JPH0456621B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a medical adhesive having excellent conductivity and adhesiveness, and a medical skin electrode using the same.

(Prior art) When using medical measurement devices such as electrocardiographs, electromyographs, electroencephalograms, and electrical skin stimulation devices, electrodes are pasted on the skin surface and these devices are connected to predetermined locations on the skin surface. An electrical connection is made. Various improvements have been made in the materials and shapes of medical skin electrodes, as well as in the means for fixing the electrodes to the skin surface. An example is shown below.

(1) The most commonly used method is to attach a metal electrode plate to the skin surface through a conductive medium such as a conductive liquid, paste, cream, or aqueous gel containing an electrolyte, but it has the following drawbacks: (1)-1 It requires skill to uniformly apply the conductive medium to the skin surface or electrode plate surface, and the application process is also complicated. It is necessary to wipe the skin surface after use; (1)-2 A fixing means such as adhesive tape is required to fix the electrode plate to the skin surface.

(1)-3 When measurements are carried out over a long period of time, the moisture contained in the conductive medium evaporates and the conductivity changes, resulting in variations in the measured values obtained.

(1)-4 In order to prevent the moisture contained in the conductive medium from evaporating during storage, it is necessary to store it in a sealed container.

(1)-5 If the fixing means loosens during measurement or if the electrode is lifted from the skin due to body movement of the person to be measured, signal transmission between the skin surface and the measuring device will be incomplete.

(1)-6 If the abrasive film of the conductive medium is thin or if there are thin parts due to uneven thickness of the abrasive film, the electrode plate may come into direct contact with the skin surface, causing burns.

(1)-7 Some components of the conductive medium may cause skin irritation or rash.

(1)-8 Depending on the electrolyte components contained in the conductive medium, excess potential on the skin surface may occur.

(2) Method (1) above, in which a sponge is impregnated and saturated with a conductive medium and a metal electrode plate is attached to the skin surface through this, is easier to operate than method (1) above. Furthermore, since it has excellent adhesion to the skin surface, it is excellent in signal transmission, and since the electrode plate does not come into contact with the skin, there is no risk of burns, but in other respects it has the same drawbacks as method (1) above. Moreover, if the pressure applied to the electrode plate by the fixing means is excessive, there is a risk that the conductive medium will ooze out from the sponge.

(3) In method (2) above, the method of using an electrode that integrates a sponge impregnated and saturated with a conductive medium, a metal electrode plate, and adhesive tape as a fixing means is an operation in which the electrode is attached to the skin surface. It is advantageous in that it is simple and the electrodes can be disposable. However, changes in conductivity due to moisture evaporation,
This method has the same drawbacks as methods (1) and (2) above in terms of skin irritation due to the conductive medium, excess potential on the skin surface due to electrolyte components, and seepage of the conductive medium from the sponge. Furthermore, since such electrodes require special packaging to prevent moisture from evaporating during storage, the product cannot be provided at a low price.

(4) In the method of (3) above, in which a natural or synthetic hydrophilic polymer containing water or an electrolyte aqueous solution is used instead of the sponge impregnated with a conductive medium, the hydrophilic polymer may be methyl cellulose, polyvinyl alcohol, polyvinyl Compounds such as pyrrolidone may be utilized. When such an electrode is used, stable measurement values can be obtained without bleeding of the conductive medium. However, the disadvantages of changes in conductivity due to moisture evaporation and excess potential on the skin surface due to electrolyte components still remain. Furthermore, when using natural hydrophilic polymers, there is a risk that microorganisms such as bacteria and mold will grow during storage. When microorganisms grow, the conductivity decreases and can cause skin irritation. If preservatives are added to prevent this, the preservatives may cause skin disorders.
In addition, the product cannot be provided at a low price because it requires special packaging to prevent moisture evaporation.
This is the same as method (3).

(5) The method of using an electrode in which a conductive adhesive layer is provided on one side of a metal electrode plate is easy to handle because the adhesive itself has conductivity, and the structure is simple. Products can be provided at low prices. The conductive adhesive used can be used mainly in the following three ways ((5)--(5)
-) prepared by

(5)- The conductive adhesive obtained by blending conductive particles such as metal or carbon with the adhesive used for patches (glass transition point (T _G ): -25℃ to -55℃) Since it does not contain any water, there is no change in conductivity due to evaporation of water. Moreover, no special packaging is required to prevent moisture evaporation. However, such adhesives and electrodes using the same have the following drawbacks.

(5)--1 The desired conductivity cannot be obtained unless a large amount of conductive particles are incorporated into the adhesive. For this reason, when a large amount of conductive particles are incorporated into an adhesive, the adhesive strength is significantly reduced.

(5)--2 When this electrode is used, electrical noise is likely to be mixed in in the voltage/current range of the biological electrode level.

(5) - In the method of obtaining a conductive adhesive by blending a water-soluble plasticizer and an electrolyte with a natural or synthetic hydrophilic polymer, the hydrophilic polymer may be polyvinyl alcohol, methyl cellulose, etc., as in the method (4) above. is used. As the water-soluble plasticizer, for example, glycerin is used, and as the electrolyte, for example, sodium chloride is used. An electrode using such a conductive adhesive is disclosed in JP-A-56-36940. Such adhesives and electrodes have the following drawbacks.

(5)--1 The conductivity of adhesives depends on the electrolyte. Electrolytes such as sodium chloride do not inherently have very high conductivity, so they need to be added in large quantities. As the proportion of electrolyte increases, the adhesive strength of the adhesive decreases.

(5)--2 A small amount of water is used to dissolve the electrolyte, but the evaporation of water changes the conductivity. Special packaging is required to prevent moisture evaporation, which makes it impossible to supply the product at a low price.

(5)--3 If natural hydrophilic polymers are used, microorganisms such as bacteria and mold may grow. If a preservative is added to prevent this, the preservative may cause skin damage.

(5)--4 Because the internal cohesive force of the adhesive is weak, so-called adhesive cracking phenomena and adhesive residue phenomena occur.
It is necessary to embed a core material in the adhesive layer to reinforce the electrode.

(5)- The method of using a polymer containing a carboxyl group and/or an alkali metal salt of a carboxyl group as a conductive adhesive has the advantage that the adhesive does not contain water, as in the method (5)- above. There is. An electrode using this is disclosed in Japanese Patent Laid-Open No. 56-36939. This adhesive and electrode also have the following drawbacks.

(5)--1 The conductivity of polymers having carboxyl groups is not originally that high. If the carboxyl group is an alkali metal salt, the conductivity will be improved, but the adhesiveness will be reduced.

(5)--2 Depending on the constitution of the person to be measured, applying an adhesive containing a carboxyl group may cause skin disorders.

(5)--3 The internal cohesive force of the adhesive is weak, resulting in adhesive cracking and adhesive residue phenomena. To prevent this, it is necessary to bury the core material.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned conventional drawbacks, and its purpose is to be able to be used in various medical measuring instruments and to be able to be applied to a predetermined place on the skin with simple operation. An object of the present invention is to provide a medical skin electrode that can be applied to the skin. Another object of the present invention is to provide a medical skin electrode in which an adhesive layer having excellent conductivity and adhesiveness is provided on the surface of the electrode plate. Still another object of the present invention is that the skin electrode can be used for:
The object of the present invention is to provide an adhesive having excellent conductivity and adhesiveness, and having the following characteristics.

(1) Adhesives that are not irritating to the skin and do not cause skin disorders due to the proliferation of microorganisms during storage; (2) Water is not an essential component of the adhesive; Adhesive that does not cause changes in conductivity; and (3) has excellent internal cohesive force, eliminating the need to embed a core material in the adhesive layer of the electrode, even if the adhesive layer is thin (usually 1.0 mm or less). Adhesive that does not cause adhesive cracking or adhesive residue.

Still another object of the present invention is to provide a medical skin electrode in which the conductive adhesive described above is provided on the surface of an electrode plate and has the following characteristics.

(1) Skin electrodes that do not peel off from the skin surface and maintain a certain level of conductivity even after long-term use; (2) Skin electrodes that do not easily allow electrical noise to enter; and (3) Skin electrodes that do not cause excessive skin surface potential. Never-before-seen skin electrodes.

(Means for Solving the Problems) The medical conductive adhesive of the present invention has a (meth)acrylamide derivative having a substituent whose terminal is a quaternary ammonium salt via an amide group; and an alkyl group. The main component is a copolymer containing an acrylic acid alkyl ester having an average carbon number of 8 or less, thereby achieving the above object. Furthermore, the medical skin electrode of the present invention includes:
A (meth)acrylamide derivative having a substituent whose end is a quaternary ammonium salt via an amide group; and a copolymer containing as a constituent an acrylic acid alkyl ester in which the average number of carbon atoms in the alkyl group is 8 or less. A conductive adhesive layer as a main component is provided on one side of the electrode plate, thereby achieving the above object.

The copolymer which is the main component of the adhesive of the present invention contains a (meth)acrylamide derivative having the following structural formula as a constituent component.

(Here, R ₁ is H or CH ₃ , R ₂ has 1 to 1 carbon atoms
The alkylene group of 6, R ₃ , R ₄ and R ₅ are CH ₃ or C ₂ H ₅ and X is Cl or Br. ) Among the compounds represented by the above structural formula, suitable examples include 3(methacrylamido)propyltrimethylammonium chloride, 3(acrylamido)propyltrimethylammonium chloride, 2(acrylamido)ethyldiethylmethylammonium chloride, 3(methacrylamido)propyltrimethylammonium chloride, and 3(methacrylamido)propyltrimethylammonium chloride. Amido)isopentyltrimethylammonium chloride, 3(methacrylamido)isopentyl-2-trimethylammonium chloride, and the like. The (meth)acrylamide derivative used in the present invention contains 15
Contained in a proportion of ~70% by weight. The (meth)acrylamide derivative is a basic element for expressing the conductivity of the copolymer, and the higher the content, the higher the conductivity of the resulting adhesive, and conversely, if the content is too low, If the content of the below-mentioned acrylic acid alkyl ester is excessive, the resulting adhesive will have low conductivity. If the (meth)acrylamide derivative is in excess, the copolymerizability with the acrylic acid alkyl ester described below will decrease, making it impossible to obtain a high molecular weight copolymer. Furthermore, since a large amount of unreacted monomer remains, the cohesive force of the adhesive decreases, causing adhesive cracking and adhesive residue phenomena. Unreacted monomers can also cause skin irritation. Furthermore, if the (meth)acrylamide derivative is in excess, the water absorption of the resulting copolymer will be too high, and as a result, conductivity will change due to moisture absorption during storage of the adhesive or when used in electrodes.

The acrylic acid alkyl ester, which is another component of the copolymer, has an alkyl group having 8 or less carbon atoms. However, acrylic acid alkyl ester is 2
A mixture of two or more species may be used, as long as the average number of carbon atoms in the alkyl group is 8 or less. The smaller the number of carbon atoms in the alkyl group, the greater the rigidity of the resulting copolymer. Therefore, a copolymer prepared using an acrylic acid alkyl ester having a short carbon chain requires the addition of a relatively large amount of the plasticizer described below. When the average carbon number of the alkyl group exceeds 8, copolymerizability with the (meth)acrylamide derivative deteriorates, and electrical conductivity decreases. Since the produced copolymer has low solubility in the solvent (alcoholic solvent), the reaction solution becomes microcolloidal, making handling inconvenient. In view of the above, butyl acrylate in which the alkyl group has 4 carbon atoms is particularly preferably used. The copolymer contains at least one component other than the (meth)acrylamide derivative.
It is prepared such that 50% by weight is acrylic acid alkyl ester. If the proportion of the acrylic acid alkyl ester is small, the resulting copolymer will not exhibit sufficient tackiness. The blending ratio of the (meth)acrylamide derivative and the acrylic acid alkyl ester is determined by the following polyfunctional monomers and other polymerizable monomers, the type and amount of the plasticizer used, and the desired tackiness of the adhesive. It is set appropriately in consideration of properties, conductivity, etc.

When copolymerization is carried out by adding a small amount of a polyfunctional monomer in addition to the above-mentioned (meth)acrylamide derivative and acrylic acid alkyl ester, the internal cohesive force of the resulting copolymer can be improved. The polyfunctional monomer refers to a monomer in which two or more (meth)acrylic acid ester groups are substituted at the molecular ends. For example, 1,6-hexane glycol dimethacrylate is preferably used. When a polyfunctional monomer is contained, crosslinking (slight crosslinking) occurs, albeit very slightly, during copolymerization, thereby increasing the internal cohesive force of the copolymer. Therefore, even if a large amount of the plasticizer described below is added, the copolymer does not become fluidized, so a pressure-sensitive adhesive with high adhesive strength can be obtained. Furthermore, during storage of the adhesive or when using an electrode using the adhesive, it does not absorb moisture and soften or flow.
Polyfunctional monomers account for 0.8 of the total polymerizable monomers during polymerization.
It is added in a proportion of not more than % by weight. If it is in excess, the resulting copolymer will have poor solubility in solvents such as alcohol and water.

Other polymerizable monomers may be copolymerized as long as they do not impair the characteristics of the copolymer of the present invention, such as electrical conductivity. Such polymerizable monomers include, for example, vinyl acetate, vinyl propionate, vinylpyrrolidone, dimethylacrylamide, diethylacrylamide, diacetone acrylamide, maleic anhydride, acrylonitrile, (meth)acrylic acid, methacrylic acid alkyl ester, Polyethylene glycol mono(meth)
There are acrylic esters, polypropylene glycol mono(meth)acrylic esters, and alkoxylalkyl (meth)acrylic esters. By appropriately selecting and containing these polymerizable monomers, it is possible to appropriately control the copolymerization reaction. By appropriately selecting the content, a copolymer having desired solubility can be obtained. These other polymerizable monomers are copolymerized so that their content is at most 40% by weight or less of the total weight.

A copolymer is obtained by subjecting the above-mentioned (meth)acrylamide derivative and acrylic acid alkyl ester, and, if necessary, a polyfunctional monomer and other polymerizable monomers to a polymerization reaction by a conventional polymerization method. Among them, solution polymerization method is preferably used.
An alcoholic solvent or the like is preferably used as the solvent, and a copolymer is produced by a radical reaction.
When a copolymer is obtained by a solution polymerization method, the above-mentioned monomer, catalyst and solvent are charged into a reactor equipped with a reflux condenser, and the reaction is carried out with stirring under an inert gas atmosphere. The reaction temperature varies depending on the type of monomer, but is usually 50 to 80°C, preferably 60 to 70°C.
As the catalyst, a commonly used azobis-based catalyst or the like is suitably used. The amount of catalyst is usually in the range of 0.2 to 0.5 mol% based on the number of moles of all monomers.
The catalyst is added to the reaction system in appropriate portions depending on the progress of the polymerization reaction. If the concentration of the reaction solution increases during the polymerization reaction and the stirring condition deteriorates, or if the reaction progresses rapidly and the reaction solution turns into a gel or there is a high possibility of a runaway reaction, an appropriate solvent is added to the reaction solution. is diluted. The concentration of monomers and the like in the reaction solution at the start of polymerization is preferably 60 to 90% by weight. The polymerization reaction is normally carried out preferably for 30 to 40 hours from the start of polymerization.

If the copolymer solution obtained in this way is applied as is, the coating film will be a tough film, but the electrical conductivity of the film will not be fully exhibited yet. However, when a suitable plasticizer is added, the copolymer becomes soft and tacky, and also becomes significantly more conductive. The internal cohesive force is also moderate and it has viscoelastic properties. In addition to water, substances that act as plasticizers include water-soluble or hydrophilic liquids such as polyhydric alcohols and polyhydric alcohol derivatives. However, as described in the prior art section, when water is used, the water evaporates from the adhesive, resulting in changes in conductivity, etc. Therefore, a plasticizer that does not contain water is suitable. Such plasticizers include high boiling water-soluble or hydrophilic liquids. For example, liquid cation interfaces such as glycerin, diglycerin, low molecular weight polyvinyl methyl ether, alkylene glycol having 4 or more carbon atoms, polyethylene glycol, polypropylene glycol, allyl alkyl alcohol, liquid polysaccharide, alkyltrimethylammonium chloride having 12 or more carbon atoms. Active agents, nonionic surfactants such as polyoxyethylene alkyl ethers or esters, fatty acid diethanolamides, sorbitan alkyl esters, sorbitan polyoxyethylene alkyl esters, etc., amphoteric surfactants such as dimethyl betaine, liquid amino acids, etc. . Among these plasticizers, glycerin and diglycerin are particularly preferably used. Two or more plasticizers may be used in combination. The amount of plasticizer varies depending on the composition of the copolymer, the type of plasticizer, the desired degree of tackiness, etc., but is usually between 20 and 140% of the copolymer.
% by weight, preferably in the range 40-80% by weight.
If a relatively hard adhesive is desired, the amount of plasticizer is reduced. If a soft adhesive is desired for attaching electrodes to hairy skin or skin with many deep wrinkles, the amount of plasticizer is increased. Care must be taken because adding too much plasticizer will increase the water absorption of the adhesive.

Plasticized copolymers also have significantly improved electrical conductivity. Although it varies depending on the composition of the copolymer, it is usually possible to add an amount of plasticizer to the copolymer to impart appropriate tackiness and at the same time to obtain appropriate conductivity.

In addition to the above-mentioned copolymer and plasticizer, the adhesive may contain a polymeric additive and the like within a range that does not impair the properties of the copolymer. As the polymer additive, a polymer soluble in alcoholic solvents is used. Examples include polyvinylpyrrolidone, vinyl acetate-vinylpyrrolidone copolymer, diacetone acrylamide-vinylpyrrolidone copolymer, partially saponified polyvinyl acetate-maleic anhydride copolymer, and vinyl acetate-maleic anhydride copolymer. , methyl vinyl ether-maleic anhydride copolymer, copolymer of 2-hydroxyethyl (meth)acrylate and (meth)acrylate, 2-hydroxypropyl (meth)acrylate and (meth)acrylic acid Examples include copolymers with esters, polyethyleneimine, methylcellulose, ethylcellulose, partially acetylated cellulose, and polyvinyl acetal. Two or more of these may be used in combination.

The above polymer additive is added for the purpose of adjusting the internal cohesive force of the adhesive. Basically, the desired internal cohesive force can be obtained by appropriately selecting the copolymer composition of the adhesive, but when it is desired to slightly change the magnitude of the internal cohesive force of an already prepared copolymer, this Polymer additives such as The polymeric additive can also be used as a mere filler, and by adding the polymeric additive, the adhesive can be provided at a low cost. Polymer additive is 20% by weight of copolymer
It can be contained in the adhesive in the following amounts: If it is in excess, the adhesiveness and conductivity of the copolymer will be impaired.

The adhesive may further contain a filler in an amount of 20% by weight or less of the copolymer. Inorganic fillers are primarily used, including zinc oxide, calcium carbonate, magnesium carbonate, silicon oxide, and calcium silicate.

The adhesive prepared in this way has sufficient electrical conductivity, but if necessary, it is also possible to further add an electrolyte to improve the electrical conductivity. Electrolytes include, for example, organic acid alkali metal salts such as sodium succinate and sodium salicylate; inorganic salts such as sodium chloride and magnesium chloride; and cationic surfactants such as octyltrimethylammonium chloride, which play a role as a plasticizer. It can also be added in conjunction with.

The conductivity of the adhesive prepared as described above is thought to be developed by the following mechanism. The quaternary ammonium salt in the side chain of the (meth)acrylamide derivative incorporated into the copolymer is easily dissociated into an ionic state. Since such quaternary ammonium salts in an ionic state are in close proximity to each other in the polymer, charge transfer occurs via the quaternary ammonium salts when a voltage is applied. Since the movement of charges occurs in a chain, a current flows. If a plasticizer such as glycerin is added to the copolymer,
Molecular chain movement of the (meth)acrylamide derivative incorporated into the copolymer becomes active. Therefore, it exhibits electrical conductivity and also has adhesive properties at the same time. The good flexibility of the molecular chain of the acrylic acid alkyl ester in the copolymer also activates the function of the (meth)acrylamide moiety having the quaternary ammonium base, and as a result, the electrical conductivity of the copolymer is improved. It is thought that it acts to increase the price.

A medical skin electrode is prepared by applying the resulting conductive adhesive layer to one side of a conductive substrate (electrode plate). For example, as shown in FIGS. 1 to 3, the skin electrode 1 of the present invention includes the conductive adhesive layer 13 provided on one side of an electrode plate 11. A release paper 14 treated with silicone or the like is pasted on the surface of the conductive adhesive layer 13 (the side that contacts the skin surface of the subject). This release paper 14 protects the conductive adhesive layer 13 and is peeled off when the skin electrode 1 is attached to the skin. A protrusion 110 is provided at one end of the electrode plate 11, and as shown in FIG.
They are electrically connected via means such as a clip. This projection 110 is covered with a suitable non-conductive sheet 15 to prevent the electrode plate 11 from coming into direct contact with the skin.

As the electrode plate 11, a conductive base material such as a metal sheet such as aluminum foil, tin foil, or nickel foil, or cloth whose surface is coated with metal is suitably used. To provide the adhesive on the surface of the electrode plate 11, for example, an organic solvent solution of the adhesive obtained by solution polymerization is cast onto a conductive substrate and dried, or an adhesive solution is poured onto the release paper 14. After spreading and drying, it may be transferred onto the surface of the electrode plate 11. The thickness of the adhesive layer 13 is 0.03mm
(30 μm) or more, preferably 0.5 to 1.5 mm. When forming a relatively thick adhesive layer with a thickness exceeding 1.5 mm, a reinforcing material may be used to maintain the entire electrode in a predetermined shape. As the reinforcing material, a coarse mesh woven fabric such as gauze is usually used and is embedded inside the adhesive layer 13.

(Function) The area of the adhesive layer on the electrode plate surface of such an electrode is 500 mm ² and the applied voltage is 100 mV at 10 Hz.
The impedance of the electrode is 8 kΩ or less when: When such electrodes with excellent conductivity are used, measurement sensitivity is improved. Since the adhesive has excellent adhesive properties, the electrode can be fixed to a predetermined skin surface without using reinforcing means for fixation, and accurate measurements can be made over a long period of time. Adhesives do not need to contain water as a plasticizer or electrolyte solvent;
The conductivity will not change due to water evaporation during use or storage of the electrode, which will not affect the measured value. Furthermore, the adhesiveness does not decrease due to water evaporation. Furthermore, since it does not contain metal powder, almost no electrical noise is detected.
Since the internal cohesive force of the adhesive is also large, a thick adhesive layer can be formed, and no reinforcing material is particularly required. When a polyfunctional monomer is added during copolymer preparation, a pressure-sensitive adhesive with even better internal cohesive strength can be obtained due to slight crosslinking. Electrodes using such adhesives do not suffer from so-called adhesive cracking or adhesive residue phenomena, regardless of the adhesive film thickness. Furthermore, since the adhesive is not a natural polymer, microorganisms will not propagate during storage and will not cause skin irritation. Since there is no need for the adhesive to contain electrolytes, excess skin potential caused by electrolytes does not occur.

(Example) The invention will now be explained with reference to examples.

Example 1 (A) Preparation of adhesive: 66.5 g (0.3
89.6 g (0.7 mol) of butyl acrylate as an acrylic acid alkyl ester and 70 g of methyl alcohol as a solvent were charged into a reaction kolben, and a polymerization reaction was carried out at 60° C. with stirring under a N ₂ stream. 4.1 g of azobisisobutyronitrile was used as a polymerization catalyst. Catalyst is 100
ml of ethyl acetate, and the solution was divided into 10 portions over 30 hours after the start of the reaction and charged into a reaction vessel. When the viscosity of the reaction solution increased, methyl alcohol was added as appropriate. The temperature was further raised to 65°C, and the reaction was continued for 8 hours. The resulting reaction solution was transparent, and the concentration of the copolymer contained was
38.3%, and the viscosity was 21000 cps at 20°C. The polymerization rate of each monomer in the copolymer was 98.1% for 3(methacrylamido)propyltrimethylammonium chloride, and 98.1% for butyl acrylate.
It was 98.8%. An adhesive solution was obtained by adding 17.0 g of diglycerin as a plasticizer to 100 g of this copolymer solution.

(B) Performance evaluation of adhesive layer formation and adhesive strength: (A)
The adhesive solution obtained in Section 1 was cast onto a polyethylene terephthalate (PET) film base material with a thickness of 50 μm so that the thickness after drying was 0.04 mm (40 μm) or more and dried. The base material on which the adhesive layer was formed was cut into a size of 2.5 cm x 2.5 cm to obtain an adhesive sheet. This was pasted on the skin surface. Avoid areas where the skin is directly bent, such as joints, when pasting. Although the adhesive sheet was left attached for 6 hours, the adhesive sheet did not come off due to daily exercise. When this sheet was removed, the adhesive layer was temporarily stretched and peeled off from the skin surface. Appropriate adhesion was felt on the skin upon peeling. No adhesive remained on the skin surface after peeling.

This adhesive sheet was cut into a tape shape of 15 mm x 150 mm, and the adhesive strength substitute characteristic value was measured by the Japanese Pharmacopoeia bandage adhesive strength test method (180° folding and peeling method). The value was 580g per 15mm width.

(C) Conductivity evaluation of adhesive layer: Apply the adhesive solution obtained in (A) on silicone release paper to determine the thickness after drying.
It was cast to a thickness of 1.0 mm (1000 μm) and dried. This adhesive was transferred onto aluminum foil. A 500 mm ² piece of aluminum foil of the same quality was further placed on the surface of the transferred adhesive layer to obtain a sandwich-shaped test piece. A sinusoidal AC voltage of 10 PH and 10 mV was applied between the two aluminum foils of this test piece, and the effective current was measured. When the impedance was calculated from that value, the value was
It was 1.2kΩ.

Example 2 (A) Preparation of adhesive: 82.7 g (0.4 mol) of 3(acrylamido)propyltrimethylammonium chloride as a (meth)acrylamide derivative and 55.2 g (0.3 mol) of 2-ethylhexyl acrylate as an acrylic acid alkyl ester. , 0.13 g of 1,6-hexane glycol dimethacrylate as a polyfunctional monomer,
A copolymer was prepared according to Example 1 (A) using 42.6 g (0.3 mol) of butyl methacrylate as a polymerizable monomer other than the above. 100g of ethyl alcohol was used as a solvent. The amount of polymerization catalyst was 4.9 g. The resulting reaction solution was a slightly milky white viscous solution, the concentration of the copolymer contained therein was 39.5%, and the viscosity was 27,000 cps at 20°C. The polymerization rate of each monomer in the copolymer is 3
(Acrylamide) Propyltrimethylammonium chloride 97.6%, 2-ethylhexyl acrylate 99.0%, butyl methacrylate
It was 100%. An adhesive solution was obtained by adding 24 g of diglycerin as a plasticizer to 100 g of this copolymer solution.

(B) Formation of adhesive layer and performance evaluation of adhesive strength: Formation of adhesive layer and evaluation of adhesive strength in the same manner as in Example 1 (B) using the adhesive solution obtained in Section (A) of this Example. I conducted an evaluation. The results were similar to those in Example 1 (B). However, the adhesive strength substitute characteristic value was 640 g per 15 mm width.

(C) Conductivity evaluation of adhesive layer: Using the adhesive solution obtained in section (A) of this example, the effective current was measured in the same manner as in Example 1 (C), and impedance was calculated. The impedance of the test piece was 0.9kΩ.

Example 3 (A) Preparation of adhesive: 108.5 g of 2(acrylamido)ethyl diethyl methylammonium chloride as a (meth)acrylamide derivative
(0.46 mol), 43.5 g (0.34 mol) of butyl acrylate as an acrylic acid alkyl ester, 0.13 g of 1,6-hexane glycol dimethacrylate as a polyfunctional monomer, and polymerizable monomers other than the above. A copolymer was prepared according to the method described in Example 1 (A) using 28.4 g (0.20 mol) of butyl methacrylate. 90g of ethyl alcohol was used as the solvent. The amount of polymerization catalyst was 4.9 g. The obtained reaction solution was a transparent viscous solution, the concentration of the copolymer contained therein was 37.2%, and the viscosity was 24000 cps at 20°C. The polymerization rate of each monomer was 97.4% for 2(acrylamido)ethyl diethyl methylammonium chloride, 99.1% for butyl acrylate, and 100% for butyl methacrylate. 20 g of benzyl alcohol and 12 g of diglycerin as plasticizers and 8 g of sodium succinate as an electrolyte were added to 100 g of the above copolymer solution to obtain an adhesive solution. Sodium succinate was dissolved in a small amount of water and added to the reaction solution at the same time as the plasticizer.

(B) Formation of adhesive layer and performance evaluation of adhesive strength: Formation of adhesive layer and evaluation of adhesive strength in the same manner as in Example 1 (B) using the adhesive solution obtained in Section (A) of this Example. I conducted an evaluation. The results were similar to those in Example 1 (B). However, the adhesive force substitute characteristic value was 550 g per 15 mm width.

(C) Conductivity evaluation of adhesive layer: Using the adhesive solution obtained in section (A) of this example, the effective current was measured in the same manner as in Example 1 (C), and impedance was calculated. The impedance of the test piece was 0.8 kΩ.

Example 4 (A) Preparation of adhesive: 58.7% of 3(methacrylamido)propyl dimethyl ethylammonium chloride as a (meth)acrylamide derivative
g (0.25 mol) and 55.1 2(acrylamido)ethyldiethylmethylammonium chloride
g (0.25 mol), 51.2 g (0.4 mol) of butyl acrylate as acrylic acid alkyl ester,
0.6g of propylene glycol dimethacrylate as a polyfunctional monomer, and 11.1g of vinyl acetate as a polymerizable monomer other than the above.
(0.1 mol) was used, and a copolymer was prepared according to the method in Example 1 (A). 70g of ethyl alcohol was used as a solvent. The amount of polymerization catalyst is 4.9
g. The obtained reaction solution was a transparent viscous solution, the concentration of the copolymer contained therein was 36.6%, and the viscosity was 29000 cps at 20°C. The polymerization rate of each monomer was 97.2% for 3(methacrylamido)propyldimethylethylammonium chloride, 97.2% for 2
(Acrylamido)ethyldiethylmethylammonium chloride was 98.9%, butyl acrylate was 98.6%, and vinyl acetate was 99.9%. 18.0 g of glycerin and low molecular weight polyvinyl methyl ether (Gantrez
M574) 12.0 g and 3.0 g of sodium chloride as an electrolyte were added to 100 g of the above copolymer solution to obtain an adhesive solution. Sodium chloride was dissolved in a small amount of water and added.

(B) Formation of adhesive layer and performance evaluation of adhesive strength: Formation of adhesive layer and evaluation of adhesive strength in the same manner as in Example 1 (B) using the adhesive solution obtained in Section (A) of this Example. I conducted an evaluation. The results were similar to those in Example 1 (B). However, the adhesive strength substitute characteristic value was 720 g per 15 mm width.

(C) Conductivity evaluation of adhesive layer: Using the adhesive solution obtained in section (A) of this example, the effective current was measured in the same manner as in Example 1 (C), and impedance was calculated. The impedance of the test piece was 0.7kΩ.

(Effects of the Invention) According to the present invention, an adhesive having excellent conductivity and adhesiveness can be obtained. The skin electrode obtained by applying this adhesive onto the electrode plate can be easily applied to the skin surface and does not require any auxiliary means for fixation. Since the adhesive does not need to contain water as a plasticizer or electrolyte solvent, there is no change in conductivity due to evaporation of water during use or storage of the electrode, and therefore accurate measurement values can be obtained. Adhesiveness does not decrease due to water evaporation. Also,
Since no special packaging is required to prevent water evaporation, the electrode can be provided at low cost. Almost no electrical noise is observed. Since the internal cohesive force of the adhesive is also large, a thick adhesive layer can be formed and no reinforcing material is particularly required. When a polyfunctional monomer is added during copolymer preparation, a pressure-sensitive adhesive with even better internal cohesive strength can be obtained due to slight crosslinking. Therefore, regardless of the thickness of the adhesive layer formed on the electrode, no adhesive cracking or adhesive residue phenomenon occurs. Since the adhesive is not a natural polymer, microorganisms will not grow during storage and will not cause skin irritation. Since the copolymer used in the adhesive is not post-crosslinked, skin irritation due to unreacted monomers does not occur. Since there is no need for the adhesive to contain electrolytes, excess skin potential caused by electrolytes does not occur. Such skin electrodes can be used in various medical measurement devices, and desired measurements can be made easily and accurately.

[Brief explanation of the drawing]

1 and 2 are a plan view and a bottom view, respectively, showing an example of the medical skin electrode 1 of the present invention, FIG. 3 is a side view thereof, and FIG. 4 is an explanatory view showing how the skin electrode 1 is used. It is. 1...Skin electrode, 2...Medical measuring device, 11
... Electrode plate, 13 ... Conductive adhesive layer, 14 ...
Release sheet, 15... Non-conductive sheet, 20...
Conductive wire, 110... protrusion.

Claims (1)

[Scope of Claims] 1. A (meth)acrylamide derivative having a substituent whose end is a quaternary ammonium salt via an amide group; and an alkyl group having an average carbon number of 8
A medical conductive adhesive whose main component is a copolymer containing the following acrylic acid alkyl ester as a constituent component. 2. The adhesive according to claim 1, wherein the copolymer contains the (meth)acrylamide derivative in a proportion of 15 to 70% by weight, and the remaining at least 50% by weight is the acrylic acid alkyl ester. agent. 3. The adhesive according to claim 1, which contains a plasticizer. 4 A (meth)acrylamide derivative having a substituent whose terminal is a quaternary ammonium salt via an amide group; and an alkyl group with an average carbon number of 8
A medical skin electrode comprising a conductive adhesive layer mainly composed of a copolymer containing the following acrylic acid alkyl ester as a constituent component, provided on one side of an electrode plate. 5. The skin according to claim 4, wherein the copolymer contains the (meth)acrylamide derivative in a proportion of 15 to 70% by weight, and the remaining at least 50% by weight is the acrylic acid alkyl ester. electrode. 6. The skin electrode according to claim 4, wherein the conductive adhesive contains a plasticizer. 7. The skin electrode according to claim 4, wherein the conductive adhesive layer has a thickness of 0.03 mm or more. 8. The skin electrode according to claim 4, wherein at least the surface of the electrode plate is made of a conductive base material. 9 The area of the conductive adhesive in contact with the electrode plate is
500 mm ² and an impedance of 8 kΩ or less when the applied voltage is 100 mV or less at 10 Hz, the skin electrode according to claim 4.