JPS59191226A - Cathode body of electron tube or the like - Google Patents

Abstract

PURPOSE:To obtain a cathode body with suitable electron emission characteristics by applying heat treatment under hydrogen atmospheres before metal ultra- fine powder is mixed in alkaline earth carbonate powder. CONSTITUTION:Before the metal ultra-fine powder whose particle diameter is less than 0.3mu is mixed in alkaline earth carbonate powder, it is heat-treated under hydrogen atmospheres. For example, the nickel powder 3 whose average particle diameter is 300Angstrom is heat-treated for five minutes at 450-850 deg.C under the hydrogen atmospheres and this powder is mixed in the alkaline earth carbonate 2 at a weight ratio of 10%. Then a nitrocellulose solution and butyl acetate are mixed in this mixing substance and a suspension or paste is obtained and then substrate metal 1 is coated with the suspension or paste. It is suitable that the coating thickness is 60-100mu when the diameter of the substrate metal 1 is 2mm.. As a result, a cathode body with high electron emission characteristics can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cathode body for an electron tube used in a cathode ray tube or the like.

Recently, high-resolution cathode ray tubes and projection cathode ray tubes used as display tubes in computer terminals are increasingly adopting high-current density cathode bodies to improve resolution by reducing the diameter of the electron beam. has been done.

Figure 1 shows an example of a high current density cathode body.
(Ba, Sr.

Ca) Alkaline earth carbonate (2) consisting of COs and ultrafine metal powder (3) consisting of nickel powder, cobalt powder, or mixed powder of nickel powder and cobalt powder with a particle size of 0.3 microns or less. A mixture is coated. As a mixture of such an alkaline earth carbonate (2) and an ultrafine metal powder (3), for example, an ultrafine metal powder (3) having a weight ratio of 1 to 50% with respect to the alkaline earth carbonate (2) is used.
) is added and mixed, nitrocellulose and butyl acetate are added and mixed to this mixture to form a suspension or paste, and then applied onto the base metal (1) by a spraying method or a printing method. The one that is coated on the surface will be adopted.

Note that (5) is a heater housed in the cathode sleeve (4) K, which is provided to heat the base metal (1).

The alkaline earth carbonate (2) is heated in the vacuum evacuation process and converted into a complex oxide of formula (1), Ba, Ca, and Sr. The CO2 generated at this time is exhausted by an exhaust pump.

(Ba, Sr, Ca)CO3-→(Ba, Sr, Ca)
0+CO,・flexion (1) In the aging process after the completion of the exhaust process, the base metal (1)
is heated to a high temperature of 900 to 100°C (Ba.

The ternary composite oxide consisting of Sr and Ca)0 reacts with Si and Mf contained in the base metal (1) to liberate Ba and the like. This reaction is expressed in equation (2).

B a O+ M? -1→B a + M f
O, , , Kawa - + - + (2) Through this reaction, for example, a part of BaO on the base metal (1) is reduced to free B
A is generated and becomes an oxygen-deficient semiconductor, 700-8o
At an operating temperature of 0.degree. C., electron emission becomes active.

On the other hand, the ultrafine metal powder (3) added to the alkaline earth carbonate (2) improves the electrical conductivity between the base metal (1) and the surface of the above-mentioned ternary composite oxide, allowing for large current extraction. It has the role of suppressing the Joule heat that sometimes occurs and preventing thermal destruction of the ternary composite oxide.

In addition, the reason why a particle size of 0.3 microns or less is selected as the ultrafine metal powder (3) is that the average particle size is 30 microns or less.
In the case of 0 people (0.03 microns), the specific surface area is 70
Since it is an extremely large value of ~10 I/re, it contributes to improving the electrical conductivity between the base metal (1) and the composite ternary oxide as described above, and also has extremely high dispersibility in the composite ternary oxide. Good things can be mentioned.

By the way, since the ultrafine metal powder (3) is produced in a dry atmosphere called the in-gas evaporation method, its surface is covered with a dense and stable oxide film. Therefore, during the aging process or operation, the oxide decomposes and releases oxygen gas, as shown in equation 31.

2 N i 0 2 N i + Ox ---
−・−−−−−−(3) This oxygen gas quickly reacts with the free barium generated in equation (2), and as shown in equation (4), becomes BaO, impairing the electron emission ability. Take shelter.

2Ba 1 υ 3 -1 → 2BaO・・・・・・・・・(4
) As described above, when ultrafine metal powder is used, there is a drawback that sufficient electron emitting ability cannot be obtained due to the influence of the oxidized layer on its surface.

This invention was made in order to eliminate the drawbacks of the conventional methods as described above.Before mixing ultrafine metal powder with alkaline earth carbonate powder, heat treatment is performed at a predetermined temperature in a hydrogen atmosphere. The purpose of this is to provide a cathode body for an electron tube with suitable electron emission characteristics.

An embodiment of the present invention will be described below.

Nickel powder of 300 particles with an average particle size of 4
Heat treatment was performed at a temperature of 50 to 850°C for 5 minutes, and then this powder was mixed with alkaline earth carbonate at a weight ratio of 10%, and further, nitrocellulose solution and butyl acetate were mixed into this mixture. It is made into a suspension or paste and applied onto the base metal (1). Coating thickness is base metal (1)
When the diameter is 2 m, 60 to 100 μ is suitable.

The cathode body for an electron tube manufactured by the above method is the first
It has the same configuration as the one in the figure.

Figure 2 shows the processing temperature (H!) of ultrafine metal powder in a hydrogen atmosphere.
This figure shows the relationship between processing temperature) and electron emission ability (emission). This figure shows that the electron emission ability deteriorates extremely at temperatures below 450°C. This is because the acid free barium on the surface of the ultrafine metal powder combines with the acid and changes into barium oxide.

On the other hand, at temperatures of 850° C. or higher, variations in electron emission ability become large. This is because the ultrafine metal powders begin to sinter together, resulting in uniform dispersion into the alkaline earth carbonate and the characteristics of the ultrafine powder disappearing. be.

Based on the above, it can be said that the appropriate heat treatment temperature for metal powder is 450 to 850°C.

In the above embodiment, the cathode body of an electron tube has been described, but similar effects can be obtained in cathode bodies of image pickup tubes, transmission tubes, and the like.

As described above, according to the present invention, since the ultrafine metal powder is heat-treated in a hydrogen atmosphere before being mixed with the alkaline earth carbonate, a cathode body having a cylindrical electron emission ability can be provided.

[Brief explanation of the drawing]

FIG. 1 is an enlarged sectional view of a cathode body for an electron tube, and FIG. 2 is an explanatory diagram showing the relationship between processing temperature of ultrafine metal powder in a hydrogen atmosphere and electron emission ability. (1)... Base metal, (2)... Alkaline earth carbonate, (3)... Ultrafine metal powder. Agent Masuo Oiwa

Claims (2)

[Claims] (1) A cathode for an electron tube, etc., formed by depositing a mixture of alkaline earth carbonate powder containing barium and ultrafine metal powder with a particle size of 0.3 microns or less on a base metal mainly composed of nickel. 1. A cathode body for an electron tube, etc., which is heat-treated in a hydrogen atmosphere before mixing ultrafine metal powder with alkaline earth carbonate powder. (2) A cathode for an electron tube or the like according to claim 1, wherein the ultrafine metal powder is nickel powder, cobalt powder, or a mixed powder of nickel powder and cobalt powder, and the heat treatment temperature thereof is 450 to 850°C. body.