12. 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 electroluminescent device of 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 into the light emitting layer 14 from the cathode 16 via the electron transport layer 15, and carriers are recombined in the light emitting layer 14 to generate excitons. This exciton is changed from the excited state to the ground state, whereby the fluorescent molecules of the light emitting layer emit light to form an image.

The organic electroluminescent device driven on the principle described above is classified into a polymer organic electroluminescent device and a low molecular organic electroluminescent device according to the molecular weight of the material for forming an organic film.

In general, in the case of using a low molecule when forming an organic film, the low molecule is easy to purify and can almost remove impurities, it is excellent in the light emission characteristics. However, there is a problem in that spin coating is not possible and heat resistance is poor, thereby deteriorating or recrystallizing by driving heat generated when driving the device.

On the other hand, when the polymer is used to form the organic film, the energy level is separated into the conduction band and the electrical appliance diagram by the superposition of the π-electron wave function in the polymer backbone, and the band gap energy corresponding to the energy difference is used. The semiconducting properties of the polymer are determined and full color can be achieved. Such polymers are referred to as "π-conjugated polymers". An electroluminescent device using poly (p-phenylenevinylene) (PPV), a polymer having conjugated double bonds, was first published in 1990 by a team of professors from RH Friend at the University of Cambridge, UK. After that, research using organic polymers has been actively conducted.

However, in order to put the LEP device into practical use, there are many problems to be solved in various aspects such as stability and luminous efficiency. Among these problems, the increase in luminous efficiency has been a major concern in LEP device research because it has a direct relationship with the increase of luminance, the reduction of driving voltage required to reach the same luminance, and the improvement of life under the same luminance. Research under this purpose consists essentially of: (i) synthesizing purely polymeric materials with high efficiency, ii) blending with polymers that can easily cause exciton transport, and iii) introducing lamination (insulating layers). Among them, the blend method is the most promising method in the manufacturing process, processing and patterning.

To date, as a result of fabricating an electroluminescent device by mixing many LEP polymers or light emitting pigments with other polymers, it has been reported that the efficiency has been increased from 5 to 10 times up to several hundred times. However, there have been few attempts to increase luminous efficiency by using a copolymer containing both an electron emission group and an area that can easily cause exciton transport.

On the other hand, it is known that if the polymer chain is hard, the vibration mode is reduced to increase the fluorescence efficiency and the stability of the light emitting device. If the copolymer of the monomer including the chromophore causing the electroluminescence and the monomer capable of causing the exciton transport well is cyclically condensed and is amorphous, the luminous efficiency is expected to increase significantly.

Accordingly, an object of the present invention is to synthesize cyclic condensed rigid poly (aceanthylene) or poly (aceanthylene-vinylcarbazole) which is a copolymer with vinyl of various compositions using a transition metal catalyst. To provide an organic electroluminescent polymer exhibiting excellent luminous efficiency.

Another object of the present invention is to provide an electroluminescent device using the electroluminescent polymer as a material for forming a light emitting layer.

In order to achieve the above and other objects, the organic electroluminescent polymer of the present invention is characterized by the following formula (1).

In the formula, l is an integer of 1 or more, m is an integer of 0 or more, and n is an integer of 10 to 10,000.

1 is a cross-sectional view showing a general organic electroluminescent device structure having a structure of a substrate / anode / hole transport layer / light emitting layer / electron transport layer / cathode.

Figure 2 is a process chart showing the manufacturing process of the electroluminescent polymer compound represented by the formula (2) and formula (3) of the present invention.

3 is a diagram showing ¹ H-NMR spectrum of the electroluminescent polymer compound represented by Chemical Formula 2 of the present invention.

4 is a diagram showing a thermogravimetric analysis curve of an electroluminescent polymer compound represented by Chemical Formula 2 of the present invention.

5 is a diagram showing a thermogravimetric analysis curve of an electroluminescent polymer compound represented by Chemical Formula 3 of the present invention.

6 is a view showing a solution and a solid PL (photoluminescence) spectrum of the electroluminescent polymer compound represented by Chemical Formula 2 of the present invention.

7 is a view showing a solid PL (photoluminescence) spectrum of the electroluminescent polymer compound represented by Formula 3 of the present invention.

8 is a diagram showing an EL (electroluminescence) spectrum of the electroluminescent polymer compound represented by Chemical Formula 2 of the present invention.

9 is a diagram showing an EL (electroluminescence) spectrum of the electroluminescent polymer compound represented by Chemical Formula 3 of the present invention.

* Description of the 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: cathode

The present invention can be achieved according to the following description with reference to the accompanying drawings.

The organic electroluminescent polymer of the present invention is used as a material for forming a light emitting layer positioned between a pair of electrodes in an electroluminescent device.

The organic electroluminescent polymer of the present invention may have a structure of Formula 2.

In Formula 2, the electroluminescent polymer when n ₁ is 10-10000 is an anthracene cyclic condensed structure known to have high efficiency, and the polymer chain is very hard. Since the stiffness rate can reduce the luminous efficiency decrease due to the intramolecular vibration mode, it is possible to suppress that the high efficiency of anthracene itself is reduced.

Therefore, an organic electroluminescent device using the electroluminescent polymer of Chemical Formula 2 as a light emitting layer may be manufactured, and the organic electroluminescent device thus manufactured may implement high luminous efficiency.

In addition, the organic electroluminescent polymer of the present invention may have a structure of Chemical Formula 3.

In Formula 3, an electroluminescent polymer when n ₂ is 1-10,000 may also be used as a light emitting layer material of the organic electroluminescent device.

The organic electroluminescent device may be manufactured using the organic light emitting polymer as the light emitting layer forming material, and one embodiment thereof is as follows.

First, an anode electrode material is coated on the substrate. Herein, a substrate used in a conventional organic electroluminescent device may be used, and a glass substrate or a transparent plastic substrate having excellent transparency, surface smoothness, ease of handling, and waterproofness is preferable. In addition, as the anode electrode material, transparent and excellent indium tin oxide (ITO), tin oxide (SnO ₂ ), zinc oxide (ZnO), and the like may be used. As the cathode forming metal, lithium (Li), magnesium (Mg), aluminum (Al), Al: Li, or the like having a small work function may be used.

The organic electroluminescent device of the present invention may be composed of the most common anode / light emitting layer / cathode and may further include a hole transport layer and / or an electron transport layer.

At this time, the light emitting layer may be formed by spin coating, the thickness is preferably in the range of 100 ~ 2000 kPa. The hole transport layer may be formed by vacuum deposition or sputtering on the anode electrode, and the electron transport layer is formed on the light emitting layer before forming the cathode. It is preferable that the thickness of the said hole transport layer and an electron transport layer is 100-2000 GPa. The hole transport layer and the electron transport layer material is not particularly limited, but is preferably N, N'-bis (3-methylphenyl) -N, N-diphenyl- [1,1'-biphenyl]-as the hole transport layer material. 4,4'-diamine (TPD) is used, and as the electron transport layer material, aluminum trihydroxyquinoline (Alq ₃ ), 1,3,4-oxadiazole derivative PBD (2- (4-biphenylyl) -5-phenyl-1,3,4-oxadiazole) and the like. The electron transport layer and the hole transport layer effectively transports the carriers to the light emitting polymer, thereby increasing the probability of light emitting coupling in the light emitting polymer. When the compound of the formula (3) is used as the light emitting layer material, since the carbazole is easy to transport holes, it is not necessary to include the major transport layer.

The organic electroluminescent device is manufactured in the order described above, that is, in the order of anode / hole transporting layer / light emitting layer / electron transporting layer / cathode, or vice versa, in the order of cathode / electron transporting layer / light emitting layer / hole transporting layer / anode. Can be.

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

Production Example

A reflux condenser was installed in a 500 ml three-necked round flask, and AlCl ₃ , carbon disulfide, and anthracene were added and cooled in an ice bath. Chloroacetyl chloride was slowly added to the dropping funnel with stirring. After dropping at -10 ° C, the reaction was carried out for 15 minutes. HCl, ice and distilled water were added to a 1 L beaker and the reaction mixture was poured. Extracted with methylene chloride and neutralized with NaHCO ₃ . The solvent was blown off on a rotary evaporator, and then separated by column chromatography using hexane to prepare 9-chloroacetylanthracene (A) (yield: 35%).

A reflux condenser was installed in a 250 ml two-necked round flask, 250 ml of carbon disulfide and 9-chloroacetylanthracene (A) were added, cooled in an ice bath, and slowly added AlCl ₃ . After refluxing in a water bath for 24 hours, the reaction was cooled, and 35 wt% HCl, ice and distilled water were poured into a 1 L beaker and the reaction mixture was poured. After recovering carbon disulfide, it was dissolved in methylene chloride, neutralized with Na ₂ CO ₃ , filtered, dried with MgSO ₄ , the solvent was removed, and recrystallized from ethanol to prepare 1-aceanthrenone (B) (yield 78%). ).

1-aceanthrenone was dissolved in methylene chloride in a 500 ml two-necked round flask, and 50 ml of methanol was added thereto. Sodium borohydride was added slowly and then refluxed for 20 minutes. After the temperature was lowered to room temperature, it was neutralized with an acetic acid aqueous solution. The mixture was washed three times with methylene chloride and then the solvent was blown off with a rotary evaporator. Recrystallization was performed by adding ethanol to prepare 1-aceanthrenol (C) (yield 95%).

Place a Dean-Stark trap in a 1 L two-necked round flask, add 700 ml of dried benzene, 1-aceanthrenol and a small amount of p-toluenesulfonic acid, reflux for 3-4 hours, cool, and add NaHCO ₃ . The reaction was terminated. Benzene was removed by a rotary evaporator, and then separated by column chromatography to obtain acetonitrile (D) as a monomer (yield 43%). This process is shown in FIG.

Example 1

Preparation of Organic Electroluminescent Polymer of Formula 2

Compound (D) prepared in Preparation Example was polymerized using various transition metal catalysts. In the polymerization process, a chlorobenzene solvent and acetonitrile were added to an ampoule equipped with a rubber stopper, and 0.05 M WCl ₆ chlorobenzene solution was added to the solution by a syringe. After stirring for 12 hours at the given temperature, 1 ml of methanol was added to terminate the reaction.

The polymer was precipitated in excess methanol, dissolved in chloroform, reprecipitated, filtered, and dried in a vacuum oven at 50 ° C. for 12 hours to obtain a polymer represented by Formula 2 (yield> 90%). The structure of the compound was confirmed by ¹ H-NMR, and the measured value is shown in FIG. 3.

Example 2

Preparation of Organic Electroluminescent Polymer of Formula 3

Compound D and vinyl carbazole prepared according to the preparation were polymerized using various transition metal catalysts at various molar ratios. The polymerization process was performed by adding chlorobenzene solvent and acetonitrile to an ampoules equipped with rubber stoppers, and adding 0.05 mL to this solution. M WCl ₆ chlorobenzene solution was added by syringe. After stirring for 12 hours at a given temperature, 1 ml of methanol was added to terminate the reaction. The polymer was precipitated in excess methanol, again dissolved in chloroform, reprecipitated, filtered, and dried in a vacuum oven at 50 ° C. for 12 hours to obtain a polymer of Formula 3 (I, II, and III) (yield> 90%).

Fabrication of Electroluminescent Devices

Example 3

After forming an indium-tin oxide (ITO) electrode on a glass substrate, a light emitting layer having a thickness of 600 Å was formed by spin coating the compound of Formula 1 on the ITO electrode. Al: Li was vacuum-deposited on the emission layer to form an aluminum-lithium electrode of 1200 Å thickness to fabricate an organic electroluminescent device.

Example 4

An organic electroluminescent device was manufactured according to the same method as Example 3 except for using the compound of Formula 2 or Formula 3 instead of the compound of Formula 1 when forming the emission layer.

Properties of Electroluminescent Polymer Compounds

In order to evaluate the properties of the organic electroluminescent polymer compound, the PL spectrum of the organic electroluminescent polymer compound (Formula 2) prepared in Example 1 is shown in FIG. PL maximum peaks in the PL spectrum were 490 nm (solution) and 490 nm (solid).

In addition, the PL spectrum of the organic electroluminescent polymer compound prepared in Example 2 is shown in FIG. Regardless of the composition of the copolymer, the PL maximum peak in the PL spectrum measured with an excitation wavelength of 365 nm was 495 nm, and a shoulder was measured at 530 nm.

EL spectra of the organic electroluminescent devices prepared according to Examples 3 and 4 are shown in FIGS. 8 and 9, respectively.

The organic electroluminescent polymer of the present invention has an anthracene cyclic condensed structure having high luminous efficiency and can exhibit excellent luminous efficiency, and can improve the stability of the device. Furthermore, by copolymerization with vinyl carbazole known as a major transport layer. In the case of the obtained copolymer, it is not necessary to prepare a hole transport layer separately in fabrication of the device, so that device fabrication is simple and excellent luminous efficiency can be exhibited.

Simple modifications and variations of the present invention are all within the scope of the present invention, and the specific scope of the present invention will be apparent from the appended claims.

Claims (2)

Polymer of the following structural formula. [Wherein l is an integer of 1 or more and 1000 or less, m is an integer of 0 or more and 1000 or less, n is an integer of 10-10000] An electroluminescent device wherein the light emitting layer forming material is the polymer of claim 1.