JPS60202624A - High sensitivity pressure sensitive conductor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a highly sensitive pressure-sensitive conductor that imparts particularly acute pressure sensitivity to a predetermined portion of a pressure-sensitive conductive sheet.

[Prior art]

For example, it is made by molding a rubber elastic material mixed with silver, copper, or other conductive particles into a sheet shape as a component of input means for so-called office automation equipment such as calculators and word processors, and pressure sensors for various automatic devices. Various pressure-sensitive conductors have been put into practical use.

However, since elastic bodies such as rubber are originally electrical insulators, it is difficult to obtain stable and desired conductive properties, and depending on the conditions, what should be a conductive sheet can easily become a semiconductor or insulating sheet. In particular, in membrane switches, which are often used in key devices today, pressure-sensitive conductors with extremely high sensitivity formed in specific parts according to the switch pattern are desired in order to enable light key touches. It is particularly difficult to form a highly sensitive pressure-sensitive conductor in which the pressure-sensitive conductivity is extremely high in some parts. As a pressure-sensitive conductor that uses a magnetic field, for example, a fluid silicone rubber base material mixed with magnetic particles is poured into a mold completely embedded with magnets, and the magnetic material is placed in the direction of the magnetic field. It has been proposed that particles are oriented and molded and hardened into a sheet. However, this proposal involves cross-linking and curing liquid rubber in a magnetic field and arranging nickel particles in one direction, forming particularly sensitive pressure-sensitive conductive parts in the desired pattern in specific parts of the sheet. It wasn't something to do. Therefore, when this sheet is used, for example, as a so-called touch switch, there is a problem in that malfunctions are likely to occur.

[Purpose of the invention]

This invention has been made in view of the above-mentioned problems, and by providing a high-sensitivity pressure-sensitive conductor that is extremely easy to use and allows for instant setting of any pattern, with high productivity, the above-mentioned problems can be solved. It aims to solve the problem.

[Structure of the invention]

This invention achieves the above object by placing a pressure-sensitive conductive sheet obtained by uniformly dispersing nickel particles in a polystyrene-based, polyurethane-based, polyester-based or vinyl chloride-based thermoplastic elastomer on a magnetic field forming body. By applying a solvent compatible with the thermoplastic elastomer to a predetermined portion of its surface, the sheet is partially melted, and only the nickel particles in the melted portion are aligned in the direction of the magnetic field. It is a sensitive pressure-sensitive conductor.

Hereinafter, the highly sensitive pressure-sensitive conductor according to the present invention will be explained in detail.

The pressure-sensitive conductor sheet constituting the present invention has pressure-sensitive conductivity obtained by uniformly dispersing nickel particles as a magnetic conductor in a polystyrene-based, polyurethane-based, polyester-based, or vinyl chloride-based thermoplastic elastomer. Obtained by molding an elastomer into a sheet using a low-pressure roller. Generally, in this type of pressure-sensitive conductor sheet, nickel, silver, copper, etc. are used as metal particles added to impart good conductivity, but in the present invention, it is necessary to use ferromagnetic material. , therefore nickel particles are selected. Further, the thermal 5'J plastic elastomer of the present invention is selected to be one that is easily dissolved in a solvent.

The present invention imparts extremely high sensitivity pressure-sensitive conductive properties to specific parts of the pressure-sensitive conductive sheet formed as described above.
The magnetism of the added nickel particles and the solvent solubility of the thermoplastic elastomer that is the sheet base material are skillfully utilized. That is, the formed pressure-sensitive conductive sheet is fixed on a magnet as a magnetic field forming body or on a known magnetic rubber or magnetic resin plate, and the sheet is applied to the surface of the fixed sheet by means such as spraying or brushing. A solvent that is compatible with the constituent thermoplastic elastomer is applied. This coating is performed to form a desired pattern depending on the application. The applied solvent dissolves the thermoplastic elastomer that restrained the nickel particles, and the nickel particles easily move and align in the direction of the magnetic field produced by the magnetic field forming body. Next, this sheet is placed on the magnetic field forming body and dried by heating to volatilize the solvent.

As a result, the nickel particles can be fixed in the thermoplastic elastomer while remaining aligned in the direction of the magnetic field, and then taken out of the magnetic field.

Note that when placing the molded pressure-sensitive conductive sheet on the magnetic field forming body, the sheet can be easily peeled off by interposing a release paper, for example. The obtained pressure-sensitive conductor becomes a highly sensitive pressure-sensitive conductor in which the patterned portion coated with the solvent has particularly sensitive pressure-sensitive conductive characteristics compared to other portions.

The highly sensitive pressure-sensitive conductor formed in this way is, for example, the first
It is suitable for application as a so-called membrane switch as shown in the figure. In the figure, reference numeral 1 indicates a high-sensitivity pattern portion formed by applying a solvent using a high-sensitivity pressure-sensitive conductor according to the present invention. 2 is a metal plate which is a lower electrode as a common electrode, and 3t'i is an upper electrode which has, for example, an electrode 3a and a leader line 3b formed on the back side of the plastic substrate in correspondence with the high-sensitivity pattern portion 1a.

The membrane switch obtained by laminating the highly sensitive pressure-sensitive conductor 1, the lower electrode 2, and the upper electrode 3 in close contact has no air space between the electrodes 1 and 2, so the electrodes may be damaged by arcing during operation. No welding or wear.

In particular, since conduction does not occur even when the leader wire portion 3b is pressed, stable performance without malfunction can be obtained.

Further, since the highly sensitive pressure-sensitive conductor sheet and the electrode are in close contact, no deterioration phenomenon due to an intervening air layer occurs.

〔Example〕

Styrene-butadiene styrenic distomer't
o I parts by weight, 30 parts by weight of polystyrene, 0 parts by weight of stearic acid
．． After kneading a mixture consisting of 5 parts by weight, 270 parts by weight of Ni particles with a particle size of 30 to 45 μm, 1 part by weight of an anti-aging agent, and 2 parts by weight of a silane coupling agent, with a hot roll at 130 to 140°C, the thickness was 0. It was divided into .21 sheets. Next, this separated sheet was placed and fixed on a magnetic rubber plate via a release paper, and then a solvent, toluene, was applied partially to the surface of the sheet with a brush.

This was dried in an oven at 50° C., then taken out and punched onto a magnetic rubber plate to obtain a pressure-sensitive conductor sheet (Sample A). On the other hand, the same distributed sheet was not placed on a magnetic rubber plate, but the surface was partially coated with the solvent toluene with a brush, and then dried in an open room at 50°C to create other pressure-sensitive conductive sheets. (Sample B).

The pressure force vs. conductive resistance characteristics of both samples were measured when pressure was applied using a smooth presser with a diameter of 6 mm, and the results were as follows.

The number of samples to be tested is 5 each.

Sample N (solvent coated on magnetic rubber plate)... Pressure force when conducting on solvent coated part 5-70y- Sample B (solvent coated without magnetic rubber plate)... Pressure force when conducting The electrical resistance of the sheets was 108 Ω or more before conduction and 100 Ω or less after conduction, and the pressing force during conduction of the sheet before solvent application was 1 kg or more in all cases.

In view of the above results, it is clear that in the high-sensitivity pressure-sensitive conductor according to the present invention (i.e., sample A above), the specific portion obtained by applying the solvent has significantly higher sensitivity than the non-coated portion. .

〔Effect of the invention〕

As explained above, according to the present invention, a pressure-sensitive conductive sheet obtained by uniformly dispersing nickel particles in a thermoplastic elastomer is partially dissolved on a magnetic field forming body using a compatible solvent. By using an extremely simple process of drying, a specific part can be formed with extremely high sensitivity, so it can be quickly applied to any high-sensitivity pattern, and is much more productive and low-cost than conventional high-sensitivity pressure-sensitive conductors. It is possible to donate the body.

[Brief explanation of drawings]

FIG. 1 is an exploded perspective view showing a preferred mode of use of the high-sensitivity pressure-sensitive conductor according to the present invention. 1... Highly sensitive pressure sensitive conductor la of the present invention
...Button part 2 coated with solvent...
・Lower electrode (common electrode) 3... Upper electrode

Claims (1)

[Claims] A pressure-sensitive conductive sheet obtained by uniformly dispersing nickel particles in a polystyrene-based, polyurethane-based, polyester-based, or vinyl chloride-based thermoplastic elastomer is placed on a magnetic field forming body with IN< and a predetermined portion of the surface thereof is coated with the thermoplastic elastomer. By applying a compatible solvent to the elastomer,
A highly sensitive pressure-sensitive conductor made by partially melting a sheet and arranging only the nickel particles in the melted portion in the direction of the magnetic field.