JP2015200592A - Capacitive type sensor sheet and capacitive type sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a capacitive type sensor sheet that has a high expansion rate, is excellent in reliability when repeatedly used and can be optimally used for measuring an amount of deformation distortion.SOLUTION: A capacitive type sensor sheet according to the present invention comprises: a dielectric layer that is composed of an elastomer composition; a front side electrode layer that is stacked on a surface of the dielectric layer; and a rear side electrode layer that is stacked on a rear surface of the dielectric layer. The front side electrode layer and the rear side electrode layer at least partially face each other across the dielectric layer, and the capacitive type sensor sheet is configured to define a portion where the front side electrode layer and the rear side electrode layer face each other across the dielectric layer as a detection unit. The front side electrode layer and the rear side electrode layer are composed of a conductive composition containing carbon nano-tubes, and the elastomer composition contains urethane rubber with polyetherpolyol as a polyol component, and HDI-based polyisocyanate as an isocyanate component.

Description

  The present invention relates to a capacitive sensor sheet and a capacitive sensor using the same.

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 electrostatic capacitance (capacitance) in a capacitive sensor is represented by the following formula (1).
C = ε ₀ ε _r S / d (1)
Here, C is a capacitance, ε ₀ is a permittivity of free space, ε _r is a relative permittivity of a dielectric layer, S is an electrode layer area, and d is an interelectrode distance.

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 the capacitive sensor sheet used in the conventional surface pressure distribution sensor, the load distribution of the measurement object can be measured, but the amount of deformation strain due to the load cannot be known.
For example, when a sensor sheet is attached to a flexible object such as a cushion and a load is applied to the sensor sheet, it has not been possible to measure how the cushion has 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 capacitance type sensor sheet used for measuring the deformation strain amount and the deformation strain distribution, the displacement amount (elongation rate) of the dielectric layer at the time of measurement exceeds 100%, depending on the use mode. It is not unusual.
Therefore, in the capacitive sensor sheet used for measuring the deformation strain amount and the like, the dielectric layer is required to have a high elongation rate. In the above-mentioned capacitance type sensor sheet, the electrode layer is required to be able to follow the dielectric layer when it is stretched and to maintain conductivity (the electric resistance does not increase).

JP 2010-43881 A

However, the capacitance-type sensor sheet described in Patent Document 1 cannot sufficiently satisfy such a requirement, and is used as a capacitance-type sensor sheet used for measurement of deformation strain amount and deformation strain distribution. It was difficult to do.
In particular, there is a problem that it is difficult to ensure reliability when the dielectric layer is repeatedly deformed while ensuring a high elongation rate.

  The present invention has been made in view of such circumstances, and its purpose is to have a high elongation rate, excellent reliability when repeatedly deformed, and suitable for use in measuring deformation strain. It is an object of the present invention to provide a capacitive sensor sheet that can be used, and a capacitive sensor including the sensor sheet.

  As a result of intensive studies to achieve the above object, the present inventors have determined that the dielectric layer is made of an elastomer composition containing a specific urethane rubber, and the electrode layer is made of a conductive composition containing carbon nanotubes. Thus, the inventors have found that the above object can be achieved, and completed the present invention.

The capacitive sensor sheet of the present invention comprises 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 side electrode layer and the back side electrode layer are at least partially opposed with the dielectric layer in between,
A capacitive sensor sheet in which the front electrode layer and the back electrode layer are opposed to each other with the dielectric layer in between.
The front side electrode layer and the back side electrode layer are made of a conductive composition containing carbon nanotubes,
The elastomer composition contains a urethane rubber having polyether polyol as a polyol component and HDI polyisocyanate as an isocyanate component.

In the capacitive sensor sheet, the elastomer composition preferably contains a plasticizer.
The capacitance type sensor sheet preferably has an elongation rate of 100% or more capable of withstanding uniaxial tension.

The capacitance type sensor of the present invention includes the above capacitance type sensor sheet,
A measuring device;
Each of the front side electrode layer and the back side electrode layer provided in the capacitance type sensor sheet, and an external wiring for connecting the measurement device,
The deformation strain amount is measured by measuring a change in capacitance in a detection unit included in the capacitance type sensor sheet.

The capacitive sensor sheet of the present invention has a high elongation rate in the plane direction, and can be suitably used for measurement of deformation strain.
In addition, since the dielectric layer constituting the capacitive sensor sheet of the present invention has a small permanent strain after being largely deformed and hardly undergoes residual strain even when repeatedly deformed (stretched), the above-mentioned capacitance The type sensor sheet is also excellent in reliability (long-term reliability) when repeatedly used.

  In addition, since the capacitive sensor of the present invention includes the capacitive sensor sheet of the present invention, the amount of deformation can be measured even when the sensor sheet is largely deformed in the plane direction, and long This is a capacitive sensor that can accurately measure the amount of deformation over a period of time.

(A) is a perspective 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. (A) is a top view which shows typically another example of the capacitive sensor sheet | seat of this invention, (b) is the BB line of the capacitive sensor sheet | seat shown to (a). It is sectional drawing. It is a top view which shows an example of the capacitive sensor provided with the capacitive sensor sheet | seat shown in FIG. 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. (A)-(d) is a perspective view for demonstrating the manufacturing process of the sensor element in an Example. 4 is a semi-logarithmic graph showing the relationship between the capacitance ratio (C _n / C ₀ ) calculated by the reliability evaluation of the sensor sheet of Example 1 and the number of repetitions of expansion and contraction. 10 is a semi-logarithmic graph showing the relationship between the capacitance ratio (C _n / C ₀ ) calculated by the reliability evaluation of the sensor sheet of Comparative Example 1 and the number of repetitions of expansion and contraction.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The capacitive sensor sheet of the present invention comprises 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 at least partially opposed with the dielectric layer in between, and the front electrode layer and the back electrode layer are detected with the dielectric layer in between. The front-side electrode layer and the back-side electrode layer are made of a conductive composition containing carbon nanotubes, and the elastomer composition has a polyether polyol as a polyol component, It contains a urethane rubber containing an HDI polyisocyanate as an isocyanate component.
The capacitive sensor sheet of the present invention may include one detection unit or may include a plurality of detection units.
Hereinafter, in this specification, the “capacitance type sensor sheet” is simply referred to as “sensor sheet”.

(1st Embodiment: Sensor sheet provided with one detection part)
Fig.1 (a) is a perspective view which shows typically an example of the sensor sheet | seat of this invention, (b) is the sectional view on the AA line of (a).

  A sensor sheet 101 according to the present invention is laminated on a sheet-like dielectric layer 102 made of an elastomer composition and the surface (front surface) of the dielectric layer 102 as shown in FIGS. The front side electrode layer 103A, the back side electrode layer 103B laminated on the back surface of the dielectric layer 102, the front side wiring 104A connected to the front side electrode layer 103A, the back side wiring 104B connected to the back side electrode layer 103B, and the front side wiring The front side connection portion 105A attached to the end of the 104A opposite to the front side electrode layer 103A, the back side connection portion 105B attached to the end of the back side wiring 104B opposite to the back side electrode layer 103B, and the dielectric layer 102 A front-side protective layer 106A and a back-side protective layer 106B are provided on the front side and the back side, respectively.

Here, the front-side electrode layer 103A and the back-side electrode layer 103B have the same plan view shape, and the front-side electrode layer 103A and the back-side electrode layer 103B face each other across the dielectric layer 102. In the sensor sheet 101, a portion where the front electrode layer 103A and the back electrode layer 103B face each other is a detection unit.
In the sensor sheet of the present invention, the front side electrode layer and the back side electrode layer included in the sensor sheet do not necessarily have to face each other across the dielectric layer, and at least a part thereof may be opposed.
In the sensor sheet of the present invention, the protective layer is not necessarily formed, and may be formed as necessary.

In the sensor sheet, since the dielectric layer is made of an elastomer composition, it can be deformed (stretched) in the plane direction, and when the dielectric layer is deformed in the plane direction (direction in which the area of the front and back surfaces changes in the dielectric layer) In accordance with the deformation, a front side electrode layer and a back side electrode layer (hereinafter, both are simply referred to as an electrode layer), and a front side protection layer and a back side protective layer (hereinafter, both are also simply referred to as a protective layer) Is deformed.
As the sensor sheet is deformed, the capacitance of the detection unit changes in correlation with the deformation amount of the dielectric layer. Therefore, the amount of deformation of the sensor sheet (dielectric layer) can be detected by detecting the change in capacitance.
The change in the capacitance can be measured by connecting to a measuring device as described later to form a capacitance type sensor.

  In the capacitance type sensor using the sensor sheet provided with one detection unit according to the present embodiment, the deformation amount of the sensor sheet can be detected. For example, the sensor sheet is attached to the measurement object. Thus, the deformation amount of the measurement object surface can be measured.

(2nd Embodiment: Sensor sheet provided with a some detection part)
Fig.2 (a) is a top view which shows typically an example of the sensor sheet | seat of this invention, (b) is BB sectional drawing of the sensor sheet | seat shown to (a).

As shown in FIGS. 2A and 2B, the sensor sheet 1 of the present invention includes a sheet-like dielectric layer 2 and a plurality of rows of strip-like layers laminated on the surface (front surface) of the dielectric layer 2. Front-side electrode layers 01A to 16A, a plurality of strip-like back-side electrode layers 01B to 16B stacked on the back surface of the dielectric layer 2, and a front side for connecting to external wiring provided at one end of the front-side electrode layers 01A to 16A The connection parts 01A1 to 16A1 and back side connection parts 01B1 to 16B1 for connecting to external wiring provided at one end of the back side electrode layers 01B to 16B are provided.
The portions where the front-side electrode layer and the back-side electrode layer are opposed to each other with the dielectric layer 2 interposed therebetween are detection portions 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” to the back electrode layers 01B to 16B. Correspond.

  Each column of the plurality of front electrode layers 01 </ b> A to 16 </ b> A has a strip shape, and a total of 16 layers are stacked 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. 2A). 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. 2A), and are arranged so as to be substantially parallel to each other.

  Each row of the plurality of rows of back-side electrode layers 01 </ b> B to 16 </ b> B has 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 01B to 16B are arranged so as to intersect (orthogonal) with the front-side electrode layers 01A to 16A at substantially right angles when viewed from the front-and-back direction (thickness direction of the dielectric layer). 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.

  The detection units C0101 to C1616 are portions where the front-side electrode layers 01A to 16A and the back-side electrode layers 01B to 16B face each other with the dielectric layer interposed therebetween (portions that overlap in the thickness direction of the dielectric layer). In the sensor sheet 1, a total of 256 (= 16 × 16) detectors C0101 to C1616 are disposed, and are disposed at substantially equal intervals over substantially the entire surface of the sensor sheet 1.

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 are 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.
In the example shown in FIG. 2, there are 256 detection units in which the front electrode layer and the back electrode layer are opposed to each other with a dielectric layer in between, and 16 × 16 = 256, but 256 detection units are independent of each other. In this case, since there are a front side electrode and a back side electrode for each detection part, 512 wires of 256 × 2 are required to detect the capacitance of the detection part. On the other hand, as in the example shown in FIG. 2, each of the front electrode layer and the back electrode layer is composed of a plurality of rows of strips arranged in parallel, and each row of the front electrode layer and the back electrode layer Are arranged so as to be substantially orthogonal when viewed in the thickness direction of the dielectric layer (front and back direction of the dielectric layer), the number of wirings for detecting the electrostatic capacitance of each detection unit is only 32 (16 + 16). . For this reason, the detection units are efficiently arranged as described above.

As will be described later, the sensor sheet having such a configuration is connected to a measuring device to form a capacitive sensor, and each of the 16 wirings is switched by an external switching circuit so that 256 detection units are provided. Capacitance of each detector can be measured while switching one place at a time.
Based on the capacitance of each detection unit, it is possible to detect not only the deformation amount in the sensor sheet but also information such as the deformation strain distribution and the deformation strain position in the sensor sheet.

As described above, the sensor sheet of the present invention may be a sensor sheet having only one detection unit or a sensor sheet having a plurality of detection units.
Of course, in the sensor sheet of the present invention, the number and arrangement of the detection units are not limited to those shown in FIGS. 1 and 2, and may be appropriately selected according to the purpose of use and required characteristics of the sensor sheet.
Further, the outer shape such as the average thickness, width and length of the sensor sheet is not particularly limited, and may be appropriately selected according to the purpose of use and required characteristics of the sensor sheet 1.

The sensor sheet of the present invention preferably has an elongation ratio that can withstand uniaxial tension of 100% or more, and more preferably 200% or more.
In the sensor sheet, since the dielectric layer is made of an elastomer composition containing a polyether rubber as a polyol component and an urethane rubber containing an HDI polyisocyanate as an isocyanate component, the elongation rate that can withstand the uniaxial tension increases. By increasing the elongation rate, the followability to deformation and movement of a flexible measurement object is improved, and the change in capacitance can be measured 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 7312, and the tensile load is restored to the original state after opening. Elongation rate refers to, for example, an elongation rate that can withstand uniaxial tension is 100%. When the elongation rate is 100% in the uniaxial direction, no breakage occurs, and the original state is restored after releasing the tensile load. (Ie, within the elastic deformation range).

Such a sensor sheet can be used as a capacitive sensor by connecting each of the front electrode layer and the back electrode layer included in the sensor sheet to a measuring device via an external wiring.
A capacitive sensor in which the sensor sheet and the measuring device are connected via an external wiring is also one aspect of the present invention.

The measuring device has a function of measuring the capacitance C of the detection unit that changes according to the deformation of the dielectric layer. As a method of measuring the capacitance C, a conventionally known method can be used. For example, a method of measuring the capacitance by measuring impedance with an AC signal such as an LCR meter or an automatic balancing bridge circuit, A method using a Schmitt trigger oscillator circuit, a method using a Schmitt trigger oscillator circuit and an F / V converter circuit in combination, a method using a CV converter circuit using an inverting amplifier circuit, and a CV converter circuit using a half-wave voltage doubler rectifier circuit The method used can be used. The measurement apparatus includes a capacitance measurement circuit, an arithmetic circuit, an amplifier circuit, a power supply circuit, and the like necessary for that purpose.
As a method for measuring the capacitance C, a measurement method using AC impedance 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 time-resolved distortion (deformation) of the measurement object, the speed of movement (deformation speed) can be measured.

Furthermore, the measurement apparatus may include a display unit that displays the measured change in capacitance, and a storage unit that stores the change in capacitance, and a monitor, arithmetic circuit, An amplifier circuit, RAM, ROM, HDD, or the like may be provided.
By providing the display unit, a change in capacitance (a deformation strain amount of the measurement object) can be confirmed in real time. Further, by providing the storage unit, deformation strain data of the measurement object can be accumulated, and the data accumulated in accordance with the use of the capacitance type sensor of the present invention can be used later.

FIG. 3 is a plan view showing an example of a capacitive sensor using the sensor sheet 1 shown in FIG.
The capacitive sensor 201 shown in FIG. 3 includes the sensor sheet 1 shown in FIG. 2, external wirings 202 and 203, and a measuring device 204.
Each of the front side connection portions 01A1 to 16A1 of the sensor sheet 1 is connected to the measuring device 204 via an external wiring 203 in which a plurality (16) of wirings are bundled. Further, each of the back side connections 01B1 to 16B1 is connected to the measuring device 204 via an external wiring 202 in which a plurality (16) of wirings are bundled.
As described above, the measurement device 204 includes various circuits for measuring the capacitance of the detection unit, a display unit, a storage unit, and the like as necessary.
In addition, as shown in FIG. 3, external wiring should just be connected only to the one end of each strip | belt-shaped body which comprises a front side electrode layer and a back side electrode layer, but may be connected to both ends depending on the case.

Hereinafter, each component of the sensor sheet will be described.
<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 FIGS. 1 and 2 or may be other shapes such as a circular shape.
The elastomer composition contains urethane rubber having polyether polyol as a polyol component and HDI polyisocyanate as an isocyanate component.
By using such urethane rubber, it has a high elongation rate compared with the case of using urethane rubber using other polyol components and isocyanate components, and it is repeatedly deformed because its tensile permanent strain and residual strain are small. The dielectric layer is excellent in reliability at the time of heating.

Examples of the polyether polyol are obtained by copolymerizing monomer materials such as polyethylene glycol, polypropylene glycol, polypropylene triol, polypropylene tetraol, polytetramethylene glycol, polytetramethylene triol, and cyclic ether for synthesizing these. And polyalkylene glycols such as copolymers, derivatives obtained by introducing side chains or branched structures into these, modified products, and mixtures thereof.
Of these, polytetramethylene glycol is preferred. The reason is that the mechanical properties are excellent.

  A commercial item can also be used as said polyether polyol. Specific examples of commercially available products include PTG-2000SN (Hodogaya Chemical Co., Ltd.), polypropylene glycol, Preminol S3003 (Asahi Glass Co., Ltd.), Pandex GCB-41 (DIC Corporation), and the like.

  The polyether polyol preferably has a number average molecular weight (Mn) of 1800-2200. This is because if it is within this range, it is more suitable for reducing the tensile permanent strain and the residual strain. On the other hand, if the number average molecular weight is too small, the elongation at break may decrease, and if the number average molecular weight is too large, it may be difficult to keep the tensile permanent strain and residual strain small.

The HDI polyisocyanate is hexamethylene diisocyanate (HDI) or a modified product thereof, and is a compound having a plurality of isocyanate groups in the molecule.
Specific examples of modified hexamethylene diisocyanate include, for example, isocyanurate-modified hexamethylene diisocyanate having an average functional group number of 2.5 to 3.5.

  The urethane rubber may be obtained by reacting a mixture containing a chain extender, a crosslinking agent, a catalyst, a vulcanization accelerator, etc., if necessary, in addition to the polyol component and the isocyanate component. good.

The elastomer composition preferably further contains a plasticizer.
By blending a plasticizer, the residual strain in the dielectric layer can be further reduced. As a result, the sensor sheet of the present invention can be repeatedly measured with high accuracy for a long period of time, even if repeated measurement with large deformation (deformation at a high elongation rate) is repeated. Measurements can be made.

The plasticizer is not particularly limited, and a conventionally known plasticizer can be used. Specific examples thereof include dialkyl phthalates such as dibutyl phthalate (DBP) and dioctyl phthalate (DOP); dioctyl adipate (DOA). ); Dialkyl adipates such as dioctyl sebacate (DOS); trimellitic esters such as tris (2-ethylhexyl) trimellitate; alkyl-substituted diphenyl ethers and the like. These may be used alone or in combination of two or more.
Of these, dioctyl sebacate (DOS) is preferred. This is because it is particularly suitable for reducing the residual strain.

  The content of the plasticizer is preferably 10 to 40 parts by weight with respect to 100 parts by weight of the urethane rubber. If it is less than 10 parts by weight, the effect of reducing the residual strain is small. On the other hand, if it exceeds 40 parts by weight, the plasticizer may bleed out during use. A more preferable blending amount is 30 to 40 parts by weight.

The elastomer composition may contain an additive such as an antioxidant, an antioxidant, a colorant, a dielectric filler, and the like in addition to the urethane rubber and the plasticizer.

  The average thickness of the dielectric layer is preferably 10 to 1000 μm from the viewpoint of increasing the capacitance C and improving the detection sensitivity, and from the viewpoint of improving the followability to the measurement object. More preferably, it is 30-200 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 as a capacitance type sensor cannot be obtained.

  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 hardness of the dielectric layer is a hardness of type C of a spring hardness test in accordance with JIS K 7312, preferably 10 to 55 °, and more preferably 20 to 45 °.
If the 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. 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 preferably has an elongation at break of 400% or more in a tensile test based on JIS K 7312.
If the elongation at break is less than 400%, when it is repeatedly stretched at a stretch rate of 200%, the durability is inferior and there is a risk of breaking.
On the other hand, the upper limit of elongation at break is not particularly limited and may be large, but in the case of urethane rubber having polyether polyol as a polyol component and HDI polyisocyanate as an isocyanate component, the upper limit is usually about 1100%. It is.

The dielectric layer preferably has a tensile set rate of 1.0% or less in a tensile set test according to JIS K 7312.
If the tensile permanent strain rate exceeds 1.0%, the measurement accuracy may be reduced when the dielectric layer is repeatedly deformed.

The dielectric layer preferably has a residual strain value measured by the following method of 10% or less. First, a method for measuring the residual strain value will be described.
The residual strain value was measured using the same method as the tensile hysteresis loss test in JIS K 7312 except that the tensile speed was 200 mm / min. Then, the deformation for returning the load to 0 was performed once, and the deformation strain amount (elongation amount) when the load was returned to 0 was calculated (unit:%).
By measuring the residual strain value using such a measurement method, the magnitude of the residual strain amount when deformed in a short time can be evaluated. When the residual strain value is small, it means that the strain hardly remains in the dielectric layer when the dielectric layer expands and contracts in a short time. Therefore, the sensor sheet using the dielectric layer having a small residual strain value is a sensor sheet that is more excellent in responsiveness.
The residual strain value is more preferably 5% or less.

<Front side electrode layer / Back side electrode layer>
The electrode layers (the front electrode layer and the back electrode layer) are both made of a conductive composition containing carbon nanotubes. Therefore, in the electrode layer, even if the electrode layer is largely deformed in accordance with the deformation of the dielectric layer, the electrode layer is less likely to increase in conductivity or vary.
Although the said front side electrode layer and back side electrode layer are normally formed using the same electroconductive composition, it is not necessary to necessarily use the electroconductive composition of the same composition.

A known carbon nanotube can be used as the carbon nanotube. The carbon nanotube may be a single-walled carbon nanotube (SWNT), a double-walled carbon nanotube (DWNT), or a multi-walled carbon nanotube (MWNT) having three or more layers (in this specification, Both are simply referred to as multi-walled carbon nanotubes). Furthermore, two or more types of carbon nanotubes having different numbers of layers may be used in combination.
Also, the shape (average length, fiber diameter, aspect ratio) of each carbon nanotube is not particularly limited, and the purpose of use of the sensor sheet, the conductivity and durability required for the sensor sheet, and further the formation of an electrode layer. Therefore, it is only necessary to make a comprehensive decision on the processing and cost for the selection.

The average length of the carbon nanotube is preferably 10 μm or more, and more preferably 50 μm or more.
The electrode layer formed using carbon nanotubes with a long fiber length is excellent in electrical conductivity, and when it is deformed following the deformation of the dielectric layer (especially when stretched), the electrical resistance hardly increases. Even if it expands and contracts repeatedly, it has an excellent characteristic that variation in electric resistance is small.
On the other hand, if the average length of the carbon nanotube is less than 10 μm, the electrical resistance may increase with the deformation of the electrode layer, or the variation in electrical resistance may increase when the electrode layer is repeatedly expanded and contracted. . In particular, such inconvenience is likely to occur when the deformation amount of the sensor sheet increases.

  On the other hand, the preferable upper limit of the average length of the carbon nanotube is 1000 μm. Carbon nanotubes with an average length exceeding 1000 μm are difficult to manufacture and obtain at present, and as will be described later, when an electrode layer is formed by applying a carbon nanotube dispersion, This is because the conductive path is difficult to be formed due to insufficient dispersibility, and as a result, the conductivity of the electrode layer may be insufficient.

  The lower limit of the average length of the carbon nanotube is preferably 100 μm, and the upper limit is preferably 600 μm. When the average length of the carbon nanotubes is within the above range, the electrical conductivity is excellent, the electrical resistance hardly increases when stretched, and the variation in electrical resistance is small when repeatedly stretched. It can be surely secured.

The fiber length of the carbon nanotube may be measured from an observation image obtained by observing the carbon nanotube with an electron microscope.
The average length may be calculated based on, for example, the fiber lengths of 10 carbon nanotubes randomly selected from the observation image of the carbon nanotubes.

  The average fiber diameter of the carbon nanotube is not particularly limited, but is preferably 0.5 to 30 nm. When the fiber diameter is less than 0.5 nm, the dispersion of the carbon nanotubes is deteriorated. As a result, the conductive path may not be widened, and the conductivity of the electrode layer may be insufficient. However, the number of carbon nanotubes may be reduced and conductivity may be insufficient. The average fiber diameter of the carbon nanotube is more preferably 5 to 20 nm.

Of the carbon nanotubes, multi-walled carbon nanotubes are preferable to single-walled carbon nanotubes.
When single-walled carbon nanotubes are used, even when carbon nanotubes having an average length in the above-mentioned preferred range are used, the electrical resistance increases, the electrical resistance increases greatly during stretching, or the electrical resistance during repeated expansion and contraction. May vary widely.
This is presumed as follows. That is, since single-walled carbon nanotubes are usually synthesized as a mixture of metallic carbon nanotubes and semiconducting carbon nanotubes, the presence of these semiconducting carbon nanotubes increases electrical resistance or increases electrical resistance when stretched. It is speculated that this is the cause of the increase or the electric resistance greatly varies during repeated expansion and contraction.
If metallic carbon nanotubes and semiconducting carbon nanotubes are separated and metallic single-walled carbon nanotubes with a long average length are used, the same electrical characteristics as when multi-walled carbon nanotubes with a long average length are used are obtained. There is a possibility that an electrode layer can be formed, but it is not easy to separate metallic carbon nanotubes from semiconducting carbon nanotubes (particularly in carbon nanotubes having a long fiber length). Since complicated operations are required, multi-walled carbon nanotubes are preferred as the carbon nanotubes as described above from the viewpoints of workability when forming the electrode layer and economical efficiency.

  The carbon nanotubes preferably have a carbon purity of 99% by weight or more. Carbon nanotubes may contain catalytic metals, dispersants, and the like in the production process. When carbon nanotubes containing a large amount of components (impurities) other than such carbon nanotubes are used, the decrease in conductivity or May cause variations in electrical resistance.

The method for producing the carbon nanotube is not particularly limited as long as it is produced by a conventionally known production method, but is preferably produced by a substrate growth method.
The substrate growth method is a kind of CVD method, and is a method for producing carbon nanotubes by growing a carbon catalyst by supplying a carbon source to a metal catalyst coated on the substrate. The substrate growth method is suitable as a carbon nanotube used in the present invention because it is a production method suitable for producing carbon nanotubes having relatively long fiber lengths and uniform fiber lengths.
When the carbon nanotube is manufactured by a substrate manufacturing method, the fiber length of the carbon nanotube is substantially the same as the growth length of the CNT forest, and when measuring the fiber length using an electron microscope What is necessary is just to measure the growth length of a CNT forest.

The conductive composition may contain, for example, a binder component in addition to the carbon nanotube.
The binder component functions as a binder material, and by including the binder component, the adhesion to the dielectric layer and the strength of the electrode layer itself can be improved, and further, an electrode layer is formed by the method described later. Since the scattering of the carbon nanotubes can be suppressed at the time, 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 with respect to can also be improved.
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 further 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, and an anti-aging agent, a plasticizer, and a softening agent. And coloring agents.
In the sensor sheet, the electrode layer may be substantially formed of only carbon nanotubes. Also in this case, sufficient adhesion with the dielectric layer can be ensured. The carbon nanotube and the dielectric layer are firmly adhered by van der Waals force or the like.

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 preferably 0.1 to 100% by weight.
Moreover, if the carbon nanotube content is increased, the conductivity of the electrode layer can be improved. Therefore, the required conductivity can be ensured even if the electrode layer is thinned, and as a result, it is easier to make the electrode layer thin and to ensure the flexibility of the electrode layer.

The average thickness of the electrode layer is preferably 0.1 to 10 μm. When the average thickness of the electrode layer is within the above range, the electrode layer can exhibit better followability to the deformation of the dielectric layer.
On the other hand, if the average thickness is less than 0.1 μm, the conductivity is insufficient, and the measurement accuracy as a sensor may be reduced. If the average thickness exceeds 10 μm, the sensor sheet becomes hard due to the reinforcing effect of the carbon nanotubes. Elasticity may decrease.

  In the present invention, the “average thickness of the electrode layer” can be measured using a laser microscope (for example, VK-9510 manufactured by Keyence Corporation). Specifically, for example, after scanning the thickness direction of the electrode layer formed on the surface of the dielectric layer in steps of 0.01 μm and measuring its 3D shape, the region where the electrode layer on the dielectric layer is laminated And in the area | region which is not laminated | stacked, the average height of the rectangular area of length 200x200 micrometers each may be measured, and the level | step difference of the average height should just be made into the average thickness of an electrode layer.

(Other embodiments)
The configuration of the sensor sheet of the present invention is not limited to the configuration of the sensor sheet shown in FIGS.
Specifically, for example, in the sensor sheet shown in FIG. 2, a protective layer may be formed on the front side and / or the back side.
For example, in the sensor sheet 1 in the embodiment shown in FIG. 2, the number of arrangement of the front side electrode layers 01A to 16A and the back side 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 producing the sensor sheet of the present invention will be described.
The 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) A step of forming electrode layers on the front and back surfaces of the dielectric layer by applying a composition containing a conductive material such as carbon nanotubes and a dispersion medium (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, the urethane rubber (or its raw material), if necessary, a dielectric filler, a plasticizer, a chain extender, a crosslinking agent, a vulcanization accelerator, a catalyst, an antioxidant, an anti-aging agent, An elastomer composition is prepared by blending additives such as a colorant at an appropriate timing.

The method for forming the dielectric layer is not particularly limited, and after preparing the raw material composition, the dielectric layer can be formed by molding by a conventionally known method.
Specifically, 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 to prepare a mixed solution. Next, after measuring the mixed solution and adjusting the temperature, the catalyst is added and stirred with an agitator or the like. After that, a predetermined amount of isocyanate component is added, and after stirring with an agitator or the like, the mixed solution (raw material composition) is immediately poured into the molding apparatus shown in FIG. A roll-wrap sheet having a predetermined thickness with a protective film is obtained. Thereafter, the dielectric layer can be produced by further cross-linking reaction in a furnace for a certain time.

FIG. 4 is a schematic diagram for explaining an example of a molding apparatus used for producing a dielectric layer.
In the molding apparatus 40 shown in FIG. 4, the raw material composition 43 is poured into a gap between a protective film 41 made of polyethylene terephthalate (PET) continuously fed from a pair of spaced apart rolls 42, 42, While proceeding with a curing reaction (crosslinking reaction) with the raw material composition 43 held in the gap, it was introduced into the heating device 44 and thermally cured with the raw material composition 43 held between a pair of PET films 41, A sheet-like dielectric layer 45 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 are formed on the front and back surfaces of the dielectric layer by applying a composition containing a conductive material and a dispersion medium.

First, carbon nanotubes are added to the dispersion medium. At this time, you may add a binder component (or raw material of a binder component), a dispersing agent, and other various additives as needed.
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.

As the dispersion medium, for example, methyl isobutyl ketone (MIBK), toluene, alcohols, water and the like can be used. 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 air brush or the like, the prepared coating solution is applied to a predetermined position on the surface of the dielectric layer and dried. 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.
The method of applying the coating liquid 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.

Further, when forming an electrode layer containing a binder component together with carbon nanotubes, first, a composition containing carbon nanotubes and a dispersion medium and not containing a binder component is 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, you may form a protective layer as needed after finishing the said process (2).
The protective layer is formed by, for example, producing a sheet-like material made of an elastomer composition using the same method as in the above step (1), cutting it into a predetermined size, and laminating it. Just do it.

Moreover, when producing a sensor sheet provided with a protective layer, starting from the protective layer on the back side, the constituent members (back-side electrode layer, dielectric layer, front-side electrode layer, front-side protective layer) are sequentially laminated thereon. A sensor element may be manufactured.
The sensor sheet of the present invention can be manufactured through such steps.

In the sensor sheet of the present invention, when the dielectric layer is deformed, the capacitance C is measured before and after the deformation, and the change amount ΔC of the capacitance before and after the deformation is calculated from the measurement result. The amount of deformation strain can be measured. Therefore, the sensor sheet of the present invention can be used for, for example, a capacitance type sensor for obtaining a deformation amount of a measurement object.
Moreover, when the said sensor sheet | seat is provided with a some detection part, it can also be used for the electrostatic capacitance type sensor for calculating | requiring the deformation distortion distribution of a measurement object.

  The capacitance type sensor using the sensor sheet of the present invention uses, for example, an expander, a rehabilitation tube, a stretchable material such as a rubber ball, a flexible material such as a cushion or an inner shoe sole, and the like. A sensor sheet can be affixed to the sensor and used as a sensor for measuring deformation on the measurement object.

In addition, the capacitive sensor of the present invention can be used as a sensor for measuring movement of an animal such as a human being as a measurement object. Specifically, for example, a sensor at any part of the body surface such as a joint, a radial artery or a carotid artery touches, a palm, a back of a hand, a sole of a foot, a back of a foot, a chest or an abdomen, a cheek or a mouth. By sticking and using the sheet, it can be used as a sensor for measuring the deformation (movement) of the body surface.
In addition, the capacitive sensor of the present invention is used by, for example, wearing a garment and attaching a sensor sheet to the surface of the garment, thereby deforming (stretching) the garment and the body of the garment. It can also be used as a sensor for measuring the following ability.

  Further, in the capacitive sensor of the present invention, for example, the user may actively deform the sensor sheet. In that case, the capacitive sensor can be used in a device for producing information reflecting the user's will based on a change in capacitance and transmitting the information.

In the capacitance type sensor of the present invention, when the sensor sheet includes a large number of detection units, the capacitance type sensor detects position information when the measurement object moves in contact with the sensor sheet. It can be used as a sensor for Furthermore, for example, it can 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.

  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.

(Example 1)
(1) 100 parts by weight of a polyether polyol (Pandex GCB-41, manufactured by DIC) and 0.05 part by weight of a catalyst (Fomrez catalyst UL-28, manufactured by Momentive) were weighed, and a rotating and revolving mixer (Nentaro Foamer) ARE-310 (manufactured by THINKY) for 1.5 minutes at 2000 rpm. 16.52 parts by weight of HDI-based polyisocyanate (Pandex GCA-11, manufactured by DIC) was added to the resulting mixture, and 1.5 rpm at 2000 rpm using a rotating / revolving mixer (Awatake Kentaro ARE-310). After stirring and mixing for 3 minutes and defoaming for 3 minutes to prepare a raw material composition for the dielectric layer, it was poured into the molding apparatus 40 shown in FIG. Cross-linking and curing were carried out under the conditions of an internal temperature of 70 ° C. and an in-furnace time of 30 minutes to obtain a roll-wrapped sheet having a predetermined thickness with a protective film. Thereafter, it was post-crosslinked in a furnace adjusted to 70 ° C. for 12 hours to obtain a sheet-like product having a thickness of 50 μm made of urethane rubber.

(2) A carbon nanotube dispersion was prepared separately from the above step (1).
That is, highly oriented carbon nanotubes manufactured by Taiyo Nippon Sanso Co., Ltd., which are multi-walled carbon nanotubes manufactured by the substrate growth method (4 to 12 layers, fiber diameter 10 to 20 nm, fiber length 150 to 300 μm, carbon purity 99. 5%) 50 mg and isopropyl alcohol (IPA) 49.5 g were weighed and mixed (carbon nanotube concentration: 0.1% by weight), and further subjected to ultrasonic treatment for 10 minutes, jet mill (Nanojet Pal JN10- Wet dispersion treatment (condition: discharge pressure 60 MPa, pass number 1 pass) using SP003 (manufactured by Joko), and then the dispersion was diluted with 50 g of isopropyl alcohol (IPA), and the carbon nanotube dispersion 10 times. To obtain a carbon nanotube dispersion having a concentration of 0.01% by weight.

(3) Next, a sensor sheet was produced through the production steps shown in FIGS.
(3-1) The sheet-like material prepared in the above step (1) was cut into 20 mm × 74 mm × thickness 50 μm to form a back side protective layer 126B. A mask (not shown) in which an opening of a predetermined shape was formed on a PET film that had been subjected to a mold release treatment was affixed to one surface (front surface) of the back side protective layer 126B. The mask is provided with openings corresponding to the back electrode layer and the back wiring, and the size of the opening is 16 mm wide × 60 mm long corresponding to the back electrode layer, and the portion corresponding to the back wiring. It is 5 mm wide x 10 mm long.

(3-2) Next, 4 g of the carbon nanotube dispersion prepared in the above step (2) was applied using an airbrush from a distance of 10 cm, naturally dried, and then heated and dried at 100 ° C. for 30 minutes, and the back electrode layer 123B and backside wiring 124B were formed. Thereafter, the mask was peeled off (see FIG. 5A). As an air brush, KIDS-102 manufactured by Airtex Co., Ltd. was used, and the nozzle was applied only for one rotation from a completely closed state.

(3-3) Next, the dielectric layer 122 was laminated on the back side protective layer 126B so as to cover the entire back side electrode layer 123B and a part of the back side wiring 124B.
The dielectric layer 122 is obtained by cutting the sheet-like material produced in the above step (1) into 20 mm × 74 mm × 50 μm thickness, and further cutting off one corner at a size of 10 mm × 7 mm × 50 μm thickness. Produced.

(3-4) Next, the front-side electrode layer 123A and the front-side wiring 124A were formed on the front side of the dielectric layer 122 using the same method as the formation of the back-side electrode layer 123B and the back-side wiring 124B (FIG. 5B). reference).

(3-5) Next, the front side protective layer 126A is laminated on the front side of the dielectric layer 122 on which the front side electrode layer 123A and the front side wiring 124A are formed so as to cover the entire front side electrode layer 123A and a part of the front side wiring 124A. Were laminated. In addition, 126 A of front side protective layers were produced by cutting the sheet-like material produced at the said process (1) into 20 mm x 67 mm x thickness 50 micrometers.
Furthermore, a copper foil tape with a conductive adhesive was attached to each end of the front side wiring 124A and the back side wiring 124B to form a front side connection part 125A and a back side connection part 125B (see FIG. 5C). Thereafter, the lead wires 130 serving as external wirings were fixed to the front-side connection portion 125A and the back-side connection portion 125B with solder.

(3-6) Next, an acrylic adhesive tape (manufactured by 3M, Y-4905 (thickness)) is formed on a portion of the front side connecting portion 125A and the back side connecting portion 125B located on the back side protective layer 126B. 0.5 mm))) and affixed via 127 to reinforce.
Further, a similar PET film 129 was attached to the opposite side of the PET film 128 across the dielectric layer 122 using the back side protective layer tack to produce a sensor sheet 121 (see FIG. 5D).

(Example 2)
A sensor sheet was produced in the same manner as in Example 1 except that a urethane rubber sheet-like material produced by the following method was used to form a dielectric layer and a protective layer.
100 parts by weight of polyether polyol (Pandex GCB-41), 40 parts by weight of plasticizer (dioctyl sebacate (DOS), manufactured by Gordo Co., Ltd.), 0.05 part by weight of catalyst (UL-28) are weighed, The mixture was stirred and mixed at 2000 rpm for 3 minutes using a rotation and revolution mixer (manufactured by THINKY, the same in the following examples and comparative examples). Next, 17.62 parts by weight of HDI-based polyisocyanate (Pandex GCA-11) was added to the obtained mixture, and the mixture was stirred and mixed at 2000 rpm for 1.5 minutes using a rotating and rotating mixer, defoamed for 3 minutes, and dielectric. After preparing the raw material composition for the layer, it was poured into the molding apparatus 40 shown in FIG. 4 and transported in a sandwich form with the protective film 41, while the furnace temperature was 70 ° C. and the furnace time was 30 minutes. Then, it was cross-linked and cured to obtain a roll-wound sheet having a predetermined thickness with a protective film. Then, after cross-linking for 12 hours in a furnace adjusted to 70 ° C., a sheet-like material made of urethane rubber was produced.

(Example 3)
A sensor sheet was produced in the same manner as in Example 1 except that a urethane rubber sheet-like material produced by the following method was used to form a dielectric layer and a protective layer.
100 parts by weight of a polyether polyol (PTG-2000SN, manufactured by Hodogaya Chemical Co., Ltd.) and 0.07 part by weight of a catalyst (UL-28) were weighed and stirred at 2000 rpm for 1.5 minutes by a rotating and rotating mixer. 15.26 parts by weight of HDI polyisocyanate (Pandex GCA-11) is added to the obtained mixture, and the mixture is stirred and mixed at 2000 rpm for 1.5 minutes using a rotating and rotating mixer, defoamed for 3 minutes, and then the dielectric layer. The raw material composition is prepared, and then injected into the molding apparatus 40 shown in FIG. 4 and is transported in a sandwich form with a protective film, and is crosslinked under the conditions of a furnace temperature of 70 ° C. and a furnace time of 30 minutes. Curing was performed to obtain a roll-wrapped sheet having a predetermined thickness with a protective film. Then, after cross-linking for 12 hours in a furnace adjusted to 70 ° C., a sheet-like material made of urethane rubber was produced.

(Comparative Example 1)
A sensor sheet was produced in the same manner as in Example 1 except that a urethane rubber sheet-like material produced by the following method was used to form a dielectric layer and a protective layer.
7.04 parts by weight of tolylene diisocyanate (Coronate T-80, manufactured by Nippon Polyurethane Co., Ltd.) is added to 100 parts by weight of a polyether polyol (Pandex GCB-41), and 1.5 minutes at 2000 rpm using a rotation and revolution mixer. After stirring and mixing and defoaming for 3 minutes to prepare a raw material composition for the dielectric layer, it was poured into the molding apparatus 40 shown in FIG. Crosslinking and curing was performed under conditions of a temperature of 150 ° C. and a furnace time of 90 minutes to obtain a roll-wrap sheet having a predetermined thickness with a protective film. Thereafter, it was post-crosslinked in a furnace adjusted to 80 ° C. for 12 hours to produce a sheet-like material made of urethane rubber.

(Comparative Example 2)
A sensor sheet was produced in the same manner as in Example 1 except that a urethane rubber sheet-like material produced by the following method was used to form a dielectric layer and a protective layer.
100 parts by weight of a polyether polyol (Pandex GCB-41) and 0.07 part by weight of a catalyst (UL-28) were weighed and stirred for 1.5 minutes at 2000 rpm with a rotating and rotating mixer. To the resulting mixture, 9.00 parts by weight of isophorone diisocyanate (Desmodur I, manufactured by Sumika Bayer Urethane Co., Ltd.) is added, stirred and mixed at 2000 rpm for 1.5 minutes using a rotating and rotating mixer, and defoamed for 3 minutes. Then, after preparing the raw material composition for the dielectric layer, it was poured into the molding apparatus 40 shown in FIG. 4 and conveyed in a sandwich form with a protective film, while the furnace temperature was 70 ° C. and the furnace time was 30 minutes. Cross-linking and curing were performed under conditions to obtain a roll-wound sheet with a predetermined thickness with a protective film. Then, after cross-linking for 12 hours in a furnace adjusted to 70 ° C., a sheet-like material made of urethane rubber was produced.

(Comparative Example 3)
A sensor sheet was produced in the same manner as in Example 1 except that a urethane rubber sheet-like material produced by the following method was used to form a dielectric layer and a protective layer.
To 100 parts by weight of polyether polyol (PTG-2000SN), 7.60 parts by weight of tolylene diisocyanate (Coronate T-80) is added, and stirred and mixed at 2000 rpm for 1.5 minutes using a rotating and rotating mixer, and then removed for 3 minutes. After foaming and preparing a raw material composition for the dielectric layer, it was poured into the molding apparatus 40 shown in FIG. The film was crosslinked and cured under a condition of 90 minutes to obtain a roll-wrap sheet having a predetermined thickness with a protective film. Thereafter, it was post-crosslinked in a furnace adjusted to 80 ° C. for 12 hours to produce a sheet-like material made of urethane rubber.

(Comparative Example 4)
A sensor sheet was produced in the same manner as in Example 1 except that a urethane rubber sheet-like material produced by the following method was used to form a dielectric layer and a protective layer.
100 parts by weight of polyether polyol (PTG-2000SN) and 0.07 part by weight of catalyst (UL-28) were weighed and stirred at 2000 rpm for 1.5 minutes by a rotating and rotating mixer. 8.32 parts by weight of isophorone diisocyanate (Desmodur I) is added to the resulting mixture, and the mixture is stirred and mixed at 2000 rpm for 1.5 minutes using a rotating and rotating mixer, defoamed for 3 minutes, and the raw material composition for the dielectric layer After the product was prepared, it was poured into the molding apparatus 40 shown in FIG. 4 and conveyed in a sandwich form with the protective film 41, while being crosslinked and cured at a furnace temperature of 100 ° C. and a furnace time of 30 minutes, A roll-wrapped sheet having a predetermined thickness with a protective film was obtained. Then, after cross-linking for 12 hours in a furnace adjusted to 70 ° C., a sheet-like material made of urethane rubber was produced.

(Comparative Example 5)
A sensor sheet was produced in the same manner as in Example 1 except that a urethane rubber sheet-like material produced by the following method was used to form a dielectric layer and a protective layer.
100 parts by weight of a hydrogenated hydroxyl group-terminated liquid polyolefin polyol (Epol, Idemitsu Kosan Co., Ltd.) and 0.07 part by weight of a catalyst (UL-28) were weighed and stirred at 2000 rpm for 1.5 minutes by a rotating and rotating mixer. To the obtained mixture, 13.76 parts by weight of HDI polyisocyanate (Pandex GCA-11) was added, stirred and mixed at 2000 rpm for 1.5 minutes using a rotation and revolution mixer, defoamed for 3 minutes, and dielectric layer The raw material composition was prepared and then poured into the molding apparatus 40 shown in FIG. 4 and conveyed in a sandwich form with the protective film 41, while the furnace temperature was 100 ° C. and the furnace time was 30 minutes. Cross-linked and cured to obtain a roll-wound sheet with a protective film and a predetermined thickness. Then, after cross-linking for 12 hours in a furnace adjusted to 70 ° C., a sheet-like material made of urethane rubber was produced.

(Comparative Example 6)
A sensor sheet was produced in the same manner as in Example 1 except that a urethane rubber sheet-like material produced by the following method was used to form a dielectric layer and a protective layer.
100 parts by weight of a polycarbonate polyol (Kuraray polyol C-3090, manufactured by Kuraray Co., Ltd.) and 0.005 part by weight of a catalyst (UL-28) were weighed and stirred at 2000 rpm for 1.5 minutes by a rotating and rotating mixer. To the obtained mixture, 10.25 parts by weight of HDI-based polyisocyanate (Pandex GCA-11) was added, stirred and mixed at 2000 rpm for 1.5 minutes using a rotating and rotating mixer, defoamed for 3 minutes, and dielectric layer The raw material composition was prepared and then poured into the molding apparatus 40 shown in FIG. 4 and conveyed in a sandwich form with the protective film 41, while the furnace temperature was 100 ° C. and the furnace time was 30 minutes. Cross-linked and cured to obtain a roll-wound sheet with a protective film and a predetermined thickness. Then, after cross-linking for 12 hours in a furnace adjusted to 70 ° C., a sheet-like material made of urethane rubber was produced.

(Comparative Example 7)
A sensor sheet was produced in the same manner as in Example 1 except that a urethane rubber sheet-like material produced by the following method was used to form a dielectric layer and a protective layer.
Weigh 100 parts by weight of hydrogenated hydroxyl-terminated liquid polyolefin polyol (Epol) and 100 parts by weight of a plasticizer based on alkyl-substituted diphenyl ether (Molesco HiLube LB-100, manufactured by MORESCO), and use a revolving mixer. The mixture was stirred and mixed at 2000 rpm for 3 minutes. Next, 0.07 part by weight of catalyst (UL-28) was added to the obtained mixture, and the mixture was stirred at 2000 rpm for 1.5 minutes by a rotation and revolution mixer. Thereafter, 11 parts by weight of isophorone diisocyanate (Desmodur I) was added, stirred for 3 minutes with a rotating and rotating mixer, defoamed for 1.5 minutes, and a raw material composition for a dielectric layer was prepared. It is injected into the forming apparatus 40 shown, sandwiched and transported by the protective film 41, and cured by cross-linking under a furnace temperature of 110 ° C. and a furnace time of 30 minutes. Obtained. Thereafter, it was post-crosslinked in a furnace adjusted to 80 ° C. for 12 hours to produce a sheet-like material made of urethane rubber.

(Comparative Example 8)
A sensor sheet was produced in the same manner as in Example 1 except that a urethane rubber sheet-like material produced by the following method was used to form a dielectric layer and a protective layer.
100 parts by weight of polycarbonate polyol (Kuraray polyol C-3090) and 0.005 part by weight of catalyst (UL-28) were weighed and stirred at 2000 rpm for 1.5 minutes by a rotating and rotating mixer. To the obtained mixture, 6.55 parts by weight of isophorone diisocyanate (Desmodur I) is added, stirred and mixed at 2000 rpm for 1.5 minutes using a rotating and rotating mixer, defoamed for 3 minutes, and the raw material composition for the dielectric layer After the product was prepared, it was poured into the molding apparatus 40 shown in FIG. 4 and conveyed in a sandwich form with the protective film 41, while being cured by crosslinking under the conditions of a furnace temperature of 110 ° C. and a furnace time of 30 minutes, A roll-wrapped sheet having a predetermined thickness with a protective film was obtained. Thereafter, it was post-crosslinked in a furnace adjusted to 80 ° C. for 12 hours to produce a sheet-like material made of urethane rubber.

  The compositions of the dielectric layers produced in the examples and comparative examples are summarized in Table 1.

(Measurement of physical properties of dielectric layer)
Each sheet-like material produced in the examples and comparative examples was subjected to a hardness test (type C hardness), a tensile test (M50, M100, breaking stress, elongation at break), and a tensile permanent strain test. All of these measurements were performed according to JIS K 7312.
Further, the residual strain value was measured (elongation: 100%). The method for measuring the residual strain value is as described above.
Furthermore, the relative dielectric constant of each sheet-like material was measured. The relative dielectric constant is determined by sandwiching a sheet-like measurement sample (sheet-like material) with an electrode of 20 mmΦ, and measuring the capacitance at a measurement frequency of 1 kHz using an LCR high tester (manufactured by Hioki Electric, 3522-50). It calculated from the thickness of the measurement sample. The results are shown in Table 2.

(Reliability evaluation of sensor sheet)
Each sensor sheet produced in Examples and Comparative Examples is connected to an LCR HiTester (manufactured by Hioki Electric Co., Ltd., 3522-50) via a lead wire, and the sensor sheet is stretched 100% in the longitudinal direction of the sensor sheet from the unstretched state. The capacitance of the detection part was measured while repeating expansion and contraction 10,000 times. At this time, the measurement conditions of the LCR HiTester are Vol. = 1V, Ave. = 8, Speed = SLOW.
Then, the capacitance C ₀ of the detection unit in a non-stretched state after being stretchable only once, and a capacitance C _n of the detection unit in a non-stretched state after being stretch n times measured, The ratio (C _n / C ₀ ) of the capacitance C was calculated. Table 2 shows the ratio (C ₁₀₀₀₀ / C ₀ ) of the capacitance C ₁₀₀₀₀ of the detection unit in the non-stretched state after being expanded and contracted 10,000 times with respect to the capacitance C ₀ .
Further, FIGS. 6 and 7 show semi-logarithmic graphs showing the relationship between the capacitance C ratio (C _n / C ₀ ) calculated in Example 1 and Comparative Example 1 and the number of repetitions of expansion and contraction.

  As shown in Table 2, a dielectric layer using a specific urethane rubber has a high elongation rate in the plane direction, a small tensile permanent strain, and residual strain hardly occurs even when repeatedly deformed (stretched). The capacitive sensor sheet of the present invention having the above dielectric layer can be used even when it is greatly deformed in the plane direction, and has excellent reliability (long-term reliability) when repeatedly used. Became clear.

  The capacitive sensor sheet of the present invention can be used for a capacitive sensor for measuring the amount of deformation strain.

1, 101, 121 Sensor sheet 2, 102, 122 Dielectric layers 01A-16A, 103A, 123A Front side electrode layers 01B-16B, 103B, 123B Back side electrode layers 01A1-16A1, 105A, 125A Front side connection parts 01B1-16B1, 105B, 125B Back side connection part C0101-C1616 Detection part 40 Molding device 41 Protective film 42 Roll 43 Raw material composition 44 Heating device 45 Dielectric layer 104A, 124A Front side wiring 104B, 124B Back side wiring 106A, 126A Front side protection layer 106B, 126B Back side protection layer 127 Acrylic adhesive tape 128 PET film 130 Lead wire 201 Capacitive sensor 202, 203 External wiring 204 Measuring device

Claims (4)

A dielectric layer made of an elastomer composition, a front-side electrode layer laminated on the surface of the dielectric layer, and a back-side electrode layer laminated on the back surface of the dielectric layer, the front-side electrode layer and the back-side electrode layer are At least a part of the dielectric layer is sandwiched,
A capacitance type sensor sheet in which the front side electrode layer and the back side electrode layer are opposed to each other with the dielectric layer in between.
The front electrode layer and the back electrode layer are made of a conductive composition containing carbon nanotubes,
The said elastomer composition contains the urethane rubber which uses polyether polyol as a polyol component and uses HDI type polyisocyanate as an isocyanate component, The electrostatic capacitance type sensor sheet characterized by the above-mentioned.   The capacitive sensor sheet according to claim 1, wherein the elastomer composition contains a plasticizer.   The electrostatic capacity type sensor sheet according to claim 1 or 2, wherein the elongation rate capable of withstanding uniaxial tension is 100% or more. The capacitive sensor sheet according to any one of claims 1 to 3,
A measuring device;
Each of the front-side electrode layer and the back-side electrode layer provided in the capacitive sensor sheet, and external wiring for connecting the measuring device,
A capacitance type sensor that measures the amount of deformation strain by measuring a change in capacitance in a detection unit of the capacitance type sensor sheet.