JPS6254230B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a shadow mask for a color picture tube suitable for use in, for example, a color television receiver.

Generally, the shadow mask type color picture tube is the
It is constructed as shown in the figure, and a funnel-shaped funnel 3 is connected to a net 2 containing an electron gun 1, and a panel 4 is joined to the funnel 3. A fluorescent surface 5 is formed on the inner surface of the panel 4, and a shadow mask 6 is disposed at a predetermined distance from the fluorescent surface 5, and the shadow mask 6 is attached to and supported by a frame 7. This frame 7 is attached to the inner wall of the panel 4. During operation, the electron beam emitted from the electron gun 1 is deflected by the deflection yoke 8 and scans the fluorescent surface 5 to reproduce an image.

By the way, the above-mentioned shadow mask 6 has conventionally been made of a single thin metal plate, as shown in FIG. 2, in which a large number of rectangular holes 9 are bored at approximately constant intervals so that their major axes face the vertical scanning direction of the electron beam. has been done.
Note that FIG. 2 is a front view of the shadow mask 6 seen from the fluorescent surface 5 side, and the rectangular hole 9 has a large rectangular hole 9a on the outside facing the fluorescent surface 5, and an elongated rectangular hole 9 on the inside.
b is the opening on the electron gun 1 side. FIG. 3 is a sectional view taken along the line Y-Y' of the shielding part 10 that defines the vertical pitch of the rectangular hole 9 in FIG. 2, and is called a bridge section. As shown in FIGS. 4a and 4b, the cross-sectional shape is the same at both the center and the periphery of the shadow mask. In the figure, 11 is an electron beam. In addition, in Figure 3,
The upper side of the figure is the fluorescent surface 5 side, and the lower side is the electron gun 1 side.

However, the color picture tube using the conventional shadow mask as described above has the following drawbacks. That is, the electron beam emitted from the electron gun 1 is blocked by the shielding part 10 when passing through the rectangular hole 9, but at this time, the electron beam 11 is blocked by a bridge at the center of the mask, as shown in FIGS. Part 1
2 and 13, and bridge portions 14 and 15 at the mask periphery. The bridge portions 12 and 13 at the center of the mask are the matching points formed by mask etching from the small bridge 16 and the large bridge 17, and their dimensions are unstable, and currently they vary by about twice as much as the variation in slit width. . This dimensional variation makes the desired shape of the electron beam non-uniform when the electron beam passes through the rectangular hole, resulting in deterioration of the white uniformity of the image when it reaches the fluorescent surface 5.

This invention was made in view of the above circumstances, and is a color picture tube that improves the white uniformity of images in the center and periphery of a color picture tube by making the cross-sectional shape of the bridge different between the center and periphery of the shadow mask. The purpose of the present invention is to provide a shadow mask for a picture tube.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. The shadow mask of the present invention, like the conventional example (FIG. 2), has a large number of rectangular holes 9 formed at approximately regular intervals in a single metal plate, with the major axis facing the vertical scanning direction of the electron beam. . In order to improve the above drawback, the cross-sectional shape of the shielding part 10 defining the vertical pitch of the rectangular hole 9 is set as shown in FIGS. 5a and 5b. That is, a is the cross-sectional shape of the shielding part 10 at the center of the mask, and b is the cross-sectional shape of the shielding part 10 at the periphery of the mask, with the upper side of the figure being the fluorescent surface side and the lower side being the electron gun side. As is clear from the figure, the cross-sectional shapes are clearly different between the center of the mask and the peripheral area of the mask, and the small width 18 and large width 19 of the mask bridge are set such that small width 18 > large width 19 at the center of the mask. The small side width 20≒large side width 21 is set in the peripheral portion of the mask.

Next, a method for manufacturing the shadow mask of the present invention having the above structure will be explained. As shown in Figure 6a and b,
The bridge width 24 of the large negative original 23 is smaller than that of the small negative original 22 at the center of the mask, and the bridge width 25 is approximately the same at the periphery of the mask. The small negative master plates 22, 26 and the large negative master plates 23, 27 are used as a pair of negative master plates, and a photosensitive liquid is applied to a steel plate with a thickness of 0.15 mm, for example, using a photographic bait engraving method.
Printing is performed through the negative master plates of the above-mentioned sizes,
The film is then developed, dried, burned, and finally etched with an etching solution.

The shadow mask of the present invention is constructed as described above and shown in the drawings, and the cross-sectional shape of the shielding part 10 that defines the vertical pitch of the many rectangular holes is different between the center part and the peripheral part of the mask. It has such excellent effects. That is, in the center of the mask, the small width 18 is larger than the large width 19, so the matching point during mask etching approaches the small width 18, and the bridge width variations are stabilized.
As a result, the shape of the electron beam when it passes through the rectangular hole is stabilized, so that the white uniformity of the image at the center of the picture tube is improved. Moreover, since the dimensions of the small width 20 and the large width 21 become approximately the same as they approach the peripheral portion of the mask, the cross-sectional area of the bridge also increases and the tensile strength increases. As a result, the amount of edge drop due to spring back during mask press molding is suppressed to the utmost, and white uniformity in the peripheral area of the picture tube is also significantly improved.

Incidentally, if it is necessary to further increase the bridge strength at the periphery of the mask, the bridge width at the center of the mask can be increased by 5 to 20 m.mu. to further increase the bridge strength.

As explained above, according to the present invention, it is possible to provide a shadow mask for a color picture tube that has great practical value.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing a generally used color picture tube, Fig. 2 is a front view showing the main parts of a conventional shadow mask, Fig. 3 is a sectional view of the shielding part in the shadow mask shown in Fig. 2, and Fig. 4 is a sectional view showing the main parts of a conventional shadow mask. Figures a and b are cross-sectional views showing the relationship between the cross-sectional shape of the shielding part and the electron beam in the central and peripheral parts of a conventional shadow mask, respectively, and Figures a and b are the central part of a shadow mask according to an embodiment of the present invention. FIGS. 6A and 6B are front views showing the same manufacturing method. 9... Rectangular hole, 10... Shielding part.

Claims (1)

[Claims] 1. In a shadow mask in which a large number of rectangular holes are formed at approximately constant intervals in a single metal plate so that the major axis faces the vertical scanning direction of the electron beam, the shielding part that defines the vertical pitch of the large number of rectangular holes is The cross-sectional shape is different between the center and periphery of the shadow mask, and the maximum width of this cross-section is located on the small hole side in the center of the shadow mask, and approximately at the center of the thickness of the shadow mask in the periphery. Features a shadow mask for color picture tubes.