JPH08124530A - Short arc type mixed metal vapor electric discharge lamp - Google Patents

Abstract

PURPOSE: To provide a short arc type mixed metal vapor electric discharge lamp for DC lighting, capable of preventing quartz glass from being perforated due to corrosion resulting from exposure to DC electric field, restraining the occurrence of bulb cloudiness near a negative electrode and giving high startability. CONSTITUTION: A negative electrode 3 and a positive electrode 4 are arranged in a quartz glass bulb formed out of a bulge section 1 and a pair of branch tube sections 2a and 2b. In addition, the branch tube sections 2a and 2b are respectively provided with airtightly sealed metallic foils 5a and 5b, and external lead wires 6a and 6b are led out from the foils 5a and 5b. Also, a trigger wire 7 is extended from the positive electrode side lead wire 6b to the negative electrode side branch tube 2a. According to this construction, startability is improved and the corrosion of quartz glass due to DC electric field is prevented.

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 application is generally lit with a rectangular wave alternating current of about 250 Hz to 500 Hz in order to avoid light pulsation. Therefore, in order to improve the startability, these mixed metal vapor discharge lamps may be provided with a heat-resistant metal trigger wire stretched from one electrode lead rod to the bulb side end of the other sealing portion. It is generally done. It has also been proposed to illuminate such a lamp with direct current.

Explaining with reference to FIG. 1, a cathode 3 and an anode 4 are arranged in a quartz glass bulb composed of a bulge portion 1 and a pair of branch pipe portions 2a and 2b. 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 anode-side branch pipe portion 2b. In this case, the position of the trigger wire 7 serves as a "stop" for the wire 7, and the position of the trigger wire 7 is The valve rising portion P is selected in the pipe portion. When this discharge lamp is used for direct current lighting in a state where the arc axis is horizontal, as shown in FIG. 3, the branch pipe in which the trigger wire 7 is tied from the inside of the branch pipe portion near the base of the anode 4 is connected. It was found that the corrosion 12 of the silica glass, which is presumed to be due to the movement of metal cations due to the direct current electric field, occurred toward the outer surface of the part, and a phenomenon occurred in which a hole was formed in about 500 hours of lighting. In addition, although white turbidity is suppressed during direct current lighting, white turbidity still occurs on the bulb wall near the cathode with the lighting time.

[0004]

The problem to be solved by the present invention is that there is no perforation due to the corrosion of quartz glass due to the DC electric field as described above, and the occurrence of clouding of the valve in the vicinity of the cathode is suppressed. Another object of the present invention is to provide a short arc type mixed metal vapor discharge lamp for direct current lighting, which has excellent properties.

[0005]

In order to solve the above problems, the short arc type mixed metal vapor discharge lamp for direct current lighting of the present invention has an external lead rod 6b connected to an anode 4 as shown in FIG. It is characterized in that the connected trigger wire 7 is fixed to a predetermined portion Q of the cathode side branch tube portion 2a.

[0006]

As a result of the experiment, it was confirmed that the above inconvenience would not occur if one end of the trigger wire 7 was tied to the cathode side branch tube portion 2a. This is because the electrode shaft of the anode 4 has a high temperature even at the root portion R during lighting of the discharge lamp, while the root portion S of the cathode shaft has a relatively low temperature, so the temperature of the quartz glass at that portion becomes sufficiently low. It is presumed that the movement of metal cations through the quartz glass due to the DC electric field does not occur. Therefore, the quartz glass does not corrode and does not leak. If the fixed position is the branch tube portion 2a on the cathode side, and the predetermined portion Q is within a range of 0 to 10 mm from the rising end of the bulging portion 1, there is no significant difference in startability regardless of where it is fixed. There wasn't.

Further, the trigger wire 7 connected to the external lead rod 6b on the anode side is laid on the outer surface of the upper part of the bulb at the position surrounding the cathode on the cathode side, thereby suppressing the ions of the luminescent metal from approaching the inner wall of the bulb. It is also expected to have the effect of suppressing clouding at the upper part of the bulb at the position surrounding the cathode.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 3 is an explanatory view of the first embodiment of the present invention.
In FIG. 3, mercury and a metal halide such as a rare earth halide and a predetermined amount of argon as a starting gas are enclosed in the bulb. 3 is a cathode and 4 is an anode. 7 is a trigger wire, which is an external lead rod 6b of the anode 4.
(Or, a metal cap connected to the lead rod 6b) is stretched over the branch tube portion 2a on the cathode side and tied to a predetermined position. For this trigger wire 7, for example, an iron-chromium alloy having excellent heat resistance is used.

FIG. 4 is an explanatory view of the second embodiment of the present invention. In a direct current discharge lamp in which a rare earth halide or an alkali metal halide is enclosed and the arc is lit horizontally, a branch line 8 is formed at a bulb portion located above the cathode tip in a direction perpendicular to the arc axis and supported by it. By electrically connecting the metal ring 9 and the trigger wire, positive ions can be prevented from approaching the inner wall of the valve, and can also serve as a means for suppressing white turbidity and suppressing the escape of alkali metal due to diffusion through quartz glass. . Incidentally, 10 is a fixing ring portion.

FIG. 5 is an explanatory view of the third embodiment of the present invention. In this embodiment, instead of the metal ring 9, a metal piece forming the forks 11a and 11b is used. The same operational effect as the second embodiment is obtained.

[0011]

As described above, according to the present invention, the startability is excellent, the quartz glass is not corroded by a direct current electric field, and the white turbidity of the bulb portion on the cathode side and the escape of alkali metal are suppressed. A short arc type mixed metal vapor discharge lamp for lighting can be provided.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a conventional discharge lamp.

FIG. 2 is an explanatory diagram of corrosion of quartz glass due to a DC electric field generated in a conventional discharge lamp.

FIG. 3 is an explanatory diagram of an embodiment of a discharge lamp according to the present invention.

FIG. 4 is an explanatory diagram of a second embodiment of the discharge lamp according to the present invention.

FIG. 5 is an explanatory diagram of a main part of a third embodiment of the discharge lamp according to the present invention.

[Explanation of symbols]

 1 Bulging part 2a, 2b Branch pipe part 3 Cathode 4 Anode 5a, 5b Metal foil 6a, 6b External lead rod 7 Trigger wire 8 Branch wire 9 Metal ring 10 Fixing ring part

Claims (2)

[Claims] 1. A short arc type mixed metal vapor discharge lamp for direct current lighting, wherein a heat-resistant trigger wire having one end connected to an anode side lead wire or an anode side base is stretched over the other end to a cathode side sealing portion. A short arc type mixed metal vapor discharge lamp characterized by the above. 2. The metal piece in which the heat-resistant trigger wire is arranged so as to surround at least a part around the cathode on the outside of the arc tube, or to be arranged so as to surround at least a part around the cathode. The short arc type mixed metal vapor discharge lamp according to claim 1, wherein the short arc type mixed metal vapor discharge lamp is connected.