JPH0286045A - High-pressure sodium lamp - Google Patents

Abstract

PURPOSE:To improve the adhesive strength on an interface and prevent the occurrence of a leak by oxidation-treating the surface in contact with the glass solder of a conductor and connecting the oxidation-treated surface and the end section of a light emitting tube. CONSTITUTION:The end section of a light emitting tube 1 is airtightly connected with an end plate 3 made of ceramic or the like and glass solder 4, and a conductor 5 is penetrated through the end plate 3. The conductor 5 is airtightly connected to the end plate 3 by glass solder 6. An oxidation-treated film 7 is formed on the surface of the portion where the conductor 5 is brought into contact with the glass solder 6, and the film 7 and the end plate 3 are connected via the glass solder 6. The oxidation-treated film 7 is stuck to the glass solder 6, the adhesive strength on the interface is improved, and the occurrence of a leak can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a structure of an electrode sealing part in a high-pressure sodium lamp.

(Prior technology) A high-pressure sodium lamp is a luminescent tube made of ceramic such as translucent alumina, with electrodes sealed at both ends, and sodium as a luminescent substance, mercury as a buffer gas metal, and a rare gas for starting. , luminous efficiency in a discharge lamp! Due to its high energy consumption, it is attracting attention as a lamp suitable for energy saving.

However, conventional high-pressure sodium lamps have a low color rendering property of about 20 to 30 in terms of average color rendering index Ra, and are not necessarily suitable for indoor lighting.

Therefore, recently, the sodium vapor pressure during lighting has been increased to
High-pressure sodium lamps with improved color rendering properties of A-55 to 85 have been developed and are becoming popular for indoor lighting.

(Problems to be Solved by the Invention) However, in the high-pressure sodium lamp with improved color rendering properties as described above, the vapor pressure of sodium is high during lighting, so there is a concern about leakage of sodium.

In other words, in this type of high-pressure sodium lamp, the end of an alumina arc tube is closed with an alumina end plate (cap), and a conductor is passed through and sealed to this end plate, and the conductor is sealed. It consists of an electrode bonded to the inner tip of the arc tube.

In this case, the alumina arc tube and the alumina end plate are hermetically bonded with glass solder, and the end plate and the conductor are also hermetically bonded with glass solder.

The conductor is made of a tube or rod made of niobium (usually mixed with 1% zirconium to prevent recrystallization at high temperatures), a metal that has a coefficient of thermal expansion close to that of alumina and is not corroded by sodium. The glass solder is composed of aluminum oxide (A)203), calcium oxide (CaO), barium oxide (Ba20), aluminum oxide (A, l?2o3), yttrium oxide (Y203), strontium oxide (SrO), etc. ing.

This type of glass solder is heated to about 1500°C to fill the gap between the end plate and the conductor and bond them together, but the adhesive strength between the niobium and glass solder interface is not sufficient. Although rare, sodium leaks could occur during lamp life.

The present invention was made based on the above circumstances, and aims to provide a high-pressure sodium lamp that can increase the adhesive strength between a conductor and a glass solder to form a reliable bond and prevent sodium leakage. It is.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides an oxidized surface for the surface of the conductor that comes into contact with the glass solder, and a glass solder between the oxidized surface and the end of the arc tube. It is characterized by being joined.

(Function) According to the present invention, since the outer surface of the conductor is oxidized, the oxidized niobium is largely diffused into the glass solder, thereby improving the adhesive strength at the interface. , Therefore, occurrence of leakage can be prevented.

(Example) The present invention will be described below based on a first example shown in FIG.

In the figure, 1 is an arc tube made of ceramic such as polycrystalline alumina or single crystal alumina, and inside it contains a predetermined amount of sodium, mercury as a buffer gas metal, and about 10 to 300 Lorr as a starting rare gas. It is filled with xenon gas or neon-argon Penning gas.

An electrode 2 is sealed at the end of the arc tube 1 .

That is, an end plate (cap) 3 also made of ceramic such as polycrystalline alumina or single crystal alumina is hermetically bonded to the end of the arc tube 1 formed of the alumina tube with a glass solder 4. A conductor 5 made of niobium passes through the end plate 3.

The conductor 5 of this embodiment has a tube shape and is hermetically joined to the end plate 3 by a glass solder 6.

In this case, an oxidized film surface 7 is formed on the surface of the conductor 5 that corresponds to the part that contacts the glass solder 6, that is, the part that gets wet with the glass solder 6, and this oxidized film surface 7 and the end plate 3 are connected to each other. are bonded via glass solder 6.

The electrode 2 is connected to the end of the conductor 5 inside the arc tube 1 . The electrode 2 is composed of an electrode shaft 8 made of tungsten and an electrode coil 9 made of tungsten wound in two layers around the electrode shaft 8, and this electrode coil 9 contains B a 2 Ca W 06 or An emitter such as Ba2O is retained.

In this configuration, the oxidized film surface 7 is formed on the outer surface of the conductor 5, and the oxidized film surface 7 is bonded to the glass solder 6, so that the oxidized niobium, that is, the oxidized Niobium is largely diffused into the glass solder 6, thereby improving the adhesive strength at the interface between the conductor 5 and the glass solder 6. The glass solder 6 and this outer end plate 3 originally have large mutual diffusion at the interface (and high adhesive strength).

Therefore, the bonding strength at the sealed portion of the conductor 5 is improved, and even when the vapor pressure of sodium is high, leakage can be prevented.

FIG. 2 shows a second embodiment of the present invention, in which the conductor 10 is rod-shaped.

In this case as well, an oxidized coating surface 7 is formed on the surface of the portion of the conductor 10 that contacts the glass solder 6, that is, the portion where the glass solder 6 gets wet.
and end plate 3 are joined via glass solder 6.

Even with such a configuration, the same effects as in the first embodiment can be achieved.

In addition, in order to form the oxidized film surface 7 on the surface of the conductor 5.10, it is also possible to oxidize the surface by heating and firing the surface with a burner etc., but in this case, Since it is difficult to maintain a constant degree of baking, there is a concern that the thickness of the oxidized film may become uneven.

For this reason, the anodizing method shown in FIG. 3 may be employed. That is, in the anodizing method shown in FIG. 3, a conductor 5 or 10 and a processing electrode 21 are placed in a dilute solution 20 of hydrochloric acid, facing each other at a distance, and the conductor 5 or 10 is used as an anode. is used as a cathode, and a voltage of, for example, 15 V is applied between them for about 20 seconds.

As a result, the dilute solution 2 of the hydrochloric acid of the conductor 5 or 10
An oxidized film surface 7 is formed on the portion that was immersed in the water.

With this method, the thickness of the oxidized coating surface 7 can be easily controlled by controlling the concentration of the diluted solution of hydrochloric acid, the value of the applied voltage, or the application time, and when baking The characteristics are more stable.

[Effects of the Invention] As explained above, according to the present invention, since the outer surface of the conductor is oxidized, the oxidized niobium is largely diffused into the glass solder, which improves the adhesive strength at the interface. This has the advantage of being able to improve the leakage and therefore prevent the occurrence of leaks.

[Brief explanation of drawings]

FIG. 1 shows a first embodiment of the present invention, and is a sectional view of the end of the arc tube of a high-pressure sodium lamp. FIG. 2 is a sectional view of the end of the arc tube, showing the second embodiment of the invention. FIG. 3 is a diagram explaining the anodizing method. DESCRIPTION OF SYMBOLS 1... Arc tube, 2... Electrode, 3... End plate, 4... Glass solder, 5, 10... Conductor, 6
... Glass solder, 7... Oxidized coating surface. Figure 1 Applicant's agent Patent attorney Takehiko Suzue Figure 2

Claims (1)

[Claims] A conductor with an electrode at the tip is passed through the end of an arc tube filled with sodium, a metal for buffer gas, and a rare gas for starting, and this conductor is connected via a glass solder to the above-mentioned light emitting tube. A high-pressure sodium lamp airtightly joined to an end of a tube, characterized in that the surface of the conductor that contacts the glass solder is an oxidized surface.