Patent Application
20250154696
The present invention relates to conductive cloths comprising a woven or knitted fabric including conductive yarns and nonconductive yarns.
Conductive cloths are widely used as an electrode cloth for a sensor in, for example, interior articles for vehicles, clothes, health, nursing care, and medical products, furniture, and the like. As to interior articles for vehicles, for example, a conductive cloth is used in a steering wheel, serving as an electrical circuit of a sensor (touch sensor) for detecting pressure applied to the steering wheel by a driver. That sensor detects a state of the driver holding the steering wheel (e.g., whether or not the driver is holding the steering wheel with their both hands, and what portion of the steering wheel is being held). Therefore, the sensor needs to accurately detect the pressure applied to the steering wheel by the driver. To this end, the conductive cloth is required to have stable conductivity.
As the above type of conductive cloth, for example, one in which a metal film layer produced by electroless metal plating is provided on a surface of a base cloth made of a constituted by nonconductive yarns has woven fabric conventionally been proposed (see, for example, Patent Document 1).
As another conductive cloth, for example, one in which a conductive pattern (conductive layer) made of a conductive material is layered on a surface of a cloth made of nonconductive fibers with an adhesive agent interposed therebetween has been proposed (see, for example, Patent Document 2).
As still another conductive cloth, for example, one in which both sides of a mesh substrate that is a nonconductive woven fabric are covered with a conductive composition has been proposed (see, for example, Patent Document 3).
In the conductive cloths described in Patent Documents 1 and 2 in which a conductive layer is put on top of a woven fabric made of nonconductive yarns, the conductive layer is likely to peel off the woven fabric or break (crack), or the like, when the cloth stretches or contracts. When such peeling off or break occurs, there is a significant change in resistance value between before and after the cloth stretches or contracts, so that the conductivity becomes unstable, leading to a reduction in electrical reliability. In addition, when the conductive layer partially peels off or breaks, the peeling off or break is likely to spread or extend in the in-plane direction, resulting in a greater change in resistance value. Furthermore, since a conductive layer is put on top of a nonconductive woven fabric in the conductive cloths described in Patent Documents 1 and 2, the cloths have conductivity in the in-plane direction, but do not have conductivity in the thickness direction, which makes the cloths less excellent in conductivity.
The conductive cloth described in Patent Document 3 has conductivity in the in-plane direction and the thickness direction. However, as with Patent Documents 1 and 2, a conductive layer is put on top of a nonconductive woven fabric, and therefore, the conductive layer is likely to peel off the woven fabric, or break, or the like.
Incidentally, in the case in which a conductive cloth is included in a sensor or the like, it is necessary to satisfactorily tightly attach the conductive cloth to an object to be measured, following the shape of the object, in order to improve the sensitivity of the sensor. Therefore, conductive cloths are required to have stretchability. If the stretchability of a conductive cloth is insufficient, the attachment to the object to be measured is also insufficiently tight. In addition, when a conductive cloth stretches or contracts, a conductive yarn is likely to break, so that a resistance change ratio due to the stretching or contraction may increase, i.e., conduction stability may decrease.
With the above problems in mind, the present invention has been made. It is an object of the present invention to provide a conductive cloth having excellent stretchability and conduction stability.
A characteristic feature of a conductive cloth according to the present invention for solving the above problems is a conductive cloth comprising a woven or knitted fabric including conductive yarns and nonconductive yarns, wherein
The conductive cloth thus configured comprises a woven or knitted fabric including conductive yarns and nonconductive yarns, and therefore, has conductivity both in the in-plane direction and the thickness direction. The combination of the conductive yarn, which is the covering yarn, and the nonconductive yarn, which has stretchability, imparts stretchability to the conductive cloth. In addition, the use of the conductive yarn in the conductive cloth imparts conductivity to the conductive cloth. Here, since the ratio (D1/D2) of the diameter (D1) of the conductive yarn and the diameter (D2) of the nonconductive yarn is at least 1.0, the conductive yarns are less likely to be buried among the nonconductive yarns, and are less likely to break, resulting in an increase in the conduction stability of the conductive cloth. Since the ratio (D1/D2) is at most 2.6, the conductive yarn is relatively flexible, resulting in an increase in the stretchability of the conductive cloth. In addition, since the ratio (a:b) of the number (a) of the conductive yarns and the number (b) of the nonconductive yarns is 1:2 to 1:40 in at least one of the warp and weft directions of the conductive cloth, the number of conductive yarns per unit area is greater than or equal to a predetermined value, and therefore, the conductivity of the conductive cloth is increased, leading to an increase in the conduction stability. In addition, the number (b) of nonconductive yarns, which have a relatively low stiffness, is increased compared to the number (a) of conductive yarns, which have a relatively high stiffness, and therefore, the stretchability of the conductive cloth is increased.
In the conductive cloth of the present invention,
In the conductive cloth thus configured, the 5 N constant load elongation ratio is at least 20%, and therefore, the stretchability of the conductive cloth is further increased.
In the conductive cloth of the present invention, the core yarn preferably has an elongation at break of at least 70%.
In the conductive cloth thus configured, the elongation at break of the core yarn is at least 70%, and therefore, the stretchability of the conductive yarn is increased, resulting in a further increase in the stretchability of the conductive cloth.
In the conductive cloth of the present invention, in the conductive yarn, the conductive sheath yarn is preferably wrapped around the core yarn with 1000 to 3000 turns per meter of the core yarn.
In the conductive cloth thus configured, the conductive yarn in which the conductive sheath yarn is wrapped around the core yarn with 1000 to 3000 turns per meter of the core yarn is used, and therefore, the conductive sheath yarn is prevented from floating during covering of the core yarn, resulting in an improvement in quality, and the stretchability of the conductive cloth is further increased.
In the conductive cloth of the present invention,
In the conductive cloth thus configured, the resistance value change ratio during 40% elongation of the conductive cloth is at most 30%, and therefore, a change in the resistance value of the conductive cloth between before and after the conductive cloth stretches decreases (i.e., a change in the resistance value in association with the stretching or contraction decreases), resulting in an increase in the conduction stability. As a result, for example, in the case in which the conductive cloth is used in a sensor, the sensitivity of the sensor can be improved.
In the conductive cloth of the present invention,
In the conductive cloth thus configured, the thickness of the conductive cloth is at most 0.6 mm, and therefore, a level difference (step) can be inhibited from occurring when the conductive cloth is included in another member. For example, in the case in which the conductive cloth is included in a sensor, such as a steering wheel sensor, a level difference can be inhibited from occurring in the sensor, and therefore, the conductive cloth does not have an adverse influence on tactile sensations on the sensor.
In the conductive cloth of the present invention,
In the conductive cloth thus configured, the space between each conductive yarn is at most 5 mm, and therefore, the number of conductive yarns per unit area is increased, resulting in an increase in the conductivity of the conductive cloth, which increases the conduction stability.
A conductive cloth according to the present invention according to the present invention will be described with reference to the accompanying drawings. It should be noted that in each figure, a configuration (structure) is exaggerated or simplified, as appropriate, for the sake of convenience, and yarns included in the structure are not exactly identical to those in actual conductive cloths in terms of size and scale relationships.
Cloths are a textile structure made of fibers. Examples of cloths include woven fabric and knitted fabric. The cloth 10 included in the conductive cloth 1 illustrated in
The nonconductive yarn 300 is a stretchable multifilament yarn. In the cloth 10 included in the conductive cloth 1, the nonconductive yarns 300 are arranged in a grid pattern, extending in the warp and weft directions. The multifilament yarn may be optionally twisted, or may be subjected to a treatment such as false twisting or fluid agitation. Here, “nonconductive yarn” is a synonym of “insulating yarn.”
The fineness (total fineness) of the nonconductive yarn 300 is preferably 22 to 167 dtex. The upper limit of the fineness of the nonconductive yarn 300 is more preferably at most 84 dtex. If the total fineness of the nonconductive yarn 300 is at most 167 dtex, the conductive cloth 1 is flexible, and the thickness of the conductive cloth 1 is relatively small, and therefore, in the case in which the conductive cloth 1 is included in a sensor or the like, the occurrence of a level difference (step) can be inhibited. Meanwhile, if the total fineness of the nonconductive yarn 300 is at least 22 dtex, the strength of the conductive cloth 1 is enhanced. The diameter (D2) of the nonconductive yarn 300 is preferably 45 to 125 μm. The upper limit of the diameter (D2) of the nonconductive yarn 300 is more preferably at most 88 μm. If the diameter (D2) of the nonconductive yarn 300 is at most 125 μm, the conductive cloth 1 is flexible, and the thickness of the conductive cloth 1 is relatively small, and therefore, in the case in which the conductive cloth 1 is included in a sensor or the like, the occurrence of a level difference (step) can be inhibited. Meanwhile, if the diameter (D2) of the nonconductive yarn 300 is at least 45 μm, the strength of the conductive cloth 1 is enhanced. It should be noted that the diameter (D2) of the nonconductive yarn 300 is described below.
A material for fibers constituting the nonconductive yarn 300 is not particularly limited. Examples of such a material include natural fibers, regenerated fibers, semisynthetic fibers, and synthetic fibers. These may be used alone or in combination. Of them, synthetic fibers are preferable because of the excellent strength thereof. Polyester fibers, such as polyethylene terephthalate and polytrimethylene terephthalate, are preferable. If the nonconductive yarn 300 is made of synthetic fibers, the nonconductive yarn 300 can be melted by a laser removal process or the like when the conductive cloth 1 is attached to the electrodes. The shape of the fiber is not particularly limited. The fiber may be either a long fiber or a short fiber. In addition, the cross-sectional shape of the fiber is not particularly limited, and may be typically circular, or alternatively, different shapes, such as flat, elliptical, triangular, hollow, Y-shaped, T-shaped, and U-shaped.
In order to have stretchability, the nonconductive yarn 300 is preferably a crimped yarn (subjected to crimping) to which crimping properties are imparted by conjugate-spinning two types of synthetic fibers (e.g., two types of polyester fibers (e.g. polyethylene terephthalate fibers and polytrimethylene terephthalate fibers)) in a side-by-side manner. A crimped yarn obtained by crimping and then false-twisting a yarn is more preferable. If the crimped yarn is subjected to DDW after the false the resultant crimped yarn is more preferable because of higher stretchability.
The elongation at break of the stretchable nonconductive yarn 300 is preferably at least 70%. If the elongation at break of the nonconductive yarn 300 is at least 70%, the stretchability of the nonconductive yarn 300 is increased, resulting in an increase in the stretchability of the conductive cloth 1. Meanwhile, the upper limit of the elongation at break of the nonconductive yarn 300 is not particularly limited, and may be set as appropriate. For example, the upper limit of the elongation at break of the nonconductive yarn 300 may be 150%. A method for measuring the “elongation at break” is described below.
The core yarn 210 used in the conductive yarn 200 is preferably a monofilament or multifilament yarn. The fineness of the core yarn 210 is preferably 22 to 167 dtex. The upper limit of the fineness of the core yarn 210 is preferably at most 84 dtex. If the fineness of the core yarn 210 is at most 167 dtex, the conductive yarn 200 is flexible, so that the flexibility of the conductive cloth 1 is increased, and therefore, the conductive cloth 1 has excellent stretchability. Meanwhile, if the fineness of the core yarn 210 is at least 22 dtex, the strength of the conductive cloth 1 can be increased. The diameter of the core yarn 210 is preferably 45 to 125 μm. The upper limit of the diameter of the core yarn 210 is preferably at most 88 μm. If the diameter of the core yarn 210 is at most 125 μm, the conductive yarn 200 is flexible, and therefore, the conductive cloth 1 can have excellent stretchability. Meanwhile, if the diameter of the core yarn 210 is at least 45 μm, the strength of the conductive cloth 1 can be increased. The diameter of the core yarn 210 herein means the greatest diameter.
A material for the core yarn 210 is not particularly limited. Examples of the material include natural fibers, regenerated semisynthetic fibers, fibers, and synthetic fibers. Synthetic fibers are preferable in terms of strength. Examples of synthetic fibers include polyester fibers. In particular, polyethylene terephthalate and polytrimethylene terephthalate are preferable.
In order to increase the stretchability of the conductive yarn 200, the core yarn 210 is preferably a crimped yarn (subjected to crimping) to which crimping properties are imparted by conjugate-spinning two types of synthetic fibers (e.g., two types of polyester fibers (e.g. polyethylene terephthalate fibers and polytrimethylene terephthalate fibers)) in a side-by-side manner. A crimped yarn obtained by crimping and then false-twisting a yarn is more preferable. If the crimped yarn is subjected to DDW after the false twisting, the resultant crimped yarn is more preferable because of higher stretchability. In addition, if the core yarn 210 is such a crimped yarn, 210 and the conductive sheath yarn 220 can have similar stretchabilities, and therefore, the conductive sheath yarn 220 can be prevented from sticking out of the conductive cloth 1 when the conductive cloth stretches, contracts, or bends.
The elongation at break of the stretchable core yarn 210 is preferably at least 70%. If the elongation at break of the core yarn 210 is at least 70%, the stretchability of the conductive yarn 200 is further increased, resulting in a further increase in the stretchability of the conductive cloth 1. Meanwhile, the upper limit of the elongation at break of the core yarn 210 is not particularly limited, and can be set as appropriate. The upper limit of the elongation at break of the core yarn 210 may, for example, be 150%.
As described above, in order to increase the conductivity of the conductive cloth 1, the conductive sheath yarn 220 preferably only includes a metal wire. The diameter of the metal wire of the conductive sheath yarn 220 is preferably 20 to 80 μm, more preferably 25 to 70 μm. If the diameter of the metal wire of the conductive sheath yarn 220 is at least 20 μm, the conductive sheath yarn 220 is less likely to break when the conductive sheath yarn 220 stretches or contracts. Therefore, a change in the resistance value of the conductive cloth 1 that occur when the conductive cloth 1 stretches or contracts is reduced. In addition, if the diameter of the metal wire of the conductive sheath yarn 220 is at most 80 μm, the stiffness of the conductive yarn 200 is not too high, and therefore, the stretchability of the conductive cloth 1 is increased. The diameter of the metal wire of the conductive sheath yarn 220 is the greatest diameter.
Examples of a material for the metal wire included in the conductive sheath yarn 220 include single metals such as aluminum, nickel, copper, titanium, magnesium, tin, zinc, iron, silver, gold, platinum, vanadium, molybdenum, tungsten, chromium, manganese, silicon, lead, bismuth, boron, germanium, arsenic, antimony, tellurium, and cobalt, and alloys thereof. Of them, alloys of copper and tin are preferable. In addition, the elongation at break of the metal wire is preferably at least 15%. If the elongation at break of the metal wire is at least 15%, the stretchability of the conductive yarn 200 is improved, and therefore, the stretchability of the conductive cloth 1 is improved. Meanwhile, the upper limit of the elongation at break of the metal wire is not particularly limited, and can be set as appropriate. The upper limit of the elongation at break of the metal wire may, for example, be 100%.
The electrical resistivity of the metal wire of the conductive sheath yarn 220 is preferably at most 5×10−5 Ω·m, more preferably at most 1.5×10−6 Ω·m, more preferably at most 5.0×10−7 Ω·m. If the electrical resistivity of the metal wire of the conductive sheath yarn 220 is at most 5×10−5 Ω·m, the conductivity of the conductive cloth 1 is increased, which also increases the conduction stability. In addition, in the case in which the conductive cloth 1 is used in a sensor, the sensitivity of the sensor can be increased.
The number of turns of the conductive sheath yarn 220 per meter of the core yarn 210 (hereinafter simply referred to as “the number of turns”) is preferably 1000 to 3000. If the number of turns of the conductive sheath yarn 220 is at least 1000, the conductive sheath yarn 220 is prevented from floating during covering of the core yarn 210, resulting in an improvement in quality. If the number of turns of the conductive sheath yarn 220 is at most 3000, the stretchability of the conductive cloth 1 is further increased.
In the case in which the conductive cloth 1 is used in the sensor illustrated in
The space between each conductive yarn 200 (
Here, the thickness of the conductive cloth 1 (i.e., the thickness of the cloth 10) is determined by the ratio (D1/D2) of the diameter (D1) of the conductive yarn 200 and the diameter (D2) of the nonconductive yarn 300. If the ratio (D1/D2) decreases, i.e., the diameter (D1) of the conductive yarn 200 decreases relative to the diameter (D2) of the nonconductive yarn 300, the stretchability of the conductive cloth 1 is improved, and meanwhile, the conductive yarns 200 are buried among the nonconductive yarns 300, likely leading to a reduction in the conductivity of the conductive cloth 1.
The strength of the conductive yarn 200 also decreases, so that the conductive yarn 200 is likely to break when the conductive cloth 1 stretches or contracts, and as a result, a change in resistance value in association with the stretching or contraction is likely to increase. In contrast to this, if the ratio (D1/D2) increases, i.e., the diameter (D1) of the conductive yarn 200 increases relative to the diameter (D2) of the nonconductive yarn 300, the conductivity of the conductive cloth 1 is improved, and meanwhile, the stiffness of the conductive yarn 200 relatively increases, so that the stretchability of the conductive cloth 1 is likely to decrease. The ratio (D1/D2) of the diameter (D1) of the conductive yarn 200 and the diameter (D2) of the nonconductive yarn 300 is preferably 1.0 to 2.6, more preferably 1.1 to 2.6, and even more preferably 1.2 to 2.4. If the ratio (D1/D2) is at least 1.0, the conductive yarns 200 are less likely to be buried among the nonconductive yarns 300, and are less likely to break, resulting in an increase in the conduction stability of the conductive cloth 1. If the ratio (D1/D2) is at most 2.6, the conductive yarn 200 is relatively flexible, resulting in an increase in the stretchability of the conductive cloth 1.
The ratio (a:b) (hereinafter also referred to as a “mixture ratio”) of the number (a) of conductive yarns 200 and the number (b) of nonconductive yarns 300 is 1:2 to 1:40, preferably 1:5 to 1:40, and more preferably 1:10 to 1:40, in at least one of the warp and weft directions of the cloth 10 (i.e., the conductive cloth 1). If the ratio (a:b) is 1:2 to 1:40 in at least one of the warp and weft directions of the cloth 10, the number of conductive yarns 200 per unit area is greater than or equal to a predetermined value, and therefore, the conductivity of the conductive cloth 1 is increased, leading to an increase in the conduction stability. In addition, the number (b) of nonconductive yarns 300, which have a relatively low stiffness, is increased compared to the number (a) of conductive yarns 200, which have a relatively high stiffness, and therefore, the stretchability of the conductive cloth 1 is increased. The ratio (a:b) is the ratio of the number (a) of conductive yarns 200 and the number (b) of nonconductive yarns 300 per unit length in at least one of the warp and weft directions in a region in which the conductive yarns 200 exist in the conductive cloth 1 (a region that may serve as a conduction portion of a sensor or the like). Specifically, the ratio (a:b) is obtained as follows: in each of ten square (angular type) regions of 30 mm in the warp direction×30 mm in the weft direction of the conductive cloth 1 arbitrarily selected so as to include the conductive yarns 200, the number (a) of conductive yarns 200 and the number (b) of nonconductive yarns 300 are counted in at least one of the warp and weft directions, the average value of the number (a) of conductive yarns 200 and the average value of the number (b) of nonconductive yarns 300 are calculated in each direction, and the ratio of the calculated average value of the number (a) of conductive yarns 200 and the average value of the number (b) of nonconductive yarns 300 is defined as the ratio (a:b). Thus, the ratio of the average values per unit length (30 mm) is obtained in each of the warp and weft directions. Thus, the ratio (a:b) is the ratio of the average value of the number (a) of conductive yarns 200 and the average value of the number (b) of nonconductive yarns 300 per unit length (30 mm) in at least one of the warp and weft directions. It should be noted that the conductive yarns 200 are preferably evenly distributed in the conductive cloth 1.
The 5 N constant load elongation ratio is represented by expression (1) using the length K1 of the conductive cloth 1 in the absence of an applied load, and the length K2 of the conductive cloth 1 in the presence of an applied load of 5 N.
A method for measuring the 5 N constant load elongation ratio is described below.
The resistance value change ratio during 40% elongation of the conductive cloth 1 is preferably at most 30%. If the resistance value change ratio during 40% elongation of the conductive cloth 1 is at most 30%, a change in the resistance value of the conductive cloth 1 between before and after the conductive cloth 1 stretches decreases (i.e., a change in the resistance value in association with the stretching or contraction decreases), and therefore, the conduction stability is increased. As a result, for example, in the case in which the conductive cloth 1 is used in a sensor, the sensitivity of the sensor can be improved. The lower limit of the resistance value change ratio during 40% elongation of the conductive cloth 1 is not particularly limited, and is typically about 58. The resistance value change ratio during 40% elongation is the change ratio (%) of the resistance value between before and after the conductive cloth 1 stretches by 40%, and is measured by a method described below.
The thickness of the conductive cloth 1 is preferably at most 0.6 mm, more preferably at most 0.5 mm. If the thickness of the conductive cloth 1 is at most 0.6 mm, then when the conductive cloth 1 is included in another member such as a sensor, a level difference (step) can be inhibited from occurring. For example, in the case in which the conductive cloth 1 is included in a sensor, such as the steering wheel sensor of the steering wheel 500, a level difference can be inhibited from occurring in the sensor, and therefore, the conductive cloth 1 does not have an adverse influence on tactile sensations on the sensor. The lower limit of the thickness of the conductive cloth 1 particularly limited, and can be set as appropriate. The lower limit of the thickness of the conductive cloth 1 may, for example, be 0.1 mm.
Conductive cloths having a characteristic feature of the present invention (Examples 1 to 17) were prepared and subjected to various measurements and assessments. For comparison, conductive cloths that do not have any characteristic feature of the present invention (Comparative Examples 1 to 4) were prepared and subjected to similar measurements and assessments. Measurement and assessment items were an elongation at break, 5 N constant load elongation ratio, and resistance value change ratio during 40% elongation. Each item is described below.
Measurement was performed in accordance with JIS L1013 using a tensile tester (Autograph AG-I/20 kN-50 kN, manufactured by Shimadzu Corporation) under conditions that the length of sample yarns was 20 cm and the constant elongation rate was 20 cm/min. The length (cm) of a sample yarn measured when a load indicates the highest value on a load-elongation curve was obtained. The elongation ratio (%) of that length to the length (20 cm) of the sample yarn before the load was applied was calculated. This procedure was performed five times. The average value of the five measurements was calculated as an elongation at break (%).
The 5 N constant load elongation ratios of the conductive cloths of Examples 1 to 15 and Comparative Examples 1 to 4, which are woven fabric, were measured in accordance with the B-method (constant load method for woven fabric) in “8.16.1 Elongation ratio” of “JIS L1096 Method for testing cloths of woven fabric and knitted fabric.” The 5 N constant load elongation ratios of the conductive cloths of Examples 16 and 17, which are knitted fabric, were measured in accordance with the D-method (constant load method for knitted fabric) in “8.16.1 Elongation ratio” of “JIS L1096 Method for testing cloths of woven fabric and knitted fabric.” Specifically, a test piece of 150 mm in the warp direction×25 mm in the weft direction was taken from each conductive cloth. The chuck spacing of a tensile tester (Autograph AG-I/20 KN-50 kN, manufactured by Shimadzu Corporation) was set to 100 mm. The test piece (width: 25 mm) was fixed with the upper and lower end thereof held by a clamp. Thereafter, the chuck spacing (elongation length) (mm) was measured when the test piece was elongated until a load of 5 N was applied. The 5 N constant load elongation ratio was calculated based on expression (2).
The 5 N constant load elongation ratio thus obtained was assessed using the following assessment criteria.
A test piece of 150 mm in the warp direction×25 mm in the weft direction was taken from each conductive cloth. Copper foil tapes were attached to the center of the test piece and spaced by a distance of 50 mm for marking. The chuck spacing of a tensile tester (Autograph AG-I/20 KN-50 kN, manufactured by Shimadzu Corporation) was set to 100 mm. The test piece (width: 25 mm) was fixed with the upper and lower end thereof held by a clamp. Thereafter, an mΩ tester was attached to the copper foil tapes. A resistance value (22) between the markings (an initial resistance value, i.e., a resistance value before stretching or contraction) was measured. Thereafter, the sample was elongated at a rate of elongation of 40 mm per minute. The elongation was stopped when the elongation ratio was 40%. After the elongation was stopped, the resistance value (Ω) between the markings was measured again using the mΩ tester (a resistance value during 40% elongation). The resistance change ratio during 40% elongation was calculated based on expression (3).
The resistance value change ratio during 40% elongation thus obtained was assessed using the following assessment criteria.
A crimped yarn (trade name: TEXBRID, manufactured by Teijin Frontier Co., Ltd.) of 33 dtex/24 f obtained by subjecting two types of fibers of polyethylene terephthalate (PET) and polytrimethylene terephthalate (PTT) to crimping, followed by false twisting and DDW (relaxation heat treatment condition: 160° C.) was used as a core yarn. A metal wire made of a Cu/Sn alloy having a diameter of 50 μm was used as a conductive sheath yarn. The conductive sheath yarn was wrapped around the core yarn to form a single covering in which the number of turns is 1500 (turns/m). Thus, a conductive yarn (covering yarn) shown in Table 1 was obtained.
The conductive yarn, and a nonconductive yarn that is the same type of yarn as that of the core yarn, were used as warp and weft yarns to weave a fabric having a 2/2 twill weave structure, and a yarn density of 120 yarns/2.54 cm in the weft direction and 140 yarns/2.54 cm in the warp direction. In this weaving, the ratio (a:b) of the average value of the number (a) of conductive yarns per unit length (30 mm) and the average value of the number (b) of nonconductive yarns per unit length (30 mm), in the weft direction, was set to 1:30. The ratio (a:b) of the average value of the number (a) of conductive yarns per unit length (30 mm) and the average value of the number (b) of nonconductive yarns per unit length (30 mm), in the warp direction, was set to 1:20. The space between each conductive yarn in one of the warp and weft directions in which the number of conductive yarns per unit area (30 mm in the warp direction×30 mm in the weft direction) is the greater (in Example 1, the warp direction) was set to 3.6 mm. The thickness of the conductive cloth was set to 0.25 mm. Thus, the conductive cloth of Example 1 having the configuration shown in Table 1 was obtained. In the conductive cloth of Example 1, the ratio (D1/D2) of the diameter (D1) of the conductive yarn and the diameter (D2) of the nonconductive yarn was 1.9 as shown in Table 1.
The materials, fineness (i.e., diameter), and elongation at break of the core yarn, and the materials, the diameter, and elongation at break of the metal wire of the conductive sheath yarn, in the conductive yarn, and the materials and fineness (i.e., diameter) of the nonconductive yarn, the ratio (a/b) of the average value of the number ((a) of conductive yarns per unit length (30 mm) and the average value of the number (b) of nonconductive yarns per unit length (30 mm) in each of the warp and weft directions, the thickness of the conductive cloth, and the space between each conductive yarn in one of the warp and weft directions in which the number of conductive yarns per unit area (30 mm in the warp direction×30 mm in the weft direction) is the greater, were changed as shown in Tables 1 to 3 and 5, and a procedure similar to that of Example 1 was performed, to obtain the conductive cloths of Examples 2 to 15 and Comparative Examples 1 to 4. It should be noted that in Example 10, two types of yarns of polyethylene terephthalate (PET) and polytrimethylene terephthalate (PTT) were used and subjected to crimping, followed by false twisting, but not DDW, and the resultant crimped yarn was used as the core yarn of the conductive yarn. The ratio (D1/D2) of the diameter (D1) of the conductive yarn and the diameter (D2) of the nonconductive yarn in the conductive cloths of Examples 2 to 15 and Comparative Examples 1 to 4 are shown in Tables 1 to 3 and 5.
A polyethylene terephthalate yarn of 22 dtex/1 f (manufactured by Toray Industries, Inc.) was used as a core yarn. A metal wire of Cu/Si alloy having a diameter of 50 μm was used as a conductive sheath yarn. The conductive sheath yarn was wrapped around the core yarn to form a single covering in which the number of turns is 1000 (turns/m). Thus, a conductive yarn (covering yarn) shown in Table 4 was obtained.
A double-sided, stockinette double knit (circular knit) having a course density of 31 (courses/25.4 mm) and a wale density of 33 (wales/25.4 mm) was prepared by a knitting machine of 26 gauges/33 inches (manufactured by Precision Fukuhara Works, Ltd.) using the above conductive yarn, and a polyethylene terephthalate insulating yarn of 84 dtex/36 f as a nonconductive yarn (the base yarn of the front structure, the base yarn of the back structure, and the linking yarn). In this preparation, the conductive yarn prepared above was knitted instead of a portion of the insulating yarns of the front structure. In this knitting, the ratio (a:b) of the average value of the number (a) of conductive yarns per unit length (30 mm) and the average value of the number (b) of insulating yarns per unit length (30 mm) in the warp direction was set to 1:5, and the space between each conductive yarn in the warp direction was set to 4.0 mm. In addition, the thickness of the conductive cloth was set to 0.54 mm. Thus, the conductive cloth of Example 16, which has a configuration shown in Table 4, was obtained. The ratio (D1/D2) of the diameter (D1) of the conductive yarn and the diameter (D2) of the nonconductive yarn in the conductive cloth of Example 16 is shown in Table 4.
A polyethylene terephthalate yarn of 56 dtex/36 f (manufactured by Nanya Kabushiki Kaisha) was used as a core yarn. A metal wire made of Cu/Si alloy having a diameter of 50 μm was used as a conductive sheath yarn. The conductive sheath yarn was wrapped around the core yarn to form a single covering in which the number of turns is 1000 (turns/m). Thus, a conductive yarn (covering yarn) shown in Table 4 was obtained.
A smooth knit (circular knit) having a course density of 33 (courses/25.4 mm) and a wale density of 35 (wales/25.4 mm) was prepared by a knitting machine of 28 gauges/33 inches (manufactured by Precision Fukuhara Works, Ltd.) using the above conductive yarn, and a polyethylene terephthalate insulating yarn of 110 dtex/36 f as a nonconductive yarn. In this preparation, the conductive yarn prepared above was knitted instead of a portion of the insulating yarns. In this knitting, the ratio (a:b) of the average value of the number (a) of conductive yarns per unit length (30 mm) and the average value of the number (b) of insulating yarns per unit length (30 mm) in the warp direction was set to 1:2, and the space between each conductive yarn in the warp direction was set to 3.0 mm. In addition, the thickness of the conductive cloth was set to 0.60 mm. Thus, the conductive cloth of Example 17, which has a configuration shown in Table 4, was obtained. The ratio (D1/D2) of the diameter (D1) of the conductive yarn and the diameter (D2) of the nonconductive yarn in the conductive cloth of Example 17 is shown in Table 4.
The configurations, measurement results, and assessment results of the conductive cloths of Examples 1 to 17 and Comparative Examples 1 to 4 are shown in Tables 1 to 5.
All of the conductive cloths of Examples 1 to 17, in which the ratio (D1/D2) of the diameter (D1) of the conductive yarn and the diameter (D2) of the nonconductive yarn is 1.0 to 2.6, and the ratio (a:b) of the number (a) of conductive yarns and the number (b) of nonconductive yarns in at least one of the warp and weft directions of the cloth is 1:2 to 1:40, had a 5 N constant load elongation ratio of at least 20%, and thus had excellent stretchability. All of the conductive cloths of Examples 1 to 17 had a resistance value change ratio during 40% elongation of at most 30%, and thus had a reduced change in the resistance value that occurs when the cloth stretches or contracts (excellent conduction stability). The results of Examples 1 to 17 demonstrated that the elongation at break of the core yarn is at least 708, and therefore, the 5 N constant load elongation ratio can be at least 20%, and the resistance value change ratio during 40% elongation can be at most 30%. The results of Examples 1 to 17 demonstrated that the diameter of the core yarn is preferably at most 125 μm, that the diameter of the metal wire of the conductive sheath yarn is preferably 20 to 80 μm, that the number of turns of the conductive sheath yarn in the conductive yarn is preferably 1000 to 3000 turns/m, that the diameter of the nonconductive yarn is preferably at most 125 μm, and that the space between each conductive yarn in one of the warp and weft directions in which the number of conductive yarns per unit area is the greater is preferably at most 5 mm. It was also demonstrated that a core yarn treated by DDW (Examples 1 to 9 and 11 to 15) has an elongation at break greater than that of a core yarn not treated by DDW (Example 10). It was also demonstrated that, for the conductive cloths of Examples 16 and 17, which are knitted fabric, an effect similar to that of the conductive cloths of Examples 1 to 15, which are woven fabric, is obtained.
In contrast to this, in Comparative Example 1, in which the ratio (a:b) of the number (a) of conductive yarns and the number (b) of nonconductive yarns is out of the range of 1:2 to 1:40 both in the warp and weft directions of the cloth (the number of conductive yarns is too small compared to the number of nonconductive yarns), the resistance value change ratio during 40% elongation is more than 30%, and thus, a change in the resistance value that occurs when the cloth stretches or contracts is not reduced. In Comparative Example 2, in which the ratio (a:b) is out of the range of 1:2 to 1:40 both in the warp weft directions of the cloth (the number of conductive yarns is too great compared to the number of nonconductive yarns), the 5 N constant load elongation ratio is less than 10%, and thus, the stretchability is considerably low. In addition, in Comparative Example 2, the conductive cloth broke during measurement of the resistance value change ratio during 40% elongation, and failed to be measured, and thus, did not have conductivity during stretching and contraction that is required to cause the conductive cloth to work. In Comparative Example 3, in which the ratio (D1/D2) of the diameter (D1) of the conductive yarn and the diameter (D2) of the nonconductive yarn is more than 2.6, the 5 N constant load elongation ratio is less than 208, and thus, the stretchability is low. In Comparative Example 4, in which the ratio (D1/D2) is less than 1.0, the resistance value change ratio during 40% elongation is more than 30%, and thus, a change in the resistance value in association with stretching and contraction was not reduced.
The conductive cloth according to the present invention is applicable as a sensor in, for example, interior articles for vehicles such as a steering wheel, clothing articles such as jackets, trousers, and globes, health and medical devices such as massage chairs and nursing care beds, furniture such as chairs and couches, and the like.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-025288 | Feb 2022 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/046574 | 12/19/2022 | WO |
