JPH04298939A - Color picture tube - Google Patents

Abstract

PURPOSE:To sharply reduce the mis-landing effect of an electron beam by geomagnetism by using a large inner magnetic shield without generating the mis-landing due to the distortion of the deflection magnetic field. CONSTITUTION:An inclined edge 8 is provided on the periphery of the opening section on the incidence side of the deflected electron beam 6 of an inner magnetic shield 3 so that the portion near the deflected electron beam 6 crosses the tube axis on the fluorescent screen side.

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 with an internal magnetic shield.

0002

2. Description of the Related Art Conventionally, as shown in FIG. 2, in a color picture tube 1, three color phosphors are arranged on a phosphor screen 2, and three polarized beams 6 impinge on the corresponding phosphors to emit light. At this time, the three-deflected electron beams 6 deviate from the preset orbits due to the influence of the earth's magnetism and do not strike the corresponding three-color phosphors accurately, causing so-called mislanding.

For example, in a large color cathode ray tube, when rotated from south to north, the deflected electron beam that should cause a green phosphor to emit light is so affected that it causes it to emit blue light.

[0004] Therefore, an internal magnetic shield 9 has been conventionally provided inside the color picture tube 1 to reduce the influence. The internal magnetic shield 9 is connected to the shadow mask structure 4
It surrounds the 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 so as to largely surround the passage area of the electron beam 6, but since the deflection magnetic area 7 of the deflection yoke 5 extends forward, the incidence of the internal magnetic shield 9 is Disturbance of the deflection magnetic field occurs at the edge 10 of the side opening, causing mislanding. Therefore,
There is a limit to the size of the internal magnetic shield 9.

[0005]

Problems to be Solved by the Invention This conventional internal magnetic shield has a problem in that there is a limit to its size, and it cannot effectively shield the earth's magnetism.

Furthermore, when the internal magnetic shield is enlarged, distortion of the deflection magnetic field occurs due to interference between the deflection magnetic field region and the edge of the entrance side aperture of the internal magnetic shield, resulting in distortion of the deflected electron beam. The orbit partially deviates from the prescribed orbit, resulting in a mislanding, so although the influence of the earth's magnetism was reduced, the overall magnetic shielding effect was low due to the influence of deflection magnetic field distortion.

SUMMARY OF THE INVENTION An object of the present invention is to provide a color picture tube in which the internal magnetic shield can be enlarged and there is no mislanding.

[0008]

[Means for Solving the Problems] The present invention provides a color picture tube equipped with a substantially quadrangular pyramidal internal magnetic shield that surrounds a region through which a deflected electron beam emitted from an electron gun passes.
A slanted edge that intersects with the tube axis on the phosphor screen side is provided in a portion of the inner magnetic shield near the deflected electron beam around the deflected electron beam incident side opening.

[0009]

Embodiments 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 internal magnetic shield 3 of the color picture tube 1 is enlarged, and the deflection magnetic field area 7 of the deflection yoke 5 is spherical with a radius R. The edge 8 of the entrance side aperture of the beam 6 has an inclination angle such that it circumscribes the spherical surface of the deflection magnetic field region 7, and extends to the vicinity of the point where the deflection electron beam 6 and the spherical surface of the deflection magnetic field region 7 intersect, forming the outermost periphery. The edge 8 is extended, and the aperture diameter is large enough to block ineffective electron beams except for the deflected electron beam 6 forming an effective screen.

[0012] As a result, when the conventional internal magnetic shield 9 shown in FIG. Although the mislanding occurred by 25 μm or more, in this example, by using the internal magnetic shield 3, there was no change in the mislanding. Moreover, this internal magnetic shield 3 has a variation of 60% in mislanding from southward to northward due to the influence of geomagnetism.
The internal magnetic shield was so effective that it could be reduced to 18 μm, which is 30%.

In the conventional internal magnetic shield 9 shown in FIG.
Similarly, with the internal magnetic shield 9 sized so that there is no interference between the deflection magnetic field region 7 and the edge 10, the amount of change in mislanding due to the influence of geomagnetism is 36 μm, which is 60%, and in this example, the amount of change was halved. .

Although the embodiment in which the edge 8 is in contact with the spherical deflection magnetic field region 7 has been described above, the effect is the same even if the edge 8 is shaped along the spherical surface of the sphere or has a stepped shape.

[0015]

Effects of the Invention As described above, the present invention provides a structure in which a portion of the internal magnetic shield near the deflected electron beam around the deflected electron beam incident side opening is tilted so as to intersect with the tube axis on the phosphor screen side. By providing the edge, it is possible to use a large internal magnetic shield without causing mislanding due to distortion of the deflection magnetic field, and has the effect of significantly reducing the amount of mislanding of the electron beam due to earth's magnetism.

[Brief explanation of drawings]

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

FIG. 2 is a sectional view of essential parts of an example of a conventional color picture tube equipped with an internal magnetic shield.

[Explanation of symbols] 1 Color picture tube 2. Fluorescent 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)

[Claims] 1. In a color picture tube comprising an internal magnetic shield having a substantially quadrangular pyramid shape that surrounds a region through which a deflected electron beam emitted from an electron gun passes, an opening on the incident side of the deflected electron beam of the internal magnetic shield; A color picture tube characterized in that a peripheral portion close to the deflected electron beam is provided with an edge inclined so as to intersect with the tube axis on the phosphor screen side.