JPH01169847A - Shadow mask for color cathode-ray tube - Google Patents

Abstract

PURPOSE:To prevent the mislanding of an electron beam caused by the distortion of a shadow bask by providing many nearly circular small holes at positions outside the perforated region of a flat shadow mask material plate to form four corners of a skirt section after press molding. CONSTITUTION:A shadow mask 1 is constituted of a perforated region 4 having many circular or slit-shaped openings, optional curved surface sections 2 containing the perforated region 4, and a skirt section 3 folded nearly perpendicularly to the curved surface sections 2, and many circular small holes 6 are provided at positions on four corners of the skirt section 3. The compression stress generated at the four corners of the skirt section 3 is made very small, and the spring back quantity is also made small. The mislanding of an electron beam, color irregularity and color drift caused by the distortion of the shadow mask can be thereby prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a shadow mask for a color cathode ray tube that is easily molded into a desired shape and provides good image display quality.

[Conventional technology]

In general, a shadow mask for a color cathode ray tube is a flat shadow mask material having an approximately rectangular outline with a perforated region having a large number of circular or slit-shaped apertures and a surrounding non-porous region without any apertures. A plate is processed by a press molding method to form a curved surface part 2 whose planar shape is nearly rectangular when viewed from above, as shown in FIG. skirt part 3
A shadow mask is formed. The shape of the curved surface portion 2 is an arbitrary curved surface, and is not limited to a spherical surface or the like, and the perforated region 4 is entirely included in this curved surface portion 2, and the outer peripheral portion of the curved surface portion 2 is This is the part without holes.

When a flat shadow mask material plate having a perforated area inside and a non-porous area on the outer periphery is press-molded into a shadow mask 1 having a shape as shown in FIG. Stress is generated, and the compressive stress becomes larger toward the outer periphery of the skirt portion 3, and particularly becomes significantly larger at locations corresponding to the four corners of the rectangular planar shape of the curved surface portion 2.

If the compressive stress becomes too large, press forming may not be sufficient.
As can be seen from the enlarged cross-sectional view after press forming shown in FIG. 3, the skirt portion 3, which should be bent at almost right angles to the curved surface portion 2, was not completely bent, and the spring bank caused the skirt portion 3 to expand outward. , it also bends into a waveform. If the shadow mask 1 with such a spring bank is forcibly fixed by welding or the like to the frame 5 (see Fig. 3) that should support and reinforce the shadow mask 1, the skirt portion 3 of the shadow mask will It is natural that distortion occurs, but it also causes distortion in the perforated region 4 of the curved surface portion 2.

[Problem that the invention seeks to solve]

In a color cathode ray tube manufactured by the above-mentioned conventional technology, which is equipped with a shadow mask that causes springback due to the large compressive stress in the skirt portion, and distortion occurs even in the perforated area 4, due to the distortion in the perforated area 4. During the manufacturing process of color cathode ray tubes, heating at 400 to 500°C several times causes the aperture position to shift from its intended position, causing the electron beam that passes through this aperture to reach the inner surface of the valve panel, where it was originally intended to reach. The dot-like or stripe-like phosphor may deviate from its position, causing so-called mislanding. To prevent such mislanding, allowances are made in the design of color cathode ray tubes, but if the amount of mislanding exceeds this design allowance, color unevenness or color shift may occur. A problem arises in that display quality deteriorates.

The present invention solves the problems of shadow masks manufactured by the above-mentioned conventional technology, and prevents excessive compressive stress from occurring in the skirt portion during press molding, and therefore prevents deterioration of display quality due to mislanding of electron beams. The purpose of the present invention is to provide a shadow mask for a color cathode ray tube.

[Means for solving problems]

In order to solve the above problems, in the present invention, a large number of holes are placed at the four corners of the skirt portion after press molding, outside the perforated area of the flat shadow mask material plate used when press molding the shadow mask. I decided to make a small, almost circular hole.

[Effect]

The shadow mask according to the present invention, like conventional shadow masks, is formed from a flat shadow mask material plate by press molding, but after molding, a large number of approximately circular small holes are formed in advance at the four corners of the skirt portion. , it is possible to absorb the compressive stress generated at the four corners of the skirt portion during press molding, and it is possible to reduce the amount of springback generated in the skirt portion. Therefore, when the shadow mask and the frame are fixed by welding, the strain generated in the perforated region of the shadow mask can be made much smaller than in the past. Therefore, the fluctuation in the position of the circular or slit-shaped apertures in the perforated area after being heated in the cathode ray tube manufacturing process is extremely small compared to the case of conventional shadow masks, and the electron beam misalignment Landing can be eliminated, and deterioration of display quality due to color unevenness, color shift, etc. can be prevented.

Note that the large number of small holes provided at locations corresponding to the four corners of the skirt portion are for absorbing compressive stress, so the shape of the holes does not need to be exactly circular. However, in order to make it easier to produce a flat shadow mask material plate by perforating it using the photo-etching method, and to make it easier to handle during press molding, many small holes with a shape that does not have an acute angle (almost circular after all) are provided ( It is safe to absorb the stress by distributing it as evenly as possible, and also to avoid any cuts during pressing.

〔Example〕

FIG. 1 is a perspective view of an embodiment of the present invention.

A shadow mask 1 for a color cathode ray tube includes a perforated region 4 having a large number of circular or slit-shaped apertures, an arbitrary curved surface portion 2 that includes the perforated region 4, and a skirt portion bent at a substantially right angle to the curved surface portion 2. 3, and a large number of small circular holes 6 are provided at the four corners of the skirt portion 3.

The shadow mask 1 according to the present invention is formed by press working from a shadow mask material plate in which a large number of small holes 6 are previously provided at the four corners of the skirt portion 3. The compressive stress generated is much smaller than in the past, and as a result, the amount of springback is also reduced, making it easier to form a predetermined shape.

Therefore, the fit with the frame that reinforces and supports the shadow mask is improved, and when the shadow mask and frame are fixed by welding, the distortion that occurs in the skirt portion 3, curved surface portion 2, perforated area 4, etc. is minimized. You can. Therefore, even after the thermal process in the cathode ray tube manufacturing process, fluctuations in the position of the circular or slit-shaped openings in the perforated region 4 are much smaller than in the conventional case, making it possible to eliminate mislanding of the electron beam. As a result, color unevenness and color shift can be eliminated.

In recent years, large-sized television receivers have become popular, and in the large-sized color cathode ray tubes used in such receivers, in order to suppress the so-called doming phenomenon caused by thermal expansion of the shadow mask, it is necessary to use materials for the shadow mask. Amber (Fe-Ni alloy, 1nvar), which has a small coefficient of thermal expansion, is sometimes used, but this material is harder than mild steel, which has traditionally been used as a shadow mask material, and it also suffers from springback during press forming. Although the size tends to increase, according to the present invention, no deterioration in display quality was observed even with a shadow mask made of amber.

〔Effect of the invention〕

As explained above, according to the present invention, the distortion after molding of the shadow mask manufactured by the press molding method can be made extremely small, so that mislanding of electron beams, color unevenness, and color shift caused by this distortion can be eliminated. I can do it.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an embodiment of the present invention, FIG. 2 is a perspective view of a conventional shadow mask, and FIG. 3 is an enlarged sectional view of the vicinity of the joint between the shadow mask and the frame after press molding. 1-Shadow mask, 2--Curved surface portion, 3--Skirt portion, 4--Perforated area, 5---Frame, 6
- Many small circular holes in the four corners of the skirt. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. A curved surface portion whose planar shape is close to a rectangle when viewed from above, which is composed of a perforated region with a large number of circular or slit-shaped holes and a surrounding non-porous region with no holes, and this curved surface portion In a color cathode ray tube shadow mask consisting of a skirt part surrounding the periphery of the curved part and bent at a substantially right angle to the curved surface part, as a flat shadow mask material plate used for press molding, in addition to openings in the perforated area, A color cathode ray characterized in that it is formed by a press molding method using a large number of approximately circular small holes provided in advance at the four corners of the rectangle of the skirt portion after molding, outside the perforated area. Shadow mask for tubes.