JPH10235727A - Mold for forming resin dome spring and manufacture of resin dome spring using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To retain clicking feeling for a long period of time and eliminate variability in operating load between respective keys by a method wherein a paralleling liner is provided between a projected mold, having a projected part having the radius of curvature of the tip end part, which is smaller than that of the dome unit of the molded dome spring, and a recessed mold, having a recessed part with a diameter smaller than that of the projected part. SOLUTION: A projected mold 7 and a recessed mold 10 are incorporated into a press molding device while paralleling liners 19 are provided at four places of the circumference between them. As a result, deviation upon incorporating the molds 7, 10 is corrected and the thickness of base part of dome spring is equalized whereby load characteristics between respective keys are equalized. The diameter of the projected part 8 of projected mold 7 is specified so as to be 5-7mm based on the diameter of the dome and the summit is formed so as to be semi-spherical shape having the radius of curvature of 4-6mm while the diameter of the recessed part 12 of the recessed mold 10 is formed so as to be smaller than that of the projected part 8 and selected from 4-6mm in accordance with the inner diameter of the dome unit. When the mold is opened after molding, the radius of curvature of the dome part becomes larger than that of the tip end unit of projected part 8 of the projected mold 7 due to returning after molding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin dome-shaped spring (hereinafter referred to as a resin dome) used for a push button switch member for confirming an input by touch operation feeling in various information devices such as a cellular phone. Called a spring)
And a method for manufacturing a resin dome spring using the same.

[0002]

2. Description of the Related Art A dome spring used in a conventional push button switch is manufactured by press-forming or pressure-forming a thin metal or resin film. Metal dome springs (hereinafter referred to as metal dome springs) are excellent in durability and heat resistance, but cannot be used when it is desired to illuminate from below the dome because they do not have transparency. Also,
When used as a contact, it must be insulated from the substrate because it itself has conductivity,
Since it is heavier than a resin film, it is not a preferable material from the viewpoint of reducing the weight of a portable device.

On the other hand, a dome spring formed of a flexible resin film is transparent and insulative, and when incorporated into equipment,
Unlike a metal dome spring, it does not require troublesome work to secure insulation and is easy to incorporate into a device as a single sheet, but in a high temperature environment, the shape of the dome part collapses and it is easy to flatten, The click feeling at the time of input may disappear. Furthermore, the number of keys of a mobile phone or the like is 20 to 25 per sheet, and if there is variation in the thickness of the base portion connecting each key, the operating load between each key varies, and the same input feeling can be obtained. In order to give a sense of incongruity, extremely accurate molding was required. Therefore, the parallelism between the upper mold and the lower mold incorporated in the press device as well as the mold accuracy is required to have an accuracy of the order of 1/100 mm.
Furthermore, setting the parallelism between the upper die and the lower die requires strict adjustment using a spacer, which requires a long setup time.

In order to improve this point, the present inventors have previously proposed in Japanese Patent Application No. 8-200345 a resin dome spring formed using a thermoplastic resin film having a glass transition temperature of 110 ° C. or higher. did. Although heat resistance is improved by this, thermoplastic resin films with a glass transition temperature of 110 ° C or higher are generally more expensive than conventionally used polyethylene terephthalate films, and a new binder for contact printing ink is also used. Had to be selected. Furthermore, there was variation in the operating load between the keys, which was not satisfactory.

[0005]

According to the present invention, the shape of the dome portion does not collapse and the click feeling at the time of input does not disappear even if it is kept in a high temperature environment of about 100 ° C. for a long time. Another object of the present invention is to provide a mold for forming a resin dome spring which does not vary in the operating load between the keys and does not give an uncomfortable feeling at the time of input, and a method of manufacturing a resin dome spring using the same.

[0006]

According to the present invention, there is provided a resin dome spring forming die having a convex portion having a convex portion whose tip has a radius of curvature smaller than that of a dome portion of a dome spring to be molded.
A parallel set liner is interposed between the concave portion having a concave portion having a smaller diameter than the convex portion. The method for manufacturing this resin dome spring uses the molding die described above,
80-500 μm thermoplastic resin film with convex temperature 180
~ 200 ℃, concave temperature 130 ~ 150 ℃, pressure 100 ~ 50
Press molding with 0 gf / 1 key for 10 to 60 seconds.

The resin dome spring molded by using the molding die and the manufacturing method described above can be preferably used for a push button switch of various information equipment and the like, and the shape of the dome portion can be obtained even in a high temperature environment of about 100 ° C. Without collapse, there is no variation in the operating load between the keys, and all give the same click feeling.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, FIG. 1 shows a resin dome spring molded by using a molding die and a manufacturing method of the present invention. The resin dome spring 1 has a plurality of dome portions 2 connected by a base portion 3, and a contact 4 is printed on the top of the dome portion 2 with conductive ink. A spacer 5 is attached to the lower surface of the resin dome spring 1. When assembling the push button switch, the resin dome spring 1 is attached via a spacer 5 to a substrate (not shown) having fixed contacts. When the push button switch is assembled, the dome portion 2 is deformed by pressing the key portion 6 and the contact 4 comes into contact with the fixed contact on the substrate side. When the pressing force is released, the elastic force of the resin dome spring 1 is released. As a result, the shape of the dome portion 2 is restored, and functions as a push button switch. Next, a molding die and a manufacturing method of the resin dome spring 1 of the present invention will be described.
This will be described with reference to FIGS.

FIG. 2 shows a process for forming a resin dome spring.
FIG. 3 is a partial cross-sectional view of a press forming apparatus incorporating the molding die of the present invention, and FIG. 3 is an enlarged cross-sectional view of a convex mold 7 incorporated in the press molding apparatus and a concave mold 10 arranged at a position facing the convex mold 7. Show. The convex 7 comprises a convex 8 and a convex base 9, and the diameter of the convex 8 is 5 when the dome diameter is 4 mm.
7mm for 5mm, 6-7mm for 7mm, 7 for 6mm
mm, the top of which is a hemisphere with a radius of curvature of 4 to 6 mm. If the diameter of the projection 8 is less than 5 mm, the strength is insufficient, and it is difficult to set the projection 8 perpendicular to the projection base 9. If it exceeds 7 mm, it may be unfavorable because adjacent keys may collide depending on the arrangement of the keys. If the radius of curvature at the top of the convex portion 8 is less than 4 mm,
If the load variation of the molded article is large and exceeds 6 mm, a long pressurization is required to obtain a desired load, which is not preferable. In the concave mold 10, a concave base 12 is provided with a concave portion 12 whose center is located on an extension of the center line of the convex portion 8. The concave portion 12 has a circular shape with a diameter of 4 to 6 mm in plan view, and the diameter of the concave portion 12 is appropriately selected according to the inner diameter of the dome portion 2 (hereinafter, referred to as dome diameter). Recess 12
When the diameter is less than 4 mm, it is difficult to obtain a good click feeling.

The convex mold 7 and the concave mold 10 are incorporated in a press forming apparatus. The convex mold 7 is disposed on a die set substrate 13 via a heat insulating plate 14 and an upper heating plate 15. The heat insulating plate 17 and the lower heat plate 18 are disposed on the upper surface 16. Then, in order to accurately obtain the parallelism between the convex mold 7 and the concave mold 10, instead of adjusting the gap between the convex mold 7 and the concave mold 10 by the conventional spacer, parallel equal heights are provided at four places around the mold. A delivery liner 19 is provided. The parallel out liner 19 is formed with the convex 7 and the concave
A dome spring in which a plurality of dome portions are connected by a base portion can be obtained by simply disposing the dome portion between the convex shape 7 and the concave shape 10 by simply press-molding. As a result, the thickness of the base portion 3 becomes equal, and a dome spring having the same load characteristics between the keys can be obtained.

Next, a method of forming a resin dome spring using the above-described forming apparatus will be described. Temperature of convex 7 and concave
The temperature of 10 is adjusted by adjusting the temperatures of the upper heating plate 15 and the lower heating plate 18 so that the convex mold 7 has a temperature of 180 to 200 ° C and the concave mold 10 has a temperature of 130 to 150 ° C. At this time, if the temperature of the convex mold 7 is lower than 180 ° C., a resin dome spring having sufficient heat resistance cannot be obtained.
When the temperature exceeds 200 ° C., a click feeling is hardly generated when pressed. If the temperature of the concave mold 10 is lower than 130 ° C., sufficient heat resistance cannot be obtained, and if it exceeds 150 ° C., the resin film 20 sticks to the convex mold 7 during press molding, making it difficult to release the mold, and the shape accuracy is easily lost. . The pressure during press molding is 100 to 500 gf
It is preferable to perform this operation within the range of the / 1 key.If the value is less than 100 gf / 1, the shape accuracy and click feeling tend to vary, and the
If the pressure exceeds the / 1 key, the mold tends to bend due to excessive pressure. The pressurization time is 10 to 60 seconds.If the pressurization time is less than 10 seconds, the heating state becomes uneven, and the shape accuracy and click feeling tend to vary.If the pressurization time exceeds 60 seconds, the dome part returns to its original state during the pressing operation. Tend to be inverted. The smaller the radius of curvature of the projection 8 is, the higher the operating load can be obtained by short-time pressurization.

The resin film 20 used for forming the resin dome spring is made of an amorphous thermoplastic resin, a crystalline thermoplastic resin, a copolymer or a mixture thereof, and is made of polyethylene terephthalate, polyethylene naphthalate, polycarbonate, polyphenylene. Sulfide and the like are exemplified. Before forming, the conductive ink serving as the contact is printed and dried by screen printing, gravure printing or the like on the top surface of the dome portion 2 after the forming to form the contact. As the binder used for the conductive ink, a binder having an SP value (solubility index; square root of the cohesive energy of a molecule) that is substantially equal to or similar to that of the resin film 20 is selected from the viewpoint of adhesion to the resin film 20. For example, when polyethylene naphthalate having an SP value of about 10.3 is used for the resin film 20, a polyester resin having an SP value of about 10.3 or a urethane resin having an SP value of about 10.0 is used as a binder for the conductive ink. The thickness of the resin film 20 is 80 to 500 μm, preferably 100 to 300 μm.
m, more preferably 100 to 200 μm.

The resin film 20 provided with the contacts is inserted between the convex mold 7 and the concave mold 10, and the printed contact is inserted into the concave mold 7.
The alignment is performed so as to be located at the center of 12 (or on the extension of the center line of the projection 8), and the respective conditions of temperature, pressure and pressurization time are selected within the above-mentioned ranges, and the dome spring is formed.
When the mold is opened after molding, the dome portion of the molded dome spring returns to form (so-called springback), and the radius of curvature of the dome portion is the radius of curvature of the tip of the convex portion 8 of the convex mold 7. Will be larger. Finally, a resin dome spring is obtained by punching out a desired shape in which a predetermined number of dome portions are connected by punching or the like. The resin dome spring thus obtained is used as a dome spring spacer on the back surface of the base portion 3 (the side where the dome portion 2 is provided) in order to adjust the load characteristics of the dome spring when assembled to a push button switch. About 1mm from dome diameter
A PET film having a large diameter and a dome portion removed by punching or the like and having a thickness of 100 to 200 μm is bonded to one or both sides of a PET film coated with an adhesive such as an acrylic adhesive.

[0014]

The present invention will be described below with reference to more specific examples and comparative examples. Example 1 A press forming apparatus shown in FIG.
A convex mold having a convex part with a radius of curvature of 5 mm at the tip and a concave part having a concave part with a diameter of 5 mm and a depth of 5 mm is set, and a parallel liner is placed between the convex and concave parts. Arranged on four sides. The parallel liner secures the parallelism between the convex and concave shapes and sets the thickness of the base of the resin dome spring. Next, the temperature of the convex is heated to 190 ° C. and the temperature of the concave is heated to 145 ° C. by the upper heating plate and the lower heating plate provided in contact with the rear surfaces of the convex and concave, respectively. A 125-μm-thick biaxially stretched PET film, which is a thermoplastic resin film with printed contacts, was pressed under a pressure of 4 kgf / 23 key (174 gf / 1 key) for 15 seconds.
The resin dome spring shown in FIG. 1 to which the keys were connected was obtained.

The operating load and click rate of the resin dome spring were measured before and after the boiling treatment. Table 1 shows the results. The operating load in the table indicates a minimum value to a maximum value, and the click rate is obtained by (operating load−minimum load at the time of clicking) / operating load. In the comprehensive evaluation column, as the resin dome spring, a good resin dome spring was indicated by a circle and an unfavorable resin dome spring was indicated by a cross.

[0016]

[Table 1]

Examples 2 to 4, Comparative Examples 1 to 3;
No. 4 formed a resin dome spring in which 23 keys were connected in the same manner as in Example 1 except for the conditions shown in Table 1. The same applies to Comparative Examples 1 to 3, Comparative Example 1 and Comparative Example 3 did not use a paralleling liner, and Comparative Example 2 set the convex temperature to 160 ° C and the concave temperature to 120 ° C. . As a result, those of Examples 1 to 4 were good as resin dome springs, but Comparative Example 1 had a large variation in operating load regardless of before and after the boiling treatment, and Comparative Example 2
In Example 2, the operating load after the boiling treatment was reduced. Comparative Example 3
In Comparative Examples 1 to 3, the variation in the operating load was large regardless of before and after the boiling treatment, and the operating load after the boiling treatment was reduced. Comparative Examples 1 to 3 were all inconvenient as resin dome springs.

[0018]

The electronic device incorporating the resin dome spring obtained by the manufacturing method of the present invention is left in an automobile at about 100 ° C., or is used as an input member for in-vehicle equipment such as a car stereo or a navigator system. When used as, the resin dome spring does not deform compared to the conventional product,
The click feeling at the time of input is not impaired, the reliability of the function as a contact is improved, and the variation in load characteristics between many connected keys is small, and there is no discomfort, so conventional metal As compared with dome springs made of steel, the weight is reduced, and the range of use is expanded. In addition, in the conventional manufacturing method, in order to make the load between a number of connected keys substantially the same, a metal spacer having a thickness of about 10 to 100 μm is obtained so that an accurate parallelism can be obtained between the convex and concave dies. Had to be fine-tuned using this method, and this setup took 1-2 hours. However, according to the manufacturing method of the present invention, a parallel set liner having the same thickness is disposed between the convex and concave molds. In this way, accurate parallelism can be obtained, and setup time can be almost eliminated. As described above, according to the manufacturing method of the present invention, a resin dome spring having extremely excellent heat resistance, load stability, and productivity can be obtained, and some of them have a large contribution to the industrial field.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of a resin dome spring formed using a molding die and a manufacturing method of the present invention.

FIG. 2 is a partial cross-sectional view showing an example of a press molding apparatus incorporating the molding die of the present invention.

FIG. 3 is an enlarged sectional view showing a convex mold and a concave mold incorporated in the press molding apparatus of FIG.

[Explanation of symbols]

 1 ... resin dome spring, 2 ... dome part, 3 ... base part, 4 ... contact point, 5 ... spacer, 6 ... key part, 7 ... convex, 8 ... convex, 9 ... convex base, 10 ... concave, 11 ... concave base part, 12 ... concave part, 13 ... die set substrate, 14 ... heat insulating plate, 15 ... Plate, 16: die set substrate, 17: heat insulation plate, 18: lower heat plate, 19: parallel liner, 20 ... ..Resin film.

Claims (2)

[Claims] 1. A convex mold having a convex portion having a radius of curvature of a tip portion smaller than a radius of curvature of a dome portion of a molded dome spring.
A mold for molding a resin dome spring, wherein a parallel liner is interposed between a concave mold having a concave part having a diameter smaller than that of the convex part. 2. A mold having a thickness of 80 mm using the mold according to claim 1.
~ 500 μm thermoplastic resin film with convex temperature 180 ~
200 ℃, concave mold temperature 130-150 ℃, pressure 100-500
A method of manufacturing a resin dome spring, which comprises pressing with a gf / 1 key for 10 to 60 seconds.