KR100565199B1 - Carbon nanotube field emission device and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a carbon nanotube field emission device and a method for manufacturing the same. In particular, in order to prevent beam spread in a planar carbon nanotube field emission device structure, the electric field is distorted by surrounding the carbon nanotube electron emission source with an insulating film. The present invention relates to a carbon nanotube field emission device and a manufacturing method for reducing a region where a beam spreads. In the conventional planar field emission device using carbon nanotubes, since the carbon nanotubes are exposed at the top of the lower plate, the emitted electrons are widely spread and the beam spreading problem that emits the phosphors of adjacent cells is severe. There was a fatal problem that was greatly lowered. In order to solve the above problems, the present invention forms an insulating film on a portion where a carbon nanotube, which is an electron emission source of the planar field emission device, is formed, and then etches away only a portion where the electron emission source is to be formed, By forming carbon nanotubes, the carbon nanotubes are surrounded by an insulating film to generate electric field distortions due to vacuum and discontinuity of the insulating film, thereby preventing electrons from being emitted by the addition of a very simple process. There is an excellent effect that can suppress the light blur and greatly improve the sharpness of the image.

Description

Carbon nanotube field emission device and manufacturing method {CARBON NANOTUBE FIELD EMISSION DEVICE AND MANUFACTURING METHOD THEREOF}

1 is a cross-sectional view showing the structure of a conventional normal gate type field emission device.

2 is a cross-sectional view showing the structure of a conventional undergate type field emission device.

3 is a cross-sectional view showing the structure of a conventional coplanar gate type field emission device.

Figure 4 is a cross-sectional view showing the structure of an embodiment of the present invention.

5a to 5b are graphs showing the degree of beam spread according to the conventional structure and the structure of one embodiment of the present invention.

Figure 6a to 6d is a cross-sectional view showing a manufacturing process of an embodiment of the present invention.

*** Explanation of symbols for main parts of drawing ***

30: glass substrate 31: gate electrode

32: lower insulating film 33: cathode electrode

34: upper insulating film 35: carbon nanotubes

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon nanotube field emission device and a method for manufacturing the same. In particular, in the planar carbon nanotube field emission device structure, the electric field is distorted by surrounding the carbon nanotube electron emission source with an insulating film to prevent beam spreading. The present invention relates to a carbon nanotube field emission device and a manufacturing method for reducing a beam spreading area.

Due to the rapid development of information and communication technology and the demand for the visualization of diversified information, the demand for electronic displays is increasing, and the required display forms are also diversified. For example, in an environment where mobility is emphasized such as a portable information device, a display having a small weight, volume, and power consumption is required, and when used as an information transmission medium for the public, display characteristics of a large viewing angle are required. In addition, in order to satisfy such demands, electronic displays require conditions such as large size, low price, high performance, high definition, thinness, and light weight, so that light and thin that can replace the existing CRT are required to satisfy these requirements. There is an urgent need for the development of flat panel display devices. Recently, as the needs of various display devices have been applied to display fields, devices using field emission have been actively developed for thin film displays that can provide high resolution while reducing size and power consumption.

The field emission device is attracting attention as a next-generation flat panel display for overcoming all the disadvantages of flat panel displays (LCD, PDP, VFD, etc.) currently being developed or produced. The field emitter display has a simple electrode structure, high-speed operation based on the same principle as the CRT, and has the advantages that the display must have such as infinite color, infinite gray scale, high brightness, and high video rate. have.

The field emission display device uses a quantum mechanical tunneling phenomenon in which electrons come out of the vacuum from the metal or conductor when a high field is applied to the metal or conductor surface (emitter) in the vacuum. At this time, the device exhibits the current-voltage characteristic according to the Fowler-Nordheim law.

Recently, the importance of field emission devices using carbon nanotubes has been recognized because of their excellent electron emission characteristics at a relatively low vacuum due to their large ratio of diameter, mechanical strength, and chemical stability. Since such carbon nanotubes have a small diameter (about 1.0 to several tens of nm), the field enhancement factor is considerably superior to conventional microtip type spin-emitting field emission tips, resulting in low electron emission. Since it can be made in a critical field (turn-on field, about 1 to 5 [V / μm]), there is an advantage that can reduce the power loss and production cost.

The carbon nanotubes may be formed by screen printing in the form of paste on the cathode or grown by chemical vapor deposition, and may be used as a photosensitive paste in order to expose the backside to the backside. do.

The structure of the conventional field emission device will be described in detail with reference to the accompanying drawings.

1 to 3 show three electrode structures of a field emission device using a conventional carbon nanotube.

1 is a conventional normal gate structure, in which an electron emission source consisting of a cathode electrode 2, an insulator 3, and a gate 4 coated with carbon nanotubes 5, and emitted electrons (e) The anode part (anode and fluorescent substance) 9 which collides with), the spacer 7 which supports the upper and lower plates 1, 8, and the sealing part 6 which hold | maintain a vacuum airtightness are comprised.

When a sufficient voltage is applied between the gate electrode 4 and the cathode electrode 2 as a driving voltage, electrons are emitted from the tips of the carbon nanotubes 5 to the anode voltage of the anode portion 9 composed of the anode electrode and the phosphor. The light is emitted by colliding with the phosphor of the anode part 9 while being accelerated by it.

Looking at the structure of the electron emission source in more detail, as shown, the cathode electrode 2, the insulating layer 3, the gate electrode 4 is formed on the substrate 1 and then the gate electrode through a photolithography process 4 and the insulating layer 3 are etched to form through holes, and then carbon nanotubes 5 are formed on the exposed cathode electrode 2. This structure replaces the electron emission source with carbon nanotubes in the structure of the conventional microtip type field emission device, and mainly uses a growth method through chemical vapor deposition. However, the structure has a high possibility of locally emitting electrons only in the vicinity of the hole having the strongest electric field, has a large amount of leakage current to the gate electrode 4 due to an asymmetrical electric field distribution, and facilitates a large area because the process procedure is difficult. As we do not, use decreases.

This has led to the emergence of planar structures in which the gate is positioned below the cathode electrode or in the same plane instead of the basic gate structure, some of which are shown in FIGS. 2 and 3.

First, FIG. 2 is a cross-sectional view of an under gate structure field emission device, in which an electric field causing electron emission is applied through the gate electrode 11 under the nanotube 14 as shown. The gate electrode 11 is formed on the glass substrate 10, and then the insulating layer 12 and the cathode electrode 13 are sequentially formed on the glass substrate 10, and then the carbon nanotubes are formed on the upper side or the side of the cathode electrode 13. The electron emission source which consists of 14 is formed and comprised. There are two methods for forming the carbon nanotubes 14, namely, a method using a photosensitive carbon nanotube paste for using a photoresist technique and a method using a non-photosensitive carbon nanotube paste. Recently, photosensitive carbon nanotube pastes and back exposure are often used to form precise electron emission sources.

3 is a cross-sectional view of a coplanar structure field emission device, in which a gate electrode 22 and a cathode electrode 23 are formed on the same layer as shown. That is, the gate electrode 22 and the cathode electrode 23 are formed on the insulating layer 21 formed on the glass substrate 20 in a single process, and then the method described above on the side or the top of the cathode electrode 23 is also performed. Carbon nanotubes 24 are formed by applying a photosensitive or non-photosensitive carbon nanotube paste such as.

The planar field emission device as described above has the advantage of reducing the driving voltage and increasing the area, but there are problems of abnormal light emission caused by dark current due to direct exposure to the anode field, and widespread emission of the electron beam.

Here, the electron beam spreads widely means that the emitted electrons reach the phosphors of other cells instead of the corresponding cells to emit light of adjacent cells, which causes a fatal problem of light bleeding and sharpness reduction. In particular, the undergate structure has a problem in that the image expression power is low despite the ease of implementation because electrons are spread to a considerably wide area.

As described above, in the planar field emission device using carbon nanotubes, since the carbon nanotubes are exposed at the top of the lower plate, electrons are widely spread and the beam spreading problem of emitting phosphors in adjacent cells is severe. There was a fatal problem that smeared or sharply lowered sharpness.

In order to solve the above-mentioned problems, the present invention forms an insulating film on a portion where carbon nanotubes, which are electron emission sources of the planar field emission device, are to be formed, and then partially removes only portions where the electron emission source is to be formed, By forming carbon nanotubes on the removed portions, the carbon nanotubes are surrounded by an insulating film to generate electric field distortion due to vacuum and discontinuity of the insulating film so that the emitted electrons do not spread so that the electron emission source and the phosphor can be corresponded one-to-one. It is an object of the present invention to provide a carbon nanotube field emission device and a manufacturing method.

In order to achieve the above object, an embodiment of the present invention comprises a gate electrode, a lower insulating film, and a cathode electrode disposed in turn on the upper glass substrate; An upper insulating film formed on the entire surface of the structure and having a through hole in an electron emission region; And carbon nanotubes formed to contact the cathode electrode in the through hole of the insulating layer.

The upper insulating film is positioned to include the initial traveling direction of the electrons emitted from the carbon nanotubes, and generates electric field distortion that prevents the initial progress of the electrons due to the discontinuity of the vacuum and the insulating film.

In addition, another embodiment of the present invention comprises the steps of forming a gate electrode, a lower insulating film, a cathode electrode on the glass substrate; Forming an upper insulating film on an upper surface of the cathode electrode and forming a through hole in an electron emission source forming portion; And forming carbon nanotubes in contact with the cathode electrode exposed by the through-holes.

Embodiments of the present invention as described above will be described in detail with reference to the accompanying drawings.

4 is a cross-sectional view showing the structure of an embodiment of the present invention, and an upper insulating film 34 surrounding the carbon nanotubes 35 is further formed in the undergate type field emission device lower panel configuration. In general, the undergate type field emission device as shown in the drawing proceeds initially in a direction opposite to the cathode electrode 33 (right in the drawing) when electrons are emitted from the carbon nanotubes 35 and then accelerated by the top anode voltage. Will be. However, in this structure, since the upper insulating film 34 is formed on the right side of the carbon nanotubes 35, the electric field is distorted as compared with the general case of being left in a vacuum state. The electric field generated by the vacuum and the discontinuity of the insulating film 34 affects the opposite direction of the initial traveling direction of the emitted electrons, thereby preventing the electrons from spreading away by the initial speed. Even if the above structure is used, the driving voltage of the device does not change since no voltage is applied to the upper insulating film 34.

5a to 5b compare the spread of the electron beam emitted from the undergate structure shown in the embodiment of the present invention and the electron beam spread in a structure without a conventional upper insulating film, Figure 5a is a conventional undergate structure The thickness of the lower insulating film is 10 μm, and FIG. 5B is measured by the structure of the exemplary embodiment of the present invention, and the thickness of the lower insulating film is also 10 μm, except for the voltage conditions and the structure of the upper insulating film. It is a case where the value of is equal to FIG.

In the case of FIG. 5A without the upper insulating film, the electron beam was formed at 170 to 500 μm as shown, and in the case of FIG. 5B having the upper insulating film structure, the electron beam was formed at 220 to 380 μm. That is, in the case of using the structure of the present invention, even with the same driving voltage and the basic structure, it is possible to obtain a focus enhancement in which the beam spread region of several hundred μm is reduced.

6A to 6D are cross-sectional views illustrating a process for manufacturing an embodiment of the present invention, in which a negative photosensitive carbon nanotube paste and a backside exposure are used as shown. Note, however, that the present invention encompasses all structures and all methods of fabricating such structures that allow the dielectric of the vacuum and discontinuity to surround the carbon nanotube electron emission source to prevent the beam from spreading by electric field distortion. do.

First, as shown in FIG. 6A, the gate electrode 31 is formed on the glass substrate 30. Here, in the case of using the glass substrate 30 having the ITO electrode formed thereon, the gate electrode 31 may be formed by patterning the ITO electrode, and in the case of using the glass substrate 30 in which the ITO electrode is not formed, the electrode transparent to the ultraviolet region. To form the gate electrode 31.

Next, as shown in FIG. 6B, a lower insulating film 32 is formed by screen printing or the like on the gate electrode 31 with an insulating material transparent to the ultraviolet region, and a material to be used as a cathode electrode is formed thereon. Subsequently, the cathode electrode 33 is formed by patterning. In this case, the material to be used as the cathode electrode may be used that is opaque to the ultraviolet region and may be transparent. If the carbon nanotubes to be formed later will be formed on the side of the cathode electrode 33, using an opaque material, If it is to be formed on top, use a transparent material. In addition, since the lower insulating layer 32 may be damaged by the etching of the cathode electrode 33, an etch stop layer may be formed between the lower insulating layer 32 and the cathode electrode 33. The transparent silicon oxide film etc. are used.

Next, as shown in FIG. 6C, an upper insulating film 34 is formed on the cathode electrode 33 using a dielectric opaque to the ultraviolet region. For this purpose, a chemical vapor deposition method or a printing method using a dielectric paste may be used. Thereafter, the upper insulating film 34 of the portion where the electron emission source is to be formed is etched to form through holes, and if necessary (when carbon nanotubes are formed on the side of the cathode electrode 33), the cathode electrode 33 is exposed. Can be removed by etching. Here, the thickness of the upper insulating film 34 is preferably smaller than the thickness of the lower insulating film 32 and thicker than the thickness of the carbon nanotubes to be formed later.

Next, as shown in FIG. 6D, a negative photosensitive carbon nanotube paste is applied to a portion defined by the opaque cathode electrode 33 and the upper insulating film 34, and exposed to the rear surface to expose carbon nanotubes 35 as electron emission sources. ). When the transparent cathode electrode 33 is used, carbon nanotubes 35 may be formed on the cathode electrode 33 as defined by the upper insulating layer 34 pattern.

As described above, the present invention can arrange the dielectric structure adjacent to the carbon nanotubes as the electron emission source to cause electric field distortion to reduce the spread of the electron beam so that the emitted electron beam can be concentrated on the phosphor.

In the carbon nanotube field emission device and the manufacturing method of the present invention as described above, after forming an insulating film on the portion where the carbon nanotube which is the electron emission source of the planar field emission device is to be formed, only the portion where the electron emission source is to be formed is removed by etching By forming carbon nanotubes on the removed portions, the carbon nanotubes are surrounded by an insulating film, which causes electric field distortion due to vacuum and discontinuity of the insulating film, thereby preventing the electrons emitted by the addition of a very simple process. There is an excellent effect that one to one correspondence with the phosphor to suppress the light blur and greatly improve the sharpness of the image.

Claims (6)

A gate electrode, a lower insulating film, and a cathode electrode sequentially disposed on the lower glass substrate; An upper insulating film formed on the entire surface of the structure and having a through hole in an electron emission region; And a carbon nanotube formed in contact with the cathode electrode in the through hole of the insulating film. The carbon nanotube field emission device of claim 1, wherein a thickness of the upper insulating layer is smaller than a thickness of the lower insulating layer and thicker than a thickness of the carbon nanotubes. The method of claim 1, wherein the upper insulating film is positioned to include the initial traveling direction of the electrons emitted from the carbon nanotubes and generates an electric field distortion that prevents the initial progress of the electrons by the discontinuity of the vacuum and the insulating film. Carbon nanotube field emission device. Forming a gate electrode, a lower insulating film, and a cathode electrode in order on the glass substrate; Forming an upper insulating film on an upper surface of the cathode electrode and forming a through hole in an electron emission source forming portion; And forming carbon nanotubes so as to contact the cathode electrodes exposed by the through-holes. The method of claim 4, wherein the cathode electrode exposed by the through-holes is etched away, and the carbon nanotubes are formed to contact the side surfaces of the exposed cathode electrodes. 6. The method of claim 4, wherein the gate electrode and the lower insulating film are formed using a material transparent to ultraviolet light, the cathode electrode is formed using a material opaque to ultraviolet light, and the upper insulating film is formed using a material opaque to ultraviolet light. After the carbon nanotubes are coated in the form of a photosensitive paste, the carbon nanotube field emission device is characterized in that it is formed by back exposure.

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