JPH076690A - Manufacture of shadow mask and press metal mold used in this manufacture - Google Patents

Abstract

PURPOSE:To provide a color cathode-ray tube with no irregular color and color mixture by adjusting height of clamp bead and spherical bead of a press metal mold in a diagonal axial direction, so as to obtain a good shadow mask with no slit deformation. CONSTITUTION:In a press metal mold for performing press molding, height of clamp bead and spherical bead is set to the lowest in a diagonal axis as compared with in major/minor axial directions of a flat mask 1. By molding with the press mold thus obtained, in the case of overhanging and drawing work, particularly in a diagonal axis in the flat mask 1, rolling tensile force is decreased at overhanging time, and further rolling tension by a spherical bead 5, formed at spherical surface molding time, is reduced. Since also slip resistance at drawing work time is decreased, good molding with no deformation in a slit 2 can be performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a shadow mask used in a color cathode ray tube and a press die suitable for the method.

[0002]

2. Description of the Related Art A shadow mask used as a color selection electrode of a color cathode ray tube usually has a structure as shown in FIGS. That is, the shadow mask 10 is formed by pressing the flat mask 1, and a spherical bead 5 is provided between an effective surface 3 having a large number of electron beam passage slits 2 and a peripheral surface 4 surrounding the effective surface 3. A skirt portion 6 is formed from the peripheral surface 4 and is bent substantially at a right angle. The spherical beads 5 are provided on the entire outer circumference of the effective surface 3 in order to suppress the deformation of the effective surface 3 during press molding and to maintain the strength for retaining the shape.

Next, a method of press-molding such a shadow mask 10 will be described. 9A to 9D are views showing a press die for forming the shadow mask 10 and a forming process. As described above, the shadow mask is formed into a dog-shaped shape by placing a flat mask on a mold and then performing overhanging and drawing. In order to perform this overhanging and drawing, as shown in FIGS. 9A to 9D, a pair of upper and lower press dies (the upper die is referred to as the punch 11 and the lower die is referred to as the pad 12) are used. A spherical bead 18 and a bead groove 17 for forming the spherical bead 5 of the shadow mask are provided on the opposing surfaces of the press die (punch 11, pad 12) so as to mesh with each other. Also, this press die (punch 11, pad 12)
A pair of upper and lower pressing dies (upper dies are referred to as outer 13 and lower dies are referred to as outer dies) that form a ring so as to surround the periphery of the A clamp bead 16 and a clamp bead groove 15 are provided so as to mesh with each other.

First, as shown in FIG.
2, the die 14 and the top surface form the same spherical surface, and the punch 11 and the outer 13 are both raised. Then, the flat mask 1 is placed on the die 14 and the pad 12. Then, as shown in FIG. 2B, when the outer 13 and the punch 11 are lowered, first, the outer 13 is moved to the die 1
4, and the peripheral portion (corresponding to the skirt portion) of the flat mask 1 is sandwiched between the clamp bead 16 and the clamp bead groove 15. At this point, the punch 11 is not in contact with the flat mask 1 yet. Next, the same figure (C)
As shown in, the punch 11 descends and the flat mask 1
Is pressed onto the pad 12 to form the effective surface 3 of the flat mask 1 into a spherical surface. At this time, the spherical beads 5 are also molded. Then, as shown in FIG.
Will descend as a unit. At this time, the periphery of the flat mask 1 is surrounded by the clamp beads 16 of the outer 13 and the die 14.
A height gauge (not shown) is provided in the clamp bead groove 15 and a gap (called a height clearance, usually about 0.5 mm) is formed between the gaps, and the skirt portion 6 is formed while adding a slip resistance between the gaps to form a bowl shape. Molded.

[0005]

However, the press die used in the press forming of the shadow mask as described above, the shape and depth of the clamp bead groove 15 of the outer 13 and the height of the clamp bead 16 of the die 14. The depth of the spherical bead groove 17 of the punch 11 and the height of the spherical bead 18 of the pad 12 were also uniform over the entire circumference. Therefore, the rolling pulling force on the flat mask 1 and the rolling pulling due to bead formation, and the sliding resistance due to the drawing process were the largest on the diagonal axis. On the other hand, in the flat mask 1, since the electron beam passing slits 2 are regularly arranged in the same direction as shown in FIG. 7, the slit 2 has a large tensile strength in the longitudinal direction and a small tensile strength in the width direction. Therefore, if the clamping force with respect to the flat mask 1 is uniform, the material of the raw material in rolling tension and drawing by clamping the clamp bead 16 by press molding, especially in the diagonal axial direction peripheral portion (corner portion) of the flat mask 1. Deflection occurs and slip resistance increases. Further, the slit 2a on the outer periphery of the diagonal axis of the flat mask 1 is pulled by the spherical beads 5 and the like formed at the same time as the spherical molding, and the bridge 2b is deformed such as a constriction and the width of the slit 2a is expanded and deformed. In a color cathode ray tube using such a shadow mask, white uniformity is lowered, and even color mixing may occur.

The present invention has been made in order to eliminate the above-mentioned conventional drawbacks. The present invention is satisfactorily press-molded to the periphery of the flat mask, especially to the outermost row portion, and the electron beam passage on the outer periphery of the diagonal axis. The holes and bridges are deformed,
An object of the present invention is to provide a shadow mask manufacturing method which is not stretched and a press die suitable for the method.

[0007]

A method for manufacturing a shadow mask according to the present invention performs overhanging and drawing while holding a periphery of a flat mask having a large number of electron beam passage holes formed on a rectangular effective surface, In the method for manufacturing a shadow mask, in which a spherical bead is formed between the effective surface and the peripheral surface thereof, the force sandwiching the periphery of the flat mask is the major axis, and the diagonal axis as compared to the minor axis direction. At the same time, the size of the spherical beads is minimized on the diagonal axis as compared with the major axis and the minor axis.

Further, the shadow mask manufacturing press die according to the present invention is used for performing overhanging and drawing while sandwiching the periphery of a flat mask having a large number of electron beam passage holes formed on a rectangular effective surface. In the press die, the height of the clamp bead provided on the facing surface of the outer and the die forming a pair that sandwiches the periphery of the flat mask is set to the minimum on the diagonal axis of the effective surface of the flat mask, and The height of the spherical beads provided on the opposing surfaces of the punch and the pad forming the pair of spherical moldings of the flat mask was minimized on the diagonal axis.

[0009]

According to the present invention, when the shadow mask is stretched and drawn, the flat mask has a small rolling tensile force particularly when it is stretched on the diagonal axis, and the rolling bead is reduced by the spherical beads formed during spherical molding. Since the slip resistance during drawing is also small,
Good molding is performed without deformation even on the effective surface of the shadow mask.

[0010]

EXAMPLES Example 1. An embodiment of the present invention will be described in detail below. FIG. 1 shows an example of a shadow mask 10 manufactured according to the present invention, in which the size of a spherical bead 5 formed between an effective surface 3 and its peripheral surface 4 is larger than that in the major axis and minor axis directions. It is minimum on the diagonal axis, and the slit 2a and the bridge 2b on the outer circumference of the diagonal axis are press-formed without being deformed or stretched.
This is because the rolling tensile force of the clamp bead groove 15 of the outer 13 and the clamp bead 16 of the die 14 that sandwich the peripheral portion of the flat mask 1 in the manufacturing process of the shadow mask shown in FIG. In order to reduce the size on the angular axis, the height of the clamp bead 16 is minimized at the portion where the diagonal axis effective surface 3 of the flat mask 1 is sandwiched, and the spherical bead 5 for increasing the deformation of the slit 2 of the flat mask 1. This is because the height of the spherical bead 18 of the pad 12 is minimized at the portion where the diagonal axis effective surface 3 of the flat mask 1 is crimped in order to reduce the rolling tensile force during formation.

2 to 5 show the essential parts of a press die for performing press molding by such a method.
FIG. 2 is a cross-sectional view of the vicinity of the clamp bead 16 along the diagonal axis of the flat mask 1 of the die 14 of the press die, and FIG. 3 is a cross-sectional view of the clamp bead 16 along the long axis and the short axis. FIG. 4 is a sectional view of the pad 12 of the press die in the vicinity of the spherical bead 18 along the diagonal axis of the flat mask 1. FIG. 5 is a similar cross-sectional view of the long axis and the short axis. That is, the heights of the clamp beads 16 and the spherical beats are the lowest on the diagonal axis rather than the long axis and the short axis, as shown in FIG. Although not shown, the clamp bead groove 15 of the outer 13 also has a shape of the clamp bead 16.
The spherical bead groove 17 of the punch 11 is also formed corresponding to the height and shape of the spherical bead 18.

If the flat mask 1 is formed by such a press die, the flat mask 1 has a small rolling tensile force when the flat mask 1 is stretched, especially in the diagonal axis, and the rolling bead 5 is formed by the spherical bead 5 that is formed when spherical molding is performed. Is reduced and the slip resistance at the time of drawing is reduced, so that the slit 2 can be satisfactorily molded without deformation. As an example, for example, in the conventional case, the width Sw in the short direction of the slit 2a at the corner changes in the range of 20 to 60 μm and the bridge 2b is also deformed, whereas in the case of the present invention, Sw is 20 μm. It can be suppressed within the range, and the deformation of the bridge 2b does not occur. In this embodiment, the case of the slit type mask is explained, but it goes without saying that it is also effective for the dot type mask.

[0013]

As described above, according to the present invention, the shadow mask can be satisfactorily extended and drawn, the effective surface can be formed to the outermost circumference, and the electron beam passage hole can be formed in any part of the effective surface. There is no deformation, and a good condition can be obtained. Therefore, the color cathode ray tube using the shadow mask manufactured according to the present invention has good uniformity.

[Brief description of drawings]

FIG. 1 is a front view of an essential part showing an example of a shadow mask manufactured by the present invention.

FIG. 2 is a cross-sectional view of a clamp bead portion of a press die according to an embodiment of the present invention, taken along a diagonal axis.

FIG. 3 is a long-axis and short-axis sectional view of a clamp bead portion of a press die according to an embodiment of the present invention.

FIG. 4 is a cross-sectional view of a spherical bead portion of a press die according to an embodiment of the present invention on a diagonal axis.

FIG. 5 is a long-axis and short-axis sectional view of a spherical bead portion of a press die according to an embodiment of the present invention.

FIG. 6 is a view showing a change in height of each of a clamp bead and a spherical bead of a press die according to an embodiment of the present invention on each axis.

FIG. 7 is a main part front view showing an example of a shadow mask according to a conventional manufacturing method.

8 is a cross-sectional view of the main parts of FIG.

FIG. 9 is an explanatory diagram showing an example of a normal shadow mask pressing process.

[Explanation of symbols]

 1 ... Flat mask 2 ... Slit 2a ... Corner slit 2b ... Bridge 3 ... Effective surface 4 ... Perimeter surface 5 ... Spherical bead 6 ... Skirt portion 10. ..Shadow mask 11 ... Punch 12 ... Pad 13 ... Outer 14 ... Die 15 ... Clamp bead groove 16 ... Clamp bead 17 ... Spherical bead groove 18 ... Spherical bead

Claims (2)

[Claims] 1. A flat mask having a large number of electron beam passage holes formed on a rectangular effective surface is clamped while being stretched and drawn to form a spherical bead between the effective surface and its peripheral surface. In the method of manufacturing a shadow mask, the force for sandwiching the periphery of the flat mask is the long axis, and the diagonal axis is minimized as compared with the short axis direction, and the size of the spherical beads is the long axis. A method for manufacturing a shadow mask, characterized in that the diagonal axis is minimized compared to the short axis. 2. A press die for performing overhanging and drawing while sandwiching the periphery of a flat mask having a large number of electron beam passage holes formed on a rectangular effective surface,
The height of the clamp bead provided on the facing surface of the outer and die forming a pair that sandwiches the periphery of the flat mask is set to the minimum on the diagonal axis of the effective surface of the flat mask,
A press die for producing a shadow mask, characterized in that the height of a spherical bead provided on an opposing surface of a punch and a pad forming a pair of spherical moldings of the flat mask is minimized on a diagonal axis.