KR100710987B1 - Organic Electroluminescent Polymer with Polyarylenic Backbone Containing 1,2-Difluorenyl-substituted Ethylene Moiety and Electroluminescent Device Prepared Using the Same - Google Patents

Abstract

The present invention relates to a green light-emitting organic electro-molecular molecule, to minimize the intermolecular interaction by introducing an ethylene group substituted with fluorene at the 1,2-position of the vinyl group in the polyarylene backbone, thereby resulting in color purity and thermal stability In addition, it shows an improvement in luminous efficiency, facilitates intermolecular or intramolecular energy transition, and has an advantage of facilitating electron or hole injection and transfer.

Polyarylene backbone, stilbene, fluorene, light emitting polymer, electroluminescent device

Description

Organic electroluminescent molecule having a polyarylene backbone containing an ethylene group substituted with fluorene at the 1,2-position of a vinyl group and an organic electroluminescent device using the same {Organic Electroluminescent Polymer with Polyarylenic Backbone Containing 1,2-Difluorenyl-substituted Ethylene Moiety and Electroluminescent Device Prepared Using the Same}

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

2 is a process diagram schematically illustrating the synthesis mechanism of compound 3 prepared according to an embodiment of the present invention.

3 is a 1 H-NMR spectrum of Compound 3 prepared according to an embodiment of the present invention.

4 is a fluorescence spectrum of the chloroform solution of Compound 3 prepared according to an embodiment of the present invention.

5 is a fluorescence spectrum on the film of Compound 3 prepared according to an embodiment of the present invention.

6 is a cross-sectional view of an electroluminescent device manufactured according to Example 4 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

17: hole transport layer (PEDOT: PSS) 18: light emitting layer made of compound 3

19: electron transport layer (LiF) 20: anode (Al)

The present invention relates to an organic electroluminescence polymer and an organic electroluminescent device (EL device) using the same. More specifically, the present invention minimizes intermolecular interactions by introducing an ethylene group substituted with fluorene at the 1,2-position of the vinyl group in the polyarylene backbone, thereby improving color purity, thermal stability, and luminous efficiency. The present invention relates to an organic light emitting polymer capable of facilitating intermolecular or intramolecular energy transition and facilitating electron or hole injection and transfer, and an organic electroluminescent device using the same.

Recently, due to the rapid growth of the optical communication and multimedia fields, the development into a highly information society has been accelerated. Accordingly, optoelectronic 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 these are combined. Until now, most displays are light-receiving, while self-emissive electroluminescence displays are fast responding and self-luminous, so they do not require backlighting and have excellent brightness. It is attracting attention as a display 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 organic electroluminescence has been reported (Appl. Phys. Letter., 51, p913 (1987); Nature, 347, p539 (1990)). Organic electroluminescence (EL) is a phenomenon in which when an electric field is applied to an organic material, electrons and holes are transferred from the cathode and the anode, respectively, to be combined within the material, and the energy generated is emitted as light. The electroluminescence of these organic materials was reported by Pope et al. In 1963. In 1987 by East et al. By Tang et al, alumina-quinone was used. Since a light emitting device having a multilayer structure having a quantum efficiency of 1% and a luminance of 1000 cd / m 2 is reported as a device made of a dye having a conjugated structure at 10 V or less, many studies have been conducted. 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 the luminous efficiency or life of the device. Substitution is proceeding with the organic electroluminescent device 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. In this regard, 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 home appliances by the overlap of the ??-electron wave function in the polymer backbone, and the band gap energy corresponding to the energy difference is applied. The semiconductor properties of the polymer are determined, and full color can be realized. Such polymers are called ??-conjugated polymers. An electroluminescent device using poly (p-phenylenevinylene) (PPV), a polymer having conjugated double bonds, was first introduced in 1990 by a team of professors from RH Friend at the University of Cambridge, UK. After being announced, researches using organic polymers have been actively conducted. Since the ??-electron conjugated polymer has a structure in which single bonds and double bonds are alternately arranged, the ??-electron conjugated polymer has a ??-electron that can move relatively freely along the bond chain without being localized. On the other hand, the polymer is excellent in heat resistance and low spin compared to the low molecule, it is easy to increase the size of the display device. By introducing various suitable substituents, polyphenylenevinylene (PPV) derivatives, polythiophene (Pth) derivatives, polyfluorene derivatives (PF), etc., which can improve processability and express various colors, have been reported. However, polyphenylene has high oxidation stability and thermal stability, but has a disadvantage of low luminous efficiency and poor solubility. In the case of polyfluorene derivatives, most studies have been conducted with blue light emitting polymers, but there is still a problem of minimizing the interaction between excitons generated in one molecule and excitons of other adjacent molecules.

Prior art associated with the present invention is as follows:

U. S. Patent No. 5,807, 974 discloses fluorene-based alternating copolymers as light emitting materials for light emitting devices. In the case of the polymer, fluorene is introduced as a main chain, and may be manufactured in a film form by various thin film formation methods (spin coating, casting, etc.).

On the other hand, US Patent No. 6,361,887 discloses 9,10-di- (2-naphthyl) anthracene-based light emitting polymers into which a fluorene group can be introduced as part of the main chain.

However, the prior art has limitations with respect to the interaction between excitons produced in one molecule and excitons in other molecules as described above.

In order to solve the above-mentioned problems of the prior art, the present inventors have continuously studied, by introducing an ethylene group substituted with fluorene at the 1,2-position of the vinyl group in the polyarylene backbone to minimize the intermolecular interaction, As a result, color purity, thermal stability, and light emission efficiency are improved, and it has been found that the effect of facilitating intermolecular or intramolecular energy transition and facilitating electron or hole injection and transfer can be obtained.

Accordingly, it is an object of the present invention to provide green light emitting organic electroluminescent molecules having high thermal and oxidative stability while minimizing intermolecular interaction, easy energy transfer and excellent luminous efficiency.

Another object of the present invention is to provide an electroluminescent device using the organic electroluminescent molecules.

In order to achieve the above and other objects, the organic electroluminescent molecule of the present invention is a green luminescent organic electroluminescent molecule having a polyarylene main chain containing an ethylene group substituted with fluorene at the 1,2-position of the vinyl group. It is represented by the following formula (1) or (2):

Wherein l, m and n are integers from 1 to 100,000, 0.1 ≦ m / (m + n) ≦ 0.9, 0.1 ≦ n / (m + n) ≦ 0.9;

Ar _{1 to} Ar ₃ is an aromatic group having 6 to 26 carbon atoms or a heteroaromatic group having 2 to 14 heteroatoms included in the aromatic ring. The aromatic group or heteroaromatic group has 1 to 2 carbon atoms. An alkyl group or an alkoxy group of 12, an aromatic group or an amine group of 6 to 14 carbon atoms is replaceable;

R ₁ to R ₃ are the same as or different from each other, hydrogen or an alkyl group having 5 to 30 carbon atoms, a cycloalkyl group, an alkenyl group, a cyanoalkyl group, an aryl group, an aryl group substituted with an alkyl group, an aryl group substituted with a silyl group, or alkoxy An aryl group in which a group is substituted; Fused aromatic rings having 6 to 24 carbon atoms; And a fluorenyl group having an alkyl group having 2 to 30 carbon atoms, a polyalkoxide group, an alkyl group or an alkoxy group substituted at the C-9 position.

Electroluminescent device for achieving another object of the present invention is formed between the anode and the cathode at least one layer comprising the organic electroluminescent molecules of Formula 1 or 2, characterized in that the layer is a light emitting layer or a hole transport layer do.

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

The organic electroluminescent molecules provided according to the present invention may be used as a material for forming a light emitting layer or a hole transport layer positioned between a pair of electrodes in an electroluminescent device, and are represented by the following Chemical Formula 1 or Chemical Formula 2.

Formula 1

Formula 2

In the above, l, m and n are integers of 1 to 100,000, 0.1 ≦ m / (m + n) ≦ 0.9, and 0.1 ≦ n / (m + n) ≦ 0.9.

Ar _{1 to} Ar ₃ is an aromatic group having 6 to 26 carbon atoms or a heteroaromatic group having 2 to 14 heteroatoms included in the aromatic ring. The aromatic group or heteroaromatic group has 1 to 2 carbon atoms. An alkyl group or an alkoxy group of 12, an aromatic group or an amine group having 6 to 14 carbon atoms can be substituted.

Ar ₁ to Ar ₃ is preferably selected from the group represented by the following general formula (3):

.

.

R ₁ to R ₃ are the same as or different from each other, hydrogen or an alkyl group having 5 to 30 carbon atoms, a cycloalkyl group, an alkenyl group, a cyanoalkyl group, an aryl group, an aryl group substituted with an alkyl group, an aryl group substituted with a silyl group, or alkoxy An aryl group in which a group is substituted; Fused aromatic rings having 6 to 24 carbon atoms; And a fluorenyl group having an aryl group substituted with an alkyl group, a polyalkoxide group, an alkyl group or an alkoxy group having 2 to 30 carbon atoms in the C-9 position.

R ₁ to R ₃ are preferably selected from the group represented by the following general formula (4).

.

.

The organic electroadhesive molecules according to the present invention can be prepared, for example, by the Yamamoto polymerization method well known in the art, the molecular weight (M _w ) is about 5000 to 500,000, and the PDI (polydispersity) of about 1 to 10 Range.

In addition, since the organic electro-adhesive molecule according to the present invention has a substituent which can impart steric hindrance at an unspecified position of the polymer main chain, pi-stacking between polymer chains is suppressed and luminous efficiency is further improved. It has increased green light emission characteristics. By introducing a bulky substituent in the molecule as described above, two-dimensional and three-dimensional interactions between the polymer chains can be prevented, and excitons can be suppressed from being quenched by the intermolecular interactions. As a result, the green electroluminescent organic electroluminescent device can be manufactured using the organic electroluminescent molecule of the present invention, and the manufactured organic electroluminescent device can realize high luminous efficiency.                     

As a specific example of the organic electroluminescent advertisement molecule represented by Formula 1, Ar ₁ and Ar ₂ are both phenylene groups, and R ₁ and R ₂ are hexyl groups. Can be mentioned.

Where l is as described above.

In addition, the green light-emitting molecule or monomer thereof specified in Chemical Formula 1 may be used as a high-efficiency green chromophore by energy transfer through copolymerization with a blue light-emitting monomer, and the light emitting polymer material may be specified by Chemical Formula 2. .

As described above, the organic electroluminescent molecules may be used as a material for forming the light emitting layer or the hole transport layer of the electroluminescent device, and one specific example of the method of manufacturing the organic electroluminescent device to which the organic electroluminescent device is applied is as follows.                     

First, an anode electrode material is coated on the substrate. Herein, a substrate used in a conventional organic electroluminescent device is 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, indium tin oxide (ITO), tin oxide (SnO ₂ ), zinc oxide (ZnO), or the like, which is transparent and has excellent conductivity, is used. As the cathode forming metal, lithium (Li), magnesium (Mg), aluminum (Al), Al: Li, and the like having a small work function are used.

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

In this case, the light emitting layer may be formed by spin coating, the thickness is preferably in the range of 10 ~ 10,000 Å. 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. The hole transport layer may be a conventional material for forming a hole transport layer, it may be used a polymer compound of formula (1) or (2). The hole transport layer and the electron transport layer material is not particularly limited, but examples of the hole transport layer material include PEDOT: PSS (poly (3,4-ethylenedioxy-thiophene) doped with poly (styrenesulfonic acid)) and N, N'-bis ( 3-methylphenyl) -N, N-diphenyl- [1,1'-biphenyl] -4,4'-diamine (TPD). In addition, the electron transport layer material is aluminum trihydroxyquinoline (Alq ₃ ), 1,3,4-oxadiazole derivative PBD (2- (4-biphenylyl) -5-phenyl-1,3,4 -oxadiazole, quinoxaline derivatives such as TPQ (1,3,4-tris [(3-penyl-6-trifluoromethyl) quinoxaline-2-yl] benzene) and triazole derivatives can be used. The electron transport layer and the hole transport layer The silver effectively transports the carriers to the light emitting polymer, thereby increasing the probability of the light emitting bond in the light emitting polymer.

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

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.

Example 1

Synthesis of (4-Bromophenyl)-(2- (7-bromo-9,9-dihexylfluoren) yl) ketone (Compound 1)

19.4 g of 9,9-dihexylfluorene and 10 g (1.3 equivalents) of aluminum (III) chloride were added to 200 ml of a carbon disulfide solution, and dissolved by stirring. Then, after the temperature was lowered to 0 ° C., 13 g (1 equivalent) of 4-bromobenzoyl chloride was slowly added in a solid state. After reacting at 0 ° C. for about 30 minutes, water was slowly added thereto, and the product was extracted using methylene chloride. Then, a flash column was separated to give compound 1 (25 g, 83%).

Example 2

Synthesis of 1,2-di (4-bromophenyl) -1,2-di (2- (9,9-dihexylfluoren) yl) ethene (Compound 2)

The temperature of the solution of 1.3 g of zinc dissolved in 35 ml of tetrahydrofuran was lowered to −10 ° C., followed by slowly dropwise addition of 3.7 g (1 equivalent) of titanium chloride (titanium (IV) chloride). 5.0 g of Compound 1 prepared in Example 1 was added by dissolving in 15 ml of tetrahydrofuran, and then heated to reflux for 1 hour by raising the temperature to 70 ° C., and then cooling the solution to room temperature. The reactant mixture solution was slowly added to an aqueous solution of potassium carbonate, extracted with methylene chloride, and separated by a column to obtain a shiny green compound 2 (2 g, 41%).

 Example 3

Polymerization of Compound (Compound 3) of Formula 5

In a 100 ml Schlenk flask, 1,2-di (4-bromophenyl) -1,2-di (2- (9,9-dihexylfluorene) yl) ethene (1,2-di (4- 1 g (0.7 mmol) of bromophenyl) -1,2-di (2- (9,9-dihexylfluoren) yl) ethene) (Compound 2) was added, dissolved in 10 ml of toluene degassed with nitrogen, and then under nitrogen. Stored. 0.44 g (1.6 mmol) of Ni (COD) ₂ as catalyst. 0.11 g (1.1 mmol) of 1.4-cyclooctadiene (COD) and 0.25 g (1.6 mmol) of dipyridyl were added to a Schlenk flask under nitrogen, 3 ml of toluene degassed with nitrogen and 3 ml of DMF. After the addition, the mixture was stirred at 80 ° C. for 30 minutes. The monomer solution prepared as described above was added to the reaction vessel, reacted for 24 hours, 2 ml of bromobenzene was added, and then terminated by reacting for 24 hours. After the reaction was completed, the reaction solution was added to 150 ml of hydrochloric acid (35 wt%): acetone: ethanol = 1: 1: 1 solution to remove the unreacted catalyst and precipitate the polymer. After filtering the polymer was dissolved in chloroform and filtered again with celite to remove the remaining catalyst. After concentration, the precipitate was reprecipitated in methanol and washed with a soxhlet for 24 hours to obtain 0.6 g of a polymer compound (Compound 3). The molecular weight (M _w ) of the compound 3 was 19,000, and the polydispersity (PDI) was 3.3.

The structure of Compound 3 obtained was confirmed using 1 H-NMR spectrum, the measured value is shown in FIG.

Fluorescence spectra in the chloroform solution of Compound 3 and fluorescence spectra in the films are shown in FIGS. 4 and 5, respectively.

The maximum wavelength peak of the PL spectrum in the chloroform solution was 532 nm and the maximum wavelength peak of the PL spectrum in the film was measured at 519 nm. This is exceptional compared to the usual case where the maximum peak of the PL spectrum on the film is red shifted by 10-20 nm or more than the maximum peak of the PL spectrum on the solution, and the position of the inflection point shown to the left of the maximum peak point of the solution phase PL spectrum. When comparing the position to the maximum peak position and comparing the position with the position of the maximum peak of the film, there is no difference in the tendency.The intermolecular π-staking is prevented by the large substituent, and thus the formation of the eximer is almost completely suppressed. . Thus, the compound 3 was confirmed to be a material having a high luminous efficiency.

Example 4

First, a first layer (PEDOT: PSS) 17 was formed to a thickness of 500 mm by spin coating on top of the patterned ITO-coated glass and then dried in a vacuum oven at 100 ° C. for 1 hour. Then, Compound 3 was dissolved in chlorobenzene and spin-coated on the first layer to form a light emitting layer 18 having a thickness of 700 kHz. Again, it was dried for 1 hour in a vacuum oven at 100 ℃. LiF was vacuum-deposited on the light emitting layer to form a layer 19 of 20 kW, and then vacuum evaporated to aluminum 700 m thick to form a cathode 20 to fabricate an organic electroluminescent device.

The green light emitting organic electro-adhesive molecules according to the present invention exhibit high oxidative stability and thermal stability by replacing all positions of the vinyl group with bulky substituents, and can exhibit excellent luminescent efficiency by minimizing the interaction between excitons. have. In addition, since it has a small number of rotation and vibration modes, it is advantageous to increase the external quantum efficiency, and the stability of the device can be improved by the advantages of high glass transition temperature (Tg) and thermal stability of the material. In particular, it has advantages of polymer light emitting material that can manufacture a device by a simple method such as spin coating and the problem of deterioration caused by driving heat generated when driving the device.

All simple modifications and variations of the present invention fall within the scope of the present invention, and the specific scope of the present invention will be apparent from the appended claims.

Claims (6)

A green light emitting organic electroluminescent molecule having a polyarylene main chain represented by the following Chemical Formula 1 or 2 and containing an ethylene group substituted with fluorene at a 1,2-position of a vinyl group: Formula 1

Formula 2

Wherein l, m and n are integers from 1 to 100,000, 0.1 ≦ m / (m + n) ≦ 0.9, 0.1 ≦ n / (m + n) ≦ 0.9; Ar _{1 to} Ar ₃ is an aromatic group having 6 to 26 carbon atoms or a heteroaromatic group having 2 to 14 heteroatoms included in the aromatic ring. The aromatic group or heteroaromatic group has 1 to 2 carbon atoms. An alkyl group or an alkoxy group of 12, an aromatic group or an amine group of 6 to 14 carbon atoms is replaceable; R ₁ to R ₃ are the same as or different from each other, hydrogen or an alkyl group having 5 to 30 carbon atoms, a cycloalkyl group, an alkenyl group, a cyanoalkyl group, an aryl group, an aryl group substituted with an alkyl group, an aryl group substituted with a silyl group, or alkoxy An aryl group in which a group is substituted; Fused aromatic rings having 10 to 24 carbon atoms; And a fluorenyl group having an alkyl group having 2 to 30 carbon atoms, a polyalkoxide group, an alkyl group or an alkoxy group substituted at the C-9 position. According to claim 1, wherein the Ar _{1 ~} Ar ₃ is selected from the group represented by the formula (3) Organic electro-molecular advertising molecule, characterized in that: Formula 3

. According to claim ₁ , R ₁ to R ₃ is an organic electro-molecular ad molecule, characterized in that selected from the group represented by the following formula (4): Formula 4

. According to claim 1, wherein Ar ₁ and Ar ₂ in the formula (1) is an phenylene (phenylene) group, R ₁ and R ₂ is an organic electro-adhesion molecule, characterized in that hexyl (hexyl) group. At least one layer including the organic electroluminescent molecules according to claim 1 is formed between the anode and the cathode, wherein the layer is a light emitting layer or a hole transport layer. The electroluminescent device according to claim 5, wherein the structure of the electroluminescent device is an anode / light emitting layer / cathode, an anode / hole transporting layer / light emitting layer / cathode, or an anode / hole transporting layer / light emitting layer / electron transporting layer / cathode.

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