JPS63294659A - Metal halide lamp - Google Patents

Abstract

PURPOSE:To restrain generation of an opaque phenomenon in an inner tube by preventing NaCl or sodium compound entering into the inner tube as impurity, or by restraining the entering amount to a minute level as much as possible. CONSTITUTION:An inner tube 1 formed of anhydrous quartz is sealed in an outer tube 2 formed of a quartz tube. Electrodes 3 formed by winding a coil around a core wire made of tungsten are sealed on both ends of the inner tube 1 in an opposing manner, while both ends are thermally insulated by a heat reflection board 4 made of a molybndenum thin plate. Mercury, mercury iodide, cesium iodide and dysprosium are sealed inside the inner tube 1 at a specified level and xenon gas of 200 Torr is also sealed. In this case, a luminous tube is washed well with pure water to remove attached impurities and it is arranged that NaCl or sodium compound does not enter in the material sealed as impurities. It is thus possible to prevent an opaque phenomenon in the inner tube and to restrain deterioration in luminous flux.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to extending the life of metal halide lamps.

[Conventional technology]

Metal halide lamps utilize the luminescence of metal iodides, especially rare earth elements such as Dy and Sc.

Due to the high activity of these elements, the anhydrous silica glass, which is the constituent material of the inner tube, is corroded and the inner surface of the wall becomes cloudy, resulting in a deterioration of the luminous flux.

Therefore, in order to create a lamp with a long life, the design should reduce the load on the tube wall, even at the expense of reducing efficiency or brightness, and reduce the temperature of the inner tube to suppress the chemical reaction that causes the clouding mentioned above. I needed to.

Examples of this type of metal halide lamp whose inner tube becomes cloudy during overload lighting include Japanese Patent Publication No. 57-44226 and Japanese Patent Publication No. 58-175251.

[Problem that the invention seeks to solve]

An object of the present invention is to provide a lamp in which cloudiness does not occur in the inner tube even under high-load lighting, or even if cloudiness occurs, the progress of cloudiness is slow, and deterioration of luminous flux due to cloudiness does not become a problem over the life of the lamp. Our goal is to provide the following.

[Means for solving problems]

The above purpose is to install NaCΩ inside the inner tube of the metal halide lamp.
Alternatively, this can be achieved by preventing the chlorine compound from being mixed in as an impurity or by reducing the amount of the above-mentioned compound mixed in as much as possible.

[Effect]

According to the inventors' studies, the speed of the chemical reaction that causes the luminescent inner tube to become cloudy is not only dependent on the temperature of the inner tube, but also due to impurities other than the luminescent substance sealed in the inner tube. It has been found that the reaction is significantly accelerated when trace amounts of intercalated NaCQ or other chlorides are present.

Therefore, in the present invention, the amount of N mixed in the inner tube is
By limiting the amount of a Cn or the amount of Cα ions to an extremely small amount, the progress of the clouding phenomenon is alleviated and the life of the lamp is extended.

〔Example〕

Two embodiments of the present invention will be described below with reference to FIG. 1st
The embodiment shown in the figure shows an ultraviolet and visible radiation discharge lamp, in which an inner tube 1 formed of an anhydrous quartz tube with a wall thickness of 1.7 m and an inner diameter of 4-m is connected to an outer tube 2 formed of a quartz tube via a stem 5. is enclosed within. At both ends of the inner tube 1, electrodes 3 made of a tungsten core wire with a diameter of 0.25 m and a coil wound thereon are sealed at a distance of 1011II+ from each other, and at both ends of the tube are heat reflecting plates 4 made of a thin molybdenum plate. It is kept warm by.

Inside the inner tube 1 are 1.5 μg of mercury, 0.5 mg of mercury iodide, and 0.5. of cesium iodide, 0.2 mm of dysprosium, and 200 Torr of xenon gas are sealed.

The above metal halide lamp has a current of 0.7A and an input of 50W.
When the lamps were turned on, approximately half of the lamps became cloudy and a decrease in brightness was observed several hundred hours after the lamps were turned on. Analysis of the contents of these cloudy lamps revealed that several micrograms of N
aCQ was detected, and NaCf1 was less than 1 ug in the remaining lamps that did not become cloudy. Therefore, the lamps were divided into two groups, and in one group, the arc tubes were thoroughly washed with pure water to remove any impurities before being sealed.

One group of lamps was prepared in such a way that NaCQ or chloride compounds did not enter the enclosure as impurities, and the other group contained 1 μ g t 10 J per 12 internal volumes of the arc tube.
When a group containing 1 g v 100 pg of Na CQ was tested for lighting, all of the lamps containing 100 μg of Na CQ became cloudy.

In the lamp containing 1 μg of NaCQ and in the lamp not containing NaCQ, no or very little white turbidity was observed, and in the lamp containing 10 μg of NaCQ, some white turbidity was observed.

In addition, Special Publick No. 57-44226. Japanese Patent Publication No. 58-1752
We also conducted various experiments on the metal halide lamp described in 51, and found that if a trace amount of a chlorine compound such as NaCQ was present, a clouding phenomenon appeared particularly noticeable during overload lighting. is Na
It was found that the total amount of CQ etc. affected the reaction rate.
When analyzing Na Cfl, the inner tube is washed with pure water and then finely crushed, and the amount of Na can be easily determined by measuring the amount of Na using solution emission spectrometry (ICPM). Furthermore, when analyzing Na CQ in a metal halide lamp whose inner tube is filled with NaI as a luminescent substance, it can be quantitatively determined by analyzing CQ using liquid chromatography.

According to the inventors' study, the amount of sodium chloride contained per 1 cm3 of the internal volume of one arc tube should be 10 μg or less, or the amount of chlorine should be 6 μg or less, and regardless of the size of the arc tube, the content The total amount of sodium chloride to be
g or less, or the total amount of chlorine was less than 6 μg, it was effective in suppressing the clouding.

〔Effect of the invention〕

As described above, according to the present invention, clouding of the inner tube is suppressed,
At the same time, wear of the electrodes is also suppressed, and therefore luminous flux deterioration is suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view of a metal halide lamp according to an embodiment of the present invention. 1... Inner tube, 2... Outer tube, 3... Electrode, 4...
heat reflector. 5... Stem.

Claims (1)

[Claims] 1. In metal halide lamps containing metal iodides or rare earth element iodides, the amount of sodium chloride contained per 1 cm^3 of the internal volume of the arc tube is 10 μg or less, or the amount of chlorine is 6 μg or less, and Regardless of the size of the arc tube, the total amount of sodium chloride contained must be 10μ
A metal halide lamp characterized in that the total amount of chlorine is 6 μg or less, or the total amount of chlorine is 6 μg or less.