JPH11345562A - Inner magnet ic shield of color cathode-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inner magnetic shield which can be improved as to the mislanding of an electron beam in the external magnetic fields of geomagnetism or the like, particularly in magnetic fields extending in the direction of the major axis of a tube surface and in the direction of tube axis. SOLUTION: An inner magnetic shield 5 is so formed that a flange portion 13 curved in the direction of tube axis Z is formed at the end of one of opposite long side face parts 5a which is located on the side of an electron beam incident opening 9, with each end of the flange part 13 joined to a short side face part 5b. Large openings 10 extending in the direction of the tube axis Z are formed in each long side face pat 5a and in symmetrical positions with respect to the tube axis Z, and a small opening 12a longer than the large opening 10 and having one end extended to the flange part 13 and a small opening 12b located outside of it are formed in the portions of the long side face part 5a outside the large openings 10 and in symmetrical positions with respect to the tube axis Z.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal magnetic shield of a color cathode ray tube, and more particularly to an internal magnetic shield of a color cathode ray tube for preventing a problem such as a color shift caused by mislanding of an electron beam caused by terrestrial magnetism.

[0002]

2. Description of the Related Art In a cathode ray tube, a so-called beam mislanding occurs in which the trajectory of an electron beam does not reach a predetermined phosphor screen position due to the influence of an external magnetic field such as terrestrial magnetism. It is known to cause undesirable results such as color shift.

FIG. 4 shows a cross section of a conventional three-gun three-electron beam type color cathode ray tube. In the figure, reference numeral 1 denotes an envelope of a color cathode ray tube, which comprises a face plate panel 1a having a fluorescent screen 2, a funnel 1b, and a neck 1c. A color selection electrode 3 is supported by a frame 4 inside the face plate panel 1a, and an internal magnetic shield 5 emits electrons from an electron gun 6 disposed in the neck 1c to reach the phosphor screen 2. It is installed so as to surround the trajectory of the beam 7. 8 is a degaussing coil.

In order to remove the influence of an external magnetic field, an internal magnetic shield 5 is provided along the funnel 1b from the color selection electrode 3. In order to enhance the blocking performance of the internal magnetic shield 5, conventionally, as shown in FIG. 5, a triangular opening is formed near a plane including the tube axis Z and the tube surface short axis Y of the long side surface portion 5a of the internal magnetic shield. (Hereinafter referred to as "opening")
10 and a V-shaped cut (hereinafter referred to as “V-cut”) at the end of the short side surface 5b on the side of the electron beam passage opening 9 side.
11) to improve the geomagnetic drift.
Further, a demagnetizing coil 8 surrounding the envelope 1 is provided to demagnetize a magnetic member in the cathode ray tube in an external magnetic field, and stabilize a reverse magnetic field formed by the magnetic member with respect to an environmental magnetic field, thereby forming an electron beam. Geomagnetic drift is reduced.

The geomagnetism has a horizontal component and a vertical component. The vertical component depends on the latitude of the earth but can be regarded as constant over a wide range, whereas the horizontal component depends on the orientation of the cathode ray tube. That is, the mislanding movement pattern differs between the case where the tube axis Z of the cathode ray tube is oriented in the north-south direction (hereinafter, referred to as “north-south magnetic field”) and the case where the tube axis Z is oriented east-west (hereinafter, referred to as “east-west magnetic field”). . For this reason, there is a problem that the opening 10 shown in FIG. 5 improves the east-west magnetic field but reduces the north-south magnetic field shielding property, and the V cut 11 improves the north-south magnetic field but reduces the east-west magnetic field shielding property. Was.

[0006]

As described above, an internal magnetic shield having improved east-west magnetic field shielding without sacrificing north-south magnetic field shielding is disclosed in, for example, Japanese Patent Application Laid-Open No. 58-1983.
No. 178945. As shown in FIG. 6, the internal magnetic shield 5 has an opening 10 and a strip-shaped opening 12 in the long side surface 5a. Thus, by forming at least two or more openings 10 and strip-shaped openings 12, the east-west magnetic field is distributed in a barrel shape in a plane perpendicular to the tube axis Z inside the inner magnetic shield 5. It is considered that the generated magnetic field is corrected to a component parallel to the long axis X of the tube surface, and as a result, mislanding is improved.

However, the internal magnetic shield 5 is made of a magnetic material thin plate of about 0.15 to 0.3 mm based on iron, and has an opening 10 formed in the long side surface 5a.
The length in the direction of the tube axis Z is 10 mm at each end of the opening 10 in order to secure the rigidity of the internal magnetic shield 5.
It is necessary to leave a portion of the magnetic material, and this portion of the magnetic material is indispensable as a magnetic path for uniformly exciting the entire magnetic shield material by the magnetic field generated by the degaussing coil. It cannot be formed over the entire length of the side surface portion 5a.

However, as the definition and size of the color cathode ray tube have been increased, the mislanding of the electron beam in the east-west magnetic field and the north-south magnetic field has been strongly required to be improved.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an internal magnetic shield capable of further improving the mislanding of an electron beam in a color cathode ray tube in two directions of an east-west magnetic field and a north-south magnetic field. With the goal.

[0010]

An internal magnetic shield of a color cathode ray tube according to the present invention is an internal magnetic shield provided so as to surround a trajectory of an electron beam incident on a color selection electrode of the color cathode ray tube. A pair of trapezoidal long side surfaces and a short side surface portion are each formed of a magnetic thin plate into a truncated quadrangular pyramid shape, and the pair of opposing long side surface portions has an end on the electron beam entrance side. A flange portion bent in the tube axis direction is formed, and both end portions thereof are connected to the pair of opposed short side surfaces, and the pair of trapezoidal long side surfaces are located at positions symmetrical to the tube axis. A large opening extending in the tube axis direction is formed,
Outside the large opening, a small opening longer than the large opening and having one end reaching the flange is formed.

Further, a short-side frame shield is provided at both corners of the short side surface portion near the color selection electrode and extends parallel to the tube axis to near the color selection electrode. .

Further, the width of the flange portion in the tube axis direction is formed to be approximately 5% of the length of the short side of the electron beam entrance.

A pair of first and second small openings having different lengths in the direction of the tube axis are respectively formed on the long side surfaces, and the first small opening has a large opening with respect to the tube axis. The second small opening is located outside the first small opening, and is located outside the first small opening and close to the color selection electrode; It is formed to have a length of about 1/4 of the portion.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be specifically described with reference to the drawings showing the embodiments. Embodiment 1 FIG. FIG. 1 is a schematic perspective view of the internal magnetic shield according to the first embodiment of the present invention. In the drawing, reference numeral 5 denotes an internal magnetic shield in which a pair of trapezoidal long side members and short side members are each formed into a truncated pyramid shape by a magnetic thin plate, and a long side portion 5a and a short side portion 5b are formed. The narrow opening side formed by the above forms the electron beam entrance 9, and a flange portion 13 bent in the tube axis Z direction is formed at the end of the long side surface 5 a on the electron beam entrance 9 side. The both ends are mechanically and magnetically connected to the tongue extending from the short side surface 5b by welding. The width L2 of the flange portion 13 in the tube axis Z direction is formed to be about 5% of the length L1 of the short side of the electron beam entrance 9 excluding the flange portion 13. In the first embodiment, the width L2 is set to L1. 166mm
In contrast, L2 was set to 8 mm.

Further, a triangular opening (hereinafter, referred to as a "large opening") 10 extending in the tube axis Z direction is formed at a position symmetrical with respect to the tube axis Z in the long side surface portion 5a. Outside the large opening 10, a rectangular opening (hereinafter, referred to as a longer opening than the large opening 10 and having one end reaching the flange 13).
A small opening 12a is formed, and a second rectangular opening having a length approximately 1/4 of that of the small opening 12a is provided outside the small opening 12a and close to the color selection electrode. A portion (hereinafter, referred to as a “small opening”) 12b is formed.

FIG. 2 is a side view showing the size and positional relationship of each opening on the long side surface of the internal magnetic shield according to the first embodiment. A plane including the tube axis Z and the tube surface short axis Y is used as a reference plane. And The hypotenuse angle of the large opening 10 is formed along the electron beam trajectory, and the small openings 12a, 12b arranged along the hypotenuse direction of the large opening 10 are also formed along the electron beam trajectory. ing.

The size of the internal magnetic shield of the first embodiment is determined by the height h of the long side surface 5a of the internal magnetic shield 5.
0 is 120 mm, and the base length w0 is 167 mm. Also, the size of the large opening 10 is such that the base m1 is 40 mm and the height h1 is 100 mm, and the size of the small opening 12a is that the width m2 is 13 mm and the height h2 is 110 mm.
The size of the second small opening 12b is such that the width m3 is 13 mm,
The height h3 is 25 mm.

The position of each opening is such that the dimension w1 from the reference plane to the center of the base of the triangle of the large opening 10 is about 30% of the base length w0 and the dimension from the center of the width of the small opening 12a. w2 is about 53% of the base length w0, and the second small opening 12
The dimension w3 to the center of the width b is about 71% of the base length w0, and the distances d1, 12a between the openings 10 and 12a.
12b, the width m2 of the small opening 12a, and the width m3 of the second small opening 12b were formed to have the same width.

Further, short-side frame shields 14 extending parallel to the tube axis Z to the vicinity of the color selection electrode are provided at both corners of the short side surface 5b near the color selection electrode. The short side frame shield 14 preferably extends to the vicinity of the color selection electrode within a range that does not block the electron beam trajectory. In the first embodiment, the height is 45 mm and the width is 4 mm.
It was formed to 7 mm.

In order to compare the shielding effect of the internal magnetic shield of the first embodiment with the above conventional example, an east-west magnetic field of 40 μT
FIG. 3 shows the result of estimating the amount of mislanding (μm) at the position of the phosphor screen generated in the north-south magnetic field of 40 μT by magnetic field analysis and beam orbit analysis. 3 in the figure
One comparative example is a part on the screen where mislanding is noticeably observed in the actual machine. Also,
The section “Examination of the optimal position of the small opening in Comparative Example 2” refers to the case where the small opening position w2 is 61% of w0 and w3 is 81% of w0 and is moved in the left and right end direction of the long side surface portion 5a. It is.

From the results of Comparative Examples 1 and 2 shown in FIG. 3, when the effect of the internal magnetic shield having only the small opening without the short side frame shield is limited to the east-west magnetic field, the effect shown in FIG. Although the comparison with Example 2 tends to be inferior, as seen in Comparative Example 2, the degree of improvement of the north-south magnetic field is excellent. In the configuration of the first embodiment (FIG. 1) to which the short side frame shield was added, it was confirmed that the improvement at the diagonal corner of the screen was more remarkable than the conventional example. Further, it is considered that the divided arrangement of the small openings 12a and 12b improves the mislanding at the end portion of the screen in the north-south magnetic field in the north-south magnetic field, and contributes to the reduction of the magnetic resistance in the long side surface portion 5a. . The optimal positions of the small openings 12a and 12b are as follows:
As w2 and w3 increase, the effect of suppressing mislanding in the east-west magnetic field decreases.
% And 71% are considered optimal.

The internal magnetic shield according to the first embodiment
Since the flange portion 13 of the long side surface portion 5a functions as a reinforcing member of the shield structure and a detour for magnetic flux flowing in the long side surface, the large opening 10 and the two small openings 12a and 12b are provided.
Among them, the height of the small opening 12a can be set longer than that of the large opening 10 as compared with the conventional example. As a result,
When the east-west magnetic field acts, the barrel-shaped magnetic field formed in the internal magnetic shield 5 is corrected, and the effect of converting the barrel-shaped magnetic field into a magnetic field component in the direction of the X-axis of the tube surface with little influence on the electron beam is improved. Mislanding can be reduced.

This effect is maximized by increasing the height of the small opening 12a until reaching the bent portions (flanges) at both ends of the long side surface portion, as in the first embodiment. Mislanding in both directions tends to worsen due to an increase in magnetic resistance with respect to a magnetic field (perpendicular magnetic field) in the Y-direction of the tube short axis. In order to avoid this deterioration, as in the first embodiment, the small opening is divided and the second small opening 1 is divided.
2b, the second small opening 12b is horizontally moved so as to be farther from the tube axis Z position, so that the magnetic resistance at both ends of the small opening can be reduced while having an effect close to the integral small opening. It is possible to reduce the mislanding in areas other than the east-west magnetic field. Note that the height of the two small openings divided into two parts, long and short, is approximately 4: 1.
It is preferable that

The presence of the flange portion 13 on the long side surface portion 5a against the north-south magnetic field further promotes the concentration of magnetic flux at the tip portion of the flange portion 13, and as a result, the magnetic field vector in the tube axis Z direction is reduced. The electron beam is converted into a magnetic field component in the Y-axis direction, and mislanding of the electron beam is suppressed by beam correction in the direction opposite to the movement due to the applied magnetic field.

The internal magnetic shield 5 according to the first embodiment
When a short side frame shield 14 extending in parallel with the tube axis Z to both bottom corners near the color selection electrode of the opposite short side surface portion 5b of the shield structure as shown in FIG. Since the magnetic flux flowing from the short side surface portion 5b to the long side surface portion 5a in the inside 5 is also branched to the color selection electrode and the frame side, the suppression of the mislanding at the screen diagonal corner is further promoted.

In addition, an increase in the magnetic resistance in the internal magnetic shield can be suppressed even with respect to the magnetic field of the degaussing coil, and stable degaussing becomes possible. Further, with the improvement of the shielding performance against the magnetic field in the longitudinal direction of the tube surface, the cut of the short side V-cut 11 which is restricted as a measure against the magnetic field of the tube axis but deteriorates the shielding performance in the longitudinal magnetic field of the tube surface It is also possible to increase the rate.

[0027]

The internal magnetic shield of the color cathode ray tube according to the present invention is formed by forming a flange bent in the tube axis direction at the end of the internal magnetic shield on the side of the electron beam entrance on the long side surface of the opposite side. The two end portions are joined to the pair of opposed short side surface members, and the long side surface portion has a large opening extending in the tube axis direction at a position symmetrical to the tube axis. Since the small opening that is longer than the large opening and one end of which reaches the flange is formed at a position symmetrical with respect to the tube axis Z, the tube surface long axis magnetic field (east-west magnetic field) and the tube axis magnetic field ( The mislanding with respect to the north-south magnetic field can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of an internal magnetic shield according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating the shape, size, and positional relationship of a large opening and a small opening.

FIG. 3 shows a mislanding amount (μm) of an electron beam at a phosphor screen position with respect to an applied magnetic field of 40 μT in the first embodiment.
FIG.

FIG. 4 is a partially cutaway side view of the color cathode ray tube.

FIG. 5 is a schematic perspective view showing a conventional internal magnetic shield.

FIG. 6 is a schematic perspective view showing an internal magnetic shield of a second conventional example.

[Explanation of symbols]

1 envelope, 1a face plate panel, 1b
Funnel, 1c neck, 2 phosphor screen, 3 color selection electrode, 4 frames, 5 internal magnetic shield, 6 electron gun, 7 electron beam, 8 degaussing coil, 9 electron beam entrance, 10 large aperture, 11V cut , 12a
Small opening, 12b Second small opening, 13 Flange, 14 Short side frame shield, 15 Long side frame shield.

Claims (4)

[Claims] 1. An internal magnetic shield disposed so as to surround a trajectory of an electron beam incident on a color selection electrode of a color cathode ray tube, wherein each of a pair of trapezoidal long side and short side portions is provided. And the end of the pair of opposing long side surfaces on the electron beam entrance side is a plane perpendicular to the tube axis direction. Both ends of the flange portion formed by bending toward the beam orbital side are connected to the pair of opposed short side surfaces, and the pair of trapezoidal long side surfaces are positioned at tube axis symmetric positions. A large opening extending in the direction, a small opening longer than the large opening and having one end reaching the flange is formed outside the large opening. Internal magnetic shield of the cathode ray tube. 2. A short side frame shield which is provided at both corners of an end portion near a color selection electrode on a short side surface portion and extends parallel to a tube axis close to the color selection electrode. 2. The internal magnetic shield of a color cathode ray tube according to claim 1, wherein: 3. The internal magnet of a color cathode ray tube according to claim 1, wherein the width of the flange portion in the direction perpendicular to the tube axis is formed to be approximately 5% of the length of the short side of the electron beam entrance. shield. 4. A pair of first and second small openings each having a different length in the tube axis direction are formed in the long side surface portion, and the first small opening is a large opening with respect to the tube axis. The second small opening is located outside the first small opening, and is located outside the first small opening and close to the color selection electrode; 2. The internal magnetic shield of a color cathode ray tube according to claim 1, wherein said internal magnetic shield is formed to have a length of about 1/4 of said portion.