JPH06103916A - Electron gun for cathode-ray tube - Google Patents

Abstract

PURPOSE:To stabilize the electric field near a shield cup and to reduce the influence to the electron beams, by preventing a temperature rise owing to the magnetic field of a deflection yoke, and a deterioration of the withstand voltage owing to the rounding-in of the flash metal of a getter. CONSTITUTION:A shield cup 20 is installed to a final acceleration electrode 2, an elastic material piece 8 pressure-contacted to a conductive film formed to the inner surface of a funnel is installed to the shield cup 20, while the shield cup 20 leads the anode high voltage fed through the conductive film and the elastic material piece to the final acceleration electrode 2. In an electron gun for cathode-ray tube which forms a co-cylindrical structure consisting of an inner cylinder 24 to which the shield cup 20 is opened, and a peripheral cylinder 25 surrounding the inner cylinder 24, the shield cup 20 is made by making the height of the inner cylinder 24 higher than the height of the peripheral cylinder 25.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode ray tube electron gun, and more particularly to a cathode ray tube electron gun having a shield cup attached to a final accelerating electrode.

[0002]

2. Description of the Related Art Generally, in a cathode ray tube, a phosphor screen is formed on an inner surface of a face portion of an envelope, and an electron gun is sealed in a funnel neck which is integrated with the face portion of the phosphor screen. An electron beam emitted from the device is deflected by a magnetic field generated by a deflection yoke mounted outside the funnel, and the phosphor screen is scanned to form an image reproducing structure.

The electron gun is usually a cathode, an electrode for controlling the emission of electrons from the cathode and for focusing the emitted electrons to form an electron beam, and an electrode for accelerating and focusing the electron beam on a phosphor screen. Etc. is composed of a plurality of electrodes. In such an electron gun, as shown in FIG. 4, the shield cup 3 is attached to the final accelerating electrode 2 located on the phosphor screen 1 side, and the funnel 4 is attached.
Of the final accelerating electrode through the conductive film 7 formed by coating from the inner surface of the large-diameter portion 5 to the inner surface of the adjacent portion of the neck 6 and a plurality of elastic metal pieces 8 attached to the conductive film 7 and pressed against the conductive film 7. 2 has an electron gun which is designed to apply a high voltage to the anode. Reference numeral 9 is a deflection yoke mounted outside the boundary between the large-diameter portion 5 of the funnel 4 and the neck 6.

Normally, the shield cup 3 is shown in FIG.
As shown in FIG. 5, the cylindrical portion 11a forming the opening 10 has a disc-shaped flange portion 12 at one end thereof. Reference numeral 13 is a flash getter attached to the shield cup 3.

In such a shield cup 3, as much as possible, the back metal of the getter 13 prevents backflow of the flash metal into the electron lens forming portion, and in terms of withstand voltage, a neck on the side of the low voltage electrode where no conductive film is applied is formed. In order to prevent the disturbance of the electric field near the shield cup 3 due to the wraparound of the electric potential, as shown in FIG. 5B, the inner cylindrical portion 11b forming the opening 10 and the outer peripheral cylindrical portion 14 surrounding the inner cylindrical portion 11b are formed. There is a co-cylindrical structure consisting of and. The height of the outer peripheral cylindrical portion 14 (height of the side wall) is equal to that of the inner cylindrical portion 11b.
Is formed higher than the height (height of the side wall) of.

[0006]

As described above, a shield cup is attached to the final accelerating electrode, which is conventionally located on the phosphor screen side, and a flash metal is attached to the electron lens forming portion of the electron gun by backflushing the getter as much as possible. In order to prevent wraparound and to prevent disturbance of the electric field near the shield cup due to the wrap-around of the neck potential on the side of the low-voltage electrode on which the conductive film for withstanding voltage is not applied, the shield cup is placed on the inner cylindrical part and this inner cylindrical part. A co-cylindrical structure consisting of an outer peripheral cylindrical portion surrounding the outer peripheral cylindrical portion, and the height of the side wall of the outer peripheral cylindrical portion is
There is one that is higher than the height of the side wall of the inner cylindrical portion.

However, when the shield cup has the above structure, for example, Hi UPF (High Uni Potential Focus)
In a projection tube equipped with a scanning electron gun, the shield cup is placed close to the deflection yoke in order to shorten the overall length, so an eddy current that cancels the change in the magnetic field generated by the deflection yoke occurs in this shield cup, and the temperature rises. Cause For example, when the horizontal deflection frequency is 31.5 kHz, the shield cup heats up to about 100 ° C. due to the eddy current.

Generally, the size of the eddy current is proportional to the area of the object through which the eddy current flows. Therefore, the eddy current generated in the shield cup can be reduced by reducing the area of the shield cup. It becomes impossible to reduce the influence of the backflush of the getter and the neck potential of the portion where the conductive film is not applied.

The present invention has been made in view of the above problems, prevents an increase in temperature due to the magnetic field generated by the deflection yoke, and is the original purpose of the shield cup, the electron lens of the electron gun by the backflush of the getter. The purpose is to prevent the flash metal from flowing into the formation part and to stabilize the electric field near the shield cup.

[0010]

An elastic metal piece attached to a final accelerating electrode and pressed against a conductive film formed on the inner surface of a funnel is attached, and an anode height supplied through the conductive film and the elastic metal piece is increased. In a cathode ray tube electron gun having a co-cylindrical structure having a shield cup for guiding a voltage to the final accelerating electrode, the shield cup forming an opening and an outer peripheral cylinder surrounding the inner cylinder. The height of the inner cylindrical portion of the shield cup was made higher than the height of the outer peripheral cylindrical portion.

[0011]

As described above, when the height of the inner cylindrical portion of the shield cup attached to the final accelerating electrode is made higher than that of the outer peripheral cylindrical portion, the conventional outer peripheral cylindrical portion has a height higher than that of the inner cylindrical portion. Compared with a high shield cup, the temperature rise can be reduced by reducing the eddy current generated by the magnetic field of the deflection yoke. In addition, the shield metal's original purpose, which is the original purpose of the getter, is to reduce the amount of flash metal entangled in the electron lens forming part of the electron gun, and the vicinity of the shield cup due to the entanglement of the neck potential at the low voltage electrode position. It can be stabilized by eliminating the disturbance of the electric field.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described based on embodiments with reference to the drawings.

FIG. 1 shows the structure of the essential part of an electron gun as one embodiment of the present invention, FIG. 2 shows its arrangement, and FIG. 3 shows the structure of a shield cup.

This electron gun accelerates and focuses the cathode, an electrode that controls the emission of electrons from the cathode and focuses the emitted electrons to form an electron beam, and the electron beam on the phosphor screen 1. It has a plurality of electrodes such as electrodes forming an electron lens, and a shield cup 20 attached to the final accelerating electrode 2 located on the phosphor screen 1 side, and the cathode and the plurality of electrodes form a pair. It is fixed integrally by an insulating support 21.

In this electron gun, the shield cup 20 is sealed inside the neck 6 by approaching the deflection yoke 9 mounted outside the boundary between the large-diameter portion 5 of the funnel 4 and the neck 6. There is.

The shield cup 20 has a co-cylindrical structure composed of an inner cylindrical portion 24 forming an opening 23 and an outer peripheral cylindrical portion 25 surrounding the inner cylindrical portion 24. Then, a plurality of elastic metal pieces 8 that are pressed against the conductive film 7 formed on the outer peripheral cylindrical portion 25 from the inner surface of the large-diameter portion 5 of the funnel 4 to the inner surface of the adjacent portion of the neck 6 where the electron gun is arranged are pressed.
, And a flash getter 13 are attached.

Further, in the electron gun of this example, in the shield cup 20, the height of the inner cylindrical portion 24 (the height of the side wall) di is higher than the height of the outer peripheral cylindrical portion 25 (the height of the side wall) do. Moreover, the height di of the inner cylindrical portion 24 is 50 to 90% of the diameter φi of the inner cylindrical portion 24, and the height do of the outer peripheral cylindrical portion 25 is the outer diameter φo of the outer cylindrical portion 25. 10
It is formed to a size of ~ 30%.

Specifically, in the case of a Hi-UPF type electron gun for a cathode ray tube having a neck inner diameter of 36.5 mm, the shield cup 20 has a diameter φi of the inner cylindrical portion 24 of 8.5 mm and a height of the inner cylindrical portion 24 is high. Di = 6.4 mm, outer diameter of outer peripheral cylindrical portion 25 φo
= 29 mm and the height of the outer peripheral cylindrical portion 25 is do = 4 mm.

By the way, as described above, the shield cup 20
With this configuration, it is possible to reduce the temperature rise due to the magnetic field generated by the deflection yoke 9, reduce the entanglement of the flash metal into the electron lens forming portion due to the backflush of the getter, and reduce the conductivity of the low voltage electrode of the electron gun. Membrane 7
It is possible to stabilize the electric field in the vicinity of the shield cup 20 due to the neck potential wraparound in the uncoated portion.

That is, the height of the inner cylindrical portion 24 is made higher than the height of the outer peripheral cylindrical portion 25, and the height di of the inner cylindrical portion 24 is set to 50 to 90% of its diameter φi.
It is possible to reduce the inflow of flash metal into the electron lens forming portion of the electron gun due to the backflash of the getter, which is the original purpose of the shield cup, and to prevent the deterioration of withstand voltage characteristics due to the inflow of flash metal. Further, the height do of the outer peripheral cylindrical portion 25 is set to the outer diameter φo of 10 to 30%, so that the neck potential of the uncoated portion of the conductive film 7 where the low voltage electrode of the electron gun is located is shunted. Can be reduced to stabilize the electric field in the vicinity of the shield cup 20 and reduce the influence on the electron beam. Moreover, since the height of the outer peripheral cylindrical portion located close to the deflection yoke 9 can be made lower than that of the conventional shield cup, the eddy current generated by the magnetic field of the deflection yoke 9 can be reduced, and the temperature rise can be reduced. Is obtained.

[0021]

When the height of the inner cylindrical portion of the shield cup attached to the final acceleration electrode is made higher than the height of the outer peripheral cylindrical portion, the conventional outer peripheral cylindrical portion has a height higher than that of the inner cylindrical portion. Compared to the cup, the eddy current generated by the magnetic field generated by the deflection yoke can be reduced, and the temperature rise can be reduced. Moreover, by reducing the amount of flash metal entangled in the electron lens forming part of the electron gun due to the backflush of the getter, which is the original purpose of the shield cup,
It is possible to prevent the breakdown voltage characteristics from deteriorating, reduce the neck potential shunt in the uncoated portion of the conductive film where the low voltage electrode of the electron gun is located, and stabilize the electric field near the shield cup. The effect that the influence on the electron beam can be reduced can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a main configuration of an electron gun which is an embodiment of the present invention.

FIG. 2 is a diagram showing an arrangement state of the electron gun.

FIG. 3 is a diagram showing a structure of a shield cup of the electron gun.

FIG. 4 is a diagram showing a configuration of main parts of a conventional electron gun and an arrangement state thereof.

5 (a) and 5 (b) are views showing structures of different shield cups of a conventional electron gun, respectively.

[Explanation of symbols]

 2 ... Final accelerating electrode 4 ... Funnel 6 ... Neck 8 ... Elastic metal piece 9 ... Deflection yoke 13 ... Flash getter 20 ... Shield cup 23 ... Opening 24 ... Inner cylinder 25 ... Outer cylinder

Claims (1)

[Claims] 1. An elastic metal piece attached to the final accelerating electrode and in pressure contact with a conductive film formed on the inner surface of a funnel, and the anode high voltage supplied through the conductive film and the elastic metal piece is applied to the anode high voltage. An electron gun for a cathode ray tube having a co-cylindrical structure having a shield cup leading to a final accelerating electrode, the shield cup forming an opening and an outer peripheral cylinder surrounding the inner cylinder. Is an electron gun for a cathode ray tube, wherein a height of the inner cylindrical portion is formed to be higher than a height of the outer peripheral cylindrical portion.