Adhesive electrode for acquiring biological signal and biological sensor

Abstract

To provide an adhesive electrode for acquiring biological signals which causes reduced stimulation to a living body, has excellent flexibility, and can maintain adhesiveness to the living body with low resistance.SOLUTION: An adhesive electrode for acquiring a biological signal according to the present invention contains a conductive polymer, an aqueous emulsion adhesive, a moisturizer, and a neutralizer, and has a pH at 25°C of 3.5 to 7.5.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an adhesive electrode for acquiring a biological signal and a biosensor. [Background technology]

[0002] Wearable biosensors that acquire bioinformation such as electrocardiogram waveforms, pulse waves, electroencephalograms, and electromyography are used in medical institutions such as hospitals and clinics, nursing homes, homes, etc. The biosensor is equipped with adhesive electrodes (bioelectrodes) for acquiring biosignals that come into contact with a living body to acquire the subject's bioinformation. When measuring the bioinformation, the biosensor is attached to the subject's skin and electrical signals related to the bioinformation are acquired by the bioelectrodes, thereby measuring the bioinformation.

[0003] As a bioelectrode for such a biosensor, for example, an adhesive sheet has been disclosed which has an adhesive layer containing a conductive organic polymer compound and an adhesive material and is used to attach to the skin surface of a wiring board (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-147659 Summary of the Invention [Problem to be solved by the invention]

[0005] However, Patent Document 1 does not consider the skin irritation and flexibility of the pressure-sensitive adhesive sheet. Because the conductive organic polymer compound used to form the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of Patent Document 1 has strong acid properties, the resulting pressure-sensitive adhesive layer also tends to have strong acid properties. Therefore, there is a problem in that when the pressure-sensitive adhesive layer comes into contact with the skin during use of the pressure-sensitive adhesive sheet, it causes strong irritation to the skin.

[0006] Furthermore, bioelectrodes are often used for long periods of time by being attached to a biological surface such as the skin, and therefore, in order for the bioelectrode to stably acquire electrical signals related to biological information from the biological surface such as the skin for a long period of time, it is important that the bioelectrode can be maintained in a stable state attached to the biological surface even if the surface of the skin stretches due to body movement.

[0007] An object of one aspect of the present invention is to provide an adhesive electrode for acquiring biological signals that reduces irritation to a living body, has excellent flexibility, and is capable of maintaining adhesiveness to a living body with low resistance. [Means for solving the problem]

[0008] One aspect of the adhesive electrode for acquiring a biological signal according to the present invention is It contains a conductive polymer, a water-based emulsion adhesive, a moisturizer, and a neutralizer. The pH at 25°C is 3.5 to 7.5. [Effects of the Invention]

[0009] One aspect of the adhesive electrode for acquiring biological signals according to the present invention reduces irritation to a living body, has excellent flexibility, and can maintain adhesiveness to a living body with low resistance. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a perspective view showing an example of an adhesive electrode for acquiring a biological signal according to an embodiment of the present invention. [Figure 2] FIG. 1 is a graph showing the relationship between the imidazole concentration and the sheet resistance of the electrode sheets of an example and comparative example 1. [Figure 3] FIG. 1 is a graph showing the relationship between the imidazole concentration and the breaking elongation of the electrode sheets of an example and a comparative example 1. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail. To facilitate understanding of the description, the same components in each drawing will be denoted by the same reference numerals, and duplicate descriptions will be omitted. The scale of each component in the drawings may differ from the actual scale. In this specification, unless otherwise specified, "to" indicating a range of values ​​means that the values ​​before and after it are included as the lower and upper limits.

[0012] <Adhesive electrodes for acquiring biological signals> An adhesive electrode for acquiring a biological signal according to this embodiment will be described. Note that the term "biological organism" refers to the human body (person) and animals such as cows, horses, pigs, chickens, dogs, and cats. The biosensor according to this embodiment can be suitably used for biological organisms, particularly for the human body. In this embodiment, a case where the biological organism is a human will be described as an example.

[0013] The adhesive electrode for acquiring a biological signal according to this embodiment is a biological electrode that is attached to a part of a living body (for example, the skin, scalp, or forehead) to detect biological information. In this embodiment, a case will be described in which the adhesive electrode for acquiring a biological signal is attached to human skin to acquire an electrical signal (biological signal) related to the human biological information. The biological signal is, for example, an electrical signal that represents an electrocardiogram waveform, an electroencephalogram, a pulse, or the like.

[0014] Fig. 1 is a perspective view showing an adhesive electrode for acquiring a biological signal according to this embodiment. As shown in Fig. 1, the adhesive electrode for acquiring a biological signal 1 has a sheet-like shape, and in a plan view, one longitudinal end (one end) of the adhesive electrode for acquiring a biological signal 1 may be formed in a substantially rectangular shape, and the other longitudinal end (the other end) may be formed in a substantially arc shape. The adhesive electrode for acquiring a biological signal 1 can be used to measure a potential difference (polarization voltage) between the skin 2 and the adhesive electrode for acquiring a biological signal 1 by, for example, attaching it to and bringing it into contact with skin 2, which is an example of a living body, and to detect an electrical signal (biological signal) related to the biological information of a subject.

[0015] The adhesive electrode 1 for acquiring a biological signal may have other shapes besides a sheet shape, such as a rod shape, etc. The shape of the adhesive electrode 1 for acquiring a biological signal in a plan view is not limited to the shape shown in Fig. 1 and may be designed into any shape appropriate depending on the application, etc., and may be formed into any shape such as a substantially rectangular, substantially polygonal, substantially circular, or substantially elliptical shape.

[0016] The adhesive electrode 1 for acquiring a biological signal may have two through holes 11 on its main surface 1a. Of the two through holes 11, the through hole 11A may be provided on one end side of the adhesive electrode 1 for acquiring a biological signal and may be formed in a thin, approximately oval shape. The through hole 11B may be provided on the other end side of the adhesive electrode 1 for acquiring a biological signal and may be formed in a approximately circular shape.

[0017] The number, position and shape of the through holes 11 provided on the main surface 1a of the adhesive electrode 1 for acquiring a biological signal are not particularly limited and may be set appropriately depending on the size of the main surface 1a of the adhesive electrode 1 for acquiring a biological signal, etc. The number of through holes 11 may be one, or may be three or more. The position of the through hole 11 may be other than one end and the other end of the main surface 1a of the adhesive electrode 1 for acquiring a biological signal, or may be in the central part. The shape of the through hole 11 may be approximately rectangular, etc.

[0018] The thickness of the adhesive electrode 1 for acquiring a biosignal may be any appropriate thickness depending on the application, size, etc., as long as strength, flexibility, low resistance, and conductivity can be ensured. The thickness of the adhesive electrode 1 for acquiring a biosignal refers to the length in the direction perpendicular to the surface of the adhesive electrode 1 for acquiring a biosignal. The thickness of the adhesive electrode 1 for acquiring a biosignal is, for example, the thickness measured at an arbitrary location on the cross section of the adhesive electrode 1 for acquiring a biosignal. When measurements are taken at multiple locations at the same location, the thickness may be the average value of the thicknesses measured at these measurement locations.

[0019] The adhesive electrode 1 for acquiring a biological signal is an electrode having adhesiveness (adhesive electrode), and contains a conductive polymer, a water-based emulsion adhesive, a moisturizer, and a neutralizer.

[0020] The present inventors have noticed that when using an adhesive electrode 1 for acquiring a biological signal containing an aqueous emulsion adhesive as a binder resin, the neutralizing agent used in the adhesive electrode 1 for acquiring a biological signal affects the irritation and flexibility of the adhesive electrode 1 for acquiring a biological signal. The present inventors have found that by including a neutralizing agent in the adhesive electrode 1 for acquiring a biological signal, it is possible to reduce irritation to the surface of the skin 2 and increase flexibility while maintaining low resistance and adhesiveness.

[0021] Examples of conductive polymers that can be used in the adhesive electrode 1 for acquiring biological signals include polythiophene-based conductive polymers, polyaniline-based conductive polymers, polypyrrole-based conductive polymers, polyacetylene-based conductive polymers, polyphenylene-based conductive polymers, and derivatives thereof, as well as composites thereof. These may be used alone or in combination. Among these, composites in which polythiophene is doped with polyaniline as a dopant are preferred. Among composites of polythiophene and polyaniline, PEDOT / PSS, in which poly3,4-ethylenedioxythiophene (PEDOT) is doped with polystyrene sulfonic acid (poly4-styrenesulfonate; PSS), is more preferred because it has a lower contact impedance with a living body and high conductivity.

[0022] The aqueous emulsion adhesive contained in the adhesive electrode 1 for acquiring a biological signal is used as a binder resin for the adhesive electrode 1. The aqueous emulsion adhesive has the function of improving the adhesiveness and flexibility of the adhesive electrode 1 for acquiring a biological signal. Therefore, by including the aqueous emulsion adhesive in the adhesive electrode 1 for acquiring a biological signal, the adhesive electrode 1 for acquiring a biological signal can have low elasticity and can improve its ability to conform to the irregularities on the surface of the skin 2.

[0023] As the aqueous emulsion pressure-sensitive adhesive, it is preferable to use an acrylic emulsion pressure-sensitive adhesive.

[0024] The acrylic emulsion pressure-sensitive adhesive is preferably a silane emulsion pressure-sensitive adhesive containing a water-dispersible copolymer and an organic liquid component that is compatible with the water-dispersible copolymer.

[0025] The water-dispersible copolymer is a polymer obtained by copolymerizing a monomer mixture containing a (meth)acrylic acid alkyl ester with a silane-based monomer copolymerizable with the (meth)acrylic acid alkyl ester.

[0026] The monomer mixture containing a (meth)acrylic acid alkyl ester is a monomer mixture containing a (meth)acrylic acid alkyl ester as a main component, preferably 50 wt % to 100 wt %.

[0027] As the (meth)acrylic acid alkyl ester, a straight-chain or branched alkyl ester having an alkyl group carbon number of 1 to 15, preferably 1 to 9, is used. Specific examples include (meth)acrylic acid alkyl esters having a straight-chain or branched alkyl group, such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, and tridecyl (meth)acrylate. These can be used alone or in combination of two or more.

[0028] The monomer mixture containing the (meth)acrylic acid alkyl ester may contain a carboxyl group-containing monomer copolymerizable with the (meth)acrylic acid alkyl ester.

[0029] The carboxyl group-containing monomer copolymerizable with the (meth)acrylic acid alkyl ester is not particularly limited as long as it is a polymerizable compound containing a carboxyl group in its structure and is copolymerizable with the (meth)acrylic acid alkyl ester, and examples thereof include (meth)acrylic acid, itaconic acid, maleic acid, maleic anhydride, 2-methacryloyloxyethyl succinic acid, etc. Acrylic acid is particularly preferred.

[0030] From the viewpoint of hydrolysis of the silane-based monomer and adjustment of the resulting adhesiveness, the carboxyl group-containing monomer is preferably contained in an amount of 0.1 wt % to 10 wt % relative to 100 wt % of the monomer mixture containing the (meth)acrylic acid alkyl ester.

[0031] The silane monomer copolymerizable with (meth)acrylic acid alkyl esters is not particularly limited as long as it is a polymerizable compound having a silicon atom and is copolymerizable with (meth)acrylic acid alkyl esters. However, silane compounds having a (meth)acryloyl group, such as (meth)acryloyloxyalkylsilane derivatives, are preferred because of their excellent copolymerizability with (meth)acrylic acid alkyl esters. Examples of silane monomers include 3-(meth)acryloyloxypropyltrimethoxysilane, 3-(meth)acryloyloxypropyltriethoxysilane, 3-(meth)acryloyloxypropylmethyldimethoxysilane, and 3-(meth)acryloyloxypropylmethyldiethoxysilane. These silane monomers can be used alone or in combination of two or more.

[0032] Furthermore, other silane-based monomers that can be used include, for example, vinyltrimethoxysilane, vinyltriethoxysilane, 4-vinylbutyltrimethoxysilane, 4-vinylbutyltriethoxysilane, 8-vinyloctyltrimethoxysilane, 8-vinyloctyltriethoxysilane, 10-methacryloyloxydecyltrimethoxysilane, 10-acryloyloxydecyltrimethoxysilane, 10-methacryloyloxydecyltriethoxysilane, and 10-acryloyloxydecyltriethoxysilane.

[0033] It is preferable that the silane-based monomer is copolymerized with the monomer mixture containing the (meth)acrylic acid alkyl ester in an amount of 0.005 wt % to 2 wt % relative to 100 wt % of the monomer mixture containing the (meth)acrylic acid alkyl ester.

[0034] By copolymerizing a silane monomer with a monomer mixture containing a (meth)acrylic acid alkyl ester, the silane compounds that serve as crosslinking points are evenly distributed within the molecules of the resulting copolymer. As a result, the aqueous emulsion pressure-sensitive adhesive, despite being a water-dispersible type, has excellent cohesion because the inside and outside of the particles are uniformly crosslinked. The addition of an organic liquid component not only makes it less irritating to the skin, but also provides excellent fixation and sweat-resistant fixation.

[0035] The aqueous dispersion copolymer may be obtained by copolymerizing a monomer copolymerizable with a (meth)acrylic acid alkyl ester other than the above-mentioned silane-based monomer and carboxyl group-containing monomer, if necessary. The monomer copolymerizable with a (meth)acrylic acid alkyl ester other than the silane-based monomer and the carboxyl group-containing monomer can be used for the purposes of adjusting the cohesive force of the adhesive electrode 1 for acquiring biological signals when the aqueous emulsion adhesive is formed into a sheet or the like, or improving compatibility with organic liquid components, and the amount used can be set as desired depending on the purpose by replacing part of the content of the (meth)acrylic acid alkyl ester.

[0036] Examples of monomers copolymerizable with (meth)acrylic acid alkyl esters other than silane-based monomers and carboxyl group-containing monomers include sulfoxyl group-containing monomers such as styrenesulfonic acid, allylsulfonic acid, sulfopropyl(meth)acrylate, (meth)acryloyloxynaphthalenesulfonic acid, and acrylamidomethylpropanesulfonic acid; hydroxyl group-containing monomers such as (meth)acrylic acid hydroxyethyl ester and (meth)acrylic acid hydroxypropyl ester; amide group-containing monomers such as (meth)acrylamide, dimethyl(meth)acrylamide, N-butylacrylamide, N-methylol(meth)acrylamide, and N-methylolpropane(meth)acrylamide; (meth)acrylic acid alkylaminoalkyl esters such as (meth)acrylic acid aminoethyl ester, (meth)acrylic acid dimethylaminoethyl ester, and (meth)acrylic acid tert-butylaminoethyl ester; and (meth)acrylic acid methoxy. Examples thereof include (meth)acrylic acid alkoxyalkyl esters such as (meth)acrylic acid diethyl ester and (meth)acrylic acid ethoxyethyl ester, (meth)acrylic acid methoxyethylene glycol ester, (meth)acrylic acid tetrahydrofurfuryl ester, (meth)acrylic acid methoxyethylene glycol ester, (meth)acrylic acid methoxydiethylene glycol ester, (meth)acrylic acid methoxypolyethylene glycol ester, and (meth)acrylic acid methoxypolypropylene glycol ester, and vinyl monomers such as (meth)acrylonitrile, vinyl acetate, vinyl propionate, N-vinyl-2-pyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidine, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinylcaprolactam, vinyloxazole, and vinylmorpholine. These can be used alone or in combination of two or more.

[0037] The water-dispersible polymer can be prepared as a water dispersion of a (meth)acrylic acid alkyl ester copolymer, for example, by subjecting a mixture of a monomer mixture containing a (meth)acrylic acid alkyl ester and a silane-based monomer to conventional emulsion polymerization.

[0038] As the polymerization method, general batch polymerization, continuous dropping polymerization, divided dropping polymerization, etc. can be adopted, and the polymerization temperature is, for example, 20°C to 100°C.

[0039] The polymerization initiator used in the polymerization is not particularly limited, and a general component used as a polymerization initiator can be used.

[0040] A chain transfer agent may be used in the polymerization to adjust the degree of polymerization. The chain transfer agent is not particularly limited, and a general component used as a chain transfer agent may be used.

[0041] In addition to the above-mentioned method, the water-dispersible copolymer may also be prepared by obtaining a copolymer of a monomer mixture containing a (meth)acrylic acid ester and a silane-based monomer by a method other than emulsion polymerization, and then dispersing the copolymer in water with an emulsifier.

[0042] The organic liquid component contained in the acrylic emulsion adhesive is blended into the water-dispersible copolymer, which not only maintains good adhesion to the surface of the skin 2, but also reduces damage to the keratin when peeled off from the surface of the skin 2, and also reduces pain when peeled off.

[0043] The organic liquid component is preferably liquid at room temperature and has good compatibility with the water-dispersible copolymer. Here, "compatibility" refers to the state in which the organic liquid component is uniformly dissolved and incorporated into the water-dispersible copolymer, and separation cannot be confirmed visually.

[0044] Examples of organic liquid components include esters of monobasic or polybasic acids having 8 to 18 carbon atoms and branched alcohols having 14 to 18 carbon atoms, and esters of unsaturated fatty acids or branched acids having 14 to 18 carbon atoms and tetrahydric or lower alcohols.

[0045] Examples of esters of monobasic or polybasic acids having 8 to 18 carbon atoms with branched alcohols having 14 to 18 carbon atoms include isostearyl laurate, isocetyl myristate, octyldodecyl myristate, isostearyl palmitate, isocetyl stearate, octyldodecyl oleate, diisostearyl adipate, diisocetyl sebacate, trioleyl trimellitate, and triisocetyl trimellitate.

[0046] Examples of unsaturated fatty acids or branched acids having 14 to 18 carbon atoms include myristoleic acid, oleic acid, linoleic acid, linolenic acid, isopalmitic acid, and isostearic acid.

[0047] Examples of tetrahydric or lower alcohols include ethylene glycol, propylene glycol, glycerin, trimethylolpropane, pentaerythritol, and sorbitan.

[0048] The content of the organic liquid component can be appropriately set according to the type of water-dispersible copolymer and organic liquid component, and may be, for example, 20 wt % to 80 wt % relative to 100 wt % of the water-dispersible copolymer.

[0049] When the acrylic emulsion adhesive is a silane emulsion adhesive, specifically, a silane emulsion adhesive containing 2-ethylhexyl acrylate, methyl methacrylate, acrylic acid, and 3-methacryloxypropyltrimethoxysilane can be used as the acrylic emulsion adhesive.

[0050] The acrylic emulsion pressure-sensitive adhesive may be a two-component or three-component acrylic emulsion pressure-sensitive adhesive containing a monomer mixture containing a (meth)acrylic acid alkyl ester and a carboxyl group-containing monomer, which may contain solvents and other components in appropriate amounts within the range that allows performance to be exhibited.

[0051] The monomer mixture containing the (meth)acrylic acid alkyl ester contained in the two-component or three-component acrylic emulsion adhesive is similar to the monomer mixture containing the (meth)acrylic acid alkyl ester contained in the above-mentioned silane-based emulsion adhesive, so details are omitted.

[0052] The carboxyl group-containing monomer is preferably a carboxyl group-containing monomer copolymerizable with a (meth)acrylic acid alkyl ester. The carboxyl group-containing monomer copolymerizable with a (meth)acrylic acid alkyl ester is the same as the carboxyl group-containing monomer contained in the above-mentioned monomer mixture containing a (meth)acrylic acid alkyl ester, and therefore details thereof will be omitted.

[0053] Specifically, the two-component acrylic emulsion adhesive may be an adhesive containing 2-ethylhexyl acrylate, which is a monomer mixture containing a (meth)acrylic acid alkyl ester, and acrylic acid, which is a carboxyl group-containing monomer mixture.

[0054] Specifically, the three-component acrylic emulsion adhesive may be an adhesive containing 2-ethylhexyl acrylate and methyl methacrylate, which are a monomer mixture containing an alkyl (meth)acrylate ester, and acrylic acid, which is a carboxyl group-containing monomer mixture.

[0055] The average particle size of the aqueous emulsion adhesive is preferably 100 nm to 1.0 μm, more preferably 100 nm to 500 nm, and even more preferably 100 nm to 300 nm. When the average particle size is within the above preferred range, adhesive strength and water resistance can be imparted to the adhesive electrode 1 for acquiring biological signals.

[0056] The shape of the aqueous emulsion pressure-sensitive adhesive is not particularly limited, and may be, for example, spherical, ellipsoidal, spindle-like, crushed, plate-like, columnar, or the like.

[0057] The average particle size refers to the volume-average particle size based on the effective diameter. The average particle size is the particle size (median diameter) when the cumulative amount of particles, starting from the smallest, accounts for 50% of the volume on a particle size distribution curve obtained by measuring the particle size distribution of an emulsion pressure-sensitive adhesive or an acrylic emulsion pressure-sensitive adhesive using, for example, laser diffraction / scattering or dynamic light scattering.

[0058] The content of the aqueous emulsion adhesive is preferably 35 wt% to 90 wt%, more preferably 40 wt% to 85 wt%, and even more preferably 50 wt% to 80 wt%, relative to 100 wt% of the adhesive electrode for acquiring biological signals. When the content of the aqueous emulsion adhesive is within the above preferred range, adhesive strength and flexibility can be imparted to the adhesive electrode for acquiring biological signals 1, and a decrease in conductivity can be suppressed.

[0059] The neutralizing agent contained in the adhesive electrode for acquiring a biological signal 1 exerts a neutralizing effect on the conductive polymer, neutralizing the conductive polymer and improving flexibility. When the conductive polymer is, for example, PEDOT-PSS, even if the PEDOT-PSS has acidic properties, the neutralizing agent can effectively exert a neutralizing effect on the PEDOT-PSS, thereby effectively neutralizing the PEDOT-PSS.

[0060] Preferred examples of the neutralizing agent include imidazole compounds.

[0061] The imidazole compound is an organic structure having an imidazole group. The imidazole group of the imidazole compound acts as a neutralizing agent, for example, in the pH range of 3.5 to 6.5. Examples of the imidazole compound include heterocyclic amines.

[0062] Examples of heterocyclic amines include imidazole, 2-methylimidazole, 2-propylimidazole, 2-undecylimidazole, 2-phenylimidazole, N-methylimidazole, 1-(2-hydroxyethyl)imidazole, 2-ethyl-4-methylimidazole, 1,2-dimethylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, and 1-cyanoethyl Examples of the neutralizing agent include 4,5-imidazoledicarboxylic acid, 4,5-imidazoledicarboxylic acid dimethyl ester, benzimidazole, 2-aminobenzimidazole, 2-aminobenzimidazole-2-sulfonic acid, 2-amino-1-methylbenzimidazole, 2-hydroxybenzimidazole, and 2-(2-pyridyl)benzimidazole. Among these, imidazole is preferred. The neutralizing agent may be an imidazole compound, which may be used alone or in combination of two or more.

[0063] The content of the neutralizer is preferably 0.5 wt% to 2.4 wt%, more preferably 0.7 wt% to 2.2 wt%, and even more preferably 1.0 wt% to 2.0 wt%, relative to 100 wt% of the adhesive electrode for acquiring biological signals.

[0064] The moisturizing agent contained in the adhesive electrode 1 for acquiring a biological signal has the function of improving the conductivity of the adhesive electrode 1 for acquiring a biological signal, as well as improving the adhesive strength and flexibility.

[0065] Examples of moisturizing agents include polyol compounds such as glycerin, ethylene glycol, propylene glycol, sorbitol, and polymers thereof, and aprotic compounds such as N-methylpyrrolidone (NMP), dimethylformaldehyde (DMF), N-N'-dimethylacetamide (DMAc), and dimethyl sulfoxide (DMSO). These may be used alone or in combination of two or more. Among these, glycerin is preferred from the viewpoint of compatibility with other components.

[0066] The content of the moisturizer is preferably 2 wt% to 60 wt%, more preferably 3 wt% to 50 wt%, and even more preferably 5 wt% to 35 wt%, relative to 100 wt% of the adhesive electrode for acquiring a biological signal. If the content of the moisturizer is within the above-mentioned preferred range, the adhesive strength of the adhesive electrode for acquiring a biological signal (1) can be improved, high adhesion to the surface of the skin (2) can be maintained, and the storage modulus can be reduced and viscoelasticity can be increased, thereby reducing the amount of noise generated during use. Furthermore, the adhesive electrode for acquiring a biological signal (1) can be prevented from absorbing water from the outside, thereby preventing swelling.

[0067] The pH of the adhesive electrode 1 for acquiring biological signals at 25°C is preferably 3.5 to 7.5, more preferably 3.7 to 7.2, and even more preferably 4.0 to 7.5.

[0068] It should be noted that a known method can be used to measure the pH of the adhesive electrode for acquiring a biological signal 1. Examples of the method for measuring the pH include a method of bringing litmus paper into contact with the adhesive electrode for acquiring a biological signal 1, or a method of bringing litmus paper into contact with a solvent (e.g., water) dropped onto the adhesive electrode for acquiring a biological signal 1 to measure the pH of the solvent, and using the pH of the solvent as the pH of the adhesive electrode for acquiring a biological signal 1.

[0069] The method for manufacturing the adhesive electrode 1 for acquiring a biological signal is not particularly limited. An example of the method for manufacturing the adhesive electrode 1 for acquiring a biological signal will be described below. For example, first, a conductive polymer and a solution containing a neutralizer (neutralizer-containing solution) are mixed to prepare a first mixed solution (conductive polymer neutralization step). The conductive polymer is neutralized by being contained in the neutralizer-containing solution.

[0070] The mixing ratio of the conductive polymer to the neutralizer-containing solution, mixing conditions such as mixing time, temperature of the neutralizer-containing solution, etc. are not particularly limited, and may be set to any appropriate size as long as the conductive polymer can be sufficiently mixed in the neutralizer-containing solution.

[0071] Next, the first mixed solution is mixed with an aqueous emulsion adhesive and a moisturizing agent to prepare a second mixed solution (mixing step).The second mixed solution is used as a composition for forming an adhesive electrode.

[0072] The mixing ratio of the first mixed solution, the aqueous emulsion adhesive, and the moisturizer, the mixing conditions such as the mixing time, the temperature of the second mixed solution, etc. are not particularly limited, and may be set to any appropriate value as long as the aqueous emulsion adhesive and the moisturizer can be sufficiently mixed into the first mixed solution.

[0073] Next, the second mixed solution is applied to the surface (coating surface) of the release substrate, and then dried to evaporate the water contained in the second mixed solution (coating and drying process). Because the aqueous emulsion adhesive has a particulate shape, by applying the second mixed solution to the coating surface of the release substrate, the aqueous emulsion adhesive bonds and fuses to itself, forming a coating film that is a cured product of the adhesive electrode-forming composition.

[0074] The release substrate can be a release liner or a core material. The release liner can be a resin film such as a polyethylene terephthalate (PET) film, a polyethylene (PE) film, a polypropylene (PP) film, a polyamide (PA) film, a polyimide (PI) film, or a fluororesin film. The core material can be a resin film such as a PET film or a PI film; a ceramic sheet; a metal film such as aluminum foil; a resin substrate reinforced with glass fiber or plastic nonwoven fiber; a silicone substrate, a glass substrate, or the like.

[0075] The method for applying the second mixed solution to the application surface of the release substrate is not particularly limited as long as it is possible to apply the second mixed solution to the release substrate, and a general application method may be used.

[0076] Examples of the coating method include roll coating, screen coating, gravure coating, spin coating, reverse coating, bar coating, blade coating, spray coating, air knife coating, dipping, dispensing, etc., and a method of dropping a small amount of the second mixed solution onto the coating surface of the substrate and spreading it with a doctor blade, etc. By these coating methods, the second mixed solution can be uniformly applied onto the coating surface.

[0077] The drying conditions for the second mixed solution applied to the coating surface of the release substrate are not particularly limited as long as they are conditions that allow the second mixed solution applied to the release substrate to be dried, and general drying conditions may be used.

[0078] The drying may be performed at room temperature or by heating using a dryer. Examples of the dryer that can be used include general dryers such as a drying oven, a vacuum oven, an air circulation oven, a hot air dryer, a far-infrared dryer, a microwave vacuum dryer, and a high-frequency dryer. The second mixed solution coated on the surface of the substrate using these dryers may be dried by heating the interior of the dryer to a high temperature, heating the substrate, blowing hot air onto the second mixed solution, or irradiating the second mixed solution with far-infrared rays, microwaves, or high-frequency waves.

[0079] The heating temperature and heating time when heating the second mixed solution using a dryer are set to a temperature and time that can evaporate the water contained in the second mixed solution. The heating temperature may be, for example, 100°C to 200°C. When the conductive composition contains a crosslinking agent, a heating temperature in the range of 100°C to 200°C can promote evaporation of the water contained in the second mixed solution. The heating time of the second mixed solution may be, for example, 0.5 minutes to 300 minutes. A heating time of 0.5 minutes to 300 minutes can sufficiently evaporate the water contained in the second mixed solution.

[0080] Next, the obtained cured product is punched (pressed) using a press or the like as needed to form one or more through-holes in the surface of the cured product and mold the outer shape of the cured product into a predetermined shape (molding step). This results in an adhesive electrode for acquiring a biological signal, which is a molded product having through-holes 11 on the surface and a predetermined outer shape.

[0081] It should be noted that molding may be performed using a laser processing machine instead of a press. The obtained cured product may have only through holes 11 formed on its surface, or only the outer shape may be molded into a predetermined shape. Furthermore, when the cured product can be used as an adhesive electrode for acquiring a biological signal as is, the cured product may be used as an adhesive electrode for acquiring a biological signal without being molded or otherwise processed.

[0082] As described above, the adhesive electrode 1 for acquiring a biological signal contains a conductive polymer, an aqueous emulsion adhesive, a moisturizer, and a neutralizer. By containing a conductive polymer and an aqueous emulsion adhesive, the adhesive electrode 1 for acquiring a biological signal exhibits conductivity and is softened while exhibiting adhesive strength to the skin 2, thereby improving conformability to the surface of the skin 2. Furthermore, by containing a moisturizer, the adhesive electrode 1 for acquiring a biological signal keeps its resistance low. Furthermore, by containing a neutralizer, the adhesive electrode 1 for acquiring a biological signal increases its flexibility, and by adjusting the pH at 25°C to 3.5 to 7.5, it is possible to reduce irritation to the skin 2. Therefore, the adhesive electrode 1 for acquiring a biological signal reduces irritation to the skin 2, has excellent flexibility, and can maintain adhesion to the skin 2 with low resistance.

[0083] The resistance of the adhesive electrode 1 for acquiring a biosignal can be evaluated by measuring the sheet resistance of the adhesive electrode 1 for acquiring a biosignal. The sheet resistance is the surface resistance of the adhesive electrode 1 for acquiring a biosignal. The sheet resistance can be measured using a general resistance measurement method, for example, by an eddy current measurement method using a non-contact resistance measuring device in accordance with JIS Z 2316-1:2014. The measurement range may be a predetermined range on the main surface of the adhesive electrode 1 for acquiring a biosignal.

[0084] The flexibility of the adhesive electrode 1 for acquiring a biosignal can be evaluated by measuring the breaking elongation (also referred to as the breaking elongation percentage) of the adhesive electrode 1 for acquiring a biosignal. The breaking elongation of the adhesive electrode 1 for acquiring a biosignal is preferably 1700% to 5000%, more preferably 2000% to 4500%, and even more preferably 2500% to 4000%. When the breaking elongation of the adhesive electrode 1 for acquiring a biosignal is within the above-mentioned preferred range, the adhesive electrode 1 for acquiring a biosignal can easily stretch while in contact with the surface of the skin 2 and can maintain contact with the surface of the skin 2. This allows the adhesive electrode 1 for acquiring a biosignal to reduce noise generated during measurement of bioinformation and to alleviate discomfort experienced by the subject. Furthermore, it is possible to prevent the adhesive electrode 1 for acquiring a biosignal from becoming too soft and causing the shape of the adhesive electrode 1 to become unstable.

[0085] The breaking elongation of the adhesive electrode 1 for acquiring a biological signal is a value expressed as a percentage, obtained by dividing the elongation in the length between the gauge points when the adhesive electrode 1 for acquiring a biological signal breaks in a tensile test by the length between the gauge points of the adhesive electrode 1 for acquiring a biological signal before the tensile test. The breaking elongation of the adhesive electrode 1 for acquiring a biological signal can be calculated by dividing the amount of elongation (L-Lo) in the length between the gauge points of the broken adhesive electrode 1 for acquiring a biological signal by the length between the gauge points of the adhesive electrode 1 for acquiring a biological signal before the tensile test, and expressing the value as a percentage, as shown in the following formula (1): Breaking elongation (%) = (L - Lo) / Lo × 100 (1) (In the formula, Lo is the gauge length of the adhesive electrode for acquiring a biological signal before the tensile test, and L is the gauge length of the adhesive electrode for acquiring a biological signal after the breakage.)

[0086] The distance between the reference points of the adhesive electrode for acquiring a biological signal is preferably set to the length in the longitudinal direction of the adhesive electrode for acquiring a biological signal 1, since the adhesive electrode for acquiring a biological signal 1 has a shape in which one end in the longitudinal direction is formed into an approximately rectangular shape and the other end is formed into an approximately arc shape when viewed in a plane.

[0087] The breaking elongation of the adhesive electrode 1 for acquiring a biosignal can be measured by conducting a tensile test using a tensile tester in accordance with JIS Z 2241. The distance between the chucks of a pair of jigs that grip both longitudinal ends of the adhesive electrode 1 for acquiring a biosignal is defined as the gauge length, and the tensile test is conducted at a predetermined pulling speed. The point at which the adhesive electrode 1 for acquiring a biosignal breaks is defined as the elongation of the adhesive electrode 1 for acquiring a biosignal.

[0088] To measure the breaking elongation of the adhesive electrode 1 for acquiring a biosignal, a rectangular electrode sheet having a predetermined size may be used as a test specimen. When pulling the rectangular electrode sheet, both ends of the short sides of the rectangular sheet may be gripped and fixed with a tensile test jig, and one or both of the pair of jigs may be moved in the longitudinal direction of the electrode sheet with a predetermined tensile strength to pull the rectangular electrode sheet. The ends of the short sides of the rectangular electrode sheet may be within a predetermined range from the surface of the short side, depending on the size of the rectangular electrode sheet, etc.

[0089] The breaking elongation of the adhesive electrode 1 for acquiring a biological signal may be an average value of the measured values ​​of a plurality of adhesive electrodes 1 for acquiring a biological signal.

[0090] The pulling direction of the adhesive electrode 1 for acquiring a biosignal when measuring the breaking elongation of the adhesive electrode 1 for acquiring a biosignal may be changed as appropriate depending on the shape of the adhesive electrode 1 for acquiring a biosignal in a planar view. For example, when the shape of the adhesive electrode 1 for acquiring a biosignal in a planar view is elliptical, the breaking elongation of the adhesive electrode for acquiring a biosignal is preferably the breaking elongation in the long axis direction of the adhesive electrode 1 for acquiring a biosignal. When the shape of the adhesive electrode 1 for acquiring a biosignal in a planar view is rectangular, the breaking elongation of the adhesive electrode 1 for acquiring a biosignal is preferably the breaking elongation in the longitudinal direction of the adhesive electrode 1 for acquiring a biosignal. When the shape of the adhesive electrode 1 for acquiring a biosignal is square in a planar view, the breaking elongation of the adhesive electrode 1 for acquiring a biosignal may be the breaking elongation in the direction of one side of the adhesive electrode 1 for acquiring a biosignal. When the adhesive electrode 1 for acquiring a biological signal has a circular shape in a plan view, the breaking elongation of the adhesive electrode 1 for acquiring a biological signal may be the breaking elongation of the diameter of the adhesive electrode 1 for acquiring a biological signal.

[0091] The adhesive electrode for acquiring a biological signal 1 can contain an imidazole compound as a neutralizing agent, which ensures that the adhesive electrode for acquiring a biological signal 1 is flexible and neutralized, thereby ensuring reduced irritation to the skin 2 and increased flexibility.

[0092] The content of the neutralizing agent in the adhesive electrode for acquiring a biological signal 1 can be set to 0.5 wt % to 2.4 wt %, which increases the flexibility of the adhesive electrode for acquiring a biological signal 1 and enables neutralization to be more reliably achieved, thereby reliably reducing irritation to the skin 2 and further increasing the flexibility.

[0093] The adhesive electrode 1 for acquiring a biological signal can use an acrylic emulsion adhesive instead of a water-based emulsion adhesive. This allows the adhesive electrode 1 for acquiring a biological signal to suppress a decrease in adhesive strength while maintaining resistance, and to reliably improve conformability to the surface of the skin 2. Therefore, the adhesive electrode 1 for acquiring a biological signal can have high adhesive strength and conformability to the surface of the skin 2.

[0094] The adhesive electrode 1 for acquiring a biological signal can use a silane emulsion adhesive containing a water-dispersible copolymer and an organic liquid component in addition to the acrylic emulsion adhesive. This reliably keeps the viscoelasticity of the adhesive electrode 1 for acquiring a biological signal low, thereby increasing the adhesive strength and further improving the conformability to the surface of the skin 2. Therefore, the adhesive electrode 1 for acquiring a biological signal can further increase its flexibility and more reliably maintain its adhesiveness.

[0095] As described above, the adhesive electrode 1 for acquiring biological signals exhibits high flexibility while reducing irritation to the skin, and can maintain adhesion with low resistance, so it can be effectively used as an electrode (bioelectrode) for biological sensors, particularly adhesive-type biological sensors that require adhesion to human skin, high flexibility, and safety for the skin.

[0096] Although the embodiments have been described above, they are presented as examples and the present invention is not limited to the above embodiments. The above embodiments can be implemented in various other forms, and various combinations, omissions, substitutions, modifications, etc. can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as set forth in the claims. [Example]

[0097] Hereinafter, the embodiment will be described in more detail with reference to examples and comparative examples, but the embodiment is not limited to these examples and comparative examples.

[0098] <Preparation of electrode sheet> [Example 1] A first mixed solution was prepared by adding 1.0 g of PEDOT / PSS pellets (Orgacon DRY, manufactured by Agfa Materials Japan) as a conductive polymer and 23 g of an imidazole solution with an imidazole concentration of 30 mM to a plastic container and mixing while stirring and degassing using a planetary stirring and degassing device. Next, 12.5 g of a silane-based emulsion adhesive (manufactured by Nitto Denko Corporation) as a binder resin and 2.0 g of glycerin (manufactured by Wako Pure Chemical Industries, Ltd.) as a humectant were added to the plastic container and mixed with the first mixed solution to prepare a uniformly mixed second mixed solution, which is a composition for forming an adhesive electrode. A coating film, which is a cured product of the adhesive composition for forming an adhesive electrode, was prepared by applying the second mixed solution and drying it. The coating film was then stamped (pressed) into a sheet with the desired rectangular shape shown in Figure 1 in plan view, to prepare an adhesive electrode sheet (bioelectrode).

[0099] The imidazole concentration in the imidazole solution is 30 mM, so the imidazole content is 0.047 g. This is approximately 52% of the silane emulsion adhesive in the silane emulsion adhesive aqueous solution, so the silane emulsion adhesive content is 6.5 g.

[0100] [Examples 2 to 5] In Example 1, the imidazole concentration of the imidazole solution used to prepare the electrode sheet was changed from 30 mM to 60 mM, 90 mM, 102 mM, or 150 mM, as shown in Table 1. The electrode sheet was prepared in the same manner as in Example 1.

[0101] <Comparative Example 1> An electrode sheet was produced in the same manner as in Example 1, except that water was used as the neutralizing agent instead of the imidazole solution used in producing the electrode sheet.

[0102] <Comparative Example 2> An electrode sheet was produced in the same manner as in Example 1, except that an aqueous sodium hydroxide solution was used instead of the neutralizing agent used in producing the electrode sheet in Example 1.

[0103] Table 1 shows the amounts of conductive polymer, silane emulsion adhesive, imidazole solution, and glycerin contained in the electrode sheets and the solid content of each of these components in each of the above examples and comparative examples.

[0104] [Table 1]

[0105] <Evaluation of electrode sheets> The pH, sheet resistance, and breaking elongation of the obtained electrode sheets of each of the examples and comparative examples were measured.

[0106] [pH] The obtained electrode sheet was wetted with drops of water, and then litmus paper was dipped into the water attached to the electrode sheet to measure the pH of the water, and this measured pH of the water was taken as the pH of the electrode sheet.

[0107] [Sheet resistance] Using a non-contact resistance measuring instrument (NC-80NC, manufactured by Napson Co., Ltd.), the sheet resistance was measured as the surface resistance of the electrode sheet by the eddy current measurement method in accordance with JIS Z 2316-1:2014. The measurement range was 0.5 mm to 150 mm from the main surface of the electrode sheet. The target value for sheet resistance was set to 100 Ω / □ to ensure high detection accuracy when the electrode sheet is used as a biological electrode. Sheet resistances of 100 Ω / □ or less were evaluated as "good," and those exceeding 100 Ω / □ were evaluated as "poor." The measurement results for the sheet resistance of the electrode sheets of each example and comparative example are shown in Table 2. The relationship between the imidazole concentration and sheet resistance of the electrode sheets of each example and comparative example 1 is shown in Figure 2.

[0108] [Elongation at break] The breaking elongation of the electrode sheet was measured using a tensile tester (AGS-J, manufactured by Shimadzu Corporation) in accordance with JIS Z 2241. The breaking elongation of the electrode sheet was measured in the longitudinal direction of the electrode sheet. For the breaking elongation measurement, an electrode sheet cut into a rectangle with a short side of 10 mm, a long side of 70 mm, and a thickness of 0.5 mm was used as a test piece (sample). Both ends of the short side of the electrode sheet were gripped and fixed with a tensile test jig. The distance between the chucks of the tensile test jig was defined as the gauge length in the longitudinal direction of the electrode sheet. The tensile test conditions were as follows. Table 2 shows the measurement results of the breaking elongation of the electrode sheets of each Example and Comparative Example. The relationship between the imidazole concentration and the breaking elongation in the longitudinal direction of the electrode sheets of each Example and Comparative Example 1 is shown in Figure 3. (Tensile test conditions) Distance between chucks of tensile test fixtures: 50 mm Tensile strength: 300mm / min

[0109] [Table 2]

[0110] As can be seen from Table 2, in each example, the sheet resistance of the electrode sheet was kept below 100 Ω / □ and the breaking elongation was sufficiently high. In contrast, in Comparative Example 1, the breaking strength of the sheet electrode was low, and in Comparative Example 2, the sheet resistance was high.

[0111] Therefore, it was confirmed that the electrode sheets of the above examples can reduce the burden on the skin while having excellent flexibility, low resistance, and maintaining adhesiveness, by setting the imidazole concentration of the imidazole used as the neutralizing agent to a predetermined value. Therefore, even if the adhesive electrode for acquiring biological signals according to this embodiment is attached to the skin of a subject for a long period of time (e.g., 24 hours), it can be said that it can be effectively used to stably measure biological information without continuously placing a burden on the subject for a long period of time.

[0112] The embodiments of the present invention are as follows, for example. <1> It contains a conductive polymer, a water-based emulsion adhesive, a moisturizer, and a neutralizer. An adhesive electrode for acquiring biological signals, having a pH of 3.5 to 7.5 at 25°C. <2> The neutralizing agent contains an imidazole compound. <1> The adhesive electrode for acquiring a biological signal according to claim 1. <3> The content of the neutralizing agent is 0.5 wt% to 2.4 wt%. <1> or <2> The adhesive electrode for acquiring a biological signal according to claim 1. <4> The aqueous emulsion pressure-sensitive adhesive is an acrylic emulsion pressure-sensitive adhesive. <1> ~ <3> 10. An adhesive electrode for acquiring a biological signal according to any one of the above. <5> The acrylic emulsion pressure-sensitive adhesive is a silane emulsion pressure-sensitive adhesive containing a water-dispersible copolymer and an organic liquid component that is compatible with the water-dispersible copolymer. <4> The adhesive electrode for acquiring a biological signal according to claim 1. <6> <1> ~ <5> A biosensor comprising the adhesive electrode for acquiring a biosignal according to any one of the above. [Explanation of symbols]

[0113] 1. Adhesive electrodes for acquiring biosignals 11, 11A, 11B through hole

Claims

1. It contains a conductive polymer, a water-based emulsion adhesive, a moisturizer, and a neutralizer. An adhesive electrode for acquiring biological signals, having a pH at 25°C of 3.5 to 7.

5.

2. The adhesive electrode for acquiring a biological signal according to claim 1 , wherein the neutralizing agent includes an imidazole compound.

3. 2. The adhesive electrode for acquiring biological signals according to claim 1, wherein the content of the neutralizing agent is 0.5 wt % to 2.4 wt %.

4. 2. The adhesive electrode for acquiring biological signals according to claim 1, wherein the aqueous emulsion adhesive is an acrylic emulsion adhesive.

5. The adhesive electrode for acquiring biological signals according to claim 4, wherein the acrylic emulsion adhesive is a silane emulsion adhesive containing a water-dispersible copolymer and an organic liquid component that is compatible with the water-dispersible copolymer.

6. A biosensor comprising the adhesive electrode for acquiring biosignals according to any one of claims 1 to 5.

Images