Adhesive sheet for attachment to skin

Abstract

Provided is an adhesive sheet for attachment to the skin, the adhesive sheet comprising an adhesive agent layer formed of an acrylic hot-melt adhesive agent, and being able to achieve, in a well-balanced manner, capabilities suitable for use in attachment to the skin. An adhesive sheet for attachment to the skin provided herein comprises an adhesive agent layer formed of an acrylic hot-melt adhesive agent containing an acrylic block copolymer and a plasticizer. The acrylic block copolymer includes a soft block and a hard block. In monomer components constituting the soft block, the content of an alkyl acrylate that has an alkyl group having 6-12 carbon atoms is 40 wt% or more. The plasticizer includes a plasticizer having an HLB of 0.5-3.

Description

Skin adhesive sheet

[0001] The present invention relates to a pressure-sensitive adhesive sheet for application to skin. This application claims priority to Japanese Patent Application No. 2023-223500, filed on December 28, 2023, the entire contents of which are incorporated herein by reference.

[0002] In the fields of medicine, sports, beauty, etc., adhesive sheets for application to the skin are sometimes used for purposes such as fixing medical devices and other measuring devices to the skin surface, protecting or decorating the skin surface, etc. It is desirable that adhesive sheets for application to the skin can exhibit good adhesion and fixation to the skin, and also have the ability to be peeled off while minimizing damage to the skin and leaving adhesive residue. Patent Documents 1 and 2 are examples of prior art documents related to adhesives or adhesive tapes for applications that are applied to the skin.

[0003] Japanese Patent No. 6724542 Japanese Patent Application Publication No. 2007-314584

[0004] In the specific examples disclosed in Patent Documents 1 and 2, the pressure-sensitive adhesive layer is formed using a solvent-based acrylic pressure-sensitive adhesive composition. Meanwhile, in recent years, there has been a trend toward the use of solvent-free pressure-sensitive adhesive compositions from the viewpoint of environmental hygiene, etc. In the field of pressure-sensitive adhesive sheets for skin application, it would be useful to provide a pressure-sensitive adhesive sheet that can be produced using a solvent-free pressure-sensitive adhesive composition, for example, a hot-melt pressure-sensitive adhesive composition, instead of the conventional solvent-based acrylic pressure-sensitive adhesive composition, and that can exhibit desired performance.

[0005] Therefore, an object of the present invention is to provide an adhesive sheet for application to the skin, which has an adhesive layer formed from an acrylic hot melt adhesive and can achieve a good balance of performance suitable for application to the skin.

[0006] The adhesive sheet for application to skin provided by this specification comprises an adhesive layer formed from an acrylic hot-melt adhesive containing an acrylic block copolymer and a plasticizer. The acrylic block copolymer has a soft block and a hard block. The monomer component constituting the soft block is an alkyl acrylate (hereinafter referred to as C ) in which the alkyl group has 6 to 12 carbon atoms. ６－１２ The content of alkyl acrylate is 40% by weight or more. The plasticizer includes a plasticizer having an HLB of 0.5 or more and 3 or less. ６－１２ A pressure-sensitive adhesive layer containing a combination of an acrylic block copolymer having a soft block with an alkyl acrylate content of 40% by weight or more and a plasticizer with an HLB of 0.5 to 3 can provide a pressure-sensitive adhesive sheet for application to the skin that has a good balance between good adhesion and fixation to the skin and good releasability from the skin (e.g., the ability to peel while minimizing damage to the skin and leaving adhesive residue). As the plasticizer, for example, a fatty acid ester having an HLB within the above range can be preferably used.

[0007] In some embodiments, the pressure-sensitive adhesive layer preferably contains a tackifier resin. The use of a tackifier resin can improve adhesion and fixation to the skin. The amount of tackifier resin used per 100 parts by weight of the acrylic block copolymer is, for example, 60 parts by weight or more and 150 parts by weight or less, taking into consideration the balance with good releasability from the skin.

[0008] In some embodiments, the tackifier resin preferably includes a tackifier resin having a softening point of 60° C. or higher and 120° C. or lower. A tackifier resin having a softening point within the above range can easily improve adhesion and fixation to the skin while minimizing the effect on good peelability from the skin.

[0009] In some embodiments, the content of the plasticizer in the pressure-sensitive adhesive layer is preferably 60 parts by weight or more and 150 parts by weight or less per 100 parts by weight of the acrylic block copolymer. By setting the content of the plasticizer within this range, it is possible to realize a pressure-sensitive adhesive sheet for application to skin that more preferably achieves both good adhesion and fixation to the skin and good releasability from the skin.

[0010] The pressure-sensitive adhesive sheet for application to skin disclosed herein may include a substrate that supports the pressure-sensitive adhesive layer. Having a substrate in a pressure-sensitive adhesive sheet for application to skin can be advantageous from the standpoint of handleability, processability, etc. of the pressure-sensitive adhesive sheet.

[0011] Appropriate combinations of the elements described in this specification may also be included within the scope of the invention for which patent protection is sought by this patent application.

[0012] 1 is a cross-sectional view schematically showing the configuration of a pressure-sensitive adhesive sheet according to one embodiment;FIG. 2 is a cross-sectional view schematically showing the configuration of a pressure-sensitive adhesive sheet according to another embodiment;FIG.

[0013] Preferred embodiments of the present invention are described below. Matters necessary for carrying out the present invention other than those specifically mentioned in this specification can be understood by those skilled in the art based on the teachings for carrying out the invention described in this specification and the common general technical knowledge at the time of filing. The present invention can be carried out based on the contents disclosed in this specification and the common general technical knowledge in the relevant field. Furthermore, in the following drawings, components and parts that perform the same function may be denoted by the same reference numerals, and redundant explanations may be omitted or simplified. Furthermore, the embodiments shown in the drawings are schematic for the purpose of clearly explaining the present invention, and do not necessarily accurately represent the size or scale of the actual product provided.

[0014] In this specification, "acrylic monomer" refers to a monomer having at least one (meth)acryloyl group in one molecule. Here, "(meth)acryloyl group" refers to an acryloyl group and a methacryloyl group in a comprehensive sense. Therefore, the concept of acrylic monomer here can include both a monomer having an acryloyl group (acrylic monomer) and a monomer having a methacryloyl group (methacrylic monomer). Similarly, in this specification, "(meth)acrylic acid" refers to an acrylic acid and a methacrylic acid in a comprehensive sense, and "(meth)acrylate" refers to an acrylate and a methacrylate in a comprehensive sense. The same applies to other similar terms.

[0015] In this specification, the "base polymer" of a PSA refers to the main component of the polymer components contained in the PSA. Similarly, when the term "base polymer" is used for other materials, it refers to the main component contained in the material. Furthermore, in this specification, "main component" refers to a component that is contained in more than 50% by weight, unless otherwise specified.

[0016] An example of the configuration of a pressure-sensitive adhesive sheet for application to skin disclosed herein is shown in Figure 1. The pressure-sensitive adhesive sheet for application to skin 1 according to this embodiment comprises a pressure-sensitive adhesive layer 10 and a substrate 20, and is configured as a single-sided pressure-sensitive adhesive sheet (a single-sided pressure-sensitive adhesive sheet with a substrate) in which one surface 10A of the pressure-sensitive adhesive layer 10 serves as the surface to be applied to an adherend (adhesive surface). The other surface 10B of the pressure-sensitive adhesive layer 10 is fixed to a first surface 20A of the substrate 20. The pressure-sensitive adhesive sheet for application to skin 1 is used by adhering the adhesive surface 10A to the skin (adherend). Before use (before application to an adherend), the pressure-sensitive adhesive sheet 1 may be in the form of a pressure-sensitive adhesive sheet with a release liner 50, in which the adhesive surface 10A is protected by a release liner 30, at least the pressure-sensitive adhesive layer side of which serves as a release surface (release surface), as shown in Figure 1, for example. Alternatively, a release liner 30 may not be used, and the second surface 20B (the surface opposite to the first surface 20A, also called the back surface) of the substrate 20 may be the release surface, and the adhesive surface 10A may be protected by being wound or laminated so that the adhesive surface 10A abuts against this second surface 20B.

[0017] The adhesive sheet for application to skin disclosed herein may be in the form of a substrate-less double-sided adhesive sheet comprising an adhesive layer 10, such as the adhesive sheet 2 for application to skin shown in FIG. 2 . In the adhesive sheet 2 according to this embodiment, both one surface 10A and the other surface 10B of the adhesive layer 10 are adhesive surfaces. Before use, the adhesive sheet 2 may be in a form in which each surface 10A, 10B of the adhesive layer 10 is protected by release liners 31, 32, with at least the adhesive layer side serving as a release surface. Alternatively, the release liner 32 may not be used, and the back surface of the release liner 31 (the surface opposite the adhesive side) serves as a release surface, with the adhesive surface 10B being protected by being wound or laminated so that the adhesive surface 10B abuts against the back surface. The adhesive sheet for application to skin disclosed herein may also be in the form of a substrate-attached double-sided adhesive sheet in which an adhesive layer is laminated on each of the first and second surfaces of a sheet-like substrate. Such a substrate-less or substrate-attached double-sided pressure-sensitive adhesive sheet (double-sided pressure-sensitive adhesive sheet) for application to skin is used by adhering at least one adhesive surface to the skin (adherend). The other adhesive surface of the double-sided pressure-sensitive adhesive sheet may be attached to the skin or to an adherend other than the skin. Alternatively, a substrate-attached single-sided pressure-sensitive adhesive sheet may be formed by laminating a substrate on the other adhesive surface of the substrate-less double-sided pressure-sensitive adhesive sheet.

[0018] <Adhesive Layer> (Acrylic Block Copolymer) The adhesive sheet for skin application disclosed herein has an adhesive layer formed from an acrylic hot-melt adhesive containing an acrylic block copolymer and a plasticizer. The acrylic block copolymer may exhibit the properties of a thermoplastic polymer (typically a thermoplastic elastomer). The adhesive layer preferably contains an acrylic block copolymer as a base polymer. An adhesive containing an acrylic block copolymer as a base polymer may be suitable for hot-melt coating. The use of a hot-melt adhesive to form the adhesive layer is preferred from the perspective of reducing environmental impact. From the perspective of reducing melt viscosity, etc., acrylic block copolymers with a linear structure are advantageous over those with a star structure or branched structure.

[0019] The acrylic block copolymer used has a structure containing at least one hard block composed of a polymer with a hard structure excellent in cohesion and elasticity and at least one soft block composed of a polymer with a soft structure excellent in viscosity. The acrylic block copolymer may be copolymerized so that the hard block (A block) and the soft block (B block) are alternately arranged, such as in the AB type, ABA type, ABAB type, ABABA type, etc. An adhesive having an acrylic block copolymer of such a structure as the base polymer can form an adhesive layer that achieves a high degree of cohesion, elasticity, and viscosity. Furthermore, an adhesive of such a composition can be preferably used as a hot-melt adhesive. Acrylic block copolymers (e.g., ABA type, ABABA type) primarily composed of a polymer with a structure in which hard blocks are arranged at both ends of the molecule are preferably used. Among these, acrylic block copolymers primarily composed of an ABA type polymer are preferred.

[0020] The monomer component constituting the soft block has a content of 40% by weight or more of alkyl acrylate in which the alkyl group has 6 to 12 carbon atoms. Here, the alkyl acrylate in which the alkyl group has 6 to 12 carbon atoms refers to an acrylic acid alkyl ester having a chain alkyl group with 6 to 12 carbon atoms at the ester terminal, that is, an alkyl acrylate represented by the following formula: CH ２ =CHCOOR １ R in １ Hereinafter, alkyl acrylates having X to Y carbon atoms will be referred to as "C Ｘ－ＹAn acrylic block copolymer having a soft block formed from monomer components of such a composition can, in combination with a specific plasticizer, form an adhesive that exhibits flexibility that allows good adhesion to microscopic irregularities that may be present on the skin surface while suppressing the decrease in cohesion caused by the plasticizer. This makes it possible to preferably realize an adhesive sheet for application to skin that achieves a good balance between good adhesion and fixation to the skin and good releasability from the skin. From the viewpoint of improving flexibility (and therefore adhesion to the skin), in some embodiments, the C in the monomer components constituting the soft block can be ６－１２ The content of alkyl acrylate is preferably 45% by weight or more (for example, approximately 50% by weight or more or more than 50% by weight), more preferably 60% by weight or more, and may be 70% by weight or more, 80% by weight or more, 90% by weight or more, 95% by weight or more, or even 100% by weight. In addition, the monomer component constituting the soft block is C at any of the above-mentioned contents (typically 40% by weight or more, preferably 45% by weight or more, for example 50% by weight or more). ７－１０ It is preferable that the compound contains alkyl acrylate, and C ８－１０ It is more preferable that the composition contains an alkyl acrylate.

[0021] C contained in the monomer component constituting the soft block ６－１２ The alkyl acrylate may be one type or two or more types. ６－１２Specific examples of alkyl acrylates include, but are not limited to, n-hexyl acrylate, n-heptyl acrylate, 2-ethylhexyl acrylate (2EHA), n-octyl acrylate, isooctyl acrylate, n-nonyl acrylate, isononyl acrylate, n-decyl acrylate, isodecyl acrylate, 2-octyl acrylate, n-undecyl acrylate, n-lauryl acrylate, etc. The technology disclosed herein can be preferably practiced, for example, using an acrylic block copolymer having a soft block formed from a monomer component containing 2EHA in any of the above-mentioned amounts (typically 40% by weight or more, preferably 45% by weight or more, for example, approximately 50% by weight or more or more than 50% by weight).

[0022] The monomer component constituting the soft block is C ６－１２ In addition to alkyl acrylate, other monomers may be contained. Examples of the other monomers include C ６－１２ Alkyl (meth)acrylates that do not fall under the category of alkyl acrylates (e.g., C ６－１２ C not corresponding to alkyl acrylate １－２０ For example, the other monomer may be C １－３ Alkyl (meth)acrylate, C ４－５ Alkyl (meth)acrylate, C １３－２０ Alkyl (meth)acrylate and C ６－１２ The alkyl methacrylate may be one or more selected from the group consisting of alkyl methacrylates. ６－１２ C not corresponding to alkyl acrylate １－２０ Specific examples of alkyl (meth)acrylate include, but are not limited to, n-butyl acrylate (BA), lauryl methacrylate, isostearyl acrylate, etc. ６－１２ C not corresponding to alkyl acrylate １－２０ The content of alkyl (meth)acrylate is C ６－１２The total amount with the alkyl acrylate is set so as not to exceed 100% by weight, and may be, for example, 60% by weight or less, 55% by weight or less, 50% by weight or less, less than 50% by weight, 40% by weight or less, 30% by weight or less, 20% by weight or less, 10% by weight or less, or 5% by weight or less.

[0023] In one embodiment, the acrylic block copolymer is ６－１２ Alkyl acrylate (e.g., 2EHA) and C ２－５ An acrylic block copolymer having a soft block composed of a monomer component with an alkyl acrylate (e.g., BA) in a weight ratio of 30 / 70 to 100 / 0 (more preferably 40 / 60 to 100 / 0, even more preferably 50 / 50 to 100 / 0, e.g., 60 / 40 to 100 / 0) can be preferably used. Such an acrylic block copolymer is suitable for forming a PSA having an excellent balance between flexibility and cohesion. For example, an acrylic block copolymer having a soft block composed of 2EHA or a monomer component containing 2EHA and BA in the above weight ratio is preferred.

[0024] In some embodiments, from the viewpoint of improving flexibility, the soft block has a glass transition temperature (Tg) determined by Fox's formula based on the composition of the monomer components constituting the soft block, which is suitably -40°C or lower, advantageously -50°C or lower, preferably lower than -55°C, more preferably -58°C or lower, and may be -60°C or lower, -62°C or lower, or -65°C or lower. The Tg based on the monomer composition of the soft block (hereinafter referred to as "Tg Ｓ The lower limit of the temperature is not particularly limited, and may be, for example, −80° C. or higher or −75° C. or higher.

[0025] Here, the Fox formula is a relational expression between the Tg of a copolymer and the glass transition temperature Tgi of a homopolymer obtained by homopolymerizing each of the monomers constituting the copolymer, as shown below: 1 / Tg=Σ(Wi / Tgi) In the Fox formula, Tg represents the glass transition temperature (unit: K) of the copolymer, Wi represents the weight fraction of monomer i in the copolymer (copolymerization ratio on a weight basis), and Tgi represents the glass transition temperature (unit: K) of a homopolymer of monomer i. When the target polymer for specifying the Tg is a homopolymer, the Tg of the homopolymer and the Tg of the target polymer will be the same.

[0026] The glass transition temperature of the homopolymer used to calculate Tg is to be a value listed in a publicly available document. For example, the glass transition temperature of a homopolymer of 2-ethylhexyl acrylate (2EHA) is -70°C, and the glass transition temperature of a homopolymer of n-butyl acrylate (BA) is -55°C. For the glass transition temperatures of homopolymers of monomers other than those listed above, the values ​​listed in "Polymer Handbook" (3rd Edition, John Wiley & Sons, Inc., 1989) are to be used. If multiple values ​​are listed in this document, the highest value is used.

[0027] The hard block contained in the acrylic block copolymer is a block that is relatively hard compared to the soft block. The hard block has a Tg (hereinafter referred to as "Tg") calculated by the Fox formula based on the composition of the monomer components that constitute the hard block. Ｈ ") is the Tg (i.e., Tg Ｓ That is, the acrylic block copolymer preferably has a Tg Ｈ [°C]-Tg ＳFrom the viewpoint of easily achieving both flexibility suitable for adhesion to the skin and cohesiveness suitable for fixation to the skin and prevention of adhesive residue upon peeling, in some embodiments, it is preferable that the Tg Ｈ [°C]-Tg Ｓ The value of [°C] is preferably 50°C or higher, more preferably 100°C or higher, and may be 130°C or higher, 150°C or higher, 160°C or higher, 165°C or higher, or 170°C or higher.

[0028] In some embodiments, the monomer components constituting the hard block are C １－３ The content of alkyl methacrylate is preferably 40% by weight or more. The technology disclosed herein can be preferably implemented using an acrylic block copolymer having a hard block of such a composition and the soft block described above. １－３ The content of alkyl methacrylate is more preferably 45% by weight or more, even more preferably 50% by weight or more (e.g., more than 50% by weight) or 60% by weight or more, and may be 70% by weight or more, 80% by weight or more, 90% by weight or more, 95% by weight or more, or even 100% by weight.

[0029] C contained in the monomer component constituting the hard block １－３ The alkyl methacrylate may be one type or two or more types. １－３ The alkyl methacrylate preferably contains at least one of methyl methacrylate (MMA) and ethyl methacrylate, and more preferably contains at least MMA. In some preferred embodiments, the monomer component constituting the hard block contains MMA in any of the above-mentioned amounts (typically 40% by weight or more, preferably 45% by weight or more, for example 50% by weight or more). In one preferred embodiment, the hard block is a block consisting of MMA.

[0030] The weight ratio of the hard block / soft block in the acrylic block copolymer is not particularly limited and may be, for example, within the range of 1 / 99 to 70 / 30. From the viewpoint of improving the flexibility of the PSA, in some embodiments, the weight ratio of the hard block / soft block is preferably 50 / 50 or less, more preferably 40 / 60 or less, and may be 30 / 70 or less, 25 / 75 or less, 20 / 80 or less, 15 / 85 or less, or 10 / 90 or less. Furthermore, from the viewpoint of easily obtaining a PSA with appropriate cohesiveness, in some embodiments, the weight ratio of the hard block / soft block is preferably 2 / 98 or more, more preferably 4 / 96 or more (e.g., 5 / 95 or more). In an acrylic block copolymer containing two or more hard blocks, the weight ratio of the total weight of the hard blocks to the soft blocks is preferably within the above range. The same applies to an acrylic block copolymer containing two or more soft blocks.

[0031] The composition of the monomer components constituting the acrylic block copolymer can be determined based on the results of NMR measurement. Specifically, the NMR measurement can be performed using, for example, an NMR device such as "AVAVCEIII-600 (with Cryo Probe)" manufactured by Bruker Biospin under the following conditions. For example, the weight ratio of 2EHA to MMA contained in the monomer raw material is: １ It can be calculated based on the peak integrated intensity ratio of 4.0 ppm (2EHA1) and 3.6 ppm (MMA1) in the H NMR spectrum. [NMR measurement conditions] Observation frequency: １ H: 600 MHz Flip angle: 30° Measurement solvent: CDCl ３ Measurement temperature: 300 K Chemical shift reference: Measurement solvent (CDCl ３ , １ H:7.25ppm)

[0032] The Mw of the acrylic block copolymer is not particularly limited, and may be, for example, 3×10 ４ ~50 x 10 ４From the viewpoint of easily obtaining a PSA having appropriate cohesiveness, in some embodiments, the Mw of the acrylic block copolymer may be about 5 × 10 ４ It is preferable that the ratio is 7×10 or more. ４ More preferably, it is 8×10 or more. ４ That's it, 9 x 10 ４ or more or 10 x 10 ４ In addition, from the viewpoint of coatability in hot melt coating, in some embodiments, the Mw of the acrylic block copolymer may be 40 × 10 or more. ４ It is appropriate that the value is 35×10 or less. ４ Preferably, it is 30×10 or less. ４ It may be 25×10 or less. ４ It may be 20 × 10 or less. ４ or less or 15 x 10 ４ or less. The Mw of the acrylic block copolymer referred to here refers to a polystyrene-equivalent value determined by performing gel permeation chromatography (GPC) on a sample prepared by dissolving the copolymer in tetrahydrofuran (THF). Specifically, the GPC measurement can be performed under the following conditions using, for example, a Tosoh Corporation "HLC-8120GPC" GPC measurement device. The Mw of other polymers and oligomers described below can also be measured in a similar manner. [GPC Measurement Conditions] Column: Tosoh Corporation, TSKgel Super HZM-H / HZ4000 / HZ3000 / HZ2000 Column size: 6.0 mm ID each × 150 mm Eluent: THF Flow rate: 0.6 mL / min Detector: differential refractometer (RI) Column temperature (measurement temperature): 40°C Sample concentration: approximately 2.0 g / L (THF solution) Sample injection volume: 20 μL

[0033] The acrylic block copolymer may contain a monomer (other monomer) other than alkyl (meth)acrylate. Examples of the other monomer include vinyl compounds having functional groups such as alkoxy groups, epoxy groups, hydroxyl groups, amino groups, amide groups, cyano groups, carboxy groups, and acid anhydride groups; vinyl esters such as vinyl acetate; aromatic vinyl compounds such as styrene; and vinyl group-containing heterocyclic compounds such as N-vinylpyrrolidone. The content of the other monomer may be approximately 20% by weight or less, approximately 10% by weight or less, or approximately 5% by weight or less of the total monomer components constituting the acrylic block copolymer. In a preferred embodiment, the acrylic block copolymer is substantially free of the other monomer. For example, an acrylic block copolymer in which the content of the other monomer is less than 1% by weight (typically 0 to 0.5% by weight) of the total monomer components or below the detection limit is preferred.

[0034] The acrylic block copolymers described above can be easily synthesized by known methods (see, for example, JP-A Nos. 2001-234146 and 1999-323072), or are readily available as commercially available products. Examples of such commercially available products include the "Clarity" series (e.g., LK9243) manufactured by Kuraray Co., Ltd.

[0035] (Plasticizer) The adhesive sheet for skin application disclosed herein comprises an adhesive layer containing a plasticizer in addition to the acrylic block copolymer. The plasticizer can be useful for increasing the flexibility of the adhesive and improving adhesion to the skin. Examples of plasticizers include fatty acid esters, higher alcohols, dicarboxylic acid esters (e.g., phthalic acid diesters such as dioctyl phthalate, diisononyl phthalate, diisodecyl phthalate, and dibutyl phthalate; adipic acid diesters such as dioctyl adipate and diisononyl adipate; sebacate diesters such as dioctyl sebacate; azelaic acid diesters such as dioctyl azelaate), tricarboxylic acid esters (e.g., trimellitic acid triesters such as trioctyl trimellitate), phosphate esters (e.g., phosphate triesters such as tricresyl phosphate), and epoxidized vegetable oils (e.g., epoxidized soybean oil and epoxidized linseed oil). Softeners such as process oils are also included in the plasticizer category. The plasticizers can be used alone or in combination of two or more.

[0036] Examples of the fatty acid ester include fatty acid esters of polyhydric alcohols such as trimethylolpropane, sorbitan, sorbitol, glycerin, and polyglycerol, epoxidized fatty acid alkyl esters such as epoxidized fatty acid octyl esters, and ethylene oxide adducts thereof. The fatty acid forming the fatty acid ester may be, for example, a fatty acid having 8 or more carbon atoms (preferably 12 or more, more preferably 14 or more, and even more preferably 16 or more) and 24 or less (preferably 22 or less, for example, 20 or less). Non-limiting specific examples of the fatty acid include lauric acid, myristic acid, palmitic acid, oleic acid, stearic acid, and isostearic acid. Specific examples of fatty acid esters include trimethylolpropane fatty acid esters such as trimethylolpropane triisostearate and trimethylolpropane trioleate; sorbitan fatty acid esters such as sorbitan monolaurate, sorbitan monostearate, sorbitan tristearate, sorbitan monooleate and sorbitan trioleate; sorbitol fatty acid esters; glycerin fatty acid esters such as glyceryl triisostearate, glyceryl diisostearate, glyceryl monoisostearate, glyceryl monostearate and glyceryl monooleate; pentaerythritol fatty acid esters; etc. In some embodiments, isostearic acid esters (e.g., trimethylolpropane triisostearate, glyceryl triisostearate, etc.) can be preferably used.

[0037] As the higher alcohol, acyclic monohydric alcohols having about 10 to 24 carbon atoms can be used. In some embodiments, higher alcohols having 14 or more carbon atoms (more preferably 16 or more, for example 18 or more) can be preferably used. Specific examples of higher alcohols include cetanol, cetostearyl alcohol, stearyl alcohol, isostearyl alcohol, hexyldecanol, and octyldodecanol.

[0038] The adhesive layer contains, as the plasticizer, a plasticizer having an HLB (Hydrophile Lipophile Balance) value of 0.5 or more and 3 or less. The use of a plasticizer having an HLB value within the above range increases the flexibility of the adhesive, improving adhesion to the skin and suppressing problems such as adhesive residue and reduced fixation performance due to excessive reduction in cohesion, thereby enabling the realization of a suitable adhesive sheet for application to the skin that balances good adhesion and fixation to the skin with good releasability from the skin (e.g., suppression of damage such as keratin peeling, suppression of adhesive residue on the skin, etc.). As the plasticizer having an HLB value within the range of 0.5 or more and 3 or less, known plasticizers (e.g., the various plasticizers described above) having the corresponding HLB value can be used. Plasticizers having an HLB value of 0.5 or more and 3 or less can be used alone or in combination of two or more. In some embodiments, a plasticizer having an HLB value within the range of 0.5 or more and 3 or less can be used in combination with a plasticizer having an HLB value outside the above range. The proportion of plasticizers having an HLB in the range of 0.5 or more and 3 or less in all plasticizers is suitably 30% by weight or more, advantageously 50% by weight or more (e.g., more than 50% by weight), may be 70% by weight or more, 80% by weight or more, 90% by weight or more, or 95% by weight or more, or may be 100% by weight.

[0039] In this specification, HLB stands for Griffin's Hydrophile-Lipophile Balance, which represents the ratio of hydrophilicity to lipophilicity as a number between 0 and 20. The definition of HLB is as described in W. C. Griffin, J. Soc. Cosmetic Chemists, 1,311 (1949), and in "Surfactant Handbook," 3rd Edition, Kogaku Toshosha Publishing, November 25, 1972, co-authored by Takahashi Etsutami, Namba Yoshiro, Koike Motoo, and Kobayashi Masao, pp. 179-182. Plasticizers having the above HLB values ​​can be selected based on the common technical knowledge of those skilled in the art, taking the above references into consideration as necessary. For materials for which nominal HLB values ​​are provided by manufacturers, etc., plasticizers may be selected based on the HLB values.

[0040] In some embodiments, the HLB of the plasticizer having an HLB in the range of 0.5 to 3 is suitably less than 3.0, and may be 2.7 or less or 2.6 or less (e.g., less than 2.6); from the viewpoint of making it easier to obtain higher fixation performance, it may be 2.5 or less, 2.2 or less, or 2.0 or less, or 1.8 or less (e.g., less than 1.8), or 1.7 or less. Furthermore, the HLB of the plasticizer having an HLB in the range of 0.5 to 3 may be, for example, 0.8 or more, 0.9 or more, 1.0 or more, 1.2 or more, or 1.4 or more. By using a plasticizer having such an HLB, it is possible to suitably realize a pressure-sensitive adhesive layer that can exhibit good fixation performance while suppressing damage to the skin, and a pressure-sensitive adhesive sheet for application to skin comprising said pressure-sensitive adhesive layer.

[0041] The content of the plasticizer having an HLB of 0.5 or more and 3 or less in the PSA layer can be, for example, in the range of 30 parts by weight or more and 200 parts by weight or less, relative to 100 parts by weight of the acrylic block copolymer. In some embodiments, the content of the plasticizer having the above HLB, relative to 100 parts by weight of the acrylic block copolymer, can be more than 30 parts by weight (e.g., 32 parts by weight or more), 40 parts by weight or more, 50 parts by weight or more or more than 50 parts by weight, 55 parts by weight or more, 60 parts by weight or more or more than 60 parts by weight, 62 parts by weight or more or 65 parts by weight or more, 70 parts by weight or more or more than 70 parts by weight, 72 parts by weight or more or 75 parts by weight or more, or 80 parts by weight or more or 85 parts by weight or more. Increasing the content of the plasticizer tends to improve the flexibility of the PSA (and therefore its adhesion to the skin). Furthermore, from the viewpoint of maintaining appropriate cohesiveness and facilitating the desired fixing performance, the content of the plasticizer having the above HLB relative to 100 parts by weight of the acrylic block copolymer is suitably 170 parts by weight or less, and in some embodiments, it is preferably 150 parts by weight or less, and may be 120 parts by weight or less, 110 parts by weight or less, 100 parts by weight or less, or less than 100 parts by weight. In embodiments in which a plasticizer having an HLB in the range of 0.5 to 3 is used in combination with a plasticizer having an HLB outside the above range, it is preferable that the total content thereof be within one of the above ranges.

[0042] (Tackifier Resin) The pressure-sensitive adhesive layer containing a plasticizer in addition to the acrylic block copolymer preferably further contains a tackifier resin. The tackifier resin can be useful for improving adhesion to the skin and fixation performance. Examples of tackifier resins include rosin-based tackifier resins, rosin derivative tackifier resins, petroleum-based tackifier resins, terpene-based tackifier resins, phenol-based tackifier resins, and ketone-based tackifier resins. These can be used alone or in combination of two or more.

[0043] Examples of the rosin-based tackifying resin include rosins such as gum rosin, wood rosin, and tall oil rosin, as well as stabilized rosins (e.g., stabilized rosins obtained by disproportionating or hydrogenating the above-mentioned rosins), polymerized rosins (e.g., polymers, typically dimers, of the above-mentioned rosins), and modified rosins (e.g., unsaturated acid-modified rosins modified with unsaturated acids such as maleic acid, fumaric acid, and (meth)acrylic acid).

[0044] Examples of rosin derivative tackifying resins include esterified products of the above rosin-based tackifying resins (for example, rosin ester resins such as stabilized rosin ester, polymerized rosin ester, and modified rosin ester), phenol-modified products of the above rosin-based tackifying resins (phenol-modified rosin), and esterified products thereof (phenol-modified rosin ester).

[0045] Examples of the petroleum-based tackifying resin include aliphatic petroleum resins, aromatic petroleum resins, aliphatic / aromatic copolymer petroleum resins, alicyclic petroleum resins, and hydrogenated versions of these (for example, alicyclic saturated hydrocarbon resins).

[0046] Examples of petroleum-based tackifying resins include aliphatic (C5) petroleum resins, aromatic (C9) petroleum resins, aliphatic / aromatic copolymer (C5 / C9) petroleum resins, styrene-based resins, and hydrogenated versions of these (e.g., alicyclic saturated hydrocarbon resins obtained by hydrogenating aromatic petroleum resins). Other examples of petroleum-based tackifying resins include coumarone-indene resins and dicyclopentadiene resins. Examples of styrene-based resins include those primarily composed of a styrene homopolymer, those primarily composed of an α-methylstyrene homopolymer, those primarily composed of a vinyltoluene homopolymer, and those primarily composed of a copolymer containing two or more of styrene, α-methylstyrene, and vinyltoluene in the monomer composition (e.g., an α-methylstyrene / styrene copolymer resin primarily composed of an α-methylstyrene / styrene copolymer). For coumarone-indene resins, resins containing coumarone and indene as monomer components constituting the resin skeleton (main chain) can be used. Examples of monomer components that can be contained in the resin skeleton other than coumarone and indene include styrene, α-methylstyrene, methylindene, vinyltoluene, and the like.

[0047] Examples of the terpene tackifying resin include α-pinene resin, β-pinene resin, aromatic modified terpene resin, and terpene phenol resin.

[0048] Examples of the ketone-based tackifying resin include ketone-based resins obtained by condensation of ketones (e.g., aliphatic ketones such as methyl ethyl ketone, methyl isobutyl ketone, and acetophenone; alicyclic ketones such as cyclohexanone and methylcyclohexanone) with formaldehyde.

[0049] In some embodiments, the tackifier resin preferably comprises one or more selected from the group consisting of rosin derivative tackifier resins (rosin ester resins, etc.) and petroleum-based tackifier resins (alicyclic saturated hydrocarbon resins, α-methylstyrene resins, etc.). Such tackifier resins make it easier to obtain a PSA sheet for application to skin that exhibits a better balance between good adhesion and fixation to the skin and good releasability from the skin.

[0050] The softening point of the tackifier resin is not particularly limited and may be, for example, within a range of about 50°C to 180°C. In some embodiments, the softening point of the tackifier resin is suitably 60°C or higher, advantageously 70°C or higher, preferably 80°C or higher, and more preferably 90°C or higher, from the viewpoint of improving fixation to the skin. Furthermore, the softening point of the tackifier resin is suitably 160°C or lower, preferably 140°C or lower, and more preferably 130°C or lower, from the viewpoint of suppressing melt viscosity and improving coatability in hot melt coating. In some embodiments, the softening point of the tackifier resin is preferably 120°C or lower (e.g., less than 120°C), more preferably 115°C or lower, and even more preferably 110°C or lower or 105°C or lower, from the viewpoint of improving adhesive strength and fixation performance while suppressing damage to the skin.

[0051] The softening point of the tackifying resin is defined as the value measured based on the softening point test method (ring and ball method) specified in JIS K5902 and JIS K2207. Specifically, the sample is melted as quickly as possible at the lowest possible temperature and carefully filled into a ring placed on a flat metal plate, avoiding the formation of bubbles. After cooling, the raised portion of the ring, including the top edge, is cut off with a slightly heated knife. Next, a holder (ring stand) is placed in a glass container (heating bath) with a diameter of at least 85 mm and a height of at least 127 mm, and glycerin is poured into it to a depth of at least 90 mm. Next, a steel ball (diameter 9.5 mm, weight 3.5 g) and the ring filled with the sample are immersed in the glycerin without touching each other, and the glycerin temperature is maintained at 20°C ± 5°C for 15 minutes. Next, the steel ball is placed in the center of the surface of the sample in the ring and placed in its fixed position on the holder. Next, keeping the distance from the top of the ring to the glycerin surface at 50 mm, place a thermometer, align the center of the thermometer's mercury bulb with the center of the ring, and heat the container. The flame of the Bunsen burner used for heating should be aimed midway between the center of the bottom and the edge of the container, ensuring even heating. After heating begins and reaching 40°C, the rate of increase in bath temperature must be 5.0 ± 0.5°C per minute. The sample gradually softens, flows down the ring, and finally touches the bottom plate, at which point the temperature is read and considered the softening point. Two or more samples should be measured at the same time, and the average value should be used.

[0052] The content of the tackifier resin in the pressure-sensitive adhesive layer is not particularly limited and can be set so as to obtain the desired effect. In some embodiments, the content of the tackifier resin relative to 100 parts by weight of the acrylic block copolymer may be, for example, 25 parts by weight or more. From the viewpoint of improving fixation performance, it is appropriate to be 35 parts by weight or more, advantageously 45 parts by weight or more, preferably 50 parts by weight or more (more than 50 parts by weight), more preferably 60 parts by weight or more, may be 70 parts by weight or more, or may be 80 parts by weight or more. Furthermore, the content of the tackifier resin relative to 100 parts by weight of the acrylic block copolymer may be, for example, 200 parts by weight or less. From the viewpoint of improving the flexibility of the pressure-sensitive adhesive, it is appropriate to be 170 parts by weight or less, preferably 150 parts by weight or less, more preferably 120 parts by weight or less, may be 110 parts by weight or less, or may be 100 parts by weight or less (for example, less than 100 parts by weight).

[0053] (Other Components) The pressure-sensitive adhesive layer may contain various additive components known in the field of pressure-sensitive adhesives, such as antioxidants (for example, phenolic antioxidants such as hindered phenols, phosphorus-based antioxidants, sulfur-based antioxidants, or combinations of two or three of these), antiaging agents, ultraviolet absorbers, light stabilizers, fillers, antistatic agents, colorants such as pigments and dyes, etc. The types and amounts of these non-essential additive components may be the same as those typically used in materials of this type.

[0054] The adhesive constituting the adhesive layer may be crosslinked as needed. For crosslinking, known crosslinking agents can be used, such as organometallic salts such as zinc stearate and barium stearate, epoxy-based crosslinking agents, isocyanate-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, metal chelate-based crosslinking agents, and melamine-based crosslinking agents. The crosslinking agents can be used alone or in combination of two or more. The amount of crosslinking agent used is not particularly limited. In one embodiment, the amount of crosslinking agent used per 100 parts by weight of the base polymer can be, for example, approximately 0.01 parts by weight or more, approximately 0.02 parts by weight or more, or approximately 0.05 parts by weight or more, and can be approximately 10 parts by weight or less, or approximately 5 parts by weight or less. In some embodiments, the adhesive constituting the adhesive layer is preferably substantially non-crosslinked. For example, it is preferable that the adhesive is substantially free of components for introducing a crosslinked structure (e.g., photocrosslinking agents, curing agents, etc.). A substantially non-crosslinked adhesive is preferred from the viewpoint of improving adhesion to the skin and also from the viewpoint of improving hot melt coatability.

[0055] In some embodiments, the adhesive layer suitably comprises 70 wt % or more, preferably 80 wt % or more, more preferably 90 wt % or more, or even 95 wt % or more, or even 97 wt % or more of the total weight of the organic components contained in the adhesive layer, based on the combined weight of the acrylic block copolymer, plasticizer, and tackifier resin. The adhesive sheet for application to skin disclosed herein can be preferably implemented in an embodiment having an adhesive layer with such a composition.

[0056] <Adhesive Sheet for Skin Application> The adhesive layer can be formed using an acrylic hot-melt adhesive of the corresponding composition. The hot-melt adhesive is typically applied in the form of a heated, melted liquid that is substantially free of organic solvents (e.g., an organic solvent content of 5 wt % or less, preferably 3 wt % or less, more preferably 1 wt % or less). The application temperature is not particularly limited, but can be, for example, about 100°C to 230°C (preferably about 130°C to 200°C). The adhesive layer is typically formed continuously, but is not limited to such a form. For example, the adhesive layer may be formed in a regular or random pattern such as a dotted or striped pattern. The adhesive sheet for skin application disclosed herein may be in the form of a sheet or a roll. Alternatively, the adhesive sheet may be further processed into various shapes.

[0057] The thickness of the adhesive layer is not particularly limited and can be set according to the purpose. In some embodiments, the thickness of the adhesive layer is suitably 5 μm or more, advantageously 10 μm or more, preferably 15 μm or more, more preferably 20 μm or more, and may be 25 μm or more, 30 μm or more, or even 35 μm or more, from the viewpoint of adhesiveness to the skin, etc. In addition, in some embodiments, the thickness of the adhesive layer may be, for example, 300 μm or less, and from the viewpoint of thinning the adhesive sheet, it is preferably 200 μm or less, more preferably 150 μm or less, may be 120 μm or less, may be 100 μm or less, may be 80 μm or less, 60 μm or less, or may be 50 μm or less.

[0058] When the adhesive sheet for application to skin disclosed herein has a substrate, the material of the substrate is not particularly limited and can be appropriately selected depending on the purpose and mode of use of the adhesive sheet, etc. Non-limiting examples of substrates that can be used include polyolefin films mainly composed of polyolefin materials such as polyethylene, polypropylene, ethylene-propylene copolymer, and ethylene-vinyl acetate copolymer; polyester films mainly composed of polyester such as polyethylene terephthalate and polybutylene terephthalate; polyvinyl chloride films mainly composed of polyvinyl chloride; polyurethane films mainly composed of polyurethane such as polyether urethane and polyester urethane; vinyl acetate resin films; polyimide resin films; polyamide resin films; fluororesin films; cellophane; thermoplastic elastomers (TPEs) (e.g., olefin-based thermoplastic elastomers) resin films such as resin films mainly composed of acrylic resin or acrylic resin; resin foam sheets such as foamed polyolefin sheets (PE foam sheets, PP foam sheets, etc.), foamed polyurethane sheets, and foamed polychloroprene rubber sheets; rubber sheets such as natural rubber sheets and butyl rubber sheets; fabrics such as woven fabrics, nonwoven fabrics, and knitted fabrics made solely or in combination with various fibrous materials (e.g., cotton, staple fiber, Manila hemp, pulp, rayon, acetate fiber, polyester fiber, polyvinyl alcohol fiber, polyamide fiber, and polyolefin fibers such as polyethylene fiber and polypropylene fiber); papers such as Japanese paper, fine paper, kraft paper, and crepe paper; and metal foils such as aluminum foil and copper foil. The substrate may also be a composite of these (for example, a laminate of two or more of these, specifically, a laminate of two or more fabrics or two or more papers, a laminate of a resin film and a fabric, or a laminate of two or more resin films). Here, the resin film is typically a non-porous resin film (for example, a resin film made of a material in which the proportion of air bubbles in the apparent volume is 3% by volume or less, typically 1% by volume or less). The resin film containing acrylic resin as a main component may be a resin film containing a material generally called acrylic rubber as a main component.

[0059] The thickness of the substrate is not particularly limited and can be set according to the purpose. In some embodiments, the thickness of the substrate may be within a range of approximately 3 μm to 3000 μm (for example, approximately 5 μm to 500 μm). The preferred thickness of the substrate may vary depending on the material of the substrate. For example, when a resin film is used as the substrate, the upper limit of the thickness is preferably 100 μm, more preferably 70 μm, and the lower limit of the thickness is preferably 3 μm, more preferably 5 μm, for example, 10 μm, 20 μm, or 30 μm. Furthermore, when fabric or paper is used as the substrate, the upper limit of the basis weight is preferably 200 g / m ２ , more preferably 150 g / m ２ , for example 100 g / m ２ , 70 g / m ２ or 50 g / m ２ The lower limit of the basis weight is preferably 5 g / m ２ , more preferably 10 g / m ２ , for example 20 g / m ２ When a foam is used as the base material, the upper limit of the thickness is preferably 3000 μm, more preferably 2000 μm, and even more preferably 1000 μm, and the lower limit of the thickness is preferably 100 μm, more preferably 200 μm, and even more preferably 300 μm.

[0060] From the viewpoint of preventing stuffiness and itching during the period when the skin-adhesive sheet is attached to the skin surface, holes may be formed in the substrate. The holes formed in the substrate can be easily obtained by applying known porosity techniques such as a metal roll, a punch, or laser irradiation. In the skin-adhesive sheet provided by this specification, the holes may be formed in the substrate by forming holes in the substrate itself and then laminating the adhesive layer thereon, or by laminating the adhesive layer on the substrate and then forming the holes. Note that when holes are formed after laminating the adhesive layer on the substrate, holes penetrating the substrate and the adhesive layer are formed.

[0061] The substrate may contain various additives, such as fillers (inorganic fillers, organic fillers, etc.), colorants (pigments, dyes, etc.), antistatic agents, antioxidants, antioxidants, ultraviolet absorbers, lubricants, etc. The proportion of the additives added is usually about 30% by weight or less (e.g., 20% by weight or less, typically 10% by weight or less) of the total weight of the substrate.

[0062] The method for providing a pressure-sensitive adhesive layer on a substrate is not particularly limited, and examples that can be used include a method in which a pressure-sensitive adhesive is directly applied to a substrate to form a pressure-sensitive adhesive layer (direct method), and a method in which a pressure-sensitive adhesive layer formed on an appropriate release surface (e.g., the release surface of a release liner) is transferred to a substrate (transfer method).

[0063] The surface of the substrate on which the pressure-sensitive adhesive layer is provided may be subjected to a surface treatment as an adhesion-facilitating treatment, such as physical treatments such as corona discharge treatment, plasma treatment, sand matting treatment, ozone exposure treatment, flame exposure treatment, high-voltage shock exposure treatment, and ionizing radiation treatment; chemical treatments such as chromate treatment; application of a coating agent (primer); etc., for the purpose of improving adhesion and retention with the pressure-sensitive adhesive layer. The surface of the substrate on which the pressure-sensitive adhesive layer is not provided (i.e., the back surface of the pressure-sensitive adhesive sheet) may be subjected to a surface treatment such as a release treatment (e.g., a release treatment with a silicone-based, long-chain alkyl-based, or other release agent) to improve rewinding properties from a roll form, or an adhesion-facilitating treatment to improve overlapping properties.

[0064] When the adhesive sheet for application to skin disclosed herein is in the form of a substrate-attached double-sided adhesive sheet having a first adhesive layer laminated on the first surface of the substrate and a second adhesive layer laminated on the second surface of the substrate, the double-sided adhesive sheet is used by adhering at least one of the first and second adhesive layers to the skin, and the other adhesive layer may be attached to the skin or to an adherend other than skin. In a substrate-attached double-sided adhesive sheet having such a configuration, the adhesive layer constituting at least the adhesive surface attached to the skin may be any of the adhesive layers described above, and the composition of the adhesive layer constituting the adhesive surface attached to an adherend other than skin is not particularly limited. In other words, the adhesive layer constituting the adhesive surface attached to an adherend other than skin may be any of the adhesive layers described above, and may be, for example, a layer containing C in the monomer components constituting the soft block. ６－１２ The adhesive layer may be an adhesive layer having an acrylic block copolymer as the base polymer with an alkyl acrylate content of less than 40% by weight (for example, the monomer component is BA), or an adhesive layer having an acrylic random copolymer as the base polymer, or an adhesive layer formed from a rubber-based adhesive, a polyester-based adhesive, a urethane-based adhesive, a polyether-based adhesive, a silicone-based adhesive, or the like.

[0065] The adhesive sheet for application to skin disclosed herein may be in a form in which the adhesive surface is protected with a release liner (in the form of an adhesive sheet with a release liner) before use (before application to an adherend) to prevent contamination of the adhesive surface, etc. The release liner is not particularly limited, and examples that can be used include release liners in which the surface of a liner substrate such as a resin film or paper has been release-treated, and release liners made of low-adhesion materials such as fluorine-based polymers (polytetrafluoroethylene, etc.) and polyolefin-based resins (polyethylene, polypropylene, etc.). For example, a silicone-based, long-chain alkyl-based, or other release treating agent can be used for the release treatment.

[0066] The matters disclosed by this specification include the following. [1] A pressure-sensitive adhesive sheet for application to skin, comprising a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer is formed from an acrylic hot-melt pressure-sensitive adhesive containing an acrylic block copolymer and a plasticizer, the acrylic block copolymer having a soft block and a hard block, the monomer component constituting the soft block having an alkyl acrylate content of 40% by weight or more, the alkyl group having 6 to 12 carbon atoms, and the plasticizer comprising a plasticizer having an HLB of 0.5 or more and 3 or less. [2] The pressure-sensitive adhesive sheet for application to skin according to [1] above, wherein the pressure-sensitive adhesive layer contains a tackifier resin. [3] The pressure-sensitive adhesive sheet for application to skin according to [2] above, wherein the content of the tackifier resin in the pressure-sensitive adhesive layer is 60 parts by weight or more and 150 parts by weight or less, relative to 100 parts by weight of the acrylic block copolymer. [4] The adhesive sheet for application to skin according to [2] or [3] above, wherein the tackifier resin comprises a tackifier resin having a softening point of 60°C or higher and 120°C or lower. [5] The adhesive sheet for application to skin according to any of [1] to [4] above, wherein the content of the plasticizer in the adhesive layer is 60 parts by weight or higher and 150 parts by weight or lower per 100 parts by weight of the acrylic block copolymer. [6] The adhesive sheet for application to skin according to any of [1] to [5] above, comprising a fatty acid ester as the plasticizer. [7] The adhesive sheet for application to skin according to any of [1] to [6] above, comprising a substrate supporting the adhesive layer.

[0067] Several examples of the present invention will be described below, but it is not intended that the present invention be limited to these specific examples. In the following description, "parts" and "%" are by weight unless otherwise specified.

[0068] <Materials Used> The materials shown in Tables 1 and 2 are as follows. (Tackifying Resins) Super Ester A-100: Arakawa Chemical Industries, Ltd., product name "Super Ester-100", rosin ester resin, softening point 95 to 105°C. Arcon M-100: Arakawa Chemical Industries, Ltd., product name "Arcon M-100", alicyclic saturated hydrocarbon resin, softening point 100°C. Arcon M-90: Arakawa Chemical Industries, Ltd., product name "Arcon M-90", alicyclic saturated hydrocarbon resin, softening point 90°C.

[0069] (Plasticizers) Rheodol SP-O30V: manufactured by Kao Corporation, product name "Rheodol SP-O30V", sorbitan trioleate, HLB 1.8. KAK TTI: manufactured by Kokyu Alcohol Kogyo Co., Ltd., product name "KAK TTI", trimethylolpropane triisostearate, HLB 1.6. TISG: manufactured by Kokyu Alcohol Kogyo Co., Ltd., product name "TISG", glyceryl triisostearate, HLB 1.6. Lisonol 20SP: manufactured by Kokyu Alcohol Kogyo Co., Ltd., product name "Lisonol 20SP", octyldodecanol, HLB 2.6. Lysolex PGIS22: manufactured by Kokyu Alcohol Kogyo Co., Ltd., product name "Lysolex PGIS22", polyglyceryl-2 diisostearate, HLB 4.1. Rheodol SP-O10V: Kao Corporation, product name "Rheodol SP-O10V", sorbitan monooleate, HLB 4.3. Rheodol TW-O106V: Kao Corporation, product name "Rheodol TW-O106V", polyoxyethylene sorbitan monooleate, HLB 10. Sunsoft Q-182S: Taiyo Chemical Co., Ltd., product name "Sunsoft Q-182S", glycerin fatty acid ester, HLB 11. Rheodol TW-L106: Kao Corporation, product name "Rheodol TW-L106", polyoxyethylene sorbitan monolaurate, HLB 13.3. Process Oil PW90: Idemitsu Kosan Co., Ltd., product name "Diana Process Oil PW90", paraffinic oil, HLB 0.

[0070] <Preparation of Pressure-Sensitive Adhesive Sheet> (Example 1) A pressure-sensitive adhesive composition according to this example was prepared by mixing 100 parts of acrylic block copolymer A, 120 parts of a tackifier resin (Super Ester A-100), and 100 parts of a plasticizer (Rheodol SP-O30V) in a heated, molten state. The acrylic block copolymer A used had a triblock structure of polyMMA block-poly2EHA block-polyMMA block (hereinafter sometimes referred to as "MMA-2EHA-MMA") and was synthesized by a known living anionic polymerization method. This acrylic block copolymer A had an MMA ratio of approximately 13% of the total monomer components and a melt flow rate (MFR) of 0.5 g / 10 min at 230°C. The pressure-sensitive adhesive composition was hot-melt coated onto the release-treated surface of a polyethylene terephthalate (PET) film, one side of which had been treated with a release agent, to form a 40 μm-thick pressure-sensitive adhesive layer. This adhesive layer was applied to a nonwoven fabric substrate (nonwoven fabric manufactured by Sanwa Paper Co., Ltd., product name "D503", thickness 75 μm, basis weight 30 g / m ２ The adhesive sheet according to this example was prepared by transferring the adhesive onto one side of a sheet of paper (fiber type: pulp, polyethylene fiber, polypropylene fiber).

[0071] (Examples 2 and 4) A pressure-sensitive adhesive composition according to each example was prepared in the same manner as in Example 1, except that the types and amounts of tackifier resin and plasticizer were as shown in Table 1. A pressure-sensitive adhesive sheet according to each example was produced in the same manner as in Example 1, except that this pressure-sensitive adhesive composition was used.

[0072] Example 3 A pressure-sensitive adhesive composition according to this example was prepared by mixing 100 parts of acrylic block copolymer B, 90 parts of a tackifier resin (Alcon M-90), and 90 parts of a plasticizer (TISG) in a heated, molten state. The acrylic block copolymer B used had a triblock structure of MMA-2EHA-MMA and was synthesized by a known living anionic polymerization method. This acrylic block copolymer B had a relatively high molecular weight compared to acrylic block copolymer A, with the proportion of MMA in the total monomer components being approximately 6% and an MFR at 190°C of 0.9 g / 10 min. A pressure-sensitive adhesive sheet according to this example was produced in the same manner as in Example 1, except for using this pressure-sensitive adhesive composition.

[0073] Example 5 A pressure-sensitive adhesive composition according to this example was prepared in the same manner as in Example 4, except that acrylic block copolymer C was used instead of acrylic block copolymer A. The acrylic block copolymer C used was an acrylic block copolymer having a triblock structure of polyMMA block-poly2EHA / BA block-polyMMA block (hereinafter sometimes referred to as "MMA-2EHA / BA-MMA") and synthesized by a known living anionic polymerization method. In this acrylic block copolymer C, the weight ratio of 2EHA to BA in the poly2EHA / BA block (i.e., copolymerization ratio on a weight basis) was 50 / 50, and the proportion of MMA in all monomer components was approximately 18%. A pressure-sensitive adhesive sheet according to this example was produced in the same manner as in Example 1, except that this pressure-sensitive adhesive composition was used.

[0074] Comparative Example 1 A pressure-sensitive adhesive composition according to this example was prepared in the same manner as in Example 1, except that acrylic block copolymer D was used instead of acrylic block copolymer A. As acrylic block copolymer D, "LA-3710" (an acrylic block copolymer having an MMA-BA-MMA triblock structure) manufactured by Kuraray Co., Ltd. was used. A pressure-sensitive adhesive sheet according to this example was produced in the same manner as in Example 1, except that this pressure-sensitive adhesive composition was used.

[0075] Comparative Examples 2 to 4 A pressure-sensitive adhesive composition according to each example was prepared in the same manner as in Example 1, except that the types and amounts of the acrylic block copolymer, tackifier resin, and plasticizer were as shown in Table 1. A pressure-sensitive adhesive sheet according to each example was produced in the same manner as in Example 1, except that this pressure-sensitive adhesive composition was used.

[0076] (Examples 6 and 7, Comparative Examples 5 to 10) A pressure-sensitive adhesive composition according to each example was prepared in the same manner as in Example 1, except that the types and amounts of the acrylic block copolymer, tackifier resin, and plasticizer were as shown in Table 2. A pressure-sensitive adhesive sheet according to each example was produced in the same manner as in Example 1, except that this pressure-sensitive adhesive composition was used.

[0077] <Evaluation> The following evaluations were performed on the inner forearms of a group of seven subjects (ages: 20s to 50s) consisting of six men and one woman. Each evaluation was performed three times per subject (i.e., N = 3), and the arithmetic mean values ​​of the three measurements taken by seven subjects are shown in the corresponding columns of Tables 1 and 2. In Table 2, the data from Examples 3 and 4 are transcribed to make it easier to see the relationship between the HLB of the plasticizer and the evaluation results.

[0078] (Skin Adhesion) The pressure-sensitive adhesive sheet according to each example was cut into a strip of 25 mm width and 50 mm length to prepare a measurement sample. The subject's forearm was held with the inside facing upward, and the sample was manually pressed against the skin on the inside of the forearm. Next, one longitudinal end of the sample was grasped with a jig attached to the push-pull gauge, and the push-pull gauge was pulled up so that the peel angle of the sample relative to the skin was approximately 90 degrees. The time from when the sample was pressed against the skin to when the push-pull gauge began to be pulled up was within 5 minutes, and the pull-up speed of the push-pull gauge was approximately 10 mm / min. The peak value observed until the entire sample was peeled off from the skin was recorded as the skin adhesive strength [N / 25 mm]. In this experiment, the skin adhesive strength was suitably 0.30 N / 25 mm or more, preferably 0.40 N / 25 mm or more (e.g., 0.50 N / 25 mm or more), and more preferably 0.60 N / 25 mm or more.

[0079] (Skin Constant Load Peel) The pressure-sensitive adhesive sheet according to each example was cut into a strip with a width of 10 mm and a length of 150 mm to prepare a measurement sample. The subject's forearm was held with the inside facing upward, and the sample was manually pressed onto the skin on the inside of the forearm. Next, a 30 g weight was attached to one end of the sample on the wrist side, and the subject's forearm was rotated so that the inside was facing downward. The time [seconds] until the sample peeled from the skin (at approximately 90 degrees to the skin) over a length of 100 mm from the end was measured. The time from the application of the sample to the skin to the start of measurement (until the subject's forearm was rotated so that the inside was facing downward) was within 5 minutes. In this experiment, the result of the skin constant load peel was suitably 6.0 seconds or more, preferably 10 seconds or more, and more preferably 15 seconds or more (e.g., 18 seconds or more, or even 20 seconds or more).

[0080] (Cortex peeling rate) The sample used to measure skin adhesive strength (the sample peeled from the inner forearm of the subject) was immersed in a dyeing solution for 30 minutes to dye the keratin attached to the adhesive surface of the sample. The dyeing solution used was an aqueous solution containing 0.05% Brilliant Green (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 0.1% Crystal Violet (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in pure water. After rinsing the dyeing solution attached to the sample with water, the adhesive surface with the stained keratin was observed using an Olympus digital microscope "DSX1000". The area ratio [%] of the stained area was calculated using image processing software (application name: PRECiV Core), and this value was taken as the keratin peeling rate [%]. In this experiment, the keratin peeling rate is preferably less than 30%, and preferably 25% or less.

[0081]

[0082]

[0083] As shown in Tables 1 and 2, 2EHA (C ６－１２The PSA sheets of Examples 1 to 7, which used a combination of any of acrylic block copolymers A to C having an alkyl acrylate (HLA) content of 40% by weight or more and a plasticizer with an HLB of 0.5 or more and 3 or less, had a skin adhesive strength of 0.30 N / 25 mm or more, a constant load skin peel measurement result of 6.0 seconds or more, and a stratum corneum peel rate of less than 30%, and exhibited a good balance between good adhesion and fixation to the skin and good releasability from the skin.

[0084] On the other hand, as shown in Table 1, in Comparative Examples 1 and 2, in which the acrylic block copolymer A used in Examples 1 and 2 was replaced with acrylic block copolymer D (an acrylic block copolymer in which 100% of the monomer components constituting the soft block are BA), the cohesive strength of the adhesive was low, and clear adhesive residue remained on the skin when measuring the skin adhesive strength. Therefore, measurements of constant-load skin peeling and keratin peeling rate were not performed for these Comparative Examples. In Comparative Examples 3 and 4, in which the amount of plasticizer used was reduced to prevent the lack of cohesive strength seen in Comparative Examples 1 and 2, the keratin peeling rate increased to over 30%.

[0085] Furthermore, as can be seen from the comparison results of Examples 3, 4, 6, and 7 with Comparative Examples 5 to 9 shown in Table 2, the results of constant load peeling from skin clearly decreased and the adhesive strength to skin also generally tended to decrease when the HLB of the plasticizer was greater than 3. Comparative Example 10, which used a plasticizer with an HLB of zero, showed poor fixation to the skin, and the sample fell off as soon as the forearm was rotated.

[0086] Although specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above.

[0087] REFERENCE SIGNS LIST 1, 2: Adhesive sheet for application to skin 10: Adhesive layer 10A: One surface (adhesive surface) 10B: Other surface 20: Substrate 20A: First surface 20B: Second surface (rear surface) 30, 31, 32: Release liner

Claims

1. A pressure-sensitive adhesive sheet for skin attachment, comprising a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer is formed of an acrylic hot-melt pressure-sensitive adhesive containing an acrylic block copolymer and a plasticizer, the acrylic block copolymer has a soft block and a hard block, the monomer component constituting the soft block has a content of an alkyl acrylate having 6 to 12 carbon atoms in the alkyl group of 40% by weight or more, and the plasticizer contains a plasticizer having an HLB of 0.5 or more and 3 or less.

2. The pressure-sensitive adhesive sheet for skin attachment according to claim 1, wherein the pressure-sensitive adhesive layer contains a tackifier resin.

3. The pressure-sensitive adhesive sheet for skin attachment according to claim 2, wherein the content of the tackifier resin in the pressure-sensitive adhesive layer is 60 parts by weight or more and 150 parts by weight or less with respect to 100 parts by weight of the acrylic block copolymer.

4. The pressure-sensitive adhesive sheet for skin attachment according to claim 2, wherein the tackifier resin contains a tackifier resin having a softening point of 60°C or more and 120°C or less.

5. The pressure-sensitive adhesive sheet for skin attachment according to any one of claims 1 to 4, wherein the content of the plasticizer in the pressure-sensitive adhesive layer is 60 parts by weight or more and 150 parts by weight or less with respect to 100 parts by weight of the acrylic block copolymer.

6. The pressure-sensitive adhesive sheet for skin attachment according to any one of claims 1 to 4, wherein the plasticizer contains a fatty acid ester.

7. The pressure-sensitive adhesive sheet for skin attachment according to any one of claims 1 to 4, comprising a base material that supports the pressure-sensitive adhesive layer.

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