JPH07105863A - Color picture tube device - Google Patents

Abstract

PURPOSE:To correct a raster distortion only by the form of a magnetic shield and the automatic correction of a deflection yolk without using the correcting circuit of a deflecting circuit, and provide an inexpensive color picture tube set. CONSTITUTION:A color picture tube device has an envelope consisting of a panel part 1 and a funnel part 2, and a circular notch part is provided on a magnetic shield body 6 mounted on the frame 5 of a shadow mask 4 arranged opposite to a phosphor screen 3 formed on the inner surface of the panel part 1. The horizontal deflecting magnetic filed of a deflection yoke 9 is shielded in four corners of the electron gun 8 side opening part of the magnetic shield body 6, and taken into the magnetic shield body 6 through the notch part, whereby the vertical pin cushion distortion of a faceplate is corrected without correction by a deflecting circuit.

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 device having a magnetic shield for shielding the influence of an external magnetic field on an electron beam in the tube.

[0002]

2. Description of the Related Art Generally, in a color picture tube device using a shadow mask as a color selection electrode, when the geomagnetism or an unnecessary external magnetic field generated from a peripheral member such as a drive circuit or a speaker enters the electron beam passage region in the tube, The electron beam is deviated from the original orbit under the influence of the unnecessary magnetic field, mislanding that does not exactly reach the desired fluorescent screen occurs, and the image quality deteriorates. In order to shield unnecessary external magnetic fields such as the earth's magnetism, a magnetic shield body is usually attached to the frame portion of the shadow mask and arranged in the electron beam passage area in the color picture tube device. The shape of this magnetic shield body, especially the shape of the electron gun side opening, is designed in consideration of the fluorescent screen arrangement of the color picture tube device and the like so as to effectively shield the unnecessary external magnetic field having a greater influence. Usually, the height of the deflection yoke is taken into consideration so as not to block the deflection magnetic field.

On the other hand, JP-A-59-66039 discloses a method of using a magnetic shield as a means for correcting the distortion of the screen shape of a color picture tube device, so-called raster distortion. As shown in FIG. 7, the four corners 21 of the electron gun side diameter small opening of the magnetic shield 6 are on the axis corresponding to at least 5% of the peak value of the axial magnetic flux density distribution of the deflection magnetic field by the deflection yoke. It is projected to the plane orthogonal to the axis passing through the points. That is, a part of the deflection magnetic field is consciously shielded by a magnetic shield body so that the pincushion distortion at the screen corner is corrected only by adjusting the deflection magnetic field without attaching a correction magnet to the deflection yoke.

However, the raster shape has a stronger pincushion distortion due to the recent increase in the size of the color picture tube, the increase in the deflection angle accompanying the reduction in thickness, and the flattening of the fluorescent screen panel. Therefore, it is indispensable to add a correction circuit to the deflection circuit to correct the raster shape.

[0005]

Generally, in an in-line type color picture tube device, three electron beams are emitted from the fluorescent screen.
A self-convergence method using the magnetic field distribution of the deflection yoke is adopted as a method of concentrating on points. In the self-convergence method, the magnetic field for concentrating the electron beam is a magnetic field in the direction of correcting the pincushion distortion at the top and bottom of the screen as a result.

However, since the distortion of the raster shape is larger as described above, it is inevitable to use the correction by the deflection circuit even for the pincushion distortion at the top and bottom of the screen which is relatively small.

However, adding a correction circuit to the deflection circuit to correct the raster distortion has the problems that it is difficult to design an appropriate correction circuit, and the number of circuit components increases, which increases the circuit cost. Was.

The present invention solves the pincushion distortion correction at the top and bottom of the screen by automatically correcting only the magnetic field distribution of the deflection yoke by optimizing the shape of the magnetic shield body without using an expensive correction circuit. It is an object of the present invention to provide an inexpensive color picture tube device.

[0009]

In order to solve the above problems, according to the present invention, an envelope including a panel portion and a funnel portion and a fluorescent surface formed on the inner surface of the panel portion are arranged so as to face each other. And a shadow mask, which is attached to the frame of the shadow mask coaxially with the tube axis with an opening having a small diameter facing the electron gun disposed in the neck portion of the funnel portion and disposed in the funnel portion. A first point is a point that is composed of a substantially quadrangular pyramid-shaped magnetic shield body and a deflection yoke attached to the outside of the neck portion, and is located on the axis of symmetry on the long side surface of the magnetic shield body. When the points that are symmetrical with respect to the axis of symmetry and are located on the long side of the small-diameter opening are the second and third points, the magnetic shield body has an arc-shaped cutout connecting the first to third points. To the side of the long side Provided, and in which at least four corners of the small-diameter opening is positioned so as to intercept the deflection magnetic field generated from the deflection yoke.

[0010]

According to the present invention, the four corners of the small opening of the magnetic shield block the larger deflection magnetic field by the above structure, and the raster is restrained from being pulled outward by the phosphor screen. In addition, the arcuate notch provided on the end face side of the small-diameter opening on the side surface of the long side of the magnetic shield body allows more horizontal deflection magnetic field to leak into the magnetic shield body, and the raster distorted inside Pull outwards.

As a result, the pincushion distortion at the top and bottom of the screen in which the screen corner portion extends outward and the vicinity of the screen vertical axis enters inward is corrected.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 schematically shows the structure of a color picture tube device which is an embodiment of the present invention. This color picture tube device has an envelope composed of a panel portion 1 and a funnel portion 2, and a phosphor screen 3 which is painted in red, green and blue is formed on the inner surface of the panel portion 1. A shadow mask 4 is attached at a predetermined interval so as to face the fluorescent screen 3. The shadow mask 4 has a porous shape and serves as a color selection electrode. A frame 5 supporting the shadow mask 4 is provided around the shadow mask 4, and the magnetic shield body 6 is provided in the frame 5.
Is attached to. A neck portion 7 is provided on the opposite side of the funnel portion 2 from the panel portion 1, and an electron gun 8 is provided inside.
Are arranged. A deflection yoke 9 is attached to the neck portion 7 so as to cover the rear end portion of the funnel portion 2,
The dotted line indicated by a in the figure represents the magnetic field distribution on the tube axis of the vertical deflection magnetic field of the deflection yoke.

The magnetic shield 6 has a plate thickness of 0.1 mm.
It is formed by molding a metal magnetic material plate of about 0.3 mm, and its appearance is a substantially quadrangular pyramid shape composed of long side surface 13 and short side surface 14 as shown in FIG. Has become. The small-diameter opening is composed of long sides 11 and short sides 12, and is a horizontally long rectangle that is substantially similar to the shape of the phosphor screen. Each side surface 14 is provided with a substantially triangular notch 16. When mounted in a color picture tube, the magnetic shield body 6 is adjusted such that the small-diameter opening side is the electron gun side and the axis of the magnetic shield body and the tube axis of the color picture tube are substantially coaxial.

The arcuate notch 15 on the long side surface 13 will be described in more detail with reference to FIG. FIG. 3a is a top view of the magnetic shield body 6 as seen from the small diameter opening side, and FIG. 3b is a front view showing the long side surface. The arcuate notch 15 on the long-side side surface 13 of the magnetic shield body 6 is provided with respect to the point A on the symmetry axis 17 of the long-side side surface 13 and the symmetry axis 17 on the long side 11 and the long-side side surface. It is provided by connecting three points, which are the target B and C points. In addition, 18 indicates the axis of symmetry of the side surface on the short side. Further, the substantially triangular notch provided on the side surface on the short side is conventionally provided in order to prevent mislanding in which the electron beam does not reach the desired fluorescent screen due to the influence of the geomagnetism in the tube axis direction. It is what has been.

In the magnetic shield body of the present invention, by optimizing the shape of the arcuate notch on the side surface on the long side and the magnetic field distribution of the deflection yoke, a horizontal deflection magnetic field is appropriately taken into the magnetic shield body, and a screen is displayed. The upper and lower pincushion distortions are corrected without using a correction circuit. For this reason,
The position of the point A on the axis of symmetry and the distance between points B and C on the long side, which determine the shape of the arcuate cutout, are the deflection angle and the curved surface of the phosphor screen of the color picture tube device in which the magnetic shield is used. It is a parameter determined by the shape and the magnetic field distribution of the deflection yoke. In particular, by determining the distance between B and C points in consideration of the landing correction effect of the magnetic shield body and the position of point C in consideration of the raster shape correction effect,
It is possible to obtain the optimum notch shape. As a means for optimizing the magnetic field distribution of the deflection yoke, it is conceivable to use the distribution shape of the winding wire or to attach a magnetic piece of an appropriate shape at an appropriate position near the opening end of the deflection yoke.

At this time, particularly, the four corners of the small-diameter opening of the magnetic shield body are equivalent to 8% to 20% with respect to the peak value of the on-axis magnetic field distribution a of the vertical deflection magnetic field of the deflection yoke shown in FIG.
The raster shape can be corrected more accurately by being located on a plane orthogonal to the tube axis passing through a considerable point on the tube axis.

This is because the effect of moving the raster corner portion inward by partially shielding the magnetic field of the yoke acting on the beam so as to pull the corner portion of the raster outward is optimized. In FIG. 4, a indicates the degree of pincushion distortion at the top and bottom of the screen depending on the four corners of the small diameter opening of the magnetic shield with respect to the peak value of the on-axis magnetic field distribution of the vertical deflection magnetic field of the deflection yoke. The degree of pincushion distortion at the top and bottom of the screen is as shown in FIG.
The ratio of the difference between the vertical size a on the vertical axis of the screen and the vertical size b at the left and right ends of the screen to the original vertical size c of the screen [(ba) / c × 100].

As can be seen from FIG. 4, when the positions of the four corners of the small-diameter opening end of the magnetic shield are 8% or less with respect to the peak value of the magnetic field distribution on the tube axis, the pincushion distortion ratio at the top and bottom of the screen is high. Exceeds 4%, the effect of correcting pincushion distortion is reduced, and the magnetic shield effect against an unnecessary external magnetic field is reduced.

On the other hand, if it is 20% or more, the deflection magnetic field generated from the deflection yoke will be shielded more than necessary, and the deflection capability will be reduced, so that a large amount of deflection power will be required. Therefore, the position corresponding to 8% to 20% is optimum.

Of the shape of the arcuate notch, the position of point A in FIG. 2 which determines the depth of the notch is equivalent to 4% with respect to the peak value of the on-axis magnetic field distribution of the vertical deflection magnetic field of the deflection yoke. By setting the position between 8% and 8%, the effect of correcting the pincushion distortion at the top and bottom of the screen becomes very high.

In FIG. 4, b shows the degree of correction of the pincushion distortion at the top and bottom of the screen depending on the position of point A. Becomes large, especially when it is 8% or more, the strain amount becomes 4
You can see that it exceeds%. On the contrary, even if the point A is lower than 4% with respect to the peak value, the horizontal deflection magnetic field itself for image correction becomes small, so that the correction effect is lost and the unnecessary external magnetic field such as geomagnetism is shielded. This is because the range is reduced and the magnetic shield effect is adversely affected.

The distance between the two BC points in FIG. 3B is a value determined according to the amount of beam landing correction. As shown in FIG. 6, the ratio of the distance between the two points BC to the length of the long side of the small-diameter side opening of the magnetic shield is 5
At 0% or less, the mislanding amount a at the corner is 25
It is not suitable because it becomes as large as μm. On the other hand, when it is 85% or more, the mislanding amount b in the intermediate portion between the vertical axis and the corner portion (so-called screen NNE portion) becomes extremely large at 45 μm or more, which is not suitable. The ratio of the distance between the two BCs to the length of the long side of the small opening of the magnetic shield body diameter is 50% to 85.
In the range of%, the mislanding amount is 25 μm or less at the corner portion and 45 μm or less at the NNE portion, which can be corrected by correcting the phosphor position when forming the phosphor screen.

As described above, according to the magnetic shield of the present invention, the pincushion distortion shape at the top and bottom of the screen is the parameter shown in FIG. showed that.

The magnetic shield body of the embodiment of the present invention shown in FIG. 2 is provided with a substantially triangular notch on the short side of the small-diameter opening end, which is provided in the conventional type. It is the same as the one described above, and is provided in consideration of the shield effect of the external magnetic field. In addition, there is substantially no effect on the raster shape correction, which is the original purpose of the present invention, and especially the pincushion distortion correction effect at the top and bottom of the screen. Therefore, the effect of the present invention is not affected even if the notch shape of the triangle is changed.

Similarly, the conventional technique of providing a window or slit of a predetermined shape on the side surface of the shield body in order to optimize the unnecessary magnetic field shield effect does not hinder the effect of the present invention.

Further, the magnetic shield body of the present invention corrects the pincushion distortion above and below the screen by shielding a part of the deflection magnetic field of the deflection yoke (in particular, the horizontal deflection magnetic field that determines the raster shape above and below the screen). Is. For this reason, the positions of the four corners of the small diameter opening in the embodiment, which are the height of the magnetic shield body, need to enter the deflection magnetic field.

Further, the arcuate notch shape is ABC3.
Although it depends on the point, in order to perform the smooth correction of the raster shape at the top and bottom of the screen, it is actually an arc shape shallower than the semicircle (center angle is smaller than 180 degrees).

[0029]

As described above, by forming the magnetic shield body in the above-described shape, in the color picture tube device of the present invention, the deflection yoke does not correct the pincushion distortion at the top and bottom of the screen without correction by the deflection circuit. The correction can be made only by the automatic correction by the magnetic field.

At the same time, a mislanding prevention effect equivalent to that of the conventional magnetic shield body is obtained, and as a result, despite a very inexpensive drive circuit, it has a high quality without raster shape distortion of the screen and mislanding. Images can be obtained.

[Brief description of drawings]

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

FIG. 2 is a perspective view of an embodiment of a magnetic shield body used in the color picture tube device of the present invention.

3A is a top view of an embodiment of a magnetic shield body used in the color picture tube device of the present invention. FIG. 3B is a front view of an embodiment of a magnetic shield body used in the color picture tube device of the present invention.

FIG. 4 is a diagram showing changes in the amount of pincushion distortion at the top and bottom of the screen depending on the position with respect to the peak value of the axial distribution of the vertical deflection magnetic field.

FIG. 5 is a diagram showing the degree of pincushion distortion at the top and bottom of the screen.

FIG. 6 shows the ratio of the distance between two BC points to the long side,
Diagram showing changes in mislanding amount

FIG. 7 is a perspective view of a conventional magnetic shield body that corrects raster distortion.

[Explanation of symbols]

 1 Panel 2 Funnel 3 Phosphor Screen 4 Shadow Mask 5 Frame 6 Magnetic Shield 7 Neck 8 Electron Gun 9 Deflection Yoke

Claims (4)

[Claims] 1. An envelope including a panel portion and a funnel portion, a shadow mask arranged to face a fluorescent surface formed on an inner surface of the panel portion, and an electron arranged in a neck portion of the funnel portion. A magnetic shield body having a substantially quadrangular pyramid shape, which is attached to the frame of the shadow mask coaxially with the tube axis with the small-diameter opening facing the gun side and is disposed in the funnel portion, and outside the neck portion. A point formed on the symmetry axis of the side surface on the long side of the magnetic shield body, which is composed of a mounted deflection yoke, is defined as a first point, and is symmetrical to the symmetry axis and on the long side of the small diameter opening. When the points to be positioned are the second and third points, the magnetic shield body is provided with arcuate notches connecting the first to third points on the long side surface, respectively, and has a small diameter opening. At least four corners of the part A color picture tube device, wherein the color picture tube device is positioned so as to block a deflection magnetic field generated from the ark. 2. The four corners of the small diameter opening of the magnetic shield body,
7. A position perpendicular to the tube axis passing through a point on the tube axis corresponding to 8% to 20% of the peak value of the magnetic flux density distribution on the tube axis of the vertical deflection magnetic field generated by the deflection yoke. 1. The color picture tube device according to 1. 3. A first point located on the symmetry axis of the long side surface of the magnetic shield body corresponds to 4% of the peak value of the on-axis magnetic flux density distribution of the vertical deflection magnetic field by the deflection yoke. The color picture tube device according to claim 1 or 2, wherein the color picture tube device is located on a plane orthogonal to the tube axis passing through a point on the tube axis corresponding to 8%. 4. The small-diameter opening of the magnetic shield body is such that the distance between two second and third points symmetrical with respect to the axis of symmetry of the magnetic shield body and located on the long side of the small-diameter opening. 50% to 85% of the length of the long side of the color picture tube device according to claim 1, 2 or 3.