KR20060047145A - A carbon nanotube, an emitter comprising the carbon nanotube and an electron emission device comprising the emitter - Google Patents

Abstract

The present invention relates to a carbon nanotube including a plurality of sub carbon nanotubes in a main carbon nanotube, an electron emission source including the same, and an electron emission device including the electron emission source. The present invention also relates to a method of manufacturing the electron emitting device.

According to the present invention, it is possible to provide carbon nanotubes having improved electron emission efficiency and improved lifetime characteristics.

Description

A carbon nanotube, an emitter comprising the carbon nanotube and an electron emission device comprising the emitter}

1 is a schematic cross-sectional view of an electron emitting device having carbon nanotubes according to the present invention on a substrate.

FIG. 2 is a transmission electron microscope (TEM) photograph of a carbon nanotube manufactured according to the present invention, and corresponds to a partially enlarged photograph of FIG. 1.

3 is a schematic cross-sectional view of one embodiment of an electron emitting device according to the present invention.

Figure 4 is a graph showing the current density measurement results of carbon nanotubes according to the present invention and carbon nanotubes according to the prior art.

<Short description of drawing symbols>

200: electron emission element 201: top plate

202: lower plate 110: lower substrate

120: cathode electrode 130: insulator layer

140: gate electrode 160: electron emission source                 

41 ... cathode 42 ... anode

The present invention relates to a carbon nanotube, an electron emission source including the same, and an electron emission device including the electron emission source. More specifically, the carbon nanotube includes a plurality of bucarbon nanotubes inside the main carbon nanotube. The present invention relates to a tube, an electron emission source including the same, and an electron emission device having the electron emission source.

An electron emission device emits electrons from an electron emission source of a cathode electrode by applying a voltage between the anode electrode and the cathode electrode to form an electric field, and impinges the electrons on a fluorescent material on the anode electrode side to emit light. It is a display device.

As an electron emission source of such an electron emitting device, a micro tip made of a metal such as molybdenum has been used in the past, but such a micro tip has a problem that the manufacturing cost increases considerably as the display area becomes large, and also in vacuum As residual gas particles collide with electrons and become ionized and the gas ions collide with the micro tip, damaging the micro tip itself, the micro tip is also destroyed, and the phosphor particles collided by the electrons fall off and contaminate the micro tip. In order to reduce the performance and lifetime of the electron emitting device, there is a problem.                         

Therefore, in recent years, carbon nanotubes have been spotlighted as a carbon-based material having excellent electronic conductivity, which has excellent conductivity and electric field concentration effect, and has a work function. This is because it is low, excellent in field emission characteristics, low voltage driving is easy, and large area is possible.

As described above, in the case of using carbon nanotubes as the electron emission source of the electron emission device, the specific surface area must be wide, and the number of emitters per unit area must be large to increase the electron emission efficiency and improve the lifetime. It becomes possible.

Accordingly, the technical problem to be achieved by the present invention is to have a large specific surface area and to have a large number of emitters per unit area, thereby providing carbon nanotubes having an improved electron emission efficiency and lifetime, and an electron emission source including the same; It is an object to provide an electron emitting device having such an electron emitting source.

In order to achieve the above object of the present invention, the first aspect of the present invention provides a carbon nanotube including a plurality of bucarbon nanotubes in the main carbon nanotube.

According to another aspect of the present invention, a second aspect of the present invention provides an electron emission source including carbon nanotubes including a plurality of bucarbon nanotubes inside a main carbon nanotube.

In order to achieve another object of the present invention, the third aspect of the present invention,

Board;                     

A cathode electrode formed on the substrate; And

The present invention provides an electron emission device including an electron emission source formed to be electrically connected to a cathode electrode formed on the substrate, and including carbon nanotubes including a plurality of sub carbon nanotubes inside the main carbon nanotubes.

In order to achieve another object of the present invention, the fourth aspect of the present invention,

Preparing a composition for forming an electron emission source including a carbon nanotube and a vehicle including a plurality of bucarbon nanotubes in the main carbon nanotube;

Printing the composition for forming an electron emission source on a substrate;

Baking the printed composition for forming an electron emission source; And

It provides a method of manufacturing an electron emitting device comprising the step of activating the fired product to obtain an electron emission source.

By using the carbon nanotubes of the present invention, it is possible to provide an electron emission device having improved electron emission efficiency and lifetime.

Hereinafter, the present invention will be described in detail.

The present invention provides a carbon nanotube including a plurality of bucarbon nanotubes in a main carbon nanotube.

In order to maximize the electron emission efficiency of the carbon nanotubes used as the electron emission source, there is a need to maximize the number of emitters under a limited area. In the present invention, by forming a plurality of bucarbon nanotubes in the main carbon nanotubes different from the existing carbon nanotube structure, it is possible to maximize the number of emitters per area than the existing carbon nanotubes, As a result, we propose a method to maximize the electron emission efficiency.

1 is a schematic cross-sectional view of an electron emitting device having carbon nanotubes according to the present invention on a substrate, and FIG. 2 is a transmission electron microscope (TEM) photograph of a carbon nanotube according to the present invention. As a partial enlarged photograph of FIG. 1 is shown. 1 and 2, the carbon nanotube according to the present invention has a plurality of (3 to 4 in the figure shown) of the carbon nanotubes inside the main carbon nanotubes, and thus, as described above In comparison, the number of emitters per limited area can be maximized.

Preferably, the main carbon nanotubes have a diameter of 10 nm to 1 μm. When the diameter of the main carbon nanotube is less than 10 nm, it is not easy to insert the carbon nanotube catalyst therein, and thus it is not easy to grow bucarbon nanotubes, which is not preferable. If the diameter of the tube exceeds 1 μm, there is a problem in that the number or orientation of the bucarbon nanotubes cannot be easily controlled, which is not preferable.

The diameter of the bucarbon nanotubes is preferably 1 nm to 100 nm. When the diameter of the bucarbon nanotube is less than 1 nm, the durability of the carbon nanotubes themselves may be deteriorated, which may be disadvantageous, and when the diameter of the bucarbon nanotube exceeds 100 nm, Bucarbon nanotubes are not preferred because they are not easy to grow inside the main carbon nanotubes.                     

In addition, since the carbon nanotubes must be grown inside the main carbon nanotubes, the diameter of the main carbon nanotubes should be larger than that of the bucarbon nanotubes.

Preferably, the main carbon nanotubes include 2 to 10 bucarbon nanotubes therein. If the number of bucarbon nanotubes is less than two, it is not preferable that sufficient electron emission efficiency increase effect is not obtained. If the number of bucarbon nanotubes exceeds 10, the field strengthening factor ( Since the field enhancement factor is large, the electric field cannot be effectively applied to the tip of the carbon nanotubes, which is not preferable.

The carbon nanotubes according to the present invention may be synthesized according to various methods including an electric discharge method, a laser deposition method, a gas phase synthesis method, a thermochemical vapor deposition method or a plasma chemical vapor deposition method. One embodiment of the carbon nanotube manufacturing method of the present invention is as follows.

First, it provides a catalyst metal on which carbon nanotubes will be grown. As the catalytic metal, for example, cobalt, nickel, iron, or an alloy thereof can be used. The catalyst metal may be formed on a substrate such as, for example, glass, quartz, silicon, or alumina (Al ₂ O ₃ ) using a thermal evaporation method, an electron beam evaporation method, or a sputtering method to form a film having a thickness of several hundreds of nm. Thereafter, the catalyst metal film is further etched to form nano-sized catalyst metal particles that are separated from each other independently. As the etching gas, ammonia gas, hydrogen gas, or hydride gas may be used. The etching gas etches the catalyst metal film along grain boundaries on the substrate to uniformly and densely form nano-sized catalyst metal particles separated from each other.

Another example of providing a metal catalyst is by using a zeolite support. The method of incorporating the metal catalyst into the zeolite support uses a method such as vacuum injection or ion exchange. As a catalyst providing method using a zeolite support, a Co / Y catalyst, a Co / ZSM-5 catalyst, a Co / Y catalyst, a Fe / Y catalyst and the like can be obtained. The catalyst using the zeolite support may be prepared using, for example, Co- (Fe) acetate solution, and the final Co or Fe content may be about 2.5% by weight.

As described above, after providing the catalyst metal on which the carbon nanotubes are to be grown, carbon nanotubes are grown on the catalyst metal. C _1-3 hydrocarbon gas is used as the carbon feed gas, and specific examples thereof include acetylene, ethylene, ethane, propylene, propane or methane gas. Carbon nanotube growth temperature is typically 700 to 800 ℃. The carbon feed gas may be simultaneously supplied with a carrier gas such as hydrogen gas or argon gas or a diluent gas such as hydride gas to control the growth rate and time of the carbon nanotubes.

The carbon nanotubes according to the present invention may be prepared by refilling the catalyst metal in the main carbon nanotubes prepared as described above and resynthesizing the plurality of bucarbon nanotubes.                     

The carbon nanotube synthesis method of the present invention has been described with reference to the synthesis method as described above, but is not limited thereto.

The carbon nanotubes immediately synthesized as described above contain a large amount of various kinds of impurities, and when these impurities are included in the electron emission source, electron emission characteristics are impaired. Can be done. The purification process includes a variety of methods commonly used in the art, such as ultrasonic cleaning, centrifugation, chemical precipitation, filtering, chromatography, and the like.

In another embodiment, the present invention provides an electron emission source comprising carbon nanotubes including a plurality of bucarbon nanotubes inside a main carbon nanotube.

The electron emission source of the present invention is formed by directly growing the carbon nanotubes on the substrate using a method such as chemical vapor deposition, or by a paste method using a paste composition containing the carbon nanotubes. Can be. Among them, the paste method is advantageous in terms of mass production ease and manufacturing cost.

When forming an electron emission source using the paste method, the electron emission source of the present invention may include at least one of an adhesive component and a firing result of the adhesive component. The adhesive component serves to improve adhesion between the carbon nanotubes and the substrate, and specific examples of the inorganic adhesive component include glass frit, silane, water glass, and the like, and specific examples of the organic adhesive component include ethyl cellulose, nitrocellulose, and the like. The same cellulose resin; Acrylic resins such as polyester acrylate, epoxy acrylate and urethane acrylate; Vinyl-based resins, and the like, and low melting point metals may also be used as the adhesive component.

In another embodiment, the present invention, a substrate; A cathode electrode formed on the substrate; And an electron emission source which is formed to be electrically connected to the cathode electrode formed on the substrate and includes carbon nanotubes including a plurality of sub carbon nanotubes inside the main carbon nanotubes. .

3 is a partial cross-sectional view of an electron emission device according to the present invention, and typically shows an electron emission device having a triode structure.

As shown, the electron emission device 200 includes an upper plate 201 and a lower plate 202, and the upper plate is an upper electrode 190 and an anode electrode 180 disposed on the lower surface 190a of the upper substrate. And a phosphor layer 170 disposed on the bottom surface 180a of the anode electrode.

The lower plate 202 has a lower surface substrate 110 disposed in parallel with the upper substrate 190 at predetermined intervals to have an inner space, and a cathode electrode disposed in a stripe shape on the lower substrate 110 ( 120, a gate electrode 140 arranged in a stripe shape to intersect the cathode electrode 120, an insulator layer 130 disposed between the gate electrode 140 and the cathode electrode 120, and the insulator layer ( 130 and an electron emission source hole 169 formed in a portion of the gate electrode 140 and the electron emission source hole 169 are disposed in the electrical source to the cathode electrode 120 and lower than the gate electrode 140 It is provided with an electron emission source 160 disposed.

The upper plate 201 and the lower plate 202 are maintained in a vacuum at a pressure lower than atmospheric pressure, and the spacer 192 supports the pressure between the upper plate and the lower plate generated by the vacuum and partitions the light emitting space 210. It is disposed between the upper plate and the lower plate.

The anode electrode 180 applies a high voltage necessary for accelerating the electrons emitted from the electron emission source 160 to allow the electrons to collide with the phosphor layer 170 at high speed. The phosphor layer is excited by the electrons and emits visible light while falling from a high energy level to a low energy level. In the case of the color electron emission device, phosphor layers of red light emission, green light emission, and blue light emission are disposed on the lower surface 180a of the anode in each of the light emitting spaces 210 constituting the unit pixel.

The gate electrode 140 serves to facilitate the emission of electrons from the electron emission source 160, and the insulator layer 130 partitions the electron emission source hole 169 and the electrons. It serves to insulate the emission source 160 and the gate electrode 140.

The electron emission source 160 that emits electrons by electric field formation is an electron emission source 160 including carbon nanotubes including a plurality of bucarbon nanotubes inside the main carbon nanotubes.

According to another embodiment of the present invention, there is provided a method of forming a composition for forming an electron emission source including a carbon nanotube and a vehicle including a plurality of bucarbon nanotubes inside a main carbon nanotube; Printing the composition for forming an electron emission source; Calcining the composition for forming an electron emission source; And activating a firing result.

One embodiment of the method of manufacturing an electron emitting device according to the present invention is as follows.

First, a composition for forming an electron emission source is prepared. The composition for forming an electron emission source includes carbon nanotubes and a vehicle.

The carbon nanotubes serve to emit electrons, and as described above, may be carbon nanotubes including a plurality of bucarbon nanotubes inside the main carbon nanotubes. Carbon nanotubes in the composition may be used in an amount of 0.1 to 30% by weight, preferably 5 to 20% by weight.

The vehicle serves to control the viscosity and printability of the composition for forming an electron emission source, which includes a polymer component and an organic solvent component.

Non-limiting examples of polymer components included in the vehicle include cellulosic resins such as ethyl cellulose, nitro cellulose, and the like; Acrylic resins such as polyester acrylate, epoxy acrylate and urethane acrylate; And a vinyl-based resin and the like, the content may be 5 to 60% by weight based on the total paste composition.

Non-limiting examples of organic solvent components included in the vehicle include butyl carbitol acetate (BCA), terpineol (TP), toluene, texanol and butyl carbitol (BC), the content of which is the entire paste composition It may be 40 to 80% by weight relative to.

The composition for forming an electron emission source may include at least one selected from the group consisting of an inorganic adhesive component, an organic adhesive component, and a low melting point metal as an adhesive component that serves to improve adhesion between the carbon nanotubes and the substrate. It may be.

 In addition, the composition for forming an electron emission source may further include a filler, a photosensitive resin, a viscosity improving agent, a resolution improving agent, and the like. Among these, the filler serves to improve the conductivity of the carbon nanotubes not sufficiently adhered to the substrate, and specific examples thereof include Ag, Al, and Pd. The photosensitive resin is used when printing the composition for forming an electron emission source according to the electron emission source formation region, and specific examples thereof include PMMA, TMPTA, methyl acrylic acid, and the like.

In addition, the composition of the present invention may further include a conventional photosensitive monomer and photoinitiator, a photosensitive resin such as polyester acrylate, or a non-photosensitive polymer such as cellulose, acrylate and vinyl, a dispersant, an antifoaming agent, and the like.

The photosensitive monomer is added as a decomposition improving agent of the pattern, and may include a thermally decomposable acrylate monomer, a benzophenone monomer, an acetphenone monomer, or a thioxanthone monomer, and more specifically, an epoxy acrylate and a polyester. Acrylate, 2,4-diethyloxanthone, or 2,2-dimethoxy-2-phenylacetophenone can be used. The content of the photosensitive monomer may be included in 3 to 40% by weight.                     

The type of photoinitiator may be used that is commonly used, the content may be included in 0.05 to 10% by weight.

The viscosity of the composition for forming an electron emission source having the composition as described above is preferably 5,000 to 50,000 cps.

Next, the prepared composition for electron emission source formation is printed on a substrate. The "substrate" is a substrate on which an electron emission source is to be formed, and a substrate commonly used in the art may be used.

The printing method is different depending on the case where the composition for electron emission source formation contains the photosensitive resin and when the photosensitive resin is not included. When the composition for electron emission source formation contains photosensitive resin, a separate photoresist pattern is unnecessary. That is, a composition for forming an electron emission source containing a photosensitive resin is coated on a substrate by printing, and the film is exposed and developed according to a desired electron emission source forming region. On the other hand, when the composition for electron emission source formation does not contain photosensitive resin, the photolithography process using a separate photoresist film pattern is required. That is, a photoresist film pattern is first formed using a photoresist film, and then the composition for forming an electron emission source is supplied by printing using the photoresist film pattern.

Thereafter, the printed composition for forming an electron emission source is fired. Through the firing step, the adhesion between the carbon nanotubes and the substrate may be improved, and durability and the like may be improved by melting and solidifying at least some adhesive components, and outgasing may be minimized. The firing temperature should be determined in consideration of the volatilization of the vehicle and the sinterable temperature and time of the adhesive component included in the composition for forming the electron emission source. Typical firing temperatures are 350 to 500 ° C, preferably 450 ° C. If the firing temperature is less than 400 ℃ may cause a problem that the volatilization such as a vehicle is not sufficiently made, and if the firing temperature exceeds 500 ℃ may cause problems of carbon nanotube damage.

Thereafter, the firing product is activated to obtain an electron emission source. The activation step may include, for example, applying an electron emission source surface treating agent including a polyimide-based polymer that may be cured into a film through a heat treatment process on the firing result, and then heat treating the same, followed by heat treatment. It can be carried out by peeling the formed film. In addition, the activation step may be performed by forming an adhesive portion having an adhesive force on the surface of the roller driven by a predetermined driving source and pressing the surface of the firing resultant at a predetermined pressure. Through this activation step, the carbon nanotubes may be exposed to the electron emission source surface or the vertical alignment of the carbon nanotubes may be controlled.

Hereinafter, preferred examples and comparative examples of the present invention are described. The following examples are only described for the purpose of more clearly expressing the present invention, and the content of the present invention is not limited to the following examples.

Manufacture of Carbon Nanotubes

Example 1.

A carbon nanotube having a diameter of 20 nm was synthesized through an alumina membrane having pores, and again, a catalyst particle was filled into the carbon nanotube using a metal catalyst salt. After removing the alumina membrane through hydrofluoric acid, the carbon nanotubes according to the present invention were prepared by regrowing the carbon nanotubes inside the carbon nanotubes by a conventional chemical vapor deposition method.

Comparative Example 1.

Carbon nanotubes were prepared by conventional chemical vapor deposition.

Preparation of the electron emission source

Example 2.

Electron emission having a viscosity of 25000 cps by mixing carbon nanotubes, glass frit, ethyl cellulose, methyl acrylic acid, and butyl carbitol acetate containing a plurality of bucarbon nanotubes inside the main carbon nanotubes prepared in Example 1 The raw composition was prepared and coated on a substrate, and then irradiated with a parallel exposure machine at an exposure energy of 2000 mJ / cm 2 using a pattern mask. After exposure, the solution was sprayed and developed, and fired at a temperature of 450 to obtain an electron emission source.

Comparative Example 2.

An electron emission source was manufactured according to the same method as Example 2 except for using the carbon nanotubes prepared in Comparative Example 1.

Current density measurement

The current density of the electron emission sources of Example 2 and Comparative Example 2 was measured, and the results are shown in FIG. 4. According to FIG. 4, it can be seen that the current density gradient of the electron emission source according to the present invention is sharper than the current density gradient of the electron emission source according to the comparative example, and thus the electron emission efficiency is excellent.

Fabrication of Electron Emission Devices

A lower surface substrate was prepared, and a plurality of transparent cathode electrodes made of an ITO material were formed on the lower surface substrate in a stripe form. Thereafter, an insulator layer is formed by screen printing a polyimide insulating material to cover the cathode electrode, and a conductor such as silver (Ag), copper (Cu), aluminum (Al), etc. having excellent conductivity is formed on an upper surface of the insulator layer. The paste was screen printed to form a gate electrode. Thereafter, the gate electrode and the insulator layer were etched to form an electron emission source hole to expose the surface of the cathode electrode, and the gate electrode was patterned by a photolithography process to form a stripe shape to cross the cathode electrodes.

Next, an electron emission source is formed by applying an electron emission source forming paste including carbon nanotubes and vehicles including a plurality of subcarbon nanotubes inside the main carbon nanotubes in the electron emission source holes, and then firing And an electron emission device was manufactured through an activation step.

According to the present invention, it is possible to provide a carbon nanotube, an electron emission source including the same, and an electron emission device including the electron emission source having an improved electron emission efficiency and improved lifetime characteristics.

Claims (9)

Carbon nanotubes comprising a plurality of bucarbon nanotubes in the main carbon nanotubes. The carbon nanotubes of claim 1, wherein the main carbon nanotubes have a diameter of 10 nm to 1 µm. The carbon nanotubes of claim 1, wherein the diameter of the bucarbon nanotubes is 1 nm to 100 nm. The carbon nanotubes of claim 1, wherein a diameter of the main carbon nanotubes is larger than a diameter of the bucarbon nanotubes. The carbon nanotubes of claim 1, wherein the carbon nanotubes are manufactured by a method selected from the group consisting of an electric discharge method, a laser deposition method, a gas phase synthesis method, a thermochemical vapor deposition method, and a plasma chemical vapor deposition method. An electron emission source comprising a carbon nanotube having a branched structure comprising a plurality of bucarbon nanotubes formed at one end of the main carbon nanotube. The electron emission source according to claim 6, wherein the electron emission source is formed by directly growing the carbon nanotubes on a substrate or by a paste method using a paste composition containing the carbon nanotubes. Board; A cathode electrode formed on the substrate; And An electron emission element formed to be electrically connected to a cathode electrode formed on the substrate, and having an electron emission source including carbon nanotubes including a plurality of bucarbon nanotubes inside the main carbon nanotubes; . Preparing a composition for forming an electron emission source including a carbon nanotube and a vehicle including a plurality of bucarbon nanotubes in the main carbon nanotube; Printing the composition for forming an electron emission source on a substrate; Baking the printed composition for forming an electron emission source; And Activating the fired product to obtain an electron emission source.

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