WO2014055844A1

WO2014055844A1 - Lead wires

Info

Publication number: WO2014055844A1
Application number: PCT/US2013/063418
Authority: WO
Inventors: Shunsuke Takaki
Original assignee: 3M Innovative Properties Company
Priority date: 2012-10-04
Filing date: 2013-10-04
Publication date: 2014-04-10
Also published as: JP2014073233A

Abstract

Lead wires including a bundle of carbon fibers (21) extending in an extending direction of the lead wire, and a reinforcing member (22) extending in the extending direction of the lead wire and reinforcing the bundle of carbon fibers held in a jacket (23) are described. Biomedical electrodes incorporating such lead wires are also described.

Description

LEAD WIRES

FIELD

[0001] The present disclosure relates to lead wires. In particular, the present disclosure relates to X- ray transmissible leads wires comprising a bundle of carbon fibers and a reinforcing member.

Bioelectrodes incorporating such lead wires are also described.

SUMMARY

[0002] In one aspect, the present disclosure provides a lead wire including a bundle of carbon fibers extending in an extending direction of the lead wire, a reinforcing member extending in the extending direction of the lead wire and reinforcing the bundle of carbon fibers, and a cover member covering the bundle of carbon fibers and the reinforcing member. The bundle of carbon fibers has an electric resistance of not more than 3 Ω per 1 cm, and the reinforcing member is X-ray transmissible.

[0003] In some embodiments, the total length of the bundle of carbon fibers in the cover member may be greater than that of the reinforcing member. In some embodiments, the bundle of carbon fibers may be wound spirally on the reinforcing member. In some embodiments, the amount of deflection of the bundle of carbon fibers in the cover member may be greater than that of the reinforcing member. In some embodiments, the reinforcing member may have heat resistance that is greater than that of the cover member.

[0004] In some embodiments, the carbon fibers comprise polyacrylonitrile-based carbon fibers. In some embodiments, the reinforcing member comprises a fiber. In some embodiments, the fiber comprises a material selected from the group consisting of resin fibers, thermoelastic fibers, natural fibers, and ceramic fibers. In some embodiments, the reinforcing member comprises a tube surrounding at least one bundle of carbon fibers. In some embodiments, the cover member comprises a material selected from the group consisting of polyvinyl chloride, polyurethane, and polyethylene.

[0005] In some embodiments, the lead wire comprises a plurality of bundles of carbon fibers. In some embodiments, the lead wire comprises a plurality of reinforcing members. [0006] In another aspect, the present disclosure provides a bioelectrode including an electrode portion, and a lead wire according to any of the various embodiments of the present disclosure in electrical connection with the electrode portion.

BRIEF DESCRIPTION OF DRAWINGS

[0007] FIG. 1 is a plan view of a bioelectrode according to an embodiment.

[0008] FIG. 2 is a cross-sectional view taken along the line 2-2 depicted in FIG. 1.

[0009] FIGS. 3A and 3B are conceptual drawings illustrating states of the reinforcing member and the bundle of carbon fibers in the cover member of an exemplary lead wire according to some embodiments of the present disclosure.

[0010] FIGS. 4A to 4D are conceptual drawings illustrating states of the reinforcing member and the bundle of carbon fibers in the cover member when viewed in a cross-section of various embodiments of the lead wire.

[0011] FIGS. 5A and 5B are conceptual drawings illustrating states of the reinforcing member and the bundle of carbon fibers in the cover member when viewed in a cross-section of additional embodiments of the lead wire.

DETAILED DESCRIPTION

[0012] Conventionally, X-ray transmissible bioelectrodes are known. For example, Japanese Unexamined Patent Application Publication No. H10-248820 describes a bioelectrode comprising a conductor layer including Ag/AgCl on a first side of an electrode substrate, and a conductive adhesive and a carbon fiber lead wire on the conductor layer.

[0013] Generally, the cost of bioelectrodes can be reduced by decreasing the amount of carbon fiber in the lead wire. However, there is a need to reduce the amount of carbon fiber while maintaining the performance as a lead wire of the bioelectrode. [0014] An embodiment of the present disclosure is described below in detail while referring to the accompanying drawings. Note that in the descriptions of the drawings, similar or identical components are assigned similar reference numbers and duplicate descriptions thereof are omitted.

[0015] A configuration of a bioelectrode 1 according to one embodiment will be described using FIGS. 1 and 2. The bioelectrode 1 has a configuration by which appearance as a shadow in an X-ray image can be prevented, even when X-ray photographed while attached to an organism. The bioelectrode 1 is an electrode that, for example, can be used for electrocardiography, electromyography, electroencephalography, and the like.

[0016] As illustrated in FIG. 1, the bioelectrode 1 includes an electrode portion 2, including conductor portion 11, that is attached to an organism in order to detect electric signals, a lead wire 3 in electrical connection with the electrode portion 2, and a connector 4 that may be connected to an electronic device (not illustrated). The electrode portion 2 is in electrical connection with a first end 3a of the lead wire 3, and the connector 4 is in electrical connection with a second end 3b.

[0017] An exposed portion 26 of lead wire 3 (shown in FIG. 3A), where a bundle of carbon fibers 21 and reinforcing member 22 are exposed by removing a portion of cover member 23, is formed at the first end 3a of the lead wire 3. The bundle of carbon fibers 21 of said exposed portion 26 is connected to the electrode portion. The connector is electrically connected to a second end 3b of the lead wire 3. An exposed portion 27 (shown in FIG. 3A), where the bundle of carbon fibers and the reinforcing member 22 are exposed by removing a portion of the cover member 23, is formed at the second end 3b of the lead wire 3, and the bundle of carbon fibers 21 of said exposed portion 27 is connected to the connector.

[0018] The electric signals detected by the electrode portion 2 are transmitted to the electronic device via the lead wire 3 and the connector 4. Note that a shape and a size of the connector 4 are not particularly limited and can be appropriately modified depending on the electronic device to which they are connected. [0019] In the example illustrated in an exploded view in FIG. 2, the electrode portion 2 includes a conductor portion 11 in electrical connection with the lead wire 3, a first support member 12 that supports the lead wire and the conductor portion, a second support member 13 that supports the lead wire between the first support member and the second support member, a conductive adhesive member 14 for attaching the electrode portion to an organism, a peeling member 16 covering the conductive adhesive member, and a tab 17 for peeling the peeling member.

[0020] Note that the terms "top" and "bottom" as used in the description below are based on the orientation of the bioelectrode illustrated in FIG. 2. The exposed portion 26 where the bundle of carbon fibers 21 and the reinforcing member 22 of the lead wire 3 are exposed is disposed so as to be sandwiched between the conductor portion 11 and the first support member 12. The exposed portion of the lead wire 3 is attached on a top face 11a of the conductor portion 11 so as to be sandwiched between the top face of the conductor portion and a bottom face 12a of the first support member. Note that an end 23a of the cover member 23 is attached to the top face 11a of the conductor portion 11 via, for example, ultrasonic bonding.

[0021] Additionally, at a portion where not connected to the conductor portion 11, the lead wire 3 is supported by the second support member 13 and supported by the bottom face 12a of the first support member 12 through the second support member 13. A top face 14a of the conductive adhesive member 14 is bonded to a bottom face lib of the conductor portion 11 and a bottom face 13b of the second support member 13. A bottom face 14b of the conductive adhesive member 14 is covered by the peeling member 16. Note that the tab 17 is attached to an edge of the bottom face 12a of the first support member 12 so as to be opposite a top face 16a of the peeling member 16. When using the bioelectrode, the peeling member 16 is peeled from the conductive adhesive member 14 by pinching at a position corresponding to the tab 17.

[0022] A substrate (e.g. an ABS disk or the like) on which a conductor layer including Ag/AgCl is printed may be used as the conductor portion 11. Alternatively, thermoplastic films on which an ink including Ag/AgCl is coated, or the like may be used as the conductor portion 11. A hydrogel including, for example, an acrylic copolymer and an electrolyte may be used as the conductive adhesive member 14. Backing tape such as, for example, medical plastic backing tape, foam backing tape, or the like may be used as the support members 12 and 13. Alternatively, papers, non-woven fabrics, or the like may be used as the support members 12 and 13. A liner such as, for example, a paper backing, a film backing coated with a silicon low adhesion backside (LAB), or the like may be used as the peeling member 16. Alternatively, a film backing on which a fluorinated remover is coated, or the like may be used as the peeling member 16. However, regarding each of the components, any product that is commercially feasible is applicable as the electrode portion 2 of the bioelectrode 1.

[0023] Note that the configuration of the electrode portion 2 illustrated in FIG. 2 is only an example and the sizes, shapes, and positional relationships of each of the components may be changed as desired. Additionally, provided that the electrode portion 2 includes at least the conductor portion 11 and the conductive adhesive member 14, the other components may be omitted as desired, or components other than those illustrated in FIG. 2 may be added.

[0024] As illustrated in FIGS. 3 to 5, the lead wire includes the bundle of carbon fibers extending in an extending direction of the lead wire, a reinforcing member extending in the extending direction of the lead wire and reinforcing the bundle of carbon fibers, and the cover member covering the bundle of carbon fibers and the reinforcing member. The lead wire is formed only from components that are X-ray transmissible. Specifically, the lead wire does not include materials that have low X-ray transmissibility such as metal materials and the like.

[0025] Note that in FIGS. 3A and 3B, simple configurations in which the lead wire 3, 103 includes one bundle of carbon fibers 21, 121 and one reinforcing member 22, 122 are illustrated as examples of configurations of the bundle of carbon fibers and the reinforcing member. However, as described in detail below, numbers, positional relationships, and the like of the bundle of carbon fibers and the reinforcing member are not limited to the examples illustrated in FIGS. 3A and 3B. [0026] A length of the lead wire is not particularly limited, but may, for example be set to be from 5 cm to 200 cm. If the length of the lead wire is less than the range described above, the length may be insufficient for attaching to an organism or it may be difficult to adjust the position of the electrode portion when attaching the electrode portion to the organism. If the length of the lead wire is greater than the range described above, the length of the lead wire may be excessive when using the bioelectrode.

[0027] Strength and bendability of the lead wire needed as the lead wire of the bioelectrode are ensured by, for example, selecting the material and size of the reinforcing member (described below), selecting the bundle of carbon fibers, adjusting the relationship between the lengths of the reinforcing member and the bundle of carbon fiber, and the like. For example, a lower limit of the tensile strength of the lead wire may be set to be 80 N or 100 N. By setting the lower limit of the tensile strength of the lead wire to be greater than or equal to the lower limit described above, disconnection during use of the bioelectrode can be prevented and sufficient strength needed as the lead wire of the bioelectrode can be ensured. An upper limit of the tensile strength of the lead wire may be set to be 200 N or 500 N. If the tensile strength of the lead wire is set to be greater than the upper limit described above, the lead wire will have excessive strength as the lead wire for the bioelectrode, which may lead to increases in cost due to ensuring said excessive strength and difficulties in bending the lead wire. Note that in this specification, the term "tensile strength of the lead wire" refers to the magnitude of the force at which all of the carbon fibers of the bundle of carbon fibers included in the lead wire break, when the lead wire is subjected to tension.

[0028] In some embodiments, the cover member is a tubular member extending in the extending direction of the lead wire and covering an outer circumference of the bundle of carbon fibers and the reinforcing member. The cover member is formed from a pliable material. Examples of the material of the cover member include polyvinyl chloride (PVC), polyurethane, polyethylene, and the like. This material may also include additives. A method for forming the cover member is not particularly limited. For example, the cover member may be molded using an extruder or may be formed by applying heat to a heat-shrinkable tube. A diameter of the cover member is not particularly limited, and may be set to be 0.5 mm to 3 mm. A thickness of the tube wall of the cover member may be set to be 0.2 mm to 1 mm. If the thickness of the tube wall of the cover member is less than the range described above, the bundle of carbon fibers housed therein may not be sufficiently protected. If the thickness of the tube wall of the cover member exceeds the range described above, the lead wire may become difficult to bend, and use as the lead wire of the bioelectrode will become difficult.

[0029] The bundle of carbon fibers is a member that functions as a conductive member in the lead wire and is configured so that individual carbon fibers are bundled. The bundle of carbon fibers is X-ray transmissible. The bundle of carbon fibers may be included in the lead wire as a single bundle (e.g. the configurations illustrated in FIGS. 4A and 4C), or may be included in the lead wire as a plurality of bundles (e.g. the configurations illustrated in FIGS. 4B and 4D). Polyacrylonitrile (PAN)-based carbon fibers in which PAN fibers are carbonized (in some embodiments, the diameter of an individual carbon fiber is from about 5 microns (μιη) to 7 μιη) may be used, or pitch-based carbon fibers in which pitch fibers are carbonized (in some embodiments, the diameter of an individual carbon fiber is from about 7 μιη to 10 μιη) may be used in the bundle of carbon fibers. When using the PAN-based carbon fibers, the tensile strength and bending strength of the bundle of carbon fibers can be increased compared to when pitch-based carbon fibers are used.

[0030] The diameter of an individual carbon fiber of the bundle of carbon fibers can be changed via the manufacturing method or the like thereof and, for example, may be from 1 μιη to 20 μιη. A total number of carbon fibers of the bundle of carbon fibers in the lead wire may be changed depending on the diameter of an individual carbon fiber or the length of the lead wire and a lower limit thereof may be set to be 500 fibers to 670 fibers. By setting the total number of carbon fibers of the bundle of carbon fibers in the lead wire to be greater than or equal to the lower limit described above, the conductivity needed as the lead wire of the bioelectrode can be ensured while suppressing cost by reducing the amount of carbon fiber. An upper limit of the total number of carbon fibers of the bundle of carbon fibers in the lead wire can be set to be 670 fibers to 700 fibers. If the total number of carbon fibers of the bundle of carbon fibers in the lead wire is set to be greater than the upper limit described above, the amount of the carbon fiber will increase and sufficient cost reduction effects may not be obtainable, regardless of being able to sufficiently ensure the conductivity needed as the lead wire of the bioelectrode. Note that in this specification, when the lead wire includes a single bundle of carbon fibers, the term "total number of carbon fibers of the bundle of carbon fibers in the lead wire" refers to the number of carbon fibers in a single bundle of carbon fibers, and when the lead wire includes a plurality of bundles of carbon fibers, the term refers to the total number of carbon fibers in all of the bundles of carbon fibers in the lead wire.

[0031] A lower limit of electric resistance per 1 cm of the bundle of carbon fibers in the lead wire may be set to be not less than 1 Ohm (Ω ), or not less than 2 Ω. If the lower limit of electric resistance per 1 cm of the bundle of carbon fibers in the lead wire is set to be less than the lower limit described above, the amount of the carbon fiber will increase and sufficient cost reduction effects may not be obtainable, regardless of being able to sufficiently ensure the conductivity needed as the lead wire of the bioelectrode. An upper limit of electric resistance per 1 cm of the bundle of carbon fibers in the lead wire may be set to be 3 Ω. By setting the electric resistance per 1 cm of the bundle of carbon fibers in the lead wire to be less than or equal to the upper limit described above, the conductivity needed as the lead wire of the bioelectrode can be ensured while suppressing cost by reducing the amount of carbon fiber. Note that when the lead wire includes a single bundle of carbon fibers, the term "electric resistance per 1 cm of the bundle of carbon fibers" refers to the electric resistance per 1 cm of the single bundle of carbon fibers, and when the lead wire includes a plurality of bundles of carbon fibers, this term refers to the electric resistance per 1 cm in a state where all of the bundles of carbon fibers in the lead wire are combined.

[0032] A lower limit of the tensile strength of the bundle of carbon fibers in the lead wire may be set to be 10 N or 20 N. By setting the tensile strength of the bundle of carbon fibers in the lead wire to be greater than or equal to the lower limit described above, the conductivity needed as the lead wire of the bioelectrode can be ensured while suppressing cost by reducing the amount of carbon fiber. An upper limit of the tensile strength of the bundle of carbon fibers in the lead wire may be set to be 80 N or 100 N. Note that in this specification, the term "tensile strength of the bundle of carbon fibers in the lead wire" refers to the magnitude of the force at which all of the carbon fibers of the bundle of carbon fibers break, when the bundle of carbon fibers included in the lead wire is subjected to tension in a state where the reinforcing member and the cover member are absent. Additionally, when the lead wire includes a single bundle of carbon fibers, the term "tensile strength of the bundle of carbon fibers in the lead wire" refers to the strength when the single bundle of carbon fibers is subjected to tension, and when the lead wire includes a plurality of bundles of carbon fibers, this temr refers to the strength when a combination of all of the bundles of carbon fibers of the lead wire are subjected to tension.

[0033] The reinforcing member, as a result of being present in the lead wire along with the bundle of carbon fibers, is a member that reinforces the bundle of carbon fibers in a tensile direction and a bending direction. The reinforcing member may be included in the lead wire as a single filament-like member (e.g. the configurations illustrated in FIGS. 4A and 4B), or may be included in the lead wire as a plurality of filament-like members (e.g. the configurations illustrated in FIGS. 4C and 4D). Additionally, each of the filament-like members constituting the reinforcing member may be a monofilament, or a member formed from a combination of a plurality of fibers, which may be twisted fibers or simply bundled fibers.

[0034] The reinforcing member is X-ray transmissible. For example, non-metal material may be applied as the material of the X-ray transmissible reinforcing member. The reinforcing member is formed only from materials that are X-ray transmissible. Examples of material that are applicable for the reinforcing member include resin fibers (e.g. polyester, nylon, polyethylene, and the like), thermoelastic fibers (e.g. Kevlar® fibers produced by DuPont and the like), natural fibers (e.g. cotton, linen and silk), ceramic fibers (e.g. glass fibers), and the like.

[0035] The tensile strength of the reinforcing member in the lead wire may be set to be greater than or equal to the tensile strength of the bundle of carbon fibers in the lead wire. As a result, the reinforcing member can more reliably reinforce the bundle of carbon fibers. However, provided that the strength needed as the lead wire of the bioelectrode is ensured, the tensile strength of the reinforcing member in the lead wire may be set to be lower than the tensile strength of the bundle of carbon fibers in the lead wire. Note that in this specification, the term "tensile strength of the reinforcing member in the lead wire" refers to the magnitude of the force at which all of the reinforcing members break, when the reinforcing member included in the lead wire is subjected to tension in a state where the bundle of carbon fibers and the cover member are absent. Additionally, when the lead wire includes a single filament- like reinforcing member, the term "tensile strength of the reinforcing member in the lead wire" refers to the strength when the single reinforcing member is subjected to tension, and when the lead wire includes a plurality of filament-like reinforcing members, this term refers to the strength when a combination of all of the reinforcing members of the lead wire are subjected to tension.

[0036] The tensile strength of the reinforcing member can be adjusted via the selection of the material of the reinforcing member, and the selection of the size of a cross-sectional area of the reinforcing member in the lead wire. After selecting the material of the reinforcing member, the size of the cross- sectional area of the reinforcing member may be set so as to obtain the desired tensile strength. For example, a lower limit of the tensile strength of the reinforcing member in the lead wire may be set to be 80 N or 100 N. By setting the tensile strength of the reinforcing member to be greater than or equal to the lower limit described above, the reinforcing member can sufficiently support the bundle of carbon fibers in the lead wire. An upper limit of the tensile strength of the reinforcing member may be set to be 150 N or 200 N. If the tensile strength of the reinforcing member exceeds the upper limit described above, in cases where the cross-section of the reinforcing member is enlarged excessively in order to ensure said tensile strength, the reinforcing member may become difficult to bend thus leading to the entire lead wire becoming difficult to bend. Note that in order to ensure bendability to the extent that usability as the lead wire of the bioelectrode is not impaired, the bending elastic modulus of the reinforcing member may be set to be the same as or less than the bending elastic modulus of the cover member.

[0037] In order to ensure the tensile strength described above, a lower limit of an outer diameter of the reinforcing member in the lead wire may be set to be 0.05 mm, and an upper limit may be set to be 2 mm or 3 mm. Note that when polyester is used as the material of the reinforcing member, the lower limit of the outer diameter of the reinforcing member may, for example, be set to be 0.5 mm, and the upper limit may be set to be 2 mm or 3 mm. When cotton thread is used as the material of the reinforcing member, the lower limit of the outer diameter of the reinforcing member may, for example, be set to be 0.5 mm, and the upper limit may be set to be 2 mm or 3 mm. When nylon is used as the material of the reinforcing member, the lower limit of the outer diameter of the reinforcing member may, for example, be set to be 0.05 mm, and the upper limit may be set to be 1 mm or 3 mm. As a result, sufficient strength, as described above, as the reinforcing member can be ensured. Note that in this specification, when a cross-sectional shape of the reinforcing member is not circular, the term "outer diameter of the reinforcing member" refers to an outer diameter when said cross-sectional shape is converted to a shape equivalent to a circle. Additionally, when the lead wire includes a plurality of the filament-like reinforcing members, the term "outer diameter of the reinforcing member" refers to an outer diameter when the cross-sectional shape of all of the reinforcing members in the lead wire is converted to a shape equivalent to a circle.

[0038] The reinforcing member may have heat resistance that is greater than that of the cover member. As a result, even when the cover member is heated in order to cover the bundle of carbon fibers and the reinforcing member with the cover member, thermal deformation of the reinforcing member can be suppressed. For example, when the cover member is molded using an extruder by extruding polyvinyl chloride (PVC) or polyurethane, a molding temperature is not more than 150 to 160 °C. In this case, polyester, cotton thread, nylon monofilament, or twist yarn may by applied as the material of the reinforcing member having heat resistance that is greater than that of the cover member.

[0039] A material that is not prone to elastic deformation or plastic deformation as a result of being subjected to tension may be used as the material of the reinforcing member. For example, a material that is less prone to elastic deformation or plastic deformation than the material of the cover member may be used as the material of the reinforcing member. When length relationships such as those illustrated in FIGS. 3A and 3B (described below) are used, even in states where the entire lead wire is stretched and the cover member is deformed and stretched, the reinforcing member may be in a load-bearing state, free of deformation and elongation. Additionally, even when the reinforcing member deforms, said deformation is restrained to an amount where the bundle of carbon fibers is not subjected to tension. [0040] Next, the relationship of the lengths of the bundle of carbon fibers and the reinforcing member will be described. Referring to FIG. 3A, a total length of the bundle of carbon fibers 21 in the cover member 23 may be longer than the reinforcing member 22. The term "total length in the cover member" refers to a length of portions of the bundle of carbon fibers and the reinforcing member excluding the exposed portions 26 and 27 that are exposed from the cover member 23, and refers to the length within the region 28 that is covered by the cover member 23.

[0041] The bundle of carbon fibers 21 and the reinforcing member 22 have a length relationship so that when the entire lead wire 3 is subjected to tension, the tension acts on the reinforcing member 22 prior to acting on the bundle of carbon fibers 21. For example, a lower limit of [the total length of the bundle of carbon fibers 21 - the total length of the reinforcing member 22] per 100 cm of the cover member 23 may be set to be 1 % or more of the total length of the reinforcing member 22, and an upper limit may be set to be 10 % or less of the total length of the reinforcing member 22.

[0042] By setting the length relationship to be greater than or equal to the lower limit described above, the reinforcing member can reliably support the bundle of carbon fibers regardless of the position in a longitudinal direction of the lead wire where the tension acts. Additionally, if the bundle of carbon fibers is longer than the upper limit described above, sufficient cost reduction effects may not be obtained, or manufacturing may become difficult due to the length of the bundle of carbon fibers in the cover member being excessively long. Note that, provided that strength needed as the lead wire of the bioelectrode is ensured, the total length of the bundle of carbon fibers in the cover member may be the same or shorter than that of the reinforcing member. Additionally, when the lead wire includes a plurality of bundles of carbon fibers, the length of each of the bundles of carbon fibers may be the same. When the lead wire includes a plurality of reinforcing members, the lengths of each of the reinforcing members may be the same or different.

[0043] As illustrated in FIG. 3A, the bundle of carbon fibers 21 may be spirally wound on the reinforcing member 22. As a result, the total length of the bundle of carbon fibers 21 in the cover member 23 will be longer than that of the reinforcing member 22. Note that when manufacturing, the bundle of carbon fibers 21 may be wound on a fixed reinforcing member 22 by circumvoluting the bundle of carbon fibers 21 around the reinforcing member 22. Alternatively, the bundle of carbon fibers 21 may be wound on a fixed reinforcing member 22 by spinning the reinforcing member 22 and the bundle of carbon fibers 21 around each other. However, in this case, the bundle of carbon fibers 21 is wound so as to render a spiral larger than that of the reinforcing member 22.

[0044] As illustrated in FIG. 3B, in the cover member 123, an amount of deflection of the bundle of carbon fibers 121 may be greater than an amount of deflection of the reinforcing member 122. As a result, the total length of the bundle of carbon fibers 121 in the cover member 123 will be longer than that of the reinforcing member 122. The deflecting state of the bundle of carbon fibers 121 refers to a state in which the bundle of carbon fibers 121 is looser than the reinforcing member 122 due to the bundle of carbon fibers 121 meandering gently near the reinforcing member 122 without being wound spirally as in FIG. 3A. The term "amount of deflection" refers to a degree of looseness of the bundle of carbon fibers 121 in the cover member 123. Note that by configuring the amount of deflection to be great, the bundle of carbon fibers 121 may be configured so that a portion thereof is spirally wound on the reinforcing member 122. Additionally, as FIGS. 3A and 3B are conceptual drawings, gaps and the spiral in the cover member and the degree of meandering are emphasized.

[0045] Next, additional examples of the configuration of the bundle of carbon fibers and the reinforcing member in the cover member will be described while referencing FIGS. 4A to 4D and FIGS. 5A and 5B. FIGS. 4A to 4D and FIGS. 5A and 5B are conceptual drawings illustrating cross-sections of the lead wire and should not be construed to illustrate size relationships, disposal relationships, or the like. Additionally, sizes and numbers of the bundle of carbon fibers and the reinforcing member are not limited to those illustrated in these drawings. Moreover, the reinforcing member per each bundle (the reinforcing member depicted by a single circle) illustrated in FIGS. 4A to 4D may be formed from a monofilament or may be a bundle of a plurality of fibers. Moreover, the tubular reinforcing member per each bundle (the reinforcing member depicted by a single tube) illustrated in FIGS. 5A and 5B may be formed from a single tube or may be a tubular bundle of a plurality of fibers. [0046] As illustrated in FIG. 4A, the lead wire 203 may include a single bundle of carbon fibers 221 and a single reinforcing member 222 in the cover member 223. With such a configuration,

manufacturing is easy because the numbers of the bundle of carbon fibers 221 and the reinforcing member 222 are small. As illustrated in FIG. 4B, the lead wire 303 may include a plurality of bundles of carbon fibers 321 and a single reinforcing member 322 in the cover member 323. By using the plurality of bundles of carbon fibers 321 (e.g. a bundle of carbon fibers 321 such as one having 500 carbon fibers per bundle may be prepared), the total number of carbon fibers in the lead wire can easily be adjusted. Note that all of the bundle of carbon fibers, or a portion of the bundle of carbon fibers may be spirally wound on the single reinforcing member.

[0047] As illustrated in FIG. 4C, the lead wire 403 may include a single bundle of carbon fibers 421 and a plurality of reinforcing members 422 in the cover member 423. By using the plurality of reinforcing members 422, supporting strength by the reinforcing members 422 can easily be adjusted. Note that the bundle of carbon fibers may be wound on one of the reinforcing members, or the plurality of reinforcing members may be gathered together and the bundle of carbon fibers may be wound thereon.

[0048] As illustrated in FIG. 4D, the lead wire 503 may include a plurality of bundles of carbon fibers 521 and a plurality of reinforcing members 522 in the cover member 523. By including the plurality of bundles of carbon fibers 521 and the plurality of reinforcing members 522, the total number of carbon fibers in the lead wire 503 and the supporting strength by the reinforcing member 522 can easily be adjusted. Note that one of the bundles of carbon fibers may be wound on one of the reinforcing members, a plurality of the bundles of carbon fibers may be wound on one of the reinforcing members, one of the bundles of carbon fibers may be wound on a plurality of the reinforcing members, or a plurality of the bundles of carbon fibers may be wound on a plurality of the reinforcing members.

[0049] As illustrated in FIG. 5A, the lead wire 603 may include a single member in which the bundle of carbon fibers 621 is surrounded by the tubular reinforcing member 622, in the cover member 623. As illustrated in FIG. 5B, the lead wire 703 may include a plurality of members in which the bundle of carbon fibers 721 is surrounded by the tubular reinforcing member 722, in the cover member 723. Note that in order to ensure bendability of the lead wire, a material with bendability greater than that of the material of the cover member is used as the material of the reinforcing member.

[0050] Next, the effects of the bioelectrode according to some embodiments of the present disclosure will be described.

[0051] A bioelectrode of the prior art includes a lead wire wherein a bundle of carbon fibers, formed from 1,000 to 3,000 carbon fibers, is covered with PVC (note that electric resistance of such a bundle of carbon fibers is not more than 3 ohms (Ω) per 1 cm). Here, because the carbon fibers in the bioelectrode are expensive members, reducing cost by reducing the amount of the carbon fibers is desirable.

However, if the amount of the carbon fibers is reduced, disconnection due to pulling and bending easily occur and conductivity also declines. On the other hand, if metal conductive wire or the like is used, the conductive wire will appear in X-ray images. Additionally, in order to ensure strength, if the thickness of the cover portion is increased by the amount that the amount of the carbon fibers was reduced, the lead wire will not bend easily and usability as a bioelectrode will decline.

[0052] In contrast, with the bioelectrodes according to embodiments of the present disclosure, the bundle of carbon fibers has an electric resistance of not more than 4 Ω per 1 cm, e.g., not more than 3 Ω per 1 cm, and, therefore, the amount of carbon fiber is suppressed to a small amount while conductivity needed as the lead wire of the bioelectrode is ensured. Additionally, strength needed as the lead wire for the bioelectrode can be ensured while the amount of carbon fiber of the bundle of carbon fibers is suppressed to a small amount because the reinforcing member reinforces the bundle of carbon fibers. Moreover, appearance in X-ray images can be prevented because the reinforcing member is X-ray transmissible. Furthermore, bendability of the lead wire can also be ensured. Thus, the amount of carbon fiber can be reduced while performance needed as the lead wire of the bioelectrode is ensured.

[0053] Hereinafter, a bioelectrode according to one aspect of the present disclosure will be described in detail based on examples, but the configuration of the bioelectrode is not limited to these examples. [0054] Setting the number of carbon fibers. First, the setting of the number of carbon fibers of the bundle of carbon fibers of the lead wire of the bioelectrode will be described. When using a bundle of carbon fibers formed from PAN-based carbon fiber as the lead wire of the bioelectrode, a bundle of carbon fibers wherein the number of carbon fibers is 1 ,000 can ensure sufficient performance for use as a lead wire (length= 5 cm to 150 cm) of an electrocardiogram monitoring electrode. If the number of carbon fibers of the bundle of carbon fibers is set to 1,000, the lead wire can ensure conductivity sufficient to fulfill the regulations of the Association for the Advancement of Medical Instrumentation (AAMI). Additionally, sufficient tensile strength and bending strength of the lead wire, as the lead wire of an electrocardiogram monitoring electrode, can be ensured.

[0055] Here, if fulfilling AAMI regulations is the only point taken into consideration, it is not necessary to set the number of carbon fibers to 1,000. When reducing the carbon fibers in order to reduce cost, for example, the number of carbon fibers in a 100 cm to 150 cm lead wire may be set to 500 to 670. If the length of the lead wire is 100 cm, the number of carbon fibers on the bundle of carbon fibers is set to 500 in order to fulfill a condition of the AC impedance at 10 Hz being not more than 1 ,000 Ω. The electric resistance of the lead wire here must be not more than 3 Ω/cm. Additionally, if the length of the lead wire is 150 cm, the number of carbon fibers on the bundle of carbon fibers is set to 670 fibers in order to fulfill the AAMI regulations. The electric resistance of the lead wire here must be not more than 3 Ω/cm.

[0056] Here, when the number of carbon fibers of the lead wire is reduced, ensuring the tensile strength is a problem. Thus, evaluations as to whether the structures could ensure performance as lead wires of an electrocardiogram monitoring bioelectrode were performed for cases where the length of the lead wire is 100 cm and the number of carbon fibers is 500 fibers, and also for cases where the length of the lead wire is 150 cm and the number of carbon fibers is 670 fibers. As described below, bioelectrodes of Working Example 1, Working Example 2, Comparative Example 1, and Comparative Example 2 were prepared and evaluated. [0057] Bioelectrode according to Comparative Example 1. A conventional bioelectrode was prepared as Comparative Example 1. An electrocardiogram monitoring bioelectrode (2269HA-15, manufactured by 3M Healthcare) was used as the bioelectrode according to Comparative Example 1. The bioelectrode according to Comparative Example 1 included a 150 cm lead wire having a bundle of carbon fibers formed from 1,000 PAN-based carbon fibers. The diameter of each of these carbon fibers was about 5 μηι to 7 μηι.

[0058] Bioelectrode of Working Example 1. The bioelectrode of Working Example 1 was manufactured using the bioelectrode according to Comparative Example 1. First, the Ag/AgCl conductor portion to which the lead wire was connected was removed from the bioelectrode according to Comparative Example 1. Additionally, the lead wire was removed from the Ag/AgCl conductor portion. The PVC cover member was removed from the lead wire and half of the carbon fibers were excluded. Thus, a bundle of carbon fibers including 500 fibers was prepared. Next, plastic twisted thread

(manufactured by Yoita Riki Kogyo K.K.) was prepared as the reinforcing member. This reinforcing member was formed by twisting polyester fibers. The diameter of the reinforcing member was 0.7 mm. The bundle of carbon fibers was spirally wound on the reinforcing member and a heat-shrinkable PVC tube (UGEB3050 HISH-Tube, manufactured by Mitsubishi Chemical Corp.) was applied thereon.

Thereafter, a heat gun was used to heat-shrink the PVC tube in order to form the cover member. The length of the lead wire was set to 100 cm. Note that the length of the reinforcing member was 100 cm, the length of the bundle of carbon fibers was 100 to 1 10 cm, and that the bundle of carbon fibers was longer than the reinforcing member. The lead wire formed in this manner was then reconnected to the Ag/AgCl conductor portion and connected to the electrode portion.

[0059] Bioelectrode of Working Example 2. Aside from the bundle of carbon fibers being formed from 670 carbon fibers and the length of the lead wire being 150 cm, the bioelectrode according to Working Example 2 was manufactured according to the same method used in Working Example 1.

[0060] Bioelectrode according to Comparative Example 2. Aside from the bundle of carbon fibers being formed from 500 carbon fibers and the reinforcing member not being included, the bioelectrode according to Comparative Example 2 was manufactured according to the same method used in Working Example 1.

[0061] Tensile strength of the lead wire of the bioelectrode according to Comparative Example 1 (number of carbon fibers: 1,000), the lead wire of the bioelectrode according to Comparative Example 2 (number of carbon fibers: 500), and the bioelectrode according to Working Example 1 (number of carbon fibers: 500, reinforcing member: polyester twisted thread) was evaluated. In the testing, the lead wires were stretched using a tensile tester (TENSILON RTC- 1250 produced by A&D Company, Limited), and the force (N) at which all of the carbon fibers in the lead wire broke was measured. The results are shown in Table 1. As shown, the tensile strength of the lead wire of Comparative Example 2 in which the reinforcing member was not included and the number of carbon fibers was 500 was about half of the tensile strength of Comparative Example 1 where the number of carbon fibers was 1,000. On the other hand, the tensile strength of the lead wire of Working Example 1 in which the number of carbon fibers was 500 and the carbon fibers were reinforced by the reinforcing member was substantially the same as the tensile strength of Comparative Example 1 in which the number of carbon fibers was 1,000.

Table 1 : Comparison of tensile strength.

[0062] AAMI regulation properties of an electrode pair of the bioelectrode according to Working Example 1 and an electrode pair of the bioelectrode according to Working Example 2 were evaluated. The following criteria were evaluated as the AAMI regulation properties. AAMI regulation properties refer to the appropriate performance of a bioelectrode as confirmed by AAMI using the following standards and testing methods. Testing methods and regulations for the minimal standards are the following four criteria.

(1) DC offset potential (DCO): <100 mV

(2) AC impedance at 10 Hz (ACZ): <2000 Ω

(3) Offset potential after 5 sec. defibrillation (SDR): <100 mV (4) Recovery speed after 5 sec. defibrillation (SLOPE): <1 mV/s (absolute value)

(Rate of change of residual polarization potential 5 sec. after charging and discharging four times)

[0063] Evaluation results of the electrode pair of the bioelectrode according to Working Example 1 are shown in Table 2. As shown, the bioelectrode having a i m lead wire in which the number of carbon fibers is 500 fulfilled the requirements of all of the AAMI regulation criteria. Electrode pair impedance was 656 Ω, which is a value that is sufficiently low for use as an electrocardiogram monitoring bioelectrode. The impedance of the lead wire of the bioelectrode was 269 Ω and the impedance of the bundle of carbon fibers in the lead wire was sufficiently lower than 3 Ω per 1 cm.

Table 2: Comparison of Working Example 1 to AAMI regulations.

[0064] Evaluation results of the electrode pair of the bioelectrode according to Working Example 2 are shown in Table 3. Two electrode pairs were evaluated for the Working Example 2 (Examples 2- 1 and 2-2). As shown, the bioelectrode having a 1.5 m lead wire in which the number of carbon fibers is

670 fulfilled the requirements of all of the AAMI regulation criteria. Electrode pair impedance was 759 and 781 Ω, which are values that are sufficiently low for use as an electrocardiogram monitoring bioelectrode. The impedance of the lead wire of the bioelectrode was 325 Ω or 312 Ω and the impedance of the bundle of carbon fibers in the lead wire was sufficiently lower than 3 Ω per 1 cm.

Table 3 : Comparison of Working Example 2 to AAMI regulations.

[0065] Waveforms of Comparative Example 1 and Working Example 2 when used to monitor an electrocardiogram were evaluated. Note that the waveform evaluations were conducted when a subject was in a static condition and when a subject was in a stressed condition. The evaluations were scored according to the standards of the following five-levels. 5: No noise or drift (excellent quality);

4: No drift or slight noise, P-waves and T-waves are detected (good quality);

3: No drift, slight noise present, P-waves and T-waves are not detected (fair quality);

2: Noise and drift present, QRS is detected (poor quality);

1 : QRS is not detected (very poor quality).

[0066] Evaluation results are shown in Table 4. As shown, a waveform having excellent quality was obtained by using the bioelectrode according to Working Example 2 for a subject in a static condition.

Baseline noise was generated when the subject was in a stressed condition, but because the subject is static when the bioelectrodes are being used, it is understood that a waveform of sufficient quality as an electrocardiogram monitoring bioelectrode can be obtained.

Table 4: Wave form comparison.

Reference Numerals used in the Fig

1... Bioelectrode

2...Electrode portion

3... Lead wire

4... Connector

12, 13... Support members

14...Conductive adhesion member

16...Peeling member

17... Tab

21...Bundle of carbon fibers

22...Reinforcing member

23... Cover member [0068] The present invention has been described in detail based on the embodiment. However, the present invention is not limited to the embodiment described above. Various modifications can be made to the present invention without deviating from the scope thereof.

Claims

What is Claimed is:

1. A lead wire comprising a bundle of carbon fibers extending in an extending direction of the lead wire, a reinforcing member extending in the extending direction of the lead wire and reinforcing the bundle of carbon fibers, and a cover member covering the bundle of carbon fibers and the reinforcing member; wherein the bundle of carbon fibers has an electric resistance of not more than 3 Ω per 1 cm, and the reinforcing member is X-ray transmissible.

2. The lead wire according to claim 1, wherein a total length of the bundle of carbon fibers in the cover member is greater than the length of the reinforcing member in the cover layer.

3. The lead wire according to claim 2, wherein the bundle of carbon fibers is spirally wound on the reinforcing member.

4. The lead wire according to claim 2, wherein an amount of deflection of the bundle of carbon fibers in the cover member is greater than that of the reinforcing member.

5. The lead wire according to any one of the preceding claims, wherein the reinforcing member has greater heat resistance than the cover member.

6. The lead wire according to any one of the preceding claims, wherein the carbon fibers comprise polyacrylonitrile-based carbon fibers.

7. The lead wire according to any one of the preceding claims, wherein reinforcing member comprises a fiber.

8. The lead wire of claim 7, wherein the fiber comprises a material selected from the group consisting of resin fibers, thermoelastic fibers, natural fibers, and ceramic fibers.

9. The lead wire according to any one of claims 1 to 6, wherein reinforcing member comprises a tube surrounding at least one bundle of carbon fibers.

10. The lead wire according to any one of the preceding claims, wherein cover member comprises a material selected from the group consisting of polyvinyl chloride, polyurethane, and polyethylene.

11. The lead wire according to any one of the preceding claims, comprising a plurality of bundles of carbon fibers.

12. The lead wire according to any one of the preceding claims, comprising a plurality of reinforcing members.

13. A bioelectrode comprising an electrode and a lead wire according to any one of the preceding claims in electrical connection with the electrode.