KR100342632B1 - Shadow mask assembly and color cathode-ray tube with the same - Google Patents

Abstract

A shadow mask assembly is provided that can effectively eliminate or effectively suppress plastic deformation of the shadow mask and the support resulting from thermal expansion of the mask during the manufacturing process of the color CRT. This assembly comprises: (a) a base that is approximately rectangular and has a window for passing the electron beam, a first pair of sides connected to each of the two long sides of the base, and a second pair connected to each of the two short sides of the base; A mask frame having sides thereof; (b) a pair of mask supports fixedly secured to each of the first pair of sides of the frame only through their central positions; And (c) a shadow mask that is approximately rectangular and is fixed to a pair of mask supports only in its two long side edge regions, wherein the mask is applied with an appropriate tension in the direction along the two short side edges of the mask, There is provided a shadow mask assembly that allows a portion of a cylindrical surface or plane to be formed by maintaining the desired shape. In addition, the second pair of sides of the frame is applied to the pair of supports along the short side edges of the mask when the second pair of sides of the frame receive a stress that is weaker than the critical stress causing plastic deformation in the mask and the pair of supports. It is elastically deformed by the applied force, thereby preventing plastic deformation of the mask and the pair of supports due to thermal expansion.

Description

SHADOW MASK ASSEMBLY AND COLOR CATHODE-RAY TUBE WITH THE SAME}

The present invention relates to a shadow mask assembly and a color cathode ray tube (CRT) having the same, and more particularly, to a shadow mask assembly having a structure in which a shadow mask is fixed to a mask frame by applying tension to the mask mask And a color CRT having the assembly thereof.

Shadow mask type color CRTs are widely used and are most prevalent. In this type of color CRT, shadow masks typically have a form that forms part of a sphere. Since the shadow mask is fixed in the vicinity of the front panel made of glass, the front panel must also have a form that forms part of the spherical surface.

In recent years, the front panel tends to have a form that forms part of a cylindrical surface or a flat surface. This is because the visibility of the color CRT can be improved. In this case, it is natural that the shadow mask should have a form that forms part of a cylindrical surface or a flat surface in the form of a panel.

However, as is known, the shadow mask is formed of a very thin rectangular metal plate and has a very low mechanical strength because it has a large number of small openings for color selection arranged regularly. As a result, the mask cannot maintain the shape of the cylindrical surface or the flat surface without incurring external force. Thus, when fixing the mask to the frame, an appropriate tension in one or two directions is typically applied to the planar mask to maintain the desired cylindrical or planar shape by applying the appropriate tension in the desired direction to the mask.

In general, when the CRT operates, many of the R, G, and B electron beams collide with the shadow mask, raising the temperature of the mask to about 100 ° C. Due to this temperature rise, the mask partially thermally expands, causing unnecessary positional variations in the color selection opening. In this state, the R, G, and B electron beams arrive at the wrong position on the fluorescent screen between the mask and the front panel, eventually degrading the color purity. This phenomenon is called "doming".

Since the probability of occurrence of the dominant phenomenon depends largely on the coefficient of thermal expansion of the shadow mask, lowering the coefficient of thermal expansion of the shadow mask also reduces the possibility of occurrence of dominant phenomenon. Thus, the easiest way to suppress the dominant phenomenon is to have as low thermal expansion as possible, such as Invar (e.g., an iron alloy containing 36% nickel) having a thermal expansion coefficient of about 1.2 ppm / K at room temperature. The mask is made of a material having a coefficient.

On the other hand, the mask frame is generally made of iron or stainless steel in consideration of the balance between mechanical properties and price. Iron or stainless steel has a coefficient of thermal expansion of about 12 to 15 ppm / K at room temperature, which is ten times the coefficient of thermal expansion of Invar.

In this case, however, there is a disadvantage that plastic deformation of the mask may occur if heat of up to about 500 ° C. is applied to the shadow mask assembly during the manufacturing process of the color CRT. The reason is that since the shadow mask is fixed to the frame so that an appropriate tension is applied, the thermal expansion difference between the mask and the frame is very large. This disadvantage can be easily overcome by manufacturing the frame in invar. However, this presents another disadvantage in terms of mechanical properties and / or price.

In view of the above disadvantages, the inventors invented an improved shadow mask assembly and filed it as Japanese Patent Application No. 11-66780 on March 12, 1999. In this assembly, the shadow mask is not fixed directly to the frame but indirectly through a mask support having a coefficient of thermal expansion that is approximately equal to the mask. The mask is fixed to the support by welding. Only the central portion of the support is fixed to the frame, thereby eliminating or suppressing the effect due to the difference in coefficient of thermal expansion.

An improved shadow mask assembly disclosed in the aforementioned application 11-66780 is disclosed in FIG. 1. For ease of understanding, only the outline of the shadow mask is shown by the dashed line.

As shown in FIG. 1, the shadow mask assembly 700 includes a shadow mask 701, a pair of mask supports 702, and a mask frame 703. Mask 701 and support 702 are made of Invar, and frame 703 is made of stainless steel.

Frame 703 includes a frame shaped base 703e and four planar sides 703a, 703b, 703c and 703d connected to each edge of the base 703e. The base 703e has a rectangular outline and has a rectangular window through which R, G, and B electron beams pass.

Side portions 703a and 703b connected to the long side edges 703ea and 703eb of the base 703e and parallel to each other, have a shape close to the same rectangle. The upper edges of the sides 703a and 703b are in the form of arcs following the cylindrical form of the mask 701. Sides 703c and 703d that are connected to short side edges 703ec and 703ed of base 703e, and are substantially parallel to each other, have the same rectangular shape. Unlike the sides 703a and 703b, the upper edge of the sides 703c and 703d is straight. The height of the sides 703a and 703b is slightly larger than the sides 703c and 703d.

The gap 703g is between the adjacent side 703c and the side 703a, between the adjacent side 703c and the feature 703b, between the adjacent side 703d and the side 703a, and between the adjacent side 703d and the side. It is formed between 703b, respectively.

The two mask supports 702 have a shape close to the same rectangle. The upper edge of the support 702, which is in the form of an arc following the cylindrical form of the mask 701, projects upwards than the sides 703a and 703b of the frame 703. The support 702 is fixed to the outer surface of the sides 703a and 703b, respectively. Each support 702 is welded only at the weld 704 located at its center on the corresponding side 703a or 703b. The ends of the support 702 near the sides 703c and 703d can be moved relative to the sides 703a and 703b.

The shadow mask 701 is in the form of a rectangular plane. The two edge regions on the long sides 701a and 701b of the mask 701 are respectively fixed to the upper edge of the support 702 by welding under the application of a specific tension along the short sides 703c and 703d of the mask. Thus, the mask 701 forms part of a particular cylindrical shape as shown in FIG.

With the shadow mask assembly 700 having the above configuration shown in FIG. 1, the support 702 not fixed to the frame 703 even if the difference in thermal expansion coefficient between the frame 703 and the support 702 is relatively large. ), The free portion can extend almost freely along the longitudinal axis of the frame 703 (ie, the X axis of FIG. 1). Therefore, the effect due to the difference in the coefficient of thermal expansion between the frame 703 and the support 702 along the X axis can be eliminated or effectively suppressed.

FIG. 2 schematically illustrates a state in which the shadow mask 701 is welded to the mask supporter 702 in the X-axis direction of FIG. 1, and FIG. 3 shows that the shadow mask 701 is provided by the supporter 702. The state after welding to 702 is seen from the X-axis direction of FIG.

As shown in FIG. 2, when the shadow mask 701 is welded to the mask support 702, the thrust F11 in two directions at room temperature is applied to the inside of the support 702, so that the side 703a of the frame 703 is provided. And 703b) causes elastic deformation inside. Such deformation may occur due to the presence of the gap 703g. Then, the edge regions of the long sides 701a and 701b of the mask 701 are welded to the upper edge of the support 702, respectively, without changing the elastic deformation of the sides 703a and 703b. After the welding operation of the mask 701 is completed, the application of the thrust F11 is stopped. At this time, the elastic deformation of the side parts 703a and 703b disappears. That is, the sides 703a and 703b automatically return to their original vertical state as shown in FIG. Accordingly, a tension F12 along the Y axis is applied to the mask 701, which causes the mask 701 to be fixed to the frame 703 without sag.

The shadow mask assembly 700 produced by the above method is assembled to the front panel of the desired color CRT. The assembly 700 then must undergo a heat treatment at about 500 ° C. during the manufacturing process of the color CRT. In this heat treatment process, the assembly 700 has the cross-sectional shape shown in FIGS. 4 and 5. After the heat treatment process, the assembly 700 has the cross-sectional shape shown in FIGS. 6 and 7.

4 and 6 are schematic cross-sectional views of the assembly 700 cut along the line IV-IV located in the vicinity of the center of the support 702 (ie, near the weld point 704) in FIG. 1. 5 and 7 are schematic cross-sectional views of the assembly 700 cut along the line V-V located in FIG. 1 near the end of the support 702 (ie, a point away from the welding point 704).

As shown in FIG. 4, in the central region of the support 702, the support 702 is welded to the support 703 via a welding point 704, so that the cross section of the assembly 700 at a high temperature of about 500 ° C. The form is the same as at room temperature. The cross-sectional shape of the assembly 700 at high temperatures is simple expansion, similar to that at room temperature, and its expansion rate depends on the coefficient of thermal expansion of the frame 703. Since the frame 703 is made of iron or stainless steel having a relatively large coefficient of thermal expansion, while the mask 701 is made of invar having a relatively small coefficient of thermal expansion, as shown in FIG. ), Excess tension F13 is applied. Thus, the central portion of the mask 701 extends excessively along the Y axis, causing partial plastic deformation in the mask 701.

On the other hand, in the end region of the support 702, since the support 702 is not fixed to the frame 703, the support 702 is pushed inward by the mask 701 as shown in FIG. This is because the thermal expansion of the mask 701 is much smaller than that of the support 703. Therefore, the thrust F14 along the Y axis is applied to the mask supporter 702 inwardly, and as shown in FIG. 5, a deformation of the upper end of the supporter 702 moves inward and the lower end thereof moves outward. do. At this time, excess tension F15 in two directions is applied to the mask 701 as a reaction of the thrust F14. Thus, plastic deformation occurs on both the mask 701 and the support 702.

The plastic deformation of the mask 701 and the support 702 generated in this way is not recovered even after the mask 701 and the support 702 return to the room temperature environment. Thus, as shown in FIG. 6, sagging occurs in the central region of the mask 701. At the same time, as shown in FIG. 7, not only sagging occurs in the end region of the mask 701, but also distortion of the support 702 is maintained. Distortion of the support 702 also causes distortion in the frame 703.

As described in detail above, in the case of using the improved shadow mask assembly 700 shown in FIG. 1, the shadow mask 701 may be formed on a mask support 702 having the same coefficient of thermal expansion as the mask 701. Only the center portion of 702 is welded to the frame 703. Thus, thermal expansion of the support 702 along the longitudinal axis direction of the support 702 (ie, in the X-axis direction or the long side portions 703ea and 703eb of the base 703 of the frame 703) can be eliminated or effectively suppressed. have. However, thermal expansion of the support 702 along the direction perpendicular to the longitudinal axis direction (ie, the Y-axis direction or the short side portions 703ec and 703ed directions of the base portion 703 of the frame 703) cannot be suppressed, so that the mask ( 701 and support 702 cause plastic deformation.

As a result, sagging occurs in the mask 701 and distortion occurs in the support 702 and the frame 703, whereby the quality of the color CRT is lowered and the quality variation of the CRT is increased.

It is therefore an object of the present invention to provide a shadow mask assembly which eliminates or effectively suppresses the elastic deformation of the shadow mask and the support due to thermal expansion of the mask frame during the manufacturing process of the color CRT, and a color CRT having the assembly. .

Another object of the present invention is to provide a shadow mask assembly which prevents sagging of the shadow mask and distortion of the support and the frame, and a color CRT having the assembly.

It is still another object of the present invention to provide a shadow mask assembly for realizing a high quality color CRT with low quality variation, and a color CRT having the assembly.

The foregoing and other objects will become apparent to those skilled in the art through the following description.

According to a first aspect of the present invention, in a shadow mask assembly,

(a) a base having an approximately rectangular and window for passing electron beams, a first pair of sides connected to each of the two long sides of the base, and a second pair of sides connected to each of the two short sides of the base; One mask frame;

(b) a pair of mask supports fixedly secured to each of the first pair of sides of the frame only through their central positions; And

(c) a shadow mask that is approximately rectangular and is fixed to a pair of mask supports only in its two long edge regions;

Including,

The mask is provided with a shadow mask assembly in which proper tension is applied in the direction along the two short side edges of the mask to allow the mask to form a portion of the cylindrical surface or plane by maintaining the desired shape.

In addition, the second pair of sides of the frame is applied to the pair of supports along the short side edges of the mask when the second pair of sides of the frame receive a stress that is weaker than the critical stress causing plastic deformation in the mask and the pair of supports. It is elastically deformed by the applied force, thereby preventing plastic deformation of the mask and the pair of supports due to thermal expansion.

In the shadow mask assembly according to the first aspect of the present invention, the second pair of sides of the frame is a direction along a short side edge of the mask when a stress below a critical stress causing plastic deformation is applied to the mask and the pair of supports. It is designed to be elastically deformed by a force applied by a pair of supports. Thus, the second pair of sides of the frame is elastically deformed before an excessive force that causes sour deformation is applied to the mask and the pair of supports.

Thus, the difference in thermal expansion between the mask and the pair of supports can be absorbed or effectively eliminated, thereby preventing plastic deformation from occurring in the mask and the pair of supports due to thermal expansion. Therefore, the sagging and / or distortion observed in the assembly 700 described above with reference to FIG. 1 does not occur.

In addition, since the deformation of the second pair of sides of the frame due to thermal expansion is elastic, the original form of the frame does not change even after the thermal expansion disappears.

In a preferred embodiment of the assembly according to the first embodiment of the invention, a gap is formed between two adjacent sides of the first pair of sides of the frame and the second pair of sides of the frame. The height of the second pair of sides is lower than that of the first pair of sides so that the second pair of sides can be elastically deformed by the tension applied to the pair of supports along the short side edges of the mask. This embodiment has the further advantage that the structure of the frame can be simplified, so that it can be produced at low cost.

In another embodiment of the assembly according to the first embodiment of the present invention, the mask and the pair of supports have a coefficient of thermal expansion of about 2 ppm / K or less at room temperature. This embodiment has the further advantage that the dope phenomenon can be prevented and the deterioration of the color purity can be prevented.

In yet another embodiment of the assembly according to the first embodiment of the invention, the mask and the pair of supports are made of invar (i.e. iron alloy containing 36% nickel) and the frame is made of iron, stainless steel and nickel -At least one material selected from the group consisting of molybdenum steel. In this embodiment, since the coefficient of thermal expansion of the mask and the pair of supports is as low as about 1.2 ppm / K, the domming phenomenon is suppressed and does not cause a problem in practical use, and it is possible to obtain suitable mechanical properties of the frame at an appropriate price.

According to a second aspect of the present invention. A color CRT is provided that includes a shadow mask assembly according to the first aspect of the invention.

Since the color CRT according to the second aspect of the present invention includes the shadow mask assembly according to the first aspect of the present invention, a high quality color CRT with little variation in quality can be realized.

1 is a schematic perspective view showing the configuration of a shadow mask assembly for a color CRT disclosed in Japanese Patent Application No. 11-66780.

FIG. 2 shows a state when the shadow mask is welded to the pair of mask supports, a schematic side view of the assembly shown in FIG. 1 seen in the X-axis direction of FIG. 1; FIG.

3 is a schematic side view of the assembly shown in FIG. 1 in the X-axis direction of FIG. 1, showing a state after the shadow mask is welded to the pair of mask supports. FIG.

4 is a schematic cross-sectional view of the assembly shown in FIG. 1 taken along line IV-IV of FIG. 1, showing the state when the assembly is heated during the manufacturing process of the color CRT.

5 is a schematic cross-sectional view of the assembly shown in FIG. 1 taken along line V-V of FIG. 1, showing the state when the assembly is heated during the manufacturing process of the color CRT.

FIG. 6 is a schematic cross-sectional view of the assembly shown in FIG. 1 taken along line IV-IV of FIG. 1, showing the state after the heat treatment during the manufacturing process of the color CRT is completed. FIG.

FIG. 7 is a schematic cross-sectional view of the assembly shown in FIG. 1 taken along the line V-V of FIG. 1, showing the state after the heat treatment during the manufacturing process of the color CRT is completed. FIG.

Fig. 8 is a schematic perspective view showing the construction of a shadow mask assembly for color CRT according to the first embodiment of the present invention.

FIG. 9 shows a state when the shadow mask is welded to the mask support pair, a schematic side view of the assembly according to the first embodiment shown in FIG. 8 seen in the X-axis direction shown in FIG. 8; FIG.

FIG. 10 is a schematic side view of the assembly according to the first embodiment shown in FIG. 8 in the X-axis direction shown in FIG. 8, showing the state after the shadow mask is welded to the mask support pair. FIG.

FIG. 11 is a schematic cross-sectional view of the assembly according to the first embodiment of FIG. 8 taken along line XI-XI of FIG. 8, showing the state when the assembly is heated during the manufacturing process of the color CRT.

FIG. 12 is a schematic cross-sectional view of the assembly according to the first embodiment of FIG. 8 taken along line XII-XII in FIG. 8, showing the state when the assembly is heated during the manufacturing process of the color CRT.

Fig. 13 is a schematic cross-sectional view of the assembly according to the first embodiment of Fig. 8 taken along the line XI-XI of Fig. 8, showing the state after the heat treatment during the manufacturing process of the color CRT is completed.

FIG. 14 is a schematic cross-sectional view of the assembly according to the first embodiment of FIG. 8 taken along the line XII-XII in FIG. 1, showing the state after the heat treatment during the manufacturing process of the color CRT is completed. FIG.

Fig. 15 is a schematic perspective view showing the construction of a shadow mask assembly for color CRT according to a second embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

100, 200, 700: shadow mask assembly

101, 201, 701: shadow mask

102, 202, 702: mask support

103, 203, 703: Mask Frame

104, 204, 704: welding point

Preferred embodiments of the present invention will be described in detail with reference to the drawings.

<First Embodiment>

As shown in FIG. 8, the shadow mask assembly 100 according to the first embodiment of the present invention includes a shadow mask 101, a pair of mask supports 102, and a mask frame 103. The mask 101 and the support 102 are made of Invar, and the frame 103 is made of stainless steel.

The frame 103 includes a frame-shaped base 103e and four flat sides 103a, 103b, 103c and 103d connected to each edge of the base 103e. The base portion 103e has a rectangular shape and has a rectangular window for passing R, G, and B electron beams.

Side portions 103a and 103b connected to the long side edges 103ea and 103eb of the base portion 103e and parallel to each other have a shape close to the same rectangle. The upper edge of the sides 103a and 103b is in the form of an arc following the cylindrical form of the mask 101. The sides 103c and 103d, which are connected to the short side edges 103ec and 103ed of the base 103e and are substantially parallel to each other, have the same rectangular shape. Unlike the sides 103a and 103b, the upper edge of the sides 103c and 103d is straight. The height of the sides 103a and 103b is slightly higher than the height of the sides 103c and 103d.

The gap 103g is between the side 103c and the side 103a, between the side 103c and the side 103b, between the side 103d and the side 103a, and between the side 103d and the side 103b. Are formed on each.

The two mask supports 102 have a shape close to the same rectangle with each other. The upper edge of the support 102, which is in the form of an arc following the cylindrical form of the mask 101, projects upwards than the sides 103a and 103b of the frame 103. The support 102 is fixed to the outer surface of the sides 103a and 103b, respectively. Each support 102 is welded to its corresponding side 103a or 103b only through its centrally located welding point 104. The ends of the support 102 near the sides 103c and 103d can be moved relative to the sides 103a and 103b.

The shadow mask 101 has a rectangular shape. The two edge regions on the long sides 101a and 101b of the mask 101 are fixed to the upper edge of the support 102, respectively, under the application of a specific tension along the short sides 103c and 103d of the mask. Thus, the mask 101 forms part of a particular cylindrical shape, as shown in FIG.

The sides 103c and 103d of the frame 103 have a height h lower than the height of the sides 103a and 103b of the frame 103. The height h is defined as the length from the top surface of the base 103e to the top edge of the side 103c or 103d. The value of the height h is such that when the external force (s) are applied in a direction perpendicular to the longitudinal axis direction of the support body 102 (ie, in the Y-axis direction of FIG. 8), the frame 103 is elastically in the same direction thereof. It is chosen so that it can be easily modified. Here, the phrase "easy elastic deformation of the frame 103" means that a weak force in the Y-axis direction at a level that does not cause plastic deformation in the mask 101 and the support 102 is generated in the frame 103. In this case, it means that the frame 103 can be elastically deformed.

The shadow mask 101 is fixed to the support 102 in the following manner.

When the mask 101 is fixed to the support 102 by welding, as shown in FIG. 9, a thrust F1 in two directions along the Y axis at room temperature is applied into the support 102 to provide the frame 103. The sides 103a and 103b are elastically deformed inward. At this time, the side parts 103a and 103b move inward near the lower end. Such deformation may occur because the gap 103g is formed, and the height h of the side portions 103c and 103d is sufficiently small. Then, the edge regions of the long sides 101a and 101b of the mask 101 are fixed by welding to the upper edge of the support 102, respectively, without changing the elastic deformation of the sides 103a and 103b. In this step, the sides 103c and 103d of the frame 103 are held by a suitable jig which is not deformed by the force F1.

When the welding process of the mask 101 is completed, application of the thrust F1 is stopped. At this time, the elastic deformation of the side parts 103a and 103b disappears. That is, the sides 103a and 103b automatically return to their original vertical form as shown in FIG. Accordingly, the tension F2 along the Y axis is applied to the mask 101, and as a result, the mask 101 can be fixed to the frame 103 by the support 102 without sagging.

The shadow mask assembly 100 according to the first embodiment manufactured by the above method is assembled to a front panel (not shown) for a desired color CRT. The assembly 100 must then undergo a heat treatment process at about 500 ° C. during the manufacturing process of the color CRT. In this heat treatment process, the assembly 100 has the cross-sectional shape shown in FIGS. 11 and 12. After the heat treatment process, the assembly 100 has the cross-sectional shape shown in FIGS. 13 and 14.

11 and 12 are schematic cross-sectional views of the assembly 100 cut along the line XI-XI located near the center of the support 102 (ie near the weld point 104) in FIG. 8. 13 and 14 are schematic cross-sectional views of the assembly 100 cut along the line XII-XII located near the end of the support 102 in FIG. 8 (ie, at a point far from the weld point 104).

Since the frame 103 is made of stainless steel having a relatively large coefficient of thermal expansion, while the mask 101 is made of an invar having a relatively small coefficient of thermal expansion, as shown in FIG. In the central region, tension F3 along the Y axis is applied to the mask 101 by the support body 102. At the same time, the thrust F4 along the Y axis is applied to the frame 103 as a reaction of the force F3.

As described above, the height h of the side portions 103c and 103d of the frame 103 is determined so that the frame 103 is elastically easily deformed. Therefore, before the magnitude of the tension F3 reaches the level causing the plastic deformation of the mask 101, elastic deformation of the frame 103 due to the thrust F4 occurs, so that the sides 103c and 103d of the frame 103 and The base 103e is distorted. Thus, the difference in thermal expansion between the mask 101 and the frame 103 caused during the heat treatment process at about 500 ° C. can be absorbed by the distortion of the portions 103c, 103d, 103e of the frame 103.

In the end region of the support 102, like its central region, elastic deformation of the frame 103 due to the thrust F4 occurs before the magnitude of the tension F3 reaches the level causing the plastic deformation of the mask 101. The distortion of the side portions 103c and 103d and the base portion 103e of the frame 103 occurs. Thus, the difference in thermal expansion between the mask 101 and the frame 103 can be absorbed in the same manner as in the central region of the support 102.

As a result, no elastic deformation occurs in the shadow mask 101, and distortion does not occur in the end portion of the support body 102. Needless to say, since the deformation of the frame 103 occurring during the heat treatment process is elastic, the frame 103 returns to its original form after the heat treatment process is completed. Therefore, if the temperature of the assembly 100 is cooled to room temperature after the heat treatment process, the assembly 100 has a cross section as shown in FIGS. 13 and 14, which is the same as the cross section before the heat treatment process.

As described above, using the shadow mask assembly 100 according to the first embodiment, the plastic deformation of the shadow mask 101 and the support 102 due to thermal expansion of the frame 103 occurring during the manufacturing process of the color CRT. May be removed or effectively suppressed. As a result, the sagging of the mask 101 and the distortion of the support body 102 and the frame 103 can be prevented from occurring. Thereby, a high quality color CRT with few quality fluctuations can be realized.

Second Embodiment

15 illustrates a shadow mask assembly 200 according to a second embodiment of the present invention, except that the shadow mask 201 is flat and fixed, and the assembly 100 according to the first embodiment of the present invention. It is the same structure.

In detail, assembly 200 includes a shadow mask 201, a pair of mask supports 202, and a mask frame 203. The mask 201 and the support 202 are made of Invar, and the frame 203 is made of stainless steel.

The frame 203 includes a frame shaped base 203e and four planar sides 203a, 203b, 203c and 203d connected to each edge of the base 203e.

The base 203e has a rectangular outline and has a rectangular opening. Sides 203a and 203b connected to the long side edges 203ea and 203eb of the base 203e and parallel to each other, respectively, have the same rectangular shape. The upper edge of the sides 203a and 203b is straight along the flat surface of the mask 201. Side portions 203c and 203d connected to the short side edges 203ec and 203ed of the base 203e and parallel to each other have the same rectangular shape. The gap 203g is between the side 203c and the side 203a, between the side 203c and the side 203b, between the side 203d and the side 203a, and between the side 203d and the side 203b. Are formed on each.

The two mask supports 202 have the same rectangular shape. The upper edge of the straight support 202 along the flat surface of the mask 101 protrudes above the sides 203a and 203b of the frame 203. The support 202 is fixed to the outer surface of the sides 203a and 203b, respectively. Each support 202 is welded to its corresponding side 203a or 203b only through its centrally located welding point 204.

The shadow mask 201 has a rectangular shape. The edge regions on the long sides 201a and 201b of the mask 201 are respectively fixed to the upper edge of the support 202 by welding under the application of tension along the short sides 201c and 201d of the mask 201. Thus, the mask 201 is kept flat.

The sides 203c and 203d of the frame 203 have a height h 'lower than the height of the sides 203a and 203b of the frame 103. The height h 'is defined as the length from the top surface of the base 203e to the top edge of the side 203c or 203d. The value of the height h 'is such that when the external force (s) are applied in a direction perpendicular to the longitudinal axis direction of the support 202 (i.e., the Y-axis direction in FIG. 15), the frame 203 is elastically in the same direction. It is chosen so that it can be easily modified. Here, the phrase "easy elastic deformation of the frame 203" has the same meaning as in the first embodiment.

The shadow mask 201 is fixed to the support 202 in the same manner as described in the first embodiment.

Using the shadow mask assembly 200 according to the second embodiment having the above configuration, the elastic deformation of the shadow mask 201 and the support 202 due to thermal expansion of the frame 203 during the manufacturing process of the color CRT is prevented. Can be removed or effectively suppressed. As a result, the sagging of the mask 201 and the distortion of the support 202 and the frame 203 can be prevented. Thereby, a high quality color CRT with few quality fluctuations can be realized.

In the above-described first and second embodiments, the sides 103c and 103d of the mask frame 103 and the sides 203c and 203d of the mask frame 203 are rectangular. Needless to say, however, if a weak force that does not cause elastic deformation in the mask 101 or 201 and the support 102 or 202 can only be elastically deformed when generated in the frame 103 or 203, they Can take other forms.

Although the present invention has been described with reference to the preferred forms, those skilled in the art will recognize that changes may be made without departing from the spirit of the invention. Therefore, the scope of the present invention is determined by the appended claims.

According to the present invention, elastic deformation of the shadow mask and the support due to thermal expansion of the mask frame during the manufacturing process of the color CRT can be eliminated or effectively suppressed, and sagging of the shadow mask and distortion of the support and the frame can be prevented from occurring. It is possible to realize high quality color CRT with little quality variation.

Claims (7)

In the shadow mask assembly, (a) a base that is approximately rectangular and has a window for passing an electron beam, a first pair of sides connected to each of the two long sides of the base, and a second pair of sides connected to each of the two short sides of the base; Mask frame provided with; (b) a pair of mask supports fixedly secured to each of the first pair of sides of the frame only through their central position; And (c) a shadow mask that is approximately rectangular and is fixed to the pair of mask supports only in its two long edge regions; Including, Appropriate tension is applied to the mask in the direction along the two short side edges of the mask, such that the mask maintains the desired shape to form a cylindrical surface or a portion of a plane, The second pair of sides of the frame is characterized in that when the second pair of sides of the frame are stressed less than a critical stress that causes plastic deformation in the mask and the pair of supports, And a shadow mask assembly elastically deformed by a force applied to the pair of supports along the short side edges to prevent plastic deformation of the mask and the pair of supports due to thermal expansion. The method of claim 1, A gap is formed between two adjacent sides of the first pair of sides and the second pair of sides of the frame, The height of the side pairs of the second pair is lower than the height of the side pairs of the first pair so that the second pair of sides are elastically provided by the tension applied to the pair of supports along the short side edge of the mask. Shadow mask assembly that allows deformation. The shadow mask assembly of claim 1, wherein the mask and the pair of supports have a coefficient of thermal expansion of about 2 ppm / K or less at room temperature. The method of claim 1, The mask and the pair of supports are made of Invar, And the frame is made of at least one material selected from the group consisting of iron, stainless steel and nickel-molybdenum steel. The method of claim 1, The pair of supports have an arcuate upper edge, And the mask is fixed to the upper edge of the arc shape to form a portion of the cylindrical surface. The method of claim 1, The pair of supports has a straight upper edge, And the mask is fixed to the straight top edge to form a portion of the flat surface. A color CRT comprising a shadow mask assembly according to claim 1.