Double-sided pressure-sensitive adhesive sheet, use thereof, and electronic appliance / device

Abstract

The present invention relates to: a double-sided pressure-sensitive adhesive sheet comprising a substrate, a first pressure-sensitive adhesive layer present on one surface of the substrate, and a second pressure-sensitive adhesive layer present on the other surface of the substrate, wherein the first pressure-sensitive adhesive layer, after one-day wear, has a keratin removal amount of 0.100 mg / cm2 or less and the second pressure-sensitive adhesive layer has an adhesive force on a phenolic substrate of 1.0 N / 15 mm or greater; a use of the double-sided pressure-sensitive adhesive sheet; and an electronic appliance / device. Specifically, the present invention relates to: a double-sided pressure-sensitive adhesive sheet which is friendly to the human skin; a use of the double-sided pressure-sensitive adhesive sheet; and an electronic appliance / device equipped with the double-sided pressure-sensitive adhesive sheet.

Description

Double-sided adhesive sheet, its use, and electronic device

[0001] The present invention relates to a double-sided pressure-sensitive adhesive sheet and use thereof, and an electronic device, and in particular to a double-sided pressure-sensitive adhesive sheet that is gentle on human skin and use thereof, and an electronic device equipped with said double-sided pressure-sensitive adhesive sheet.

[0002] Double-sided pressure-sensitive adhesive sheets are used in a variety of fields, including the medical field, the decorative field, the optical equipment field, etc. In particular, when double-sided pressure-sensitive adhesive sheets are used to secure electronic devices such as hearing aids and biosensors, body jewelry, etc. to human skin, the double-sided pressure-sensitive adhesive sheets are required to have high adhesion to human skin and to be gentle on human skin.

[0003] For example, Patent Document 1 discloses a double-sided pressure-sensitive adhesive sheet for application to the skin, which has a surface free energy of the adhesive surface of the double-sided pressure-sensitive adhesive sheet within a specific range and has excellent adhesion to adhesive objects such as electronic devices.

[0004] Japanese Patent Application Laid-Open No. 2023-23326

[0005] However, a double-sided PSA sheet that is sufficiently gentle on human skin has not yet been obtained, and there is a strong demand for its development.

[0006] In view of the above problems, the present invention aims to provide a double-sided pressure-sensitive adhesive sheet that is gentle on human skin, a method for using the double-sided pressure-sensitive adhesive sheet, and an electronic device that includes the double-sided pressure-sensitive adhesive sheet.

[0007] The present inventors conducted extensive research to solve the above-mentioned problems, and as a result, found that the above-mentioned problems could be solved by controlling the amount of keratin peeling after a double-sided pressure-sensitive adhesive sheet has been attached to human skin for one day and the adhesive strength between the double-sided pressure-sensitive adhesive sheet and a phenolic substrate within specific ranges, and thus completed the present invention. That is, the present invention is as follows: [1] A pressure-sensitive adhesive sheet having a substrate, a first pressure-sensitive adhesive layer present on one side of the substrate, and a second pressure-sensitive adhesive layer present on the other side of the substrate, wherein the amount of keratin peeling of the first pressure-sensitive adhesive layer after one day of attachment is 0.100 mg / cm ２

[0023]

[0024] A double-sided pressure-sensitive adhesive sheet, wherein the adhesive strength of the second pressure-sensitive adhesive layer to a phenolic substrate is 1.0 N / 15 mm or more. [2] The double-sided pressure-sensitive adhesive sheet according to [1] above, wherein the adhesive strength of the first pressure-sensitive adhesive layer to human skin is 0.5 to 3.0 N / 15 mm. [3] The double-sided pressure-sensitive adhesive sheet according to [1] or [2] above, wherein the first pressure-sensitive adhesive layer is a layer made of a pressure-sensitive adhesive containing a hydroxyl-terminated urethane prepolymer and a polyisocyanate compound. [4] The double-sided pressure-sensitive adhesive sheet according to [3] above, wherein the pressure-sensitive adhesive further contains a tackifying resin. [5] The double-sided pressure-sensitive adhesive sheet according to [3] or [4] 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. [6] The double-sided pressure-sensitive adhesive sheet according to [5] above, wherein the tin-free catalyst contains at least one of zinc and bismuth. [7] The double-sided pressure-sensitive adhesive sheet according to [5] or [6] above, wherein the oxyalkylene polymer has an average content of structural units based on ethylene oxide of 8 to 55% by mass. [8] The double-sided pressure-sensitive adhesive sheet according to any of [5] to [7] above, wherein the oxyalkylene polymer has an average number of hydroxyl groups per molecule of 1.5 to 3.0. [9] The double-sided pressure-sensitive adhesive sheet according to any of [5] to [8] above, wherein the oxyalkylene polymer comprises an oxyalkylene polymer A having an average number of hydroxyl groups per molecule of 2 or more, and an oxyalkylene polymer B having one hydroxyl group per molecule.

[10] The double-sided pressure-sensitive adhesive sheet according to [9] above, wherein the oxyalkylene polymer A comprises an oxyalkylene polymer A1 having three hydroxyl groups per molecule, and an oxyalkylene polymer A2 having two hydroxyl groups per molecule.

[11] The double-sided pressure-sensitive adhesive sheet according to any one of [1] to

[10] above, wherein the second pressure-sensitive adhesive layer is a layer made of a pressure-sensitive adhesive containing a hydroxyl group-terminated urethane prepolymer and a polyisocyanate compound.

[12] The double-sided pressure-sensitive adhesive sheet according to any one of [1] to

[11] above, wherein the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer are both layers made of a pressure-sensitive adhesive containing a hydroxyl group-terminated urethane prepolymer and a polyisocyanate compound.

[13] Use of the double-sided pressure-sensitive adhesive sheet according to any one of [1] to

[12] above, wherein the first pressure-sensitive adhesive layer is attached to human skin.

[14] Use of the double-sided pressure-sensitive adhesive sheet according to

[13] above, wherein the second pressure-sensitive adhesive layer is attached to an electronic device.

[15] Use of the double-sided pressure-sensitive adhesive sheet according to

[14] above, wherein the electronic device is a flexible device.

[16] An electronic device comprising the double-sided pressure-sensitive adhesive sheet according to any one of [1] to

[12] above.

[0008] According to the present invention, it is possible to provide a double-sided PSA sheet that is gentle on human skin, a use thereof, and an electronic device that includes the double-sided PSA sheet.

[0009] The present invention is described in detail below. In this specification, preferred definitions can be adopted arbitrarily, and combinations of preferred values ​​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 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 obtain "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 a value shown in the examples. In this specification, "human skin" may also be simply referred to as "skin." 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]) of the isocyanate group to be reacted with 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 of the isocyanate group to the active hydrogen-containing group (e.g., hydroxyl group) is 85%.

[0010] [Double-Sided Pressure-Sensitive Adhesive Sheet] In an embodiment of the present invention (hereinafter sometimes simply referred to as "the present embodiment"), the double-sided pressure-sensitive adhesive sheet may be used by adhering one pressure-sensitive adhesive layer to human skin and the other pressure-sensitive adhesive layer to a phenolic substrate. In this case, the pressure-sensitive adhesive layer attached to the human skin may be referred to as the "first pressure-sensitive adhesive layer," and the pressure-sensitive adhesive layer attached to the phenolic substrate may be referred to as the "second pressure-sensitive adhesive layer."

[0011] The adhesive strength of the first pressure-sensitive adhesive layer in the double-sided pressure-sensitive adhesive sheet to human skin is not particularly limited, but is preferably 0.5 to 3.0 N / 15 mm, more preferably 0.5 to 2.0 N / 15 mm, even more preferably 0.7 to 2.0 N / 15 mm, still more preferably 0.9 to 2.0 N / 15 mm, and particularly preferably 0.9 to 1.6 N / 15 mm. When the adhesive strength of the first pressure-sensitive adhesive layer to human skin is equal to or greater than the lower limit, the double-sided pressure-sensitive adhesive sheet adheres well to the skin. When the adhesive strength of the first pressure-sensitive adhesive layer to human skin is equal to or less than the upper limit, the condition of the skin after peeling the double-sided pressure-sensitive adhesive sheet from the skin is good, resulting in excellent skin-friendliness. Note that the "adhesive strength to human skin" herein is measured using the same method as in the Examples.

[0012] The amount of keratin peeled after the first pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive sheet was attached to human skin for one day ("amount of keratin peeled after one day of attachment") was 0.100 mg / cm ２ There is no particular limitation as long as it is less than 0.060 mg / cm ２ or less, more preferably 0.050 mg / cm ２ More preferably, 0.040 mg / cm or less ２ More preferably, the concentration is 0.030 mg / cm or less. ２ Below, particularly preferably 0.020 mg / cm ２ Below 0.015 mg / cm, most preferably ２ When the amount of keratin peeled after one day of application is equal to or less than the upper limit, the condition of the skin after the double-sided pressure-sensitive adhesive sheet is peeled off from the skin is good, and the sheet is therefore gentle on human skin. Note that the "amount of keratin peeled after one day of application" here is measured using the same method as in the Examples.

[0013] When the first pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive sheet is applied to human skin and the user 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, and particularly preferably 12 days or more. A long-term adhesion of 4 days or more can be said to have excellent long-term adhesion to human skin. Furthermore, 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 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 results in good skin condition after the double-sided pressure-sensitive adhesive sheet is peeled off from the skin, and therefore is excellent in gentleness to human skin. The above "long-term adhesion" and the above "effects after long-term adhesion" may both 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.

[0014] The adhesive strength of the second adhesive layer in the double-sided pressure-sensitive adhesive sheet to a phenolic substrate is not particularly limited as long as it is 1.0 N / 15 mm or greater, but is preferably 1.0 to 8.0 N / 15 mm, more preferably 1.2 to 7.5 N / 15 mm, and particularly preferably 1.5 to 7.0 N / 15 mm. When the adhesive strength of the second adhesive layer to a phenolic substrate is equal to or greater than the lower limit, the double-sided pressure-sensitive adhesive sheet adheres well to the phenolic substrate, resulting in excellent fixation of the wearable device. When the adhesive strength of the second adhesive layer to a phenolic substrate is equal to or less than the upper limit, the double-sided pressure-sensitive adhesive sheet can be easily peeled off when using the wearable device repeatedly, resulting in excellent convenience. Note that the "adhesive strength to a phenolic substrate" herein is measured using the same method as in the Examples.

[0015] The thickness of the double-sided PSA sheet is not particularly limited, but is preferably 20 to 200 μm, more preferably 25 to 180 μm, and particularly preferably 30 to 150 μm. When the thickness of the double-sided PSA sheet is within the above range, it can be attached to the skin for a long period of time with little discomfort when attached.

[0016] The double-sided pressure-sensitive adhesive sheet includes at least a substrate and pressure-sensitive adhesive layers provided on both sides of the substrate, specifically, a substrate, a first pressure-sensitive adhesive layer on one side of the substrate, and a second pressure-sensitive adhesive layer on the other side of the substrate.

[0017] The first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer may each be a single layer or multiple layers. The multiple pressure-sensitive adhesive layers provided on the double-sided pressure-sensitive adhesive sheet may be the same pressure-sensitive adhesive layer, or may be pressure-sensitive adhesive layers with different compositions, thicknesses, physical properties, etc.

[0018] The first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer may be the same pressure-sensitive adhesive layer, or may be pressure-sensitive adhesive layers that differ in composition, thickness, physical properties, etc. In one embodiment, the double-sided pressure-sensitive adhesive sheet of the present invention can use a urethane-based pressure-sensitive adhesive obtained by curing a pressure-sensitive adhesive composition described below in both the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer.

[0019] (Substrate) The substrate is preferably made of a material that allows the double-sided pressure-sensitive adhesive sheet to conform well to the shape of the skin or device and is unlikely to break during use. The material of the substrate is not particularly limited, and examples include resin films, cloth, paper, etc. These may be used alone or in combination of two or more types. Furthermore, composite materials such as laminates may also be used.

[0020] The material of the resin film is not particularly limited, and examples thereof include polyurethane; polyamide; acrylic resin; polyolefins such as polyethylene, polypropylene, and ethylene-vinyl acetate copolymer; and polyester. These may be used alone, or two or more may be used in combination. Among these, polyurethane and polyamide are preferred, and thermoplastic polyurethane is more preferred, from the viewpoint of good moisture permeability when applied to the skin. The form of the fabric is not particularly limited, and examples thereof include woven fabric, nonwoven fabric, knitted fabric, and net. These may be used alone, or two or more may be used in combination. The material of the fabric is not particularly limited, and examples thereof include resins as materials for the resin film described above; natural fibers such as cotton, silk, and wool; and the like. These may be used alone, or two or more may be used in combination.

[0021] The substrate may or may not include an auxiliary layer. Examples of the auxiliary layer are not particularly limited, and include a colored layer, an undercoat layer, an antistatic layer, and the like provided on the surface of the substrate.

[0022] The surface of the substrate may be subjected to a surface treatment such as a physical treatment such as corona discharge treatment, plasma treatment, sand matting treatment, ozone exposure treatment, flame exposure treatment, high-voltage shock exposure treatment, or ionizing radiation treatment; a chemical treatment such as chromic acid treatment; or an easy-adhesion treatment using a coating agent (primer), for the purpose of improving adhesion and retention with the pressure-sensitive adhesive layer. The surface treatment for improving adhesion is preferably applied to the entire surface of the substrate layer.

[0023] The thickness of the substrate is not particularly limited, but from the viewpoints of ensuring conformability to the shape of the skin and the device and preventing the substrate from breaking when the double-sided pressure-sensitive adhesive sheet is used, it is preferably 1 to 500 μm, more preferably 5 to 100 μm, and particularly preferably 10 to 30 μm.

[0024] (Adhesive Layer) The adhesive forming the adhesive layer of the double-sided adhesive sheet is not particularly limited, as long as the first adhesive layer exhibits a predetermined amount of keratin peeling after application for one day and the second adhesive layer exhibits a predetermined adhesive strength, and examples thereof include urethane-based adhesives, acrylic-based adhesives, silicone-based adhesives, rubber-based adhesives (natural rubber-based, synthetic rubber-based, mixtures thereof, etc.), polyester-based adhesives, polyether-based adhesives, polyamide-based adhesives, fluorine-based adhesives, etc. These may be used alone or in combination of two or more.

[0025] The surface of the adhesive layer of the double-sided pressure-sensitive adhesive sheet is preferably covered with a release liner to protect the surface of the adhesive layer before use. The release liner is appropriately peeled off from the surface of the adhesive layer when using the double-sided pressure-sensitive adhesive sheet. Release liners used in known adhesive tapes for skin can be used. Examples of release liners include fine paper or glassine paper coated with a release agent such as silicone resin or fluororesin; parchment paper; resin anchor coated or polyethylene-laminated fine paper coated with a release agent such as silicone resin or fluororesin; and transparent resin films such as polyester films. The thickness of the release liner is not particularly limited, but is preferably 5 to 200 μm, more preferably 10 to 100 μm, and particularly preferably 20 to 50 μm, from the viewpoints of protecting the adhesive layer and enabling easy peeling during use.

[0026] (First Pressure-Sensitive Adhesive Layer) From the viewpoint of gentleness to the skin, the pressure-sensitive adhesive forming the first pressure-sensitive adhesive layer is preferably a urethane-based pressure-sensitive adhesive obtained by curing the pressure-sensitive adhesive composition described below. The urethane-based pressure-sensitive adhesive obtained by curing the pressure-sensitive adhesive composition described below provides good adhesion of the pressure-sensitive adhesive layer to the skin, is less likely to leave adhesive residue, and can be suitably applied to the skin.

[0027] The thickness of the first adhesive layer 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.

[0028] <Adhesive Composition> The adhesive composition contains, for example, a hydroxyl group-terminated urethane prepolymer and a polyisocyanate compound, and optionally contains a tackifier resin and other components.

[0029] 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.

[0030] <<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.

[0031] 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.

[0032] -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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] --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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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 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 polymer A1, polymer A2, and polymer B in the oxyalkylene polymer. 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 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.

[0041] 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. １３The 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 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 synthetic raw materials for 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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: １３ When 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.

[0048] 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.

[0049] --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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] -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.

[0055] 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.

[0056] 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.

[0057] -Tin-free catalyst- A tin-free catalyst is a urethane-forming catalyst that does not contain tin. From the viewpoint of obtaining a low-toxicity, skin-friendly adhesive, it is preferable that the adhesive does not contain tin or tin compounds.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] <<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.

[0067] Examples of diisocyanate compounds include the same diisocyanate compounds as those 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 with 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.

[0068] <<Tackifier Resin>> The PSA composition may further contain a tackifier resin, if necessary. The tackifier resin may include a tackifier resin having a softening point of 70°C or higher, or a tackifier resin having a softening point of less than 70°C, or both. Among these, from the viewpoint of easily obtaining a PSA that has sufficient adhesive strength and is less likely to leave adhesive residue when peeled from the skin, it is preferable to include a tackifier resin having a softening point of 70°C or higher, and it is more preferable to include only a tackifier resin having a softening point of 70°C or higher. Furthermore, the tackifier resin may include a tackifier resin having a hydroxyl group, a tackifier resin not having a hydroxyl group, or both. Among these, from the viewpoint of appropriately suppressing adhesive strength to the skin and further improving water resistance, it is preferable to include a tackifier resin not having a hydroxyl group.

[0069] The tackifier resin is not particularly limited, and examples thereof include rosin-based tackifier resins, terpene-based tackifier resins, alicyclic saturated 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 or styrene-based tackifier resins are preferred from the viewpoint of improving adhesive strength to skin and SUS steel plate, terpene-based tackifier resins are more preferred from the viewpoint of improving adhesive strength to phenolic resins, and styrene-based tackifier resins are more preferred from the viewpoint of suppressing coloration of the adhesive.

[0070] The rosin-based tackifying resin is not particularly limited, and examples thereof include 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. The above-mentioned various other rosin derivatives are not particularly limited and include, for example, rosin esters such as those obtained by esterifying unmodified rosin with alcohols (i.e., rosin esters) and those obtained by esterifying modified rosin with alcohols (i.e., modified rosin esters); unsaturated fatty acid-modified rosins obtained by modifying unmodified rosin and 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 resins. These may be used alone or in combination of two or more. Among these, rosin ester-based tackifying resins are preferred.

[0071] The rosin-based tackifying resin may be a commercially available product, and examples thereof include "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," all manufactured by Harima Chemical Co., Ltd.; and "Foral 105-E," "Foral 85-E," and "Foral" manufactured by Eastman Chemical. AX-E" and the like; Arakawa Chemical Industries, Ltd.'s "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", "Pine Crystal KR-140", and the like; GUANGDONG Examples include "KF382S", "KF392S", "KF364", "KF384S", "KF394S", "KF398S", "KF399S", "KF452S", "KF462S", "KF454S", "KF464S", "KP120", "KP130", "KP140", "KP150", "K107", "K108" manufactured by KOMO. These may be used alone, or two or more types may be used in combination.

[0072] The terpene-based tackifying resin is not particularly limited, and examples thereof include terpene resins such as α-pinene polymers, β-pinene polymers, and dipentene polymers; and modified terpene resins obtained by modifying these terpene resins (phenol-modified, aromatic-modified, hydrogenation-modified, hydrocarbon-modified, etc.). The modified terpene resin is not particularly limited, and examples thereof include terpene-modified phenolic resins; aromatic-modified terpene resins such as styrene-modified terpene resins; and hydrogenated terpene resins. Of these, it is preferable to use aromatic-modified terpene resins. One or more of the above terpene-based tackifying resins (e.g., aromatic-modified terpene resins) that differ in type, properties (e.g., softening point), etc. may be used in combination.

[0073] The terpene-based tackifying resin may be a commercially available product. Examples of commercially available terpene-based tackifying resins include, but are not limited to, YS Resin SX100 (manufactured by Yasuhara Chemical Co., Ltd.), YS Polystar T130 (manufactured by Yasuhara Chemical Co., Ltd.), and Alcon M115 (manufactured by Arakawa Chemical Industries, Ltd.). These may be used alone or in combination of two or more.

[0074] The hydrocarbon-based tackifying resin is not particularly limited, and examples thereof include 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, coumarone-indene resins, and other hydrocarbon resins. These may be used alone or in combination of two or more. Among these, alicyclic saturated hydrocarbon resins are preferred.

[0075] The styrene-based tackifying resin is not particularly limited, and examples thereof include 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 in combination of two or more. Among these, 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, with styrene homopolymers, α-methylstyrene homopolymers, α-methylstyrene / styrene copolymers, and partially hydrogenated products thereof being more preferred, and styrene homopolymers being particularly preferred.

[0076] The styrene-based tackifying resin may be a commercially available product. The commercially available styrene-based tackifying resin is not particularly limited, and examples thereof include "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" and the like; "FTR0100", "FTR2120", "FTR2140", "FTR6100", "FTR6110", "FTR6125", "FTR7100", "FTR8100", "FTR8120", "FMR0150" and the like manufactured by Mitsui Chemicals, Inc.; "Kristalex F85", "Kristalex F100", "Kristalex F115", "Kristalex 1120", "Kristalex 3070", "Kristalex 3085", "Kristalex 3100", "Kristalex 5140" and the like manufactured by Eastman Chemical. These may be used alone or in combination of two or more.

[0077] The acrylic tackifying resin is not particularly limited, and examples thereof include acrylic tackifying resins based on acrylic polymers (homopolymers or copolymers) using one or more (meth)acrylic acid alkyl esters as a monomer component. The (meth)acrylic acid alkyl ester is not particularly limited, and examples thereof 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, ...butyl (meth)acrylate, butyl (meth)acrylate, butyl (meth)acrylate, butyl (meth)acrylate, butyl (meth)acrylate, butyl (meth)acrylate, butyl (meth)acrylate, butyl (meth)acrylate, butyl (meth)acrylate, butyl (meth)acrylate, butyl (meth)acrylate, butyl (meth)acrylate, butyl (meth)acrylate, butyl (meth)acrylate, butyl (meth)acrylate, butyl (meth)acrylate, butyl (meth)acrylate, butyl (meth)acrylate, butyl (meth)acrylate, butyl (meth)acrylate, butyl (meth)acrylate, butyl (meth)acrylate, butyl (meth)acrylate, Examples of (meth)acrylic acid alkyl esters having an alkyl group having 1 to 20 carbon atoms include nonyl (meth)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. Among these, (meth)acrylic acid alkyl esters having a linear or branched alkyl group having 4 to 18 carbon atoms are preferred.

[0078] The acrylic polymer may contain, as necessary, units corresponding to other monomer components copolymerizable with the alkyl (meth)acrylate.

[0079] The content of the tackifier resin 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, the content 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 per 100 parts by mass of the hydroxyl group-terminated urethane prepolymer.

[0080] <<Other Components>> The pressure-sensitive adhesive composition may contain other components in addition to the hydroxyl-terminated urethane prepolymer, polyisocyanate compound, and tackifying 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 contained. 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 pressure-sensitive adhesive composition (excluding the solvent) is not particularly limited, but from the viewpoint of fully exhibiting the effects of the present invention, it is preferably 85% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and even preferably 100% by mass.

[0081] The plasticizer is not particularly limited and can be selected from the viewpoints of compatibility with other components and wettability of the pressure-sensitive adhesive layer to the adherend. Examples include fatty acid esters having 8 to 30 carbon atoms and phosphate esters. These may be used alone or in combination of two or more. The antioxidant is not particularly limited and examples include phenol-based, amine-based, sulfur-based, and phosphorus-based antioxidants that contribute to suppressing thermal degradation of the pressure-sensitive adhesive layer. These may be used alone or in combination of two or more. Among these, phenol-based antioxidants are preferred from the viewpoint of low toxicity to the skin. The antistatic agent is not particularly limited and examples include inorganic salts; ionic liquids containing imidazolium ions, pyridinium ions, ammonium ions, etc.; surfactants; and other compounds that contribute to suppressing damage to circuit patterns due to electrostatic discharge. These may be used alone or in combination of two or more. The filler is not particularly limited and examples include talc, calcium carbonate, and titanium oxide. These may be used alone or in combination of two or more. The ultraviolet absorber is not particularly limited, and examples thereof include benzophenone-based, benzotriazole-based, salicylic acid-based, oxalic acid anilide-based, cyanoacrylate-based, and triazine-based ultraviolet absorbers. These may be used alone or in combination of two or more. The light stabilizer is not particularly limited, and examples thereof include hindered amine-based light stabilizers and ultraviolet stabilizers. These may be used alone or in combination of two or more. The conductivity imparting agent is not particularly limited, and examples thereof include metal microparticles such as silver nanoparticles. These may be used alone or in combination of two or more. The leveling agent is not particularly limited, and examples thereof include polymer-based leveling agents such as acrylic, vinyl, silicone, and fluorine-based. These may be used alone or in combination of two or more.

[0082] 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.

[0083] <Method for producing the first pressure-sensitive adhesive layer> In one embodiment of the double-sided pressure-sensitive adhesive sheet of the present invention, a pressure-sensitive adhesive containing a hydroxyl-terminated urethane prepolymer and a polyisocyanate compound (a urethane-based pressure-sensitive adhesive obtained by curing the above-mentioned pressure-sensitive adhesive composition) can be used as the first pressure-sensitive adhesive layer. The use of a urethane-based pressure-sensitive adhesive tends to reduce the amount of keratin peeling after one day of application of the pressure-sensitive adhesive layer. The urethane-based pressure-sensitive adhesive is obtained as a reaction product of the hydroxyl-terminated urethane prepolymer and the polyisocyanate compound in the pressure-sensitive adhesive composition. As described below, for example, the urethane-based pressure-sensitive adhesive can be formed into a pressure-sensitive adhesive layer by applying the pressure-sensitive adhesive composition to a substrate and curing it.

[0084] 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.

[0085] In the reaction between the hydroxyl-terminated urethane prepolymer and the polyisocyanate compound, a catalyst and a solvent may be used as necessary. When a catalyst is used, the above-mentioned tin-free urethane catalyst can be used. The urethane 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 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, 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] The formation of the first pressure-sensitive adhesive layer 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 a pressure-sensitive adhesive layer by, for example, hot air drying at 40 to 80°C to cure the composition in order to sufficiently volatilize the solvent contained in the pressure-sensitive adhesive composition.

[0090] (Second Pressure-Sensitive Adhesive Layer) The pressure-sensitive adhesive forming the second pressure-sensitive adhesive layer is not particularly limited as long as it has an adhesive strength to a phenolic substrate of 1.0 N / 15 mm or more, and known pressure-sensitive adhesives can be used. Examples of known pressure-sensitive adhesives include urethane-based pressure-sensitive adhesives, acrylic-based pressure-sensitive adhesives, and silicone-based pressure-sensitive adhesives. These may be used alone or in combination of two or more. From the viewpoint of high adhesive strength to a phenolic substrate, a pressure-sensitive adhesive containing a hydroxyl-terminated urethane prepolymer and a polyisocyanate compound (a urethane-based pressure-sensitive adhesive obtained by curing the above-mentioned pressure-sensitive adhesive composition) is preferred as the pressure-sensitive adhesive forming the second pressure-sensitive adhesive layer. When a pressure-sensitive adhesive containing a hydroxyl-terminated urethane prepolymer and a polyisocyanate compound (a urethane-based pressure-sensitive adhesive obtained by curing the above-mentioned pressure-sensitive adhesive composition) is used as the second pressure-sensitive adhesive layer, the pressure-sensitive adhesive may further contain a tackifying resin and may be the same as or different from the first pressure-sensitive adhesive layer. Among these, from the viewpoint of simplifying the manufacturing process, it is preferable that the second pressure-sensitive adhesive layer is the same as the first pressure-sensitive adhesive layer. Furthermore, the second pressure-sensitive adhesive layer can be manufactured, for example, by the same method as the manufacturing method of the first pressure-sensitive adhesive layer described above.

[0091] The thickness of the second pressure-sensitive adhesive layer is not particularly limited, but is preferably 5 to 100 μm, more preferably 10 to 80 μm, and particularly preferably 15 to 50 μm. When the thickness of the second pressure-sensitive adhesive layer is equal to or greater than the lower limit, the adhesive strength to the substrate tends to be good. When the thickness of the second pressure-sensitive adhesive layer is equal to or less than the upper limit, the adhesiveness to the irregularities of the device is excellent, making the second pressure-sensitive adhesive layer suitable for application to a wearable device.

[0092] [Use of Double-Sided Pressure-Sensitive Adhesive Sheet] The double-sided pressure-sensitive adhesive sheet is used for applications in which it is attached to human skin, due to its excellent gentleness to human skin. Furthermore, the double-sided pressure-sensitive adhesive sheet has excellent adhesive strength to patches, and is therefore used for applications in which patches such as electronic device patches are attached to human skin. The first pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive sheet is preferably attached to human skin, due to its excellent adhesion to human skin. The second pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive sheet is preferably attached to the patch, due to its excellent adhesion to phenolic resins.

[0093] [Electronic Device] By attaching the double-sided pressure-sensitive adhesive sheet to an electronic device, an electronic device comprising the double-sided pressure-sensitive adhesive sheet can be obtained. When the double-sided pressure-sensitive adhesive sheet has excellent flexibility, the electronic device may be a rigid device, a semi-flexible device, or a flexible device, but a flexible device is preferred.

[0094] The flexible device to be attached to the skin is not particularly limited, and examples thereof include biosensors, environmental sensors, etc. These may be used alone, or two or more types may be used in combination. The detection target of the biosensor is not particularly limited, and examples thereof include cardiac potential, acceleration, heartbeat interval, pulse interval, respiratory interval, electrocardiogram, electromyogram, activity level, blood pressure, body temperature, electroencephalogram, etc. These may be used alone, or two or more types may be used in combination.

[0095] 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.

[0096] [Measurement Methods] The methods for measuring various physical properties in the following synthesis examples are as follows.

[0097] <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

[0098] <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.

[0099] <Hydroxyl Value> The hydroxyl value was determined in accordance with Method B (automatic potentiometric titration) of JIS K 1557-1:2007.

[0100] <Degree of Unsaturation> The degree of unsaturation was measured in accordance with JIS K 1557-3:2007.

[0101] <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.

[0102] <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.

[0103] [Materials Used] Details of the materials used in the following synthesis examples and 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 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. Tackifier resin 1: styrene resin: "YS Resin (registered trademark) SX100", manufactured by Yasuhara Chemical Co., Ltd., softening point 100°C. Tackifier resin 2: terpene phenol resin: "YS Polystar (registered trademark) T130", manufactured by Yasuhara Chemical Co., Ltd., softening point 130°C. Silicone-based adhesive: "2476P", manufactured by 3M. Acrylic-based adhesive 1: "4076P", manufactured by 3M. Acrylic-based adhesive 2: "Yuhada-ban", manufactured by Nitto Denko Corporation. Acrylic-based adhesive 3: "1525L", manufactured by 3M.

[0104] [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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] 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.

[0109]

[0110] [Synthesis of hydroxyl group-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 zinc (Zn)-containing urethanization catalyst was added, and the mixture was mixed at 40 ° C., followed by the addition of 1.7 parts by mass of HDI (isocyanate index 85), and the mixture was allowed to react 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, yielding 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 16.5% by mass).

[0111] Synthesis Examples 2-2 to 2-3 Solutions of hydroxyl-terminated urethane prepolymers U2 and U3 were prepared in the same manner as in Synthesis Example 2-1 using the formulations shown in Table 2. The average number of hydroxyl groups per molecule of the oxyalkylene polymers (oxyalkylene polymers A1, A2, and B) of the hydroxyl-terminated urethane prepolymer U2 and the hydroxyl-terminated urethane prepolymer U3 was 2.2.

[0112] Table 2 shows the blending compositions of the oxyalkylene polymer, diisocyanate compound and catalyst in Synthesis Examples 2-1 to 2-3.

[0113]

[0114] [Preparation of Pressure-Sensitive Adhesive Composition] (Synthesis Example 3-1) 100 parts by mass of a 50% by mass solution of hydroxyl-terminated urethane prepolymer U1 and 5 parts by mass of a curing agent were mixed to prepare a pressure-sensitive adhesive composition N1.

[0115] Synthesis Examples 3-2 to 3-3 Using the formulations shown in Table 3, pressure-sensitive adhesive compositions N2 to N3 were produced in the same manner as in Synthesis Example 3-1.

[0116] Synthesis Example 3-4 90 parts by mass of a 50% by mass solution of hydroxyl-terminated urethane prepolymer U1, 5 parts by mass of curing agent, and 10 parts by mass of tackifier resin 1 were mixed to prepare a pressure-sensitive adhesive composition N4.

[0117] Synthesis Example 3-5 90 parts by mass of a 50% by mass solution of hydroxyl-terminated urethane prepolymer U1, 5 parts by mass of curing agent, and 10 parts by mass of tackifier resin 2 were mixed to prepare PSA composition N5.

[0118]

[0119] [Production of double-sided PSA sheet for evaluation] (Example 1) After degassing, PSA composition N1 was applied to a polyester film (thickness 38 μm) serving as a release liner using a knife coater and dried at 100°C for 2 minutes to form a PSA layer with a thickness of 25 μm. A thermoplastic polyurethane (TPU) film (thickness 15 μm) serving as a substrate was laminated onto this PSA layer and cured in a hot air dryer at 40°C for 3 days to form a sheet having a PSA layer on one side. A silicone-based PSA was adhesively laminated to the TPU film on the side opposite the PSA layer to produce the double-sided PSA sheet of Example 1 having PSA layers on both sides.

[0120] (Examples 2 to 3, 5, and 7) Double-sided PSA sheets of Examples 2 to 3, 5, and 7 were produced in the same manner as in Example 1, except that a first PSA layer formed from a hydroxyl group-terminated urethane prepolymer shown in Table 4 was used, and a second PSA layer shown in Table 4 was used.

[0121] (Example 4) After completing the formation of the PSA layer using hydroxyl-terminated urethane prepolymer U1 in Example 1, 100 parts by mass of a 50% by mass solution of hydroxyl-terminated urethane prepolymer U1 and 5 parts by mass of a curing agent were mixed and degassed on the TPU film on the side opposite the PSA layer, and then the mixture was applied to the TPU film with a knife coater and dried for 2 minutes at 100°C to form a PSA layer with a thickness of 25 μm. A polyester film (thickness 38 μm) was laminated onto the PSA layer as a release liner, and the mixture was cured in a hot air dryer at 40°C for 3 days to produce the double-sided PSA sheet of Example 4.

[0122] (Examples 6, 8, and 10 to 15) Double-sided PSA sheets of Examples 6, 8, and 10 to 15 were prepared in the same manner as in Example 4, except that the first PSA layer and second PSA layer formed from the hydroxyl group-terminated urethane prepolymers shown in Table 4 were used.

[0123] Example 9 A double-sided PSA sheet of Example 9 having PSA layers on both sides was prepared by bonding a silicone PSA to one side of a TPU film and an acrylic PSA 2 to the opposite side with an adhesive.

[0124] [Evaluation of Double-Sided PSA Sheets] The double-sided PSA sheets produced in the above examples were subjected to the following various evaluations. The evaluation results are shown in Table 4. Examples 1 to 8 and 10 to 15 are working examples, and Example 9 is a comparative example.

[0125] <Adhesive Strength> (1) Against Phenol Resin The second adhesive layer side of a double-sided PSA sheet (100 mm long, 15 mm wide) from which the release liner had been peeled was placed on a phenolic resin plate ("SUMILITE (registered trademark) PL-1102" manufactured by Sumitomo Bakelite Co., Ltd.; 125 mm long, 30 mm wide, 2 mm thick), and a rubber roller was rolled back and forth from the first adhesive layer side of the double-sided PSA sheet at a load of 2 kg and a speed of 300 mm / min, thereby pressing the second adhesive layer onto the phenolic resin plate. After leaving the sheet to stand for 20 minutes, the double-sided PSA sheet 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) using a method in accordance with JIS Z 0237:2009. Table 4 shows the average of three measured values. 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 phenolic resin plates, which are typical materials used for sealing circuit patterns in wearable devices, is sufficient. On the other hand, in the case of evaluation C, the adhesive strength to phenolic resin was insufficient.

[0126] (2) To Skin In the above (1) To Phenol Resin, adhesive strength was measured in the same manner except that the phenolic resin plate was replaced with the skin of the forearm of humans (three subjects), and the first adhesive layer was attached instead of the second adhesive layer. 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 4 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 Evaluation A indicates that the adhesive strength to the skin is adequate and can be said to be gentle on the skin. On the other hand, evaluation B indicates that the adhesive strength to the skin is insufficient. In addition, in the case of evaluation C, it was difficult to peel off from the skin and sometimes caused pain when peeling off.

[0127] <Amount of keratin peeled after one day of application> In the same manner as in the measurement of adhesive strength to skin in (2) above, the first adhesive layer of the double-sided pressure-sensitive adhesive sheet was pressed onto the skin of the forearm of humans (three subjects), the rest time after pressing the double-sided pressure-sensitive adhesive sheet was changed from 20 minutes to one day, and the double-sided pressure-sensitive adhesive sheet was peeled off in the same manner as in the measurement of adhesive strength to skin in (2) above. A measurement sample measuring 20 mm in length and 15 mm in width was cut out from the peeled double-sided pressure-sensitive adhesive sheet, and the amount of keratin peeled off (protein amount [mg / cm ]) was measured using a "Protein Assay Lowry Kit" (manufactured by Nacalai Tesque, Inc.). ２ The amount of keratin peeled after one day of application was evaluated according to the following evaluation criteria. Table 4 shows the average of three measurements. The measured amount of keratin peeled after one day of application was evaluated according to the following evaluation criteria. [Evaluation criteria (amount of keratin peeled after one day of application)] A: 0.100 mg / cm ２ Below B: 0.100mg / cm ２Very low C: Not measurable (peeling off) In the case of rating A, it can be said that the load of the first adhesive layer on the skin is sufficiently small. In the case of rating B, a large amount of keratin was peeled off, causing a large load on the skin and sometimes causing pain when peeling off. In the case of rating C, the patch could not be left on the skin for a day and peeled off midway, so it was not possible to evaluate.

[0128] <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 first adhesive layer of the double-sided adhesive sheet 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 sheet peeled off (long-term adhesion strength) was measured, and upon peeling (if the adhesive sheet 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 sheet), the presence or absence of adhesive residue and skin abnormalities (redness, itching, etc.) was confirmed (effects after long-term adhesion). Table 4 shows the values ​​and evaluation based on three measurements. The measured long-term adhesion was also evaluated according to the following evaluation criteria. [Evaluation criteria (effects after long-term application)] A: 0% of subjects were found to have adhesive residue, redness, or itching on the skin B: No adhesive residue was found, but the percentage of subjects who were found to have redness or itching on the skin exceeded 0%. In the case of evaluation A, it can be said that the load of the first adhesive layer on the skin is sufficiently small. On the other hand, in the case of evaluation B, it cannot be said that the load of the first adhesive layer on the skin is sufficiently small.

[0129]

[0130] As can be seen from the evaluation results shown in Table 4, the double-sided PSA sheets of Examples 1 to 8 and 10 to 15 were found to have appropriate adhesive strength to phenolic resin and skin. Furthermore, the double-sided PSA sheets of Examples 1 to 8 and 10 to 15 were found to have low levels of keratin peeling after one day of application, demonstrating their gentleness to the skin. Furthermore, the double-sided PSA sheets of Examples 1 to 8 and 10 to 15 were found to have good long-term adhesion (long-term adhesion strength and effects after long-term application).

Claims

1. A skin patch having a substrate, a first adhesive layer on one side of the substrate, and a second adhesive layer on the other side of the substrate, wherein the amount of keratin peeled off from the first adhesive layer after application for one day is 0.100 mg / cm ２ or less, and the adhesive strength of the second adhesive layer to a phenolic substrate is 1.0 N / 15 mm or more.

2. The double-sided pressure-sensitive adhesive sheet according to claim 1, wherein the adhesive strength of the first pressure-sensitive adhesive layer to human skin is 0.5 to 3.0 N / 15 mm.

3. The double-sided adhesive sheet according to claim 1 or 2, wherein the first adhesive layer is a layer made of an adhesive containing a hydroxyl-terminated urethane prepolymer and a polyisocyanate compound.

4. The double-sided pressure-sensitive adhesive sheet according to claim 3, wherein the pressure-sensitive adhesive further comprises a tackifier resin.

5. The double-sided pressure-sensitive adhesive sheet according to claim 3, 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.

6. The double-sided pressure-sensitive adhesive sheet according to claim 5, wherein the tin-free catalyst contains at least one of zinc and bismuth.

7. The double-sided pressure-sensitive adhesive sheet according to claim 5, wherein the oxyalkylene polymer has an average content of structural units based on ethylene oxide of 8 to 55 mass %.

8. The double-sided pressure-sensitive adhesive sheet according to claim 5, wherein the oxyalkylene polymer has an average number of hydroxyl groups per molecule of 1.5 to 3.

0.

9. The double-sided pressure-sensitive adhesive sheet according to claim 5, wherein the oxyalkylene polymer comprises 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.

10. The double-sided pressure-sensitive adhesive sheet according to claim 9, wherein the oxyalkylene polymer A includes an oxyalkylene polymer A1 having three hydroxyl groups per molecule, and an oxyalkylene polymer A2 having two hydroxyl groups per molecule.

11. The double-sided adhesive sheet according to claim 1 or 2, wherein the second adhesive layer is a layer made of an adhesive containing a hydroxyl-terminated urethane prepolymer and a polyisocyanate compound.

12. A double-sided adhesive sheet as described in claim 1 or 2, wherein the first adhesive layer and the second adhesive layer are both layers made of an adhesive containing a hydroxyl group-terminated urethane prepolymer and a polyisocyanate compound.

13. Use of the double-sided adhesive sheet according to claim 1 or 2, in which the first adhesive layer is attached to the skin of a human body.

14. Use of the double-sided adhesive sheet according to claim 13, wherein the second adhesive layer is attached to an electronic device.

15. Use of the double-sided pressure-sensitive adhesive sheet according to claim 14, wherein the electronic device is a flexible device.

16. An electronic device comprising the double-sided adhesive sheet according to claim 1 or 2.

Images