JPH0646038Y2 - Touch switch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a touch switch having excellent corrosion resistance.

[Prior Art] Touch switches are often used to open and close circuits of various electric devices. For example, touch switches are used as keyboard switches around water in washing machines, baths, toilets, kitchen appliances, etc. Its use is increasing for the purpose of improving. As these touch switches, those of air gap type and those of pressure sensitive conductive rubber type are known.

In the air gap method, as shown in FIG. 3, by pressing the flexible film 11 which is the wiring substrate, the upper and lower electrodes 12-13 are brought into contact with each other at the time of pressurization to obtain conductivity, and at the time of depressurization. Due to the resilience of the flexible film 11, the air 15 insulates the electrodes 12 and 13 from each other.

In the pressure-sensitive conductive rubber system, as shown in FIG. 4, a pressure-sensitive conductive rubber 16 is interposed between both electrodes 12-13 so that the electrodes 12-13 are electrically conductive when pressure is applied to the electrode substrate and depressurized. It is to obtain insulation. Note that the pressure-sensitive conductive rubber 16 has a characteristic of rapidly exhibiting conductivity under a constant pressure in the pressing direction, and is generally one in which a predetermined amount of conductive particles such as carbon black and metal particles are dispersed in silicone rubber. Target. In this case, the conductivity is obtained by the conductive particles coming into contact and communication with each other in the pressing direction, and the insulating property is obtained by the insufficient contact of the conductive particles during depressurization due to the elasticity of the silicone rubber.

The air gap method has a defect that cracks or blisters are generated in the airtight portion due to temperature change during use and the sensitivity is lowered, or the function is lost due to intrusion of water or the like.

The pressure-sensitive conductive rubber method has a drawback that when the conductive particles are carbon black, the sensitivity is poor due to insufficient conductivity, and when the conductive particles are metal particles, the function disappears due to corrosion. There is.

In addition, since the pressure-sensitive conductive rubber does not have adhesiveness to the circuit, it requires a separate fixing means such as adhesive tape or spacers so as not to move from the electrode part, and the work process is complicated. It will also be an obstacle to the miniaturization of light, thin, short and small products.

Further, since the pressure-sensitive conductive rubber is generally impermeable to light, it is difficult to see through the electrode in the case of a transparent electrode such as an indium oxide (ITO) electrode. It cannot be used as the upper touch switch.

[Problems to be solved by the device]

The present invention can exhibit excellent switching characteristics even in corrosive environments such as around water, and can also exhibit excellent resolution for high-density electrode arrangements.
Further, it is an object of the present invention to provide a touch switch that can be made to be light transmissive.

[Means for Solving the Problems]

That is, in the touch switch of the present invention, the electrode substrate of at least one of the two facing electrodes is made of a flexible material, and the electrodes on the two faces are brought into conduction when the electrode substrate is pressed. With the touch switch,
Between the two electrodes, (a) conductive particles having at least the surface of which has corrosion resistance, and (b) when the electrode substrate is depressurized, the size exceeds the particle size of the conductive particles, and the electrode substrate is deformable under pressure. And (c) a thin layer containing a pressure-sensitive deformable particle and (c) an adhesive substance having fluidity when the electrode substrate is pressed as an essential component.

1 and 2 are schematic sectional views showing a touch switch according to the present invention, in which a thin layer composed of (a), (b) and (c) is provided between electrodes. Normally, as shown in FIG. 1, the upper and lower electrodes 12-13 are formed by the pressure-deformable insulating particles 2.
The spaces are insulated. By pressurizing the electrode substrate forming the wiring board 1 to press between the electrodes 12-13 in FIG. 1, the insulating particles 2 are deformed as shown in FIG. The upper and lower electrodes 12-13 are electrically connected. At this time, the composition forming the thin layer that has flowed out to portions other than the electrode portion is absorbed by the flexibility of the upper wiring substrate 11.

As the electrode substrate of the upper electrode, a flexible wiring substrate 11, for example, a plastic film such as polyester or polyimide, or a thin glass epoxy (glass cloth substrate epoxy resin laminated plate) is used as a substrate. The printed wiring board is often used.

As the lower electrode substrate, a rigid wiring substrate 14,
For example, a wiring board having paper phenol, glass epoxy, glass, or ceramic as a base material is generally used.

When the pressure between the electrodes 12 and 13 in FIG. 2 is released, the insulating particles 2 which are pressurizable and deformable return to the state shown in FIG. 1 between the electrodes 12 and 13 and the electrodes are insulated.

The conductive particle 1 is a conductive particle having at least its surface resistant to corrosion. For example, the core is a simple substance of metal particles such as Au or Ni, or a polymer substance such as plastic or rubber, or ceramics, metal or metal oxide. Au, Ni, on its surface
A material coated with Ag, Cu, or a corrosion-resistant metal such as ITO is used.

Corrosion resistance is a characteristic that can withstand the corrosive environment of the touch switch. The environment includes high humidity such as around water and corrosive gas atmosphere, and the material can be determined in consideration of these.

These conductive particles 1 are generally harder than the insulating particles 2 in the usage environment of the touch switch, and have almost no pressure deformability.

At least the surface of the conductive particles 1 used in the present invention is Au.
When it is, it is preferably applied because it has excellent conductivity and corrosion resistance. Since Au, ITO, etc. can be formed even in a thin layer, light transmission can be imparted by forming them on the surface layer using glass or a polymer substance as a nucleus, which is advantageous when used as a transparent touch sensor. .

The surface of these conductive particles 1 may be subjected to a surface treatment such as a rust preventive treatment as long as the conductivity is not impaired.

As the pressure-deformable insulating particles 2, hollow micro-containers (hereinafter referred to as micro-balloons) are preferably applicable, and spongy particles and the like are also applicable.

As a microballoon, for example, a flexible plastic such as polyurethane or polyester or an elastomer such as acrylonitrile-butadiene rubber or natural rubber is used as a wall material, and a gas such as air or carbon dioxide or a liquid such as water or oil is used as a core material. It is better to use. The insulating particles 2 are more preferable in that the inside thereof is in a pressurized state by using a foaming agent as the core material in order to increase the switching speed.

Conventional methods such as an interfacial polymerization method and a coacervation method can be applied to the method for producing these microballoons. Since these wall materials can be formed in a thin layer, they can be made light transmissive.

Regarding the particle diameters of the conductive particles 1 and the insulating particles 2 used in the present invention, it is necessary for the switching function that the insulating particles have a size exceeding the particle diameters of the conductive particles during depressurization. Preferably, the particle size of the pressure-deformable particles is that of the insulating particles.
1.5 to 3 times. The particle size of these particles 1 and 2 is not particularly limited, but it is 5 μm due to the handling property of the particles in production.
It is preferably about m to 5,000 μm.

The adhesive substance 3 may be any substance that has adhesiveness to the electrode surface, can fix the insulating particles to the electrode, and has fluidity when the pressure is applied between the electrode surfaces 12-13.

Examples of such substances include, for example, acrylic acid ester, natural rubber and the like, and it is possible to intentionally adjust the fluidity by adding a tackifier, a flexibilizer or the like, if necessary. . In order to increase the switching speed, it is preferable that the viscosity be as low as possible.

The conductive particles 1 and the insulating particles 2 occupy about 0.5 to 10% by volume of the adhesive substance 3, and the ratio of the conductive particles to the insulating particles is preferably around the same volume% in terms of the switching function.

As a method of forming a thin layer from the above composition, it may be directly formed on the electrode by roll or printing, or the above composition may be formed into a film or sheet on a peelable separator, A normal means such as attaching to an electrode may be used.

The thickness of the thin layer is preferably equal to the size of the insulating particles 2 when depressurized, because the switching sensitivity can be improved.

[Action]

In the present invention, since at least the surface of the conductive particles has corrosion resistance, it is possible to obtain stable conductivity even in a corrosive environment. Also, since the insulating particles have pressure deformability, they have a switching effect. Demonstrate. Furthermore, since these conductive particles and insulating particles are dispersed in a sticky substance that has fluidity when pressed, it is possible to attach insulating particles to the electrode surface to form a thin layer, so a separate fixing means is required. It is not necessary, and the electrode surface can also be prevented from corrosion. Further, since fine particles can be used as the conductive particles and the insulating particles, it is possible to deal with high-density electrode arrangement.

Further, the conductive particles and the insulating particles have light transmissivity because the addition amount thereof may be as small as 10% by volume or less, and these particles themselves can impart light transmissivity to the adhesive substance. Since the refractive indices of and can be approximated, a transparent touch switch can be used.

Since the conductive particles act as spacer particles when the pressure is applied between the electrodes, they also have the recognizability of pressing the switch.

[Effect of device]

As described in detail above, the touch switch according to the present invention can exhibit excellent switching characteristics even in corrosive environments such as around water, and has excellent resolution even for high-density electrode arrangements. It is possible to exert. Further, it is possible to impart light transmittance, and its practical value is extremely large.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an insulating state between upper and lower electrodes of a touch switch according to the present invention, and FIG. 2 is a schematic sectional view showing a conduction state between upper and lower electrodes of a touch switch according to the present invention,
3 and 4 are schematic sectional views showing a conventional touch switch. DESCRIPTION OF SYMBOLS 1 conductive particles, 2 insulating particles that can be deformed under pressure 3 adhesive material 11 upper wiring board 12 upper electrode, 13 lower electrode 14 lower wiring board, 15 air 16 pressure-sensitive conductive rubber

Claims (1)

[Scope of utility model registration request] 1. An electrode substrate of at least one of the two facing electrodes is made of a flexible material, and the electrodes on the two faces are brought into a conductive state when the electrode substrate is pressed. In the touch switch, between the electrodes on the two surfaces (a)
Conductive particles at least the surface of which has corrosion resistance, (b)
Pressure-deformable particles having a size exceeding the particle diameter of the conductive particles when the electrode substrate is depressurized and having deformability under the pressure of the electrode substrate, and (c) an adhesive having fluidity when the electrode substrate is pressed. A touch switch formed by forming a thin layer containing a volatile substance as an essential component.