JP2006040599A - Electrode, discharge lamp and manufacturing method of electrode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode capable of reducing inclination with respect to an electrode rod of a cup-like electrode. <P>SOLUTION: This electrode is equipped with the electrode rod 6 having one end connected to a bottom plate 7a of the cup-like electrode 7. The bottom plate 7a of the cup-like electrode 7 is supported by a peripheral edge part 6a on one end face of the electrode rod 6, and a central part 7b of the bottom plate of the cup-like electrode 7 is welded to a central part 6b on one end face of the electrode rod 6 by laser-welding. The one end face of the electrode rod 6 is nearly perpendicularly intersected with the axial center of the electrode rod 6; and the surface roughness of the one end face is set to 1 to 10 μm by the maximum height Rmax. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a discharge lamp applied to, for example, a backlight for a liquid crystal display.

  FIG. 9 is a cross-sectional view showing a configuration of a discharge lamp, such as a cold cathode fluorescent lamp 100, applied to a backlight for a liquid crystal display or the like.

  The cold cathode fluorescent lamp 100 includes a glass tube 102 having a substantially straight tube shape in which rare gas and mercury are enclosed, a phosphor 103 applied to the inner surface of the glass bulb 102, and both ends inside the glass bulb 102. And an electrode 104 provided.

  The electrode 104 is obtained by attaching a cup-shaped electrode 106 having a cup-shaped bottom made of molybdenum and having a recess formed on one end face of an electrode rod 105 made of molybdenum or tungsten by laser welding. Further, both ends of the glass bulb 102 are hermetically sealed with a bead glass 107 made of tungsten glass, and an electrode rod 105 is provided so as to penetrate the bead glass 107.

Then, the bottom surface of the cup-shaped electrode 106 is formed in a concave shape having the same shape as the welded portion at the tip of the electrode rod 105, and the center of the cup-shaped electrode 106 and the electrode rod 105 is formed by forming a tapered shape that invites the tip of the electrode rod 105. They can be combined and the welding accuracy is improved (see Patent Document 1).
Utility Model Registration No. 3101379

  In the configuration of the prior art described above, the diameter d1 of the electrode rod 105 of the electrode 104 used in the cold cathode fluorescent lamp 100 is as thin as about 1 mm. The bottom plate 106a is welded.

  However, as shown in FIG. 10, depending on the size and position of the beam diameter of the laser 120 irradiated on the bottom surface of the cup-shaped electrode 106, the corner portion 105 b of the electrode rod 105 may be different from the other end surface of the electrode rod 105. There is a problem that it melts deeper than the portion, and the axis of the cup electrode 106 is inclined with respect to the axis of the electrode rod 105.

  In the cold cathode fluorescent lamp 100 shown in FIG. 9 described above, since the difference between the inner diameter D1 of the glass bulb 102 and the outer diameter D2 of the cup-shaped electrode 106 is small, the cup-shaped electrode 106 is inclined with respect to the electrode rod 105. When the inserted electrode 104 is inserted into the glass bulb 102, the inserted cup-shaped electrode 106 and the phosphor 103 are too close to each other, so that a leak current flows from the electrode 104 to the phosphor 103 side, or the inclination is inclined. In a severe case, there is a problem that the phosphor 103 is peeled off when the electrode 104 is inserted, resulting in a quality defect.

  The present invention has been made in view of the above problems, and an electrode capable of reducing the inclination of the axis of the cup-shaped electrode with respect to the axis of the electrode rod, a manufacturing method thereof, and a discharge having good quality. To provide a lamp.

  The electrode according to claim 1 of the present invention is an electrode including an electrode rod having one end connected to the bottom plate of the cup-shaped electrode, and the bottom plate of the cup-shaped electrode is located along the outer periphery of one end surface of the electrode rod. The center part of the bottom plate of the cup-shaped electrode and the center part of one end surface of the electrode bar are welded.

  According to an eighth aspect of the present invention, there is provided a discharge lamp comprising the electrode according to the first aspect at an end of a glass tube, and a phosphor is deposited on the inner periphery of the glass tube.

  A method for producing an electrode according to claim 12 of the present invention is a method for producing an electrode by abutting and welding a bottom plate of a cup-shaped electrode and one end face of an electrode rod, wherein the axis of the cup-shaped electrode and the electrode A step of abutting the bottom plate of the cup-shaped electrode and one end surface of the electrode rod with each other while making the axial center of the electrode rod coincide with each other in a vertical direction, and then the cup-shaped electrode and the electrode rod Is irradiated with laser light from the opening side of the cup-shaped electrode, the bottom plate of the cup-shaped electrode is supported along the outer periphery of one end surface of the electrode rod, and the center of the bottom plate of the cup-shaped electrode And a step of welding the central portion of one end surface of the electrode rod.

  According to the present invention, it is possible to provide an electrode that can reduce the inclination of the cup-shaped electrode with respect to the electrode rod, a manufacturing method thereof, and a discharge lamp with good quality.

  Hereinafter, the discharge lamp according to the present embodiment will be described with reference to the drawings.

  As shown in FIG. 1, a cold cathode fluorescent lamp 1 which is a discharge lamp according to a first embodiment of the present invention includes a rare gas which is a mixed gas of Ne95% and Ar5% with a pressure of 8 kPa at 20 ° C. A glass tube 2 having a substantially straight tube shape in which 1.7 ± 0.5 mg of mercury is enclosed, a phosphor 3 applied to the inner surface of the glass bulb 2, and both ends of the glass bulb 2 are provided. The electrode 4 is provided. In the electrode 4, a cup-shaped electrode 7 is welded to one end surface of the electrode rod 6, and an external lead wire 8 is welded to the other end surface of the electrode rod 6.

  The glass bulb 2 is made of borosilicate glass having an inner diameter D1 of 2 mm, a thickness of 0.5 mm, and a total length of 720 mm. Both ends of the glass bulb 2 are hermetically sealed with a bead glass 5 made of tungsten glass, and an electrode rod 6 having a diameter d1 made of tungsten (W) of 0.8 mm and a length of 3.2 mm penetrates the bead glass 5. Provided. At this time, the thickness of the phosphor applied to the inner surface of the glass bulb 2 is about 20 μm, and the distance d between the inner surface 2a of the glass bulb and the outer surface of the cup-shaped electrode 7 is in the range of 0.04 mm <d ≦ 0.2 mm. Is provided.

  As shown in FIG. 2, the end face 6a in the glass bulb 3 of the electrode rod 6 has a cup shape with a length L of 2 to 6 mm made of a metal such as nickel (Ni), molybdenum (Mo) or niobium (Nb). The bottom plate 7a of the electrode 7 is attached by, for example, laser welding. The bottom plate 7a of the cup-shaped electrode 7 is formed in a planar shape. At this time, the bottom plate 7a of the cup-shaped electrode 7 is supported by the outer peripheral side portion 6a of the one end surface of the electrode rod 6, and the central portion 7b of the bottom plate 7a of the cup-shaped electrode 7 and the central portion 6b of the one end surface of the electrode rod 6 are Welded. After the welding, the axis of the electrode rod 6 is substantially orthogonal to the bottom plate 7a of the cup-shaped electrode 7.

  The one end surface of the electrode rod 6 on the bottom plate 7a side of the cup-shaped electrode 7 preferably has a surface roughness of a maximum height Rmax 1 μm or more and 10 μm or less, and more preferably a maximum height Rmax 3 μm ± 2 μm. Moreover, it is preferable that the squareness of the one end face of the electrode rod 6 (angle variation of one end face of 90 degrees with respect to the axis of the electrode rod 6) is 1 degree or less.

  In addition, an electron emitting material 9 such as an oxide or alloy of an alkali metal or alkaline earth metal such as Cs, Li, or Mg is applied to a part of the outer peripheral surface of the cup-shaped electrode 7.

Example 1
The cold cathode fluorescent lamp 1 includes a borosilicate glass bulb 2 having a mercury filling amount of 1.7 mg, an inner diameter D1 of 3 mm, a thickness of 0.5 mm and a total length of 720 mm, a phosphor 3 having a thickness of about 20 μm, and a glass bulb. An electrode having a distance d between the inner surface 2a and the outer surface of the cup electrode 7 of 0.2 mm (the outer diameter D2 of the cup electrode 7 is 2.6 mm), a diameter of 0.8 mm, and a length of 3.2 mm made of tungsten (W). The rod 6 is a cup-shaped electrode 7 having a length L of 3 mm and barium on a part of the outer peripheral surface. Three types were manufactured, and the lamp current during lighting was set to 6 mA, and the sputtering amount and mercury consumption after about 20,000 hours were examined. The results are shown in FIGS.

  As is clear from FIG. 7 and FIG. 8, any of the three types of metals has a higher mercury consumption as the sputtering amount increases. Further, mercury consumption after about 20,000 hours increases in the order of about 30 μg for niobium (Nb), about 70 μg for molybdenum (Mo), and about 100 μg for nickel (Ni). Therefore, the longest-life material of the cup-shaped electrode 7 is niobium (Nb).

  When the inner diameter D1 of the glass bulb 2 is in the range of 1 to 6 mm, when the mercury filling amount is 1.7 ± 0.5 mg, the distance d between the inner surface 2a of the glass bulb and the outer surface of the cup-shaped electrode 7 is 0. The above effect can be obtained even in the case where 04 mm <d ≦ 0.2 mm and the case where the length of the cup-shaped electrode in the axial center direction is 2 to 6 mm.

  Next, functions and effects of the electrode 4 and the cold cathode fluorescent lamp 1 will be described.

  As shown in FIGS. 2 and 3, the electrode 4 according to the first embodiment of the present invention is configured such that the bottom plate 7 a of the cup-shaped electrode 7 is supported by the outer peripheral side portion 6 a of one end face of the electrode rod 6 and the cup-shaped electrode 7. Since the center portion 7b of the bottom plate and the center portion 6b of the one end surface of the electrode rod 6 are welded, the inclination of the axis of the cup-shaped electrode 7 with respect to the axis of the electrode rod 6 can be suppressed. And as shown in FIG. 1, when this electrode 4 is provided at the end of the glass bulb 2 of the cold cathode fluorescent lamp 1, it is possible to prevent the cup-shaped electrode 7 and the phosphor 3 from being too close, When no leakage current flows from the electrode 4 to the phosphor 3 side and the electrode 4 is inserted from the end of the glass bulb 2 of the cold cathode fluorescent lamp 1 into the inside, the phosphor 3 is It is possible to prevent quality defects such as peeling off.

  As shown in FIG. 3, since the welding is performed by laser welding that can easily narrow the beam shape of the laser beam, the laser beam is applied to the central portion 6b of one end surface of the thin electrode rod 6 having a diameter d1 of 0.8 mm. Irradiation can melt the central portion 6b.

  Moreover, the inclination of the axial center of the cup-shaped electrode 7 with respect to the axial center of the electrode rod 6 can be further suppressed by setting the squareness of the one end surface of the electrode rod 6 to 1 degree or less.

  Furthermore, the welding strength of the electrode rod 6 and the cup-shaped electrode 7 is also improved by setting the surface roughness of the one end surface of the electrode rod 6 to a maximum height Rmax of 1 μm or more and 10 μm or less.

  As shown in FIGS. 1, 7, and 8, the cup-shaped electrode 7 is made of a metal such as niobium (Nb) or molybdenum (Mo), so that the cup-shaped electrode 7 is formed into the cold cathode fluorescent lamp 1. When used, excessive sputtering can be suppressed and the consumption rate of mercury can be suppressed, and the life of the cold cathode fluorescent lamp 1 can be extended.

  As shown in FIG. 1, the cold cathode fluorescent lamp 1 according to the first embodiment of the present invention has a distance d between the inner surface of the glass bulb 2 and the outer surface of the cup electrode 7 of 0.04 mm <d ≦ 0.2 mm. Due to the range, the inner surface 2a of the glass bulb 2 and the outer surface of the cup-shaped electrode 7 can be discharged even in a low temperature use environment where the discharge proceeds mainly on the inner surface of the cup-shaped electrode 7 and the amount of spatter is larger than the normal temperature. There is no discharge transfer to the gap, and it is possible to suppress the mass consumption of mercury due to sputtering in a short period of time, and it is possible to suppress the shortening of the life due to early electrode consumption.

  Further, since the cup-shaped electrode 7 is made of niobium (Nb) and the axial length L is in the range of 2 to 6 mm, the life of the cold cathode fluorescent lamp 1 can be extended to about 60,000 hours. . However, if the length L in the axial direction is less than 2, the discharge becomes an abnormal glow discharge, and the amount of sputtering becomes several times that of a normal glow discharge, so that a desired lamp life cannot be obtained. When the length L in the direction exceeds 6 mm, the end of the glass bulb 2 that does not contribute to light emission becomes long, and a desired brightness cannot be obtained.

  Furthermore, environmental problems can be reduced by enclosing 1.7 ± 0.5 mg of mercury in the glass bulb 2.

  Then, the manufacturing method of the electrode 4 in 1st Embodiment of this invention is demonstrated.

  As shown in FIG. 2 to FIG. 4, the manufacturing method of the electrode 4 in the first embodiment of the present invention is a cup made of niobium (Nb) held in its holding portion by using a vertical mechanism (not shown). The bottom electrode 7a of the cup-shaped electrode 7 is aligned with the axial center of the electrode electrode 6 made of tungsten (W) and the axial center of the electrode electrode 6 made of tungsten (W). The electrode rod 6 is abutted against each other while being pressed against each other.

  Next, when the laser irradiation unit 20 irradiates the butted portion between the cup-shaped electrode 7 and the electrode rod 6 from the opening side of the cup-shaped electrode 7, for example, as shown in FIG. 4, the cup-shaped electrode 7. The bottom plate 7a of the electrode rod 6 is supported by the outer peripheral side portion 6a of the electrode rod 6, and the central portion 7b of the bottom plate 7a of the cup-shaped electrode 7 and the central portion 6b of the one end surface of the electrode rod 6 are as shown in FIG. Welded in shape.

  In this welding, the cup-shaped electrode 7 and the electrode rod 6 are melted on the surface to form an alloy film 21. The alloy film 21 stabilizes and improves the bonding strength, and the cup-shaped electrode 7 and the electrode rod 6 are fixed. I think.

  Moreover, the beam shape with which the laser beam 20a is irradiated onto the bottom plate 7a of the cup-shaped electrode 7 is smaller than the outer diameter d1 of the electrode bar 6 by adjusting the output of the laser irradiation unit and the like, and one end surface of the electrode bar 6 The shape is almost the same. Thereby, only the center part 6b of the one end surface of the electrode rod 6 and the bottom plate 7a of the cup-shaped electrode 7 are welded, and the electrode 4 is manufactured.

  Further, since the axis of the cup-shaped electrode 7 and the axis of the electrode rod 6 are welded so as to coincide with each other in the vertical direction, the molten metal of the cup-shaped electrode 7 and the electrode rod 6 is moved to the outer periphery of the electrode rod 6. Since it is difficult to move to the surface side, it can be formed into an electrode that can reduce the inclination of the axis of the cup-like electrode 7 with respect to the axis of the electrode rod 6.

  In the embodiment of the present invention, the beam shape with which the laser beam 20a is applied to the bottom plate 7a of the cup-like electrode 7 is an example in which the shape of one end face of the electrode bar 6 is substantially the same as shown in FIG. Although described, it is not restricted to this, The cross shape (refer FIG. 5) which can be drawn (shaded part) with respect to the one end surface of the electrode rod 6 and a triangular shape (refer FIG. 6) may be sufficient. That is, the beam shape is such that the bottom plate 7 a of the cup-shaped electrode 7 (or the bottom surface of the cup-shaped electrode 7) is supported by the outer peripheral side portion 6 a of one end surface of the electrode rod 6 and the center of the bottom plate 7 a of the cup-shaped electrode 7. What is necessary is just to be able to weld and fix the portion 7b and the central portion 6b of the one end surface of the electrode rod 6.

  In addition, the cup-shaped electrode 7 is made of niobium (Nb) and the electrode rod 6 is made of tungsten (W). However, the present invention is not limited to this, and the cup-like electrode 7 is made of nickel (Ni). Even if tungsten having a melting point higher than that of the cup-shaped electrode 7 is used, welding can be performed by irradiating the laser beam 20a.

  In addition, the axis of the cup-shaped electrode 7 and the axis of the electrode rod 6 are aligned with each other in the vertical direction and irradiated with the laser beam 20a and welded. Further, welding may be performed by irradiating the laser beam 20a with the axis of the electrode rod 6 aligned with the axis of the electrode rod 6 in the horizontal direction.

  The present invention is applied to discharge lamps such as cold cathode fluorescent lamps for liquid crystal backlights and external electrode fluorescent lamps that require an electrode that can reduce the inclination of the axis of the cup-shaped electrode with respect to the axis of the electrode rod. Can do.

Sectional drawing which shows the structure of the cold cathode type fluorescent lamp concerning this Embodiment The perspective view which shows the structure of the electrode used for a lamp same as the above. Partial sectional view showing the configuration of the electrode The figure which shows the manufacturing method of the electrode The figure which shows the modification of the beam shape of the laser beam used for the manufacturing method of the electrode The figure which shows the modification of the beam shape of the laser beam used for the manufacturing method of the electrode The figure which shows the sputtering amount when changing the electrode material in the cold cathode fluorescent lamp which concerns on this Embodiment. Figure showing mercury consumption when the electrode material is changed in the lamp Sectional view showing the configuration of a conventional cold cathode fluorescent lamp Partial sectional view showing the configuration of the electrodes used in the lamp

Explanation of symbols

2 Glass bulb 3 Phosphor 4 Electrode 6 Electrode rod 7 Cup-shaped electrode 7a Bottom plate of cup-shaped electrode

Claims (14)

An electrode having an electrode rod having one end connected to the bottom plate of the cup-shaped electrode, the bottom plate of the cup-shaped electrode being supported along the outer periphery of one end surface of the electrode rod, and the bottom plate of the cup-shaped electrode An electrode, wherein a central portion and a central portion of one end face of the electrode rod are welded. 2. The electrode according to claim 1, wherein the welding is performed by laser welding. The electrode according to claim 1, wherein one end surface of the electrode rod is substantially orthogonal to the axis of the electrode rod. 4. The electrode according to claim 3, wherein the squareness of the one end surface of the electrode rod is 1 degree or less with respect to the axial center of the electrode rod. The electrode according to claim 3 or 4, wherein the surface roughness of one end face of the electrode rod has a maximum height Rmax of 1 µm or more and 10 µm or less. The electrode according to any one of claims 1 to 5, wherein the cup-like electrode is made of a metal of niobium (Nb) or molybdenum (Mo). A discharge lamp comprising the electrode according to any one of claims 1 to 6 at an end of a glass bulb. A discharge lamp comprising the electrode according to any one of claims 1 to 6 at an end of a glass bulb, wherein a phosphor is deposited on an inner surface side of the glass bulb. The discharge lamp according to claim 8, wherein a distance d between the inner surface of the glass bulb and the outer surface of the cup-shaped electrode is in a range of 0.04 mm <d ≦ 0.2 mm. The discharge lamp according to claim 9, wherein the axial length of the cup-shaped electrode is in a range of 2 to 6 mm. The discharge lamp according to any one of claims 8 to 10, wherein a mercury amount of 1.7 ± 0.5 mg is enclosed in the glass tube. A method of manufacturing an electrode by abutting and welding a bottom plate of a cup-shaped electrode and one end face of an electrode rod, wherein the axis of the cup-shaped electrode and the axis of the electrode rod are aligned in the vertical direction, A step of abutting the bottom plate of the cup-shaped electrode and one end surface of the electrode rod against each other; and then, a portion of the butted portion of the cup-shaped electrode and the electrode rod is lasered from the opening side of the cup-shaped electrode Irradiate light, the bottom plate of the cup-shaped electrode is supported along the outer periphery of the one end surface of the electrode rod, and the central portion of the bottom plate of the cup-shaped electrode and the central portion of the one end surface of the electrode rod are welded The manufacturing method of the electrode provided with the process to do. The method of manufacturing an electrode according to claim 11, wherein the electrode rod is formed of a material having a melting point higher than that of the cup-shaped electrode. The method for manufacturing an electrode according to claim 12 or 13, wherein an end surface shape of the electrode rod and a beam shape of the laser beam are substantially the same as an end surface shape of the electrode rod.

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