JPH10106434A - Manufacture of shadow mask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain a spring back quantity after molding by lowering a punch, temporarily stopping fabricating operation in a condition of lightly coming into surface contact with a shadow mask raw material, and heating a shadow mask up to a desired temperature. SOLUTION: A pad 2 descends, and a periphery of a skirt expected part 8a of a shadow mask raw material 8 is fixed by a clamp surface of the pad 2, a clamp groove 2b and a bead 4b of a die 4. Next, a punch 1 descends, and comes into contact with the precedently placed shadow mask raw material 8, and in a condition where the punch 1 and the shadow mask raw material 8 slightly come into surface contact with each other, fabricating operation of the next process is temporarily stopped until the shadow mask 8 reaches a desired temperature (heated to 180 to 230 deg.C for 1 to 5 seconds). After the shadow mask 8 reaches the desired temperature, the punch 1 descends further, and starts to mold a curved surface of the shadow mask 8. Afterwards, a curved surface part of the shadow mask 8 and an annular curved surface bead are molded. A spring back quantity after molding can be restrained by such heating work.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a shadow mask, and more particularly to a method of manufacturing a shadow mask in which a shadow mask material plate is heated to a desired temperature and then formed using a forming apparatus.

[0002]

2. Description of the Related Art In general, a shadow mask for a color cathode ray tube is formed by forming a thin flat plate of a shadow mask material plate in which slit-shaped or round electron beam passage holes having a size of a micron unit are perforated in a predetermined arrangement. Is fixed to a glass panel and has a function of defining a correspondence between an electron beam emitted from an electron gun and a phosphor.

[0003] On the inner surface of the glass panel, red, green and blue phosphors are exposed and arranged at positions corresponding to the electron beam passage holes. If the relative position between the phosphor and the electron beam shifts, the electron beam emitted from the electron gun and passing through the electron beam passage hole of the shadow mask cannot reach a predetermined phosphor, causing color shift and color bleeding. Or

[0004] One of the factors causing the displacement between the electron beam passage hole and the phosphor is a thermal expansion deformation of the shadow mask called doming. As a countermeasure to reduce this doming, iron /
Nickel-based Invar alloy materials have been used as shadow mask materials.

A conventional shadow mask forming apparatus and a forming order using the Invar alloy material will be described (see Japanese Patent Application Laid-Open No. 5-342985). FIG. 2 is a cross-sectional view of an essential part showing an example of a state where a shadow mask material plate is placed on a conventional shadow mask forming apparatus. As shown in the figure, this molding apparatus aims at the final shape of the shadow mask and, in order to form the curved surface of the shadow mask as an upper mold, takes into account the springback of the shadow mask material plate 8 and the convex curved surface portion 1a. And a punch 1 having a side wall 1b for forming a skirt portion 18a (see FIG. 3) having an outer peripheral shape and a final shape, and a pad 2 disposed on the outer periphery of the punch 1 and having a clamp surface 2a and a clamp groove 2b. Are arranged. In the lower die, a shedder 3 having an upper surface having the same curved surface as the curved surface portion 1a of the punch 1 and a shedder 3 arranged on the outer periphery of the shedder 3 so as to face the pad 2 and a shadow together with the pad 2 It comprises a clamp surface 4c for holding the periphery of the mask material plate 8 and a die 4 on which a bead 4b is formed.

The punch 1 and the pad 2 are respectively fixed to an inner rod 5 and an outer rod 6 of the molding apparatus, and the shedder 3 is lifted upward by a die cushion rod 7 of the molding apparatus. Further, the die 4 partially rides around the shedder 3 and moves up and down as the shedder 3 goes up and down. When a shadow mask made of an Invar alloy material is formed by using a forming apparatus having such a configuration, since a springback amount is large in forming at normal temperature, a punch which is not shown but is in contact with the shadow mask material plate 8 is provided. In general, the pad 1, the shedder 3, and the die 4 are heated to about 200 ° C. by a heating device and molded.

FIG. 3 is a perspective view showing a situation in which wrinkles 9 occur on the outer periphery of the curved portion of the shadow mask due to springback of the shadow mask. As shown in the figure, the skirt portion 18a of the shadow mask 18 tends to spread outward due to springback, so that large wrinkles occur on the outer periphery of the curved surface portion of the shadow mask. The mechanical properties of a metal material have a property that the proof stress decreases as the temperature increases. In order to reduce the amount of springback by utilizing this property, molding is generally performed at an elevated temperature.

FIG. 4 is a flowchart of a conventional shadow mask forming process. Referring to the flowchart shown in FIG. 4 and the cross-sectional view of the main part of the shadow mask forming apparatus shown in FIG.
A process of forming the shadow mask 18 from the shadow mask blank 8 will be schematically described.

A shadow mask material plate 8 placed at a predetermined position on a die 4 which is a lower mold of the shadow mask forming apparatus,
It is formed in the following order. In the process A (predetermined skirt pressing step), the pad 2 descends,
And clamp surfaces 2a, 4c, clamp grooves 2b, beads 4b
The periphery of the planned skirt portion 8a of the shadow mask material plate 8 is fixed with the die 4 having the above.

In step C (curved surface forming step), the punch 1 descends and comes into contact with the previously placed shadow mask material plate 8 to start curved surface forming, and until the punch 1 contacts the upper surface of the shedder 3. The overhang is performed to form a shadow mask curved surface portion and an annular curved bead.

In the process D (predetermined skirt portion separating process), when the punch 1 starts to descend by contacting the shedder 3, the die 4 also descends, but the pad 2 stops descending by the stopper (not shown). A gap is formed between the diver 4 and the pad 2, and the fixing of the peripheral portion of the shadow mask blank 8 is released.

In step E (skirt part forming step),
After the die 4 reaches the lowest point, the punch 1 continues to descend and is bent between the inner wall 4a of the die 4 and the side wall 1b of the punch 1 to form the skirt portion 18a. That is, in this step, a prototype of the shadow mask 18 having the skirt portion 18a from the shadow mask material plate 8 is completed.

Further, the punch 1 reaches the lowest point and keeps its state for several seconds. Next, the punch 1 starts to rise.
At this time, the shadow mask 18 rises with the rise of the punch 1, and the end surface of the skirt portion 18 a contacts the clamp surface 2 a of the pad 2. The shadow mask 18 stops in this state and stops in this state, but since the punch 1 continues to rise, the shadow mask 18 and the punch 1 are completely separated. This operation is called knockout. The subsequent steps are omitted.

[0014]

As described above, the bent back skirt portion 18a of the shadow mask 18 made of an Invar alloy material has a springback effect due to the characteristics of the metal material. In order to suppress the springback amount, in the shadow mask forming step, the punch 1, the pad 2, the shedder 3, and the die 4, which are the portions that come into contact with the shadow mask material plate 8, are maintained at about 200 ° C. by a heating device. Consideration has been given to hot forming.

However, in the above-described method of manufacturing a shadow mask, each part that comes into contact with the shadow mask material plate 8, for example, the punch 1, the pad 2, the shedder 3, and the die 4, can be heated to a predetermined temperature. Since this is a continuous series of molding steps, the contact time between these parts and the shadow mask material plate 8 is extremely short (approximately 0 seconds).
Therefore, the shadow mask material plate 8 itself does not reach the desired temperature. Therefore, springback may remain in the shadow mask, and when the shadow mask is incorporated in the cathode ray tube, thermal expansion deformation called doming may occur. This causes color shift and color bleeding because the electron beam passing through the electron beam passage hole provided in the shadow mask cannot reach the center of the predetermined phosphor. In view of the above, the present invention has been proposed in view of the above-described problems. An object of the present invention is to provide a means for forming a curved surface after heating a shadow mask material plate itself to a desired temperature to minimize the amount of springback. It is another object of the present invention to provide a shadow mask capable of minimizing thermal expansion.

[0016]

SUMMARY OF THE INVENTION The present invention has been proposed for the purpose of solving the above problems, and has a pad for pressing a peripheral portion of a shadow mask material plate and the shadow mask provided opposite to the pad. A die for holding the material plate,
A punch that slides on the inner wall of the pad and the die to form a predetermined curved surface portion and a skirt portion on the shadow mask material plate, and a shedder that is provided to face the punch and holds the shadow mask material plate, In a method of manufacturing a shadow mask using a molding apparatus having means for heating a pad, a die, a punch, and a shedder, one of a series of molding steps is performed.
Immediately before a shadow mask curved surface forming step as a process, a method of manufacturing a shadow mask to which a mask material plate heating step of adding a mask material plate heating step of raising a mask material plate to a desired temperature by holding a punch in contact with a mask material plate and maintaining the surface contact state. I will provide a.

Further, the present invention provides a method of manufacturing a shadow mask, wherein the heating time of the mask material plate heating step is 1 to 5 seconds.

Further, the present invention provides a method for manufacturing a shadow mask, wherein a desired temperature of the mask material plate heating step is 180 to 230 ° C.

[0019]

Embodiments of the present invention will be described with reference to the drawings. The main object of the present invention is to suppress the springback of the Invar alloy material by adding only the manufacturing conditions without modifying the molding apparatus of the conventional equipment shown in FIG. FIG. 1 is a flowchart of a shadow mask forming step according to the present invention. Since the shadow mask forming apparatus is the same as the conventional apparatus, it will be described with reference to the cross-sectional view of the main part in FIG. A process of forming the shadow mask 18 from the shadow mask material plate 8 will be schematically described with reference to a flow chart of FIG. 4 showing a conventional forming process and a sectional view of a main part of the shadow mask forming apparatus shown in FIG.

The shadow mask material plate 8 placed at a predetermined position on the die 4 which is the lower mold of the shadow mask forming apparatus,
It is formed in the following order. Step A
In the (predetermined skirt portion pressing step), the pad 2 descends, and the pad 2 and the die 4 having the clamp surfaces 2a and 4c, the clamp groove 2b, and the bead 4b move around the planned skirt portion 8a of the shadow mask material plate 8 around the skirt. Fix it.

Next, in the shadow mask manufacturing method according to the present invention, a main step B (a mask material plate heating step) is added. This step B (mask material plate heating step) is added as a step immediately before step C (curved surface forming step), and a heating time for raising the shadow mask material plate 8 to a desired temperature is set. The purpose of this is to sufficiently heat.

This step B (mask material plate heating step)
The punch 1 descends and comes into contact with the previously placed shadow mask blank 8, and the punch 1 and the shadow mask blank 8
The method is characterized in that the shaping operation for the next step is temporarily stopped until the shadow mask material plate 8 reaches a desired temperature and the shadow mask material plate 8 is heated in a state in which the surfaces of the surfaces are in light surface contact. In this state, the surface of the punch 1 and the surface of the shadow mask blank 8 are in light contact with each other. In this state, the shadow mask blank 8 is heated not only by the punch 1 but also by the pad 2, the shedder 3 and the die 4. Become. The relationship between the desired temperature and the heating time is experimentally set at the desired temperature and the heating time at which the springback amount is minimized, and the desired temperature of the shadow mask blank 8 is set to 180 to 23.
Experiments have shown that a suitable heating time is 1 to 5 seconds in order to maintain the temperature at 0 ° C.

Next, in step C (curved surface forming step), after the shadow mask material plate 8 reaches a desired temperature,
The punch 1 is further lowered to start forming the curved surface of the shadow mask blank 8, and the punch 1 is extended until the punch 1 contacts the upper surface of the shedder 3 to form a shadow mask curved surface portion and an annular curved bead. Steps D (a step of isolating the planned skirt) and steps E
(The skirt portion forming step) is the same as the conventional one, and therefore the description thereof is omitted here.

[0024]

As described above, according to the method of manufacturing a shadow mask of the present invention, a mask material plate heating step in step B is additionally set, and the skirt portion is formed after the shadow mask material plate is heated to a desired temperature. By processing, a means for suppressing the amount of springback after molding is provided. Accordingly, the shadow mask formed by this means has very little springback remaining.
According to the shadow mask manufacturing method of the present invention, when the formed shadow mask is incorporated into the cathode ray tube, thermal expansion deformation called doming does not occur. As a result, the thermal expansion deformation of the shadow mask is eliminated, and the electron beam passing through the electron beam passage hole provided in the shadow mask surely strikes a predetermined phosphor. That is, color shift and color bleeding failure due to thermal expansion of the shadow mask are eliminated.

[Brief description of the drawings]

FIG. 1 is a flowchart of a shadow mask forming process according to the present invention.

FIG. 2 is a sectional view of a main part of an example of a conventional shadow mask forming apparatus.

FIG. 3 is a perspective view showing a situation in which wrinkles occur on the outer periphery of a curved portion of a shadow mask.

FIG. 4 is a flowchart of a conventional shadow mask molding process.

[Explanation of symbols]

 Reference Signs List 1 punch 1a curved surface portion 1b side wall 2 pad 2a, 4c clamping surface 3 shedder 4 die 4a inner wall 4b bead 5 inner rod 6 outer rod 7 die cushion rod 8 shadow mask material plate 8a scheduled skirt 9 wrinkle 18 shadow mask 18a skirt

Claims (3)

[Claims] A pad for pressing a peripheral portion of a shadow mask material plate, a die provided opposite to the pad for holding the shadow mask material plate, and a pad sliding on an inner wall of the pad and the die. A punch for forming a predetermined curved surface portion and a skirt portion on a shadow mask material plate, and a shedder provided to face the punch and holding the shadow mask material plate, and the pad, die, punch, and shedder In a method of manufacturing a shadow mask including a series of steps of pressing a planned skirt, forming a curved surface, separating a planned skirt portion, and forming a skirt portion using a forming device having a means for heating the skirt portion, immediately before the curved surface forming step, A mask material plate heating step of bringing the punch into contact with the mask material plate to maintain the surface contact state and raising the mask material plate to a desired temperature is added. Method of manufacturing a shadow mask according to claim. 2. The heating time of said mask material plate heating step is one.
2. The method for manufacturing a shadow mask according to claim 1, wherein the time is from 5 to 5 seconds. 3. The method according to claim 1, wherein the desired temperature of the mask material plate heating step is 1
2. The method according to claim 1, wherein the temperature is 80 to 230 [deg.] C.