JPS6039740A - Shadow mask - Google Patents

Abstract

PURPOSE:To suppress a doming event by forming a bent section near the central part of the mutually opposed sides of a rectangular aperture plate and deflecting the aperture plate by thermal expansion so as to become remote from a panel. CONSTITUTION:In the rectangular aperture plate 1 of a shadow mask 7, a bent section 4 is formed near a skirt section 3 in the vicinity of the central part of mutually opposed sides in the X- and Y-axis directions and a step section 5 is provided between the bent section and the skirt section 3 in proper width and then the diagonal cross section is formed as a shape without the bent section 4. In addition, when the aperture plate 1 is thermally expanded due to the bombardment of an electron beam, the central location is deflected so as to become remote from the panel of a cathode-ray tube and the diagonal location is deflected in the reverse direction with this. As a result, a stable picture can be obtained by effectively suppressing doming by thermal expansion.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a shadow mask applied to a color cathode ray tube.

[Prior Art] One type of thermal deformation of a shadow mask is the doming phenomenon. This doming phenomenon will be briefly explained.

Figure 1 shows a cross section of a shadow mask conventionally used in color cathode ray tubes. (1) is made of a thin iron plate, has a convex curved surface, and has many regularly arranged small holes or slits. The aperture plate (2) is a frame that is held in a color cathode ray tube envelope (not shown) and supports the aperture plate (1), and is generally made of a slightly thick metal plate formed into an annular shape.

The frame (2) has a cylindrical part (2a) extending along the normal line (also called the tube axis of a cathode ray tube) set at the center of the aperture plate (1), and the aperture plate (1) It has a skirt part (3) on the periphery that is fitted onto the cylindrical part (2a) of the frame (2), and the cylindrical part (2a) and the skirt part (3) are fixed by welding or the like. ing.

Hereinafter, a combination of the aperture plate (1) and the frame (2) as described above will be referred to as a shadow mask.

When a color cathode ray tube using such a shadow mask is operated, an electron beam emitted from an electron gun (not shown) passes through a small hole in the aperture plate (1) and causes a phosphor dot to emit light. Most of the beam impinges on the aperture plate CI) and heats it. On the other hand frame (2
) has a small amount of incident electron beams and the heat capacity of the frame (2) is large, so the temperature rise is small and the temperature rise rate is slow. Therefore, during operation of the color cathode ray tube, especially immediately after the start of operation (usually after 2 to 3 minutes), the thermal expansion of the aperture plate (1) is larger than that of the frame (2), and the center of the aperture plate (+) M1 point force % M Shifts to bulge to the IO point. This is the doming phenomenon. For this reason, the electron beam passing through the small hole in the aperture plate (1) does not strike the regular phosphor dots correctly, resulting in undesirable color shift.

Generally, the screen (phosphor screen) of a color cathode ray tube has a substantially rectangular shape, and correspondingly, the shadow mask also has a substantially rectangular shape. In this case, as an effective means to reduce the above-mentioned doming, the overlap between the cylindrical part (2a) and the skirt part (3゛) can be set at eight points in total, including the corners of this rectangular shape and the middle part of each side! A so-called 8-point welding method has been devised. FIG. 2 shows the distribution of welding points using this 8-point welding method. In the figure, (lO) is the welding point. Although this 8-point welding method has excellent effects, it cannot be said to have completely solved the problem with wide deflection angle and panel-shaped cathode ray tubes, that is, recent color cathode ray tubes with nearly flat aperture plates. , Further improvements were desired.

Before describing the details of this development, FIG. 3 shows a typical example of the distribution of the deviation of the electron beam projection point from the correct position due to doming when eight-point welding is employed. In the same figure,
(11) is a panel with a convex curve, and the dotted line is a fluorescent screen (12)
The arrows indicate how the electron beam that has passed through the small holes in the seven-percha board (1) on the inner surface of the panel (11) deviates from its correct position. In addition,
The panel (11) is symmetrical vertically and horizontally with respect to the X-axis and Y-axis drawn in the figure, so only one quadrant is shown.

The distribution of this shift is generally characterized entirely inward (panel (
11)), but in the diagonal periphery, there are parts where the deviation occurs outward.

On the X and Y axes, the deviation points inward over the entire area, and there is a point where the deviation is maximum near the middle on both axes, and one of these gives the maximum deviation throughout the screen. is normal.

A situation in which the deviation is always in the inward direction on the X and Y axes is shown in FIG. 4, which is a cross section including these axes. Aperture plate (1
) has the shape of a solid line before deformation, and consider specific electron beam passing holes Ml and M2 on this. The electron beams (+01) and (102) departing from the deflection center O are respectively
1. It passes through M2 and hits the inner surface PI and P2 of the panel (11). This is the correct firing position. Next, when doming occurs, the center of the aperture plate (1) bulges forward as shown by the dotted line, resulting in the hole M1
, M2 transition to M 1o and M 2o, respectively,
The injection points of the electron beams passing through these are Plo,
Transition to P2o. Here, M 1g and M 20 are Ml and M2, respectively, approximately along the tube axis to the panel (11).
Since it is in the direction approaching , PI' + P as shown in the figure
20 are located inside PI and P2, respectively, resulting in the inside slip mentioned above.

Next, FIG. 5, which is a cross section including the diagonal line, shows a situation where the distribution of deviation is reversed halfway along the diagonal line.

In this figure, the solid line and the dotted line indicate the occurrence and post-doming occurrence, respectively, as in FIG. 4.

As shown in the figure, the beam projection point P1 on the panel (11) corresponding to the hole Ml between the center and the periphery of the aperture plate (1) is located on the inside due to doming as in the previous figure 4. However, due to P2 doming corresponding to hole M2 which is relatively close to the periphery, it is displaced outward. The reason for this is that when the skirt part (3) of the aperture plate (1) is domed on the diagonal, the welding point (1o) on the diagonal
This is because the hole M2 moves outward as M2o as a result of falling down in the direction of the arrow with the fulcrum being the fulcrum. The reason why the skirt part (3) does not fall so much on the X and Y axes, and is particularly large in the diagonal parts, is due to the shape of the aperture plate (1) and the lack of holes around it, which makes it difficult to maintain strength. This can be explained by the fact that there are strong parts, but detailed explanation will be omitted here.

Now, returning to Figure 3, in order to reduce the influence of the shift of the beam projection point due to doming, which has the distribution shown in the figure, it is necessary to reduce the large internal shift components that occur on the X and Y axes. be. Such an inward deviation component occurs because the seven pertier plate (1) bulges toward the panel (11) as explained in FIG. 4. Therefore, this problem can be improved by moving the aperture plate (1) away from the panel (11) as the aperture plate (1) thermally expands.

However, if the entire aperture plate (1) is moved away from the panel (11), the outward shift that occurs near the outermost periphery of the diagonal portion will be magnified.

[Summary of the Invention] This invention was made in view of the above-mentioned problem, and it specifies the shape near the center of at least one pair of rectangular sides facing each other in the peripheral part of the aperture plate, and By configuring this part to be displaced away from the panel during expansion, and the diagonal part to be displaced less than or in the opposite direction, doming can be effectively suppressed and contribute to ensuring a stable image. The purpose is to provide a shadow mask that can be used.

[Embodiment of the Invention] FIG. 6 is a perspective view showing an example of a shadow mask according to the present invention, and the same parts as in FIGS. 1 to 5 are denoted by the same reference numerals, and a description thereof will be omitted.

In the same figure, the aperture plate (1) has a bent part (4) near the skirt part (3) in the cross section in the X and Y axis directions, and an appropriate distance is formed between this and the skirt part (3). It has a step portion (5) of a width (FIG. 7(A)). On the other hand, in the diagonal cross section, there is no bent portion (4) as described above (FIG. 7(B)).

This will be explained in more detail with reference to FIG. That is, at the bending part (4), the tangent T around the conventional curved surface and the step part (5) form an angle θ, and the step part (5)
) is arranged so that it is on the panel (11) side of the extension of the tangent line T. Furthermore, the step portion (5) has an appropriate @ statement.

According to such a configuration, when the aperture plate (1) undergoes thermal expansion, if the peripheral portion of the curved surface of the seven percha plate (1) tries to extend in the direction of the tangent line T due to this expansion, it will break. Music section (4), step section (5) and step section (
5) and the skirt portion (3) as a whole acts as a hinge, and the entire aperture plate (1) can be moved in the direction away from the tunnel (ll) as shown by the dotted line in Fig. 8. .

This makes it possible to reduce as much as possible the adverse effects caused by the doming of the aperture plate (1) toward the panel (11) shown in FIG. Moreover, since the cross-sectional shape shown in FIG. 7(A) is not used in the diagonal portion, the phenomenon explained in FIG. 5 above remains near the diagonal portion.
In the end, as a whole, it is possible to effectively correct any undesirable impact points of the electron beam due to doming shown in FIG.

In the operation shown in FIG. 3, in order for the aperture plate (1) to thermally expand and move away from the panel (11) efficiently as the aperture plate (1) expands, θ must be large to some extent.
Generally speaking, it is preferable that the step part (5) be perpendicular to the tube axis or slightly larger than that;
5) is preferably longer.

By the way, in the diagonal part, as mentioned earlier, such a bent part (
4) and the step part (5) should not be provided as shown in Figure 7 (B), or even if they are provided, the movement will be weak, so θ should be gradually reduced from the center of the side to the diagonal. The sentences shall gradually become smaller.

Regarding the above distribution of θ, in some cases O may be set to a negative value in the diagonal part, that is, the step part (5) is the aperture plate (1).
In some cases, it may be desirable for the tangent T around the curved surface of the electron beam to be on the side other than the panel (11) side in order to reduce the outward movement of the electron beam projection point as described in FIG.

An example is shown in FIG. The figure (A) shows a cross section in the X or Y axis direction, and the figure (B) shows a cross section in the diagonal direction.

In addition, in order to further demonstrate the effects of the bending part (0) and the step part (5), especially in the cross section in the X and Y axis directions,
As shown in FIG. 10, it is also possible to reduce the thickness of the aperture plate (1) near the step portion (5) by etching or the like. If this is done, the stem and tap portion (5) will be more likely to be bent as explained in FIG. Therefore, the amount of displacement of the aperture plate (1) away from the panel (11) due to thermal expansion can be further increased. In this case, in addition to gradually decreasing θ or the curve as described above as it approaches the diagonal cross section, it is also possible to keep θ and the curve constant and gradually increase the thickness of the step part (5). It is possible. Of course, the thickness of the aperture plate (1) does not necessarily need to be uniformly thinned in the vicinity of the step portion (5), but a concave-convex pattern can be applied by etching so as to effectively obtain the same deflection characteristics as a thinned plate. Also good.

In addition, in general color cathode ray tubes for television receivers, the small holes in the perforation plate (1) are usually
A so-called S-I-live phosphor screen is used, which has a rectangular shape elongated in the axial direction and has a phosphor screen mosaic elongated in this direction. In such a case, the shift of the electron beam projection point due to thermal expansion of the aperture plate (1) in FIG. 3 is often not a problem near the Y-axis.

Therefore, in such a case, the above-described structure in which the bent portion (4) and step portion (5) are provided only needs to be formed near the X-axis cross section.

In the above embodiment, the skirt portion (3) of the aperture plate (1) is fitted onto the cylindrical portion (2a) of the frame (2). Even when the skirt portion (3) is assembled by fitting inside the cylindrical portion (2a) of the frame (2), the skirt portion (3)
) and the cylindrical part (2a), the deviation distribution shown in Fig. 3 is often obtained.
) is also applied to those embedded within.

[Effects of the Invention] As described above, the present invention forms a bent portion in the aperture located near the center of at least one pair of opposing sides of a rectangular aperture, and connects the bent portion to the skirt. A step part is formed between the part and the part, and the step part is set to be on the panel side of the tangent at the peripheral part of the aperture plate, so that when the aperture plate undergoes thermal expansion, the part near the bent part Doming can be suppressed by configuring the panel so that it is displaced in the direction away from the panel, and by configuring the diagonal portion so that the amount of displacement is less than or in the opposite direction than the above amount, thereby making it possible to suppress doming and thereby create a stable image. It can provide a shadow mask that is advantageous for obtaining

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view to explain the structure of the shadow mask and the doming phenomenon, Figure 2 is an explanatory diagram of the welding position between the aperture plate and the frame, and Figure 3 is the beam injection point due to doming of the conventional shadow mask. FIG. 4 is a detailed diagram of the doming phenomenon in the X or Y axis cross section of a conventional shadow mask, FIG. 5 is an explanatory diagram of the doming phenomenon in the same diagonal plane, and FIG. 6 is a diagram of the invention A perspective view showing an example of a shadow mask according to FIG. 7(A), (
B) is a sectional view in the X and Y axis directions and a diagonal sectional view of the shadow mask in FIG. 6, FIG.
), (B) and FIG. 10 are cross-sectional views showing modifications of the main parts of the present invention. (1)...Aperture plate, (2) ---Frame,
(2a)...Tubular part, (3)...Skirt part, (4
)...Bending part, (5)...Step part, (11)...
・-Panel. Note that the same reference numerals in the figures indicate the same or corresponding parts. Agent Masuo Oiwa

Claims (6)

[Claims] (1) A substantially rectangular aperture plate that is curved in a convex shape toward the inner surface of the panel and has a large number of small holes, and a center plate that is connected to the periphery of the aperture plate and stands at the center of the aperture plate. The frame includes a skirt portion projecting along a line, and a frame having a cylindrical portion that fits into the skirt portion, and is located near the center of at least one pair of opposing sides of the rectangular shape. A bent portion bent along the side is formed in the peripheral portion of the aperture plate, a step portion is formed between the bent portion and the skirt portion, and the step portion is formed in the bent portion of the bent portion. The aperture plate is set on the side closer to the panel with respect to the tangent to the curved surface of the aperture plate passing through the center normal at a position near the inner side, so that when the aperture plate undergoes thermal expansion, the area near the folded line moves away from the panel. 7. A shadow mask characterized in that the shadow mask is configured such that the amount of displacement is smaller than or in the opposite direction near the diagonal portion. (2) The shadow mask according to claim 1, wherein the skirt portion and the cylindrical portion are connected and fixed at four locations at the center of each side of the rectangular shape and at four locations at diagonal corners. (3) The shadow mask according to claim 1, wherein the width of the step portion is set to be gradually narrower from the center of the side to the diagonal portion. (4) A patent in which the bending angle of the above-mentioned bending part is set so that, when the direction in which the step part is on the panel side is positive, the bending angle is maximum at the center of the side and smaller at the diagonal part. A shadow mask according to claim 1. (5) The shadow mask according to claim 1, wherein the effective plate thickness of the step portion based on the deflection characteristics is set to be thinner at the center of the side and thicker at the diagonal portion. (6) The small hole provided in the aperture plate is a long hole that runs approximately in the direction of one side of a rectangular shape, and the pair of sides on which the bent part and the step part are provided are the length of the long hole. The shadow mask according to claim 1, which is the side along the axis.