JP2004200037A - Color cathode-ray tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color cathode-ray tube capable of minimizing shifting of an electron beam caused by earth magnetism applied in a tube axial direction and sufficiently correcting mis-landing using an internal magnetic shield alone without addition of a cancel coil or the like. <P>SOLUTION: The color cathode-ray tube 1 has the internal magnetic shield 9 provided to surround the electron beam 10 emitted from an electron gun 6 and travelling toward a substantially rectangular phosphor screen 2. The space between a longer-side wall of the shield 9 and the electron beam 10 at the maximum deflection is greater in a region closer to an opening on the phosphor screen side than in a region closer to an opening on the electron gun side, with a midpoint between the opening on the electron gun side and the opening on the phosphor screen side serving as a boundary, and the space is almost constant or gradually broadens from the midpoint toward the opening on the phosphor screen side. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a color cathode ray tube used for a computer monitor, a television receiver, and the like, and particularly to an internal magnetic shield for shielding an external magnetic field such as terrestrial magnetism.
[0002]
[Prior art]
Conventionally, in a color cathode ray tube, in order to prevent a mislanding caused by an electron beam being subjected to Lorentz force due to terrestrial magnetism and bending its trajectory, shielding terrestrial magnetism or controlling the flow of terrestrial magnetism It is common practice to provide an internal magnetic shield in the tube.
[0003]
As an example of the internal magnetic shield, as disclosed in Patent Document 1, there is a shape in which an opening on the phosphor screen side of the internal magnetic shield at the corner of the screen of the color cathode ray tube is close to the electron beam.
[0004]
Further, for example, as in Patent Document 2, in the vicinity of the opening of the internal magnetic shield on the phosphor screen side, the inner magnetic shield extends in the direction of the phosphor screen in parallel with the frame member, and has a wide gap in the tube axis direction with the frame member. In some cases, the width of the frame attachment part is increased.
[0005]
[Patent Document 1]
JP-A-7-182981 [Patent Document 2]
Japanese Patent Application Laid-Open No. Hei 10-247559
[Problems to be solved by the invention]
However, in the above-described conventional technology, in a situation where the resolution is rapidly increasing as in recent years and the design of a margin allowable for mislanding is strict, it is necessary to sufficiently correct mislanding only by the internal magnetic shield. Is becoming more difficult. For this reason, a technique of further adding a cancel coil for generating a magnetic field for canceling mislanding is also used, but this has a problem that the number of components increases and the cost increases.
[0007]
The present invention has been made to solve the above-described problems, and has as its object to provide a color cathode ray tube capable of sufficiently correcting mislanding with an internal magnetic shield alone without adding a cancel coil or the like. .
[0008]
[Means for Solving the Problems]
In order to solve the above problems, a color cathode ray tube of the present invention is a color cathode ray tube having an internal magnetic shield provided so as to surround an electron beam emitted from an electron gun and directed toward a substantially rectangular phosphor screen, The distance between the long side wall of the internal magnetic shield and the electron beam at the time of maximum deflection is on the phosphor screen side opening side with respect to the middle point between the electron gun side opening and the phosphor screen side opening. It is wider than the electron gun side opening side and is substantially constant or gradually spreads from the intermediate point toward the phosphor screen side opening.
[0009]
By doing so, it is possible to minimize the movement of the electron beam due to the geomagnetism applied in the tube axis direction.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
[0011]
FIG. 1 is a schematic sectional view showing an example of a color cathode ray tube according to the present invention. The color cathode ray tube 1 has an envelope composed of a panel 3 having a stripe-shaped phosphor screen 2 formed on an inner surface thereof, and a funnel 4 mounted behind the panel 3. The main components in the tube include an electron gun 6 provided inside the neck portion 5 of the funnel 4, a color selection electrode 7 facing the phosphor screen 2 and a frame 8 supporting the same, and an internal magnetism for shielding or controlling terrestrial magnetism. There is a shield 9 and the like. During operation of the color picture tube, an electron beam 10 emitted from the electron gun 6 is deflected and scanned by a deflection yoke (not shown) mounted on the outer periphery of the funnel, thereby displaying an image on the phosphor screen 2. Form the screen.
[0012]
Here, the internal magnetic shield 9 that best represents the features of the present invention will be described in more detail. As shown in FIG. 2, the inner magnetic shield 9 has a shape that forms a part of a hollow substantially quadrangular pyramid, and the diameter increases from the electron gun side opening 11 to the phosphor screen side opening 12. In addition, as the side walls, there are two long side walls 13 located on the long sides of the phosphor screen having a substantially rectangular shape, and two short sides 14 located on the short sides. A bent portion 15 is provided at an intermediate point between the electron gun side opening 11 of the short side wall 14 and the phosphor screen side opening 12, and as shown in FIG. The distance between the internal magnetic shield 9 and the electron beam 10 at the time of maximum deflection is larger than the distance from the opening 11 to the bent portion 15, and as the distance from the bent portion 15 toward the phosphor screen 2 increases, the distance gradually increases. The spacing is wide.
[0013]
The implications of having such a configuration will be described below.
[0014]
In general, the internal magnetic shield of a color cathode ray tube is provided to suppress the harmful effect of the terrestrial magnetism on the electron beam. Among the terrestrial magnetism, the terrestrial magnetism flowing in the color cathode ray tube in the vertical direction of the screen and the terrestrial magnetism flowing in the horizontal direction of the screen are included. Is easy to shield with an internal magnetic shield, but difficult for geomagnetism flowing in the tube axis direction. This is due to the fact that the inner magnetic shield has a cavity shape surrounding the tube axis and the trajectory of the electron beam. For this reason, the electron beam moves due to the influence of terrestrial magnetism in the tube axis direction, and a color shift called mislanding tends to occur.
[0015]
Here, a description will be given of a magnetic field distribution in the internal magnetic shield when geomagnetism is applied in the tube axis direction of the color cathode ray tube. When the color cathode ray tube receives geomagnetism in the tube axis direction, the internal magnetic shield sucks the tube axis magnetic field from one side of the electron gun side opening and the phosphor screen side opening, and blows out the tube axis magnetic field from the other side. It becomes. In addition, in such suction and blowing, naturally, not only a component in the tube axis direction but also a component in the screen vertical direction and a component in the screen horizontal direction occur. FIG. 3 is a partial cross-sectional view of an upper half of a screen horizontal axis of a general color cathode ray tube having an internal magnetic shield as viewed from a plane defined by a screen vertical axis and a tube axis. In FIG. 3, when a terrestrial magnetism 16 (hereinafter, referred to as a tube axis magnetic field) in a tube axis direction is applied from the electron gun side to the screen side (phosphor screen side), the electron gun side inside the internal magnetic shield. An upward vertical magnetic field 17 is generated near the long side wall 13a, and a downward vertical magnetic field 18 is generated near the long side wall 13b on the phosphor screen side.
[0016]
FIG. 4 is a model diagram for explaining the behavior of electrons in the internal magnetic shield with respect to the partial sectional view of the color cathode ray tube of FIG. In the drawing, Z indicates the tube axis direction, and the direction from the electron gun side to the phosphor screen is a plus direction. X indicates the horizontal direction of the screen and Y indicates the vertical direction of the screen. When viewing the screen of the color cathode ray tube, the horizontal direction indicates the direction from left to right, and the vertical direction indicates the direction from bottom to top. Direction.
[0017]
In the internal magnetic shield, near the long side wall 13a on the electron gun side, as shown in FIG. 4A, the electrons 19a generate a current 20 in the −Y direction due to the deflection of the electron beam upward in the screen. (Because an electron has a negative charge, the direction of the current is opposite and downward.) A first force 21 in the −X direction generated by the tube axis magnetic field 16 in the + Z direction, and a tube axis with a positive electron beam Direction (from the electron gun to the phosphor screen), the current 22 in the −Z direction (the direction of the current is reversed because the electrons 16 have a negative charge, and the direction of the + Y direction generated in the internal magnetic shield). And a second force 23 in the + X direction generated by the directional magnetic field 17 and a combined force 24.
[0018]
In the vicinity of the long side wall 13b on the phosphor screen side in the internal magnetic shield, as shown in FIG. 4B, the electrons 19b are supplied with a current 20 in the −Y direction and a tube in the + Z direction in the same manner as described above. A first force 21 in the −X direction due to the axial magnetic field 16, a current 22 in the −Z direction due to the electron beam traveling in the positive tube axis direction, and a vertical magnetic field 18 in the −Y direction generated in the internal magnetic shield. And a third force 25 in the −X direction generated by the addition of the second force 25.
[0019]
When an electron receives such a combined force, the trajectory of the electron beam moves at that portion. Here, the first force 21 cannot be eliminated, but the combined force can be minimized by increasing the second force 23 or decreasing the third force 25.
[0020]
In the present invention, a bent portion is formed at an intermediate point between the electron gun side opening and the phosphor screen side opening of the long side wall of the internal magnetic shield, and the bent portion is separated from the phosphor screen by the bent portion. On the side, the distance between the internal magnetic shield and the electron beam trajectory at the time of maximum deflection is wider than that from the opening on the electron gun side to the bend, and the connection with the frame from the bend to the phosphor screen side. Up to this interval. By doing so, the long side wall of the electron gun is brought closer to the electron beam trajectory at the time of maximum deflection, and the long side wall of the phosphor screen is kept away from the electron beam trajectory at the time of maximum deflection, and acts on electrons. The resultant force is reduced. As a result, it is possible to minimize the movement of the electron beam due to terrestrial magnetism applied in the tube axis direction, and to reduce mislanding.
[0021]
The bent portion provided at an intermediate point between the electron gun side opening and the phosphor screen side opening has all the side walls (two long side walls and two short side walls) of the internal magnetic shield as shown in FIG. ), Or may be provided only on two long side walls located on the long side of the phosphor screen. According to the principle described above, the direction in which electrons move due to the tube axis magnetic field is the X direction at the top and bottom of the screen (that is, the long side of the screen) and the Y direction at the left and right of the screen (that is, the short side of the screen). However, in fact, many color cathode ray tubes have a phosphor screen in which a large number of stripe-shaped phosphor regions extending in the Y direction are formed, so that movement of electrons in the Y direction directly causes problems such as color misregistration. Is not caused. However, considering the ease of making the internal magnetic shield, it is preferable to provide the bent portion not only on the long side wall but also on the short side wall.
[0022]
Regarding the position of the bent portion, the following experiment was conducted. FIG. 5 shows an electron beam due to terrestrial magnetism applied in the tube axis direction when the position of the bent portion of the internal magnetic shield, that is, the position of the intermediate point is changed for a color cathode ray tube for a wide TV having a screen diagonal size of 76 cm. 9 shows a result of simulating a change in a moving amount. The horizontal axis represents the height of the internal magnetic shield 9 shown in FIG. 1 (the length from the electron gun side end to the portion connected to the frame on the phosphor screen side), and is bent from the electron gun side end. Represents the ratio of B / A (B / A × 100) when the distance to the portion is B, and the vertical axis indicates the moving amount of the electron beam generated by the tube axis magnetic field at the upper and lower ends of the screen of the color cathode ray tube. ing. Here, other magnetic fields (deflection magnetic field, geomagnetism in the horizontal or vertical direction of the screen, etc.) are not taken into consideration.
[0023]
As can be seen from FIG. 5, when the B / A ratio increases from 0% (that is, no bent portion), the amount of electron beam movement decreases, reaches a local minimum value near 50%, and then increases as the ratio increases. The beam movement becomes large again. When the B / A ratio is 65% or more, the amount of electron beam movement is larger than when there is no bent portion. This indicates that it is effective to provide the bent portion at a position where the B / A ratio is around 50%. The movement of the electron beam caused by the tube axis magnetic field is preferably suppressed to about 20 μm, and the maximum allowable is 22 to 23 μm. For this reason, the position of the bent portion is preferably such that the ratio of B / A is in the range of 30 to 60%. As described above, by setting the position where the bent portion is provided such that the ratio of B / A is within the range of 30% to 60%, a vertical magnetic field (newly generated in the internal magnetic shield by the tube axis magnetic field) is generated. A bent portion is provided near the position where the polarity (direction) of the vertical magnetic fields 17 and 18 changes in the portion described with reference to FIGS. 3 and 4, that is, near the zero position. It is considered that the movement of the beam can be kept small. Even when the screen size of the color cathode ray tube is different and the height of the internal magnetic shield is different, it is preferable that the B / A ratio is in the range of 30 to 60% as a position suitable for providing the bent portion.
[0024]
In the present embodiment, a color cathode ray tube for a wide TV having a screen diagonal size of 76 cm is taken as an example, but a dimension example of the internal magnetic shield in this case is shown below. The height (dimension A in FIG. 1) of the internal magnetic shield is 170 mm, and at the opening on the phosphor screen side, as shown in FIG. 2, the horizontal diameter H ₁ = 580 mm, the vertical diameter V ₁ = 330 mm, and the electron gun side opening. , The horizontal diameter H ₂ = 240 mm and the vertical diameter V ₂ = 130 mm. The distance between the inner magnetic shield and the electron beam trajectory at the time of maximum deflection is such that the minimum distance on the electron gun side opening side from the intermediate point is 12 mm, and the maximum distance on the phosphor screen side opening side is 30 mm.
[0025]
In the description so far, the internal magnetic shield is configured to gradually widen the interval between the electron beam at the time of maximum deflection as it approaches the phosphor screen side opening side from the bent portion. However, as shown in FIG. The distance between the inner magnetic shield 9 and the electron beam 10 at the time of maximum deflection may be made substantially constant from 15 to the phosphor screen side opening side. In any case, the portion of the long side wall or the short side wall of the internal magnetic shield up to the portion connected to the frame may be considered, and the internal magnetic shield is attached to the frame further on the phosphor screen side than the connection portion. There is no problem to bend like this.
[0026]
Further, it is not always necessary to form a bent portion between the electron gun side opening and the phosphor screen side opening on the long side wall or the short side wall of the internal magnetic shield, and they may be connected by a gently curved curved surface. In this case as well, the center position of the curved surface is such that the B / A ratio is in the range of 30 to 60%, and from the inflection point on the phosphor screen side to the inflection point from the electron gun side opening. The distance between the internal magnetic shield and the electron beam trajectory at the time of maximum deflection is wider than before, and this distance gradually increases from the inflection point to the phosphor screen side to the connection with the frame, or The shape is almost constant.
[0027]
【The invention's effect】
As described above, according to the present invention, the movement of the electron beam due to the geomagnetism applied in the tube axis direction can be minimized, and the internal magnetic shield alone can be used without using a correction system such as a cancel coil. Only by this, it is possible to correct mislanding due to terrestrial magnetism particularly applied in the pipe axis direction.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing an example of a color cathode ray tube according to the present invention. FIG. 2 is a perspective view showing an internal magnetic shield in an example of the color cathode ray tube according to the present invention. FIG. 4 is a model diagram showing the behavior of electrons in the internal magnetic shield of a general color cathode ray tube. FIG. 5 is a diagram showing changes in the bent portion of the internal magnetic shield in an example of the color cathode ray tube according to the present invention. FIG. 6 is a diagram showing a change in the amount of electron beam movement. FIG. 6 is a schematic sectional view showing another example of the color cathode ray tube according to the present invention.
REFERENCE SIGNS LIST 1 color cathode ray tube 2 phosphor screen 6 electron gun 9 internal magnetic shield 10 electron beam 15 bent part

Claims (4)

In a color cathode ray tube having an internal magnetic shield provided so as to surround an electron beam emitted from an electron gun toward a substantially rectangular phosphor screen, a long side wall of the internal magnetic shield and the electron beam at the time of maximum deflection are provided. Is wider than the electron gun-side opening side on the phosphor screen-side opening side from the middle point between the electron gun-side opening and the phosphor screen-side opening, and from the intermediate point. A color cathode ray tube, which is substantially constant or gradually widens toward the phosphor screen side opening. 2. The color cathode ray tube according to claim 1, wherein the intermediate point is located at a position 30 to 60% from the electron gun side opening with respect to the total height of the internal magnetic shield. 3. The color cathode ray tube according to claim 1, wherein the long side wall of the internal magnetic shield has a bent portion at the intermediate point. The interval between the short side wall of the internal magnetic shield and the electron beam at the time of maximum deflection is wider at the phosphor screen side opening side than at the electron gun side opening side with respect to the intermediate point, and 4. The color cathode ray tube according to claim 1, wherein said color cathode ray tube is substantially constant or gradually widened from a point toward said phosphor screen side opening.

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