JP2005166681A - Discharge tube and electrode for discharge tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To optionally control current density in discharging in addition to the attainment of a longer life and lower power consumption. <P>SOLUTION: A carbon-based electrode composed of carbon powder and amorphous carbon is used as an electrode 6 (6'). The carbon-based electrode is manufactured by mixing carbon powder such as graphite to a resin such as a furan resin or a chlorinated vinyl chloride resin, which forms amorphous carbon after baking and is molded into a desired shape, and baking it twice at different temperatures and in different atmospheres. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to discharge tubes and discharge tube electrodes for hot cathodes and cold cathodes, and more particularly to discharge tubes and discharge tube electrodes having a long life and low power consumption.

  As a conventional discharge tube, for example, in a liquid crystal display device such as a personal computer, a word processor, and a liquid crystal television, a cold cathode discharge tube is generally used as a light source for a liquid crystal backlight. That is, there is known a cold cathode discharge tube whose main configuration is shown in FIGS. 1A and 1B (Japanese Patent Laid-Open No. 11-233303). (A) is a transverse sectional view, and (b) is a longitudinal sectional view. In FIG. 1, reference numeral 1 denotes a glass tube containing a discharge medium (rare gas, mercury, etc.), and 2 denotes a phosphor layer formed on the inner wall surface of the glass tube 1.

  3 and 3 'are a pair of electrodes sealed at both ends of the glass tube 1, 4 is an electron-emitting material layer formed covering the outer peripheral surface of the electrodes 3 and 3', and 5 and 5 'are electrodes. 3, 3 ', which is an introduction line for supplying required power from the outside of the glass tube 1. The electrodes 3 and 3 'are Ni cylindrical electrodes or the like, and the leading ends of the lead wires 5 and 5' sealed and introduced at the end of the glass tube 1 are fitted and welded electrically and mechanically. It is configured to connect and hold to function as a discharge electrode. Furthermore, the electron-emitting material layer 4 is formed by applying and baking an alkaline earth metal oxide powder such as Ba, Ca, and Sr.

  When this type of cold cathode discharge tube is attached to a corresponding lighting device and is energized through lead-in wires 5 and 5 ', discharge between the electrodes 3 and 3' starts and irradiates (radiates) ultraviolet rays. And this ultraviolet-ray is converted into visible light in the fluorescent substance layer 2, The required visible light is light-emitted, and the function as a light source is comprised. When the discharge medium directly emits visible light, the formation of the phosphor layer can be omitted.

  By the way, when using the cold cathode discharge tube, not only the downsizing and high luminous efficiency of the cold cathode discharge tube are desired, but also low power consumption and long life are required in terms of downsizing and high performance of the entire apparatus. That is also required. In response to such demands, studies have been mainly made on oxides in the electron-emitting material layer.

  However, the cold cathode discharge tube having the above configuration still has the following problems and still has practical problems. In other words, the cold cathodes 3 and 3 'provided in and installed in the cold cathode discharge tube are consumed by processing or deformation during the manufacturing process, thermal expansion or ion bombardment during lighting, There is a problem that the layer 4 is cracked or the electron-emitting material layer 4 is peeled off or dropped, resulting in a loss of sustainability of required functions and a long life.

  In order to solve the above-described problems, an object of the present invention is to provide a discharge tube and a discharge tube electrode capable of arbitrarily controlling the current density in discharge while at the same time extending the life and reducing the power consumption.

  According to the present invention, there is provided a discharge tube comprising a sealed container and a pair of electrodes disposed opposite to each other in the sealed container, wherein at least one of the pair of electrodes is a carbon-based electrode. The above problem is solved.

  According to the present invention, there is also provided a discharge tube electrode comprising carbon and used as an electrode of a discharge tube in a sealed container.

  The aforementioned carbon-based electrode preferably includes carbon powder and amorphous carbon.

  The aforementioned carbon-based electrode preferably further contains a metal or metalloid compound.

  In order to improve electron emission, the carbon powder preferably contains carbon nanotubes and carbon nanofibers.

  Further, the shape of the carbon-based electrode used for the discharge tube electrode is preferably a circular columnar column, a square columnar prism, a coil, a cone, or a cylinder. By adopting such a shape, it is possible to further prevent the electrode from being consumed by ion bombardment.

  The carbon-based electrode used in the present invention comprises a resin composition having a formability and a high carbon residue yield after firing, carbon powder, and optionally one or more metal compounds and metalloid compounds. In order to control the discharge characteristics and current density according to the dimensions and shape of the discharge tube, and to mix the mixture, the cylindrical shape of the circular cross section, the rectangular shape of the square cross section, the coil shape, the conical shape, the cylindrical shape, etc. It is manufactured by shaping into a desired shape and firing the shaped product.

  Examples of the carbon powder include carbon black, graphite, coke powder, and the like. The type and amount of carbon powder to be used are appropriately selected depending on the resistance value / shape and discharge characteristics of the target electrode. Although it can also be used as a mixture, it is particularly preferable to use graphite from the viewpoint of simplicity of shape control. In order to facilitate shaping and structure control, highly oriented pyrolytic graphite having an average particle size of 100 μm or less. It is desirable to be selected from (HOPG), quiche graphite, natural graphite, artificial graphite, and vapor grown carbon fiber having a diameter of 200 nm or less.

  Carbon nanotubes and carbon nanofibers are defect-free “single-layer” tubes formed by rolling graphite hexagonal mesh planes into cylinders, or “multi-layer” tube-like materials in which they are nested, and have a diameter of 15 nm or less. Nanotubes are tens of nanometers to several micrometers. A region having a diameter of about 15 to 100 nm is called a nanofiber. It is produced by arc discharge method, vapor phase pyrolysis method, laser sublimation method, electrolysis method, fluidized catalyst method, etc. Recently, hollow tube-like or sometimes empty fiber has been proposed by polymer blend method. In this case, it is used as a carbon nanotube or carbon nanofiber in a broad sense including both hollow and non-empty.

  Metals and metalloid compounds include commonly available metal carbides, metalloid carbides, metal borides and metalloid borides, metal silicides and metalloid silicides, metal nitrides and metalloid nitrides, metal oxides, Examples include semi-metal oxides. The type and amount of the metal / metalloid compound to be used is appropriately selected depending on the desired filament resistance and shape and the type of film to be formed 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.

  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, cobuna resin, etc. are used, and there is little thermal structural change with time. From the above, preferably, a furan resin and / or a phenol resin is 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.

  For the purpose of providing the necessary characteristics as an electrode for a discharge tube, a graphite resin and, if necessary, a metal compound and a semi-metal compound are mixed with a polymer resin that becomes amorphous carbon after firing, and then sufficiently mixed using a mixer. To 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 cylindrical shape with a circular cross section, a rectangular shape with a square cross section, a coil shape, a conical shape, or a cylindrical shape. The molded body is subjected to a carbon precursor conversion treatment and a solidification treatment in an air oven, and then calcinated in an inert gas atmosphere such as nitrogen and argon while controlling the temperature rising rate to finish carbonization. A carbon-based electrode for a discharge tube electrode of a carbon composite composed of carbon and graphite powder, carbon nanotube, carbon nanofiber, metal compound, and metalloid compound is obtained.

  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. Therefore, it is appropriate to carry out at 50 ° C. or less up to 500 ° C. and 100 ° C. or less per hour thereafter.

  In the present invention, in order to obtain high temperature heat resistance, in an inert atmosphere or in vacuum, the temperature is higher by 260 ° C. or more and 500 ° C. or less than the temperature used as the discharge tube electrode, preferably about 300 ° C. By performing the calcination carbonization treatment, it is possible to achieve more stable discharge characteristics, lower power consumption, and longer life.

  In the discharge tube electrode of the present invention, graphite edge portions, carbon nanotubes, and carbon nanofibers having excellent electron emission properties are uniformly and amorphously obtained by carbonizing a polymer resin having excellent moldability. By controlling the orientation in one direction and making it a composite of amorphous carbon and graphite, carbon nanotubes, and carbon nanofibers, the graphite edges with excellent electron emission characteristics and the sharp carbon of carbon nanotubes / carbon nanofibers can be made uniform. In addition, it is possible to form an electrode having an arbitrary shape capable of electron emission by being uniformly exposed and having a small work function and a small threshold voltage for electron emission. In addition, since it is excellent in heat resistance, there is no inrush current when it is used repeatedly, a stable discharge current is obtained, and a long life is obtained.

  In a discharge tube in which a pair of discharge tube electrodes are arranged in a sealed container, the use of the carbon-based electrode obtained as described above for at least one of the pair of discharge tube electrodes enables long life and low It functions as a discharge tube and a discharge tube electrode for power consumption.

  Hereinafter, the present invention will be described more specifically with reference to FIG. 1, but the present invention is not limited to this embodiment.

Example 1
As a composition, 40 parts by mass of a chlorinated vinyl chloride resin (T-741 manufactured by Nippon Carbide), 20 parts by mass of a furan resin (VF303 manufactured by Hitachi Chemical), 40 parts by mass of natural graphite fine powder (average particle size 5 μm manufactured by Nippon Graphite) Then, 20 parts by mass of diallyl phthalate monomer is added as a plasticizer, dispersed, mixed, formed into a thin wire by extrusion molding, and then fired at 1000 ° C. in a nitrogen gas atmosphere and 2000 ° C. in an argon gas atmosphere to form a cylindrical shape A carbon-based electrode was obtained.

  2 (a) and 2 (b) show an example in which the carbon-based electrode of the present invention is used in a cold cathode discharge tube of the type shown in FIG. 1, (a) is a cross-sectional view, and (b) is a longitudinal section FIG. 2 (a) and 2 (b), 1 is a straight tube type glass tube that encloses a discharge medium (rare gas, mercury, etc.), 2 is a phosphor layer formed on the inner wall surface of the glass tube 1, 6 'is a pair of electrodes sealed at both ends of the glass tube 1, 4 is a coating layer of an electron radioactive material provided on the outer peripheral surface of the electrodes 6 and 6', and 5 and 5 'are electrodes 3 and 3'. It is an introduction line that connects and supplies required power from the outside of the glass tube 1.

When the above-described cylindrical carbon-based electrodes are used as the electrodes 6 and 6 ', discharge is easily started between the electrodes, and ultraviolet rays are converted into visible light by the phosphor layer 2 to form a discharge tube with high luminous efficiency. It worked. In the case of Example 1, for example, it was easily turned on by applying a tube voltage of about 200 Vrms, required light emission luminance was obtained, and stable discharge was obtained for a long time.
Example 2
As a composition, 50 parts by mass of carbon nanofiber (Showa Denko average diameter 100 nm) and 50 parts by mass of diallyl phthalate monomer as plasticizer are added to 50 parts by mass of chlorinated vinyl chloride resin (T-741 made by Nippon Carbide). Then, it was dispersed, mixed, extruded, and then fired at 1000 ° C. in a nitrogen gas atmosphere and further at 1500 ° C. in a vacuum to obtain a cylindrical carbon-based electrode.

When the obtained cylindrical carbon-based electrode is used and energized in the same manner as in Example 1, discharge easily starts between the electrodes, and ultraviolet light is converted into visible light by the phosphor layer 2 to form a discharge tube with high luminous efficiency. It worked. In the case of Example 2, for example, it was easily turned on by applying a tube voltage of about 190 Vrms, required light emission luminance was obtained, and stable discharge was obtained for a long time.
Example 3
As a composition, 50 parts by mass of chlorinated vinyl chloride resin (T-741 manufactured by Nippon Carbide), 25 parts by mass of natural graphite fine powder (average particle size 5 μm manufactured by Nippon Graphite), and carbon nanofiber (average diameter 100 nm manufactured by Showa Denko) 25 parts by mass and 20 parts by mass of diallyl phthalate monomer as a plasticizer are added, dispersed, mixed, extruded, and then fired at 1000 ° C. in a nitrogen gas atmosphere and further at 1500 ° C. in a vacuum. A carbon-like electrode was obtained.

  When the obtained cylindrical carbon-based electrode is used and energized in the same manner as in Example 1, discharge easily starts between the electrodes, and ultraviolet light is converted into visible light by the phosphor layer 2, so that the discharge tube has high luminous efficiency. It worked. In the case of Example 3, for example, it was easily turned on by applying a tube voltage of about 200 Vrms, required light emission luminance was obtained, and stable discharge was obtained for a long time.

  As described above, in the discharge tube electrodes disposed in a pair as opposed to each other in the sealed container of the present invention, the discharge tube electrode using the carbon-based electrode dramatically improves the long life and low power consumption. This has been found and the present invention has been completed.

It is a figure which shows the principal part structure of the conventional cold cathode discharge tube. It is a figure which shows the principal part structure of the cold cathode discharge tube using the carbon-type electrode of this invention.

Claims (12)

  A sealed container and a pair of electrodes arranged oppositely in the sealed container, wherein at least one of the pair of electrodes is baked twice at different temperatures and in different atmospheres in the range of 700 to 2800 ° C. A discharge tube that is a carbon-based electrode.   The discharge tube according to claim 1, wherein the temperature of the first firing is 1000 ° C, and the temperature of the second firing exceeds 1000 ° C.   The discharge tube according to claim 1 or 2, wherein the carbon-based electrode includes carbon powder and amorphous carbon.   The discharge tube according to claim 3, wherein the carbon-based electrode further contains a metal or a metalloid compound.   The discharge tube according to claim 3 or 4, wherein the carbon powder includes carbon nanotubes or carbon nanofibers.   The discharge tube according to claim 1, wherein the carbon-based electrode has a columnar shape, a cylindrical shape, a coil shape, or a cone shape.   An electrode for a discharge tube that contains carbon and is used as an electrode of a discharge tube in a sealed container and is carbonized by firing twice at different temperatures and in different atmospheres in the range of 700 to 2800 ° C.   The discharge tube electrode according to claim 7, wherein the first firing temperature is 1000 ° C., and the second firing temperature exceeds 1000 ° C. 9.   The discharge tube electrode according to claim 7 or 8, comprising carbon powder and amorphous carbon.   The discharge tube electrode according to claim 9, further comprising a metal or metalloid compound.   The electrode for a discharge tube according to claim 9 or 10, wherein the carbon powder includes carbon nanotubes or carbon nanofibers.   The discharge tube electrode according to any one of claims 7 to 11, which has a columnar shape, a cylindrical shape, a coil shape, or a cone shape.

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