JP3159577B2 - Color picture tube equipment - 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 apparatus having a magnetic shield in a tube for shielding the influence of an external magnetic field on an electron beam.

[0002]

2. Description of the Related Art In general, in a color picture tube apparatus using a shadow mask as a color selection electrode, when an external magnetic field generated from peripheral members such as a driving circuit and a speaker enters an electron beam passing area in the tube, The electron beam deviates from the original trajectory under the influence of the unnecessary magnetic field, causing a mislanding that does not accurately reach a desired phosphor screen, thereby deteriorating the image quality. In order to shield an unnecessary external magnetic field such as the terrestrial magnetism, a magnetic shield is usually mounted in the frame portion of the shadow mask in the color picture tube device and disposed in the electron beam passage area. The shape of the magnetic shield body, especially the shape of the electron gun side opening, is designed in consideration of the arrangement of the fluorescent screen of the color picture tube device, etc., so as to be able to effectively shield an unnecessary external magnetic field having a greater influence. Usually, the height of the deflection yoke is considered so as not to block the deflection magnetic field.

On the other hand, Japanese Patent Application Laid-Open No. 59-66039 discloses a method using a magnetic shield as a means for correcting the so-called raster distortion of the screen shape of a color picture tube device. This means that, as shown in FIG. 7, the four corners 21 of the small opening on the electron gun side of the magnetic shield 6 are set on the axis corresponding to at least 5% of the peak value of the on-axis magnetic flux density distribution of the deflection magnetic field by the deflection yoke. It protrudes to the plane perpendicular to the axis passing through the point. That is, by intentionally shielding a part of the deflecting magnetic field with the magnetic shield, the pincushion distortion at the corner of the screen is corrected only by adjusting the deflecting magnetic field without attaching a correcting magnet to the deflecting yoke.

[0004] However, the raster shape has a stronger pincushion distortion due to the recent increase in the deflection angle due to the enlargement and thinning of the color picture tube and the flattening of the fluorescent screen panel. For this reason, it has been essential to add a correction circuit to the deflection circuit to correct the raster shape.

[0005]

In general, in an in-line type color picture tube device, three electron beams are irradiated on a phosphor screen by one.
As a method of concentrating on a point, a self-convergence method using a magnetic field distribution of a deflection yoke is adopted. In the self-convergence method, the magnetic field for concentrating the electron beam is a magnetic field in the direction for correcting pincushion distortion at the top and bottom of the screen as a result.

However, as described above, since the raster-shaped distortion has become larger, it has been necessary to use a deflection circuit to correct even relatively small pincushion distortions at the top and bottom of the screen.

However, correcting raster distortion by adding a correction circuit to a deflection circuit has problems in that it is difficult to design a proper correction circuit, and the circuit cost increases because the number of circuit components increases. Was.

According to the present invention, the correction of pincushion distortion at the top and bottom of the screen is solved by automatic correction using only the magnetic field distribution of the deflection yoke by optimizing the shape of the magnetic shield without using an expensive correction circuit. Accordingly, an object of the present invention is to provide an inexpensive color picture tube device.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems. A color picture tube apparatus according to the present invention comprises: an envelope comprising a panel portion and a funnel portion; A shadow mask disposed opposite to a fluorescent screen formed on the inner surface of the portion, and a tube shaft disposed on a frame of the shadow mask with a small-diameter opening directed toward an electron gun disposed within a neck portion of the funnel portion. A substantially quadrangular pyramid-shaped magnetic shield body attached to the funnel part and coaxially attached thereto, and a deflection yoke mounted on the outside of the neck part, and a long side surface of the magnetic shield body When a point located on the axis of symmetry is a first point, and a point symmetrical to the axis of symmetry and on a long side of the small-diameter opening is a second point and a third point, the magnetic shield body Are the first to third An arc-shaped notch connecting the points is provided on each of the long side surfaces, and four corners of the small opening correspond to 8% of the peak value of the on-axis magnetic flux density distribution of the vertical deflection magnetic field by the deflection yoke. The first point is located on a plane orthogonal to the tube axis passing through a point on the tube axis equivalent to 20%,
It is located on a plane perpendicular to the tube axis passing through a point on the tube axis corresponding to 4% to 8% of the peak value of the magnetic flux density distribution on the tube axis of the vertical magnetic field by the deflection yoke.

[0010]

According to the present invention, the four corners of the small-diameter opening of the magnetic shield block more deflection magnetic fields and suppress the raster from being pulled outward by the fluorescent screen. In addition, the notch on the circular arc provided on the end face side of the small-diameter opening on the side of the long side of the magnetic shield body allows more horizontal deflection magnetic field to leak into the magnetic shield body and removes the raster that was distorted inside. Pull outward.

As a result, the pincushion distortion at the top and bottom of the screen in which the screen corner extends outward and the vicinity of the screen vertical axis enters inside 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 apparatus according to an embodiment of the present invention. This color picture tube device has an envelope composed of a panel section 1 and a funnel section 2. On the inner surface of the panel section 1, there is formed a fluorescent screen 3 which is painted in red, green and blue. A shadow mask 4 is attached at a predetermined interval so as to face the fluorescent screen 3. This shadow mask 4 has a porous shape and plays a role of a color selection electrode. At the periphery of the shadow mask 4, there is a frame 5 for supporting the shadow mask 4, and the magnetic shield 6
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 the neck portion 7.
Is arranged. A deflection yoke 9 is attached to the neck 7 so as to cover the rear end of the funnel 2.
The dotted line indicated by a in the figure represents the on-tube magnetic field distribution of the vertical deflection magnetic field of the deflection yoke.

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

The arc-shaped 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 6 as viewed from the small-diameter opening side, and FIG. 3B is a front view showing a long side surface. The arc-shaped notch 15 on the long side surface 13 of the magnetic shield 6 is positioned between the point A on the symmetric axis 17 of the long side surface 13 and the symmetric axis 17 on the long side 11 and the long side surface. And two points B and C, which are the target, are connected. Reference numeral 18 denotes the axis of symmetry of the short side surface. In addition, a substantially triangular notch provided on the short side surface is provided conventionally to prevent mislanding in which the electron beam does not reach a desired fluorescent screen due to the influence of geomagnetism particularly in the tube axis direction. It is what is being done.

In the magnetic shield of the present invention, by optimizing the shape of the arc-shaped notch on the side surface on the long side and the magnetic field distribution of the deflection yoke, the horizontal deflection magnetic field is appropriately taken into the magnetic shield in a suitable manner. The upper and lower pincushion distortions are corrected without using a correction circuit. For this reason,
The position of point A on the axis of symmetry and the distance between B and C2 points on the long side, which determine the shape of the arc-shaped notch, are determined by the deflection angle and the curved surface of the fluorescent screen of the color picture tube device using the magnetic shield. These parameters are determined by the shape and the magnetic field distribution of the deflection yoke. In particular, by determining the distance between the two points B and C in consideration of the landing correction effect of the magnetic shield and the position of the point C in consideration of the raster shape correction effect,
An optimal notch shape can be obtained. Means for optimizing the magnetic field distribution of the deflection yoke may be based on the distribution shape of the winding or by attaching a magnetic piece of an appropriate shape at an appropriate position near the opening end of the deflection yoke.

At this time, in particular, the four corners of the small-diameter opening of the magnetic shield are set to 8% to 20% corresponding 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.
By being located on a plane orthogonal to the tube axis passing through a considerable point on the tube axis, the raster shape can be corrected more accurately.

This is because the effect of partially shielding the magnetic field of the yoke acting on the beam and moving the raster corner portion inward so as to pull the corner portion of the raster outward is optimized. 4A shows the degree of pincushion distortion at the top and bottom of the screen due to the positions of the four corners of the small-diameter opening of the magnetic shield with respect to the peak value of the magnetic field distribution on the tube axis of the vertical deflection magnetic field of the deflection yoke. Note that the degree of pincushion distortion at the top and bottom of the screen is as shown in FIG.
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 relative to the original screen vertical size c [(ba) / c × 100].

As can be seen from FIG. 4, the ratio of the pincushion distortion at the top and bottom of the screen at the point where the four corner positions of the small-diameter opening end of the magnetic shield body are 8% or less of the peak value of the magnetic field distribution on the tube axis. Exceeds 4%, the effect of correcting pincushion distortion is reduced, and the magnetic shielding effect against unnecessary external magnetic fields is reduced.

Conversely, if it is 20% or more, the deflection magnetic field generated from the deflection yoke is shielded more than necessary, and the deflection capability is reduced, so that a large deflection power is required. Therefore, the position corresponding to 8% to 20% is optimal.

In the shape of the arc-shaped notch, the position of the 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 to a position corresponding to ８8%, the effect of correcting pincushion distortion at the top and bottom of the screen becomes very high.

FIG. 4B shows the degree of correction of the pincushion distortion at the top and bottom of the screen based on the position of point A. The pincushion distortion at the top and bottom of the screen sharply starts at a position 7% of the peak value. In particular, when the amount is 8% or more, the amount of distortion is 4
%. Conversely, even if the point A is set at a position lower than 4% with respect to the peak value, the correction effect is lost because the horizontal deflection magnetic field itself taken in for the image correction is reduced, and unnecessary external magnetic fields such as terrestrial magnetism are shielded. This is because the reduced range adversely affects the magnetic shielding effect.

The distance between the two points BC in FIG. 3B is a value determined in accordance with the correction amount of the beam landing. 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 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, if 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 remarkably large at 45 μm or more, which is not appropriate. The ratio of the distance between the two points BC to the length of the long side of the small-diameter magnetic shield opening is 50% to 85%.
%, The mislanding amount is 25 μm or less at the corner portion and 45 μm or less at the NNE portion, and can be corrected by correcting the phosphor position at the time of forming the phosphor screen.

As described above, with the magnetic shield of the present invention, the pincushion distortion shape at the top and bottom of the screen is improved by 2.5% or less with respect to the conventional parameter of about 4.5% by the parameters shown in FIG. showed that.

The magnetic shield according to the embodiment of the present invention shown in FIG. 2 has a substantially triangular cut in the short side of the small-diameter opening end, which is provided in the conventional type. This is provided in consideration of the shielding effect of the external magnetic field. In addition, there is substantially no effect on the raster shape correction which is the original gist of the present invention, particularly, the pincushion distortion correction effect at the top and bottom of the screen. Therefore, even if this triangular notch shape is changed, the effect of the present invention is not affected at all.

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

The magnetic shield of the present invention corrects pincushion distortion at the top and bottom of the screen by shielding a part of the deflection magnetic field of the deflection yoke (particularly, the horizontal deflection magnetic field that determines the raster shape at the top and bottom of the screen). It is. For this reason, it is necessary that the positions of the four corners of the small-diameter opening in the embodiment, which is the height of the magnetic shield, enter the deflection magnetic field.

Further, the shape of the arc-shaped notch is ABC3.
Although it is determined by the point, in order to perform the gentle correction of the raster shape at the top and bottom of the screen, it is actually an arc shape shallower than a semicircle (the central angle is smaller than 180 degrees).

[0029]

As described above, by forming the magnetic shield into the shape described above, the color picture tube device of the present invention can provide the deflection yoke without correcting the pincushion distortion at the top and bottom of the screen by the deflection circuit. The correction can be performed only by the automatic correction using the magnetic field.

At the same time, the effect of preventing mislanding is equivalent to that of the conventional magnetic shield. As a result, despite the very inexpensive driving circuit, high quality without raster distortion of the screen and mislanding. Images can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a 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 used in the color picture tube device of the present invention.

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

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

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

FIG. 6 is a graph showing a ratio of a distance between two BCs to a long side.
Diagram to show change in mislanding amount

FIG. 7 is a perspective view of a conventional magnetic shield body for correcting raster distortion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Panel part 2 Funnel part 3 Phosphor screen 4 Shadow mask 5 Frame 6 Magnetic shield body 7 Neck part 8 Electron gun 9 Deflection yoke

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-66039 (JP, A) JP-A-58-166625 (JP, A) Jpn. Field (Int.Cl. ⁷ , DB name) H01J 29/02

Claims (2)

(57) [Claims] 1. An envelope comprising a panel portion and a funnel portion, a shadow mask arranged to face a phosphor screen formed on an inner surface of the panel portion, and an electron arranged in a neck portion of the funnel portion. A substantially quadrangular pyramid-shaped magnetic shield body attached to the frame of the shadow mask coaxially with the tube axis with the small-diameter opening facing the gun side and disposed in the funnel portion, and outside the neck portion. The first point is a point that is located on a symmetric axis of a long side surface of the magnetic shield body, and is located on a long side of the small-diameter opening symmetrical to the symmetric axis. when a point located to the point of the second and third, the magnetic shield body arcuate notch connecting points of the first to third are respectively provided on the long side face, the small opening The four corners are
Of the magnetic flux density distribution on the tube axis of the vertical deflection magnetic field by the directional yoke
Pass the point on the pipe axis equivalent to 8% to 20% of the peak value
The first point is located on a plane perpendicular to the tube axis,
Peak of magnetic flux density distribution on the tube axis of vertical magnetic field by deflection yoke
Pipe axis passing through a point on the pipe axis equivalent to 4% to 8%
A color picture tube device, wherein the color picture tube device is located on a plane perpendicular to the plane . 2. A distance between the second and third points.
The separation is the length of the long side of the small-diameter opening of the magnetic shield.
2. A color picture tube device according to claim 1, wherein said color picture tube device has a height of 50% to 85% .