KR20100029538A - Manufacturing method of electron emitters containing carbon nanotubes and binders and the carbon nanotube electron emitters manufactured thereby - Google Patents

Abstract

PURPOSE: An electron emission source manufacturing method and a carbon nanotube electron emission source thereof are provided to form an electron emission film with superior adhesive force by coating a carbon nanotube binder mixed solution to a cathode substrate. CONSTITUTION: A carbon nanotube dispersion solution is manufactured by dispersing refined carbon nanotube to a polarity or a non-polar solvent. The carbon nanotube binder mixed solution is manufactured by mixing the carbon nanotube and the binder. The carbon nanotube binder mixed solution is coated in the cathode substrate by using a spraying method. An electron emission film is formed by solidifying the binder material. The carbon nanotube electron emission source is formed by executing a taping process.

Description

Manufacturing method of electron emitter using a one-component carbon nanotube binder mixture liquid and carbon nanotube electron emitter for field emission device manufactured by the present invention {manufacturing method of electron emitters containing carbon nanotubes and binders and the carbon nanotube electron emitters manufactured}

The present invention relates to a method for producing a carbon nanotube electron emission source by a spray method using a one-component carbon nanotube binder mixture liquid, and to a carbon nanotube electron emission source for a field emission device produced by the same, in particular carbon nanotubes and Production of an electron emission source using a one-component carbon nanotube binder mixture solution, in which a one-component liquid mixture containing a binder is coated on a cathode substrate by a spray method to increase adhesion between the substrate and the carbon nanotube electron emission source, thereby exhibiting stable field emission characteristics. A method and a carbon nanotube electron emission source for a field emission device produced thereby.

In general, field emission (FE) is a physical phenomenon in which electrons are emitted by a tunneling effect on a solid surface when an external strong electric field is applied, and the electrons bound below the solid Fermi energy are thinned by a strong electric field. Because tunnels are released by tunneling, they are highly dependent on the strength of the electric field and the work function of the solid.

The device using the field emission principle has excellent luminous efficiency, light and small size, and is environmentally friendly, and thus can be applied to general illumination light sources, displays, and LCD back light units. In addition, it can be applied to the field of electron source such as THz vacuum element, X-ray tube, ionization gauge, etc., which require stable high current density.

Recently, many studies on carbon nanotubes have been conducted as electron emission sources for field emission devices. Carbon nanotubes have excellent field concentration effects, low work function, and chemical stability due to large aspect ratio and high electrical conductivity. This high value is expected to be an ideal electron emission source for the field emission devices.

Known methods for producing carbon nanotube electron emission sources include a direct growth method in which carbon nanotubes are grown directly on a cathode substrate by chemical vapor deposition and a paste mixed with an organic-inorganic binder and carbon nanotubes. Method of manufacturing by screen printing (Korean Patent Office Publication No. 2003-0083790), electrophoresis method by applying an electric field to a solution in which carbon nanotubes are dispersed and depositing it on a substrate, airbrush the carbon nanotube dispersion solution Spray method to be deposited on the cathode by using a.

The direct growth method is an ideal manufacturing method because of strong adhesion between the carbon nanotubes and the cathode substrate and easy control of the structure such as length, diameter, and density of the carbon nanotubes, but the large area is difficult and due to the high growth temperature of the carbon nanotubes. Constraints on cathode electrodes are severe and difficult to commercialize.

The screen printing method using the paste has the advantage of having a large area, strong adhesion to the substrate, and no limitation of temperature, but it is difficult to control the length and density of carbon nanotubes, and it is difficult to form a thin film during printing. It is difficult to obtain emission characteristics. In addition, organic solvents used to maintain the viscosity of various organic-inorganic binders and pastes remain after the firing process of the paste, and thus the lifetime of the carbon nanotube electron emission source is reduced when the field is released. have.

The electrophoresis method and the spray method has the advantage of easy large area and easy manufacturing process, but the weak adhesion of the carbon nanotubes and the substrate has a disadvantage that the desorption phenomenon of the carbon nanotubes occurs during the field emission.

In order to solve this problem, according to the "method of manufacturing a carbon nanotube field emitter using a thin metal layer" of the Republic of Korea Patent Publication No. 10-0679209, a thin metal layer having a low melting point is deposited on the cathode substrate and carbon nanotubes After spray coating the dispersion solution, the adhesion between the carbon nanotubes and the substrate was increased by vacuum heat treatment at a temperature similar to the melting point of the metal. However, this is a disadvantage that can not be applied to a flexible polymer substrate.

In addition, according to the "field emission emitter electrode manufacturing method" of the Republic of Korea Patent Publication No. 10-0691161, using a conductive metal layer or a conductive polymer layer as a cathode substrate, a carrier gas sprayed at a subsonic or supersonic speed of carbon nanotube solution By adhering the carbon nanotubes to the substrate by using the adhesion to the substrate was increased. However, this method uses only a soft substrate and has the disadvantage of degrading the field emission characteristics due to damage of carbon nanotubes due to collision.

The present invention is to solve the above problems, by forming a thin carbon nanotube electron emission source on the cathode substrate by a spray method using a one-component carbon nanotube binder mixture liquid, high emission current through improved adhesion to the substrate and An object of the present invention is to provide a method for producing an electron emission source using a one-component carbon nanotube binder mixture solution that exhibits stable field emission characteristics and a carbon nanotube electron emission source for a field emission device manufactured thereby.

In order to solve the above problems, the present invention, after coating a one-component carbon nanotube binder mixture liquid mixed with carbon nanotubes and a binder on the cathode substrate by spraying, and curing the binder to form an electron emission film, Method for producing an electron emission source using a one-component carbon nanotube binder mixture liquid characterized in that the carbon nanotube electron emission source is formed through surface activation by the taping process and the carbon nanotube electron emission source for the field emission device manufactured thereby To be a technical point.

In addition, the present invention comprises the steps of preparing a carbon nanotube dispersion solution by dispersing the purified carbon nanotubes in a polar or non-polar solvent; A second step of preparing a carbon nanotube binder mixture liquid by mixing the carbon nanotubes and the binder dispersed in the solvent of the first step; A third step of coating the carbon nanotube binder mixture solution of the second step on the cathode substrate by a spray method; A fourth step of drying the solvent contained in the resultant of the third step and curing the binder material to form an electron emission layer; The fifth step of forming a carbon nanotube electron emission source through surface activation by performing a taping process on the electron emission film of the fourth step; electron emission using a one-component carbon nanotube binder mixture comprising a The original manufacturing method and the carbon nanotube electron emission source for the field emission device using the same are another technical gist.

Herein, the cathode substrate is preferably a flexible conductive polymer film, and in particular, any one of conductive polymer, metal nanoparticles, and carbon nanotubes is coated on any one of PET, PES, and PC to have a sheet resistance of 1 kΩ / sq or less. It is more preferable to use the thing.

In addition, the cathode substrate is preferably a substrate on which a conductive film is coated on any one of a metal substrate, a polymer, an insulator, and a semiconductor substrate.

In addition, the carbon nanotubes, it is preferably made of one selected from single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes and mixtures thereof.

In addition, the electron-emitting film, the binder content in the coating of the carbon nanotube binder mixture on the cathode substrate is preferably 0.1 to 70 parts by weight based on 100 parts by weight of the carbon nanotubes and the binder mixture.

In addition, the binder is selected from an organic material including a material selected from thermoplastic resins, thermosetting resins, photocurable resins, silane compounds, titanium compounds, polymer copolymers, self-assembled resins, conductive polymers and combinations thereof. It is preferred to consist of species.

Here, the carbon nanotubes, the outer diameter is preferably 0.5 to 50nm or less, the thickness of the electron-emitting film is 0.5㎛ or less, it is preferable that the viscosity of the carbon nanotube binder mixture liquid is 3000cps or less.

According to the present invention, by coating the one-component carbon nanotube binder mixture on the cathode substrate by the spray method, it is possible to implement a thin electron-emitting film excellent in adhesion, high emission current and uniform and stable field emission characteristics In addition, it is easy to obtain a large area, and can be manufactured at room temperature, so that it can be applied to a flexible polymer cathode substrate and various substrates, and the manufacturing process is simple, thereby reducing the manufacturing cost.

In addition, since the one-component carbon nanotube binder mixture liquid does not use any other additives or dispersants, the binder material used is also cured, and thus the lifetime of the carbon nanotube electron emission source of the field emission device is reduced even in continuous use. There is no effect.

The present invention is to form an electron-emitting film by coating the one-component carbon nanotube binder mixture solution prepared by mixing the carbon nanotubes and the binder on one side of the cathode substrate (hereinafter referred to as the upper portion for convenience of description).

The cathode substrate is a flexible conductive polymer film, or a metal substrate or a polymer coated with a conductive film on any one of an insulator and a semiconductor substrate. In addition, the flexible conductive polymer film is coated with a conductive film on any one of a flexible substrate, PET (polyethylene terephthalate), PES (polyethylene styrene) and PC (polycarbonate). The conductive film is preferably coated with any one of a conductive polymer, metal nanoparticles and carbon nanotubes to have a sheet resistance of 1 k 1 / sq or less.

In the case where the cathode substrate is used as a flexible material, by coating the one-component carbon nanotube binder mixture according to the present invention with a spray to form an electron emission film, a flexible field emission device can be obtained and thinner by the spray method. It is possible to implement, and the adhesion to the cathode substrate is improved carbon nanotubes to play a role as a stable electron emission source.

In addition, in forming the electron emission layer by coating the one-component carbon nanotube binder mixture on the cathode substrate, the binder content is preferably 0.1 to 70 parts by weight based on 100 parts by weight of the carbon nanotubes and the binder mixture.

Herein, the carbon nanotubes may be selected from any one of single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes having an outer diameter of 0.5 nm to 50 nm or less.

And the carbon nanotubes are dissolved in a solvent to disperse the primary, wherein the solvent includes a polar or non-polar solvent, preferably acetone, methyl ethyl ketone, methyl alcohol, ethyl alcohol, isopropyl alcohol, butyl alcohol, Ethylene glycol, polyethylene glycol, tetrahydrofuran, dimethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone, hexane, cyclohexanone, toluene, chloroform, distilled water, dichlorobenzene, dimethylbenzene, Trimethylbenzene, pyridine, methylnaphthalene, nitromethane, acrylonitrile, octadecylamine, aniline, dimethyl sulfoxide is selected from the group consisting of one or more carbon nanotube dispersion solution is prepared.

In addition, the ultrasonic dispersion method or ball milling method is used to uniformly disperse in the solvent, and in the ultrasonic device having a power of 50 to 700 W in the frequency range of 20 kHz to 50 kHz depending on the capacity of the carbon nanotubes and the amount of the solvent. Apply for hours to 60 hours to achieve a uniform dispersion of carbon nanotubes in the solvent.

Here, before the carbon nanotube dispersion solution is prepared, surface functionalization may be selectively performed through acid treatment to ensure dispersibility and dispersion stability of the carbon nanotube, the solvent, and the binder. In the acid treatment process, the acid solution is used by selecting one of nitric acid, hydrochloric acid, sulfuric acid and a mixture thereof, whereby carboxyl groups are introduced into the carbon nanotube ends and the surface. Purified carbon nanotubes are washed with distilled water to remove residual acid solution, and finally filtered and dried to obtain carbon nanotubes substituted with carboxyl groups. The purified carbon nanotubes are dispersed in the solvent to prepare a carbon nanotube dispersion solution, and a binder to be described later is mixed therein.

In preparing the carbon nanotube dispersion solution dispersed in the solvent, the binder is mixed or the binder solution is mixed with the polar or non-polar solvent to prepare a separate binder solution and mixed with the carbon nanotube dispersion solution dispersed in the solvent, carbon nanotube and The carbon nanotube binder mixed with the binder is prepared.

In general, the binder content is an important factor that determines the adhesion, electrical conductivity, and dispersibility of the cathode substrate of carbon nanotubes. As the binder content increases, the dispersibility and adhesion of the cathode substrate increase, while the electrical conductivity decreases. By selecting the optimal binder content to prepare a carbon nanotube binder mixture liquid.

Here, the binder may be used including a material selected from a polymer resin, preferably, a thermoplastic resin, a thermosetting resin, a photocurable resin, a silane compound, a titanium compound, a polymer copolymer, a self-assembled resin, a conductive polymer, and a combination thereof. Can be.

The one-component carbon nanotube binder mixture is provided in a one-component form in which no other additives or dispersants are added, so that the lifetime of the carbon nanotube electron emission source of the field emission device does not decrease even in continuous use.

Here, the coating method of the carbon nanotube binder mixture liquid on the cathode substrate is a spray method, and the thinning can be realized by using the carbon nanotube binder mixture liquid to obtain uniform field emission characteristics, and also It is easy to increase the area, and can be manufactured at room temperature, and can be applied to a flexible polymer cathode substrate, and the manufacturing process is simple and economical.

The spray coating method is coated on the cathode substrate with a thickness of 0.5 μm or less, and the electron emitting film according to the present invention is completed by drying the solvent and curing the binder material.

The spray-coated electron-emitting film undergoes surface activation using a taping method, through which carbon nanotubes are aligned vertically on the cathode substrate, thereby serving as a substantial electron emission source.

Hereinafter will be described a preferred embodiment of the present invention.

First, the one-component carbon nanotube binder mixture was prepared by the following procedure.

0.1g of thin-walled multilayered-walled carbon nanotubes in agglomerated state and 100 ml of nitric acid (HNO ₃ ) solution having a concentration of 50 vol% were placed in a 500 ml Erlenmeyer flask and dispersed with a sonicator for 1 hour.

After refluxing the prepared solution for 4 hours, the acid solution remaining in the carbon nanotubes was removed through filtration four times or more using an filtration paper (Alumina filter, 0.1um), followed by drying. The thin-walled multi-walled carbon nanotubes were prepared in which impurities (metal catalysts, etc.) were removed and carboxyl groups (-COOH) were substituted.

Then, the multi-walled carbon nanotube dispersion solution was prepared as follows.

50 mg of carboxyl-substituted multi-walled carbon nanotubes, 200 ml of dimethylformamide (DMF), tetrahydofuran (THF), ethanol, acetone, and dimethylacetamide (DMAc) were mixed in an Erlenmeyer flask for 3 hours Dispersion prepared a carbon nanotube dispersion solution.

The binder is mixed in the solution, the binder is prepared by the thermosetting epoxy to 25 parts by weight with respect to carbon nanotubes and 100 parts by weight of binder, respectively, and then treated with an ultrasonic wave for 2 hours to prepare a carbon nanotube epoxy binder mixture solution. .

The carbon nanotube binder mixture solution prepared above was spray coated on a gold plated silicon substrate under conditions of a spray flow rate of 0.5 ml / min and a nozzle speed of 200 mm / sec. After spray coating, solvent removal and curing of the binder were completed at 200 ° C. for 30 minutes using a hot air dryer.

The carbon nanotube epoxy binder substrate prepared above was subjected to a field emission experiment by surface activation by taping.

1 is a diagram of a cathode substrate on which a carbon nanotube electron emission source manufactured according to an embodiment of the present invention is formed.

2 is a view showing a photograph taken with a scanning electron microscope (SEM) of the cross-section of the carbon nanotube electron emission source before and after the surface activation process by taping prepared according to an embodiment of the present invention. As shown, it was confirmed that the carbon nanotube electron emission sources of uniform length were vertically aligned after surface activation.

3 is a view showing the surface emission state from the carbon nanotube electron emission source prepared according to the embodiment of the present invention, it was able to confirm a uniform and stable surface emission state by the carbon nanotube electron emission source. As the anode, an ITO glass substrate coated with a phosphor was used.

Figure 4 is a view showing the field emission characteristics under the high electric field of the carbon nanotube electron emission source prepared in accordance with an embodiment of the present invention, the substrate adhesion of the carbon nanotube electron source from a stable and high current density is quite excellent I could confirm it.

1 is a diagram of a cathode substrate having a carbon nanotube electron emission source formed according to an embodiment of the present invention.

Figure 2 is a view of the carbon nanotube electron emission source before and after the surface activation process through taping prepared according to an embodiment of the present invention.

3 is a view showing a surface emission state from the carbon nanotube electron emission source prepared according to an embodiment of the present invention.

4 is a view showing field emission characteristics under high electric field of a carbon nanotube electron emission source prepared according to an embodiment of the present invention.

Claims (12)

After coating a one-component carbon nanotube binder mixture solution in which carbon nanotubes and a binder are mixed on the cathode substrate by using a spray method, and curing the binder to form an electron emission layer, carbon nanotubes are activated by surface activation by a taping process. An electron emission source manufacturing method using a one-component carbon nanotube binder mixture liquid, characterized in that to form a tube electron emission source. Dispersing the purified carbon nanotubes in a polar or nonpolar solvent to prepare a carbon nanotube dispersion solution; A second step of preparing a carbon nanotube binder mixture liquid by mixing the carbon nanotubes and the binder dispersed in the solvent of the first step; A third step of coating the carbon nanotube binder mixture solution of the second step on the cathode substrate by a spray method; A fourth step of drying the solvent contained in the resultant of the third step and curing the binder material to form an electron emission layer; The fifth step of forming a carbon nanotube electron emission source through surface activation by performing a taping process on the electron emission film of the fourth step; electron emission using a one-component carbon nanotube binder mixture comprising a Original manufacturing method. The method of claim 1 or 2, wherein the cathode substrate, Method for producing an electron emission source using a one-component carbon nanotube binder mixture liquid, characterized in that the flexible conductive polymer film. The method of claim 3, wherein the flexible conductive polymer film, Coating of any one of conductive polymer, metal nanoparticles and carbon nanotubes on any one of PET, PES and PC, which are flexible substrates, to produce an electron emission source using a one-component carbon nanotube binder mixture liquid having a sheet resistance of 1 kΩ / sq or less. Way. The method of claim 1 or 2, wherein the cathode substrate, A method of manufacturing an electron emission source using a one-component carbon nanotube binder mixture liquid, characterized in that the substrate is coated with a conductive film on any one of a metal substrate, a polymer, an insulator, and a semiconductor substrate. The method of claim 1 or 2, wherein the carbon nanotubes, A method for producing an electron emission source using a one-component carbon nanotube binder mixture liquid, characterized in that it consists of one selected from single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, and mixtures thereof. The method according to claim 1 or 2, wherein the electron emission film, In the coating of the carbon nanotube binder mixture on the cathode substrate, the binder content is 0.1 to 70 parts by weight based on 100 parts by weight of the carbon nanotube and the binder mixture, the electron emission using the one-component carbon nanotube binder mixture liquid. Original manufacturing method. The method of claim 1 or 2, wherein the binder, Thermoplastic resin, thermosetting resin, photocurable resin, silane compound, titanium compound, polymer copolymer, self-assembled resin, conductive polymer, and a combination of organic materials including a material selected from a combination thereof Method for producing an electron emission source using a one-component carbon nanotube binder mixture liquid. The method of claim 1 or 2, wherein the carbon nanotubes, An electron emission source manufacturing method using a one-component carbon nanotube binder mixture liquid, characterized in that the outer diameter is 0.5 to 50nm or less. The method of claim 1 or 2, wherein the electron-emitting film has a thickness of 0.5 µm or less. The method of claim 1 or 2, wherein the viscosity of the carbon nanotube binder mixture is 3000 cps or less. A carbon nanotube electron emission source for a field emission device manufactured by the method according to claim 1 or 2.

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