Deep eutectic liquid, biometric electrode composition, biometric electrode, and method for producing biometric electrode

Abstract

To provide a deep eutectic liquid that has high ionic conductivity and is safe even when brought into contact with a living body, and a biometric electrode composition containing the deep eutectic liquid, the biometric electrode composition being capable of being attached to skin to rapidly collect signals, causing no residue on skin, stably acquiring biological signals over a long period, and forming a biological contact layer for a biometric electrode.SOLUTION: A deep eutectic liquid is a mixture of a hydrogen bond donor compound and a hydrogen bond acceptor compound, wherein the hydrogen bond donor compound is a compound having a structure in which 2 to 100 monomers each having a hydroxyl group are bonded, as represented by general formula (1), the hydrogen bond acceptor compound is a specific compound containing a monomer having a quaternary ammonium cation or a quaternary phosphonium cation, and the deep eutectic liquid exists as a liquid at 25°C.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a deep eutectic liquid, a bioelectrode composition, a bioelectrode, and a method for manufacturing a bioelectrode. [Background technology]

[0002] In recent years, the development of wearable devices has progressed along with the spread of IoT (Internet of Things). Typical examples are watches and eyeglasses that can connect to the internet. Furthermore, wearable devices that can constantly monitor the state of the body are needed in the medical and sports fields, and these are expected to be growth areas in the future.

[0003] In the medical field, wearable devices that monitor the state of the body's organs by sensing weak currents, such as in electrocardiograms, which detect heart activity through electrical signals, are being considered. Electrocardiograms are measured by wearing electrodes coated with conductive paste on the body, but this is a one-time, short-term measurement. In contrast, the goal of developing medical wearable devices like those mentioned above is to develop devices that can continuously monitor health status for several weeks. Therefore, bioelectrodes used in medical wearable devices must not change in conductivity even with long-term use and must not cause skin allergies. In addition to these, they must also be lightweight and low-cost to manufacture.

[0004] Wearable medical devices include those that are attached to the body and those that are incorporated into clothing. One proposed type of bioelectrode that is attached to the body is a water-soluble gel containing water and electrolytes, the same materials used in the conductive paste mentioned above (Patent Document 1). The water-soluble gel contains sodium, potassium, and calcium as electrolytes in a water-soluble polymer that retains water, and converts changes in ion concentration from the skin into electricity. Meanwhile, one proposed type that is incorporated into clothing is a method that uses a cloth fabric with conductive polymers such as PEDOT-PSS (Poly-3,4-ethylenedioxythiophene-Polystyrenesulfonate) or silver paste incorporated into the fibers as an electrode (Patent Document 2).

[0005] However, when using the water-soluble gel containing water and electrolytes, there is a problem that the conductivity is lost when the water dries out. On the other hand, when using metals with a high tendency to ionize, such as copper, there is a risk of causing skin allergies in some people, and when using conductive polymers such as PEDOT-PSS, there is also a risk of causing skin allergies due to the conductive polymer's strong acidity, and there is also the problem of the conductive polymer peeling off from the fabric during washing.

[0006] Furthermore, due to their excellent electrical conductivity, the use of metal nanowires, carbon black, carbon nanotubes, and the like as electrode materials has also been investigated (Patent Documents 3, 4, and 5). Metal nanowires have a high probability of contact between wires, allowing current to flow with a small amount of additive. However, metal nanowires are thin materials with sharp tips, which can cause skin allergies. Carbon nanotubes are also irritating to living organisms for the same reason. Carbon black is not as toxic as carbon nanotubes, but it is somewhat irritating to the skin. Thus, even if a material itself does not cause an allergic reaction, its biocompatibility may be impaired depending on the material's shape or irritability, making it difficult to achieve both electrical conductivity and biocompatibility.

[0007] Metal films are highly conductive, so one might think they would function as excellent bioelectrodes, but this is not necessarily the case. When the heart beats, not only a weak current is released from the skin, but also sodium ions, potassium ions, and calcium ions. For this reason, it is necessary to convert the change in ion concentration into an electric current, but precious metals, which are difficult to ionize, are inefficient at converting ions from the skin into an electric current. Therefore, bioelectrodes using precious metals have high impedance, and there is high resistance to the passage of electricity between them and the skin.

[0008] A lithium ion conductive composite for solid electrolytes has been proposed, which uses a silicon atom-containing compound having a segment containing lithium ions. It is known that this composite has good electrical conductivity and a good lithium ion transport number at the temperature at which the battery is used, as well as excellent mechanical properties, moldability, and adhesion to electrodes, resulting in a highly safe battery with reduced or eliminated risks such as fire and leakage (Patent Document 6).

[0009] Bioelectrodes with added ionic polymers have been proposed (Patent Documents 7, 8, 9, and 10). Bioelectrodes made by adding ionic polymers and carbon powder to a silicone adhesive have adhesive properties, making it possible to collect biosignals even when attached to the skin for long periods of time. Ionic polymers do not pass through the skin, so they are not irritating to the skin and are highly biocompatible.

[0010] Silicone is an insulator by nature, but the combination of ionic polymer and carbon powder improves its ionic conductivity, allowing it to function as a bioelectrode. However, further improvements in ionic conductivity are needed to improve performance.

[0011] The aforementioned Patent Documents 7, 8, 9, and 10 show that silicone compound additives with polyether chains are effective in improving ionic conductivity. Polyether chains are also used to improve the ionic conductivity of lithium-ion polymer batteries and are effective in improving ionic conductivity. However, the ionic conductivity of aqueous gels is lower than that of hydrous gels, and further improvement of ionic conductivity is necessary.

[0012] Bioelectrodes need to be able to pick up signals immediately after being attached to the skin. With gel electrodes, the ion concentrations of the skin and the electrode are similar, allowing ions to move in and out smoothly, and the ions move quickly in the hydrogel, so signals can be detected immediately after being attached to the skin. On the other hand, with dry electrodes, it takes a long time for a signal to be detected after being attached to the skin. This is thought to be because a signal is not produced until the ions released from the skin are saturated on the surface of the dry electrode.

[0013] Furthermore, the aforementioned Patent Documents 7, 8, 9, and 10 disclose bioelectrodes that use ionic polymers alone or in combination with compounds containing resins, conductive particles, and polyglycerin. However, because ionic polymers exist as solids in a dry state, they are likely to exist as solids in dry electrodes. Although solid electrolytes are also known, the ionic conductivity of the ionic polymers described in the aforementioned Patent Documents 7, 8, 9, and 10 has not been confirmed. Furthermore, because liquids generally have higher ionic conductivity than solids, ionic polymers localized in dry electrodes are likely to be at a disadvantage in terms of ionic conductivity. Therefore, ionic polymers are likely to have inferior ionic conductivity to aqueous gels.

[0014] On the other hand, a material called a deep eutectic liquid is known, which is obtained by mixing a hydrogen bond donor compound with a hydrogen bond acceptor compound. The characteristics of deep eutectic liquids include being liquid at room temperature, having a low vapor pressure, not volatilizing like water, being flame retardant, thermally stable, electrochemically stable, electrically conductive, low cost, environmentally friendly, and low toxicity. Because deep eutectic liquids are liquids, incorporating them into dry electrodes is expected to reduce ionic conductivity and interface resistance with living organisms.

[0015] However, because there are a wide variety of combinations of deep eutectic liquids, when used in dry electrodes, they must be composed of materials that are not skin irritating or toxic, i.e., the hydrogen bond donor and hydrogen bond acceptor compounds must each be selected from biocompatible materials.

[0016] Patent Document 11 shows a food product containing a flavor composition using a deep eutectic liquid. Because food products are ingested into the human body, they must be biocompatible and non-toxic. Examples of such deep eutectic liquids include amino acids, sugars, and compounds produced in the body, and these compounds are thought to be suitable for application to dry electrodes.

[0017] By incorporating such biocompatible deep eutectic liquid into dry electrodes, it is expected that the ionic conductivity of the dry electrodes will be improved. Furthermore, because deep eutectic liquid is liquid, it can reduce the interfacial resistance between the living body and the dry electrodes. As a result, signals can be acquired immediately after application to the skin, and there is no baseline drift even when moving, enabling stable acquisition of biosignals.

[0018] Furthermore, Patent Documents 12, 13, and 14 disclose conductive resins using deep eutectic liquids, methods for manufacturing the same, and sensors incorporating the conductive resins. Deep eutectic liquids can be volatilized in specific combinations, forming porous structures. The porous films produced in this way are highly pressure-sensitive and can be used as resistance-change sensors, attached to the human body to acquire biometric information. However, because resistance changes cause noise in bioelectrodes, conductive resins produced in this way cannot acquire stable signals as bioelectrodes.

[0019] Furthermore, Patent Documents 15 and 16 disclose bioelectrodes and wearable devices using ionic liquids. Ionic liquids are liquid materials with properties similar to those of deep eutectic liquids, and when incorporated into bioelectrodes, they are thought to be effective in reducing interfacial resistance with living organisms. However, because many ionic liquids contain compounds that are biotoxic, they have rarely been used as biomaterials. In fact, the 1-butyl-3-methylimidazolium tetrafluoroborate and 1-ethyl-3-methylimidazolium tetracyanoborate shown in Patent Documents 15 and 16 are compounds that may cause chemical burns and are toxic through the skin, and are therefore considered to be suitable for short-term wear and not for long-term use.

[0020] As such, bioelectrodes for wearable devices need to be able to acquire biosignals immediately after application to the skin and stably for a long period of time, but the development of dry electrodes has posed many problems. Therefore, there is a need for the development of bioelectrodes that are highly ionic conductive, made of materials that are safe for contact with the body, can be attached and removed without leaving any residue or irritation on the skin, and can acquire biosignals stably for a long period of time immediately after application to the skin. [Prior art documents] [Patent documents]

[0021] [Patent Document 1] International Publication No. 2013-039151 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-100673 [Patent Document 3] Japanese Patent Application Publication No. 05-095924 [Patent Document 4] Japanese Patent Application Laid-Open No. 2003-225217 [Patent Document 5] Japanese Patent Application Publication No. 2015-019806 [Patent Document 6] Japanese Patent Application Laid-Open No. 2007-059092 [Patent Document 7] Japanese Patent Application Publication No. 2019-180467 [Patent Document 8] Patent Publication No. 2021-115458 [Patent Document 9] Japanese Patent Publication No. 2022-075537 [Patent Document 10] Japanese Patent Publication No. 2022-075544 [Patent Document 11] Special Publication No. 2016-538405 [Patent Document 12] Japanese Patent Publication No. 2022-085568 [Patent Document 13] Japanese Patent Publication No. 2022-085569 [Patent Document 14] Japanese Patent Application Publication No. 2023-176396 [Patent Document 15] Japanese Patent Application Laid-Open No. 2015-016166 [Patent Document 16] Japanese Patent Application Laid-Open No. 2015-077226 Summary of the Invention [Problem to be solved by the invention]

[0022] The present invention has been made to solve the above problems, and aims to provide a deep eutectic liquid that has high ionic conductivity and is safe even when in contact with a living body; a bioelectrode composition containing the deep eutectic liquid that can be applied to the skin to quickly collect signals, does not leave any residue on the skin, can stably acquire biosignals for a long period of time, and can form a biocontact layer for a bioelectrode; a bioelectrode in which a biocontact layer is formed from the bioelectrode composition; and a method for manufacturing the same. [Means for solving the problem]

[0023] In order to solve the above problems, the present invention provides a deep eutectic liquid that is a mixture of a hydrogen bond donor compound and a hydrogen bond accepting compound, wherein the hydrogen bond donor compound is a compound having a structure in which 2 to 100 hydroxyl group-containing monomers are bonded, as shown in the following general formula (1), and the hydrogen bond accepting compound is a compound containing a monomer having a quaternary ammonium cation shown in the following general formulas (2) to (6), or a quaternary phosphonium cation shown in the following general formula (7), and the deep eutectic liquid exists as a liquid at 25°C. [ka] (In the formula, X represents a single bond or a linear, branched, or cyclic divalent hydrocarbon group having 1 to 30 carbon atoms, which may be substituted with or interrupted by a heteroatom. Y and Z represent a linear, branched, or cyclic divalent hydrocarbon group having 1 to 5 carbon atoms, which may be substituted with or interrupted by a heteroatom. A and B represent a hydrogen atom, a hydroxyl group, an amino group, a halogen atom, or an alkyl group or an alkyl group terminally substituted with a siloxane, which may be substituted with or interrupted by a heteroatom. Y and Z may be the same or different. A and B may be the same or different. m is an integer of 1 to 100 and represents a repetition of a chemical structural unit. n is an integer of 1 to 4 and represents a repetition of a chemical structural unit, provided that 2≦m×n≦100 is satisfied.) [ka] (In the formula, R1~R 12 R1 to R2 are a linear, branched, or cyclic monovalent hydrocarbon group having 1 to 30 carbon atoms, a hydrogen atom, a hydroxyl group, an amino group, a nitro group, or a halogen atom, which may be substituted with a heteroatom, may be interposed between heteroatoms, or may be a zwitterion having an anion moiety. 12 may be the same or different.)

[0024] Such a deep eutectic liquid has high ionic conductivity and is safe for contact with living organisms.

[0025] In the present invention, the monomer having a hydroxyl group is preferably glycerin.

[0026] Such a deep eutectic liquid has higher ionic conductivity and is safer even when it comes into contact with living organisms.

[0027] In this case, the hydrogen bond donor compound is preferably a polyglycerin-modified silicone represented by the following general formula (8) or (9). [ka] (In the formula, R1' are each independent and may be the same or different from each other, and are a hydrogen atom, a linear or branched alkyl group having 1 to 50 carbon atoms, or a phenyl group, and may contain an ether group or may be a silicone chain represented by general formula (10). R2' is a group having a polyglycerin structure represented by general formula (8)-1 or general formula (8)-2. R3' are each independent and may be the same or different from each other, and are R1' or R2'. R4' are each independent and may be the same or different from each other, and are R1' or R2'. or an oxygen atom. When R4' is an oxygen atom, two R4' may be bonded to form a single ether group, which may form a ring together with the silicon atom to which they are bonded. a' may be the same or different and is 0 to 100, b' is 0 to 100, and a' + b' is 0 to 200. However, when b' is 0, at least one of R3' is the above-mentioned R2'. R5' is an alkylene group having 2 to 10 carbon atoms or an aralkylene group having 7 to 10 carbon atoms. R6' and R7' are alkylene groups having 2 to 6 carbon atoms, and R7' may be an ether group. c' is 0 to 20, and d' is 2 to 20.

[0028] If a deep eutectic liquid using the above compound is used, a bioelectrode using a bioelectrode composition containing this will have biocompatibility and ionic conductivity, and can be attached to the skin to quickly collect signals, allowing for stable, long-term acquisition of biosignals.

[0029] The present invention also provides a bioelectrode composition, which contains the above-described deep eutectic liquid.

[0030] Such a bioelectrode composition can be applied to the skin to quickly collect signals, does not leave any residue on the skin, and can form a biocontact layer for a bioelectrode that can stably acquire biosignals for a long period of time.

[0031] In the present invention, the bioelectrode composition preferably contains a binder (A).

[0032] By including the binder (A), the bioelectrode composition can prevent the elution of the deep eutectic liquid and exhibit adhesiveness.

[0033] In this case, the binder (A) is preferably one or more resins selected from silicone resins, polyurethane resins, and polyacrylic resins.

[0034] Such a binder (A) has good adhesion to the living body and can prevent the binder from remaining on the skin.

[0035] In the present invention, the bioelectrode composition preferably contains conductive particles (B).

[0036] In this case, it is preferable that the conductive particles (B) contain one or more types selected from carbon powder, gold, silver, silver chloride, platinum, aluminum, magnesium, tin, tungsten, iron, copper, nickel, stainless steel, chromium, titanium, molybdenum, ruthenium, and indium.

[0037] In this case, the carbon powder is preferably either or both of carbon black and carbon nanotubes.

[0038] Such conductive particles (B) can reduce the interface resistance between the bioelectrode and the living body.

[0039] In the present invention, it is also preferable that the bioelectrode composition further contains glycerin.

[0040] When the bioelectrode composition contains glycerin, the interface resistance with the living body can be further reduced and the ionic conductivity can be further increased.

[0041] The present invention also provides a bioelectrode having a conductive substrate and a biocontact layer formed on the conductive substrate, wherein the biocontact layer contains a cured product of the bioelectrode composition described above.

[0042] The bioelectrode of the present invention has a biocontact layer containing the cured product of the above-mentioned bioelectrode composition, and therefore has excellent conductivity and biocompatibility, is lightweight, and can be manufactured at low cost. It can prevent a significant decrease in conductivity whether it is wet or dry, does not leave any residue on the skin, and can be attached to the skin to quickly collect signals.

[0043] In this case, the conductive substrate preferably contains one or more selected from gold, silver, silver chloride, platinum, aluminum, magnesium, tin, tungsten, iron, copper, nickel, stainless steel, chromium, titanium, and carbon.

[0044] As described above, various conductive substrates can be used in the bioelectrode of the present invention.

[0045] The present invention also provides a method for manufacturing a bioelectrode having a conductive substrate and a biocontact layer formed on the conductive substrate, in which the bioelectrode composition described above is applied to the conductive substrate and cured to form the biocontact layer.

[0046] This manufacturing method makes it possible to easily and inexpensively manufacture a bioelectrode that is highly conductive and biocompatible, lightweight, and can prevent a significant decrease in conductivity whether wet or dry, and that can be attached to the skin to quickly collect signals.

[0047] In this case, it is preferable to use a conductive substrate containing one or more selected from gold, silver, silver chloride, platinum, aluminum, magnesium, tin, tungsten, iron, copper, nickel, stainless steel, chromium, titanium, and carbon.

[0048] As described above, in the method for producing a bioelectrode of the present invention, various conductive substrates can be used.

[0049] Furthermore, the present invention provides a method for manufacturing a bioelectrode having a conductive substrate and a biocontact layer formed on the conductive substrate, in which the bioelectrode composition described above is applied to a release substrate, cured, and patterned, and the patterned product is transferred onto the conductive substrate to form the biocontact layer.

[0050] This manufacturing method makes it possible to easily and inexpensively manufacture bioelectrodes that are highly conductive and biocompatible, lightweight, and can prevent a significant decrease in conductivity whether wet or dry, and that can be attached to the skin to quickly collect signals, and also allows for decorative designs. [Effects of the Invention]

[0051] As described above, the deep eutectic liquid of the present invention has biocompatibility and ionic conductivity and can be used in a bioelectrode composition. Furthermore, the bioelectrode composition of the present invention can form a biocontact layer for a bioelectrode that is excellent in electrical conductivity and biocompatibility, lightweight, can be produced at low cost, can prevent a significant decrease in electrical conductivity whether wet or dry, can be applied to the skin to quickly collect signals, does not leave any residue on the skin, and can stably measure biosignals for a long period of time. [Brief explanation of the drawings]

[0052] [Figure 1] 1 is a schematic cross-sectional view showing an example of a bioelectrode of the present invention. [Figure 2] 1 is a schematic cross-sectional view showing an example of a bioelectrode of the present invention attached to a living body. [Figure 3] FIG. 1 is a schematic diagram of a bioelectrode produced in an example of the present invention after printing. [Figure 4] FIG. 1 is a schematic diagram showing one of the bioelectrodes produced in the examples of the present invention cut out and attached with an adhesive layer. [Figure 5]1 is a diagram showing the locations where electrodes and earths are attached to the human body when measuring biosignals in an embodiment of the present invention. FIG. [Figure 6] 1 is a diagram showing an electrocardiogram waveform obtained using a bioelectrode according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0053] As described above, there has been a need for the development of a deep eutectic liquid that has high ionic conductivity and is safe to come into contact with living organisms, a bioelectrode composition containing the deep eutectic liquid that can be applied to the skin to quickly collect signals, does not leave any residue on the skin, and allows stable acquisition of biosignals over a long period of time, a bioelectrode, and a method for manufacturing the bioelectrode.

[0054] Sodium, potassium, and calcium ions are released from the skin surface in tandem with the heartbeat. Bioelectrodes must convert the increase or decrease in the ions released from the skin into an electrical signal. To do this, materials with excellent ionic conductivity are required to transmit the increase or decrease in ions.

[0055] Ionic liquids have attracted attention as materials with ionic conductivity. These materials exist as liquids at room temperature, and therefore exhibit high electrical conductivity despite their organic structure. Furthermore, they are ionic compounds, but because they exhibit the rare characteristic of existing as liquids at room temperature, they also possess ionic conductivity. However, ionic liquids are generally highly toxic to living organisms and therefore cannot be used in bioelectrodes.

[0056] Incidentally, a material known as a deep eutectic liquid is known. A deep eutectic liquid is a material in which the eutectic melting point is depressed by mixing a hydrogen bond donor compound with a hydrogen bond accepting compound, and the liquid becomes liquid at around room temperature. Deep eutectic liquids are known to exhibit properties similar to those of ionic liquids, and there are a wide variety of materials to choose from. Therefore, we discovered that by selecting an ionic compound as the hydrogen bond accepting compound of a deep eutectic liquid, it is possible to create a deep eutectic liquid with ionic conductivity.

[0057] Furthermore, biocompatibility is important when using deep eutectic liquids in bioelectrodes. Possible materials for deep eutectic liquids include compounds used in living organisms, such as sugars and amino acids, as well as medium- to high-molecular-weight compounds, such as oligomers and polymers. By selecting from such materials, a deep eutectic liquid that is not biotoxic can be obtained.

[0058] However, there have been few reports of deep eutectic liquids of oligomers or polymers to date, with most reports being of deep eutectic liquids made from monomers such as sugars and amino acids. Deep eutectic liquids are being considered for use as solvents and battery materials, both of which require low viscosity. Therefore, it is expected that deep eutectic liquids of medium to high molecular weight materials will have high viscosity, and therefore have not been studied much to date. Another possible reason is that polymers have a lower degree of freedom in molecular movement than monomers, making them less likely to form hydrogen bonds.

[0059] As a result of extensive research into the above-mentioned problems, the inventors have interestingly discovered a deep eutectic liquid using an oligomer in which two or more monomers are bonded, and have found that its use as a bioelectrode composition can improve the acquisition of biosignals, thereby completing the present invention.

[0060] That is, the present invention provides a deep eutectic liquid which is a mixture of a hydrogen bond donor compound and a hydrogen bond accepting compound, wherein the hydrogen bond donor compound is a compound having a structure in which 2 to 100 hydroxyl group-containing monomers are bonded, as shown in the following general formula (1), the hydrogen bond accepting compound is a compound containing a monomer having a quaternary ammonium cation shown in the following general formulas (2) to (6), or a quaternary phosphonium cation shown in the following general formula (7), and the deep eutectic liquid exists as a liquid at 25°C. [ka] (In the formula, X represents a single bond or a linear, branched, or cyclic divalent hydrocarbon group having 1 to 30 carbon atoms, which may be substituted with or interrupted by a heteroatom. Y and Z represent a linear, branched, or cyclic divalent hydrocarbon group having 1 to 5 carbon atoms, which may be substituted with or interrupted by a heteroatom. A and B represent a hydrogen atom, a hydroxyl group, an amino group, a halogen atom, or an alkyl group or an alkyl group terminally substituted with a siloxane, which may be substituted with or interrupted by a heteroatom. Y and Z may be the same or different. A and B may be the same or different. m is an integer of 1 to 100 and represents a repetition of a chemical structural unit. n is an integer of 1 to 4 and represents a repetition of a chemical structural unit, provided that 2≦m×n≦100 is satisfied.) [ka] (In the formula, R1~R 12 R1 to R2 are a linear, branched, or cyclic monovalent hydrocarbon group having 1 to 30 carbon atoms, a hydrogen atom, a hydroxyl group, an amino group, a nitro group, or a halogen atom, which may be substituted with a heteroatom, may be interposed between heteroatoms, or may be a zwitterion having an anion moiety. 12 may be the same or different.)

[0061] The deep eutectic liquid and bioelectrode composition of the present invention have excellent conductivity and biocompatibility, are lightweight, and can be produced at low cost. They can prevent a significant decrease in conductivity and adhesion whether wet or dry, can be applied to the skin to quickly collect signals, do not leave residue on the skin, and can form a biocontact layer for a bioelectrode that can stably acquire biosignals for a long period of time.

[0062] The present invention will be described in detail below, but the present invention is not limited thereto.

[0063] [Deep eutectic liquid] The deep eutectic liquid of the present invention is a deep eutectic liquid that is a mixture of a hydrogen bond donor compound and a hydrogen bond accepting compound, wherein the hydrogen bond donor compound is a compound having a structure in which 2 to 100 hydroxyl group-containing monomers are bonded, as shown in the following general formula (1), the hydrogen bond accepting compound is a compound containing a monomer having a quaternary ammonium cation shown in the following general formulas (2) to (6), or a quaternary phosphonium cation shown in the following general formula (7), and the deep eutectic liquid exists as a liquid at 25°C. [ka] (In the formula, X represents a single bond or a linear, branched, or cyclic divalent hydrocarbon group having 1 to 30 carbon atoms, which may be substituted with or interrupted by a heteroatom. Y and Z represent a linear, branched, or cyclic divalent hydrocarbon group having 1 to 5 carbon atoms, which may be substituted with or interrupted by a heteroatom. A and B represent a hydrogen atom, a hydroxyl group, an amino group, a halogen atom, or an alkyl group or an alkyl group terminally substituted with a siloxane, which may be substituted with or interrupted by a heteroatom. Y and Z may be the same or different. A and B may be the same or different. m is an integer of 1 to 100 and represents a repetition of a chemical structural unit. n is an integer of 1 to 4 and represents a repetition of a chemical structural unit, provided that 2≦m×n≦100 is satisfied.) [ka] (In the formula, R1~R 12 R1 to R2 are a linear, branched, or cyclic monovalent hydrocarbon group having 1 to 30 carbon atoms, a hydrogen atom, a hydroxyl group, an amino group, a nitro group, or a halogen atom, which may be substituted with a heteroatom, may be interposed between heteroatoms, or may be a zwitterion having an anion moiety. 12 may be the same or different.)

[0064] The hydrogen bond donor compound is a compound having a structure in which 2 to 100 hydroxyl group-containing monomers are bonded, as shown in the general formula (1). Specific examples of hydroxyl group-containing monomers include vinyl alcohol, glycerin, 2-hydroxyethyl acrylate, 4-hydroxybutyl acrylate, propylene glycol monoacrylate, 4-vinylphenol, 4-allylphenol, 4-vinyl-1,2-benzenediol, and 4-allyl-1,2-benzenediol. In the present invention, the hydroxyl group-containing monomer is preferably glycerin, and the hydrogen bond donor compound is more preferably a polyglycerin-modified silicone represented by the following general formula (8) or (9). [ka] (In the formula, R1' are each independent and may be the same or different from each other, and are a hydrogen atom, a linear or branched alkyl group having 1 to 50 carbon atoms, or a phenyl group, and may contain an ether group or may be a silicone chain represented by general formula (10). R2' is a group having a polyglycerin structure represented by general formula (8)-1 or general formula (8)-2. R3' are each independent and may be the same or different from each other, and are R1' or R2'. R4' are each independent and may be the same or different from each other, and are R1' or R2'. or an oxygen atom. When R4' is an oxygen atom, two R4' may be bonded to form a single ether group, which may form a ring together with the silicon atom to which they are bonded. a' may be the same or different and is 0 to 100, b' is 0 to 100, and a' + b' is 0 to 200. However, when b' is 0, at least one of R3' is the above-mentioned R2'. R5' is an alkylene group having 2 to 10 carbon atoms or an aralkylene group having 7 to 10 carbon atoms. R6' and R7' are alkylene groups having 2 to 6 carbon atoms, and R7' may be an ether group. c' is 0 to 20, and d' is 2 to 20.

[0065] The polyglycerin-modified silicone has, for example, the following structure: [ka]

[0066] [ka]

[0067] [ka]

[0068] [ka]

[0069] [ka]

[0070] [ka]

[0071] [ka]

[0072] [ka]

[0073] [ka]

[0074] [ka] (In the formula, a', b', c', and d' are as defined above.)

[0075] The hydrogen-bond-accepting compound is a compound containing a monomer having a quaternary ammonium cation represented by the general formulas (2) to (6) above or a quaternary phosphonium cation represented by the general formula (7) above. Specific examples include ammonium salts such as choline chloride, betaine, and tetrabutylammonium chloride; imidazole salts including 1-ethyl-3-methylimidazolium cations and 1-butyl-3-methylimidazolium cations; pyridinium salts such as 1-butylpyridinium chloride; pyrrolidinium salts such as 1-butyl-1-methylpyrrolidinium chloride; piperidinium salts such as 1-butyl-1-methylpiperidinium chloride; and phosphonium salts such as tributyl(methyl)phosphonium dimethylphosphate. Biocompatible hydrogen-bond-accepting compounds are not limited to the above compounds; for example, derivatives of these compounds are also candidates for deep eutectic liquid materials.

[0076] Deep eutectic liquids are often obtained by mixing the biocompatible hydrogen bond donor compound and the biocompatible hydrogen bond acceptor compound in equimolar ratios, typically in molar ratios ranging from 1:1 to 10:1 or 1:1 to 5:1, although other molar ratios have also been observed.

[0077] [Bioelectrode composition] The present invention provides a bioelectrode composition, which contains the above-described deep eutectic liquid.

[0078] [Binder (A)] The bioelectrode composition of the present invention can contain a binder (A) in addition to the deep eutectic liquid. That is, it is preferable that the bioelectrode composition contains the binder (A). For example, the bioelectrode composition of the present invention can contain one or more resins selected from silicone resins, acrylic resins, and urethane resins. That is, it is preferable that the binder (A) is one or more resins selected from silicone resins, polyurethane resins, and polyacrylic resins. By including one or more resins selected from silicone resins, acrylic resins, and urethane resins, it is possible to provide a bioelectrode including a biocontact layer with excellent elasticity.

[0079] The binder (A) that can be incorporated into the bioelectrode composition of the present invention can be, for example, a component that prevents the elution of the deep eutectic liquid and exhibits adhesiveness. When the bioelectrode composition contains the conductive particles (B) described below, the binder (A) can hold these powders. The binder (A) may be either a thermosetting resin or a photocurable resin, or both, and is particularly preferably one or more resins selected from silicone-based resins, acrylic-based resins, and urethane-based resins.

[0080] The adhesive silicone resin may be an addition reaction curing type or a radical crosslinking reaction curing type. Examples of the addition reaction curing type include diorganosiloxane having an alkenyl group, RSiO, as described in JP 2015-193803 A. 0.5 and SiO2 units, organohydrogenpolysiloxane having a plurality of SiH groups, platinum catalyst, addition reaction inhibitor, and organic solvent. Examples of radical crosslinking reaction curing types include diorganopolysiloxanes that may or may not have alkenyl groups, R3SiO 0.5 and those containing an MQ resin having SiO2 units, an organic peroxide, and an organic solvent can be used, where R is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 10 carbon atoms.

[0081] It is also possible to use a polysiloxane-resin integrated compound formed by the condensation reaction of MQ resin with polysiloxane that has silanols at the polymer end or side chain. MQ resin contains a large amount of silanols, so adding this improves adhesive strength, but because it is not crosslinkable, it is not molecularly bonded to the polysiloxane. By integrating polysiloxane and resin as described above, adhesive strength can be increased.

[0082] In addition, modified siloxanes having groups selected from amino groups, oxirane groups, oxetane groups, polyether groups, hydroxy groups, carboxy groups, mercapto groups, methacryl groups, acrylic groups, phenol groups, silanol groups, carboxylic anhydride groups, aryl groups, aralkyl groups, amide groups, ester groups, and lactone rings can also be added to the silicone resin. The addition of modified siloxanes improves the dispersibility of the deep eutectic liquid in the silicone resin. The modified siloxanes may be modified at one end, both ends, or the side chain of the siloxane.

[0083] The adhesive acrylic resin may be, for example, one having a hydrophilic (meth)acrylic acid ester or a long-chain hydrophobic (meth)acrylic acid ester as a repeating unit, as described in JP 2016-011338 A. In some cases, a (meth)acrylic acid ester having a functional group or a (meth)acrylic acid ester having a siloxane bond may be copolymerized.

[0084] As the adhesive urethane-based resin, for example, those having a urethane bond and a polyether or polyester bond, a polycarbonate bond, or a siloxane bond, as described in JP 2016-065238 A, can be used.

[0085] Furthermore, in order to prevent peeling of the biocontact layer from the conductive substrate, the binder (A) in the bioelectrode composition of the present invention preferably has high adhesiveness to the conductive substrate. To ensure high compatibility of the binder (A) with the conductive substrate and salt, it is effective to use a highly polar resin. Examples of such resins include resins having one or more bonds selected from ether bonds, ester bonds, amide bonds, imide bonds, urethane bonds, thiourethane bonds, and thiol groups, as well as polyacrylic resins, polyamide resins, polyimide resins, polyurethane resins, and polythiourethane resins. On the other hand, since the biocontact layer comes into contact with the living body, it is susceptible to the effects of sweat from the living body. Therefore, in the bioelectrode composition of the present invention, it is preferable that the binder (A) be highly water-repellent and resistant to hydrolysis. To ensure high water-repellency and resistance to hydrolysis, it is effective to use a resin containing a silicon atom.

[0086] Silicon-containing polyacrylic resins include polymers with silicone in the main chain and polymers with silicon atoms in the side chain, both of which can be used suitably. Examples of polymers with silicone in the main chain include siloxanes or silsesquioxanes with (meth)acrylpropyl groups. In this case, the (meth)acryl moiety can be polymerized and cured by adding a photoradical generator.

[0087] Suitable examples of silicon-containing polyamide resins include the polyamide silicone resins described in JP 2011-079946 A and U.S. Patent No. 5,981,680. Such polyamide silicone resins can be synthesized by combining, for example, a silicone compound having amino groups at both ends or a non-silicone compound having amino groups at both ends with a non-silicone compound having carboxy groups at both ends or a silicone compound having carboxy groups at both ends.

[0088] Alternatively, polyamic acid obtained by reacting a carboxylic acid anhydride with an amine before cyclization may be used. To crosslink the carboxyl groups of the polyamic acid, an epoxy or oxetane crosslinking agent may be used, or the carboxyl groups may be esterified with hydroxyethyl (meth)acrylate to effect photoradical crosslinking of the (meth)acrylate moiety.

[0089] Suitable examples of silicon-containing polyimide resins include the polyimide silicone resins described in JP-A-2002-332305. Polyimide resins have very high viscosity, but can be made low-viscosity by blending a (meth)acrylic monomer as a solvent and crosslinking agent.

[0090] Examples of polyurethane resins containing silicon atoms include polyurethane silicone resins. In such polyurethane silicone resins, crosslinking via urethane bonds can be achieved by blending and heating a compound having isocyanate groups at both ends with a compound having hydroxyl groups at the ends. In this case, it is necessary for either the compound having isocyanate groups at both ends or the compound having hydroxyl groups at the ends, or both, to contain silicon atoms (siloxane bonds). Alternatively, as described in JP 2005-320418 A, photocrosslinking can be achieved by blending a urethane (meth)acrylate monomer with a polysiloxane. Furthermore, photocrosslinking can also be achieved by photocrosslinking a polymer having both siloxane and urethane bonds and (meth)acrylate groups at the ends. In particular, the silicone chains attached to the side chains described in JP 2018-123304 A and JP 2019-070109 A are preferred because the polyurethane main chain has high strength and high elasticity.

[0091] Silicon-containing polythiourethane resins can be obtained by reacting a compound having a thiol group with a compound having an isocyanate group, as long as either of them contains a silicon atom. Furthermore, if the compound has a (meth)acrylate group at its terminal, it can also be photocured.

[0092] In the silicone resin, diorganosiloxane having the above-mentioned alkenyl group, R3SiO 0.5 In addition to MQ resins containing SiO2 units and organohydrogenpolysiloxanes containing multiple SiH groups, the addition of modified siloxanes containing groups selected from amino groups, oxirane groups, oxetane groups, polyether groups, hydroxy groups, carboxy groups, mercapto groups, methacryl groups, acrylic groups, phenol groups, silanol groups, carboxylic anhydride groups, aryl groups, aralkyl groups, amide groups, ester groups, and lactone rings can improve compatibility with conductive substrates and salts.

[0093] In the bioelectrode composition of the present invention, the blending amount of the binder (A) is preferably 0 to 2,000 parts by mass, more preferably 10 to 1,000 parts by mass, per 100 parts by mass of the deep eutectic liquid. The binder (A) may be used singly or in combination of two or more types.

[0094] As described below, the bioelectrode of the present invention comprises a cured product of a bioelectrode composition containing a deep eutectic liquid. By curing the bioelectrode composition, the adhesion of the biocontact layer to both the skin and the conductive substrate is improved. The curing method is not particularly limited, and a common method can be used, such as heat and / or light, or a crosslinking reaction using an acid or base catalyst. The crosslinking reaction can be carried out by appropriately selecting a method from the Crosslinking Reaction Handbook by Nakayama Yasuharu, Chapter 2, pp. 51-371, Maruzen Publishing (2013).

[0095] Diorganosiloxanes having alkenyl groups and organohydrogenpolysiloxanes having multiple SiH groups can be crosslinked by an addition reaction using a platinum catalyst.

[0096] Examples of platinum catalysts include platinum-based catalysts such as chloroplatinic acid, an alcohol solution of chloroplatinic acid, a reaction product of chloroplatinic acid and an alcohol, a reaction product of chloroplatinic acid and an olefin compound, a reaction product of chloroplatinic acid and a vinyl group-containing siloxane, a platinum-olefin complex, a platinum-vinyl group-containing siloxane complex, and platinum group metal-based catalysts such as a rhodium complex and a ruthenium complex. These catalysts may also be used dissolved or dispersed in an alcohol-based, hydrocarbon-based, or siloxane-based solvent.

[0097] The amount of platinum catalyst added is preferably in the range of 5 to 2,000 ppm, particularly 10 to 500 ppm, per 100 parts by mass of the binder (A).

[0098] When an addition-curing silicone resin is used, an addition reaction inhibitor may be added as a quencher to prevent the platinum catalyst from acting in the solution and in a low-temperature environment after coating formation and before heat curing. Specific examples include 3-methyl-1-butyn-3-ol, 3-methyl-1-pentyn-3-ol, 3,5-dimethyl-1-hexyn-3-ol, 1-ethynylcyclohexanol, 3-methyl-3-trimethylsiloxy-1-butyne, 3-methyl-3-trimethylsiloxy-1-pentyne, 3,5-dimethyl-3-trimethylsiloxy-1-hexyne, 1-ethynyl-1-trimethylsiloxycyclohexane, bis(2,2-dimethyl-3-butynoxy)dimethylsilane, 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane, and 1,1,3,3-tetramethyl-1,3-divinyldisiloxane.

[0099] The amount of the addition reaction inhibitor added is preferably in the range of 0 to 10 parts by mass, particularly 0.05 to 3 parts by mass, per 100 parts by mass of the binder (A).

[0100] Examples of photocuring methods include using a resin having a (meth)acrylate end or an olefin end, adding a crosslinking agent whose end is a (meth)acrylate, olefin, or thiol group, and adding a photoradical generator that generates radicals when exposed to light, and using a resin or crosslinking agent that has an oxirane group, oxetane group, or vinyl ether group, and adding a photoacid generator that generates acid when exposed to light.

[0101] Photoradical generators include acetophenone, 4,4'-dimethoxybenzyl, benzil, benzoin, benzophenone, 2-benzoylbenzoic acid, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin butyl ether, benzoin isobutyl ether, 4-benzoylbenzoic acid, 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-biimidazole, methyl 2-benzoylbenzoate, 2-(1,3-benzodioxol-5-yl)-4,6-bis(trichloromethyl)-1,3,5-triazine, and 2-benzyl 2-(dimethylamino)-4'-morpholinobutyrophenone, 4,4'-dichlorobenzophenone, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,4-diethylthioxanthen-9-one, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO), 1,4-dibenzoylbenzene, 2-ethylanthraquinone, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methylpropiophenone, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, 2-isonitrosopropiophenone, and 2-phenyl-2-(p-toluenesulfonyloxy)acetophenone.

[0102] Curing can also be achieved by adding a thermally decomposable radical generator. Examples of thermally decomposable radical generators include 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(methylpropionamidine) hydrochloride, 2,2'-azobis[2-(2-imidazolin-2-yl)propane]hydrochloride, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(cyclohexane-1-carbonitrile), 1[(1-cyano-1-methylethyl)azo]formamide, 2,2'-azobis[2-methyl- N-(2-hydroxyethyl)propionamide], 2,2'-azobis[N-(2-propenyl)-2-methylpropionamide], 2,2'-azobis(N-butyl-2-methylpropionamide), dimethyl-2,2'-azobis(isobutyrate), 4,4'-azobis(4-cyanopentanoic acid), dimethyl-2,2'-azobis(2-methylpropionate), benzoyl peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, di-tert-butyl peroxide, di-tert-amyl peroxide, di-n-butyl peroxide, and dicumyl peroxide.

[0103] Examples of the photoacid generator include sulfonium salts, iodonium salts, sulfonyldiazomethane, N-sulfonyloxyimide, and oxime-O-sulfonate-type acid generators, etc. Specific examples of the photoacid generator include those described in paragraphs

[0122] to

[0142] of JP2008-111103A and JP2009-080474A.

[0104] The amount of the radical generator or photoacid generator added is preferably in the range of 0.1 to 50 parts by mass per 100 parts by mass of the binder (A).

[0105] Among these, R is used as the binder (A). x SiO (4-x) / 2Particularly preferred binders include silicone resins having SiO2 units (where R is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 10 carbon atoms, and x is in the range of 2.5 to 3.5), diorganosiloxanes having alkenyl groups, and organohydrogenpolysiloxanes having SiH groups. Such binders (A) are compatible with the deep eutectic liquid, preventing salt elution and imparting higher adhesiveness to the tissue-contacting layer.

[0106] [Conductive particles (B)] The bioelectrode composition preferably contains conductive particles (B). Specific examples of the conductive particles (B) include carbon powder and metal powder. That is, the conductive particles (B) preferably contain one or more particles selected from carbon powder, gold, silver, silver chloride, platinum, aluminum, magnesium, tin, tungsten, iron, copper, nickel, stainless steel, chromium, titanium, molybdenum, ruthenium, and indium.

[0107] [Metal powder] To enhance electronic conductivity, the bioelectrode composition of the present invention may contain a metal powder selected from gold, silver, silver chloride, platinum, copper, tin, titanium, nickel, aluminum, magnesium, tungsten, iron, stainless steel, molybdenum, ruthenium, chromium, and indium. The amount of metal powder added is preferably in the range of 1 to 50 parts by mass per 100 parts by mass of the binder (A).

[0108] As the type of metal powder, gold, silver, and platinum are preferred from the viewpoint of conductivity, and silver, copper, tin, titanium, nickel, aluminum, tungsten, molybdenum, ruthenium, and chromium are preferred from the viewpoint of cost. Noble metals are preferred from the viewpoint of biocompatibility. Overall, silver is most preferred from these viewpoints.

[0109] The shape of the metal powder can be spherical, discoid, flake, or needle-like, but the addition of flake-shaped powder is preferred as it has the highest conductivity. The metal powder should have a size of 100 μm or less and a tap density of 5 g / cm. 3 The specific surface area is 0.5m 2 Flakes with a relatively low density and a large specific surface area of ​​1 / g or more are preferred. Here, the size is a value determined by laser diffraction, the tap density (packed bulk density) is a value measured using a Powder Tester PT-X manufactured by Horikawa Micron Corporation, and the specific surface area is a value measured by liquid nitrogen adsorption (77K) (Microtrac BEL, BELSORP-max) in accordance with the method for measuring the specific surface area of ​​powders by gas adsorption.

[0110] [Carbon powder] Carbon powder can be added as the conductive particles (B). Examples of carbon powder (carbon material) include carbon black, graphite, carbon nanotubes, and carbon fibers. The carbon nanotubes may be single-walled or multi-walled, and their surfaces may be modified with organic groups. The amount of carbon material added is preferably in the range of 1 to 50 parts by mass per 100 parts by mass of the binder (A). The carbon powder is preferably either carbon black or carbon nanotubes, or both.

[0111] [Organic solvents] In addition, an organic solvent can be added to the bioelectrode composition of the present invention. Specific examples of the organic solvent include toluene, xylene, cumene, 1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, styrene, α-methylstyrene, butylbenzene, sec-butylbenzene, isobutylbenzene, cymene, diethylbenzene, 2-ethyl-p-xylene, 2-propyltoluene, 3-propyltoluene, 4-propyltoluene, 1,2,3,5-tetramethyltoluene, 1,2,4,5-tetramethyltoluene, and tetrahydrofuran. naphthalene, 4-phenyl-1-butene, tert-amylbenzene, amylbenzene, 2-tert-butyltoluene, 3-tert-butyltoluene, 4-tert-butyltoluene, 5-isopropyl-m-xylene, 3-methylethylbenzene, tert-butyl-3-ethylbenzene, 4-tert-butyl-o-xylene, 5-tert-butyl-m-xylene, tert-butyl-p-xylene, 1,2-diisopropylbenzene, 1,3-diisopropylbenzene, 1,4-diisopropylbenzene Aromatic hydrocarbon solvents such as isopropylbenzene, dipropylbenzene, pentamethylbenzene, hexamethylbenzene, hexylbenzene, and 1,3,5-triethylbenzene, n-heptane, isoheptane, 3-methylhexane, 2,3-dimethylpentane, 3-ethylpentane, 1,6-heptadiene, 5-methyl-1-hexyne, norbornane, norbornene, dicyclopentadiene, 1-methyl-1,4-cyclohexadiene, 1-heptyne, 2-heptyne, cycloheptane, cyclohexane, Heptene, 1,3-dimethylcyclopentane, ethylcyclopentane, methylcyclohexane, 1-methyl-1-cyclohexene, 3-methyl-1-cyclohexene, methylenecyclohexane, 4-methyl-1-cyclohexene, 2-methyl-1-hexene, 2-methyl-2-hexene, 1-heptene, 2-heptene, 3-heptene, n-octane, 2,2-dimethylhexane, 2,3-dimethylhexane, 2,4-dimethylhexane, 2,5-dimethylhexane, 3,3-dimethylhexane, 3,4-dimethylhexane, 3-ethyl-2-methylpentane, 3-ethyl-3-methylpentane, 2-methylheptane, 3-methylheptane, 4-methylheptane, 2,2,3-trimethylpentane, 2,2,4-trimethylpentane, cyclooctane, cyclooctene, 1,2-dimethylcyclohexane, 1,3-dimethylcyclohexane, 1,4-dimethylcyclohexane, ethylcyclohexane, vinylcyclohexane, isopropylcyclopentane, 2,2-dimethyl-3-hexene, 2,4-dimethyl-1-hexene, 2,5-dimethyl-1- Hexene, 2,5-dimethyl-2-hexene, 3,3-dimethyl-1-hexene, 3,4-dimethyl-1-hexene, 4,4-dimethyl-1-hexene, 2-ethyl-1-hexene, 2-methyl-1-heptene, 1-octene, 2-octene, 3-octene, 4-octene, 1,7-octadiene, 1-octyne, 2-octyne, 3-octyne, 4-octyne, n-nonane, 2,3-dimethylheptane, 2,4-dimethylheptane, 2,5-dimethylheptane, 3,3-dimethylheptane, 3,4-dimethylheptane, 3,5-dimethylheptane, 4-ethylhexene ethylheptane, 2-methyloctane, 3-methyloctane, 4-methyloctane, 2,2,4,4-tetramethylpentane, 2,2,4-trimethylhexane, 2,2,5-trimethylhexane, 2,2-dimethyl-3-heptene, 2,3-dimethyl-3-heptene, 2,4-dimethyl-1-heptene, 2,6-dimethyl-1-heptene, 2,6-dimethyl-3-heptene, 3,5-dimethyl-3-heptene, 2,4,4-trimethyl-1-hexene, 3,5,5-trimethyl-1-hexene, 1-ethyl-2-methylcyclohexane, 1-ethyl-3 -methylcyclohexane, 1-ethyl-4-methylcyclohexane, propylcyclohexane, isopropylcyclohexane, 1,1,3-trimethylcyclohexane, 1,1,4-trimethylcyclohexane, 1,2,3-trimethylcyclohexane, 1,2,4-trimethylcyclohexane, 1,3,5-trimethylcyclohexane, allylcyclohexane, hydrindane, 1,8-nonadiene, 1-nonyne, 2-nonyne, 3-nonyne, 4-nonyne, 1-nonene, 2-nonene, 3-nonene, 4-nonene, n-decane, 3,3-dimethyloctane, 3,5-dimethyloctane, 4,4-dimethyloctane, 3-ethyl-3-methylheptane, 2-methylnonane, 3-methylnonane, 4-methylnonane, tert-butylcyclohexane, butylcyclohexane, isobutylcyclohexane, 4-isopropyl-1-methylcyclohexane, pentylcyclopentane, 1,1,3,5-tetramethylcyclohexane, cyclododecane, 1-decene, 2-decene, 3-decene, 4-decene, 5-decene, 1,9-decadiene, decahydronaphthalene, 1-decyne, 2-decyne, 3-decyne, 4-decyne, 5-decyne, 1,5,9-decyne Katriene, 2,6-dimethyl-2,4,6-octatriene, limonene, myrcene, 1,2,3,4,5-pentamethylcyclopentadiene, α-phellandrene, pinene, terpinene, tetrahydrodicyclopentadiene, 5,6-dihydrodicyclopentadiene, dicyclopentadiene, 1,4-decadiyne, 1,5-decadiyne, 1,9-decadiyne, 2,8-decadiyne, 4,6-decadiyne, n-undecane, amylcyclohexane, 1-undecene, 1,10-undecadiene, 1-undecyne, 3-undecyne, 5-undecyne, tricyclo[6.2.1.0], 2,7]Undec-4-ene, n-dodecane, 2-methylundecane, 3-methylundecane, 4-methylundecane, 5-methylundecane, 2,2,4,6,6-pentamethylheptane, 1,3-dimethyladamantane, 1-ethyladamantane, 1,5,9-cyclododecatriene, 1,2,4-trivinylcyclohexane, and aliphatic hydrocarbon solvents such as isoparaffin, cyclohexanone, cyclopentanone, 2-octanone, 2-nonanone, 2-heptanone, 3-heptanone, 4-heptanone, 2-hexanone, 3-hexanone, diisobutyl ketone ketone solvents such as methyl cyclohexanone, methyl n-pentyl ketone, etc.; alcohol solvents such as 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, etc.; propylene glycol monomethyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, propylene glycol dimethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol Examples of the solvent include ether solvents such as glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monopentyl ether, diethylene glycol monoheptyl ether, diethylene glycol diethyl ether, diethylene glycol dipropyl ether, diethylene glycol dibutyl ether, diisopropyl ether, diisobutyl ether, diisopentyl ether, di-n-pentyl ether, methylcyclopentyl ether, methylcyclohexyl ether, di-n-butyl ether, di-sec-butyl ether, di-sec-pentyl ether, di-tert-amyl ether, di-n-hexyl ether, and anisole; ester solvents such as propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate, tert-butyl propionate, and propylene glycol mono-tert-butyl ether acetate; and lactone solvents such as γ-butyrolactone.

[0112] Furthermore, water can be added as a solvent to the bioelectrode composition of the present invention.

[0113] The amount of organic solvent or water added is preferably in the range of 70 to 150 parts by mass per 100 parts by mass of the binder (A).

[0114] [Tackifier] Furthermore, a tackifier may be added to the bioelectrode composition of the present invention to impart adhesiveness to a living body. Examples of such tackifiers include silicone resins, non-crosslinked siloxanes, non-crosslinked poly(meth)acrylates, and non-crosslinked polyethers. The amount added is preferably in the range of 1 to 20 parts by mass per 100 parts by mass of the binder (A).

[0115] [Crosslinking agent] An epoxy-based crosslinking agent can also be added to the bioelectrode composition of the present invention. In this case, the crosslinking agent is a compound having multiple epoxy groups or oxetane groups in one molecule. The amount added is preferably in the range of 1 to 30 parts by mass per 100 parts by mass of the binder (A).

[0116] [Crosslinking catalyst] A crosslinking catalyst for crosslinking the epoxy groups or oxetane groups can also be added to the bioelectrode composition of the present invention. Examples of the crosslinking catalyst include those described in paragraphs

[0027] to

[0029] of JP-A-2019-503406. The amount of the catalyst added is preferably in the range of 0.01 to 10 parts by mass per 100 parts by mass of the binder (A).

[0117] [Ionic additives] The bioelectrode composition of the present invention can contain an ionic additive to increase ionic conductivity. Considering biocompatibility, examples of suitable additives include sodium chloride, potassium chloride, calcium chloride, saccharin, acesulfame potassium, and the salts disclosed in JP 2018-044147 A, JP 2018-059050 A, JP 2018-059052 A, and JP 2018-130534 A can be mentioned.

[0118] Furthermore, the bioelectrode composition preferably contains glycerin, and the amount of glycerin added is preferably in the range of 1 to 30 parts by mass relative to 100 parts by mass of the binder (A).

[0119] [Compound (C) having a polyglycerol structure] A compound (C) having a polyglycerin structure can be added to the bioelectrode composition of the present invention to improve ionic conductivity and reduce contact impedance with the skin. Examples of the compound (C) having a polyglycerin structure include polyglycerin (glycerin dimer to decamer) and polyglycerin-modified silicone (polyglyceryl-3 polydimethylsiloxyethyl dimethicone, lauryl polyglyceryl-3 polydimethylsiloxyethyl dimethicone). The amount added is preferably in the range of 1 to 30 parts by mass per 100 parts by mass of the binder (A).

[0120] As described above, the bioelectrode composition of the present invention can form a biocontact layer for a bioelectrode that is excellent in conductivity and biocompatibility, lightweight, and can be produced at low cost. It can prevent a significant decrease in conductivity even when wet or dry, and can be applied to the skin to quickly collect signals without leaving any residue. The biocontact layer formed by curing the bioelectrode composition of the present invention exhibits excellent conductivity, allowing it to efficiently transmit electrical signals from the living body, for example, the skin, to the device. Furthermore, this biocontact layer exhibits excellent biocompatibility, preventing allergies even when worn on the skin for long periods of time. The conductivity can be further improved by adding a conductivity enhancer such as a carbon material. Furthermore, by combining the bioelectrode composition of the present invention with a resin that has adhesiveness and stretchability, a bioelectrode with particularly high adhesive strength and stretchability can be produced. Furthermore, the bioelectrode composition of the present invention can improve its stretchability and adhesion to the skin by adding additives, etc. Furthermore, the stretchability and adhesion can be adjusted by appropriately adjusting the type and amount of the deep eutectic liquid used in the bioelectrode composition of the present invention, the composition of the binder (A), the amount of conductive particles (B), and the thickness of the biocontact layer.

[0121] <Bioelectrode> The present invention also provides a bioelectrode having a conductive substrate and a biocontact layer formed on the conductive substrate, wherein the biocontact layer contains a cured product of the bioelectrode composition described above.

[0122] The bioelectrode of the present invention will be described in detail below with reference to the drawings, but the present invention is not limited thereto.

[0123] Fig. 1 is a schematic cross-sectional view showing an example of a bioelectrode of the present invention. The bioelectrode 1 in Fig. 1 has a conductive substrate 2 and a biocontact layer 3 formed on the conductive substrate 2. The biocontact layer 3 is a layer in which a deep eutectic liquid 5 and conductive particles 4 are dispersed in a resin 6. The resin 6 is, for example, the compound (C) having a polyglycerin structure and the binder resin (A) described above. The biocontact layer 3 is an example of a cured product of the bioelectrode composition of the present invention.

[0124] When using the bioelectrode 1 shown in FIG. 1 , as shown in FIG. 2 , the biocontact layer 3 (i.e., a layer in which a deep eutectic liquid 5 and conductive particles 4 are dispersed in a resin 6) is brought into contact with a living body 7, and an electrical signal is extracted from the living body 7 via the deep eutectic liquid 5 and conductive particles 4. This signal is then transmitted to a sensor device (not shown) via the conductive substrate 2. Thus, a biocontact layer containing a cured product of the bioelectrode composition of the present invention can achieve both electrical conductivity and biocompatibility due to the deep eutectic liquid. Furthermore, because it is adhesive, the contact area with the skin is constant, enabling stable and highly sensitive electrical signals from the skin to be obtained. In particular, as described above, the bioelectrode composition of the present invention can form a biocontact layer that can be applied to the skin and rapidly collect signals. Therefore, the bioelectrode 1 shown in FIG. 1 can be applied to a living body 7 as shown in FIG. 2 and rapidly collect signals.

[0125] Each of the constituent materials of the bioelectrode of the present invention will be described in more detail below.

[0126] [Conductive base material] The bioelectrode of the present invention has a conductive substrate. This conductive substrate is usually electrically connected to a sensor device or the like, and conducts an electrical signal extracted from a living body via a biocontact layer to the sensor device or the like.

[0127] The conductive substrate is not particularly limited as long as it is conductive, but it is preferable that the conductive substrate contains at least one metal selected from gold, silver, silver chloride, platinum, aluminum, magnesium, tin, tungsten, iron, copper, nickel, stainless steel, chromium, titanium, and carbon.

[0128] The conductive substrate is not particularly limited and may be a hard conductive substrate, a flexible conductive film, a substrate in which a conductive paste is coated on a stretchable film, a fabric coated with a conductive paste, or a fabric in which a conductive polymer is kneaded. The conductive substrate may be flat, uneven, or a mesh-like structure made of woven metal wires, and may be selected appropriately depending on the intended use of the bioelectrode. Among these, considering that the bioelectrode will be attached to the skin, stretchable films and substrates in which a conductive paste is coated on a fabric are preferred. Examples of stretchable films include polyurethane and polyester. The conductive paste may be a mixture of a conductive powder such as carbon, silver, gold, or copper with a solvent in a stretchable resin such as polyurethane, polyester, silicone, or nitrile resin.

[0129] [Body contact layer] The bioelectrode of the present invention has a biocontact layer formed on a conductive substrate. This biocontact layer is the part that actually comes into contact with the living body when the bioelectrode is used, and is conductive. The biocontact layer is an adhesive resin layer that contains the deep eutectic liquid described above, and optionally additives such as a binder (A), conductive particles (B), glycerin, and a compound (C) having a polyglycerin structure.

[0130] The adhesive strength of the biological contact layer is preferably in the range of 0.5 N / 24 mm to 20 N / 24 mm. The adhesive strength is generally measured using the method specified in JIS Z 0237. While metal substrates such as stainless steel (SUS) or polyethylene terephthalate (PET) substrates can be used as substrates, human skin can also be used for measurement. The surface energy of human skin is lower than that of metals and various plastics, and is close to that of Teflon (registered trademark). Therefore, human skin has low adhesive properties.

[0131] The thickness of the biocontact layer of the bioelectrode is preferably 1 μm to 5 mm, more preferably 2 μm to 3 mm. The thinner the biocontact layer, the weaker the adhesive strength, but the more flexible it is, the lighter it is, and the better it fits to the skin. The thickness of the biocontact layer can be selected based on the balance between adhesiveness and texture on the skin.

[0132] Furthermore, in the bioelectrode of the present invention, similar to conventional bioelectrodes (e.g., the bioelectrode described in JP 2004-033468 A), a separate adhesive film may be provided on the biocontact layer to prevent the bioelectrode from peeling off from the living body during use. When a separate adhesive film is provided, it may be formed using an adhesive film material such as an acrylic, urethane, or silicone type. Silicone types are particularly preferred because they have high oxygen permeability, allowing the skin to breathe while attached, are highly water-repellent, and are less likely to lose adhesiveness due to sweat, and are also less irritating to the skin. Note that the biocontact layer of the bioelectrode of the present invention does not necessarily require the separate adhesive film, because peeling off from the living body can be prevented by adding a tackifier to the biocontact layer or by using a resin with good adhesiveness to the living body, as described above.

[0133] When using the bioelectrode of the present invention in a wearable device, the wiring between the biocontact layer and the sensor device and other components are not particularly limited, and for example, those described in JP 2004-033468 A can be applied.

[0134] As described above, the bioelectrode of the present invention includes a biocontact layer containing the cured product of the bioelectrode composition of the present invention. This bioelectrode has excellent electrical conductivity and biocompatibility, is lightweight, can be manufactured at low cost, and prevents a significant decrease in conductivity even when wet or dry. It can be applied to the skin to quickly collect signals and does not leave any residue on the skin. The biocontact layer of the bioelectrode of the present invention exhibits excellent electrical conductivity, allowing it to efficiently transmit electrical signals from the living body, for example, the skin, to a device. Furthermore, this biocontact layer exhibits excellent biocompatibility, preventing allergies even when worn on the skin for long periods of time. The conductivity of the biocontact layer of the bioelectrode of the present invention can be further improved by adding a metal powder. Furthermore, by combining the biocontact layer of the present invention with a resin having adhesiveness and stretchability, a bioelectrode with particularly high adhesive strength and stretchability can be manufactured. Furthermore, the stretchability and adhesiveness of the biocontact layer to the skin can be improved by adding an additive or the like to the biocontact layer. Furthermore, the stretchability and adhesiveness of the biocontact layer can be adjusted by appropriately adjusting the type and amount of the deep eutectic liquid of the present invention, the composition of the binder (A), the amount of the conductive particles (B), and the thickness of the biocontact layer. Therefore, such a bioelectrode of the present invention is particularly suitable as a bioelectrode used in a medical wearable device.

[0135] <Method of manufacturing bioelectrodes> The present invention also provides a method for manufacturing a bioelectrode having a conductive substrate and a biocontact layer formed on the conductive substrate, in which the bioelectrode composition described above is applied to the conductive substrate and cured to form the biocontact layer.

[0136] The present invention also provides a method for manufacturing a bioelectrode having a conductive substrate and a biocontact layer formed on the conductive substrate, in which the bioelectrode composition described above is applied to a release substrate, cured, and patterned, and the patterned product is transferred onto the conductive substrate to form the biocontact layer.

[0137] The conductive substrate, the biological contact layer, and the like used in the method for producing a biological electrode of the present invention may be the same as those described above.

[0138] [Release base material] The release substrate used in the method for producing a bioelectrode of the present invention may be, for example, a fluorine-based release film (SSIA or FSD5) manufactured by Nippa Corp. The bioelectrode composition of the present invention is applied to such a release substrate and cured.

[0139] The method for forming the biocontact layer on the conductive substrate is not particularly limited, and suitable methods include, for example, dip coating, spray coating, spin coating, roll coating, flow coating, doctor coating, screen printing, flexographic printing, gravure printing, stencil printing, inkjet printing, etc. Other methods include solid film formation using a comma coater or slit coater, and pattern printing using screen printing or stencil printing.

[0140] The method for curing the bioelectrode composition is not particularly limited and may be appropriately selected depending on the type of deep eutectic liquid and binder (A) contained in the bioelectrode composition, but for example, it is preferable to cure it using either heat or light, or both. Alternatively, a catalyst that generates an acid or a base may be added to the bioelectrode composition to cause a crosslinking reaction and cure the composition.

[0141] The temperature for heating is not particularly limited and may be appropriately selected depending on the type of deep eutectic liquid and binder (A) contained in the bioelectrode composition, but is preferably about 50 to 250°C, for example.

[0142] When heating and light irradiation are combined, heating and light irradiation may be performed simultaneously, or heating may be performed after light irradiation, or light irradiation may be performed after heating. Furthermore, air drying may be performed after the coating film is heated to evaporate the solvent.

[0143] In the case of a solid film, the biocontact layer can be formed by laminating it with a release film, cutting it into the desired pattern with scissors or a cutter, peeling off one of the release films, transferring it onto a conductive substrate, and attaching it, and then peeling off the second release film.

[0144] In the case of pattern printing such as screen printing or stencil printing, any pattern can be printed, and the pattern can be transferred onto a conductive substrate and attached to form a living body contact layer.

[0145] Before applying the biocontact layer of the present invention to the skin, the skin can be wiped with gauze, absorbent cotton, nonwoven fabric, etc. containing water or alcohol to remove oils and grease from the skin and moisten the skin, thereby improving the sensitivity of biosignals. If the skin is dry, ions are not released from the skin. Moistening the skin and the biocontact layer promotes the release of ions from the skin, improving the sensitivity of biosignals. It is preferable to soak the absorbent cotton, nonwoven fabric, gauze, etc. in water or a water-containing water-soluble alcohol such as ethanol, glycerin, ethylene glycol, or diethylene glycol.

[0146] As described above, the manufacturing method of the bioelectrode of the present invention makes it possible to easily and inexpensively manufacture the bioelectrode of the present invention, which has excellent conductivity and biocompatibility, is lightweight, and can prevent a significant decrease in conductivity whether it is wet or dry, can be attached to the skin to quickly collect signals, and does not leave any residue on the skin. [Example]

[0147] The present invention will be specifically described below using examples and comparative examples, but the present invention is not limited to these. In the following, "Me" represents a methyl group and "Vi" represents a vinyl group.

[0148] [Deep eutectic liquid] The hydrogen bond donor compounds and hydrogen bond acceptor compounds blended into the deep eutectic liquids of the examples are shown below. Hydrogen bond donor compounds Polyglycerin-modified silicone: Shin-Etsu Chemical Co., Ltd. KF-6100 Polyglycerin: Polyglycerin #310 manufactured by Sakamoto Pharmaceutical Industry Co., Ltd. Polyglycerin #500 Polyglycerin #750 Hydrogen-bond accepting compounds Quaternary ammonium cation-containing monomer: Choline chloride manufactured by Tokyo Chemical Industry Co., Ltd. Betaine Anhydrous

[0149] Deep eutectic liquids 1 to 9 added to the bioelectrode compositions of the examples were synthesized as follows. A hydrogen bond donor compound and a hydrogen bond acceptor compound were mixed in a predetermined molar ratio in a reaction vessel and heated in an oven at 125°C for 3 to 6 hours. Deep eutectic liquids 1 to 9 synthesized in this way are shown below. All of the obtained deep eutectic liquids 1 to 9 were liquid at 25°C.

[0150] [Table 1]

[0151] [Binder resin (A)] Siloxane compounds 1 to 4, which were blended as silicone resins in the bioelectrode compositions of the Examples and Comparative Examples, are shown below. The viscosity was measured using a Brookfield cone-plate viscometer with a cone rotor R of 12 mm, a cone angle of 3°, and a rotation speed of 10 rpm. (Siloxane Compound 1) Siloxane compound 1 was a vinyl-containing polydimethylsiloxane with a viscosity of 27,000 mPa·s in a 30% toluene solution, an alkenyl group content of 0.007 mol / 100 g, and molecular chain ends blocked with SiMe2Vi groups. (Siloxane Compound 2) Me3SiO 0.5 MQ resin polysiloxane (Me3SiO 0.5 A 60% toluene solution of siloxane compound 2 (SiO2 unit / SiO2 unit = 0.8) was used as siloxane compound 2. (Siloxane Compound 3) 40 parts by mass of vinyl-containing polydimethylsiloxane whose molecular chain ends are capped with OH, having a viscosity of 42,000 mPa·s in a 30% toluene solution and an alkenyl group content of 0.007 mol / 100 g, Me3SiO 0.5 MQ resin polysiloxane (Me3SiO 0.5 A solution consisting of 100 parts by mass of a 60% toluene solution of SiO2 (SiO2 units / SiO2 units = 0.8) and 26.7 parts by mass of toluene was heated under reflux for 4 hours and then cooled to obtain siloxane compound 3, in which polydimethylsiloxane was bonded to the MQ resin. (Siloxane Compound 4) As the methyl hydrogen silicone oil, KF-99 manufactured by Shin-Etsu Chemical Co., Ltd. was used.

[0152] The acrylic polymer 1 used as the acrylic resin in the bioelectrode compositions of the Examples and Comparative Examples is shown below. The molecular weight (Mw) and dispersity (Mw / Mn) of the resulting polymer were determined by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as the solvent. The measurement temperature was 40°C. Acrylic Polymer 1 Mw=655,000 Mw / Mn=2.32 [ka] (The number of repetitions in the formula indicates the average value.)

[0153] The urethane resins 1 to 3 blended as urethane resins in the bioelectrode compositions of the Examples and Comparative Examples are shown below. The molecular weight (Mw) and dispersity (Mw / Mn) of the resulting resins were determined by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as the solvent. The measurement temperature was 40°C.

[0154] [ka] (The number of repetitions in the formula indicates the average value. l is 12, m is 100, and n is 110.)

[0155] [Conductive particles (B)] The conductive particles (B) blended in the bioelectrode compositions of the Examples and Comparative Examples are shown below. Metal powder: Silver powder: Sigma-Aldrich silver flakes, diameter 10 μm Gold powder: Sigma-Aldrich gold powder, diameter 10μm or less Tin powder: Sigma-Aldrich tin powder, diameter 45μm or less Titanium powder: Sigma-Aldrich titanium powder, diameter 45 μm or less Copper powder: Copper powder manufactured by Sigma-Aldrich, diameter 45 μm or less Carbon black: Denka Black Li-400 manufactured by Denka Multi-walled carbon nanotubes: Sigma-Aldrich, diameter 110-170 nm, length 5-9 μm

[0156] [Crosslinking agent] The crosslinking agents blended in the bioelectrode compositions of the Examples and Comparative Examples are shown below. [ka]

[0157] [Organic solvent (E)] The organic solvents (E) blended in the bioelectrode compositions of the Examples and Comparative Examples are shown below. EDE: Diethylene glycol diethyl ether BE: Diethylene glycol butyl ether Isopar G (ExxonMobil): Isoparaffin

[0158] [Additives] The platinum catalysts and reaction inhibitors blended as additives in the bioelectrode compositions of the Examples and Comparative Examples are shown below. Platinum catalyst: CAT-PL-56 manufactured by Shin-Etsu Chemical Co., Ltd. Reaction inhibitor: 1-ethynylcyclohexanol manufactured by Tokyo Chemical Industry Co., Ltd.

[0159] [Ionic materials] Ionic polymer 1 used in the comparative example was synthesized as follows. A 30% by mass solution of each monomer in cyclopentanone was placed in a reaction vessel and mixed. The reaction vessel was cooled to -70°C under a nitrogen atmosphere, and degassing under reduced pressure and nitrogen blowing were repeated three times. After the temperature was raised to room temperature, 0.01 mol of azobisisobutyronitrile (AIBN) was added as a polymerization initiator per 1 mol of the total monomers, and the temperature was raised to 60°C, followed by reaction for 15 hours. After drying the solvent, the composition of the resulting polymer was as follows: 1 The ionic polymer 1 was synthesized as follows: 1H-NMR. The molecular weight (Mw) and dispersity (Mw / Mn) of the polymer were determined by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent. The measurement temperature was 40°C. The ionic polymer 1 synthesized in this manner is shown below.

[0160] Ionic Polymer 1 Mw=44,400 Mw / Mn=1.94 [ka] (The number of repetitions in the formula indicates the average value.)

[0161] [Examples 1 to 22, Comparative Examples 1 to 7] Bioelectrode compositions (bioelectrode compositions 1 to 22, comparative bioelectrode compositions 1 to 7) were prepared by blending deep eutectic liquid, binder resin, conductive particles, organic solvent, additives (platinum catalyst, reaction inhibitor, crosslinker, etc.), and ionic material according to the compositions shown in Tables 2 to 4.

[0162] [Table 2]

[0163] [Table 3]

[0164] [Table 4]

[0165] (Preparation of samples for biosignal evaluation) A conductive paste (Dotite FA-333, manufactured by Fujikura Kasei) was screen-printed onto a thermoplastic urethane (TPU) film (ST-604) manufactured by Bemis Corporation. The resulting coating was then baked in an oven at 120°C for 10 minutes to print a keyhole-shaped conductive pattern consisting of a circular portion with a diameter of 2 cm and a rectangular portion. The bioelectrode compositions listed in Tables 2 to 4 were then screen-printed onto the circular portion of the printed conductive pattern. The coating was air-dried at room temperature for 10 minutes and then baked in an oven at 125°C for 10 minutes to evaporate the solvent and cure. A biocontact layer, a cured product of each bioelectrode composition, was obtained by curing (Examples 1 to 22, Comparative Examples 1 to 7).

[0166] Figure 3 is a schematic diagram of the bioelectrode produced in the example after printing. As shown in Figure 3, multiple bioelectrodes 1 were produced on a thermoplastic urethane film 20. Each bioelectrode 1 included a keyhole-shaped conductive pattern 2 as a conductive substrate and a biocontact layer 3 formed on the circular portion of the conductive pattern 2.

[0167] Next, as shown in Figure 4, the thermoplastic urethane film 20 on which the bioelectrode 1 was printed was cut out and double-sided tape 21 was attached to it, thereby producing three bioelectrode samples 10 (samples for evaluating biosignals) for each bioelectrode composition.

[0168] (Measurement of the thickness of the biological contact layer) The thickness of the biocontact layer of each bioelectrode sample prepared as described above was measured using a micrometer. The results are shown in Table 5.

[0169] (Biological signal measurement) The conductive wiring pattern of the bioelectrode, made of conductive paste, was connected with a conductive wire to the NeXus10 MARKII (a multi-sensor physiological measurement system) manufactured by MindMedia, a Dutch company. The positive electrode of the electrocardiograph was attached to the LA location on the left forearm, the negative electrode to the RA location on the right forearm, and the ground to the G location, as shown in Figure 5. Immediately after attachment, electrocardiogram measurement was started, and the initial potential of the electrocardiogram waveform consisting of P, Q, R, S, and T waves shown in Figure 6 and baseline fluctuations of the electrocardiogram waveform were evaluated. The results are shown in Table 5. Alternatively, the electrode surface or skin may be wiped with gauze soaked in a solution containing 70% ethanol and 30% water immediately before attachment.

[0170] [Early potential criteria for ECG signals] ○○: Potential is -50,000 μV or more and less than +50,000 μV ○: Potential is -100,000 μV or more and less than -50,000 μV, or +50,000 μV or more and less than +100,000 μV △: Less than -100,000 μV or more than +100,000 μV ×: Initial electrocardiogram not measurable

[0171] [Criteria for determining baseline potential fluctuations in ECG signals] ○: During the 10-minute electrocardiogram measurement, the potential fluctuates by less than 20,000 μV relative to the initial potential. △: During the 10-minute electrocardiogram measurement, there is a potential fluctuation of 20,000 μV or more and less than 50,000 μV relative to the initial potential. ×: During the 10-minute electrocardiogram measurement, there is a potential fluctuation of 50,000 μV or more relative to the initial potential.

[0172] [Table 5]

[0173] As shown in Table 5, in Examples 1 to 22 in which a biocontact layer was formed which was a cured product of bioelectrode compositions 1 to 22 containing the deep eutectic liquid of the present invention having the specific structure described above, binder resin (A), and conductive particles (B), it was possible to obtain a biosignal (ECG signal) immediately after application to the body.

[0174] On the other hand, the comparative bioelectrode composition 1 of Comparative Example 1 contained an ionic polymer compound, a binder resin (A), and conductive particles (B), but did not contain a deep eutectic liquid. As a result, the comparative bioelectrode composition 1 of Comparative Example 1 did not obtain a biosignal from the initial stage of measurement. This is thought to be because the ionic polymer was a solid, and therefore its ionic conductivity was inferior to that of a deep eutectic liquid.

[0175] Furthermore, the comparative bioelectrode compositions 2 and 4 of Comparative Examples 2 and 4 contained an ionic polymer compound, a binder resin (A), conductive particles (B), and the hydrogen bond donor compound used in the examples, but did not contain a hydrogen bond acceptor compound and did not contain a deep eutectic liquid. As a result, biosignals could be acquired from the initial stage, but the baseline potential fluctuation of the ECG signal was large. This is presumably because the inclusion of the hydrogen bond donor compound provided good adhesion to the living body, allowing biosignals to be acquired from the initial stage. However, the poor ionic conductivity of the electrode caused a polarization voltage to be generated between the living body and the electrode, resulting in large potential fluctuations.

[0176] Furthermore, comparative bioelectrode compositions 3 and 5 in Comparative Examples 3 and 5 did not contain an ionic polymer compound, but the results did not change significantly whether or not an ionic polymer compound was present. This is thought to be because the ionic polymer compound had insufficient ionic conductivity, which resulted in a polarization voltage being generated between the living body and the electrode, resulting in large potential fluctuations.

[0177] Comparative bioelectrode compositions 6 and 7 in Comparative Examples 6 and 7 contained choline chloride and betaine anhydride as ionic materials, but because they were solids, water was used to disperse them. However, when they were applied and formed into a film, they precipitated as a solid, which is thought to have no ionic conductivity and prevented biosignals from being acquired.

[0178] From the above, it has become clear that the deep eutectic liquid, the bioelectrode composition using the same, the bioelectrode using the composition, and the method for manufacturing a bioelectrode of the present invention can quickly obtain a stable biosignal. In other words, the deep eutectic liquid, the bioelectrode composition using the same, the bioelectrode using the composition, and the method for manufacturing a bioelectrode of the present invention can provide a bioelectrode composition and a bioelectrode that can quickly obtain a stable biosignal when attached to a living body.

[0179] The present specification includes the following aspects. [1]: A deep eutectic liquid which is a mixture of a hydrogen bond donor compound and a hydrogen bond accepting compound, wherein the hydrogen bond donor compound is a compound having a structure in which 2 to 100 hydroxyl group-containing monomers are bonded, as shown in the following general formula (1), and the hydrogen bond accepting compound is a compound containing a monomer having a quaternary ammonium cation shown in the following general formulas (2) to (6), or a quaternary phosphonium cation shown in the following general formula (7), and the deep eutectic liquid exists as a liquid at 25°C. [ka] (In the formula, X represents a single bond or a linear, branched, or cyclic divalent hydrocarbon group having 1 to 30 carbon atoms, which may be substituted with or interrupted by a heteroatom. Y and Z represent a linear, branched, or cyclic divalent hydrocarbon group having 1 to 5 carbon atoms, which may be substituted with or interrupted by a heteroatom. A and B represent a hydrogen atom, a hydroxyl group, an amino group, a halogen atom, or an alkyl group or an alkyl group terminally substituted with a siloxane, which may be substituted with or interrupted by a heteroatom. Y and Z may be the same or different. A and B may be the same or different. m is an integer of 1 to 100 and represents a repetition of a chemical structural unit. n is an integer of 1 to 4 and represents a repetition of a chemical structural unit, provided that 2≦m×n≦100 is satisfied.) [ka] (In the formula, R1~R 12 R1 to R2 are a linear, branched, or cyclic monovalent hydrocarbon group having 1 to 30 carbon atoms, a hydrogen atom, a hydroxyl group, an amino group, a nitro group, or a halogen atom, which may be substituted with a heteroatom, may be interposed between heteroatoms, or may be a zwitterion having an anion moiety. 12 may be the same or different.) [2]: The deep eutectic liquid according to [1] above, characterized in that the monomer having a hydroxyl group is glycerin. [3]: The deep eutectic liquid according to [2] above, wherein the hydrogen bond donor compound is a polyglycerin-modified silicone represented by the following general formula (8) or (9): [ka] (In the formula, R1' are each independent and may be the same or different from each other, and are a hydrogen atom, a linear or branched alkyl group having 1 to 50 carbon atoms, or a phenyl group, and may contain an ether group or may be a silicone chain represented by general formula (10). R2' is a group having a polyglycerin structure represented by general formula (8)-1 or general formula (8)-2. R3' are each independent and may be the same or different from each other, and are R1' or R2'. R4' are each independent and may be the same or different from each other, and are R1' or R2'. or an oxygen atom. When R4' is an oxygen atom, two R4' may be bonded to form a single ether group, which may form a ring together with the silicon atom to which they are bonded. a' may be the same or different and is 0 to 100, b' is 0 to 100, and a' + b' is 0 to 200. However, when b' is 0, at least one of R3' is the above-mentioned R2'. R5' is an alkylene group having 2 to 10 carbon atoms or an aralkylene group having 7 to 10 carbon atoms. R6' and R7' are alkylene groups having 2 to 6 carbon atoms, and R7' may be an ether group. c' is 0 to 20, and d' is 2 to 20. [4]: A bioelectrode composition, characterized in that it contains any one of the deep eutectic liquids described above in [1] to [3]. [5]: The bioelectrode composition according to the above [4], characterized in that the bioelectrode composition contains a binder (A). [6]: The bioelectrode composition according to the above [5], wherein the binder (A) is one or more resins selected from the group consisting of silicone resins, polyurethane resins, and polyacrylic resins. [7]: The bioelectrode composition according to any one of [4] to [6] above, characterized in that the bioelectrode composition contains conductive particles (B). [8]: The bioelectrode composition according to [7], characterized in that the conductive particles (B) contain one or more selected from carbon powder, gold, silver, silver chloride, platinum, aluminum, magnesium, tin, tungsten, iron, copper, nickel, stainless steel, chromium, titanium, molybdenum, ruthenium, and indium. [9]: The bioelectrode composition according to [8], wherein the carbon powder is either or both of carbon black and carbon nanotubes.

[10] : The bioelectrode composition according to any one of [4] to [9] above, further characterized in that the bioelectrode composition contains glycerin.

[11] : A bioelectrode having a conductive substrate and a biocontact layer formed on the conductive substrate, characterized in that the biocontact layer contains a cured product of the bioelectrode composition of any one of [4] to

[10] above.

[12] : The bioelectrode according to

[11] , characterized in that the conductive substrate contains one or more selected from gold, silver, silver chloride, platinum, aluminum, magnesium, tin, tungsten, iron, copper, nickel, stainless steel, chromium, titanium, and carbon.

[13] : A method for manufacturing a bioelectrode having a conductive substrate and a biocontact layer formed on the conductive substrate, characterized in that the bioelectrode composition according to any one of [4] to

[10] above is applied to the conductive substrate and cured to form the biocontact layer.

[14] : The method for manufacturing a bioelectrode according to

[13] above, characterized in that the conductive substrate contains one or more selected from gold, silver, silver chloride, platinum, aluminum, magnesium, tin, tungsten, iron, copper, nickel, stainless steel, chromium, titanium, and carbon.

[15] : A method for manufacturing a bioelectrode having a conductive substrate and a biocontact layer formed on the conductive substrate, characterized in that the bioelectrode composition according to any one of [4] to

[10] above is applied to a release substrate, cured, and patterned, and then transferred onto the conductive substrate to form the biocontact layer.

[0180] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits similar effects is included within the technical scope of the present invention. [Explanation of symbols]

[0181] 1...bioelectrode, 2...conductive substrate (conductive pattern), 3...biocontact layer, 4... Conductive particles, 5... Deep eutectic liquid, 6... Resin, 7... Living body, 10... Living body electrode sample, 20... Thermoplastic urethane film, 21...Double-sided tape.

Claims

1. A deep eutectic liquid which is a mixture of a hydrogen bond donor compound and a hydrogen bond accepting compound, wherein the hydrogen bond donor compound is a compound having a structure in which 2 to 100 hydroxyl group-containing monomers are bonded, as shown in the following general formula (1), and the hydrogen bond accepting compound is a compound containing a monomer having a quaternary ammonium cation shown in the following general formulas (2) to (6), or a quaternary phosphonium cation shown in the following general formula (7), and the deep eutectic liquid exists as a liquid at 25°C. 【Chemistry 1】 (In the formula, X represents a single bond or a linear, branched, or cyclic divalent hydrocarbon group having 1 to 30 carbon atoms, which may be substituted with or interrupted by a heteroatom. Y and Z represent a linear, branched, or cyclic divalent hydrocarbon group having 1 to 5 carbon atoms, which may be substituted with or interrupted by a heteroatom. A and B represent a hydrogen atom, a hydroxyl group, an amino group, a halogen atom, or an alkyl group or an alkyl group terminally substituted with a siloxane, which may be substituted with or interrupted by a heteroatom. Y and Z may be the same or different. A and B may be the same or different. m is an integer from 1 to 100 and represents a repetition of a chemical structural unit. n is an integer from 1 to 4 and represents a repetition of a chemical structural unit, provided that 2≦m×n≦100 is satisfied.) 【Chemistry 2】 (In the formula, R １ ~R １２ R is a linear, branched, or cyclic monovalent hydrocarbon group having 1 to 30 carbon atoms, a hydrogen atom, a hydroxyl group, an amino group, a nitro group, or a halogen atom, which may be substituted with a heteroatom, may be interposed between heteroatoms, or may be a zwitterion having an anion moiety. １ ~R １２ may be the same or different.)

2. The deep eutectic liquid according to claim 1, characterized in that the monomer having a hydroxyl group is glycerin.

3. The deep eutectic liquid according to claim 2, characterized in that the hydrogen bond donor compound is a polyglycerin-modified silicone represented by the following general formula (8) or (9): 【Transformation 3】 (In the formula, R １ R' are each independent and may be the same or different, and each represent a hydrogen atom, a linear or branched alkyl group having 1 to 50 carbon atoms, or a phenyl group, and may contain an ether group or may be a silicone chain represented by the general formula (10). ２ R' is a group having a polyglycerin structure represented by general formula (8)-1 or general formula (8)-2. ３ ' are each independent and may be the same or different from each other, １ ' or the R ２ '. R ４ ' are each independent and may be the same or different from each other, １ ', the R ２ ', or an oxygen atom. ４ When R ′ is an oxygen atom, two R ４ a' may be bonded to form a single ether group and may form a ring together with the silicon atom to which they are bonded. a' may be the same or different and ranges from 0 to 100, b' ranges from 0 to 100, and a'+b' ranges from 0 to 200. However, when b' is 0, R ３ At least one of the R ２ '. R ５ R' is an alkylene group having 2 to 10 carbon atoms or an aralkylene group having 7 to 10 carbon atoms. ６ ' and R ７ ' is an alkylene group having 2 to 6 carbon atoms, and R ７ may be an ether group; c' is 0 to 20, and d' is 2 to 20.

4. A bioelectrode composition, comprising the deep eutectic liquid according to any one of claims 1 to 3.

5. The bioelectrode composition according to claim 4, characterized in that the bioelectrode composition contains a binder (A).

6. 6. The bioelectrode composition according to claim 5, wherein the binder (A) is one or more resins selected from the group consisting of silicone resins, polyurethane resins, and polyacrylic resins.

7. 5. The bioelectrode composition according to claim 4, wherein the bioelectrode composition contains conductive particles (B).

8. The bioelectrode composition according to claim 7, characterized in that the conductive particles (B) contain one or more selected from carbon powder, gold, silver, silver chloride, platinum, aluminum, magnesium, tin, tungsten, iron, copper, nickel, stainless steel, chromium, titanium, molybdenum, ruthenium, and indium.

9. 9. The bioelectrode composition according to claim 8, wherein the carbon powder is either or both of carbon black and carbon nanotubes.

10. The bioelectrode composition according to claim 4, further comprising glycerin.

11. A bioelectrode having a conductive substrate and a biocontact layer formed on the conductive substrate, wherein the biocontact layer comprises a cured product of the bioelectrode composition according to claim 4.

12. The bioelectrode according to claim 11, characterized in that the conductive substrate contains one or more selected from gold, silver, silver chloride, platinum, aluminum, magnesium, tin, tungsten, iron, copper, nickel, stainless steel, chromium, titanium, and carbon.

13. A method for manufacturing a bioelectrode having a conductive substrate and a biocontact layer formed on the conductive substrate, characterized in that the bioelectrode composition according to claim 4 is applied to the conductive substrate and cured to form the biocontact layer.

14. The method for manufacturing a bioelectrode according to claim 13, characterized in that the conductive substrate contains one or more selected from gold, silver, silver chloride, platinum, aluminum, magnesium, tin, tungsten, iron, copper, nickel, stainless steel, chromium, titanium, and carbon.

15. A method for manufacturing a bioelectrode having a conductive substrate and a biocontact layer formed on the conductive substrate, characterized in that the bioelectrode composition according to claim 4 is applied to a release substrate, cured, and patterned, and the patterned product is transferred onto the conductive substrate to form the biocontact layer.

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