JP2001185042A - Cathode ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To overcome problems that miss landing by earth magnetism tends to be remarkably deteriorated and properties of lateral magnetic field and tube axis NS is in relation of trade off as variation rate is nearly equal and symbols become reversed, but that it is impossible to improve both properties at the same time. SOLUTION: A skirt in the vicinity of center of longer side in skirts of a magnetism shield body is coupled with a head of a frame. Other skirts are disposed at a certain distance from a mask frame to prevent contact with the mask frame.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode ray tube, and more particularly to a joint shape and form of a frame and an internal magnetic shield for improving geomagnetic characteristics.

[0002]

2. Description of the Related Art FIG. 8 shows a conventional cathode ray tube of a television or a personal computer monitor, in which a deflection yoke deflects an electron beam emitted from an electron gun vertically and horizontally, and scans the entire screen to form an image. Reproduce. At this time, when an external magnetic field such as terrestrial magnetism acts on the cathode ray tube, the electron beam is distorted,
Mislanding that does not reach a predetermined position with respect to the phosphor on the panel occurs. As a countermeasure, an internal magnetic shield is provided in the cathode ray tube.

Since it is impossible to completely shield an external magnetic field, the role of an internal magnetic shield is to provide a certain degree of magnetic field shielding and to change the direction of the magnetic field lines so that the electron beam is not subjected to a force, or to a certain part. It is to correct the received force.

[0004] Except in special cases, the main cause of the external magnetic field is terrestrial magnetism. Geomagnetism is divided into a horizontal component and a vertical component. As is well known, the vertical component changes the landing almost uniformly over the entire screen, and does not pose a problem because the correction is performed by a correction lens or the like when the fluorescent screen is formed. The horizontal magnetic field 100 varies in size and direction depending on the relative position of the magnetic field and the CRT as shown in FIG. 9, and is generally divided into a tube axis direction 101 and a lateral direction 102 of the CRT.

After all, when considering the shield by geomagnetism,
It is necessary to satisfy the characteristics by the transverse magnetic field, which is the component of the horizontal component of the terrestrial magnetism, and the magnetic field in the tube axis direction. When the characteristics are evaluated by a CRT, a magnetic field equivalent to the geomagnetism is applied from the outside, and the amount of change in beam landing at that time is measured. As shown in FIG. 10, the measurement points are four corners, and the upper and lower central portions on the short side (hereinafter referred to as NS portions).
Particularly important characteristics here are: (1) Characteristics of the corner portion when a lateral magnetic field is applied (hereinafter referred to as “lateral corner”).

(2) When a magnetic field in the tube axis direction is applied, N
Characteristics of S part (hereinafter referred to as “tube axis NS”). It is.

The shape of the internal magnetic shield is generally formed by opposing long side walls and opposing short side walls as shown in FIG. 11, and has an opening at the center. In addition, the internal magnetic shield has a V-shaped notch in FIG. 12 formed on the short side wall.

In a recent system in which a tension is applied to a mask, the joining between the internal magnetic shield and the frame is performed by a method disclosed in Japanese Patent Laid-Open No. Hei 6-333507,
The method shown in FIG. 13 was common.

[0009]

In recent years, CRTs having a large screen and a flat face plate have become mainstream. In this type of CRT, mislanding due to terrestrial magnetism tends to be significantly deteriorated in the magnetic shield of the related art. For example, in a conventional 25 ″ CRT, both the horizontal corner and the tube axis NS are about 10 μm, but the horizontal corner is 15 μm and the tube axis NS is 30 μm.

[0010] In order to improve the characteristics of the structure shown in FIG. 13, optimization is achieved by changing the depth and width of the notch.
The amount of change in the beam landing with respect to the external magnetic field equivalent to the geomagnetism was improved to (lateral magnetic field, tube axis NS) = (21 μm, 23 μm). However, as shown in FIG. Are in a trade-off relationship with almost the same rate of change and opposite signs, and it was impossible to improve both characteristics simultaneously.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has an internal structure that reduces mislanding due to distortion of an electron beam due to an external magnetic field such as terrestrial magnetism and reduces color shift and color unevenness over the entire screen. It is intended to provide a magnetic shield.

[0012]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention contemplates a method of joining an extension (hereinafter referred to as a skirt) of an end of a magnetic shield to a shadow mask and a mask frame. I do.

There are the following three variations.

(1) In the skirt portion of the magnetic shield, the skirt portion near the center of the long side and the vicinity of the top of the frame are joined. The other skirt portion is provided with a certain distance from the mask frame so as not to make contact with the mask frame.

(2) The skirt portion of the magnetic shield exists only near the center of the long side.

(2) In the structure of (2), the skirt portion is in contact with or joined to the frame.

(3) The skirt portion of the magnetic shield is present only near the center of the long side.

The other portion of the long side of the magnetic shield has a certain distance from the top of the frame.

According to the present invention, mislanding of an electron beam due to an external magnetic field such as terrestrial magnetism is reduced.

In particular, it is possible to provide a magnetic shield that simultaneously improves the horizontal corner and the tube axis NS.

[0021]

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

(Embodiment 1) FIG. 1 shows Embodiment 1 of the present invention.
3A and 3B are a perspective view and a side view of an internal magnetic shield and a mask frame of a 25 "stretch-mask type CRT. The internal magnetic shield is formed by opposing long side walls and opposing short side walls. An opening is provided at the center, and a notch is formed on a short side wall of the opening on the deflection center side.

A skirt portion 1 having a length of 3 to 6 cm is provided at the end of the long side of the internal magnetic shield on the mask frame side.

The skirt has a width of about 40 cm.

At this time, the outer shape of the magnetic shield is shown in FIG.
However, as shown in FIG. 1, the skirt 1 is in contact with the frame only near the center of the long side 2 of the frame, and the other skirts have a distance of 4 mm from the side of the frame. is there.

At this time, the variation of the beam landing with respect to the external magnetic field equivalent to the terrestrial magnetism is (transverse magnetic field, tube axis NS) = (19 μm, 21 μm).

Furthermore, while improving the transverse magnetic field characteristics,
As shown in FIG. 2, a slit is provided in a part of the skirt portion to improve the ease and reliability of manufacture.

At this time, with respect to an external magnetic field equivalent to the earth magnetism,
The change amount of the beam landing was (transverse magnetic field, tube axis NS) = (16 μm, 20 μm), and the magnetic characteristics, particularly the horizontal magnetic field characteristics were improved without a relatively simple shape and without increasing the number of manufacturing steps.

(Embodiment 2) Fig. 3 is a perspective view and a side view of an internal magnetic shield and a mask frame in a 25 "stretched mask type CRT according to Embodiment 2 of the present invention. In the embodiment, the geomagnetic characteristics were improved by changing the length of the skirt in the lateral direction.

FIG. 4 shows a change in the beam landing amount when the length of the skirt portion in the long side direction (hereinafter referred to as L) is changed. Here, the original length L0 is about 40 cm
It is. When L is shortened from 40 cm, the center part on the side of the rope is symmetrical, and both ends are cut by equal lengths.

As shown in FIG. 4, as L is reduced, the transverse magnetic field characteristics are greatly improved. Further, the tube axis NS does not change much compared to the case where the cutout shape of the short side wall portion is changed. However, when the length is shorter than 4 to 5 cm, the characteristics of the tube axis NS deteriorate significantly.

It is considered that the magnetic characteristics are improved in the first and second embodiments for the following reasons.

The magnetic field applied from the lateral direction easily flows into the mask frame when the skirt portion is L = 40 cm.

This is particularly remarkable when the skirt portion is in contact with the frame, and when the distance between the mask frame and the skirt portion is large, magnetic coupling is small and magnetic flux does not easily flow through the mask frame.

When a magnetic field exceeding a certain level is applied,
The magnetic flux that has exceeded the magnetic capacity of the mask frame and has flowed into the mask frame from the magnetic shield will overflow into space.

As a result, it is considered that an undesired electric field is applied to the electron beam to greatly change the beam landing.

At this time, at the same time, the tube axis NS gradually degrades.

This is because when a magnetic field is applied in the tube axis direction, the magnetic resistance is relatively small due to the anisotropy of the shadow mask.

For this reason, even if L becomes small, the magnetic flux easily flows from the magnetic shield to the frame and the shadow mask, so that the deterioration is smaller than that of the horizontal corner. When L is less than 4 or 5, the sudden deterioration is because the magnetic flux from the magnetic shield is less likely to flow and an undesired magnetic field blows out into the space.

In this embodiment, L = 12 cm.

At this time, with respect to an external magnetic field equivalent to the earth magnetism,
The amount of change in beam landing was (transverse magnetic field, tube axis NS) = (11 μm, 21 μm), and the magnetic characteristics were greatly improved.

(Embodiment 3) FIG. 5 shows an internal magnetic shield according to Embodiment 2 of the present invention. This internal magnetic shield is for further improving the characteristics of the second embodiment. L = 12 cm, and the end of the skirt is brought into contact with the frame. As a result, when a magnetic field is applied in the tube axis direction, the magnetic flux flowing from the magnetic seal body easily flows in the frame mask direction. Because of this, the characteristics of the horizontal corners are short, as L = 12, so that they hardly deteriorate.

At this time, with respect to an external magnetic field equivalent to geomagnetism,
The amount of change in beam landing was (transverse magnetic field, tube axis NS) = (12 μm, 18 μm).

As a method of contact at this time, it has been experimentally confirmed that the magnetic shield body is bent deeply in advance in anticipation of contact with the frame at the time of pressing, or that contact by welding is preferably performed.

Further, it was experimentally confirmed that the effect of the joint portion near the top of the frame as shown in FIG. 6 was more effective.

At this time, with respect to an external magnetic field equivalent to the earth magnetism,
The change amount of the beam landing is (transverse magnetic field, tube axis NS) = (12 μm, 16 μm).

In Embodiments 1 and 2, the same effect can be obtained even if the ratio between the gap and the contact portion is appropriately changed. In addition, as shown in FIG. 7, it is more effective to provide a gap in the long side portion of the magnetic shield without a skirt to reduce the flow of magnetic flux with the frame.

In FIGS. 1 to 6, the distance between the magnetic shield and the mask frame is drawn slightly apart for easy understanding.

By using the internal magnetic shield as described above, it is possible to reduce or cancel the force of the electron beam received from an external magnetic field such as terrestrial magnetism on the orbit to the phosphor screen. As a result, the force received by the electron beam was reduced, mislanding due to distortion of the electron beam was reduced, and color shift and color unevenness were prevented over the entire screen. In this embodiment, a 25 "CRT is assumed.
The size of the skirt at that time is CRT
It depends on. Further, notches or the like may be formed in the shape of the skirt portion to further control two characteristics.

[0050]

As described above, according to the first embodiment of the present invention,
In the second embodiment as well, by connecting the skirt portion of the magnetic shield with the vicinity of the center of the frame, the amount of change in beam landing with respect to an external magnetic field equivalent to the geomagnetism is greatly improved simultaneously with the transverse magnetic field and the tube axis NS.

By using the internal magnetic shield as described above, it is possible to reduce or cancel the force that the electron beam receives from an external magnetic field such as terrestrial magnetism on the orbit to the fluorescent screen.

As a result, the force applied to the electron beam was reduced, the mislanding due to the distortion of the electron beam was reduced, and color shift and color unevenness were prevented over the entire screen.

[Brief description of the drawings]

FIG. 1 is a view showing a magnetic shield and a mask frame according to an embodiment of the present invention;

FIG. 2 is a view showing a case where the shape of a skirt portion is changed in FIG. 1;

FIG. 3 is a view showing a magnetic shield and a mask frame according to a second embodiment of the present invention;

FIG. 4 is a view showing experimental results of a lateral length of a skirt portion and magnetic characteristics.

FIG. 5 is a diagram in a case where the skirt portion and the side surface of the frame portion in FIG. 3 are connected;

FIG. 6 is a diagram in a case where the skirt portion and the top portion of the frame portion in FIG. 3 are connected.

FIG. 7 is a diagram of the vicinity of an end of a long side of the magnetic shield in the second embodiment when cut off.

FIG. 8 shows a conventional cathode ray tube.

FIG. 9 is a diagram illustrating a relative position between a horizontal magnetic field and a CRT.

FIG. 10 is a diagram showing landing measurement points on a CRT screen.

FIG. 11 is a diagram showing a conventional general magnetic shield body.

FIG. 12 is a diagram showing a conventional magnetic shield having a V-shaped notch.

FIG. 13 is a view showing a magnetic shield used for a conventional tension mask.

FIG. 14 is a diagram showing a relationship between a notch width and a landing change amount.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Skirt part 100 Horizontal magnetic field 101 Tube axis direction 102 Lateral direction

[Procedure amendment]

[Submission date] June 30, 2000 (2006.3.3)
0)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Hiroshi Iwamoto 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Takayuki Yonezawa 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F term (reference) 5C031 CC05

Claims (8)

[Claims] 1. A cathode ray tube having at least a mask, a frame, and an internal magnetic shield, wherein the magnetic shield has an extension at an end on a mask side thereof, and the magnetic shield is attached to the frame in a central region of a long side of the frame. A cathode ray tube, which is in contact with the cathode ray tube. 2. The cathode ray tube according to claim 1, wherein the contact portion with the frame is the top of the frame. 3. The cathode ray tube according to claim 1, wherein a gap is provided between the mask-side extension of the magnetic shield not in contact with the frame and the frame. 4. The cathode ray tube according to claim 1, wherein the extension of the mask-side end of the magnetic shield is located only at the center of the long side of the frame. 5. The cathode ray tube according to claim 1, wherein the length of the contact portion is not more than 1/2 of the length of the long side. 6. The cathode ray tube according to claim 1, wherein the shield extension and the frame are joined by welding. 7. The magnetic shield according to claim 4, wherein a portion of the long side of the magnetic shield that has no extension of the mask-side end of the magnetic shield is not in contact with the frame. A cathode ray tube as described. 8. The magnetic shield body according to claim 1, further comprising a notch in an extension of the mask-side end.
7. The cathode ray tube according to any one of items 1 to 6, above.