JP2024059574A - Conductive Sheet - Google Patents

Abstract

The present invention provides a conductive sheet with excellent film-forming properties and biocompatibility. The present invention provides a conductive sheet in which a film containing polythiophene containing a specific structural unit and a polymer film are laminated, the thickness of the film being 50 to 1,000 nm, and the thickness of the film being 200 to 10,000 nm. [Selected Figures] None

Description

Application for application of Article 30, Paragraph 2 of the Patent Act has been filed. 1. Date held: October 21, 2022 Meeting name and location: 2022 Selftron Study Group Station Conference Tokyo 5F 501 ABS Conference Room (5F Sapia Tower, 1-7-12 Marunouchi, Chiyoda-ku, Tokyo) Publisher: Shinji Takeoka 2. Date posted on website: July 4, 2023 Website address: https://main.spsj.or.jp/ipc/2023/ Publisher: Hiroaki Taniguchi, Mao Nagata, Yuichi Yano, and Shinji Takeoka 3. Date: July 21, 2023 Meeting name and location: The 13th SPSJ International Polymer Conference (IPC2023) Sapporo Convention Center (1-1-1 Higashisapporo 6-jo, Shiroishi-ku, Sapporo, Hokkaido) Disclosure: Hiroaki Taniguchi, Mao Nagata, Yuichi Yano, and Shinji Takeoka

The present invention relates to a conductive sheet that can be used for bioelectrodes, etc.

When measuring cardiac potential using an electrocardiograph, an electrocardiogram electrode (e.g., Reddat (registered trademark) electrocardiogram electrode) made of a base material and a conductive adhesive is used. This electrocardiogram electrode is known as a type of bioelectrode, but because it is about 1 mm thick and has low flexibility, it is designed to be used in a resting state, and it is difficult to use it to measure potential fluctuations in the human body when active.

In recent years, there has been an increasing need to measure potential fluctuations such as myoelectric potential and cardiac potential of the human body during activity in order to contribute to disease prevention, healthy life expectancy promotion, and improvements in sports medicine. To meet such needs, there is a demand for the development of flexible electrodes in which the electrode layer can deform to conform to the unevenness of the attachment surface of the living body and adhere closely to the surface, thereby minimizing discomfort when worn. Flexible electrodes using PEDOT:PSS have been reported (for example, Patent Document 1).

International Publication No. 2021/095480

The flexible electrode described in Patent Document 1 uses a PEDOT:PSS film in its electrode layer, but it is preferable to use additives such as fluorine-based surfactants in combination to improve film-forming properties. In this case, there are issues with the biocompatibility of the additives, and improvements are required.

One aspect of the present invention aims to provide a conductive sheet that combines good film-forming properties with excellent biocompatibility.

As a result of extensive research, the inventors discovered that the conductive sheet described below can solve the above problems, and thus completed the present invention.

That is, one aspect of the present invention relates to a conductive sheet as shown below.

[1] A conductive sheet in which a film (A) containing polythiophene containing at least one structural unit selected from the group consisting of structural units represented by the following general formula (1) and structural units represented by the following general formula (2) and a polymer film (B) are laminated, the conductive sheet being characterized in that the thickness of the film (A) is 50 to 1,000 nm and the thickness of the film (B) is 200 to 10,000 nm.

[In general formulas (1) and (2), ^R2 represents a hydrogen atom, a methyl group, an ethyl group, a linear or branched alkyl group having 3 to 6 carbon atoms, or a fluorine atom, m represents an integer of 1 to 10, and n represents 0 or 1.]
[2] The conductive sheet according to [1], wherein the film (B) is formed from at least one polymer selected from the group consisting of styrene-butadiene copolymers, polylactic acid, polycaprolactone, polydimethylsiloxane, polyurethane, natural rubber, acrylic polymers, methacrylic polymers, vinyl alcohol polymers, polysaccharides, and polystyrene.

According to one aspect of the present invention, a conductive sheet that combines good film-forming properties and excellent biocompatibility can be provided.

FIG. 1 is a cross-sectional view illustrating a layer structure of an example of a conductive sheet according to an embodiment of the present invention. FIG. 1 is a cross-sectional view illustrating a layer structure of an example of a conductive sheet according to an embodiment of the present invention. FIG. 1 is a cross-sectional view illustrating a layer structure of an example of a conductive sheet according to an embodiment of the present invention. FIG. 1 is a cross-sectional view illustrating a layer structure of an example of a conductive sheet according to an embodiment of the present invention. FIG. 2 is a diagram showing the state of a water droplet on a two-layer laminate sheet when a contact angle is measured in one embodiment. 13 is an electromyogram obtained using the conductive sheet electrode prepared in Example 4. 13 is an electromyogram obtained using the conductive sheet electrode prepared in Example 5.

One embodiment of the present invention will be described in detail below. In this specification, unless otherwise specified, "A to B" representing a numerical range means "A or more, B or less."

Summary of the Invention
One embodiment of the present invention provides a conductive sheet suitable for flexible electrodes such as bioelectrodes. The electrodes are used in applications such as measuring potential fluctuations such as myoelectric potential and cardiac potential of an active human body, and functional electrical stimulation applications in treating paralysis associated with neurological diseases such as stroke or spinal cord injury. Conventional metal electrodes have difficulty in adhering to the irregularities of the surface of a living body. In addition, when a metal electrode is implanted in a living tissue to perform functional electrical stimulation, chronic inflammation or localized nerve weakness occurs at the insertion site, making long-term use difficult.

Flexible electrodes made of conductive polymers, which are softer and lighter conductive materials than metal electrodes, have excellent adhesion to biological surfaces such as the skin and can easily follow bending and stretching of the surface on which they are attached. In addition, because they are not uncomfortable to wear, they are expected to be applied in fields such as healthcare and sports science.

As shown in Patent Document 1, PEDOT:PSS has been proposed as a conductive polymer contained in the conductive sheet as a flexible electrode, which is a material that exhibits high conductivity. PEDOT:PSS stands for poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate. However, PEDOT:PSS alone cannot exhibit conductivity, and polar solvents or surfactants are used in combination as additives. It has been pointed out that such additives can cause biotoxicity by eluting into the in vivo environment. It is also known that when PEDOT:PSS swells in liquid, the function of PSS acting as a dopant for PEDOT decreases.

The conductive sheet according to one embodiment of the present invention contains polythiophene (A1) as a conductive polymer, which will be described later. Polythiophene (A1) makes it possible to form a film with good conductivity without the need for additives such as fluorine-based surfactants. Therefore, the conductive sheet according to one embodiment of the present invention can provide a bioelectrode with excellent biocompatibility. In addition, such a conductive sheet has better water resistance than conventionally known flexible electrodes. This allows for continuous long-term wear in the body, reducing the hassle of electrode replacement and enabling continuous measurement of biological data over an unprecedented long period of time.

The use of such conductive sheets can promote the spread of bioelectrodes in fields such as healthcare and sports science. In addition, because it is possible to provide bioelectrodes that can be used for a long period of time, the amount of bioelectrodes that are discarded can be reduced. This effect also contributes to the achievement of the goals of "3. Good health and well-being" and "12. Sustainable consumption and production patterns" of the Sustainable Development Goals (SDGs) advocated by the United Nations.

[Conductive sheet]
Fig. 1 is a cross-sectional view showing a schematic layer structure of a conductive sheet 1 according to the present embodiment. As shown in Fig. 1, the conductive sheet 1 according to one embodiment of the present invention is formed by laminating a film (A) containing polythiophene and a polymer film (B) described later. In this specification, the film (A) containing polythiophene may be simply referred to as "film (A)" and the polymer film (B) may be simply referred to as "film (B)".

<Film containing polythiophene (A)>
The film (A) is a film (A) containing a polythiophene containing at least one structural unit selected from the group consisting of a structural unit represented by the following general formula (1) and a structural unit represented by the following general formula (2). For convenience of explanation, such a polythiophene may be referred to as polythiophene (A1).

[In general formulas (1) and (2), ^R2 represents a hydrogen atom, a methyl group, an ethyl group, a linear or branched alkyl group having 3 to 6 carbon atoms, or a fluorine atom, m represents an integer of 1 to 10, and n represents 0 or 1.]
The film (A) functions as a conductive layer in the conductive sheet 1. The film (A) may be electrically connected to an external connection electrode of a biomeasuring instrument or the like. For example, a through hole may be formed in a part of the film (A) and/or the film (B), and the conductive material filled in the through hole may function as a connector to electrically connect the film (A) to the external connection electrode. Also, a connector formed of a conductive material may be provided at the end of the film (A), and the film (A) may be electrically connected to the external connection electrode via the connector.

The membrane (A) has flexibility so that it can deform, for example, to conform to the surface of the body surface to which it is attached. Such flexibility can be achieved by the membrane (A) containing polythiophene (A1), a conductive polymer, as a conductive material.

With respect to ^R2 in the above general formulas (1) and (2), the linear or branched alkyl group having 3 to 6 carbon atoms is not particularly limited, and examples thereof include an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a neopentyl group, a tert-pentyl group, a cyclopentyl group, an n-hexyl group, a 2-ethylbutyl group, and a cyclohexyl group.

From the viewpoint of film-forming properties, the above ^R2 is preferably a hydrogen atom, a methyl group, an ethyl group, or a fluorine atom.

In the above general formulas (1) and (2), m represents an integer of 1 to 10, and from the viewpoint of film-forming properties, it is preferably an integer of 1 to 6, more preferably an integer of 1 to 4, and even more preferably 2 or 3.

In the above general formulas (1) and (2), n represents 0 or 1, and it is preferable that n is 1 in terms of excellent electrical conductivity.

The structural unit represented by the above general formula (2) represents the doped state of the structural unit represented by the above general formula (1).

Dopants that cause an insulator-metal transition by doping can be divided into acceptors and donors. The former enter close to the polymer chain of a conductive polymer and take away π electrons from the conjugated system of the main chain. As a result, a positive charge (hole) is injected into the main chain, so it is also called a p-type dopant. Conversely, the latter donates electrons to the conjugated system of the main chain, and these electrons move through the conjugated system of the main chain, so it is also called an n-type dopant.

In this embodiment, the dopant is a sulfo group or a sulfonate group that is covalently bonded within the polymer molecule, and is a p-type dopant. A polymer that exhibits conductivity without the addition of an external dopant is called a self-doped polymer.

Polythiophene (A1) can be produced by polymerizing a thiophene monomer represented by the following general formula (4) in water or an alcohol solvent in the presence of an oxidizing agent, and then optionally treating with an acid.

[In the general formula (4), M represents a hydrogen ion or a metal ion. ^R2 represents a hydrogen atom, a methyl group, an ethyl group, a linear or branched alkyl group having 3 to 6 carbon atoms, or a fluorine atom. m represents an integer of 1 to 10, and n represents 0 or 1.]
The metal ion represented by M in the above general formula (4) is not particularly limited, but examples thereof include transition metal ions, precious metal ions, non-ferrous metal ions, alkali metal ions (e.g., Li ions, Na ions, and K ions), alkaline earth metal ions, and the like.

When the polymer obtained after polymerization of the thiophene monomer represented by general formula (4) is a metal salt, M can be converted to a hydrogen ion by treating the obtained metal salt polymer with an acid.

The thiophene monomer represented by the above general formula (4) is not particularly limited, but specifically includes 6-(2,3-dihydro-thieno[3,4-b][1,4]dioxin-2-yl)hexane-1-sulfonic acid, sodium 6-(2,3-dihydro-thieno[3,4-b][1,4]dioxin-2-yl)hexane-1-sulfonate, lithium 6-(2,3-dihydro-thieno[3,4-b][1,4]dioxin-2-yl)hexane-1-sulfonate, 8-(2,3-dihydro-thieno[3,4-b][1,4]dioxin-2-yl)hexane-1-sulfonic acid, sodium 8-(2,3-dihydro-thieno[3,4-b][1,4]dioxin-2-yl)octane-1-sulfonic acid, and potassium 8-(2,3-dihydro-thieno[3,4-b][1,4]dioxin-2-yl)octane-1-sulfonic acid, 3-[(2,3-dihydrothieno[3,4-b][1,4]dioxin-2-yl)methoxy]-1-propane sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-propanesulfonate, potassium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-methyl-1-propanesulfonate, sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-ethyl-1-propanesulfonate, sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-ethyl-1-propanesulfonate, sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-propyl-1-propanesulfonate, sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-butyl-1-propanesulfonate, sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-pentyl-1-propanesulfonate, sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-hexyl-1-propanesulfonate thorium, sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-isopropyl-1-propanesulfonate, sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-isobutyl-1-propanesulfonate, sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-isopentyl-1-propanesulfonate, sodium 3-[(2,3-dihydrothieno[3,4-b] -[1,4]dioxin-2-yl)methoxy]-1-fluoro-1-propanesulfonic acid sodium salt, 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-methyl-1-propanesulfonic acid potassium salt, 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-methyl-1-propanesulfonic acid, 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-methyl-1-propanesulfonic acid a ammonium, 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-methyl-1-propanesulfonate triethylammonium, 4-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-butanesulfonate sodium, 4-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-butanesulfonate potassium, 4-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-butanesulfonate ) methoxy]-1-methyl-1-butanesulfonate sodium, 4-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl) methoxy]-1-methyl-1-butanesulfonate potassium, 4-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl) methoxy]-1-fluoro-1-butanesulfonate sodium, and 4-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl) methoxy]-1-fluoro-1-butanesulfonate potassium are examples.

The conductivity of the film (A) is not particularly limited, but it is preferable that the conductivity (electrical conductivity) in the film state is 10 S/cm or more.

In addition, polythiophene (A1) synthesized based on publicly known information can also be used.

The content of polythiophene (A1) in film (A) may be 0.01 to 100% by weight, and from the viewpoint of electrical conductivity, it is preferably 0.05 to 80% by weight, and more preferably 0.1 to 70% by weight.

The membrane (A) may contain a compound (A2) capable of forming an ion pair with the sulfonic acid group of the polythiophene (A1). The compound (A2) capable of forming an ion pair with the sulfonic acid group is not particularly limited, but examples thereof include alkali metal compounds, ammonia, organic amine compounds, and quaternary ammonium salts. These compounds (A2) react with the sulfonic acid group of the polythiophene (A1) to form alkali metal ion salts, ammonium ion salts, organic ammonium ion salts, and quaternary ammonium ion salts of the polythiophene (A1).

The above-mentioned alkali metal compounds are not particularly limited, but examples thereof include alkali metal salt compounds (e.g., lithium chloride, potassium chloride, sodium chloride, rubidium chloride, cesium chloride, lithium bromide, potassium bromide, sodium bromide, rubidium bromide, cesium bromide, etc.) and alkali metal hydroxides (e.g., lithium hydroxide, potassium hydroxide, sodium hydroxide, rubidium hydroxide, cesium hydroxide, etc.).

If the film (A) contains the above-mentioned alkali metal compound, at least a portion of the polythiophene (A1) contained in the film (A) forms an alkali metal ion salt. The above-mentioned alkali metal ion is not particularly limited, but examples thereof include lithium ions, potassium ions, sodium ions, rubidium ions, and cesium ions.

The organic amine compound is not particularly limited, but examples thereof include primary, secondary, or tertiary organic amine compounds having a total carbon number of 1 to 30. More specifically, examples thereof include methylamine, dimethylamine, trimethylamine, ethylamine, triethylamine, normal-propylamine, isopropylamine, normal-butylamine, hexylamine, ethanolamine, dimethylaminoethanol, methylaminoethanol, diethanolamine, N-methyldiethanolamine, triethanolamine, 3-amino-1,2-propanediol, 3-methylamino-1,2-propanediol, 3-dimethylamino-1,2-propanediol, 2-amino-2-hydroxymethyl-1,3-propanediol, 1,4-butanediamine, triisobutylamine, triisopentylamine, triisooctylamine, imidazole, N-methylimidazole, 1,2-dimethylimidazole, pyridine, picoline, and lutidine.

If the film (A) contains the organic amine compound, at least a part of the polythiophene (A1) contained in the film (A) forms an organic ammonium ion salt. The organic ammonium ion is not particularly limited, but examples thereof include primary, secondary, and tertiary organic ammonium ions having a total carbon number of 1 to 30. More specifically, examples of the organic ammonium ion include methylammonium, dimethylammonium, trimethylammonium, ethylammonium, triethylammonium, normal-propylammonium, isopropylammonium, normal-butylammonium, hexylammonium, 2-hydroxyethylammonium, N,N-dimethyl-N-(2-hydroxyethyl)ammonium, N-methyl-N-(2-hydroxyethyl)ammonium, di(2-hydroxyethyl)ammonium, and the like. ammonium, N-methyl-N,N-di(2-hydroxyethyl)ammonium, N,N,N-tri(2-hydroxyethyl)ammonium, 2,3-dihydroxypropylammonium, N-methyl-N-(2,3-dihydroxypropyl)ammonium, N,N-dimethyl-N-(2,3-dihydroxypropyl)ammonium, 1,4-butanediammonium, triisobutylammonium, triisopentylammonium, triisooctylammonium, imidazole cation, N-methylimidazole cation, 1,2-dimethylimidazole cation, pyridinium ion, picolinium ion, or lutidinium ion.

The above-mentioned quaternary ammonium salts are not particularly limited, but examples thereof include tetramethylammonium chloride, tetraethylammonium chloride, tetra-n-propylammonium chloride, tetra-n-butylammonium chloride, and tetra-n-hexylammonium chloride.

If the film (A) contains the above-mentioned quaternary ammonium salt, at least a portion of the polythiophene (A1) contained in the film (A) forms a quaternary ammonium ion salt. The quaternary ammonium ion is not particularly limited, but examples thereof include tetramethylammonium ion, tetraethylammonium ion, tetra-n-propylammonium ion, tetra-n-butylammonium ion, and tetra-n-hexylammonium ion.

From the viewpoint of availability, the compound (A2) capable of forming an ion pair with a sulfonic acid group is preferably an alkali metal hydroxide, ammonia, or a primary, secondary, or tertiary organic amine compound having a total carbon number of 1 to 16. Examples of the primary, secondary, or tertiary organic amine compound having a total carbon number of 1 to 16 include methylamine, dimethylamine, trimethylamine, ethylamine, triethylamine, normal-propylamine, isopropylamine, normal-butylamine, hexylamine, ethanolamine, dimethylaminoethanol, methylaminoethanol, diethanolamine, N-methyldiethanolamine, triethanolamine, 3-amino-1,2-propanediol, 3-methylamino-1,2-propanediol, 3-dimethylamino-1,2-propanediol, 1,4-butanediamine, triisobutylamine, triisopentylamine, imidazole, N-methylimidazole, 1,2-dimethylimidazole, pyridine, picoline, and lutidine.

When the membrane (A) contains a compound (A2) capable of forming an ion pair with the sulfonic acid group, a part or all of the polythiophene (A1) containing at least one structural unit selected from the group consisting of the structural unit represented by the general formula (1) and the structural unit represented by the general formula (2) interacts with the compound (A2). Then, a polythiophene (A1) containing at least one structural unit selected from the group consisting of the structural unit represented by the general formula (1') and the structural unit represented by the general formula (2') below is formed. That is, a mixture of the polythiophene (A1) containing at least one structural unit selected from the group consisting of the structural unit represented by the general formula (1) and the structural unit represented by the general formula (2) and the compound (A2) above and the polythiophene (A1) containing at least one structural unit selected from the group consisting of the structural unit represented by the general formula (1') and the structural unit represented by the general formula (2') are the same.

[In general formulas (1') and (2'), the definitions and preferred ranges of R ² , m, and n are the same as those in general formulas ( ¹ ) and (2). M represents a hydrogen ion, an alkali metal ion, an ammonium ion, an organic ammonium ion, or a quaternary ammonium ion.]
The alkali metal ion, ammonium ion, organic ammonium ion, and quaternary ammonium ion in M are as described above.

The content of the compound (A2) capable of forming an ion pair with the above-mentioned sulfonic acid group in the membrane (A) is preferably 0.001 to 20% by weight, more preferably 0.01 to 20% by weight, and even more preferably 0.1 to 20% by weight.

The shape of the film (A) in a planar view is not particularly limited, and may be, for example, a circle, an ellipse, a square, a rectangle, or a polygon. In this specification, the "planar view" of the conductive sheet 1 may refer to the state in which the conductive sheet 1 placed on a flat surface is viewed from a direction perpendicular to one of the surfaces of the conductive sheet 1.

<Polymer membrane (B)>
The film (B) is a film formed of a polymer. The film (B) is laminated on either one surface of the film (A). The film (B) may function as a support layer for the film (A), which is a conductive layer in the conductive sheet 1.

The polymer forming the film (B) is not particularly limited, but may be at least one polymer selected from the group consisting of styrene-butadiene copolymers such as styrene-butadiene-block polymers, polylactic acid, polycaprolactone, polydimethylsiloxane, polyurethane, natural rubber, acrylic polymers, methacrylic polymers, vinyl alcohol polymers, polysaccharides, and polystyrene. The film (B) may be a film formed from one of these polymers, or may be a film formed from a mixture of two or more polymers. If the film (B) is formed from such a polymer, the flexibility of the film (B) is good, and therefore the flexibility of the conductive sheet 1 can be well ensured. In addition, the film (B) may be a film formed mainly from a polymer, and does not prevent the film (B) from containing additives or unavoidable impurities.

The shape of the membrane (B) in a planar view is not particularly limited, and may be, for example, a circle, an ellipse, a square, a rectangle, or a polygon. The shape of the membrane (B) in a planar view may be similar to the shape of the membrane (A) in a planar view.

Also, as shown in FIG. 1, the membrane (B) may have a larger area in plan view than the membrane (A). In other words, the membrane (B) contains the membrane (A) in plan view, and the membrane (A) may entirely overlap the membrane (B), but the membrane (B) may have a portion that does not overlap with the membrane (A). When the conductive sheet 1 is attached to the surface of the living body, it is preferable that the conductive membrane (A) is located closer to the surface of the living body than the membrane (B). In this case, if the membrane (B) has the above-mentioned size, a portion of the membrane (B) can come into contact with the surface of the living body and be in close contact with it when the conductive sheet 1 is attached to the surface of the living body.

As shown in FIG. 2, the membrane (B) may have a pattern of communicating holes (B1) formed therein, in which case the communicating holes (B1) are filled with the membrane (A). The pattern of communicating holes (B1) can be created by a coating method described later. Examples of printing methods for forming the pattern of communicating holes (B1) include gravure coating and flexographic printing. The conductive sheet 1 shown in FIG. 2 can be used as an electrode sheet regardless of which of the two surfaces is in contact with the surface of a living body.

From the viewpoint of improving the adhesion of membrane (B) to both the biological surface and membrane (A), the polymer forming membrane (B) is preferably polyurethane. When membrane (B) is formed from polyurethane, membrane (B) can be more firmly attached to membrane (A) by subjecting one surface of membrane (B) in contact with membrane (A) to a corona discharge treatment and treating said surface with a diamino group-containing silane coupling agent. An example of this diamino group-containing silane coupling agent is 3-(2-aminoethyl)aminopropyltrimethoxysilane.

The area of membrane (A) in a plan view may be larger than membrane (B) or may be the same as membrane (B). Moreover, regardless of the areas of membrane (A) and membrane (B), a portion of membrane (A) does not have to overlap membrane (B).

<Other membranes, etc.>
The conductive sheet 1 may be a two-layer film in which the film (A) and the film (B) are laminated, or may further have another film laminated thereon. When the conductive sheet 1 is made of three or more layers, it is sufficient that the film (A) and the film (B) are laminated adjacent to each other.

Examples of other films include a water-permeable film, a water-soluble sacrificial film, and a protective film (C). The water-permeable film may be a layer that functions as a support for the film (A) and the film (B). The water-soluble sacrificial film may be a layer formed of a water-soluble material and formed on a bilayer film in which the film (A) and the film (B) are laminated, and functions as a support. Alternatively, the water-soluble sacrificial film may function as a layer that bonds the bilayer film in which the film (A) and the film (B) are laminated to the water-permeable film or the substrate. In addition, the water-soluble sacrificial film may function as a layer that peels off the bilayer film in which the film (A) and the film (B) are laminated from the water-permeable film or the substrate. In addition, the film in contact with the water-soluble sacrificial film and the bilayer film may be the film (A) or the film (B).

The water-permeable membrane may be made of a material that allows water to pass through, and examples of such materials include nonwoven fabric made of cellulose or resin, or sponge or mesh made of resin. The thickness of the water-permeable membrane may be about 0.03 to 3 mm from the viewpoint of ease of transport and storage of the conductive sheet 1. If the conductive sheet 1 has such a water-permeable membrane, the conductive sheet 1 can be easily transported and stored.

The water-soluble sacrificial membrane may be formed on a bilayer membrane in which membrane (A) and membrane (B) are laminated, and may have the strength of a carrier and may be formed of a water-soluble material that dissolves in water. Alternatively, the water-soluble sacrificial membrane may be formed of a water-soluble material that can bond the bilayer membrane in which membrane (A) and membrane (B) are laminated to the water-permeable membrane or substrate, and may be formed of a water-soluble material that dissolves in water. Examples of such water-soluble materials include starch, polyvinyl alcohol, polyacrylic acid, and polyethylene glycol. Such water-soluble materials can reliably bond membranes (A) and (B) to the water-permeable membrane, and can be dissolved by water that has permeated the water-permeable membrane to reliably peel membranes (A) and (B) from the water-permeable membrane.

As shown in FIG. 3, the conductive sheet 1 may be provided with a protective film (C). The protective film (C) is laminated so as to cover the membranes (A) and (B) and protects the membranes (A) and (B). It is preferable to use a commercially available medical moisture-permeable waterproof film or the like for the protective film (C).

When the conductive sheet 1 has a two-layer membrane in which the membrane (A) and the membrane (B) are laminated, and further has a water-permeable membrane, a water-soluble sacrificial membrane, and/or a protective membrane (C), the conductive sheet 1 is easy to transport and store, and is also easy to attach to the attachment surface of the conductive sheet 1.

The conductive sheet 1 may further include a component other than the laminated film. For example, as shown in FIG. 4, the conductive sheet 1 may include a conductor (D). A portion of the conductor (D) is in contact with the film (A). By including the conductor (D), the conductive sheet 1 can be electrically connected to, for example, a potential difference measuring device.

Examples of the conductive wire (D) include platinum wire, gold wire, silver wire, copper wire, aluminum wire, iron wire, carbon fiber, conductive fiber, etc.

<Method of manufacturing conductive sheet>
Below, an example will be given of a method for manufacturing the conductive sheet 1 according to this embodiment and a method for attaching it to the surface of a living body, but the method for manufacturing and attaching the conductive sheet 1 is not limited to this.

As a first example of a method for manufacturing a conductive sheet 1, a method for manufacturing a conductive sheet 1 that is a laminate in which a film (A), a film (B), and a water-soluble sacrificial film are stacked in this order will be described.

A solution containing polythiophene (A1) is applied onto the substrate described below, and then heat-treated and dried at a predetermined temperature to form a film (A). A solution of the polymer that forms the film (B) is applied onto the substrate (A), and then heat-treated and dried at a predetermined temperature to form a laminated film of film (B). A solution containing the water-soluble material is applied onto the substrate (B), and then heat-treated and dried at a predetermined temperature to form a laminated film of a water-soluble sacrificial film, which is then heat-treated and completely dried at a predetermined temperature. Through the above operations, a conductive sheet 1 can be manufactured, which is a laminate in which the film (A), film (B), and water-soluble sacrificial film are laminated on the substrate in this order.

As a second example of a method for manufacturing a conductive sheet 1, a method for manufacturing a conductive sheet 1 that is a laminate in which a membrane (A), a membrane (B), a water-soluble sacrificial membrane, and a water-permeable membrane are stacked in this order will be described.

A solution containing polythiophene (A1) is applied onto the substrate described below, and then heat-treated and dried at a predetermined temperature to form a film (A). A solution of a polymer forming the film (B) is applied onto the substrate (A), and then heat-treated and dried at a predetermined temperature to form a laminated film of the film (B). A solution containing the water-soluble material is applied onto the substrate (B), and then heat-treated and dried at a predetermined temperature to form a laminated film of a water-soluble sacrificial film. After applying the solution containing the water-soluble material, a water-permeable film is placed on the applied surface before it is completely dried, and the coating film made of the solution containing the water-soluble material is dried, thereby bonding the water-soluble sacrificial film and the water-permeable film. Through the above operations, a conductive sheet 1 can be manufactured, which is a laminate in which the film (A), film (B), water-soluble sacrificial film, and water-permeable film are laminated on the substrate in this order.

As a third example of a method for manufacturing a conductive sheet 1, a method for manufacturing a conductive sheet 1 that is a laminate in which a film (A), a film (B), and a frame made of adhesive tape are attached to the outer periphery of the surface of the film (B) will be described.

A solution containing polythiophene (A1) is applied onto the substrate described below, and then heat-treated and dried at a predetermined temperature to form the film (A). A solution of the polymer that forms the film (B) is applied onto the entire surface of the film (A), and then heat-treated and dried at a predetermined temperature to form the film (B). Next, adhesive tape is attached to the outer periphery of the surface of the film (B), thereby producing the conductive sheet 1, which is a laminate in which the film (A), the film (B), and a frame made of adhesive tape are installed on the outer periphery of the surface of the film (B), on the substrate. By installing adhesive tape on the outer periphery of the surface of the film (B), the structural retention of the laminated film can be increased, making it easier to peel off only the substrate.

As a fourth example of a method for manufacturing a conductive sheet 1, a method for manufacturing a conductive sheet 1 that is a laminate in which a water-permeable membrane, a water-soluble sacrificial membrane, membrane (B), and membrane (A) are stacked in this order will be described.

A water-permeable membrane is placed on the substrate, which will be described later. A solution containing the water-soluble material is applied to the surface of the water-permeable membrane, and then the solution is heat-treated at a predetermined temperature and dried to form a water-soluble sacrificial membrane. A solution of the polymer that forms the membrane (B) is applied to the water-soluble sacrificial membrane, and then the solution is heat-treated at a predetermined temperature and dried to form a laminated membrane of membrane (B). A solution containing polythiophene (A1) is applied to the membrane (B), and then the solution is heat-treated at a predetermined temperature and dried to form a laminated membrane of membrane (A). Through the above operations, a conductive sheet 1, which is a laminated body in which a water-permeable membrane, a water-soluble sacrificial membrane, a membrane (B), and a membrane (A) are laminated in this order, can be manufactured on the substrate.

As a fifth example of a method for manufacturing a conductive sheet 1, a method for manufacturing a conductive sheet 1 that is a laminate in which a film (B), a film (A), and a frame made of adhesive tape are attached to the outer periphery of the surface of the film (A) will be described.

A solution of the polymer that forms the above-mentioned film (B) is applied to the substrate described below, and then heat-treated and dried at a predetermined temperature to form the film (B). A solution containing polythiophene (A1) is applied to the above-mentioned film (B), and then heat-treated and dried at a predetermined temperature to form the film (A). Next, by attaching an adhesive tape to the outer periphery of the film (A), a conductive sheet 1 can be manufactured, which is a laminate in which the film (B), the film (A), and a frame made of adhesive tape are installed on the outer periphery of the surface of the film (A) on the substrate. By installing the adhesive tape on the outer periphery of the surface of the film (A), the structural retention of the laminated film can be increased, and the substrate can be easily peeled off.

In the above-mentioned example of the method for manufacturing the conductive sheet 1, the film (B) may have a through hole (B1). For example, a mask with a predetermined area of openings is applied onto the film on which the film (B) is to be formed, a solution containing a polymer is applied onto the mask to print the film, and then the mask is removed and the film is heat-treated at a predetermined temperature and dried, thereby laminating the film (B) having the through hole (B1).

As a sixth example of the method for producing the conductive sheet 1, a method for producing the conductive sheet 1, which is a laminate in which the film (A), film (B), and film (A) are laminated in this order, will be described. A solution of the polymer that forms the above-mentioned film (B) is applied to a substrate described later, and then heat-treated and dried at a predetermined temperature to form the film (B). A solution containing polythiophene (A1) is applied to the above-mentioned film (B), and then heat-treated and dried at a predetermined temperature to form the film (A). The laminate film consisting of the film (B) and the film (A) is peeled off from the substrate, and folded so that the fold lines on the film (B) side are hidden inside, thereby producing the conductive sheet 1, which is a laminate in which the film (A), film (B), and film (A) are laminated in this order.

The thicknesses of the film (A), the film (B), and the water-soluble sacrificial film can be controlled by adjusting the concentration of the polythiophene (A1), the concentration of the polymer, and/or the concentration of the water-soluble material in the coating solution used.

In addition, when film (A) or film (B) is formed directly on the substrate as in the first, second, third, fifth and sixth examples of the manufacturing method of the conductive sheet 1 described above, it is preferable that a release agent is applied to the substrate in advance. By applying the release agent, the conductive sheet 1 including film (A) and film (B) can be easily peeled off from the substrate after the post-processing is performed.

<Method of attaching the conductive sheet to the biological surface>
To explain a first example of the method of attaching the conductive sheet 1 to the attachment surface, only the substrate is peeled off from a laminate in which the substrate, the film (A), the film (B), and the water-soluble sacrificial film are laminated in this order, to obtain a conductive sheet 1 in which the film (A), the film (B), and the water-soluble sacrificial film are laminated in this order. Next, the conductive sheet 1 is placed on the water surface with the water-soluble sacrificial film facing down, and the water-soluble sacrificial film side is immersed in water to dissolve, so that only the conductive sheet 1 consisting of the film (A) and the film (B) can be floated on the water surface or in the water. This can be scooped up and attached to an attachment surface such as a living body surface, or attached to another substrate. For example, the conductive sheet 1 floating on the water surface or in the water can be scooped up on a mesh film and attached to an attachment surface such as a living body surface.

To explain a second example of the method of attaching the conductive sheet 1 to the attachment surface, only the substrate is peeled off from a laminate in which the substrate, the membrane (A), the membrane (B), the water-soluble sacrificial membrane, and the water-permeable membrane are laminated in this order, to obtain a conductive sheet 1 in which the membrane (A), the membrane (B), the water-soluble sacrificial membrane, and the water-permeable membrane are laminated in this order. Next, the conductive sheet 1 is placed on the attachment surface such as a biological surface so that the membrane (A) comes into contact with the attachment surface. Next, water is supplied to the water-permeable membrane of the conductive sheet 1, and the water-soluble sacrificial membrane is dissolved by the water that has permeated the water-permeable membrane, and the water-soluble sacrificial membrane is removed. This allows the water-permeable membrane to be peeled off from the conductive sheet 1 consisting of the membrane (A) and the membrane (B). By such an operation, the conductive sheet 1 consisting of the membrane (A) and the membrane (B) can be attached to the biological surface.

To explain a third example of the method of attaching the conductive sheet 1 to a mounting surface, the conductive sheet 1 consisting of the membrane (A), membrane (B), and frame can be peeled off from the substrate by utilizing the strength of the frame made of adhesive tape from a laminate having a substrate, membrane (A), membrane (B), and a frame made of adhesive tape attached to the outer periphery of the surface of membrane (B). The conductive sheet 1 can be attached to the mounting surface such as a biological surface so that membrane (A) comes into contact with the mounting surface. At this time, it is preferable that the biological surface is slightly wet, and the conductive sheet 1 can be stably attached to the biological surface by drying the conductive sheet 1 after mounting. The frame portion is then cut off.

As shown in FIG. 3, the conductive sheet 1 may have a protective film (C) laminated thereon to cover the membrane (A) and membrane (B), and the membrane (A) and membrane (B) may be protected by the protective film (C). When the protective film (C) is formed in the manner shown in FIG. 3, the membrane (A) can be brought into contact with the surface of the living body through the through hole (B1) of the membrane (B).

It is preferable to use a commercially available medical moisture-permeable waterproof film, etc., for the protective film (C).

To explain a fourth example of the method of attaching the conductive sheet 1 to a mounting surface, a conductive sheet 1 is obtained in which the film (A), film (B), and film (A) are laminated in this order based on the sixth example of the manufacturing method of the conductive sheet 1 described above. The conductive sheet 1 can be attached to the mounting surface such as a biological surface so that the film (A) comes into contact with the mounting surface. At this time, it is preferable that the biological surface is slightly wet, and the conductive sheet 1 can be stably attached to the biological surface by drying the conductive sheet 1 after attachment. By such an operation, the conductive sheet 1 consisting of the film (A), film (B), and film (A) can be attached to the biological surface.

In addition, the conductive sheet 1 can be electrically connected to a potential difference measuring device by installing a conductor (D) that contacts the membrane (A) as shown in Figure 4.

Examples of the conductive wire (D) include platinum wire, gold wire, silver wire, copper wire, aluminum wire, iron wire, carbon fiber, conductive fiber, etc.

<Thickness of conductive sheet>
The conductive sheet 1 is preferably thin. The thickness of the conductive sheet 1 indicates the length of the conductive sheet 1 in the lamination direction of the film (A) and the film (B). It is generally known that the bending rigidity of the conductive sheet 1 is proportional to the cube of the thickness of the sheet. From the viewpoint of improving the adhesion to the surface of a living body, the conductive sheet 1 is preferably highly flexible, in other words, is preferably low in bending rigidity.

From the viewpoint of improving the flexibility of the conductive sheet 1, the thickness of the film (A) may be 50 to 1,000 nm, preferably 50 to 500 nm, and more preferably 50 to 250 nm. The thickness of the film (B) may be 200 to 10,000 nm, preferably 200 to 5,000 nm, and more preferably 200 to 600 nm.

If the membranes (A) and (B) have such thicknesses, the bending rigidity of the conductive sheet 1 can be made sufficiently small as described above, so that the adhesiveness of the conductive sheet 1 to the surface of the living body can be ensured satisfactorily.

The drying atmosphere for each film may be air, an inert gas, a vacuum, or a reduced pressure. From the viewpoint of preventing deterioration of the polymer film, an inert gas such as nitrogen or argon is preferable.

The drying temperature after coating of each film is not particularly limited as long as it is a temperature at which a uniform conductive film can be obtained, but is preferably in the range of room temperature to 300°C, more preferably in the range of room temperature to 250°C, and even more preferably in the range of room temperature to 200°C. In this specification, room temperature refers to 15 to 25°C.

The substrate is preferably non-transparent and has excellent flatness. Examples of the substrate include, but are not limited to, a glass plate, a plastic plate, a polyester plate, a polyacrylate plate, a polycarbonate plate, a metal plate, a metal oxide plate, a ceramic plate, or a resist substrate.

The above coating method is not particularly limited, but examples include casting, dipping, bar coating, roll coating, gravure coating, flexographic printing, spray coating, spin coating, inkjet printing, and screen printing.

As a method for preparing a solution containing polythiophene (A1), for example, polythiophene (A1) and, if necessary, compound (A2) and a solvent are mixed and homogenized by stirring or the like. In this case, other additives may be added as necessary before mixing.

Here, the temperature during mixing is not particularly limited, but may be, for example, room temperature or heated. Preferably, the temperature is 0°C or higher and 100°C or lower.

The atmosphere in which the mixture is mixed is not particularly limited, but may be air or an inert gas.

When mixing a solution containing polythiophene (A1), in addition to the general mixing and dissolving operation using a stirrer tip or stirring blade, ultrasonic irradiation and homogenization treatment (for example, using a mechanical homogenizer, ultrasonic homogenizer, high-pressure homogenizer, etc.) may be performed. When homogenization treatment is performed, it is preferable to perform it at a low temperature to prevent thermal degradation of the polymer.

The pH of the solution containing polythiophene (A1) is preferably 1.5 to 5.0, more preferably 2.0 to 4.0, even more preferably 2.5 to 3.5, even more preferably 2.75 to 3.25, and particularly preferably 3.0. The pH of the solution can be adjusted by the type and content of compound (A2) capable of forming an ion pair with a sulfonic acid group.

For the solution containing polythiophene (A1), the solvent is not particularly limited as long as it contains water, but it may also contain a non-aqueous solvent. The non-aqueous solvent is not particularly limited, but examples thereof include an organic solvent or an electrolyte solution.

Organic solvents include alcohols, aprotic polar organic solvents, polyhydric alcohols, cyclic sulfones, lactones, etc.

Examples of alcohols include methanol, ethanol, propanol, butanol, methoxyethanol, ethoxyethanol, butoxyethanol, and ethylene glycol. Examples of aprotic polar organic solvents include dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and 1-methyl-2-pyrrolidone. Examples of polyhydric alcohols include ethylene glycol, propylene glycol, and polyglycerin. Examples of cyclic sulfones include sulfolane. Examples of lactones include γ-butyrolactone and other lactones.

The solvent may be a mixed solvent of water and an alcohol and/or an aprotic polar organic solvent. In this case, the content of the alcohol and/or the aprotic polar organic solvent in the solution is preferably 0.001 to 20% by weight, more preferably 0.01 to 15% by weight, and even more preferably 0.1 to 10% by weight, in terms of excellent operability.

The content of polythiophene (A1) in the solution containing polythiophene (A1) is not particularly limited as long as it is 0.01 to 10% by weight. Since such a solution is dried and dehydrated after application, a good uniform film can be obtained by keeping the content within the above range.

The concentration of the solution containing polythiophene (A1) may be adjusted by the compounding ratio, or may be adjusted by concentrating after compounding. The concentration method may be a method of distilling off the solvent under reduced pressure, or a method of using an ultrafiltration membrane.

The particle size of the solid content in the solution containing polythiophene (A1) is not particularly limited, but the smaller the particle size, the better the water solubility, which is also desirable from the viewpoint of the electrical conductivity of the film (A) and the uniform film formation during film formation. For example, when the solid content concentration of the above solution prepared at room temperature or under heating is 10% by weight or less, it is preferable that the particle size (D50) of the solid content is 0.02 μm or less.

The viscosity (20°C) of the solution containing polythiophene (A1) is preferably 200 mPa·s or less, more preferably 100 mPa·s or less, and even more preferably 50 mPa·s or less.

The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. The technical scope of the present invention also includes embodiments obtained by appropriately combining the technical means disclosed in different embodiments.

The present invention will be described in detail below with reference to examples. However, the present invention should not be construed as being limited in any way by these examples.

Example 1
A glass substrate (22 mm x 22 mm) was spin-coated with 400 μL of a 5 wt% polydimethylsiloxane solution (6000 rpm, 150 sec) and cured in air (95°C, 1 hr) to produce a peeling layer of several tens of nm. The solvent for the polydimethylsiloxane solution was a mixed solvent with a volume ratio of hexane:ethyl acetate of 3:1. The surface of the peeling layer was made hydrophilic by plasma treatment (45 mA, 133 Pa, 30 sec). The plasma-treated surface of the peeling layer was spin-coated with 400 μL of Selfron (registered trademark) S100 (manufactured by Tosoh Corporation) (1500 rpm, 60 sec), and then annealed in vacuum (150°C, 30 min) to produce a conductive layer. Selfron
Since S100 contains the polythiophene (A1) according to one embodiment of the present invention, the conductive layer obtained here corresponds to the film (A) according to one embodiment of the present invention.

A support layer was fabricated by spin-coating (4000 rpm, 20 sec) 400 μL of a tetrahydrofuran solution of 5% by weight styrene-butadiene-block polymer (Sigma-Aldrich) onto the conductive layer and curing (80°C, 1 hr) in air. The support layer obtained here corresponds to the film (B) according to one embodiment of the present invention.

A polyvinyl alcohol layer was produced on the support layer by drop casting (80°C, 18 min) a 10 wt% aqueous solution of polyvinyl alcohol (Kanto Chemical Co., Ltd.) on a hot plate. The polyvinyl alcohol layer obtained here corresponds to a water-soluble sacrificial film. The resulting Selfron S100/styrene-butadiene-block polymer/polyvinyl alcohol three-layer laminate was peeled off from the glass substrate.

The three-layer laminate was placed in Milli-Q (registered trademark) water to dissolve the polyvinyl alcohol layer corresponding to the water-soluble sacrificial film (RT. 20 min), and a Selfron S100/styrene-butadiene-block polymer two-layer laminate sheet was obtained. The two-layer laminate sheet obtained here and the above-mentioned three-layer laminate each correspond to a conductive sheet according to one embodiment of the present invention. The obtained two-layer laminate sheet was adhered to a PET film substrate so that the styrene-butadiene-block polymer surface was in contact with the PET surface.

Example 2
A glass substrate (22 mm x 22 mm) was spin-coated with 400 μL of a 5 wt% polydimethylsiloxane solution (6000 rpm, 150 sec) and cured in air (95°C, 1 hr) to produce a peeling layer of several tens of nm. The solvent for the polydimethylsiloxane solution was a mixed solvent with a volume ratio of hexane:ethyl acetate of 3:1. The surface of the peeling layer was made hydrophilic by plasma treatment (45 mA, 133 Pa, 30 sec). The plasma-treated surface of the peeling layer was spin-coated with 400 μL of Selfron (registered trademark) S100 (manufactured by Tosoh Corporation) (1500 rpm, 60 sec), and then annealed in vacuum (150°C, 30 min) to produce a conductive layer. Selfron
Since S100 contains the polythiophene (A1) according to one embodiment of the present invention, the conductive layer obtained here corresponds to the film (A) according to one embodiment of the present invention.

A support layer was fabricated by spin-coating (4000 rpm, 20 sec) 400 μL of a tetrahydrofuran solution of 5% by weight styrene-butadiene-block polymer (Sigma-Aldrich) onto the conductive layer and curing (80°C, 1 hr) in air. The support layer obtained here corresponds to the film (B) according to one embodiment of the present invention.

A 2 mm wide tape was attached to the top four sides of the film (B) of the obtained Selfron S100/styrene-butadiene block polymer two-layer laminate to form a frame. The frame was then pulled up to peel off the conductive sheet consisting of the Selfron S100/styrene-butadiene block polymer two-layer laminate and the frame from the glass substrate.

Then, the conductive sheet consisting of the two-layer laminate of Selfron S100/styrene-butadiene block polymer and the frame was attached to a PET film substrate so that the styrene-butadiene block polymer surface was in contact with the PET surface. The tape frame was then cut and removed. Through the above operations, a conductive sheet consisting of the two-layer laminate of Selfron S100/styrene-butadiene block polymer was produced on the PET film substrate.

Comparative Example 1
A plasticizer, dipropylene glycol (5 vol%), and a surfactant, Zonyl (registered trademark) FS-300 (1 vol%, Sigma-Aldrich), were added to a conductive polymer, PEDOT:PSS (Clevios PH1000, Heraeus), and the mixture was stirred overnight. The obtained solution was spin-coated (2000 rpm, 40 sec) onto a glass substrate (22 mm x 22 mm), followed by annealing (150°C, 30 min), to prepare a conductive layer. A 5 wt% styrene-butadiene-block polymer tetrahydrofuran solution (400 μL) was spin-coated (4000 rpm, 20 sec) onto the conductive layer, followed by curing (80°C, 1 hr) in air, to prepare a support layer.

A polyvinyl alcohol layer was prepared on the support layer by drop casting (80°C, 18 min) a 10 wt% aqueous polyvinyl alcohol solution (400 μL) on a hot plate. The three-layer laminate was peeled off from the glass substrate and placed in Milli-Q water to dissolve the polyvinyl alcohol layer (RT, 20 min), yielding a PEDOT:PSS/styrene-butadiene-block polymer two-layer laminate sheet. The obtained two-layer laminate sheet was adhered to a PET film substrate so that the styrene-butadiene-block polymer surface was in contact with the PET surface.

<Film thickness of two-layer laminate sheet>
The thickness of the films obtained in the examples and comparative examples was measured using a stylus step gauge (Dektak XT, manufactured by Bruker Corporation).

The thickness of each layer of the Selfron S100/styrene-butadiene block polymer two-layer laminate sheet of Example 1 was 125 nm for the film containing Selfron S100 (A) and 440 nm for the film of styrene-butadiene block polymer (B).

In Comparative Example 1, the thickness of each layer of the PEDOT:PSS/styrene-butadiene-block polymer two-layer laminate sheet was 120 nm for the film containing PEDOT:PSS and 440 nm for the film containing styrene-butadiene-block polymer.

<Water resistance evaluation of two-layer laminated sheet>
The two-layer laminated sheets adhered to the PET film substrate produced in the examples and comparative examples were immersed in Milli-Q water (37°C), and after a certain time, the two-layer laminated sheets were taken out and cured in the air (80°C, 1 hr).
The sheet resistance was measured using a measuring instrument (MSP T-601, manufactured by Mitsubishi Chemical Corporation). The initial sheet resistance was used as a reference, and the increase in the sheet resistance was examined over time.

As shown in Table 1 above, the two-layer laminate sheet of Example 1 was found to have a small rate of increase in sheet resistivity and excellent water resistance.

<Evaluation of hydrophobicity of two-layer laminated sheet>
The bilayer laminated sheets attached to the PET film substrates produced in the examples and comparative examples were immersed in phosphate buffered saline (37°C, 5% _CO2 ), and after a certain time, the bilayer laminated sheets were taken out and cured in the atmosphere (80°C, 1 hr). Then, 0.5 μL of water was dropped onto the bilayer laminated sheets, and the contact angle was measured using an automatic contact angle meter (DM401, manufactured by KYOWA). The immersion time conditions were changed to examine the change in the contact angle over time.

Figure 5 shows the state of a water droplet on the two-layer laminate sheet when the contact angle was measured. As shown in Figure 5 and Table 2 above, the two-layer laminate sheet of Example 1 had a larger contact angle than the two-layer laminate sheet of Comparative Example 1, and it was found that good hydrophobicity was maintained for a long period of time.

<Cytotoxicity evaluation of bilayered sheets>
The bilayer laminated sheets prepared in the examples and comparative examples were sterilized with UV light in a clean bench. Then, 0.66 mL of cell culture solution was prepared, and the bilayer laminated sheet was contacted with the cell culture solution with the conductive layer as the contact surface (37°C, 24±1 hr). The cell culture solution from which the bilayer laminated sheet was removed was diluted 2-fold or 3-fold, and this was used as the test solution to carry out a cytotoxicity test using Premix WST-1 (Water soluble Tetrazolium salts, Cell Proliferation Assay System, manufactured by Takara Bio).

In Table 3 above, "CS" indicates Gibco (registered trademark) bovine serum, "FBS" indicates fetal bovine serum, "HS" indicates Gibco horse serum, and "PS" indicates penicillin-streptomycin solution. All contents (%) indicate volume %. NIH3T3 is a mouse embryonic fibroblast cell line, C2C12 is a mouse rhabdomyoblast cell line derived from mouse rhabdomyoblast, and PC12 is a cell line derived from rat adrenal pheochromocytoma. All of these cell lines were purchased from the Riken Cell Bank.

As shown in Table 3 above, the two-layer laminate sheet of Example 1 was found to have low cytotoxicity and excellent biocompatibility.

<Production example of two-layer laminate sheet>
Example 3
A commercially available screen plate having a circular pattern of a plurality of through holes with a diameter of 2 cm was placed on water transfer paper (4 cm x 8 cm, manufactured by Takara Line Corporation), and 400 μL of a 5 wt% polydimethylsiloxane solution was placed on the screen plate and screen printed, followed by curing in air (95°C, 30 min) to prepare a support layer (diameter 2 cm, film thickness 400 nm). The support layer obtained here corresponds to the film (B) according to one embodiment of the present invention. The surface of the support layer was hydrophilized by subjecting the surface to plasma treatment (45 mA, 133 Pa, 30 sec). A commercially available screen plate having a circular pattern with a diameter of 1.5 cm was placed on the plasma-treated surface of the support layer, and 400 μL of Selfron (registered trademark) S100 (manufactured by Tosoh Corporation) was placed on the screen plate and screen-printed, followed by curing in a vacuum (150° C., 30 min) to prepare a conductive layer (diameter 1.5 cm, film thickness 200 nn). Since Selfron S100 contains the polythiophene (A1) according to one embodiment of the present invention, the conductive layer obtained here corresponds to the film (A) according to one embodiment of the present invention.

By the above operations, the water transfer paper/polydimethylsiloxane/Selftron S100
A laminate was prepared.

Water was allowed to penetrate the resulting water transfer paper/polydimethylsiloxane/Selftron S100 laminate from the back side of the water transfer paper to isolate a two-layer laminate sheet made of polydimethylsiloxane/Selftron S100. The two-layer laminate sheet obtained here corresponds to a conductive sheet according to one embodiment of the present invention. The two-layer laminate sheet was transferred onto the skin with the membrane (A) side serving as the contact surface.

Example 4
A 5 wt% polydimethylsiloxane solution of 400 μL was spin-coated (6000 rpm, 150 sec) on a glass substrate (30 mm x 30 mm) and cured in air (95 ° C, 1 hr) to produce a peeling layer of several tens of nm. The solvent for the polydimethylsiloxane solution was a mixed solvent with a volume ratio of hexane:ethyl acetate of 3:1. A support layer was produced by spin-coating (4000 rpm, 20 sec) 400 μL of a 5 wt% styrene-butadiene-block polymer (Sigma-Aldrich) tetrahydrofuran solution on the peeling layer and curing (80 ° C, 1 hr) in air. The support layer obtained here corresponds to the film (B) according to one embodiment of the present invention.

The surface of the support layer was made hydrophilic by plasma treatment (45 mA, 133 Pa, 30 sec). 400 μL of Selfron (registered trademark) S100 (manufactured by Tosoh Corporation) was spin-coated (1500 rpm, 60 sec) onto the plasma-treated surface of the support layer, and then annealed in vacuum (150° C., 30 min) to produce a conductive layer. The conductivity of the obtained conductive layer was 241 S/cm. Since Selfron S100 contains the polythiophene (A1) according to one embodiment of the present invention, the conductive layer obtained here corresponds to the film (A) according to one embodiment of the present invention.

A 2 mm wide tape was attached to the four sides of the film (A) of the obtained two-layer laminate consisting of styrene-butadiene-block polymer/Selftron S100 to form a frame. At this time, the position of the tape was adjusted so that the inside of the frame was 20 mm x 20 mm. The frame was then pulled up to peel off the conductive sheet consisting of the styrene-butadiene-block polymer/Selftron S100 two-layer laminate and the frame from the glass substrate.

Then, the conductive sheet consisting of the styrene-butadiene-block polymer/Selftron S100/two-layer laminate and the frame was attached to a release film substrate (Panapeel SG-2 cut to 50 mm x 50 mm, manufactured by Panac Corporation) so that the Selfron S100 surface (the surface of the film (A)) was in contact with the release film surface. The tape frame was then cut and removed. Through the above operations, a conductive sheet consisting of the styrene-butadiene-block polymer/Selftron S100 two-layer laminate was produced on the release film substrate.

Then, the surface of the film (B) was placed and pressed onto a water transfer paper (4 cm x 8 cm, manufactured by Takara Line Corporation) equipped with a water-soluble sacrificial layer made of starch. The release film was peeled off from the resulting laminate of water transfer paper/water-soluble sacrificial layer/styrene-butadiene-block polymer/Selftron S100/release film, and the water transfer paper was folded so that the water transfer papers overlapped each other while water was permeated from the back side of the water transfer paper to dissolve the starch in the water-soluble sacrificial layer. One of the membranes (A) of the laminate, which now has membranes (A) on both sides, was placed on the skin as a contact surface, and the water transfer paper was pulled out and pressed onto the skin, transferring a conductive sheet consisting of a three-layer laminate of Selfron S100/styrene-butadiene-block polymer/Selftron S100 onto the skin.

The three-layer laminate was transferred to two locations on the inner forearm (the area closer to the elbow than the wrist) about 2 cm apart to form bioelectrodes. The bioelectrodes were connected to a wireless electromyographic sensor LP-WS1223 (manufactured by Logical Products) to measure the myoelectric potential of the forearm muscles. The measurement results are shown in Figure 6.

Example 5
A conductive sheet was prepared by the same procedure as in Example 4, except that the annealing temperature of Selftron S100 was changed from 150° C. to 200° C., and the myoelectric potential was measured. The electrical conductivity was 385 S/cm. The myoelectric potential measurement results are shown in FIG. 7.

The conductive sheet according to one embodiment of the present invention can be used, for example, as a bioelectrode.

1 Conductive sheet A Film containing polythiophene B Polymer film C Protective film D Conductive wire

Claims (2)

A conductive sheet in which a film (A) containing polythiophene containing at least one structural unit selected from the group consisting of a structural unit represented by the following general formula (1) and a structural unit represented by the following general formula (2) and a polymer film (B) are laminated,
A conductive sheet, characterized in that the thickness of the film (A) is 50 to 1,000 nm, and the thickness of the film (B) is 200 to 10,000 nm.
[In general formulas (1) and (2), ^R2 represents a hydrogen atom, a methyl group, an ethyl group, a linear or branched alkyl group having 3 to 6 carbon atoms, or a fluorine atom, m represents an integer of 1 to 10, and n represents 0 or 1.] The conductive sheet according to claim 1, wherein the film (B) is a film formed from at least one polymer selected from the group consisting of styrene-butadiene copolymer, polylactic acid, polycaprolactone, polydimethylsiloxane, polyurethane, natural rubber, acrylic polymer, methacrylic polymer, vinyl alcohol polymer, polysaccharide, and polystyrene.

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