JPS6349336B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a shadow mask that provides a bright color picture tube with good white uniformity. Color picture tubes are bright and
It is necessary to obtain good images of white uniforms. For this purpose, as shown in FIG.
It is required that a forms a correct rectangle of a predetermined width. Furthermore, as shown in FIG. 1, the bridge image 3a
Most preferably, both have parallel edges. However, in an actual shadow mask, as shown in FIG. 2, the small diameter portion 5a of the long through hole 5 formed in the metal plate 4 is a long hole with rounded ends, and the opening 5b is also square. It has a slightly rounded rectangular shape. This is considered unavoidable in the prior art.

When an electron beam is obliquely incident on such a through hole 5, the electron beam B1 that has entered the center of the through hole 5 passes through as is, as shown in FIG. However, the electron beam B incident on the corner of the end of the through hole 5
2 passes near the inner surface of the small diameter portion 5a, but is blocked by the inner surface of the opening 5b. Moreover, a part of it is scattered by this inner surface and enters an undesired part of the phosphor surface. Further, the electron beam B3 incident on the outside of the small diameter portion 5a of the through hole 5 is blocked here. Therefore, as shown in FIG. 4, in the image of the electron beam obliquely incident on such a through hole 5, one corner 6a on the fluorescent surface 1 is particularly greatly recessed, and the other corners 6b, 6b is formed as a slightly concave rectangular image 6. In this case, the bridge image 7 becomes extremely wide at one end 7a.

If such an electron beam image 6 is formed, the area of the bridge image 7 will become very large, so not only will the image inevitably become dark, but also the white uniformity will be poor due to the shape of the bridge image 7. Moreover, to make matters worse, the angle of incidence of the electron beam on the through hole 5 is significantly different between the center and the periphery of the shadow mask, and as a result, local brightness and local white uniformity differ in each part of the image plane. It's something that comes with it.

The present invention has been made to eliminate such drawbacks of the prior art, and the opening has a pincushion shape with four corners projecting outward. in this case,
If only the small hole side is made to protrude, the problem of beam chipping, where the electron beam is blocked, will not be improved, and as the incident angle of the beam increases toward the periphery, the electron beam striking the corner of the large hole will not be improved. The amount increases, and these become scattered electrons that hit unnecessary portions of the phosphor, resulting in a decrease in color purity and contrast. On the other hand, even if only the large hole side is protruded, it is unavoidable that the hole will be rounded using general photoetching techniques. The brightness will decrease accordingly. Therefore, in the present invention, the minimum diameter part of the through hole of the shadow mask has a rectangular shape with corners close to right angles,
By forming both the large and small openings of the above-mentioned through-hole into a pincushion shape with their rectangular corners protruding outward, an electron beam image is formed in a rectangular shape over the entire image plane. Thus, it is possible to obtain a picture tube with good brightness distribution and white uniformity, and to provide a shadow mask that is easy to manufacture.

Hereinafter, details of the present invention will be explained with reference to the drawings.

5 to 7 show embodiments of the shadow mask of the present invention. This has a large number of through holes 8, 8 connected to a metal plate 4 via a bridge 9. The small diameter part 8a of the through hole 8 has a nearly rectangular shape with corners close to right angles, and the large opening The side 8c (hereinafter simply referred to as the large hole portion) has a rectangular shape with large corners projecting outward. On the other hand, the small hole side 8b of the opening of the shadow mask (hereinafter simply referred to as the small hole)
As shown in FIG. 6, the rectangular corner has a pincushion shape with outwardly projecting corners.

If an electron beam is obliquely incident on such a hole 8, the electron beam B1 incident on the center of the hole 8 will pass through the hole 8 as shown in FIG.
Since the inner surface of the large hole 8c is largely recessed, the electron beam B2 that is incident close to the corner of the small diameter portion 8a passes therethrough without being blocked. Therefore, as shown in FIG. 8, the image of the electron beam that has passed through such a through hole 8 becomes a substantially rectangular image 10 on the fluorescent surface 1, and the corner 10a thereof also has a shape close to a right angle. , the edges of the bridge shadow 11 are almost parallel.

According to the experiment, as shown in Figure 5,
In the bridge 9 on the large hole 8c side, the width at the center is D1, the width at the end is D2, and D2/D1 is
The most favorable results were obtained when the ratio was between 0.48 and 0.77. Furthermore, in the bridge 9 between the small holes 8b, as shown in FIG. 6, when the width at the center is D3 and the width at the end is D4, D4/D3 is 0.77 or more.
Good results were obtained when it was less than 1.00.

Next, a method for manufacturing the above shadow mask will be explained. First, as shown in FIG. 9 and a partially enlarged FIG. A large dot negative film 15 and a transparent plate 12 as shown in FIG.
A small dot negative film 18 is prepared in which a large number of elongated pincushion-shaped non-transparent small dots 16, 16 corresponding to the large dots 13, 13 are connected through gaps 17, 17. In the large dot negative film 15, as shown in FIG. 10, the width at the center of the gap 14 is d1, and the width at the end is d
2, it is desirable that d2/d1 be in the range of 0.48 to 0.77. Further, in the small dot negative film 18, as shown in FIG.
When the width at the center is d3 and the width at the end is d4, it is desirable that d4/d3 be in the range of 0.77 or more and less than 1.00.

Then, as shown in FIG. 12, the metal plate 19 coated with a photosensitive resin and dried is sandwiched between the large dot negative film 15 and the small dot negative film 18, and an exposure device (not shown) is applied from both sides of the metal plate. Then, the photosensitive resin film on the metal plate 19 is exposed to light to print a negative film pattern, and the resin other than the portions corresponding to the predetermined patterns of the large dots 13 and small dots 16 is rendered water-insoluble. Then, by developing the exposed metal plate 19 and then etching it in a conventional manner, the corners are largely etched and the aforementioned shadow mask can be obtained.

In this way, in the present invention, the corner of the small diameter part of the through hole of the shadow mask has a rectangular shape close to a right angle, and the corners of the rectangle protrude outward for both the large and small openings. The electron beam is not blocked by the inner wall surface. Therefore, it is possible to obtain a rectangular electron beam image corresponding to the shape of the small diameter portion, and the corners are close to right angles, and the use of this mask has the advantage that a color picture tube with uniform brightness distribution and good white uniformity can be obtained.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing an example of a preferred shape of an electron beam image on the panel surface of a color picture tube;
The figure is an enlarged front view showing the main parts of an example of a conventional shadow mask, FIG.
5 and 6 are enlarged front views showing main parts of the embodiment of the shadow mask of the present invention, and FIG. The large hole side, FIG. 6 is the small hole side, FIG. 7 is a sectional view of the shadow mask shown in FIGS. 5 and 6, and FIG. 8 is an explanatory diagram of an electron beam image obtained by the shadow mask of this embodiment. FIG. 9 is a partial front view of a large dot negative film for obtaining a shadow mask according to an embodiment of the present invention, FIG. 10 is an enlarged front view of the main part, and FIG. 11 is a small dot used in combination with this large dot negative film. A partial rear view of one embodiment of the negative film, FIG.
FIG. 12 is an explanatory view showing one step of manufacturing the shadow mask shown in FIG. 5 using both the negative films shown in FIGS. 4... Metal plate, 5, 8... Through hole, 5a, 8a... Small diameter part of the through hole, 9... Bridge, 8b... Small hole part, 8c...
Large hole, 12...transparent plate, 13, 16...dot, 1
9...Metal plate coated with photosensitive resin.

Claims (1)

[Claims] 1 A large number of elongated through holes consisting of openings of large holes and small holes and small diameter portions are connected through bridges in a metal plate, the small diameter portion of the through holes is rectangular, and the large hole A shadow mask characterized in that the four corners of both the openings of the small hole and the small hole are shaped like a pincushion and protrude outward.