JP2003138240A - Conductive adhesive composition for bioelectrode, its production method, and bioelectrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive adhesive composition which is free from the problem of remaining of a raw material monomer, has sufficient adhesive power and holding power, needing no backing with a pressure-sensitive adhesive tape, and can be produced by a short-time cross-linking or curing operation after continuous coating and coating. SOLUTION: This conductive adhesive composition for a bioelectrode contains a base polymer, a humectant, and an electrolyte. The base polymer contains a pressure-sensitive adhesive polymer obtained by cross-linking or curing a water-soluble or water-absorbent urethane acrylate oligomer and has a glass transition temperature (Tg) of 0 deg. or lower.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a conductive adhesive composition, and more particularly to a conductive adhesive composition for bioelectrodes.

[0002]

2. Description of the Related Art Since a conductive adhesive for a biomedical electrode has conductivity by ionic conduction, it has more adhesive force and holding power than the case of using a hydrophilic gel or adhesive mainly using salts as an electrolyte. In some cases, an adhesive composed of two or more phases, which forms a hydrophobic adhesive phase into a hydrophilic conductive adhesive phase, is used to increase the adhesive strength. In each method, there is a conductive adhesive having characteristics depending on the composition and manufacturing method. The main conventional methods will be described below.

Acrylic monomers such as KCl and NaCl
It is formed by blending an electrolytic solution in which salts such as are dissolved, a polyhydric alcohol such as glycerin, propylene glycol, and polyethylene glycol as a moisturizer, and curing a mixed liquid to which an ultraviolet (UV) initiator is added by UV or the like. , Gels and adhesives having ionic conductivity are widely used. As an example of these, U.S. Pat. No. 4,524,08
No. 7, No. 4,539,996 and No. 4,848,
No. 353 (Engel et al.), An acrylic acid or a neutralized acrylic acid is mixed with water, KCl, glycerin, a UV initiator and the like, and a liquid is irradiated with UV to produce a conductive adhesive. is there. Also, US Pat. No. 5,078,138
As shown in the specification (Strand et al.), Acrylic acid or an acrylic acid neutralized product is further added with N- for the purpose of enhancing the adhesive strength.
Example in which vinylpyrrolidone is added and copolymerized, N-vinylacetamide is irradiated with UV to a mixed solution of polyethylene glycol # 200 diacrylate, N-methylolacrylamide, hydroxyacrylate, water, NaCl, glycerin, UV initiator, etc. There is an example in which a conductive adhesive is manufactured by In these conventional techniques, there is a problem that unreacted monomer remains in the cured product because UV polymerization is performed from the monomer mixture. Therefore, in order to reduce the amount of residual monomer, it is generally necessary to irradiate low-intensity UV light for a long time to polymerize and cure, and the curing time becomes long, and there is a problem in increasing productivity. In addition, since some of these polymers have hydrophilic properties and therefore do not have high skin adhesiveness, the absorption of sweat from the skin causes the adhesive to swell or the adhesive strength to decrease, so Backing with an adhesive tape or the like was necessary for pasting the time.

An example of using an adhesive consisting of two or more phases forming a hydrophobic adhesive phase together with a hydrophilic conductive adhesive phase in order to enhance the adhesive strength and the holding power is disclosed in US Pat.
0,557 and 5,853,750 (Di
etz et al.). According to these references, isooctyl acrylate (IOA) and acrylic acid (A
A hydrophobic adhesive phase made of a polymer obtained by polymerizing a monomer containing A) is combined with a hydrophilic conductive phase and a bicontinuous structure (2
It is manufactured to have a phase continuous structure). JP 2001
JP-A-181597 (Takataka et al.) Has a high moisturizing power by allowing a hydrophobic adhesive phase made of a polymer obtained by polymerizing a monomer containing isooctyl acrylate (IOA) and acrylic acid (AA) to coexist with a hydrophilic conductive phase. In a system containing 35% of trimethylbetaine, which is an amino acid moisturizing agent, isooctyl acrylate (I
Disclosed is a two-phase conductive adhesive obtained by forming a mini-emulsion phase of a monomer containing OA) and acrylic acid (AA) and polymerizing it. These have been made possible to have higher adhesive strength and holding power than the hydrophilic conductive adhesives used up to now, but again, a UV polymerization curing process from a mixed liquid of monomers is necessary. Therefore, in order to sufficiently reduce the amount of residual monomer, it is necessary to irradiate low-intensity UV light for a long time to polymerize and cure, and it takes a long curing time and there is a problem in increasing productivity.

In order to solve the above problems, it has been proposed to preliminarily polymerize a monomer into a polymer and use the polymer to prepare a conductive adhesive. US Pat. No. 5,27
No. 6,079 (Duan et al.) Irradiates polyvinylpyrrolidone (PVP) with gamma rays to form partial crosslinks between polymers, and then a gel solution in which water, KCl and glycerin are dissolved is applied and partially dried. Then, the conductive adhesive is formed. This has enabled high-speed coating with a coater that normally has a drying oven, but since the degree of cross-linking cannot be increased, it absorbs sweat from the skin and becomes a low-viscosity liquid again, resulting in a decrease in adhesive strength. was there.

In JP-A-62-270134, JP-A-2-261882, and JP-A-4-13618 (Shikinami et al.), Lithium perchlorate is dissolved in a polyol and reacted with polyisocyanate or the like. After the segmented polyurethane sheet is polymerized and formed, it is made to contain water in a humidifying process to produce a conductive adhesive. However, the polymerization of the segmented polyurethane takes time, continuous coating is difficult, and the humidification process also takes time, resulting in poor productivity.

Japanese Patent Laid-Open No. 2001-151973 (Ishii et al.) Polymerizes a copolymer of N-vinylacetamide / sodium acrylate and prepares a gel in a mixed solution of this copolymer, water and glycerin. Although it is disclosed that a gel is prepared by crosslinking with a dry aluminum hydroxide gel or sorbitol glycidyl ether as an agent, it takes a long time of several days for these crosslinking to proceed and cause gelation. However, there was a problem that it was difficult to handle in terms of productivity.

US Pat. No. 5,660,178 (K
(antner et al.) discloses a conductive adhesive formed by previously preparing a water-soluble acrylic oligomer and irradiating it with UV to a liquid in which water, glycerin and a UV initiator are dissolved. Since this solution does not contain a monomer, it can be crosslinked by irradiation with a high-intensity UV lamp for a short time, and thus a conductive adhesive was obtained in a short time. However, although this conductive adhesive has tack, it has a weak adhesive force and holding power, so that a backing such as an adhesive tape is necessary for long-term attachment as a bioelectrode. In addition, since the viscosity of the solution before UV irradiation is not so high, it is not suitable for continuous sheet-like application, and the solution needs to be potted and cured in the recessed concave portions of the bioelectrode, which is a constraint on manufacturing. It was

US Pat. No. 6,232,366 (W
(ang et al.) discloses a method for producing a conductive adhesive in which an acrylic polymer having water content, conductivity and thermoplasticity is prepared in advance and applied with a hot melt coater. Forced mixing of hydrophilic acrylic conductive phase with relatively low adhesive strength and hydrophobic acrylic adhesive consisting of IOA (isooctyl acrylate) / AA (acrylic acid) with a biaxial extruder together with a surfactant. However, it is described that ion-crosslinking is performed by adding an amine-functional polymer and high-speed coating is performed. Since this conductive adhesive has high adhesive strength and holding power, it does not require lining such as an adhesive tape for long-term application as a bioelectrode, but due to the restrictions of formulation, sufficient glycerin, a water retention agent, is sufficient. Since it cannot be added in a sufficient amount, there is a problem that it is difficult to retain the water necessary for obtaining sufficient electric characteristics under low humidity and it is easy to dry.

[0010]

SUMMARY OF THE INVENTION The object of the present invention is to have sufficient adhesive force and holding power without the problem of residual raw material monomers, and therefore, without requiring backing of an adhesive tape,
Moreover, it is an object of the present invention to provide a conductive adhesive composition which can be manufactured by continuous coating and short-time crosslinking or curing operation after coating.

[0011]

According to the present invention, in a conductive adhesive composition comprising a base polymer, a humectant and an electrolyte, the base polymer crosslinks or cures a water-soluble or water-absorbing urethane acrylate oligomer. A pressure-sensitive adhesive polymer obtained as described above, and a glass transition temperature (Tg) of the base polymer is 0 ° C. or lower, a conductive adhesive composition for a bioelectrode,
Will be provided. Since such an adhesive composition does not contain a monomer as a raw material, there is no problem due to residual monomer. Further, the adhesive composition can be obtained by continuous coating using a coating device such as a hot melt coater and then a simple crosslinking or curing operation. Further, sufficient adhesive strength and holding power can be obtained without backing the adhesive tape. The conductive adhesive composition of the present invention comprises a water-soluble or water-absorbing urethane acrylate oligomer, a humectant, an electrolyte and water, and has a viscosity of 2,000 to 100 at a temperature of 40 ° C or higher and lower than 100 ° C. 000mP
The conductive adhesive composition precursor which is aS is 40 ° C. or higher and 10
It can be prepared by heating to a temperature below 0 ° C., mixing, applying this to a substrate, and then post-crosslinking or curing the urethane acrylate oligomer. According to this method, an adhesive composition can be produced with high productivity by continuously applying a coating liquid having an appropriate viscosity and then performing a crosslinking or curing operation for a short time.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Water-soluble or water-absorbing urethane acrylate oligomer / base polymer As a base polymer for the conductive adhesive composition for a bioelectrode of the present invention, the bioelectrode is cut through the adhesive composition to the skin. Since it is affixed to the skin, it is required that it has less skin irritation. From this point of view, the urethane acrylate adhesive is desirable because it is less irritating to the skin than the acrylic adhesive. Therefore, urethane acrylate oligomer is desirable as the oligomer that is crosslinked or cured to form the base polymer of the conductive adhesive composition. An isocyanate compound having two or more isocyanate groups is used as a raw material for the production of a urethane acrylate oligomer, and even if the isocyanate group remains when the oligomer or the base polymer obtained by crosslinking or curing the same is produced, it is bonded. Since the agent composition is used in the presence of water, it is considered that the isocyanate group is decomposed to reduce the harmfulness.

The base polymer obtained by crosslinking or curing needs to have a glass transition temperature (Tg) lower than the use temperature. This is because it is necessary to have pressure-sensitive adhesiveness when attached to the skin and be able to flexibly deform along the skin shape. Therefore, the urethane acrylate oligomer has a glass transition temperature (Tg) of 0 ° C. or lower after crosslinking or curing. Further, in order for the adhesive composition to have sufficient ionic conductivity, it is desirable that the base polymer itself has water retention. For this reason, it is desirable that the urethane acrylate oligomer include hydrophilic moieties, eg, polyalkylene oxide moieties such as polyethylene oxide or polypropylene oxide. Further, the urethane acrylate oligomer is mixed with a moisturizing agent, an electrolyte and water to form a coating liquid. Therefore, the urethane acrylate oligomer is water-soluble or water-absorbent. The urethane acrylate oligomer is 2,000 to 100,000 mPaS at a temperature of the coating liquid containing the urethane acrylate oligomer, the moisturizer, the electrolyte and water at 40 ° C or higher and lower than 100 ° C in order to enable hot melt coating of the coating liquid. Should be selected.

Suitable urethane acrylate oligomers that can be used in the present invention include polyalkylene glycols, organic isocyanates having two or more isocyanate groups,
And an oligomer obtained by polymerizing a reaction mixture containing a compound having both a functional group reactive with an isocyanate group and a (meth) acryloyl group at the same time. The organic isocyanate is a polyisocyanate having two or more isocyanate groups, for example polyisocyanate or polyisocyanurate, but preferably diisocyanate. In such a case, since the oligomer is linear, the viscosity of the coating liquid containing the oligomer can be suppressed to be low.

Examples of the organic isocyanate include isophorone diisocyanate, hexamethylene diisocyanate, norbornane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, trimethylhexamethylene diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated diphenylmethane diisocyanate,
It can be at least one selected from diphenylmethane diisocyanate.

The polyalkylene glycol is, for example, polyethylene glycol or polypropylene glycol. The polyalkylene glycol is usually 200 to 80.
It has a molecular weight of 0. If it is more than 800, it may not be possible to give sufficient adhesion and holding power to the oligomer and consequently to the base polymer.
On the other hand, when it is less than 200, the hydrophilicity is not sufficient, and the conductive properties of the adhesive composition may be insufficient.

A compound having a functional group reactive with an isocyanate group and a (meth) acryloyl group at the same time (hereinafter, also referred to as "(meth) acryloyl group-containing compound").
The (meth) acryloyl group serves as a reactive site for crosslinking or curing the urethane acrylate oligomer. Examples of such compounds include acrylates and methacrylates having a hydroxyl group and a (meth) acryloyl group at the same time, such as hydroxyalkyl (meth) acrylate. Further, two or more functional groups reactive with an isocyanate group can be present in one molecule.

The urethane acrylate oligomer used in the present invention has, for example, the following general formula (meth).
It can be an acrylate-containing urethane oligomer.

[0019]

[Chemical 1]

(Wherein R ¹ is a divalent residue of a diisocyanate, R ² is a divalent residue of a polyalkylene glycol or a (meth) acryloyl group-containing compound, and R ³ is a polyalkylene glycol or (Meta)
It is a divalent residue of an acryloyl group-containing compound, and n is a weight average molecular weight of the oligomer of 10,000 to 100,0.
It is an integer such that it has at least one (meth) acryloyl group in the molecule). With the above-mentioned weight average molecular weight, a coating solution containing a urethane acrylate oligomer, a moisturizer, an electrolyte and water is 40 ° C or higher and 100 ° C.
2,000-100,000 mPa at temperatures below
It is sufficient to obtain S, which enables hot melt coating.

A commercially available urethane acrylate oligomer suitable for producing a base polymer for an adhesive composition is PSA-903 adhesive (trade name) manufactured by Kyoei Chemical Co., Ltd.
(Tg after crosslinking or curing: −34 ° C.),
In addition, PSA-90 having a different acrylate content from this
3-1, PSA-903-2, PUS-903 UV curable water-soluble urethane acrylate can be mentioned.

The base polymer includes, in addition to the above urethane acrylate oligomer, other hydrophilic polymers,
For example, polyacrylic acid or sodium polyacrylate may be blended. However, in the case of a polymer that cannot be post-crosslinked or cured together with the urethane acrylate oligomer, the adhesive composition is liable to remain on the skin when the bioelectrode is peeled from the skin, that is, a so-called adhesive residue is likely to occur. It is desired to be about 50% or less based on the mass of the base polymer.

The urethane acrylate oligomer is usually mixed with other components such as water, a moisturizing agent and an electrolyte to form a coating solution, which is then coated on a substrate. An adhesive composition for a bioelectrode is obtained by post-crosslinking or curing the oligomer with an energy ray such as ultraviolet ray (UV) or electron beam (EB) in the obtained coating film. By post-crosslinking or curing, the conductive adhesive composition should have sufficient adhesive strength and holding power, thereby preventing the adhesive from remaining adhesive on the skin and abrupt decrease in adhesive strength due to absorption of sweat. You can
When crosslinking or curing by UV, usually
A UV initiator is added to the coating liquid. The type of UV initiator matches the energy band of the UV lamp used and must be selected in consideration of skin irritation, safety, solubility, and odor after irradiation. Since the coating stock solution contains water, it is preferable to use a water-soluble or hydrophilic UV initiator. Non-limiting examples of initiators include benzophenones substituted with ionic groups, hydrophilic groups or both, thioxanthones substituted with ionic groups, hydrophilic groups or both, 4-substituted- (2-hydroxy- Examples thereof include those selected from the group consisting of phenyl ketones such as 2-propyl phenyl ketone (wherein the 4-substituent is an ionic or hydrophilic group), etc. Particularly preferred UV initiators are from Ciba Geigy. Irgacure-2959 [(1- (4- (2-hydroxy)
-Phenyl) -2-2-hydroxy-2-methyl-1-
Propan-1-one)]. The amount of the initiator added is determined as a suitable composition from the relationship between the UV irradiation amount and the adhesive property, but considering the compounding balance of the adhesive, the compounding amount is 0.01 to 10% by mass based on the mass of the oligomer.
And preferably in the range of 0.05 to 5% by mass. An initiator is not necessary in the case of crosslinking or curing using an electron beam.

UV irradiation can be carried out using low or medium pressure mercury lamps and low intensity fluorescent lamps. It is also possible to use combinations of these lamps. In this case, a lamp that has different emission spectra and emits the strongest light in the wavelength range of 280 to 400 nm is preferable. The total irradiation dose during UV irradiation is usually 1
It is about 0 to 1000 mJ / cm ² . In the case of the present invention,
Since an oligomer is used, there is no concern about residual monomers, so post-crosslinking or curing can be performed with low irradiation energy in a short time by a high-intensity UV lamp, and an adhesive composition can be produced at high speed. is there.

Electrolyte In order to form a conductive adhesive composition for a bioelectrode, it is necessary to add an electrolyte for causing ionic conduction. The electrolyte may be an inorganic salt or an organic salt, but an inorganic salt such as KCl, NaCl or LiCl is usually used. The addition amount is an amount necessary to obtain sufficient ionic conductivity, but considering the irritation to the skin, it is 0.1 to 5% by mass, preferably 0.1% by mass based on the mass of the adhesive composition. The amount is 5 to 3% by mass. As a solvent for dissolving the electrolyte, not only water but also an organic solvent can be used.
Skin irritation, safety, ionic conductivity (especially migration speed)
In view of the above, it is most preferable to use water, and the addition amount thereof is 15 to 50% by mass based on the mass of the adhesive composition. Mass% is desirable.

Moisturizer When used as a conductive adhesive composition for bioelectrodes,
It is necessary to secure the water necessary for maintaining sufficient conductivity during the storage period of the bioelectrode, the period from opening the package to use, and the period of use after being attached to the skin. Therefore, a humectant is added to the composition in order to suppress the drying of the adhesive composition. As the moisturizer, polyhydric alcohols such as glycerin, propylene glycol and polyethylene glycol are used. Since each moisturizer has different moisturizing power depending on the type, an amount necessary for maintaining necessary water content is added. For example, in the case of glycerin, about 7% by mass of water can be retained under the environment of 20 ° C.-20% relative humidity (RH). In order to keep 5% by weight of water in the conductive adhesive under this environment, about 69
Mass% glycerin is required. Considering the blending balance of the adhesive, the blending amount is in the range of 10 to 80% by mass, preferably 20 to 50% by mass, and not only the moisturizing effect but also the performance balance such as electric characteristics and adhesive strength are considered. It is necessary to decide the amount to be added.

When a polyhydric alcohol is used as a moisturizing agent, its moisturizing power is relatively low. Therefore, in consideration of use under low humidity conditions, a relatively large amount must be added. In this case, there may be a restriction on the blending amount of other components, and there may be a constraint on the blending balance range with good overall characteristics. For this reason, it is effective to use an amino acid moisturizing agent that exerts a great moisturizing effect even when added in a small amount. A non-limiting example is AQUA from Ajinomoto.
Examples include DEW (trade name) (trimethylbetaine), DL-pyrrolidonecarboxylic acid (PCA), and sodium DL-polypyrrolidonecarboxylate (PCA-Na). AQ
20 ℃ -20% R of UADEW (Trimethylbetaine)
The moisturizing amount in the H environment is about 40% by mass. Therefore, the restrictions on the blending balance of the other components are considerably reduced. However, these moisturizers, unlike the above polyhydric alcohols, have no plasticizing effect on the composition,
When the water content is low, the adhesive is hardened and the adhesion is reduced. In order to avoid this, the polyhydric alcohols represented by the above-mentioned glycerin, propylene glycol and polyethylene glycol, which also have a function as a plasticizer, are simultaneously added and used together with the above-mentioned high performance amino acid moisturizer. However, if an amino acid moisturizer is added at a high concentration, a salting-out effect will occur and dissolved oligomers will precipitate, so the amount of amino acid moisturizer and polyhydric alcohol added should be the required moisturizing amount. And the flexibility of the adhesive is obtained,
It is necessary to determine the blending balance of each component in consideration of the stability of the coating solution. Also,
The composition should be balanced so that the electrical properties other than the moisturizing effect and the adhesive strength can be satisfied.

Method for Producing Conductive Adhesive Composition In the present invention, the urethane acrylate oligomer as described above is used as a precursor for the base polymer so that the adhesive force and the holding force can be obtained by hot melt coating even in a water-containing system. It has become possible to produce a sufficient adhesive composition of One embodiment of the present invention is a conductive material comprising the above water-soluble or water-absorbing urethane acrylate oligomer, a humectant and an electrolyte, and having a viscosity of 2,000 to 100,000 mPaS at a temperature of 40 ° C or higher and lower than 100 ° C. Adhesive precursor composition is heated to a temperature of 40 ° C. or higher and lower than 100 ° C., mixed, applied to a substrate, and then the urethane acrylate oligomer is post-crosslinked or cured. It is a method for producing a conductive adhesive composition for a biomedical electrode.

First, a coating solution is prepared by mixing and dissolving components such as water, an electrolyte, a humectant, a urethane acrylate oligomer, and optionally a UV initiator. Mixing and dissolution of the coating liquid can be performed at room temperature, but the viscosity of the coating liquid becomes too high, load on the mixer is applied, and the mixing speed becomes slow.
Use a high-viscosity mixer equipped with a pressure kettle or condenser, a kneader, or an extruder to prevent water from evaporating at a temperature of 100 ° C or lower.
A uniform coating liquid can be formed by mixing and dissolving at a temperature of not less than 100 ° C and less than 100 ° C. Specifically, the oligomer is added from the former stage of the extruder of the hot melt coater, and the solution is fed by the screw. On the other hand, a mixed solution in which water, a water retention agent, an electrolyte, a UV initiator and the like are pre-dissolved is fed from a middle stage of the extruder by a gear pump so that the oligomer and the mixed solution are mixed in the extruder. After mixing, the composition is applied onto a substrate such as a polyester liner and post-crosslinked or cured with an energy ray such as UV or EB to produce an adhesive composition. By crosslinking or curing,
Adhesive force and cohesive force suitable for the bioelectrode adhesive composition are imparted.

In the coating liquid containing the above urethane acrylate oligomer, the viscosity at a temperature of 40 ° C. or higher and lower than 100 ° C. can be adjusted to 2,000 to 100,000 mPaS. The above viscosities at the above temperatures are particularly suitable for continuous coating with a hot melt coater. 20 coating liquids
When a low-viscosity solution of less than 00 mPaS is applied to a substrate such as a polyester liner using a continuous coater through a knife or an extrusion die, there are problems such as sagging and an excessively thin coating film. Therefore, there is a problem in the process such that it is necessary to impregnate a thin non-woven fabric or paper called scrim with the coating liquid. In addition, coating cannot be performed with a high-viscosity solution having a viscosity of 100,000 mPaS or more,
When heated above 0 ° C., the water content evaporates significantly, so that it was impossible to apply the water-containing adhesive composition. The adhesive composition precursor containing the oligomer of the present invention can be mixed and melted in a so-called warm melt state at a temperature of 40 ° C. or higher and lower than 100 ° C. and applied by an extrusion die or the like. As a result, the mixing and dissolving process of the raw materials and the coating process can be simultaneously performed by the same apparatus, and the present invention is a highly productive manufacturing method. Further, since the coating liquid is rapidly cooled after being coated with the extrusion die, the coating liquid does not sag and the thickness of the coating film does not decrease. However, in order to increase the tensile strength of the adhesive itself, a thin non-woven fabric or paper called scrim may be impregnated with the coating liquid.

The thickness of the conductive adhesive layer of the biomedical electrode depends on the mode of use, but is usually 0.1 to 4 mm, preferably 0.
It is 5 to 2 mm. If the layer is too thin, it cannot prevent drying, and if it is too thick, the bioelectrode may be bulky and difficult to use.

Structure of bioelectrode The bioelectrode formed so as to include the adhesive layer made of the conductive adhesive composition of the present invention is particularly useful for diagnosis, monitoring and treatment in the medical field. In its basic form, the bioelectrode contacts the skin of the patient or subject, and has a conductive adhesive layer,
It comprises electrode terminals that allow mutual electrical communication with an electrical diagnostic device, therapeutic device or electrosurgical device. FIG. 1 shows a cross-sectional view of one mode of the bioelectrode. In the living body electrode 1, the backing film 2 has a stud 3 on the upper surface side and an eyelet 4 on the lower surface side, and the stud 3 and the eyelet 4 are meshed in an electrically contacting state. The stud 3 provides an electrical connection with an electric meter. Further, the eyelet 4 holds the stud 3 and makes an electrical connection with the adhesive layer 5 below the eyelet 4 and made of a conductive adhesive composition. The adhesive surface of the adhesive layer 5 is protected by the liner 6 until the biological electrode is used. The backing film 2 is usually a non-conductive film, and for example, a non-woven fabric laminated with a polyethylene film can be used. As the stud 3, a conductor made of stainless steel or carbon black can be used. The eyelet 4 may be, for example, a plastic with a silver / silver chloride coating.
The liner 6 can be a polyester film such as polyethylene terephthalate.

An example of a bioelectrode in which the conductive adhesive composition of the present invention can be used is, for example, US Pat. No. 4,524,08.
No. 7, No. 4,539,996, No. 4,554,9
No. 24, No. 4,848,353, No. 4,846.
No. 185, No. 4,771, 783, No. 4,71
5,382, 5,012,810 and 5,5
No. 133,356. The conductive adhesive composition of the bioelectrode disclosed therein can be replaced with the adhesive composition of the present invention.

[0034]

Examples (Example 1) As a reactive urethane acrylate oligomer, Light Tack P manufactured by Kyoei Chemical Co., Ltd. of Japan
The SA-903 water soluble urethane acrylate oligomer was first evaluated. This material contains 1.5% by weight of UV photoinitiator in urethane acrylate oligomer. Four
% KCl solution at 5%, 10%, 15%, 20% and 2%
PSA with different water content blended at 5% blending ratio
Several mixtures containing -903 were made in a planetary mixer controlled at a temperature of 80 ° C. 0.6 with a hand coater having a heating mechanism controlled at a temperature of 80 ° C.
The mixed solution was applied to a PET liner in a thickness of 25 mm (25 MIL), and another PET liner was stacked on the PET liner. Total energy of 360 mJ by high pressure mercury lamp (80 W / cm)
The mixture was cured (crosslinked) between the two PET liners at / cm ² . The cured material was a soft, somewhat tacky, odorless pressure sensitive adhesive sheet.

The cured adhesive sheet was processed into a bioelectrode. As shown in FIG. 1, the structure of the bioelectrode is PET.
Hardened adhesive sheet on one side of the liner, M laminated with polyethylene film on polypropylene non-woven fabric
iliken backing film, Mi from USA
It consists of Ag / AgCl eyelets, carbon studs supplied by Cron Products.

DC offset potential (DCO), AC impedance (ACZ), offset potential (SDR) at 5 seconds after defibrillation recovery, and recovery speed (Slope) at 5 seconds after defibrillation recovery for the assembled electrode. Was evaluated for AAMI standard characteristics. What is the AAMI standard characteristic?
I is the proper performance established for biomedical electrodes used in ECG disposable electrodes, employing the following criteria and test methods. The test method and standard concerning the minimum standard are the following four items: (1) DC offset 100 mV or less (2) AC impedance 2000 Ω or less (3) Offset potential 5 mV after defibrillation 100 mV or less (4) After defibrillation Recovery speed after 5 seconds 0 to -1.0 mV / s (change rate of remanent polarization potential 5 seconds after 4 times charge / discharge).

Therefore, in this characteristic evaluation test, the evaluation tests of the above-mentioned four items were performed by the ECG electrode tester, Xtrat.
ek ET-68A (trade name, manufactured by Xtratek) was used.

The adhesive test (skin adhesion test) of the adhesive sheet of this example was carried out as follows. First, the obtained adhesive sheet was processed as shown in FIG.
A 3.2 cm square bioelectrode was obtained. The test piece was attached to the forearm of the subject, and a 1 Kg roller was rolled to apply it evenly. The test piece was peeled off immediately after application using a mechanical disengagement tool called an adhesion tester. Strip strip conditions were at a rate of 12 inches / minute in the 180 degree direction.
The adhesive strength (adhesive strength) of each electrode is 3.2 cm wide.
It was recorded in g per unit [g / 3.2 cm]. Table-1 is A
The AMI standardized characteristics and the adhesive strength of the test subject's forearm to the adhesive composition are shown.

[0039]

[Table 1]

In order to obtain sufficient electrical characteristics of the AAMI standard and appropriate adhesive strength to human skin, it was necessary to add 25% of a 4% KCl solution. However, even with the 5% blend, the values of SDR and SLOPE were proper values, and only ACZ was high. It is believed that the addition of a plasticizer that aids ionic conduction will reduce the ACZ value and increase the adhesion.

(Example-2) In order to assist ionic conduction and retain sufficient water under low humidity, glycerin, propylene glycol and PEG (polyethylene glycol) 300 were used as moisturizers for polyhydric alcohols. Added to the mixture as described in Example-1. The blending balance of 4% KCl satisfies the AAMI standard characteristics in Example 1, and 2
It was set to 5%. Table-2 shows some formulations when using various moisturizers.

[0042]

[Table 2]

Glycerin was dissolved only up to 20%, and propylene glycol was dissolved even at 50%, but 40% and 50% became low viscosity solutions. PEG30
No. 0 dissolved up to 30%, but separated at 40%.
For the formulations which were not separated, mixing, coating and curing were carried out in the same manner as described in Example-1, and the bioelectrode processing and evaluation were also conducted in the same manner as described in Example-1. I did.

Table 3 shows the AAMI standard characteristics and the adhesive strength of the test subject's forearm to the adhesive composition.

[0045]

[Table 3]

When propylene glycol was added at 40% and 50%, the cured product became a paste-like gel, and therefore,
It was not suitable as a conductive adhesive composition. 20%, 3
The cured product added with 0% has a sufficiently low AC impedance,
A good conductive adhesive composition having high adhesive strength was obtained. In order to investigate the minimum water content for satisfying the electrical characteristics (AAMI standard) when propylene glycol was used as a moisturizing agent for polyhydric alcohols, the 4% KCl content was lowered again for the combination of PRO2 and PRO3. An adhesive composition was prepared. Table 4 shows the composition, and Table 5 shows the evaluation results.

[0047]

[Table 4]

[0048]

[Table 5]

As the amount of the moisturizing agent increased, sufficient electric characteristics were obtained even with a low water content. A water content of about 15% was required to obtain sufficient AAMI standard characteristics. Considering the water loss in the hot melt coater and the drying of the electrode, it is desirable to set the water content to 20% or more in order to secure sufficient electric characteristics.

(Example-3) In order to maintain a higher water content under low humidity, 15-20 at 20 ° C-20% RH.
Aqua Deu (trimethyl betaine) from Ajinomoto Co., which has a moisturizing effect of mass%, was used in combination. In this example, Aqua Dew was added to the mixed liquid of Example-2 using propylene glycol as a moisturizer. Aqua Dew can maintain a wide range of water content, but at a high concentration, it is difficult to add a large amount because the dissolved oligomer becomes insoluble due to the salting-out effect, but the moisturizing effect is increased as compared with polyhydric alcohol alone.

Table 6 shows some formulations using propylene glycol as a humectant and plasticizer with Aquadew as an additional humectant. Each formulation contains 10%, 2% to control the flexibility of the conductive adhesive under low humidity.
With three propylene glycol loading levels of 0% and 30%, the Aquadew addition level was set at 5% and 10%. The blending balance of 4% KCl was set to 25% in consideration of water loss in the hot melt coating step and sufficient initial AAMI standard characteristics.

[0052]

[Table 6]

With the addition of 10% or more of Aqua Dew, the oligomer was separated due to the salting-out effect and a uniform solution could not be formed.

Mixing of an adhesive composition having such a composition,
Application and curing were done in the same manner as described in Example-1. Example of working method and evaluation method of biological electrode-
It was done in the same way as described in 1. Table 7 shows the AAMI standard characteristics and the adhesive strength of the test subject's forearm to the conductive adhesive.

[0055]

[Table 7]

The system in which 30% propylene glycol and 5% aquadew were added increased the moisturizing effect, but the cohesive force of the adhesive increased due to the salting out effect, and the adhesive force decreased.

(Example 4) As a reactive urethane acrylate oligomer, a light tack PSA-903 water-soluble urethane acrylate oligomer (without an initiator) manufactured by Kyoeisha Chemical Co., Ltd. of Japan was used. This material does not contain a UV photoinitiator and is therefore available from Ciba-Geigy Irga.
A small amount of 1- (4- that can be used as cure-2959
(2-Hydroxy) -phenyl) -2-2-hydroxy-2-methyl-1-propan-1-one) was added in an amount of 0.5% by weight. As a moisturizer, 20% propylene glycol and 10% PEG300 were added, and the water content (4
% KCI solution) was 25%. Table-8 shows the formulations tested.

[0058]

[Table 8]

Before applying the mixed solution, the PSA-
Raw materials other than 903 were mixed and dissolved in a mixing ratio and stocked. The temperature of the hot melt coater system, such as the extruder, coating die head, and other units, should be 80-
Set at 85 ° C, put PSA-903 urethane acrylate oligomer from the hopper of the extruder,
Extruded with a screw. From the middle of the extruder, a mixed solution other than PSA-903 which had been dissolved in advance was fed by a gear pump so as to have a predetermined composition and mixed.
The mixed solution that merged in the extruder is extruded from the coating die and placed on the PET liner at 0.6 mm (25
(MIL) and applied with a PET liner.
The coating was immediately cooled on a chill roll. After that, the total energy is 360 by the high pressure mercury lamp (160W / cm).
The coating film was cured (crosslinked) at mJ / cm ² , and the material cured by the winder was recovered. The hot melt coater was able to apply the mixture for the conductive adhesive according to the invention very rapidly and with high productivity.

Using the conductive adhesive composition obtained by such a preparation method, a bioelectrode was processed and evaluated in the same manner as described in Example-1. Table-9 shows AAMI
The standard characteristics and the adhesive strength of the test subject's forearm to the conductive adhesive composition are shown.

[0061]

[Table 9]

Low AC that fully satisfies AAMI standard characteristics
A conductive adhesive and bioelectrode with impedance and adhesive strength suitable for skin were obtained.

[0063]

Since the conductive adhesive composition of the present invention does not contain a monomer as a raw material, there is no problem due to residual monomer. Further, the adhesive composition can be obtained by continuous coating using a coating device such as a hot melt coater and then a simple crosslinking or curing operation. Further, sufficient adhesive strength and holding power can be obtained without backing the adhesive tape.

[Brief description of drawings]

FIG. 1 shows a cross-sectional view of one embodiment of a bioelectrode in which a conductive adhesive composition of the present invention can be used.

[Explanation of symbols]

1 ... Biological electrode 2 ... Backing film 3 ... Stud 4 ... Eyelet 5 ... Adhesive layer 6 ... Liner

Continued front page    F term (reference) 4C053 BB06 BB32                 4J027 AG01 AG04 AG23 AG24 AG27                       BA01 CA13 CA14 CA29 CA31                       CA33 CB10 CC05 CD09                 4J040 EF051 EF131 EF181 EF281                       EF301 FA09 FA291 HA096                       HA126 HB10 HB11 HB19                       JB01 JB09 JB10 KA13 KA16                       KA38 KA39 LA01 LA06 LA08                       LA09 MA15 NA02 PA32 PA33                 5G301 DA17 DA59 DD03 DE01

Claims (6)

[Claims] 1. A conductive adhesive composition comprising a base polymer, a humectant and an electrolyte, wherein the base polymer is a pressure-sensitive adhesive polymer obtained by crosslinking or curing a water-soluble or water-absorbing urethane acrylate oligomer. A conductive adhesive composition for bioelectrodes, which comprises the base polymer and has a glass transition temperature (Tg) of 0 ° C. or lower. 2. The reaction in which the urethane acrylate oligomer comprises polyalkylene glycol, an organic isocyanate having two or more isocyanate groups, and a compound having a functional group reactive with an isocyanate group and a (meth) acryloyl group at the same time. The conductive adhesive composition for a bioelectrode according to claim 1, which is an oligomer obtained by polymerizing the mixture. 3. The moisturizer contains polyhydric alcohols,
The conductive adhesive composition for a bioelectrode according to claim 1 or 2. 4. The conductive adhesive composition for a bioelectrode according to claim 3, wherein the moisturizer further contains an amino acid moisturizer. 5. A biological electrode comprising an adhesive layer containing the conductive adhesive composition for a biological electrode according to any one of claims 1 to 4, and an electrode terminal connected to the adhesive layer. 6. A water-soluble or water-absorbing urethane acrylate oligomer, a humectant and an electrolyte, and 4
Viscosity at a temperature of 0 ° C or higher and lower than 100 ° C is 2,000
A conductive adhesive composition precursor having a viscosity of 100,000 to 100,000 mPaS is heated to a temperature of 40 ° C. or higher and lower than 100 ° C., mixed, applied to a substrate, and then the urethane acrylate oligomer is post-crosslinked or cured. A method for producing a conductive adhesive composition for a biomedical electrode, comprising: