JPH11144681A - Lamp and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lamp capable of reducing change in lamp characteristics and preventing cracks that may be an initial point of lamp breakage. SOLUTION: To a lamp having a sealing member for sealing an opening of a light emitting tube 1 and an electrode linked with the sealing member to protrude to the inside of the light emitting tube 1, a junction part between the sealing member and the electrode is constituted so as to be more vulnerable to the sealing member and the electrode. In addition, the junction part is constituted by an intermediate layer indentenpent of the sealing member and the electrode, and the intermediate layer contains Mo and W, with the thickness being 200 micrometers or less except 0.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lamp structure using an arc tube, and more particularly, to an electrode sealing structure using welding.

[0002]

2. Description of the Related Art As a typical electrode structure of a lamp using an arc tube, a tungsten shaft having a tungsten coil fixed to a tip portion like a lamp using a quartz arc tube shown in FIG. An internal electrode made of and an external electrode for an external terminal are connected to each other via a molybdenum foil so as to be conductive, and the electrode portion is heated while heating the end of the arc tube in order to make the inside and outside of the arc tube airtight. One that is welded together with the electrode is mentioned.

Further, in order to obtain more excellent lighting characteristics, for example, a point light source, a functionally graded material having a substantially columnar shape in which the composition is gradually inclined from a quartz-rich portion to a molybdenum-rich portion is used. Various techniques such as shortening the distance and increasing the internal pressure in the arc tube have also been considered.

[0004]

However, in the case of an electrode structure using molybdenum foil, a part of the welded portion to the quartz arc tube is usually simultaneously welded to a part of the tungsten shaft portion constituting the internal electrode. For this reason, there is a problem that cracks occur due to a difference in thermal expansion coefficient between quartz and tungsten due to a change in thermal cycle at the time of welding, turning on and off of a lamp, and so on.

On the other hand, for example, Japanese Patent Application Laid-Open No. 63-22 / 1988
As disclosed in Japanese Patent No. 8563, a technique has been proposed in which the length and the diameter of the shaft portion to be welded are defined and avoided, but the process is complicated due to the requirement of precision in manufacturing, and the diameter is further increased. There was a problem that it could not cope with big things. It can also be avoided by designing a clearance between the tungsten shaft and the quartz, but in this case, the luminescent material that has entered the clearance portion does not contribute to light emission or does not contribute to light emission at all. However, there is a problem that a desired lamp characteristic cannot be obtained due to a factor that sometimes contributes to light emission.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a lamp capable of reducing a change in lamp characteristics and preventing a crack which may be a starting point of lamp breakdown.

[0007]

According to the present invention, a lamp having a sealing member for sealing an opening of an arc tube and an electrode joined to the sealing member and projecting into the arc tube. In contrast, the joint between the sealing member and the electrode is configured to be in a fragile state, such as brittle brittleness, elasticity is low, or bonding strength is weaker than the sealing member and the electrode. In this way, the cracks are stopped in the fragile layer while preventing the ingress of the sealing gas, thereby reducing the change in lamp characteristics. Can be prevented.

The joining portion between the sealing member and the electrode may be configured so that the joining portion is weak (the same material as the sealing member or the electrode may be used). An intermediate layer that is fragile may be provided from the viewpoint of productivity. In the case where the intermediate layer is provided, the components of the intermediate layer are connected to the connection member side and the internal electrode shaft side by selecting a component or configuration that forms a fragile intermediate layer at least after sealing. The intermediate layer can be prevented from being cracked or peeled off by the intermediate layer against cracks on the connection member side generated when the member contracts, and cracks on the connection member side can be prevented. For example, with respect to the bonding strength with either the electrode surface or the sealing member surface, the bonding strength with either one can be selected, and a component that can be expected to prevent cracks as described above can be selected. Those lower than the electrodes and the sealing member can also be selected. As specific components, W, Mo, and the like are desirable in consideration of conditions such as strength and heat resistance temperature, but other components may be used as long as they have the above properties.

Regarding the thickness of the intermediate layer, when the intermediate layer is thick, there is a possibility that a crack is generated between the internal electrode shaft and the sealing member due to a thermal expansion of the intermediate layer itself. For this reason, a thinner one is preferable. The preferable thickness of the intermediate layer is desirably 200 μm or less.

In the case where an intermediate layer is provided, particularly at a portion where the sealing member seals the opening,
Since the abundance ratio of the insulating material is larger than the abundance ratio of the conductive material, a space is provided between the insulating portion and the electrode to prevent cracks due to a difference in thermal expansion coefficient. For such lamps, improvement of lamp characteristics can be expected by preventing the sealing gas from entering the space.

Next, as a manufacturing method in the case of providing an intermediate layer, a method that can be performed uniformly and easily even for a complicated shape in order to effectively prevent cracks is preferable. Any method can be used as long as the above-mentioned object can be realized.
There is a method in which the components of the intermediate layer are previously applied to the outer surface of the internal electrode shaft with a paste brush so as to have a uniform thickness, or are applied using dipping, followed by a drying and firing process. Alternatively, the foil of the intermediate layer component may be wound in advance on the outer surface of the internal electrode shaft and treated in the same manner. In addition, it is possible to obtain a suitable thickness of the intermediate layer by the above manufacturing method.

As described above, according to the present invention, a crack which can be a starting point of lamp destruction can be prevented and a change in lamp characteristics can be prevented by a simple method of providing a fragile layer at a welded portion between an electrode and a sealing member. You can get a small lamp.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to further clarify the structure and operation of the present invention described above, preferred embodiments of the present invention will be described below. In the embodiments described below, quartz is used as a sealing member material and an intermediate layer is provided, but the present invention is not limited to this.

FIG. 1 shows an electrode structure of a lamp according to an embodiment of the present invention. FIG. 1 shows a lamp using an electrode structure made of a functionally graded material.
a, an arc tube made of quartz having an end portion 1b, having an internal electrode 2 having a tungsten coil fixed to the tip of a tungsten shaft facing the light emitting portion, and an external electrode 3 made of tungsten facing the outside of the arc tube. The connecting member 4 made of a functional material is positioned inside the arc tube end 1b, and the quartz portion of the connecting member is welded to the arc tube inner portion to hermetically seal the inside and the outside of the arc tube. A desired luminescent substance such as Hg, metal halide, and rare gas is introduced into the arc tube.

FIG. 2 shows an enlarged view of the electrode. Connecting member 4 having quartz-rich portion 5 to molybdenum-rich portion 6
In the quartz-rich portion, there is located a tungsten shaft having a tip portion fixed to the molybdenum-rich portion and constituting an internal electrode having a molybdenum film as an intermediate layer on the surface. Between the rich portions of each composition, both compositions are gradually inclined.

As shown in FIG. 3, the intermediate layer is not in a state in which the molybdenum particles are completely sintered, but in a state in which the particles are partially welded to each other (point contact), and a space is formed between the particles. I have. On the side facing the connection member, the quartz of the connection member is melted and penetrates between the particles to form a strong bond with the intermediate layer, while the side facing the internal electrode has the particles in the point contact. It becomes a fragile state in which tungsten is bonded in a point contact state with each other or with particles. For this reason,
The stress caused by the contraction of tungsten is released by removing the bond between the particle and tungsten at the point contact (moving so that the tungsten slides on the particle), and is transmitted as a crack to the quartz side of the connecting member through the particle gap. Is gone. Further, since the molybdenum particles on the quartz side of the non-connecting member each have a degree of freedom, even if the particles themselves contract, the stress is not transmitted.

The intermediate layer is produced by applying a paste brush made of molybdenum or the like on the outer surface of the tungsten shaft of the internal electrode so as to have a uniform winding thickness, or by applying dipping, and then using a drier. After drying sufficiently, it is calcined at about 1100 ° C to 1500 ° C,
After that, a mixed slurry of molybdenum and quartz was injected into an acrylic cylinder placed on a disc-shaped plaster mold, and a hole extending to the molybdenum-rich layer was formed in the center of the column-shaped functionally graded material on the quartz-rich side. It is obtained by inserting the internal electrode on which the molybdenum thin film is formed in the hole, and firing in a vacuum furnace.

When the diameter of the sealing member is increased,
Since cracks may occur due to the difference in the thermal expansion coefficient around the electrodes, it is desirable to form all the joints as fragile layers.

The embodiment using the present functionally graded material can be similarly applied to the case where a conventional molybdenum foil is used for the connection member. In particular, in contrast to the conventional method of simply using a molybdenum foil and an electrode for sealing, on the molybdenum-rich side of the functionally graded material connecting member, it is possible to secure a wide energizable contact area between the molybdenum foil and the connecting member. Therefore, better current-carrying characteristics can be obtained.

Next, the results of the effect of preventing cracking of the lamp and reducing the change in lamp characteristics according to the above embodiment will be described.

Table 1 shows the results obtained by using a tungsten shaft having a filler formed on the surface and having different diameters, together with silica, and observing cracks with a stereoscopic microscope. Cracks were all formed when the tungsten having no filler was evaluated in the same manner.

[0022]

[Table 1]

Further, Table 2 shows that lamp characteristics were evaluated under the following conditions using a connecting member made of a functionally graded material in which contact between the tungsten shaft and quartz was avoided by forming a space, and a filler was used. The result of comparing the one provided and the one not provided is shown. In the case where the filler is provided, since there is no cavity as compared with the case where no filler is provided, the amount of mercury vapor is large and the lamp voltage is high. Further, since the mercury vapor does not accumulate in the space serving as the coolest part, the voltage drop after lighting is reduced. As a result, good lighting characteristics are obtained.

[0024]

[Table 2]

As described above, according to the above-described embodiment, it is possible to prevent a crack which may be a starting point of lamp destruction, and at the same time, obtain a lamp having a small change in lamp characteristics. The lamp thus obtained is also suitable for illumination in optical measurement in which a change in lamp characteristics affects the measurement result, for example.

The present invention is not limited to the above embodiment, but can be implemented in various modes without departing from the gist of the invention.

[Brief description of the drawings]

FIG. 1 is a sectional view of a lamp according to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of a lamp according to an embodiment of the present invention.

FIG. 3 is an enlarged view of an intermediate layer according to an embodiment of the present invention.

FIG. 4 shows an example of a conventional lamp using molybdenum foil as an electrode.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Arc tube 21a ... Light-emitting part of arc tube 31b ... End of arc tube 2 ... Internal electrode 4 ... Connection member 5 ... Molybdenum-rich part 6 ... Quartz-rich part

Claims (9)

[Claims] 1. A lamp having a sealing member for sealing an opening of an arc tube and an electrode joined to the sealing member and protruding into the arc tube, wherein the sealing member is joined to the electrode. The part is weaker than the sealing member and the electrode. 2. A sealing member for sealing an opening of an arc tube, an electrode joined to the sealing member and protruding into the arc tube, and the sealing member is insulated from a conductive material. And a lamp using a functionally graded material in which the abundance ratio of the insulating material is greater than the abundance ratio of the conductive material in a portion where the sealing member seals the opening while containing the conductive material. The joint between the member and the electrode is weaker than the sealing member and the electrode. 3. The lamp according to claim 2, wherein the joint is formed between at least an insulating portion of the sealing member and an electrode. 4. The lamp according to claim 1, wherein the joint is formed by an intermediate layer that is separate from the sealing member and the electrode. 5. The lamp according to claim 4, wherein the intermediate layer contains Mo and W. 6. The intermediate layer having a thickness of 200 μm or less (0
5. The lamp according to claim 4, wherein: 7. A sealing member for sealing an opening of an arc tube, and an electrode joined to the sealing member and protruding into the arc tube, wherein the sealing member and the electrode are welded together. In the method of manufacturing a lamp that is sealed by performing, a forming layer configured to be weaker than the sealing member and the electrode at least after sealing is formed on the surface of the electrode in advance. Lamp manufacturing method. 8. The thickness of the formation layer is 200 μm or less (0
8. The method for manufacturing a lamp according to claim 7, wherein 9. The sealing member contains a conductive material and an insulating material, and at a portion where the sealing member seals an opening, the ratio of the insulating material to the ratio of the conductive material is determined. 8. The method according to claim 7, wherein a larger functionally graded material is used.