JPS5832887B2 - Manufacturing method of luminous tube body for metal vapor discharge lamp - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an arc tube body for a metal vapor discharge lamp such as a metal halide lamp or a high-pressure sodium lamp.

In recent years, metal vapor discharge lamps have attracted attention because of their high lamp efficiency and energy savings.

In particular, high-pressure sodium lamps have high lamp efficiency, and their luminous tubes are made of a tube-shaped translucent alumina porcelain with caps made of alumina porcelain at both ends that are equipped with discharge electrode insertion holes that also serve as introduction paths for the encapsulated luminescent material. It is known that the lamp is sealed using a frit, but because the area covered by the glass seal is large, if a lamp using this arc tube is flashed repeatedly, it may cause sudden thermal shock and contact with high-temperature sodium gas. This caused the seal glass to corrode, crack, etc., destroying the airtight seal, causing the gas sealed inside the arc tube to leak, increasing the probability that the lamp would not be able to be lit, and shortening the life of the lamp. .

In addition, in order to eliminate the drawbacks caused by the glass seal described above, we have fitted a tube-shaped alumina porcelain molded product with an alumina porcelain cap molded product whose firing shrinkage rate is smaller than that of the tube-shaped molded product, and integrated the molded alumina porcelain product with the fired alumina porcelain molded product. Porcelain luminous tube bodies are also known, but in order to change the firing shrinkage rate of the tube and cap, it is not only necessary to change the composition of the alumina porcelain or the molding pressure, but also , firing shrinkage progresses most at 1400 to 1600°C, and both the tube and the cap become brittle at this temperature, so tubes with a large firing shrinkage rate will be in a state where the cap is shrink-fitted, causing cracks in the tube. In addition, even if no cracks occur, due to residual stress, cracks may occur during use of the discharge lamp, and the encapsulated luminescent material may leak. Therefore, the alumina porcelain composition, molding conditions, and firing conditions are It required strict control and was expensive.

The present invention was made in order to eliminate the above-mentioned drawbacks, and is a method for manufacturing a translucent ceramic tube used as an arc tube of a metal vapor discharge lamp. This is a method of manufacturing a luminous tube body for a metal vapor discharge lamp, which involves forming a material into a tube-like material, fitting a cap made of an alumina base material with a water content of 5% by weight or less to both ends of the material, then drying and firing it. .

The details of the present invention will be explained along the manufacturing process.

Fine alumina powder, which becomes translucent alumina porcelain through final firing, is mixed with a sintering aid, a hydrophilic organic substance that decomposes or volatizes during preliminary firing, and water, with a moisture content of 15 to 3.
A base material for forming a tube having a moisture content of 0% by weight and a base material for forming a cap having a moisture content of 5% by weight or less are prepared.

It is desirable that the molding base material for the tube and cap be the same except for moisture so that the tube and cap can fit together after molding and be integrated during the firing process, but the cap does not necessarily need to be translucent; Since sealing with the discharge electrode and mechanical strength are required, an alumina base material containing silica that has firing shrinkage and thermal expansion coefficient similar to that of the tube may be used.

The moisture range is the most important condition for the present invention, and the reason why the moisture content of the molded material for the tube is set to 15 to 30% by weight is that if the moisture content is in a range other than this range, it will not fit well with the cap molded body described later. This is because it interferes with the

In other words, if the moisture content of the base material is less than 15% by weight, the amount of drying shrinkage of the tube will be small and it will not fit perfectly with the cap, and if the moisture content of the base material is more than 30% by weight, the plasticity of the base material will be large and it will be difficult to form it into a tube shape. However, when fitting the cap, it not only becomes difficult to work, but also
This is because moisture locally penetrates into the cap from the tube, making it impossible to create a uniform, integrally fitted product.

In addition, the reason why the moisture content of the base material for the cap is 5% by weight or less is that when the moisture content of the base material is 5% by weight or more, the amount of drying shrinkage is large, so the shrinkage during drying coincides with the shrinkage of the tube. If drying shrinkage occurs after a delay, complete bonding becomes difficult and due to the shape of the cap, powder pressing is suitable for forming the cap.If the moisture content is 5% by weight or more, the mold of the press machine will This is because the desired product cannot be obtained due to the powder adhering to the surface.

Next, using a base material with a moisture content of 15 to 30% by weight, it is formed into a tubular material using an extrusion molding machine or a wet press machine, while using a base material with a moisture content of 5% by weight or less, a press machine or a pressed material is formed. By mechanical finishing method etc.
Two caps are molded for each tube-shaped material.

Next, caps are fitted into the openings at both ends of the tubular material, and then dried to integrate the tube and the cap.

It is desirable that this fitting be carried out immediately after the tubular material and the cap are molded, otherwise the moisture content of the two will change and it will be difficult to uniformly integrate them.

No special method is required for drying, and normal hot air drying, vacuum drying, etc. used in the ceramic industry may be used, but it is desirable to avoid rapid drying and to dry uniformly and gradually.

During this drying process, the tube shape with a large amount of moisture evaporates will shrink significantly, and the cap shape with a low moisture content will shrink less, so the interface between the two will be sufficiently compatible and an integral bond will be achieved.

After drying, the integral molded body is preliminarily calcined in air in order to decompose or volatilize and remove organic matter in the molded body.

The firing temperature can be determined depending on the type of organic material, but it is preferably 1100°C or lower so that the activity of the powder in the molded body does not deteriorate, and it is better to raise the temperature slowly if the base material for forming the tube and the base material for forming the cap are different. .

After pre-baking, 170℃ in reducing atmosphere or vacuum atmosphere.
By heating to 0 to 1950[deg.] C. and proceeding with sintering, an arc tube body for a metal vapor discharge lamp in which a translucent tube and a cap are integrated can be obtained.

Example 1 Finely powdered alumina with a purity of 99.99% and a particle size of 0.1 to 0.2 microns is used as a raw material, and magnesium oxide 0.0
5 wt. 10 types (1, 3, 5, 7, 10° 15.20, 25, 30, 3
5% by weight) was prepared using a kneader.

A cap of the shape shown in FIG. 1a was molded using a powder press at a pressure of 1.5 t/- from a mixture of four types of mixtures having a water content of 1 to 7% by weight.

Further, six types of formulations containing 10 to 35% by weight of water were used to form tubes in the shape shown in Figure 1 using a vacuum kneading machine.

Immediately after molding these four types of caps and six types of tubes, caps were fitted to both ends of the tubes, and then they were placed in a hot air dryer at 80° C. and dried day and night.

Next, it was placed in an electric furnace and heated at 800°C for 3 hours to completely remove organic matter, then placed in a hydrogen atmosphere furnace and heated at 1800°C for 3 hours.
A translucent alumina tube was produced by baking for a period of time.

The cap-fitting portions at both ends of the 24 types of translucent alumina arc tubes obtained in this way were subjected to visual inspection and IJ-test using a helium leak tester, and the results were as shown in Figure 2. The relationship between the water weight % of the alumina base material for tubes, the water weight % of the alumina base material for caps, and the pass rate (maximum) was obtained.

From this relationship, it can be seen that caps obtained with moisture content of 1, 3, and 5% by weight of the base material for forming caps, which is within the scope of the present invention, and 15% by weight.
, 20, 25, and 30% by weight of water content in the product group, there were no cracks in the fitting part, and even in the airtightness test using a helium leak detector, the result was 100-1 Oat-cc. /sec
The following airtightness was confirmed, and the pass rate was 90.
% or more.

On the other hand, cap molding bases with a moisture content of more than 5% by weight and tube molding bases with a moisture content of less than 15% by weight or over 30% by weight, which are outside the scope of the present invention, have cracks in appearance. However, many products failed the airtightness test, and the pass rate was low.

Example 2 In the same manner as in Example 1, a tube as shown in Figure 1 was produced by extrusion molding using a mixed and prepared base material with a water content of 25% by weight.

On the other hand, using the same fine powder alumina, it has a purity of 99.9.
% of fine powder and silicon oxide powder are added, and the weight ratio is 624
A mixed powder was prepared, and 3% by weight of vinyl acetate and 3% by weight of water were added thereto and thoroughly mixed in a kneader.The cap shown in FIG. 1a was press-molded using a powder press using this mixture.

The tube and this cap were fitted together and dried in a hot air dryer for a day and night, then heated in an electric furnace at 800° C. for 3 hours to remove organic substances, and then placed in a hydrogen atmosphere furnace while flowing ammonia decomposition gas. It was fired at 1700°C for 6 hours to obtain a translucent alumina tube.

The obtained alumina tube had a good fitting condition with the caps at both ends, and an airtightness test using a helium leak detector showed that it was 10-10 atm -CC/SecC/S
The cap part has a mullite composition, and its thermal expansion coefficient is 5 x 10-6/'C, which is similar to the electrode material molybdenum tungsten, making it suitable for electrode seals. This was confirmed.

As described above, according to the method of manufacturing an arc tube body for a metal vapor discharge lamp of the present invention, the tube of the light emitting part and the cap to which the discharge lamp electrode is attached are integrally molded by only adjusting the moisture content, and the molding composition and This luminous tube body for metal vapor discharge lamps is not only inexpensive as it does not require any special firing conditions, but also has an airtight tube and cap that are highly resistant to thermal shock during lamp lighting and corrosion resistance against the enclosed luminescent material. Therefore, the present invention contributes to the development of industry.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the shapes of the a-cap and b-tube created in Examples 1 and 2 of the present invention, and FIG. 2 shows the moisture content of the alumina base material for tubes in Example 1 of the present invention
It is a graph showing the relationship between the water content of the alumina base material for the cap and the acceptance rate of the luminous tube body which is an integrally sintered product combining them.

Claims (1)

[Claims] 1. A method for manufacturing a translucent ceramic tube used as an arc tube of a metal vapor discharge lamp, wherein the water content is 15 to 30% by weight.
An alumina base material having a water content of 5% by weight or less is formed into a tube-shaped material, caps made of an alumina base material with a moisture content of 5% by weight or less are fitted to both ends of the tube-like material, and then dried.
A method for manufacturing a luminous tube body for a metal vapor discharge lamp, which is characterized by firing. 2. The method for manufacturing an arc tube body for a metal vapor discharge lamp according to claim 1, wherein the tubular material and the alumina base material of the cap material are the same. 3. The luminous tube body for a metal vapor discharge lamp according to claim 1, characterized in that an alumina base material having light transmitting properties after firing is used as the tube material, and an alumina base material containing silica is used as the cap material. manufacturing method.