JP2003031110A - Electron emission element, display device and manufacturing method of electron emission element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electron emission element, a display device and a manufacturing method of an electron emission element in which a protrusion with a pointed top end that is used as, for example, a micro cathode can be formed instantaneously, and reduction of process time and manufacturing cost can be achieved. SOLUTION: By heat fusing the surface of the electron emission metal 2 locally, a drill-shape protrusion 8 is formed in the process of re-solidification of the heat-fused metal. By irradiating laser beam, the surface of the electron emission metal 2 is heat fused locally. A porous metal is used for the electron emission metal 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron-emitting device, a display device and a method for manufacturing an electron-emitting device.

[0002]

2. Description of the Related Art Conventionally, as a method of forming a microcathode having a sharp tip in a field electron emission display device (FED), for example, as disclosed in JP-A-7-249370 and JP-A-10-507576. In addition, a method using an etching technique or a method using crystal growth such as CVD is generally used.

However, in such a conventional method, it is necessary to use a multi-step chemical reaction process or a thermal reaction process, which causes a problem that the process time increases and the manufacturing cost increases. There is.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and an object thereof is to be able to instantaneously form a projection having a sharp tip used as, for example, a microcathode, An electron-emitting device capable of reducing the process time and the manufacturing cost,
A method of manufacturing a display device and an electron-emitting device.

[0005]

The inventor of the present invention locally and instantaneously heats and melts the surface of an electron-emitting metal and gradually solidifies it from the surroundings to form a conical projection having a sharp tip. The inventors have found that they can be achieved and have completed the present invention.

In other words, in order to achieve the above object, the electron-emitting device according to the present invention has a pyramidal shape formed by locally heat-melting the surface of an electron-emitting metal and resolidifying the heat-melted metal. It has a protrusion. Preferably, the electron emitting metal is a porous metal. Alternatively, the periphery of the electron emitting metal other than the surface is covered with a low thermal conductivity member having a lower thermal conductivity than that of the electron emitting metal. Preferably, the low thermal conductivity member is a ceramic material. Alternatively, the low thermal conductivity member is a porous metal powder sintered body.

A cathode ray tube according to the present invention is characterized in that the above-mentioned electron-emitting device is formed on a cathode structure of an electron gun.

The flat panel display device of the present invention is characterized in that the above-mentioned electron-emitting devices are arranged in a matrix as microcathodes.

In the scanning microscope of the present invention, the electron-emitting device described above is mounted as a metal probe.

The method for manufacturing an electron-emitting device according to the present invention is characterized in that the surface of the electron-emitting metal is locally heat-melted and the conical protrusion is formed by the re-solidification process of the heat-melted metal.

Preferably, the surface of the electron emitting metal is locally melted by irradiating an energy beam such as a laser beam. Preferably, a porous metal is used as the electron emitting metal. Preferably, a sintered body of metal powder is used as the porous metal. Alternatively, the periphery of the electron emitting metal other than the surface is covered with a low thermal conductivity member having a lower thermal conductivity than that of the electron emitting metal.

In the present invention, as the electron emitting metal,
Although not particularly limited, it is preferable to realize a metal surface having a low work function, such as W, Ba and C.
Examples include a, Al, Ir and the like.

[0013]

When a very limited part of the surface of the electron emitting metal is heated by an energy beam such as a high-intensity laser beam, the energy distribution of the beam becomes high at the center of the beam axis and becomes lower toward the periphery. For this reason,
The metal surface irradiated by the beam becomes a liquid with low viscosity (low density) in the central part of the heating, the viscosity of the liquid metal increases with distance from it, and the original solid metal remains in the outer peripheral part. Are formed, and the part that becomes liquid rises due to surface tension.

After that, when the laser irradiation is stopped, the molten metal begins to solidify, but the conditions are set so that the heat diffusion rate from the region concerned is sufficiently slow and gradually solidifies from the outer peripheral portion of the melt.

The liquid is a state in which the bonding state of the atoms is partially broken, and the solid is a state in which the bonding between the atoms is established. Therefore, when it begins to solidify from the outer peripheral portion by heat conduction, it goes to the center. As the solidification progresses in the direction, the liquid metal surface is pulled obliquely downward, which is the direction in which the bonds between metal atoms are established, and the molten metal with low viscosity at high temperature remains in the center due to surface tension. . As a result, it begins to dent from the outer peripheral portion, the central portion bulges, and after the heat removal is completed, a shape with a sharp central portion is finally obtained.

That is, although metals generally have good thermal conductivity, they try to locally concentrate heat energy that is comparable to the heat conduction rate of the metal, and reduce the heat escape of the metal as much as possible. Conical protrusions (point cathodes) can be formed by using physical properties (structure that achieves low thermal conductivity).

In order to concentrate the energy locally, for example, a high-intensity laser beam is used. With a laser beam having a low energy density, it takes time for the metal at the irradiation point to melt, and during that time, heat escapes due to thermal diffusion in the metal substrate, which prevents the generation of a liquid metal having low viscosity and fluidity. On the other hand, when a laser beam having an excessively high energy density is used, the molten metal is vaporized, vaporized, or turned into plasma, and disappears from the metal substrate, so that the point cathode cannot be formed.

Therefore, how much energy density of the laser is used to realize a state in which a certain region is melted for a certain period of time is adjusted by the melting point and the specific heat of the metal substrate irradiated with the laser beam. For example, when using porous (porosity 20%) tungsten as the metal substrate, the laser beam diameter is 0.2 mm to 0.05 m.
It is preferable to adopt a laser beam condition of m, 80 to 200 mJ. The irradiation time of the laser beam is not particularly limited, but is, for example, about 0.1 to 2 msec.

As the electron-emitting metal is melted for a long time and the melted metal hardens more slowly than the surroundings, a higher protrusion is formed at the center of the depression. In order to realize this, the physical properties of the metal substrate (structure that achieves low thermal conductivity) that reduces the escape of heat are required.

In the present invention, when the electron emitting metal is a porous metal, a cavity is included in the metal, and the heat conduction cross-sectional area can be reduced. As a result, a high protrusion is formed at the center of the depression.

Further, in the present invention, heat conduction can be suppressed by using a structure in which an electron emitting metal having a low work function is surrounded by a low thermal conductivity member having a low thermal conductivity. As a result, a high protrusion is formed at the center of the depression.
As the low thermal conductivity member, a metal with low thermal conductivity, a porous body obtained by sintering it, or a porous ceramic can be used. When the low thermal conductivity member is made of an electrically insulating member such as porous ceramics, it is necessary to separately wire the electron emitting metal with an electric conductor.

According to the present invention, the conical protrusions used as, for example, field electron emission cathodes can be formed instantaneously, so that the process time and the number of man-hours required for manufacturing a device having the conical protrusions can be reduced. It can be reduced, which contributes to the reduction of the manufacturing cost.

In the present invention, most of the conical-projections forming conditions can be controlled by, for example, laser beam generating conditions. The laser beam generation conditions can be controlled by a digital electronic circuit, and complicated control of chemical reaction conditions (temperature, pressure, gas concentration, etc.) in the conventional production process is unnecessary.

Further, in the present invention, the position where the conical protrusion is formed can be any position as long as it can be irradiated with an energy beam such as a laser beam, so that the degree of freedom of the position where the conical protrusion is formed is increased.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below based on the embodiments shown in the drawings. 1A to 1C are process drawings showing a method for manufacturing a field electron emission device according to one embodiment of the present invention, and FIGS. 2A and 2B show another embodiment of the present invention. FIG. 3 is a schematic cross-sectional view of a CRT, FIG. 4 is a schematic cross-sectional view of an FED of the FED, and FIG. 5 is an electron-emitting device according to an embodiment of the present invention. 6 is a graph showing the relationship between the irradiation energy of the laser beam and the height of the protrusions.

First Embodiment As shown in FIG. 1A, in this embodiment, first, a metal substrate 2 is prepared. Although not particularly limited, the metal substrate 2 is composed of an electron emitting metal that realizes a metal surface having a low work function. Specifically, the metal substrate 2 is made of, for example, one kind of W, Ba, Ca, Al, Ir, etc., an alloy thereof, or a laminated structure of these metals or alloys.

Next, in this embodiment, a part of the surface of the metal substrate 2 is locally irradiated with the high-intensity laser beam LB. The irradiation condition of the laser beam LB is determined so that the energy is locally concentrated. With a laser beam having a low energy density, it takes time for the metal at the irradiation point to melt, and during that time, heat escapes due to thermal diffusion in the metal substrate 2 and the liquid metal 6 having low viscosity and fluidity 6
Is prevented from occurring. On the other hand, when the laser beam LB having too high energy density is used, the melted metal is vaporized, vaporized, or turned into plasma, and disappears from the metal base 2 to form a conical protrusion (point cathode) described later. 8 cannot be formed.

For this reason, the energy density of the laser used to achieve a state in which a certain region is melted for a certain period of time is adjusted by the melting point and the specific heat of the metal substrate 2 irradiated with the laser beam LB. It For example, when using porous (porosity 20%) tungsten as the metal substrate 2, the laser beam diameter is 0.2 mm to.
It is preferable to adopt a laser beam condition of 0.05 mm and 100 to 200 mJ.

In such a laser beam LB, the energy distribution of the laser beam LB is high at the center of the beam axis and becomes lower toward the periphery. Therefore, as shown in FIG. 1 (A), the metal surface irradiated with the laser beam becomes a liquid metal portion 6 having a low viscosity (low density) at the central heating portion, and a liquid metal portion having a higher viscosity as the distance from the metal metal portion 6 increases. Four
Is formed. In addition, a state where the original solid metal remains as it is is formed on the outer peripheral portion of the liquid metal portion 4 having high viscosity,
These liquid metal parts 4 and 6 rise due to surface tension. Although the boundary between the liquid metal portions 4 and 6 and the boundary between the liquid metal portion 4 and the solid metal substrate 2 are clearly illustrated in FIG. 1A, in reality, they are not clear and are continuous. Has changed to.

After this, when the laser irradiation is stopped, the molten metal begins to solidify, but the conditions are set so that the heat diffusion rate from the region is sufficiently slow and gradually solidifies from the melted outer peripheral portion.

The liquid is in a state in which the bonding state of the atoms is partially broken, and the solid is in a state in which the bonding between the atoms is established. As indicated by an arrow D shown in B), solidification proceeds in the direction toward the center, so that the liquid metal surface is pulled obliquely downward, which is a direction in which a bond between metal atoms is established, and has a low viscosity at high temperature. The melted metal has a surface tension that causes the central part 5
Will remain. As a result, it starts to dent from the outer periphery 3,
After the central portion 5 swells and the heat removal is completed, as shown in FIG. 1C, the conical protrusions 8 having a sharp central portion are finally obtained.

That is, although metals generally have good thermal conductivity, they try to locally concentrate heat energy that is comparable to the heat conduction rate of the metal, and reduce the heat escape of the metal as much as possible. The conical protrusions (point cathodes) 8 can be formed by using the physical properties (structure that achieves low thermal conductivity).

As the electron-emitting metal is melted for a long time and the melted metal hardens more slowly than the surroundings, a higher protrusion is formed at the center of the depression. In order to realize this, the physical properties of the metal substrate (structure that achieves low thermal conductivity) that reduces the escape of heat are required.

Therefore, as shown in FIG. 2 (A), when the electron-emitting metal is the porous metal substrate 2a, a cavity is included in the porous metal, and the heat conduction cross-sectional area is reduced. Can be made. In this case, in the liquid metal portions 4 and 6, the pits of the outer peripheral portion 3 are enlarged by the amount of the pores of the porous metal burned out, but a high protrusion is formed in the central portion of the pits.

Further, as shown in FIG. 2B, a structure is used in which each electron-emitting metal 7 arranged in an island shape and having a low work function is surrounded by a substrate 2b made of a low thermal conductivity member having a low thermal conductivity. Therefore, heat conduction can be suppressed. As a result, laser irradiation on the surface of the metal 7 forms a high protrusion in the center of the depression. As the low thermal conductivity member, a metal with low thermal conductivity, a porous body obtained by sintering it, or a porous ceramic can be used. When the low thermal conductivity member is made of an electrically insulating member such as porous ceramic, it is necessary to separately wire the electron emitting metal 7 with an electric conductor.

According to this embodiment, the conical protrusions 8 used as, for example, field electron emission cathodes can be formed instantaneously, so that the process time required for manufacturing a device having the conical protrusions 8 and The number of manufacturing steps can be reduced, which contributes to a reduction in manufacturing cost.

Further, in the present embodiment, most of the conditions for forming the conical protrusions 8 can be controlled, for example, under the laser beam generation conditions. The laser beam generation conditions can be controlled by a digital electronic circuit, and complicated control of chemical reaction conditions (temperature, pressure, gas concentration, etc.) in the conventional production process is unnecessary.

Further, in the present embodiment, the conical protrusions 8 may be formed at any positions where they can be irradiated with an energy beam such as a laser beam.
The degree of freedom in the position of forming the is increased.

Second Embodiment In this embodiment, the cone-shaped projections 8 are formed on the electron beam emitting surface of the cathode structure of the electron gun 16 of the cathode ray tube (CRT) 10 shown in FIG. 3 in the same manner as in the first embodiment. To form.

The CRT 10 shown in FIG. 3 has a panel glass 12 having a fluorescent surface formed on its inner surface, and a funnel glass 14 bonded to this panel glass and containing an electron gun 16 in its neck portion. The electron beam emitted from the electron gun 16 is deflected by the deflection yoke 18,
Through the aperture grille 20 as a color selection electrode mounted on the inner surface side of the panel glass 12, the fluorescent screen is hit and the fluorescent screen is caused to emit light to display a predetermined image.

Third Embodiment In the present embodiment, in the field electron emission display device (FED) shown in FIG. 4, the data electrode layers 32 having a predetermined pattern formed on the inner surface of the rear substrate 31 are arranged in a matrix. The microcathode 38 to be formed is formed by a method similar to the method of forming the conical protrusion 8 in the first embodiment.

In the FED 30 shown in FIG. 4, electron beams emitted by scanning from a plurality of field emission type microcathodes 38 arranged in a matrix form a predetermined pattern on the inner surface of a transparent front substrate 33 such as a glass substrate. It is a display device that displays an image by irradiating the formed phosphor screen 40 to emit light. A high vacuum is maintained between the rear substrate 31 and the front substrate 33.

Each micro-cathode 38 has a rear substrate 31.
Insulating layer 36 and gate electrode layer 3 formed on the inner surface of
7 is formed on the bottom of the cathode hole 35 formed in a predetermined pattern by a method similar to the method of forming the conical protrusion 8 in the first embodiment.

Fourth Embodiment In this embodiment, a metal probe of a scanning tunnel microscope (not shown) is formed by a method similar to the method of forming the conical protrusion 8 in the first embodiment. The present invention is
The present invention is not limited to the above-described embodiments, but can be variously modified within the scope of the present invention.

[0045]

EXAMPLES The present invention will be described below based on more detailed examples, but the present invention is not limited to these examples.

Example 1 A high-intensity laser (Nd excitation: YA) was formed on the surface of a porous metal substrate (porosity 20%) obtained by sintering tungsten metal powder.
G / 1.064 μm wavelength), the laser beam diameter was 80 μm, and the irradiation was performed for about 0.3 msec under the laser beam conditions of about 100 mJ, and the predetermined portion was instantly heated. It was confirmed that the conical protrusions shown in FIG. 5 could be obtained.

Example 2 The irradiation energy amount of the laser beam is 50 to 250 (m).
J) and laser irradiation time,
0.6 (msec), 0.8 (msec), 1.0 (m
sec) except that it was changed to
A conical protrusion was formed. FIG. 6 shows the relationship between the projection height of the formed conical projections and the irradiation energy amount. As shown in FIG. 6, it was found that there is an irradiation energy amount capable of maximizing the projection height for each irradiation time.

[0048]

As described above, according to the present invention, a conical protrusion used as, for example, a field electron emission cathode can be instantaneously formed. Therefore, a device having the conical protrusion can be formed. The process time and the number of manufacturing steps required for manufacturing can be reduced, which contributes to the reduction of the manufacturing cost.

Further, in the present invention, most of the conical-projections forming conditions can be controlled, for example, by the laser beam generating conditions. The laser beam generation conditions can be controlled by a digital electronic circuit, and complicated control of chemical reaction conditions (temperature, pressure, gas concentration, etc.) in the conventional production process is unnecessary.

Further, in the present invention, the position where the conical protrusion is formed may be any position as long as it can be irradiated with an energy beam such as a laser beam, so that the degree of freedom of the position where the conical protrusion is formed is increased.

[Brief description of drawings]

1A to 1C are process diagrams showing a method for manufacturing a field electron emission device according to an embodiment of the present invention.

FIG. 2A and FIG. 2B are cross-sectional views of a main part showing one step of a method of manufacturing a field electron emission device according to another embodiment of the present invention.

FIG. 3 is a schematic diagram of a CRT.

FIG. 4 is a sectional view of an essential part of the FED.

FIG. 5 is a photograph of an electron-emitting device according to an embodiment of the present invention.

FIG. 6 is a graph showing the relationship between laser beam irradiation energy and protrusion height.

[Explanation of symbols]

2 ... Metal substrate 2a ... Porous metal substrate 2b ... Base 3 ... Outer periphery 4, 6 ... Liquid metal part 5 ... Central part 7 ... Electron emitting metal 8 ... Conical protrusion 10 ... Cathode ray tube (CRT) 16 ... Electron gun 30 ... Field Emission Display Device (FED) 38 ... Micro cathode

Claims (13)

[Claims] 1. An electron-emitting device having a conical projection formed by locally heat-melting a surface of an electron-emitting metal and resolidifying the heat-melted metal. 2. The electron emitting device according to claim 1, wherein the electron emitting metal is a porous metal. 3. The periphery other than the surface of the electron emitting metal is
The electron-emitting device according to claim 1, wherein the electron-emitting device is covered with a low thermal conductivity member having a thermal conductivity lower than that of the electron-emitting metal. 4. The electron-emitting device according to claim 3, wherein the low thermal conductivity member is a ceramic material. 5. The electron-emitting device according to claim 3, wherein the low thermal conductivity member is a porous metal powder sintered body. 6. A cathode ray tube, wherein the electron-emitting device according to claim 1 is formed on a cathode structure of an electron gun. 7. A flat-panel display device, wherein the electron-emitting devices according to claim 1 are arranged in a matrix as microcathodes. 8. A scanning microscope in which the electron-emitting device according to claim 1 is mounted as a metal probe. 9. A method of manufacturing an electron-emitting device, characterized in that the surface of an electron-emitting metal is locally heat-melted, and a conical protrusion is formed by a process of re-solidifying the heat-melted metal. 10. The method for manufacturing an electron-emitting device according to claim 9, wherein the surface of the electron-emitting metal is locally heat-melted by irradiating with an energy beam. 11. The method for manufacturing an electron-emitting device according to claim 9, wherein a porous metal is used as the electron-emitting metal. 12. The method of manufacturing an electron-emitting device according to claim 11, wherein a sintered body of metal powder is used as the porous metal. 13. The electron-emitting device according to claim 9, wherein the periphery of the electron-emitting metal other than the surface is covered with a low thermal conductivity member having a lower thermal conductivity than that of the electron-emitting metal. Production method.