JPH08112822A - Cover member for push button switch, and its preparation - Google Patents

Abstract

PURPOSE: To obtain easily a cover member for a push button switch with a low stroke and a high click ratio by integrating a thin thickness part and a base part of a draw processed polyethylene terephthalate with a key top part made of a high hardness resin with a Shore D hardness of at least a specified value. CONSTITUTION: A cover member 1 for push button switch is prepd. by molding integratedly a base part 2 and a thin thickness part 3 prepd. by draw processing of a PET sheet with a key top part 4 prepd. by casting of a high hardness resin with a Shore D hardness of at least 40 deg.. If necessary, an electrically conductive contact point 5 and a key top printing part 6 for letters, numerals, marks, etc., are provided thereon, but this electrically conductive contact point 5 is prepd. by performing electrically conductive printing on a PET sheet before draw processing or after molding integrally and the printing of letters, numerals, marks, etc., on the key top part is performed by screen printing and pad printing. In addition, as there exists no deviation of positioning which causes decrease in feeling of operation and pushing force for inputting is applied uniformly and at the central part of a PET dome, a stable feeling of operation (feel of click) can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention satisfies a cover member for a push button switch, particularly a thin device, and has a stroke of 0.5 mm.
The present invention relates to a cover member for a push button switch used in a calculator, a remote controller, a telephone, an OA device, a home electric appliance and the like, which is small as follows and has a high click rate of 30% or more, and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for thinner cover members for push button switches, but it is most preferable to obtain a click feeling when recognizing an input. There is a demand for a spring mechanism capable of providing a click feeling with a short stroke as well as reducing the thickness of each part such as a key top part.

This click feeling is calculated as a click rate from the curve showing the relationship between the stroke and the load shown in FIG. 5, and the point a is the peak load, the point b is the make load, and the click rate = (a It is calculated as −b) / a × 100 (%). Conventionally, a polyethylene terephthalate (hereinafter abbreviated as PET) is used as a spring mechanism for generating a high click rate with a short stroke of about 0.5 mm or less. ) A thin-walled portion obtained by drawing a sheet into an inverted arm shape and conductively printing a movable contact at a predetermined position as required, a so-called PET dome is often used.

[0004]

This PET dome has the advantages that it has a simple structure and can be manufactured at a relatively low cost, but it also has a clear and stable operation feeling (clicking) as shown in FIG. In order to obtain the feeling), generally, a pusher 14 for pushing the central portion of the PET dome 13 and a key top portion 15 on which characters and symbols are printed are installed, but this is a component. Due to the increase in the number of points, there is a disadvantage that the original features of thinning and cost reduction cannot be fully utilized. For this reason, as shown in FIG. 4, a silicone rubber molded body 16 is used for the pusher 14 and the key top portion 15 as shown in FIG. 4, but this silicone rubber molded body is made of a normal resin. Since the hardness of the PET dome is lower than that of the PET dome, the click feeling of the PET dome is attenuated and cannot be transmitted sufficiently.

Further, the PET dome has a drawback in that a sufficient feeling cannot be obtained unless the apex of the PET dome is pressed, and the feeling is significantly deteriorated when the position of the pressing element is displaced, and therefore, there is a problem that a plurality of PET domes cannot be obtained. When the keys are mixed, the input switch has a very serious defect that the operation feeling is different and the malfunction occurs unless the pusher and the PET dome are properly aligned.

[0006]

The present invention relates to a cover member for a push button switch and a method for manufacturing the same, which solves the above disadvantages and problems, and the cover member for a push button switch is made of drawn PET. The thin-walled part and the base part are made into a key top part made of a high hardness resin having a Shore D hardness of 40 degrees or more, and this manufacturing method is performed by drawing a PET sheet. After forming the thin portion and the base portion of the cover member for the push button switch, a high hardness resin having a Shore D hardness of 40 degrees or more is cast on the same mold, and is cured by reaction to form the key top portion. It is characterized by integrating both.

That is, the present inventor has conducted various studies to develop a cover member for a push button switch which generates a high click rate with a low stroke, and as a result, a PET sheet is drawn on a mold into a predetermined reverse arm shape and the push button is pressed. After forming the thin part and the base part of the switch cover member, cast the key top part from a high hardness resin with a Shore D hardness of 40 degrees or more in the same mold and react it to cure. When these are integrally molded, the stroke is 0.5 mm or less and the click rate is 30.
The present invention has been completed by finding that it is possible to easily obtain a target cover member for a push button switch having a low stroke and a high click rate of not less than%. This will be described in more detail below.

[0008]

The present invention relates to a cover member for a push button switch that generates a high click rate (30% or more) with a low stroke (0.5 mm or less), which is a thin portion and a base portion formed by drawing a PET sheet. And a key top part made of a high hardness resin having a Shore D hardness of 40 degrees or more is integrally formed. However, if necessary, a movable contact is provided by conductive printing or the like. The
Characters, figures, etc. are printed on the key top portion.

The push button switch cover member is made of PE.
Since the key top part made of high-hardness resin is formed and integrated directly on the T dome, there is no positional deviation that causes a reduction in the feeling of operation, and the pressing force at the time of input is evenly applied to the central part of the PET dome. So always stable operation feeling (click feeling)
And the key top part is integrated, so the assembly is excellent, and because the key top part is made of high-hardness resin, the operation feeling (click feeling) of the PET dome is less attenuated, The advantage of being clear is given.

The push button switch cover member of the present invention is, for example, the one shown in FIG. FIG. 1 is a vertical sectional view of a cover member for a push button switch according to the present invention.
The push button switch cover member 1 is formed by integrally molding a base portion 2 and a thin portion 3 formed by drawing a PET sheet and a key top portion 4 formed by cast molding of a high hardness resin. If necessary, the conductive contact part 5, letters,
A key top printing unit 6 for numbers and symbols is provided,
The conductive contact portion 5 may be conductively printed on a PET sheet before being drawn, or may be conductively printed after molding and integration. Screens and pads are used for printing characters, numbers and symbols on the key top portion. For example, a known method may be used.

The thickness of the PET sheet used here is
If it is less than 25 μm, the peak load becomes too low and the click feeling deteriorates. If it is thicker than 250 μm, the peak load becomes too high and the operability deteriorates.
The thickness is preferably set to μm, preferably 75 to 125 μm, and this may be appropriately selected from this range according to the operation load of the switch and the operation feeling (click feeling). In addition, this PET
The sheet is inserted into the mold and pressed by pressing,
At this time, if necessary, 60 at 200 ° C to prevent shrinkage.
The heat treatment may be carried out for about a minute, and the drawing may be carried out at a sheet temperature of about 150 to 200 ° C. if necessary. After that, an appropriate amount of high-hardness resin, which will be the key-top portion, may be injected from the opening of the upper mold, and may be reaction-cured to be integrated.

The high-hardness resin used here may be selected from general resins such as silicone-based, urethane-based, epoxy-based, acrylic-based, and PET-based resins, which are preferably in liquid form for molding. , Preferably with a viscosity of 500
Poise or less makes filling into the mold easy and dropping with various known discharge devices such as plunger type, pump dispenser, air dispenser, roller type tube pump dispenser, piano touch type tube dispenser, etc. Filling becomes possible.

In addition, it is necessary that the hardness of this product is high in order to reduce the attenuation of the operation feeling (click feeling) as much as possible. Therefore, it is necessary that the Shore D hardness is 40 degrees or more. To be done. This curing method is generally heat curing, and it is particularly preferable that the PET sheet is heated when it is drawn. However, when the drawing is not accompanied by heat, a two-component curing type or Curing by electron beam may be used, and in the case of transparent or translucent, an ultraviolet curing method may be appropriately selected.

A thin portion formed from this PET sheet,
The base part and the key top part made of high-hardness resin are integrally molded by urethane-based, epoxy-based, acrylic-based, and PET-based resins that chemically bond and bond the resin forming the key top part during reaction curing. It is preferable to use an unsaturated polyester such as, but when using a silicone type excellent in heat resistance, weather resistance, yellowing resistance, etc., a primer may be used as an adhesive if necessary. .

The push button switch cover member according to the present invention may be manufactured by the method shown in FIG. Figure 2
2 (a), (b), and (c) are vertical cross-sectional views in the order of manufacturing steps of the cover member for a push button switch according to the present invention. This manufacturing process is performed as shown in FIG. A lower molding die 7 having a convex portion in the shape of one or a plurality of reverse arms and a concave portion in the shape of a reverse arm that forms a cavity corresponding to this, and a portion corresponding to the key top portion is a through hole. The PET sheet 10 is placed between the upper mold 8 and pressure is applied, and if necessary, heating is performed to draw.

Next, as shown in FIG. 2 (b), the PET sheet 10 is drawn and held in the mold, and the above-mentioned various discharges are made from the through holes corresponding to the key tops of the upper mold 8. A hard liquid resin is dropped and filled by a device 12 to form a key top portion 11. At this time, in order to keep the liquid level constant, it is preferable to provide a step 9 of about 0.1 to 1.0 mm on the entire circumference of the side surface of the through hole of the upper mold. Subsequently, as shown in FIG. 2C, the resin is cured by a method such as heating to be integrated with the PET sheet 10 that has been drawn, and then the mold is opened to take out the product and the cover member for the push button switch of the present invention. 1 is obtained.

[0017]

EXAMPLES Next, examples and comparative examples of the present invention will be described. Example 1 A liquid urethane resin, Coronate 4048 [trade name, manufactured by Nippon Polyurethane Co., Ltd.], was dried at about 80 ° C. in a dry nitrogen gas atmosphere.
After heating and melting, the reaction vessel was charged with a predetermined amount and degassed under reduced pressure (5 to 10 mmHg) at about 75 ° C., then 44-methylenebis, 2
-Chloraniline is separately melted at about 110 ° C and added at a ratio of 18 parts by weight to 100 parts by weight of the previously heated Coronate 4048 and stirred to form a liquid urethane resin formulation.

Then, Lumirror 100S (trade name, manufactured by Toray Industries, Inc.) as a PET was placed in a mold heated to 150 ° C., pressure was applied to perform reverse arm-shaped drawing, and then the mold was not opened. A liquid urethane resin mixture that has been compounded and adjusted in advance is used by using an air dispenser AD3000VH [trade name of Iwashita Engineering Co., Ltd.], and is dropped into the through holes corresponding to the key top portion of the upper mold, and after curing Then, the molded product was taken out from the mold, and 10 hard resin key tops and the drawn PET sheet were connected in series to obtain an integrated body. In addition, in order to print characters on the top surface of the key top of this molded product, 20 parts by weight of titanium oxide A-220 [trade name of Ishihara Sangyo Co., Ltd.] was added as a pigment to the liquid urethane resin mixture described above. , Kneading and dispersing to make a white paste ink,
The molded body was screen-printed and put in a drying oven set at 150 ° C. for 120 minutes to dry and cure the ink.

Next, in order to print the movable contact portion, 100 parts by weight of the conductive urethane paste MCP-2601 [trade name of Mitsui Toatsu Chemicals, Inc.] was added to the curing agent Orestar (trade name of the same company). 10 parts by weight of a conductive ink was mixed to form a conductive ink, which was pad-printed on the PET sheet surface on the back surface of the key top of the molded body, and placed in a drying oven set at 80 ° C for 30 minutes,
When the ink was dried and cured, a character print and a movable contact were printed, and ten hard key tops with a key size of φ5 mm and a PET diaphragm sheet were connected in series to obtain a cover member for a push button switch. The peak load of this push button switch cover member is about 180 to 220g, and the stroke is 0.5.
mm, the click rate at this time is about 30 to 50%, and this value shows almost no change even if the position where the key top is pressed is shifted by about 1 mm, as shown in Tables 1 and 2 below. It was

Example 2 High hardness silicone resin dimethyldiphenyl silicone resin X32-1195 [trade name of Shin-Etsu Chemical Co., Ltd.] 100 parts by weight of crosslinking agent CX-1195 [trade name of Shin-Etsu Chemical Co., Ltd.] ] 10 parts by weight of curing catalyst X-93-555 [trade name of Shin-Etsu Chemical Co., Ltd.] 0.4 part by weight was used as a base material, and a coloring agent STVX683 [product of Dainichiseika Kogyo KK] [Name]]
A PET sheet is drawn in the same manner as in Example 1 above.
Drop-fill the upper mold through hole of the mold heated to 150 ℃,
After curing, the molded product was taken out of the mold to obtain a molded product in which a high hardness resin key top and a drawn PET sheet were integrated.

In order to print characters on the top surface of the key top of this molded product, the above-mentioned dimethylphenyl silicone resin is used.
20 parts by weight of titanium oxide / A-220 [trade name of Ishihara Sangyo Co., Ltd.] as a pigment was added to 100 parts by weight of the pigment, kneaded and dispersed to form a white paste-like ink, which was screen printed.
The ink was dried and cured by placing it in a drying oven set at 00 ° C for 60 minutes. Next, the movable contact portion is printed and cured in the same manner as in the above-described first embodiment. In this way, character printing and movable contact are printed, and the key size is φ5 mm, and 10 high hardness key tops and PET are used. A cover member for a push button switch in which diaphragm sheets are continuous and integrated is obtained. The peak load of this push button switch cover member is approximately 180 to 220.
g, stroke 0.5 mm, click rate at this time is about 30
It was ~ 50%. This value is 1mm when pressing the key top
Almost no change was observed even with a slight shift, and these showed the results shown in Tables 1 and 2 described later.

COMPARATIVE EXAMPLE 1 A conventionally known push button switch having a structure in which a high hardness resin key top as shown in FIG. 3, a pusher and a PET dome are combined in separate pieces, and has 10 keys, and the dome diameter is 5 mm.
When the operating characteristics were measured, the peak load was about 150 to 230 g, the stroke was 0.5 mm, and the click rate at this time was about 30 to 50%, which is equivalent to the cover member for the push button switch of the present invention. However, the position of the pusher is 0.2, 0.4, 0.6, 0.8m from the center of the dome.
m When measured by displacing each, the click rates are about 30-45%, 15-25%, 10-20%, 5-15%, respectively, and the operation feeling (click feeling) is significantly reduced due to misalignment. The results are shown in Tables 1 and 2 described later.

Comparative Example 2 As shown in FIG. 4, a conventionally known push button switch having a constitution in which a molded body made of silicone rubber in which a key top and a pressing element are integrated and the PET dome of Comparative Example 1 are combined with another piece is used. When we prepared and measured the operating characteristics, the click feeling of the PET dome was attenuated by the silicone rubber molding,
The click rate is about 20-30%. Further, when the position of the presser was shifted as in Comparative Example 1, the click rates became about 20 to 30%, 10 to 20%, 5 to 15% and 0 to 10%, respectively, and the operation feeling (click feeling) was further reduced. However, these results were as shown in Tables 1 and 2 below.

[0024]

[Table 1]

[Table 2]

[0025]

The cover member for a push button switch of the present invention comprises:
Corresponding to thinner devices, high hardness resin key tops are formed and integrated directly on the PET dome that generates a high click rate (30% or more) with a low stroke (0.5 mm or less), resulting in misalignment. The operation feeling (click feeling) is not reduced, and the pressing force at the time of input is evenly applied to the center portion of the PET dome, and as a result, a stable operation feeling (click feeling) is always obtained. In addition, the key top part is integrated, so it has excellent assembly characteristics. Furthermore, the key top part is made of high-hardness resin, and the operation feeling (click feeling) of the PET dome is less attenuated and becomes clear. Advantages are given.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an example of a cover member for a push button switch according to the present invention.

2 (a), (b) and (c) are vertical sectional views showing a manufacturing process order of a cover member for a push button switch according to the present invention.

FIG. 3 is a vertical sectional view of an example of a conventional cover member for a push button switch.

FIG. 4 is a vertical sectional view showing another example of a conventional cover member for a push button switch.

FIG. 5 is an example of a curve showing a relationship between a stroke of the cover member for a push button switch and a load for explaining a click feeling of the cover member for a push button switch.

[Explanation of Codes] 1 ... Cover member for push button switch 2 ... Base portion 3 ... Thin portion 4, 11, 15 ... Key top portion 5 ... Conductive contact portion 6 ... Key top printing portion 7 ... Lower mold 8 ... Top metal Mold 9 ... Leveling adjustment step 10 ... PET sheet 12 ... Discharge device 13 ... PET dome 14 ... Presser 16 ... Silicone rubber molding

Claims (2)

[Claims] 1. A push button switch characterized by integrating a thin portion and a base portion made of drawn polyethylene terephthalate and a key top portion made of a high hardness resin having a Shore D hardness of 40 degrees or more. Cover member. 2. A sheet made of polyethylene terephthalate is drawn to form a thin portion and a base portion of a cover member for a push button switch, and then a high hardness resin having a Shore D hardness of 40 degrees or more is poured on the same mold. A method of manufacturing a cover member for a push button switch, which comprises molding and reaction-curing to form a key top portion, and integrating the both.