JP3537201B2 - Conductive pressure-sensitive adhesive and electrode pad using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive pressure-sensitive adhesive and an electrode pad using the same.

[0002]

2. Description of the Related Art Conventionally, as an electrode used in contact with a living body, a weak current due to a low frequency is introduced into a body to induce blood flow, and to reduce pain such as stiff shoulders and lower back pain with the expectation of a massage effect. Electrode for medical treatment, medical electrode for extracting electrocardiogram and electromyogram etc. by taking out the weak current in the body outside the body, earth electrode used when using an electric scalpel, cosmetic electrode used for hair removal treatment of waste hair Various electrodes are known.

[0003] Electrode pads having conductivity are used for these electrodes as a contact medium with the surface of a living body. Generally, a water-soluble polymer such as sodium polyacrylate or polyvinyl alcohol is added to an ion pad such as sodium chloride. A hydrogel type containing a dissociating electrolyte and water as a conductive medium as essential components is widely used.

[0004] However, the above-mentioned hydrogel electrode pad is an excellent electrode pad that satisfies both functions of conductivity and adhesiveness. However, since it contains a relatively large amount of water, the gel pad is affected by the influence of atmospheric humidity. , The moisture content is liable to fluctuate, and an expensive sealing packaging material is required to stabilize the moisture content.
Further, by sticking over a long period of time, sweat absorbed from the living body is absorbed, and characteristics such as a decrease in adhesive strength are caused.

Accordingly, non-aqueous conductive adhesives that do not require water have been actively developed. Examples of such a non-aqueous conductive pressure-sensitive adhesive include, for example, JP-A-62-1396.
No. 28 or JP-A-3-267041, an ether part is present in the pressure-sensitive adhesive composition, and a cation of a dissociable salt such as a lithium salt is coordinated to the ether part. The use of an ionic conductor that expresses conductivity by the movement of cations has been proposed.

[0006] Since these non-aqueous conductive adhesives do not contain water, they do not have the problems of the above-mentioned conventional hydrous type, but they are necessary for reattachment as compared with the hydrous type. It is a pressure-sensitive adhesive that has poor repetitive adhesiveness, is not sufficiently satisfactory in terms of conductivity, and still has room for improvement.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems of a conventional conductive adhesive used for an electrode pad, particularly an aqueous gel type adhesive. An object of the present invention is to provide a conductive pressure-sensitive adhesive which exhibits conductivity and has excellent adhesiveness, and also has excellent repetitive adhesiveness (re-adhesiveness) which is a characteristic required for re-attaching.

It is another object of the present invention to provide an electrode pad using the above-mentioned conductive adhesive.

[0009]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have used polyester polyol as a skeletal polymer of a non-aqueous conductive pressure-sensitive adhesive, containing an ionic compound and The inventor has found that a conductive pressure-sensitive adhesive that solves the above object can be obtained by containing an organic solvent and crosslinking with a specific crosslinking agent, thereby completing the present invention.

That is, the conductive pressure-sensitive adhesive of the present invention is obtained by crosslinking a composition comprising a polyester polyol, an ionic compound and a solvent capable of dissolving the ionic compound as essential components with an isocyanate compound. It is characterized by becoming.

A particularly preferred embodiment is a pressure-sensitive adhesive further containing a plasticizer, which has good re-adhesiveness to a living body.

The electrode pad of the present invention is obtained by molding the above-mentioned conductive adhesive into a pad shape.

The polyester polyol used in the present invention is one which is easily compatible with ionic compounds and solvents described below uniformly and can exhibit good conductivity. Such polyester polyols include, for example, dibasic acids such as adipic acid, isophthalic acid, terephthalic acid, ethylene glycol, propylene glycol,
Polyethylene glycol, polypropylene glycol,
A dibasic acid-based polyester polyol obtained by reacting a diol such as 3-methyl-1,5-pentanediol, 1,4-butanediol, 1,9-nonanediol, or methyloctanediol; β-methyl-δ- Polylactone-based polyols obtained by ring-opening polymerization of cyclic monomers such as valerolactone and ε-caprolactone, poly (3-methyl-
Polycarbonate polyols such as 1,5-pentane methylene carbonate) and poly (nonanediol carbonate) can be used. Among them, those having a melting point of room temperature or lower, that is, those having a melting point of room temperature or less are preferable from the viewpoint of compatibility with ionic compounds and solvents described below together with the development of good adhesiveness, and a polylactone-based polyol is suitably used. be able to. Content is 30 to 90
% By weight, preferably in the range of 50 to 80% by weight.

In the pressure-sensitive adhesive of the present invention, the ionic compound to be added for exhibiting conductivity is, for example, a cation selected from alkali metals and alkaline earth metals such as lithium, sodium, potassium and magnesium. And inorganic salts consisting of halogen ions such as chloride ion and iodine ion, and anions such as perchlorate ion, thiocyanate ion, trifluoromethanesulfonate ion and toluenesulfonate ion, and lithium stearylsulfonate. And ionic compounds such as quaternary ammonium salts. Among these ionic compounds, it is particularly preferable to use a lithium salt having a relatively small energy at the time of ion dissociation and having a high mobility in a solvent described later. Specific compounds include LiBr, LiI, LiClO ₄ , LiSCN, L
iCF ₃ SO _{3 and the} like. The compounding amount of the ionic compound can be arbitrarily changed depending on the compounding amount of a solvent described later, and is usually 0.01 to 30 in the adhesive.
% By weight, preferably in the range of 1 to 20% by weight.
When the amount of the ionic compound is less than 0.01% by weight, the conductivity is inferior. When the amount exceeds 30% by weight, the amount of the ionic compound to be blended exceeds the saturation solubility and is not completely dissolved, Recrystallization may cause a decrease in conductivity.

The solvent used in the present invention is one that dissolves the ionic compound and has an affinity for the polyester polyol. Further, those which hardly volatilize under normal temperature or moderate heating are preferable, and have a boiling point of 180 ° C. or more, preferably 22 ° C.
Use one at 0 ° C or higher. Examples of such a solvent include polyhydric alcohols such as ethylene glycol and propylene glycol, polyalkylene glycols such as polyethylene glycol, polypropylene glycol, polyethylene glycol monomethyl ether and polyethylene glycol dimethyl ether, and poly (oxyethylene-oxypropylene) alkyl. Alkyl ethers such as ethers, polyols such as polyether polyols, polyester polyols, polycarbonate polyols, polycaprolactone polyols, carbonates such as ethylene carbonate and propylene carbonate, cyclic esters such as caprolactone, sulfolane, dimethylimidazolidinone and the like Polyhydric alcohol fatty acids such as heterocyclic compounds and glycol dicaprylate Stell,
Examples thereof include polyoxyethylene alkylphenyl ether, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, and polyoxyethylene sorbitan fatty acid ester.
The compounding amount of such a solvent can be arbitrarily changed depending on the type and the compounding amount of the ionic compound, but in order to exhibit excellent conductivity, a larger compounding amount is preferable because the dielectric constant becomes higher. . However, when the compounding amount is large, the cohesiveness is reduced when a molded article such as an electrode pad is formed. Therefore, the pressure-sensitive adhesive of the present invention preferably contains 10 to 70% by weight, and practically 15 to 50% by weight. It is desirable to adjust the range of%.

The conductive pressure-sensitive adhesive of the present invention comprises the above essential components and exhibits a liquid state at normal temperature. Therefore, when molded into an electrode pad as described below, generally applied on a carrier such as a separator,
Although a method of drying to remove the solvent is employed, a repelling phenomenon is likely to occur due to the surface tension of the separator surface.
It is also conceivable to increase the solution viscosity by causing the solvent content to decrease before crosslinking with the isocyanate compound. However, it is expected that the solution viscosity will decrease due to heating in the crosslinking step and a repelling phenomenon will occur. Therefore, in the present invention, in addition to the above-mentioned essential components, a rubber component or a resin component is used as a plastic resin (plasticizer) in order to improve the wettability on a separator used as a carrier during the manufacturing process as an optional component. It can be blended in the range of up to 30% by weight. Such components include, for example, isoprene rubber, butadiene rubber, styrene / butadiene rubber, epichlorohydrin rubber, epichlorohydrin / polyethylene oxide rubber, polyvinyl methyl ether, polyvinyl ethyl ether, polyvinyl acetate, poly (ethylene / vinyl acetate), styrene / isoprene / Styrene rubber and the like can be used. Among these, it is preferable to use polyvinyl alkyl ether or epichlorohydrin rubber from the viewpoint of compatibility with the above-mentioned solvent.

In addition to the above-mentioned plastic resin, a liquid plasticizer generally used as a compatibilizer between the polyester polyol and the solvent can be incorporated into the pressure-sensitive adhesive in an amount not exceeding 30% by weight. Specifically, olive oil,
Vegetable oils such as castor oil, mineral oils such as process oils,
And ester oils such as dibutyl phthalate, dioctyl phthalate, diethyl adipate, and isopropyl myristate.

Further, in order to impart adhesiveness to the pressure-sensitive adhesive of the present invention to improve the adhesiveness when a molded article such as an electrode pad is formed, various rosin-based resins, terpene-based resins, petroleum-based resins, phenols, and the like. A tackifier such as a resin, a xylene resin, a styrene resin, a coumarone indene resin, or a dicyclopentadiene resin can be blended in the composition in an amount not exceeding 40% by weight.

As other optional components, various fillers, coloring agents such as pigments, antioxidants, ultraviolet absorbers, and the like can be added in optional amounts as needed.

The conductive pressure-sensitive adhesive of the present invention is obtained by blending the above essential components and optional components and then crosslinking them. For the crosslinking reaction, an isocyanate compound which causes a crosslinking reaction by heating is used. As the isocyanate compound that can be used, for example, phenylene diisocyanate, 2,3-toluylene isocyanate, 4,4-
Diisocyanates such as diphenylmethane diisocyanate, hexamethylene diisocyanate, and hydrogenated products of 4,4-diphenylmethane diisocyanate; adducts obtained by reacting hexamethylene isocyanate with trimethylolpropane; And isocyanates. These isocyanate compounds react with the polyester polyol to form a three-dimensional crosslink in a matrix.

In general, the higher the crosslinking density, the lower the adhesive strength.
If the cross-linking density is low, the cohesive strength will be insufficient. Therefore, it is important to adjust the degree of cross-linking in order to balance the tackiness and the cohesiveness. As an adjustment method, there is a method of adjusting the type, blending amount, molecular weight, number of functional groups, and the like of the polyester polyol and the isocyanate compound. Usually, the viscosity average molecular weight of the polyester polyol is in the range of several hundreds to tens of thousands, but it is preferable to select the type of the isocyanate compound to be used according to the molecular weight of the polyester polyol. That is, when a bifunctional polyester polyol having a viscosity average molecular weight of several hundreds is used, it is necessary to use at least a trifunctional isocyanate compound in order to form a three-dimensional matrix. However, in this case, if an isocyanate compound having a low molecular weight is used, a relatively large amount of the isocyanate compound is required to impart a suitable cohesive force, and as a result, the crosslink density is increased, and the adhesive strength is reduced. There is a risk. Therefore, by appropriately blending the bifunctional isocyanate compound, the molecular weight between crosslinks becomes moderately large, and the adhesive strength and the cohesive strength can be balanced. On the other hand, when a trifunctional polyester polyol having a viscosity average molecular weight of tens of thousands is used, the number of functional groups in the pressure-sensitive adhesive increases and the reactivity decreases. Therefore, a polyfunctional isocyanate compound having a large molecular weight should be used. Is not preferable, and it is preferable to use a bifunctional isocyanate compound having a small molecular weight.

Next, an example of a method for obtaining the conductive adhesive and the electrode pad of the present invention will be described below.

First, optional components such as a plasticizer and a viscosity modifier are blended, if necessary, with essential components comprising a polyester polyol, an ionic compound and a solvent capable of dissolving the ionic compound. Prepare the composition.

Next, this composition is mixed with an isocyanate compound to form a uniform solution, and this solution is coated on an arbitrary carrier such as a separator and crosslinked by heating to form a sheet-like electrode of the present invention. Make a pad. In addition, the electrode pad of the present invention can be obtained by applying a conductive paint on one surface of a plastic film such as a polyester film or a polyethylene film, depositing a metal film, or laminating a metal foil, in addition to the above. A structure in which an electrode pad having the above composition is formed on the conductive surface of the conductive support may be used.

[0025]

EXAMPLES Hereinafter, the conductive pressure-sensitive adhesive of the present invention and an electrode pad using the same will be specifically described with reference to examples. The present invention is not limited to the following embodiments, and it goes without saying that various applications are possible without departing from the technical idea of the present invention.
In the following examples, parts and% all mean parts by weight and% by weight.

Example 1 4 parts of lithium perchlorate were dissolved in 20 parts of dimethyl polyethylene glycol, and 80 parts of polycaprolactone diol (viscosity average molecular weight: 2,000) and 0.1 part of dioctyltin dilaurate were added and mixed with stirring. Later, polyisocyanate 8 obtained by adducting trimethylolpropane 8
Parts were added and mixed uniformly. This was coated on a polyester separator so as to have a thickness of 1 mm, and was heated and crosslinked at 100 ° C. to produce a sheet-like electrode pad made of a transparent conductive adhesive.

The impedance of the obtained sheet-like electrode pad was 1.5 × 10 ⁴ Ω, and the adhesive strength was 286 g. When this electrode pad was used for a low-frequency treatment device, it had good adhesion to the human body and had a good feeling of wearing.

Further, when it was repeatedly adhered to a human body nine times, good adhesiveness was maintained, and the tenth adhesive strength was 143 g.

Example 2 4 parts of lithium perchlorate were dissolved in 20 parts of dimethyl polyethylene glycol, and 80 parts of polycarbonate diol (viscosity average molecular weight: 2,000) and 0.1 part of dioctyltin dilaurate were added thereto, followed by stirring and mixing. Then, 7 parts of polyisocyanate adducted with trimethylolpropane was added and uniformly mixed. This was coated on a polyester separator so as to have a thickness of 1 mm, and was heated and crosslinked at 100 ° C. to produce a sheet-like electrode pad made of a transparent conductive adhesive.

The impedance of the obtained sheet-like electrode pad was 2.3 × 10 ⁴ Ω, and the adhesive strength was 226 g. When this electrode pad was used for a low-frequency treatment device, it had good adhesion to the human body and had a good feeling of wearing.

Further, when it was repeatedly adhered to the human body nine times, good adhesiveness was maintained, and the adhesive strength at the tenth time was 112 g.

Example 3 3 parts of lithium perchlorate was dissolved in a mixed solution of 10 parts of dimethylpolyethylene glycol and 10 parts of ethyl acetate.
Polyester diol (3-methyl-1,5-pentanediol / adipic acid system, viscosity average molecular weight 300
0) 100 parts and 0.1 part of dioctyltin dilaurate were added and stirred and mixed, and then 12 parts of polyisocyanate adducted with trimethylolpropane was added and mixed uniformly. This is placed on a polyester separator with a thickness of 1 mm.
, And crosslinked by heating at 100 ° C. to volatilize the ethyl acetate to prepare a sheet-like electrode pad made of a transparent conductive adhesive having a thickness of about 1 mm after drying.

The obtained sheet-shaped electrode pad had an impedance of 7.5 × 10 ⁴ Ω and an adhesive strength of 178 g.

Further, when it was repeatedly adhered to a human body nine times, good adhesiveness was maintained, and the tenth adhesive strength was 138 g.

Example 4 4 parts of lithium perchlorate were dissolved in 40 parts of dimethyl polyethylene glycol, and 60 parts of polycaprolactone triol (viscosity average molecular weight: 3000) and 0.1 part of dioctyltin dilaurate were added and mixed with stirring. Thereafter, 5 parts of polymethylene polyphenyl polyisocyanate was added and uniformly mixed. This was coated on a polyester separator so as to have a thickness of 1 mm, and was heated and crosslinked at 100 ° C. to produce a sheet-like electrode pad made of a transparent conductive adhesive.

The obtained sheet-like electrode pad had an impedance of 4.4 × 10 ⁴ Ω and an adhesive strength of 265 g.

Furthermore, when it was repeatedly adhered to the human body nine times, good adhesiveness was maintained, and the adhesive strength at the tenth time was 96 g.

Example 5 Lithium perchlorate (4 parts) was dissolved in dimethyl polyethylene glycol (20 parts).
-Methyl-1,5-pentanediol / adipic acid system,
(Viscosity average molecular weight 5000), 80 parts, dioctyltin dilaurate 0.1 part, and polyvinyl methyl ether 30 parts were added and stirred and mixed, and then trimethylolpropane adducted polyisocyanate 8 parts was added and uniformly mixed. This was applied on a polyester separator so as to have a thickness of 1 mm, and was heated and crosslinked at 70 ° C. to produce a sheet-like electrode pad made of a transparent conductive adhesive slightly yellowish. This composition had less cissing after heat crosslinking than that in which polyvinyl methyl ether was not blended, and had good film-forming properties.

The obtained sheet-shaped electrode pad had an impedance of 4.5 × 10 ⁴ Ω and an adhesive strength of 312 g.

Furthermore, when it was repeatedly adhered to the human body nine times, good adhesiveness was maintained, and the adhesive strength at the tenth time was 106 g.

The impedance and adhesive strength measured in each of the above examples were measured by the following methods.

<Impedance> An electrode pad (10 mm × 10 mm) obtained from a conductive adhesive was sandwiched between two copper plates, and the impedance when an alternating voltage of 1 kHz and 1 mV was applied was measured using an LCR meter.

<Adhesive Strength> The same electrode pad as used in the above impedance test was placed on a sample stage of a rheometer tester, and a probe (area 12φ, weight 10
After fixing g), the electrode pad was brought into contact with the probe for 10 seconds, and the force (adhesive force) when the probe was peeled off at a speed of 50 mm / min was measured.

[0044]

As described above, the conductive pressure-sensitive adhesive of the present invention is
Polyester polyol is used as a skeletal component during gel formation, and is crosslinked with an isocyanate compound. Therefore, the balance between conductivity and tackiness is excellent, and the repetitive adhesiveness (re-adhesion property) required when reattaching is required. Adhesiveness)
It is also excellent.

Further, since the electrode pad obtained from the conductive adhesive having such characteristics has excellent conductivity, the electrode pad for treatment, the electrode for medical use, the ground electrode,
It is useful as a pad for various electrodes such as a cosmetic electrode.

──────────────────────────────────────────────────続 き Continuation of front page (51) Int.Cl. ⁷ Identification symbol FI // C09J 167/02 A61B 5/04 300Y (56) References JP-A-62-86076 (JP, A) JP-A-54- 1400 (JP, A) JP-A-1-266161 (JP, A) JP-A-62-139628 (JP, A) JP-A-3-266704 (JP, A) JP-A-2-261882 (JP, A) JP-A-62-207380 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C09J 4/00-201/10 A61B 5/408 A61K 9/70 A61N 1/04

Claims (4)

(57) [Claims] 1. An electrically conductive pressure-sensitive adhesive obtained by crosslinking a composition containing a polyester polyol, an ionic compound, and a solvent capable of dissolving the ionic compound as essential components with an isocyanate compound. 2. The conductive pressure-sensitive adhesive according to claim 1, further comprising a plasticizer. 3. A polyester polyol of 30 to 90% by weight, a solvent of 10 to 70% by weight and an ionic compound of 0.1 to 90% by weight.
3. The conductive pressure-sensitive adhesive according to claim 2, which is contained in the range of 01 to 30% by weight. 4. An electrode pad comprising the conductive pressure-sensitive adhesive according to claim 1.