JP2006280735A - Biomedical electrode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biomedical electrode used for devices such as an electrocardiograph, an electromyograph, and an electroencephalograph, with high sensitivity of detection to bioelectric signals and high speed of detection, and excellent in the reversibility of the electrode potential. <P>SOLUTION: The biomedical electrode is characterized by a conductive electrode substrate, silver carried on the electrode substrate, and a mixture of silver chloride and boron oxide. The mixture further includes at least one of platinum, indium oxide, ruthenium oxide, silver oxide and silver sulfide. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a living body electrode for detecting a weak electric signal generated from a living body, such as a potential, in devices such as an electrocardiograph, an electromyograph, and an electroencephalograph which are frequently used in medical diagnosis and the like.

  The bioelectric signal detection electrode currently used in the medical field includes a reusable electrode made of a metal powder, a paste of silver powder and silver chloride powder, and printing on a conductive electrode substrate. There is a disposable electrode provided. When measuring an electrocardiogram or an electroencephalogram, the electrical signal from the living body is extremely weak, about several mV, and in order to detect such a weak electrical signal from the living body, the electrode potential is stable and the electrode impedance Is required to be small and no noise voltage is generated. Specifically, the standard for disposable electrocardiogram examination electrodes (AAMI-EC12: Association for the Advancement of Medical Instrumentation EC-12) established by the American National Standards Institute (ANSI) Electrode gel or electrolyte cream is applied between the electrode and the electrode surface, or a pair of electrodes is applied. (1) A 100 μA direct current is applied for 1 minute, and a voltage value 1 minute after shutting off is an offset voltage of 100 mV or more. (DCO: Direct Current Offset voltage), (2) 10 Hz, 100 μAp-p (Ap-p: (maximum current value−minimum current value) of AC) The average value of the impedance when applied does not exceed 2 KΩ (ACZ: Alternate Current impedance, impedance is denoted as Z), (3) Charge / discharge of 200 V of the absolute value of the polarization voltage of the pair of electrodes is four times. It is required not to exceed 100 mV after each 5 seconds. In order to satisfy the characteristics of these three items, it is important that the electrode exhibits an electrode reaction with a good reversibility, and a silver-silver chloride electrode is the most suitable as a biological electrode showing an electrode reaction with a good reversibility. Known as.

  As a method for producing a silver-silver chloride electrode, for example, (1) a method of electrochemically treating silver foil to form a thin surface layer of silver chloride on the silver foil (anodic oxidation method), (2) silver particles and After compressing the mixed powder of silver chloride particles, a method of forming a pellet-type electrode by heating and sintering (sintering method), (3) a method of printing or applying a silver-silver chloride paste on a conductive substrate ( Paste method) (see, for example, Patent Document 1).

However, the silver-silver chloride electrode produced by the method as described above has an extremely high electrical resistance of silver chloride, and the thick silver chloride-containing layer increases the impedance of the silver-silver chloride electrode. In other words, the bioelectric signal is attenuated at a circuit portion in contact with the signal line, and the detection sensitivity of the bioelectric signal is lowered. On the other hand, if the silver chloride-containing layer is made thin in order to reduce the impedance of the silver-silver chloride electrode, the silver-silver chloride electrode potential becomes unstable and the reversibility of the silver-silver chloride electrode potential becomes worse. This causes problems such as a decrease in detection speed.
JP-A-5-176903

  An object of the present invention is to provide a biomedical electrode that has high bioelectric signal detection sensitivity, high detection speed, and excellent reversibility of electrode potential.

  According to the present invention, there is provided a biological electrode comprising a conductive electrode substrate and a mixture of silver, silver chloride and boron oxide supported on the electrode substrate.

  Hereinafter, the biological electrode of the present invention will be described in more detail.

  Examples of the electrode substrate in the present invention include silver, titanium, copper, nickel, cobalt, tin, and the like, alloys based on these metals, stainless steel, carbon fibers, conductive resins such as conductive resins, or What provided the thin layer of this electroconductive support body etc. on the nonelectroconductive support body (plastic etc.) can be used. The surface of the electrode substrate may be roughened in advance.

  For example, in the case of an electrode substrate made of titanium or a titanium alloy (hereinafter referred to as a titanium substrate), the surface can be roughened by pretreatment by the method described below.

  First, after degreasing the surface of the titanium substrate according to a conventional method, for example, washing with alcohol and / or electrolysis in an alkaline aqueous solution, the hydrogen fluoride concentration is in the range of 1 to 20% by weight, particularly 5 to 10% by weight. By treating with hydrofluoric acid or a mixed acid of hydrogen fluoride and other acids such as nitric acid or sulfuric acid, the oxide film on the surface of the titanium substrate is removed and the grain boundaries of the titanium grain boundaries are roughened. The acid treatment can be performed at a temperature of from room temperature to about 40 ° C. for a few minutes to a dozen minutes depending on the surface condition of the titanium substrate. A blasting process may be used in combination in order to sufficiently roughen the surface.

  The surface of the titanium substrate treated in this way is brought into contact with concentrated sulfuric acid to roughen the inner surface of the titanium crystal grain boundary in a protruding manner and to form a thin film of titanium hydride on the surface of the titanium substrate. Concentrated sulfuric acid to be used generally has a concentration of about 40 to 80% by weight, preferably about 50 to 60% by weight, and this concentrated sulfuric acid has a small amount of sodium sulfate or the like for the purpose of stabilizing the treatment if necessary. Or a sulfate thereof may be added.

  The shape of the electrode substrate is not particularly limited as long as it can contact a living body and stably catch a weak bioelectric signal. For example, a flat plate shape, a curved plate shape, a perforated plate shape, a rod shape, It can have a shape such as a plate net.

  According to the present invention, a mixture of silver, silver chloride and boron oxide is supported on the surface of the electrode substrate as described above. Examples of the supporting method include a method of pasting a mixture of silver powder, silver chloride powder and boron-containing powder and printing or applying the mixture on an electrode substrate (pasting method), silver powder, silver chloride powder and boron-containing powder. A method of forming a pellet-type electrode by compressing the mixture and then sintering by heating (pelletizing method) can be used.

  In the pasting method, for example, silver powder, silver chloride powder and boron-containing powder are mixed with an organic solvent to prepare a paste, and this paste is screen-printed or roller-coated on an electrode substrate, and then in an oxygen-containing atmosphere. For example, it can be performed by heat treatment in air. The heat treatment temperature is preferably about 300 to about 600 ° C., particularly about 350 to about 450 ° C. The organic solvent can be used without any particular limitation as long as it can uniformly disperse silver powder, silver chloride powder and boron-containing powder in an oxygen-containing atmosphere. Specifically, for example, Examples include terpineol, ethylene glycol, and liquid paraffin. Among these, terpineol is preferable. In the present specification, the “paste” includes a liquid from a low viscosity to a clay-like high viscosity.

  Moreover, the pelletizing method is, for example, forming a pellet by pressing a mixture of silver powder, silver chloride powder and boron-containing powder under a load of 1 to 1.5 MPa using a pellet forming machine, for example, It can be carried out by placing on an electrode substrate and heat-treating in an oxygen-containing atmosphere. The heat treatment temperature is preferably about 300 to about 600 ° C., particularly about 350 to about 450 ° C.

  The boron-containing powder used in the pasting method and pelletizing method is decomposed by heat treatment in an oxygen-containing atmosphere to generate boron oxide, and substantially forms a solid decomposition product other than boron oxide. What is not performed is preferable, and specific examples include boric acid and ammonium borate. Among these, boric acid is preferable.

  The particle size of the silver powder, silver chloride powder and boron-containing powder used in the pasting method and pelletizing method is not strictly limited, but is usually in the range of 1 μm to 500 μm, particularly 10 μm to 100 μm. Those having an average particle size are preferred.

Thus, a biomedical electrode in which a mixture of silver, silver chloride and boron oxide is supported on a conductive electrode substrate is obtained. The relative proportions of silver, silver chloride and boron oxide supported on the electrode substrate in the electrode are not strictly limited and can vary over a wide range, but the total amount of silver, silver chloride and boron oxide In general, silver is 30-50 mol%, especially 35-46 mol%, silver chloride is 40-59 mol%, especially 45-56 mol%, and boron oxide (as BO _x ) is 1-50 mol%, especially 2 A range of ˜20 mol% is preferable.

  Further, if necessary, the mixture of silver, silver chloride and boron oxide can include at least one conductive powder of carbon, platinum, iridium oxide, ruthenium oxide, silver oxide and silver sulfide, thereby The stability of the electrode characteristics can be improved.

  Such a conductive powder can be mixed in the pelletizing mixture prior to the paste preparation stage or pressure forming. The blending amount is usually 0.1 to 0.5 mg, particularly preferably 0.2 to 0.3 mg, based on the total amount of silver, silver chloride and boron oxide. May have an average particle size in the range of usually 1 to 500 μm, preferably 10 to 100 μm.

  Platinum, iridium oxide, and ruthenium oxide are decomposed by heat treatment in an oxygen-containing atmosphere to produce these substances, and other than these substances, precursor forms that do not form solid decomposition products, for example, chloride It can be mixed in the paste or pelletizing mixture in the form of platinic acid, iridium chloride, ruthenium chloride or the like.

  The biomedical electrode provided by the present invention has high bioelectric signal detection sensitivity, high detection speed, and excellent reversibility of the electrode potential. An electrocardiograph, electromyograph, It is extremely useful as a biological electrode for devices such as electroencephalographs.

  Hereinafter, the present invention will be described more specifically with reference to examples.

Example 1
A titanium substrate having t = 0.5 mm, L = 20 mm and W = 10 mm was degreased by washing with ethanol, immersed in hydrofluoric acid (10% by weight) for 30 seconds, washed thoroughly, and then heated with sulfuric acid (120 ° C. , 50 wt.%) For 60 seconds and then thoroughly washed twice to remove the oxide film on the surface of the titanium substrate and roughen the titanium crystal grain boundary unit to produce an electrode substrate A. .

On the other hand, silver powder, silver chloride powder, and boric acid powder were weighed 5.0 g, 9.0 g, and 0.5 g, respectively, and a mixture of 40 mol%: 53 mol%: 7 mol% was prepared as Ag: AgCl: BO _x . . Further, 2.0 g of terpineol was added and sufficiently kneaded to prepare paste A.

  A paste A is screen-printed on the electrode substrate A using a screen of t = 0.5 mm L = 10 mm and W = 10 mm, dried in the air for 30 minutes, and then heat-treated at 400 ° C. in the air for 30 minutes. Example electrode 1 was prepared in which a mixture layer of silver, silver chloride and boron oxide was formed on the surface of the substrate.

Example 2
Silver powder, silver chloride powder, and boric acid powder were weighed 4.7 g, 9.0 g, and 0.2 g, respectively, and a mixture of 40 mol%: 57 mol%: 3 mol% as Ag: AgCl: BO _x was prepared. 2.0 g of terpineol was added and sufficiently kneaded to prepare paste B.

  Example electrode 2 in which a mixture layer of silver, silver chloride and boron oxide was formed on the surface of the electrode substrate was produced in the same manner as in Example 1 except that paste B was used instead of paste A.

Example 3
4.0 g, 6.0 g, and 0.8 g of silver powder, silver chloride powder, and boric acid powder were weighed, and a mixture of 40 mol%: 46 mol%: 14 mol% was prepared as Ag: AgCl: BO _x , and 2.0 g of terpineol was added and sufficiently kneaded to prepare paste C.

  Example electrode 3 in which a mixture layer of silver, silver chloride and boron oxide was formed on the surface of the electrode substrate was produced in the same manner as in Example 1 except that paste C was used instead of paste A.

Example 4
A carbon sheet (manufactured by Toray Industries, Inc., TGP-H-060F, ^t 0.2 mm, ^L 20 mm, ^W 10 mm, porosity 83%) is prepared as an electrode substrate B, and the electrode substrate B is used in place of the electrode substrate A Example electrode 4 in which a mixture layer of silver, silver chloride and boron oxide was formed on the surface of the electrode substrate was produced in the same manner as Example 1.

Example 5
An electrode base C having t = 0.5 mm, L = 20 mm, and W = 10 mm is prepared using a silver alloy composed of 92.5 wt% silver-7.5 wt% copper, and the electrode base C is used instead of the electrode base A. Example electrode 5 in which a mixture layer of silver, silver chloride and boron oxide was formed on the surface of the electrode substrate was produced in the same manner as Example 1 except for the above.

Example 6
Silver powder, silver chloride powder, boric acid powder and carbon powder (manufactured by Cabot, Vulcan XC-72R) were weighed 4.3 g, 7.5 g, 0.4 g and 0.01 g, respectively, Ag: AgCl: H ₃ BO ₃ : A mixture having a ratio of 40 mol%: 53 mol%: 6 mol%: 1 mol% as C was prepared. Furthermore, 2.0 g of terpineol was added and sufficiently kneaded to prepare paste B.

  Example electrode 6 in which a mixture layer of silver, silver chloride, boron oxide and carbon was formed on the surface of the electrode substrate was produced in the same manner as in Example 1 except that paste B was used instead of paste A.

Example 7
Weigh 4.3g, 7.5g, 0.4g and 0.6g of silver powder, silver chloride powder, boric acid powder and chloroplatinic acid hexahydrate, respectively, add 12.0g of butanol and mix well Then, a mixture of Ag: AgCl: BO _x : Pt in a ratio of 40 mol%: 53 mol%: 6 mol%: 1 mol% was prepared, and further 2.0 g of terpineol was added and sufficiently kneaded to prepare paste C.

  Example electrode 7 in which a mixture layer of silver, silver chloride, boron oxide and platinum was formed on the surface of the electrode substrate was produced in the same manner as in Example 1 except that paste C was used instead of paste A.

Example 8
Weigh 4.3g, 7.5g, 0.4g and 0.6g of silver powder, silver chloride powder, boric acid powder and chloroiridate hexahydrate, respectively, and add 12.0g of butanol and mix well Then, a mixture of Ag: AgCl: BO _x : IrO _{x in} a ratio of 40 mol%: 53 mol%: 6 mol%: 1 mol% was prepared, and further 2.0 g of terpineol was added and sufficiently kneaded to prepare paste D.

  Example electrode 8 in which a mixture layer of silver, silver chloride, boron oxide and iridium oxide was formed on the surface of the electrode substrate was produced in the same manner as in Example 1 except that paste D was used instead of paste A.

Example 9
Silver powder, silver chloride powder, boric acid powder, and ruthenium chloride were weighed 4.3 g, 7.5 g, 0.4 g, and 0.3 g, respectively, but 12.0 g of butanol was added and mixed well, and Ag: AgCl A mixture of 40 mol%: 53 mol%: 6 mol%: 1 mol% in the ratio of: BO _x : RuO _x was prepared, and 2.0 g of terpineol was further added and sufficiently kneaded to prepare paste E.

  Example electrode 9 in which a mixture layer of silver, silver chloride, boron oxide and ruthenium oxide was formed on the surface of the electrode substrate was produced in the same manner as in Example 1 except that paste E was used instead of paste A.

Example 10
A silver plate ( ^t 0.5 mm × ^W 10 mm × ^L 20 mm) was degreased with ethanol to prepare an electrode substrate D.

Silver powder, silver chloride powder, boric acid powder, and silver oxide powder were weighed 4.3 g, 7.5 g, 0.4 g, and 0.1 g, respectively, and 12.0 g of butanol was added and mixed well. Ag: A mixture of AgCl: BO _x : AgO _{x in} a ratio of 40 mol%: 53 mol%: 6 mol%: 1 mol% was prepared, and 2.0 g of terpineol was further added and sufficiently kneaded to prepare paste F.

  A mixture layer of silver, silver chloride, boron oxide and silver oxide is formed on the surface of the electrode substrate in the same manner as in Example 1 except that paste F is used instead of paste A and electrode substrate D is used instead of electrode substrate A. Example electrode 10 was prepared.

Example 11
Silver powder, silver chloride powder, boric acid powder and silver sulfide powder were weighed 4.3 g, 7.5 g, 0.4 g, and 0.1 g, respectively, and 12.0 g of butanol was added and mixed well. Ag: AgCl : _BO x: 40mol% as _{AgS x: 53mol%: 6mol%} : to produce a mixture of ratio of 1 mol%, further to prepare a paste G was sufficiently kneaded added terpineol 2.0 g.

  Example electrode 11 was produced in the same manner as in Example 1 except that paste G was used instead of paste A and electrode base D was used instead of electrode base A.

Example 12
Silver powder, silver chloride powder, and boric acid powder were weighed 4.3 g, 7.5 g, and 0.4 g, respectively, and mixed well to obtain a ratio of 40 mol%: 53 mol%: 7 mol% as Ag: AgCl: BO _x. Of mixture A was obtained.

  0.3 mg of the obtained mixture A was weighed and press-molded for 1 minute at a load of 1.2 MPa using a pellet molding machine to obtain pellets of t = 0.5 mm φ = 0.8 mm.

  The resulting pellet 0.3 g was placed on the electrode substrate C produced in Example 5 and heat-treated at 500 ° C. for 30 minutes in the atmosphere to form a mixture layer of silver, silver chloride and boron oxide on the surface of the electrode substrate. Example electrode 12 was produced.

Comparative Example 1
Silver powder and silver chloride powder were weighed and mixed thoroughly with 4.3 g and 7.5 g, respectively, to prepare a mixture of 43 mol%: 57 mol% as Ag: AgCl, and further 2.0 g of terpineol was added and kneaded thoroughly Thus, paste H was produced.

  A comparative electrode 1 in which a mixture layer of silver and silver chloride was formed on the surface of the electrode substrate was produced in the same manner as in Example 8 except that paste H was used instead of paste A.

Comparative Example 2
Silver powder and silver chloride powder were each weighed 4.3 g and 7.5 g and mixed well to prepare a mixture B of 43 mol%: 57 mol% as Ag: AgCl.

  A comparative example electrode 2 in which a mixture layer of silver and silver chloride was formed on the electrode substrate surface was produced in the same manner as in Example 12 except that the mixture B was used in place of the mixture A.

  Two each of Example electrodes 1 to 12 and Comparative Example electrode 1 and Comparative Example electrode 2 prepared in the above Examples and Comparative Examples were used, and about 0.4 g of keratin cream (manufactured by Fukuda Denshi Co., Ltd.) was carried on the surface of each electrode. Are applied uniformly, and the two electrodes are bonded so that the keratin cream is on the inside. Electrode pair characteristics: (1) DC 100 μA is applied for 1 minute, and the voltage value 1 minute after shutting down (hereinafter referred to as DCO) (2) Impedance value (hereinafter referred to as ACZ) when 100 μAp-p was applied at 10 Hz was measured. The results are shown in Table 1. In addition, the electrode pair characteristics after 100 electrocardiographic waveform measurements were measured for Example electrode 1, Example electrode 7, Example electrode 8, Example electrode 11 and Comparative example electrode 1, and the results are shown in Table 2. Show.

  The low DCO value of the electrode pair characteristic means that the detection speed of the repetitively generated bioelectric signal is high and the reversibility of the electrode potential is excellent, and the low ACZ value means that the detection sensitivity is high. Means.

  From the results of Table 1, it can be seen that the example electrode of the present invention is a biological electrode with low DCO and ACZ, high bioelectric signal detection sensitivity, high detection speed, and excellent reversibility of electrode potential. Recognize. Moreover, from the results in Table 2, it can be seen that the stability of the electrode characteristics of the biological electrode is improved by further adding platinum, iridium oxide or silver sulfide to the mixture of silver, silver chloride and boron oxide.

Claims (2)

  A biological electrode comprising an electrode base having conductivity and a mixture of silver, silver chloride and boron oxide supported on the electrode base.   The biological electrode according to claim 1, wherein the mixture further contains at least one of carbon, platinum, iridium oxide, ruthenium oxide, silver oxide, and silver sulfide.