JPH0483769A - Sealing composition - Google Patents

Abstract

PURPOSE:To obtain the title composition having excellent wetting property with heat resistant metal of alumina ceramic tube and Nb tube, etc., as well as excellent resistance to Na and causing no crack of an emitting tube in heat cycle when a light is turned on or of by constituting the title composition from specific amounts of Al2O3, CaO, Y2O3, SrO and ZrO2. CONSTITUTION:The aimed composition composed of 35-50wt.% Al2O3, 35-50wt.% CaO, 5-15wt.% Y2O3, 3-10wt.% SrO and 1-5wt.% ZrO2.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a sealing composition used for sealing ceramics to ceramics or ceramics to metals, particularly for high-pressure sodium lamps made of translucent alumina ceramics. The present invention relates to improvements in a sealing composition used when sealing the end of an arc tube with a ceramic or heat-resistant metal member.

[Prior Art] A sealing composition used when sealing the end of a translucent alumina ceramic tube conventionally used as an arc tube for high-pressure sodium lamps with alumina ceramics or a heat-resistant metal member such as niobium or molybdenum. As, A1□O
, -CaO-MgO system, A 120. -Ca O-B
A sealant based on aO, Al□○, -CaO-8iO2, or Al2O, -Cao-5rO is used.

These sealing compositions have sufficient heat resistance for use in lamps, complete airtightness against temperature changes when the temperature of the sealing part increases and decreases, and corrosion resistance against high-pressure sodium vapor during lamp operation. sexuality is required.

[Problems to be Solved by the Invention] Recently, compact high-color rendering type high-pressure sodium lamps are often used for store lighting. Compared to high-efficiency lamps that can be lit using mercury lamp ballasts, these compact, high-color-rendering, high-pressure sodium lamps have higher temperatures in their sealing members, which causes sodium to erode more quickly into the sealing members. This can result in significant changes in lamp light color during lamp life. This makes the lamp unsuitable for indoor lighting in stores and the like.

[! l! Means for Solving the Problem] The present invention was made in view of the above, and the present invention has been made in view of the above-mentioned problems.
z0,5~15%, 5r03~10%, ZrO21~5
%. Another object of the present invention is to provide a sealing composition that exhibits little change in lamp light color until the end of its life, no change in lamp characteristics, and excellent heat resistance and corrosion resistance.

[Example] Embodiments according to the present invention will be described below with reference to FIG.

In the figure, 1 is a monolithic type translucent alumina ceramic tube with an inner diameter of 4.0 mm and a length of 26 mm, and niobium tubes 3, 3 with an outer diameter of 2.0 mm and electrodes 2, 2 at the tips are attached to both ends of the ceramic tube 1. Place and sealant (sealing composition)
4. Seal the niobium tubes 3, 3 as described below via step 4. Note that the sealing agent is melted in a vacuum at a high temperature of 1450° C., and then cooled and solidified to complete the sealing. and,
A predetermined amount of sodium amalgam containing 25 weight percent sodium and xenon gas is sealed from one exhaust pipe of the niobium tube, and after exhausting, the end of the niobium exhaust pipe is sealed by plasma welding to produce an arc tube.

Here, an example of manufacturing the sealant will be described.

As a sealing composition, in terms of oxide, Al2O3 35-50%, CaO35-50%,
Y2O35~15%, Sr03~10%, ZrO21~
The raw material powder is mixed to a concentration of 5%, mixed and ground in a ball mill for several hours using an amide solvent, and then dried.

Note that when the raw material is carbonate, it is calcined to form an oxide.

After that, a binder such as polyvinyl alcohol is added, and the material is made into granules through repeated mixing, crushing, and drying. After this prepared material is press-molded into the desired shape, it is possible to prevent the binder from scattering and to maintain the formation of the molded product. Therefore, it is fired at around 1200℃.

Then, this fired product was placed at both ends of an arc tube for a high-pressure sodium lamp, and heated for 1,400 hours in a vacuum or in an inert atmosphere.
The sealing composition is melted by heating at a temperature around 0.degree. C., and then cooled and solidified to perform sealing.

Next, each component of the sealing composition according to the present invention and its composition ratio will be explained. A1□03 has the effect of strengthening the bond with alumina ceramics and making the coefficient of thermal expansion of the sealing member approximate that of alumina ceramics.

CaO is intended to strengthen the bond with the niobium tube, and Y2
O3, Sr○ and ZrO2 have the effect of increasing sodium resistance in a high temperature atmosphere during lamp lighting.

In addition, the composition ratio of the sealing composition of the present invention is Al□0335-50%, CaO35-50%, Y,
0.5-15%, Sr○ 3-10%, Zr0.1-5
% range.

It has good wettability with heat-resistant metals such as alumina ceramic tubes and niobium tubes, and does not cause cracks or leaks in the sealed part even during heat cycles of temperature rise and fall when the lamp is turned on and off. It can withstand high temperature sodium vapor while the lamp is lit. Particularly, as mentioned above, the effect of mixing and adding ZrO2 is recognized in sealants that require higher sodium resistance than conventional lamps, such as small-sized high-color-rendering high-pressure sodium lamps. However, no effect is observed when the composition ratio exceeds 5% by weight.

Next, an experimental example will be explained.

As shown in Figure 1, the arc tube was sealed in quartz glass with an inner diameter of 8 mm and a length of 60 mm using sealing compositions having various composition ratios as a sealant for the arc tube, and then placed in a high temperature bath at 850°C. The temperature was raised and lowered in a cycle of 7 hours on and 1 hour off, and it was measured whether the sodium in the arc tube disappeared from the arc tube through the sealant. Here, the sodium resistance test can be determined based on the fact that when sodium disappears from the arc tube, the quartz glass is attacked by sodium and becomes devitrified.

Table 1 As is clear from Table 1, samples Nα1 and 2 met the test conditions (850°C for 7000 hours) and were good, but both Nci3, 4, and 5 showed sodium leakage by 6000 hours. Occurred.

Next, both ends of the arc tube were sealed using the sealants of samples Nα1, 2 and Nα3, 4 to complete the lamp built into the outer bulb, and a cycle of 7 hours on and 1 hour off was completed. 6000
A lighting test was conducted for up to an hour.

The changes in lamp voltage and color temperature as the lighting time elapses are as shown in Figures 2 and 3, and while samples Nα1 and 2 are good, samples &3.4 have large changes and cannot be used for practical use. .

In this way, Al2O,,CaO,SrO,Y2O,,Z
By selecting the composition ratio of the five components of rO2 within an appropriate range, a sealing composition with excellent heat resistance and sodium resistance can be obtained.

[Effects of the Invention] As is clear from the above description, the sealing composition according to the present invention has a weight percentage of A1□0335-50%, Ca
O35-50%, Y2O.

By selecting a range of 5 to 15%, SrO3 to 10%, and ZrO2 1 to 5%, it has good wettability with heat-resistant metals such as alumina ceramic tubes and niobium tubes, and is resistant to temperature rise when the lamp is turned on and off. It does not cause cracks or leaks in the arc tube even during temperature-lowering heat cycles, and can withstand high-temperature sodium vapor during lamp operation. Particularly, remarkable effects are observed in lamps that require stricter sodium resistance, such as small-sized high color rendering lamps.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of an arc tube before sealing according to an embodiment of the present invention, Figure 2 is a diagram showing the relationship between lighting time and lamp voltage, and Figure 3 is a diagram showing the relationship between lighting time and color temperature. FIG. Figure 1

Claims (1)

[Claims] (1) Al_2O_35-50% in weight percent,
CaO35-50%, Y_2O_35-15%, SrO
A sealing composition characterized by comprising 3 to 10% of ZrO and 21 to 5% of ZrO.