JPH0668847A - Cathode for electron tube - Google Patents

Abstract

PURPOSE:To provide a cathode for an electron tube in which consumptiion of an emitter by ion impact is small, and which can be used as a direct heat type device. CONSTITUTION:A main material 1 comprises a wire material of tungsten. The main material 1 has a number of fine recesses 3 in the surface, and an emitter 2 comprising electron emitting material is filled in each recess 3. Three of the main materials 1 in which the emitters 2 are filled are twisted with each other. As the emitters 2 are filled in the recesses 3, an exposed surface of the emitters 2 to the surface area of the main material 1 becomes small, and a consumption speed by ion impact or vaporization is reduced. Since the main material 1 comprises the wire material, an electric resistance between both ends of the main material 1 can be set large, thereby a cathode can be applied as a direct heat type device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron tube cathode used in an electron tube such as a discharge lamp having a bulb filled with a gas.

[0002]

2. Description of the Related Art Generally, in an electron tube such as a discharge lamp in which a gas is filled in a bulb, as shown in FIG. By depositing the different emitter 2 substantially uniformly, the emission of the thermoelectrons e is facilitated. The emitter 2 is made of a slurry-like electron emitting material as a main material 1.
It is usually formed by applying to the surface of.

[0003]

By the way, in a discharge lamp having a bulb filled with gas, ions i formed by ionization of gas collide with a cathode, and a phenomenon called ion bombardment or ion bombardment occurs. It has been known. As described above, since the emitter 2 is formed by coating the surface of the main material 1 with a slurry-like electron emitting substance, the emitter 2 is ion-impacted on the substantially entire surface of the main material 1. Will be received. Therefore, the evaporation rate of the emitter 2 is high (the small circle p in FIG. 3 indicates the scattered electron emission material). That is, since the emitter 2 is consumed by ion bombardment in addition to evaporation by heating, there is a problem that the life of the emitter 2 is shortened. When the emitter 2 is consumed, the electron emission material that evaporates and scatters adheres to the inner peripheral surface of the bulb to reduce the brightness, and the emission efficiency of thermions decreases, so that the excitation and ionization of the enclosed gas hardly occur. Therefore, the discharge lamp becomes difficult to light, and the life of the emitter 2 is one of the reasons for limiting the life of the discharge lamp.

On the other hand, a cathode called an impregnated electrode in which the emitter 2 is embedded in the main material 1 has been proposed. In this type of cathode, since the emitter 2 is embedded in the main material 1, the exposed area of the emitter 2 with respect to the surface of the main material 1 is small, and the consumption speed of the emitter 2 is lower than that of the conventional structure. have. However, in this type of cathode, since the main material 1 is formed in a flat plate shape, the electric resistance of the main material 1 is small, and even if the main material 1 is energized as a direct heating type cathode, There is a problem that heat cannot be generated sufficiently. That is,
If it is used for a low pressure discharge lamp such as a fluorescent lamp,
Although it is necessary to form a directly heated cathode, the impregnated electrode is used only as an indirectly heated cathode because of its low electric resistance, and is not currently used in a low pressure discharge lamp.

The present invention is intended to solve the above-mentioned problems, and the consumption of the emitter due to ion bombardment is small,
Moreover, it is intended to provide a cathode for an electron tube which can be used as a direct heating type.

[0006]

In order to achieve the above object, the present invention provides a direct heating type cathode used for an electron tube in which a gas is sealed in a bulb, which comprises a main material made of a metal wire and a main material. A plurality of main materials are twisted together with an emitter made of an electron emitting substance filled in a large number of minute recesses formed on the surface of the material.

[0007]

According to the above construction, since the main material is formed of a metal wire and a large number of recesses are formed on the surface of the main material to fill the emitter, the electrical resistance between both ends of the main material is reduced. It can be made large, and the heating temperature of the main material due to energization of the main material can be raised. Further, since the emitter is filled in the recess formed on the surface of the main material, the exposed area of the emitter with respect to the surface area of the main material is smaller than when the emitter is deposited on the entire surface of the main material, The probability of receiving an ion bombardment is reduced. As a result, the evaporation rate of the emitter is reduced as compared with the conventional case. Moreover, since the plurality of main materials are twisted together, the electron emission material evaporated from the emitter is deposited on the other main materials at the positions where the main materials face each other, and the consumption of the emitter is suppressed. It will be. Also, by making the recess deeper, it is possible to make the contact area between the main material and the emitter larger than in the conventional configuration, and it is possible to reduce only ion bombardment without reducing the radiation amount of thermoelectrons. is there.

[0008]

EXAMPLES In the following examples, a low-pressure discharge lamp (for example, a fluorescent lamp) having a small partial pressure of the enclosed gas will be described, but the technical idea of the present invention can be applied to other electron tubes. A gas formed of a translucent material is filled with a gas such as an inert gas or a metal vapor, and at least a pair of electrodes are arranged to face each other. In the type in which an alternating voltage is applied between both electrodes, an electron-emitting substance is deposited on the surface of each electrode so that thermoelectrons are emitted from each electrode,
In the type in which a DC voltage is applied between both electrodes, an electron-emitting substance is deposited on the surface of the electrode connected to the negative side so that thermoelectrons are emitted. The electrode on which the electron emission material is deposited will be called the cathode.

As shown in FIG. 1, the cathode is a main material 1 made of a wire made of a heat-resistant metal material such as tungsten,
It is composed of an emitter 2 made of an electron emitting substance such as an alkaline earth oxide deposited on a main material 1. Three main members 1 are provided and twisted with each other so that the cross-sectional area of a conventional wire forming a filament and the cross-sectional area of the three main members 1 combined are substantially equal.

A large number of recesses 3 are formed on the entire surface of the main material 1. The opening diameter of the recess 3 is set smaller than the thickness of the ion sheath formed around the cathode. The recess 3 is formed by using an excimer laser so as to have a circular cross section, for example. This recess 3 is filled with the emitter 2, and after the emitter 2 is filled,
The main material 1 of the book is twisted together.

In the structure described above, the portion of the surface of the cathode that receives the ion bombardment where the emitter 2 is exposed is
Since the recess 3 is only open and exposed on the outer periphery of the twisted main material 1, if the emitter 2 is exposed on the entire surface of the main material 1, Most of the ions flying toward the emitter 2 collided with the emitter 2, whereas as shown in FIG.
There is a case where the emitter 2 collides with the main material 1 and a case where the main material 1 does not collide with the emitter 2 and the probability that the emitter 2 receives the ion bombardment is reduced. In addition, even if the emitter 2 is subjected to ion bombardment and a part thereof scatters (small circle p in FIG. 2 indicates scattered electron emission material) and a recess is formed in the emitter 2, the diameter of the recess 3 is equal to that of the ion. Since it is smaller than the thickness of the sheath, plasma is not generated in the recess 3 and the probability that the emitter 2 is subjected to ion bombardment does not change. In addition, at the portion where the twisted main materials 1 face each other, the electron emission material p scattered by the evaporation of the emitter 2 is attached to the other main material 1, and the amount of the electron emission material p scattered to the outside. Is significantly reduced, and the life of the emitter 2 is extended. Furthermore, since the area where the emitter 2 is exposed on the surface of the main material 1 is small, the amount of evaporation of the emitter due to heat is significantly reduced as compared with the conventional configuration.

[0012]

As described above, according to the present invention, since the main material is formed of a metal wire and a large number of recesses are formed on the surface of the main material to fill the emitter, the gap between both ends of the main material is reduced. Has a merit that a large electric resistance can be obtained and the heating temperature of the main material can be raised by energizing the main material. That is, it becomes possible to use it as a direct heating type for a cathode of a low pressure discharge lamp or the like. Further, since the emitter is filled in the recess formed on the surface of the main material, the exposed area of the emitter with respect to the surface area of the main material is smaller than when the emitter is deposited on the entire surface of the main material, As a result, the probability of receiving ion bombardment is reduced, and the evaporation rate of the emitter is reduced as compared with the conventional case. Moreover, since the plurality of main materials are twisted together, the electron emission material evaporated from the emitter is deposited on the other main materials at the positions where the main materials face each other, and the consumption of the emitter is suppressed. Has the advantage.

[Brief description of drawings]

FIG. 1 shows an embodiment, (a) is a side view, and (b) is a sectional view.

FIG. 2 is an explanatory diagram showing the behavior of electrons and ions in the example.

FIG. 3 is a cross-sectional view showing a conventional example.

[Explanation of symbols]

 1 Main material 2 Emitter 3 Recessed e Electron i Ion p Emitted and scattered electron emission material

Claims (1)

[Claims] 1. A direct heating cathode used for an electron tube in which a gas is sealed in a bulb, the main material being a metal wire rod,
A cathode for an electron tube, comprising: an emitter made of an electron-emitting substance filled in a large number of minute recesses formed on the surface of a main material, and a plurality of main materials twisted together.