JPH07201249A - Rubber contact switch - Google Patents

Abstract

PURPOSE:To provide a rubber contact switch with which favorable operation feeling to produce strong click feeling can be provided in spite of usage of raw material of thermoplastic elastomer resin, and provide a rubber contact switch having high heat-resistant restoration property by which a movable contact part can be restored to an initial condition securely together with a pushbutton part even under a high-temperature operation condition. CONSTITUTION:A rubber contact switch 5 comprises a thick pushbutton part 3 protruded from a thick base part through a thin dome part 2, and a movable contact part 4 on the back surface side of it, which are integrally formed by injection moulding of thermoplastic elastomer resin composite. Thickness of the dome part 2 is set to be within a range of 0.10-0.30mm, a standing angle is set to be within a range of 35-60deg., a click ratio is set to be within 20-80%, and heat treatment of 80-120 deg.C is applied for 5-120min. especially.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber contact switch which is widely used as a push button mechanism in various small electronic devices, and more particularly to a rubber contact switch which is made of a thermoplastic elastomer resin and has a strong click feeling. .

[0002]

2. Description of the Related Art In recent years, there has been a remarkable spread of small electronic devices such as electronic calculators and mobile phones starting with calculators. These small electronic devices are generally provided with a large number of small push button switches, and as the push button switches, rubber contact switches that provide a tactile click feeling are often used.

The rubber contact switch is disclosed in Japanese Patent Publication No. 1-37819, Japanese Unexamined Patent Publication No. 63-92428, Japanese Unexamined Patent Publication No. 2-121815, and the like. The push button portion having a thick wall and the movable contact portion on the back side thereof are integrally formed of silicone rubber or the like. This rubber contact switch pushes the push button section by its elastic restoring force when the dome section clicks and bends when the push button section is pressed, and the pushing force of the push button section is released. No spring is required and the structure is extremely simple. Moreover, since it is possible to obtain a tactile clickable elastomer feel, it is suitable as a push button for the various small electronic devices described above.

[0004]

By the way, although the above-mentioned rubber contact switch made of silicone rubber has excellent heat resistance and little temperature dependence, it is (i) vulcanized for a long time because it is made of silicone rubber. A process is required and productivity is poor, (ii) thermosetting is not recyclable, (iii) poor secondary workability such as adhesion and printing, (iv) unsuitable as a high load switch, There are various problems such as. Another problem is that the click feeling is weak and the operation feeling is not so good.

Under these circumstances, a thermoplastic contact elastomer resin that does not require a vulcanization step, can be injection-molded, has high productivity, and can be recycled is used as a material for the rubber contact switch. I'm getting smashed.

However, a rubber contact switch having a strong click feeling and a good operation feeling cannot be obtained only by using a thermoplastic elastomer resin as a material. Further, the thermoplastic elastomer resin has a problem in practicality under high temperature, such as a decrease in physical properties due to temperature rise, an increase in plastic deformation and an increase in permanent set. For this reason, for example, when using a thermoplastic elastomer resin as a material for rubber contact switches of various electronic devices that may be left in a car room under the hot sun, etc., when the push button is kept pressed under high temperature use conditions. In addition, the dome portion may be plastically deformed to deteriorate the recoverability of the movable contact portion together with the push button portion, and the movable contact portion may adhere to the substrate.

The present invention has been proposed in order to solve the above-mentioned problems, and although it is made of a thermoplastic elastomer resin, it has a strong click feeling,
The main purpose is to provide a rubber contact switch that provides a good feeling of operation. In addition to this, a rubber with high heat resistance that can reliably return the movable contact part together with the push button part to the initial state even under high temperature use conditions. It is also intended to provide a contact switch.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to achieve the above-mentioned object, and as a result, even in a rubber contact switch made of a thermoplastic elastomer resin, the wall thickness of the dome portion, the dome portion Depending on the rising angle of
It was also found that depending on the heat treatment, a good feeling of operation with a strong clicking sensation and a high resistance to heat recovery can be obtained.

That is, a rubber in which a thick push button portion protruding from a thick base portion through a thin dome portion and a movable contact portion on the back side thereof are integrally formed by injection molding using a thermoplastic elastomer resin as a material. In the contact switch, the wall thickness of the dome is 0.10 to 0.3.
In the range of 0 mm (preferably 0.15 to 0.25 mm) and the rising angle of the dome part in the range of 35 to 60 degrees (preferably 35 to 50 degrees), the click rate is 20 to 80% (preferably). Is 35 to 65%, more preferably 40 to 60%). Also, 80 to 120
5 to 120 ° C. (preferably 85 to 100 ° C.)
When applied over a period of minutes (preferably 30 to 60 minutes), a rubber contact switch with particularly high operability can be obtained.

Here, the click rate means that the maximum load (peak load) when the dome part clicks and bends in accordance with the pressing operation of the push button part is P1 and the minimum buckling load (click load) is P2. At this time, it is an index of click feeling displayed as in [Equation 1], and if this is large, a strong click feeling can be obtained.

[0011]

[Equation 1]

The thermoplastic elastomer resin used as the material has a Shore hardness of D25 to D60 (preferably D28).
.About.D35), the impact resilience is preferably 50% or more (maximum about 80%), and an appropriate polyamide-based, polyurethane-based, polyolefin-based, polyester-based, fluorine-based, or nitrile-based material can be used. Among them, the polyester-based elastomer resin is most preferable as a material for the rubber contact switch because it has physical properties suitable for injection molding.

[0013]

[Function] Here, a rubber having a thick push button portion projecting from a thick base portion through a thin dome portion and a movable contact portion on the back side integrally formed by injection molding using a thermoplastic elastomer resin as a material. In the contact switch, if the wall thickness of the dome is less than 0.10 mm, the fluidity of the material during injection molding will be poor, and if it is greater than 0.30 mm, the click rate will be 20% or less and the click feeling will be weak, which is good. I can't get a good feel. Further, even when the rising angle of the dome portion is smaller than 35 degrees, the click rate becomes smaller than 20%, the click feeling is weak, and a good operation feeling cannot be obtained. When the click rate is 20% or less, the click feeling is weak as described above, and a good operation feeling cannot be obtained. When the click rate is 70% or more, the heat resistance cannot be restored.

Further, in the present invention, the dome portion has a wall thickness of 0.1.
In the range of 0 to 0.30 mm, the rising angle of the dome part is set in the range of 35 to 60 degrees, and the click rate is 2
The range is 0 to 80%, and the heat treatment at 80 to 120 ° C. is 5 to
Since it is applied for 120 minutes, it is possible to obtain a good operation feeling with a strong click feeling and to have an excellent heat recovery property. When the heat treatment temperature is lower than 80 ° C, no change in the physical properties of the material is observed, and when it is higher than 120 ° C, the heat resistance of the material is problematic.

When the linear distance in the free state of the dome portion is L1 and the linear distance in the bent state after the click operation is L2, the dome portion before and after the compression is expressed by (L2 / L1) × 100. When the linear distance ratio is 90% or more, a tensile stress is generated in the dome portion due to the pressing operation of the push button portion, the dimension of the dome portion expands and becomes permanent strain, and the dome portion is not returned to the free state. As it becomes worse, the above ratio is 60
% Or more and 90% or less is preferable.

[0016]

【Example】

Examples 1 to 6 As shown in FIG. 1, a rubber integrally including a thick push button portion 3 protruding from a thick base portion 1 through a thin dome portion 2 and a movable contact portion 4 on the back side thereof. The contact switch 5 has a push button portion 3 having a diameter d of 5 mm and a pushing stroke of 0.8 mm, and the dome portion 2 has a wall thickness t.
Also, a plurality of types shown in [Table 1] with different rising angles α were injection-molded with a thermoplastic elastomer resin.

The thermoplastic elastomer resin used is a polyester elastomer (Grelax E200, which is a block copolymer having a hard segment of polybutylene terephthalate and a soft segment of polyether).
LV; manufactured by Dainippon Ink and Chemicals, Inc., the Shore hardness is 30 degrees, and the impact resilience is 74%.

With respect to each rubber contact switch 5 obtained, the peak load P1 and the click load P2 (see FIG. 2) when the dome portion 2 clicks and bends in accordance with the pressing operation of the push button portion 3 are compressed. 30m with test machine
It was pressed at a speed of m / min for measurement, and the click rate CL was obtained by the above-mentioned equation (1). The results are shown in [Table 1]. These were rubber contact switches that provided a good click feeling and a good operation feeling.

Comparative Example 1 The wall thickness t of the dome portion 2 is 0.18 mm, the rising angle α of the dome portion 2 is 38 degrees, and the linear distance ratio of the dome portion 2 is 12.
4%, rubber contact switch with push button diameter d of 3 mm and push stroke of 0.8 mm
The same resin as in Example 1 was injection molded. The results of the same measurement as in Example 1 of this rubber contact switch are shown in [Table 1]. This rubber contact switch has a peak load P1 of 220g and a click load P2 of 178g.
The click rate CL was 19%, and a good operation feeling was not obtained.

Embodiments 7 to 18 A plurality of types of the push button portion 3 having a diameter d of 5 mm and a pushing stroke of 0.8 and having different wall thickness t and rising angle α of the dome portion 2 shown in [Table 2] are used. A rubber contact switch was injection-molded with the same resin as in Example 1, and each switch was heat-treated at 100 ° C. for 30 minutes and measured in the same manner as in Example 1. The results are shown in [Table 2]. These are also rubber contact switches that provide a good click feeling and a good operation feeling.

Each rubber contact switch is kept at 80 ° C. for 96 hours by pressing the push button portion 3 to compress the dome portion 2 (see FIG. 3), and then cooled to room temperature (23 ° C.). Then, the pressed state of the push button portion 3 was released, and the quality of the returnability of the dome portion 2 to the free state was judged by the return height of the push button portion 3. All of the rubber contact switches were elastically returned to the free state and were excellent in heat resistance recovery.

Comparative Example 2 The wall thickness t of the dome portion 2 is 0.12 mm, the rising angle α of the dome portion 2 is 52 degrees, and the linear distance ratio of the dome portion 2 is 62.
%, The diameter d of the push button portion 3 is 5 mm, and the pressing stroke is 0.8 mm.
Injection molding was performed using the same resin as in Example 1, and heat treatment was performed under the same conditions as in Example 7. This rubber contact switch was measured in the same manner as in Example 1, and the results are shown in [Table 2]. The heat-resisting recoverability of this rubber contact switch is shown in Example 7.
However, the dome portion 2 was bent and deformed, and the height of the push button portion 3 did not return to the free state.

[0023]

[Table 1]

[0024]

[Table 2]

The symbols in [Table 1] and [Table 2] are as follows. t: wall thickness of dome part (mm) α: rising angle of dome part (degree) γ: linear distance ratio of dome part (%) P1: peak load (grf) P2: click load (grf) CL: click rate ( %)

[0026]

As described above, according to the present invention, the following effects can be obtained. (1) High productivity because no long vulcanization process is required,
In addition, since it is thermoplastic, it can be recycled, and it is possible to provide a rubber contact switch that is excellent in secondary workability such as adhesion and printing.

(2) The thin dome portion is also well injection-molded, and a strong click feeling can be obtained when the push button portion is pressed, so that a rubber contact switch having a good operation feeling can be provided.

(3) High heat resistance, that is, the push button portion and the movable contact portion on the back side thereof are completely returned to the initial state even after the push button portion is held in the pressed state for a certain period of time under high temperature use conditions. Can provide rubber contact switch.

[Brief description of drawings]

FIG. 1 is a sectional view of a rubber contact switch according to each embodiment of the present invention in a free state.

FIG. 2 is a diagram showing load characteristics of a rubber contact switch according to each embodiment of the present invention.

FIG. 3 is a cross-sectional view of a rubber contact switch according to each embodiment of the present invention when a push button portion is pressed.

[Explanation of symbols] 1 thick base part 2 dome part 3 push button part 4 movable contact part 5 rubber contact switch

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masahiko Fuyumuro 560-1, Imafukucho, Ashikaga City, Tochigi Prefecture (72) Inventor Hiroshi Ohira 1-2-5 Shibuya, Shibuya-ku, Tokyo Kenwood Corporation (72) Inventor Daisuke Mizushima Kosmo Kajigaya Prestige 304 378-3 Shimosakunobu Takatsu-ku, Kawasaki-shi, Kanagawa

Claims (2)

[Claims] 1. A rubber in which a thick push button portion protruding from a thick base portion through a thin dome portion and a movable contact portion on the back side thereof are integrally formed by injection molding of a thermoplastic elastomer resin composition. In the contact switch, the wall thickness of the dome portion is set in the range of 0.10 to 0.30 mm, the rising angle of the dome portion is set in the range of 35 to 60 degrees, and the click rate is in the range of 20 to 80%. Rubber contact switch characterized by 2. The rubber contact switch according to claim 1, wherein heat treatment at 80 to 120 ° C. is performed for 5 to 120 minutes.