JPH0479468B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a discharge lamp, particularly a discharge lamp to which a metal halide containing sodium is added.

Structure of conventional example and its problems In addition to mercury, sodium iodide, thallium iodide, indium iodide, scandium iodide,
Discharge lamps are known that have improved luminous efficiency and color rendering properties compared to ordinary high-pressure mercury lamps by adding one or more metal halides such as cesium iodide.

In such discharge lamps, if a compound such as sodium iodide, which has a relatively low vapor pressure, is present in the arc tube, (a) the arc tube wall temperature should be adjusted during lamp operation.
Maintaining the temperature at 600°C or higher to maintain discharge while the lamp is lit; (b) Maintaining the end of the arc tube at a high temperature above a certain temperature to prevent metal halides from condensing around the electrodes after the lamp is turned off. Therefore, it is necessary to satisfy conditions such as improving the restart performance of the lamp. Various methods have been used in the past to solve the problems of metal halide-added discharge lamps.

For example, it has been proposed to provide a heat-resistant metal cap, a zirconia white powder layer, a white powder layer of titania or boron nitride, a carbon black powder layer, etc. as a heat shielding film on the wall surrounding the electrode portion of the arc tube. In particular, in recent years, as a means to improve heat shielding properties, a two-layer structure has been adopted in which the first layer is a white zirconia film and the second layer is a black carbon film to further increase heat shielding properties.

However, in the above-mentioned two-layer arc tube, the adhesion between the zirconia layer and the carbon layer is not strong enough, and the carbon layer peels off due to vibrations during handling, resulting in insufficient heat shielding and heat retention effects. However, the vapor pressure of iodide could not be sufficiently increased, leading to problems such as a decrease in luminous efficiency and a decrease in color rendering properties. Additionally, there was a drawback that the restart characteristics were insufficient. Furthermore, since two layers are applied, the process is complicated, such as applying one layer → drying → baking → painting two layers → drying → baking, and it is necessary to prepare two types of suspension for coating, which costs man-hours and materials. There were also problems on the surface. Another drawback was that the film peeled off due to thermal deterioration during its life.

Purpose of the Invention The present invention is capable of sufficiently increasing the vapor pressure of a metal halide containing at least sodium in an arc tube to improve restart characteristics, color rendering properties, etc.
Further, the present invention provides a discharge lamp in which the structure of the heat shielding layer is simple and the number of man-hours and material costs can be reduced.

Structure of the Invention The present invention provides a heat shielding layer made of black titania on at least one outer surface of the tube end surrounding the electrode portion of a quartz arc tube to which a gold layer halide containing at least a sodium halide is added together with mercury. It is characterized by a discharge lamp provided.

Therefore, the above-mentioned discharge lamp uses a black titania layer, which is a dense powder with almost the same particle size as white titania and less than 1μ, and has excellent heat shielding properties, so it is not possible to use the conventional two-layer shield. It can exhibit the same heat retention effect and heat shielding performance as a thermal film. Furthermore, since only one layer of heat shielding film is required and the adhesion is strong, the conventional problem of film peeling between the first and second layers can be solved, so that
Conventional drawbacks in terms of luminous efficiency, color rendering properties, and restart characteristics can be overcome. Furthermore, the coating and baking process and material preparation can be simplified, and furthermore, since there is no need to use carbon, there are also advantages in the manufacturing cycle, such as no black stains.

Description of examples Examples of the present invention will be described below.

54 mg of mercury, 21 mg of sodium iodide, and scandium iodide in a quartz arc tube with an inner diameter of 20 mm and a distance between electrodes of 40 mm.
A discharge lamp with a rating of 400W was manufactured by filling 4.5mg of cesium iodide and 0.5mg of cesium iodide with argon.
Around the single-discharge electrode of the quartz arc tube, around the outside of the tube wall,
A suspension of black titania powder with a particle size of 0.2 microns (trade name: Titanium Black) mixed with butyl complex acid, nitrocellulose, and a small amount of low melting point glass powder was applied, dried and baked to form a heat shielding layer of about 20 microns.

As a result of checking the characteristics of the above discharge lamp by lighting it vertically in a direction with the heat shield layer facing downwards, we found that:
The luminous flux is 40,000 lumens when lit for the initial 100 hours, which is a 6% increase compared to the conventional lamp with a double-layered heat shielding film and a peeled carbon film.The color rendering properties are also good, and the restart voltage is lower than the conventional 185V. It dropped to 160V. Furthermore, even after 2,500 hours of lamp lighting time had elapsed, no peeling of the black titania heat shielding layer or deterioration of heat shielding properties was observed, and no significant adverse effects on lamp characteristics occurred.

Furthermore, even in discharge lamps in which thallium, sodium, and indium iodides are added instead of the halides sealed in the arc tube, the drawbacks of conventional lamps with heat shielding layers can be overcome and the characteristics stabilized. Ta.

In the example, the black titania layer was provided on only one end of the arc tube, but it may be provided on both ends of the arc tube if necessary. However, in the case of vertical lighting, in order to equalize the temperature at the top and bottom of the arc tube, black titanium oxide is applied only to the lower tube end, and heat shielding is applied to the upper tube end.
A material whose heat reflectivity is inferior to black titanium oxide may be provided.

Effects of the Invention As explained above, the present invention maintains the tube wall temperature sufficiently high during lighting in a discharge lamp in which a metal halide containing sodium is added to the arc tube, increases the vapor pressure of the metal halide, and regenerates the discharge lamp. Starting characteristics and color rendering properties can be improved. Furthermore, since the heat shielding layer can be made of black titania alone, the number of man-hours and material costs can be reduced.

Claims (1)

[Claims] 1. A heat shielding layer made of black titania is provided on the outer surface of at least one end of a quartz arc tube that surrounds an electrode part of a quartz arc tube to which a metal halide containing at least a sodium halide is added together with mercury. electric light.