Bioelectrode and method for manufacturing bioelectrode

Abstract

A bioelectrode (10) is provided with a conductive sheet body (11). The conductive sheet body (11) has: an outer peripheral part (16) in which a plurality of slits (22) that open to the outside in the radial direction are radially disposed; and a central part (15) that is positioned radially inward with respect to the outer peripheral part (16). The outer peripheral part (16) is bent on one side (A1) in a first direction (A) intersecting a surface (11b) of the conductive sheet body (11), over the entire circumference starting from a boundary (20) between the outer peripheral part (16) and the central part (15).

Description

Bioelectrode and method for manufacturing the same

[0001] The present invention relates to a bioelectrode and a method for manufacturing the bioelectrode.

[0002] Traditionally, passive electrodes and recently developed active electrodes have been known as bioelectrodes for acquiring electrical signals from living organisms or applying electrical stimuli to living organisms. Passive electrodes use conductive paste or conductive gel. For this reason, it can be difficult to place passive electrodes between the hair covering the scalp, especially when measuring electroencephalograms or event-related potentials. Furthermore, passive electrodes require washing or cleaning the hair to remove the conductive paste or conductive gel after measurement, which is cumbersome. Furthermore, passive electrodes often fail to measure properly because the electrode lifts up due to standing hair.

[0003] On the other hand, active electrodes, due to the high internal resistance and high sensitivity of the amplifier, can measure electroencephalograms and event-related potentials by inserting a pin-holder-shaped electrode made of metal or conductive rubber between the hair and contacting it with the scalp without using conductive paste. In other words, active electrodes can electrically create a high impedance close to the skin on the electrode side, preventing the occurrence of artifacts. This allows active electrodes to solve problems caused by high impedance on the skin surface and vibration of the electrode lead wires. Furthermore, active electrodes can acquire electrical signals derived from living organisms by inserting a pin-holder-shaped electrode made of metal or conductive rubber between the hair and contacting it with the scalp without using conductive paste (see, for example, Non-Patent Documents 1 and 2).

[0004] Sammy Krachunov and Alexander J. Casson, “3D Printed Dry EEG Electrodes”, [online], Sensors 2016, 16(10), 1635, [Retrieved July 6, 2023], Internet<URL: https: / / doi.org / 10.3390 / s16101635> "Parthenon Electrode, Dry and Gel Combination Type AP-P130(A)-08: AP-P130(A)-15" (Product Catalog), [online], Miyuki Giken Co., Ltd., [Retrieved July 6, 2023], Internet<URL: https: / / www.miyuki-net.co.jp / jp / products / catalog / AP-P130(A).pdf>

[0005] However, as shown in Non-Patent Documents 1 and 2, conventional active electrodes often have a pin-holder-shaped tip. Therefore, conventional active electrodes have a small contact area with the skin, are bulky, and require strong pressure to stabilize contact. This results in high contact pressure on the scalp, causing discomfort and many other issues, and there are many limitations on use.

[0006] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a bioelectrode that can be brought into contact with the scalp and can eliminate scalp discomfort, etc., and a method for manufacturing a bioelectrode.

[0007] In order to solve the above problems, the present invention proposes the following means: A bioelectrode according to one aspect of the present invention is a bioelectrode including a conductive sheet body, the conductive sheet body having an outer circumferential portion in which a plurality of slits opening radially outward are arranged in a radial pattern, and a central portion located radially inward relative to the outer circumferential portion, and the outer circumferential portion is bent to one side in a first direction intersecting with a surface of the conductive sheet body, starting from a boundary between the outer circumferential portion and the central portion, over the entire circumference.

[0008] Another aspect of the present invention relates to a method for manufacturing a bioelectrode, in which a plurality of slits that open radially outward are formed radially on the outer periphery of a conductive sheet body, and the conductive sheet body is folded starting from the boundary between the outer periphery and the central portion to one side in a first direction that intersects with the surface of the conductive sheet body to form a bioelectrode.

[0009] According to the present invention, the device can be brought into contact with the scalp, thereby eliminating any discomfort felt by the scalp.

[0010] 1 is a side view showing a state in which a first biomeasurement system including a bioelectrode according to a first embodiment of the present invention is attached to a head; FIG. 2 is a side view showing a state in which a second biomeasurement system including a bioelectrode according to the first embodiment is attached to a head; FIG. 3 is a side view showing a bioelectrode according to the first embodiment; FIG. 4 is a perspective view showing the bioelectrode according to the first embodiment, viewed from the metal contact side; FIG. 5 is a perspective view showing the bioelectrode according to the first embodiment, viewed from the electrode portion side; FIG. 6 is a cross-sectional view of the bioelectrode according to the first embodiment, with a main portion cut away; FIG. 7 is a cross-sectional view showing an expanded state of a conductive sheet body in the bioelectrode according to the first embodiment; FIG. 8 is a plan view showing an expanded state of a core material in the bioelectrode according to the first embodiment; FIG. 9 is a plan view showing an expanded state of a conductive sheet body in the bioelectrode according to the first embodiment; FIG. 10 is a diagram illustrating an example in which a conductive sheet, a thermoplastic adhesive tape, and a core material are overlapped and fixed with metal contacts in a manufacturing method of a bioelectrode according to the first embodiment; FIG. 11 is a plan view showing an example in which the outer periphery of the conductive sheet body is folded in a manufacturing method of a bioelectrode according to the first embodiment; FIG. 12 is a cross-sectional view showing an example in which a conductive sheet body is fixed into a three-dimensional shape in a manufacturing method of a bioelectrode according to the first embodiment. FIG. 10 is a cross-sectional view showing a developed state of a conductive sheet body in a bioelectrode according to a second embodiment of the present invention.

[0011] A bioelectrode and a method for manufacturing the bioelectrode according to one embodiment of the present invention will be described below with reference to FIGS. 1 to 14. [First Embodiment] <Biometrics System> As shown in FIG. 1, a first biometrics system 1A includes a head cap 2A, multiple bioelectrodes 10, and a measurement device 70. The head cap 2A is formed in a hemispherical shape so that it fits over the head 4 from above. The head cap 2A is stretchable so that it can be crimped to fit the entire head 4. Multiple bioelectrodes 10 are provided on the inner circumferential surface of the head cap 2A. The multiple bioelectrodes 10 can be freely installed on the inner circumferential surface of the head cap 2A, but the international standard 10-20 method, for example, can also be used. By crimping the entire head 4, the head cap 2A can stably contact the multiple bioelectrodes 10 with the skin of the head 4. In this way, by providing multiple bioelectrodes 10 and integrating them into the head cap 2A, the multiple bioelectrodes 10 can be quickly attached and removed.

[0012] The plurality of bioelectrodes 10 are connected to a connector 6. The connector 6 is connected to a measurement device 70 via wiring (harness) 7. Therefore, the plurality of bioelectrodes 10 are connected to the connector 6, and are thereby connected to the measurement device 70 via the connector 6 and the wiring 7. In the first embodiment, an example is described in which the wiring 7 is routed outside the head cap 2A, but the wiring 7 may also be routed inside the head cap 2A. By routeing the wiring 7 through the head cap 2A, handling of the first biomeasurement system 1A can be facilitated. The measurement device 70 records biosignals and provides electrical stimulation by acquiring electrical signals derived from the living body and applying electrical stimulation to the living body with the plurality of bioelectrodes 10 in contact with the scalp of the head 4.

[0013] As shown in FIG. 2 , the second biomeasurement system 1B includes a headband 2B instead of the head cap 2A, but otherwise has the same configuration as the first biomeasurement system 1A. The headband 2B is formed in a band shape so that it can be placed around the head 4. The headband 2B has elasticity that allows it to be crimped around the head 4. Multiple bioelectrodes 10 are provided on the inner circumferential surface of the headband 2B. The multiple bioelectrodes 10 can be freely placed on the inner circumferential surface of the headband 2B, but the international standard 10-20 method, etc., can also be used. The headband 2B crimps around the head 4, allowing the multiple bioelectrodes 10 to be in stable contact with the skin of the head 4. In this way, by providing and integrating multiple bioelectrodes 10 into the headband 2B, the multiple bioelectrodes 10 can be quickly attached and removed.

[0014] In the first embodiment, an example will be described in which the bioelectrodes 10 of the first biomeasurement system 1A and the second biomeasurement system 1B are applied to the scalp of the head 4, but this is not limiting. For example, the bioelectrodes 10 may be applied to measuring an electromyogram or electrocardiogram of the whole body of a subject with body hair. Specifically, the bioelectrodes 10 may be applied to measuring electroencephalograms, event-related potentials, oculo- (retinal) potentials, visual evoked potentials, auditory evoked potentials, myoelectric potentials, bioimpedance measurements, cardiac potentials, and the like, as well as electrical stimulation.

[0015] Human hair is diverse, and can be long, coarse, curly, short, or soft. Therefore, the bioelectrode 10 is configured to be suitable as an active electrode for long, coarse, curly, or other types of hair. A bioelectrode 100 suitable as an active electrode for short, soft, or other types of hair will be described in the second embodiment of FIG. 14. The bioelectrode 10 is not limited to humans, and may also be used for animals other than humans.

[0016] <Bioelectrode> The bioelectrode 10 will be described in detail below. As shown in Figures 3 to 5, the bioelectrode 10 includes a conductive sheet body 11, a metal contact 12, and a cover 13. The bioelectrode 10 is formed so that the tip portion 11a of the conductive sheet body 11 contacts the skin of the head 4 (see Figures 1 and 2). The bioelectrode 10 is also formed so that the metal contact 12 is connected to the connector 6 (see Figures 1 and 2).

[0017] <Conductive Sheet> The conductive sheet 11 has a central portion 15 and an outer peripheral portion 16. The central portion 15 is circular and located at the center of the conductive sheet 11. The outer peripheral portion 16 is integrally formed radially outward of the central portion 15. The outer peripheral portion 16 is folded around the entire circumference, starting from a boundary 20 (see also FIG. 13 ) between the outer peripheral portion 16 and the central portion 15, toward one side A1 in a first direction A (the thickness direction of the conductive sheet 11) that intersects with the surface 11b of the conductive sheet 11 (specifically, the central portion 15). The boundary 20 is preferably located as close to the center of the conductive sheet 11 as possible. By locating the boundary 20 closer to the center of the conductive sheet 11, the electrode portion 24 (described later) can be made longer. Longer electrode portions 24 facilitate appropriate application, particularly for voluminous hair.

[0018] As shown in FIGS. 5 and 6 , the outer peripheral portion 16 has multiple slits 22 arranged from the vicinity of the central portion 15 toward the distal end 11a of the conductive sheet body 11. In the outer peripheral portion 16, multiple portions (hereinafter referred to as electrode portions 24) located between adjacent circumferential slits 22 are formed in a comb-like, brush-like, or strip-like shape. In the illustrated example, the multiple electrode portions 24 are arranged so as to overlap from the center of the conductive sheet body 11 to the radially outer side. Of the multiple electrode portions 24, the electrode portions 24 arranged on the outer periphery may be arranged side by side on the same circumference. Furthermore, the electrode portions 24 are formed with a wider circumferential width at the distal end 11a than at the proximal end. This allows the electrode portions 24 to be in stable contact with the skin of the head 4 (see FIGS. 1 and 2 ).

[0019] Here, the outer peripheral portion 16 is, for example, inserted into a cylindrical guide and bent at approximately 90°. Therefore, when the outer peripheral portion 16 is bent using the cylindrical guide, the plurality of electrode portions 24 are bent sequentially. As a result, the electrode portions 24 bent first are moved toward the center by the electrode portions 24 bent later. As a result, the plurality of electrode portions 24 are arranged so as to overlap on the radially outer side, and are arranged side by side on the same circumference on the outer periphery. As another example, all of the electrode portions 24 may be arranged side by side on the same circumference.

[0020] 7 and 8, the conductive sheet body 11 includes two conductive sheets 30, two thermoplastic adhesives 31, and a core material 32. Note that Fig. 8 is a cross-sectional view showing the conductive sheet body 11 in an unfolded state before the outer periphery 16 of the conductive sheet body 11 is folded to one side A1 in the first direction A.

[0021] <Conductive Sheets> Two conductive sheets 30 are located on either side of each other in the first direction A. The conductive sheets 30 are circular when unfolded. The conductive sheets 30 may be, for example, a conductive fabric obtained by imparting electrical conductivity to a circular fabric. Examples of the conductive fabric include silver-plated fabric and conductive polymer-coated fabric. Examples of conductive materials that impart electrical conductivity to fabric include conductive polymers, conductive particles, ions, and ionic liquids. Examples of the conductive particles include metal particles, carbon black, graphite, graphene, and carbon nanofibers. The two conductive sheets 30 are folded toward one side A1 in the first direction A starting from the boundary 20 between the outer periphery 16 and the central portion 15. In the first embodiment, an example in which conductive fabrics are used as the conductive sheets 30 is described, but the present invention is not limited thereto. For example, the conductive sheets 30 may be sheets impregnated with or laminated with a conductive liquid or gel.

[0022] <Thermoplastic Adhesive> A thermoplastic adhesive (e.g., hot melt tape, seam tape) 31 is attached to the opposing inner surfaces 30a of two conductive sheets (i.e., conductive fabrics) 30. That is, the two thermoplastic adhesives 31 are disposed between the two conductive sheets 30. The two thermoplastic adhesives 31 join the two conductive sheets 30 by thermocompression bonding while they are stacked in the first direction A. The thermoplastic adhesive 31 is made of a polymer or the like that melts and bonds with heat and hardens when cooled.

[0023] In the illustrated example, a polymer layer of thermoplastic adhesive 31 is laminated between two conductive sheets 30 as a core material for the two conductive sheets 30. This allows the polymer layer to maintain the three-dimensional shape of the folded two conductive sheets 30. The polymer layer maintains the flexibility of the two conductive sheets 30 and can stably maintain the three-dimensional shape of the two conductive sheets 30 folded starting from the boundary 20 between the outer periphery 16 and the center 15. Hereinafter, the thermoplastic adhesive 31 may also be referred to as the "thermoplastic adhesive tape 31."

[0024] Furthermore, when processing the outer periphery 16 of the conductive sheet body 11 into a three-dimensional shape by folding it from the boundary 20 to one side A1 in the first direction A, the thermoplastic adhesive tape 31 is heated while the outer periphery 16 is folded. The thermoplastic adhesive tape 31 is then cooled to ambient temperature (room temperature). This allows the two conductive sheets 30 to be fixed in the folded three-dimensional shape by the thermoplastic adhesive tape 31. The thermoplastic adhesive tape 31 (i.e., the polymer layer) has flexibility (flexibility). This allows the outer periphery 16 of the conductive sheet body 11 to have flexibility so that it can fit to heads with short or soft hair.

[0025] In order to apply the bioelectrode 10 as an active electrode to long, coarse, curly hair, etc., it may be difficult to spread the hairs and reach the scalp with a three-layer structure that adds a polymer layer between the two conductive sheets 30. Therefore, in this embodiment, a core material 32 is added between the two conductive sheets 30.

[0026] <Core Material> As shown in Figures 8 and 9, the core material 32 is laminated (disposed) between thermoplastic adhesive tapes 31 attached to two conductive sheets 30. Note that Figures 8 and 9 are plan views showing the unfolded state of the core material 32 before folding the outer periphery 16 of the conductive sheet body 11 toward one side A1 in the first direction A. The core material 32 is formed into a circular shape in the unfolded state. The core material 32 is formed, for example, as a flexible polymer sheet made of PET (polyethylene terephthalate), polystyrene, nylon, PVA (polyvinyl alcohol), or the like. In the unfolded state, the outer periphery 32a of the core material 32 is formed to have a diameter larger than the outer periphery 15a of the central portion 15 and a diameter smaller than the outer periphery of the outer periphery 16 (i.e., the tip portion 11a of the conductive sheet body 11).

[0027] As shown in Figures 9 and 10, a plurality of slits 22 are formed in the outer peripheral portion 32b of the core material 32 together with the conductive sheet 30 and the thermoplastic adhesive tape 31. Note that Figure 10 is a plan view showing the unfolded state before the outer peripheral portion 16 of the conductive sheet body 11 is folded toward one side A1 in the first direction A. The plurality of slits 22 are formed radially toward the tip end 11a of the conductive sheet body 11 in the outer peripheral portion (the portion corresponding to the outer peripheral portion 16) of the conductive sheet 30 and the outer peripheral portion 32b of the core material 32. The plurality of slits 22 are formed at intervals in the circumferential direction. The tip ends 22a of the plurality of slits 22 open radially outward at the tip end 11a of the conductive sheet body 11. The base ends 22b of the plurality of slits 22 are located radially inward from the outer peripheral portion 32b of the core material 32 and radially outward from the boundary 20 between the outer peripheral portion 32b and the central portion 15.

[0028] 7 and 9 , the core material 32 is folded along the entire periphery of the two conductive sheets 30 toward one side A1 in the first direction A, starting from the boundary 20 between the outer periphery 16 and the central portion 15. The core material 32 is fixed between the two thermoplastic adhesive tapes 31 (i.e., the polymer layers) by heating the two thermoplastic adhesive tapes 31 and then cooling them to ambient temperature. Thus, the core material 32 maintains the flexibility of the two conductive sheets 30 and can stably hold the two conductive sheets 30 in the folded shape.

[0029] By stacking (arranging) the core material 32 between the two conductive sheets 30 in this manner, the tension of the two conductive sheets 30 can be increased. Therefore, the conductive sheet body 11 can spread the hairs, allowing the conductive sheet body 11 to reach the scalp. This allows the bioelectrode 10 to function as an active electrode for, for example, long hair, coarse hair, or curly hair. Furthermore, the outer periphery 32a of the core material 32 is larger in diameter than the outer periphery 15a of the central portion 15 and smaller in diameter than the outer periphery of the outer periphery 16 (the tip end 11a of the conductive sheet body 11). Therefore, the outer periphery 32a of the core material 32 is located closer to the central portion 15 than the tip end 11a of the conductive sheet body 11. The tip end 11a of the conductive sheet body 11 is the portion that comes into contact with the skin of the head 4. This maintains the flexibility of the tip end 11a of the conductive sheet body 11, which comes into contact with the skin of the head 4. That is, the tip of the electrode portion 24 (see FIGS. 5 and 6) of the conductive sheet 11 can be kept flexible.

[0030] <Metal Contact> As shown in Figures 7 and 10, a metal contact 12 is provided in the central portion 15 of the conductive sheet body 11. For example, a commonly known dot button is used as the metal contact 12. In the first embodiment, an example in which a dot button is used as the metal contact 12 will be described, but the metal contact 12 is not limited to a dot button. The metal contact 12 includes a female portion 41 and a male portion 42.

[0031] The female part 41 is a female button made of, for example, conductive stainless steel (SUS). The female part 41 has a base 41a whose outer periphery is circular. The base 41a of the female part 41 is disposed on an outer surface 15b (one side) in the first direction A in the central part 15. The male part 42 is a male button made of, for example, conductive SUS. The male part 42 has a base 41a whose outer periphery is circular. The base 42a of the male part 42 is disposed on an inner surface 15c (the other side) in the first direction A in the central part 15. In the first embodiment, an example in which the metal contacts 12 are made of SUS will be described, but the metal contacts 12 are not limited to SUS.

[0032] The female portion 41 and the male portion 42 are hammered together in the first direction A so as to sandwich the central portion 15 from both sides in the first direction A. The metal contact 12 is fixed to the central portion 15 by fitting the recessed portion 41b of the female portion 41 into the protruding portion 42b of the male portion 42. The female portion 41 of the metal contact 12 is disposed outside the central portion 15. The recessed portion 41b of the female portion 41 protrudes outward from the base 41a. The connectors 6 (see FIGS. 1 and 2) of the first biomeasurement system 1A and the second biomeasurement system 1B are connected to the recessed portion 41b of the female portion 41 from the outside.

[0033] <Cover> As shown in Figures 3 and 4, the cover 13 is attached to the conductive sheet body 11. The cover 13 is formed into a cylindrical shape from, for example, a resin material. The cover 13 has a cover main body 51 and a reduced diameter portion 52. The cover main body 51 is formed into a cylindrical shape so as to contact the outer periphery 16 from the outside in the radial direction and cover the outer periphery 16. The tip end 51a of the cover main body 51 is located on the tip end 11a side of the conductive sheet body 11 in the first direction A. The tip end 51a of the cover main body 51 is arranged with a distance L1 between the tip end 11a of the conductive sheet body 11 and the central portion 15 side in the first direction A. A reduced diameter portion 52 is integrally formed with the base end 51b of the cover main body 51.

[0034] The reduced diameter portion 52 extends radially inward from the base end 51b of the cover body 51 toward the metal contact 12 (specifically, the base 41a of the female portion 41). The reduced diameter portion 52 is ring-shaped and contacts the radially outer edge 15d of the base 41a of the female portion 41 of the central portion 15 from the outside, covering the edge 15d. That is, the cover 13 is formed so as to continuously cover the central portion 15 from the edge 15d to partway along the outer periphery 16. This makes it easier to more stably secure the conductive sheet 11 in the three-dimensional shape in which the outer periphery 16 of the conductive sheet 11 is folded. Furthermore, the distal end 11a of the conductive sheet 11, which comes into contact with the skin of the head 4, can be kept flexible. That is, the distal end of the electrode portion 24 of the conductive sheet 11 can be kept flexible.

[0035] <Method of Manufacturing Bioelectrode> Next, a method of manufacturing the bioelectrode 10 will be described with reference to Figures 5, 6, and 11 to 13. Specifically, as shown in Figures 5 and 6, an example will be described in which the bioelectrode 10 is small, with a height H of about 1.0 cm, and the electrode portion 24 is formed in a wide comb shape (strip shape) with a circumferential length L2 of about 0.4 cm (see also Figure 12 for the circumferential length L2).

[0036] As shown in FIG. 11 , two conductive sheets 30 are formed into a circle with an outer diameter D1 of 2.5 cm. In the embodiment, an example in which the conductive sheets 30 are formed with an outer diameter D1 of 2.5 cm will be described, but this is not limited to this. For example, the outer diameter D1 of the conductive sheets 30 may be adjusted within a range of 2 to 5 cm depending on the application of the bioelectrode 10. Thermoplastic adhesive tape 31 (only one of the thermoplastic adhesive tapes 31 is shown) is attached to the opposing inner surfaces of the two conductive sheets 30. A PET sheet is formed as a core material 32 into a circle with an outer diameter D2 of 2.0 cm. The core material 32 is formed with a diameter larger than the center portion 15 (see FIG. 5 ) and smaller than the conductive sheets 30.

[0037] A core material 32 is placed between thermoplastic adhesive tapes 31 attached to two conductive sheets 30. The two conductive sheets 30, the two thermoplastic adhesive tapes 31, and the core material 32 are overlapped coaxially. A metal contact 12 is driven into the center of the two conductive sheets 30, the two thermoplastic adhesive tapes 31, and the core material 32 and fixed. The metal contact 12 has an outer diameter D3 of 0.9 cm. Note that the laminate including the two conductive sheets 30, the two thermoplastic adhesive tapes 31, and the core material 32 may be heated before or after driving in the metal contact 12, to firmly bond the conductive sheets 30 and the core material 32 with the thermoplastic adhesive tape 31.

[0038] As shown in FIG. 12 , multiple slits 22 are formed radially in the outer peripheries (regions corresponding to the outer peripheries 16) of the two overlapping conductive sheets 30 and two thermoplastic adhesive tapes 31, and in the outer periphery 32b of the core material 32. That is, multiple slits 22 are formed radially in the outer periphery 16 of the conductive sheet body 11 in an unfolded state. The length L3 of the slits 22 is preferably set radially inward from the outer periphery of the conductive sheet 30 so that (1) it reaches the outer periphery of the core material 32, and (2) it does not reach the outer periphery of the metal contact 12. For example, in this embodiment, the length L3 of the slits 22 is set to 0.3 to 0.7 cm. Note that, for example, a length L3 of 0.6 cm is preferred, but is not limited to this. Sixteen multiple slits 22 are formed at intervals in the circumferential direction. In the first embodiment, the number of multiple slits 22 is described as 16, but this is not limited to this. For example, it is preferable to adjust the number of slits 22 within the range of 16 to 32 depending on the condition of the hair, the outer diameter and thickness of the fabric, etc.

[0039] The tips 22a of the multiple slits 22 are opened radially outward at the tip portion 11a of the conductive sheet body 11. The base ends 22b of the multiple slits 22 are arranged radially inward from the outer circumferential portion 32b of the core material 32 and radially outward from the boundary 20 between the outer circumferential portion 16 and the central portion 15. After forming the multiple slits 22 in the outer circumferential portion 16 of the unfolded conductive sheet body 11, the outer circumferential portion 16 of the conductive sheet body 11 is folded from the boundary 20 as shown by the arrow toward one side A1 in the first direction A (see FIG. 13 ) around the entire circumference. Here, the distance from the boundary 20 to the tip portion 11a of the conductive sheet body 11 is set to L4 = 0.75 cm.

[0040] 13 , the outer periphery 16 of the conductive sheet body 11 is folded from the boundary 20 to one side A1 in the first direction A as shown by the arrow, and the thermoplastic adhesive tape 31 is then heated. The thermoplastic adhesive tape 31 is then cooled to ambient temperature. This allows the outer periphery 32 b of the conductive sheet body 11 to be fixed in the folded three-dimensional shape.

[0041] 5 and 6 , a plurality of slits 22 can be arranged in the outer peripheral portion 16 in the radial direction from the vicinity of the central portion 15 toward the tip (i.e., the tip portion 11a of the conductive sheet body 11). Therefore, in the outer peripheral portion 16, the electrode portions 24 located between adjacent slits 22 in the circumferential direction can be formed in a comb shape (strip shape). This allows the bioelectrode 10 to be formed by the manufacturing method for the bioelectrode 10.

[0042] According to the manufacturing method of the bioelectrode 10, the conductive sheet 30 had an outer diameter D1 of 2.5 cm, the core material 32 had an outer diameter D2 of 2.0 cm, and the metal contact 12 had an outer diameter D3 of 0.9 cm. There were 16 slits 22, each with a length L3 of 0.3 to 0.7 cm. Furthermore, the outer periphery 16 of the conductive sheet 11 was folded starting from a boundary 20 that was a distance L4 of 0.75 cm from the tip 11a of the conductive sheet 11.

[0043] This allows the bioelectrode 10 to be formed with a height H of approximately 1.0 cm. This allows the height (thickness) of the bioelectrode 10 to be kept small. Furthermore, the electrode portion 24 can be formed in a comb shape (strip shape) with a circumferential length L2 of approximately 4 mm, ensuring a wide circumferential width at the tip of the electrode portion 24. This allows the electrode portion 24 to be in stable contact with the skin of the head 4 (see Figures 1 and 2). The reason for keeping the height of the bioelectrode 10 small will be explained in detail later.

[0044] <Functions and Effects of Bioelectrode> The bioelectrode 10 of the first embodiment described above can achieve the following functions and effects. That is, as shown in Figures 5 and 6, the outer peripheral portion 16 is folded to one side A1 in the first direction A around the entire circumference, starting from the boundary 20 between the outer peripheral portion 16 and the central portion 15. This allows the electrode portions 24 located between adjacent slits 22 in the outer peripheral portion 16 of the conductive sheet body 11 in the circumferential direction to function like a comb (brush). Therefore, the electrode portions 24 of the conductive sheet body 11 can be brought into contact with the scalp through the gaps in the hair.

[0045] Furthermore, the bioelectrode 10 is made of a conductive sheet 11. This allows the tip 11a of the conductive sheet 11, which comes into contact with the skin of the head 4, to be kept flexible. That is, the tip of the electrode portion 24 on the conductive sheet 11 can be kept flexible. This eliminates any discomfort felt by the scalp when the electrode portion 24 comes into contact with it.

[0046] 7 and 8, by laminating a core material 32 between two conductive sheets 30, the conductive sheet body 11 is provided with an appropriate hardness, and it becomes easier to secure the outer periphery 16 of the conductive sheet body 11 in a folded three-dimensional shape. This improves the durability and quality of the bioelectrode 10. Meanwhile, because the core material 32 has a smaller diameter than the outer periphery 16, flexibility can be secured at the tip of the electrode portion 24 of the conductive sheet body 11. This can eliminate any discomfort felt by the scalp when the electrode portion 24 comes into contact with the scalp.

[0047] Furthermore, a conductive fabric is used for the conductive sheet 30. This ensures good flexibility of the conductive sheet 30. This eliminates any discomfort felt by the scalp when the electrode portion 24 comes into contact with the scalp.

[0048] In addition, dot buttons are used for the metal contacts 12, and the female part 41 on one side and the male part 42 on the other side are sandwiched from both sides of the conductive sheet body 11 and fixed to the central part 15. This makes it possible to easily fix the metal contacts 12 to the central part 15 of the conductive sheet body 11.

[0049] 3 and 4, the bioelectrode 10 is provided with a cylindrical cover 13 that continuously covers the entire area from the edge 15d of the central portion 15 to the middle of the outer periphery 16. By covering the outer periphery 16 from the outside with the cylindrical cover 13, the outer periphery 16 can be more effectively secured in its folded shape. This improves the durability and quality of the bioelectrode 10.

[0050] The reason for keeping the height of the bioelectrode 10 small will now be explained. Conventional active electrodes are often pin-frog-shaped, with pin-frog-shaped electrodes arranged in rows on a metal substrate and connected to a connector. Therefore, conventional active electrodes are tall due to the substrate and pin-frog-shaped electrodes. In contrast, the bioelectrode 10 of the first embodiment is formed by folding a conductive sheet body 11, which is made by joining a thin, flat sheet-like conductive fabric as the conductive sheet 30, to the minimum necessary length of the electrode portion 24. This allows the height of the bioelectrode 10 to be kept small. Maintaining a comfortable fit for the bioelectrode 10 reduces the effects of motion artifacts.

[0051] Furthermore, the conductive sheet 11 is flexible overall (particularly the electrode portion 24). Therefore, by pressing down the bioelectrode 10 from the outside with a head cap 2A or a head band 2B (both see FIG. 1), the conductive sheet 11 bends appropriately and sinks between the hair. This allows the height of the bioelectrode 10 to be further reduced. As a result, with the head cap 2A or the head band 2B attached to the head 4 (see FIG. 1), it is easy to wear a helmet, a hat, VR goggles, etc. over the head cap 2A or the head band 2B.

[0052] The bioelectrode 10 also uses a conductive fabric as the conductive sheet 30. The conductive fabric has moisture-retaining properties, which allows the bioelectrode 10 to be used as a wet electrode (semi-dry electrode) impregnated with a conductive liquid or paste, enabling low-noise measurements, and also enabling measurements with conventional non-active electrode biomeasurement devices.

[0053] <Actions and Effects of the Manufacturing Method of the Bioelectrode> Furthermore, according to the manufacturing method of the bioelectrode 10 of the first embodiment described above, the following actions and effects can be obtained. That is, as shown in Figures 12 and 13 , a plurality of slits 22 are formed radially in the outer peripheral portion 16 of the conductive sheet body 11 in an unfolded state. Furthermore, the outer peripheral portion 16 in which the plurality of slits 22 are formed is folded from the boundary 20 with the central portion 15 as a starting point all around to one side A1 in the first direction A to form the bioelectrode 10. This makes it possible to easily manufacture the bioelectrode 10 (see Figure 3 ) having comb-shaped (strip-shaped) electrode portions 24 located between circumferentially adjacent slits 22 in the outer peripheral portion 16.

[0054] 5 and 6, the bioelectrode 10 formed by the manufacturing method of the bioelectrode 10 allows the electrode portion 24 formed on the outer periphery 16 of the conductive sheet body 11 to function like a comb. Therefore, the electrode portion 24 can be brought into contact with the scalp through the gaps in the hair. Furthermore, the bioelectrode 10 is formed from the conductive sheet body 11. Therefore, the tip portion 11a of the conductive sheet body 11 that comes into contact with the skin of the head 4 can be kept flexible. In other words, the tip portion of the electrode portion 24 on the conductive sheet body 11 can be kept flexible. This can eliminate any discomfort felt by the scalp when the electrode portion 24 comes into contact with it.

[0055] [Second embodiment] Next, a second embodiment of the bioelectrode 10 in the first embodiment will be described with reference to Fig. 14. Note that in the bioelectrode 100 of the second embodiment, the same or similar configurations and methods as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. The bioelectrode 100 of the second embodiment is configured to be applicable as an active electrode for, for example, short hair, soft hair, etc.

[0056] As shown in Fig. 14 , the bioelectrode 100 of the second embodiment is similar to the first embodiment in configuration, except that the conductive sheet 11 of the first embodiment is replaced with a conductive sheet 101. Fig. 14 is a cross-sectional view showing the unfolded state of the conductive sheet 101 before folding the outer periphery 106 of the conductive sheet 101 toward one side A1 in the first direction A. The conductive sheet 101 is the conductive sheet 11 of the first embodiment from which the core material 32 has been removed. That is, the conductive sheet 101 includes two conductive sheets 30 and two thermoplastic adhesive tapes 31. The two conductive sheets 30 are located on both sides in the first direction A, as in the first embodiment. The two thermoplastic adhesive tapes 31 are disposed between the two conductive sheets 30 and join the two conductive sheets 30, as in the first embodiment.

[0057] The conductive sheet body 101 has a polymer layer of thermoplastic adhesive tape 31 laminated between two conductive sheets 30 as a core material for the two conductive sheets 30. This allows the polymer layer to maintain the three-dimensional shape of the folded two conductive sheets 30. The polymer layer of the conductive sheet 30 maintains the flexibility of the two conductive sheets 30 and can stably maintain the three-dimensional shape of the two conductive sheets 30 folded starting from the boundary 120 between the outer periphery 106 and the center 105.

[0058] Furthermore, when processing the outer periphery 106 of the conductive sheet body 101 into a three-dimensional shape by folding it from the boundary 120 to one side A1 in the first direction A, the thermoplastic adhesive tape 31 is heated while the outer periphery 106 is folded. The thermoplastic adhesive tape 31 is then cooled to ambient temperature. This allows the two conductive sheets 30 to be fixed in the folded three-dimensional shape by the thermoplastic adhesive tape 31. The thermoplastic adhesive tape 31 (i.e., the polymer layer) has flexibility (flexibility). This allows the outer periphery 16 of the conductive sheet body 11 to have flexibility so that it can fit to heads with short or soft hair.

[0059] <Actions and Effects> The bioelectrode 100 of the second embodiment described above can achieve the following actions and effects. That is, as shown in Fig. 14, by joining two conductive sheets 30 with two thermoplastic adhesive tapes 31, the thermoplastic adhesive tapes 31 can be cooled to ambient temperature and hardened. This makes it easier to maintain the conductive sheet body 101 in its folded shape. As a result, as in the first embodiment, the electrode portion (not shown) of the conductive sheet body 101 can be brought into contact with the scalp through the gaps in the hair.

[0060] Furthermore, the thermoplastic adhesive tape 31 hardens at ambient temperature while retaining flexibility, which eliminates discomfort felt by the scalp when the electrode portion (not shown) of the conductive sheet 101 comes into contact with the scalp, as in the first embodiment.

[0061] The technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

[0062] In the above embodiment, an example has been described in which the conductive sheet bodies 11 and 101 are formed from two conductive sheets 30, but this is not limiting. As another example, for example, the conductive sheet bodies 11 and 101 may be formed from a single conductive sheet 30.

[0063] In addition, the components in this embodiment can be replaced with well-known components as appropriate, without departing from the spirit of the present invention.

[0064] 10,100...bioelectrode, 11,101...conductive sheet body, 11b...surface, 12...metal contact, 13...cover, 15...central portion, 16...periphery, 20,120...boundary, 22...slit, 24...electrode portion (portion located between adjacent slits in the circumferential direction on the outer periphery), 30...conductive sheet, 31...thermoplastic adhesive tape (thermoplastic adhesive), 32...core material, 41...female portion, 42...male portion, A...first direction, A1...one side.

Claims

1. A bioelectrode comprising a conductive sheet body, the conductive sheet body having an outer peripheral portion having a plurality of slits arranged radially outward and opening radially outward, and a central portion located radially inward from the outer peripheral portion, the outer peripheral portion being folded to one side in a first direction intersecting with the surface of the conductive sheet body around the entire circumference starting from the boundary between the outer peripheral portion and the central portion.

2. The bioelectrode described in claim 1, wherein the conductive sheet body comprises: two conductive sheets located on either side in the first direction; and a core material laminated between the two conductive sheets, the core material having a larger diameter than the central portion and a smaller diameter than the outer periphery.

3. The bioelectrode described in claim 1, wherein the conductive sheet body comprises: two conductive sheets located on either side in the first direction; and a thermoplastic adhesive disposed between the two conductive sheets and bonding the two conductive sheets.

4. The bioelectrode according to claim 2 or 3, wherein the conductive sheet is a conductive fabric.

5. A bioelectrode as claimed in any one of claims 1 to 3, comprising a metal contact provided in the central portion, the metal contact being a dot button that is fixed to the central portion by sandwiching the conductive sheet body from both sides in the first direction at the central portion and engaging one female part with the other male part.

6. The bioelectrode according to any one of claims 1 to 3, further comprising a cylindrical cover that covers the outer periphery.

7. A method for manufacturing a bioelectrode, comprising forming a plurality of slits radially outward on the outer periphery of a conductive sheet body, and folding the conductive sheet body, starting from the boundary between the outer periphery and the center, to one side in a first direction intersecting the surface of the conductive sheet body to form a bioelectrode.

Images