JPH0668846A - Cathode for electron tube - Google Patents

Abstract

PURPOSE:To reduce consumption of an emitter by ion impact, and enable application of a cathode as a direct heat type device. CONSTITUTION:A main material 1 comprises a thin plate of tungsten, and it has a zig-zag shape like a crank. 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. 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 is formed in a zig-zag line, 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. In addition, because the recess 3 has a larger cross sectional surface at an inner part than around an aperture, a filled quantity of the emitter 2 is large, thereby the life of the emitter 2 becomes long.

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 having a bulb filled with a gas, 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. 5 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 in an electron tube in which a gas is sealed in a bulb, in which a thin metal plate is linearly punched. The main material and an emitter made of an electron-emitting substance filled in a large number of minute recesses formed on at least one surface of the front and back surfaces of the main material, and the recess has an area of a cross section parallel to the opening surface. It is formed in a shape that is larger inside than near the opening.

[0007]

According to the above structure, since the main material is formed by punching a thin metal plate into a linear shape, the distance between both ends of the main material is increased and the width of the line between both ends of the main material is increased. By narrowing, the electrical resistance of the main material can be increased, and the heating temperature of the main material due to energization of the main material can be increased. Further, since a recess is formed on at least one of the front and back surfaces of the main material, and the emitter is filled in this recess, the exposed area of the emitter with respect to the surface area of the main material has It is smaller than that of the structure in which (1) is deposited, and as a result, 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. 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. In addition, the recess is formed in a shape in which the area of the cross section parallel to the opening surface is larger inside the opening than in the vicinity of the opening. The amount of the emitter that can be filled in the recess can be increased and the life of the emitter can be extended as compared with the case where the emitter is formed into the shape.

[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 composed of a main material 1 made of a heat-resistant metal material such as tungsten, and a main material 1.
And an emitter 2 made of an electron emitting substance such as an alkaline earth oxide. The main material 1 is processed into a linear shape by a method such as chemical etching, and here, a crank-shaped meandering line is formed. The line is formed, for example, such that the main material 1 has a plate thickness of 100 μm and the line has a width of 200 μm, and the cross-sectional area of the wire forming the conventional filament and the cross-sectional area of the line are set to be substantially equal. . Here, the plate pressure of the main material 1 and the width of the line are not intended to be limited, but are set according to the intended use. Further, the shape of the main material 1 may be another shape.

A large number of recesses 3 are formed on the surface of the main material 1 over the entire surface. Each recess 3 is formed in a shape in which the area of a cross section parallel to the opening surface is larger inside than in the vicinity of the opening. The opening diameter of the recess 3 is set to be smaller than the thickness of the ion sheath formed around the cathode. The opening shape of the recess 3 is, for example, circular, and the opening diameter is 50 μm using an excimer laser.
The depth is 50 μm, and the maximum inner diameter in a cross section parallel to the opening surface is 100 μm. In order to form such a recess 3 by using an excimer laser, as shown in FIG. 2, the irradiation direction L of the laser beam 1 is inclined with respect to the normal line n of the surface of the main material 1 by a certain angle, The main material 1 may be rotated about one normal line n. For example,
If the main material 1 is rotated at 90 degrees apart into four positions, as shown in FIG. 3, a recess 3 having an inner cross shape when viewed from the direction of the normal line n of the main material 1 is formed. You can The emitter 2 is filled in the recess 3.

In the structure described above, the surface of the cathode that receives the ion bombardment is the only part where the emitter 2 is exposed, and the recess 3 is open. Therefore, the emitter 2 is formed on the entire surface of the main material 1. When exposed, most of the ions flying toward the main material 1 collided with the emitter 2, while the ions i collided with the emitter 2 as shown in FIG. , The case where it collides with the main material 1 without colliding with the emitter 2,
Will reduce the probability of being subjected to ion bombardment. That is, the probability that the emitter 2 receives an ion bombardment is
Since it is proportional to the aperture ratio, the probability that the emitter 2 is subjected to ion bombardment is significantly reduced as compared with the conventional configuration in which the recess 3 is not formed. Further, even if the emitter 2 is subjected to ion bombardment and a part thereof is scattered (a small circle p in FIG. 4 indicates the scattered electron emission material) to form a dent 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. Furthermore, the emitter 2 is the main material 1.
Since the area exposed on the surface of the is small, the amount of evaporation of the emitter due to heat is also significantly reduced as compared with the conventional configuration. Moreover, since the recess 3 is formed in a shape in which the area of the cross section parallel to the opening surface is larger inside than in the vicinity of the opening, comparison is made when the recess 3 having a uniform cross-sectional area is formed. Then, if the opening diameters are the same, the amount of the emitter 2 that can be filled in the recess 3 increases, and as a result, the life of the emitter 2 becomes longer.

[0012]

As described above, according to the present invention, since the main material is formed by linearly punching a thin metal plate, the distance between both ends of the main material is increased and the line between both ends of the main material is extended. By narrowing the width, the electric resistance of the main material can be increased, and the heating temperature of the main material due to energization of the main material can be increased. That is, it can be used as an electrode of a low pressure discharge lamp or the like as a direct heating type cathode. Further, since a recess is formed on at least one of the front and back surfaces of the main material, and the emitter is filled in this recess, the exposed area of the emitter relative to the surface area of the main material is relatively small, and the probability of receiving ion bombardment is high. Reduced,
The effect is that the consumption speed of the emitter is reduced as compared with the conventional one. 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. It has the advantage of being. Furthermore, the recess is formed in a shape in which the area of the cross section parallel to the opening surface is larger inside than near the opening.
The amount of emitter that can be filled in the recess can be increased as compared with the case where the recess is formed in a shape with a constant cross-sectional area while reducing the consumption of the emitter due to ion bombardment. Has the effect of having a long life.

[Brief description of drawings]

FIG. 1 shows an embodiment, (a) is a plan view, and (b) is a sectional view taken along line XX of FIG.

FIG. 2 is a schematic view showing a method of forming a recess in an example.

FIG. 3 shows an embodiment, (a) is a partial front view of a main material,
(B) is a partial cross-sectional view of the main material.

FIG. 4 is an explanatory diagram showing the behavior of electrons and ions in the example.

FIG. 5 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 type cathode used for an electron tube in which a gas is sealed in a bulb, which is formed on at least one of the front and back surfaces of a main material obtained by punching a thin metal plate into a linear shape. An emitter made of an electron-emitting substance filled in a large number of minute recesses is provided, and the recesses are formed in such a shape that the area of the cross section parallel to the opening surface is larger inside than near the opening. Characteristic electron tube cathode.