JPH04188543A - Color image receiving tube - Google Patents

Abstract

PURPOSE:To reduce the amount of electron beam mislanding generated by terrestrial magnetism by enlarging the internal magnetic shield while influence of mislanding due to distortion of deflective magnetic field is suppressed. CONSTITUTION:A color image receiving tube 1 forms an image by making deflection scan for an electron beam 3, which is emitted by an electron gun 2, using a deflection yoke 4 furnished at the funnel cone part, and a pyramidal internal magnetic shield 6 is installed in such a way as surrounding this electron beam 3. In this internal magnetic shield 6, the central part 12 of each edge member of an electron beam incident opening 7 formed by the side walls of the pyramid is given a height (h) which is smaller than the overall height H of the internal magnetic shield, and thereby the lines of magnetic force at the corners are concentrated while curved. This decreases landing error of the electron beam in tangential direction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color picture tube, and more particularly to the shape of an internal magnetic shield.

[Conventional technology]

In the conventional color picture tube 1, as shown in a schematic cross-sectional view in FIG. 6, three-color phosphors are arranged on a phosphor screen 8, and an electron beam 3 impinges on the opposing phosphors to emit light. At this time, the electron beam 3 deviates from a predetermined orbit due to the influence of the earth's magnetism and does not strike the opposing phosphor accurately, causing so-called mislanding. For example, in a large color picture tube,
When the direction is changed from south to north, the electron beam that should cause the green phosphor to emit light is so affected that it causes it to emit blue light. Therefore, an internal magnetic shield 5 has been conventionally provided inside the color picture tube 1 to reduce the influence.

Now, it is desirable that the internal magnetic shield 5 is attached to the shadow mask structure 9 and largely surrounds the passage area of the electron beam 3 received by the deflection yoke 10, but since the deflection magnetic field area 11 of the deflection yoke 10 is spread forward, In the green part of the entrance side opening of the internal magnetic shield 5, the deflection magnetic field is distorted, and the trajectory of the electron beam being deflected is shifted, causing mislanding.

[Problem to be solved by the invention]

With this conventional internal magnetic shield, there is a limit to its size, and it cannot effectively shield the earth's magnetic field. Alternatively, 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 side wall portion of the entrance side opening of the internal shield, and the trajectory of the deflected electron beam is partially distorted. Although the influence of the earth's magnetic field was reduced to prevent deviation from the planned orbit and mislanding, overall the effect was small due to the influence of deflection magnetic field distortion.

[Means to solve the problem]

In the internal magnetic shield of the present invention, the height of the center of each of the four sides of the electron beam entrance side aperture is approximately 80% of the total height of the magnetic shield. Concentrate on the four corners of the pyramid,
By reducing the magnetic field component perpendicular to the electron beam deflected in the direction of the corner, the amount of deviation in the direction orthogonal to the deflection direction of the electron beam according to Fleming's law is reduced, resulting in the amount of mislaunching caused by the earth's magnetism. can be reduced.

〔Example〕

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a schematic sectional view of a color picture tube according to an embodiment of the present invention. A color picture tube 1 directs an electron beam 3 emitted from an electron gun 2 through a deflection yoke 4 provided at a funnel cone portion.
An image is formed by performing deflection scanning. A quadrangular pyramidal internal magnetic shield 5 that surrounds the electron beam 3
is provided.

As shown schematically in FIG. 2, the internal magnetic shield 6 according to the present invention has a quadrangular pyramid-shaped side wall, and the incident amount of the electron beam is lower than the lower central portion 12 of each side. By making the height h lower, the lines of magnetic force are curved and concentrated, as shown in FIG. 4, which shows the lines of magnetic force of a horizontal magnetic field at a part of the corner (one corner is shown). For this reason, as shown in FIG. 3, conventionally, a current 14 deflected in one corner direction by magnetic lines of force 13 in the direction of the tube axis receives a force in a perpendicular direction 15, and the electron beam is oriented in a tangential direction centered on the tube axis. Although an error occurs, the curved lines of magnetic force 16 produce a component in the deflection direction, and the magnetic field component in the tube axis direction decreases. Therefore, the landing error of the electron beam in the tangential direction is reduced by 8.

Now, as the height h of the central portion of each side is further reduced, the magnetic shielding effect near the central portion of each side decreases, and the degree of curvature of the magnetic lines of force also becomes approximately constant.

However, the deflection magnetic field region 11 extends to the vicinity of the opening of the internal magnetic shield 6, and if there is a side wall of the opening at approximately the same distance from the deflection yoke, the deflection magnetic field is somewhat shielded on all four sides, reducing the deflection efficiency. Although it is constant in each direction, if the height of the central part 12 of each side is extremely low, the shielding effect of the central part 12 of each side will be reduced and the deflection efficiency will be improved, and the launching of the electron beam will be As shown in FIG. 5(C), the error increases in the center portion 12 of each side in the outward direction from the tube axis. Therefore, the height h of the center portion of each side is determined to be optimal with respect to the total height H.

This relationship is shown in FIG. 5(a).

Curve A in FIG. 5a shows the amount of electron beam movement due to the horizontal component (north-south direction) of the earth's magnetism, as shown in FIG. 5(b). The curved opening is located at the center of each side, as shown in Figure 5(c).
and mislanding.

In Figure 5(a), at the h/H90% point, the electron beam movement is improved by 7μ, and the mislanding (curve opening) remains unchanged, so the improvement effect is 20% and effective. be. For the point where h/H is 70%, the beam movement is 15
The mislanding that has been improved by μ changes (deteriorates) by 10 μ, and the improvement effect is 5 μ, which is an improvement of about 14%, which is the limit at which a practical effect can be confirmed. Further, when h/H is 60%, the electron beam movement amount is improved by 16 μ, but the mislanding increases by 25 μ, resulting in a deterioration of 9 μ or more, and no improvement is recognized. Therefore, h/
When H is 80%, the electron beam movement amount is improved by 13μ, and the mislanding changes by about 2μ, so the improvement is 11μ, which is an improvement effect of about 30%. Therefore, h/
The improvement effect of H is observed in the range of about 70 to 90%. Preferably h/H is selected to be about 80-90%, with the most desirable value being about 80%.

Although the above example shows the case where the center portion of each side is 70 to 90% of the total height, the height may be adjusted on the long and short sides.

〔Effect of the invention〕

As explained above, the present invention has the effect of suppressing the influence of mislaunching due to distortion of the deflection magnetic field, increasing the size of the internal magnetic shield, and reducing the amount of mislaunching of electron beams caused by earth's magnetism.

For example, compared to the case where the height of the conventional internal shield is 40 mm, when the internal shield height is 60 mm and the height of the center of each side is 48 mm, the amount of mislaunching of the electron beam is approximately 30 mm. % reduction was possible.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an internal magnetic shield provided inside a color image receiver according to an embodiment of the present invention. FIG. 2 is a sketch of an internal magnetic shield according to an embodiment of the present invention. FIG. 3 is a diagram showing the direction of the force exerted by the horizontal component of the earth's magnetic field when the electron beam is deflected to the corner of the screen. FIG. 4 is an explanatory diagram in which the horizontal component of the earth's magnetism due to the internal magnetic shield of the present invention becomes curved lines of magnetic force. Figure 5 (a) shows the ratio of the height of the central part of the side of the opening of the internal magnetic shield to the metal height and the electron beam mislanding, and (b) shows the horizontal component of the geomagnetic field at the corner of the screen. FIG. 3 is a diagram showing electron beam mislanding directions. (C) is a diagram showing that the beam launching error increases in the outward direction from the tube axis at the center of each side. Inertiasu notation th final example Eo ~ cutable shame note 1...
Color picture tube, 5... Internal magnetic shield, 6.
. . . Internal magnetic shield of the present invention, 7 . . . Incident side opening, 9 . . . Shadow mask structure, 11.
... Deflection magnetic field region, 12 ... Central part of each side, 13 ... Lines of magnetic force in the tube axis direction, 14 ...
Direction of current deflected in one corner direction, 16...
・Curved magnetic field lines. Agent Patent Attorney Susumu Uchihara (b) Small Tag Figure 6

Claims (1)

[Claims] In a color picture tube equipped with a nearly quadrangular pyramid-shaped magnetic shield that surrounds the electron beam passage area emitted from the electron gun, the center of each of the four sides of the electron beam entrance opening in the side wall forming the quadrangular pyramid shape. The magnetic shield has a height of about 70 to 90% of the total height of the magnetic shield, and the highest point is the point where the four sides meet, and the part that reaches the center of each side is a gentle curve or straight line. color picture tube.