JP2002313254A - Color cathode-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color cathode-ray tube, in which deterioration of color purity of the display image is reduced and improvement in image quality can be made. SOLUTION: The shadow mask 12 is formed in a gently-sloping dome shape and comprises a mask main face 20 of nearly rectangular shape having an electron beam passing hole 19 and a skirt part 18 that extends from the periphery of the effective part of the mask and bent in a direction nearly orthogonal to the mask main face at right angles. The mask main face comprises an effective region 20a of nearly rectangular shape, in which the electron passing holes 19 are formed, a non-hole region 20b of nearly rectangular shape that is positioned around the effective region, and a bead part 22 provided in the non- hole region. The bead part has an outer periphery bead 24, that extends throughout the circumference of the outer periphery of the non-hole region and at least an inner side bead 26, that is provided inside the outer bead and in the non-hole region, and the outer bead and the inner side bead protrude more toward the electron gun side rather than to the extended part of the effective region.

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 having a press-formed shadow mask.

[0002]

2. Description of the Related Art In general, an in-line type color cathode ray tube comprises a glass panel having a substantially rectangular effective portion,
A vacuum envelope comprising a glass funnel connected to the panel and a cylindrical glass neck connected to a small diameter portion of the funnel is provided. On the inner surface of the effective portion of the panel, a phosphor screen including a three-color phosphor layer in a dot shape or a stripe shape emitting blue, green, and red light and a black light-shielding layer is formed. Further, a shadow mask having a large number of electron beam passage holes is arranged in the vacuum envelope so as to face the phosphor screen. Further, in the neck, an in-line type electron gun that emits three electron beams arranged in a line on the same axis is arranged, and a deflection yoke is mounted from the outer periphery of the neck to the outer peripheral surface of the funnel. ing.

In the color cathode ray tube having the above structure, three electron beams emitted from an electron gun are horizontally and vertically deflected by a horizontal and vertical deflection magnetic field generated by a deflection yoke, and a phosphor screen is irradiated with a high frequency wave via a shadow mask. And a vertical scan at a low frequency to display a color image. At this time, the electron beam emitted from the electron gun strikes the phosphor screen at a certain incident angle and undergoes color selection on a shadow mask according to the incident angle. Therefore, the three electron beams correspond one-to-one to each of the red, blue, and green colors of the phosphor screen.

In the above color cathode ray tube, the shadow mask is made of an invar material (iron-nickel alloy) having a thickness of 0.08 to 0.3 mm and has a flat surface in which electron beam passage holes are formed in advance. The mask base material is formed into a desired shape by press molding. Pressed shadow masks have a radius of curvature of approximately 500
An approximately rectangular mask main surface formed into a gentle dome shape of about 2000 mm, and a skirt portion extending to the electron gun side substantially at right angles from the periphery of the mask main surface;
A large number of electron beam passage holes are provided in the main surface of the mask. In addition, a bead is formed over the entire periphery at the peripheral portion of the mask main surface.

[0005] Such a shadow mask is welded and fixed to a rectangular mask frame via a skirt portion. Usually, the mask frame is formed of an iron material. The shadow mask is detachably supported on the panel by engaging an elastic support attached to the mask frame with stud pins projecting from the panel.

[0006]

In a color cathode ray tube, the diameter of an electron beam is about 130 μm, and the diameter of an electron beam passage hole is about 110 μm. for that reason,
When the electron beam impinges on the phosphor screen through the through hole of the shadow mask, the electron beam impinges on the shadow mask, causing the shadow mask to generate heat.

Accordingly, heat is also transmitted to the mask frame fixed to the shadow mask, and the mask frame also generates heat. At this time, the coefficient of thermal expansion of the mask frame is larger than the coefficient of thermal expansion of the shadow mask, and the amount of thermal expansion is larger in the mask frame. Therefore, when the shadow mask and the mask frame are heated and thermally expanded, the skirt portion of the shadow mask welded to the mask frame is pulled outward by the mask k frame.

In this case, the vicinity of the horizontal axis end and the vicinity of the vertical axis end of the main surface of the shadow mask are deformed so as to protrude toward the electron gun. As a result, the mask main surface loses the target curved surface shape, and it becomes difficult to accurately select the color of the electron beam by the shadow mask. Therefore, the color purity of the displayed image is degraded, and the image quality is lowered.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to reduce the displacement of a mask main surface due to the thermal expansion of a mask frame and to improve the image quality of a color cathode ray. To provide tubes.

[0010]

In order to achieve the above object, a color cathode ray tube according to the present invention comprises a panel having an inner surface provided with a phosphor screen, and a panel arranged opposite to the phosphor screen,
An electron gun that emits an electron beam toward the phosphor screen, a shadow mask that is disposed to face the phosphor screen and has a large number of electron beam passage holes through which the electron beams pass;
The shadow mask is formed by press molding, and has a substantially rectangular mask main surface formed on a curved surface, and a skirt connected to the periphery of the mask main surface and bent substantially at right angles to the electron gun side with respect to the mask main surface. The mask main surface has a substantially rectangular effective area in which the electron beam passage holes are formed, and a substantially rectangular frame shape which is located around the effective area and does not have the electron beam passage holes. And a bead portion provided in the non-porous region, wherein the bead portion extends over substantially the entire outer peripheral edge of the non-porous region, and an inside of the outer peripheral bead. And at least one inner bead provided side by side with the outer peripheral bead, wherein the outer bead and the inner bead project toward the electron gun with respect to an extension surface of the effective area. .

Further, according to the color cathode ray tube according to the present invention, the inner bead is provided at least closer to the periphery of the effective area than to the middle between the outer bead and the periphery of the effective area. It is characterized by containing one bead.

Further, according to the color cathode ray tube according to the present invention, the non-porous area including the outer bead and the inner bead has a plurality of steps of step-shaped cross sections which become lower from the effective area toward the skirt. It is characterized by having.

According to the color cathode ray tube configured as described above, even if the skirt portion of the shadow mask is pulled outward due to the thermal expansion of the mask frame, the tensile displacement of the skirt portion is reduced by the outer bead and the inner bead. Absorption and displacement of the mask main surface can be reduced. As a result, it is possible to obtain a color cathode ray tube with reduced color purity deterioration of a display image and improved image quality.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a color cathode ray tube according to an embodiment of the present invention will be described in detail with reference to the drawings. As shown in FIG. 1, the color cathode ray tube includes a vacuum envelope 10, which has a skirt portion 2 around its periphery.
And a substantially rectangular panel 1, a funnel 4 connected to a skirt portion of the panel, and a cylindrical neck 3 connected to a small diameter portion of the funnel. On the inner surface of the panel 1, a plurality of phosphor layers each emitting red, blue, and green light, and a phosphor screen 6 including a black light-shielding layer are formed. A deflection yoke 7 having horizontal and vertical deflection coils is mounted on the outer periphery of the neck 3 to the funnel 4.

In the neck 3, a center beam 8 passing on the same horizontal plane toward the phosphor of the phosphor screen 6 is provided.
An electron gun 9 that emits three electron beams arranged in a row, including G and a pair of side beams 8R and 8B, is arranged.
Since the trajectory of the electron beam changes due to the influence of the magnetic field, the inside of the joint between the panel 1 and the funnel 4
An inner shield 11 for shielding an external magnetic field is provided.

In the vacuum envelope 10, a shadow mask 12 is provided facing the phosphor screen 6 functioning as a phosphor screen.
Are mounted on a rectangular mask frame 14. As will be described later, the shadow mask 12 has a mask main surface 20 in which a large number of electron beam passage holes for color identification are formed, and a skirt portion extending from the periphery of the mask main surface and fixed to the mask frame. 18 and
And is formed by press molding. The shadow mask 12 is detachably supported on the panel by connecting an elastic support 15 fixed to the mask frame 14 to a stud pin 17 protruding from the inner surface of the skirt portion 2 of the panel 1. ing.

The vacuum envelope 10 including the panel 1 is
It has a tube axis Z extending through the center of the panel and the electron gun 9, a long axis (horizontal axis) X extending perpendicular to the tube axis, and a short axis (vertical axis) Y extending perpendicular to the tube axis and the long axis. are doing.

In the color cathode ray tube configured as described above, the three electron beams 8B and 8 emitted from the electron gun 9 are used.
G and 8R are deflected by a deflection yoke 7 mounted outside the funnel 4, and the phosphor screen 6 is horizontally and vertically scanned through an electron beam passage hole of a shadow mask 12, thereby displaying a color image.

As shown in FIGS. 2 and 3, the shadow mask 12 has a substantially rectangular mask main surface 20 formed in a gentle dome shape, and a skirt portion 18 extending substantially perpendicular to the mask main surface. And are integrally provided. The mask main surface 20 has a substantially rectangular effective area 20a in which a large number of electron beam passage holes 19 are formed at a predetermined arrangement pitch, and has an electron beam passage hole which is located around the effective portion. It has a rectangular frame-shaped non-porous region 20b and a bead portion 22 provided in the non-porous region. The bead portion 22 is necessary to press the mask base material when the mask main surface 20 is overhang-formed in the shadow mask press molding.

The shadow mask 12 is arranged inside the mask frame 14 and, for example, a skirt 18
Each diagonal portion 18c, the central portion in the longitudinal direction of each long side portion 18a,
The skirt portion is welded to the mask frame 14 at a height of 1 to 10 mm from the end of the skirt portion on the side of the electron gun at eight points in the center in the longitudinal direction of each short side portion 18b. Shadow mask 12
Is formed of, for example, an invar material, and the mask frame 14 is formed of, for example, an iron material.

The bead portion 22 has an outer peripheral edge of the non-perforated region 20b, that is, an outer peripheral bead 24 extending over substantially the entire outer peripheral edge of the mask main surface 20, and a position beside the outer peripheral bead inside the outer peripheral bead. And an inner bead 26 formed. And the outer bead 24 and the inner bead 26
Each protrudes toward the electron gun 9 from the extended surface of the effective area 20a of the mask main surface 20.

Each of the inner beads 26 has a pair of long-side beads 26 extending along the long side of the mask main surface 20.
a and a pair of short side beads 26b each extending along the short side of the mask main surface. Each long side bead 26a and short side bead 26b are provided in the peripheral part of the mask main surface 20, excluding the corners. That is,
Each long side bead 26a is formed in a range of about 80% around the center of the long side of the mask main surface 20 in the longitudinal direction. Similarly, each short side bead 26b is formed on the mask main surface 20b.
Are formed in a range of about 80% around the center of the short side in the longitudinal direction.

As shown in FIG. 4, each long side bead 26a has a radius of curvature larger than the radius of curvature along the long side of the mask main surface 20. Similarly, each short side bead 26 b also has a radius of curvature larger than the radius of curvature along the short side of the mask main surface 20. Further, the inner bead 26 is provided closer to the periphery of the effective area than the middle between the periphery of the mask main surface 20 and the periphery of the effective area 20a.

By providing the outer bead 24 and the inner bead 26 as shown in FIGS. 2, 3 and 5, the mask including the outer bead 24 and the inner bead 26 at each side of the mask main surface 20. The hole region 20b has a plurality of stepped cross-sections that gradually decrease from the effective region 20a toward the skirt portion 18. Also, whether the non-porous area 20b is the same as the extension surface 30 of the surface of the effective area 20a,
Alternatively, it is formed so as to be located closer to the electron gun than this extended surface. Further, both the outer bead 24 and the inner bead 26 are formed such that the apex angle is about 45 degrees or more, preferably 90 degrees or more.

In the sectional shape of the present embodiment shown in FIG. 5, the periphery of the non-perforated region 20b is located on the extension surface 30 of the surface of the effective region 20a. However, as shown in FIG. 6, the cross-sectional shape may be such that the periphery of the non-porous region 20b is the lowest.

According to the color cathode ray tube configured as described above, the shadow mask 12 includes the bead portion 22 provided on the peripheral portion thereof, and the bead portion includes the outer bead 24 and the inner bead 26. It is configured to have. Therefore, even when the skirt portion 18 of the shadow mask 12 is pulled outward due to the thermal expansion of the mask frame 14, the displacement of the mask main surface 20 can be reduced. Therefore, it is possible to obtain a color cathode ray tube with reduced color purity deterioration of a displayed image and improved image quality.

For example, the shadow mask 1 having the above configuration
2 is applied to a 17-inch in-line type color cathode ray tube, the effective area of the shadow mask usually has a length of about 315 mm in the major axis X direction and a length of 235 in the minor axis Y direction.
mm, and the mask main surface 20a including the bead portion 22 has a length in the major axis X direction of about 330 mm,
It has a substantially rectangular shape with a length in the short axis Y direction of about 250 mm.

Then, the electron beam is applied to the shadow mask 12.
By colliding, the shadow mask 12 made of, for example, Invar material is heated and generates heat. Accordingly, heat is also transmitted to the mask frame 14 to which the shadow mask 12 is fixed by welding, and the mask frame also generates heat. Thermal expansion coefficient αm of shadow mask 12 and mask frame 14
The relationship with the thermal expansion coefficient αf is αm <αf, and the thermal expansion of the mask frame 14 is larger. Therefore, due to the thermal expansion of the mask frame 14, the skirt portion 18 of the shadow mask 12 becomes
At this time, the long-axis end and the short-axis end of the mask main surface 20 receive a force displaced toward the electron gun.

However, the shadow mask 12
Has a bead portion 22 formed in two steps, so that the bead portion 22 can absorb the tensile displacement of the skirt portion 18 and reduce the curved surface displacement of the mask main surface 20.

FIG. 7 shows the result of comparing the displacement of the mask main surface when the mask frame thermally expands with respect to the shadow mask according to the present embodiment and another shadow mask. Here, as a comparative example 1, a shadow mask having only an outer bead formed over the entire outer peripheral edge of the mask main surface, and as a comparative example 2, a shadow mask having an outer bead and an inner bead. Is shown. In Comparative Example 2, the outer bead protrudes toward the electron gun, the inner bead protrudes from the mask main surface toward the phosphor screen, and each bead has a vertex angle smaller than 45 degrees.

As can be seen from FIG. 7, in Comparative Example 1, the bead could not sufficiently absorb the tensile displacement of the skirt portion, and the long axis end and the short axis end (not shown) of the main surface of the mask were exposed to the electron gun. Displaces to the side. In Comparative Example 2,
In spite of having the inner bead, the bead becomes too strong and cannot sufficiently absorb the tensile displacement of the skirt portion. Therefore, in Comparative Example 2, as in Comparative Example 1, the long axis end and the not-shown short axis end of the mask main surface are displaced toward the electron gun.

On the other hand, according to the present embodiment, by providing the above-described bead structure, the tensile displacement of the skirt portion can be sufficiently absorbed, and the mask main surface 20 can be compared with Comparative Examples 1 and 2. Is reduced by about half. Thereby, the deterioration of the color purity of the displayed image was reduced, and the improvement of the image quality was recognized.

Further, as described above, according to the present embodiment, both the outer bead 24 and the inner bead 26 of the bead portion 22 project from the mask main surface 20 toward the electron gun, and these beads are Non-porous area 2 formed
0b is the same as the extended surface of the surface of the effective area 20a, or is located closer to the electron gun than this extended surface. Therefore, at the time of press molding, the continuity of the mask main surface 20 is not impaired by the bead portion, and the shadow mask 12 can be accurately formed into a target shape.

The present invention is not limited to the above-described embodiment, but can be variously modified within the scope of the present invention. For example, in the above-described embodiment, one inner bead is used, but two or more inner beads may be provided between each side of the mask main surface effective area and the outer peripheral bead. Further, the inner bead may be formed continuously over the entire circumference of the mask main surface.

However, at the diagonal portion of the shadow mask, the influence of the spread of the skirt on the mask main surface is smaller than near the long axis end and near the short axis end. Further, when a plurality of step-like structures are used for the beads near the diagonal during press molding of the shadow mask, the diameter of the electron beam passage hole provided at the outermost diagonal of the shadow mask may increase and the diameter may increase. . Therefore, if there is no such extension of the electron beam passage hole, it is desirable to use a plurality of stepped bead structures also on the periphery of the diagonal portion of the mask main surface.

[0036]

As described in detail above, according to the present invention,
An outer peripheral bead and an inner bead are provided side by side on the peripheral edge of the shadow mask main surface to form a multi-step stair structure, thereby reducing displacement of the mask main surface due to pulling of the skirt portion of the shadow mask due to thermal expansion of the mask frame. Thus, a color cathode ray tube with improved image quality can be provided.

[Brief description of the drawings]

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

FIG. 2 is a perspective view showing a shadow mask in the color cathode ray tube.

FIG. 3 is an exploded perspective view showing a part of the shadow mask and the mask frame.

FIG. 4 is a cross-sectional view taken along a long side of a mask main surface of the shadow mask.

FIG. 5 is a sectional view showing a bead portion of the shadow mask.

FIG. 6 is a sectional view showing a modified example of a bead portion of the shadow mask.

FIG. 7 is a diagram showing a state of displacement of a mask main surface when a skirt portion is pulled by thermal expansion of a mask frame in a shadow mask according to the present embodiment and a shadow mask according to a comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Panel 3 ... Neck 4 ... Funnel 6 ... Phosphor screen 9 ... Electron gun 10 ... Vacuum envelope 12 ... Shadow mask 18 ... Skirt part 18a ... Long side skirt part 18b ... Short side skirt part 19 ... Electron beam Passing hole 20: Mask main surface 20a: Effective area 20b: Non-porous area 22: Bead 24: Outer peripheral bead 26: Inner bead 26a: Long side bead 26b: Short side bead

Claims (6)

[Claims] 1. A panel having a fluorescent screen provided on an inner surface thereof, an electron gun disposed to face the fluorescent screen and emitting an electron beam toward the fluorescent screen, and disposed to face the fluorescent screen. A shadow mask having a large number of electron beam passage holes through which the electron beams pass, wherein the shadow mask is formed by press molding, and has a substantially rectangular mask main surface formed on a curved surface; and a mask main surface. A skirt portion which is connected to the periphery of the mask and bent substantially at right angles to the electron gun side with respect to the mask main surface, and the mask main surface has a substantially rectangular effective area in which the electron beam passage holes are formed, A substantially rectangular frame-shaped non-porous area which is located around the effective area and does not have the electron beam passage hole, and a bead provided in the non-porous area; Almost the entire circumference of An outer peripheral bead, and at least one inner bead provided alongside the outer peripheral bead inside the outer peripheral bead, wherein the outer bead and the inner bead are larger than an extension surface of the effective area. A color cathode ray tube protruding toward the electron gun. 2. The color cathode ray tube according to claim 1, wherein the inner bead is provided except for a corner of the main surface of the mask. 3. The internal bead includes at least one bead provided closer to a peripheral edge of the effective area than an intermediate point between the outer peripheral bead and the peripheral edge of the effective area. The color cathode ray tube according to claim 1 or 2, wherein 4. The color cathode ray tube according to claim 1, wherein said inner bead has a radius of curvature larger than a radius of curvature of said mask main surface. 5. The non-perforated region including the outer bead and the inner bead has a plurality of step-shaped cross sections that become lower from the effective region toward the skirt portion. 5. The color cathode ray tube according to any one of 4. 6. The color cathode ray tube according to claim 1, wherein the outer bead and the inner bead each have an apex angle of about 45 degrees or more.