JP2001006538A - Manufacture of color cathode-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the shape retaining strength of a shadow mask to prevent its deformation and to reduce maintenance and repair expenses and energy required for tempering by annealing the flat shadow mask with its effective part mainly bulged into a curved surface without being annealed to draw a skirt part around the effective part. SOLUTION: An effective part 12 having bored holes 13 is shaped into a curved surface by means of bulging without annealing a flat shadow mask 18, and an annular reinforcing beat 20 for restraining the deformation of the effective part 12 is formed in the circumference of the effective part 12. Thereafter, the projecting surface of the effective part 12 is oriented upward, and the shadow mask is annealed by keeping it at 500-850 deg.C for around five minutes in a wet hydrogen atmosphere when it is made of an invar material. Thereafter, a skirt part 14 is formed around the effective part 12 through the reinforcing beat 20 by means of drawing so that a shadow mask 15 is shaped. Thereby, the strength of the shadow mask is enhanced without degrading the characteristics of a color cathode-ray tube.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a color cathode ray tube, and more particularly, to a method for manufacturing a color cathode ray tube in which the shape holding strength of a shadow mask is increased.

[0002]

2. Description of the Related Art Generally, a color cathode ray tube has an envelope comprising a substantially rectangular panel 1 and a funnel-like funnel 2, as shown in FIG. A phosphor screen 3 is formed, and a substantially rectangular shadow mask structure 4 is arranged inside the phosphor screen 3 so as to face the phosphor screen 3. On the other hand, an electron gun 8 that emits three electron beams 7B, 7G, 7R is sealed in the neck 6 of the funnel 2. And this electron gun 8
The three electron beams 7B, 7G, 7R emitted from the light source are deflected by a deflection yoke 10 mounted on the outside of the funnel 2, and the phosphor screen 3 is horizontally and vertically scanned through a shadow mask 4 to display a color image. It is formed in the structure which does.

The above-mentioned shadow mask structure 4 is for selecting the three electron beams 7B, 7G, 7R so as to properly land on the corresponding three-color phosphor layers. As shown in FIG. A substantially rectangular shadow mask 15 having a large number of through-holes 13 formed in an effective portion 12 having a curved surface facing the screen and a skirt portion 14 provided around the effective portion 12, and a skirt portion of the shadow mask 15 And a substantially rectangular mask frame 16 attached to the mask frame 16.

Conventionally, the shadow mask 15 is formed of a low carbon steel sheet. However, the shadow mask 15 made of the low carbon steel sheet has a large coefficient of thermal expansion and has a high coefficient of thermal expansion.
When heated by the collision of G, 7R, it swells in the direction of the phosphor screen, causing a color shift. In order to prevent the color shift due to this thermal expansion, a shadow mask 15 made of a low thermal expansion material such as an amber material (iron / nickel alloy) has been put to practical use. This shadow mask 15 is mainly used for a display tube or the like that requires high image quality.

Generally, as shown in FIG. 8, a shadow mask 15 is formed by forming a through hole in a thin metal plate such as the above low carbon steel plate or invar material by a photoetching method.
And (b), the plate-shaped shadow mask 18
After annealing the flat plate-shaped shadow mask 18 in a wet hydrogen atmosphere, overhanging is performed as shown in FIG.
As shown in FIG. 2C, the skirt portion 14 is manufactured by forming the effective portion 12 having the through hole into a curved surface, and then forming the skirt portion 14 by drawing. The annealing is a method for growing the crystal structure of a thin metal sheet so that a desired shape can be easily formed. In the shadow mask 15 made of an amber material, 880 to 930 is used.
It is performed at ℃.

[0006]

As described above, conventionally,
The shadow mask of the color cathode ray tube was made of a low carbon steel sheet with a large coefficient of thermal expansion, but it was made of a low thermal expansion material such as amber material to prevent color shift when heated by the collision of electron beams. Has been put to practical use.

In general, a shadow mask is formed by forming through holes in a thin metal plate such as a low carbon steel plate or an invar material by a photo-etching method to form a plate-shaped shadow mask, and annealing the plate-shaped shadow mask in a wet hydrogen atmosphere. After that, the effective portion having the through-hole formed therein is formed into a curved surface by overhanging, and then the skirt portion is formed by drawing. The shadow mask made of amber material is annealed at 880 to 930 ° C. I am doing it.

[0008] However, if a flat plate-shaped shadow mask made of Invar material is annealed at the above-mentioned temperature, the shaping becomes easy. Easy to deform.

Conventionally, in order to increase the shape holding strength,
Although measures are taken by means such as increasing the thickness of the shadow mask or increasing the curvature of the effective portion of the shadow mask, these measures have limitations and sometimes sacrifice the characteristics of a color cathode ray tube. Further, the conventional shadow mask manufacturing method has problems that the annealing temperature is high, the maintenance cost of the annealing furnace is high, and large energy consumption is required.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and enhances the shape holding strength of a shadow mask without sacrificing the characteristics of a color cathode ray tube and reduces the energy required for annealing. The aim is to get the method.

[0011]

SUMMARY OF THE INVENTION A step of annealing a plate-shaped shadow mask having a large number of through holes formed in an effective portion, a step of forming the effective portion into a curved surface by overhanging, and a process of drawing the curved surface by drawing. Forming a skirt portion around the formed effective portion; anda method of manufacturing a color cathode ray tube having a skirt portion around the effective portion having a curved surface from the step of forming the skirt portion without annealing the flat plate-shaped shadow mask. Mainly, the effective portion is overhanged on a curved surface, the overhanged shadow mask is annealed, and then the skirt portion is drawn around the effective portion.

The plate-shaped shadow mask is made of an invar material.

Further, the annealing is performed at 500 to 850 ° C.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the main steps of manufacturing a color cathode ray tube. In a color cathode ray tube, first, a through hole is formed in a substantially rectangular area of a thin metal plate made of a low thermal expansion material such as low carbon steel or amber material by a photo etching method, and the area where the through hole is formed is effectively used. A flat shadow mask to be used as a part is manufactured. Next, the plate-shaped shadow mask is formed into a substantially rectangular shadow mask having a skirt portion formed around the effective portion by press-forming the effective portion into a curved surface. Next, the shadow mask and a separately formed substantially rectangular mask frame are welded to assemble a substantially rectangular shadow mask structure.

Next, an elastic support is welded to the mask frame of the shadow mask structure, and the elastic support is detachably engaged with a stud pin provided on a substantially rectangular panel to form a panel / mask assembly. Assemble the solid. Next,
For the panel / mask assembly, a phosphor screen is formed on an inner surface of the panel by a photoengraving method using the shadow mask assembly as an optical mask. Next, the shadow mask structure used as the optical mask is mounted on the panel on which the phosphor screen is formed. Then, the panel on which the shadow mask structure is mounted is combined with a funnel-shaped funnel having a conductive film formed on the inner surface, and these panels and the funnel are joined by frit glass. Next, the separately assembled electron gun is sealed in the neck of the joined funnel. Next, the envelope composed of the sealed panel and the funnel of the electron gun is evacuated.

Next, finishing processes such as flashing of the getter disposed in the envelope, aging for activating the cathode, and high voltage treatment for increasing the withstand voltage are performed.
Thereafter, it is manufactured by performing a characteristic inspection.

FIG. 2 shows a shadow mask forming process in this embodiment. As shown in FIG. 8, a conventional shadow mask is formed by annealing a flat plate-shaped shadow mask, and then turning the effective portion having the through hole into a curved surface,
Although the skirt portion is formed around the effective portion, in this embodiment, the flat shadow mask 18 manufactured in the previous step shown in FIGS. 3A and 3B can be formed without annealing. As shown in FIG. 3 (c), the effective portion 12 in which the through hole 13 is formed is formed into a curved surface by overhanging processing (the first portion).
Step molding). Further, in the shadow mask of the illustrated example, an annular reinforcing beat 20 for suppressing deformation of the effective portion 12 is formed on the outer periphery of the effective portion 12 at the same time. Thereafter, annealing is performed in a wet hydrogen atmosphere with the convex surface of the effective portion 12 formed into the curved surface facing upward. In the case of a shadow mask made of amber material, this annealing is performed by maintaining the temperature at 500 to 850 ° C. for about 5 minutes. Then, as shown in FIG. 3D, the skirt portion 14 is formed around the effective portion 12 through the reinforcing beat 20 by drawing (second stage molding) to form the shadow mask 15.

As described above, the plate-shaped shadow mask 18
When the effective portion 12 having the through-hole 13 formed therein is formed into a curved surface without annealing, the effective portion 12 is formed into a curved surface, then annealed, and then the skirt portion 14 is formed. The shadow mask 15 can be formed at a lower annealing temperature, and the shape holding strength of the shadow mask can be reduced without performing means for deteriorating the characteristics of the color cathode ray tube, such as increasing the thickness of the shadow mask or increasing the curvature of the effective portion. And the deformation of the shadow mask after the color cathode ray tube manufacturing process and after the manufacturing can be prevented. Moreover, since the annealing temperature is low, the life of the annealing furnace is about three times longer than that of the conventional one, the maintenance cost can be reduced, and the energy required for annealing can be reduced.

FIG. 4 shows a shadow mask made of an amber material to be incorporated in a color cathode ray tube having a diagonal dimension of 46 cm, at an annealing temperature of 600 ° C. and a thickness test of a shadow mask formed by the method of the above embodiment and a drop test. The relationship with the shape retention strength is shown in comparison with that of a shadow mask molded by a conventional molding method. Line 22 is a shadow mask formed by the method of this embodiment, line 23
Is the shape retention strength of the shadow mask formed by the conventional forming method.

As shown in FIG. 4, the shadow mask according to the method of this embodiment has a shape holding strength that is about 30% or more higher than that of a shadow mask formed by a conventional molding method, is less likely to be deformed, and has a small thickness. Even if it is 0.10 mm, if the curvature of the effective portion is relatively large, it is within a practical range. However, in practice, the thickness of the plate-shaped shadow mask is 0.11 mm or more because of a deformation in handling the flat-plate-shaped shadow mask before molding. Even in the case of a large color cathode ray tube having a diagonal dimension of 46 cm or more, a shadow mask having a plate thickness of 0.12 mm can be practically used.

The reason why a shadow mask having a large shape retention strength can be obtained by the two-stage molding as described above is as follows.

In a conventional shadow mask, after forming an effective portion having a curved surface, a skirt portion is subsequently formed.
If the shadow mask material (flat shadow mask) is hard, it will break, wrinkle,
Distortion, deformation, etc. occur, making it impossible to mold into a predetermined shape. In order to avoid this, conventionally, the shadow mask material was annealed at around 900 ° C. to recrystallize the shadow mask material in an easily moldable state, softened and then formed. However, when analyzing the shaping of the shadow mask, if the shaping is performed in a hard state that does not anneal, the above-described problems such as breakage occur in the stage of narrowing down the skirt portion after forming the effective portion. On the other hand, the most important portion as the shadow mask is the effective portion, and it has been found that this effective portion can be formed into a predetermined curved surface without breaking even in a hard state without annealing. Moreover, even after annealing, the formed effective portion has a lower crystallization speed than that of the non-formed portion (the portion to be a skirt portion) and maintains its hardness.

For this reason, the effective portion is formed without annealing, and then the annealing is performed to minimize the reduction of the shape holding strength of the effective portion, and the skirt portion is not required to be processed with high precision. Molding can be enabled. In other words, in this case, the annealing may be performed by recrystallizing the shadow mask material to some extent and lowering the hardness to such an extent that the skirt portion can be formed, thereby obtaining a shadow mask having a large shape holding strength.

In particular, the recrystallization of the invar material has a relationship shown by a straight line 25 in FIG. 5 with the annealing temperature. That is, recrystallization starts at the level 2 temperature shown on the horizontal axis,
Recrystallization does not occur in the temperature range of level 1 lower than level 2. Further, recrystallization is completed at the temperature of level 4 and a mixed state occurs in the temperature range of levels 2 and 4. For this reason, by regulating the annealing temperature to be slightly higher than level 2 and slightly lower than level 4 to 500 to 850 ° C., the skirt portion can be formed with acceptable accuracy without breaking or the like.

[0026]

As described above, without annealing the flat-plate-shaped shadow mask, the effective portion having the perforated hole is formed into a curved surface, and after forming the effective portion, annealing is performed, and then the skirt portion is formed. Then, the shadow mask can be formed at a lower annealing temperature than before, and the shadow mask can be formed without performing means for deteriorating the characteristics of the color cathode ray tube, such as increasing the thickness of the shadow mask or increasing the curvature of the effective portion. And the deformation of the shadow mask after the production of the color cathode ray tube and the production thereof can be prevented.
Moreover, since the annealing temperature is low, the life of the annealing furnace is prolonged, the maintenance cost is reduced, and the energy required for annealing can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of a color cathode ray tube manufacturing process according to an embodiment of the present invention.

FIG. 2 is a diagram showing a shadow mask manufacturing process in the color cathode ray tube manufacturing process.

3A and 3B are views for explaining the method of manufacturing the shadow mask. FIG. 3A is a plan view of a flat shadow mask used for manufacturing the shadow mask, and FIG. 3 (c) is a side view of a shadow mask in which an effective portion is formed, and FIG. 3 (d) is a side view of a shadow mask in which an effective portion and a cover portion are formed.

FIG. 4 is a diagram showing a relationship between a plate thickness and a shape holding strength of a shadow mask according to an embodiment of the present invention, in comparison with that of a conventional shadow mask.

FIG. 5 is a diagram for explaining a relationship between an annealing temperature of an invar material and recrystallization.

FIG. 6 is a diagram showing a configuration of a color cathode ray tube.

FIG. 7A is a plan view showing the configuration of a shadow mask structure, and FIG. 7B is a cross-sectional view thereof.

FIG. 8 is a diagram showing a manufacturing process of a conventional shadow mask.

9A and 9B are views for explaining a conventional method of manufacturing a shadow mask, wherein FIG. 9A is a plan view of a flat shadow mask used for manufacturing the shadow mask, FIG. 9B is a side view thereof, FIG. 9C is a side view of the formed shadow mask.

[Explanation of symbols]

 Reference Signs List 12 effective portion 13 through hole 14 skirt portion 15 shadow mask 18 flat plate shadow mask

Claims (3)

[Claims] 1. A step of annealing a plate-shaped shadow mask having a large number of through holes in an effective portion, a step of forming the effective portion into a curved surface by overhanging, and a process of forming the effective portion into a curved surface by drawing. Forming a shadow mask having a skirt around an effective portion formed of a curved surface from a step of forming a skirt around the portion, wherein the flat shadow mask is mainly annealed without annealing the flat plate-shaped shadow mask. A method of manufacturing a color cathode ray tube, comprising: projecting a portion into a curved surface; annealing the projected shadow mask; and then drawing a skirt around the effective portion. 2. The method according to claim 1, wherein the flat shadow mask is made of an invar material. 3. The method for producing a color cathode ray tube according to claim 1, wherein the annealing is performed at 500 to 850 ° C.