KR20100006524A - Method for producing a carbon nanotube field electron emitter and field electron emission device comprising the field electron emitter produced by the same - Google Patents

Abstract

PURPOSE: A method for producing a carbon nanotube field electron emitter and a field electron emission device comprising a field electron emitter produced by the same are provided to obtain the uniform and excellent field emission electron source. CONSTITUTION: An aqueous solution of the carbon nanotube-nucleic acid complex is manufactured. The carbon nanotube - nucleic acid complex is precipitated on the substrate through an electrophoresis mode. The substrate including the precipitated carbon nanotube - nucleic acid complex is manufactured. The nucleic acid is comprised of the DNA, and RNA or PNA. The nucleic acid is comprised of the single strand or the double-strand nucleic acid. The aqueous solution is comprised of water or the TAE buffer solution.

Description

A method for producing a carbon nanotube field electron emitter and field electron emission device comprising the field electron emitter produced by the same}

The present invention relates to a method for producing a carbon nanotube field electron emission source and a field electron emission device comprising the field electron emission source produced thereby.

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

Carbon nanotube (CNT) with excellent electron conductivity has excellent conductivity and electric field concentration effect, low work function and excellent field emission characteristics, which enables low voltage driving and large area, making it ideal for electron emission devices. It is expected as a field emission source.

Carbon nanotubes generally refer to a material formed in the shape of a hexagonal honeycomb cylinder by combining three different carbon atoms with one carbon atom, and are known to have diameters of several to several hundred nanometers and a length of about 10 μm. The carbon nanotubes are composed of graphite having a hexagonal carbon-bonded outer wall, and the single-walled carbon nanotube (SWCNT) depends on whether one graphite (C) layer is one layer or several layers. ) Or multi-walled carbon nanotubes (MWCNTs), and in particular, when the single-walled carbon nanotubes are formed in bundles, they are divided into single-walled carbon nanotubes. According to the structure of the graphite layer formed, the carbon nanotubes may have characteristics of an electrical conductor or a semiconductor.

In addition, the carbon nanotubes have a wide specific surface area, high electrical conductivity, uniform pore distribution, high mechanical strength, and chemically stable properties.

It is known to apply carbon nanotubes as field emitters of field emission devices. For example, a method of manufacturing a field emission source containing carbon nanotubes may include, for example, carbon nanotube growth using a CVD method, a paste using a composition for forming a field emission source containing carbon nanotubes, and electrophoretic deposition. Included. When carbon nanotubes were deposited on a substrate by electrophoretic deposition, the carbon nanotubes were electrophoretically deposited in a dispersed state in an organic solvent such as acetone, ethanol, DMF (dimethylformamide) or benzene. By using the organic solvent, in order to form the device structure on the substrate, a material which is not soluble in the organic solvent, for example, an inorganic material, was used. In addition, the voltage applied to the electrophoresis was high, it was difficult to form a uniform electron emission source.

The present invention provides a method for efficiently preparing a carbon nanotube field electron emission source in an aqueous solvent.

The present invention also provides a field electron-emitting device having excellent electron emission characteristics produced by the above method.

One embodiment of the present invention comprises the steps of preparing an aqueous solution of carbon nanotube-nucleic acid complex; And electrophoretic deposition of the carbon nanotube-nucleic acid composite on the substrate, to prepare a substrate on which the carbon nanotube-nucleic acid composite is deposited, thereby providing a method for producing a carbon nanotube field electron emission source.

Another embodiment of the present invention is a carbon nanotube-nucleic acid complex prepared according to the method for producing a carbon nanotube field electron emission source is deposited, the first substrate having a cathode electrode electrically connected to the complex; And a second substrate disposed to face the first substrate and having an anode electrode; And a fluorescent layer which emits light by electrons emitted from the first substrate.

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

One embodiment of the present invention comprises the steps of preparing an aqueous solution of carbon nanotube-nucleic acid complex; And electrophoretic deposition of the carbon nanotube-nucleic acid composite on the substrate, to prepare a substrate on which the carbon nanotube-nucleic acid composite is deposited: providing a method for producing a carbon nanotube electric electron emission source comprising: .

One embodiment of the present invention comprises the step of preparing an aqueous solution of carbon nanotube-nucleic acid complex.

The nucleic acid may be DNA, RNA, or PNA. The nucleic acid may be isolated from natural nucleic acid, synthetic or semisynthetic. The nucleic acid may be a single stranded or double stranded nucleic acid. Preferably, the nucleic acid is single stranded and smaller than the length of the carbon nanotubes, for example, may be 50-200 times smaller. For example, the nucleic acid may be a transfer RNA. The nucleic acid may be a treatment, for example, a heat treatment, to remove the secondary or tertiary structure in the molecule.

The carbon nanotubes are single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, chemically modified carbon nanotubes, metallic carbon nanotubes, semiconductor carbon nanotubes, metallized carbon nanotubes, and combinations thereof. It may be selected from the group consisting of.

The aqueous solution may include a buffer used for electrophoresis of water or nucleic acid. Examples of such buffers include TAE, TBE, and PBS buffers. The TAE (Tris, acetic acid, and EDTA) buffer may be a buffer containing a concentration of Tris 4 to 20 mM, acetic acid 1.8 to 9 mM, EDTA 1 to 5 mM.

The aqueous solution of the carbon nanotube-nucleic acid complex may be a dispersion of carbon nanotubes and nucleic acids obtained by mixing and dispersing the carbon nanotubes and the nucleic acid in an aqueous solution. The dispersion may be, for example, by ultrasonication. The dispersion obtained can be centrifuged for example in the precipitation removal process. A uniform dispersion of carbon nanotubes and nucleic acids is obtained by the precipitation removal process.

The carbon nanotubes and the nucleic acid may be mixed in a ratio of 1: 1 to 4: 1 by weight.

One embodiment of the present invention includes the step of electrophoretic deposition of the carbon nanotube-nucleic acid complex on a substrate, to prepare a substrate on which the carbon nanotube-nucleic acid complex is deposited.

The term "electrophoretic deposition" refers to the movement of colloidal particles suspended in a liquid medium by electric force to deposit on an electrode. It is known in the art to deposit carbon nanotubes on a substrate, such as a conductive substrate, by electrophoretic deposition.

The substrate is a substrate provided with an electrically conductive material, and can operate as an electrode. For example, it may be a glass substrate provided in ITO. The electrophoretic deposition is performed by applying an alternating voltage in a state in which the substrate is a cathode and a counter electrode, for example, a Pt electrode, is an anode electrode, and the cathode and anode electrodes are immersed in an aqueous solution of a carbon nanotube-nucleic acid complex. Can be. The AC voltage may be made at 5 to 40V, preferably 5 to 15V when the spacing between electrodes is 1 to 2 cm. The time for applying the voltage may be appropriately adjusted, but may be, for example, 3 to 5 minutes.

In addition, the substrate may have a patterned photoresist layer. Photoresist is a photosensitive material, used to form patterned surfaces by photolithography. The photoresist includes a positive photoresist in which a portion exposed to light becomes soluble to a photoresist developer and a negative photoresist in which a portion exposed to light becomes relatively insoluble to a photoresist developer. Included. Photoresists are organic materials, including, for example, photoresists composed of a mixture of diazonaphthoquinone (DNQ) and Novolac resin (phenol formaldehyder resin), epoxy based polymers (eg SU-8 photoresist). It is not limited to these examples. Such organic photoresists are easier to selectively remove from the substrate after electrophoretic deposition, as compared to inorganic materials. Removal of the photoresist may be accomplished by physical peeling, or by a solvent such as acetone or a photoresist stripper.

In one embodiment of the method of the present invention, the method further comprises electrophoretic deposition of the carbon nanotube-nucleic acid complex on the patterned region on the substrate, and removing the photoresist layer. The patterned area may be used a patterned method known in the art, for example photolithography. The photoresist layer may be removed by a peel or a solvent such as acetone, a photoresist stripper, or the like. The patterned region may vary in shape and density of the pattern depending on the desired density of carbon nanotubes deposited on the substrate. For example, circular or rectangular patterned regions may be arranged in an array shape. In this case, an array of field electron emission sources is formed by deposition of the carbon nanotube-nucleic acid complex. This can be appropriately adjusted by those skilled in the art according to the electron emission characteristics of the obtained field electron emission source.

In one embodiment of the method of the present invention, further comprising the step of sintering the substrate on which the carbon nanotube-nucleic acid composite is deposited. The sintering may be to heat at 200 to 500 ℃, preferably 350 ℃ to 400 ℃. Sintering removes the nucleic acid portion of the carbon nanotube-nucleic acid complex.

One embodiment of the method of the present invention may include the step of activating by taping the substrate on which the carbon nanotubes are deposited. Taping refers to attaching and detaching one or more selected from an adhesive tape, a liquid polymer, and an elastic rubber onto the substrate. According to the method of the present invention, in addition to activating the carbon nanotubes to act as a field electron emission source by the sintering treatment, it can be further activated by the taping step.

The carbon nanotube field electron emission source obtained by the above method can be applied to a field electron emission device.

Therefore, another embodiment of the present invention, the carbon nanotube-nucleic acid complex prepared according to the method of the present invention is deposited, the first substrate having a cathode electrode electrically connected to the complex; And a second substrate disposed to face the first substrate and having an anode electrode; And a fluorescent layer which emits light by electrons emitted from the first substrate.

An embodiment of such a field electron emission device is shown in FIG. 5. FIG. 5 schematically illustrates an electron emitting device having a triode structure among the field electron emitting devices according to the present invention. The electron emission device 200 illustrated in FIG. 5 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 a field emission source hole 169 formed in a portion of the gate electrode 140, disposed in the field emission source hole 169, and energized with the cathode electrode 120 and lower than the gate electrode 140. And a field emission source 160 disposed therein. Details of the field emission source 160 are the same as described above.

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 field emission source 160 to allow the electrons to collide with the phosphor layer 170 at high speed. The phosphor of the phosphor layer is excited by the electrons and emits visible light while falling from a high energy level to a low energy level.

The gate electrode 140 functions to easily discharge electrons from the field emission source 160, and the insulator layer 130 partitions the field emission hole 169 and emits the field. It functions to insulate the circle 160 and the gate electrode 140.

Although the field emission device of the present invention has been described with an electron emission device having a triode structure as shown in FIG. 5 by way of example, the present invention includes not only the triode structure, but also the electron emitting device having other structures including the dipole tube. . In addition, it is possible to prevent damage to the field emission device in which the gate electrode is disposed below the cathode electrode, the gate electrode and / or the cathode electrode due to the arc that is assumed to be caused by the discharge phenomenon, and to focus the electrons emitted from the field emission source. It can also be used for field emission devices with a grid / mesh to ensure. On the other hand, it is also possible to apply the structure of the field emission device to another display device or a backlight unit.

According to the method for producing the carbon nanotube field electron emission source of the present invention, the carbon nanotube field electron emission source can be produced easily and efficiently with the field electron emission source having excellent electron emission characteristics.

According to the field electron emission device of the present invention, the field electron emission source characteristics are uniform and excellent.

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are for illustrative purposes only, and the scope of the present invention is not limited by these examples.

Example 1: Carbon nanotube-nucleic acid complex Electric field  Electronic Emission source  Produce

First, carbon nanotubes and nucleic acids were mixed in an aqueous solution to prepare an aqueous solution of a carbon nanotube-nucleic acid complex. Carbon nanotubes are single-walled carbon nanotubes (manufactured by Carbolex), and those having a diameter of 1.2 to 1.5 nm and a length of 2 to 5 μm were used. As the nucleic acid, total RNA or transfer RNA (Sacharomyces ceverisiae) derived from yeast (Takar) was used. The total RNA includes ribosomal RNA, transition RNA and messenger RNA. The transfer RNA has a length of 73 to 93bp, that is, 26 to 33nm, and is smaller than the length of the carbon nanotubes.

When mixed, the nucleic acid was heated at 65 ° C. for 15 minutes. This heat treatment is to remove the secondary structure of the nucleic acid, and to induce the nucleic acid without secondary structure to bond with the carbon nanotubes. The carbon nanotubes were treated with a rod sonicator (UP400s, Heilsher) at 150 W for 6 hours in an aqueous solution to disperse the carbon nanotubes. Next, the heat-treated nucleic acid aqueous solution was mixed with the dispersed carbon nanotube aqueous solution, and then TAE buffer was added to pH 8.0, and then the ultrasonic treatment (MXB6, Grant, UK) at 4 ° C. was performed at 100W. After treatment for a time, the carbon nanotube-nucleic acid complex was dispersed in an aqueous solution. The TAE (Tris, acetic acid, and EDTA) buffer is a buffer containing a concentration of Tris 4 to 20mM, acetic acid 1.8 to 9mM, EDTA 1 to 5mM.

The solution of the sonicated carbon nanotube-nucleic acid complex was centrifuged at 2,000 to 4,000 rpm to remove the precipitate to obtain a solution in which the carbon nanotube-nucleic acid complex was dispersed.

Next, a glass container is immersed in the solution in which the carbon nanotube-nucleic acid complex is dispersed, and a + power source is connected to the ITO electrode of the substrate coated with an ITO electrode having a patterned photoresist layer, and is opposed to the substrate. The power supply was connected to the counter electrode, the Pt electrode, and the alternating voltage was applied. The distance between the ITO electrode and the Pt electrode was 0.5-2 cm, and a voltage of 8-40 V was applied for 0.5-8 minutes. The photoresist pattern on the substrate was prepared as follows. First, ITO was coated on a glass substrate by sputtering coating to form an ITO layer having a thickness of 200 nm, thereby making an ITO electrode. Next, photoresist (AZ1512, Clariant) was spin coated on the ITO layer to form a photoresist layer having a thickness of about 1.2 μm. Next, 365 (I-line) nm light was irradiated through the mask, and the irradiated part was developed using the acetone developer. As a result, an array of circles was formed on a rectangular glass substrate having a width of 9.3 cm and a length of 400 mm, and a distance of 300 mm between a dot and a circle. By applying the voltage, carbon nanotube-nucleic acid was deposited on an array of circles on the substrate to prepare an array of carbon nanotube-nucleic acid.

Next, the photoresist remaining unpatterned was removed by acetone. Next, the substrate from which the photoresist was removed was dried at 90 ° C. for 30 minutes, and then heat-treated at 400 ° C. for 30 minutes. As a control, no heat treatment was performed at 400 ° C.

Next, a polypropylene adhesive tape was attached to the heat-treated substrate and then peeled off to activate the carbon nanotube electron emission source. As a control, one that did not undergo the taping step was used.

1 is a view showing an example of a method of manufacturing a field electron emission source according to an embodiment of the method of the present invention. According to FIG. 1, an ITO electrode is coated on a glass substrate, a photoresist is coated on the ITO layer, and the photoresist is patterned by photolithography. Carbon nanotube-nucleic acid was deposited on the patterned region by electrophoretic deposition on the obtained patterned substrate, the photoresist was removed, and heat treatment was performed. In addition, carbon nanotube electron emission sources were selectively activated by taping.

Example 2: Effect of Taping Treatment for Activation of Carbon Nanotube Electron Source

In this example, the effect of the taping treatment on the electron emission characteristics of the field electron emission source prepared according to Example 1 was confirmed. Confirmation of the electron emission characteristics was carried out by arranging the anode electrodes coated with the green phosphor 240 占 퐉 apart from each other in the electron emission source obtained according to Example 1 and when not, and applying a predetermined voltage. , The electrons emitted from the electron emission source is measured as a current, or the phosphor Luminescence was photographed with a digital camera to obtain an image.

FIG. 2 is a diagram showing field electron emission characteristics when only heat treatment and both heat treatment and taping treatment are performed. As shown in FIG. 2, the electric field emission characteristics were not significantly different between the heat treatment and the heat treatment and the taping treatment. This indicates that according to the method of the present invention, activation of the electron emission source by surface treatment is not necessary. In Fig. 2, 2.20 V / µm and 2.12 V / µm represent threshold values.

3 is a diagram illustrating electron emission characteristics of an electron emission source when the heat treatment is not performed. As shown in FIG. 3, the electron emission characteristic in the case of taping without heat treatment did not improve the electron emission characteristic in comparison with the case in which the taping treatment was not performed. In FIG. 3, 2.82 V / µm and 2.99 V / µm represent threshold values.

4 is a diagram showing an electron emission image of an electron emission source manufactured at each step of the method of manufacturing a field electron emission source according to one embodiment of the method of the present invention. 4A is a phosphor emission image when 1100V (4.58V / μm, 1.17mA) is applied after PR removal after deposition, and B is heat-treated at 400 ° C. for 30 minutes in a nitrogen atmosphere after PR removal, Phosphor emission image when 900V (3.75V / μm, 2.25mA) is applied. B is an activation method that does not undergo a taping process, and indicates that a uniform field electron emission effect can be obtained without going through a taping process. C is a phosphor emission image when 900V (3.75V / μm, 2mA) is applied after heat treatment at 400 ° C. for 30 minutes in a nitrogen atmosphere after PR removal, and then taping. As shown in C, it can be seen that there is a region in which the electron emission source is lost due to the taping process and electrons are not emitted.

Example 3: Effect of Nucleic Acids and Buffer Types on the Electron Emission Characteristics of Carbon Nanotube Electron Emission Sources

In this example, the effect of the type of nucleic acid and the type of buffer on the electron emission characteristics of the carbon nanotube electron emission source was confirmed.

The composition of the nucleic acid and the buffer used are shown in Table 1 below.

Table 1.

sample Distilled water (ml) SWCNT (mg) RNA (mg) TAE buffer additive Tris EDTA Acetic acid One 200 40 40 (total RNA) - - - - 2 200 40 40 (total RNA) 4mM 1.0mM 1.8mM - 3 200 40 40 (total RNA) 20mM 5.0mM 9 mM - 4 200 40 40 (total RNA) 40mM 10 mM 1.8mM - 5 200 40 10 (t-RNA) 4mM 1.0mM 1.8mM - 6 200 20 10 (t-RNA) 4mM 1.0mM 1.8mM - 7 200 20 10 (t-RNA) 4mM 1.0mM 1.8mM 1% SDS 8 200 80 16 (t-RNA) 4mM 1.0mM 1.8mM -

In Table 1, Tris represents Tris (2-amino-2- (hydroxymethyl) -1,3-propandiol and EDTA represents ethylenediaminetetraacetic acid.

Using the composition according to Table 1 and the degree of deposition of the carbon nanotube-nucleic acid composite according to Example 1 was investigated. As a result, Samples 1-7 were deposited, of which Sample 5 was deposited most uniformly. In the case of Sample 7, the deposition time was longer than that in the case of not containing SDS.

From the above results, in the case of nucleic acids, the use of tRNA compared to the total RNA had a good effect on the electron emission characteristics. In addition, by using TAE buffer, it was possible to obtain a field electron emission source having excellent field emission characteristics without addition of a surfactant such as SDS.

1 is a view showing an example of a method of manufacturing a field electron emission source according to an embodiment of the method of the present invention.

2 is a diagram showing the field electron emission characteristics when only heat treatment; and both heat treatment and taping treatment.

3 is a diagram illustrating electron emission characteristics of an electron emission source when the heat treatment is not performed.

4 is a diagram showing an electron emission image of an electron emission source manufactured at each step of the method of manufacturing a field electron emission source according to one embodiment of the method of the present invention.

FIG. 5 schematically illustrates an electron emitting device having a triode structure among the field electron emitting devices according to the present invention.

<Short description of drawing symbols>

1: substrate 2: catalyst layer

3: plate-shaped ultrasonic vibrator 4: rod-shaped ultrasonic vibrator

5: carbon source material

110: lower substrate 120: cathode electrode

130: insulator layer 140: gate electrode

160: field emission source 170: phosphor layer

180: anode electrode 190: upper substrate

Claims (13)

Preparing an aqueous solution of a carbon nanotube-nucleic acid complex; And And electrophoretic deposition of the carbon nanotube-nucleic acid composite on the substrate to prepare a substrate on which the carbon nanotube-nucleic acid composite is deposited. The method of claim 1, wherein the nucleic acid is DNA, RNA, or PNA. The method of claim 1, wherein the nucleic acid is a single stranded or double stranded nucleic acid. The method of claim 1, wherein the aqueous solution is water or TAE buffer solution. The method of claim 1, wherein the aqueous solution of the carbon nanotube-nucleic acid complex comprises: mixing and sonicating the carbon nanotube and the nucleic acid in the aqueous solution; And removing the precipitate by centrifugation to obtain an aqueous solution of carbon nanotube-nucleic acid. The method of claim 5, wherein the carbon nanotubes and the nucleic acid are mixed in a ratio of 1: 1 to 4: 1 by weight. The method of claim 1, wherein the substrate is a substrate having a patterned photoresist layer. 8. The method of claim 7, further comprising electrophoretically depositing the carbon nanotube-nucleic acid composite onto a patterned region on the substrate and removing the photoresist layer. The method of claim 1, wherein the carbon nanotube-nucleic acid composite comprises at least one of sintering and activating the deposited substrate. 10. The method of claim 9, wherein the sintering is heated at 200 to 500 ° C. The method of claim 9, wherein the activation is taped. The method of claim 1, wherein said electrophoretic deposition is comprised between 5 and 15V. A first substrate having a carbon nanotube-nucleic acid composite formed in accordance with any one of claims 1 to 11 deposited thereon and having a cathode electrode electrically connected to the composite; And A second substrate disposed to face the first substrate and having an anode electrode; And And a fluorescent layer which emits light by electrons emitted from the first substrate.

Images