JPS6214784Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to the arrangement shape of a degaussing coil for demagnetizing a shadow mask of a color cathode ray tube.

2. Description of the Related Art In color television receivers, the cathode ray tube is equipped with a shadow mask, which is known to be magnetized by the earth's magnetic field, causing color unevenness on the reproduced screen. Therefore, in order to prevent the color unevenness that occurs in this manner, a conventional method has been adopted in which a degaussing coil is disposed around the outer periphery of the cathode ray tube, and when the power is turned on, attenuated alternating current is passed through the coil to demagnetize the shadow mask.

Problems to be solved by the invention Various types of degaussing coils have already been proposed regarding the number of turns and shapes of the coils, but there are some types, such as dot type or in-line type.
With the recent development of various cathode ray tubes, there has been a desire for a corresponding one that can be simplified and demagnetized more efficiently. In this case, since cathode ray tubes usually have metal fittings at their four corners for attaching to the cabinet, the shape of the degaussing coil must be particularly considered to ensure that the effect is not hindered by the above-mentioned attachment parts. Ta.

This proposal was made in view of these points,
The purpose of this invention is to provide a coil shape suitable for recent cathode ray tubes and a simple and efficient degaussing coil device.

In particular, the present invention is most suitable for use in color cathode ray tubes that use an in-line array of electron guns so that the electron beam emitted from the gun hits three primary color phosphors that are sequentially arranged horizontally in vertical stripes. However, it is an object of the present invention to provide a demagnetizing coil device that can obtain the same demagnetizing effect even when the shadow mask is dot-shaped, for example.

Means for Solving the Problems In the present invention, an electron beam emitted from an electron gun hits three primary color phosphors arranged in an array on the inner surface of the face plate through a shadow mask placed near the inner surface of the face plate. A degaussing coil device applied to color cathode ray tubes, in which a coil having one loop bundle is arranged along the outer periphery near the face plate of the cathode ray tube, and the ring formed by the coil is The upper side of the square is arranged along the upper side of one side of the shadow mask opposite to the face plate, and the lower side of the square is arranged along the upper side of one side of the shadow mask opposite to the face plate. It is arranged along the lower side of the shadow mask, and is arranged so that the left and right sides of the rectangular shape intersect from one side to the other side of the shadow mask.

Embodiment Hereinafter, for convenience of explanation, the present invention will be explained along with its function using an example of a cathode ray tube having a vertical striped shadow mask.

In the northern hemisphere, the direction of magnetization of the shadow mask due to the vertical component of the earth's magnetism is the direction of the arrow shown in FIG. 1. That is, the surface of the shadow mask M is magnetized downward. In the southern hemisphere, it is magnetized upward. Also, the direction of magnetization due to the horizontal component of the earth's magnetic field is the second
As shown in the figure. Figure 2A shows a case where the axial direction of the cathode ray tube CRT and the magnetic field lines of the horizontal component are parallel, and Figure 2B shows the case where the surface of the shadow mask M is parallel to the horizontal component, that is, perpendicular to the axis of the cathode ray tube CRT. Indicates when there is a relationship.

When the shadow mask is magnetized in the directions shown in FIGS. 1 and 2, a force acts on the beam landing in the direction of the arrow shown in FIG. 3, causing color shift.
In other words, due to the magnetization effect of the vertical component force in Figure 1, the third
As shown in Figure A, the beam passing through the shadow mask is deflected in the horizontal direction. In response to the magnetizing action of the horizontal force component shown in FIG. 2A, the beam is deflected in the direction shown in FIG. 3B.

In this case, it is almost unaffected because it is parallel to the magnetic field lines near the center axis of the cathode ray tube CRT, but the perpendicular component of the magnetic field lines is occurs, so it is subject to deflection. That is, the beam landing becomes larger as it approaches the outer periphery of the screen. Further, when the beam is magnetized in the direction shown in FIG. 2B by the horizontal force of the earth's magnetism, the beam is deflected by the force in the direction shown in FIG. 3C.
Therefore, the beam is radiated in a helical manner near the outer periphery of the screen due to both vertical and horizontal components. By the way, the arrangement of the phosphors in the screen image of the in-line stripe tube is as shown in Figure 4, in which the phosphors R, G, and B of each color are sequentially arranged horizontally in a vertical stripe shape, and the boundaries between each A black stripe L1 is arranged. Further, the striped phosphors R, G, and B of similar colors are separated by a horizontal boundary zone L2 to form a unit picture element C. Figure 5 shows an example of a shadow mask, which is formed in a similar shape to the phosphor pattern in the screen image (Figure 4), divided by vertical frames 1 ₁ and horizontal frames 1 ₂ , and has the same shape as one picture element. It has a hole H. Here, this one picture element is of course larger than the unit picture element C mentioned above.

When beam landing is performed normally, the hole H of the mask and the picture element perfectly match, and no color shift occurs. When the beam is deflected laterally as shown in Figure 3A by the magnetization of the shadow mask,
The beam hits the area between the black stripes L1 and does not hit the part of the phosphor that should be hit, resulting in color shift. Also, at this time, the shadow of the vertical frame _l1 of the shadow mask M appears in the picture element portion, and the brightness is slightly lowered. In the case of deflection as shown in Figure 3B, the horizontally deflected portion causes color shift as in Figure 3B, but for vertical deflection, the phosphor is vertically deflected. Because of the striped shape, color shift does not occur, and the only difference is that the shadow of the horizontal frame 12 of the shadow mask M enters the picture element portion, resulting in a slight decrease in brightness. When the light is deflected only in the vertical direction as shown in FIG. 3C, only a decrease in brightness occurs. Therefore, color shifts occur at the top, bottom, and four corners of the screen.

Therefore, depending on the arrangement of the receiver, changes in beam landing occur due to the combinations of A and B in Figure 3 and the combinations of A and C in Figure 3. In the former case, color shift occurs overall, but only in the upper and lower four corners. In the latter case, since it is only in the direction shown in FIG. 3A, uniform color shift occurs throughout.
To remove this, the magnetization states shown in FIGS. 1 and 2A can be erased.

The present invention can provide a degaussing coil device having an efficient and simple configuration for removing the influence of earth's magnetic field in the above-mentioned inline striped pipe.

FIG. 7 is a side view of a degaussing coil device according to an embodiment of the present invention, and FIG. 8 is a front view thereof. Reference numeral 1 is a color cathode ray tube having an in-line electron gun and three primary color phosphors arranged horizontally in a vertical stripe pattern, and 2 is its screen surface. 4 is a degaussing coil having one loop bundle around which a conducting wire is wound. The upper half thereof is provided along the outer periphery of the cathode ray tube 1, and the space between A and B is arranged parallel to the front side of the extended surface of the shadow mask 3. The remaining half has a portion CD and E-F that diagonally crosses the shadow mask surface, and a portion D-E that is parallel to A-B on the back side.

The lines of magnetic force formed between A and B and between D and E act obliquely across the surface of the shadow mask 3. Therefore, the component forces of these lines of magnetic force act on the shadow mask surface in a direction perpendicular to the ground, erasing the magnetization due to earth's magnetism. Also, the inclined part C
Similarly, -D and E-F act on the shadow mask 3 as component forces having vertical magnetic flux changes. Therefore, components that affect the cathode ray tube 1 are removed, and in particular, since the loop bundle can be brought close to the outer periphery of the shadow mask 3, the magnetic field is strong in the outer periphery, and the influence of the earth's magnetic field in that area is suppressed not only in the vertical direction but also in the horizontal direction. It becomes possible to powerfully remove the effects. Moreover, this shape is practical because it does not interfere with the mounting structure of the cathode ray tube to the cabinet.

FIG. 9 is a side view showing another embodiment of the present invention. The only difference from the embodiment shown in FIG. 7 is that the degaussing coil 4 is formed linearly when viewed from the side. similarly configured.

As described above, in the present invention, a coil 4 having one loop bundle is arranged along the outer periphery of the screen surface 2 of the cathode ray tube 1, in other words, near the face plate of the cathode ray tube, and the coil 4 is formed by the coil 4. The ring forms an approximately rectangular shape when viewed from the face plate,
The rectangular upper side A-B is arranged along the upper side of one surface of the shadow mask 3 facing the face plate, and the rectangular lower side E-D is arranged along the upper side of one surface of the shadow mask 3 opposite to the above-mentioned one surface. The shadow mask 3 is arranged along the lower side of the other surface, and is arranged so that the rectangular left and right side portions C-F intersect from one surface to the other surface of the shadow mask 3.

Effects of the invention Therefore, according to the present invention, since the electron beam's reach is short near the center plane of the shadow mask,
In places where the influence of vertical magnetization of the earth's magnetic field is large, this can be counteracted by using the shadow mask itself as a magnetic path, and at the same time, near the corners of the shadow mask, the beam reaches a long distance, so the vertical direction of the earth's magnetic field The effects of both horizontal magnetization can be canceled out by generating the strongest magnetic field.

[Brief explanation of the drawing]

1 and 2 are diagrams showing the magnetization direction of the shadow mask M due to the earth's magnetism, FIG. 3 is a diagram showing the direction in which beam landing is deflected by the magnetization of the shadow mask, and FIG. 4 is a diagram showing the pattern of the phosphor. FIG. 5 is a diagram showing the configuration of the shadow mask,
FIG. 6 is a side view of a degaussing coil device according to an embodiment of the present invention, FIG. 7 is a front view thereof, and FIG. 8 is a side view of a degaussing coil device according to another embodiment of the present invention.

Claims (1)

[Claims for Utility Model Registration] A color cathode ray tube in which an electron beam emitted from an electron gun strikes three primary color phosphors arranged in an array on the inner surface of the face plate through a shadow mask disposed near the inner surface of the face plate. A degaussing coil device applied to the cathode ray tube, wherein a coil having one loop bundle is arranged along the outer periphery near the face plate of the cathode ray tube,
The ring formed by the coil has a substantially rectangular shape when viewed from the face plate, and the upper side of this rectangular shape is arranged along the upper side of one surface of the shadow mask on the side facing the face plate, and A lower side of the rectangular shape is arranged along a lower side of one surface of the shadow mask and the other surface on the opposite side, and left and right side portions of the rectangular shape intersect from one surface of the shadow mask to the other surface. A degaussing coil device characterized in that the degaussing coil device is arranged so that