JP2701566B2 - Color picture tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color picture tube, and more particularly to a color picture tube having an internal magnetic shield.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 2, in a color picture tube 1, a three-color phosphor is arranged on a phosphor screen 2, and a three-deflected beam 6 shines on a corresponding phosphor to emit light. At this time, the three-deflected electron beam 6 deviates from a preset trajectory due to the influence of terrestrial magnetism, does not accurately strike the corresponding three-color phosphor, and causes so-called mislanding.

For example, in the case of a large color cathode ray tube, when rotating from south to north, the deflection electron beam that should emit the green phosphor is so affected as to emit blue light.

Therefore, an internal magnetic shield 9 is conventionally provided inside the color picture tube 1 to reduce the influence thereof. The inner magnetic shield 9 is provided for the shadow mask structure 4.
And surrounds a passage area of the deflected electron beam 6 deflected by the deflection yoke 5. In this case, it is desirable to make the internal magnetic shield 9 as large as possible to largely surround the passage area of the electron beam 6, but since the deflecting magnetic area 7 of the deflecting yoke 5 extends forward, the incidence of the internal magnetic shield 9 is increased. Distortion of the deflecting magnetic field occurs at the edge 10 of the side opening, which causes mislanding. Therefore,
The size of the internal magnetic shield 9 has a limit.

[0005]

However, the conventional internal magnetic shield has a problem in that the size of the internal magnetic shield is limited, and it is not possible to effectively shield the terrestrial magnetism.

When the size of the internal magnetic shield is increased, deflection magnetic field distortion occurs due to interference between the deflecting magnetic field region and the edge of the entrance opening of the internal magnetic shield. Since the orbit partially deviates from the predetermined orbit to cause a mislanding, the influence of the terrestrial magnetism is reduced, but the effect of the deflection magnetic field is reduced, so that the magnetic shield effect is generally small.

SUMMARY OF THE INVENTION An object of the present invention is to provide a color picture tube capable of increasing the size of an internal magnetic shield and free from mislanding.

In a color picture tube provided with a substantially quadrangular pyramid-shaped internal magnetic shield surrounding a region through which a deflected electron beam emitted from an electron gun passes, in a color picture tube, the periphery of the deflected electron beam entrance side opening of the internal magnetic shield is provided. An extended line intersects the portion near the deflection electron beam on the tube axis on the phosphor screen side .
A color picture tube characterized by having a sloping edge along the direction of the color picture tube.

[0009]

Next, embodiments of the present invention will be described with reference to the drawings.

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

As shown in FIG. 1, the size of the internal magnetic shield 3 of the color picture tube 1 is large, and the deflection magnetic field region 7 of the deflection yoke 5 is spherical with a radius R. The edge 8 of the entrance opening of the beam 6 has an inclination angle such that the edge 8 circumscribes the spherical surface of the deflecting magnetic field region 7, and extends to the vicinity of the intersection of the deflecting electron beam 6 forming the outermost periphery and the spherical surface of the deflecting magnetic field region 7. The edge 8 extends and has an opening diameter enough to block an invalid electron beam except for the deflection electron beam 6 forming an effective screen.

As a result, when the conventional internal magnetic shield 9 shown in FIG. 2 is enlarged, interference between the edge 10 and the deflecting magnetic field region 7 of the deflecting yoke 5 causes an error at the corner of the screen. Although the landing was 25 μm or more, in the present embodiment, the use of the internal magnetic shield 3 did not change the mislanding. In addition, the inner magnetic shield 3 has a mislanding variation of 60 from south to north due to the influence of geomagnetism.
In the case of μm, the internal magnetic shield was as effective as 30% of 18 μm.

The conventional internal magnetic shield 9 shown in FIG.
Similarly, in the internal magnetic shield 9 having a size with no interference between the deflecting magnetic field region 7 and the edge 10, the variation of the mislanding due to the influence of the terrestrial magnetism is 60%, that is, 36 μm, and in this embodiment, the variation is reduced by half. .

Although the embodiment in which the edge 8 is in contact with the spherical deflecting magnetic field region 7 has been described above, the same effect can be obtained even if the edge 8 has a shape along a spherical surface or a step.

[0015]

As described above, according to the present invention, the portion of the internal magnetic shield which is close to the deflection electron beam around the deflection electron beam incident side opening is inclined so as to intersect the tube axis on the fluorescent screen side. By providing the edge, it is possible to use a large internal magnetic shield without causing mislanding due to the distortion of the deflection magnetic field, and this has the effect of significantly reducing the amount of mislanding of the electron beam due to terrestrial magnetism.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view of a main part of an example of a conventional color picture tube provided with an internal magnetic shield.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 color picture tube 2 phosphor screen 3, 9 internal magnetic shield 4 shadow mask structure 5 deflection yoke 6 electron beam 7 deflection magnetic field area 8, 10 edge

Claims (1)

(57) [Claims] 1. A color picture tube provided with a substantially quadrangular pyramid-shaped internal magnetic shield surrounding a region through which a deflected electron beam emitted from an electron gun passes, wherein the deflected electron beam incident side opening of the internal magnetic shield is provided. An extension line intersects the part near the deflected electron beam on the tube axis on the phosphor screen side
A color picture tube characterized by having a sloping edge along the direction in which the color picture is taken.