JP7841551B2 - Biosensors and biosignal measurement systems - Google Patents

Description

This invention relates to bioelectrodes, biosensors, and biosignal measurement systems.

Various developments have been made in bioelectrodes. One such technology is the one described in Patent Document 1. Patent Document 1 describes a bioelectrode comprising a base material made of an elastic material (a conductive protrusion) and a structure (base) formed on the surface of the base material (Claim 1, Figure 2). It is stated that this base material is formed by compounding a nanocarbon material into an elastic base material (paragraph 0068).

Japanese Patent Publication No. 2016-163688

However, as a result of the inventor's investigation, it was found that there is room for improvement in terms of measurement stability in the biomedical electrode described in Patent Document 1.

In conventional bioelectrodes, the columnar elastic body that contacts the biological surface and functions as a sensor either has a conductive layer formed over its entire surface to ensure conductivity, or, as in the case of the base material described in Patent Document 1 above, the entire body is composed of a conductive material.

Further investigation by the inventors revealed that when measuring biopotential using a columnar elastic body entirely covered with a conductive material, the resistance fluctuates significantly, potentially generating noise. While the detailed mechanism is unclear, it is thought that when the columnar elastic body contacts a biological surface, and its outer surface deforms in a contracting direction while its inner surface expands, the resistance values on or near the surface of the elastic columnar portion fluctuate significantly between the outer and inner surfaces.

Based on these findings, further intensive research revealed that by obtaining conductivity in a columnar elastic body through conductive wires running through its interior, fluctuations in resistance during deformation of the columnar elastic body can be suppressed. Furthermore, by making the tip of the columnar elastic body approximately conical, it becomes easier to conform to the biological surface compared to a cylindrical tip, suppressing large deformations during biological contact. This reduces noise and, as a result, improves measurement stability, leading to the completion of the present invention.

According to the present invention,
Plate-shaped support part,
A substantially conical elastic columnar portion is provided on one surface of the plate-shaped support portion,
A conductive resin layer formed to cover the tip of the elastic columnar portion,
A conductive wire is electrically connected to the conductive resin layer and is positioned inside the elastic columnar portion from the tip end towards the base end,
A biomedical electrode is provided that includes the following features.

Furthermore, according to the present invention, a biosensor equipped with the above-mentioned bioelectrode is provided.
Furthermore, according to the present invention, a biosignal measurement system equipped with the above-mentioned biosensor is provided.

According to the present invention, a bioelectrode with excellent measurement stability, a biosensor using the same, and a biosignal measurement system are provided.

This is a schematic diagram showing an example of a biomedical electrode according to this embodiment. (a) is a perspective view, and (b) is a cross-sectional view taken along line A-A in (a). This is a schematic diagram showing an overview of the biosensor of this embodiment.

In this embodiment, the directions of front, back, left, right, up, and down are defined and explained as shown in the figure. However, these are defined for convenience in order to easily explain the relative relationships of the components. Therefore, they do not limit the direction during manufacturing or use of the product that embodies the present invention.
In all drawings, similar components are denoted by the same reference numerals, and explanations are omitted where appropriate. Furthermore, the drawings are schematic and do not necessarily correspond to actual dimensional proportions.
In this specification, the term "abbreviated" means, unless otherwise explicitly stated, a range that takes into account manufacturing tolerances, variations, etc.

This section outlines the biomedical electrodes of this embodiment.
The bioelectrode comprises a plate-shaped support portion, a substantially conical elastic columnar portion provided on one surface of the plate-shaped support portion, a conductive resin layer formed to cover the tip of the elastic columnar portion, and a conductive wire electrically connected to the conductive resin layer and arranged inside the elastic columnar portion from the tip side to the base side.

The inventors have obtained the following findings.
To date, methods have been investigated for ensuring conductivity in the elastic columnar portion of biomedical electrodes, including forming the entire surface with a conductive resin layer and constructing the elastic columnar portion itself from a conductive material.
However, it has been found that when the elastic columnar structure comes into contact with a biological surface, the resistance of the elastic columnar structure, which is composed of a conductive resin layer and conductive material, may fluctuate due to the stretching and contracting deformation between the inside and outside of the elastic columnar structure, potentially generating noise. Furthermore, there is a risk of wire breakage occurring in the conductive resin layer in areas where the deformation is significant during the deformation of the elastic columnar structure.

In contrast, a structure that uses conductive wires placed inside an elastic columnar section to achieve electrical conductivity can suppress fluctuations in resistance during deformation, compared to a structure that achieves conductivity using the method described above.
The detailed mechanism is not clear, but the following is a possible explanation.
When in contact with a biological surface, the outer part of the elastic columnar portion deforms in the contraction direction, and the inner part deforms in the tension direction. At this time, the conductive wire passing through the interior of the elastic columnar portion undergoes relatively smaller deformation and deformation strain compared to the surface or near the surface of the elastic columnar portion. Therefore, even when the elastic columnar portion deforms significantly from the time of contact, fluctuations in the resistance value from the initial resistance (resistance at contact) are suppressed, thus stably suppressing the generation of noise.

Furthermore, the roughly conical columnar elastic section conforms more easily to the surface of a living organism when in contact with it, compared to a cylindrical structure. Therefore, under the same pressing force, large deformations are suppressed. This helps to reduce the increase in fluctuations in contact resistance.

Therefore, the bioelectrode of this embodiment can suppress noise generation during biological contact, thereby improving measurement stability.

The bioelectrode of this embodiment can detect potential fluctuations from living organisms, such as electroencephalograms (EEGs), heart rates, muscle activity, and nervous system activity. The bioelectrode can be further equipped with connectors and electronic components to form a biosensor that can be connected to external devices. This biosensor is wearable. By analyzing the bioelectric potentials, such as EEGs, detected by the biosensor, a biosignal measurement system tailored to various applications can be constructed.

The configuration of the biomedical electrode in this embodiment will be described in detail below.

Figure 1 is a schematic diagram showing an overview of the biomedical electrode 100 of this embodiment, where (a) is a perspective view and (b) is a cross-sectional view taken along line A-A in (a).

The biomedical electrode 100 shown in Figure 1 comprises a plate-shaped support portion 10, an elastic columnar portion (columnar portion 20), and a conductive resin layer 30.
The plate-shaped support portion 10 is made of an insulating elastic member and may have at least one columnar portion 20 on one of its surfaces 12. The columnar portion 20 is made of an insulating elastic member and may have at least a tip portion 26 that is substantially conical in shape. The conductive resin layer 30 is made of a conductive elastic member and may be formed to cover the surface of at least the tip 22 (part of the tip portion 26) of the columnar portion 20. The conductive wire 60 is arranged inside the columnar portion 20 so as to be electrically connected to the conductive resin layer 30.

When the tip of the bioelectrode 100 comes into contact with the object to be measured, the bioelectrical signal detected by the columnar portion 20 can be transmitted via the conductive resin layer 30 and the conductive wire 60 to the external connection portion 110 (connector) provided on the plate-shaped support portion 10. The bioelectrical signal detected by the bioelectrode 100 is then transmitted externally via the connector.

The top view shape of the plate-shaped support portion 10 may be, for example, an ellipse or a perfect circle, or an approximate polygon such as a square, rectangle, pentagon, or hexagon. The corners of the polygon may be rounded (radius).
Here, "top view" means observing from the top direction when looking from the tip 22 of the columnar portion 20 toward the plate-shaped support portion 10.

One surface 12 of the plate-shaped support portion 10 may be a flat surface, or it may have a curved surface that curves outward. Here, the one surface 12 may be a surface that passes through at least three contact points where the inclined surface 28 of the columnar portion 20 and the plate-shaped support portion 10 meet. Furthermore, there may be no interface between the plate-shaped support portion 10 and the columnar portion 20, and the structure may be seamless.

The other surface 14 of the plate-shaped support portion 10 may have a structure that allows connection to a connector. For example, on the other surface 14 opposite to the surface 12, electrodes that can be electrically connected to a connector may be embedded with a portion exposed.
Furthermore, at least a part or all of the other surface 14 may be covered with a conductive elastic member. The conductive elastic member may be made of the same material as the conductive resin layer 30. Note that the side surface of the plate-shaped support portion 10 does not need to be covered with a conductive elastic member.

The plate-shaped support portion 10 may be formed as an integral member with the columnar portion 20. That is, the plate-shaped support portion 10 can be formed by integrating it with multiple columnar portions 20 using the same resin material. For example, by molding a curable elastomer composition, such as the silicone rubber-based curable composition described later, a molded body can be obtained in which the plate-shaped support portion 10 and multiple columnar portions 20 are seamlessly joined. This makes it possible to realize an elastic molded body with excellent flexibility and strength.

Each of the plate-shaped support portion 10 and the columnar portion 20 may be made of insulating silicone rubber (rubber molded body) containing silicone rubber, without containing conductive fillers, as one of the insulating elastic members.

The columnar portion 20 may be provided on one or more plate-shaped support portions 10.
The top view shape of the columnar portion 20 may be a roughly circular shape such as an ellipse or a perfect circle, or a roughly polygonal shape such as a square, rectangle, pentagon, or hexagon. The top view shape of the columnar portion 20 and the top view shape of the plate-shaped support portion 10 may be the same. Among these, a roughly circular shape, preferably a perfect circle, can improve measurement stability.

Furthermore, the outer edge of the base end 24 of the columnar portion 20 in a top view may be configured to have the same area as one surface 12 of the plate-shaped support portion 10 in a top view, or it may be configured to have a smaller area. By increasing the contact area between the columnar portion 20 and the plate-shaped support portion 10, the durability of the biomedical electrode 100 can be improved.

The tip 26 of the columnar portion 20 may be composed of, for example, a roughly hemispherical, ellipsoidal, conical, or frustoconical shape. Among these, a roughly hemispherical or ellipsoidal shape is used from the viewpoint of measurement stability.

The tip 22 of the columnar portion 20 may be rounded (radius). This can suppress snagging on the body during contact and improve attachment stability. In addition, it makes demolding after molding easier, thus improving manufacturing stability.
In one cross-sectional view passing through the tip 22, the radius of the tip 22 is, for example, 0.25 mm to 5 mm, more preferably 0.5 mm to 3 mm. By keeping it within this range, mounting stability and measurement stability can be improved.

The columnar portion 20 has an inclined surface 28 on at least a portion of its periphery when viewed from above. The inclination angle θ of the inclined surface 28 refers to the angle formed between the side surface (inclined surface 28) of the base portion 24 of the columnar portion 20 and the surface 12 in a cross-sectional view passing through the tip 22 of the columnar portion 20, as shown in Figure 1(b).
The inclination angle θ of the inclined surface 28 is, for example, 10 to 89 degrees, preferably 15 to 85 degrees, more preferably 20 to 75 degrees, and even more preferably 30 to 65 degrees. Setting it above the lower limit improves the ability to follow the measurement surface. Setting it below the upper limit suppresses variations in the deformation state.

The inclination angle of the inclined surface 29 of the tip portion 26 (the angle between the inclined surface 29 and the surface 12) may be the same as the inclination angle θ of the inclined surface 28 of the base portion 24, but it may also be configured to be slightly smaller than the inclination angle θ. This allows for appropriate adjustment of the angle between the inclination angle θ and the radius. A corner or radius may be formed between the inclined surface 29 of the tip portion 26 and the inclined surface 28 of the base portion 24, but it may also be configured seamlessly.

The central axis of the columnar portion 20 may coincide with the center of the plate-shaped support portion 10 in the cross-section passing through the tip 22, but it may also have an eccentric structure. The central axis of the eccentric columnar portion 20 may be configured to be inclined toward the side from the central portion of the plate-shaped support portion 10.

When the height of the plate-shaped support portion 10 is H1 and the height of the columnar portion 20 is H2, H2/H1 is, for example, 0.5 to 20, preferably 1 to 15, and more preferably 2 to 10. By keeping it within this range, measurement stability and manufacturing stability can be improved.

The columnar portion 20 is equipped with a conductive wire 60 inside.
The conductive wire 60 is electrically connected to the conductive resin layer 30 covering the tip 22, and is positioned inside the columnar portion 20 from the tip portion 26 toward the base portion 24.

The conductive wire 60 can be of known origin, but for example, it may be made of conductive fiber.
As conductive fibers, one or more selected from the group consisting of metal fibers, metal-coated fibers, carbon fibers, conductive polymer fibers, conductive polymer-coated fibers, and conductive paste-coated fibers can be used. These may be used individually or in combination of two or more types.

The metal material of the above-mentioned metal fiber and metal-coated fiber is not limited as long as it is conductive, but examples include copper, silver, gold, nickel, tin, lead, zinc, bismuth, antimony, stainless steel, aluminum, silver/silver chloride, and alloys thereof. These may be used individually or in combination of two or more. Among these, silver can be used from the viewpoint of conductivity. Furthermore, it is preferable that the metal material does not contain metals that are harmful to the environment, such as chromium.

The fiber materials for the metal-coated fibers, conductive polymer-coated fibers, and conductive paste-coated fibers are not particularly limited, but may be synthetic fibers, semi-synthetic fibers, or natural fibers. Among these, polyester, nylon, polyurethane, silk, and cotton are preferred. These may be used individually or in combination of two or more.

Examples of the carbon fibers mentioned above include PAN-based carbon fibers and pitch-based carbon fibers.

The conductive polymer material used for the above-mentioned conductive polymer fibers and conductive polymer-coated fibers is, for example, a mixture of conductive polymers and binder resins such as polythiophene, polypyrrole, polyaniline, polyacetylene, polyphenylenevinylene, polynaphthalene, and their derivatives, or an aqueous solution of a conductive polymer such as PEDOT-PSS ((3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid)).

The resin material contained in the conductive paste-coated fiber described above is not particularly limited, but it is preferably elastic. For example, it may include one or more materials selected from the group consisting of silicone rubber, urethane rubber, fluororubber, nitrile rubber, acrylic rubber, styrene rubber, chloroprene rubber, and ethylene propylene rubber. These may be used individually or in combination of two or more materials.

The conductive filler contained in the conductive paste of the conductive paste-coated fiber described above is not particularly limited, and known conductive materials may be used. It may include one or more selected from the group consisting of metal particles, metal fibers, metal-coated fibers, carbon black, acetylene black, graphite, carbon fibers, carbon nanotubes, conductive polymers, conductive polymer-coated fibers, and metal nanowires.

The metals constituting the conductive filler described above are not particularly limited, but may include, for example, at least one of copper, silver, gold, nickel, tin, lead, zinc, bismuth, antimony, silver/silver chloride, or alloys thereof, or two or more of these. Among these, silver or copper are preferred due to their high conductivity and availability.

The conductive wire 60 may be composed of a twisted yarn made by twisting together multiple linear conductive fibers. This suppresses the breakage of the conductive wire 60 during deformation.

In this specification, coating of conductive fibers includes not only simply covering the outer surface of the fiber material, but also, in the case of twisted yarns formed by twisting single fibers together, impregnating the interfiber gaps within the yarn with a metal, conductive polymer, or conductive paste, thereby coating each individual single fiber constituting the yarn.

The tensile break elongation of the conductive wire 60 is, for example, 1% or more to 50%, preferably 1.5% or more to 45%. By keeping the value within this range, excessive deformation of the columnar portion 20 can be suppressed while suppressing breakage during deformation.
Various arrangement structures can be adopted for the conductive wire 60, as long as it conducts electrical conductivity inside the columnar portion 20.
For example, the tip of the conductive wire 60 may be a protruding structure, a structure that is substantially flush with the surface 29 of the tip 22 or tip portion 26 of the columnar portion 20, or a structure that is embedded. A protruding structure may be used from the viewpoint of connection stability with the conductive resin layer 30. The protruding portion of the tip of the conductive wire 60 is partially or entirely covered with the conductive resin layer 30.

The discharge structure at the tip of the conductive wire 60 can be either without a fold, with a fold, or wrapped around the surface of the tip 26 of the columnar portion 20. Furthermore, the conductive wire 60 may not pass through the central axis of the columnar portion 20, but may be inclined relative to the central axis.

The other end of the conductive wire 60, opposite to its tip, may be configured in any way as long as it can be electrically connected to the connector connected to the other surface 14 of the plate-shaped support portion 10. For example, the other end of the conductive wire 60 may pass through the base end 24 of the columnar portion 20 and extend further to one surface 12, a side, or the other surface 14 of the plate-shaped support portion 10. The other end of the conductive wire 60 may be electrically connected to the connector via a conductive resin layer 30 provided on the other surface 14.

The conductive resin layer 30 may be configured to cover at least the surface of the tip 22 of the columnar portion 20, or it may be configured to cover from the tip 22 to the tip 26 of the columnar portion 20, or from the tip 22 to partway up the base portion 24. In other words, it is sufficient that it is configured not to cover the entire surface of the columnar portion 20.
The conductive resin layer 30 may be configured to cover one surface 12 and the other surface 14 of the plate-shaped support portion 10, spaced apart from the portion covering the tip 22.

The conductive resin layer 30 is composed of conductive silicone rubber containing a conductive filler and silicone rubber, serving as one of the conductive elastic members. For example, the conductive resin layer 30 can be formed by applying a conductive solution (conductive silicone rubber-based curable composition) – which is an insulating silicone rubber-based curable composition without the conductive filler described later – to the molded body. The adhesion of the conductive resin layer 30 can be improved by using the same type of silicone rubber material as that used for the plate-shaped support portion 10 and the columnar portion 20.

The above-mentioned conductive filler may be a known conductive material, but may also include one or more selected from the group consisting of metal particles, silver/silver chloride particles, metal fibers, metal-coated fibers, carbon black, acetylene black, graphite, carbon fibers, carbon nanotubes, conductive polymers, conductive polymer-coated fibers, and metal nanowires.

The metals constituting the conductive filler described above are not particularly limited, but may include, for example, at least one of copper, silver, gold, nickel, tin, lead, zinc, bismuth, antimony, silver/silver chloride, or alloys thereof, or two or more of these. Among these, silver or copper are preferred due to their high conductivity and availability.

The lower limit of the conductive filler content is, for example, 30% by mass or more, preferably 35% by mass or more, and more preferably 40% by mass or more, relative to 100% by mass of the silicone rubber in the conductive resin layer 30. This enhances the transmission of bioelectrical signals, even in the case of a thin film. On the other hand, the upper limit of the conductive filler content is, for example, 90% by mass or less, preferably 85% by mass or less, and more preferably 80% by mass or less, relative to 100% by mass of the silicone rubber in the conductive resin layer 30. This enhances the durability of the conductive resin layer 30 against deformation of the columnar portion 20.

The lower limit of the thickness of the conductive resin layer 30 is, for example, 5 μm or more, preferably 8 μm or more, and more preferably 10 μm or more. This enhances durability during repeated use. On the other hand, the upper limit of the thickness of the conductive resin layer 30 is, for example, 200 μm or less, preferably 150 μm or less, more preferably 100 μm or less, and even more preferably 50 μm or less. This maintains the ease of deformation of the columnar portion 20. Furthermore, by making it a thin film, fluctuations from the desired value in the rubber hardness A of the columnar portion 20 can be suppressed. In a cross-sectional view of the columnar portion 20, it is preferable that the thickness of the conductive resin layer 30 on the tip 22 or at least a portion of the side surface of the columnar portion 20 is within the above numerical range.

The thickness of the conductive resin layer 30 may be configured such that the thickness D1 on the surface of the tip 22 of the columnar portion 20 is thicker than the thickness D2 on the surface of the other surface 14 of the plate-shaped support portion 10. For example, after applying the conductive solution described above, a portion of the columnar portion 20 coated with the conductive resin layer 30 may be dipped (immersion coated) in a paste-like conductive solution. This allows for a relatively thick film to be applied to the tip 22 of the columnar portion 20 and to a predetermined portion from the tip 22 (for example, 1/2, 1/3, or 1/4 of the entire columnar portion 20). It is preferable that this thick film is provided along the entire circumferential direction of the tip of the columnar portion 20. This suppresses peeling of the conductive resin layer 30 at the tip and prevents damage such as wire breakage of the columnar portion 20. Therefore, the durability of the biomedical electrode 100 can be improved.

In this embodiment, the Type A durometer hardness on the surface of the columnar portion 20 (elastic columnar portion), measured at 37°C in accordance with JIS K 6253 (1997), is defined as rubber hardness A.
The measurement target for rubber hardness A can be a columnar portion 20, a plate-shaped support portion 10 when the columnar portion 20 and the plate-shaped support portion 10 are formed as an integrated member, or the silicone rubber constituting these components. Furthermore, if the conductive resin layer 30 is thin and has little effect on rubber hardness A, the columnar portion 20 or plate-shaped support portion 10 with the conductive resin layer 30 formed on its surface may be used as the measurement target. Test pieces can be prepared from these and used as the measurement target (sample). Multiple test pieces stacked together may be used as the sample thickness. Note that even if the distance from the indenter to the edge of the test piece is less than 12 mm, it is acceptable as long as there is a certain distance.

The lower limit of the rubber hardness A is, for example, 15 or higher, preferably 18 or higher, and more preferably 20 or higher. This allows for lower contact resistance and increased electroencephalogram (EEG) acquisition rate. On the other hand, the upper limit of the rubber hardness A is 65 or lower, preferably 53 or lower, and more preferably 50 or lower. This allows for lower contact resistance. Furthermore, the columnar portion 20 can easily deform upon contact with the measurement area, conforming to the shape of the measurement area, thereby improving the user's wearing comfort and suppressing discomfort during prolonged use.

Here, we will describe the above-mentioned silicone rubber-based curable composition.
The above-mentioned silicone rubber can be composed of a cured product of a silicone rubber-based curable composition. 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 (primary curing), followed by post-baking at 100 to 200°C for 1 to 4 hours (secondary curing).

Insulating silicone rubber is silicone rubber that does not contain conductive fillers, while conductive silicone rubber is silicone rubber that contains conductive fillers.

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

The insulating silicone rubber curable composition and the conductive silicone rubber curable composition may contain the same type of vinyl group-containing linear organopolysiloxane. The same type of vinyl group-containing linear organopolysiloxane only needs to contain at least the same vinyl group functional group and have a linear structure, and may differ in the amount of vinyl groups in the molecule, the molecular weight distribution, or the amount added.
Furthermore, the insulating silicone rubber-based curable composition and the conductive silicone rubber-based curable composition may further contain different vinyl group-containing organopolysiloxanes.

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

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

The vinyl group content of the vinyl group-containing linear organopolysiloxane (A1) is not particularly limited, but preferably it has two or more vinyl groups in the molecule and is 15 mol% or less, more preferably 0.01 to 12 mol%. This optimizes the amount of vinyl groups in the vinyl group-containing linear organopolysiloxane (A1), ensuring the formation of a network with the components described later. In this embodiment, "~" means including the numerical values at both ends.

In this specification, the vinyl group content refers to the mole percentage of vinyl group-containing siloxane units, where the total number of units constituting the vinyl group-containing linear organopolysiloxane (A1) is considered to be 100 mol%. However, it is assumed that there is one vinyl group per vinyl group-containing siloxane unit.

Furthermore, the degree of polymerization of the vinyl group-containing linear organopolysiloxane (A1) is not particularly limited, but is preferably in the range of approximately 1,000 to 10,000, and more preferably 2,000 to 5,000. The degree of polymerization can be determined, for example, by the number-average degree of polymerization (or number-average molecular weight) in polystyrene terms in GPC (gel permeation chromatography) using chloroform as the 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 approximately 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-mentioned range, the heat resistance, flame retardancy, and chemical stability of the resulting silicone rubber can be improved.

The vinyl group-containing linear organopolysiloxane (A1) is preferably one having the structure represented by the following formula (1).

In formula (1), ^R1 is a substituted or unsubstituted alkyl group, alkenyl group, aryl group, or a hydrocarbon group having 1 to 10 carbon atoms. Examples of alkyl groups having 1 to 10 carbon atoms include methyl, ethyl, and propyl groups, with methyl being preferred. Examples of alkenyl groups having 1 to 10 carbon atoms include vinyl, allyl, and butenyl groups, with vinyl being preferred. Examples of aryl groups having 1 to 10 carbon atoms include phenyl.

Furthermore, ^R2 is a substituted or unsubstituted alkyl group, alkenyl group, aryl group, or a hydrocarbon group having 1 to 10 carbon atoms. Examples of alkyl groups having 1 to 10 carbon atoms include methyl, ethyl, and propyl groups, with methyl being preferred. Examples of alkenyl groups having 1 to 10 carbon atoms include vinyl, allyl, and butenyl groups. An example of an aryl group having 1 to 10 carbon atoms is the phenyl group.

Furthermore, ^R3 is a substituted or unsubstituted alkyl group, aryl group, or hydrocarbon group having 1 to 8 carbon atoms. Examples of alkyl groups having 1 to 8 carbon atoms include methyl, ethyl, and propyl groups, with methyl being preferred. An example of an aryl group having 1 to 8 carbon atoms is the phenyl group.

Furthermore, examples of substituents for ^R1 and ^R2 in formula (1) include methyl groups and vinyl groups, and examples of substituents for ^R3 include methyl groups.

In equation (1), the multiple ^R1s are independent of each other and may be different from each other or the same. The same applies to ^R2 and ^R3 .

Furthermore, m and n are the number 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 from 0 to 1000, and n is preferably from 2000 to 5000.

Furthermore, a specific structure of the vinyl group-containing linear organopolysiloxane (A1) represented by formula (1) can be found, for example, in the structure represented by formula (1-1) below.

In formula (1-1), ^R1 and ^R2 are each independently a methyl group or a vinyl group, and at least one of them is a vinyl group.

Furthermore, it is preferable that the vinyl group-containing linear organopolysiloxane (A1) contains a first vinyl group-containing linear organopolysiloxane (A1-1) having two or more vinyl groups in the molecule and a vinyl group content of 0.4 mol% or less, and a second vinyl group-containing linear organopolysiloxane (A1-2) having a vinyl group content of 0.5 to 15 mol%. By combining the first vinyl group-containing linear organopolysiloxane (A1-1), which has a typical vinyl group content, with the second vinyl group-containing linear organopolysiloxane (A1-2), which has a high vinyl group content, the vinyl groups can be unevenly distributed, allowing for more effective formation of crosslink density variations within the crosslinking network of the silicone rubber. As a result, the tear strength of the silicone rubber can be more effectively increased.

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

Furthermore, 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%.

Furthermore, when combining the first vinyl group-containing linear organopolysiloxane (A1-1) and the second vinyl group-containing linear organopolysiloxane (A1-2), the ratio of (A1-1) to (A1-2) is not particularly limited, but for example, a weight ratio of (A1-1):(A1-2) of 50:50 to 95:5 is preferred, and a weight ratio of 80:20 to 90:10 is more preferred.

Furthermore, the first and second vinyl group-containing linear organopolysiloxanes (A1-1) and (A1-2) may be used individually or in combination of two or more types.

Furthermore, the vinyl group-containing organopolysiloxane (A) may also include a vinyl group-containing branched organopolysiloxane (A2) having a branched structure.

<<Organohydrogenpolysiloxane (B)>>
The silicone rubber-based curable composition of this embodiment may contain a crosslinking agent. The crosslinking agent may include organohydrogenpolysiloxane (B).
Organohydrogenpolysiloxanes (B) are classified into linear organohydrogenpolysiloxanes (B1) having a linear structure and branched organohydrogenpolysiloxanes (B2) having a branched structure, and a compound may contain either one or both of these.

The insulating silicone rubber curable composition and the conductive silicone rubber curable composition may contain the same type of crosslinking agent. The same type of crosslinking agent only needs to have a common structure such as a linear or branched structure, and may have different molecular weight distributions and different functional groups, and the amount added may also differ.
Furthermore, the insulating silicone rubber-based curable composition and the conductive silicone rubber-based curable composition may further contain different crosslinking agents.

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

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

Furthermore, the weight-average molecular weight of linear organohydrogenpolysiloxane (B1) can be measured, for example, by converting it to polystyrene equivalent using GPC (gel permeation chromatography) with chloroform as the developing solvent.

Furthermore, it is preferable that the linear organohydrogenpolysiloxane (B1) does not typically contain vinyl groups. This effectively prevents the crosslinking reaction from proceeding within the linear organohydrogenpolysiloxane (B1) molecule.

As the linear organohydrogenpolysiloxane (B1) described above, one having the 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, hydrocarbon group, or hydride group having 1 to 10 carbon atoms. Examples of alkyl groups having 1 to 10 carbon atoms include methyl, ethyl, and propyl groups, with methyl being preferred. Examples of alkenyl groups having 1 to 10 carbon atoms include vinyl, allyl, and butenyl groups. Examples of aryl groups having 1 to 10 carbon atoms include phenyl.

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

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

Furthermore, ^R6 is a substituted or unsubstituted alkyl group, aryl group, or hydrocarbon group having 1 to 8 carbon atoms. Examples of alkyl groups having 1 to 8 carbon atoms include methyl, ethyl, and propyl groups, with methyl being preferred. An example of an aryl group having 1 to 8 carbon atoms is the phenyl group. Multiple ^R6s are independent of each other and may be different from each other or the same.

In formula (2), examples of substituents ^R4 , ^R5 , and ^R6 include methyl groups and vinyl groups, and methyl groups are preferred from the viewpoint of preventing intramolecular crosslinking reactions.

Furthermore, m and n are the number 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.

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

The branched organohydrogenpolysiloxane (B2) has a branched structure, forming regions with high crosslink density, and is a component that greatly contributes to the formation of a dense-sparse crosslink structure within the silicone rubber system. Furthermore, similar to the linear organohydrogenpolysiloxane (B1) described above, it has a structure in which hydrogen is directly bonded to Si (≡Si-H), and is a polymer that undergoes hydrosilylation reactions with the vinyl groups of vinyl group-containing organopolysiloxane (A), as well as with the vinyl groups of components blended into the silicone rubber curable composition, thereby crosslinking these components.

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

Furthermore, it is preferable that the branched organohydrogenpolysiloxane (B2) typically does not contain vinyl groups. This effectively prevents the crosslinking reaction from proceeding within the branched organohydrogenpolysiloxane (B2) molecule.

Furthermore, the branched organohydrogenpolysiloxane (B2) is preferably the one shown in 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), R ⁷ is a monovalent organic group, a is an integer in the range of 1 to 3, 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.)

In formula (c), ^R7 is a monovalent organic group, preferably a substituted or unsubstituted alkyl group, aryl group, or hydrocarbon group having 1 to 10 carbon atoms. Examples of alkyl groups having 1 to 10 carbon atoms include methyl, ethyl, and propyl groups, with methyl being preferred. An example of an aryl group having 1 to 10 carbon atoms is the phenyl group.

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

Furthermore, in equation (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 their structure, specifically whether they are linear or branched. The number of alkyl groups R attached to Si (R/Si), where Si is considered as 1, ranges from 1.8 to 2.1 for linear organohydrogenpolysiloxane (B1) and from 0.8 to 1.7 for branched organohydrogenpolysiloxane (B2).

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

Furthermore, a specific example of a branched organohydrogenpolysiloxane (B2) is one having the structure represented by the following formula (3).

In formula (3), ^R7 is a substituted or unsubstituted alkyl group, aryl group, or a hydrocarbon group combining these, or a hydrogen atom, having 1 to 8 carbon atoms. Examples of alkyl groups having 1 to 8 carbon atoms include methyl, ethyl, and propyl groups, with methyl being preferred. An example of an aryl group having 1 to 8 carbon atoms is the phenyl group. Examples of substituents on ^R7 include methyl groups.

In equation (3), the multiple ^R7s are independent of each other and may be different from each other or the same.

Furthermore, in equation (3), "-O-Si≡" indicates that Si has a branched structure that extends in three dimensions.

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

Furthermore, 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, it is preferable that the total amount of hydride groups in the linear organohydrogenpolysiloxane (B1) and the branched organohydrogenpolysiloxane (B2) is 0.5 to 5 moles, and more preferably 1 to 3.5 moles, per mole of vinyl groups in the vinyl group-containing linear organohydrogenpolysiloxane (A1). This ensures the reliable formation of a crosslinking network between the linear organohydrogenpolysiloxane (B1) and the branched organohydrogenpolysiloxane (B2) and the vinyl group-containing linear organohydrogenpolysiloxane (A1).

<<Silica particles (C)>>
The silicone rubber-based curable composition according to this embodiment includes a non-conductive filler. The non-conductive filler may also include silica particles (C) as needed. This can improve the hardness and mechanical strength of the elastomer.

The insulating silicone rubber curable composition and the conductive silicone rubber curable composition may contain the same type of non-conductive filler. The same type of non-conductive filler only needs to have at least common constituent materials, and may differ in particle size, specific surface area, surface treatment agent, or the amount added.
Furthermore, the insulating silicone rubber-based curable composition and the conductive silicone rubber-based curable composition may further contain different silane coupling agents.

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

The silica particles (C) preferably have a specific surface area of, for example, 50 to 400 ^m² /g by the BET method, and more preferably 100 to 400 ^m² /g. The average primary particle size of the silica particles (C) is preferably 1 to 100 nm, and more preferably about 5 to 20 nm.

By using silica particles (C) within the specified range of specific surface area and average particle size, the hardness and mechanical strength of the resulting silicone rubber can be improved, particularly its tensile strength.

<<Silane coupling agent (D)>>
The silicone rubber-based curable 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 form a hydroxyl group, and this hydroxyl group undergoes a dehydration condensation reaction with the hydroxyl groups on the surface of the silica particles (C), thereby modifying the surface of the silica particles (C).

The insulating silicone rubber curable composition and the conductive silicone rubber curable composition may contain the same type of silane coupling agent. The same type of silane coupling agent only needs to have at least a common functional group, and other functional groups in the molecule and the amount added may differ.
Furthermore, the insulating silicone rubber-based curable composition and the conductive silicone rubber-based curable composition may further contain different silane coupling agents.

Furthermore, this silane coupling agent (D) may include a silane coupling agent having hydrophobic groups. This imparts these hydrophobic groups to the surface of the silica particles (C), thereby reducing the cohesive force of the silica particles (C) in the silicone rubber curable composition and, consequently, in the silicone rubber itself (reducing aggregation due to hydrogen bonding by silanol groups). As a result, it is presumed that the dispersibility of the silica particles (C) in the silicone rubber curable composition improves. This increases the interface between the silica particles (C) and the rubber matrix, thereby enhancing the reinforcing effect of the silica particles (C). Furthermore, it is presumed that the slipperiness of the silica particles (C) within the matrix improves during deformation of the rubber matrix. Finally, the improved dispersibility and slipperiness of the silica particles (C) improve the mechanical strength of the silicone rubber due to the silica particles (C) (e.g., tensile strength and tear strength).

Furthermore, the silane coupling agent (D) may include a silane coupling agent having vinyl groups. This introduces vinyl groups to the surface of the silica particles (C). Therefore, during the curing of the silicone rubber-based curable composition—that is, when the vinyl groups of the vinyl group-containing organopolysiloxane (A) and the hydride groups of the organohydrogenpolysiloxane (B) undergo a hydrosilylation reaction to form a network (crosslinked structure)—the vinyl groups of the silica particles (C) also participate in the hydrosilylation reaction with the hydride groups of the organohydrogenpolysiloxane (B), thus incorporating the silica particles (C) into the network. This allows for lower hardness and higher modulus of the resulting silicone rubber.

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 silane coupling agents (D) include those represented by the following formula (4).

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

Hydrophobic groups are alkyl groups, aryl groups, or hydrocarbon groups with 1 to 6 carbon atoms, such as methyl, ethyl, propyl, and phenyl groups. Among these, methyl groups are particularly preferred.

Furthermore, hydrophilic groups include, for example, hydroxyl groups, sulfonic acid groups, carboxyl groups, or carbonyl groups, with hydroxyl groups being particularly preferred. While hydrophilic groups may be included as functional groups, their absence is preferable from the viewpoint of imparting hydrophobicity to the silane coupling agent (D).

Furthermore, hydrolyzable groups include alkoxy groups such as methoxy groups 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 a silazane group as a hydrolyzable group will have two (Y _n -Si-) structures in formula (4) above, due to their structural characteristics.

Specific examples of the silane coupling agent (D) represented by the above formula (4) are as follows:
Examples of functional groups having a hydrophobic group include 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. Among these, silane coupling agents having a trimethylsilyl group, which includes one or more selected from the group consisting of hexamethyldisilazane, trimethylchlorosilane, trimethylmethoxysilane, and trimethylethoxysilane, are preferred.

Examples of functional groups 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, a silane coupling agent having a vinyl group-containing organosilyl group, comprising one or more selected from the group consisting of methacryloxypropyltriethoxysilane, methacryloxypropyltrimethoxysilane, methacryloxypropylmethyldiethoxysilane, methacryloxypropylmethyldimethoxysilane, divinyltetramethyldisilazane, vinyltriethoxysilane, vinyltrimethoxysilane, and vinylmethyldimethoxysilane, is preferred.

Furthermore, when the silane coupling agent (D) includes two types: a silane coupling agent having a trimethylsilyl group and a silane coupling agent having a vinyl group-containing organosilyl group, it is preferable that the hydrophobic agent includes hexamethyldisilazane and the vinyl group includes divinyltetramethyldisilazane.

When using a silane coupling agent (D1) having a trimethylsilyl group and a silane coupling agent (D2) having a vinyl group-containing organosilyl group in combination, the ratio of (D1) to (D2) is not particularly limited, but for example, the weight ratio of (D1):(D2) is 1:0.001 to 1:0.35, preferably 1:0.01 to 1:0.20, and more preferably 1:0.03 to 1:0.15. By using such a numerical range, the desired physical properties of the silicone rubber can be obtained. Specifically, a balance can be achieved between the dispersibility of silica in the rubber and the crosslinking properties of the rubber.

In this embodiment, the lower limit of the silane coupling agent (D) content 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 parts by weight of the total amount of vinyl group-containing organopolysiloxane (A). The upper limit of the silane coupling agent (D) content is preferably 100% by mass or less, more preferably 80% by mass or less, and even more preferably 40% by mass or less, based on 100 parts by weight of the total amount of vinyl group-containing organopolysiloxane (A).
By setting the content of the silane coupling agent (D) to above the lower limit, the adhesion between the columnar portion containing the elastomer and the conductive resin layer can be improved. This can also contribute to improving the mechanical strength of the silicone rubber. Furthermore, by setting the content of the silane coupling agent (D) to below the upper limit, the silicone rubber can acquire appropriate mechanical properties.

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

The insulating silicone rubber curable composition and the conductive silicone rubber curable composition may contain the same type of catalyst. The same type of catalyst only needs to have at least common constituent materials, and may contain different compositions, and the amounts added may also differ.
Furthermore, the insulating silicone rubber-based curable composition and the conductive silicone rubber-based curable composition may further contain different catalysts.

As platinum or a platinum compound (E), known materials can be used, such as platinum black, platinum supported on silica or carbon black, chloroplatinic acid or an alcoholic solution of chloroplatinic acid, a complex salt of chloroplatinic acid and an olefin, or a complex salt of chloroplatinic acid and a vinylsiloxane.

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

In this embodiment, the content of platinum or platinum compound (E) in the silicone rubber curable composition refers to the catalytic amount and can be set as appropriate, but specifically, the amount of platinum group metal is 0.01 to 1000 ppm by weight per 100 parts by weight of the total amount of vinyl group-containing organopolysiloxane (A), silica particles (C), and silane coupling agent (D), preferably 0.1 to 500 ppm.
By setting the content of platinum or platinum compound (E) above the lower limit, the silicone rubber-based curable composition can be cured at an appropriate rate. Furthermore, by setting the content of platinum or platinum compound (E) below the upper limit, it is possible to reduce manufacturing costs.

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

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

(Other ingredients)
Furthermore, the silicone rubber-based curable composition of this embodiment may further contain other components in addition to the components (A) to (F) described above. Examples of these other components include inorganic fillers other than 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; additives such as reaction inhibitors, dispersants, pigments, dyes, antistatic agents, antioxidants, flame retardants, and thermal conductivity enhancers.

The conductive solution (conductive silicone rubber composition) according to this embodiment contains, in addition to the above-mentioned silicone rubber-based curable composition which does not contain a conductive filler, the above-mentioned conductive filler and solvent.

Various known solvents can be used as the solvent mentioned above, but for example, high-boiling point solvents may be included. These may be used individually or in combination of two or more.

Examples of the above solvents include, for example, aliphatic hydrocarbons such as pentane, hexane, cyclohexane, heptane, methylcyclohexane, ethylcyclohexane, octane, decane, dodecane, and tetradecane; aromatic hydrocarbons such as benzene, toluene, ethylbenzene, xylene, trifluoromethylbenzene, and benzotrifluoride; ethers such as diethyl ether, diisopropyl ether, dibutyl ether, cyclopentyl methyl ether, cyclopentyl ethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl 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; and sulfoxides such as dimethyl sulfoxide and diethyl sulfoxide. These can be used individually or in combination of two or more types.

The above conductive solution can be made to have a viscosity suitable for various coating methods, such as spray coating and dip coating, by adjusting the amount of solids in the solution.

Furthermore, when the conductive solution contains the conductive filler and the silica particles (C), the lower limit of the silica particle (C) content in the conductive resin layer 30 can be, for example, 1% by mass or more, preferably 3% by mass or more, and more preferably 5% by mass or more, based on 100% by mass of the total amount of silica particles (C) and conductive filler. This improves the mechanical strength of the conductive resin layer 30. On the other hand, the upper limit of the silica particle (C) content in the conductive resin layer 30 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 allows for a balance between conductivity and mechanical strength or flexibility in the conductive resin layer 30.

Conductive silicone rubber can be obtained by heating and drying the conductive solution as needed.
The conductive silicone rubber may also be configured without silicone oil. This prevents a decrease in conductivity due to silicone oil bleeding out onto the surface of the conductive resin layer 30.

An example of a method for manufacturing the biomedical electrode 100 of this embodiment may include the following steps.
First, the above-mentioned silicone rubber-based curable composition is heated and pressurized using a mold to obtain a molded body having a plate-shaped support portion 10 and a columnar portion 20 (molding process).

Next, the conductive wire 60 is inserted into the columnar portion 20 (conductive wire insertion step). For example, the conductive wire 60 can be passed through the columnar portion 20 using a needle. Mass production is possible by using a sewing machine.
Alternatively, insert molding may be used during the molding process, in which the silicone rubber-based curable composition is introduced into the molding space where the conductive wire 60 is placed, and then molded under pressure and heat.

Next, the tip portion 26 of the columnar portion 20 of the obtained molded body is dipped in the conductive solution and heated and dried (tip coating step). Alternatively, the conductive solution may be sprayed onto the tip portion 26 and then heated and dried. This forms a conductive resin layer 30 that covers the tip portion 22 of the columnar portion 20.
Subsequently, a post-curing (annealing) process is performed at a predetermined temperature and under specified temperature conditions.
As described above, a biomedical electrode 100 can be manufactured.

As an example of another manufacturing method, the following steps may be included.
In the molding process, for example, a mold having multiple recesses is used to obtain a molded sheet in which a set of multiple columnar portions 20 and plate-shaped support portions 10 is formed.
Next, in the conductive wire insertion process, conductive wires 60 are inserted into multiple columnar portions 20 in the molded sheet.
Next, in the tip coating process, a conductive resin layer 30 is formed at the tip portions 26 of the multiple columnar portions 20 in the molded sheet, covering at least the tip 22.
Next, individual molded bodies comprising a plate-shaped support portion 10, a columnar portion 20, a conductive wire 60, and a conductive resin layer 30 are removed from the molded sheet (fragmentation step). As a method of removal, for example, a method of punching out the molded sheet may be employed.
Subsequently, each individual molded piece is post-cured in an annealing process.
Based on the above, a biomedical electrode 100 can be manufactured.

Furthermore, after the molding process described above and before the conductive wire insertion process, the tip 26 of the columnar portion 20 may be cut into a desired shape to form an inclined surface. Alternatively, instead of cutting, the inclined surface may be formed on the tip 26 of the columnar portion 20 by mold molding.

The bioelectrode 100 of this embodiment can detect bioelectrical signals generated from biological activities such as those of the brain, heart, muscles, and nerves. Because this bioelectrode 100 is flexible, it offers excellent attachment to the scalp and is therefore suitable for use as an electrode for electroencephalography (EEG) measurement.

The electroencephalogram (EEG) measurement electrodes using biomedical electrodes 100 are expected to be utilized in BMI (Brain-Machine Interface) applications.

Furthermore, the bioelectrode 100 can be used as a simple and reusable dry sensor, rather than a wet sensor that requires gel application to the measurement area. Compared to spring-loaded metal pin-type dry sensors, the bioelectrode 100 offers greater flexibility, reducing pain and discomfort for the subject (user). Additionally, its miniaturization allows it to be integrated into wearable devices.

The biosensor of this embodiment will now be described.
Figure 2 is a schematic diagram showing an overview of an example of a biosensor 200.
The biosensor 200 of this embodiment includes a bioelectrode 100, and may further include an external connection part 110 connected to the bioelectrode 100.

The external connection part 110 may be detachably attached to the plate-shaped support part 10 of the biomedical electrode 100, or it may be fixed to the plate-shaped support part 10.

The external connection section 110 is more robust than silicone rubber from a durability standpoint and includes at least an external electrode section that is conductive. The external electrode section is made of, for example, metal. This external electrode section can transmit bioelectrical signals detected by the bioelectrode 100 to an external electronic component. The shape of the external electrode section is not particularly limited, but it is configured to allow connection to an electronic component or wiring. For example, the external connection section 110 may be made of a metal snap button and have a structure that electrically connects to external wiring or electrodes on a circuit board via contact pins.

The biosensor 200 may further include electronic components that can be electrically connected via the external connection part 110. Various known components can be used as electronic components depending on the application, but examples include amplifiers, AD converters, CPUs, memory, communication circuits, wireless communication units, analog filters, capacitors, resistors, and batteries. One or more of these may be modularized on a circuit board. This allows the biosensor 200 to be used as a wearable device.
Additionally, other sensors such as acceleration sensors, temperature sensors, and pressure sensors may be used in combination as electronic components.

The biosensor 200 comprises one or more bioelectrodes 100. The biosensor 200 may be mounted on a device for attachment to a living body, such as a headgear or armband.

The biosignal measurement system of this embodiment will now be described.
The biosignal measurement system of this embodiment includes a biosensor 200. The biosignal measurement system may be a system (measuring device) that displays, analyzes, or stores data received from the biosensor 200.

The embodiments of the present invention have been described above, but these are merely examples, and various other configurations can be adopted. Furthermore, the present invention is not limited to the embodiments described above; modifications, improvements, etc., within the scope of achieving the objectives of the present invention are included.

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

The raw material components shown in Table 1 are as follows:

(Organopolysiloxane containing vinyl group (A))
(A1-1): First vinyl group-containing linear organopolysiloxane: vinyl group content is 0.04 mol%, Mn = 2.2 × ^10⁵ , Mw = 4.8 × ^10⁵ ), vinyl group-containing dimethylpolysiloxane synthesized by the following synthesis scheme 1 (structure represented by formula (1-1) above)
(A1-2): Second vinyl group-containing linear organopolysiloxane: Vinyl group content is 0.93 mol%, vinyl group-containing dimethylpolysiloxane synthesized by the following synthesis scheme 2 (structure represented by formula (1-1) above, where ^R1 and ^R2 are vinyl groups)

(Organohydrogenpolysiloxane (B))
(B): Organohydrogenpolysiloxane: Momentive Corporation, "TC-25D"

(Silica particles (C))
(C): Silica microparticles (particle size 7 nm, specific surface area 300 ^m² /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): Platinum or platinum compound: Momentive Corporation, "TC-25A"

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

(Metal powder (G))
(G1): Silver powder, manufactured by Tokuriki Chemical Research Institute, product name "TC-101", median diameter d ₅₀ : 8.0 μm, aspect ratio 16.4, average major diameter 4.6 μm

(Synthesis of vinyl group-containing organopolysiloxane (A))
[Synthesis Scheme 1: Synthesis of the 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).
Specifically, 74.7 g (252 mmol) of octamethylcyclotetrasiloxane and 0.1 g of potassium silicate were placed in a 300 mL separable flask equipped with a condenser and stirring blades, which had been purged with Ar gas. The mixture was then heated and stirred at 120°C for 30 minutes. An increase in viscosity was observed during this process.
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 stirred again at 155°C for 4 hours.
Furthermore, after 4 hours, the mixture was diluted with 250 mL of toluene and washed three times with water. The organic layer after washing was reprecipitated and purified by washing several times with 1.5 L of methanol to separate the oligomer and polymer. The obtained polymer was dried under reduced pressure at 60°C overnight to obtain the first vinyl group-containing linear organopolysiloxane (A1-1) (Mn = 2, 2 × ^10⁵ , Mw = 4, 8 × ^10⁵ ). The vinyl group content, calculated by 1H-NMR spectroscopy, was 0.04 mol%.

[Synthesis Scheme 2: Synthesis of the second vinyl group-containing linear organopolysiloxane (A1-2)]
In the synthesis step of (A1-1) described above, 0.86 g (2.5 mmol) of 2,4,6,8-tetramethyl2,4,6,8-tetravinylcyclotetrasiloxane was added in addition to 74.7 g (252 mmol) of octamethylcyclotetrasiloxane. Except for this difference, the second vinyl group-containing linear organopolysiloxane (A1-2) was synthesized in the same manner as the synthesis step of (A1-1), as shown in formula (6) below. The vinyl group content, calculated by 1H-NMR spectroscopy, was 0.93 mol%.

<Preparation of silicone rubber-based curable compositions>
A silicone rubber-based curable composition was prepared as follows.
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. Then, silica particles (C) were added to the mixture and kneaded further to obtain a compound (silicone rubber compound).
Here, the kneading after the addition of silica particles (C) was carried out in two steps: the first step of kneading under a nitrogen atmosphere at 60-90°C for 1 hour for the coupling reaction, and the second step of kneading under a reduced pressure atmosphere at 160-180°C for 2 hours to remove the by-product (ammonia). After that, it was cooled, and the remaining 10% vinyl group-containing organopolysiloxane (A) was added in two parts and kneaded for 20 minutes.
Next, organohydrogenpolysiloxane (B), platinum, or a platinum compound (E) were added to 100 parts by weight of the obtained mixture (silicone rubber compound) in the proportions shown in Table 1 below, and the mixture was kneaded with a roll to obtain silicone rubber-based curable composition A (elastomer composition).

<Preparation of conductive solution for dip coating>
The obtained 13.7 parts by weight of silicone rubber-based curable composition A was immersed in 31.8 parts by weight of decane (solvent), then stirred with a rotating/revolving mixer, and after adding 54.5 parts by weight of metal powder (G1), it was kneaded with a three-roll mixer to obtain a conductive paste (conductive solution for dip coating).

<Preparation of conductive solution for spray painting>
The obtained 13.7 parts by weight of silicone rubber-based curable composition A was immersed in 31.8 parts by weight of decane (solvent), then stirred in a rotating/revolving mixer, and after adding 54.5 parts by weight of metal powder (G1), it was kneaded with a three-roll mixer to obtain a resin varnish. Subsequently, the resin varnish was diluted by adding 2.5 times its volume of decane and stirring in a rotating/revolving mixer to obtain a conductive solution for spray coating.

<Fabrication of biomedical electrodes>
(Example 1)
The silicone rubber-based curable composition A obtained above was heated at 180°C and 10 MPa for 10 minutes using a mold having multiple molding spaces (recesses) for plate-shaped support parts and substantially conical columnar parts to cure it, thereby obtaining a molded body in which the plate-shaped support parts and columnar parts were integrated within each recess (molding process).
A conductive wire A (manufactured by Mitsufuji Co., Ltd., AGposs, thickness: 100d/34f, tensile strength at break: 29.3%) was passed through the columnar portion of the obtained molded body using a sewing needle (conductive wire insertion step).
Next, the tip of the columnar part of the molded body (the region from the tip to about 1/2 L, where L is the total length of the columnar part) and the other surface of the plate-shaped support part were dipped in the above-mentioned <conductive solution for dip coating> and heated and dried at 120°C for 30 minutes (tip coating step).
Subsequently, a post-curing process was performed at 140°C for 2 hours (annealing process).
Based on the above, a biomedical electrode A having a substantially conical columnar portion 20 on a plate-shaped support portion 10 was obtained, as shown in Figure 1.
In the biomedical electrode A, the inclination angle θ was 53 degrees, the radius of the tip 22 was 1.5 mm, the tip of the conductive wire 60 protruded beyond the tip 22 of the columnar portion 20, and it was covered with a conductive resin layer 30.

(Example 2)
A biomedical electrode B was obtained in the same manner as in Example 1, except that conductive wire B (manufactured by Mitsufuji Co., Ltd., AGposs, thickness: 70d/24f, tensile strength at break: 27.9%) was used instead of conductive wire A.

(Example 3)
A biomedical electrode C was obtained in the same manner as in Example 1, except that conductive wire C (manufactured by Nippon Seisen Co., Ltd., metal fiber stainless steel fiber Naslon, SUS304, thickness: 0.22 mm, tensile break elongation: 1.6%) was used instead of conductive wire A.

(Comparative Example 1)
A molded body for the above-mentioned <fabrication of biomedical electrodes> was obtained in the same manner as in Example 1.
Without performing the conductive wire insertion process, the above-mentioned <conductive solution for spray coating> was spray-coated onto the entire surface of the obtained molded body, and heated and dried at 120°C for 30 minutes to form a conductive resin layer over the entire surface of the molded body. Subsequently, post-curing was performed at 140°C for 2 hours to obtain biomedical electrode D.

The obtained biomedical electrodes A through D were evaluated against the following evaluation criteria. The evaluation results are shown in Table 2.

(Mounting stability)
The above-described <Preparation of Biomedical Electrode> was carried out in the same manner as in Example 1, and a 2 mmφ steel ball (high-carbon chromium bearing steel material manufactured by Tsubaki Nakashima) was attached to the tip so as to connect to a conductive wire, thereby obtaining the biomedical electrode E of Comparative Example 2.

When the tip of the columnar portion of the biomedical electrode E of Comparative Example 2 was pressed against the back of the subject's head, and the measuring probe of a push-pull gauge (manufactured by Nidec-Shimpo Corporation, product name: Digital Force Gauge FGJN-2) was pressed against the other side of the biomedical electrode E opposite the tip with a constant load of 15 N, the subject reported feeling pain and being unable to tolerate it for more than a short time.

In contrast, when biomedical electrodes A to C of Examples 1 to 3 were used, the evaluation indicated that while there was a tactile sensation, it was not bothersome, or no pain was felt. Therefore, it was found that biomedical electrodes A to C of Examples 1 to 3 exhibited superior attachment stability compared to biomedical electrode E of Comparative Example 2.

(Measurement stability)
<Construction of an electroencephalogram (EEG) measurement system>
As shown in Figure 2, an external connection part 110 (a metal snap button with a structure that allows the cable end to be attached) was attached to the other side 14 of the bioelectrode 100 obtained in the above-mentioned <Fabrication of Bioelectrodes> via a conductive resin layer. A disposable electrode cord (Miyuki Giken Co., Ltd., product name: AP-C131-015) and a portable electroencephalograph (Miyuki Giken Co., Ltd., product name: PolymateMini AP-108) were electrically connected to this external connection part 110 in this order to create an electroencephalogram measurement system. The portable electroencephalograph was connected to a laptop computer via Bluetooth, and contact resistance with the head was acquired using a waveform display program (Miyuki Giken Co., Ltd., product name: Mobile Acquisition Monitor). The left earlobe was used as the ground and reference.

Next, a headgear for measuring electroencephalography (a headgear with a node configuration based on the International 10/20 method, molded using a 3D printer) was attached to the subject's head.
Subsequently, the tip 26 of the bioelectrode 100 was brought into contact with the back of the subject's head. While pressing the tip 26 of the columnar portion 20 of the bioelectrode 100 against the back of the subject's head (0z), the measuring probe of a push-pull gauge (manufactured by Nidec-Shimpo Corporation, product name: Digital Force Gauge FGJN-2) was pressed against the external connection portion 110 of the bioelectrode 100, first with a load of 7N, then gradually releasing the force. The contact resistance (kΩ) was continuously measured at 5N, 3N, and 1N loads to evaluate the change in contact resistance with respect to the load. The results are shown in Table 2.

Based on Table 2, it was found that the biomedical electrode of Example 1 exhibited a smaller change in contact resistance (Δ(7N-5N)) during the initial stage of load change compared to Comparative Example 1.

Based on the above, it was found that biomedical electrodes A to C of Examples 1 to 3 exhibit superior attachment stability compared to biomedical electrode E of Comparative Example 2, and superior measurement stability compared to biomedical electrode D of Comparative Example 1.

10 Plate-shaped support part 12 One surface 14 Other surface 20 Columnar part 22 Tip 24 Base end 26 Tip 28 Inclined surface 29 Inclined surface 30 Conductive resin layer 60 Conductive wire 100 Biomedical electrode 110 External connection part 200 Biosensor

Claims (13)

Insulating plate-shaped support part,
A substantially conical insulating elastic columnar portion is provided on one surface of the insulating plate-shaped support portion,
A conductive resin layer formed to cover the tip of the insulating elastic columnar portion,
A conductive wire is electrically connected to the conductive resin layer and is arranged inside the insulating elastic columnar portion and the insulating plate-shaped support portion from the tip end to the base end .
A biomedical electrode equipped with,
An external connection unit that electrically connects to the bioelectrode and transmits the bioelectrical signal detected by the bioelectrode to the outside,
A biosensor equipped with [specific features/equipment ]. A biosensor according to claim 1,
A biosensor in which the tip of the insulating elastic columnar part is formed in one of the following shapes: approximately hemispherical, ellipsoidal, conical, frustoconical, pyramidal, or approximately pyramidal. A biosensor according to claim 1 or 2,
A biosensor having a Type A durometer hardness of 15 to 65 on the surface of the insulating elastic columnar part, measured at 37°C in accordance with JIS K 6253 (1997). A biosensor according to any one of claims 1 to 3,
A biosensor in which the insulating plate-shaped support portion and the insulating elastic columnar portion are formed as an integrated member. A biosensor according to any one of claims 1 to 4,
A biosensor in which the aforementioned conductive wire is made of conductive fibers. A biosensor according to any one of claims 1 to 5,
A biosensor in which the conductive wire is composed of a twisted yarn made by twisting together multiple linear conductive fibers. A biosensor according to claim 6,
A biosensor wherein the conductive fiber includes one or more selected from the group consisting of metal fibers, metal-coated fibers, carbon fibers, conductive polymer fibers, conductive polymer-coated fibers, and conductive paste-coated fibers. A biosensor according to any one of claims 1 to 7,
A biosensor in which the insulating elastic columnar portion is made of insulating silicone rubber containing silicone rubber. A biosensor according to any one of claims 1 to 8,
A biosensor in which the conductive resin layer is composed of conductive filler and conductive silicone rubber containing silicone rubber. A biosensor according to claim 9,
A biosensor in which the content of the conductive filler is 30% by mass or more and 90% by mass or less based on 100% by mass of the silicone rubber. A biosensor according to claim 9 or 10,
A biosensor wherein the conductive filler includes one or more selected from the group consisting of metal particles, silver/silver chloride particles, metal fibers, metal-coated fibers, carbon black, acetylene black, graphite, carbon fibers, carbon nanotubes, conductive polymers, conductive polymer-coated fibers, and metal nanowires . A biosensor according to any one of claims 1 to 11,
A biosensor used in electrodes for measuring electroencephalography (EEG). A biosignal measurement system comprising a biosensor according to any one of claims 1 to 12 .