JPS61236288A - Color image receiving tube device - Google Patents

Abstract

PURPOSE:To obtain an image receiving device which has a little influence upon a terrestrial magnetic component in every direction by removing the Y- directional component of terrestrial magnetism from a color image receiving tube by an external magnetic shield and correcting the Z-directional component by a terrestrial magnetism canceling coil. CONSTITUTION:The external magnetic shield is a soft iron plate, etc., arranged cylindrically surrounding the periphery of a funnel 4. The coil 30 is arranged on the flank of the funnel 4 inside the external magnetic shield 20 at a proper interval (d). This coil 30 is wound about the center axis of the color image receiving tube 1 and connected to a DC power source 32 through a lead wire 31. Consequently, mislanding due to the (x)-directional and (y)-directional components of the terrestrial magnetism are removed by the external magnetic shield 20. Mislanding caused by the (z)-directional component of the terrestrial magnetism is prevented by flowing a proper-level DC current to the coil 30 and canceling said component of the terrestrial magnetism. This current is set at an installation site.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a color picture tube device, and more particularly to a color picture tube device that eliminates mislanding caused by the earth's magnetic shadow t.

[Prior Art] FIG. 2 is a partially cutaway perspective view of a color picture tube device to which the present invention is applied. The color picture tube (1) has a phosphor screen (3) provided on the inner surface of the panel (2).
2) a substantially pyramid-shaped funnel (4) connected to the
A vibrator-like neck part (5) connected to this funnel (4), a normal 3
It has a plurality of electron guns (6) that generate wooden electron beams, and a shadow mask (10) made of a thin metal plate is arranged inside the fluorescent screen (3) at an appropriate distance. has been done. Note that the mechanism for holding the shadow mask (10) within the color picture tube (1) will be omitted from illustration and description. The shadow mask (10) is provided with numerous regular rectangular holes (11). The hole (!1) is
They are arranged almost parallel to each other so that their longitudinal direction is perpendicular to the central axis (tube axis) of the color picture tube (1), and they are usually arranged in a row in the longitudinal direction, and in a direction perpendicular to this. These rows are repeatedly arranged at approximately equal intervals.

Now, in the following explanation, the central axis of this color picture tube (1) is assumed to be two directions, and the direction perpendicular to this and parallel to the longitudinal direction of the hole (ll) is the X direction, and the direction orthogonal to the y and zPii directions. Let the direction be the X direction.

FIG. 3 shows the phosphor screen (3) viewed from the front. The phosphor screen (3) usually consists of a repeating pattern of three types of phosphor stripes (3a) that are arranged at substantially equal intervals in the X direction and emit light in different colors parallel to the X direction.
The set corresponds to another one of the holes (11) of the shadow mask (10) connected in the X direction.

When the color picture tube (1) is operated, the electron beam emitted from the electron gun (6) is deflected by a magnetic deflection device (Fig. The light is deflected by the light source (not shown) and bent in a desired direction, passes through the hole (11) of the shadow mask (10), reaches the phosphor screen (3), and causes it to emit light. At this time, each of the three electron beams has three types of phosphor stripes (3
Which of a) will be emitted is determined in advance. That is, the distance between the three-dimensional electron guns (6), the distance and width in the X direction of the holes (ll) of the shadow mask (10), the distance between the shadow mask (10) and the phosphor screen (3), and the phosphor stripes ( 3a) and the distance between adjacent holes (1
1) and the like in the X direction are set to be predetermined values. If this correct relationship is impaired, a particular electron beam will not accurately strike the predetermined phosphor stripe (3a). This situation is called a mislanding, and when there is a mislanding,
In general, color unevenness and poor color purity occur, and the fluorescent screen (3)
It becomes difficult to accurately reproduce the hue on a partial or entire surface.

The cause of mislanding is the color picture tube (+
) There are various possible causes including poor assembly accuracy, one of which is that the electron beam is bent in an undesirable direction by the earth's magnetic field, resulting in mislanding.

This mislanding due to geomagnetism will be explained below.

As is well known, there is a geomagnetic field at a location on Earth, and the operation of the color picture tube is affected by this. The influence of the earth's magnetic field varies depending on the location on the earth and the direction in which the color picture tube is installed, but the influence of the magnetic field on x, y, and z
This can be understood by breaking it down into directional components and examining the influence of each component.

FIG. 4 shows that the point of impact of the electron beam on the fluorescent screen (3) in the color picture tube (1) shown in FIG.
FIG. 4 is a diagram showing roughly how it changes depending on each of the y and z components.

Figure (a) shows the influence of the X component of geomagnetism.

When there is an It will collide with the point moved in the X direction from the position when there is no target). This direction of movement is marked with an arrow + or - in the figure. The + or - direction is determined by whether the X component of the earth's magnetism is oriented +X or -X. This also applies to other components described later. However, as mentioned above, since the phosphor stripes (3a) extend long in the y direction on the inner surface of the panel (2), the displacement of the beam projection point in the y direction is substantially harmless. , there is no need to treat it as a mislanding.Of course, if you observe it strictly, the direction of movement may be tilted from the y direction due to the curved surface of the inner surface of the panel, but as a first approximation, it is only the y direction. It is safe to assume that it will be moved to .

Figure 4(b) shows how the beam launch point moves due to the y-direction component of the earth's magnetism.Similar to the above, the launch point moves in the X direction due to the left hand rule of F1/Ming, and therefore It can be seen that an undesirable mislanding occurs.

Figure 4(c) shows the movement of the beam injection point due to the two-directional acid component of the geomagnetic field. In this case, the electron beam reaching the center of the screen is in the same direction as the geomagnetic component, so there is no effect. However, since the trajectory of the electron beam that reaches the periphery of the screen has components perpendicular to the two directions, this component and the two magnetic components create a force, and similarly, according to Fleming's left-hand rule, the impact point This occurs in a direction that rotates the entire screen, and therefore undesirable mislanding occurs at the corner portions and long i22 portions of the screen (5-toe side in the figure).

[Problems to be solved by the invention] In order to improve this situation, a color picture tube (1)
It was devised to place a magnetic shield on the outside of the

Figure 5 shows an example of this 81-magnetic shield. The external magnetic shield (20) is made of a thin plate such as a soft iron plate, and covers the outer surface of the funnel (4), forming a conical shape that is approximately the same shape as the funnel (4). .

However, according to experiments, when such an external magnetic shield (20) is used, it is effective in reducing the movement of the beam launch point due to the X and Y direction components of the earth's magnetic field, that is, the mislanding, but the mislanding due to the Z direction component is reduced. It is not very effective in preventing W during landing, and in order to obtain a sufficient effect, the length of the external magnetic shield (20) shown in text in the figure must be made sufficiently large, so that the external magnetic shield (20) has a neck part (5
) I found that I had to extend this to cover the entire area.

However, such a magnetic shield not only increases the cost, but also makes the entire color picture tube device bulky.
In addition to severe restrictions on cabinet design, this type of shield requires a large-scale demagnetizing device for degaussing the shield plate, which is a major inconvenience.

Therefore, in order to improve this problem, it was devised to arrange a magnetic shield inside the funnel (4) of the color picture tube (1). An example of such a magnetic shield is shown in FIG. 6. The internal magnetic shield (21) is made of a thin plate such as a soft iron plate, has a conical shape approximately similar to the funnel (4), and has a shadow mask (lO ) is integrally attached to the outer periphery of the shadow mask (10), and the funnel (4) is attached by an appropriate holding mechanism (not shown) at the same time as the shadow mask (10).
is fixed inside.

However, according to experiments, when such an internal magnetic shield (21) is used, it is more reliable than the external magnetic shield (20) shown in Fig. However, on the other hand, it was found that mislanding caused by the X component of the geomagnetic field, which was not a real problem in the past, became a problem. This is due to the following reasons. That is,
When the internal magnetic shield (21) as described above is provided, the panel (2) has a rectangular shape, which is a general color picture tube (
In 1), the direction of movement of the electron beam injection point due to the X component of the earth's magnetism is as shown in Figure 7, and the corner part, which previously moved almost completely in the y direction, now moves in the y direction. This is because it ends up moving at an angle. Referring to FIG. 8, after the magnetic flux Bx due to the earth's magnetism distributed in the X direction enters the internal magnetic shield (21),
This is thought to be because the electron beam is once in the path of the electron beam at the corner portion, as shown by BX' in the figure, and the electron beam is bent by this magnetic flux (magnetic field).

Various measures have been taken to counter this, such as changing the shape of the four corners of the internal magnetic shield (21), but in the end, all of these measures impair the effectiveness of preventing mislandings caused by the two-directional acid content of the earth's magnetic field. It has almost been found that it is impossible to obtain an internal magnetic shield (21) having a satisfactory shielding effect against geomagnetic components in all directions.

Another known method for preventing the influence of the earth's magnetic field is to wind a coil around the color picture tube (1) and run a current through it to cancel out the earth's magnetic field. In order to cancel the earth's magnetism with an electric current, several sets of coils and a power supply are required, and complicated adjustment of the current setting is required for each installation location and direction of the color picture tube, which is not very practical.

This invention was made in order to solve the above-mentioned conventional problems, and provides a color picture tube device that provides a satisfactory shielding effect against geomagnetic components in any direction and has a relatively simple structure. is intended to provide.

[Means for Solving the Problems] According to the present invention, a color picture tube is provided with an external magnetic shield and a coil for canceling the earth's magnetic field.

[Function] In this invention, mislanding caused by the y-direction component of the earth's magnetism is removed by placing a magnetic shield outside the color picture tube, and mislanding caused by the two-direction acid component of the earth's magnetism is removed by the magnetic shield. is canceled out and removed by passing current through a separately placed coil.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention in which (2
0) is an external magnetic shield, which is made of a high permeability magnetic material such as a soft iron plate formed into a funnel (cylindrical shape surrounding the outer periphery of 0). (30) is a coil;
The side of the funnel (0) and the external magnetic shield (20
) and is placed at an appropriate distance d from it. This coil (30) is wound around the central axis (2 axes) of the color picture tube (1), and the polarity and magnitude of the current can be changed through the lead wire (31). It is connected to a DC power supply (32) that can be used.

Hereinafter, in a color picture tube device configured as shown in L,
Movement of the electron beam injection point due to the X- and Y-direction components of the earth's magnetism, that is, mislanding, can be eliminated by the external magnetic shield (20). In general, even in the external magnetic shield (20), disturbances in the geomagnetic flux in the X direction occur at the corners of the magnetic shield as described in FIG.
4) Since the distance between the electron beam and the corner of the shielding material where the disturbance occurs is long, it is difficult for the magnetic flux disturbance to have an adverse effect. The direction of movement of the beam's impact point can be reduced as a whole while being maintained as shown in FIGS. 4(a) and 4(b).

Next, the movement of the electron beam injection point caused by the two-directional acid content of the earth's magnetic field, that is, the mislanding, is caused by the coil (3
IF can be prevented by applying a DC current of an appropriate magnitude to 0) to cancel out the above-mentioned component of earth's magnetism. Here, if the coil (30) has a simple shape as shown in Figure 1, it cannot generate a magnetic field that is uniform enough to completely cancel out the two components of the earth's magnetism. It is sufficiently possible to suppress the movement of the beam projection point to a non-harmful extent. Generally, the current flowing through the coil (30) is set at the installation site depending on the geomagnetic situation at the location where the color picture tube device is installed, that is, the strength of the two components.

By the way, the coil (3o) is an external magnetic shield (2o)
and are arranged at an interval d. The reason is that, first, if the two are in close contact with each other, the magnetic flux generated by the current will concentrate only in the vicinity of the adjacent shield member, and will not properly penetrate into the interior of the color picture tube (1). This is because it becomes difficult. Second, the amount of magnetic flux that the coil (30) effectively generates inside the color picture tube (1) varies greatly depending on the degree of demagnetization of the shield member, and the coil (30) effectively generates magnetic flux inside the color picture tube (1).
This is because setting the current to be applied to 30) becomes troublesome. That is, demagnetization is generally performed by winding a coil around the outside of the external magnetic shield (20) and automatically passing an alternating attenuation current through it when the color picture tube device is not in operation. Effective magnetic permeability changes significantly depending on the presence or absence of .

Therefore, the coil (30) is connected to the external magnetic shield (20
), they should be placed inside with a distance d between them, or they should be placed shifted in two directions as shown in FIG. Here, the distance d is preferably 1/15 or more of the maximum outer diameter (indicated by D in FIG. 2) of the panel (2) of the color picture tube (1).

In the example shown in FIG. 5, the external magnetic shield (20) has a conical shape that follows the outer shape of the funnel (4) as a whole, but in the example shown in FIG. 1, it is simply cylindrical.

The conventional external magnetic shield was formed into a conical shape as described above in order to reduce the shielding effect against the two-directional acid content of the earth's magnetic field as much as possible, but in the case of the present invention, the two-way magnetic shield
Since there is no need to expect a shielding effect for directional acid from the external magnetic shield (20), it is not necessary to have a conical shape (1
). In fact, if we consider preventing the influence of disturbance of the magnetic field in the X or It can be said that a cylindrical shape is more desirable than a conical shape. Note that even if the external magnetic shield is formed into a cylindrical shape in this way, the shielding effect of the X-direction component of earth's magnetism will not deteriorate significantly.

FIG. 10 shows another embodiment of the invention. In this embodiment, an external magnetic shield (20) is used to shield the X-direction component of the earth's magnetism. Therefore, the most important part of this external magnetic shield (20) is:
These are both side surfaces (20a) extending in the X direction, and the other portions are the extensions of the external magnetic shield (20) that will not fatally impair the shielding effect even if they are not present. The narrower the range, the smaller the problem caused by the proximity of the external magnetic shield (20) and the coil (30) mentioned above. This is after removing the part.

However, even in this case, it is necessary to make efforts to prevent the X-direction component of the earth's magnetism flowing in the X-direction from passing through the interior of the color picture tube (1) as much as possible. A small portion (20b) of the shield member extending in the X direction is left at both ends of both side surfaces (2Qa).

FIG. 11 shows another embodiment of the invention,
The external magnetic shield (20) is divided into two parts (2Qc) and (20d) along a plane perpendicular to the two axes, and the coil (30) is arranged in the gap provided between the two parts. Coil (3
0), there is usually a preferable position for correcting the mislanding distribution due to the two components of the geomagnetic field shown in Figure 4(c), but in that case, the external magnetic shield (2
The structure of this embodiment can prevent the above-mentioned disadvantages caused by the proximity of the coil (30) and the coil (30). In this case as well, since the external magnetic shield (20) is not intended to shield the influence of the two components of earth's magnetism, no problem will occur even if the shield member is divided into two parts and the magnetic resistance in two directions increases. .

[Effects of the Invention] As described above, according to the present invention, the movement of the electron beam injection point caused by the X-direction component of the earth's magnetism is maintained as it is, which is originally harmless, and mislanding due to the X-direction component is prevented. Movements that cause negative effects can be removed by an external magnetic shield, and movements that cause mislanding due to bidirectional acid content can be corrected by passing a direct current through a coil wound perpendicular to the Z-axis. This has the effect of providing a color picture tube device that is less affected by geomagnetic components in all directions.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of a color picture tube device according to the present invention, in which (a) is a partially cutaway front view, (b) is a perspective view, and FIG. 2 is a partially cutaway perspective view illustrating a striped color picture tube. , Figure 3 is a front view of the fluorescent screen of the color picture tube in Figure 2, and Figures 4 (a), (b), and (c) explain the influence of each component of the earth's magnetic field on the electron beam projection point. Figure for, No. 5
Figure 6 is a partial cross-sectional front view of a color picture tube with a conventional external magnetic shield. Figure 6 is a cross-sectional view of a color picture tube with a conventional internal magnetic shield. Figure 7 is a diagram using the internal magnetic shield shown in Figure 6. [No. 6, Figure 8 is for explaining the direction in which the beam projection point moves due to the X component of the earth's
Figures 9 to 11 are diagrams showing other embodiments of the present invention, and Figures 9 to 11 are diagrams showing a state in which magnetic flux disturbance occurs due to the X component of earth's magnetism in the internal magnetic shield. (1)...Color picture tube, (2)...Panel, (3
)...Fluorescent screen, (4)...Funnel, (5)...
・Neck part, (6)... Electron gun, (10)... Shadow mask, (20)... External magnetic shield, (3
0)...Phil. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (7)

[Claims] (1) A color picture tube having a panel, a funnel, and a neck part, a shadow mask arranged at a predetermined distance from the phosphor screen formed on the inner surface of the panel, and an electron gun housed in the neck part. and an external magnetic shield disposed to cover the outer surface of the picture tube, and a coil wound in a plane perpendicular to the central axis of the neck portion at a distance from the external magnetic shield. A color picture tube device featuring: (2) The color picture tube device according to claim 1, wherein the shadow mask has a large number of substantially rectangular holes arranged in parallel. (3) The color picture tube device according to claim 1, wherein the external magnetic shield surrounds the funnel. (4) The color picture tube device according to claim 2, wherein the external magnetic shield is arranged on the outer surface of the funnel in parallel to the longitudinal direction of the hole in the shadow mask. (5) The color picture tube device according to claim 1, wherein the external magnetic shield is divided into at least two parts by cutting along a plane substantially perpendicular to the central axis of the neck portion. (6) The color picture tube device according to claim 1, wherein the coil is disposed between the external magnetic shield and the funnel. (7) The color picture tube device according to claim 1, wherein the coil is wound with a position shifted in the direction of the central axis of the neck portion with respect to the external magnetic shield.