JPS6123643B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pressure-sensitive resistance element with a new configuration.

Conventionally, conductive rubber-like elastic bodies for pressure-sensitive resistance elements have been prepared by mixing and dispersing metal powder or carbon black in an insulating rubber elastic body, or by dispersing conductive particles in a sponge-like body. Various products have been developed. These are caused by the applied pressure increasing the chances of contact between particles in the rubber-like elastic body and/or increasing the actual contact area with the electrode that is in contact with it, thereby increasing the resistance value between the counter electrode. It has a mechanism that makes it smaller. This applied pressure compresses and deforms the conductive rubber-like elastic body.
As a result, peeling shear acts between the insulating rubber elastic matrix and the conductive particles, and even if adhesive or coupling agent is used between the matrix and the particles to strengthen the adhesive force, , the repeated applied pressure causes the matrix and conductive particles to separate due to large strain deformation, reducing the initial resistance ~
It has the disadvantage that it is difficult to maintain the pressure relationship and has low reliability. In order to improve these drawbacks by reducing the amount of compression deformation, there are disadvantages such as the thickness in the compression direction being limited to a thin material and fine adjustment of the relationship between pressure and resistance value being extremely difficult.

For example, US Patent No. 4199637, US Patent No. 4203088
No. 4210895, No. 4209481, etc. disclose pressure-sensitive resistance elements having a structure in which the number of needle-like bodies penetrating within the contact electrode area increases with applied pressure. These have the disadvantage of losing their reliability due to permanent deformation such as buckling or bending of the linear or needle-like bodies. Therefore, pressure-sensitive resistance devices using these conductive rubber-like elastic bodies have the disadvantage of being used within a very limited range of specifications.

Furthermore, as shown in the drawings of Japanese Patent Publication No. 55-26565, a pressure-sensitive resistance structure is made of an elastic material A with conductive particles mixed in its surface layer by pressure.
A pressure-sensitive resistor is shown that is configured to increase the distribution density of the group, while increasing the distribution density of the elastic body B group in which conductive particles are not mixed inside the structure. However, since this is made by mixing and dispersing elastic bodies A group and B group so that the above functions are exhibited, the structure is complicated, and therefore process control is difficult and costs are high. In addition to this disadvantage, there are also variations in quality and instability in the pressure-sensitive resistor.

Furthermore, Japanese Utility Model Publication No. 49-32692 discloses a conductive sponge whose electrical resistance value changes depending on the degree of compression. The inner walls are repeatedly stretched and bent due to bulging or protruding deformation, and in the case of home rubber or open cell sponge, the inner walls of the cells are bent at acute angles, so in both cases fatigue of the inner walls of the cells occurs. There is a disadvantage that it tends to occur early.

The present invention aims to provide a pressure-sensitive resistance element which solves these disadvantages and disadvantages, and which comprises agglomerated granules made of a rubber-like elastic material whose surface layer is electrically conductive between electrodes. When pressed, the contact area between the electrode and the granules and between the granules increases due to side-by-side and/or bulging deformation due to the pressure of the granules, and when the pressure is released, the contact area decreases. The present invention relates to a pressure-sensitive resistance element characterized in that it is configured as follows.

According to the present invention, the granules constituting the agglomerate of the conductive rubber elastic body protrude or bulge in response to pressure,
This mechanism increases the contact area between the granules and changes the electrical resistance value, so the structure is not as complicated as conventional ones.
Furthermore, fatigue is extremely unlikely to occur and reliability is extremely high.

The conductive rubber-like elastic granules used in the present invention are made by mixing and dispersing a conductive material such as metal powder or carbon black in an insulating rubber-elastic matrix. It may be a material in which a conductive rubber coating layer is formed on the surface of an insulating rubber elastic material that has been made into granules in advance, or a conductive rubber elastic material fine particle is formed on the surface of an insulating rubber elastic material particle. A conductive rubber-like elastic material with a resistivity of 10 ^-4 ohm・cm~
It is desirable that it be within the range of 10 ⁴ ohm cm.

The conductive rubber-like elastic body is used in the form of granules, which can be obtained by molding and vulcanizing the conductive rubber-like elastic body into granules of a predetermined shape when manufacturing the conductive rubber-like elastic body by vulcanization. In addition, it may be obtained by crushing, cutting, or cutting a conductive rubber-like elastic body in the form of a sheet, rod, lump, string, etc. into particles of an appropriate size. Therefore, the cross-sectional shape or projected shape of these granules is not particularly limited, and includes all shapes shown in powder engineering, as well as ring shapes, pipe shapes, hollow bodies, porous bodies, etc.

No matter which of these particles the granules are, their maximum outer diameter is 10 μm to 10 mm (preferably or 50 μm to 10 mm).
5mm), and the actual area of the cross section is 75μm ² ~ 100mm ²
(preferably 200 μm ² to 75 mm ² ). If this is too small, it will be difficult to construct a pressure-sensitive resistance element with the above-mentioned functions. In other words, the balance between the frictional force between the granules and the elastic restoring force of each granule tends to be poor, and the elastic restoring force in the agglomerated state is insufficient, making it difficult to finely adjust the relationship between the applied pressure and the resistance value. becomes.
On the other hand, if this granular material is too large, the ratio of surface area to volume of this conductive rubber-like elastic material becomes small, and the specific resistance of the bulging surface due to compression during pressing tends to increase. In addition to the amount of change in resistance not changing much, there is a disadvantage that when compressed, the frictional force due to side elongation of the surface of the granular material becomes large, making cracking more likely to occur on the surface.

Incidentally, as long as the particles of the conductive rubber-like elastic material have an average diameter within the above-mentioned range, there is no problem in principle even if the particles are of different sizes, but it is preferable that the particles have a uniform diameter or have a particle distribution width. It is better to use them as small as possible and even in the same shape.

In the present invention, the above-mentioned granules are arranged between the electrodes in an agglomerated state, but this agglomerated state means that the granules form a stacked structure, and the granules do not separate one by one. The porosity of each granule, excluding hollow structures and porous structures, is 5 to 80%, and the actual volume of the granule is in a densely packed state, an ordered stacked state, or a sparsely packed and deposited state. It is preferably 10 to 75%, more preferably 20 to 70%, although it varies depending on the situation. If it is less than 5%, it is difficult to obtain a large amount of change in resistance value, and if it is more than 80%, resistance value increases due to elongation of the granule surface or friction deterioration between granules tends to occur, and adhesion between granules tends to occur. Therefore, maintaining reliability becomes difficult.

In the present invention, the agglomerated state of the granules has an external shape of a plate, columnar, annular, or spherical body, and the outer diameter surface of the granular material has a smooth surface, a rough surface, or an uneven surface.

The appearance shape of such agglomerated granules has a thickness and height in the direction of applied pressure of 0.5 to 0.5 times when the average maximum outer diameter of the selected granules is large.
5 times, 0.5 times ~ if the smaller one is used
It is best to do this at a magnification of 100 times, and in combination with the above-mentioned effective ranges for the outside diameter and porosity of the granules, this is effective in further increasing reliability.

This agglomeration state is usually caused by the arrangement between electrodes, which does not limit the contact or separation of the electrodes when not in operation, but the periphery of the plane perpendicular to the direction of pressing should be in contact with other solid members as much as possible. It's better not to have it. If it is in contact with a flexible rubber-like elastic body that easily returns to its original thickness when the pressure is released, the above-mentioned return is assisted by the elastic behavior of the rubber-like elastic body, so that it is conveniently integrated. Things are even better.

The agglomerated state of granules is achieved by laying granules of vulcanized conductive rubber in a flat shape, then laying granules of unvulcanized conductive rubber that can be vulcanized in layers, alternating and stacking them as necessary. Then, during vulcanization, the porosity may be maintained, placed in a mold, and vulcanized by hot pressure. Alternatively, the granules may be all unvulcanized conductive rubber that can be vulcanized at first, and hot air vulcanization or steam vulcanization may be performed while maintaining the granules in a deposited state. Alternatively, vulcanized conductive rubber particles and vulcanizable unvulcanized rubber particles may be uniformly dispersed and mixed in an appropriate ratio and deposited, and then vulcanized. Furthermore, conductive and/or insulating vulcanized and/or unvulcanized rubber particles may be deposited in a liquid-permeable bottom container, such as a sieve or colander, to remain fluid at room temperature and after curing. A method of curing the liquid rubber raw material in a wet state without filtration or bubbling of a packed bed in a distillation column by immersing it in a rubber liquid raw material that exhibits a rubber elastic body and becomes conductive may be used. In the case of silicone rubber, the liquid rubber raw material may be either a one-component type or a two-component type, curing at room temperature or heating, and a solvent may be used. The granules may be laid out in a single layer on a flat surface to form an agglomerate.

The electrodes arranged on the granular bodies in the agglomerated state (agglomerate 2 in the drawings) of the present invention are flexible, rigid,
Those formed by etching on a substrate, or conventionally known pin-shaped, plate-shaped, ribbon-shaped contacts, wire-shaped, flexible, elastic thin metal plates, flexible synthetic resins, synthetic rubber, etc. It may be in the form of a sheet, integrated into a plate, or formed by vapor deposition or sputtering, and may be plated with a precious metal if necessary.

The electrodes are arranged such that they sandwich the agglomerated state, are arranged in parallel on the surface of the agglomerated state, or at least one electrode penetrates the agglomerated state, and the number of electrodes is 2 to 3 per one agglomerated state. Placed above poles.

To explain the specific content of the present invention based on the drawings, FIG. 1 shows a schematic cross-sectional view of a pressure-sensitive resistance element having a structure in which conductive particles 1 are arranged as agglomerates 2 between electrodes 3 and 3'. In the figure, a shows the non-pressed state and b shows the pressed state. As can be seen from figure b, pressing increases the contact area between the electrode and the conductive particles, and the particles come into contact with each other.As a result, the resistance between electrodes 3 and 3' increases when no pressure is applied (figure a).
It is much smaller than .

Figure 2 shows a different configuration of the electrode arrangement, in which, as shown in figure a, a layer 5 is provided on one side of the support plate 4 to fix the agglomerate 2 made of conductive particles. . This 5 may be either conductive or insulating. And on the opposite support plate 4' there is a counter electrode 3,
3', 3'' are provided. Of course, this counter electrode only needs to have two or more poles. Figure b shows the state in which the conductive particles are pressed against the electrode surface in Figure a. As a result, conduction is established between 3, 3', and 3''.

Figures 3, 4 and 5 show a few examples of devices to which the pressure-sensitive resistance element of the present invention is applied, such as calculators, sensor switches for telephones and other microcomputer devices, and electronic devices. Sensor switches for equipment, multi-item input devices or resistors - push-button-shaped or under-key keyboard devices for electronic musical instruments or electronic toys that increase the pressure range to enable after-control of performance effects; and
It is used in pressure sensors for ME, etc.
The support plate 4 in FIG. 3 may be a flexible body or a rigid body. Reference numeral 6 in FIGS. 3 to 5 indicates an insulating rubber elastic body, which may be a porous body, a foam, or a molded body made of insulating rubber elastic particles in an agglomerated state.

As can be seen from the explanation based on the above drawings, the present invention allows each particle of the conductive rubber-like granules to conduct electricity.
It is not necessary that the electronic device has 100% reliability; it is sufficient that the above-mentioned functions (effects) can be achieved in the state of agglomeration of the granules. By handling established fields in the fields of particle engineering and chemical engineering, quality control for electrical and electronic equipment, automation of processing equipment, assembly equipment, etc. will be extremely easy. This means that even if one or two of the particles in an agglomeration are defective and do not have the functions according to the present invention, the functions in one agglomerate, for example, as shown in FIGS. 3 and 4. This is actually a very great advantage in the sense that with the structure shown in FIG. 5, there will be no defects in each agglomerate unit.

Another advantage of the present invention is that the resistance-pressure relationship can be easily adjusted, increasing the volume to free surface area ratio of the particle solids when the elastomer particles are compressively deformed. Then,
Creep inside the particles is reduced, and the range of resistance-pressure changes due to synergistic area changes due to changes in the contact area between the particles and the counter electrode is increased, making adjustment easier and increasing reliability. It gives you the advantage of being

[Brief explanation of the drawing]

FIG. 1 shows a schematic sectional view showing the most basic structure of a pressure-sensitive resistance element according to the present invention, in which figure a shows a non-pressed state and figure b shows a pressed state.
FIG. 2 shows a schematic cross-sectional view of a pressure-sensitive resistance element with a different electrode arrangement, in which figure a shows the non-pressed state and figure b shows the pressed state. FIGS. 3a and 3b show how the device is used as a sensor switch, FIGS. 4a and 4b show how it is used as a keyboard switch, and FIGS. 5a and 5b show how it is used as an ME pressure sensor. 1... Conductive particles, 2... Agglomerates, 3,3',
3″, 3... Electrode, 4, 4'... Support plate, 5...
A layer for fixing the agglomerate 2, 6... an insulating elastic body.

Claims (1)

[Claims] 1. Granular bodies made of a rubber-like elastic material whose surface layer is electrically conductive are disposed between the electrodes in an agglomerated state, and when pressed, the electrodes are A pressure-sensitive resistance element characterized in that the contact area between the granules and the granules increases, and when the pressure is released, the contact area decreases.