JP2004063469A - Manufacturing method of electrode for discharge lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for manufacturing with relative ease an electrode for a discharge lamp, in which the dark part is shortened and a reduction in strength by welding and an increase in power consumption amount can be prevented, in a manufacturing method of the electrode for the discharge lamp such as a cold cathode fluorescent lamp used as a backlight of an LCD (liquid crystal display) for a personal computer, etc. <P>SOLUTION: The electrode for the discharge lamp in which an electrode part arranged in a glass bulb and a sealed wire part of which the one end part is connected to the electrode part and the other end part is connected to an external lead wire are integrally molded is obtained by injection-molding a raw material powder in a predetermined shape and by sintering in a non-oxidizing atmosphere. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing electrodes of a discharge lamp such as a cold cathode fluorescent lamp used as a backlight of a liquid crystal display (LCD) such as a personal computer.
[0002]
[Prior art]
A liquid crystal display (LCD) used in OA equipment such as a personal computer and a word processor incorporates a backlight for illuminating the LCD. As a light source of the backlight, a cold cathode fluorescent lamp is used.
[0003]
The electrode portion of a cold cathode fluorescent lamp or the like is composed of an electrode portion, a sealing wire portion, and an external lead wire. The electrode portion has a cup shape, and its material is niobium, molybdenum, nickel, tungsten, or the like. In addition, since the sealing wire portion is glass-sealed, it is made of tungsten, molybdenum, kovar, or dimet wire whose thermal expansion coefficient is similar to that of quartz glass. Further, the material of the external lead wire is nickel or the like. These parts are usually joined by resistance welding to form electrodes.
[0004]
[Problems to be solved by the invention]
Since the overall size of this type of liquid crystal display device is determined by the shape and dimensions of the OA equipment, the frame size surrounding the liquid crystal screen is made as small as possible while keeping the size of the entire liquid crystal display device constant, and the liquid crystal screen is made as large as possible Is required. In order to meet this demand, it is necessary to make the length of the light emitting part as long as possible while keeping the length of the cold cathode fluorescent lamp for backlight constant, that is, to make the dark part of the lamp as short as possible. Become.
[0005]
In many cases, a notebook personal computer or the like uses a battery as a power supply, so that it is required to reduce the power consumption of the backlight. Further, in order to increase the brightness and reduce the power consumption, it is required to improve the discharge characteristics of the electrodes.
[0006]
In this type of conventional lamp, as shown in FIG. 4, the electrode portion 4 'and the sealing wire 3' were separately manufactured and joined by welding, so that in addition to the length of the joint itself, resistance welding was performed. Since it is necessary to have a gripping margin at the time of joining, etc., it is difficult to reduce the length to a certain size or more, and the cost for joining is also high. In addition, since the electrical resistance of the junction is higher than that of the other portions, there is also a problem that the power consumption increases accordingly.
[0007]
Furthermore, at the time of joining by resistance welding, tungsten and molybdenum recrystallized, and this was one of the causes of destruction of the joint. Wires such as tungsten, molybdenum, and Kovar used as the sealing wire 3 'are manufactured by wire drawing. However, in the case of metals having relatively low ductility such as tungsten and molybdenum, longitudinal scratches caused by wire drawing are produced. Had a leak problem.
[0008]
Accordingly, the present invention provides a manufacturing method capable of relatively easily manufacturing an electrode for a discharge lamp in which the dark portion of the lamp is as short as possible and in which the problem of strength reduction due to welding and the increase in power consumption can be prevented. The challenge is to do that.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, the present invention employs the following configuration. That is, the method of manufacturing an electrode for a discharge lamp according to the present invention includes a sealing method in which an electrode portion disposed in a glass bulb is connected to the electrode portion at one end and an external lead wire is connected to the other end. A method for manufacturing an electrode for a discharge lamp in which a wire portion is integrally formed, wherein a raw material powder is formed into a predetermined shape by injection molding, and then sintered in a non-oxidizing atmosphere. .
[0010]
The material for the discharge lamp electrode is preferably tungsten or molybdenum or a material obtained by adding 0.05 to 1% by weight of nickel to them, and lanthanum oxide, yttrium oxide, cerium oxide, strontium oxide as a discharge characteristic improving agent. , Calcium oxide, zirconium oxide, hafnium oxide, barium oxide, thorium oxide, and lanthanum boride are more preferably those containing 0.1 to 4 wt% of one or more of them.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a specific description will be given based on an embodiment of the present invention illustrated in the drawings. FIG. 1 is a partial sectional view of a discharge cold cathode fluorescent lamp. The fluorescent lamp 1 is, for example, a straight tube having an outer diameter of about 2.6 mm, an inner diameter of 1.6 mm, and a length of about 200 mm. In terms of material, sealing portions 5 and 5 are provided at both ends of a tubular glass bulb 2 made of borosilicate glass or aluminosilicate glass having a linear expansion coefficient of 5 to 5.5 ppm, and an electrode portion is provided on the sealing portion. An electrode (integrated electrode) 10 in which the sealing wire 4 and the sealing wire 3 are integrated is sealed. A fluorescent film 11 is provided on the inner surface of the glass bulb 2.
[0012]
The integrated electrode 10 is made of tungsten, molybdenum, or an alloy thereof. In the following description, an example using tungsten as a material will be described. The sealing portion 3 of the integrated electrode 10 has an outer diameter of about 0.8 mm, for example, and is sealed by a bead glass coating layer 7 made of borosilicate glass as shown in FIG. The electrode part 4 is a cup type having an outer diameter of 1.2 mm and an inner diameter of 0.9 mm, and has a length of about 5 mm. The external lead wire 8 is a nickel wire.
[0013]
The electrode portion 4 is cup-shaped in which a hollow portion 4a is formed. In the hollow portion, lanthanum oxide, yttrium oxide, cerium oxide, strontium oxide, calcium oxide, zirconium oxide, oxide It is preferable to fill one or more of the group consisting of hafnium, barium oxide, thorium oxide, and lanthanum boride.
[0014]
The integrated electrode 10 is manufactured, for example, as follows. First, an appropriate amount of a doping agent and a discharge characteristic improving agent are added to tungsten powder or molybdenum powder having a particle size on the order of microns, and after hydrogen reduction, an organic binder is added and injection molding is performed. The shape of the molded body is a shape in which the electrode part and the sealing part are integrated. By sintering the obtained molded body at a high temperature of 1800 ° C. or higher, an electrode having a relative density of about 98% can be obtained.
[0015]
Embodiment 1
Nickel nitrate was dissolved in water or ethanol and doped into a tungsten powder having an average particle size of 0.8 μm so as to have a nickel amount equivalent to 0.2 wt%. In this case, the amount of nickel is preferably 0.05 to 1 w%. If the nickel content is less than this, tungsten will not be densified below the economical sintering temperature of 2000 ° C. If the content is more than 1 wt%, the electric conductivity is reduced, and the performance as an electrode is deteriorated.
[0016]
Lanthanum oxide (La ₂ O ₃ ), yttrium oxide (Y ₂ O ₃ ), cerium oxide (CeO ₂ ), strontium oxide (SrO), calcium oxide (CaO ₂ ) are used as discharge characteristics improvers in the tungsten powder doped as described above. ), Zirconium oxide (ZrO ₂ ), hafnium oxide (HfO ₂ ), barium oxide (BaO), thorium oxide (ThO ₂ ), and lanthanum boride (LaB ₆ ) in a total amount of 0.1%. It is preferable to add 1 to 4% by weight. The addition of these oxides or borides may be carried out in the form of a powder or as a liquid and sprinkled. If the discharge property improving agent is less than 0.1%, it is not possible to expect a rise in recrystallization temperature and an improvement in discharge properties. On the other hand, if it is more than 4%, the strength of the obtained electrode decreases, which is not preferable.
[0017]
After drying the obtained powder, it was reduced at 800 ° C. in hydrogen. Thereafter, the reduced powder is kneaded with an organic binder for injection molding, such as a copolymer of ethylene vinyl acetate, butyl methacrylate, and polystyrene, paraffin wax, butyl phthalate, and stearic acid. And This was put into an injection molding machine maintained at 150 to 160 ° C., and injection-molded in a predetermined mold. The dimensions of the obtained molded body were an outer diameter of 1.6 mm, an inner diameter of 1.2 mm, and a total length of 6.8 mm.
[0018]
The obtained molded body was gradually heated to 800 ° C. in a hydrogen atmosphere and degreased. Then, it was sintered in hydrogen at 1850 ° C. for 30 minutes to obtain an integrated electrode made of a sintered body having an outer diameter of 1.2 mm, an inner diameter of 0.9 mm, and a total length of 5 mm. The shape is shown in FIG. The relative density of the obtained sintered body was 98%.
[0019]
A nickel wire 8 as an external lead wire was joined to the integrated electrode 10 obtained as described above by resistance welding. Thereafter, the sealing wire portion 3 was heated with a heater in a non-oxidizing atmosphere, and the borosilicate glass 7 was welded. As a result, the integrated electrode and the glass winding portion (sealing portion 5) were physically and air-tightly bonded. In order to ensure this adhesion, an annular concave or convex portion may be provided on the outer periphery of the sealing wire portion 3 of the integrated electrode. The length of the glass winding was 2-3 mm, and the outer diameter was about 2 mm.
[0020]
The end of the arc tube (glass bulb) was welded to the above-mentioned glass winding portion and sealed, followed by annealing treatment. Subsequently, a cold cathode fluorescent lamp was completed through an evacuation step in the arc tube, a mercury introduction step, and a lead wire soldering step.
[0021]
Embodiment 2
Molybdenum powder having an average particle size of 1.0 μm was doped with nickel nitrate dissolved in water or ethanol so as to obtain a nickel amount equivalent to 0.2 wt%. In this case, the amount of nickel is preferably 0.05 to 1 w%. If the nickel content is less than this, molybdenum will not be densified below the economical sintering temperature of 2000 ° C. If the content is more than 1 wt%, the electric conductivity is reduced, and the performance as an electrode is deteriorated.
[0022]
Lanthanum oxide (La ₂ O ₃ ), yttrium oxide (Y ₂ O ₃ ), cerium oxide (CeO ₂ ), strontium oxide (SrO), calcium oxide (CaO), zirconium oxide as a discharge property improver for the doped molybdenum powder (ZrO ₂ ), one or more of hafnium oxide (HfO ₂ ), barium oxide (BaO), thorium oxide (ThO ₂ ), and lanthanum boride (LaB ₆ ) in powder or liquid form in a total amount It is preferable to add so as to be 0.1 to 4 wt%. When the addition amount is less than 0.1%, the recrystallization temperature rise and the improvement of the discharge characteristics cannot be expected. On the contrary, when it is more than 3%, the strength of the obtained electrode is reduced, and neither is preferable. .
[0023]
After drying the obtained powder, it was reduced at 800 ° C. in hydrogen. Thereafter, the reduced powder is kneaded with an organic binder for injection molding, such as a copolymer of ethylene vinyl acetate, butyl methacrylate, and polystyrene, paraffin wax, butyl phthalate, and stearic acid. And This was put into an injection molding machine maintained at 150 to 160 ° C., and injection-molded in a predetermined mold. The dimensions of the obtained molded body were an outer diameter of 1.6 mm, an inner diameter of 1.2 mm, and a total length of 6.8 mm.
[0024]
The obtained molded body was gradually heated to 800 ° C. in a hydrogen atmosphere and degreased. Then, it was sintered at 1650 ° C. for 30 minutes in hydrogen to obtain an integrated electrode 10 composed of a sintered body having an outer diameter of 1.2 mm, an inner diameter of 0.9 mm, and a total length of 5 mm. In addition, the sealing wire part 3 is provided with a ring-shaped convex part (shown in FIG. 3) 9 in order to ensure sealing. A ring-shaped concave portion may be provided instead of the convex portion 9. The relative density of the obtained sintered body was 98.5%.
[0025]
A nickel wire 8 as an external lead wire was joined to the integrated electrode obtained as described above by resistance welding. Thereafter, the sealing wire portion 3 of the integrated electrode 10 was heated by a heater in a non-oxidizing atmosphere to weld the aluminoborosilicate glass. Thereby, the integrated electrode and the glass winding part were physically and air-tightly bonded. The length of the glass winding was 2-3 mm, and the outer diameter was about 2 mm.
[0026]
The end of the arc tube was welded to the above-mentioned glass winding portion and sealed, and then an annealing treatment was performed. Subsequently, a cold cathode fluorescent lamp was completed through an evacuation step in the arc tube, a mercury introduction step, and a lead wire soldering step.
[0027]
【The invention's effect】
As is apparent from the above description, according to the method for manufacturing an electrode for a discharge lamp according to the present invention, since the raw material powder is molded and sintered by injection molding, the electrode portion arranged in the glass bulb and the glass are used. An electrode for a discharge lamp in which a sealing portion to be sealed is integrally formed can be manufactured easily and relatively inexpensively. The electrode obtained in this manner does not require a margin for gripping for welding and the like, and the overall length can be reduced by about 20%. As a specific example, the conventional total length of 6 mm could be reduced to 5 mm. Also, the cost for joining was reduced. In addition, since the wire drawing process is not required, no scratch is generated in the axial direction, and the slow leak at the introduction wire portion is reduced. Further, lanthanum oxide (La ₂ O ₃ ), yttrium oxide (Y ₂ O ₃ ), cerium oxide (CeO ₂ ), strontium oxide (SrO), calcium oxide (CaO), zirconium oxide (ZrO ₂ ), hafnium oxide (HfO) ₂ ) By adding an appropriate amount of one or more of barium oxide (BaO), thorium oxide (ThO ₂ ), and lanthanum boride (LaB ₆ ), the recrystallization temperature increases, and The breakage of the joint due to the embrittlement of tungsten or molybdenum due to the heat of the first embodiment can be avoided. In addition, the discharge characteristics were also improved due to the decrease in the work function of the electrode.
[Brief description of the drawings]
FIG. 1 is a partial sectional view of a discharge lamp.
FIG. 2 is a sectional view of a main part showing an embodiment of the present invention.
FIG. 3 is a sectional view of a main part showing an embodiment different from the above.
FIG. 4 is a cross-sectional view illustrating a conventional discharge electrode.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Discharge lamp 2 Glass bulb 3 Sealing wire part 4 Electrode part 8 External lead wire 9 Convex part 10 Integrated electrode

Claims (3)

An electrode portion for a discharge lamp, which is formed by integrally molding an electrode portion disposed in a glass bulb and a sealing wire portion having one end connected to the electrode portion and the other end connected to an external lead wire. A method for producing an electrode for a discharge lamp, comprising: forming a raw material powder into a predetermined shape by injection molding, followed by sintering in a non-oxidizing atmosphere. The method for producing an electrode for a discharge lamp according to claim 1, wherein a raw material powder containing tungsten or molybdenum or nickel to which 0.05 to 1 wt% is added is used. In the components, one or more of the group consisting of lanthanum oxide, yttrium oxide, cerium oxide, strontium oxide, calcium oxide, zirconium oxide, hafnium oxide, barium oxide, thorium oxide, and lanthanum boride is 0.1% The method for producing an electrode for a discharge lamp according to claim 1, wherein the content is about 4 wt%.

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