JPH06162950A - Shadow mask type color cathode-ray tube - Google Patents

Abstract

PURPOSE:To enable a doming phenomenon to be effectively reduced by applying a smaller radius of curvature by the predetermined amount to the periphery of a shadow mask than to the center section thereof. CONSTITUTION:The bulb 1 of a 20'' type color cathode-ray tube is constituted of a neck section 1a, a funnel 1b of infundibulaform and a panel section 1c for sealing the open end of the funnel 1b with frit glass. In this case, the radius of curvature R1 at the center section of a 20'' type shadow mask 6 is kept at 1,500mm and the radius of curvature R2 at a peripheral section approximately 170mm off the center is made approximately 63% of R1, or 950mm. Also, the average radius of curvature of the whole mask 6 is kept at approximately 150mm. According to this construction, a doming phenomenon can be effectively reduced with relatively simple constitution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shadow mask type color cathode ray tube, and more particularly to the curvature of a shadow mask.

[0002]

2. Description of the Related Art Generally, in a shadow mask type color cathode ray tube (hereinafter referred to as "CPT"), a landing error caused by thermal expansion of a shadow mask is inevitable. Here, the local expansion of the shadow mask due to the thermal expansion thereof is usually referred to as doming. This doming phenomenon tends to become larger as the shadow mask is closer to a flat surface, and become smaller as the shadow mask is curved. Then, various measures are taken to reduce the doming phenomenon. For example, a method of reducing the radius of curvature of the shadow mask and reducing the doming phenomenon by adopting a variable pitch mask has been proposed. However, since the shadow mask has a variable pitch, it is necessary to increase the peripheral pitch, which has a limit. Further, in recent years, there is a tendency to make the shadow mask pitch itself fine in order to reproduce fine characters, and it is difficult to adopt a variable pitch. On the other hand, there is a tendency to flatten the CPT phosphor screen, which makes the doming phenomenon more difficult.

[0003]

SUMMARY OF THE INVENTION Therefore, the present invention has been made in view of the above-mentioned problems, and an object of the present invention is to improve the doming characteristic while the fluorescent screen and the shadow mask tend to be flat. (EN) Provided is a shadow mask type color CRT which has improved the above.

[0004]

In order to achieve such an object, the present invention pays attention to the fact that the doming phenomenon of the shadow mask is more problematic in the peripheral portion than in the central portion of the screen, and the periphery of the shadow mask is noted. The radius of curvature of the part is smaller than that of the central part. Further, not only the shadow mask but also the curvature of the inner surface of the panel has a similar tendency.

[0005]

[Function] Even if the shadow mask is made flatter,
Since the radius of curvature of the peripheral portion of the shadow mask is relatively smaller than the radius of curvature of the central portion, the doming phenomenon is reduced.

[0006]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a sectional view of the essential parts showing an embodiment of a shadow mask type color cathode ray tube according to the present invention.
In the figure, a bulb 1 of a 20-inch color cathode-ray tube is composed of a neck portion 1a, a funnel-shaped funnel portion 1b, and a panel portion 1c which seals the open end of the funnel portion 1b via a frit glass 2. The neck portion 1a
The electron gun assembly 4 mounted on the stem 3 is enclosed inside,
Further, a fluorescent surface 5 is formed on the inner surface of the panel portion 1c, and a shadow mask 6 is arranged on the inner surface of the panel portion 1c so as to face the fluorescent surface 5, and the shadow mask 6 is used as a mask support 7 Are fixedly arranged on the inner wall. In this case, in the 20-shaped shadow mask 6, the radius of curvature R ₁ of the central portion is 1500 mm, and the radius of curvature R ₂ of the peripheral portion that is about 170 mm away from the center is approximately 63% of the central radius of curvature.
And the average radius of curvature of the entire mask is about 1
It is 150 mm. Further, in this case, the inner surface side of the panel portion 1c is also configured to have a radius of curvature substantially equal to the radius of curvature of the shadow mask 6 in the central portion and the peripheral portion.

[0008] Typically, the landing error amount generated by the doming phenomenon, empirically almost R ¹ · ³ (wherein, R
Is known to be proportional to the radius of curvature of the shadow mask in that portion. Therefore, in the above-described embodiment, by reducing the radius of curvature of the shadow mask 6 between the central portion and the peripheral portion, the doming amount can be reduced by about 22% as compared with the conventional structure having a single radius of curvature. did it.

FIG. 2 is a cross-sectional view of the essential parts showing another embodiment of the shadow mask type color cathode-ray tube according to the present invention, in which the same parts as in FIG. In the figure,
The difference from FIG. 1 is that the shadow mask 6'is a variable pitch mask, and the radius of curvature of the peripheral portion of the shadow mask 6'is made smaller than the radius of curvature of the central portion, thereby reducing the doming amount described above. The effect can be further promoted.

[0010]

As described above, according to the present invention, the doming phenomenon can be effectively reduced with a relatively simple structure and without making a large change in appearance such as a pitch change. In particular, the extremely excellent effect that the recent flattening of the fluorescent screen can be realized very easily is obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional configuration diagram of main parts showing an embodiment of a shadow mask type color CRT according to the present invention.

FIG. 2 is a cross-sectional configuration diagram of main parts showing another embodiment of the present invention.

[Explanation of Codes] 1 ... Valve, 1a ... Neck,
1b ... Funnel part, 1c ... Panel part, 2
... Frit glass, 3 ... Stem, 4 ... Electron gun structure, 5 ... Fluorescent surface, 6 ... Shadow mask, 6 '... Variable pitch shadow mask, 7 ... Mask support.

Claims (1)

[Claims] 1. A shadow mask type color cathode-ray tube in which a shadow mask is arranged to face a panel inner surface on which a fluorescent screen is formed, and a portion in which a radius of curvature of a peripheral portion of the shadow mask is approximately 63% of a radius of curvature of a central portion is formed. A shadow mask type color cathode ray tube characterized by being provided.