KR20070044693A - Electron emission device - Google Patents

Abstract

An object of the present invention is to provide an electron emitting device of a novel structure that can prevent the screen effect to improve the electron emission efficiency. To this end, in the present invention, the first substrate; A cathode electrode disposed on the first substrate; A gate electrode disposed to be electrically insulated from the cathode electrode; An insulator layer disposed between the cathode electrode and the gate electrode to insulate the cathode electrode and the gate electrode; An electron emission source hole formed in the insulator layer and the gate electrode to expose the cathode electrode; A seed layer disposed in the electron emission hole and formed to have a height higher from the periphery toward the center; A catalyst layer formed on the seed layer; And a plurality of electron emission emitters having a distance between the bases attached to the catalyst layer less than the distance between the ends and having a large size.

Description

Electron emission device

1 is a perspective view schematically showing the configuration of a conventional electron emitting device and a display device.

2 is a cross-sectional view taken along the line II-II of FIG.

3 is a cross-sectional view showing rfir surface of the electron emission source of the electron emission device shown in FIGS. 1 and 2;

4 is a cross-sectional view schematically showing the configuration of an electron emitting device according to a first embodiment of the present invention.

5 is an enlarged view of portion IV of FIG. 4;

6 is a cross-sectional view schematically showing the configuration of an electron emitting device according to a second embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

60: spacer 70: phosphor layer

80: anode electrode 90: second substrate

100, 200: electron emission display device

101, 200: electron emission device

102: front panel 103: light emitting space

110: first substrate 120: cathode electrode

130: first insulator layer 131: electron emission source hole

135: second insulator layer 140: gate electrode

145: focusing electrode 150, 250: electron emission source

151: carbon nanotube 251: seed layer

252: catalyst layer 253: electron-emitting material

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron emission element, and more particularly to an electron emission element having an increased electron emission efficiency.

In general, an electron emission device includes a method using a hot cathode and a cold cathode as an electron emission source. Examples of electron emission devices using a cold cathode include field emission device (FED) type, surface conduction emitter (SCE) type, metal insulator metal (MIM) type, metal insulator semiconductor (MIS) type, and ballistic electron surface emitting (BSE) type. ) And the like are known.

The FED type uses the principle that electrons are easily released due to electric field difference in vacuum when a material having a low work function or a high beta function is used as an electron emission source. Molybdenum (Mo), Tip structure with the main material made of silicon (Si) etc., carbon-based materials such as graphite and DLC (Diamond Like Carbon), and recent nano tube or nano wire Devices using nanomaterials such as electron emission sources have been developed.

The SCE type is a device in which an electron emission source is formed by providing a conductive thin film between a first electrode and a second electrode disposed to face each other on a first substrate and providing a micro crack in the conductive thin film. The device uses a principle that electrons are emitted from an electron emission source that is a micro crack by applying a voltage to the electrodes to flow a current to the surface of the conductive thin film.

The MIM type and the MIS type electron emission devices each form an electron emission source having a metal-dielectric layer-metal (MIM) and metal-dielectric layer-semiconductor (MIS) structure, and are disposed between two metals or metals with a dielectric layer interposed therebetween. When a voltage is applied between semiconductors, a device using the principle of emitting electrons is moved and accelerated from a metal or semiconductor having a high electron potential toward a metal having a low electron potential.

The BSE type uses the principle that electrons travel without scattering when the size of the semiconductor is reduced to a dimension area smaller than the average free stroke of the electrons in the semiconductor, thereby forming an electron supply layer made of a metal or a semiconductor on an ohmic electrode. And an insulator layer and a metal thin film formed on the electron supply layer to emit electrons by applying power to the ohmic electrode and the metal thin film.

Among them, the FED type electron emission device can be classified into a top gate type and an under gate type according to the arrangement of the cathode electrode and the gate electrode, depending on the number of electrodes used. It can be divided into a pole tube, a triode or a quadrupole. An example of implementing a display device using an FED type electron emission device is illustrated in FIGS. 1 and 2.

1 is a partial perspective view showing a schematic configuration of a conventional top gate type electron emission display device, and FIG. 2 is a cross-sectional view taken along the line II-II of FIG. 1.

As shown in FIGS. 1 and 2, the conventional electron emission display apparatus 100 includes an electron emission element 101 and a front panel 102 that are arranged side by side to form a light emitting space 103 that is a vacuum. A spacer 60 is provided to maintain a gap between the electron emission element 101 and the front panel 102.

The electron emission device 101 may include a first substrate 110, gate electrodes 140, cathode electrodes 120, and the gate electrode 140 arranged to intersect on the first substrate 110. And an insulator layer 130 disposed between the cathode electrode 120 and the gate electrode 140 to electrically insulate the cathode electrode 120.

Electron emission holes 131 are formed in regions where the gate electrodes 140 and the cathode electrode 120 cross each other, and an electron emission source 150 is disposed therein.

The front panel 102 includes a second substrate 90, an anode electrode 80 disposed on the bottom surface of the second substrate 90, and a phosphor layer 70 disposed on the bottom surface of the anode electrode 80. do.

FIG. 3 schematically shows an enlarged view of the surface of the electron emission source of the electron emission device shown in FIGS. 1 and 2.

As shown in FIG. 3, when the carbon nanotube is used as an electron emission material, the carbon nanotubes 151 distributed on the surface of the electron emission source 150 may not be uniformly distributed, and the carbon nanotubes may be disposed in a specific portion ⓐ. The tube 151 may be concentrated, and the density of the carbon nanotubes 151 may be distributed in a portion ⓑ. In this case, electron emission occurs more smoothly in the portion ⓑ where the carbon nanotubes 151 have a lower distribution density than in the portion ⓐ where the carbon nanotubes 151 are concentrated. This is because the electric field is formed like a line referred to as ⓕ) in the drawing. That is, in the place where the carbon nanotubes 151 are aggregated, since an electric field is not formed around each carbon nanotube 151 and an electric field is formed around the entirety of the concentrated carbon nanotubes 151, The inner carbon nanotubes do not contribute to the electron emission. This phenomenon is called a screen effect, and there is a need to develop an electron emitting device having a new structure that can prevent the screen effect and improve electron emission efficiency. In addition, there is a need to develop an electron emission display device having a significantly improved luminous efficiency due to an increase in luminance as an electron emission amount is increased by using an electron emission element having a new structure capable of preventing such a screen effect.

The present invention is to solve the above problems, it is an object of the present invention to provide an electron emitting device of a novel structure that can improve the electron emission efficiency by preventing the screen effect.

An object of the present invention as described above, the first substrate; A cathode electrode disposed on the first substrate; A gate electrode disposed to be electrically insulated from the cathode electrode; An insulator layer disposed between the cathode electrode and the gate electrode to insulate the cathode electrode and the gate electrode; An electron emission source hole formed in the insulator layer and the gate electrode to expose the cathode electrode; A seed layer disposed in the electron emission hole and formed to have a height higher from the periphery toward the center; A catalyst layer formed on the seed layer; And an electron emission device comprising a plurality of electron emission emitters, wherein the distance between the bases attached to the catalyst layer is less than the distance between the ends, and wherein the evaporation source is large.

Here, the seed layer is preferably formed in a substantially hemispherical shape, the catalyst layer is preferably formed of a metal material or made of a metal salt (metal salt) having a weak acid anion group.

Here, the metal salt preferably includes at least one selected from the group consisting of an acetate group, an oxalate group, and a carbonate group, and the metal salt is iron (Fe), nickel (Ni), cobalt. It is preferable to include at least one selected from the group consisting of (Co) and yttrium (Y).

The display device may further include a second insulator layer covering an upper side of the gate electrode, and a focusing electrode insulated from the gate electrode by the second insulator layer, and disposed on the upper side of the second insulator layer. The anode electrode and the gate electrode may be disposed to extend in a direction crossing each other.

Hereinafter, preferred embodiments of the electron emission device according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 4 is a view schematically showing the configuration of the electron emitting device according to the first embodiment of the present invention, and FIG. 5 is an enlarged view of part V of FIG. 4.

As shown in FIGS. 4 and 5, the electron emission device 200 according to the first embodiment of the present invention may include a first substrate 110, a cathode electrode 120, a gate electrode 140, and a first electrode. An insulator layer 130 and an electron emission source 250.

The first substrate 110 is a plate-shaped member having a predetermined thickness. Quartz glass, glass containing a small amount of impurities such as Na, plate glass, a glass substrate coated with SiO ₂ , aluminum oxide, or a ceramic substrate may be used. have. In addition, when implementing a flexible display apparatus, a flexible material may be used.

The cathode electrode 120 is disposed to extend in one direction on the first substrate 110 and may be made of a conventional electrically conductive material. For example, metals such as Al, Ti, Cr, Ni, Au, Ag, Mo, W, Pt, Cu, Pd or alloys thereof, glass and metals or metal oxides such as Pd, Ag, RuO ₂ , Pd-Ag It may be made of a printed conductor consisting of a transparent conductor such as In ₂ O ₃ or SnO ₂ , or a semiconductor material such as polysilicon.

The gate electrode 140 may be disposed with the cathode electrode 120 and the insulator layer 130 interposed therebetween, and may be made of a conventional electrically conductive material like the cathode electrode 120.

The insulator layer 130 is disposed between the gate electrode 140 and the cathode electrode 120 to insulate the cathode electrode 120 and the gate electrode 140 to generate a short between the two electrodes. prevent.

The electron emission source 250 may include a seed layer 251 formed narrower from a periphery to a central portion, a catalyst layer 252 formed on a surface of the seed layer 251, and an electron emission material formed on the catalyst layer 252. 253).

The seed layer 251 may be made of a material such as, for example, polyimide (PI). In this case, the electron emission source hole 131 may be filled with PI to a predetermined thickness, and side etching may be actively performed so that the shape of the PI becomes narrower from the periphery to the center portion.

Alternatively, the seed layer 251 may be formed to be close to hemispherical. That is, when PI is dropped into the electron emission source hole 131 by a predetermined amount in the liquid state, it is formed into a shape that is close to hemispherical by the surface tension of the liquid. In this state, the PI may be solidified to form the seed layer 251 in a shape close to hemispherical shape.

The catalyst layer 252 is formed on the surface of the seed layer 251. The catalyst layer 252 may be formed of a metal material, and in this case, may be formed by e-beam sputtering.

Alternatively, the catalyst layer 252 may be made of metal salt. In this case, the catalyst layer 252 is formed by applying a solution in which a metal salt is dissolved in a predetermined solvent on the seed layer and drying it. Here, the solution may be applied onto the seed layer 251 by spin coating or dipping.

Here, the metal salt preferably has a weak acid anion group so that it can be dissolved in a strong base developer such as TMAH (Tetramethylammonium Hydroxide). The weak acid anion group may be at least one selected from the group consisting of an acetate group, an oxalate group, and a carbonate group. In addition, the metal salt may include at least one selected from the group consisting of iron (Fe), nickel (Ni), cobalt (Co), and yttrium (Y). In addition, at least one of ethylene glycol and ethanol may be used as the solvent. In this case, the metal salt preferably has a solubility of about 1 mM or more at room temperature with respect to the solvent. In addition, the metal salt is preferably insoluble in acetone, isopropyl alcohol, and a solvent for a photoresist strip.

When the seed layer 251 is made of a material having no electrical conductivity, such as PI, the catalyst layer 252 is made of a material having electrical conductivity. Thus, a voltage applied to the cathode electrode 120 may be applied to the catalyst layer 252 and the electron emission material 253.

The electron emission material 253 may be formed of a material such as a carbon nano tube (CNT) having a small work function, a large beta function, and a large fineness formed on the catalyst layer 252. Alternatively, the carbon nanotubes are preferably made of carbon-based materials such as graphite, diamond, diamond-like carbon, or nanomaterials such as nanowires, nanoneedles, and nanorods. In particular, since the carbon nanotubes have excellent electron emission characteristics and are easily driven at low voltage, the carbon nanotubes are advantageous for large area of a display device using the same as an electron emission material.

The electron emission device 200 having the configuration as described above may apply the negative voltage to the cathode electrode and the positive voltage to the gate electrode to emit electrons from the electron emission source.

On the other hand, the electron emitting device described so far can be used in a display device for generating an image by generating visible light. In order to configure the display device, the second substrate 90 arranged in parallel with the first substrate 110 of the electron emission device according to the present invention, the anode electrode 80 provided on the second substrate 90 and the It further includes a phosphor layer 70 provided on the anode electrode (80).

In addition, the cathode electrode 120 and the gate electrode 140 may be disposed to cross each other in order to implement an image instead of simply generating visible light as a lamp.

In addition, electron emission source holes 131 are formed in regions where the gate electrodes 140 and the cathode electrode 120 cross each other, and the electron emission source 250 is disposed therein.

The electron emission device 200 including the first substrate 110 and the front panel 102 including the second substrate 90 are opposed to each other at a predetermined interval to form a light emitting space, and the electron Spacers 60 are disposed to maintain the gap between the emitting element 200 and the front panel 102. The spacer 60 may be made of an insulating material.

In addition, in order to maintain the vacuum inside, the circumference of the space formed by the electron emission element 200 and the front panel 102 is sealed, and the air inside is exhausted.

An electron emission display device having such a configuration operates as follows.

Electrons are emitted from the electron emission source 250 installed on the cathode electrode 120 by applying a negative voltage to the cathode electrode 120 and applying a positive voltage to the gate electrode 140 for electron emission. To be possible. In addition, a strong (+) voltage is applied to the anode electrode 80 to accelerate electrons emitted toward the anode electrode 80. When the voltage is applied in this way, electrons are emitted from the needle-like materials constituting the electron emission source 250, proceed toward the gate electrode 140, and are accelerated toward the anode electrode 80. Electrons accelerated toward the anode electrode 80 hit the phosphor layer 70 positioned on the anode electrode 80 to generate visible light.

On the other hand, the voltage applied to the electron emission sources constituting the pixel is made uniform by the resistive layer 125 used in the electron emission element of the first embodiment of the present invention, so that the luminance uniformity between pixels is increased and the image quality is improved. .

Hereinafter, a method of manufacturing an electron emission device according to a first embodiment of the present invention. The manufacturing method described below is only one embodiment and is not necessarily to be manufactured by the following method.

First, materials for forming the first substrate 110, the cathode electrode 120, the insulator layer 130, and the gate electrode 140 are sequentially stacked to have a predetermined thickness. Lamination is preferably performed by a process such as screen printing.

Next, a mask pattern is formed on the upper surface of the gate electrode 140 with a predetermined thickness. The mask pattern is formed to form an electron emission hole, and is performed by a photolithography process in which a photoresist (PR) is applied and a pattern is formed using UV or E-beam. .

Next, the gate electrode 140, the insulator layer 130, and the cathode electrode 120 are etched using the mask pattern to form an electron emission source hole 131. The etching process uses wet etching using an etchant, dry etching using an corrosive gas, or an ion beam according to the material and thickness of the gate electrode 140, the insulator layer 130, and the cathode electrode 120. It can be made by a micro machining method.

Then, the PI in the liquid state is dropped in the center of the electron emission hole. In the liquid state, PI is disposed on the cathode electrode at a predetermined contact angle by surface tension and solidified to form a seed layer. The formed seed layer is made into a shape that is substantially hemispherical.

Then, a catalyst layer is formed on the surface of the seed layer using e-beam sputtering or the like. When the catalyst layer is completed, carbon nanotubes are grown on the surface of the catalyst layer by using a chemical vapor deposition (CVD) direct growth method using a reactive gas.

Through the same method as described above, an electron emitting device according to the present invention can be manufactured.

6 is a partial cross-sectional view showing a schematic configuration of an electron emitting device according to a second embodiment of the present invention.

As shown in FIG. 6, in the electron emission device according to the second embodiment of the present invention, the second insulator layer 135 and the focusing electrode 145 are added to the structure of the electron emission device of the first embodiment described above. .

The focusing electrode 145 is installed to be electrically insulated from the gate electrode 140 by the second insulator layer 135. In addition, electrons emitted from the electron emission source 250 by the electric field formed by the cathode electrode 120 and the gate electrode 140 may be used as shown in FIGS. 1 to 3 of the front panel 102 as much as possible. It functions to go straight toward the anode electrode (80). The material of the focusing electrode 145 is made of a material having excellent electrical conductivity like the cathode electrode 120 and the gate electrode 140.

In the case of the electron emission device further including the focusing electrode 145, the electron emission source can be formed in a substantially hemispherical shape as shown in FIGS. 4 and 5, and the carbon nanotubes are grown using the shape. By doing so, the distance between the ends of the carbon nanotubes used as the electron emission material may be formed to be far from each other. Accordingly, the screen effect can be suppressed so that electron emission can occur smoothly.

As described above, in the electron emission device according to the present invention, end portions of the carbon-based material or nanomaterials used as the electron emission material are formed to be farther from each other than the base. Accordingly, the screen effect can be avoided and electron emission can occur more smoothly.

In addition, in the case of implementing the electron emission display device using the electron emission device having a new structure that can prevent such a screen effect, the luminance is increased as the amount of electron emission is increased can greatly improve the luminous efficiency of the device.

In addition, according to the present invention, the electron-emitting device having the above effects can be easily manufactured in a simple process.

Although the present invention has been described with reference to the embodiments shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims (8)

A first substrate; A cathode electrode disposed on the first substrate; A gate electrode disposed to be electrically insulated from the cathode electrode; An insulator layer disposed between the cathode electrode and the gate electrode to insulate the cathode electrode and the gate electrode; An electron emission source hole formed in the insulator layer and the gate electrode to expose the cathode electrode; A seed layer disposed in the electron emission hole and formed to have a height higher from the periphery toward the center; A catalyst layer formed on the seed layer; And An electron emission device comprising a plurality of electron emission emitters, wherein the distance between the bases attached to the catalyst layer is smaller than the distance between the ends, and the elongation is large. The method of claim 1, And the seed layer is substantially hemispherical in shape. The method of claim 1, And the catalyst layer is formed of a metal material. The method of claim 1, The catalyst layer is an electron emission device, characterized in that consisting of a metal salt (metal salt) having a weak acid anion group. The method of claim 1, And the metal salt comprises at least one selected from the group consisting of acetate groups, oxalate groups, and carbonate groups. The electron emission device of claim 1, wherein the metal salt comprises at least one selected from the group consisting of iron (Fe), nickel (Ni), cobalt (Co), and yttrium (Y). The method of claim 1, A second insulator layer covering an upper side of the gate electrode; And a focusing electrode insulated from the gate electrode by the second insulator layer and disposed above the second insulator layer. The method of claim 1, And the cathode electrode and the gate electrode extend in a direction crossing each other.

Images