JP4266679B2 - Electron emission source and manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electron emission source and a manufacturing method thereof, and the electron emission source can be applied to, for example, a display, a high-speed high-frequency electronic device, an imaging device, and the like.
[0002]
[Prior art]
For example, in a conventional cold cathode electron emission device (Field Emission Cathode), an electron emission portion (emitter) called a so-called Spindt type is formed in a spire shape and emits electrons therefrom. The spire portion is made of a semiconductor or metal such as Si, Mo, Nb, W, and a gate electrode is formed around it. By applying a voltage between the spire portion (so-called cathode) and the gate electrode, Electrons are emitted from the spire portion. Conventionally, the emission part of these materials has a problem that the surface work function changes when gas such as hydrogen in the atmosphere is adsorbed, so that there is a problem that the obtained current fluctuates, and in order to prevent it, 10 ⁻⁸ Torr or more Need to be kept in a high vacuum. Moreover, since the value of the work function is large, there is a problem that the threshold voltage for electron emission is large.
[0003]
Carbon-based materials (diamond, amorphous carbon, diamond-like carbon, and carbon nanotube) have attracted attention as electron emission materials that can overcome the above problems. Theoretically, the vacuum potential of these materials is low, so that electron emission at a low threshold is possible. Further, a stable emission current can be obtained with little fluctuation due to adsorbed atoms.
[0004]
A carbon nanotube used for electron emission is described in Japanese Patent Publication No. 7-92463. This is a structure for an electron microscope and cannot be arranged in an array by providing a grid electrode in the vicinity.
On the other hand, JP 2000-208027 A discloses a method in which a cathode is formed by, for example, applying a mixture of a fibrous object such as carbon nanotubes and a conductive paste onto a substrate. It is difficult to control the amount and direction of the nanotubes.
Also, after forming a diamond crystal, it is almost impossible and difficult to process into the required shape.
[0005]
There are various methods for forming an artificial diamond film. For example, there is a method of chemical vapor deposition using a hot filament CVD apparatus as a simple formation method. In this method, carbon radicals are generated in a sealed reaction chamber so that only gases other than a specific gas are mixed, and these are deposited on a predetermined substrate or the like.
Hydrogen gas or reaction gas is introduced into the reaction chamber, and a thermal filament such as tungsten to decompose the gas and generate radicals such as carbon radicals and a substrate such as silicon wafer, quartz, metal, or diamond are installed. The
An example of such a conventional apparatus is shown in FIG. A substrate holder 12 and a substrate 14, a thermocouple 16, and a filament 18 are placed in the reaction chamber 10. The substrate holder 12 is made of refractory metal such as molybdenum or ceramic. Moreover, the board | substrate 14 uses the board | substrate of various materials according to the objective. In order to form a film with this apparatus, the hot filament 18 is brought close to the substrate 14 to bring the substrate 14 to a high temperature, and a raw material gas is introduced into the reaction chamber 10 from the pipe 20 to cause a thermal decomposition reaction of the raw material gas. A material is deposited on the substrate 14. The power source 22 is used for heating the filament, and the thermocouple 16 is used for measuring the substrate temperature. In addition, the exhaust pipe 24 is evacuated using a vacuum pump or the like.
[Patent Document 1]
Japanese Patent Publication No. 7-92463 [Patent Document 2]
JP 2000-208027 A [0006]
[Problems to be solved by the invention]
As described above, the Spindt-type electron generator has a problem that the current obtained varies because the work function of the surface changes when a gas such as hydrogen in the atmosphere is adsorbed to the electron emission portion. In order to prevent this, it is necessary to keep it in a high vacuum of 10 ⁻⁸ Torr or more. Moreover, since the value of the work function is large, there is a problem that the threshold voltage for electron emission is large.
[0007]
Also, in the electron gun used for the cathode ray tube, high efficiency and low power consumption are problems as in the cold cathode method. Basically, a low work function and a low electron emission threshold voltage are desired. ing.
On the other hand, it is almost impossible and difficult to process into a required shape after forming a diamond crystal.
[0008]
The present invention has been made in view of the above-mentioned circumstances. By applying a hot filament CVD apparatus, it does not require a high vacuum as in, for example, a conventional FED (Field Emission Display), and operates stably with a large current. In addition, an FED that can be operated at a low voltage and can be operated individually in an array is realized. In the cathode ray tube, the efficiency can be improved and the power consumption can be reduced, and the electron emission is uniform. An object of the present invention is to provide an electron gun having excellent stability, high brightness, and low power consumption.
[0009]
[Means for Solving the Problems]
According to the present invention, an electron emission source and manufacturing method manufactured by a hot filament CVD apparatus using a hot filament CVD apparatus having a hot filament that decomposes a reaction gas to generate radicals and using a carbon-based filament as the hot filament. A composition having a formability as a hot filament and showing a high carbon residue yield after firing, carbon powder such as carbon black, graphite and coke powder, and if necessary, a kind of metal compound and metalloid compound Alternatively, by using a carbon-based filament that is obtained by mixing and firing two or more kinds of cylinders with a circular cross section, a rectangular shape with a square cross section, a plate shape, and a coil shape as a hot filament and deposition substrate, An electron emission source in which carbon-based materials such as graphite and diamond are deposited in the shape of protrusions on the surface of the filament. By the production method, the problem is solved.
[0010]
That is, the electron emission source of the present invention comprises a carbon-based substrate and a carbon crystal formed on the surface of the carbon-based substrate.
The carbon-based substrate includes carbon powder and glassy carbon obtained by carbonizing a glassy carbon starting material mixed with the carbon powder.
In the method for producing an electron emission source of the present invention, a carbon-based substrate is placed in a carbon-containing gas atmosphere, and the carbon-based gas is decomposed by energizing the carbon-based substrate, whereby the surface of the carbon-based substrate is And depositing a carbon crystal.
[0011]
The carbon-based base material (carbon-based filament) used in the present invention is a glassy carbon starting material, a resin composition having a formability and a high carbon residue yield after firing, carbon powder, and if necessary In order to control the temperature and the resistance value, one or more metal compounds and / or metalloid compounds are mixed, and the mixture is adjusted to the shape of the CVD apparatus, the shape as the final electron emission source, etc. It is manufactured by shaping into a desired shape such as a cylindrical shape with a cross section, a rectangular shape with a square cross section, a plate shape, or a coil shape, and firing the shaped product.
[0012]
Examples of the carbon powder include carbon black, graphite, fullerene, carbon nanotube, carbon nanofiber, coke powder, and the like. The type and amount of carbon powder to be used depend on the resistance value / shape of the target filament and the target CVD. Is selected as appropriate depending on the type of carbon-based material deposited in step 1, and can be used alone or in a mixture of two or more. However, it is particularly preferable to use graphite, carbon nanotubes, or carbon nanofibers because of easy shape control. In order to facilitate shape control and structure control, it is selected from highly oriented pyrolytic graphite (HOPG) having an average particle size of 100 μm or less, quiche graphite, natural graphite, artificial graphite, and vapor grown carbon fiber having a diameter of 200 nm or less. It is desirable that
[0013]
Metals and metalloid compounds of the present invention are generally available metal carbides, metalloid carbides, metal borides / metalloid borides, metal silicides / metalloid silicides, metal nitrides / metalloid nitrides, metal oxides And metal / metalloid oxides. The type and amount of the metal / metalloid compound to be used is appropriately selected according to the resistance value / shape of the target filament and the type of carbon-based material to be deposited by the target CVD, and can be used alone or in a mixture of two or more. However, from the viewpoint of resistance value control and heat resistance, it is particularly preferable to use boron carbide, silicon carbide, or boron nitride.
[0014]
The resin composition having a formability and showing a high carbon residue yield after firing is an amorphous carbon, preferably a polymer capable of becoming non-graphitizable carbon that does not progress graphitization when used at high temperatures. It is a resin and shows high carbon residue yield by generating intermolecular cross-linking during heating in the pre-carbonization stage and making it three-dimensional, and at the time of calcination carbonization, graphite powder, metal compound, metalloid compound It is a kind of a thermosetting resin or a thermoplastic resin, or a composite of two or more kinds. Here, as the thermosetting resin, phenol resin, furan resin, epoxy resin, xylene resin, benzoxazine resin, unsaturated polyester resin, melamine resin, alkyd resin, copna resin, etc. are used, and there is little thermal structural change with time. From the above, preferably a furan resin and a phenol resin are used. Further, as the thermoplastic resin, polychlorinated vinyl chloride resin, polyacrylonitrile, polyamide, polyimide, etc. are used, preferably from the ease of moldability and ease of handling when complexed with furan resin or phenol resin. Polychlorinated vinyl chloride resin is used.
[0015]
For the purpose of providing the necessary characteristics as a hot filament / deposition substrate, a polymer resin that becomes amorphous carbon after firing and a graphite powder, metal compound, metalloid compound are appropriately selected and then sufficiently mixed using a mixer. Disperse. Next, this mixture is controlled in a unidirectional orientation of fine graphite powder, metal compound, and metalloid compound using a molding machine that is used for ordinary plastic molding such as a film forming machine or an extrusion molding machine. While being equalized, it is formed into a desired shape such as a circular cylindrical shape, a rectangular rectangular shape, a plate shape, or a coil shape. The molded body is subjected to carbon precursor conversion treatment and solidification treatment in an air oven, and then calcined by controlling the temperature rise rate in an inert gas atmosphere such as nitrogen or argon, thereby completing carbonization. A carbon composite hot filament / deposition substrate made of carbon and graphite powder, a metal compound, and a metalloid compound is obtained.
[0016]
Here, carbonization is performed by heating and raising the temperature to about 700 to 2800 ° C. in an inert gas atmosphere or under vacuum, but if the heating rate during carbonization is large, the shape of the shaped body is deformed or fine cracks are generated. Defects such as occur. Accordingly, it is appropriate that the temperature is 50 ° C. or less up to 500 ° C. and 100 ° C. or less after that.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
An electron emission source and a manufacturing method manufactured by a hot filament CVD apparatus using a carbon filament as a hot filament using a hot filament CVD apparatus having a hot filament that decomposes a reaction gas and generates radicals according to the present invention Will be described.
[0018]
FIG. 2 shows a hot filament CVD apparatus using a carbon-based filament as the hot filament of the present invention.
The carbon-based filament 36 of the present invention is placed in a sealed chamber 30 made of heat-resistant glass or the like.
After filling the chamber 30 with methyl alcohol and energizing the carbon filament, raising the temperature and evaporating the methyl alcohol or the like to create a reaction gas atmosphere such as methyl alcohol, or after evacuating the chamber to a certain level, Create a gas atmosphere such as methyl alcohol by flowing at a flow rate.
Reaction gases such as methyl alcohol are decomposed by the carbon filament 36 to generate radicals such as carbon radicals, and carbonaceous substances such as graphite and diamond are generated on the filament surface.
[0019]
Here, the temperature of the carbon-based filament is controlled by the input current and the applied voltage.
Further, by appropriately operating the temperature of the filament, the concentration and flow rate of the reaction gas, etc., it becomes possible to control the properties and shape of the carbonaceous material deposited on the filament surface.
[0020]
【Example】
EXAMPLES Next, although an Example demonstrates this invention further more concretely, this invention is not limited at all by this Example.
Example 1
As a composition, 40 parts of chlorinated vinyl chloride resin (T-741 made by Nippon Carbide), 20 parts of furan resin (VF303 made by Hitachi Chemical), 40 parts of natural graphite fine powder (average particle size of Japan Graphite 5 μm), plasticizer 20 parts of diallyl phthalate monomer is added, dispersed, mixed, extruded to form a thin wire, and then fired at 1000 ° C. in a nitrogen gas atmosphere and 2300 ° C. in an argon gas atmosphere to obtain a cylindrical carbon filament. Obtained.
[0021]
As shown in FIG. 2, a cylindrical carbon-based filament is placed as the filament 36 in a sealed heat-resistant glass chamber 30.
The chamber 30 is filled with methyl alcohol, the carbon filament 36 is energized, the temperature is increased, and the methyl alcohol is evaporated to form a methyl alcohol gas atmosphere. The filament temperature was controlled to 2050 ° C. to decompose the methyl alcohol gas to generate carbon radicals, and a CVD deposit was obtained on the filament surface. As a result, a cylindrical electron emission source was obtained.
As a result of observing the deposit with an SEM (scanning electron microscope), the projection-shaped substances shown in FIGS. 3 and 4 were observed and identified as graphite by Raman spectroscopy.
[0022]
(Example 2)
As a composition, 20 parts of diallyl phthalate monomer as a plasticizer are added to 50 parts of chlorinated vinyl chloride resin (T-741 manufactured by Nippon Carbide) and 50 parts of natural graphite fine powder (average particle size 5 μm manufactured by Nippon Graphite). Then, it was dispersed, mixed, and formed into a plate shape by extrusion, and then fired at 1000 ° C. in a nitrogen gas atmosphere and further at 2100 ° C. in a vacuum to obtain a plate filament.
[0023]
The plate-like filament was used as the filament, and a CVD deposit was obtained on the filament surface in the same manner as in Example 1. As a result, a plate-like electron emission source was obtained.
As a result of observing the deposit with an SEM, the projection-like substance shown in FIG. 5 was observed, and was identified as graphite by Raman spectroscopy.
[0024]
(Example 3)
As composition, diallyl phthalate monomer as plasticizer for 50 parts of chlorinated vinyl chloride resin (T-741 manufactured by Nippon Carbide), 25 parts of carbon nanofiber, and 25 parts of natural graphite fine powder (average particle size 5 μm manufactured by Nippon Graphite) Was added, dispersed and mixed, formed into a rectangular shape by extrusion, and then fired at 1000 ° C. in a nitrogen gas atmosphere and further at 1500 ° C. in a vacuum to obtain a rectangular filament.
[0025]
The rectangular filament was used as the filament, and a CVD deposit was obtained on the filament surface in the same manner as in Example 1. As a result, a rectangular electron emission source was obtained.
As a result of observing the deposit by SEM, polyhedral particles were observed and identified as diamond by Raman spectroscopy.
[0026]
As the electron emission source cathode electrode obtained in Examples 1 to 3, an anode electrode plate made of a glass substrate coated with a phosphor and a transparent conductive film was placed on the opposite side through a spacer, and the electrode was placed between the electrodes in a vacuum. When an electric field was applied, the phosphor emission phenomenon was confirmed over the entire surface.
[0027]
【The invention's effect】
As described above, the electron emission source manufactured by the hot filament CVD apparatus of the present invention can be used as a cathode by arranging a single element or a plurality of elements as necessary, and can operate at a low vacuum degree, with a stable large current. Operation, low voltage operation and low power consumption are possible, it is easily formed, and its industrial value is very large.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a general hot filament CVD apparatus.
FIG. 2 is a diagram showing a configuration of a hot filament CVD apparatus used in the present invention.
3 is an SEM photograph of the electron emission source obtained in Example 1. FIG.
4 is a SEM photograph of the electron emission source obtained in Example 1. FIG.
5 is a SEM photograph of the electron emission source obtained in Example 2. FIG.

Claims (3)

Place the carbon-based substrate in a carbon-containing gas atmosphere,
A method for producing an electron emission source, comprising: depositing carbon crystals on a surface of the carbon-based substrate by decomposing the carbon-containing gas by energizing the carbon-based substrate. The method according to claim 1, wherein the carbon-based substrate includes carbon powder and glassy carbon obtained by carbonizing a glassy carbon starting material mixed with the carbon powder. The method of claim 2 , wherein the carbon-based substrate further comprises a metal or metalloid compound.

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