JP2002298752A - Shadow mask structure and color cathode-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color cathode-ray tube in which the drift phenomenon according to the conventional technique is suppressed, such that a tension 71 pulling to the four inside corners is applied to the shadow mask 43 originating from a thread winding deformation of a mask frame 41, that the shadow mask 43 assumes a cylindrical surface at room temperature but its central part 43A is willing to become a plane owing to the tension 71 in association with a temperature rise, and that the Q-value of the central part 43A enlarges to cause dislocation of an electron beam and phosphor to result in a drop of the color purity, as called a drift. SOLUTION: The top face of the longer edge member 11A of the mask frame and the top face of a mask support 12 are both formed in circular arcs, and the radius of curvature R1 of the top end face of the mask support 12 is made greater than the radius of curvature R2 of the top end face of the longer edge member 11A of the mask frame, and the top end face of the mask support 12 is fixed in such a way as protruding from the top end face of the longer edge member 11A of the mask frame.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a color CRT shadow mask structure and a color CRT mounting the same.

[0002]

2. Description of the Related Art In recent years, color CRTs having a flat glass panel surface have been increasing and are called flat color CRTs. However, even in a flat color cathode ray tube, the glass panel has a cylindrical surface with a thin center and a thick periphery.
The first reason is that if the thickness of the glass panel is uniform, the pressure resistance of the glass bulb is low and there is a risk of implosion.
The second is that if the thickness of the glass panel is uniform, the image looks concave and unnatural.

In order to keep the distance between the shadow mask and the inner surface of the glass panel, which is called the Q value, constant irrespective of the location, the shadow mask is also formed on a cylindrical surface having substantially the same radius as the inner surface of the glass panel. In particular, the shadow mask of a display color cathode ray tube is made of a low thermal expansion coefficient alloy such as an invar alloy in order to prevent a decrease in color purity due to thermal expansion.

While an invar alloy is suitable for a shadow mask, an invar alloy is not suitable for a mask frame because of its cost, strength and elasticity, and stainless steel is suitable. However, if an Invar alloy shadow mask is directly fixed to a stainless steel mask frame, the shadow mask is deformed due to a difference in thermal expansion coefficient, so that it is inconvenient.

In order to solve this problem, the present applicant has filed an invention in which an invar alloy mask support is attached to the long side of a stainless steel mask frame and a shadow mask is fixed to the mask support (Japanese Patent Application Laid-Open No. 2000-231888). Gazette). Hereinafter, this is referred to as a conventional shadow mask structure.

FIG. 4 shows an example 4 of a conventional shadow mask structure.
0 (JP-A-2000-231888, FIG. 5). This shadow mask structure 40 has a pair of long sides 41.
A and a rectangular frame-shaped mask frame 41 composed of a pair of short sides 41B. A mask support 42 is provided on the long side 41A of the mask frame, and the long side of the shadow mask 43 is fixed to the mask support upper end surface 42A. I have. Since the mask support 42 and the shadow mask 43 are both Invar alloys, they have the same coefficient of thermal expansion, so that deformation of the shadow mask 43 can be avoided. On the other hand, since the mask frame 41 is made of 13 chrome stainless steel, it has good strength and elasticity and is inexpensive.

[0007]

The conventional shadow mask structure of the present applicant has no problem in the basic structure,
It turned out that the following problems still exist. It is an object of the present invention to solve these problems and to make a conventional shadow mask structure more complete. Another object of the present invention is to realize a color cathode ray tube excellent in color purity without drift by mounting such a shadow mask structure.

When a color CRT is used, more than half of the accelerated electron beam collides with the shadow mask 43. Therefore, the temperature of the shadow mask structure 40 rises to about 60 ° C. The thermal expansion coefficient of Invar alloy is about 1.2 ppm
/ ° C, the coefficient of thermal expansion of 13 chrome stainless steel is about 12 pp
Because of m / ° C., the thermal expansion of the mask frame 41 is about 10 times that of the shadow mask 43. Therefore, the shapes of the mask frame 41 and the shadow mask 43 change as described below.

FIG. 5 is a plan view of a conventional shadow mask structure 40 at normal temperature (about 25 ° C.). As shown, the mask frame 41 is rectangular at room temperature. However, when the temperature reaches about 60 ° C., a thread winding shape as shown in FIG. FIG. 6 is exaggerated for the sake of explanation. FIG. 7 shows only the shadow mask 43 extracted from FIG.
Due to the pincushion deformation of the mask frame 41, tensions 71 are applied to the four corners of the shadow mask 43 as shown in FIG. In the conventional shadow mask structure 40, as shown in FIG. 4, the upper end face 41A of the mask frame has a straight line and the upper end face 42A of the mask support has an arc shape.
The amount of protrusion of the mask support 42 from the center is large at the center of the long side 41A of the mask frame and small at both ends. For this reason, the pincushion deformation of the mask frame 41 is easily transmitted to both ends of the shadow mask 43, so that the tension 71 for pulling the shadow mask 43 to the four corners is strong.

At normal temperature, the shadow mask 43 has a cylindrical surface, but when the temperature rises, the tension 71 pulls the shadow mask 43 to the four corners, so that the central portion 43A (shaded portion) of the shadow mask is deformed from the cylindrical surface to approach a flat surface. . As a result, the distance (Q value) of the center portion 43A of the shadow mask from the glass panel becomes large, so that the positions of the electron beam and the phosphor are shifted and the color purity is reduced. Immediately after the use of the color cathode ray tube, the color purity is good because the temperature of the mask frame 41 has not risen, but the color purity gradually decreases as the temperature of the mask frame 41 gradually increases as time passes. This phenomenon is called drift and is not desirable. The present invention provides a color cathode ray tube which suppresses the occurrence of the drift.

[0011]

In order to solve the problems of the conventional shadow mask structure, in the shadow mask structure of the present invention, both the upper end face of the longer side of the mask frame and the upper end face of the mask support are made substantially arcuate, and the mask support is formed. The radius of curvature of the upper end surface of the body was set to be equal to or greater than the radius of curvature of the upper end surface of the long side of the mask frame, and the upper end surface of the mask support was fixed so as to protrude from the upper end surface of the long side of the mask frame. Due to the difference in the radius of curvature between the upper end face of the longer side of the mask frame and the upper end face of the mask support, the protruding amount of the mask support is larger at both ends of the longer side of the mask frame than at the center of the longer side of the mask frame.

When the temperature rises and the mask frame is deformed into a pincushion shape, the amount of protrusion of the mask support is large at both ends of the long side of the mask frame. Deform. This alleviates the increase in tension that pulls the shadow mask to the four corners of the mask frame, and reduces the Q at the center of the shadow mask.
The change in the value is reduced, and the decrease in color purity is not visually recognized.

According to a first aspect of the present invention, there is provided a substantially rectangular frame-shaped mask frame having a pair of long sides and a pair of short sides, and a mask support is provided on the long side of the mask frame. In a shadow mask structure in which the long side of the shadow mask is fixed to the upper end face and the thermal expansion coefficients of the mask support and the shadow mask are substantially equal, the upper end face of the longer side of the mask frame and the upper end face of the mask support are substantially arc-shaped. Wherein the radius of curvature of the upper end surface of the mask support is equal to or greater than the radius of curvature of the upper end surface of the long side of the mask frame.
A shadow mask structure, wherein an upper end surface of the mask support protrudes from an upper end surface of a long side of the mask frame and is fixed.

According to a second aspect of the present invention, in the shadow mask structure of the first aspect, the amount of protrusion of the upper end surface of the mask support from the upper end surface of the long side of the mask frame is zero at the center of the long side of the mask frame. 0.2-1m
m, and is greater than or equal to a central protrusion amount at both ends of the long side of the mask frame.

The invention according to claim 3 is the first or second invention.
The shadow mask structure according to claim 1, wherein the mask frame is made of 13 chrome stainless steel, and the shadow mask and the mask support are made of Invar alloy.

The invention described in claim 4 is the first invention.
A color cathode ray tube equipped with any one of the shadow mask structures according to Item 3.

By mounting the shadow mask structure according to any one of claims 1 to 3, the color cathode ray tube having no drift because the Q value and the color purity do not substantially change even when the temperature of the shadow mask structure increases. realizable.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a shadow mask structure according to the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of Embodiment 10 of the shadow mask structure of the present invention. Example 10 of the shadow mask structure of the present invention is for a 19-inch flat color cathode-ray tube, and its approximate dimensions are 360 mm long and 2 short sides.
70 mm, height 40 mm. As shown in the figure, a mask support 12 has its central portion 12A fixed to the long side 11A of the mask frame 11 having a substantially rectangular frame shape by welding.
The longer side 13A of the substantially rectangular shadow mask 13 is seam-welded to the upper end surface of the mask support 12.
In the figure, in order to make the internal structure of the mask frame 11 easy to see, the shadow mask 13 has a long side 13A and a short side 1A.
3B, only the perforated portion boundary 13C is indicated by a two-dot chain line. The long side 11A of the mask frame 11 is 3 mm in thickness, the short side 11B is 13 chrome stainless steel having a thickness of 2.2 mm, the mask support 12 is an invar alloy having a thickness of 3 mm, the shadow mask 1
3 is an Invar alloy having a thickness of 100 μm.

FIG. 2 is a three-view drawing of Embodiment 10 of the shadow mask structure of the present invention. Mask support 1 as shown
(2) The upper end surface has an average radius of curvature R1, a mask frame long side 11
The upper end surface of A has a substantially arc shape with an average radius of curvature R2. Here, radius R1> radius R2, specifically R1 = 7000
8000 mm, R2 = 2250 to 2400 mm.
The amount of protrusion of the upper end face of the mask support 12 is L1 at the center of the long side 11A of the mask frame,
L2 at both ends of 1A. Specifically, L1 = 0.2
１1 mm, L2 = L1 + (3 to 8 mm). L1,
Since the appropriate length of L2 varies depending on the strengths of the mask frame 11 and the shadow mask 13, it is desirable to determine the length by experiment.

FIGS. 1 and 2 show the shape of the shadow mask structure 10 of the present invention at normal temperature. FIG. 3 shows the shape of the shadow mask structure 10 of the present invention when the temperature rises next. Show. Like the conventional shadow mask structure 40,
Due to the temperature rise, the mask frame 11 is deformed into a thread winding shape. At this time, A near the center of the long side 11A of the mask frame
As shown in the cross-sectional view taken along the line -A ', the shape of the mask support 12 does not change from that at normal temperature. However, mask frame long side 11
In the vicinity of both ends A, as shown in the BB 'cross-sectional view, the mask support 12 is elastically deformed inward by an amount corresponding to the extension of the vertical length of the short side 11B of the mask frame (arrow in the figure). This alleviates the increase in tension that pulls the shadow mask 13 to the four corners of the mask frame 11, reduces the change in the Q value at the central portion of the shadow mask 13, and makes it difficult to visually recognize a decrease in color purity. Since the elastic deformation of the mask support 12 returns to its original state when the temperature drops, problems such as the sag of the shadow mask 13 do not occur.

[0021]

In order to solve the problems of the conventional shadow mask structure, in the shadow mask structure of the present invention, both the upper end face of the longer side of the mask frame and the upper end face of the mask support are substantially arcuate, and the upper end face of the mask support is formed. The radius of curvature was set to be equal to or larger than the radius of curvature of the upper end face of the long side of the mask frame, and the upper end face of the mask support was fixed so as to protrude from the upper end face of the long side of the mask frame. Due to the difference in the radius of curvature between the upper end face of the mask frame long side and the upper end face of the mask support, the protrusion amount of the mask support at both ends of the long side of the mask frame is larger than at the center of the long side of the mask frame.

When the temperature rises and the mask frame is deformed into a pincushion shape, the protruding amount of the mask support is large at both ends of the long side of the mask frame. Deform. This alleviates the increase in tension that pulls the shadow mask to the four corners of the mask frame, and reduces the Q at the center of the shadow mask.
The change in the value is reduced, and the decrease in color purity is not visually recognized.

[Brief description of the drawings]

FIG. 1 shows a shadow mask structure according to a tenth embodiment of the present invention.
Perspective view of

FIG. 2 shows Embodiment 10 of the shadow mask structure of the present invention.
View of the room at normal temperature (about 25 ℃)

FIG. 3 shows a shadow mask structure according to a tenth embodiment of the present invention.
Three views at about 60 ℃

FIG. 4 is a perspective view of an example 40 of a conventional shadow mask structure.

FIG. 5 shows a conventional shadow mask structure 40 at room temperature (about 2 ° C.).
5 ° C)

FIG. 6 is a plan view of a conventional shadow mask structure 40 at about 60 ° C.

FIG. 7 is a plan view of a shadow mask 43 of a conventional shadow mask structure 40 at about 60 ° C.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Shadow mask structure 11 Mask frame 11A Mask frame long side 11B Mask frame short side 12 Mask support 13 Shadow mask 13A Shadow mask long side 40 Shadow mask structure 41 Mask frame 41A Mask frame long side 41B Mask frame short side 42 Mask support 42A Mask support upper end surface 43 Shadow mask 43A Shadow mask central part 71 Tension

Claims (4)

[Claims] 1. A substantially rectangular frame-shaped mask frame comprising a pair of long sides and a pair of short sides, a mask support is provided on a long side of the mask frame, and a shadow mask length is provided on an upper end face of the mask support. In a shadow mask assembly having fixed sides and substantially equal thermal expansion coefficients of the mask support and the shadow mask, the upper end face of the longer side of the mask frame and the upper end face of the mask support are substantially arc-shaped, and A shadow mask, wherein a radius of curvature of an upper end surface of the body is equal to or larger than a radius of curvature of an upper end surface of the long side of the mask frame, and an upper end surface of the mask support protrudes from the upper end surface of the long side of the mask frame and is fixed. Structure. 2. The shadow mask structure according to claim 1, wherein the amount of protrusion of the upper end surface of the mask support from the upper end surface of the long side of the mask frame is 0.2 to 1 mm at the center of the long side of the mask frame. A shadow mask structure, wherein the length of both ends of the long side of the mask frame is equal to or greater than the central protrusion amount. 3. The shadow mask structure according to claim 1, wherein said mask frame is made of 13 chrome stainless steel, and said shadow mask and said mask support are made of Invar alloy. 4. A color CRT equipped with the shadow mask structure according to claim 1.