JPS633418B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a shadow mask type color cathode ray tube in which the appearance of the phosphor screen is improved.

Before explaining the details of the present invention, conventional embodiments and their problems that form the background of the present invention will be described below.

FIGS. 1a and 1b are external views of the phosphor screen of a conventional color cathode ray tube. In this figure, on the panel 2 of the color cathode ray tube 1, an effective screen edge line 3, which is a virtual line, is assumed. The area surrounded by this line is the effective light emitting area where the screen is projected, and the phosphor stripe 4 is coated within this area. Note that in FIGS. 1a and 1b, only a portion of the phosphor stripe 4 is shown for the sake of simplification.

The shape of the effective screen edge line 3 is almost rectangular, but due to the outer circumferential shape of the panel 2 and from the design point of view, normally both the long and short sides are not straight lines, but have a slightly convex radius toward the outside. It forms an arc.

Hereinafter, for convenience of explanation, x and y coordinates are determined corresponding to this rectangle as shown in FIGS. 1a and 1b. That is, the center of the panel 2 is taken as the origin, the long side direction is x, and the short side direction is Y.

As shown in FIG. 1a, the phosphor stripes 4 are normally provided substantially parallel to the y-axis. However, when such a phosphor stripe 4 is provided, the shape of the side of the effective screen edge line 3 forms an outwardly bulging R arc as described above, and therefore, as shown in the short side of FIG. As such, the ends of the phosphor stripes 4 often look unsightly in a step-like manner. For this reason, on the short side, the effective screen edge line 3 is intentionally made straight instead of an R arc, and as shown in FIG. It was devised to create a shape that bulged outward to match the shape of the shaft end, and this type of configuration has now become commonplace. Further, the phosphor stripes 4 are formed by projection of light from near the center of deflection of a shadow mask having slot-shaped holes corresponding thereto. Therefore, in order to obtain the phosphor stripes 4 as shown in FIG. 1b, for example, it is common to use a shadow mask having a similar arrangement of slots, and an example of such a shadow mask is shown below. Shown in Figure 2.

In FIG. 2, a shadow mask 10 has numerous slots 11 that are elongated in the y direction. The slots 11 are arranged in a line (hereinafter referred to as a slot line) in the long side direction as shown by a dashed line 12 in the figure, and adjacent slot lines 12 have a substantially constant interval P. Of course, the slot edge line 13 surrounding all the slots 11 also forms an R arc corresponding to the effective screen edge line 3 of the phosphor screen.

In FIG. 2, only a portion of the slot 11 and the slot line 12 are shown for the sake of simplification.

As is well known, when a color cathode ray tube having a shadow mask is operated, most of the electron beams from the electron gun impinge on the shadow mask, increasing its temperature. As a result, the shadow mask undergoes thermal expansion, resulting in non-negligible thermal deformation. Among these thermal deformations, one that is difficult to countermeasure is that a relatively small area (approximately 20mmφ to 100mmφ in a circle) is particularly bright when displaying a stationary or nearly static screen, so this corresponding area of the shadow mask may be affected locally. As the temperature rises, only this part of the shadow mask, which is normally formed into an almost spherical shape that is convex toward the panel, undergoes significant thermal expansion compared to the rest, causing what is called local doming, where it locally bulges toward the panel. There is a phenomenon called

The above-mentioned local doming occurs because, although a locally heated portion undergoes thermal expansion, the surrounding portion does not undergo thermal expansion.
When the shape area of the heated part and the temperature rise are constant, the amount of doming, that is, the amount of bulge perpendicular to the surface of this part of the shadow mask, can be calculated by assuming that the problematic part of the shadow mask is approximately a spherical surface, and the radius of curvature It is known that they are approximately proportional (the circumstances between these are described theoretically, for example, in the Journal of the Television Society, Vol. 31, No. 6, June 1977, p. 50). That is, in order to reduce local doming, it is effective to design a shadow mask with a small radius of curvature, which will be explained with reference to FIG.

FIG. 3 is an x-axis sectional view of the panel 2 and the shadow mask 10. In this figure, a conventional shadow mask is represented by a dotted line 10a. As shown in FIG. 3, the cross section of the conventional shadow mask 10a was a single R arc with a substantially constant radius of curvature, but in the new shadow mask 10,
The central portion has a concave surface extending away from the panel 2, and the portion from the intermediate portion to the peripheral portion is convex toward the panel 2 such that the radius of curvature is smaller than that of the concave surface. The curved surface configuration of the shadow mask 10 can be achieved as follows.

FIG. 4 shows a diagram in which the vertical axis represents the size of the slot line spacing P shown in FIG. 2, and the horizontal axis represents the distance from the center. In FIG. 4, the slot line spacing P of the conventional shadow mask 10a is almost constant as described above, but the slot line spacing P of the new shadow mask 10 is maximum at the center and peripheral areas, as shown by the solid line. and is minimized in the middle. It is known that the distance between the shadow mask 10 and the panel 2 is approximately proportional to the slot line distance P of the shadow mask 10 when the shadow mask 10 is of the same size. A curved surface of the shadow mask 10 as shown by the solid line in the figure is obtained. Shadow mask 1 like this
By setting it to 0, it was possible to make local doming extremely small, but it was found that the following problems occurred.

As shown in FIG. 1, the long and short sides of the effective screen edge line 3 of the phosphor screen form an R arc, and correspondingly, as shown in FIG. 2, the slot edge line 13 of the conventional shadow mask also As mentioned above, the curved surface of the new shadow mask 10 shown in FIG. 3 has an almost R-shaped arc, and as shown in FIG. If the arc is approximately R, as shown in Figure 5, on the long side 3a of the effective screen edge line 3 of the phosphor screen, the center part will have a convex shape that is extremely outward, and the middle part will have a slightly concave shape. It was found that the appearance was extremely unsightly.

In the case of a conventional color cathode ray tube, the panel 2 has a substantially single R curved surface, and the cross section passing through the center of the shadow mask 10a has a substantially single R curve.
If it is a circular arc and the effective screen edge line 3 of the phosphor screen is a single R circular arc, the shadow mask 10a is geometrically
The long side 13a of the slot edge line 13 should also have a substantially single R arc shape, but this is caused by the complicated change in the curvature of the shadow mask 10 as described above. For example, FIG. 6 is for explaining the y-axis cross section, but both shadow masks 1
Even if the long sides 13a of the slot edge lines 13 of 0 and 10a are at the same distance _yM , if the distance between the shadow mask and the panel 2 is different, the projection point of the light ray from the deflection center will be different. That is,
Even if the size of the slot edge line 13 of the shadow mask is the same, the larger the distance between the shadow mask 10 and the panel 2, the larger the effective screen edge line 3 of the phosphor screen will be, resulting in the drawback explained in FIG. .

This invention was made in order to eliminate the above-mentioned drawbacks, and includes a panel in which a phosphor is coated within the edge line of an approximately rectangular effective screen, and a large number of slots arranged in opposition to the panel. The appearance of the phosphor screen is improved by changing at least the curvature of the long side of the slot edge line approximately corresponding to the distance between the shadow mask and the panel in the long side direction. The aim is to provide high quality color cathode ray tubes.

Embodiments of the present invention will be described below based on the drawings.

FIG. 7 shows a shadow mask 10 according to an embodiment of the invention. In this figure, 11 represents a slot, 12 a slot line, and 13 a slot edge line. Here, the long side 13a of the slot edge line 13
is the new shadow mask 10 shown in Figure 3 in advance.
curvature change, that is, shadow mask 10 and panel 2
It has a shape that roughly corresponds to the distance in the long side direction. That is, the long side 13 of the slot edge line 13
A is formed to have a concave shape at the center, and a convex shape projecting outward with a larger curvature than the center at the middle between the center and the periphery. When a phosphor screen is formed using the shadow mask 10 having the slot edge line 13 having such a shape, the effective screen edge line becomes a substantially single R arc, and the appearance of the phosphor screen is improved.

Further, the curved surface configuration of the shadow mask 10 of the present invention shown in FIG.
Although the explanation has been given only for a concave surface that moves away from the panel, it does not necessarily have to be like this, and as shown in Figure 8, the center area can be almost flat or slightly convex toward the panel side. In that case, the shadow mask 1 shown in FIG.
The shape of the long side 13a of the slot edge line 13 may be configured to be substantially flat in the center or slightly convex outward.

As described above, according to the present invention, the slot edge line of the shadow mask is improved in response to the special curvature change of the shadow mask due to improvement of doming, and a color cathode ray tube with a good-looking phosphor screen is provided. be able to.

[Brief explanation of the drawing]

Figures 1a and b are front views showing the effective screen of the panel, Figure 2 is a front view of a conventional shadow mask corresponding to Figure 1b, and Figure 3 is an x-axis cross section of a shadow mask to which the present invention is applied. Shape explanatory diagram, 4th
The figure is an explanatory diagram of the slot line spacing of the shadow mask shown in Figure 3, Figure 5 is a front view showing the effective screen of a panel formed by a conventional shadow mask, and Figure 6 is a supplementary explanatory diagram of Figure 5. , FIG. 7 is a front view of a shadow mask according to an embodiment of the present invention, and FIG. 8 is a supplementary explanatory diagram of the present invention. 2... Panel, 3... Effective screen edge line, 4... Phosphor, 10... Shadow mask, 11... Slot, 13... Slot edge line. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A panel comprising a substantially rectangular effective screen edge line coated with phosphor, and a shadow mask disposed opposite to the panel and having a large number of slots in the slot edge line, at least A shadow mask type color cathode ray tube, characterized in that the curvature of the long side of the slot edge line is changed approximately corresponding to the distance between the shadow mask and the panel in the long side direction. 2. A shadow mask type color cathode ray tube according to claim 1, wherein the curvature of the long side of the slot edge line is concave at the center and outwardly convex at the middle between the center and the periphery. 3. The shadow mask type color cathode ray tube according to claim 2, wherein the curvature of the long side of the slot edge line is larger at an intermediate portion between the center and the peripheral portion than at the center.