JPH0887984A - Short arc type mixed metal vapor discharge lamp - Google Patents

Abstract

PURPOSE: To prevent corrosion of quartz glass due to an electric field of direct current and improve the starting property of a discharge lamp by fixing a triger wire connected with an external lead wire in a cathode side at a point at a prescribed gap from a bulb rising up part of a branched tube part in an anode side. CONSTITUTION: A triger wire 7 connected with an external lead wire in a cathode side is bound to a point parted from the bulb rising up end P by 3mm or more, for example 5mm, in a branched tube part 2b in an anode side. Consequently, the driving temperature of quartz glass which composes the bulb becomes sufficiently low and metal ions which pass through the quartz glass due to an electric field of direct current do not shift. As a result, corrosion of the quartz glass does not occur and leakage of metal ions is prevented and at the same time the starting property is scarcely deteriorated dependingly on the installation way of the wire 7 and almost the same starting property as that of a conventional one can be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a short arc type mixed metal vapor discharge lamp for direct current lighting.

[0002]

2. Description of the Related Art A short arc type mixed metal vapor discharge lamp capable of obtaining high brightness and high color rendering is used as a backlight of a liquid crystal projector. The discharge lamp for this purpose is generally lit by a rectangular wave AC of about 250HZ-500Hz in order to avoid light pulsation. Therefore, in order to improve the startability, these mixed metal vapor discharge lamps must be equipped with a heat-resistant metallic trigger wire stretched from one electrode lead rod to the pinch part on the valve side end of the other sealing part. Is commonly practiced.

Explaining with reference to FIG. 2, a cathode 3 and an anode 4 are arranged in a quartz glass bulb composed of a bulging portion 1 and a pair of branch pipe portions 2a and 2b, and the branch pipe portions are respectively provided. Airtightly sealed metal foils 5a and 5b are provided, and external lead wires 6a and 6b are drawn from this metal foil. In this structure, the trigger wire 7 is stretched from the cathode side lead wire 6a to the branch tube portion 5b on the anode side. In this case, as a "stop" for the wire 7, its position is the branch on the anode side. The valve rising portion P is selected in the pipe portion. Also on the cathode side, the valve rising portion Q was selected as the "stop" so that the wire 7 was not too far from the valve surface. When this discharge lamp is used for direct current lighting, as shown in FIG. 3, from the inside of the branch pipe portion near the base of the anode 4 toward the outer surface (P) of the branch pipe portion to which the trigger wire 7 is connected. , Corrosion of quartz glass presumed to be due to movement of metal cations by DC electric field 8
It was found that a phenomenon occurs, and a phenomenon occurs in which a hole is formed after about 500 hours of lighting.

[0004]

The problem to be solved by the present invention is to prevent direct current electric field from corroding the quartz glass and to provide excellent starting performance of the direct current lighting short arc type mixed metal vapor discharge lamp. To provide.

[0005]

SUMMARY OF THE INVENTION In order to solve the above problems, a DC lighting short arc type mixed metal vapor discharge lamp of the present invention has a trigger wire connected to a cathode side external lead wire and a valve rising of an anode side branch pipe portion. It is characterized in that it is fixed at a position on the branch pipe portion 3 mm or more, more preferably about 5 mm away from the portion P.

[0006]

As a result of the experiment, if one end of the trigger wire is tied to a branch pipe position which is separated from the valve rising end P of the anode side branch pipe by 3 mm or more, the operating temperature of the quartz glass becomes sufficiently low, and It was confirmed that such inconvenience did not occur. It is presumed that this is because the operating temperature of the quartz glass is sufficiently low and the movement of metal ions through the quartz glass due to the DC electric field does not occur at a position 3 mm or more away from the rising end P of the bulb on the anode side branch tube portion. It
Therefore, the quartz glass does not corrode and does not leak. Moreover, the startability similar to the conventional one can be realized with almost no deterioration in the startability due to the above-mentioned mounting method of the trigger wire.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view of a main part of a DC lighting short arc type mixed metal vapor discharge lamp of the present invention, in which a predetermined amount of mercury, a metal halide and a starting gas of argon is enclosed in a bulb. This discharge lamp is used as a backlight of a liquid crystal projector, and has an electric rating of power consumption of about 125 W, voltage of about 60 V, and current of about 2.
At 1A, the target life is about 5000 hours, which is the time when 50% of the initial light amount is maintained. In this discharge lamp, the trigger wire 7 connected to the cathode side external lead wire
At the anode side branch pipe portion 2b,
It is tied at a position more than 3 mm, for example, 5 mm apart. The trigger wire 7 is made of iron-chromium alloy.

In the above embodiment, the target life of 5000
Corrosion did not occur near the end P even after a lapse of time, and the wire 7 was slightly separated from the bulb surface near the end P, but the lighting startability was good.

[0009]

As described above, according to the present invention, it is possible to obtain a DC lighting short arc type mixed metal vapor discharge lamp which is excellent in startability and does not cause corrosion of quartz glass by a DC electric field.

[Brief description of drawings]

FIG. 1 is an explanatory view of a main part of an embodiment of a DC lighting short arc type mixed metal vapor discharge lamp of the present invention.

FIG. 2 is an explanatory view of a conventional DC lighting short arc type mixed metal vapor discharge lamp.

FIG. 3 is an explanatory diagram of corrosion in an anode side branch pipe portion.

[Explanation of symbols]

 3 Cathode 4 Anode 7 Trigger wire

Claims (1)

[Claims] 1. A short arc type mixed metal vapor discharge lamp of direct current lighting, comprising a bulb composed of a bulging portion and a pair of branch pipe portions, the heat resistant trigger wire having one end connected to a cathode side lead wire. A short arc type mixed metal vapor discharge lamp, characterized in that the other end is stretched over a position on the anode side branch pipe portion at a distance of 3 mm or more from the bulb rising portion.