JP2021182004A - Method for manufacturing distortion sensor element, and distortion sensor element - Google Patents

Abstract

To provide a distortion sensor element which is easily manufactured, and of which electrical connection is easily made.SOLUTION: A method for manufacturing a distortion sensor element which comprises a CNT (carbon nanotube) film 11 including a plurality of CNT fibers pulled and aligned in one direction, resin layers 12, 13 respectively coating the front and back of the CNT film 11, and a pair of electrodes 14 laminated on both sides of a resin layer coating body consisting of the CNT film 11 and the resin layers 12, 13 and electrically connected to the CNT film 11, includes the steps of: irradiating, with a laser, at least a part of the surfaces of both sides of the resin layer coating body; and filling, with an electroconductive material, a connection hole 16 formed in the resin layer 12 in the laser irradiation step.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for manufacturing a strain sensor element and a strain sensor element.

A laminate having a thin-film conductive elastomer layer and an insulating elastomer layer laminated on both sides of the conductive elastomer layer is formed in a band shape, and a change in resistance of the conductive elastomer layer due to expansion and contraction in the longitudinal direction is detected. Strain sensor elements are known (see, for example, Japanese Patent Application Laid-Open No. 2000-258112).

The strain sensor element described in the publication is a pair of electrodes that are inserted between the conductive elastomer layer and the insulating elastomer layer at both ends in the longitudinal direction and project in the longitudinal direction from the conductive elastomer layer and the insulating elastomer layer. By providing a conductor for use, it is possible to detect a change in resistance of the conductive elastomer layer.

In such a strain sensor element, it is necessary to arrange an electrode conductor in advance when laminating the conductive elastomer layer and the insulating elastomer layer, the manufacturing process is complicated, and the design change is not easy. ..

Further, a strain sensor element using carbon nanotubes (CNT) as a resistor has also been proposed (see JP-A-2011-47702). This strain sensor element has a CNT film made of a plurality of carbon nanotubes oriented in a predetermined direction. It is said that this strain sensor element can cope with a large strain because the CNT film can expand and contract relatively large in the orientation direction of the carbon nanotubes or in the direction perpendicular to the orientation direction.

In the strain sensor element using this CNT film, a CNT film is formed on the surface of a stretchable sheet-like substrate, and after patterning the CNT film, electrodes are connected to both ends of the pattern of the CNT film using conductive paste. Manufactured by That is, the manufacturing process of this strain sensor element is complicated, and it is not easy to change the design.

Japanese Unexamined Patent Publication No. 2000-258112 Japanese Unexamined Patent Publication No. 2011-47702

The present invention has been made based on such circumstances, and an object of the present invention is to provide a method for manufacturing a strain sensor element and a strain sensor element that can be manufactured relatively easily and relatively easily by design change.

The invention made to solve the above problems includes a CNT film or CNT thread containing a plurality of CNT fibers aligned in one direction, a resin layer coated on the front and back surfaces of the CNT film or the outer periphery of the CNT thread, and the above-mentioned invention. A method for manufacturing a strain sensor element, which is laminated on both end regions of a resin layer coating body of a CNT film or a CNT thread and includes a pair of electrodes electrically connected to the CNT film or the CNT thread, wherein the resin layer coating is provided. A strain sensor element comprising a step of irradiating at least a part of the surface of both end regions of the body with a laser and a step of filling a hole formed in the resin layer with a conductive material in the laser irradiation step. It is a manufacturing method of.

Prior to the laser irradiation step, a step of applying a laser absorbing material to the surfaces of both end regions of the resin layer coating is further provided, and the laser is applied to at least a part of the coating film obtained in the coating step in the laser irradiation step. It is good to irradiate.

It is preferable that the laser absorbing material is an ink in which carbon black fine particles are dispersed in a volatile solvent.

The average diameter of the holes formed in the resin layer is preferably 0.5 mm or more and 2.0 mm or less.

In the laser irradiation step, a plurality of holes may be formed in each end region of the resin layer covering body, and in the conductive material filling step, the conductive material may be applied across the plurality of holes in each end region.

Another invention made to solve the above problems is a CNT film or CNT thread containing a plurality of CNT fibers aligned in one direction, and a resin coated on the front and back surfaces of the CNT film or the outer periphery of the CNT thread. A strain sensor element comprising a layer and a pair of electrodes laminated on both end regions of the resin layer coating of the CNT film or the CNT thread and electrically connected to the CNT film or the CNT thread, wherein the resin is provided. It is a strain sensor element characterized in that the layer has a connection hole leading to a CNT film or a CNT thread, and the electrode contains a conductive material filled in the connection hole.

The strain sensor element may further include a laser absorbing material layer existing between the surface of the resin layer around the connection hole and the electrode.

The method for manufacturing the strain sensor element can easily and accurately form holes in the resin layer for exposing CNTs by irradiating both end regions of the resin layer coating of the CNT film or CNT yarn with a laser. By filling the pores of the resin layer with a conductive material, electrical connection to the CNT film or CNT thread can be made relatively easily, so that the strain sensor element can be manufactured relatively easily. Further, since the laser irradiation position can be easily changed, it is relatively easy to change the design of the strain sensor element in the method of manufacturing the strain sensor element. For the same reason, the strain sensor element is configured to include a conductive material in which an electrode is filled in a connection hole of a resin layer, so that a design change can be made relatively easily and can be manufactured relatively easily.

It is a schematic cross-sectional view of the strain sensor element of one Embodiment of this invention. It is a schematic plan view of the strain sensor element of FIG. It is a flowchart which shows the procedure of the manufacturing method of the strain sensor element of FIG. It is a schematic cross-sectional view of the strain sensor element different from FIG. It is a schematic plan view which shows one reference form of a strain sensor element. It is a schematic cross-sectional view of the strain sensor element of FIG. It is a schematic plan view of the plate-shaped electrode for a strain sensor element different from FIG. It is a schematic cross-sectional view of the strain sensor element different from FIG. 6 is a schematic cross-sectional view of a strain sensor element different from FIGS. 6 and 8.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.

[First Embodiment]
The strain sensor element of the first embodiment of the present invention shown in FIGS. 1 and 2 is formed in a band shape and includes a CNT film 11 containing a plurality of CNT fibers aligned in the longitudinal direction, and covers the front and back surfaces of the CNT film 11. The resin layers 12 and 13 to be formed are laminated on the front side of the resin layer covering body composed of the CNT films 11 and the resin layers 12 and 13 at both ends in the CNT fiber alignment direction, and are electrically connected to the CNT film 11. A pair of electrodes 14 and a laser absorbing material layer 15 partially present between the resin layer 12 on the front side and the electrodes 14 are provided. The “front” refers to the side on which the pair of electrodes 14 are arranged, and the “back” refers to the opposite side thereof, and does not necessarily mean the front and back in the usage state of the strain sensor element.

<CNT film>
The CNT film 11 is composed of a layer formed of a plurality of CNT fibers aligned in one direction, and a material (hereinafter, simply "insulating elastomer") having an insulating elastomer as a main component, which is a resin layer described later, on the front and back layers. The CNT fiber and the insulating elastomer are composited and formed into a film by laminating the CNT film 11 and impregnating the front and back layers of the CNT film 11 with the insulating elastomer (at least from the surface layer side of the CNT film 11). Has been done. The CNT film 11 has elasticity due to the elastic force of the insulating elastomer, and can expand and contract at least in the longitudinal direction. When the CNT film 11 is elongated at least in the longitudinal direction, the CNT fibers are separated from each other to increase the electric resistance, and when the CNT fibers are contracted due to the elastic force, the CNT fibers are brought into contact with each other again and the electric resistance is reduced. The CNT film 11 may contain insulating fibers made of, for example, synthetic resin in order to suppress the contact rate between the CNT fibers and adjust the electric resistance.

Since the CNT film 11 is laminated with at least the surface layer impregnated with the insulating elastomer, the insulating elastomer covers the CNT fiber bundle described later, and the insulating elastomer guides the expansion / contraction direction of the plurality of CNT fiber bundles. It also functions as a guide member. As a result, the strain sensor can re-contact the CNT fibers separated at the time of expansion at the same site at the time of contraction, and can prevent a decrease in the detection accuracy of the expansion / contraction strain due to repeated use. Further, according to such a configuration, it is easy to maintain the contact relationship between the plurality of CNT fibers, and it is easy to adjust the elasticity of the plurality of CNT fibers. Therefore, the expansion and contraction strain of the CNT film 11 can be detected more accurately. Further, in order to further facilitate the maintenance of such a contact relationship and the adjustment of the elasticity, it is preferable that the back layer (region near the back surface) of the CNT film 11 is also impregnated with the insulating elastomer. At this time, since at least a part of the surface layer of the CNT fiber bundle is impregnated with the insulating elastomer, the bonding force between the CNT fiber bundle and the insulating elastomer is also enhanced.

(CNT fiber)
The CNT fibers constituting the CNT film 11 can each be formed from a plurality of CNT single fibers. Here, the CNT single fiber means one long carbon nanotube. Further, the CNT fiber has a connecting portion in which the ends of the CNT single fibers are connected to each other. The CNT single fibers are connected to each other in the longitudinal direction of these CNT single fibers. In this way, in the CNT film 11, the CNT single fibers are connected to each other in the longitudinal direction, so that the CNT film 11 having a large orientation length of the CNT fibers can be formed, and the length in the longitudinal direction of the strain sensor can be increased. It can be increased to improve sensitivity.

Further, the plurality of CNT fibers constituting the CNT film 11 may form a network structure. Specifically, the plurality of CNT fibers may be connected or in contact with each other in a mesh pattern by a connecting portion or the like in which the CNT single fibers are connected to each other. At this time, at this connecting portion, the ends of three or more CNT single fibers may be bonded, or the ends of the two CNT single fibers and the intermediate portion of the other single fibers may be bonded. By forming such a network structure of a plurality of CNT fibers, the CNT fibers come into close contact with each other, and the resistance of the CNT film 11 can be reduced.

Further, the CNT film 11 may have a CNT fiber bundle composed of a plurality of CNT fibers oriented in the longitudinal direction. When the CNT film 11 has a plurality of CNT fiber bundles oriented in the longitudinal direction, the CNT fibers are cut, separated, and the cutting space (gap) of the CNT fiber bundle is applied when the CNT film 11 is strained so as to be stretched in the expansion and contraction direction. ), The resistance of the CNT film 11 changes more accurately.

More specifically, the CNT fiber bundle has a bundle structure composed of a plurality of CNT fibers, and in any cross section of the CNT fiber bundle, the CNT fibers that are not cut and the CNT fibers are cut and separated. Both gaps will exist. Further, since the surface layer of the plurality of CNT fiber bundles is coated with an insulating elastomer, the pressure in this gap is considered to be lower than the atmospheric pressure (negative pressure), and therefore, when the strain sensor 1 contracts. At (when the strain is released), the contraction of the strain sensor 1 is urged by the contraction force of this gap. Further, since the friction between the CNT fibers is reduced in this gap, the movement of the CNT fibers is not easily restricted.

The CNT film 11 may have a single-layer structure in which a plurality of CNT fibers or a plurality of CNT fiber bundles are arranged substantially in parallel in a plane, or may have a multilayer structure. However, in order to secure a certain degree of conductivity, it is preferable to have a multi-layer structure.

As the CNT single fiber, either a single-walled nanotube (SWNT) or a multi-walled multi-walled nanotube (MWNT) can be used, but MWNT is preferable from the viewpoint of conductivity and heat capacity, and the diameter is 1. MWNTs of 5 nm or more and 100 nm or less are more preferable.

The CNT single fiber can be produced by a known method, for example, by a CVD method, an arc method, a laser ablation method, a DIPS method, a CoMoCAT method, or the like. Among these, it is preferable to produce carbon nanotubes (MWNT) of a desired size by a CVD method using iron as a catalyst and ethylene gas from the viewpoint of being able to efficiently obtain carbon nanotubes (MWNT). In this case, a crystal of carbon nanotubes having a desired length is obtained by forming an iron or nickel thin film as a catalyst on a substrate such as a quartz glass substrate or a silicon substrate with an oxide film and growing the carbon nanotubes in vertical orientation. Can be done.

The average length of the CNT film 11 in the longitudinal direction is not particularly limited and can be freely selected depending on the measurement target using the strain sensor element, but can be, for example, 1 cm or more and 20 cm or less.

The average length in the longitudinal direction in the region sandwiched between the pair of electrodes 14 in the plan view of the CNT film 11 can be freely selected according to the measurement target using the strain sensor element. The average length can be, for example, 2 mm or more and 18 cm or less.

The average length in the longitudinal direction in the region overlapping the pair of electrodes 14 in the plan view of the CNT film 11 is appropriately selected depending on the fixing method to the measurement target, the wiring method to the electrodes 14, and the like, and is, for example, 3 mm or more. It can be 5 cm or less.

The average width of the CNT film 11 can be freely selected according to the measurement target using the strain sensor element. The lower limit of the average width between the electrodes 14 of the CNT film 11 is preferably 0.5 mm, more preferably 0.8 mm. On the other hand, the upper limit of the average width of the CNT film 11 is preferably 10 cm, more preferably 5 cm. If the average width of the CNT film 11 is less than the lower limit, the electrical resistance of the CNT film 11 may become excessively large or may vary. On the contrary, when the average width of the CNT film 11 exceeds the upper limit, the strain sensor element may become large, and the applicable measurement target may be excessively limited.

The lower limit of the average thickness of the CNT film 11 is preferably 1 μm, more preferably 10 μm. On the other hand, the upper limit of the average thickness of the CNT film 11 is preferably 5 mm, more preferably 1 mm. If the average thickness of the CNT film 11 is less than the lower limit, it may be difficult to form the CNT film 11 or the resistance may increase too much. On the contrary, when the average thickness of the CNT film 11 exceeds the upper limit, the sensitivity to strain may decrease.

As the lower limit of the electric resistance (value measured between the pair of electrodes 14) in the state where the CNT film 11 is not distorted, 10Ω is preferable, and 100Ω is more preferable. On the other hand, as the upper limit of the electric resistance in the state where the CNT film 11 is not distorted, 100 kΩ is preferable, and 10 kΩ is more preferable. If the electrical resistance of the CNT film 11 in the absence of distortion is less than the lower limit, the current for detecting elongation strain increases, and the power consumption of the strain sensor element may increase. On the contrary, when the electric resistance of the CNT film 11 without distortion exceeds the upper limit, the voltage of the detection circuit becomes high, and it is difficult to reduce the size and power saving of the device that processes the output of the distortion sensor element. There is a risk of becoming.

<Resin layer>
The pair of resin layers 12 and 13 are made of an insulating elastomer and are laminated on both sides of the CNT film 11 (the above-mentioned front and back layers), respectively. The resin layers 12 and 13 are made of the above-mentioned insulating elastomer and cover both sides of the CNT film 11 to protect the CNT film 11.

(Insulating elastomer)
As the insulating elastomer impregnated at least on the surface layer of the CNT film 11, a thermoplastic elastomer may be used. The thermoplastic elastomer can contain various synthetic resins.

Examples of the thermoplastic elastomer include styrene-based elastomers, olefin-based elastomers, polyester-based elastomers, and the like.

Examples of the thermoplastic elastomer include polyurethane (PUR), polyimide (PI), polyethylene (PE), high density polyethylene (HDPE), medium density polyethylene (MDPE), low density polyethylene (LDPE), polypropylene (PP), and poly. Vinyl chloride (PVC), polyvinylidene chloride, polystyrene (PS), polyvinyl acetate (PVAc), acrylonitrile butadiene styrene resin (ABS), acrylonitrile styrene resin (AS), polymethylmethacrylic (PMMA), polyamide (PA), Examples thereof include polyacetal (POM), polycarbonate (PC), modified polyphenylene ether (m-PPE), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), cyclic polyolefin (COP) and the like.

Further, as the insulating elastomer impregnating at least the surface layer of the CNT film 11, rubber made of a synthetic thermosetting elastomer may be used.

Examples of the rubber include natural rubber (NR), butyl rubber (IIR), isoprene rubber (IR), ethylene / propylene rubber (EPDM), butadiene rubber (BR), urethane rubber (U), and styrene / butadiene rubber (SBR). , Silicone rubber (Q), chloroprene rubber (CR), chlorosulfonized polyethylene rubber (CSM), acrylonitrile butadiene rubber (NBR), chlorinated polyethylene (CM), acrylic rubber (ACM), epichlorohydrin rubber (CO, ECO), Fluoro rubber (FKM), polydimethylsiloxane (PDMS) and the like can be mentioned. Of these, natural rubber is preferable from the viewpoint of strength and the like.

It is preferable that the insulating elastomer is impregnated into at least the surface layer of a plurality of CNT fibers by coating with an aqueous emulsion. The aqueous emulsion means an emulsion in which the main component of the dispersion medium is water. Since carbon nanotubes are highly hydrophobic, when an insulating elastomer is impregnated by coating with an aqueous emulsion, the insulating elastomer does not completely penetrate between a plurality of CNT fibers. That is, the surface layer of the plurality of CNT fiber layers is impregnated with the insulating elastomer, but the insulating elastomer does not impregnate the entire region in the cross section of each CNT fiber in the thickness direction. As a result, the insulating elastomer completely penetrates between the plurality of CNT fibers and suppresses the influence of the resistance change of the CNT film 11, and the sensitivity to the distortion of the CNT film 11 due to the presence of the insulating elastomer is lowered. Can be suppressed.

The main component of the dispersion medium of the aqueous emulsion is water, but other hydrophilic dispersion medium such as alcohol may be contained.

Further, the insulating elastomer may contain a coupling agent. When the material containing the insulating elastomer as a main component contains a coupling agent, the insulating elastomer and the CNT fiber can be crosslinked to improve the bonding force between the insulating elastomer and the CNT fiber.

As the coupling agent, for example, an amino coupling agent such as an aminosilane coupling agent, an aminotitanium coupling agent, an aminoaluminum coupling agent, a silane coupling agent, or the like can be used.

Further, the insulating elastomer preferably contains a dispersant having adsorptivity to CNT fibers. Dispersants having such adsorptivity include those having a salt structure in the adsorbing group portion (for example, an alkylammonium salt) and hydrophobic groups of CNT fibers (for example, an alkyl chain or an aromatic ring). Those having a hydrophilic group (for example, polyether, etc.) that can interact with each other in the molecule can be used.

In the laminated structure of these resin layers 12 and 13 and the CNT film 11, a material for forming another layer (or film) may be formed on any layer (or film) by coating or the like, and each layer (or film) may be formed. Alternatively, it may be formed by welding or welding of a film), or may be formed by bonding each layer (or film) using a thermoplastic adhesive. Further, the resin layers 12 and 13 may be formed integrally with the insulating elastomer that at least partially impregnates the surface layer and the back layer of the CNT film 11. That is, in the step of forming the CNT film 11, the insulating elastomer may be applied so as to stay on the front and back of the plurality of CNT fibers and form the resin layers 12 and 13 without impregnating the plurality of CNT fibers. Further, the resin layers 12 and 13 may have a multilayer structure composed of a plurality of different layers. In that case, it is advisable to combine it with a material having high springiness. Specifically, it is preferable to use polyurethane as a material having high springiness.

As the lower limit of the average thickness of each of the resin layers 12 and 13, 10 μm is preferable, and 15 μm is more preferable. On the other hand, as the upper limit of the average thickness of the resin layers 12 and 13, 5 mm is preferable, and 2 mm is more preferable. If the average thickness of the resin layers 12 and 13 is less than the lower limit, the CNT film 11 may not be sufficiently protected. On the contrary, when the average thickness of the resin layers 12 and 13 exceeds the upper limit, the strain sensor 1 may become unnecessarily thick, or the elastic modulus of the CNT film 11 may increase, which may hinder the deformation of the measurement target. be. The average thicknesses of the resin layers 12 and 13 on the front and back may be different from each other.

Further, the resin layer 12 on the front side has a plurality of connection holes 16 leading to the CNT film 11 in the laminated region (both end regions) of the electrodes 14. It is preferable to form a plurality of the connection holes 16 in each end region in order to improve the connection strength of the electrode 14 to the CNT film 11. Further, it is preferable that the plurality of connection holes 16 are regularly arranged at a constant pitch in order to suppress the decrease in strength of the resin layer 2 and facilitate the production. The connection hole 16 may be formed in a notch shape that opens at the outer edge of the strain sensor element in a plan view.

(Connection hole)
The lower limit of the average diameter of the connection hole 16 is preferably 0.5 mm, more preferably 0.7 mm. On the other hand, the upper limit of the average diameter of the connection hole 16 is preferably 2.0 mm, more preferably 1.5 mm. If the average diameter of the connection holes 16 is less than the lower limit, the connection of the electrodes 14 to the CNT film 11 may be uncertain. On the contrary, when the average diameter of the connection hole 16 exceeds the upper limit, the CNT film 11 may be easily damaged when the connection hole 16 is formed.

The lower limit of the total area ratio of the connection holes 16 with respect to the electrode 14 is preferably 3%, more preferably 5%. On the other hand, as the upper limit of the total area ratio of the connection hole 16 with respect to the electrode 14, 60% is preferable, and 50% is more preferable. If the total area ratio of the connection holes 16 to the electrodes 14 is less than the lower limit, the connection strength of the electrodes 14 to the CNT film 11 may be insufficient. On the contrary, when the total area ratio of the connection holes 16 with respect to the electrodes 14 exceeds the upper limit, the CNT film 11 may be easily damaged when the connection holes 16 are formed.

<Electrode>
The pair of electrodes 14 are formed of a conductive material that fills the connection holes 16. The conductive material may be laminated on the surface of the connection hole 16 and the resin layer 12 and the laser absorbing material layer 15 around the connection hole 16 to increase the surface area and facilitate the electrical connection.

The electrode 14 may have additional conductors, such as copper foil, laminated on the surface side of the conductive material that fills the connection holes 16. That is, the electrode 14 may include a conductive material that is filled in the connection hole 16 as a part thereof. Since the electrode 14 has a copper foil or the like on the surface of the conductive material, the lead wire can be easily soldered to the electrode 14.

(Conductive material)
As the conductive material filled in the connection hole 16, for example, a conductive paste, a conductive paint, or the like can be used. That is, the electrode 14 can be formed by applying and curing a conductive paste or a conductive paint. As the conductive paste and the conductive coating material, commercially available ones containing conductive fine particles made of, for example, silver, copper or the like can be used.

The lower limit of the average thickness of the conductive material on the resin layer 12 is preferably 10 μm, more preferably 15 μm. On the other hand, the upper limit of the average thickness of the conductive material on the resin layer 12 is preferably 50 μm, more preferably 20 μm. If the average thickness of the conductive material on the resin layer 12 is less than the lower limit, it may be difficult to uniformly laminate the conductive material. On the contrary, when the average thickness of the conductive material on the resin layer 12 exceeds the upper limit, the manufacturing cost may be unnecessarily increased.

<Laser absorption material layer>
The laser absorption material layer 15 is interposed between the surface of the resin layer 12 around the connection hole 16 and the electrode 14. The laser absorption material layer 15 may be arranged only in the vicinity of the connection hole 16, or may be arranged in substantially the entire laminated region of the electrode 14 except for the inside of the connection hole 16.

The lower limit of the average thickness of the laser absorbing material layer 15 is preferably 1 μm, more preferably 2 μm. On the other hand, the upper limit of the average thickness of the laser absorbing material layer 15 is preferably 15 μm, more preferably 10 μm. If the average thickness of the laser absorption material layer 15 is less than the lower limit, the laser absorption material layer 15 may not sufficiently promote the formation of the connection hole 16, and the manufacturing efficiency of the strain sensor element may decrease. On the contrary, when the average thickness of the laser absorbing material layer 15 exceeds the upper limit, the electrode 14 may be easily peeled off.

(Laser absorption material)
The laser absorber forming the laser absorber material layer 15 can include fine particles made of a material having a relatively large laser absorption rate and a binder thereof.

As the fine particles, various pigments and the like can be used, although it depends on the wavelength of the laser used to form the connection hole 16. Among them, as the fine particles, carbon black, which has a relatively high laser absorptivity and has conductivity so as not to hinder the electrical connection between the CNT film 11 and the electrode 14, is particularly preferably used.

As the binder, various polymer binders can be used.

〔Production method〕
As shown in FIG. 3, the strain sensor element is a step of applying a laser absorbing material to the surfaces of both end regions of a resin layer covering body in which the CNT film 11 is coated with the resin layers 12 and 13 <Step S1: Laser absorbing material. Coating step>, step of irradiating at least a part of the surface of both end regions of the resin layer coating with laser <step S2: laser irradiation step>, and conductivity to the holes formed in the resin layer 12 in the laser irradiation step. It can be manufactured by a method including a step of filling a sex material <step S3: a step of filling a conductive material> and a step of cutting out a strain sensor element from a resin layer coating body <step S4: a cutting step>.

<Laser absorption material application process>
In the laser absorbing material coating step of step S1, a coating film of the laser absorbing material is applied to the surface of both end regions of a plurality of portions of the laminate of the large-sized CNT film 11 and the pair of resin layers 12 and 13 used as the strain sensor element. To form. That is, the method for manufacturing the strain sensor manufactures a plurality of strain sensors at one time.

The application of the laser absorbing material can be performed by using a printing technique such as screen printing, but may be performed by using a simpler method such as brush coating.

(Laser absorption material)
The laser absorbing material can be applied using a laser absorbing material-dispersed ink in which fine particles having a relatively large laser absorption rate are dispersed in a solvent. The laser absorbent material dispersion ink includes, for example, an optional additive such as a dispersant for dispersing fine particles, a binder for retaining fine particles after the solvent has volatilized, and a surfactant for improving coatability. Can be used.

As the solvent of the laser absorbing material dispersion ink, it is preferable to use a volatile organic solvent such as toluene, acetone, methanol, methyl ethyl ketone, isopropyl alcohol or the like so that it can volatilize immediately after coating to form a stable coating film.

<Laser irradiation process>
In the laser irradiation step of step S2, at least a part of the coating film obtained in the coating step is irradiated with the laser. As a result, the laser absorbing material absorbs the laser and generates heat, and the resin layer 12 is thermally decomposed to form the connection hole 16.

The laser output is selected according to the diameter of the connection hole 16 and the material of the resin layer 12, but generally, the lower limit of the laser output is preferably 3 W, more preferably 5 W. On the other hand, the upper limit of the laser output is preferably 30 W, more preferably 20 W. If the laser output is less than the lower limit, the connection hole 16 may not be formed. On the contrary, when the output of the laser exceeds the upper limit, the surrounding resin layer 12 and the CNT film 11 may be damaged when the connection hole 16 is formed.

<Conductive material filling process>
In the step of filling the conductive material in step S3, the conductive material is applied to the surface of both end regions of the resin layer covering in which the connecting hole 16 is formed, so that the inside of the connecting hole 16 is filled with the conductive material. A coating film of a conductive material is formed on the surface of the resin layer 12 around the connection hole 16. The coating film of this conductive material forms at least a part of the electrode 14.

When a plurality of connection holes 16 in each end region are formed, it is preferable to apply the conductive material across the plurality of connection holes 16 in each end region in this conductive material filling step. In this way, by applying the conductive material across the plurality of connection holes 16 in each end region, the electrical connection between the CNT film 11 and the electrode 14 can be further ensured.

As a method of applying the conductive material, for example, a printing technique such as screen printing may be used, but a simpler method such as brush coating may be used.

<Cutout process>
In the cutting step of step S4, a plurality of strain sensor elements are cut out from the resin layer coating body on which the electrode 14 is formed.

The strain sensor element may be cut out by punching using a die and a punch, or the contour of the strain sensor element may be sequentially separated by a cutter or the like.

<Advantage>
Since the strain sensor element forms the electrode 14 by filling the connection hole 16 with a conductive material, the electrical connection between the CNT film 11 and the electrode 14 is relatively easy. Further, since the strain sensor element forms the connection hole 16 by the laser, it is relatively easy to change the design.

[Second Embodiment]
The strain sensor element according to the second embodiment of the present invention, which shows a cross section in one end region in FIG. 4, has a CNT thread 21 containing a plurality of CNT fibers aligned in one direction and an outer periphery of the CNT film 21. The resin layer 22 to be coated, a pair of electrodes 23 laminated on both end regions of the coating body formed by the resin layer 22 of the CNT yarn 21 and electrically connected to the CNT yarn 21, and the resin layer 22 and the electrodes 23. It is provided with a laser absorbing material layer 24 that partially exists between them.

<CNT thread>
The configuration of the CNT thread 21 of the sensor element of FIG. 4 can be the same as the configuration of the CNT film 11 of the sensor element of FIG. 1 except that the CNT fibers are arranged in a thread shape. When arranging the CNT fibers in a thread shape, the CNT fibers may be twisted together.

<Resin layer>
The resin layer 22 has one or more connection holes 25 leading to the CNT thread 21 in each end region. When forming a plurality of connection holes 25, they may be formed so as to open in different directions around the central axis of the CNT thread 21, but they are arranged in the axial direction so as to open in the same direction around the central axis of the CNT thread 21. The formation facilitates processing.

Other configurations of the resin layer 22 of the sensor element of FIG. 4 can be the same as the configurations of the resin layers 12 and 13 of the sensor element of FIG. 1 except that they are laminated on the entire circumference without front and back surfaces. ..

<Electrode>
The pair of electrodes 23 contains a conductive material that fills the connection holes 25. Further, the electrode 23 may have a further conductor such as a copper foil laminated on the surface side of the conductive material filled in the connection hole 25.

(Conductive material)
As the conductive material of the electrode 23 of the sensor element of FIG. 4, the same material as that of the conductive material of the electrode 14 of the sensor element of FIG. 1 can be used.

〔Production method〕
The strain sensor element includes a step of applying a laser absorbing material to the surface of both end regions of the resin layer covering body in which the CNT thread 21 is coated with the resin layer 22 to form the laser absorbing material layer 24, and a step of forming the laser absorbing material layer 24. A method comprising a step of irradiating at least a part of the surface of both end regions with a laser and a step of filling a connection hole 25 formed in the resin layer 22 with a conductive material in the laser irradiation step to form an electrode 23. Can be manufactured by

Since the strain sensor element is thread-like, it can be used as a thread constituting a woven fabric or a thread sewn on a cloth, and can be used to form a cloth in which strain can be detected.

[Other embodiments]
The embodiments do not limit the configuration of the present invention. Accordingly, the embodiments may be omitted, replaced or added to components of each of the embodiments based on the description of the present specification and common general knowledge, all of which are construed as belonging to the scope of the present invention. Should be.

The strain sensor element may not have a laser absorber layer when the laser absorption rate of the resin layer is relatively large. Therefore, in the method for manufacturing the strain sensor element, the laser absorber coating step can be omitted.

Further, in the method for manufacturing the strain sensor element, the resin layer coating body of the CNT film may be cut out into the shape of the strain sensor element, and then a connection hole may be formed in the resin layer to apply the conductive material.

Further, the strain sensor element provided with the CNT thread may be coated with a laser absorbing material and a conductive material over the entire circumference. Further, the planar shape of the connection hole opened by the irradiation of the laser does not have to be limited to a circle.

Hereinafter, a reference form of the strain sensor element related to the present invention will be described.

[First reference form]
The strain sensor element of the first reference embodiment of the present invention shown in FIGS. 5 and 6 is formed in a band shape and is covered with a CNT film 1 containing a plurality of CNT fibers aligned in the longitudinal direction and the front and back surfaces of the CNT film 1. The pair of resin layers 2 and 3 to be formed, and the surface of the resin layer coating body composed of the CNT film 1 and the resin layers 2 and 3, are laminated on both ends in the alignment direction of the CNT fibers, and are electrically connected to the CNT film 1. A pair of plate-shaped electrodes 4 to be connected to each other and a pair of sandwiching sheets 5 arranged so as to face the plate-shaped electrodes 4 in both end regions on the back side of the resin layer coating film are provided.

In the strain sensor element, at least a part of the pair of plate-shaped electrodes 4 is embedded in the resin layer 2 on the front side. More specifically, the pair of plate-shaped electrodes 4 are implanted in the thickness direction from the surface side of the resin layer 2 on the front side. At least a part of each of the pair of plate-shaped electrodes 4 is exposed from the resin layer 2, and each exposed portion is connected to an external wiring (not shown).

<CNT film>
The CNT film 1 is composed of a layer formed of a plurality of CNT fibers aligned in one direction, and a material (hereinafter, simply "insulating elastomer") having an insulating elastomer as a main component, which is a resin layer described later, on the front and back layers. The CNT fiber and the insulating elastomer are composited to form a film by laminating the CNT film 1 and impregnating the front and back layers of the CNT film 1 with the insulating elastomer (at least from the surface layer side of the CNT film 1). Has been done. The CNT film 1 has elasticity due to the elastic force of the insulating elastomer, and can expand and contract at least in the longitudinal direction. When the CNT film 1 is elongated at least in the longitudinal direction, the CNT fibers are separated from each other and the electric resistance is increased, and when the CNT fibers are contracted by the elastic force, the CNT fibers are brought into contact with each other again and the electric resistance is reduced. The CNT film 1 may contain insulating fibers made of, for example, a synthetic resin in order to suppress the contact rate between the CNT fibers and adjust the electric resistance.

Since the CNT film 1 is laminated with at least the surface layer impregnated with the insulating elastomer, the insulating elastomer covers the CNT fiber bundle described later, and the insulating elastomer guides the expansion / contraction direction of the plurality of CNT fiber bundles. It also functions as a guide member. As a result, the strain sensor can re-contact the CNT fibers separated at the time of expansion at the same site at the time of contraction, and can prevent a decrease in the detection accuracy of the expansion / contraction strain due to repeated use. Further, according to such a configuration, it is easy to maintain the contact relationship between the plurality of CNT fibers, and it is easy to adjust the elasticity of the plurality of CNT fibers. Therefore, the expansion and contraction strain of the CNT film 1 can be detected more accurately. Further, in order to further facilitate the maintenance of such a contact relationship and the adjustment of the elasticity, it is preferable that the back layer (region near the back surface) of the CNT film 1 is also impregnated with the insulating elastomer. At this time, since at least a part of the surface layer of the CNT fiber bundle is impregnated with the insulating elastomer, the bonding force between the CNT fiber bundle and the insulating elastomer is also enhanced.

(CNT fiber)
The CNT fibers constituting the CNT film 1 can be formed from a plurality of CNT single fibers. Here, the CNT single fiber means one long carbon nanotube. Further, the CNT fiber has a connecting portion in which the ends of the CNT single fibers are connected to each other. The CNT single fibers are connected to each other in the longitudinal direction of these CNT single fibers. In this way, in the CNT film 1, the CNT single fibers are connected to each other in the longitudinal direction, so that the CNT film 1 having a large orientation length of the CNT fibers can be formed, and the length in the longitudinal direction of the strain sensor can be increased. It can be increased to improve sensitivity.

Further, the plurality of CNT fibers constituting the CNT film 1 may form a network structure. Specifically, the plurality of CNT fibers may be connected or in contact with each other in a mesh pattern by a connecting portion or the like in which the CNT single fibers are connected to each other. At this time, at this connecting portion, the ends of three or more CNT single fibers may be bonded, or the ends of the two CNT single fibers and the intermediate portion of the other single fibers may be bonded. By forming such a network structure of a plurality of CNT fibers, the CNT fibers come into close contact with each other, and the resistance of the CNT film 1 can be reduced.

Further, the CNT film 1 may have a CNT fiber bundle composed of a plurality of CNT fibers oriented in the longitudinal direction. When the CNT film 1 has a plurality of CNT fiber bundles oriented in the longitudinal direction, the CNT fibers are cut, separated, and the cutting space (gap) of the CNT fiber bundle is applied when the CNT film 1 is strained so as to be stretched in the expansion and contraction direction. ), The resistance of the CNT film 1 changes more accurately.

More specifically, the CNT fiber bundle has a bundle structure composed of a plurality of CNT fibers, and in any cross section of the CNT fiber bundle, the CNT fibers that are not cut and the CNT fibers are cut and separated. Both gaps will exist. Further, since the surface layer of the plurality of CNT fiber bundles is coated with an insulating elastomer, the pressure in this gap is considered to be lower than the atmospheric pressure (negative pressure), and therefore, when the strain sensor 1 contracts. At (when the strain is released), the contraction of the strain sensor 1 is urged by the contraction force of this gap. Further, since the friction between the CNT fibers is reduced in this gap, the movement of the CNT fibers is not easily restricted.

The CNT film 1 may have a single-layer structure in which a plurality of CNT fibers or a plurality of CNT fiber bundles are arranged substantially in parallel in a plane, or may have a multilayer structure. However, in order to secure a certain degree of conductivity, it is preferable to have a multi-layer structure.

As the CNT single fiber, either a single-walled nanotube (SWNT) or a multi-walled multi-walled nanotube (MWNT) can be used, but MWNT is preferable from the viewpoint of conductivity and heat capacity, and the diameter is 1. MWNTs of 5 nm or more and 100 nm or less are more preferable.

The CNT single fiber can be produced by a known method, for example, by a CVD method, an arc method, a laser ablation method, a DIPS method, a CoMoCAT method, or the like. Among these, it is preferable to produce carbon nanotubes (MWNT) of a desired size by a CVD method using iron as a catalyst and ethylene gas from the viewpoint of being able to efficiently obtain carbon nanotubes (MWNT). In this case, a crystal of carbon nanotubes having a desired length is obtained by forming an iron or nickel thin film as a catalyst on a substrate such as a quartz glass substrate or a silicon substrate with an oxide film and growing the carbon nanotubes in vertical orientation. Can be done.

The average length of the CNT film 1 in the longitudinal direction is not particularly limited and can be freely selected depending on the measurement target using the strain sensor element, but can be, for example, 1 cm or more and 20 cm or less.

The average length in the longitudinal direction in the region sandwiched between the pair of plate-shaped electrodes 4 in the plan view of the CNT film 1 can be freely selected according to the measurement target using the strain sensor element. The average length can be, for example, 2 mm or more and 18 cm or less.

The average length in the longitudinal direction in the region overlapping the pair of plate-shaped electrodes 4 in the plan view of the CNT film 1 is appropriately selected depending on the fixing method to the measurement target, the wiring method to the plate-shaped electrodes 4, and the like. For example, it can be 3 mm or more and 5 cm or less.

The average width of the CNT film 1 can be freely selected according to the measurement target using the strain sensor element. As the lower limit of the average width of the CNT film 1, 1 mm is preferable, and 2 mm is more preferable. On the other hand, the upper limit of the average width of the CNT film 1 is preferably 10 cm, more preferably 5 cm. If the average width of the CNT film 1 is less than the lower limit, the electrical resistance of the CNT film 1 may become excessively large or may vary. On the contrary, when the average width of the CNT film 1 exceeds the upper limit, the strain sensor element becomes large, and the applicable measurement target may be excessively limited.

The lower limit of the average thickness of the CNT film 1 is preferably 1 μm, more preferably 10 μm. On the other hand, the upper limit of the average thickness of the CNT film 1 is preferably 5 mm, more preferably 1 mm. If the average thickness of the CNT film 1 is less than the lower limit, it may be difficult to form the CNT film 1 or the resistance may increase too much. On the contrary, when the average thickness of the CNT film 1 exceeds the upper limit, the sensitivity to strain may decrease.

As the lower limit of the electric resistance (value measured between the pair of plate-shaped electrodes 4) in the state where the CNT film 1 is not distorted, 10Ω is preferable, and 100Ω is more preferable. On the other hand, as the upper limit of the electric resistance in the state where the CNT film 1 is not distorted, 100 kΩ is preferable, and 10 kΩ is more preferable. If the electrical resistance of the CNT film 1 in the absence of distortion is less than the lower limit, the current for detecting elongation strain increases, and the power consumption of the strain sensor element may increase. On the contrary, when the electric resistance of the CNT film 1 without distortion exceeds the upper limit, the voltage of the detection circuit becomes high, and it is difficult to reduce the size and power saving of the device that processes the output of the distortion sensor element. There is a risk of becoming.

<Resin layer>
The pair of resin layers 2 and 3 are made of an insulating elastomer and are laminated on both sides (the above-mentioned front and back layers) of the CNT film 1, respectively. The resin layers 2 and 3 are made of the above-mentioned insulating elastomer and cover both sides of the CNT film 1 to protect the CNT film 1.

(Insulating elastomer)
As the insulating elastomer impregnating at least the surface layer of the CNT film 1, a thermoplastic elastomer may be used. The thermoplastic elastomer can contain various synthetic resins.

Examples of the thermoplastic elastomer include styrene-based elastomers, olefin-based elastomers, polyester-based elastomers, and the like.

Examples of the thermoplastic elastomer include polyurethane (PUR), polyimide (PI), polyethylene (PE), high density polyethylene (HDPE), medium density polyethylene (MDPE), low density polyethylene (LDPE), polypropylene (PP), and poly. Vinyl chloride (PVC), polyvinylidene chloride, polystyrene (PS), polyvinyl acetate (PVAc), acrylonitrile butadiene styrene resin (ABS), acrylonitrile styrene resin (AS), polymethylmethacrylic (PMMA), polyamide (PA), Examples thereof include polyacetal (POM), polycarbonate (PC), modified polyphenylene ether (m-PPE), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), cyclic polyolefin (COP) and the like.

Further, as the insulating elastomer impregnating at least the surface layer of the CNT film 1, rubber made of a synthetic thermosetting elastomer may be used.

Examples of the rubber include natural rubber (NR), butyl rubber (IIR), isoprene rubber (IR), ethylene / propylene rubber (EPDM), butadiene rubber (BR), urethane rubber (U), and styrene / butadiene rubber (SBR). , Silicone rubber (Q), chloroprene rubber (CR), chlorosulfonized polyethylene rubber (CSM), acrylonitrile butadiene rubber (NBR), chlorinated polyethylene (CM), acrylic rubber (ACM), epichlorohydrin rubber (CO, ECO), Fluoro rubber (FKM), polydimethylsiloxane (PDMS) and the like can be mentioned. Of these, natural rubber is preferable from the viewpoint of strength and the like.

It is preferable that the insulating elastomer is impregnated into at least the surface layer of a plurality of CNT fibers by coating with an aqueous emulsion. The aqueous emulsion means an emulsion in which the main component of the dispersion medium is water. Since carbon nanotubes are highly hydrophobic, when an insulating elastomer is impregnated by coating with an aqueous emulsion, the insulating elastomer does not completely penetrate between a plurality of CNT fibers. That is, the surface layer of the plurality of CNT fiber layers is impregnated with the insulating elastomer, but the insulating elastomer does not impregnate the entire region in the cross section of each CNT fiber in the thickness direction. As a result, the insulating elastomer completely penetrates between the plurality of CNT fibers and suppresses the influence of the resistance change of the CNT film 1, and the sensitivity to the strain of the CNT film 1 due to the presence of the insulating elastomer is lowered. Can be suppressed.

The main component of the dispersion medium of the aqueous emulsion is water, but other hydrophilic dispersion medium such as alcohol may be contained.

Further, the insulating elastomer may contain a coupling agent. When the material containing the insulating elastomer as a main component contains a coupling agent, the insulating elastomer and the CNT fiber can be crosslinked to improve the bonding force between the insulating elastomer and the CNT fiber.

As the coupling agent, for example, an amino coupling agent such as an aminosilane coupling agent, an aminotitanium coupling agent, an aminoaluminum coupling agent, a silane coupling agent, or the like can be used.

Further, the insulating elastomer preferably contains a dispersant having adsorptivity to CNT fibers. Dispersants having such adsorptivity include those having a salt structure in the adsorbing group portion (for example, an alkylammonium salt) and hydrophobic groups of CNT fibers (for example, an alkyl chain or an aromatic ring). Those having a hydrophilic group (for example, polyether, etc.) that can interact with each other in the molecule can be used.

In the laminated structure of these resin layers 2 and 3 and the CNT film 1, a material for forming another layer (or film) may be formed on any layer (or film) by coating or the like, and each layer (or film) may be formed. Alternatively, it may be formed by welding or welding of a film), or may be formed by bonding each layer (or film) using a thermoplastic adhesive. Further, the resin layers 2 and 3 may be formed integrally with the insulating elastomer that at least partially impregnates the surface layer and the back layer of the CNT film 1. That is, in the step of forming the CNT film 1, the insulating elastomer may be applied so as not to impregnate the plurality of CNT fibers but to stay on the front and back of the plurality of CNT fibers to form the resin layers 2 and 3. Further, the resin layers 2 and 3 may have a multilayer structure composed of a plurality of different layers. In that case, it is advisable to combine it with a material having high springiness. Specifically, it is preferable to use polyurethane as a material having high springiness.

The lower limit of the average thickness of each of the resin layers 2 and 3 is preferably 10 μm, more preferably 15 μm. On the other hand, the upper limit of the average thickness of the resin layers 2 and 3 is preferably 5 mm, more preferably 2 mm. If the average thickness of the resin layers 2 and 3 is less than the lower limit, the CNT film 1 may not be sufficiently protected, or the embedded plate-shaped electrode 4 may easily fall off. On the contrary, when the average thickness of the resin layers 2 and 3 exceeds the upper limit, the strain sensor 1 may become unnecessarily thick, or the elastic modulus of the CNT film 1 may increase, which may hinder the deformation of the measurement target. Therefore, it may not be easy to embed the plate-shaped electrode 4. The average thicknesses of the resin layers 2 and 3 on the front and back may be different from each other.

<Plate-shaped electrode>
As the plate-shaped electrode 4, a substantially plate-shaped conductor is used. As such a conductor, for example, a sheet-like material, a net-like material, or the like is used. Examples of the material of the plate-shaped electrode 4 include metals such as copper, aluminum, nickel, and stainless steel, and carbon. The plate-shaped electrode 4 may have, for example, a protrusion penetrating the CNT film 1, a protrusion for connecting to an external wiring, or the like.

As shown in the figure, the plate-shaped electrode 4 preferably has a plurality of through holes 4a. The through hole 4a of the plate-shaped electrode 4 is composed of, for example, a hole formed in a sheet-like material, an opening between strands of a net-like material, and the like. Further, the through holes 4a of the plate-shaped electrode 4 are not only independent of each other, but also, as illustrated in FIG. 7, a slit-shaped or notched-shaped opening at the peripheral edge of the plate-shaped electrode 4. May be good.

As described above, since the plate-shaped electrode 4 has a plurality of through holes 4a, when the plate-shaped electrode 4 is embedded in the resin layer 2 on the front side, the material constituting the resin layer 2 is the through hole 4a of the plate-shaped electrode 4. Since it can escape into the resin layer 2, the plate-shaped electrode 4 can be embedded in the resin layer 2 relatively easily. Further, the material for forming the resin layer 2 that has flowed into the through hole 4a increases the contact area between the plate-shaped electrode 4 and the resin layer 2, thereby making the holding of the plate-shaped electrode 4 more reliable.

The plate-shaped electrode 4 is at least a resin on the front side so that the resin layer 2 can be fluidized by pressing the plate-shaped electrode 4 against the resin layer 2 on the front side while heating the plate-shaped electrode 4, so that the plate-shaped electrode 4 can be embedded in the resin layer 2. It is preferable that the portion embedded in the layer 2 has a high thermal conductivity.

As the lower limit of the thermal conductivity of the embedded portion of the plate-shaped electrode 4, 5 W / (m · K) is preferable, and 10 W / (m · K) is more preferable. If the thermal conductivity of the embedded portion of the plate-shaped electrode 4 does not reach the lower limit, it may be difficult to transfer heat to the resin layer 2 on the front side for flow, and it may not be easy to embed the plate-shaped electrode 4. be.

It is preferable that the plate-shaped electrode 4 has flexibility so that it can be bent at the time of embedding and the resin layer 2 on the surface side can be smoothly extruded outward in a plan view. Further, by fixing the flexible plate-shaped electrode 4 in a bent state, a resin layer 2 having a wedge-shaped cross section is left between the plate-shaped electrode 4 and the CNT film 1, and the plate-shaped electrode 4 is formed. The contact area between the electrode 4 and the resin layer 2 is increased, and the effect of preventing the plate-shaped electrode 4 from being detached can also be obtained.

In order to increase the contact area with the resin layer 2 in this way, the flexible plate-shaped electrode 4 pushes the central portion into the resin layer 2 on the surface side, and the outer peripheral portion in a plan view is the surface of the resin layer 2. It is preferable to bury it so as to protrude from the. Further, in order to facilitate such embedding, the plate-shaped electrode 4 may be formed by combining a plurality of types of materials so that the thermal conductivity of the central portion becomes large in a plan view. Further, in order to increase the contact area between the plate-shaped electrode 4 and the CNT film 1, the flexibility of the peripheral portion of the plate-shaped electrode 4 may be larger than that of the central portion in contact with the CNT film 1. The flexibility of the plate-shaped electrode 4 may be adjusted by, for example, the size, shape, arrangement density, and the like of the through hole 4a.

Further, it is preferable that the plate-shaped electrode 4 has a convex shape so as to bulge toward the CNT film 1 in a state of being fixed so as to be connected to the CNT film 1. It is more preferable that this convex shape is formed by bending the plate-shaped electrode 4. Since the plate-shaped electrode 4 has such a convex shape, the resin layer 2 can be smoothly extruded outward in a plan view when the plate-shaped electrode 4 is embedded. Further, since the plate-shaped electrode 4 is convex, the contact area between the plate-shaped electrode 4 and the CNT film 1 can be increased to further improve the electrical connection. Further, the convex plate-shaped electrode 4 can sandwich not only the CNT film 1 and the resin layer 3 on the back side but also the resin layer 2 on the front side between the peripheral portion thereof and the sandwiching sheet 5. It is hard to break because the tension is dispersed.

The plate-shaped electrode 4 having such a convex portion is embedded so that at least the tip in the thickness direction of the convex portion reaches the surface of the CNT film 1. More preferably, the plate-shaped electrode 4 abuts on the CNT fibers at different positions in the thickness direction of the CNT film 1 so that a more reliable electrical connection with the CNT film 1 can be obtained in the thickness direction of the convex portion. It is embedded so that the tip reaches the back surface of the CNT film 1.

Further, it is preferable that the plate-shaped electrode 4 does not substantially expand and contract during use of the strain sensor element. In addition, "substantially non-expandable" means a region (hereinafter, also referred to as "expandable region") arranged between the pair of plate-shaped electrodes 4 in a plan view during measurement using the strain sensor element. It means that the ratio of the expansion / contraction ratio of the plate-shaped electrode 4 in the longitudinal direction to the expansion / contraction ratio in the longitudinal direction is 1/100 or less, preferably 1/1000 or less.

Further, the number of digits of the ratio of the expansion / contraction ratio of the expansion / contraction region to the expansion / contraction ratio of the plate-shaped electrode 4 during the measurement using the strain sensor element is preferably larger than the number of digits of the effective numerical value in the measurement, and is two or more digits larger. Is more preferable.

The lower limit of the average thickness of the plate-shaped electrode 4 (in the case of a mesh shape, the average wire diameter) is preferably 10 μm, more preferably 50 μm. On the other hand, the upper limit of the average thickness of the plate-shaped electrode 4 is preferably 1 mm, more preferably 0.5 mm. If the average thickness of the plate-shaped electrode 4 is less than the lower limit, the plate-shaped electrode 4 may be broken due to bending or the like. On the contrary, when the average thickness of the plate-shaped electrode 4 exceeds the upper limit, the strain sensor element may become unnecessarily thick, or the flexibility of the non-stretchable region is insufficient, so that the plate-shaped electrode 4 cannot be properly attached to the measurement target. There is a risk.

The planar shape of the plate-shaped electrode 4 can be substantially the same as the planar shape of the end region of the CNT film 1. As shown in FIG. 5, the plate-shaped electrode 4 may be formed to be slightly smaller than the end region of the CNT film 1 so as not to protrude from the CNT film 1 in a plan view. By leaving the resin layer 2 on the surface side whose thickness has not been reduced by burying the plate-shaped electrode 4 around the plate-shaped electrode 4, it is possible to suppress a decrease in the strength of the resin layer 2.

As the plate-shaped electrode 4 satisfying the above conditions, for example, a wire mesh made of stainless steel and formed of a wire having an average wire diameter of 3 μm or more and 100 μm or less and having a nominal opening of 5 μm or more and 100 μm or less can be used.

(Pinch sheet)
The sandwiching sheet 5 is laminated on the other surface of the resin layers 2 and 3 so as to cover the other surface of the non-stretchable region. The sandwiching sheet 5 can be laminated using, for example, an adhesive. As the adhesive, for example, a pressure-sensitive adhesive, a curable adhesive, a thermoplastic adhesive, or the like can be used. Examples of the pressure-sensitive adhesive include acrylic pressure-sensitive adhesives and the like. Examples of the curable adhesive include epoxy adhesives and the like.

Like the plate-shaped electrode 4, the sandwiching sheet 5 does not substantially expand and contract during use of the strain sensor element, and prevents expansion and contraction of the non-expandable region. That is, the sandwiching sheet 5 sandwiches the non-stretchable region of the resin layers 2 and 3 and the CNT film 1 between the plate-shaped electrode 4 and the plate-shaped electrode 4, thereby more reliably preventing the stretchable region from expanding and contracting. Therefore, by providing the sandwiching sheet 5, the strain sensor element is more clearly divided into the non-stretchable region and the stretchable region of the resin layers 2 and 3 and the CNT film 1. Therefore, the strain sensor element has a high correlation between the amount of expansion and contraction and the electrical resistance of the CNT film 1, and is excellent in strain detection accuracy.

The material of the sandwiching sheet 5 may be any material having sufficient non-stretchability, and may be conductive or insulating. Specifically, as the sandwiching sheet 5, for example, a resin sheet containing polyimide, polyethylene terephthalate or the like as a main component, a woven fabric such as glass cloth, or the like can be used. Further, as the sandwiching sheet 5, a commercially available adhesive tape on which an adhesive is laminated in advance may be used.

The lower limit of the average thickness of the sandwiching sheet 5 is preferably 20 μm, more preferably 50 μm. On the other hand, the upper limit of the average thickness of the sandwiching sheet 5 is preferably 1 mm, more preferably 0.5 mm. If the average thickness of the sandwiching sheet 5 is less than the lower limit, the sandwiching sheet 5 may be broken due to bending or the like. On the contrary, when the average thickness of the sandwiching sheet 5 exceeds the upper limit, the strain sensor element may become unnecessarily thick, or the non-stretchable region may be insufficiently flexible and may not be properly attached to the measurement target. There is.

<Manufacturing method>
The strain sensor element is a step of forming a sheet body having a laminated structure of the CNT film 1 and the resin layers 2 and 3, and a step of cutting the sheet body to form a CNT film 1 and the resin layers 2 and 3 having a desired planar shape. A step of forming a laminate (coating body), a step of embedding a plate-shaped electrode 4 in a resin layer 2 on the front surface side of both ends of the laminate, and a pair of sandwiching sheets on the back surface side of both ends of the laminate. It can be manufactured by a method including a step of adhering 5.

In the burying step, the plate-shaped electrode 4 is pushed into the resin layer 2 on the surface side by pressing a relatively high-temperature heating member against the surface of the plate-shaped electrode 4. That is, the heat of the heating member is transferred to the contact region of the resin layer 2 with the plate-shaped electrode 4 via the plate-shaped electrode 4, so that the material forming the resin layer 2 is fluidized and the fluidized material is repelled. The plate-shaped electrode 4 is allowed to enter the inside of the resin layer 2. Therefore, the temperature of the heating member is preferably 10 ° C. or higher and 50 ° C. or lower higher than the softening point of the resin layer 2 on the surface side. For simplicity, for example, a soldering iron or the like can be used as the heating member.

<Advantage>
The strain sensor element is an electrode for wiring in the CNT film 1 by cutting a sheet body in which the CNT film 1 is coated with the resin layers 2 and 3 to an arbitrary size and then embedding the plate-shaped electrode 4 in the resin layer 2. Can be connected, so it can be manufactured relatively easily. Further, as described above, since the strain sensor element later embeds the plate-shaped electrode 4 in the covering body cut out from the sheet body to an arbitrary size, the shape of the covering body cut out from the sheet body can be arbitrarily changed. It can be done and the design change is relatively easy.

[Second reference form]
The strain sensor element of the second reference embodiment of the present invention shown in FIG. 8 is formed in a band shape and contains a plurality of CNT fibers aligned in the longitudinal direction, and a pair of CNT films 1 coated on the front and back surfaces of the CNT film 1. The CNT fibers 2 and 3 are laminated on the front side of the resin layer covering body composed of the CNT films 1 and the resin layers 2 and 3 at both ends in the alignment direction of the CNT fibers, and are electrically connected to the CNT film 1. On the CNT film 1 side of the plate-shaped electrode 4, the pair of plate-shaped electrodes 4 and the pair of sandwiching sheets 5 arranged so as to face the plate-shaped electrode 4 in the both end regions on the back side of the resin layer covering body. It comprises a pair of intervening conductive fabrics 6.

The CNT film 1, the resin layer 2, 3 and the plate-shaped electrode 4 and the sandwiching sheet 5 in the strain sensor element of FIG. 8 are the CNT film 1, the resin layer 2, 3 and the plate-shaped electrode 4 and the sandwiching sheet 5 in the strain sensor element of FIG. Since it is the same as the sheet 5, the duplicate description will be omitted.

<Conductive fabric>
The conductive fabric 6 is formed from a woven or knitted fabric of conductive fibers. The conductive cloth 6 is interposed between the CNT film 1 and the plate-shaped electrode 4, and abuts on both the CNT film 1 and the plate-shaped electrode 4. The conductive cloth 6 has fine irregularities formed by conductive fibers on the front and back surfaces, and the fine irregularities abut on the CNT film 1 and the plate-shaped electrode 4 at many points. Thereby, the conductive cloth 6 improves the conductivity between the CNT film 1 and the plate-shaped electrode 4.

In this conductive fabric 6, in order to hold the plate-shaped electrode 4 by the forming material of the resin layer 2, the forming material of the resin layer 2 on the surface side can permeate in a molten state and pass through in the thickness direction. The coarse one is used.

The lower limit of the average thickness of the conductive fabric 6 is preferably 10 μm, more preferably 15 μm. On the other hand, as the upper limit of the average thickness of the conductive cloth 6, 3 mm is preferable, and 1 mm is more preferable. If the average thickness of the conductive cloth 6 is less than the lower limit, the conductive cloth 6 may be torn due to insufficient strength when the plate-shaped electrode 4 is embedded. On the contrary, when the average thickness of the conductive cloth 6 exceeds the upper limit, the material for forming the resin layer 3 cannot penetrate the conductive cloth 6 when the plate-shaped electrode 4 is embedded, and the plate-shaped electrode 4 is held. It may not be possible.

The conductive cloth 6 is preferably larger than the plate-shaped electrode 4 in a plan view so that the entire back surface of the plate-shaped electrode 4 after embedding can be reliably covered.

As the conductive cloth 6, a commercially available conductive adhesive tape having a conductive adhesive coated on one surface of the conductive cloth may be used. The conductive cloth 6 made of the conductive adhesive tape is attached to the front surface of the resin layer 2 on the front surface side or the back surface of the plate-shaped electrode 4 before the plate-shaped electrode 4 is embedded to prevent misalignment, and the plate-shaped electrode 4 is formed. The burial work of 4 is facilitated. The conductive pressure-sensitive adhesive of the conductive pressure-sensitive adhesive tape can assist the electrical contact between the conductive cloth 6 and the CNT film 1 or the plate-shaped electrode 4, while the conductive pressure-sensitive adhesive is plate-shaped like the material for forming the resin layer 3. Since it is pushed away by the electrode 4, it does not hinder the embedding of the plate-shaped electrode 4.

[Third reference form]
The strain sensor element of the third reference embodiment of the present invention shown in FIG. 9 has a CNT film 1 formed in a band shape and containing a plurality of CNT fibers aligned in the longitudinal direction, and a resin coated on the front and back surfaces of the CNT film 1. A pair of layers 2 and 3 laminated on the front side of the resin layer covering body composed of the CNT film 1 and the resin layers 2 and 3 at both ends in the CNT fiber alignment direction and electrically connected to the CNT film 1. A plate-shaped electrode 4, a pair of sandwiching sheets 5 arranged so as to face the plate-shaped electrode 4 in both end regions on the back side of the resin layer coating body, and a conductive impregnating at least a part of the plate-shaped electrode 4. The sex paste 7 is provided.

The CNT film 1, the resin layer 2, 3 and the plate-shaped electrode 4 and the sandwiching sheet 5 in the strain sensor element of FIG. 9 are the CNT film 1, the resin layer 2, 3 and the plate-shaped electrode 4 and the sandwiching sheet 5 in the strain sensor element of FIG. Since it is the same as the sheet 5, the duplicate description will be omitted.

When the plate-shaped electrode 4 is heated and pressurized and embedded in the resin layer 2 on the front side so as to come into contact with the CNT film 1, the material for forming the resin layer 2 enters the plurality of through holes 4a of the plate-shaped electrode 4. However, the material for forming the resin layer 2 is not always completely filled in the plurality of through holes 4a of the plate-shaped electrode 4. In particular, when a wire mesh or the like having a complicated shape of the through hole 4a is used as the plate-shaped electrode 4, a space is likely to be left inside the through hole 4a of the plate-shaped electrode 4, for example, at the intersection of metal wires. Therefore, by filling the space left in the through hole 4a of the plate-shaped electrode 4 with the conductive paste 7, the reliability of the electrical connection between the plate-shaped electrode 4 and the CNT film 1 can be further improved.

<Conductive paste>
As the conductive paste 7, a paste in which conductive fine particles are dispersed in a resin matrix can be used, and specifically, for example, a commercially available silver paste or the like can be used. After embedding the plate-shaped electrode 4, the conductive paste 7 may be applied from the surface side of the plate-shaped electrode 4 to impregnate the inside of the plate-shaped electrode 4.

<Advantage>
The strain sensor element is formed by cutting a sheet body in which the CNT film 1 is coated with the resin layers 2 and 3 to an arbitrary size, forming an opening in the resin layer 2 by laser irradiation, and filling the opening with a material. Since the electrode 8 is embedded, the shape of the covering body cut out from the sheet body can be arbitrarily changed, and the design change is relatively easy.

Further, since the strain sensor element thermally decomposes the insulating elastomer on the surface layers of the resin layer 2 and the CNT film 1 by irradiation with a laser to expose the CNT fibers, the electrical connection between the CNT fibers and the electrode 8 is made. Is relatively certain.

The strain sensor element may include one or a plurality of CNT threads including a plurality of CNT fibers aligned in a direction connecting the pair of plate-shaped electrodes instead of the CNT film in each of the above-described embodiments. In this case, the CNT yarn is impregnated with the insulating elastomer in the region near the outer peripheral surface. Further, the resin layer is integrated on the front and back sides to cover the outer circumference of the CNT yarn. When a plurality of CNT threads are provided, it is preferable that the plate-shaped electrode is convexly curved so as to have a substantially equal cross section in the width direction perpendicular to the alignment direction of the CNT fibers so as to come into contact with each CNT thread.

[Transformation of reference form]
In the reference form, the components of each part can be omitted, replaced or added based on the description of the present specification and the common general technical knowledge.

In the strain sensor element, at least a part of the plate-shaped electrode may be exposed so as to be wireable. Therefore, even if the entire plate-shaped electrode is embedded so as to be located on the back surface side of the front surface of the resin layer, it is sufficient that the resin layer has an opening accessible to the plate-shaped electrode.

In the strain sensor element, the CNT film may have a planar shape in which the width of the expansion / contraction region is smaller than that of both end regions.

The strain sensor element is provided with a conductive paste that is applied to the plate-shaped electrode from the surface side and impregnated into the plate-shaped electrode even when the conductive cloth is interposed on the CNT film or the CNT thread side of the plate-shaped electrode. May be good.

In the manufacture of the strain sensor element, for heating when the plate-shaped electrode is embedded in the resin layer, a method of generating heat of the plate-shaped electrode itself by energizing the plate-shaped electrode or applying a high-frequency magnetic field may be used.

In the strain sensor element, the CNT film becomes a conductive elastomer by impregnating the resin layer laminated on the surface thereof, but it can also be impregnated with the resin before laminating the resin layer.

In the strain sensor element of the fifth embodiment, the region where the resin layer is thermally decomposed by the laser is filled with the electrode forming material, but an electrode made of a solid may be arranged in the region. In that case, the electrode forming material and the conductive adhesive may be filled together.

Further, in the case of a strain sensor element having a plurality of CNT films or CNT threads, the CNTs of the plurality of CNT films or CNT threads can be directly contacted with each other and electrically connected by laser irradiation.

Further, the method of electrically connecting the CNT film or the CNT thread by this laser irradiation is not limited to the sensor element having the CNT film or the CNT thread, but is not limited to the electrical connection of the conductive thread in which the metal wire or the conductive fiber is coated with the resin layer. Can also be applied. Therefore, an electrode can be formed by irradiating a cloth woven with a conductive thread or a cloth sewn with a conductive thread with a laser to fill an electrode forming material, and electrical connection with an external circuit or the like can be made. In this case as well, it is preferable to apply a paint that increases the laser absorption rate to the position where the laser is irradiated in advance. It is also possible to form a cloth using the conductive thread coated with the resin layer, and the user can optionally form wiring in the cloth on the cloth. Specifically, all or part of the yarn constituting the fabric is a conductive yarn coated with a resin layer. By irradiating with a racer, the resin layer of any conductive yarn can be opened and used as wiring. Further, by opening the resin layer between the conductive threads and electrically connecting them at the portion, it is possible to form a bent wiring or a multi-layer wiring. It is also possible to reduce the resistance value of the wiring by connecting a plurality of wiring arranged in parallel.

The strain sensor element according to the present invention can be suitably used as a sensor for a wearable device or the like.

1 CNT film 2, 3 Resin layer 4 Plate-shaped electrode 4a Through hole 5 Holding sheet 6 Conductive cloth 7 Conductive paste 11 CNT film 12, 13 Resin layer 14 Electrode 15 Laser absorbing material layer 16 Connection hole 21 CNT thread 22 Resin layer 23 Electrode 24 Laser absorbing material layer 25 Connection hole S1 Laser absorbing material coating step S2 Laser irradiation step S3 Conductive material filling step S4 Cutting step

Claims (16)

A CNT film or CNT thread containing a plurality of CNT fibers aligned in one direction,
The resin layer coated on the front and back of the CNT film or the outer circumference of the CNT thread,
A method for manufacturing a strain sensor element, which is laminated on both end regions of the resin layer coating of the CNT film or the CNT thread and includes a pair of electrodes electrically connected to the CNT film or the CNT thread.
A laser irradiation step of forming a connection hole leading to the CNT film or the CNT thread in the resin layer by irradiating at least a part of the surface of both end regions of the resin layer covering body with a laser.
A method for manufacturing a strain sensor element, which comprises a step of filling the connection hole with a conductive material. Prior to the laser irradiation step, a step of applying a laser absorbing material to the surfaces of both end regions of the resin layer covering body is further provided.
The method for manufacturing a strain sensor element according to claim 1, wherein at least a part of the coating film obtained in the coating step in the laser irradiation step is irradiated with a laser. The method for manufacturing a strain sensor element according to claim 2, wherein the laser absorbing material is an ink in which carbon black fine particles are dispersed in a volatile solvent. The resin layer is made of an insulating elastomer and is made of an insulating elastomer.
The strain sensor element according to claim 1, claim 2 or claim 3, further comprising the CNT film impregnated with the insulating elastomer and having at least a part of a surface layer in which the CNT fiber and the insulating elastomer are composited. Production method. The method for manufacturing a strain sensor element according to any one of claims 1 to 4, wherein the average diameter of the connection holes formed in the resin layer is 0.5 mm or more and 2.0 mm or less. The method for manufacturing a strain sensor element according to any one of claims 1 to 5, further comprising the CNT film having a diameter of 5 mm or less. The method for manufacturing a strain sensor element according to any one of claims 1 to 6, wherein the upper limit of the output of the laser is 30 W. In the laser irradiation step, a plurality of the connection holes are formed in each end region of the resin layer coating body.
The method for manufacturing a strain sensor element according to any one of claims 1 to 7, wherein the conductive material is applied across the plurality of connection holes in each end region in the conductive material filling step. A CNT film or CNT thread containing a plurality of CNT fibers aligned in one direction,
The resin layer coated on the front and back of the CNT film or the outer circumference of the CNT thread,
A strain sensor element laminated on both end regions of the resin layer coating of the CNT film or the CNT thread and provided with a pair of electrodes electrically connected to the CNT film or the CNT thread.
The resin layer has a connection hole leading to the CNT film or the CNT thread.
A strain sensor element, wherein the electrode contains a conductive material filled in the connection hole. The strain sensor element according to claim 9, further comprising a laser absorbing material layer existing between the surface of the resin layer around the connection hole and the electrode. The strain sensor element according to claim 10, wherein the laser absorbing material is an ink in which carbon black fine particles are dispersed in a volatile solvent. The resin layer is made of an insulating elastomer and is made of an insulating elastomer.
The strain sensor element according to claim 8 to 11, further comprising the CNT film having the CNT film impregnated with the insulating elastomer and having a surface layer in which the CNT fiber and the insulating elastomer are composited at least in a part. The strain sensor element according to claim 8, wherein the average diameter of the connection holes is 0.5 mm or more and 2.0 mm or less. The strain sensor element according to any one of claims 8 to 13, further comprising the CNT film having a diameter of 5 mm or less. The strain sensor element according to any one of claims 8 to 14, wherein the connection hole is formed by a laser having an output of 30 W or less. The resin layer has a plurality of the connection holes in each end region.
The method for manufacturing a strain sensor element according to any one of claims 8 to 15, wherein the conductive material is arranged so as to straddle the plurality of connection holes in each end region.

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