JPH11260278A - Color cathode-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color cathode-ray tube that hardly causes image screen defects or the degradation of a withstand voltage characteristic by reducing splashes in welding a mask frame to a magnetic shield. SOLUTION: This is a color cathode-ray tube composed of supporting a shadow mask 25 composed of a mask body 26 and a mask frame 29, mounted to the peripheral part of the mask body inside a panel 22, and welding a magnetic shield 36 located inside a funnel to the mask frame 29. In this case, the plate thickness of the part of the mask frame 29, to which the magnetic shield 36 is welded, is so formed as to be set thinner than that of other parts.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color cathode ray tube, and more particularly to a color cathode ray tube having improved means for fixing a magnetic shield to a mask frame.

[0002]

2. Description of the Related Art As shown in FIGS. 4 and 5, a color cathode ray tube generally has an envelope comprising a panel 2 provided with a skirt portion 1 at a peripheral portion and a funnel 3 having a funnel shape. A phosphor screen 4 made of a three-color phosphor layer is provided on the inner surface of the phosphor screen 2. A shadow mask 5 is arranged inside the phosphor screen 4 so as to face the phosphor screen 4. The shadow mask 5 has a mask body 6 having a large number of electron beam passage holes formed on a surface facing the phosphor screen 4, and an inner protrusion at one end of a side wall attached to a periphery of the mask body 6. An L-shaped mask frame 7 is provided, and the elastic support attached to the side wall of the mask frame 7 is engaged with a stud pin provided on the inner surface of the skirt portion 1 of the panel 2 to thereby provide a panel. 2 is supported inside. On the other hand, three electron beams 10B, 10G,
An electron gun 11 for emitting 10R is provided. A magnetic shield 13 for shielding an external magnetic field such as terrestrial magnetism is arranged inside the large-diameter portion 12 of the funnel 3. The three electron beams 10B emitted from the electron gun 11
, 10G, 10R are deflected by a deflection yoke 15 mounted on the outside of the funnel 3, and the phosphor screen 4 is horizontally and vertically scanned through a shadow mask 5, so that a color image is displayed. .

The magnetic shield 13 is formed in a trapezoidal cylindrical shape, and a projection 17 provided at an end portion on the side of the large diameter portion is spotted on the inner projection of the mask frame 7 as shown by a point 18. It is attached by welding.

[0004]

As described above, in order to shield an external magnetic field such as terrestrial magnetism, the magnetic shield disposed inside the large-diameter portion of the funnel is formed in a trapezoidal cylindrical shape. It is attached to the shadow mask by spot welding the overhang provided at the side end to the inside overhang of the mask frame.

However, the magnetic shield has a reduced thickness for the purpose of satisfying the required magnetic characteristics and reducing the weight. On the other hand, the mask frame needs to be thicker in view of the strength of supporting the mask body, and is considerably thicker than the magnetic shield. Therefore, in order to weld these magnetic shields having different plate thicknesses to the mask frame, a welding current sufficient to melt the thick mask frame is necessary.
The welding current for the magnetic shield having a small thickness becomes excessive, and a large amount of splash is generated.

[0006] The splash adheres to the shadow mask and closes the electron beam passage hole of the mask main body, causing not only a screen defect but also an electrode of an electron gun to deteriorate the withstand voltage characteristic. Cause.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is intended to reduce a splash at the time of welding a mask frame and a magnetic shield, thereby making it difficult to cause screen defects and deterioration of withstand voltage characteristics. It is intended to constitute.

[0008]

A shadow mask comprising a mask body and a mask frame attached to a peripheral portion of the mask body is disposed inside the panel, the envelope comprising a panel and a funnel. In the color cathode-ray tube in which the magnetic shield located inside the funnel is welded to the mask frame of the shadow mask, the thickness of the portion where the magnetic shield of the mask frame is welded is formed thinner than the other portions.

Further, the portion of the mask frame to which the magnetic shield is welded is formed to have a thickness substantially equal to the thickness of the magnetic shield.

[0010]

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

FIG. 3 shows a color cathode ray tube which is one embodiment of the present invention. This color cathode ray tube has a substantially rectangular panel 22 provided with a skirt 21 around the main surface 20.
And a funnel 23 having a funnel shape.
On the inner surface of the main surface portion 20 of the panel 22, a phosphor screen 24 made of a three-color phosphor layer that emits blue, green, and red light is provided. Further, a shadow mask 25 is arranged inside the phosphor screen 24 so as to face the phosphor screen 24.
As shown in FIG. 1, the shadow mask 25 includes a mask body 26 having a large number of electron beam passage holes formed on a surface facing the phosphor screen 24,
6 includes a mask frame 29 having an L-shaped cross section provided with an inner protrusion 28 at one end of a side wall 27 attached to the periphery of the elastic support 30 attached to the side wall 27 of the mask frame 29. Skirt 21 of panel 22
It is supported inside the panel 22 by engaging with a stud pin 31 provided on the inner surface. On the other hand, in the neck 33 of the funnel 23, the three electron beams 34B and 34
An electron gun 35 for emitting G, 34R is provided. A magnetic shield 36 for shielding an external magnetic field such as terrestrial magnetism is arranged inside the large-diameter portion 35 of the funnel 23.

Reference numeral 37 denotes a deflection yoke for deflecting the three electron beams 34B, 34G and 34R emitted from the electron gun 35.

The magnetic shield 36 is formed in a trapezoidal cylindrical shape, and is provided with an overhang portion 39 at the large-diameter portion end, and the overhang portion 39 is formed by spot welding the mask frame 29 at a plurality of welding points. It is welded to the inner overhang 28.

Particularly, in this embodiment, as shown in FIG.
A plurality of, in the illustrated example, eight concave portions 40 are formed on the inner surface side of the, and the magnetic shield 36 is welded by these concave portions 40. Mask frame 2 in the recess 38
The thickness tF of No. 9 is smaller than the thickness of the other portions, and is substantially the same as the thickness tS of the overhang portion 39 of the magnetic shield 36.

As described above, the recess 40 is formed in the overhang portion 28 of the mask frame 29, and the thickness tF of the recess 40 is substantially the same as the thickness tS of the overhang portion 39 of the magnetic shield 36. When the magnetic shield 36 is welded in the recess 40, the welding current can be reduced and the splash at the time of welding can be reduced as compared with the conventional welding of the magnetic shield and the mask frame. Can be. As a result, clogging of the electron beam passage holes of the shadow mask and deterioration of the withstand voltage characteristics can be reduced. In addition, since the portion of the mask frame 29 where the plate thickness is reduced is limited to the limited concave area required for welding, the strength of the mask frame 29 is not reduced.

[0016]

As described above, when the thickness of the portion to be welded of the magnetic shield of the mask frame attached to the mask main body is made thinner than the thickness of the other portions, the mask frame of the magnetic shield conventionally performed is used. The welding current can be reduced and the splash during welding can be reduced as compared with welding to the surface, thereby reducing the clogging of the electron beam passage hole of the shadow mask and the deterioration of the withstand voltage characteristics. it can. Moreover, since the portion where the plate thickness of the mask frame is reduced is limited to a limited area required for welding, the effect of not reducing the strength of the mask frame can be obtained.

[Brief description of the drawings]

FIG. 1A is a plan view showing a main part of a color CRT according to an embodiment of the present invention, and FIG. 1B is a sectional view thereof.

FIG. 2 is a diagram showing a structure of a welded portion between a mask frame and a magnetic shield.

FIG. 3 is a diagram showing a configuration of a color CRT according to an embodiment of the present invention.

FIG. 4 is a diagram for explaining a configuration of a conventional color cathode ray tube.

FIG. 5 is a plan view showing a main part of the conventional color cathode ray tube.

[Explanation of symbols]

 22 panel 23 funnel 25 shadow mask 26 mask body 29 mask frame 36 magnetic shield 40 recess

Claims (2)

[Claims] 1. A shadow mask comprising a mask body and a mask frame attached to a peripheral portion of the mask body is disposed inside the panel, the envelope including a panel and a funnel. In a color cathode-ray tube in which a magnetic shield located inside the funnel is welded to a mask frame, the mask frame is formed such that a thickness of a portion where the magnetic shield is welded is smaller than a thickness of other portions. A color cathode ray tube characterized by the following. 2. The color cathode ray tube according to claim 1, wherein a portion of the magnetic shield of the mask frame to be welded is formed to have substantially the same thickness as the thickness of the magnetic shield.