JPS6057172B2 - oxide cathode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an oxide cathode, and particularly to an oxide cathode that can maintain electron radioactivity over a long period of time.

Generally, cathodes are used in receiver tubes, discharge tubes, or cathode ray tubes, but the cathodes used in the cathode ray tubes mentioned above usually operate quickly and display images instantly.

It is required to be able to demonstrate That is, a short starch ink time is required. On the other hand, the above-mentioned cathode is classified into indirectly heated type and directly heated type. The starch ink time for the above-mentioned indirect heating type is approximately 2 (sub) ec, but for the direct heating type, this time is extremely short at 1 to 2 seconds, and this direct heating type is a fast acting type. It is most suitable as FIG. 1 is a sectional view of a main part of an example of a directly heated oxide cathode.

In the figure, 1 is a base that generates heat when current is supplied, and 2 is a terminal thereof. In addition, 3 is an alkaline earth metal oxide (hereinafter referred to as oxide) that has electron radioactivity.
and is coated on the substrate 1. Here, the substrate 1 needs to have a thickness of 100 μm or less, preferably 60 μm or less, in order to increase the electrical resistance as much as possible, reduce the heat capacity, and shorten the starch ink time. . The metal plate material used for the substrate of the directly heated oxide cathode having such a structure must satisfy the following requirements.

That is, 1. High temperature strength.

2. High electrical specific resistance.

3. The electron radioactivity of the oxide cathode can be increased.

etc.

Therefore, W
A Ni alloy containing either or both of and Mo and Zr as a reducing agent has been proposed. That is,
W and Mo increase the high temperature strength and electrical resistivity of the substrate 1,
Since Zr has a low vapor pressure, it is hardly consumed by evaporation, and since the melting point of its intermetallic compound is high, high-temperature strength does not decrease even if it is contained in an amount exceeding the solid solubility limit. A layer of reaction products formed at the interface between the substrate and the oxide when reacting with the radioactive oxide, a so-called intermediate layer, has almost no adverse effect on the electron emission characteristics. However, even if a metal plate material with such a composition is used as a substrate, the reducing agent is consumed quickly because the plate thickness is extremely thin, and therefore it is difficult to maintain the electron radioactivity of the oxide cathode for a long period of time. It has drawbacks such as difficulty.

Therefore, an object of the present invention has been made to eliminate the above-mentioned drawbacks, and to control the consumption rate of the reducing agent so that the electron emission characteristics of the oxide cathode can be maintained for a long period of time. The purpose of the present invention is to provide an oxide cathode.

In order to achieve such an object, the oxide cathode according to the present invention has a Ca oxide layer formed between a base metal and an oxide having electron-emitting properties.

The oxide cathode according to the present invention will be described in detail below with reference to the drawings. As is well known, the electron radioactivity of an oxide cathode is
This is maintained by the stoichiometric excess a (barium) present in the oxide, which is usually produced by the reaction of the oxide with an active metal, called the reducing agent, in the base metal.

Therefore, the electron radioactivity of the oxide cathode is consumed by the reaction of the reducing agent in the base metal with the oxide or by evaporation. It is lost when the rate of generation of is no longer sufficient. This Ba production rate is determined by the fact that the reducing agent is supplied to the interface with the oxide by diffusion through the base metal. It depends on the rate and the rate at which the oxide and the reducing agent react, and is equal to the slower of the two, but the reaction between the oxide and the reducing agent cannot proceed faster than the rate at which the reducing agent is supplied. The production rate of is at its maximum when it is equal to the reducing agent supply rate. So. In the case of the reaction of Mg, Sl, Al, Zr, which are widely used as reducing agents for oxide cathodes, with oxides, the rate of Ba production is equal to their supply rate. Therefore, when Mg, Si, AI, and Zr are used as reducing agents, their consumption rates are determined by their diffusion rates in the base metal, and electron radioactivity is emitted over a relatively short period of time. lost to. Therefore, it is difficult to maintain electron radioactivity over a long period of time, especially in the case of a directly heated oxide cathode in which the thickness of the base metal is limited. Now, the feed rate of the reducing agent, as determined by the rate of diffusion in the base metal, decreases with time.

The electron radioactivity of the oxide cathode is sometimes lost when the supply rate of the reducing agent falls below a certain level, and the rate of generation of the toxin is no longer sufficient. This means that more Ba than necessary is produced at the beginning of the operation of the cathode. Therefore, the reducing agent is wasted in vain. Further, the excessive amount of traction generated is not only unnecessary for the operation of the cathode, but also may cause adverse effects such as causing electric field radiation if it evaporates from the surface of the cathode and adheres to the surrounding area. Therefore, if the reaction between the oxide and the reducing agent could be controlled, it would be possible to lengthen the electron emission lifetime of the oxide cathode and prevent the negative effects of Ba evaporation, thereby achieving extremely desirable results. It seems possible.

For this purpose, a layer for controlling the reaction between the oxide and the reducing agent may be formed between the oxide and the base metal. The present invention uses a Ca oxide layer having low reactivity with a reducing agent as this reaction control layer. Here, Table 1 shown below shows that W has a weight ratio of 27.5% and W has a weight ratio of 1.5%.
It consists of an alloy of 6% Zr and the rest Ni, and has a thickness of 3
Carbonate of Ba, Sr, and Ca units each on a 0 μm plate material,
These are the results of X-ray diffraction examination of the intermediate layer formed when a carbonate consisting of three elements (Ba, Sr, Ca) was applied and treated in vacuum at 1000° C. for 1 hour.

Note that at this time, only the Zr intermediate layer was detected, and the W intermediate layer was not detected. Therefore, as can be seen from Table 1 above, the reactivity of Zr with Ca oxides is extremely low compared to that with Ba residues and Sr oxides. As a result, the base metal and the normal (Ba-Sr) binary or (B
By forming an oxide layer consisting of Ca alone to an appropriate thickness between the oxide consisting of the ternary a-Sr-Ca), the supply of the reducing agent to the interface between the base metal and the oxide layer can be controlled. This prevents the reducing agent from being wasted unnecessarily. Therefore, the electron radioactivity of the oxide cathode can be maintained for a long time. FIG. 2 is a sectional view of a main part showing an example of an oxide cathode according to the present invention.

In the figure, reference numeral 4 denotes a base body, and this base body 4 is made of an alloy consisting of 27.5% W by weight, 0.4% Zr by weight, and the rest being Ni as the main component. It is constructed from a thick plate. And this base 4
A Ca oxide layer 5 with a thickness of 5 μm is deposited on the upper surface, and the surface of this Ca oxide layer 5 is coated with (Ba-S).
An oxide layer 6 made of the ternary element r-Ca is deposited to constitute an oxide cathode. In the oxide cathode configured in this way, by providing the Ca oxide layer 5 between the base 4 and the oxide layer 6, Zr as a reducing agent in the base 4 is supplied to the oxide layer 6, for example. As a result, the rate of consumption of the reducing agent during operation is controlled, and the electron emissivity of the oxide cathode can be maintained for a long period of time.

Furthermore, when the oxide cathode constructed in this manner was actually mounted on a color cathode ray tube, data on the operating time dependence of the amount of electron radiation as shown in characteristic 1 in FIG. 3 was obtained.

Here, characteristic (2) shows the dependence of the amount of electron emission on operating time in the conventional case, that is, when the Ca oxide layer 5 is not formed. Therefore, as is clear from both characteristics 1 and (2), the oxide cathode according to the present invention has a significantly longer operating time and has a longer life, as shown by characteristic I. In the above embodiment, the case where the thickness of the Ca oxide layer 5 was 5 μm was explained, but the present invention is not limited to this, and if the thickness exceeds 30 pm, Not enough electron radioactivity was obtained, and 1
If the thickness is less than μm, the effect cannot be sufficiently obtained.

Therefore, the optimum thickness is in the range of 1 to 30 μm. In addition, in the above example, the weight ratio of the base was 27.5.
% of W, 0.4% of Zr by weight, and the remaining Ni is used. However, the present invention is not limited to this, and the amounts of W and Zr may be In this case, if the w amount is less than 20 wt%, sufficient electrical resistivity and high temperature strength cannot be ensured, and if it exceeds 30 wt%, the solid solubility limit is exceeded, so heating and cooling are not required. As the process is repeated, W will precipitate.

Therefore, the range of 20 to (9)% is the optimum amount for practical use. Further, if the Zr amount is less than 0.02 Wt%, good initial properties cannot be obtained, and if it exceeds 5 Wt%, a low melting point eutectic is formed, resulting in a decrease in high temperature strength properties. Therefore, the range of 0.02 to 5 Wt% is the optimum amount for practical use. Also, other reducing agents such as M
Even when g, Al, and Sl are used, the same effects as described above can be obtained. Furthermore, some or all of W may be MO
In this case, the MO is 10Wt.
If it is less than 22 Wt%, sufficient electrical resistivity and high-temperature strength cannot be ensured, and if it exceeds 22 Wt%, the solid solubility limit is exceeded and MO will precipitate during repeated heating and cooling. Therefore, the range of 10 to 10% is the optimum amount for practical use. As explained above, in the oxide cathode according to the present invention, the supply of the reducing agent is controlled by forming the Ca oxide layer between the base metal and the electron-emitting alkaline earth metal oxide layer. This suppresses consumption of the reducing agent during operation and maintains the electron radioactivity of the oxide cathode over a long period of time, resulting in extremely excellent effects such as significantly extending its life.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a main part showing an example of a conventional oxide cathode, FIG. 2 is a cross-sectional view of a main part showing an example of an oxide cathode according to the present invention, and FIG. FIG. 3 is a characteristic diagram showing the operation time dependence of the amount of electron radiation. 1... Base, 2... Terminal, 3...
... Alkaline earth metal oxide layer, 4 ... Substrate, 5
...Ca oxide layer, 6... Alkaline earth metal oxide layer.

Claims (1)

[Scope of Claims] 1. An oxide cathode in which an electron-emitting alkaline earth metal oxide layer is formed on a base metal mainly composed of Ni and containing a reducing agent, wherein the base metal and the alkaline earth metal An oxide cathode characterized in that a Ca oxide layer is formed between oxide layers. 2. The oxide cathode according to claim 1, wherein the base metal is an alloy consisting of 20 to 30% W by weight, 0.02 to 5% Zr by weight, and Ni as a main component. 3. The oxide cathode according to claim 1, wherein the base metal is an alloy consisting of Mo in a weight ratio of 10 to 22%, Zr in a weight ratio of 0.02 to 5%, and Ni as a main component. 4 As the base metal, 10 to 22% by weight of Mo, 8% or less of W by weight, and 0.02 to 5% of Zr by weight
The oxide cathode according to claim 1, which uses an alloy consisting of Ni as a main component.