JP2000260343A - Color cathode ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color cathode ray tube capable of controlling thermal deformation of a shadow mask structure developed in practical usage and preventing degradation of the color purity. SOLUTION: This color cathode ray tube has an envelope comprises a panel with a phosphor screen formed inside and a funnel, a shadow mask having a rectangular curved surface 13 arranged oppositely to the phosphor screen and having electron beam path holes 12, and a skirt part 14 bent at the periphery of the curved surface 13, and an almost rectangular frame supporting the skirt part 14 of the shadow mask, elastic supports locking the frame to the panel. A plurality of bead parts 15 are placed so as to be concentrated at the center of the side of skirt part 14 of the shadow mask.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color cathode ray tube, and more particularly, to a color cathode ray tube having an improved skirt portion of a shadow mask.

[0002]

2. Description of the Related Art A color cathode ray tube for displaying a color image usually has a panel having a fluorescent screen formed on an inner surface thereof, and an envelope made of a funnel connected to the panel. The phosphor screen formed on the inner surface of the panel is composed of a plurality of phosphor layers respectively emitting red, green, and blue light, and emits a plurality of electron beams corresponding to the emission color of the phosphor screen to the neck of the funnel. An electron gun is located.

Further, a shadow mask having a color selection electrode fixed to a frame is provided inside the panel between the electron gun and the phosphor screen, and the electron beam emitted from the electron gun is shaped to have a specific color. An electron beam spot is projected on the phosphor screen.

Further, the frame is supported by the panel in a state where the frame is engaged with a panel pin provided on an inner wall surface of the panel via an elastic support (holder).

The shadow mask has, for example, a curved surface portion formed of, for example, Invar material and having a large number of electron beam passage holes, and a skirt portion bent from a peripheral portion of the curved surface portion and hanging down toward the funnel. .

The frame is made of, for example, mild steel, and has a side wall formed so as to have a substantially rectangular planar shape.
And a bottom surface vertically erected from the side wall.

The skirt portion of the shadow mask is welded to the side wall of the frame to form a shadow mask structure in which the shadow mask and the frame are integrated.

Here, an example of the shadow mask structure is shown in FIG.
This will be described with reference to FIG.

As shown in FIG. 16, a skirt portion 6 of a substantially rectangular shadow mask 61 is provided on a substantially rectangular frame 51.
The tongue pieces 63, 64, 65 formed substantially at the center of the two diagonals and the long sides and short sides are fixed.

Further, as shown in FIG. 16, the rectangular frame 51 has a side wall 51a to which a shadow mask 61 is fixed, and a bottom surface 51b serving as a beam for increasing the strength of the frame 51. are doing.

When the shadow mask 61 is press-molded, the lower portion of the skirt portion 62 expands outward at the long side central portion 61a and the short side central portion 61b of the shadow mask 61 as compared with the upper portion of the skirt portion 62. Structure.

For this reason, when the shape of the shadow mask 61 from the panel side is confirmed, as shown in FIG. 17, the central portion 61a of the long side and the central portion 61b of the short side bulge from the vicinity of each diagonal portion. Become.

The factor of such a barrel shape results from the fact that the lower portion of the skirt portion 62 has excess material in the lower portion compared to the upper portion.

Further, when the shadow mask 61 is welded to the side wall 51a of the frame 51 with the skirt 62 open, the side wall 51b compresses the skirt 62, so that the electron beam of the shadow mask 61 is compressed. Excessive force is applied to the through hole, and the through hole is welded in a state different from the press-formed state (the curved surface rises around the through hole), and distortion remains in the curved surface part.

The through hole of the shadow mask 61 and the phosphor screen of the panel are very close to each other and maintain a close positional relationship. For this reason, if the through-hole portion of the shadow mask 61 is distorted, if the shadow mask 61 thermally expands with the energy of the electron beam, the spot of the electron beam that has passed through the shadow mask 61 at the portion where the distortion remains remains. However, it is not possible to completely match the phosphor screen of the target color, and as a result, the color purity of the emission color of the phosphor screen may be reduced.

For example, when observing the landing state of the electron beam with respect to the fluorescent screen with an observation device such as a microscope, the landing change direction may be reversed at a portion where distortion remains, and in such a case, the color purity is extremely deteriorated. Remarkable.

[0017]

In order to solve such a problem, conventionally, a notch is formed in a skirt portion of a shadow mask, and press forming is performed to improve the formability of the skirt portion. Japanese Patent Application Laid-Open No. 9-306
As disclosed in Japanese Patent Publication No. 373, in consideration of the expansion amount of the shadow mask skirt portion, the central portion on the side is curved toward the through hole so that distortion during molding does not remain on the curved surface portion of the shadow mask. Attempts have been made to do so.

In Japanese Patent Application Laid-Open No. 60-130032, an emboss is provided at the shadow mask fixing portion of the frame to increase the clearance between the shadow mask and the frame. A method for suppressing color purity deterioration without being deformed by being pushed by the hologram, that is, by making the passage hole always exist on the predetermined electron beam orbit.

However, when the upper portion of the skirt is curved as in Japanese Patent Application Laid-Open No. 9-306373, the non-porous portion of the shadow mask is reduced, and conversely, the curved portion of the shadow mask is distorted. There is a problem that the influence is exerted.

Further, in a configuration in which an emboss is provided at a shadow mask fixing portion of a frame as disclosed in Japanese Patent Application Laid-Open No. Sho 60-130032, it is difficult to suppress partial deformation of the shadow mask.

Therefore, the present invention provides a color cathode ray tube in which the structure of the skirt portion of the shadow mask is improved, thermal deformation of the shadow mask structure which occurs during actual use is suppressed, and deterioration of color purity is prevented. Is what you do.

[0022]

According to the first aspect of the present invention,
An envelope comprising a panel and a funnel having a fluorescent surface formed on an inner surface, a rectangular portion having an electron beam passage hole disposed opposite to the fluorescent surface, and a fold from a peripheral portion of the curved portion. In a color cathode ray tube having a shadow mask having a curved skirt portion, a substantially rectangular frame for supporting the skirt portion of the shadow mask, and an elastic support for locking the frame to the panel, The skirt portion is provided with a plurality of bead portions that are arranged substantially parallel to the tube axis and occupy the entire tube axis direction of the skirt portion or a plurality of bead portions that occupy only the funnel side in the tube axis direction. It is characterized by the following.

According to the present invention, the skirt portion of the shadow mask is arranged in a direction substantially parallel to the tube axis and has a plurality of beads occupying the entire skirt portion in the tube axis direction or a plurality of beads occupying only the funnel side in the tube axis direction. Since a plurality of bead portions including bead portions are provided, a plurality of bead portions occupying the entire tube axis direction or a plurality of bead portions occupying only the funnel side in the tube axis direction provide a shadow mask at the time of shadow mask molding. The skirt part of the mask can be formed with high precision, the thermal deformation of the skirt part of the shadow mask that occurs during actual use can be suppressed, and the passage hole can be maintained at a fixed position, thereby preventing the deterioration of color purity can do.

According to a second aspect of the present invention, there is provided an envelope comprising a panel and a funnel having a fluorescent screen formed on an inner surface thereof, and a rectangular electron beam passage hole disposed opposite to the fluorescent screen. A shadow mask having a curved surface portion and a skirt portion bent from a peripheral portion of the curved surface portion, a substantially rectangular frame supporting the skirt portion of the shadow mask, and an elastic support member for locking the frame to the panel. In the color cathode ray tube having: a plurality of bead portions occupying the entire tube axis direction of the skirt portion or a plurality of bead portions occupying only the funnel side in the tube axis direction in an arrangement substantially parallel to the tube axis in the skirt portion of the shadow mask. And a depth of at least one bead portion of the plurality of bead portions occupying the entire tube axis direction of the skirt portion is determined. And it is characterized in that it is deeper than the curved portion of the skirt portion in An'neru side.

According to this invention, the function of the invention described in claim 1 is exhibited, and in particular, the depth of at least one bead portion of the plurality of bead portions occupying the entire tube axis direction is adjusted by the funnel of the skirt portion. Because the side is formed deeper than the curved surface side of the skirt, the funnel side of the skirt can absorb excess when shading the shadow mask, and the thermal deformation of the skirt of the shadow mask can be suppressed more reliably.
The passage hole can be maintained at a fixed position.

According to a third aspect of the present invention, in the color cathode ray tube according to the first or second aspect, the bead portion occupying the whole of the skirt portion of the shadow mask in the tube axis direction is formed at the center on the side of the shadow mask and the frame. It is characterized in that at least two or more are provided between the fixing portion and the fixing portion of the corner portion, and the interval between the bead portions or the interval between the welded portion and the bead portion is not constant.

According to the structure of the bead portion occupying the entire tube axis direction in the present invention, it is possible to more reliably suppress the thermal deformation of the skirt portion of the shadow mask and maintain the passage hole portion at a fixed position. .

According to a fourth aspect of the present invention, in the color cathode ray tube according to any one of the first to third aspects, the distance between the center fixing portion of the side of the skirt portion of the shadow mask and the bead portion is equal to the distance between the corner portion and the bead portion. It is characterized by being smaller than the interval between the parts.

According to the present invention, in particular, it is possible to reliably suppress the thermal deformation of the skirt portion near the side center fixing portion of the skirt portion of the shadow mask and to keep the passage hole portion at a fixed position.

According to a fifth aspect of the present invention, in the color cathode ray tube according to any one of the first to fourth aspects, a skirt notch portion is formed between the bead portion and the side center fixing portion of the skirt portion of the shadow mask. It is characterized by having been done.

The configuration in which the skirt notch portion is formed between the side center fixing portion of the skirt portion and the bead portion as in the present invention ensures the thermal deformation of the skirt portion near the side center fixing portion of the skirt portion of the shadow mask. , And the passage hole can be maintained at a fixed position.

According to a sixth aspect of the present invention, in the color cathode ray tube according to any one of the first to fifth aspects, the bead portion occupying the entire tube axis direction of the skirt portion of the shadow mask has a depth on the curved surface side. The height of the shadow mask is not more than 2/3 of a non-hole formed between the electron beam passage hole and the skirt in the curved surface of the shadow mask.

According to the present invention, the depth of the bead portion occupying the entire tube axis direction of the skirt portion of the shadow mask on the curved surface side is made not more than 2/3 of that of the non-hole portion. The strength of the curved surface portion can be secured, and the moldability of the shadow mask can be maintained.

According to a seventh aspect of the present invention, in the color cathode ray tube according to any one of the first to sixth aspects, a bead portion occupying the whole of the skirt portion of the shadow mask in the tube axis direction is in the tube axis direction. The cross-sectional shape in the direction perpendicular to the skirt portion is formed in a substantially semicircular or U-shape that gradually increases from the curved surface side of the skirt portion to the funnel side of the skirt portion.

According to the present invention, the shape of the bead occupying the entire tube axis direction is gradually increased from the curved surface side of the skirt portion to the funnel side of the skirt portion in a direction perpendicular to the tube axis direction. As in the case of the second aspect of the present invention, the funnel side of the skirt portion can absorb the excess thickness at the time of molding the shadow mask, and the heat of the skirt portion of the shadow mask can be absorbed. Deformation can be suppressed more reliably, and the passage hole can be maintained at a fixed position.

According to an eighth aspect of the present invention, in the color cathode ray tube according to the first aspect, at least one of the beads occupying the entire tube axis direction of the skirt portion of the shadow mask is orthogonal to the tube axis direction. The cross-sectional shape in the direction in which the skirt portion has a curved surface side and the funnel side of the skirt portion has a substantially semicircular or U-shape having the same depth.

According to the present invention, at least one of the bead portions occupying the entire tube axis direction has a cross-sectional shape in a direction orthogonal to the tube axis direction, the curved surface side of the skirt portion and the funnel side of the skirt portion. With this configuration, it is possible to absorb the excess thickness at the time of molding the shadow mask, and to more surely prevent the thermal deformation of the skirt portion of the shadow mask. Thus, the passage hole can be maintained at a fixed position.

[0038]

Embodiments of the present invention will be described below in detail.

FIGS. 1 and 2 show a color cathode ray tube 1 according to an embodiment of the present invention.
Has a panel 3 having a fluorescent screen 2 formed on an inner surface thereof, and an envelope 5 including a funnel 4 connected to the panel 3.

The fluorescent screen 2 formed on the inner surface of the panel 3
An electron gun 6 that emits electron beams 7R, 7G, and 7B corresponding to the emission colors of the phosphor screen 2 is provided at a neck portion of the funnel 4 and includes a plurality of phosphor layers that emit light of red, green, and blue, respectively. Are located.

Further, a shadow mask 11 having a color selection electrode fixed to a frame 10 is provided inside the panel 3 between the electron gun 6 and the phosphor screen 2, and an electron beam 7 R emitted from the electron gun 6 is provided. , 7G, and 7B, and project an electron beam spot on the phosphor screen 2 of a specific color.

The frame 10 is provided with an elastic support 1.
The panel 3 is detachably supported by the panel 3 in a state where the panel pin 3a is provided on the inner wall surface of the panel 3 via a 6 (holder).

The shadow mask 11 is formed in a rectangular shape as a whole by, for example, an invar material. As shown in FIGS. 3 and 4, a curved surface portion 13 having a large number of electron beam passage holes 12 and a peripheral portion of the curved surface portion 13 are provided. Bent from the funnel 4
And a skirt portion 14 depending from the side.
The vicinity of the peripheral portion of the curved surface portion 13 is a non-porous portion 13a.

The frame 10 is made of, for example, mild steel, and is formed so as to have a substantially rectangular planar shape, and a bottom surface portion 1 vertically connected to the side wall portion 10a.
0b.

A predetermined position of the skirt portion 14 of the shadow mask 11 is welded to the side wall portion 10a of the frame 10 to form a shadow mask structure in which the shadow mask 11 and the frame 10 are integrated.

Next, the detailed structure of the skirt portion 14 of the shadow mask 11 according to the present embodiment will be described with reference to FIGS.

The basic structure of the skirt portion 14 is as follows. The shape of the bead portion 15 formed on the skirt portion 14 when the shadow mask 11 is formed is determined by changing the shape of the bead portion 15 below the skirt portion 14 (the funnel 4 side) when the shadow mask is formed. By increasing (or increasing the number of) the upper portion (curved portion 13 side) of the skirt portion 14 so that the lower portion of the skirt portion 14 of the shadow mask 11 can be prevented from expanding in a barrel shape, the beads can be further absorbed. Part 15 is shadow mask 1
Irregularities near the center on the side of 1 (l,
(Each interval of m, m ', and n is different), so that the skirt portion 11 does not expand at the center on the side. This prevents the curved surface portion 13 of the shadow mask 11 from being distorted when the frame 10 is assembled.

FIGS. 3 and 5 show the skirt portion 14 of the shadow mask 11 between the welding point (x mark) at the center of each of the long and short sides and the corner portion along the pipe axis direction. This shows an example in which three bead portions 15 are arranged on each side.

In this case, when the shadow mask 11 is a single body, the skirt portion 11 has a barrel-shaped central portion on the side. Therefore, the bead portion 15 is arranged closer to the center on the side. Further, since the lower portion of the skirt portion 14 (on the funnel 4 side) has a larger excess thickness and a larger degree of expansion, as shown in FIG. The depth t2 of the lower part of the skirt 14
Is large (t1 <t2).

If the bead portion 15 is formed in the non-porous portion 13a between the electron beam passage hole 12 and the skirt portion 14 of the shadow mask 11 in a dark manner, the bead portion 15 becomes too strong (hard). The distortion generated during the assembly of the frame 10 is suppressed by the bead portion 15 and, on the contrary, a slight distortion is generated in the bead portion 15, and as shown in FIG. 7, the skirt portion 14, the non-porous portion 13a, and the electron beam Distortion is given to the passage hole 12, which causes a decrease in accuracy.

For this reason, as shown in FIG.
a of a bead portion 15 having a semicircular cross section at a
Is, for example, about 以下 or less of the width L of the non-porous portion 13a (a ≦
By setting L / 2 or less, the skirt portion 14, the non-porous portion 13a, and the electron beam passage hole 12 of the shadow mask 11 can be formed with high accuracy.

With such a configuration, even when the frame 10 is assembled to the shadow mask 11, no extra force is transmitted from the skirt portion 14 of the shadow mask 11 to the curved surface portion 13.

As a result, the curved surface portion 13 is not distorted, and the shadow mask 11 is moved by the electron beams 7R, 7G, 7D.
Even if thermal expansion occurs with the energy of B, local thermal deformation of the shadow mask 11 is unlikely to occur. In particular, the landing positions of the electron beams 7R, 7G, and 7B partially at the horizontal and vertical ends of the phosphor screen 2 Deviation is suppressed, and color purity deterioration can be effectively prevented.

Of the beads 15, some of the beads 15 may be provided only on the funnel 4 side instead of the entire skirt 14 in the tube axis direction. The excess meat can be absorbed.

Further, it is of course possible to form a skirt notch portion 17 between the bead portion 15 and the central portion on the side of the skirt portion 14 of the shadow mask 11, and in this case also, The excess thickness at the time of shadow mask molding can be absorbed.

Next, various embodiments of the bead portion 15 will be described with reference to FIGS.

In the example shown in FIG. 8, the depth of the bead portion 15 having a semicircular cross section shown in FIG. 6 on the side of the non-porous portion 13a is reduced so that the vicinity of the boundary between the non-porous portion 13a and the skirt portion 14 is reduced. FIG. 9 shows an example in which the bead portion 15 having a semicircular cross section shown in FIG. 6 has the depth on the non-porous portion 13a side deeper toward the non-porous portion 13a. FIG. 11 shows an example in which a bead portion 15 having a shape substantially similar to a generally conical shape is formed instead of the bead portion 15 having a semicircular cross section shown in FIG.

In each of these, the shape of the bead portion 15 is
The cross-sectional shape in a direction perpendicular to the tube axis direction is a substantially semicircular shape that gradually increases from the curved surface portion 13 side of the skirt portion 11 to the funnel 4 side. Can be absorbed, the thermal deformation of the skirt portion 14 of the shadow mask 11 can be suppressed more reliably, and the electron beam passage hole 12 can be maintained at a fixed position.

FIG. 10 shows a shape of the bead portion 15 having a substantially semicircular cross section in a direction perpendicular to the tube axis direction which is equal from the curved surface portion 13 side of the skirt portion 11 to the funnel 4 side. In this case, too, the excess thickness at the time of molding the shadow mask can be absorbed, the thermal deformation of the skirt portion 14 of the shadow mask 11 can be more reliably suppressed, and the electron beam passage hole 12 is maintained at a fixed position. Becomes possible.

FIGS. 13 to 15 show that the cross-sectional shape in the direction perpendicular to the pipe axis direction gradually increases from the curved surface portion 13 side of the skirt portion 14 to the funnel 4 side of the skirt portion 14, ie, the funnel 4 side has a deeper core. FIG. 3 shows each bead portion 15 in a shape having a shape.

The examples shown in FIGS. 13 to 15 correspond to FIG.
15 to FIG. 15, the depth of the bead portion 15 on the curved surface portion 13 side of the skirt portion 14 is reduced in order.

Each of the beads 15 shown in FIG. 13 to FIG.
The side can absorb the excess thickness at the time of molding the shadow mask, the thermal deformation of the skirt portion 14 of the shadow mask 11 can be suppressed more reliably, and the electron beam passage hole 12 can be maintained at a fixed position.

FIG. 12 shows that the cross-sectional shape in the direction perpendicular to the tube axis direction is the same as the curved surface portion 13 side of the skirt portion 14 and the funnel 4 side.
A bead portion 15 and a semi-circular groove 18 having the same U shape on the side
1 shows a non-porous portion 13a provided with a.

In this case, too, the excess thickness at the time of molding the shadow mask can be absorbed, and the skirt portion 14 of the shadow mask 11 can be absorbed.
Is more reliably suppressed, and the electron beam passage hole 12 can be maintained at a fixed position.

In addition, a bead portion 15 having a substantially semicircular cross-section is provided with respect to the skirt portion 14 of the shadow mask 11 described above.
Also, a structure in which a bead portion group formed by appropriately combining the U-shaped bead portion 15 can absorb the excess thickness at the time of shading the shadow mask similarly to the above-described case.
Thermal deformation of the skirt portion 14 can be more reliably suppressed, and the electron beam passage hole 12 can be maintained at a fixed position.

[0066]

According to the present invention described above, only a plurality of beads which occupy the entire skirt portion in the tube axis direction and are arranged substantially in parallel with the tube axis on the skirt portion of the shadow mask and only the funnel side in the tube axis direction. Are formed in various forms as described above.

Therefore, the skirt portion of the shadow mask can be formed with high precision at the time of shaping the shadow mask, thermal deformation of the shadow mask which occurs during actual use is suppressed, color deterioration is prevented, and good image quality is realized. A color cathode ray tube capable of performing the above-mentioned steps can be provided.

[Brief description of the drawings]

FIG. 1 is an external perspective view of a color cathode ray tube according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of the color cathode ray tube of the present embodiment.

FIG. 3 is a perspective view showing a shadow mask of the present embodiment.

FIG. 4 is a front view showing the shadow mask of the present embodiment.

FIG. 5 is an enlarged explanatory view of a shadow mask in which a bead portion is formed on a skirt portion in the present embodiment.

FIG. 6 is an explanatory diagram of dimensions of a bead formed on a skirt according to the present embodiment.

FIG. 7 is an explanatory diagram of distortion generated in a shadow mask bonded to a mask in the present embodiment.

FIG. 8 is a partial perspective view showing an example of a bead portion having a semicircular cross section in the present embodiment.

FIG. 9 is a partial perspective view showing another example of a bead portion having a semicircular cross section in the present embodiment.

FIG. 10 is a partial perspective view showing still another example of a bead portion having a semicircular cross section in the present embodiment.

FIG. 11 is a partial perspective view showing a substantially conical bead portion in the present embodiment.

FIG. 12 is a partial perspective view showing an example of a bead portion having a U-shaped cross section in the present embodiment.

FIG. 13 is a partial perspective view showing another example of a bead portion having a U-shaped cross section in the present embodiment.

FIG. 14 is a partial perspective view showing still another example of a bead portion having a U-shaped cross section in the present embodiment.

FIG. 15 is a partial perspective view showing still another example of a bead portion having a U-shaped cross section in the present embodiment.

FIG. 16 is a diagram showing a conventional shadow mask and frame.

FIG. 17 is a front view of a conventional shadow mask viewed from the panel side.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Color cathode ray tube 2 Phosphor screen 3 Panel 4 Funnel 5 Enclosure 6 Electron gun 10 Frame 11 Shadow mask 12 Electron beam passage hole 13 Curved surface part 14 Skirt part 15 Bead part 16 Elastic support

Claims (8)

[Claims] 1. An envelope comprising a panel and a funnel having a fluorescent screen formed on an inner surface thereof, a rectangular surface having an electron beam passage hole disposed opposite to the fluorescent surface, and the curved surface A color cathode ray tube comprising: a shadow mask having a skirt bent from the periphery of the shadow mask; a substantially rectangular frame for supporting the skirt of the shadow mask; and an elastic support for locking the frame to the panel. In the shadow mask, a plurality of beads comprising a plurality of beads occupying the entire tube axis direction of the skirt portion or a plurality of beads occupying only the funnel side in the tube axis direction in an arrangement substantially parallel to the tube axis. A color cathode ray tube characterized by having a group. 2. An envelope comprising a panel and a funnel having a fluorescent surface formed on an inner surface thereof; a rectangular portion having an electron beam passage hole disposed opposite to the fluorescent surface; and a curved surface portion having the same. A color cathode ray tube comprising: a shadow mask having a skirt bent from the periphery of the shadow mask; a substantially rectangular frame for supporting the skirt of the shadow mask; and an elastic support for locking the frame to the panel. In the shadow mask, a plurality of beads including a plurality of beads occupying the entire tube axis direction of the skirt portion and a plurality of beads occupying only the funnel side in the tube axis direction in an arrangement substantially parallel to the tube axis. The depth of at least one bead portion of the plurality of bead portions occupying the entire tube axis direction of the skirt portion is provided on the funnel side of the skirt portion. Color cathode ray tube, characterized in that, being deeper than the curved portion of the skirt portion Te. 3. A bead portion occupying the whole of the skirt portion of the shadow mask in the tube axis direction has at least two or more bead portions between the shadow mask, the center fixing portion on the side of the frame, and the fixing portion at the corner portion, 3. The color cathode ray tube according to claim 1, wherein an interval between the bead portions or an interval between the welded portion and the bead portion is not constant. 4. The collar according to claim 1, wherein a distance between the side center fixing portion of the skirt portion of the shadow mask and the bead portion is smaller than a distance between the corner portion and the bead portion. Cathode ray tube. 5. The color cathode ray tube according to claim 1, wherein a skirt notch portion is formed between the side center fixing portion of the skirt portion of the shadow mask and the bead portion. . 6. The depth of the bead portion occupying the entire tube axis direction of the skirt portion of the shadow mask on the curved surface portion side is between the electron beam passage hole portion and the skirt portion of the curved surface portion of the shadow mask. The color cathode ray tube according to any one of claims 1 to 5, wherein the diameter of the color cathode ray tube is equal to or less than 2/3 of a non-porous portion to be formed. 7. A bead portion occupying the entire tube axis direction of the skirt portion of the shadow mask has a cross-sectional shape in a direction orthogonal to the tube axis direction gradually increasing from the curved surface side of the skirt portion to the funnel side of the skirt portion. 7. The color cathode ray tube according to claim 1, wherein the color cathode ray tube is formed in a substantially semicircular or U-shape. 8. At least one of the bead portions occupying the entire tube axis direction of the skirt portion of the shadow mask has a cross-sectional shape in a direction perpendicular to the tube axis direction, the curved surface side of the skirt portion and the skirt portion. 2. The color cathode ray tube according to claim 1, wherein the color cathode ray tube is formed in a substantially semicircular shape or a U shape having the same depth on the funnel side.