JP2024104034A - Flexible sheet electrode, biosensor and biosignal measuring device - Google Patents

Abstract

A flexible sheet electrode that is excellent in reducing noise during measurement is provided.
[Solution] The flexible sheet electrode of the present invention is a flexible sheet electrode that is brought into contact with a subject's skin to acquire biosignals, and comprises a flexible substrate, an elastomeric electrode layer provided on the flexible substrate, and an electrolyte retention layer formed on at least a portion of the surface of the elastomeric electrode layer and retaining a liquid electrolyte.
[Selected Figure] Figure 1

Description

The present invention relates to a flexible sheet electrode, a biosensor, and a biosignal measuring device.

Various developments have been made so far regarding sheet electrodes. One such technology is disclosed in Japanese Patent Laid-Open No. 2003-233663.
Patent Document 1 describes clothing equipped with bioelectrodes, and gives examples of using films or sheets made of conductive fibers or conductive polymers as the bioelectrodes (see, for example, paragraph 0042 of Patent Document 1).

JP 2021-115377 A

However, it was found that the bioelectrode in Patent Document 1 leaves room for improvement in terms of reducing noise when measuring bioelectrical signals.

After further investigation, the inventors discovered that by contacting the surface of the elastomer electrode layer in the flexible sheet electrode with the skin of the subject via an electrolyte retention layer that retains a liquid electrolyte, it is possible to reduce the contact resistance when in contact with the skin, thereby realizing a flexible sheet electrode that can reduce noise when measuring bioelectrical signals, and thus completing the present invention.

According to one aspect of the present invention, the following flexible sheet electrode, biosensor, and biosignal measuring device are provided.

1. A flexible sheet electrode that is brought into contact with the skin of a subject to acquire a biosignal,
A flexible substrate;
an elastomeric electrode layer provided on the flexible substrate;
an electrolyte retention layer formed on at least a portion of the surface of the elastomeric electrode layer and retaining a liquid electrolyte;
A flexible sheet electrode comprising:
2. The flexible sheet electrode according to 1.,
The flexible sheet electrode, wherein the electrolyte retention layer comprises a hydrogel having moisture therein.
3. The flexible sheet electrode according to 1. or 2.,
A flexible sheet electrode, wherein the bioimpedance between the flexible sheet electrodes is 120 kΩ or less when measured at 10 Hz with the electrolyte retention layer in contact with the skin of a subject.
4. The flexible sheet electrode according to any one of 1. to 3.,
A flexible sheet electrode, wherein the electrolyte retention layer is configured to cover at least a portion of a side of the elastomeric electrode layer.
5. The flexible sheet electrode according to any one of 1 to 4,
The flexible sheet electrode has a tack peak value on the surface of the electrolyte retention layer of 0.8 N or more and 20 N or less.
6. The flexible sheet electrode according to any one of 1. to 5.,
A flexible sheet electrode, wherein at least a portion of the electrolyte retention layer is covered with a watertight member prior to use.
7. The flexible sheet electrode according to any one of 1. to 6.,
A flexible sheet electrode, wherein the biosignal is any one of a cardiac potential, a myoelectric potential, and a skin potential.
8. The flexible sheet electrode according to any one of 1. to 7.,
A flexible sheet electrode, wherein H1 and H2 satisfy 0.01≦H2/H1≦30, where H1 is the thickness of the elastomer electrode layer and H2 is the thickness of the electrolyte retention layer.
9. The flexible sheet electrode according to any one of 1. to 8.,
A flexible sheet electrode, wherein the elastomeric electrode layer includes a conductive elastomer layer on a surface thereof.
10. The flexible sheet electrode according to 9.,
The flexible sheet electrode, wherein the conductive elastomer layer comprises a conductive filler and a silicone rubber.
11. The flexible sheet electrode according to claim 9 or 10,
The flexible sheet electrode, wherein the conductive elastomeric layer further comprises a non-conductive filler.
12. The flexible sheet electrode according to any one of 9. to 11.,
A flexible sheet electrode, wherein the conductive elastomer layer is composed of a printed layer of a conductive paste containing a conductive filler and silicone rubber.
13. The flexible sheet electrode according to any one of 1. to 12.,
A flexible sheet electrode that can be attached to clothing.
14. A biosensor comprising the flexible sheet electrode according to any one of 1. to 13.
15. A biosignal measuring device comprising the biosensor according to 14.

The present invention provides a flexible sheet that can reduce noise when measuring bioelectrical signals, and a biosensor and biosignal measuring device that use the same.

1A and 1B are diagrams illustrating an example of the configuration of a flexible sheet electrode according to an embodiment of the present invention, in which Fig. 1A is a cross-sectional view and Fig. 1B is a top view. 11 is a cross-sectional view showing a schematic example of a modified flexible sheet electrode of the present embodiment. FIG. FIG. 2 is a top view illustrating an example of the configuration of the biosensor according to the present embodiment. 4 is a cross-sectional view taken along the line BB in FIG. 3. 1 is a schematic diagram for explaining an example of the configuration of a biological signal measuring device of an embodiment of the present invention.

The following describes an embodiment of the present invention with reference to the drawings. Note that in all drawings, similar components are given similar reference symbols and descriptions are omitted where appropriate. Also, the drawings are schematic and do not correspond to the actual dimensional ratios.

An overview of the flexible sheet electrode of this embodiment is given below.

The flexible sheet electrode of this embodiment comprises a flexible substrate, an elastomeric electrode layer provided on the flexible substrate, and an electrolyte retention layer formed on at least a portion of the surface of the elastomeric electrode layer and retaining a liquid electrolyte. The flexible sheet electrode is used to acquire biosignals by contacting the skin of a subject.

The flexible sheet electrode of the present embodiment can reduce noise when measuring bioelectrical signals.
One of the mechanisms of noise reduction is that the surface of the elastomeric electrode layer is brought into contact with the skin of the subject through the electrolyte retention layer, thereby reducing the contact resistance during skin contact. It is presumed that the reason for the reduction in contact resistance is that when the elastomeric electrode layer is brought into contact with the skin, the liquid electrolyte migrates to the skin, reducing the resistance of the skin surface.
When the surface of the subject's skin becomes dry due to the season or indoor equipment, the contact resistance may increase. The flexible sheet electrode of this embodiment can measure bioelectric signals from skin in any dry state.

The flexible sheet electrode of this embodiment can also include a gel electrolyte retention layer. It is believed that the gel electrolyte retention layer can deform to fit the skin of the subject and fill in small gaps between small irregularities on the skin surface, making it possible to further reduce contact resistance when in contact with the skin.

In this embodiment, the bioimpedance between the two flexible sheet electrodes measured under the following measurement conditions with the electrolyte retention layer in contact with the skin of the subject is, for example, 120 kΩ or less, preferably 100 kΩ or less, and more preferably 80 kΩ or less, thereby realizing a flexible sheet electrode with further reduced noise in the bioelectric signal.
(Measurement condition)
・Measurement frequency: 10Hz
Measurement location: Both wrists (no skin preparation)
Measurement device: Bioimpedance meter (Melon Technox, MI-IC-N)
・Measurement environment: Humidity 40RH%, room temperature 20℃
Measurement time: The measurement is taken 4 minutes after the electrolyte retention layer of the flexible sheet electrode is attached to each of both wrists.

Moreover, according to this embodiment, a stretchable and/or bendable flexible sheet electrode can be realized.
Such a flexible sheet electrode can stably measure bioelectric potentials by suppressing disconnection in the elastomeric electrode layer even when the substrate is deformed by expansion, contraction, bending, etc. Furthermore, even when the substrate is deformed, the flexible sheet electrode is prevented from peeling off from the flexible substrate, and the adhesion between the two can be maintained.

The flexible sheet electrode can be used for various purposes, but can also be used as an electrode for a biosensor.
A biosensor can acquire a biosignal generated by a biological activity such as a heartbeat, a muscle activity, a nervous system activity, etc. An example of a biosensor can acquire the magnitude or variation of at least one biopotential (biological signal) such as a cardiac potential, a myoelectric potential, or a skin potential.

Biosensors can be used in a variety of applications, including wearable devices, which are devices that can be attached to either the body or clothing.
The flexible sheet electrode of the biosensor is stretchable and can follow the surface shape of the body and the movement of the body. Such a flexible sheet electrode may be attached directly to the body or may be attached to the body via a body-attached member (clothing). For example, the clothing with the biosensor may have a configuration in which the biosensor is sewn into the clothing or a configuration in which the biosensor is used as part of the clothing.

The biosensor may further include a connector, electronic components, etc., and may be configured to communicate with an external device via wired or wireless communication. In addition, by analyzing biosignals such as cardiac potentials acquired by the biosensor, biosignal measurement systems can be constructed for a variety of purposes.

The flexible sheet electrode and biosensor of this embodiment, as well as the biosignal measuring device and bioelectrical signal measuring system using them, are expected to be usable in a variety of situations, including physical diagnosis, health management, fitness, rehabilitation, and nursing care.

The following describes in detail each component of the flexible sheet electrode of this embodiment.

<Flexible sheet electrode>
1 is a top view showing an example of the configuration of a flexible sheet electrode 1. Fig. 1(a) is a cross-sectional view taken along line AA of Fig. 1(b) of the flexible sheet electrode 1, and Fig. 1(b) is a top view of the flexible sheet electrode 1.

As shown in FIG. 1(a), the flexible sheet electrode 1 comprises a flexible substrate 10, an elastomeric electrode layer 2 formed on the surface of the flexible substrate 10, and an electrolyte retention layer 70 formed on the surface of the elastomeric electrode layer 2.

When measuring bioelectrical signals using the flexible sheet electrode 1, the electrolyte retention layer 70 comes into contact with the subject's skin, establishing electrical continuity between the skin and the elastomeric electrode layer 2.

The liquid electrolyte contained in the electrolyte retention layer 70 may be, for example, water containing an electrolyte or an ionic liquid. It is preferable to use an electrolyte that does not affect the living body, and it is preferable to use an electrolyte derived from the living body, such as salt.

The electrolyte retention layer 70 that retains liquid electrolyte can be a layer formed by including liquid electrolyte inside a porous base material such as a gel-like material, or a layer formed of liquid electrolyte with high viscosity and suppressed flow. Retention here means that the state of the layer is maintained unless it is subjected to external influences such as external force or evaporation.

As an example of the electrolyte retention layer 70, a gel-like electrolyte retention layer 70 is preferable, and it is more preferable that it contains a hydrogel having moisture inside. The gel-like electrolyte retention layer 70 can be assumed to be able to deform along the skin of the subject and fill in the gaps between small irregularities on the skin surface, making it possible to further reduce the contact resistance when in contact with the skin. In addition, since the adhesion to the skin can be improved, it is possible to suppress the positional shift of the elastomer electrode layer 2 during measurement.

There are no particular limitations on the gel-like material as long as it is capable of absorbing sufficient water and has sufficient strength and flexibility when pressed against the skin; for example, acrylic hydrogel or silicone hydrogel can be used.
The water content in the gel material may be, for example, 20 to 30 wt %, or 15 to 25 wt %, etc.
When the gel-like member contains salt water, the salt water content can be 20 to 30 wt % and the salt content can be 4 to 6 wt %. The electrolyte retention layer 70 may be formed by using a hydrogel that does not contain salt but has water, and that absorbs salt from the skin that the hydrogel comes into contact with.

The electrolyte retention layer 70 may be configured to cover at least a portion of the surface of the elastomeric electrode layer 2, and may preferably cover 80% or more, 90% or more, or may cover the entire surface (100%) of the elastomeric electrode layer 2. Increasing the coverage area can further reduce contact resistance. In addition, skin adhesion can be improved.

Using the cross-sectional view of the flexible sheet electrode 1 in FIG. 1(a), the thickness of the elastomeric electrode layer 2 is defined as H1, and the thickness of the electrolyte retention layer 70 is defined as H2. In this case, H1 and H2 may be configured to satisfy, for example, 0.01≦H2/H1≦30, preferably 0.02≦H2/H1≦20, and more preferably 0.05≦H2/H1≦15. By setting H2/H1 to be equal to or greater than the lower limit, the effect of reducing the skin surface resistance can be obtained. Furthermore, by setting H2/H1 to be equal to or less than the upper limit, the effect of improving biosignal acquisition can be obtained.

The electrolyte retention layer 70 may be configured so that the lower limit of the tack peak value on the surface is, for example, 0.8 N or more, preferably 1.0 N or more, and more preferably 1.5 N or more. This increases the adhesion between the user's skin and the electrolyte retention layer 70, and prevents the flexible sheet electrode 1 from peeling off during measurement. Also, it prevents the flexible sheet electrode 1 from shifting out of position during measurement.
The electrolyte retention layer 70 may be configured so that the upper limit of the tack peak value on the surface is, for example, 20 N or less, preferably 10 N or less, and more preferably 5 N or less. This makes it easier to separate the electrolyte retention layer 70 from the user's skin, making it easier to attach and detach the flexible sheet electrode 1. In addition, the pain felt when removing the electrode can be reduced.

The procedure for measuring the above tack peak value is as follows.
An aluminum probe having a flat surface with an area of ¹⁵⁰ mm2 is brought into contact with the surface of a test object under the following conditions: probe movement speed: 2.3 mm/sec, probe crimping strength: 12 N, and crimping time: 6 seconds. The flat surface of the aluminum probe is then peeled upward at a probe movement speed of 2.3 mm/sec. The tack peak value on the surface of the test object is measured five times in a probe tack test, and the average of the five measured values is regarded as the tack peak value.

At least a portion of the electrolyte retention layer 70 may be covered with a watertight material before use. This prevents the liquid in the electrolyte retention layer 70 from drying out, and allows the effect of reducing contact resistance to be stably exerted even after storage.

The electrolyte retention layer 70 may be removable and/or replaceable.
When it is removable, it can be stored in a container made of a watertight material until immediately before use, attached to the elastomer electrode layer 2 when in use, and stored in the container after use.
If the electrolyte retention layer 70 is replaceable, multiple types of electrolyte retention layer 70 with different sizes, shapes, and materials may be prepared so that an appropriate electrolyte retention layer 70 can be selected depending on the condition of the subject's skin, the usage environment, etc.

As shown in FIG. 1(a), the elastomer electrode layer 2 is composed of a conductive elastomer layer 20, but is not limited to this and may be configured to include at least a conductive elastomer layer 20 on the surface.

FIG. 2 is a cross-sectional view showing an example of a modified elastomeric electrode layer 2 of a flexible sheet electrode 1. As shown in FIG.
The elastomeric electrode layer 2 may include a laminate that is not impregnated into the flexible substrate 10, and an impregnated layer that is impregnated into the flexible substrate 10. This can improve the adhesion between the elastomeric electrode layer 2 and the flexible sheet electrode 1.
Furthermore, an insulating elastomer layer may be included in a portion of the elastomer electrode layer 2. This can improve the durability of the flexible substrate 10.

The elastomeric electrode layer 2 in FIG. 2(a) includes an elastomeric electrode layer 20 and an insulating elastomer layer 60a in the laminate, and an insulating elastomer layer 60b in the impregnated layer.
The elastomeric electrode layer 2 of FIG. 2(b) includes a conductive elastomer layer 20a in the laminate, and a conductive elastomer layer 20a and an insulating elastomer layer 60 in the impregnated layer.
The elastomeric electrode layer 2 of FIG. 2(c) includes a conductive elastomer layer 20a in the laminate and a conductive elastomer layer 20b in the impregnated layer.

The lower limit of the deposition amount of the conductive elastomer layer 20 contained in the elastomer electrode layer 2 is, for example, 10 mg/ ^cm2 or more, preferably 15 mg/ ^cm2 or more, and more preferably 20 mg/ ^cm2 or more. This can increase the conductivity.
The upper limit of the adhesion amount of the conductive elastomer layer 20 contained in the elastomer electrode layer 2 is, for example, 100 mg/ ^cm2 or less, preferably 80 mg/ ^cm2 or less, and more preferably 60 mg/ ^cm2 or less. This makes it possible to suppress a decrease in the flexibility of the flexible sheet electrode.

As shown in FIG. 2(c) etc., the electrolyte retention layer 70 may be formed only on the surface of the elastomeric electrode layer 2, but as shown in FIG. 2(d), the electrolyte retention layer 70 may be formed from the surface of the elastomeric electrode layer 2 to a portion of the side surface. In other words, the electrolyte retention layer 70 may be configured to cover at least a portion or the entire surface of the side surface of the elastomeric electrode layer 2 (the side surface of the elastomeric electrode layer 2 during stacking). This can prevent the electrolyte retention layer 70 from falling off from the elastomeric electrode layer 2 during use.

The elastomeric electrode layer 2 is configured in a sheet shape as shown in FIG. 1(b), and when viewed from the top surface of the flexible sheet electrode 1, the top view shape may be, for example, a square shape, a circle shape, an ellipse shape, or any other polygonal shape.
In this specification, the term "sheet-like" means that, when the thickness of the elastomeric electrode layer 2 of the laminated portion formed on the surface of the flexible sheet electrode 1 is D (mm) and the area of one surface 22 of the elastomeric electrode layer 2 in a top view is S ( ^mm2 ), S and D are, for example, 50≦S/D, preferably 200≦S/D, and more preferably 400≦S/D. The upper limit of S/D may be set according to the measurement site of the subject and is not particularly limited, but may be, for example, S/D≦ ¹⁰⁷ .

The elastomeric electrode layer 2 has elasticity.
In this specification, the term "stretchability" refers to the rate of elongation when stretched in a predetermined direction. The predetermined direction may be, for example, the direction in which the elastomeric electrode layer 2, specifically the elastomeric electrode layer 2, has the maximum length in the top view of FIG. 1. When the elastomeric electrode layer 2 has a rectangular shape in top view, it may be stretched in the diagonal direction.
Having elasticity when stretched in this extension direction means that the elongation rate can be extended to, for example, 10% or more, preferably 20% or more, and more preferably 50% or more, and that the conductive elastomer layer 20 does not break at that elongation rate.

The conductive elastomer layer 20 in the elastomer electrode layer 2 may be formed by a printing method using a conductive paste containing a conductive elastomer. That is, one example of the conductive elastomer layer 20 is composed of a printed layer of conductive paste. This makes it possible to provide a flexible sheet electrode with excellent design freedom in the sheet electrode design.

The flexible substrate 10 is not particularly limited as long as it is a substrate that can be stretched and/or bent, but may be, for example, a fibrous substrate, a porous elastomer substrate, or an elastomer substrate. The elastomer substrate may contain an insulating elastomer, as described below.

Examples of fiber structural materials for the fiber substrate include natural fibers such as plant fibers and animal fibers; and chemical fibers such as inorganic fibers, regenerated fibers, semi-synthetic fibers, and synthetic fibers. These may be used alone or in combination of two or more. Among these, from the viewpoint of durability, chemical fibers may be used, and synthetic fibers such as acrylic, polyester, nylon, and polyurethane may also be used.

The fiber substrate may be any known fiber substrate, but may be made of, for example, either an insulating material or a conductive material, or both.

The lower limit of the basis weight of the fiber base material is, for example, 10 g/m ² or more, preferably 20 g/m ² or more, and more preferably 30 g/m ² or more. This can increase the mechanical strength.
On the other hand, the upper limit of the basis weight of the fiber base material is, for example, 500 g/m ² or less, preferably 400 g/m ² or less, and more preferably 350 g/m ² or less. This can suppress a decrease in flexibility. Also, the degree of impregnation of the conductive elastomer layer can be increased.

The structure of the fiber substrate is not limited, but from the viewpoint of flexibility, woven or knitted fabrics may be used.

The upper limit of the thickness of the flexible substrate 10 can be set according to the application, and may be, for example, 10 mm or less, preferably 1 mm or less, but from the viewpoint of use as a wearable device, it is more preferably 600 μm or less. By setting the thickness to 600 μm or less, a thin film sheet-like biosensor can be realized.
From the viewpoint of mechanical strength, the lower limit of the thickness of the flexible substrate 10 is, for example, 10 μm or more, preferably 50 μm or more, and more preferably 100 μm or more.

As an example of a method for manufacturing the flexible sheet electrode 1, a method using screen printing will be described.
First, a support is placed on a workbench, and the flexible substrate 10 is placed on the support.
Next, a mask having a predetermined opening pattern shape is placed on the flexible substrate 10 .
Next, the insulating paste and/or the conductive paste is applied onto the flexible substrate 10 using a squeegee through a mask. The order in which the insulating paste and the conductive paste are applied can be changed as appropriate depending on the laminated structure of the elastomer electrode layer 2. A drying treatment may be performed between applications as necessary.
Next, the insulating paste and/or the conductive paste is subjected to a curing treatment. When the insulating paste and/or the conductive paste contains a silicone rubber-based curable composition, the curing temperature can be, for example, 160° C. to 220° C., and the curing time can be 1 hour to 3 hours, etc. After or before the curing treatment, the mask is removed.

Thereafter, an electrolyte retention layer 70 is formed on the surface of the elastomer electrode layer 2 formed from the conductive paste or the insulating paste and the conductive paste.
For example, a liquid electrolyte may be layered (coated) on the elastomer electrode layer 2 by a known means such as coating, or a gel-like material containing a liquid electrolyte may be layered (coated) on the elastomer electrode layer 2.
In this manner, flexible sheet electrode 1 is obtained.

The flexible sheet electrode 1 can be stored in a humid environment or by covering the electrolyte retention layer 70 in the flexible sheet electrode 1 with a watertight material. The watertight material can be a housing that contains the entire flexible sheet electrode 1 or a film that protects only the electrolyte retention layer 70.

A possible method for repairing the flexible sheet electrode 1 is to remove the electrolyte retention layer 70 from the elastomeric electrode layer 2 and install a new electrolyte retention layer 70 on the elastomeric electrode layer 2. By replacing the electrolyte retention layer 70, the body of the flexible sheet electrode 1 can be reused.

Here, we will explain the materials that make up the elastomer electrode layer 2.

When the elastomeric electrode layer 2 includes the conductive elastomer layers 20, 20a, and 20b, each of the layers may be made of a conductive elastomer. When the elastomeric electrode layer 2 includes the insulating elastomer layers 60, 60a, and 60b, each of the layers may be made of an insulating elastomer.
The insulating elastomer and the conductive elastomer may comprise the same or different elastomeric materials.

Examples of the insulating elastomer that can be used include silicone rubber, urethane rubber, fluororubber, nitrile rubber, acrylic rubber, styrene rubber, chloroprene rubber, ethylene propylene rubber, etc. Among these, the elastomer includes one or more thermosetting elastomers (elastomer materials) selected from the group consisting of silicone rubber, urethane rubber, and fluororubber.
The insulating elastomer may be composed of an elastomer material alone, or may be composed to include an elastomer material and a non-conductive filler. An example of the insulating elastomer includes silicone rubber, and preferably includes silicone rubber and a non-conductive filler. Silicone rubber is chemically stable among elastomers, and also has excellent mechanical strength.
Among these, from the viewpoint of hygiene, it is preferable to use silicone rubber, which has high biocompatibility, as the elastomer material.

The conductive elastomer may be, for example, silicone rubber, urethane rubber, fluororubber, nitrile rubber, acrylic rubber, styrene rubber, chloroprene rubber, ethylene propylene rubber, etc. Among these, the elastomer includes one or more thermosetting elastomers (elastomer materials) selected from the group consisting of silicone rubber, urethane rubber, and fluororubber, and a conductive filler.
A preferred example of the conductive elastomer includes silicone rubber and a conductive filler, which can enhance the elasticity and conductivity of the conductive elastomer.

At least one of the insulating elastomer and the conductive elastomer, and preferably both, may contain a non-conductive filler. As the non-conductive filler, known materials may be used, such as silica particles, silicone rubber particles, talc, etc. Among these, silica particles may be included.

The conductive filler may include, for example, one or more selected from the group consisting of powdered or fibrous metal-based fillers, carbon-based fillers, metal oxide fillers, and metal-plated fillers. Among these, metal-based fillers such as silver powder may be used as the conductive filler.

The conductive elastomer may further contain a non-conductive filler in addition to the conductive filler. This enhances the mechanical properties of the conductive elastomer.

As a specific example, the conductive elastomer layer 20 may contain silver powder, preferably flake-shaped silver powder, as a conductive filler, thereby improving the electrical conductivity and further the elastic conductivity.
The conductive elastomer layer 20 may also contain silver powder and silica particles as a non-conductive filler, thereby improving the stretch durability of the conductive elastomer layer 20.

At least two, or all, of the conductive elastomer of the conductive elastomer layer 20 and the insulating elastomer of the insulating elastomer layer 60 may be configured to include the same elastomer material.

In this specification, containing the same elastomer material means containing at least one of the same type of elastomer material among the types of thermosetting elastomers exemplified above.
When the same silicone rubber is contained, the silicone rubber may be constituted by a cured product of a silicone rubber-based curable composition containing a vinyl group-containing organopolysiloxane.
From the standpoint of mechanical strength, etc., it is preferable that the insulating elastomer layer 60 and/or the conductive elastomer layer 20 contain silicone rubber.

The insulating elastomer may be composed of a cured product of a silicone rubber-based curable composition containing a vinyl group-containing organopolysiloxane. The conductive elastomer may be composed of a conductive filler and a cured product of a silicone rubber-based curable composition containing a vinyl group-containing organopolysiloxane.

The components of the silicone rubber-based curable composition are described in detail below.

In this specification, containing the same silicone rubber means that the silicone rubber-based curable composition contains at least the same type of vinyl group-containing linear organopolysiloxane, and may further contain one or more selected from the group consisting of the same type of crosslinking agent, the same type of non-conductive filler, the same type of silane coupling agent, and the same type of catalyst.

The same type of vinyl group-containing linear organopolysiloxane is sufficient if it contains at least the same vinyl group as the functional group and has a linear shape, but may differ in the amount of vinyl groups in the molecule, the molecular weight distribution, or the amount added.

Crosslinking agents of the same type are sufficient if they have at least a common structure, such as a linear or branched structure, and may have different molecular weight distributions or functional groups in the molecule, or may have different amounts added.

Non-conductive fillers of the same type are sufficient if they have at least a common constituent material, but may differ in particle size, specific surface area, surface treatment agent, or amount of added surface treatment agent.

Silane coupling agents of the same type are sufficient if they have at least a common functional group, but may differ in other functional groups in the molecule or in the amount added.

Catalysts of the same type are those that have at least common constituent materials, but may contain different compositions or may be added in different amounts.

The silicone rubber-based curable composition constituting the same silicone rubber may further contain one or more different types of vinyl group-containing linear organopolysiloxanes, crosslinking agents, non-conductive fillers, silane coupling agents, and catalysts.

The silicone rubber-based hardening composition of this embodiment may contain a vinyl group-containing organopolysiloxane (A). The vinyl group-containing organopolysiloxane (A) is a polymer that is the main component of the silicone rubber-based hardening composition of this embodiment.

The vinyl group-containing organopolysiloxane (A) may include a vinyl group-containing linear organopolysiloxane (A1) having a linear structure.

The vinyl group-containing linear organopolysiloxane (A1) has a linear structure and contains vinyl groups, which become crosslinking points during curing.

The vinyl group content of the vinyl group-containing linear organopolysiloxane (A1) is not particularly limited, but for example, it is preferable that the vinyl group content is 15 mol% or less and that the vinyl group content is 2 or more in the molecule. This optimizes the amount of vinyl groups in the vinyl group-containing linear organopolysiloxane (A1), and ensures the formation of a network with each component described below.

In this specification, "~" indicates that the upper and lower limits are included unless otherwise specified.

In this specification, the vinyl group content refers to the mol % of vinyl group-containing siloxane units when all units constituting the vinyl group-containing linear organopolysiloxane (A1) are taken as 100 mol %. However, it is considered that there is one vinyl group per vinyl group-containing siloxane unit.

The degree of polymerization of the vinyl group-containing linear organopolysiloxane (A1) is not particularly limited, but is preferably within the range of about 1,000 to 10,000, and more preferably about 2,000 to 5,000. The degree of polymerization can be determined, for example, as the number average degree of polymerization (or number average molecular weight) in terms of polystyrene in gel permeation chromatography (GPC) using chloroform as a developing solvent.

Furthermore, the specific gravity of the vinyl group-containing linear organopolysiloxane (A1) is not particularly limited, but is preferably in the range of about 0.9 to 1.1.

By using a vinyl group-containing linear organopolysiloxane (A1) having a degree of polymerization and specific gravity within the above ranges, the heat resistance, flame retardancy, chemical stability, etc. of the resulting silicone rubber can be improved.

As the vinyl group-containing linear organopolysiloxane (A1), it is particularly preferable that it has a structure represented by the following formula (1).

In formula (1), R ¹ is a substituted or unsubstituted alkyl group, alkenyl group, aryl group, or a hydrocarbon group consisting of a combination thereof, each having 1 to 10 carbon atoms. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, and a propyl group, with a methyl group being preferred. Examples of the alkenyl group having 1 to 10 carbon atoms include a vinyl group, an allyl group, and a butenyl group, with a vinyl group being preferred. Examples of the aryl group having 1 to 10 carbon atoms include a phenyl group.

Furthermore, ^R2 is a substituted or unsubstituted alkyl group, alkenyl group, aryl group, or a hydrocarbon group that is a combination of these groups, each having 1 to 10 carbon atoms. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, and a propyl group, and among these, a methyl group is preferable. Examples of the alkenyl group having 1 to 10 carbon atoms include a vinyl group, an allyl group, and a butenyl group. Examples of the aryl group having 1 to 10 carbon atoms include a phenyl group.

^R3 is a substituted or unsubstituted alkyl group having 1 to 8 carbon atoms, an aryl group, or a hydrocarbon group consisting of a combination thereof. Examples of the alkyl group having 1 to 8 carbon atoms include a methyl group, an ethyl group, and a propyl group, and among these, a methyl group is preferable. Examples of the aryl group having 1 to 8 carbon atoms include a phenyl group.

In addition, examples of the substituents of R ¹ and R ² in the formula (1) include a methyl group and a vinyl group, and examples of the substituent of R ³ include a methyl group.

In formula (1), R ¹ 's are independent of each other and may be different from each other or may be the same as each other. The same applies to R ² and R ³ .

Furthermore, m and n are the numbers of repeating units constituting the vinyl group-containing linear organopolysiloxane (A1) represented by formula (1), where m is an integer from 0 to 2000 and n is an integer from 1000 to 10000. m is preferably 0 to 1000, and n is preferably 2000 to 5000.

Specific examples of the vinyl group-containing linear organopolysiloxane (A1) represented by formula (1) include those represented by the following formula (1-1):

In formula (1-1), R ¹ and R ² each independently represent a methyl group or a vinyl group, and at least one of them is a vinyl group.

The vinyl group-containing linear organopolysiloxane (A1) may contain a first vinyl group-containing linear organopolysiloxane (A1-1) having two or more vinyl groups in the molecule and having a vinyl group content of 0.4 mol% or less. The vinyl group content of the first vinyl group-containing linear organopolysiloxane (A1-1) may be 0.1 mol% or less.

The vinyl group-containing linear organopolysiloxane (A1) may also contain a first vinyl group-containing linear organopolysiloxane (A1-1) and a second vinyl group-containing linear organopolysiloxane (A1-2) having a vinyl group content of 0.5 to 15 mol %.

By combining a first vinyl group-containing linear organopolysiloxane (A1-1) with a second vinyl group-containing linear organopolysiloxane (A1-2) with a high vinyl group content as the raw rubber, which is the raw material for silicone rubber, it is possible to unevenly distribute the vinyl groups and more effectively form a crosslinking density distribution in the crosslinked network of the silicone rubber. As a result, the tear strength of the silicone rubber can be more effectively increased.

Specifically, as the vinyl group-containing linear organopolysiloxane (A1), it is preferable to use, for example, a first vinyl group-containing linear organopolysiloxane (A1-1) having two or more units in which R1 is a vinyl group and/or a unit in which R2 is a vinyl group in the molecule, and containing 0.4 mol% or less of these units in the above formula (1-1), and a second vinyl group-containing linear organopolysiloxane (A1-2) containing 0.5 to 15 mol% of units in which R1 is a vinyl group and/or a unit in which R2 is a vinyl group.

The first vinyl group-containing linear organopolysiloxane (A1-1) preferably has a vinyl group content of 0.01 to 0.2 mol %. The second vinyl group-containing linear organopolysiloxane (A1-2) preferably has a vinyl group content of 0.8 to 12 mol %.

When the first vinyl group-containing linear organopolysiloxane (A1-1) and the second vinyl group-containing linear organopolysiloxane (A1-2) are combined and blended, the ratio of (A1-1) to (A1-2) is not particularly limited, but for example, the weight ratio of (A1-1):(A1-2) is preferably 50:50 to 95:5, and more preferably 80:20 to 90:10.

The first and second vinyl group-containing linear organopolysiloxanes (A1-1) and (A1-2) may each be used alone or in combination of two or more.

The vinyl group-containing organopolysiloxane (A) may also contain a vinyl group-containing branched organopolysiloxane (A2) having a branched structure.

<<Organohydrogenpolysiloxane (B)>>
The silicone rubber-based hardenable composition of this embodiment can contain an organohydrogenpolysiloxane (B).
The organohydrogenpolysiloxane (B) is classified into a linear organohydrogenpolysiloxane (B1) having a linear structure and a branched organohydrogenpolysiloxane (B2) having a branched structure, and may contain either one or both of these.

The linear organohydrogenpolysiloxane (B1) has a linear structure and a structure in which hydrogen is directly bonded to Si (≡Si-H), and undergoes a hydrosilylation reaction with the vinyl groups of the vinyl group-containing organopolysiloxane (A) and with the vinyl groups of the components blended into the silicone rubber-based curable composition, forming a polymer that crosslinks these components.

The molecular weight of the linear organohydrogenpolysiloxane (B1) is not particularly limited, but for example, the weight average molecular weight is preferably 20,000 or less, and more preferably 1,000 or more and 10,000 or less.

The weight average molecular weight of the linear organohydrogenpolysiloxane (B1) can be measured, for example, by polystyrene conversion using GPC (gel permeation chromatography) with chloroform as the developing solvent.

In addition, it is generally preferred that the linear organohydrogenpolysiloxane (B1) does not have a vinyl group. This effectively prevents the crosslinking reaction from proceeding within the molecule of the linear organohydrogenpolysiloxane (B1).

As the linear organohydrogenpolysiloxane (B1) described above, for example, one having a structure represented by the following formula (2) is preferably used.

In formula (2), ^R4 is a substituted or unsubstituted alkyl group, alkenyl group, aryl group, a hydrocarbon group combining these groups, or a hydride group having 1 to 10 carbon atoms. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, and a propyl group, and among these, a methyl group is preferable. Examples of the alkenyl group having 1 to 10 carbon atoms include a vinyl group, an allyl group, and a butenyl group. Examples of the aryl group having 1 to 10 carbon atoms include a phenyl group.

Furthermore, ^R5 is a substituted or unsubstituted alkyl group, alkenyl group, aryl group, a hydrocarbon group combining these groups, or a hydride group having 1 to 10 carbon atoms. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, and a propyl group, and among these, a methyl group is preferable. Examples of the alkenyl group having 1 to 10 carbon atoms include a vinyl group, an allyl group, and a butenyl group. Examples of the aryl group having 1 to 10 carbon atoms include a phenyl group.

In addition, in formula (2), the multiple ^R4s are independent of each other and may be different from each other or may be the same. The same applies to ^R5 . However, among the multiple ^R4s and ^R5s , at least two or more are hydrido groups.

Furthermore, ^R6 is a substituted or unsubstituted alkyl group having 1 to 8 carbon atoms, an aryl group, or a hydrocarbon group that is a combination of these. Examples of the alkyl group having 1 to 8 carbon atoms include a methyl group, an ethyl group, and a propyl group, and among these, a methyl group is preferable. Examples of the aryl group having 1 to 8 carbon atoms include a phenyl group. The multiple ^R6s are independent of each other and may be different from each other or the same.

In addition, examples of the substituents R ⁴ , R ⁵ and R ⁶ in the formula (2) include a methyl group and a vinyl group, and from the viewpoint of preventing an intramolecular crosslinking reaction, a methyl group is preferable.

Furthermore, m and n are the numbers of repeating units constituting the linear organohydrogenpolysiloxane (B1) represented by formula (2), where m is an integer from 2 to 150 and n is an integer from 2 to 150. Preferably, m is an integer from 2 to 100 and n is an integer from 2 to 100.

The linear organohydrogenpolysiloxane (B1) may be used alone or in combination of two or more.

The branched organohydrogenpolysiloxane (B2) has a branched structure, and therefore forms regions with high crosslink density, making it a component that contributes greatly to the formation of a sparsely-dense crosslink structure in the silicone rubber system. In addition, like the linear organohydrogenpolysiloxane (B1), it has a structure in which hydrogen is directly bonded to silicon (≡Si-H), and undergoes a hydrosilylation reaction with the vinyl groups of the vinyl group-containing organopolysiloxane (A) and with the vinyl groups of the components blended into the silicone rubber-based curable composition, forming a polymer that crosslinks these components.

The specific gravity of the branched organohydrogenpolysiloxane (B2) is in the range of 0.9 to 0.95.

Furthermore, it is generally preferred that the branched organohydrogenpolysiloxane (B2) does not have a vinyl group. This effectively prevents the crosslinking reaction from proceeding within the molecule of the branched organohydrogenpolysiloxane (B2).

In addition, the branched organohydrogenpolysiloxane (B2) is preferably one represented by the following average composition formula (c):

Average composition formula (c)
(H _a (R ⁷ ) _3-a SiO _1/2 ) _m (SiO _4/2 ) _n
(In formula (c), ^R7 is a monovalent organic group, a is an integer ranging from 1 to 3, m is the number of H _a ( ^R7 ) _3-a SiO _1/2 units, and n is the number of SiO _4/2 units.)

In formula (c), ^R7 is a monovalent organic group, preferably a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, an aryl group, or a hydrocarbon group consisting of a combination thereof. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, and a propyl group, and among these, a methyl group is preferred. Examples of the aryl group having 1 to 10 carbon atoms include a phenyl group.

In formula (c), a is the number of hydride groups (hydrogen atoms directly bonded to Si) and is an integer ranging from 1 to 3, preferably 1.

In addition, in formula (c), m is the number of H _a (R ⁷ ) _3-a SiO _1/2 units, and n is the number of SiO _4/2 units.

Branched organohydrogenpolysiloxane (B2) has a branched structure. Linear organohydrogenpolysiloxane (B1) and branched organohydrogenpolysiloxane (B2) differ in that their structures are linear or branched, and the number of alkyl groups R bonded to Si (R/Si), where the number of Si is 1, is in the range of 1.8 to 2.1 for linear organohydrogenpolysiloxane (B1) and 0.8 to 1.7 for branched organohydrogenpolysiloxane (B2).

In addition, because the branched organohydrogenpolysiloxane (B2) has a branched structure, for example, when heated in a nitrogen atmosphere to 1000°C at a heating rate of 10°C/min, the amount of residue is 5% or more. In contrast, because the linear organohydrogenpolysiloxane (B1) is linear, the amount of residue after heating under the above conditions is almost zero.

Specific examples of branched organohydrogenpolysiloxane (B2) include those having a structure represented by the following formula (3):

In formula (3), ^R7 is a substituted or unsubstituted alkyl group having 1 to 8 carbon atoms, an aryl group, or a hydrocarbon group consisting of a combination thereof, or a hydrogen atom. Examples of the alkyl group having 1 to 8 carbon atoms include a methyl group, an ethyl group, and a propyl group, and among these, a methyl group is preferable. Examples of the aryl group having 1 to 8 carbon atoms include a phenyl group. Examples of the substituent of ^R7 include a methyl group.

In addition, in formula (3), multiple R ^7s are independent of each other and may be different from each other or may be the same.

In addition, in formula (3), "-O-Si≡" indicates that Si has a branched structure that extends three-dimensionally.

The branched organohydrogenpolysiloxane (B2) may be used alone or in combination of two or more.

In addition, the amount of hydrogen atoms (hydride groups) directly bonded to Si in the linear organohydrogenpolysiloxane (B1) and the branched organohydrogenpolysiloxane (B2) is not particularly limited. However, in the silicone rubber-based curable composition, the total amount of hydride groups in the linear organohydrogenpolysiloxane (B1) and the branched organohydrogenpolysiloxane (B2) is preferably 0.5 to 5 moles, more preferably 1 to 3.5 moles, per mole of vinyl groups in the vinyl group-containing linear organopolysiloxane (A1). This ensures that a crosslinked network is formed between the linear organohydrogenpolysiloxane (B1) and the branched organohydrogenpolysiloxane (B2) and the vinyl group-containing linear organopolysiloxane (A1).

<<Silica Particles (C)>>
The silicone rubber-based hardenable composition of this embodiment may contain silica particles (C) as a non-conductive filler, if necessary.

The silica particles (C) are not particularly limited, but for example, fumed silica, calcined silica, precipitated silica, etc. may be used. These may be used alone or in combination of two or more types.

The silica particles (C) preferably have a specific surface area, as measured by the BET method, of, for example, 50 to 400 m ² /g, and more preferably 100 to 400 m ² /g, and the average primary particle size of the silica particles (C) is preferably, for example, 1 to 100 nm, and more preferably about 5 to 20 nm.

By using silica particles (C) that have a specific surface area and average particle size within this range, the hardness and mechanical strength of the silicone rubber formed can be improved, particularly the tensile strength.

<<Silane coupling agent (D)>>
The silicone rubber-based hardenable composition of this embodiment may contain a silane coupling agent (D).
The silane coupling agent (D) may have a hydrolyzable group. The hydrolyzable group is hydrolyzed by water to become a hydroxyl group, and the hydroxyl group undergoes a dehydration condensation reaction with the hydroxyl group on the surface of the silica particles (C), thereby modifying the surface of the silica particles (C).

The silane coupling agent (D) may contain a silane coupling agent having a hydrophobic group. This provides the surface of the silica particles (C) with this hydrophobic group, which reduces the cohesive force of the silica particles (C) in the silicone rubber-based curable composition and, in turn, in the silicone rubber (reducing the cohesion caused by hydrogen bonds due to silanol groups). As a result, it is presumed that the dispersibility of the silica particles in the silicone rubber-based curable composition is improved. This increases the interface between the silica particles and the rubber matrix, enhancing the reinforcing effect of the silica particles. Furthermore, it is presumed that the slipperiness of the silica particles in the matrix is improved during deformation of the rubber matrix. And, due to the improved dispersibility and slipperiness of the silica particles (C), the mechanical strength (e.g., tensile strength, tear strength, etc.) of the silicone rubber due to the silica particles (C) is improved.

Furthermore, the silane coupling agent (D) may contain a silane coupling agent having a vinyl group. This introduces a vinyl group onto the surface of the silica particles (C). Therefore, when the silicone rubber-based curable composition is cured, that is, when the vinyl group of the vinyl group-containing organopolysiloxane (A) and the hydride group of the organohydrogenpolysiloxane (B) undergo a hydrosilylation reaction to form a network (crosslinked structure), the vinyl group of the silica particles (C) also participates in the hydrosilylation reaction with the hydride group of the organohydrogenpolysiloxane (B), and the silica particles (C) are also incorporated into the network. This allows the formed silicone rubber to have a low hardness and a high modulus.

As the silane coupling agent (D), a silane coupling agent having a hydrophobic group and a silane coupling agent having a vinyl group can be used in combination.

Examples of the silane coupling agent (D) include those represented by the following formula (4):

Y _n -Si-(X) _4-n ...(4)
In the above formula (4), n represents an integer of 1 to 3. Y represents a functional group having a hydrophobic group, a hydrophilic group, or a vinyl group. When n is 1, it is a hydrophobic group. When n is 2 or 3, at least one of them is a hydrophobic group. X represents a hydrolyzable group.

The hydrophobic group is an alkyl group having 1 to 6 carbon atoms, an aryl group, or a hydrocarbon group that is a combination of these. Examples include a methyl group, an ethyl group, a propyl group, and a phenyl group, and among these, a methyl group is particularly preferred.

Examples of hydrophilic groups include hydroxyl groups, sulfonic acid groups, carboxyl groups, and carbonyl groups, and among these, hydroxyl groups are particularly preferred. Note that hydrophilic groups may be included as functional groups, but it is preferable that they are not included from the viewpoint of imparting hydrophobicity to the silane coupling agent (D).

Further, examples of the hydrolyzable group include alkoxy groups such as methoxy and ethoxy groups, chloro groups, and silazane groups, among which silazane groups are preferred due to their high reactivity with silica particles (C). Note that those having silazane groups as hydrolyzable groups have two (Y _n -Si-) structures in the above formula (4) due to their structural characteristics.

Specific examples of the silane coupling agent (D) represented by the above formula (4) include, for example, alkoxysilanes such as methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, and decyltrimethoxysilane; chlorosilanes such as methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, and phenyltrichlorosilane; and hexamethyldisilazane, which have a hydrophobic group as a functional group. Examples of the silane having a vinyl group include alkoxysilanes such as methacryloxypropyltriethoxysilane, methacryloxypropyltrimethoxysilane, methacryloxypropylmethyldiethoxysilane, methacryloxypropylmethyldimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, and vinylmethyldimethoxysilane; chlorosilanes such as vinyltrichlorosilane and vinylmethyldichlorosilane; and divinyltetramethyldisilazane. Among these, taking into consideration the above description, it is particularly preferable that the silane having a hydrophobic group is hexamethyldisilazane, and the silane having a vinyl group is divinyltetramethyldisilazane.

In this embodiment, the lower limit of the content of the silane coupling agent (D) is preferably 1 mass% or more, more preferably 3 mass% or more, and even more preferably 5 mass% or more, based on 100 parts by weight of the total amount of the vinyl group-containing organopolysiloxane (A).The upper limit of the content of the silane coupling agent (D) is preferably 100 mass% or less, more preferably 80 mass% or less, and even more preferably 40 mass% or less, based on 100 parts by weight of the total amount of the vinyl group-containing organopolysiloxane (A).
By making the content of silane coupling agent (D) above the lower limit, when using silica particles (C), it can contribute to improving the mechanical strength of the silicone rubber as a whole.In addition, by making the content of silane coupling agent (D) below the upper limit, the silicone rubber can have appropriate mechanical properties.

<<Platinum or platinum compound (E)>>
The silicone rubber-based hardenable composition of this embodiment may contain platinum or a platinum compound (E).
The platinum or platinum compound (E) is a catalytic component that acts as a catalyst during curing. The amount of platinum or platinum compound (E) added is a catalytic amount.

As the platinum or platinum compound (E), known substances can be used, such as platinum black, platinum supported on silica or carbon black, chloroplatinic acid or an alcohol solution of chloroplatinic acid, a complex salt of chloroplatinic acid and an olefin, and a complex salt of chloroplatinic acid and a vinyl siloxane.

The platinum or platinum compound (E) may be used alone or in combination of two or more.

<<Water (F)>>
Furthermore, the silicone rubber-based hardening composition of this embodiment may contain water (F) in addition to the above components (A) to (E).

Water (F) functions as a dispersion medium to disperse each component contained in the silicone rubber-based curable composition, and is also a component that contributes to the reaction between the silica particles (C) and the silane coupling agent (D). Therefore, the silica particles (C) and the silane coupling agent (D) can be more reliably linked to each other in the silicone rubber, and uniform properties can be exhibited overall.

Furthermore, when water (F) is contained, its content can be set appropriately, but specifically, for example, it is preferably in the range of 10 to 100 parts by weight, and more preferably in the range of 30 to 70 parts by weight, per 100 parts by weight of the silane coupling agent (D). This allows the reaction between the silane coupling agent (D) and the silica particles (C) to proceed more reliably.

(Other ingredients)
Furthermore, the silicone rubber-based hardening composition of the present embodiment may further contain other components in addition to the above components (A) to (F), such as inorganic fillers other than the silica particles (C), such as diatomaceous earth, iron oxide, zinc oxide, titanium oxide, barium oxide, magnesium oxide, cerium oxide, calcium carbonate, magnesium carbonate, zinc carbonate, glass wool, and mica, as well as additives such as reaction inhibitors, dispersants, pigments, dyes, antistatic agents, antioxidants, flame retardants, and thermal conductivity improvers.

In addition, the content ratio of each component in the silicone rubber-based hardening composition is not particularly limited, but is set, for example, as follows.

In this embodiment, the upper limit of the content of silica particles (C) may be, for example, 60 parts by weight or less, preferably 50 parts by weight or less, and more preferably 40 parts by weight or less, relative to 100 parts by weight of the total amount of vinyl group-containing organopolysiloxane (A). This allows for a balance between mechanical strength such as hardness and tensile strength. The lower limit of the content of silica particles (C) is not particularly limited, and may be, for example, 10 parts by weight or more, relative to 100 parts by weight of the total amount of vinyl group-containing organopolysiloxane (A).

The silane coupling agent (D) is preferably contained in an amount of 5 parts by weight or more and 100 parts by weight or less, and more preferably 5 parts by weight or more and 40 parts by weight or less, per 100 parts by weight of the vinyl group-containing organopolysiloxane (A). This can reliably improve the dispersibility of the silica particles (C) in the silicone rubber-based curable composition.

The content of organohydrogenpolysiloxane (B) is preferably, for example, 0.5 parts by weight or more and 20 parts by weight or less, and more preferably 0.8 parts by weight or more and 15 parts by weight or less, per 100 parts by weight of the total amount of vinyl group-containing organopolysiloxane (A), silica particles (C), and silane coupling agent (D). By keeping the content of (B) within the above range, a more effective curing reaction may be achieved.

The content of platinum or platinum compound (E) means a catalytic amount and can be set appropriately, but specifically, it is an amount such that the platinum group metal in this component is 0.01 to 1000 ppm by weight, preferably 0.1 to 500 ppm, relative to the total amount of vinyl group-containing organopolysiloxane (A), silica particles (C), and silane coupling agent (D). By making the content of platinum or platinum compound (E) equal to or greater than the above lower limit, the obtained silicone rubber composition can be sufficiently cured. By making the content of platinum or platinum compound (E) equal to or less than the above upper limit, the curing speed of the obtained silicone rubber composition can be improved.

Furthermore, when water (F) is contained, its content can be set appropriately, but specifically, for example, it is preferably in the range of 10 to 100 parts by weight, and more preferably in the range of 30 to 70 parts by weight, per 100 parts by weight of the silane coupling agent (D). This allows the reaction between the silane coupling agent (D) and the silica particles (C) to proceed more reliably.

In this embodiment, the hardness, tensile strength, breaking elongation, and tear strength can be controlled by appropriately selecting, for example, the type and amount of each component contained in the silicone rubber-based hardening composition, the preparation method of the silicone rubber-based hardening composition, and the like. Among these, for example, appropriately controlling the type and blending ratio of the resin constituting the silicone rubber, the crosslinking density and crosslinking structure of the resin, improving the blending ratio of the inorganic filler and the bond of the inorganic filler with the rubber, using a first vinyl group-containing linear organopolysiloxane (A1-1) having a vinyl group content of 0.4 mol% or less, using a silane coupling agent having a vinyl group, and appropriately adjusting the content of the silica particles (C) and the content of the silane coupling agent can be cited as elements for setting the hardness, tensile strength, breaking elongation, and tear strength to the desired numerical range.

<Method of manufacturing silicone rubber>
Next, a method for producing the silicone rubber of this embodiment will be described.
In the method for producing the silicone rubber of this embodiment, a silicone rubber-based hardening composition is prepared, and the silicone rubber can be obtained by hardening the silicone rubber-based hardening composition.
Details are provided below.

First, the components of the silicone rubber-based hardening composition are mixed uniformly using any kneading device to prepare the silicone rubber-based hardening composition.

[1] For example, a predetermined amount of vinyl group-containing organopolysiloxane (A), silica particles (C), and silane coupling agent (D) are weighed out, and then kneaded using any kneading device to obtain a kneaded product containing these components (A), (C), and (D).

It is preferable to prepare this mixture by first kneading the vinyl group-containing organopolysiloxane (A) with the silane coupling agent (D) and then kneading (mixing) the silica particles (C). This further improves the dispersibility of the silica particles (C) in the vinyl group-containing organopolysiloxane (A).

When obtaining this kneaded mixture, water (F) may be added to the kneaded mixture of components (A), (C), and (D) as necessary. This allows the reaction between the silane coupling agent (D) and the silica particles (C) to proceed more reliably.

Furthermore, it is preferable that the kneading of each of the components (A), (C), and (D) is carried out through a first step of heating at a first temperature and a second step of heating at a second temperature. This allows the surface of the silica particles (C) to be surface-treated with the coupling agent (D) in the first step, and allows the by-products generated by the reaction between the silica particles (C) and the coupling agent (D) to be reliably removed from the kneaded mixture in the second step. Thereafter, component (A) may be added to the obtained kneaded mixture as necessary, and further kneaded. This allows the compatibility of the components in the kneaded mixture to be improved.

The first temperature is preferably, for example, about 40 to 120°C, and more preferably, for example, about 60 to 90°C. The second temperature is preferably, for example, about 130 to 210°C, and more preferably, for example, about 160 to 180°C.

The atmosphere in the first step is preferably an inert atmosphere such as a nitrogen atmosphere, and the atmosphere in the second step is preferably a reduced pressure atmosphere.

Furthermore, the time for the first step is, for example, preferably about 0.3 to 1.5 hours, and more preferably about 0.5 to 1.2 hours. The time for the second step is, for example, preferably about 0.7 to 3.0 hours, and more preferably about 1.0 to 2.0 hours.

By setting the above conditions for the first and second steps, the above effects can be obtained more significantly.

[2] Next, predetermined amounts of organohydrogenpolysiloxane (B) and platinum or platinum compound (E) are weighed out, and then, using any kneading device, the components (B) and (E) are kneaded into the mixture prepared in the above step [1] to obtain a silicone rubber-based curable composition. The obtained silicone rubber-based curable composition may be a paste containing a solvent.

When mixing the components (B) and (E), it is preferable to first mix the mixture prepared in step [1] above with the organohydrogenpolysiloxane (B), and then mix the mixture prepared in step [1] above with platinum or a platinum compound (E), and then mix the mixtures together. This allows the components (A) to (E) to be reliably dispersed in the silicone rubber-based curable composition without allowing the reaction between the vinyl group-containing organopolysiloxane (A) and the organohydrogenpolysiloxane (B) to proceed.

The temperature at which components (B) and (E) are kneaded is, for example, preferably about 10 to 70°C, and more preferably about 25 to 30°C, as the roll setting temperature.

Furthermore, the kneading time is preferably, for example, about 5 minutes to 1 hour, and more preferably about 10 to 40 minutes.

In the above steps [1] and [2], by setting the temperature within the above range, the progress of the reaction between the vinyl group-containing organopolysiloxane (A) and the organohydrogenpolysiloxane (B) can be more accurately prevented or suppressed. In addition, in the above steps [1] and [2], by setting the kneading time within the above range, each of the components (A) to (E) can be more reliably dispersed in the silicone rubber-based curable composition.

The kneading device used in each step [1] and [2] is not particularly limited, but may be, for example, a kneader, a two-roll mill, a Banbury mixer (continuous kneader), a pressure kneader, etc.

In addition, in this step [2], a reaction inhibitor such as 1-ethynylcyclohexanol may be added to the kneaded mixture. This makes it possible to more accurately prevent or inhibit the progress of the reaction between the vinyl group-containing organopolysiloxane (A) and the organohydrogenpolysiloxane (B) even if the temperature of the kneaded mixture is set to a relatively high temperature.

[3] Next, the silicone rubber-based curable composition is cured to form silicone rubber.

In this embodiment, the curing process of the silicone rubber-based curable resin composition is carried out, for example, by heating at 100 to 250°C for 1 to 30 minutes (first curing) and then post-baking at 200°C for 1 to 4 hours (secondary curing).

Through the above steps, a silicone rubber consisting of a cured product of the silicone rubber-based curable resin composition is obtained.

[3] Next, the silicone rubber-based hardening composition obtained in step [2] is dissolved in a solvent to obtain an insulating paste.
[3] Next, the silicone rubber-based hardening composition obtained in step [2] is dissolved in a solvent, and a conductive filler is added to obtain a conductive paste.

(solvent)
The conductive paste and the insulating paste contain a solvent.
As the solvent, various known solvents can be used, including, for example, high boiling point solvents. These may be used alone or in combination of two or more kinds.

The lower limit of the boiling point of the high boiling point solvent is, for example, 100°C or higher, preferably 130°C or higher, and more preferably 150°C or higher. This can improve the printing stability of screen printing and the like. On the other hand, the upper limit of the boiling point of the high boiling point solvent is not particularly limited, but may be, for example, 300°C or lower, 290°C or lower, or 280°C or lower. This can suppress excessive thermal history during wiring formation, thereby preventing damage to the base and maintaining the shape of the wiring formed from the conductive paste in a good condition.

The solvent can be appropriately selected from the viewpoint of the solubility and boiling point of the silicone rubber-based curable resin composition, but can include, for example, aliphatic hydrocarbons having 5 to 20 carbon atoms, preferably aliphatic hydrocarbons having 8 to 18 carbon atoms, and more preferably aliphatic hydrocarbons having 10 to 15 carbon atoms.

Examples of the solvent include aliphatic hydrocarbons such as pentane, hexane, cyclohexane, heptane, methylcyclohexane, ethylcyclohexane, octane, decane, dodecane, and tetradecane; aromatic hydrocarbons such as benzene, toluene, ethylbenzene, xylene, mesitylene, trifluoromethylbenzene, and benzotrifluoride; diethyl ether, diisopropyl ether, dibutyl ether, cyclopentyl methyl ether, cyclopentyl ethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, and diethylene glycol dimethyl ether. Examples of such an ether include ethers such as ethanol monobutyl ether, dipropylene glycol dimethyl ether, dipropylene glycol methyl-n-propyl ether, 1,4-dioxane, 1,3-dioxane, and tetrahydrofuran; haloalkanes such as dichloromethane, chloroform, 1,1-dichloroethane, 1,2-dichloroethane, 1,1,1-trichloroethane, and 1,1,2-trichloroethane; carboxylic acid amides such as N,N-dimethylformamide and N,N-dimethylacetamide; sulfoxides such as dimethyl sulfoxide and diethyl sulfoxide; and esters such as diethyl carbonate. These may be used alone or in combination of two or more.
The solvent used here may be appropriately selected from among solvents capable of uniformly dissolving or dispersing the components in the conductive paste.

The solvent may include a first solvent having an upper limit of the polar term (δ _p ) of the Hansen solubility parameter of, for example, 10 MPa ^1/2 or less, preferably 7 MPa ^1/2 or less, and more preferably 5.5 MPa ^1/2 or less. This allows the silicone rubber-based curable resin composition to have good dispersibility and solubility in the paste. The lower limit of the polar term (δ _p ) of the first solvent is not particularly limited, but may be, for example, 0 Pa ^1/2 or more.

The upper limit of the hydrogen bond term (δ _h ) of the Hansen solubility parameter in the first solvent is, for example, 20 MPa ^1/2 or less, preferably 10 MPa ^1/2 or less, and more preferably 7 MPa ^1/2 or less. This allows the silicone rubber-based curable resin composition to have good dispersibility and solubility in the paste. The lower limit of the hydrogen bond term (δ _h ) of the first solvent is not particularly limited, but may be, for example, 0 Pa ^1/2 or more.

Hansen solubility parameter (HSP) is an index that indicates the solubility of a substance, i.e., how much a substance dissolves in another substance. HSP expresses solubility as a three-dimensional vector. This three-dimensional vector can be typically expressed by a dispersion term (δ _d ), a polar term (δ _p ), and a hydrogen bond term (δ _h ). Vectors that are similar to each other can be judged to have high solubility. The similarity of vectors can be judged by the distance of the Hansen solubility parameter (HSP distance).

As used herein, the Hansen Solubility Parameter (HSP value) can be calculated using software called HSPiP (Hansen Solubility Parameters in Practice), where the computer software HSPiP developed by Hansen and Abbott includes a function for calculating HSP distances and a database of Hansen parameters for various resins and solvents or non-solvents.
The solubility of each resin in pure solvents and mixed solvents of good and poor solvents is investigated, and the results are entered into the HSPiP software to calculate D: dispersion term, P: polarity term, H: hydrogen bond term, and R0: radius of the solubility sphere.

The solvent of this embodiment may be selected, for example, from elastomers or structural units constituting the elastomers, with small differences in HSP distance, polarity term, or hydrogen bond term between the solvent and the elastomer.

The lower limit of the viscosity of the conductive paste and/or insulating paste when measured at a shear rate of 20 [1/s] at room temperature of 25°C is, for example, 1 Pa·s or more, preferably 5 Pa·s or more, and more preferably 10 Pa·s or more. This can improve film-forming properties. Also, shape retention can be improved even when forming a thick film. On the other hand, the upper limit of the viscosity of the conductive paste and/or insulating paste at room temperature of 25°C is, for example, 100 Pa·s or less, preferably 90 Pa·s or less, and more preferably 80 Pa·s or less. This can improve the printability of the paste.

The viscosity measured at room temperature of 25°C at a shear rate of 1 [1/s] is defined as η1, the viscosity measured at a shear rate of 5 [1/s] is defined as η5, and the thixotropic index is defined as the viscosity ratio (η1/η5).
In this case, the lower limit of the thixotropic index of the conductive paste and/or the insulating paste is, for example, 1.0 or more, preferably 1.1 or more, and more preferably 1.2 or more. This allows the shape of the wiring obtained by the printing method to be stably maintained. On the other hand, the upper limit of the thixotropic index of the conductive paste and/or the insulating paste is, for example, 3.0 or less, preferably 2.5 or less, and more preferably 2.0 or less. This allows the paste to be easily printed.

The content of the silicone rubber-based curable composition in the insulating paste is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more, based on 100% by mass of the insulating paste. The content of the silicone rubber-based curable composition in the insulating paste is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 35% by mass or less, based on 100% by mass of the insulating paste.

(Conductive filler)
As the conductive filler, a known conductive material may be used, but metal powder (G) may also be used.
The metal constituting the metal powder (G) is not particularly limited, but may include, for example, at least one of copper, silver, gold, nickel, tin, lead, zinc, bismuth, antimony, or metal powder alloyed with these, or two or more of these.
Of these, the metal powder (G) preferably contains silver or copper, that is, silver powder or copper powder, because of their high electrical conductivity and ready availability.
These metal powders (G) may also be coated with other metals.

In this embodiment, there is no restriction on the shape of the metal powder (G), but conventional shapes such as dendritic, spherical, and scale-shaped shapes can be used. Among these, scale-shaped metal powder (G) may be used.

The particle size of the metal powder (G) is not limited, but is preferably 0.001 μm or more, more preferably 0.01 μm or more, and even more preferably 0.1 μm or more, in terms of average particle size D _50. The particle size of the metal powder (G) is preferably 1,000 μm or less, more preferably 100 μm or less, and even more preferably 20 μm or less, in terms of average particle size D ₅₀ .
By setting the average particle size _D50 in this range, the silicone rubber can exhibit appropriate electrical conductivity.
The particle size of the metal powder (G) can be defined as the average particle size of 200 arbitrarily selected metal powder particles, for example, by observing the conductive paste or silicone rubber molded using the conductive paste with a transmission electron microscope or the like and performing image analysis.

The content of the conductive filler in the conductive paste is preferably 20% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more, based on the total amount of the conductive paste. The content of the conductive filler in the conductive paste is preferably 85% by mass or less, more preferably 75% by mass or less, and even more preferably 65% by mass or less, based on the total amount of the conductive paste.
By setting the content of the conductive filler to be equal to or greater than the above lower limit, the silicone rubber can have appropriate conductive properties, while by setting the content of the conductive filler to be equal to or less than the above upper limit, the silicone rubber can have appropriate flexibility.

The content of the silicone rubber-based hardening composition in the conductive paste is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, based on 100% by mass of the conductive paste. The content of the silicone rubber-based hardening composition in the conductive paste is preferably 25% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less, based on 100% by mass of the conductive paste.
By making the content of the silicone rubber-based hardening composition equal to or greater than the above lower limit, the silicone rubber can have an appropriate flexibility, while by making the content of the silicone rubber-based hardening composition equal to or less than the above upper limit, the mechanical strength of the silicone rubber can be improved.

The lower limit of the content of silica particles (C) in the conductive paste can be, for example, 1% by mass or more, preferably 3% by mass or more, and more preferably 4% by mass or more, based on 100% by mass of the total amount of silica particles (C) and conductive filler. This can improve the mechanical strength of the silicone rubber. On the other hand, the upper limit of the content of the silica particles (C) in the conductive paste can be, for example, 20% by mass or less, preferably 15% by mass or less, and more preferably 10% by mass or less, based on 100% by mass of the total amount of silica particles (C) and conductive filler. This can balance the elastic electrical properties and mechanical strength of the silicone rubber.

The lower limit of the conductive filler content in the conductive cured product obtained by curing the conductive paste that constitutes the conductive elastomer layer 20 is, for example, 50% by mass or more, preferably 60% by mass or more, and more preferably 70% by mass or more, based on 100% by mass of the conductive cured product. This improves the elastic electrical properties. On the other hand, the upper limit of the conductive filler content in the conductive cured product is, for example, 90% by mass or less, preferably 88% by mass or less, and more preferably 85% by mass or less, based on 100% by mass of the conductive elastomer layer 20. This prevents deterioration of rubber properties such as elasticity.

The lower limit of the content of silica particles (C) in the conductive cured product obtained by curing the conductive paste constituting the conductive elastomer layer 20 can be, for example, 1% by mass or more, preferably 3% by mass or more, and more preferably 4% by mass or more, based on 100% by mass of the total amount of silica particles (C) and conductive filler. This can improve the mechanical strength of the silicone rubber. On the other hand, the upper limit of the content of silica particles (C) in the conductive cured product can be, for example, 20% by mass or less, preferably 15% by mass or less, and more preferably 10% by mass or less, based on 100% by mass of the total amount of silica particles (C) and conductive filler. This can balance the elastic electrical properties and mechanical strength of the silicone rubber.

<Biosensor>
The biosensor is not particularly limited as long as it includes the flexible sheet electrode 1 described above.
Fig. 3 is a top view showing an example of the configuration of the biosensor 100. Fig. 4 is a cross-sectional view taken along line BB of Fig. 3.
The biosensor 100 comprises a flexible sheet electrode 1 having a flexible substrate 10 and an elastomeric electrode layer 2 that includes a conductive elastomer layer 20 .
3 to 5, an electrolyte retention layer 70 (not shown) is formed on the entire surface of the elastomer electrode layer 2.

The biosensor 100 can detect bioelectrical signals generated by biological activity of the heart, muscles, skin, nerves, etc. by making one surface 22 of the conductive elastomer layer 20 conform to the body of the subject. This biosensor 100 can be suitably used as a sensor for measuring electrocardiogram waveforms when using a flexible sheet electrode 1 having multiple elastomer electrode layers 2 in the in-plane direction of the flexible substrate 10, or when using multiple flexible sheet electrodes 1 provided as separate members.

Subjects may include humans and non-human animals.

The biosensor 100 can be used as a dry sensor that is convenient and can be used repeatedly.
The biosensor 100 and flexible sheet electrode 1 of this embodiment can be applied to skin that has not been pretreated, but if necessary, the skin of the subject at the measurement site may be pretreated before use.
Examples of pretreatment include applying an adhesive such as gel, applying a moisturizer such as water or cream, removing dirt with alcohol or the like, and polishing the skin.

When viewed from above, the flexible substrate 10 has an electrode formation region in which an elastomer electrode layer 2 (conductive elastomer layer 20) is formed. In this electrode formation region, the flexible substrate 10 and the conductive elastomer layer 20 are in close contact with each other when the substrate is not stretched or stretched, thereby increasing the mechanical strength of the entire biosensor 100.

The flexible substrate 10 may also have a non-electrode region around the electrically conductive region where the conductive elastomer layer 20 is not formed. This non-electrode region can be fitted with a sewing thread, snap button, or other attachment for installation on clothing, etc. Alternatively, when the biosensor 100 is wrapped around the body, such as the wrist or ankle, the non-electrode region of the flexible substrate 10 may be overlapped in the thickness direction to secure it to the body.

As shown in FIG. 3, an example of the flexible substrate 10 has at least a portion, for example the main body 12, in the shape of a band that can be wrapped around the body. Such a biosensor 100 has a structure suitable for a band-mounted bioelectrode that can be wrapped around a part of the body, such as the wrist or ankle.

The band-shaped flexible substrate 10 in FIG. 3 may have a main body 12 and an extension portion 14 that protrudes in the in-plane direction of the main body 12. Even when the main body 12 is deformed into a ring structure or the like, deformation of the extension portion 14 is suppressed. This makes it possible to suppress connection failures in the external connection portion 30 attached to the extension portion 14.

The elastomeric electrode layer 2 comes into contact with the body when the biosensor 100 is in use, and can conform closely to the contact surface, conforming to the surface shape and deformations of the body.

The biosensor 100 may be configured to be connected to the outside through the conductive elastomer layer 20, or may be configured to be connected through a connection portion 26 that is a separate member electrically connected to the conductive elastomer layer 20. The connection portion 26 may be configured to be electrically connected to the conductive elastomer layer 20 via an elastic wiring 24, as shown in FIG.
An insulating cover layer for preventing contact with the skin may be formed on at least a portion of the surface of the elastomer electrode layer 2, specifically, on at least one surface of the conductive elastomer layer 20, the elastic wiring 24, and the connection portion 26. This insulating cover layer may be made of an insulating elastomer, preferably insulating silicone rubber.

The conductive elastomer layer 20, the elastic wiring 24 and the connection portion 26 are made of the same/different conductive elastomers, and are preferably made of the same conductive elastomer.

Each part constituting the conductive elastomer layer 20 may be composed of a printed layer formed by a printing method using a conductive paste, more specifically, a conductive paste containing a conductive filler and silicone rubber. In this case, each part including the conductive elastomer layer 20, the elastic wiring 24, and the connection part 26 may be configured seamlessly with each other.

The external connection section 30 can transmit the bioelectrical signal detected through the conductive elastomer layer 20 to an external device such as an electronic component.

The biosensor 100 in FIG.
The external connection part 30 is provided on the flexible substrate 10 on the side opposite to the conductive elastomer layer 20. For example, the external connection part 30 in Fig. 2 is formed on the other surface 13 of the flexible substrate 10. This prevents the external connection part 30 from coming into contact with the body together with the conductive elastomer layer 20 when the biosensor 100 is in use, and can suppress interference with detection of bioelectrical signals.

The external connection portion 30 is not particularly limited as long as it is configured to be electrically connected to the conductive elastomer layer 20, but is made of a conductive material such as a metal material or a conductive elastomer.

The shape of the external connection part 30 is not particularly limited, but may be a connector that can be connected to an electronic component, or may have a structure that allows easy installation of wiring.

An example of the external connection portion 30 may be a metallic snap button.
4 is a male snap button, and is fixed to the flexible substrate 10 using a mounting plate 32 and a mounting pin 34, which are metal mounting fixtures. The fixing method of sandwiching the flexible substrate 10 between the external connection part 30 and the mounting plate 32 can suppress misalignment of the fixed position of the external connection part 30.
The mounting pin 34 comes into contact with a portion of the conductive elastomer layer 20 , for example, the connection portion 26 , and can establish electrical continuity between the conductive elastomer layer 20 and the external connection portion 30 .

In addition, a portion or the entire surface of the mounting plate 32 in FIG. 4 is covered with an insulating protective layer 52. The insulating protective layer 52 can prevent contact between the mounting plate 32 and the body. The insulating protective layer 52 may be made of any insulating material, and may be made of, for example, an insulating elastomer such as silicone rubber.

<Biological signal measuring device>
The biological signal measuring device of this embodiment will be described.
FIG. 5 is a diagram illustrating an example of the configuration of the biological signal measuring device 200. As shown in FIG.

The biosignal measuring device is not particularly limited as long as it includes the above-mentioned biosensor.
The biosignal measuring device includes one biosensor 100, but depending on the application, may include two or more independent biosensors 100. Each biosensor may be directly attached to the body, or may be attached to a body attachment member such as clothing.

The biosignal measuring device includes electronic components that can be electrically connected to the biosensor 100.

The electronic components may be any known component depending on the application, such as an amplifier, an AD converter, a CPU, a memory, a communication circuit, a wireless communication unit, an analog filter, a capacitor, a resistor, a battery, etc. One or more of these may be modularized on a circuit board, allowing the biosignal measuring device to be used as a wearable device.
Further, other sensors such as an acceleration sensor, a temperature sensor, and a pressure sensor may be used in combination as the electronic components.

The biosignal measuring device 200 in FIG. 5 includes a biosensor 100, a connector 210, a cable 220, a sensor module 230, and a computer 240.

The connector 210 has a structure that allows it to be electrically connected to the external connection portion 30 of the biosensor 100, and may have, for example, a female snap button.
The cable 220 electrically connects the connector 210 to a sensor module 230 and a computer 240 which are electronic components.
The sensor module 230 may be an ECG sensor module for measuring electrocardiogram waveforms. The sensor module 230 may include electrical circuitry to suppress interference from external RF sources, line frequencies, and electrical noise, thereby suppressing noise when measuring bioelectrical signals.
The computer 240 can acquire bioelectric signals and generate and output waveforms of bioelectric potentials such as surface electromyograms, electrocardiograms, skin potentials, and electroencephalograms. The computer 240 may be a single-board computer configured with a printed circuit board including a CPU, peripheral components, an input/output interface, a connector, and the like.

The biological signal measuring system of this embodiment will be described.
A biosignal measurement system may be a system that displays, analyzes and/or stores data (biosignals) received from a biosensor.

The above describes the embodiments of the present invention, but these are merely examples of the present invention, and various configurations other than those described above can be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and modifications and improvements within the scope of the present invention are included in the present invention.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to the description of these examples.

The raw material components shown in Table 1 are as follows.
(A1-1): First vinyl group-containing linear organopolysiloxane: a vinyl group-containing dimethylpolysiloxane (having a structure represented by the above formula (1-1)) synthesized according to the following synthesis scheme 1.
(A1-2): Second vinyl group-containing linear organopolysiloxane: a vinyl group-containing dimethylpolysiloxane synthesized according to the following synthesis scheme 2 (a structure represented by the above formula (1-1) in which R ¹ and R ² are vinyl groups).

(Organohydrogenpolysiloxane (B))
(B-1): Organohydrogenpolysiloxane: "TC-25D" manufactured by Momentive Corporation

(Silica Particles (C))
(C-1): Silica fine particles (particle size 7 nm, specific surface area 300 m ² /g), manufactured by Nippon Aerosil Co., Ltd., "AEROSIL300"

(Silane Coupling Agent (D))
(D-1): Hexamethyldisilazane (HMDZ), manufactured by Gelest, "HEXAMETHYLDISILAZANE (SIH6110.1)"
(D-2) Divinyltetramethyldisilazane, manufactured by Gelest, "1,3-DIVINYLTETRAMETHYLDISILAZANE (SID4612.0)"

(Platinum or platinum compound (E))
(E-1): Platinum compound (manufactured by Momentive, product name "TC-25A")

(Water (F))
(F): Pure water

(Metal Powder (G))
(G1): Silver powder, manufactured by Tokuriki Chemical Laboratory Co., Ltd., product name "TC-101", median diameter d ₅₀ : 8.0 μm, aspect ratio 16.4, average major axis 4.6 μm

(Synthesis of vinyl group-containing organopolysiloxane (A))
[Synthesis Scheme 1: Synthesis of First Vinyl Group-Containing Linear Organopolysiloxane (A1-1)]
A first vinyl group-containing linear organopolysiloxane (A1-1) was synthesized according to the following formula (5).
That is, 74.7 g (252 mmol) of octamethylcyclotetrasiloxane and 0.1 g of potassium siliconate were placed in a 300 mL separable flask equipped with a cooling tube and stirring blade and substituted with Ar gas, and the temperature was raised and the mixture was stirred for 30 minutes at 120° C. During this time, an increase in viscosity was confirmed.
The temperature was then raised to 155° C. and stirring was continued for 3 hours. After 3 hours, 0.1 g (0.6 mmol) of 1,3-divinyltetramethyldisiloxane was added and the mixture was further stirred at 155° C. for 4 hours.
After 4 hours, the mixture was diluted with 250 mL of toluene and washed three times with water. The washed organic layer was washed several times with 1.5 L of methanol for reprecipitation purification, and the oligomer and polymer were separated. The resulting polymer was dried overnight at 60° C. under reduced pressure to obtain a first vinyl group-containing linear organopolysiloxane (A1-1) (Mn=2.2×10 ⁵ , Mw=4.8×10 ⁵ ). The vinyl group content calculated by H-NMR spectrum measurement was 0.04 mol%.

[Synthesis Scheme 2: Synthesis of second vinyl group-containing linear organopolysiloxane (A1-2)]
A second vinyl-containing linear organopolysiloxane (A1-2) was synthesized as shown in the following formula (6) (Mn=2.3×10 ⁵ , Mw=5.0×10 ⁵ ). The vinyl group content calculated by H-NMR spectrum measurement was 0.93 mol %.

(Preparation of Silicone Rubber-Based Curable Composition)
Silicone rubber-based curable compositions Samples 1 and 2 were prepared according to the following procedure.
First, a mixture of 90% vinyl group-containing organopolysiloxane (A), silane coupling agent (D), and water (F) was pre-kneaded in the proportions shown in Table 1 below, and then silica particles (C) were added to the mixture and further kneaded to obtain a kneaded product (silicone rubber compound).
Here, the kneading after the addition of the silica particles (C) was carried out through a first step of kneading for 1 hour under conditions of 60 to 90°C in a nitrogen atmosphere for the coupling reaction, and a second step of kneading for 2 hours under conditions of 160 to 180°C in a reduced pressure atmosphere for the removal of the by-product (ammonia), followed by cooling, and then adding the remaining 10% of the vinyl group-containing organopolysiloxane (A) in two portions and kneading for 20 minutes.
Next, organohydrogenpolysiloxane (B) and platinum or a platinum compound (E) were added to 100 parts by weight of the resulting kneaded product (silicone rubber compound) in the proportions shown in Table 2 below, and the mixture was kneaded with a roll to obtain a silicone rubber-based curable composition.

(Preparation of Conductive Paste)
The obtained silicone rubber-based hardening composition of Sample 1 (15.3 parts by weight) was immersed in 34.8 parts by weight of decane (solvent), then stirred with a centrifugal mixer, 65.2 parts by weight of metal powder (G1) was added, and the mixture was further kneaded with a centrifugal mixer to obtain a conductive paste 1 having a total content of silicone rubber-based hardening composition and metal powder (G1) of 69.8% by weight.

(Preparation of flexible sheet electrodes)
<Examples 1 to 3>
The silicone rubber-based hardening composition of Sample 2 was pressed at 170° C. and 10 MPa for 10 minutes to form a sheet, and was then primarily hardened. Subsequently, the sheet was secondary hardened at 200° C. for 4 hours to obtain a flexible substrate 10 (a sheet-shaped cured product of the silicone rubber-based hardening composition) having dimensions of 30 cm long x 20 cm wide x 0.6 mm thick.
Using the obtained conductive paste 1, squeegee printing was performed through a mask having a predetermined pattern under the conditions shown in Table 2, and curing was performed at 180°C for a certain time to form a coating film corresponding to the elastomer electrode layer 2 (conductive elastomer layer 20) on the surface of the flexible substrate 10.
Thereafter, a hydrogel having a water content of 25% and a salt content of 5 wt % was applied to the surface of the elastomer electrode layer 2 and irradiated with UV light to form an electrolyte retention layer 70 having a thickness ratio of H2/H1 as shown in Table 2.
In this manner, the flexible sheet electrode 1 shown in FIG. 1 was produced.

<Comparative Example 1>
A flexible sheet electrode was prepared in the same manner as in Example 1, except that the electrolyte retention layer was not formed.

The following items were evaluated for the obtained flexible sheet electrodes. The results are shown in Table 2.

(Impedance measurement)
A flexible sheet electrode 1 was fixed to the skin of the subject's left wrist and right wrist with the electrolyte retention layer 70 in contact with each other, and bioimpedance was measured via the two flexible sheet electrodes 1 based on the measurement conditions below.
In Comparative Example 1, the flexible sheet electrode 1 was fixed using tape with the surface of the elastomer electrode layer 2 in contact with the measurement position without the electrolyte retention layer 70 interposed therebetween.
(Measurement condition)
・Measurement frequency: 10Hz
Measurement location: Both wrists (no skin preparation)
Measurement device: Bioimpedance meter (Melon Technox, MI-IC-N)
・Measurement environment: Humidity 40RH%, room temperature 20℃
Measurement time: Measurement was performed 4 minutes after electrolyte retention layer 70 of flexible sheet electrode 1 was attached to each of both wrists.

(Measurement of tack peak value)
An aluminum probe having a flat surface with an area of ¹⁵⁰ mm2 was brought into contact with the surface of the object to be measured under the conditions of a probe moving speed of 2.3 mm/sec, a probe crimping strength of 12 N, and a crimping time of 6 seconds, and the flat surface of the aluminum probe was then peeled upward at a probe moving speed of 2.3 mm/sec. The tack peak value on the surface of the object to be measured by the probe tack test was measured five times, and the average of the five measured values was taken as the above-mentioned tack peak value.
The object of measurement was the surface of electrolyte retention layer 70 of flexible sheet electrode 1 in Examples 1 to 3, and the surface of elastomer electrode layer 2 of flexible sheet electrode 1 in Comparative Example 1.

It was confirmed that the flexible sheet electrodes of Examples 1 to 3 showed almost no change from the tack peak value before storage even after being stored in a sealed container for one month.

(Wearability evaluation)
In the flexible sheet electrodes 1 of Examples 1 to 3, the surface of the electrolyte retention layer 70 was adhered to the skin of one of the subject's wrist, and then the subject's elbow was bent 90 degrees to bring the wrist from a horizontal position into a vertical position, and the vertical position was then maintained.
During such arm movements, if the flexible sheet electrode 1 remained attached to the skin, the fit was judged to be good, and if the flexible sheet electrode 1 peeled off from the skin during arm movements, the fit was judged to be poor.
In addition, in the flexible sheet electrode 1 of Comparative Example 1, the surface of the elastomeric electrode layer 2 was brought into close contact with the skin of one wrist of the subject without being fixed with tape.

(Noise reduction evaluation)
In the obtained flexible sheet electrodes of Examples 1 to 3 and Comparative Example 1, an external connection part (a male metal snap button) was attached to the other side of the flexible substrate opposite to the side on which the elastomeric electrode layer 2 was formed, and the external connection part and the elastomeric electrode layer 2 were electrically connected to obtain a biosensor.
Three biosensors were prepared, and each of the external connection parts of the three biosensors was connected to BITalino (manufactured by Plux Corporation) via an electrode cable with a connector (female snap button) and an ECG sensor (manufactured by Plux Corporation) to create an electrocardiogram measuring device (biosensor).
The flexible sheet electrodes on one side of the three biosensors were attached directly to the subject's skin, and the subject's cardiac potential was measured using a three-point lead method (measurement point, reference, body earth) (measurement environment: humidity 40 RH%, room temperature 20°C).
As a result of the above, it was confirmed that electrocardiogram waveforms can be monitored by using a biosensor equipped with the flexible sheet electrodes of each embodiment.
In the electrocardiogram waveform immediately after monitoring, if the R wave and/or ST segment could be clearly identified, it was evaluated as noise in the electrocardiogram waveform being suppressed (good), and if the R wave and ST segment could not be clearly identified, it was evaluated as noise suppression being insufficient to a practical extent (unacceptable).

The flexible sheet electrodes of Examples 1 to 3 showed excellent stability in measuring biosignals compared to Comparative Example 1, due to reduced noise during bioelectric potential measurement. The flexible sheet electrodes of Examples 1 to 3 also showed excellent wearability. Such flexible sheet electrodes of each Example are suitable for biosensors.

1 Flexible sheet electrode 2 Elastomer electrode layer 10 Flexible substrate 11 One side 12 Main body 13 Other side 14 Extension section 20 Conductive elastomer layer 20a Conductive elastomer layer 20b Conductive elastomer layer 22 One side 24 Elastic wiring 26 Connection section 30 External connection section 32 Mounting plate 34 Mounting pin 50 Protective layer 52 Insulating protective layer 60 Insulating elastomer layer 60a Insulating elastomer layer 60b Insulating elastomer layer 70 Electrolyte retention layer 100 Biosensor 200 Biosignal measuring device 210 Connector 220 Cable 230 Sensor module 240 Computer

Claims (15)

A flexible sheet electrode that is brought into contact with the skin of a subject to acquire a biosignal,
A flexible substrate;
an elastomeric electrode layer provided on the flexible substrate;
an electrolyte retention layer formed on at least a portion of the surface of the elastomeric electrode layer and retaining a liquid electrolyte;
A flexible sheet electrode comprising: 2. The flexible sheet electrode of claim 1,
The flexible sheet electrode, wherein the electrolyte retention layer comprises a hydrogel having moisture therein. 2. The flexible sheet electrode of claim 1,
A flexible sheet electrode, wherein the bioimpedance between the flexible sheet electrodes is 120 kΩ or less when measured at 10 Hz with the electrolyte retention layer in contact with the skin of a subject. 2. The flexible sheet electrode of claim 1,
A flexible sheet electrode, wherein the electrolyte retention layer is configured to cover at least a portion of a side of the elastomeric electrode layer. 2. The flexible sheet electrode of claim 1,
The flexible sheet electrode has a tack peak value on the surface of the electrolyte retention layer of 0.8 N or more and 20 N or less. 2. The flexible sheet electrode of claim 1,
A flexible sheet electrode, wherein at least a portion of the electrolyte retention layer is covered with a watertight member prior to use. 2. The flexible sheet electrode of claim 1,
A flexible sheet electrode, wherein the biosignal is any one of a cardiac potential, a myoelectric potential, and a skin potential. 2. The flexible sheet electrode of claim 1,
A flexible sheet electrode, wherein H1 and H2 satisfy 0.01≦H2/H1≦30, where H1 is the thickness of the elastomer electrode layer and H2 is the thickness of the electrolyte retention layer. 2. The flexible sheet electrode of claim 1,
A flexible sheet electrode, wherein the elastomeric electrode layer includes a conductive elastomer layer on a surface thereof. 10. The flexible sheet electrode of claim 9,
The flexible sheet electrode, wherein the conductive elastomer layer comprises a conductive filler and a silicone rubber. 10. The flexible sheet electrode of claim 9,
The flexible sheet electrode, wherein the conductive elastomeric layer further comprises a non-conductive filler. 10. The flexible sheet electrode of claim 9,
A flexible sheet electrode, wherein the conductive elastomer layer is composed of a printed layer of a conductive paste containing a conductive filler and silicone rubber. 2. The flexible sheet electrode of claim 1,
A flexible sheet electrode that can be attached to clothing. A biosensor comprising a flexible sheet electrode according to any one of claims 1 to 13. A biosignal measuring device comprising the biosensor according to claim 14.

Images