JPH03176959A - Metal halide lamp - Google Patents

Abstract

PURPOSE:To prevent the extinction of Na by providing a power feed line formed with a ultraviolet ray absorbing film on the surface along the side of a light emitting tube having a pair of main electrodes and containing a metal halogenide such as Hg, rare gas and Na in it. CONSTITUTION:A pair of electrodes are provided and a metal halogenide of NaI, TlI, TmI3, HoI3, DyI3 is sealed in addition to Ar and Hg as the starting gas in a light emitting tube 1 made of quartz glass. A film 4 made of ZnO and having the ultraviolet ray absorbing characteristic is coated on the surface of a power feed lead wire 3 arranged along the side of the light emitting tube 1. Ultraviolet rays from the light emitting tube 1 are absorbed by the film 4, the generation of photoelectrons is prevented, and the extinction of Na is prevented.

Description

[Detailed description of the invention] Industrial applications The present invention relates to metal halide lamps.

Conventional technology Metal halide lamps are characterized by high efficiency and high color rendering properties due to the light emitted from the metal sealed inside the arc tube, and are attracting attention as lamps that can replace the mercury lamps that have been widely used in the past. In recent years, as lighting devices have become lower in wattage and more compact, they are increasingly being used for indoor lighting such as store lighting.

Generally, in a metal halide lamp, if there is a metal part to which a voltage is applied, such as a power supply lead, near the arc tube, photoelectrons are emitted from the metal due to ultraviolet rays from the arc tube.
These photoelectrons reach the outer wall of the arc tube and have a negative potential, so
It is well known that sodium ions inside the arc tube pass through quartz and disappear outside the arc tube.

When the sodium in the arc tube disappears, phenomena such as an increase in lamp voltage and a change in light color occur.

In order to prevent such loss of sodium, conventional metal halide lamps employ a structure in which the power supply conductor is covered with an insulating insulator tube or is distanced from the arc tube.

Problems to be Solved by the Invention However, with a compact straight-tube lamp, it is difficult to maintain a large distance between the power supply conductor and the luminous tube, and when an insulating insulator tube is used, There was a problem that inappropriate shadows were created.

The present invention was made to solve these problems, and provides a compact metal halide lamp that prevents sodium loss.

Means for Solving the Problems The metal halide lamp of the present invention includes an arc tube having a pair of main electrodes and encapsulating a plurality of metal halides including mercury, dilute scum, and sodium halide;
A power supply conductor is provided along the side of the arc tube and has a surface coated with a coating having ultraviolet absorption properties.

The ultraviolet light from the working arc tube is absorbed by a coating on the power supply conductor that has ultraviolet absorption properties and prevents the generation of photoelectrons. Therefore, the sodium sealed in the arc tube can be prevented from disappearing. Furthermore, since no insulating insulator tube is used, unnecessary shadows will not be produced even when used in a spotlight or the like.

Embodiment FIG. 1 shows a 70W metal halide lamp according to an embodiment of the present invention. In the figure, an arc tube 1 made of quartz glass with an inner diameter of 9 mm has a pair of electrodes (not shown) inside it.
In addition to 200 torr of argon and 13 mg of mercury as starting gases, 1.1 mg of NaI, 0.
3mg, Tm130.7mg, No 130, 7m
g, D y I 30 , 7 mg of metal halide is encapsulated. This arc tube is provided inside the outer tube 2. A coating 4 made of zinc oxide and having ultraviolet absorption properties is coated on the surface of a power supply conductor 3 disposed along the side of the arc tube 1 .

In FIG. 1, 5 indicates a getter, and 6 indicates a cap.

With the above structure, the metal halide lamp according to the embodiment of the present invention absorbs the ultraviolet rays from the arc tube 1 by the coating 4 having ultraviolet absorbing properties formed on the surface of the power supply conductor 3, and generates photoelectrons. Therefore, the sodium sealed in the arc tube 1 does not disappear, and an increase in lamp voltage and a change in light color can be prevented. Furthermore, since no insulating insulator tube is used, unnecessary shadows will not be produced even when used in a spotlight or the like.

In a life test of this lamp, the luminous flux maintenance rate after 6000 hours of lighting was 80%, and the lamp voltage increase was 6V, showing good characteristics, and no sodium loss occurred from the arc tube.

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, the arc tube has a pair of main electrodes and a plurality of metal halides including mercury, a rare gas, and a sodium halide are sealed therein. By forming a coating having ultraviolet absorbing properties on the power supply conductor arranged in the same direction, it is possible to provide a compact metal halide lamp that prevents sodium loss.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway front view of a metal halide lamp which is an embodiment of the present invention. 1... Arc tube, 2... Outer tube, 3...
...Power supply ring line, 4...Coating, 5...
...Getter, 6...Case.

Claims (1)

[Claims] An arc tube has a pair of main electrodes and is filled with a plurality of metal halides including mercury, rare gas, and sodium halide. 1. A metal halide lamp, comprising: a power supply conductor having a coating formed thereon.