JP2002056810A - Discharge electrode assembly, manufacturing method for discharge electrode assembly, and discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a discharge electrode assembly capable of securing excellent strength without requiring high machining accuracy or a complicated structure in connection of an electrode member and a conductive wire. SOLUTION: This discharge electrode assembly 1 has a bead glass 2, the conductive wire 3 penetratingly fixed to the bead glass 2, and the bottomed tube-like electrode member 5 welded to the tip of the conductive wire 3 which is projected from the bead glass 2. An inner tube bottom part 7 of the electrode member 5 has a recessed fused trace 7A generated by welding an outer tube bottom part to the tip part of the conductive wire 3 from the inside of the tube. The fused trace 7A is formed by laser-welding, for example. Thereby, thermal influence upon the bead glass 2 is small because a fusion source is present on the electrode member 5 apart from the conductive wire 3 during welding. Because the thermal influence upon the bead glass 2 can be structurally reduced, the required welding strength can be easily obtained. Deterioration of a seal state between the bead glass 2 and the conductive wire 3 or crack generation in the bead glass 2 can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge electrode assembly applied to a tube-type cold-cathode fluorescent lamp and the like, a method of manufacturing the same, and a discharge lamp using the discharge electrode assembly.

[0002]

2. Description of the Related Art In a cold cathode fluorescent lamp used as a backlight of a liquid crystal display, a discharge electrode assembly is used to seal discharge electrodes at both ends of a glass container. This discharge electrode assembly is formed by fixing a conductive wire through a bead glass and fixing a bottomed cylindrical electrode member to the tip of the conductive wire protruding from the bead glass. When sealing the discharge electrode, insert the electrode member inside the hollow cylindrical glass bulb, position the bead glass at the opening of the glass bulb, heat the opening of the glass bulb in this state, and push in the centripetal direction. By applying pressure, the opening of the glass bulb is melted integrally with the bead glass and sealed.

[0003] By the way, a discharge lamp used for a backlight of a liquid crystal display or the like is strongly required to be reduced in size and a tube, and accordingly, it is necessary to consider a discharge electrode assembly as well. At this time, if spot welding is employed as a means for fixing the electrode member to the conductive wire, welding defects are likely to occur because the welding target is small and the material is thin. Therefore, the present inventors have studied resistance welding. That is, a relatively high voltage is applied to both ends of the conductive wire, and heat generated by contact resistance between the conductive wire and the electrode member is used. Also, Japanese Patent Application Laid-Open
Japanese Patent Publication No. 0-21876 discloses a technique in which a cylindrical electrode member is fitted to a conductive wire and fixed in an engaging manner.

[0004]

However, when resistance welding is used, current always flows through the conductive wire, and it is apparent that excessive heat is generated not only in the contact resistance portion but also in the portion of the conductive wire penetrating the bead glass. Was. It has been clarified that the heat generated may cause incomplete sealing between the conductive wire and the glass or cause cracks in the bead glass. In order to avoid this, the current or voltage of resistance welding must be limited, and if it is excessively limited, welding failure between the conductive wire and the electrode member occurs, and it is apparent that the control is not easy. Was done. In the technology described in Japanese Patent Application Laid-Open No. H10-21876, a cylindrical electrode member is fixedly engaged with a conductive wire unless the processing accuracy of the component is increased in accordance with the miniaturization of the discharge electrode assembly. Is expected to be difficult.

An object of the present invention is to provide a discharge electrode assembly which can secure good strength without requiring a complicated structure and high machining accuracy for coupling an electrode member and a conductive wire.

Another object of the present invention is to provide a method of manufacturing a discharge electrode assembly which can easily obtain good strength for coupling an electrode member and a conductive wire.

Another object of the present invention is to provide a small and highly reliable discharge lamp.

[0008]

Means for Solving the Problems [1] A discharge electrode assembly according to the present invention comprises a bead glass, a conductive wire penetrated through the bead glass, and a tip of a conductive wire protruding from the bead glass. A cylindrical electrode member with a bottom, and a cylindrical inner bottom of the electrode member having a concave melting mark in which a cylindrical outer bottom is welded to the tip of the conductive wire from the inner side of the cylindrical. Become. The welding mark having a concave bottom in the cylinder of the electrode member is formed by, for example, laser welding the bottom of the electrode member from the inside of the cylinder to the tip of the conductive wire.

According to the structure in which the bottom of the outer tube is welded to the tip of the conductive wire from the inner side of the tube of the electrode member, since the melting source at the time of welding is on the electrode member remote from the conductive wire, the bead glass is formed. The effect of heat is small. Since the thermal effect on the bead glass can be reduced structurally, it is easy to obtain the necessary welding strength. Therefore, it is possible to prevent a decrease in reliability due to poor welding, and it is possible to suppress or reduce a situation in which the sealing state between the bead glass and the conductive wire is deteriorated and a crack is generated in the bead glass. The above means,
Compared with the structure in which the contact portion between the conductive wire and the electrode member is spot-welded from the outside, in this case, since the fusion source at the time of welding is directly on the conductive wire, the structure of the present invention can be applied to bead glass even compared to them. Has a small thermal effect. Further, the structure of the present invention has less thermal influence on the bead glass, and it is easy to obtain a necessary welding strength, as compared with resistance welding in which Joule heat is always generated in each part of the conductive wire. In addition, since the electrode member is not fixed to the conductive wire via a mechanical engagement state, it is not necessary to increase the processing accuracy of the electrode member, the conductive wire, and other components even when the discharge electrode assembly is downsized. . In addition, when the contact portion between the conductive wire and the electrode member is laser-welded from the outside, three or more welds must be made in the circumferential direction of the contact portion.
The number of work steps increases, which is not practical.

[0010] The electrode member is, for example, cylindrical.
The outer diameter is 0.5 mm or more and 3 mm or less. The true value of the above means is exhibited in such a small structure.

[2] In the manufacture of the discharge electrode assembly, for example, a process of holding a conductive wire that is sealed through a bead glass, and a process of holding the held conductive wire at a tip protruding from the bead glass. A process of pressing the bottom outside the cylinder of the bottomed cylindrical electrode member, and a laser welding process of irradiating a laser beam inside the cylinder of the electrode member and welding the bottom of the electrode member to the tip of the conductive wire. including. By employing this manufacturing method, the discharge electrode assembly can be easily manufactured.

In particular, by employing laser welding, it is easy to achieve good welding strength with a conductive wire even when a small electrode member having an outer diameter of 0.5 mm or more and 3 mm or less is used.

The laser welding process is performed, for example, in a nitrogen atmosphere. However, oxygen or oxide may be attached to the electrode member before the laser welding process is performed. Oxidation may occur in a cylinder accompanied by Therefore, by performing a process of supplying hydrogen gas into the cylinder in parallel with the laser welding process, hydrogen mixed with oxygen explosively expands due to the heat of laser welding, thereby removing oxides and oxygen in the electrode member cylinder. Blows off and prevents new oxidation. Therefore, it is useful to prevent a situation in which the oxide of the electrode member sputters on the inner surface of the glass container of the discharge lamp to lower the brightness of the lamp or shorten the lamp life.

[3] The present invention, which focuses on a discharge lamp, is a discharge lamp in which a bottomed cylindrical electrode member is welded to the tip of a conductive wire introduced into both ends of a glass container. The inner bottom portion of the member has a structure having a concave melting mark in which the outer bottom portion is welded from the inner side to the tip of the conductive wire from the inner side. With such a structure, for the same reason as the discharge electrode assembly according to the present invention, the sealing state between the glass container and the conductive wire is suppressed from being deteriorated by heat when the electrode member is welded to the conductive wire. Therefore, a small and highly reliable discharge lamp can be realized.

[0015]

FIG. 1 is an axial sectional view showing an example of a discharge electrode assembly according to the present invention. The discharge electrode assembly 1 shown in FIG. 1 includes a bead glass 2, a sealing metal wire 3 penetratingly fixed to the bead glass 2, a lead wire 4 welded to the sealing metal wire 3, and protruding from the bead glass 2. A cylindrical electrode member 5 with a bottom welded to the tip of the sealed metal wire 3. A portion indicated by reference numeral 6 is a welded portion between the sealing metal wire 3 and the lead wire 4 and is raised or thickened in a bump-like manner.

The bead glass 2 is formed of a material corresponding to the material of the glass bulb of the discharge lamp to which the bead glass 2 is applied, and is made of, for example, borosilicate glass or tungsten glass. The bead glass 2 is fixed by being melt-wound around the sealing metal wire 3. The sealing metal wire 3 is made of a Kovar wire or a tungsten wire or the like having excellent sealing properties with the bead glass 2. The lead wire 4 is made of, for example, a nickel wire or a dumet wire. The welded sealing metal wire 3 and lead wire 4 are an example of a conductive wire. The electrode member 5 includes:
Although not particularly limited, it is made of a press-formed nickel cup. The inner bottom 7 of the electrode member 5 has a concave melting mark 7A in which the outer bottom is welded to the tip of the sealing metal wire 3 from the inside of the cylinder. FIG. 2 illustrates the state of the molten mark 7A as viewed from the opening of the electrode member 3. The concave welding mark 7A is a mark formed by, for example, laser welding the bottom of the electrode member 5 to the tip of the sealing metal wire 3 from the inside of the cylinder. FIG. 3 shows a state in which the electrode member 5 is applied to the end of the sealing metal wire 3 before performing the laser welding.
Prior to laser welding, the bottom 7 in the cylinder of the electrode member 5 remains in a press-formed shape, has no welding mark 7A, and is not recessed. The electrode member 5
After or before welding, a so-called electron emitting material such as a compound containing an alkaline earth metal such as barium may be applied to the peripheral surface.

A method for manufacturing the discharge electrode assembly 1 will be described. The outline of the manufacturing method will be described first.
Then, the lead wire 4 is welded, and then the bead glass 2 is wound around the sealing metal wire 3 in a molten state and sealed and fixed. Finally, the electrode member 5 is laser-welded to the sealing metal wire 3.

The laser welding operation will be described in detail. FIG. 4 illustrates an assembling apparatus for laser welding. Reference numeral 10 denotes a conveyor, which is a counterclockwise clockwise intermediate part 1A (see FIG. 3) in which a lead wire 4 is welded to the sealing metal wire 3 and a bead glass 2 is sealed and fixed to the sealing metal wire 3. Carry out intermittently. Reference numeral 11 denotes a turntable which rotates 45 ° for every one pitch of the intermittent conveyance of the conveyor. Intermediate part 1
A is transported with the sealing metal wire 3 facing upward. Conveyor 1
At the position of Ca of 0, the intermediate part 1A is moved to the position of Ta on the turntable 11 via a transfer mechanism not shown. The presence or absence of the intermediate part 1A is detected by a sensor (not shown) at the position of Tb on the turntable. The laser irradiation unit 12 is located immediately above the Tc position of the turntable.
Is disposed on the right side thereof, and a part feeder 13 capable of supplying the electrode members 5 one by one is provided.
The electrode member supplied from 3 is held by the chuck 14 and moved to the Tc position, where the bottom surface of the electrode member 5 is pressed against the upper end surface of the sealing metal wire 3, and in this state, the electrode member 5
The laser beam is irradiated from the laser irradiation unit 12 from the inside of the tube toward the bottom 7, and the electrode member 5 is welded to the sealing metal wire 3. The discharge electrode assembly 1 thus assembled is carried to the position Td by the turntable 11, and
Here, the transfer mechanism (not shown) is used to transfer the C
It is moved to position d and transported to the next step.

FIG. 5 illustrates details of a laser irradiation portion in the assembling apparatus of FIG. The turntable 11 holds conductive wires 3 and 4 that penetrate the bead glass 2 and are sealed. The outer bottom of the electrode member 5 supported by the chuck 14 is pressed against the tip of the held sealing metal wire 3 protruding from the bead glass 2. In this state, the laser irradiation unit 12 irradiates the inside of the cylinder of the electrode member 5 with laser light, and the bottom of the electrode member 5 is welded to the tip of the sealing metal wire 3. By employing this manufacturing method, the discharge electrode assembly 1 can be easily manufactured. In particular, by using laser welding,
Even when a small electrode member 5 having an outer diameter of 0.5 mm or more and 3 mm or less is used, it is easy to achieve good welding strength with the sealing metal wire 3.

The laser welding process is performed, for example, in a nitrogen atmosphere. Further, by performing a process of supplying hydrogen gas into the cylinder of the electrode member 5 in parallel with the laser welding process, it is possible to prevent oxidation which may occur particularly in the cylinder of the electrode member 5 due to heat of laser welding. Can be. Accordingly, it is useful to prevent a situation in which the oxide in the cylinder is sputtered on the inner surface of the glass container of the discharge lamp described below to lower the luminance and shorten the lamp life.

FIG. 6 illustrates a discharge lamp 20 employing the discharge electrode assembly constructed as described above. 21
Is a glass container made of the same glass as the bead glass 2. For example, in the case of a low-pressure mercury vapor discharge lamp, a phosphor paint 22 is applied to the inner periphery of a glass container 21, and mercury vapor and A rare gas such as argon or neon is filled and hermetically sealed. The conductive wire, for example, the sealing metal wire 3 welded to the lead wire 4 is introduced into both ends of the glass container 21, and the bottomed cylindrical electrode member 5 is welded and fixed to the leading end thereof. This electrode member 5 is configured using the discharge electrode assembly 1 of FIG. For example, as illustrated in FIG. 7, the discharge electrode assembly 1 is inserted into a cylindrical glass bulb 21A having both ends opened, and when the opening of the glass bulb 21A is heated and softened, it contracts in the centripetal direction (the direction of arrow F). The pressing force acts to integrally fuse and bond the bead glass 2, whereby the electrode member 5 is obtained inside the hermetically sealed glass container 21. In this hermetic sealing step, the exhaust inside the glass container 21 and the filling of mercury or a rare gas are also performed. For the filling of mercury, a mercury amalgam or a so-called mercury releasing alloy may be used. In the discharge lamp 20 configured as described above, the in-cylinder bottom 7 of the electrode member 5 is provided in the same manner as described above.
It has a recessed melting mark 7A when the bottom of the tube is welded to the tip of the sealing metal wire 3 from the inside of the tube.

As described above, according to the structure in which the electrode member 5 is welded from the inside of the tube to the tip of the sealing metal wire 3, the melting starts from the bottom 7 in the tube of the electrode member 5. The molten state spreads to the tip of the sealing metal wire 3, and the melt at the bottom 7 in the cylinder and the melt at the tip of the sealing metal wire 3 mix and solidify to form an electrode member 5 and the sealing metal wire 3. Is welded. That is, the welding source at the time of welding is on the electrode member 5 distant from the sealing metal wire 3. Therefore, the thermal effect on the bead glass 2 during the welding operation is small. Structurally beaded glass 2
Therefore, it is easy to obtain the necessary welding strength because the thermal influence on the welding can be reduced. As a result, it is possible to prevent a decrease in reliability due to poor welding, and to suppress or reduce a situation in which the sealing state between the bead glass 2 and the sealing metal wire 3 is deteriorated or a crack is generated in the bead glass 2. Can be. When the above structure is compared with a structure in which the contact portion between the sealing metal wire and the electrode member is spot-welded from the outside, in this case, since the fusion source at the time of welding is directly on the sealing metal wire, compared with them. Also, the structure of the present invention shown in FIG. 1 has a small thermal effect on the bead glass 2. Also, compared to resistance welding in which Joule heat is constantly generated in each of the conductive wires 3 and 4, the structure of the present invention shown in FIG. 1 has less thermal influence on the bead glass 2, and it is easy to obtain the required welding strength. is there. Further, the structure of the present invention shown in FIG. 1 is not a structure in which the electrode member 5 is fixed to the sealing metal wire 3 via a mechanical engagement state. Therefore, even when the discharge electrode assembly 1 is downsized, the electrode member 5 and the sealing member are not fixed. It is not necessary to increase the processing accuracy for components such as the metal wire 3. For example, the electrode member 5 is cylindrical and has an outer diameter of 0.5 mm or more and 3 mm or less. In order to cope with such miniaturization, the electrode structure shown in FIG. No high processing accuracy is required for parts such as No. 3, and welding work is also easy due to laser welding. When the contact portion between the sealing metal wire 3 and the electrode member 5 is laser-welded from the outside, in order to obtain welding strength, welding must be performed at three or more locations in the circumferential direction of the contact portion. It is not practical to increase.

FIG. 8 shows a bending test result of the discharge electrode assembly 1 by laser welding of FIG. In this test, the lead wire 4 was supported, and the number of times the electrode member 5 was bent at an angle of 45 ° with respect to the axis thereof was repeated until the process of bending the electrode member 5 in the forward and backward directions was broken. The number of subjects is shown in a frequency distribution. FIG. 9 shows a similar bending test result for the case where resistance welding was performed as a comparative example. As is apparent from comparison between the two, the welding strength is higher in laser welding. Figure 1
0 indicates the result of the tensile test of the electrode member against the sealing metal wire. According to this, the laser welding was able to obtain a stronger tensile strength than the resistance welding.

According to the discharge lamp 20 using the discharge electrode assembly according to the present invention, the sealing state between the glass container 21 and the sealing metal wire 3 is such that the electrode member 5 is welded to the sealing metal wire 3. Deterioration due to heat at that time is suppressed, and the welding strength of the electrode member 5 to the sealing metal wire 3 is strong, so that high reliability can be realized even in a small size.

Also, since the process of welding the electrode member 5 to the tip of the sealing metal wire 3 from the inside of the tube is performed, for example, in a nitrogen atmosphere, oxidation is unlikely to occur in portions other than the inside of the tube accompanied by melting. . In a cylinder accompanied by melting, oxidation may occur through oxygen or oxide attached in the air, but by supplying hydrogen gas into the cylinder of the electrode member 5 in parallel with the laser welding process, Hydrogen mixed with oxygen explosively expands due to the heat of laser welding to blow off oxides and oxygen in the cylinder of the electrode member 5 and prevent new oxidation. FIG. 11 shows accelerated lighting of a discharge lamp having an electrode structure without oxidation by laser welding supplied with hydrogen gas and a discharge lamp according to a comparative example having an electrode structure in which an oxide adheres to the surface of an electrode member by laser welding. The results of the test are shown. Here, a tube current of 5.5 mArms was passed through a test lamp having a glass container having an outer shape of 2.6 mm and a total length of 321 mm, and an accelerated lighting test was performed in an environment of 0 ° C. The outer diameter of the electrode member 5 is, for example, 1.4 mm. It was revealed that the luminance decay rate of the former was significantly lower than that of the latter.
This is because the oxide is prevented from adhering to the inner surface of the glass container of the discharge lamp.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited thereto, and various modifications can be made without departing from the gist of the invention. Needless to say.

For example, the electrode member is not limited to a cylindrical shape, but may have an appropriate shape such as a triangular prism, a quadrangular prism, or a truncated cone. Further, the inside of the electrode member may be later filled with an electron emitting substance or a getter substance. The material of each component of the discharge electrode assembly is not limited to the above, and can be appropriately changed. Further, the discharge lamp according to the present invention is not limited to a low-pressure mercury vapor discharge lamp, but can be applied to a discharge lamp containing a rare gas and containing no mercury vapor.

[0028]

According to the discharge electrode assembly of the present invention,
Good strength can be ensured without requiring a complicated structure and high processing accuracy for coupling the electrode member and the conductive wire.

According to the method for manufacturing a discharge electrode assembly of the present invention of the present invention, it is possible to easily obtain good strength for coupling the electrode member and the conductive wire.

Further, according to the present invention, a small and highly reliable discharge lamp can be realized.

[Brief description of the drawings]

FIG. 1 is an axial sectional view showing an example of a discharge electrode assembly according to the present invention.

FIG. 2 is a plan view showing a state of a melting mark as viewed from an opening of an electrode member.

FIG. 3 is an axial sectional view showing a state in which an electrode member is applied to a tip of the sealing metal wire before performing laser welding.

FIG. 4 is a schematic plan view illustrating an assembling apparatus for laser welding.

FIG. 5 is a front sectional view illustrating details of a laser irradiation part in the assembling apparatus of FIG. 4;

FIG. 6 is an axial cross-sectional view illustrating a discharge lamp employing the discharge electrode assembly of FIG. 1;

FIG. 7 is an axial sectional view schematically showing a method of incorporating a discharge electrode assembly into a discharge lamp.

FIG. 8 is an explanatory view showing a bending test result of the discharge electrode assembly by laser welding of FIG. 1;

FIG. 9 is an explanatory view showing a bending test result for a discharge electrode assembly subjected to resistance welding as a comparative example.

FIG. 10 is an explanatory diagram showing a result of a tensile test of an electrode member with respect to a sealing metal wire.

FIG. 11 is a graph showing the results of luminance decay in accelerated lighting tests of a discharge lamp having an electrode structure without oxide and a discharge lamp having an electrode structure with oxide by laser welding from the inside of a cylinder supplied with hydrogen gas. FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Discharge electrode assembly 2 Bead glass 3 Sealing metal wire 4 Lead wire 5 Electrode member 7 In-cylinder bottom 7A Depressed melting mark 10 Conveyor 11 Turntable 12 Laser irradiation unit 13 Parts feeder 14 Chuck 20 Discharge lamp 21 Glass container

Claims (9)

[Claims] 1. An electrode member comprising: a bead glass; a conductive wire penetrating through the bead glass; and a bottomed cylindrical electrode member welded to a tip of the conductive wire protruding from the bead glass. A discharge electrode assembly, characterized in that it has a concave melting mark in which the bottom of the tube is welded to the tip of the conductive wire from the inside of the tube at the bottom of the tube. 2. An electrode member comprising: a bead glass; a conductive wire penetrating through the bead glass; and a bottomed cylindrical electrode member welded to a tip of the conductive wire protruding from the bead glass. A discharge electrode assembly, the bottom of which is laser welded from the inside of the tube to the tip of the conductive wire. 3. The discharge electrode assembly according to claim 1, wherein the electrode member has a cylindrical shape, and has an outer diameter of 0.5 mm or more and 3 mm or less. 4. A process for holding a conductive wire penetrated through a bead glass and sealing the conductive wire, and attaching a bottom portion of a cylindrical electrode member having a bottom to a tip end of the held conductive wire protruding from the bead glass. Manufacturing a discharge electrode assembly, comprising: a pressure welding process; and a laser welding process of irradiating a laser beam into a cylinder of the electrode member to weld a bottom portion of the electrode member to a tip of the conductive wire. Method. 5. The method for manufacturing a discharge electrode assembly according to claim 4, wherein a process of supplying hydrogen gas into said cylinder is performed in parallel with said laser welding process. 6. The method for manufacturing a discharge electrode assembly according to claim 4, wherein said electrode member has a cylindrical shape, and an outer diameter is 0.5 mm or more and 3 mm or less. 7. A discharge lamp in which a cylindrical electrode member having a bottom is welded to a tip end of a conductive wire introduced to both ends of a glass container, wherein a bottom of the electrode member has an inner tube. A discharge lamp, characterized in that the discharge lamp further comprises a concave melting mark formed by welding a bottom portion of the outer tube to the end of the conductive wire. 8. A discharge lamp in which a bottomed cylindrical electrode member is welded to the tip of a conductive wire introduced into both ends of a glass container, wherein the bottom of the electrode member is formed from the inner side of the tube. A discharge lamp characterized by being laser-welded to the tip of a lamp. 9. The discharge lamp according to claim 7, wherein the electrode member has a cylindrical shape, and has an outer diameter of 0.5 mm or more and 3 mm or less.