JP2001268587A - Display device - Google Patents

Abstract

(57) [Problem] To provide a display device using a cathode ray tube which can sufficiently suppress color misregistration and can realize extremely high image quality. A cathode ray tube having a color selection electrode fixed to a frame under tension and an internal magnetic shield for magnetically shielding an electron beam, and a degaussing coil disposed on a funnel of the cathode ray tube 16. A display device comprising: a first and a second degaussing coil 16a;
The display device in which the distance in the tube axis direction at the position where the interlinking surface of 6b intersects the surface of the internal magnetic shield is 以下 or less of the distance in the tube axis direction from the color selection electrode to the rear end of the internal magnetic shield. .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a cathode ray tube (hereinafter, referred to as a cathode ray tube).
CRT. ), Particularly to a display device such as a television.

[0002]

2. Description of the Related Art Generally, in a CRT, an electron beam emitted from an electron beam emitting means such as an electron gun passes through a pore of a color selection electrode and lands on a phosphor.
Emit red, green, or blue light.

Hereinafter, a display device including a conventional CRT, for example, a color television will be described with reference to FIGS. Each figure shows only those structures that are deeply related to changes in the trajectory of the electron beam due to the external magnetic field of the color television. In FIG. 8, a conventional color television has a color selection electrode including a color selection electrode 20 and a frame 21 between a display panel 10 having a phosphor screen and an electron gun 13 for emitting an electron beam toward the display panel 10. There is a structure. Also,
The color television has the color selection electrode assembly and the internal magnetic shield 1.
2 is provided.
Further, the color television includes a funnel 14, which is joined to the display panel 10 so as to cover the electron gun 13 and the external magnetic field shield structure 18, a neck 19, an explosion-proof band 15, and a degaussing coil 16 disposed on the funnel 14. Have.

FIG. 9 is a side view of the conventional display device shown in FIG. 8, in which the color selection electrode 20, the angle 21a, and the upper and lower inner magnetic shields 12 which are housed inside the CRT and are not normally visible are shown. FIG. 4 is an explanatory side view showing a positional relationship between a degaussing coil 16 and an external magnetic field shield structure 18 with a projection position shown in a side view of the display device.

[0005] As shown in FIG. 10, a typical example of a color selection electrode structure including a color selection electrode 20 and a frame 21 is a shadow mask structure 11a. The shadow mask structure 11a is one in which a color selection electrode 20 having a large number of pores formed therein is curved into a predetermined shape by pressing and fixed to a frame 21 by welding. When trying to make the screen of the CRT flat, it is necessary to make this shadow mask (color selection electrode) nearly flat, and the amount of deformation due to thermal expansion of the shadow mask caused by the temperature rise due to the collision of the electron beam is the shadow mask. Becomes closer to flat, and the function may be impaired due to a shift in the positional relationship with the phosphor.

As a solution to this, as shown in FIG.
A so-called tension mask structure 11 in which a color selection electrode 20 having a large number of pores formed thereon is fixed to a frame 21 with tension applied only in the vertical direction of the screen.
A scheme using b has been proposed. According to this method,
Tension mask structure 11b with tension applied
Absorbs elongation of thermal expansion caused by electron beam collision and prevents deformation.

However, when an external magnetic field such as terrestrial magnetism is received while the electron beam reaches the fluorescent screen of the display panel 10 from the electron gun 13, the electron beam receives Lorentz force, and its trajectory changes, and the original landing changes. A part or all of the beam spot lands on a point deviated from the point and hits a phosphor different from the phosphor that should originally emit light, causing a so-called color shift.

In order to suppress the color shift, an internal magnetic shield 12 is provided, and an external magnetic field shield structure 18 is constituted by the internal magnetic shield 12 and the color selection electrode structure. Color shift is suppressed.

A conventional external magnetic field shield structure includes an angle 21a as a first frame made of, for example, Fe material;
For example, an arm 21b, which is a second frame made of a prismatic Fe material, a tension mask structure 11b, which is a color selection electrode structure formed of, for example, a color selection electrode 20 made of Fe material, and an internal magnet made of, for example, Fe material Shield 1
And 2.

Further, a degauss operation is performed to improve the magnetic shielding effect. The degauss operation means that when the external magnetic field shield structure 18 including the color selection electrode structure such as the tension mask structure 11b is considered as a magnetic circuit, an attenuated alternating magnetic field is applied to the external magnetic field shield structure 18 in the presence of geomagnetism as a bias magnetic field. This operation is performed by supplying an attenuated alternating current to the first degaussing coil 16a and the second degaussing coil 16b.

An approximately quadrangular first degaussing coil 16a of the degaussing coil passes above the color selection electrode 20, passes through a corner above the color selection electrode 20, reaches a funnel, and follows an electron gun along the funnel 14. It passes through the lower part near the neck surrounding the neck 13, along the funnel 14 on the opposite side surface, through the upper corner of the color selection electrode 20, and above the color selection electrode 20. The substantially quadrangular second degaussing coil 16b passes under the color selection electrode 20, passes through the corner below the color selection electrode 20, reaches the funnel, and follows the ridge line of the funnel 14 into the electron gun 13b.
Through the lower part near the neck 19 surrounding the funnel 14 along the ridge line of the funnel 14 on the opposite side surface.
Through the lower corner of the color selection electrode 20. The first degaussing coil 16a and the second degaussing coil 16b are formed of a single connected coil, are arranged in a vertically asymmetrical eight-shape, are connected to a power supply circuit, and have a magnetomotive force of 1000 to 1000. It is about 4000AT.

Here, the "ridge line" of the funnel 14 refers to a ridge line from the corner of the rectangular display panel to the neck of the funnel. In this case, the ridge line may not be clear because the funnel cross section becomes circular as approaching the neck side, but it is assumed that the ridge line extends from the corner of the rectangular display panel.

In this degauss operation, since the terrestrial magnetism is applied as a bias magnetic field, after the degauss operation, the external magnetic field shield structure 18 including the tension mask structure 11b is more likely to be positioned in the direction of the terrestrial magnetism as the bias magnetic field than in the case where only the terrestrial magnetism is used. Large magnetization is also generated. Due to the magnetization generated in the direction of the terrestrial magnetism, a magnetic field for canceling the terrestrial magnetism is generated inside the external magnetic field shield structure 18. As a result, a magnetic shielding effect is exhibited, a change in the trajectory of the electron beam due to an external magnetic field can be suppressed, and color shift can be suppressed. Therefore, of the magnetic fluxes generated by the degaussing coil 16, by increasing the magnetic flux flowing to the external magnetic field shield structure 18 including the tension mask structure 11b,
It is important to generate enough magnetization to cancel the terrestrial magnetism after the degauss operation in order to reduce the influence of the terrestrial magnetism of the electron beam.

[0014]

However, in the tension mask structure 11b as described above, the color selection electrode 2 is not provided.
Frame 21 which applies tension to the color selection electrode 2
And an arm 21 as a second frame supporting the angle 21a.
Therefore, there is a portion without a geomagnetic shield in the side direction due to the structure. Therefore, arm 2
The horizontal magnetic field component of terrestrial magnetism, which is an external magnetic field in the side direction of 1b and the tube axis direction of the CRT, is not sufficiently shielded.
Further, since the color selection electrode 20 is supported in a state where tension is applied, the magnetic permeability is reduced due to magnetostriction. Further, the magnetic flux generated by the conventional demagnetizing coil which is arranged vertically apart from each other and arranged in an up / down asymmetrical figure eight shape flows non-uniformly into the tension mask structure 11b having a small magnetic permeability. In some cases, a part of the generated magnetic flux did not effectively flow to the tension mask structure 11b.

The conventional degaussing coil 16 shown in FIG.
The size of the magnetization in the color selection electrode 20 after the degauss operation was set on a 5-inch CRT, and the magnitude of the magnetization was analyzed in detail in the first embodiment. As a result, the color after the degauss operation by the conventional degaussing coil 16 was obtained. FIG. 3A shows the magnetization generated in the selection electrode 20. This figure 3
As shown in (a), since the magnetization in the color selection electrode is not sufficient, the horizontal magnetic field component of the terrestrial magnetism is not sufficiently shielded. Therefore, the change of the trajectory of the electron beam due to the horizontal magnetic field component cannot be sufficiently suppressed, and there is a problem that a color shift occurs.

Accordingly, in view of the above problems, the present invention enhances the magnetic shielding effect by sufficiently magnetizing the color selection electrode by degauss operation, and can sufficiently suppress color misregistration as compared with the related art, thereby realizing extremely high image quality. It is an object of the present invention to provide a display device using a CRT that can be used.

[0017]

The above object can be attained by the following present invention.

That is, the display device of the present invention comprises a cathode ray tube having a color selection electrode fixed to a frame under tension, an internal magnetic shield for magnetically shielding an electron beam, and a funnel of the cathode ray tube. A degaussing coil, wherein the degaussing coil comprises a pair of upper and lower first and second degaussing coils, and the interlinking surfaces of the first and second degaussing coils are: The distance in the tube axis direction from the color selection electrode surface at a position intersecting with the surface of the internal magnetic shield is 1 / the distance in the tube axis direction from the surface center of the color selection electrode to the rear end of the internal magnetic shield. The display device is characterized in that the number is 2 or less.

Here, at the time of the degauss operation, the demagnetizing coil is used as a magnetic flux generation source, and the external magnetic field shield structure including the color selection electrodes, the frame, and the internal magnetic shield is considered as a magnetic circuit. In this case, as described above, the first and second
The distance in the tube axis direction from the color selection electrode surface at the position where the interlinking surface formed by the degaussing coil intersects with the surface of the internal magnetic shield (hereinafter referred to as “interlinking distance”) corresponds to the display panel side of the funnel. With the front side and the neck side being the rear side, the distance in the tube axis direction from the center of the surface of the color selection electrode to the rear end of the internal magnetic shield (hereinafter, referred to as “external magnetic field shield length”) is equal to or less than ２. As a result, the distance between the degaussing coil and the tension mask becomes shorter. This also increases the inclination between the linkage surface of the degaussing coil and the internal magnetic shield, and increases the cross-sectional area of the linkage surface of the degaussing coil perpendicular to the internal magnetic shield. Increase. As a result, of the magnetic flux generated by the degaussing coil, the magnetic flux flowing through the magnetic circuit increases, and the magnetic flux flowing through the tension mask structure increases. For this reason, after the degauss operation performed in the presence of the terrestrial magnetism, which is the bias magnetic field, the external magnetic field shield structure including the tension mask structure generates a larger magnetization in the direction of the terrestrial magnetism, which is the bias magnetic field, than the conventional magnetic field. A magnetic field for canceling geomagnetism is generated inside. As a result, the magnetic shielding effect is increased, the change in the trajectory of the electron beam due to the external magnetic field in the horizontal direction is sufficiently suppressed, and the color shift can be sufficiently suppressed.

Here, the "linkage surface" of the degaussing coil refers to a curved surface of which the magnetic flux component penetrating the curved surface is composed only of a perpendicular component of the curved surface, out of the curved surfaces having the degaussing coil as an outer periphery. The side surface shape of the degaussing coil in the side view explanatory diagram of (a) corresponds to the shape seen from the side where the outer circumference of the interlinking surface overlaps.

The "distance in the tube axis direction" here means a projected distance to the tube axis for a certain distance, that is, a component of the distance in the tube axis direction. The intersecting portion between the interlinking surface and the surface of the internal magnetic shield may be a point, a line segment or a curve, and the interlinking distance may have a certain width. The short distance is defined as the linkage distance.
Further, it is desirable that both the linkage distance of the linkage surface of the first degaussing coil and the linkage distance of the linkage surface of the second degaussing coil are 以下 or less of the length of the external magnetic field shield structure.

Here, as the magnetization at the center of the surface of the color selection electrode increases, the magnetization of the entire external magnetic field shield structure also increases,
The magnetic field for canceling the geomagnetism also increases. Also, the ratio A / B between the linkage distance A and the external magnetic shield structure length B,
As shown in the graph (FIG. 4) showing the relationship between the magnetization intensity at the center of the plane of the tension mask (color selection electrode) and the ratio A / of the linkage distance A of the degaussing coil and the length B of the external magnetic shield structure. As B becomes smaller, the degaussing coil becomes closer to the tension mask, and the magnetic field applied to the tension mask becomes stronger. When the shape of the degaussing coil is complicated, it is known that the strength of the magnetic field sharply increases as the distance decreases, though it depends on the direction. In this case, in order to suppress color misregistration, in the present invention, in order to generate a magnetic field for canceling terrestrial magnetism as the entire external magnetic field shield structure, the magnitude of magnetization at the plane center of the color selection electrode needs to be 0.046 T or more. In order to satisfy this, it has been found from the graph that the ratio A / B should be within the range of 1/2 or less (the hatched portion in FIG. 4). If the position where the intersecting surface of the first and second demagnetizing coils intersects with the surface of the internal magnetic shield substantially overlaps with the surface of the color selection electrode, the interlinking distance A becomes 0, so the ratio A / B is 0.

Incidentally, a configuration in which the interlinking surfaces of the first and second degaussing coils intersect the surface of the internal magnetic shield a plurality of times can be adopted, and in this case, the interlinking surface closest to the color selection electrode is provided. The distance may be 以下 or less of the length of the external magnetic field shield structure.

Further, the display device of the present invention is the display device, wherein the internal magnetic shield partially has a convex portion toward the funnel side.

Further, the display device of the present invention is the display device, wherein the internal magnetic shield partially has a curved portion toward the funnel side.

As described above, the internal magnetic shield is provided with a convex portion or a curved portion on a part thereof toward the funnel side, so that the linkage distance can be reduced to 1 / the length of the external magnetic shield structure.
It becomes easy to set it to 2 or less.

Here, “toward the funnel side” means
It means from the center of the tube axis to the funnel side,
That is, this means a case where a convex portion or a curved portion is provided from the inside to the outside.

The internal magnetic shield is desirably formed of a flat or curved surface extending from the frame supporting the color selection electrodes in the direction of the electron beam emitting means. Further, since the interlinking surfaces of the upper and lower demagnetizing coils exist above and below the funnel, in order to further reduce the interlinking distance, it is preferable that the convex portions or the curved portions are provided on the upper and lower internal magnetic shield surfaces. . In addition, as the convex portion or the curved portion, when at least a part of the surface of the internal magnetic shield is provided with various shapes such as a stepped shape, a triangular pyramid shape, a quadrangular pyramid shape, a trapezoidal shape, a hemispherical shape, etc. Either one of the surfaces of the internal magnetic shield, or a case where a curved surface that is uniformly convex on the funnel side over at least one entire surface, or
These can be used in combination.

Further, in the display device according to the present invention, the first and second degaussing coils each include a parallel portion extending substantially in parallel along an upper side or a lower side of the color selection electrode; The display device according to any one of claims 1 to 3, wherein the display device has a wrap-around portion that extends from both ends of the funnel to a side surface inside the ridge line of the funnel.

Each of the first and second degaussing coils has a parallel portion extending substantially in parallel along the upper side or lower side of the color selection electrode, and a side surface inside the ridge line of the funnel from both ends of the parallel portion. By providing the wraparound part, the linkage distance can be reduced to half of the length of the external magnetic shield structure.
It becomes easier to:

The display device according to the present invention is characterized in that the first and second degaussing coils are vertically symmetrically arranged.

By arranging the first and second demagnetizing coils vertically symmetrically, the demagnetizing magnetic field is uniformly applied to the external magnetic field shield structure including the tension mask structure without waste. For this reason, after the degauss operation, a sufficiently large magnetization that cancels the terrestrial magnetism is generated in the external magnetic field shield structure, the magnetic shielding effect is increased, and the change in the trajectory of the electron beam due to the external magnetic field in the horizontal direction is sufficiently suppressed. The displacement can be sufficiently suppressed.

The display device of the present invention is characterized in that the first and second degaussing coils include a portion disposed on an explosion-proof band at a parallel portion or a wraparound portion.

As described above, by providing the portions disposed on the explosion-proof band in the parallel portions or the wraparound portions of the respective degaussing coils, the parallel portions or the wraparound portions of the degaussing coils are provided on the explosion-proof band. The external magnetic field, including the tension mask structure, of the magnetic flux generated by the degaussing coil, because of the presence of the provided portion and the linkage distance of the degaussing coil being equal to or less than half the length of the external magnetic field shield structure. Since the shield structure can further include an explosion-proof band, the magnetic flux flowing through the external magnetic field shield structure increases, and the demagnetizing magnetic field is effectively applied to the external magnetic field shield structure. For this reason, after the degauss operation, a sufficiently large magnetization that cancels the terrestrial magnetism is generated in the external magnetic field shield structure, the magnetic shielding effect is increased, and the change in the trajectory of the electron beam due to the external magnetic field in the horizontal direction is sufficiently suppressed. The displacement can be sufficiently suppressed.

[0035]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to facilitate understanding of the present invention, the present invention will be described with reference to the following embodiments. Each of the drawings shows only a structure that is closely related to a change in the trajectory of an electron beam due to an external magnetic field of the color television according to the embodiment. The display device is a color television having a CRT.

First Embodiment (FIGS. 1 and 2) In FIG. 1, a color television according to a first embodiment includes a display panel 10 having a phosphor screen and an electron beam.
An external magnetic shield structure 18 including a tension mask structure 11b, which is a color selection electrode structure, and an internal magnetic shield 12 is provided between the electron gun 13 and the electron gun 13 that emits light toward the electron gun 13. A funnel 14 joined to the display panel 10 so as to cover the first demagnetizing coil 16a and a second
And a degaussing coil 16b.

The internal magnetic shield 12 is composed of a plane extending from the frame 21 to the electron gun 13 side, and has a convex portion on a part of the surface toward the funnel side. This is a structure in which a part intersects the interlinking plane of the degaussing coil. The tension mask structure 11b includes the color selection electrode 20.
And a frame 21 that supports the edge of the color selection electrode 20 in a state where tension is applied.
A first frame 21a supporting the color selection electrode 20,
And a second frame 21b supporting the frame 21a.

FIG. 2A shows the display device according to the first embodiment shown in FIG. 1 in which the color selection electrode 20, the angle 21a, and the upper and lower internal magnets which are housed inside the CRT and cannot be viewed normally. FIG. 3 is an explanatory side view showing a positional relationship between a degaussing coil 16 and an external magnetic field shield structure 18 with a side projection position of a shield 12 shown in a side view of the display device. FIG. 2B is a rear view showing the disposition state of the degaussing coil.

The edge of the color selection electrode 20 is supported with a tension of about 80 to 160 kg so that the color selection electrode 20 is made almost flat to make the screen of the CRT flat.
Thereby, the elongation of the increased thermal expansion is absorbed, and the deformation of the color selection electrode 20 can be prevented. However, the relative permeability, which was about 500 before the tension was applied, has been reduced to about 200 by the application of the tension, and the magnetic flux is less likely to flow than when supported without tension, canceling the geomagnetism. However, it is hardly magnetized.

The external magnetic shield structure has, for example, a thickness of 4.
Angle 2 which is the first frame made of 5 mm Fe material
1a, an arm 21b as a second frame made of, for example, a prismatic Fe material having a side of 15.5 mm, and a color selection electrode 20 made of, for example, a 0.1 mm thick Fe material. Tension mask structure 11 which is a structure
b and an internal magnetic shield 12 made of, for example, a Fe material having a thickness of 0.15 mm.

The explosion-proof band has a high magnetic permeability, a width of 5% to 20% of a diagonal dimension of the display panel, and is disposed around the color selection electrode. In a 25-inch CRT, the diagonal dimension is 635 mm, and the explosion-proof band has a width of, for example, 55 m.
m, a thickness of 1.0 mm, made of an Fe material having a relative magnetic permeability of about 3000. The panel side end is disposed 30 mm from the color selection electrode 20 and the neck side end is disposed 25 mm from the color selection electrode 20.

The saddle-shaped first degaussing coil 16a of the degaussing coil is connected to the upper side of the color selection electrode 20 from the parallel portion 16a-1 extending substantially parallel along the upper side of the color selection electrode 20. Through the corner of the second frame 21b
Of the second frame 21b on the opposite side via the wrap-around portion 16a-2 wrapping in the side direction of the second frame 21b and the vicinity of the neck 19 surrounding the electron gun 13. , Through the corner of the upper side of the color selection electrode 20, and to the parallel portion 16a-1 extending in parallel along the upper side of the color selection electrode 20. The first degaussing coil 16a and the second degaussing coil 16b are vertically symmetrically located above or below the color selection electrode 20 at the color selection electrode 2.
It is arranged 3 mm on the neck side from 0 and connected to a power supply circuit, and its magnetomotive force is 2300 AT.

In the vicinity of the color selection electrode 20, the distance in the tube axis direction from the color selection electrode surface at the position where the interlinking surfaces of the first and second degaussing coils intersect with the surface of the internal magnetic shield (interlinking distance). A is 45 mm, for example, and the distance (external magnetic shield assembly length) B from the color selection electrode 20 to the rear end of the external magnetic shield assembly 18 is 170 mm, for example.
And the ratio A / B is 以下 or less.

Here, “near” the color selection electrode 20 means
It means a portion that falls within the range of the distance in the tube axis direction between the color selection electrode and the frame end so that a large amount of magnetic flux generated from the degaussing coil flows to the color selection electrode.

The electron beam emitted from the electron gun 13 is
The light passes through the pores of the color selection electrode 20 and lands on the phosphor of the display panel 10 to emit any one of red, green, and blue.

The conventional degaussing coil shown in FIG. 7 and the degaussing coil according to the present embodiment (Example 1) shown in FIG.
FIG. 3 shows the result of numerical analysis of the magnitude of the magnetization of the color selection electrode 20 after setting the CRT on a 5-inch CRT and performing the degauss operation. Numerical analysis considers the hysteresis magnetic properties of magnetic materials by curling model theory,
A non-linear magnetic field analysis is performed by a three-dimensional finite element method, and an analysis region is divided into about 70,000 finite elements.

By performing the degauss operation in the presence of the terrestrial magnetism as the bias magnetic field, after the degauss operation, a larger magnetization is generated in the external magnetic field shield structure including the color selection electrode 20 in the direction of the terrestrial magnetism as the bias magnetic field. And
A magnetic field for canceling geomagnetism is generated inside the external magnetic field shield structure. Therefore, it can be said that the greater the magnetization of the color selection electrode 20 after degauss and the more uniform, the more uniform the geomagnetism can be.

FIG. 4 is a graph showing the relationship between the ratio A / B between the linkage distance A and the length B of the external magnetic field shield structure and the magnitude of magnetization at the center of the plane of the tension mask (color selection electrode). is there. Numerical analysis results of the conventional example, the first embodiment, and the second embodiment are plotted in the graph.
The larger the magnetization at the center of the surface of the color selection electrode, the larger the magnetic field for canceling the geomagnetism as the whole external magnetic field shield structure. On the other hand, the smaller the ratio A / B between the linkage distance A of the degaussing coil and the length B of the external magnetic field shield structure, the closer the degaussing coil becomes to the tension mask, and the magnetic field exerted on the tension mask sharply increases. In this case, in order to suppress color misregistration, in the present invention, in order to generate a magnetic field for canceling terrestrial magnetism as the entire external magnetic field shield structure, the magnitude of magnetization at the center of the plane of the color selection electrode is set to 0.046T.
The above is considered necessary, and a requirement that the ratio A / B is 以下 or less has been found as a necessary requirement to satisfy the requirement, and the first embodiment satisfies this requirement.

That is, the inner magnetic shield 12 has a convex portion on a part thereof toward the funnel side, and the position where the interlinking surface of the degaussing coil intersects near the color selection electrode 20 due to the convex portion. Since the distance is １ ／ or less of the length of the external magnetic shield structure, the degaussing coil 16 in the degauss operation is used.
As for the magnetic flux generated from a and 16b, the magnetic flux 30 flowing in parallel along the internal magnetic shield 12 increases, and the magnetic flux flowing into the tension mask structure increases. Further, on the left and right side surfaces of the funnel, the first and second degaussing coils 16a, 16
By providing wrap-around portions 16a-2, 3, 16b-2, and 3b that wrap around the inner side of the ridge line of the funnel 14 in b, the inclination between the linkage surface of the degaussing coil and the internal magnetic shield 12 increases. Since the cross-sectional area of the linkage surface of the degaussing coil perpendicular to the internal magnetic shield 12 increases, the magnetic flux 30 flowing in parallel along the internal magnetic shield 12 increases. As a result, in the degauss operation, each degaussing coil 16
The magnetic fluxes generated from the a and 16b efficiently flow through the external magnetic field shield structure 18 constituted by the tension mask structure 11b and the internal magnetic shield 12. For this reason, as shown in FIG. 3, after the degauss operation, the magnetization of the color selection electrode increases, that is, a sufficiently large magnetization for canceling the terrestrial magnetism is generated in the external magnetic field shield structure 18 including the tension mask structure 11b, The shielding effect is improved, the change in the trajectory of the electron beam due to the external magnetic field is suppressed, and the color shift is suppressed.

Second Embodiment FIG. 5 is an explanatory side view showing a shape of an internal magnetic shield and an installation position of a degaussing coil according to a second embodiment of the present invention. The display device according to the second embodiment includes a portion extending around the first and second demagnetizing coils on the left and right side surfaces of the funnel near the tension mask structure, substantially parallel to the vertical side of the display panel, and The first and second embodiments differ from the first embodiment in that the left and right sides of the funnel are provided with portions where the coils are parallel to each other.

In the external magnetic field shield assembly 18, the distance (linkage distance) A in the tube axis direction at the position where the linkage surface of the demagnetizing coil intersects the surface of the internal magnetic shield 12 on the color selection electrode side is, for example, 3 mm. Since the distance B from the color selection electrode 20 to the rear end of the internal magnetic shield 12 (length of the external magnetic shield structure) is, for example, 170 mm, the ratio A
/ B is smaller than 1/2.

The demagnetizing coil according to the second embodiment (Example 2) shown in FIG. 5 is set on a 25-inch CRT, and the magnitude of magnetization of the color selection electrode 20 after the degauss operation by numerical analysis is shown in FIG. . Numerical analysis considers the hysteresis magnetic property of the magnetic material by the curling model theory, and
A non-linear magnetic field analysis is performed by the three-dimensional finite element method, and the analysis region is divided into about 70,000 finite elements.

First and second degaussing coils 16a, 16b
In addition, on the left and right side surfaces of the funnel in the vicinity of the tension mask structure 11b, a parallel portion extending substantially parallel to the side of the color selection electrode 20, and a wrap around from the end of the parallel portion to the funnel side surface. By providing a portion where the first degaussing coil 16a and the second degaussing coil 16b are parallel to each other in the wraparound portion, C
The leakage of the magnetic flux between the upper and lower degaussing coils on the RT side is reduced, and the inclination between the linkage surface of the degaussing coil and the internal magnetic shield 12 is increased. The magnetic flux 30 flowing in parallel along the inner magnetic shield 12 due to the large cross-sectional area
Increase. As a result, of the magnetic flux generated by the demagnetizing coil, the magnetic flux flowing to the external magnetic field shield structure 18 including the tension mask structure 11b increases, so that the demagnetizing magnetic field is effectively applied to the external magnetic field shield structure 18. Therefore, FIG.
As shown in the figure, after the degauss operation, a sufficiently large magnetization is generated in the color selection electrode, that is, a sufficiently large magnetization to cancel the terrestrial magnetism is generated in the external magnetic field shield structure including the color selection electrode, and the magnetic shielding effect is large. Therefore, the change in the trajectory of the electron beam due to the external magnetic field in the horizontal direction can be sufficiently suppressed, the color shift can be sufficiently suppressed, and high image quality can be realized.

In the above embodiment, in the external magnetic field shield structure, the distance in the tube axis direction where the linkage surface of the degaussing coil intersects with the surface of the internal magnetic shield is determined from the center of the surface of the color selection electrode to the internal magnetic field. As a means for reducing the distance in the tube axis direction to the rear end of the shield to 以下 or less, the case where the inner magnetic shield is provided with a convex portion radially outward from the tube axis has been described as an example. Also in the case where a curved portion is provided in a part of the internal magnetic shield, similar to the above embodiment,
The magnitude of magnetization of the color selection electrode after degauss increases,
The magnetic shielding effect is improved, the orbital change of the electron beam due to the external magnetic field is suppressed, and the color shift is suppressed. In the case where a curved portion is provided in a part of the internal magnetic shield 12 in FIG. 7, the radius of curvature of the curved portion is 110 mm, and in the vicinity of the color selection electrode 20, the linkage surface of the degaussing coil is the surface of the internal magnetic shield 12. The distance A in the direction of the tube axis at the position intersecting with
The distance B in the tube axis direction from the center of the surface of the color selection electrode 20 to the rear end of the internal magnetic shield 12 is, for example, 170 mm, and the ratio A / B is 1/2.
Less than.

In the above description of the present invention, a case has been described in which the present invention is applied to a tension mask type in which a color selection electrode having a large number of pores is fixed to a frame with tension applied only in the vertical direction of the screen. However, the present invention is not limited to this, and a method of fixing a color selection electrode having a large number of pores in a state where tension is applied in both the vertical direction and the horizontal direction of the screen and a method called an aperture grille The present invention can be applied to all methods of fixing the color selection electrode to the frame with tension applied thereto, such as a method of fixing the strip to the frame with tension applied in the vertical direction of the screen, and has the same effect. .

The shape of the degaussing coil can be changed as desired.
A parallel portion extending substantially parallel to the first and second degaussing coils along the upper side or lower side of the color selection electrode, and a wraparound portion extending from both ends of the parallel portion to a side surface inside the ridge line of the funnel. And the like, a saddle shape, a boat shape, and other shapes may be adopted. In this case, the parallel portion desirably includes a straight line portion.

When the color selection electrode is fixed to the frame in a state where tension is applied to the screen in the left and right direction, the arrangement of the degaussing coil may be changed from the arrangement of the degaussing coil to the left or right with respect to the tube axis. In this case, the same effect as the present invention can be obtained.

In the above embodiment, the case of using a tension mask (color selection electrode) made of an Fe material has been described as an example, but a display device using a tension mask made of another magnetic material such as a Ni-Fe material is described. Also applicable to

In the above embodiment, the case of the explosion-proof band made of Fe material has been described as an example, but the present invention can be applied to a display device using an explosion-proof band made of another magnetic material such as Ni-Fe material.

Further, in the above embodiment, the case of the internal magnetic shield made of Fe material has been described as an example, but the present invention can also be applied to a display device using an internal magnetic shield made of another magnetic material such as permalloy material.

In the above embodiment, a 25-inch color television has been described as an example. However, the present invention can be applied to a display device using a cathode ray tube of another inch size.

In the above embodiment, a color television was described as an example. However, the present invention is not limited to this.
It can be applied to other display devices using a cathode ray tube, such as a T display monitor.

[0063]

In the display device using the cathode ray tube according to the present invention, the direction of the tube axis from the color selection electrode surface at the position where the interlinking surfaces of the first and second degaussing coils intersect with the surface of the internal magnetic shield. Is less than or equal to 1/2 of the distance in the tube axis direction from the center of the surface of the color selection electrode to the rear end of the internal magnetic shield, thereby reducing the distance between the internal magnetic shield and the degaussing coil. The inclination between the linkage surface of the degaussing coil and the internal magnetic shield increases, and the cross-sectional area of the linkage surface of the degaussing coil perpendicular to the internal magnetic shield increases, so that the magnetic flux flowing parallel to the internal magnetic shield increases. As a result, of the magnetic flux generated by the degaussing coil, the magnetic flux flowing to the external magnetic field shield structure increases, so that the demagnetizing magnetic field is effectively applied to the external magnetic field shield structure.

Therefore, by performing the degauss operation in the presence of the geomagnetic field as the bias magnetic field, after the degauss operation, a larger magnetization is generated in the external magnetic field shield structure including the color selection electrode in the direction of the geomagnetic field as the bias magnetic field. However, a magnetic field for canceling geomagnetism is generated inside the external magnetic field shield structure. As a result, the magnetic shielding effect is increased, the change in the trajectory of the electron beam due to the external magnetic field in the horizontal direction is sufficiently suppressed, the color shift can be sufficiently suppressed, and high image quality can be realized.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a configuration of a display device according to a first embodiment.

FIG. 2 is a side view illustrating the shape of the internal magnetic shield according to the first embodiment and the positional relationship between the degaussing coil and the external magnetic field shield assembly, and a rear view illustrating the arrangement of the degaussing coil ( b).

FIG. 3 is a magnetization distribution diagram of a color selection electrode obtained by a numerical analysis after a degauss operation using a conventional internal magnetic shield and degaussing coil (a) and the internal magnetic shield and degaussing coil (b) of the first embodiment.

FIG. 4 is a graph showing the relationship between the ratio A / B between the linkage distance A and the length B of the external magnetic field shield structure and the magnitude of magnetization at the center of the plane of the color selection electrode.

FIG. 5 is an explanatory side view showing a shape of an internal magnetic shield and a positional relationship between a degaussing coil and an external magnetic field shield structure according to a second embodiment.

FIG. 6 is a magnetization distribution diagram of a color selection electrode by numerical analysis after a degauss operation by an internal magnetic shield and a degaussing coil according to a second embodiment.

FIG. 7 is an explanatory side view showing a shape of an internal magnetic shield and a positional relationship between a degaussing coil and an external magnetic field shield structure according to a third embodiment.

FIG. 8 is a perspective view illustrating a configuration of a conventional display device.

FIG. 9 is an explanatory side view showing a positional relationship between a shape of an internal magnetic shield and a degaussing coil in a conventional CRT.

FIG. 10 is a perspective view showing a shadow mask structure in an external magnetic field shield structure of a conventional CRT.

FIG. 11 is a perspective view showing a tension mask structure in an external magnetic field shield structure of a conventional CRT.

[Explanation of symbols]

H _ver Vertical magnetic field _Hew East-west magnetic field H _tube tube magnetic field 10 Display panel 11a Shadow mask structure 11b Tension mask structure 12 Internal magnetic shield 13 Electron gun 14 Funnel 15 Explosion-proof band 16a First degaussing coil 16a-1 First
Parallel part 16a-2 Second parallel part 16a-3 Surrounding part 16a-4 Surrounding part 16a-5 Second
Parallel part 16b Second degaussing coil 16b-1 First
Parallel part 16b-2 Second parallel part 16b-3 Surrounding part 16b-4 Surrounding part 16b-5 Second
Parallel part 17 Electron beam trajectory 18 External magnetic field shield structure 19 Neck 20 Color selection electrode 21 Frame 21a Angle 21b Arm 30 Magnetic flux

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Miyoko Okutani 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Hisanori Nagase 1006 Odaka Kadoma Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. 72) Inventor Kaneyoshi Takaura 1006 Kadoma, Kazuma, Osaka Pref. Matsushita Electric Industrial Co., Ltd. 5C060 CM04 CM10

Claims (6)

[Claims] 1. A cathode ray tube having a color selection electrode fixed to a frame under tension and an internal magnetic shield for magnetically shielding an electron beam, and a degaussing coil disposed in a funnel of the cathode ray tube Wherein the degaussing coil comprises a pair of upper and lower first degaussing coils and a second degaussing coil, and the interlinking surfaces of the first and second degaussing coils correspond to the surface of the internal magnetic shield. The distance in the tube axis direction from the surface of the color selection electrode at the crossing position is 以下 or less of the distance in the tube axis direction from the center of the surface of the color selection electrode to the rear end of the internal magnetic shield. Characteristic display device. 2. The display device according to claim 1, wherein the internal magnetic shield has a part provided with a convex portion toward a funnel side. 3. The display device according to claim 1, wherein the internal magnetic shield has a curved portion on a part thereof toward a funnel side. 4. The first and second degaussing coils each include a parallel portion extending substantially parallel along an upper side or a lower side of the color selection electrode, and a ridge line of the funnel from both ends of the parallel portion. The display device according to any one of claims 1 to 3, further comprising a wrap-around portion that wraps around the inner side surface. 5. The display device according to claim 1, wherein the first and second degaussing coils are vertically symmetrically arranged. 6. The device according to claim 1, wherein the first and second degaussing coils have a portion disposed on an explosion-proof band at the parallel portion or the wraparound portion. Display device.