JPH01102829A - Cathode of electron tube and its manufacture - Google Patents

Abstract

PURPOSE:To shorten the aging time, provide good initial characteristic, and prolong the life with high current density by allowing an alkaline earth metal oxide layer to contain dispersed powder of Ba3Sc4O9. CONSTITUTION:0.1-20wt.% Ba3Sc4O9 powder prepared previously is dispersed uniformly in an alkaline earth metal oxide layer. That is, barium carbonate (changed into barium oxide already at the time of reaction) and scandium oxide are mixed and heated for a sufficiently long time, and Ba3Sc4O9 as product is added dispersedly in the alkali earth metal oxide layer. Thereby Ba3Sc4O9 is distributed uniformly in electron emitting substance to allow acquistion of highly uniform and stable electron emitting characteristics from the initial period.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electron tube cathode that exhibits stable electron emission characteristics over a long period of time at high current density, and a method for manufacturing the same.

[Conventional technology]

With the increasing definition of color picture tubes, display tubes, and image pickup tubes,
There is a strong demand for the cathodes of these electron tubes to have electron emission characteristics that are stable at high current densities over long periods of time.

In order to meet these demands, for example, Japanese Patent Laid-Open No. 61-27
Japanese Patent No. 1732 discloses an alkaline earth metal oxide layer in which scandium oxide powder is dispersed. The scandium oxide powder dispersed in this alkaline earth metal oxide is an alkaline earth metal oxide, such as B
Composite oxide Ba-5cyO produced by reaction with aO
is dispersed in the electron-emitting material, and this composite oxide undergoes thermal decomposition during operation of the cathode and is released ii! Make it easier to generate lBa. Therefore, an intermediate layer was formed by the reaction between the sheet metal alkaline earth metal oxide and reducing elements such as St and Mg contained in the base metal, and this intermediate layer suppressed the generation of free Ba. Even so, there will be no shortage of talent among playing MBas.

In addition, some of the Sc in the double oxide is liberated and becomes metallic scandium, which is distributed throughout the electron-emitting material.
It increases the conductivity of the electron-emitting material and compensates for the decrease in conductivity caused by the intermediate layer.

[Problem that the invention seeks to solve]

The inventors conducted nine production tests on an electron tube cathode using the above conventional technology containing scandium oxide powder dispersed in an alkaline earth metal oxide layer, and found that it had a very long aging time to stabilize the electron emission characteristics. It has been found that there are problems in that it takes time and the electron emission characteristics are non-uniform.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the conventional technology, and to provide an electron tube cathode and its manufacturing method that requires short aging time, has stable initial electron emission characteristics, and is highly uniform between products. shall be.

[Means for solving problems]

In order to solve the above problems, in the present invention, in an electron tube cathode in which an alkaline earth metal oxide layer containing barium is formed on the surface of a nickel base metal, the alkaline earth metal oxide layer is prepared separately in advance. Ba, 5
C40,7FA powder was uniformly dispersed and included at 0.1 to 20% by weight.

BayoSC4O9 is made by heating a mixed powder of barium carbonate and scandium oxide to 1000 to 1200 in a non-reducing atmosphere.
It can be synthesized by heating at ℃ for 15 to 30 hours.

Furthermore, conventionally, when actually manufacturing so-called oxide cathodes, carbonates of alkaline earth metals, which are stable even in the atmosphere, have been used, but when manufacturing the electron tube cathode according to the present invention, Also, B a 3 S synthesized in advance
After C4O9 powder is mixed with alkaline earth carbonate powder and dispersed uniformly, this mixture is deposited in a layer on the surface of the base metal and thermally decomposed to form uniformly dispersed Ba.
It is used by changing to an alkaline earth metal oxide layer containing 3Sc4O9 powder.

[Effect]

Barium carbonate (already converted to barium oxide at the time of reaction) and scandium oxide are mixed in advance, heated, and reacted for a sufficient amount of time to produce B a35 C4O.
Since Ba3Sc4O9 is dispersed and added to the alkaline earth metal oxide layer, compared to conventional methods, Ba3Sc4O9 is uniformly present in the electron emitting material, resulting in highly uniform and stable electron emission characteristics from the beginning. can get. That is, in the conventional case where an electron tube cathode is formed by directly adding scandium oxide 5cz03 powder to an alkaline earth metal carbonate, scandium oxide and the alkaline earth metal are added during aging or subsequent operation. Because the oxide layer reacts, a change occurs in the oxide layer,
Moreover, it seems that it takes a long time to stabilize and obtain good electron emission.

Note that the reaction product of barium carbonate and scandium oxide may vary depending on their mixing ratio, such as the above-mentioned Ba3Sc4.
In addition to 0y, Ba2Sc2O5, B a S C204
can also be obtained, and all of them have the effect of improving the electron emission characteristics, but among these reaction products, Ba3Sc4Oq
It was found that the best effect of improving electron emission characteristics was obtained when .

At this time, Ba3Sc4O+ obtained by reaction production
A small amount of BazSczOg1BaScz04.
Alternatively, even if unreacted SC20m remained, there was no effect at all.

〔Example〕

An embodiment of the present invention will be described below. When barium carbonate and scandium oxide powders are mixed in a molar ratio of 3=2 and heat treated in the atmosphere at 1000 to 1200'C for 15 to 30 hours, Ba3Sc4O9 is produced. This barium scandate was added in an amount of 5% by weight to ternary carbonate powder of barium, calcium, and strontium and mixed, and to this was added nitrocellulose lacquer butyl acetate and mixed by rolling to prepare a suspension.

This suspension was sprayed onto the base metal surface for approximately 80 minutes.
It is coated to a thickness of IIm, heated with a heater during the vacuum evacuation process to decompose the carbonate into oxides, and further heated to 900 to 1100°C.
We fabricated a cathode that underwent an activation process to obtain stable electron emission characteristics when heated.

When the cathode manufactured as described above was used in a diode tube and tested, an electron emission characteristic of 1 to 2 A/ctA was obtained at a cathode operating temperature of 700 to 800°C, and a large number of cathodes were tested. It was manufactured and tested, and good uniformity was observed.

FIG. 1 shows an embodiment of the present invention, in which 1 is a cathode sleeve, 2 is a nickel base, 3 is an electron-emitting material according to the present invention, and 4 is a heater.

FIG. 2 shows the temporal change in electron emission when this cathode is mounted in a cathode ray tube and operated at the rated heater voltage of 11 oz. In the figure, 1 is the cathode according to the present invention, 2 is Ba3
This is the case of a cathode to which Sc4O9 was not added. As is clear from this figure, Ba3Sc40 is used in the electron emitting material layer.
By dispersing g, good electron emission characteristics can be maintained for a long period of time.

In the above example, 5% by weight of Ba3Sc4O9 powder was added, but the amount of Ba3Sc40g added was reduced to 0.5% by weight. When the amount of IM is less than 1%, the effect is small and it is not practical. On the other hand, when the amount added is more than 20% by weight, the initial characteristics deteriorate and it is not practical.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to manufacture an electron tube cathode that requires only a short aging time, has good initial characteristics, has a long life with high current density, and has good uniformity.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the present invention, and FIG. 2 is a diagram showing changes over time in the electron emission characteristics of the cathode according to the present invention. l・-・Cathode sleeve, 2-Nickel base, 3・-
Electron-emitting substance according to the present invention, 4-hinik. Representative Patent Attorney Katsuma Ogawa: 1... Cathode sleeve 2... Nickel base 3... Electron emitting material 4... Heater operating time (unit: 2,000 hours)

Claims (1)

[Claims] 1. In an electron tube cathode in which an alkaline earth metal oxide layer containing barium is formed on a nickel base metal surface, Ba_3Sc_4O_
An electron tube cathode characterized by containing 9 powder dispersed therein. 2. The content of Ba_3Sc_4O_9 powder is 0.1 to 2.
The electron tube cathode according to claim 1, wherein the content is 0% by weight. 3. Mix Ba_3Sc_4O_9 synthesized in advance with barium-containing alkaline earth metal carbonate powder and disperse it uniformly, then apply this mixture to the base metal surface in a layer and heat decompose it. , uniformly dispersed Ba_3S
A method for manufacturing an electron tube cathode, comprising forming an alkaline earth metal oxide layer containing s_4O_9 powder. 4. By heating a mixed powder of barium carbonate and scandium oxide in a non-reducing atmosphere, Ba_3Sc_
The method for manufacturing an electron tube cathode according to claim 3, which comprises synthesizing 4O_9.