JP7622303B1 - Substrate sheet with fiber electrodes - Google Patents

Abstract

The present invention aims to provide a base sheet with a fiber electrode that has a conductive performance that enables sufficient acquisition of biosignals, which are weak electrical signals unconsciously emitted from the body, and that can provide electrical stimulation by inputting electrical signals, and that can stably conduct electrical signals when performing various operations, and that is less susceptible to deterioration or change in conductive performance even with repeated use, and a product that includes the base sheet with a fiber electrode. The base sheet with a fiber electrode of the present invention includes a base sheet and a fiber electrode constituted by an embroidered portion containing conductive thread, and satisfies all of the following characteristics (1) to (4).
(1) The size of the embroidered portion on the surface of the fiber electrode is 0.1 ^cm2 or more.
(2) The conductive yarn is a composite yarn containing organic fibers and metal fibers.
(3) The content of metal fibers in the embroidery portion is 0.001 to 0.1 g/ ^cm2 .
(4) The surface resistance of the fiber electrode surface is 15 Ω/cm ² or less.

Description

The present invention relates to a base sheet with a fiber electrode, which comprises a base sheet and a fiber electrode constituted by an embroidered portion containing conductive thread.

In recent years, there has been a demand for electrodes that can collect biosignals, which are weak electrical signals that are unconsciously emitted from the body. Biosignals generally refer to signals emitted from within the body due to biological phenomena such as heart rate, brain waves, pulse, breathing, sweating, and movement. Accumulating and analyzing such biosignals can be used not only for health management, but also for efficient sports training and in the medical field. Meanwhile, in contrast to acquiring biosignals, various research has been conducted on electrodes that input electrical signals to living organisms such as muscles and nerves and provide electrical stimulation. Surface electrode types that are attached directly to the skin are often used in home low-frequency therapeutic devices.

Electrodes that can reliably obtain weak electrical signals and/or input electrical signals or impart electrical stimulation must have low electrical resistance, provide a stable and appropriate sense of electrical stimulation, be comfortable to use over long periods of time since they come into direct contact with the living body or skin, and be easy to handle. To date, electrodes that use thin metal plates, gel electrodes, and rubber electrodes, as well as textile-shaped electrodes in which conductive threads are incorporated into some of the fibers that make up the woven or knitted fabric, have been proposed.

Among these, knitted and woven fabrics have been proposed as textile-shaped electrodes. Known conductive threads include fibers containing fine particles such as carbon, metal-coated fibers with a metal such as copper coated on the fiber surface, multiple twisted metal threads made of aluminum or tungsten, and composites of these metal threads with organic fibers. However, knitted fabrics are highly elastic and prone to fluctuations in electrical resistance, while woven fabrics have stable electrical resistance but suffer from a large loss of conductive thread during production, resulting in poor productivity.

Therefore, as a fiber electrode using conductive thread in a form other than knitted or woven fabric, for example, Patent Document 1 proposes an embroidered electrode formed by embroidering conductive thread to make the electrode soft to the touch and highly flexible. However, the conductive thread described in Patent Document 1 is a silver-plated polyamide fiber, and the surface resistance value is not sufficiently low. Also, a garment with an embroidered electrode is proposed, and it is described as being "suitable for performing electrocardiogram (ECG) measurements of humans in a walking state." However, because it uses silver-plated polyamide fiber, it has the disadvantage that the silver plating on the fiber surface peels off with repeated use, and the conductive performance deteriorates with long-term use.

Patent No. 4787161

Considering convenience in daily life, it is preferable to attach embroidered electrodes to clothing in order to acquire biosignals, which are weak electrical signals, or to input electrical signals and apply electrical stimulation. Furthermore, in order to acquire biosignals and/or provide electrical stimulation to healthy individuals, it is necessary to be able to conduct electrical signals stably at all times, assuming all kinds of movements are performed. Furthermore, such clothing is naturally used repeatedly, and it is required that repeated use does not cause a decrease or change in its conductive performance.

As described above, a fiber electrode that has the conductive performance to fully acquire biosignals, which are weak electrical signals, and to input electrical signals to provide electrical stimulation, can stably conduct electrical signals when performing various operations, and further has conductive performance that is unlikely to deteriorate or change even with repeated use, and a textile product having such a fiber electrode have not yet been proposed.

The present invention aims to provide a base sheet with a fiber electrode that has a conductive performance that enables it to fully acquire biosignals, which are weak electrical signals that are unconsciously emitted from the body, and to apply electrical stimulation by inputting electrical signals, and whose conductive performance is unlikely to deteriorate or change even with repeated use, and a product that includes the base sheet with a fiber electrode.

The inventors have discovered that the above-mentioned problems can be solved by using a composite yarn containing organic fibers and metal fibers as a conductive yarn, forming a fiber electrode having an embroidered portion on a base sheet where the conductive yarn is stitched, and adjusting the size of the embroidered portion on the surface of the fiber electrode, the content of metal fibers contained in the embroidered portion, and the surface resistance value on the surface of the fiber electrode within specific ranges, and thus arrived at the present invention.

That is, the present invention provides the following aspects.
＜1＞
A base sheet with a fiber electrode comprising a base sheet and a fiber electrode constituted by an embroidered portion including conductive thread, the base sheet with a fiber electrode satisfying all of the following characteristics (1) to (4).
(1) The size of the embroidered portion on the surface of the fiber electrode is 0.1 ^cm2 or more.
(2) The conductive yarn is a composite yarn containing organic fibers and metal fibers.
(3) The content of metal fibers in the embroidery portion is 0.001 to 0.1 g/ ^cm2 .
(4) The surface resistance of the fiber electrode surface is 15 Ω/cm ² or less.
＜2＞
The substrate sheet with fiber electrodes according to <1>, wherein the metal fibers contained in the conductive yarn have a diameter of 2 to 150 μm.
＜3＞
The substrate sheet with fiber electrodes according to <1> or <2>, wherein the absolute value of the change in surface resistance of the fiber electrode surface after 30 friction tests is 1 Ω/cm ² or less.
＜4＞
<4> The substrate sheet with a fiber electrode according to any one of <1> to <3>, wherein the fiber electrode has a dimensional retention rate of 85% or more after 50 washings.
＜5＞
The substrate sheet with fiber electrodes according to any one of <1> to <4>, wherein a thickness index T calculated by the following formula is 4.0 or less.
Thickness index T=(T2-T1)/T1
(T1: thickness of the base sheet with fiber electrodes, T2: maximum thickness of the base sheet with fiber electrodes when folded in half in a direction perpendicular to the embroidery direction of the conductive thread on which the fiber electrodes are embroidered and so that the fiber electrodes face each other)
＜6＞
<6> The substrate sheet with a fiber electrode according to any one of <1> to <5>, wherein the porosity in the embroidered portion is 18% or less.
＜７＞
The substrate sheet with a fiber electrode according to any one of <1> to <6>, wherein the embroidered portion has stitches in which conductive threads are arranged to cross each other.
＜8＞
The substrate sheet with a fiber electrode according to any one of <1> to <7>, wherein the fiber electrode has a water absorbing agent on a surface thereof.
＜9＞
<9> A product having, at least in a part thereof, the substrate sheet with a fiber electrode according to any one of <1> to <8>.

The base sheet with fiber electrodes of the present invention has an embroidered portion formed on the base sheet and stitched with conductive thread that functions as an electrode, and satisfies all of the above characteristics (1) to (4). Therefore, the base sheet has excellent conductive performance for fully acquiring biosignals, which are weak electrical signals unconsciously emitted from the body, and for inputting electrical signals to impart electrical stimulation, and can stably conduct electrical signals when performing various operations by making stable contact with the skin. Furthermore, the base sheet with fiber electrodes of the present invention is resistant to deterioration or change in conductive performance even with repeated use.

Therefore, the base sheet with fiber electrodes of the present invention is preferably used as a biological electrode, and by providing it on at least a part of a base, it can be used as a product that can acquire biological signals and/or impart electrical signals or electrical stimuli. Furthermore, when the base sheet with fiber electrodes of the present invention is used as part of clothing, it can be suitably used as clothing that allows health management and wear that allows efficient sports training, and can also be suitably used as a supporter to assist walking.

1 is a photograph in place of a drawing showing one embodiment of a substrate sheet with a fiber electrode of the present invention. FIG. 10 is an explanatory diagram showing the image analysis of the substrate sheet with a fiber electrode obtained in Example 2.

<Substrate sheet with fiber electrodes>
The base sheet with a fiber electrode of the present invention includes a base sheet and a fiber electrode constituted by an embroidered portion including a conductive thread. The base sheet with a fiber electrode of the present invention will be described in detail below.

[Base sheet]
The substrate sheet in the present invention is not particularly limited as long as it can form a fiber electrode composed of an embroidered portion containing a conductive thread thereon, and examples thereof include woven fabrics, knitted fabrics, nonwoven fabrics, felt, rubber, resin sheets, films, and foam sheets. The substrate sheet is preferably one having an excessively large elongation characteristic, for example, a woven fabric, from the viewpoint of maintaining dimensional stability when stitching an embroidered portion thereon, or during use or washing of a product having a substrate sheet with a fiber electrode. In addition, it is also preferable to use a material having water retention for the substrate sheet from the viewpoint of further improving the conduction of electrical signals and increasing the moisture content around the fiber electrode. Examples of materials having water retention include materials with low water permeability such as rubber, film, and foam sheets; brushed woven fabrics, knitted fabrics, and nonwoven fabrics. The substrate sheet may be a single sheet, or may be a laminate in which one or more materials are layered.

When the base sheet is a woven fabric, examples of the type of fabric include plain weave, twill weave, satin weave, pile weave, and variations of these weaves. When the base sheet is a knitted fabric, the type of knitted fabric may be either warp knit or weft knit. Examples of warp knits include denbigh knit, cord knit, and atlas knit, and specific examples include tricot half and tricot satin. Examples of weft knits include plain knit, rib knit, purl knit, and smooth knit, and specific examples include jersey, pique, and smooth.

When the base sheet is a nonwoven fabric, the nonwoven fabric may be obtained by any of the following methods: wet laying, chemical bonding, thermal bonding, needle punching, spunlace, stitch bonding, air laying, spun bonding, and melt blowing. When the base sheet is a felt, the felt may be, for example, a felt made by fulling.

When the base sheet is a woven or knitted fabric, the fibers used in weaving or weaving may be filaments or spun yarns using staple fibers. Examples of types of filaments and staple fibers include synthetic fibers such as polyester, nylon, vinylon, polyurethane, and polypropylene; vegetable fibers such as cotton, hemp, and bamboo; regenerated fibers such as viscose rayon, solvent-spun cellulose fibers, and lyocell; animal hair fibers such as sheep, cashmere, camel, angora, mohair, alpaca, mink, and seal; and modal fibers.

[Fiber electrode]
The fiber electrode in the present invention is an electrode formed by embroidering the base sheet with conductive thread. The stitches that appear on the surface by embroidery are the stitches. In the present invention, the surface of the fiber electrode is the surface on which most of the stitches of the conductive thread are present. On the other hand, the surface on which the stitches of the lower thread appear is the back surface of the fiber electrode. The fiber electrode in the present invention is an electrode formed by forming an embroidered part with conductive thread on the base sheet, and is not an electrode in an embodiment in which the base sheet itself, such as a knitted fabric or woven fabric, contains conductive thread, that is, an electrode in an embodiment in which at least a part of the thread constituting the base sheet itself uses conductive thread. Therefore, the fiber electrode in the present invention does not stretch excessively itself and shows a stable surface resistance value. In addition, the fiber electrode in the present invention has conductive threads more densely and exposed on the surface of the fiber electrode compared to the back surface, so that it is possible to conduct electric signals more efficiently than an electrode in an embodiment in which conductive threads are used as threads constituting the base sheet itself, such as a knitted fabric or woven fabric.

The fiber electrode may be composed of only one embroidered part on a base sheet with a conductive thread stitched thereon, or may be composed of multiple embroidered parts. When a fiber electrode has multiple embroidered parts, the number is not limited and can be changed appropriately depending on the type of electrical signal to be collected, or the application, such as the acquisition and/or input of electrical signals. The aspects and characteristic values of the fiber electrode are described below. In the case of a fiber electrode having multiple embroidered parts on a base sheet, it is preferable that each embroidered part has the following aspects and characteristics.

The shape of the embroidered portion is not particularly limited as long as it is possible to acquire and input biosignals, and can be appropriately selected depending on the application, such as round, oval, triangular, rectangular, polygonal, or a shape with uneven parts.

[Features of fiber electrodes (1)]
The fiber electrode of the present invention is characterized in that the size (area) of the part on the surface of the fiber electrode where stitches are present, i.e., the embroidered part, is 0.1 ^cm2 or more, and preferably 0.2 ^cm2 or more.

If the size (area) of the embroidered portion is less than 0.1 ^cm2 , the ability to acquire biosignals will be poor. On the other hand, the upper limit of the size of the embroidered portion is not particularly limited, but is usually 150 ^cm2 or less, preferably 100 ^cm2 or less, more preferably 50 ^cm2 or less, even more preferably 25 ^cm2 or less, and even more preferably 20 ^cm2 or less. If the size of the embroidered portion exceeds 150 ^cm2 , noise other than biosignals will be easily acquired, which is not preferable.

Specifically, the size (area) of the embroidery portion is preferably 0.1 to 150 cm ² , more preferably 0.2 to 100 cm ² , even more preferably 0.2 to 50 cm ² , still more preferably 0.2 to 25 cm ² , and particularly preferably 0.2 to 20 cm ² .

[Features of fiber electrodes (2)]
The conductive yarn used to form the fiber electrode in the present invention is a composite yarn containing organic fibers and metal fibers. The use of the composite yarn containing organic fibers and metal fibers can solve the problem of durability against repeated use that occurs when using metal-plated yarn, that is, the problem of deterioration of conductive performance due to peeling or separation of metal from the fiber electrode due to repeated use.

The conductive yarn is a composite yarn containing organic fibers and metal fibers, and is preferably a twisted yarn made by twisting together the above-mentioned two fibers, and more preferably a twisted yarn made by covering a core yarn with a sheath yarn (hereinafter sometimes referred to as a "core-sheath composite twisted yarn").

(Organic Fiber)
Examples of organic fibers used in the conductive yarn of the present invention include natural fibers such as cotton, hemp, wool, and silk; synthetic fibers such as polyester, nylon, acrylic, polyolefin, para-aramid, meta-aramid, polyarylate, and polybenzoxazole; and regenerated fibers such as rayon. Among these, it is preferable to use multifilaments of synthetic fibers such as nylon and polyester, from the viewpoint of high versatility and excellent durability.

As described later, in order to expose more of the metal fibers on the surface of the fiber electrode, water-soluble fibers such as water-soluble vinylon and alkali-soluble fibers that can be dissolved in an alkaline solution can be used as the organic fibers. Examples of alkali-soluble fibers include fibers made of polycaprolactone resin, polylactic acid resin, polyhydroxybutyrate resin, polyglycolic acid resin, polyethylene adipate resin, and copolymerized polyester resin using a specific copolymerization component. Of these, fibers made of copolymerized polyester resin and/or polylactic acid resin are preferred.

Examples of copolymerized polyester resins include those in which an aromatic dicarboxylic acid having a metal sulfonate group is included as a copolymerization component in the acid component constituting the polyester. Examples of aromatic dicarboxylic acids having a metal sulfonate group include 5-sodium sulfoisophthalic acid, 5-potassium sulfoisophthalic acid, 5-lithium sulfoisophthalic acid, sodium sulfonaphthalenedicarboxylic acid, sodium sulfophenyldicarboxylic acid, and 5-sodium sulfoterephthalic acid. When the total amount of all acid components in the copolymerized polyester resin is taken as 100 mol %, it is preferable that the aromatic dicarboxylic acid is included in an amount of 0.5 to 5 mol %.

The organic fiber may be in the form of any of spun yarn, filament yarn, composite yarn, and a combination of these yarns, but among these, it is preferable to use a multifilament as described above. The organic fiber may be raw yarn that has not been false-twisted, or may be false-twisted yarn. The organic fiber may be a twisted yarn made from raw yarn or false-twisted yarn.

The cross-sectional shape of the organic fiber is not particularly limited, and may be any of a circular cross section, an irregular cross section, a hollow cross section, etc. The organic fiber may contain titanium dioxide, silicon dioxide, pigments, etc., depending on the properties to be imparted.

The organic fiber is preferably a spun yarn or a multifilament. If it is a spun yarn, the thickness is preferably 10 to 100, more preferably 15 to 80, and even more preferably 20 to 70. If it is a multifilament, the single fiber fineness is preferably 0.3 to 10 dtex, the number of single fibers is preferably 5 to 150, and the total fineness is preferably 8 to 330 dtex. The total fineness is more preferably 10 to 170 dtex, and even more preferably 20 to 100 dtex.

(Metal Fiber)
Examples of metal fibers used in the conductive thread of the present invention include metal-coated fibers obtained by coating, plating, metal deposition, or sputtering a fiber surface with a metal such as copper, nickel, or silver; metal fibers made of metals (simple elements) such as aluminum and tungsten; and conductive fibers such as fibers containing fine particles of carbon, conductive ceramic, or metal. In the present invention, of these, from the viewpoint of increasing conductivity, it is preferable to use metal fibers made of simple metals, and it is more preferable to use metal yarns, which are metal fibers made of simple metals and are continuous metal wires.

Examples of materials for metal fibers made of a single metal include gold, silver, copper, brass, platinum, iron, steel, zinc, tin, nickel, stainless steel, aluminum, tungsten, and molybdenum. Of these, at least one filament selected from tungsten, molybdenum, and stainless steel is preferable because of its excellent corrosion resistance and strength, and tungsten is more preferable, with tungsten metal yarn being even more preferable. These metals may be used alone or in combination of two or more kinds. The material for the metal fiber may also be an alloy made of two or more kinds of metals.

In addition, the metal fibers used in the conductive yarn of the present invention may be monofilament yarns of the aforementioned metal fibers (for example, monofilament yarns (metal yarns) of metal fibers made of a single metal or monofilament yarns of metal-coated fibers, etc.), or multifilament yarns in which multiple types of metal fibers are twisted or aligned may be used.

When using a single monofilament thread of metal fiber, it is preferable that the monofilament thread is not twisted (single twist). When using a combination of multiple types of metal fibers, it is preferable that the multifilament thread is made of multiple types of metal fibers twisted together (single twisted).

There are no particular restrictions on the thickness of the metal fibers, but the diameter of the metal fibers is preferably 2 to 150 μm, more preferably 2 to 100 μm, even more preferably 5 to 50 μm, and even more preferably 10 to 20 μm. If the diameter is less than 2 μm, the composite thread will have poor conductivity and strength. If the diameter exceeds 150 μm, defects are likely to occur when forming the embroidery part using the composite thread, and the metal fibers on the surface of the obtained fiber electrode will be more noticeable in appearance, resulting in poor flexibility and texture.

The electrical resistance of the metal fiber (metal thread) is preferably 1×10 ^-4 to 1×10 ¹⁰ Ω/m, more preferably 1×10 ^-4 to 1×10 ⁵ Ω/m, and even more preferably 1×10 ^-4 to 1×10 ³ Ω/m. In the present invention, the electrical resistance of the metal fiber (metal thread) is measured in an environment of 23° C. using a 1 m sample of the metal fiber, and the average electrical resistance of five samples is used.

(Sheath-core composite twisted yarn)
The conductive yarn in the present invention is preferably a core-sheath composite twisted yarn formed by covering a core yarn with a sheath yarn, as described above. The core-sheath composite twisted yarn is a twisted yarn made of a core yarn and a sheath yarn that is wound around the outer periphery of the core yarn and covers it, and it is preferable that both the core yarn and the sheath yarn are twisted yarns containing organic fibers.

As a more specific form of the core-sheath composite twisted yarn, the following form 1 or form 2 is preferable.
Form 1: Two types of sheath yarns, a metal fiber and an organic fiber B, are wound around a core yarn made of an organic fiber A in the S or Z twist direction.
Form 2: A sheath yarn of organic fiber B is wound around a core yarn made of organic fiber A and metal fiber in the S or Z twist direction.

In the present invention, by using a core-sheath composite twisted yarn as in form 1 or form 2 as the conductive yarn, the fiber electrode can easily follow the movements of various actions and can stably contact the skin, stably acquiring biosignals and inputting electrical signals to provide electrical stimulation. In addition, durability against repeated use, shape stability after washing, and operability during embroidery are also excellent.

When the core-sheath composite twisted yarn is used, the organic fiber A used for the core yarn and the organic fiber B used for the sheath yarn may be of the same type or different types. In addition, the conductive yarn is preferably a twisted yarn N obtained by twisting two or more core-sheath composite twisted yarns (twisted yarns M) of form 1 or form 2. By using the twisted yarn N as the conductive yarn, the metal fibers contained in each twisted yarn M come into contact with each other in the twisted yarn N, resulting in a twisted yarn with better conductive performance. Therefore, by using the twisted yarn N, the number of contact points between the metal fibers in the fiber electrode increases, and a fiber electrode with better conductive performance can be obtained. The number of twisted yarns is preferably 2 to 9, and more preferably 4 to 8. If the number of twisted yarns is within the above range, the number of contact points between the metal fibers can be increased, and since the twisted yarn N does not become too thick, the surface of the fiber electrode does not become thick or hard when used in the fiber electrode, and the fiber electrode can easily follow the movements of various operations.

In addition, when the fiber electrode comes into contact with the object to which the electric signal is to be transmitted or received, that is, the surface of a living body that emits or receives an electric signal, it is preferable to have more metal fibers exposed on the surface of the conductive yarn, and more metal fibers exposed on the surface of the fiber electrode, so that more metal fibers in the conductive yarn can come into contact with the surface of the living body. Examples of methods for exposing more metal fibers on the surface of the conductive yarn include arranging metal fibers in the sheath yarn of the core-sheath composite twisted yarn (the above-mentioned form 1), or performing twisting processing so that the metal fibers appear on the yarn surface. Examples of methods for exposing more metal fibers on the surface of the fiber electrode include using water-soluble fibers such as water-soluble vinylon or alkali-soluble fibers that can be dissolved in an alkaline solution as at least a part of the organic fibers in the core-sheath composite twisted yarn, embroidering the core-sheath composite twisted yarn on a base sheet, and then dissolving the water-soluble fibers or alkali-soluble fibers using hot water or an alkaline solution. In this case, it is preferable to use water-soluble fibers or alkali-soluble fibers as the organic fibers of the sheath yarn of the core-sheath composite twisted yarn. Specifically, it is more preferable that after embroidering the core-sheath composite twisted yarn, all of the water-soluble fibers or alkali-soluble fibers of the sheath yarn are dissolved, so that only the organic fibers of the core yarn and the metallic fibers of the sheath yarn remain on the surface of the obtained fiber electrode.

[Features of fiber electrodes (3)]
In order to obtain a fiber electrode according to the present invention with a conductive performance capable of sufficiently acquiring a biosignal, which is a weak electrical signal, and/or imparting an electrical stimulus, the embroidered portion in which the conductive thread is stitched must have a certain density of conductive threads and a specific amount of metal fibers. That is, the fiber electrode according to the present invention must have a metal fiber content of 0.001 to 0.1 g/cm ² in the embroidered portion, and preferably 0.003 to 0.08 g/cm ^2. If the metal fiber content is less than 0.001 g/cm ² , the metal fiber content is too low to sufficiently acquire a biosignal, while if it exceeds 0.1 g/cm ² , the metal fiber content is too high, making the surface of the embroidered electrode hard, making it difficult to follow the movements of various actions, and causing a poor texture when in contact with the skin. When using tungsten, which is the most preferred metal fiber, the content of the metal fibers in the embroidery portion is preferably 0.003 to 0.05 g/ ^cm2 , more preferably 0.003 to 0.03 g/ ^cm2 , even more preferably 0.004 to 0.02 g/ ^cm2 , and particularly preferably 0.004 to 0.01 g/ ^cm2 .

The content of the organic fibers in the embroidered portion will vary depending on the type of organic fiber, but when multifilaments (e.g., polyester multifilaments) are used, the content is preferably 0.001 to 0.5 g/ ^cm2 , more preferably 0.003 to 0.1 g/ ^cm2 , and even more preferably 0.003 to 0.05 g/ ^cm2 .

Furthermore, in order to reduce the electrical resistance on the surface of the fiber electrode and to produce a fiber electrode that exhibits the surface resistance value described below, it is necessary for the conductive thread to be present at a certain density in the embroidered portion where the conductive thread is stitched. For this reason, the length (total length) of the metal fibers in the conductive thread contained in the embroidered portion is preferably 100 to 900 cm/ ^cm2 , more preferably 120 to 500 cm/ ^cm2 , and even more preferably 150 to 400 cm/ ^cm2 .

[Features of fiber electrodes (4)]
The fiber electrode of the present invention must have a surface resistance of 15 Ω/cm2 or ^less on the fiber electrode surface, preferably 13 Ω/cm2 ^{or less} , more preferably 10 Ω/cm2 or ^less , even more preferably 5 Ω/cm2 or ^less , even more preferably 3 Ω/cm2 or ^less , and particularly preferably 2 Ω/ ^cm2 or less. The surface resistance of the fiber electrode surface is an index showing the conductive performance of the fiber electrode. If the surface resistance of the fiber electrode surface exceeds 15 Ω/ ^cm2 , it becomes difficult to sufficiently acquire a biosignal, which is a weak electrical signal, or to input an electrical signal to a living body and apply an electrical stimulus.

In the present invention, the surface resistance value on the surface of the fiber electrode is a value obtained by the following measurement method.
Method for measuring surface resistance: The surface resistance was measured using a digital tester at the two longest points between any two points on the surface of the fiber electrode, and the measured value was converted from the electrode size (area) to a unit area value, which was taken as the surface resistance per ^cm2 . The surface resistance was measured six times for each of eight fiber electrodes, and the average of the 48 measurements was taken as the surface resistance. The measurement was performed in an environment with a temperature of 20°C and a humidity of 65%.

[Features of fiber electrodes (5)]
As described below, the fiber electrode of the present invention is often used as a product attached to a base material such as a woven fabric, knitted fabric, nonwoven fabric, felt, rubber, resin sheet, film, etc., and such products are often worn on a living body and are often used repeatedly. Therefore, the fiber electrode of the present invention has an absolute value of the change in surface resistance after 30 friction tests on the fiber electrode surface of preferably 1 Ω/cm2 ^or less, more preferably 0.5 Ω/cm2 or ^less , and even more preferably 0.3 Ω/ ^cm2 or less. By satisfying this value, it is possible to maintain the conductive performance even after repeated use (excellent durability of conductive performance).

In the present invention, the change in surface resistance on the fiber electrode surface after 30 friction tests is a value obtained by the following measurement method.

Measurement method of change in surface resistance: First, the surface resistance of the fiber electrode before the friction test is measured by the above method. Next, in the friction tester type II (Gakushin type) method of JIS L 0849: 2013 (test method for color fastness to friction), the fiber electrode is attached to the friction element side of the friction tester type II (Gakushin type) method, and the white cotton cloth for friction is attached to the test piece table side, except that the fiber electrode is rubbed back and forth against the white cotton cloth for friction 30 times based on the case of the dry test of the friction tester type II (Gakushin type) method, specifically, under the conditions of a load of 2N, a speed of 30 reciprocations per minute, and a reciprocation distance of 100 mm. After the friction test, the fiber electrode is removed from the friction element, and the surface resistance of the fiber electrode is measured by the above method. Then, the absolute value of the difference in the surface resistance of the fiber electrode before and after the friction test is taken as the change.

[Features of fiber electrodes (6)]
As described above, the fiber electrode of the present invention is washed frequently. Therefore, the fiber electrode of the present invention preferably has a dimensional retention of 85% or more, more preferably 90% or more, after 50 washes. If the dimensional retention is less than 85% after 50 washes, the conductive performance is likely to be reduced or changed due to dimensional changes caused by repeated washing.

In the present invention, the dimensional retention after 50 washes is a value obtained by the following measurement method and calculation formula.
Dimensional retention after 50 washes: First, measure the surface area of the fiber electrode before the washing test. Next, perform 50 wash tests based on the C4M method of JIS L 1930:2014 (home washing test method for textile products). Use the A method (hanging dry) as the drying method. Then, measure the surface area of the fiber electrode after the washing test. Then, calculate the dimensional retention (%) by the following formula.
Dimensional retention rate (%) after 50 washings = [(surface area of fiber electrode after washing test) / (surface area of fiber electrode before washing test)] x 100

[Features of fiber electrodes (7)]
The fiber electrode in the present invention is formed by embroidering conductive threads on a base sheet, and therefore has flexibility. The flexibility of the base sheet with fiber electrodes is evaluated using a thickness index T calculated by the following formula. The closer the value of the thickness index T is to 1, the easier it is to bend the electrode part on which the fiber electrodes are formed, and the higher the flexibility, and the larger the value of the thickness index T is, the harder it is to bend the electrode part on which the fiber electrodes are formed, and the lower the flexibility. For example, when a hard material such as a plastic plate is used as the base sheet, the base sheet with fiber electrodes cannot be folded in half, T2 cannot be measured, and it can be said that it has no flexibility. The thickness (mm) is measured according to the A method (JIS method) of "8.4 Thickness" of JIS L 1096:2010 (Fabric test method for woven and knitted fabrics).
Thickness index T=(T2-T1)/T1
(T1: thickness of the base sheet with fiber electrodes, T2: maximum thickness of the base sheet with fiber electrodes when folded in half in a direction perpendicular to the embroidery direction of the conductive thread on which the fiber electrodes are embroidered and so that the fiber electrodes face each other)

In the substrate sheet with fiber electrodes of the present invention, the thickness index T is preferably 4.0 or less, more preferably 3.0 or less, and even more preferably 2.8 or less. If the thickness index T is 4.0 or less, the electrode part on which the fiber electrodes are formed has sufficient flexibility, so that the electrode part can stably contact the skin and easily conduct electrical signals stably when performing various operations. Usually, the surface embroidered with thread has a certain degree of hardness, and the hardness varies depending on the thickness and number of threads, the density of the embroidered part, etc. Therefore, the lower limit of the thickness index T is not particularly limited, but is usually 1.0 or more, and may be 1.2 or more.

In the substrate sheet with fiber electrodes of the present invention, the thickness index T is preferably 1.0 to 4.0, more preferably 1.0 to 3.0, and even more preferably 1.0 to 2.8. In the substrate sheet with fiber electrodes of the present invention, the thickness index T may be preferably 1.2 to 4.0, 1.2 to 3.0, or 1.2 to 2.8.

[Features of fiber electrodes (8)]
In the fiber electrode of the present invention, the conductive thread is present at a certain density in the embroidered portion where the conductive thread is stitched, but depending on the thickness of the conductive thread and the embroidery conditions, there may be a void portion where the conductive thread is not stitched in the embroidered portion, i.e., where the conductive thread does not exist. In the base sheet with fiber electrode of the present invention, the ratio of the void portion in the embroidered portion of the fiber electrode (porosity) is preferably 18% or less, more preferably 14% or less, even more preferably 10% or less, even more preferably 8% or less, and particularly preferably 6% or less. When the porosity is 18% or less, the conductive thread is present at a high density in the embroidered portion, and the number of contact points between the metal fibers increases, thereby obtaining a fiber electrode with better conductive performance. The lower limit of the porosity is not particularly limited as long as the effects of the above-mentioned conductive performance and flexibility are not impaired.

The porosity of the embroidered portion of the fiber electrode can be determined by image analysis, for example, using "ImageJ" (Wayne Rasband, National Institutes of Health) as image analysis software. As an image analysis method, a threshold value is set at the brightness boundary between the void portion in the embroidered portion and the portion where the conductive thread is present for the captured image of the base sheet with the fiber electrode, and the brightness is binarized. Generally, when binarized into white and black, the portion where the conductive thread is present becomes white and the void portion becomes black, so that the white portion can be identified as the portion where the conductive thread is present and the black portion as the void portion. The porosity is obtained by calculating the ratio of the total area of the void portions identified as voids to the total area of the embroidered portion.

[Features of fiber electrodes (9)]
The fiber electrode of the present invention preferably has an impedance of a specific value or less as an index showing that an electrical signal can be easily acquired and input on the surface of a living body. In the present invention, the impedance is evaluated by a test in accordance with ANSI/AAMI EC12:2000. The AC impedance of the fiber electrode of the present invention is preferably 2 kΩ (2000Ω) or less, more preferably 1000Ω or less, even more preferably 100Ω or less, even more preferably 50Ω or less, even more preferably 30Ω or less, and particularly preferably 10Ω or less. In addition, the above standard requires that the impedance of a biological electrode at 10 Hz and not exceeding 100 μA p-p (A p-p: difference between the maximum current value and the minimum current value measured with an alternating current) must be 2 kΩ or less. If the fiber electrode of the present invention has an AC impedance of 2 kΩ or less, the impedance between the surface of a living body and the fiber electrode is small, making it easier to acquire and input electrical signals.

In the present invention, the AC impedance of the fiber electrode is a value obtained by the following measurement method.

Method for measuring AC impedance of fiber electrodes: Measurements are performed in accordance with ANSI/AAMI EC12:2000. Specifically, the procedure is as follows. Two substrate sheets with fiber electrodes are stacked so that the embroidered portions are joined to obtain a pair of samples. Then, a 100g weight is placed on top of the samples to apply pressure, and the AC impedance at 10 Hz is measured under conditions of 23°C and 40% humidity. The AC impedance is measured for five samples, and the average value is used.

The fiber electrode of the present invention has a small effect on impedance characteristics even when exposed to the atmosphere for a long time. That is, when a conventional gel electrode is exposed to the atmosphere for a long time, the gel evaporates, and the impedance tends to increase and the impedance characteristics tend to be poor. On the other hand, the fiber electrode of the present invention has a small effect on impedance characteristics because the impedance does not change significantly even when exposed to the atmosphere for a long time by adopting the above-mentioned configuration. Therefore, the fiber electrode of the present invention has an AC impedance of preferably 2 kΩ (2000Ω) or less, more preferably 1000Ω or less, even more preferably 100Ω or less, even more preferably 50Ω or less, even more preferably 30Ω or less, and particularly preferably 10Ω or less after being left at 23°C x 55% RH for 24 hours.

In the present invention, the AC impedance of the fiber electrode after being left at 23°C x 55% RH for 24 hours is a value obtained by the following measurement method. The base sheet with the fiber electrode is left in an environment of 23°C x 55% RH for 24 hours, and then the AC impedance is measured by the same method as above. The AC impedance is measured for four samples, and the average value is used.

The base sheet with fiber electrode of the present invention is often used by being attached to a living body as a product attached to a part of a substrate, and when used for such purposes, the frequency of washing is also high. Therefore, in order to minimize the effect on impedance characteristics even after repeated washing and to stably acquire and input electrical signals, the fiber electrode of the present invention has an AC impedance of preferably 2 kΩ (2000Ω) or less, more preferably 1000Ω or less, even more preferably 100Ω or less, even more preferably 50Ω or less, even more preferably 40Ω or less, and particularly preferably 10Ω or less after 50 washes.

In the present invention, the AC impedance of the fiber electrode after 50 washes is a value obtained by the following measurement method. The base sheet with the fiber electrode is washed 50 times based on the C4M method of JIS L 1930:2014 (Home Laundry Test Method for Textile Products). The drying method used is Method A (hang-dry). The AC impedance is then measured in the same manner as above. The AC impedance is measured for four samples, and the average value is used.

[Features of fiber electrodes (10)]
The fiber electrode in the present invention may have water absorption properties due to water absorption processing. The water absorption processing method is not particularly limited, but examples include a method of attaching a compound (water absorbent) having a hydrophilic group to the surface of the fiber electrode by coating, adsorption, or exhaustion. Specifically, any of padding method, exhaustion method, spray method, kiss roll coater method, slit coater method, etc. may be adopted to apply an aqueous solution containing a water absorbent to the surface of the fiber electrode, and the treatment may be performed under normal temperature and normal pressure conditions, or a dry heat treatment may be performed at 105 to 190 ° C for 30 to 150 seconds. In addition, a conductive thread having water absorption properties may be used to form the fiber electrode. The water absorption processing may be performed on at least the surface of the fiber electrode, and may be performed on both the front and back sides of the fiber electrode.

In the present invention, by imparting water absorbency to the surface of the fiber electrode, the effect of further improving the conductive performance and the effect of lowering the impedance can be obtained. In addition, when the fiber product of the present invention is worn on the human body, it is possible to suppress the fiber electrode surface from easily separating from the wearer's skin due to sweat, and to reduce the discomfort caused by sweat remaining on the skin surface without being absorbed by the fiber electrode.

<Method of manufacturing base sheet with fiber electrode>
The method for producing the base sheet with the fiber electrode of the present invention is not particularly limited, and examples thereof include a method of forming a fiber electrode composed of an embroidered portion by embroidering the base sheet with the conductive thread. Methods for forming a fiber electrode having the above characteristics include using the conductive thread in the embroidered portion, forming the embroidered portion by machine embroidery, forming the types of stitches (stitches that appear on the surface by embroidery) shown below, or forming the stitch lengths, row intervals, and offset values shown below.

Types of stitches include running stitch, cross stitch, tatami stitch, and chain stitch. Of these, running stitch and tatami stitch are preferred.

The stitch length is preferably 1 to 10 mm, and more preferably 2 to 8 mm. The row spacing is preferably 0.1 to 1.5 mm, and more preferably 0.3 to 1.3 mm. Note that row spacing refers to the spacing between stitch lines when forming stitches, but in the case of a backstitch line such as tatami stitch, it refers to the spacing between stitch line 1 and stitch line 2 when stitch line 1, backstitch line, and stitch line 2 are formed in that order.

The offset value refers to the absolute value of the length of the shift between the needle drop points of adjacent stitch lines, but in the case of a backstitch line as described above, it refers to the absolute value of the length of the shift between the needle drop points of a stitch line and the backstitch line adjacent to it. The offset value is preferably 0.5 to 1.0 mm, and more preferably 0.6 to 0.9 mm.

It is preferable that the embroidered portion where the conductive thread is stitched onto the base sheet has stitches arranged so that the conductive thread crosses in two different directions. For example, a running stitch may be performed with understitching in the weft direction, and then with a lockstitch in the warp direction. By having such understitching, the number of contact points between the metal fibers in the embroidered portion increases, further improving the conductive performance.

When the two different directions are the warp and weft directions, the two threads cross at 90 degrees, but the angle at which the two threads cross is preferably 20 to 160 degrees, and more preferably 30 to 150 degrees.

The stitch type, stitch length, row spacing, and offset value of the understitching may be the same as those of the main stitching described above, but it is preferable that the row spacing of the understitching be 2 to 6 times that of the main stitching.

<Applications of the base sheet with fiber electrodes>
The base sheet with fiber electrodes of the present invention can be used as a biological electrode. Preferred usage modes of the base sheet with fiber electrodes used for a biological electrode include a mode in which the base sheet can directly contact a living body to obtain a biological signal and/or provide an electric signal or electric stimulation, such as an electrode for obtaining a biological signal such as a cardiac potential, a myoelectric potential, or an electroencephalogram, and an electrode for providing an electric stimulation to a living body, such as a low-frequency, high-frequency, or EMS electrode.

As described below, a biological electrode using the base sheet with fiber electrode of the present invention can be attached to at least a part of a base and used as a product that can acquire biological signals and/or impart electrical signals or electrical stimuli.

<Products Having Substrate Sheets with Fiber Electrodes>
The product of the present invention has a base sheet with a fiber electrode. Examples of the product having a base sheet with a fiber electrode include a product having a base (woven fabric, knitted fabric, nonwoven fabric, felt, rubber, resin sheet, film, etc.) on which a fiber electrode is directly formed at least partially, and a product having a base sheet with a fiber electrode fixed to the base. The base sheet with a fiber electrode may be detachable from the base.

An example of a substrate having fiber electrodes formed directly on it is one in which embroidery is formed on the substrate itself by stitching conductive thread directly onto the substrate. In this case, the substrate corresponds to the substrate sheet of the substrate sheet with fiber electrodes.

The method of fixing the substrate sheet with fiber electrodes to the substrate is not particularly limited, but examples thereof include adhesion, sewing using conductive thread, and soldering. The method of making the substrate sheet detachable is also not particularly limited, but examples thereof include providing magnets, buttons, hooks, snap buttons, and hook-and-loop fasteners on the substrate and the substrate sheet with fiber electrodes. Products that allow the substrate sheet with fiber electrodes to be detached have the advantage that the substrate sheet with fiber electrodes can be installed so that an electrical signal can be acquired or input at a desired location, or the substrate sheet with fiber electrodes can be installed and used on another substrate. The substrate sheet with fiber electrodes of the present invention is washable, but by washing only the substrate with the substrate sheet with fiber electrodes removed during washing, the load on the substrate sheet with fiber electrodes can be reduced and the durability of the substrate sheet with fiber electrodes can be improved.

The base sheet with fiber electrodes may be fixed entirely to the substrate, or at least partially. When only a portion of the base sheet with fiber electrodes is fixed to the substrate, expansion and contraction of the product is less likely to be hindered by the base sheet with fiber electrodes, that is, when the product is attached to a living body and expands and contracts due to bodily movements, and the base sheet with fiber electrodes can flexibly follow the movements of the body, achieving a high fit of the fiber electrodes to the surface of the living body.

Products having a base sheet with fiber electrodes are not particularly limited, but examples thereof include textile products. When the textile product is clothing, the clothing may be either upper or lower clothing, and specific examples include innerwear, sportswear, hospital clothing, nightwear, various uniforms, etc. In addition to clothing, the base sheet with fiber electrodes can also be attached to various types of clothing that come into contact with a part of the living body, and can be used for, for example, wristbands, gloves, socks, supporters, corsets, belly wraps, hats, and belt-like items such as belts and bands. In the case of a belt-like item, for example, two fiber electrodes can be attached to one belt-like item to form a product in which the two fiber electrodes are integrated, and the product can be easily set by wearing it on the part where the biosignal is to be acquired or the electrical signal is to be input. Specific examples include chest belts, abdominal belts, and leg belts. In addition to the above-mentioned textile products, the base sheet with fiber electrodes can also be used for products that come into contact with a part of the living body, and can also be used for products such as watches, chairs, beds, carpets, handlebars, and various covers. A product having such a fiber electrode can be used as a product capable of acquiring biosignals and/or imparting electrical signals or electrical stimuli by using the fiber electrode as a biological electrode as described above.

Products having a base sheet with fiber electrodes may be equipped with wiring, connectors, electronic control units such as biosignal detection devices and electrical stimulation devices, and electronic control units that can be attached and detached via connectors, as necessary, to ensure electrical continuity.

The type of connector attached to the fiber electrode of the base sheet with fiber electrode of the present invention is not particularly limited, but when used in products such as the above-mentioned clothing, supporters, covers, etc., small and lightweight connectors are preferred to prevent discomfort to the user due to contact with the body, and examples of such connectors include snap buttons and conductive seal-shaped connectors, as well as soldering, adhesion with conductive paste, sewing with conductive thread, magnets, hooks, etc. In order to prevent noise from being generated when acquiring or inputting an electrical signal through the fiber electrode of the present invention, it is preferable that these connectors are insulated. For example, insulated buttons made of stainless steel are preferably used from the viewpoint of excellent washing durability.

In products having a base sheet with fiber electrodes, the number of fiber electrodes attached to the base may be multiple and can be changed as appropriate depending on the type of biosignal to be collected, or the application, such as obtaining a biosignal and/or electrical stimulation by inputting an electrical signal, but it is preferable for the number to be 1 to 50, and more preferably 1 to 25.

Furthermore, when the fiber electrode of the present invention is used as a biological electrode, for example, by providing two or more fiber electrodes on the skin side of the product, it is possible to measure cardiac potential, muscle potential, etc. It is also possible to measure pulse, respiration, movement state, etc. by providing fiber electrodes on the skin side or surface of the product and measuring changes in body impedance.

The location of the fiber electrode can be changed as appropriate depending on the type of biosignal to be collected, or the purpose of obtaining the biosignal and/or electrical stimulation by inputting an electrical signal. For example, when measuring electrocardiogram, it is preferable to place the electrode near the left chest, and when measuring electromyogram or electroencephalogram, it is preferable to place the electrode near the muscle or brain to be measured.

The biosignals collected by the fiber electrode of the present invention are measured over a long period of time using various devices depending on the purpose, analyzed as various data, and used in health management, sports training, the medical field, etc. In addition, by inputting an electrical signal to a muscle or nerve using the fiber electrode of the present invention, it can be used as a device that applies electrical stimulation in the medical field and training applications, games and toys, etc., or as an electrode for measuring the impedance of a living body.

The present invention will be described in more detail below with reference to examples. The measurement and evaluation methods for various characteristic values in the examples are as follows:

(a) The amount of metallic fibers and organic fibers contained in the embroidery part and the length (total length) of the metallic fibers
The fiber electrode was separated into organic fibers and metal fibers, and the weight of each and the length (total length) of the metal fibers were measured. The content (g/ ^{cm2) of the metal fibers or organic fibers in the embroidered part was calculated from the area of the embroidered part and the weight of the metal fibers or organic fibers. The length (total length) (cm/cm2 )} of the metal fibers in the embroidered part was also calculated from the area of the embroidered part and the length (total length) of the metal fibers.

(b) Electrical Resistance Value of Metal Fibers For one metal fiber in the core-sheath composite twisted yarn constituting the conductive yarn used in the Examples and Comparative Examples, a 1 m sample was used to measure the electrical resistance value in an environment of 23° C. using a digital tester (OHM Digital Multi Tester TDB-401, manufactured by Ohm Electric Co., Ltd.). The average electrical resistance value of the five samples was taken as the electrical resistance value of the metal fiber.

(c) Surface resistance value on fiber electrode surface The surface resistance value was measured at the two points with the longest distance when any two points were connected on the fiber electrode surface using a digital tester (OHM Digital Multi Tester TDB-401, manufactured by Ohm Electric Co., Ltd.), and the measured value was converted from the electrode size (area) to a unit area, which was defined as the surface resistance value per ^cm2 . The surface resistance value was measured six times for each of eight fiber electrodes, and the average value of a total of 48 measured values was defined as the surface resistance value. The measurement was performed in an environment of 20°C and humidity of 65%.

(d) Change in surface resistance after 30 friction tests on the surface of the fiber electrode First, the surface resistance of the fiber electrode before the friction test was measured by the method described in (c). Next, in the friction tester II type (Gakushin type) method of JIS L 0849: 2013 (test method for color fastness to friction), except that the fiber electrode was attached to the friction element side of the friction tester II type and the white cotton cloth for friction was attached to the test piece table side, the fiber electrode was rubbed back and forth against the white cotton cloth for friction 30 times based on the case of the dry test of the friction tester II type (Gakushin type) method, specifically, under the conditions of a load of 2N, a speed of 30 reciprocations per minute, and a reciprocation distance of 100 mm. The fiber electrode was removed from the friction element after the friction test, and the surface resistance of the fiber electrode was measured by the method described above. Then, the absolute value of the difference between the surface resistance of the fiber electrode before and after the friction test was taken as the change.

(e) Dimensional retention rate after 50 washes First, the surface area of the fiber electrode before the washing test was measured. Next, a washing test was performed 50 times based on the C4M method of JIS L 1930:2014 (home washing test method for textile products). The drying method used was Method A (hanging and drying). Then, the surface area of the fiber electrode after the washing test was measured. Then, the dimensional retention rate (%) was calculated by the following formula.
Dimensional retention rate (%) after 50 washings = [(surface area of fiber electrode after washing test) / (surface area of fiber electrode before washing test)] x 100

(f) Flexibility According to JIS L 1096:2010 (Testing methods for woven and knitted fabrics), "8.4 Thickness", Method A (JIS method), the thickness T1 (mm) of the fabric sheet with fiber electrodes was measured using a thickness measuring instrument (Ozaki Manufacturing Co., Ltd., Peacock Model H). Next, the fiber electrodes were folded in half in a direction perpendicular to the embroidery direction of the embroidered conductive thread and so that the fiber electrodes faced each other, and the maximum thickness T2 (mm) of the fabric sheet with fiber electrodes in this state was measured in the same manner as above. Using the measured values of T1 and T2, the thickness index T was calculated according to the following formula to evaluate the flexibility.
Thickness index T=(T2-T1)/T1
(T1: thickness of the base sheet with fiber electrodes, T2: maximum thickness of the base sheet with fiber electrodes when folded in half in a direction perpendicular to the embroidery direction of the conductive thread on which the fiber electrodes are embroidered and so that the fiber electrodes face each other)

(g) Porosity in the embroidered part of the fiber electrode For the fabricated base sheet with fiber electrodes, the ratio of the total area of the void parts where no conductive thread exists per any 2 cm x 2 cm area (total area 4 cm ² ) of the embroidered part was calculated to obtain the void ratio (%). Specifically, the void ratio (%) was calculated by binarizing the brightness of an image taken from directly above the center of the embroidered part of the base sheet with fiber electrodes using the image analysis software "ImageJ" (Wayne Rasband, National Institutes of Health), setting the threshold value of the brightness boundary between the void parts in the embroidered part and the part where the conductive thread exists to 80. In addition, in the calculation of the void ratio, if the part that is not a void is calculated as a void part and greatly affects the void ratio, the image was manually edited and the part that is not a void was calculated as the part where the conductive thread exists. FIG. 2 is an explanatory diagram showing the image analysis of the base sheet with fiber electrodes obtained in Example 2. FIG. 2(a) is an image obtained by converting a photograph taken from directly above the center of the embroidered portion of a base sheet with a fiber electrode into an 8-bit image, and FIG. 2(b) is an image showing the result of extracting void portions in order to calculate the porosity by image analysis, in which the portions 4 where the conductive threads exist are shown in white and the void portions 3 are shown in black.

(h) Impedance in the initial state The impedance of the fiber electrode in the initial state was measured in accordance with ANSI/AAMI EC12:2000. Specifically, the measurement was performed by the following method. Two sheets of base material sheets with fiber electrodes prepared in the examples, comparative examples, and reference examples were prepared. A stainless steel one-sided rivet (terminal) with a diameter of 10 mm was attached to the embroidered part of a square of 1 cm x 1 cm (the small square part at the top of the convex electrode shown in Figure 1). At that time, the metal fittings on the surface side of the fiber electrode were protected with an insulating material. Then, two base material sheets with fiber electrodes were stacked so that the embroidered parts were joined to obtain a pair of samples. Then, a crocodile clip-type measurement probe terminal was connected to the rivet of each fiber electrode under pressure with a 100 g weight placed on top of the sample, and the AC impedance at 10 Hz was measured under conditions of 23 ° C. and 40% humidity. An impedance analyzer (HIOKI ELECTRIC CO., LTD., IM3570) was used to measure the AC impedance. The AC impedance was measured for the five samples, and the average value was taken as the impedance of the fiber electrode in its initial state.

(i) Impedance after exposure to air The base sheet with fiber electrodes prepared in the Examples, Comparative Examples, and Reference Examples was left in an environment of 23°C x 55% RH for 24 hours. Thereafter, the AC impedance at 10 Hz was measured using the obtained samples by the method described in (h) above. The AC impedance was measured for four samples, and the average value was taken as the impedance of the fiber electrodes after exposure to air.

(j) Impedance after 50 washes Based on the C4M method of JIS L 1930:2014 (Home washing test method for textile products), the fabricated substrate sheet with fiber electrodes was washed 50 times to obtain a sample. The drying method was Method A (hang-dry). Using the obtained sample, the AC impedance at 10 Hz was measured by the method described in (h). The AC impedance was measured for four samples, and the average value was taken as the impedance of the fiber electrode after 50 washes.

Example 1
The following core yarn and sheath yarn were prepared as conductive yarns, and twisted at 300 turns/m (S twist) using a covering twisting machine to obtain a core-sheath composite twisted yarn in which one core yarn was covered with two sheath yarns. Seven of the obtained core-sheath composite twisted yarns were then twisted together to obtain a conductive yarn.

(Configuration of core-sheath composite twisted yarn)
Core yarn: Organic fiber A, polyester multifilament (55 dtex/144 f) x 1 Sheath yarn: Metal fiber, tungsten metal yarn (diameter 13 μm) x 1 Sheath yarn: Organic fiber B, nylon 6 multifilament (13 dtex/7 f) x 1

(Base sheet)
Needle-punched nonwoven fabric made of polyester staple fibers (thickness 1.19 mm, basis weight 240 g/ ^m2 )

Next, the conductive thread was used for the main stitching and understitching, and the polyester multifilament (organic fiber A) used for the core thread was used for the lower thread (the thread appearing on the back surface of the fiber electrode). A single-head embroidery machine (TMEZ-SC, manufactured by Tajima Industries Co., Ltd.) was used to embroider the base sheet in the following configuration to form the fiber electrode shown in Figure 1 (having an embroidered portion consisting of a 2 cm x 2 cm square and a 1 cm x 1 cm square), thereby producing a base sheet with a fiber electrode.
Main stitch: Stitch type = Tatami stitch, stitch length = 3 mm, row spacing = 1.2 mm, offset value = 0.77 mm
Understitch: Stitch type = tatami stitch, stitch length = 2 mm, row spacing = 6 mm, no offset. In the understitch and lockstitch, the conductive threads cross at right angles (90 degree intersecting angle) in the warp and weft directions.

Example 2
The following core yarn and sheath yarn were prepared as conductive yarns, and a core-sheath composite twisted yarn was obtained in the same manner as in Example 1. Next, five of the obtained core-sheath composite twisted yarns were plyed together to obtain a conductive yarn.

(Configuration of core-sheath composite twisted yarn)
Core yarn: Organic fiber A, polyester multifilament (55 dtex/144 f) x 1 Sheath yarn: Metal fiber, tungsten metal yarn (diameter 13 μm) x 1 Sheath yarn: Organic fiber B, nylon 6 multifilament (13 dtex/7 f) x 1

(Base sheet)
Needle-punched nonwoven fabric made of polyester staple fibers (thickness 1.19 mm, basis weight 240 g/ ^m2 )

Next, a base sheet with a fiber electrode was produced in the same manner as in Example 1, except that the base sheet was embroidered in the following manner using the conductive thread in the main stitching and understitching.
Main stitch: Stitch type = Tatami stitch, stitch length = 3 mm, row spacing = 0.77 mm, offset value = 0.77 mm
Understitch: Stitch type = tatami stitch, stitch length = 2 mm, row spacing = 6 mm, no offset. In the understitch and lockstitch, the conductive threads cross at right angles (90 degree intersecting angle) in the warp and weft directions.

Example 3
The base sheet with the fiber electrode prepared in Example 2 was impregnated in an aqueous solution obtained by adding a polyester-based SR agent "Parasorb PET2" (manufactured by Ohara Palladium Co., Ltd.) as a water absorbing agent to water (5 g per 100 ml), and the water absorbing agent was adhered to the front and back surfaces of the fiber electrode. Then, the base sheet with the fiber electrode that had been subjected to water absorption processing was prepared by drying for 20 minutes in a dryer at 100°C.

Example 4
The following core yarn and sheath yarn were prepared as conductive yarns, and twisted at 300 turns/m (S twist) using a covering twisting machine to obtain a core-sheath composite twisted yarn in which one core yarn was covered with two sheath yarns. Five of the obtained core-sheath composite twisted yarns were then twisted together to obtain a conductive yarn.

(Configuration of core-sheath composite twisted yarn)
Core yarn: Organic fiber A, polyester multifilament (55 dtex/144 f) x 1 Sheath yarn: Metal fiber, tungsten metal yarn (diameter 13 μm) x 1 Sheath yarn: Organic fiber B, polylactic acid filament (33 dtex/18 f) x 1

(Base sheet)
Needle-punched nonwoven fabric made of polyester staple fibers (thickness 1.19 mm, basis weight 240 g/ ^m2 )

Next, the conductive thread was used for the main stitching and understitching, and the polyester multifilament (organic fiber A) used for the core thread was used for the lower thread (thread appearing on the back surface of the fiber electrode), and embroidery was performed on the base sheet using a single-head embroidery machine (TMEZ-SC, manufactured by Tajima Industries Co., Ltd.) in the following configuration. Thereafter, the polylactic acid filaments in the conductive thread were alkaline-eluted using a known device, and the fiber electrode shown in FIG. 1 (having an embroidered portion consisting of a 2 cm x 2 cm square and a 1 cm x 1 cm square) was formed, thereby producing a base sheet with a fiber electrode. The surface of the fiber electrode of the obtained base sheet with a fiber electrode had a large amount of exposed metal fibers due to the elution of the polylactic acid filaments.
Main stitch: Stitch type = Tatami stitch, stitch length = 3 mm, row spacing = 0.8 mm, offset value = 0.77 mm
Understitch: Stitch type = tatami stitch, stitch length = 2 mm, row spacing = 6 mm, no offset. In the understitch and lockstitch, the conductive threads cross at right angles (90 degree intersecting angle) in the warp and weft directions.

Example 5
A base sheet with a fiber electrode was produced in the same manner as in Example 4, except that a laminate having the following configuration was used as the base sheet.
(Base sheet)
Laminate: A laminate in which a surface knitted fabric, a film, and a back knitted fabric are laminated in this order (thickness: 0.755 mm, basis weight: 284 g/ ^m2 )
Surface knit: Warp knit made of polyethylene terephthalate yarn (75 dtex 72 fil) Film: Film made of polycarbonate-based polyurethane resin Back knit: Warp knit made of polyethylene terephthalate yarn (56 dtex 36 fil)

<Comparative Example 1>
The following metal-plated threads were used as conductive threads:
(Metal-plated thread)
Ag-plated thread (Osaka Electric Industry Co., Ltd., ODEX, 78dtex/24f)

Next, embroidery was performed on the base sheet in the following manner in the same manner as in Example 2, except that the conductive thread was used in the main stitching and understitching, to produce a base sheet with a fiber electrode.
Main stitch: Stitch type = Tatami stitch, stitch length = 3 mm, row spacing = 0.77 mm, offset value = 0.77 mm
Understitch: Stitch type = tatami stitch, stitch length = 2 mm, row spacing = 6 mm, no offset. In the understitch and lockstitch, the conductive threads cross at right angles (90 degree intersecting angle) in the warp and weft directions.

<Reference Example 1>
Instead of the conductive yarn, a ply-twisted yarn made by plying five polyester multifilaments (55 dtex/144f) was prepared. Then, the ply-twisted yarn was used in the main stitching and understitching, and the laminate used in Example 5 was used as the base sheet. In the same manner as in Example 2, except that, embroidery was performed on the base sheet with the following configuration, to produce a base sheet with a fiber electrode.
Main stitch: Stitch type = Tatami stitch, stitch length = 3 mm, row spacing = 0.77 mm, offset value = 0.77 mm
Understitch: Stitch type = tatami stitch, stitch length = 2 mm, row spacing = 6 mm, no offset. In the understitch and lockstitch, the conductive threads cross at right angles (90 degree intersecting angle) in the warp and weft directions.

<Reference Example 2>
The electrocardiogram electrode "Blue Sensor" (model number: SP-00-S) manufactured by Metz was used.

The structure and physical properties of the substrate sheets with fiber electrodes prepared in Examples 1 to 5, Comparative Example 1, and Reference Example 1 are shown in Table 1.

As is clear from Table 1, the base sheet with fiber electrode obtained in Examples 1 to 5 satisfies all of the above characteristics (1) to (4), and therefore has excellent conductive performance capable of acquiring biosignals, which are weak electrical signals, and is also unlikely to deteriorate or change in conductive performance even when used repeatedly. In addition, the base sheet with fiber electrode obtained in Examples 1 to 5 has excellent initial impedance, and has little effect on impedance characteristics even after long exposure to the atmosphere and repeated washing. In addition, as is clear from the comparison with Reference Example 1, which does not contain conductive thread and has no conductivity, the fiber electrodes of the base sheet with fiber electrode obtained in Examples 1 to 5 have excellent electrical properties and are practically usable as bioelectrodes. The base sheet with fiber electrode obtained in Examples 1 to 5 also had a thickness index T that was not significantly different from that of Reference Example 1, in which the embroidery part was formed with thread that did not contain metal fibers, and was smaller than the gel electrode of Reference Example 2, and had excellent flexibility. In addition, it was found that the fiber electrodes of the base sheet with fiber electrode obtained in Examples 1 to 5 had a small porosity and the embroidery part with conductive thread was densely formed.

On the other hand, the substrate sheet with fiber electrodes obtained in Comparative Example 1 had a high surface resistance value on the surface of the fiber electrodes, poor electrical conductivity, and also had poor impedance compared to the substrate sheets with fiber electrodes obtained in Examples 1 to 5. Furthermore, when the substrate sheet with fiber electrodes obtained in Comparative Example 1 was used repeatedly, the surface resistance value of the metal-plated yarn surface was high, the electrical conductivity was poor, and the electrical conductivity was reduced due to partial peeling of the metal, resulting in poor durability.

1: Base sheet 2: Fiber electrode (embroidery part)
3: Void area (black)
4: Part where conductive thread is present (white)

Claims (8)

A base sheet with a fiber electrode comprising a base sheet and a fiber electrode constituted by an embroidered portion including a conductive thread, the base sheet with a fiber electrode satisfying all of the following characteristics (1) to ( 5 ):
(1) The size of the embroidered portion on the surface of the fiber electrode is 0.1 ^cm2 or more.
(2) The conductive yarn is a composite yarn containing organic fibers and metal fibers.
(3) The content of metal fibers in the embroidery portion is 0.001 to 0.1 g/ ^cm2 .
(4) The surface resistance of the fiber electrode surface is 15 Ω/cm ² or less.
(5) The thickness index T calculated by the following formula is 4.0 or less.
Thickness index T=(T2-T1)/T1
(T1: thickness of the base sheet with fiber electrodes, T2: maximum thickness of the base sheet with fiber electrodes when folded in half in a direction perpendicular to the embroidery direction of the conductive thread on which the fiber electrodes are embroidered and so that the fiber electrodes face each other) The substrate sheet with fiber electrodes according to claim 1, in which the metal fibers contained in the conductive yarn have a diameter of 2 to 150 μm. 2. The substrate sheet with fiber electrodes according to claim 1, wherein the absolute value of the change in surface resistance of the fiber electrode surface after 30 friction tests is 1 Ω/cm ² or less. The substrate sheet with fiber electrodes according to claim 1, wherein the fiber electrodes have a dimensional retention rate of 85% or more after 50 washes. The substrate sheet with fiber electrodes according to claim 1, in which the porosity in the embroidered portion is 18% or less. The substrate sheet with fiber electrodes according to claim 1, wherein the embroidered portion has stitches in which conductive threads are arranged to cross each other. The substrate sheet with fiber electrodes according to claim 1, which has a water absorbent on the surface of the fiber electrodes. A product having at least a part thereof the substrate sheet with a fiber electrode according to any one of claims 1 to 7 .