Adhesive sheet

Abstract

Provided is an adhesive sheet that has a support layer and an adhesive agent layer which is adjacent to the support layer. The support layer is formed from a water dispersion material (S). The adhesive agent layer is formed from a water dispersion material (A). The water dispersion material (S) and the water dispersion material (A) each contain a polymer having a hydrolyzable silyl group.

Description

adhesive sheet

[0001] The present invention relates to a pressure-sensitive adhesive sheet. This application claims priority to Japanese Patent Application No. 2023-097837, filed on June 14, 2023, the entire contents of which are incorporated herein by reference.

[0002] Generally, pressure-sensitive adhesives (also referred to as pressure-sensitive adhesives; the same applies hereinafter) are in a soft solid (viscoelastic) state at temperatures around room temperature and have the property of easily adhering to an adherend when pressure is applied. Taking advantage of this property, pressure-sensitive adhesives are widely used for purposes such as joining and fixing components in smartphones and other portable electronic devices, for example, in the form of a substrate-attached double-sided pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer on a supporting substrate. Patent Document 1 is an example of a technical document relating to substrate-attached pressure-sensitive adhesive sheets.

[0003] Japanese Patent No. 4442922

[0004] Patent Document 1 discloses a pressure-sensitive adhesive sheet in which both the support and the pressure-sensitive adhesive layer are formed from a coating film of a polymer aqueous dispersion. Forming both the support and the pressure-sensitive adhesive layer from a polymer aqueous dispersion is preferable from the viewpoint of environmental hygiene. However, the technology described in Patent Document 1 tends to result in insufficient adhesion between the support and the pressure-sensitive adhesive layer. Insufficient adhesion between the support and the pressure-sensitive adhesive layer can cause inconveniences such as the support peeling off and lifting from the pressure-sensitive adhesive layer over time when the pressure-sensitive adhesive sheet is attached to a curved surface, or leaving adhesive residue when the pressure-sensitive adhesive sheet attached to the adherend is peeled off for rework or recycling the adherend.

[0005] The present invention was created in consideration of the above circumstances, and aims to provide an adhesive sheet in which both the support layer and the adhesive layer are formed from water-dispersible materials and which has good adhesion between the support layer and the adhesive layer.

[0006] According to this specification, a PSA sheet is provided having a support layer and a PSA layer adjacent to the support layer. The support layer is formed from a water-dispersible material (S). The PSA layer is formed from a water-dispersible material (A). Both the water-dispersible material (S) and the water-dispersible material (A) contain a polymer having a hydrolyzable silyl group (hereinafter also referred to as a hydrolyzable silyl group-containing polymer). With the above configuration, a PSA sheet can be realized in which both the support layer and the PSA layer are formed from water-dispersible materials, and the support layer and the PSA layer have good adhesion to each other.

[0007] In some preferred embodiments, the water-dispersible material (S) contains, as the polymer having a hydrolyzable silyl group, at least one selected from the group consisting of an acrylic polymer having a hydrolyzable silyl group, a urethane acrylic polymer having a hydrolyzable silyl group, and a urethane polymer having a hydrolyzable silyl group. These hydrolyzable silyl group-containing polymers are preferred from the viewpoints of ease of preparation of the water-dispersible material (S) containing the polymer and ease of adjustment of the amount of hydrolyzable silyl groups contained in the polymer. Furthermore, the water-dispersible material (S) containing at least one hydrolyzable silyl group-containing polymer selected from the above group is suitable for forming a support layer having good flexibility (e.g., ability to conform to the surface shape of an adherend) and impact resistance.

[0008] In some preferred embodiments, the water-dispersible material (S) contains a polymer having a hydrolyzable silyl group derived from a silane coupling agent as the polymer having a hydrolyzable silyl group. Hereinafter, a polymer having a hydrolyzable silyl group derived from a silane coupling agent may be referred to as a polymer obtained using a silane coupling agent. A polymer having a hydrolyzable silyl group can be preferably obtained by using a silane coupling agent. The amount of the silane coupling agent used in the polymer obtained using the silane coupling agent is preferably 0.001 parts by weight or more per 100 parts by weight of polymer-forming components other than the silane coupling agent, from the viewpoint of optimally exhibiting the effect of improving the adhesion between the support layer and the pressure-sensitive adhesive layer.

[0009] In some preferred embodiments, the water-dispersible material (A) contains an acrylic polymer having a hydrolyzable silyl group derived from a silane coupling agent as the polymer having a hydrolyzable silyl group. The acrylic polymer having a hydrolyzable silyl group can be preferably obtained by using a silane coupling agent. The amount of the silane coupling agent used in the acrylic polymer is preferably 0.001 parts by weight or more per 100 parts by weight of the acrylic polymer-forming components other than the silane coupling agent, from the viewpoint of optimally exhibiting the effect of improving the adhesion between the support layer and the pressure-sensitive adhesive layer.

[0010] 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.

[0011] 1 is a schematic cross-sectional view showing the configuration of a pressure-sensitive adhesive sheet according to one embodiment. FIG. 2 is an explanatory view showing a schematic method for evaluating interlayer adhesion.

[0012] 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.

[0013] In this specification, the term "adhesive" refers to a material that is in a soft solid (viscoelastic) state at temperatures around room temperature and has the property of adhering to an adherend under pressure. The adhesive referred to here is generally a material having a complex tensile modulus E ＊ (1Hz) <10 ７ dyne / cm ２ The material may be a material having the properties satisfying the above (typically, a material having the above properties at 25°C).

[0014] In this specification, "(meth)acryloyl" refers to acryloyl and methacryloyl in a comprehensive sense. Similarly, "(meth)acrylate" refers to acrylate and methacrylate in a comprehensive sense, and "(meth)acrylic" refers to acrylic and methacrylic in a comprehensive sense.

[0015] In this specification, the term "acrylic polymer" refers to a polymer containing more than 50% by weight of monomer units derived from an acrylic monomer as the monomer units constituting the polymer. The acrylic monomer refers to a monomer having at least one (meth)acryloyl group in one molecule.

[0016] In this specification, the term "water-dispersed" refers to a form in which at least a portion of the components are dispersed in water. For example, a "water-dispersed PSA composition" refers to a composition that contains a PSA composition and water, and in which at least a portion of the PSA composition is dispersed in water. The water-dispersed type also includes a suspended state and an emulsified state.

[0017] <Configuration of Pressure-Sensitive Adhesive Sheet> The pressure-sensitive adhesive sheet disclosed herein includes at least a support layer and a pressure-sensitive adhesive layer adjacent to the support layer. The concept of pressure-sensitive adhesive sheet as used herein may include those referred to as pressure-sensitive adhesive tape, pressure-sensitive adhesive label, pressure-sensitive adhesive film, etc. The pressure-sensitive adhesive layer is typically formed continuously, but is not limited to such a form. For example, the pressure-sensitive adhesive layer may be formed in a regular or random pattern such as a dotted or striped pattern. The pressure-sensitive adhesive sheet may be in the form of a roll or a sheet. Alternatively, the pressure-sensitive adhesive sheet may be processed into various shapes.

[0018] The PSA sheet disclosed herein may be in the form of, for example, a single-sided PSA sheet having the cross-sectional structure schematically shown in Figure 1. The PSA sheet 1 has a sheet-like support layer (support substrate) 10 and a PSA layer 20 adjacent to one surface 10A of the support layer 10. The PSA sheet 1 is used by attaching the surface 20A of the PSA layer 20, which is the adhesive surface 1A, to an adherend. The back surface 10B of the support layer 10 (the surface opposite to one surface 10A) also serves as the back surface 1B of the PSA sheet 1 and constitutes the outer surface of the PSA sheet 1. Before use (i.e., before attachment to an adherend), the PSA sheet 1 may be in the form of a release-liner PSA sheet 50, in which the adhesive surface 1A is protected by a release liner 30, at least the adhesive surface 1A side of which serves as a release surface. Alternatively, the other surface (back surface) 10B of support layer 10 may be the release surface, and the pressure-sensitive adhesive layer 20 may be brought into contact with the back surface by winding the pressure-sensitive adhesive sheet 1 into a roll, thereby protecting the surface (adhesive surface 1A). The pressure-sensitive adhesive sheet disclosed herein may also be in the form of a double-sided pressure-sensitive adhesive sheet having, in addition to the pressure-sensitive adhesive layer adjacent to one surface of the support layer, a further pressure-sensitive adhesive layer adjacent to the other surface of the support layer.

[0019] <Adhesive Layer> In the technology disclosed herein, the type of adhesive constituting the adhesive layer is not particularly limited. The adhesive may contain, as a base polymer, one or more of various rubber-like polymers that can be used in the field of adhesives, such as acrylic polymers, rubber polymers (natural rubber, synthetic rubber, mixtures thereof, etc.), polyester polymers, urethane polymers, polyether polymers, silicone polymers, polyamide polymers, and fluorine-based polymers.

[0020] The "base polymer" of a pressure-sensitive adhesive refers to the main component of the rubbery polymer contained in the pressure-sensitive adhesive, and is not to be construed in any other limiting sense. The rubbery polymer refers to a polymer that exhibits rubber elasticity in a temperature range around room temperature. In this specification, the term "main component" refers to a component that accounts for more than 50% by weight, unless otherwise specified.

[0021] The PSA sheet disclosed herein has a PSA layer formed from a water-dispersible material (A). In this specification, the water-dispersible material (A) refers to a material in which at least a portion of the PSA layer-forming material is dispersed in an aqueous medium. The aqueous medium refers to water or a mixed solvent or dispersion medium (aqueous solvent or aqueous dispersion medium) containing water as the main component. A typical example of the water-dispersible material (A) used to form the PSA layer is a water-dispersible PSA composition containing an adhesive polymer in the form of an aqueous emulsion.

[0022] The water-dispersible material (A) contains a polymer having a hydrolyzable silyl group. The hydrolyzable silyl group is a functional group that generates at least one (preferably two or three) silanol group upon hydrolysis. The hydrolyzable silyl group in the water-dispersible material (A) may be in a form before hydrolysis, a form after hydrolysis, or an intermediate form therebetween (partially hydrolyzed form). Typically, the hydrolyzable silyl groups contained in the water-dispersible material (A) are mostly in a form after hydrolysis. In the PSA sheet disclosed herein, the water-dispersible material (A) contains a polymer having a hydrolyzable silyl group, and the water-dispersible material (S) for forming the support layer also contains a polymer having a hydrolyzable silyl group. By this, the silanol groups generated from the hydrolyzable silyl groups of these polymers form a crosslinked structure (e.g., a crosslinked structure due to a condensation reaction of silanol groups (silanol condensation)) between the PSA layer formed from the water-dispersible material (A) and the support layer formed from the water-dispersible material (S), contributing to improved adhesion between the PSA layer and the support layer. Furthermore, since each of the water-dispersible materials (A) and (S) contains a hydrolyzable silyl group in the form of a hydrolyzable silyl group-containing polymer, the migration of the hydrolyzable silyl group or the silanol group generated by its hydrolysis into the adjacent layer is prevented or suppressed, and the degree of crosslinking in each layer can be precisely controlled. This is particularly significant in an embodiment in which, for example, one of the water-dispersible materials (A) and (S) is coated on an appropriate surface, and then the other water-dispersible material is coated thereon (wet-on-wet coating), and then dried to produce a PSA sheet.

[0023] Representative examples of the hydrolyzable silyl group include a trialkoxysilyl group and a dialkoxysilyl group. Examples of the trialkoxysilyl group include a group represented by the general formula: -SiR １１ R １２ R １３ ; where R １１ , R １２ and R １３are each independently selected from alkoxy groups having 1 to 4 carbon atoms (preferably 1 to 3, more preferably 1 to 2). Specific examples of alkoxy groups having 1 to 4 carbon atoms include methoxy, ethoxy, propoxy, and isopropoxy groups, and preferred examples from the viewpoint of hydrolysis reactivity include methoxy and ethoxy groups. Suitable examples of the trialkoxysilyl group include trimethoxysilyl and triethoxysilyl groups. From the viewpoint of hydrolysis reactivity and the like, a trimethoxysilyl group can be preferably used in some embodiments. Furthermore, from the viewpoint of dispersion stability of the water-dispersible material (A), a triethoxysilyl group can be preferably used in some embodiments.

[0024] Examples of dialkoxysilyl groups include those represented by the general formula: -SiR ２１ R １２ R １３ an alkyldialkoxysilyl group represented by the formula: ２１ is an alkyl group having 1 to 4 carbon atoms (preferably 1 to 3, more preferably 1 to 2), and R １２ and R １３ are each independently selected from alkoxy groups having 1 to 4 carbon atoms (preferably 1 to 3, more preferably 1 to 2). Specific examples of alkyl groups having 1 to 4 carbon atoms include methyl, ethyl, propyl, and isopropyl groups. From the viewpoint of ease of reaction of silanol groups generated from the alkoxy groups, preferred examples include methyl and ethyl groups, with methyl being more preferred. Specific examples of alkoxy groups having 1 to 4 carbon atoms include methoxy, ethoxy, propoxy, and isopropoxy groups. From the viewpoint of hydrolysis reactivity, preferred examples include methoxy and ethoxy groups. Suitable examples of the dialkoxysilyl groups include methyldimethoxysilyl and methyldiethoxysilyl groups.

[0025] In the polymer having a hydrolyzable silyl group, the type of hydrolyzable silyl group possessed by the polymer may be one type or two or more types.In some embodiments, from the viewpoint of uniformly proceeding the hydrolysis reaction and the reaction of silanol groups, a polymer containing only one type of hydrolyzable silyl group may be preferably employed.In addition, the water-dispersible material (A) may contain only one type of polymer having a hydrolyzable silyl group, or may contain two or more types.The embodiment containing only one type of polymer having a hydrolyzable silyl group may be advantageous from the viewpoint of easy adjustment of the degree of intralayer crosslinking and / or interlayer crosslinking due to the reaction of silanol groups.

[0026] Methods for obtaining a polymer having a hydrolyzable silyl group include, for example, (a) a method in which a hydrolyzable silyl group-containing monomer having a hydrolyzable silyl group and a polymerizable functional group (for example, a radically polymerizable functional group such as an ethylenically unsaturated group) in the molecule is used, and the hydrolyzable silyl group-containing monomer is copolymerized with another monomer; (b) a method in which a hydrolyzable silyl group-containing compound having a hydrolyzable silyl group and a reactive functional group X in the molecule and a primary polymer having a functional group Y that reacts with the reactive functional group X are used, and the functional group Y in the primary polymer is reacted with the reactive functional group X in the hydrolyzable silyl group-containing compound; and other known methods can be appropriately employed for preparation.

[0027] In some embodiments, a method using a silane coupling agent can be preferably adopted as a method for obtaining a polymer having a hydrolyzable silyl group. By using a silane coupling agent, a polymer having a hydrolyzable silyl group derived from the silane coupling agent can be obtained. The silane coupling agent is a compound having a hydrolyzable silyl group and a reactive functional group in the molecule. Examples of the reactive functional group include ethylenically unsaturated groups such as acryloyl, methacryloyl, vinyl, and styryl groups. From the viewpoint of polymerization reactivity, preferred ethylenically unsaturated groups include acryloyl and methacryloyl groups. The above method (a) can be preferably carried out in an embodiment in which a silane coupling agent having a hydrolyzable silyl group and an ethylenically unsaturated group in the molecule is used as the hydrolyzable silyl group-containing monomer.

[0028] Other examples of the reactive functional group include an epoxy group, an amino group, a ureido group, an isocyanate group, and a mercapto group. The isocyanate group may form an isocyanurate structure. The method (b) above can be preferably carried out in an embodiment in which a silane coupling agent having such a reactive functional group (reactive functional group X) is used as the hydrolyzable silyl group-containing compound. Examples of combinations of the reactive functional group X and the functional group Y include, but are not limited to, a combination of an epoxy group and a carboxy group, a combination of an epoxy group and an amino group (listed in the order of reactive functional group X, functional group Y; the same applies below), a combination of an amino group and a carboxy group, a combination of an amino group and an epoxy group, a combination of an amino group and an isocyanate group, a combination of an isocyanate group and a hydroxyl group, a combination of an isocyanate group and a carboxy group, and a combination of an isocyanate group and an amino group.

[0029] Non-limiting specific examples of silane coupling agents that can be used to prepare a polymer having a hydrolyzable silyl group include (meth)acryloyl group-containing silane coupling agents such as 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, and 3-(meth)acryloxypropylmethyldiethoxysilane; vinyl group-containing silane coupling agents such as vinyltrimethoxysilane and vinyltriethoxysilane; styryl group-containing silane coupling agents such as styryltrimethoxysilane; epoxy group-containing silane coupling agents such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; Examples of suitable silane coupling agents include silane coupling agents containing an isocyanate group (which may form an isocyanurate structure), such as cyanatepropyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, and tris-(trimethoxysilylpropyl)isocyanurate; amino group-containing silane coupling agents, such as 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, and 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine; ureido group-containing silane coupling agents, such as 3-ureidopropyltrialkoxysilane; and mercapto group-containing silane coupling agents, such as 3-mercaptopropyltrimethoxysilane and 2-mercaptopropylmethyldimethoxysilane.

[0030] In the polymer that has the hydrolyzable silyl group derived from silane coupling agent, the amount of silane coupling agent used is appropriately set so as to obtain desired effect.In some embodiments, the amount of silane coupling agent used in the polymer that has the hydrolyzable silyl group derived from silane coupling agent can be for example 0.001 parts by weight or more with respect to 100 parts by weight of polymer-forming components other than silane coupling agent, from the viewpoint of better exhibiting the effect of improving the adhesion between support layer and pressure-sensitive adhesive layer, generally be appropriate to be 0.005 parts by weight or more, be advantageous to be 0.01 parts by weight or more, be preferably 0.02 parts by weight or more or 0.03 parts by weight or more, be more preferably 0.05 parts by weight or more or 0.08 parts by weight or more, can be 0.1 parts by weight or more, can be 0.2 parts by weight or more, can be 0.3 parts by weight or more or 0.5 parts by weight or more. In some embodiments, the amount of the silane coupling agent used can be, for example, 5.0 parts by weight or less per 100 parts by weight of the polymer-forming components other than the silane coupling agent. From the viewpoint of the storage stability of the water-dispersible material (A) (for example, the stability of the dispersed state over time), it is usually appropriate to use 3.0 parts by weight or less, advantageously 2.0 parts by weight or less, preferably 1.5 parts by weight or less, more preferably 1.0 parts by weight or less, or may be 0.8 parts by weight or less, 0.5 parts by weight or less, 0.3 parts by weight or less, 0.2 parts by weight or less, or 0.1 parts by weight or less.

[0031] In some embodiments, the hydrolyzable silyl group-containing polymer contained in the water-dispersible material (A) is preferably the base polymer of the adhesive layer formed from the water-dispersible material (A).For example, it is preferred that more than 50% by weight (more preferably 65% ​​by weight or more, even more preferably 75% by weight or more, for example 85% by weight or more) of the polymer components contained in the water-dispersible material (A) is a hydrolyzable silyl group-containing polymer.The content of the hydrolyzable silyl group-containing polymer in the polymer components contained in the water-dispersible material (A) may be 100% by weight, or may be less than 100% by weight, 99.5% by weight or less, or 99% by weight or less, from the viewpoint of obtaining the effects of using other polymers used as needed (for example, adjusting the viscosity and coating properties of the water-dispersible material (A), adjusting adhesive performance, etc.).

[0032] In some embodiments of the PSA sheet disclosed herein, a PSA comprising an acrylic polymer or a rubber polymer as a base polymer can be preferably used as the PSA constituting the PSA layer from the viewpoints of adhesive performance, cost, etc. Among these, a PSA having an acrylic polymer as a base polymer (acrylic PSA) is preferred from the viewpoints of ease of preparation of the water-dispersible material (A) used to form the PSA layer.

[0033] The following description will mainly focus on adhesive layers made of acrylic adhesives, i.e., adhesive sheets having acrylic adhesive layers, but it is not intended to limit the adhesive layers of the adhesive sheets disclosed herein to those made of acrylic adhesives.

[0034] (Acrylic Polymer) In some preferred embodiments, the PSA layer contains an acrylic polymer as a base polymer. The PSA layer may be formed from a water-dispersible material (A) containing an acrylic polymer as a main component of the polymer components.

[0035] The acrylic polymer is preferably a polymer of a monomer raw material (monomer component) containing, for example, an alkyl(meth)acrylate as a main monomer, preferably further containing a monomer having a hydrolyzable silyl group and a radically polymerizable functional group in the molecule, and which may further contain a secondary monomer copolymerizable with the main monomer. Here, the main monomer refers to a component that accounts for more than 50% by weight of the monomer composition in the monomer raw material. The monomer raw material may also contain a material derived from a renewable organic resource (biomass material) or a monomer having a structural moiety derived from biomass (e.g., a linear alkyl group).

[0036] As the alkyl(meth)acrylate, for example, a compound represented by the following formula (1) can be suitably used: CH ２ = C(R １ ) COOR ２ (1) Here, R in the above formula (1) １ is a hydrogen atom or a methyl group. ２ is a chain alkyl group having 1 to 20 carbon atoms (hereinafter, this range of carbon atoms is referred to as "C １－２０ From the viewpoint of the storage modulus of the adhesive, R ２ is C １－１４ alkyl(meth)acrylates in which R ２ is C １－１０ More preferred is alkyl(meth)acrylate, which is a chain alkyl group represented by the formula R ２ Alkyl (meth)acrylates in which is a butyl group or a 2-ethylhexyl group are particularly preferred.

[0037] R ２ is C １－２０Examples of alkyl(meth)acrylates, which are chain alkyl groups, include methyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, isopropyl(meth)acrylate, n-butyl(meth)acrylate, isobutyl(meth)acrylate, s-butyl(meth)acrylate, pentyl(meth)acrylate, isopentyl(meth)acrylate, hexyl(meth)acrylate, heptyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, n-octyl(meth)acrylate, 2-octyl(meth)acrylate, Examples of alkyl (meth)acrylates include acrylate, isooctyl (meth)acrylate, 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. These alkyl (meth)acrylates can be used alone or in combination of two or more. Preferred alkyl (meth)acrylates include n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA).

[0038] The technology disclosed herein is a method for preparing a polymerizable compound in which the monomer component is R ２ is C ４－１０ Among the alkyl(meth)acrylates contained in the monomer component, R ２ is C ４－１０ alkyl (meth)acrylate (C ４－１０ This method can be preferably carried out in an embodiment in which the total amount of the chain alkyl (meth)acrylates (typically the total amount of BA and 2EHA) is 70% by weight or more (typically 80% by weight or more). ４－１０In the embodiment in which a chain alkyl (meth)acrylate is used, the proportion of 2EHA is not particularly limited, and ４－１０ In the chain alkyl (meth)acrylate, the content is suitably more than 50% by weight, and from the viewpoint of impact resistance, the content is preferably 70% by weight or more, more preferably 90% by weight or more, and even more preferably 95% by weight or more (for example, 95 to 100% by weight).

[0039] The alkyl(meth)acrylate is R ２ is C ４－１０ In the case where the alkyl (meth)acrylate (typically at least one of BA and 2EHA) is a chain alkyl group represented by the formula (1), other alkyl (meth)acrylates (R ２ is C ４ Less than or C １０ The total amount of alkyl(meth)acrylates (which are chain alkyl groups of more than 1000) in the monomer components constituting the acrylic polymer is preferably about 30% by weight or less (for example, 20% by weight or less, typically 15% by weight or less). From the viewpoint of obtaining the effect of the other alkyl(meth)acrylates, the total amount is preferably about 1% by weight or more (for example, 5% by weight or more, typically 10% by weight or more) in the monomer components. The other alkyl(meth)acrylates include alkyl(meth)acrylates of the formula (1) R ２ is C １－３ Preferably, alkyl(meth)acrylates, which are chain alkyl groups, are used. Specific examples thereof include methyl acrylate (MA), methyl methacrylate (MMA), and ethyl acrylate (EA). Among these, MA is more preferred.

[0040] The PSA layer according to some embodiments may be formed from a water-dispersible material (A) containing a hydrolyzable silyl group-containing acrylic polymer (preferably a hydrolyzable silyl group-containing acrylic polymer containing a hydrolyzable silyl group-containing acrylic polymer as the main polymer). The hydrolyzable silyl group-containing acrylic polymer may be a polymer of a monomer component containing an alkyl(meth)acrylate as the main monomer and further containing a monomer having a hydrolyzable silyl group and a radically polymerizable functional group in the molecule (e.g., an alkoxysilyl group-containing monomer). Examples of alkoxysilyl group-containing monomers include 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, and styryltrimethoxysilane. The alkoxysilyl group-containing monomers may be used alone or in combination of two or more. Among these, alkoxysilyl group-containing monomers having (meth)acryloyl groups are preferred. By copolymerizing the alkoxysilyl group-containing monomer, a crosslinked structure can be introduced into the PSA layer formed from the PSA composition (water-dispersible material (A)) containing an acrylic polymer by a condensation reaction of silanol groups (silanol condensation). The crosslinked structure can also be formed between the PSA layer and the support layer formed from the water-dispersible material (B) containing the hydrolyzable silyl group-containing polymer. This can improve the adhesion between the PSA layer and the support layer.

[0041] When an alkoxysilyl group-containing monomer (typically, a silane coupling agent having an ethylenically unsaturated group) is copolymerized with the acrylic polymer, the amount of the alkoxysilyl group-containing monomer used in the above monomer component can be, for example, 0.001 parts by weight or more relative to 100 parts by weight of monomers other than the alkoxysilyl group-containing monomer (i.e., acrylic polymer-forming components other than the alkoxysilyl group-containing monomer). From the viewpoint of better exerting the effect of improving the adhesion between the support layer and the pressure-sensitive adhesive layer, it is usually appropriate to set it to 0.005 parts by weight or more, advantageously 0.01 parts by weight or more, preferably 0.02 parts by weight or more or 0.03 parts by weight or more, more preferably 0.05 parts by weight or more or 0.08 parts by weight or more, and may be 0.1 parts by weight or more, 0.2 parts by weight or more, 0.3 parts by weight or more, or 0.5 parts by weight or more. In some embodiments, the amount of the alkoxysilyl group-containing monomer used in the above monomer component can be, for example, 5.0 parts by weight or less per 100 parts by weight of the monomer other than the alkoxysilyl group-containing monomer. From the viewpoint of the storage stability (e.g., dispersion stability) of the water-dispersible material (A), it is usually appropriate to set it to 3.0 parts by weight or less, advantageously 2.0 parts by weight or less, preferably 1.5 parts by weight or less, more preferably 1.0 part by weight or less, or may be 0.8 parts by weight or less, 0.5 parts by weight or less, 0.3 parts by weight or less, 0.2 parts by weight or less, or 0.1 parts by weight or less.

[0042] A minor monomer copolymerizable with the alkyl (meth)acrylate main monomer can be useful for introducing crosslinking points into the acrylic polymer or for increasing the cohesive strength of the acrylic polymer. Examples of the minor monomer include the following functional group-containing monomers, which can be used singly or in combination of two or more: Carboxy group-containing monomers: ethylenically unsaturated monocarboxylic acids such as acrylic acid (AA), methacrylic acid (MAA), and crotonic acid; ethylenically unsaturated dicarboxylic acids such as maleic acid, itaconic acid, and citraconic acid, and their anhydrides (maleic anhydride, itaconic anhydride, etc.); Hydroxyl group-containing monomers: hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate; and unsaturated alcohols such as vinyl alcohol and allyl alcohol. Amide group-containing monomers: for example, (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-butyl(meth)acrylamide, N-methylol(meth)acrylamide, N-methylolpropane(meth)acrylamide, N-methoxymethyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide. Amino group-containing monomers: for example, aminoethyl(meth)acrylate, N,N-dimethylaminoethyl(meth)acrylate, t-butylaminoethyl(meth)acrylate. Epoxy group-containing monomers: for example, glycidyl(meth)acrylate, methylglycidyl(meth)acrylate, allyl glycidyl ether. Cyano group-containing monomers: for example, acrylonitrile, methacrylonitrile. Keto group-containing monomers: for example, diacetone(meth)acrylamide, diacetone(meth)acrylate, vinyl methyl ketone, vinyl ethyl ketone, allyl acetoacetate, vinyl acetoacetate.Monomers having a nitrogen atom-containing ring: for example, N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-vinylmorpholine, N-vinylcaprolactam, and N-(meth)acryloylmorpholine.

[0043] Among the functional group-containing monomers, carboxy group-containing monomers, hydroxy group-containing monomers, and cyano group-containing monomers are preferred, and carboxy group-containing monomers are more preferred, since they can suitably realize the introduction of crosslinking points and the improvement of cohesive strength as described above.Among the carboxy group-containing monomers, AA and MAA are preferred.

[0044] In some preferred embodiments, AA and MAA are used in combination as the functional group-containing monomer. A PSA composition containing an acrylic polymer with such a monomer composition (i.e., copolymer composition) can provide a PSA sheet with higher performance (e.g., better repulsion resistance). The weight ratio of AA to MAA (AA / MAA) can be, for example, in the range of approximately 0.1 to 10, more preferably approximately 0.3 or more, even more preferably 0.5 or more, and particularly preferably 1.0 or more (e.g., greater than 1.0). Furthermore, the weight ratio (AA / MAA) is more preferably approximately 5 or less (typically 4 or less). By having AA / MAA within the above range, there is a tendency for the effect of improving repulsion resistance to be sufficiently obtained, and after the PSA sheet is produced, there is a tendency for the adhesive properties to have excellent stability over time.

[0045] When a functional group-containing monomer is copolymerized into an acrylic polymer, the proportion of the functional group-containing monomer in the total monomer components constituting the acrylic polymer is not particularly limited. Generally, from the viewpoint of achieving a good balance between cohesive strength and adhesiveness, the proportion of the functional group-containing monomer is preferably about 0.1 wt% or more (e.g., 0.5 wt% or more, typically 1 wt% or more). Furthermore, taking into account the adhesive effect of alkyl (meth)acrylate, it is preferable to set the proportion to about 40 wt% or less (e.g., 30 wt% or less, typically 20 wt% or less). When a carboxy group-containing monomer is copolymerized into an acrylic polymer, the proportion of the carboxy group-containing monomer in the total monomer components is suitably 15 wt% or less from the viewpoint of adhesive properties such as adhesive strength, and may be, for example, 10 wt% or less. In some preferred embodiments, the proportion of the carboxy group-containing monomer in the total monomer components is 5 wt% or less, or may be 3 wt% or less, from the viewpoint of impact resistance. On the other hand, in some embodiments, the proportion may be, for example, 0.1 wt% or more, or may be 0.5 wt% or more, from the viewpoint of cohesive strength, etc. The technology disclosed herein can be preferably implemented in an embodiment in which the proportion of the carboxyl group-containing monomer in the total monomer components is 1% by weight or more, or 1.5% by weight or more.

[0046] Furthermore, for the purpose of increasing the cohesive strength of the acrylic polymer, copolymerization components other than the above-mentioned minor monomers can be used. Examples of such copolymerization components include vinyl ester monomers such as vinyl acetate and vinyl propionate; aromatic vinyl compounds such as styrene, substituted styrenes (α-methylstyrene, etc.) and vinyltoluene; cycloalkyl(meth)acrylates such as cyclohexyl(meth)acrylate, cyclopentyl(meth)acrylate and isobornyl(meth)acrylate; aryl(meth)acrylates (e.g., phenyl(meth)acrylate), aryloxyalkyl(meth)acrylates (e.g., phenoxyethyl(meth)acrylate), arylalkyl(meth)acrylates, and the like. aromatic ring-containing (meth)acrylates such as (meth)acrylates (for example, benzyl (meth)acrylate); olefin-based monomers such as ethylene, propylene, isoprene, butadiene, and isobutylene; chlorine-containing monomers such as vinyl chloride and vinylidene chloride; isocyanate group-containing monomers such as 2-(meth)acryloyloxyethyl isocyanate; alkoxy group-containing monomers such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; vinyl ether-based monomers such as methyl vinyl ether and ethyl vinyl ether; and the like.

[0047] Other examples of copolymerizable components other than the above-mentioned secondary monomers include monomers having multiple functional groups in one molecule. Examples of such polyfunctional monomers include 1,6-hexanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, glycerin di(meth)acrylate, epoxy acrylate, polyester acrylate, urethane acrylate, divinylbenzene, butyl di(meth)acrylate, hexyl di(meth)acrylate, and the like.

[0048] The amount of copolymerization components other than the above-described secondary monomers is not particularly limited and may be appropriately selected depending on the purpose and application. For example, the amount is preferably 10% by weight or less of the monomer components constituting the acrylic polymer, and may be 3% by weight or less, or may be less than 1% by weight (for example, 0% by weight or more and less than 1% by weight).

[0049] In the technology disclosed herein, the acrylic polymer used as the base polymer of the pressure-sensitive adhesive layer is suitably designed so that the glass transition temperature (Tg) of the polymer is −25°C or lower (typically −75°C or higher and −25°C or lower). The Tg of the acrylic polymer may preferably be −40°C or lower (e.g., −70°C or higher and −40°C or lower), more preferably −50°C or lower (typically −70°C or higher and −50°C or lower). Impact resistance tends to be improved by using an acrylic polymer with a low Tg. In addition, setting the Tg of the acrylic polymer to the above-mentioned upper limit or lower is also preferable from the viewpoints of improving adhesive strength and adhesion to the support layer. The Tg of the acrylic polymer can be adjusted by the type and amount ratio of monomers used in synthesizing the polymer.

[0050] Here, the Tg of an acrylic polymer refers to the Tg calculated by Fox's formula based on the composition of the monomer components used in synthesizing the polymer. The Fox formula, as shown below, is a relationship 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: 1 / Tg=Σ(Wi / Tgi) In the Fox formula, Tg represents the glass transition temperature of the copolymer (unit: K), Wi represents the weight fraction of monomer i in the copolymer (copolymerization ratio on a weight basis), and Tgi represents the glass transition temperature of a homopolymer of monomer i (unit: K).

[0051] The glass transition temperatures of the homopolymers used to calculate Tg are values ​​listed in publicly available documents. For example, for the monomers listed below, the following values ​​are used as the glass transition temperatures of the homopolymers of the monomers: 2-ethylhexyl acrylate -70°C n-butyl acrylate -55°C Methyl methacrylate 105°C Methyl acrylate 8°C Vinyl acetate 32°C Acrylic acid 106°C Methacrylic acid 228°C

[0052] For the glass transition temperatures of homopolymers of monomers other than those listed above, the values ​​given in "Polymer Handbook" (3rd Edition, John Wiley & Sons, Inc., 1989) shall be used. When multiple values ​​are given in this document, the highest value shall be used.

[0053] For monomers for which the glass transition temperature of the homopolymer is not listed in the Polymer Handbook, the value obtained by the following measurement method will be used (see Japanese Patent Application Publication No. 2007-51271). Specifically, 100 parts by weight of the monomer, 0.2 parts by weight of azobisisobutyronitrile, and 200 parts by weight of ethyl acetate as a polymerization solvent are charged into a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser, and the mixture is stirred for 1 hour while passing nitrogen gas through. After removing oxygen from the polymerization system in this manner, the temperature is raised to 63°C and the reaction is allowed to proceed for 10 hours. The mixture is then cooled to room temperature to obtain a homopolymer solution with a solids concentration of 33% by weight. This homopolymer solution is then cast onto a release liner and dried to prepare a test sample (sheet-like homopolymer) with a thickness of approximately 2 mm. This test sample was punched out into a disk shape with a diameter of 7.9 mm, sandwiched between parallel plates, and subjected to a shear strain of 1 Hz using a viscoelasticity tester (ARES, manufactured by Rheometrics Corporation). Viscoelasticity was measured in a shear mode at a temperature range of −70 to 150°C and a heating rate of 5°C / min, and the peak top temperature of tan δ was taken as the Tg of the homopolymer.

[0054] The water-dispersible material (A) containing the above-described acrylic polymer can be preferably prepared, for example, by emulsion polymerization. The emulsion polymerization method is not particularly limited, and various monomer supply methods, polymerization conditions, materials used, etc. similar to those of conventionally known general emulsion polymerizations can be appropriately adopted. For example, as the monomer supply method, a batch charging method in which all monomer raw materials are supplied at once, a continuous supply (dropping) method, a divided supply (dropping) method, etc. can be appropriately adopted. The monomer raw materials may be added dropwise in the form of an aqueous emulsion (emulsified liquid). The polymerization temperature can be, for example, about 20°C or higher (usually 40°C or higher), and is suitably about 100°C or lower (usually 80°C or lower).

[0055] According to the emulsion polymerization, it is possible to prepare a polymerization liquid (acrylic polymer emulsion) in the form of an emulsion in which an acrylic polymer is dispersed in water. The water-dispersible material (A) can be preferably produced, for example, using the polymerization liquid or a polymerization liquid that has been subjected to an appropriate post-treatment. Alternatively, an acrylic polymer may be synthesized using a polymerization method other than emulsion polymerization (e.g., solution polymerization, photopolymerization, bulk polymerization, etc.), and the polymer may be dispersed in water to prepare an acrylic polymer emulsion.

[0056] The initiator used for polymerization can be appropriately selected from conventionally known polymerization initiators depending on the type of polymerization method, for example, 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylpropionamidine) disulfate, 2,2'-azobis(2-methylpropionamidine) dihydrochloride, 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]hydrate, 2,2'-azobis(N,N'-dimethyleneisobutylamidine), 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride, etc. azo-based initiators such as those listed above; persulfate-based initiators such as potassium persulfate and ammonium persulfate; peroxide-based initiators such as benzoyl peroxide, t-butyl hydroperoxide, and hydrogen peroxide; substituted ethane-based initiators such as phenyl-substituted ethane; carbonyl-based initiators such as aromatic carbonyl compounds; and redox-based initiators such as a combination of a persulfate and sodium hydrogen sulfite, or a combination of a peroxide and sodium ascorbate. These polymerization initiators can be used alone or in combination of two or more.

[0057] The amount of the polymerization initiator used is not particularly limited as long as it is a normal amount, and can be selected, for example, from the range of about 0.005 parts by weight or more (preferably 0.01 parts by weight or more) to about 1 part by weight or less (preferably 0.8 parts by weight or less) per 100 parts by weight of the total monomer components.

[0058] During polymerization, a chain transfer agent (which may also be understood as a molecular weight regulator or polymerization degree regulator) may be used as needed. Examples of the chain transfer agent include mercaptans such as dodecyl mercaptan (dodecanethiol), lauryl mercaptan, glycidyl mercaptan, 2-mercaptoethanol, mercaptoacetic acid, 2-ethylhexyl thioglycolate, and 2,3-dimercapto-1-propanol, as well as α-methylstyrene dimer. Such chain transfer agents may be used alone or in combination of two or more.

[0059] The amount of the chain transfer agent used can be about 0.001 part by weight or more (typically about 0.005 part by weight or more, for example, about 0.001 part by weight or more) relative to 100 parts by weight of the monomer components, and can be, for example, about 5 parts by weight or less (typically about 2 parts by weight or less, for example, about 1 part by weight or less). By setting the amount of the chain transfer agent used in an appropriate range, a desired polymerization rate can be obtained.

[0060] Emulsion polymerization of the monomer raw materials is typically carried out in the presence of a surfactant (emulsifier). The amount of surfactant used is not particularly limited. In consideration of polymerization stability and dispersion stability of the polymerization reaction product, the amount of surfactant used is typically 0.1 parts by weight or more, preferably 0.5 parts by weight or more, per 100 parts by weight of the monomer raw materials. From the viewpoint of achieving even higher stability, the amount may be 1.0 parts by weight or more, or even 1.5 parts by weight or more. Furthermore, the amount of surfactant used may be, for example, 10 parts by weight or less per 100 parts by weight of the monomer raw materials. On the other hand, from the viewpoint of adhesive properties, it is desirable to limit the amount of surfactant (especially non-reactive surfactant) used. From this viewpoint, the amount of surfactant used is typically preferably 5 parts by weight or less, but may also be 4 parts by weight or less, 3 parts by weight or less, or 2.5 parts by weight or less, per 100 parts by weight of the monomer raw materials.

[0061] As the surfactant, known anionic surfactants, nonionic surfactants, cationic surfactants, etc. can be used. Usually, anionic or nonionic surfactants are preferred. Surfactants having a reactive functional group (typically a radically polymerizable functional group) may also be used. Hereinafter, surfactants having a reactive functional group will be referred to as reactive surfactants, and in contrast, general surfactants not having a reactive functional group will be referred to as non-reactive surfactants. The surfactants can be used alone or in combination of two or more.

[0062] Examples of non-reactive anionic surfactants include alkyl sulfates such as lauryl sulfate and octadecyl sulfate; fatty acid salts; alkylbenzenesulfonates such as nonylbenzenesulfonate and dodecylbenzenesulfonate; naphthalenesulfonates such as dodecylnaphthalenesulfonate; alkyldiphenyletherdisulfonates such as dodecyldiphenyletherdisulfonates; polyoxyethylene alkylether sulfates such as polyoxyethyleneoctadecylethersulfonate and polyoxyethylenelaurylethersulfonate; polyoxyethylene alkylphenylether sulfates such as polyoxyethylenelaurylphenylethersulfonate; polyoxyethylene styrenated phenylether sulfate; sulfosuccinates such as laurylsulfosuccinate and polyoxyethylenelaurylsulfosuccinate; polyoxyethylene alkylether phosphates; polyoxyethylene alkylether acetates; etc. When anionic surfactants form salts, these salts can be, for example, metal salts (preferably monovalent metal salts) such as sodium salts, potassium salts, calcium salts, magnesium salts, etc., ammonium salts, amine salts, etc.

[0063] Examples of non-reactive nonionic surfactants include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether and polyoxyethylene stearyl ether; polyoxyethylene alkyl phenyl ethers such as polyoxyethylene octylphenyl ether and polyoxyethylene nonylphenyl ether; sorbitan fatty acid esters such as sorbitan monolaurate, sorbitan monostearate and polyoxyethylene sorbitan monolaurate; polyoxyethylene glyceryl ether fatty acid esters; polyoxyethylene-polyoxypropylene block copolymers; and the like.

[0064] As the reactive surfactant, those having a polymerizable (typically radically polymerizable) functional group can be preferably used. For example, a reactive surfactant having a structure in which a radically polymerizable functional group is introduced into the anionic surfactant or nonionic surfactant as described above can be used. The type of radically polymerizable functional group is not particularly limited, and can be, for example, an alkenyl group, an acryloyl group, a methacryloyl group, a vinyl group, a vinyl ether group (vinyloxy group), an allyl ether group (allyloxy group), etc. Specific examples of the alkenyl group include a propenyl group and an isopropenyl group (CH ２ =C(CH ３ The concept of propenyl group here includes 1-propenyl group (CH ３ -CH=CH-) and 2-propenyl group (CH ２ =CH-CH ２ -; sometimes referred to as an allyl group.

[0065] Examples of anionic reactive surfactants include polyoxyethylene (allyloxymethyl) alkyl ether sulfates (e.g., ammonium salts), polyoxyethylene nonylpropenyl phenyl ether sulfates (e.g., ammonium salts), alkyl allyl sulfosuccinates (e.g., sodium salts), methacryloxy polyoxypropylene sulfates (e.g., sodium salts), polyoxyalkylene alkenyl ether sulfates (e.g., ammonium salts in which the alkenyl group terminates in an isopropenyl group).When anionic reactive surfactants form salts, the salts may be, for example, metal salts such as sodium salts, or non-metal salts such as ammonium salts or amine salts.Examples of nonionic reactive surfactants include polyoxyethylene nonylpropenyl phenyl ether.

[0066] Commercially available reactive surfactants include those manufactured by Daiichi Kogyo Seiyaku Co., Ltd. under the trade names "Aqualon HS-05," "Aqualon HS-10," "Aqualon HS-1025," "Aqualon HS-20," "Aqualon KH-10," "Aqualon KH-1025," "Aqualon KH-05," "Aqualon BC-0515," "Aqualon BC-10," "Aqualon BC-1025," "Aqualon BC-20," "Aqualon BC-2020," "Aqualon RN-20," "Aqualon RN-30," "Aqualon RN-50," and Examples of such products include Aqualon AR-10, Aqualon AR-20, Aqualon AR-1025, and Aqualon AR-2020, ADEKA Corporation products under the trade names Adeka Reasop SE-10N and Adeka Reasop SR-1025, Kao Corporation products under the trade names Latemul PD-104, Latemul PD-420, Latemul PD-430, and Latemul PD-450, Sanyo Chemical Industries, Ltd. products under the trade names Eleminol JS-20 and Eleminol RS-3000, and Nippon Nyukazai Co., Ltd. product under the trade name Antox MS-60.

[0067] In some embodiments, an anionic reactive surfactant may be preferably used from the viewpoint of emulsification performance, etc. When a nonionic reactive surfactant is used, more preferable results may be achieved by using it in combination with another surfactant, for example, an anionic reactive surfactant, an anionic nonreactive surfactant, a nonionic nonreactive surfactant, etc.

[0068] In embodiments using a surfactant, the surfactant preferably contains a reactive surfactant from the viewpoint of adhesive properties. In other words, it is preferable that at least a portion of the surfactant used is a reactive surfactant. By emulsion polymerizing the monomer raw materials in the presence of a reactive surfactant, the reactive surfactant can react and be incorporated into the acrylic polymer. Incorporation of the reactive surfactant into the acrylic polymer reduces the amount of free surfactant. The reactive surfactant incorporated into the acrylic polymer is restricted in its movement within the adhesive layer, making it less likely to bleed out to the surface of the adhesive layer. Therefore, polymerization using a reactive surfactant can be advantageous for achieving both polymerization stability and the adhesive properties of the adhesive layer obtained from the adhesive composition containing the polymerized acrylic polymer. To achieve better adhesive properties, the proportion of the reactive surfactant in the total weight of the surfactants used during emulsion polymerization can be 50 wt% or more, more preferably 70 wt% or more. For example, an embodiment using only the reactive surfactant as the surfactant can be preferably adopted. In this specification, "containing a reactive surfactant" refers to the concept of containing the reactive surfactant in a state after its reactive functional group (e.g., a radically polymerizable functional group) has reacted. The reactive surfactant in the technology disclosed herein is typically contained in the water-dispersed PSA composition or PSA layer in a form in which at least a portion of the surfactant is incorporated into the acrylic polymer as described above.

[0069] The weight average molecular weight (Mw) of the acrylic polymer is not particularly limited, and may be, for example, 10 × 10 ４ ~500 x 10 ４ Here, the Mw of the acrylic polymer refers to the Mw of the toluene-soluble portion (sol portion) of the acrylic polymer. The Mw of the acrylic polymer refers to a value calculated in terms of standard polystyrene based on GPC (gel permeation chromatography). From the viewpoint of improving adhesive properties, the Mw of the acrylic polymer is preferably 150×10 ４ or less, more preferably 100 x 10 ４In addition, from the viewpoint of cohesion properties, the Mw of the acrylic polymer is preferably 20×10 or less. ４ More preferably, 30×10 ４ or more (for example, 40 x 10 ４ (or more).

[0070] (Tackifier Resin) In some preferred embodiments, the PSA layer contains a tackifier resin. This makes it easier to obtain a PSA sheet that exhibits excellent adhesive properties (e.g., adhesive strength, repulsion resistance). Examples of tackifier resins include rosin-based tackifier resins (including 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.

[0071] 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). Examples of the rosin derivative tackifying resin include esters of the above-mentioned rosin-based resins (e.g., rosin esters such as stabilized rosin esters and polymerized rosin esters), phenol-modified rosin-based resins (phenol-modified rosins), and esters thereof (phenol-modified rosin esters). Examples of the petroleum-based tackifying resin include aliphatic petroleum resins, aromatic petroleum resins, copolymerized petroleum resins, alicyclic petroleum resins, and hydrogenated versions of these. Examples of the terpene-based tackifying resins include α-pinene resins, β-pinene resins, aromatic-modified terpene-based resins, terpene-phenol-based resins, etc. Examples of the ketone-based tackifying resins 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, etc.

[0072] Examples of tackifying resins that can be preferably used in the technology disclosed herein include rosin-based tackifying resins and terpene-based tackifying resins. Suitable examples of rosin-based tackifying resins include stabilized rosin esters and polymerized rosin esters. Suitable examples of terpene-based tackifying resins include terpene phenol-based resins.

[0073] The softening point of the tackifier resin used is not particularly limited. From the viewpoint of improving cohesive strength, the softening point of the tackifier resin may be, for example, 80°C or higher, preferably 90°C or higher, or may be 100°C or higher, 120°C or higher, or 130°C or higher.

[0074] Although not particularly limited, in some embodiments, the tackifier resin may include a high-softening-point tackifier resin having a softening point of 140°C or higher. The softening point of the high-softening-point tackifier resin is preferably 145°C or higher, and may be, for example, 150°C or higher, 155°C or higher, 160°C or higher, or 165°C or higher. Use of the high-softening-point tackifier resin can favorably achieve both adhesion and cohesiveness. There is no particular upper limit for the softening point of the tackifier resin, but from the viewpoints of compatibility, low-temperature properties, etc., it is usually appropriate that the softening point be 200°C or lower, preferably 180°C or lower, and may be 175°C or lower.

[0075] 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.

[0076] In an embodiment in which the PSA layer disclosed herein contains a tackifier resin, it is preferable to use a water-dispersed tackifier resin (also referred to as a tackifier resin emulsion) as the tackifier resin. In such an embodiment, the water-dispersed PSA composition (water-dispersed material (A)) used to form the PSA layer contains the tackifier resin in the form of an emulsion in which the tackifier resin is dispersed in water. For example, by mixing an aqueous emulsion of an acrylic polymer (which may be an acrylic polymer having a hydrolyzable silyl group) with an emulsion of the tackifier resin, a PSA composition containing these components in the desired ratio can be easily prepared. It is preferable to use a tackifier resin emulsion that is substantially free of at least aromatic hydrocarbon solvents (more preferably, substantially free of aromatic hydrocarbon solvents and other organic solvents).

[0077] Such a tackifier resin emulsion may be prepared using a surfactant (emulsifier) ​​as needed. Surfactants that can be used in preparing the tackifier resin emulsion can be selected from one or more surfactants similar to those that can be used in preparing the acrylic polymer emulsion. Typically, anionic or nonionic surfactants are preferred. The surfactants used in preparing the acrylic polymer emulsion and the surfactants used in preparing the tackifier resin emulsion may be the same or different. For example, preferred embodiments include using an anionic surfactant in the preparation of both emulsions, using a nonionic surfactant in both emulsions, or using an anionic surfactant in one emulsion and a nonionic surfactant in the other. The amount of surfactant used is not particularly limited as long as it is an amount that allows the tackifier resin to be prepared into an emulsion. For example, the amount can be approximately 0.2 parts by weight or more (preferably 0.5 parts by weight or more) and approximately 10 parts by weight or less (preferably 5 parts by weight or less) per 100 parts by weight (solids basis) of the tackifier resin.

[0078] In order to optimally utilize the effects of its use, the amount of tackifier resin used (based on solids content) is typically 1 part by weight or more per 100 parts by weight of base polymer (e.g., acrylic polymer), preferably 3 parts by weight or more (e.g., 5 parts by weight or more), more preferably 12 parts by weight or more, and even more preferably 16 parts by weight or more. According to the technology disclosed herein, good adhesive properties can be achieved in an embodiment containing 22 parts by weight or more (e.g., 25 parts by weight or more) of tackifier resin per 100 parts by weight of base polymer. Furthermore, in terms of cohesive strength, etc., the amount of tackifier resin used is typically 90 parts by weight or less per 100 parts by weight of base polymer, preferably 70 parts by weight or less, more preferably 55 parts by weight or less, and even more preferably 50 parts by weight or less (e.g., 45 parts by weight or less, typically 40 parts by weight or less).

[0079] When the PSA layer disclosed herein contains a high-softening point tackifying resin, it may be possible to use only the high-softening point tackifying resin as the tackifying resin from the viewpoint of cohesive strength, etc. Furthermore, in order to balance the adhesive properties taking into account the flexibility of the PSA layer, adhesion to the support layer, etc., in some embodiments, a high-softening point tackifying resin may be used in combination with a tackifying resin having a lower softening point (e.g., a tackifying resin having a softening point of 120°C or less, or 110°C or less). In such embodiments, the proportion of the high-softening point tackifying resin in the total tackifying resin used may be, for example, 20% by weight or more, 40% by weight or more, or 60% by weight or more. The proportion of the high-softening point tackifying resin may be, for example, 90% by weight or less, 80% by weight or less, or 70% by weight or less. Limiting the amount of the high-softening point tackifying resin used to a predetermined amount or less may be advantageous from the viewpoint of impact resistance.

[0080] (Polyacrylic Acid) In some embodiments, the PSA layer may contain polyacrylic acid. For example, by incorporating an appropriate amount of polyacrylic acid having an appropriate number average molecular weight into the water-dispersible material (A), the water resistance of the PSA layer formed from the water-dispersible material (A) can be improved.

[0081] The molecular weight of the polyacrylic acid is not particularly limited, and for example, the number average molecular weight (Mn) is 2000 or more and 550 × 10 ４ The following polyacrylic acids can be used: In some preferred embodiments, the Mn of the polyacrylic acid is 3000 or more and 500×10 ４ or less, or 5000 or more, 500 x 10 ４ When the Mn of polyacrylic acid is high, the effect of improving water resistance tends to be more easily exhibited. From this viewpoint, the Mn of polyacrylic acid is 1 × 10 ４ or more (e.g., 5 x 10 ４ or more), and more preferably 10 × 10 ４ or more, and more preferably 15×10 ４ That is 20 x 10 ４ On the other hand, if the Mn of the polyacrylic acid is too high, the viscosity of the water-dispersible material (A) increases rapidly due to the addition of the polyacrylic acid, which may cause problems such as a decrease in coatability, and it may be difficult to incorporate an amount of polyacrylic acid suitable for improving water resistance. From this viewpoint, the Mn of the polyacrylic acid is 400×10 ４ It is preferable that the value is equal to or less than 300×10 ４ or less, and more preferably 200×10 ４ In one embodiment of the technology disclosed herein, the Mn of the polyacrylic acid is 150×10 ４ It may be less than or equal to 100×10 ４ It may be 75×10 or less. ４ It may be 50×10 or less. ４ Less than 35 x 10 ４ The following is also acceptable.

[0082] In this specification, the number average molecular weight (Mn) refers to a value calculated as a standard polyethylene glycol / polyethylene oxide, measured by GPC.

[0083] In embodiments using polyacrylic acid, the amount of polyacrylic acid used can be set so that the effects of its addition are optimally exhibited. In some embodiments, polyacrylic acid is used in an amount of 0.3 parts by weight or more and 7 parts by weight or less per 100 parts by weight of base polymer. The amount of polyacrylic acid per 100 parts by weight of base polymer is more preferably 0.4 parts by weight or more, and even more preferably 0.5 parts by weight or more. In some embodiments, the amount of polyacrylic acid per 100 parts by weight of base polymer may be 1 part by weight or more, or even 1.5 parts by weight or more. Furthermore, from the viewpoint of coatability and forming a PSA layer with good surface condition, the amount of polyacrylic acid per 100 parts by weight of base polymer is more preferably 6 parts by weight or less, and even more preferably 5 parts by weight or less (e.g., 4.5 parts by weight or less). In one embodiment of the technology disclosed herein, the amount of polyacrylic acid per 100 parts by weight of base polymer may be 4.25 parts by weight or less, or even 4 parts by weight or less.

[0084] (Crosslinking Agent) The water-dispersible material (A) used to form the pressure-sensitive adhesive layer may contain a crosslinking agent as an optional component. The pressure-sensitive adhesive layer in the technology disclosed herein may contain the crosslinking agent in a form after crosslinking reaction, a form before crosslinking reaction, a partially crosslinked form, an intermediate or composite form thereof, or the like. The crosslinking agent is typically contained in the pressure-sensitive adhesive layer exclusively in a form after crosslinking reaction.

[0085] The type of crosslinking agent is not particularly limited, and can be appropriately selected from, for example, isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, melamine-based crosslinking agents, peroxide-based crosslinking agents, urea-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, carbodiimide-based crosslinking agents, hydrazine-based crosslinking agents, and amine-based crosslinking agents. The crosslinking agent used here may be oil-soluble or water-soluble. One crosslinking agent may be used alone, or two or more crosslinking agents may be used in combination. The amount of crosslinking agent used is not particularly limited, and is, for example, approximately 10 parts by weight or less (e.g., approximately 0.001 to 10 parts by weight) per 100 parts by weight of the base polymer, preferably approximately 5 parts by weight or less (0.01 to 5 parts by weight). The technology disclosed herein can be preferably implemented in an embodiment using a pressure-sensitive adhesive composition that does not contain a crosslinking agent.

[0086] (Other Additive Components) In the technology disclosed herein, the water-dispersible material (A) used to form the pressure-sensitive adhesive layer may contain, as needed, an acid or base (such as aqueous ammonia) used for purposes such as pH adjustment. Examples of other optional components that may be incorporated into the water-dispersible material (A) as needed include viscosity modifiers, leveling agents, crosslinking aids, release modifiers, plasticizers, softeners, fillers, colorants (pigments, dyes, etc.), antistatic agents, antioxidants, UV absorbers, antioxidants, light stabilizers, preservatives, etc. As for such various additives, conventionally known ones can be used in the usual way, and as they do not particularly characterize the present invention, detailed description thereof will be omitted.

[0087] (Thickness of Pressure-Sensitive Adhesive Layer) The thickness of the pressure-sensitive adhesive layer is usually approximately 2 μm or more. From the viewpoint of adhesive properties (e.g., impact resistance, adhesive strength, repulsion resistance, etc.), it is preferably approximately 5 μm or more, more preferably 8 μm or more. A thickness of the pressure-sensitive adhesive layer that is not too small is also advantageous from the viewpoint of improving interlayer adhesion with the support layer. In some embodiments, the thickness of the pressure-sensitive adhesive layer may be 10 μm or more, 15 μm or more (e.g., 18 μm or more), 20 μm or more, 30 μm or more, or 40 μm or more. Furthermore, the thickness of the pressure-sensitive adhesive layer is suitably approximately 100 μm or less. From the viewpoint of drying property and foam prevention when forming a pressure-sensitive adhesive layer from the water-dispersible material (A) (e.g., when preparing a pressure-sensitive adhesive sheet by applying the water-dispersible material (A) and the water-dispersible material (S) wet-on-wet and then drying them), the thickness of the pressure-sensitive adhesive layer is advantageously 70 μm or less, preferably 50 μm or less, and may be 35 μm or less, or may be 25 μm or less. In some embodiments, the thickness of the PSA layer is preferably about 20 μm or less, more preferably 16 μm or less, even more preferably 14 μm or less, and particularly preferably 12 μm or less. A PSA sheet having a PSA layer with a limited thickness can effectively meet the demand for thinner and lighter products.

[0088] <Support Layer> The support layer disclosed herein is formed from a water-dispersible material (S). In this specification, the term "water-dispersible material (S)" refers to a material in which at least a portion of the support layer-forming material is dispersed in an aqueous medium. The term "aqueous medium" refers to water or a mixed solvent or dispersion medium (aqueous solvent or aqueous dispersion medium) containing water as the main component. A typical example of the water-dispersible material (S) used to form the support layer is an aqueous dispersion (support layer-forming composition) of a support layer-forming material such as a polymer. By forming the pressure-sensitive adhesive layer and the support layer from the water-dispersible material (A) and the water-dispersible material (S), respectively, component migration between the pressure-sensitive adhesive layer and the support layer in the resulting pressure-sensitive adhesive sheet can be prevented or suppressed. The reduced interlayer component migration means that the pressure-sensitive adhesive sheet is less likely to experience changes in its properties over time due to component migration, which is preferable in practice.

[0089] The water-dispersible material (S) contains a polymer having a hydrolyzable silyl group (hydrolyzable silyl group-containing polymer). The meaning of the hydrolyzable silyl group in the hydrolyzable silyl group-containing polymer contained in the water-dispersible material (S), the form in which the hydrolyzable silyl group is present in the water-dispersible material (S), examples of the hydrolyzable silyl group (including representative examples, specific examples, preferred examples, etc.) are the same as those of the hydrolyzable silyl group-containing polymer contained in the water-dispersible material (A), and therefore redundant explanations will be omitted.

[0090] In the polymer that has the hydrolyzable silyl group derived from silane coupling agent, the amount of silane coupling agent used is appropriately set so as to obtain desired effect.In some embodiments, the amount of silane coupling agent used in the polymer that has above-mentioned hydrolyzable silyl group can be for example 0.001 parts by weight or more with respect to 100 parts by weight of polymer forming components other than silane coupling agent, from the viewpoint of better exhibiting the effect of improving the adhesion between support layer and pressure-sensitive adhesive layer, generally be appropriate to be 0.005 parts by weight or more, be advantageous to be 0.01 parts by weight or more, be preferably 0.02 parts by weight or more or 0.03 parts by weight or more, be more preferably 0.05 parts by weight or more or 0.08 parts by weight or more, can be 0.1 parts by weight or more, can be 0.2 parts by weight or more, can be 0.3 parts by weight or more or 0.5 parts by weight or more. In some embodiments, the amount of the silane coupling agent used can be, for example, 5.0 parts by weight or less relative to 100 parts by weight of the polymer-forming components other than the silane coupling agent. From the viewpoint of the storage stability of the water-dispersible material (S) (for example, the stability of the dispersed state over time), it is usually appropriate to use 3.0 parts by weight or less, and it is advantageous to use 2.0 parts by weight or less, preferably 1.5 parts by weight or less, more preferably 1.0 parts by weight or less, and may be 0.8 parts by weight or less, 0.5 parts by weight or less, 0.3 parts by weight or less, 0.2 parts by weight or less, or 0.1 parts by weight or less.

[0091] In some embodiments, the hydrolyzable silyl group-containing polymer contained in the water-dispersible material (S) is preferably the base polymer of the support layer formed from the water-dispersible material (S). For example, it is preferred that more than 50% by weight (more preferably 65% ​​by weight or more, even more preferably 75% by weight or more, for example 85% by weight or more) of the polymer components contained in the water-dispersible material (S) be hydrolyzable silyl group-containing polymer. The content of the hydrolyzable silyl group-containing polymer in the polymer components contained in the water-dispersible material (S) may be 100% by weight, or may be less than 100% by weight (99.5% by weight or less, 99% by weight or less, etc.) from the viewpoint of obtaining the effects of using other polymers used as needed (e.g., adjusting the viscosity and coatability of the water-dispersible material (S), adjusting the adhesive performance, etc.).

[0092] The water-dispersible material (S) may contain a surfactant for the purposes of dispersibility, dispersion stability, etc. of the material, or may be substantially free of a surfactant. Here, "the water-dispersible material (S) is substantially free of a surfactant" means that a surfactant is not intentionally used, and for example, the content of surfactant in the water-dispersible material (S) is less than 0.1 wt % (e.g., less than 0.01 wt % or less than 0.001 wt %) based on the solid content. In an embodiment in which the water-dispersible material (S) contains a surfactant, the surfactant can be appropriately selected, for example, from those exemplified as surfactants that can be used in the water-dispersible material (A).

[0093] From the viewpoint of adhesion to the pressure-sensitive adhesive layer, the support layer is preferably a non-foamed layer (typically, a non-foamed resin layer). In this specification, the term "non-foamed layer" refers to a substantially non-porous layer, and is a concept that is distinguished from so-called nonwoven fabrics and woven fabrics (i.e., a concept that excludes nonwoven fabrics and woven fabrics). The non-foamed resin layer refers to a resin layer that has not been intentionally treated to form a foam. Specifically, the non-foamed resin layer may be a resin layer having an expansion ratio of less than 1.1 times (for example, less than 1.05 times, typically less than 1.01 times).

[0094] In an embodiment in which the support layer is a resin layer (preferably a non-foamed resin layer), the resin material constituting the support layer can be any of a variety of resin materials capable of forming the resin layer using an aqueous dispersion material (S) containing a hydrolyzable silyl group-containing polymer. Examples of resin materials constituting the support layer include acrylic resins containing an acrylic polymer as the main polymer (the main component of the polymer component); polyurethane resins containing a urethane polymer as the main polymer; urethane-acrylic resins containing a urethane-acrylic polymer as the main polymer; polyolefin resins; vinyl chloride resins (PVC) such as soft polyvinyl chloride; silicones such as silicone rubber; blends and hybrids (also referred to as composites) of the above resins; and the like. Examples of the resin hybrids include the urethane-acrylic polymers (urethane-acrylic hybrids) and silicone-urethane hybrids. The material constituting the support layer may be rubbers (including those generally referred to as rubbers and thermoplastic elastomers). One or more of the above materials can be used as the support layer-forming material. In view of ease of preparation of the water-dispersible material (S), preferred materials include acrylic resins, urethane resins, and urethane acrylic resins.

[0095] According to some preferred embodiments, the pressure-sensitive adhesive sheet has a support layer formed from an aqueous dispersion material (S) containing at least one hydrolyzable silyl group-containing polymer selected from the group consisting of an acrylic polymer having a hydrolyzable silyl group (a hydrolyzable silyl group-containing acrylic polymer), a urethane polymer having a hydrolyzable silyl group (a hydrolyzable silyl group-containing urethane polymer), and a urethane acrylic polymer having a hydrolyzable silyl group (a hydrolyzable silyl group-containing urethane acrylic polymer). A pressure-sensitive adhesive sheet having such a support layer exhibits moderate cohesion due to the silanol groups generated from the hydrolyzable silyl group-containing polymer forming a crosslinked structure within the support layer, and the silanol groups form a crosslinked structure between the support layer and the adjacent pressure-sensitive adhesive layer, thereby achieving good interlayer adhesion. Furthermore, the aqueous dispersion material (S) containing the hydrolyzable silyl group-containing polymer tends to be suitable for forming a support layer with good flexibility and impact resistance. Furthermore, the hydrolyzable silyl group-containing polymer is preferred because the amount of hydrolyzable silyl groups contained in the polymer and the properties of the support layer, such as flexibility, strength, and low-temperature resistance, can be easily adjusted, for example, by selecting the composition of the monomer components.

[0096] (Hydrolyzable Silyl Group-Containing Acrylic Polymer) In embodiments in which the water-dispersible material (S) contains a hydrolyzable silyl group-containing acrylic polymer, the acrylic polymer is preferably, for example, a polymer of a monomer component containing at least an alkyl(meth)acrylate and a monomer having a hydrolyzable silyl group and a radically polymerizable functional group in the molecule (e.g., a monomer having an alkoxysilyl group), and may further contain other monomers. The alkyl(meth)acrylate may preferably be a compound represented by the above-mentioned formula (1) (which may be a compound having an alkyl group derived from biomass). In some embodiments, the content of the alkyl(meth)acrylate in the monomer component constituting the hydrolyzable silyl group-containing acrylic polymer may be, for example, 25% by weight or more, 40% by weight or more, 50% by weight or more, 65% by weight or more, 80% by weight or more, 85% by weight or more, or 90% by weight or more. Furthermore, the content of the alkyl(meth)acrylate in the above-mentioned monomer component is typically less than 100% by weight. In some embodiments, from the viewpoint of easily obtaining the effect of copolymerization of the silane coupling agent having the polymerizable functional group (for example, the effect of improving interlayer adhesion) and the effect of using other monomers used as optional components, the content of alkyl (meth)acrylate in the monomer component is suitably 99.5% by weight or less, advantageously 99% by weight or less, or may be 98% by weight or less, 97% by weight or less, 95% by weight or less, 80% by weight or less, 70% by weight or less, 60% by weight or less, or 50% by weight or less.

[0097] In some embodiments, the monomer component constituting the hydrolyzable silyl group-containing acrylic polymer is, from the viewpoint of the strength of the support layer, R ２ is C １－２ Alkyl (meth)acrylate (i.e., C １－２ It is preferable that the copolymer contains alkyl (meth)acrylate. １－２The alkyl (meth)acrylate may be used alone or in combination of two or more. For example, the monomer component preferably contains at least one of methyl methacrylate (MMA) and methyl acrylate (MA), and more preferably contains at least MMA. C in the monomer component constituting the hydrolyzable silyl group-containing acrylic polymer １－２ The content of alkyl (meth)acrylate can be, for example, 5% by weight or more, 15% by weight or more, 25% by weight or more, 35% by weight or more, or 45% by weight or more. In addition, from the viewpoint of balancing the effects of the use of other monomers, in some embodiments, C in the above-mentioned monomer component １－２ The content of alkyl (meth)acrylate can be, for example, 70% by weight or less, 60% by weight or less, 50% by weight or less, or less than 50% by weight.

[0098] In some embodiments, the monomer component constituting the hydrolyzable silyl group-containing acrylic polymer may be selected from the group consisting of R ２ is C ３－９ It is possible to include alkyl (meth)acrylate, which is a chain alkyl group of the formula C. ３－９ Examples of the chain alkyl (meth)acrylate include n-butyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, 2-octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, and isononyl (meth)acrylate. ３－９ The chain alkyl (meth)acrylates can be used alone or in combination of two or more. ３－９The content of the chain alkyl (meth)acrylate can be, for example, 5% by weight or more, 15% by weight or more, 25% by weight or more, or 35% by weight or more. In addition, from the viewpoint of balancing the effects of the use of other monomers, in some embodiments, C in the above-mentioned monomer component ３－９ The content of the chain alkyl (meth)acrylate can be, for example, 70% by weight or less, 60% by weight or less, 50% by weight or less, or less than 50% by weight. １－２ Alkyl (meth)acrylate and C ３－９ It may also contain a chain alkyl (meth)acrylate in combination.

[0099] As the monomer having a hydrolyzable silyl group and a polymerizable functional group (for example, an ethylenically unsaturated group) in the molecule, one or more kinds can be selected from the same hydrolyzable silyl group-containing monomers that can be used to prepare the hydrolyzable silyl group-containing polymer contained in the water-dispersible material (A).In some embodiments, as the hydrolyzable silyl group-containing monomer, one or more kinds can be preferably selected from the silane coupling agent having a hydrolyzable silyl group and an ethylenically unsaturated group in the molecule (for example, the above-mentioned (meth)acryloyl group-containing silane coupling agent, vinyl group-containing silane coupling agent, styryl group-containing silane coupling agent, etc.).

[0100] In some embodiments, the monomer component constituting the hydrolyzable silyl group-containing acrylic polymer comprises an alkoxysilyl group-containing monomer.The amount of the alkoxysilyl group-containing monomer used in the above-mentioned monomer component can be, for example, 0.001 parts by weight or more relative to 100 parts by weight of the monomer other than the alkoxysilyl group-containing monomer (i.e., the acrylic polymer-forming component other than the alkoxysilyl group-containing monomer).From the viewpoint of better exhibiting the effect of improving the adhesion between the support layer and the pressure-sensitive adhesive layer, it is usually appropriate to make it 0.005 parts by weight or more, advantageously 0.01 parts by weight or more, preferably 0.02 parts by weight or more or 0.03 parts by weight or more, more preferably 0.05 parts by weight or more or 0.08 parts by weight or more, and may be 0.1 parts by weight or more, 0.2 parts by weight or more, 0.3 parts by weight or more, or 0.5 parts by weight or more. In some embodiments, the amount of the alkoxysilyl group-containing monomer used can be, for example, 5.0 parts by weight or less, relative to 100 parts by weight of the monomer other than the alkoxysilyl group-containing monomer. From the viewpoint of the storage stability (e.g., dispersion stability) of the water-dispersible material (A), it is usually appropriate to set it to 3.0 parts by weight or less, and it is advantageous to set it to 2.0 parts by weight or less, preferably 1.5 parts by weight or less, more preferably 1.0 part by weight or less, and may be 0.8 parts by weight or less, 0.5 parts by weight or less, 0.3 parts by weight or less, 0.2 parts by weight or less, or 0.1 parts by weight or less.

[0101] The monomer component constituting the hydrolyzable silyl group-containing acrylic polymer may contain, as the other monomer, one or more functional group-containing monomers such as a carboxy group-containing monomer, a hydroxy group-containing monomer, an amide group-containing monomer, an amino group-containing monomer, an epoxy group-containing monomer, a cyano group-containing monomer, a keto group-containing monomer, a monomer having a nitrogen atom-containing ring, etc. Specific examples of each functional group-containing monomer are the same as those exemplified in relation to the water-dispersible material (A), and therefore, redundant explanations will be omitted.

[0102] Among the functional group-containing monomers, carboxy group-containing monomers, hydroxy group-containing monomers, and cyano group-containing monomers are preferred, and carboxy group-containing monomers are more preferred, as they can suitably introduce crosslinking points and improve cohesive strength.Among the carboxy group-containing monomers, AA and MAA are preferred.

[0103] When a functional group-containing monomer is copolymerized with a hydrolyzable silyl group-containing acrylic polymer, the proportion of the functional group-containing monomer in the total monomer components constituting the acrylic polymer is not particularly limited.Usually, from the viewpoint of achieving a good balance between cohesion and adhesion, it is preferable that the proportion of the functional group-containing monomer in the total monomer components constituting the acrylic polymer is about 0.1 wt% or more (for example, 0.5 wt% or more, typically 1 wt% or more).In addition, taking into account the adhesive effect of alkyl (meth)acrylate, it is preferable that the proportion of the functional group-containing monomer is about 40 wt% or less (for example, 30 wt% or less, typically 20 wt% or less).

[0104] When a carboxyl group-containing monomer is copolymerized with a hydrolyzable silyl group-containing acrylic polymer, the proportion of the carboxyl group-containing monomer in the total monomer components is suitably 20% by weight or less, for example, 15% by weight or less, from the viewpoint of adhesive properties such as adhesive strength. In some preferred embodiments, the proportion of the carboxyl group-containing monomer in the total monomer components is 10% by weight or less, or even 5% by weight or less, from the viewpoint of impact resistance. On the other hand, in some embodiments, from the viewpoint of cohesion, the proportion may be, for example, 0.1% by weight or more, 0.5% by weight or more, 1.0% by weight or more, 2.0% by weight or more, or 3.0% by weight or more (for example, 4.0% by weight or more).

[0105] The water-dispersible material (S) containing a hydrolyzable silyl group-containing acrylic polymer can be preferably prepared, for example, by emulsion polymerization. The emulsion polymerization can be appropriately carried out by appropriately referring to the explanation for the preparation of the water-dispersible material (A) containing a hydrolyzable silyl group-containing acrylic polymer, so detailed explanations are omitted.

[0106] In some embodiments, the hydrolyzable silyl group-containing acrylic polymer contained in the water-dispersible material (S) is suitably designed so that the Tg of the polymer is −30° C. or higher (typically −30° C. or higher and 40° C. or lower). From the viewpoints of the strength of the support layer and the handleability of the PSA sheet, the Tg of the acrylic polymer is preferably −20° C. or higher, more preferably −10° C. or higher, and even more preferably −5° C. or higher; for example, it may be 0° C. or higher, 5° C. or higher, 10° C. or higher, or 15° C. or higher. Furthermore, in some embodiments, from the viewpoints of flexibility, impact resistance, etc., the Tg of the acrylic polymer is suitably 35° C. or lower, advantageously 30° C. or lower, preferably 25° C. or lower, more preferably 20° C. or lower, and may be 15° C. or lower, 10° C. or lower, or 5° C. or lower. The Tg of the acrylic polymer is determined in the same manner as for the acrylic polymer that can be contained in the PSA layer.

[0107] (Hydrolyzable Silyl Group-Containing Urethane Polymer) In an embodiment in which the water-dispersible material (S) contains a hydrolyzable silyl group-containing urethane polymer, the urethane polymer is typically a polymer compound synthesized by a method comprising polyaddition reaction of a polyol (e.g., a diol) and a polyisocyanate (e.g., a diisocyanate) in an appropriate ratio. The hydrolyzable silyl group-containing urethane polymer may be any of an ether-based polyurethane, an ester-based polyurethane, and a carbonate-based polyurethane. In some preferred embodiments, the hydrolyzable silyl group-containing urethane polymer may be an ether-based polyurethane having a hydrolyzable silyl group or an ester-based polyurethane having a hydrolyzable silyl group. From the viewpoints of flexibility and impact resistance, an ether-based polyurethane having a hydrolyzable silyl group is more preferred.

[0108] The polyol is not particularly limited, and one or more suitable polyols can be selected from various diols, polyester polyols, polyether polyols, carbonate diols, etc. Specific examples of polyols include diols such as ethylene glycol, diethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,8-octanediol, polytetramethylene ether glycol (PTMG), polyethylene glycol, and polypropylene glycol; polyester polyols which are polycondensates of the above diols and dicarboxylic acids (e.g., adipic acid, azelaic acid, sebacic acid, and dimer acid); and carbonate diols such as polyalkylene carbonate diols. The above diols and dicarboxylic acids may be biologically derived materials (biomass materials). In the case of a polymer polyol (e.g., PTMG), its number average molecular weight (Mn) may be, for example, 10,000 or less, and from the viewpoints of reactivity and handleability, it is preferably 5,000 or less, and may be 3,000 or less, 2,000 or less, or 1,000 or less. Furthermore, the Mn of the polymer polyol may be, for example, 200 or more, 400 or more, 600 or more, 800 or more, or 1,000 or more. The Mn of the polymer polyol can be measured by GPC as a value converted into a standard polyethylene glycol / polyethylene oxide. When a nominal value of the number average molecular weight is provided by a manufacturer, etc., this value can be used.

[0109] The polyisocyanate is not particularly limited, and one or more suitable polyisocyanates may be selected from aromatic, aliphatic, and alicyclic diisocyanates, and polymers of these diisocyanates (e.g., dimers and trimers), and the like, and these may be used in combination. Specific examples of polyisocyanates include tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, 1,5-naphthylene diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, butane-1,4-diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, cyclohexane-1,4-diisocyanate, dicyclohexylmethane-4,4-diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, methylcyclohexane diisocyanate, and m-tetramethylxylylene diisocyanate.

[0110] The ratio of the polyol component and the polyisocyanate component used to form the urethane polymer is appropriately set so as to obtain the desired structure and mechanical properties. In some embodiments, the NCO / OH equivalent ratio (hereinafter referred to as "NCO / OH ratio") may be, for example, about 0.8 or more and 3.0 or less, or may be greater than 1.0 (e.g., 1.1 or more) and 2.5 or less, or may be 1.1 or more and 2.0 or less, or may be 1.1 or more and 1.5 or less.

[0111] The polyaddition reaction between the polyol and the polyisocyanate may be accelerated by a catalyst. Examples of the catalyst include organometallic catalysts such as organotin catalysts (dibutyltin dilaurate, dibutyltin maleate, etc.) and organozinc catalysts (zinc 2-ethylcaproate, etc.), metal salts such as tin chloride and zinc chloride, organic bases such as tertiary amine compounds, and organic acids such as acetic acid.

[0112] In addition to the polyol and polyisocyanate, other copolymerization components (e.g., carboxylic acid, etc.) may be incorporated into the urethane polymer. The amount of the other copolymerization components is suitably less than 10% by weight (e.g., 0 to 3% by weight) of the urethane polymer.

[0113] The hydrolyzable silyl group-containing urethane polymer can be obtained, for example, by preparing a silane coupling agent having a reactive functional group X and a urethane polymer having a functional group Y, and reacting the functional group Y of the urethane polymer with the reactive functional group X of the silane coupling agent. Examples of combinations of the reactive functional group X and the functional group Y are the same as those exemplified in relation to the water-dispersible material (A), so redundant explanations will be omitted. For example, a urethane polymer having a hydrolyzable silyl group derived from the silane coupling agent can be obtained by reacting an isocyanate group-containing urethane polymer with an amino group-containing silane coupling agent; a carboxy group-containing urethane polymer with an epoxy group-containing silane coupling agent; a carboxy group-containing urethane polymer with an amino group-containing silane coupling agent; a carboxy group-containing urethane polymer with an isocyanate group-containing silane coupling agent; a hydroxyl group-containing urethane polymer with an isocyanate group-containing silane coupling agent; or the like. The isocyanate group-containing urethane polymer can be obtained, for example, by setting the ratio of the amounts of polyol and polyisocyanate used so that the NCO / OH ratio is greater than 1.0 (for example, about 1.1 to 3.0, preferably about 1.2 to 2.0). As the urethane polymer having functional group Y, a commercially available urethane polymer having functional group Y (for example, a urethane polymer in the form of a dispersion in water) may be used.

[0114] The amount of silane coupling agent used in the hydrolyzable silyl group-containing urethane polymer can be, for example, 0.001 parts by weight or more per 100 parts by weight of polymer-forming components other than the silane coupling agent. From the viewpoint of better exerting the effect of improving the adhesion between the support layer and the pressure-sensitive adhesive layer, it is usually appropriate to use 0.005 parts by weight or more, advantageously 0.01 parts by weight or more, preferably 0.02 parts by weight or more or 0.03 parts by weight or more, more preferably 0.05 parts by weight or more or 0.08 parts by weight or more, and may also be 0.1 parts by weight or more, 0.2 parts by weight or more, 0.3 parts by weight or more, or 0.5 parts by weight or more. In some embodiments, the amount of the silane coupling agent used can be, for example, 5.0 parts by weight or less relative to 100 parts by weight of the polymer-forming components other than the silane coupling agent. From the viewpoint of the storage stability (e.g., dispersion stability) of the water-dispersible material (A), it is usually appropriate to set it to 3.0 parts by weight or less, and it is advantageous to set it to 2.0 parts by weight or less, preferably 1.5 parts by weight or less, more preferably 1.0 part by weight or less, and may be 0.8 parts by weight or less, 0.5 parts by weight or less, 0.3 parts by weight or less, 0.2 parts by weight or less, or 0.1 parts by weight or less.

[0115] (Hydrolyzable Silyl Group-Containing Urethane Acrylic Polymer) In embodiments in which the water-dispersible material (S) contains a hydrolyzable silyl group-containing urethane acrylic polymer, the urethane acrylic polymer may be, for example, a copolymer of a urethane polymer (radical-polymerizable urethane polymer) having a radical-polymerizable functional group introduced therein and a monomer component (acrylic component) containing an acrylic monomer (e.g., alkyl(meth)acrylate) and a hydrolyzable silyl group-containing monomer. The weight ratio (urethane / acrylic ratio) of the radical-polymerizable urethane polymer (urethane component) to the acrylic component is not particularly limited and may be, for example, within a range of 5 / 95 to 95 / 5, 10 / 90 to 90 / 10, or 80 / 20 to 20 / 80. In some preferred embodiments, the urethane / acrylic ratio may be, for example, within a range of 5 / 90 to 70 / 30, 10 / 90 to 60 / 40, or 20 / 80 to 50 / 50. A hydrolyzable silyl group-containing urethane acrylic polymer having a urethane / acrylic ratio within any of the above-mentioned ranges makes it easy to realize a pressure-sensitive adhesive sheet that achieves a good balance between the strength of the support and the adhesion between the support and the pressure-sensitive adhesive layer.

[0116] The monomer component used as the acrylic component can be appropriately selected from various monomers similar to those used in the above-described monomer components constituting the hydrolyzable silyl group-containing acrylic polymer. For example, the monomer component may include at least an alkyl(meth)acrylate and a monomer having a hydrolyzable silyl group and a radically polymerizable functional group in the molecule (e.g., a monomer having an alkoxysilyl group), and may further include other monomers (such as a carboxy group-containing monomer). As the alkyl(meth)acrylate, a compound represented by the above-described formula (1) (which may be a compound having an alkyl group derived from biomass) can be suitably used. In some embodiments, the content of the alkyl(meth)acrylate in the monomer components constituting the hydrolyzable silyl group-containing acrylic polymer can be appropriately set by referring to the examples of the alkyl(meth)acrylate content in the monomer components constituting the above-described hydrolyzable silyl group-containing acrylic polymer. The same applies to the amount of the other monomers used.

[0117] In some embodiments, the monomer component used as the acrylic component is selected from the group consisting of R ２ is C １－２ Alkyl (meth)acrylate (i.e., C １－２ It is preferable that the copolymer contains alkyl (meth)acrylate. １－２ The alkyl (meth)acrylate may be used alone or in combination of two or more. For example, the monomer component preferably contains at least one of MMA and MA, and more preferably contains at least MMA. １－２ The content of alkyl (meth)acrylate can be, for example, 5% by weight or more, 15% by weight or more, 25% by weight or more, 35% by weight or more, 45% by weight or more, 50% by weight or more, more than 50% by weight, or 55% by weight or more. １－２The content of alkyl (meth)acrylate can be, for example, 85% by weight or less, 75% by weight or less, or 65% by weight or less.

[0118] In some embodiments, the monomer component used as the acrylic component may be selected from the group consisting of R in formula (1) and R in formula (1) from the viewpoint of flexibility, impact resistance, etc. of the support layer. ２ is C ３－９ It is possible to include alkyl (meth)acrylate, which is a chain alkyl group of the formula C. ３－９ Examples of the chain alkyl (meth)acrylate are the same as those for the hydrolyzable silyl group-containing acrylic polymer, and therefore, redundant descriptions will be omitted. ３－９ The chain alkyl (meth)acrylates can be used alone or in combination of two or more. ３－９ The content of the chain alkyl (meth)acrylate can be, for example, 5% by weight or more, 15% by weight or more, or 25% by weight or more. ３－９ The content of the chain alkyl (meth)acrylate can be, for example, 70% by weight or less, 60% by weight or less, 50% by weight or less, or 40% by weight or less. １－２ Alkyl (meth)acrylate and C ３－９ It may also contain a chain alkyl (meth)acrylate in combination.

[0119] In some embodiments, the monomer component used as the acrylic component suitably has a Tg of −30° C. or higher (typically −30° C. or higher and 40° C. or lower) calculated based on the composition of the monomer component using the Fox formula. From the viewpoints of the strength of the support layer and the handleability of the PSA sheet, the Tg based on the composition of the acrylic component is preferably −20° C. or higher, more preferably −10° C. or higher, and even more preferably −5° C. or higher; for example, it may be 0° C. or higher, 5° C. or higher, 10° C. or higher, or 15° C. or higher, 20° C. or higher, 25° C. or higher, or 30° C. or higher. Furthermore, in some embodiments, from the viewpoints of flexibility, impact resistance, etc., the Tg based on the composition of the monomer component is suitably 60° C. or higher, advantageously 50° C. or lower, preferably 45° C. or lower, more preferably 40° C. or lower, and may be 35° C. or lower, or may be 30° C. or lower. The Tg based on the composition of the above monomer components can be determined in the same manner as for the acrylic polymer that can be contained in the pressure-sensitive adhesive layer, except that the Fox equation is applied to only the monomer components used as the above acrylic component.

[0120] The urethane component of the hydrolyzable silyl group-containing urethane acrylic polymer can be appropriately selected from, for example, the various polyols and polyisocyanates exemplified above as materials (which may be biomass materials) that can be used in the synthesis of the hydrolyzable silyl group-containing urethane polymer. The polyurethane formed from such a urethane component may be any of ether-based polyurethane, ester-based polyurethane, and carbonate-based polyurethane. In some embodiments, the polyurethane may be an ether-based polyurethane or an ester-based polyurethane. From the viewpoint of flexibility and impact resistance, ether-based polyurethane is more preferred. The NCO / OH ratio of the urethane component is not particularly limited and may be, for example, 0.8 or more and 3.0 or less. In some embodiments, the NCO / OH ratio may be, for example, greater than 1.0 (e.g., 1.1 or more), 1.2 or more, 1.3 or more, or 1.4 or more, from the viewpoint of ease of synthesis of the hydrolyzable silyl group-containing urethane acrylic polymer. Furthermore, in some embodiments, the NCO / OH ratio may be, for example, 2.5 or less, 2.0 or less, or 1.8 or less.

[0121] Examples of the water-dispersible material (S) containing a hydrolyzable silyl group-containing urethane acrylic polymer include: (1) using an acrylic monomer (typically an acrylic monomer not containing a hydrolyzable silyl group-containing monomer) as a diluent, reacting a diol with a diisocyanate in the acrylic monomer to form a urethane polymer; (2) subsequently introducing a radically polymerizable functional group into the urethane polymer in the acrylic monomer to form a radically polymerizable urethane polymer; (3) subsequently adding water and a hydrolyzable silyl group-containing monomer (for example, an alkoxy group-containing monomer such as an alkoxy group (meth)acrylate, which may be a silane coupling agent) to emulsify the resulting mixture; (4) heating the resulting emulsion to an appropriate temperature and copolymerizing the radically polymerizable urethane polymer, the acrylic monomer, and the hydrolyzable silyl group-containing monomer under an inert gas atmosphere using an appropriate polymerization initiator; and (5) using the resulting aqueous dispersion (aqueous dispersion of a hydrolyzable silyl group-containing urethane acrylic polymer) as is, or after suitable post-treatment (additive addition, pH adjustment, solids adjustment, viscosity adjustment, etc.) as necessary.

[0122] In some embodiments, the emulsification can be carried out by, for example, adding a surfactant to the product obtained in step (2) and mixing, followed by adding water and a hydrolyzable silyl group-containing monomer to emulsify. The surfactant can be selected from the various surfactants described in relation to the water-dispersible material (A). In some embodiments, it is preferable that at least a portion of the surfactant used is a reactive surfactant. Furthermore, in some embodiments, from the viewpoints of dispersion stability during polymerization, storage stability of the water-dispersible material (S), and homogeneity of the support layer formed from the water-dispersible material (S), it is preferable that the emulsification be carried out so that the median diameter is less than 3 μm (more preferably less than 1 μm, e.g., 50 nm or more and less than 500 nm).

[0123] When the hydrolyzable silyl group in the hydrolyzable silyl group-containing urethane acrylic polymer is derived from a silane coupling agent, the amount of silane coupling agent used can be, for example, 0.001 parts by weight or more relative to 100 parts by weight of the polymer-forming components other than the silane coupling agent. From the viewpoint of better exerting the effect of improving the adhesion between the support layer and the pressure-sensitive adhesive layer, it is usually appropriate to use an amount of 0.005 parts by weight or more, advantageously 0.01 parts by weight or more, preferably 0.02 parts by weight or more or 0.03 parts by weight or more, more preferably 0.05 parts by weight or more or 0.08 parts by weight or more, and may also be 0.1 parts by weight or more, 0.2 parts by weight or more, 0.3 parts by weight or more, or 0.5 parts by weight or more. In some embodiments, the amount of the silane coupling agent used can be, for example, 5.0 parts by weight or less relative to 100 parts by weight of the polymer-forming components other than the silane coupling agent. From the viewpoint of the storage stability (e.g., dispersion stability) of the water-dispersible material (A), it is usually appropriate to set it to 3.0 parts by weight or less, and it is advantageous to set it to 2.0 parts by weight or less, preferably 1.5 parts by weight or less, more preferably 1.0 part by weight or less, and may be 0.8 parts by weight or less, 0.5 parts by weight or less, 0.3 parts by weight or less, 0.2 parts by weight or less, or 0.1 parts by weight or less.

[0124] (Other Components) In some embodiments, the support layer may contain filler particles in addition to the various resins described above. As the filler particles, either organic or inorganic materials can be used, and inorganic materials such as metal filler particles, metal oxide fillers such as silica, metal hydroxide filler particles, and carbonates such as calcium carbonate are preferably used. The filler particles can be used alone or in combination of two or more. From the viewpoint of dispersibility in the resin, the filler particles are preferably added in the form of an aqueous dispersion. The particle size of the filler particles is not particularly limited, and fillers of an appropriate size can be used depending on the thickness, dispersibility, etc. of the support layer to which the filler particles are added.

[0125] In embodiments in which the support layer contains filler particles, the content of the filler particles is not particularly limited. From the viewpoint of effectively exerting the effect of adding the filler particles, the amount of the filler particles is, for example, 1 part by weight or more, suitably 10 parts by weight or more, or even 20 parts by weight or more, or even 30 parts by weight or more, per 100 parts by weight of the polymer component contained in the support layer. The upper limit of the amount of the filler particles is, for example, less than 100 parts by weight, suitably about 70 parts by weight or less, per 100 parts by weight of the polymer component. In other embodiments, the content of the filler particles in the support is, for example, less than 30 parts by weight, or even less than 10 parts by weight, per 100 parts by weight of the polymer component contained in the support layer. The support layer disclosed herein may be substantially free of filler particles.

[0126] The support layer may contain, as necessary, various additives such as a leveling agent, a thickener, an antioxidant, an antioxidant, an ultraviolet absorber, an antistatic agent, a lubricant, a plasticizer, a colorant (pigment, dye, etc., for example, carbon black), a preservative, etc. The surface of the support layer (particularly the surface on the pressure-sensitive adhesive layer side) may be subjected to a known or conventional surface treatment, such as a corona discharge treatment, a plasma treatment, or the application of a primer.

[0127] The support layer may have a single layer structure, or a multi-layer structure of two, three, or more layers. For example, the support layer may be substantially composed of a resin layer formed from the above-mentioned water-dispersible material (S). The support layer may include an auxiliary layer in addition to the resin layer. The auxiliary layer may be, for example, a decorative layer such as a printing layer, an antistatic layer, a release treatment layer, a surface protection layer, or the like. The auxiliary layer may be located on the side opposite the pressure-sensitive adhesive layer, or may be located between layers in a support layer with a two-layer or more structure.

[0128] (Thickness of the support layer) The thickness of the support layer may be, for example, approximately 2 μm or more. From the viewpoint of the strength, handling, impact resistance, etc. of the pressure-sensitive adhesive sheet, it is usually appropriate to be 3 μm or more, preferably 5 μm or more, more preferably 7 μm or more, even more preferably 9 μm or more, 10 μm or more, 15 μm or more, 18 μm or more, 20 μm or more, 30 μm or more, or 40 μm or more. Furthermore, the thickness of the support layer is suitably approximately 100 μm or less. From the viewpoint of drying property and foam prevention when forming the support layer from the water-dispersible material (S) (for example, when the water-dispersible material (A) and the water-dispersible material (S) are applied wet-on-wet and then dried to produce a pressure-sensitive adhesive sheet), it is advantageous to be 70 μm or less, preferably 50 μm or less, and may be 35 μm or less, or may be 25 μm or less. In some embodiments, the thickness of the support layer is preferably about 20 μm or less, more preferably 16 μm or less, even more preferably 14 μm or less, and particularly preferably 12 μm or less. A PSA sheet having a support layer with a limited thickness can effectively meet the demand for thinner and lighter weight.

[0129] <Release Liner> In the technology disclosed herein, a release liner can be used during the formation of the adhesive layer, the preparation of the support layer, the preparation of the adhesive sheet, and the storage, distribution, and shaping of the adhesive sheet before use. The release liner is not particularly limited, and examples include release liners having a release treatment layer on the surface of a liner substrate such as a resin film (e.g., polyester film typified by polyethylene terephthalate (PET) film, polypropylene film, etc.) or paper, and release liners made of low-adhesion materials (e.g., fluorine-based polymers such as polytetrafluoroethylene, polyolefin-based resins mainly composed of linear low-density polyethylene, etc.). The release treatment layer can be formed by surface-treating the liner substrate with, for example, a silicone-based, long-chain alkyl-based, fluorine-based, molybdenum sulfide, or other release treating agent. The release liner may be made of a biological material (biomass material), a recyclable material, or a recycled material (also referred to as a recycled material).

[0130] <Method for Producing Pressure-Sensitive Adhesive Sheet> The pressure-sensitive adhesive sheet disclosed herein can be produced by any of various methods capable of producing a pressure-sensitive adhesive sheet having a configuration in which a support layer and a pressure-sensitive adhesive layer are adjacent to each other. For example, (1) a method in which a water-dispersible material (A) is applied to the release-treated surface of a release liner and dried to form a PSA layer on the release liner, and the PSA layer is then laminated to a support layer formed by applying and drying a water-dispersible material (S) (hereinafter also referred to as a "lamination method"); (2) a method in which a water-dispersible material (A) is directly applied to a support layer formed by applying and drying a water-dispersible material (S) and then dried, or a method in which a water-dispersible material (S) is directly applied to a PSA layer formed by applying and drying a water-dispersible material (A) and then dried (hereinafter also referred to as a "wet-on-dry method" or "WOD method"); (3) a method in which a water-dispersible material (A) is applied to the release-treated surface of a release liner, a water-dispersible material (S) is applied thereon, and then the whole is dried (hereinafter also referred to as a "wet-on-wet method" or "WOW method"); etc. can be employed. From the viewpoint of increasing the efficiency of crosslinking (e.g., silanol crosslinking) between the pressure-sensitive adhesive layer and the support layer, the WOD method and the WOW method are more advantageous than the lamination method, with the WOW method being more preferred. Furthermore, the WOW method requires only a single curing treatment step, such as drying, for the entire surface, which is advantageous in terms of productivity. In the technology disclosed herein, both the pressure-sensitive adhesive layer and the support layer are formed from water-dispersible materials. Therefore, compared to embodiments in which one or both layers are formed from an organic solvent solution (solvent-based composition) or a photocurable pressure-sensitive adhesive composition, even in pressure-sensitive adhesive sheets obtained by the WOW method, interlayer mixing (regions where components of one layer have penetrated into the other layer) is less likely to occur, and the composition and structure of each layer can be precisely controlled. When applying the water-dispersible materials (A) and (S) using the WOW method, various methods and conditions that are less likely to cause interlayer mixing can be selected.Examples of such methods include a method in which a die coater having multiple manifolds is used to continuously overcoat or simultaneously coat (co-extrude) the water-dispersible material (A) and the water-dispersible material (S) through different manifolds, or a method in which the water-dispersible material (A) and the water-dispersible material (S) are simultaneously coated using a die coater having a multi-layer manifold with two or more layers; a method in which one water-dispersible material is coated using any method (for example, a conventional coater such as a gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, bar coater, knife coater, or spray coater), and then the other water-dispersible material is coated on top of it using, for example, a dispenser or bar coater; and a method in which any combination or repetition of these methods is used.

[0131] The adhesive strength of the PSA sheet disclosed herein is not particularly limited. In some embodiments, the PSA sheet may have a 180-degree peel strength (peeling strength from SUS plate) of, for example, 5 N / 20 mm or more after being attached to a stainless steel plate and held at 23°C and 50% RH for 30 minutes. PSA sheets exhibiting such properties may be preferably used as highly adhesive PSA sheets that firmly secure articles or components. The PSA peel strength is preferably 6 N / 20 mm or more, and may be 7 N / 20 mm or more. In some preferred embodiments, the PSA peel strength is, for example, 8 N / 20 mm or more, more preferably 10 N / 20 mm or more, and may even be 12 N / 20 mm or more. The upper limit of the PSA peel strength is not particularly limited, and may be, for example, approximately 30 N / 20 mm or less, or may be 25 N / 20 mm or less.

[0132] The peel strength of a pressure-sensitive adhesive sheet from a SUS plate is measured as follows. A pressure-sensitive adhesive sheet is cut to a size of 20 mm wide and 100 mm long to prepare a test piece. Under an environment of 23°C and 50% RH, the test piece is pressure-bonded to a stainless steel plate (SUS304BA plate) as an adherend by rolling it back and forth once with a 2 kg roller. After holding it under an environment of 23°C and 50% RH for 30 minutes, the 180-degree peel strength [N / 20 mm] is measured using a tensile tester at a tensile speed of 300 mm / min in accordance with JIS Z0237. The measurement is performed three times (i.e., N = 3), and the average value is taken as the peel strength of the pressure-sensitive adhesive sheet from a SUS plate. If necessary, the test piece may be reinforced with a backing material having appropriate strength. As the backing material, for example, a commercially available single-sided adhesive sheet having a polyester base material with a thickness of about 25 μm (polyester adhesive tape manufactured by Nitto Denko Corporation, product name "No. 31B#25") can be used.

[0133] <Applications> Taking advantage of the advantage of good adhesion between the support layer and the pressure-sensitive adhesive layer, the pressure-sensitive adhesive sheet disclosed herein can be preferably used in a form in which it is attached to various products or components constituting the products, for applications such as fixing, joining, molding, decorating, protecting, and supporting the products or components. In particular, it can be preferably used for fixing the above-mentioned products or components. For example, portable electronic devices are at risk of being dropped due to their usage, and pressure-sensitive adhesive sheets used in portable electronic devices may be required to have impact resistance. Pressure-sensitive adhesive sheets with good adhesion between the support layer and the pressure-sensitive adhesive layer are excellent in maintaining adhesion between the above-mentioned layers against impact. Therefore, the pressure-sensitive adhesive sheet disclosed herein is also suitable for use in portable electronic devices.

[0134] Non-limiting examples of the portable electronic devices include mobile phones, smartphones, tablet computers, notebook computers, various wearable devices (for example, wristwear devices worn on the wrist like a wristwatch, modular devices worn on a part of the body with a clip or strap, eyewear devices including eyeglasses (monocular and binocular, including head-mounted devices), clothing devices attached to shirts, socks, hats, etc. as accessories, earwear devices attached to the ears like earphones), digital cameras, digital video cameras, audio equipment (portable music players, IC recorders, etc.), calculators (calculators, etc.), portable game devices, electronic dictionaries, electronic organizers, e-books, in-car information devices, portable radios, portable televisions, portable printers, portable scanners, portable modems, etc. In this specification, the term "portable" does not simply mean that the device is portable, but rather means that the device has a level of portability that allows an individual (average adult) to carry it relatively easily.

[0135] The present specification discloses the following: [1] A PSA sheet having a support layer and a PSA layer adjacent to the support layer, wherein the support layer is formed from a water-dispersible material (S), and the PSA layer is formed from a water-dispersible material (A), and both the water-dispersible material (S) and the water-dispersible material (A) contain a polymer having a hydrolyzable silyl group. [2] The PSA sheet according to [1] above, wherein the water-dispersible material (S) contains, as the polymer having a hydrolyzable silyl group, at least one selected from the group consisting of an acrylic polymer having a hydrolyzable silyl group, a urethane acrylic polymer having a hydrolyzable silyl group, and a urethane polymer having a hydrolyzable silyl group. [3] The pressure-sensitive adhesive sheet according to [1] or [2], wherein the water-dispersible material (S) contains a polymer having a hydrolyzable silyl group derived from a silane coupling agent as the polymer having a hydrolyzable silyl group, and the amount of silane coupling agent used in the polymer is 0.001 part by weight or more per 100 parts by weight of polymer-forming components other than the silane coupling agent. [4] The pressure-sensitive adhesive sheet according to any one of [1] to [3], wherein the water-dispersible material (A) contains an acrylic polymer having a hydrolyzable silyl group derived from a silane coupling agent as the polymer having a hydrolyzable silyl group. [5] The pressure-sensitive adhesive sheet according to [4], wherein the amount of silane coupling agent used in the acrylic polymer is 0.001 part by weight or more per 100 parts by weight of acrylic polymer-forming components other than the silane coupling agent.

[0136] Several examples of the present invention will be described below, but it is not intended that the present invention be limited to those shown in these examples. In the following description, "parts" and "%" are based on weight unless otherwise specified. Furthermore, the amount of each material used is based on solid content unless otherwise specified.

[0137] Example 1 Preparation of Support Layer-Forming Composition Sua1 116 g of polytetramethylene ether glycol (product name "PTMG1000" manufactured by Mitsubishi Chemical Corporation) was placed in a reaction vessel equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser. 333.3 g of acrylic monomers (106.1 g of n-butyl acrylate (BA), 212.2 g of methyl methacrylate (MMA), and 15 g of acrylic acid (AA)) were added and dissolved, and the atmosphere was replaced with nitrogen while stirring for approximately 1 hour. The system was heated in a water bath set to 65°C. After confirming that the temperature of the solution in the reaction vessel had reached 65°C, 33.9 g of 1,3-bis(isocyanatomethyl)cyclohexane (H6-XDI manufactured by Mitsui Chemicals, Inc.) was added (NCO / OH ratio = 1.5). After confirming that the solution was generating heat, the temperature was maintained by cooling. After the heat generation subsided, 12 mg of dibutyltin(IV) dilaurate (Wako Pure Chemical Industries, Ltd.) was added and the mixture was allowed to react at 65°C for 2 hours. Next, 16.8 g of 4-hydroxybutyl acrylate (4HBA) was added and the mixture was allowed to react for another 2 hours, after which the system was cooled. In this way, a urethane / acrylic monomer mixed solution containing a urethane polymer having an acryloyl group derived from 4HBA introduced therein and an acrylic monomer was obtained.

[0138] To 200 g of the obtained urethane / acrylic monomer mixed solution, 6 g (3 parts per 100 parts of the mixed solution) of a reactive surfactant (trade name "Aqualon KH-1025", manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) was added on a solids basis and mixed. Distilled water was added to this mixture in an amount such that the concentration of the urethane / acrylic monomer mixed solution became 45%, and then 0.02 g (0.01 parts per 100 parts of the urethane / acrylic monomer mixed solution) of 3-methacryloxypropyltrimethoxysilane (silane coupling agent, trade name "KBM-503", manufactured by Shin-Etsu Chemical Co., Ltd.) was added. The mixture was emulsified using a high-speed emulsifying disperser (Homomixer, manufactured by Primix Corporation) and further subjected to a micronization treatment using a wet microparticler (Starburst Mini, manufactured by Sugino Machine Co., Ltd.) to obtain a median diameter (d ５０ An emulsion having a median diameter (d ) of less than 500 nm was obtained. ５０ ) was measured using a particle size distribution measuring device based on the laser diffraction / scattering method.

[0139] 400 g of the resulting emulsion was placed in a reaction vessel equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser, and the atmosphere was replaced with nitrogen for approximately 2 hours while stirring. The system was heated in a water bath set to 60 °C, and 120 mg of a polymerization initiator (product name "VA-057", manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added. The reaction was allowed to proceed for 5 hours while maintaining the temperature of the contents of the reaction vessel at 60 °C. The system was then cooled to obtain an aqueous dispersion of a urethane acrylic polymer copolymerized with 3-methacryloxypropyltrimethoxysilane. To this aqueous dispersion (urethane acrylic aqueous dispersion), 1 part of a carboxylic acid copolymer (product name "Aron B-500", manufactured by Toagosei Co., Ltd.) was added per 100 parts of the solids content of the aqueous dispersion, and the pH was adjusted to 8 with 10% aqueous ammonia to prepare a support layer-forming composition Sua1.

[0140] (Preparation of Pressure-Sensitive Adhesive Composition A1) 0.07 parts of a reactive surfactant (trade name "Aqualon KH-1025", manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) and 61.1 parts of distilled water were placed in a reaction vessel equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser, and the atmosphere was replaced with nitrogen at 60° C. for 1 hour with stirring. Thereafter, 0.10 parts of a polymerization initiator (trade name "VA-057", manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added thereto. To this mixture, 85 parts of 2-ethylhexyl acrylate (2EHA), 13 parts of methyl acrylate (MA), 1.25 parts of acrylic acid (AA), 0.75 parts of methacrylic acid (MAA), 0.025 parts of t-dodecanethiol (chain transfer agent), 0.02 parts of 3-methacryloxypropyltrimethoxysilane (trade name "KBM-503", manufactured by Shin-Etsu Chemical Co., Ltd.), and 1.93 parts of the reactive surfactant were emulsified in 28 parts of distilled water, and the emulsion polymerization was allowed to proceed while gradually adding dropwise thereto at 60°C over 4 hours. After maintaining the mixture at 60°C for 3 hours, 0.05 parts of the polymerization initiator was added, and the mixture was further maintained at 60°C for 2 hours. The system was cooled to room temperature, and the pH was adjusted to 7 using 10% aqueous ammonia as a pH adjuster. In this manner, an aqueous dispersion of acrylic polymer P1 was prepared. The solids concentration of this aqueous dispersion was 50.5%, and the sol weight-average molecular weight (Mw) of the acrylic polymer P1 was 340,000. The sol weight-average molecular weight (Mw) was determined by GPC, as described above, for the soluble component (sol component) eluted by drying the aqueous dispersion of the acrylic polymer P1 at 100° C. for 3 minutes and then immersing it in toluene.

[0141] To the aqueous dispersion of the acrylic polymer P1, 30 parts of a tackifier resin (polymerized rosin ester, trade name "Superester E-865NT", manufactured by Arakawa Chemical Industries, Ltd., softening point 160°C) were added relative to 100 parts of the solid content of the aqueous dispersion, and 2 parts of a leveling agent (trade name "Pelex OT-P", manufactured by Kao Corporation) were further added. Thereafter, the pH was adjusted to 8 with 10% aqueous ammonia to prepare PSA composition A1.

[0142] (Preparation of Pressure-Sensitive Adhesive Sheet) The pressure-sensitive adhesive composition A1 and the support layer-forming composition Sua1 obtained as described above were simultaneously coated onto the silicone-treated surface of a 38 μm polyethylene terephthalate (PET) release liner (trade name "Diafoil MRF38", manufactured by Mitsubishi Chemical Corporation) using a die coater with a three-layer manifold so that the thickness of the pressure-sensitive adhesive layer and the support layer after drying would each be 10 μm (wet-on-wet coating method). Next, the entire product was heated and dried at 100 ° C. for 3 minutes to form a pressure-sensitive adhesive layer / support layer laminate on the release liner. Thereafter, the product was aged overnight in a dryer at 50 ° C. to obtain a pressure-sensitive adhesive sheet (substrate-attached pressure-sensitive adhesive sheet) according to Example 1.

[0143] Examples 2 and 3 Support layer-forming compositions Sua2 and Sua3 were prepared in the same manner as for the preparation of support layer-forming composition S1, except that the amount of 3-methacryloxypropyltrimethoxysilane (silane coupling agent) added relative to 100 parts of the urethane / acrylic monomer mixed liquid was changed as shown in Table 1. Pressure-sensitive adhesive sheets according to Examples 2 and 3 were obtained in the same manner as in Example 1, except that support layer-forming compositions Sua2 and Sua3 were used, respectively, instead of support layer-forming composition S1.

[0144] <Comparative Example 1> A support layer-forming composition Sua4 was prepared in the same manner as the preparation of the support layer-forming composition S1, except that 3-methacryloxypropyltrimethoxysilane (silane coupling agent) was not used. A pressure-sensitive adhesive sheet according to Comparative Example 1 was obtained in the same manner as in Example 1, except that the support layer-forming composition Sua4 was used instead of the support layer-forming composition S1.

[0145] Example 4 (Preparation of Support Layer Forming Composition Sa1) 4.1 g (solids basis) of a reactive surfactant (trade name "Aqualon KH-1025", manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) (3 parts per 100 parts of acrylic monomer) was added to 135.8 g of acrylic monomer (65.2 g of BA, 65.2 g of MMA, 5.4 g of AA) and mixed. Distilled water was added to this mixture in an amount such that the concentration of the acrylic monomer was 40%, and then 0.14 g (0.1 part per 100 parts of acrylic monomer) of 3-methacryloxypropyltrimethoxysilane (silane coupling agent, trade name "KBM-503", manufactured by Shin-Etsu Chemical Co., Ltd.) was added. The mixture was emulsified using a high-speed emulsifying disperser (homomix, manufactured by Primix Corporation) to prepare an emulsion.

[0146] The resulting emulsion was placed in a reaction vessel equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser, and the atmosphere was replaced with nitrogen for approximately 2 hours while stirring. The system was heated in a water bath set to 60°C, and 136 mg of a polymerization initiator (product name "VA-057" manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added. The reaction was allowed to proceed for 4 hours while maintaining the temperature of the contents of the reaction vessel at 60°C. The system was then cooled to obtain an aqueous dispersion of an acrylic polymer copolymerized with 3-methacryloxypropyltrimethoxysilane. To this aqueous dispersion, 1 part of a carboxylic acid copolymer (product name "Aron B-500" manufactured by Toagosei Co., Ltd.) was added per 100 parts of the solids content of the aqueous dispersion, and the pH was adjusted to 8 with 10% aqueous ammonia to prepare a support layer-forming composition Sa1.

[0147] (Preparation of Pressure-Sensitive Adhesive Sheet) A pressure-sensitive adhesive sheet according to Example 4 was obtained in the same manner as in Example 1, except that the support layer-forming composition Sa1 was used instead of the support layer-forming composition Sua1.

[0148] <Comparative Example 2> A support layer-forming composition Sa2 was prepared in the same manner as the preparation of the support layer-forming composition Sa1, except that 3-methacryloxypropyltrimethoxysilane (silane coupling agent) was not used. A pressure-sensitive adhesive sheet according to Comparative Example 2 was obtained in the same manner as in Example 4, except that the support layer-forming composition Sa2 was used instead of the support layer-forming composition Sa1.

[0149] <Evaluation> The interlayer adhesion between the support layer and the pressure-sensitive adhesive layer was evaluated as follows. Specifically, the pressure-sensitive adhesive sheet obtained in each example was cut to a size of 20 mm wide and 100 mm long to prepare a test sample. As shown in FIG. 2 , a 51 μm-thick single-sided pressure-sensitive adhesive tape (polyester pressure-sensitive adhesive tape manufactured by Nitto Denko Corporation, product name "No. 31B#25") was prepared as a pressure-sensitive adhesive sheet 62 for applying peel force, and the adhesive surface of the pressure-sensitive adhesive sheet 62 was attached to the adhesive surface of the test sample 40 (the surface of the pressure-sensitive adhesive layer 20). Furthermore, a 160 μm-thick double-sided pressure-sensitive adhesive tape (double-sided pressure-sensitive adhesive tape manufactured by Nitto Denko Corporation, product name "No. 5000NS") was prepared as a back-fixing pressure-sensitive adhesive sheet 64, and one adhesive surface of this pressure-sensitive adhesive sheet 64 was attached to a stainless steel plate 66. Next, in an environment of 23°C and 50% RH, the bonded assembly of the test sample 40 and adhesive sheet 62 prepared above was placed on the other adhesive surface of the adhesive sheet 64, with the back surface of the test sample 40 (the surface of the support layer 10) facing the adhesive sheet 64, and pressed together by moving a 2 kg roller back and forth once.

[0150] The resulting laminate was held in an environment of 23°C and 50% RH for 30 minutes, after which the stainless steel plate 66 and the adhesive sheet 62 were fixed to the chucks of a tensile tester, and the 180° peel strength [N / 20 mm] was measured at a tensile speed of 30 mm / min in accordance with JIS Z0237. The measurement was performed three times (i.e., N = 3), and the average value was used as the fracture strength of the laminate. The laminate was also observed after the measurement, and the fracture morphology was classified into four types: interfacial fracture, interlaminar fracture, support layer cohesive failure, and adhesive layer cohesive failure. The interfacial fracture refers to a fracture of the laminate at the interface between the adhesive sheet 64 for backside fixing and the support layer 10, i.e., a fracture of the adhesive sheet 40 together with the adhesive sheet 62 peeling off from the adhesive sheet 64 as a unit. The interlayer failure refers to a form in which the laminate is broken between the support layer 10 and the pressure-sensitive adhesive layer 20 that constitute the pressure-sensitive adhesive sheet 40, i.e., a form in which the pressure-sensitive adhesive layer 20 is peeled off from the support layer 10 together with the pressure-sensitive adhesive sheet 62, leaving the support layer 10 on the pressure-sensitive adhesive sheet 64. The support layer cohesive failure refers to a form in which failure occurs within the support layer 10, and typically refers to a form in which a portion of the support layer 10 is left on the pressure-sensitive adhesive sheet 64 side, and the remainder of the support layer 10 is peeled off together with the pressure-sensitive adhesive layer 20 and the pressure-sensitive adhesive sheet 62. The pressure-sensitive adhesive layer cohesive failure refers to a form in which failure occurs within the pressure-sensitive adhesive layer 20, and typically refers to a form in which a portion of the pressure-sensitive adhesive layer 20 is left on the support 10 side, and the remainder of the pressure-sensitive adhesive layer 20 is peeled off together with the pressure-sensitive adhesive sheet 62. The pressure-sensitive adhesive sheets according to each example all showed the same form of failure in three measurements.

[0151] An overview of each example and the evaluation results are shown in Tables 1 and 2. In the above interlayer adhesion evaluation, it can be said that a pressure-sensitive adhesive sheet in which the failure mode is interfacial failure has better interlayer adhesion between the support layer and the pressure-sensitive adhesive layer than a pressure-sensitive adhesive sheet in which the failure mode is interlayer failure. Furthermore, in a pressure-sensitive adhesive sheet in which the failure mode is interlayer failure, the above-mentioned breaking strength value can be regarded as a numerical value representing the interlayer adhesion strength between the support layer and the pressure-sensitive adhesive layer. It can be said that in a pressure-sensitive adhesive sheet in which the failure mode is interfacial failure, the interlayer adhesion strength between the support layer and the pressure-sensitive adhesive layer is at least higher than the above-mentioned breaking strength value.

[0152]

[0153]

[0154] As shown in Table 1, in a configuration in which the base polymer of the support layer was a urethane acrylic polymer, the PSA sheets of Examples 1 to 3, in which both the support layer and the PSA layer were formed from an aqueous dispersion material containing a polymer bonded to a silane coupling agent, all failed in the form of interfacial failure in the above-mentioned adhesion evaluation. This indicates that the adhesion between the support layer 10 and the PSA layer 20 constituting the PSA sheet 40 in FIG. 2 was sufficiently high relative to the adhesion between the adhesive surface of the PSA sheet 64 and the support layer 10. Better results were obtained in Examples 2 and 3 (particularly Example 2). On the other hand, the PSA sheet of Comparative Example 1, in which the support layer was formed from an aqueous dispersion material not containing a polymer bonded to a silane coupling agent, failed in the form of cohesive failure in the above-mentioned adhesion evaluation, indicating that the cohesive strength of the support itself was insufficient.

[0155] Furthermore, as shown in Table 2, in a configuration in which the base polymer of the support layer is an acrylic polymer, the PSA sheet of Example 4, in which both the support layer and the PSA layer were formed from an aqueous dispersion material containing a polymer bonded with a silane coupling agent, failed in the form of interfacial failure in the above adhesion strength evaluation, and the adhesion between the support layer and the PSA layer was sufficiently high. On the other hand, the PSA sheet of Comparative Example 2, in which the support layer was formed from an aqueous dispersion material that did not contain a polymer bonded with a silane coupling agent, failed in the form of interlayer failure in the above adhesion strength evaluation. This indicates that the adhesion between the support layer 10 and the PSA layer 20 constituting the PSA sheet 40 in Figure 2 is insufficient compared to the adhesion between the adhesive surface of the PSA sheet 64 and the support layer 10.

[0156] 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.

[0157] DESCRIPTION OF SYMBOLS 1 Pressure-sensitive adhesive sheet 10 Support layer 20 Pressure-sensitive adhesive layer 30 Release liner 40 Test sample 50 Pressure-sensitive adhesive sheet with release liner 62 Pressure-sensitive adhesive sheet (for applying peeling force) 64 Pressure-sensitive adhesive sheet (for fixing to rear surface) 66 Stainless steel plate

Claims

1. A pressure-sensitive adhesive sheet having a support layer and an adhesive layer adjacent to the support layer, wherein the support layer is formed from a water-dispersible material (S), and the adhesive layer is formed from a water-dispersible material (A), and each of the water-dispersible material (S) and the water-dispersible material (A) contains a polymer having a hydrolyzable silyl group.

2. The adhesive sheet according to claim 1, wherein the water-dispersible material (S) includes, as the polymer having a hydrolyzable silyl group, at least one selected from the group consisting of an acrylic polymer having a hydrolyzable silyl group, a urethane acrylic polymer having a hydrolyzable silyl group, and a urethane polymer having a hydrolyzable silyl group.

3. The adhesive sheet according to claim 1 or 2, wherein the water-dispersible material (S) contains a polymer having a hydrolyzable silyl group derived from a silane coupling agent as the polymer having a hydrolyzable silyl group, and the amount of silane coupling agent used in the polymer is 0.001 parts by weight or more per 100 parts by weight of polymer-forming components other than the silane coupling agent.

4. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the water-dispersible material (A) contains, as the polymer having a hydrolyzable silyl group, an acrylic polymer having a hydrolyzable silyl group derived from a silane coupling agent.

5. The pressure-sensitive adhesive sheet according to claim 4, wherein the amount of the silane coupling agent used in the acrylic polymer is 0.001 part by weight or more per 100 parts by weight of the acrylic polymer-forming components other than the silane coupling agent.

Images