Electrode pad

Abstract

An electrode pad (1) used by being attached to a living body is provided with a surface material (10), a conductive layer (20) laminated on the surface material (10), and a hydrogel layer (30) laminated on the conductive layer (20) so as to cover the conductive layer (20). The hydrogel layer (30) contains: a polymer matrix that is a polymer of a (meth) acrylic monomer; water; a wetting agent; and an organic acid and an organic acid salt. The organic acids and organic acid salts include at least one group of organic acids and organic acid salts selected from the group consisting of succinic acid and succinate salts, tartaric acid and tartrate salts, gluconic acid and gluconate salts, and lactic acid and lactate salts. The content of the organic acid and the organic acid salt is 0.50-10 mass% with respect to 100 mass% of the hydrogel.

Description

Technical Field

[0001] The present invention relates to electrode pads. Background Art

[0002] An electrode pad using a hydrogel sheet having both adhesiveness and conductivity is known.

[0003] Patent Document 1 discloses a patch comprising a support and an adhesive layer disposed on the support, wherein the adhesive layer contains varenicline or a pharmaceutically acceptable varenicline salt as a drug. The patch has high drug skin permeability and excellent formulation stability and formulation properties.

[0004] Patent document 2 discloses a conductive laminated hydrogel sheet having at least two hydrogel sheets, wherein a conductive hydrogel sheet containing a large amount of inorganic salt is arranged on the positive electrode side, and a conductive hydrogel sheet containing an inorganic salt less than the amount of the inorganic salt contained in the conductive hydrogel sheet and at least one acid is arranged on the negative electrode side. The hydrogel sheet can substantially suppress the increase in pH and / or the decrease in conductivity even when a direct current is applied for a constant time.

[0005] Patent document 3 discloses an electrode pad that can suppress heat generation when using high current, can suppress the occurrence of skin damage when peeling from the skin, and further, does not have the situation where chemical solutions or the like penetrate during use and the adhesion is weakened. In Patent document 3, when the electrode pad is peeled from the skin after use, there is a concern that skin damage may occur, especially for the elderly and infants, due to the strong adhesive force, but this problem is solved by setting the adhesive force and area ratio of the adhesive gel and surface material, etc., which are components of the electrode pad, to a specific range.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent No. 5485135

[0009] Patent Document 2: Japanese Patent No. 6535310

[0010] Patent Document 3: Japanese Patent No. 6757372 Summary of the invention

[0011] Problem that the invention aims to solve

[0012] In Patent Document 3, the adhesive force and area ratio of the adhesive gel and surface material, which are components of the electrode pad, are set within a specific range, thereby suppressing the occurrence of skin damage when peeling off the skin. In this way, it is required to suppress the occurrence of skin damage when peeling off the electrode pad from the skin and to improve the mildness of the adhesive force to the skin.

[0013] When the adhesive force of the hydrogel itself is reduced in order to suppress skin damage, the adhesive force with the conductive layer is reduced accordingly, and there is a possibility that the hydrogel will remain on the skin when the electrode pad is attached to the skin and then peeled off. On the other hand, when the adhesive force of the hydrogel itself is increased, the adhesive force with the conductive layer is increased, and the possibility of the hydrogel remaining on the skin can be suppressed. However, the adhesive force with the skin is also increased, so it is meaningless.

[0014] The problem to be solved by the present invention is to provide an electrode pad having excellent adhesion between a conductive layer and a hydrogel layer without increasing adhesion to the skin.

[0015] Solutions for solving problems

[0016] The present inventors have found that the above-mentioned problems can be solved by using specific organic acids and organic acid salts as pH adjusters and conductivity-imparting agents contained in hydrogels, and have completed the invention.

[0017] The present invention includes the embodiments described below.

[0018] Item 1. An electrode pad, which is attached to a living body for use, the electrode pad comprising:

[0019] Surface material,

[0020] A conductive layer laminated on the surface material, and

[0021] a hydrogel layer laminated on the conductive layer so as to cover the conductive layer,

[0022] The aforementioned hydrogel layer comprises:

[0023] Polymer matrix,

[0024] water,

[0025] Wetting agents, and

[0026] Organic acids and organic acid salts,

[0027] The polymer matrix is ​​a polymer of (meth)acrylic monomers,

[0028] The organic acid and the organic acid salt include at least one organic acid and organic acid salt selected from the group consisting of succinic acid and succinate, tartaric acid and tartrate, gluconic acid and gluconate, and lactic acid and lactate,

[0029] The total content of the organic acid and the organic acid salt is 0.50 to 10% by mass based on 100% by mass of the hydrogel.

[0030] Item 2. The electrode pad according to Item 1, wherein the pH of the hydrogel layer is 3.0 to 7.5.

[0031] Item 3. The electrode pad according to Item 2, wherein the conductive layer includes an electrode, and the electrode includes at least one selected from the group consisting of aluminum foil, tin foil, and stainless steel foil.

[0032] Item 4. The electrode pad according to Item 1, wherein the polymer matrix is ​​a copolymer of a (meth)acrylic monomer and a cross-linking monomer.

[0033] Item 5. The electrode pad according to Item 4, wherein the content of the polymer matrix is ​​10 to 40% by mass based on 100% by mass of the hydrogel.

[0034] Item 6. The electrode pad according to Item 4, wherein the (meth)acrylic monomer comprises at least one selected from the group consisting of (meth)acrylamide, (meth)acrylic acid, dimethyl(meth)acrylamide, diacetone(meth)acrylamide, tert-butylacrylamidesulfonic acid, and salts thereof.

[0035] Item 7. The electrode pad according to Item 1, wherein the wetting agent includes at least one selected from the group consisting of polyols, polyoxyalkylene alkyl ethers, and / or sugars.

[0036] Item 8. The electrode pad according to Item 7, wherein the wetting agent comprises a polyol.

[0037] The polyol includes at least one selected from the group consisting of ethylene glycol, triethylene glycol, propylene glycol, polypropylene glycol, polyethylene glycol, polyglycerol, and glycerol.

[0038] Item 9. The electrode pad according to Item 7, wherein the wetting agent comprises a polyoxyalkylene alkyl ether.

[0039] The polyoxyalkylene alkyl ether includes at least one selected from the group consisting of methyl glucoside polyoxyethylene ether and polyoxyethylene alkyl ether.

[0040] Item 10. The electrode pad according to Item 7, wherein the wetting agent contains sugar,

[0041] The aforementioned sugar includes at least one selected from the group consisting of monosaccharides, disaccharides and polysaccharides.

[0042] Item 11. The electrode pad according to any one of Items 1 to 10, which is used as a ground electrode for an electrosurgical instrument.

[0043] Item 12. A hydrogel comprising:

[0044] Polymer matrix,

[0045] water,

[0046] Wetting agents, and

[0047] Organic acids and organic acid salts,

[0048] The polymer matrix is ​​a polymer of (meth)acrylic monomers,

[0049] The organic acid and the organic acid salt include at least one organic acid and organic acid salt selected from the group consisting of succinic acid and succinate, tartaric acid and tartrate, gluconic acid and gluconate, and lactic acid and lactate,

[0050] The total content of the organic acid and the organic acid salt is 0.50 to 10% by mass based on 100% by mass of the hydrogel.

[0051] Item 13. A method for using a hydrogel for manufacturing an electrode pad for use attached to a biological body, the hydrogel comprising:

[0052] Polymer matrix,

[0053] water,

[0054] Wetting agents, and

[0055] Organic acids and organic acid salts,

[0056] The polymer matrix is ​​a polymer of (meth)acrylic monomers,

[0057] The organic acid and the organic acid salt include at least one organic acid and organic acid salt selected from the group consisting of succinic acid and succinate, tartaric acid and tartrate, gluconic acid and gluconate, and lactic acid and lactate,

[0058] The total content of the organic acid and the organic acid salt is 0.50 to 10% by mass based on 100% by mass of the hydrogel.

[0059] Effects of the Invention

[0060] According to the present invention, an electrode pad having excellent adhesion between a conductive layer and a hydrogel layer without increasing the adhesion of the electrode pad to the skin is provided, so that skin damage is suppressed when the electrode pad is peeled off from the skin. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 It is a top view of one embodiment of the electrode pad of the present invention.

[0062] Figure 2 To remove the hydrogel layer and the covering film Figure 1 Top view of the electrode pad.

[0063] Figure 3 for Figure 2 Section view on line AA. DETAILED DESCRIPTION

[0064] In this specification, unless otherwise explicitly stated in this specification or unless clearly contradicted by the context, the singular form (a, an, the) includes the singular and the plural.

[0065] In this specification, the term “comprise” is a concept including “consist essentially of” and “consist only of”.

[0066] In the numerical range of the staged recording in this specification, the upper limit or lower limit of the numerical range of a certain stage can be arbitrarily combined with the upper limit or lower limit of the numerical range of other stages. In addition, in the numerical range recorded in this specification, the upper limit or lower limit of the numerical range can also be replaced by the value shown in the embodiment or the value derived from the embodiment without doubt. Furthermore, in this specification, the numerical value connected with "~" refers to the numerical range including the numerical values ​​before and after "~" as the lower limit and the upper limit.

[0067] Hereinafter, embodiments of the present invention will be described in detail.

[0068] Electrode pads

[0069] Figure 1 It is a top view of one embodiment of the electrode pad of the present invention. Figure 2 To remove the hydrogel layer and the covering film Figure 1 Top view of the electrode pad. Figure 3 for Figure 2 Section view on line AA.

[0070] Figure 1 In the electrosurgical device (not shown), the electrode pad 1 is used as a counter electrode of a scalpel tip electrode as an electrosurgical instrument. That is, the electrode pad is a ground electrode that reduces the current density of the high-frequency current flowing from the device body through the scalpel tip electrode into the living body over a wide area and recovers it.

[0071] The electrosurgical device is composed of a device body having a high-frequency generating circuit, a scalpel tip electrode electrically connected to the device body through a lead wire, and an electrode pad 1 electrically connected to the device body through the same lead wire 2. When the electrosurgical device is used, the electrode pad 1 is attached to a living body such as a human patient, and a high-frequency current is applied from the device body to between the electrode pad 1 and the scalpel tip electrode, and the front end portion of the scalpel tip electrode performs incision and coagulation. The configuration of the scalpel tip electrode and the device body is the same as the existing configuration, so the description is omitted.

[0072] like Figures 1 to 3 As shown in FIG. 1 , the electrode pad 1 of the present embodiment comprises: a surface material 10; a conductive layer 20 laminated on the surface material 10 in the region other than the peripheral portion; and a hydrogel layer 30 laminated on the conductive layer 20. The surface material 10 has an adhesive layer 11 on the side to be attached to the living body, and has a tongue portion 12 that can be connected to the lead 2 at the center of one end of the main body portion having a substantially rectangular shape in a plan view. A transparent cover film 40 is releasably attached to the adhesive layer 11 and the hydrogel layer 30 exposed at the peripheral portion of the surface material 10, and by covering the hydrogel layer 30, the hydrogel layer 30 is protected and prevented from drying. Furthermore, in the present embodiment, a peeling convex piece 13 is provided at one corner of the surface material 10 as a continuous part of the surface material 10. The adhesive layer 11 is not present on the peeling convex piece 13, so that when the electrode pad 1 is used, the entire cover film 40 can be easily peeled off by removing the peeling convex piece 13. It should be noted that the electrode pad 1 is not limited to the shape shown in the figure, and may be substantially circular in plan view or substantially rectangular in plan view without the tongue portion 12 or the peeling protrusion 13 protruding from one end of the surface material 10 .

[0073] The surface material 10 can be a resin film with shape stability and flexibility. As the resin film, for example, non-conductive films such as polyethylene terephthalate film, polypropylene film, polyethylene film, etc. can be cited. Alternatively, the surface material 10 can also be paper, non-woven fabric, foam sheet or a composite sheet laminated with these and a resin film. In order to improve the appearance of the electrode pad 1, decorative printing can be applied to the surface material 10. From the perspective of operability, the thickness of the surface material 10 is preferably set to about 10μm to 200μm, but is not limited thereto.

[0074] The adhesive constituting the adhesive layer 11 can be applied as long as it has good skin adhesion and little skin irritation. Specifically, examples of adhesives include rubber-based adhesives, vinyl acetate-based adhesives, ethylene-vinyl acetate-based adhesives, polyvinyl alcohol-based adhesives, polyvinyl acetal-based adhesives, acrylic adhesives, polyamide-based adhesives, polyethylene-based adhesives, cellulose-based adhesives, etc. In addition, by utilizing the adhesive force of the adhesive layer 11, sufficient adhesion to the organism can be exerted, and the situation that chemical solutions, etc. of the electrode pad 1 penetrate into the inside of the electrode pad 1 from the outer edge of the electrode pad 1 in use can be prevented, and the reduction of the adhesive force of the electrode pad 1 can be prevented, and the occurrence of skin damage when the electrode pad 1 is peeled off from the skin can be suppressed.

[0075] The conductive layer 20 is laminated and integrated with the surface material 10 in the area other than the peripheral portion of the surface material 10. The lead 2 is connected to and extends from the surface of the surface material 10 opposite to the surface on which the conductive layer 20 is provided. The lead 2 can be connected to the surface material 10 in the connection portion 22 formed on the tongue portion 12 of the surface material 10. The conductive layer 20 extends on the tongue portion 12 of the surface material 10 and surrounds the connection portion 22. The connection member 22 is formed of a conductive material, is connected to the lead 2 and the conductive layer 20, and functions to electrically connect the lead 2 to the conductive layer 20. One or more connection portions 22 may be provided for each lead, or one connection portion 22 may be provided for a plurality of leads. In the present embodiment, two connection portions 22 are provided for each lead along the length direction of each lead. The connection method of the lead 2 and the conductive layer 20 is not particularly limited. For example, the following methods can be suitably adopted: a method of riveting one end of the lead 2 to the conductive layer 20 using a connection portion 22 that extends through the surface material 10 and extends along the circumferential direction of one end of the lead 2 and is crimped to one end of the lead 2; a method disclosed in Japanese Patent Application Laid-Open No. 2007-175159, in which a connection tool for connecting in a state where the conductive layer 20 and the lead 2 are overlapped is used separately to hold the conductive layer 20 and the lead 2 in a state of sandwiching; etc. In addition, as required, the connection portion between the lead 2 and the conductive layer 20 can be insulated by winding an insulating tape or the like in a manner so that the one end of the lead 2 and the conductive layer 20 do not contact the biological body and cause electric shock.

[0076] The conductive layer 20 comprises a laminate of a resin film 20a such as a polyethylene terephthalate film and an electrode 20b. The resin film 20a is used as a reinforcing material for the electrode 20b, and the function of the electrode 20b can be maintained even if the conductive layer 20 is deformed along the surface of the organism. The electrode 20b is not particularly limited as long as the resistance is small. For example, the electrode 20b can be a metal foil such as aluminum foil, tin foil, stainless steel foil, copper foil, nickel foil, etc., or a conductive material such as carbon, silver, silver chloride can be formed by coating the resin film 20a in a layered manner together with a binder such as a synthetic resin. From the viewpoint of conductivity, the electrode 20b is preferably a metal foil, preferably at least one selected from the group consisting of aluminum foil, tin foil and stainless steel foil, and is more preferably an aluminum foil from the viewpoints of light weight, cost, safety, processability, etc.

[0077] In this embodiment, the thickness of the conductive layer 20 refers to the thickness of the electrode 20b when the conductive layer 20 is a laminate of the resin film 20a and the electrode 20b, and refers to the thickness of the electrode 20b when the conductive layer 20 is composed of only the electrode 20b. If the thickness of the conductive layer 20 is too thick, the flexibility is reduced, and the electrode pad 1 cannot be deformed along the biological body, and the adhesion of the electrode pad 1 to the biological body is sometimes reduced. If it is too thin, the mechanical strength is sometimes reduced, so it is appropriately set in consideration of the balance between them. The thickness of the conductive layer 20 is preferably 3.0 μm or more and 25 μm or less, and particularly preferably 9.0 μm or more and 15 μm or less.

[0078] In this embodiment, if Figure 2 and Figure 3 As shown, the conductive layer 20 (and the hydrogel layer 30 thereon) is divided into two predetermined areas in an insulated state, and a lead 2 is connected to each conductive layer 20 on the tongue portion 12. The conductive layer 20 is divided into two parts in an insulated state, and the lead 2 is connected to each conductive layer 20. Therefore, during the use of the electrode pad 1, even if one lead 2 is separated from the conductive layer 20, the other lead 2 can maintain electrical connection with the conductive layer 20.

[0079] Although not shown in the figure, the resin film 20a between the surface material 10 and the electrode 20b can be closely attached by means of an adhesive layer disposed between the surface material 10 and the resin film 20a. As the adhesive constituting the adhesive layer, various adhesives known in the past can be applied, specifically, for example, rubber adhesives, vinyl acetate adhesives, ethylene-vinyl acetate adhesives, polyvinyl alcohol adhesives, polyvinyl acetal adhesives, acrylic adhesives, polyamide adhesives, polyethylene adhesives, cellulose adhesives, etc. can be cited.

[0080] like Figure 3As shown, a hydrogel layer 30 having a planar shape that matches the planar shape of the conductive layer 20 is provided on the conductive layer 20. The hydrogel layer 30 is a hydrogel having an adhesive force to a living body.

[0081] The thickness of the hydrogel layer 30 is not particularly limited, but is preferably 0.30 mm to 2.0 mm. In terms of adhesive strength, the hydrogel layer 30 is preferably 0.30 mm or more, and in terms of the effect of the electrode pad 1, the hydrogel layer 30 is sufficient when it is 2.0 mm or less. The details of the hydrogel constituting the hydrogel layer 30 are described below.

[0082] Hydrogel

[0083] The hydrogel constituting the hydrogel layer 30 comprises: a polymer matrix which is a polymer of a (meth)acrylic monomer, water, a wetting agent, and an organic acid and an organic acid salt, wherein the organic acid and the organic acid salt comprise at least one group of organic acids and organic acid salts selected from the group consisting of succinic acid and succinate, tartaric acid and tartrate, gluconic acid and gluconate, and lactic acid and lactate, and the total content of the organic acids and organic acid salts is 0.50 to 10% by mass relative to 100% by mass of the aforementioned hydrogel.

[0084] The polymer matrix preferably contains 10 to 40% by mass in 100% by mass of the hydrogel, and more preferably contains 13 to 35% by mass. If the content is 10% by mass or more, the hydrogel has sufficient shape retention and is not prone to worry about becoming too soft or easily broken. In addition, if the content is 40% by mass or less, it is not easy to worry about the softness of the hydrogel being impaired.

[0085] The polymer matrix can be formed of a copolymer of a (meth)acrylic monomer and a crosslinking monomer.

[0086] (Meth)acrylic monomers are a general term for monomers that have an acryloyl group (H2C=CH-C(=O)-) or a methacryloyl group (H2C=C(CH3)-C(=O)-) and can form a polymer by polymerization. (Meth)acrylic monomers are monofunctional monomers that have one polymerizable carbon-carbon double bond in the molecule and are non-crosslinking monomers. (Meth)acrylic monomers can also refer to monofunctional monomers that have one ethylenically unsaturated group.

[0087] The (meth)acrylic monomer may also be referred to as a (meth)acrylic monofunctional monomer.

[0088] As the (meth)acrylic monomer, preferably used is a (meth)acrylamide monomer, a (meth)acrylate monomer, (meth)acrylic acid or a salt thereof, etc. These compounds may be used alone or in combination of two or more.

[0089] More specifically, the polymer matrix is ​​formed of a copolymer of a (meth)acrylic monomer and a crosslinking monomer.

[0090] Specific examples of the (meth)acrylamide monomers include: (meth)acrylamide; N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide and other N,N-dialkyl (meth)acrylamide; N-isopropyl (meth)acrylamide, N-methyl (meth)acrylamide, N-ethyl (meth)acrylamide, N-propyl (meth)acrylamide and other N-alkyl (meth)acrylamide; N-hydroxyethyl (meth)acrylamide, N-hydroxymethyl (meth)acrylamide and other N-hydroxyalkyl (meth)acrylamide; N-ethoxymethyl (meth)acrylamide, N-propoxymethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide and other N-alkoxyalkyl(meth)acrylamide, N-isobutoxymethyl(meth)acrylamide, N-pentyloxymethyl(meth)acrylamide, N-hexyloxymethyl(meth)acrylamide, N-heptyloxymethyl(meth)acrylamide, N-octyloxymethyl(meth)acrylamide, N-ethoxyethyl(meth)acrylamide, N-propoxyethyl(meth)acrylamide, N-butoxyethyl(meth)acrylamide, etc.; cationic acrylamide compounds containing an amino group such as dimethylaminopropyl(meth)acrylamide; anionic acrylic monomers or salts thereof containing a sulfonic acid group such as 4-acryloylmorpholine and tert-butylacrylamidesulfonic acid; and derivatives thereof. Among them, 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 salts thereof are preferred, but the present invention is not limited thereto.

[0091] Specific examples of (meth)acrylates include one or more selected from the group consisting of alkyl (meth)acrylates having an alkyl group with 1 to 18 carbon atoms, 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, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-pentyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, n-lauryl (meth)acrylate, tridecyl (meth)acrylate, and n-stearyl (meth)acrylate; and cyclohexyl (meth)acrylate, isoborneol (meth)acrylate, and the like. alicyclic (meth)acrylates such as (meth)acrylate, 1-adamantyl (meth)acrylate, etc.; (meth)acrylates containing an alkoxy group such as (meth)acrylate 2-methoxyethyl (meth)acrylate, ethoxyethoxyethyl (meth)acrylate, methoxytriethylene glycol (meth)acrylate, etc.; (meth)acrylates containing hydroxyalkyl (meth)acrylates such as (meth)acrylate 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, etc. (the aromatic group is optionally bonded to the hydroxyalkyl group via an ether bond); glycerol mono(meth)acrylate; polyalkylene glycol mono(meth)acrylates such as polyethylene glycol mono(meth)acrylate and polyethylene glycol-polypropylene glycol copolymer; (meth)acrylates having an aromatic ring such as benzyl (meth)acrylate; and (meth)acrylates having a heterocyclic ring such as tetrahydrofurfuryl (meth)acrylate, but are not limited thereto.

[0092] The hydrogel may contain acrylic acid or its salt as a (meth) acrylic acid monomer, or may not contain acrylic acid or its salt. By allowing an appropriate amount of acrylic acid to remain in the hydrogel, the existing adhesive force of the hydrogel can be maintained and the hardness can be increased. Specific examples of (meth) acrylic acid or its salt include acrylic acid, methacrylic acid, sodium acrylate, potassium acrylate, potassium methacrylate, etc. These monomers can be used alone or in combination of two or more monomers.

[0093] In order to obtain a hydrogel having excellent adhesion to the conductive layer without increasing adhesion to the skin, the (meth)acrylic monomer is preferably at least one selected from the group consisting of (meth)acrylamide, (meth)acrylic acid, dimethyl (meth)acrylamide, diacetone (meth)acrylamide, tert-butyl acrylamide sulfonic acid and salts thereof.

[0094] The amount of (meth) acrylic monomer added to the hydrogel is preferably in the range of 10% to 40% by mass, and more preferably 15% to 35% by mass, relative to 100% by mass of the hydrogel. If the amount of (meth) acrylic monomer added is within the above range, it is preferred from the viewpoint of the shape, adhesion, operability and flexibility of the hydrogel. If the content of (meth) acrylic monomer is 10% by mass or more, the shape stability can be maintained, the aggregation and retention of the hydrogel itself can be maintained, and a hydrogel with moderate adhesion can be obtained. In addition, if the content is 40% by mass or less, a hydrogel with moderate adhesion and flexibility is obtained.

[0095] As a crosslinking monomer, it is preferred to use a monomer having two or more polymerizable carbon-carbon double bonds in the molecule. Specifically, it can be cited: N, N'-methylenebis (meth) acrylamide, N, N'-ethylenebis (meth) acrylamide, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, glycerol di (meth) acrylate, glycerol tri (meth) acrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate and other multifunctional (meth) acrylamide or multifunctional (meth) acrylate, tetraallyloxyethane, diallyl ammonium chloride, etc., which can be used alone or in combination of two or more. It should be noted that as the above-mentioned crosslinking monomer having two or more polymerizable double bonds in the molecule, a polyglycerol derivative described in Japanese Patent No. 2803886, which is a multifunctional compound having two or more (meth) acryloyl groups or vinyl groups and a molecular weight of 400 or more, can also be used. The polyfunctional (meth)acrylamide, the polyfunctional (meth)acrylate, and the polyglycerol derivative are included in the acrylic monomers.

[0096] The amount of cross-linking monomer added to the hydrogel is preferably in the range of 0.010% to 0.50% by mass, and more preferably in the range of 0.010% to 0.10% by mass, relative to 100% by mass of the hydrogel. If the amount of cross-linking monomer added is within the above range, it is preferred from the viewpoint of the shape, adhesion, operability and flexibility of the hydrogel. If the amount added is 0.010% by mass or more, it is not easy to worry about the reduced shape stability caused by the low cross-linking density, and a hydrogel with moderate adhesion without reducing the cohesive force and the holding power of the hydrogel itself is obtained. In addition, it is not easy to worry about the deterioration of the operability of the gel sheet such as a part of the gel material remaining on the adherend when peeling. When the content is less than 0.50% by mass, a hydrogel with moderate adhesion is obtained, and it is not easy to worry about the softness of the hydrogel being impaired.

[0097] The copolymer of a (meth)acrylic acid monofunctional monomer and a crosslinking monomer preferably does not contain additional monomers constituting the copolymer other than the (meth)acrylic acid monofunctional monomer and the crosslinking monomer, but may contain the additional monomers. As the additional monomers, vinylamide monofunctional monomers such as N-vinylpyrrolidone, N-vinylacetamide, and N-vinylformamide; nonionic monofunctional monomers such as allyl alcohol, styrene monomers, etc. can be used. These monofunctional monomers can be used alone or in combination of two or more.

[0098] The water content in the hydrogel is not particularly limited, but is preferably 10 to 60% by mass, more preferably 10 to 40% by mass, relative to the hydrogel. If the water content is 10% by mass or more, the water content of the hydrogel relative to the equilibrium water content will not be excessively reduced, and it is not easy to worry about deterioration (such as swelling, etc.) due to the hygroscopicity of the hydrogel. In addition, if the water content is 60% by mass or less, the water content of the hydrogel relative to the equilibrium water content will not be excessively increased, and it is not easy to worry about deterioration (such as shrinkage, etc.) due to drying of the hydrogel.

[0099] There are no particular limitations on the wetting agent, and examples thereof include: glycols such as ethylene glycol, triethylene glycol, 1,6-hexanediol, 1,9-nonanediol, propylene glycol, and butylene glycol; trivalent or higher polyols such as glycerol, pentaerythritol, and sorbitol; polyol condensates such as polyethylene glycol, polypropylene glycol, and polyglycerol; polyol modified bodies such as polyoxyethylene glycerol; polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene isostearyl ether, and methyl glucoside polyoxyethylene ether; polyoxypropylene alkyl ethers such as methyl glucoside polyoxypropylene ether; polyoxypropylene lauryl ether, polyoxypropylene stearyl ether, and polyoxypropylene isostearyl ether; monosaccharides such as xylose, arabinose, glucose, galactose, and mannose; disaccharides such as sucrose, maltose, cellobiose, and lactose; oligosaccharides such as maltotriose; polysaccharides such as xylan, starch, cellulose, chitin, and chitosan; and the like. Amino sugars of these sugars and N-acetylated products thereof can also be used. The sugars may be in the D form or the L form. These wetting agents may be used alone or in combination of two or more.

[0100] The wetting agent preferably contains at least one selected from the group consisting of polyols, polyoxyalkylene alkyl ethers and / or sugars.

[0101] The content of the wetting agent in the hydrogel is not particularly limited, but is preferably in the range of 20 to 70% by mass, more preferably in the range of 25 to 65% by mass, relative to the hydrogel. The content of the wetting agent is preferably greater than the content of water, but may be less than the content of water. In terms of the moisture retention and plasticity of the hydrogel, the content of the wetting agent is preferably 20% by mass or more, and in terms of the amount of the wetting agent that can be retained by the polymer matrix and the adhesiveness of the hydrogel, it is preferably 70% by mass or less.

[0102] The organic acid and the organic acid salt function as electrolytes added to improve the conductivity of the hydrogel. The organic acid and the organic acid salt include at least one selected from the group consisting of succinic acid and succinate, tartaric acid and tartrate, gluconic acid and gluconate, and lactic acid and lactate.

[0103] By using the combination of the above four organic acids and salts thereof, an electrode pad and / or hydrogel having excellent adhesion to the conductive layer without increasing the adhesive force to the skin can be obtained.

[0104] The organic acid and the organic acid salt may be any one of succinic acid and succinate, tartaric acid and tartrate, gluconic acid and gluconate, or lactic acid and lactate, or may be two or more of the above.

[0105] The organic acid salt may be an alkali metal salt of an organic acid (eg, sodium salt, potassium salt, etc.), an alkaline earth metal salt of an organic acid (eg, magnesium salt, calcium salt, etc.), or an ammonium salt, and is preferably an alkali metal salt of an organic acid.

[0106] If the total content of the organic acid and the organic acid salt is less than 0.50 mass %, the adhesion between the hydrogel and the conductive layer may not be sufficiently improved.

[0107] If the content of the organic acid and the organic acid salt exceeds 10% by mass, these substances become difficult to dissolve in the hydrogel, and there is a possibility that crystals will precipitate inside the hydrogel or the dissolution of other components will be hindered.

[0108] The mixing ratio of the organic acid (the total in the case of multiple types) and the organic acid salt (the total in the case of multiple types) in the hydrogel is not particularly limited. In terms of the relaxation of the adhesion of the electrode pad and / or the hydrogel to the skin and the excellent adhesion between the electrode pad and / or the hydrogel and the conductive layer, the mass ratio is preferably 1:20 to 20:1.

[0109] The hydrogel may optionally contain an electrolyte other than the above-mentioned organic acid and organic acid salt. The electrolyte supplements the conductivity of the hydrogel.

[0110] The electrolyte is not particularly limited, and for example, sulfates, carbonates, nitrates, and the like of various metals are preferably used.

[0111] The hydrogel preferably does not contain a halogenated metal salt, but may optionally contain a small amount of a halogenated metal salt. The content of the halogenated metal salt in the hydrogel is, for example, 1.0% by mass or less.

[0112] The hydrogel may contain other additives as required, such as bactericides, rust inhibitors, mildew inhibitors, antioxidants, dispersants, defoamers, stabilizers, fragrances, surfactants, colorants, etc.

[0113] The pH of the hydrogel and the hydrogel layer composed of the hydrogel is preferably 3.0 to 7.5. In order to prevent the dissolution of the conductive layer caused by the acid in the hydrogel layer, a pH of 3.0 or more is preferred. In order to prevent chemical burns to the skin, a pH of 3.0 or more is also preferred. In order to prevent the dissolution of the conductive layer caused by the alkali in the hydrogel layer, a pH of 7.5 or less is preferred. In order to prevent chemical burns to the skin, a pH of 7.5 or less is also preferred.

[0114] The adhesive force between the hydrogel layer and the conductive layer of the hydrogel of the present embodiment measured with reference to JIS-Z0237:2009 is preferably 1.0 N / mm or more, more preferably 1.5 N / mm or more. The upper limit of the adhesive force is not particularly limited, and is, for example, 10 N / mm or less. In this range, the adhesive force between the hydrogel layer and the conductive layer is excellent. The following describes a method for measuring the adhesive force between the hydrogel layer and the conductive layer measured with reference to JIS-Z0237:2009.

[0115] <Measurement of the adhesive strength between the hydrogel layer and the conductive layer of the electrode pad>

[0116] The electrode pad is cut into 20 mm × 120 mm, and a synthetic paper with a thickness of 80 μm (e.g., "Peach coat paper SE80" manufactured by NISSHINBOPAPER PRODUCTS INC. or "FGS80" manufactured by YUPO CORPORATION) is lined on the hydrogel surface to form a test piece. Afterwards, a double-sided tape (NW-20 manufactured by NICHIBAN Co., Ltd.) is pasted on the surface material side of the electrode pad so that one side of the double-sided tape is adhered to the bakelite board. Afterwards, the hydrogel layer and the conductive layer are peeled off by 10 mm. Afterwards, the peach coat paper is clamped in the gripper of a rheometer (CR-500DX manufactured by Sun Scientific Co., Ltd.) serving as a measuring device, and peeled off at an angle of 90 degrees and a speed of 300 mm / min with reference to JIS-Z0237:2009 under the measuring conditions. The stress value (N / 20 mm) at the specified peeling time (30, 40, 50, 60, 70 mm) from the measurement start point was measured, and the average value was calculated from the values ​​of N=3 (a total of 15 points), and this value was used as the adhesion of the hydrogel to the conductive layer. The measurement environment was a temperature of 23°C and a humidity of 55%.

[0117] The adhesive force between the hydrogel layer and the skin of the hydrogel of the present embodiment measured with reference to JIS-Z0237:2009 is preferably 0.20 N / 20 mm or more and 2.0 N / 20 mm or less, and more preferably 0.30 N / 20 mm or more and 2.0 N / 20 mm or less. Within this range, the adhesive force between the hydrogel layer and the skin is good, and the hydrogel layer can be easily peeled off from the skin. The following describes a method for measuring the adhesive force between the hydrogel layer and the skin measured with reference to JIS-Z0237:2009.

[0118] <Measurement of adhesion between the hydrogel layer of the electrode pad and the skin>

[0119] The electrode pad is cut into 20 mm × 120 mm, and a double-sided tape (NW-20 manufactured by NICHIBAN Co., Ltd.) is pasted on the surface material, and a synthetic paper with a thickness of 80 μm (for example, "Peach coat paper SE80" manufactured by NISSHINBO PAPER PRODUCTS INC. or "FGS80" manufactured by YUPO CORPORATION) is further lined thereon to prepare a test piece. The surface of the test piece from which the PET film (base film) has been peeled off is adhered to the inner side of the forearm of a human body. The end of the test piece is clamped in a rheometer (CR-500DX manufactured by Sun Scientific Co., Ltd.) as a measuring device, and the peeling is performed under the measuring conditions of an angle of 180 degrees and a speed of 300 mm / min with reference to JIS-Z0237:2009. The stress value (N / 20 mm) at the specified peeling time (50, 60, 70, 80, 90 mm) from the measurement start point was measured, and the average value was calculated from the values ​​of 3 people (a total of 15 points), and this value was used as the adhesive force of the hydrogel to the skin. The measurement environment was implemented at a temperature of 23°C and a humidity of 55%.

[0120] In terms of the mildness of the adhesion of the hydrogel to the skin and the difficulty in causing peeling between the hydrogel layer and the conductive layer, the adhesion obtained in the <Measurement of adhesion between the hydrogel layer and the conductive layer of the electrode pad> measured with reference to JIS-Z0237:2009 is preferably 1.0 N / 20 mm or more, and the ratio to the adhesion obtained in the <Measurement of adhesion between the hydrogel layer and the skin of the electrode pad> measured with reference to JIS-Z0237:2009 is 2.0 or more.

[0121] Method for producing hydrogel

[0122] The various materials of the hydrogel are mixed with a polymerization initiator and stirred, and the obtained mixed solution is subjected to heat or ultraviolet irradiation, etc., to polymerize and crosslink, thereby obtaining a hydrogel. It should be noted that the mixing includes not only a state where the solute is not mixed with water but is dispersed in water, but also a state where the solute is mixed with water to form a uniform phase of the mixture dissolved.

[0123] The polymerization initiator may be a thermal polymerization initiator or a photopolymerization initiator, and a known thermal polymerization initiator or photopolymerization initiator for polymerizing a (meth)acrylic monomer may be used. Alternatively, polymerization / crosslinking may be performed by irradiation with radiation such as electron beams or gamma rays.

[0124] As a thermal polymerization initiator, there is no particular limitation as long as free radicals are generated by thermal cleavage, for example, organic peroxides such as benzoyl peroxide; azobiscyanovaleric acid, azobisisobutyronitrile, azobisamidinopropane dihydrochloride and other azo-based polymerization initiators; persulfates such as potassium persulfate and ammonium persulfate, etc. These thermal polymerization initiators can be used alone or in combination of two or more. In addition, as needed, a redox initiator composed of a reducing agent such as ferrous sulfate and pyrosulfite and a peroxide such as hydrogen peroxide, sodium thiosulfate, and peroxodisulfate can also be used in combination with a thermal polymerization initiator.

[0125] The photopolymerization initiator is not particularly limited as long as it is cleaved by ultraviolet light or visible light to generate radicals, and examples thereof include α-hydroxyketone, α-aminoketone, benzyl dimethyl ketal, bisacylphosphine oxide, and metallocene. More specifically, 2-hydroxy-2-methyl-1-phenyl-1-propanone (product name: DAROCUR 1173, manufactured by Ciba Specialty Chemicals Inc.), 1-hydroxy-cyclohexyl-phenyl-ketone (product name: Irgacure 184, manufactured by Ciba Specialty Chemicals Inc.), 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propanone (product name: Irgacure 2959, manufactured by Ciba Specialty Chemicals Inc.), 2-methyl-1-[(methylthio)phenyl]-2-morpholino-1-propanone (product name: Irgacure 907, manufactured by Ciba Specialty Chemicals Inc.), 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone (product name: Irgacure 369, manufactured by Ciba Specialty Chemicals Inc.), and 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propanone (product name: Irgacure 2959, manufactured by Ciba Specialty Chemicals Inc.) are mentioned. Chemicals Inc., manufactured), 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-1-propanone (product name: Irgacure 127, manufactured by Ciba Specialty Chemicals Inc.), etc. These can be used alone or in combination of two or more.

[0126] The content of the polymerization initiator is not particularly limited, but is preferably 0.010% by mass or more, and preferably 1.0% by mass or less, relative to the amount of the polymerization initiator removed from the compounding liquid (also referred to as the monomer compounding liquid) of the composition before polymerization. Furthermore, when polymerization and crosslinking are performed by ultraviolet irradiation, the cumulative irradiation amount of ultraviolet rays varies depending on the content of the polymerization initiator, and is preferably 800 mJ / cm 2 ~10000mJ / cm2 The range is preferably 2000 mJ / cm 2 ~10000mJ / cm 2 If the cumulative irradiation is set to 2000mJ / cm 2 The above is more preferable because the amount of residual monomers in the hydrogel can be reduced to a safe range that does not cause skin irritation.

[0127] After the prepared mixed liquid is injected into the template or container, the non-crosslinking monomer and the crosslinking monomer are polymerized and crosslinked to form a polymer matrix composed of a copolymer of the non-crosslinking monomer and the crosslinking monomer, thereby forming a hydrogel layer 30 of a desired shape. By injecting the mixed liquid into a container of a desired shape, the hydrogel layer 30 can be made into a sheet of any desired shape, such as a roughly rectangular shape in top view or a roughly circular shape in top view.

[0128] Alternatively, the compounding liquid may be injected between the laminate of the surface material 10 having the adhesive layer 11 and the conductive layer 20 and the cover film 40, and a polymerization cross-linking reaction may be performed while maintaining a constant thickness to form a sheet-like hydrogel layer 30. Alternatively, the compounding liquid may be applied as a thin layer on the conductive layer 20 and the cover film 40, and a polymerization cross-linking reaction may be performed to form a film-like hydrogel layer 30.

[0129] When ultraviolet rays are irradiated to polymerize and crosslink, the cumulative irradiation dose to the mixed solution varies depending on the composition of the mixed solution and is not particularly limited. Generally, in order to fully promote the polymerization reaction, the cumulative irradiation dose is only 1000 mJ / cm 2 The above is preferred. If the cumulative irradiation dose is set to 1000 mJ / cm 2 In addition, although there is no upper limit on the cumulative irradiation amount, there may be problems such as excessive irradiation leading to large-scale equipment, unnecessary energy usage, or the need to remove the generated heat, so it is desirable to set the irradiation amount to the minimum required.

[0130] The disclosures of all patent applications and documents cited in this specification are incorporated herein by reference in their entirety.

[0131] The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these.

[0132] Example

[0133] 1. Fabrication of Electrode Pads

[0134] Example 1

[0135] (1) Method for preparing hydrogel layer

[0136] Using a stirring / mixing container, first, 10% by mass of acrylamide as a non-crosslinking monomer, 10% by mass of diacetone acrylamide, 0.10% by mass of N,N'-methylenebisacrylamide as a crosslinking monomer, 30% by mass of ion-exchanged water, 45% by mass of methyl glucoside polyoxyethylene ether (METHYL GLUCETH-10) as a wetting agent, 2.0% by mass of succinic acid as an organic acid, 1.4% by mass of disodium succinate as an organic acid salt, and 1.5% by mass in total of other additives including a preservative, an initiator, a binder, and a chelating agent were added, and stirred until completely dissolved to obtain a mixed liquid.

[0137] Next, the obtained mixed solution was dripped onto a 100 μm thick PET film (base film) coated with silicone, and a 40 μm thick PET film (top film) coated with silicone was covered on the dripped mixed solution to form a predetermined thickness, and irradiated with an energy of 3000 mJ / cm using a metal halide lamp. 2 The mixed liquid was polymerized by ultraviolet rays to form a sheet-like hydrogel layer with a thickness of 0.50 mm.

[0138] (2) Method for making electrode pad

[0139] The hydrogel layer obtained in 1. is set to have an area S1 = 100 cm 2 The hydrogel layer was cut out in a manner such that a conductive layer of the same size and shape (laminated aluminum foil 9.0 μm and PET film 50 μm as a reinforcing material made by UACJ Co., Ltd.) was attached to the cut hydrogel layer. Further, a surface material area S2 = 118 cm 2 The surface material with adhesive layer (a PE film is laminated on a polypropylene nonwoven fabric, and the adhesive is set to an acrylic adhesive and the adhesive coating amount is set to 50 g / m 2 , Width b of the peripheral part (refer to Figure 2 ) is set to 9.0 mm), and is punched into a specified shape to obtain the electrode pad of Example 1 with a specified size and shape.

[0140] Embodiments 2 to 11

[0141] Each electrode pad of Examples 2 to 11 was produced under the same conditions as in Example 1, except that the mass % of each component was changed as shown in Table 1.

[0142] Comparative Examples 1 to 6

[0143] Each electrode pad of Comparative Examples 1 to 6 was produced under the same conditions as in Example 1, except that the mass % of each component was changed as shown in Table 1.

[0144] 2. Evaluation of Hydrogel and Electrode Pads

[0145] (1) Adhesion between the hydrogel layer and the conductive layer of the electrode pad

[0146] Each electrode pad of Examples 1 to 11 and Comparative Examples 1 to 6 prepared in "1. Production of Electrode Pads" was cut into pieces of 20 mm × 120 mm, and a synthetic paper ("Peachcoat paper SE80" manufactured by NISSHINBO PAPER PRODUCTS INC.) with a thickness of 80 μm was lined on the hydrogel surface to form a test piece. Thereafter, a double-sided tape (NW-20 manufactured by NICHIBAN Co., Ltd.) was affixed to the surface material side of the electrode pad, and one side of the double-sided tape was adhered to the bakelite board. Thereafter, the hydrogel layer and the conductive layer were peeled off by 10 mm. Thereafter, the peach coat paper was clamped in a rheometer (CR-500DX manufactured by Sun Scientific Co., Ltd.) as a measuring device, and the measurement was carried out under the conditions of an angle of 90 degrees and a speed of 300 mm / min with reference to JIS-Z0237:2009. The stress value (N / 20 mm) at the specified peeling time (30, 40, 50, 60, 70 mm) from the measurement start point was measured, and the average value was calculated from the values ​​of N=3 (a total of 15 points), and this value was used as the adhesion of the hydrogel to the conductive layer. The measurement environment was a temperature of 23°C and a humidity of 55%.

[0147] 2. Adhesion of the hydrogel layer of the electrode pad to the skin

[0148] Each electrode pad of Examples 1 to 11 and Comparative Examples 1 to 6 prepared in "1. Production of Electrode Pads" was cut into 20 mm × 120 mm, and a double-sided tape (NW-20 manufactured by NICHIBAN Co., Ltd.) was pasted on the surface material, and a synthetic paper with a thickness of 80 μm ("Peach coat paper SE80" manufactured by NISSHINBO PAPER PRODUCTS INC.) was further lined thereon to prepare a test piece. The surface of the test piece from which the PET film (base film) was peeled off was adhered to the inner side of the forearm of a human body. The end of the test piece was clamped in a rheometer (CR-500DX manufactured by Sun Scientific Co., Ltd.) as a measuring device, and the measurement was carried out under the conditions of an angle of 180 degrees and a speed of 300 mm / min with reference to JIS-Z0237:2009. The stress value (N / 20 mm) at the specified peeling time (30, 40, 50, 60, 70 mm) from the measurement start point was measured, and the average value was calculated from the values ​​of 3 people (a total of 15 points), and this value was used as the adhesive force of the hydrogel to the skin. The measurement environment was a temperature of 23°C and a humidity of 55%.

[0149] 3. Stability of the conductive layer

[0150] The electrode pad prepared in (2) of "1. Preparation of electrode pad" was stored in an oven at 50 degrees for 70 days, and then irradiated with LED light from the surface material side of the electrode pad to visually check the surface state of the conductive layer.

[0151] As the evaluation criteria, a case where no corrosion holes were visually observed was rated as “A”, and a case where 1 or more and less than 10 corrosion holes were visually observed was rated as “B”.

[0152] [Table 1]

[0153]

Claims

1. An electrode pad, which is attached to a biological body for use, the electrode pad comprising: Surface material, A conductive layer laminated on the surface material, and a hydrogel layer stacked on the conductive layer so as to cover the conductive layer, The hydrogel layer comprises: Polymer matrix, water, Wetting agents, and Organic acids and organic acid salts, The polymer matrix is ​​a polymer of (meth)acrylic monomers, The organic acid and the organic acid salt include at least one organic acid and organic acid salt selected from the group consisting of succinic acid and succinate, tartaric acid and tartrate, gluconic acid and gluconate, and lactic acid and lactate, The total content of the organic acid and the organic acid salt is 0.50 to 10% by mass relative to 100% by mass of the hydrogel.

2. The electrode pad according to claim 1, wherein: The pH of the hydrogel layer is 3.0-7.

5.

3. The electrode pad according to claim 2, wherein: The conductive layer includes an electrode, and the electrode includes at least one selected from the group consisting of aluminum foil, tin foil, and stainless steel foil.

4. The electrode pad according to claim 1, wherein: The polymer matrix is ​​a copolymer of a (meth)acrylic monomer and a cross-linking monomer.

5. The electrode pad according to claim 4, wherein: The content of the polymer matrix is ​​10 to 40% by mass relative to 100% by mass of the hydrogel.

6. The electrode pad according to claim 4, wherein: The (meth)acrylic monomer includes at least one selected from the group consisting of (meth)acrylamide, (meth)acrylic acid, dimethyl(meth)acrylamide, diacetone(meth)acrylamide, tert-butylacrylamidesulfonic acid, and salts thereof.

7. The electrode pad according to claim 1, wherein: The humectant includes at least one selected from the group consisting of polyols, polyoxyalkylene alkyl ethers and / or sugars.

8. The electrode pad according to claim 7, wherein: The wetting agent comprises a polyol, The polyol includes at least one selected from the group consisting of ethylene glycol, triethylene glycol, propylene glycol, polypropylene glycol, polyethylene glycol, polyglycerol, and glycerol.

9. The electrode pad according to claim 7, wherein: The wetting agent comprises a polyoxyalkylene alkyl ether, The polyoxyalkylene alkyl ether includes at least one selected from the group consisting of methyl glucoside polyoxyethylene ether and polyoxyethylene alkyl ether.

10. The electrode pad according to claim 7, wherein: The humectant comprises sugar, The sugar includes at least one selected from the group consisting of monosaccharides, disaccharides, and polysaccharides.

11. The electrode pad according to any one of claims 1 to 10, used as a ground electrode for an electrosurgical instrument.

12. A hydrogel comprising: Polymer matrix, water, Wetting agents, and Organic acids and organic acid salts, The polymer matrix is ​​a polymer of (meth)acrylic monomers, The organic acid and the organic acid salt include at least one organic acid and organic acid salt selected from the group consisting of succinic acid and succinate, tartaric acid and tartrate, gluconic acid and gluconate, and lactic acid and lactate, The total content of the organic acid and the organic acid salt is 0.50 to 10% by mass relative to 100% by mass of the hydrogel.

13. A method for using a hydrogel to manufacture an electrode pad for use attached to a biological body, the hydrogel comprising: Polymer matrix, water, Wetting agents, and Organic acids and organic acid salts, The polymer matrix is ​​a polymer of (meth)acrylic monomers, The organic acid and the organic acid salt include at least one organic acid and organic acid salt selected from the group consisting of succinic acid and succinate, tartaric acid and tartrate, gluconic acid and gluconate, and lactic acid and lactate, The total content of the organic acid and the organic acid salt is 0.50 to 10% by mass relative to 100% by mass of the hydrogel.

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