JP7789571B2 - Stretchable conductive fabric - Google Patents

Description

The present invention relates to a stretchable conductive fabric that is applied with a metal coating and that can be used as a wearable device, electromagnetic wave shielding material, sensor electrode material, etc., and that comprises a fabric that at least partially contains crimped yarns that include composite fibers made of two polyester resin components with different heat shrinkage rates.

In recent years, wearable devices have been developed, which are electronic devices with input/output and communication functions that are worn on the body. Among these, conductive fabrics can be used as wearable devices by incorporating electronic components and sensors.

Wearable devices made from conductive fabrics can measure the biosignals and movements of humans and animals when worn, and are used in the medical and healthcare fields, as well as in a variety of industries such as the environment and construction.

Conventional techniques for imparting conductivity to fabrics include weaving or knitting conductive yarns (e.g., Patent Document 1) and printing a conductive paste (e.g., Patent Document 2).

However, the method of weaving or knitting conductive threads has problems such as the need for special equipment and limited freedom in the shape of the conductive pattern. The method of printing conductive paste can sometimes result in insufficient conductivity, which requires increasing the amount of paste printed to increase conductivity, which tends to make the fabric stiff and heavy. Furthermore, there is also the risk of cracking due to an inability to adapt to the flexibility of the fabric.

As a technology for imparting stretchability and conductivity to fabrics, an electromagnetic wave shielding sheet has been proposed in which a conductive film is formed on the surface of the yarn that forms the woven or knitted stitches (Patent Document 3). However, woven fabrics made with normal yarns, such as common false-twisted (textured) yarns, have insufficient stretchability, while knitted fabrics, while having sufficient stretchability, have problems with conductivity when stretched. Furthermore, knitted fabrics or those made with elastic yarns may be prone to excessive stretch.

If the threads containing the metal coating stretch too much, the metal coating will break and conductivity will decrease. On the other hand, if the fabric does not have enough elasticity, as is the case with fabrics made from general false-twisted yarn, its usability will decrease. There is a need for the development of conductive fabrics that have excellent elasticity and flexibility, as well as highly reliable conductivity, making them suitable for wearable devices, etc.

Stretchable fabrics using composite fibers made of two types of polyester resins with different shrinkage properties have been proposed as fabrics with excellent elasticity (e.g., Patent Document 4). However, it is not known that imparting conductivity to such stretchable fabrics can result in conductive fabrics with excellent both elasticity and conductivity.

JP 2013-019064 A JP 2014-151018 A Japanese Patent Application Publication No. 11-354981 Japanese Patent Application Laid-Open No. 2019-157321

The objective of the present invention is to provide a stretchable conductive fabric that is suitable for use as an electrode, possessing sufficient stretchability, and that maintains highly reliable conductivity even when a metal coating is applied without breaking due to stretching.

After extensive research, the inventors discovered that a fabric containing at least a portion of a crimped yarn containing a composite fiber made of two polyester resin components with different thermal shrinkage rates, to which a metal coating is applied, has sufficient stretchability, and the applied metal coating is resistant to breakage due to stretching, allowing high conductivity to be maintained, resulting in a stretchable conductive fabric suitable for use in wearable devices (electrodes), leading to the completion of the present invention.

That is, the present invention relates to the following stretchable conductive fabric.
(1) A stretchable conductive fabric comprising a woven fabric containing crimped yarns in at least some of the warp and/or weft yarns and having a metal coating applied thereto, characterized in that the ratio of crimped yarns to all fibers constituting the woven fabric is 25 to 45% by mass, and the stress at 30% elongation in at least one direction of the warp and/or weft yarns is 10 N/cm or less.

(2) The stretchable conductive fabric described in (1), characterized in that, in at least one direction of the warp and/or weft, the increase in resistance value when stretched 30% relative to the unstretched resistance value is 30% or less.

(3) The stretchable conductive fabric according to (1), characterized in that the crimped yarn is a composite fiber selected from the group consisting of a combination of polyethylene terephthalate resin and polybutylene terephthalate resin, a combination of polyethylene terephthalate resin and polytrimethylene terephthalate resin, and a combination of two polyethylene terephthalate resins having mutually different physical properties, and the structure of the composite fiber is a side-by-side type or an eccentric core-sheath type .

(4) The stretchable conductive fabric according to (1), wherein the woven fabric containing crimped yarns in at least a portion of the warp and/or weft threads is a woven fabric containing crimped yarns in only one of the warp and weft threads .

(5) The stretchable conductive fabric according to (1), wherein the shrinkage rate of the woven fabric after thermal processing is 10 to 50%.

The stretchable conductive fabric of the present invention has sufficient stretchability, especially excellent stretchability after the application of a metal coating, so the applied metal coating does not break due to stretching and maintains high conductivity. It also has excellent flexibility and ability to follow shape changes such as bending. The stretchable conductive fabric of the present invention can be suitably used in wearable devices, electromagnetic wave shielding materials, sensor electrode materials, etc.

1 is a micrograph (plan view) showing an example of the stretchable conductive fabric of the present invention.

The stretchable conductive fabric of the present invention is a fabric made of a woven fabric containing crimped yarns in at least some of the warp and/or weft threads and having a metal coating applied thereto, characterized in that the stress at 30% elongation in at least one direction of the warp and/or weft threads is 10 N/cm or less.
In the following description, the fabric (woven fabric) before the metal coating is applied will be referred to as a "highly stretchable fabric," and the fabric after the metal coating is applied will be referred to as a "stretchable conductive fabric."

1. Woven Fabric Comprising Crimped Yarn The fabric constituting the stretchable conductive fabric of the present invention is a woven fabric containing crimped yarn in at least some of the warp and/or weft yarns. Here, crimped yarn is an elastic yarn that is formed into fine crimps by thermal processing, giving it bulk and stretchability.

There are no particular restrictions on the crimped yarn as long as it has these properties, but examples include those obtained by heat-treating composite fibers that combine two or more resin components with different physical properties, including shrinkage properties such as heat shrinkage rate.

Composite fibers are fibers that contain two or more fiber components in a single filament yarn, and these filament yarns can be used alone or bundled together to form threads and used to form fabrics.

The composite fibers used in the present invention are not particularly limited as long as they can be crimped by thermal processing or the like, but for example, composite fibers selected from the group consisting of the following (a) to (c) can be used.

(a) a combination of polyethylene terephthalate resin (PET) and polybutylene terephthalate resin (PBT);
(b) a combination of polyethylene terephthalate resin (PET) and polytrimethylene terephthalate resin (PTT);
(c) A combination of two types of polyethylene terephthalate resin (PET) with different physical properties.

Concomitant fibers made from the combination (a) and those made from the combination (b) may have differences in heat shrinkage (for example, boiling shrinkage as a filament measured in accordance with JIS L1017) due to differences in crystal structure, copolymerization components, viscosity, molecular weight, etc., which is thought to be one of the factors that cause crimping.

(c) is a combination of the same PET but with different physical properties. Such physical properties include heat shrinkage. An example of a composite fiber made from the combination of (c) is a combination of PETs with different heat shrinkage (boiling point values) due to differences in crystal structure, copolymerization components, viscosity, etc.

If two polyethylene terephthalate resins with different heat shrinkage rates are used, the one with the relatively higher heat shrinkage rate is designated as component (A) and the one with the relatively lower heat shrinkage rate is designated as component (B), then, for example, component (A) can be one with a filament boiling point of 10% or more (preferably 15% or more), and component (B) can be one with a filament boiling point of less than 10% (preferably 5% or less).

As long as component (A) has a relatively higher heat shrinkage rate than component (B), there are no particular restrictions on the difference, but it is desirable to combine components (A) and (B) so that the heat shrinkage rate of component (A) is 0.1 to 4% higher than the heat shrinkage rate of component (B).

Examples of combinations of polyester resins with different heat shrinkage rates include a combination of polyethylene terephthalate and a high-shrinkage copolyester, or a combination of two types of polyethylene terephthalate with different viscosities.

High-shrinkage copolymer polyester is a material that has an increased shrinkage rate due to the inclusion of a certain third component (copolymer component) in the diol component and/or dicarboxylic acid that make up polyethylene terephthalate.

Examples of the third component that is copolymerized to produce a high-shrinkage copolymer polyester include diol compounds such as diethylene glycol, 2,2-bis[4-(2-hydroxyethoxy)phenyl]propane, and 1,4-butanediol, and carboxylic acid compounds such as adipic acid, azelaic acid, and isophthalic acid.

Among these, it is preferable to use a polyester copolymerized with 2,2-bis[4-(2-hydroxyethoxy)phenyl]propane and/or isophthalic acid. In this case, the copolymerization ratio of the two components is not particularly limited, but it is preferable that 2,2-bis[4-(2-hydroxyethoxy)phenyl]propane be 2 to 6 mol% in the diol component and isophthalic acid be 4 to 8 mol% in the dicarboxylic acid component.

That is, in order to fully achieve the desired heat shrinkage rate and shrinkage force, the 2,2-bis[4-(2-hydroxyethoxy)phenyl]propane content is preferably 2 mol% or more, and in order to avoid discoloration due to the polymer's light resistance, it is preferably 6 mol% or less. Furthermore, in order to fully satisfy the shrinkage rate, the isophthalic acid content is preferably 4 mol% or more, and in order to easily maintain the polymer's melting point and heat resistance, it is preferably 8 mol% or less.

The main component of high-shrink polyester is a polyester made from terephthalic acid and ethylene glycol, but it may also contain other components such as monomers that improve dyeability and compounds that improve heat resistance.

Any of the above polyester resin components may contain various known compounding agents as needed during production or molding, including pigments, matting agents, fluorescent brighteners, ultraviolet absorbers, antioxidants, antistatic agents, and ether bond inhibitors such as organic amines and organic carboxylic acid amides.

Generally, composite fibers are produced by thermally melting two or more raw polymers with different properties and fusing them while spinning them from a spinneret (composite spinning nozzle) (composite spinning method). Types of composite fibers include the side-by-side type, in which multiple (usually two types) fibers are spun simultaneously and bonded together to form a multi-layer (usually two-layer) fiber cross section; the sheath-core type, in which the core component is spun so that it is coated with the sheath component, resulting in a concentric core and sheath structure; and the eccentric sheath-core type, in which the core and sheath are not concentric but are offset from one another.

The side-by-side joining configuration may be any known shape, such as a round cross section, cocoon shape, triangular cross section, Y cross section, U cross section, or flat cross section, as long as it exhibits the crimping performance required in the present invention. Of these, a cocoon shape, in which two approximately round cross sections are joined, is preferred.

The structure of the composite fiber that can be used in the present invention is not particularly limited, but preferred examples include a side-by-side type or an eccentric core-sheath type. Examples of the side-by-side type include those in which the two different polyester components (e.g., any combination of (a) to (c)) are bonded together.

Examples of eccentric core-sheath types include those that use PET for the core and PBT for the sheath, those that use PET for the core and PTT for the sheath, and those that use a component (B) with a relatively low heat shrinkage rate for the core and a component (A) with a relatively high heat shrinkage rate for the sheath.

The thickness (single yarn fineness) of the composite fiber (monofilament yarn) obtained in this manner is preferably 33 to 330 dtex, more preferably 33 to 110 dtex.

Preferred composite fibers of the present invention include combinations of PET and PBT, PET and PTT, and PET and high-shrinkage copolymerized PET.

The crimped yarn of the present invention is preferably a multifilament yarn (latently crimped multifilament yarn) containing the composite fiber described above that has been thermally processed. Fine crimps are formed by the thermal processing, resulting in a resilient yarn with bulk and stretchability, and a highly stretchable fabric made from the yarn.

The multifilament yarn (latently crimped multifilament yarn) before heat processing is made by bundling multiple monofilament yarns made of composite fibers, and can be produced by conventional methods, such as bundling multiple monofilament yarns after melt spinning, or melt spinning them all at once using a melt spinning device with multiple composite spinning nozzles.

This latent crimp multifilament yarn may contain fibers other than the composite fibers described above. The other fibers may be mixed with the composite fibers to form the latent crimp multifilament yarn or crimped yarn. The other fibers may be selected from natural fibers, chemical fibers, and synthetic fibers. However, synthetic fibers are preferred, and polyester-based synthetic fibers are particularly preferred, as they can withstand the plating process used to form the metal coating described below.

The thickness (total fineness) of the latent crimped multifilament yarn is preferably 33 to 330 dtex, more preferably 33 to 110 dtex, and the number of filaments is preferably 6 to 96.

The heat processing of the latent crimped multifilament yarn may be carried out in the thread form before it is formed into a fabric (woven fabric, knitted fabric, etc.), or the fabric may be formed using the latent crimped multifilament yarn before heat processing, and then the fabric may be heat processed. Preferably, the fabric is formed using the latent crimped multifilament yarn, and then the fabric is heat processed. The heat processing method preferably involves immersion in hot water.

Crimped yarns that can be used in the present invention include commercially available products such as TEXBRID (registered trademark) manufactured by Chori MODA Co., Ltd. and FlexFusion (registered trademark) manufactured by Shinyu Co., Ltd., which are made using PET/PBT composite fibers; Solotex (registered trademark) manufactured by Teijin Frontier Co., Ltd., which are made using PET/PTT composite fibers; Lycra (registered trademark) T400 manufactured by Toray Opelontex Co., Ltd., which are made using PET/PET composite fibers; and Espandy (registered trademark) manufactured by KB Seiren Co., Ltd., which are made using PET/PET composite fibers.

The fabric that constitutes the stretchable conductive fabric of the present invention is made of woven fabric. Woven fabrics have the advantage that they do not stretch too much, so their conductivity does not decrease (resistance does not increase) when they deform due to stretching. The woven fabric of the present invention is a highly stretchable fabric that contains the above-mentioned crimped yarn in at least some of its constituent fibers (warp and/or weft).

The fabric may be woven in any of the following weaves: plain weave, twill weave, satin weave, etc. Plain weave is preferred because it minimizes misalignment when stretched diagonally.

The woven fabric of the present invention contains crimped yarns as at least a part of the constituent fibers, and the proportion of the crimped yarns to the total fibers constituting the woven fabric is 25 to 45% by mass.

The fibers (thread-like) that make up the woven fabric can also include fibers (thread-like) other than the crimped yarns mentioned above. The other fibers are not particularly limited and can be selected from natural fibers, chemical fibers, and synthetic fibers. Synthetic fibers, especially polyester fibers, are preferred because they can withstand plating.

It is desirable to form other fibers into threads separate from the crimped yarn and interweave them when forming the fabric. For example, one possible approach would be to alternately insert crimped yarn and threads made of other fibers as weft threads.

The woven fabric of the present invention contains crimped yarns in at least some of the warp and/or weft yarns. Both the warp and weft yarns may contain the crimped yarns, or only one of the warp and weft yarns may contain the crimped yarns. A woven fabric that uses crimped yarns in both the warp and weft yarns can maintain thread continuity in two directions, so it can be expected to maintain conductivity regardless of the stretch direction.

There are no particular restrictions on the proportion of crimped yarn in the warp or weft yarns that make up the woven fabric, but it is preferable that 10 to 100% by mass be crimped yarn. The proportions of crimped yarn in the warp and weft may be the same or different.

When crimped yarns are used for the warp yarns, the entire warp yarns may be crimped yarns, or only some of the warp yarns may be crimped yarns. It is preferable that 10 to 100% by mass of the warp yarns be crimped yarns. When crimped yarns are used for the weft yarns, the entire weft yarns may be crimped yarns, or only some of the weft yarns may be crimped yarns. It is preferable that 10 to 100% by mass of the weft yarns be crimped yarns.

The fabric that constitutes the stretchable conductive fabric of the present invention is a woven fabric (highly stretchable fabric) containing crimped yarns in at least some of the warp and/or weft yarns. This can be made into a woven fabric (highly stretchable fabric) containing crimped yarns by weaving the latent crimped multifilament yarn and then heat processing it. Methods for heat processing the woven fabric include immersing the fabric in hot water. In this case, immersion in hot water (100°C) for 1 to 90 minutes is preferred, but there are no particular limitations.

In addition, by weaving using crimped yarns that have been thermally processed in advance using latent crimped multifilament yarns, it is possible to produce a fabric containing crimped yarns in at least some of the warp and/or weft yarns.

Although it depends on the ratio of crimped yarn to the total fibers constituting the fabric (highly stretchable fabric) containing crimped yarn and the structure of the fabric, the shrinkage rate of the fabric (highly stretchable fabric) after heat processing is preferably 10 to 50%. The heat shrinkage rate of fabrics can be measured using JIS L1096 8.39 Method B (boiling water immersion method).

The stretchability of highly stretchable fabrics is not particularly limited, but the elongation (breaking elongation) in the direction of the warp and/or weft yarns that contain at least a portion of crimped yarns (hereinafter referred to as "the direction of the warp and/or weft yarns that contain at least a portion of crimped yarns") is preferably 30% or more, and more preferably 30 to 90%. The elongation (breaking elongation) of the fabrics used in this invention is a value measured in accordance with JIS L1096 8.14 Method B (grab method), except that the sample width (grab width) was 10 mm.

The highly stretchable fabric preferably has a warp density of 50 to 200 threads per inch and a weft density of 40 to 200 threads per inch, and more preferably is a plain weave fabric with such a weave density.

2. Metal Coating The stretchable conductive fabric of the present invention is provided with a metal coating. The layer configuration of the metal coating is not particularly limited, but a single or two-layer configuration is preferred. The thickness of the coating is not too large, the texture of the fabric is maintained, and manufacturing costs can be reduced. When the metal coating consists of two layers, the two layers may be formed by different methods using the same type of metal, or the two layers may be formed by different metals.

Metal species that can be used to form the metal coating include copper, nickel, gold, silver, tin, zinc, iron, and cobalt. Of these, copper, silver, or copper and nickel (two-layer coating) are preferred.

The metal loading of the metal coating is preferably, but not limited to, 5 to 60 g/m ² , more preferably 17 to 43 g/m ^2. When a two-layer metal coating is formed, the thickness of the first metal coating is preferably 5 to 50 g/m ² , more preferably 15 to 35 g/m ² , and the thickness of the second metal coating is preferably 1 to 20 g/m ² , more preferably 2 to 8 g/m ² .

3. Stretchable Conductive Fabric The stretchable conductive fabric of the present invention (fabric provided with a metal coating) preferably has a basis weight of 40 to 230 g/ ^m2 , more preferably 40 to 170 g/ ^m2 . The amount of metal provided by the metal coating is preferably 5 to 60 g/ ^m2 , more preferably 17 to 43 g/ ^m2 . The metal provision rate of the metal coating is preferably 10 to 60 mass%, more preferably 17 to 45 mass%, relative to the total amount of the stretchable conductive fabric.

The thickness of the stretchable conductive fabric of the present invention is preferably 0.10 to 0.65 mm, more preferably 0.15 to 0.35 mm.
The stretchable conductive fabric of the present invention has excellent stretchability, and the elongation (breaking elongation) in the warp and/or weft direction (i.e., at least one direction of the warp direction and the weft direction) is preferably 30% or more, more preferably 30 to 90%. Note that the elongation (breaking elongation) of the fabric in the present invention is a value measured in accordance with JIS L1096 8.14 Method B (grab method) except that the sample width (grab width) was set to 10 mm.

The stress at 30% elongation in the warp and/or weft direction of the stretchable conductive fabric of the present invention (i.e., at least one of the warp and weft directions) is 10 N/cm or less, preferably 7 N/cm or less, and more preferably 5 N/cm or less. There is no particular lower limit for the stress at 30% elongation, but it is preferably 0.1 N/cm or more. Here, "warp and/or weft direction" refers to either the warp direction or the weft direction, or both.

More desirably, the stress at 30% elongation in at least one direction of the warp and/or weft yarns that contain at least a portion of crimped yarns (the direction of the warp and/or weft yarns that contain at least a portion of crimped yarns) is 10 N/cm or less, preferably 7 N/cm or less, and more preferably 5 N/cm or less.

The stress at 30% elongation indicates how easily a fabric stretches, with a lower value indicating a greater degree of stretch. The stretchable conductive fabric of the present invention (after application of the metal coating) is exceptionally easy to handle because it is particularly stretchable, and does not require excessive stress when stretching, making it less likely for the metal coating to break.

The stress at extension is measured by stretching the sample using the same method and conditions as for measuring the elongation at break, and reading the stress value at an intermediate stage before breakage. The stress at extension in this invention is a value measured in accordance with JIS L1096 8.14 Method B (Grab Method), except that the sample width and grip width are 10 mm. That is, the value measured with a chuck distance of 100 mm, a sample width (grip width) of 10 mm, and a tensile speed of 150 mm/min.

The conductivity of the stretchable conductive fabric is not particularly limited, but it is preferable that the resistance value (electrode distance 50 mm) when unstretched be 0.001 to 100 Ω in at least one of the warp and weft directions, and that the increase in resistance value when stretched 30% compared to the unstretched resistance value be +30% or less.

More preferably, in at least one direction of the warp and/or weft yarns that contain at least a portion of crimped yarns (the direction of the warp and/or weft yarns that contain at least a portion of crimped yarns), the resistance value when unstretched (electrode distance 50 mm) is 0.001 to 100 Ω, and the increase in resistance value when stretched 30% compared to the unstretched resistance value is +30% or less.

In other words, the stretchable conductive fabric of the present invention exhibits stable conductivity without a significant increase in resistance even when stretched, allowing it to maintain high conductivity. The unstretched resistance is measured using an arbitrary milliohm tester with a sample width of 10 mm and an electrode distance of 50 mm (initial). Resistance measurement during stretching can be performed by stretching the sample in the same manner as in the measurement of stress at stretching described above, and then contacting the measurement electrodes of the milliohm tester with the sample when the sample reaches a predetermined elongation rate. For example, resistance at 30% stretching can be measured using a milliohm tester after stretching the sample in the same manner as in the measurement of stress at stretching, at which point the sample reaches 30% elongation.

4. Method for Producing Stretchable Conductive Fabric The stretchable conductive fabric of the present invention can be produced by a method including a step of providing a metal coating on a highly stretchable fabric made of a woven fabric at least partially containing crimped yarn.

(1) Manufacturing process of highly stretchable fabric By thermally processing the fabric obtained by weaving the above-mentioned latent crimped multifilament yarn, a highly stretchable fabric consisting of a fabric containing at least a portion of the crimped yarn can be obtained. A method for thermally processing the fabric includes immersing the fabric in hot water. In this case, the fabric may be immersed in hot water (100°C) for 1 to 90 minutes, but is not limited to this.

The highly stretchable fabric of the present invention can also be obtained by first heat-processing the latent crimped multifilament yarn and then forming a woven fabric. A preferred method is to form a woven fabric using the latent crimped multifilament yarn and then heat-process it.

The thickness of the highly stretchable fabric thus obtained (the fabric before the metal coating is applied) is not particularly limited, but is preferably 0.10 to 0.65 mm, more preferably 0.15 to 0.35 mm.
When the highly stretchable fabric is a woven fabric, it preferably has a warp density of 50 to 200 threads/inch and a weft density of 40 to 200 threads/inch, and more preferably is a plain weave having such a weave density.

The stretchability of the resulting highly stretchable fabric is not particularly limited, but it is preferable that the elongation rate in at least one direction, the warp direction and/or the weft direction, is 30 to 60%. Furthermore, the stress at 30% elongation of the highly stretchable fabric is preferably 8 N/cm or less, and more preferably 5 N/cm or less.

(2) Metal Coating Application Process Methods for applying a metal coating to a highly stretchable fabric made of a woven fabric at least partially containing the crimped yarn of the present invention include vapor deposition, sputtering, electroplating, and electroless plating. Of these, electroplating and/or electroless plating are preferred. In consideration of the uniformity and conductivity of the metal coating, electroless plating or a combination of electroless plating and electroplating is particularly preferred.

When forming a single layer of metal film, it is preferable to use electroless plating. When forming a two-layer metal film, it is preferable to use a method that combines electroless plating and electroplating. When laminating two layers, two layers of the same metal may be laminated, or different metals may be laminated. Metals used to apply metal films include copper, nickel, gold, silver, tin, zinc, iron, and cobalt, with copper, silver, or copper and nickel (two layers) being preferred.

A particularly preferred metal plating method in the present invention is to perform electroless copper plating followed by electrolytic nickel plating, thereby laminating two metal plating layers of copper and nickel.

(3) Electroless Plating Treatment Electroless plating treatment is carried out by a known method. After a pretreatment in which an electroless plating catalyst is applied to a highly stretchable fabric to activate it, the fabric is brought into contact with an electroless plating treatment solution containing a desired metal to deposit a metal film.

An example of an electroless plating catalyst is a solution containing metal ions that can be reduced to form a metal with plating catalytic activity. Examples of metals with plating catalytic activity include copper, nickel, silver, tin, rhodium, palladium, gold, and platinum, but it is preferable to use palladium, which has high plating catalytic activity.

Palladium ions are particularly preferred as metal ions that can be reduced to metals with plating catalytic activity. Examples of compounds that produce palladium ions include palladium chloride, palladium bromide, palladium acetate, palladium sulfate, palladium nitrate, palladium acetylacetonate, and palladium oxide. Among these, palladium chloride, which is widely used as a general catalyst, is preferred because it is relatively easy to obtain.

The solvent used for the metal ion-containing solution is not particularly limited, but is preferably water.
The metal ion concentration in the metal ion-containing solution is preferably 10 to 80 g/L, more preferably 20 to 50 g/L.

The reaction temperature when the highly stretchable fabric is brought into contact with the metal ion-containing solution is 10°C to 80°C, preferably 10°C to 50°C. The contact time with the metal ion-containing solution is preferably 10 to 800 seconds, more preferably 30 to 500 seconds.

After contacting the highly stretchable fabric with the metal ion-containing solution, it is preferable to rinse the fabric with water to remove non-specifically attached metal ions. Any known washing method can be used as the water rinsing method.

A preferred reduction method is to contact the fabric with adsorbed metal ions with an acidic treatment solution containing a reducing agent (hereinafter referred to as the reducing treatment solution). Examples of reducing agents used in the acidic treatment solution include dimethylamine borane, sodium hypophosphite, hydrazine, diethylamine, ascorbic acid, and fluoroboric acid (tetrafluoroboric acid).

The reducing agent concentration in the reduction treatment solution is preferably 5 to 20 g/L. The solvent used in the reduction treatment solution is not particularly limited, but water is preferred. The pH of the reduction treatment solution is preferably 6 or less, more preferably 2 to 6, and even more preferably 3 to 5.9.

The highly stretchable fabric is contacted with the reduction treatment solution for 30 to 600 seconds, preferably 60 to 300 seconds. The contact temperature is 10 to 80°C, preferably 30 to 50°C. After contact with the reduction treatment solution, the fabric is washed with water to remove any non-specifically attached reducing agent. After the reduction treatment, washing and drying can be performed as necessary to obtain a fabric with plating catalytic activity.

A known electroless plating method can be used for the electroless plating process. The metal used for electroless plating is at least one metal selected from the group consisting of copper, nickel, tin, and silver, or an alloy thereof (such as an alloy of copper and tin). Copper and nickel are preferred, and copper is particularly preferred.

An existing plating bath can be used for electroless plating, and the fabric can be immersed in this plating bath. The reaction time and temperature for electroless plating can be adjusted appropriately depending on the plating film thickness, but the preferred plating time is 1 to 20 minutes, and the preferred temperature is 30 to 50°C.

A copper film is preferred as the metal film formed by electroless plating. The metal amount of the metal film obtained by electroless plating is preferably 5 to 60 g/m ² , more preferably 17 to 43 g/m ² .

After the electroless plating film is formed, the fabric can be washed with water as needed to remove any non-specifically adhering plating solution.

(4) Electroplating Treatment When electroplating is performed after the electroless plating treatment, a general electroplating method can be used. Nickel electroplating is preferably used as the electroplating method. The plating solution used in nickel electroplating can use a nickel sulfate solution as a metal supply source. A commercially available nickel electroplating solution may also be used. Various surfactants, brighteners, antioxidants, etc. may be added to the electroplating solution.

The electroplating conditions are not particularly limited as long as they are set within a range that allows the formation of a metal plating layer of the desired thickness. Typical conditions include a plating solution temperature of 20 to 40°C, a current density of 0.3 to 5.0 A/ ^dm2 , and a treatment time of 30 to 600 seconds.

The metal coating formed by electroplating is preferably a nickel coating, and the metal amount of the metal coating obtained by electroplating is preferably 5 to 60 g/m ² , more preferably 17 to 43 g/m ² .

The present invention will be described below using examples, but the present invention is not limited in any way by these examples.

Example 1
(1) Yarn Form In producing the fabric, the yarn forms prepared were: a false twist textured yarn made of polyethylene terephthalate yarn (55.6 dtex/36 filaments) as the warp yarn; and a latent crimped multifilament yarn (55.6 dtex/36 filaments; manufactured by Chori Co., Ltd.) made of a side-by-side composite fiber of polyethylene terephthalate and polybutylene terephthalate as the weft yarn.

(2) Highly stretchable fabric A woven fabric (plain weave, warp density: 82 threads/inch, weft density: 52 threads/inch) was produced using the multifilament yarn. The resulting fabric (plain weave) was immersed in hot water (100°C) for 5 minutes for thermal processing to form crimps. The proportion of crimped yarns to the total fabric was 39% by mass.

The stretchability (breaking elongation) of this fabric is 33% in the warp direction and 85% in the weft direction. The stress of this fabric at 30% elongation is 9.2 N/cm in the warp direction and 0.5 N/cm in the weft direction.
In the present examples, the breaking elongation was measured using an autograph (AG-IS) manufactured by Shimadzu Corporation at a sample width of 10 mm and a tensile speed of 150 mm/min. The stress at 30% elongation was measured using an autograph (AG-IS) manufactured by Shimadzu Corporation at a sample width of 10 mm and a tensile speed of 150 mm/min.

(3) Formation of Metal Coating The obtained fabric was immersed for 2 minutes in a treatment aqueous solution containing 0.2 g/L of palladium chloride, 12.5 g/L of stannous chloride, and 250 ml/L of 36% hydrochloric acid at 20°C, followed by rinsing with water. Subsequently, the fabric was immersed for 2 minutes in 0.1 N hydrofluoric acid at 40°C, followed by rinsing with water. Next, the fabric was immersed for 3 minutes in an electroless copper plating solution consisting of 8.2 g/L of copper chloride, 9 ml/L of 37% formalin, and 33 ml/L of 32% sodium hydroxide at 40°C, followed by rinsing with water.

Next, the fabric was immersed in an electrolytic nickel plating solution containing 300 g/L of nickel sulfate, 30 g/L of sodium citrate, and a pH of 5.5 at 25°C for 3 minutes at a current density of 0.5 A/ ^dm2 to deposit nickel, and then rinsed with water and dried to obtain a stretchable conductive fabric having two metal plating layers, a copper plating layer and a nickel plating layer, and having a total thickness of 0.2 mm.
The resulting stretchable conductive fabric had a basis weight of 75 g/m ² , and the metal imparting rate of the metal coating to the total amount of the stretchable conductive fabric was 30 mass %.

(4) Evaluation of Each Physical Property A micrograph (plan view) of the obtained stretchable conductive fabric is shown in Figure 1. This photograph was taken at a magnification of 140x using a digital microscope device (manufactured by HiROX Corporation).

When the resulting stretchable conductive fabric was stretched in the weft direction, the elongation rate (breaking elongation) was 85%. The elongation rate (breaking elongation) was measured using an autograph (AG-IS) manufactured by Shimadzu Corporation, with a sample width (grip width) of 10 mm and a pulling speed of 150 mm/min.

The stress at elongation was measured using an Autograph (AG-IS) manufactured by Shimadzu Corporation. The sample was elongated in the weft direction with a sample width (grip width) of 10 mm and a tensile speed of 150 mm/min, and the stress was measured at 10%, 20%, 30%, and 40% elongation.

The resistance value of the resulting stretchable conductive fabric (at 40% elongation) was 0.30 Ω. Resistance values were also determined at 0% elongation (initial value), 10%, 20%, and 30% elongation. Resistance values were measured using a Hioki E.E. Corporation milliohm tester (RM-3545) with a sample width of 10 mm and an electrode distance of 50 mm (initial value). The results are shown in Table 1.

<Comparative Example>
The same procedure as in Example 1 was carried out except that both the warp and weft yarns were false twist textured yarns made of polyethylene terephthalate yarn (55.6 dtex/36 filaments). The results are shown in Table 1.

The stretchable conductive fabric of the present invention has sufficient stretchability and can maintain high conductivity without the applied metal coating breaking due to stretching. It also has excellent flexibility and ability to follow shape changes such as bending. Such a stretchable conductive fabric of the present invention can be suitably used in wearable devices, electromagnetic wave shielding materials, sensor electrode materials, etc.

Claims (5)

A stretchable conductive fabric comprising a woven fabric containing crimped yarns in at least some of the warp and/or weft yarns and having a metal coating applied thereto, characterized in that the ratio of crimped yarns to all fibers constituting the woven fabric is 25 to 45 mass %, and the stress at 30% elongation in at least one direction of the warp and/or weft yarns is 10 N/cm or less. The stretchable conductive fabric according to claim 1, characterized in that, in at least one direction of the warp and/or weft yarns, the increase in resistance value when stretched 30% relative to the unstretched resistance value is +30% or less. 2. The stretchable conductive fabric according to claim 1, wherein the crimped yarn is a composite fiber selected from the group consisting of a combination of polyethylene terephthalate resin and polybutylene terephthalate resin, a combination of polyethylene terephthalate resin and polytrimethylene terephthalate resin, and a combination of two polyethylene terephthalate resins having different physical properties, and the structure of the composite fiber is a side-by-side type or an eccentric core-sheath type . The stretchable conductive fabric according to claim 1, wherein the woven fabric containing crimped yarns in at least a portion of the warp and/or weft yarns is a woven fabric containing crimped yarns in only one of the warp and weft yarns . The stretchable conductive fabric according to claim 1 , wherein the shrinkage rate of the woven fabric after thermal processing is 10 to 50% .