JPH099283A - Color picture tube device - Google Patents

Abstract

PURPOSE: To provide a color picture tube device without generating the deterioration of color purity, color shade or the deterioration of display performance for the rotation of a screen, etc., even when an external DC magnetic field of several to ten odd times that of geomagnetism is applied to the display surface of a color picture tube. CONSTITUTION: A first coil 1 is arranged in a box shape chassis 3 in which the color picture tube 10 is housed and whose front is opened by locating between the display surface 10a of the color picture tube and a deflecting yoke 14 and in parallel with the display surface 10a. Moreover, a second coil 2 is arranged in the chassis 3 by confronting the respective upper and lower surface of four corner corner parts of the display surface 10a of the color picture tube 10 and also, setting in parallel with the upper and lower surfaces. Driving parts 4, 5 which generate a magnetic field to cancel the influence of the external DC magnetic field are provided in the first and second coils.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color picture tube device provided with a measure for eliminating the influence of an external DC magnetic field.

[0002]

2. Description of the Related Art Generally, a picture tube (CRT) 10 is shown in FIG.
As shown in, the electron beam 1 emitted from the electron gun 11
2 is projected onto a phosphor 13 coated on the inner surface of the display surface to be converted into light, and this electron beam 12 is deflected by a deflection yoke 14 in horizontal and vertical directions at a predetermined cycle, An image is reproduced on the display surface 10a of the picture tube 10 by controlling the intensity of the electron beam 12.

In the case of a color picture tube, as shown in FIG. 4, three electron guns 1 for red (R), green (G) and blue (B) are used.
1, a three-color phosphor 13 of red, green, and blue, and a color selection mechanism 15 (for example, an aperture grill) provided so as to face the phosphor surface coated with the phosphor 13, Three
The electron beams 12 emitted from the two electron guns 11 are deflected by the deflection yoke 14, meet at the color selection mechanism 15, and accurately collide with the phosphors 13 in front of them, thereby reproducing the correct color. It has become so.

However, when an external DC magnetic field (magnetic field including geomagnetism) is present at the installation location of the picture tube 10, the electron beam 12
Under the influence, the orbit is shifted according to Fleming's law, and the fluorescent substance 13 may collide with a portion other than the fluorescent substance 13 which should originally collide. Such a state is called mislanding, which causes deterioration of color purity and color unevenness.

Considering, for example, the earth magnetism as the external magnetic field, the vertical magnetic field component is considered to be always constant regardless of the orientation of the apparatus, so that it is only necessary to make adjustment once according to the magnetic field at the installation location. However, with respect to the magnetic field components in the left-right direction and the tube axis direction, how the device is affected depends on the direction.

In this case, the influence of the magnetic field component in the horizontal direction can be reduced to some extent by adopting an internal magnetic shield or an external magnetic shield for the picture tube, and the same applies to the magnetic field component in the vertical direction. As for the magnetic field component in the axial direction, the display surface side of the picture tube cannot be magnetically shielded, so that the influence as shown in FIG. 5 occurs.

FIG. 5 (a) shows changes in landing due to geomagnetism, FIG. 5 (b) shows rotation of the screen due to geomagnetism, and dotted lines show the case where there is no magnetic field. The solid line shows the state when geomagnetism is applied. The display surface of the picture tube 10 is facing south, and the geomagnetism passes vertically from the front side to the back side of the display surface. Therefore, the electron beam projecting to the center of the display surface is not affected by the geomagnetism.

The following method has been proposed as a method for reducing the influence of the geomagnetism incident in the tube axis direction.
For example, in Japanese Unexamined Patent Publication No. 6-70331, a screen rotation is generated between a deflection yoke outside the cathode ray tube and an anode button, which generates a magnetic field in a direction opposite to a horizontal geomagnetic component perpendicular to the tube surface. A cathode ray tube in which a correction coil is arranged to reduce the influence of geomagnetism is shown. Further, Japanese Patent Publication No. 6-69221 discloses a coil provided between a shadow mask and a deflection yoke, which is wound in a plane perpendicular to the neck so as to wrap around the outer circumference of a color picture tube. A color picture tube device is shown in which the screen rotation and mislanding can be corrected by positioning the coils.

[0009]

However, in any of the above cases, although it is effective for an external magnetic field having a weak level of geomagnetism, it is a strong external magnetic field that is several times to ten times as strong as the earth's magnetism. There is a problem that it cannot be canceled in the environment where a strong external DC magnetic field is generated, such as in the vicinity of a non-magnetic field such as a DC magnetic field (for example, an MRI apparatus), a DC high voltage transmission line, a subway line, or the like. is there. This is because the magnetic field generated by the coil described above is not completely equivalent to the geomagnetism in the tube axis direction.
Although it is possible to cope with an external magnetic field that is as weak as the earth's magnetism, it is not possible to cope with a strong external magnetic field even by increasing the magnetic field generated by the coil.

According to the present invention, even if an external DC magnetic field of several times to several tens of times that of the earth's magnetism is applied to the display surface of the color picture tube, deterioration of display performance such as color purity deterioration, color unevenness, or screen rotation occurs. The purpose is to provide a color picture tube device which does not exist.

[0011]

In a color picture tube apparatus according to the present invention, an electron beam from an electron gun built in a neck portion is deflected by a deflection yoke, and a color selection mechanism arranged in proximity to a display surface. Is located between the display screen of the color picture tube and the deflection yoke, and is parallel to the display surface. A first coil arranged in parallel to the side surfaces of the color picture tube at four corners of the display surface of the color picture tube and parallel to the side surfaces; The coil is provided with a drive unit that generates a magnetic field in a direction that cancels the influence of the external DC magnetic field.

Further, in this case, when the color selection mechanism is an aperture grill type, the second coil is arranged so as to face the upper and lower surfaces of the four corners of the display surface of the color picture tube, and the color selection mechanism is dot-in-line. In the case of a shape shadow mask, it is desirable that the second coil is arranged so as to face the upper, lower, left and right surfaces of the four corners of the display surface of the color picture tube.

Further, it is convenient that the first coil and the second coil house a color picture tube and are fixedly installed in the chassis in a box-shaped chassis having an open front surface.

[0014]

Since the present invention is constructed as described above,
When a direct current external magnetic field of a level close to normal earth magnetism is applied in the tube axis direction, a direct current is first applied to the first coil located on the outer periphery of the color picture tube to generate a magnetic field in the direction opposite to the external magnetic field, and the external magnetic field is generated. By canceling, the color purity and the color unevenness are corrected over the entire display surface, and the rotation of the screen is also improved.

Further, when an extremely strong external magnetic field is applied, deterioration of color purity remains in the peripheral portion of the color picture tube only by the action of the first coil, so that when the color selection mechanism is an aperture grill. Is configured to generate a magnetic field in the vertical direction by applying a direct current to each of the second coils provided so as to face the upper surface and the lower surface of the four corners of the display surface of the color picture tube. It is deflected to the left and right to correct the deterioration of color purity in the peripheral portion.

When the color selection mechanism is a dot in-line type shadow mask, a direct current is applied to each of the second coils provided on the four corners of the display surface of the color picture tube so as to face each other, and a horizontal direction is provided. A vertical magnetic field is generated to deflect the electron beam in the vertical and horizontal directions to correct the deterioration of color purity in the peripheral portion. The drive unit that supplies a direct current to the first and second coils is individually installed and adjusted in consideration of variations in characteristics of individual color picture tubes and nonuniformity of an external magnetic field applied.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. Note that the same or corresponding parts as those described in the section of the related art are designated by the same reference numerals. FIG. 1 (a),
(B), FIG. 2 shows an embodiment of the present invention.
FIG. 3A is a front view of the chassis 3 that houses the color picture tube 10, the front surface of which is open, and the color picture tube 10 is housed from the front side. FIG. 1B is a side view of the color picture tube device with the color picture tube 10 housed in the chassis 3. FIG. 2 is an exploded perspective view of this color picture tube device. In this embodiment, a 21-inch aperture grill type with an internal magnetic shield is used as the color picture tube 10, and a normal iron one is used as the chassis 3.

As shown in the figure, inside the chassis 3,
A first coil 1 closely wound in a rectangular shape is attached, and its position is between the display surface 10a and the deflection yoke 14 when the color picture tube 10 is housed in the chassis 3, and the display is performed. The position is parallel to the surface 10a. However, since the primary purpose is to correct the color purity and the secondary purpose is to correct the screen rotation, the first coil 1 is brought closer to the display surface 10a side.

The specific specifications of the first coil 1 are as follows: external dimensions: 370 mm × 450 mm, winding specifications: 0.4
φ × 100T, the correction current is 0.1 A (DC) max. This is because the color picture tube 10 is 21 inches, and the specifications are naturally different for other sizes.

A drive unit 4 is connected to the first coil 1 as shown in the figure, and the display performance is deteriorated due to the influence of an external magnetic field (deterioration in color purity, color unevenness, screen rotation). Is corrected in the whole area of the display screen by 0.1A (DC) m
A correction current can be passed through the first coil 1 within the range of ax.

Further, as shown in the figure, the second coil 2 (2a, 2b, 2c, 2d) wound in a rectangular shape is attached to the upper and lower surfaces of the four corners of the chassis 3 so as to be in close contact with each other. . The position is such that when the color picture tube 10 is housed in the chassis 3, it faces the upper and lower surfaces of the four corners of the display surface 10a and is parallel to the respective surfaces.

Specific specifications of the second coil 2 are as follows: external dimensions are 55 mm × 135 mm, and winding specifications are 0.25φ × 2.
00T, the correction current is 0.2A (DC) max. This is because the color picture tube 10 is 21 inches,
For other sizes, the specifications will naturally be different.

Further, as shown in the figure, the drive parts 5 (5a, 5b, 5c, 5d) are connected to the second coil 2 as well, and the second coil 2 is connected within the range of 0.2A (DC) max. A correction current can be passed through the coil 2 and a magnetic field can be generated in the vertical direction.

The reason why the second coil 2 is provided is that when the external magnetic field applied to the color picture tube is strong and the directionality thereof is not uniform, the correction current supplied to the first coil 1 alone is used for display. This is because it is almost impossible to solve the deterioration of the color purity around the screen. The second coil is arranged so as to face the upper and lower surfaces of the four corners of the display surface of the color picture tube because the color picture tube in this embodiment employs the aperture grill type color selection mechanism. This is because, due to its structure, there is no deterioration in color purity due to vertical electron beam fluctuations, but there is deterioration in color purity due to horizontal electron beam fluctuations.

A strong external magnetic field, which is several times to several tens of times that of the earth's magnetism, such as a magnetic field of an MRI apparatus, is applied to the color picture tube and cannot be corrected by the first coil 1 alone.
When the color purity deteriorates at the four corners on the periphery of the display surface, a correction current is passed from each drive unit 5 to the second coil 2 to generate a vertical magnetic field and deflect the electron beam in the left-right direction. This makes it possible to correct the deterioration of color purity. At that time,
Considering the non-uniformity of the external magnetic field and the non-uniformity of the beam landing of the color picture tube itself, the strength of the generated vertical magnetic field is adjusted independently.

When it is necessary to further correct the screen rotation, a circular coil is added above the deflection yoke 14 to generate a magnetic field that cancels the magnetic field in the tube axis direction, and the correction is performed. Good. In the above embodiment, the first
The coil 1 has a rectangular shape and is attached and fixed to the chassis 3. This is configured to improve workability when replacing the color picture tube 10, and is circular and is directly attached to the color picture tube 10. You may do it.

Further, in the above embodiment, since the color picture tube adopting the aperture grill type color selecting mechanism is adopted, the second coil 2 is arranged on the upper and lower surfaces of the four corners of the color picture tube 10. In the case of a color picture tube that employs a dot-in-line type shadow mask, the color purity will deteriorate even if the electron beam fluctuates in the vertical direction. Need to be added to correct the color purity.

[0028]

As described above, according to the present invention,
Even when a strong external magnetic field that is several times to several tens of times stronger than the earth's magnetism is applied to the color picture tube, the influence of the external magnetic field can be canceled and the display performance can be kept good.

[Brief description of drawings]

FIG. 1A is a front view of a chassis of a color picture tube device according to the present invention, and FIG. 1B is a side view of the color picture tube device.

FIG. 2 is an exploded perspective view of a color picture tube device.

FIG. 3 is a sectional view of a color picture tube.

FIG. 4 is a principle view of an aperture grill type color picture tube.

FIG. 5 is a diagram showing an influence of geomagnetism applied in the tube axis direction on an image, FIG. 5 (a) is a diagram showing a change in landing,
(B) is a figure showing rotation of a screen by geomagnetism.

[Explanation of symbols]

 1 1st coil 2 2nd coil 3 Chassis 4 Drive part 5 Drive part 10 Color picture tube 11 Electron gun 12 Electron beam 13 Fluorescent substance 14 Deflection yoke 15 Color selection mechanism

Claims (4)

[Claims] 1. A color is obtained by deflecting an electron beam from an electron gun built into a neck portion by a deflection yoke and selectively projecting it onto a phosphor inside a display surface by a color selection mechanism arranged close to the display surface. A color picture tube with a built-in internal magnetic shield for displaying, a first coil located between the display surface of the color picture tube and a deflection yoke, and arranged in parallel with the display surface; and the color picture tube A second coil that is arranged parallel to the side surfaces and faces each side surface at the four corners of the display surface, and a magnetic field in a direction that cancels the influence of the external DC magnetic field on the first and second coils. A color picture tube device, comprising: a drive unit for generating the color picture tube. 2. The color selection mechanism is an aperture grill type, and the second coil is a display screen of a color picture tube.
The color picture tube device according to claim 1, wherein the color picture tube device is arranged so as to face the upper and lower surfaces of the corner portion. 3. The color selection mechanism is a dot in-line type shadow mask, and the second coil is arranged so as to face the upper, lower, left and right surfaces of the four corners of the display surface of the color picture tube. The color picture tube device according to claim 1. 4. The first coil and the second coil are installed in a box-shaped chassis that houses the color picture tube and has an open front surface.
The color picture tube device according to claim 1.