JPH11120932A - Color cathode-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent lowering of the contrast due to halation by arranging a large number of dents in the part to which an electron beam is collided of the inner surface of a mask skirt part bent and formed in the mask skirt bending part of a shadow mask. SOLUTION: A number of semi-spherical dents 41 are arranged in a dent arrangement part 31 substantially at equal intervals, and the dents 41 reflect the electron beam incident from a neck side to the neck side as much as possible to significantly reduce the beam reflection on a phosphor screen side and reduce the beam halation. Namely, although the incident electron beam is collided to the inner surfaces of the semi-spherical dents 41, the reflected beam is turned to the neck side since the inner surfaces are inclined on the neck side in the colliding points. Further, the electron beam incident on the upper side from the dent arrangement part 31 is interrupted by the flange part 13 of a mask frame 7 without causing the halation, and the electron beam collided to the vicinity of a mask skirt bent part 16 is also interrupted by the dead area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a color cathode ray tube using a shadow mask, and more particularly to a surface processing shape of an inner peripheral surface of a mask skirt around a shadow mask.

[0002]

2. Description of the Related Art FIG. 7 is a partially cutaway perspective view of a color cathode ray tube used in a general color television.

As shown in FIG. 7, three electron beams 6 radiated from a cathode of an electron gun 1 mounted on a neck portion of an envelope including a panel 4 and a funnel 5 are mounted on the neck portion. The light is deflected by a deflection yoke (not shown) and passed through the opening of the shadow mask 3.
Project a color image on top.

FIG. 8 is an enlarged cross-sectional view of an end portion of a shadow mask structure and a panel. As shown in FIG.
A shadow mask structure in which a shadow mask 3 is held by a mask frame 7 is fixed to a panel 4 via a mask support spring 9 and a mask support pin 10 inside an envelope formed by the mask 4 and a funnel 5. , An internal magnetic shield 8 is provided. Mask frame 7
Is composed of a surface facing the side surface of the panel 4 and the flange portion 13 and has an L-shaped cross section.

[0005] The shadow mask 3 is formed on the phosphor screen 2 of the panel 4.
A large number of opening holes are formed on the surface facing the mask frame 7 and a mask skirt portion 11 fixed to the mask frame 7 is provided at a peripheral portion. The mask skirt portion 11 is formed by bending the periphery of the shadow mask 3 at the mask skirt bending portion 16.

[0006]

Generally, when deflecting and scanning an electron beam, in order to prevent the screen from being chipped, the perforated portion 12 of the shadow mask 3 (the apertures through which the electron beam can pass and which have a distribution of apertures) are formed. In this case, a so-called overscan is performed, which is performed to the outside of the range.
At this time, the flange portion 13 plays a role of cutting a part of the overscanned electron beam and preventing halation of the overscanned electron beam on the phosphor screen 2 due to reflected electrons.

[0007] However, it is difficult to completely prevent halation only by the flange portion 13. That is, as shown in FIG. 8, between the electron beam 21 passing through the end of the perforated portion 12 and the electron beam 23 passing through the outermost portion without being cut by the flange portion 13 (in FIG. The electron beam 22 passing through the shadow mask 3 passes without being cut by the flange portion 13.
Reflects on the inner surface of.

In particular, the electron beams 22 and 23 projecting on the inner surface of the mask skirt portion 11 (in FIG.
The electron beam passing through the area indicated by 5) collides with the inner surface of the mask skirt portion 11 and then, as secondary reflected electrons, wraps around the phosphor screen 2 to directly cause halation disturbance on the phosphor screen 2.

In order to prevent such halation,
It is desirable to make the first range 14 as small as possible. However, the size of the first range 14 is usually not constant due to fine adjustment of the size design of the perforated portion 12 or adjustment of the interval between the panel 4 and the shadow mask 3 during manufacturing. Considering the design margin and manufacturing variation,
For example, in a 29-inch color cathode ray tube, the size of the first range 14 is set to 7 to 15 [mm],
It was difficult to effectively reduce halation.

The present invention has been made in order to solve such a problem. In particular, reflected electrons of an overscan electron beam that strikes a mask skirt portion of a shadow mask enter a phosphor screen and generate image halation. An object of the present invention is to provide a color cathode ray tube which does not cause a problem of causing a decrease in contrast.

[0011]

According to the present invention, there is provided a color cathode ray tube including a shadow mask assembly including a shadow mask and a mask frame for holding the shadow mask in an envelope. A mask skirt formed by bending the mask skirt at a bent portion, and a large number of depressions are arranged in a portion of the inner surface of the mask skirt where the electron beam collides. ).

According to this structure, the electron beam incident on the mask skirt hits the inner surface of the depression and is reflected on the neck side, so that the reflection on the phosphor screen side is greatly reduced, and the beam halation on the phosphor screen can be reduced. .

Preferably, the depression has a semi-elliptical spherical shape or a long groove shape.

According to this configuration, a depression having an area equal to or larger than the hemispherical depression can be realized by a depression shallower than the hemispherical depression. Since it can be suppressed and the area of the flat portion between the adjacent depressions can be reduced, the reflection of the electron beam on the fluorescent screen side can be further reduced.

Further, it is preferable that the depressions are arranged in a direction in which a longitudinal direction thereof is substantially parallel to the bent portion of the mask skirt.

According to this configuration, the area of the flat portion between the adjacent depressions can be reduced, and furthermore, the reflection of the electron beam from the inner surface of the depression toward the phosphor screen can be effectively prevented. That is, since the cross section of the dent is semicircular in the direction perpendicular to the bent portion of the mask skirt, the electron beam is not reflected on the phosphor screen side.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A color cathode ray tube according to the present invention has the following features in a mask skirt portion of a shadow mask. The basic configuration is the same as that of the above-mentioned conventional color cathode ray tube, and the description is omitted.

FIG. 1 is a perspective view of a shadow mask used in the color cathode ray tube of the present invention. Shadow mask 3
The mask skirt includes a perforated portion 12 in which a number of openings (not shown) are arranged on a surface facing the phosphor screen of the panel, and a mask skirt portion 11 formed by being bent at a mask skirt bent portion 16. In the area of the inner surface of the section 11 where the overscan electron beam collides, a recess arrangement section 31 is provided.

FIG. 2 is an enlarged sectional view showing the shadow mask structure and the end of the panel. A large number of hemispherical depressions 41 are arranged in the depression arrangement portion 31 at substantially equal intervals, and the depressions 41 reflect an electron beam incident from the neck side (electron gun side) to the neck side as much as possible to form a fluorescent screen. This greatly reduces the beam reflection to the side and reduces the beam halation. That is, as shown in FIG.
Numerals 2 to 44 correspond to the inner surface of the hemispherical depression 41. Since the inner surface of the depression 41 is inclined toward the neck at the point of projection, the reflected beam also goes toward the neck.

On the other hand, in the conventional mask skirt portion, as shown in FIG. 9, an electron beam obliquely projected from the neck side enters the phosphor screen in a state close to specular reflection, and direct beam halation occurs. Was the cause.

Further, the electron beam which is to be incident on the upper side (neck side) of the recess arrangement portion 31 is cut off by the flange portion 13 of the mask frame 7 and does not cause halation. Mask skirt bent part 1
The electron beam projecting very close to 6 does not directly cause beam halation since it is cut off by a dead area having no opening between the skirt bent portion 16 and the end of the perforated portion 12.

The recess arrangement portion 31 may be formed by arranging a large number of hemispherical recesses 41 at regular intervals as shown in FIG.

Next, the preferred shape and size of the depression will be described. As shown in FIG.
Since the electron beam 45 that collides with the intermediate portion 46 is reflected on the phosphor screen side similarly to the conventional shadow mask, reducing the area of the intermediate portion 46 as much as possible is a key to reducing the beam halation. Become. Therefore, depression 4
It is desirable to make the diameter of one as large as possible.

By the way, in order to reflect as much as possible the electron beam that has hit the mask skirt portion 11 in the neck direction, it is necessary to form a hemispherical recess having a depth of half the diameter of the recess 41. . Such a depression can be formed by etching, for example, as described in JP-A-4-47649.

However, the shadow mask has a thickness of 0.25.
Since a thin plate of about [mm] is formed, if the thin plate is etched too deeply, there is a problem that the strength of the shadow mask is rapidly reduced. For example,
If a concave depression having a diameter larger than the thickness of the shadow mask is formed, the minimum thickness of the shadow mask at that portion is reduced to half or less of the original thickness, so that the strength of the shadow mask is maintained. It is desirable to avoid such processing.

Therefore, as shown in FIG. 5, a semi-elliptical spherical shape (a shape obtained by dividing a rugby ball vertically) 6
1 are arranged in a direction parallel to the mask skirt bent portion 16, the depth of the deepest portion of the depression 61 is の of the minor axis of the ellipse.
Therefore, the plate thickness at the deepest part of the depression 61 is not made too thin. That is, when the minor axis of the ellipse is the same as the diameter of the hemispherical depression 41, a depression having a larger area can be provided while maintaining the same maximum depth as the hemispherical depression 41. And the shadow mask has sufficient strength.

Next, as an example of a more preferable shape of the depression, FIG. 6 shows a configuration in which semi-cylindrical depressions 71 are arranged so that the longitudinal direction thereof is parallel to the mask skirt bent portion 16.

A hemispherical recess 41 as shown in FIG.
Is arranged, the electron beam incident on the center line 51 of the depression 41 can be reflected in the neck direction, but a part of the electron beam incident on the other area is reflected on the phosphor screen side. Therefore, it is inevitable that some beam halation occurs. This is because the cross section is a circular arc shape (cross section AA ′ in FIG. 4) that is shallower than a semicircle, and the bottom surface of the depression is also inclined in a direction parallel to the mask skirt bent portion 16. It is.

Therefore, as shown in FIG. 6, an elongated semi-cylindrical recess 71 is formed in a direction perpendicular to the electron beam incident direction, that is, in a direction parallel to the mask skirt bent portion 16.
, The beam halation can be effectively reduced. This is due to the fact that in any direction perpendicular to the mask skirt bent portion 16
(AA ′ cross section in FIG. 6) is semicircular, and the bottom surface of the recess 71 is not inclined in the direction parallel to the mask skirt bent portion 16, so that the electron beam to the phosphor screen side This is because no reflection occurs.

On the other hand, for example, when the longitudinal direction of the dent is arranged at right angles to the mask skirt bent portion 16, most of the electron beam reflected on the inner surface of the dent will proceed to the fluorescent screen side as it is. Therefore, the same effect cannot be obtained.

Although the embodiment in which the recesses having the same shape and the same size are arranged at equal intervals has been described above, it is possible to further reduce the area of the intermediate portion by providing fine recesses between the recesses. It is effective.

[0032]

As described above, in the color cathode ray tube of the present invention, by providing a large number of depressions in the mask skirt portion of the shadow mask, the reflected electrons of the overscanning electron beam impinging on the mask skirt portion emit fluorescent light. It is possible to provide a color cathode ray tube which prevents the occurrence of image halation and does not cause a decrease in contrast as image halation.

[Brief description of the drawings]

FIG. 1 is a perspective view of a shadow mask used in a color cathode ray tube of the present invention.

FIG. 2 is an enlarged sectional view of an end portion of the same shadow mask structure and panel.

FIG. 3 is a partially enlarged sectional view of a mask skirt portion of the shadow mask.

FIG. 4 is a partially enlarged plan view of the mask skirt portion.

FIG. 5 is a partially enlarged plan view of the mask skirt.

FIG. 6 is a partially enlarged plan view of the mask skirt portion.

FIG. 7 is a partially cutaway perspective view of a conventional color cathode ray tube.

FIG. 8 is an enlarged cross-sectional view of a conventional shadow mask structure and panel of a color cathode ray tube.

FIG. 9 is a partially enlarged cross-sectional view of a mask skirt portion of a conventional shadow mask.

[Explanation of symbols]

 Reference Signs List 3 shadow mask 7 mask frame 11 mask skirt part 13 flange part 16 mask skirt bent part 31 depression arrangement part 41, 61, 71 depression

Claims (3)

[Claims] 1. A color cathode ray tube including a shadow mask structure including a shadow mask and a mask frame holding the shadow mask in an envelope, wherein the shadow mask is formed by being bent at a mask skirt bending portion. A color cathode ray tube having a mask skirt portion, wherein a number of depressions are arranged in a portion of the inner surface of the mask skirt where an electron beam projects. 2. The color cathode ray tube according to claim 1, wherein the depression has a semi-elliptical spherical shape or a long groove shape. 3. The color cathode ray tube according to claim 2, wherein the depressions are arranged in a direction in which a longitudinal direction thereof is substantially parallel to the bent portion of the mask skirt.