WO2011024821A1 - 放電ランプ用電極およびその製造方法 - Google Patents
放電ランプ用電極およびその製造方法 Download PDFInfo
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- WO2011024821A1 WO2011024821A1 PCT/JP2010/064312 JP2010064312W WO2011024821A1 WO 2011024821 A1 WO2011024821 A1 WO 2011024821A1 JP 2010064312 W JP2010064312 W JP 2010064312W WO 2011024821 A1 WO2011024821 A1 WO 2011024821A1
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- electrode
- mayenite compound
- powder
- sintered body
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J61/00—Gas-discharge or vapour-discharge lamps
- H01J61/02—Details
- H01J61/04—Electrodes; Screens; Shields
- H01J61/06—Main electrodes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J61/00—Gas-discharge or vapour-discharge lamps
- H01J61/02—Details
- H01J61/04—Electrodes; Screens; Shields
- H01J61/06—Main electrodes
- H01J61/067—Main electrodes for low-pressure discharge lamps
- H01J61/0675—Main electrodes for low-pressure discharge lamps characterised by the material of the electrode
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J61/00—Gas-discharge or vapour-discharge lamps
- H01J61/02—Details
- H01J61/04—Electrodes; Screens; Shields
- H01J61/06—Main electrodes
- H01J61/067—Main electrodes for low-pressure discharge lamps
- H01J61/0672—Main electrodes for low-pressure discharge lamps characterised by the construction of the electrode
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
- H01J9/02—Manufacture of electrodes or electrode systems
- H01J9/04—Manufacture of electrodes or electrode systems of thermionic cathodes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
- H01J9/02—Manufacture of electrodes or electrode systems
- H01J9/04—Manufacture of electrodes or electrode systems of thermionic cathodes
- H01J9/042—Manufacture, activation of the emissive part
Definitions
- the present invention relates to a discharge lamp, and more particularly to a hot cathode fluorescent lamp.
- Fluorescent lamps are widely used in applications such as lighting, backlights for display devices, and light irradiation in various production processes.
- a filament made of tungsten or molybdenum is generally used for the electrode of the hot cathode fluorescent lamp.
- the filament is usually coated with an electron-emitting material called an emitter.
- the emitter has a function of lowering the work function of the electrode and promoting thermionic emission during discharge.
- an alkaline earth metal oxide such as barium oxide (BaO), strontium oxide (SrO), or calcium oxide (CaO) is usually used (for example, Patent Document 1).
- Non-patent Document 1 a single crystal conductive mayenite compound is used as an electrode for thermal field emission.
- Non-Patent Document 1 the single crystal conductive mayenite compound described in Non-Patent Document 1 is not intended for use as an electrode of a fluorescent lamp. Therefore, it is unclear whether or not appropriate thermionic emission characteristics can be obtained when such an electrode is used in a fluorescent lamp. Furthermore, an electrode using a single crystal material has a problem that manufacturing is extremely complicated.
- This invention is made
- an electrode for a discharge lamp having an electrode main body that emits thermoelectrons, wherein the electrode main body is composed of a sintered body of a conductive mayenite compound.
- the electrode main body portion includes a cluster structure having a neck portion formed by bonding particles, and the surface of the cluster structure is configured such that the particles partially protrude.
- a dimensional uneven structure may be provided.
- the electrode body may further contain an alkaline earth metal oxide.
- the alkaline earth metal oxide may be at least one oxide selected from the group consisting of barium oxide (BaO), strontium oxide (SrO), and calcium oxide (CaO). May be included.
- a method of manufacturing an electrode for a discharge lamp having an electrode main body that emits thermoelectrons The electrode body is (1a) preparing a powder containing a mayenite compound; (1b) forming a molded body from the powder; (1c) firing the molded body to obtain a sintered body; (1d) imparting conductivity to the sintered body; The manufacturing method formed by is provided.
- a method of manufacturing an electrode for a discharge lamp having an electrode main body that emits thermoelectrons is (2a) preparing a powder containing a mayenite compound; (2b) forming a molded body from the powder; (2c) firing the molded body to obtain a sintered body having conductivity; The manufacturing method formed by is provided.
- the step (1d) and the step (2c) may include a step of heat-treating the sintered body in a reducing atmosphere.
- an electrode for a discharge lamp that can be used properly over a long period of time and a discharge lamp including such an electrode. Moreover, it becomes possible to provide the manufacturing method of such an electrode.
- FIG. 1 is a partially enlarged cross-sectional view showing a schematic example of a fluorescent lamp according to the present invention.
- FIG. 2 is a schematic view showing an example of the configuration of the electrode according to the present invention.
- FIG. 3 is a schematic view showing an example of the configuration of a conventional electrode.
- FIG. 4 is a photograph showing an example of the surface morphology of the conductive mayenite compound sintered body used in the electrode according to the present invention.
- FIGS. 5A to 5C are schematic views schematically showing an example of the formation process of the neck portion of the conductive mayenite compound sintered body.
- FIG. 6 is a flowchart schematically showing an example of a method for manufacturing an electrode main body of an electrode according to the present invention.
- FIG. 1 is a partially enlarged cross-sectional view showing a schematic example of a fluorescent lamp according to the present invention.
- FIG. 2 is a schematic view showing an example of the configuration of the electrode according to the present invention.
- FIG. 3 is a
- FIG. 7 is a flowchart schematically showing an example of another method for manufacturing the electrode main body of the electrode according to the present invention.
- FIG. 8 is an SEM photograph showing one surface form of the electrode according to Example 2.
- FIG. 9 is an SEM photograph showing one surface form of an electrode according to Comparative Example 2.
- FIG. 10 is a graph showing the relationship between the applied voltage of the electrode according to Example 3 and the thermionic emission current.
- FIG. 11 is a graph showing a Richardson plot of the electrode according to Example 3.
- FIG. 12 is an SEM photograph showing the surface form of the electrode according to Comparative Example 2 after the arc discharge test.
- FIG. 13 is a graph showing the relationship between Ar energy and sputtering rate when Ar is incident on BaO or mayenite compound.
- FIG. 1 is a partially enlarged cross-sectional view of a straight tube fluorescent lamp as an example of a fluorescent lamp, which is an embodiment of a discharge lamp preferably applied in the present invention.
- FIG. 2 schematically shows an example of the configuration of the electrodes included in the fluorescent lamp shown in FIG. Although the left side portion of the fluorescent lamp is not shown in FIG. 1, it will be apparent to those skilled in the art that this portion has a substantially symmetrical configuration with the right side portion of the illustrated fluorescent lamp.
- the fluorescent lamp 10 includes a tubular bulb 30 made of glass having a discharge space 20, an electrode 40, and a plug 50.
- a protective film 60 and a phosphor 70 are installed on the inner surface of the bulb 30.
- a discharge gas is sealed in the discharge space 20, and the discharge gas contains a rare gas.
- the discharge gas for example, an argon gas containing mercury is used.
- the protective film 60 has a role of preventing the inner wall of the fluorescent lamp from being blackened by preventing elution of sodium contained in the bulb 30 and suppressing generation of mainly mercury and sodium compounds.
- the plug 50 is provided at both ends of the fluorescent lamp 10 so as to support the bulb 30 and has a pin portion 55.
- the electrode 40 is sealed at both ends of the valve 30.
- the electrode 40 includes an electrode main body 41 having two end portions 41a and 41b, and support wires 45a and 45b electrically joined to the end portions 41a and 41b, respectively.
- the support wires 45 a and 45 b have conductivity, and the other ends are electrically connected to the respective pin portions 55 of the plug 50. Further, the support lines 45 a and 45 b have a role of supporting the electrode main body 41.
- the structure of the electrode 40 is merely an example, and it is obvious to those skilled in the art that the electrode 40 can take other structures.
- the electrode body 41 of the electrode 40 has a prismatic shape, but the shape of the electrode body 41 is not limited to this, and may be a linear structure, for example.
- the linear structure includes a coil-like structure.
- the shape of the cross section in the direction perpendicular to the longitudinal direction of the linear structure may be, for example, a circle, an ellipse, or a rectangle.
- the end portions 41 a and 41 b of the electrode main body 41 have a smaller cross section than the center portion of the electrode main body 41, but the end portions 41 a and 41 b of the electrode main body 41 are It may have the same cross-sectional dimension as the central portion of the portion 41.
- the electrode main body 41 and the support wires 45a and 45b are formed as separate elements. However, the electrode main body 41 and the support wires 45a and 45b may be integrated.
- FIG. 3 is a schematic view schematically showing an example of the configuration of a conventional electrode.
- the conventional electrode 140 has a filament 142 having two end portions 141a and 141b, and support wires 145a and 145b electrically joined to the end portions 141a and 141b, respectively.
- the support wires 145a and 145b have conductivity, and the other ends are electrically connected to the respective pin portions of the plug of the fluorescent lamp.
- the support lines 145a and 145b have a role of supporting the filament 142.
- the filament 142 is composed of a coil of metal such as tungsten (W) or molybdenum (Mo).
- the filament 142 is covered with an electron-emitting substance called an emitter 146.
- an alkaline earth metal oxide such as barium oxide (BaO), strontium oxide (SrO), or calcium oxide (CaO) is used. This is because an alkaline earth metal oxide generally has a low work function and can promote thermionic emission by applying a small voltage.
- the emitter 146 composed of an alkaline earth metal oxide material is easily consumed over time.
- barium oxide has a melting point and a boiling point of about 1923 ° C. and 2000 ° C., respectively
- calcium oxide (CaO) has a melting point and a boiling point of about 2572 ° C. and 2850 ° C., respectively.
- the melting point and boiling point are close. Therefore, from these physical property values, alkaline earth metal oxides are expected to have a relatively high vapor pressure at high temperatures.
- the emitter 146 heated to a high temperature during use of the fluorescent lamp is volatilized due to the influence of (1), and the emitter 146 becomes a filament during use due to the influence of (2). It is considered that the emitter 146 is consumed in a relatively short time because it falls off from 142.
- the emitter 146 when the emitter 146 is consumed, the luminous efficiency (more specifically, thermionic emission efficiency) of the fluorescent lamp decreases. In addition, when the emitter 146 is exhausted severely, the filament 142 is exposed, which easily causes disconnection of the electrode, resulting in a problem that the life of the fluorescent lamp is shortened.
- the electrode 40 does not have a structure in which the emitter 146 is coated on the filament 142 as in the prior art. That is, the fluorescent lamp 10 of the present invention is characterized in that the electrode main body 41 of the electrode 40 is composed of a sintered body of a conductive mayenite compound.
- the conductive mayenite compound is relatively stable even in a high temperature range exceeding 1100 ° C., and has a problem that it volatilizes during use of a fluorescent lamp like an alkaline earth metal oxide. Does not occur.
- the electrode main body 41 since the conventional metal filament is not required, the electrode main body 41 has a structure that does not have an interface between the metal filament and the emitter, which are feared of adhesion.
- the electrode 40 by constituting the electrode 40 with a sintered body of the mayenite compound, the problem that the emitter heated at a high temperature is volatilized or dropped during use of the fluorescent lamp is reduced.
- the electrode according to the present invention does not have a filament as in the prior art, there is no possibility of disconnection of the electrode due to exposure of the filament after the emitter is consumed. For this reason, in this invention, it becomes possible to use a fluorescent lamp appropriately over a long period of time.
- Non-patent Document 1 an example using a single crystal conductive mayenite compound as an electrode for thermal field emission has been reported.
- this document does not assume use as an electrode of a fluorescent lamp. Therefore, it is unclear whether or not appropriate thermionic emission characteristics can be obtained when an electrode composed of a single crystal conductive mayenite compound is used in a fluorescent lamp.
- an electrode made of a single crystal conductive mayenite compound has a relatively large work function.
- there is a problem that an electrode using a single crystal material is very complicated to manufacture.
- the electrode body 41 of the electrode 40 is composed of a (polycrystalline) sintered body of a conductive mayenite compound.
- FIG. 4 as an example, the surface form when an electrode body 41 composed of a sintered body of a conductive mayenite compound formed using a mayenite compound powder is observed with a scanning electron microscope (SEM). Shown (3000 times).
- the sintered body of the conductive mayenite compound has a cluster structure having a large number of neck portions formed by bonding particles, and the surface is constituted by partially protruding particles. It exhibits a three-dimensional uneven structure.
- the “particle” does not necessarily indicate a powder of a mayenite compound before sintering, but also means a portion that is in the form of particles when the sintered body is observed.
- FIG. 5 is a schematic view schematically showing an example of the formation process of the neck portion of the conductive mayenite compound sintered body.
- the particles are distributed inside the dense portion having a relatively smooth surface, and the particles are present on the surface. It can also be a form that partially protrudes.
- the structure of the sintered body as shown in FIG. 4 is formed in the course of firing the particles, and the mayenite compound or other crystals composed of constituent elements of the compound are reprecipitated on the surface of the sintered body. This is presumed to be a complicated phenomenon due to the simultaneous sintering of the mayenite compound powder.
- thermoelectrons when a sintered body having a surface structure as shown in FIG. 4 is used as a material for an electrode, its surface area increases dramatically, and more thermoelectrons can be emitted. It becomes easier to obtain a larger current. Therefore, extremely good thermionic properties can be obtained as compared with an electrode composed of a conventional single crystal conductive mayenite compound.
- the sintered body of the conductive mayenite compound of the present invention can be effectively used for electrodes such as fluorescent lamps. Further, according to the present invention, there is an effect that the electrode manufacturing method becomes extremely simple.
- the dimension of the projecting portion indicated by ⁇ (hereinafter referred to as “domain diameter”) is about 0.1 ⁇ m to 10 ⁇ m.
- domain diameter is about 0.1 ⁇ m to 10 ⁇ m.
- the electrode body 41 of the electrode 40 according to the present invention is composed of a sintered body of a conductive mayenite compound.
- the “mayenite compound” is a generic term for 12CaO ⁇ 7Al 2 O 3 (hereinafter also referred to as “C12A7”) having a cage ( ⁇ ) structure and a compound (same type compound) having a crystal structure equivalent to C12A7. .
- a mayenite compound includes oxygen ions in a cage, and these oxygen ions are particularly referred to as “free oxygen ions”.
- the “free oxygen ions” can be partially or completely replaced with electrons by reduction treatment or the like, and in particular, those having an electron density of 1.0 ⁇ 10 15 cm ⁇ 3 or more have “conductivity. It is called “mayenite compound”. Since the “conductive mayenite compound” has conductivity as its name indicates, it can be used as an electrode material as in the present invention.
- the electron density of the “conductive mayenite compound” is preferably 1.0 ⁇ 10 18 cm ⁇ 3 or more, more preferably 1.0 ⁇ 10 19 cm ⁇ 3 or more. More preferably, it is 0 ⁇ 10 20 cm ⁇ 3 or more.
- the electron density of the conductive mayenite compound is lower than 1.0 ⁇ 10 18 cm ⁇ 3 , the resistance of the electrode when used for the electrode may increase.
- the electron density of conductive mayenite means a measured value of spin density calculated by measurement with an electron spin resonance apparatus or calculated by measurement of an absorption coefficient.
- the measured value of the spin density is smaller than 10 19 cm ⁇ 3 , it is preferable to use an electron spin resonance apparatus (ESR apparatus), and when it exceeds 10 18 cm ⁇ 3 , Thus, it is preferable to calculate the electron density.
- ESR apparatus electron spin resonance apparatus
- the intensity of light absorption by electrons in the cage of conductive mayenite is measured, and the absorption coefficient at 2.8 eV is obtained.
- the electron density of the conductive mayenite is quantified using the fact that the obtained absorption coefficient is proportional to the electron density.
- the conductive mayenite is powder or the like and it is difficult to measure the transmission spectrum with a photometer, the light diffusion spectrum is measured using an integrating sphere, and the conductive mayenite is obtained from the value obtained by the Kubelka-Munk method. The electron density is calculated.
- the conductive mayenite compound has a crystal structure equivalent to the C12A7 crystal structure composed of calcium (Ca), aluminum (Al) and oxygen (O), calcium (Ca), aluminum (Al ) And oxygen (O) may be partially or wholly substituted with another atom or atomic group.
- a part of calcium (Ca) is magnesium (Mg), strontium (Sr), barium (Ba), lithium (Li), sodium (Na), chromium (Cr), manganese (Mn), cerium (Ce). , Cobalt (Co), nickel (Ni) and / or copper (Cu) and the like may be substituted.
- a part of aluminum (Al) is silicon (Si), germanium (Ge), boron (B), gallium (Ga), titanium (Ti), manganese (Mn), iron (Fe), cerium (Ce).
- Praseodymium (Pr), scandium (Sc), lanthanum (La), yttrium (Y), europium (Eu), yttrium (Yb), cobalt (Co), nickel (Ni) and / or terbium (Tb) May be.
- the oxygen in the cage skeleton may be substituted with nitrogen (N) or the like.
- the conductive mayenite compound is preferably a 12CaO ⁇ 7Al 2 O 3 compound, a 12SrO ⁇ 7Al 2 O 3 compound, a mixed crystal compound thereof, or an isomorphous compound thereof.
- the following compounds (1) to (4) are considered as the conductive mayenite compound.
- Mg magnesium
- Sr strontium
- Ca 1-z Sr z calcium strontium aluminate
- y and z are 0.1 or less.
- the free oxygen ion in the cage is an anion such as H ⁇ , H 2 ⁇ , H 2 ⁇ , O ⁇ , O 2 ⁇ , OH ⁇ , F ⁇ , Cl ⁇ , Br ⁇ , S 2 ⁇ or Au ⁇ .
- an anion such as H ⁇ , H 2 ⁇ , H 2 ⁇ , O ⁇ , O 2 ⁇ , OH ⁇ , F ⁇ , Cl ⁇ , Br ⁇ , S 2 ⁇ or Au ⁇ .
- Both cation and anion are substituted, for example wadalite Ca 12 Al 10 Si 4 O 32 : 6Cl ⁇ .
- the electrode main-body part 41 may be comprised only with an electroconductive mayenite compound, it may contain another additive substance.
- Another additive material includes, for example, an alkaline earth metal oxide.
- the alkaline earth metal oxide barium oxide (BaO), strontium oxide (SrO), calcium oxide (CaO), or the like is preferable.
- the electrode body 41 contains the conductive mayenite compound and such an oxide at the same time, excellent thermionic emission characteristics over a wide temperature range from a low temperature range (up to about 800 ° C.) to a high temperature range (up to about 1300 ° C.). Is obtained.
- Another additive substance is added in the range of, for example, 1 wt% to 50 wt% with respect to the total weight of the electrode main body 41.
- the resistance value of the electrode body 41 may be in the range of 0.1 ⁇ to 100 ⁇ .
- the resistance value of the electrode body 41 is preferably in the range of 0.5 to 50 ⁇ , more preferably in the range of 1 to 20 ⁇ , and even more preferably in the range of 2 to 10 ⁇ .
- the resistance value is smaller than 0.1 ⁇ , the current flowing through the entire circuit increases, and it may not be possible to selectively heat only the electrodes. On the other hand, if it is greater than 100 ⁇ , it becomes difficult for the current to flow, and the electrode may not be heated sufficiently.
- the conductivity of the conductive mayenite compound can be adjusted relatively easily by heat treatment in a reducing atmosphere described later. Therefore, the resistance value of the electrode main body 41 can also be controlled relatively easily. The resistance value can also be controlled by the density of the sintered body.
- phosphor 70 examples include europium activated yttrium oxide phosphor, cerium terbium activated lanthanum phosphate phosphor, europium activated strontium halophosphate phosphor, europium activated barium magnesium aluminate phosphor, europium manganese activated barium magnesium An aluminate phosphor, a terbium activated cerium aluminate phosphor, a terbium activated cerium magnesium aluminate phosphor, an antimony activated calcium halophosphate phosphor, or the like can be used alone or in combination.
- the shape, size, wattage, light color and color rendering properties, etc. emitted by the fluorescent lamp are not particularly limited.
- the shape is not limited to the straight pipe as shown in FIG. 1, and may be a round shape, a double ring shape, a twin shape, a compact shape, a U shape, a light bulb shape, or the like.
- the size may be 4 to 110.
- the wattage may be, for example, several watts to hundreds tens of watts.
- Examples of the light color include daylight color, daylight white color, white color, warm white color, and light bulb color.
- the manufacturing method of the electrode body 41 is roughly divided into two methods depending on the difference in the process of imparting conductivity to the mayenite compound.
- the first method is a method of imparting conductivity to the mayenite compound after sintering the powder of the mayenite compound to obtain a sintered body and then processing the sintered body into a desired shape.
- the second method is a method of imparting conductivity at the same time when a sintered body is obtained by sintering a powder of a mayenite compound.
- FIG. 6 shows a flowchart of the first method.
- the first method includes a step of preparing a powder containing a mayenite compound (step 110: S110), a step of forming a molded body containing the powder (step 120: S120), and the molding.
- the body is fired to obtain a sintered body (step 130: S130), and the obtained sintered body is subjected to a process of imparting conductivity (step 140: S140).
- step 110: S110 a powder containing a mayenite compound
- step 120: S120 a step of forming a molded body containing the powder
- step 140 a process of imparting conductivity
- a mayenite compound powder having an average particle size of about 1 ⁇ m to 10 ⁇ m is prepared.
- the average particle size of the powder is preferably 2 ⁇ m or more and 6 ⁇ m or less. If the average particle size is smaller than 1 ⁇ m, it is difficult to agglomerate the powder and make it further finer, and if it is larger than 10 ⁇ m, sintering may not proceed easily.
- the mayenite compound powder is prepared by coarsely pulverizing the mayenite compound raw material and further pulverizing the coarse powder to a fine particle.
- a stamp mill, an automatic mortar, or the like is used for the coarsening of the raw material.
- a ball mill, a bead mill, or the like is used to pulverize the coarse powder to the fine powder having the above average particle diameter.
- Step 120 Next, a compact containing the mayenite compound powder is produced.
- the method for producing the molded body is not particularly limited, and the molded body may be produced through a paste (or slurry; hereinafter the same) or by pressure molding of a powder or paste.
- the paste may be prepared by adding the above-mentioned prepared powder together with a binder to a solvent and stirring.
- a binder either an organic binder or an inorganic binder can be used.
- the organic binder include nitrocellulose, ethyl cellulose, polyethylene oxide, methyl cellulose, hydroxylpropyl methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, sodium polyacrylate, polyacrylamide, polyvinyl butyral, polyethylene, polypropylene, polystyrene, and ethylene-acetic acid.
- Vinyl copolymers, acrylic resins, polyamide resins and the like can be used.
- group a metal alkoxide type
- the blending amount of the binder is preferably 0.5 to 60% by volume with respect to the prepared powder.
- a plasticizer, a dispersant, and a lubricant may be added.
- Plasticizers can add plasticity during molding.
- the dispersant breaks up powder agglomerates and improves dispersibility.
- the lubricant reduces friction between powders, improves fluidity, and facilitates molding.
- the plasticizer for example, glycerin, polyethylene glycol, dibutyl phthalate and the like can be used.
- the dispersant for example, fatty acids, phosphate esters, synthetic surfactants, benzenesulfonic acid, and the like can be used.
- the lubricant for example, polyethylene glycol ethyl ether, polyoxyethylene ester, or the like can be used.
- a molded body can be obtained by extrusion molding or injection molding the paste.
- a molded body having a desired shape may be formed by placing the above-described prepared powder or paste in a mold and pressurizing the mold.
- Step 130 Next, the obtained molded body is fired.
- the molded body may be previously held at a temperature range of 50 ° C. to 200 ° C. for about 20 to 30 minutes, and the solvent may be volatilized and removed.
- the molded body may be held in advance at a temperature range of 200 to 800 ° C. for about 20 to 30 minutes to remove the binder. Alternatively, both processes may be performed simultaneously.
- Calcination conditions are not particularly limited.
- the firing treatment is performed, for example, in an air atmosphere, a vacuum, or an inert gas atmosphere.
- the firing temperature is, for example, in the range of 1200 ° C. to 1415 ° C., and preferably in the range of 1250 ° C. to 1350 ° C.
- the temperature is lower than 1200 ° C., the sintering is insufficient, and the obtained sintered body may be brittle.
- the firing temperature is higher than 1415 ° C., the melting of the powder proceeds and the shape of the molded body may not be maintained.
- the time for maintaining the temperature may be adjusted so as to complete the sintering of the compact, but is preferably 5 minutes or more, more preferably 10 minutes or more, and even more preferably 15 minutes or more. If the holding time is shorter than 5 minutes, the sintering may not proceed sufficiently. Further, even if the holding time is increased, there is no particular problem in terms of characteristics, but considering the manufacturing cost, the holding time is preferably within 6 hours.
- the obtained sintered body is then processed into a desired shape.
- the machining method is not particularly limited, and machining, electric discharge machining, laser machining, or the like may be applied.
- Step 140 Next, the process which provides electroconductivity with respect to the obtained sintered compact (mayenite compound) is performed.
- Conductivity can be imparted to the sintered body by heat-treating the sintered body in a reducing atmosphere.
- the reducing atmosphere means an atmosphere or a reduced pressure environment in which a reducing agent is present at a site in contact with the atmosphere and an oxygen partial pressure is 10 ⁇ 3 Pa or less.
- a powder of carbon or aluminum may be mixed with the raw material of the mayenite compound, and carbon, calcium, aluminum, or titanium may be installed at a site in contact with the atmosphere.
- carbon a method in which the molded body is put in a carbon container and fired under vacuum is exemplified.
- the oxygen partial pressure is, for example, 10 ⁇ 5 Pa or less, preferably 10 ⁇ 10 Pa or less, and more preferably 10 ⁇ 15 Pa. When the oxygen partial pressure is 10 ⁇ 3 Pa or more, sufficient conductivity may not be obtained.
- the heat treatment temperature is in the range of 600 to 1415 ° C.
- the heat treatment temperature is preferably in the range of 1000 ° C. to 1400 ° C., more preferably in the range of 1200 to 1370 ° C., and still more preferably in the range of 1300 ° C. to 1350 ° C.
- the temperature of heat processing is lower than 600 degreeC, there exists a possibility that sufficient electroconductivity may not be provided to a mayenite compound.
- the heat treatment temperature is higher than 1415 ° C., the sintered body may be melted and the shape of the formed body may not be maintained.
- the heat treatment time is preferably in the range of 5 minutes to 6 hours, more preferably in the range of 10 minutes to 4 hours, and further preferably in the range of 15 minutes to 2 hours. If the holding time is less than 5 minutes, sufficient conductivity may not be obtained. Further, even if the holding time is increased, there is no particular problem in terms of characteristics, but considering the manufacturing cost, the holding time is preferably within 6 hours.
- the electrode main body part which consists of an electroconductive mayenite compound can be produced according to the above process.
- FIG. 7 shows a flowchart of the second method.
- the second method includes a step of preparing a powder containing a mayenite compound (step 210: S210), a step of forming a molded body containing the powder (step 220: S220), and the molding.
- the body is fired to obtain a sintered body, and at the same time, the step of imparting conductivity to the sintered body (step 230: S230).
- Step 210 and Step 220 are the same as Step 110 and Step 120 of the first method described above.
- step 230 will be described in detail below.
- Step 230 the molded body obtained in step 220 is fired by the firing process.
- the molded body may be previously held at a temperature range of 50 ° C. to 200 ° C. for about 20 to 30 minutes, and the solvent may be volatilized and removed.
- the molded body may be held in advance at a temperature range of 200 to 800 ° C. for about 20 to 30 minutes to remove the binder. Alternatively, both processes may be performed simultaneously.
- the firing treatment can be performed by heat-treating the molded body in a reducing atmosphere.
- the reducing atmosphere means an inert gas atmosphere in which a reducing agent is present at a site in contact with the atmosphere and an oxygen partial pressure of 10 ⁇ 3 Pa or less, or a reduced pressure environment.
- a reducing agent for example, carbon or aluminum powder may be mixed with the raw material, and carbon, calcium, aluminum, or titanium may be installed at a site in contact with the atmosphere.
- carbon a method in which the molded body is put in a carbon container and fired under vacuum is exemplified.
- the oxygen partial pressure is preferably 10 ⁇ 5 Pa or less, more preferably 10 ⁇ 10 Pa, and even more preferably 10 ⁇ 15 Pa or less.
- the oxygen partial pressure is higher than 10 ⁇ 3 Pa, there is a possibility that sufficient conductivity cannot be imparted to the mayenite compound.
- Calcination temperature is in the range of 1200 ° C to 1415 ° C.
- the firing temperature is more preferably in the range of 1250 ° C to 1350 ° C.
- the firing temperature is lower than 1200 ° C., the sintering becomes difficult to proceed, and the obtained sintered body may become brittle.
- the firing temperature is higher than 1415 ° C., the melting of the powder proceeds and the shape of the molded body may not be maintained.
- the firing time may be any time as long as the sintering of the compact is completed and sufficient conductivity is imparted.
- the holding time may be, for example, in the range of 5 minutes to 6 hours, preferably in the range of 10 minutes to 4 hours, and more preferably in the range of 15 minutes to 2 hours.
- When holding time is less than 5 minutes there exists a possibility that sufficient electroconductivity may not be provided to a mayenite compound. Further, even if the holding time is lengthened, there is no particular problem in terms of characteristics, but in consideration of the production cost, it is preferably within 6 hours.
- the electrode main body part which consists of an electroconductive mayenite compound can be produced according to the above process.
- the manufacturing method of the present invention has been described by taking as an example the case where the electrode main body portion is composed of only a conductive mayenite compound.
- the mayenite compound powder is formed, for example, with a desired alkaline earth metal carbonate in the steps 110 and 210 described above. What is necessary is just to add powder and prepare mixed powder. However, when such a mixed powder is used as a starting material, a treatment for removing CO 2 generated in the course of the reaction is required. This is because if the CO 2 remains, mercury in the fluorescent lamp is deteriorated and luminous efficiency is lowered.
- the removal of CO 2 may be performed, for example, by holding the molded body at a temperature of 800 ° C. to 1200 ° C. for about 20 to 30 minutes in advance under a nitrogen atmosphere or a vacuum.
- a slurry containing alkaline earth metal carbonate (eg, BaCO 3 ) powder is applied to the filament.
- alkaline earth metal carbonate eg, BaCO 3
- the filament is energized to heat the filament.
- the carbonate powder is decomposed into oxides, and an emitter made of an alkaline earth metal oxide is formed on the filament.
- the electrode body portion is composed only of the conductive mayenite compound
- carbon dioxide (CO 2 ) is used because the alkaline earth metal carbonate is not used as a starting material when forming the emitter.
- a bulb having an internal space filled with mercury and a rare gas, a phosphor installed on the inner surface of the bulb, and an electrode for generating and maintaining a discharge in the internal space
- a discharge lamp is provided in which the electrode body is made of a sintered body of a conductive mayenite compound.
- the fluorescent lamp shown in FIG. 1 is provided.
- This fluorescent lamp has a bulb 30 having a protective film 60 and a phosphor 70 applied on the inner surface, and in the internal space of the bulb, mercury (Hg) gas for phosphor excitation and argon (Ar) as a rare gas. ) And are filled.
- an electrode 40 for generating and maintaining a discharge is installed in the internal space.
- the electrode 40 is composed of a sintered body of a mayenite compound. In such a fluorescent lamp, electrode consumption during discharge is suppressed and stable characteristics can be maintained over a long period of time.
- Example 1 The electrode sample comprised with the sintered compact of the electroconductive mayenite compound was formed with the following method.
- the powder A1 had only a 12CaO ⁇ 7Al 2 O 3 structure, and the powder A1 was a (non-conductive) mayenite compound. Further, when the electron density of the powder A1 was determined by an ESR apparatus, the electron density was less than 1 ⁇ 10 15 cm ⁇ 3 .
- the powder A1 was pressure-molded at a pressure of 2 MPa to produce a disk-shaped molded body having a diameter of 1 cm and a thickness of 5 mm. Furthermore, this molded body was heated to 1350 ° C. to obtain a sintered body. The obtained sintered body was put in a carbon container with a lid, and this carbon container was put in an electric furnace having an oxygen partial pressure of 10 ⁇ 3 Pa or less (that is, the aforementioned “reducing atmosphere”) in a vacuum. Hold for 2 hours at ° C. Further, the obtained sample was pulverized using a dry ball mill to obtain a powder A2. As a result of the measurement by the laser diffraction scattering method described above, the average particle size of the powder A2 was 5 ⁇ m.
- the light diffusion reflection spectrum was measured, and the electron density of powder A2 was determined by the Kubelka-Munk method.
- the electron density of the powder A2 was 7 ⁇ 10 18 cm ⁇ 3 , and it was confirmed that the powder A2 was a conductive mayenite compound.
- powder A2 was pressure-molded to produce a disk-shaped molded body having a diameter of 1 cm and a thickness of 5 mm.
- This molded body was put in a carbon container with a lid, and the inside of the container was evacuated to 10 ⁇ 3 Pa or less and held at 1300 ° C. for 2 hours. Thereby, the sintered compact B was obtained.
- a square columnar sample was prepared by grinding the sintered body B.
- the dimensions of the square columnar sample are about 2 mm long ⁇ about 2 mm wide ⁇ about 10 mm high.
- this square columnar sample was subjected to heat treatment.
- the heat treatment was performed by holding a square columnar sample in a carbon container at 1325 ° C. for 2 hours under a vacuum environment with an oxygen partial pressure of 10 ⁇ 3 Pa or less.
- the electrode according to Example 1 thus obtained was measured for the light diffuse reflection spectrum, and the electron density was determined by the Kubelka-Munk method. As a result, the electron density was 3 ⁇ 10 20 cm ⁇ 3 . Moreover, it was confirmed by X-ray diffraction that the electrode according to Example 1 had only a 12CaO ⁇ 7Al 2 O 3 structure, and the electrode according to Example 1 was a mayenite compound. In addition, the weight of the conductive mayenite compound serving as the electrode main body was 109 mg.
- platinum was vapor-deposited on both ends (region of 1 mm from the end face) of the electrode according to Example 1.
- the resistance value was 4 ⁇ .
- Example 2 The powder A1 was further pulverized by a wet ball mill using isopropyl alcohol as a solvent. The pulverized powder was suction filtered and dried in air at 80 ° C. to obtain a powder A3. The average particle diameter of the powder A3 was 5 ⁇ m.
- the electron density was calculated
- the electron density of the powder A3 was less than 1 ⁇ 10 15 cm ⁇ 3
- the powder A3 was a non-conductive mayenite compound.
- powder A3 and polyvinyl alcohol as a binder were mixed at a weight ratio of 99: 1, and this mixture was poured into a mold.
- a pressure of 2 MPa was applied to the mold to obtain a quadrangular columnar shaped body.
- the size of the molded body is about 2 mm long ⁇ about 2 mm wide ⁇ about 10 mm high.
- the molded body was held at 300 ° C. for 30 minutes in an air atmosphere to remove the binder contained in the molded body.
- the compact was placed in a carbon container with a lid, and this was placed in an electric furnace.
- the compact was heat-treated in a reducing atmosphere in which the electric furnace was evacuated and the oxygen partial pressure in the furnace was 10 ⁇ 3 Pa or less.
- the heat treatment temperature was 1325 ° C. and the holding time was 2 hours.
- an electrode made of a mayenite compound was obtained.
- the dimensions of the electrode were about 1.9 mm long ⁇ about 1.9 mm wide ⁇ about 9.7 mm high.
- the electrode according to Example 2 obtained in this way, the light diffuse reflection spectrum was measured, and the electron density was determined by the Kubelka-Munk method. As a result, the electron density was 3 ⁇ 10 20 cm ⁇ 3 . Moreover, it was confirmed by X-ray diffraction that the electrode according to Example 2 had only a 12CaO ⁇ 7Al 2 O 3 structure, and the electrode according to Example 2 was a mayenite compound. Moreover, the weight of the conductive mayenite compound serving as the electrode main body was 94 mg.
- platinum was vapor-deposited on both ends (region of 1 mm from the end face) of the electrode according to Example 2.
- the resistance value was 5 ⁇ .
- Comparative Example 1 A so-called double coil tungsten filament (W-460100 manufactured by Niraco) was used as an electrode sample (electrode according to Comparative Example 1) as it was.
- electrode according to Comparative Example 2 an electrode sample (hereinafter, referred to as “electrode according to Comparative Example 2”) in which an emitter was installed on a filament was obtained.
- the emitter was composed only of barium oxide (BaO).
- the weight of the deposited emitter was 17 mg.
- each electrode (About the surface form of each electrode) The surface of each electrode (excluding the electrode according to Comparative Example 1) obtained by the above method was observed using an FE-SEM apparatus (S-4300, manufactured by Hitachi, Ltd.).
- Example 8 and 9 show the surface forms of the electrode according to Example 2 (observed at 3000 times) and the electrode according to Comparative Example 2 (observed at 6000 times), respectively.
- the electrode according to Example 2 had a three-dimensional uneven structure in which the tip of a cluster lump having a large number of neck portions formed by combining particles with each other protruded in a complicated manner. .
- the surface form of the electrode according to Example 1 was almost the same as that of Example 2.
- the electrode according to Comparative Example 2 had a structure in which the relatively flat island portions that were covered were partially separated by a large groove.
- thermoelectric emission characteristics evaluation The thermionic emission characteristics of each electrode were evaluated by the following method.
- sample electrode one of the electrodes described above (hereinafter, referred to as "sample electrode") and was placed the collector electrode so that the distance 7cm from the electrode, a vacuum chamber for about 10 - The air was exhausted to 4 Pa.
- the sample electrode was energized with a voltage of 1 kV applied between both electrodes. Then, when the sample electrode was heated to a predetermined temperature, the thermoelectrons radiated from the sample electrode (actually, the current value flowing through the collector electrode) were measured.
- the temperatures of the sample electrodes were 900 ° C., 1000 ° C., 1100 ° C., 1200 ° C., and 1300 ° C., respectively.
- the temperature of the sample electrode was measured with a radiation thermometer (manufactured by Minolta, Inc., TR-630).
- Example 1 and Example 2 have good thermionic emission characteristics in a wide temperature range of 900 ° C. to 1300 ° C.
- Electrode according to Example 3 The work function of an electrode sample composed of a sintered body of a conductive mayenite compound (hereinafter referred to as “electrode according to Example 3”) was evaluated by the following method.
- the electrode according to Example 3 was produced by the following method.
- the above-mentioned powder A1 was pressure-molded with a pressure of 2 MPa to produce a disk-shaped molded body having a diameter of 1 cm and a thickness of 1 mm.
- this molded body was put into a carbon container with a lid, and the container was heated in an electric furnace in a reduced pressure atmosphere of 10 ⁇ 3 Pa or less to obtain a sintered body.
- the heat treatment temperature was 1350 ° C. and the holding time was 2 hours.
- the obtained sintered body had a 12CaO.7Al 2 O 3 structure, and the crystal orientation was not unevenly distributed in a specific direction, so that it was confirmed to be a polycrystalline body.
- the light diffuse reflection spectrum of the obtained sintered body was measured, and the electron density of the sintered body was determined by the Kubelka-Munk method. As a result, the electron density was 3 ⁇ 10 20 cm ⁇ 3 .
- the single crystal of the mayenite compound is produced by the Czochralski method or the floating zone method, and a single crystal cannot be obtained by the production method as in the present application.
- this sintered body was roughly pulverized in an agate mortar to obtain a sample having a size of about 1 mm square.
- Platinum was vapor-deposited on one side of the sample, and the sample was deposited on a copper plate (30 mm square, 3 mm thick) via a conductive adhesive (Dotite XA-819A manufactured by Fujikura Kasei) with the platinum vapor-deposited surface serving as a bonding surface. Glued. Then, this copper plate was hold
- the gap between the tip of the sintered body of the mayenite compound and a normal copper plate electrode (30 mm square, 3 mm thickness) was 0.1 mm, and both electrodes were vacuumed Placed in the chamber. Both electrodes were arranged so that the copper plates were parallel.
- the inside of the vacuum chamber was evacuated to about 10 ⁇ 4 Pa.
- the surface (copper plate side) of the electrode according to Example 3 was heated with a carbon heater to adjust the electrode to the test temperature.
- the test temperatures were 50 ° C, 68 ° C, 77 ° C, 86 ° C, and 115 ° C.
- thermoelectron emission current generated from the electrode according to Example 3 was measured.
- FIG. 10 collectively shows the results obtained at each temperature of 50 ° C. to 115 ° C.
- the horizontal axis represents the square root of the applied voltage (kV)
- the vertical axis represents the ln logarithm of the thermoelectron emission current I ( ⁇ A).
- the saturation emission current Is when the applied voltage was 0 at each temperature was obtained by extrapolation.
- the work function ⁇ of the electrode according to Example 3 was calculated by the Richardson plot method using the saturated emission current Is.
- the index ln (Is / T 2 ) obtained from the saturated emission current Is and the measured temperature T is plotted against the reciprocal (1 / kT) of the product of the temperature and the Boltzmann constant k.
- the work function ⁇ of the electrode is calculated from the slope of the straight line obtained in (1) (Basics of vacuum nanoelectronics, by Eihiko Yamamoto, Japan Society for the Promotion of Science, P80-81).
- FIG. 11 shows the result of the Richardson plot. From the slope of the straight line in this plot, the work function of the electrode according to Example 3 was predicted to be about 0.6 eV. In addition, the same figure shows simultaneously the result at the time of using the electroconductive mayenite compound of a single crystal described in the above-mentioned nonpatent literature 1 as an electrode. In this case, the work function of the electrode was reported to be about 2.1 eV, and it was found that the work function of the electrode according to Example 3 was significantly reduced compared to the electrode made of single crystal conductive mayenite. .
- any one of the above-mentioned sample electrodes is set as a cathode in the vacuum chamber, a tungsten electrode is set as an anode so as to be a distance of 5 mm from the electrode, and the vacuum chamber is exhausted to about 10 ⁇ 4 Pa. did.
- Ar gas was introduced into the vacuum chamber, and the internal pressure was set to 338 Pa. Furthermore, a voltage of 100 V was applied between the sample electrode (cathode) and the tungsten electrode (anode).
- the sample electrode was energized and arc discharge was performed.
- the energization amount of the sample electrode was adjusted so that the arc discharge current was 0.2 A, and the temperature of the sample electrode at this time was measured with the above-mentioned radiation thermometer.
- FIG. 12 shows the surface form of the electrode according to Comparative Example 2 after the test. From the comparison between FIG. 12 and FIG. 9, the electrode according to Comparative Example 2 shows that the surface morphology is greatly changed by the arc discharge test, that is, in FIG. 12, the groove is deeper than the groove in FIG. 9. It can be seen that the island is separated into smaller areas.
- Example 4 Simulation calculation of sputtering resistance of BaO and mayenite compound
- the sputtering rate of the mayenite compound was calculated when Ar atoms were perpendicularly incident on the sample (target) by the Monte Carlo method.
- the TRIM code J. F. Ziegler, JP Biersack, U. Littmark, “The Stopping and Range of Ions in Solid”, vol. 1 of series “Popping and Range on Ps. , New York (1984)
- the sputtering rate was also calculated for BaO.
- the sputtering rate is the number of target atoms sputtered per incident atom or ion, and the smaller the value, the harder it is to sputter.
- the density of the mayenite compound and BaO as the target was set to 3.55 eV / atom for the mayenite compound and 3.90 eV / atom for BaO.
- the eV / atom used here is a unit indicating an energy value per one atom of the material.
- the discharge gas of fluorescent lamps currently in practical use is a mixed gas containing Ar as a main component. Therefore, in Example 4, a simulation was performed for Ar as a flying atom. In this simulation, the efficiency at which the constituent atoms of the mayenite compound or BaO jump out of the material surface by sputtering when the kinetic energy of Ar is changed in the range of 0.1 to 1.0 keV is estimated.
- FIG. 13 shows the calculation result when the sputtering rate of BaO is 1 when 0.1 keV Ar is incident. In all energy regions in FIG. 11, the sputtering rate of the mayenite compound is shown to be lower than that of BaO. From the above, it was found that the mayenite compound exhibits higher sputtering resistance than BaO against Ar, which is a discharge gas for a fluorescent lamp.
- an electrode composed of a sintered body of a mayenite compound is stable in a wide temperature range and has a good thermoelectron emission characteristic as compared with a conventional electrode. Therefore, in a fluorescent lamp having an electrode composed of a sintered body of a mayenite compound, consumption of the electrode during discharge is suppressed, and stable characteristics can be maintained over a long period of time.
- the present invention can be applied to a fluorescent lamp having an electrode for discharge.
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Abstract
Description
水銀および希ガスが充填された内部空間を有するバルブと、
該バルブの内表面に設置された蛍光体と、
前記内部空間で放電を発生、維持させる電極と、
を有する放電ランプであって、
前記内部空間で放電を発生、維持させる電極は、前述の特徴を有する電極である、放電ランプが提供される。
熱電子を放出させる電極本体部を有する放電ランプ用の電極の製造方法であって、
前記電極本体部は、
(1a)マイエナイト化合物を含む粉末を準備するステップと、
(1b)前記粉末から成形体を形成するステップと、
(1c)前記成形体を焼成して焼結体を得るステップと、
(1d)前記焼結体に導電性を付与するステップと、
により形成される、製造方法が提供される。
熱電子を放出させる電極本体部を有する放電ランプ用の電極の製造方法であって、
前記電極本体部は、
(2a)マイエナイト化合物を含む粉末を準備するステップと、
(2b)前記粉末から成形体を形成するステップと、
(2c)前記成形体を焼成して、導電性を有する焼結体を得るステップと、
により形成される、製造方法が提供される。
次に、本発明による蛍光ランプの電極40および蛍光体70について、詳しく説明する。なお、バルブ30、プラグ50および保護膜60等の部材に関しては、その仕様は、当業者には十分に明らかであるので、記載を省略する。
前述のように、本発明による電極40の電極本体部41は、導電性マイエナイト化合物の焼結体で構成される。
蛍光体70としては、例えば、ユーロピウム付活酸化イットリウム蛍光体、セリウムテルビウム付活燐酸ランタン蛍光体、ユーロピウム付活ハロ燐酸ストロンチウム蛍光体、ユーロピウム付活バリウムマグネシウムアルミネート蛍光体、ユーロピウムマンガン付活バリウムマグネシウムアルミネート蛍光体、テルビウム付活セリウムアルミネート蛍光体、テルビウム付活セリウムマグネシウムアルミネート蛍光体、およびアンチモン付活ハロ燐酸カルシウム蛍光体などを単独、または混合して使用できる。
次に、本発明による電極40の電極本体部41の製造方法について説明する。
図6には、第1の方法のフロー図を示す。
まず、平均粒径1μm~10μm程度のマイエナイト化合物粉末が準備される。特に、粉末の平均粒径は、2μm以上6μm以下であることが好ましい。なお、平均粒径が1μmより小さいと、粉末が凝集してそれ以上の微粉化することが困難であり、10μmより大きいと、焼結が進みにくくなるおそれがある。
次に、マイエナイト化合物粉末を含む成形体が作製される。
次に、得られた成形体が焼成される。なお、成形体が溶媒を含む場合は、予め成形体を50℃~200℃の温度範囲で20~30分程度保持し、溶媒を揮発させて除去しても良い。また、成形体がバインダを含む場合は、予め成形体を200~800℃の温度範囲で20~30分程度保持し、バインダを除去しても良い。あるいは、両者の処理を同時に行っても良い。
次に、得られた焼結体(マイエナイト化合物)に対して導電性を付与する処理が行われる。
図7には、第2の方法のフロー図を示す。
このステップでは、焼成処理によって、ステップ220によって得られた成形体が焼成される。なお、成形体が溶媒を含む場合は、予め成形体を50℃~200℃の温度範囲で20~30分程度保持し、溶媒を揮発させて除去しても良い。また、成形体がバインダを含む場合は、予め成形体を200~800℃の温度範囲で20~30分程度保持し、バインダを除去しておいても良い。あるいは、両者の処理を同時に行っても良い。
以下の方法により、導電性マイエナイト化合物の焼結体で構成された電極サンプルを形成した。
炭酸カルシウム(CaCO3)と酸化アルミニウム(Al2O3)の粉末を、モル比で12:7となるように混合した後、この混合粉末を大気中、1300℃で6時間保持した。次に、得られた焼結体を自動乳鉢で粉砕し、粉末(以下、粉末A1と称する)を得た。レーザ回折散乱法(SALD-2100、島津製作所社製)により、この粉末A1の粒度を測定したところ、平均粒径は、20μmであった。また、X線回折により、粉末A1は、12CaO・7Al2O3構造だけを有し、粉末A1は、(非導電性)マイエナイト化合物であることが確認された。さらに、ESR装置により、粉末A1の電子密度を求めたところ、電子密度は、1×1015cm-3未満であった。
次に、粉末A2を加圧成形して、直径1cm、厚み5mmの円盤形状の成形体を作製した。この成形体を蓋付きカーボン容器に入れ、容器内を10-3Pa以下の真空とし、1300℃で2時間保持した。これにより、焼結体Bを得た。
イソプロピルアルコールを溶媒とする湿式ボールミルにより、前述の粉末A1をさらに粉砕した。粉砕粉を吸引ろ過し、80℃空気中で乾燥して、粉末A3を得た。粉末A3の平均粒径は、5μmであった。
いわゆるダブルコイル構造のタングステンフィラメント(ニラコ社製W-460100)を、そのまま電極サンプル(比較例1に係る電極)として使用した。
前述のタングステンフィラメントのコイル部に、炭酸バリウム(関東化学社製)の粉末を付与し、酸素分圧が10-3Pa以下の真空下でフィラメントに通電した。電圧は、8Vとし、フィラメント温度は、約1000℃、通電時間は15分とした。
以上の方法により得られた各電極(比較例1に係る電極を除く)の表面を、FE-SEM装置(日立製作所製S-4300)を用いて観察した。
以下の方法により、各電極の熱電子放出特性を評価した。
以下の方法で、導電性マイエナイト化合物の焼結体で構成された電極サンプル(以下、「実施例3に係る電極」と称する)の仕事関数を評価した。
実施例3に係る電極は、以下の方法により作製した。
この実施例3に係る電極を用い、マイエナイト化合物の焼結体の先端部と、通常の銅板電極(30mm角、厚さ3mm)との間隔が0.1mmとなるようにして、両電極を真空チャンバ内に配置した。両電極は、銅板が平行となるように配置した。次に、真空チャンバ内を約10-4Paまで排気した。実施例3に係る電極の表面(銅板側)を、カーボンヒーターで加熱し、電極を試験温度に調整した。試験温度は、50℃、68℃、77℃、86℃、および115℃とした。
図10には、50℃~115℃の各温度において得られた結果をまとめて示す。図10において、横軸は、印加電圧(kV)の平方根で示しており、縦軸は、熱電子放出電流I(μA)のln対数で示している。
以下の方法により、実施例1、実施例2および比較例1、比較例2に係る電極のアーク放電試験を実施した。
(BaOとマイエナイト化合物の耐スパッタ性のシミュレーション計算)
モンテカルロ法によってAr原子が試料(ターゲット)に垂直入射した場合について、マイエナイト化合物のスパッタリング率を算出した。計算には、TRIMコード(J.F.Ziegler,J.P.Biersack,U.Littmark,“TheStopping and Range of Ions in Solid”,vol.1 of series“Stopping and Range of Ions in Matters”,Pergamon Press,New York(1984)を参照)を用いた。比較のため、BaOについてもスパッタリング率を計算した。スパッタリング率は、入射原子またはイオン1つにつき、スパッタリングされたターゲット原子の数であり、数値が小さいほど、スパッタリングされ難いことを示す。
本出願は、2009年8月25日出願の日本国特許出願2009-194799に基づくものであり、その内容はここに参照として取り込まれる。
20 放電空間
30 バルブ
40 電極
41 電極本体部
41a、41b 端部
45a、45b 支持線
50 プラグ
55 ピン部
60 保護膜
70 蛍光体
140 従来の電極
141a、141b 端部
142 フィラメント
145a、145b 支持線
146 エミッタ
Claims (9)
- 熱電子を放出させる電極本体部を有する放電ランプ用の電極であって、
前記電極本体部は、導電性マイエナイト化合物の焼結体で構成される、電極。 - 前記電極本体部は、粒子同士が結合して形成されたネック部を有するクラスタ構造を備え、前記クラスタ構造の表面は、粒子が部分的に突出して構成された3次元凹凸構造を有する、請求項1に記載の電極。
- 前記電極本体部は、さらにアルカリ土類金属の酸化物を含む、請求項1または2に記載の電極。
- 前記アルカリ土類金属の酸化物は、酸化バリウム(BaO)、酸化ストロンチウム(SrO)および酸化カルシウム(CaO)からなる群より選定された少なくとも1種の酸化物を含む、請求項3に記載の電極。
- 水銀および希ガスが充填された内部空間を有するバルブと、
該バルブの内表面に設置された蛍光体と、
前記内部空間で放電を発生、維持させる電極と、
を有する放電ランプであって、
前記電極は、請求項1乃至4のいずれか一つに記載の電極である、放電ランプ。 - 熱電子を放出させる電極本体部を有する放電ランプ用の電極の製造方法であって、
前記電極本体部は、
(1a)マイエナイト化合物を含む粉末を準備するステップと、
(1b)前記粉末から成形体を形成するステップと、
(1c)前記成形体を焼成して焼結体を得るステップと、
(1d)前記焼結体に導電性を付与するステップと、
により形成される、製造方法。 - 熱電子を放出させる電極本体部を有する放電ランプ用の電極の製造方法であって、
前記電極本体部は、
(2a)マイエナイト化合物を含む粉末を準備するステップと、
(2b)前記粉末から成形体を形成するステップと、
(2c)前記成形体を焼成して、導電性を有する焼結体を得るステップと、
により形成される、製造方法。 - 前記ステップ(1d)は、前記焼結体を還元性雰囲気で熱処理するステップを有する、請求項6に記載の製造方法。
- 前記ステップ(2c)は、前記焼結体を還元性雰囲気で熱処理するステップを有する、請求項7に記載の製造方法。
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JP2011528806A JPWO2011024821A1 (ja) | 2009-08-25 | 2010-08-24 | 放電ランプ用電極およびその製造方法 |
EP10811871A EP2472557A1 (en) | 2009-08-25 | 2010-08-24 | Electrode for discharge lamp, and process for production thereof |
US13/403,325 US20120153805A1 (en) | 2009-08-25 | 2012-02-23 | Electrode for discharge lamp and manufacturing method thereof |
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EP (1) | EP2472557A1 (ja) |
JP (1) | JPWO2011024821A1 (ja) |
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WO2012157460A1 (ja) * | 2011-05-13 | 2012-11-22 | 旭硝子株式会社 | 導電性マイエナイト化合物を含む電極の製造方法 |
WO2014034473A1 (ja) | 2012-08-30 | 2014-03-06 | 国立大学法人東京工業大学 | 導電性マイエナイト型化合物粉末の製造方法 |
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JP6042320B2 (ja) * | 2013-12-25 | 2016-12-14 | 株式会社ノリタケカンパニーリミテド | 電極材料とその利用 |
KR102488528B1 (ko) * | 2017-09-20 | 2023-01-17 | 마테리온 프레시젼 옵틱스 (상하이) 리미티드 | 무기질 바인더를 갖는 인광체 휠 |
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JPWO2011024821A1 (ja) | 2013-01-31 |
EP2472557A1 (en) | 2012-07-04 |
KR20120065337A (ko) | 2012-06-20 |
US20120153805A1 (en) | 2012-06-21 |
CN102484031A (zh) | 2012-05-30 |
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