JP2001076641A - Shadow mask structure and cdolor cathode-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the plastic deformation of a shadow mask and mask supports by elastically deforming the short sides of a mask frame at stresses smaller than the stress, at which the shadow mask and mask supports are plastically deformed. SOLUTION: Long sides of a nearly rectangular shadow mask 101 are welded and fixed to the upper end faces of a pair of mask supports 102 by the application of tensile force. Fixed sections 104 near the center of a pair of mask supports 102 are welded and fixed to a pair of long sides 103L of a nearly rectangular picture frame-shaped mask frame 103. A pair of short sides 103S of the mask frame 103 are deformed elastically at stresses smaller than the stress at which the shadow mask 101 and the mask supports 102 are plastically deformed. The difference in the thermal expansion quartiles between the shadow mask 101 and mask frame 103 is absorbed by the deflation which is the elastic deformation of the mask frame 103, no plastic deformation or no torsion occur on the shadow mask 101 and mask supports 102.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shadow mask type color cathode ray tube, and more particularly to a shadow mask type color cathode ray tube having a structure in which a shadow mask is tensioned in one direction.

[0002]

2. Description of the Related Art In a widespread shadow mask type color cathode ray tube, the shape of a shadow mask forms a part of a spherical surface (hereinafter, abbreviated as a spherical surface), and the screen shape is also made to be spherical. Was customary. However, recently, in order to make the screen easier to see, color cathode ray tubes whose screen shape is a plane or a part of a cylindrical surface (hereinafter abbreviated as a cylindrical surface) are increasing.

In this case, the shadow mask also needs to be flat or cylindrical in accordance with the screen shape. However, as is well known, the shadow mask is an extremely thin metal plate, and has extremely low rigidity due to the myriad of electron beam passage holes, and cannot maintain its shape independently on a flat or cylindrical surface. Therefore, the planar shadow mask is applied with tension in one or two directions from the mask frame, and the cylindrical shadow mask is applied with tension in one direction from the mask frame to maintain the shape.

When a color cathode ray tube is used, a considerable portion of the electron beam collides with the shadow mask, so that the temperature of the shadow mask rises to nearly 100 ° C. As a result, when the shadow mask partially expands and the position of the electron beam passage hole shifts, the color purity decreases. This phenomenon is called doming. Doming is greatly affected by the coefficient of thermal expansion of the shadow mask, and the smaller the coefficient of thermal expansion, the smaller the doming. Therefore, the easiest way to avoid doming is to make the shadow mask a material with a low coefficient of thermal expansion, for example, Invar (36% nickel-iron alloy).
(The thermal expansion coefficient of Invar is about 1.2 ppm / K at room temperature.)

[0005] On the other hand, the mask frame is usually made of iron or stainless steel in view of a balance between mechanical properties and price. The thermal expansion coefficients of iron and stainless steel are about 12 to 15 ppm / K at room temperature, which is almost 10 times that of Invar. As described above, the shadow mask is mounted on the mask frame so that tension is applied. For this reason, there is a problem that the difference in the amount of thermal expansion between the shadow mask and the mask frame is large when the color cathode ray tube is heated to a maximum of about 500 ° C. in the manufacturing process, and plastic deformation remains in the shadow mask. (If the mask frame is also made of Invar, the problem of the coefficient of thermal expansion can be solved, but the problems of mechanical properties and price will arise separately.)

[0006] In order to solve the above-mentioned problem, the present inventors have made the invention (Japanese Patent Application No. 11-066780),
Instead of mounting the shadow mask directly on the mask frame, the shadow mask is welded and fixed to a mask support having the same thermal expansion coefficient as the shadow mask, and the mask support is used to eliminate the effect of the difference in the thermal expansion coefficient between the mask frame and the mask support. A shadow mask structure is provided, in which only the central part of the body is fixed to the mask frame.

[0007] The shadow mask structure 700 according to one embodiment of the present invention.
7 is shown in FIG. In FIG. 7, a substantially rectangular Invar shadow mask 701 (only the outer periphery is shown by a two-dot chain line for easy viewing) is fixed by welding to the long sides of the pair of Invar mask supports 702 by applying tension. The mask support 702 has only a fixed portion 704 near the center welded and fixed to opposing long sides of a substantially rectangular frame-shaped stainless steel mask frame 703.

Next, problems of the shadow mask structure 700 will be described.

FIG. 8 is a side view of the conventional shadow mask structure 700 when the shadow mask 701 is welded to the mask support 702 as viewed from the direction A in FIG. At normal temperature, the pressing force F is applied from both left and right sides of the mask support 702.
Is applied, the mask frame 703 is elastically deformed inward and held, and in this state, the shadow mask 701 is fixed to the upper end surface of the mask support 702 by welding.

When the pressing force F is removed after the welding of the shadow mask 701 is completed, the mask frame 703 returns to its original shape, and the tension is applied to the shadow mask 701 as shown in FIG.

Thereafter, it is inevitable that the shadow mask structure 700 is heated to about 500 ° C. during the manufacturing process of the color CRT. The shadow mask structure 70 during the heating
The state of 0 is shown in the XX ′ sectional view and the YY ′ sectional view of FIG. Here, the positions of XX ′ and YY ′ are near the center of the mask support 702 (fixed portion 7), as shown in FIG.
04) and near the end.

As shown in FIG. 10, a cross section taken along the line XX ′, the mask support 70
Since 2 is fixed to the mask frame 703, the cross-sectional shape is the same as that at normal temperature and the entire cross-section is simply enlarged in a similar manner. However, the enlargement ratio is the mask frame 70
3, the shadow mask 701
Is stretched by excessive tension and partially undergoes plastic deformation.

On the other hand, near the end of the mask support 702, as shown in FIG.
02 is not fixed to the mask frame 703,
It is pulled by the shadow mask 701 whose thermal expansion is smaller than that of the mask frame 703, and is deformed into a C shape as shown in the figure. In this case, the reaction force is applied to the shadow mask 701, and as a result, the shadow mask 701,
Plastic deformation occurs in both of the mask supports 702.

When the temperature returns to room temperature after heating due to the above-described effects, the vicinity of the center of the mask support 702 is shown in FIG.
As shown in the cross-sectional view, the shadow mask 701 sags. In the vicinity of the end of the mask support 702, FIG.
As shown in the Y 'cross-sectional view, the shadow mask 701 sags and the mask support 702 has a C-shaped twist.

[0015]

Problems to be Solved by the Invention Japanese Patent Application No. Hei 11
No. 066780, that is, without directly mounting the shadow mask on the mask frame, the shadow mask is welded and fixed to a mask support having the same thermal expansion coefficient as the shadow mask, and the thermal expansion coefficient of the mask frame and the mask support is fixed. In order to further enhance the practicality of the shadow mask structure, in which only the center part of the mask support is fixed to the mask frame to eliminate the effect of the difference, the heat history during the color cathode ray tube manufacturing process makes the shadow mask near the center of the mask support SUMMARY OF THE INVENTION It is an object of the present invention to solve the problem that the shadow mask is sagged near the edge of the mask support and the C-shaped twist remains on the mask support.

[0016]

According to a first aspect of the present invention, there is provided a mask frame having a substantially rectangular frame shape and a pair of long sides of the mask frame having only a central portion. A pair of mask supports to which is fixed,
In a shadow mask structure composed of a substantially rectangular shadow mask fixed by applying tension to the pair of long sides thereof on the mask support, at a stress smaller than a stress at which the shadow mask and the mask support undergo plastic deformation. The short side of the mask frame is elastically deformed, whereby plastic deformation of the shadow mask and the mask support is prevented.

According to a second aspect of the present invention, the thermal expansion coefficients of the shadow mask and the mask support are substantially equal to each other, and are 2 ppm / K or less at room temperature.

According to a third aspect of the present invention, the material of the shadow mask and the mask support is invar (36% nickel-iron alloy), and the material of the mask frame is iron, stainless steel, chromium molybdenum. It is a steel or a combination of the above materials.

According to a fourth aspect of the present invention, the shape of the shadow mask is a cylindrical surface.

According to a fifth aspect of the present invention, the shape of the shadow mask is flat.

According to a sixth aspect of the present invention, there is provided a color CRT having the shadow mask structure according to any one of the first to fifth aspects.

[0022]

[Effects] It is inevitable that the shadow mask structure is heated to about 500 ° C. during the color cathode ray tube manufacturing process. At this time, the thermal expansion of the mask frame is smaller than the thermal expansion of the shadow mask and the mask support. Much larger. Conventionally, the rigidity of the mask frame was superior to that of the shadow mask and the mask support.Therefore, the shadow mask was stretched by an excessive force due to the difference in the amount of thermal expansion between the two, causing partial plastic deformation and the mask support. There was a problem that the non-fixed portion was pulled by the shadow mask and deformed into a C shape.

However, in the present invention, the short side of the mask frame undergoes elastic deformation before the shadow mask and the mask support are pulled by an excessive force that causes plastic deformation, and the difference in the amount of thermal expansion is absorbed there. As a result, plastic deformation of the shadow mask and the mask support is avoided. Therefore, when the temperature returns to room temperature after heating, the sag and the twist do not occur in the shadow mask and the mask support as in the related art. The mask frame also has a predetermined shape because the elastic deformation returns to its original state.

Further, since the thermal expansion coefficient of the shadow mask and that of the mask support are almost equal and are 2 ppm / K or less at room temperature, doming can be easily avoided and a decrease in color purity can be prevented.

Further, since the shadow mask and the mask support are made of Invar, the coefficient of thermal expansion of the shadow mask and the mask support can be reduced to about 1.2 ppm / K at room temperature, so that there is no practical problem with doming. Further, by making the mask frame made of iron, stainless steel, chromium molybdenum steel, or a combination of the above materials, the mechanical properties and cost of the mask frame become favorable.

Further, by making the shadow mask a cylindrical surface or a flat surface, the shadow mask structure is suitable for a color CRT having a cylindrical or flat screen.

By providing the shadow mask structure of the present invention, high-quality and high-quality dispersion can be achieved without sagging of the shadow mask due to plastic deformation of the shadow mask, the mask support and the mask frame during the color cathode ray tube manufacturing process. A color cylindrical tube with no cylindrical surface or flat surface is realized.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the shadow mask structure of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a shadow mask structure according to a first embodiment of the present invention. As shown in FIG. 1, a substantially rectangular shadow mask 1
01 (only the outer periphery is shown by a two-dot chain line for the sake of simplicity of the drawing) is fixed by welding to the upper end surfaces of the pair of mask supports 102 by applying tension to the long sides thereof.
Reference numeral 02 denotes a pair of long sides 103L of a mask frame 103 having a substantially rectangular frame shape, and a fixing portion 104 near the center thereof is fixed by welding. The feature of the present invention is that the shadow mask 10
1. A pair of short sides 10 of the mask frame 103 at a stress smaller than the stress at which the mask support 102 plastically deforms.
3S is elastically deformed. This allows the shadow mask 101 and the mask support 102 to be described below.
Is prevented from being plastically deformed.

FIG. 2 is a side view of the shadow mask structure 100 according to the first embodiment of the present invention when the shadow mask 101 is welded to the mask support 102 as viewed from the direction A in FIG. At normal temperature, a pressing force F is applied from both the left and right sides of the mask support 102, and the mask frame 103 is elastically deformed and held inward.
1 is fixed to the upper end surface of the mask support 102 by welding. At this time, the short side 103S of the mask frame 103 is fixed by a jig (not shown) so as not to be deformed.

When the pressing force F is removed after the welding of the shadow mask 101 is completed, the mask frame 103 returns to its original shape, and the tension is applied to the shadow mask 101 as shown in FIG.

Thereafter, the shadow mask structure 100 is heated to about 500 ° C. during the manufacturing process of the color cathode ray tube. The state of the shadow mask structure 100 during the heating is indicated by X in FIG.
It is shown in the -X 'cross-sectional view and the YY' cross-sectional view. Where X-
The positions of X 'and YY' are near the center (near the fixed portion 104) and near the end of the mask support 102, respectively, as shown in FIG.

The thermal expansion of the mask frame 103 is larger than that of the shadow mask 101 and the mask support 102 both in the vicinity of the center and in the vicinity of the end of the mask support 102, but as a feature of the present invention, FIG. Sectional view,
As shown in the YY ′ cross-sectional view, the mask frame 103 is elastically deformed by a smaller stress than the shadow mask 101 and the mask support 102 are plastically deformed, and the difference in the amount of thermal expansion between the shadow mask 101 and the mask frame 103 is increased. Is absorbed by bending, which is an elastic deformation of the mask frame 103. Therefore, no plastic deformation occurs in the shadow mask 101 and the mask support 102, and the mask support 102 does not twist near the edge of the mask support 102.

As a result, when the temperature of the mask support 102 is returned to normal temperature after heating, as shown in the sectional view along the line XX 'of FIG.
As shown in the Y ′ cross-sectional view, sagging, twisting, and the like remain in the shadow mask 101 and the mask support 102, and a cross-sectional shape that is the same as before heating can be obtained. Further, since the deformation of the mask frame 103 during heating was elastic deformation, the shape returns to the same shape as before heating after heating.

FIG. 6 is a perspective view of a shadow mask structure 200 according to a second embodiment of the present invention. In FIG. 6, 201 is a shadow mask, 202 is a mask support, 203 is a mask frame, and 204 is a fixing part to the mask frame 203 near the center of the mask support 202. The difference of the second embodiment from the first embodiment is that the shadow mask 101 of the first embodiment has a cylindrical shape, whereas the shadow mask structure 200 of the second embodiment has a cylindrical shape.
, The shadow mask 201 is flat.

500 in the color cathode ray tube manufacturing process
When the mask frame 203 is elastically deformed by a stress smaller than plastic deformation of the shadow mask 201 and the mask support 202, the shadow mask 2 is heated.
01 and the mask frame 203 are absorbed by the deflection of the mask frame 203, and after heating, the shadow mask 201, the mask support 202, and the mask frame 2 are heated.
The mechanism that no plastic deformation remains in any of the components 03 is the same as that of the shadow mask structure 100 of the first embodiment, and a detailed description thereof will be omitted.

[0036]

As described above, by providing the shadow mask assembly for a color cathode ray tube of the present invention, the shadow mask, the mask support, and the shadow mask caused by the plastic deformation of the mask frame during the color cathode ray tube manufacturing process are provided. A high-quality, consistent cylindrical or flat color cathode-ray tube without sagging is realized.

[Brief description of the drawings]

FIG. 1 is a perspective view of a shadow mask structure according to a first embodiment of the present invention.

FIG. 2 is a side view of the shadow mask structure according to the first embodiment of the present invention at the time of shadow mask welding.

FIG. 3 is a side view of the shadow mask structure according to the first embodiment of the present invention after the completion of the shadow mask welding.

FIG. 4 is a cross-sectional view of the shadow mask structure according to the first embodiment of the present invention when it is heated.

FIG. 5 is a sectional view of the shadow mask structure according to the first embodiment of the present invention after heating;

FIG. 6 is a perspective view of a shadow mask structure according to a second embodiment of the present invention.

FIG. 7 is a perspective view of a conventional shadow mask structure.

FIG. 8 is a side view of a conventional shadow mask structure during shadow mask welding.

FIG. 9 is a side view of the conventional shadow mask structure after the completion of the shadow mask welding.

FIG. 10 is a cross-sectional view of a conventional shadow mask structure when heated.

FIG. 11 is a cross-sectional view of a conventional shadow mask structure after heating.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 shadow mask structure 101 shadow mask 102 mask support 103 mask frame 103L mask frame long side 103S mask frame short side 104 fixing unit 200 shadow mask structure 201 shadow mask 202 mask support 203 mask frame 204 fixing unit 700 shadow mask structure 701 shadow Mask 702 Mask support 703 Mask frame 704 Fixed part

Claims (6)

[Claims] 1. A mask frame having a substantially rectangular frame shape, a pair of mask supports having only a central portion fixed to a pair of long sides of the mask frame, and a tension applied between the pair of long sides by the mask support. In a shadow mask structure composed of a substantially rectangular shadow mask applied and fixed, the short side of the mask frame is elastically deformed at a stress smaller than the stress at which the shadow mask and the mask support undergo plastic deformation. A shadow mask structure wherein plastic deformation of the shadow mask and the mask support is prevented. 2. The shadow mask structure according to claim 1, wherein the thermal expansion coefficients of the shadow mask and the mask support are substantially equal and 2 ppm / K or less at room temperature. 3. The shadow mask structure according to claim 1, wherein said shadow mask and said mask support are made of Invar (36% nickel-iron alloy), and said mask frame is made of iron, stainless steel, chromium molybdenum. A shadow mask structure comprising steel or a combination of the above materials. 4. The shadow mask structure according to claim 1, wherein the shape of said shadow mask is a part of a cylindrical surface. 5. The shadow mask structure according to claim 1, wherein said shadow mask has a flat shape. 6. A color CRT comprising the shadow mask structure according to claim 1.