JPS5816583B2 - Manufacturing method of electron emitting hot cathode - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a method for manufacturing an electron emitting hot cathode.
In particular, the present invention relates to a method of manufacturing an electron-emitting hot cathode having a structure in which a base metal and a heating element are bonded via an insulating layer.

In general, indirectly heated hot cathodes are often used in electron tubes such as cathode ray tubes.

The shape of such a hot cathode differs slightly depending on the electron tube used, but its basic structure consists of a cathode part consisting of a base metal and an electron-emitting substance coated on a part of its surface, and this cathode part. including a heating element disposed proximate to the heating element.

In particular, in a hot cathode having a structure in which a base metal and a heating element are bonded via an insulating layer, the original function of the base metal is often impaired in this bonding step.

A detailed explanation will be given below with reference to the drawings.

FIG. 1 is a partially cutaway perspective view showing a schematic structure of a hot cathode having the above-described structure.

The structure will be described with reference to FIG. 1. A base metal 1 is adhered to an insulating layer 2, and a part of the metal base 1 is electrically connected to the legs of a current-carrying terminal 3 buried in the insulating layer 2. Ru.

A heating portion 5 of a heating element 4 is embedded inside the insulating layer 2 .

An electron radioactive substance 6 is applied to the surface of the base metal 1.

As the electron radioactive substance 6, barium oxide or a composite oxide of barium, strontium, and calcium, which has excellent performance, is often used.

In the above configuration, for example, barium oxide as the electron radioactive substance 6 is a reducing metal that is contained inside the base metal 1 when the base metal 1 is heated to a high temperature of about 1000°C. It reacts with magnesium, silicon, etc., is reduced, becomes free barium, and participates in thermionic emission.

That is, it will be understood that the reducing metal contained inside the base metal 1 plays an extremely important role for the hot cathode.

As mentioned above, since the hot cathode may be heated to about 1000° C., ceramics such as steatite and zircon are generally used for the insulating layer 2.

These ceramics are obtained by molding powder raw materials such as magnesium oxide, silicon oxide, or salt oxide using an organic resin as a binder, and then firing at a high temperature.

Therefore, in the hot cathode having the above-described structure, a nickel plate or the like containing a predetermined amount of a reducing metal in advance is processed into a desired shape to form the base metal 1, and this base metal 1 should become the insulating layer 2. It is manufactured by applying a binder to a ceramic raw material and blackening it, then firing it at a high temperature.

- This is to improve the adhesion between the base metal 1 and the insulating layer 2 and achieve higher thermal conductivity.

However, in the method for manufacturing a hot cathode as described above, problems as described below are encountered.

Generally, organic matter used as a binder is burned by oxygen in the atmosphere during high-temperature firing and is released as a gas.

However, when the above-mentioned base metal 1 is heated in such an oxygen atmosphere to a temperature higher than about 1000°C to 1100°C, which is the porcelain-forming temperature of ceramic raw materials, not only nickel but also reducing metals are oxidized. (For example, it becomes magnesium oxide or silicon dioxide) and loses its original reducing function.

Therefore, in such a case, there is an additional limitation that a material that vaporizes by thermal decomposition even in an inert atmosphere or a vacuum must be selected as the binder material.

Note that even if the amount of oxygen present in the inert atmosphere or vacuum is small, the oxidation of the reducing metal is unavoidable because the firing temperature is high.

Therefore, great efforts must be made to prevent oxygen from entering the atmosphere during firing.

Further, since the raw materials of ceramics undergo firing shrinkage during the process of turning into porcelain, the surface may become smooth and the adhesion to the base metal 1 may be reduced.

Furthermore, this decrease in adhesion is also due to the difference in heat shrinkability between the ceramic and the base metal.

In this way, in a hot cathode in which the base metal 1 is directly bonded to the heating element 3 via the insulating layer 2, the heating element 3
There are various drawbacks due to the simultaneous execution of the process of embedding the base metal 1 in the insulator layer 2 made of ceramic to make it porcelain, and the process of bonding the base metal 1 to the insulator layer 2.

Therefore, the main object of the present invention is to provide a method for manufacturing an electron-emitting hot cathode, which makes it possible to eliminate the above-mentioned drawbacks.

In summary, this invention attempts to embed a heating element in an insulating material layer, porcelain it, and then bond the base metal by thermal spraying.

Other objects and features of the present invention will become more apparent from the detailed description given below with reference to the drawings.

FIG. 2 is a diagram for explaining one embodiment of the present invention.

An embodiment of the present invention will be described with reference to FIG. 2. With the legs of the current-carrying terminal 3 and the heating element 4 buried therein, the insulating layer 2 is formed through a porcelain process.

The steps described so far are almost the same as the conventional ones.

A metal spray gun 7 is placed facing a predetermined surface of the insulator layer 2 .

The placement distance varies depending on the type of metal, but a good thermal spray coating can be obtained when the distance is 10Cr/L or more and 25Cr/L or less, and in the case of nickel, which is often used as the base metal, it should be placed at about 10Cr/L to 151Cr/L. was found to be relatively good.

Further, the adhesion of the sprayed metal is maximized when the metal spray gun 7 is held so as to face perpendicularly to the spraying surface.

The insulating layer 2 has a predetermined shape (in FIG. 1, a portion extending to the upper surface of the insulating layer 2 and both current-carrying terminals 3, 3).
The mask 8 is brought into close contact so that the base metal surface is formed.

In the above arrangement, the base metal substance 9 is thermally sprayed,
A base metal 10 having a desired thickness and shape is formed.

The thickness can be arbitrarily adjusted by the thermal spraying time, and the shape can be arbitrarily adjusted by the shape of the cutout portion of the mask 8.

If the surface to be formed on the base metal 10 is large or spreads over two surfaces, move the metal spray gun 7 or the insulator layer 2 vertically or horizontally to obtain a uniform film thickness. adjust.

If necessary, the surface of the insulating layer 2 can be shaped into a desired shape by polishing or the like in advance.

At this time, the surface to be sprayed does not need to be flat.

Depending on the type of base metal 9, it may react with oxygen molecules in the air during flight from the metal spray gun 7 to the insulating layer 2, resulting in severe oxidation and may no longer be able to perform its original function as a base metal. be.

In such cases, oxidation can be advantageously prevented by thermal spraying in an atmosphere of an inert gas such as nitrogen.

In order to improve the adhesive strength of the sprayed base metal 10 and remove undesired oxidized portions, it is desirable to perform a heat treatment in a reducing atmosphere after spraying.

For example, when the base metal 10 is nickel, a good hot cathode can be obtained by heat treatment at about 1000° C. for 10 to 30 minutes in a hydrogen gas atmosphere.

The insulator layer 2 can be heat-treated in hydrogen gas in this way.
This is because it has been made into porcelain in advance, and this is also one of the features of this invention.

As described above, according to the present invention, since the base metal is formed by metal spraying on the insulating material layer that has been porcelained in advance, various adverse effects on the base metal due to porcelainization can be advantageously prevented. Can be done.

Further, since thermal spraying is used, the base metal can be formed into any shape regardless of the type of the base metal or the material or shape of the surface to be thermally sprayed.

Furthermore, the work for forming the base metal can be performed extremely easily.

Furthermore, since it can be easily mass-produced, its industrial value is extremely high.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view showing the schematic structure of a hot cathode having a configuration to which the present invention is advantageously applied. FIG. 2 is a diagram for explaining one embodiment of the present invention. In the figure, 2 is an insulating layer, 7 is a metal spray gun, 8 is a mask, 9 is a base metal material, and 10 is a base metal.

Claims (1)

[Scope of Claims] 1. An insulating layer, a heating element embedded in the insulating layer, a base metal coated on the surface of the insulating layer, and an electron radiation coated on the surface of the base metal. In the method for manufacturing an electron-emitting hot cathode, the base metal is formed by spraying a base metal material constituting the base metal onto the surface of the insulating material layer. manufacturing method. 2. The method of manufacturing an electron-emitting hot cathode according to claim 1, wherein the thermal spraying for forming the base metal is performed in an inert gas atmosphere. 3 After the thermal spraying step for forming the base metal,
3. The method for manufacturing an electron-emitting hot cathode according to claim 1 or 2, further comprising the step of heat-treating the formed base metal in a reducing atmosphere.