JPH039241Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an electron tube equipped with a hot cathode. More specifically, the present invention applies to cathode ray tubes such as picture tubes,
Provides an electrode structure that enables degassing of electrodes at the required high temperature through high-frequency heating, which is essential in the process of manufacturing image pickup tubes and other electron tubes, and that also provides stable cathode emission. It is something to do.

FIG. 1 shows an example of a conventionally known small MS type image pickup tube. In order to perform the exhaust necessary when manufacturing an image pickup tube, which is one of the electron tubes,
Attach the tip tube 1 to a vacuum pump (not shown). Then, while drawing a high vacuum around 10 ^-7 Torr inside the tube, the high-frequency heating coil 2 that heats the electrodes such as the G1 electrode 5 or the G2 electrode 6 sequentially heats the electrodes in the tube to several 100 degrees Celsius. A method is used in which the absorbed gas is sufficiently discharged, and then the cathode (not shown) is heated by a heater incorporated in the cathode to activate the thermionic emission surface.

After the evacuation process is completed, the chip tube 1 is melted and cut, and the getter 3 is deposited on the inner surface of the glass outer tube 4 by high frequency heating. Here, the high-frequency magnetic flux 10 generated from the high-frequency heating coil 2 for heating the electrode spreads at both ends of the coil, so the heating range is not limited to the length l of the high-frequency coil 2; Wide range above and below coil 2 (several mm to several tens of mm)
It extends to.

Therefore, in order to avoid heating unnecessary areas, a heating prevention plate 16 is disposed in close contact with the high-frequency heating coil 2 to control the heating range.

However, in reality, electrodes with various shapes must be placed in separate positions due to electro-optical requirements, which can lead to extreme differences in the heating temperature of each electrode. There are some inconveniences. In particular, since the diameter of the outer tube 4 of an image pickup tube for high-definition television is larger than that of a conventional tube, the difference in the degree of heating becomes significant. In this manner, in the conventional heating and exhaust treatment, the maximum heating temperature of the electrode is limited by the electrode that is most easily heated, making it impossible to increase the baking temperature of other electrodes. As a result, sufficient gas release from the electrode becomes impossible or takes a long time, making it impossible or insufficient to activate the cathode to ensure long-term stable emission. .

The purpose of the present invention is to provide an electron tube having such an electrode arrangement or structure that enables uniform heating of each electrode and ensures stable and highly efficient cathode emission. It's about doing.

In order to achieve this purpose, the present invention provides an electron tube having a plurality of electrodes each having a central opening through which an electron beam passes.
The structure is such that a slit is provided in each electrode.

Hereinafter, the present invention will be described in detail with reference to the drawings.

Here, an embodiment will be described in which the present invention is applied to the MS type image pickup tube shown in the first figure.

In Figure 1, 5 is the G1 electrode, 6 is the G2 electrode,
12 is a deflectron electrode made of a metal thin film deposited on the inner surface of the outer tube 4; 13 is a reflector electrode with a central opening whose main purpose is to absorb the electron beam returning from the target; 14 is an electron gun block. (including G1 electrode 5 and G2 electrode 6) and outer tube 4
This is a holder made of insulating material for aligning and installing.

As the reflector electrode 13, a disk-shaped electrode with a diameter approximately equal to the inner diameter d ₄ of the outer tube 4 is used due to electro-optical requirements, but the other electrodes are cylindrical electrodes with a diameter of about d ₄ /2 or A cylindrical electrode with a lid on one end is used.

The plate thickness of these electrodes is approximately equal for all electrodes, for example, approximately 0.2 mm in consideration of uniform heating.

Generally, the heating range and heating temperature are controlled by the length l, number of turns, diameter d ₁ , diameter d ₅ of the winding of the high-frequency heating coil 2, and the thickness l ₁ , inner diameter d ₆ , and material of the heating prevention plate 16. This is done by appropriately selecting the following. However, according to experiments conducted by the applicant, if there is a difference of two or more times in the diameter of the image pickup tube electrodes, it is impossible to maintain a heating balance between the larger diameter electrode and the smaller diameter electrode. This was confirmed.

For example, in a high-resolution 1-inch MS type image pickup tube for high-definition television, the diameter of the reflector electrode 13 is
The diameter of the other electrode group is 8 mm, but in this case, there is a temperature of about 200°C between the reflector electrode and the other electrode group.
A temperature difference of .

In order to eliminate such drawbacks, in one embodiment of the present invention, as shown in FIGS.
3) In addition to providing a central opening for the electron beam to pass through, a slit 25 is newly provided. That is, FIG. 2A shows an embodiment in which the reflecting plate electrode 13 is provided with a central opening and one slit connected to the central opening. Further, FIG. 2B shows another embodiment in which the same electrode is provided with a plurality of independent slits in addition to the central opening, and the slits are cut out to the edge of the electrode 13 to form an open structure.

Here, the optimum shape, size, number, etc. of the slits are selected as necessary so as to obtain the desired baking temperature.

When the reflector electrode 13 is provided with a slit other than the central opening in this manner, eddy currents generated due to the high frequency magnetic field are prevented, so that over-burning of the electrode due to generation of Joule heat can be prevented. As a result, even for small image pickup tubes or other electron tubes with electrode structures that are forced to undergo abnormal heating during heating and exhaust due to electro-optical requirements, high-frequency heating conditions are required during heating and exhausting. It becomes possible to vent gas from the electrodes in alignment. Therefore, activation of the cathode can be performed under ideal conditions, and long-term stable emission of the cathode can be easily ensured.

For example, the ultra-high resolution BI (Barium
When an electron gun using a cathode (Impregnated) is incorporated, and the diameter of the reflector electrode 13 is 23 mm and the diameter of the electron gun part (G1 electrode 5 and G2 electrode 6) is about 8 mm, the slit 25 according to the present invention If not added to the reflector electrode 13, the reflector electrode
Even when heated to around 700°C, this electron gun could only be heated to below 500°C. As a result, the desired cathode emission could only be secured to a fraction of the design value.

However, by providing the slits shown in FIG. 2A in the reflector electrode 13, the entire electrode can be heated to approximately the desired temperature of 700°C, and the design value of the emission (i.e., several A/cm ² above) were able to be stably secured.

As is clear from the above explanation, the present invention is applicable not only to MS type or MM type image pickup tubes.
Of course, it is widely applicable to all other electron tubes having electrodes of different sizes.

As explained above, according to the present invention, it is possible to prevent heat generation due to eddy current by providing a slit in an electrode having a central opening, so that electrodes having various shapes or arrangements can be heated at a uniform temperature. This makes it possible to obtain good emission characteristics of the cathode.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional configuration diagram showing a conventionally known small MS type image pickup tube, and FIGS. 2A and 2B are plan views each showing a disc-shaped electrode with a slit according to an embodiment of the present invention. 1...Chip tube, 2...High frequency heating coil,
3...Getter, 4...Outer tube, 5...G1 electrode, 6
...G2 electrode, 9...Indium ring, 10...
... Lines of magnetic force, 12 ... Deflectron, 13 ... Reflection plate electrode, 14 ... Holder, 15 ... Stem, 16
... Heating prevention plate, 17 ... Space between stem and electron gun, 18 ... Stem pin, 25 ... Slit.

Claims (1)

[Claims for Utility Model Registration] 1. An electron gun block that emits an electron beam toward a predetermined portion of a vacuum envelope tube, a target provided at a predetermined portion of the envelope tube, and a target from the electron gun block. a disk-shaped or cylindrical electrode having a central opening for passing an electron beam reaching the tube axis and having slits radial to the tube axis; An electron tube characterized in that the slit reduces eddy currents that occur when electricity is applied to a high-frequency heating coil for heating. 2. The electron tube according to claim 1, which is a registered utility model, characterized in that the central opening provided in the electrode is connected to the slit. 3. The slit provided in the electrode,
The electron tube according to claim 1, which has been registered as a utility model, is characterized in that it has an open structure extending to the outer periphery of the electrode.