JPH043388Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a gas-filled discharge tube filled with a rare gas, such as a xenon lamp, and particularly relates to improvements in the electrodes of the discharge tube.

(Prior art) A gas-filled discharge tube, for example, as shown in a schematic cross-sectional view in FIG. When a DC voltage 4 is applied between both electrodes 1, electrons are emitted from the cathode side and collide with the rare gas 3 sealed inside, causing an electric discharge and forming the rare gas 3. They emit light in different colors and are used for various purposes such as illumination and measurement light sources.

Electrode 1 used in such a gas-filled discharge tube
As shown in Figure 2, tungsten rods and molybdenum rods with sharp tips are generally used, but these materials have a high work function, so electrons are difficult to emit unless the temperature reaches 2000℃ or higher. During discharge, it is constantly exposed to high temperatures of around 2200°C due to sparks at the start of discharge and electron reverse shock during discharge. As a result, as shown in FIG. 3, which is an enlarged cross-sectional view of the tip of the electrode 1, the sharp tip of the electrode 1 becomes damaged and rounded, making it increasingly difficult for electrons to be emitted, making it impossible to sustain stable discharge.

In order to eliminate the above-mentioned drawbacks, as shown in FIG. 4, which is an enlarged sectional view of the tip of the electrode 1, an electron radioactive substance is added to the tip of the tungsten rod 6 in the gap between the porous body of the high-melting point metal powder. It has been considered that an impregnated electrode is brazed with, for example, molybdenum wax material, and the tip thereof is made sharp.

In this structure, a metal with a low work function such as barium is impregnated as an electron radioactive substance, so
Electron radiation can be easily obtained at temperatures around ℃, and since these electron-radioactive substances are located in the gaps between high-melting point metal powders, they are protected from reverse impact of electrons, and there is no need to raise the temperature too high. Therefore, there is almost no damage to the high melting point metal powder itself. However, since electron emission is relatively easy, electron emission is likely to occur not only from the tip 51 but also from corners such as the tapered corner 52 and the brazed part 53 with the tungsten rod 6, preventing discharge. Easily stable.

(Problems to be solved by the invention) As mentioned above, the electrodes of conventional discharge tubes do not work unless the temperature is high, and the electrode tips are easily worn out. However, the disadvantage is that stable discharge cannot be obtained.

(Means for solving the problem) The present invention was devised in view of the above-mentioned drawbacks, and uses a porous high melting point metal body impregnated with an electron radioactive substance at least at the tip of the electrode on the electron emission side. , the tip is made sharp, and the sharpened tip reduces the work function and facilitates electron emission.
The purpose is to deposit a metal coating of one of Ir, Ru, Re, and Os.

(Function) The discharge tube according to the present invention uses an impregnated electrode in which a porous high-melting point metal body is impregnated with an electron radioactive substance, so electron emission can be obtained at a very low temperature, and furthermore, only the tip part Since a metal coating is applied to the electrode to facilitate electron emission, it is easy to emit electrons only from the tip, and it is difficult to emit electrons from other parts, so that a stable discharge can be obtained.

(Example) FIG. 1a is a cross-sectional view of a discharge tube that is an example of the present invention, and FIG. 1b is an enlarged cross-sectional view of the tip of the electrode 7 on the side that emits electrons. In this embodiment, the electron emitting side electrode 7 is of an impregnated type in which the tip of a high melting point metal rod 71 is impregnated with an electron radioactive substance in the gap between the porous high melting point metal powder sintered body and the tip of the high melting point metal rod 71 as in the conventional example shown in FIG. The electrode 72 was fixed with a brazing material, the tip of the impregnated electrode 72 was sharpened, and a metal coating 73 such as Ir, Ru, Re, Os, etc. having a low work function and facilitating electron emission was coated on the tip. It is something.

Metals such as Ir, Ru, Re, and Os have a low work function of about 1.6 eV, which is considerably lower than the 1.8 to 1.9 eV work function of impregnated electrodes impregnated with electron radioactive substances such as Ba. Electron radiation can be stably obtained. In this case, the metal coating 73 is not limited to single metals such as Ir, Ru, Re, and Os, but may also be alloys or oxides of these metals, or other metals that facilitate electron emission.

When a voltage of about 20 V is applied between both electrodes of this discharge tube, a discharge occurs, and a luminescent color corresponding to the type of gas 3 filled inside the glass tube is emitted.

In this embodiment, an example in which an impregnated electrode is used only as the electrode on the electron emission side has been described, but it goes without saying that the operation can also be performed even if the electrode according to the present invention is used as the electrode on the other side.

(Effects of the invention) According to the invention, since the electron emitting side electrode of the discharge tube is at a low temperature and electrons are easily emitted only from the tip, stable discharge can be obtained with less wear and tear on the electrode.

[Brief explanation of drawings]

Figure 1a is a schematic cross-sectional view of a discharge tube that is an embodiment of the present invention, Figure 1b is an enlarged view of the tip of an electrode that is an embodiment of the present invention, and Figure 2 is a schematic diagram of a conventional discharge tube. A cross-sectional view, FIG. 3 is an enlarged view of the tip of a conventional discharge tube electrode showing how it is used, and FIG. 4 is another embodiment of the conventional electrode tip. 1... Electrode, 2... Glass tube, 3... Rare gas,
4... Power supply, 7 ... Electrode, 71... High melting point metal rod, 72... Impregnated electrode, 73... Metal coating.

Claims (1)

[Scope of utility model registration request] Two electrodes with sharp tips placed opposite each other,
In a glass tube in which the two electrodes are sealed inside, and in a discharge tube in which a rare gas is sealed in the glass tube, the tip of at least one electrode is impregnated with a porous high melting point metal body and an electron radioactive substance. A discharge characterized in that it is formed by an impregnated electrode, and a metal film of any one of Ir, Ru, Re, and Os that reduces the work function is deposited on the sharpened tip of the impregnated electrode. tube.