JP2019137821A - Conductive adhesive gel sheet - Google Patents

Abstract

To provide a conductive adhesive gel sheet capable of maintaining stable conductivity and skin adhesive force hardly being affected under high humidity or by environment in contact with sweat or effusion from skin surface, and generating almost no peeling or shift even with skin adhesion over long time.SOLUTION: The above described problem is solved by a conductive adhesive gel sheet containing a continuous phase containing at least a hydrophilic crosslinked polymer and an electrolyte, and a hydrophobic crosslinked polymer particle dispersed in the continuous phase and having particle diameter of 1 to 100 nm.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a conductive adhesive gel sheet. More specifically, the present invention relates to a conductive adhesive gel sheet having transparency in addition to stable conductivity and skin adhesive force which are not easily affected by temperature, humidity and the like. The conductive pressure-sensitive adhesive gel sheet of the present invention is suitably used as a pressure-sensitive adhesive for attaching a wearable sensing device or electrode, which is being developed in the field of medicine or healthcare, to the skin surface.

In recent years, in the fields of medical care and healthcare, research and development of real-time sensing technology related to human biological information using advanced information communication technology such as the Internet and big data analysis and data processing / analysis technology has been extensively performed.
In order to accurately measure information in heart rate and electrocardiogram measurement using a wearable device attached to the skin surface, it is desirable that the sensing device is in stable and physical contact. Therefore, it is often brought into contact with the skin via a conductive adhesive. The adhesive that is applied to the skin surface for a long time, such as a wearable device, is not only difficult to cause stuffiness and irritation of the skin, but also in an environment where it is exposed to high humidity and sweat from the skin surface. Therefore, it is necessary to have stable conductivity and skin adhesiveness which are not easily affected by the skin.

  Moreover, since it is necessary for the wearable device to be accompanied by fashionability such that the wearer does not feel uncomfortable in its appearance, the adhesive is required to be transparent. As a pressure-sensitive adhesive for skin application satisfying these characteristics, a pressure-sensitive adhesive containing a hydrophobic pressure-sensitive adhesive polymer in a conductive continuous phase is suitably used. Prior art documents relating to such an adhesive include Patent Documents 1 to 3 (Japanese Patent Publication No. 11-510530: Patent Document 1, Japanese Patent Application Laid-Open No. 2001-181597: Patent Document 2, Japanese Patent Application Laid-Open No. 2013-117029: Patent document 3) is mentioned. Patent Documents 1 to 3 describe a two-phase continuous pressure-sensitive adhesive having a continuous phase or a dispersed phase of a hydrophobic pressure-sensitive adhesive polymer and a continuous phase of a hydrophilic polymer, a biological electrode, a mammalian skin hull, and a drug delivery device Is described as having utility.

Japanese National Patent Publication No. 11-510530 JP 2001-181597 A JP 2013-117029 A

However, in Patent Documents 1 to 3, the size of each continuous phase and its size are required in that the adhesive is intended to be applied to the skin surface for a long time, and it is difficult for the skin to be stuffy or rash. Significance is not shown.
In addition, Patent Document 1 has a general relative humidity of 50 to 60% in that it is required to have stable conductivity and skin adhesion that are not easily affected by an environment that is exposed to high humidity or sweat from the skin surface. Under the environment, there is a problem that the conductivity is reduced by drying.
In Patent Documents 2 and 3, betaine and choline chloride containing glycerin, trimethylamine groups and high moisture retention are added in order to prevent the decrease in conductivity due to drying, but moisture absorption, bathing and showering under high humidity of 90% relative humidity. There is a problem that the adhesive force is reduced due to swelling due to absorption of water from the outside such as water and sweat from the skin surface.

The inventors of the present invention diligently studied in various test examples, and conducted in a state where hydrophobic crosslinked polymer particles having a particle diameter of 1 to 100 nm or less were dispersed in a continuous phase containing at least a hydrophilic crosslinked polymer and an electrolytic solution. An adhesive gel sheet was formed. The obtained conductive pressure-sensitive adhesive gel sheet is kept transparent, and in addition, the hydrophobic crosslinked polymer particles do not block micron-sized sweat pores. As a result, it can be expected that skin will be stuffy and irritated even when applied for a long time. Furthermore, since the dihydric alcohol having 3 or 4 carbon atoms, which is conventionally used as a moisturizing agent or antibacterial agent in the cosmetics field, does not excessively increase the moisture absorption / water absorption performance of the conductive adhesive gel sheet, It has been newly found that it acts as a solvent for an electrolytic solution containing an inorganic salt that retains conductivity without causing a decrease in adhesive force due to absorption and swelling of perspiration and exudate.
Thus, according to the present invention, a conductive adhesive comprising a continuous phase containing at least a hydrophilic crosslinked polymer and an electrolyte, and hydrophobic crosslinked polymer particles having a particle diameter of 1 to 100 nm dispersed in the continuous phase. A gel sheet is provided.

  According to the conductive pressure-sensitive adhesive gel sheet of the present invention, it is possible to maintain stable conductivity and skin adhesive force that are not easily affected by an environment that is exposed to sweat or exudate from the skin surface under high humidity. It is possible to realize a conductive adhesive gel sheet that hardly peels off or shifts.

In addition, in the case of any one or combination of the following, it is possible to maintain stable conductivity and skin adhesion that are not easily affected by the environment exposed to high humidity, sweat or exudate from the skin surface, and long-lasting skin. It is possible to realize a higher performance conductive adhesive gel sheet that hardly peels off or slips even when applied.
(1) The electrolytic solution contains water, an inorganic salt, and a dihydric alcohol having 3 or 4 carbon atoms, and the electrolytic solution, water, and the dihydric alcohol having 3 or 4 carbon atoms are represented by the following relational formula:
25 <W1 <50 Formula (1)
0.2 <W2 / W3 <5.0 Formula (2)
(W1, W2, and W3 in the above formula mean the mass% of the electrolyte, water, and the dihydric alcohol having 3 or 4 carbon atoms with respect to the conductive adhesive gel sheet)
It is contained in the conductive adhesive gel sheet in an amount satisfying the above.
(2) The conductive pressure-sensitive adhesive gel sheet further contains a nonionic surfactant.
(3) The dihydric alcohol having 3 or 4 carbon atoms is 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 2,3-butanediol, and 1,4-butanediol. Selected from.

(4) The hydrophobic crosslinked polymer particles include a polymer derived from an alkyl acrylate having a branched alkyl group having 8 to 10 carbon atoms at the terminal of the ester group.
(5) The hydrophilic crosslinked polymer is at least acrylic acid or a salt thereof, acrylamide, acrylamide methylpropanesulfonic acid or a salt thereof, N, N-dimethylacrylamide, N, N-diethylacrylamide, acryloylmorpholine, methoxypolyethylene glycol acrylate, methoxy Polymers derived from acrylic monomers selected from polypropylene glycol acrylate, hydroxy polyethylene glycol acrylate, hydroxy polypropylene glycol acrylate and methoxydipropylene glycol acrylate are included.
(6) The hydrophobic crosslinked polymer particles and the hydrophilic crosslinked polymer are at least tripropylene glycol diacrylate, ethylene glycol diacrylate, polyethylene glycol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate and Polymers derived from bifunctional acrylic monomers selected from N, N-methylenebisacrylamide are included.

(7) The inorganic salt contains an inorganic chlorine compound.
(8) When the conductive adhesive gel sheet is measured by the AC impedance method immediately after exposure in a temperature 23 ° C.-humidity 50% environment and after exposure for 24 hours, the real part Z of the impedance at a frequency of 1 kHz 'Indicates 500Ω or less.
(9) The conductive adhesive gel sheet is used for mounting the wearable sensing device on the skin surface.

1 is a cross-sectional view of a gel sheet of Example 1. FIG.

Hereinafter, the conductive adhesive gel sheet according to the present invention (hereinafter simply referred to as a gel sheet) will be described in detail. The present invention is not limited to the following description, and can be variously modified within the scope of the gist thereof.
For example, as shown in FIG. 1 as a cross-sectional view, the gel sheet includes a continuous phase and particles dispersed in the continuous phase. The particles have a particle size of 1 to 100 nm. When the particle size is less than 1 nm, the decrease in adhesive strength under high humidity may be large. When it is larger than 100 nm, the transparency of the sheet may be lowered. A preferable particle diameter is 1 to 200 nm, and more preferably 5 to 100 nm.

The gel sheet preferably has a real part Z ′ of an impedance at a frequency of 1 kHz of 500Ω or less when the gel sheet is measured by an AC impedance method immediately after being exposed to a temperature of 23 ° C. and a humidity of 50% and after being exposed for 24 hours. . In the case of 500Ω or less, it is preferable in terms of accurate acquisition of biological data such as cardiac potential, myoelectric potential and brain wave. The real part Z ′ is more preferably 300Ω or less, and still more preferably 100Ω or less.
The gel sheet preferably has a 90 ° peel adhesive strength to the bakelite plate of 10 to 2000 g / 20 mm. When it is less than 10 g / 20 mm, sufficient skin adhesive strength may not be obtained. When it is larger than 2000 g / 20 mm, the skin adhesive strength is too strong, and the keratin may peel off or the adhesive residue may be generated. The 90 ° peel adhesive strength is more preferably 50 to 1500 g / 20 mm, and still more preferably 100 to 1000 g / 20 mm.
The continuous phase includes at least a hydrophilic crosslinked polymer and an electrolyte, and the particles are composed of a hydrophobic crosslinked polymer.

(1) Hydrophilic cross-linked polymer The hydrophilic cross-linked polymer is not particularly limited as long as it has hydrophilicity, is cross-linked, and can be used. For example, a polymer derived from a monofunctional monomer and a crosslinkable monomer may be used. Here, the hydrophilicity is derived from carboxylic acid and / or salt thereof, sulfonic acid and / or salt thereof, acrylamide and / or derivative thereof, hydroxyl group, trimethylammonium group and / or salt thereof, polyethylene glycol and polypropylene glycol. This means that the polymer chain has a highly polar functional group such as

(A) Monofunctional monomer The hydrophilic polymer includes a polymer derived from a monofunctional monomer.
Monofunctional monomers include acrylamide, N-methylacrylamide, N-ethylacrylamide, N-propylacrylamide, N-isopropylacrylamide, N-butylacrylamide, N, N-dimethylacrylamide, N, N-diethylacrylamide, acryloylmorpholine, etc. Non-electrolytic acrylamide derivatives, tertiary butyl acrylamide sulfonic acid (TBAS) or salts thereof, N, N-dimethylaminoethyl acrylamide (DMAEAA) hydrochloride, N, N-dimethylaminopropyl acrylamide (DMAPAA) hydrochloride, acrylamide methyl Electrolyte acrylamide derivatives such as propanesulfonic acid or its salt, (meth) acrylic acid or its salt, maleic acid or its salt, itaconic acid or its salt, sulfopropylmedium Electrolyte acrylic derivatives such as acrylate (SPM) or its salts, (meth) acryloyloxyethyltrimethylammonium chloride (QDM), methoxypolyethylene glycol acrylate, methoxypolypropylene glycol acrylate, hydroxypolyethylene glycol acrylate, hydroxypolypropylene glycol acrylate, methoxydipropylene Nonelectrolytic acrylic derivatives such as glycol acrylate, hydroxyethyl (meth) acrylate, polyethylene glycol (meth) acrylate, vinylamide derivatives such as vinylpyrrolidone, vinylacetamide, and vinylformamide, and hydrophilic monofunctional monomers such as allyl alcohol are suitable. Used. Any one monofunctional monomer may be used alone, or two or more monofunctional monomers may be used in combination.

  Among monofunctional monomers, acrylic acid is easy to suppress irritation to the skin because it is highly reactive and easily suppresses the remaining monomer, or because it has a high molecular weight and low skin primary irritation index (PI). Or a salt thereof, acrylamide, acrylamidomethylpropane sulfonic acid or a salt thereof, N, N-dimethylacrylamide, N, N-diethylacrylamide, acryloylmorpholine, methoxypolyethylene glycol acrylate, methoxypolypropylene glycol acrylate, hydroxypolyethylene glycol acrylate, hydroxypolypropylene glycol Acrylate and methoxydipropylene glycol acrylate are more preferable.

(B) Crosslinkable monomer A polyfunctional monomer can be used as the crosslinkable monomer.
Among the polyfunctional monomers, examples of the bifunctional acrylic monomer include about 4 to about 10 carbon atoms such as 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, and 1,9-nonanediol diacrylate. Alkyl diacrylate, polyethylene glycol diacrylate, N, N-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 are preferably used. Any one kind of bifunctional acrylic monomers may be used alone, or two or more kinds may be used in combination.

Among the above-mentioned bifunctional acrylic monomers, it has high reactivity and is easy to suppress the remaining of the monomer, or has a high molecular weight and low skin primary irritation index (P.I.I.), thereby suppressing irritation to the skin. Tripropylene glycol diacrylate, ethylene glycol diacrylate, polyethylene glycol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, and N, N-methylenebisacrylamide are more preferable.
The polyfunctional monomer may be a trifunctional monomer, a tetrafunctional monomer, or a monomer having five or more functionalities.
It is preferable that the usage-amount of a crosslinkable monomer is the range of 0.01-5 mass parts with respect to 100 mass parts of monofunctional monomers. If the amount is less than 0.01 parts by mass, the cohesive force of the pressure-sensitive adhesive is weak, and thus the adhesive force may be lowered. If the amount is more than 5 parts by mass, the elongation of the pressure-sensitive adhesive may be reduced and the adhesive force may be weakened. In addition, the usage-amount of a monomer is substantially the same as the abundance of the polymer derived from it.

(2) Hydrophobic crosslinked polymer The hydrophobic crosslinked polymer is not particularly limited as long as it has hydrophobicity, is crosslinked, and can be used for a gel sheet. For example, a polymer derived from a monofunctional monomer and a crosslinkable monomer may be used. Here, hydrophobic means that the polymer chain has an alkyl group having 4 or more carbon atoms, an aliphatic ring, or an aromatic ring.
(A) Monofunctional monomer The hydrophobic polymer includes a polymer derived from a monofunctional monomer.
The monofunctional monomer is preferably an alkyl acrylate having a branched alkyl group having 8 to 10 carbon atoms at the terminal of the ester group. Examples of the branched alkyl group having 8 to 10 carbon atoms include an isooctyl group, an isononyl group, and an isodecyl group. Specific examples include isooctyl acrylate, isononyl acrylate, and isodecyl acrylate with low odor and low skin primary irritation index (P.I.I.). Any one monofunctional monomer may be used alone, or two or more monofunctional monomers may be used in combination.

  As long as the effects of the present invention are not impaired, the branched or straight chain alkyl acrylate having 1 to 7 carbon atoms, and the branched or straight chain alkyl acrylate, dicyclopentenyl acrylate, dicyclopentanyl acrylate having 11 to 18 carbon atoms. , Isobornyl acrylate, tetrafurfuryl acrylate, phenoxyethyl acrylate, phenoxydiethylene glycol acrylate, and the like may be copolymerized with an alkyl acrylate having a branched alkyl group having 8 to 10 carbon atoms at the terminal of the ester group. Such monomers are suitable for forming a hydrophobic cross-linked polymer having tackiness. As the monofunctional monomer used for the hydrophobic cross-linked polymer, any one kind may be used alone, or two or more kinds may be used in combination.

(B) Crosslinkable monomer As a crosslinkable monomer, the polyfunctional monomer illustrated in the column of the said hydrophilic crosslinked polymer can be used.
It is preferable that the usage-amount of a crosslinkable monomer is the range of 0.01-5 mass parts with respect to 100 mass parts of monofunctional monomers. If the amount is less than 0.01 parts by mass, the cohesive force of the pressure-sensitive adhesive is weak, and thus the adhesive force may be lowered. If the amount is more than 5 parts by mass, the elongation of the pressure-sensitive adhesive may be reduced and the adhesive force may be weakened. In addition, the usage-amount of a monomer is substantially the same as the abundance of the polymer derived from it.

(3) Electrolytic Solution The electrolytic solution preferably contains water, an inorganic salt, and a dihydric alcohol having 3 or 4 carbon atoms (hereinafter also simply referred to as a dihydric alcohol).
(A) Inorganic salts Examples of inorganic salts include alkali metal halides such as sodium halide, lithium halide, and potassium halide; alkaline earth metal halides such as magnesium halide and calcium halide; other metal halogens And the like. Moreover, hypochlorite, chlorite, chlorate, perchlorate, sulfate, carbonate, nitrate, and phosphate of various metals are also preferably used as the inorganic salt. Examples of the inorganic salt include inorganic salts such as ammonium salts and various complex salts; salts of monovalent organic carboxylic acids such as acetic acid, benzoic acid and lactic acid; salts of polyvalent organic carboxylic acids such as tartaric acid; phthalic acid, succinic acid, Monovalent or divalent or higher salts of polyvalent carboxylic acids such as adipic acid and citric acid; metal salts of organic acids such as sulfonic acids and amino acids are preferably used. Any one of the inorganic salts may be used alone, or two or more may be used in combination.
Among these, as the inorganic salt (electrolyte), a monovalent metal inorganic chlorine compound useful when a silver-silver chloride electrode is used as the electrode is preferably used. Specific examples include potassium chloride, lithium chloride, and sodium chloride. Inorganic chlorine compounds have different hydration radii and molar conductivity of ions in the electrolyte depending on the type, and therefore any one of them may be used alone according to the intended conductivity and moisture retention. Two or more kinds may be used in combination.

(B) Dihydric alcohol having 3 or 4 carbon atoms The dihydric alcohol preferably has a relative dielectric constant of 10 or more, and has a relative dielectric constant of 20 or more, because of the ease of ion dissociation of the electrolyte. Are more preferable, and those having a relative dielectric constant of 30 or more are more preferable. Specific examples include 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 2,3-butanediol, 1,4-butanediol, and the like. Any one kind of dihydric alcohol may be used alone, or two or more kinds may be used in combination. In particular, 1,3-butanediol is preferably used.

(C) Content The electrolytic solution, water, and the dihydric alcohol electrolytic solution having 3 or 4 carbon atoms have the following relational formula:
25 <W1 <50 Formula (1)
0.2 <W2 / W3 <5.0 Formula (2)
(W1, W2, and W3 in the above formula mean the mass% of the electrolyte solution, water, and the dihydric alcohol having 3 or 4 carbon atoms with respect to the gel sheet)
It is preferable to be contained in the gel sheet in an amount satisfying the above.
When W1 is 25% by mass or less, the conductivity may decrease. When it is 50% by mass or more, the transparency of the sheet may be lowered. W1 is more preferably more than 25% by mass and less than 50% by mass, and more preferably 35 to 45% by mass.
When W2 / W3 is 0.2 or less, the initial conductivity may be lowered. In the case of 5.0 or more, the conductive stability under low humidity may be deteriorated. W2 / W3 is more preferably 0.5 to 4.0, and still more preferably 1.0 to 3.0.
W2 is preferably 10 to 30% by mass, and more preferably 13 to 25% by mass. When W2 is less than 10% by mass, the initial conductivity may be lowered. If it is more than 30% by mass, the sheet may become cloudy. W3 is preferably 5 to 30% by mass, and more preferably 10 to 25% by mass. When W3 is less than 5% by mass, the initial conductivity may be lowered. When the amount is more than 30% by mass, the electrolytic solution may bleed from the sheet and the adhesive strength may decrease.
The content of the inorganic salt is preferably 0.1 to 5% by mass and more preferably 0.5 to 3% by mass based on the total amount of the gel sheet. If it is these ranges, electrolyte will melt | dissolve in the water and dihydric alcohol in electrolyte solution, and can provide electroconductivity to a gel sheet.

(4) Nonionic surfactant The gel sheet may further contain a nonionic surfactant in order to improve the dispersibility of the hydrophilic crosslinked polymer and the hydrophobic crosslinked polymer particles. The nonionic surfactant is preferably compatible with the hydrophobic and hydrophilic polymerization composition before polymerization, and can be easily dissolved or dispersed even when blended in a large amount. This is because the molecular mobility of the surfactant is increased due to good compatibility with the polymerized composition, and solubilization is likely to be facilitated by the formation of aggregates by the surfactant.

  Specific examples of the nonionic surfactant that preferably satisfies the above conditions include POE sorbitan fatty acid esters such as POE sorbitan monooleate, POE sorbitan monostearate, POE sorbitan dioleate, and POE sorbitan tetraoleate. , POE sorbite monolaurate, POE sorbite monooleate, POE sorbite fatty acid esters such as POE sorbite monostearate, POE glycerin monostearate, POE glycerin monoisostearate, POE glycerin triisostearate POE glycerin fatty acid esters such as rate, POE monooleate, POE fatty acid esters such as POE distearate, POE lauryl ether, POE oleyl ether, POE POE alkyl ethers such as allyl ether, POE behenyl ether, POE2-octyldodecyl ether, POE cholestanol ether, POE alkylphenyl ethers such as POE octylphenyl ether and POE nonylphenyl ether, pluronic types such as brulon, POE POP cetyl ether, POE / POP2-decyl tetradecyl ether, POE / POP monobutyl ether, POE / POP alkyl ethers such as POE / POP glycerin ether, Tetra POE / tetra POP ethylenediamine condensates such as Tetronic, POE castor oil POE hydrogenated castor oil, POE propylene glycol fatty acid ester, POE alkylamine, POE fatty acid amide and the like. Here, POE and POP are abbreviations for polyoxyethylene and polyoxypropylene, respectively. Any one nonionic surfactant may be used alone, or two or more nonionic surfactants may be used in combination.

Among the nonionic surfactants, POE lauryl ether, POE oleyl ether, POE stearyl ether, POE isostearyl ether, and POE behenyl ether are preferable.
The content of the nonionic surfactant is preferably 5 to 30% by mass, and more preferably 15 to 25% by mass based on the total amount of the gel sheet. When the amount of the nonionic surfactant is less than 5% by mass, the sheet may become cloudy and the adhesive strength may decrease. When the amount is more than 30% by mass, the compounded liquid may be in a sol form and may be difficult to handle.

(5) Other components The gel sheet may contain a moisturizing agent as long as the appearance and the adhesive force are not deteriorated. Specific examples include ethylene glycol, polyethylene glycol, glycerin, polyglycerin, ethylene oxide adduct of glycerin, betaine, pyrrolidone carboxylic acid, sodium pyrrolidone carboxylate, sodium hyaluronate, hyaluronic acid and the like. The content of the humectant is preferably 5% by mass or less based on the total amount of the gel sheet. When there are more moisturizing agents than 5 mass%, a sheet may become cloudy and adhesive force may fall.
The gel sheet may contain other additives as required. Examples of other additives include pH adjusters, rust inhibitors, fungicides, antiseptics, antioxidants, antifoaming agents, stabilizers, and coloring inhibitors.
The gel sheet may include a reinforcing fiber sheet as a core material. Examples of the shape of the core material include woven fabric, knitted fabric, non-woven fabric, laminated fabric, and chopped strand mat. Examples of the constituent material of the core material include one or more selected from reinforcing fibers such as polyester fiber, polyamide fiber, aramid fiber, vinylon fiber, carbon fiber, glass fiber, and polyolefin fiber. Moreover, in order to improve the fiber impregnation property of the gel sheet, the fiber may be treated with an amine, epoxy, or methacrylic silane coupling agent.
The reinforcing fiber sheet may be located in and / or on the surface of the gel sheet, and may be mixed uniformly throughout.

(6) Application The gel sheet can be used for any application as long as it is intended to ensure electrical conductivity between members and to fix both members by adhesive force. A particularly suitable application is an application in which a wearable sensing device (for example, an electrode) is attached to the skin surface.
(7) Production method The gel sheet comprises a step of forming a polymerizable composition containing a raw material for forming a hydrophilic cross-linked polymer, an electrolyte, and a raw material for forming hydrophobic cross-linked polymer particles into a sheet (molding step), and a polymerizable property. It can manufacture by passing through the process (polymerization process) of superposing | polymerizing a composition with a polymerization initiator.

(A) Molding process Molding into a sheet is not particularly limited, and a known method can be employed. For example, a method of pouring the polymerizable composition into a mold having a desired shape can be mentioned. As another method, a method of pouring a polymerizable composition between protective films made of two resin films and maintaining a constant thickness can also be mentioned.
(B) Polymerization process The molded polymerizable composition becomes a gel sheet by polymerization. Examples of the polymerization include a free radical polymerization reaction, a living radical polymerization reaction, and a living anion polymerization reaction. The polymerization reaction can be initiated by applying energy such as heat, ultraviolet rays, and electron beams. As a polymerization initiator, a well-known polymerization initiator according to energy, such as heat, light (an ultraviolet ray, visible light, etc.), an electron beam, can be used. As the polymerization initiator, a photopolymerization initiator is preferable.

  The photopolymerization initiator is not particularly limited as long as it can be cleaved with ultraviolet rays or visible rays to generate radicals. For example, α-hydroxyketone, α-aminoketone, benzylmethyl ketal, bisacylphosphine oxide, metallocene and the like can be mentioned. More specifically, 2-hydroxy-2-methyl-1-phenyl-propan-1-one (for example, product name: Darocur (registered trademark) 1173, manufactured by IGM RESINS), 2-hydroxy-1- {4 -[4- (2-hydroxy-2-methyl-propionyl) -benzyl] phenyl} -2-methyl-propan-1-one (for example, product name: Omnirad (registered trademark) 127, manufactured by IGM RESINS), 1 -[4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one (for example, product name: Omnirad (registered trademark) 2959, manufactured by IGM RESINS), 2, 2-dimethoxy-1,2-diphenylethane-1-one (for example, product name: Omnirad® 651, IGM RESI) S), 1-hydroxy-cyclohexyl-phenyl-ketone (for example, product name: Omnirad (registered trademark) 184, IGM RESINS), 2-methyl-1- (4-methylthiophenyl) -2-morpholinopro Pan-1-one (for example, product name: Omnirad (registered trademark) 907, manufactured by IGM RESINS), 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one (for example, , Product name: Omnirad (registered trademark) 369, manufactured by IGM RESINS), oligo {2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl] propanone} (for example, Ezacure (registered trademark)) ONE, manufactured by Nippon Kayaku Co., Ltd.). Any one of these photopolymerization initiators may be used alone, or two or more thereof may be used in combination. Among them, 2-hydroxy-1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] phenyl} -2-methyl-propan-1-one is preferable. The photopolymerization initiator can be included in the polymerizable composition in various amounts depending on the desired effect. The content of the photopolymerization initiator is usually in the range of 0.01 to 5% by mass, preferably in the range of 0.05 to 3% by mass, based on the total amount of the polymerizable composition.

(C) Other process When a gel sheet equips a reinforcing fiber sheet as a core material, a core material can be included in a gel sheet as follows, for example. In the molding step, when pouring the polymerizable composition into the mold, a method of arranging the reinforcing fiber sheet in the mold before, during and after pouring can be mentioned. Moreover, the method of putting a reinforcing fiber sheet between a pair of gel sheets by mounting a reinforcing fiber sheet on a gel sheet, and mounting another gel sheet on it is also mentioned.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto. First, measurement methods of various physical properties measured in the examples are described.
(Sheet appearance)
The appearance of the sheet was visually evaluated for transparency.

(Real part of impedance Z ')
After the gel sheet with both sides protected by the protective film prepared in the examples was cut into 20 mm squares, the protective film on one side was peeled off and the adhesive surface was exposed, and the temperature was 23 ° C.-humidity 50% and the temperature 40 ° C.-humidity 90 % Of the environment. After the exposure, the other protective film is peeled off, the gel sheet is sandwiched between two nickel plates, and an LCR meter (manufactured by Tecpel, device name: LCR612) is used to measure the real part of the impedance (resistance component) at a frequency of 1 kHz. Z ′ [Ω] was measured.
The measurement was performed on the gel sheet immediately after the exposure (initial stage) and after the exposure for 24 hours in the state exposed to each environment of temperature 23 ° C.-humidity 50% and temperature 40 ° C.-humidity 90%.

(Particle size)
A gel sheet sample was frozen using a liquid nitrogen refrigerant, and a section was cut out with a knife. The section was prepared as an ultrathin section having a thickness of 80 to 90 nm using a “Leica EM UC7” ultramicrotome and a “Leica EM FC7” freeze cutting system manufactured by Leica Microsystems. Cutting conditions were a trimming temperature of −60 ° C. and a cutting temperature of −80 ° C. Subsequently, the ultrathin sections were photographed with an “H-7600” transmission electron microscope manufactured by Hitachi High-Technologies Corporation and an “ER-B” CCD camera system manufactured by AMT. Staining at the time of preparing an ultrathin section was performed by dipping for 3 to 5 minutes using a 2% phosphotungstic acid solution as a staining agent. The diameters of 20 particles arbitrarily selected from the obtained observation images were measured, and the range of the minimum value and the maximum value in the obtained measurement values was defined as the particle diameter.

(Moisture change rate)
The gel sheet with both sides protected by the protective film prepared in the examples was cut into 50 mm squares, and then the protective film on one side was peeled off to expose the adhesive surface, and the temperature was 23 ° C.-humidity 50% and the temperature 40 ° C.-humidity 90 % Of each environment. After the exposure, the mass of the gel sheet was measured.
The measurement was performed on the gel sheet immediately after the exposure (initial stage) and after the exposure for 24 hours in the state exposed to each environment of temperature 23 ° C.-humidity 50% and temperature 40 ° C.-humidity 90%.
A value calculated from the obtained measured value according to the following formula was defined as a moisture change rate.
Moisture change rate =
(Mass after exposure for 24 hours-Mass immediately after exposure) / Mass immediately after exposure x 100 [%]

(Adhesive force)
The initial (immediately after exposure) adhesive strength was measured by the following method. After the gel sheet was cut into a strip shape having a width of 20 mm and a length of 100 mm, the protective film on one side was peeled off and a backing material was affixed. Thereafter, the protective film on the other side is peeled off, and is attached to a bakelite plate having a thickness of 2 mm, a length of 125 mm, and a width of 25 mm, and is reciprocated once by a 2 kg roller. It was set to XT Plus (manufactured by Stable Micro Systems). Thereafter, in accordance with JIS Z 0237: 2009, the peel strength when peeled in the 90 ° direction when the length direction of the sample was set to 0 ° at a speed of 300 mm / min was measured as the adhesive strength.
The strip-shaped gel sheet is left exposed in a thermo-hygrostat set at 40 ° C-90% humidity, with the adhesive film peeled off and exposed to bakelite after 24 hours. A value obtained by measuring 90 ° peel adhesion in the same manner as described above was defined as the anti-sweat adhesive force.

Example 1
Isooctyl acrylate: 20 parts by mass, methoxypolyethylene glycol (n = 9) oleyl ether: 10 parts by mass, acrylic acid: 15 parts by mass, 1,9-nonanediol diacrylate (1.9NDDA): 0.50 parts by mass, Photopolymerization initiator (Omnirad 127): 0.68 parts by mass, surfactant (polyoxyethylene (n = 9) oleyl ether): 20 parts by mass was mixed to obtain a mixture. Sodium chloride: 1 part by mass, ion-exchanged water: 14 parts by mass, 1,3-butanediol: 20 parts by mass were mixed to obtain an electrolytic solution. The polymerizable composition was obtained by adding the electrolytic solution to the mixture and mixing. The polymerizable composition was colorless and transparent.
After sufficiently defoaming the polymerizable composition, the polymerizable composition is allowed to flow between the upper and lower protective films (PET film), the thickness is adjusted to 0.8 mm with a roller, and then using a Heraeus Light Hammer 10 UV lamp system, A gel sheet was obtained by irradiating with an ultraviolet ray having an accumulated light amount of 4000 mJ / cm ² and polymerizing. The gel sheet was colorless and transparent.
From the TEM image (cross-sectional view) shown in FIG. 1, the gel sheet has a state in which hydrophobic crosslinked polymer particles having a particle diameter of 5 to 70 nm are dispersed in a continuous phase containing at least a hydrophilic crosslinked polymer and an electrolytic solution. It was confirmed.

Examples 2-12 and Comparative Examples 1-11
A gel sheet was produced in the same manner as in Example 1 except that the raw materials were changed to those shown in Tables 1 to 3. The physical properties of Examples 1 to 12 and Comparative Examples 1 to 11 are shown in Tables 1 to 3.

  From Tables 1 to 3, the gel sheets of Examples 1 to 12 can maintain stable electrical conductivity and skin adhesiveness that are not easily affected by high humidity, or the environment in contact with sweat or exudate from the skin surface, and for a long time. It can be seen that there is almost no peeling or slippage even when the skin is applied to the skin.

(1) Hydrophilic crosslinked polymer The hydrophilic crosslinked polymer is not particularly limited as long as it has hydrophilicity and is crosslinked and can be used for a gel sheet . For example, a polymer derived from a monofunctional monomer and a crosslinkable monomer may be used. Here, the hydrophilicity is derived from carboxylic acid and / or salt thereof, sulfonic acid and / or salt thereof, acrylamide and / or derivative thereof, hydroxyl group, trimethylammonium group and / or salt thereof, polyethylene glycol and polypropylene glycol. This means that the polymer chain has a highly polar functional group such as

Example 1
Isooctyl acrylate: 20 parts by mass, methoxypolyethylene glycol (n = 9) acrylate : 10 parts by mass, acrylic acid: 15 parts by mass, 1,9-nonanediol diacrylate (1.9NDDA): 0.50 parts by mass, light Polymerization initiator (Omnirad 127): 0.68 parts by mass, surfactant (polyoxyethylene (n = 9) oleyl ether): 20 parts by mass was mixed to obtain a mixture. Sodium chloride: 1 part by mass, ion-exchanged water: 14 parts by mass, 1,3-butanediol: 20 parts by mass were mixed to obtain an electrolytic solution. The polymerizable composition was obtained by adding the electrolytic solution to the mixture and mixing. The polymerizable composition was colorless and transparent.
After sufficiently defoaming the polymerizable composition, the polymerizable composition is allowed to flow between the upper and lower protective films (PET film), the thickness is adjusted to 0.8 mm with a roller, and then using a Heraeus Light Hammer 10 UV lamp system, A gel sheet was obtained by irradiating with an ultraviolet ray having an accumulated light amount of 4000 mJ / cm ² and polymerizing. The gel sheet was colorless and transparent.
From the TEM image (cross-sectional view) shown in FIG. 1, the gel sheet has a state in which hydrophobic crosslinked polymer particles having a particle diameter of 5 to 70 nm are dispersed in a continuous phase containing at least a hydrophilic crosslinked polymer and an electrolytic solution. It was confirmed.

Claims (10)

A conductive pressure-sensitive adhesive gel sheet comprising: a continuous phase containing at least a hydrophilic crosslinked polymer and an electrolyte; and hydrophobic crosslinked polymer particles having a particle diameter of 1 to 100 nm dispersed in the continuous phase. The electrolytic solution contains water, an inorganic salt, and a dihydric alcohol having 3 or 4 carbon atoms, and the electrolytic solution, water, and the dihydric alcohol having 3 or 4 carbon atoms are represented by the following relational formula:
25 <W1 <50 Formula (1)
0.2 <W2 / W3 <5.0 Formula (2)
(W1, W2, and W3 in the above formula mean the mass% of the electrolyte, water, and the dihydric alcohol having 3 or 4 carbon atoms with respect to the conductive adhesive gel sheet)
The electroconductive adhesive gel sheet of Claim 1 contained in the said electroconductive adhesive gel sheet in the quantity which satisfy | fills. The conductive adhesive gel sheet according to claim 1, wherein the conductive adhesive gel sheet further contains a nonionic surfactant. The dihydric alcohol having 3 or 4 carbon atoms is selected from 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 2,3-butanediol and 1,4-butanediol The conductive adhesive gel sheet according to any one of claims 1 to 3. The conductive adhesive gel sheet according to any one of claims 1 to 4, wherein the hydrophobic crosslinked polymer particles include a polymer derived from an alkyl acrylate having a branched alkyl group having at least 8 to 10 carbon atoms at the terminal of the ester group. . The hydrophilic crosslinked polymer is at least acrylic acid or a salt thereof, acrylamide, acrylamide methylpropanesulfonic acid or a salt thereof, N, N-dimethylacrylamide, N, N-diethylacrylamide, acryloylmorpholine, methoxypolyethylene glycol acrylate, methoxypolypropylene glycol The conductive adhesive gel sheet according to any one of claims 1 to 5, comprising a polymer derived from an acrylic monomer selected from acrylate, hydroxy polyethylene glycol acrylate, hydroxy polypropylene glycol acrylate and methoxydipropylene glycol acrylate. The hydrophobic crosslinked polymer particles and the hydrophilic crosslinked polymer are at least tripropylene glycol diacrylate, ethylene glycol diacrylate, polyethylene glycol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate and N, The conductive adhesive gel sheet according to any one of claims 1 to 6, comprising a polymer derived from a bifunctional acrylic monomer selected from N-methylenebisacrylamide. The conductive adhesive gel sheet according to claim 1, wherein the inorganic salt contains an inorganic chlorine compound. When the conductive pressure-sensitive adhesive gel sheet was measured by the AC impedance method immediately after exposure in a temperature 23 ° C.-humidity 50% environment and after exposure for 24 hours, the real part Z ′ of the impedance at a frequency of 1 kHz. The conductive pressure-sensitive adhesive gel sheet according to any one of claims 1 to 8, wherein a value of 500Ω or less. The conductive adhesive gel sheet according to any one of claims 1 to 9, wherein the conductive adhesive gel sheet is used for mounting a wearable sensing device on a skin surface.