JPS6089036A - Color picture tube - Google Patents

Abstract

PURPOSE:To make the stretching of the pores during press-forming uniform so as to improve the quality of the periphery of the fluorescent screen by making the pore diameter of the peripheral 6 rows of the shadow mask of the color picture tube 10-50% smaller than the pore diameter of the remaining part. CONSTITUTION:A shadow mask 1 in a color picture tube having a negative guard band, dot-type fluorescent surface is formed so that the shadow mask will have an effective pore part 2 and uneffective pore part 3. At the same time, the pore diameter of the pripheral 6 rows of the effective pore part 2 is made 10- 50% smaller than that of the remaining part. As the change rate of the equivalent plate thickness is reduced by half in the peripheral part which is the border between the effective pore part and the uneffective pore part 3, the stretching of the shadow mask during press-forming is made uniform and generation of defects during forming, such as deflection, can be avoided. Also, as the effect of the pore diameter of the fluorescent body on the fluorescent surface can be reduced, the quality of the fluorescent film and its purity can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a shadow mask for a color picture tube. In a conventional color picture tube with a negative guard band/dot type phosphor surface, the diameter of the phosphor hole is made smaller at the periphery of the screen in order to increase the purity margin around the screen. In the shadow mask used in this color picture tube, the hole diameter is the same or gradually decreases from the center to the periphery, as shown in FIGS. 1 and 2. At this time, the effective hole portion 2, which is the hole provided in the shadow mask 1, has an equivalent plate thickness that is 20 to 50 inches thinner than the other non-effective hole portion 3.

For this reason, the shadow mask has effective hole 2 during press molding.
The elongation is large and the elongation of the non-effective hole 3 is small, so the outer edge of the effective hole 2 is strongly elongated and the hole diameter at the outer edge of the effective hole becomes 20 to 50% larger. In this case, the diameter of the phosphor hole at the outer edge of the phosphor film becomes large, creating white unevenness and resulting in a defect. Also, as mentioned above,
Since the shadow mask 1 is not stretched uniformly during press molding, the curved surface of the pressed shadow mask 1 may be warped, resulting in defects in which the shadow mask 1 is not formed properly.

As one of the countermeasures, the ineffective hole 3 of the shadow mask 1 is
As shown in FIGS. 3 and 4, a non-through hole 5 is provided to reduce the equivalent plate thickness of the non-effective hole portion 3 by 10 to 30 inches, and the elongation during press molding is increased to form the effective hole portion 2. A method is being adopted to approach the growth of

However, with this countermeasure, the ineffective hole 3 of the shadow mask 1
Since the equivalent plate thickness is thinner, the mechanical strength is reduced. The present invention provides a shuttle mask which improves the quality of the phosphor film at the outer edge of the phosphor surface without reducing the uniform plate thickness of the ineffective holes 3.

The following is a detailed explanation using figures. In a color picture tube with a conventional negative guard band dot type screen, the curves of the phosphor hole diameter distribution on the phosphor surface and the hole diameter distribution of the shadow mask are shown in Figure 5. To the center as shown by C-D in Figure 6 and Figure 7,
The settings are the same or smaller. At this time, the hole diameters of the conventional negative guard band type dot-shaped shadow mask have the same distribution as shown by the broken line curve FG in FIGS. 5, 6, and 7.

FIG. 10 shows the pore size distribution of a shadow mask according to an embodiment of the present invention. FIG. 11 shows an enlarged view of the outermost edge DD' curve. As shown in Figures 8 and 9, by making the hole diameter within 6 rows of the shadow mask at the outer edge 10 to 50 inches smaller than the hole diameter of the shadow mask in the tube and other parts, the rate of change in the equivalent plate thickness is reduced. Since it is halved at the outer edge, which is the boundary between the part 2 and the ineffective hole part 3, the elongation of the shadow mask during press molding is made uniform, and molding defects such as deflection do not occur. In addition, by reducing the hole diameter at the outer edge of the shadow mask, we can prevent the extreme elongation of the hole diameter seen in the past, which is a problem with conventional shadow masks. It disappears. Furthermore, because the hole diameter of the shadow mask is small, the diameter of the phosphor holes on the phosphor surface becomes smaller in the area within 6 rows of the outermost edge.
There is no adverse effect, and a color picture tube with a superior phosphor film can be provided. Furthermore, from the above explanation, it is clear that the present invention is equally effective for positive guard band type dot type color picture tubes, and is similarly effective for striped type color picture tubes.

[Brief explanation of the drawing]

Is Figure 1 an example of a conventional shadow mask? FIG. FIG. 2 is a graph showing an example of the pore diameter between A and B in FIG. 1. Fig. 3 is a plan view showing an example of a conventional countermeasure mask, and Fig. 4 shows a cross-sectional view along E-87. Examples of the hole diameter of a shadow mask and the diameter of a phosphor hole in a color picture tube using this shadow mask are shown. FIG. 8 shows a shadow mask for explaining the present invention, and FIG. 9 shows its Hu1
A cross-sectional view is shown between the two. FIG. 1θ shows an example of the hole diameter of the shadow mask, and FIG. 11 shows an enlarged view of the section DD'. 1...Shadow mask, 2...Effective hole portion of shadow mask, 3...Ineffective hole portion of shadow mask, 4...Non-through hole portion , 5...
・Non-through hole, 6... Countermeasure hole, A... Center part of shadow mask, B... Diagonal outer edge of effective area of shadow mask, C... Shadow mask A part pore diameter, D, D'... Shadow mask 28 part pore diameter, F... Fluorescent film A part hole diameter, G...
・8 part hole diameter of fluorescent film. Agent Patent Attorney Susumu Uchihara 5-

Claims (1)

[Claims] A color picture tube equipped with a shadow mask, characterized in that the hole diameter within six rows of the outer edge of the shadow mask is 10 to 50% smaller than the hole diameter of the other portions of the shadow mask.