KR20070046597A - A composition for preparing an electron emission source, a method for preparing an electron emission source by using the same and the electron emission device comprising the electron emission source prepared by using the method - Google Patents

Abstract

The present invention relates to a composition for forming an electron emission source comprising individual carbon nanotubes (isolated CNT) and a vehicle, a method for producing an electron emission source using the same, and an electron emission device having an electron emission source manufactured using the same. By using the composition for forming an electron emission source, an electron emission source with improved current density can be obtained.

Description

A composition for forming an electron emission source, a method of manufacturing an electron emission source using the same, and an electron emission device having an electron emission source manufactured using the same, a method for preparing an electron emission source by using the same and the electron emission device comprising the electron emission source prepared by using the method}

1 is a cross-sectional view schematically showing an embodiment of an electron emitting device of the present invention,

2A is a TEM photograph of a conventional electron emission source,

2b is a TEM photograph of the electron emission source according to the present invention;

3 shows a current density graph of a conventional electron emitter and an electron emitter according to the present invention.

<Short description of drawing symbols>

110: lower substrate 120: cathode electrode

130: insulator layer 140: gate electrode

160: electron emission source 170: phosphor layer

180: anode electrode 190: upper substrate

The present invention relates to a composition for forming an electron emission source, a method for producing an electron emission source using the same, and an electron emission device having an electron emission source manufactured using the same, and more specifically, individual carbon nanotubes (CNTs). The present invention relates to a composition for forming an electron emission source, a method for producing an electron emission source using the same, and an electron emission device having an electron emission source manufactured using the same. By using the composition for forming an electron emission source, an electron emission source having an improved current density can be obtained, and an electron emission device having improved reliability can be obtained.

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

Carbon nanotubes with excellent electron conductivity are expected to be an ideal electron emission source for electron-emitting devices because they have excellent conductivity and electric field concentration effect, low work function, excellent field emission characteristics, low voltage driving, and large area. .

The method for producing an electron emission source containing carbon nanotubes includes, for example, a carbon nanotube growth method using a CVD method or the like, a paste method using an electron emission source formation composition containing carbon nanotubes and a vehicle. By using the above paste method, the manufacturing cost is low and the electron emission source can be formed in a large area. Compositions for forming electron emission sources, including carbon nanotubes, are described, for example, in US Pat. No. 6,436,221.

However, the electron emission method using the conventional paste method has conventionally used bundled carbon nanotubes (bundled CNT). The bundle-type carbon nanotubes are bundles of a plurality of carbon nanotube strands formed together, and the bundle-type carbon nanotubes are made by using an arc-discharge method, a laser vaporization method, a CVD method, and the like, which are known as the synthesis of SWCNT. Since the bundle-type carbon nanotubes have a large diameter, they are not suitable for obtaining an aspect ratio that is large enough to obtain a desired current density. Therefore, improvement thereof is required.

The present invention is to solve the problems of the prior art as described above, it is an object to provide a composition for forming an electron emission source for individual carbon nanotubes and vehicles. In addition, a method of manufacturing an electron emission source using the composition for forming an electron emission source, and an electron emission device having an electron emission source manufactured from the composition for forming an electron emission source is also provided.

In order to achieve the above object of the present invention, a first aspect of the present invention provides a composition for forming an electron emission source comprising individual carbon nanotubes and a vehicle.

In order to achieve the above object of the present invention, the second aspect of the present invention provides a composition for forming an electron emission source as described above, printing the composition for forming an electron emission source on a substrate, and It provides a method for producing an electron emission source comprising the step of firing the printed composition for forming an electron emission source.

In order to achieve the another object of the present invention, a third aspect of the present invention, the first substrate and the second substrate disposed to face each other, the cathode electrode formed on the first substrate, and the cathode electrode and electrically connected And an electron emission source formed on the second substrate, an anode electrode formed on the second substrate, and a fluorescent layer emitting light by electrons emitted from the electron emission source, wherein the electron emission source is used for forming an electron emission source as described above. Provided is an electron emitting device manufactured using the composition.

Since the electron emission source includes individual carbon nanotubes, the electron emission source may have an improved current density. By using such an electron emission source, an electron emission device having improved reliability can be obtained.

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

The composition for forming an electron emission source of the present invention includes individual carbon nanotubes and a vehicle.

Carbon nanotubes are carbon allotropes in which graphite sheets are rounded to a nano-sized diameter to form tubes. have.

In the present specification, the individual carbon nanotubes (isolated CNT) is a term for indicating a state in which carbon nanotube strands are present without being bound together. Given the meaning of these individual carbon nanotubes, the term as opposed to the individual carbon nanotubes is a bundle of carbon nanotubes (bundled CNTs). The bundle type carbon nanotubes is a term representing a state in which a plurality of carbon nanotube strands are aggregated together.

The individual carbon nanotubes consist of one carbon nanotube strand. Such individual carbon nanotubes may have a diameter of 0.4 nm to 2 nm, preferably 0.4 nm to 1.5 nm. This is because the individual carbon nanotubes according to the present invention consist of one carbon nanotube strand. In general, the bundle-type carbon nanotubes are composed of 10 to 100 carbon nanotube strands, and considering that they have a diameter of 5 nm to 30 nm, it can be seen that the diameter of the individual carbon nanotubes falls within a very small range. have.

Therefore, the length of the individual carbon nanotubes according to the present invention was about 10㎛ as observed by SEM can have an aspect ratio of 5000 to 25000, more preferably 6700 to 25000 aspect ratio. This is because the individual carbon nanotubes according to the present invention can have a very small diameter as described above. Considering that the bundle type carbon nanotubes generally have an aspect ratio of 300 to 2000, it can be seen that the aspect ratio of the individual carbon nanotubes belongs to a very large range.

As such, individual carbon nanotubes according to the present invention can be prepared using various known methods. For example, the individual carbon nanotubes may be obtained by forming a substrate having an iron catalyst metal layer having a nano size and heating the substrate in the presence of a carbon-containing gas.

The carbon-containing gas may be any gas containing carbon, for example, hydrocarbon gas, carbon monoxide gas, or the like. The heating of the substrate in the presence of a carbon-containing gas may be carried out, for example, at a temperature of 600 ° C. to 100 ° C.

One more specific example of the method for producing the individual carbon nanotubes is as follows.

First, a 150 µg / mL solution of ferric nitrate nonahydrate in 2-propanol is prepared and stirred for 2 minutes. Thereafter, the prepared silicon substrate is immersed in the solution for 10 seconds, washed with hexane and dried. As a result, an iron catalyst metal layer having a nano size can be formed on the substrate. The substrate is mounted in a tube furnace and then annealed for 15 minutes at a temperature of 700 ° C. under an atmosphere of 600 sccm of argon and 400 sccm of hydrogen. Then, by feeding ethylene at 0.5 sccm for 6 minutes and then cooling the furnace under argon atmosphere, individual carbon nanotubes according to the present invention can be obtained.

On the other hand, the vehicle included in the electron emission source composition controls the printability and viscosity of the composition for forming an electron emission source, and serves to transport individual carbon nanotubes. The vehicle may consist of a resin component and a solvent component.

The resin component may be, for example, a cellulose resin such as ethyl cellulose, nitro cellulose or the like; Acrylic resins such as polyester acrylate, epoxy acrylate, urethane acrylate and the like; At least one of a vinyl-based resin such as polyvinyl acetate, polyvinyl butyral, polyvinyl ether, and the like may be included, but is not limited thereto.

The solvent component is, for example, at least one of terpineol, butyl carbitol (BC), butyl carbitol acetate (BCA), toluene and texanol It may include. Among these, it is preferable to contain terpineol.

The content of the resin component may be 100 to 500 parts by weight, more preferably 200 to 300 parts by weight based on 100 parts by weight of the carbon-based material. On the other hand, the content of the solvent component may be 500 to 1500 parts by weight, preferably 800 to 1200 parts by weight based on 100 parts by weight of the carbon-based material. When the content of the vehicle consisting of the resin component and the solvent component is outside the above range may cause a problem that the printability and flowability of the composition for forming an electron emission source is lowered. In particular, when the content of the vehicle exceeds the above range, there is a problem that the drying time may be too long.

In addition, the composition for forming an electron emission source of the present invention may further include an adhesive component, a filler, and the like as necessary.

The adhesive component serves to attach the electron emission source to the substrate, and may be, for example, an inorganic binder. Non-limiting examples of such inorganic binders include frit, silane, water glass, and the like, and two or more of these may be mixed and used. The frit may be made of, for example, lead oxide-zinc oxide-boron oxide (PbO-ZnO-B ₂ O ₃ ). Among the inorganic binders, frit is preferable.

The content of the inorganic binder in the composition for forming an electron emission source may be 10 to 50 parts by weight, preferably 15 to 35 parts by weight based on 100 parts by weight of the carbon-based material. When the content of the inorganic binder is less than 10 parts by weight based on 100 parts by weight of the carbon-based material, satisfactory adhesive strength cannot be obtained, and when the content of the inorganic binder exceeds 50 parts by weight, printability may be deteriorated.

The filler is a material that serves to improve the conductivity of the carbon-based material that is not sufficiently adhered to the substrate, non-limiting examples thereof include Ag, Al, Pd.

The composition for forming an electron emission source of the present invention comprising a material as described above may have a viscosity of 3,000 to 50,000 cps, preferably 5,000 to 30,000 cps. If it is out of the viscosity range, a problem may arise that the workability is poor.

The electron emission source manufacturing method of the present invention uses the composition for forming an electron emission source of the present invention as described above. More specifically, the electron emission source manufacturing method of the present invention comprises the steps of providing a composition for forming an electron emission source; Printing the composition for forming an electron emission source; And baking the printed composition for forming an electron emission source.

First, a composition for forming an electron emission source is prepared with the components and contents as described above. Detailed description of the composition for forming an electron emission source is the same as described above, and thus will be omitted.

Thereafter, the provided composition for forming an electron emission source is printed on a substrate. The "substrate" is a substrate on which an electron emission source is to be formed, which may be different depending on the electron emission element to be formed, which is easily recognized by those skilled in the art. For example, the "substrate" may be a cathode when manufacturing an electron emission device having a gate electrode between a cathode and an anode, and an electron emission device having a gate electrode disposed below the cathode. In manufacturing, the insulating layer may be an insulating layer that insulates the cathode and the gate electrode.

The step of printing the composition for forming an electron emission source is different depending on the case of including the photosensitive resin and the case of not including the photosensitive resin. First, 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 applied onto a substrate, and then exposed and developed according to the desired electron emission source formation 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 pattern is required. That is, a photoresist 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 pattern.

As described above, the composition for forming an electron emission source is subjected to a firing step. Carbon nanotubes in the composition for forming an electron emission source may be improved in the composition for forming an electron emission source through a firing step, at least some of the vehicles may be volatilized, and other inorganic binders may be melted and solidified, thereby contributing to the durability of the electron emission source. Will be. The firing temperature should be determined in consideration of the volatilization temperature and time of the vehicle included in the composition for electron emission source formation. Typical firing temperatures are 400 ° C 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, if the firing temperature exceeds 500 ℃ may cause a problem that the manufacturing cost rises, the substrate may be damaged.

The firing step may be performed in the presence of an inert gas to prevent deterioration of the carbon nanotubes. The inert gas may be, for example, nitrogen gas, argon gas, neon gas, xenon gas, and a mixed gas of two or more thereof.

The calcined resultant surface is optionally subjected to an activation step for vertical alignment, surface exposure, and the like of the carbon nanotubes. According to one embodiment of the activation step, after applying a solution that can be cured in the form of a film through a heat treatment process, for example, an electron emission source surface treatment agent containing a polyimide-based polymer on the firing result, and then heat treatment Then, the film formed by the heat treatment is peeled off. According to another embodiment of the activation step, the activation process may be performed by forming an adhesive part having an adhesive force on the surface of the roller driven by a predetermined driving source and pressing the surface of the firing product at a predetermined pressure. Through this activation step, the carbon nanotubes may be controlled to be exposed or vertically aligned to the electron emission surface.

The electron emission source according to the present invention which can be produced as such is suitable for use in an electron emission element used as a display element or a backlight unit.

One embodiment of an electron emission device having an electron emission source of the present invention as described above is shown in FIG. 1. 1 schematically shows an electron emitting device having a triode structure among various electron emitting devices according to the present invention. The electron emission device 200 illustrated in FIG. 1 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 electricity supply to the cathode electrode 120 and lower than the gate electrode 140. And an electron emission source 160 disposed therein. Detailed description of the electron emission source 160 is the same as described above, and thus will be omitted.

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 required for acceleration of electrons emitted from the electron 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 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-emitting device of the present invention has been described with an electron-emitting device having a triode structure as shown in FIG. 1 as an example, but the present invention includes not only the triode structure, but also an electron emitting device having another structure including a dipole tube. In addition, it is possible to prevent damage to the electron emission element 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 electron emission source. It can also be used for electron emitting devices with grids / meshes to ensure the safety. On the other hand, it is also possible to apply the structure of the electron emitting device to the display 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

Example

First, 1 g of individual carbon nanotube powder (self-produced), 0.2 g of frit (8000L, manufactured by Emerging Industries), 5 g of polyester acrylate, and 5 g of benzophenone were added to 10 g of terpineol, followed by stirring, and a viscosity of 30,000 cps. A composition for forming an electron emission source having was prepared. The composition for forming an electron emission source was applied onto a prepared substrate having a Cr gate electrode, an insulating film, and an ITO electrode, and then irradiated with a parallel exposure machine at an exposure energy of 2000 mJ / cm ² . Thereafter, the film was developed using acetone, and the composition for electron emission source formation was printed on the electron emission source formation region defined by the photoresist pattern. Thereafter, the mixture was calcined in the presence of a temperature of 450 ° C. and nitrogen gas to form an electron emission source. Subsequently, a substrate using ITO as a fluorescent film and an anode electrode was disposed so as to be oriented with the substrate on which the electron emission source was formed, and a spacer was formed between the substrates to maintain the cell gap between the substrates. The electron emitting device is referred to as sample 1.

Comparative example

An electron emission device was formed in the same manner as in the above example, except that a bundle type carbon nanotube (manufactured by Iljin Nanotech Co., Ltd.) was used instead of the individual carbon nanotubes. This is called sample A.

Evaluation example  One

The electron emission sources of Samples A and 1 were observed by TEM, and the results are shown in FIGS. 2A and 2B, respectively. In the case of Sample A, there is a bundle of carbon nanotubes consisting of a plurality of strands as can be observed from FIG. 2A, but in the case of Sample 1, individual carbon nanotubes consisting of one carbon nanotube strand as can be observed from FIG. 2B. It can be seen that there exists.

Evaluation example  2

The current densities of the electron emission sources of Samples A and 1 were measured using a pulse power source and an ammeter, respectively, and are shown in FIG. 3. Referring to FIG. 3, it can be seen that current-voltage characteristics of Sample 1 are superior to Sample A. FIG. Sample 1 also showed better current stability over time measured at current (200mA). Accordingly, Sample 1 showed superior performance in current density, lifetime, and the like as Sample A.

By using the composition for forming an electron emission source of the present invention, an electron emission source including individual carbon nanotubes can be obtained. Since the individual carbon nanotubes have a small diameter and a large aspect ratio, the electron emission source including the individual carbon nanotubes may have an excellent current density.

Although the above has been described with reference to preferred embodiments of the present invention, those skilled in the art can variously modify and modify the present invention without departing from the spirit and scope of the invention as set forth in the claims below. It will be appreciated that it can be changed.

Claims (6)

A composition for forming an electron emission source comprising individual carbon nanotubes (isolated CNT) and a vehicle. The composition of claim 1, wherein the individual carbon nanotubes have an average diameter of 0.4 nm to 2 nm. The composition of claim 1, wherein an aspect ratio of the individual carbon nanotubes is 5000 to 25000. Providing a composition for forming an electron emission source of any one of claims 1 to 3; Printing the composition for forming an electron emission source on a substrate; And Baking the printed composition for forming an electron emission source; Electron emitter manufacturing method comprising a. The electron emission source of claim 4, wherein the printing of the electron emission source forming composition is performed by applying the electron emission source forming composition to a substrate and then exposing and developing the electron emission source forming region. Manufacturing method. A first substrate and a second substrate disposed to face each other; A cathode electrode formed on the first substrate; An electron emission source formed to be electrically connected to the cathode electrode; An anode electrode formed on the second substrate; And An electron emission device comprising a fluorescent layer for emitting light by electrons emitted from the electron emission source, wherein the electron emission source is manufactured using the composition for forming an electron emission source of any one of claims 1 to 3.

Images