JP3153597B2 - 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 in which an internal magnetic shield for shielding an electron beam from an external magnetic field is disposed.

[0002]

2. Description of the Related Art Generally, as shown in FIG. 8, a color picture tube having a shadow mask as a color selection electrode has a substantially rectangular glass panel 1 and a funnel-shaped glass panel integrally joined to the panel 1. A phosphor screen 3 made of a three-color phosphor layer is formed on the inner surface of the panel 1.
And a substantially rectangular shadow mask 4 inside
Is arranged. The shadow mask 4 includes a mask body 5 having a large number of electron beam passage holes formed therein, and a frame 6 attached to a periphery of the mask body 5. In the neck 7 of the funnel 2, there are three electron beams 8B,
An electron gun 9 for emitting 8G and 8R is arranged. And
The three electron beams 8B, 8G, and 8R emitted from the electron gun 9 are deflected by a magnetic field generated by a deflection yoke 11 mounted outside the boundary between the large diameter portion 10 of the funnel 2 and the neck 7, and The phosphor screen 3 is formed into a structure for displaying a color image on the phosphor screen 3 by scanning the phosphor screen 3 horizontally and vertically.

In the above color picture tube,
When an undesired magnetic field generated from geomagnetism or an external circuit enters the passage area of the three electron beams 8B, 8G, 8R, the three electron beams 8B, 8G, 8R are affected by the undesired magnetic field. ,
The trajectory deviates from the original trajectory, causing a so-called mislanding, resulting in deterioration of color purity. Therefore, in the above color picture tube, the internal magnetic shield 12 is usually arranged inside the large diameter portion 10 of the funnel 2 where the three electron beams 8B, 8G, 8R are most susceptible to the magnetic field.

The internal magnetic shield 12 has a thickness of 0.1 to 0.1 mm.
Formed by molding a metal magnetic plate of about 0.3 mm,
Basically, as shown in FIG. 9, it is formed in a hollow trapezoidal shape having a rectangular cross section with a large-diameter opening 14 on the shadow mask side and a small-diameter opening 15 on the electron gun side. The portion 14 is attached to the frame 6 of the shadow mask 4 by fixing means such as welding, and is disposed inside the large-diameter portion 10 of the funnel 2 with the small-diameter opening end 15 facing the electron gun 9.

[0005] As described above, the basic structure of the internal magnetic shield 12 has a hollow trapezoidal shape having a rectangular cross section. However, since this basic structure does not sufficiently shield an external magnetic field, various shapes for more appropriately shielding the external magnetic field are used. An internal magnetic shield with a structure has been developed. One example is the Japanese Utility Model Application 57-30954.
As shown in FIG. 10, the large-diameter opening 14 fixed to the frame of the shadow mask has a horizontal axis (X axis) perpendicular to the tube axis (Z axis) in a short side and a vertical axis as shown in FIG. An internal magnetic shield 12 having a rectangular cross-section having a long side in the (Y-axis) direction, but having a small-diameter opening 15 on the electron gun side substantially in the shape of a rhombus having vertexes on a horizontal axis and a vertical axis is shown. ing.

[0006]

As described above, in a conventional color picture tube, in order to shield an undesired magnetic field generated from geomagnetism against an electron beam or an external circuit, an inside of a large diameter portion of a funnel is provided. A magnetic shield is arranged. The basic structure of this internal magnetic shield is a hollow trapezoidal shape with a rectangular cross section. However, this basic structure does not sufficiently shield an external magnetic field, so that the internal magnetic shield has various shapes and structures that more appropriately shield the external magnetic field. Is being developed.

However, any of the conventional internal magnetic shields does not sufficiently shield an undesired magnetic field, and in particular, terrestrial magnetism incident in the tube axis direction greatly deviates the trajectory of the electron beam.
There is a problem that color purity is deteriorated and a good image cannot be obtained.

The present invention has been made in view of the above problems, and has a structure in which an internal magnetic shield is configured to shield an external magnetic field such as terrestrial magnetism in a good manner, thereby providing a color picture tube for displaying a good image. With the goal.

[0009]

SUMMARY OF THE INVENTION The present invention has an envelope comprising a panel and a funnel, and is attached to a frame of a shadow mask disposed opposite to a phosphor screen formed on an inner surface of the panel, and is provided inside a neck of the funnel. A color picture tube having a rectangular cross-section hollow trapezoidal internal magnetic shield disposed inside the funnel with the electron gun side disposed at the small-diameter opening side as the small-diameter opening side of the internal magnetic shield From the diagonal end to the long side and short side respectively
At a cutting angle in the range of 25 to 50 ° from the corner end, and
The height on the center axis of the side is 50 to 85% of the height of the diagonal end.
A notch with a range of cut depth was formed.

[0010]

The external magnetic field exerting an electromagnetic force on the electron beam emitted from the electron gun to change its trajectory is a component in a direction perpendicular to the trajectory of the electron beam. Therefore, in order to reduce the electromagnetic force that changes the trajectory, the following may be performed.

(A) Enhancing the shielding effect against an external magnetic field and reducing the external magnetic field itself that links with the electron beam. (B) Inducing the external magnetic field to be parallel to the electron beam and linking with the electron beam. Therefore, a notch is formed on each of the long side and the short side from the diagonal end of the small-diameter opening located on the electron gun side of the internal magnetic shield as described above, and the diagonal of the notch is formed. By adjusting the cut angle and the cut depth from the end, the external magnetic field entering the internal magnetic shield is adjusted, and the external magnetic field entering the internal magnetic shield is reduced to the diagonal end on the small-diameter opening side. And an internal magnetic shield that effectively shields an external magnetic field that disturbs the trajectory of the electron beam.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings based on embodiments.

FIG. 1 shows a color picture tube as an embodiment of the present invention. The color picture tube has an envelope composed of a substantially rectangular glass panel 1 and a funnel-shaped glass funnel 2 integrally joined to the panel 1.
1 A phosphor screen 3 comprising a three-color phosphor layer that emits blue, green, and red light is formed on the inner surface.
Opposite to 3, a shadow mask 4 is disposed inside. The shadow mask 4 includes a mask body 5 having a large number of electron beam passage holes formed therein, and a frame 6 attached to a periphery of the mask body 5. An electron gun 9 for emitting three electron beams 8B, 8G, 8R is arranged in a neck 7 of the funnel 2. Further, inside the large-diameter portion 10 of the funnel 2, an internal magnetic shield 20 that shields the three electron beams 8B, 8G, and 8R from an undesired magnetic field generated from geomagnetism or an external circuit is disposed.

Reference numeral 11 denotes a deflection yoke mounted outside the boundary between the large diameter portion 10 of the funnel 2 and the neck 7.

The internal magnetic shield 20 has a thickness of 0.1 to 0.1 mm.
It is formed by molding a metal magnetic plate of about 0.3 mm, and has a rectangular trapezoidal hollow trapezoidal shape with a large-diameter opening 21 on the shadow mask 4 side and a small-diameter opening 22 on the electron gun 9 side. As shown in FIG. 2, the angle θV and the short side 24 from the four diagonal ends of the small-diameter opening 22 with respect to the central axis 25 of the long side 23.
At a cutting angle inclined at an angle θV with respect to the central axis 26 of
The height at the diagonal end of the small-diameter opening 22 is HD, and the long side 23 is
When the height of the short side 24 at each central axis 25, 26 is HV, cutouts 29, 30 having a depth of HD-HV are formed.
Then, the large-diameter opening 21 is attached to the frame of the shadow mask by fixing means such as welding, and the notches 29, 30 are attached.
The small-diameter opening 22 formed with is formed inside the large-diameter portion of the funnel with the electron gun side.

By the way, in general, in order to reduce the influence of terrestrial magnetism on an electron beam, it is sufficient to reduce the electromagnetic force that the electron beam receives from terrestrial magnetism. Then, as shown in FIG. 3, if the geomagnetism 32 of the magnetic flux density BN (vector) interlinks with the electron beam 7 at an angle φ, the electromagnetic force exerted on the electron beam 7 by the geomagnetism 32 Since the component 32a is a right angle component, it is necessary to reduce the component 32a perpendicular to the electron beam 7 in order to reduce the electromagnetic force that the electron beam 7 receives from the geomagnetism 32. This can be done as follows.

(B) Enhancing the shielding effect against the terrestrial magnetism 32 and reducing the terrestrial magnetism 32 itself interlinking with the electron beam 7 (b) Inducing the terrestrial magnetism 32 so as to be parallel to the electron beam 7, reducing the angle φ interlinked with chains for these (a) is allowed to be achieved by increasing the height HD of the internal magnetic shield 20 shown in FIG. 2
Noh . This is especially true for geomagnetism (hereinafter N / S
32, which significantly reduces the beam movement due to the N / S geomagnetism. On the other hand, the influence of the electron beam on the horizontal geomagnetism (hereinafter referred to as E / W geomagnetism) perpendicular to the tube axis is N / S.
It is 1/3 or less of the case of geomagnetism. That is, for the E / W geomagnetism, the beam movement amount is reduced by increasing the height HD of the internal magnetic shield 20, but the degree of the decrease is not so remarkable as in the case of the N / S geomagnetism. .

However, as described above, the beam movement amount due to the E / W terrestrial magnetism is one of the beam movement amount due to the N / S terrestrial magnetism.
Therefore, in order to reduce the influence of terrestrial magnetism on the electron beam, that is, the amount of beam movement due to terrestrial magnetism, it is preferable to reduce the amount of beam movement due to N / S terrestrial magnetism. It is desired to make the height HD of the 20 as high as possible. But internal magnetic shield
If the height HD of 20 is too high, it will be magnetically coupled with the leakage magnetic field of the deflection yoke 11, and the convergence deviation and landing deviation of the three electron beams 7B, 7G, 7R will increase.

Therefore, the height HD of the internal magnetic shield 20
Is set as high as possible within a range not magnetically coupled to the leakage magnetic field of the deflection yoke 11 and deteriorating the characteristics of the color picture tube.

FIG. 4 shows the relationship between the height HD of the internal magnetic shield in a 20-inch color picture tube and the amount of beam movement due to terrestrial magnetism. Line 34a represents the beam movement amount due to N / S geomagnetism, and line 34b represents the beam movement amount due to E / W geomagnetism. As can be seen from this figure, when the height HD of the internal magnetic shield is increased, the beam movement amount due to the E / W terrestrial magnetism does not change much, but the beam movement amount due to the N / S terrestrial magnetism increases as the height HD increases. It will be greatly reduced with this.

With respect to (b), the cut angle θV from the four diagonal ends of the small-diameter opening 22 on the electron gun 9 side of the internal magnetic shield 20 to the long side 23 and the short side 24 is optimal. By setting to, the N / S geomagnetism can be concentrated at each diagonal end of the opening 22 having a small diameter, and the influence of the geomagnetism on the three electron beams 8B, 8G, and 8R can be reduced.

That is, the electron beam is geomagnetic (static magnetic field).
The force F (vector) received from is given by BN (vector) as the magnetic flux density of the N / S geomagnetism, B as the component perpendicular to the electron beam of the magnetic flux density BN, and I as the electric charge of the electron.

## EQU1 ## F = BN × I = B × I sinＩ (see FIG. 3).

Here, when the cut angle θV formed on the long side 23 and the short side 24 of the internal magnetic shield 20 is reduced, the N / N
S geomagnetism is concentrated on the diagonal end of the small-diameter opening 22 and N / S
The direction of geomagnetism changes, N / S geomagnetism and electron beam 8B,
The directions of 8G and 8R gradually coincide. as a result,
When ψ in the equation shown in Equation 1 approaches 0 °, the electromagnetic force exerted on the electron beams 7B, 7G, and 7R of the N / S geomagnetism attenuates, and the beam movement amount due to the N / S geomagnetism decreases.

FIG. 5 shows the relationship between the cut angle θV formed on the long side and the short side of the internal magnetic shield of a 20-inch color picture tube and the amount of beam movement due to terrestrial magnetism. A curve 35a indicates a beam movement amount due to N / S geomagnetism, and a curve 35b indicates a beam movement amount due to E / W geomagnetism. When the cutting angle θV is reduced as shown by the curve 35a, the beam movement amount due to the N / S geomagnetism decreases as described above. However, when the cutting angle θV is 75 ° or more, the concentration of the N / S geomagnetism on the diagonal portion occurs, but the degree of concentration is reduced, and the effect of reducing the beam movement amount is reduced. The cutting angle θV is 0 ° or less, that is, the cutting angle θV is set such that the cutting angle θV is inclined in the outward direction of each side with respect to a line passing through a diagonal portion parallel to the center line of the long side and the short side of the internal magnetic shield. Assuming θV, N /
The amount of the S geomagnetism entering the internal magnetic shield increases, and the effect of reducing the beam movement decreases.

It should be noted that notch 2
When the grooves 9 and 30 are formed, the E / W geomagnetism easily enters the internal magnetic shield 20 from the cutouts 29 and 30.
As shown by the curve 35b, the beam movement amount increases as the cutting angle θV decreases, and increases sharply especially when the cutting angle θV becomes 0 ° or less. However, as described above, the E / W geomagnetism does not significantly affect the beam movement amount as compared with the N / S geomagnetism (1/3 or less of the N / S geomagnetism). The effect is less than in the case of N / S geomagnetism.

As described above, in order to achieve (b),
An N / S geomagnetic field is formed by forming a cut at an optimum cut angle θV from the four diagonal ends of the small-diameter opening 22 on the electron gun 9 side of the internal magnetic shield 20 to the long side 23 and the short side 24. Is concentrated on each diagonal end of the small-diameter opening 22 to reduce the influence of terrestrial magnetism. For this purpose, the notch 29 is formed in the long side 23 and the short side 24 of the internal magnetic shield 20. , 30, the geomagnetism easily enters the internal magnetic shield 20 from the cutouts 29, 30.

FIG. 6 shows the relationship between the depth HD-HV of the notch formed in the long side of the internal magnetic shield of the 20-inch color picture tube and the amount of beam movement due to terrestrial magnetism. A curve 36a represents the total beam movement amount due to the N / S geomagnetism, and a curve 36c represents the beam movement amount particularly near the central axis of the long side due to the N / S geomagnetism. curve
As shown in 36a, the ratio HV / HD of the height HV on the central axis of the long side where the notch is formed and the height HD of the internal magnetic shield is reduced (the notch 27 becomes deeper). Accordingly, the overall beam movement due to the N / S geomagnetism decreases, but when the HV / HD becomes 50% or less, the amount of the N / S geomagnetism that enters the internal magnetic shield through the cutout portion is reduced accordingly. The beam movement amount tends to increase. In particular, when the HV / HD becomes 50% or less, the increase in the beam movement amount near the central axis 23 on the long side becomes remarkable as shown by the curve 36c. When HV / HD is 85% or more and the depth of the notch is small, the effect of reducing the overall beam movement amount due to N / S geomagnetism decreases.

On the other hand, as for the relationship between the depth HD-HV of the notch 30 formed in the short side 24 and the beam movement amount due to terrestrial magnetism, as shown in FIG. As shown in a curve 37a for the total beam movement due to the above, and as shown in a curve 37c for the beam movement near the central axis of the long side due to N / S geomagnetism, the case of the long side shown in FIG. It is almost the same tendency.

Incidentally, for the E / W geomagnetism, if the notches 29 and 30 are formed as described above, these notches 29 and 30 are formed.
Notch to facilitate entry into the internal magnetic shield 20
As the depth HD-HV of 29, 30 increases, E /
The amount of beam movement due to W geomagnetism increases. However, the beam movement amount is 1/1 of the beam movement amount due to N / S geomagnetism.
3 or less, smaller than N / S geomagnetism.

Accordingly, the shape of the internal magnetic shield 20 necessary for optimally shielding an external magnetic field such as terrestrial magnetism and displaying a good image from the above-described results is determined by the shape of the diagonal end of the small-diameter opening 22. The height HD is magnetically coupled with the leakage magnetic field from the deflection yoke 11 so that convergence distortion and landing deviation do not occur. The small-diameter opening 22 has a long side 23 from each diagonal end. And the short side 24 has a cut angle θV = 0-75 °, and the long side 23 and the short side 24 have a small height Hv on the central axes 25 and 26 of the long side 23 and the short side 24. The height HD of the diagonal end of the part 22 is 50 to
85% (Hv / HD = 50-85%) notch 29,
By forming such an internal magnetic shield 20 inside the funnel 2, an external magnetic field such as terrestrial magnetism can be effectively shielded and the electron beams 8B, 8G, 8R can be optimized. And the color picture tube having good landing characteristics can be eliminated. Needless to say, the cut angle and the cut depth to the long side and the short side of the internal magnetic shield slightly vary within the above-mentioned optimum range depending on the type of the color picture tube.

[0031]

According to the present invention, the internal magnetic shield having a rectangular trapezoidal hollow cross section disposed inside the funnel is cut into a long side and a short side from the diagonal end of the small-diameter opening on the electron gun side, respectively. When a notch with a predetermined notch depth is formed,
Effectively shields the external magnetic field in the tube axis direction and the horizontal axis direction perpendicular to the tube axis, especially the external magnetic field in the tube axis direction, eliminates disturbance of the trajectory of the electron beam, and provides a color picture tube with good landing characteristics. be able to.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a color picture tube according to an embodiment of the present invention.

2A is a perspective view showing the shape of the internal magnetic shield, FIG. 2B is a diagram showing the shape of the long side thereof, and FIG.
(C) is a diagram showing the shape of the short side.

FIG. 3 is a diagram for explaining a relationship between an electron beam and geomagnetism linked to the electron beam.

FIG. 4 is a diagram showing the relationship between the height of an internal magnetic shield and the amount of beam movement.

FIG. 5 is a diagram illustrating a relationship between a cutting angle and a beam movement amount from a diagonal end of a small diameter opening side of an internal magnetic shield.

FIG. 6 is a diagram showing the relationship between the depth of a notch on the long side of the internal magnetic shield and the amount of beam movement.

FIG. 7 is a diagram showing the relationship between the depth of a cutout on the short side of the internal magnetic shield and the beam movement amount.

FIG. 8 is a diagram showing a configuration of a conventional color picture tube.

FIG. 9 is a diagram showing a basic shape of a conventional internal magnetic shield.

10 (a) is a plan view showing a shape of a conventional improved internal magnetic shield, FIG. 10 (b) is a view showing a long side thereof, and FIG. 10 (c) is a short side thereof. FIG.

[Explanation of symbols]

 1 ... panel 2 ... funnel 3 ... phosphor screen 4 ... shadow mask 6 ... frame 7 ... neck 8B, 8G, 8R ... 3 electron beam 9 ... electron gun 11 ... deflection yoke 20 ... internal magnetic shield 21 ... large diameter aperture Part 22 ... Small diameter opening 23 ... Long side 24 ... Short side 29 ... Long side notch 30 ... Short side notch

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01J 29/02

Claims (1)

(57) [Claims] An enclosure comprising a panel and a funnel is mounted on a frame of a shadow mask disposed opposite a phosphor screen formed on an inner surface of the panel, and is disposed in a neck of the funnel. A color picture tube having a rectangular cross-section hollow trapezoidal internal magnetic shield disposed inside the funnel with the electron gun side as the small-diameter opening, and a diagonal of the small-diameter opening of the internal magnetic shield. From the end to the long side and the short side, respectively, 25 to 50 from the diagonal end
Angle of cut in the range of ° and the height of each side on the central axis
Cutting depth in the range of 50 to 85% of the height of the diagonal end
A color picture tube characterized by having a notch formed therein.