KR20030038044A - A carbon nanotube emitter composition for field emision device and preparation method of the same - Google Patents

Abstract

PURPOSE: Composition material for forming carbon nano-tube emitter of a field emission device and a manufacturing method thereof are provided to manufacture a field emission device having favorable display quality due to large emission site and even brightness. CONSTITUTION: Composition material for forming carbon nano-tube emitter of a field emission device comprises carbon nano-tube, organic binder resin, glass frit and organic solvent. It is preferable that content ratio of the carbon nano-tube with respect to the composition material may be weight percent of 15 to 50. Moreover, the carbon nano-tube may be annealed at temperature of 300 to 2000°C under vacuum atmosphere during 10 minutes to 100 hours. Content ratio of the organic binder resin with respect to the composition material may be weight percent of 5 to 15. The organic solvent may be selected from one solvent of butyl carbitol acetate(BCA), terpineol(TP) and butyl carbitol(BC). Further, the organic solvent may be composite solvent of butyl carbitol acetate and terpineol.

Description

A composition for forming a carbon nanotube emitter of a field emission device and a method of manufacturing the same {A CARBON NANOTUBE EMITTER COMPOSITION FOR FIELD EMISION DEVICE AND PREPARATION METHOD OF THE SAME}

[Industrial use]

The present invention relates to a composition for forming carbon nanotube emitters of field emission devices and a method of manufacturing the same. More specifically, the present invention relates to carbon nanotube emitters of field emission devices having high emission sites and high quality and uniform luminescence. It relates to a composition for forming a site and a manufacturing method thereof.

[Prior art]

In general, a field emission device forms a strong electric field in an emitter, which emits electrons, and emits cold electrons by a tunneling effect, and the emitted electrons move in a vacuum to collide with a fluorescent film formed on the anode electrode. It is a display element that implements a predetermined image by emitting a phosphor.

The field emission display device can save energy compared to a device (thermal electron emission source) using heat energy and can prolong life. Such a field emission display device uses a spin't type field emission array made mainly of a metal such as molybdenum (Mo) or a semiconductor material such as silicon (Si). It uses the principle of emitting electrons by applying an electric field to the micro tip using a gate electrode.

However, the metal or semiconductor material used as the micro tip of the field emission display device has a problem that the voltage applied to the gate electrode must be high due to a large work function. In addition, since the residual gas particles in the vacuum collide with the electrons and ionize, and the gas ions collide with the micro tip to damage the micro tip, the micro tip may be destroyed. Because of the contamination, there is a problem in that the performance and lifespan of the field emission display device are reduced.

In order to improve this, a method of forming a thick film using carbon nanotubes as an electron emission source has been used. Carbon nanotubes have a low electron emission field, excellent chemical stability, and mechanically strong properties. Therefore, carbon nanotubes are expected to replace conventional metals or semiconductor materials as electron emission sources.

The thick carbon nanotube emitter is prepared by preparing a paste including carbon nanotube powder, an organic binder resin, and a solvent, by screen printing on an electrode, and then firing at a high temperature of 400 ° C. or higher under an air atmosphere. However, in general, carbon-based materials are very unstable at high temperatures of 400 ° C. or higher in an oxygen-containing air atmosphere, and a large amount of carbon nanotubes are lost during firing. There was this.

As a method for solving this problem, a method of heat treatment at less than 400 ° C. has been proposed, but at this temperature, the paste composition cannot be sintered, thereby lowering the adhesive strength, and the binder resin resin components are not removed, which may adversely affect the degree of vacuum.

In addition, in manufacturing a carbon nanotube field emission display device using a thick film method, a method of adding a fine metal powder was used to increase the adhesion properties and conductivity of the thick film. However, when the thick film surface is covered with the fine metal powder, there is a problem that the field emission characteristics of the device is reduced.

As a method for solving the above various problems, Korean Patent Application No. 2000-28656 discloses a method of treating the surface of a carbon nanotube thick film by mechanical polishing. Through mechanical polishing, fine metals on the surface of the carbon nanotubes are removed to obtain uniform light emission over the entire surface even in a low electric field. However, in the case of the triode structure having the insulating layer and the gate electrode layer on the carbon nanotube, the surface treatment by mechanical polishing as described above is not easy, and in the case of the highly integrated device having the small line width and the line distance, It is difficult to obtain a large area of uniform electron emission due to a short, and it is difficult to obtain high density because screen printing is performed in a patterned form.

As another method, Korean Patent Application No. 2000-57116 describes a method of protruding carbon nanotubes to the surface during the development process using a photosensitive resin, but the stability of the photosensitive material against field emission should be ensured. Stabilization time is required.

The present invention is to solve the above-described problems, an object of the present invention is to provide a composition for forming carbon nanotube emitters for producing a field emission device having a high quality, uniform luminescence with many emission sites will be.

Another object of the present invention is to provide a method for preparing the composition for forming carbon nanotube emitters.

It is still another object of the present invention to provide a field emission device having high emission sites and high quality and uniform luminance.

1A to 1B are field emission image photographs when an electric field of 1,2 kV is applied to a thick carbon nanotube thick film according to Example 1 and Comparative Example 1. FIG.

2a to 2b are SEM images of the carbon nanotube field emission device thick film according to Example 1 and Comparative Example 1.

3A to 3B are photographs showing field emission images of a 4.5 ″ panel when an electric field is applied to the carbon nanotube field emission devices according to Example 1 and Comparative Example 1. FIG.

Figure 4 is a photograph showing the printing line of the carbon nanotubes of Example 5.

5 is an optical micrograph showing the printing line of the carbon nanotubes of Example 5.

6 is a field emission image photograph of the field emission device including the carbon nanotubes of Example 5. FIG.

In order to achieve the above object, the present invention comprises a carbon nanotube, an organic binder resin, glass frit and an organic solvent, the content of the carbon nanotube is 15 to 50% by weight of the carbon nanotube of the field emission device relative to the composition Provided is a composition for forming an emitter.

The present invention also comprises the steps of (a) mixing the organic binder resin and the organic solvent; (b) mixing the carbon nanotube powder and the glass frit; And (c) mixing the mixture of step (a) and the mixture of step (b) to prepare a composition in paste form, wherein the content of the carbon nanotube powder is from 15 to 50 with respect to the composition. Provided is a method for producing a composition for forming carbon nanotube emitters of a field emission device in weight%.

The present invention also provides a field emission device comprising a carbon nanotube emitter formed by extruding the composition for forming a carbon nanotube emitter.

Hereinafter, the present invention will be described in more detail.

The composition for forming a carbon nanotube emitter used for preparing a field emission device including the carbon nanotube emitter of the present invention includes carbon nanotubes, an organic binder resin, a glass frit, and an organic solvent, and the content of the carbon nanotubes. It is 15 to 50% by weight based on the silver composition.

In order to provide sufficient emission sites for the field emission device, the present invention allows the content of carbon nanotubes to be 15 to 50% by weight based on the total composition for forming carbon nanotube emitters. If the content of the carbon nanotubes mixed in the composition is less than 15% by weight, it is impossible to provide sufficient emission sites for the field emission device. If the content of the carbon nanotubes exceeds 50% by weight, the viscosity of the composition may be too high. Sex is worse.

Organic binder resins contained in the composition for forming carbon nanotube emitters of the present invention include ethyl cellulose, nitro cellulose, and acrylic resins. In addition, the content of the organic binder resin to be added is preferably 5 to 15% by weight based on the composition. When the content of the organic binder resin is less than 5% by weight, the viscosity of the composition is lowered, so that printability, flowability, etc. are poor, and pattern formation is difficult. When the content of the organic binder resin is more than 15% by weight, the viscosity of the composition is too high. There is a problem that it is difficult to increase the content of carbon nanotubes.

The composition for forming carbon nanotube emitters of the present invention is prepared by adding a glass frit and an organic solvent to the carbon nanotubes and the organic binder resin.

As the content of carbon nanotubes increases, the viscosity decreases the printability. However, if the boiling point is around 200 ° C. and an organic solvent capable of dissolving the organic binder resin such as ethyl cellulose, nitro cellulose, acrylic resin, etc. is added, the viscosity of the composition does not increase even if the content of carbon nanotubes is increased. The sex does not worsen. As the organic solvent, when at least one organic solvent selected from the group consisting of butyl carbitol acetate (BCA), terpineol (TP), and butyl carbitol (BC) is added, the organic solvent dissolves the binder resin to form carbon. The viscosity of the composition for forming a nanotube emitter can be lowered, and thus the viscosity of the composition for forming a carbon nanotube emitter does not increase even if the carbon nanotube is further added as much as the content corresponding to the dissolved binder resin. Therefore, the content of the carbon nanotubes added to increase the number of emission sites, it is possible to manufacture a field emission device having a high quality and uniform luminescence.

When using the said organic solvent, it is preferable to mix and use two or more types. In addition, it is more preferable to use an organic solvent in which butyl carbitol acetate (BCA) and terpineol (TP) are mixed in the organic solvent. At this time, the mixing volume ratio of the mixed organic solvent of butyl carbitol acetate (BCA) and terpineol (TP) is preferably 5: 5 to 6: 4.

The viscosity of the carbon nanotube emitter forming composition is preferably 30,000cp to 100,000cp. If the viscosity of the composition for forming carbon nanotube emitters is less than 30,000 cps, the pattern spreads and is not clear. If the viscosity of the composition for forming carbon nanotube emitters exceeds 100,000 cps, printability is deteriorated.

When the carbon nanotubes used in the composition for forming carbon nanotube emitters of the present invention are prepared by heat treatment in advance in a vacuum atmosphere, the composition for forming carbon nanotube emitters with improved thermal stability can be prepared.

When the carbon nanotubes are heat-treated in a vacuum atmosphere, incomplete parts are crystallized and amorphous carbons around the carbon nanotubes are crystallized into graphite to form a carbon nanotube protective layer, thereby increasing thermal stability.

The carbon nanotubes are preferably heat-treated at 300 ℃ to 2000 ℃. If the heat treatment temperature is less than 300 ℃ there is a problem that the amorphous carbon is not crystallized.

In addition, the carbon nanotubes are preferably heat-treated for 10 minutes to 100 hours. If the heat treatment time exceeds 100 hours, there is a problem that the productivity is lowered, and if the heat treatment time is less than 10 minutes, there is a problem that the amorphous carbon is not crystallized.

As described above, the carbon nanotubes heat-treated at high temperatures may crystallize amorphous carbons that easily react with oxygen, thereby increasing thermal properties of the carbon powder even in an air atmosphere. As a result, a considerable amount of carbon materials remain after the thermal firing to increase the emission site, and the emission current increases by about 400 times, resulting in stable light emission at high voltage.

The present invention also comprises the steps of (a) mixing the organic binder resin and the organic solvent; (b) mixing the carbon nanotube powder and the glass frit; And (c) mixing the mixture of step (a) and the mixture of step (b) to prepare a composition in paste form, wherein the content of the carbon nanotube powder is from 15 to 50 with respect to the composition. Provided is a method for producing a composition for forming carbon nanotube emitters of a field emission device in weight%.

First, an organic binder resin and an organic solvent are mixed (step (a)).

The organic binder resin may be ethyl cellulose, nitro cellulose, acrylic resin, or the like. In addition, the content of the organic binder resin to be added is preferably 5 to 15% by weight based on the composition. When the content of the organic binder resin is less than 5% by weight, the viscosity of the composition is lowered, so that printability, flowability, etc. are poor, and pattern formation is difficult. When the content of the organic binder resin is more than 15% by weight, the viscosity of the composition is too high. There is a problem that it is difficult to increase the content of carbon nanotubes.

In addition, the organic solvent is preferably at least one organic solvent selected from the group consisting of butyl carbitol acetate (BCA), terpineol (TP) and butyl carbitol (BC). It is more preferable to mix and use two or more types of said organic solvents. In addition, it is more preferable to use a mixed organic solvent of butyl carbitol acetate (BCA) and terpineol (TP) in the organic solvent. At this time, the mixing volume ratio of the mixed organic solvent of butyl carbitol acetate (BCA) and terpineol (TP) is preferably 5: 5 to 6: 4.

The viscosity of the mixture of the organic binder resin and the organic solvent is preferably 1,000 cps to 20,000 cps. If the viscosity of the mixture is less than 1,000cp, there is a problem that the viscosity of the mixture is too low to function properly as a binder for binding the carbon nanotubes, and if the viscosity of the mixture exceeds 20,000cp, the content of the carbon nanobube powder added should be limited. There is a problem.

In a second step, carbon nanotube powder and glass frit are mixed (step (b)). As a mixing method, mix using a ball mill or a commonly used mixer.

The carbon nanotube powder may be prepared by heat treatment in advance in a vacuum atmosphere to prepare a composition for forming carbon nanotube emitters having improved thermal stability.

When the carbon nanotubes are heat-treated in a vacuum atmosphere, incomplete parts are crystallized and amorphous carbons around the carbon nanotubes are crystallized into graphite to form a carbon nanotube protective layer, thereby increasing thermal stability.

The carbon nanotubes are preferably heat-treated at 300 ℃ to 2000 ℃. If the heat treatment temperature is less than 300 ℃ there is a problem that the amorphous carbon is not crystallized.

In addition, the carbon nanotubes are preferably heat-treated for 10 minutes to 100 hours. If the heat treatment time exceeds 100 hours, there is a problem that the productivity is lowered, and if the heat treatment time is less than 10 minutes, there is a problem that the amorphous carbon is not crystallized.

As described above, the carbon nanotubes heat-treated at high temperatures may crystallize amorphous carbons that easily react with oxygen, thereby increasing thermal properties of the carbon powder even in an air atmosphere. As a result, a considerable amount of carbon material remains after the thermal firing, and the emission site increases, and the emission current increases by about 400 times, resulting in stable light emission at high voltage.

After the carbon nanotube powder and the glass frit are mixed, the carbon nanotube emitter of the field emission device is prepared by mixing the mixture of step (a) and the mixture of step (b) to prepare a composition in paste form. To prepare a composition for formation (step (c)).

The viscosity of the carbon nanotube emitter forming composition is preferably 30,000cp to 100,000cp. If the viscosity of the composition for forming carbon nanotube emitters is less than 30,000 cps, the pattern spreads and is not clear. If the viscosity of the composition for forming carbon nanotube emitters exceeds 100,000 cps, printability is deteriorated.

The present invention also provides a carbon nanotube field emission device formed by extruding the carbon nanotube emitter forming composition.

The carbon nanotube emitter forming composition of the present invention in a paste state is coated on a negative electrode plate to form a carbon nanotube thick film, and the carbon nanotube thick film is heat-treated to prepare a carbon nanotube emitter.

The coating process may be carried out using spin coating, screen printing, roll coating or the like.

In order to sinter the paste composition of the carbon nanotubes, a high temperature baking heat treatment process is performed. When manufacturing a carbon nanotube thick film type negative electrode, a heat treatment process is necessary to minimize the increase in adhesion between the carbon nanotubes and the negative electrode and outgassing and to remove the organic binder resin component.

The high temperature baking heat treatment conditions are determined in consideration of the temperature at which the resin component included in the paste composition can evaporate and the glass frit components can be sintered.

When the firing temperature is 0 to 200 ° C., the resin may evaporate, but the glass frit component is not sintered, thereby lowering the adhesive strength to the thick film, and the organic binder resin component remains, which may adversely affect the degree of vacuum. When the firing temperature is 200 to 400 ° C., the organic binder resin burns out, and the glass frit component is not sufficiently sintered, thereby lowering the adhesive strength with the thick film. However, when the firing temperature is 400 ° C. to 600 ° C. or higher, the glass frit is sintered with fluidity, which is preferable because the adhesion to the thick film is improved. If the heat treatment temperature exceeds 600 ℃ there is a problem that the carbon nanotubes are lost in combination with oxygen.

Carbon nanotubes, except when the purity of the powder is very high, when the carbon nanotube paste is heat-treated at about 400 ℃ or more, the carbon nanotubes contained in the paste are rapidly lost to carbon monoxide, carbon dioxide, etc. by oxygen, etc. However, the number of carbon nanotubes contributing to the actual emission is very small.

However, as in the present invention, when the content of the carbon nanotubes is 15% by weight or more, even if the high temperature firing temperature is 400 ° C to 600 ° C, the carbon nanotubes do not decrease and the number of sites contributing to the emission is preferable. .

The heat treatment process is preferably carried out in a furnace of air, nitrogen, inert gas or vacuum.

In addition, the number of emission sites can be increased without performing a separate surface treatment on the surface of the carbon nanotube thick film, thereby simplifying the process.

Using the carbon nanotube emitter prepared in the same manner as described above it can be produced a three-pole electrode carbon nanotube field emission device.

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.

(Example 1)

Ethyl cellulose was added to a mixed organic solvent of butyl carbitol acetate (BCA) and terpineol (TP) (5: 5 by volume). Next, carbon nanotubes and glass frit were mixed, and a paste was prepared by adding a mixture of the mixed organic solvent and ethyl cellulose thereto. The contents of ethyl cellulose and carbon nanotubes mixed in the paste were 10 and 25% by weight, respectively. In addition, the viscosity of this paste was 60,000cp. The paste was screen printed on a negative electrode plate to form a thick film, and the carbon nanotube emitter was heat-treated at 450 ° C. for 1 hour to form a carbon nanotube emitter.

(Example 2)

The same procedure as in Example 1 was carried out except that a butyl carbitol acetate (BCA) and terpineol (TP) (6: 4 vol. Ratio) mixed organic solvent was used.

(Example 3)

The same procedure as in Example 1 was carried out except that nitro cellulose was used instead of ethyl cellulose.

(Example 4)

The same procedure as in Example 1 was carried out except that acrylic resin was used instead of ethyl cellulose.

(Example 5)

Carbon nanotubes were carried out in the same manner as in Example 1 except that the carbon nanotubes were preheated at 1,300 ° C. for 2 hours under a vacuum atmosphere.

(Comparative Example 1)

The same process as in Example 1 was conducted except that no organic solvent was used.

1A to 1B are field emission image photographs when an electric field of 1,2 kV is applied to a thick carbon nanotube thick film according to Example 1 and Comparative Example 1. FIG. As shown in FIG. 1A, the cathode thick film of Example 1 has more emission sites and uniform distribution of the emission sites than the cathode thick film of Comparative Example 1 shown in FIG. 1B.

2A to 2B are SEM photographs of the thick films of the carbon nanotube field emission devices according to Example 1 and Comparative Example 1. FIG. In Figure 2a, the part that looks like a thread represents pure carbon nanotubes. As shown in FIG. 2A, the thick film of the carbon nanotube field emission device manufactured by the method of Example 1 of the present invention is thicker than the thick film of the carbon nanotube field emission device manufactured by the method of Comparative Example 1 shown in FIG. 2B. It can be seen that more carbon nanotubes are distributed.

3A to 3B are photographs showing field emission images of a 4.5 ”panel when an electric field of 1.2 kV is applied to the thick film of the carbon nanotube field emission devices according to Example 1 and Comparative Example 1. FIG. As shown in FIG. 3A, it can be seen that the field emission device of Example 1 has higher emission sites than the Comparative Example 1 shown in FIG.

Figure 4 is a photograph showing the printing line of the carbon nanotubes of Example 5. As shown in FIG. 4, screen printing of the vacuum heat-treated carbon nanotubes on the negative electrode plate increases the amount of carbon nanotubes present on the negative electrode plate, indicating that the color of the negative electrode plate is very black.

5 is an optical micrograph showing the printing line of the carbon nanotubes of Example 5. As shown in FIG. 5, when the negative electrode thick film is formed using the vacuum heat-treated carbon nanotubes, it can be seen that the amount of carbon nanotubes remaining in the screen printing line is very large.

6 is a field emission image photograph when a voltage of 1.2 kV is applied to a field emission device including the heat-treated carbon nanotubes of Example 5. FIG. As shown in FIG. 6, it can be seen that when the negative electrode thick film is formed by using the vacuum heat-treated carbon nanotubes, the amount of carbon nanotubes remaining increases and the emission sites increase. In addition, it exhibited stable light emission characteristics even at a high voltage of 2 kV.

The carbon nanotube field emission device manufactured by using the carbon nanotube paste for forming carbon nanotube thick film of the present invention has a lot of emission sites, and thus has high quality and uniform luminescence. In addition, there is an advantage that the surface treatment process of the carbon nanotube thick film can be omitted.

Claims (10)

Carbon nanotubes, organic binder resin, glass frit and an organic solvent, the content of the carbon nanotubes is 15 to 50% by weight of the composition for forming carbon nanotube emitters of the field emission device. The composition of claim 1, wherein the carbon nanotubes are heat-treated at 300 ° C. to 2000 ° C. for 10 minutes to 100 hours in a vacuum atmosphere. The composition of claim 1, wherein the content of the organic binder resin is 5 to 15% by weight based on the composition. The carbon nanotube emi of the field emission device of claim 1, wherein the organic solvent is at least one solvent selected from the group consisting of butyl carbitol acetate (BCA), terpineol (TP), and butyl carbitol (BC). Composition for forming the foundation. The composition of claim 1, wherein the organic solvent is a mixed solvent of butyl carbitol acetate (BCA) and terpineol (TP). water. The composition of claim 5, wherein the mixed volume ratio of the butyl carbitol acetate (BCA) and terpineol (TP) is 5: 5 to 6: 4. The composition of claim 1, wherein the composition has a viscosity of 30,000 cps to 100,000 cps. A carbon nanotube field emission device comprising carbon nanotubes formed by extruding a composition for forming carbon nanotube emitters of the field emission device of claim 1. (a) mixing an organic binder resin and an organic solvent; (b) mixing the carbon nanotube powder and the glass frit; And (c) mixing the mixture of step (a) and the mixture of step (b) to prepare a composition in paste form, The content of the carbon nanotube powder is 15 to 50% by weight of the composition for producing a composition for forming a carbon nanotube emitter of the field emission device. A field emission device comprising carbon nanotubes formed by extruding a composition for forming carbon nanotube emitters of a field emission device manufactured by the method of claim 9.