JPS62145620A - Impregnated cathode - Google Patents

Abstract

PURPOSE:To realize a long life of an electronic tube, by providing an electronic radiation side of a porous pellet with a mask, which has an opening smaller in size than the porous pellet, in close adhesion so that emitter agent can be prevented from excessively vaporizing and adhering to a grid electrode to avoid characteristic deterioration caused by changes in shape and dimension of electronic beam-limiting hole. CONSTITUTION:Pointed ends of a sleeve are bent inside, and a mask 14 having an opening 14A smaller in diameter than a pellet 13 is inserted between the bent part and the pellet 13. This state makes the mask 14 closely adhere to an electronic radiation side. The sleeve 11, cap 12, and mask 14 are all made of molybdenum. A diameter D2 of the opening 14A in the mask 14 is set up by 1.5 times D1. Hence, the amount of emitter vaporization radiated to the first grid electrode 5 can be suppressed, and focus characteristics can be prevented from deteriorating caused by changes in shape and dimension of the grid electrode due to excessive vaporizing adhesion, to realize a long life of an electronic tube.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an impregnated cathode used in display tubes such as color cathode ray tubes and electron tubes such as image pickup tubes.

[Conventional technology]

FIG. 7 shows an example of the structure of a conventionally used impregnated cathode (Japanese Patent Application Laid-Open No. 60-62034).

In the figure, a cap 3 is attached to the tip of a sleeve 2 that houses a heater 1 inside, and the cap 3 is filled with porous pellets 4 made of a high-melting point metal impregnated with an emitter agent. .

The life of the cathode (so-called emission deterioration) is basically determined by the decrease in the amount of emitter agent, so in order to extend the life, it is sufficient to increase the amount of emitter. The portion of the pellet 4 that has been allowed to dry is enlarged. The area itself where the electron beam is emitted toward the target screen is
Although it is defined by the beam-limiting aperture diameter (so-called electron lens diameter) DI of the first grid electrode 5, pellets are generally used that are twice the beam-limiting aperture diameter and four times or more in terms of area ratio.

[Problem that the invention seeks to solve]

However, when the pellet size is increased in this way, excessive oxides adhere to the electrodes during the manufacturing process of the electron tube or in the early stages of use, changing the shape and dimensions of the electron beam limiting hole and shortening the life of the electron tube. There was a problem in that the long life characteristic of the impregnated cathode could not be fully utilized.

The object of the present invention is to provide an impregnated cathode which suppresses excessive evaporation and deposition of an emitter agent and prevents changes in shape and dimensions of electron beam limiting holes in a grid electrode.

[Means for solving problems]

The above problem is caused by the fact that a mask having an opening smaller than the porous pellet is provided in close contact with the electron emitting side of the porous pellet.

[Effect]

The apertures in the mask define the evaporation of the emitter agent.

〔Example〕

FIG. 1 is a sectional view showing an embodiment of the present invention.

In the same figure, 11 is a sleeve, and the heater 1 is accommodated therein in the same way as shown in FIG. This sleeve 1
A cap 12 is attached to the tip of the pellet 1, and the inside thereof is filled with a porous pellet 13 made of tungsten impregnated with an emitter agent such as BaO.

The above structure is basically the same as the structure shown in FIG. 7, but in this embodiment, the tip of the sleeve 11 is bent inward, and there is a pellet in the bent portion. In this state, the mask 14 is in close contact with the electron emission side of the pellet 13. Sleeve 11, cap 12, and mask 14 are all made of molybdenum.

Such a cathode 20 is constructed by placing a grid electrode group 2 inside the neck of a cathode ray tube pulp 21 as shown in FIG. 2, for example.
The emitted electron beam is deflected by a deflection coil 23 and impinges on a fluorescent surface 24. 5 is the first grid electrode in the grid electrode group 22 that is closest to the cathode.

Here, as mentioned above, conventionally the pellet diameter was more than twice the beam limiting aperture diameter D1 of the first grid electrode 5, whereas in this embodiment the diameter D2 of the aperture 14A of the mask 14 is 1 times the diameter D1 of the first grid electrode 5. It is set to .5 times. This results in
To suppress the amount of emitter evaporation emitted toward the first grid electrode 5, to prevent deterioration of focus characteristics caused by changes in the shape and dimensions of the grid electrode due to excessive evaporation deposition, and to extend the life of the electron tube. I can do it.

The mask 14 needs to be in close contact with the pellet 13.

For example, in Fig. 3, the commonly used values are the beam limiting aperture diameter D1'i of 10.5 μm and the distance d between the cathode and the beam limiting hole of 100 μm. satecon j19
1983 Television Society National Conference 2-8), Mask 1
FIG. 4 shows changes in the emitter evaporation area (ie, the amount of evaporation) of the cathode depending on the position of the mask 14, in other words, the gap G between the cathode (pellet) and the mask, when the opening diameter D2 of No. 4 is 20 μm. Originally, the emitter agent evaporates toward the first grid 5 in a straight line, so when the mask 14 is in close contact with the pellet 20, the evaporation area is the area of a circle with radius a (=10 μm). If there is a gap G between and the cathode, the radius a −1−
This is the area of the circle b. When the gap G=10 μm, the area ratio increases to 1.49, and when G=20 μm, it increases to 2.25, and the life span decreases accordingly.

Therefore, it is necessary for the mask to keep an eye on the pellets, and it is desirable that the gap G between the two be at most 5 μm or less.

In the embodiment described above, the mask 14 is provided separately from the sleeve 11, but this does not necessarily have to be provided separately.
For example, as shown in FIG. 5, the tip of the sleeve 15 may be bent and the bent portion may also be used as a mask. Of course, the diameter of the opening 15A is made smaller than the diameter of the pellet 13 to suppress the amount of evaporation of the emitter agent.

Alternatively, as shown in FIG. 6, a mask may be provided integrally with the pellet 16. For example, the mass layer 17 is formed by placing a ring-shaped N1-Mo alloy plate on the surface of the porous pellet 16 made of tungsten or by applying a powder paste and heating it at 1400 to 1500°C. The pellet 16 can be formed by impregnating the pellet 16 with an emitter agent such as BaO. The exposed portion 18 of the porous pellet 16 corresponds to the opening.

In each of the embodiments described above, the sleeve, cap, and mask are made of molybdenum or an alloy thereof, but tungsten or an alloy thereof may also be used. Unlike film/tar, which is commonly used in the manufacture of sleeves and caps, these films do not adsorb gas and become brittle during the flushing process, so the film thickness can be reduced, and high-definition televisions, etc. This makes it possible to respond to mass production.

〔Effect of the invention〕

As explained above, according to the present invention, by providing a mask having an opening smaller than the porous pellet in close contact with the electron emitting side of the porous pellet, excessive evaporation of the emitter agent can be avoided and It is possible to suppress the adhesion of electron beams, prevent deterioration of characteristics due to changes in the shape and dimensions of the electron beam restriction hole, and extend the life of the electron tube.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing one embodiment of the present invention, Fig. 2 is a configuration diagram showing how it is incorporated into a cathode ray tube, Fig. 3 is a diagram for explaining the degree of adhesion of the mask, and Fig. 4 is the adhesion. 5 and 6 are cross-sectional views showing other embodiments of the present invention, and FIG.
The figure is a sectional view showing a conventional example. 1... Heater, 11... Sleeve, 12.
...Chara 7', 13.16...Porous pellet, 14...Mask, 14A, 15A, 18.
...Opening, 15...Mask and sleeve, 17
...mask layer.

Claims (1)

[Claims] 1. At the tip of the cylindrical sleeve housing the heater inside,
In an impregnated cathode equipped with a cap filled with porous pellets made of a high-melting point metal impregnated with an emitter agent, a mask having an opening smaller than the porous pellet is tightly attached to the electron emission side of the porous pellet. An impregnated cathode characterized in that it is provided as an impregnated cathode. 2. The impregnated cathode according to claim 1, wherein the sleeve, cap, and mask are made of molybdenum, tungsten, or an alloy thereof.