Deflection yoke and color cathode ray tube comprising the deflection yoke

Abstract: A deflection yoke which is capable of sufficiently reducing a high order raster distortion (gullwing) at the upper and lower edges of the screen without damaging coil wires of the screen side flange portion at the time of winding the horizontal deflection coil. A deflection yoke is formed with a saddle shaped horizontal deflection coil (30), a saddle shaped vertical deflection coil (31) located outside the horizontal deflection coil, and a ferrite core (32) located outside the vertical deflection coil. The center portion of the screen side flange portion of one selected from the group consisting of the saddle (24) shaped horizontal deflection coil and the saddle shaped vertical deflection coil forms a projection towards the screen side.

Description: The present invention relates to deflection yokes and color cathode ray tubes with the deflection yokes. In the current color cathode ray tubes used as a display monitor such as windows, information is very often displayed in the peripheral regions of the screen. Therefore a technology enabling minute image display in such regions is being required. Since the raster distortion is one of the important elements in determining the image quality in the peripheral regions of the screen, the standard for the raster distortion of the screen, which depends on the magnetic field distribution of the deflection yoke itself, has become very demanding. In general, the magnetic field distribution at the screen side cone portion of a saddle shaped coil used as a horizontal deflection coil is designed to include a strong pincushion distortion in order to eliminate the raster distortion at the upper and lower edges of the screen. However, when it includes significant fifth-order pincushion distortion, an upper and lower high order raster distortion called gullwing emerges. Since a high order raster distortion such as the gullwing deteriorates the visual image quality drastically, it should be prevented. In general, the vertical magnetic field distribution of a deflection yoke used in a color cathode ray tube for display monitoring has a barrel distortion entirely from the electron gun side to the screen side with respect to the self-convergence. Then, since the raster distortion at the right and left edges of the screen has a pincushion shape when such a barrel distortion is included, the distortion is eliminated by supplying a correction current from the circuit side of the display monitor toward the horizontal deflection coil. However, since the correction current in general has a wave form to correct a third-order pincushion distortion, when a raster distortion at the right and left edges of the screen includes a gullwing which is a high order distortion, the correction current can not completely eliminate the distortion. On the other hand, as mentioned above, since the gullwing drastically deteriorates the visual image quality, it should be prevented. In order to meet such requirements, a method of reducing a high order raster distortion such as a gullwing at the upper and lower edges of the screen by forming a dent toward the central axis of the cathode ray tube at the center of the screen side flange portion of the horizontal deflection coil is proposed in US-A-4 233 582. Another method of reducing the gullwing at the upper and lower edges of the screen by having the screen side flange portion of the horizontal deflection coil of a polygonal shape is advocated in US-A-4 229 720. By analogy, these methods can be applied to a vertical deflection coil to reduce the gullwing at the right and left edges of the screen. Further, a method of reducing a high order raster distortion by forming a projection toward the electron gun side at the right and left edges of the screen side flange portion of a saddle shaped coil is proposed in JP-A-216738/1990. However, in the method disclosed in US-A-4 233 582, in the pressing process to provide a dent toward the central axis of the cathode ray tube at the center of the screen side flange portion of a horizontal deflection coil or a vertical deflection coil, there is a problem that it is highly likely that the insulating coating layer of a coil wire is damaged due to the excessive stretching of the coil wire in production. Further, if the dent is formed too deep, since the dent comes in contact with the funnel portion of the cathode ray tube when the deflection yoke is attached to the cathode ray tube, there is a problem in production or designing in that it is sometimes difficult to form a dent sufficient to remove a high order raster distortion such as the gullwing. Further, if a dent is formed too deep, since the dent comes in contact with the cone portion of the horizontal deflection coil when assembling the deflection yoke, there is a problem in production or designing in that it is sometimes difficult to form a dent sufficient to remove the gullwing. Further, in the method disclosed in US-A-4 229 720, there is a problem in production in that coil wires are liable to be deformed and damaged at the apexes of the polygon-shaped screen side flange portion of the horizontal deflection coil or the vertical deflection coil. In general, a ferrite core is used in a deflection yoke to strengthen the deflection magnetic field strength but the ferrite core also alleviates the magnetic field distortion formed by the deflection coil itself (hereinafter abbreviated ferrite core effect on the field distribution). Therefore even if the horizontal magnetic field distortion is controlled by the winding distribution of the deflection coil to minimize the deflection aberration, since the magnetic field distortion is alleviated by the ferrite core effect on the field distribution of the ferrite core, there is a problem that the correction sensitivity of the deflection aberration deteriorates to that extent. In the method disclosed in JP-A-216738/1990, in the pressing process to provide a projection at the right and left edges of the screen side flange portion of the saddle shaped coil, there is a problem in that it is highly likely that the insulation coating layer of a coil wire is damaged due to the excessive stretching of the coil wire in production. Further, if the projection is formed too high, since the horizontal deflection coil, the vertical deflection coil and the ferrite core come in contact with each other when the deflection yoke is assembled, there is a problem in production or designing in that it is difficult to form a projection sufficient to remove a high order raster distortion. In order to solve the above mentioned problems of conventional arts, an object of the present invention is to provide a deflection yoke which can sufficiently decrease a gullwing without the risk of damaging coil wires of the screen side flange portion at the time of winding of the horizontal deflection coil or the vertical deflection coil. Another object of the present invention is to provide a deflection yoke which can sufficiently decrease a high order raster distortion without the risk of damaging the coil wires of the screen side flange portion of the saddle shaped coil at the time of wiring the saddle shaped coil, or contacting the horizontal deflection coil, the vertical deflection coil and the ferrite core with each other at the time of assembling the deflection yoke. It is a further object of the present invention to provide a deflection yoke which can sufficiently decrease a high order raster distortion without the risk of damaging the coil wires of the screen side flange portion at the time of winding the saddle shaped coil or the horizontal deflection coil, or contacting the saddle shaped coil or the horizontal deflection coil to the glass funnel at the time of attaching the deflection yoke. It is another object of the present invention to provide a color cathode ray tube which can sufficiently decrease a high order raster distortion such as the gullwing to improve the image quality. These objects are solved by the features of the claims. A first aspect of deflection yokes of the present invention comprises at least a saddle shaped horizontal deflection coil, a saddle shaped vertical deflection coil located outside the saddle shaped horizontal deflection coil and a core located outside the saddle shaped vertical deflection coil wherein the center of the screen side flange portion of one selected from the group consisting of the saddle shaped horizontal deflection coil and saddle-shaped vertical deflection coil comprises a projection toward the screen side. Thus, the screen side flange portion of one selected from the group consisting of the saddle shaped horizontal deflection coil and the saddle shaped vertical deflection coil is located closer to the screen side relative to the both side portions. As a result, when a fifth-order pincushion distortion is included in the distortion condition of the horizontal magnetic field distribution at the upper and lower regions and a local high order barrel shaped distortion is included at the upper and lower regions of the screen of the color cathode ray tube, the fifth-order barrel distortion is emphasized relatively at the upper and lower regions of the distortion condition of the horizontal magnetic field distribution to provide a good linear condition without having a high order upper and lower raster distortion. Further, since the screen side flange portion of the saddle shaped coil does not have an inflection point as in conventional arts, problems including the damage of the coil wires at the time of winding the horizontal deflection coil as well as the contact of the horizontal deflection coil, vertical deflection coil and ferrite core with each other in assembling the deflection yoke are avoided. A second aspect of deflection yokes of the present invention comprises at least a saddle shaped horizontal deflection coil, a saddle shaped vertical deflection coil located outside the saddle shaped horizontal deflection coil and a core located outside the saddle shaped vertical deflection coil, wherein the center of the screen side flange portion of one selected from the group consisting of the saddle shaped horizontal deflection coil and the saddle shaped vertical deflection coil comprises a dent toward the electron gun side. Thus, the screen side flange portion of the saddle shaped coil is located closer to the electron gun side relative to the both side portions. As a result, when a fifth-order barrel distortion is included in the distortion condition of the horizontal magnetic field distribution at the upper and lower regions and a local high order pincushion shaped distortion is included at the upper and lower regions of the screen of the color cathode ray tube, the fifth-order pincushion distortion is emphasized relatively at the upper and lower regions of the distortion condition of the horizontal magnetic field distribution to provide a good linear condition without having a high order upper and lower raster distortion. Further, since the screen side flange portion of the saddle shaped coil does not have an inflection point as in conventional arts, problems including the damage to the coil wires at the time of winding the horizontal deflection coil as well as the contact of the horizontal deflection coil, the vertical deflection coil and ferrite core in assembling the deflection yoke are avoided. In a preferable embodiment of the above mentioned first or second aspect of deflection yokes of the present invention in which the surface of the screen side flange portion of the saddle shaped coil opposing a glass funnel of a color cathode ray tube is formed to have the contour conforming to the surface of the opposing glass funnel, since the screen side flange portion of one selected from the group consisting of the saddle shaped horizontal deflection coil and the saddle shaped vertical deflection coil is located closer to the electron beam, the correction sensitivity and the energy loss of the raster distortion at the screen side flange portion of the saddle shaped coil become maximum and minimum, respectively. The above mentioned first aspect of color cathode ray tubes of the present invention comprises a color cathode ray tube main body comprising a glass panel portion and a glass funnel portion connected to the rear part of the glass panel portion, and a deflection-yoke comprising at least an electron gun located at the rear of the cathode ray tube main body, a saddle shaped horizontal deflection coil located at the rear periphery of the cathode ray tube main body, a saddle shaped vertical deflection coil located outside the saddle shaped horizontal deflection coil and a core located outside the saddle shaped vertical deflection coil wherein the center of the screen side flange portion of one selected from the group consisting of the saddle shaped horizontal deflection coil and the saddle shaped vertical deflection coil comprises a projection toward the screen side, and the following advantages can thus be achieved. That is, since the above mentioned deflection yoke of the first aspect of the present invention is used, as mentioned above, a fifth-order pincushion distortion is included in the distortion condition of the horizontal magnetic field distribution at the upper and lower regions, and when a high order local barrel shaped distortion is included at the upper and lower regions of the screen of the color cathode ray tube, the fifth-order barrel distortion is emphasized relatively at the upper and lower regions of the distortion condition of the horizontal magnetic field distribution. As a result, since the upper and lower raster distortion becomes preferably linear without a high order distortion, the image quality of the color cathode ray tube becomes improved. The above mentioned second aspect of color cathode ray tubes of the present invention comprises a color cathode ray tube main body comprising a glass panel portion and a glass funnel portion connected to the rear part of the glass panel portion, and a deflection yoke comprising at least an electron gun located at the rear of the cathode ray tube main body, a saddle shaped horizontal deflection coil located at the rear periphery of the cathode ray tube main body, a saddle shaped vertical deflection coil located outside the saddle shaped horizontal deflection coil and a core located outside the saddle shaped vertical deflection coil, wherein the center of the screen side flange portion of one selected from the group consisting of the saddle shaped horizontal deflection coil and the saddle shaped vertical deflection coil comprises a dent toward the electron gun side, and the following advantages can thus be achieved. That is, since the above mentioned deflection yoke of the second aspect of the present invention is used, as mentioned above, a fifth-order barrel distortion is included in the distortion condition of the horizontal magnetic field distribution at the upper and lower regions, and when a high order local pincushion shaped distortion is included at the upper and lower regions of the screen of the color cathode ray tube, the fifth-order pincushion distortion is emphasized relatively at the upper and lower regions of the distortion condition of the horizontal magnetic field distribution. As a result, since the upper and lower raster distortion becomes preferably linear without a high order distortion, the image quality of the color cathode ray tube becomes improved. FIG. 1 is a plan view of a deflection yoke of Example 1 of the present invention. FIG. 2 is a side view of a deflection yoke of FIG. 1. FIG. 3 is a diagram illustrating the deflection condition of the horizontal magnetic field distribution at the screen side of Example 1 of the present invention. FIG. 4 is a diagram illustrating the upper and lower raster distortion of Example 1 of the present invention. FIG. 5 is a plan view of a deflection yoke of Example 2 of the present invention. FIG. 6 is a side view of the deflection yoke of FIG. 5. FIG. 7 is a diagram illustrating the distortion condition of the horizontal magnetic field distribution at the screen side of Example 2 of the present invention. FIG. 8 is a diagram illustrating the upper and lower raster distortion of Example 2 of the present invention. FIG. 9 is a diagram illustrating the magnetic field generated at the screen side flange portion and cone portion of the saddle shaped coil. FIG. 10 is a plan view of a cathode ray tube of Example 3 of the present invention. <Example 1> FIG. 1 is a plan view illustrating the first Example of deflection yokes of the present invention and FIG. 2 is a side view of the deflection yoke of FIG. 1. As can be seen in FIG. 1 and FIG. 2, the deflection yoke comprises the saddle shaped horizontal deflection coil 30, the saddle shaped vertical deflection coil 31 located outside the horizontal deflection coil 30, and the ferrite core 32 located outside the vertical deflection coil 31. As described in FIG. 1, the screen side flange portion 24 of the horizontal deflection coil 30 is formed to have a projection toward the screen side with the top portion at the point crossing the tube axis (Z axis) 25. The projection size a is set to be 30 mm away from the maximum projection line 27 of the screen side cone portion 26. As described in FIG. 2, the surface 34 of the screen side flange portion of the horizontal deflection coil 30 opposing the glass funnel portion of the color cathode ray tube 33 is formed to conform to the shape of the surface of the opposing glass funnel portion 33. By this, since the screen side flange portion 24 of the horizontal deflection coil 30 can be placed close to the electron beam, the correction sensitivity of the raster distortion and the energy loss at the screen side flange portion 24 of the horizontal deflection coil 30 become maximum and minimum, respectively. FIG. 1 shows a plan view of the screen side flange portion 28 of a horizontal deflection coil with a conventional, approximately circular shape by the chain double-dashed line, which is a straight line. In this case, the condition of the horizontal magnetic field distribution at the cross section along the horizontal axis (X axis) - the vertical axis (Y axis) at a screen side position 29 is as illustrated by the solid line in FIG. 3, and the upper and lower raster distortion may generate local barrel shaped high order distortion 39a, 39b at the upper and lower portions of a color cathode ray tube as illustrated in FIG. 4. Such barrel shaped high order distortion 39a, 39b are generated because the condition of the horizontal magnetic field distortion of FIG. 3 includes the fifth-order pincushion distortion in the regions of the upper portion 38a and the lower portion 38b. On the other hand, if the screen side flange portion 24 of the horizontal deflection coil 30 is formed to have a projection toward the screen side as in this Example, since the upper portion 35 and the lower portion 36 of the screen side flange portion 24 are closer to the screen side relative to the both side portions 37, the fifth-order barrel distortion is relatively emphasized in the regions of the upper portion 38a and the lower portion 38b of the distortion condition of the horizontal magnetic field distribution in FIG. 3 and the distortion condition of the horizontal magnetic field distribution becomes as the chain double-dashed line in FIG. 3. As a result, the upper and lower raster distortion is corrected to have a preferable linear shape without a high order distortion as illustrated by the chain double-dashed line in FIG. 4. Further, since the deflection yoke of this Example does not have an inflection point at the screen side flange portion 24 of the horizontal deflection coil 30 unlike conventional arts, problems such as the damage in production to the coil wires at the time of winding the horizontal deflection coil 30 as well as the contact of the horizontal deflection coil 30, the vertical deflection coil 31 and the ferrite core 32 with each other at the time of assembling the deflection yoke can be prevented. Although the screen side flange portion 24 of the horizontal deflection coil 30 is formed to have a projection with the projection size a of 30 mm away from the maximum projection line 27 of the screen side cone portion 26, the size is not limited thereto. <Example 2> FIG. 5 is a plan view illustrating the second Example of deflection yokes of the present invention and FIG. 6 is a side view of the deflection yoke of FIG. 5. As can be seen in FIG. 5 and FIG. 6, the deflection yoke comprises the saddle shaped horizontal deflection coil 45, the saddle shaped vertical deflection coil 46 located outside the horizontal deflection coil 45, and the ferrite core 47 located outside the vertical deflection coil 46. As described in FIG. 5, the screen side flange portion 40 of the horizontal deflection coil 45 is formed to have a dent toward the electron gun side with the bottom portion at the point crossing the tube axis (Z axis) 41. The dent size b is set to be 15 mm away from the maximum projection line 42 of the screen side flange portion 40. As described in FIG. 6, the surface opposing the glass funnel portion of the color cathode ray tube 33 48 of the screen side flange portion of the horizontal deflection coil 45 is formed to have the shape conforming to the shape of the surface of the opposing glass funnel portion 33. By this, since the screen side flange portion 40 of the horizontal deflection coil 45 can be placed close to the electron beam, the correction sensitivity of the raster distortion and the energy loss at the screen side flange portion 40 of the horizontal deflection coil 45 become maximum and minimum, respectively. FIG. 5 shows a plan view of the screen side flange portion 43 of a horizontal deflection coil 45 which has a conventional, approximately circular shape by a chain double-dashed line, which is a straight line. In this case, the condition of the horizontal magnetic field distribution at the cross section along the horizontal axis (X axis) - the vertical axis (Y axis) at a screen side position 44 is as illustrated by the solid line in FIG. 7, and the upper and lower raster distortion may generate local pincushion shaped high order distortion 54a, 54b at the upper and lower portions of a color cathode ray tube as illustrated in FIG. 8. Such pincushion shaped high order distortion 54a, 54b are generated because the condition of the horizontal magnetic field distortion of FIG. 7 includes the fifth-order barrel distortion in the regions of the upper portion 52a and the lower portion 52b. On the other hand, if the screen side flange portion 40 of the horizontal deflection coil 45 is formed to have a dent toward the screen side as in this Example, since the upper portion 49 and the lower portion 50 of the screen side flange portion 40 are closer to the electron gun relative to the both side portions 51, the fifth-order pincushion distortion is relatively emphasized in the regions of the upper portion 52a and the lower portion 52b of the distortion condition of the horizontal magnetic field distribution in FIG. 7 and the distortion condition of the horizontal magnetic field distribution becomes as the chain double-dashed line in FIG. 7. As a result, the upper and lower raster distortion is corrected to have a preferable linear form without a high order distortion as illustrated by the chain double-dashed line in FIG. 8. Further, since the deflection yoke of this Example does not have an inflection point at the screen side flange portion 40 of the horizontal deflection coil 45 unlike conventional arts, problems such as the damage in production to the coil wires at the time of winding the horizontal deflection coil 45 as well as the contact of the horizontal deflection coil 45, the vertical deflection coil 46 and the ferrite core 47 with each other at the time of assembling the deflection yoke can be prevented. Although the screen side flange portion 40 of the horizontal deflection coil 45 is formed to have a dent with the dent size b of 15 mm away from the maximum projection line 42 of the screen side flange portion 40, the size is not limited thereto. Further, although the embodiment wherein the screen side flange portion 24 of the saddle shaped horizontal deflection coil 30 is formed to-have a projection toward the screen side, or the embodiment wherein the screen side flange portion 40 of the horizontal deflection coil 45 is formed to have a dent toward the electron gun side are described in the above mentioned Example 1 and Example 2, the present invention is not limited to these embodiments. And the same effect of reducing a high order raster distortion can be achieved in an embodiment wherein the screen side flange portion of the saddle shaped vertical deflection coil 31 is formed to have a projection toward the screen side, or an embodiment wherein the screen side flange portion of the saddle shaped vertical deflection coil 46 is formed to have a dent toward the electron gun side. <Example 3> FIG. 10 is a plan view illustrating the third Example of color cathode ray tubes of the present invention. As can be seen in FIG. 10, the color cathode ray tube main body 60 comprises glass panel portion 61, and glass funnel portion 33 connected to the rear part of the glass panel portion 61. An electron gun (not shown in FIG. 10) is provided behind the glass funnel portion 33. The deflection yoke, comprising the saddle shaped horizontal deflection coil 30, the saddle shaped vertical deflection coil 31 located outside the horizontal deflection coil 30 and the ferrite core 32 located outside the vertical deflection coil 31, is located in the rear periphery of the glass funnel portion 33. That is, the deflection yoke with the structure shown in Example 1 is used in the color cathode ray tube of this Example (see FIG. 1, FIG. 2). The screen side flange portion 24 of the horizontal deflection coil 30 is formed to have a projection toward the screen side with the top portion at the point crossing the tube axis (Z axis) 25. The projection size a is set to be 30 mm away from the maximum projection line 27 of the screen side cone portion 26. The deflection yoke with the structure described in the above mentioned first Example is used and the fifth-order barrel distortion is emphasized to have a preferable linear raster distortion at the upper and lower portions without a high order distortion when the distortion conditions of the horizontal magnetic field include the fifth-order pincushion distortion. Although the deflection yoke with the structure described in the above mentioned Example 1 is used in this Example, the structure of the yoke is not limited thereto. When the distortion condition of the horizontal magnetic field distribution includes the fifth-order barrel distortion, by using the deflection yoke with the structure described in the above mentioned Example 2, the fifth-order pincushion distortion is emphasized and the upper and lower raster distortion is corrected to be the preferable linear one without a high order distortion as mentioned above. In general; the magnetic field at the screen side of a deflection yoke is much more sensitive than the magnetic field at the electron gun side with respect to controlling the raster distortion. Therefore, methods such as controlling the raster distortion in the magnetic field generated by the screen side flange portion of the saddle shaped coil are highly effective.

Claims: A deflection yoke comprising a saddle shaped horizontal deflection coil (30), a saddle shaped vertical deflection coil (31) located outside the saddle shaped horizontal deflection coil (30), and a core (32) located outside the saddle shaped vertical deflection coil (31), wherein the center portion of the screen side flange portion (24) of one selected from the group consisting of the saddle shaped horizontal deflection coil (30) and the saddle shaped vertical deflection coil (31) forms a projection toward the screen side. A deflection yoke comprising a saddle shaped horizontal deflection coil (45), a saddle shaped vertical deflection coil (46) located outside the saddle shaped horizontal deflection coil (45), and a core (47) located outside the saddle shaped vertical deflection coil (46), wherein the center portion of the screen side flange portion (40) of one selected from the group consisting of the saddle shaped horizontal deflection coil (45) and the saddle shaped vertical deflection coil (46) forms a dent toward the electron gun side. The deflection yoke according to claim 1 or 2, wherein the surface of the screen side flange portion (24,40) of one selected from the group consisting of the saddle shaped horizontal deflection coil (30,45) and the saddle shaped vertical deflection coil (31,46) opposing to a glass funnel portion of a color cathode ray tube is formed to conform to the surface of the glass funnel portion. A color cathode ray tube comprising a color cathode ray tube main body (60) which comprises a glass panel portion (61) and a glass funnel portion (33) connected to the rear part of the glass panel portion (61), and a deflection yoke which comprises an electron gun located to the rear part of the color cathode ray tube main body (60), a saddle shaped horizontal deflection coil (30) located at the rear periphery of the color cathode ray tube main body (60), a saddle shaped vertical deflection coil (31) located outside the saddle shaped horizontal deflection coil (30) and a core (32) located outside the saddle shaped vertical deflection coil (31), wherein the center portion of the screen side flange portion of one selected from the group consisting of the saddle shaped horizontal deflection coil (30) and the saddle shaped vertical deflection coil (31) forms a projection toward the screen side. A color cathode ray tube comprising a color cathode ray tube main body (60) which comprises a glass panel portion (61) and a glass funnel portion (33) connected to the rear part of the glass panel portion (61), and a deflection yoke which comprises an electron gun located to the rear part of the color cathode ray tube main body(60 a saddle shaped horizontal deflection coil (45) located at the rear periphery of the color cathode ray tube main body (60), a saddle shaped vertical deflection coil (46) located outside the saddle shaped horizontal deflection coil (45) and a core (47) located outside the saddle shaped vertical deflection coil (46), wherein the center portion of the screen side flange portion of one selected from the group consisting of the saddle shaped horizontal deflection coil (45) and the saddle shaped vertical deflection coil (46) forms a dent toward the electron gun side. The color cathode ray tube according to claim 4 or 5, wherein the surface of the screen side flange portion of one selected from the group consisting of the saddle shaped horizontal deflection coil (30,45) and the saddle shaped vertical deflection coil (31,46) opposing to the glass funnel portion (33) of the color cathode ray tube is formed to conform to the surface of the glass funnel portion.

Inventors: HONDA MASANOBU, SHIMADA KOJI, HONDA, MASANOBU, SHIMADA, KOJI
Applicants: MATSUSHITA ELECTRONICS CORP, MATSUSHITA ELECTRONICS CORPORATION
Application year: 1995
Main classification: H01J29
IPC codes: H01J29