JP6666958B2 - Capacitance type extension sensor system - Google Patents

Description

  The present invention relates to a capacitance-type elongation sensor system including a stretchable base material and a flexible sensor element.

For example, as described in Patent Literature 1, a capacitance-type sensor is attached to a living body or clothes, and the movement of the living body such as the respiratory rate and bending and stretching of a joint is measured. As represented by the following formula (a), in the capacitance type sensor, when the thickness of the dielectric layer is extended and the distance between the electrode layers is reduced, the capacitance is increased. At the same time, as the area of the electrode layer increases, the capacitance increases. According to the capacitance type sensor, the movement of the living body can be measured based on a change in capacitance due to expansion and contraction of the sensor.
C = ε ₀ ε _r S / d (a)
[C: capacitance, ε ₀ : dielectric constant of vacuum, ε _r : relative dielectric constant of dielectric layer, S: area of electrode layer, d: distance between electrode layers]

JP-A-2017-201324 JP 2018-49036 A JP-A-2006-153729

  The capacitance of the capacitance type sensor is measured by applying an AC voltage between the electrodes. In order to measure a quick movement of a living body, it is better to increase the measurement frequency. However, when the measurement frequency is increased, the leakage current increases, which increases the power consumption and is not economical. If the power consumption is large, the battery is quickly consumed when driven by a battery, which is inconvenient. Conversely, when the measurement frequency is lowered, the power consumption is reduced, but it is difficult to measure the rapid movement of the living body. Therefore, it is desirable to change the measurement frequency according to the movement to be measured.

  As described in Patent Documents 1 to 3, an elastomer is used for the dielectric layer from the viewpoint of making the capacitance type sensor flexible. In this case, when the measurement frequency changes, the dielectric constant of the dielectric layer changes. The dielectric constant of the dielectric layer is affected by a polarization structure such as electronic polarization, orientation polarization, and ionic polarization. Usually, many additives such as a cross-linking agent, a cross-linking accelerator and a dispersant are blended with the elastomer. When these residues are ionized by an electric field, the ions are inverted and polarization occurs (ion polarization). That is, when an ionic component is present in the dielectric layer, many charges are generated due to ionic polarization, and the dielectric constant increases. However, ion polarization requires inversion of the ions themselves. Therefore, when the frequency is increased, the speed at which the ions are inverted cannot keep up with the frequency. Therefore, in the low frequency region, the increase in the dielectric constant due to ionic polarization is large, whereas in the high frequency region, the increase in the dielectric constant is hardly observed. Therefore, when an ion component is contained in the dielectric layer, the influence of ion polarization becomes large particularly in a low frequency region of 100 Hz or less, and the change in the dielectric constant due to the level of the measurement frequency becomes remarkable. As shown in the above equation (a), when the dielectric constant of the dielectric layer changes, the capacitance changes, so that the sensitivity of the sensor greatly changes. Therefore, when using an elastomer for the dielectric layer, it is difficult to change the measurement frequency according to the movement to be measured. Also, from the viewpoint of EMC (Electromagnetic Compatibility), when it is necessary to change the measurement frequency in order to reduce electromagnetic wave noise, it is necessary to take measures such as changing the components of the capacitance measurement circuit.

  The present invention has been made in view of such circumstances, and includes a sensor element having a dielectric layer in which a change in relative dielectric constant due to a measurement frequency is small even if an elastomer is included, and can measure movement of a living body and the like. An object of the present invention is to provide a simple capacitance-type elongation sensor system.

  The capacitance-type elongation sensor system of the present invention is a capacitance-type elongation sensor system including a stretchable base material and an elongation sensor disposed on the base material, wherein the elongation sensor is an elastomer. And a sensor element having a plurality of electrode layers disposed with the dielectric layer interposed therebetween.When the measurement frequency is in the range of 0.1 Hz to 10 kHz, the maximum relative permittivity of the dielectric layer is It is characterized by being not more than 10 times the minimum relative permittivity.

  The sensor element constituting the capacitance type elongation sensor system of the present invention includes a dielectric layer having an elastomer and having a small change in relative permittivity in a measurement frequency range of 0.1 Hz to 10 kHz. For example, the measurement frequency used for measuring the movement of the living body is appropriately about 1 Hz to 100 Hz. According to the sensor element of the present invention, since the relative permittivity of the dielectric layer does not easily change in a range including the frequency, the capacitance does not easily change even if the measurement frequency is changed according to the movement of the living body. Therefore, it is possible to set the optimum measurement frequency for the movement to be measured without changing the components of the measurement circuit, and it is possible to accurately measure various movements of the living body. Further, by setting the measurement frequency while avoiding the frequency at which noise is desired to be reduced, it is easy to comply with EMC regulations. That is, the fact that the measurement frequency can be easily changed is also effective for noise suppression.

  According to the capacitance-type elongation sensor system of the present invention, the elongation sensor is arranged on a stretchable base material. For example, when the substrate is a supporter or the like, or simply wearing it, or when the substrate is clothing, the body movement can be easily measured by simply wearing it.

  The relative dielectric constant tends to increase as the measurement frequency decreases. Therefore, if the relative dielectric constant at the measurement frequency of 0.1 Hz is 10 times or less than the relative dielectric constant at the time of 10 kHz (10000 Hz), “in the range of 0.1 Hz or more and 10 kHz or less, The maximum relative permittivity of the dielectric layer is 10 times or less of the minimum relative permittivity. "

FIG. 1 is a top view of an embodiment of a capacitance type elongation sensor system of the present invention. It is II-II sectional drawing of FIG. It is a top view of the extension sensor arrange | positioned at the base material. FIG. 3 is a schematic cross-sectional view of the stretch sensor in the front-rear direction. 6 is a graph showing a change in capacitance with respect to an amount of elongation in an A direction. 6 is a graph showing a change in capacitance with respect to an elongation amount in a B direction.

  Hereinafter, an embodiment of a capacitance type extension sensor system of the present invention will be described. First, an embodiment of the capacitance type elongation sensor system of the present invention will be described with reference to the drawings. FIG. 1 shows a top view of the capacitance type elongation sensor system of the present embodiment. FIG. 2 is a sectional view taken along line II-II of FIG. In FIG. 2, the vertical direction corresponds to the thickness direction of the elongation sensor. As shown in FIGS. 1 and 2, the capacitance-type extension sensor system 1 includes an extension sensor 2, a base material 3, and a control device 4. In the present embodiment, the left-right direction of the substrate 3 is defined as a measurement direction, and the front-rear direction is defined as a vertical direction perpendicular to the measurement direction.

  The base material 3 is compression wear (cloth using elastic fibers) and has elasticity. The elongation sensor 2 is arranged on the upper surface of the base member 3 so as to extend in a band shape in the left-right direction. The Young's modulus of the elongation sensor 2 is 20 MPa or less. The value of “Young's modulus × thickness” of the elongation sensor 2 is at least 10 times the value of “Young's modulus × thickness” of the substrate 3. The elongation sensor 2 includes a sensor element 20, an adhesive layer 21, and a protective layer 22.

  The sensor element 20 has a rectangular thin film shape. The length of the long side (length in the left-right direction) of the sensor element 20 is at least five times the length of the short side (length in the front-rear direction). The sensor element 20 includes a dielectric layer 200 and a pair of electrode layers 201 and 202.

  The dielectric layer 200 is formed of a crosslinked product obtained by crosslinking a polymer of a carboxyl group-modified hydrogenated nitrile rubber with a metal alkoxide compound, tetrakis (2-ethylhexyloxy) titanium. The crosslinked product is included in the concept of the elastomer in the present invention. The relative dielectric constant of the dielectric layer 200 is 13 (measurement frequency 100 Hz), and the maximum relative permittivity in the range of the measurement frequency of 0.1 Hz to 10 kHz is 10 times or less of the minimum relative permittivity.

  Each of the electrode layers 201 and 202 has a crosslinked product of acrylic rubber polymer crosslinked with a metal alkoxide compound, tetrakis (2-ethylhexyloxy) titanium, and thin graphite. The crosslinked product is included in the concept of the elastomer in the present invention. The electrode layer 201 is disposed on the upper surface of the dielectric layer 200. The wiring 40 is connected to the left end of the electrode layer 201. The electrode layer 202 is disposed on the lower surface of the dielectric layer 200. The wiring 41 is connected to the left end of the electrode layer 202.

  The adhesive layer 21 is disposed between the substrate 3 and the sensor element 20. The adhesive layer 21 is made of a urethane-based thermoplastic elastomer having a softening point of about 100 ° C. The base material 3 and the sensor element 20 are bonded by the bonding layer 21. The adhesive layer 21 has a Young's modulus of 50 MPa or less and a breaking elongation of 10% or more.

  The protective layer 22 is arranged so as to cover the sensor element 20 and forms the outermost layer of the stretch sensor 2. The protective layer 22 is made of the same urethane-based thermoplastic elastomer as the adhesive layer 21.

  The control device 4 includes a battery and a capacitance detection unit. The battery applies an AC voltage between the electrode layers 201 and 202 via the wirings 40 and 41. The capacitance detection unit detects the capacitance based on the amplitude of the flowing current and the phase difference with respect to the voltage.

  For example, when the base member 3 expands with the movement of the human body, the elongation sensor 2 also expands together with the base member 3. Then, the dielectric layer 200 is stretched, the distance between the electrode layers 201 and 202 is reduced, and the area of the electrode layers 201 and 202 is increased. As a result, the capacitance of the sensor element 20 increases. The control device 4 stores a map indicating the relationship between the change in capacitance and the amount of extension of the sensor element 20 in advance. Therefore, the amount of elongation of the sensor element 20, that is, the amount of elongation of the measurement site is calculated from the amount of change in the capacitance before and after the expansion.

  The sensor element 20 of the present embodiment includes the dielectric layer 200 having a small change in the relative dielectric constant when the measurement frequency is in the range of 0.1 Hz to 10 kHz. Therefore, even if the measurement frequency is changed, the capacitance hardly changes. Therefore, it is possible to set the optimum measurement frequency for the movement to be measured without changing the components of the control device 4, and it is possible to accurately measure various movements of the living body. Further, since the measurement frequency can be easily changed, it is also effective for noise suppression.

  The base material 3 of the present embodiment is compression wear. Therefore, the body movement can be easily measured only by wearing the compression wear. Here, the sensor element 20 has a rectangular shape in which the ratio (aspect ratio) between the long side and the short side is 5 times or more. Although the details will be described later, by setting the long side of the sensor element 20 to the elongation measurement direction and setting the flexibility of the elongation sensor 2 with respect to the base material 3 to a predetermined range, the elongation sensor 2 and the base material 3 extend together, and mainly in the vertical direction, only the base material 3 extends. In this way, the amount of elongation in the measurement direction can be measured selectively and without hindering the movement of the body.

  The elongation sensor 2 of the present embodiment is adhered to the base material 3 by an adhesive layer 21. The adhesive layer 21 is not an essential component, but by using a flexible and heat-pressable thermoplastic elastomer, the extension sensor 2 can be easily fixed to the substrate 3 while maintaining the flexibility of the extension sensor 2. Become. The outermost layer of the elongation sensor 2 is formed of the protective layer 22. The protective layer 22 is not an essential component, but by arranging the protective layer 22, various functions such as insulation, moisture resistance, and durability can be imparted to the elongation sensor 2.

  The capacitance-type elongation sensor system of the present invention is not limited to the above-described embodiment, and may be implemented in various forms with modifications and improvements that can be made by those skilled in the art without departing from the gist of the present invention. be able to. Next, individual members constituting the capacitance-type elongation sensor system of the present invention will be described.

<Substrate>
The type of the substrate is not particularly limited as long as it has elasticity. For example, a cloth, a polymer sheet, a cloth combining a cloth and a polymer, and the like can be given. The cloth may be any of a woven fabric, a knitted fabric, and a nonwoven fabric using synthetic fibers such as elastic fibers or natural fibers. As the polymer, an elastomer or a foam thereof is suitable. Examples of the combination of a cloth and a polymer include a laminate obtained by laminating a cloth and a polymer sheet, and a coating treatment in which a polymer solution is applied to a cloth or a cloth is immersed in a polymer solution. From the viewpoint of being able to follow the movement of a living body, it is desirable that the base material be capable of stretching 10% or more. For example, if a supporter, compression wear, or the like is selected as a base material, the movement of a living body can be easily measured simply by wearing them.

<Elongation sensor>
The elongation sensor includes a sensor element having a dielectric layer having an elastomer and a plurality of electrode layers disposed with the dielectric layer interposed therebetween.

[Sensor element]
(1) Dielectric layer The dielectric layer has an elastomer. The elastomer includes a crosslinked rubber and a thermoplastic elastomer, and one of these can be used alone, or two or more can be used in combination. From the viewpoint of increasing the capacitance and improving the measurement sensitivity, an elastomer having a large relative dielectric constant is desirable as the elastomer. Specifically, those having a relative dielectric constant of 10 or more (measurement frequency 100 Hz) are preferable. Examples of the elastomer having a large relative dielectric constant include nitrile rubber (NBR), hydrogenated nitrile rubber (H-NBR), acrylic rubber, natural rubber, isoprene rubber, ethylene-vinyl acetate copolymer, and ethylene-vinyl acetate-acryl. Acid ester copolymers, butyl rubber, styrene-butadiene rubber (SBR), fluorine rubber, epichlorohydrin rubber, chloroprene rubber, chlorinated polyethylene, chlorosulfonated polyethylene, and the like. Further, an elastomer modified by introducing a functional group or the like may be used. Examples of the modified elastomer include a carboxyl group-modified nitrile rubber (X-NBR) and a carboxyl group-modified hydrogenated nitrile rubber (XH-NBR). Since the thermoplastic elastomer does not use a crosslinking agent, impurities are less likely to enter. Examples of the thermoplastic elastomer include styrene-based (SBS, SEBS, SEPS), olefin-based (TPO), PVC-based (TPVC), urethane-based (TPU), ester-based (TPEE), amide-based (TPAE), and a combination thereof. Examples include polymers and blends. Among them, nitrile rubber and hydrogenated nitrile rubber are preferable because of their excellent durability and relative dielectric constant, and carboxyl group-modified nitrile rubber because of their ability to crosslink by reacting with a metal alkoxide compound described below, Carboxyl group-modified hydrogenated nitrile rubber is preferred.

  When the measurement frequency is in the range of 0.1 Hz to 10 kHz, the maximum relative permittivity of the dielectric layer is 10 times or less the minimum relative permittivity. It is more preferable that it is 8 times or less, and more preferably 5 times or less. In order to realize a dielectric layer whose relative dielectric constant hardly changes depending on the measurement frequency, it is desirable to reduce impurities and ionic components contained in the dielectric layer as much as possible. For example, when sulfur is used as a crosslinking agent, decomposition products such as sulfur and a vulcanization accelerator often remain in the elastomer after crosslinking, in addition to unreacted sulfur and a vulcanization accelerator. These reaction residues become components that ionize and generate ionic polarization. Therefore, in order to reduce the ionic component contained in the dielectric layer, it is desirable to use a metal alkoxide compound as the crosslinking agent. Examples of the metal alkoxide compound include tetra-n-butoxytitanium, tetra-n-butoxyzirconium, tetra-n-butoxysilane, acetoalkoxyaluminum diisopropylate, tetra-i-propoxytitanium, tetraethoxysilane, tetrakis (2-ethylhexyl) Oxy) titanium, titanium butoxide dimer and the like.

  From the viewpoint of increasing the relative dielectric constant of the dielectric layer, a dielectric substance may be added to the elastomer. As the dielectric substance, dielectric particles, semiconductors and the like are suitable.

  When adding dielectric particles to the elastomer, it is desirable to remove impurities and ionic components from the dielectric particles by washing in advance. That is, the dielectric layer may be formed using a dispersion in which the powder of the washed dielectric particles is mixed with the polymer solution of the elastomer. When cleaning the dielectric particles, a liquid that forms a metal complex such as acetylacetone may be used as the cleaning liquid. When a liquid that forms a metal complex is used, impurities in the metal oxide can be easily removed. As the dielectric particles, barium titanate, potassium niobate, potassium sodium niobate, potassium lithium sodium niobate, lead zirconate titanate, lanthanum-doped lead zirconate titanate, strontium titanate, bismuth titanate, bismuth titanate Inorganic particles such as barium are preferred.

  When a semiconductor is added to the elastomer, the relative dielectric constant can be increased while maintaining high electric resistance. Semiconductors include inorganic semiconductors described later and organic semiconductors such as polyaniline and polythiophene. From the viewpoint of increasing the carrier concentration and preventing impurities from entering, semiconductor inorganic particles are preferable.

  As the inorganic semiconductor particles, p-type or n-type semiconductor particles made of an inorganic material may be used. The p-type or n-type semiconductor may be any of a material obtained by doping an intrinsic semiconductor with a small amount of a predetermined element, a material exhibiting p-type or n-type such as an oxide and a chalcogenide. Chalcogenides include sulfides, selenides, and tellurides. Of these, oxides or sulfides, especially metal oxides or metal sulfides, are preferred from the viewpoint of stability and safety.

Examples of the p-type metal oxide and metal sulfide include a compound containing nickel, a compound containing monovalent copper, and a compound containing cobalt. Specific examples include nickel oxide, copper oxide, and a composite oxide of cobalt and sodium (eg, Na _x CoO ₄ ).

  Examples of the n-type metal oxide include zinc oxide, titanium oxide, zirconium oxide, indium oxide, bismuth oxide, vanadium oxide, tantalum oxide, niobium oxide, tungsten oxide, tin oxide, iron oxide, potassium tantalate, and barium titanate. , Calcium titanate and strontium titanate. Metal sulfides include cadmium sulfide, zinc sulfide, indium sulfide, and the like.

  From the viewpoint of increasing the carrier concentration in the particles and increasing the effect of improving the relative dielectric constant, metal oxides and metal sulfides are those in which elements are partially substituted or those in which a predetermined element is slightly doped. Is desirable. Among them, barium titanate doped with La, Nb, Ta, Y, Ca, Mg, Mn, titanium oxide doped with Nb, Ta, Sb, P, N, tin oxide with P, Sb , Al doped, zinc oxide doped with Al and Ga, and indium oxide doped with Sn are preferable. Further, a material doped with a plurality of elements may be used. In addition, oxygen vacancies may be generated by reduction annealing or the like to increase the carrier concentration. Since the optimum value of the element doping differs depending on the base particles to be doped, it may be determined as appropriate. For example, it is desirable that the doping amount is 0.01 mol% or more and 20 mol% or less. When the doping amount is less than 0.01 mol%, the effect of improving the relative dielectric constant is small, and when the doping amount exceeds 20 mol%, the relative dielectric constant is rather reduced. More preferably, it is 0.5 mol% or more and 10 mol% or less.

The content of the dielectric substance may be appropriately determined so that the dielectric layer has desired dielectric constant, volume resistivity, flexibility, and the like. For example, the content of the dielectric substance may be 5 parts by mass or more and 100 parts by mass or less based on 100 parts by mass of the elastomer. From the viewpoint of reducing power consumption, it is desirable that the volume resistivity of the dielectric layer be 10 ¹⁰ Ω · cm or more. 10 ¹² Ω · cm or more is preferable. The thickness of the dielectric layer is desirably 1 μm or more and 200 μm or less, and more desirably 100 μm or less, from the viewpoint that the movement of the living body is not easily inhibited.

(2) Electrode layer The material of the electrode layer is not particularly limited, but the electrode layer is desirably flexible so as to follow the deformation of the dielectric layer. For example, the electrode layer may be formed from a conductive paint in which a conductive material is mixed with a binder such as oil or elastomer. Alternatively, the electrode layer may be formed by knitting carbon fibers or metal fibers in a mesh shape. When the former conductive paint is employed, it is desirable to use an elastomer as a binder from the viewpoint of forming an electrode layer whose electric resistance is unlikely to increase even when stretched. Examples of elastomers include crosslinked rubbers such as silicone rubber, NBR, ethylene-propylene-diene rubber (EPDM), natural rubber, SBR, acrylic rubber, urethane rubber, epichlorohydrin rubber, chlorosulfonated polyethylene, chlorinated polyethylene, and styrene. And thermoplastic elastomers such as olefins, vinyl chlorides, urethanes, esters and amides. Further, an elastomer modified by introducing a functional group, such as an epoxy group-modified acrylic rubber and a carboxyl group-modified hydrogenated nitrile rubber, may be used. Examples of conductive materials include carbon materials such as carbon black, Ketjen black, carbon nanotubes, and thin graphite, and silver, gold, copper, nickel, rhodium, palladium, chromium, titanium, platinum, iron, and alloys thereof. Metal powder may be used.

  In particular, when thin graphite is used as the conductive material, the electric resistance of the electrode layer can be reduced, so that the capacitance does not easily decrease even when the measurement frequency is high. Further, even if the length of the electrode layer is increased, the electric resistance is hardly increased, so that the sensor element can be elongated in a strip shape. Furthermore, since the electrode layer can be made thinner, it can be made more flexible. The thin graphite is graphite that has been delaminated in advance and thinned. Graphene is one layer of graphite (graphite), and has a structure in which six-membered rings of carbon atoms are connected in a plane. Thin graphite is a stacked body of a plurality of graphenes, and the number of stacked graphenes in the thin graphite is smaller than that of graphite, and is desirably several to several hundred layers.

  The electrode layer may contain additives such as a crosslinking agent, a dispersant, a reinforcing agent, a plasticizer, an antioxidant, and a coloring agent, if necessary, in addition to the binder and the conductive material. It is desirable that the electrode layer also has a small amount of impurities and ionic components so that the ionic components do not move to the dielectric layer. Therefore, when an elastomer is used as the binder, it is desirable to use a metal alkoxide compound as the crosslinking agent from the viewpoint of reducing the ionic components contained in the electrode layer. The metal alkoxide compound is as described in (1) above.

<Relationship between base material and elongation sensor>
As represented by the above equation (a), C = ε ₀ ε _r S / d, the capacitance of the elongation sensor changes in proportion to the area of the electrode layer. For example, when measuring the amount of elongation in a certain direction in the movement of the living body, the flexibility of the base material and the elongation sensor is high, and when the electrode layer extends in the plane direction due to the movement of the living body, it is not a change in the area in one direction to be measured. Since the capacitance is calculated based on the change in the area of the entire surface, the amount of elongation in one direction cannot be accurately measured. That is, since the elongation is detected not only in one direction to be measured but also in another direction, the measurement accuracy is reduced. This occurs because the elongation sensor is flexible. For example, if the elongation sensor is hardened and hardly deformed, the elongation of the electrode layer in the surface direction can be suppressed. However, when the flexibility of the elongation sensor is reduced, not only does it not follow the movement of the living body, but rather it may hinder the movement. In this case, the elongation amount cannot be accurately measured.

  In this regard, according to the sensor device described in Patent Document 1, the sensor main body is integrated with a cloth having anisotropy (a cloth that easily stretches in one direction and hardly expands in a direction orthogonal to the one direction). Thus, the direction of expansion and contraction of the sensor main body is restricted to one direction which is the direction of easy expansion and contraction of the cloth, and the amount of expansion of the sensor main body and the change in the area of the electrode layer are made proportional. However, using a cloth that stretches in only one direction impedes the movement of the living body in the direction in which the cloth is difficult to stretch (the direction of difficulty in stretching), so the amount of elongation in one direction can be accurately determined without restricting the movement of the living body. It is not possible to solve the problem of measuring in a short time.

Therefore, in a preferred embodiment of the present invention, the aspect ratio of the sensor element is defined according to the direction to be measured, the Young's modulus of the elongation sensor is defined, and the relationship with the Young's modulus of the substrate is defined. That is, in the capacitance type elongation sensor system of the present invention, when one of the directions in which the base material expands and contracts is defined as a measurement direction, and a direction perpendicular to the measurement direction is defined as a vertical direction, the measurement in the sensor element is performed. The length in the direction is at least 5 times the length in the vertical direction, the Young's modulus of the elongation sensor is 20 MPa or less, the Young's modulus of the elongation sensor is E ₁ (MPa), and the thickness is T ₁ (mm). ), When the Young's modulus of the substrate is E ₂ (MPa) and the thickness is T ₂ (mm), it is desirable to satisfy the following expression (i). More preferably, it is desirable to satisfy the following expression (ii).
10 ≦ (E ₁ × T ₁ ) / (E ₂ × T ₂ ) (i)
15 ≦ (E ₁ × T ₁ ) / (E ₂ × T ₂ ) (ii)
In this embodiment, the elongation direction of the sensor element coincides with the measurement direction, and the flexibility of the elongation sensor with respect to the base material is set in a predetermined range, so that the elongation sensor and the base material expand together in the measurement direction. In the vertical direction, only the substrate mainly expands. That is, since the extension sensor does not extend, it is not necessary to detect the extension in the vertical direction. By doing so, only the amount of elongation in the measurement direction can be accurately measured without inhibiting the movement of the living body.

  In this specification, a value obtained by dividing a stress of 5% elongation by a strain at that time in a stress-strain curve obtained by a tensile test based on JIS K 6251: 2017 is defined as a Young's modulus. The test piece is a strip-shaped No. 2 shape, and the tensile speed is 500 mm / min.

  The arrangement of the elongation sensor with respect to the substrate is not particularly limited. For example, the sensor element may be directly fixed to the base such that the electrode layer of the sensor element is in contact with the base. Alternatively, as shown in the above embodiment, the sensor element may be indirectly fixed to the base material with an adhesive, a thermoplastic elastomer sheet or the like. That is, the elongation sensor may have another member such as an adhesive layer between the base material and the sensor element. On the other hand, as shown in the above embodiment, from the viewpoint of insulating and protecting the sensor element, a protective layer may be arranged outside the sensor element (on the side opposite to the base material) so as to cover the sensor element. . That is, the elongation sensor may have another member such as a protective layer in the outermost layer.

  In the case where the elongation sensor has a member other than the sensor element, the Young's modulus of the elongation sensor in the formulas (i) and (ii) is, as shown in an embodiment described later, the Young's modulus of each member, Is calculated by adding the values obtained by multiplying the ratio of the thickness to the total. Hereinafter, the adhesive layer and the protective layer will be described.

[Adhesive layer]
The material of the adhesive layer is not particularly limited as long as the electrode layer of the sensor element and the substrate can be bonded. From the viewpoint of not lowering the flexibility of the elongation sensor, it is desirable to use a thermoplastic elastomer as the adhesive layer. If the softening point of the thermoplastic elastomer is too low, environmental durability is poor. Therefore, for example, when a thermoplastic elastomer having a softening point of 60 ° C. or more and 150 ° C. or less is used, the sensor element can be easily fixed to the substrate by heating and pressing with an iron or the like while satisfying environmental durability. it can. Suitable thermoplastic elastomers include ether-based urethane and ester-based urethane from the viewpoint of flexibility.

  From the viewpoint of following the expansion and contraction of the sensor element and ensuring the flexibility of the elongation sensor, it is preferable that the Young's modulus of the adhesive layer be 50 MPa or less and the breaking elongation be 10% or more. In this specification, elongation at break measured by a tensile test based on JIS K6251: 2017 is defined as elongation at break. A dumbbell-shaped No. 2 test piece was used, and the tensile speed was 500 mm / min.

[Protective layer]
The material of the protective layer may be appropriately determined in consideration of insulation, moisture resistance, durability, and the like. From the viewpoint of not lowering the flexibility of the elongation sensor, it is desirable to use a thermoplastic elastomer also for the protective layer. The material of the protective layer may be the same as or different from that of the adhesive layer. Like the adhesive layer, it is desirable that the Young's modulus of the protective layer be 50 MPa or less and the elongation at break be 10% or more from the viewpoint of following the expansion and contraction of the sensor element and ensuring the flexibility of the elongation sensor.

<Control device>
The capacitance type extension sensor system of the present invention includes, in addition to the extension sensor arranged on the base material, a control device for processing an output signal from the extension sensor, a display device for displaying a measurement result, and the like. What is necessary is just to comprise. For example, as shown in the above embodiment, when the battery is driven, troublesome connection with a wire can be eliminated, which is suitable for wearable use. When the measurement frequency is reduced, the operation time can be increased while suppressing the power consumption of the battery. According to the sensor element of the present invention, the relative permittivity of the dielectric layer hardly changes even in a low-frequency region, and thus the sensor element is suitable for battery driving.

  Next, the present invention will be described more specifically with reference to examples.

(1) Measurement of relative permittivity Seven types of dielectric layers made of different materials were manufactured, and the relative permittivity was measured in a measurement frequency range of 0.1 to 10000 Hz.

<Manufacture of dielectric layer>
[Dielectric layer 1]
First, a polymer of carboxyl group-modified hydrogenated nitrile rubber (XH-NBR) ("Tervan (registered trademark) XT8888" manufactured by LANXESS) was dissolved in acetylacetone to prepare a polymer solution having a solid content of 12% by mass. . Next, 5 parts by mass of an acetylacetone solution (concentration: 20% by mass) of tetrakis (2-ethylhexyloxy) titanium (TOT) as a crosslinking agent was added to 100 parts by mass of the prepared polymer solution. Then, the polymer solution was applied onto a polyethylene terephthalate (PET) substrate (the same applies hereinafter), dried, and then heated at 150 ° C. for 60 minutes to produce the dielectric layer 1.

[Dielectric layer 2]
First, tin oxide (SnO ₂ ) powder doped with phosphorus (P) (“EPSP2” manufactured by Mitsubishi Materials Corporation) was dispersed in acetylacetone to prepare a dispersion having a concentration of 12% by mass. The powder used is a powder of n-type inorganic semiconductor particles. Next, 100 parts by mass of the same polymer solution as that of the dielectric layer 1 was mixed with 13 parts by mass of the prepared dispersion to prepare a mixed solution. Subsequently, 5 parts by mass of an acetylacetone solution (concentration: 20% by mass) of tetrakis (2-ethylhexyloxy) titanium as a crosslinking agent was added to the prepared mixture. Then, the mixed solution was applied on a substrate, dried, and then heated at 150 ° C. for 60 minutes to produce the dielectric layer 2.

[Dielectric layer 3]
First, barium titanate powder was put into acetylacetone, stirred, and allowed to stand for 24 hours. Thereafter, the powder was separated by filtration and vacuum-dried to produce a washed barium titanate powder. Cleaned barium titanate powder is included in the concept of dielectric particles. Next, the washed barium titanate powder was added to the polymer solution to which the same crosslinking agent solution as that of the dielectric layer 1 was added to prepare a dispersion. The washed barium titanate powder was added in an amount of 80 parts by mass with respect to 100 parts by mass of the polymer in the polymer solution. Then, the dispersion was applied on a substrate, dried, and then heated at 150 ° C. for 60 minutes to produce a dielectric layer 3.

[Dielectric layer 4]
First, a powder composed of tin oxide (SnO ₂ ) doped with antimony (Sb) and titanium oxide (TiO ₂ ) (“FT-1000” manufactured by Ishihara Sangyo Co., Ltd.) was dispersed in acetylacetone, and the concentration was 12% by mass. Was prepared. The powder used is a powder of n-type inorganic semiconductor particles. Next, 100 parts by mass of the same polymer solution as that of the dielectric layer 1 was mixed with 13 parts by mass of the prepared dispersion to prepare a mixed solution. Subsequently, 5 parts by mass of an acetylacetone solution (concentration: 20% by mass) of tetrakis (2-ethylhexyloxy) titanium as a crosslinking agent was added to the prepared mixture. Then, the mixed solution was applied on a substrate, dried, and then heated at 150 ° C. for 60 minutes to produce a dielectric layer 4.

[Dielectric layer 5]
First, 30.0 parts by mass of a polycarbonate diol ("Duranol (registered trademark) T5650J", molecular weight 800, manufactured by Asahi Kasei Corporation) was placed in a reaction vessel, and dehydration under reduced pressure was performed for 2 hours while stirring. Next, the inside of the reaction vessel was replaced with nitrogen. Then, 46.6 parts by mass of hexamethylene diisocyanate ("Duranate (registered trademark) D201" manufactured by Asahi Kasei Corporation) and 1,4-phenylene diisocyanate (manufactured by Tokyo Chemical Industry Co., Ltd.) 6.05 were placed in the reaction vessel. Then, the mixture was stirred for 4 hours at 100 ° C. in a nitrogen stream to synthesize an isocyanate-terminated prepolymer A. Subsequently, 20.0 parts by mass of polycarbonate diol (same as above) and the synthesized isocyanate-terminated prepolymer A18 After mixing, the urethane reaction liquid was prepared by mixing and stirring the mixture under reduced pressure and then defoaming under reduced pressure to prepare a urethane reaction liquid. By heating at 150 ° C. for 3 hours, a dielectric layer 5 made of urethane rubber was manufactured.

[Dielectric layer 6]
A dielectric layer 6 was manufactured in the same manner as the dielectric layer 3, except that the barium titanate powder was used without washing.

[Dielectric layer 7]
Carboxyl group-modified hydrogenated nitrile rubber polymer (same as above), sulfur, silica (“Aerosil (registered trademark) 380” manufactured by Nippon Aerosil Co., Ltd.), plasticizer (tricresyl phosphate), antioxidant, etc. Sanshin Chemical Industry Co., Ltd. "Suncellar (registered trademark) CZ-G" and "Suncellar 22C", Tsurumi Chemical Industry Co., Ltd. "Sulfax (registered trademark) T10", Ouchi Shinko Chemical Industry Co., Ltd. Noctizer (registered trademark) SS ") and kneaded with a roll to produce an unvulcanized rubber. This unvulcanized rubber was formed into a sheet shape by a press machine to produce a dielectric layer 7.

表１に示すように、誘電層１〜４によると、測定周波数が０．１Ｈｚの時の比誘電率が、１００００Ｈｚの時の比誘電率に対して１０倍以下であった。すなわち、誘電層１〜４は、「測定周波数が０．１Ｈｚ以上１０ｋＨｚ以下の範囲において、誘電層の最大比誘電率は最小比誘電率の１０倍以下である」という要件を満足するといえる。この点において、誘電層１〜４は、本発明の実施例に相当する。これに対して、誘電層５〜７によると、測定周波数が１〜０．１Ｈｚと低くなると比誘電率が急激に大きくなった。この点において、誘電層５〜７は、本発明の比較例に相当する。 <Measurement results of relative permittivity>
The manufactured dielectric layers 1 to 7 are placed on a sample holder (made by Solartron, model 12962A), and used together with a dielectric constant measurement interface (manufactured by the company, model 1296) and a frequency response analyzer (manufactured by the company, model 1255B). And the relative permittivity were measured. Table 1 shows the measurement results of the relative permittivity.

As shown in Table 1, according to the dielectric layers 1 to 4, the relative dielectric constant at a measurement frequency of 0.1 Hz was 10 times or less the relative dielectric constant at 10,000 Hz. That is, it can be said that the dielectric layers 1 to 4 satisfy the requirement that “the maximum relative permittivity of the dielectric layer is 10 times or less the minimum relative permittivity in the range of the measurement frequency of 0.1 Hz or more and 10 kHz or less”. In this regard, the dielectric layers 1-4 correspond to embodiments of the present invention. On the other hand, according to the dielectric layers 5 to 7, the relative dielectric constant sharply increased when the measurement frequency decreased to 1 to 0.1 Hz. In this regard, the dielectric layers 5 to 7 correspond to comparative examples of the present invention.

  As described above, the ionic component contributes to polarization in a low frequency region, and has an effect of increasing the dielectric constant. Therefore, the reason why the frequency dependence of the relative permittivity is small in the dielectric layers 1 to 4 is that the impurities and the ionic components contained in the dielectric layers are small. Specifically, in the dielectric layers 1 to 4, a metal alkoxide compound from which a cross-linking residue hardly appears was used as a cross-linking agent. In the dielectric layers 2 and 4, an n-type inorganic semiconductor powder having a small ionic component was blended as a dielectric substance. In the dielectric layer 3, as the dielectric substance, dielectric particles from which ionic components were removed by washing were blended. Comparing the dielectric layer 3 and the dielectric layer 6, which differ only in the presence or absence of cleaning of the blended dielectric particles, the effect of the ionic component in the low frequency region is clear. The dielectric layer 5 using urethane rubber and the dielectric layer 6 using sulfur as a cross-linking agent are considered to have many impurities and ionic components.

  The dielectric layers 2 to 4 contain a dielectric substance. For this reason, as can be seen by comparing the case where the measurement frequency is 100 Hz, for example, the relative dielectric constant is higher than that of the other dielectric layers. Therefore, when the dielectric layers 2 to 4 are used, a capacitance sensor having a large capacitance and high sensitivity can be realized.

  Table 1 also shows the Young's modulus and elongation at break of each dielectric layer. According to the dielectric layers 1 to 4, since the value of the elongation at break is large, the amount of elongation can be measured without inhibiting the movement of the object to be measured.

(2) Measurement of Capacitance An elongation sensor was formed using the dielectric layer 1 manufactured by the measurement of the relative permittivity, and was adhered to a substrate to manufacture an electrostatic capacitance type elongation sensor system. Then, a change in capacitance when the base material was stretched in one direction was measured.

<Manufacture of capacitance type elongation sensor system>
[Example 1]
(1) Electrode layer 1
First, a conductive material dispersion was prepared by adding 18 parts by weight of a dispersant and a solvent to 50 parts by weight of a conductive material. Next, the prepared conductive material dispersion was pulverized by a wet jet mill (“NanoVita (registered trademark)” manufactured by Yoshida Kikai Kogyo Co., Ltd.). By the pass operation, the pulverization process was performed three times in total (three pass process). The first pass was performed with a straight nozzle (nozzle diameter 170 μm) and a processing pressure of 90 MPa, and the second and subsequent passes were performed with a cross nozzle (nozzle diameter 170 μm) and a processing pressure of 130 MPa. Then, a polymer solution obtained by dissolving 82 parts by mass of a polymer in a solvent was added to the conductive material dispersion liquid after the pulverization treatment and mixed to prepare a liquid composition. The obtained liquid composition was applied on a PET substrate at a target thickness of 15 μm by a bar coating method, and the coating was cured by heating at 150 ° C. for 2 hours. Thus, the electrode layer 1 was manufactured. The materials used for manufacturing the electrode layer 1 are as follows.
Polymer: carboxyl group-modified hydrogenated nitrile rubber ("Terban XT8889" manufactured by LANXESS)
Conductive material: Thin graphite (I-Tech "iGurafen-α")
Dispersant: high molecular weight polyester acid amidoamine salt (Kusumoto Kasei Co., Ltd. "Disparon (registered trademark) DA7301")
Solvent: Acetylacetone (2) Elongation sensor First, the manufactured electrode layer is superimposed on a urethane-based thermoplastic elastomer thin film (“UH370” manufactured by Nippon Matai Co., Ltd., thickness 25 μm, elongation at break 320%), and then vacuum pressed. Glued. Next, the dielectric layer 1 was overlaid on the upper surface of the electrode layer, and bonded by a vacuum press. Further, the manufactured electrode layer was overlapped on the upper surface of the dielectric layer 1 and bonded by a vacuum press. Finally, a thermoplastic elastomer thin film (same as above) was overlaid on the upper surface of the electrode layer and bonded by a vacuum press. Thus, an elongation sensor composed of “thermoplastic elastomer thin film / electrode layer / dielectric layer 1 / electrode layer / thermoplastic elastomer thin film” was manufactured.

(3) Capacitance type elongation sensor system The manufactured elongation sensor is placed on the upper surface of the compression ware (TESLA, all-season long-sleeved, 0.4 mm thick) which is the base material, and heated with an iron from above. The elongation sensor and the substrate were bonded by melting the thermoplastic elastomer thin film. Then, a connector was attached to the upper surface end of the base material, and the electrode layer of the elongation sensor was electrically connected to a control device (not shown) by wiring. Thus, a capacitance type elongation sensor system was manufactured. FIG. 3 shows a top view of the elongation sensor arranged on the base material. In FIG. 3, the extension sensor is hatched for convenience of explanation. FIG. 4 shows a schematic cross-sectional view in the front-rear direction of the stretch sensor. 3 and 4, members corresponding to those in FIGS. 1 and 2 are denoted by the same reference numerals.

  As shown in FIGS. 3 and 4, the elongation sensor 2 is adhered to the upper surface of the substrate 3. The elongation sensor 2 includes a sensor element 20, an adhesive layer 21, and a protective layer 22. The sensor element 20 includes a dielectric layer 200 and a pair of electrode layers 201 and 202. The dielectric layer 200 has a rectangular thin film shape of 10 mm in length (length in the front-rear direction), 60 mm in width (length in the left-right direction), and 98 μm in thickness. Each of the electrode layers 201 and 202 has a rectangular thin film shape having a length of 8 mm, a width of 50 mm, and a thickness of 15 μm. The size of the pressure-sensitive portion where the dielectric layer 200 and the electrode layers 201 and 202 overlap in the thickness direction is 8 mm long and 50 mm wide. The adhesive layer 21 is made of a thermoplastic elastomer thin film, and has a rectangular thin film shape having a length of 10 mm, a width of 60 mm, and a thickness of 25 μm. Similarly, the protective layer 22 is also formed of a thermoplastic elastomer thin film, and has a rectangular thin film shape of 10 mm long, 60 mm wide and 25 μm thick. A connector 42 is attached to the left end of the extension sensor 2. The electrode layers 201 and 202 of the elongation sensor 2 and a control device (not shown) are electrically connected to each other via a connector 42 by wiring.

[Example 2]
An elongation sensor was manufactured in the same manner as in Example 1 except that the thicknesses of the adhesive layer and the protective layer laminated on both sides of the sensor element were each changed to twice. Specifically, two thermoplastic elastomer thin films were arranged on both sides of the sensor element.

[Example 3]
An elongation sensor was manufactured in the same manner as in Example 1 except that the thicknesses of the adhesive layer and the protective layer laminated on both sides of the sensor element were each changed to four times. Specifically, four thermoplastic elastomer thin films were arranged on both sides of the sensor element.

[Example 4]
An elongation sensor was manufactured in the same manner as in Example 1 except that the electrode layer 2 was disposed instead of the electrode layer 1. The method for manufacturing the electrode layer 2 is as follows. First, 23 parts by mass of Ketjen black as a conductive material was added to a polymer solution in which 100 parts by mass of a carboxyl group-modified hydrogenated nitrile rubber (same as the electrode layer 1) was dissolved in acetylacetone, and kneaded. Next, the kneaded material was repeatedly passed through three rolls five times to obtain a slurry. Then, 5 parts by mass of tetrakis (2-ethylhexyloxy) titanium as a cross-linking agent is added to the obtained slurry, and the mixture is kneaded with an air stirrer. Then, the slurry is coated on a PET substrate by a bar coating method to a target thickness of 15 μm. And applied. This was heated at 150 ° C. for 1 hour to cure the coating film to produce the electrode layer 2.

[Reference Example 1]
An electrostatic capacity type elongation sensor system was manufactured in the same manner as in Example 3 except that the type of the base material was changed. The waist rubber part (1.4 mm in thickness) of the training inner made by Darchen was used for the base material.

[Reference Example 2]
An elongation sensor was manufactured in the same manner as in Example 3, except that the type of the thermoplastic elastomer thin film was changed. That is, a polyamide-based thermoplastic elastomer thin film (“NT140” manufactured by Nippon Matai Co., Ltd., thickness 25 μm, elongation at break 300%) was used for the adhesive layer and the protective layer.

Table 2 summarizes the specifications of the elongation sensor and the base material in each capacitance type elongation sensor system.

<Capacitance measurement result>
As shown in FIG. 3, the rear direction among the directions of expansion and contraction of the base material was set as A direction, and the right direction was set as B direction. The direction A corresponds to the short direction of the extension sensor, and the direction B corresponds to the longitudinal direction of the extension sensor. First, the center of the rear side of the substrate was gripped, and the capacitance when the substrate was extended in the A direction was measured. FIG. 5 shows a change in capacitance with respect to the amount of elongation in the A direction. Next, the capacitance was measured when the center of the right side of the substrate was gripped and the substrate was extended in the B direction. FIG. 6 shows a change in capacitance with respect to the amount of elongation in the B direction. In the elongation sensor system of Reference Example 2, since the elongation sensor was hard (Young's modulus 75.1 MPa> 20 MPa) and had poor elasticity, the capacitance was not measured with respect to the amount of elongation.

As shown in FIG. 6, when the base material was stretched in the same B direction as the longitudinal direction of the stretch sensor, almost no difference in the change in the capacitance was observed between the stretch sensor systems. On the other hand, as shown in FIG. 5, when the base material was stretched in the same direction A as the short direction of the stretch sensor, the difference in the stretch sensor system was remarkable in the change in capacitance. In the elongation sensor systems of Examples 1 to 4, which satisfy the following requirements (1) to (3), the elongation sensor is harder than the base material. Only the base material is deformed, and the elongation sensor hardly deforms. Therefore, in the region where the amount of elongation was small, almost no change was observed in the value of the capacitance. As the base material was further stretched and the stretch sensor was slightly deformed, the capacitance increased accordingly. On the other hand, in the elongation sensor system of Reference Example 1 in which the base material was hard and did not satisfy the following requirement (3), the capacitance increased even in a region where the amount of elongation was small. In addition, in the elongation sensor system of Reference Example 2 in which the adhesive layer and the protective layer are hard (Young's modulus 90 MPa) and do not have elasticity, and do not satisfy the following requirement (2), when the elongation sensor is expanded, Since it does not return to the state, continuous operation cannot be measured. Therefore, the elongation sensor system of Reference Example 2 is not suitable for use in measuring continuous movement of a living body.
(1) The length of the sensor element in the longitudinal direction (B direction) is at least 5 times the length in the short direction (A direction).
(2) The Young's modulus of the elongation sensor is 20 MPa or less.
(3) When the Young's modulus of the elongation sensor is E ₁ (MPa), the thickness is T ₁ (mm), the Young's modulus of the substrate is E ₂ (MPa), and the thickness is T ₂ (mm), The value of ( ₁ × T ₁ ) / (E ₂ × T ₂ ) (the value of (A) / (B) in Table 2) is 10 or more.

  As described above, when the requirements of (1) to (3) are satisfied, the difference in flexibility between the base material and the elongation sensor and the fact that the elongation sensor is difficult to expand in the lateral direction are used to increase the elongation. Only the amount of elongation of the sensor in the longitudinal direction can be selectively detected. Therefore, according to the elongation sensor systems of Examples 1 to 4, by setting the direction in which the amount of elongation is to be measured to the longitudinal direction (B direction) of the elongation sensor, the amount of elongation in the direction to be measured can be accurately measured. .

  INDUSTRIAL APPLICABILITY The capacitance type extension sensor system of the present invention is suitable for measurement of biological information such as a respiratory state and a heart rate, and measurement of various operations such as bending and stretching of a joint and holding and opening a hand. The capacitance type stretch sensor system of the present invention is useful in medical, nursing, health care, training, and other fields.

1: Capacitive type elongation sensor sensor system, 2: elongation sensor, 3: base material, 4: control device, 20: sensor element, 21: adhesive layer, 22: protective layer, 40, 41: wiring, 42: connector , 200: dielectric layer, 201, 202: electrode layer

Claims (8)

A substrate having elasticity and an elongation sensor arranged on the substrate, a capacitance-type elongation sensor system comprising:
該伸beauty sensor includes a dielectric layer having a elastomer comprising crosslinked with metal alkoxide compound, are disposed to sandwich the dielectric layer, and a plurality of electrode layers that have a elastomer and a conductive material formed by crosslinking with a metal alkoxide compound And a sensor element having
A capacitance-type elongation sensor system, wherein the maximum relative dielectric constant of the dielectric layer is 10 times or less the minimum relative dielectric constant when the measurement frequency is in the range of 0.1 Hz to 10 kHz. One of the directions in which the base material expands and contracts is defined as a measurement direction, and a direction perpendicular to the measurement direction is defined as a vertical direction,
The length of the sensor element in the measurement direction is at least 5 times the length in the vertical direction,
The elongation sensor has a Young's modulus of 20 MPa or less,
When the Young's modulus of the elongation sensor is E ₁ (MPa), the thickness is T ₁ (mm), the Young's modulus of the substrate is E ₂ (MPa), and the thickness is T ₂ (mm), The capacitance type elongation sensor system according to claim 1, wherein (i) is satisfied.
10 ≦ (E ₁ × T ₁ ) / (E ₂ × T ₂ ) (i)   3. The capacitance-type stretch sensor system according to claim 1, wherein the stretch sensor includes an adhesive layer disposed between the sensor element and the substrate. 4.   The capacitance type elongation sensor system according to claim 3, wherein the adhesive layer includes a thermoplastic elastomer.   The capacitance type elongation sensor system according to claim 3 or 4, wherein the adhesive layer has a Young's modulus of 50 MPa or less and a breaking elongation of 10% or more.   The static elastomer according to any one of claims 1 to 5, wherein the elastomer of the dielectric layer is at least one selected from nitrile rubber, hydrogenated nitrile rubber, carboxyl group-modified nitrile rubber, and carboxyl group-modified hydrogenated nitrile rubber. Capacitance type elongation sensor system.   The capacitance type elongation sensor system according to claim 1, wherein the conductive material includes thin graphite.   The capacitance type elongation sensor system according to claim 1, wherein the substrate is a cloth.

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