Conductive member, biological electrode, and biological signal measurement device

Abstract

The present invention provides a conductive member, a biological electrode, and a biological signal measurement device with reduced volume resistivity. The conductive member contains silicone rubber and a conductive agent, and the total content of cyclic dimethylpolysiloxane having 3 or more and 24 or less silicon atoms is 5000 ppm or less.

Description

Technical Field

[0001] The present invention relates to a conductive member, a biological electrode, and a biological signal measurement device. Background Art

[0002] In Patent Document 1, the following biological electrode is disclosed: It includes a resin layer in which particles having a surface covered with gold, silver, or platinum are dispersed.

[0003] In Patent Document 2, a biological electrode containing acrylonitrile-styrene (AS) resin, acrylonitrile-butadiene-styrene (ABS) resin, and carbon fiber is disclosed.

[0004] [Prior Art Documents]

[0005] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Laid-Open No. 2018-11931

[0007] [Patent Document 2] Japanese Patent Laid-Open No. 2018-33769 Summary of the Invention

[0008] [Problems to be Solved by the Invention]

[0009] An object of the present invention is to provide a conductive member containing silicone rubber and a conductive agent, and having a lower volume resistivity as compared with a conductive member in which the total content of cyclic dimethylpolysiloxane having a silicon number of 3 or more and 24 or less exceeds 5000 ppm.

[0010] [Technical Means for Solving the Problems]

[0011] Specific means for solving the above problems include the following forms.

[0012] <1> A conductive member containing silicone rubber and a conductive agent, and having a total content of cyclic dimethylpolysiloxane having a silicon number of 3 or more and 24 or less of 5000 ppm or less.

[0013] <2> The conductive member according to <1>, wherein the total content of cyclic dimethylpolysiloxane having a silicon number of 3 or more and 12 or less is 500 ppm or less.

[0014] <3> The conductive member according to <1> or <2>, wherein the conductive agent contains carbon black.

[0015] <4> The conductive member according to <3>, wherein the carbon black comprises two or more types of carbon black having different dibutyl phthalate (DBP) oil absorption amounts.

[0016] <5> The conductive member according to <3> or <4>, wherein the carbon black comprises a first carbon black having a DBP oil absorption amount of less than 200 cm 3 / 100 g, and a second carbon black having a DBP oil absorption amount of 200 cm 3 / 100 g or more.

[0017] <6> The conductive member according to <5>, wherein the absolute value of the difference between the DBP oil absorption amount of the first carbon black and the DBP oil absorption amount of the second carbon black is 70 cm 3 / 100 g or more and 400 cm 3 / 100 g or less.

[0018] <7> The conductive member according to any one of <1> to <6>, wherein the volume resistivity is 1 × 10 5 Ω·cm or less.

[0019] <8> The conductive member according to any one of <1> to <7>, wherein the rubber hardness is 30° or more and 60° or less.

[0020] <9> A biological electrode comprising the conductive member according to any one of <1> to <8> as a biological contact portion that contacts a living body.

[0021] <10> A biological signal measurement device comprising the biological electrode according to <9>, and measuring a biological signal.

[0022] <11> The biological signal measurement device according to <10>, wherein the biological signal is an electroencephalogram.

[0023] [Advantages of the Invention]

[0024] According to the invention of <1> or <3>, there is provided a conductive member having a lower volume resistivity as compared with a conductive member in which the total content of cyclic dimethylpolysiloxane having a silicon number of 3 or more and 24 or less exceeds 5000 ppm.

[0025] According to the invention of <2>, there is provided a conductive member having a lower volume resistivity as compared with a conductive member in which the total content of cyclic dimethylpolysiloxane having a silicon number of 3 or more and 12 or less exceeds 500 ppm.

[0026] The invention according to <4>, <5> or <6> provides a conductive member that is excellent in both low resistance and dynamic followability compared to a conductive member containing only one type of carbon black having the same DBP oil absorption amount.

[0027] The invention according to <7> provides a conductive member that is excellent in the detection accuracy of biological signals compared to a conductive member having a volume resistivity exceeding 1 × 10 5 Ω·cm.

[0028] The invention according to <8> provides a conductive member that is excellent in dynamic followability compared to a conductive member having a rubber hardness exceeding 60°.

[0029] The invention according to <9> provides a biological electrode that is excellent in the detection accuracy of biological signals compared to a case where a conductive member includes a total content of cyclic dimethylpolysiloxane having a silicon number of 3 or more and 24 or less exceeding 5000 ppm.

[0030] The invention according to <10> provides a biological signal measurement device that is excellent in the detection accuracy of biological signals compared to a case where a conductive member includes a total content of cyclic dimethylpolysiloxane having a silicon number of 3 or more and 24 or less exceeding 5000 ppm.

[0031] The invention according to <11> provides a biological signal measurement device that is excellent in the detection accuracy of brain waves compared to a case where a conductive member includes a total content of cyclic dimethylpolysiloxane having a silicon number of 3 or more and 24 or less exceeding 5000 ppm. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a schematic perspective view showing an example of the biological electrode of the present embodiment.

[0033] Figure 2 is a schematic perspective view showing another example of the biological electrode of the present embodiment.

[0034] Figure 3 is a block diagram showing an example of the biological signal measurement device of the present embodiment.

[0035] [DESCRIPTION OF SYMBOLS]

[0036] 10: Biological electrode

[0037] 12: Conductive member

[0038] 14: Substrate

[0039] 20: Holding member

[0040] 22: Biological signal processing unit

[0041] 24: Display unit

[0042] 26: Input unit

[0043] 28: Communication interface

[0044] 30: Control unit

[0045] 101: Biological signal measurement device Detailed implementation manners

[0046] Hereinafter, embodiments of the present disclosure will be described. These descriptions and examples are illustrative of the embodiments and do not limit the scope of the embodiments.

[0047] In the present disclosure, a numerical range represented by "~" means a range including the values described before and after "~" as the minimum value and the maximum value, respectively.

[0048] In the numerical ranges described step by step in the present disclosure, the upper limit value or the lower limit value described in one numerical range may also be replaced with the upper limit value or the lower limit value of other numerically described ranges. In addition, in the numerical ranges described in the present disclosure, the upper limit value or the lower limit value of the numerical range may also be replaced with the value shown in the examples.

[0049] When the embodiments are described with reference to the drawings in the present disclosure, the configuration of the embodiments is not limited to the configuration shown in the drawings. In addition, the sizes of the components in each drawing are conceptual sizes, and the relative relationship of the sizes between the components is not limited thereto.

[0050] In the present disclosure, each component may also include a plurality of corresponding substances. When the amount of each component in the composition is mentioned in the present disclosure, when there are a plurality of substances corresponding to each component in the composition, unless otherwise specified, it means the total amount of the plurality of substances present in the composition.

[0051] In the present disclosure, a plurality of particles corresponding to each component may also be included. When there are a plurality of particles corresponding to each component in the composition, unless otherwise specified, the particle size of each component means the value of the mixture of the plurality of particles present in the composition.

[0052] <Conductive member>

[0053] The conductive member of the present embodiment contains silicone rubber and a conductive agent, and the total content (mass basis) of cyclic dimethylpolysiloxane having 3 or more and 24 or less silicon atoms is 5000 ppm or less. ppm is an abbreviation for parts per million (ppm).

[0054] The cyclic dimethylpolysiloxane with a silicon number of 3 or more and 24 or less is a chemical substance represented by the following chemical formula. In the following chemical formula, n is an integer of 3 or more and 24 or less.

[0055] In the present disclosure, the cyclic dimethylpolysiloxane with a silicon number of n is referred to as "Dn cyclic dimethylpolysiloxane", and the cyclic dimethylpolysiloxane with a silicon number of 3 or more and 24 or less is referred to as "D3 - D24 cyclic dimethylpolysiloxane".

[0056] [Chemical formula 1]

[0057]

[0058] Previously, as a conductive member for a biological contact portion constituting a biological electrode, a conductive member in which a conductive agent (such as carbon black) is blended in silicone rubber has been known. Silicone rubber has excellent biological safety, but it is insulating, so a conductive agent is blended to impart conductivity.

[0059] The inventors of the present invention have found through research that the volume resistivity of the produced conductive member is higher than the designed value. Further research has revealed that by reducing the content of D3 - D24 cyclic dimethylpolysiloxane, the volume resistivity can be lowered.

[0060] To date, it has been known that an organic polysiloxane with a small molecular weight volatilizes in an electrical device and forms an insulating film containing silica on the surface of the member. However, it is speculated that the mechanism for providing a conductive member with a reduced volume resistivity in the present embodiment is not to suppress the formation of the insulating film, but rather to reduce the amount of D3 - D24 cyclic dimethylpolysiloxane contained in the conductive member itself. The reason is that when a test is conducted in an open space immediately after manufacturing the conductive member (i.e., in a state where it is difficult to form an insulating film on the surface of the conductive member), the volume resistivity of the conductive member is correlated with the content of D3 - D24 cyclic dimethylpolysiloxane.

[0061] In a conductive member containing silicone rubber and a conductive agent, if the total content of D3 - D24 cyclic dimethylpolysiloxane exceeds 5000 ppm, the volume resistivity of the conductive member is too high, and it is difficult to accurately measure biological signals. From the perspective of reducing the volume resistivity of the conductive member, the total content of D3 - D24 cyclic dimethylpolysiloxane contained in the conductive member is 5000 ppm or less, more preferably 4000 ppm or less, and still more preferably 3000 ppm or less. From the perspective of reducing the volume resistivity of the conductive member, the less the total content of D3 - D24 cyclic dimethylpolysiloxane contained in the conductive member, the more preferable.

[0062] In terms of reducing the volume resistivity of the conductive member, it can be said that the lower the total content of D3 to D24 cyclic dimethylpolysiloxane in the conductive member of the present embodiment, the more preferable, and the most preferable is 0 ppm. However, by the method of removing D3 to D24 cyclic dimethylpolysiloxane from the conductive member (details will be described later), sometimes the rubber hardness of the silicone rubber increases and the flexibility of the conductive member decreases. Therefore, it is preferable to stably implement the method for removing D3 to D24 cyclic dimethylpolysiloxane. Therefore, a certain level of D3 to D24 cyclic dimethylpolysiloxane content is allowed. The lower limit of the content of D3 to D24 cyclic dimethylpolysiloxane contained in the conductive member of the present embodiment is, for example, 0 ppm or more, more than 0 ppm, 1 ppm or more, 5 ppm or more, 10 ppm or more, 50 ppm or more, 100 ppm or more, or 500 ppm or more.

[0063] In the present embodiment, the total content (ppm) of D3 to D24 cyclic dimethylpolysiloxane is a value obtained by converting {the total amount of D3 to D24 cyclic dimethylpolysiloxane contained in the conductive member ÷ the total amount of the conductive member} into parts per million, and is based on mass.

[0064] The total amount of D3 to D24 cyclic dimethylpolysiloxane contained in the conductive member is measured by the headspace method using a gas chromatograph-mass spectrometer (manufactured by Shimadzu Corporation, GCMS-QP2020) and a non-polar column (manufactured by Restek Corporation, Rtx-1, 10157, film thickness 1.00 μm, length 60 m, inner diameter 0.32 mm). The specific determination method is as follows.

[0065] The conductive member is immersed in a solvent that dissolves the silicone rubber (for example, 10 ml of acetone containing n-tetradecane (20 μg / ml)) to dissolve the silicone rubber. A part of the liquid component is taken out and placed in a glass vial. The glass vial is sealed with a lid and heated to 190 °C in 3 minutes. The volatile components in the glass vial are introduced into the column, and D3 to D24 cyclic dimethylpolysiloxane is detected under the following conditions.

[0066] · Carrier gas type: Helium

[0067] · Carrier gas pressure: 120 kPa (constant pressure)

[0068] · Oven temperature: 40 °C (5 minutes) → (15 °C / min) → 250 °C (6 minutes) (total 25 minutes)

[0069] · Ion source temperature: 260 °C

[0070] · Interface temperature: 260 °C

[0071] A standard curve is prepared using a standard solution with a concentration changed by diluting a reference substance (D4 cyclic dimethyl polysiloxane, i.e., octamethylcyclotetrasiloxane) with ethanol. Based on the peak areas of D3, D4, …, D23, D24 that appear in the chromatogram of the sample and the standard curve of the reference substance, the amounts of D3, D4, …, D23, D24 are determined, and the total amount of D3 to D24 is calculated. Furthermore, the total content (ppm) of D3 to D24 cyclic dimethyl polysiloxane relative to the total amount of the conductive member is calculated.

[0072] From the viewpoint of reducing the volume resistivity, in the conductive member of the present embodiment, the total content of cyclic dimethyl polysiloxane having 3 or more and 12 or less silicon atoms (referred to as "D3 to D12 cyclic dimethyl polysiloxane") is preferably 500 ppm or less, more preferably 400 ppm or less, and still more preferably 300 ppm or less.

[0073] The lower limit of the content of D3 to D12 cyclic dimethyl polysiloxane contained in the conductive member of the present embodiment is, for example, 0 ppm or more, more than 0 ppm, 1 ppm or more, 5 ppm or more, 10 ppm or more, 50 ppm or more, or 100 ppm or more.

[0074] Examples of the use of the conductive member of the present embodiment include the biological contact portion of a biological electrode, an earpiece, the nose pad unit of glasses, the anti-slip portion of a hat, etc.

[0075] Hereinafter, the components, composition, physical properties, etc. of the conductive member of the present embodiment will be described in detail.

[0076] - Silicone rubber -

[0077] Examples of the rubber raw material of silicone rubber include: kneaded silicone rubber, liquid silicone rubber, room temperature curing silicone rubber, high temperature curing silicone rubber, condensation reaction type silicone rubber, addition reaction type silicone rubber, ultraviolet curing type silicone rubber, etc.

[0078] Examples of the rubber raw material of silicone rubber include: methyl silicone rubber (MQ), vinyl methyl silicone rubber (VMQ), phenyl methyl silicone rubber (PMQ), phenyl vinyl methyl silicone rubber (PVMQ), fluorovinyl methyl silicone rubber (FVMQ), etc.

[0079] According to the type of curing reaction, various additives can be added to the rubber raw material of silicone rubber. Examples of the additives include: vulcanizing agent, vulcanization accelerator, platinum catalyst for crosslinking, addition reaction controller (for example, quencher that inhibits the action of the platinum catalyst in a low temperature environment), crosslinking agent, photoacid generator, photoradical generator, etc.

[0080] - Conductive agent -

[0081] The conductive agent can be any one of an electron - conductive conductive agent, an ion - conductive conductive agent, a conductive polymer, etc. The conductive agent is preferably conductive particles. For example, carbon black; particles of metals such as gold, silver, and copper; particles of metal oxides such as titanium oxide, zinc oxide, and tin oxide; particles of barium sulfate, aluminum borate, potassium titanate, etc. Among the above - mentioned conductive agents, from the viewpoint of good affinity with silicone rubber, carbon black is preferred.

[0082] From the viewpoint of dispersibility in silicone rubber, the average primary particle diameter of the conductive agent is preferably 10 nm or more and 100 nm or less, more preferably 20 nm or more and 80 nm or less, and still more preferably 25 nm or more and 50 nm or less.

[0083] The average primary particle diameter of the conductive agent is measured by the following method.

[0084] The conductive member is cut by microtomy to obtain a specimen with a thickness of 200 nm, and the cross - section is observed using a Transmission Electron Microscope (TEM). The major axis diameters of 50 primary particles of the conductive agent are measured, and their arithmetic mean is taken as the average primary particle diameter.

[0085] With respect to 100 parts by mass of silicone rubber, the total content of the conductive agent is, for example, 40 parts by mass or more and 80 parts by mass or less.

[0086] - Carbon black -

[0087] Examples of carbon black include furnace black, thermal black, channel black, Ketjen black, acetylene black, and color black.

[0088] In order to achieve low resistance of the conductive member, carbon black with a high DBP oil absorption is more effective than carbon black with a low DBP oil absorption.

[0089] On the other hand, compared with carbon black with a high DBP oil absorption, carbon black with a low DBP oil absorption has a higher reinforcing effect on the rubber material. Therefore, if carbon black with a high DBP oil absorption is formulated, the rubber hardness of the conductive member tends to increase. Therefore, in order to improve the dynamic followability of the conductive member, carbon black with a low DBP oil absorption is more effective than carbon black with a high DBP oil absorption. In addition, by the method of removing cyclic dimethyl polysiloxane D3 to D24 from the conductive member (details will be described later), sometimes the rubber hardness of the silicone rubber increases and the flexibility of the conductive member decreases. Therefore, considering this point, it is ideal to use carbon black with a low DBP oil absorption.

[0090] Therefore, from the perspective of achieving both low resistance and good dynamic followability of the conductive member, the conductive member of the present embodiment preferably contains both carbon black with a relatively low DBP oil absorption and carbon black with a relatively high DBP oil absorption. Specifically, it preferably contains a first carbon black with a DBP oil absorption of less than 200 cm 3 / 100 g (preferably 50 cm 3 / 100 g or more and less than 200 cm 3 / 100 g), and a second carbon black with a DBP oil absorption of 200 cm 3 / 100 g or more (preferably 200 cm 3 / 100 g or more and less than 500 cm 3 / 100 g).

[0091] The DBP oil absorption of carbon black is the amount (cm 3 ) of dibutyl phthalate (DBP) absorbed by 100 g of carbon black, and is a value defined by American Society Testing and Materials (ASTM) D2414-6TT.

[0092] Regarding the first carbon black and the second carbon black, from the perspective of achieving both low resistance and good dynamic followability of the conductive member, the absolute value of the difference in DBP oil absorption between the two

[0093] is preferably 70 cm 3 / 100 g or more and 400 cm 3 / 100 g or less,

[0094] more preferably 100 cm 3 / 100 g or more and 350 cm 3 / 100 g or less,

[0095] even more preferably 120 cm 3 / 100 g or more and 300 cm 3 / 100 g or less.

[0096] Furthermore, it is preferably 150 cm 3 / 100 g or more and 250 cm 3 / 100 g or less.

[0097] When two or more types of the first carbon black are used in combination, the DBP oil absorption amount of the first carbon black means the weighted average obtained by weighting the DBP oil absorption amounts of the respective carbon blacks equivalent to the first carbon black using the content ratio (mass basis) of the respective carbon blacks. When two or more types of the second carbon black are used in combination, the DBP oil absorption amount of the second carbon black means the weighted average obtained by weighting the DBP oil absorption amounts of the respective carbon blacks equivalent to the second carbon black using the content ratio (mass basis) of the respective carbon blacks.

[0098] The DBP oil absorption amount of the entire carbon black contained in the conductive member (means the weighted average obtained by weighting the DBP oil absorption amounts of the respective carbon blacks using the content ratio (mass basis) of the respective carbon blacks.)

[0099] It is preferably 80 cm 3 / 100 g or more and 450 cm 3 / 100 g or less,

[0100] More preferably, it is 90 cm 3 / 100 g or more and 400 cm 3 / 100 g or less,

[0101] Furthermore, it is preferably 100 cm 3 / 100 g or more and 350 cm 3 / 100 g or less,

[0102] Furthermore, it is preferably 120 cm 3 / 100 g or more and 300 cm 3 / 100 g or less.

[0103] Examples of the first carbon black include the following carbon blacks.

[0104] · Asahi Thermal, manufactured by Asahi Carbon Co., Ltd., DBP oil absorption amount 28 cm 3 / 100 g

[0105] · Asahi #50U, manufactured by Asahi Carbon Co., Ltd., DBP oil absorption amount 63 cm 3 / 100 g

[0106] · Asahi #70L, manufactured by Asahi Carbon Co., Ltd., DBP oil absorption amount 75 cm 3 / 100 g

[0107] · #3030B, manufactured by Mitsubishi Chemical Corporation, DBP oil absorption amount 130 cm 3 / 100 g

[0108] · #3050B, manufactured by Mitsubishi Chemical Corporation, DBP oil absorption 175 cm 3 / 100 g

[0109] As the second carbon black, for example, the following carbon blacks can be mentioned.

[0110] · Asahi F-200SHS, manufactured by Asahi Carbon Co., Ltd., DBP oil absorption 220 cm 3 / 100 g

[0111] · ECP200L, manufactured by Lion Specialty Chemicals Co., Ltd., DBP oil absorption 300 cm 3 / 100 g

[0112] · EC300J, manufactured by Lion Specialty Chemicals Co., Ltd., DBP oil absorption 365 cm 3 / 100 g

[0113] · ECP600JD, manufactured by Lion Specialty Chemicals Co., Ltd., DBP oil absorption 495 cm 3 / 100 g

[0114] As the carbon black, oxidized carbon black having oxygen-containing functional groups (carboxyl group, quinone group, lactone group, hydroxyl group, etc.) formed on its surface by oxidation treatment is preferred. The oxidized carbon black can be obtained by the following methods: air oxidation method in which carbon black reacts with air in a high-temperature environment; oxidation method in which carbon black reacts with nitrogen oxides or ozone at room temperature; oxidation method in which carbon black is air-oxidized at high temperature and then ozone-oxidized at low temperature, etc.

[0115] The pH of the carbon black is preferably 2 or more and 10 or less, more preferably 5 or more and 9 or less. The pH of the carbon black is the pH of a dispersion prepared by adding 50 g of carbon black to 1000 ml of water at 20 °C and stirring, and is a value measured by the pH measurement method specified in Japanese Industrial Standards (JIS) Z8802:2011.

[0116] From the viewpoint of dispersibility in silicone rubber, the average primary particle size of the carbon black is preferably 10 nm or more and 100 nm or less, more preferably 20 nm or more and 80 nm or less, and still more preferably 25 nm or more and 50 nm or less.

[0117] The average primary particle size of the carbon black is measured by the following method.

[0118] The conductive member was cut by microtomy to obtain a specimen with a thickness of 200 nm, and the cross-section was observed using a transmission electron microscope (TEM). The major axis diameters of 50 primary particles of carbon black were measured, and their arithmetic mean was taken as the average primary particle diameter.

[0119] From the viewpoint of achieving both low resistance and dynamic followability of the conductive member, the total content of carbon black is preferably 40 parts by mass or more and 80 parts by mass or less, more preferably 50 parts by mass or more and 70 parts by mass or less, relative to 100 parts by mass of silicone rubber.

[0120] From the viewpoint of achieving both low resistance and dynamic followability of the conductive member, the content of the second carbon black is preferably 10 parts by mass or more and 30 parts by mass or less, more preferably 15 parts by mass or more and 25 parts by mass or less, relative to 100 parts by mass of silicone rubber.

[0121] The content of the second carbon black is, for example, 10 mass% or more and 80 mass% or less, 15 mass% or more and 75 mass% or less, 20 mass% or more and 70 mass% or less, 25 mass% or more and 65 mass% or less, relative to the total of the first carbon black and the second carbon black.

[0122] -Other additives-

[0123] Examples of other additives include: blowing agents, flame retardants, antioxidants, ultraviolet absorbers, foam stabilizers, fillers (such as silica, calcium carbonate), coupling agents (added, for example, for the purpose of improving the dispersibility of carbon black), colorants, and the like.

[0124] -Manufacturing method of the conductive member-

[0125] The manufacturing method of the conductive member of the present embodiment is not particularly limited. The conductive member of the present embodiment is manufactured, for example, by putting a rubber compound containing a silicone rubber raw material, a conductive agent, and other additives into a mold and heating it.

[0126] The cyclic dimethylpolysiloxanes D3 to D24 contained in the silicone rubber can be removed by heating the silicone rubber to volatilize them. Therefore, the manufacturing method of the conductive member of the present embodiment preferably includes: a vulcanization step for hardening the silicone rubber raw material; and a heating step for removing the cyclic dimethylpolysiloxanes D3 to D24 from the hardened silicone rubber.

[0127] The vulcanization step is, for example, a step of heating the rubber compound placed in the mold. The heating temperature and heating time in the vulcanization step are selected according to the type of the hardening reaction of the silicone rubber raw material and the composition of the silicone rubber raw material.

[0128] For the heating process of removing cyclic dimethylsiloxanes D3 - D24 from the self - cured silicone rubber, it is preferable to set the heating conditions according to the thickness of the silicone rubber. In order to remove cyclic dimethylsiloxanes D3 - D24, the thicker the silicone rubber, the higher the heating temperature or the longer the heating time is preferably. On the other hand, there is a tendency that the higher the heating temperature or the longer the heating time, the harder the silicone rubber becomes. Therefore, it is preferable to set the heating conditions so as not to impair the dynamic followability of the silicone rubber. As examples of the heating temperature, 100°C - 300°C, 150°C - 250°C can be cited. The heating temperature can be constant or variable. As examples of the heating time, 1 hour - 14 hours, 3 hours - 12 hours can be cited.

[0129] In order to promote the volatilization of cyclic dimethylsiloxanes D3 - D24, the heating process can also be carried out under reduced pressure. In order to inhibit the attachment of the volatilized cyclic dimethylsiloxanes D3 - D24 to the surface of the conductive member, it is also preferable to carry out the heat treatment while evacuating the gas in the heating furnace using a vacuum pump.

[0130] Shot blasting, sand blasting, liquid spraying and other spraying treatments can also be performed on the surface of the conductive member after the heat treatment.

[0131] - Physical property values of the conductive member -

[0132] The conductive member of the present embodiment is applicable to the biological contact portion of a biological electrode for measuring a weak potential inside a living body through an electrode provided on the surface of the living body. The ideal physical property values when applying the conductive member of the present embodiment to the biological contact portion of a biological electrode are as follows.

[0133] From the viewpoint of reducing resistance, the volume resistivity of the conductive member is preferably 1×10 5 Ω·cm or less, more preferably 1×10 4 Ω·cm or less, and still more preferably 1×10 3 Ω·cm or less.

[0134] The volume resistivity of the conductive member is a value obtained by the following measurement method.

[0135] For a sheet-shaped conductive member, in accordance with JIS K6911:1995, using a measurement jig (R12702A / B Resistivity Chamber, manufactured by Advantest Corporation) and a high-resistance meter (R8340A Digital Ultra-High Resistance / Microammeter, manufactured by Advantest Corporation), a voltage adjusted such that the electric field (applied voltage / specimen thickness) becomes 1000 V / cm is applied for 30 seconds, and then the current value is read and calculated using the following formula.

[0136] Volume resistivity (Ω·cm) = 19.63 cm 2 × Applied voltage (V) / (Current value (A) × Specimen thickness (cm))

[0137] From the viewpoint of dynamic followability, the rubber hardness of the conductive member is preferably 20° or more and 80° or less, more preferably 30° or more and 60° or less, and still more preferably 35° or more and 55° or less.

[0138] Here, the rubber hardness is the Shore A hardness. The Shore A hardness is read as the value at 15 seconds of measurement time using a Type A durometer in accordance with JIS K6253-3:2012.

[0139] From the viewpoint of the adhesion to the biological surface, the surface roughness of the biological contact surface in the conductive member is preferably 5 μm or more and 50 μm or less, more preferably 10 μm or more and 40 μm or less.

[0140] Here, the surface roughness is the ten-point mean roughness Rz specified in JIS B0601:1994. The ten-point mean roughness Rz is measured using a surface roughness measuring machine (Surfcom 1400A manufactured by Tokyo Seimitsu Co., Ltd.) under the conditions of a cut-off of 0.8 mm, a measurement length of 4.0 mm, and a traverse speed of 0.3 mm / sec. The arithmetic mean of the ten-point mean roughness Rz at three places is taken as the surface roughness of the biological contact surface.

[0141] <Biological Electrode>

[0142] The biological electrode of the present embodiment includes the conductive member of the present embodiment as a biological contact portion that contacts the organism. In the biological electrode of the present embodiment, as long as at least the biological contact portion that contacts the organism is the conductive member of the present embodiment, the entire electrode may also be the conductive member of the present embodiment.

[0143] The biological electrode of the present embodiment is applicable to an electrode of a biological measurement device for measuring biological signals such as electroencephalogram, heart rate, and pulse. Specifically, the biological electrode is applicable to, for example: 1) a biological electrode for electroencephalogram measurement inserted into the external auditory canal; 2) a biological electrode for electroencephalogram measurement hung on the auricle; 3) a biological electrode for electroencephalogram measurement provided on the forehead or the entire head; 4) a biological electrode for pulse measurement or heart rate measurement provided on the arm, foot, chest, or abdomen, etc.

[0144] The biological electrode of the present embodiment has, for example, a sheet-like shape. The sheet-like biological electrode is, for example, a structure including only the conductive member of the present embodiment (that is, a structure that is entirely the conductive member of the present embodiment, Figure 1 ), or a structure having a substrate and the conductive member of the present embodiment disposed on the substrate (that is, a structure having the conductive member of the present embodiment and other members). In Figure 1 , 10 represents the biological electrode, and 12 represents the conductive member.

[0145] The shape of the biological electrode of the present embodiment is not limited to sheet-like. The shape of the biological electrode of the present embodiment can be selected according to the use. The shape of the biological electrode of the present embodiment can be a structure including a substrate and a plurality of protruding conductive members disposed on the substrate ( Figure 2 ). In Figure 2 , 10 represents the biological electrode, 12 represents the conductive member, and 14 represents the substrate.

[0146] <Biological signal measurement device>

[0147] The biological signal measurement device of the present embodiment is a device for measuring biological signals and includes the biological electrode of the present embodiment.

[0148] Since the biological electrode of the present embodiment has a low resistance, the biological signal measurement device of the present embodiment has excellent measurement accuracy and is thus suitable for an electroencephalogram measurement device for measuring electroencephalogram.

[0149] The biological signal measurement device of the present embodiment is, for example: 1) an electroencephalogram measurement device including a biological electrode inserted into the external auditory canal; 2) an electroencephalogram measurement device including a biological electrode hung on the auricle; 3) an electroencephalogram measurement device including a biological electrode provided on the forehead or the entire head; 4) a pulse measurement device or a heart rate measurement device including a biological electrode provided on the arm, foot, chest, or abdomen, etc.

[0150] The biological signal measurement device of the present embodiment has, for example, Figure 3The configuration shown. The biological signal measurement device 101 includes: a biological electrode 10; a holding member 20 that holds the biological electrode 10; a biological signal processing unit 22 that processes biological signals (such as signals of electroencephalogram, pulse, heart rate, etc.) obtained by the biological electrode 10; a display unit 24 that displays various information including information related to the biological signal; an input unit 26 that inputs operation information, etc. to the biological signal measurement device 101; a communication interface 28 that sends the processed signal to an external device; and a control unit 30 that controls each part of the biological signal measurement device 101.

[0151] The holding member 20 is a member having a shape corresponding to uses such as an electroencephalogram measurement use inserted into the external auditory canal, an electroencephalogram measurement use hung on the auricle, an electroencephalogram measurement use provided on the forehead or the entire head, and a pulse measurement use or a heart rate measurement use provided on the arm, foot, chest, or abdomen.

[0152] The biological signal processing unit 22 includes various processing circuits such as a signal amplification circuit, for example.

[0153] The display unit 24 includes a liquid crystal display, for example. The display unit 24 may also adopt a touch screen method and function as the input unit 26.

[0154] The input unit 26 includes various input devices such as a pointing device (mouse, etc.), a keyboard, and buttons.

[0155] The communication interface 28 is an interface for communicating with an external device (a personal computer or a mobile terminal for biological signal measurement), and uses standards such as Ethernet (registered trademark), fiber distributed data interface (FDDI), and Wi-Fi (registered trademark), for example.

[0156] Although not shown, the control unit 30 includes a Central Processing Unit (CPU), a Read Only Memory (ROM), a Random Access Memory (RAM), a memory, and an input / output interface (I / O), and each component is connected via a bus so as to be communicable with each other.

[0157] The CPU is the central processing unit, which is used to execute various programs or control each part. That is, the CPU reads a program from the ROM or the memory and uses the RAM as the working area to execute the program. The CPU controls the various components and performs various arithmetic processes according to the program recorded in the ROM or the memory. The ROM stores various programs and various data. The RAM temporarily stores programs or data as the working area. The memory includes a hard disk drive (HDD), a solid state drive (SSD), or a flash memory, and stores various programs and various data including the operating system.

[0158] The configuration of the biological signal measuring device of the present embodiment is not limited, and a configuration corresponding to the biological signal of the measurement object can be adopted. The biological signal measuring device may also be a terminal device that only sends the measured biological signal to an external device without displaying information related to the measured biological signal.

[0159] Examples

[0160] Hereinafter, the embodiments of the invention will be described in detail by way of examples, but the embodiments of the invention are not limited by any of the above examples.

[0161] <Example 1>

[0162] The following materials were mixed using a pressure kneader to produce a base compound.

[0163]

[0164] 1.5 parts by mass of a curing agent C-8A (manufactured by Shin-Etsu Chemical Co., Ltd.) was added to the base compound to obtain a rubber compound. The rubber compound was placed in a mold with a thickness of 2 mm and heated at 165 °C for 15 minutes (vulcanization process), and then heated at 200 °C for 8 hours (heating process for removing D3 - D24 cyclic dimethylpolysiloxane) to obtain a rubber sheet. The rubber sheet was cut into a square with a side length of 50 mm to be used as a biological electrode.

[0165] <Examples 2 to 14, Comparative Examples 1 to 2>

[0166] Except for changing the temperature and time of the heating process for removing D3 - D24 cyclic dimethylpolysiloxane (the "additional heating temperature" and "additional heating time" recorded in Table 1), or changing the type and amount (parts by mass) of carbon black as recorded in Table 1, rubber sheets were obtained in the same manner as in Example 1 to be used as biological electrodes.

[0167] <Performance Evaluation>

[0168] -Measurement of physical property values-

[0169] For the rubber sheets of each example and comparative example, the content of cyclic dimethylpolysiloxane (ppm), volume resistivity (Ω·cm), and rubber hardness (Shore A hardness, °) were measured using the measurement methods described above.

[0170] -Measurement of voltage waveform-

[0171] An experiment for measuring the simulated brain wave was conducted as follows.

[0172] A function generator (33120A manufactured by Hewlett-Packard, a 15 MHz function / arbitrary waveform generator) and a frequency measuring device were prepared.

[0173] First, for the purpose of obtaining a reference voltage waveform, the output side of the function generator was connected to the input side of the frequency measuring device without passing through the biological electrode. At the time of the connection, two crocodile clip cables with a total length of 10 cm were connected and used. An AC voltage signal of 10 μV / 10 Hz was sent from the function generator, the voltage waveform was measured using the frequency measuring device, and the voltage waveform data was output to a personal computer (PC). The average value obtained by averaging the peak-to-peak values of one cycle of 50 cycles was calculated (this average value is referred to as "Rpp").

[0174] Next, a biological electrode (rubber sheet) was placed between the two crocodile clip cables, and the function generator and the frequency measuring device were connected via the biological electrode (that is, the connection order was set as function generator - crocodile clip cable - biological electrode - crocodile clip cable - frequency measuring device). An AC voltage signal of 10 μV / 10 Hz was sent from the function generator, the voltage waveform was measured using the frequency measuring device, and the voltage waveform data was output to the PC. The average value obtained by averaging the peak-to-peak values of one cycle of 50 cycles was calculated (this average value is referred to as "Spp").

[0175] Then, the ratio of the difference was calculated by the following formula and classified into A to D.

[0176] Formula… |Rpp - Spp| ÷ Rpp × 100 (%)

[0177] A (◎): The ratio of the difference is 0.5% or less.

[0178] B (○): The ratio of the difference exceeds 0.5% and is 1.0% or less.

[0179] C(△): The ratio of the difference exceeds 1.0% and is 1.5% or less.

[0180] D(×): The ratio of the difference exceeds 1.5%.

[0181] The numbers in parentheses recorded in Table 1 are the values of (Rpp - Spp).

[0182] [Table 1]

[0183]

[0184] From the above results, it can be seen that the biological electrode of the present embodiment has excellent measurement accuracy of the voltage waveform compared with the biological electrode of the comparative example.

[0185] The details of the carbon black recorded in Table 1 are as follows.

[0186] · Asahi Thermal: Carbon black, manufactured by Asahi Carbon Co., Ltd., DBP oil absorption 28 cm 3 / 100 g, average primary particle size 80 nm.

[0187] · Asahi #50U: Carbon black, manufactured by Asahi Carbon Co., Ltd., DBP oil absorption 63 cm 3 / 100 g, average primary particle size 70 nm.

[0188] · #3030B: Carbon black, manufactured by Mitsubishi Chemical Corporation, DBP oil absorption 130 cm 3 / 100 g, average primary particle size 55 nm.

[0189] · FX35: Carbon black, manufactured by Denka Co., Ltd., DBP oil absorption 220 cm 3 / 100 g, average primary particle size 26 nm.

[0190] · ECP200L: Ketjenblack, manufactured by Lion Specialty Chemicals Co., Ltd., DBP oil absorption 300 cm 3 / 100 g, average primary particle size 35 nm.

[0191] · EC300J: Ketjenblack, manufactured by Lion Specialty Chemicals Co., Ltd., DBP oil absorption 365 cm 3 / 100 g, average primary particle size 39.5 nm.

[0192] · Lionite CB: Carbon black, manufactured by Lion Specialty Chemicals Co., Ltd., DBP oil absorption 378 cm 3 / 100g, average primary particle size 28 nm.

[0193] · HS500: Carbon black, manufactured by Asahi Carbon Co., Ltd., DBP oil absorption 500 cm 3 / 100g, average primary particle size 38 nm.

Claims

1. A conductive member contains silicone rubber and a conductive agent, and the total content of cyclic dimethylpolysiloxane with a silicon number of 3 or more and 24 or less is 5000 ppm or less. The conductive agent contains two or more types of carbon blacks with different dibutyl phthalate oil absorption amounts, and the carbon black contains a first carbon black with a dibutyl phthalate oil absorption amount of less than 200 cm 3 / 100 g, and a second carbon black with a dibutyl phthalate oil absorption amount of 200 cm 3 / 100 g or more. Based on 100 parts by mass of silicone rubber, the total content of carbon black is 50 parts by mass or more and 70 parts by mass or less. Based on 100 parts by mass of silicone rubber, the content of the second carbon black is 15 parts by mass or more and 25 parts by mass or less. Based on 100 parts by mass of silicone rubber, the content of the first carbon black is 25 parts by mass or more and 55 parts by mass or less.

2. The conductive member according to claim 1, wherein, the total content of cyclic dimethylpolysiloxane with a silicon number of 3 or more and 12 or less is 500 ppm or less.

3. The conductive member according to claim 1 or 2, wherein, The absolute value of the difference between the dibutyl phthalate absorption of the first carbon black and the dibutyl phthalate absorption of the second carbon black is 70 cm 3 / 100 g or more and 400 cm 3 / 100 g or less.

4. The conductive member according to claim 1 or 2, wherein, The volume resistivity is 1×10 5 Ω·cm or less.

5. The conductive member according to claim 1 or 2, wherein, the rubber hardness is 30° or more and 60° or less.

6. A biological electrode includes the conductive member according to any one of claims 1 to 5 as a biological contact portion that contacts a living body.

7. A biological signal measurement device includes the biological electrode according to claim 6 and measures a biological signal.

8. The biological signal measurement device according to claim 7, wherein, the biological signal is an electroencephalogram.

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