JP6505164B2 - Capacitive sensor sheet and sensor device - Google Patents

Description

  The present invention relates to a capacitive sensor sheet and a sensor device.

In the field of rehabilitation (hereinafter referred to simply as rehabilitation), the exercise amount of a patient with motor paralysis such as paresis or hemiplegia, measurement of the movement amount and range of movement of joints, etc., heart rate of the patient at training and at rest Measurement of respiration rate etc. is performed on a daily basis.
Also in the field of medical care, monitoring of the heart rate and respiration rate of patients and elderly people requiring care is routinely performed.

As a method of measuring the amount of movement of a patient and the amount of movement of a joint or the like, a method using a ruler, a method using a goniometer, and a method using an myoelectric sensor have been adopted.
However, in these methods, although the bending condition of the elbow or knee joint can be measured, there are many places where measurement is difficult, such as movement of the scapula, movement of the hips, movement of the expression, and the like.
Also, as a method of measuring a larger movement of the body, a measurement method using motion capture has been proposed (see, for example, Patent Document 1). However, the method using motion capture requires a large scale system as a whole of the measurement system, making it difficult to carry the measurement system, making preparation before the measurement complicated, and furthermore, the shadow of the imaging means (camera) There was a problem that the movement of the becoming part could not be measured.

In addition, as a method of monitoring the heart rate and respiration rate of a patient etc. over time, for example, Patent Document 2 discloses a pair of conductive cloths having stretchability on both sides of a sheet-like dielectric which can be elastically deformed in all directions. A method has been proposed that uses a capacitive pressure sensor that is deployed and configured.
However, in the method described in Patent Document 2, in order to monitor the heart rate and the respiration rate by placing a capacitive pressure sensor under the human body in a state of lying down, in a state where the body is being moved, such as during rehabilitation training. Measurement was difficult.
In addition, since the capacitance type pressure sensor is a sensor that measures the change in capacitance due to the deformation in the thickness direction of the dielectric layer, it is difficult to measure the deformation in the surface direction of the dielectric layer in the first place. It was not possible to measure the exercise state of

WO 2005/096939 JP, 2005-315831, A

Under these circumstances, the inventors of the present invention have developed an electrostatic sensor based on a technical idea different from that of a conventional capacitive sensor as a capacitive sensor capable of tracking deformation of a living body surface. We have proposed a capacitive sensor device.
That is, it is composed of a sheet-like first dielectric layer composed of an elastomer composition, and a conductive composition containing carbon nanotubes, and at least one of the first dielectric layer is sandwiched between the surface and the back of the first dielectric layer. A first electrode layer and a second electrode layer formed to face each other, and a portion where the first electrode layer and the second electrode layer face each other is used as a detection portion; A sensor device is proposed that includes a sensor element that reversibly deforms so as to change its area, and a measuring device that measures a change in capacitance in the detection unit.

In such a sensor device, the sensor element includes a dielectric layer made of an elastomer composition and a conductive layer made of a conductive composition containing carbon nanotubes, and reversibly so that the areas of the front and back surfaces of the dielectric layer change. Deform. Therefore, for example, when the sensor element is attached to a living body to track the deformation of the surface of the living body, even if the surface of the living body is greatly deformed, the amount of deformation can be measured as the amount of change in capacitance. Therefore, with such a sensor device, the motion state of the body can be measured, and the measurement can be performed even while the body is moving, such as during rehabilitation training.
However, such a sensor element has been required to be improved in terms of sensitivity and accuracy as described below.

Generally, the capacitance (capacitance) in a capacitive sensor is expressed by the following equation (1).
C = ε ₀ ε _r S / d (1)
Here, C is a capacitance, ε 0 is a dielectric constant of free space, ε r is a dielectric constant of a dielectric layer, S is an electrode layer area, and d is a distance between electrodes.
Then, in the above sensor element, when the sensor element is deformed in the plane direction (deformed so that the areas of the front and back surfaces of the dielectric layer change), a conductive layer made of a conductive composition containing carbon nanotubes following the deformation of the dielectric layer Is deformed, that is, the value of S in the above equation (1) changes, and as a result, the value of capacitance C changes. Therefore, the deformation amount of the sensor element can be detected based on the change amount ΔC of the capacitance C.
On the other hand, when the dielectric layer extends in a uniaxial direction, the conductive layer also extends in the same direction according to the extension of the dielectric layer, and the area increases. At this time, the dielectric layer may shrink in a direction (width direction) perpendicular to the stretching direction as it stretches. Then, following the contraction in the width direction of the dielectric layer, the conductive layer may also contract in the direction (width direction) perpendicular to the extension direction. When such contraction in the width direction of the conductive layer occurs, the correlation between the amount of extension of the dielectric layer (conductive layer) and the amount of increase in the area decreases, and as a result, the measurement sensitivity and the measurement accuracy decrease. is there.
Therefore, as described above, improvement in sensitivity and accuracy is required.

The present inventors have repeatedly studied to meet such needs and completed the present invention.
The capacitance-type sensor sheet of the present invention comprises a sheet-like dielectric layer comprising an elastomer composition, and a conductive composition containing a conductive material, and the dielectric layer is sandwiched between the front and back surfaces of the dielectric layer. And a first electrode layer and a second electrode layer formed so as to at least partially face each other, wherein the opposing portion of the first electrode layer and the second electrode layer is used as a detection portion, and the front and back surfaces of the dielectric layer A sensor body which reversibly deforms so as to change its area, and a stretchable cloth fabric integrated with the sensor body, wherein the cloth fabric has stretch anisotropy. .

  In the capacitance type sensor sheet of the present invention, the cloth body is integrated with the sensor body, and the cloth cloth has stretch anisotropy. Therefore, when the sensor body is stretched in the easily stretchable direction of the fabric, the conductive layer stretches in the stretch direction but hardly stretches in the direction (width direction) perpendicular to the stretch direction. Therefore, when the sensor body is expanded, the area of the electrode layer is increased in proportion to the amount of expansion of the sensor body. As a result, in the sensor sheet of the present invention, regardless of the expansion rate of the sensor body, the expansion amount of the sensor body and the capacitance of the detection unit maintain a proportional relationship.

In the capacitance type sensor sheet according to the present invention, the fabric has a ratio of 5% modulus in the hard stretch direction to 5% modulus in the fast stretch direction ([M5 in the hard stretch direction / M5 in the easy stretch direction]) It is preferably 10 or more.
In the capacitive sensor sheet, the conductive material is preferably at least a carbon nanotube.
Further, in the above-mentioned capacitance type sensor sheet, it is preferable that the above-mentioned elastomer composition contains urethane rubber.

A sensor device according to the present invention is characterized by including the capacitance-type sensor sheet according to the present invention, and a measuring device for measuring a change in capacitance in the detection unit.
Since the sensor device of the present invention includes the capacitance-type sensor sheet of the present invention, it is possible to accurately measure the amount of deformation of a non-measurement object based on the amount of change in capacitance of the sensor sheet. it can.

  According to the present invention, it is possible to provide a capacitive sensor sheet and a sensor device for measuring the amount of deformation of an object to be measured with high sensitivity and high accuracy.

It is the schematic which shows an example of the sensor apparatus of this invention. (A) is a perspective view which shows typically an example of the sensor main body which comprises the capacitance-type sensor sheet | seat of this invention, (b) is the sectional view on the AA line of (a). (A) is a perspective view which shows typically an example of the electrostatic capacitance type sensor sheet | seat of this invention, (b) is a BB sectional drawing of (a). (A) is a perspective view which shows typically another example of the sensor main body which comprises the capacitance-type sensor sheet | seat of this invention, (b) is CC sectional view taken on the line of (a) . 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 | seat of this invention is equipped. (A)-(c) is a perspective view for demonstrating the preparation processes of the sensor main body in an Example. (A)-(d) is a perspective view for demonstrating the preparation processes of the electrostatic capacitance type sensor sheet in an Example. It is a graph which shows the measurement result of the electrostatic capacitance at the time of making the electrostatic capacitance type sensor sheet | seat of Example 1 reciprocate extension operation. It is a graph which shows the measurement result of the electrostatic capacitance at the time of making the electrostatic capacitance type sensor sheet | seat of Example 2 reciprocate extension operation. It is a graph which shows the measurement result of the electrostatic capacitance at the time of making the electrostatic capacitance type sensor sheet | seat of the comparative example 1 reciprocate extension operation. It is a graph which shows the measurement result of the electrostatic capacitance at the time of making the electrostatic capacitance type sensor sheet | seat of the comparative example 2 reciprocate extension operation. It is a graph which shows the measurement result of the electrostatic capacitance at the time of making the electrostatic capacitance type sensor sheet | seat of the comparative example 3 reciprocate extension operation. It is a graph which shows the measurement result of the electrostatic capacitance at the time of making the electrostatic capacitance type sensor sheet | seat of the comparative example 4 reciprocate extension operation.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The capacitive sensor sheet (hereinafter, also simply referred to as a sensor sheet) of the present invention comprises a sheet-like dielectric layer comprising an elastomer composition and a conductive composition comprising a conductive material, and the surface of the dielectric layer and It has a first electrode layer and a second electrode layer formed on each of the back surfaces so as to at least partially face each other with the dielectric layer interposed therebetween, and detects the facing portion of the first electrode layer and the second electrode layer A sensor body that reversibly deforms so as to change the area of the front and back surfaces of the dielectric layer, and a stretchable cloth fabric integrated with the sensor body; It has the directionality.
A sensor device of the present invention includes the capacitance-type sensor sheet of the present invention, and a measuring device that measures a change in capacitance in the detection unit.

FIG. 1 is a schematic view showing an example of a sensor device of the present invention, and provided with a capacitive sensor sheet of the present invention.
Fig.2 (a) is a perspective view which shows typically an example of the sensor main body which comprises the capacitance-type sensor sheet | seat of this invention, (b) is the sectional view on the AA line of (a).
Fig.3 (a) is a perspective view which shows an example of an electrostatic capacitance type sensor sheet provided with the sensor main body shown in FIG. 2, (b) is a BB sectional drawing of (a).

  As shown in FIG. 1, the sensor device 1 according to the present invention displays the measurement result of the sensor sheet 2 according to the present invention, the measuring device 3 electrically connected to the sensor sheet 2, and the measuring device 3. And a display 4 for the user.

As shown in FIGS. 3A and 3B, the sensor sheet 2 includes a sensor body 10 and a cloth fabric 20A having stretch anisotropy laminated on both sides (front and back sides) of the sensor body 10, Includes 20B.
As shown in FIGS. 2A and 2B, the sensor body 10 has a sheet-like dielectric layer 11 made of an elastomer composition and a front side electrode layer 12A formed on the surface (front side) of the dielectric layer 11. , Back side electrode layer 12B formed on the back side of dielectric layer 11, front side wiring 13A connected to front side electrode layer 12A, back side wiring 13B connected to back side electrode layer 12B, and front side electrode layer of front side wiring 13A A front side connection portion 14A attached to the end opposite to 12A, a back side connection portion 14B attached to the end opposite to the back side electrode layer 12B of the back side wiring 13B, and a front side and a back side of the dielectric layer 11 And a front side protective layer 15A and a rear side protective layer 15B laminated to each other.

Here, the front side electrode layer 12A and the back side electrode layer 12B have the same shape in plan view, and the whole of the front side electrode layer 12A and the back side electrode layer 12B oppose each other with the dielectric layer 11 interposed therebetween. In the sensor main body 10, the opposing portion of the front side electrode layer 12A and the back side electrode layer 12B serves as a detection unit.
In the present invention, the front side electrode layer and the rear side electrode layer provided in the sensor main body do not necessarily have to be opposed to each other across the dielectric layer, and at least a part thereof may be opposed.
In the sensor main body 10, the front side electrode layer 12A corresponds to the first electrode layer, and the back side electrode layer 12B corresponds to the second electrode layer.

In the sensor body 10, since the dielectric layer 11 is made of an elastomer composition, it can be deformed (stretched) in the surface direction, and when the dielectric layer 11 is deformed in the surface direction, the surface side electrode layer 12A follows the deformation. The back side electrode layer 12B, and the front side protective layer 15A and the back side protective layer 15B (hereinafter both are simply referred to as a protective layer) are deformed.
Then, with the deformation of the sensor main body 10, the capacitance of the detection unit changes in correlation with the amount of deformation of the dielectric layer 11 (change in area of the electrode layer). Therefore, in the sensor device 1, the deformation amount of the sensor sheet 2 can be detected by detecting the change in the capacitance of the detection unit.
Furthermore, in the sensor device 1, since the sensor sheet 2 is provided with a cloth to be described later, the amount of deformation in the axial direction of the sensor main body 10 is substantially detected by detecting a change in capacitance of the detection unit. can do.

The cloth fabrics 20A and 20B are respectively laminated on the front and back sides of the sensor body 10 via an adhesive layer (not shown).
Here, the cloths 20A and 20B are both cloths having expansion anisotropy, and are laminated so as to cover the entire detection unit when the sensor sheet 2 is viewed in plan. Further, the cloth fabrics 20A and 20B are stacked so that the longitudinal direction (left and right direction in the drawing) of the sensor main body 10 is the easy stretch direction, and the direction perpendicular to the longitudinal direction is the hard stretch direction.

The sensor sheet 2 includes a non-stretchable member 21 and handles 22A and 22B.
These are optional members, and the capacitive sensor sheet of the present invention does not necessarily have to be provided.
The non-stretchable member 21 is stacked on the upper surface of the sensor main body 10 and does not overlap with the detection portion when the sensor sheet 2 is viewed in plan, and at least the front side wiring 13A and the back side wiring 13B, and the front side connecting portion 14A. And the back side connection part 14B.
In the sensor sheet 2 provided with such a non-stretchable member 21, when the sensor sheet 2 is stretched, the detection portion of the sensor main body stretches, and the portion of the sensor body covered with the non-stretchable member 21 stretches Since it becomes difficult to do so, the expansion and contraction of the detection unit more reliably reflects the deformation of the object to be measured. Therefore, when the sensor sheet 2 is provided with the non-stretchable member 21, the sensor device 1 has more excellent measurement sensitivity.

The grips 22A and 22B are disposed at both ends of the sensor main body 10 in the direction of easy extension and contraction, and are held by two cloth fabrics 20A and 20B.
The handle 22A, 22B has a role to be gripped by the user or to fix the sensor sheet at a predetermined position when the sensor sheet 2 is extended or retracted.

  In the sensor sheet 2, the cloth fabrics 20A and 20B have stretch anisotropy. Therefore, when the sensor body 10 extends in the longitudinal direction, the sensor body 10 can be prevented from contracting in the direction (width direction) perpendicular to the longitudinal direction as the amount of extension increases. As a result, in the sensor sheet 2, the capacitance of the detection unit increases according to the amount of extension of the sensor body 10, and the correlation (proportional relationship) between the amount of extension and the capacitance is the amount of extension of the sensor body 10 Is maintained, or when the sensor body is repeatedly extended and contracted. Therefore, the sensor device 1 can measure the amount of extension of the sensor main body 10 with high sensitivity and high accuracy.

  The measuring instrument 3 includes a Schmitt trigger oscillation circuit 3a for converting the capacitance C into the frequency signal F, an F / V conversion circuit 3b for converting the frequency signal F into the voltage signal V, and a power supply circuit (not shown) After the capacitance C detected by the detection unit of the sensor sheet 2 is converted into the frequency signal F, the capacitance C is further converted into the voltage signal V and transmitted to the display 4. In addition, the structure of the measuring device 3 is not necessarily limited to such a structure so that it may mention later.

The display unit 4 includes a monitor 4a, an arithmetic circuit 4b, and a storage unit 4c, and causes the monitor 4a to display a change in the capacitance C of the detection unit measured by the measuring instrument 3. Store changes as recorded data.
The display 4 may calculate the amount of deformation of the object to be measured by the arithmetic circuit 4b based on the voltage signal V received from the measuring instrument 3 and display the amount of deformation of the object to be measured on the monitor 4a.
As the display 4, a computer provided with a storage unit such as a CPU, a RAM, a ROM, and an HDD, a monitor, various input / output interfaces, and the like can be used.

Such a sensor device 1 can be used by attaching the sensor sheet 2 to an object to be measured.
Therefore, the adhesive layer for sticking the sensor sheet 2 to a measurement object may be formed in the outermost layer of the sensor sheet 2.

  The sensor device 1 can track the deformation of the living body surface, for example, by sticking the sensor sheet 2 on the living body surface and using it. At this time, the sensor sheet 2 may be directly attached to the surface of the living body, or may be indirectly attached to the surface of the living body via a covering material for covering the surface of the living body such as clothes, a supporter or a bandage.

  When the sensor sheet 2 is used by sticking on the surface of a living body such as skin, the sensor sheet stretches and contracts following the deformation (elongation, atrophy, expansion, contraction, etc.) of the surface of the living body, Accordingly, the capacitance of the detection unit changes. Therefore, the sensor device 1 can measure the amount of deformation of the surface of the living body by measuring the capacitance of the detection unit. Then, by measuring the amount of deformation of the surface of the living body, it is possible to acquire life activity information and motion information of the living body correlated with the deformation of the surface of the living body.

In the sensor device of the present invention, for example, a pulse rate (heart rate), a respiration rate, a size of respiration, etc. can be measured as the life activity information.
Further, the motion information of the living body is not particularly limited, and the motion state can be measured by the sensor device if the motion of the surface of the living body is extended and contracted by contraction of the muscle during the exercise. Specifically, for example, the amount of bending when bending a joint (bending angle), movement of cheeks during pronunciation / uttering, movement of expression muscles, movement of shoulder blades, movement of masticatory muscles, movement of back, waist Bending, chest swelling, thigh and calf contraction due to muscle contraction, throat movement during swallowing, foot movement, hand movement, finger movement, sole movement, blink movement, skin It is possible to measure the ease of growth of the

  When measuring the pulse rate (heart rate) with the above-mentioned sensor device, affix the sensor sheet to the place where the pulse on the surface of the living body touches (for example, radial artery, carotid artery etc.) and measure the capacitance for a predetermined time By continuing to do so, you can get your heart rate. This is because the skin expands and contracts in accordance with the pulse, and the number of expansions and contractions becomes the pulse rate.

  When the respiration rate is measured by the above-mentioned sensor device, the respiration rate can be acquired by sticking the sensor sheet on a chest part or the like on the surface of the living body and measuring the capacitance for a predetermined time. This is because the chest skin stretches in response to breathing, and the number of stretchings matches the breathing rate.

  When measuring the bending amount of a joint with the above-mentioned sensor device, a sensor sheet is stuck on a measuring object site, and the amount of bending of a measuring object site is acquired by measuring capacitance while moving the measuring object site. Can. This is because the skin of that portion expands and contracts in accordance with the movement of the measurement target portion, and the bending amount of the measurement target portion can be calculated from the amount of expansion and contraction.

In addition, when the sensor sheet is attached to the periphery of the mouth (such as a cheek) and the capacitance is measured while uttering in that state (or while attempting to utter even if it is not possible to actually utter it). Since the skin around the mouth is deformed according to the type of the vocalization, the capacitance changes in accordance with the deformation of the skin. Therefore, it is possible to obtain correlation information between the movement of the skin around the mouth at the time of speech, the value of the capacitance, and the manner of the change.
This allows, for example, the following.
As training of the expression muscle, for example, by attaching the sensor sheet symmetrically, it is possible to quantitatively measure the movement of the skin or to visualize in real time. Therefore, while looking at the left and right signal waveforms, it is possible to consciously train so that the signals overlap, or to perform rehabilitation training to restore function to a symmetrical natural expression.

  In addition, attach the sensor sheet to the ankles or the back of the foot, and measure the capacitance while performing exercises such as "step on", "jump", "stand on toe", "rest" in this state. In this case, the skin is deformed in response to the movement of the foot, and the capacitance is changed in accordance with the deformation of the skin. Therefore, the movement of the foot can be identified based on the value of the capacitance and the manner of the change.

  In addition, attach the above sensor sheet to the palm or the back of the hand, and in that state, while doing exercises such as "open hand", "close hand", "put an arbitrary finger", "do jerking" etc. When the capacitance is measured, the skin is deformed according to the movement of the hand, and the capacitance is changed according to the deformation of the skin. Therefore, the movement of the hand can be identified based on the value of the capacitance and the manner of change.

As described above, in the sensor device of the present invention, various life activity information and motion information of the living body can be measured by sticking the sensor sheet on the surface of the living body such as the skin and using it.
When measuring life activity information and motion information of a living body using the above-mentioned sensor device, the relationship between the type of motion and the value of capacitance and the manner of the change is acquired in advance as calibration information for each living body to be measured It is preferable to keep it. This is because even if there are individual differences, it can be measured more accurately.

Further, when the sensor sheet 2 is used by being attached via a covering material such as clothes or a supporter, deformation information of the covering material can also be measured.
For example, if the above sensor sheet is attached to a training underwear and exercise is performed in that state, the training underwear fabric is stretched or returned to its original state following the movement of the body. Deform. Therefore, the capacitance changes in accordance with the deformation (stretching) of the fabric. Therefore, in the above-mentioned sensor device, the deformation of the training underwear (covering material) can be measured based on the value of the capacitance and the manner of change.

The sensor device of the present invention may comprise a plurality of sensor sheets. In this case, the same type of information may be obtained at different points simultaneously, or different types of information may be obtained simultaneously.
When two or more sensor sheets are provided, for example, the sensor sheet is attached to the body symmetrically on the left and right (for example, the back of the right foot and the back of the left foot), and foot stepping is performed in that state. Can measure the balance of the movement of
Also, for example, by attaching sensor sheets to the left and right ankles, knee joints, and hip joints respectively and walking in that state, balance of movement of the left and right feet, bending amount of each movable part, movement of each movable part The rhythm can be measured. Furthermore, more advanced walking motion information can also be obtained by using in combination with existing walking measurement devices such as shoe-shaped or mat-shaped pressure distribution sensor products, for example.
These pieces of information are useful as information for determining the menu of sports training and rehabilitation training.

Of course, the method of using the sensor device of the present invention is not limited to the above-described method of applying to the surface of a living body. The sensor device may be, for example, an expander, a rehabilitation tube, a rubber ball, a rubber balloon, an elastic material such as an air bag, or a flexible material such as a cushion or a shoe inner, and the like. Can also be used as a sensor device for measuring the deformation of a measurement object.
Further, in the sensor device of the present invention, the sensor sheet can be used as a substitute for the interface of the myoelectric sensor of the electric prosthetic hand.
Further, in the sensor device of the present invention, the sensor sheet can also be used as an input terminal of an input interface of a person with severe physical and mental disabilities.
In the sensor device of the present invention, the sensor sheet may be attached to the finger of a glove, and the glove may be used as a glove type interface of a virtual device or the like.

In the capacitance type sensor sheet according to the present invention, the sensor main body includes the second dielectric layer and the third dielectric layer in addition to the first electrode layer and the second electrode layer formed on the dielectric layer (first dielectric layer) and both surfaces thereof. An electrode layer may be provided.
Fig.4 (a) is a perspective view which shows typically another example of the sensor main body which comprises the capacitance-type sensor sheet | seat of this invention, (b) is CC sectional view taken on the line of (a) It is.
The sensor main body 40 shown in FIGS. 4 (a) and 4 (b) has a sheet-shaped first dielectric layer 41A made of an elastomer composition and a first surface formed on the surface (front surface) of the first dielectric layer 41A. An electrode layer 42A, a second electrode layer 42B formed on the back surface of the first dielectric layer 41, a second dielectric layer 41B laminated to cover the first electrode layer 42A on the front side of the first dielectric layer 41A; And a third electrode layer 42C formed on the surface of the second dielectric layer 41B. Furthermore, the sensor main body 40 includes a first wire 43A connected to the first electrode layer 42A, a second wire 43B connected to the second electrode layer 42B, and a third wire 43C connected to the third electrode layer 42C. A first connection portion 44A attached to an end of the first wire 43A opposite to the first electrode layer 42A, and a second connection 43B attached to an end of the second wire 43B opposite to the second electrode layer 42B. A second connection portion 44B and a third connection portion 44C attached to an end of the third wiring 43C opposite to the third electrode layer 42C. Further, in the sensor body 40, a back side protective layer 45B and a front side protective layer 45A are provided on the back side of the first dielectric layer 41A and the front side of the second dielectric layer 41B.

  Here, the first to third electrode layers 42A to 42C have the same shape in plan view. In addition, the entire first electrode layer 42A and the second electrode layer 42B face each other with the first dielectric layer 41A interposed therebetween, and the first electrode layer 42A and the third electrode layer 42C sandwich the second dielectric layer 41B. The whole is opposite. In the sensor main body 40, a portion where the first electrode layer 42A and the second electrode layer 42B face each other, and a portion where the first electrode layer 42A and the third electrode layer 42C face each other serve as a detection portion. The sum of the capacitance of the facing portion of the second electrode layer 42B and the capacitance of the facing portion of the first electrode layer 42A and the third electrode layer 42C is the capacitance of the detection unit.

A sensor sheet provided with such a sensor main body 40 is suitable for eliminating a measurement error due to noise and for more accurately measuring a change in capacitance.
I will explain this in more detail. In the case of tracking the deformation of the living body surface using the sensor device of the present invention, the living body surface is a conductor, so the living body surface comes in direct contact with the electrode layer as well as the protective layer. Contact or proximity to the living body itself causes noise.
On the other hand, in the sensor device provided with the sensor sheet having the sensor main body 40, the measurement error due to the noise can be more reliably eliminated. Moreover, the sensor sheet of the structure shown in FIG. 4 can be used without distinction of front and back.

Hereinafter, each member provided in the capacitance type sensor sheet of the present invention will be described in detail.
<Sensor sheet>
<< Dielectric layer >>
The dielectric layer is a sheet made of an elastomer composition, and can be reversibly deformed so as to change the area of its front and back surfaces. In the present invention, the front and back surfaces of the sheet-like dielectric layer mean the front and back surfaces of the dielectric layer.
As said elastomer composition, what contains an elastomer and the other option component as needed is mentioned.
Examples of the elastomer include natural rubber, isoprene rubber, nitrile rubber (NBR), ethylene propylene rubber (EPDM), styrene butadiene rubber (SBR), butadiene rubber (BR), chloroprene rubber (CR), silicone rubber, fluorine Rubber, acrylic rubber, hydrogenated nitrile rubber, urethane rubber and the like can be mentioned. These may be used alone or in combination of two or more.
Among these, urethane rubber and silicone rubber are preferable. It is because permanent set (or permanent set) is small. Furthermore, urethane rubber is particularly preferable in terms of excellent adhesion to carbon nanotubes as compared to silicone rubber.

  The urethane rubber is formed by reacting at least a polyol component and an isocyanate component, and as a specific example, for example, an olefin-based urethane rubber containing an olefin-based polyol as a polyol component, and an ester containing an ester-based polyol as a polyol component Examples thereof include urethane rubbers, ether-based urethane rubbers having an ether-based polyol as a polyol component, carbonate-based urethane rubbers having a carbonate-based polyol as a polyol component, and castor oil-based urethane rubbers having a castor oil-based polyol as a polyol component. These may be used alone or in combination of two or more. Moreover, the said urethane rubber may use together 2 or more types of said polyol components.

Examples of the olefin-based polyol include Epol (manufactured by Idemitsu Kosan Co., Ltd.).
Moreover, as said ester type polyol, Polylight 8651 (made by DIC Corporation) etc. are mentioned, for example.
Moreover, as said ether type polyol, for example, polyoxy tetramethylene glycol, PTG-2000SN (made by Hodogaya Chemical Industry Co., Ltd.), polypropylene glycol, Preminor S3003 (made by Asahi Glass Co., Ltd.), Pandex GCB-41 (made by DIC company) Etc.

It does not specifically limit as said isocyanate component, The conventionally well-known isocyanate component can be used.
Moreover, when synthesizing the above-mentioned urethane rubber, a chain extender, a crosslinking agent, a catalyst, a vulcanization accelerator and the like may be added to the reaction system, if necessary.

  Further, the elastomer composition may contain, in addition to the elastomer, additives such as a plasticizer, an antioxidant, an antiaging agent, a coloring agent, a dielectric filler and the like.

  The average thickness of the dielectric layer is preferably 10 to 1000 μm from the viewpoint of increasing the capacitance C to improve the detection sensitivity and improving the followability to the object to be measured, It is more preferable that it is 30-200 micrometers.

The dielectric layer is preferably deformable so that the length increases by 30% or more in the uniaxial direction. This is because a dielectric layer having such characteristics is suitable for following and deforming a measurement object when it is used by being attached to the measurement object.
Here, being able to deform so as to increase the length by 30% or more means that even if the length is increased by 30% when the dielectric layer is elongated by applying a load (the elongation is taken as 30%) It means that it does not do, and when the load is released, it restores to its original state (ie in the elastic deformation range).
The extensible elongation in the uniaxial direction of the dielectric layer is more preferably 50% or more, still more preferably 100% or more, and particularly preferably 200% or more.
The stretchable expansion rate in the uniaxial direction of the dielectric layer can be controlled by the design (material, shape, etc.) of the dielectric layer.

  The relative dielectric constant at normal temperature of the dielectric layer is preferably 2 or more, more preferably 5 or more. If the dielectric constant of the dielectric layer is less than 2, the capacitance C may be small, and sufficient sensitivity as a sensor sheet may not be obtained.

  The Young's modulus of the dielectric layer is preferably 0.1 to 10 MPa. If the Young's modulus is less than 0.1 MPa, the dielectric layer may be too soft, high quality processing may be difficult, and sufficient measurement accuracy may not be obtained. On the other hand, when the Young's modulus exceeds 10 MPa, the dielectric layer is too hard, and when the object to be measured is about to be deformed, the deformation may be inhibited.

The hardness of the dielectric layer is a hardness (JIS A hardness) using a type A durometer according to JIS K 6253, or 0 to 30 °, or a type C durometer according to JIS K 7321. The hardness used (JIS C hardness) is preferably 10 to 55 °.
If the dielectric layer is too soft, high-quality processing may be difficult, and sufficient measurement accuracy may not be ensured. If the dielectric layer is too hard, the deformation of the object to be measured is impeded. There is a fear.

  When the sensor sheet has a plurality of dielectric layers, each dielectric layer does not necessarily have to be composed of an elastomer composition of the same composition, but it is preferred to be composed of an elastomer composition of the same composition . It is because it shows the same behavior at the time of expansion and contraction.

<< Electrode layer >>
The electrode layer is made of a conductive composition containing a conductive material.
Here, each of the electrode layers may be composed of conductive compositions of the same composition, or may be composed of conductive compositions of different compositions. However, it is preferable to be comprised from the conductive composition of the same composition.
Examples of the conductive material include carbon nanotubes, graphene, carbon nanohorns, carbon fibers, conductive carbon black, graphite, metal nanowires, metal nanoparticles, conductive polymers, and the like. These may be used alone or in combination of two or more.
As the conductive material, carbon nanotubes are preferable. This is because it is suitable for the formation of an electrode layer which deforms following the deformation of the dielectric layer.

A well-known carbon nanotube can be used as said carbon nanotube, A single-walled carbon nanotube (SWNT) may be used, Moreover, the double-walled carbon nanotube (DWNT) or the multilayer carbon nanotube (MWNT) of three or more layers (In the present specification, both are simply referred to simply as multi-walled carbon nanotubes). Furthermore, two or more types of carbon nanotubes having different numbers of layers may be used in combination.
Further, the shape (average length, fiber diameter, aspect ratio) of each carbon nanotube is not particularly limited, either, and the purpose of use of the sensor device, conductivity and durability required for the sensor sheet, and an electrode layer are formed. It is sufficient to judge the treatment and cost for the purpose comprehensively and select it appropriately.

10 micrometers or more are preferable and, as for the average length of the said carbon nanotube, 50 micrometers or more are more preferable. The electrode layer formed using carbon nanotubes having such a long fiber length is excellent in conductivity, and the electric resistance hardly increases when it is deformed following the deformation of the dielectric layer (particularly when it is elongated). Furthermore, even if it is repeatedly expanded and contracted, it is because it has the outstanding characteristic that variation in electrical resistance is small.
On the other hand, if the average length of the carbon nanotubes is less than 10 μm, the electrical resistance may increase with the deformation of the electrode layer, or the electrical resistance may increase when the electrode layer is repeatedly expanded and contracted. . Such a problem is likely to occur particularly when the amount of deformation of the sensor sheet (dielectric layer) increases.

  The preferred upper limit of the average length of the carbon nanotubes is 1000 μm. Carbon nanotubes having an average length of more than 1000 μm are currently difficult to manufacture and obtain. Also, as described later, when the electrode layer is formed by applying a carbon nanotube dispersion liquid, the conductive path is difficult to be formed because the dispersibility of the carbon nanotube is insufficient, and as a result, the conductivity of the electrode layer is There is concern that it will be insufficient.

  The lower limit of the average length of the carbon nanotubes is more preferably 100 μm, and the upper limit is more preferably 600 μm. When the average length of the carbon nanotube is in the above range, the excellent properties such as excellent conductivity, little increase in electrical resistance at the time of elongation, and small variation in electrical resistance at the time of repeated expansion and contraction are obtained at a high level It can be secured securely.

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

Although the average fiber diameter of the said carbon nanotube is not specifically limited, 0.5-30 nm is preferable.
If the fiber diameter is less than 0.5 nm, the dispersion of carbon nanotubes will be poor, as a result, the conductive path may not spread and the conductivity of the electrode layer may be insufficient. However, the number of carbon nanotubes may decrease and the conductivity may be insufficient. The average fiber diameter of the carbon nanotube is more preferably 5 to 20 nm.

Among 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-described preferable range are used, the electric resistance is increased, the electric resistance is greatly increased at the time of elongation, or the electric resistance is at the time of repeated expansion and contraction. It may vary widely.
I guess about this as follows. That is, since single-walled carbon nanotubes are usually synthesized as a mixture of metallic carbon nanotubes and semiconductive carbon nanotubes, the presence of the semiconductive carbon nanotubes may increase the electrical resistance or increase the electrical resistance at the time of elongation. It is presumed that the cause of the increase or the large variation in electrical resistance at the time of repeated expansion and contraction.
If metallic carbon nanotubes and semiconductive carbon nanotubes are separated and metallic single-walled carbon nanotubes with long average length are used, the same electric characteristics as in the case of using multi-walled carbon nanotubes with long average length are obtained. There is a possibility that the provided electrode layer can be formed. However, separation of metallic carbon nanotubes and semiconductive carbon nanotubes is not easy (especially in carbon nanotubes with a long fiber length), and separation of both requires complicated work, so an electrode layer is formed. As described above from the viewpoint of ease of work and economy, the multi-walled carbon nanotube is preferable as the carbon nanotube.

  The carbon nanotube preferably has a carbon purity of 99% by weight or more. A carbon nanotube may contain a catalyst metal, a dispersing agent, etc. in its manufacturing process, and when carbon nanotubes containing a large amount of components (impurities) other than such carbon nanotubes are used, the conductivity is lowered 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 one of the CVD methods, and is a method of producing a carbon nanotube by growing a metal catalyst coated on a substrate by supplying a carbon source. 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 a relatively long fiber length and a uniform fiber length.
When the carbon nanotube is manufactured by the substrate manufacturing method, the fiber length of the carbon nanotube is substantially the same as the growth length of the CNT forest, and when the fiber length is measured using an electron microscope, The growth length of the CNT forest may be measured.

The conductive composition may contain, for example, a binder component in addition to the conductive material such as carbon nanotubes.
The binder component functions as a connecting 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, the electrode layer is formed by the method described later. Since scattering of a conductive material such as a carbon nanotube can be suppressed when carrying out, safety when forming an electrode layer can also be enhanced.

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 above-mentioned binder component, crude rubber (natural rubber and synthetic rubber in a non-vulcanized state) can also be used, and by using such a material having relatively weak elasticity, deformation of the dielectric layer can be achieved. Can also be enhanced.
The binder component is particularly preferably the same as the elastomer constituting the dielectric layer. This is because the adhesion between the dielectric layer and the electrode layer can be significantly improved.

The conductive composition may further contain various additives in addition to the conductive material such as carbon nanotube and the binder component. Examples of the additive include a dispersant for enhancing the dispersibility of the conductive material, a crosslinking agent for the binder component, a vulcanization accelerator, a vulcanization assistant, and an anti-aging agent, a plasticizer, and a softener. And colorants.
In the sensor sheet, when the conductive material is a carbon nanotube, the electrode layer may be substantially formed only of the carbon nanotube. Also in this case, sufficient adhesion can be secured between the dielectric layer and the carbon nanotube and the dielectric layer are firmly adhered by van der Waals force or the like.

The content of the carbon nanotube in the electrode layer is not particularly limited as long as it is a concentration at which conductivity is exhibited, and when it contains a binder component, although it varies depending on the type of the binder component, It is preferable that it is 0.1 to 100 weight%.
In addition, if the content of carbon nanotubes is increased, the conductivity of the electrode layer can be improved. Therefore, the required conductivity can be ensured even if the electrode layer is made thin, and as a result, it becomes 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 in the above range, the electrode layer can exhibit more 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 as a sensor sheet may decrease. On the other hand, if it exceeds 10 μm, the sensor sheet may be reinforced by the reinforcing effect of a conductive material such as carbon nanotube. As a result, the elasticity of the sensor sheet may be reduced, and deformation of the surface of the living body may be inhibited when the sensor sheet is attached to the surface of the living body directly or through a covering material.

  In the present invention, the “average thickness of the electrode layer” can be measured, for example, using a laser microscope (for example, VK-9510 manufactured by Keyence Corporation). Specifically, the thickness direction of the electrode layer formed on the surface of the dielectric layer is scanned in steps of 0.01 μm, and the 3D shape is measured, and then the region where the electrode layer on the dielectric layer is stacked and the lamination In the non-area, the average height of the rectangular area of 200 × 200 μm may be measured, and the step of the average height may be the average thickness of the electrode layer.

<< Fabric cloth >>
The above fabric has stretch anisotropy. The above-mentioned stretch anisotropy means a property in which the degree of stretchability differs significantly depending on the direction, that is, a property in which it is easy to stretch in one direction and hardly stretches in a direction substantially orthogonal to the one direction.
In the present specification, the above-mentioned stretchable direction is referred to as a direction of easy extension and contraction, and the above-mentioned direction of hardly stretch is referred to as a direction of difficult stretch.
The fabric is not particularly limited as long as it has stretch anisotropy, and may be a woven fabric, a knitted fabric, or a non-woven fabric.

The above fabric has a ratio of 5% modulus in the difficult stretch direction to 5% modulus in the easy stretch direction ([M5 in the hard stretch direction / M5 in the easy stretch direction, hereinafter also referred to as “anisotropic M5”), It is preferably 5 or more, more preferably 10 or more.
By using a cloth with a large anisotropy M5, the sensitivity and accuracy of the sensor sheet can be further improved.
As for the said anisotropy M5, 100 or more are more preferable, and 150 or more are still more preferable.
Moreover, the upper limit of the said anisotropy M5 is not specifically limited, It is so preferable that it is large.

  On the other hand, even in the case of a stretchable fabric, a fabric having a small difference between stretchability in one direction and stretchability in a direction substantially orthogonal to the one direction, specifically, it is relatively elongated A fabric having a ratio of a 5% modulus in a direction substantially perpendicular to the one direction to a 5% modulus in one easy direction is less than 2 in the present invention does not correspond to the stretch anisotropic fabric in the present invention, and the present specification The book says stretchy isotropic cloth.

The modulus of the fabric is preferably greater than the modulus of the sensor body at the maximum service elongation of the sensor body.
In the capacitance type sensor sheet of the present invention, the use extension rate of the sensor main body can be arbitrarily selected according to the amount of deformation of the measurement object. For example, if the extension rate of the sensor body is up to 200% by deformation of the measurement object, the maximum use extension rate of the sensor body can be 200%.
On the other hand, when the object to be measured is significantly deformed beyond the user's (measured person's) expected range, for example, the sensor main body exceeds 200% when the sensor main body having a maximum use elongation rate of 200% is used. When the object to be measured is largely deformed so as to extend, the sensor body may be damaged.
Here, when the fabric has a modulus higher than that of the sensor body at the maximum use elongation rate (for example, 200%) of the sensor body (for example, 200% modulus of the fabric is 200% of the sensor body) In the case of being larger than the modulus), the cloth can function as a stopper for suppressing the extension beyond the tolerance of the sensor body, and the sensor body can be prevented from being broken.

In the sensor sheet, it is preferable that the cloth be formed so as to cover the entire detection unit when the sensor sheet is viewed in plan.
Thereby, the contraction in the direction (width direction) perpendicular to the extension direction of the sensor body can be reliably suppressed.

  In the sensor sheet, as shown in FIGS. 2 and 3, the cloth may be provided on both sides of the sensor body, or may be provided on only one side of the sensor body.

In the sensor sheet, the cloth is integrated with the sensor body using, for example, an adhesive.
Examples of the pressure-sensitive adhesive include acrylic pressure-sensitive adhesives, urethane-based pressure-sensitive adhesives, rubber-based pressure-sensitive adhesives, silicone-based pressure-sensitive adhesives and the like.
Here, each adhesive may be of a solvent type, an emulsion type, or a hot melt type. The pressure-sensitive adhesive may be appropriately selected and used according to the use mode and the like of the sensor device. However, the pressure-sensitive adhesive needs to have flexibility not to inhibit the expansion and contraction of the dielectric layer.

<< Others >>
As in the example shown in FIGS. 2 and 3, the sensor sheet is formed with the first wiring (front side wiring), the second wiring (back side wiring), and the third wiring connected to the electrode layer as needed. It may be
Each of these wirings does not inhibit the deformation of the dielectric layer, and may be any one as long as the conductivity is maintained even if the dielectric layer is deformed. As a specific example thereof, for example, the same as the electrode layer What consists of an electroconductive composition is mentioned.
Furthermore, as in the example shown in FIGS. 2 and 3, the first connection portion (front side connection for connection to the external wiring) is provided at the end of each of the above described wirings on the opposite side to the electrode layer. Part), the 2nd connection part (back side connection part), and the 3rd connection part may be formed. As each of these connection parts, what was formed, for example using copper foil etc. is mentioned.

As in the example shown in FIGS. 2 and 4, the sensor body may have a protective layer laminated on the outermost layer on the front side and / or the back side, if necessary. By providing the protective layer, it is possible to protect a conductive portion (electrode layer and the like) of the sensor sheet, and to enhance the strength and durability of the sensor sheet.
The material of the protective layer is not particularly limited, and may be appropriately selected according to the required characteristics. Specific examples thereof include, for example, the same elastomer composition as the material of the dielectric layer.

The adhesive layer may be formed in the outermost layer on the back side of the sensor sheet. Thereby, the said sensor sheet can be stuck on measurement object objects, such as a biological body surface, through the adhesion layer.
It does not specifically limit as said adhesion layer, For example, the layer which consists of an acrylic adhesive, a urethane adhesive, a rubber adhesive, a silicone adhesive etc. is mentioned.
Here, each adhesive may be of a solvent type, an emulsion type, or a hot melt type. The pressure-sensitive adhesive may be appropriately selected and used according to the use mode and the like of the sensor device. However, the pressure-sensitive adhesive layer needs to have flexibility not to inhibit the expansion and contraction of the dielectric layer.

The said sensor sheet may be equipped with the non-stretchable member so that parts (wiring and a connection part) other than the detection part of a sensor main body may be covered like the example shown in FIG. As described above, the measurement sensitivity is further improved.
The non-stretchable member is not particularly limited as long as it is made of a non-stretchable material, and examples thereof include non-stretchable cloth, non-stretchable resin sheet, and the like.

The sensor sheet may be equipped with a handle as required, as in the example shown in FIG.
The material and shape of the handle are not particularly limited as long as the performance of the sensor main body is not impaired, and may be appropriately selected in consideration of the use mode.

  The above-mentioned electrode at the time of 100% extension of the second cycle when 1000 cycles of expansion and contraction in which the above-mentioned sensor sheet is extended 100% in a uniaxial direction and then returned to the non-extension state as one cycle. Change rate of the electrical resistance of the electrode layer at 100% elongation at 1000th cycle to the electrical resistance of the layer ([Electric resistance at 100% elongation at 1000th cycle]-[2nd cycle, at 100% elongation] It is preferable that the absolute value of the electric resistance value] / [the electric resistance value at 100% elongation in the second cycle] × 100) be small. Specifically, it is preferably 10% or less, more preferably 5% or less.

  Here, the reason for evaluating the electrical resistance of the electrode layer after the second cycle instead of the first cycle is that the electrode at the time of extension in the first extension (first cycle) extended from the unstretched state This is because the behavior of the layer (the manner of the change of the electrical resistance) is largely different from that at the time of expansion and contraction after the second cycle (the second cycle). It is presumed that the reason for this is that the state of carbon nanotubes and the like constituting the electrode layer is stabilized only by stretching once after the sensor sheet is manufactured.

The sensor sheet can be manufactured, for example, through the following steps. Here, the case where an electrode layer is formed using a conductive composition containing carbon nanotubes will be described as an example.
(1) a step of producing a dielectric layer comprising an elastomer composition (step (1)), and
(2) applying a composition containing carbon nanotubes and a dispersion medium to a dielectric layer to form an electrode layer (step (2));
(3) A process (step (3)) of integrating the sensor body manufactured through the steps (1) and (2) with the cloth (step (3))
It can be manufactured by passing through.

[Step (1)]
In this step, a dielectric layer made of an elastomer composition is produced.
First, according to the elastomer (or its raw material) as a raw material composition, if necessary, a chain extender, a crosslinking agent, a vulcanization accelerator, a catalyst, a dielectric filler, a plasticizer, an antioxidant, an antiaging agent, a coloring agent, etc. The raw material composition which mix | blended the additive of 5 is prepared. Next, a dielectric layer is produced by molding this raw material composition. A conventionally known method can be adopted as a molding method.

Specifically, for example, when forming a dielectric layer containing urethane rubber, the following method can be used.
First, the polyol component, the plasticizer and the antioxidant are weighed, and mixed under stirring for a fixed time under heating and reduced pressure to prepare a mixed solution. Next, the mixed solution is measured, and after adjusting the temperature, a 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 etc., the mixed solution is immediately injected into the forming apparatus shown in FIG. A sheet of a predetermined thickness is obtained. Thereafter, the dielectric layer can be manufactured by post-crosslinking for a predetermined time in an oven.

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

  The above-mentioned dielectric layer may be prepared using a general-purpose film forming apparatus such as various coating apparatus, bar coat, doctor blade or the like or a film forming method after preparing the raw material composition.

[Step (2)]
In this step, a composition containing a carbon nanotube and a dispersion medium (carbon nanotube dispersion liquid) is applied, and then the dispersion medium is removed by a drying process to form an electrode layer integrated with the dielectric layer. .

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

  Examples of the dispersion medium include toluene, methyl isobutyl ketone (MIBK), alcohols, water and the like. These dispersion media may be used alone or in combination of two or more.

  In the above-mentioned coating solution, the concentration of carbon nanotubes is preferably 0.01 to 10% by weight. If the concentration is less than 0.01% by weight, the concentration of carbon nanotubes may be too low, which may require repeated application. On the other hand, if it exceeds 10% by weight, the viscosity of the coating solution may be too high, and the reaggregation may reduce the dispersibility of carbon nanotubes, which may make it difficult to form a uniform electrode layer.

Subsequently, a coating solution is applied to a predetermined position on the surface of the dielectric layer by spray coating or the like and dried. At this time, if necessary, the above-mentioned coating solution may be applied after masking the position where the electrode layer is not formed on the surface of the dielectric layer.
The drying conditions of the coating solution are not particularly limited, and may be appropriately selected according to the type of dispersion medium, the composition of the elastomer composition, and the like.
The method of applying the coating solution is not limited to spray coating, and other methods such as screen printing and ink jet printing may also be employed.

After the dielectric layer and the electrode layer are formed through the steps (1) and (2), wiring and a connection portion connected to the electrode layer are further formed, if necessary.
The formation of the wiring connected to the electrode layer is performed, for example, by applying the carbon nanotube dispersion liquid (coating liquid) to a predetermined place using the same method as the formation of the electrode layer, and drying the same. be able to. Further, the formation of the wiring may be performed simultaneously with the formation of the electrode layer.
The formation of the connection portion can be performed, for example, by attaching a copper foil or the like to a predetermined end of the wiring.

  Moreover, when manufacturing the sensor main body provided with a structure as shown in FIG. 4, first, two dielectric layers which consist of an elastomer composition are produced by the method of said process (1). Next, an electrode layer is formed on one surface of the dielectric layer by the method of the step (2), and an electrode layer is formed on one surface of the other dielectric layer. Thereafter, the two dielectric layers on each of which the electrode layer is formed are attached in a direction in which the electrode layers do not overlap with each other. After that, a wire and a connection portion connected to the electrode layer may be formed as necessary.

Moreover, after forming the said electrode layer and forming the said wiring and the said connection part as needed, you may further form a protective layer in the outermost layer of front side and / or a back side.
The formation of the protective layer may be carried out, for example, by preparing a sheet-like article made of an elastomer composition using the same method as the step (1), cutting it into a predetermined size, laminating it, etc. It is good.
Moreover, when producing the sensor sheet provided with the protective layer, it starts from the protective layer on the back side, and the constituent members (second electrode layer, first dielectric layer, first electrode layer, (second dielectric layer) are sequentially stacked thereon The sensor main body may be manufactured by laminating the third electrode layer) and the front side protective layer).
The sensor main body can be manufactured through such a process.

[Step (3)]
In this process, the cloth is attached to the sensor body.
First, a stretch anisotropic cloth cut into a predetermined direction and size is prepared.
Next, an adhesive layer is formed on one side of the fabric, and the fabric is attached to the sensor body via the adhesive layer so that the direction of easy extension and contraction of the fabric matches the extension direction of the sensor body. paste. The order of cutting the cloth and forming the adhesive layer may be reversed.
In the present process, the cloth may be attached to both sides of the sensor main body, or may be attached to only one side of the sensor main body.

The cloth is attached so as to cover the detection portion of the sensor main body at least in a plan view.
When the cloth is attached to both sides of the sensor main body, the sensor main body may be embedded between the two cloths so that the entire outer periphery of the cloth may be bonded to each other.
In this step, if necessary, a non-shrinkable member or a handle may be attached.
By passing through such a process, the sensor sheet of the present invention can be manufactured.

Although the sensor main body shown in FIGS. 2 and 4 includes one detection unit, in the present invention, the number of detection units of the sensor main body is not limited to one, and a plurality of detection units may be used. It may be provided.
As a specific example thereof, for example, a plurality of rows of strip-like electrode layers are formed on the front and back surfaces of the dielectric layer as the front side electrode layer and the back side electrode layer, and when viewed in plan, the row of the front side electrode layer and the back side electrode One example is a sensor body arranged to be orthogonal to the row of layers. In such a sensor main body, a plurality of portions where the front side electrode layer and the back side electrode layer face each other with the dielectric layer interposed therebetween become detection portions, and the detection portions are arranged in a lattice.

<Instrument>
The measuring device is electrically connected to the sensor sheet (the sensor body), and has a function of measuring the capacitance C of the detection unit, which changes in accordance with the deformation of the dielectric layer. A conventionally known method can be used as a method of measuring the capacitance C, and the measuring instrument is provided with a capacitance measurement circuit, an arithmetic circuit, an amplification circuit, a power supply circuit, etc. necessary for that. .
As a method (circuit) for measuring the capacitance C, for example, a CV conversion circuit (such as an LCR meter) using an automatic balance bridge circuit, a CV conversion circuit using an inverting amplification circuit, and a half-wave voltage doubler rectification circuit A CV conversion circuit used, a CF oscillation circuit using a Schmitt trigger oscillation circuit, a method using a Schmitt trigger oscillation circuit and an F / V conversion circuit in combination, and the like can be mentioned.

In the sensor element of the present invention, the connection between the sensor sheet and the measuring instrument is preferably performed as follows.
(1-1) The sensor main body includes two dielectric layers (first and second dielectric layers) as shown in FIG. 4 and electrode layers (first to third dielectric layers) on both surfaces of each dielectric layer. When the measuring instrument is a measuring instrument using a CF oscillating circuit such as a Schmitt trigger oscillating circuit that oscillates with the electrostatic capacitance C and resistance R of the detecting unit and measures a change in the electrostatic capacitance .
In this case, it is preferable to connect the first electrode layer to the oscillation block (detection block) and to ground the second electrode layer and the third electrode layer (connected to the GND side).
By connecting the sensor main body and the measuring instrument in this way, the effect of noise is eliminated even if either the front side or the back side of the sensor main body is connected close to the object to be measured such as a living body, more accurately The change in capacitance can be measured.

(1-2) The sensor main body is a sensor main body having two dielectric layers as shown in FIG. 4 and electrode layers on both sides of each dielectric layer, and the measuring instrument is a half-wave voltage doubler rectifier circuit or reverse An alternating current signal generated by another block (for example, an alternating current application device) such as an amplification circuit or an automatic balance bridge circuit is passed through the sensor main body, and an AC impedance change due to a capacitance change of the sensor main body is measured or an impedance change is used If it is a measuring instrument using a CV conversion circuit of the type that generates a voltage change.
In this case, it is preferable to connect the first electrode layer to the detection block and to connect the second electrode layer and the third electrode layer to a block that generates an alternating current signal.
By connecting the sensor main body and the measuring instrument in this way, the effect of noise is eliminated even if either the front side or the back side of the sensor main body is connected close to the object to be measured such as a living body, more accurately The change in capacitance can be measured.

(2-1) The sensor main body is a sensor main body having one dielectric layer as shown in FIG. 2 and electrode layers (front side electrode layer and back side electrode layer) on both sides thereof, and a measuring instrument is Schmidt In the case of a measuring instrument using a CF conversion circuit such as a trigger oscillation circuit.
In this case, the front side electrode layer is connected to the oscillation block (detection block) in the measuring instrument, the back side electrode layer is grounded (connected to the GND side), and the sensor main body is the measurement target such as a living body on the back side. It is preferable to stick so as to be close to an object.
By attaching the sensor body to a living body or the like in such a direction and connecting the sensor body and the measuring instrument as described above, the influence of noise can be eliminated and the change in capacitance can be measured more accurately. it can.

(2-2) The sensor main body is a sensor main body having one dielectric layer as shown in FIG. 2 and electrode layers (front side electrode layer and rear side electrode layer) on both sides thereof, and the measuring instrument is a half. In the case of a measuring instrument using a CV conversion circuit such as a wave voltage doubler rectifier circuit, an inverting amplifier circuit, or an automatic balance bridge circuit.
In this case, the front side electrode layer is connected to the detection block in the measuring instrument, the back side electrode layer is connected to the block that generates an alternating current signal, and the back side of the sensor main body approaches the measurement object such as a living body. It is preferable to stick as follows.
By attaching the sensor body to a living body or the like in such a direction and connecting the sensor body and the measuring instrument as described above, the influence of noise can be eliminated and the change in capacitance can be measured more accurately. it can.

<Display>
The sensor device of the present invention may be provided with a display as in the example shown in FIG. Thereby, the user of the above-mentioned sensor device can confirm the information about change of electric capacity C by modification of a measuring object in real time. The display includes a monitor, an arithmetic circuit, an amplifier circuit, a power supply circuit and the like necessary for that purpose.

In addition, the display may include a storage unit such as a RAM, a ROM, or an HDD in order to store the measurement result of the capacitance C as in the example illustrated in FIG. 1.
For example, when the sensor device of the present invention is used for a person who performs sports training or rehabilitation training, information based on a change in capacitance C related to motion information of a living body can be confirmed after training. Therefore, the implementer can confirm the degree of achievement of the training and also encourages the implementer. In addition, by confirming the degree of achievement of training, it is possible to utilize the information for making a new training menu.
The storage unit may be included in the measuring device.
Terminal devices such as a personal computer, a smartphone, and a tablet may be used as the display.

  Moreover, in the sensor device 1 shown in FIG. 1, the connection between the measuring device 3 and the display 4 is wired, but in the sensor device of the present invention, these connections need to be wired. Alternatively, they may be connected wirelessly. Depending on the usage of the sensor device, it may be easier to use if the measuring instrument and the display are physically separated.

  Hereinafter, the present invention will be more specifically described by way of examples, but the present invention is not limited to the following examples.

<Fabrication of sensor body>
6 (a) to 6 (d) are perspective views for explaining the manufacturing process of the sensor main body in the embodiment. Here, the sensor main body shown in FIG. 2 was produced.
(1) Preparation of Dielectric Layer 40 parts by weight of a plasticizer (dioctyl sulfonate) and isocyanate (Pandex GCA-11, manufactured by DIC) 17 parts by weight to 100 parts by weight of a polyol (Pandex GCB-41, manufactured by DIC) Then, .62 parts by weight were added and mixed by stirring with an agitator for 90 seconds to prepare a raw material composition for a dielectric layer. Next, the raw material composition is injected into the forming apparatus 30 shown in FIG. 5, and while being transported in a sandwich state with the protective film 31, it is crosslinked and cured under the conditions of an oven temperature of 70 ° C. and an oven time of 30 minutes to protect A roll-wound sheet of a predetermined thickness with a film was obtained. Thereafter, post-crosslinking was carried out for 12 hours in a furnace adjusted to 70 ° C. to prepare a sheet made of a polyether urethane elastomer. The obtained urethane sheet was cut into 14 mm × 80 mm × thickness 100 μm, and further, a corner portion was cut off with a size of 7 mm × 20 mm × thickness 100 μm to prepare a dielectric layer.

Further, with respect to the manufactured dielectric layer, when the elongation at break (%) and the relative dielectric constant were measured, the elongation at break (%) was 505% and the relative dielectric constant was 5.8.
Here, the elongation at break was measured in accordance with JIS K 6251. The relative dielectric constant is measured by measuring the capacitance at a measurement frequency of 1 kHz using an LCR high tester (3522-50 manufactured by Hioki Electric Co., Ltd.) with an electrode of 20 mm in diameter, and from the electrode area and the thickness of the measurement data The relative dielectric constant was calculated.

(2) Preparation of electrode layer material Highly-oriented carbon nanotubes (layer number 4 to 12 layers, fiber diameter 10 to 20 nm, fiber length 150 to 40) manufactured by Taiyo Nisshinsha Co., Ltd., which are multi-walled carbon nanotubes manufactured by substrate growth method Add 30 mg of 300 μm, 99.5% carbon purity) to 30 g of isopropyl alcohol (IPA), apply a wet dispersion treatment using a jet mill (Nanojet Pal JN10-SP003, manufactured by Haruka Co., Ltd.), and dilute twice A carbon nanotube dispersion having a concentration of 0.05% by weight was obtained.

(3) Preparation of Protective Layer Using a method similar to the preparation of (1) dielectric layer described above, it is made of polyether urethane elastomer, 14 mm × 80 mm × 50 μm thick back side protective layer, and 14 mm × 60 mm × thickness A 50 μm-thick front side protective layer was produced.

(4) Preparation of Sensor Body First, on one side (surface) of the back side protective layer 15B prepared in the above step (3), a mask in which an opening having a predetermined shape is formed in the release-treated PET film (see FIG. I stuck it).
The mask is provided with an opening corresponding to the back side electrode layer and the back side wiring, and the size of the opening is such that the portion corresponding to the back side electrode layer is 10 mm wide × 50 mm long and the portion corresponding to the back side wiring is It is 5 mm wide × 20 mm long.

Next, the carbon nanotube dispersion prepared in the step (2) was applied using an air brush from a distance of 10 cm so that the amount of application per unit area (cm ² ) was 0.223 g. Subsequently, the resultant was dried at 100 ° C. for 10 minutes to form a back side electrode layer 12B and a back side wiring 13B. Thereafter, the mask was peeled off (see FIG. 6 (a)).

Next, the dielectric layer 11 produced in the above step (1) was laminated on the back side protective layer 15B so as to cover the entire back side electrode layer 12B and a part of the back side wiring 13B.
Furthermore, the front side electrode layer 12A and the front side wiring 13A were formed on the front side of the dielectric layer 11 using the same method as the formation of the back side electrode layer 12B and the rear side wiring 13B (see FIG. 6B).

Next, on the front side of the dielectric layer 11 on which the front side electrode layer 12A and the front side wiring 13A are formed, the front side manufactured in the above step (3) so as to cover the whole front side electrode layer 12A and a part of the front side wiring 13A. Protective layer 15A was laminated by lamination.
Furthermore, copper foil was attached to each end of front side wiring 13A and back side wiring 13B, and it was set as front side connection part 14A and back side connection part 14B. Thereafter, lead wires 19 serving as external wires are fixed to the front side connection portion 14A and the rear side connection portion 14B by soldering to form the sensor main body 10 (see FIG. 6C).

<Preparation of cloth>
As a cloth cloth, the cloth cloth was prepared below.
(A) Stretching anisotropic fabric A: Super Stretch II (purchased from Santoku Co., Ltd., Quality: 90% nylon, 10% polyurethane, 600 μm thick)
(B) Stretchable anisotropic fabric B: manufactured by Pip, Pip Kinesiology (registered trademark), thickness 600 μm
(C) Stretch isotropic fabric A: 2 WAY tricot (purchased from Yuzawaya, Quality: 85% nylon, 15% polyurethane, 700 μm thick)
(D) Stretchable isotropic fabric B: Lycra mat (purchased from Crystal Clover, quality: nylon 83%, polyurethane 17%, thickness 600 μm)
(E) Stretchable isotropic fabric C: Toray developed product (quality: polyester 95%, polyurethane 5%, thickness 350 μm)

<Production of adhesive layer>
50 parts by weight of methyl ethyl ketone (MEK) and 2 parts by weight of a curing agent (L-45, manufactured by Soken Chemical Co., Ltd.) are added to 50 parts by weight of an adhesive (Sukken Chemical Co., Ltd., SK dyne 1720). The mixture was obtained by mixing (2000 rpm, 120 seconds) and defoaming (2000 rpm, 120 seconds) using a company-made model number: ARE-310). Next, the obtained mixture is formed into a film with a wet film thickness of 100 μm on a PET film (50E-0010KF, manufactured by Fujimori Kogyo Co., Ltd.) whose surface has been subjected to a release treatment, and then a blasting oven is used. It was cured under conditions of 100 ° C. for 30 minutes to prepare a pressure-sensitive adhesive layer having a thickness of 30 μm after curing.

Example 1
A sensor sheet in which the sensor body and the cloth were integrated was manufactured by the following method.
7 (a) to 7 (d) are perspective views for explaining the method of manufacturing the sensor sheet in the embodiment.

(1) The adhesive layer produced by the method mentioned above was transcribe | transferred on the single side | surface of said expansion-contraction anisotropic fabric A.
Thereafter, the stretchable anisotropic fabric A was cut into a size of horizontal 115 mm × vertical 30 mm. At this time, it was cut so that the width was in the direction of easy expansion and contraction, and the length was in the direction of vertical expansion and contraction.

(2) The stretchable anisotropic fabric 20B cut on the back side of the sensor main body 10 manufactured by the above-described method was attached. At this time, the end of the sensor body 10 opposite to the side on which the wiring (front side wiring 13A and back side wiring 13B) is formed is located 15 mm from one end in the longitudinal direction (horizontal direction) of the stretchable anisotropic fabric 20B. The stretchable anisotropic fabric 20B was pasted as shown in FIG. 7 (a).

(3) Next, nylon woven belts 22A and 22B were attached to both ends of the stretchable anisotropic fabric 20B as handles for fixing the sensor sheet to a tensile tester in a test described later ((3) See FIG. 7 (b)). At this time, pasting of the weave belts 22A and 22B was performed using a double-sided tape (Teraoka Seisakusho No. 777). Further, the woven belt 22B is attached so that the end portion is disposed also on a part of the upper surface of the sensor main body 10 (a position not overlapping with the detection portion in a plan view).

(4) Next, in order to prevent the expansion and contraction of the dielectric layer other than the detection portion in the sensor main body 10, a non-stretchable fabric (made by Towa fabric Industrial Co., Ltd.) 21) was pasted so as to cover the wiring (front side wiring 13A and back side wiring 13B) and the connection part (front side connecting part 14A and back side connecting part 14B) via a double-sided tape (Teraoka No. 777) 7 (c)).
(5) Thereafter, the stretchable anisotropic fabric 20A cut in the above (1) was attached also to the surface side of the sensor body to complete the sensor sheet 2 (see FIG. 7 (d)).

(Example 2)
A sensor sheet was produced in the same manner as in Example 1 except that the stretch anisotropic fabric B was used in place of the stretch anisotropic fabric A.
However, the stretchable anisotropic fabric B is a product having an adhesive layer on one side, and the transfer of the adhesive layer is not performed, and the stretchable anisotropic fabric B is pasted through the adhesive layer included in the stretchable anisotropic fabric B I added it.

(Comparative example 1)
A sensor sheet was produced in the same manner as in Example 1 except that the stretchable isotropic fabric A was used in place of the stretchable anisotropic fabric A.

(Comparative example 2)
A sensor sheet was produced in the same manner as in Example 1 except that the stretchable isotropic fabric B was used in place of the stretchable anisotropic fabric A.

(Comparative example 3)
A sensor sheet was produced in the same manner as in Example 1 except that the stretchable isotropic fabric C was used in place of the stretchable anisotropic fabric A.

(Comparative example 4)
The wiring and the connection of the wiring (the front wiring 13A and the rear wiring 13B) and the connection portion (the front connection portion 14A and the rear connection 14B) of the sensor main body 10 manufactured by the method described above and the upper surface of the front protective layer 15A Via a double-sided tape (Teraoka Seisakusho No. 777) at an end of the side opposite to the side provided with the unit (left side in FIG. 6 (c)) and at a position not overlapping the detection unit in plan view A non-stretchable cloth similar to that of Example 1 was attached to make a sensor sheet (measurement sample) in the evaluation described later.

(Evaluation)
The following evaluation was performed about the sensor sheet which concerns on an Example and a comparative example. The results are shown in Table 1.

(1) Tensile Properties of Fabrics Regarding the tensile properties of fabrics used in Examples 1 and 2 and Comparative Examples 1 to 3, “5% modulus (M5)”, “10% modulus (M10)”, “50% Modulus (M50), "100% modulus (M100)", "200% modulus (M200)", "break elongation", "break load" and "constant load elongation" were measured, and further "anisotropic M5" And "anisotropic M50" was calculated.
Here, in the measurement of “constant load elongation”, the elongation rate at 600 N / m (approximately 5 times M200 of Comparative Example 4) was measured. In addition, “anisotropic M5” and “anisotropic M50” were calculated based on the measured values of “M5” and “M50” of the horizontal and vertical, respectively.

Specifically, the cloth material was cut and cut into a width of 35 mm and a length of 100 mm as a test piece. At this time, three sheets of samples orthogonal to each other in the length direction were produced (for example, in the case of producing a test piece of the stretch anisotropic fabric A, three samples whose length direction is the easy stretch direction (horizontal direction) And three samples whose length direction is the difficult stretching direction (vertical direction) were produced).
Next, hold both ends 25 mm in the length direction of each sample with a chuck, measure at a tensile speed of 500 mm / min using a universal tensile compression tester (Instron model 1175), and then "anisotropic M5" And "anisotropic M50" was calculated.
The average values are shown in Table 1 as a result.

(2) Characteristics of the sensor sheet The sensor sheet according to the embodiment and the comparative example is attached to a universal tensile and compression tester (Instron 1175 type), and the sensor sheet is pulled in 5 mm increments (10% elongation rate) and kept stationary. The capacitance was measured at a measurement frequency of 5 kHz using an LCR high tester (3522-50 manufactured by Hioki Denki Co., Ltd.).

(2-1) Evaluation of sensitivity In the above measurement, based on the capacitance at no elongation (0% elongation) and the capacitance at 40% elongation, the sensor sheet is calculated according to the following formula (2) The sensitivity (pF /%) was calculated.
Sensitivity (pF /%) = [amount of change in capacitance ΔC _{0% → 40%} ] / 40% (2)

(2-2) Evaluation of Hysteresis A sensor sheet is attached to a tensile tester, and from no elongation (0%) to a predetermined elongation rate (40% in Example 2, 80% in other Examples and Comparative Examples) After the extension, the expansion and contraction operation was performed three times to return to the non-extension state. After that, the capacitance at 10% extension of the first round trip (the electrostatic capacity (first round, 10%)) and the capacitance at 10% extension of the second round trip (electrostatic capacity (2 The hysteresis (%) of the sensor sheet was calculated according to the following calculation formula (3) based on the second forward pass, 10%)).
Hysteresis (%) = [electrostatic capacitance (2nd trip, 10%)] / [electrostatic capacitance (1st trip, 10%)]-1) × 100 (3)
Moreover, the graph of the measurement result of the electrostatic capacitance at the time of reciprocation expansion | extension operation | movement was shown to FIGS.

From the results shown in Table 1, it is clear that the sensitivity is improved by integrating the stretch anisotropic cloth fabric into the sensor body.
In addition, if the fabric is stretch anisotropic, the sensor body is not inhibited from stretching and the sensor sheet in which the stretch anisotropic fabric is integrated with the sensor body maintains the same hysteresis as the sensor body. It became clear.

Reference Signs List 1 sensor device 2 sensor sheet 3 measuring instrument 3a, 400 Schmitt trigger oscillation circuit 3b F / V conversion circuit 4 display 4a monitor 4b arithmetic circuit 4c storage unit 10, 40 sensor main body 11 dielectric layer (first dielectric layer)
12A Front side electrode layer (first electrode layer)
12B back side electrode layer (second electrode layer)
13A front side wiring 13B back side wiring 14A front side connection portion 14B back side connection portion 15A, 45A front side protective layer 15B, 45B back side protective layer 20A, 20B cloth 21 non-stretchable member 22A, 22B handle 41A first dielectric layer 41B second dielectric Layer 42A First electrode layer 42B Second electrode layer 42C Third electrode layer 43A First wire 43B Second wire 43C Third wire 44A First connection portion 44B Second connection portion 44C Third connection portion

Claims (4)

A first dielectric layer sheet of elastomeric composition, a conductive composition containing a conductive material, at least a portion across said first dielectric layer on each of the front and rear surfaces of the first dielectric layer It has a first electrode layer and a second electrode layer formed to face each other, and the facing portion of the first electrode layer and the second electrode layer is used as a detection portion, and the area of the front and back surfaces of the dielectric layer changes. Sensor body that reversibly deforms,
And a cloth integrated with the sensor body;
The cloth fabric is a cloth fabric having an easy stretch direction and a hard stretch direction, and exhibiting stretch anisotropy,
The capacitance type sensor sheet, wherein the detection portion is deformed so as to extend in the same direction as the easily stretchable direction of the cloth. The sensor main body further includes a second dielectric layer stacked on the first electrode layer, and a third dielectric layer formed on the surface of the second dielectric layer opposite to the side on which the first electrode layer is formed. The capacitive sensor sheet according to claim 1, comprising: an electrode layer.   The capacitance-type sensor sheet according to claim 1 or 2, wherein the modulus of the fabric is larger than the modulus of the sensor body at the maximum use elongation rate of the sensor body. A capacitive sensor sheet according to any one of claims 1 to 3 ;
A measuring instrument that measures a change in capacitance in the detection unit ;
A sensor device comprising
The first electrode layer is connected to a detection block of the meter,
The sensor device, wherein the second electrode layer is close to a measurement object and connected to the GND side of the measuring device.