JPS6016056B2 - press cathode - Google Patents

Description

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

As cathodes used in cathode ray tubes and the like, there are generally various types of cathodes, such as oxide cathodes, competitively bonded cathodes, and pressed cathodes, among which there is a Ni pressed cathode, which can operate at relatively low temperatures.

Conventional press cathodes include Ni powder and BaC0
3. Alkaline earth metal carbonate powder such as SrC03 or Ba, Ca, Sr composite carbonate (side CaSr) 3C03 and reducing metal such as W, Ta, Mo, Zr, B, Ti, Si or phantom. A mixture consisting of powder and powder is press-molded under appropriate pressure to attach it to the cathode body. After this attachment, the cathode is assembled into a predetermined position within the cathode ray tube, for example, and the cathode is heated while being evacuated. That is, the cathode is heated to about 1100° C. to thermally decompose the alkali metal, thereby producing matrix 0, Sr◯, Ca0, etc. When thermal activation, aging, etc. are performed, these products further react with the reducing metal to generate Ba, Sr, Ca, etc., which cause emissions. That is, this reaction occurs based on, for example, 2 paddy 03 monopod 1 C02 capture 0 1 W → Ba 3 W 0 6 1 paper a.

Incidentally, the emission characteristics and lifetime of such a press cathode are affected by the type and content of the reducing agent.

For example, considering that the operating temperature of pressed cathodes used in cathode ray tubes is around 800° C., tungsten W is said to be the most suitable reducing agent. However, even when tungsten W is used, the life of the cathode varies depending on its content. Figure 1 shows the change in cathode life (relative value on a logarithmic scale) with respect to the W content (parts by weight) when tungsten W is used as a reducing agent, and the mark 0 indicates the reduction of conventional W alone. This is the lifespan of the cathode when used as an agent. The cathode constituent materials used for the measurements marked with ○ in Figure 1 were Ni powder: 70 parts by weight, and (
It is a mixture of 3 parts by weight of mother CaSr)3C03 powder and W powder (the content is varied).

As can be seen from the circles in FIG. 1, the life of the cathode increases as the W content decreases. However, if the W content is less than 1 part by weight, uniform dispersion becomes difficult, and as a result, when W alone is used as the reducing agent, there is a limit to the life of the cathode. On the other hand, the reason why the life of the cathode is not extended is thought to be due to the unfavorable reaction phenomenon that occurs during the decomposition activation treatment.

That is, when decomposition activation treatment is performed, gas is generated in the initial stage. The following reactions can be considered to occur at this initial stage. For example, regarding Shigeru C03, “BaC03
→Bb○1C02 ...... Wind $
Fist C030W → Spot 3W0613C0... Field' The above arc reaction is necessary because it generates Ba○, which is the emission source.

However, the reaction of the song consumes phosphorus 3W06, which contributes to emissions in a stable form, and is a reaction that we do not want to occur. This reaction [B-] is unique to the pre-cathode and can naturally occur if BaCQ and W are in contact with each other. ) is compared with the equilibrium pressure Pg2 of CO gas generated in the reaction of P seal (
Rib) = 7 x 10-3 (at 10,000 k) P stage (side) = 1 x 1 pi (at 10,000 k'), 'B
) reactions occur preferentially.

Therefore, the reaction of {B' that occurs at the initial stage of this decomposition activity causes the disadvantage that the life of the pre-cathode is shortened. Note that reactions corresponding to the above-mentioned reactions of wind and {B} may occur in CaC03 and SrC03 as well. The present invention was invented to correct the above-mentioned defects, and uses heat-resistant and inert metal powder such as Ni, AaC03, S03, (marrow, Sr, Ca).
A mixture of an alkali metal salt powder such as 3CQ, a reducing metal powder made of W, and a powder made of at least one of cerium Ce or manganese Mn is press-molded. This relates to a press cathode consisting of According to such a configuration, undesirable reactions such as the reaction [B-] that occur in the initial stage of the decomposition activation treatment are suppressed,
Moreover, the generation of alkali metal oxides such as Sr○ and Ca0, which are emission sources, increases, and the life of the cathode becomes considerably longer.For example, when considering the mother CO3, Mn or Ce is added. This makes it easier for the following reaction to occur: BaC030Mn→Ba○1M
n○tenCO.・．． ．．・．． {C'C030Ce → 2Ba○1Ce020CO... Wind And the equilibrium pressure of CO gas generated in the reaction of {C) P Eclipse and the equilibrium pressure of CO gas generated in the reaction of the plate Pg4 has the following value.

P & (Ribs) = 9 x 1 pi (at 1000ok) P & (
) = 1 x 1 pi (at 1000oK) Therefore, from the above equilibrium pressures Pg3 and Pg4, the reactions that occur in the initial stage of decomposition activity are likely to preferentially occur in the reactions [C' and (2)]. , and accordingly the reaction of the legs is suppressed.

Furthermore, since the mother 0, which is an emission source, becomes a product through the reaction '' and the reaction (2), the life of the pre-cathode can be significantly extended in exchange for suppressing the reaction {8}. Note that if the content of Mn or Ce is too large, the life of the cathode will be adversely reduced. This is thought to be because a reaction between Mn or Ce and the mother ○ occurs, and the seam 0, which contributes to emissions, is consumed. Therefore, it is desirable that the amount of Mn or Ce be such that Mn or Ce is consumed in the reaction between the above and the plate. Next, an embodiment in which the present invention is applied to a press cathode for a cathode ray tube will be described with reference to the drawings.

In this example, 7 parts by weight of Ni powder such as nickel carbonyl (average particle size: 5 French) was used as a matrix material, and (Ca, Sr) as an alkali metal carbonate was used.
3 parts by weight of 3C03 powder (average particle size 1 French), 1 part by weight W powder (average particle size 1 to 2 r), which is a reducing metal,
M is a metal active against alkali IJ metal carbonates.
n powder (average particle size 1 French): 1 to 2 parts by weight are mixed.

These mixtures are mixed with an organic solvent such as acetone and milled using a ball mill. Thereafter, the solvent is removed by vacuum evacuation, etc., and after drying with infrared rays, the above-mentioned overflow product is nitrated. It is dispersed in a solvent consisting of cellulose and isoamyl acetate to form a paste, left to stand naturally to solidify, and then granulated to give an average particle size of 10 to 20 μm. Next, the mixed powder obtained in this way was placed in a jig 1 as shown in FIGS. 2 and 3.
It is stuffed into the nickel cap member 2 placed above. This cap portion 2 is approximately cylindrical and has a circular hole 3 provided in its upper portion. The mixture packed in the cap member 2 is then pressed from the direction of the arrow 4 through an indenter 5 with a pressure of 5 to 1' to form a powder compact 6. This compacted powder body 6 is compactly compressed, closes the hole 3, and comes into close contact with the inner surface of the cap member 2, so that it will not fall off. The cap member 2 packed with the powder compact 6 in this way is attached to the cathode sleeve 7 made of Ni, for example, by electric welding or the like as shown in FIG. sleeve 7
A heater 9 is placed inside. Further, the inner surface of the sleeve 7 can be subjected to a blackening treatment if necessary. The lifespan of the press cathode 8 constructed in this manner is indicated by the △ and x marks in FIG.

△ indicates when 2 parts by weight of Mn is added, and x indicates when 1 part by weight of Mn is added. In both cases, an elongation of 20% to 40% is observed compared to the case of W alone (marked as 0). Although the present invention has been described above based on one embodiment, it will be understood that further modifications can be made based on the technical idea of the present invention.
For example, in the above embodiments, NiW alloy powder or W powder whose surface is coated with Ni may be used as the reducing agent. In addition to Nj powder, metal powders having heat resistance, inertness, and conductivity may be used as matrix materials, such as A
u, Pt, etc. can also be used. Furthermore, at least one of Ce and Mn may be added depending on the type of reducing agent.

According to the present invention described above, by adding an appropriate amount of at least one of Mn and Ce active to alkali metal carbonates, the reaction of the above-mentioned Tsukuda or the corresponding above-mentioned list can be achieved. In addition, the reaction between Mn or Ce and the alkali metal carbonate generates the emission source S or Ca, and as a result, the reaction of this type of pre-cathode is suppressed. It is possible to extend the lifespan.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a comparison of the lifespan of a conventional press cathode and that of the present invention, and FIGS. 2 to 4 are cross-sectional views showing one embodiment of the press cathode of the present invention at the top of the process. 2 is a cap member, 3 is a hole, 6 is a powder compact, 7 is a sleeve, and 9 is a heater. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. A heat-resistant and inert metal powder, an alkaline earth metal carbonate powder, a reducing metal powder made of tungsten W, and a powder made of at least one of cerium Ce or manganese Mn. A pressed cathode made by pressing a mixture of and.