JPS61218048A - Cathode-ray tube device - Google Patents

Abstract

PURPOSE:To avoid the bad influence of the earth magnetism on image quality by shielding the unnecessary magnetic field near the electron gun by installing a rear shield with high permeability extending in the back of the deflection york coaxially with the axis of the cathode. CONSTITUTION:A cylindrical rear shield 12 made of a material with high permeability such as permalloy has an expanded front opening 12a located close to the rear end of a deflection york 8. The rear end 12b of the rear shield 12 located in the back of a magnetic assembly 11 has a small diameter. Due to the rear shield 12, the magnetic flux lines from the rear of the deflection york 8 flows into the shield 12 without migrating into a neck 3. Consequently, unnecessary magnetic flux lines extending along the axis of a cathode-ray tube 7 are remarkably shielded near an electron gun 13.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a cathode ray tube device used as a display device such as a color television device or a display device.

[Conventional technology]

FIG. 8 is a partially cutaway view of a conventional cathode ray tube device disclosed in Japanese Utility Model Application No. 49-45184.

In the figure, (1) is the cathode ray tube panel, (2) is the funnel, (3) is the neck, (4) is the frame, (
5) is a shadow mask, and (6) is an internal magnetic shield member.

FIG. 4 is a partially cutaway sectional view of a cathode ray tube device as a display device for a cockpit display posted by Toshiba Shiview A'142Jζ. In the figure, (7) is a cathode ray tube, (8) is a deflection yoke, (9) is a convergence yoke, and (6) is a magnetic shield case.

Here, the role of the magnetic shielding member (case) (6) and αQ will be described. This type of device applies a magnetic field to an electron beam to deflect it to a predetermined position and generate fluorescence. Therefore, if an unnecessary magnetic field such as the earth's magnetism is within the electron beam orbit, the screen will rotate or shift. In addition, in the case of a color cathode ray tube, adverse effects occur such as mislanding in which a given electron beam does not hit the corresponding phosphor, and misconvergence in which eight electrons do not concentrate at one point.

For this reason, cathode ray tubes have traditionally been equipped with low magnetic resistance members near the electron beam trajectory to bypass unnecessary magnetic fields.
Measures are taken to prevent unnecessary magnetic fields from entering the electron beam orbit Gζ.

Figure 8 shows a magnetic shield member (6) as a low magnetic resistance member.
) is arranged in a cathode ray tube (7) circle,
FIG. 4 shows an example in which the magnetic shielding member (case) α1 is arranged outside the cathode ray tube (7).

[Problems to be Solved by the Invention] The internal magnetic shield system shown in FIG. 8 is the mainstream of conventional cathode ray tubes (7), especially color cathode ray tubes. An iron plate is used for the internal magnetic shield member (6). This material is inexpensive and can provide a certain degree of shielding effect. However, as the standards for changes in image quality due to geomagnetism are becoming stricter, this internal magnetic shield member (6) alone is not effective enough to meet the above standards, but it is possible to use high magnetic permeability materials such as roy.
A sufficient shielding effect can be obtained. However, since the entire cathode ray tube (7) is covered with expensive permalloy, the cost of the product is unavoidably high.

This invention was made to solve the above-mentioned problems, and aims to provide a cathode ray tube device that can avoid the adverse effects of earth's magnetism on image quality, and can suppress the associated cost increase. .

[Means to resolve the problem]

The cathode ray tube device according to the present invention includes a low magnetic resistance internal magnetic shield member provided in the funnel portion, and a high magnetic permeability magnetic shield member (hereinafter referred to as
8 cathode ray tubes (referred to as rear shield members).

[Function] In this invention, the rear shield member shields unnecessary magnetic fields near the electron gun, and in particular prevents external magnetic flux such as earth's magnetism in a direction that coincides with the tube axis of the cathode ray tube from concentrating at the rear of the deflection yoke. The unnecessary magnetic flux is guided to the outside of the cathode ray tube without passing near the electron gun.

〔Example〕

FIG. 1 shows an example of a cathode ray tube device according to the present invention, and parts that are the same as those in the conventional device are given the same reference numerals and explanations will be omitted.

(l is a magnet assembly, (l is a substantially cylindrical rear shield member made of a high magnetic permeability material, such as permalloy, and the front end opening (12a) close to the rear end of the deflection yoke (8) is widened at the end.) The magnet assembly is formed to have a large diameter, and the rear end (12b) extending rearward across the magnet assembly is formed to have a small diameter.

The above rear shield member Q4 is installed on the small diameter part (12b).
Close the neck (3) of the cathode ray tube (7) and tighten it from the outside, or attach a rear shield member to a part of the molded part (usually a plastic molded part) at the rear of the deflection yoke (8). This can easily be done by providing a hook for attachment and fixing to this hook.

Next, the operation of the above structure will be explained with reference to FIG.

Figure 2 (2) shows the flow of magnetic flux lines such as the earth's magnetic field (100) inside and outside the cathode ray tube (7) in a direction that coincides with the tube axis of the cathode ray tube (7) when the rear shield member α is not provided. It is something. As you can see from this figure, the geomagnetic field (10
0), if only the internal magnetic shield member (6) is used, the funnel part (2) and the deflection yoke (8) are shielded to some extent, but the area from the rear of the deflection yoke (3) to the neck part (3) is shielded to some extent. On the contrary, the magnetic flux tends to concentrate. Figure 2 (8) shows the flow of magnetic flux lines under similar conditions when the rear shield member α with the above configuration is provided. Because of the presence of the rear shield member Q, the magnetic flux lines from the rear of the deflection yoke (8) are directed to the neck (
3) (flows into the rear shield member (1) side. Therefore, unnecessary magnetic flux lines in the direction that coincides with the tube axis of the cathode ray tube (7) are
It exhibits a remarkable shielding effect in the vicinity of the electron gun (II) compared to the case where only the electron gun (II) It was possible to make the number 815.

Note that the shape of the rear shield member α is not limited to the shape of the above example, but may be a simple cylindrical shape, and can be selected as appropriate. In addition, the front end of the rear shield member (lj!a) is connected to the deflection yoke (
8), the same effect can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, since the high permeability rear shield member extending rearward from the deflection yoke or its adjacent portion is provided coaxially with the tube axis of the cathode ray tube, Unnecessary external magnetic flux lines are reliably shielded even near the electron gun, and this has the effect of suppressing image quality performance deterioration, especially convergence change, caused by external unnecessary magnetic flux lines such as geomagnetism. In addition, since the rear shield member is only in the vicinity of the deflection yoke and magnet assembly, there is no material cost burden even if permalloy or the like is used.
It also has the advantage of being inexpensive to manufacture.

[Brief explanation of drawings]

FIG. 1 is a schematic side view showing a cathode ray tube device according to an embodiment of the present invention, and FIG. Figure 9 and Figure 2) are diagrams showing the flow of external magnetic flux lines in the direction that coincides with the tube axis of the cathode ray tube when a rear shield member is provided, and Figure 8 is a diagram showing the flow of external magnetic flux lines in the direction that coincides with the tube axis of the cathode ray tube when a rear shield member is provided. FIG. 4 is a partially cutaway perspective view of a conventional external magnetic shield type cathode ray tube device. (2)...funergi≠, (3)...neck part,
(6)... Internal magnetic shielding member, (7)... Shade 8
I-ray tube, (8)... Deflection side, (1... Magnet assembly, 0'4... Magnetic shielding member (
rear shield member), (12a)...front end, (12
b)...Rear end. In addition, the same reference numerals indicate the same or equivalent parts.

Claims (3)

[Claims] (1) An internal magnetic shield member made of a low magnetic resistance material disposed within the funnel portion of the cathode ray tube, a deflection yoke attached to the cone portion of the cathode ray tube to generate a deflection magnetic field for the electron beam, and It is equipped with a magnet assembly that is attached to the neck part and generates a static magnetic field that corrects the trajectory of the electron beam, and is made of a high magnetic permeability material. A cathode ray tube device characterized in that a magnetic shielding member extending to the cathode ray tube is attached coaxially with the tube axis of the cathode ray tube. (2) The cathode ray tube device according to claim 1, wherein at least a portion of the magnetic shielding member is cylindrical. (3) The cathode ray tube device according to claim 1 or 2, wherein the magnetic shielding member has an opening at one end on the deflection yoke side in a shape that widens toward the end, and an opening at the other end in a small diameter shape.