Biological sensor

Abstract

A biological sensor that is affixed to a living body and acquires a biological signal, said biological sensor including: a housing; a base material that is provided to the housing on the living body side thereof; an electrode that is provided to the base material on the living body side thereof; and an adhesive layer that fixes the housing to the living body, wherein the adhesive layer includes a urethane-based adhesive.

Description

biosensor

[0001] The present invention relates to a biosensor, and more particularly to a biosensor that is less likely to generate noise even when used for a long period of time.

[0002] Biometric sensors are used to measure biological information such as electrocardiogram waveforms, pulse waves, electroencephalograms, body temperature, electromyography, blood pressure, pulse rate, blood sugar levels, etc. in medical institutions such as hospitals and clinics, nursing homes, homes, etc. The biological sensor is equipped with electrodes that come into contact with a living body, and when measuring biological information, the biological sensor is attached to the skin of a subject, the electrodes are brought into contact with the skin of the subject, and the electrodes detect physical and chemical changes in the living body, thereby measuring the biological information.

[0003] For example, Patent Document 1 discloses a biosensor that includes a housing, a substrate provided on the living body side of the housing, and electrodes provided on the living body side of the substrate, wherein the substrate has a breaking elongation rate of 30 to 500%, and the electrodes have a static friction coefficient of 3.0 to 7.0. The biosensor described in Patent Document 1 is less likely to generate noise because the electrodes are less likely to shift position even during exercise, making it possible to stably acquire electrocardiogram waveforms even during exercise.

[0004] Japanese Patent Application Laid-Open No. 2022-81415

[0005] However, the biosensor described in Patent Document 1 was not designed for long-term use, and therefore a biosensor that can stably measure bioinformation even after long-term use, i.e., a biosensor that is less likely to generate noise even after long-term use, has not yet been obtained, and there is a strong demand for its development.

[0006] In view of the above problems, an object of the present invention is to provide a biosensor that is less likely to generate noise even when used for a long period of time.

[0007] As a result of intensive research into solving the above problems, the inventors discovered that the above problems can be solved by using a specific adhesive layer as the adhesive layer that fixes the biosensor to the living body, and thus completed the present invention.

[0008] The present invention is as follows: [1] A biosensor that is attached to a living body to acquire a biosignal, the biosensor comprising: a housing; a base material provided on the living body side of the housing; electrodes provided on the living body side of the base material; and an adhesive layer that fixes the housing to the living body, the adhesive layer including a urethane-based adhesive. [2] The biosensor according to [1] above, comprising: a base adhesive layer that is provided on the living body side of the base material and to which the electrodes are attached; a sensor main body that is connected to the electrodes and acquires bioinformation; and another base material on which the sensor main body is placed, the biosensor comprising: the housing having a recess formed in a concave shape on the living body side; the base material having a hole at a position corresponding to the recess; and the recess and the hole forming a storage space that stores the sensor main body. [3] The biosensor according to [2] above, wherein the electrode has a through-hole that allows the base adhesive layer to be exposed when attached to the base adhesive layer. [4] The biosensor according to any one of [1] to [3] above, wherein the adhesive layer has an average content of ethylene oxide-based structural units of 60% by mass or less. [5] The biosensor according to any one of [1] to [4] above, wherein the urethane-based adhesive is a cured product of an adhesive composition containing a hydroxyl-terminated urethane prepolymer and a polyisocyanate compound. [6] The biosensor according to [5] above, wherein the adhesive composition has an average content of ethylene oxide-based structural units of 60% by mass or less. [7] The biosensor according to [5] or [6] above, wherein the hydroxyl-terminated urethane prepolymer is a reaction product of an oxyalkylene polymer and a diisocyanate compound in the presence of a tin-free catalyst. [8] The biosensor according to [7] above, wherein the tin-free catalyst contains at least one metal selected from the group consisting of zinc and bismuth. [9] The biosensor according to [7] or [8] above, wherein the oxyalkylene polymer has an average content of ethylene oxide-based structural units of 60% by mass or less.

[10] The biosensor according to any one of [7] to [9] above, wherein the oxyalkylene polymer has an average number of hydroxyl groups per molecule of 1.5 to 3.0.

[11] The biosensor according to any one of [7] to

[10] above, wherein the oxyalkylene polymer includes an oxyalkylene polymer A having an average number of hydroxyl groups per molecule of 2 or more, and an oxyalkylene polymer B having an average number of hydroxyl groups per molecule of 1.

[12] The biosensor according to

[11] above, wherein the oxyalkylene polymer A includes an oxyalkylene polymer A1 having an average number of hydroxyl groups per molecule of 3, and an oxyalkylene polymer A2 having an average number of hydroxyl groups per molecule of 2.

[0009] The present invention provides a biosensor that is less susceptible to noise even when used for a long period of time. This effect is presumably achieved because the specific adhesive layer that fixes the biosensor to the living body has a good balance between adhesive strength to the skin and adhesive strength to devices such as the biosensor, which reduces floating and displacement of the biosensor over a long period of time.

[0010] Fig. 1 is a perspective view showing an example of the configuration of a biosensor of the present invention. Fig. 2 is an exploded perspective view of Fig. 1. Fig. 3 is a cross-sectional view taken along III-III in Fig. 1. Fig. 4 is a plan view showing an example of the configuration of a sensor unit. Fig. 5 is an explanatory diagram showing an example of a noise-free electrocardiogram waveform. Fig. 6 is a diagram explaining the signal-to-noise ratio of an electrocardiogram waveform.

[0011] The present invention will be described in detail below. In this specification, the preferred definitions can be adopted arbitrarily, and combinations of preferred definitions are considered more preferable. In this specification, the term "XX to YY" means "XX or more and YY or less." In this specification, the lower and upper limits of preferred numerical ranges (e.g., ranges of content, etc.) described in stages can be independently combined. For example, the description "preferably 10 to 90, more preferably 30 to 60" can be combined with the "preferable lower limit (10)" and the "more preferable upper limit (60)" to form "10 to 60." Furthermore, in the numerical ranges described in this specification, the upper or lower limit of the numerical range may be replaced with the values ​​shown in the examples. The number average molecular weight (Mn) and weight average molecular weight (Mw) are polystyrene-equivalent molecular weights determined by gel permeation chromatography (GPC) based on a calibration curve prepared using standard polystyrene samples. The isocyanate index is the equivalent ratio ([isocyanate group] / [active hydrogen-containing group]) between the isocyanate group to be reacted and the active hydrogen-containing group (e.g., hydroxyl group), and is expressed as a percentage. For example, an isocyanate index of 85 indicates that the equivalent ratio between the isocyanate group and the active hydrogen-containing group (e.g., hydroxyl group) is 85%. Living organisms refer to the human body (sometimes referred to as "human") and animals such as cows, horses, pigs, chickens, dogs, and cats. In this specification, the term "double-sided PSA sheet" refers to a sheet having a substrate for a double-sided PSA sheet and PSA layers of the same and / or different types on both sides of the substrate. The PSA layers may be formed from a single type of PSA or two or more types of PSA. In this specification, the term "solid content" refers to the non-volatile content excluding volatile substances such as solvents, and indicates components that remain without volatilization when the PSA composition is dried, including those that are liquid, syrup-like, or wax-like at room temperature. The total solid content can also be calculated from the charge amount.

[0012] [Biosensor] A biosensor according to an embodiment of the present invention (hereinafter sometimes simply referred to as "the present embodiment") can be attached to a living body to acquire a biosignal. In particular, it is suitable for use on the human body. The biosensor according to the present embodiment is an adhesive biosensor that is attached to the skin of a living body to measure bioinformation. Note that, in the present embodiment, a case where the living body is a human body will be described as an example, but the living body is not limited to a human body.

[0013] FIG. 1 is a perspective view showing an example of the configuration of a biosensor according to this embodiment, FIG. 2 is an exploded perspective view of FIG. 1, and FIG. 3 is a cross-sectional view taken along line III-III of FIG. 1. While FIG. 1 illustrates an elliptical biosensor, the shape of the biosensor is not limited to an elliptical shape. As shown in FIGS. 1 to 3, the biosensor 10 of this embodiment is a plate-like (sheet-like) member in a plan view. The biosensor 10 of this embodiment includes a housing (cover member) 100, a base material (foam sheet 200) provided on the living body side of the housing 100, electrodes 300 provided on the living body side of the base material (foam sheet 200), and an adhesive layer 400 that secures the housing (cover member) 100 to the living body. The adhesive layer 400 contains a urethane-based adhesive. The biosensor 10 of this embodiment may further include a sensor unit 500, a release paper 600, etc. Biosensor 10 is formed by attaching foam sheet 200, electrodes 300, and adhesive layer 400 to skin 20 of a living body, and acquires a biosignal from skin 20 via electrode 300. When not in use, biosensor 10 may have release paper 600 on the surfaces of foam sheet 200, electrodes 300, and adhesive layer 400 that are attached to skin 20. When in use, release paper 600 is peeled off, and biosensor 10 can be attached to the surface of skin 20.

[0014] The housing 100, the foam sheet 200, and the release paper 600 have the same external shape in a plan view. The sensor unit 500 is placed on the adhesive layer 400 and housed in the storage space S formed by the housing 100 and the foam sheet 200.

[0015] In this specification, a three-dimensional Cartesian coordinate system with three axes (X-axis, Y-axis, and Z-axis) is used, with the short axis direction of the biosensor being the X-axis direction, the long axis direction being the Y-axis direction, and the height direction (thickness direction) being the Z-axis direction. The direction opposite to the side (attached side) of the biosensor that is attached to the living body (subject) is the +Z-axis direction, and the side (attached side) that is attached to the living body (subject) is the -Z-axis direction. In the following explanation, for convenience of explanation, the +Z-axis side may be referred to as the upper side or top, and the -Z-axis side as the lower side or bottom, but this does not represent a universal hierarchical relationship.

[0016] (Housing) As shown in FIGS. 1 to 3 , the housing 100 is located at the outermost position (+Z-axis direction) of the biosensor 10 and is adhered to the upper surface of the foam sheet 200. The housing 100 has a protrusion 110 at the center in the longitudinal direction (Y-axis direction) that protrudes in a substantially dome-like shape toward the height direction (+Z-axis direction) of FIG. 1 , and a recess 110a formed in a concave shape toward the living body on the inner side (attachment side) of the protrusion 110. The lower surface (attachment side surface) of the housing 100 is flat. On the inner side (attachment side) of the protrusion 110, a storage space S for storing the sensor unit 500 is formed by the recess 110a on the inner surface of the protrusion 110 and a foam base material 2110 (foam sheet 200) having a hole 2110a (through-hole 200a) at a position corresponding to the recess 110a.

[0017] The material for forming the housing 100 is not particularly limited, and examples thereof include flexible materials such as silicone rubber, fluororubber, and urethane rubber. These may be used alone or in combination of two or more. The housing 100 can be formed by using a base resin such as polyethylene terephthalate (PET) as a support and laminating the flexible material on the surface of the support. Forming the housing 100 using the flexible material protects the sensor unit 500 placed in the storage space S of the housing 100 and absorbs impacts applied to the biosensor 10 from the top side, thereby reducing the impact on the sensor unit 500.

[0018] The thickness of the top surface and side walls of the protruding portion 110a of the housing 100 is not particularly limited, but is preferably 1.5 to 3 mm. The thickness of the flat portions 120a and 120b of the housing 100 is not particularly limited, but is preferably 0.5 to 1 mm. If the flat portions 120a and 120b of the housing 100 are thin, they are more flexible than the protruding portion 110a. Therefore, when the biosensor 10 is attached to the skin 20, it can easily deform in accordance with deformation of the surface of the skin 20 due to bodily movements such as stretching, bending, and twisting. This can alleviate stress applied to the flat portions 120a and 120b when the surface of the skin 20 is deformed, making it less likely that the biosensor 10 will peel off from the skin 20. By making the thickness of the top surface and side walls of the protruding portion 110a of the housing 100 thicker than the thickness of the flat portions 120a and 120b provided on both ends of the housing 100 in the longitudinal direction (Y-axis direction), the flexibility of the protruding portion 110 can be made lower than the flexibility of the flat portions 120a and 120b, making it possible to protect the sensor unit 500 from external forces applied to the biosensor 10.

[0019] There are no particular restrictions on the outer periphery of the flat portions 120a and 120b of the housing 100, but from the viewpoint of increasing the flexibility of the outer periphery of the flat portions 120a and 120b and improving the wearing comfort of the biosensor, it is preferable that the thickness of the outer periphery be gradually reduced toward the ends.

[0020] The hardness (Shore A hardness) of the housing 100 is not particularly limited, but is preferably 40 to 70, more preferably 50 to 60, from the viewpoint of excellent deformability of the biosensor during body movement.

[0021] (Base Material (Foam Sheet)) As shown in Fig. 3 , foam sheet 200 is provided by adhering it to the underside of housing 100. Foam sheet 200 has through-holes 200a at positions corresponding to protrusions 110 of housing 100. Through-holes 200a allow sensor body 520 of sensor unit 500 to be stored in storage space S formed by recess 110a on the inner surface of housing 100 and through-hole 200a without being obstructed by foam sheet 200.

[0022] The foam sheet 200 has a foam adhesive layer 210 and a housing adhesive layer 220 provided on the surface facing the housing 100 (in the +Z-axis direction).

[0023] <Foam patch layer> As shown in Figure 3, the foam patch layer 210 has a foam base material (also called a foam) 2110 and a base material adhesive layer 2120 provided on the surface of the foam base material 2110 facing the living body (in the -Z axis direction).

[0024] <<Foam Base Material>> There are no particular limitations on the foam base material 2110, but a flexible, waterproof, and moisture-permeable porous body is preferred. There are no particular limitations on the porous body, but from the viewpoint of releasing water vapor due to sweat or the like generated from the skin 20 to which the biosensor 10 is attached to the outside, preferred examples include foam materials such as open-cell, closed-cell, and semi-closed-cell foams.

[0025] The material for forming the foam substrate 2110 is not particularly limited, and examples thereof include thermoplastic resins such as polyurethane resins, polystyrene resins, polyolefin resins, silicone resins, acrylic resins, vinyl chloride resins, and polyester resins. These may be used alone or in combination of two or more.

[0026] There are no particular limitations on the thickness of the foam substrate 2110, but it is preferably 0.5 to 1.5 mm.

[0027] The foam base material 2110 has a hole 2110a at a position corresponding to the protrusion 110 of the housing 100. By forming the adhesive layer for the base material 2120 and the adhesive layer for the housing 220 on the surface of the foam base material 2110 other than the hole 2110a, the through hole 200a can be formed.

[0028] <<Adhesive layer for substrate>> As shown in Figure 3, adhesive layer for substrate 2120 is attached to the underside (-Z axis direction) of foam substrate 2110 and has the function of adhering foam substrate 2110 and electrode 300 together.

[0029] The base adhesive layer 2120 may or may not be moisture permeable. Moisture permeability allows water vapor and the like generated from the skin 20 to which the biosensor 10 is attached to escape to the foam base material 2110 via the base adhesive layer 2120. Furthermore, as described above, the foam base material 2110 has a porous structure, and therefore can release water vapor to the outside of the biosensor 10 via the housing adhesive layer 220. This weakens the adhesive strength of the base adhesive layer 2120 to the skin 20 due to moisture accumulated at the interface between the skin 20 and the base adhesive layer 2120, preventing the biosensor 10 from peeling off from the skin 20.

[0030] The moisture permeability of the adhesive layer for base material 2120 is not particularly limited, but from the viewpoint of being able to transmit sweat and the like to the outside and suppress the load on skin 20, it is preferably 1 to 10,000 (g / m ２ ·day), more preferably 10 to 10,000 (g / m ２ ・day).

[0031] Examples of adhesives used in the substrate adhesive layer 2120 include acrylic adhesives and urethane adhesives described below. These may be used alone or in combination of two or more. Furthermore, the substrate adhesive layer 2120 can be a double-sided adhesive sheet formed from the above-mentioned adhesives.

[0032] From the viewpoint of improving moisture permeability while maintaining adhesive strength, it is preferable that a wavy pattern (web pattern) is formed on the surface of the substrate adhesive layer 2120, in which adhesive-forming portions where adhesive is present and non-adhesive-forming portions where no adhesive are present are alternately formed. The width of the adhesive-forming portions is not particularly limited, but from the viewpoint of improving moisture permeability while maintaining adhesive strength, it is preferably 500 to 1000 μm. The width of the non-adhesive-forming portions is not particularly limited, but from the viewpoint of improving moisture permeability while maintaining adhesive strength, it is preferably 1500 to 5000 μm.

[0033] The thickness of the substrate adhesive layer 2120 is not particularly limited, but from the viewpoint of making the biosensor thinner, it is preferably 10 to 300 μm, more preferably 50 to 200 μm, and particularly preferably 70 to 110 μm.

[0034] 3, the adhesive layer for housing 220 is provided in a state of being attached to the upper surface (+Z-axis direction) of the foam base material 2110. The adhesive layer for housing 220 is attached to the upper surface of the foam base material 2110 at a position corresponding to the flat surface on the attachment side (-Y-axis direction) of the housing 100, and has the function of adhering the foam base material 2110 and the housing 100 together.

[0035] Examples of adhesives used in the housing adhesive layer 220 include acrylic adhesives, silicone adhesives, and urethane adhesives described below. These may be used alone or in combination of two or more. The housing adhesive layer 220 may be a double-sided adhesive sheet formed with any of the above adhesives.

[0036] The thickness of the adhesive layer 220 for the casing is not particularly limited, but is preferably 10 to 300 μm.

[0037] 3, the electrode 300 is attached to the underside of the base adhesive layer 2120, which is the attachment side (-Z axis direction), with a portion of the electrode 300 on the sensor main body 520 side connected to the wiring 530a and 530b, and is sandwiched between the base adhesive layer 2120 and the adhesive layer 400. The portion of the electrode 300 that is not sandwiched between the base adhesive layer 2120 and the adhesive layer 400 comes into contact with a living body. When the biosensor 10 is attached to the skin 20, the electrode 300 comes into contact with the skin 20, making it possible to detect biosignals such as an electrocardiogram waveform, an electroencephalogram, and a pulse rate.

[0038] The electrode 300 may be an electrode sheet formed from a cured product of a conductive composition containing a conductive polymer and a binder resin, a metal, an alloy, or the like, in a sheet shape. The conductive polymer in the conductive composition is contained in a dispersed state in the binder resin.

[0039] The conductive polymer is not particularly limited, and examples thereof include polythiophene-based conductive polymers, polyaniline-based conductive polymers, polypyrrole-based conductive polymers, polyacetylene-based conductive polymers, polyphenylene-based conductive polymers, and derivatives thereof, as well as composites thereof. These may be used alone, or two or more may be used in combination. Among these, from the viewpoint of obtaining excellent contact impedance with a living body and conductivity, a composite of a polythiophene-based conductive polymer and a polyaniline-based conductive polymer is preferred, and a composite of poly(3,4-ethylenedioxythiophene) (sometimes simply referred to as "PEDOT"), a type of polythiophene-based conductive polymer, and polystyrene sulfonic acid (sometimes simply referred to as "PSS"), a type of polyaniline-based conductive polymer, is more preferred.

[0040] It is preferable that the electrode 300 has a plurality of through holes 310 on the surface that comes into contact with the skin 20. This allows the electrode 300, when attached to the adhesive layer 2120 for the base material, to be exposed from the through holes 310 on the side that is attached to the skin 20, thereby improving the adhesion between the electrode 300 and the skin 20.

[0041] (Adhesive Layer) The adhesive used in the adhesive layer 400 is not particularly limited as long as it contains a urethane-based adhesive, but from the viewpoint of minimizing the effects on the skin and ensuring adhesion between the skin and the biosensor, a urethane-based adhesive obtained by curing an adhesive composition described below is preferred. Alternatively, the adhesive layer 400 can be a double-sided adhesive sheet, at least one side of which is formed with an adhesive containing the urethane-based adhesive. When a double-sided adhesive sheet is used, there are no particular limitations, but from the viewpoint of minimizing the effects on the skin, it is preferred that the side made of the urethane-based adhesive be adhered to the skin 20.

[0042] The content of the urethane-based adhesive in the adhesive layer 400 is not particularly limited, but from the viewpoint of minimizing the effect on the skin and ensuring adhesive strength between the skin and the biosensor, the content is preferably 80% by mass or more, more preferably 90% by mass or more, and particularly preferably 100% by mass, relative to 100% by mass of the adhesive layer.

[0043] The content of ethylene oxide-based structural units (hereinafter abbreviated as "EO units") in the pressure-sensitive adhesive layer 400 is not particularly limited, but from the viewpoint of obtaining a pressure-sensitive adhesive that is gentle on the skin and has a good balance between adhesive strength to the skin and adhesive strength to a device, it is preferably 60% by mass or less, more preferably 8 to 55% by mass, even more preferably 10 to 50% by mass, still more preferably 12 to 40% by mass, and particularly preferably 15 to 25% by mass. The EO unit content in the pressure-sensitive adhesive layer 400 is derived from the EO units that constitute the oxyalkylene chain of the oxyalkylene polymer in the hydroxyl-terminated urethane prepolymer, and １３ It can be determined by analyzing the monomer composition of the oxyalkylene chain in the pressure-sensitive adhesive layer by C-NMR (nuclear magnetic resonance) measurement.

[0044] The thickness of the adhesive layer 400 is not particularly limited, but from the viewpoint of ensuring good adhesive strength to the skin, it is preferably 5 to 100 μm, more preferably 10 to 80 μm, and particularly preferably 20 to 50 μm.

[0045] The adhesive strength of the adhesive layer 400 to the skin 20 is not particularly limited, but is preferably 0.5 to 3.0 N / 15 mm, more preferably 0.7 to 3.0 N / 15 mm, and particularly preferably 1.0 to 2.9 N / 15 mm. When the adhesive strength of the adhesive layer 400 to the skin 20 is equal to or greater than the lower limit, the adhesiveness of the adhesive layer 400 to the skin 20 is good. When the adhesive strength of the adhesive layer 400 to the skin 20 is equal to or less than the upper limit, the condition of the skin 20 after the adhesive layer 400 is peeled from the skin 20 is good, and therefore, the effects on the skin 20 can be suppressed. Note that the "adhesive strength to the skin 20" here is measured by the same method as in the examples.

[0046] The adhesive strength of the adhesive layer 400 to the phenolic substrate is not particularly limited, but is preferably 2.0 N / 15 mm or more, more preferably 2.0 to 8.0 N / 15 mm, even more preferably 3.0 to 8.0 N / 15 mm, and particularly preferably 3.5 to 7.5 N / 15 mm. When the adhesive strength of the adhesive layer 400 to the phenolic substrate is equal to or greater than the lower limit, the adhesive layer 400 adheres well to the biosensor, resulting in excellent fixation of the biosensor. When the adhesive strength of the adhesive layer 400 to the phenolic substrate is equal to or less than the upper limit, the adhesive layer 400 can be easily peeled off when using the biosensor repeatedly, resulting in excellent convenience. Note that the "adhesive strength to the phenolic substrate" herein is measured using the same method as in the Examples.

[0047] The difference between the adhesive strength of the adhesive layer 400 to the phenolic resin and the adhesive strength to the skin is not particularly limited, but is preferably 1.8 N / 15 mm or more, and more preferably 2.5 N / 15 mm or more. When there is such a difference, the balance between the adhesive strength to the skin and the adhesive strength to the device is good, and it can be said that there is a low load on the skin to which the device is fixed.

[0048] The toxicity of the adhesive layer 400 is not particularly limited, but from the viewpoint of application to the skin, it is preferable that the adhesive layer 400 be low in toxicity, and the colony formation rate in a cytotoxicity test using the colony formation method specified in ISO 10993-5:2009 is preferably 50% or more, more preferably 70% or more.

[0049] When the pressure-sensitive adhesive layer 400 is applied to human skin and the patient goes about their daily lives, the period until the double-sided pressure-sensitive adhesive sheet peels off from the skin (hereinafter, sometimes simply referred to as "long-term adhesion") is not particularly limited, but is preferably 4 days or more, more preferably 8 days or more, even more preferably 12 days or more, and particularly preferably 14 days or more. A long-term adhesion of 4 days or more can be said to have excellent long-term adhesion to human skin. In the above case, the percentage of people (subjects) who experienced skin abnormalities (redness, itching, etc.) after the double-sided pressure-sensitive adhesive sheet peeled off or was removed from the skin (hereinafter, sometimes simply referred to as "effects after long-term adhesion") is not particularly limited, but is preferably 0%. A 0% effect after long-term adhesion means that the skin condition is good after the double-sided pressure-sensitive adhesive sheet is peeled off, resulting in little impact on the skin. Note that both the "long-term adhesion" and the "effects after long-term adhesion" may be collectively referred to as "long-term adhesion." The "long-term adhesion strength" herein is measured in the same manner as in Examples. The "effect after long-term adhesion" herein is measured in the same manner as in Examples.

[0050] (Urethane-Based Pressure-Sensitive Adhesive) The urethane-based pressure-sensitive adhesive is, for example, obtained by curing a pressure-sensitive adhesive composition containing a hydroxyl-terminated urethane prepolymer and a polyisocyanate compound.

[0051] <Adhesive Composition> The adhesive composition contains, for example, a hydroxyl group-terminated urethane prepolymer and a polyisocyanate compound, and may contain a tackifying resin, other components, and the like, as necessary.

[0052] The content of ethylene oxide-based structural units (hereinafter abbreviated as "EO units") in the pressure-sensitive adhesive composition is not particularly limited, but from the viewpoint of obtaining a pressure-sensitive adhesive that is gentle on the skin and has a good balance between adhesive strength to the skin and adhesive strength to a device, it is preferably 60% by mass or less, more preferably 8 to 55% by mass, even more preferably 10 to 50% by mass, still more preferably 12 to 40% by mass, and particularly preferably 15 to 25% by mass. The EO unit content in the pressure-sensitive adhesive composition is derived from the EO units that constitute the oxyalkylene chain of the oxyalkylene polymer in the hydroxyl-terminated urethane prepolymer, and １３ It can be determined by analyzing the monomer composition of the oxyalkylene chain in the pressure-sensitive adhesive composition by C-NMR (nuclear magnetic resonance) measurement.

[0053] <<Hydroxyl-Terminated Urethane Prepolymer>> The hydroxyl-terminated urethane prepolymer is, for example, a reaction product of an oxyalkylene polymer and a diisocyanate compound in the presence of a tin-free catalyst.

[0054] The EO unit content in the hydroxyl-terminated urethane prepolymer is not particularly limited, but is preferably 60% by mass or less, more preferably 5 to 55% by mass, even more preferably 10 to 50% by mass, even more preferably 12 to 40% by mass, and particularly preferably 15 to 25% by mass. By having the EO unit content in the hydroxyl-terminated urethane prepolymer within the above range, it is easy to obtain a PSA that is gentle on the skin and has a good balance of adhesion to the skin and adhesion to a device. The EO unit content in the hydroxyl-terminated urethane prepolymer was determined as a weighted average of the EO unit content in each component of the raw materials. Note that, like the EO unit content in the PSA composition, the EO unit content in the hydroxyl-terminated urethane prepolymer is also determined as follows: １３ It can also be determined by C-NMR measurement.

[0055] -Oxyalkylene Polymer- The average content of EO units in the oxyalkylene polymer is not particularly limited, but is preferably 60% by mass or less, more preferably 8 to 55% by mass, even more preferably 10 to 50% by mass, even more preferably 12 to 40% by mass, and particularly preferably 15 to 25% by mass. The average content of EO units in the oxyalkylene polymer refers to the weighted average value of the EO unit contents in each oxyalkylene polymer based on the blend amounts of multiple oxyalkylene polymers used in the synthesis of the hydroxyl group-terminated urethane prepolymer. The EO unit content in each oxyalkylene polymer is a value calculated based on the EO blend amount of the raw material in the synthesis of the oxyalkylene polymer. Note that the EO unit content in the oxyalkylene polymer, like the EO unit content in the pressure-sensitive adhesive composition, １３ When the average content of EO units in the oxyalkylene polymer is within the above range, it is easy to obtain a pressure-sensitive adhesive that is gentle on the skin and has a good balance between adhesive strength to the skin and adhesive strength to a device.

[0056] The average number of hydroxyl groups per molecule of the oxyalkylene polymer is not particularly limited, but from the viewpoint of obtaining a pressure-sensitive adhesive that is gentle on the skin and has a good balance between adhesion to the skin and adhesion to a device, it is preferably 1.5 to 3.0, more preferably 1.7 to 2.8, and particularly preferably 1.9 to 2.6. The average number of hydroxyl groups per molecule of the oxyalkylene polymer refers to a weighted average value based on the blend amounts of multiple oxyalkylene polymers used in the synthesis of the hydroxyl-terminated urethane prepolymer. The oxyalkylene polymer may be one type of oxyalkylene polymer, or two or more types of oxyalkylene polymers.

[0057] The oxyalkylene polymer preferably includes an oxyalkylene polymer A (hereinafter sometimes simply referred to as "polymer A") having two or more hydroxyl groups per molecule, and an oxyalkylene polymer B (hereinafter sometimes simply referred to as "polymer B") having one hydroxyl group per molecule. It is preferred that the hydroxyl groups of polymer A and polymer B react with the isocyanate groups of the diisocyanate compound to form urethane bonds, and that the unreacted hydroxyl groups are terminal hydroxyl groups of the molecular chain of the hydroxyl-terminated urethane prepolymer.

[0058] The total content of polymer A and polymer B in the oxyalkylene polymer is not particularly limited, but is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 100% by mass. The content ratio of polymer A to polymer B in the oxyalkylene polymer is not particularly limited, but from the viewpoint of obtaining a pressure-sensitive adhesive having a good balance between adhesive strength to skin and adhesive strength to a device, the mass ratio is preferably 10 / 90 to 95 / 5, more preferably 30 / 70 to 90 / 10, even more preferably 50 / 50 to 85 / 15, and particularly preferably 60 / 40 to 85 / 15.

[0059] --Oxyalkylene Polymer A-- Polymer A has two or more hydroxyl groups per molecule, preferably two to six. Polymer A may be one type of oxyalkylene polymer, or two or more types of oxyalkylene polymers. When polymer A is composed of two or more types of oxyalkylene polymers, the adhesive strength of the adhesive can be easily adjusted. When polymer A is composed of two or more types of oxyalkylene polymers, the average number of hydroxyl groups per molecule of polymer A is not particularly limited, but is preferably 2.1 to 3.0, more preferably 2.2 to 2.9, and particularly preferably 2.3 to 2.8. When the average number of hydroxyl groups of polymer A is within the above range, stress on the skin to which the device is fixed is reduced, and an adhesive that is less likely to leave adhesive residue on the skin can be obtained. The average number of hydroxyl groups per molecule of polymer A can be calculated from the measured hydroxyl value and Mn of polymer A using the formula: hydroxyl value × Mn / 56100. The hydroxyl value can be measured by the method described in the Examples.

[0060] When polymer A is composed of two or more oxyalkylene polymers, examples of polymer A include an oxyalkylene polymer A1 having three hydroxyl groups per molecule (hereinafter sometimes simply referred to as "polymer A1") and an oxyalkylene polymer A2 having two hydroxyl groups per molecule (hereinafter sometimes simply referred to as "polymer A2"). Polymer A1 may be a single type or two or more types. Similarly, polymer A2 may be a single type or two or more types. Polymer A may contain an oxyalkylene polymer having four or more hydroxyl groups per molecule. When polymer A is composed of polymer A1 and polymer A2, the weighted average value based on the composition ratio (blending amount) of polymer A1 and polymer A2, where polymer A1 has three hydroxyl groups per molecule and polymer A2 has two hydroxyl groups per molecule, can be considered to be the average number of hydroxyl groups of polymer A.

[0061] The total amount of polymer A1 and polymer A2 in 100 parts by mass of polymer A is not particularly limited, but is preferably 85 parts by mass or more, more preferably 90 parts by mass or more, and particularly preferably 95 parts by mass or more, from the viewpoint of ease of adjusting the adhesive strength of the pressure-sensitive adhesive, etc. It is particularly preferred that the total amount of polymer A1 and polymer A2 in 100 parts by mass of polymer A is 100 parts by mass, i.e., polymer A consists of polymer A1 and polymer A2.

[0062] The content of polymer A1 is not particularly limited, but from the viewpoint of good adhesive strength of the pressure-sensitive adhesive and suppression of adhesive residue, it is preferably 20 parts by mass or more, more preferably 25 to 95 parts by mass, and particularly preferably 30 to 90 parts by mass, per 100 parts by mass of the total of polymer A1 and polymer A2. The content of polymer A2 is not particularly limited, but from the same viewpoint, it is preferably 80 parts by mass or less, more preferably 5 to 75 parts by mass, and particularly preferably 10 to 70 parts by mass, per 100 parts by mass of the total of polymer A1 and polymer A2.

[0063] For example, when polymer A consists of polymer A1 and polymer A2, the content of polymer A1 is not particularly limited, but from the viewpoint of obtaining a pressure-sensitive adhesive having a good balance between adhesive strength to skin and adhesive strength to a device, it is preferably 10 to 45 parts by mass, more preferably 15 to 40 parts by mass, and particularly preferably 30 to 40 parts by mass, per 100 parts by mass of the total of polymer A1, polymer A2, and polymer B in the oxyalkylene polymer. The content of polymer A2 is not particularly limited, but from the same viewpoint, it is preferably 15 to 50 parts by mass, more preferably 30 to 50 parts by mass, and particularly preferably 40 to 50 parts by mass, per 100 parts by mass of the total of polymer A1, polymer A2, and polymer B in the oxyalkylene polymer. The content ratios of polymer A1, polymer A2, and polymer B are preferably polymer A2, polymer A1, and polymer B, in descending order.

[0064] The average content of EO units in polymer A is not particularly limited, but is preferably 0 to 80% by mass, more preferably 0 to 70% by mass, even more preferably 0 to 60% by mass, and particularly preferably 0 to 50% by mass. １３ The monomer composition of the oxyalkylene chain in polymer A can be analyzed and determined by C-NMR measurement. For example, when the oxyalkylene chain in polymer A is composed of EO units and structural units based on propylene oxide (hereinafter abbreviated as "PO units"), the EO unit content can be calculated based on the area of ​​the peak representing the methylene group of the EO unit and the area of ​​the peak representing the methyl group of the PO unit. When polymer A is composed of, for example, polymer A1 and polymer A2, the EO unit contents of polymer A1 and polymer A2 are similar. The average EO unit content in polymer A can be considered to be a value calculated from the amount of EO blended in the raw materials for synthesizing polymer A. When polymer A is composed of, for example, polymer A1 and polymer A2, the EO unit content of polymer A can be considered to be the weighted average of the EO unit content of polymer A1 and the EO unit content of polymer A2 based on the compositional proportions (blending amounts) of polymer A1 and polymer A2.

[0065] The Mn of polymer A is not particularly limited, but from the viewpoints of achieving good adhesive strength of the PSA, suppressing adhesive residue, and forming a PSA layer with good flexibility, it is preferably 1,000 to 50,000, more preferably 5,000 to 30,000, and particularly preferably 8,000 to 25,000. The Mw / Mn (molecular weight distribution) of polymer A is not particularly limited, but from the viewpoints of being close to 1 and having a narrow molecular weight distribution, the hydroxyl-terminated urethane prepolymer is less likely to become highly viscous and the synthesis is more efficient, it is preferably 1.25 or less, more preferably 1.22 or less, and particularly preferably 1.20 or less. The unsaturation degree of polymer A is also not particularly limited, but from the viewpoints of achieving good curing properties of the hydroxyl-terminated urethane prepolymer and suppressing adhesive residue of the PSA, it is preferable that it is closer to 0 meq / g, preferably 0.020 meq / g or less, more preferably 0.018 meq / g or less, and particularly preferably 0.015 meq / g or less. When polymer A is composed of two or more kinds of oxyalkylene polymers, it is preferable that each of the oxyalkylene polymers has Mn, Mw / Mn and degree of unsaturation within the above ranges.

[0066] The synthesis method of polymer A is not particularly limited, and for example, it can be obtained by ring-opening addition polymerization of a compound having a cyclic ether structure, preferably an alkylene oxide, with an initiator having two or more active hydrogens in the presence of a catalyst. When polymer A consists of polymer A1 and polymer A2, a method can also be used in which an initiator having three active hydrogens and an initiator having two active hydrogens are used in combination to perform ring-opening addition polymerization of a compound having a cyclic ether structure, thereby simultaneously producing polymer A1 and polymer A2. From the viewpoint of more accurately adjusting the blending amounts of polymer A1 and polymer A2, a method is preferred in which polymer A1 obtained by ring-opening addition polymerization of a compound having a cyclic ether structure with an initiator having three active hydrogens and polymer A2 obtained by ring-opening addition polymerization of a compound having a cyclic ether structure with an initiator having two active hydrogens are separately synthesized and then mixed.

[0067] The compound having a cyclic ether structure may be linear or branched. The number of carbon atoms in the compound having a cyclic ether structure is not particularly limited, but is preferably 2 to 14, more preferably 2 to 10, and particularly preferably 2 to 4. The compound having a cyclic ether structure is not particularly limited, and examples thereof include ethylene oxide (EO), propylene oxide (PO), 1,2-butylene oxide, 2,3-butylene oxide, methyl glycidyl ether, butyl glycidyl ether, 2-ethylhexyl glycidyl ether, lauryl glycidyl ether, hexyl glycidyl ether, and tetrahydrofuran. These may be used alone or in combination of two or more. Among these, EO and PO are preferred.

[0068] When two or more compounds having a cyclic ether structure are used in combination, the arrangement of the oxyalkylene groups derived from each compound in the polymer A may be random or block.

[0069] Examples of groups having active hydrogen in the initiator include hydroxyl groups, carboxyl groups, and amino groups having a hydrogen atom bonded to a nitrogen atom. These may be used alone, or two or more may be used in combination. Among these, hydroxyl groups are preferred, and alcoholic hydroxyl groups are more preferred. Examples of initiators having three hydroxyl groups include glycerin, trimethylolethane, trimethylolpropane, and 1,2,6-hexanetriol. These may be used alone, or two or more may be used in combination. Examples of initiators having two hydroxyl groups include ethylene glycol, diethylene glycol, propylene glycol, and dipropylene glycol. These may be used alone, or two or more may be used in combination.

[0070] The number of active hydrogens in the initiator usually corresponds to the number of hydroxyl groups per molecule of the oxyalkylene polymer. Polymer A1 can be synthesized, for example, using glycerin as an initiator. Polymer A2 can be synthesized, for example, using propylene glycol as an initiator. The initiators used as raw materials for synthesizing the oxyalkylene polymer are: １３When polymer A is composed of polymer A1 and polymer A2, the type and amount of polymer A can be identified by C-NMR measurement. １３ The ratio of polymer A1 to polymer A2 is determined by determining the content of oxyalkylene groups such as EO units and PO units bound to each initiator from information on the type and amount of the initiator obtained by C-NMR measurement.

[0071] Ring-opening addition polymerization can be carried out using known catalysts, such as alkali catalysts such as potassium hydroxide, transition metal compound-porphyrin complex catalysts such as complexes obtained by reacting an organoaluminum compound with porphyrin, composite metal cyanide complex catalysts, and catalysts made of phosphazene compounds. Among these catalysts, composite metal cyanide complex (DMC) catalysts are preferred because they tend to produce oxyalkylene polymers with narrow molecular weight distributions and relatively low viscosity. Known compounds can be used as composite metal cyanide complexes, such as zinc hexacyanocobaltate complexes with tert-butanol as a ligand. Synthesis of oxyalkylene polymers by ring-opening addition polymerization using a DMC catalyst can be carried out by known methods, for example, production methods described in WO 2003 / 062301, WO 2004 / 067633, JP 2004-269776 A, JP 2005-15786 A, WO 2013 / 065802, JP 2015-10162 A, etc. can be applied.

[0072] --Oxyalkylene Polymer B-- The oxyalkylene polymer B has one hydroxyl group per molecule. As the polymer B, one type of oxyalkylene polymer may be used alone, or two or more types of oxyalkylene polymers may be used. The number of hydroxyl groups of the polymer B is, like that of the polymer A, １３ This can be confirmed by identifying the type and amount of the initiator used in the synthesis by C-NMR measurement.

[0073] The Mn of polymer B is not particularly limited, but from the viewpoints of forming a pressure-sensitive adhesive layer with good flexibility, good adhesive strength of the pressure-sensitive adhesive, and suppression of adhesive residue, it is preferably 4,000 to 30,000, more preferably 4,500 to 25,000, and particularly preferably 5,000 to 20,000. The Mw / Mn of polymer B is not particularly limited, but from the viewpoints of being close to 1 and having a narrow molecular weight distribution, the hydroxyl-terminated urethane prepolymer is less likely to become highly viscous and synthesis efficiency is improved, it is preferably less than 1.20, more preferably less than 1.13, and particularly preferably less than 1.10. The degree of unsaturation of polymer B is also not particularly limited, but from the viewpoints of good curing properties of the hydroxyl-terminated urethane prepolymer and suppression of adhesive residue in the pressure-sensitive adhesive layer, it is preferably 0.015 meq / g or less, more preferably 0.013 meq / g or less, and particularly preferably 0.010 meq / g or less, with values ​​closer to 0 meq / g being preferable. When polymer B is composed of two or more kinds of oxyalkylene polymers, it is preferable that each of the oxyalkylene polymers has Mn, Mw / Mn and degree of unsaturation within the above ranges.

[0074] The synthesis method of polymer B is not particularly limited, and can be obtained, for example, by ring-opening addition polymerization of a compound having a cyclic ether structure, preferably an alkylene oxide, with an initiator having one active hydrogen in the presence of a catalyst. The compound having a cyclic ether structure is the same as that described for polymer A. Preferably, PO is used alone, or EO and PO are used in combination.

[0075] The average content of EO units in polymer B is not particularly limited, but from the viewpoint of obtaining a pressure-sensitive adhesive having a good balance between adhesive strength to skin and adhesive strength to a device and having suppressed crystallinity, it is preferably 0 to 80 mass%, more preferably 0 to 60 mass%, and particularly preferably 0 to 50 mass%. The average content of EO units in polymer B can be determined in the same manner as for polymer A.

[0076] Examples of the group having an active hydrogen in the initiator include the same as those in the case of Polymer A. These may be used alone, or two or more may be used in combination. Among these, a hydroxyl group is preferred, and an alcoholic hydroxyl group is more preferred. As the initiator having one hydroxyl group, from the viewpoint of ease of availability, for example, monohydric alcohols having 2 to 4 carbon atoms such as n-propanol, isopropanol, n-butanol, sec-butanol, isobutanol, and tert-butanol are preferred. These may be used alone, or two or more may be used in combination. Among these, n-butanol, sec-butanol, isobutanol, and tert-butanol are preferred. The ring-opening addition polymerization can be carried out by a known method, as in the case of Polymer A.

[0077] The content of polymer B is not particularly limited, but from the same viewpoint, it is preferably 5 to 40 parts by mass, more preferably 10 to 35 parts by mass, and particularly preferably 10 to 20 parts by mass, per 100 parts by mass of the total of polymer A1, polymer A2, and polymer B in the oxyalkylene polymer.

[0078] -Diisocyanate Compound- The diisocyanate compound used in the synthesis of the hydroxyl group-terminated urethane prepolymer is an organic compound having two isocyanate groups per molecule. There are no particular limitations on the diisocyanate compound, and examples include aliphatic diisocyanate compounds, alicyclic diisocyanate compounds, aromatic diisocyanate compounds, and araliphatic diisocyanate compounds. These may be used alone or in combination of two or more.

[0079] The aliphatic diisocyanate compound may be either linear or branched. The aliphatic diisocyanate compound is not particularly limited, and examples thereof include tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), dodecamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2-methylpentane-1,5-diisocyanate, and 3-methylpentane-1,5-diisocyanate. These may be used alone or in combination of two or more. The alicyclic diisocyanate compound is not particularly limited, and examples thereof include isophorone diisocyanate (IPDI), hydrogenated xylylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate (HMDI), 1,4-cyclohexane diisocyanate, methylcyclohexylene diisocyanate, and 1,3-bis(isocyanatomethyl)cyclohexane. These may be used alone or in combination of two or more. The aromatic diisocyanate compound is not particularly limited, and examples thereof include tolylene diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate (MDI), 4,4'-dibenzyl diisocyanate, 1,5-naphthylene diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, dialkyldiphenylmethane diisocyanate, and tetraalkyldiphenylmethane diisocyanate. These may be used alone, or two or more may be used in combination. The aromatic aliphatic diisocyanate compound is not particularly limited, and examples thereof include xylylene diisocyanate and tetramethylxylylene diisocyanate (TMXDI). These may be used alone, or two or more may be used in combination. Among these, from the viewpoint of obtaining a pressure-sensitive adhesive layer having good curability of the hydroxyl group-terminated urethane prepolymer and good flexibility, HDI, IPDI, HMDI and TMXDI are preferred, and HDI is more preferred.

[0080] Furthermore, as the diisocyanate compound, a bifunctional isocyanate-terminated urethane prepolymer obtained by previously reacting the above-mentioned diisocyanate compound with a diol (for example, ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, etc.) can also be used.

[0081] -Tin-free catalyst- A tin-free catalyst is a urethane-forming catalyst that does not contain tin. From the viewpoint of obtaining a pressure-sensitive adhesive that is low in toxicity and has little effect on the skin, it is preferable that the pressure-sensitive adhesive does not contain tin or tin compounds.

[0082] The tin-free catalyst is not particularly limited, and examples thereof include tertiary amine catalysts and organometallic catalysts containing metals other than tin. These may be used alone or in combination of two or more. Among these, organometallic catalysts are preferred from the viewpoint of better reaction promotion. The metal contained in the organometallic catalyst containing a metal other than tin is not particularly limited, and examples thereof include zinc, bismuth, titanium, lead, iron, cobalt, and zirconium. These may be used alone or in combination of two or more. Among these, zinc and bismuth are preferred, and zinc is more preferred from the viewpoint of low toxicity to the skin, ease of handling, etc.

[0083] The tertiary amine catalyst is not particularly limited, and examples thereof include triethylamine, triethylenediamine, 1,8-diazabicyclo[5.4.0]-7-undecene (DBU), and the like. These may be used alone, or two or more types may be used in combination. The organometallic catalyst containing a metal other than tin is not particularly limited, and examples thereof include zinc carboxylates such as zinc naphthenate and zinc 2-ethylhexanoate, zinc compounds such as zinc acetylacetonate, and the like; bismuth compounds such as bismuth 2-ethylhexanoate and bismuth neodecanoate, and the like; titanium compounds such as dibutyltitanium dichloride, tetrabutyltitanium, and butoxytitanium trichloride, and the like; lead compounds such as lead oleate, lead 2-ethylhexanoate, lead benzoate, and lead naphthenate, and the like; iron compounds such as iron 2-ethylhexanoate and iron acetylacetonate, and the like; cobalt compounds such as cobalt benzoate and cobalt 2-ethylhexanoate, and the like; and zirconium compounds such as zirconium naphthenate. These may be used alone or in combination of two or more.

[0084] The amount of the tin-free catalyst used in the reaction of the oxyalkylene polymer with the diisocyanate compound is not particularly limited, but from the viewpoint of a good reaction-accelerating effect and a reduction in the amount of residual metal components, the amount is preferably more than 0.001 part by mass and less than 0.05 part by mass, more preferably 0.005 to 0.045 parts by mass, and particularly preferably 0.01 to 0.04 parts by mass, relative to 100 parts by mass of the oxyalkylene polymer.

[0085] The method for producing the hydroxyl-terminated urethane prepolymer is not particularly limited, and examples thereof include a method in which an oxyalkylene polymer, a diisocyanate compound, a catalyst, and a solvent are all charged into a reaction vessel at once, and a method in which a diisocyanate compound is added dropwise or the like to a reaction vessel charged with an oxyalkylene polymer, a catalyst, and a solvent.As a method for producing the hydroxyl-terminated urethane prepolymer, a method in which a diisocyanate compound is added later is preferred from the viewpoint of ease of control of the molecular weight distribution of the hydroxyl-terminated urethane prepolymer due to preferential reaction of low-molecular-weight components in the synthetic raw materials.

[0086] The solvent used in the production of the hydroxyl-terminated urethane prepolymer is not particularly limited, and examples thereof include ketones such as acetone and methyl ethyl ketone; esters such as ethyl acetate; and aromatic hydrocarbons such as toluene and xylene. These may be used alone or in combination of two or more. When a solvent is used in the production of the hydroxyl-terminated urethane prepolymer, there are no particular limitations on the amount used, but from the viewpoints of uniformity of the reaction system and synthesis efficiency, the amount used is preferably 50 to 500 parts by mass, more preferably 70 to 400 parts by mass, and particularly preferably 80 to 300 parts by mass per 100 parts by mass of the oxyalkylene polymer in total.

[0087] The isocyanate index in the production of a hydroxyl-terminated urethane prepolymer (reaction of an oxyalkylene polymer with a diisocyanate compound) is not particularly limited, but from the viewpoint of efficiently obtaining a hydroxyl-terminated urethane prepolymer having an appropriate molecular chain length, it is preferably less than 100, more preferably 30 to 95, and particularly preferably 50 to 95.

[0088] The reaction temperature in producing the hydroxyl group-terminated urethane prepolymer is not particularly limited, but from the viewpoint of promoting the urethanization reaction and suppressing side reactions, it is preferably less than 100° C., more preferably 70 to 95° C., and particularly preferably 75 to 90° C. After completion of the reaction, a reaction terminator such as acetylacetone may be added to deactivate the catalyst.

[0089] The average number of hydroxyl groups per molecule of the hydroxyl-terminated urethane prepolymer is not particularly limited, but from the viewpoint of obtaining a pressure-sensitive adhesive having a good balance between adhesive strength to skin and adhesive strength to a device, it is preferably less than 3.0, more preferably 1.7 to 2.9, and particularly preferably 1.8 to 2.5.

[0090] <<Polyisocyanate Compound>> The polyisocyanate compound is a curing agent for the hydroxyl group-terminated urethane prepolymer. The polyisocyanate compound is a compound having two or more isocyanate groups per molecule, and may be used alone or in combination of two or more. As the polyisocyanate compound, from the viewpoints of availability and reactivity, a diisocyanate compound is preferred. Furthermore, from the viewpoints of good adhesive strength of the pressure-sensitive adhesive and suppression of adhesive residue, a polyisocyanate compound having three or more isocyanate groups per molecule is preferred.

[0091] Specific examples of diisocyanate compounds include the same as the specific examples of diisocyanate compounds constituting the above-mentioned hydroxyl group-terminated urethane prepolymer. These may be used alone, or two or more may be used in combination. Examples of polyisocyanate compounds having three or more isocyanate groups per molecule include isocyanurate-modified compounds, biuret-modified compounds, and allophanate-modified compounds, which are derivatives of the above-mentioned diisocyanate compounds, as well as trifunctional or higher isocyanate group-terminated urethane prepolymers (adducts), which are reaction products of diisocyanate compounds and polyols (e.g., trimethylolpropane) having three or more hydroxyl groups per molecule. These may be used alone, or two or more may be used in combination.

[0092] <<Tackifier Resin>> The PSA composition may contain a tackifier resin. There are no particular limitations on the tackifier resin, and the PSA composition may contain one or both of a tackifier resin having a softening point of 70°C or higher and a tackifier resin having a softening point below 70°C. However, the PSA composition preferably contains a tackifier resin having a softening point of 70°C or higher, and more preferably a tackifier resin having a softening point of 70°C or higher. By including a tackifier resin having a softening point of 70°C or higher, it is easy to obtain a PSA that has sufficient adhesive strength and is reduced in residue on the skin when peeled from the skin.

[0093] Specific examples of tackifier resins include, but are not limited to, rosin-based tackifier resins, terpene-based tackifier resins, hydrocarbon-based tackifier resins, styrene-based tackifier resins, and acrylic tackifier resins. These may be used alone or in combination of two or more. Among these, terpene-based tackifier resins and styrene-based tackifier resins are preferred from the viewpoint of improving adhesive strength to skin and SUS steel sheets. Terpene-based tackifier resins are more preferred from the viewpoint of good adhesive strength to phenolic resins. Furthermore, styrene-based tackifier resins are more preferred from the viewpoint of reducing coloration of the adhesive. The adhesive composition according to this embodiment can suitably contain either a tackifier resin having a hydroxyl group or a tackifier resin not having a hydroxyl group. However, from the viewpoint of appropriately suppressing adhesive strength to skin and further improving water resistance, a tackifier resin not having a hydroxyl group is preferably used. The adhesive composition according to this embodiment does not necessarily need to contain a tackifier resin not having a hydroxyl group.

[0094] - Rosin-Based Tackifying Resin - Specific examples of rosin-based tackifying resins are not particularly limited and include, for example, unmodified rosins (raw rosins) such as gum rosin, wood rosin, and tall oil rosin; modified rosins obtained by modifying these unmodified rosins through hydrogenation, disproportionation, polymerization, etc. (hydrogenated rosin, disproportionated rosin, polymerized rosin, other chemically modified rosins, etc.; the same applies hereinafter); and various other rosin derivatives. These may be used alone or in combination of two or more. Specific examples of the rosin derivative include, but are not limited to, rosin esters such as those obtained by esterifying unmodified rosin with alcohols (i.e., rosin esters) and modified rosin with alcohols (i.e., modified rosin esters); unsaturated fatty acid-modified rosins obtained by modifying unmodified or modified rosin with unsaturated fatty acids; unsaturated fatty acid-modified rosin esters obtained by modifying rosin esters with unsaturated fatty acids; rosin alcohols obtained by reducing the carboxyl groups of unmodified rosin, modified rosin, unsaturated fatty acid-modified rosin, or unsaturated fatty acid-modified rosin esters; metal salts of rosins (especially rosin esters), such as unmodified rosin, modified rosin, and various rosin derivatives; and rosin phenolic resins obtained by adding phenol to rosins (unmodified rosin, modified rosin, various rosin derivatives, etc.) using an acid catalyst and then thermally polymerizing the resulting rosin. These may be used alone or in combination of two or more. Among these, rosin ester-based tackifying resins are preferred.

[0095] The rosin-based tackifying resin may be a commercially available product. Specific examples of commercially available rosin-based tackifying resins include, but are not limited to, "HARIESTER TF," "HARIESTER S," "NEOTALL G2," "NEOTALL 101N," "NEOTALL 125HK," "HARITACK 8LJA," "HARITACK ER95," "HARITACK SE10," "HARITACK PH," "HARITACK F85," "HARITACK F105," "HARITACK FK100," "HARITACK FK125," and "HARITACK PCJ" manufactured by Harima Chemical Co., Ltd.; and "Foral 105-E," "Foral 85-E," and "Foral" manufactured by Eastman Chemical. AX-E" manufactured by Arakawa Chemical Industries, Ltd.; "Superester A-75", "Superester A-100", "Superester A-115", "Superester A-125", "Pensel A", "Pensel AZ", "Pensel C", "Pensel D-125", "Pine Crystal KE-100", "Pine Crystal KE-311", "Pine Crystal KE-359", "Pine Crystal KE-604", and "Pine Crystal KR-140" manufactured by GUANGDONG KOMO Group Co., Ltd. Examples of such products include "KF382S", "KF392S", "KF364", "KF384S", "KF394S", "KF398S", "KF399S", "KF452S", "KF462S", "KF454S", "KF464S", "KP120", "KP130", "KP140", "KP150", "K107", and "K108".

[0096] -Terpene-Based Tackifying Resin- Specific examples of terpene-based tackifying resins include, but are not limited to, terpene resins such as α-pinene polymers, β-pinene polymers, and dipentene polymers; modified terpene resins obtained by modifying these terpene resins (phenol-modified, aromatic-modified, hydrogenated, hydrocarbon-modified, etc.); and the like. These may be used alone, or two or more may be used in combination. Specific examples of the modified terpene resins include, but are not limited to, terpene-modified phenolic resins, aromatic-modified terpene resins (e.g., styrene-modified terpene resins), and hydrogenated terpene resins. These may be used alone, or two or more may be used in combination. Among these, aromatic-modified terpene resins are preferred. Commercially available terpene-based tackifying resins can be used. Specific examples of commercially available terpene-based tackifying resins include, but are not limited to, YS Polystar T130 (manufactured by Yasuhara Chemical Co., Ltd.).

[0097] -Hydrocarbon-Based Tackifying Resin- Specific examples of hydrocarbon-based tackifying resins are not particularly limited, and include various hydrocarbon resins such as aliphatic (C5) petroleum resins, aromatic (C9) petroleum resins, aliphatic / aromatic copolymer (C5 / C9) petroleum resins, hydrogenated products thereof (e.g., alicyclic petroleum resins (alicyclic saturated hydrocarbon resins) obtained by hydrogenating aromatic petroleum resins), various modified products thereof (e.g., maleic anhydride modified products), coumarone resins, and coumarone-indene resins. These may be used alone, or two or more may be used in combination. Among these, alicyclic saturated hydrocarbon resins are preferred. Commercially available hydrocarbon-based tackifying resins can be used. Specific examples of commercially available hydrocarbon-based tackifying resins are not particularly limited, and include, for example, Alcon M115 (manufactured by Arakawa Chemical Industries, Ltd.).

[0098] -Styrene-based tackifying resin- Specific examples of styrene-based tackifying resins are not particularly limited, and include, for example, styrene homopolymers, α-methylstyrene homopolymers, α-methylstyrene / styrene copolymers, styrene / aliphatic copolymers, α-methylstyrene / styrene / aliphatic copolymers, C9-based petroleum resins, C5 / C9-based petroleum resins, phenol-modified styrene resins, and hydrogenated products thereof. These may be used alone, or two or more may be used in combination. Among these, in terms of excellent compatibility with the (meth)acrylic block copolymer, styrene homopolymers, α-methylstyrene homopolymers, α-methylstyrene / styrene copolymers, styrene / aliphatic polymers, α-methylstyrene / styrene / aliphatic copolymers, phenol-modified styrene resins, and partially hydrogenated products thereof are preferred, styrene homopolymers, α-methylstyrene homopolymers, α-methylstyrene / styrene copolymers, and partially hydrogenated products thereof are more preferred, and styrene homopolymers are particularly preferred.

[0099] The styrene-based tackifying resin may be a commercially available product. Specific examples of commercially available styrene-based tackifying resins are not particularly limited, and include, for example, "SYLVARES SA-85," "SYLVARES SA-100," "SYLVARES SA-120," "SYLVARES SA-140," and "SYLVARES 520" manufactured by Arizona Chemical; "ESCOLETZ ECR-213" and "ESCOLETZ ECR-807" manufactured by ExxonMobil; and "YS Resin" manufactured by Yasuhara Chemical Co., Ltd. SX100"; "FTR0100", "FTR2120", "FTR2140", "FTR6100", "FTR6110", "FTR6125", "FTR7100", "FTR8100", "FTR8120", and "FMR0150" manufactured by Mitsui Chemicals, Inc.; and "Kristalex F85", "Kristalex F100", "Kristalex F115", "Kristalex 1120", "Kristalex 3070", "Kristalex 3085", "Kristalex 3100", and "Kristalex 5140" manufactured by Eastman Chemical.

[0100] -Acrylic Tackifying Resin- Specific examples of acrylic tackifying resins are not particularly limited and include, for example, acrylic tackifying resins based on acrylic polymers (homopolymers or copolymers) using one or more (meth)acrylic acid alkyl esters as a monomer component. Specific examples of (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, and methyl (meth)acrylate. Examples of (meth)acrylic acid C1-20 alkyl esters include nonyl acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate. These may be used alone or in combination of two or more. Among these, (meth)acrylic acid alkyl esters having a linear or branched alkyl group having 4 to 18 carbon atoms are preferably used.

[0101] The acrylic polymer may contain, as necessary, units corresponding to other monomer components copolymerizable with the alkyl (meth)acrylate.

[0102] The amount of tackifier resin used per 100 parts by mass of hydroxyl group-terminated urethane prepolymer is not particularly limited, but from the viewpoint of obtaining a PSA that has sufficient adhesive strength to devices and sealants and also has sufficient long-term water resistance, it is preferably 0.5 to 150 parts by mass, more preferably 1.0 to 100 parts by mass, even more preferably 3.0 to 50 parts by mass, and particularly preferably 5.0 to 40 parts by mass.

[0103] <<Other Components>> The PSA composition may contain other components in addition to the hydroxyl-terminated urethane prepolymer, polyisocyanate compound, and tackifier resin. Examples of other components include various additives such as plasticizers, antioxidants, antistatic agents, fillers, UV absorbers, light stabilizers, conductivity-imparting agents, and leveling agents. A solvent may also be included. The other components may be used alone or in combination of two or more, and may be blended in a content range that does not impair the effects of the present invention. The total content of the hydroxyl-terminated urethane prepolymer and polyisocyanate compound in the PSA composition (excluding the solvent) is not particularly limited, but is preferably 85% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 100% by mass, from the viewpoint of fully exhibiting the effects of the present invention.

[0104] The content of the hydroxyl group-terminated urethane prepolymer relative to the total of the hydroxyl group-terminated urethane prepolymer and the polyisocyanate compound is not particularly limited, but from the viewpoint of fully exerting the effects of the present invention, it is preferably 50 to 98 mass%, more preferably 60 to 95 mass%, and particularly preferably 70 to 93 mass%.

[0105] The content of the polyisocyanate compound relative to the total of the hydroxyl group-terminated urethane prepolymer and the polyisocyanate compound is not particularly limited, but from the viewpoint of fully exerting the effects of the present invention, it is preferably 2 to 50 mass%, more preferably 5 to 40 mass%, and particularly preferably 7 to 30 mass%.

[0106] The method for producing a pressure-sensitive adhesive composition involves reacting an oxyalkylene polymer and a diisocyanate compound in the presence of a tin-free catalyst to obtain a hydroxyl-terminated urethane prepolymer, and then mixing the hydroxyl-terminated urethane prepolymer with a polyisocyanate compound to produce the pressure-sensitive adhesive composition. The hydroxyl-terminated urethane prepolymer is reacted with a polyisocyanate compound to preferably obtain a urethane-based pressure-sensitive adhesive. When mixing the hydroxyl-terminated urethane prepolymer with the polyisocyanate compound, a tackifying resin and other components that may be contained in the pressure-sensitive adhesive composition described above may also be mixed.

[0107] <Method for manufacturing a urethane-based adhesive layer obtained by curing an adhesive composition> By using a urethane-based adhesive layer obtained by curing the above-mentioned adhesive composition, it is possible to obtain an adhesive layer 400 that minimizes effects on the skin and ensures adhesive strength between the skin and a biosensor. The urethane-based adhesive is obtained as a reaction product between a hydroxyl-terminated urethane prepolymer in the adhesive composition and a polyisocyanate compound. As described below, for example, the adhesive composition can be applied to a substrate and cured, whereby the urethane-based adhesive can be formed into an adhesive layer.

[0108] Depending on the manner of use of the pressure-sensitive adhesive layer, the pressure-sensitive adhesive composition may be a one-component type in which a hydroxyl group-terminated urethane prepolymer and a polyisocyanate compound as a curing agent are pre-mixed, or may be a two-component type consisting of a first part containing a hydroxyl group-terminated urethane prepolymer and a second part containing a polyisocyanate compound as a curing agent.

[0109] In the reaction between the hydroxyl-terminated urethane prepolymer and the polyisocyanate compound, a catalyst and a solvent may or may not be used, as necessary. When a catalyst is used, the above-mentioned tin-free urethane catalyst can be used. The catalyst may be the same as or different from the catalyst used in the synthesis of the hydroxyl-terminated urethane prepolymer. If the catalyst used in the synthesis of the hydroxyl-terminated urethane prepolymer remains, the remaining catalyst may also exert a catalytic effect in the reaction between the hydroxyl-terminated urethane prepolymer and the polyisocyanate compound. When a catalyst is added during the reaction between the hydroxyl-terminated urethane prepolymer and the polyisocyanate compound, the amount added is not particularly limited, but is preferably more than 0.001 parts by mass and less than 0.05 parts by mass, more preferably 0.005 to 0.045 parts by mass, and particularly preferably 0.01 to 0.04 parts by mass, per 100 parts by mass of the hydroxyl-terminated urethane prepolymer and the polyisocyanate compound combined. When a catalyst is added, it is preferable to add a reaction terminator to deactivate the catalyst after completion of the reaction.

[0110] Examples of solvents used in the reaction between the hydroxyl-terminated urethane prepolymer and the polyisocyanate compound include those similar to those used in the synthesis of the hydroxyl-terminated urethane prepolymer described above. The solvent may be the same as or different from that used in the synthesis of the hydroxyl-terminated urethane prepolymer. If any solvent remains from the synthesis of the hydroxyl-terminated urethane prepolymer, it may be used as is. When a solvent is used, the amount used is not particularly limited, but is preferably 50 to 500 parts by mass, more preferably 70 to 400 parts by mass, and particularly preferably 80 to 300 parts by mass per 100 parts by mass of the total of the hydroxyl-terminated urethane prepolymer and the polyisocyanate compound.

[0111] The reaction temperature between the hydroxyl group-terminated urethane prepolymer and the polyisocyanate compound is not particularly limited, but from the viewpoint of promoting the urethanization reaction and suppressing side reactions, it is preferably less than 120°C, more preferably 40 to 110°C, and particularly preferably 50 to 100°C.

[0112] The isocyanate index of the polyisocyanate compound to be reacted with the hydroxyl-terminated urethane prepolymer is not particularly limited, but is preferably greater than 100, more preferably 101 to 1,500, and particularly preferably 105 to 1,000.

[0113] The formation of the pressure-sensitive adhesive layer 400 is not particularly limited and can be performed using a known method. Examples include a method of applying a pressure-sensitive adhesive composition to a release liner, curing the composition to form a pressure-sensitive adhesive layer, and laminating a substrate; a method of applying a pressure-sensitive adhesive composition to a substrate, curing the composition to form a pressure-sensitive adhesive layer, and laminating a release liner; and the like. These methods may be used alone, or two or more types may be used in combination. The method of applying the pressure-sensitive adhesive composition is not particularly limited, and known methods such as bar coating, knife coating, roll coating, blade coating, die coating, microgravure coating, comma coating, slot die coating, lip coating, and cast coating can be used. These methods may be used alone, or two or more types may be used in combination. After application, it is preferable to form the pressure-sensitive adhesive layer by, for example, hot air drying at 40 to 80°C to sufficiently volatilize the solvent contained in the pressure-sensitive adhesive composition and curing it.

[0114] (Sensor Unit) Fig. 4 is a plan view showing the configuration of the sensor unit 500. Note that the two-dot chain line in Fig. 4 indicates the outer diameter of the housing 100 and the electrodes 300. As shown in Fig. 4, the sensor unit 500 has another base material (flexible substrate 510) on which various components for acquiring biological information are mounted, a sensor main body 520, wirings 530a and 530b connected to the sensor main body 520 in the longitudinal direction, and a battery 540.

[0115] The flexible substrate 510 is a resin substrate, and the sensor body 520 and the wirings 530a and 530b are integrally formed on the flexible substrate 510.

[0116] As shown in Fig. 3, one end of the wiring 530a and 530b is connected to the electrode 300. As shown in Fig. 4, the other end of the wiring 530a is connected to a switch or the like mounted on the component mounting portion 5210 along the outer periphery of the sensor main body 520. The other end of the wiring 530b is also connected to a switch or the like mounted on the component mounting portion 5210, similar to the wiring 530a. The wiring 530a and 530b may be formed in a wiring layer on either the front or back side of the flexible substrate 510.

[0117] As shown in FIG. 4, the sensor main body 520 has a component mounting section 5210 which is a control section, and a battery mounting section 5220 .

[0118] The component mounting unit 5210 has various components mounted on the flexible substrate 510, such as a CPU and integrated circuit that process biosignals acquired from a living body to generate biosignal data, a switch that activates the biosensor 10, a flash memory that stores the biosignals, and a light-emitting element. Circuit examples using the various components are omitted. The component mounting unit 5210 operates using power supplied from a battery 540 attached to the battery attachment unit 5220.

[0119] The component mounting unit 5210 transmits the information to an external device such as an operation checking device that checks the initial operation, or a reading device that reads the biometric information from the biometric sensor 10, via wired or wireless communication.

[0120] The battery mounting section 5220 supplies power to the integrated circuits and the like mounted on the component mounting section 5210. A battery 540 is mounted in the battery mounting section 5220, as shown in FIG.

[0121] 3, in order to protect the adhesive layer 400 and the electrodes 300, it is preferable to attach a release paper 600 to the attachment surface side (-Z axis direction) of the biosensor 10 until the biosensor 10 is attached to the skin 20. By peeling the release paper 600 from the adhesive layer 400 and the electrodes 300 at the time of use, the adhesive strength of the adhesive layer 400 can be maintained.

[0122] (Method for Manufacturing Biosensor) There are no particular limitations on the method for manufacturing the biosensor, and any appropriate method can be used. An example of the method for manufacturing the biosensor will be described below.

[0123] 1 are prepared, and the sensor unit 500 is placed on the adhesive layer 400. After that, the housing 100, foam sheet 200, electrode 300, adhesive layer 400, and adhesive layer 400 are laminated in this order from the housing 100 side toward the adhesive layer 400 side. A release paper 600 may be attached to the surfaces of the foam sheet 200 and adhesive layer 400 that are to be attached to the living body. The manufacturing methods for the housing 100, foam sheet 200, and adhesive layer 400 are not particularly limited as long as they can be used to manufacture these, and any suitable manufacturing method can be used.

[0124] The manufacturing method of the electrode 300 is not particularly limited as long as it is a method that can manufacture the electrode 300, and any suitable manufacturing method can be used. For example, a manufacturing method using a conductive composition described below can be used.

[0125] <Conductive Composition> The conductive composition generally contains a conductive polymer and a binder resin, and may contain a crosslinking agent, a plasticizer, a solvent, other additives, and the like, as needed.

[0126] <<Conductive Polymer>> The conductive polymer may be a solid material formed into pellets of the polymer described above in the description of the "electrode," or may be used as an aqueous solution dissolved in a solvent. Examples of the solvent that can be used include organic solvents and aqueous solvents. The organic solvent is not particularly limited, and examples thereof include ketones such as acetone and methyl ethyl ketone (MEK); esters such as ethyl acetate; ethers such as propylene glycol monomethyl ether; and amides such as N,N-dimethylformamide. These may be used alone, or two or more may be used in combination. The aqueous solvent is not particularly limited, and examples thereof include water; and alcohols such as methanol, ethanol, propanol, and isopropanol. These may be used alone, or two or more may be used in combination.

[0127] The content of the conductive polymer is not particularly limited, but from the viewpoint of obtaining a cured product obtained by curing the conductive composition with excellent conductivity, toughness, and flexibility, the content is preferably 0.20 to 20 parts by mass, more preferably 2.5 to 15 parts by mass, and particularly preferably 3.0 to 12 parts by mass, relative to 100 parts by mass of the conductive composition.

[0128] <<Binder Resin>> As the binder resin, either a water-soluble polymer or a water-insoluble polymer may be used, but from the viewpoint of compatibility with other components contained in the conductive composition, it is preferable to use a water-soluble polymer. Note that the water-soluble polymer may include a polymer that is not completely soluble in water and has hydrophilicity (hydrophilic polymer).

[0129] The water-soluble polymer is not particularly limited, and examples thereof include sugars such as agarose, polyvinyl alcohol (PVA), modified polyvinyl alcohol, polypyrrole, and hydroxyl group-containing polymers such as copolymers of acrylic acid and sodium acrylate. These may be used alone or in combination of two or more. Among these, polyvinyl alcohol and modified polyvinyl alcohol are preferred, and modified polyvinyl alcohol is more preferred.

[0130] The content of the binder resin is not particularly limited, but from the viewpoint of obtaining a cured product obtained by curing the conductive composition with excellent conductivity, toughness, and flexibility, the content is preferably 5 to 80 parts by mass, more preferably 10 to 75 parts by mass, and particularly preferably 20 to 70 parts by mass, relative to 100 parts by mass of the conductive composition.

[0131] The binder resin may be used as a solution in a solvent. The solvent is not particularly limited, and the same solvents as those used for the conductive polymer may be used.

[0132] The conductive composition preferably further contains at least one of a crosslinker and a plasticizer from the viewpoint of imparting toughness and flexibility to a cured product obtained by curing the conductive composition. Toughness refers to the property of achieving both excellent strength and elongation. Toughness does not include a property in which one of strength and elongation is significantly excellent while the other is significantly low, but rather a property of having an excellent balance of both strength and elongation. Flexibility refers to the property of being able to suppress the occurrence of damage such as breakage at the bent portion after bending a cured product containing the conductive composition.

[0133] <<Crosslinking Agent>> The crosslinking agent has the function of crosslinking the binder resin and improving the toughness of the cured product obtained by curing the conductive composition. When the binder resin is a hydroxyl group-containing polymer, the crosslinking agent preferably has reactivity with the hydroxyl group.

[0134] The crosslinking agent is not particularly limited, and examples thereof include zirconium compounds such as zirconium salts; titanium compounds such as titanium salts; boron compounds such as boric acid; isocyanate compounds such as blocked isocyanates; aldehyde compounds such as sodium glyoxylate, formaldehyde, acetaldehyde, glyoxal, and glutaraldehyde; alkoxyl group-containing compounds, methylol group-containing compounds, and the like. These may be used alone or in combination of two or more. Among these, when the binder resin is polyvinyl alcohol, sodium glyoxylate is preferred from the viewpoint of maintaining the performance of the cured product obtained by curing the conductive composition.

[0135] The content of the crosslinking agent is not particularly limited, but from the viewpoint of ensuring the toughness and flexibility of the cured product obtained by curing the conductive composition, the content is preferably 0.01 to 1.5 parts by mass, more preferably 0.2 to 1.2 parts by mass, and particularly preferably 0.4 to 1.0 part by mass, relative to 100 parts by mass of the conductive composition.

[0136] The crosslinking agent may or may not be used in the form of a solution dissolved in a solvent, and the solvent may be the same as that used for the conductive polymer.

[0137] <<Plasticizer>> A plasticizer has the function of improving the conductivity, tensile elongation, and flexibility of a cured product obtained by curing a conductive composition. There are no particular limitations on the plasticizer, and examples thereof include polyol compounds such as glycerin, ethylene glycol, propylene glycol, sorbitol, and polymers thereof; and aprotic compounds such as N-methylpyrrolidone (NMP), dimethylformaldehyde (DMF), N,N-dimethylacetamide (DMAc), and dimethyl sulfoxide (DMSO). These may be used alone or in combination of two or more. Among these, glycerin is preferred from the viewpoint of compatibility with other components.

[0138] The content of the plasticizer is not particularly limited, but from the viewpoint of ensuring the toughness and flexibility of the cured product obtained by curing the conductive composition, it is preferably 0.2 to 80 parts by mass, more preferably 1.0 to 75 parts by mass, and particularly preferably 10 to 70 parts by mass, relative to 100 parts by mass of the conductive composition.

[0139] <<Solvent>> The conductive composition may or may not contain a solvent in any proportion. As the solvent, an organic solvent or an aqueous solvent can be used. Among these, it is preferable to use an aqueous solvent. The organic solvent is not particularly limited, and examples thereof include ketones such as acetone and methyl ethyl ketone (MEK); esters such as ethyl acetate; ethers such as propylene glycol monomethyl ether; and amides such as N,N-dimethylformamide. These may be used alone or in combination of two or more. The aqueous solvent is not particularly limited, and examples thereof include water; and alcohols such as methanol, ethanol, propanol, and isopropanol. These may be used alone or in combination of two or more.

[0140] <<Other Additives>> The conductive composition may contain other additives in addition to the above components. The other additives are not particularly limited, and examples thereof include various known additives such as surfactants, softeners, stabilizers, leveling agents, antioxidants, hydrolysis inhibitors, expanders, thickeners, colorants, and fillers. A solvent may also be contained. The other additives may be used alone or in combination of two or more, and may be blended in an amount within a range that does not impair the effects of the present invention.

[0141] <Method for manufacturing an electrode> A conductive composition containing a conductive polymer and a binder resin is prepared by mixing a conductive polymer and a binder resin in a predetermined ratio. The conductive composition may or may not further contain at least one of a crosslinker and a plasticizer in a predetermined ratio. The conductive composition may be used as an aqueous solution of the conductive composition dissolved in the above-mentioned solvent (sometimes simply referred to as an "aqueous conductive composition solution").

[0142] After applying the conductive composition to the surface of the release substrate, the conductive composition is heated to promote a crosslinking reaction of the binder resin contained in the conductive composition, resulting in a cured product of the conductive composition. If necessary, the surface of the obtained cured product is punched using a press or the like (sometimes simply referred to as "pressing") to form one or more through-holes 310 in the surface of the cured product and shape the outer shape of the cured product into a predetermined shape, thereby obtaining an electrode 300. Forming may also be performed using a laser processing machine instead of a press. A single through-hole 310 may be formed, or two or more through-holes 310 may be formed. If the cured product can be used as a bioelectrode as is, it may be used as a bioelectrode without further molding or other processing.

[0143] The conductive polymer, binder resin, cross-linking agent, plasticizer, and other additives contained in the electrode 300 have contents equivalent to the amounts added when the conductive composition was prepared.

[0144] The release substrate is not particularly limited, and examples thereof include resin films such as polyethylene terephthalate (PET) film, polyethylene (PE) film, polypropylene (PP) film, polyamide (PA) film, polyimide (PI) film, and fluororesin film. These may be used alone or in combination of two or more.

[0145] The method for applying the conductive composition onto the release substrate is not particularly limited, and known methods can be used, such as roll coating, screen coating, gravure coating, spin coating, reverse coating, bar coating, blade coating, air knife coating, dipping, dispensing, etc., or a method in which a small amount of the conductive composition is dropped onto the substrate and spread with a doctor blade. These may be used alone or in combination of two or more.

[0146] The method for heating the conductive composition is not particularly limited, and known methods such as a drying oven, a vacuum oven, an air circulation oven, a hot air dryer, a far-infrared dryer, a microwave reduced pressure dryer, a high-frequency dryer, etc. These may be used alone or in combination of two or more.

[0147] The heating temperature of the conductive composition is not particularly limited as long as it is a temperature that can promote curing of the binder resin contained in the conductive composition, but is preferably 100 to 200°C.

[0148] The heating time for the conductive composition is not particularly limited, but is preferably 0.5 to 300 minutes, more preferably 3 to 120 minutes, from the viewpoint of promoting the curing of the binder resin contained in the conductive composition. (Release Paper) The biosensor 10 is not particularly limited, but from the viewpoint of protecting the surfaces of the foam sheet 200, the electrodes 300, and the adhesive layer 400 that are attached to the living body, it is preferable that the surfaces of the foam sheet 200, the electrodes 300, and the adhesive layer 400 that are attached to the living body are covered with release paper 600 when the biosensor 10 is not in use. The release paper is appropriately peeled off when the biosensor 10 is used. Examples of release paper that can be used include those used in known adhesive tapes for skin. Examples of release paper include fine paper or glassine paper coated with a release agent such as silicone resin or fluororesin; parchment paper; fine paper that is anchor-coated with resin or laminated with polyethylene and coated with a release agent such as silicone resin or fluororesin; and transparent resin films such as polyester film. These may be used alone or in combination. The thickness of the release paper is not particularly limited, but from the viewpoint of protecting the adhesive layer and making it easy to peel off during use, it is preferably 5 to 200 μm, more preferably 10 to 100 μm, and particularly preferably 20 to 50 μm.

[0149] The present invention will be specifically described below based on examples, but the present invention is not limited to the following examples, and various modifications are possible within the scope of the gist of the present invention.

[0150] [Measurement Methods in Synthesis Examples] The methods for measuring various physical properties in the following synthesis examples are as follows.

[0151] <Number average molecular weight (Mn) and weight average molecular weight (Mw)> Mn and Mw were measured by gel permeation chromatography (GPC) under the following measurement conditions (polystyrene equivalent), and the molecular weight distribution (Mw / Mn) was calculated from these values. [Measurement conditions] - Instrument used: "HLC-8320GPC", manufactured by Tosoh Corporation - Column used: "TSKgel (registered trademark) SuperMultiporeHZ-M", manufactured by Tosoh Corporation - Detector: Refractive index (RI) detector - Detection temperature: 40°C - Eluent: Tetrahydrofuran - Flow rate: 0.350 mL / min - Sample concentration: 0.5% by mass - Sample injection amount: 10 μL - Standard sample: Polystyrene

[0152] <Ethylene oxide (EO) unit content> The EO unit content of each oxyalkylene polymer was determined based on the amounts of propylene oxide (PO) and EO used in the synthesis, and the amount of EO charged was considered to be the EO unit content in the oxyalkylene polymer. The EO unit content of the hydroxyl group-terminated urethane prepolymer was determined as the weighted average of the EO unit contents in each of the raw material components.

[0153] <Hydroxyl Value> The hydroxyl value was determined in accordance with Method B (automatic potentiometric titration) of JIS K 1557-1:2007.

[0154] <Degree of Unsaturation> The degree of unsaturation was measured in accordance with JIS K 1557-3:2007.

[0155] <Average number of hydroxyl groups per molecule of oxyalkylene polymer A> The average number of hydroxyl groups per molecule of oxyalkylene polymer A was determined by calculating the weighted average of the numbers of hydroxyl groups per molecule of oxyalkylene polymers A1 and A2 used as oxyalkylene polymer A (the number of hydroxyl groups per molecule of the initiator used in the synthesis of each oxyalkylene polymer) based on the blending amount of each oxyalkylene polymer.

[0156] <Average Number of Hydroxyl Groups per Molecule of Hydroxyl-Terminated Urethane Prepolymer> The number of hydroxyl groups per molecule of each oxyalkylene polymer (oxyalkylene polymers A1, A2, and B) used in the synthesis of the hydroxyl-terminated urethane prepolymer was weighted and averaged based on the blending amount of each oxyalkylene polymer, and this value was regarded as the average number of hydroxyl groups per molecule of the hydroxyl-terminated urethane prepolymer.

[0157] [Materials Used] Details of the synthesis examples and materials used in the examples are shown below: TBA-DMC catalyst: zinc hexacyanocobaltate complex with tert-butanol as a ligand Glycerin Propylene glycol n-butanol Propylene oxide (PO) Ethylene oxide (EO) Adsorbent: synthetic magnesium silicate, "Kyoward (registered trademark) 600S", manufactured by Kyowa Chemical Industry Co., Ltd. Urethane catalyst: zinc (Zn)-containing urethane catalyst (zinc carboxylate), "K-KAT XK627", manufactured by KING INDUSTRIES, Inc. Diisocyanate compound: hexamethylene diisocyanate (HDI), "Duranate (registered trademark) 50M-HDI", manufactured by Asahi Kasei Corporation Toluene Ethyl acetate Curing agent (polyisocyanate compound): HDI-based polyisocyanate, "Duranate E402-80B", manufactured by Asahi Kasei Corporation; solid content approximately 80% by mass PEDOT / PSS pellets: conductive polymer, "Orgacon DRY", manufactured by Agfa Materials Japan, Inc. Modified PVA aqueous solution: aqueous solution containing binder resin and modified PVA (concentration: 10%), "Gohsenex Z-410", manufactured by The Nippon Synthetic Chemical Industry Co., Ltd. Isopropanol Polyethylene terephthalate (PET) film: release substrate Foam substrate A: foam substrate 2110, thickness: 0.5 mm, "Folec (registered trademark)", manufactured by Inoac Corporation Long-term application tape 1: adhesive layer 2120 for base material, thickness: 70 μm, web pattern (width of adhesive-free area: approximately 500 μm, width of non-adhesive-free area: approximately 1500 μm), double-sided adhesive sheet, manufactured by Nitto Denko Corporation. Silicone tape 1: adhesive layer 220 for housing, thickness: 60 μm, "ST503(HC)60", manufactured by Nitto Denko Corporation. Isononyl acrylate, 2-methoxyethyl acrylate, acrylic acid, glyceryl tricaprylate, rosin esters; "HARITACK PCJ", manufactured by Harima Chemicals Co., Ltd. Trifunctional isocyanate compound; "Coronate HL", manufactured by Tosoh Corporation.

[0158] [Synthesis of Oxyalkylene Polymer] (Synthesis Example 1-1) 1000 g of glycerin as an initiator and a TBA-DMC catalyst (metal concentration 46 ppm by mass) were placed in a pressure vessel, and the vessel was purged with nitrogen. The reaction solution was heated to 135°C while stirring, and 120 g of propylene oxide (PO) was added and reacted. After the temperature rise of the reaction solution stopped, it was cooled to 135°C, and while stirring the reaction solution, 3782.4 g of PO and 945.6 g of ethylene oxide (EO) were added to the vessel. After confirming that the internal pressure had stopped changing, an adsorbent was added, and neutralization and catalyst removal were performed to obtain oxyalkylene polymer 1-1, which is polymer A1.

[0159] Synthesis Example 1-2 Oxyalkylene polymer 1-2, which was polymer A2, was synthesized in the same manner as in Synthesis Example 1-1, except that the initiator in Synthesis Example 1-1 was changed from glycerin to propylene glycol.

[0160] Synthesis Example 1-3 An oxyalkylene polymer 1-3, which was polymer A1, was synthesized in the same manner as in Synthesis Example 1-1, except that EO was not added.

[0161] Synthesis Example 1-4 Oxyalkylene polymer 1-4, which was polymer A2, was synthesized in the same manner as in Synthesis Example 1-2, except that EO was not added.

[0162] Synthesis Example 1-5 Oxyalkylene polymer 1-5, which is polymer B, was synthesized in the same manner as in Synthesis Example 1-1, except that the initiator in Synthesis Example 1-1 was changed from glycerin to n-butanol, and after cooling the reaction solution, 2364 g of PO was added instead of EO. Table 1 shows various physical properties of oxyalkylene polymers 1-1 to 1-5.

[0163]

[0164] [Synthesis of Hydroxyl-Terminated Urethane Prepolymer] (Synthesis Example 2-1) A reaction vessel equipped with a thermometer, a stirrer, and a cooling tube was charged with 36.0 parts by mass of oxyalkylene polymer 1-1, 48.0 parts by mass of oxyalkylene polymer 1-2, 16.0 parts by mass of oxyalkylene polymer 1-5, 50.6 parts by mass of toluene, and 50.6 parts by mass of ethyl acetate, and 0.038 parts by mass of a urethanization catalyst was added and mixed at 40 ° C., after which 1.7 parts by mass of a diisocyanate compound (isocyanate index 85) was added and reacted at 80 ° C. The average number of hydroxyl groups per molecule of the blended oxyalkylene polymer A (oxyalkylene polymers A1 and A2) was 2.4, and the average number of hydroxyl groups per molecule of the oxyalkylene polymers (oxyalkylene polymers A1, A2, and B) was 2.2. The mixture was appropriately diluted with ethyl acetate and maintained at 80°C for 7 hours to allow the reaction to proceed, thereby obtaining a 50% by mass solution of a transparent hydroxyl-terminated urethane prepolymer U1 (average number of hydroxyl groups per molecule of oxyalkylene polymer (oxyalkylene polymers A1, A2, and B) 2.2, EO unit content 17% by mass).

[0165] Synthesis Example 2-2 A solution of hydroxyl-terminated urethane prepolymer U2 was produced in the same manner as in Synthesis Example 2-1 using the formulation shown in Table 2. The average number of hydroxyl groups per molecule of the oxyalkylene polymers (oxyalkylene polymers A1, A2, and B) of hydroxyl-terminated urethane prepolymer U2 was 2.2, and the EO unit content was 7% by mass.

[0166] Table 2 shows the blending compositions of the oxyalkylene polymer, diisocyanate compound and urethanization catalyst in Synthesis Examples 2-1 and 2-2.

[0167]

[0168] [Manufacturing of Biosensor] (Example 1) <Manufacturing of Housing A> Housing A was manufactured by forming a coating layer made of silicone rubber with a Shore A hardness of 40 on a support formed using PET as the base resin, and molding the coating layer into a predetermined shape.

[0169] <Production of Foam Sheet A> A rectangular polyolefin foam sheet was expanded three times to obtain a sheet-like foam substrate A (foam substrate 2110). Long-term application tape 1 (substrate adhesive layer 2120) was formed on the underside of foam substrate A (foam substrate 2110), thereby forming foam adhesive layer 210. Thereafter, silicone tape 1 (casing adhesive layer 220) was formed on the upper surface of foam adhesive layer 210, thereby producing foam sheet A (foam sheet 200).

[0170] <Production of Electrode A> 0.38 parts by mass of PEDOT / PSS pellets, 10.0 parts by mass of a modified PVA aqueous solution, 2.0 parts by mass of glycerin (plasticizer), 1.6 parts by mass of isopropanol, and 6.5 parts by mass of water were added to an ultrasonic bath. The aqueous solution containing these components was then mixed in the ultrasonic bath for 30 minutes to prepare a uniform conductive composition aqueous solution A. The prepared conductive composition aqueous solution A was applied to a polyethylene terephthalate (PET) film using an applicator. The PET film coated with the conductive composition aqueous solution A was then transported to a drying oven, where the conductive composition aqueous solution A was heated and dried at 135°C for 3 minutes to prepare a cured conductive composition. The cured product was then stamped (pressed) into a desired shape to form a sheet, producing electrode A, an electrode sheet (bioelectrode).

[0171] <Production of Pressure-Sensitive Adhesive Layer of Example 1> A liquid (pressure-sensitive adhesive composition) obtained by mixing 100 parts by mass of a 50% by mass solution of hydroxyl group-terminated urethane prepolymer U1 and 5 parts by mass of a curing agent was degassed, and then applied to a polyester film release paper using a knife coater. The resulting mixture was then dried at 100°C for 2 minutes to form a pressure-sensitive adhesive layer of Example 1 having a thickness of 25 µm.

[0172] <Manufacture of the biosensor of Example 1> A sensor unit equipped with a battery capable of measuring an electrocardiogram and a control unit was placed in the center of the upper surface (the surface not covered with the release paper) of the adhesive layer of Example 1. Then, with the foam sheet A sandwiched between the base adhesive layer of the foam sheet A and the adhesive layer of Example 1, a pair of electrodes A were attached to the attachment surface of the base adhesive layer, and the electrodes A were connected to the wiring of the sensor unit. Furthermore, a housing A was laminated on the foam sheet A so that the sensor unit was positioned within the storage space formed by the foam sheet A and the housing A, thereby producing the biosensor of Example 1.

[0173] Example 2 An adhesive layer and a biosensor of Example 2 were produced in the same manner as in Example 1, except that hydroxyl-terminated urethane prepolymer U2 was used instead of hydroxyl-terminated urethane prepolymer U1 in Example 1.

[0174] Example 3 An adhesive layer and a biosensor of Example 3 were prepared in the same manner as in Example 1, except that 100 parts by mass of an acrylic adhesive solution (acrylic adhesive composition: solid content 40% by mass) prepared as follows was used instead of a liquid (urethane adhesive composition) prepared by mixing 100 parts by mass of a 50% by mass solution of hydroxyl group-terminated urethane prepolymer U1 and 5 parts by mass of a curing agent in Example 1. The acrylic pressure-sensitive adhesive solution (acrylic pressure-sensitive adhesive composition: solids content 40% by mass) was prepared by uniformly blending 100 parts by mass of an acrylic copolymer (a copolymer consisting of isononyl acrylate:2-methoxyethyl acrylate:acrylic acid=65 parts by mass:30 parts by mass:5 parts by mass) in toluene with 20 parts by mass of glyceryl tricaprylate, 10 parts by mass of a rosin ester (trade name: HARITACK PCJ, manufactured by Harima Chemicals Co., Ltd.) as a tackifying resin, and 0.07 parts by mass of a trifunctional isocyanate compound (trade name: CORONATE HL, manufactured by Tosoh Corporation) as a crosslinking agent.

[0175] [Evaluation of Pressure-Sensitive Adhesive Layer] The pressure-sensitive adhesive layers produced in the above examples were subjected to the following various evaluations. The evaluation results are shown in Table 3. Examples 1 and 2 are working examples, and Example 3 is a comparative example.

[0176] <Adhesive Strength> (1) Against Phenol Resin The pressure-sensitive adhesive layer (the side not coated with release paper) was placed on a phenolic resin plate ("SUMILITE (registered trademark) PL-1102", manufactured by Sumitomo Bakelite Co., Ltd.; length 125 mm, width 30 mm, thickness 2 mm), and a rubber roller was rolled back and forth once at a load of 2 kg and a speed of 300 mm / min from the side opposite the pressure-sensitive adhesive layer (the side coated with release paper) to press the pressure-sensitive adhesive layer onto the phenolic resin plate. After leaving to stand for 20 minutes, the pressure-sensitive adhesive layer was peeled off at a peel angle of 90° and a speed of 300 mm / min, thereby measuring the adhesive strength when the adherend was a phenolic resin (against phenolic resin) according to a method in accordance with JIS Z 0237:2009. Table 3 shows the average of three measurements. The measured adhesive strength was evaluated according to the following evaluation criteria. [Evaluation criteria (against phenolic resin)] A: 2.0 N / 15 mm or more B: 1.0 N / 15 mm or more but less than 2.0 N / 15 mm C: Less than 1.0 N / 15 mm In the cases of evaluations A and B, it can be said that the adhesive strength to the biosensor is sufficient. On the other hand, in the case of evaluation C, it cannot be said that the adhesive strength to the phenolic resin is sufficient.

[0177] (2) To Skin In the above (1) To Phenol Resin, adhesive strength was measured in the same manner, except that instead of the phenolic resin plate, the skin of the forearm of humans (three subjects) was used as the adherend. The humans (three subjects) were (1) Gender: Male, Race: Japanese, Age: 30s, (2) Gender: Male, Race: Japanese, Age: 20s, and (3) Gender: Female, Race: Japanese, Age: 30s. Table 3 shows the average of three measurements. The measured adhesive strength was evaluated according to the following evaluation criteria. [Evaluation Criteria (To Skin)] A: 0.5 to 3.0 N / 15 mm B: Less than 0.5 N / 15 mm C: More than 3.0 N / 15 mm In the case of Evaluation A, the adhesive strength to the skin was moderate and can be said to be gentle on the skin. On the other hand, in the case of Evaluation B, the adhesive strength to the skin was insufficient. In addition, in the case of Evaluation C, the adhesive was difficult to peel from the skin and sometimes caused pain when peeling.

[0178] (3) Difference in Adhesion Strength Between Phenolic Resin and Skin The difference in adhesion strength between the phenolic resin and the skin was calculated by subtracting the adhesion strength to the skin from the adhesion strength to the phenolic resin measured above. The difference in adhesion strength between the phenolic resin and the skin was evaluated using the following evaluation criteria. [Evaluation criteria (difference in adhesion strength between the phenolic resin and the skin)] A: 2.5 N / 15 mm or more B: 1.8 N / 15 mm or more but less than 2.5 N / 15 mm C: Less than 1.8 N / 15 mm In the cases of evaluations A and B, it can be said that the biosensor can be fixed and detached while minimizing the impact on the skin. On the other hand, in the case of evaluation C, it cannot be said that the biosensor can be fixed and detached while minimizing the impact on the skin.

[0179] <Cytotoxicity Test> A cytotoxicity test (cell line: V79 cells, medium: MEM10 medium) was performed on the adhesive layer using the colony formation method by extraction in accordance with ISO 10993-5:2009 "Biological evaluation of medical devices - Part 5: In vitro cytotoxicity testing," and the colony formation rate was determined. The test solution used was an extract obtained by extracting 1 g of the adhesive layer in medium at 37°C for 24 hours. Table 3 shows the average colony formation rate based on three measurements, evaluated according to the following evaluation criteria. [Evaluation Criteria] A: 70% or more B: 50% or more but less than 70% C: Less than 50% In the cases of evaluations A and B, there is no or very weak cytotoxicity, and it can be said that the biosensor with the adhesive layer has little effect on the skin. On the other hand, in the case of evaluation C, there is stronger cytotoxicity, and it cannot be said that the biosensor with the adhesive layer has little effect on the skin.

[0180] <Long-term Adhesion (Long-term Adhesion Strength and Effects After Long-term Adhesion)> In the same manner as in the measurement of adhesive strength to skin in (2) above, the adhesive layer (the side not covered with the release paper) was pressed onto the skin of the forearm of humans (3 subjects), and the subjects continued their daily lives (work, shower, sleep, etc.) in this state for up to 14 days. The number of days until the adhesive layer peeled off was counted to evaluate the long-term adhesion strength. In addition, the presence or absence of adhesive residue and effects on the skin (redness, itching, etc.) upon peeling was confirmed to evaluate the effects after long-term adhesion. Note that if the adhesive layer remained attached for 14 days, it was peeled off by hand while maintaining a 90° angle between the skin of the forearm and the adhesive layer to check for adhesive residue and effects on the skin (redness, itching, etc.). Table 3 shows the evaluation of the long-term adhesion strength based on three measurements. The measured effects after long-term adhesion were evaluated according to the following evaluation criteria. [Evaluation criteria (effects after long-term application)] A: 0% of subjects showed adhesive residue, redness and itching of the skin. B: No adhesive residue was observed, but more than 0% of subjects showed redness and itching of the skin. C: The application did not last for 14 days. In addition, more than 0% of subjects showed redness and itching of the skin after peeling from the skin. In the case of evaluation A, it can be said that the stress of the adhesive layer on the skin is sufficiently small. On the other hand, in the case of evaluation B, it cannot be said that the stress of the adhesive layer on the skin is sufficiently small.

[0181] [Evaluation of Biosensors] The following various evaluations were carried out for each biosensor manufactured in the above examples. The evaluation results are shown in Table 3. Examples 1 and 2 are working examples, and Example 3 is a comparative example. Note that the "humans (3 subjects)" described below are the same as those used in (2) for measuring adhesive strength to skin.

[0182] <Noise Measurement> The biosensors manufactured in each example were attached to the skin of three human subjects for 24 hours to measure electrocardiograms and obtain electrocardiogram waveforms. When noise is absent, the electrocardiogram waveform consists of P waves, QRS waves, and T waves, as shown in Figure 5. From the obtained electrocardiogram waveform, as shown in Figure 6, the amplitude of the RS wave, which is composed of the R wave and the S wave in the QRS wave, was determined as the signal (S), and the amplitude of the noise, which is the amplitude of the waveform between adjacent R waves, was determined as the noise (N). The S / N ratio, which is the ratio of the signal (S) to the noise (N), was then calculated. The S / N ratio was calculated by averaging three randomly selected waveforms. Table 3 shows the average S / N ratios based on three measurements, evaluated according to the following criteria: [Evaluation Criteria] A: S / N ratio of 8 or more B: S / N ratio of 5 or more but less than 8 C: S / N ratio of less than 5 A rating of A indicates a biosensor that is sufficiently resistant to noise even when used for a long period of time. On the other hand, in the cases of the evaluations B and C, it cannot be said that the biosensor is sufficiently resistant to noise even after long-term use.

[0183] <Skin Observation> In the noise measurement, the biosensor was attached to the skin of three human subjects for 24 hours, and then the biosensor was removed from the skin. The condition of the skin where the biosensor had been attached was visually observed. Table 3 shows the observation results, evaluated according to the following evaluation criteria. [Evaluation Criteria] A: No redness was observed at the skin attachment point, and there was no problem. B: There was slight redness at the skin attachment point, but there was no problem. C: There was severe redness at the skin attachment point. D: There was roughness at the skin attachment point to the extent that the biosensor could not be attached again. In the cases of ratings A and B, it can be said that the biosensor sufficiently suppressed its effects on the skin even after long-term use. On the other hand, in the cases of ratings C and D, it cannot be said that the biosensor sufficiently suppressed its effects on the skin even after long-term use.

[0184] <Durability> In the noise measurement, the biosensor was attached to the skin of three human subjects for 24 hours. Furthermore, while attached to the subjects' skin, the biosensor was exposed to water in accordance with the "Waterproof Standard: JIS C 0920-1993 (IPX4)." After 24 hours of attachment, the biosensor was peeled off and the condition of the biosensor was observed. Table 3 shows the observation results, evaluated according to the following evaluation criteria. [Evaluation Criteria] A: No water absorption or tearing was observed, and there were no problems. B: No problems within the range of use, with some water absorption or tearing observed, but the impact on measurement was limited. C: Water absorption or tearing caused peeling or other issues, significantly affecting measurement. D: Water absorption or tearing caused peeling or other issues, making 24-hour measurement impossible. Evaluations A and B indicate biosensors capable of long-term measurement. Evaluations C and D, on the other hand, indicate biosensors not capable of long-term measurement.

[0185]

[0186] As can be seen from the evaluation results shown in Table 3, the biosensors of Examples 1 and 2 were found to generate less noise than the biosensor of Example 3. Furthermore, the biosensors of Examples 1 and 2 were found to have better skin observation results, i.e., less impact on the skin, than the biosensor of Example 3. Furthermore, the adhesive layers of Examples 1 and 2 provided in the biosensors of Examples 1 and 2 were found to have lower cytotoxicity and less impact on the skin than the adhesive layer of Example 3 provided in the biosensor of Example 3.

[0187] REFERENCE SIGNS LIST 10 Biosensor 20 Skin 100 Housing 110 Protruding portion of housing 110a Inner recess of protruding portion of housing 120a and 120b Flat portion of housing 200 Foam sheet 200a Through hole of foam sheet 210 Foam adhesive layer 2110 Foam base material 2110a Hole portion 2120 Adhesive layer for base material 220 Adhesive layer for housing 300 Electrode 310 Through hole 400 Adhesive layer 500 Sensor portion 510 Flexible substrate (resin substrate) 520 Sensor body 5210 Component mounting portion 5220 Battery mounting portion 530a and 530b Wiring 540 Battery 600 Release paper

Claims

1. A biosensor that is attached to a living body to acquire a biological signal, comprising: a housing; a base material provided on the living body side of the housing; an electrode provided on the living body side of the base material; and an adhesive layer that fixes the housing to the living body, wherein the adhesive layer contains a urethane-based adhesive.

2. A biosensor according to claim 1, further comprising: a base material adhesive layer provided on the living body side of the base material to which the electrode is attached; a sensor body connected to the electrode to acquire biological information; and another base material on which the sensor body is installed, wherein the housing has a recess formed in a concave shape on the living body side, the base material has a hole at a position corresponding to the recess, and the recess and the hole form an accommodation space for accommodating the sensor body.

3. The biosensor according to claim 2, wherein the electrode has a through hole through which the base material adhesive layer can be exposed in a state where the electrode is attached to the base material adhesive layer.

4. The biosensor according to claim 1, wherein the average content of structural units based on ethylene oxide in the adhesive layer is 60% by mass or less.

5. The biosensor according to any one of claims 1 to 4, wherein the urethane-based adhesive is a cured product of an adhesive composition containing a hydroxyl-terminated urethane prepolymer and a polyisocyanate compound.

6. The biosensor according to claim 5, wherein the average content of structural units based on ethylene oxide in the adhesive composition is 60% by mass or less.

7. The biosensor according to claim 5, wherein the hydroxyl-terminated urethane prepolymer is a reaction product of an oxyalkylene polymer and a diisocyanate compound in the presence of a tin-free catalyst.

8. The biosensor according to claim 7, wherein the tin-free catalyst contains at least one metal selected from the group consisting of zinc and bismuth.

9. The biosensor according to claim 7, wherein the average content of structural units based on ethylene oxide in the oxyalkylene polymer is 60% by mass or less.

10. The biosensor according to claim 7, wherein the average number of hydroxyl groups per molecule of the oxyalkylene polymer is 1.5 to 3.

0.

11. The biosensor according to claim 7, wherein the oxyalkylene polymer contains an oxyalkylene polymer A having an average number of hydroxyl groups per molecule of 2 or more and an oxyalkylene polymer B having 1 hydroxyl group per molecule.

12. The biosensor according to claim 11, wherein the oxyalkylene polymer A includes an oxyalkylene polymer A1 having 3 hydroxyl groups per molecule and an oxyalkylene polymer A2 having 2 hydroxyl groups per molecule.

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