JP3976725B2 - Cathode ray tube - Google Patents

Description

  The present invention relates to a cathode ray tube with less mislanding of an electron beam due to an external magnetic field such as geomagnetism.

  The light emission principle of a general color cathode ray tube will be briefly described. The electron beam emitted from the electron beam emitting means, which is an electron gun, passes through the electron beam passing pores formed in the shadow mask and hits the phosphor, which is the landing point of the electron beam, so that red, green , One of the determined colors of blue is emitted. The phosphor is installed inside the panel.

  Such a color cathode ray tube is used in, for example, a television receiver. Here, since an external magnetic field such as geomagnetism exists on the earth, the color cathode ray tube is affected by the external magnetic field such as geomagnetism. That is, when an external magnetic field such as geomagnetism acts on the color cathode ray tube, the electron beam is distorted by receiving Lorentzka. As a result, so-called mislanding occurs in which the electron beam does not reach a predetermined position of the phosphor. As a result, in the color cathode ray tube, an undesirable phenomenon such as color misregistration occurs, and the quality of the display image is lowered. In order to prevent this, an internal magnetic shield is generally provided inside the color cathode ray tube so as to surround the electron beam passage path.

  Various methods have been proposed for converting geomagnetism into a magnetic field in a direction in which color misregistration or the like does not occur with an internal magnetic shield (see, for example, Patent Document 1). FIG. 8 is a perspective view showing a configuration of a conventional magnetic shield structure 100. The magnetic shield structure 100 includes an internal magnetic shield 101 and a frame 109. As shown in FIG. 8, the conventional internal magnetic shield 101 is composed of a substantially trapezoidal pair of opposing long side plates 102 and a substantially trapezoidal pair of opposing short side plates 103. It consists of a pyramid surface. An open portion 104 for passing an electron beam is formed at the top of the quadrangular pyramid. Further, a substantially trapezoidal notch 105 is formed on the opening 104 side of the short side plate 103.

  In the conventional internal magnetic shield 101, a long side skirt 106 is installed at the bottom of the long side plate 102, and a short side skirt 107 is installed at the bottom of the short side plate 103. The long side skirt 106 and the short side skirt 107 are disposed along the side wall 109a of the frame 109 holding a shadow mask (not shown). 9 is a cross-sectional view taken along the line BB ′ of FIG. As shown in FIG. 9, the long side skirt 106 of the internal magnetic shield 101 is installed along the side wall 109a so as to contact the side wall 109a. As shown in FIG. 9, the frame 109 includes a flange portion 110 and holds the shadow mask 108.

  In addition, a method of reducing magnetic flux leaking to the electron beam trajectory by using an internal magnetic shield has been proposed (see, for example, Patent Document 2). FIG. 11 is a cross-sectional view showing a configuration of a long side skirt 116 and a frame 119 of another conventional internal magnetic shield 111. As shown in FIG. 11, the long side skirt 116 is installed in parallel to the side wall 119a of the frame 119, extends in the direction of the shadow mask 118, and the long side skirt 116 and the side wall 119a have a distance. Installed. By setting it as such a structure, the magnetic flux which leaks from the flange part 120 of the flame | frame 119 can be reduced.

  Evaluation of the shielding performance against the geomagnetism of the cathode ray tube is performed by applying a magnetic field equivalent to the geomagnetism from the outside of the cathode ray tube and measuring the landing change amount of the electron beam in the phosphor at that time. FIG. 7 is a schematic diagram for showing the position of the display screen of the cathode ray tube. An example of the landing change amount measurement point will be described with reference to FIG. For example, as shown in FIG. 7, the upper and lower central portions (hereinafter referred to as NS portion 73) of the long side portion of the screen 70, the corner portion 71 of the screen 70, and the midpoint (hereinafter referred to as the NS portion 73 and the corner portion 71) NNE unit 72) is a measurement point.

  By the way, in the case of a color cathode ray tube having a stripe type phosphor screen, mislanding of an electron beam is caused by a Lorentzka Fx that the electron beam receives in the horizontal direction (hereinafter referred to as the X-axis direction). The Lorentzka Fx is exerted on the electron beam by magnetic fields in the vertical direction (hereinafter referred to as the Y-axis direction) and the tube axis direction (hereinafter referred to as the Z-axis direction). The Lorentz force Fx (N) is the electron charge amount e (C), the magnetic flux density in the Y-axis direction By (T), the velocity of the electron beam in the Y-axis direction Vy (m / s), and the Z-axis direction. The magnetic flux density is expressed by the following equation (1), where Bz (T) is the electron beam velocity in the Z-axis direction and Vz (m / s).

Fx = e × (By × Vz−Bz × Vy) (1)
Here, the velocity Vy (m / s) of the electron beam in the Y-axis direction and the velocity Vz (m / s) of the electron beam in the Z-axis direction are determined by the operating voltage and deflection angle of the electron beam. In order to prevent color misregistration in screen display, the Lorentzka Fx (N) that the electron beam receives in the X-axis direction may be reduced. For this purpose, the balance between the magnetic flux density By in the Y-axis direction and the magnetic flux density Bz (T) in the Z-axis direction may be adjusted from Equation (1). In addition, the mislanding amount of the electron beam is determined by the integral value of the Lorentz force Fx (N) received by the electron beam on the trajectory of the electron beam from the deflection center to the phosphor.

  Here, because of the structure of the cathode ray tube, it is necessary to ensure the trajectory of the electron beam, so the magnetic field in the Z-axis direction cannot be completely shielded by the internal magnetic shield. Therefore, when geomagnetism in the Z-axis direction is applied, most of the magnetic flux is not shielded, so that the magnetic flux density Bz (T) in the Z-axis direction increases. In this case, in Equation (1), in order to reduce the Lorentzka Fx (N) that the electron beam receives in the X-axis direction, the By term that only cancels the Bz term: (Bz × Vy): (By × Vz) Need to produce. In the electron beam trajectory reaching the corner portion 71 of the screen 70 in FIG. 7 by the prior art such as Patent Document 1, the By term: (By × Vz) that only cancels the Bz term: (Bz × Vy) is created. Can do. However, in the NS portion 73 and the NNE portion 72 of the screen 70, it has not been realized to create a By term: (By × Vz) sufficient to cancel the Bz term: (Bz × Vy).

  The present inventors have made various studies on the cathode ray tubes disclosed in Patent Documents 1 and 2. First, regarding the cathode ray tube magnetic shield structure 100 disclosed in Patent Document 1 as shown in FIG. 8, the action of the notch 105 provided on the short side plate 103 of the internal magnetic shield 101 is shown. investigated. The contents of this examination will be described below.

  Generally, magnetic poles are generated at the end of the magnetic body along the geomagnetic direction. Similarly, in the cathode ray tube, a magnetic pole is generated at the end of the magnetic shield structure 100 made of a magnetic material, which includes the internal magnetic shield 101, the shadow mask 108 (see FIG. 9), and the frame 109. The magnetic pole has the effect of changing the direction of the magnetic flux. For example, when geomagnetism in the Z-axis direction is applied to the cathode ray tube, a part of the component in the Z-axis direction is converted into a magnetic flux in the Y-axis direction (the strength of the magnetic flux is represented by a magnetic flux density By (T). ). In particular, since a strong magnetic pole is generated at the end of the inner magnetic shield 101 on the opening 104 side, the absolute value of the magnetic flux density By (T) is large.

  On the other hand, almost no magnetic pole is generated in the central portion of the magnetic body along the geomagnetic direction. Therefore, the force that changes the direction of the magnetic flux is weak at the center of the magnetic body. Therefore, the absolute value of the magnetic flux density By (T) in the Y-axis direction is smaller in the central portion in the Z-axis direction of the magnetic shield structure 100 than in the opening 104 side end of the internal magnetic shield 101 described above.

  Although a magnetic pole is also generated in the vicinity of the shadow mask 108 surface, the absolute value of the magnetic flux density By (T) in the Y-axis direction is smaller than the end of the internal magnetic shield 101 on the opening 104 side. This is because the shadow mask 108 absorbs the magnetic flux, thereby reducing the magnetic flux leaking into the space.

  As shown in FIG. 8, in the conventional cathode ray tube, a notch 105 is formed on the opening 104 side of the short side plate 103 of the internal magnetic shield 101. Therefore, the cutout portion 105 becomes an end portion of the magnetic shield structure 100, and a magnetic pole is generated in the cutout portion 105.

  Since the magnetic poles are provided along the electron beam trajectory, the absolute value of the integral value of the magnetic flux density By (T) in the Y-axis direction on the electron beam trajectory increases, and the Bz term in the equation (1): (Bz XVy) acts to cancel. In this case, the sign of the integral value of the magnetic flux density By (T) is negative.

  Therefore, by providing the substantially trapezoidal cutout portion 105 in the short side plate 103 along the trajectory of the electron beam reaching the corner portion 71 (see FIG. 7) of the screen 70, the electron beam reaching the corner portion 71 is provided. The absolute value of the integral value of the magnetic flux density By (T) on the orbit can be increased. As a result, in the corner portion 71 of the screen 70, the influence of the geomagnetic Z-axis direction component can be reduced, and problems such as color misregistration can be avoided.

  On the other hand, the trajectory of the electron beam reaching the NS portion 73 (see FIG. 7) of the screen 70 is far away from the notch portion 105 provided in the short side plate 103. Therefore, in the electron beam that reaches the NS section 73, the By term: (By × Vz) that only cancels the Bz term: (Bz × Vy) in the equation (1) does not occur. Similarly, since the trajectory of the electron beam that reaches the NNE portion 72 (see FIG. 7) of the screen 70 is also away from the notch portion 105, the By that only cancels the Bz term: (Bz × Vy) in the equation (1). Term: (By × Vz) does not occur.

  The experimental results regarding the above consideration will be described. FIG. 10 is a graph showing the relationship between the position on the electron beam trajectory measured from a shadow mask in a conventional cathode ray tube and the ratio of the geomagnetism to the tube axis direction (Z-axis direction) component. As a conventional cathode ray tube, a cathode ray tube provided with the magnetic shield structure 100 shown in FIG. 8 was used. This cathode ray tube has a notch 105 formed in the short side plate 103 of the internal magnetic shield 101.

A vertical axis of FIG. 10, and the ratio of magnetic flux density By A (T) for the terrestrial magnetism in the tube axis component _{B Z0 (T) (By /} B Z0 × 100 (%)), the terrestrial magnetism in the tube axis (Z axis) component It is a percentage of the magnetic flux density By (T) with respect to B _Z0 (T). Specifically, it is a value obtained by By / B _Z0 × 100 (%). Further, the position on the electron beam trajectory in the tube axis direction measured from the shadow mask 108 (see FIG. 9), which is the horizontal axis in FIG. 10, is the case where the distance from the shadow mask 108 surface to the deflection center is 100%. The distance in the Z-axis direction of the electron beam from the shadow mask 108 surface toward the electron gun side is shown as a percentage. Note that the inside of the inner magnetic shield structure 100 is in the range of 0 to 80%.

  In FIG. 10, the solid line indicates the ratio of the magnetic flux density in the electron beam trajectory reaching the corner at the lower right of the screen, and the broken line indicates NS at the lower side of the center of the screen. It is the ratio of the magnetic flux density in the electron beam trajectory reaching the part.

  As shown in FIG. 10, in the electron beam trajectory reaching the corner portion, the By term: (By × Vz) having an action of canceling the Bz term: (Bz × Vy) in the equation (1) becomes large. No color misregistration occurs in the part. However, in the electron beam trajectory reaching the NS portion, a color shift occurs because a By term: (By × Vz) that only cancels the Bz term: (Bz × Vy) cannot be obtained.

  Next, regarding the cathode ray tube disclosed in Patent Document 2 as shown in FIG. 11, the action of the long side skirt 116 of the internal magnetic shield 111 was examined. The examination results will be described below.

  By extending the long side skirt 116 of the inner magnetic shield 111 in the panel direction (Z-axis direction) parallel to the side wall 119a of the frame 119 and separating the long side skirt 116 from the frame 119a, the flange of the frame 119 The magnetic flux leaking from the portion 120 can be reduced.

  Since the position of the flange portion 120 corresponds to a position of 10% on the horizontal axis of FIG. 10 described above, it can be seen from FIG. 10 that the direction of the magnetic flux in the Y-axis direction is positive. If the integral value of the magnetic flux density By (T) in the Y-axis direction is positive, it acts to promote the Bz term: (Bz × Vy) in equation (1). Therefore, it is a desirable phenomenon that the magnetic flux leaking from the flange portion 120 is reduced.

However, in the cathode ray tube structure of Patent Document 2, the integral value (in this case, the sign is negative) of the magnetic flux density By (T) in the Y-axis direction on the electron beam trajectory decreases. This corresponds to a position of 80% on the horizontal axis of FIG. That is, the negative component of the magnetic flux density By (T) is the largest. This is because the magnetic pole at the electron gun side end of the internal magnetic shield 111 corresponding to the position of 80% on the horizontal axis in FIG. 10 (that is, the position where the negative component of the magnetic flux density By (T) is the largest) is long. This is because the side skirt 116 is weakened by being separated from the frame 119.
JP 2002-184319 A Japanese Patent Laid-Open No. 10-247459

  As described above, in the conventional cathode ray tube, especially when the geomagnetism in the tube axis direction acts on the color cathode ray tube, the mislanding amount in the NS portion 73 of the screen 70 and the NNE portion 72 of the screen 70 shown in FIG. There has been a problem that color misregistration due to increase occurs. Such a tendency becomes more conspicuous in a color cathode ray tube in which a shadow mask is tensioned. This is because, by applying tension to the shadow mask, the magnetic characteristics of the shadow mask are reduced by magnetostriction, and the leakage magnetic flux on the electron beam trajectory increases. In recent years, a color cathode ray tube having a flat panel often employs a tension mask system in which a shadow mask is tensioned. Therefore, it is extremely important to solve the color shift problem due to geomagnetism.

  The present invention has been made to solve the above-described problems, and reduces the amount of mislanding due to the influence of an external magnetic field such as geomagnetism, particularly the geomagnetism of the tube axis component, and there is little color misregistration and color unevenness on the entire screen. An object is to provide a cathode ray tube.

In order to achieve the above object, a cathode ray tube according to the present invention includes an envelope made up of a panel and a funnel, a phosphor screen formed on the inner surface of the panel, and a shadow disposed facing the phosphor screen. A cathode ray tube having a mask, a frame for holding the shadow mask, and an internal magnetic shield installed in the funnel, wherein the internal magnetic shield is a pair of substantially trapezoidal long pieces arranged to face each other. The pair of long side plates having a substantially trapezoidal shape, in which a side plate and a pair of substantially trapezoidal short side plates disposed opposite to each other are combined to form a part of a substantially quadrangular pyramid surface. comprising a long side skirt connected to the lower bottom of the long side skirts are parallel to the side walls of the frame, is provided so as to extend in the panel direction, the long side skirts, the long side The have notches on either side of the central portion of the lower base and parallel direction are formed, the distal end portion of the long side skirts, present on the reverse side of the panel than the shadow mask, of the long sides skirt The distance along the tube axis direction between the tip portion and the shadow mask is 6 mm or less.

  According to the cathode ray tube of the present invention, mislanding of the electron beam can be suppressed and occurrence of color misregistration can be prevented.

  According to the cathode ray tube of the present embodiment, the magnetic pole at the electron gun side end of the internal magnetic shield is strong. Thereby, the influence on the electron beam by an external magnetic field such as geomagnetism (especially the geomagnetism of the tube axis component) can be reduced, and the amount of mislanding caused by the distortion of the electron beam can be reduced. Thereby, color shift and color unevenness can be reduced in the entire screen.

  Preferably, the long side skirt and the frame are joined. Thereby, the shadow mask, the long side frame, and the internal magnetic shield can be integrated. Therefore, the magnetic pole at the end of the inner magnetic shield on the electron gun side becomes stronger, and the influence of the external magnetic field such as geomagnetism on the electron beam can be reduced. Therefore, the amount of mislanding caused by the distortion of the electron beam can be reduced. Thereby, color shift and color unevenness can be reduced in the entire screen.

  Preferably, the frame includes a flange portion disposed substantially parallel to the shadow mask, and the flange portion is not in contact with the internal magnetic shield. Thereby, it is possible to prevent the magnetic flux from leaking from the flange portion to the space on the electron beam trajectory. Thereby, color shift and color unevenness can be reduced in the entire screen.

  Hereinafter, more specific embodiments of the present invention will be described.

  FIG. 1 is a sectional view in the vertical direction passing through the tube axis, showing the configuration of the cathode ray tube 1 according to the embodiment of the present invention. In this specification, the tube axis direction is the Z-axis direction, the horizontal direction is the X-axis direction, and the vertical direction is the Y-axis direction.

  As shown in FIG. 1, the panel 2 and the funnel 3 are integrated, and the envelope 4 is formed. A phosphor screen 5 is formed on the inner surface of the panel 2, and an aluminum thin film layer (not shown) is formed in close contact therewith. A shadow mask 6 is placed away from the phosphor screen 5 and facing it. The shadow mask 6 is held by being stretched on the frame 7. The frame 7 is held by the panel 2 by hooking a leaf spring-like elastic support (not shown) installed on the outer wall surface thereof to a panel pin (not shown) planted on the inner surface of the panel 2. ing. An electron gun 8 is built in the neck portion of the funnel 3. A deflection yoke 9 is provided on the outer peripheral surface of the funnel 3. The deflection yoke 9 functions to deflect the electron beam 11 emitted from the electron gun 8 in the horizontal direction and the vertical direction. The deflected electron beam 11 scans the phosphor screen 5 so that an image is displayed on the screen of the panel 2. An internal magnetic shield 10 is installed in the envelope 4 in the region between the frame 7 and the deflection yoke 9 in the tube axis direction (Z-axis direction).

  FIG. 2 shows an exploded view of the magnetic shield structure 15 including the frame 7 on which the shadow mask 6 is stretched, the internal magnetic shield 10, and the electron shield 12 for trimming an extra electron beam that reaches outside the effective plane of the screen. It is a perspective view.

  The frame 7 includes a pair of long side frames 7a arranged in parallel with a predetermined distance apart, and a pair of short side frames 7b arranged with a predetermined distance apart. The long side frame 7a is formed by bending a plate-like metal into a substantially L-shaped cross section. The short side frame 7b is formed by bending a square columnar metal column into a substantially U-shape. As shown in FIG. 2, the pair of short side frames 7 b are installed on the side surfaces of the pair of long side frames 7 a so as to have a substantially rectangular frame shape, and the joints are welded to form the frame 7. Further, a shadow mask 6 is stretched on the phosphor screen (not shown) side of the pair of long side frames 7a, that is, on the lower free end in FIG.

  The internal magnetic shield 10 includes a pair of substantially trapezoidal long side plates 10a arranged opposite to each other and a pair of substantially trapezoidal short side plates 10b arranged opposite to each other to form a part of a substantially quadrangular pyramid surface. It is the structure combined so that it may form. The internal magnetic shield 10 further includes a long side skirt 13 on the lower bottom side of the trapezoidal long side plate 10a. The internal magnetic shield 10 further includes a short side skirt 14 on the lower bottom side of the trapezoidal short side plate 10b.

  A leaf spring-like elastic support (not shown) for attaching the internal magnetic shield 10 to the panel is attached to the outer wall surfaces of the pair of long side frames 7a and the pair of short side frames 7b.

  FIG. 3 is a perspective view showing the configuration of the magnetic shield structure 15 of the present embodiment. The magnetic shield structure 15 includes an internal magnetic shield 10, a shadow mask 6, and a frame 7, and is a combination of the exploded perspective view shown in FIG.

  The long side frame 7a of the frame 7 is made of, for example, an Fe—Cr—Mo material having a thickness of 1.4 mm. The short side frame 7b of the frame 7 is made of, for example, an Fe—Cr—Mo material having a thickness of 15 mm. The shadow mask 6 is made of, for example, an Fe—Mn—Nl material having a thickness of 0.1 mm. The inner magnetic shield 10 is made of a mild steel material having a thickness of 0.15 mm, for example. The relative permeability of each of the long side frame 7a is 130, the short side frame 7b is 250, the shadow mask 6 is 500, and the internal magnetic shield 10 is 1000.

  FIG. 4 is a cross-sectional view taken along the line A-A ′ of FIG. 3. The long side frame 7 a is substantially L-shaped and has a flange portion 16. The flange portion 16 is a portion of the long side frame 7a that is disposed substantially parallel to the shadow mask 6. In the long side frame 7a, a flange portion 16 is provided at an end portion opposite to the free end 7d on which the shadow mask 6 is stretched, and the flange portion 16 is a plane perpendicular to the tube axis (Z axis). It consists of a flat plate. The long side skirt 13 is parallel to the side wall 7c of the long side frame 7a and extends to the panel (not shown) side, that is, the lower side in FIG. The front end portion 13a of the long side skirt 13 is present on the opposite side (electron gun (not shown) side) of the panel (not shown) from the shadow mask 6, that is, on the upper side in FIG. Further, when the distance along the tube axis direction (Z-axis direction) between the front end portion 13a of the long side skirt 13 and the lower surface of the shadow mask 6 in FIG. 4 is d, the distance d is 6 mm or less. . The reason for this configuration will be described below with reference to FIG.

  6 changes the distance d along the tube axis direction (Z-axis direction) between the tip 13a of the long side skirt 13 shown in FIG. 4 and the lower surface of the shadow mask 6 in FIG. 7 is a graph showing measurement results obtained by measuring the integral value of the magnetic flux density distribution By in the Y-axis direction on the electron beam trajectory reaching the NS section 73 of the screen 70 shown in FIG.

  As shown in FIG. 6, it can be seen that when the distance d is 6 mm or less, the absolute value of the integrated value of By increases rapidly. Therefore, by setting the distance d to 6 mm or less, the By term: (By × Vz) for reducing the influence of the Bz term: (Bz × Vy) in the above-described equation (1) can be increased. That is, by setting the distance d to 6 mm or less, the effect of reducing the orbital deviation of the electron beam 11 can be rapidly increased.

  In addition, the structure which extended further the front-end | tip part 13a of the long side skirt 13 to the panel (not shown) side rather than the lower surface in FIG. 4 of the shadow mask 6 may be sufficient. However, as can be seen from FIG. 6, even if the tip 13a of the long side skirt 13 is further extended to the panel (not shown) side than the lower surface of the shadow mask 6 in FIG. 4 (in this case, the distance d). The integral value of the magnetic flux density distribution By does not change. That is, the effect of strengthening the magnetic pole at the end of the inner magnetic shield 10 on the electron gun 8 side is saturated. When the tip 13a of the long side skirt 13 is further extended to the panel (not shown) side of the shadow mask 6 than the lower surface in FIG. 4, it can be extended only to the extent that no structural inconvenience occurs. Needless to explain.

  Moreover, as shown in FIG. 4, it is preferable that the long side skirt 13 of the internal magnetic shield 10 is joined to the side wall 7c of the long side frame 7a. For the welding, spot welding or the like can be used. The long side frame 7a and the shadow mask 6 are joined by welding. Therefore, when the long side skirt 13 is joined to the side wall 7c of the long side frame 7a, the long side skirt 13 and the shadow mask mask 6 are magnetically connected via the long side frame 7a. Therefore, the magnetic flux in the inner magnetic shield 10 easily flows to the shadow mask 6 through the frame 7 and the magnetic flux flow of the entire magnetic shield structure 15 is strengthened. Therefore, the magnetic poles at the end of the inner magnetic shield 10 shown in FIG. 1 on the electron gun 8 side can be strengthened. Thereby, even on the electron beam trajectory reaching the NS part 73 and the NNE part 72 of the screen 70 in FIG. 7, compared with the case where the long side skirt 13 of the internal magnetic shield 10 is not joined to the long side frame 7a, the above-mentioned ( It is possible to increase the By term: (By × Vz) for reducing the influence of the Bz term: (Bz × Vy) in the equation (1).

  Next, in the cathode ray tube 1 of the present embodiment, the measurement result of the magnetic flux density distribution on the electron beam trajectory reaching the screen NS portion will be described with reference to FIG. The long side skirt of the internal magnetic shield was joined to the long side frame.

5 gives a geomagnetic tube axis component (Z-axis component) to the magnetic shield structure 15 of the cathode ray tube 1 of the present embodiment shown in FIG. 1, and the NS portion 73 of the screen 70 shown in FIG. It is a graph which shows the result of having measured the magnetic flux density distribution By of the Y-axis direction on the electron beam 11 orbit which arrives. 5, as in FIG. 10, the ratio (By / B _Z0 × 100) of the position (%) on the electron beam trajectory in the tube axis direction measured from the shadow mask and the magnetic flux density By to the geomagnetic tube axis component B _Z0 . ) (%). In FIG. 5, as a comparative example, the magnetic flux density distribution (conventional example 1) of the cathode ray tube in the configuration of Patent Document 1 is indicated by a broken line, and the magnetic flux density distribution of the cathode ray tube in the configuration of Patent Document 2 is indicated by a dashed line .

  According to this measurement result, the cathode ray tube of the present embodiment can increase the absolute value of the negative magnetic flux density on the electron beam trajectory reaching the screen NS portion as compared with the conventional examples 1 and 2. I understood. In particular, it can also be seen that the effect is great at the end of the inner magnetic shield 10 of FIG. 1 on the side of the electron gun 8 (where the position is about 80%).

  As shown in FIG. 4, the flange portion 16 of the long side frame 7 a preferably has a structure in which the upper surface does not contact the internal magnetic shield 10. Thus, by making the flange portion 16 of the frame 7 and the internal magnetic shield 10 non-contact, it is possible to prevent magnetic flux from leaking from the flange portion 16 to the space on the electron beam trajectory.

  A specific mislanding amount measurement result when the cathode ray tube 1 of the present embodiment shown in FIG. 1 is operated will be described below. Here, when a lateral (X-axis direction) magnetic field is applied, a mislanding amount (hereinafter referred to as a transverse magnetic field corner) of the corner portion 71 of the screen 70 shown in FIG. 7 and a tube axis direction (Z-axis direction). The mislanding amount (hereinafter referred to as tube axis magnetic field corner) of the corner portion 71 of the screen 70 shown in FIG. 7 when a magnetic field is applied, and the NS of the screen 70 shown in FIG. 7 when a tube axis direction magnetic field is applied. Mislanding amount of the portion 73 (hereinafter referred to as tube axis magnetic field NS) and mislanding amount of the NNE portion 72 of the screen 70 shown in FIG. 7 when a tube axis direction magnetic field is applied (hereinafter referred to as tube axis magnetic field NNE). It shows. In this measurement, a 29 type color cathode ray tube was used.

  In an environment where the geomagnetism is 50 μT, the conventional transverse magnetic field corner, tube axis magnetic field corner, tube axis magnetic field NS and tube axis magnetic field NNE were 20 μm, 20 μm, 35 μm and 35 μm, respectively. However, in the cathode ray tube 1 of the present embodiment, the transverse magnetic field corner, the tube axis magnetic field corner, the tube axis magnetic field NS, and the tube axis magnetic field NNE are 20 μm, 15 μm, 28 μm, and 28 μm, respectively, in an environment where the geomagnetism is 50 μT. It was. Thus, in the cathode ray tube according to the present embodiment, the mislanding amount is reduced in the tube axis magnetic field corner, the tube axis magnetic field NS, and the tube axis magnetic field NNE as compared with the conventional cathode ray tube. From this result, it can be seen that according to the cathode ray tube 1 of the present embodiment, the mislanding amount of the electron beam 11 can be reduced and the occurrence of color misregistration can be suppressed.

  In the cathode ray tube of the present embodiment, a cathode ray tube equipped with a tension mask is used. However, a press-type mask not applied with tension, that is, a cathode ray tube equipped with a so-called press mask has the same configuration as described above. There are similar effects.

  In the present embodiment, the material of the frame is not particularly limited. For example, an iron-based material or an invar material may be used. In this embodiment, an internal magnetic shield made of mild steel is used as an example. However, a cathode ray tube using an internal magnetic shield made of another magnetic material such as an invar material may be used, and similar effects are obtained. Play. In this embodiment, a 29-type color cathode ray tube is used as an example, but the same effect can be obtained by using the same configuration even with other sizes of cathode ray tubes.

  Note that the material and structure of the components specifically shown in the present embodiment are merely examples, and the present invention is not limited to these specific examples.

  The cathode ray tube of the present invention is useful as a display device such as a television receiver.

Sectional drawing of the up-down direction which passes along a tube axis | shaft which shows the structure of the cathode ray tube which concerns on embodiment of this invention 1 is an exploded perspective view of a magnetic shield structure according to an embodiment of the present invention. The perspective view which shows the structure of the magnetic shield structure which concerns on embodiment of this invention AA 'arrow sectional view of FIG. The graph which shows the relationship between the position on the electron beam orbit measured from the shadow mask in the cathode ray tube according to the present embodiment and the conventional cathode ray tube and the ratio of the geomagnetism to the tube axis component Graph showing the relationship between the distance between the long side skirt and the shadow mask and the integral value of the magnetic flux density distribution in the Y-axis direction in the cathode ray tube according to the present embodiment Schematic diagram showing the position of the cathode ray tube screen A perspective view showing a configuration of a conventional magnetic shield structure BB 'arrow sectional drawing of FIG. Graph showing the relationship between the position on the electron beam trajectory measured from the shadow mask in a conventional cathode ray tube and the ratio of the geomagnetism to the tube axis component Sectional drawing which shows the structure of another conventional magnetic shield and frame

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cathode ray tube 2 Panel 3 Funnel 4 Envelope 5 Phosphor screen 6 Shadow mask 7 Frame 7a Long side frame 7b Short side frame 7c Side wall 7d Free end 8 Electron gun 9 Deflection yoke 10 Internal magnetic shield 10a Long side plate 10b Short side Side plate 11 Electron beam 12 Electron shield 13 Long side skirt 13a Tip part 14 Short side skirt 15 Magnetic shield structure 16 Flange part 70 Screen 71 Corner part 72 NNE part 73 NS part 100 Magnetic shield structure 101, 111 Internal magnetic shield 102 Long side plate 103 Short side plate 104 Open part 105 Notch part 106, 116 Long side skirt 107 Short side skirt 108, 118 Shadow mask 109, 119 Frame 109a, 119a Side wall 110, 120 Flange part

Claims (3)

An envelope composed of a panel and a funnel; a phosphor screen formed on the inner surface of the panel; a shadow mask disposed opposite to the phosphor screen; a frame for holding the shadow mask; A cathode ray tube having an internal magnetic shield installed in
In the internal magnetic shield, a pair of substantially trapezoidal long side plates arranged opposite to each other and a pair of substantially trapezoidal short side plates arranged opposite to each other form a part of a substantially quadrangular pyramid surface. A long side skirt connected to the lower bases of the pair of long side plates that are substantially trapezoidal in shape,
The long side skirt is provided so as to extend in the panel direction parallel to the side wall of the frame,
In the long side skirt, notches are formed on both sides of a central portion in a direction parallel to the lower bottom side of the long side plate,
The tip of the long side skirt is present on the opposite side of the panel from the shadow mask, and the distance along the tube axis direction between the tip of the long side skirt and the shadow mask is 6 mm or less. A cathode ray tube.   The cathode ray tube according to claim 1, wherein the long side skirt and the frame are joined. The frame includes a flange portion installed substantially parallel to the shadow mask,
The cathode ray tube according to claim 1, wherein the flange portion is not in contact with the internal magnetic shield.

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