JP6165002B2 - Elastic flexible sensor - Google Patents

Description

  The present invention relates to an elastic (stretchable) flexible sensor (hereinafter sometimes abbreviated as “EF sensor” as appropriate).

  Such an EF sensor is generally configured by laminating and forming a conductive layer (sensor electrode) on a stretchable elastomer base material (Patent Document 1).

  This EF sensor detects displacements (various deformations) that occur in the sensor unit, such as stretching, bending, and twisting. For example, an extension sensor for a human body or a sensor that detects the behavior of a sleeping person (patent document) 2). This FE sensor has a characteristic that there is a large resistance value change (voltage change) in the low extension region because the necessary load increases as the extension becomes higher. Conventionally, the main focus of development has been on the selection of the material of the elastomer base material or the structure of the conductive layer in response to such a demand. A silicone rubber material is used as the elastomer base material, and a liquid silicone rubber binder is used as the conductive layer. A mixture of conductive fillers (carbon, metal powder) is known.

JP 2008-177259 A JP 2008-173226 A

  However, the conventional EF sensor has a problem that, unless a certain amount of displacement (elongation) is given, the electrical characteristics cannot be changed while maintaining a low initial resistance value, and sensing in a low extension region is difficult. It was.

  In pursuit of this problem, the present inventors have found that a major reason why it is difficult to perform sensing in a low extension region in a conventional EF sensor is the planar shape of the sensor. A conventional EF sensor has a strip shape with a constant width or a planar shape with a constant area (Patent Document 2), and thus sensing in a low extension region is difficult. Patent documents in this field are interested in the material structure or laminated structure of the elastomer base material and the electrode layer, and as a result, there are many examples in which the planar shape is not mentioned.

  In general, an EF sensor is provided with an extension portion between force application portions at both ends (electrode portion, a portion that grips (adheres) a measurement object to give extension). The inventors of the present invention have found that the electrical characteristics can be changed even in a low stretch region by making the width of the stretched portion narrow by a certain width, thereby completing the present invention. In other words, the electrical characteristics of the EF sensor use the fact that the conductive path between the conductive fillers of the conductive layer changes when a certain displacement is applied, especially when a displacement (elongation) is applied in the low extension region. In addition, a shape in which a considerable strain of the sensor extension portion is large is desirable.

The present invention relates to an EF sensor having an elastomer base material and a stretchable conductive layer formed on the elastomer base material , and having a wide and large area at both end portions, and the position between the two adhesion portions. An extension portion narrower than the attachment portion, and the extension portion includes a narrow extension concentration portion at the center portion and a pair of reduced width portions connecting both ends of the narrow extension concentration portion to the attachment force portions at both ends. The narrow-width extension concentrated portion has a constant width, the reduced-width portion reduces the width from the applied portion toward the narrow-width stretch concentrated portion , and the elastomer base material and the stretchable conductive layer Is characterized in that the planar shape in the direction orthogonal to the stacking direction is the same . An elastomer insulating layer thinner than the thickness of the elastomer base material can be laminated on the stretched portion. The stretchable conductive layer may have a thickness of 100 to 150 μm, and the elastomer insulating layer may have a thickness of 10 to 40 μm.

  The reduced width portion preferably has a step-like reduced width shape in which the width is reduced stepwise, but a tapered reduced width shape in which the width is reduced in a tapered shape is also possible. Furthermore, the width of the reduced width portion and the width of the narrow extension concentration portion may be the same.

  The width of the narrow extension concentrated portion is preferably 1 to 3 mm, and the length is preferably 4 to 20 mm. If the width of the narrow stretch concentrated portion is less than 1 mm, the mechanical strength is insufficient (there is a possibility of breaking during stretching), and if it exceeds 3 mm, the change in electrical characteristics with respect to elongation becomes inconspicuous. Also, if the length of the narrow extension concentrated portion is less than 4 mm, the electrical characteristic change with respect to elongation does not appear remarkably, and if it exceeds 20 mm, it is not practical as a sensor.

  The lengths of the reduced width portions are each preferably 1 to 8 mm. Further, when viewed in terms of the total length of the narrow extension concentrated portion and the reduced width portion, the length is preferably 10 to 20 mm.

  From another point of view, the width of the connecting portion (boundary portion) between the reduced width portion and the both-side applied force portion is 5 to 7 mm, and the reduced width portion is reduced so that the width of the narrow extension concentration portion is 1 to 3 mm. .

The elastomer base material of the present EF sensor can be composed of a silicone rubber insulating base material, and the elastomer insulating layer can be composed of a silicone rubber insulating layer.

  The stretchable conductive layer is practically composed of conductive powder and a conductive paste containing a silicone rubber polymer as a binder.

  It is preferable to use silver powder as the conductive powder. In addition, when the conductive powder is a mixed system of irregularly shaped particles (flaky particles) and spherical particles, depending on the shape of the narrow extension concentrated portion and the reduced width portion, the reverse characteristic has a region where the resistance value decreases with extension. EF sensor can be obtained. On the other hand, when the conductive powder is composed only of amorphous particles, a forward characteristic EF sensor whose resistance value increases with expansion can be obtained (an inverse characteristic EF sensor cannot be obtained). In addition, an amorphous particle means the particle | grains of a shape of about 2-10 by aspect ratio.

  The average particle size (measured with a scanning electron microscope (SEM)) of the conductive powder is preferably 1 to 5 μm.

  The binder rubber polymer of the conductive paste is preferably an addition type liquid silicone rubber.

  The conductive paste contains silicone rubber, conductive powder, and a solvent.

  The elastic flexible sensor of the present invention can be used as, for example, a pressure-sensitive sensor, a bending sensor, or a torsion sensor that utilizes a change in electrical resistance.

  According to the present invention, an EF sensor that can be used even in a low-elongation region can be obtained, and a sensor whose electrical characteristics can be controlled by changing its shape can be obtained. Moreover, according to the EF sensor having the reverse characteristic, since the power is consumed only when the narrowed portion expands and contracts and sensing is performed, an energy saving sensor can be obtained.

(A) is a top view of the elastic flexible sensor by this invention, (B) is a schematic cross section along the BB line of (A). It is a top view which mainly shows the expansion | extension part which mainly shows the 1st Example of the elastic flexible sensor by this invention. It is an enlarged plan view of the expansion | extension part which shows the 2nd Example. It is an enlarged plan view of the expansion | extension part which shows the 3rd and 7th Example. It is a graph which shows the measurement result of the amount of elongation-voltage change of the said Examples 1 thru | or 3. It is a top view which mainly shows the expansion | extension part which mainly shows the 4th Example of the elastic flexible sensor by this invention. It is an enlarged plan view of the expansion | extension part which shows the 5th Example. It is an enlarged plan view of the expansion | extension part which shows the 6th Example. It is a graph which shows the measurement result of the amount of elongation-voltage change of the said Examples 4 thru | or 7 and the comparative examples 1 and 2. FIG.

  FIG. 1 shows an example of the shape of an EF sensor 10 according to the present invention. The EF sensor 10 includes an elastomer base material 11, a stretchable conductive layer 12 on the elastomer base material 11, and an elastomer insulation on the stretchable conductive layer 12, as shown in the cross section of FIG. It has a laminated structure including the layer 13 and can be expanded and contracted. The thicknesses of the elastomer substrate 11, the stretchable conductive layer 12, and the elastomer insulation layer 13 are 200 to 2000 μm, 100 to 150 μm, and 10 to 40 μm, respectively.

  As shown in FIG. 2A, the EF sensor 10 has a vertical (left / right) symmetrical shape in a plan view, and is formed between a wide and large area of the applied force portions 20 at both ends and between the applied force portions 20. And a narrow extension 30 positioned there. The stretched portion 30 is stretched by holding the force-bearing portions 20 at both ends with a stretching device (tensile tester) and applying a tensile force. The elastomer insulating layer 13 is formed only on the extended portion 30 to prevent electric shock.

  The extension portion 30 has a narrow extension concentration portion 31 at the center and a pair of reduced width portions 32 that connect both ends in the length direction of the narrow extension concentration portion 31 to the force applying portion 20. Whereas the narrow width concentrating portion 31 has a constant width, the contracted width portion 32 reduces the width from the applied portion 20 to the narrow width concentrating portion 31. The boundary 33 between the force applying portion 20 and the extended portion 30 is defined as the edge of the elastomer insulating layer 13.

  The reduced width portion 32 can have a mode in which the width is reduced stepwise as shown by a solid line in FIG. 1A and a mode in which the width is reduced in a taper shape as shown by a broken line in FIG. . Further, a mode is also possible in which the width of the reduced width portion 32 is the same as that of the small width extension concentration portion 31 (the width is rapidly reduced (stepwise) at the boundary portion 33).

  Incidentally, a test piece called a dumbbell shape for performing a physical property test of a rubber material has a shape in which the force-applying portions 20 at both ends are connected by a constant width strip 30X as indicated by a chain line in FIG.

  Compared with this conventional dumbbell shape, the present embodiment is characteristic in that the width of the small-width extension concentration portion 31 is reduced. In this way, by forming the narrow stretch concentration portion 31 via the narrow width portion 32, the electrical characteristics can be changed even in the low stretch region. The reason is considered that elongation concentrates on the narrow stretch-concentration portion 31 with a narrow width, and the resistance value (that is, the resistance value between the stretched portions 30 at both ends) clearly changes with the elongation. In addition, by forming the narrow extension concentrated portion 31 via the reduced width portion 32, the narrow stretch concentrated portion 31 is locally attached to the narrow stretch concentrated portion 31 while avoiding breakage (stress concentration) due to a sudden change in width. It tends to cause distortion.

  As shown in FIG. 1A, when the dimensions A to K of the narrow extension concentrated portion 31 and the reduced width portion 32 of the extended portion 30 are taken, the width F of the narrow extended concentrated portion 31 is set to 1 to 3 mm. The length C is preferably 4 to 20 mm. If the width F of the small-width stretch concentration portion 31 is less than 1 mm, the mechanical strength is insufficient (there is a risk of breakage during stretching), and if it exceeds 3 mm, the change in electrical characteristics with respect to elongation becomes inconspicuous. Also, if the length C of the narrow extension concentration portion 31 is less than 4 mm, the change in electrical characteristics with respect to elongation does not appear remarkably.

  The length (D + E) of each of the reduced width portions 32 is preferably 1 to 8 mm. Moreover, when it sees by the total length (A) of the narrow expansion | extension concentrated part 31 and the reduced width part 32, it is good to set it as 10-20 mm.

  From another point of view, the width B of the boundary portion 33 between the reduced width portion 32 and the both-end applied portion 20 is 1 to 7 mm, and the reduced width portion 32 makes the width F of the small-width extension concentrated portion 31 become 1 to 3 mm. Shrink to

  More generally, the narrow extension concentrated portion 31 and the reduced width portion 32 are 10 ≦ A ≦ 20, 1 ≦ B ≦ 5, 2 ≦ C when taking dimensions A to K as shown in FIG. It is preferable to satisfy ≦ 20, 0 ≦ D ≦ 4.5, 0 ≦ E ≦ 4.5, 1 ≦ F ≦ 3, 0 ≦ J ≦ 1, and 0 ≦ K ≦ 1.

  Further, when the width is reduced in a tapered shape as indicated by the broken line in FIG. 1A, the reduced width portion 32 is preferably reduced in width by 40% or more from the boundary portion 33 to the narrow extension concentration portion 31. Further, in the relationship between the length of the reduced diameter portion 32 and the amount of diameter reduction, the ratio of the diameter reduction amount / length is preferably 6 to 25%.

  The elastomer base material 11 and the elastomer insulating layer 13 can be composed of at least a silicone rubber insulating base material. The stretchable conductive layer 12 can be composed of at least conductive powder and a conductive paste containing a silicone rubber polymer as a binder. The binder rubber polymer of the conductive paste is preferably an addition type liquid silicone rubber. The conductive paste contains silicone rubber, conductive powder, and a solvent.

  It is preferable to use silver powder as the conductive powder. In addition, the conductive powder can have a mixed system of amorphous particles (flaky particles) and spherical particles, or a single system of only amorphous particles (flaky particles). In the mixed system, an EF sensor having a reverse characteristic in which the resistance value decreases with expansion depending on the shapes of the small-width extension concentration portion 31 and the reduction width portion 32 can be obtained as described in the following specific examples. . On the other hand, with a single system, it was confirmed that an EF sensor having a forward characteristic in which the resistance value increases with expansion (an EF sensor having a reverse characteristic cannot be obtained) is obtained.

  The average particle size of the conductive powder is preferably 1 to 5 μm.

Next, specific examples will be described.
Test Outline The EF sensor 10 having the elastomer base material 11, the stretchable conductive layer 12 and the elastomer insulating layer 13, which will be described in detail below, is processed into the following shape, and these are applied in a state where a constant current is applied between the both end force applying portions 20. The voltage change when extending at a constant speed was examined.

<Examples 1, 2, and 3, Comparative Examples 1 and 2>
<Sample preparation>
Preparation of EF sensor test piece (binder rubber polymer)
Liquid silicone rubber KE1820 (manufactured by Shin-Etsu Chemical Co., Ltd.).
(Conductive powder)
Amorphous silver particles having an average particle diameter of about 1 to 5 μm (SF-70, manufactured by Ferro Japan Co., Ltd., aspect ratio 5, density 10.5 g / cm ³ ) and spherical silver particles having an average particle diameter of about 2 μm (SPN- 10JS, manufactured by Mitsui Kinzoku Co., Ltd., density 10.5 g / cm ³ ) mixed at a ratio of amorphous silver particles: spherical silver particles = 7: 3 (weight ratio). The average particle size was measured by SEM (scanning electron microscope).
(solvent)
YS-150, a mixed solvent of aromatic hydrocarbons manufactured by Yamaichi Chemical Co., Ltd.
(Conductive paste)
The binder rubber polymer and the conductive powder were mixed at 2: 8 (weight ratio) and dispersed with a three-roll mill, and then the viscosity was adjusted with a solvent to obtain a conductive paste.
(Method for producing elastomer substrate 11)
Silicone rubber polymer "KE-951" (manufactured by Shin-Etsu Chemical Co., Ltd.), "TSE-2623U" (manufactured by Momentive Performance Materials Japan) and "TSE-2627U" (momentive performance materials Japan) Manufactured rubber), a processing aid “MR-14” and a cross-linking agent “C23-N” (manufactured by Shin-Etsu Chemical Co., Ltd.) are heated at 150 ° C. for 5 minutes by far-infrared rays to obtain a silicone rubber sample. It was. The hardness of the obtained rubber sample was Hs50 (measured with a JISK6253 durometer (type A)).
(Method for producing stretchable conductive layer 12)
Using a metal mask having a thickness of 200 μm, the conductive paste prepared by mixing the binder rubber polymer and silver powder at a ratio of 2: 8 (weight ratio) is glued to the elastomer base material 11 at 100 ° C. for 30 minutes. Test pieces having electrode shapes each having a thickness of about 150 μm (measured by SEM) were prepared by heating and curing at 180 ° C. for 1 hour.
(Method for producing elastomer insulating layer 13)
A silicone rubber polymer (“KE1820” manufactured by Shin-Etsu Chemical Co., Ltd.) is glued on the narrow stretch concentration portion 31 and the narrow width portion 32 on the surface of the stretchable conductive layer 12, and heated and cured at 100 ° C. for 1 hour. An elastomer insulating layer 13 having a thickness of about 40 μm was produced.

Planar shape of the EF sensor 10 according to the first, second, and third embodiments The planar shapes of the small-width extension concentrated portion 31 and the narrow-width portion 32 of the EF sensor 10 according to the first, second, and third embodiments are shown in FIGS. Table 1 shows. In addition, the width | variety of the both ends force-applying part 20 is 25 mm, and length is 40 mm (length 15mm of a fixed width part, length 25mm of the taper width part to the expansion-contraction part 30).
(Table 1)
Example No. ABCD E F J K (unit: mm)
1 20 1 20 1
2 20 5 8 3
3 10 5 4 1.5 1.5 1 1 1 1
(Values not listed are 0)
Planar Shape of EF Sensors of Comparative Examples 1 and 2 Comparative Example 1 is a test piece having a dumbbell shape 30X shown by a chain line in FIG. 1A, and its width B is 5 mm.
Comparative Example 2 is a test piece in which the entire width including the both-end applied portion 20 is 6 mm.

(Evaluation method)
As the stretching device, a tensile testing machine (model: STROGRAPH VES 5D, manufactured by Toyo Seiki Co., Ltd.) was used. A voltage monitor GR3500 (manufactured by Keyence) was used for measuring the voltage change during extension. The power supply used was HIOKI 7020 (manufactured by HIOKI), and the change in voltage was measured when it was extended at an extension speed of 50 mm / min while passing a constant current of 10 mA.

(Evaluation results)
FIG. 5 shows the measurement results of the expansion ratio and voltage change of Examples 1, 2, and 3. According to this result, at least 8.7 to 14.5 (9 to 15)% stretch region in Example 1, and at least 9.7 to 20.0 (10 to 20)% stretch region in Example 2, In Example 3, at least in the stretch region of 3.5 to 11.5 (3 to 12)%, a characteristic (reverse property) in which the voltage decreases (the resistance value decreases) as the stretch rate increases is obtained.

<Examples 4, 5, and 6>
In Examples 4 to 6, amorphous silver particles (flaky silver particles) (density 10.5 g / cm ³ ) having an average particle diameter of 1 to 5 μm were used as the conductive powder. Other sensor test piece structures are the same as those in Examples 1, 2, and 3.
The planar shapes of the small-width extension concentrated portion 31 and the reduced-width portion 32 of the EF sensors 10 of Examples 4, 5, and 6 are shown in FIGS. 6, 7, and 8 and Table 2 below.

(Table 2)
Example No. ABCD E F J K (unit: mm)
4 20 5 4 1
5 10 5 4 3
6 10 5 4 1.5 1.5 1 1 1 1
(Values not listed are 0)

(Evaluation results)
FIG. 9 shows the measurement results of the expansion ratio and voltage change of Examples 4, 5, and 6 and Comparative Examples 1 and 2. According to this result, at least 11.0-35.5 (11-36)% stretch region in Example 4, at least 17.4-40.5 (18-41)% stretch region in Example 5, In Example 6, a characteristic (forward characteristic) in which the voltage increased (the resistance value increased) as the expansion ratio increased was obtained in an expansion region of at least 8.1 to 24.5 (8 to 25)%. On the other hand, in Comparative Examples 1 and 2, only forward characteristics can be obtained only in a high stretch region (50 to 70%).

  In the embodiment (Examples 1 to 3) in which a mixed system of irregularly shaped particles (flaky particles) and spherical particles is used as the conductive powder (silver powder), depending on the planar shape of the specific narrow stretched portion 31 and the narrowed portion 32 In the embodiments (Examples 4 to 7) in which reverse characteristics are obtained and only a single system of irregularly shaped particles (flaked particles) is used, the reason why forward characteristics are obtained (reverse characteristics cannot be obtained) is not always clear. is not. As a result of extending the narrow extension concentration portion 31, the present inventors approach the amorphous particles and the spherical particles in the thickness direction of the conductive layer in the mixed system (the connection between the conductive particles increases) and the resistance value decreases. On the other hand, in the single system, it is inferred that the resistance value increases because the particles in the length direction are more separated than the particles in the thickness direction of the conductive layer.

DESCRIPTION OF SYMBOLS 10 Elastic flexible sensor 11 Elastomer base material 12 Stretchable conductive layer 13 Elastomeric insulating layer 20 Applying part 30 Extension part 31 Small extension concentration part 32 Reduction part 33 Boundary part

Claims (13)

A stretchable elastic flexible sensor having an elastomer base material and a stretchable conductive layer formed on the elastomer base material,
Having a wide and large area of both ends, and an extension portion positioned between the two areas and narrower than the force portion;
In addition, the extension portion has a narrow extension concentration portion at the center and a pair of reduced width portions connecting both ends of the narrow extension concentration portion to the force applying portions at both ends, and the narrow extension concentration portion is constant. The width is reduced, and the reduced width part is reduced from the applied part toward the narrow extension concentrated part,
The elastomer base material and the stretchable conductive layer have the same planar shape in a direction perpendicular to the laminating direction,
Elastic flexible sensor characterized by 2. The elastic flexible sensor according to claim 1, wherein an elastomer insulating layer thinner than the thickness of the elastomer base material is laminated on the stretched portion . 3. The elastic flexible sensor according to claim 2, wherein the stretchable conductive layer has a thickness of 100 to 150 [mu] m, and the elastomer insulation layer has a thickness of 10 to 40 [mu] m. 4. The elastic flexible sensor according to claim 1, wherein the reduced width portion has a stepped reduced width shape that reduces the width in a stepped manner. 5. 4. The elastic flexible sensor according to claim 1, wherein the reduced width portion has a tapered reduced width shape. The elastic flexible sensor according to any one of claims 1 to 5 , wherein the width of the small stretched and concentrated portion is 1 to 3 mm and the length is 4 to 20 mm. The elastic flexible sensor according to any one of claims 1 to 6 , wherein a length of the reduced width portion is 1 to 8 mm. The elastic flexible sensor according to any one of claims 2 to 7 , wherein the elastomer base material is made of a silicone rubber insulating base material, and the stretchable conductive layer is a conductive material containing a conductive powder and a silicone rubber polymer as a binder. An elastic flexible sensor made of a conductive paste, wherein the elastomer insulating layer is made of a silicone rubber insulating layer . The elastic flexible sensor according to claim 8, wherein the conductive powder is silver powder. 9. The elastic flexible sensor according to claim 8, wherein the conductive powder is a mixed system of amorphous particles and spherical particles. 11. The elastic flexible sensor according to claim 8, wherein the conductive powder has a particle size of 1 to 5 [mu] m. The elastic flexible sensor according to any one of claims 8 to 10 , wherein the binder rubber polymer of the conductive part paste is an addition type liquid silicone rubber. 11. The elastic flexible sensor according to claim 8, wherein the conductive part paste includes silicone rubber, conductive powder, and a solvent.

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