JP2638858B2 - Arc tube manufacturing method - Google Patents

Description

The present invention relates to an improvement in a discharge lamp in which electrodes are sealed at both ends of an arc tube and one or more metal halides are enclosed inside the arc tube together with mercury and a rare gas. In particular, the present invention relates to an improvement in a method for manufacturing an arc tube enclosing the metal halide.

[Prior Art] Scandium and sodium halides are one type of metal vapor discharge lamps in which electrodes are sealed at both ends of a quartz arc tube and one or more metal halides are sealed inside together with mercury and a rare gas. In particular, a scandium-sodium discharge lamp sealed with iodide is known.

This type of discharge lamp has better color rendering properties due to a unique spectrum over the entire visible region due to scandium emission.

When manufacturing the arc tube of a discharge lamp, there is the following method as a method of enclosing a metal halide in the arc tube. Here, an example of an arc tube in which scandium iodide (ScI ₃ ) and sodium iodide (NaI) are sealed as metal halides will be described.

(1) As a method of directly encapsulating a metal halide in an arc tube, a mixture of ScI ₃ and NaI or a mixture of ScI ₃ and NaI is used.

(2) As a method of producing a metal halide in the arc tube, to generate a ScI _3, scandium oxide (Sc
₂ O ₃ ), a reducing metal such as aluminum (Al) or silicon (Si), and mercury iodide (HgI ₂ ) are sealed together with NaI, and after lighting, are reacted in an arc tube to produce ScI ₃ . In this case, Sc ₂ O ₃ may be applied to the electrodes in advance.

(3) In order to generate ScI ₃ similarly to the above (2), scandium metal (Sc) and HgI ₂ are sealed together with NaI, and ScI and HgI ₂ are reacted after lighting to generate ScI ₃ .

However, in the method (1), ScI ₃ is a very active substance, has a very high hygroscopicity in air, is easily hydrolyzed, and absorbs a small amount of water even if present. We take great care in its handling. The same applies to the case of a mixture of ScI ₃ and NaI.

Therefore, in this method, there is a great risk that moisture will be introduced into the arc tube, and if moisture exists in the arc tube, the arc tube will be blackened soon after the discharge lamp is turned on, or its starting characteristics will deteriorate.

Next, in the method (2), a metal halide to be used is NaI and HgI _2, HgI ₂ is a very stable substance in air compared to ScI ₃ Further, since NaI relatively easy to handle There is little danger of bringing moisture into the arc tube.

However, when Sc ₂ O ₃ is used, the process of generating ScI ₃
Alternatively, there is a danger that oxygen will be generated from Sc ₂ O ₃ that is excessively present during lighting, and the generation of oxygen in the arc tube will lead to blackening of the arc tube. Therefore, this method requires precise control of the amount of Sc ₂ O ₃ and control of its reaction.

Furthermore, in the method (3), although there is no problem such as the above-described generation of oxygen, it is difficult to seal a required amount of Sc metal in the arc tube.

That is, when encapsulating Sc metal in the arc tube, Sc may be a metal foil, a metal wire, or the like, but it is necessary to weigh the enclosing amount one by one or to cut out accurately,
It is difficult to control the amount accurately and it is not suitable for mass production.

[Problems to be Solved by the Invention] In the cases of the above (1) and (2), it is possible to melt and mix each metal halide, or to compact the powder as a powder, and into the arc tube. It is relatively easy to encapsulate the required amount of Sc as a scandium compound.

However, in the case of the above (3), in order to make the Sc metal into a powdery form, since Sc is a very hard metal, hydrogen is adsorbed on a lump of Sc, and hydrogen is embrittled to form a powdery form. Although it is produced by crushing, the powder of Sc obtained in this way contains:
Usually, a few percent by weight of hydrogen is stored. Therefore, this Sc powder cannot be directly enclosed in the arc tube.

This is because if hydrogen is present in the arc tube, it will be an interfering gas when starting the discharge lamp. Therefore, in order to enclose the Sc powder in the arc tube, it is necessary to perform a dehydrogenation treatment. Heating in a vacuum is optimal for dehydrogenation treatment, and hydrogen can be removed almost completely at a heating temperature of about 1,000 ° C.

However, when such a treatment is performed, there is a disadvantage that the Sc powders are sintered together and cannot be handled as powder.

In addition, the method of using the Sc powder can be mixed with the powder of the other inclusions and integrally press-molded, so that the control of the sealing amount is simple and suitable for mass production.

[Means for Solving the Problems] The present invention has been made in view of the above points, and at least one kind of metal halide to be sealed in an arc tube contains a predetermined ratio of powder of the metal and high melting point metal. A mixture with a powder is heated in a vacuum to dehydrogenate the mixture, and then the mixture and another metal halide are integrated and sealed in an arc tube. In particular, scandium ( Sc) powder and tungsten (W) powder in a weight ratio of Sc: W = 2: 1 to 1: 3, and heating the mixture at a temperature of at least 1000 ° C. in vacuum After the dehydrogenation treatment, the mixture and another metal halide are integrated and sealed in the arc tube. The encapsulation of the metal halide in the arc tube is easy, and the encapsulation is performed. An arc tube that can accurately control the volume and is suitable for mass production Not only to provide a manufacturing method, and an object thereof is to provide a discharge lamp which has excellent starting characteristics and light emission characteristics based on this method.

Example Hereinafter, an example according to the present invention will be described. First,
As a method of producing the metal powder of the metal halide contributing to the light emission, for example, to produce a metal powder of scandium (Sc), a method of “squeezing” with a metal saw and a method of mechanically pulverizing There is a method (milling) to do.

In the former case, the treatment is carried out in oil to prevent Sc from being oxidized. At that time, impurities are liable to be mixed in and the powder is not so fine.

Therefore, a method of mechanical pulverization is adopted. In this method, in order to increase the pulverization efficiency and improve the properties of the produced powder, after the embrittlement treatment is performed, hydrogen is absorbed to form a hydrogen compound to be embrittled.

By this method, a relatively fine powder of Sc can be obtained, and the powder can be further pulverized with a milk bee or the like. However, this Sc powder contains a large amount of hydrogen, and when enclosed in an arc tube, dehydrogenation is required.

Next, the optimum amount of scandium (Sc) powder and tungsten (W) powder to be sealed according to one embodiment of the present invention will be described.

As described above, the Sc powder is treated at a heating temperature of about 1,000 ° C. in a vacuum to dehydrogenate the Sc powder, but before the treatment, the Sc powder is sintered at the temperature of 1,000 ° C. A mixture is prepared by mixing W powder which is a high melting point metal which is not bonded. Therefore, mixed Sc powder (10 μm) and W powder (1 μm)
Table 1 shows the sintering state of the powder obtained by treating a material obtained by mixing m) with a predetermined ratio by weight at a heating temperature of about 1,000 ° C. in vacuum.

As is clear from Table 1, when the Sc powder and the W powder are heated at about 1,000 ° C. in a state where the weight ratio of W is more than 2: 1, the Sc powders are strongly attached to each other. The powder was easily restored to the original powder form after the treatment.

Also, 99% or more of the hydrogen adsorbed on Sc could be removed.

As described above, it can be understood that the use of the Sc powder allows easy control of the filling amount since the powder can be mixed with the powder of the other filling material and press-formed integrally.

Further, when the discharge lamp in which the mixture of the Sc and W powders is sealed in the arc tube is turned on, the W powder in the arc tube does not react with the halide, and the discharge lamp as shown in FIG. When the light is turned on, it accumulates at the lowest position in the arc tube.

In the figure, reference numeral 1 denotes a tube made of quartz glass, sealing portions 2a and 2b are formed at both ends thereof, and electrodes 3a and 3b and an auxiliary electrode 4 made of tungsten are sealed via molybdenum foils 5a, 5b and 5c. Inside, scandium and sodium iodides are sealed together with mercury and argon gas. Further, tungsten powder 6 is accumulated on the inner wall of the arc tube at the base of the electrode of the lower sealing portion cup-shaped portion h.

This part is also the coolest part of the arc tube when the discharge lamp is lit.

And, as described above, since the powder of W accumulates in the coolest part of the arc tube to form a black part, the heat is absorbed and the temperature of the coolest part rises, and the vapor pressure of ScI ₃ and NaI rises. And the color temperature is lowered, so that the color rendering properties can be improved. Here, S in a discharge lamp with a tube input of 400 watts
Table 2 shows the relationship between the mixing ratio of the c-powder and the W-powder, the spread of the W-powder in the coldest part, and the emission characteristics thereof.

As is apparent from Table 2, when W is excessively encapsulated, W
Since the spread of the powder becomes large and the heat absorption becomes large, the color temperature becomes too low and the color characteristics are impaired.

In addition, when the lighting direction is other than the vertical lighting as shown in FIG. 1, the powder of W spreads in the central portion of the arc tube, causing light to be blocked, thereby reducing the luminous flux.

Therefore, the amount of W powder mixed with Sc powder is expressed as Sc: W =
It is necessary to stop at about 1: 3.

As described above, by mixing the tungsten powder with the scandium powder in a weight ratio of 2: 1 to 1: 3, the powder does not solidify even when the Sc is dehydrogenated by vacuum heating. And the powder of Sc (mixed powder of Sc and W) and the powder of sodium iodide, mercury iodide, etc. can be integrated and compacted. The required amount of Sc can be accurately enclosed.

Also, the enclosed W powder accumulates in the coolest part of the arc tube,
Since the temperature of the coldest part of the arc tube can be increased, the vapor pressure of sodium iodide and scandium iodide can be increased, and the emission characteristics such as color characteristics can be enhanced.

In the above-described embodiment, the scandium and tungsten powders are described as the powder of the metal contributing to light emission and the powder of the high melting point metal. However, as other metals, the powder of scandium and molybdenum or the dysprosium powder is used. And tungsten or molybdenum powder.

Further, other than the above, it is also possible to use, for example, aluminum oxide or the like which does not sinter at the temperature at which the luminescent metal is heated.

[Effects of the Invention] As is apparent from the above description, the method for manufacturing an arc tube according to the present invention can encapsulate a metal halide that contributes to light emission as a powder of the metal, and thus can accurately determine the amount of the enclosed metal halide. , And can save labor by mass production.

Further, a discharge lamp manufactured based on this method has advantages such as excellent starting characteristics and luminous characteristics, and thus has a great industrial value.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view showing an embodiment of an arc tube according to the present invention.

Claims (2)

(57) [Claims] 1. A method for manufacturing an arc tube for a metal vapor discharge lamp in which at least a metal halide of scandium or dysprosium is encapsulated in an arc tube, wherein at least one type of metal halide encapsulated in the arc tube is a predetermined one. A mixture of the powder of the metal and the powder of the high melting point metal in a ratio, and after heating the mixture in a vacuum to perform a dehydrogenation treatment, the mixture is integrated with another metal halide. A method for manufacturing an arc tube, wherein the arc tube is sealed in the arc tube. 2. The mixture of metals is scandium (Sc).
Powder and tungsten (W) powder in a weight ratio of Sc: W
= 2: 1 to 1: 3, and heating the mixture at a temperature of at least 1000 ° C. in a vacuum to perform dehydrogenation treatment. Then, the mixture and other metal halides are integrated into an arc tube. 3. The method for manufacturing an arc tube according to claim 1, wherein the arc tube is enclosed.