Biomedical electrodes

Abstract

To provide a biomedical electrode equipped with a hydrogel in the electrode portion, which can be attached even after prolonged exposure to water, causes less pain during device attachment, and has stable sensing capabilities. [Solution] A bioelectrode comprising a surface substrate 1, a conductive layer 2 disposed on the surface substrate 1, a conductive connection terminal 3 penetrating the surface substrate 1 and the conductive layer 2, a hydrogel layer 4 that contacts the conductive layer 2 at a position away from the connection terminal 3 and electrically connects with the connection terminal 3, and an organogel layer 6 disposed around the hydrogel layer 4 and above the conductive layer 2.

Description

Technical Field

[0001] The present invention relates to an electrode for living body. The present disclosure relates to an electrode for living body, and more particularly to an electrode for living body provided with a hydrogel.

Background Art

[0002] In recent years, due to the increasing health awareness, various wearable devices have emerged. Examples of the electrode for living body required for this wearable device include a textile type electrode and an adhesive type electrode. The textile type is made into an electrode by coating or mixing a conductive substance into fibers, but when sensing biological information, the contact resistance is high and the sensing stability is lacking. On the other hand, examples of the adhesive type electrode include an electrode using a hydrogel for the electrode portion. In the electrode using a hydrogel, the contact resistance value can be lowered and stable sensing is possible, but the need for long-term (several days to one week) attachment to the electrode for living body, such as use involving bathing, has been increasing.

[0003] Patent Document 1 discloses a living body electrode including an electrode element to which a conductive gel layer is adhered at one end, and a tape that holds the other end of the electrode element and is adhered to the living body surface, wherein the tape is formed of a thin film that is flexible and stretchable, and a reinforcing cover film that covers the surface of the tape opposite to the surface adhered to the living body in a peelable manner is provided on the tape.

[0004] Conventional hydrogels have problems such as easily absorbing moisture from the outside in high-humidity environments, causing the gel to swell easily, reducing its adhesive strength in a short time, and making it easy for the hydrogel to detach from the skin or device. Patent Document 2 discloses a hydrogel that improves the reduction in adhesive strength in high-humidity environments by using a compound exhibiting a relatively hydrophobic structure, specifically polyoxyalkylene alkyl ether or sugar, as a plasticizer instead of conventional polyhydric alcohols. This hydrogel suppresses swelling of the gel due to the intrusion of moisture from the outside, and maintains its high initial adhesive strength.

[0005] Patent Document 3 discloses an acrylic medical adhesive suitably used in bandages, adhesive dressings, poultices, etc., and a medical topical material formed using the same. Such medical adhesives have good skin adhesion, cause almost no skin irritation, cause very little keratin damage, and are safe. Furthermore, even when applied to medical devices or equipment made of materials that are prone to plasticizer migration, such as unplasticized polyvinyl chloride, these advantageous properties are not impaired.

[0006] Patent Document 4 discloses an electrode fixing member for fixing electrodes used to apply electrical stimulation to the head. Using this electrode fixing member, displacement of the electrodes is suppressed even when the electrodes are used for a long period of time. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 3623124 [Patent Document 2] Patent No. 7037639 [Patent Document 3] Patent No. 2539330 [Patent Document 4] Patent No. 7204088 [Overview of the project] [Problems that the invention aims to solve]

[0008] In use involving harsh water exposure such as showering or bathing, electrodes using hydrogels as described in Patent Documents 1 and 2, which have a large contact area with the skin, suffer from insufficient water resistance and are prone to peeling off the skin. While it is possible to attach the electrode for extended periods by incorporating a non-conductive adhesive on the outer circumference of the electrode as described in Patent Document 3, there is still a concern that it may peel off the skin in use involving prolonged water exposure. In addition, since the adhesive is usually thin, only a few tens of micrometers thick, if the electrode has a rigid connector like a snap, there is a concern that it may cause pain when attaching the device to the subject. Physical fixation of the electrode as described in Patent Document 4 is expected to be cumbersome for the user and is undesirable from a usability standpoint.

[0009] One of the purposes of this disclosure is to provide a biomedical electrode that has a hydrogel portion in the electrode area, can be attached even after prolonged exposure to water, causes less pain when the device is attached, and has stable sensing. [Means for solving the problem]

[0010] This disclosure includes, for example, the following subjects:

[0011] Section 1. A bioelectrode comprising: a surface substrate; a conductive layer disposed on the surface substrate; a plurality of conductive connection terminals penetrating the surface substrate and the conductive layer; a hydrogel layer in contact with the conductive layer at a position away from the connection terminals and electrically connected to the connection terminals; and an organogel layer disposed around the hydrogel layer and above the conductive layer. Section 2. The biomedical electrode according to claim 1, wherein the organogel is an organogel comprising a polymer matrix, a plasticizer, and water, wherein the water content relative to the total amount of the organogel is less than 1.0% by mass, the polymer matrix comprises a polymerizable monomer having an alicyclic hydrocarbon in its structure (meth)acrylic acid ester, and the plasticizer is a liquid or paste-like plasticizer at 25°C comprising at least one selected from the group consisting of aliphatic hydrocarbons, fatty acid esters, and silicone oils, the initial adhesive strength of the organogel to a bakelite plate is 1.0 N / 20 mm or more, and the adhesive strength retention rate after immersion in water for 1 hour is 90% or more. Section 3. The bioelectrode according to item 1, further comprising an insulating layer on a conductive layer, wherein an organogel is disposed on the insulating layer. Section 4. The biomedical electrode according to item 1, wherein the organogel layer is in contact with the connection terminal. Section 5. The biomedical electrode according to item 1, wherein the thickness of the organogel layer is 0.1 mm to 3 mm. Section 6. The biomedical electrode according to claims 1 to 5, wherein the hydrogel layer is a hydrogel containing a polymer matrix, water, and a polyhydric alcohol, and the polymer matrix is ​​a copolymer of one or more monofunctional monomers selected from (meth)acrylamide monomers and (meth)acrylic acid esters and a crosslinkable monomer. Section 7. The biomedical electrode according to item 1 or 5, wherein the thickness of the hydrogel layer is 0.1 mm to 3 mm. Section 8. The ratio of the thickness of the hydrogel layer to the thickness of the organogel layer surrounding each of the hydrogel layers is such that, when the thickness of the hydrogel layer is A (mm) and the thickness of the organogel layer is B (mm), the relationship 1 ≤ A / B ≤ 2.5 is satisfied, according to any one of items 1 to 5. Section 9. The conductive connection terminals include a plurality of conductive connection terminals separated from each other, the hydrogel layer includes a plurality of hydrogel layers electrically connected to each of the plurality of conductive connection terminals, and the organogel layer is disposed around each of the hydrogel layers and above the conductive layer. The biological electrode according to claims 1 to 5.

Effect of the Invention

[0012] According to the present disclosure, there is provided a biological electrode having a hydrogel in an electrode portion, which can be attached even when exposed to water for a long time, has less pain when a device is worn, and has sensing stability.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Modes for Carrying Out the Invention

[0014] In this specification, "comprising" is a concept that also includes "consisting essentially of" and "consisting of".

[0015] In this specification, "(meth)acryl" includes acrylic, methacrylic, or both.

[0016] In this specification, "film" refers to a thin film with a thickness of less than 250 μm, and "sheet" refers to a plate-like member with a thickness of 250 μm or more.

[0017] In the numerical ranges described stepwise in this specification, the upper or lower limit of a numerical range in one step can be arbitrarily combined with the upper or lower limit of a numerical range in another step. Furthermore, in the numerical ranges described in this specification, the upper or lower limit of a numerical range may be replaced with values ​​shown in the examples or values ​​that can be uniquely derived from the examples. Moreover, in this specification, numbers connected by "~" mean a numerical range that includes the numbers before and after "~" as the lower and upper limits.

[0018] The embodiments included in this disclosure will be described further below. The embodiments described below are examples of typical embodiments of this disclosure and do not limit the scope of the invention.

[0019] Figure 1 is a schematic plan view of a bioelectrode according to the first embodiment of the present invention, and Figure 2 is a schematic cross-sectional view of the bioelectrode of Figure 1 along line AA. This bioelectrode comprises a surface substrate 1, a conductive layer 2 disposed on the surface substrate 1, a plurality (two in the drawing) of conductive connection terminals 3 that penetrate the surface substrate 1 and the conductive layer 2 and are spaced apart from each other, a plurality of hydrogel layers 4 that contact the conductive layer 2 at a position away from the connection terminals 3 and are electrically connected to each of the connection terminals 2, and an organogel layer 6 disposed around each hydrogel layer 4 and above the conductive layer 2. Preferably, the organogel layer 6 is disposed as a single continuous layer around each hydrogel layer 4 and above the conductive layer 2. The conductive layer 2, the connection terminals 3, and the hydrogel layer 4 constitute the electrode portion.

[0020] The bioelectrode further comprises an insulating layer 5 placed on the conductive layer 2, an insulating film 7 placed across the two connection terminals 3, and a release layer 8 that is in contact with the hydrogel layer 4 and the organogel layer 6 and placed on the hydrogel layer 4 and the organogel layer 6. The release layer 8 is also called a release film. For the sake of easier understanding of the invention's structure, the surface substrate 1 and connection terminals 3 are omitted in Figure 1.

[0021] In this embodiment, the surface substrate 1 has an elongated shape, particularly a roughly rectangular shape in plan view, but is not limited thereto. The surface substrate 1 may be, for example, a film, nonwoven fabric, or foam sheet made of synthetic resin. Examples of synthetic resin films include non-conductive films such as polyethylene terephthalate film, polypropylene film, and polyethylene film. Furthermore, two or more composite materials may be used for the surface substrate 1.

[0022] The conductive layer 2 is provided at two locations on the surface substrate 1, separated from each other. The conductive layer 2 comprises a linearly extending wiring portion 2a whose end contacts the connection terminal 3, and an end portion 2b that is continuous with the wiring portion 2a and on which the hydrogel layer 4 is positioned. The wiring portion 2a and the end portion 2b can be formed by printing a conductive ink containing a conductive material such as metal (Ag), silver chloride (AgCl), a combination of silver and silver chloride (Ag / AgCl), or conductive carbon onto a layer adjacent to the conductive layer 2 (e.g., the surface substrate 1), or by laminating a conductive film containing a conductive material such as metal foil (aluminum, stainless steel, Ag, etc.) or conductive carbon onto a layer adjacent to the conductive layer 2 (e.g., the surface substrate 1). Preferably, the conductive layer 2 (i.e., the wiring portion 2a and the end portion 2b) is a conductive ink layer on which the conductive ink is printed.

[0023] The connector 3 may be a snap (also called a hook) made of metal or metal-plated metal. Examples of snaps include, but are not limited to, a combination of a cap (also called a head) and a spring (also called a socket), or a combination of a stud (also called a prong) and a post (also called a pin). Since the combination of a cap and a spring constitutes a female member having a concave portion, and the combination of a stud and a pin constitutes a male member having a convex portion, the connector 3 can be connected by snap fastening to a male or female member of a medical device (e.g., an electrocardiograph, electromyograph, electroencephalograph, pulse wave meter, etc.) that measures and / or records the electrical signals of a living organism.

[0024] The hydrogel layer 4 is in contact with and positioned on the end portion 2b of the conductive layer 2. In this embodiment, in a plan view, the hydrogel layer 4 is larger than the end portion 2b, completely covering the end portion 2b and extending beyond it to contact the surface substrate 1. When the release layer 8 is removed, the upper surface of the hydrogel layer 4 is exposed to air. The lateral position (left-right direction in the figure) of the hydrogel layer 4 is away from (offset) the connection terminal 3.

[0025] Preferably, the hydrogel layer 4 consists only of a number of hydrogel layers corresponding to the number of connection terminals 3, which are placed on the end portion 2b of the conductive layer 2, and is not provided in other parts of the biomedical electrode. The thickness of the hydrogel layer 4 is not particularly limited and is, for example, 0.1 mm to 3 mm.

[0026] The hydrogel constituting the hydrogel layer 4 may be any conductive hydrogel used in biomedical electrodes, and such hydrogels are well known. Preferably, the hydrogel is a hydrogel containing a polymer matrix, water, and a polyhydric alcohol, wherein the polymer matrix is ​​a copolymer of one or more monofunctional monomers selected from (meth)acrylamide monomers and (meth)acrylic acid esters and a crosslinkable monomer.

[0027] A monofunctional monomer is a monofunctional monomer that has one polymerizable carbon-carbon double bond in its molecule and is a non-crosslinked monomer.

[0028] Specific examples of (meth)acrylamide monomers include (meth)acrylamide; N,N-dialkyl(meth)acrylamides such as N,N-dimethyl(meth)acrylamide and N,N-diethyl(meth)acrylamide; N-alkyl(meth)acrylamides such as N-isopropyl(meth)acrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, and N-propyl(meth)acrylamide; N-hydroxyalkyl(meth)acrylamides such as N-hydroxyethyl(meth)acrylamide and N-hydroxymethyl(meth)acrylamide; N-ethoxymethyl(meth)acrylamide, N-propoxymethyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide, and N-iso Examples include N-alkoxyalkyl(meth)acrylamides such as butoxymethyl(meth)acrylamide, N-pentoxymethyl(meth)acrylamide, N-hexyloxymethyl(meth)acrylamide, N-heptoxymethyl(meth)acrylamide, N-octoxymethyl(meth)acrylamide, N-ethoxyethyl(meth)acrylamide, N-propoxyethyl(meth)acrylamide, and N-butoxyethyl(meth)acrylamide; cationic acrylamide compounds containing amino groups such as dimethylaminopropyl(meth)acrylamide; anionic acrylic monomers containing sulfonic acid groups such as 4-acryloylmorpholine and tert-butylacrylamidesulfonic acid, or their salts; and derivatives thereof. Among these, one or more selected from the group consisting of (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-propyl(meth)acrylamide, N-hydroxyethyl(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, dimethylaminopropyl(meth)acrylamide, 4-acryloylmorpholine, tert-butylacrylamidesulfonic acid and its salts are preferred, but are not limited thereto.

[0029] Specific examples of (meth)acrylic acid esters include alkyl (meth)acrylates with 1 to 18 carbon atoms in the alkyl group, such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. Alkyl methacrylates such as n-nonyl methacrylate, isononyl methacrylate, n-pentyl methacrylate, n-decyl methacrylate, isodecyl methacrylate, n-lauryl methacrylate, tridecyl methacrylate, and n-stearyl methacrylate; alicyclic methacrylates such as cyclohexyl methacrylate, isobornyl methacrylate, and 1-adamantyl methacrylate; and 2-methoxyethyl methacrylate. Examples include, but are not limited to, one or more selected from the group consisting of: alkoxy group-containing (meth)acrylic acid esters such as ethoxyethoxyethyl (meth)acrylate, methoxytriethylene glycol (meth)acrylate, etc.; hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate (which may have an aryl group bonded to the hydroxyalkyl group via an ether link); glycerin mono(meth)acrylate; polyalkylene glycol mono(meth)acrylate such as polyethylene glycol mono(meth)acrylate and polyethylene glycol-polypropylene glycol copolymer; (meth)acrylic acid esters having an aromatic ring such as benzyl (meth)acrylate; and (meth)acrylic acid esters having a heterocyclic ring such as tetrahydrofurfuryl (meth)acrylate. The amount of one or more monofunctional monomers selected from (meth)acrylamide monomers and (meth)acrylic acid esters added is preferably in the range of 98.5% to 99.97% by mass relative to the total amount of polymer matrix.

[0030] As the crosslinkable monomer, it is preferable to use a monomer having two or more polymerizable carbon-carbon double bonds in its molecule. Specifically, examples include polyfunctional (meth)acrylamides or polyfunctional (meth)acrylic acid esters such as methylenebis(meth)acrylamide, ethylenebis(meth)acrylamide, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, glycerin di(meth)acrylate, and glycerin tri(meth)acrylate, as well as tetraallyloxyethane and diallylammonium chloride, which can be used individually or in combination of two or more. In addition, as the crosslinkable monomer having two or more polymerizable double bonds in its molecule, polyglycerin derivatives that are polyfunctional compounds having two or more (meth)acryloyl groups or vinyl groups and having a molecular weight of 400 or more, as described in Japanese Patent Publication No. 2803886, can also be used. The above-mentioned polyfunctional (meth)acrylamides, polyfunctional (meth)acrylic acid esters, and polyglycerin derivatives are included in acrylic monomers.

[0031] The amount of crosslinkable monomer added is preferably in the range of 0.03% to 1.5% by mass relative to the total amount of polymer matrix.

[0032] The water content in the hydrogel is not particularly limited, but is preferably 10 to 60% by mass, and more preferably 10 to 45% by mass, relative to the hydrogel.

[0033] Polyhydric alcohols are added to the hydrogel to impart wetting properties. The polyhydric alcohols are not particularly limited and include, for example, diols such as ethylene glycol, triethylene glycol, 1,6-hexanediol, 1,9-nonanediol, propylene glycol, and butanediol; trihydric or higher polyhydric alcohols such as glycerin, pentaerythritol, and sorbitol; polyhydric alcohol condensates such as polyethylene glycol, polypropylene glycol, and polyglycerin; and polyhydric alcohol modified products such as polyoxyethylene glycerin. Among polyhydric alcohols, it is preferable to use polyhydric alcohols that are liquid in the hydrogel's operating temperature range (for example, around 20°C when used indoors). Specifically, one or more selected from the group consisting of ethylene glycol, triethylene glycol, propylene glycol, polypropylene glycol, polyethylene glycol, polyglycerin, and glycerin are preferred.

[0034] The polyhydric alcohol content in the hydrogel is not particularly limited, but is preferably in the range of 20 to 70% by mass relative to the hydrogel, and more preferably in the range of 25 to 65% by mass.

[0035] Hydrogels may contain other additives as needed. Examples of other additives include acrylic acid, electrolytes, pH adjusters, rust inhibitors, fungicides, antioxidants, defoamers, stabilizers, surfactants, and colorants.

[0036] The insulating layer 5 is positioned in contact with the conductive layer 2 so as to cover the linear wiring portion 2a of the conductive layer 2 between the connection terminal 3 and the hydrogel layer 4.

[0037] The organogel layer 6 is positioned around each hydrogel layer 4, on top of the insulating layer 5 placed on top of the conductive layer 2, and on top of the insulating film 7, in contact with the hydrogel layer 4, insulating layer 5, and insulating film 7, respectively. As can be seen from Figures 1 and 2, in this embodiment, the organogel 6 is a single continuous component, and the release layer 8 is in contact only with the hydrogel layer 4 and the organogel layer 6. When the release layer 8 is removed, the hydrogel layer 4 and the organogel layer 6 are exposed to air and adhere to the subject's skin. The thickness of the organogel layer 6 is not particularly limited and is, for example, 0.1 mm to 3 mm.

[0038] The width of the organogel 6 placed around the periphery of the electrode portion (perpendicular to the thickness direction of the organogel layer) can be set arbitrarily. From the viewpoint of long-term adhesion and sensing stability, it is preferable that the width is 2 mm or more, and more preferably 3 mm or more, at the narrowest point from the edge of the hydrogel 4 on the conductive layer 2 (especially the terminal portion 2b). The storage modulus of the organogel is preferably 2000 Pa to 8000 Pa, and more preferably 3000 Pa to 7000 Pa. If the storage modulus is 3000 Pa or higher, the organogel is not too soft, and its mechanical strength and handling properties are good. If the storage modulus is 7000 Pa or lower, the organogel is not too hard, it has good cushioning properties, and pain is less likely to be felt when the electrodes are attached. In this invention, the storage modulus is measured by the following method. Viscoelasticity measurements will be performed using a viscoelasticity measuring device (Anton Paar MR-102) at 23°C and a frequency of 0.1 Hz with a strain of 1%. The jig consists of a 25φ stainless steel parallel plate with a 25φ gel piece attached. After applying a load to the point where the load becomes 1N, the storage modulus will be calculated at 0.1 Hz.

[0039] The ratio of the thickness of the hydrogel layer 4 to the thickness of the organogel layer 6 is more preferable in terms of sensing stability of the bioelectrode if it satisfies the relationship 1 ≤ A / B ≤ 2.5, where A (mm) is the thickness of the hydrogel layer 4 and B (mm) is the thickness of the organogel layer 6. Sensing stability refers to the ability to measure the target biological information without disturbance in the measurement waveform.

[0040] In this specification, as shown by "A" and "B" in Figure 2, the "thickness of the hydrogel layer 4" when measuring the A / B ratio refers to the thickness of the hydrogel layer 4 above the conductive layer 2. The "thickness of the organogel layer 6" refers to the portion of the organogel layer 6 adjacent to the hydrogel layer 4, where the conductive layer 2 is not located beneath the organogel layer 6. For example, the thickness B of the organogel layer 6 can be measured from either of the organogel layer 6 portions at both ends in the longitudinal direction of the biomedical electrode in Figure 2. In the embodiment shown in Figure 2, the thickness of the conductor 2 is much lower than the thickness of the hydrogel layer 4 (usually less than one-tenth), so the thickness of the hydrogel layer 4 and the thickness of the organogel layer 6 are approximately the same, and A / B can be considered to be 1.

[0041] The organogel constituting the organogel layer 6 is not particularly limited, but preferably it is an organogel containing a polymer matrix and a plasticizer, wherein the water content relative to the total amount of organogel is less than 1.0% by mass, the polymerizable monomer constituting the high molecular weight matrix contains a (meth)acrylic acid ester having an alicyclic hydrocarbon in its structure, the plasticizer is a liquid or paste-like plasticizer at 25°C containing at least one selected from the group consisting of aliphatic hydrocarbons, fatty acid esters and silicone oils, the initial adhesive strength to the bakelite plate is 1.0 N / 20 mm or more, and the adhesive strength retention rate after immersion in water for 1 hour is 90% or more. In this application, the initial adhesive strength of the organogel constituting the organogel layer of the bioelectrode, the adhesive strength after immersion in water, and the adhesive strength retention rate are measured by the following method.

[0042] ·Measurement of initial adhesion force Each organogel was cut to a size of 20 mm wide x 120 mm long to form a test specimen. The PET film was peeled off one side of the test specimen, and the peeled side was attached to a bakelite plate and set in a Tensilon (Orientec Co., Ltd. "RTE-1210"). Subsequently, in accordance with JIS Z 0237, the load was measured when peeling the test specimen at a speed of 300 mm / min in a 90° direction under conditions of 23°C and 55% relative humidity, and the measured load value (N / 20 mm) was defined as the initial adhesive strength of the organogel.

[0043] ·Measurement of adhesion force after immersion in water Each organogel was cut to a size of 20 mm wide x 120 mm long to form a test specimen. The PET film was peeled off one side of the test specimen, and it was immersed in water for 1 hour and left to stand. After that, the test specimen was removed from the water and the surface moisture was removed. Then, the side of the test specimen from which the film had been peeled off was attached to a bakelite plate, and the load was measured when peeling the test specimen in a 90° direction at a speed of 300 mm / min in an environment of 23°C and 55% relative humidity, in accordance with JIS Z 0237. The measured load value (N / 20 mm) was defined as the adhesive strength of the organogel after immersion in water.

[0044] ·Calculation of adhesion force retention rate The adhesion retention rate of the organogel is calculated using the following formula. Adhesive force retention rate (%)=F1 / F0×100 F0: Initial tackiness of organogel. F1: Adhesion strength of organogel after immersion in water.

[0045] As (meth)acrylic acid esters having an alicyclic hydrocarbon in their structure, for example, one or more selected from the group consisting of 4-t-butylcyclohexyl acrylate, isobornyl acrylate, 1,4-cyclohexanedimethanol monoacrylate, and 3,3,5-trimethylcyclohexyl acrylate can be used. From the viewpoint of adhesiveness, it is preferable to use one or both of 4-t-butylcyclohexyl acrylate and 3,3,5-trimethylcyclohexyl acrylate.

[0046] From the viewpoint of obtaining an organogel with excellent water resistance, adhesive durability, and appearance, the amount of (meth)acrylic acid ester having an alicyclic hydrocarbon in its structure is preferably 30% by mass or more, more preferably 50% by mass or more, and even more preferably 70% by mass or more, relative to the total amount of polymer matrix.

[0047] From the viewpoint of obtaining an organogel with excellent water resistance, adhesive durability, and appearance, the amount of (meth)acrylic acid ester having an alicyclic hydrocarbon in its structure is preferably in the range of 10 to 90% by mass, more preferably in the range of 40 to 80% by mass, and even more preferably in the range of 50 to 70% by mass, relative to the total amount of organogel.

[0048] In one particular embodiment, the organogel further comprises, as polymerizable monomers constituting the polymer matrix, at least one monomer selected from the group consisting of (meth)acrylamide monomers and (meth)acrylic acid ester monomers. However, neither the (meth)acrylamide monomer nor the (meth)acrylic acid ester monomer includes a (meth)acrylic acid ester having an alicyclic hydrocarbon in its structure.

[0049] The physical properties of the organogel, such as adhesiveness and flexibility, can be adjusted by including, as polymerizable monomers constituting the polymer matrix, (meth)acrylic acid esters having alicyclic hydrocarbons in their structure, and further including at least one monomer selected from the group consisting of (meth)acrylamide monomers and (meth)acrylic acid ester monomers. Examples of (meth)acrylamide monomers and (meth)acrylic acid ester monomers are as described with respect to the (meth)acrylamide monomers and (meth)acrylic acid ester monomers that are components of hydrogel layer 4.

[0050] When the organogel contains at least one monomer selected from the group consisting of (meth)acrylamide monomers and (meth)acrylic acid ester monomers, the amount of at least one monomer selected from the group consisting of (meth)acrylamide monomers and (meth)acrylic acid ester monomers is preferably in the range of 1.0 to 60% by mass, and more preferably in the range of 5.0 to 50% by mass, relative to the total amount of polymer matrix, from the viewpoint of water resistance, durability of adhesiveness, and appearance.

[0051] Furthermore, the amount of at least one monomer selected from the group consisting of (meth)acrylamide monomers and (meth)acrylic acid ester monomers is preferably in the range of 1.0 to 40% by mass, and more preferably in the range of 3.0 to 30% by mass, relative to the total amount of organogel, from the viewpoint of water resistance, durability of adhesiveness, and appearance.

[0052] Crosslinkable monomers can be added to the polymer matrix of the organogel, or they can be omitted. The addition of crosslinkable monomers is preferable from the viewpoint of maintaining the shape of the organogel. An example of a crosslinkable monomer is the crosslinkable monomer that is a component of hydrogel layer 4, as explained earlier.

[0053] The amount of crosslinkable monomers is not particularly limited, but from the viewpoint of the adhesiveness and flexibility of the organogel, it is preferably in the range of 0.10 to 3.0% by mass relative to the total amount of polymer matrix, and more preferably in the range of 0.50 to 2.0% by mass.

[0054] Polymerization initiators may be added to form a polymer matrix. The amount of polymerization initiator is not particularly limited, but from the viewpoint of the strength and shape retention of the organogel, it is preferably in the range of 1.0 to 5.0% by mass, and more preferably in the range of 1.0 to 3.0% by mass, relative to the total amount of polymer matrix.

[0055] The type of polymerization initiator is not particularly limited and may be either a photopolymerization initiator or a thermal polymerization initiator. When forming the organogel into a sheet, a photopolymerization initiator can preferably be used. Examples of photopolymerization initiators include acetophenone-based polymerization initiators, azo-based polymerization initiators, thioxanthone-based polymerization initiators, benzophenone-based polymerization initiators, acylphosphine oxide-based polymerization initiators, oxime ester-based polymerization initiators, benzoin-based polymerization initiators, and benzyl ketal-based polymerization initiators. More preferably, 2-hydroxy-2-methylpropiophenone can be used.

[0056] The plasticizer is a liquid or paste-like plasticizer at 25°C, comprising at least one selected from the group consisting of aliphatic hydrocarbons, fatty acid esters, and silicone oils. By adding a plasticizer of this composition, an organogel with excellent water resistance and appropriate elasticity can be obtained.

[0057] Examples of aliphatic hydrocarbons include liquid paraffin, squalane, hydrogenated polyisobutene, and hydrogenated polydecene. From the viewpoint of obtaining excellent water resistance and appropriate elasticity, it is preferable that the aliphatic hydrocarbons include one or more selected from the group consisting of liquid paraffin, squalane, hydrogenated polyisobutene, and hydrogenated polydecene.

[0058] Examples of fatty acid esters include glycerin fatty acid esters, polyglycerin fatty acid esters, propylene glycol fatty acid esters, sorbitan fatty acid esters, and fatty acid methyl esters. More specifically, castor oil and glyceryl triisostearate are examples. From the viewpoint of obtaining excellent water resistance and appropriate elasticity, it is preferable that the fatty acid ester contains one or more selected from the group consisting of glycerin fatty acid esters, polyglycerin fatty acid esters, propylene glycol fatty acid esters, sorbitan fatty acid esters, and fatty acid methyl esters. More specifically, it is preferable to contain either or both castor oil and glyceryl triisostearate.

[0059] Examples of silicone oils include straight silicone oil, cyclic silicone oil, methyl hydrogen silicone oil, branched silicone oil, alkyl-modified silicone oil, alcohol-modified silicone oil, and amino-modified silicone oil. From the viewpoint of obtaining excellent water resistance and appropriate elasticity, it is preferable that the silicone oil contains one or more types selected from the group consisting of straight silicone oil, cyclic silicone oil, methyl hydrogen silicone oil, branched silicone oil, alkyl-modified silicone oil, alcohol-modified silicone oil, and amino-modified silicone oil.

[0060] The plasticizer content is not particularly limited, but is preferably in the range of 15 to 120% by mass relative to the total amount of polymer matrix, more preferably in the range of 20 to 120% by mass, even more preferably in the range of 40 to 100% by mass, and particularly preferably in the range of 50 to 80% by mass.

[0061] The plasticizer content is not particularly limited, but is preferably in the range of 10 to 60% by mass relative to the total amount of organogel, more preferably in the range of 25 to 55% by mass, and even more preferably in the range of 35 to 50% by mass.

[0062] The organogel of the present invention has a water content of less than 1.0% by mass. From the viewpoint of hydrolysis, the water content of the organogel is preferably less than 0.80% by mass, more preferably less than 0.50% by mass, and particularly preferably no water content, relative to the total amount of organogel.

[0063] The water content of organogels can be measured by the following method.

[0064] A test sample is prepared by weighing out an arbitrary mass of organogel, placing it in a vial, and sealing it with an aluminum cap. The test sample is then placed in a moisture vaporizer. The vial is then heated to 125°C to vaporize the water in the sample, and the mass of the vaporized water is measured using a moisture measuring device. The measured mass of vaporized water is divided by the mass of the weighed organogel, and this value is multiplied by 100 to obtain the moisture content (%) of the organogel. The moisture content of the organogel can typically be measured by the method described in the examples.

[0065] The organogel of the present invention may contain additives other than those mentioned above, if necessary. Examples of such additives include rust inhibitors, mold inhibitors, antioxidants, defoamers, stabilizers, surfactants, colorants, thickeners, humectants, and fragrances.

[0066] The organogels that make up organogel 6 can be manufactured by the following method.

[0067] First, the process includes a step of mixing an alicyclic hydrocarbon (meth)acrylic acid ester with a plasticizer to obtain a mixture. The mixture may further contain at least one monomer selected from the group consisting of (meth)acrylamide monomers and (meth)acrylic acid ester monomers, a crosslinkable monomer, a polymerization initiator, and one or more additives (rust inhibitors, mold inhibitors, antioxidants, defoamers, stabilizers, surfactants, colorants and thickeners, humectants, and fragrances). The polymerization of the (meth)acrylic acid ester is promoted by including a polymerization initiator in the mixture. These materials are as described above as components of the organogel.

[0068] When mixing an alicyclic hydrocarbon (meth)acrylic acid ester with a plasticizer, these components may be mixed all at once, or they may be mixed separately.

[0069] Next, the mixture can be poured into a container of the desired shape and cured to form the organogel. When forming it into a sheet, for example, the mixture can be dropped onto a film, a PET film can be placed on top, the mixture can be spread evenly, fixed to a desired thickness, and then cured to form the organogel.

[0070] The curing method is not particularly limited, and known methods can be used. When curing by polymerization reaction induced by ultraviolet irradiation, the cumulative ultraviolet irradiation dose is 1000 mJ / cm². 2 It is desirable that the above be the case.

[0071] The insulating film 7 is positioned across the two connection terminals 3, and both ends of the insulating film 7 in the longitudinal direction are in contact with the two insulating layers 5 and positioned on top of the two insulating layers 5. The insulating film 7, as an insulating layer, only needs to insulate between the connection terminals 3 and the organogel layer 6, and the material is not particularly limited.

[0072] The release layer 8 may be a release sheet or a release film. The release layer is not particularly limited, and for example, a sheet or film made of a synthetic resin such as polyethylene, polyolefin resin such as polypropylene, or polyester resin such as polyethylene terephthalate or polyethylene naphthalate, which have undergone silicone release treatment, can be used.

[0073] The bioelectrode of the first embodiment has an organogel layer 6 around each hydrogel layer 4 that is electrically connected to the connection terminal and above the conductive layer 2, so that it can be attached even after prolonged exposure to water, causes less pain when the device is attached, and has sensing stability. The bioelectrode is preferably disposable.

[0074] Next, an example of a method for manufacturing a bioelectrode according to the first embodiment will be described. First, a surface substrate 1 is placed on a flat surface. Next, a conductive layer 2, such as electrode wiring, is provided on the surface substrate 1. Next, a plurality of connecting members 3 are placed at positions far apart from each other so as to penetrate the surface substrate 1 and the conductive layer 2. A hydrogel layer 4 is prepared by preparing a hydrogel composition and curing it. An organogel layer 6 is prepared by preparing an organogel composition and curing it. The hydrogel layer 4 and the organogel layer 6 are separately installed on the assembly of the surface substrate 1, the conductive layer 2, and the connecting members 3. Before installing the organogel layer 6, an insulating layer 5 may be placed on the conductive layer 2, and / or an insulating film 7 may be placed on the connecting members 3. Finally, a release layer 8 is placed on the opposite side from the surface substrate 1 so as to cover the hydrogel layer 4 and the organogel layer 6.

[0075] The biomedical electrodes of the present invention can be used as medical electrodes, including electrocardiogram electrodes and electromyogram electrodes, as well as electrodes for electrical stimulation devices used in transcutaneous electrical stimulation therapy (TENS), neuromuscular electrical stimulation therapy (EMS), microcurrent therapy, etc., but are not limited to these uses. Figure 3 is a schematic cross-sectional view of a comparative example bioelectrode. This multi-pole electrode, like the bioelectrode of the first embodiment shown in Figure 2, comprises a surface substrate 1, a conductive layer 2, multiple connection terminals 3, a hydrogel layer 4, an insulating layer 5, an insulating film 7, and a release layer 8, but lacks an organogel layer 6. Because there is a wide space between the surface substrate 1 and the release layer 8 between the two hydrogel layers 4, the electrode is prone to lifting due to the subject's movements while wearing it, causing pain due to pressure on the skin by the connection terminals 3, and maintaining adhesion when exposed to water for a long time because the adhesive surface to the skin is only the portion of the hydrogel layer 4. Furthermore, when attached to the skin, there are no materials that can be attached to the skin around the two hydrogel layers 4, resulting in unstable sensing.

[0076] Figure 4 is a schematic cross-sectional view of a biomedical electrode of another comparative example. This multi-pole electrode further comprises a hydrogel layer 4a on top of the insulating film 7, compared to the example in Figure 3. The hydrogel layer 4a is in contact with both the insulating film 7 and the release layer 8. The hydrogel layer 4a contains hydrogel, and the hydrogel constituting the hydrogel layer 4a can be the same as the hydrogel exemplified for the hydrogel layer 4. In this example, because the hydrogel layer 4a is located between the two hydrogel layers 4, lifting of the electrode when the subject wears it does not occur or is unlikely to occur. Also, because the hydrogel is water-soluble, it is difficult to maintain adhesion by exposing it to water for a long time. Furthermore, because there is no material to be attached to the skin around the two hydrogel layers 4 on both sides, sensing remains unstable.

[0077] Figure 5 is a schematic cross-sectional view of another comparative example of a multi-pole electrode. Compared to the example in Figure 3, this multi-pole electrode has an adhesive 9a as an adhesive material around each of the two hydrogel layers 4, and an adhesive 9b on top of an insulating film. The adhesives 9a and 9b may also be adhesive tapes. The adhesives 9a and 9b are known adhesives such as acrylic adhesives. In this example, because the adhesive 9b is present between the two hydrogel layers 4, lifting does not occur or is unlikely to occur when the subject wears the electrode. However, because the adhesives 9a and 9b are thin, pain may occur due to pressure on the skin by the connection terminals 3. Also, it is difficult to maintain adhesion when exposed to water for a long time. When using adhesives 9a and 9b, acrylic adhesives, which are common as adhesives, have strong adhesive strength, and unreacted components may remain, which may cause skin problems such as redness and itching. Also, because there is a height difference between the two hydrogel layers 4 and the adhesives 9a and 9b on both sides, sensing may still be somewhat unstable.

[0078] In the embodiment of the bioelectrode shown in Figure 6-8 below, the description of the same components that have the same reference numerals as the bioelectrode in the first embodiment shown in Figure 2 will be omitted. Figure 6 is a schematic cross-sectional view of a bioelectrode according to the second embodiment. In the first embodiment shown in Figure 2, a single insulating film 7 spans over two connection terminals 3, whereas in the second embodiment, an insulating film 7 is individually placed on each connection terminal 3 so as to cover the upper end surface of each connection terminal 3.

[0079] Figure 7 is a schematic cross-sectional view of a bioelectrode according to the third embodiment. In the first embodiment shown in Figure 2, a single insulating film 7 spans over the two connection terminals 3, whereas in the third embodiment, the insulating film 7 is omitted. The organogel layer 6 is in contact with the two connection terminals 3 at its upper end surface. Since the organogel 6 performs the insulating function even without the insulating film 7, it is advantageous in that the number of components and manufacturing processes of the bioelectrode can be reduced.

[0080] Figure 8 is a schematic cross-sectional view of the bioelectrode of the fourth embodiment. This embodiment is an offset type unipolar bioelectrode in which the bioelectrode has one connection terminal 3, the connection terminal 3 penetrates the surface substrate 1 and the conductive layer 2, and the hydrogel layer 4 contacts the conductive layer 2 at a position away from the connection terminal 3 and electrically connects with the connection terminal 3. Similar to the bioelectrodes of the first to third embodiments, an organogel layer 6 is arranged around the hydrogel layer 4 and above the conductive layer 2. Therefore, it can be attached even after prolonged exposure to water, causes less pain when the device is attached, and has sensing stability.

[0081] While specific embodiments of the present invention have been described so far, the present invention is not limited thereto, and various modifications are possible as follows. Figures 1, 6, and 7 illustrate biomedical electrodes with two electrode sections, but multi-electrode electrodes with three or more electrode sections may also be used.

[0082] The shape of the biomedical electrode is not limited to a long, rectangular shape; it may be any other shape, such as roughly rectangular or roughly circular in plan view.

[0083] The conductive layer 2 may be a single continuous wire and does not necessarily have a wire portion 2a and an end portion 2b with different shapes. Furthermore, the wire portion 2a may be curved or grid-like, or the end portion 2b may be approximately circular or rectangular, taking a shape different from the embodiment shown in Figure 1. In the first embodiment, as shown in Figure 2, the hydrogel layer 4 was larger than the end portion 2b, completely covering the end portion 2b and extending beyond it. However, as shown in the second and third embodiments in Figures 6 and 7, the hydrogel layer 4 may be approximately the same size as the end portion 2b. In the first embodiment, the release layer 8 is in contact with the hydrogel layer 4 and the organogel layer 6. However, as shown in the second embodiment in Figure 6, the height of part of the organogel layer 6 (part of the area around the hydrogel layer 4 in Figure 6) or all of it may be lower than that of the hydrogel layer 4. In other words, the organogel layer 6 does not have to be in direct contact with the release layer 8.

[0084] - Either or both of the insulating layer 5 and the insulating film 7 may be omitted. If the insulating layer 5 is omitted, the organogel layer 6 may be placed in contact with the conductive layer 2 so as to cover the linear wiring portion 2a of the conductive layer 2. If the insulating film 7 is in contact, the organogel layer 6 may be placed across the two connection terminals 3 and in contact with the two connection terminals 3.

[0085] All patent applications and disclosures cited herein are incorporated herein by reference in their entirety.

[0086] The following examples are for illustrative purposes only and are not intended to limit the technical scope of the present invention in any way. Unless otherwise specified, reagents are obtained or prepared from commercially available sources or according to methods commonly used in the art or procedures described in prior art. [Examples]

[0087] 1. Manufacturing of electrodes Preparation of monomer mixture solution (hydrogel) Using a stirring and mixing vessel, 20% by mass of acrylamide as a non-crosslinking monomer, 0.060% by mass of N,N'-methylenebisacrylamide as a crosslinking monomer, 18.5% by mass of deionized water, and 56% by mass of glycerin as a humectant were added and uniformly dispersed. Next, 2.5% by mass of sodium chloride as an electrolyte, and 2.94% by mass of other additives including sodium citrate, sodium benzoate, polyacrylic acid, and a photopolymerization initiator were added and stirred until completely dissolved to obtain a monomer mixture. The obtained monomer mixture was dropped onto a silicone-coated PET film. Another silicone-coated PET film was placed on top to evenly spread the liquid and fix it to a predetermined thickness. A metal halide lamp was then used to heat it at an energy rate of 3000 mJ / cm². 2 A sheet-like hydrogel was manufactured by irradiating it with ultraviolet light.

[0088] Preparation of monomer mixture solution (organogel) To 100 parts by mass of 4-t-butylcyclohexyl acrylate (trade name "TBCHA", manufactured by KJ Chemicals Co., Ltd.), 2.0 parts by mass of 2-hydroxy-2-methylpropiophenone (trade name "Omnirad 1173", manufactured by IGM Resins BV) was added as a polymerization initiator, stirred, and completely dissolved. To the resulting solution, 66.6 parts by mass of liquid paraffin (trade name "Liquid Paraffin No. 380-S", manufactured by Sanko Chemical Industry Co., Ltd.) was added as a plasticizer, stirred, and a colorless, transparent monomer mixture was obtained. The obtained monomer mixture was dropped onto a silicone-coated PET film. Another silicone-coated PET film was placed over it to evenly spread the liquid and fix it to a predetermined thickness. A metal halide lamp was then used to heat it at an energy rate of 3000 mJ / cm². 2 A sheet-like organogel was manufactured by irradiating it with ultraviolet light.

[0089] Creation of electrode surface substrate A 75μm thick PET film was screen printed and dried using silver ink (Fujikura Chemicals Co., Ltd., part number XA-3513) to create a predetermined electrode wiring pattern (in this case, a distance of 125mm between two electrodes, an electrode diameter of 10mm, and a wiring width of 2mm). Next, an insulating ink (insulating layer) was printed onto the electrode wiring (wiring width of 3mm (the electrode portion was not printed)) and dried. Then, ABS snaps coated with silver chloride and carbon were fitted or crimped onto the electrode wiring at a predetermined snap distance (in this case, a snap distance of 20mm or a single electrode), and an insulating film was applied to cover the snaps to form the electrode surface substrate.

[0090] Example 1 In addition to the electrode portion on the electrode surface substrate, a 0.5 mm thick organogel was bonded to it, and then a 0.5 mm thick hydrogel was bonded to the electrode portion to complete the electrode. The electrode configuration of Example 1 is the same as the electrode in Figure 7, except that the release layer 8 is absent.

[0091] Example 2 The electrode was completed in the same manner as in Example 1, except that the thickness of the hydrogel layer was changed to 1.0 mm.

[0092] Example 3 The electrode was completed in the same manner as in Example 1, except that the thickness of the organogel was changed to 0.2 mm.

[0093] Example 4 The electrode was completed in the same manner as in Example 1, except that the number of hooks that are mated or crimped onto the electrode wiring was changed to one (one electrode).

[0094] Comparative Example 1 A 0.5 mm thick hydrogel was bonded to the electrode portion, and insulating seals were applied to the hook and wiring portions to complete the electrode. The electrode configuration of Comparative Example 1 is the same as the electrode in Figure 3, except that the release layer 8 is absent.

[0095] Comparative Example 2 A 0.5 mm thick hydrogel was bonded to the electrode portion, insulating seals were applied to the hook and wiring portions, and a 0.5 mm thick hydrogel was applied on the hook and wiring portions so as not to come into contact with the gel on the electrode portion, thereby completing the electrode. The electrode configuration of Comparative Example 2 is the same as the electrode in Figure 4, except that there is no release layer 8.

[0096] Comparative Example 3 In the electrode surface substrate, an adhesive tape manufactured by Nichiban (product number 414125) was attached to the area other than the electrode portion, and then a 0.5 mm thick hydrogel was attached to the electrode portion to complete the electrode. The electrode configuration of Comparative Example 3 is the same as the electrode in Figure 5, except that the release layer 8 is absent.

[0097] 2. Electrode Evaluation Method Lifting during device attachment Fifteen trained panelists attached the prepared electrodes to their chests, and then attached a wearable heart rate sensor, "myBeat" (manufactured by Union Tool Co., Ltd.), via the electrodes to acquire biometric information. After that, they climbed a 20-step staircase once and once, and the degree of detachment directly below the sensor device was checked. A "○" indicated that there was no gap between the electrode and the skin interface, and a "×" indicated that there was a gap.

[0098] Pain during device attachment Fifteen trained panel members attached the created electrodes to their chests, and then attached a wearable heart rate sensor "myBeat" (manufactured by Union Tool Co., Ltd.) to acquire biometric information from above the electrodes. During attachment, a "○" was used if no pain was felt directly below the snap, and a "×" was used if pain was felt directly below the snap.

[0099] Long-term sticking property of electrode Fifteen trained panelists had electrodes attached to their chests and performed daily activities, including bathing and exercise, for five days. If 10 or more participants experienced electrode detachment from their skin during daily activities, the result was marked "×"; 3-9 participants were marked "△"; and 2 or fewer participants were marked "○".

[0100] Skin damage Fifteen trained panelists attached the prepared electrodes to their chests for 12 hours, and the condition of their skin was observed after removal. A rating of "×" was given if five or more people experienced redness, itching, etc., "△" if 2-4 people experienced redness or itching, and "○" if 1 or fewer people experienced redness or itching.

[0101] Sensing stability Fifteen trained panel members had electrodes attached to their chests, and then a wearable heart rate sensor, "myBeat" (manufactured by Union Tool Co., Ltd.), which can acquire biometric information, was attached via the electrodes. Heart rate was measured immediately after attachment, the sensor was removed, and the participants performed daily activities including bathing and exercise for five days, then the sensor was reattached and heart rate was measured again. A "○" was given if the heart rate waveform was measured without disturbance both immediately after attachment and after five days, and a "△" was given if the electrocardiogram waveform was disturbed at either the time immediately after attachment or after five days, resulting in unsuccessful measurement. A "×" was also given if the electrodes fell off the skin during the five days of daily activities.

[0102] The bioelectrodes in Examples 1-4 all received a "○" rating. In the bioelectrodes in Examples 2 and 3, the HG / OG thickness ratio exceeded 1.0, and the height of the organogel was lower than the height of the hydrogel. However, when the device was attached to the skin, the organogel on the outer periphery of the hydrogel also adhered closely to the skin, resulting in good stability in terms of device attachment, lifting, and sensing.

[0103] The initial adhesive strength, adhesive strength after immersion in water, and adhesive strength retention rate of the organogels used in the manufacture of biomedical electrodes in Examples 1-4 and Comparative Examples 1-3 were measured according to the measurement method described herein. The initial adhesive strength of the organogels was 18-22 N / 20mm, the adhesive strength after immersion in water was 17-20 N / 20mm, and the adhesive strength retention rate was 90.9-94.4%.

[0104] The bioelectrode in Comparative Example 1 experienced lifting due to the subject's movements, caused pain during device attachment, was difficult to wear for extended periods, and exhibited unstable sensing. The bioelectrode in Comparative Example 2 showed good performance in terms of lifting, but was difficult to wear for extended periods and exhibited unstable sensing. The bioelectrode in Comparative Example 3 caused pain, slight skin irritation due to the adhesive, and exhibited somewhat unstable sensing.

[0105] [Table 1] [Explanation of Symbols]

[0106] 1...Surface substrate, 2...Conductive layer, 3...Connecting terminal, 4...Hydrogel layer, 5...Insulating layer, 6...Organogel layer.

Claims

1. A bioelectrode comprising: a surface substrate; a conductive layer disposed on the surface substrate; a conductive connection terminal penetrating the surface substrate and the conductive layer; a hydrogel layer in contact with the conductive layer at a position away from the connection terminal and electrically connected to the connection terminal; and an organogel layer disposed around the hydrogel layer and above the conductive layer.

2. The biomedical electrode according to claim 1, wherein the organogel is an organogel comprising a polymer matrix, a plasticizer, and water, wherein the water content relative to the total amount of the organogel is less than 1.0% by mass, the polymer matrix comprises a polymerizable monomer having an alicyclic hydrocarbon in its structure (meth)acrylic acid ester, and the plasticizer is a liquid or paste-like plasticizer at 25°C comprising at least one selected from the group consisting of aliphatic hydrocarbons, fatty acid esters, and silicone oils, the initial adhesive strength of the organogel to a bakelite plate is 1.0 N / 20 mm or more, and the adhesive strength retention rate after immersion in water for 1 hour is 90% or more.

3. A biomedical electrode according to claim 1, further comprising an insulating layer on a conductive layer, wherein an organogel is disposed on the insulating layer.

4. The bioelectrode according to claim 1, wherein the organogel layer is in contact with the connection terminal.

5. The biomedical electrode according to claim 1, wherein the thickness of the organogel layer is 0.1 mm to 3 mm.

6. The bioelectrode according to any one of claims 1 to 5, wherein the hydrogel layer is a hydrogel comprising a polymer matrix, water, and a polyhydric alcohol, and the polymer matrix is ​​a copolymer of one or more monofunctional monomers selected from (meth)acrylamide monomers and (meth)acrylic acid esters and a crosslinkable monomer.

7. The biomedical electrode according to claim 1 or 5, wherein the thickness of the hydrogel layer is 0.1 mm to 3 mm.

8. The biomedical electrode according to any one of claims 1 to 5, wherein the ratio of the thickness of the hydrogel layer to the thickness of the organogel layer satisfies the relationship 1 ≤ A / B ≤ 2.5, where A (mm) is the thickness of the hydrogel layer and B (mm) is the thickness of the organogel layer.

9. The bioelectrode according to any one of claims 1 to 5, wherein the conductive connection terminals include a plurality of conductive connection terminals that are spaced apart from each other, the hydrogel layer includes a plurality of hydrogel layers that are electrically connected to each of the plurality of conductive connection terminals, and the organogel layer is disposed around each of the hydrogel layers and above the conductive layer.

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