JP2022056684A - Conductive fiber structure and bioelectrode - Google Patents

Abstract

To provide a conductive fiber structure capable of improving washing durability.SOLUTION: Provided is a conductive fiber structure including a base material composed of a fiber bundle that includes synthetic fibers, and a conductive resin present in the base material. The fiber bundle is composed of a fiber region where fibers exist and a non-fiber region where no fibers exist. The conductive fiber structure, inside the fiber bundle on a cut surface where the fiber bundle is cut in a direction orthogonal to a fiber longer direction, includes a non-fiber region where an area ratio of the fiber region/the non-fiber region in a circle with a diameter of 30 μm having four or more points of centroid on a single fiber cross section is 20/80 to 80/20, and an area ratio of the conductive resin in the non-fiber region is 40 to 90%. The conductive resin contains a conductive polymer.SELECTED DRAWING: Figure 1

Description

The present invention relates to a conductive fiber structure containing a substrate composed of a fiber bundle containing synthetic fibers and a conductive resin existing in the substrate, and a bioelectrode including the same as an electrode.

In recent years, many electrodes have been developed that can measure the heart rate and electrical biological signals of humans and animals by using conductive fibers, or wearable sensors using the electrodes. In addition, electrical muscle stimulation (EMS) applications that actively promote muscle movement by applying electrical stimulation to living organisms, especially muscles, through electrodes are being actively developed. These have the purpose of improving people's safety and health. As the electrode required for this purpose, it is desirable to bring it into contact with the biological surface in a planar manner, and the washing durability must be high. For EMS applications, the resistance value of the electrode must be 1000Ω or less, and if it exceeds 1000Ω, the electrode may generate heat and cause an accident.

Conventionally, the base fiber is impregnated with a conductor containing a conductive polymer such as PEDOT-PSS (poly 3,4-ethylenedioxythiophene-polystyrene sulfonic acid) as an electrode for surface contact with the biological surface and / or. A conductive polymer fiber is produced by adhering the conductor to the substrate fiber, and a bioelectrode using this conductive polymer fiber has been developed (see Patent Document 1 (Japanese Patent Laid-Open No. 5706539)). ..

Further, as an electrode with improved washing durability, a conductive resin containing a conductive polymer is supported in the gap between the single fibers constituting the fiber structure, and the cross section of the fiber structure in the thickness direction is observed. A conductive fiber structure having an area ratio of 15% or more of the conductive resin existing in a region of 15 to 30 μm from the surface layer has been developed (Patent Document 2 (International Publication No. 2017/183463). )reference).

Furthermore, in recent years, a technique has been developed in which PEDOT-PTS (poly 3,4-ethylenedioxythiophene-p-toluenesulfonic acid), which has higher conductivity than PEDOT-PSS as a conductive polymer, is applied to the surface of the substrate. By uniformly adhering the conductive polymer in a non-crystalline state, the washing durability is improved (see Patent Document 3 (Japanese Patent No. 6476480)).

Japanese Patent No. 5706539 International Publication No. 2017/183464 Pamphlet Japanese Patent No. 6476480

However, Patent Document 1 uses a conductive polymer fiber in which a large amount of a conductor adheres to the fiber surface layer, and an electrode obtained by processing such a conductive polymer fiber into a textile shape never has washing durability. It wasn't expensive, it wasn't enough. Further, in Patent Document 1, only silk fiber is actually used as the base fiber, and the structure is such that the conductor containing the conductive polymer is in close contact with the base fiber, but synthetic fiber is particularly used. If so, the compatibility with the conductive polymer is poor and the adhesiveness is inferior, so that the conductors are unlikely to be in close contact with each other. In addition, even if the conductors are in close contact with each other immediately after production, the conductors are peeled off and fall off during washing, and the conductivity is insufficiently reduced.

In the conductive fiber structure disclosed in Patent Document 2, when the cross section in the thickness direction is observed, the area ratio of the conductive resin existing in the region of 15 to 30 μm from the surface layer is 15% or more. It is described in this document that the conductive resin is supported in the gaps between the fibers, but by impregnating the fibers deeply, flexibility and washing durability can be obtained. The region of 15 to 30 μm from the surface layer in the thickness direction differs depending on the thickness of the conductive fiber structure, the fiber diameter of the fibers constituting the conductive fiber structure, and the like, and therefore does not necessarily represent the deep part. Further, even if the conductive resin is supported inside the fiber structure, the washing durability may be insufficient.

Further, in the embodiment of Patent Document 2, the dispersed particle size is fine particles of 200 nm or less, and by applying a conductive resin containing a binder resin, the conductive resin is supported between the fibers, that is, adhered. Therefore, it is said that the conductivity is maintained even after washing 30 times. However, in such an embodiment, since the incompatible conductive resin is only supported between the fibers in the end, the performance cannot be maintained in a practical number of washings. That is, when the conductive fiber structure containing the conductive resin is washed, the conductive substance is sequentially dropped from the surface layer due to frictional resistance with the washing machine, impact force between the laundry and the like. When washing is repeated further, the conductive substance carried on the fiber surface is removed, and then the conductive substance is sequentially removed from the outer layer portion of the fiber toward the inner layer. Therefore, even if the method of supporting the conductive polymer on the fiber, that is, adhering it, has conductivity up to 30 times of washing, it is assumed that the washing is performed once every 3 days, and 100 times of washing in consideration of practicality for about 1 year. Under the harsh conditions, the conductive substance fell off and the conductivity could not be exhibited.

Although Patent Document 3 describes that a conductive polymer can be uniformly adhered, it is intended for adhesion to the surface of a base material, and in particular, when a synthetic fiber is used as a base material, the molecule thereof. Due to the lack of structure and hydrophilicity, the compatibility with the conductive polymer is poor, and it is difficult to allow it to exist inside the fiber bundle, so there is room for improvement in washing durability.

Further, in Patent Documents 2 and 3, the evaluation of the washing durability is performed only about 30 times and 10 times, and it cannot be said that the evaluation considers the practicality. It is essential that the clothing described in Patent Documents 2 and 3 come into contact with human skin. That is, it is necessary to measure the electrocardiogram in order to operate as a sensor, and in order to apply electric massage and muscle stimulation, electricity flows when other clothing exists between the conductive fiber structure. This is because the performance cannot be exhibited. Clothes that come into contact with human skin in this way are generally used repeatedly after being washed due to the problem of odor caused by sweat. Although the frequency of wearing varies depending on the wearing scene, considering the use for one year, 30 times of washing is worn once every 12 days, which is not very practical. If it is washed 100 times, it will be worn once every 3 to 4 days, which is a level that can be said to be practical.

The present invention has been made based on such a problem, and an object of the present invention is to provide a conductive fiber structure and a bioelectrode capable of improving washing durability.

As a result of diligent studies to achieve the above object, the inventors of the present invention have made a conductive fiber containing a base material composed of a fiber bundle containing synthetic fibers and a conductive resin existing in the base material. A conductive fiber structure in which a fiber region and a non-fiber region exist in a specific area in the fiber bundle cross section, and the area occupied by the conductive resin in the non-fiber region is a specific ratio. Found that it has excellent washing durability because the conductive resin can be held inside the fiber bundle, and the present invention has been completed.

That is, the present invention can be configured in the following aspects.
[Aspect 1]
A conductive fiber structure containing a substrate composed of a fiber bundle containing synthetic fibers and a conductive resin existing in the substrate.
The fiber bundle is composed of a fiber region in which fibers are present and a non-fiber region in which fibers are not present.
In the fiber bundle of the cut surface obtained by cutting the fiber bundle in a direction orthogonal to the fiber longitudinal direction, the area ratio of the fiber region / non-fiber region in the circle having a diameter of 30 μm containing four or more points of gravity of the single fiber cross section is , 20/80 to 80/20 (preferably 30/70 to 75/25, more preferably 40/60 to 65/35), and the area ratio of the conductive resin in the non-fiber region is 40 to 40. A conductive fiber structure containing a non-fiber region of 90% (preferably 45 to 80%, more preferably 50 to 75%), wherein the conductive resin contains a conductive polymer.
[Aspect 2]
The conductive fiber structure according to the first aspect, wherein the conductive resin exists in the form of a sponge and / or a boundary film having communication holes between the separated single fibers.
[Aspect 3]
A conductive fiber structure according to aspect 1 or 2, wherein the synthetic fiber constituting the base material has a deformed cross section having three or more recesses.
[Aspect 4]
The conductive fiber structure according to any one of aspects 1 to 3, wherein the substrate has a single fiber fineness of 0.5 to 4 dtex (preferably 0.7 to 3 dtex, more preferably 1.0 to 2). A conductive fiber structure comprising synthetic fibers of .5 dtex).
[Aspect 5]
The conductive fiber structure according to any one of aspects 1 to 4, having a surface resistivity of 200 Ω / □ or less (preferably 150 Ω / □ or less, more preferably 100 Ω / □ or less) after washing 100 times. Is a conductive fiber structure.
[Aspect 6]
A bioelectrode comprising the conductive fiber structure according to any one of aspects 1 to 5 as an electrode.

According to the conductive fiber structure of the present invention, the conductive resin can be held in the fiber bundle even after washing a larger number of times in consideration of actual wearing, and the washing durability is excellent.

The present invention will be more clearly understood from the following description of preferred embodiments with reference to the accompanying drawings. However, embodiments and drawings are for illustration and illustration purposes only and should not be used to define the scope of the invention. The scope of the invention is determined by the appended claims.
6 is an enlarged photograph (magnification: 800 times) showing a cross section of the conductive fiber structure obtained in Example 1. 6 is an enlarged photograph (magnification: 800 times) showing a cross section of the conductive fiber structure obtained in Example 2. 6 is an enlarged photograph (magnification: 1000 times) showing a cross section of the conductive fiber structure obtained in Example 3. It is a schematic cross-sectional view which shows the example of the deformed cross section which has the concave part of the fiber cross-sectional shape of 3 points or more.

[Conductive fiber structure]
The conductive fiber structure of the present invention includes a base material composed of a fiber bundle containing synthetic fibers and a conductive resin existing in the base material. A fiber bundle is a bundle formed by combining two or more single fibers, and is a multifilament yarn without twist immediately after spinning, or a yarn obtained by processing twisted yarn, false twist, interlace, etc. Is also included. The conductive resin may be present in at least a part of the base material, and the range of the area ratio and the area ratio described later may be satisfied by at least the portion where the conductive resin is present.

The conductive fiber structure of the present invention is composed of a fiber region in which fibers are present and a non-fiber region in which fibers are not present on a cut surface obtained by cutting a fiber bundle in a direction orthogonal to the fiber longitudinal direction. The fiber region indicates a region of the fiber itself constituting the fiber bundle. The non-fiber region indicates a region in which a non-fiber is present, that is, a region in which an air layer, a conductive resin, or the like is present. It may be a region where a sex resin is present. Further, the air layer indicates a region in which a substance such as a fiber or a conductive resin does not exist and is a void.

The conductive fiber structure of the present invention is a fiber region / non-fiber in a circle having a diameter of 30 μm in which four or more centers of gravity of a single fiber cross section are inserted on a cut surface obtained by cutting a fiber bundle in a direction orthogonal to the fiber longitudinal direction. The area ratio of the area is 20/80 to 80/20. In the present invention, the inside of a circle having a diameter of 30 μm in which four or more points of the center of gravity of the cross section of a single fiber are inserted indicates a portion determined by the method described later, and indicates a portion corresponding to the inside of the fiber bundle. Inside the fiber bundle, the area ratio between the fiber region and the non-fiber region is set to a specific range, and the distance between the single fibers is widened to some extent to create a space where the air layer and the conductive resin can exist inside the fiber bundle. Since it can be secured and the conductive resin can be held in the fiber bundle, the washing durability can be improved. The area ratio of the fiber region / non-fiber region in a circle having a diameter of 30 μm containing four or more centers of gravity of the single fiber cross section is preferably 30/70 to 75/25, more preferably 40/60 to 65/35. May be good.

The conductive fiber structure of the present invention is contained in a non-fiber region within a circle having a diameter of 30 μm in which four or more centers of gravity of a single fiber cross section are inserted on a cut surface obtained by cutting a fiber bundle in a direction orthogonal to the fiber longitudinal direction. The ratio (area) occupied by the conductive resin is 40 to 90%. By setting the area ratio of the conductive resin in the non-fiber region to a specific range and the presence of a specific amount of the conductive resin that can be held in the fiber bundle, the conductivity can be maintained and the washing durability is improved. Can be made to. The proportion (area) of the conductive resin in the non-fiber region is preferably 45 to 80%, more preferably 50 to 75% within a circle having a diameter of 30 μm containing four or more centers of gravity of the single fiber cross section. May be good.

In the conductive fiber structure of the present invention, the conductive resin may be present at least inside the fiber bundle, and may be further adhered to the outer surface of the fiber bundle. Further, in the conductive fiber structure of the present invention, the conductive resin may be adhered to the synthetic fiber inside and / or outside the fiber bundle, but there may be a portion where the conductive resin is not adhered. Even when the adhesiveness between the conductive resin and the synthetic fiber is low, the conductive resin existing on the outside of the fiber bundle falls off during washing, but by confining the conductive resin inside the fiber bundle, during washing. It can be prevented from falling off.

In the present invention, the area ratio of the fiber region / non-fiber region and the area ratio of the conductive resin in the non-fiber region are determined by the following methods. The center of gravity is determined by image analysis on a cut surface photograph (SEM) of the conductive fiber structure, but first it is necessary to distinguish between synthetic fibers, conductive resin and air layer. If other materials are present, it is necessary to distinguish those materials as well. For example, as a pretreatment, it is preferable to treat the conductive fiber structure with osmium and clarify the boundary surface thereof. Since osmium is adsorbed on the conductive polymer but not on the synthetic fiber, the boundary surface is clarified. can do. After distinguishing the boundaries between the synthetic fiber, the conductive resin and the air layer with image analysis software, the center of gravity of the single fiber cross section of the synthetic fiber is specified from the analysis software, and the position is plotted on the cut surface photograph. After that, select the center of gravity of the four single fiber cross sections, draw a circle with a diameter of 30 μm centered on the center of gravity of the four points, search for a part in which the center of gravity of the single fiber cross section fits at four points or more, and search for the part of the relevant part. The area ratio of the fiber region / non-fiber region and the area ratio of the conductive resin in the non-fiber region can be calculated by image analysis software. When the base material is composed of a plurality of types of fiber bundles in a structure such as a woven fabric or a knitted fabric, at least one type of fiber bundle may satisfy the above-mentioned specific area ratio and area ratio.

Further, in the conductive fiber structure of the present invention, an air layer is present as a non-fiber region at a specific ratio inside the fiber bundle on the cut surface obtained by cutting the fiber bundle in a direction orthogonal to the fiber longitudinal direction. As a result, the washing durability can be improved, probably because the air layer acts as a cushion against the impact during washing, and the flexibility is further excellent. The area ratio of the conductive resin / air layer may be 40/60 to 90/10, preferably 45/55, in the non-fiber region within a circle having a diameter of 30 μm containing four or more centers of gravity of the single fiber cross section. It may be ~ 80/20, more preferably 50/50 to 75/25.

The conductive resin may be present in the form of a sponge and / or a boundary film between the separated single fibers. The sponge-like shape refers to a shape in which the conductive resin existing between the single fibers porously contains an air layer (void). The boundary film-like structure means that the conductive resin has a film-like structure formed by surface tension acting between adjacent single fibers when the conductive resin dries during production. The presence of the conductive resin in the form of sponge and boundary film means that the conductive resin exists in the form of sponge and the boundary film in one fiber bundle in the conductive fiber structure. Of the plurality of fiber bundles in the conductive fiber structure, the fiber bundle in which the conductive resin exists in the form of a sponge and the fiber in which the conductive resin exists in the form of a boundary film may be mixed. Bundles may be mixed. By having the shape in which the conductive resin is filled between the adjacent single fibers but including the voids between the single fibers, the washing durability can be improved and the flexibility is excellent.

The weight of the conductive fiber structure of the present invention can be appropriately determined depending on the intended use, and the weight is not particularly limited, but may be, for example, about 50 to 300 g / m ² .

The conductive fiber structure of the present invention may have a surface resistivity of 200 Ω / □ or less after washing 100 times, preferably 150 Ω / □ or less, and more preferably 100 Ω / □ or less. The lower limit of the surface resistivity after washing 100 times may be, for example, 0.1 Ω / □ or more. Further, it is preferable that the surface resistivity is within the above range even after washing 200 times. The surface resistivity after washing 100 times is a value measured by the method described in Examples described later.

(Base material)
The base material is not particularly limited as long as it is composed of a fiber bundle containing synthetic fibers, and examples thereof include fabrics such as woven fabrics, knitted fabrics, and non-woven fabrics, but woven fabrics and knitted fabrics may be preferable.
In the present invention, it is possible to maintain the conductivity even when an elastic woven fabric or a knitted fabric, which has been difficult to maintain the conductivity in the past, is used as a base material. That is, it has been very difficult to use a knitted fabric having high stretchability as a base material among the conventional conductive fiber structures. The fiber bundles that form the loops of the knitted fabric are usually under relatively low tension and are spread out in the lateral direction of the fiber axis, but when the knitted fabric is pulled, the loops are tensioned and the fiber bundles are stretched. As a result, the structure is deformed. Deformation of this structure promotes the separation of the fiber bundle and the conductive resin, and finally a large amount of the conductive resin is shed and the conductivity is lost. Therefore, a knit is used as the base material of the conductive fiber structure. It was difficult.
On the other hand, since the conductive fiber structure of the present invention forms a structure in which the conductive resin exists inside the fiber bundle, the conductive resin does not fall off even if the knitted loop is deformed, and the stretchability is stretchable. Conductivity can be maintained even with a high knitted fabric. Further, for the same reason as described above, the conductivity can be maintained even for a woven fabric having high stretchability using a polyurethane elastic yarn, a side-by-side type high crimp yarn, or the like.

The synthetic fiber is a fiber formed by using a fiber-forming synthetic polymer, and may be formed from one kind of synthetic polymer or two or more kinds of synthetic polymers. .. Examples of the synthetic fiber include polyolefin fibers formed from polyolefin resins such as polyethylene and polypropylene; polyester fibers formed from polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, and polylactic acid; Polyamide-based fibers formed from polyamide-based resins such as polyamide 6, polyamide 66, polyamide 11, polyamide 12, polyamide 610, and polyamide 612; polyurethane fibers formed from polyurethane-based resins; acrylic fibers formed from polyacrylonitrile and Acrylic fibers; Examples thereof include acrylate-based fibers formed from acrylate-based resins such as polyacrylic acid and polymethacrylic acid. These fibers may be used alone or in combination of two or more. Of these fibers, polyester fibers, polyamide fibers, and polyurethane fibers are preferably used. The conductive fiber structure of the present invention can be present inside the fiber bundle even when synthetic fibers that are not compatible with the conductive polymer are used as the base material, and thus the washing durability is improved. Excellent. For example, the proportion of the fibers constituting the base material containing synthetic fibers may be 50% by mass or more, preferably 60% by mass or more, and more preferably 70% by mass or more. The upper limit of the proportion of synthetic fibers is not particularly limited, but may be 100% by mass. The fibers constituting the base material may contain various natural fibers, semi-synthetic fibers and the like in addition to synthetic fibers. For example, natural fibers such as cotton, hemp, wool and pulp; regenerated fibers such as rayon, polynosic and cupra; semi-synthetic fibers such as acetate and triacetate may be contained.

The synthetic fiber constituting the base material may be a non-composite fiber or a composite fiber (core-sheath type composite fiber, sea-island type composite fiber, side-by-side type composite fiber, etc.). The cross-sectional shape of the synthetic fiber is not particularly limited, and may be a round cross section, a flat cross section other than the round cross section, a hollow cross section, or any other irregular cross section, but between single fibers. From the viewpoint of expanding the space, it is preferable that the synthetic fiber contains a fiber having a modified cross section having recesses having three or more cross-sectional shapes (for example, 3 to 6 points) in the fiber bundle. The concave portion means a portion having a portion recessed toward the inside of the fiber on the outer circumference of the cross section of the single fiber. When fibers having such an irregular cross-sectional shape are included, even if the single fibers are close to each other, a space is created between the single fibers due to the recesses, so that the liquid containing the conductive resin can be permeated by the capillary phenomenon. At the same time, a large amount of conductive resin can be embraced. Synthetic fibers include straight synthetic fibers without crimping and false twisted yarns that have been crimped. Either form may be used, but in order to develop the capillary phenomenon more strongly. It is preferable to have a crimped shape that has been subjected to false twisting. In particular, it is more preferable to perform false twisting on a deformed cross-section fiber having three or more recesses because a part of the recesses is deformed into a cylindrical shape and the liquid sucked in from the straight fibers is hard to be released. Examples of the deformed cross section having recesses having three or more cross-sectional shapes include a multi-leaf shape or a star shape (for example, 3 to 6-leaf shape) as shown in FIG. Preferably, the fiber may contain a fiber having a modified cross section having a recess having a cross-sectional shape of 4 points or more. The fiber bundle may contain one or more kinds of fibers having a cross-sectional shape. For example, in a fiber bundle, a fiber having a deformed cross section having a recess in which the cross-sectional shape has three or more points with respect to the total fineness of all the fibers. The ratio of the total fineness may be 50% or more, preferably 60% or more, more preferably 70% or more, and this upper limit is not particularly limited, but may be 100%.

The single fiber fineness of the synthetic fiber constituting the base material may be 0.5 to 4 dtex, and by using the synthetic fiber having the single fiber fineness in such a range, the space between the single fibers can be secured and the space between the single fibers can be secured. The flexibility of the conductive fiber structure can be improved. The single fiber fineness of the synthetic fiber constituting the base material may be preferably 0.7 to 3 dtex, more preferably 1.0 to 2.5 dtex. The synthetic fiber having a single fiber fineness may be contained in an amount of 40% by mass or more, preferably 50% by mass or more, of the fibers constituting the base material. The upper limit of the proportion of the synthetic fiber having the single fiber fineness among the fibers constituting the base material is not particularly limited, but may be 100% by mass. The single fiber fineness is a value measured by the method described in Examples described later.

The number of single fibers constituting the fiber bundle may be adjusted according to the intended use, and may be, for example, 10 to 500 fibers, preferably 20 to 200 fibers, and more preferably 30 to 100 fibers. .. Further, the fineness of one fiber bundle may be, for example, 20 to 500 dtex, preferably 30 to 200 dtex, and more preferably 35 to 110 dtex.

(Conductive resin)
The conductive resin contains a conductive polymer. The conductive polymer is a polymer having conductivity. The conductive polymer is not particularly limited as long as it can impart conductivity to the conductive fiber structure, and known conductive polymers can be used. For example, polythiophene, polypyrrole, polyaniline, poly (p-phenylene sulfide) can be used. ), Polyacetylene, poly (p-phenylene vinylene), polynaphthalene, derivatives thereof and the like, and a composite of these and a dopant is preferably used. These conductive polymers may be used alone or in combination of two or more. Among these conductive polymers, water-soluble conductive polymers (for example, polythiophene, polypyrrole, polyaniline, poly (p-phenylene sulfide), derivatives thereof, etc.) are preferable, and from the viewpoint of having high conductivity, they are preferable. A polymer containing a thiophene derivative as a monomer component is preferable, and a composite of a polymer containing a thiophene derivative as a monomer component and a dopant is more preferable.

As the polymer containing a thiophene derivative as a monomer component, poly (3,4-disubstituted thiophene) is preferable. Of the poly (3,4-disubstituted thiophene), poly (3,4-diC _{1-4 alkoxythiophene) or poly (3,4-C 1-4 alkylenedioxythiophene} ) is preferable and specific. Poly (3,4-ethylenedioxythiophene) [PEDOT], or a derivative thereof, is more preferably used.

Examples of the dopant include halogen, inorganic acid or salt thereof, low molecular weight sulfonic acid or salt thereof, low molecular weight carboxylic acid or salt thereof, sulfonic acid polymers (for example, polystyrene sulfonic acid [PSS], polyvinyl sulfonic acid, polyisoprene). Sulfuric acid and the like), and carboxylic acid polymers (for example, polyacrylic acid, polymethacrylic acid, polymaleic acid and the like) and the like can be mentioned. These dopants may be used alone or in combination of two or more. As a dopant used as a composite with a polymer containing a thiophene derivative as a monomer component, low molecular weight sulfonic acid or a salt thereof, low molecular weight carboxylic acid or a salt thereof, or sulfonic acid polymers from the viewpoint of imparting high conductivity. Is preferably used, examples of the low molecular weight sulfonic acid include C _1-12 alkyl sulfonic acid, benzene sulfonic acid, toluene sulfonic acid, and perfluoro C _1-12 alkyl sulfonic acid, and examples of the low molecular weight sulfonic acid include tri. Fluoroacetic acid, salicylic acid and the like can be mentioned, and examples of the sulfonic acid polymers include polystyrene sulfonic acid and polyvinyl sulfonic acid. Specifically, the dopant used as a complex with poly (3,4-ethylenedioxythiophene) is p-toluenesulfonic acid [pTS] or an iron salt thereof, trifluoroacetic acid or a salt thereof, or polystyrene sulfonic acid. Is preferable, and p-toluenesulfonic acid or an iron salt thereof is more preferable from the viewpoint of imparting higher conductivity.

The conductive resin may contain a resin other than the conductive polymer, and examples thereof include an oxidizing agent. The oxidizing agent is an additive used in a polymerization reaction for synthesizing a conductive polymer, and is, for example, an iron salt of an inorganic acid such as ferric chloride, ferric sulfate, ferrous nitrate, etc .; ferric chloride, Copper salt of inorganic acid such as cupric sulfate; persulfate such as ammonium persulfate, sodium persulfate, potassium persulfate; periodate such as potassium periodate; organic such as iron salt of p-toluenesulfonic acid Iron salts of acid; examples include aluminum chloride, nitrosonium tetrafluoroborate, boron trifluoride, bromine, iodine and the like. These oxidizing agents may be used alone or in combination of two or more.

The conductive resin has high conductivity, for example, may have an electric conductivity of 1 × 10 ⁻² S / cm or more, preferably 0.3 S / cm or more, more preferably 1.0 S. It may have an electric conductivity of / cm or more. The upper limit of the electric conductivity of the conductive resin may be, for example, 1000 S / cm.

[Manufacturing method of conductive fiber structure]
The method for producing a conductive fiber structure of the present invention includes a coating step of applying a conductive resin forming solution to a base material composed of a fiber bundle containing synthetic fibers, and a conductive resin forming solution applied to the base material. It may include at least a permeation step of infiltrating the fiber bundle and a polymerization step of polymerizing in the conductive resin forming solution permeated into the substrate to synthesize the conductive polymer.

In the coating step, when the conductive resin forming solution is applied to the substrate, it may be applied by a known coating method such as a dipping method, a coating method, or a spraying method. From the viewpoint of immersing the conductive resin forming solution in the base material and synthesizing the conductive polymer inside the base material, a coating method, a spray method, or the like is preferable. The conductive resin forming solution may be applied to the entire surface of the base material or a part thereof, depending on the purpose.

In the coating step, tension may not be applied to the substrate from the viewpoint of increasing the permeability of the conductive resin forming solution. By not applying tension to the base material, it is possible to create a space in which a large amount of the conductive resin is embraced in the fiber bundle. As a method of applying the conductive resin forming solution without applying tension to the base material, a method of applying the conductive resin forming solution while the base material is allowed to stand on a predetermined base material may be used, for example. It may be performed by a batch method or a continuous method by belt transport or the like.

The conductive resin forming solution is a solution containing a component capable of forming a conductive polymer, and may contain a monomer of the conductive polymer. From the viewpoint of facilitating the permeation of the conductive resin forming solution into the fiber bundle in the subsequent permeation step, it is preferable to use a solution containing a monomer constituting the conductive polymer. The conductive resin forming solution may contain a thiophene derivative as a monomer, preferably a poly (3,4-ethylenedioxythiophene) monomer (for example, 3,4-ethylenedioxythiophene). May include.

When a solution containing a monomer of a conductive polymer is used as the conductive resin forming solution, it may contain components that contribute to the polymerization of the monomer such as an oxidizing agent, a catalyst, and a polymerization initiator. For example, when the monomer is a thiophene derivative, a polymer containing the thiophene derivative as a monomer component can be obtained by oxidative polymerization using an oxidizing agent, and the above-mentioned oxidizing agent may be contained, preferably an inorganic acid. It may contain an iron salt of an organic acid or an iron salt of an organic acid. Further, when an iron salt of a low molecular weight sulfonic acid or an iron salt of a low molecular weight carboxylic acid is contained, it can function as an oxidizing agent and also as a dopant. Preferably, by using an iron salt of p-toluenesulfonic acid, it can function as both an oxidizing agent and a dopant.

The solvent used for the conductive resin forming solution is not particularly limited as long as it can dissolve a component capable of forming a conductive polymer, and is, for example, water; alcohols such as methanol, ethanol, 2-propanol, 1-propanol, and glycerin. Kind: Ethylene glycols such as ethylene glycol, diethylene glycol and triethylene glycol; propylene glycols such as propylene glycol, dipropylene glycol and tripropylene glycol; tetrahydrofuran; acetone; acetonitrile and the like. These solvents may be used alone or in combination of two or more. Preferably, at least one solvent selected from the group consisting of water, alcohols, ethylene glycols, and acetonitrile may be used.

When a solution containing a monomer of a conductive polymer is used as the conductive resin forming solution, it is preferable to use ethanol as the solvent. When a conductive resin forming solution using ethanol as a solvent is applied to a base material and the monomer of the conductive polymer is polymerized in the base material, the solvent can be removed at a relatively low temperature.

The conductive resin forming solution may contain various additives in addition to the components capable of forming the conductive polymer.

In the method for producing a conductive fiber structure of the present invention, it is preferable to apply the conductive resin forming solution three times or more as described later, and the amount of the conductive resin forming solution applied to the substrate per application is preferably three times or more. It is preferable that the amount of permeation is secured and the maximum amount is such that droplets do not fall from the substrate.

In the permeation step, the conductive resin forming solution can be permeated into the fiber bundle. The permeation step is not particularly limited as long as the conductive resin forming solution can be permeated to the inside of the fiber bundle of the base material, and the method of permeating the base material is performed by a known method such as a press, a roll press, or a belt press. be able to.

In the polymerization step, the polymerization may be promoted in the conductive resin forming solution permeated into the substrate to synthesize the conductive polymer. In the polymerization step, heating may be performed from the viewpoint of accelerating the polymerization reaction of the monomer of the conductive polymer, and in the case of a polymerization system in which the polymerization proceeds at room temperature, heating may be performed from the viewpoint of controlling the polymerization reaction. It may be reacted at room temperature without the reaction. For example, when 3,4-ethylenedioxythiophene and an oxidizing agent are mixed, it is preferable to carry out a polymerization reaction at room temperature.

In the method for producing a conductive fiber structure of the present invention, it is preferable to apply the conductive resin forming solution again to the substrate to which the conductive resin is applied, and it is preferable to apply the conductive resin forming solution again, and the specific fiber region / non-fiber region. From the viewpoint of satisfying the area ratio and the area ratio of the conductive resin in the non-fiber region, it is preferable to perform the coating step and the permeation step three times or more. 3 to 5 steps from applying the conductive resin forming solution to the base material to obtaining a base material to which the conductive resin is attached (including at least a coating step and a permeation step, and if necessary, a polymerization step). It may be applied repeatedly.

Further, by forming the conductive resin in a plurality of times rather than forming the conductive resin at one time, the conductive resin can be formed into a sponge-like and / or boundary film-like structure inside the fiber bundle. That is, the conductive fiber structure in which the conductive resin is present can be obtained by going through the coating step and the permeation step at least three times, but the conductive fiber structure that has been subjected to the coating step and the permeation step once is again subjected to the coating step and the permeation step. By performing the coating step and the permeation step, the previously existing conductive resin and the conductive resin in the reapplied conductive resin forming solution adhere to each other, and the sponge-like or boundary having a communication hole adhered or peeled off from the substrate. It can have a film-like structure, which is preferable from the viewpoint of forming an air layer inside the fiber bundle.

[Bioelectrode]
The conductive fiber structure of the present invention can be used as a bioelectrode capable of directly contacting a living body to acquire an electric signal and / or to give an electric signal. The conductive fiber structure of the present invention is used as an electrode member, and its shape and size are not particularly limited as long as it can be brought into surface contact with a biological surface.

In the bioelectrode of the present invention, a resin layer may be laminated on the conductive fiber structure as an electrically insulating layer. The resin layer may be in the shape of a fabric such as a woven fabric, a knitted fabric, or a non-woven fabric, or may be in the shape of a film, a sheet, or the like.

Examples of the bioelectrode of the present invention include a bioelectrode that detects an electric signal from a living body such as a heartbeat, and a bioelectrode that applies electrical stimulation to a living body such as electrical muscle stimulation (EMS). The bio-electrode of the present invention is not particularly limited as long as it is in direct contact with the living body because the conductive fiber structure used has a fit of the living body, and in addition to pads, gloves, belts, etc., it is suitable for washing durability. Various clothing such as underwear (shirts, blouses, T-shirts, tank tops, camisole, spaghetti strap shirts, tube tops, halter tops, brassieres, trousers, pants, girdles, socks, tights, stockings, singlets, leotards, swimwear. , Wet suits, etc.), footwear (leather shoes, sneakers, boots, sandals, pumps, mules, slippers, etc.), headbands, wristbands, neckbands, bellybands, suspenders, gloves, watches, hats, supporters, bandages, etc. At least a part of the above may be configured.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto. In the following Examples and Comparative Examples, various physical properties were measured by the following methods.

[Single fiber fineness]
The total fineness of the fiber bundles constituting the base material was measured according to JIS L 1013 "Chemical fiber filament yarn test method". Then, the value obtained by dividing the total fineness by the number of filaments constituting the fiber bundle was taken as the single fiber fineness.

[Metsuke]
The basis weight (g / m ² ) was measured according to 8.3 of JIS L 1096 “Dough test method for woven fabrics and knitted fabrics”.

[Area ratio, area ratio]
First, the conductive fiber structure is cut with a razor to prepare an observation sample in which the cross section of the fabric is exposed. Then, the sample is subjected to electronic staining treatment by gas phase staining treatment at room temperature (23 ° C.) using osmium tetroxide and subjected to microscopic observation. Observation is performed using a scanning electron microscope (SEM) (“SU-70” manufactured by Hitachi High-Technologies Corporation), and the cross section of the conductive fiber structure treated with osmium at 23 ° C. under high vacuum and at an observation magnification of 800 times. Was imaged.
The obtained image was segmented with the image analysis software "Avizo for EM systems software" manufactured by Thermo Fisher Scientific, and the fiber region and the non-fiber region were separated. Further, in the non-fiber region, the air layer region and the conductive resin region were separated by the same segmentation. The center of gravity of each single fiber cross section was determined by image analysis software. After that, select 4 points from the center of gravity determined by the image analysis software, draw a circle with a diameter of 30 μm centered on the center of gravity of the 4 points, and if 4 or more points of the center of gravity of the single fiber cross section are included in the circle. The inside of the circle was decided as the target area. In the region, the fiber region and the non-fiber region are separated by the above segmentation, and in the non-fiber region, the air layer region and the conductive resin region are further divided, and then the respective areas are calculated and the area ratio is calculated. I asked. The above area determination and area ratio calculation were taken as the number of measurements at one point. Similarly, measure at least three regions in another circle with a diameter of 30 μm containing four or more points of center of gravity, calculate the average value, and calculate the area ratio of the fiber region / non-fiber region and the conductive resin in the non-fiber region. The area ratio to occupy was calculated.

[Surface resistivity]
A test piece obtained by cutting a conductive fiber structure into a size of 10 cm × 10 cm is placed on a hard plate-like material having no surface unevenness such as a glass plate, and the surface resistivity (Ω / □) is measured by a low resistivity meter (Co., Ltd.). Measurement was performed at 20 ° C. and 40% RH environment using a four-probe resistivity meter “Loresta-AX MCP-T370” and a probe “ESP probe MCP-TP08P” manufactured by Mitsubishi Chemical Analytech.

[Washing durability]
Using a test piece obtained by cutting the conductive fiber structure into 10 cm × 10 cm, the surface resistivity after washing by the 100-time repetition method was measured by a method according to the JIS L 0217 (2012) 103 method. As the washing machine, a fully automatic washing machine (TOSHIBA AW-6D6) was used.

[Example 1]
Polyethylene terephthalate containing 2.5 wt% of titanium oxide produced by a conventional method [η] = 0.657 is melt-spun at a spinning speed of 3700 m / min, and a cross-section POY raw yarn having four recesses of 70dtex48 filaments is performed. Got Next, the present POY raw yarn was subjected to normal false twisting at a false twist ratio of 1.32 times and a heater temperature of 185 ° C. to obtain a false twist processed yarn of 56dtex48 filament. After preparing a knitted fabric with a mesh structure using the yarn and a 22dtex monofilament polyurethane elastic yarn (manufactured by Asahi Kasei Corporation) on the front surface and a polyester round cross section false twisted yarn (manufactured by Nanya Co., Ltd.) of SD33dtex12 filament on the back surface. , A bare mesh fabric dyed by a usual dyeing method was obtained. The content of synthetic fibers having a single fiber fineness of 0.5 to 4 dtex in this fabric was 93% by mass.
Conductivity obtained by mixing a monomer solution of PEDOT (Heraeus CleviosM-V2), an iron salt of pTS (Heraeus CleviosC-B40V2) as an oxidizing agent and a dopant, and ethanol as a solvent using this bare mesh dough as a base material. After the sex resin forming solution was uniformly applied to the upper part of the base material in the coating step, the conductive resin forming solution was infiltrated into the inside of the fiber bundle in the infiltration step. Then, it was heated at 55 ° C. for 12 minutes and then kept in a constant temperature bath at 25 ° C. and a humidity of 60% for 1 hour to polymerize the PEDOT monomer. The ratio of the iron salt of pTS to the monomer of PEDOT was 40: 2, and the ratio of the oxidizing agent (iron salt of pTS) to the total of ethanol and the oxidizing agent (iron salt of pTS) was It was set to 30% by mass. The coating amount was set to a ratio of 1 g / 20 cm ² , which is the maximum amount at which droplets do not fall from the fabric. In this way, polymerization was carried out in a state of being infiltrated into the substrate, PEDOT was synthesized, a conductive resin was formed on the fiber surface and in the fiber bundle space, and a once-applied conductive fiber structure was obtained.
Next, since the maximum amount of droplets not dropped from the substrate in one application was 1 g / 20 cm ² , in order to include a sufficient amount of conductive resin in the substrate, the conductivity after one application was applied. Using the fiber structure as a further base material, the second and third coatings, permeation and polymerization were carried out in the same manner as described above to obtain a conductive fiber structure coated three times.
After cutting the cross section of the obtained conductive fiber structure, it was dyed with osmium and the cross section was observed. As a result, the conductive resin exhibited a sponge-like structure with communication holes in which granular particles were laminated (). Figure 1). Further, in the obtained conductive fiber structure, the area ratio of the fiber region to the non-fiber region in a circle having a diameter of 30 μm containing four points of the center of gravity of the cross section of the single fiber was in the range of 55/45. The area ratio of the conductive resin to the non-fiber region was 65%. These area ratios and area ratios were calculated by observing the cross section of the fiber bundle used on the surface. The surface resistivity of the conductive fiber structure was 5Ω / □. After washing the conductive fiber structure 100 times continuously, the surface resistivity was measured in the same manner, and the surface resistivity was 74Ω / □, which was low even after washing.

[Example 2]
Polyethylene terephthalate containing 2.5 wt% of titanium oxide produced by a conventional method [η] = 0.657 is melt-spun at a spinning speed of 3750 m / min, and a cross-section POY raw yarn having four recesses of 110 dtex48 filaments is performed. Got Next, this POY raw yarn was subjected to normal false twisting at a false twist ratio of 1.34 times and a heater temperature of 180 ° C. to obtain a 1-heater false twist processed yarn of 88dtex48 filament. The warp is made by twisting the yarn at 200 t / m in the S direction, and the weft is made of FD84dtex24 filament with a polyester round cross section of 1 heater. A warp and double structure was woven using a twisted yarn. Then, a woven fabric that had been dyed by a usual dyeing method was obtained. The content of synthetic fibers having a single fiber fineness of 0.5 to 4 dtex in this woven fabric was 100% by mass. The coating amount was set to a ratio of 0.8 g / 20 cm ² , which is the maximum amount at which droplets do not fall from the fabric.
When this woven fabric was used as a base material, the maximum amount at which droplets did not fall from the base material in one application was 0.8 g / 20 cm ² . Therefore, in order to include a sufficient amount of the conductive resin in the base material, the amount of the conductive resin forming solution applied at one time is set to 0.8 g / 20 cm ² , which is the maximum absorption amount of the textile, in the examples. A series of coating, permeation, and polymerization steps were carried out three times in the same manner as in No. 1 to obtain a three-time coated conductive fiber structure.
After cutting the cross section of the obtained conductive fiber structure, it was dyed with osmium and the cross section was observed. It exhibited the structure of (Fig. 2). In the obtained conductive fiber structure, the area ratio of the fiber region to the non-fiber region in a circle having a diameter of 30 μm containing four centers of gravity of the cross section of the single fiber was in the range of 72/28. The area ratio of the conductive resin to the non-fiber region was 57%. These area ratios and area ratios were calculated by observing the cross section of the fiber bundle used for the warp. The surface resistivity of the conductive fiber structure was 3Ω / □. After washing the conductive fiber structure 100 times continuously, the surface resistivity was measured in the same manner, and the surface resistivity was 16Ω / □, which was low even after washing.

[Example 3]
Polyethylene terephthalate containing 0.4 wt% of titanium oxide produced by a conventional method [η] = 0.676 is melt-spun by a direct-spinning drawing method, and a 33dtex18 filament has a high shrinkage round cross section with a boiling water shrinkage rate of 15%. A drawn yarn was obtained. Further, using the same resin, high-speed spinning at a spinning speed of 4800 m / min was carried out to obtain a low shrinkage triangular cross-section yarn of 33dtex18 filament having three recesses having a boiling water shrinkage rate of 3.2%. Next, both yarns were subjected to air entanglement treatment using an interlaced nozzle to obtain a different shrinkage mixed yarn of 66dtex36 filament. The yarn is twisted at 1800 t / m in the S direction to form a warp, and the weft is a drawn yarn of 110 dtex72 filament with a boiling water shrinkage rate of 7%, which is also directly connected and drawn by spinning, and 2500 t / m in the S and Z directions. A raw machine was made with a satin structure using the one that had been plyed. This raw machine was dyed with a relaxing treatment so that the difference in shrinkage rate became large, and a different shrinkage mixed fiber satin fabric was obtained. The content of synthetic fibers having a single fiber fineness of 0.5 to 4 dtex in this woven fabric was 100% by mass.
When this woven fabric was used as a base material, the maximum amount at which droplets did not fall from the base material in one application was 0.6 g / 20 cm ² . Therefore, in order to include a sufficient amount of the conductive resin in the base material, the amount of the conductive resin forming solution applied at one time is set to 0.6 g / 20 cm ² , which is the maximum absorption amount of the textile, in the examples. The same series of coating, permeation, and polymerization steps as in No. 1 was performed three times to obtain a three-time coated conductive fiber structure.
After cutting the cross section of the obtained conductive fiber structure, it was dyed with osmium and the cross section was observed. As a result, the conductive resin had a structure like a thin film or a plate stuck between the fibers. It had a partially sponge-like structure (Fig. 3). In the obtained conductive fiber structure, the area ratio of the fiber region to the non-fiber region in a circle having a diameter of 30 μm containing four points of the center of gravity of the cross section of the single fiber was in the range of 75/25. The area ratio of the conductive resin to the non-fiber region was 68%. These area ratios and area ratios were calculated by observing the cross section of the fiber bundle used for the warp. The surface resistivity of the conductive fiber structure was 7Ω / □. After washing the conductive fiber structure 100 times continuously, the surface resistivity was measured in the same manner. The surface resistivity was 326 Ω / □, and the surface resistivity increased after washing, but it was within the permissible range.

[Comparative Example 1]
Polyethylene terephthalate containing 2.0 wt% of titanium oxide produced by a conventional method [η] = 0.674 is melt-spun by a direct-spinning drawing method, and a normal shrinkage round cross section with a boiling water shrinkage rate of 7% for 84dtex72 filaments. A drawn yarn was obtained. A taffeta raw machine was produced in which the yarn was used for warp and weft without twisting. This raw machine was dyed by a usual dyeing method to obtain a taffeta woven fabric. The content of synthetic fibers having a single fiber fineness of 0.5 to 4 dtex in this woven fabric was 100% by mass.
When this woven fabric was used as a base material, the maximum amount that droplets did not fall from the base material in one application was 0.4 g / 20 cm ² , and the conductive resin content for permeation was insufficient. The coating amount of the conductive resin forming solution per time is 0.4 g / 20 cm ² , which is the maximum absorption amount of the woven fabric, and the same series of coating, permeation, and polymerization steps as in Example 1 are performed three times. The conductive fiber structure of the above was obtained.
After cutting the cross section of the obtained conductive fiber structure, it was dyed with osmium and the cross section was observed. Was. In the obtained conductive fiber structure, the area ratio of the fiber region to the non-fiber region in a circle having a diameter of 30 μm containing four points of the center of gravity of the cross section of the single fiber was in the range of 70/30. The area ratio of the conductive resin to the non-fiber region was 35%. The surface resistivity of the conductive fiber structure was 16Ω / □. After washing the conductive fiber structure 100 times continuously, the surface resistivity was measured in the same manner, and the measurement became impossible. After washing, the conductive resin almost fell off and the conductivity was lost.

As shown in Table 1, the conductive fiber structures of Examples 1 to 3 have an area ratio of a specific fiber region / non-fiber region and an area ratio of the conductive resin in the non-fiber region. Even after washing 100 times in view of practicality, the conductive resin is retained inside the fiber bundle, and the conductivity can be maintained. The conductive fiber structures of Examples 1 and 2 were particularly excellent in washing durability.

On the other hand, in Comparative Example 1, since the area ratio of the conductive resin in the non-fiber region was not within a specific range, the conductive resin was almost completely removed by washing 100 times, and the washing durability was inferior.

The conductive textile structure of the present invention can be used as a bioelectrode for detecting an electric signal from a living body such as heartbeat, a bioelectrode for applying electrical stimulation to a living body such as electrical muscle stimulation (EMS), and the like. .. Since such bioelectrodes are derived from the fiber structure and have good fit to the living body, they are suitable for those that come into direct contact with the living body, and because they have excellent washing durability, they are added to, for example, pads, gloves, belts and the like. It can be used as at least a part of various clothing such as underwear, footwear, headband, wristband, neckband, belly band, hat, suspenders, gloves, watches, supporters, masks, bandages and the like.

As described above, the preferred embodiment of the present invention has been described, but various additions, changes or deletions can be made without departing from the spirit of the present invention, and such things are also included in the scope of the present invention. Will be.

Claims (6)

A conductive fiber structure containing a substrate composed of a fiber bundle containing synthetic fibers and a conductive resin existing in the substrate.
The fiber bundle is composed of a fiber region in which fibers are present and a non-fiber region in which fibers are not present.
In the fiber bundle of the cut surface obtained by cutting the fiber bundle in a direction orthogonal to the fiber longitudinal direction, the area ratio of the fiber region / non-fiber region in the circle having a diameter of 30 μm containing four or more points of gravity of the single fiber cross section is , 20/80 to 80/20, and the non-fiber region in which the area ratio of the conductive resin occupies 40 to 90% in the non-fiber region is included, and the conductive resin contains a conductive polymer. Sex fiber structure. The conductive fiber structure according to claim 1, wherein the conductive resin exists in the form of a sponge and / or a boundary film having communication holes between the separated single fibers. The conductive fiber structure according to claim 1 or 2, wherein the synthetic fiber constituting the base material has a deformed cross section having three or more recesses. The conductive fiber structure according to any one of claims 1 to 3, wherein the substrate contains synthetic fibers having a single fiber fineness of 0.5 to 4 dtex. The conductive fiber structure according to any one of claims 1 to 4, wherein the surface resistivity after washing 100 times is 200 Ω / □ or less. A bioelectrode comprising the conductive fiber structure according to any one of claims 1 to 5 as an electrode.

Images