JP2007329124A - Contact member for push-button switch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a contact member for a push-button switch excellent in environmental resistance characteristics. <P>SOLUTION: The contact member 4 for a push-button switch is one made to contain a conductive filler in a silicone system rubber material, and as the conductive filler, a metal system conductive filler constituted by containing metal showing more ionization tendency than copper and carbon black are contained. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a contact member for a push button switch used as a switch part of a mobile phone, an in-vehicle electronic device, a personal computer, a remote control, etc., and particularly, such as a power window and a mirror switch that require a relatively high current. The present invention relates to a contact member for a push button switch used in an in-vehicle electronic device.

2. Description of the Related Art Conventionally, there is known a push-button switch contact member made of a silicone rubber material as a main material and containing nickel powder and a silane coupling agent (for example, see Patent Document 1).
Japanese Patent Laid-Open No. 5-151853

  However, the above-described conventional pushbutton switch contact member has a tendency that nickel is gradually oxidized and the contact resistance value is increased particularly in a high temperature and high humidity environment.

  An object of this invention is to provide the contact member for pushbutton switches excellent in environmental resistance.

  The contact member for a push button switch according to the present invention is a contact member for a push button switch in which a conductive filler is contained in a silicone rubber material, and includes a metal-based conductive material including a metal that exhibits an ionization tendency higher than that of copper. It is characterized by containing a functional filler and carbon black.

  In the contact member for a pushbutton switch according to the present invention, carbon black is included in addition to the metallic conductive filler. Since carbon black is a porous material, it has a large surface area and high hygroscopicity. Therefore, even when the contact member for the pushbutton switch is placed in an environment such as high temperature and high humidity, moisture is absorbed by the carbon black, and the metal contained in the metal-based conductive filler is difficult to oxidize. As a result, it is possible to improve the environmental resistance of the contact member for the pushbutton switch even if the metal-based conductive filler contains an easily oxidized metal that exhibits an ionization tendency higher than that of copper.

  Moreover, it is preferable that the metal-based conductive filler is configured such that a metal that exhibits an ionization tendency higher than copper is coated with a metal that exhibits an ionization tendency smaller than that of copper.

  The metal-based conductive filler is preferably metal-coated graphite in which graphite particles are coated with a metal that exhibits an ionization tendency higher than that of copper.

  In general, in a pushbutton switch, a part of the contact member for the pushbutton switch slides and accumulates on the substrate by repeated keystrokes. For this reason, when a single metal is contained in the pushbutton switch contact member as in the prior art, metal particles having a low resistance value slide down and accumulate on the substrate. When a bridge is formed between the electrodes by the metal particles thus deposited, there is a problem that the electrodes are short-circuited. In order to solve this problem, it is considered that only the graphite particles having a higher resistance value than the metal particles are contained in the contact member for the push button switch. In this way, compared to the case of metal particles, if a large number of graphite particles do not accumulate on the substrate, a short circuit does not occur, so that the occurrence of a short circuit is suppressed. It can no longer be obtained.

  However, when metal-coated graphite is contained in the contact member for the pushbutton switch, low resistance and high energization keying performance can be realized.

  Moreover, it is preferable that metal content in a metal covering graphite is 15 weight%-85 weight%.

  Moreover, it is preferable that the average particle diameter of a graphite particle is 45 micrometers-150 micrometers. In this way, it is possible to obtain a pushbutton switch contact member that includes an appropriate amount of graphite particles and is excellent in durability.

The specific resistance of the metal in the metal-coated graphite at 0 ° C. is preferably 10 × 10 ⁻⁶ Ωcm or less.

  Moreover, it is preferable to contain 150 to 950 parts by weight of a metallic conductive filler with respect to 100 parts by weight of the silicone rubber material. By doing so, it is possible to obtain a pushbutton switch contact member having sufficient electrical conductivity and excellent durability.

  Moreover, it is preferable to contain carbon black 0.7weight part or more and less than 23.3 weight part with respect to 100 weight part of silicone type rubber materials. In this way, it is possible to manufacture a contact member for a pushbutton switch that is low in resistance and excellent in environmental resistance while preventing deterioration in workability.

  ADVANTAGE OF THE INVENTION According to this invention, the contact member for pushbutton switches excellent in environmental resistance can be provided.

  Preferred embodiments of the present invention will be described with reference to the drawings. Note that in the description, the same reference numerals are used for the same elements or elements having the same function, and redundant description is omitted.

  A pushbutton switch cover member 1 to which the pushbutton switch contact member 4 according to the present embodiment is applied will be described with reference to FIG. FIG. 1 is a vertical cross-sectional view of a pushbutton switch cover member to which a pushbutton switch contact member according to the present embodiment is applied.

  The push button switch cover member 1 includes a key top 2, a pressing portion 3, a push button switch contact member 4, a thin portion 5, and a support portion 6. The push button switch cover member 1 configured as described above operates as follows when attached to an electronic device such as a power window or a mirror switch. First, when the key top 2 is pressed, the thin portion 5 is bent and the pressing portion 3 is pressed down. When the pressing part 3 is pushed down, the contact member 4 arranged at the tip of the pressing part 3 comes into contact with the fixed contact arranged facing the substrate. As a result, the push button switch corresponding to the pressed key top 2 becomes conductive.

  The contact member 4 for a push button switch according to the present embodiment is formed by containing a conductive filler in a silicone rubber material. Specifically, as a conductive filler, a silicone-based rubber material contains a metallic conductive filler composed of a metal that exhibits an ionization tendency higher than copper and carbon black (non-metallic conductive filler). I am letting.

  As such a metal-type conductive filler, what was comprised by the metal which shows the ionization tendency more than copper being coat | covered with the metal which shows an ionization tendency smaller than copper can be used, for example, silver coating nickel is mentioned. Silver-coated nickel is obtained by coating nickel particles showing an ionization tendency higher than copper with silver showing an ionization tendency smaller than that of copper.

  In addition, as such a metal-based conductive filler, metal-coated graphite in which graphite particles are coated with a metal exhibiting an ionization tendency higher than copper can be used, and examples thereof include nickel-coated graphite. Nickel-coated graphite is obtained by coating graphite particles with nickel that exhibits an ionization tendency higher than that of copper. When the metal-coated graphite is used, since the graphite particles are included, even if a part of the push button switch contact member 4 slides and accumulates on the substrate, the occurrence of a short circuit is suppressed, and the graphite particles are covered with the metal. Therefore, low resistance can be realized.

  When metal-coated graphite is used as the metal-based conductive filler, the metal content in the metal-coated graphite is preferably 15% by weight to 85% by weight. If the metal content in the metal-coated graphite is less than 15% by weight, the ratio of the metal covering each of the graphite particles becomes too small, and a sufficiently low resistance cannot be obtained. When the metal content in the metal-coated graphite exceeds 85% by weight, the ratio of the metal covering the graphite particles increases so that the cost increases.

  The average particle diameter of the graphite particles in the metal-coated graphite is preferably 45 μm to 150 μm because it is possible to obtain a contact member 4 for a pushbutton switch that includes an appropriate amount of graphite particles and is excellent in durability.

Furthermore, the specific resistance at 0 ° C. of the metal in the metal-coated graphite is preferably 10 × 10 ⁻⁶ Ωcm or less. Examples of the metal having an ionization tendency higher than that of copper and having a specific resistance of 10 × 10 ⁻⁶ Ωcm or less at 0 ° C. include copper, nickel (6.2 × 10 ⁻⁶ Ωcm), and aluminum.

  The content of these metallic conductive fillers is preferably 150 to 950 parts by weight with respect to 100 parts by weight of the silicone rubber material. When the content of the metallic conductive filler is less than 150 parts by weight with respect to 100 parts by weight of the silicone rubber material, sufficient conductivity cannot be obtained. When the content of the metal conductive filler exceeds 950 parts by weight with respect to 100 parts by weight of the silicone rubber material, the silicone rubber material cannot sufficiently exhibit the strength as rubber. In consideration of these characteristics, the metal-based conductive filler is more preferably contained in an amount of 180 to 400 parts by weight with respect to 100 parts by weight of the silicone-based rubber material, and 230 parts by weight with respect to 100 parts by weight of the silicone-based rubber material. More preferably, it is contained in an amount of 300 to 300 parts by weight.

  Carbon black is a porous (microporous) material and has excellent hygroscopicity. Therefore, the water in the environment around the push button switch contact member 4 can be absorbed by the carbon black. As carbon black, for example, granular Denka black can be used.

  Carbon black is preferably contained in an amount of 0.7 parts by weight or more and less than 23.3 parts by weight with respect to 100 parts by weight of the silicone rubber material. When the content of carbon black with respect to 100 parts by weight of the silicone-based rubber material is 0.7 parts by weight or more, the moisture absorption effect by the carbon black is sufficiently exhibited, and the environmental resistance tends to be further improved. When the content of carbon black with respect to 100 parts by weight of the silicone rubber material is 23.3 parts by weight or more, the volume of the additive becomes too large with respect to the silicone rubber material, so that the effect of the silicone rubber material as a binder is achieved. Is not sufficiently exhibited, the rollability of the roll deteriorates during the kneading operation of the silicone rubber material and other additives, and the kneading time tends to be long.

  Further, since the contact resistance value increases as the carbon black content increases, the carbon black content is more preferably less than 14.0 parts by weight with respect to 100 parts by weight of the silicone rubber material. Therefore, when carbon black is contained in an amount of 0.7 parts by weight or more and less than 14.0 parts by weight with respect to 100 parts by weight of the silicone rubber material, the contact member for the pushbutton switch has sufficiently low resistance and excellent environmental resistance. 4 can be obtained, and can be suitably used for a vehicle-mounted switch or the like in which a relatively high current flows.

  As described above, in the present embodiment, the pushbutton switch contact member 4 includes carbon black in addition to the metal-based conductive filler. Therefore, even when the push-button switch contact member 4 is placed in an environment such as high temperature and high humidity, moisture is absorbed by the carbon black, and the metal contained in the metal-based conductive filler is difficult to oxidize. As a result, it is possible to improve the environmental resistance of the contact member for the pushbutton switch even if the metal-based conductive filler contains an easily oxidized metal that exhibits an ionization tendency higher than that of copper.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on Example 1 and Comparative Example 1, this invention is not limited to a following example.

Example 1
First, each compounding material shown in Table 1 was kneaded with a roll. Next, the kneaded material was poured into a molding die and subjected to heat compression molding at 160 ° C. for 5 minutes under the conditions of 20.594 MPa (= 210 kgf / cm ² ). Thereby, a conductive rubber sheet having a thickness of 0.5 mm was obtained.

  Next, the obtained conductive rubber sheet was punched with a punch having a diameter of 3 mm. As a result, a push button switch contact member 4 having a diameter of 3 mm was obtained. Then, the obtained pushbutton switch contact member 4 is placed at a predetermined position of the pushbutton switch molding die, and a predetermined blended raw material rubber is injected into the pushbutton switch molding die to perform heat compression molding under predetermined conditions. By doing so, the cover member 1 for pushbutton switches was obtained.

(Comparative Example 1)
A contact member for a pushbutton switch of Comparative Example 1 was obtained in the same manner as Example 1 except that each compounding material shown in Table 2 was used. Then, the push button switch cover member of Comparative Example 1 was obtained in the same manner as in Example 1 by using the obtained push button switch contact member.

  Next, a high-temperature test and a high-temperature and high-humidity test are performed on each push-button switch cover member provided with each push-button switch contact member of Example 1 and Comparative Example 1 described above, and the push-button switch contacts before and after the test. The contact resistance value of each member was measured. Here, in the high temperature test, the cover members for the push button switches of Example 1 and Comparative Example 1 were left in an atmosphere of 85 ° C. for 500 hours. In the high temperature and high humidity test, the push button switch cover members of Example 1 and Comparative Example 1 were left in an atmosphere of 65 ° C. and 95% RH for 500 hours. As a measuring instrument for measuring the contact resistance value, a digital multimeter “DIGITAL MULTITIMER R6561” (manufactured by Advantest Co., Ltd.) was used. As the substrate of the push button switch, a comb-tooth type gold plating substrate having both electrode spacing and electrode width of 0.5 mm was used, and the load from above on the push button switch was set to 500 g.

The test results are shown in Table 3. As shown in Table 3, in the pushbutton switch cover member 1 of Example 1, the contact resistance value changed from 0.315Ω to 0.327Ω before and after the test in the high-temperature test, and in the high-temperature and high-humidity test. The contact resistance value changed from 0.315Ω to 0.606Ω before and after the test. On the other hand, as shown in Table 3, in the cover member for the pushbutton switch of Comparative Example 1, the contact resistance value changed from 0.399Ω to 0.430Ω before and after the test in the high temperature test, and the high temperature and high humidity test. The contact resistance value changed from 0.417Ω to 1.162Ω before and after the test. That is, in the push button switch cover member 1 of Example 1, an increase in the contact resistance value after the high temperature test and after the high temperature and high humidity test was suppressed as compared with the push button switch cover member of Comparative Example 1. This is because the metal-based conductive filler is hardly oxidized due to the moisture absorption action of the carbon black contained in the push-button switch contact member 4 of the first embodiment. Therefore, it was confirmed that the environmental resistance of the contact member 4 for pushbutton switch of Example 1 was improved.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on Examples 2-1 to 2-8 and Comparative Example 2, this invention is not limited to a following example.

(Example 2)
Except having used each compounding material shown by Table 4, it carried out similarly to Example 1, and obtained the contact member 4 for pushbutton switches of Examples 2-1 to 2-8, respectively. Then, using each of the obtained push button switch contact members 4, the push button switch cover members 1 of Examples 2-1 to 2-8 were obtained in the same manner as in Example 1.

(Comparative Example 2)
A contact member for a pushbutton switch of Comparative Example 2 was obtained in the same manner as Example 1 except that each compounding material shown in Table 5 was used. Then, the push button switch cover member 1 of Comparative Example 2 was obtained in the same manner as in Example 1 by using the obtained push button switch contact member.

  Next, for each pushbutton switch cover member provided with each of the pushbutton switch contact members of Examples 2-1 to 2-8 and Comparative Example 2, the high temperature test and the high temperature and high humidity were performed under the same conditions as in Example 1 and Comparative Example 2. The test was performed, and the contact resistance value of the contact member for the push button switch before and after the test was measured.

The test results are shown in Table 6. As shown in Table 6, in the pushbutton switch cover member 1 of Examples 2-1 to 2-8, the contact resistance value was 0.244Ω to 0.334Ω before and after the test in the high temperature test. 240Ω to 0.230Ω, 0.240Ω to 0.228Ω, 0.256Ω to 0.260Ω, 0.251Ω to 0.252Ω, 0.93Ω to 0.98Ω, 1.94Ω to 1.95Ω, 6.23Ω In the high temperature and high humidity test, the contact resistance value is 0.264Ω to 0.421Ω, 0.248Ω to 0.314Ω, 0.233Ω to 0.333Ω before and after the test, The values changed from 0.286Ω to 0.345Ω, 0.304Ω to 0.349Ω, 1.10Ω to 1.18Ω, 2.35Ω to 2.36Ω, and 5.97Ω to 5.99Ω. On the other hand, as shown in Table 6, in the cover member for the pushbutton switch of Comparative Example 2, the contact resistance value changed from 0.253Ω to 0.297Ω before and after the test in the high temperature test, and the high temperature and high humidity test. The contact resistance value changed from 0.267Ω to 0.535Ω before and after the test. That is, in the push button switch cover member 1 of Examples 2-1 to 2-8, the increase in the contact resistance value after the high temperature and high humidity test was suppressed as compared with the push button switch cover member of Comparative Example 2. Therefore, it was confirmed that the environmental resistance of the contact member 4 for a pushbutton switch of Example 2 was improved.

  Hereinafter, the present invention will be described in more detail based on each pushbutton switch cover member provided with each of the pushbutton switch contact members obtained in the first embodiment and the second embodiment. It is not limited to examples.

First, in order to confirm the initial electrical characteristics of the push button switch contact member 4 obtained in the first embodiment, the contact resistance value and the initial voltage of the push button switch using the push button switch contact member 4 obtained in the first embodiment are used. The fall value was measured. Table 7 shows the measurement results of the contact resistance value and the initial voltage drop value.

  Conditions for measuring the contact resistance values and initial voltage drop values shown in Table 7 are as follows. First, a digital multimeter “DIGITAL MULTITIMER R6561” (manufactured by Advantest Co., Ltd.) is used as a measuring instrument for measuring a contact resistance value, and a voltage / current generator “DC VOLTAGE” is used as a measuring instrument for measuring an initial voltage drop value. CURRENT SOURCE / MONITOR TR6143 (manufactured by Advantest Corporation) was used. The voltage limit of this voltage / current generator was set to 12 V in accordance with a general automobile battery. In addition, a comb-shaped gold-plated substrate having an electrode interval and an electrode width of 0.5 mm was used as the push button switch substrate, and the load from above on the push button switch was set to 200 g. Furthermore, the determination criteria at the time of measurement were that energization was possible and the voltage drop value was 1 V or less.

  The contact resistance value measured under these various conditions was 0.315Ω, and the initial voltage drop value required to pass a current of 1000 mA was 0.402V. That is, even when a high current of 1000 mA was passed, the voltage drop value was significantly lower than 1 V, which is the criterion. Thereby, it was proved that the contact member obtained in Example 1 was sufficiently practical even under a high current.

Next, in order to confirm the durability of the contact member 4 for a push button switch obtained in Example 1, the push button switch using the contact member 4 for a push button switch obtained in Example 1 and An energization keying test was performed using each of the push button switches using the contact member for the push button switch. Table 8 shows the results of this energization keying test.

  Various conditions for carrying out the energization keying test shown in Table 8 are as follows. First, a push-up type key press was used as a key press for pressing the pushbutton switch. Further, the load from above on the push button switch attached to the key press was set to 200 g, and the push amount from below to the push button switch was set to 2 mm, and the push button switch was pushed up 100,000 times a second in total. Further, the voltage / current generator “DC VOLTAGE CURRENT SOURCE / MONITOR TR6143” described above was used as a measuring instrument for measuring the conduction state of the pushbutton switch, and the voltage limit of the voltage / current generator was set to 12V. Also, if a voltage of 12V or more, which is the voltage limit, is generated in the voltage / current generator, or if an abnormality (for example, combustion due to a short circuit) occurs in the middle of 100,000 keystrokes, the continuity is poor. Judged that there was. In addition, as a substrate for the push button switch, a comb-tooth type gold plating substrate having an electrode interval and an electrode width of 0.5 mm was used.

  As a result of conducting the energization keying test under such various conditions, the contact member obtained in Example 1 was energized without being judged as a poor conduction up to 200 mA even after being keyed 100,000 times. did. That is, it was found that the conduction limit current value at the time of keying 100,000 times in the contact member obtained in Example 1 was 200 mA. On the other hand, in the contact member obtained in Example 2, the conduction limit current value at the time of keystroke 100,000 times was 20 mA.

  Based on these results, it has been demonstrated that the use of nickel-coated graphite for the metallic conductive filler of the pushbutton switch contact member 4 can reliably improve the conduction limit current value after being keyed 100,000 times. It was done.

FIG. 1 is a vertical cross-sectional view of a pushbutton switch cover member to which a pushbutton switch contact member according to the present embodiment is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Cover member for pushbutton switches, 2 ... Key top, 3 ... Press part, 4 ... Contact member, 5 ... Thin part, 6 ... Support part.

Claims (8)

A contact member for a pushbutton switch containing a conductive filler in a silicone rubber material,
A contact member for a pushbutton switch, characterized in that the conductive filler contains a metal-based conductive filler that contains a metal that exhibits an ionization tendency higher than copper and carbon black.   2. The contact member for a pushbutton switch according to claim 1, wherein the metal-based conductive filler is formed by coating a metal having an ionization tendency higher than copper with a metal having an ionization tendency smaller than that of copper. .   2. The contact member for a pushbutton switch according to claim 1, wherein the metal-based conductive filler is metal-coated graphite in which graphite particles are coated with a metal having an ionization tendency higher than that of copper.   4. The contact member for a pushbutton switch according to claim 3, wherein the metal content in the metal-coated graphite is 15% by weight to 85% by weight.   5. The pushbutton switch contact member according to claim 3, wherein an average particle diameter of the graphite particles is 45 μm to 150 μm. 6. The pushbutton switch contact member according to claim 3, wherein the metal-coated graphite has a specific resistance at 0 ° C. of 10 × 10 ⁻⁶ Ωcm or less.   The push-button switch according to any one of claims 2 to 6, wherein the metal-based conductive filler is contained in an amount of 150 to 950 parts by weight with respect to 100 parts by weight of the silicone-based rubber material. Contact member.   The carbon black is contained in an amount of 0.7 parts by weight or more and less than 23.3 parts by weight with respect to 100 parts by weight of the silicone-based rubber material. Contact member for pushbutton switch.

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