JPS6158943B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention includes metal halides and mercury in the arc tube.
This invention relates to metal vapor discharge lamps filled with metals such as rare gases and rare earths. Arc tube materials for metal vapor discharge lamps are first of all translucent,
It must be excellent in terms of heat resistance, airtightness, and ease of processing, but it is also important that it has the property of not being corroded by the encapsulated metal. Although quartz glass has conventionally been widely used as a material that satisfies the former condition, it has become clear that the above-mentioned corrosion cannot be ignored when a metal such as sodium iodide or a rare earth is encapsulated as a luminescent material. That is, sodium iodide tends to disappear as atoms or ions through the wall of the arc tube and out of the tube during lamp operation, and rare earth metals tend to react with quartz glass to form oxides.
For this reason, metal vapor discharge lamps filled with any metal have poor operating characteristics and a short lifespan. Therefore, as an improvement on this, a method was proposed in which a high melting point oxide was coated on the inner surface of the quartz glass arc tube. However, when applying a thin film of these oxides, conventionally, fine powder of these oxides is dispersed in a solvent such as nitrocellulose and butyl acetate, applied to the inner surface of the arc tube, dried, and then the arc tube is removed. The method used was to heat the material to over 1000℃ and sinter it. Therefore, a dense film could not be obtained, and the encapsulated metal easily passed through the gaps between the relatively large crystal grains present in these films, reached the inner surface of the quartz glass, and reacted therewith. Furthermore, the thin film deposited by such a method has a disadvantage that it has poor adhesion to quartz glass and is easily peeled off. From this point of view, it has also been proposed to form the high melting point oxide thin film as a vapor deposited film by, for example, chemical vapor deposition. However, in this case as well, when the reaction temperature was raised to 1000°C or higher, relatively large crystals grew, and it was found that the diffusion of the metal through the gaps between the crystal grains could not be ignored. The present invention has been made as a result of taking these matters into consideration, and the present inventors have deposited a vapor-deposited film of a certain kind of high-melting point oxide on the inner wall of a quartz glass arc tube in an amorphous state, that is, It has been confirmed that depositing the crystal grains so that they are small enough that no sharp diffraction lines are observed in X-ray diffraction, or having no crystal structure, is very effective in solving the above problem. The details will be explained below. FIG. 1 is a block diagram of an arc tube embodying the present invention, in which main electrodes 2,
3 is sealed, and a starting electrode 4 is sealed adjacent to one main electrode 3. These electrodes are connected to an outer conductor 6 via a molybdenum foil 5 sealed to the end of the bulb 1. Further, on the inner wall surface of the bulb 1, an oxide vapor-deposited film 7 of at least one of rare earth, tantalum, zirconium, hafnium, niobium, and aluminum is deposited in an amorphous state. In such an arc tube, mercury,
Required amounts of metal iodides, rare gases, and rare earth metals are sealed. The amorphous oxide thin film useful for preventing the reaction between the encapsulated metal and the quartz glass can be formed, for example, by a chemical vapor deposition method utilizing thermal decomposition of metal alcoholates shown in Table 1.

[Table] Figure 2 shows the equipment used to realize this. In order to form a vapor deposited film on the inner surface of the arc tube using this device, first, the inside of the quartz glass tube 8 for the arc tube is removed from the cylinder 9, and the stopcock 10 is opened.
The carrier gas is replaced by a carrier gas flowing into the base glass tube 8 through the flow meter 11, and heated by the heating device 12 to a required temperature. Next, the heating device 13 is activated to increase the vapor pressure of the metal alcoholate contained in the metal alcoholate reservoir 14 to the required value. Furthermore, this steam is transferred to a stop stock 15, a carrier gas flowing into the metal alcoholate reservoir 14 via a flow meter 16, a carrier gas passing through a flow meter 11, a cylinder 17, a stop stock 18,
It is caused to flow into the base glass tube together with the reaction gas passing through the flow meter 19, and is thermally decomposed to form a vapor deposited film of an amorphous metal oxide on its inner surface. The effects of the above deposited film will be explained below with reference to Examples. Example Using the device shown in Figure 2,
A vapor-deposited film of amorphous yttrium oxide was formed on the inner surface of a 20 mm quartz glass tube. That is, the temperature of the yttrium isopropylate (Y(OC ₃ H ₇ ) ₃ ) reservoir 14 is 90°C, the temperature of the base glass tube 8 is 600°C,
Assuming that the flow rates of carrier gas (nitrogen) and reaction gas (oxygen) are 200c.c./min and 2c.c./min, respectively,
A deposited film with a thickness of about 1000 Å was obtained on the inner surface of the base glass tube. In addition, in order to investigate the crystallinity of the deposited film obtained in this way, an X-ray diffraction experiment was conducted using a diffractometer on the deposited film with a thickness of 2μ, and no sharp diffraction lines were observed, indicating that it was amorphous. ,
Furthermore, it was confirmed that this property did not change at all even if the deposited film was heated at 1200°C for 10 hours. Next, a base glass tube with a vapor-deposited film of about 1000 Å thick formed on the inside is processed into an arc tube, and mercury, thallium iodide, mercury iodide, and disprosium metals are sealed inside the tube to produce a 400W metal halide lamp. was created and the luminous flux maintenance rate was investigated. FIG. 3 shows lumen maintenance curves for a lamp according to the present invention and a conventional lamp. In this figure, a shows the luminous flux maintenance factor curve of the lamp according to the present invention, and b shows a vapor-deposited film of the same thickness on the inner surface of the arc tube, but YCl ₃ is used as the reactant.
Therefore, since the reaction temperature was set to 1200℃, the luminous flux maintenance curve of the lamp in which this film is crystalline,
Furthermore, c shows the luminous flux maintenance curve of a lamp without a deposited film. As is clear from this figure, it can be seen that the working characteristics of the lamp according to the present invention are significantly improved compared to the conventional lamp. Although the effects of the amorphous yttrium oxide vapor deposited film have been described above, similar effects were also observed in the vapor deposited films of amorphous oxides of other rare earths, zirconium, hafnium, tantalum, niobium, and aluminum. In addition, in the above-mentioned lamps in which sodium iodide is added to increase the stability of the arc,
It was confirmed that the amorphous oxide vapor deposited film according to the present invention exerts similar effects. From the detailed description above, it is clear that the amorphous oxide thin film according to the present invention prevents corrosion of the quartz glass arc tube by the enclosed metal, particularly rare earth metal, and improves the working characteristics.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an arc tube of a metal vapor discharge lamp according to the present invention, and FIG. 2 is a diagram showing an apparatus for forming an amorphous oxide thin film according to the present invention by chemical vapor deposition. FIG. 3 is a lumen maintenance factor curve diagram of a lamp according to the present invention and a conventional lamp.

Claims (1)

[Claims] 1 Containing rare earth metals and halogens in the arc tube,
Alternatively, these are further filled with a filler containing sodium halide, and at least one of rare earth, zirconium, hafnium, tantalum, niobium, and aluminum oxides is deposited in the form of an amorphous vapor deposited film on the inner surface of the arc tube. A metal vapor discharge lamp characterized by: