JPS61176028A - Impregnated type cathode - Google Patents

Abstract

PURPOSE:To obtain good electron emission characteristics by raising the bottom of a cup with a narrow recessed groove left behind around the bottom and making the lower surface of a pellet and the inner surface of the cup bottom come in close contact with each other. CONSTITUTION:The bottom of a cup 6 is raised with a narrow recessed groove left behind around the bottom. As a result, the lower surface of a pellet 5 and the inner surface of the bottom of the cup 6 can well come in close contact with each other. In addition, the temperature of the pellet 5 rises up to desired level without unevennesses and with accuracy by the heating of a heating 1. Consequently, good electron emission characteristics can be obtained with uniformity between products.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention provides an impregnated cathode with improved thermal efficiency and uniform electron emission characteristics, which is particularly suitable for cathode ray tubes that require high current density. Regarding.

[Background of the invention]

BACKGROUND ART Impregnated cathodes have been known as electron-emitting cathodes that are suitable for use under severe conditions such as operating at high current densities and being subjected to ion bombardment. Initially, it was mainly used for the cathodes of microwave tubes exposed to so-called back bombardment, but as the demand for high-brightness, high-definition display images for cathode ray tubes increased, it began to be widely used for cathode ray tubes, etc. A trend has emerged.

Figure 2(a) is a side sectional view of a conventional impregnated cathode;
b) is a side cross-sectional view of the main part thereof, in which 1 is the heater, 2
is a disk, 3 is a sleeve, 4 is a cup, and 5 is a pellet. The pellet 5 is usually made of a porous sintered body such as tungsten, and an oxide cathode material (however, it is slightly different from the so-called oxide cathode material that has been widely used, and contains barium or calcium oxides as well as alumina, etc.). As can be inferred from its material and manufacturing method, it is somewhat brittle and has poor machinability, and both end faces are usually polished. This pellet 5 is fitted into a cup 4 made by pressing a metal plate to compensate for the fragility of the pellet 5, and then this cup 4
is fitted and fixed to the end of the sleeve 3, and the bottom of the cup 4 is heated by the heater 1 inserted into the sleeve 3, thereby raising the temperature of the pellet 5 to about 1150°C and emitting electrons. Ta.

However, when the impregnated cathode having the conventional structure shown in FIGS. 2(a) and 2(b) is used, there is a problem that variations in electron emission characteristics are noticeable and the yield is poor.

[Purpose of the invention]

An object of the present invention is to provide an impregnated cathode that has less variation in electron emission characteristics and can be used in mass-produced products such as cathode ray tubes.

[Summary of the invention]

In order to achieve the above object, in the present invention, most of the bottom surface of the cup is raised leaving a slight groove around the periphery, so that the bottom surface of the pellet and the inner surface of the bottom of the cup are brought into close contact.

As a result of the inventor's investigation into the causes of variations in electron emission characteristics of conventional impregnated cathodes, it was found that products with poor electron emission characteristics were found to A gap remains between the lower surface and the bottom inner surface of the cup 4, and for this reason, even when the cup 4 is heated by the heater 1, heat is not sufficiently conducted to the pellet 5, and the temperature of the pellet 5 is insufficiently raised. This is because it was estimated that the electron emission characteristics were poor. Conventionally, in the normal press working method, the connecting part between the cylindrical surface and the bottom of the cup is rounded (this is common sense, but this slight rounding prevents the pellet from being completely flat up to the polished periphery). It seems that the lower surface did not come into close contact with the bottom inner surface of cup 4.

In the present invention, the above-described structure is adopted so that the cup can be easily pressed and the lower surface of the pellet fitted in the cup is in close contact with most of the inner surface of the bottom of the cup. However, if the flatness of the inner surface of the cup bottom is not good after raising the bottom of the cup, further processing must be performed to improve the flatness. Therefore: Although the processing cost of the cup will be higher than before, The price is extremely small compared to the price of other components that make up the cathode ray tube, and compared to the effect of improving the electron emission characteristics of the cathode obtained by improving the cup shape, the increase in cup processing costs is No problem at all.

(Embodiment of the invention) FIG. 1(a) is a side sectional view of an embodiment of the present invention, FIG.
) is a side sectional view of the main part of the same embodiment, and in Figure 0, 6 is a cup whose bottom is raised leaving a slight groove around the bottom according to the present invention, and other symbols are the same as in Figure 2. be. The assembly method and adjustment method are the same as those for the conventional impregnated cathode shown in Fig. 2, but the bottom surface of the pellet 5 and the bottom inner surface of the cup 6 can be brought into close contact, and the heater l
By heating the pellets 5, the temperature of the pellets 5 was reliably raised to the desired temperature without variation, and good electron emission characteristics with uniformity among the products were obtained.

〔Effect of the invention〕

As explained above, according to the present invention, an impregnated cathode with good electron emission characteristics and greatly improved uniformity between products can be obtained with only a slight increase in processing cost.

[Brief explanation of drawings]

FIG. 1(a) is a side sectional view of one embodiment of the present invention, FIG. 1(b)
) is a side sectional view of the main part of the same embodiment, FIG. 2(a) is a side sectional view of a conventional impregnated cathode, and FIG. 2(b) is a side sectional view of the main part thereof. l-7-ta, 2--disk, total--sleeve, 5-
Peleft, 6--Cup according to the present invention. ,(,,::' Figure 1 (b) Figure 2 (L) (b)

Claims (1)

[Claims] A pellet made by impregnating a porous metal sintered body with an oxide cathode material is fitted into a metal plate cup, which is fitted and fixed to the end of the sleeve, and the pellet is heated by a heater inserted into the sleeve. In an impregnated cathode in which electrons are emitted from the pellet by heating through the bottom of the cup, most of the bottom of the cup is raised leaving a slight groove around the periphery, and the bottom surface of the cup is raised to form a line between the bottom surface of the pellet and the inner surface of the bottom of the cup. An impregnated cathode characterized by closely adhering.