TWI393166B - Welding process for discharge electrode, discharge electrode welded by the process and fluorescent discharge tube provided with the discharge electrode - Google Patents

Description

Welding method of discharge electrode, discharge electrode welded by the method, and fluorescent discharge tube having the same

The present invention relates to, for example, a bottomed cylindrical discharge electrode provided on a fluorescent discharge tube using a liquid crystal backlight, a method of soldering between the electrode support wires, and the like.

In the liquid crystal device, the backlight uses a small fluorescent discharge tube. As shown in FIG. 4, the fluorescent discharge tube includes a glass tube 50 in which a fluorescent film (not shown) is formed on the inner wall surface, and a discharge gas (rare gas such as argon gas or mercury vapor) is sealed inside; A bottomed cylindrical discharge electrode 51 constituting a pair of cold cathodes is disposed at both ends of the inside of the glass tube 50. The discharge electrode 51 has a tube portion 52 having an open end, and the other end of the tube portion 52 is closed by a plate portion 53 to form a cup shape, and the tube portion 52 is integrally formed with the end plate portion 53. One end of the shaft-shaped electrode supporting wire 57 penetrating through the end portion of the glass tube 50 and sealed is welded to the end plate portion 53, and the other end of the electrode supporting wire 57 is connected to the wire 58. The electrode supporting wire 57 is formed of W (tungsten) or Mo (molybdenum) which is a high melting point metal, and is welded to the discharge electrode 51 by laser welding or electric resistance welding.

The discharge electrode 51 is a small-sized fluorescent discharge tube such as a backlight. For example, the inner diameter is about 1.5 mm, the total length is about 5 mm, and the thickness of the tube portion 52 is about 0.1 to 0.15 mm. Usually, the pure Ni plate is integrally molded by deep drawing. It has a bottomed tube shape. In addition, Japanese Laid-Open Patent Publication No. 2002-289138 (Patent Document 1) proposes a discharge electrode having a double layer structure in which an inner layer is formed of Nb, Ta, Ti, or the like, and an outer layer is formed of Ni.

The discharge electrode 51 and the electrode supporting wire 57 abut the front end portion of the electrode supporting wire 57 against the outer surface of the end plate portion 53 of the discharge electrode 51, and irradiate the laser beam from the inside of the discharge electrode 51 toward the end plate portion 53. Spot welding is performed by partially melting the abutting portions of the two. However, in such a soldering method, the inner surface of the end plate portion of the electrode is easily oxidized to form an oxide film. Since the portion having the discharge action is mainly concentrated on the inner surface side of the discharge electrode, if an oxide film is formed on the inner surface of the end plate portion, problems such as discharge, deterioration in discharge characteristics, and electrode damage of the electrode outer surface also occur.

A welding method for preventing internal oxidation of a discharge electrode is proposed in Japanese Laid-Open Patent Publication No. 2003-272520 (Patent Document 2). This method is a method in which a concave portion into which an electrode supporting wire can be embedded is formed in an end plate portion of a discharge electrode, and a laser beam is irradiated from the outside of a peripheral wall of the concave portion in a state in which the electrode supporting wire is embedded in the concave portion.

Patent Document 1: Japanese Laid-Open Patent Publication No. 2002-289138, Patent Document 2: Japanese Patent Laid-Open No. 2003-272520

However, in the method of Patent Document 2, since it is necessary to form a concave portion for embedding the electrode supporting wire on the end plate portion, it is not possible to form the discharge electrode by deep drawing forming suitable for mass production, and it is necessary to adopt special forming such as multi-stage forging. method. In particular, when the discharge electrode uses an electrode having a two-layer structure, it is difficult to form a concave portion in the end plate portion, and in fact, it cannot be a welding target. Moreover, a gap is likely to occur between the electrode supporting wire and the bottom surface of the concave portion. If a gap occurs, a discharge phenomenon occurs between the tip end of the electrode supporting wire and the bottom surface of the concave portion, causing a problem that the discharge characteristics of the fluorescent discharge tube are deteriorated.

The present invention has been made in view of the above problems, and an object thereof is to provide a case where a concave portion is formed on an end plate portion of a discharge electrode having a bottomed cylindrical shape without forming a gap between the discharge electrode and the electrode support wire. A welding method of a discharge electrode capable of performing laser welding.

The welding method of the discharge electrode of the present invention is to discharge the electrode (the other end of the tube portion having one end open is closed by the end plate portion, and the tube portion and the end plate portion are integrally formed), and the electrode supporting wire (which is high by a melting point metal forming method for welding; comprising: step of crimping the front end portion of the electrode supporting wire to the outer surface of the end plate portion of the discharge electrode to be butted; and not irradiating the laser beam irradiation region Including the end plate portion, the laser beam is irradiated only to the vicinity of the tip end portion of the electrode supporting wire, and the tip end portion of the electrode supporting wire is heated to partially melt the end plate portion of the tip end portion but to the front end portion. a step of embedding in the molten portion of the end plate portion; and a step of cooling and solidifying the molten portion.

According to the welding method, since the laser beam is irradiated only to the vicinity of the front end portion of the electrode supporting wire, the front end portion is heated, and the discharge electrode end plate portion to which the front end portion abuts is locally melted, and the front end portion is buried. In the molten portion of the end plate portion, the molten portion is cooled and solidified, so that the front end portion of the electrode can be supported even if the end plate portion is flat without forming a concave portion on the discharge electrode end plate portion. It is in close contact with the end plate portion and is firmly welded. Therefore, the discharge electrode can be easily formed, and the manufacturing cost thereof can be reduced, and a gap does not occur between the end plate portion and the front end portion of the electrode support wire, so that the discharge characteristics are not deteriorated.

In the above welding method, the discharge electrode may be a discharge electrode having a single-layer structure formed of a monolithic pure Ni or a Ni-based alloy containing Ni as a main component. Further, an outer layer formed of a pure Ni or a Ni-based alloy containing Ni as a main component, and an inner layer laminated on the inner side of the outer layer may be used, and the inner layer may be made of Nb, Ta, Ti or the like. A two-layer structured discharge electrode formed of a high melting point alloy as a main component.

By using the double-layered structure discharge electrode, the heated tip end portion of the electrode support wire partially melts the end plate portion, and the front end portion can be easily buried in the outer layer when buried in the molten portion. Further, the inner layer formed of the high-melting-point metal prevents the embedding thereof, so that when the front end portion of the electrode supporting wire is butted against the outer surface of the end plate portion, it is not necessary to strictly adjust the crimping force. Therefore, the front end portion of the electrode supporting wire can be easily and surely buried in the outer layer of the end plate portion of the discharge electrode. Further, the heating of the front end portion of the electrode supporting wire is performed by irradiation with a laser beam, and thus the melting time of the outer layer forming the end plate portion is extremely short. Therefore, a high-melting-point metal mainly forming an inner layer having a discharge function and a Ni-based alloy containing pure Ni or Ni as a main component (hereinafter referred to as "Ni-based metal" collectively) are hardly formed. Alloying. Therefore, there is no concern that the discharge characteristics of the inner layer are not changed during use.

Further, in the above welding method, the discharge electrode may have an outer layer (formed of pure Ni or a Ni-based alloy containing Ni as a main component), an intermediate layer (which is laminated on the inner side of the outer layer, and made of a steel material) A three-layer structure discharge electrode is formed) and an inner layer (which is laminated on the inner side of the intermediate layer). Preferably, the inner layer is made of Nb, Ta, Ti, or the like. Formed by a high melting point alloy.

According to the discharge electrode of the three-layer structure, since the steel material forming the intermediate layer is superior in solderability to the Ni-based metal, the front end portion of the electrode support wire can be easily and surely buried in the outer layer or the intermediate layer.

Further, the discharge electrode of the present invention has a discharge tube at one end and an end plate portion closed at the other end, and a discharge electrode integrally formed with the tube portion and the end plate portion, wherein the discharge electrode is in the end plate portion of the discharge electrode. On the outer surface, an electrode supporting wire formed of a high melting point metal is welded by the above-described welding method. Further, the fluorescent discharge tube of the present invention includes a glass tube in which a discharge gas is sealed, and a discharge electrode that is provided at both ends of the inside of the glass tube and constitutes a pair of cold cathodes, wherein the discharge electrode is used as described above. The electrode supports the discharge electrode to which the wire is welded, and the electrode support wire penetrates the end of the glass tube and is sealed.

a discharge electrode having an electrode support wire welded thereto according to the soldering method of the present invention, and a fluorescent discharge tube having the discharge electrode, because the electrode supports the front end portion of the wire, and no void is formed in the outer layer of the end plate portion of the discharge electrode In the case of firm solder joint, it is durable and has good discharge characteristics. At the same time, since it is not necessary to form a concave portion in the end plate portion of the discharge electrode, it is easy to form and the manufacturing cost can be reduced.

As described above, according to the welding method of the present invention, it is not necessary to form a concave portion in the end plate portion of the discharge electrode, and the front end portion of the electrode support wire can be firmly joined without forming a void in the end plate portion even in a flat shape. . Therefore, the discharge electrode can be easily formed, and the manufacturing cost can be reduced, and there is no concern that the discharge characteristics are deteriorated. Further, the discharge electrode and the fluorescent discharge tube of the present invention can achieve the same effect.

First, a welding assisting device for carrying out a welding method according to an embodiment of the present invention will be described. As shown in FIG. 1 , the welding assisting device includes a first holder 1 (which can hold the discharge electrode 11 detachably in the vertical direction) and a second holder 2 (which can detachably hold the shaft in the vertical direction) The electrode supports the wire 20 and is provided with a support shaft 8) that positions the lower end. Between the first holder 1 and the second holder 2, a plurality of laser beam irradiation units 3 are provided at an appropriate interval in the circumferential direction, for example, three at intervals of 120°.

A pressing member 4 is provided at an upper end of the first holder 1, and the pressing member 4 has a pressing plate 5 that mounts the discharge electrode 11 in the first holder 1 and is positioned in the radial direction. The upper end of the discharge electrode 11 is pressed downward. Further, the pressing member 4 is provided with the movable arm 6 so that the pressing plate 5 can be held between the holding position where the discharge electrode 11 is held by the first holder 1 and the avoidance position where the discharge electrode 11 is not held. It is freely movable, and the pressing plate 5 can be lifted and lowered at the holding position. When the pressing plate 5 is lowered onto the discharge electrode 11 at the holding position, the discharge electrode 11 held on the first holder 1 is supported toward the electrode by a means for applying an elastic force (not shown) by a spring or a weight or the like. The wire 20 is pressed sideways.

Further, a gas supply pipe 7 is attached to the pressing member 4, and the gas supply pipe 7 is directed toward the discharge electrode 11 via the opening provided at the center of the pressing plate 5 in a state where the pressing plate 5 is pressed against the discharge electrode 11. An inert gas such as an Ar gas is supplied inside. Further, a gas supply pipe (not shown) for supplying an inert gas such as Ar gas is provided on the welded portion between the electrode supporting wire 20 and the discharge electrode 11. Further, the pressing force of the pressing plate 5 is about 0 to 0.5 N, and usually about 0.4 to 0.5 N. When the pressing force on the electrode supporting wire 20 is sufficient by the load of the discharge electrode 11 itself, it is not necessary. The pressing member 4 is provided.

The discharge electrode 11 is a cup-shaped (bottomed cylindrical) electrode whose one end is an open tube portion 12 and whose other end is closed by the end plate portion 13, and the tube portion 12 and the end plate portion 13 are integrally formed. On the outer surface of the center of the plate portion 13, an electrode supporting wire 20 formed of a high melting point metal such as W (melting point 3380 ° C) or Mo (melting point 2630 ° C) is laser-welded.

As shown in FIG. 1, the discharge electrode 11 has a two-layer structure electrode in which an inner layer 15 made of a high melting point metal is formed in an inner layer of an outer layer 14 made of a Ni-based metal. The entire thickness of the discharge electrode 11 is about 0.1 to 0.2 mm, and the weldability of the electrode supporting wire 20 can be ensured. The outer layer 14 may be at least about 20 μm, and usually preferably about 20 to 50 μm. Further, the inner layer 15 is usually set to be 20 to 100 μm, preferably about 40 to 80 μm. The discharge electrode 11 is produced by subjecting a disk-shaped blank formed by press-forming a two-layer composite plate material to a molding material and performing deep drawing.

The Ni-based metal forming the outer layer 14 is made of pure Ni or a Ni-based alloy containing Ni as a main component. The Ni-based alloy preferably has a Ni content of 80 mass% or more, particularly preferably 85 mass% or more. The Ni-based alloy may be used alone or in combination of 1.0 to 12.0 mass% of a metal such as Nb or Ta, and the other Ni-Nb alloy, Ni-Ta alloy composed of Ni and unavoidable impurities, Ni-Nb-Ta alloy. If Nb or Ta is added in such a degree, it does not hinder the formability, and has an effect of improving the corrosion resistance to mercury vapor, thereby improving the durability of the electrode.

Further, it is preferable that the high-melting-point metal forming the inner layer 15 is made of Nb, Ta, or Nb alloy containing such a main component, which is not easily degraded in discharge characteristics compared with Ni. Ta alloy. It is particularly preferable to use Nb because the processability is superior, and the Nb amount of the Nb alloy is preferably 90 mass% or more, particularly preferably 95 mass% or more. Since the melting point of Ni is 1453 ° C, Nb is 2520 ° C, and Ta is 3250 ° C.

In the practice of the welding method of the present embodiment, first, the first step is performed on the outer surface of the end plate portion 13 of the discharge electrode 11, and the end portion of the electrode supporting wire 20 is crimped in a state of being crimped. In other words, the electrode supporting wire 20 is inserted into the support hole of the second holder 2, and the discharge electrode 11 is placed in the support hole of the first holder 1, and the end plate portion 13 is brought into contact with the second holder. The front end portion (upper end portion) of the electrode supporting wire 20 held by the second member. Then, the pressing plate 5 of the pressing member 4 is moved from the avoiding position to the holding position, and is placed on the upper end opening of the discharge electrode 11 and pressed.

Next, in the second step, the laser beam irradiation region does not include the end plate portion, and only the vicinity of the front end portion of the electrode support wire 20 is irradiated with the laser beam, and the front end portion of the electrode support wire 20 is heated to the front end portion. The butted end plate portion 13 is partially melted, and the front end portion is buried in the molten portion of the end plate portion 13. In other words, an inert gas such as an Ar gas is blown into the contact portion between the inside of the discharge electrode 11 and the electrode support wire 20, The laser beam LB is irradiated only to the vicinity of the abutting portion of the electrode supporting wire 20, and the heating electrode supports the leading end portion of the wire 20. The heating temperature must be higher than the melting point of the Ni-based metal forming the outer layer 14 of the discharge electrode 11, preferably about 1400 ° C or higher, and lower than the melting point of the high melting point metal forming the inner layer 15 described above. Thereby, the outer layer 14 of the end plate portion 13 where the tip end portion of the electrode supporting wire 20 abuts is partially melted, and the front end portion of the electrode supporting wire 20 can be buried in the molten portion of the outer layer 14. Since the inner layer 15 of the discharge electrode 11 is formed of a high melting point metal, the front end portion of the electrode supporting wire 20 does not enter the inner layer 15 under a pressing force of about 0.5N.

By embedding the front end portion of the electrode supporting wire 20 in the molten portion of the outer layer 14 of the end plate portion 13, the molten metal overflowing from the molten portion forms a ridge portion which is in close contact with the front end portion of the electrode supporting wire 20 as shown in FIG. 19.

Then, in the third step, the molten portion and the molten metal overflowing therefrom are cooled and solidified. As a result, the electrode supporting wire 20 can be firmly bonded to the discharge electrode 11 without forming a void. After the electrode support wire 20 is welded, the injection of the inert gas is stopped, and the pressing member 4 is moved together with the gas introduction pipe 7 to the avoidance position. Then, the discharge electrode 11 to which the electrode supporting wire 20 is welded is taken out from the first holder 1 by an appropriate conveying means.

In the above embodiment, the discharge electrode 11 is an electrode having a two-layer structure, but may be formed of only a single layer material of a Ni-based metal, or may be formed of a Ni-based metal as the outer layer 14 as shown in FIG. On the inner surface, an intermediate layer 16 formed of a steel material is laminated, and an inner layer 15 is formed on the inner side to form a discharge electrode 11A having a three-layer structure. The steel material forming the intermediate layer 16 is superior in weldability to the Ni-based metal, and stainless steel is preferably used in consideration of material corrosion resistance and stability. The inner layer 15 may be formed of the above-described Ni-based metal, Nb, Ta, or a Nb alloy or a Ta alloy having such a main component.

When the discharge electrode is formed of a single-layer material of Ni-based metal, it is feared that the end portion of the heated electrode support wire excessively enters the end plate portion, and even the state of protruding inside occurs. To avoid this, simply set the pressing force to a small value. Further, when the pressing force is increased to about 0.5 N, as shown in FIG. 1, the specification member 9 (which lowers the pressing plate 5 of the pressing member 4, which is specified within a predetermined range) is provided at the lower end of the pressing plate 5. You can easily avoid this problem.

Further, in the above embodiment, the discharge electrode 11 is welded and disposed above the electrode support wire 20, but the discharge electrode 11 may be disposed below and the electrode support wire 20 may be disposed above.

Further, in the above embodiment, the discharge electrode welding of the present invention is carried out by using the welding assisting device shown in Fig. 1. However, in the practice of the present invention, the welding assisting device is not necessarily used, and the welding assisting device is also The design can be changed as appropriate.

In the following, the present invention will be more specifically described by the examples, but the invention is not construed as being limited to the embodiments.

(Example)

A composite plate in which a pure Ni layer having a thickness of 100 μm and a pure Nb having a thickness of 50 μm were laminated and diffusion bonded were prepared. From which a round blank material is taken by cutting, and then deep drawing is performed to obtain an outer diameter of 1.7 mm and a length. 5mm bottomed cylindrical discharge electrode. On the other hand, a pure Mo electrode supporting wire having an outer diameter of φ 0.8 mm and a length of 3 mm is prepared, and a laser irradiation unit which is disposed at equal intervals of 120° using the above-described welding aid using a YAG laser welding machine is used. In the welding condition, the laser beam LB is irradiated at a position below about 0.2 mm from the front end of the electrode supporting wire 20, and laser welding is performed.

. Welding condition Oscillation wavelength: 1.064 μ m, laser beam diameter at irradiation position: 0.4 μ m, laser output: 13 J/P, pressing load: 0.44 N, sealing gas for anti-oxidation: Ar gas

After welding, the joint strength of the electrode support wires was measured and found to be 120N. When welding is performed by a conventional welding method (a method of irradiating a laser beam from the inside of a discharge electrode and welding an electrode supporting wire), the joint strength is about 90 to 100 N, and thus the joint strength is considerably improved compared with the conventional one. Further, the welded discharge electrode is cut along the longitudinal direction of the center line, and the cross section of the welded portion is observed. As a result, as shown in Fig. 2, the front end portion of the electrode supporting wire 20 is buried in the outer layer 14 of the end plate portion 13 of the discharge electrode 11. The ridge portion 19 is in close contact with the outer periphery of the front end portion, and is firmly joined without leaving a gap.

1. . . 1st holder

2. . . 2nd holder

3. . . Laser beam irradiation unit

4. . . Pressing member

5. . . Press plate

6. . . Movable arm

7. . . Gas supply pipe

8. . . Support shaft

9. . . Normative component

11, 11A, 51. . . Discharge electrode

12, 52. . . Tube department

13,53. . . End plate

14. . . Outer layer

15. . . Inner layer

16. . . middle layer

19. . . Uplift

20, 57. . . Electrode support wire

50. . . Glass tube

58. . . wire

LB. . . Laser beam

Fig. 1 is an explanatory view of a welding assisting device and a welding method according to an embodiment.

Fig. 2 is a cross-sectional view showing a state in which the discharge electrode and the electrode support wire after welding are joined.

3 is a cross-sectional view of a discharge electrode of a three-layer structure.

Fig. 4 is a cross-sectional view showing an essential part of a fluorescent discharge tube having a discharge electrode for a fluorescent discharge tube.

1. . . 1st holder

2. . . 2nd holder

3. . . Laser beam irradiation unit

4. . . Pressing member

5. . . Press plate

6. . . Movable arm

7. . . Gas supply pipe

8. . . Support shaft

9. . . Normative component

11. . . Discharge electrode

12. . . Tube department

13. . . End plate

14. . . Outer layer

15. . . Inner layer

20. . . Electrode support wire

LB. . . Laser beam

Claims (6)

A welding electrode welding method is characterized in that a discharge electrode is closed at the other end of an open tube portion with an end plate portion, and the tube portion and the end plate portion are integrally formed; and the electrode supporting wire is made of a high melting point And a method of performing soldering, comprising: step of bonding the front end portion of the electrode supporting wire to the outer surface of the end plate portion of the discharge electrode to perform docking; and not irradiating the laser beam in the irradiation region Including the end plate portion, the laser beam is irradiated only to the vicinity of the front end portion of the electrode supporting wire, and the front end portion of the electrode supporting wire is heated to locally melt the end plate portion abutting the front end portion, and a step of embedding the tip end portion in the molten portion of the end plate portion; and a step of cooling and solidifying the molten portion. The method of welding a discharge electrode according to the first aspect of the invention, wherein the discharge electrode is formed of pure Ni or a Ni-based alloy containing Ni as a main component. The method of welding a discharge electrode according to the first aspect of the invention, wherein the discharge electrode comprises: an outer layer formed of pure Ni or a Ni-based alloy containing Ni as a main component; and an inner layer laminated on the outer layer The inner layer is formed of Nb, Ta, Ti or a high melting point alloy containing these as main components. The method for welding a discharge electrode according to the first aspect of the invention, wherein the discharge electrode comprises: an outer layer formed of pure Ni or a Ni-based alloy containing Ni as a main component; and an intermediate layer laminated on the inner side of the outer layer; And formed of a steel material; and an inner layer laminated on the inner side of the intermediate layer; and the inner layer is formed of Nb, Ta, Ti or a high melting point alloy containing the main components. A discharge electrode is a discharge electrode in which an end portion of an open tube portion is closed at an end plate portion, and the tube portion and the end plate portion are integrally formed, wherein an outer surface of the end plate portion of the discharge electrode is formed An electrode supporting wire formed of a high melting point metal is welded by a welding method according to any one of claims 1 to 4. A fluorescent discharge tube comprising: a glass tube sealed with a discharge gas; and a discharge electrode disposed at both ends of the inside of the glass tube and constituting a pair of cold cathodes; wherein the discharge electrode application is used In the discharge electrode of the fifth aspect of the patent, the electrode supporting wire is inserted through the end of the glass tube and sealed.