KR101000662B1 - Field emission device - Google Patents

Abstract

The present invention provides a triple electrode formed by a carbon nanotube, a cathode electrode, and an insulating layer by forming a shielding electrode between a cathode and a gate electrode formed on the same plane in a counter electrode undergate structure using a carbon nanotube as a field emission emitter. And a field emission device capable of shielding the electric field from the electric field by the gate electrode and improving the uniformity of the field emission, comprising: a gate line formed over the glass substrate; An insulating layer having a through hole formed through the gate line to expose a portion of the gate line; A cathode electrode having a carbon nanotube formed on a portion of the insulating layer; A gate electrode connected to the exposed gate line and formed on the same plane as the cathode electrode; And a shielding electrode disposed between the gate electrode and the cathode electrode and formed on a portion of the insulating layer.

Description

Field emission device {FIELD EMISSION DEVICE}

1 is a cross-sectional view showing an example of a three-electrode field emission device using a conventional carbon nanotube.

Figure 2 is a cross-sectional view showing an example of the field emission device of the undergate structure using a conventional carbon nanotube.

3 is a plan view and a cross-sectional view showing an example of a field emission device having a counter electrode undergate structure using a conventional carbon nanotube.

4 is a plan view and a cross-sectional view showing an example of the field emission device of the counter electrode undergate structure of the present invention.

5A to 5B are plan views showing still another example of the field emission device of the counter electrode undergate structure according to the present invention;

DESCRIPTION OF REFERENCE NUMERALS

30: glass substrate 31: gate line

32: insulating layer 33: cathode electrode

34: gate electrode 35: carbon nanotube

40: shielding electrode

The present invention relates to a field emission device, in particular, in a counter electrode undergate structure using carbon nanotubes as field emission emitters, a shielding electrode is formed between a cathode electrode and a gate electrode formed on the same plane to form a carbon nanotube and a cathode. The field emission element which can shield the triple point formed by the electrode and the insulating layer from the electric field by a gate electrode, and can improve the uniformity of field emission.

 With 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 cost, high performance, high definition, thinness, and light weight, and thus, light and thin that can replace the existing CRT 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 information communication flat panel display that overcomes all the disadvantages of flat panel displays (LCD, PDP, VFD, etc.) currently being developed or produced. The field emission device has a simple electrode structure, high-speed operation using the same principle as the CRT, and has the advantages of a display such as infinite color, infinite gray scale, high luminance, and high video rate. .

Field emission devices utilize quantum mechanical tunneling which causes electrons to exit the vacuum from the metal or conductor when a high field is applied on the metal or conductor surface (emitter) in the vacuum. In this case, the device exhibits current-voltage characteristics according to the Fowler-Nordheim law. The field emission device is composed of an anode portion which emits an electron emission source and the emitted electrons collide with each other to emit light, a spacer supporting the upper and lower plates, and a sealing portion for maintaining a vacuum tightness.

Recently, the importance of the field emission device using the carbon nanotubes (CNT) because of the mechanically strong, chemically stable and excellent electron emission characteristics at a relatively low vacuum degree has been recognized. Since such carbon nanotubes have a small diameter (about 1.0 to several tens of nanometers), the field enhancement factor is considerably superior to the conventional microtip type spin emission field emission tips, and thus the emission threshold is low. Since it can be made in a turn-on field (about 1 to 5 [V / μm]), there is an advantage of reducing power loss and production cost. Referring to the conventional field emission device and a method of manufacturing the same in detail with reference to the accompanying drawings as follows.

1 is a cross-sectional view of an example of a three-electrode structure of a field emission device using a conventional carbon nanotube. As shown, the resistive layer 12, the insulating layer 14, and the gate electrode 15 are sequentially formed on the silicon substrate 11, and the gate electrode 15 and the insulating layer 14 are formed by photolithography. After etching a portion to form a hole, the catalyst transition metal layer 13 is formed on the resistive layer 12 at the bottom of the hole through evaporation, and the entire silicon substrate 11 is about 600-900 [deg.] C. The carbon nanotubes 16 are selectively formed only on the catalyst transition metal layer 13 through a thermal chemical vapor deposition method using a hydrocarbon gas or a plasma chemical vapor deposition method by heating to a temperature range. .

In this case, since the carbon nanotubes 16 are selectively formed only on the catalyst transition metal layer 13, the larger the area of the catalyst transition metal layer 13, the larger the area of the carbon nanotubes 16. As such, when the area of the carbon nanotubes 16 increases, the electric field applied through the gate electrode 15 is not concentrated, so that the beam of the emitted electrons is spread and the electron emission region is not even. Only the local electron emission is likely to occur only, and the leakage current to the gate electrode 15 is problematic due to an asymmetric electric field distribution.

In order to solve the above problems, structures of the carbon nanotube field emission device having the gate electrode positioned at the same or lower position than the cathode electrode have been proposed.

2 is a cross-sectional view of an example of a field emission device having an under gate structure using a conventional carbon nanotube. As shown, the electric field causing the electron emission is applied to the gate electrode 21 under the carbon nanotubes 24. The gate electrode 21 is formed on the glass substrate 20, and the insulating layer 22 and the cathode electrode 23 are sequentially formed on the glass substrate 20, and then the carbon nanotube mixed slurry is formed on the cathode electrode 23. Is applied by screen printing or the like to form a carbon nanotube 24 through a series of binder removal processes.

However, the field emission device of the undergate structure has a disadvantage in that the turn-on voltage is relatively high because the gate electrode 21 is positioned below the cathode electrode 24, and is abnormal due to the high pressure of the upper anode electrode (not shown). There is a problem that light emission may appear.

3 is a plan view and a cross-sectional view of a counter electrode undergate structure field emission device using a conventional carbon nanotube, and unlike FIG. 2, through holes are formed in the upper insulating layer 32 of the lower gate line 31. Thus, the gate electrode 34 is formed on the same plane as the cathode electrode 33. As shown in the drawing, the gate electrode 34 and the cathode electrode 33 are formed on the same plane, and the turn-on voltage at which the electron emission occurs in the carbon nanotube 35 is low, and thus the driving voltage can be lowered. . This structure insulates a portion of the gate line 31 by exposing and etching processes so that the gate line 31 passing under the cathode electrode 33 is coplanar with the cathode electrode 33. A through hole is formed in the layer 32 and the part is filled with metal.

However, in the field emission device of the counter electrode undergate structure, a triple point is formed between the cathode electrode, the CNT, and the insulating layer, where an electric field is formed by the voltage applied to the gate electrode, and the CNTs near the triple point are different from each other. Compared to CNTs, the shielding effect is relatively low, which results in a large improvement in the electric field, resulting in a large field emission compared to other points. Since the direction of the electric field is also distorted by the triple point, the field emission occurs in a direction different from that of the CNT located elsewhere, which causes a problem of beam spreading.

In the field emission device of the count electrode undergate structure using the conventional carbon nanotubes as described above, the triple point formed between the cathode electrode, the CNT, and the insulating layer increases the field emission by the electric field caused by the voltage applied to the gate electrode. There was a problem of non-uniformity and beam spreading.

Accordingly, in view of the above problems, the present invention forms a shielding electrode for shielding a triple point formed between the cathode electrode and a gate electrode formed on the same plane from an electric field of the gate electrode, thereby forming a triple point formed by the CNT, the cathode electrode, and the insulating layer. It is an object of the present invention to provide a field emission device capable of shielding from an electric field by a gate electrode and improving the uniformity of field emission.

Gate line formed on the glass substrate of the present invention for achieving the above object; An insulating layer having a through hole formed through the gate line to expose a portion of the gate line; A cathode electrode having a carbon nanotube formed on a portion of the insulating layer; A gate electrode connected to the exposed gate line and formed on the same plane as the cathode electrode; And a shielding electrode disposed between the gate electrode and the cathode electrode and formed on a portion of the insulating layer.

The shielding electrode may be formed to be spaced apart from the cathode electrode.

In addition, the shielding electrode is connected to the cathode electrode, and has the same potential as the cathode electrode.

The shielding electrode may be formed when the cathode electrode is formed.

With reference to the accompanying drawings, a preferred embodiment of the field emission device of the present invention having the above characteristics will be described.

4 is a plan view and a cross-sectional view of a lower plate of the counter electrode undergate structure field emission device using carbon nanotubes according to the present invention. As shown in the drawing, the shielding electrode 40 is added between the gate electrode 34 and the cathode electrode 33 in the bottom plate structure of the conventional counter electrode undergate structure field emission device.

The shielding electrode 40 generates a triple point formed by the cathode electrode 33, the CNT 35 formed on the cathode electrode 33, and the insulating layer 32 by the voltage applied to the gate electrode 34. It performs a function of shielding from an electric field, and is formed spaced apart from the cathode electrode 33, as shown.                     

Then, the manufacturing process for the field emission device of the counter electrode undergate structure according to the present invention having the structure as described above is as follows.

First, a gate layer 31 is formed by forming and patterning a conductive layer on the glass substrate 30, which is a lower substrate. The gate line 31 serves as a common line connecting the gate electrode 34.

Next, after the insulating layer 32 is formed on the entire upper surface of the formed structure, the insulating layer 32 is etched to expose a portion of the gate line 31 to form a through hole.

Next, a conductive layer is formed on the structure to fill the through hole, and a conductive layer is formed on the structure and then patterned to form a gate layer 34 and a cathode connected to the gate line 31 through the through hole. The electrode 33 and the shielding electrode 40 are formed.

Finally, carbon nanotubes 35 are formed at the edges of the cathode electrode 33 by screen printing.

As such, the present invention does not need to add a new process because the shielding electrodes are formed together at the time of forming the cathode electrode.

As can be seen from the plan view of the field emission device shown in FIG. 4, the shielding electrode 40 is formed in a floating type spaced apart from the cathode electrode 33, but may be formed in connection with the cathode electrode 33. have.                     

5A and 5B show a bottom plan view of yet another embodiment according to the present invention. As shown, since the shielding electrode 40 is connected to the cathode electrode 33, it is applied to the shielding electrode 40. The potential becomes equal to the potential applied to the cathode electrode 33.

As described above, the present invention can shield the triple point where the cathode electrode, the CNT, and the insulating layer meet by using the shielding electrode from the electric field generated by the gate electrode to uniform the field emission of the CNT.

As described in detail above, the present invention forms a shielding electrode for shielding the triple point formed between the cathode electrode and the gate electrode formed on the same plane from the electric field of the gate electrode, thereby eliminating the triple point formed by the CNT, the cathode electrode, and the insulating layer. There is an effect of shielding from the electric field by the gate electrode and improving the uniformity of the field emission.

Claims (4)

A gate line formed on the glass substrate; An insulating layer having a through hole formed through the gate line to expose a portion of the gate line; A cathode electrode having a carbon nanotube formed on a portion of the insulating layer; A gate electrode connected to the exposed gate line and formed on the same plane as the cathode electrode; And And a shielding electrode disposed between the gate electrode and the cathode electrode and formed on a portion of the insulating layer. delete delete delete

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