JP2000082608A - Pressure sensitive resistor and pressure sensitive sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure sensitive resistor for operating the change of an electric resistance value with high sensitivity and for realizing excellent reproducibility and durability. SOLUTION: This pressure sensitive resistor is constituted of base polymer 10 made of resin in a range in which share hardness is JIS A50 or more and JIS D80 or less, conductive materials 2, and packing materials 3 with elasticity higher than that of the base polymer 10 in which the rate of a mean grain diameter to rough film thickness is 0.25-2. The conductive materials 2 and the packing materials 3 are dispersed in the base polymer 10 and formed like a film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure-sensitive resistor used in a pressure transducer such as a pressure-sensitive sensor, and more particularly to a pressure-sensitive resistor having improved sensitivity and reliability.

[0002]

2. Description of the Related Art Conventionally, as a pressure conversion device for changing an electric resistance value by pressure, for example, a pressure conversion device utilizing a volume resistance change of a resistor interposed between electrodes, or a surface contact resistance change between electric contacts is used. There are things to use. The former typically uses a conductive rubber in which a conductive filler is dispersed as the resistor. As for the latter, there is one in which a semiconductor material layer is provided on one of the electrical contacts, as shown in, for example, Japanese Patent Publication No. 5-22398.

[0003]

However, the conventional pressure converter has the following problems. That is, the conventional pressure converter has still low sensitivity to pressure,
The detectable pressure range (load range) is also narrow. Therefore, it is possible to use the pressure conversion device for a switch or the like, but it cannot exhibit sufficient performance for use as a pressure-sensitive sensor for linearly detecting a load. Further, in the case of using the above-mentioned change in volume resistance using conductive rubber, reproducibility and durability are poor. Therefore, in order to construct an excellent pressure transducer that can be used as a pressure-sensitive sensor,
The development of a pressure-sensitive resistor having excellent characteristics has been desired.

The present invention has been made in view of the above-mentioned conventional problems, and provides a pressure-sensitive resistor which can change the electric resistance value with high sensitivity and which is excellent in reproducibility and durability. What you want to do.

[0005]

According to the first aspect of the present invention, there is provided a base polymer made of a resin having a Shore hardness in a range of JIS A50 or more and JIS D80 or less, a conductive material, and an elastic modulus higher than that of the base polymer. And a filler having an average particle size ratio of 0.25 to 2 with respect to a target film thickness, wherein the conductive material and the filler are dispersed in the base polymer to form a film. Characteristic pressure-sensitive resistor.

The most remarkable point in the present invention is that a resin having the above-mentioned specific hardness is used as a base polymer, and a filler having the above-mentioned properties is dispersed in the resin.

The Shore hardness of the base polymer is JIS
If it is less than A50, plastic deformation of the pressure-sensitive resistor tends to occur, and there is a problem that sufficient durability cannot be obtained. On the other hand, when the pressure-sensitive resistor exceeds JIS D80, there is a problem that, for example, when the pressure-sensitive resistor is formed in a film shape, it is difficult to bend it.

The elastic modulus for specifying one of the characteristics of the filler is a proportional coefficient between stress and strain. In other words, the larger the elastic modulus, the smaller the distortion when the same stress acts. Therefore, when the same stress acts on the base polymer and the filler, the base polymer is more distorted.

As the above-mentioned filler, a filler having a ratio of the average particle diameter to the target film thickness of the pressure-sensitive resistor of 0.25 to 2 is used. When a filler having a ratio of the average particle diameter to the target film thickness of the pressure-sensitive resistor of less than 0.25 is used, the surface roughness of the pressure-sensitive resistor becomes too small, and the effect of the addition of the filler described later is reduced. There is a problem that it does not appear. On the other hand, if a filler having a ratio of the average particle diameter to the target film thickness of the piezoresistive element larger than 2 is used, the surface roughness of the piezoresistive element becomes too large, and the contact with the piezoresistive element becomes impossible. There is a problem that it will be sufficient. Further, the filler is dispersed in the base polymer. The term “dispersion” as used herein refers to a state in which the filler is hardly aggregated and dispersed alone.

Next, the operation and effect of the pressure-sensitive resistor according to the first aspect will be described. Considering the case where the above-mentioned pressure-sensitive resistor is interposed between the electrical contacts of the pressure-sensitive sensor, the contact state on the surface of the pressure-sensitive resistor between the above-mentioned contacts when the applied load is in a low load range is considered. And the surface contact resistance changes.

In this case, the surface of the pressure-sensitive resistor has a moderately increased surface roughness due to the dispersion of the filler in which the ratio of the average particle diameter to the target film thickness of the pressure-sensitive resistor is 0.25 to 2. It is in a state where it has been done. Therefore, a sudden increase in the contact area due to an increase in the load can be mitigated. Thus, the pressure-sensitive resistor can moderately change the resistance value with respect to the change in the applied load in a low load range.

In a high load range, after the increase in the contact area is saturated, the internal resistance starts to change due to deformation of the pressure-sensitive resistor itself. The change in internal resistance at this time is
The size can be increased by the presence of the filler. That is, since the elastic modulus of the filler is higher than that of the base polymer, the deformation of the pressure-sensitive resistor occurs in a state concentrated around the filler. As a result, a large number of conductive materials located around the filler cause a large change in the state of contact with each other according to a change in load. As a result, the state of the conductive network due to the conductive material dispersed in the base polymer changes, and the resistance value decreases. Therefore, the above-mentioned pressure-sensitive resistor can increase the sensitivity of the electric resistance change to the load change even in the high load range.

As described above, the pressure-sensitive resistor can maintain a high sensitivity of a change in electric resistance to a change in load from a low load range to a high load range, and can improve the reproducibility thereof. Obtainable.

Next, as described in claim 2, the surface roughness of the pressure-sensitive resistor formed in a film shape is Rz 5 to 20 μm.
It is preferably a value within the range of m. As a result, the sensitivity of the electrical resistance change to the load change in the low load range can be maintained at a practical level.

Preferably, the base polymer is one of a polyester resin and an epoxy resin. In this case, the range of the Shore hardness of the base polymer can be easily secured. By using a thermosetting synthetic resin such as a polyester resin or an epoxy resin having the above-described hardness, a pressure-sensitive resistor that is less likely to be plastically deformed and has excellent durability can be obtained.

Further, as the fourth aspect, carbon black can be used as the conductive member. Also, as the carbon black, conductive carbon such as acetylene black or furnace black can be used.

Preferably, the conductive member has an average particle size of 20 to 100 nm. When the average particle size of the conductive member is less than 20 nm,
There is a possibility that a problem of large variation in conductivity may occur. On the other hand, if it exceeds 100 nm, a film of the pressure-sensitive resistor may become brittle.

Further, as described in claim 7, a spherical silicone resin can be used as the filler. The spherical silicone resin can be obtained by subjecting the cured silicone resin mass to a fine particle treatment.

Preferably, the amount of the filler is 5 to 40% by weight.
If the addition weight of the filler is less than 5% by weight, there is a problem that the effect of the addition of the filler is not sufficiently exhibited. On the other hand, if the addition weight of the filler exceeds 40% by weight, the contact with the pressure-sensitive resistor becomes insufficient, and there is a problem that good pressure-sensitive characteristics cannot be obtained.

Next, the invention according to claim 9 is based on claim 1
9. A pair of electrodes arranged so as to oppose the pressure-sensitive resistor according to any one of Nos. To 8 via a predetermined gap, and to sandwich the opposing pressure-sensitive resistor from both sides; A pressure-sensitive sensor, comprising: a film disposed so as to sandwich a pair of electrodes from both sides.

According to a tenth aspect of the present invention, there is provided the pressure-sensitive resistor according to any one of the first to eighth aspects, wherein the pressure-sensitive resistor is formed on a first film. The pressure-sensitive sensor comprises a plurality of electrodes arranged via a gap and a second film supporting the plurality of electrodes.

According to an eleventh aspect of the present invention, the pair of pressure-sensitive resistors arranged via a predetermined gap and the pair of opposed pressure-sensitive resistors are arranged so as to sandwich the pair of pressure-sensitive resistors from both sides. A pair of electrodes, and a film arranged so as to sandwich the pair of electrodes from both sides. When the load applied to the film is in a low load range, the pair of senses increases according to the increase in the applied load. After the contact area of the piezoresistor gradually increases, the load applied to the film becomes a high load range, and after the increase in the contact area of the pair of piezoresistors saturates, the load increases according to the applied load. A pressure-sensitive sensor is configured to reduce internal resistance by deforming the pair of pressure-sensitive resistors themselves.

According to a twelfth aspect of the present invention, there is provided a pressure-sensitive resistor formed on a first film, and at least two electrodes disposed at a predetermined gap from the pressure-sensitive resistor. And a second film supporting the plurality of electrodes. When a load applied to at least one of the first and second films is in a low load range, the second film is increased in accordance with an increase in the applied load. The contact area between the two electrodes and the pressure-sensitive resistor gradually increases, and the load applied to at least one of the first and second films becomes a high load range. The pressure-sensitive sensor is configured to reduce internal resistance by deforming the pressure-sensitive resistor itself according to an increase in an applied load after an increase in an area of contact with the sensor is saturated.

By configuring the pressure-sensitive sensor according to the ninth to twelfth aspects, the sensitivity of a change in electric resistance to a change in load is maintained at high sensitivity from a low load range to a high load range. A pressure-sensitive sensor capable of performing the above-described operations can be obtained.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 A pressure-sensitive resistor according to an embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to FIG. As shown in FIG. 1, the pressure-sensitive resistor 1 of this example has a Shore hardness of JIS A50 or more,
D80 or less, a base polymer 10 made of a thermosetting synthetic resin, a conductive material 2 made of carbon black, and an elastic modulus higher than that of the base polymer 10 and the target film thickness of the pressure-sensitive resistor 1 Filler 3 made of spherical silicone resin having an average particle size ratio of 0.25 to 2
Consists of The filler 3 is the base polymer 1
It is uniformly dispersed in 0.

The production of the pressure-sensitive resistor 1 was performed as follows. First, as the base polymer 10, a polyester resin having a Shore hardness after curing of JIS A60 was prepared. In addition, a spherical silicon resin was prepared in which the ratio of the average particle diameter to the target film thickness of the acetylene black as the conductive material 2 and the pressure-sensitive resistor 1 as the filler 3 was 1.5.
The filler 3 is obtained by making the hardened silicone resin mass into fine particles.

Next, these raw materials are blended so that the compounding ratio of the obtained pressure-sensitive resistor 1 is 80 parts by weight of the base polymer 10, 20 parts by weight of the conductive material 2 and 10 parts by weight of the filler 3. I do. At this time, an appropriate amount of a solvent, a surfactant and the like can be added. Next, these raw materials are subjected to a dispersion treatment using a three-roll mill or the like to produce a paste-shaped pressure-sensitive resistor (hereinafter, referred to as a pressure-sensitive resistor paste).

In this pressure-sensitive resistance paste, the filler 3 made of the above-mentioned spherical silicon resin is in a state of being uniformly dispersed. It is considered that this is because, as described above, the spherical silicon resin is obtained by making the particles into the above-described fine particles, so that a spherical monodispersed fine powder can be obtained and aggregation can be reduced.

Next, a film 5 made of PET (polyethylene terephthalate), PEI (polyetherimide) or the like is prepared, and the above-mentioned pressure-sensitive resistor paste is provided on this film by a screen printing method or the like so as to have a desired pattern. . Next, in the hot air circulation path, the temperature 12
By maintaining the temperature at 0 to 150 ° C. for 1 to 2 hours, a pressure-sensitive resistor 1 as shown in FIG. 1 was obtained. In this case, the surface roughness of the pressure-sensitive resistor 1 was determined as the surface roughness by dispersing a spherical silicon resin having a ratio of an average particle diameter to a target film thickness of the pressure-sensitive resistor 1 of 1.5. It is contained in a preferable range of Rz5 to 20 μm.

Next, the operation and effect of this embodiment will be described. In the pressure-sensitive resistor 1 of the present embodiment, as shown in FIG. 2, the filler 3 made of the spherical silicone resin having the specific size is substantially uniformly dispersed in the base polymer. The surface is in a state where the surface roughness is appropriately increased.

Here, as shown in FIG. 2, it is assumed that two pressure-sensitive resistors are interposed between the electrical contacts of the pressure-sensitive sensor. In this case, when a load is applied,
Due to the influence of the above-mentioned moderate surface roughness, the contact area gradually increases from the convex portion, so that a rapid increase in the contact area is moderated. Therefore, in the pressure-sensitive resistor 1, the change in the surface contact resistance with respect to the load becomes gentle, and the sensitivity of the change in the electric resistance with respect to the load in a low load region is maintained in a practical state.

In the high load range, after the increase in the contact area is saturated, the internal resistance starts to change due to the deformation of the pressure-sensitive resistor itself. At this time, the filler 3 is made of a spherical silicone resin, and its elastic modulus is higher than that of the base polymer 10. Therefore, as shown in FIGS.
The deformation of the pressure-sensitive resistor 1 occurs in a state where the filler 3 itself is not deformed so much and concentrated around the periphery.

As a result, as shown in FIG. 3B, the large number of conductive materials 2 made of carbon black located around the filler 3 cause a large change in the state of contact with each other according to the change in load. , For example, a new conductive network e (FIG. 3B) is formed. Therefore, the pressure-sensitive resistor 1
Can make the electric resistance change with respect to the load change highly sensitive even in the high load region.

As described above, the pressure-sensitive resistor 1 of this embodiment can maintain high sensitivity characteristics from a low load range to a high load range, and can obtain reproducibility thereof. In addition, since the pressure-sensitive resistor 1 uses a thermosetting polyester resin having the above-described hardness characteristics as the base polymer 10, it is difficult to be plastically deformed, and excellent durability can be obtained.

Embodiment 2 In this embodiment, the pressure-sensitive resistor 1 of Embodiment 1 (sample E
A pressure-sensitive sensor 7 was manufactured using 1), and its performance was evaluated. Further, in this example, a plurality of pressure-sensitive resistors in which the compounding fee, hardness, and the like of each component were changed were prepared (samples E2 to E5, C
1, C2).

Table 1 shows the components and the like of the prepared pressure-sensitive resistors. The sample E1 is the pressure-sensitive resistor 1 in the first embodiment as described above. Sample E2 is obtained by increasing the blending amount of the filler 3 of sample E1 by 10 parts by weight. Sample E
Reference numeral 3 denotes the size of the filler 3 in the sample E2 such that the ratio of the average particle diameter to the target thickness of the pressure-sensitive resistor 1 becomes 0.6.

In the sample E4, the base polymer 10 in the sample E1 was changed to an epoxy resin having a Shore hardness of JIS A80 and the blending amount was increased to 85 parts by weight.
Further, the amount of acetylene black was reduced to 15 parts by weight. In sample E5, the base polymer 10 in sample E1 was changed to an epoxy resin having a Shore hardness of JIS D70. Each of the samples E1 to E5 is a product of the present invention, and is similar to the sample E1 except for the features described above.

Sample C1 is a comparative example in which the amount of filler 3 in sample E1 was 0. Sample C2 is a commercially available product generally sold as a pressure-sensitive resistor (trade name: FSR
PART # 302 (manufactured by Interlink Corp.)).

Next, each of the pressure-sensitive resistors (E1 to E5, C
1, C2) to produce a pressure-sensitive sensor 7. As shown in FIG. 4, the pressure-sensitive sensor 7 has a conductor (electrode) 72 made of resin Ag provided on a base film 71 made of PET, PEI or the like, and the pressure-sensitive resistor 1 provided on the conductor 72. . Then, the two sets of pressure-sensitive resistors 1 face each other via the spacer 75, thereby forming the facing electrode type pressure-sensitive sensor 7 having the space layer 70. The method of disposing each pressure sensitive resistor 1 is the same as that of the first embodiment.

Next, the pressure sensitivity was measured using each of the pressure sensors 7 described above. The pressure sensitivity is indicated by the arrow A on the pressure sensor 77.
(FIG. 4) A load in the direction was applied, and the slope was determined by a gradient of a change in electric resistance value with respect to the load. In addition, as shown in FIG.
Performed from R2.

Table 1 shows the measurement results. As can be seen from Table 1, the products of the present invention (E1 to E5) all exhibited better pressure sensitivity characteristics than the comparative products (C1, C2). From these results, it can be seen that the configuration of the present invention is very effective in improving the characteristics of the pressure-sensitive resistor.

[0042]

[Table 1]

In this embodiment, the pressure-sensitive sensor 7 (FIG. 4) on the facing electrode side is used as described above, but instead of this, a shorting bar type pressure-sensitive sensor 8 as shown in FIG.
The same operation and effect can be obtained also when using. This shorting bar type pressure sensor 8 is, as shown in FIG.
The pressure-sensitive resistor 1 is provided directly on the base film 81, and a conductor (electrode) 8 is provided on the base film 81 to face the pressure-sensitive resistor 1.
2 is divided and arranged. Reference numeral 85 denotes a spacer.

In this shorting bar type pressure sensor, a pair of electrodes are arranged in a comb shape, and when receiving a load, the width of the contact surface between the pair of electrodes and the pressure sensitive resistor 1 increases. Things. In the first and second embodiments, the spherical silicon resin is used as the filler 3. However, the present invention is not limited to this, and other materials having the above-described characteristics may be used. For example, a thermal expansion capsule (micro balloon) or a resin other than a silicone resin may be used.

In the above-described embodiment, the thickness of the pressure-sensitive resistor 1 is set to an arbitrary value in the range of 5 to 20 μm in order to reduce the thickness of the pressure-sensitive sensor 7. . The average particle size of the filler 3 dispersed in the pressure-sensitive resistor 1 is set in the range of 5 to 40 μm in accordance with the target film thickness. The ratio of the average particle size of No. 3 can be in the range of 0.25 to 2. Further, the thickness of the pressure-sensitive resistor 1 is set to 5 to 20 μm.
And the average particle size of the filler 3 is 5
By setting the thickness to 40 μm, the surface roughness of the pressure-sensitive resistor 1 can be set to Rz 5 to 20 μm.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a configuration of a pressure-sensitive resistor according to a first embodiment.

FIG. 2 is an explanatory diagram showing a surface state of a pressure-sensitive resistor according to the first embodiment.

FIGS. 3A and 3B show a first embodiment (a) before pressurization and (b).
Explanatory drawing which shows the state of the conductive network by the conductive material after pressurization.

FIG. 4 is an explanatory diagram illustrating a configuration of a pressure-sensitive sensor according to a second embodiment.

FIG. 5 is an explanatory diagram showing a configuration of another pressure-sensitive sensor according to the second embodiment.

[Explanation of symbols]

 1. . . 9. pressure-sensitive resistor, . . 1. base polymer; . . 2. conductive material (carbon black); . . Filler (spherical silicone resin),

Claims (12)

[Claims] 1. Shore hardness is JIS A50 or more, JI
A base polymer made of a resin having an SD of 80 or less, a conductive material, and a material having an elastic modulus higher than that of the base polymer and having a ratio of an average particle diameter to a target film thickness of 0.2;
5. A pressure-sensitive resistor comprising: 5 to 2 fillers, wherein the conductive material and the filler are dispersed in the base polymer to form a film. 2. The pressure-sensitive resistor according to claim 1, wherein the surface roughness of the pressure-sensitive resistor formed in a film shape has a value within a range of Rz5 to 20 μm. 3. The pressure-sensitive resistor according to claim 1, wherein the base polymer is one of a polyester resin and an epoxy resin. 4. The method according to claim 1, wherein:
A pressure-sensitive resistor, wherein the conductive member is carbon black. 5. The pressure-sensitive resistor according to claim 4, wherein said carbon black is one of acetylene black and furnace black. 6. The method according to claim 1, wherein:
The pressure-sensitive resistor according to claim 1, wherein the conductive member has an average particle size of 20 to 100 nm. 7. The method according to claim 1, wherein:
A pressure-sensitive resistor, wherein the filler is a spherical silicone resin. 8. The method according to claim 1, wherein:
The amount of the filler added is 5 to 40% by weight. 9. The pressure-sensitive resistor according to any one of claims 1 to 8, wherein the pressure-sensitive resistor is opposed to the pressure-sensitive resistor via a predetermined gap, and is arranged so as to sandwich the opposed pressure-sensitive resistor from both sides. A pressure-sensitive sensor comprising: a pair of electrodes formed as described above; and a film disposed so as to sandwich the pair of electrodes from both sides. 10. The pressure-sensitive resistor according to claim 1, formed on a first film, and a plurality of pressure-sensitive resistors arranged with a predetermined gap from the pressure-sensitive resistor. A pressure-sensitive sensor comprising: an electrode; and a second film supporting the plurality of electrodes. 11. A pair of pressure-sensitive resistors arranged via a predetermined gap, a pair of electrodes arranged to sandwich the pair of opposed pressure-sensitive resistors from both sides, and the pair of pressure-sensitive resistors. When the load applied to the film is in a low load range, the contact area of the pair of pressure-sensitive resistors gradually increases in accordance with the increase in the applied load. After the load applied to the film becomes a high load range and the increase in the contact area of the pair of pressure-sensitive resistors is saturated, the pair of pressure-sensitive resistors themselves are increased in accordance with the applied load. A pressure-sensitive sensor configured to reduce internal resistance by deformation. 12. A pressure-sensitive resistor formed on a first film, at least two electrodes disposed with a predetermined gap from the pressure-sensitive resistor, and a second electrode supporting the plurality of electrodes. And when the load applied to at least one of the first and second films is in a low load range, the two electrodes and the pressure-sensitive resistor are increased in accordance with the increase in the applied load. Gradually increases the contact area of
And the load applied to at least one of the second film and the second film is in a high load range, and after the increase in the contact area between the two electrodes and the pressure-sensitive resistor is saturated, the load is increased in accordance with the applied load. A pressure-sensitive sensor configured to reduce internal resistance by deformation of a piezoresistor itself.