KR100241114B1 - Polymer composition for emitting layer of light emitting electrochemical display - Google Patents

Abstract

The polymer composition for the light emitting layer of the electrochemical light emitting display of the present invention is a 10-15 wt% light emitting polymer having a polythiophene as a main chain, 5-10 wt% of a solid polymer electrolyte, and a lithium salt as an ion dopant It is a composition which melt | dissolved 5-15 wt% in a solvent. One of the light emitting polymers used in the present invention is a polythiophene derivative, and poly (2 (3-thienyl) ethanol n-butoxycarbonyl methyl urethane having a urethane group introduced at 3-position in the polythiophene polymer. poly (2 (3-thienyl) ethanol n-butoxycarbonyl methylurethane: PURET). Another of the light emitting polymers used in the present invention is a polythiophene represented

Poly (3- (3,6,9-trioxydecyl) thiophene) having aliphatic alkyloxy and ethylene oxide group introduced at 3-position in the polymer (pol y (3- (3,6,9-trioxy decyl) thiophene): PTODT).

Description

Polymer composition for light emitting layer of electrochemical light emitting display

1 is a view showing the layer structure of the light emitting polymer device.

2 is a ¹ H-NMR spectrum of an acrylonitrile-methymethacrylate-styrene (AMS) as a solid polymer electrolyte.

3 is a graph showing a voltage-current curve at forward and reverse bias of the electrochemical light emitting display of the present invention.

4 is a graph showing a voltage-current curve of the electrochemical light emitting display of Examples 1 to 8 according to the type of solid polymer electrolyte.

5 is a graph showing a voltage-current curve of an electroluminescence (EL) display of a comparative example using MEH-PPV as a light emitting layer.

[Field of Invention]

The present invention relates to a polymer composition applied to the light emitting layer of the electrochemical light emitting display. More specifically, the present invention is superior to the conventional poly (p-phenylenevinylene) (PPV) light emitting polymer by applying a polythiophene derivative, a conductive polymer, The present invention relates to an organic electroluminescent polymer having excellent light transmittance, environmental resistance, adhesion to a substrate, thin film formation ability, stability to an electric field, and a composition thereof.

[Background of invention]

In the modern information electronics industry, optoelectronic devices that convert light energy into electrical energy or convert electrical energy into light energy are very important. Such semiconductor optoelectronic devices can be broadly classified into electroluminescent devices, semiconductor laser devices, light receiving devices, and the like. A flat panel display is a light and small element that solves the inconvenience of image realization by a conventional CRT method, and technically, a device having a CRT level or more. In the early stages, wall-mounted TVs became the main purpose, but in the 21st century's information and multimedia era, many uses such as computer monitors, notebook PCs, PDA terminals, etc. were developed. Until now, most displays are light-receiving, while self-emissive electroluminescence displays have fast response and self-emissive, so they do not need backlight and have excellent brightness. Much research is in progress. In the case of an electroluminescent (EL) device made of an inorganic material, a driving voltage is required to be AC 200V or more, and the manufacturing method of the device is made by vacuum deposition, so it is difficult to enlarge the size and the price is also expensive. However, since 1987, when Eastman Kodak published a device made of a pigment having a π-conjugated structure called alumina-quinone, research into electroluminescent (EL) devices using organic materials has been active. In the case of organic materials, the synthesis route is simple, so that various types of materials can be easily synthesized and color tuning is possible, while the mechanical strength is low and crystallization by heat occurs. Substitution is progressing with electroluminescent devices. The superposition of the π-electron wavefunction in the polymer backbone separates the energy level into the conduction band and the consumer electronics, and the semiconductor properties of the polymer are determined by the band gap energy corresponding to the energy difference. color) is possible. Such polymers are called "π-conjugated polymers." A study on the electroluminescence of polymers was published in 1974 by the Keiichi Kaneto group, which showed electroluminescence in high electric fields of poly (ethylene terephthalate). In 1990, a light emitting device made of poly (p-phenylene vinylene) (PPV) was announced for the first time, and an electroluminescence display using π-electron conjugated polymer was introduced. As a representative organic electroluminescent polymer, PPV, a derivative of π-conjugated polymer, is typically used.

In the case of poly (p-phenylene vinylene) derivatives, which are representative materials of polymer EL, polymers have a limitation in mass production due to poor solubility in organic solvents, polymerization time and polymerization yield. In general, PPV organic electroluminescent (EL) materials have the following problems. First, in the case of a polysulfonium precursor, which is a precursor of PPV, polymerization time and yield are very low and expensive. Secondly, to make a complete PPV derivative, the sulfonium salt must be completely removed, which is difficult to remove completely. Third, when the thin film (600 Å) is formed, unreacted sulfonium salts are gradually removed, resulting in pin holes, etc., resulting in poor film uniformity. Fourth, soluble PPV can be synthesized, but the synthesis and polymerization conditions are very demanding.

In the present invention, in order to solve the above problems, by applying a polythiophene derivative, which is a conductive polymer, the electro-optic properties are superior to that of the conventional PPV light-emitting polymer, light transmittance, environmental resistance, adhesion to the substrate, thin film Organic electroluminescent (EL) polymers with excellent forming ability and stability against electric fields have been produced.

[Purpose of invention]

An object of the present invention is to provide a light emitting polymer composition for a light emitting layer of a light emitting display excellent in electro-optic properties.

Another object of the present invention is to provide a light emitting polymer composition for a light emitting layer having excellent light transmittance, environmental resistance, adhesion to a substrate, thin film formation ability, and stability to an electric field.

It is still another object of the present invention to provide a polymer composition for a light emitting layer of a light emitting display that has a lower driving voltage than a conventional PPV derivative and can be driven even in forward and reverse bias.

[Summary of invention]

The polymer composition for the light emitting layer of the electrochemical light emitting display of the present invention is a 10-15 wt% light emitting polymer having a polythiophene as a main chain, 5-10 wt% of a solid polymer electrolyte, and a lithium salt as an ion dopant It is a composition which melt | dissolved 5-15 wt% in a solvent.

One of the light emitting polymers used in the present invention is a polythiophene derivative, and poly (2 (3-thienyl) ethanol having a urethane group introduced at the 3-position in the polythiophene polymer represented by the following structural formula (I): n-butoxycarbonyl methylurethane)) (Poly (2 (3-thienyl) ethanol n-butoxycarbonyl methylurethane): PURET):

P is an integer of about 50-100.

The other one of the light emitting polymers used in the present invention is a poly (introduced with an aliphatic alkyloxy and an ethylene oxide group) at the 3-position in the polythiophene polymer represented by the following structural formula (II) 3- (3,6,9-trioxydecyl) thiophene) (poly (3- (3,6,9-trioxy decyl) thiophene): PTODT):

P is an integer of about 50-100.

The ion dopant used in the present invention is lithium perchlorate (LiClO ₄ ), and the solid polymer electrolyte is an acrylonitrile-methymethacrylate-styrene (AMS), acrylonitrile, methyl methacrylate and styrene. Acrylonitrile-methylmethacrylate (AM) consisting of ronitrile and methyl methacrylate, polyether-polyester (PES) consisting of polyether and polyester, and polyethylene oxide (PEO).

The electrochemical light emitting display manufactured using the electrochemical light emitting polymer of the present invention has a much lower driving voltage than the light emitting display using the conventional PPV derivative and can be driven in a forward and reverse bias.

Hereinafter, specific contents of the present invention will be described in detail below.

Detailed Description of the Invention

In the light emitting mechanism of a general light emitting polymer, holes are formed at the anode and electrons are formed at the cathode, and holes and electrons are recombined in the light emitting polymer layer. The single state exciton is formed by recombination, and the light is emitted by radial decay, and the luminous efficiency is determined. Therefore, in order for the transport of the carrier to be similar, the injected hole and electron mobility must be balanced. However, in general, the hole transport is much more advantageous, causing an imbalance between the carriers and reducing the efficiency. Particularly, since the π-electron conjugated polymer has much larger hole movement, a multi-layered device incorporating an electron transport layer having good electron mobility is fabricated to compensate for this.

The present invention is a new type of mechanism that overcomes these shortcomings, that is, the light emitting polymer expresses the light by a variable electro-chemical reaction and at this time the lithium to the light emitting polymer in order to maintain the stabilization of the charge (charge) Electro-chemical cell driving method by adding a salt (Li-salt) and adding a solid polymer electrolyte to increase the maximum ionic conductivity and charge mobility of the lithium salt The present invention relates to a light emitting polymer display. Most importantly, the formulation ratio of the lithium salt of the light emitting polymer to the solid polymer electrolyte determines the characteristics of the light emitting device.

The polymer composition for the light emitting layer of the present invention is a composition in which 10 to 15 wt% of a light emitting polymer having a polythiophene as its main chain, 5 to 10 wt% of a solid polymer electrolyte, and 5 to 15 wt% of a lithium salt as an ion dopant are dissolved in a solvent. to be.

One of the light emitting polymers used in the present invention is a polythiophene derivative, and poly (2 (3-thienyl) ethanol having a urethane group introduced at the 3-position in the polythiophene polymer represented by the following structural formula (I): n-butoxycarbonyl methylurethane)) (Poly (2 (3-thienyl) ethanol n-butoxycarbonyl methylurethane): PURET):

P is an integer of about 50-100.

The other one of the light emitting polymers used in the present invention is a poly (introduced with an aliphatic alkyloxy and an ethylene oxide group) at the 3-position in the polythiophene polymer represented by the following structural formula (II) 3- (3,6,9-trioxydecyl) thiophene) (poly (3- (3,6,9-trioxy decyl) thiophene): PTODT):

The method for preparing PURET is shown in the following scheme. 2- (3-thienyl) ethanol and tetrahydrofuran were reacted for 48 hours at room temperature under a dibutyltindilaurate catalyst to prepare URET, and FeCl ₃ and CHCl ₃ were added to the URET to prepare PURET.

In the above formula, AA is an aliphatic alkyloxy group (CH ₂ ) _n CH ₃ (where n is 1 to 12), BB is (OCH ₂ CH ₂ ) _m CH ₃ as an ethylene oxide (ehtylene oxide) group Where m is 1-4.

The lithium salt used as the ion dopant in the present invention is lithium perchlorate (LiClO ₄ ). The solid polymer electrolyte in the present invention is a terpolymer (AMS) consisting of acrylonitrile, methyl methacrylate and styrene, a binary polymer (AM) consisting of acrylonitrile and methyl methacrylate, polyether and polyester. Binary polymer (PES), and polyethylene oxide (PEO). Among them, AMS and PES are represented by the following formulas (III) and (IV), respectively.

Generally, a light emitting layer polymer composition of a light emitting display uses a solvent to dissolve a light emitting polymer, a solid polymer electrolyte, and an ion dopant. Solvents used are THF and CHCl ₃ . In addition, the polymer composition generally further includes a plasticizer, and plasticizers include ethylene carbonate and propylene carbonate.

The light emitting polymer, the solid polymer electrolyte, and lithium perchlorrate of the present invention are soluble in organic solvents, and in particular, dissolved in 5.0 wt% in THF or chloroform solvent, and then the thickness control is achieved by spin coating. The thin film thus formed forms a uniform film without pin-holes, and has a disadvantage in that phase separation with a solid polymer electrolyte having a high molecular weight but excellent adhesion to a substrate.

In the present invention, by applying a polythiophene derivative, a conductive polymer that has not been used as an electrochemical light emitting display, the driving voltage is much lower than that of the conventional PPV derivative and can be driven even in forward and reverse bias. The display can be manufactured and its electro-optical properties are excellent. In addition, when the light-emitting polymer is combined with the solid polymer electrolyte, it is shown to increase by about 10 to 100 times than the conventional ionic conductivity. The organic electroluminescent (EL) polymer of the present invention is an organic electroluminescent polymer having excellent light transmittance, environmental resistance, adhesion to a substrate, thin film forming ability, and stability to an electric field to be provided as an electronic material.

The invention can be better understood by the following examples, which are intended for the purpose of illustration of the invention and are not intended to limit the scope of protection defined by the appended claims.

EXAMPLE

[Production of Light-Emitting Polymer]

[(1) Preparation of poly (2 (3-thienyl) ethanol n-butoxycarbonyl methylurethane)) Poly (2- (3-thienyl) ethanol n-butoxycarbonyl methyl-urethane)) (PURET)]

Into a 250 ml three-necked flask, add 100 ml of tetrahydrofuran dehydrated at room temperature while injecting nitrogen, and 15 g (0.117 mole) of 2- (3-thienyl) thanol) Put it. As a catalyst, 3 drops of dibutyl tin dilaurate (dibu tyltindilaurate) is added and stirred and mixed well. Maintain the room temperature using a water bath, and gradually add 1.3 equivalents (23.9 g) of isocyanatoacetic acid n-butylester. The reaction is stirred at room temperature for about 6 hours and then poured into 10% aqueous HCl solution, stirred and washed three times with water. Diethylether is further added to separate the organic layer. The separated organic layer was washed three times with water, dried over anhydrous magnesium sulfate and filtered. The solvent was evaporated from the filtrate to give a viscous clear liquid, and a compound having an Rf value of 0.45 was developed using hexane / ethyl acetate (3/1) as a silica gel column. Separated. The solvent was evaporated from the separated developing solution to finally obtain URET (FW: 285.36) as a viscous clear liquid, and the yield was 87%.

Dry FeCl ₃ (0.1M, 16.2g) was added to a three-necked flask with CHCl ₃ (200ml) and kept at about 0-5 ° C. in an ice bath, followed by vigorous stirring under nitrogen atmosphere for about 10 minutes. In this reactor, 2- (3-thienyl) ethanol n-butoxycarbonyl methylurethane) (2- (3-Thienyl) ethanol n-Butoxycarbonyl methylurethane: URET) (0.025M, 6.8 g) was dissolved in 20 ml CHCl ₃ . It was then added dropwise to the Dry FeCl ₃ (0.1M, 16.2g) / CHCl ₃ solution over a dropping funnel using a dropping funnel. Under the above conditions, the polymer formed by polymerization for 4 hours was precipitated in MeOH (1000 cc) and filtered to obtain a polymer. In order to remove residual metal salts, a Soxhlet extractor is used to extract the yellow solution until it disappears, yielding a pure polymer in about 85% yield.

[(2) Preparation of poly (3- (3,6,9-trioxydecyl) thiophene) Poly (3- (3,6,9-trioxydecy l) thiophene) (PTODT)]

78 mmol of 3-thiophene ethanol was reacted with 2 g of sodium hydride (THF) in THF (30 ml) until a suspension state was obtained. 14.6 g of 1-bromo-2- (2-methoxyethoxy) ethane was slowly added to the reaction mixture, followed by reflux for 24 hours. After completion of the reaction by adding a small amount of HCl solution, the organic solvent was extracted with ether, dried and then removed with solvent, and then separated by vacuum distillation, the yield was about 50% 3- ( 3,6,9-trioxydecyl) thiophene (3- (3,6,9-trioxydecyl) thiophene) (TODT) was synthesized. Dry FeCl ₃ (1,458g, 9mmole) is suspended in 20ml chloroform for 15 minutes (suspension) and TODT (1.18g, 3mmol) is added together with 10ml of chloroform. After polymerization at 30 ° C. for 48 hours, 200 ml were precipitated in methanol. In order to remove unreacted FeCl _{3, it} is removed using methanol as a soxhlet apparatus. The polymerization yield is about 75%.

[Manufacture of Solid Polymer Electrolyte]

In order to synthesize terpolymers by emulsion polymerization, a reactor equipped with a mechanical mixer, a condenser, a nitrogen inlet and a feed inlet is installed. In order to remove impurities such as oxygen and water present in the reactor, high-purity nitrogen was used for 1 hour at 60 ° C. AN (acrylonitrile), MMA (methyl methacrylate), and ST (styrene) monomers corresponding to the composition of the terpolymer obtained are quantified and dissolved in 200 ml of secondary middle water. To this is added 0.8 g of sodium lauryl sulfate (CH ₃ (CH ₂ ) ₁₁ OSO ₃ Na) and 0.16 g of potassium hydrogen-phosphate (K ₂ HPO ₄ ). When a mixture of monomers, emulsifiers and the like is thoroughly mixed, these solutions are injected into the reactor. When the injection of the reactants is completed, the speed of the stirrer is fixed at 600 rpm, and the temperature of the reactor and the cooler is maintained at 60 and 10 ° C, respectively. When the temperature of the reactants reaches 60 ° C, 0.16 g of an initiator potassium persulfate (K ₂ S ₂ O ₈ ) is dissolved in 20 ml of secondary distilled water, and then introduced into the reactor. It can be seen that as the reaction proceeds, the molecular weight of the polymer increases, thereby increasing the viscosity of the reactant to precipitate white fine particles. After the reaction proceeds at 60 ° C. for 8 to 10 hours, the resulting solution is precipitated in an aqueous solution of Al ₂ (SO ₄ ) ₃ causing agglomeration of latex. The precipitated polymer is filtered using a filter paper, washed again with hot distilled water to remove unreacted monomers, initiators, emulsifiers, and the like, and the above process is repeated five times. The filtered product is dried in a vacuum oven at 100 ° C. for at least 24 hours to obtain a white powder.

Solid polymer electrolytes used in the present invention include AM, PEO, PEG, and PES in addition to AMS, which can also be prepared by conventional methods.

2 is the ¹ H-NMR spectrum of the terpolymer.

[Manufacture of Polymer Composition for Light-Emitting Layer (Examples 1 to 8)]

A solid polymer electrolyte, a light emitting polymer and an ion dopant were dissolved in a solvent to prepare a polymer composition for a light emitting layer of a light emitting display according to the present invention. Table 1 shows the type and content of each component.

TABLE 1

[Production of light emitting electrochemical display]

Using a polymer composition of the present invention prepared in Examples 1 to 8, a single layer type device was manufactured. In the device of FIG. 1, an ITO electrode is formed on a glass substrate, a polymer composition is coated on the ITO again, and finally an aluminum layer is formed. In order to manufacture flat panel displays using electrochemical light emitting polymers, glass substrates coated with ITO transparent electrodes are thoroughly cleaned, and then the transparent electrodes are patterned using photoresist resign and the organic light emitting polymer coating machine After coating to a thickness of about 500Å by baking (baking) completely removed a small amount of solvent (solvent). In order to form an electrode, an aluminum metal was vacuum deposited while maintaining a vacuum degree of 1 × 10 ⁻⁵ Torr or less. The film thickness and film growth rate during Al deposition were controlled using a film thickness monitor. When the emission area was 2mm ^{2, the} composition voltage used forward and reverse bias voltage. Ion dopants contained in the polymer composition exhibited maximum ionic conductivity, and the results are shown in Table 2.

TABLE 2

[Electro-optic Characteristic Evaluation]

The PURET light emitting polymer having a urethane group prepared above exhibited a maximum UV-absorption wavelength at about 450 nm in a chloroform solvent. When the excitation wavelength was 351 nm, the fluorescence spectrum showed maximum absorption at about 590 nm. 3 is a current-voltage curve at forward and reverse bias, and in general luminescent polymers, the current-voltage curve is determined by a reversible electrochemical reaction. The symmetrical and electrochemical light emitting polymers prepared in Examples 1 to 8 start to flow current at about ± 2V and show much lower driving voltage than conventional light emitting polymers. This is similar to the band gap of HOMO and LUMO of the light emitting polymer and the degree of light emission is proportional to the amount of injected current. 4 shows that the turn on voltage is different depending on the type of the solid polymer electrolyte.

Comparative Example

Comparative Example compared the electro-optic properties when using a PPV derivative. 5 shows a current-voltage curve when MEH-PPV is used as the light emitting layer. You can see the current flows slowly when the turn on voltage is about 7V. This indicates that the driving voltage due to the electrochemical light emitting mechanism is higher than the driving voltage due to the conventional light emitting mechanism, which indicates that the resistance is significantly reduced by the electrochemical reaction.

Simple modifications and variations of the present invention can be readily used by those skilled in the art, and all such variations or modifications can be considered to be included within the scope of the present invention.

Claims (8)

10 to 15 wt% of a light emitting polymer having a polythiophene as a main chain, 5 to 10 wt% of a solid polymer electrolyte, and 5 to 15 wt% of a lithium salt as an ion dopant are prepared in a solvent. Polymer composition for electrochemical light emitting display light emitting layer characterized in that. The poly [2 (3-thienyl) ethanol n-butoxy carbo having a urethane group introduced at a 3-position in the polythiophene polymer represented by the following structural formula (I): Nyl methylurethane] (poly (2 (3-thienyl) ethanol n-butoxycarbonyl methylurethane)) polymer composition for the light emitting layer of the electrochemical light-emitting display, characterized in that:

In the above, p is an integer of about 50-100. The polymer composition for a light emitting layer of an electrochemical light emitting display according to claim 1, wherein the light emitting polymer is represented by the following Formula (II).

In the above formula, AA is an aliphatic alkyloxy group (CH ₂ ) _n CH ₃ (where n is 1 to 12), BB is (OCH ₂ CH ₂ ) _m CH ₃ as an ethylene oxide (ehtylene oxide) group Where m is 1-4. The light emitting layer polymer composition of claim 3, wherein the light emitting polymer is poly (3-3,6,9-trioxydecyl) thiophene) (P TODT). The polymer composition of claim 1, wherein the lithium salt is lithium perchlorate (LiClO ₄ ). The method of claim 1, wherein the solid polymer electrolyte is a ternary polymer (AMS) consisting of acrylonitrile, methyl methacrylate and styrene, a binary polymer (AM) consisting of acrylonitrile and methyl methacrylate, polyether and A polymer composition for the light emitting layer of an electrochemical light emitting display, characterized in that it is selected from the group consisting of a binary polymer (PES) made of polyester, and polyethylene oxide (PEO). The polymer composition for a light emitting layer of an electrochemical light emitting display according to claim 1, wherein the solvent is THF or CHCl ₃ . An electrochemical light emitting display made of the polymer composition according to any one of claims 1 to 7.

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