JPS62128945A - Sealing composition - Google Patents

Abstract

PURPOSE:To obtain the titled sealing composition having excellent resistance to halogen and high airtightness and softening point and capable of obtaining a good seal by incorporating La2O3, Dy2O3, Y2O3, Al2O3, BeO, and B2O3 in a specified ratio to prepare the composition. CONSTITUTION:The composition contg., by weight, 10-90% La2O3, 20-85% Dy2O3, 2-60% Y2O3, 5-60% Al2O3, 5-45% BeO, and 3-35% B2O3 is prepared. The composition is used for bonding a ceramic and a ceramic or a ceramic and a metal. Consequently, the sealing composition having excellent wettability, contg. no bubbles, and capable of uniformly sealing with high adhesive strength is obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a sealing material for translucent alumina ceramic tubes, and particularly to a sealing material used in metal halide lamps using alumina ceramic tubes that are lit at high temperatures. This invention relates to improvements in wearing compositions.

[Prior art and its problems Fused silica is used as the material for the arc tube of cometal halide lamps. In arc tubes using this material, the maximum allowable temperature during lighting is approximately 900°C, so Dy I
,,Cs 1. Even if it is attempted to achieve high efficiency and high color rendering properties by making low vapor pressure substances such as TI I and S c2I emit light, sufficient vapor pressure cannot be obtained at this maximum allowable temperature.

For this purpose, a translucent alumina ceramic tube, which is used as an arc tube material for high-pressure sodium lamps, is used as a chemically and thermally stable material compared to metal halide lamps, which have an even longer operating time and maximum allowable temperature. There is. The maximum allowable temperature of this translucent alumina ceramic tube is about 1200° C., and it is highly chemically stable to many halides. Both ends of this translucent alumina ceramic tube are sealed using a cermet disk and a sealing material.

As this sealing material, La, ○, -B201-p2o.

-Al□O, -MgO frit, Dy20. -A
1□0. - S i O2-based frit, M n O-A
1.

0, -8i○2 series frit, B e O-A 1□0.
-S jO2-Mgo-B, 03 series Fritz 1~, Be0
-A 1□03-B2O, -P2O, -S iO2-based frit, BeO-B, 0. -Al□○, -5in, frits, etc. are known.

However, these sealants soften and cause the cermet disk to lift when the tube wall load increases to the operating temperature required to light the arc tube with high efficiency and high color rendering. There were many things that led to leaks.

Further, among these sealing phase components, those containing alkaline earth metal oxides in particular react with metal halides added to the arc tube to become alkaline earth metal halides, which are released into the discharge space and emit light. Therefore, the added metal halide becomes an oxide, and the supply of the added metal halide into the discharge space decreases, causing the efficiency and color rendering properties to deviate significantly from the initial design values.

Furthermore, the luminous flux maintenance rate of a metal halide lamp using the above-mentioned sealing material and an alumina ceramic tube is extremely poor, and the wall of the arc tube is severely darkened. This tube wall blackening occurs because tungsten, the electrode material, adheres to the tube wall.
It has been pointed out that silicon (Si) is involved in the scattering of tungsten. Therefore, by using a frit that does not contain SiO, a ceramic metal halide lamp with a good luminous flux maintenance rate can be obtained. In other words, it is necessary that the sealing material does not contain SiO2 in order to achieve good life characteristics.

[Object of the Invention] The present invention has been made in view of the above points, and does not use SiO2 as a sealing composition.

By selecting an appropriate sealing oxide, the disadvantages of conventional sealing materials have been eliminated or reduced.It has high halogen resistance and a high softening point, has good wetting properties, and does not contain air bubbles. The object of the present invention is to provide a sealing material that not only enables uniform sealing with high adhesive strength but also improves lamp life characteristics.

[Structure and operation of the invention A sealing material for a metal halide lamp using a core alumina ceramic tube must satisfy the following conditions.

First, a strong seal that maintains airtightness and high mechanical strength can be obtained even when the lamp is on, and the sealing composition must be a low vapor pressure substance to reduce the amount of impurities entering the discharge space. It is. In addition, it has good wetting properties for alumina ceramic tubes and cermet disks made of alumina-tungsten, and is
It is necessary that the linear thermal expansion coefficients of the alumina ceramic tube, cermet disk, and sealing material are almost the same, and that there is no reaction between additives in the arc tube such as metal halides and the sealing material during lighting. be.

Furthermore, in order to improve the luminous flux maintenance factor of the ceramic metal halide, it is necessary that the sealing phase component does not contain SiO2. This is because the added halide and the sealing material react to generate SiO, which decomposes further and becomes S.
This Si becomes iodide and is released into the discharge space, deposited on the electrode, and a low melting point alloy of tungsten and silicon is formed, which scatters during lamp lighting. This scattered tungsten adheres to the inner surface of the arc tube, turning the arc tube black and reducing the luminous flux.

As a result of conducting experiments to satisfy the above conditions, L a
7.03D Y2O, -Y2O, -Al□○, -BeO
It was found that the -B, O, type sealing material exhibited good sealing properties. In particular, the addition of -BeO improves the wetting properties for the alumina ceramic tube, so that the sealing material is uniformly inserted between the alumina ceramic tube and the cermet disk.

Furthermore, the presence of many crystal phases in the sealing material contributes to chemical stability.

Furthermore, La20zD'jz○3-Y, O,
-A1.0. The composition range of the -BeO-B203 sealing material is as follows. .

L a20. : 10-90% by weight DyzOs: 2o-85% by weight Y2O, = 2-60% by weight A1□○, : 5-60% by weight BaO: 5-45% by weight B20. : 3 to 35% by weight Here, if the amount of La2O3 and Dy2O3 is 90% to 85% by weight or more, the coefficient of thermal expansion becomes small and cracks are likely to occur in the alumina ceramic tube at the sealed portion. On the other hand, if the content is less than 10% by weight or less than 20% by weight, the melting point will be 1600° C. or higher, which poses a practical problem. Y2O3
When the amount of is less than 2% by weight or more than 60% by weight,
Similar to the above, the melting point is 1600'C or higher, which poses a practical problem. If the amount of A1□o3 is 60% by weight or more, the melting point will be too high, and if it is less than 5% by weight, the melting point will be too low to 900° C. or less, which is a practical problem. When the amount of BaO is 45% by weight or more.

The coefficient of thermal expansion becomes larger than A1□O1, and a crank occurs in the sealed portion. On the other hand, if it is less than 5% by weight, the airtightness will be lowered due to the lowered wetting properties. When the amount of B2O3 is 35% by weight or more, the coefficient of thermal expansion increases,
Cracks are likely to occur in the sealed area. On the other hand, if it is less than 3% by weight, the melting point will be 1600° C. or higher, which poses a practical problem.

Therefore, when the above oxide components are appropriately blended within the composition range specified in ``2'', halogen resistance is excellent and the linear thermal expansion coefficients of the alumina ceramic tube and the cermet disk suitably match, resulting in high airtightness.

In addition, good sealing with a high softening point can be obtained.

[Example〕 Next, embodiments according to the present invention will be described.

After mechanically mixing the respective oxide components having the composition shown in Table 1, the mixture is mixed with an organic binder, formed into a suitably sized washer or small disk, and fired.

This molded sealing material is placed between the end of the alumina ceramic tube and the sealed portion of the end disk, and the sealed portion is heated to 1400°C to 1500°C in vacuum or rare gas to melt the sealing material. Seal the outer part.

In each of the examples in Table 1, there are some differences in the vitrification reaction temperature, viscosity when melted, etc. of the sealing materials, but all the sealing materials have good airtightness and do not pose any practical problems. The sealing state was shown. Using a sealing material having the composition shown in Table 1, an alumina ceramic tube and a cermet disk were sealed to create an arc tube. In addition, Dye: 4.0■, T I I is inside the arc tube.
:0.7mg, Dy:0.7■, LiI:1.0■
, Hg: 8.0■ is enclosed, 150W゛
Although the lamp was lit for a long time with a tube input of And the luminous flux maintenance rate of the lamp after being lit for s, ooo hours is 85
%, and the luminous flux maintenance rate after 5,000 hours of lighting was significantly improved to 60% compared to the conventional lamp using a sealing material containing SiO2.

[Effects of the Invention] As is clear from the above description, the sealing composition according to the present invention has high halogen resistance, a high softening point, good 1M resistance, and high adhesive strength without bubbles. Uniform sealing is possible.

Furthermore, since the oxide composition does not contain SiO,
A low melting point alloy of tungsten and silica is not formed, and electrode deterioration is eliminated, so that the luminous flux maintenance factor can be improved.

Claims (1)

[Claims] 10-90% La_2O_3, 20-85% by weight
Dy_2O_3, 2-60% Y_2O_3, 5-6
0% Al_2O_3, 5-45% BeO, and 3-
A sealing composition for sealing ceramic and ceramic or ceramic and metal, containing 35% B_2O_3.