JPH031420A - Electron cathode tube - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electron tube cathode used in a picture tube or the like, and more particularly to an electron tube cathode with improved electron emission characteristics.

[Prior Art] Conventionally, electron tube cathodes used in picture tubes and the like are made by coating barium (Ba) on a base metal consisting mainly of nickel (Ni) and containing a small amount of silicon (Si) as a reducing agent. A so-called oxide cathode in which an oxide layer of an alkaline earth metal containing an alkali earth metal is formed is often used.

This oxide cathode is made to react with a reducing agent and an oxide to generate free atoms from the oxide, and to emit electrons using the free atoms as donors (sources) of electron emission.

FIG. 2 is a schematic cross-sectional view showing an example of a conventional electron tube cathode, in which a cap-shaped base metal (1), a cylindrical sleeve (2)
It consists of an electron emitting material layer (5) made of barium oxide coated on a base metal (1). (3)
is a heater for heating the cathode.

This electron emitting material layer (5) is formed by the following steps. That is, after barium carbonate is mixed with an organic solvent in which nitrocellulose or the like is dissolved, it is deposited on the base metal (1) by a method such as spraying or electrodeposition.

Such a cathode is then incorporated into an electron tube, and heated to approximately 1000°C by a heater (3) during the evacuation process to create a vacuum inside the electron tube, and the barium carbonate is thermally decomposed as shown in the following equation. It is converted to barium oxide by

BaCO54BaO+GO A reduction reaction occurs.

2BaO+Si-+ 2Ba+SiO2...++ (
B) The free barium produced in this reaction acts as a donor for electron emission. Moreover, at this time, the reaction shown in the following formula also occurs simultaneously.

SiO2+2BaO-+Ba, SiO4...” (
C) As mentioned above, free barium that acts as a donor plays a role in electron emission, but as shown in equations (B) and (C), reaction products such as Sin, Ba2Sin4, etc. (5) and the boundary (11) of the base metal (1)
) is generated. This reaction product accumulates rapidly near the boundary and forms a barrier called an intermediate layer, which prevents silicon from diffusing and makes it difficult to generate free barium, which is a donor. Another problem is that this intermediate layer has high resistance and obstructs the flow of electron emission current.

To solve this problem, as shown in Figure 3, a scandium (Sc) or scandium oxide (SC203) film (4) is applied to the surface of the base metal (1) by vacuum evaporation, plating, or spraying. It is disclosed in Japanese Patent Application No. 122659/1983 that a reaction product such as Ba2SiO4 is dissociated by depositing the material to a thickness of 0.1 to 10 .mu.m by a method or the like.

However, in this invention, when a film is formed by vacuum evaporation or plating, it takes a long time to form the film and requires expensive equipment. In addition, even if spraying is legal,
．． It was difficult to uniformly form a very thin film of 1 to 10 μm, and the yield was poor. Further, in the case of vacuum evaporation or plating methods, there is a problem that the reducing metal becomes difficult to diffuse from the base gold R (1) to the electron emitting material layer (5), and the electron emission characteristics are unstable. Furthermore, there was also the problem that the electron emitting material layer (5) peeled off from the coating (4) during long-term operation.

[Problem to be solved by the invention] Since the conventional electron tube cathode is configured as described above,
There were problems in that mass production and quality stability were lacking.

This invention was made to solve the above-mentioned problems, and aims to provide an electron tube cathode that is excellent in mass productivity and has stable quality such as electron emission characteristics.

[Means for Solving the Problems] The electron tube cathode according to the present invention has a sintered layer of nickel powder containing scandium oxide provided on a base metal, and an electron emitting material layer deposited on the sintered layer. Characterized by points.

[Function] The nickel powder sintered layer of the present invention firmly adheres to the base metal and has scandium oxide dispersed in the sintered layer in an appropriate manner.Furthermore, this sintered layer has an appropriate surface Due to the roughness and pores, it is possible to firmly adhere the electron-emitting substance, and it is also possible to facilitate the diffusion of the reducing metal. Therefore, it is possible to prevent the formation of an intermediate layer, and it is easy to manufacture, does not peel off, and has stable electron emission characteristics.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1st
The figure is a schematic structural sectional view showing this embodiment, and the same components as those of the conventional example shown in FIGS. 2 and 3 are given the same reference numerals, and the explanation thereof will be omitted.

In the figure, (6) is a nickel powder sintered layer, which is a sintered layer of nickel powder (6a) containing scandium oxide (6b) dispersed on the base metal (1).

This nickel powder sintered layer (6) is formed as follows. Nickel powder (6a) with an average particle size of 10 to 30 μm
1 to 10% by weight of scandieum oxide powder (6
b), and this mixed powder is added to an organic solvent in which nitrocellulose is dissolved to form a suspension, and the suspension is applied onto the base metal (1) to a thickness of 20 to 30 μm by a method such as spraying. Next, in a hydrogen atmosphere or a vacuum atmosphere, about 1000
Base metal (1) by heat treatment at ℃ for 10 minutes
A sintered nickel powder layer (6) is formed on which nickel powder (6a) containing scandium oxide (6b) is welded.

On this nickel powder sintered layer (6), as in the conventional example, an electron emitting material is applied, for example, by spraying at a concentration of 50 to 100.
Apply to a thickness of μm. The electron emitting material layer (5) contains at least barium (Ba) and also contains an alkaline earth metal oxide containing strontium (Sr) or calcium (Ca) as a main component.

In this way, according to this example, scandium oxide powder (6b) is dispersed and mixed in nickel powder (6a),
Overall production was improved due to the simple process of depositing on the base metal (1) by a simple method such as spraying and then heat-treating in a non-oxidizing atmosphere. Furthermore, since it is a sintered layer, the layer has a moderate amount of pores. Therefore, the reducing metal from the base metal (1) easily diffuses into the electron emitting material layer (5), and it is possible to reduce the variation in initial electron emission characteristics that has been a problem in the past.

In addition, a nickel powder sintered layer (6) and an electron emitting material layer (5)
The interface with the electron-emitting material layer (
The adhesion of 5) was improved, and the peeling of the electron emitting material was reduced.

Next, the effect of suppressing the generation of the intermediate layer during operation will be explained. The gist of the patent application is 1982-122 (15
9, and will be briefly described here. The scandium oxide (6b) in the nickel powder sintered layer (6) causes the following reaction with the nickel powder (ea) or the nickel of the base metal (1).

Sc, 03+1ONi→2ScNis+30...
・(DJ) The product 5CNts in this reaction causes the following reaction with Ba2SiO4, which is a component of the intermediate layer.

16ScNi, +9Ba2SiO4-+ 4Ba3Sc
40. +6Ba+9Si+8ONi (E) Since 3a2Si04 is thus dissociated and not accumulated, the generation of an intermediate layer is suppressed.

[Effects of the Invention] According to this invention, a sintered layer of nickel powder containing scandium oxide is formed on a base metal, and the layer is coated with an electron emitting substance, so it can be manufactured efficiently and at low cost. In addition, it is possible to obtain a highly reliable electron tube cathode with stable electron emission characteristics.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a schematic enlarged sectional view of one embodiment of the present invention, and FIG.
The figure is a schematic enlarged sectional view of a conventional electron tube cathode, and FIG. 3 is an enlarged schematic sectional view of an improved conventional electron tube cathode. (1)...Base metal, (5)...Electron emitting material layer,
(6)...nickel powder sintered layer, (6a)...nickel powder, (6b)...scandium oxide. In each figure, the same reference numerals indicate the same or equivalent parts. Figure 1

Claims (1)

[Claims] (1) A cathode base metal mainly composed of nickel and containing at least silicon, a sintered nickel powder layer formed on the surface of the base metal in which scandium oxide is dispersed, and a sintered layer of nickel powder in which scandium oxide is dispersed. An electron tube cathode comprising an electron emitting material layer formed on a surface of an alkaline earth metal oxide containing at least barium.