JP2002279912A - Picture tube device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a landing movement as a factor in a color shift by suppressing leakage, at a corner portion in a magnetic shield of a transverse magnetic field entering a narrow side face of the magnetic shield. SOLUTION: At least one transverse slit is formed near the bottom of the magnetic shield for increasing the magnetic resistance of the portion.

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 used for televisions, computer displays, etc., and more particularly to a picture tube using a tension mask.

[0002]

2. Description of the Related Art In a color picture tube, as shown in FIG. 1, a glass bulb comprising a panel 6 and a funnel 7 is evacuated, and a shadow mask 3, a frame 2 supporting the shadow mask 3, an electron beam An electron gun 9 for emitting the electron beam 5 and focusing by an electric field lens is enclosed therein, and a deflection yoke 8 for deflecting the electron beam 5 is mounted so as to surround the funnel. The magnetic shield 1 is mounted on the frame 2, and is used to solve the problem that the influence of the terrestrial magnetism on the electron beam changes depending on the area where the picture tube is used and the direction in which the screen faces, and the landing characteristics change. It plays a role of shielding the light and reducing the influence on the electron beam. The following inventions have been proposed in order to improve the geomagnetic properties by the magnetic shield. For example, in Japanese Patent Application Laid-Open No. 54-25157, as shown in FIG. 9, the long side wall surface 22 of the magnetic shield is provided with an opening window 30 having a length in the side wall direction of １ ／ or more of the length of the side wall portion. Means for suppressing the effect of the residual magnetic field on the magnetic shield after the degaussing by the degaussing coil on the electron beam is described. As shown in FIG. 10, Japanese Patent Publication No. 63-67307 discloses that the width of the magnetic shield extends in the direction perpendicular to the tube axis on the long side wall surface 22 of the magnetic shield in the direction corresponding to the traveling direction of the electron beam. There is a description of the invention that has at least two openings 31 that are not more than one-third of the existing length, and is configured to be symmetric with respect to the central axis of the side wall portion. Thus, when a magnetic field in the lateral direction is incident from the short side wall surface 21, the upper and lower barrel type magnetic field inside the magnetic shield is suppressed, and the influence on landing is reduced.

[0003]

However, in FIG. 5, which shows a cross section of a magnetic shield perpendicular to the tube axis,
When a horizontal magnetic field (hereinafter referred to as a lateral magnetic field) 24 is incident on the short side wall surface 21 of the magnetic shield, a leakage magnetic field that cannot be particularly shielded at a corner of the magnetic shield is large, and the Y direction caused by the leakage magnetic field is large. It has been found in our experiments that the magnetic field By generates an asymmetric pattern in which the electron beam moves in the upper part inward and the lower part outward in the upper corner of the screen as shown in FIG. In a TV tube, the phosphor is vertically formed in a stripe shape, so that the vertical beam movement does not cause color shift, but the horizontal beam movement causes a horizontal landing movement and the image quality due to the color shift. The remarkable deterioration of occurs. The present invention provides means for solving the problems in consideration of the above problems.

[0004]

At least one horizontally elongated slit hole is provided on the short side wall surface of the magnetic shield at a height near the bottom surface of the magnetic shield in contact with the frame. Further, the position where the slit is provided is such that the height of the shield from the bottom surface of the magnetic shield in the tube axis direction is h, and in a direction perpendicular to the tube axis on the side surface, from the central axis of the short side surface to the shield end surface. In the height direction, the distance from the bottom of the magnetic shield is 0.
It is preferable that the distance from the center axis of the short side surface is 0.4 w or more in a range of 3 h. It is more effective to combine with a tension mask.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be specifically described below with reference to the drawings. FIG. 3 shows an embodiment of the magnetic shield 1 according to the present invention. Long side wall 2
2, a short side wall surface 21, and a protruding portion 24 for shielding a magnetic field from entering the gap portion 10 between the frame and the mask portion of the tension type shadow mask shown in FIG. A plurality of horizontally long slit holes 23 are provided in the short side wall surface 21. FIG. 4 is a front view of the short side wall surface 21 of the magnetic shield. In the present embodiment, 3
In a 6-inch 120 ° deflection angle magnetic shield for a TV picture tube having an aspect ratio of 16: 9, two sets of horizontally long slit holes having a width of 5 mm and a length of 10 mm are arranged at a distance of 20 mm on the line of the bottom surface 26 of the magnetic shield. ing. As a result, in the portion where the slit is provided, the magnetic resistance is increased, so that the flow of magnetism becomes difficult, and the leakage magnetic field 25 caused by the transverse magnetic field shown in FIG. 5 is also reduced. Therefore, the magnetic field By in the Y direction generated by the leakage magnetic field is reduced, and accordingly, the beam movement and the landing movement amount in FIG. 6 are also reduced. FIG. 7 compares By with and without the slit. The horizontal axis represents the distance in the shield height direction with the position of the bottom surface of the magnetic shield taken as 0, and the above-mentioned By when a horizontal magnetic field of 0.5 G is applied is plotted on the vertical axis. Obviously, it can be seen that by providing the slit holes, By is reduced. In FIG. 8, similarly, the horizontal axis has a slit (△ point) and no slit (ス リ ッ ト
2), and the measured values of the landing movement amount are plotted on the vertical axis. In consideration of the variation, actual measurements were respectively performed with three TV tubes, and the averaged values were connected together by arrows. From this figure, it can be seen that the provision of the slit 23 reduces the amount of landing movement and makes color shift less likely to occur. As described above, it was confirmed by experiments that the problem of color misregistration can be improved by providing the slits 23. In this embodiment, the slit hole 2
3 is arranged at the position of the bottom surface of the magnetic shield, but is not necessarily limited to this. In order to define the position of the slit hole, in FIG. 4, the distance w between the center axis 28 of the side surface and the horizontal end portion 29 of the magnetic shield, the magnetic shield bottom surface 26 where the magnetic shield contacts the frame, and the neck of the magnetic shield are shown. The height h in the tube axis direction between the side end surface 27 is defined. At this time, the position where the slit hole is provided is within a range of 0.3 h in the vertical direction with the magnetic shield bottom surface 26 as the center in the height direction, and at a distance of 0.
Experiments have also confirmed that the above effect can be obtained if the position is 4 w or more. The slit hole may be a single large oblong hole, but it is preferable to divide the slit hole into a plurality of slit holes in terms of the strength of the magnetic shield. In the above range, the slit holes may be arranged in a plurality of rows. Although it is desirable to arrange the slit holes 23 symmetrically with respect to the axis 28, in some cases, the hole shape or arrangement may be changed asymmetrically to remove the asymmetric component of the geomagnetic characteristics.

In this embodiment, the case where the short side surface of the magnetic shield is a single plane has been described. However, the side surface may be bent in the middle or have a step. In a tension mask having a thin mask plate and a gap between the frame portion and the mask, the problem to be solved by the present invention is remarkably exhibited. Therefore, the effect is more remarkable in combination with the tension mask.

[0007]

According to the present invention, the leakage magnetic field at the corner of the short side wall, which is generated when a horizontal magnetic field (lateral magnetic field) is incident on the short side wall of the magnetic shield, is reduced, and the color due to the landing movement is reduced. The displacement can be suppressed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a color picture tube using a magnetic shield of the present invention.

FIG. 2 is a diagram showing a structure of a tension type shadow mask.

FIG. 3 is a diagram showing a magnetic shield of the present invention.

FIG. 4 is a diagram showing a short side wall surface of the magnetic shield of the present invention.

FIG. 5 is a diagram showing a leakage magnetic field at a corner inside a magnetic shield;

FIG. 6 is a diagram showing movement of an electron beam viewed from a screen due to a leakage magnetic field inside a magnetic shield.

FIG. 7 is a diagram showing the effect of reducing the leakage magnetic field By when the present invention is used.

FIG. 8 is a view showing an effect of reducing a landing movement amount due to a lateral magnetic field when the present invention is used.

FIG. 9 is a diagram showing a first example of a conventional magnetic shield.

FIG. 10 is a diagram showing a second example of a conventional magnetic shield.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 magnetic shield 2 frame 3 shadow mask 4 phosphor screen 5 electron beam 6 panel 7 funnel 8 deflection yoke 9 electron gun 10 gap between frame and mask on short side 11 slot-shaped electron beam passage hole provided in shadow mask Reference Signs List 12 Damper wire for suppressing vibration 13 Tension force applied vertically to shadow mask 21 Short side wall surface of magnetic shield 22 Long side wall surface of magnetic shield 23 Slit hole provided in magnetic shield of present invention 24 Frame and mask Projection for shielding terrestrial magnetism in gap 10 of magnetic field 25 Leakage magnetic field at corner of magnetic shield 26 Magnetic shield bottom surface 27 Neck side end surface of magnetic shield 28 Center axis on short side surface of magnetic shield 30 Prior art magnetism Provided with shield First example of a provided opening 31 Second example of an opening provided by a magnetic shield of the prior art

Claims (3)

[Claims] At a height position near a bottom surface of a magnetic shield in contact with a frame, a short side wall surface of the magnetic shield is provided at a height position.
A color picture tube comprising at least one horizontally elongated slit hole. 2. The position where the slit is provided is a height of the shield from the bottom surface of the magnetic shield in the tube axis direction h, and a distance from a center axis of the short side surface in a direction perpendicular to the tube axis on the side surface. Assuming that the distance to the shield end face is w, in the height direction, the distance from the bottom to the top of the magnetic shield is 0.
2. The color picture tube according to claim 1, wherein the distance from the center axis of the short side surface is 0.4 w or more in a range of 3 h. 3. 3. The color picture tube according to claim 1, wherein the color picture tube is combined with a tension mask.