KR20090026422A - Composition for electron emitter and electron emitter - Google Patents

Abstract

Composition for electron emitter and an electron emitter using the same are provided to improve the field emission performance by coating the carbon nanotube with the titanium oxide film. A carbon nanotube is included about the whole composition to 1.5 through 10 weight percent. The copolymer resin is included about the whole composition to 5 through 25 weight percent. The photo polymerization initiator is included about the whole composition to 1 through 5 weight percent. The photo monomer is included about the whole composition to 5 through 10 weight percent. The inorganic system binder is included about the whole composition to 1 through 5 weight percent.

Description

Composition for forming field emission device and field emission device using same. {Composition for electron emitter and electron emitter}

The present invention relates to a composition for forming a field emission device and a field emission device manufactured using the same, and particularly to a composition for forming a field emission device comprising a carbon nanotube coated with titanium oxide film and a field emission device manufactured using the same. It is about.

In general, a field emission device emits electrons from an emitter, which is a field emission material formed on a cathode electrode, by using a quantum mechanical tunneling effect, and the emitted electrons collide with a fluorescent film attached to the anode electrode to emit a desired image. It is an element to make. Among these field emission devices, the spin type of the emitter tip emits electrons at the tip of the emitter tip when a positive voltage is applied from the external gate electrode to the cone-shaped emitter tip of molybdenum or silicon. The display panel may collide with the anode to serve as a display device. However, the spin type emitter is difficult to form the electrode in a fine pattern, the operation voltage is very high and there is a problem that the performance is deteriorated due to deterioration of the tip.

In order to improve the problems of the field emission device using the silicon tip, a field emission device using carbon nanotubes, which are chemically and mechanically strong and has excellent field emission characteristics, has been proposed. Field emission devices using carbon nanotubes have attempted to form photosensitive paste compositions and develop them with a developing solution or electrophoresis in order to form carbon nanotubes in the form of particles in the form of cathodes with fine patterns.

However, there is a problem that the contact between the carbon nanotubes and the electrode is not made completely, so that the contact resistance increases or the polymer material remaining after the emitter is formed prevents the emission of the carbon nanotubes. In addition, binders, dispersants, and photosensitizers included in the paste evaporate when the emitter emits current, resulting in poor vacuum, which shortens the lifespan of the field emission device. There is a problem that falls to less than 30,000 hours.

On the other hand, the field emission device using a carbon nanotube is generally formed in a triode structure. The field emission device of the triode structure has an anode substrate and a cathode substrate. An anode electrode is formed on the anode substrate. The cathode substrate is disposed facing the anode substrate. The cathode electrode and the insulating layer are formed on the cathode substrate, and the gate electrode is formed on the insulating layer. An emitter made of carbon nanotubes is formed on the cathode. As such, the cathode substrate has a structure having an insulating layer and a gate electrode in addition to the cathode electrode and the emitter. For this purpose, the cathode substrate is subjected to processes such as deposition, photoresist coating, exposure, development, etching, and photoresist removal. Carbon nanotube emitter electrode is formed on the substrate in the last step, and is produced by firing at a high temperature of 400 ℃ or more.

However, during the manufacturing process of the carbon nanotube emitter, the dispersion state of the carbon nanotubes is uneven, so that uneven field emission occurs between the devices, and the amount of carbon nanotubes exposed on the surface is small so that sufficient current density cannot be obtained. do. Therefore, there is a problem in that the number of emitters needs to be increased by increasing the content of expensive carbon nanotubes.

The present invention has been made to solve the above-described problems, an object of the present invention is to provide a field emission device that the carbon nanotube emitter is evenly distributed to improve the field emission characteristics, the life of the emitter is improved. Another object of the present invention is to provide a composition for forming a field emission device for manufacturing a field emission device having improved field emission characteristics and an improved lifetime of the emitter.

In order to achieve the above object, the composition for forming a field emission device according to the present invention is a carbon nanotube coated with a titanium oxide film (TiO _X ), an acrylic copolymer resin, a photopolymerization initiator, a photopolymerization monomer, an inorganic binder, It is characterized by containing an organic solvent.

In order to achieve another object of the present invention, the field emission device according to the invention is characterized in that it is produced using the composition for forming a field emission device.

According to the present invention of the above configuration, by coating the carbon nanotubes with a titanium oxide film, the field emission performance is improved, and further the life of the field emission device is improved.

Hereinafter, a composition for forming a field emission device and a field emission device manufactured using the same according to a preferred embodiment of the present invention.

The composition for forming a field emission device of the present invention includes a carbon nanotube coated with a titanium oxide film, an acrylic copolymer resin, a photopolymerization initiator, a photopolymerization monomer, an inorganic binder, a conductive metal powder, and an organic solvent.

Carbon nanotubes use either single-walled or double-walled carbon nanotubes, which are known to have excellent field emission characteristics, and multi-walled carbon nanotubes having a thickness of 3 to 20 nm. When the content of carbon nanotubes in the composition for forming a field emission device is less than 1% by weight, the current density of the field emission device may be lowered. When it exceeds 10% by weight, the field emission device may be formed due to the high surface area of the carbon nanotubes. The print workability of the composition is poor. Therefore, the carbon nanotubes are preferably contained in 1 to 10% by weight based on the composition for forming a field emission device. In addition, the carbon nanotubes used in the present invention are coated with a titanium oxide film, the process of coating the titanium oxide film on the carbon nanotubes will be described later.

The acrylic copolymer resin uses a copolymer resin of glycidyl (meth) acrylate and (meth) acrylic acid, but glycidyl methacrylate, epoxy acrylate, urethane acrylate and the like can be used. On the other hand, in addition to the acrylic resin dissolved in the aqueous alkali solution, hydroxylpropyl cellulose having a dissolving power in water can be mixed and used in a 1/5 to 1/10 weight ratio of the acrylic resin. When the content of the acrylic copolymer resin exceeds 25% by weight, the carbon nanotubes are not sufficiently exposed to the surface or the contact resistance is high, and the field emission characteristics are deteriorated by the residual resin component after firing. When the content of the acrylic copolymer resin is 5% by weight or less, sufficient developability may not be obtained at the time of pattern formation. Therefore, the acrylic copolymer resin is preferably contained in 5 to 25% by weight relative to the composition for forming a field emission device.

As the photopolymerization monomer, trimethylolpropane triacrylate, trimethylolpropane ethoxy triacrylate, pentaerythritol triacrylate, dipentaerythritol hexaacrylate (Dipentaerythritol Hexa) Acrylate) and the like may be used a compound having two or more double bonds, preferably two or more monomers are used in combination. When the content of the photopolymerization monomer is more than 10% by weight, the pattern hardening during development is severe due to the high degree of curing, and the straightness of the pattern is deteriorated.When the content is less than 5% by weight, normal pattern implementation is difficult due to the low sensitivity and the degree of curing. The straightness of the pattern is also worsened. Therefore, the photopolymerization monomer is preferably contained in 5 to 10% by weight based on the composition for forming a field emission device.

As a photoinitiator, a benzophenone series, an acetphenone series, or a thioxanthone type compound can be used. When the content of the photopolymerization initiator is less than 1% by weight, sufficient polymerization does not occur at the time of exposure, and when the content is more than 5% by weight, the reaction occurs at the time of exposure so that an appropriate pattern may not be obtained during development. Therefore, the photopolymerization initiator is preferably contained in 1 to 5% by weight based on the composition for forming a field emission device.

Inorganic binders include lead borosilicate, borosilicate bismuth frit, B ₂ O ₃ ㆍ SiO ₂ ㆍ MO and B ₂ O ₃ ㆍ SiO ₂ ㆍ M'O (where M is a divalent metal ion and M 'is a monovalent metal) Ions) can be used. If the content of the inorganic binder is less than 1% by weight, there is a problem in that the adhesion between the substrate and the electrode is weakened after sintering, and the electrode is separated. Therefore, the inorganic binder is preferably contained in 1 to 5% by weight based on the composition for forming a field emission device.

The conductive metal powder may be silver, copper, indium-tin oxide (ITO) powder, etc., having excellent conductivity, so as to smoothly supply a current to the carbon nanotube emitter. Use particles. If the content of the conductive metal powder is less than 1% by weight, a smooth current supply effect may not be obtained. If the content is more than 30% by weight, the carbon nanotubes may be prevented from being present on the surface to reduce the current density. Therefore, the conductive metal powder is preferably contained in 1 to 30% by weight based on the composition for forming a field emission device.

Organic solvents include terpineol (TP: terpineol), texanol, carbitol acetate (CA), butyl carbitol acetate (BCA), benzil alcohol, phenoxyethanol It is preferable to use a solvent having a high boiling point such as (Phenoxyethanol). The content of the organic solvent is not particularly limited, but is preferably contained in 15 to 80% by weight based on the composition for forming a field emission device.

Hereinafter, a composition for forming a field emission device and a method of manufacturing the field emission device of the present invention will be described.

First, carbon nanotubes coated with titanium oxide film and organic solvents are mixed, and the carbon nanotubes are first dispersed using an ultrasonic generator having a power of 1 Kw or more, and then the mixed solution is flowed into a fine tube at high pressure and high speed. Disperse once more using shear force. In this case, in order to improve the field emission characteristics of the carbon nanotubes, the surface of the carbon nanotubes coated with the titanium oxide film may be coated with a material that does not dissolve in an organic solvent. For example, after dissolving sucrose insoluble in organic solvents in water, the carbon nanotubes may be mixed, followed by performing the aforementioned dispersion process and drying.

Thereafter, an acrylic copolymer resin, a photopolymerization monomer, a photopolymerization initiator, an inorganic binder, and a conductive metal powder are added to the organic solvent in which the carbon nanotubes are dispersed, mixed, and then premixed with a mixer such as a planetary mixer. And adjusting the distance between rolls of a 3-roll mill and passing two or more times, preferably five or more times, to evenly disperse the carbon nanotubes, the photopolymerization initiator, the inorganic binder, and the conductive metal powder. A composition for forming an emission device is prepared.

The composition for forming the field emission device thus prepared was printed on the surface of the substrate using a screen printing machine equipped with a screen mask such as SUS 325 mesh or SUS 400 mesh, and the substrate was then heated at 80 ° C. in a convection oven. The organic solvent is evaporated to dryness. The substrate is then exposed using a mask of the designed pattern. In this case, the exposure energy is preferably 200 to 1000 mJ / cm 2, and is adjusted according to the desired film thickness. Then, 0.1 wt% to 2 wt% of sodium carbonate solution is sprayed and developed on the exposed film, and washed with pure water. Ultrasonic cleaners can be used to effectively remove residues during cleaning. Thereafter, the developing film is fired at a temperature of 400 to 500 ° C. for 20 to 40 minutes in air or nitrogen to manufacture a field emission device. In this case, when the firing temperature is 400 ℃ or less, there is a problem that the organic material is not removed and the field emission characteristics are deteriorated or the inorganic binder that imparts adhesion to the substrate is not melted, so that film removal may occur. There is a problem that the field emission characteristics are degraded due to oxidation or thermal decomposition.

Hereinafter will be described in more detail through embodiments of the present invention. However, the following examples are for the purpose of more clearly expressing the present invention, and the contents of the present invention are not limited to the following examples.

Table 1 below summarizes the contents of the comparative example and the substances included in each example. Then, for each of the comparative examples and examples to prepare a composition for forming a field emission device through the following process, to produce a field emission device using this, and carried out a life test for the produced field emission device.

Comparative example Example 1 Example 2 Example 3 Carbon nanotubes 2% 0% 0% 0% TiO _X 30 wt% coated carbon nanotubes  0%  2.85%  0%  0% TiO _X 46 wt% Coated Carbon Nanotubes  0%  0%  3.7%  0% TiO _X 61 wt% Coated Carbon Nanotubes  0%  0%  0%  5.13% Texanol 20% 20% 20% 20% Elbasite 10% 10% 10% 10% Terpinol 20% 20% 20% 20% Trimethylolpropaneethoxytriacrylate  2%  2%  2%  2% Trimethylolpropanetriacrylate  2%  2%  2%  2% Irgacure 369 1.5% 1.5% 1.5% 1.5% Darocur ITX 1.5% 1.5% 1.5% 1.5% Inorganic binder One% One% One% One% Silver (Ag) 20% 19.15% 18.3% 16.87% Texanol 10% 10% 10% 10% Terpinol 10% 10% 10% 10% system 100% 100% 100% 100%

Comparative Example

2% by weight of carbon nanotubes and 20% by weight of texanol were mixed and predispersed by applying a 3 kW ultrasonic wave, followed by a pressure of 18000 psig into a disperser (Microfluidizer Inc., USA) using a 100 μm diameter tube. Pass it through once to disperse the carbon nanotubes. Then, 10% by weight of commercially available Elvasite was dissolved in 20% by weight of terpinol, and added to a mixed solution in which carbon nanotubes were dispersed, followed by stirring with 2% by weight of trimethylropropaneethoxytriacrylate as a photopolymerization monomer and trimethyl. 2% by weight of propanetriacrylate, 1% by weight of Irgacure 369 (Ciba Chemicals) and 1% by weight of Darocur ITX (Ciba Chemicals), 2% by weight of inorganic binder, 20% by weight of silver (Ag) powder 10 wt% of Texanol and 10 wt% of Terpinol were added and stirred for 30 minutes. Thereafter, the mixture is passed through a three-roll mill five or more times to prepare a composition for forming a field emission device. Then, as described above, the field emission device was manufactured through the printing, drying, exposure, development, and cleaning processes using the composition for forming the field emission device.

<Example 1>, <Example 2>, and <Example 3> are the same methods as those of <Comparative Example> described above while changing the content of the composition contained in the composition for forming the field emission device according to <Table 1>. Was carried out.

In addition, the carbon nanotubes coated with the titanium oxide film used in Examples 1, 2, and 3 are manufactured by the following process. At this time, according to Examples 1, 2, 3 was prepared while changing the content of titanium coated on the carbon nanotubes.

1. Make an aqueous solution of titanium chloride (TiC13), and add carbon nanotube powder to this solution. Thereafter, ultrasonic treatment and stirring are performed for 10 minutes for uniform dispersion.

2. Sodium borohydride (NaBH ₄ ) used as a reducing agent was prepared such that the molar ratio of NaBH ₄ / TiCl ₃ was 10.

3. The reactants were continuously stirred while slowly adding an aqueous sodium borohydride solution to an aqueous titanium chloride solution in which carbon nanotube powder was dispersed, and quenched to room temperature after the reaction.

4. The carbon nanotube coated with the titanium oxide film (TiO ₂ ) prepared through the above process is sonicated for 10 minutes, and then removed from room temperature to remove by-products such as sodium chloride (NaCl) and boron hydroxide (B (OH) ₃ ). Dispersed in distilled water at 80 ℃, and washed twice using a filter paper having a pore size of 0.2㎛, and recovered the carbon nanotube powder coated with titanium oxide film (TiO ₂ ) through lyophilization.

5. The recovered carbon nanotube powder was heat treated as follows to improve the crystallinity of the titanium oxide film (TiO ₂ ). A carbon nanotube coated with titanium oxide is placed in an alumina tube furnace, and air is removed by flowing 2% hydrogen gas at a flow rate of 50 ml / min for 30 minutes, and 5 ° C / min under the same gas atmosphere. The temperature was raised to 600 ° C. at a heating rate of 2 ° C., and the temperature was raised to 700 ° C. at a temperature rising rate of 2 ° C./min, followed by heat treatment at 700 ° C. for 2 hours. Thereafter, the carbon nanotubes were naturally cooled in the tubular furnace to prepare carbon nanotubes coated with titanium oxide.

Hereinafter, the carbon nanotubes manufactured through the above process will be identified through the accompanying drawings, and the effects of the field emission devices manufactured using the same will be confirmed.

1 is a scanning electron micrograph of a carbon nanotube coated with a titanium oxide film, Figure 2a is a transmission electron micrograph of a carbon nanotube coated with a titanium oxide film, Figure 2b is an enlarged view of Figure 2a, Figure 3a It is a graph which shows the field emission quantity of the field emission element produced by the <comparative example>, and FIG. 3B is a graph which shows the field emission amount of the field emission element produced by <Examples 1,2,3>.

1 to 2B, it can be seen that the titanium oxide film is evenly coated on the surface of the carbon nanotubes.

In addition, as shown in FIGS. 3A and 3B, in the case of the carbon nanotubes not coated with the titanium oxide film, the field emission amount drops to 50% of the initial field emission amount within several hours. On the other hand, in the case of carbon nanotubes coated with titanium oxide film, there is a slight difference depending on the content of the coated titanium oxide film, but it takes 10 to 22 hours for the field emission amount to drop to 50% of the initial field emission amount. You can check. Therefore, it can be seen that the lifespan of the field emission device is extended, and through additional calculations, when the field emission device made of carbon nanotubes coated with titanium oxide is mounted on an actual panel, the lifespan of the field emission device can be over 30000 hours. It can be seen that.

1 is a scanning electron micrograph of a carbon nanotube coated with a titanium oxide film.

2A is a transmission electron microscope photograph of a carbon nanotube coated with a titanium oxide film.

FIG. 2B is an enlarged photograph of FIG. 2A.

3A is a graph showing the field emission amount of the field emission device manufactured by Comparative Example.

3B is a graph showing the amount of field emission of the field emission device fabricated in <Examples 1,2,3>.

<Description of the symbols for the main parts of the drawings>

Field emission amount of the field emission device made of carbon nanotubes coated with A1 ... titanium oxide film at 30% of the total weight

Field emission amount of field emission device made of carbon nanotubes coated with A2 ... titanium oxide film at 46% of total weight

Field emission amount of the field emission device made of carbon nanotubes coated with A3 ... titanium oxide film at 61% of the total weight

Claims (4)

A composition for forming a field emission device, comprising carbon nanotubes coated with a titanium oxide film (TiO _X ), an acrylic copolymer resin, a photopolymerization initiator, a photopolymerization monomer, an inorganic binder, and an organic solvent. The method of claim 1, The carbon nanotubes are included in 1.5 to 10 weight percent of the total composition, The copolymer resin is included in 5 to 25 weight percent of the total composition, The photopolymerization initiator is included in 1 to 5% by weight based on the total composition, The photopolymerization monomer is included in 5 to 10 weight percent of the total composition, The inorganic binder is a composition for forming a field emission device, characterized in that contained in 1 to 5% by weight relative to the total composition. The method of claim 1, The composition for forming a field emission device further includes a conductive metal powder, The conductive powder is a composition for forming a field emission device, characterized in that contained in 1 to 30% by weight relative to the total composition. The field emission device manufactured using the composition for forming a field emission device according to any one of claims 1 to 3.

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