JPH08276435A - Manufacture of contact rubber - Google Patents

Abstract

PURPOSE: To mount conductive chips one by one at a dug part by so charging the chips in a mold that a conductive layer side is brought into contact with the mold surface, charging unvulcanized rubber thereon, and integrally molding it. CONSTITUTION: A sheetlike laminate in which an insulating rubber layer having a non-sticky treated surface is laminated on a conductive layer at the surface in which non-sticky treatment is not executed is punched in a predetermined shape to obtain a conductive chip. After the chip is so charged in a mold that the conductive layer is brought into contact with the mold surface, unvulcanized rubber is charged on the chip of the mold, and integrally molded to manufacture a contact rubber. More particularly, the conductive chip 29 which is non-sticky treated is so charged that the conductive layer side is brought into contact with the contact forming dug part 30 surface of the mold 31 for manufacturing the contact rubber. Then, after unvulcanized silicone rubber 34 is charged in an air gap 33 between the mold 31 and a key top forming mold 32, it is thermally cured to manufacture the contact rubber 35.

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 contact rubber used as a contact rubber for input of an electronic device such as a telephone, a calculator and an AV device.

[0002]

2. Description of the Related Art As shown in FIG. 6, a general form of a contact rubber a used as an input device of the above electronic equipment is a key top portion b which bulges upward and a thin portion c. Base part d extending laterally around the bottom surface and key top part b
And a movable convex portion f having a conductive contact portion e at its tip. When the operator presses the top surface of the key top portion b, the thin portion c flexes and pushes down the key top portion b, and the conductive contact portion e at the tip of the movable convex portion f is placed on the circuit board (not shown). The circuit is closed by contact with the fixed contact portion provided. The operator touches the key top b
When the finger is released from the top surface of the, the thin portion c returns to the old state and pushes up the key top portion b, and the conductive contact portion e separates from the fixed contact portion, so that the circuit opens.

Generally, the contact rubber main body (entire rubber-like portion excluding the conductive contact portion e from the contact rubber a) is made of an insulating rubber-like elastic material typified by natural rubber, various synthetic rubbers or thermoplastic elastomers. And processed by various methods such as compression molding and injection molding. Among the rubber-like elastic bodies, silicone rubber is often used, which has preferable properties required for contact rubbers, such as electric insulation, cold resistance, heat resistance, precision moldability, and rebound elasticity. The method of forming the conductive contact portion e on the contact rubber body is as follows.
A method in which only the contact rubber main body is manufactured in advance, conductive ink is arranged on a portion where the conductive contact portion e is formed by a method such as a screen printing method, and the cured ink is provided.
After manufacturing a conductive chip by punching a laminated body in which a rubber layer is laminated on a metal plate into a predetermined shape, the metal chip is attached to the conductive chip forming part of the mold having a molding part corresponding to the shape of the contact rubber body. There is a method (see JP-A-63-96822) in which the contact rubber main body and the conductive chip are integrally heat-cured and integrated by mounting them in contact with the mold surface and filling the mold with silicone rubber. However, the above-mentioned method of printing the conductive ink is not suitable for long-term use or low resistance value application because the conductive contact portion e cannot be thickened.
In contrast to this, the method of forming a contact portion using a conductive tip is suitable for low resistance value applications because the conductive contact portion e can have an arbitrary thickness and one side has a metal surface.

[0004]

FIG. 7 shows a partially enlarged vertical sectional view of a conductive chip used for manufacturing a conventional contact rubber. This conductive chip g is composed of a conductive layer k formed by sequentially providing a nickel plating layer i and a gold plating layer j on nickel silver h and an insulating rubber layer m. The surface of the conductive layer k side and the surface of the insulating rubber layer m side are also formed. Both are almost smooth. A process of obtaining the conductive chip g from the sheet-shaped laminated body n having the same structure is shown in the order of steps with reference to FIGS. For punching the conductive tip g from the sheet-shaped laminate n, the conductive tip g
A punching jig or device provided with a cylindrical blade p having substantially the same outer shape and size as the above is used. However, when this punching process is continuously performed, as shown in FIGS. 8 (c) and 8 (d),
The surface of the punched conductive chip g on the side of the insulating rubber layer m is attached to the surface of the punched conductive chip g on the side of the conductive layer k,
8A and 8B are piled up one after another in the state shown in FIG.
A block body q as shown in (f) is formed.

Therefore, when the conductive tip g is mounted on the digging portion for forming the contact portion of the molding die to manufacture the contact rubber a, only one conductive tip g is originally the digging portion. As shown in FIGS. 9 (a) and 9 (b), a block body q in which a plurality of conductive chips g are stacked is attached to the place where it is attached to r, which is integrated with the unvulcanized rubber. When it is turned into a resin, a part of it is separated by the flow of the resin to make a part that should originally be insulative into a conductive state. The part falls off, and the contact rubber a having the designed stroke cannot be obtained. Therefore, in order to prevent such a disadvantage, if the work of disassembling the block body q is carried out when the conductive tip g is loaded in the dug portion r, the mold temperature is lowered and the contact in the semi-vulcanized state is brought about. Rubber was formed and the processing time was long. Therefore, it is an object of the present invention to ensure that the conductive chip is always set to 1 when the conductive chip is attached to the contact portion forming dug portion of the molding die to manufacture the contact rubber.
It is another object of the present invention to provide a method of manufacturing contact rubbers that can be individually attached to the dug portion.

[0006]

According to the method for producing a contact rubber according to the present invention, an insulating rubber layer having a non-adhesive surface is laminated on a conductive layer on a surface having no non-adhesive surface. The sheet-like laminated body is punched into a predetermined shape to form a conductive chip.The conductive chip is placed in a molding die so that the conductive layer contacts the mold surface, and unvulcanized rubber is electrically conductive to the molding die. It is characterized by being filled on a chip and integrally molded. Further, in the manufacturing method according to the present invention, the insulating rubber layer is made of silicone rubber, and the conductive layer is a silicone rubber containing 30 to 75% by weight of carbon black, or nickel silver and gold plating are sequentially applied to nickel silver. The surface of the insulating rubber layer is made of either of the ultraviolet rays with wavelengths of 184.9 nm and 253.7 nm.
In the range of 20,000mj / cm ^2, or irradiated below irradiance 150 mW / cm ^2, either providing a plurality of projections on its surface, or by serving as a both a suitably be subjected to non-adhesive treatment To do.

Hereinafter, the present invention will be described in detail. In the method for producing a contact rubber according to the present invention, the first sheet-like laminate to be prepared is one in which an insulating rubber layer whose surface is subjected to a non-adhesive treatment is laminated on a conductive layer. In this sheet-shaped laminate, the insulating rubber layer is made of silicone rubber, and the conductive layer is either a silicone rubber containing 30 to 75% by weight of carbon black, or nickel silver and gold plated sequentially on nickel silver. It is preferable that The conductive layer may also be a mixture of silver powder and nickel powder in silicone rubber. The blending amount of carbon black in the silicone rubber is preferably more than 30% by weight in order to satisfy the conduction function, and when it exceeds 75% by weight, it becomes difficult to uniformly blend in the silicone rubber. It is good to set it as the weight%. Since the total thickness of the sheet-shaped laminate may be equal to the thickness of the conductive chip to be obtained, it may be in the range of 0.3 to 2 mm. The ratio of the thickness of the insulating rubber layer to the thickness of the conductive layer is not particularly specified, but the thicker the conductive layer is, the lower the resistance value can be set.

The non-stick treatment on the surface of the insulating rubber layer is
When continuously punching the conductive chips from the sheet-shaped laminated body, the insulating rubber layer surface of the conductive chips is in contact with the conductive layer surface of another conductive chip to prevent the two from sticking together. The timing may be before or after the insulating rubber layer and the conductive layer are laminated. Non-adhesive treatment can be performed at 184.9 nm and 2 nm, especially when the insulating rubber layer is silicone rubber.
Ultraviolet light with a wavelength of 53.7 nm is integrated light intensity 200-20,000 mj / cm ²
In the range of 1, the irradiation is performed with an irradiance of less than 150 mW / cm ² , the surface is provided with a plurality of protrusions, or both are performed. When selecting a non-adhesive treatment method, it is important to avoid a treatment that loses the conductive function or durability of the conductive layer. Generally speaking, ultraviolet rays are light with a wavelength in the range of 100 to 380 nm in a broad sense (200 to 280 nm in a narrow sense), and it is not possible to wash glass plates, metals, and ceramic plates with organic substances such as oil attached by this irradiation. As is well known, the inventors of the present invention, when irradiated with ultraviolet rays under the above conditions, preferably in the presence of oxygen gas, modify the insulating rubber layer surface of the sheet-shaped laminate to be non-adhesive without deterioration. I found that I could do it.

The ultraviolet rays having the wavelengths of 184.9 nm and 253.7 nm may be radiated independently at different times, but considering the working environment and productivity, it is preferable to radiate the ultraviolet rays of two kinds of wavelengths at the same time. This is the absorption of ultraviolet rays having a wavelength of 184.9 nm, in air or oxygen (O ₂₎ rich atmosphere or oxygen (O ₂₎ is replaced atmosphere, oxygen (O ₂₎ reacts as follows, ozone (O ₃ ) to generate. O ₂ → O +
O, O + O ₂ → O ₃ On the other hand, ozone (O ₃ ) is decomposed by absorption of ultraviolet rays having a wavelength of 253.7 nm. In general, ozone (O ₃ ) has an extremely strong oxidizing power, and if it is taken in a large amount by the human body, it may impair health. Therefore,
In order not to raise the ozone concentration in the air more than necessary,
It is important that the irradiation with 253.7 nm ultraviolet light is performed almost simultaneously with the irradiation with the 184.9 nm wavelength ultraviolet light, or after the irradiation with the 184.9 nm wavelength ultraviolet light. Ozone generated here (O ₃ )
It is presumed that the strong oxidative power of is modified on the surface of the insulating rubber layer of the laminate. That is, the surface becomes physically rough and the coefficient of static friction becomes small, and the number of carbon atoms (C) decreases and the oxygen atoms (O) increase chemically. In the case of a commercially available low-pressure mercury lamp, 90% of the 253.7 nm UV light is
It may be used because it emits a few% of 4.9 nm ultraviolet light.

It is preferable to irradiate the surface of the insulating rubber layer with ultraviolet rays of two different wavelengths in an integrated light amount of 200 to 20,000 mj / cm ² . If it is less than 200 mj / cm ² , the treatment effect is not sufficient, and if it exceeds 20,000 mj / cm ² , the sheet-shaped laminate is deteriorated. Also, the accumulated light intensity is 200 to 20,000.
Even within the range of mj / cm ² , it is not appropriate unless the irradiance is less than 150 mW / cm ² . In other words, even if surface modification is attempted in a short time, if the distance between the ultraviolet light emitting lamp and the surface of the insulating rubber layer of the sheet-shaped laminate is extremely small, the irradiance becomes too large and the surface of the insulating rubber layer deteriorates. Will end up. The lower limit of the irradiance is preferably 10 mW / cm ² or more in consideration of the processing time in practical use and the allowable size of the device. The UV irradiation may be a furnace type for batch processing, or may be a conveyor type furnace, but the sheet-shaped laminate is provided so that ultraviolet rays are not concentratedly irradiated to only a part of the sheet-shaped laminate. It is desirable to have a mechanism that allows itself or the ultraviolet light emitting lamp to move at a constant speed.

The sheet-like laminated body thus obtained is then punched into a predetermined shape to form a conductive chip. The punching method is not particularly limited, and a conventional punching device and punching jig are used. Can be used. Regarding the punching direction, when the conductive layer consists of a metal plating layer, if punching is done so that the punching blade enters from the metal plating surface, the insulating rubber layer spreads after punching, so here it plays the role of a seal and the contact point. Since there is no gap between the dug portion for forming a portion and the conductive tip, the inflow of unvulcanized rubber can be prevented. The conductive chips that are obtained generally have a columnar shape, and their sizes are φ2-10 mm and thickness 0.3 mm.
It is preferable that the thickness is ˜2 mm. FIG. 1A is a partially enlarged vertical sectional view of the conductive chip 1 thus obtained. In this conductive chip 1, a conductive layer 2 in which nickel plating layer 4 and gold plating layer 5 are laminated in this order on nickel silver 3 is shown. This conductive layer 2 contains conductive particles such as carbon black and silver. It may be a thing. Further, 6 is an insulating rubber layer, and 7 is its ultraviolet irradiation surface.

Another method of making the surface of the insulating rubber layer of the conductive chip non-adhesive is to provide a plurality of protrusions on the surface of the insulating rubber layer. FIG. 1B is a partially enlarged vertical sectional view of the conductive chip 11 thus obtained, which is the same as FIG. 1A except that a plurality of protrusions 8 are provided on the surface of the insulating rubber layer 6. It is a composition. Convex size and arrangement density are the same as the insulating rubber layer surface of the conductive chip that was previously punched during continuous punching work.
It is desirable to set such that the conductive layer surface of the subsequently punched conductive chip does not stick to the conductive layer surface even if it is momentarily brought into close contact with the punched pressure when the pressure is released. Therefore, it is slightly different depending on the punching pressure, the material forming the conductive layer, the work place temperature, and the work place humidity. For example, the punching pressure is 100 kg / c
m ^2, workshop temperature 28 ° C., if workplace humidity of 60% RH, the conductive tip insulating rubber layer is made of gold-plated layer conductive layer of silicone rubber, diameter 0.01 to 0.5 mm in height 0.01~1mm
The effect was recognized when the cylindrical convexes of were provided at an arrangement density of 50 to 100 pieces / cm ² . Further, when the conductive layer surface of the silicone rubber blended with carbon black 40 wt%, the convex diameter is 0.05 to 1.5 mm height having a cylindrical outer shape of 0.03~0.8mm, 50~ 100 pieces / cm ² Adhesion between the conductive chips was not observed when they were provided at the arrangement density of.

An example of a method for forming a protrusion on the surface of the insulating rubber layer of the conductive chip is shown in the order of steps with reference to FIGS. A dugout 23 having a shape corresponding to a convex is previously provided on the surface of the insulating rubber layer forming die 22 of the sheet-shaped laminate manufacturing die 21, and the conductive member 25 is loaded on the conductive member loading die 24 surface. [Fig. 2 (a)], then unvulcanized insulating rubber raw material 26 is filled [Fig. 2 (b)], and the mixture is heated and cured to obtain a sheet-like laminate 27 [Fig. 2 (c)]. )]. The dug 23 may be formed by electric discharge machining, or may be formed by blasting or the like if it is uniformly treated. FIG. 3 (a)
~ (F) is a sheet-like laminate having a convex surface on the insulating rubber layer
FIG. 23 is a vertical cross-sectional view showing a process of obtaining a large number of conductive chips 29 from 27 by a continuous punching operation using a cylindrical blade 28 similar to the conventional one in the order of steps. Unlike the conventional method, the method of the present invention does not stack conductive chips to form a block body. The insulating rubber layer having a convex surface may be further irradiated with ultraviolet rays under the above-mentioned conditions.

The conductive chip 29 which has been subjected to the non-adhesive treatment is shown in FIG.
As shown in the perspective views of (a) and (b), when the contact-portion-forming dug portion 30 of the contact rubber manufacturing die (not shown) is loaded, the conductive chips 29 are surely provided one by one in a predetermined manner. Can be loaded at any place. 5 (a) to 5 (c) show a process of charging the conductive tip 29 into a contact rubber manufacturing die, filling unvulcanized rubber onto the conductive tip of the molding die, and integrally molding. , Are shown in a vertical cross-sectional view in the order of steps. The conductive chip 29 is inserted so that its conductive layer side is in contact with the contact portion forming dug portion 30 surface of the contact rubber manufacturing die 31 [FIG. 5 (a)], and then the contact rubber manufacturing die 31 is formed. An unvulcanized silicone rubber 34 is filled in a space 33 between the key top portion forming die 32 and the die 32 [Fig.
(B)], When cured by heating, the contact rubber 35 according to the present invention is obtained [FIG. 5 (c)].

[0015]

In the contact rubber of the present invention, the surface of the insulating rubber layer of the conductive chip is subjected to a non-adhesive treatment. Therefore, even if continuous punching is performed, the conductive chip first punched and the conductive chip subsequently punched And do not stick.

[0016]

【Example】

Example 1 A dent having a depth of 0.05 mm and a diameter of 0.5 mm was formed by blasting on the surface of a mold for forming an insulating rubber layer of a mold for forming a sheet-shaped laminate. This sheet-shaped laminate forming die is heated to 175 ° C.
After heating to nickel, a nickel-plated layer (0.5 μm) is provided on nickel silver (JIS 2) (50 μm), and a conductive member having a gold-plated layer (10 μm) on the nickel-plated layer is laminated in sheet form. It is loaded in the dug portion for forming the conductive layer of the body forming mold, and 100 parts by weight of silicone rubber compound KE-941U (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) and 2 parts by weight of the cross-linking agent C-8 (same as above). An unvulcanized silicone rubber raw material prepared is placed on the conductive member, the mold is closed and heated and pressed,
A sheet-like laminate having a thickness of 0.55 mm and including a conductive layer and an insulating rubber layer was obtained. This sheet-shaped laminate was punched from the surface of the gold-plated layer with a punching jig to obtain a conductive chip of φ3.8 mm. The contact rubber forming mold is heated to 175 ° C in advance, and the conductive tip is loaded in the contact part forming dug portion so that the gold-plated surface is in contact with the mold, and the silicone rubber compound KE-951U ( (Same as above) 100 parts by weight of cross-linking agent C-8 (Same as above) and 2 parts by weight of unvulcanized silicone rubber are filled in the dug portion for forming the contact rubber body, and the mold is closed. It was cured by heating (curing time: 3 minutes) to obtain a contact rubber having a conductive contact portion. Molding was carried out for 500 shots by this method, but since the conductive chips were not adhered to each other, no problem related to the formation of the conductive contact portion occurred. The total molding time for 500 shots is
It was 2,500 minutes.

Comparative Example 1 A sheet-shaped laminate forming die having an insulating rubber layer forming portion having a smooth surface was heated to 175 ° C., and the conductive member and the silicone rubber raw material used in Example 1 were heat-cured. To obtain a sheet-shaped laminate. This sheet-shaped laminate was punched by the same method as in Example 1 to obtain a conductive chip. Next, when the same work as in Example 1 was tried using the contact rubber forming mold of Example 1, a large number of block bodies in which 2 to 7 conductive chips were adhered to each other were produced. Manually separate this as much as possible,
It was loaded in a predetermined dug portion for forming a contact portion and integrally molded with unvulcanized rubber. We performed 500 shots molding work by this method, and the good product rate was 70%. Of the defective products, 10% had conductive parts other than the specified parts, and 12% had conductive chips on the contact rubber. Multiple strokes were provided, and some of them were separated from the mold after being released from the mold, resulting in a stroke failure. The remaining 8% was obtained by unvulcanizing or foaming a part of the contact rubber. The total molding time for 500 shots was 3,540 minutes.

Example 2, Comparative Example 2, Comparative Example 3 and Comparative Example 4 100 parts by weight of silicone rubber compound KE-9510U (same as above), 100 parts by weight of silicone raw rubber KE-78VBS (same as above), crosslinking agent C-8 (Same as above) A conductive sheet having a thickness of 0.25 mm was manufactured by a roll curing device using an unvulcanized raw material of a conductive silicone rubber containing 2 parts by weight and 40 parts by weight of carbon black. This conductive sheet was used in Comparative Example 1 175
Unvulcanized rubber raw material consisting of 100 parts by weight of KE-9710U (same as above) and C-82 parts by weight after being loaded in the digging part for loading the conductive member of the sheet-shaped laminate molding die heated to ℃ Fill the
It was heat-cured to obtain a sheet-shaped laminate. A plurality of these were molded. Next, the obtained plurality of sheet-shaped laminates were irradiated with ultraviolet rays on the surface of the insulating rubber layer under various conditions.

These sheet-like laminates were continuously punched out under the same conditions as in the method of Example 1 and Comparative Example 1 to obtain conductive chips having different insulating rubber layer surface states. Each of the obtained conductive chips was molded with the same contact rubber forming mold as in Example 1 and Comparative Example 1 under the same raw material of unvulcanized rubber and under the same molding condition for each 500 shots. in the range but of 200~20,000mj / cm ^2, irradiance 150mW / cm ²
Although the contact rubber provided with the conductive contact part using the sheet-like laminate irradiated with less than 2% had good yield and good productivity, the ultraviolet irradiation treatment was not applied or the integrated light amount was 200 mj even if it was applied. In the case of using the sheet-shaped laminate having a value of less than / cm ² , the conductive chips were likely to form a block, and the yield rate and productivity were low. Further, even if the ultraviolet irradiation treatment was performed, the sheet-like laminate having an integrated light amount of more than 20,000 mj / cm ² was deteriorated, so that a contact rubber using the same could not be manufactured.

[0020]

[Table 1]

[0021]

According to the present invention, a contact rubber having a low-resistance conductive contact portion can be manufactured with a high yield rate and good workability.

[Brief description of drawings]

1A and 1B are partially enlarged vertical sectional views of an example of a conductive chip used in a method for producing a contact rubber according to the present invention.

2A to 2C are vertical cross-sectional views showing a method of manufacturing a sheet-shaped laminate used in the present invention in the order of steps.

3 (a) to 3 (f) are vertical cross-sectional views showing, in the order of steps, an example of a process for obtaining a conductive chip used in the present invention from a sheet-shaped laminate having the same structure.

4 (a) and 4 (b) are perspective views showing states of a conductive chip used in the present invention before and after loading into a contact rubber forming dug portion, respectively.

5 (a) to 5 (c) are vertical cross-sectional views showing, in the order of steps, the work of integrating the conductive chip and the contact rubber body used in the present invention.

FIG. 6 is a vertical sectional view of a conventional contact rubber.

FIG. 7 is a partially enlarged vertical cross-sectional view of a conductive chip used for manufacturing a conventional contact rubber.

8A to 8F are vertical cross-sectional views showing, in the order of steps, processes of obtaining a conductive chip used in a conventional method from a sheet-shaped laminate having the same structure.

9 (a) and 9 (b) are perspective views showing states of a conventional conductive chip before and after being loaded in a contact rubber forming dug portion, respectively.

[Explanation of symbols]

1, 11 ... Conductive chip, 2 ... Conductive layer,
3 ... nickel silver, 4 ... nickel plated layer, 5 ... gold plated layer, 6 ... insulating rubber layer, 7 ... ultraviolet irradiation surface, 8 ... convex, 21
... Mold for sheet-like laminate production, 22 ... Mold for forming insulating rubber layer, 23 ... Digging, 24 ... Mold for loading conductive member, 25 ... Conductive member,
26: Insulating rubber material, 27: Sheet-like laminate,
28: Cylindrical blade, 29: Conductive tip,
30: dug portion for forming contact portion, 31: die for manufacturing contact rubber, 32: die for forming key top portion, 33: void, 34: unvulcanized silicone rubber, 35: contact rubber.

Claims (3)

[Claims] 1. A sheet-like laminated body, in which an insulating rubber layer having a non-adhesive treatment on the surface is laminated on a conductive layer on a surface not having the non-adhesive treatment on the surface, is punched into a predetermined shape to be electrically conductive. It is characterized in that it is made into a chip, the conductive chip is charged into a molding die so that the conductive layer side is in contact with the mold surface, unvulcanized rubber is filled on the conductive chip of the molding die, and integrally molded. Method of manufacturing contact rubber. 2. The insulating rubber layer is made of silicone rubber, and the conductive layer is made of either silicone rubber containing 30 to 75% by weight of carbon black or nickel-silver plated nickel and gold in sequence. A method for producing a contact rubber according to claim 1. 3. The insulating rubber layer has 184.9 nm and 2
By irradiating ultraviolet rays with a wavelength of 53.7 nm with an integrated light intensity of 200 to 20,000 mj / cm ² at an irradiance of less than 150 mW / cm ² , or by providing multiple convexes, or by both. The method for producing a contact rubber according to claim 1, wherein a non-adhesive treatment is performed.