JP2014219214A - Capacitance type sensor sheet and sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a capacitance type sensor sheet that has a high expansion rate, that can follow deformation or movement of a flexible measurement object, that is excellent in durability against expanding/contracting deformation or repeated deformation, and that can be used for measuring a distortion amount of the expanding/contracting deformation and/or distortion distribution of the expanding/contracting deformation.SOLUTION: The capacitance type sensor sheet comprises: a dielectric layer comprising an elastomer composition; a front side electrode layer that is laminated on a front surface of the dielectric layer; and a rear side electrode layer that is laminated on a rear surface of the dielectric layer. The front side electrode layer and the rear side electrode layer are formed of a conductive composition comprising a monolayer carbon nanotube with an average length of 100 μm or longer and an aspect ratio of 1000 or more. The capacitance type sensor sheet is used for measuring the distortion amount of the expanding/contracting deformation and/or the distortion distribution of the expanding/contracting deformation.

Description

The present invention relates to a capacitance type sensor sheet, in particular, a capacitance type sensor sheet used for measuring the amount of stretch deformation strain and / or distribution of stretch deformation strain, and a static sensor using this capacitance type sensor sheet. The present invention relates to a capacitive sensor.

The capacitance type sensor sheet can detect the uneven shape of the measurement object from the capacitance change between the pair of electrode layers, and can be used for sensors such as a surface pressure distribution sensor and a strain gauge. Generally, the capacitance (capacitance) in a capacitance type sensor is expressed by the following equation (1).
C = ε ₀ ε _r S / d (1)
Here, C is the capacitance, ε ₀ is the permittivity of free space, ε _r is the relative permittivity of the dielectric layer, S is the electrode layer area, and d is the distance between the electrodes.

Conventionally, as a capacitive sensor sheet used as a surface pressure distribution sensor, for example, a dielectric layer made of an elastomer, and a pair of electrode layers (a front side electrode and a back side electrode) formed including an elastomer and a conductive filler, And a pair of electrode layers formed so as to sandwich a dielectric layer is known (for example, see Patent Document 1).
Such a sensor sheet has a characteristic that the change in capacitance is relatively large because the dielectric layer is made of an elastomer.

However, with a capacitive sensor sheet used in a conventional surface pressure distribution sensor, the load distribution of the measurement object can be measured, but the amount of deformation due to the load cannot be known. For example, when the sensor seat is attached to a flexible object such as a cushion and a load is applied to the sensor seat, it is not possible to measure how the cushion is deformed.

In addition, the capacitance type sensor sheet used as the surface pressure distribution sensor usually has a dielectric layer displacement amount (elongation rate) of about several percent during measurement. For this reason, even a flexible dielectric layer has flexibility, but the elongation rate is about several percent.
On the other hand, in the capacitive sensor sheet used for measuring the amount of stretch deformation strain and / or distribution of the stretch deformation strain, the displacement amount (elongation rate) of the dielectric layer at the time of measurement is dependent on the use mode. It is not uncommon to exceed 100%.
Therefore, in the capacitive sensor sheet used for measuring the amount of stretch deformation strain and / or distribution of stretch deformation strain, the dielectric layer is required to have a high elongation rate, and when the dielectric layer is stretched on the electrode layer, In addition, it is required to be able to follow it and maintain conductivity (electrical resistance does not increase).
The capacitance type sensor sheet described in Patent Document 1 cannot sufficiently satisfy such a requirement, and is used for measurement of the amount of stretch deformation strain and / or distribution of stretch deformation strain. It was difficult to use as a sensor sheet. In particular, when an electrode layer is formed using a conductive filler such as carbon black, the conductive path is easily cut when the electrode layer is stretched along with the elongation of the dielectric layer, and the amount of stretch deformation strain and / or stretch It could not be used to measure the deformation strain distribution.

JP 2010-43881 A

The capacitance type sensor sheet used for the elastic deformation strain amount sensor and / or the elastic deformation strain distribution sensor has a high elongation rate in the dielectric layer and the electrode layer, and the sensor sheet is subjected to large elastic deformation and repeated deformation. However, the electrode layer is required to have excellent durability such as a decrease in conductivity (increase in electric resistance) of the electrode layer.

The present invention has been made in view of such circumstances, and the object thereof is to have a high elongation rate, to follow the deformation and operation of a flexible measurement object, and to perform elastic deformation and repetition. An object of the present invention is to provide a capacitive sensor sheet that is excellent in durability against deformation and can be used to measure the amount of stretch deformation strain and / or distribution of stretch deformation strain.

The capacitive sensor sheet of the present invention is
A dielectric layer made of an elastomer composition, a front electrode layer laminated on the surface of the dielectric layer, and a back electrode layer laminated on the back surface of the dielectric layer;
The front electrode layer and the back electrode layer are made of a conductive composition containing single-walled carbon nanotubes having an average length of 100 μm or more and an aspect ratio of 1000 or more,
It is used for measuring the amount of stretch deformation strain and / or the distribution of stretch deformation strain.

The capacitance type sensor sheet of the present invention preferably has an elongation rate of 30% or more capable of withstanding uniaxial tension.

In the capacitive sensor sheet of the present invention, the average thickness of the front electrode layer and the back electrode layer is preferably 0.1 to 10 μm.
In the capacitive sensor sheet of the present invention, the front electrode layer and the back electrode layer are each composed of a plurality of strips arranged in parallel, and the front electrode layer and the back electrode layer are viewed from the front and back directions. It is preferable that they are arranged so as to intersect at substantially right angles.
Also,
The front-side electrode layer and the back-side electrode layer are preferably formed by applying a coating solution containing the conductive composition.

The capacitive sensor of the present invention is
A capacitive sensor sheet of the present invention;
Measuring means;
Each of the front side electrode layer and the back side electrode layer provided in the capacitance type sensor sheet includes an external wiring that connects the measurement unit, and
The elastic deformation strain amount and / or the elastic deformation strain distribution is measured.

The capacitance-type sensor sheet of the present invention has a conductive composition in which the electrode layers (the front-side electrode layer and the back-side electrode layer) include ultra-long single-walled carbon nanotubes (SWNT) having a long average length and a high aspect ratio. Because it is made of a material, the conductive path of the electrode layer is not cut due to expansion and deformation and repeated deformation, and the conductivity of the electrode layer is decreased due to expansion and deformation (increase in electric resistance). Since it does not occur, it has excellent durability (long-term reliability), has a high elongation rate, and can follow the deformation and movement of a flexible measurement object. It can be suitably used for a capacitive sensor that measures strain distribution.

Since the capacitive sensor of the present invention includes the capacitive sensor sheet of the present invention, it measures the amount of stretch deformation and / or distribution of stretch deformation excellent in measurement accuracy and durability (long-term reliability). It is a capacitance type sensor.

(A) is a top view which shows typically an example of the capacitive sensor sheet of this invention, (b) is the sectional view on the AA line of the capacitive sensor sheet shown to (a). It is. It is a schematic diagram which shows an example of the electrostatic capacitance type sensor using the electrostatic capacitance type sensor sheet | seat shown in FIG. It is a top view which shows typically another example of the electrostatic capacitance type sensor sheet | seat of this invention. It is sectional drawing which shows typically another example of the electrostatic capacitance type sensor sheet | seat of this invention. It is a schematic diagram for demonstrating an example of the shaping | molding apparatus used for preparation of the dielectric layer with which the electrostatic capacitance type sensor sheet of this invention is provided. It is a graph which shows the measurement result which performed evaluation 1 to sample 1 for evaluation. It is a graph which shows the measurement result which performed evaluation 1 to sample 2 for evaluation. It is a graph which shows the measurement result which performed evaluation 1 to sample 3 for evaluation. It is a graph which shows the measurement result of evaluation 2. It is a schematic diagram for demonstrating the sensor sheet | seat used for evaluation 3. FIG. 4 is a graph showing a measurement result obtained by measuring a change in capacitance with respect to deformation of the sensor sheet 1. 4 is a graph showing a measurement result obtained by measuring a change in capacitance with respect to deformation of the sensor sheet 2. 4 is a graph showing a measurement result obtained by measuring a change in capacitance with respect to deformation of a sensor sheet 3.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1A is a top view schematically showing an example of the capacitive sensor sheet of the present invention, and FIG. 1B is an AA line of the capacitive sensor sheet shown in FIG. It is sectional drawing.

As shown in FIGS. 1 (a) and 1 (b), a capacitive sensor sheet 1 of the present invention has a sheet-like dielectric layer 2 and a specific laminated on the surface (front surface) of the dielectric layer 2. Strip-shaped front electrode layers 01A to 16A made of a conductive composition, strip-shaped back electrode layers 01B to 16B made of a specific conductive composition laminated on the back surface of the dielectric layer 2, and front electrode layers 01A to 16A Front-side connection portions 01A1 to 16A1 for connecting to external wiring provided at one end of the backside, and back-side connection portions 01B1 to 16B1 for connecting to external wiring provided to one end of the back-side electrode layers 01B to 16B.
The portions where the front-side electrode layer and the back-side electrode layer intersect in the front-back direction (thickness direction of the dielectric layer) are detection units C0101 to C1616. In the detection unit code “CXXΔΔ”, the upper two digits “XX” correspond to the front electrode layers 01A to 16A, and the lower two digits “ΔΔ” indicate the back electrode layers 01B to 01B. Corresponding to 16B.

The front-side electrode layers 01A to 16A each have a strip shape, and a total of 16 layers are laminated on the surface of the dielectric layer 2. The front-side electrode layers 01A to 16A each extend in the X direction (the left-right direction in FIG. 1A). The front-side electrode layers 01A to 16A are spaced apart from each other at predetermined intervals in the Y direction (the vertical direction in FIG. 1A), and are arranged so as to be substantially parallel to each other.

The back electrode layers 01 </ b> B to 16 </ b> B each have a band shape, and a total of 16 layers are stacked on the back surface of the dielectric layer 2. The back-side electrode layers 01B to 16B are arranged so as to intersect the front-side electrode layers 01A to 16A at a substantially right angle when viewed from the front and back directions, respectively. That is, the back side electrode layers 01B to 16B each extend in the Y direction. Further, the back-side electrode layers 01B to 16B are arranged so as to be substantially parallel to each other at a predetermined interval in the X direction.

By arranging the front side electrode layers 01A to 16A and the back side electrode layers 01B to 16B in this manner, the number of electrode layers and the number of electrode wires can be reduced when measuring the position and size of deformation of the measurement object. can do. That is, in the case of the said aspect, the detection part will be arrange | positioned efficiently.

More specifically, in the example shown in FIG. 1, there are 256 detection units in which the front electrode layer and the back electrode layer intersect in the thickness direction at 16 × 16 = 256. In the case where they are formed independently, there are a front side electrode and a back side electrode for each detection unit, and thus 256 wires of 256 × 2 are required to detect the capacitance of the detection unit. On the other hand, as in the example shown in FIG. 1, the front electrode layer and the back electrode layer are formed of a plurality of strips arranged in parallel, and the front electrode layer and the back electrode layer are viewed from the front and back directions. In the case where they are arranged so as to intersect at substantially right angles, only 32 wires of 16 + 16 are required for detecting the electrostatic capacitance of the detection unit.
For this reason, the detection units are efficiently arranged as described above.

And, in the capacitive sensor sheet having such a configuration, as will be described later, the capacitive sensor sheet is connected to a measuring means, and each of the 16 wires is switched by an external switching circuit. Capacitance of each detection unit can be measured while switching 256 detection units one by one, and as a result, the amount of distortion of each detection unit and the positional information of the distortion in the capacitive sensor sheet are detected. can do.

The capacitance type sensor sheet of the present invention preferably has an elongation ratio of 30% or more, more preferably 50% or more, still more preferably 100% or more, 200%, which can withstand uniaxial tension. The above is particularly preferable.
This is because, by increasing the elongation rate, the followability to deformation and movement of the flexible measurement object is improved, and it becomes possible to perform measurement more accurately and in a wide measurement range.
In the present invention, the elongation rate that can withstand uniaxial tension is an elongation rate equal to or lower than the elongation at break in a tensile test based on JIS K 6251, and restores the original state after releasing the tensile load. Elongation rate, for example, 30% elongation rate that can withstand uniaxial tension does not lead to breakage when stretched 30% in the uniaxial direction, and restores the original state after releasing the tensile load (Ie, within the elastic deformation range).

In the capacitance type sensor sheet, the elongation rate that can withstand uniaxial tension depends on the materials of the dielectric layer and the electrode layer, but in the present invention, the electrode layer has an average length of 100 μm or more and an aspect ratio of 1000. Since it consists of the conductive composition containing the above single-walled carbon nanotube, when it has such an electrode layer, the elongation rate which can endure uniaxial tension will be 200% or more at the electrode layer side. Therefore, in the capacitive sensor sheet of the present invention, the material of the dielectric layer may be appropriately selected according to the required elongation rate.

As will be described later, the capacitance type sensor sheet 1 having such a configuration becomes a capacitance type sensor by connecting each of the front side electrode layer and the back side electrode layer to a measuring means via an external wiring, and is expanded and contracted. It is possible to measure the strain amount and / or the stretch deformation strain distribution.

Examples of the capacitive sensor using the capacitive sensor sheet 1 shown in FIG. 1 include those having the configuration shown in FIG.
FIG. 2 is a schematic diagram showing an example of a capacitive sensor using the capacitive sensor sheet shown in FIG.

A capacitive sensor 101 shown in FIG. 2 includes the capacitive sensor sheet 1 shown in FIG. 1, external wirings 102 and 103, and measuring means 104.
Each of the front side connection parts 01A1 to 16A1 of the capacitance type sensor sheet 1 is connected to the measuring means 104 via the external wiring 103 in which a plurality of (16) wirings are bundled, and the back side connection part 01B1. 16B1 are connected to the measuring means 104 via the external wiring 102 in which a plurality (16) of wirings are bundled.
The external wiring may be connected to only one end of the front side electrode layer and the back side electrode layer as shown in FIG. 2, but may be connected to both ends depending on circumstances.

Although not shown, the measurement unit 104 includes a power supply circuit, an arithmetic circuit, a capacitance, a measurement circuit, a pixel switching circuit, a display device, and the like as necessary. Specific examples thereof include, for example, an LCR meter. Can be mentioned.
A capacitive sensor provided with such a capacitive sensor sheet is also one aspect of the present invention.

Note that the external shape such as the average thickness, width, and length of the capacitive sensor sheet 1 can be appropriately changed depending on the application of the capacitive sensor sheet 1 used.

Further, in the capacitance type sensor sheet using the capacitance type sensor sheet of the present invention, the method for measuring the capacitance is not particularly limited, but the capacitance is measured by measuring the impedance with an AC signal such as an LCR meter. A measurement method using AC impedance, such as a method of measuring capacitance or a method of measuring capacitance by changing the voltage of the output signal according to the impedance of the AC signal, is preferable.
The measurement method using AC impedance is excellent in repeatability even when measuring using a high frequency signal. By using a high frequency signal, not only the impedance does not become too large, but also the measurement accuracy can be improved. The time required for the capacitance measurement can be shortened, and the sensor can increase the number of measurements per hour. Therefore, for example, by measuring the distortion (deformation) of the measurement object in a time-resolved manner, it is also suitable for measurement for detecting the speed of movement.
And since the electrostatic capacitance type sensor sheet | seat is provided with the electrode layer of the structure mentioned later in this invention, it is suitable for the measurement using a high frequency signal.

Hereinafter, each component of the capacitive sensor sheet will be described.
<Front side electrode layer / Back side electrode layer>
Both the front-side electrode layer and the back-side electrode layer are made of a conductive composition containing single-walled carbon nanotubes having an average length of 100 μm or more and an aspect ratio of 1000 or more. Hereinafter, the front side electrode layer and the back side electrode layer are also simply referred to as an electrode layer.
In addition, although the said front side electrode layer and the back side electrode layer are normally formed using the same material, it does not necessarily need to use the same material.

In the capacitive sensor sheet of the present invention, it is extremely important that the electrode layer is made of a conductive composition containing single-walled carbon nanotubes (SWNTs) having an average length of 100 μm or more and an aspect ratio of 1000 or more. It is.
By using such a conductive composition containing carbon nanotubes, as described above, a high elongation rate (elongation rate of 200% or more) can be imparted to the electrode layer, so that the electrode layer (front side electrode layer / back side electrode) The layer) exhibits excellent stretchability and can improve the followability to deformation of the dielectric layer. In addition, when the dielectric layer is repeatedly stretched, it has excellent long-term reliability because there is little variation in electrical resistance. The reason for this is considered to be that in the case of the above-mentioned carbon nanotube, the carbon nanotube itself easily expands and contracts, and as a result, the conductive path is less likely to be cut when the electrode layer extends following the dielectric layer.
Also, when long carbon nanotubes are used, conductivity is ensured with a smaller number of electrical contacts than when short carbon nanotubes are used, and one carbon nanotube is an electrode with another carbon nanotube. Since the number of contacts increases, a higher-dimensional electrical network can be formed, which is considered to be the reason why the conductive path is difficult to cut.

In the present invention, it is advantageous from the following points to use the specific carbon nanotubes described above.
As a method for improving the conductivity of the electrode layer made of carbon nanotubes, generally, a method of coating or mixing the electrode layer with a low molecular material such as a charge transfer material or an ionic liquid as a dopant can be considered. However, when a dopant is used in the electrode layer provided in the capacitive sensor sheet of the present invention, there is a concern that the dopant migrates into the dielectric layer, and when the dopant migrates into the dielectric layer, the insulating properties of the dielectric layer There is a concern about decrease in volume resistivity (decrease in volume resistivity) and decrease in durability during repeated use, and as a result, measurement accuracy may decrease.
On the other hand, when single-walled carbon nanotubes (SWNT) having an average length of 100 μm or more and an aspect ratio of 1000 or more are used as carbon nanotubes, sufficient conductivity is ensured for the electrode layer without using a dopant. Can be given.

The average length of the carbon nanotube is preferably 300 μm or more, and more preferably 600 μm or more.
The aspect ratio of the carbon nanotube is preferably 10,000 or more, and more preferably 30000 or more.

The carbon nanotubes preferably have a carbon purity of 99% by weight or more.
When the electrode layer is formed using carbon nanotubes containing a large amount of impurities, the conductivity and elongation rate of the electrode layer may decrease, the elastic modulus of the electrode layer increases, the sensor sheet becomes hard, This is because the stretchability may be reduced.

Specific examples of the carbon nanotube include Super Growth CNT (provided by AIST).

In addition to the carbon nanotube, the conductive composition may contain a binder component as a connecting material for the carbon nanotube.
By containing the binder component, the adhesion to the dielectric layer and the strength of the electrode layer itself can be improved, and further, the scattering of carbon nanotubes is suppressed when the electrode layer is formed by the method described later. Therefore, the safety at the time of forming the electrode layer can be improved.
Examples of the binder component include butyl rubber, ethylene propylene rubber, polyethylene, chlorosulfonated polyethylene, natural rubber, isoprene rubber, butadiene rubber, styrene / butadiene rubber, polystyrene, chloroprene rubber, nitrile rubber, polymethyl methacrylate, polyacetic acid. Examples thereof include vinyl, polyvinyl chloride, acrylic rubber, styrene-ethylene-butylene-styrene block copolymer (SEBS), and the like.
In addition, as the binder component, raw rubber (non-vulcanized natural rubber and synthetic rubber) can also be used. By using such a relatively weak material, deformation of the dielectric layer is possible. The followability of the electrode layer can be improved.

The binder component preferably has a solubility parameter (SP value [cal / cm ³ ) ^1/2 ] similar to that of the elastomer constituting the dielectric layer, and the absolute value of the difference between the solubility parameters (SP value) is 1 The following are more preferable. This is because the closer the solubility parameter, the better the adhesion between the electrode layer and the dielectric layer.
In the present invention, the SP value is a value calculated by Fedors' estimation method.
In particular, the binder component is preferably the same type as the elastomer constituting the dielectric layer. This is because the adhesion between the dielectric layer and the electrode layer can be remarkably improved.

The conductive composition may contain various additives in addition to the carbon nanotube and the binder component. Examples of the additive include a dispersant for enhancing the dispersibility of carbon nanotubes, a crosslinking agent for a binder component, a vulcanization accelerator, a vulcanization aid, an anti-aging agent, a plasticizer, a softening agent, and a colorant. Etc.
Here, when the conductive composition contains a plasticizer and the elastomer composition for forming the dielectric layer also contains a plasticizer, the plasticizer concentration in both compositions is the same. Is preferred. This is because the migration of the plasticizer between the dielectric layer and the electrode layer can be prevented, thereby suppressing the occurrence of warpage and wrinkles in the capacitive sensor sheet.
In the capacitive sensor sheet of the present invention, the electrode layer can be formed substantially only from the carbon nanotubes.

The content of carbon nanotubes in the electrode layer is not particularly limited as long as it is a concentration at which conductivity is exhibited. When the binder component is contained, it varies depending on the type of the binder component, but the total solid component of the electrode layer is different. It is preferable that it is 0.1 to 100 weight%.
By increasing the content of carbon nanotubes, it is possible to suppress a decrease in conductivity (increase in electric resistance) of the electrode layer when it is repeatedly deformed, and to have excellent durability.
On the other hand, if the amount of carbon nanotubes is small and the amount of binder components is large, it is necessary to increase the film thickness in order to obtain the required conductivity, resulting in increased elasticity of the electrode layer and deformation of the measurement object. Or a buffer layer against displacement, the measurement accuracy may be reduced.

The average thickness of the electrode layer (the average thickness of each of the front-side electrode layer and the back-side electrode layer) is preferably 0.1 to 10 μm. This is because, when the average thickness of the electrode layer is within the above range, the electrode layer can exhibit excellent followability to the deformation of the dielectric layer.
On the other hand, if the average thickness is less than 0.1 μm, the conductivity may be insufficient and the measurement accuracy may be lowered. On the other hand, if the average thickness is more than 10 μm, the capacitance sensor sheet may have a reinforcing effect of carbon nanotubes. It becomes hard, the followability to a measuring object falls, and there exists a possibility of inhibiting deformations, such as expansion and contraction.

In the present invention, the “average thickness of the electrode layer” is measured using a laser microscope (for example, VK-9510 manufactured by Keyence Corporation).
Specifically, after scanning the thickness direction of the electrode layer laminated on the surface of the dielectric layer in steps of 0.01 μm and measuring its 3D shape, the region where the electrode layer is laminated on the surface of the dielectric layer and In the non-stacked region, the average height of each rectangular region of length 200 × width 200 μm is measured, and the step of the average height is defined as the average thickness of the electrode layer.

The transparency (visible light transmittance) of the front side electrode layer and the back side electrode layer is not particularly limited, and may be transparent or opaque.
In the capacitance type sensor sheet of the present invention, since the dielectric layer is made of an elastomer composition containing urethane rubber, and can be easily made a transparent dielectric layer, the front electrode layer and the back electrode layer By increasing the transparency, it is possible to obtain a capacitive sensor sheet that is transparent as a whole. However, when an electrode layer is formed using a conductive composition containing carbon nanotubes, the carbon nanotubes require pretreatment such as advanced dispersion treatment and purification treatment, which makes the electrode layer formation process complicated and economical. Disadvantageous.
On the other hand, the transparency of the electrode layer does not affect the performance as a capacitive sensor sheet.
Therefore, when transparency is required as the capacitive sensor sheet, a transparent electrode layer (for example, visible light (550 nm light) transmittance of 85% or more) may be formed; otherwise, it is opaque. A simple electrode layer may be formed, and an opaque electrode layer can be manufactured more easily and at a lower cost.

<Dielectric layer>
The dielectric layer has a sheet shape and is made of an elastomer composition. The shape in plan view is not particularly limited, and may be rectangular as shown in FIG. 1 or may be other shapes such as a circular shape.
The elastomer composition includes at least natural rubber, isoprene rubber, nitrile rubber (NBR), ethylene propylene rubber (EPDM), styrene-butadiene rubber (SBR), butadiene rubber (BR), chloroprene rubber (CR), silicone rubber, fluorine. Examples thereof include rubber, acrylic rubber, hydrogenated nitrile rubber, and urethane rubber.
Among these, urethane rubber or silicone rubber is preferable. This is because the permanent set (or permanent elongation) is small. If the permanent set is small, the initial capacitance (capacitance at no load) hardly changes even after repeated use (for example, 1000 times of expansion and contraction), and it is excellent as a capacitive sensor sheet. Measurement accuracy can be maintained over a long period of time.
Furthermore, urethane rubber is particularly preferable from the viewpoint of excellent adhesion to carbon nanotubes.

The urethane rubber is not particularly limited, and is an olefin urethane rubber having an olefin polyol as a polyol component, an ester urethane rubber having an ester polyol as a polyol component, an ether urethane rubber having an ether polyol as a polyol component, and a carbonate. Examples thereof include carbonate-based urethane rubber using a polyol as a polyol component and castor oil-based urethane rubber using a castor oil-based polyol as a polyol component. These may be used alone or in combination of two or more.
The urethane rubber may be a combination of two or more polyol components.
Among these, olefinic urethane rubber is preferable from the viewpoint of high volume resistivity, and ester urethane rubber is preferable from the viewpoint of high elongation and high relative dielectric constant.
Of course, various urethane rubbers can be mixed in consideration of volume resistivity, elongation rate and dielectric constant to be applied to the dielectric layer.

Examples of the olefin-based polyol include Epol (made by Idemitsu Kosan Co., Ltd.) and the like.
Examples of the ester-based polyol include Polylite 8651 (manufactured by DIC).
Examples of the ether polyol include polyoxytetramethylene glycol, PTG-2000SN (Hodogaya Chemical Co., Ltd.), polypropylene glycol, and Preminol S3003 (Asahi Glass Co., Ltd.).

In addition to the elastomer, the elastomer composition may contain additives such as a plasticizer, a chain extender, a crosslinking agent, a catalyst, a vulcanization accelerator, an antioxidant, an antioxidant, and a colorant.

The elastomer composition may further contain a dielectric filler such as barium titanate. Thereby, the capacitance C can be increased, and as a result, the detection sensitivity of the capacitance type sensor sheet can be increased.
When the dielectric filler is contained, its content in the elastomer composition is usually more than 0% by volume and about 25% by volume or less.
When the content of the dielectric filler exceeds 25% by volume, the hardness of the dielectric layer may increase or permanent set may increase. Further, when forming a dielectric layer made of urethane rubber, the liquid viscosity before curing becomes high, so that it may be difficult to form a highly accurate thin film.

The average thickness of the dielectric layer is preferably 10 to 1000 μm from the viewpoint of improving the detection sensitivity by increasing the capacitance C and improving the followability to the measurement object. More preferably, it is -200 micrometers.

The dielectric layer has a relative dielectric constant at room temperature of preferably 2 or more, more preferably 5 or more. When the relative dielectric constant of the dielectric layer is less than 2, the capacitance C becomes small, and there is a possibility that sufficient sensitivity cannot be obtained when used as a sensor.

The Young's modulus of the dielectric layer is preferably 0.1 to 1 MPa. When the Young's modulus is less than 0.1 MPa, the dielectric layer is too soft, high quality processing is difficult, and sufficient measurement accuracy may not be obtained. On the other hand, if the Young's modulus exceeds 1 MPa, the dielectric layer is too hard, and when the deformation load of the measurement object is small, the deformation operation of the measurement object is hindered, and the measurement result may not match the measurement purpose. .

The dielectric layer has a hardness using a type A durometer in accordance with JIS K 6253 (JIS A hardness) and is 0 to 30 °, or a type C durometer in accordance with JIS K 7321. The used hardness (JIS C hardness) is preferably 10 to 55 °.
If the C hardness is less than 10 °, the dielectric layer is too soft, making high-quality processing difficult, and sufficient measurement accuracy may not be ensured. On the other hand, if it exceeds 55 °, the dielectric layer is too hard. Therefore, when the deformation load of the measurement object is small, the deformation operation of the measurement object is hindered, and the measurement result may not match the measurement purpose.

<Detection unit: C0101 to C1616 in FIG. 1>
As shown by hatching in FIG. 1, the detection units C0101 to C1616 are arranged in portions (overlapping portions) where the front side electrode layers 01A to 16A and the back side electrode layers 01B to 16B intersect in the thickness direction of the dielectric layer. ing. In the capacitive sensor sheet 1, a total of 256 detection units C0101 to C1616 (= 16 × 16) are arranged. The detection units C0101 to C1616 are arranged at substantially equal intervals over substantially the entire surface of the capacitive sensor sheet 1. The detection units C0101 to C1616 include a part of the front electrode layers 01A to 16A, a part of the back electrode layers 01B to 16B, and a part of the dielectric layer 2, respectively.

In the capacitance type sensor sheet of the present invention having such a configuration, the change amount ΔC of the capacitance is detected from the capacitance C before placing the measurement object and the capacitance C after placing the measurement object. Thus, the amount of expansion / contraction deformation strain and the distribution of expansion / contraction deformation strain can be obtained.
In addition, the capacitive sensor sheet of the present invention has a high elongation rate, and can be repeatedly stretched by 30% or more in one axial direction, and can follow the deformation and operation of a flexible measurement object. And, it is excellent in durability against expansion and contraction deformation and repetitive deformation. For example, the shape of the measurement object can be traced, or the movement of the measurement object can be directly detected.

(Other embodiments)
The configuration of the capacitive sensor sheet of the present invention is not limited to the configuration of the capacitive sensor sheet shown in FIG. 1, and may have the configuration shown in FIG. 3, for example. .
FIG. 3 is a top view schematically showing another example of the capacitive sensor sheet of the present invention.

The capacitive sensor sheet 1 ′ shown in FIG. 3 includes a sheet-like dielectric layer 2 ′, strip-shaped front electrode layers 01D to 16D laminated on the surface of the dielectric layer 2 ′, and a back surface of the dielectric layer 2 ′. The laminated strip-like back electrode layers 01E to 16E, one end of the front electrode layers 01D to 16D, the front wirings 01d to 16d extending to the outer edge of the dielectric layer 2 ', and the back electrode layers 01E to 16E And back-side wirings 01e to 16e extending to the outer edge of the dielectric layer 2 '.
The portions where the front-side electrode layer and the back-side electrode layer intersect in the front-back direction (thickness direction of the dielectric layer) are detection units F0101 to F1616. In the symbol “FXXX” of the detection unit, the upper two digits “XX” correspond to the front electrode layers 01D to 16D, and the lower two digits “ΔΔ” indicate the back electrode layers 01E to 01D. Corresponding to 16E.

The front electrode layers 01D to 16D each have a strip shape, and a total of 16 layers are laminated on the surface of the dielectric layer 2 ′. The front side electrode layers 01D to 16D each extend in the X direction (left and right direction in FIG. 3). The front-side electrode layers 01D to 16D are respectively arranged so as to be substantially parallel to each other at a predetermined interval in the Y direction (vertical direction in FIG. 3). The left ends of the front side electrode layers 01D to 16D are connected to linear front side wirings 01d to 16d extending in the Y direction, respectively. The other ends of the front-side wirings 01d to 16d extend to the outer edge portion of the dielectric layer 2 '.

The back-side electrode layers 01E to 16E each have a strip shape, and a total of 16 layers are laminated on the back surface of the dielectric layer 2 ′. The back-side electrode layers 01E to 16E are arranged so as to intersect with the front-side electrode layers 01D to 16D at substantially right angles when viewed from the front-back direction. That is, the back side electrode layers 01E to 16E each extend in the Y direction. In addition, the back side electrode layers 01E to 16E are arranged so as to be substantially parallel to each other at a predetermined interval in the X direction. One end (upper end) of the back-side electrode layers 01E to 16E is connected to linear back-side wirings 01e to 16e extending in the X direction. The other ends of the back-side wirings 01e to 16e extend to the outer edge portion of the dielectric layer 2 '.

In such a capacitive sensor sheet 1 ′, the material constituting the front side wiring and the back side wiring is not particularly limited, and materials conventionally used for electrical wiring can be used. Each wiring (front side wiring and back side wiring) can be stretched and deformed by having the same configuration as the layer, which is preferable because it does not hinder the deformation of the sensor sheet by the measurement object.
More specifically, using the same conductive composition as the conductive composition on which the electrode layer is formed, the front side wiring and the back side wiring are formed so that the line width is narrow and the thickness is thick. Thus, while ensuring sufficient electrical conductivity, it is possible to follow the sensor sheet without impairing the stretchability, and it is possible to provide a wiring that can withstand repeated stretching similarly to the electrode layer.
On the other hand, for example, when the front-side wiring and the back-side wiring are formed using a metal material, it is disadvantageous because the stretchability of the portion where the wiring is formed may be impaired.

The other ends of the front-side wirings 01d to 16d and the other ends of the back-side wirings 01e to 16e are not shown, but are connected to a connector having a metal contact. Can be connected.

The capacitive sensor sheet 1 ′ having such a configuration also measures each of the front side electrode layer and the back side electrode layer via external wiring, similarly to the capacitive type sensor sheet 1 shown in FIGS. By connecting to the means, a capacitive sensor is obtained.

The capacitance type sensor sheet of the present invention may have a configuration as shown in FIG.
FIG. 4 is a cross-sectional view schematically showing another example of the capacitive sensor sheet of the present invention.

The capacitive sensor sheet 44 shown in FIG. 4 is the same as the capacitive sensor sheet 1 shown in FIG. 1 except that the front side overcoat layer 44A is formed on the outermost layer on the front side, and the back side overcoat layer is on the outermost layer on the back side. 44B is formed.

In the capacitive sensor sheet having such a configuration, since the electrode layer is covered with the overcoat layer, the electrode layer can be protected from an impact from the outside, and a member outside the electrode layer It is possible to suppress conduction.
When forming the overcoat layer, the purpose is not limited to the protection of the electrode layer.For example, by forming a colored overcoat layer, the electrode layer can be made invisible from the outside, By coloring only a part, it is possible to impart design properties to the capacitive sensor sheet. The surface of the overcoat layer may be printed.
Further, for example, by making the overcoat layer a layer having adhesiveness or tackiness, the measurement object can be attached to the capacitive sensor sheet, and, for example, the surface of the overcoat layer has a coefficient of friction. And a low μ surface layer with a low thickness.

As a specific example of providing design properties to the overcoat layer (when printing on the surface), for example, the capacitive sensor sheet of the present invention is used as an input interface for a flexible and stretchable touch panel. In this case, for example, a pseudo button at the input position, a keyboard, a product logo, or the like is printed on the surface of the overcoat layer.

When the surface of the overcoat layer is printed, for example, water-based ink, solvent-based ink, UV curable ink, or the like may be used by inkjet printing, screen printing, gravure printing, or the like.
More specifically, for example, in the case of a solvent-based ink, a conventionally known solvent-based ink mainly composed of a solvent, a pigment, a vehicle, and an auxiliary agent blended as necessary may be used. Here, examples of the solvent include glycol ether solvents such as diethylene glycol diethyl ether, tetraethylene glycol dimethyl ether and tetraethylene glycol monobutyl ether, lactone solvents such as γ-butyrolactone, low boiling aromatic naphtha, and propylene glycol monomethyl ether. Examples include acetate. Examples of the pigment include carbon black (black), copper phthalocyanine (cyan), dimethylquinacridone (magenta), pigment yellow (yellow), titanium oxide, aluminum oxide, zirconium oxide, and nickel compounds. Various pigments are known and of course not limited to the above.

The material of the overcoat layer is not particularly limited and may be appropriately selected depending on the purpose of formation. For example, a colorant (pigment) may be added to the same composition as the elastomer composition constituting the dielectric layer as necessary. And a composition containing a dye) can be preferably used.
In the capacitive sensor sheet of the present invention, the overcoat layer may be formed only on either the front side or the back side.

Furthermore, the present invention can be carried out in various modifications and improvements in addition to the above embodiment.
For example, in the capacitive sensor sheet 1 in the embodiment shown in FIG. 1, the number of arrangement of the front electrode layers 01A to 16A and the back electrode layers 01B to 16B is 16, but the arrangement number is not particularly limited. Further, the crossing angle of the front electrode layers 01A to 16A and the back electrode layers 01B to 16B in the above embodiment is not particularly limited.

Next, a method for manufacturing the capacitive sensor sheet of the present invention will be described.
The capacitance type sensor sheet is, for example,
(1) a step of forming a dielectric layer made of an elastomer composition (hereinafter also referred to as “step (1)”), and (2) application of a composition containing carbon nanotubes and a dispersion medium, Step of forming an electrode layer on the back surface (hereinafter also referred to as “step (2)”)
It can manufacture by going through.
Hereinafter, it demonstrates in order of a process.

[Step (1)]
In this step, a dielectric layer made of an elastomer composition is formed. First, as an elastomer composition, an elastomer (or a raw material thereof), if necessary, a dielectric filler, a plasticizer, a chain extender, a crosslinking agent, a vulcanization accelerator, a catalyst, an antioxidant, an anti-aging agent, a colorant, etc. An elastomer composition containing the additives is prepared.
The method for forming the dielectric layer is not particularly limited, and after preparing a mixture containing raw materials, the dielectric layer can be formed by molding by a conventionally known method.
Specifically, when forming a dielectric layer containing urethane rubber as a dielectric layer, for example, a polyol component, a plasticizer, and an antioxidant are weighed, and stirred and mixed for a certain time under heating and reduced pressure. Prepare. Next, after measuring the mixed solution and adjusting the temperature, the catalyst is added and stirred with an agitator or the like. Thereafter, a predetermined amount of an isocyanate component is added, and after stirring with an agitator or the like, the mixed solution is immediately poured into a molding apparatus shown in FIG. A roll-wrapped sheet having a predetermined thickness is obtained. Thereafter, the dielectric layer can be produced by further performing a crosslinking reaction in a furnace for a certain period of time.

FIG. 5 is a schematic diagram for explaining an example of a molding apparatus used for producing the dielectric layer. In the molding apparatus 30 shown in FIG. 5, the raw material composition 33 is poured into a gap between a protective film 31 made of polyethylene terephthalate (PET) that is continuously fed from a pair of rolls 32 and 32 ′ that are spaced apart from each other. The curing reaction (crosslinking reaction) is allowed to proceed while holding the raw material composition 33 in the gap, and is introduced into the heating device 34, and the raw material composition 33 is thermally cured while being held between the pair of PET films 31. Then, the sheet-like dielectric layer 35 is formed.

Moreover, after preparing a raw material composition, you may form a dielectric layer using general purpose film-forming apparatuses, such as various coating apparatuses, a bar coat, a doctor blade, and the film-forming method.

[Step (2)]
In this step, electrode layers (front-side electrode layer and back-side electrode layer) are formed on the front and back surfaces of the dielectric layer by applying a composition containing carbon nanotubes and a dispersion medium.

Specifically, first, carbon nanotubes are added to a dispersion medium such as toluene. At this time, if necessary, a binder component (or a raw material for the binder component), a dispersant, and other various additives may be added.
Next, a coating liquid is prepared by dispersing (or dissolving) each component including carbon nanotubes in a dispersion medium using a wet disperser. Here, for example, an existing disperser such as an ultrasonic disperser, a jet mill, or a bead mill may be used for dispersion.

In the preparation of the coating solution, the dispersion medium is not limited to toluene, and other examples include methyl isobutyl ketone (MIBK), alcohols, and water. These dispersion media may be used independently and may be used together 2 or more types.
In the coating solution, the concentration of the carbon nanotube is preferably 0.01 to 10% by weight.
If it is less than 0.01% by weight, the concentration of the carbon nanotubes may be too thin to be repeatedly applied. On the other hand, if it exceeds 10% by weight, the viscosity of the coating solution becomes too high, and the carbon nanotubes are re-aggregated. In some cases, it is difficult to form a uniform electrode layer.

Subsequently, using an airbrush or the like, a coating solution prepared in a predetermined shape (band shape) is applied to a predetermined position on the surface of the dielectric layer and dried. For example, the electrode layer has a width of about 1 mm to 20 mm, a length of about 50 mm to 500 mm, and is formed so as to be substantially parallel to each other with an interval of about 1 mm to 5 mm.
At this time, if necessary, the coating liquid may be applied after masking a position where the electrode layer on the surface of the dielectric layer is not formed.
The drying conditions for the coating solution are not particularly limited, and may be appropriately selected according to the type of the dispersion medium.

Moreover, the method of applying the coating liquid of the conductive composition is not limited to the method using an air brush, and other methods such as a screen printing method and an ink jet printing method can also be employed.

In some cases, before the electrode layer is formed on the surface of the dielectric layer, the surface of the dielectric layer may be subjected to a pretreatment in order to improve the adhesion between the two, but the pretreatment is not necessarily required. If the dielectric layer is a dielectric layer made of an elastomer composition containing urethane rubber, the adhesiveness to the carbon nanotubes is excellent, so that sufficient adhesiveness can be secured between the two without performing pretreatment.

In addition, when forming an electrode layer containing a binder component together with carbon nanotubes, a composition containing carbon nanotubes and a dispersion medium and not containing a binder component is first applied and dried, and then the binder component (or its raw material) is applied. ) And a dispersion liquid containing a dispersion medium may be applied and dried to form the electrode layer.
In this case, since a dispersion medium different from the dispersion medium for dispersing the carbon nanotubes can be used as a dispersion medium for dispersing the binder component (or its raw material), there are few restrictions on the selection of the dispersion medium, A coating liquid in which the binder component (or its raw material) is reliably dispersed can be prepared.
Examples of the dispersion medium for dispersing the binder component include hexane, acetone, isopropyl alcohol and the like in addition to the dispersion medium for dispersing the carbon nanotubes described above.

Moreover, when manufacturing the capacitance type sensor sheet provided with the above-mentioned overcoat layer, after finishing the step (2), an overcoat layer material may be applied to form an overcoat layer. .
For the formation of the overcoat layer, for example, various coating apparatuses, general-purpose film forming apparatuses such as a bar coat, a doctor blade, and a film forming method can be used.
It is also possible to form an overcoat layer separately and bond the cross-linked or semi-cross-linked sheet to the dielectric layer on which the electrode layer is formed by laminating. Also good.
The capacitive sensor sheet of the present invention can be manufactured through such steps.

Moreover, the capacitive sensor sheet provided with the overcoat layer can also be manufactured through the following steps, for example.
That is, one overcoat layer is first prepared, and then an electrode layer (front side electrode layer or back side electrode layer) is formed on the overcoat layer by the same method as in the above step (2). Thereafter, a dielectric layer made of an elastomer composition containing urethane rubber, which has been separately prepared, is pasted on the electrode layer (laminate). Subsequently, an electrode layer (back side electrode layer or front side electrode layer) is formed on the dielectric layer by the same method as in the above step (2), and finally the other overcoat layer is formed.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

<Production of dielectric layer>
(Production Example 1: Dielectric layer made of urethane rubber)
100 parts by mass of hydrogenated hydroxyl-terminated liquid polyolefin polyol (Epol, Idemitsu Kosan Co., Ltd.) and 100 parts by mass of high-temperature lubricating oil (Moleco High Lube LB-100, manufactured by MORESCO) mainly composed of alkyl-substituted diphenyl ether The mixture was stirred and mixed at 2000 rpm for 3 minutes using a rotation and revolution mixer (manufactured by THINKY). Next, 0.07 part by mass of a catalyst (Fomrez catalyst UL-28, manufactured by Momentive) was added to the obtained mixture, and the mixture was stirred for 1.5 minutes with a rotation and revolution mixer. Thereafter, 11 parts by mass of isophorone diisocyanate (Desmodur I, manufactured by Sumika Bayer Urethane Co., Ltd.) was added, stirred for 3 minutes with a rotating / revolving mixer, defoamed for 1.5 minutes, and then added to the molding apparatus 30 shown in FIG. While being injected and transported in a sandwich form with a protective film, it was cross-linked and cured under conditions of a furnace temperature of 110 ° C. and a furnace time of 30 minutes to obtain a roll-wound sheet with a predetermined thickness with a protective film.
Thereafter, after cross-linking in a furnace adjusted to 80 ° C. for 12 hours, a dielectric layer having a layer thickness of 100 μm made of an elastomer composition containing an olefinic urethane rubber was produced.

(Production Example 2: Urethane rubber dielectric layer)
A dielectric layer made of urethane rubber was produced in the same manner as in Production Example 1 except that the thickness of the dielectric layer was 50 μm.

The dielectric layers produced in Production Examples 1 and 2 were measured for elongation at break (%), volume resistivity (Ωcm), and relative dielectric constant. The elongation at break (%) was 218% and the relative dielectric constant was 2. It was 9.
Here, the elongation at break was measured according to JIS K 6251.
The relative dielectric constant was calculated from the electrode area and the thickness of the measurement sample by sandwiching a sheet-shaped measurement sample (dielectric layer) with an electrode having a diameter of 20 mm and measuring the capacitance with an LCR high tester.

<Preparation of electrode layer material>
(Preparation Example 1)
As the carbon nanotube, super-growth CNT (hereinafter also referred to as “SGCNT”) (single-walled carbon nanotube, the median fiber diameter is about 3 nm, the growth length is 500 μm to 700 μm, the aspect ratio is about 100,000, the carbon purity is 99.000. 9%, provided by National Institute of Advanced Industrial Science and Technology) 120 mg of toluene was added to 280 ml of toluene, stirred for 5 minutes at 100 rpm using a magnetic stirrer, then wet using a jet mill (Nanojet PAL JN10-SP003, manufactured by Joko) The dispersion process was performed and the coating liquid for electrode layer formation (A-1) was obtained.
The growth length of the carbon nanotube refers to the height of the forest grown on the growth substrate when the carbon nanotube is produced.

(Preparation Example 2)
As a carbon nanotube, VGCF-X (multi-walled carbon nanotube, length 3 μm, aspect ratio about 200, carbon purity 95% or more, registered trademark, manufactured by Showa Denko KK) 120 mg was added to 280 ml of toluene, and a magnetic stirrer was used at 100 rpm. After stirring for 5 minutes, followed by ultrasonic treatment for 5 minutes, wet dispersion treatment was performed using a jet mill (Nanojet PAL JN10-SP003, manufactured by Joko), and the electrode layer forming coating solution (A-2) was applied. Obtained.

(Preparation Example 3)
As a carbon nanotube, 120 mg of KH SWCNT ED (single-walled carbon nanotube, length 5 to 50 μm, aspect ratio about 3800, carbon purity 80 to 90% or more, manufactured by KH Chemical) was added to 280 ml of toluene, and a magnetic stirrer was used. The mixture was stirred at 100 rpm for 12 hours, followed by ultrasonic treatment for 60 minutes, and then wet dispersion treatment was performed using a jet mill (Nanojet PAL JN10-SP003, manufactured by Joko Corporation) to form an electrode layer forming coating solution (A-3). )

(Evaluation 1: Measurement of change in electrical resistance against repeated deformation)
The urethane rubber dielectric layer produced in Production Example 2 was cut into a width of 8 cm and a length of 8 cm, and the electrode layer-forming coating solution (A-1) prepared by the above-described method (A-1), ( A-2) or (A-3) is applied in a belt shape with an airbrush and dried at 80 ° C. for 1 hour to form an electrode layer having a width of 20 mm and a length of 50 mm. Sample 1 for evaluation (for electrode layer formation) Coating solution (A-1) is used), evaluation sample 2 (using electrode layer forming coating solution (A-2)) and evaluation sample 3 (using electrode layer forming coating solution (A-3)) Was made.
The coating amount of the electrode layer forming coating solution was 8 ml for the electrode layer forming coating solutions (A-1) and (A-2), and 32 ml for the electrode layer forming coating solution (A-3).
Thereafter, each of the evaluation samples was repeatedly stretched and deformed to 100% in one axial direction, and the electrical resistance at both ends of the strip electrode was measured. That is, first, elongation was performed once in one axis direction up to 100%, a deformation history was added, this was repeated, and the change in the electrical resistance was measured.
The results of evaluation samples 1 to 3 are shown in FIGS.
It can be evaluated that the smaller the increase in electrical resistance, the better the durability against repeated deformation without lowering the conductivity.
Here, in FIGS. 6 to 8, the lowermost line in each figure represents the change in electrical resistance when extending to 100% in the first uniaxial direction (during the forward path), and the expansion rate is 100%. The other line (upper line) extending from the point representing the electrical resistance value at the time represents the change in electrical resistance when returning from the first elongation rate of 100% to the elongation rate of 0% (on the return path). The number of repetitions is one for the forward and return routes. Similarly, two lines whose resistance value at the time of 100% elongation extends from the second point from the bottom represents the change in the electric resistance of the second repetition number, and among these, the lower line is the outward path of the second repetition number. In this case, the upper line represents the change in electrical resistance during the second return. Similarly, changes in electrical resistance after the third repetition are also shown in FIGS.

From the results shown in FIGS. 6 to 8, when VGCF-X or KH SWCNT ED having a short average length is used as the carbon nanotube, the electrical resistance greatly increases as the number of repetitions of 100% elongation increases. On the other hand, when SGCNT with a long average length and a large aspect ratio is used as the carbon nanotube, it is understood that the change in electrical resistance is kept small and constant even when the number of repetitions of 100% elongation is increased. From these facts, it was revealed that the latter is superior in durability.

(Evaluation 2: Measurement of change in electrical resistance with respect to change in elongation)
In the same manner as in Evaluation 1, evaluation samples 1 to 3 were prepared. Each evaluation sample was stretched to 200% in the uniaxial direction by the same method as in Evaluation 1, and the resistance value at each stretching was measured. The results are shown in FIG.
From the results shown in FIG. 9, when VGCF-X or KH SWCNT ED having a short average length is used as the carbon nanotube, the electrical resistance greatly increases as the elongation rate increases. It was revealed that when SGCNT having a long average length and a large aspect ratio was used as the nanotube, the electrical resistance did not increase so much even if the elongation ratio increased. Thereby, it became clear that the capacitive sensor sheet of the present invention is suitable as a sensor having a large displacement.

(Evaluation 3: Measurement of change in capacitance with deformation of sensor sheet)
A single pixel sensor sheet was prepared and the change in capacitance with deformation was measured.
FIG. 10 is a top view schematically showing the sensor sheet used in this evaluation.

(Sensor sheet 1 (Example 1))
The dielectric layer made of urethane rubber produced in Production Example 1 is cut into a width of 8 cm and a length of 8 cm, and the electrode layer forming coating solution A-1 is applied in a band shape with an airbrush to the central portion of one side and dried. A back electrode layer (01B ′ in FIG. 10) of the book was formed. The back electrode layer has an average thickness of about 1 μm, a width of 10 mm, and a length of 80 mm.
Subsequently, the electrode layer-forming coating liquid A-1 is applied to the surface opposite to the dielectric layer and dried to have a plane having a short piece perpendicular to the back-side electrode layer as shown in FIG. A front electrode layer (01A ′ in FIG. 10) having an L-shape in view was formed.
Thereafter, one end of each of the front side electrode layer and the back side electrode layer is reinforced with a copper foil having a thickness of 0.1 mm so that the front side connection part and the back side connection part (01A'1 and 01B in FIG. '1) was formed, and the sensor sheet 1 was obtained.

(Sensor sheet 2 (Comparative Example 1))
A sensor sheet 2 was prepared in the same manner as the sensor sheet 1 except that the electrode layer forming coating liquid A-2 was used instead of the electrode layer forming coating liquid A-1.

(Sensor sheet 3 (Comparative example 2))
A sensor sheet 3 was prepared in the same manner as the sensor sheet 1 except that the electrode layer forming coating liquid A-3 was used instead of the electrode layer forming coating liquid A-1.

Each of the sensor sheets 1 to 3 is constrained on the resin frame 23 on two sides as shown in FIG. 10, and the connection part of each sensor sheet is connected to an LCR meter (manufactured by Hioki Electric Co., Ltd., LCR HiTester 3522-50) The connection was repeated, and uniaxial stretching was repeated until the frames were stretched to 100% in the uniaxial direction, and the change in capacitance at that time was measured. Here, the change in capacitance was measured at measurement frequencies of 500 Hz and 5 kHz. The conditions other than the measurement frequency of the LCR HiTester were measured in a voltage of 1 V, an average number of times: 8 times, a measurement speed of SLOW 1, and an AUTO range.
In FIG. 10, 01A 'is a front electrode layer, 01B' is a back electrode layer, 01A'1 is a front connection part, 01B'1 is a back connection part, C'0101 is a detection part, and 21 is a capacitive sensor. Sheet 22 is a dielectric layer.
About the measurement result, the graph which plotted the electrostatic capacitance with respect to the expansion | extension rate of uniaxial expansion | extension is shown to FIGS. Here, the sensor sheet 1 is shown in FIG. 11, the sensor sheet 2 is shown in FIG. 12, and the sensor sheet 3 is shown in FIG. In each graph, the electrostatic capacity at the first, tenth, 100th, and 1000th round trips when uniaxial extension is repeated 1000 times is plotted.

From the results of FIGS. 11 to 13, for example, the following matters became clear.
In the sensor sheet 1 (Example 1), the capacitance increased almost linearly from the steady state to the 100% stretched state regardless of the measurement frequency and the number of repeated deformations, and no variation was recognized in the value. Moreover, the measured value of the electrostatic capacitance almost coincides with the calculated value.
In the sensor sheet 2 (Comparative Example 1), when the measurement frequency is a low frequency (500 Hz), the same result as the sensor sheet 1 was obtained, but when the measurement frequency was a high frequency (5 kHz), the number of repetitions As the value increased, the measured capacitance value varied.
In the sensor sheet 3 (Comparative Example 2), the same result as the sensor sheet 1 was obtained when the measurement frequency was low (500 Hz), but when the measurement frequency was high (5 kHz), the elongation rate was As the value increases, the measured capacitance value deviates significantly from the calculated value.
From these facts, it was revealed that the capacitance type sensor sheet having an electrode layer using ultra-long single-walled carbon nanotubes is excellent in measurement accuracy in repeated measurement at a high frequency.

The capacitive sensor sheet of the present invention can be suitably used as a capacitive sensor sheet for measuring the amount of stretch deformation strain and / or distribution of stretch deformation strain.
The capacitive sensor using the capacitive sensor sheet of the present invention is used as, for example, a sensor for tracing the shape of a flexible object or a sensor for measuring the movement of a measurement object such as a person. be able to. More specifically, for example, it is possible to measure (detect) the deformation of the shoe sole inner by the sole, the deformation of the seat cushion by the heel, and the like. For example, it can also be used as an input interface for a touch panel.
The capacitance type sensor of the present invention can also be used for measurement at a light shielding portion that cannot be measured by an optical motion capture which is an existing sensor.

DESCRIPTION OF SYMBOLS 1, 1 'Capacitance type sensor sheet 2, 2' Dielectric layer 01A1-16A1 Front side connection part 01A-16A, 01D-16D Front side electrode layer 01B1-16B1 Back side connection part 01B-16B, 01E-16E Back side electrode layer C0101- C1616, F0101 to F1616 Detectors 01d to 16d Front side wirings 01e to 16e Back side wiring 21 Capacitive sensor sheet 22 Dielectric layer 23 made of elastomer Resin frame 01A 'Front side electrode layer 01A'1 Front side connection part 01B' Back side electrode layer 01B '1 Back side connection part C'0101 Detection part 101 Capacitance type sensors 102 and 103 External wiring 104 Measuring means

Claims (6)

A dielectric layer made of an elastomer composition, a front electrode layer laminated on the surface of the dielectric layer, and a back electrode layer laminated on the back surface of the dielectric layer;
The front electrode layer and the back electrode layer are made of a conductive composition containing single-walled carbon nanotubes having an average length of 100 μm or more and an aspect ratio of 1000 or more,
A capacitance-type sensor sheet used for measuring a stretching deformation strain amount and / or a stretching deformation strain distribution. The electrostatic capacity type sensor sheet according to claim 1 whose extension rate which can endure uniaxial tension is 30% or more. The capacitance type sensor sheet according to claim 1 or 2, wherein each of the front electrode layer and the back electrode layer has an average thickness of 0.1 to 10 µm. The front-side electrode layer and the back-side electrode layer are each composed of a plurality of strips arranged in parallel, and the front-side electrode layer and the back-side electrode layer are arranged so as to intersect at a substantially right angle when viewed from the front-back direction. The capacitive sensor sheet according to any one of 1 to 3. The capacitive sensor sheet according to any one of claims 1 to 4, wherein the front electrode layer and the back electrode layer are formed by application of a coating liquid containing the conductive composition. The capacitive sensor sheet according to any one of claims 1 to 5,
Measuring means;
Each of the front side electrode layer and the back side electrode layer provided in the capacitance type sensor sheet includes an external wiring that connects the measurement unit, and
A capacitance type sensor that measures an amount of expansion / contraction deformation strain and / or distribution of expansion / contraction deformation strain.

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