Method for manufacturing biological electrode

Abstract

This invention provides a method for manufacturing a bioelectrode that can easily produce a bioelectrode that suppresses the time-dependent increase in resistance value associated with strain. The method for manufacturing the bioelectrode includes the following steps: adding fumed silica to condensed silver powder to obtain a mixed silver powder; and forming a conductive rubber body containing silicone rubber and the mixed silver powder.

Description

Technical Field

[0001] The present invention relates to a method for producing a biological electrode, for example, to a method for producing a biological electrode containing silver powder. Background Art

[0002] In the past, thin plates of highly conductive metals such as gold, silver, platinum and copper were used as biological electrode materials. These highly conductive metal biological electrode materials have poor adhesion to the skin and are insufficient for detecting electrical signals from the skin. Therefore, when using these highly conductive metal biological electrode materials, in order to improve the detection of electrical signals from the skin, it is necessary to apply gel, ointment and paste on the skin. In this case, since the applied material used remains on the hair, etc., it will cause discomfort, so post-treatment such as shampooing is required.

[0003] Therefore, in recent years, as an electrode that does not require the application of a paste or the like, a conductive silicone rubber electrode prepared by mixing conductive carbon particles in silicone rubber has been proposed (see Patent Document 1). In addition, as a technology for imparting stretchability to a wiring substrate that can be mounted on a human body, etc., a technology in which a substrate constituting a wiring substrate and a coating layer include an elastomer, and the elastomer includes silicone rubber has been proposed (see Patent Document 2).

[0004] The biological electrode described in Patent Document 1 is an electrode made of a rubber material, so it can be used repeatedly, and because it is soft, it has good adhesion to the skin. In addition, because it has both electronic conduction and ion conduction, it has high conductivity and is resistant to strain, and the surface in contact with the skin conducts electricity through silver, so even in dry conditions where the contact impedance is low and no paste is used, stable measurements can be performed.

[0005] Prior Art Literature

[0006] Patent Literature

[0007] Patent Document 1: International Publication No. 2018 / 008688;

[0008] Patent document 2: Japanese Patent Application Publication No. 2017-117861. Summary of the invention

[0009] Problem that the invention aims to solve

[0010] However, the bioelectrode described in Patent Document 1 is a rubber electrode and can be used repeatedly. However, there is a problem that the resistance value of the rubber electrode increases due to strain caused by repeated use. In addition, the silver powder used in the rubber electrode has strong cohesive force and forms a block during manufacturing, so it is difficult to evenly disperse it in the liquid silicone rubber. Therefore, for example, when manufacturing the bioelectrode, it is necessary to perform operations such as sieving and mixing the silver powder used just before preparing the material, and there is also a problem that the manufacturing process becomes complicated.

[0011] The present invention has been made in view of such actual conditions, and provides a method for easily manufacturing a biological electrode in which a temporal increase in resistance value due to strain is suppressed.

[0012] Means used to solve problems

[0013] According to the present invention, there is provided a method for producing a biological electrode as shown below.

[0014] [1] A method for manufacturing a biological electrode, comprising the following steps:

[0015] Adding fumed silica to agglomerated silver powder and mixing them to obtain a mixed silver powder in which the silver powder and the fumed silica are dispersed; and

[0016] A conductive rubber body containing silicone rubber and the mixed silver powder is formed.

[0017] [2] The method for producing a biological electrode according to [1], wherein hydrophobic fumed silica is used as the fumed silica.

[0018] [3] The method for producing a biological electrode according to [1] or [2], wherein 1 to 5 parts by mass of the fumed silica is added to 100 parts by mass of the agglomerated silver powder.

[0019] [4] The method for manufacturing a biological electrode according to any one of [1] to [3], wherein in the step of forming the conductive rubber body, the mixed silver powder is added to a room temperature curing liquid silicone rubber to prepare a silver powder-containing paste, and the obtained silver powder-containing paste is cured to form the conductive rubber body.

[0020] [5] The method for producing a biological electrode according to any one of [1] to [4], wherein in the step of forming the conductive rubber body, the conductive rubber body is formed to have a layered shape.

[0021] [6] The method for producing a biological electrode according to any one of [1] to [4], wherein in the step of forming the conductive rubber body, the conductive rubber body is formed to have a brush-like shape.

[0022] [7] A rubber for a biological electrode, comprising at least silicone rubber, agglomerated silver powder, and fumed silica, wherein the fumed silica is contained in an amount of 1 to 5 parts by mass based on 100 parts by mass of the agglomerated silver powder.

[0023] [8] A rubber electrode comprising the rubber for biological electrode described in [7].

[0024] Effects of the Invention

[0025] According to the method for producing a biological electrode of the present invention, a biological electrode in which a temporal increase in resistance value due to strain is suppressed can be easily produced. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 1 is a schematic cross-sectional view showing an example of a biological electrode obtained by the method for producing a biological electrode according to an embodiment of the present invention.

[0027] Figure 2 It is an explanatory diagram showing a usage state of a biological electrode obtained by the method for producing a biological electrode according to an embodiment of the present invention.

[0028] Figure 3A This is an explanatory diagram of a signal transmission member of a biological electrode obtained by the method for producing a biological electrode according to an embodiment of the present invention.

[0029] Figure 3B This is an explanatory diagram of another example of the signal transmission member of the biological electrode obtained by the method for producing the biological electrode according to the embodiment of the present invention.

[0030] Figure 4 It is a diagram showing another structural example of a biological electrode obtained by the method for producing a biological electrode according to an embodiment of the present invention.

[0031] Figure 5 This is a perspective view showing another example of a biological electrode obtained by the method for producing a biological electrode according to the embodiment of the present invention.

[0032] Figure 6 This is a cross-sectional view showing another example of a biological electrode obtained by the method for producing a biological electrode according to the embodiment of the present invention.

[0033] Figure 7 This is a plan view showing another example of a biological electrode obtained by the method for producing a biological electrode according to the embodiment of the present invention.

[0034] Figure 8This is a partial side view of another example of a biological electrode obtained by the method for producing a biological electrode according to an embodiment of the present invention.

[0035] Fig. 9 It is a graph which shows the result of the sieving rate test.

[0036] Fig.10 This is a graph showing the measurement results of the volume resistivity of the biological electrodes (before the load is applied) in Examples 1 and 2 and Comparative Example 1.

[0037] Fig.11 This is a graph showing the measurement results of the volume resistivity of the biological electrodes (after the load was applied) in Examples 1 and 2 and Comparative Example 1.

[0038] Fig.12 This is an explanatory diagram for explaining a method for measuring the volume resistivity of a biological electrode. DETAILED DESCRIPTION

[0039] <Biological Electrode>

[0040] The biological electrode obtained by the manufacturing method of the biological electrode of the embodiment of the present invention has a conductive rubber body containing silicone rubber and silver powder. The biological electrode may also have a conductive substrate as needed. In the case where the biological electrode has a conductive substrate, a conductive rubber body is provided on the conductive substrate. As for the conductive rubber body constituting the biological electrode, since the silver powder is uniformly dispersed in the conductive rubber body, the increase in the resistance value over time accompanying the strain is suppressed. The shape of the conductive rubber body constituting the biological electrode is not particularly limited, and can be made into a desired shape according to the type and surface shape of the measured object such as a layer, a brush, a concave and convex shape. Such a biological electrode has good fit with the body of the subject, has a soft skin touch, is not easy to produce discomfort even if it is closely attached for a long time, and can maintain stable contact with the body of the subject. In addition, even if it is a three-dimensional shape such as a brush, it can show high conductivity and can perform stable measurement with less noise. In addition, since it is not necessary to use gel, etc., it can also be stably measured in the measurement under dry conditions, and the method of use is also simple.

[0041] Hereinafter, a biological electrode obtained by a manufacturing method according to an embodiment of the present invention (hereinafter also referred to as "the manufacturing method according to the present embodiment") will be described in detail with reference to the drawings. It should be noted that the present invention is not limited to the following embodiments.

[0042] Figure 11 is a schematic cross-sectional view showing an example of a biological electrode obtained by the manufacturing method according to the present embodiment. The biological electrode 1 according to the present embodiment is suitable for at least one of sensing an electrical signal from a biological body and transmitting electrical stimulation to a biological body. Figure 1 As shown in FIG. 1 , the biological electrode 1 includes a conductive substrate 11 made of conductive silicone rubber, and a conductive rubber body 12 provided on the conductive substrate 11. Figure 1 In the example of , the conductive rubber body 12 has a layered shape. That is, the biological electrode 1 is provided with a conductive rubber layer in which the conductive rubber body 12 covers the conductive substrate 11 containing conductive silicone rubber. Thus, the adhesion of the conductive rubber body 12 to the biological body can be further improved.

[0043] Figure 2 1 is an explanatory diagram showing a use state of a biological electrode obtained by the method for manufacturing a biological electrode according to the present embodiment. Figure 2 As shown, the biological electrode 1, for example, is in a state where a signal transmission component 13 connected to a measuring device (not shown) is connected to the surface of a conductive substrate 11, and the surface of a conductive rubber body 12 is brought into contact with a biological body 14. As a result, an electrical signal from the biological body 14 is transmitted to the measuring device via the conductive rubber body 12, the conductive substrate 11, and the signal transmission component 13, so that the electrical signal from the biological body 14 can be measured. The biological electrode 1 is used in direct contact with the biological body, so the conductive rubber body 12 has a predetermined contact area (the area of ​​the outermost surface). The contact area between the conductive rubber body 12 and the biological body is preferably 0.2 cm 2 Over and 13cm 2 Less than 1 cm, more preferably 1 cm 2 Over and 8cm 2 Below, more preferably 3cm 2 Over and 7cm 2 By setting the contact area of ​​the conductive rubber body 12 within the above range, the impedance can be reduced and noise can be effectively prevented from entering. In addition, the measurement result is not affected by the movement of the body, and the biological electrode 1 can be brought into contact with a smaller part of the biological body.

[0044] Figure 3A as well as Figure 3B This is an explanatory diagram of a signal transmission member of a biological electrode obtained by the method for producing a biological electrode according to the present embodiment. Figure 3AThe illustrated example shows an example of using a covered wire 15 as a signal transmission member 13. The covered wire 15 includes a metal core wire 151 having conductivity, and a resin coating 152 that covers the core wire 151. In the covered wire 15, the front end portion of the core wire 151 is exposed from the coating 152. The exposed front end portion of the core wire 151 is fixed to the surface of the conductive substrate 11 by an adhesive tape 153 or the like. With such a structure, the electrical signal flowing in the conductive substrate 11 is transmitted to the outside through the core wire 151 through the covered wire 15, so that the electrical signal from the biological body 14 can be transmitted to the outside.

[0045] Figure 3B The example shown shows an example of using a flexible printed substrate 16 as the signal transmission member 13. The flexible printed substrate 16 includes a resin base film 161 and a metal conductor foil 162 provided on the base film 161. The conductor foil 162 is copper or gold-plated copper. With such a structure, the electrical signal flowing in the conductive substrate 11 is transmitted to the outside through the conductor foil 162 through the flexible printed substrate 16, so that the electrical signal from the biological body 14 can be transmitted to the outside.

[0046] exist Figure 3A In the example shown, the covered wire 15 having a predetermined thickness as the signal transmission member 13 is arranged on the upper surface side of the conductive substrate 11. Therefore, when the biological electrode 1 is attached to the biological body 14, the biological body 14 (see Figure 2 , the same below) directly contacts the conductive rubber body 12 and applies an uneven load based on the thickness of the coated wire 15, so that the mounting portion of the biological body 14 feels uneven. Figure 3B In the example shown, the surface of the thin-plate-shaped flexible printed substrate 16 as the signal transmission member 13 is substantially flush with the surface of the conductive base material 11. As a result, it is difficult for the conductive rubber body 12 to be loaded by the thickness of the flexible printed substrate 16, so that even if it is mounted for a long time, the mounting portion is unlikely to feel unevenness, which can reduce discomfort, and the biological electrode 1 can be made lighter and smaller.

[0047] Figure 4 2 is a diagram showing another structural example of a bioelectrode obtained by the method for manufacturing a bioelectrode according to the present embodiment. Figure 4 In the example shown, the biological electrode 2 includes an insulating layer 17 provided on the conductive substrate 11. The insulating layer 17 contains insulating rubber. In the biological electrode 2, even if the insulating layer 17 is provided on the conductive substrate 11, the surface of the conductive substrate 11 does not directly contact the biological body 14, so the transmission of the electrical signal from the biological body 14 is not hindered by the insulating layer 17. In addition, when the insulating layer 17 is provided, Figure 3BAs shown, by providing a flexible printed substrate 16 as the signal transmission member 13, the surface of the flexible printed substrate 16 and the surface of the conductive substrate 11 become substantially flush with each other, so that the insulating layer 17 can be stably maintained and the biological electrode 2 can be prevented from bending. Hereinafter, various components of the biological electrode will be described in detail.

[0048] The conductive rubber body 12 contains silicone rubber, silver powder, and additives such as a dispersant as needed. As the silicone rubber contained in the conductive rubber body 12, for example, a room temperature curing liquid silicone rubber can be cited. Room temperature curing silicone rubber refers to silicone rubber that is in a liquid or paste state before curing and generally undergoes a curing reaction at 20°C to 100°C to become a rubber elastic body. In the curing reaction, there are curing reactions that gradually proceed due to moisture (water) in the air, and curing reactions that immediately proceed by adding a curing agent to the main agent, and any type of curing reaction can be used in the present invention. It should be noted that moisture-curing substances are sometimes classified as a one-component type, and substances to which a curing agent is added are sometimes classified as a two-component type.

[0049] As room temperature curing liquid silicone rubber, commercially available products can be used. For example, as liquid silicone rubber, trade names "KE-106" (manufactured by Shin-Etsu Chemical Co., Ltd.) and trade names "CAT-RG" (manufactured by Shin-Etsu Chemical Co., Ltd.) can be used. In addition, the liquid silicone rubber can be used alone or in combination of multiple types.

[0050] From the viewpoint of improving conductivity, the conductive rubber body 12 contains 50 to 600 parts by mass, preferably 100 to 400 parts by mass of silver powder based on 100 parts by mass of silicone rubber.

[0051] The silver powder contained in the conductive rubber body 12 may include at least one selected from agglomerated silver powder, flaky silver powder, and the like. As the silver powder contained in the conductive rubber body 12, at least a mixed silver powder composed of silver powder and fumed silica obtained by adding fumed silica to agglomerated silver powder and mixing them is used. In the mixed silver powder, the agglomerated silver powder and fumed silica are sometimes mixed and dispersed by a disperser, and part of the agglomerated silver powder is crushed and fined. For example, part of the agglomerated silver powder used in the preparation of the mixed silver powder may become primary particles or finer particles near the primary particles due to crushing and dispersion, and may be dispersed in the conductive rubber body 12 in the form of such finer particles. In addition, the mixing of fumed silica and silver powder can effectively suppress the re-agglomeration of the silver powder and improve the fluidity of the silver powder.

[0052] Agglomerated silver powder refers to silver powder in which a plurality of granular primary particles are aggregated into a three-dimensional shape. Examples of agglomerated silver powder include "G-35" (manufactured by DOWA Electronics Co., Ltd.).

[0053] Flake silver powder is silver powder having a scale-like shape, and examples thereof include trade names "FA-D-3" and "FA-2-3" (both manufactured by DOWA Electronics Co., Ltd.).

[0054] The average particle size of the silver powder is not particularly limited as long as it is within the range that can impart conductivity to the conductive rubber body 12. For example, the average particle size of the agglomerated silver powder is preferably 4 μm or more and 8 μm or less. The average particle size of the flaky silver powder is preferably 5 μm or more and 15 μm or less. It should be noted that the above average particle size is the average particle size of the silver powder in the primary particles. The average particle size of the silver powder is the average diameter measured by electron microscope photographs and calculated by arithmetic average.

[0055] There is no particular limitation on the mixing ratio of the agglomerated silver powder to the flaky silver powder. For example, the mixing ratio (mass ratio) of the agglomerated silver powder to the flaky silver powder is preferably 1:5 to 5:1.

[0056] Fumed silica is composed of tiny nano-sized silica particles. The silver powder contained in the conductive rubber body 12 is added to the liquid silicone rubber in the form of a mixed silver powder (i.e., a mixed powder composed of silver powder and fumed silica) in which fumed silica is added to agglomerated silver powder and mixed. The mixed silver powder suppresses the aggregation of silver powder particles by mixing silver powder particles and fumed silica. Therefore, the mixed silver powder composed of silver powder and fumed silica has extremely excellent fluidity in liquid silicone rubber. Since the mixed silver powder has excellent fluidity, the handling of the material used to make the conductive rubber body 12 becomes easy. In addition, the dispersibility inside the rubber when it is mixed with silicone rubber is improved, the compatibility with rubber is good, and the strain resistance of the conductive rubber body 12 is improved. As a result, the biological electrode 1 suppresses the increase in resistance value over time accompanied by strain.

[0057] Usually, fumed silica is roughly divided into hydrophobic fumed silica and hydrophilic fumed silica. As fumed silica, hydrophobic fumed silica is preferably used. As hydrophobic fumed silica, for example, trade name "AEROSIL R972" (manufactured by AEROSIL, Japan) and the like can be cited. As hydrophilic fumed silica, for example, trade name "AEROSIL200" (manufactured by AEROSIL, Japan) and the like can be cited.

[0058] The amount of silver powder can be appropriately set within the range that can impart conductivity. For example, with respect to 100 parts by mass of liquid silicone rubber, the amount of silver powder is preferably in the range of 50 to 500 parts by mass, and particularly preferably in the range of 100 to 300 parts by mass. It should be noted that at least a portion of the silver powder is mixed with the liquid silicone rubber in the form of a mixed silver powder containing fumed silica. Therefore, the amount of the mixed silver powder containing silver powder is determined in consideration of the amount of fumed silica added.

[0059] In addition to the above components, the conductive rubber body 12 may further include other components within the range that does not impair the effects of the present invention. As other components, for example, reinforcing agents, fillers such as dry silica, anti-aging agents, processing aids, plasticizers and other agents commonly used in the rubber industry may be appropriately formulated.

[0060] The conductive rubber body 12 may further contain modified silicone as a dispersant. As the modified silicone, silicone having a modified side chain introduced into a main chain composed of a siloxane bond (-Si-O-; also referred to as a silicone chain) can be preferably used, for example, silicones including polyether modification, polyether alkyl co-modification, polyglycerol modification, polyglycerol alkyl co-modification, etc. can be cited. The modified side chain preferably includes an ether bond (-COC-).

[0061] As polyether-modified silicone, silicone having a main chain consisting of a silicone chain and a side chain consisting of a polyether chain introduced therein can be used. As polyether-alkyl co-modified silicone, silicone having a main chain consisting of a silicone chain and a side chain consisting of a polyether chain and a side chain consisting of an alkyl chain introduced therein can be used. As polyglycerol-modified silicone, silicone having a main chain consisting of a silicone chain and a side chain consisting of a polyglycerol chain introduced therein can be used. As polyglycerol-alkyl co-modified silicone, silicone having a main chain consisting of a silicone chain and a side chain consisting of a polyglycerol chain and a side chain consisting of an alkyl chain introduced therein can be used. Among these, polyether-modified silicone and polyglycerol-modified silicone are particularly preferred.

[0062] The thickness of the conductive rubber body 12 is not particularly limited as long as it is within a range that can impart conductivity to the conductive rubber body 12. The thickness of the conductive rubber body 12 is preferably 18 μm or more and 80 μm or less from the viewpoint of improving the conductivity of the biological electrode and ensuring the flexibility of the biological electrode, and is more preferably 30 μm or more and 60 μm or less from the viewpoint of improving the adhesion between the conductive substrate 11 and the conductive rubber body 12 and preventing the conductive rubber body 12 from peeling off and reducing the contact impedance with the biological body.

[0063] The conductive substrate 11 is an arbitrary component for supporting the conductive rubber body 12. There is no particular limitation on the material of the conductive substrate 11 as long as it has conductivity. For example, a conductive silicone rubber having the same structure as the conductive rubber body 12 can be used. It should be noted that the details of the conductive silicone rubber having the same structure as the conductive rubber body 12 are as described above. In addition, as the material of the conductive substrate 11, a conductive silicone rubber containing silicone rubber and conductive particles can also be used. By containing a conductive silicone rubber, the conductive substrate 11 can improve the adhesion between the conductive substrate 11 and the conductive rubber body 12. As the silicone rubber, liquid silicone rubber is preferably used, for example, an organosilicon polymer is used. As the organosilicon polymer, an organosilicon polymer having a siloxane bond (-Si-O-) as the main chain and a hydrocarbon group such as a methyl group, a phenyl group, a vinyl group, or hydrogen as a side chain is preferably used. As the silicone rubber, an addition reaction type silicone rubber can be used, and a condensation reaction type silicone rubber can also be used. Addition reaction type silicone rubber is silicone rubber cured by addition reaction, and examples thereof include silicone rubber having hydrogen or vinyl as a side chain. In addition, condensation reaction type silicone rubber is silicone rubber cured by condensation reaction, and examples thereof include silicone rubber having hydroxyl groups at the ends. Among them, addition reaction type silicone rubber is preferred from the viewpoint of more appropriately maintaining adhesion with the conductive rubber body 12. These silicone rubbers may be used alone or in combination of two or more.

[0064] As the conductive particles, conductive carbon particles such as various carbon blacks can be used. There is no limitation on the conductive carbon particles as long as they can impart conductivity to the conductive substrate 11. As conductive carbon particles, for example, various carbon particles such as carbon black and graphite can be cited. As carbon black, Ketjen black, acetylene black, etc. can be cited. They can be used alone or in combination of two or more. Among them, from the viewpoint of improving the conductivity of the conductive substrate 11, Ketjen black is preferred as carbon black.

[0065] The average particle size of the conductive particles is not particularly limited as long as it is within the range that can impart conductivity to the conductive substrate 11. The average particle size of the conductive particles is preferably 0.1 μm or more and 100 μm or less, and more preferably 1 μm or more and 30 μm or less, from the viewpoint of improving the conductivity of the conductive substrate 11 and ensuring the flexibility of the conductive substrate 11. The average particle size of the conductive particles is an average diameter measured by electron micrographs and calculated by arithmetic mean.

[0066] The content of the conductive particles in the conductive substrate 11 is not particularly limited as long as it is within a range that can impart conductivity to the conductive substrate 11. The content of the conductive particles in the conductive substrate 11 is preferably 10% by mass or more and 70% by mass or less, and more preferably 20% by mass or more and 50% by mass or less, relative to the total mass of the conductive substrate 11, from the viewpoint of improving the conductivity of the conductive substrate 11 and ensuring the flexibility of the conductive substrate 11.

[0067] As the conductive silicone rubber contained in the conductive substrate 11, for example, a commercially available product such as "KE-3801M-U" (manufactured by Shin-Etsu Chemical Co., Ltd.) can be used.

[0068] The conductive substrate 11 may be a conductive substrate obtained by crosslinking the conductive silicone rubber using a crosslinking agent. For example, a commercially available product such as "C-8A" (content of 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane is 80% by mass, manufactured by Shin-Etsu Chemical Co., Ltd.) may be used as the crosslinking agent.

[0069] The thickness of the conductive substrate 11 is not particularly limited as long as the flexibility of the conductive substrate 11 can be ensured, but is preferably 0.1 mm to 2 mm, and more preferably 0.4 mm to 1.5 mm.

[0070] Figures 5 to 8 : is a diagram showing another example of a biological electrode obtained by the manufacturing method involved in this embodiment. It should be noted that, Figure 5 is a stereogram of a biological electrode 3, Figure 6 is a side view of the biological electrode 3, Figure 7 is a top view of the biological electrode 3, Figure 8 It is a partial side view showing only the protrusion 22 a constituting the biological electrode 3 .

[0071] like Figure 5 to Figure 7 As shown in FIG. 1 , the biological electrode 3 is composed of a conductive rubber body having a disk 21 and a protrusion 22 provided on one surface of the disk 21. Such a conductive rubber body can be used in the same manner as Figure 1 The conductive rubber body 12 shown in the figure is made of conductive silicone rubber. The protrusion 22 has a brush-like shape consisting of a plurality of protrusions 22a. The protrusion 22 is composed of a protrusion 22a arranged at the center of the disk 21 and a plurality of protrusions 22a arranged on the circumference with the protrusion 22a as the center. A connecting member 23 is provided on the other main surface of the disk 21.

[0072] like Figure 8As shown, the protrusion 22a includes a main body 221a and a front end 222a provided on the main body 221a. The main body 221a has a substantially cylindrical shape, and one end side is provided on the disk 21. The front end 222a has a substantially conical shape with a hemispherical apex side, and the bottom surface is provided on the surface of the other end side of the main body 221a.

[0073] Figures 5 to 8 In the biological electrode 3 shown, a plurality of protrusions 22a are formed into brush-shaped terminals and contact the human body. At this time, the vertex side of the front end portion 222a of the protrusion 22a is in a hemispherical shape, so there is no discomfort when it contacts the skin, and the softness of the protrusion 22a also makes it fit the skin well. In addition, since the surface in contact with the skin is conductive due to silver, stable measurement can be performed even in dry conditions where the contact impedance is low and no paste is used. This embodiment can also be applied to a biological electrode 3 having a conductive rubber body having such a brush-shaped terminal.

[0074] <Method for producing biological electrode>

[0075] A method for manufacturing a biological electrode according to an embodiment of the present invention is a method for manufacturing a biological electrode comprising the following steps: adding fumed silica to agglomerated silver powder and mixing them to obtain a mixed silver powder in which silver powder and fumed silica are dispersed; and forming a conductive rubber body containing silicone rubber and the mixed silver powder.

[0076] In the process of obtaining a mixed silver powder containing silver powder and fumed silica, sometimes the condensed silver powder and fumed silica are mixed and dispersed by, for example, a disperser, and a part of the condensed silver powder is crushed and micronized. For example, a part of the condensed silver powder used in the preparation of the mixed silver powder sometimes becomes a primary particle or a finer particle near the primary particle due to crushing and dispersion, and can also be included in the mixed silver powder in the form of such fine particles. In addition, the mixing of fumed silica and silver powder can effectively inhibit the re-agglomeration of silver powder and improve the fluidity of silver powder (in other words, mixed silver powder). By making such a mixed silver powder contained in silicone rubber to form a conductive rubber body, the conductive rubber body constituting the biological electrode can evenly disperse the silver powder in the conductive rubber body, and effectively suppress the increase in resistance value over time accompanied by strain. In addition, the conductive rubber body constituting the biological electrode has good fit with the subject's body, and is not easy to cause discomfort even if it is tightly attached for a long time with a soft skin touch, and can maintain stable contact with the subject's body. In addition, even a three-dimensional shape such as a brush can show high conductivity, and stable measurement with little noise can be performed. In addition, since there is no need to use gel, etc., stable measurement can be performed even in dry conditions, and the method of use is also simple. It should be noted that the conductivity of the obtained conductive rubber body is not affected by the presence or absence of the addition of fumed silica, and the above-mentioned effects can be achieved, and a biological electrode with excellent conductivity can be manufactured.

[0077] The process of obtaining the mixed silver powder is a process of preparing agglomerated silver powder and fumed silica, adding fumed silica to the agglomerated silver powder, and pre-dispersing it by a disperser or the like. As described above, the mixed silver powder is preferably mixed and dispersed by a disperser. It should be noted that the agglomerated silver powder and fumed silica can also be initially mixed manually or by a mixer, and then the agglomerated silver powder can be crushed and dispersed by a disperser. Through this process, the agglomerated silver powder becomes a primary particle or a finer particle near the primary particle. There is no particular limitation on the disperser, and for example, a known device for crushing powders such as a household grinder can be used. There is no particular limitation on the dispersion time of the disperser, and it is preferably dispersed for a time sufficient to form a stable dispersion system. For example, as a dispersion time, 1 to 10 minutes can be cited.

[0078] Agglomerated silver powder includes, for example, trade name "G-35" (manufactured by DOWA Electronics Co., Ltd.). The average particle size of the silver powder is not particularly limited as long as it is within a range that can impart conductivity to the conductive rubber body 12. The average particle size of the silver powder is preferably 4 μm to 8 μm.

[0079] Fumed silica can use hydrophobic fumed silica, or hydrophilic fumed silica, and more preferably hydrophobic fumed silica. When using hydrophobic fumed silica, compared with hydrophilic fumed silica, it can be considered that the dispersibility of silver powder is further improved and the operability is further improved. As hydrophobic fumed silica, for example, trade name "AEROSIL R972" (manufactured by AEROSIL, Japan) etc. can be cited. As hydrophilic fumed silica, for example, trade name "AEROSIL 200" (manufactured by AEROSIL, Japan) etc. can be cited.

[0080] The mixing ratio of the agglomerated silver powder and the fumed silica is not particularly limited. For example, the fumed silica is preferably in an amount of 1 to 5 parts by mass based on 100 parts by mass of the agglomerated silver powder.

[0081] The step of forming a conductive rubber body containing silicone rubber and mixed silver powder is a step of mixing silicone rubber and the mixed silver powder obtained by the above step to form a conductive rubber body of a desired shape. In the step of forming a conductive rubber body, in addition to the above-mentioned mixed silver powder, it is preferred to further add flaky silver powder to form a conductive rubber body. Examples of flaky silver powder include trade names "FA-D-3" and "FA-2-3" (both manufactured by DOWA Electronics Co., Ltd.). The mixing ratio (mass ratio) of agglomerated silver powder to flaky silver powder is preferably 1:5 to 5:1.

[0082] In the process of forming the conductive rubber body, the conductive rubber body may be formed on a conductive substrate (a) or formed alone (b). In the case of forming the conductive rubber body on a conductive substrate (a), for example, a method of applying a silver powder paste containing liquid silicone rubber, mixed silver powder, and, as required, a crosslinking agent, modified silicone, etc. on a conductive substrate, and then heating and curing the silver powder paste may be cited. The substance formed by curing the silver powder paste becomes a conductive rubber body. In addition, in the case of forming the conductive rubber body alone (b), a method of injecting the silver powder paste into a molding die having a predetermined internal shape and then heating the silver powder paste in the molding die to cure the silver powder paste may be cited. Typically, in the case of (a), a layered conductive rubber body can be formed on a conductive substrate, and in the case of (b), a conductive rubber body having a desired shape such as a brush shape can be formed.

[0083] Hereinafter, an example of a process for forming a conductive rubber body will be specifically described. In the case of (a) forming a conductive rubber body on a conductive substrate, first, prepare a conductive substrate. The conductive substrate may be a commercially available material or may be newly made. In the case of a newly made conductive substrate, for example, a conductive silicone rubber containing a specified amount of conductive particles and a cross-linking agent are kneaded at room temperature (above 20°C and below 40°C) for more than 1 minute and less than 1 hour using a kneading machine such as a roller to obtain a blank. Then, the kneaded blank is cross-linked once under the conditions of more than 100°C and less than 300°C, for more than 1 minute and less than 1 hour, and then secondary cross-linked under the conditions of more than 150°C and less than 350°C, for more than 1 hour and less than 10 hours, thereby producing a conductive substrate.

[0084] Next, liquid silicone rubber, mixed silver powder, and a cross-linking agent are stirred for a specified time by a mixer or the like to prepare a silver powder paste. The temperature during stirring can be, for example, room temperature (above 20°C and below 40°C). The stirring time can be, for example, more than 1 minute and less than 1 hour. Next, the silver powder paste is applied on a conductive substrate. In the application of the silver powder paste on the conductive substrate, for example, dipping, spraying, roller coating, flow coating, inkjet, screen printing, etc. are used. The coating thickness of the silver powder paste is preferably more than 25μm and less than 200μm, and more preferably more than 35μm and less than 100μm. As a result, the adhesion of the conductive rubber body to the conductive substrate can be improved, so it is easy to prevent the conductive rubber body from peeling off from the conductive substrate, and the contact impedance can be reduced. Next, the silver powder paste is cured. In this process, for example, the silver powder paste can be cured by heating the silver powder paste to a specified temperature within a specified time. The heating time of the silver powder-containing paste is preferably 10 to 120 minutes, more preferably 15 to 90 minutes, and further preferably 20 to 45 minutes. In addition, the heating temperature of the silver powder-containing paste is preferably 100 to 200° C., more preferably 120 to 180° C., and further preferably 140 to 160° C. The silver powder-containing paste can be cured by heating at 150° C. for 30 minutes, for example.

[0085] When (b) is used to form a conductive rubber body alone, a silver powder paste is prepared in the same manner as in the above-mentioned case (a). Next, after the silver powder paste is injected into a mold corresponding to a desired shape such as a brush shape, a primary crosslinking based on stamping crosslinking is performed. Then, a secondary crosslinking is further performed. Specifically, the kneaded blank is primary crosslinked under the conditions of 100° C. to 300° C. and 1 minute to 1 hour, and then a secondary crosslinking is performed under the conditions of 150° C. to 350° C. and 1 hour to 10 hours to produce a conductive rubber body.

[0086] After forming the conductive rubber body as described in (a) or (b), the conductive rubber body may be immersed in an inorganic salt-containing solution at a temperature of 70° C. to 180° C. During the immersion in the inorganic salt-containing solution, the inorganic salt, anions and cations derived from the inorganic salt effectively penetrate into the conductive rubber body. The inorganic salt-containing solution preferably contains an inorganic salt, a solvent for dissolving the inorganic salt, and other additives as needed.

[0087] As the inorganic salt contained in the inorganic salt solution, there is no particular limitation as long as it is an inorganic salt that can penetrate into the conductive rubber body. It is preferred to use at least one inorganic salt selected from the group consisting of chloride salts, sulfide salts and carbonate salts. As the inorganic salt, it is more preferred to use at least one inorganic salt selected from the group consisting of sodium chloride, potassium chloride, lithium chloride, calcium chloride, magnesium chloride, sodium sulfate, potassium sulfate, lithium sulfate, calcium sulfate, magnesium sulfate, sodium carbonate, potassium carbonate, lithium carbonate, calcium carbonate and magnesium carbonate. These inorganic salts can be used alone or in combination of two or more. Among them, as an inorganic salt, from the viewpoint of solubility in a solvent and ion mobility, chloride salts are preferred, and chloride salts of alkali metals such as sodium chloride, potassium chloride and lithium chloride are more preferred. From the viewpoints of cheapness, safety to the human body and ion exchangeability with the salt contained in human sweat, sodium chloride is further preferred. In addition, the conductive rubber body may contain halide ions, sulfate ions and carbonate ions as anions derived from inorganic salts. As halide ions, chloride ions (Cl - ). The conductive rubber may contain Li + 、Na + , K + Mg 2+ , Ca 2+ As cations derived from inorganic salts. Such inorganic salts, anions and cations derived from inorganic salts penetrate into the conductive rubber body, suppressing the potential fluctuation based on the polarization voltage in the conductive rubber body, thereby effectively reducing the potential fluctuation noise. The concentration of the inorganic salt in the inorganic salt-containing solution is preferably 0.1 mol / L or more, more preferably 0.5 mol / L or more and 20 mol / L or less. By making the concentration of the inorganic salt in the inorganic salt-containing solution within these ranges, the inorganic salt, anions and cations derived from the inorganic salt can be effectively penetrated into the conductive rubber body.

[0088] As the solvent contained in the inorganic salt solution, there is no particular restriction as long as it is a solvent that can dissolve the inorganic salt. As the solvent, for example, ketones such as water, acetone, alcohols such as methanol and ethanol can be cited. These solvents can be used alone or in combination of two or more. Among them, from the viewpoint of safety and cheapness, preferably water, ethanol or a mixture of water and ethanol, from the viewpoint of safety and cheapness, preferably water.

[0089] In the process of immersing the conductive rubber body in the inorganic salt solution, it is preferred that the conductive rubber body is immersed in the inorganic salt solution under pressurized conditions. More preferably, the conductive rubber body is immersed in the inorganic salt solution under a pressure of more than 1 atmosphere and less than 10 atmospheres, and further preferably under a pressure of more than 2 atmospheres and less than 3 atmospheres. Under pressurized conditions, by immersing the conductive rubber body in the inorganic salt solution, the penetration rate of the inorganic salt, the anion and the cation derived from the inorganic salt in the conductive rubber body is made faster, thereby effectively increasing the concentration of the inorganic salt, the anion and the cation in the conductive rubber body. As a result, the potential variation noise of the biological electrode can be effectively reduced. The pressurization method is not particularly limited, for example, a method of increasing the pressure in the closed container after configuring the conductive rubber body in a closed container (such as an autoclave) injected with an inorganic salt solution can be cited.

[0090] The time for immersing the conductive rubber body in the inorganic salt-containing solution can be appropriately changed according to the temperature of the inorganic salt-containing solution, the inorganic salt concentration in the inorganic salt-containing solution, the pressure during pressurization, etc. The immersion time of the conductive rubber body in the inorganic salt-containing solution is preferably 15 minutes to 180 minutes, more preferably 30 minutes to 120 minutes, and even more preferably 45 minutes to 90 minutes, from the viewpoint of efficiently dispersing the inorganic salt, anions and cations derived from the inorganic salt in the conductive rubber body.

[0091] As described above, the method for producing a biological electrode according to the present embodiment includes the step of adding fumed silica to agglomerated silver powder and dispersing the powder in advance using a disperser or the like, and adding the mixed silver powder obtained in this step to silicone rubber to form a conductive rubber body.

[0092] <Rubber for biological electrode and rubber electrode>

[0093] Next, the rubber for biological electrodes according to the embodiment of the present invention is described. The rubber for biological electrodes according to the present embodiment is a rubber for biological electrodes comprising at least silicone rubber, agglomerated silver powder and fumed silica. Moreover, the rubber for biological electrodes contains 1 to 5 parts by mass of fumed silica relative to 100 parts by mass of agglomerated silver powder. The so-called agglomerated silver powder does not include flaky silver powder in a scale-like shape, and for example, a plurality of granular primary particles can be cited as silver powder agglomerated into a three-dimensional shape. The rubber for biological electrodes preferably also contains flaky silver powder. The mixing ratio (mass ratio) of agglomerated silver powder to flaky silver powder is preferably 1:5 to 5:1. As the rubber for biological electrodes according to the present embodiment, for example, a conductive rubber body manufactured by the manufacturing method of the biological electrode described above can be cited. The rubber for biological electrodes according to the present embodiment suppresses the increase in resistance value over time accompanied by strain. Next, the rubber electrode according to the embodiment of the present invention is described. The rubber electrode according to the present embodiment is a rubber electrode composed of the above-mentioned rubber for biological electrodes. As the rubber electrode according to the embodiment, for example, there can be mentioned a biological electrode produced by the biological electrode production method described above.

[0094] Example

[0095] Hereinafter, the present invention will be described in more detail based on examples performed to clarify the effects of the present invention. It should be noted that the present invention is not limited in any way to the following examples and comparative examples.

[0096] <Preparation of mixed silver powder>

[0097] The sample mixed in the following blending amount was dispersed in a dispersing machine (home grinding machine) for 2 minutes to prepare mixed silver powders 1 to 4 containing silver powder and fumed silica. It should be noted that the following pure silver particles ("G-35" manufactured by DOWA Electronics Co., Ltd.) used in the preparation of mixed silver powders 1 to 4 were agglomerated silver powders at the time of their preparation.

[0098] (Composition of mixed silver powder 1)

[0099] Pure silver particles ("G-35" manufactured by DOWA Electronics Co., Ltd.) 100 parts by mass

[0100] Hydrophobic fumed silica ("G-35AEROSIL R972" manufactured by AEROSIL Japan, average primary particle size 16 nm) 1 part by mass

[0101] (Composition of mixed silver powder 2)

[0102] Pure silver particles ("G-35" manufactured by DOWA Electronics Co., Ltd.) 100 parts by mass

[0103] · Hydrophilic fumed silica ("G-35AEROSIL200" manufactured by AEROSIL Japan, average primary particle size 12 nm) 1 part by mass

[0104] (Composition of mixed silver powder 3)

[0105] Pure silver particles ("G-35" manufactured by DOWA Electronics Co., Ltd.) 100 parts by mass

[0106] Hydrophobic fumed silica ("G-35AEROSIL R972" manufactured by AEROSIL Japan, average primary particle size 16 nm) 2 parts by mass

[0107] (Preparation ingredients of mixed silver powder 4)

[0108] Pure silver particles ("G-35" manufactured by DOWA Electronics Co., Ltd.) 100 parts by mass

[0109] Hydrophilic fumed silica ("G-35AEROSIL200" manufactured by AEROSIL Japan, average primary particle size 12 nm) 2 parts by mass

[0110] <Sieving rate test of mixed silver powder>

[0111] The mixed silver powders 1 and 2 were sieved using sieves with mesh sizes of 45 μm or 100 μm, respectively, and the mass ratio of the powders passing through each sieve (hereinafter referred to as "screening rate") was calculated. It should be noted that when screening each powder, the sieve was shaken by hand while the side of the sieve was hit with a wooden hammer. The results of the screening rate test are shown in Figure 1. Fig. 9 shown.

[0112] Fig. 9 : is a graph showing the results of the sieving rate test of the mixed silver powders 1 and 2. Fig. 9 In the figure, the vertical axis represents the screening rate [%], and the horizontal axis represents the mesh size of the sieve. Fig. 9 In FIG. 1 , the test results using a sieve with a mesh size of 45 μm are shown on the right side of the graph, and the test results using a sieve with a mesh size of 100 μm are shown on the left side of the graph.

[0113] like Fig. 9 As shown, the mixed silver powders 1 and 2 in which fumed silica is blended into pure silver particles show good sieving rates in sieving using a sieve with a mesh size of 45 μm or 100 μm, respectively. In particular, the mixed silver powder 1 in which hydrophobic fumed silica is blended has a very high sieving rate in each sieving and is very easy to operate.

[0114] (Example 1)

[0115] The following blended components were mixed for 30 seconds using a centrifugal stirrer, cross-linked under pressure at 150°C for 10 minutes (primary cross-linking), and then cross-linked in an oven at 150°C for 30 minutes (secondary cross-linking) to produce the bioelectrode of Example 1 composed of silicone rubber. The bioelectrode of Example 1 was formed into a cylindrical shape with an end face diameter of 10 mm and an axial length of 5 mm. In addition, the produced bioelectrode was immersed in a 10% NaCl aqueous solution and heated and pressurized for 1 hour under the conditions of 121°C and 2 atmospheres. The bioelectrode of Example 1 was designated as "conductive rubber body 1". The pure silver particles ("FA-2-3" manufactured by DOWA Electronics Co., Ltd.) in the following blended components were flaky silver powders during their preparation.

[0116] (Composition components of conductive rubber body 1)

[0117] Room temperature curing liquid silicone rubber (a mixture of "KE-106" and "CAT-RG" manufactured by Shin-Etsu Chemical Co., Ltd. at a ratio of 10:1) 100 parts by mass

[0118] · 150 parts by mass of the above mixed silver powder

[0119] Pure silver particles ("FA-2-3" manufactured by DOWA Electronics Co., Ltd.) 150 parts by mass

[0120] Silicone oil 1 ("KF-6015" manufactured by Shin-Etsu Chemical Co., Ltd.) 10 parts by mass

[0121] Silicone oil 2 ("KF-6106" manufactured by Shin-Etsu Chemical Co., Ltd.) 10 parts by mass

[0122] (Example 2)

[0123] The bioelectrode of Example 2 was prepared by the same method as Example 1 except that the following blended components were changed to the following blended components. The bioelectrode of Example 2 is referred to as "conductive rubber body 2".

[0124] (Composition of the conductive rubber body 2)

[0125] Room temperature curing liquid silicone rubber (a mixture of "KE-106" and "CAT-RG" manufactured by Shin-Etsu Chemical Co., Ltd. at a ratio of 10:1) 100 parts by mass

[0126] · 150 parts by mass of the above mixed silver powder

[0127] Pure silver particles ("FA-2-3" manufactured by DOWA Electronics Co., Ltd.) 150 parts by mass

[0128] Silicone oil 1 ("KF-6015" manufactured by Shin-Etsu Chemical Co., Ltd.) 10 parts by mass

[0129] Silicone oil 2 ("KF-6106" manufactured by Shin-Etsu Chemical Co., Ltd.) 10 parts by mass

[0130] (Comparative Example 1)

[0131] The bioelectrode of Comparative Example 1 was prepared by the same method as in Example 1 except that the following blended components were changed to the following blended components. The bioelectrode of Comparative Example 1 was referred to as "conductive rubber body 3".

[0132] (Composition of the conductive rubber body 3)

[0133] Room temperature curing liquid silicone rubber (a mixture of "KE-106" and "CAT-RG" manufactured by Shin-Etsu Chemical Co., Ltd. at a ratio of 10:1) 100 parts by mass

[0134] Pure silver particles ("G-35" manufactured by DOWA Electronics Co., Ltd.) 150 parts by mass

[0135] Pure silver particles ("FA-2-3" manufactured by DOWA Electronics Co., Ltd.) 150 parts by mass

[0136] Silicone oil 1 ("KF-6015" manufactured by Shin-Etsu Chemical Co., Ltd.) 10 parts by mass

[0137] Silicone oil 2 ("KF-6106" manufactured by Shin-Etsu Chemical Co., Ltd.) 10 parts by mass

[0138] <Volume Resistivity>

[0139] The volume resistivity [Ω·cm] of the biological electrodes in Examples 1 and 2 and Comparative Example 1 was measured by the following measurement method. The measurement results of the volume resistivity are shown in Fig.10 It should be noted that Fig.10 The volume resistivity values ​​shown are values ​​measured immediately after the production of each biological electrode without applying a load or the like to the biological electrode.

[0140] Measurement of volume resistivity of biological electrodes Fig.12 The resistivity measurement is performed using the plate-shaped resistivity measurement components 31 and 32 shown. Fig.12 This is an explanatory diagram for explaining a method for measuring the volume resistivity of a biological electrode. Fig.12 (a) is a top view of a resistivity measuring component for measuring the volume resistivity of a biological electrode. Fig.12(b) shows a side view for explaining the method of measuring the volume resistivity of a biological electrode. The resistivity measuring parts 31 and 32 are two plate-like parts in a set, and measuring electrodes 33 and 34 formed by gold plating are arranged on their respective surfaces. The size of the measuring electrodes 33 and 34 is 20 mm in length and 40 mm in width. Fig.12 In (a), the range surrounded by the dotted lines indicated by the reference numerals 37 and 38 is the biological electrode 30 (see Fig.12 (b)) Sample placement. Fig.12 As shown in (b), when measuring the volume resistivity of the biological electrode 30, the biological electrode 30 is clamped by two plate-shaped resistivity measuring parts 31 and 32, a constant current of 100 mA is applied to the two resistivity measuring parts 31 and 32, and the potential difference between the measuring electrodes 33 and 34 arranged opposite to each other while clamping the biological electrode 30 is measured. Fig.12 In FIG. 1 , symbol 35 indicates a constant current power supply for applying a constant current, and symbol 36 indicates a voltmeter for measuring a potential difference. The volume resistivity of the biological electrode 30 is calculated based on Ohm's law from the current value applied by the constant current power supply 35, the potential difference measured by the voltmeter 36, and the cross-sectional area and thickness of the biological electrode 30. Fig.12 As shown in (b), when measuring the potential difference between the measuring electrodes 33 and 34, two plate-shaped resistivity measuring parts 31 and 32 sandwiching the biological electrode 20 are placed horizontally, and a weight of 100 g is placed on the resistivity measuring part 31 on the vertical upper side. The constant current power supply 35 and the voltmeter 36 take into account the resistance of the measuring electrodes 33 and 34 themselves and the electrical contacts with the measuring electrodes 33 and 34 to be sufficiently away from the sample placement positions 37 and 38. In addition, the electrical contact of the constant current power supply 35 is set to a position 8 mm away from one side edge of the measuring electrodes 33 and 34, and the electrical contact of the voltmeter 36 is set to a position further away from the electrical contact of the constant current power supply 35 by 8 mm in the same direction. The size of the measuring electrodes 33 and 34 is appropriately changed according to the size of the biological electrode 30 as a sample.

[0141] Fig.10 : is a graph showing the measurement results of the volume resistivity of the biological electrode (before the load is applied) in Examples 1 and 2 and Comparative Example 1. Fig.10 In the figure, the vertical axis represents volume resistivity [Ω·cm]. Figure 1As shown, it can be seen that the volume resistivity of the bioelectrode of Example 1 using the mixed silver powder 3 and the bioelectrode of Example 2 using the mixed silver powder 4 is not significantly different from the volume resistivity of the bioelectrode of Comparative Example 1 using silver powder (pure silver particles) directly, and the addition of fumed silica has no significant effect on the conductivity of the bioelectrode just after production. It should be noted that, when comparing the volume resistivity of the bioelectrodes of Examples 1 and 2, it can be seen that the volume resistivity of the bioelectrode of Example 2 using hydrophilic fumed silica is higher.

[0142] <Strain resistance test>

[0143] For the biological electrodes in Examples 1, 2 and Comparative Example 1, the load was applied by the following method, and the volume resistivity [Ω·cm] of each biological electrode was measured over time immediately after the load was applied. The volume resistivity of the biological electrode was measured as described above. For each biological electrode formed into a cylindrical shape with an end face diameter of 10 mm and an axial length of 5 mm, a load of 1 kgf was applied 10,000 times. It should be noted that the load application cycle was set to 5,760 times / hour. The volume resistivity measurement results are shown in Fig.11 .

[0144] Fig.11 : is a graph showing the measurement results of the volume resistivity of the biological electrodes (after the load is applied) in Examples 1 and 2 and Comparative Example 1. Fig.11 In the graph, the vertical axis represents volume resistivity [Ω·cm], and the horizontal axis represents the elapsed time [minutes] from the end of the load application. Fig.11 It is a single logarithmic chart with a logarithmic scale on the horizontal axis. Fig.11 , we can know the time-dependent change of volume resistivity from the time point when the additional load of each biological electrode ends. Fig.11 In the graph shown, the volume resistivity [Ω·cm] value of each biological electrode before the load is applied is plotted at 0.1 minutes, which is the origin of the horizontal axis (for example, refer to Fig.10 ).

[0145] like Fig.11 As shown in FIG. 1 , the volume resistivity of the biological electrode of Comparative Example 1, which directly used silver powder (pure silver particles), increased to about 5 times compared with that before the addition of the load. Although it was confirmed that the volume resistivity of the biological electrode of Comparative Example 1 showed a tendency to gradually decrease thereafter, it was more than 4 times compared with that before the addition of the load at the time point of 1 day after the end of the addition of the load, and the subsequent decrease in the volume resistivity became extremely slow, and actually stagnated at a value of more than 4 times.

[0146] On the other hand, the increase in volume resistivity of the biological electrodes of Examples 1 and 2 using a mixed silver powder composed of silver powder and fumed silica was suppressed to about 2 times compared to before the load was added. The rate of gradual decrease in volume resistivity is smaller than that of Comparative Example 1. Therefore, it can be seen that the change in resistivity of the biological electrodes of Examples 1 and 2 relative to strain becomes smaller. Therefore, for example, when these biological electrodes are used as rubber electrodes for electroencephalogram measurement, they can become electrodes whose conductivity is unlikely to deteriorate even during pressing operations and repeated use during use. In addition, from the results of the sieving rate test of the above-mentioned mixed silver powder, it can be seen that the manufacturing method using mixed silver powders 3 and 4 composed of silver powder and fumed silica has extremely good operability during operation.

[0147] Industrial Applicability

[0148] As described above, the biological electrode obtained by the manufacturing method of the present invention is particularly suitable for use in various fields such as medical measuring instruments, wearable information devices, game devices, brain-computer interfaces, medicine, nursing, welfare, autonomous driving, and electronic wiring.

[0149] Explanation of symbols

[0150] 1, 2, 3: biological electrodes;

[0151] 11: Conductive substrate;

[0152] 12: Conductive rubber body;

[0153] 13: signal transmission components;

[0154] 14: Organism;

[0155] 15: Coated wire;

[0156] 151: core wire;

[0157] 152: Covering parts;

[0158] 16: Flexible printed substrate;

[0159] 161: basement membrane;

[0160] 162: Conductor foil;

[0161] 17: Insulation layer;

[0162] 21: disc;

[0163] 22: protrusion;

[0164] 22a: protrusion;

[0165] 30: biological electrode;

[0166] 31, 32: Resistivity measurement components;

[0167] 33, 34: electrodes for measurement;

[0168] 35: Constant current power supply;

[0169] 36: Voltmeter;

[0170] 37, 38: Sample placement position;

[0171] 221a: Main body;

[0172] 222a: Front end portion.

Claims

1. A method for manufacturing a biological electrode, comprising the following steps: Adding 1 to 5 parts by mass of fumed silica to 100 parts by mass of silver powder in which silver powder having an average primary particle size of 4 μm or more and 8 μm or less is agglomerated into a three-dimensional shape, and crushing and dispersing the agglomerated silver powder using a disperser to obtain a mixed silver powder in which the silver powder and the fumed silica are dispersed; and A conductive rubber body containing silicone rubber and the mixed silver powder is formed.

2. The method for manufacturing a biological electrode according to claim 1, wherein: As the fumed silica, hydrophobic fumed silica is used.

3. The method for producing a biological electrode according to claim 1 or 2, wherein: In the step of forming the conductive rubber body, the mixed silver powder is added to a room temperature curing liquid silicone rubber to prepare a silver powder-containing paste, and the obtained silver powder-containing paste is cured to form the conductive rubber body.

4. The method for producing a biological electrode according to claim 1 or 2, wherein: In the step of forming the conductive rubber body, the conductive rubber body is formed to have a layered shape.

5. The method for producing a biological electrode according to claim 1 or 2, wherein: In the step of forming the conductive rubber body, the conductive rubber body is formed to have a brush-like shape.

6. A rubber for biological electrodes prepared by the method according to any one of claims 1 to 5, comprising at least silicone rubber, agglomerated silver powder and fumed silica, The fumed silica is contained in an amount of 1 to 5 parts by mass based on 100 parts by mass of the agglomerated silver powder. 7 . A rubber electrode, comprising the rubber for biological electrode according to claim 6 .

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