KR100508544B1 - Method for manufacturing carbon nanotube - emitter performing field emission - Google Patents

Abstract

Provided are methods for making carbon nanotubes (emitters) for field emission. The production method according to an aspect of the present invention proposes a method for producing a carbon nanotube emitter using a silicon-based polymer. In this manufacturing method, a paste is prepared by mixing carbon nanotube powder and a silicon-based polymer, and a paste is printed on the cathode to form a carbon nanotube film. The silicon-based polymer mixed in the coated paste forms carbon nanotubes. After the carbon nanotube film is heat-treated to bind on the cathode to cure the silicon-based polymer in a silicide shape, the carbon nanotube film is surface treated to induce the end of the carbon nanotube to be exposed to the outside of the surface. Here, the methyl polymer may be methyl phenyl silicon resin.

Description

Method for manufacturing carbon nanotube-emitter performing field emission

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a field emission display (FED) device, and more particularly, to a method of forming an emitter that emits electrons by an electric field using carbon nanotubes. will be.

The most widely used display so far is CRT. CRTs have excellent characteristics in terms of brightness, color purity and field of view. On the other hand, the products are very thick and have relatively heavy weight. Accordingly, the CRT can be said to be unsuitable for portable use.

To compensate for the weaknesses of CRTs, liquid crystal displays (LCDs), which are thin-film displays, are replacing the CRT market. However, liquid crystal displays are satisfactory in terms of thickness but have a problem in terms of brightness and viewing angle, and thus their use range is limited. In addition, as a large display, a plasma display panel (PDP) is in the spotlight and is preparing for commercialization. PD has the advantage of bigger screen size and wider viewing angle than LCD, but it is not possible to carry it because of weakness that power consumption is large and it is impossible to reduce screen size. In addition, field emission type display (FED) has been tried as a display. Since FED satisfies both the viewing angle, the power consumption, and the thickness of the product, there is an advantage that can supplement the weaknesses of both displays. It is actively underway and invests a lot for commercialization.

In the process of manufacturing such a display, various methods of forming films are used. The film making methods used in the manufacturing of displays are generally divided into thin film and thick film methods. In addition, various methods for forming shapes by patterning the films after forming the films have also been proposed. In the case of forming a thin film, after forming a film, a photosensitive material is applied to the film to form a primary shape, and the film is etched by dry etching or wet etching. This method is known as photo lithography. In the case of the thick film method, the desired material is mixed with the photosensitive polymer solution, and the film is made by spin coating, and then light is made to form the desired shape. The material to be coated is mixed with a suitable resin and then screen printed. You can also create shapes using the method. The method of forming and patterning such a film may be selected and applied in consideration of the properties of the film.

The method of making the shape of the film in the display varies slightly depending on the display, but in the case of the thick film, such photo etching and printing methods are mainly used. For example, the fluorescent film formation of the CRT and the color filter of the LCD use a photolithography method using a photosensitive resin that reacts to light, and the shape of the fluorescent film of the plasma display panel is made by a printing method. The printing method is simpler than the photolithography method using a photosensitive resin, and the resin used has various advantages.

On the other hand, in the case of a field emission display, the structure mainly employing a tip type emitter has been studied.

1 is a cross-sectional view schematically illustrating a conventional tip-type field emission display.

Referring to FIG. 1, the back glass 10 and the front glass 20 are separated by a sealing wall 90, and a cathode 30 is introduced on the back glass 10. On the cathode 30 a micro sized tip 40 is introduced. The tips 40 may be separated from each other by the insulating layer 50, and a gate electrode 60 is introduced on the insulating layer 50. An anode node 80 is introduced on the windshield 20 opposite to the tip 40 and a fluorescent film 70 is introduced on the anode 80 to form a field emission display.

Such a tip field emission display has a weak manufacturing cost because a semiconductor process is used in the manufacturing process. Attempts have been made to use carbon nanotubes as emitters for field emission in order to improve the weaknesses of such tip type field emission displays.

2 is a schematic cross-sectional view for explaining a field emission display in the form of a typical carbon nanotube. 3 is an enlarged cross-sectional view of part A of FIG. 2. 4 is a cross-sectional view schematically illustrating the state of carbon nanotubes when a carbon nanotube film is formed of a thick film.

Referring to FIGS. 2 and 3, the tip 40 as shown in FIG. 1 may be replaced with the carbon nanotubes 41 to implement a field emission display in the form of carbon nanotubes.

As such, when the carbon nanotubes 41 are used as emitters, a method of laying the carbon nanotubes 41 on a predetermined medium, for example, the cathode 30, is mainly studied.

The carbon nanotube 41 film containing the carbon nanotubes 41 is mainly formed using a thick film method. In the case where only the carbon nanotubes 41 are included in the carbon nanotubes 41 formed by the thick film method, the shape of the carbon nanotubes 41 is laid as shown in FIG. It is observed that Therefore, after the carbon nanotube 41 film is formed by the thick film method, surface treatment is performed to allow the ends of the carbon nanotubes 41 to stand upright or at least obliquely.

Surface treatment is performed after the heat treatment process of the film | membrane which formed the shape. By the way, the carbon nanotube 41 film thus far tends to have a very weak strength or adhesion of the film after heat treatment, resulting in limitation of surface treatment method and excessive dropout. That is, the phenomenon that the carbon nanotubes 41 fall off from the cathode 30 according to the surface treatment frequently occurs. In addition, the adhesion of the carbon nanotube 41 film is weak, the dropout phenomenon of the carbon nanotube 41 film due to the applied electric field may occur, which may cause a problem of deteriorating electron emission characteristics.

The technical problem to be achieved by the present invention is to prepare a carbon nanotube emitter for electric field emission that can improve the adhesion of the carbon nanotube film to the underlying film quality using a new binder when forming the carbon nanotube film To provide a way.

One aspect of the present invention for achieving the above technical problem, proposes a method for producing a carbon nanotube emitter using a silicon-based polymer.

The manufacturing method comprises the steps of preparing a paste by mixing carbon nanotubes powder and silicon-based polymer, introducing a cathode, and applying the paste on the cathode to apply carbon nanotubes. Forming a film, heat treating the carbon nanotube film so that the silicon-based polymer mixed in the applied paste binds the carbon nanotubes on the cathode, and curing the silicon-based polymer, and Surface treatment may be configured to include the step of inducing the end of the carbon nanotube to be exposed to the outside of the surface.

Here, the silicon-based polymer may be methyl phenyl silicon resin.

The preparing of the paste may further include adding alpha terpineol as an additive to maintain the viscosity in the paste.

Coating the paste to form a carbon nanotube film may be performed by a printing method.

According to the present invention, the adhesion of the carbon nanotube film to the lower film quality can be improved, and the carbon nanotube film can have an increased strength.

Hereinafter, the present invention will be described in detail with reference to specific embodiments. However, embodiments of the present invention described may be modified in many different forms, and the scope of the present invention should not be construed as being limited by the embodiments described below. It is to be understood that the embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art. Therefore, it is preferable to understand that the shape of an element etc. in the drawing are exaggerated in order to emphasize clearer description. Elements denoted by the same reference numerals in the drawings means the same element. In addition, where a layer is described as being "on" another layer or substrate, the layer may exist in direct contact with the other layer or substrate, or a third layer may be interposed therebetween. Can be.

Hereinafter, with reference to the accompanying drawings will be described embodiments of the present invention;

In the embodiment of the present invention, when forming a carbon nanotube film including carbon nanotubes in order to use the carbon nanotubes as an emitter, a binder that serves to hold the carbon nanotubes is used as a silicon-based polymer. present.

Currently, carbon nanotubes can implement a very low threshold voltage for generating and emitting electrons, and many studies have been attempted to apply them to displays and light emitting devices. In particular, the research for applying carbon nanotubes as cathodes to cathodes, which are electron generating devices of CRTs or field emission display devices, has been in progress.

In order to use carbon nanotubes in a cathode, these carbon nanotubes are bound or grown on a medium to be used as a cathode. In other words, there is a method of using carbon nanotubes as a powder and a method of directly growing on a cathode in a vacuum chamber. Growing in vacuum chambers is known to have costly vulnerabilities. On the other hand, the method of forming a shape into a thick film using powder has advantages of cost and easy process.

As a method of forming a shape with a thick film, a printing method using a polymer resin and a method using a photosensitive resin can be used. The printing method allows for simplicity in the process and versatility in the choice of polymer resins used as binders. On the other hand, when the photosensitive resin is used, it is difficult to uniformly disperse the carbon nanotubes in the process of limiting the photosensitive resin and preparing the suspension. Example of the present invention proposes to form a carbon nanotube film using a binder solution in which carbon nanotubes are dispersed using a printing method in order to overcome the difficulties in using a photosensitive resin.

When carbon nanotubes are used as emitters for field emission, carbon nanotubes must not lie on the surface of the underlying medium, such as the cathode, in order to emit electrons at relatively low voltages and to achieve good electrical properties. You should stand upright or at an angle. This is to make it easier for the electrons to stick out from the ends of the carbon nanotubes.

Substantially examining the carbon nanotubes in detail at the particle level, the shape of the particles of the carbon nanotubes is a tube shape having a width of about 30 nm or less and a length of about several μm. Therefore, when a film is formed using the powder of carbon nanotubes and observed with a scanning electron microscope, it can be observed that the particles of the carbon nanotubes lie parallel to the glass surface serving as the substrate. More carbon nanotubes lie down, resulting in a lower current density and a higher voltage for emitting electrons. Therefore, in order to increase the current density emitted from the carbon nanotubes in order to have the carbon nanotubes upright on the substrate surface in the carbon nanotube film, the carbon nanotube film is generally formed by a thick film method or the like. Surface treatment is performed on the surface in various ways.

In such a surface treatment process, the phenomenon in which the carbon nanotube film falls from the lower medium may frequently occur. In the embodiment of the present invention, a method of increasing the adhesion or adhesion of the carbon nanotube film formed by introducing a silicon-based polymer as a new binder is disclosed. present.

Surface treatment of the carbon nanotube film formed by screen printing or the like is performed after heat treatment of the carbon nanotube film having a shape. Heat treatment is a process of curing the silicon-based polymer used as a binder constituting the carbon nanotube film. After the carbon nanotube film is formed by using the binders up to now, the film formed through heat treatment tends to have a very weak strength or adhesion, and thus the limitation of the surface treatment method and excessive dropout of the film occur frequently.

Since the silicon-based polymer proposed in the embodiment of the present invention implements a bond based on very strong silicon through heat treatment, the carbon nanotube film exhibits very strong strength and bonding strength or adhesion and adhesion. Accordingly, it is possible to more effectively prevent the phenomenon that the carbon nanotube film falls off during subsequent surface treatment. In addition, when a strong electric field is applied to the carbon nanotube film for field emission, the phenomenon of the carbon nanotube film falling off can be effectively prevented.

FIG. 5 is a process flowchart schematically illustrating a method of manufacturing a carbon nanotube emitter for electric field emission according to an embodiment of the present invention.

6 is a cross-sectional view schematically illustrating a carbon nanotube emitter formed by a method of manufacturing a carbon nanotube emitter for electric field emission according to an embodiment of the present invention.

5 and 6, a carbon nanotube film is formed on the bottom film of any particular medium to produce a carbon nanotube emitter. In this case, the carbon nanotube film may be formed by various methods, but will be described in detail by taking a case where the carbon nanotube film is formed by a screen printing method using a paste.

In order to form the carbon nanotube film by screen printing, a paste to be used for printing is first prepared by mixing the carbon nanotube and the silicon-based polymer (501 in FIG. 5). The carbon nanotubes may be made of powder. Various methods for synthesizing carbon nanotubes have been developed. For example, carbon nanotube powder may be synthesized using arc discharge or powdered carbon nanotubes grown by chemical vapor growth may be used.

Silicone polymer used as a binder has a polymer structure centered on a silicon element. For example, methyl phenyl silicon resin may be used as the silicon-based polymer.

The carbon nanotubes of the powder and the silicon-based polymer as a binder are mixed to prepare a paste for printing. At this time, the viscosity adjustment additive may be further added to the paste so that the viscosity of the silicone-based polymer is more suitable for paste production. As such additives, alpha terpineol may be used. In addition, various additives may be added in the preparation of such pastes, which have other functions than the viscosity adjustment as necessary.

After the carbon nanotube-silicone polymer paste is prepared as described above, a carbon nanotube film is formed using the paste (503 of FIG. 5). At this time, the cathode 300 may be introduced as shown in FIG. 6 as a lower film on which the carbon nanotube film 400 is to be formed. In the case where the field emission carbon nanotube emitter described in the embodiment of the present invention is used in the field emission display as shown in FIG. 2, the cathode 300 is formed as the lower film quality on which the carbon nanotube film 400 is to be formed. Will be introduced. The cathode 300 may be in a state formed on the glass substrate 100 in the case of the field emission display.

The carbon nanotube-silicone-based polymer paste is coated on the cathode 300 by screen printing. In this case, a stainless steel No. 325 mesh may be used as a printing mesh. In addition, this screen printing method has the advantage of giving a shape to the carbon nanotube film 400 with the coating through printing. That is, the printed carbon nanotube film 400 may be patterned in a shape that occupies a predetermined area.

The carbon nanotube film 400 is printed and then heat treated to cause a curing reaction on the silicon polymer of the paste to be cured (505 in FIG. 5). The heat treatment may proceed at a temperature of approximately 400 ° C. Accordingly, the carbon nanotube film 400 is cured to bind to the lower film quality, for example, the cathode 300. As shown in FIG. 6, the silicon-based polymer (450 of FIG. 6), for example, methyl phenyl silicone resin, is cross-liked around the silicon element by such heat treatment to harden to a silicide shape. . The silicon-based polymer cured in silicite shape holds the carbon nanotubes 410, thereby greatly improving the strength of the membrane, and not allowing the carbon nanotubes 410 to fall off. Will be maintained. That is, the cured silicon-based polymer 450 is to hold the carbon nanotubes to strongly bind to the cathode 300 of the lower film quality. This is because the silicon-based polymer 450 is cured into a silicide-like polymer by heat treatment.

The carbon nanotube film 400 heat-treated as described above is surface treated to induce the carbon nanotubes 410 to be exposed to the outside of the surface of the film 400 (507 in FIG. 5). This surface treatment process can proceed in a variety of known ways. For example, sand paper may be used to rub the surface to expose the ends of the carbon nanotubes 410.

As described above, the surface treatment process is often performed by applying a physical force to the carbon nanotube film 400. However, when the cured silicon-based polymer 450 is fixed to the carbon nanotubes 410 as in the embodiment of the present invention, since the strength of the carbon nanotube film 400 is realized very high, in the surface treatment process The carbon nanotube film 400 may be effectively prevented from falling off and falling off from the surface of the cathode 300.

Through this process, a carbon nanotube emitter for field emission is constructed as shown in FIG. 6. Such carbon nanotube emitters may be used for field emission of light emitting devices, and may be applied as field emission emitters to field emission display devices as described with reference to FIGS. 2 and 3.

As mentioned above, although this invention was demonstrated in detail through the specific Example, this invention is not limited to this, It is clear that the deformation | transformation and improvement are possible by the person of ordinary skill in the art within the technical idea of this invention.

According to the present invention as described above, the paste for printing can be prepared by mixing the carbon nanotubes and the silicon-based polymer. The heat treatment of the printed carbon nanotube film by such a paste causes the silicone-based polymer to cure to a silicide shape and strongly bind the carbon nanotubes to the lower film quality, for example, the cathode, and to greatly increase the strength of the entire film. As such, the strength of the carbon nanotube film can be greatly increased, so that the carbon nanotube film can be effectively prevented from falling off during the surface treatment of the carbon nanotube film. In addition, when the emitter for the field emission is manufactured using the carbon nanotube film as described above and applied to the field emission device, a strong electric field is applied to the carbon nanotube to effectively prevent the carbon nanotube from falling off.

1 is a schematic cross-sectional view for explaining a conventional field emission display in the form of a tip (tip).

2 is a schematic cross-sectional view for explaining a field emission display in the form of typical carbon nanotubes.

3 is an enlarged cross-sectional view of part A of FIG. 2.

4 is a cross-sectional view schematically illustrating the state of carbon nanotubes when a carbon nanotube film is formed of a thick film.

FIG. 5 is a process flowchart schematically illustrating a method of manufacturing a carbon nanotube emitter for electric field emission according to an embodiment of the present invention.

6 is a cross-sectional view schematically illustrating a carbon nanotube emitter formed by a method of manufacturing a carbon nanotube emitter for electric field emission according to an embodiment of the present invention.

Claims (4)

Preparing a paste by mixing carbon nanotubes powder and a silicon-based polymer; Introducing a cathode; Applying the paste on the cathode to form a carbon nanotube film; Curing the silicon-based polymer by heat-treating the carbon nanotube film so that the silicon-based polymer mixed in the applied paste binds the carbon nanotubes on the cathode; And Surface treating the carbon nanotube film to induce the ends of the carbon nanotubes to be exposed to the outside of the surface of the carbon nanotube emitter. The method of claim 1, wherein the silicon-based polymer A method for producing a carbon nanotube emitter, characterized in that it comprises methyl phenyl silicon resin. The method of claim 1, wherein preparing the paste The method of manufacturing a carbon nanotube emitter further comprises the step of adding alpha terpineol as an additive to maintain the viscosity in the paste. The method of claim 1, Forming a carbon nanotube film by applying the paste is a method for producing a carbon nanotube emitter, characterized in that the printing is carried out.