JP2002313248A - Internal magnetic shield and cathode-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal magnetic shield and a cathode-ray tube, that can easily make balancing of the mis-landing quantity due to the earth's magnetism in the tube axis direction and the mis-landing quantity due to the earth's magnetism in the horizontal direction and can suppress the mis-landing quantity all over the screen of the cathode-ray tube, and further, can display proper image having no drift or unevenness of color. SOLUTION: This internal magnetic shield for the cathode-ray tube has a pair of long side walls 1 opposed to each other and a pair of short side walls 2 opposed to each other and has an opening part 3 surrounded by these in the center, and a screen part 5, that is cut out and bent up, is formed on the short sidewalls.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal magnetic shield provided in a cathode ray tube for reducing mislanding of an electron beam due to an external magnetic field such as terrestrial magnetism, and a cathode ray tube having the same.

[0002]

2. Description of the Related Art FIG. 7 is a schematic sectional view of a conventional cathode ray tube for a television or a personal computer monitor. The electron beam 71 emitted from the electron gun 70 is deflected in the vertical and horizontal directions by the deflection yoke 72, and is scanned over the entire screen to reproduce an image. At this time, when an external magnetic field such as terrestrial magnetism acts on the cathode ray tube, the trajectory of the electron beam 71 is distorted, and does not reach a desired position of the phosphor screen 74 on the front panel 73, resulting in mislanding. As a countermeasure, an internal magnetic shield 75 for shielding geomagnetism and the like is provided in the cathode ray tube.

As shown in FIGS. 8 and 9, the internal magnetic shield is arranged in a horizontal direction (X direction in the drawing) and a vertical direction (Y direction in the drawing).
And shields external magnetic fields such as geomagnetism from the tube axis direction (Z direction in the figure). Generally, as shown in FIG.
It has a pair of long side walls 76 facing each other and a pair of short side walls 77 facing each other. An opening 78 is formed in the center. 1
No. 92643, Japanese Unexamined Patent Publication No. 5-159713, etc., an internal magnetic shield in which a substantially V-shaped V-shaped notch 79 is formed, and a short side wall 77 as shown in FIG.
The internal magnetic shield without the V notch 79 was used.

[0004]

As described above, in the internal magnetic shield having no cutout on the short side wall, when an external magnetic field such as terrestrial magnetism acts in the horizontal direction, it is completely shielded and has an effect. Although the landing amount is small, when acting in the tube axis direction, the mislanding amount tends to increase in the peripheral portion of the screen. In particular, a remarkable mislanding has occurred at the screen corner, which is the extreme end.

Further, in an internal magnetic shield in which a notch, for example, a substantially V-shaped notch is formed in a short side wall, the notch is formed when an external magnetic field such as terrestrial magnetism acts in a horizontal direction. Although it was not completely shielded and mislanding occurred, the amount of mislanding when acting in the tube axis direction was smaller than when there was no notch.

As described above, the amount of mislanding caused by geomagnetism in the tube axis direction and the amount of mislanding caused by geomagnetism in the horizontal direction vary greatly depending on the shape of the cutout on the short side wall.
There is a trade-off relationship. It is not preferable that the mislanding amount changes depending on the installation direction of the cathode ray tube,
For this purpose, it is preferable that the two mislanding amounts are substantially the same. However, when trying to balance the two mislanding amounts, it is difficult to keep the mislanding amount small over the entire screen.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. The present invention reduces the amount of mislanding due to geomagnetism in the horizontal direction while suppressing the amount of mislanding caused by geomagnetism in the tube axis direction. It is an object of the present invention to provide an internal magnetic shield capable of reducing the amount of mislanding over the entire screen while maintaining the balance of the above. Still another object of the present invention is to provide a cathode ray tube capable of displaying a good image with little color shift and color unevenness over the entire screen by including the above internal magnetic shield.

[0008]

To achieve the above object, the present invention has the following constitution. The first internal magnetic shield of the present invention has a pair of long side walls facing each other and a pair of short side walls facing each other, and is an internal magnetic shield for a cathode ray tube having an opening surrounded by these at the center. A notch and a bent portion are formed on the short side wall.

A second internal magnetic shield according to the present invention has a pair of long side walls facing each other and a pair of short side walls facing each other, and has a central opening with an opening surrounded by these. The internal magnetic shield is characterized in that a plurality of notched and bent partitions are formed in parallel on the short side wall.

According to the first and second internal magnetic shields, the amount of mislanding due to the terrestrial magnetism is reduced while the amount of mislanding due to the terrestrial magnetism in the tube axis direction is suppressed, and the two mislanding amounts are easily balanced. To reduce the amount of mislanding in the entire screen.

Further, the cathode ray tube of the present invention comprises an envelope comprising a front panel and a funnel, a phosphor screen formed on the inner surface of the front panel, and a color selector disposed opposite to the phosphor screen. A cathode ray tube having an electrode, an electron gun disposed in the funnel, and an internal magnetic shield disposed between the color selection electrode and the electron gun, wherein the internal magnetic shield is the first or the first. Second
Characterized in that it is an internal magnetic shield.

According to such a cathode ray tube, it is possible to provide a cathode ray tube capable of displaying a good image with little color shift and color unevenness over the entire screen regardless of the installation direction.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A cathode ray tube according to an embodiment of the present invention will be described below with reference to FIGS.

(First Embodiment) FIG. 1 is a schematic perspective view of an internal magnetic shield according to a first embodiment of the present invention. The internal magnetic shield according to the first embodiment includes a pair of substantially trapezoidal opposed long side walls 1 and a pair of substantially trapezoidal opposed short side walls 2, which are formed by forming a part of a quadrangular pyramid surface. It is configured to be joined to form.

At the center of the internal magnetic shield, a long side wall 1
And an opening 3 surrounded by the short side wall 2. The internal magnetic shield is arranged in the cathode ray tube such that the narrow side (upper side in FIG. 1) is on the electron gun side and the wide side (lower side in FIG. 1) is on the phosphor screen side. Pass the electron beam. On the short side wall 2, a notch 4 and a notch-folded partition 5 are formed from the end on the electron gun side toward the phosphor screen.

In FIG. 1, the X coordinate direction is the horizontal direction, the Y coordinate direction is the vertical direction, and the Z coordinate direction is the tube axis direction.

FIG. 2 is a side view of the internal magnetic shield of FIG. 1 as viewed from the short side wall 2 side. Notch 4 and partition 5
Is a symmetrical shape in FIG. 2, the partition 5 is substantially triangular, and is notched and bent substantially parallel to the phosphor screen.
The electron beam orbit near the short side wall 2 or the direction substantially parallel to the tube axis.

FIG. 8 shows a conventional internal magnetic shield.
This is an internal magnetic shield having the same outer shape as that of the embodiment, in which all the partition portions 5 are cut out, and the partition portions 5 are eliminated to form one V-shaped notch portion 79 having a substantially V shape.

FIG. 3 shows a mislanding at the corner of the screen due to the terrestrial magnetism in the tube axis direction and the terrestrial magnetism in the horizontal direction when the internal magnetic shield shown in FIGS. 1 and 8 is used in a cathode ray tube having a diagonal size of 25 inches. Indicates the amount.

As shown in FIG. 3, the cathode ray tube using the internal magnetic shield having the partition 5 shown in FIG.
Compared to the conventional cathode ray tube with no internal magnetic shield, the amount of mislanding is almost the same for terrestrial magnetism, and there is a partition for horizontal terrestrial magnetism. It can be seen that the amount of mislanding is smaller in the cathode ray tube using the internal magnetic shield described above.

This is because the geomagnetism in the tube axis direction is attracted to the opening end 6 and the cut side 7 in FIG. 1, and the attracted magnetic field cancels out the force applied to the electron beam in the internal magnetic shield. Since a magnetic field is formed to reduce the amount of mislanding due to geomagnetism in the tube axis direction, FIG.
8 and FIG. 8, since the opening side end 6 has the same shape and the cutting side 7 has substantially the same length, the amount of mislanding can be suppressed to substantially the same.

On the other hand, the geomagnetism in the horizontal direction is not shielded in FIG. 8 because there is no partition 5, which affects the electron beam trajectory and increases the amount of mislanding. However, in FIG. The amount of mislanding is reduced because it is shielded and has little effect on the electron beam trajectory.

By using the above-described internal magnetic shield, the amount of mislanding caused by horizontal geomagnetism is reduced while the amount of mislanding caused by geomagnetism in the tube axis direction is suppressed. In addition, the amount of mislanding can be reduced in the entire screen. It goes without saying that the partition portion 5 may be formed in a substantially square shape.

(Embodiment 2) FIG. 4 is a schematic perspective view of an internal magnetic shield according to Embodiment 2 of the present invention. The internal magnetic shield according to the second embodiment has a pair of substantially trapezoidal opposed long side walls 1 and a pair of substantially trapezoidal opposed short side walls 2, which are formed by forming a part of a quadrangular pyramid surface. It is configured to be joined to form.

At the center of the internal magnetic shield, a long side wall 1
And an opening 3 surrounded by the short side wall 2. The internal magnetic shield is arranged in the cathode ray tube such that the narrow side (upper side in FIG. 4) is on the electron gun side and the wide side (lower side in FIG. 4) is on the phosphor screen side. Pass the electron beam.

On the short side wall 2, a plurality of partitions 8 which are notched and bent from the end on the electron gun side toward the phosphor screen side are formed substantially in parallel with the phosphor screen and in parallel. The direction is substantially parallel to the electron beam orbit near the short side wall 2 or the tube axis. The partition 8 forms a partition 9 and the partition 9 has a substantially V-shape.

FIG. 9 shows a conventional internal magnetic shield.
This is an internal magnetic shield having the same outer shape and no partition 8 on the short side wall 2, that is, no notch.

FIG. 5 shows a mislanding at the corner of the screen due to the terrestrial magnetism in the tube axis direction and the terrestrial magnetism when the internal magnetic shield shown in FIGS. 4 and 9 is used in a cathode ray tube having a diagonal size of 25 inches. Indicates the amount.

As shown in FIG. 5, the cathode ray tube using the internal magnetic shield having the partition 8 shown in FIG. Thus, it can be seen that the mislanding amount is small, and the mislanding amount is substantially the same for the geomagnetism in the horizontal direction.

This is because the terrestrial magnetism in the tube axis direction is attracted to the opening side end 10 and the cut side 11, and the attracted magnetic field forms a demagnetizing field which cancels out the force applied to the electron beam in the internal magnetic shield. In addition, the amount of mislanding caused by geomagnetism in the pipe axis direction is reduced. Also,
In FIG. 4, the geomagnetic field in the horizontal direction is shielded due to the presence of the partition 8, and the influence on the electron beam trajectory is small. Therefore, the mislanding amount is reduced by the absence of the partition 8 in FIG. It was able to be suppressed equally.

By using the internal magnetic shield as described above, the amount of mislanding due to geomagnetism in the horizontal direction is reduced while the amount of mislanding caused by geomagnetism in the tube axis direction is suppressed, and the amount of mislanding can be easily balanced. In addition, the amount of mislanding can be reduced in the entire screen.

(Embodiment 3) FIG. 6 is a schematic sectional view of a color cathode ray tube 20 of the present invention. The front panel 21 and the funnel 22 are integrated to form an envelope 23. An inner surface of the front panel 21 has a substantially rectangular phosphor screen 2.
4 are formed. A color selection electrode (for example, a shadow mask) 25 is provided on the frame 26 so as to be spaced from and opposed to the phosphor screen 24.

The frame 26 is hooked on a leaf spring-like elastic support (not shown) provided on the outer peripheral surface thereof,
It is held on the front panel 21. An electron gun 27 is built in the neck of the funnel 22. On the electron gun 27 side of the frame 26, an internal magnetic shield 30 is mounted on the frame 26. A deflection yoke 29 for deflecting and scanning the electron beam 28 from the electron gun 27 is provided on the outer peripheral surface of the funnel 22.

In the above-described color cathode ray tube 20 of the present invention, the internal magnetic shield described in the first or second embodiment is used as the internal magnetic shield 30.

As described above, such an internal magnetic shield 30 forms a demagnetizing field for canceling the force received by the electron beam 28 on the orbit to the phosphor screen 24 with respect to the terrestrial magnetism in the tube axis direction. In addition, the magnetic field can be shielded against horizontal geomagnetism, so the force received by the electron beam is reduced, mislanding due to distortion of the electron beam trajectory is reduced, and color shift and An image without color unevenness can be displayed.

Further, while the amount of mislanding is reduced over the entire screen, the amount of mislanding due to terrestrial magnetism in the tube axis direction and the amount of mislanding due to terrestrial magnetism can be easily balanced. However, it is possible to always display an image with less color shift and color unevenness.

In the internal magnetic shields according to the first to third embodiments, an example has been described in which the partition portion is provided by being notched and bent. However, the present invention is not limited to such a configuration. May be provided.

Further, in the internal magnetic shields of the first to third embodiments, the cut sides and the ends of the notch and the partition are shown as straight lines, but the present invention is not limited to such a configuration. That is, as long as the object of the present invention can be achieved,
The cut sides and ends of the notch and the partition may be slightly curved.

The material of the internal magnetic shield of the present invention is not particularly limited, and a material having high magnetic permeability, for example, iron or the like can be used as in the conventional case. The manufacturing method can be the same as a conventional method such as pressing.

[0040]

As described above, according to the internal magnetic shield of the present invention, the mislanding amount due to the horizontal geomagnetism is reduced while the mislanding amount due to the geomagnetism in the tube axis direction is suppressed, and both mislandings can be easily performed. It is an object of the present invention to provide an internal magnetic shield that can balance the amounts and reduce the amount of mislanding over the entire screen. Further, the present invention can provide a cathode ray tube capable of displaying a good image with less color shift and color unevenness over the entire screen by including the above-mentioned internal magnetic shield.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of an internal magnetic shield according to a first embodiment of the present invention.

FIG. 2 is a side view of the internal magnetic shield according to the first embodiment of the present invention as viewed from a short side wall side;

FIG. 3 is a comparison diagram of the amount of mislanding due to terrestrial magnetism when using the internal magnetic shield according to the first embodiment of the present invention and a conventional internal magnetic shield

FIG. 4 is a schematic perspective view of an internal magnetic shield according to a second embodiment of the present invention;

FIG. 5 is a comparison diagram of the amount of mislanding caused by terrestrial magnetism when the internal magnetic shield according to the second embodiment of the present invention and another conventional internal magnetic shield are used.

FIG. 6 is a sectional view showing a schematic configuration of a cathode ray tube of the present invention.

FIG. 7 is a schematic sectional view of a conventional cathode ray tube.

FIG. 8 is a schematic perspective view of a conventional internal magnetic shield.

FIG. 9 is a schematic perspective view of another conventional internal magnetic shield.

DESCRIPTION OF SYMBOLS 1 Long side wall 2 Short side wall 3 Opening 4 Notch 5, 8 Partition 6, 10 Opening end 7, 11 Cutting side 9 Partitions group 20 Color cathode ray tube 21 Front panel 22 Funnel 23 Envelope 24 phosphor screen 25 color selection electrode 26 frame 27 electron gun 28 electron beam 29 deflection yoke 30 internal magnetic shield

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Shinichiro Hatta 1006 Kazuma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. F-term (reference) 5C031 CC02

Claims (8)

[Claims] 1. An internal magnetic shield for a cathode ray tube having a pair of opposed long side walls and a pair of opposed short side walls, and having an opening surrounded by these at the center,
The internal magnetic shield, wherein a notched and bent screen portion is formed on the short side wall. 2. The internal magnetic shield according to claim 1, wherein the partition is oriented in a direction substantially parallel to an electron beam orbit or a tube axis near the short side wall. 3. The internal magnetic shield according to claim 1, wherein the partition portion is notched and bent substantially parallel to the phosphor screen. 4. The internal magnetic shield according to claim 1, wherein the partition has a substantially triangular or substantially quadrangular shape. 5. An internal magnetic shield for a cathode ray tube, comprising a pair of opposed long side walls and a pair of opposed short side walls, and having an opening surrounded by these in the center,
An internal magnetic shield, wherein a plurality of notched and bent screen portions are formed in parallel on the short side wall. 6. The internal magnetic shield according to claim 5, wherein the width of the plurality of partitions decreases toward the phosphor screen, and the group of the partitions is substantially V-shaped. 7. An envelope comprising a front panel and a funnel, a phosphor screen formed on an inner surface of the front panel, a color selection electrode arranged to face the phosphor screen, and With an arranged electron gun,
A cathode ray tube having an internal magnetic shield disposed between the color selection electrode and the electron gun, wherein the internal magnetic shield is the internal magnetic shield according to claim 1. 8. An envelope comprising a front panel and a funnel, a phosphor screen formed on the inner surface of the front panel, a color selection electrode arranged to face the phosphor screen, and With an arranged electron gun,
A cathode ray tube having an internal magnetic shield disposed between the color selection electrode and the electron gun, wherein the internal magnetic shield is the internal magnetic shield according to claim 5.