Water-dispersed adhesive composition, adhesive, adhesive sheet, and laminate

Abstract

The present invention provides a water-dispersed adhesive composition which is suitable for the production of an adhesive that has improved adhesive force when placed in a high-humidity environment. A water-dispersed adhesive composition according to an embodiment of the present invention contains a base polymer and another polymer having a functional group that is capable of reacting with the base polymer.

Description

Water-dispersible adhesive composition, adhesive, adhesive sheet, and laminate

[0001] The present invention relates to a water-dispersible adhesive composition, an adhesive, an adhesive sheet, and a laminate.

[0002] Generally, adhesives exhibit a soft solid (viscoelastic) state at temperatures around room temperature and readily adhere to a substrate under pressure. Taking advantage of these properties, adhesives are widely used for purposes such as joining and fixing components within electronic devices like smartphones. In particular, sheets made of adhesives (adhesive sheets) are suitable for the aforementioned purposes of joining and fixing components.

[0003] As an adhesive, for example, an adhesive formed from a water-dispersible adhesive composition is known (for example, Patent Document 1).

[0004] Japanese Patent Publication No. 2003-313525

[0005] Water-dispersible adhesive compositions offer advantages in terms of reducing the amount of organic solvents used in the production of adhesives, thereby reducing health hazards and improving environmental hygiene. On the other hand, our studies have shown that adhesives formed from water-dispersible adhesive compositions tend to lose their adhesive strength when placed in a high-humidity environment.

[0006] The object of the present invention is to provide a water-dispersible adhesive composition suitable for producing an adhesive with improved tackiness when placed in a high-humidity environment.

[0007] [1] A water-dispersible adhesive composition according to an embodiment of the present invention comprises a base polymer and another polymer having a functional group that can react with the base polymer. [2] In the water-dispersible adhesive composition described in [1] above, the functional group may include a silanol group. [3] In the water-dispersible adhesive composition described in [1] or [2] above, the other polymer may include a urethane polymer. [4] In the water-dispersible adhesive composition described in any of [1] to [3] above, the glass transition temperature of the other polymer may be 100°C or less. [5] In the water-dispersible adhesive composition described in any of [1] to [4] above, the content of the other polymer may be 0.1 parts by weight or more per 100 parts by weight of the base polymer. [6] In the water-dispersible adhesive composition described in any of [1] to [5] above, the base polymer may include a (meth)acrylic polymer. [7] In the water-dispersible adhesive composition described in [6] above, the (meth)acrylic polymer may have structural units derived from an alkyl (meth)acrylate ester. [8] In the water-dispersible adhesive composition described in [6] or [7] above, the (meth)acrylic polymer may have structural units derived from a carboxyl group-containing monomer. [9] In the water-dispersible adhesive composition described in any of [6] to [8] above, the (meth)acrylic polymer may have structural units derived from an alkoxysilyl group-containing monomer.

[10] In the water-dispersible adhesive composition described in any of [6] to [9] above, the (meth)acrylic polymer may have structural units derived from a reactive surfactant.

[11] An adhesive according to an embodiment of the present invention is formed from a water-dispersible adhesive composition described in any of [1] to

[10] above.

[12] An adhesive sheet according to an embodiment of the present invention is made from the adhesive described in

[11] above.

[13] The adhesive sheet described in

[12] above may have a thickness of 50 μm or less.

[14] The adhesive sheet described in

[12] or

[13] above may have a peeling force F1 of 3.0 N / 20 mm or more determined by the following test R1.Test R1: The adhesive sheet is bonded to a stainless steel plate (SUS304BA plate) and left to stand for 30 minutes in an atmosphere of 60°C and 95% RH. After standing, the adhesive sheet is peeled off the stainless steel plate in an atmosphere of 60°C and 95% RH at a peeling speed of 300 mm / min and a peeling angle of 180°. The maximum force required at this time is specified as the peeling force F1.

[15] The adhesive sheet described in any of

[12] to

[14] above may be used to fix components in electronic equipment.

[16] A laminate according to an embodiment of the present invention comprises the adhesive sheet described in any of

[12] to

[15] above, a base material, and

[0008] According to embodiments of the present invention, it is possible to provide a water-dispersible adhesive composition suitable for producing an adhesive with improved adhesive strength when placed in a high-humidity environment.

[0009] This is a schematic cross-sectional view of an adhesive sheet according to one embodiment of the present invention. This is a schematic cross-sectional view showing an example of a laminate comprising the adhesive sheet of the present invention. This is a schematic cross-sectional view showing another example of a laminate comprising the adhesive sheet of the present invention.

[0010] [Regarding Terminology] In this specification, where the term "weight" appears, it may be interpreted as "mass," which is the commonly used SI unit for weight. The reverse is also true.

[0011] In this specification, the expression "(meth)acrylic" means "acrylic and / or methacrylic," the expression "(meth)acrylate" means "acrylate and / or methacrylate," the expression "(meth)allyl" means "allyl and / or methallyl," and the expression "(meth)acrolein" means "acrolein and / or metacrolein."

[0012] In this specification, "water-dispersible adhesive composition" means an adhesive composition comprising a dispersion medium containing water and a component dispersed in the dispersion medium (for example, a base polymer emulsified in the dispersion medium).

[0013] ≪≪1. Water-dispersible adhesive composition≫≫ A water-dispersible adhesive composition according to an embodiment of the present invention (hereinafter sometimes simply referred to as "adhesive composition") comprises a base polymer and another polymer having a functional group F that can react with the base polymer.

[0014] When an adhesive is formed from a conventional water-dispersible adhesive composition, a structure is typically formed in which particles containing the base polymer are directly crosslinked. In this crosslinked structure, when stress is applied that attempts to peel the adhesive away from the adherend, stress tends to concentrate at the adhesive interface between the adhesive and the adherend, causing the adhesive to easily peel off the adherend. According to the inventors' research, this tendency can be particularly pronounced in high-humidity environments.

[0015] In contrast, according to the adhesive composition of this embodiment, when the adhesive is formed, the base polymer reacts with other polymers, allowing other polymers to be incorporated into the crosslinked structure. For example, a structure can be formed in which particles containing the base polymer are crosslinked with other polymers. With this crosslinked structure, stress is dispersed by the crosslinked portion between the particles containing the base polymer and the other polymers, thus mitigating the concentration of stress at the adhesive interface with the adherend, and the adhesive tends to be less likely to peel off the adherend. According to the inventors' studies, the adhesive formed from the adhesive composition of this embodiment tends not to lose its adhesive strength even when placed in a high-humidity environment (and even a high-temperature, high-humidity environment).

[0016] ≪1-1. Base Polymer≫ As described above, the adhesive composition according to the embodiment of the present invention includes a base polymer. The base polymer may be one type or two or more types. Preferably, the base polymer is a rubbery polymer that exhibits rubber elasticity in the temperature range around room temperature.

[0017] Examples of base polymers include (meth)acrylic polymers, rubber polymers (natural rubber, synthetic rubber, mixtures thereof, etc.), polyester polymers, urethane polymers, polyether polymers, polyamide polymers, and fluorine polymers. In adhesive compositions, it is preferable that the base polymer includes a (meth)acrylic polymer. The following describes (meth)acrylic polymers as base polymers in detail.

[0018] <1-1-a. (meth)acrylate alkyl esters> The (meth)acrylic polymer preferably contains constituent units derived from (meth)acrylate alkyl esters. There may be only one type of (meth)acrylate alkyl ester, or there may be two or more types. The (meth)acrylate alkyl ester preferably has an alkyl group having 1 to 20 carbon atoms in its side chain. The number of carbon atoms in the alkyl group may be 1 to 14, 1 to 10, and even 4 to 10. The alkyl group may be linear or branched.

[0019] Examples of alkyl methacrylates 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, octyl (meth)acrylate, and isooctyl (meth)acrylate. Examples include acrylates, 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. The alkyl (meth)acrylate preferably contains at least one selected from the group consisting of n-butyl acrylate (BA), 2-ethylhexyl acrylate (2EHA), and n-octyl acrylate (nOA).

[0020] The content of constituent units derived from alkyl methacrylate in the (meth)acrylic polymer is, for example, 10% by weight or more, and may be 25% by weight or more, 50% by weight or more, 75% by weight or more, 80% by weight or more, 85% by weight or more, 90% by weight or more, 95% by weight or more, and even 98% by weight or more. The above content is, for example, 99% by weight or less, and may in some cases be 95% by weight or less, 90% by weight or less, and even 85% by weight or less.

[0021] Furthermore, if the alkyl (meth)acrylate contains BA, the content of constituent units derived from BA in the (meth)acrylic polymer may be 25% to 85% by weight. Similarly, if the alkyl (meth)acrylate contains 2EHA, the content of constituent units derived from 2EHA in the (meth)acrylic polymer may be 25% to 85% by weight. If the alkyl (meth)acrylate contains nOA, the content of constituent units derived from nOA in the (meth)acrylic polymer may be 25% to 85% by weight.

[0022] Furthermore, the ratio (by weight) of the content of constituent units derived from alkyl (meth)acrylate esters having a C4-C10 alkyl group in the side chain to the total content (by weight) of all constituent units derived from alkyl (meth)acrylate esters in the (meth)acrylic polymer is, for example, 70% or more, and may be 80% or more.

[0023] The sum of the content (by weight) of structural units derived from alkyl (meth)acrylate esters having C1-C3 alkyl groups in their side chains and the content (by weight) of structural units derived from alkyl (meth)acrylate esters having C11 or more alkyl groups in their side chains in the (meth)acrylic polymer is, for example, 30% by weight or less, 20% by weight or less, and even 15% by weight or less. The above sum may be 1% by weight or more, 5% by weight or more, and even 10% by weight or more. The (meth)acrylic polymer does not have to contain structural units derived from alkyl (meth)acrylate esters having C1-C3 alkyl groups in their side chains, or structural units derived from alkyl (meth)acrylate esters having C11 or more alkyl groups in their side chains.

[0024] <1-1-b. Carboxyl Group-Containing Monomers> The (meth)acrylic polymer preferably contains structural units derived from carboxyl group-containing monomers. These structural units can contribute to the stabilization of the (meth)acrylic polymer (more specifically, particles containing the (meth)acrylic polymer) in the adhesive composition. Furthermore, these structural units can also introduce crosslinking points and improve cohesive force. The carboxyl group-containing monomer may be one type or two or more types.

[0025] A carboxyl group-containing monomer has at least one carboxyl group and at least one ethylenically unsaturated group in one molecule. Examples of ethylenically unsaturated groups are (meth)acryloyl, vinyl, and (meth)allyl groups. The carboxyl group-containing monomer may also be a (meth)acrylic monomer.

[0026] Examples of carboxyl group-containing monomers include ethylenically unsaturated monocarboxylic acids such as (meth)acrylic acid and crotonic acid; ethylenically unsaturated dicarboxylic acids such as maleic acid, itaconic acid, and citraconic acid, and their anhydrides (maleic anhydride, itaconic anhydride, etc.). Preferably, the carboxyl group-containing monomer contains at least one selected from the group consisting of acrylic acid (AA) and methacrylic acid (MAA).

[0027] The content of constituent units derived from carboxyl group-containing monomers in the (meth)acrylic polymer is, for example, 15% by weight or less, and may be 10% by weight or less, 5% by weight or less, or even 3% by weight or less. The above content is, for example, 0.1% by weight or more, and may be 0.5% by weight or more, 1% by weight or more, or even 1.5% by weight or more. If the carboxyl group-containing monomer contains (meth)acrylic acid, the content of constituent units derived from (meth)acrylic acid in the (meth)acrylic polymer may be 1% by weight to 5% by weight.

[0028] The carboxyl group-containing monomer may contain both AA and MAA. In this case, the adhesive sheet formed from the adhesive composition may have excellent properties such as rebound resistance. The ratio of the content of constituent units derived from AA (by weight) to the content of constituent units derived from MAA (by weight) in the (meth)acrylic polymer (AA / MAA) is, for example, 0.1 to 10, and may be 0.3 or more, or even 0.5 or more. The above ratio may be 5 or less, or 4 or less. When the ratio (AA / MAA) is within the above range, the rebound resistance of the adhesive sheet tends to improve, and the long-term stability of the adhesive properties also tends to be excellent.

[0029] <1-1-c. Alkoxysilyl group-containing monomers> The (meth)acrylic polymer preferably further contains constituent units derived from alkoxysilyl group-containing monomers. There may be only one type of alkoxysilyl group-containing monomer or two or more types.

[0030] Alkoxysilyl group-containing monomers have at least one alkoxysilyl group and at least one ethylenically unsaturated group in one molecule. The number of alkoxysilyl groups may be two or more, or it may be two or three. Examples of ethylenically unsaturated groups are the same as those described above in the description of carboxyl group-containing monomers. Alkoxysilyl group-containing monomers may also be (meth)acrylic monomers.

[0031] Alkoxysilyl group-containing monomers undergo hydrolysis, for example, during emulsification and / or emulsion polymerization in the presence of water, to form silanol groups (-SiOH). That is, when a (meth)acrylic polymer is synthesized using an alkoxysilyl group-containing monomer in the presence of water, the constituent units derived from the alkoxysilyl group-containing monomer have, for example, silanol groups. In this case, when forming an adhesive from the adhesive composition, the silanol groups undergo a condensation reaction, causing the (meth)acrylic polymer to crosslink (silanol crosslinking). According to this method, a structure can be formed in the adhesive in which particles containing the (meth)acrylic polymer are crosslinked with each other.

[0032] Examples of monomers containing an alkoxysilyl group include 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, and 3-(meth)acryloxypropylmethyldiethoxysilane.

[0033] The content of constituent units derived from alkoxysilyl group-containing monomers in the (meth)acrylic polymer is, for example, 0.001% by weight or more, and may be 0.005% by weight or more, or even 0.01% by weight or more. The above content may be, for example, 1.0% by weight or less, 0.5% by weight or less, 0.1% by weight or less, 0.05% by weight or less, or even 0.03% by weight or less. When the content is within the above range, the adhesive strength of the adhesive tends to improve. However, the (meth)acrylic polymer may, in some cases, not contain constituent units derived from alkoxysilyl group-containing monomers.

[0034] <1-1-d. Reactive Surfactants> (Meth)acrylic polymers may further contain constituent units derived from reactive surfactants. In this specification, reactive surfactant means a surfactant (emulsifier) ​​containing an ethylenically unsaturated group. Examples of ethylenically unsaturated groups are the same as those described above in the description of carboxyl group-containing monomers. Reactive surfactants can function, for example, as emulsifiers for synthesizing (meth)acrylic polymers by emulsion polymerization, and can also function as monomers copolymerized with alkyl (meth)acrylates, etc. By using reactive surfactants, the surfactant is less likely to bleed out from the adhesive, and the adhesive strength tends to decrease less.

[0035] The reactive surfactant may be one type or two or more types. Examples of reactive surfactants include those in which a group containing an ethylenically unsaturated group is introduced to a surfactant (non-reactive surfactant) as described later in section 1-3. Surfactants. The reactive surfactant may include, for example, at least one selected from the group consisting of anionic reactive surfactants and nonionic reactive surfactants, and preferably includes anionic reactive surfactants.

[0036] A group containing an ethylenically unsaturated group is typically a polymerizable functional group (especially a radically polymerizable functional group). Examples of the group containing an ethylenically unsaturated group include a 1-propenyl group, a 2-propenyl group (allyl group), an isopropenyl group, a (meth)acryloyl group, a vinyl group, a vinyl ether group (vinyloxy group), an allyl ether group (allyloxy group), and the like.

[0037] Examples of the anionic reactive surfactant include polyoxyethylene (allyloxymethyl) alkyl ether sulfate (e.g., ammonium salt), polyoxyethylene nonylpropenyl phenyl ether sulfate (e.g., ammonium salt), alkyl allyl sulfosuccinate (e.g., sodium salt), methacryloxypolyoxypropylene sulfate ester salt (e.g., sodium salt), polyoxyalkylene alkenyl ether sulfate (e.g., ammonium salt having an isopropenyl group at the terminal), and the like. When the anionic reactive surfactant forms a salt, the salt may be a metal salt such as a sodium salt, or a non-metal salt such as an ammonium salt or an amine salt.

[0038] Examples of the nonionic reactive surfactant include polyoxyethylene nonylpropenyl phenyl ether and the like.

[0039] Examples of commercially available reactive surfactants include products named "Aquaron HS-05", "Aquaron HS-10", "Aquaron HS-1025", "Aquaron HS-20", "Aquaron KH-10", "Aquaron KH-1025", "Aquaron KH-05", "Aquaron BC-0515", "Aquaron BC-10", "Aquaron BC-1025", "Aquaron BC-20", "Aquaron BC-2020", "Aquaron RN-20", "Aquaron RN-30", "Aquaron RN-50", "Aquaron AR-10", "Aquaron AR-20", "Aquaron AR-1025", "Aquaron AR-2020" manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.; products named "Adekaria Soap SE-10N", "Adekaria Soap SR-1025" manufactured by ADEKA Corporation; products named "Latemul PD-104", "Latemul PD-420", "Latemul PD-430", "Latemul PD-450" manufactured by Kao Corporation; products named "Eleminol JS-20", "Eleminol RS-3000" manufactured by Sanyo Chemical Industries, Ltd.; products named "Antox MS-60" manufactured by Nippon Emulsion Co., Ltd., and the like.

[0040] The content rate of the structural unit derived from the reactive surfactant in the (meth)acrylic polymer is, for example, 10% by weight or less, and may be 7% by weight or less, 5% by weight or less, or even 3% by weight or less. The lower limit of the above content rate is, for example, 0.01% by weight or more, and may be 0.1% by weight or more, 0.5% by weight or more, or even 1% by weight or more. The (meth)acrylic polymer may not contain a structural unit derived from the reactive surfactant.

[0041] <1-1-e. Other Monomers> The (meth)acrylic polymer may contain a structural unit derived from other copolymerization monomers other than those described above. The other copolymerization monomers may be only one kind or two or more kinds. Examples of the other copolymerization monomers include functional group-containing monomers. The structural unit derived from the functional group-containing monomer can achieve the introduction of crosslinking points and the improvement of cohesive force.

[0042] Examples of functional group-containing monomers include hydroxyl group-containing monomers such as hydroxyalkyl (meth)acrylates like 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate, as well as unsaturated alcohols like vinyl alcohol and allyl alcohol; amide group-containing monomers such as (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N-butyl (meth)acrylamide, N-methylol (meth)acrylamide, N-methylolpropane (meth)acrylamide, N-methoxymethyl (meth)acrylamide, and N-butoxymethyl (meth)acrylamide; and aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and t-butylaminoethyl (meth)acrylate. Examples include monomers containing amino groups; monomers containing epoxy groups such as glycidyl (meth)acrylate, methylglycidyl (meth)acrylate, and allyl glycidyl ether; monomers containing cyano groups such as acrylonitrile and methacrylonitrile; monomers containing keto groups such as diacetone (meth)acrylamide, diacetone (meth)acrylate, vinyl methyl ketone, vinyl ethyl ketone, allyl acetacetate, and vinyl acetacetate; and monomers having nitrogen atom-containing rings such as 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] The content of structural units derived from functional group-containing monomers in the (meth)acrylic polymer is, for example, 0.1% by weight or more, and may be 0.5% by weight or more, or even 1% by weight or more. The above content is, for example, 40% by weight or less, and may be 30% by weight or less, 20% by weight or less, 10% by weight or less, or even 5% by weight or less. The (meth)acrylic polymer does not need to contain structural units derived from functional group-containing monomers.

[0044] Other copolymer monomers are not limited to the functional group-containing monomers described above, but include, for example, vinyl ester monomers such as vinyl acetate and vinyl propionate; aromatic vinyl compounds such as styrene, substituted styrene (e.g., α-methylstyrene), 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) and aryloxyalkyl (meth)acrylates (e.g., phenoxyethyl (meth)acrylate). These may include aromatic ring-containing (meth)acrylates such as arylalkyl (meth)acrylates (e.g., benzyl (meth)acrylate); olefin 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; and vinyl ether monomers such as methyl vinyl ether and ethyl vinyl ether.

[0045] Furthermore, polyfunctional monomers can also be used as other copolymer monomers. Examples of polyfunctional monomers include compounds having two or more ethylenically unsaturated groups, such as 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, Examples include 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(meth)acrylate, polyester(meth)acrylate, urethane(meth)acrylate, divinylbenzene, butyl di(meth)acrylate, and hexyl di(meth)acrylate.

[0046] The content of constituent units derived from other copolymer monomers (especially other copolymer monomers other than functional group-containing monomers) in the (meth)acrylic polymer is, for example, 10% by weight or less, and may be 3% by weight or less, or even less than 1% by weight. The (meth)acrylic polymer may not contain any constituent units derived from other copolymer monomers.

[0047] <1-1-f. Method for producing (meth)acrylic polymers> (Meth)acrylic polymers can be synthesized, for example, by emulsion polymerization. By emulsion polymerization, a polymer emulsion can be prepared in which the (meth)acrylic polymer is dispersed in a dispersion medium. Methods of emulsion polymerization include a batch-feed method in which monomer components are supplied all at once, a monomer dropwise method, and a monomer emulsion dropwise method. In the monomer dropwise method, a continuous dropwise method or a divided dropwise method can be appropriately selected. These methods can be combined as appropriate. The reaction conditions for emulsion polymerization can be appropriately adjusted according to the monomer components, etc. For example, the polymerization temperature may be, for example, 20°C or higher, or 40°C or higher. The polymerization temperature may be, for example, 100°C or lower, or 80°C or lower. The polymerization time is, for example, 10 minutes to 24 hours.

[0048] In emulsion polymerization, surfactants, polymerization initiators, and, if necessary, chain transfer agents can be used as appropriate. In emulsion polymerization, it is preferable to use the reactive surfactants described above as the surfactant. As the surfactant, surfactants (non-reactive surfactants) described in section 1-3. Surfactants may also be used.

[0049] The amount of surfactant used is, for example, 0.1 parts by weight or more per 100 parts by weight of monomer component, and may be 0.5 parts by weight or more, 1.0 part by weight or more, or even 1.5 parts by weight or more. The above amount used is, for example, 10 parts by weight or less per 100 parts by weight of monomer component, and may be 5 parts by weight or less, 4 parts by weight or less, 3 parts by weight or less, or even 2.5 parts by weight or less.

[0050] Furthermore, the content of reactive surfactants in the surfactant used for emulsion polymerization is, for example, 50% by weight or more, and may be 70% by weight or more. In emulsion polymerization, it is preferable to use only reactive surfactants as the surfactant.

[0051] Examples of polymerization initiators include 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'-dimethylene isobutylamidine), and 2,2'-azobis[2-(2-I Examples of polymerization initiators include azo-based initiators such as midazolin-2-yl)propane dihydrochloride; 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 combinations of persulfate and sodium bisulfite, or combinations of peroxide and sodium ascorbate. The polymerization initiator may be one type or two or more types.

[0052] The amount of polymerization initiator used is, for example, 0.005 parts by weight or more, and may be 0.01 parts by weight or more, per 100 parts by weight of monomer component. The above amount used is, for example, 1 part by weight or less, and may be 0.8 parts by weight or less, per 100 parts by weight of monomer component.

[0053] Examples of chain transfer agents 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.

[0054] The amount of chain transfer agent used is, for example, 0.001 parts by weight or more, 0.005 parts by weight or more, or even 0.01 parts by weight or more, per 100 parts by weight of monomer component. The above amount used is, for example, 5 parts by weight or less, 2 parts by weight or less, or even 1 part by weight or less, per 100 parts by weight of monomer component.

[0055] In emulsion polymerization, it is preferable to use a dispersion medium containing water. The dispersion medium may also contain an organic solvent along with water. The amount of dispersion medium used is, for example, 30 to 150 parts by weight per 100 parts by weight of monomer component, and may be 30 to 80 parts by weight, or even 40 to 70 parts by weight.

[0056] (Meth)acrylic polymers can also be synthesized by methods other than emulsion polymerization. Other methods include solution polymerization, bulk polymerization, suspension polymerization, and photopolymerization. In this case, a polymer emulsion may be prepared by dispersing the synthesized (meth)acrylic polymer in a dispersion medium using a surfactant.

[0057] <1-1-g. Base Polymers> The following section provides a detailed description of the physical properties of the base polymers (particularly (meth)acrylic polymers) contained in the adhesive composition.

[0058] The glass transition temperature (Tg) of the base polymer, as a theoretically calculated value obtained by the FOX formula, is, for example, -25°C or lower, but may also be -35°C or lower, -40°C or lower, or even -50°C or lower. Base polymers with a low Tg are suitable for improving adhesion and other properties. The above Tg may be, for example, -75°C or higher, but may also be -70°C or higher.

[0059] The weight-average molecular weight of the base polymer is, for example, 10 × 10 4 ~500 x 10 4 The above weight-average molecular weight is 150 × 10⁻⁶, from the viewpoint of improving adhesive properties. 4 The following may also be the case: 100 x 10 4 The following may also be used. The above weight-average molecular weight is 20 × 10 from the viewpoint of aggregation properties, etc. 4 It may be more than 30 x 10 4 Furthermore, 40 x 10 4 The above is also acceptable. The weight-average molecular weight is determined from the value calculated by GPC (gel permeation chromatography) and converted to polystyrene equivalent.

[0060] The base polymer is typically emulsified in the adhesive composition. In the adhesive composition, the emulsification of the base polymer may form particles containing the base polymer. In other words, the adhesive composition may have particles containing the base polymer. These particles may consist substantially of the base polymer alone. The particles may not be aggregated in the adhesive composition and may exist as single particles (primary particles), or they may aggregate in the adhesive composition to form aggregates. These particles may be of a core-shell type, having a core and a shell covering the core.

[0061] In the adhesive composition, the average particle size of the particles containing the base polymer is, for example, 1000 nm or less, and may be 700 nm or less, 500 nm or less, 400 nm or less, 300 nm or less, or even 200 nm or less. The lower limit of the average particle size is not particularly limited and may be, for example, 50 nm or more, or 100 nm or more. The average particle size of the particles containing the base polymer refers to the value measured by the dynamic light scattering method in accordance with the provisions of Japanese Industrial Standard (JIS) Z8828:2019. As a measuring device, for example, the product name "ELSZ neo" manufactured by Otsuka Electronics Co., Ltd. or an equivalent product can be used. The average particle size of the particles containing the base polymer can be adjusted by the reaction conditions during the synthesis of the base polymer.

[0062] The polydispersity index (PDI) of particles containing the base polymer is, for example, 0.2 or less, and may be 0.15 or less, or even 0.1 or less. The lower limit of the polydispersity index is not particularly limited, but is, for example, 0.01 or more. The polydispersity index can be measured by the dynamic light scattering method described above.

[0063] In this embodiment, the gel fraction determined by the following test G may be, for example, 30% or more, 40% or more, 45% or more, 50% or more, or even 55% or more. The upper limit of the gel fraction may be, for example, 95% or less, 90% or less, 80% or less, 70% or less, or even 65% or less. The gel fraction is preferably 50% to 70%. Test G: A solid is obtained by drying an aqueous dispersion containing a base polymer. A test specimen is obtained by wrapping the solid with a stretched porous membrane of polytetrafluoroethylene and tying it with kite string. The test specimen is immersed in a container filled with ethyl acetate and left to stand at 23°C for 5 days. After standing, the test specimen is removed from the container and dried in a dryer set to 130°C for 1 hour. The gel fraction of the solid obtained by drying the aqueous dispersion is calculated based on the weight of the test specimen before and after the above operations.

[0064] The gel fraction can be determined in detail by the following method. First, an aqueous dispersion containing the base polymer is prepared. As this aqueous dispersion, the polymer emulsion described in section <1-1-f. Method for producing (meth)acrylic polymers> can be used. Next, the aqueous dispersion is applied onto the release liner using an applicator to form a coating film. A solid can be obtained by drying the coating film. The drying conditions for the coating film are set, for example, so that the content of the dispersion medium remaining in the obtained solid is 1000 wt ppm or less, preferably 500 wt ppm or less. The drying of the coating film may be carried out, for example, at 130°C for 1 hour.

[0065] Next, a small piece is obtained by scraping off a portion of the obtained solid. Then, the obtained small piece is wrapped in a stretched porous polytetrafluoroethylene membrane and tied with kite string. This gives a test specimen. Next, the total weight (weight A) of the solid piece, the stretched porous membrane, and the kite string is measured. The total weight of the stretched porous membrane and kite string used is defined as weight B. Next, the test specimen is immersed in a container filled with ethyl acetate and left to stand at 23°C for 5 days. After standing, the test specimen is removed from the container and dried in a dryer set to 130°C for 1 hour, and then the weight C of the test specimen is measured. Based on the following formula, the gel fraction of the solid obtained by drying the aqueous dispersion can be calculated from weights A, B, and C. Gel fraction (weight %) = (C - B) / (A - B) × 100

[0066] The base polymer content in the adhesive composition is, for example, 10% by weight or more, and may be 20% by weight or more, 30% by weight or more, 40% by weight or more, or even 50% by weight or more. The upper limit of the above content is not particularly limited, and is, for example, 90% by weight or less.

[0067] ≪1-2. Other Polymers≫ As described above, the adhesive composition according to the embodiments of the present invention includes other polymers having a functional group F that can react with the base polymer. The other polymers are not particularly limited, as long as they have at least one functional group F in one molecule and have a different composition from the base polymer. There may be only one other polymer or two or more other polymers.

[0068] The functional group F reacts, in particular, with the functional group contained in the base polymer. For example, if the base polymer contains a silanol group, it is preferable that the functional group F of the other polymer also contains a silanol group. Examples of base polymers containing a silanol group include (meth)acrylic polymers containing structural units derived from alkoxysilyl group-containing monomers. These (meth)acrylic polymers typically have silanol groups formed by the hydrolysis of alkoxysilyl groups.

[0069] When both the base polymer and the other polymer contain silanol groups, a condensation reaction occurs between the silanol groups of the base polymer and the silanol groups of the other polymer during the formation of the adhesive from the adhesive composition. This can result in the formation of a crosslinked structure incorporating the other polymer. For example, particles containing the base polymer may be crosslinked via the other polymer. As described above, this crosslinked structure is suitable for mitigating stress concentration at the adhesive interface and tends to suppress the peeling of the adhesive from the adherend.

[0070] Other examples of polymers include urethane polymers and (meth)acrylic polymers. It is preferable that the other polymers include urethane polymers, and particularly preferable that they include urethane polymers having a silanol group as functional group F. Urethane polymers having a silanol group are sometimes called self-crosslinked polyurethane resins. The following will describe urethane polymers having a silanol group in detail.

[0071] <1-2-a. Urethane Polymers> Urethane polymers having silanol groups can be formed, for example, by reacting a hydrolyzable silicon group-containing compound having at least one active hydrogen group in its molecule with a urethane prepolymer, and then dispersing or dissolving it in water and hydrolyzing it.

[0072] A hydrolyzable silicon group in a hydrolyzable silicon group-containing compound refers to a group to which a hydrolyzable group that is hydrolyzed by water is bonded to a silicon atom. Examples of hydrolyzable groups include hydrogen atoms, halogen atoms, alkoxy groups, acyloxy groups, amino groups, amide groups, aminooxy groups, and mercapto groups, with alkoxy groups being preferred. The number of hydrolyzable groups bonded to a single silicon atom is, for example, 1 to 3, with 2 to 3 being preferred.

[0073] As mentioned above, the number of active hydrogen groups in a hydrolyzable silicon group-containing compound is one or more, and preferably two or more. Examples of active hydrogen groups include amino groups, hydroxyl groups, and mercapto groups.

[0074] Examples of hydrolyzable silicon group-containing compounds include γ-(2-aminoethyl)aminopropyltrimethoxysilane, γ-(2-aminoethyl)aminopropyltriethoxysilane, γ-(2-aminoethyl)aminopropyldimethoxysilane, γ-(2-aminoethyl)aminopropyldiethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyldimethoxysilane, γ-aminopropyldiethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, γ-mercaptopropyltriethoxysilane, and γ-mercaptopropyldiethoxysilane. The hydrolyzable silicon group-containing compound may be one type or two or more types.

[0075] Urethane prepolymers can be obtained by reacting a compound having at least two active hydrogen groups in one molecule with a polyisocyanate compound having at least two isocyanate groups in one molecule.

[0076] In compounds having at least two active hydrogen groups, examples of active hydrogen groups include amino groups, hydroxyl groups, and mercapto groups, with hydroxyl groups being preferred. Compounds having hydroxyl groups as active hydrogen groups tend to have a high reaction rate with polyisocyanate compounds and exhibit excellent reactivity.

[0077] Examples of compounds having at least two active hydrogen groups include polycarbonate polyols, polyester polyols, polyether polyols, polyesteramide polyols, acrylic polyols, and polyurethane polyols. This compound may consist of only one type or two or more types.

[0078] Examples of polyisocyanate compounds having at least two isocyanate groups include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and 2,6-diisocyanate methylcaproate. Aliphatic isocyanates such as: 1,3-cyclopentane diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 1,2-bis(isocyanate methyl)cyclohexane, 1,4-bis(isocyanate methyl)cyclohexane, 1, Alicyclic diisocyanates such as 3-bis(isocyanate-methyl)cyclohexane; aromatic diisocyanates such as m-xylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-tole diisocyanate, 2,6-tole diisocyanate, 4,4'-toluidine diisocyanate, dianisidine diisocyanate, and 4,4'-diphenyl ether diisocyanate. Polyisocyanates including: aromatic aliphatic diisocyanates such as ω,ω'-diisocyanate-1,3-dimethylbenzene, ω,ω'-diisocyanate-1,4-dimethylbenzene, and ω,ω'-diisocyanate-1,4-diethylbenzene; triisocyanates such as triphenylmethane-4,4'-4''-triisocyanate, 1,3,5-triisocyanatebenzene, and 2,4,6-triisocyanatetoluene; and tetraisocyanates such as 4,4'-diphenyldimethylmethane-2,2',5,5'-tetraisocyanate.Examples include polyisocyanate derivatives obtained from polyisocyanates and dimers, trimers, biuret, allophanate, or carbodiimide derived from polyisocyanates; adducts of low molecular weight polyols (less than 200 molecular weight) such as ethylene glycol, propylene glycol, and butylene glycol to polyisocyanates; and adducts of polyester polyols, polyether polyols, polycarbonate polyols, polyesteramide polyols, acrylic polyols, polyurethane polyols, etc., to polyisocyanates. The polyisocyanate compound may be a single compound or two or more compounds.

[0079] The urethane prepolymer may further have hydrophilic groups. These hydrophilic groups tend to make the synthesized urethane polymer more dispersible in water, facilitating the preparation of aqueous emulsions (aqueous dispersions) of the urethane polymer. A urethane prepolymer having hydrophilic groups can be produced, for example, by further copolymerizing a compound that has at least one active hydrogen group in its molecule and also has hydrophilic groups during the synthesis of the urethane prepolymer. Examples of hydrophilic groups include carboxyl groups, sulfonic acid groups, sulfonate groups, and polyoxyethylene groups.

[0080] Examples of compounds having hydrophilic groups include carboxyl group-containing compounds such as 2,2-dimethylolpropionic acid, 2,2-dimethylolbutyric acid, 2,2-dimethylolvaleric acid, dioxymaleic acid, 2,6-dioxybenzoic acid, and 3,4-diaminobenzoic acid; derivatives of these carboxyl group-containing compounds; polyester polyols obtained by copolymerizing these carboxyl group-containing compounds; reaction products of compounds having acid anhydride groups such as maleic anhydride, phthalic anhydride, succinic anhydride, trimellitic anhydride, and pyromellitic anhydride with compounds having active hydrogen groups; derivatives of these reaction products; sulfonic acid-containing compounds such as 2-oxyethanesulfonic acid, phenolsulfonic acid, sulfobenzoic acid, sulfosuccinic acid, 5-sulfoisofalic acid, and sulfanilic acid; derivatives of these sulfonic acid-containing compounds; and polyester polyols obtained by copolymerizing these sulfonic acid-containing compounds. The compounds having hydrophilic groups may be one type or two or more types.

[0081] Examples of commercially available urethane polymers include the Takelac WS series manufactured by Mitsui Chemicals.

[0082] <1-2-b. Other Polymers> Below, the physical properties of other polymers (especially urethane polymers) included in the adhesive composition will be described in detail.

[0083] The glass transition temperature (Tg) of the other polymer may be, for example, 100°C or less, and may also be 90°C or less, 80°C or less, or even 70°C or less. The above Tg may be, for example, 0°C or more, and may also be 10°C or more, 20°C or more, 30°C or more, 35°C or more, or even 40°C or more. When the Tg of the other polymer is within the above range, the adhesiveness of the adhesive tends to improve.

[0084] The Tg of other polymers can be measured by differential scanning calorimetry (DSC) in accordance with the provisions of JIS K7121:1987. DSC should be performed under the conditions of a measurement temperature range of -100°C to 160°C and a heating rate of 20°C / min.

[0085] It is preferable that the other polymers are dissolved in the adhesive composition. In other words, it is preferable that no particles containing the other polymers are formed in the adhesive composition. However, the other polymers may be emulsified in the adhesive composition, which may result in the formation of particles containing the other polymers. Furthermore, if the other polymers have hydrophilic groups, it tends to be easier to prepare an aqueous emulsion (aqueous dispersion) of the other polymers.

[0086] The content of other polymers in the adhesive composition is, for example, 0.01 parts by weight or more, and may be 0.1 parts by weight or more, 0.5 parts by weight or more, or even 1 part by weight or more, per 100 parts by weight of the base polymer. The above content is, for example, 20 parts by weight or less, and may be 10 parts by weight or less, 8 parts by weight or less, or even 5 parts by weight or less, per 100 parts by weight of the base polymer. The above content is preferably 1 to 5 parts by weight per 100 parts by weight of the base polymer. When the content of other polymers is within the above range, the adhesiveness of the adhesive tends to improve.

[0087] ≪1-3. Surfactants≫ The adhesive composition according to the embodiment of the present invention may further contain surfactants. In this specification, surfactants contained in the adhesive composition mean surfactants other than reactive surfactants incorporated into the (meth)acrylic polymer (base polymer), and are sometimes referred to as free surfactants. Examples of free surfactants include unreacted reactive surfactants remaining after the synthesis of the (meth)acrylic polymer, and non-reactive surfactants that do not contain ethylenically unsaturated groups. Free surfactants may also include additives such as leveling agents.

[0088] Surfactants may be one type or two or more types. Surfactants are typically anionic surfactants. Examples of non-reactive anionic surfactants include alkyl sulfates such as lauryl sulfate and octadecyl sulfate; fatty acid salts; alkylbenzene sulfons such as nonylbenzenesulfonate and dodecylbenzenesulfonate; naphthalene sulfons such as dodecylnaphthalenesulfonate; alkyldiphenyl ether disulfons such as dodecyldiphenyl ether disulfonate; polyoxyethylene alkyl ether sulfates such as polyoxyethylene octadecyl ether sulfate and polyoxyethylene lauryl ether sulfate; polyoxyethylene alkylphenyl ether sulfates such as polyoxyethylene laurylphenyl ether sulfate; polyoxyethylene styrene phenyl ether sulfate; sulfosuccinates such as lauryl sulfosuccinate and polyoxyethylene lauryl sulfosuccinate; polyoxyethylene alkyl ether phosphates; and polyoxyethylene alkyl ether acetates. Examples of reactive anionic surfactants are those mentioned above in section <1-1-d. Reactive Surfactants>.

[0089] The surfactant contained in the adhesive composition may be a nonionic surfactant, a cationic surfactant, or the like. Examples of nonreactive nonionic surfactants include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether and polyoxyethylene stearyl ether; polyoxyethylene alkylphenyl 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; and polyoxyethylene-polyoxypropylene block copolymer. Examples of reactive nonionic surfactants are those mentioned above in section <1-1-d. Reactive Surfactants>.

[0090] The surfactant content in the adhesive composition is, for example, 0.01 parts by weight or more, and may be 0.05 parts by weight or more, 0.1 parts by weight or more, or even 0.5 parts by weight or more, per 100 parts by weight of the base polymer. The above content is, for example, 10 parts by weight or less, and may be 5 parts by weight or less, 3 parts by weight or less, 1 part by weight or less, or even 0.8 parts by weight or less, per 100 parts by weight of the base polymer.

[0091] ≪1-4. Thickeners≫ The adhesive composition may further contain a thickener. The thickener tends to reduce the fluidity of the adhesive composition and suppress repelling during coating.

[0092] The thickening agent may be one type or two or more types. Preferably, the thickening agent contains a resin that forms hydrogen bonds with the base polymer. Examples of such thickening agents include carboxylic acid copolymer thickeners, polyacrylic acid thickeners, urethane thickeners, and polyvinyl alcohol thickeners.

[0093] Carboxylic acid copolymer thickeners are, for example, emulsion-type thickeners containing a carboxylic acid copolymer. Carboxylic acid copolymers are, for example, copolymers of monomer components containing carboxyl group-containing acrylic monomers. Commercially available carboxylic acid copolymer thickeners include "Aron B-300K", "Aron B-500", "Aron A-7055", and "Aron A-7075" manufactured by Toagosei Co., Ltd., with "Aron B-500" being preferred.

[0094] Examples of polyacrylic acid thickeners include polyacrylic acid (hompolymer of acrylic acid), sodium polyacrylate, and ammonium polyacrylate. Commercially available polyacrylic acid thickeners include "Aron A-10H" (polyacrylic acid), "Aron A-20L" (sodium polyacrylate), "Aron A-7100" (sodium polyacrylate), "Aron A-30" (ammonium polyacrylate), and "Aron A-7195" manufactured by Toagosei Co., Ltd., with "Aron A-10H" being preferred.

[0095] A urethane thickener is, for example, a urethane compound having urethane bonds and polyether chains in its molecule, which can exhibit a thickening effect in water by the association of urethane bonds with each other. Commercially available urethane thickeners include "Adekanol UH-462", "Adekanol UH-752", "Adekanol UH-140S", "Adekanol UH-420", "Adekanol UH-438", "Adekanol UH-472", "Adekanol UH-450", "Adekanol UH-450VF", "Adekanol UH-540", "Adekanol UH-550", "Adekanol UH-541VF", "Adekanol UH-526", and "Adekanol UH-530", with "Adekanol UH-450VF" being preferred.

[0096] The thickener may be a solvent that forms hydrogen bonds with the base polymer, etc. Examples of such thickeners include glycols such as ethylene glycol, propylene glycol, glycerin, and 1,3-butanediol; N-methylpyrrolidone (NMP); and cellosolves such as methyl cellosolve, ethyl cellosolve, propyl cellosolve, butyl cellosolve, and acetate cellosolve.

[0097] The thickening agent is not limited to those mentioned above, as long as it has a thickening effect. Other examples of thickening agents include toluene.

[0098] The amount of thickener in the adhesive composition is not particularly limited, and may be, for example, 0.01 parts by weight or more, 0.05 parts by weight or more, or even 0.1 parts by weight or more, per 100 parts by weight of the base polymer. The above amount may be, for example, 10 parts by weight or less, 5 parts by weight or less, 1 part by weight or less, or even 0.8 parts by weight or less, per 100 parts by weight of the base polymer. The adhesive composition may not contain a thickener at all.

[0099] ≪1-5. Dispersion Medium≫ The adhesive composition contains water as a dispersion medium. The adhesive composition is typically an oil-in-water (O / W) emulsion. An adhesive composition containing water as a dispersion medium can significantly reduce the amount of organic solvent removed by heating during the preparation of the adhesive. This not only reduces the amount of fuel required to burn the organic solvent removed by heating in an osmother, etc., but also reduces the amount of CO2 emitted by the combustion of the organic solvent. However, the adhesive composition may contain an organic solvent in addition to water as a dispersion medium. The content of the dispersion medium in the adhesive composition is not particularly limited, and is, for example, 10% to 90% by weight.

[0100] ≪1-6. Additives≫ The adhesive composition may contain any other suitable additives as long as they do not impair the effects of the present invention. There may be only one or more other additives. Examples of other additives include tackifiers, crosslinking agents, pH adjusters, silane coupling agents, leveling agents, viscosity modifiers, crosslinking aids, release modifiers, plasticizers, softeners, fillers, colorants (pigments, dyes, etc.), antistatic agents, anti-aging agents, UV absorbers, antioxidants, light stabilizers, and preservatives.

[0101] Examples of tackifiers include rosin-based resins, rosin derivative resins, petroleum-based resins, terpene-based resins, phenol-based resins, and ketone-based resins.

[0102] Examples of crosslinking agents include 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.

[0103] The content of other additives in the adhesive composition is not particularly limited, and is, for example, 0.01% to 10% by weight. The adhesive composition may be substantially free of other additives.

[0104] ≪1-7. Physical Properties of Adhesive Compositions≫ The adhesive composition is preferably neutral. In a neutral adhesive composition, particles containing the base polymer (especially (meth)acrylic polymers) are less likely to aggregate, and tend to have high stability. The pH of the adhesive composition is, for example, 6.0 to 8.0, and may also be 6.5 to 7.5. The pH of the adhesive composition is preferably 7.0.

[0105] The viscosity of the adhesive composition is, for example, 10 mPa·s to 20,000 mPa·s under conditions of pH 7.0 and a temperature of 25°C.

[0106] ≪1-8. Method for Producing Adhesive Compositions≫ Adhesive compositions can be prepared, for example, by the following method. First, an emulsion containing a base polymer (especially a (meth)acrylic polymer) is prepared. This emulsion may be a polymerization solution obtained by synthesizing the base polymer by emulsion polymerization, or it may be a dispersion solution obtained by dispersing a base polymer synthesized by a method other than emulsion polymerization in a dispersion medium. Next, an adhesive composition can be prepared by adding various additives to this emulsion and mixing.

[0107] ≪≪2. Adhesive≫≫ The adhesive according to the embodiment of the present invention is formed from the adhesive composition described above. More specifically, the adhesive is a cured or dried product of the adhesive composition. The adhesive contains materials derived from the adhesive composition.

[0108] The physical properties, manufacturing methods, and applications of the adhesive can be found in the explanation in section 3, "Adhesive Sheets."

[0109] ≪≪3. Adhesive Sheet≫≫ ≪3-1. Adhesive Sheet≫ An example of an adhesive sheet according to an embodiment of the present invention is shown in Figure 1. The adhesive sheet 1 in Figure 1 is a sheet composed of the adhesive described above. In other words, the adhesive sheet 1 is an adhesive sheet formed from the adhesive composition described above.

[0110] Adhesive sheet 1 preferably has a peel force F1 of 3.0 N / 20 mm or more, as determined by the following test R1. Test R1: Adhesive sheet 1 is attached to a stainless steel plate (SUS304BA plate) and left to stand for 30 minutes in an atmosphere of 60°C and 95% RH. After standing, adhesive sheet 1 is peeled off the stainless steel plate under the conditions of a peel speed of 300 mm / min and a peel angle of 180° in an atmosphere of 60°C and 95% RH. The maximum force required at this time is identified as the peel force F1.

[0111] The peeling force F1 of the adhesive sheet 1 can be measured by the following method. First, a laminate of the adhesive sheet 1 and the release liner is prepared. Next, the above laminate is placed on top of a polyethylene terephthalate film (PET film: thickness 25 μm) via the adhesive sheet 1, and these are pressed together using a hand roller. This obtains a laminate comprising the release liner / adhesive sheet 1 / PET film in this order. Next, this laminate is cut into strips measuring 100 mm in length and 20 mm in width. The release liner is peeled off the laminate, a stainless steel plate (SUS304BA plate) is placed on the exposed surface of the adhesive sheet, and these are pressed together by passing a 2 kg roller back and forth once. The SUS304BA plate is obtained by applying bright annealing treatment to a SUS304 plate obtained by cold rolling, and then further applying adjustment rolling to improve gloss.

[0112] Next, the laminate of stainless steel plate / adhesive sheet 1 / PET film is set in a tensile testing machine with a constant temperature chamber and left to stand for 30 minutes in an atmosphere of 60°C and 95% RH. Immediately after standing, the adhesive sheet 1 (specifically, the laminate of adhesive sheet 1 / PET film) is peeled from the stainless steel plate using the above tensile testing machine in an atmosphere of 60°C and 95% RH at a peeling speed of 300 mm / min and a peeling angle of 180°. At this time, the maximum value of the force required to peel the adhesive sheet 1 from the stainless steel plate (peel strength) is identified as the peeling force F1.

[0113] The peeling force F1 is preferably 3.0 N / 20 mm or more, as described above, but may also be 3.3 N / 20 mm or more, 3.5 N / 20 mm or more, 3.8 N / 20 mm or more, 4.0 N / 20 mm or more, 4.3 N / 20 mm or more, and even 4.5 N / 20 mm or more. The upper limit of the peeling force F1 is not particularly limited and may be, for example, 20.0 N / 20 mm or less, or 10.0 N / 20 mm or less.

[0114] Adhesive sheet 1 is more preferably of which the peeling force F2 determined by the following test R2 is 3.0 N / 20 mm or more. Test R2: Adhesive sheet 1 is attached to a stainless steel plate (SUS304BA plate) and left to stand for 30 minutes in an atmosphere of 23°C and 50% RH. After standing, adhesive sheet 1 is peeled off the stainless steel plate under the conditions of a peeling speed of 300 mm / min and a peeling angle of 180° in an atmosphere of 23°C and 50% RH. The maximum value of the force required at this time is identified as the peeling force F2.

[0115] The peel force F2 of the adhesive sheet 1 can be measured by the following method. First, a laminate of stainless steel plate / adhesive sheet 1 / PET film is prepared using the method described above for the peel force F1. This laminate is left to stand for 30 minutes in an atmosphere of 23°C and 50% RH. After standing, the adhesive sheet 1 (specifically, the adhesive sheet 1 / PET film laminate) is peeled from the stainless steel plate using a tensile testing machine under conditions of a peel speed of 300 mm / min and a peel angle of 180° in an atmosphere of 23°C and 50% RH. At this time, the maximum value of the force (peel strength) required to peel the adhesive sheet 1 from the stainless steel plate is identified as the peel force F2.

[0116] The peeling force F2 is preferably 3.0 N / 20 mm or more, as described above, but may also be 4.0 N / 20 mm or more, 5.0 N / 20 mm or more, 6.0 N / 20 mm or more, 6.5 N / 20 mm or more, 6.8 N / 20 mm or more, 7.0 N / 20 mm or more, 7.3 N / 20 mm or more, and even 7.5 N / 20 mm or more. The upper limit of the peeling force F2 is not particularly limited, and may be, for example, 30.0 N / 20 mm or less, or 20.0 N / 20 mm or less.

[0117] The ratio of the peeling force F1 (N / 20mm) to the peeling force F2 (N / 20mm) (F1 / F2) is preferably greater than 35%, and may be 40% or more, 45% or more, 50% or more, 55% or more, or even 60% or more. The upper limit of the above ratio is, for example, 100% or less, and may be 80% or less.

[0118] The thickness of the adhesive sheet 1 is, for example, 1 μm or more, and may be 2 μm or more, 5 μm or more, 10 μm or more, or even 20 μm or more. The thickness of the adhesive sheet 1 is, for example, 100 μm or less, and may be 80 μm or less, or even 50 μm or less. The thickness of the adhesive sheet 1 is preferably 1 μm to 50 μm.

[0119] ≪3-2. Method for Manufacturing Adhesive Sheets≫ The adhesive sheet 1 can be manufactured, for example, by the following method. First, the above-mentioned adhesive composition is applied to a release liner to form a coating film. The method of applying the adhesive composition is not particularly limited and includes methods such as roll coating, kiss roll coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, and extrusion coating using a die coater. The adhesive composition may be applied by printing methods such as gravure printing, offset printing, screen printing, and inkjet printing, or by using a quantitative coating device such as a dispenser.

[0120] There are no particular restrictions on the material or composition of the release liner, and a suitable one can be selected from known release liners. For example, a release liner having a release treatment applied to at least one surface of the liner substrate can be suitably used. As the liner substrate, those described later in section 4-4, Substrates, can be used, and examples include various plastic films, papers, cloths, rubber sheets, foam sheets, metal foils, and composites thereof.

[0121] The release treatment applied to the liner substrate typically involves forming a release layer using a release agent. Known or conventional release agents can be used, such as silicone-based, fluorine-based, or long-chain alkyl-based release agents. If the liner substrate is composed of a fluorine-based polymer or a low-polarity polymer and has low adhesion, the liner substrate itself may be used as a release liner without applying a release treatment. However, the surface of a low-adhesion liner substrate may be treated with a release treatment. Examples of the fluorine-based polymers mentioned above include polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, and chlorofluoroethylene-vinylidene fluoride copolymer. Examples of the low-polarity polymers mentioned above include olefin resins such as polyethylene and polypropylene.

[0122] The thickness of the liner substrate and the release treatment layer of the release liner is not particularly limited and can be appropriately selected according to the purpose. The total thickness of the release liner is, for example, 15 μm or more, and may be 15 μm to 500 μm, or even 25 μm to 500 μm.

[0123] Next, the adhesive sheet 1 can be formed by drying the coated film. Drying the coated film can be carried out, for example, under heating conditions. The heating temperature of the coated film is, for example, 80°C to 170°C. The heating time of the coated film is, for example, 0.5 minutes to 30 minutes.

[0124] ≪3-3. Applications of the Adhesive Sheet≫ The adhesive sheet 1 can be preferably used for applications such as fixing, joining, molding, decorating, protecting, and supporting products and components, in a manner in which it is attached to various products that can be used in environments where water resistance and humidity resistance are required, or to components that make up such products. The adhesive sheet 1 is preferably used to fix the above-mentioned products and components, and is particularly preferably used to fix components inside electronic devices.

[0125] Examples of environments requiring water and humidity resistance include environments where temperature and humidity fluctuate significantly (e.g., bathrooms and kitchens in homes, and outdoor areas exposed to rain and wind). Examples of the products mentioned above include home appliances, office automation equipment, vehicles (e.g., automobiles), housing equipment (including furniture and furnishings), and portable devices.

[0126] Examples of home appliances include televisions (CRT, LCD, plasma, OLED, etc.), DVD players and other AV equipment, microwave ovens, rice cookers, washing machines, washer-dryers, vacuum cleaners, refrigerators, freezers, kettles, air conditioners, dishwashers, air purifiers, lighting fixtures, clocks, thermometers, PDAs (personal digital assistance devices), and landline telephones. Examples of office automation equipment include word processors, electronic dictionaries, desktop computers, laptop computers, CRT displays, LCD displays, OLED displays, printers, scanners, copiers, fax machines, and multifunction devices that combine two or more of these functions. Examples of vehicles include automobiles and trains. Examples of residential equipment (including furniture and furnishings) include baths, vanity units, toilets, cupboards, bookshelves, tables, dressers, and window panes. Examples of portable devices include mobile phones, smartphones, tablet computers, laptop computers, various wearable devices, digital cameras, digital video cameras, audio equipment (portable music players, IC recorders, etc.), calculators, portable game consoles, electronic dictionaries, electronic organizers, e-books, in-car information systems, portable radios, portable televisions, portable printers, portable scanners, portable modems, and other portable electronic devices, as well as mechanical watches, pocket watches, flashlights, and hand mirrors.

[0127] ≪≪4. Laminate≫≫ A laminate according to an embodiment of the present invention comprises, for example, the adhesive sheet 1 described above and a release liner. By peeling the release liner from the laminate and placing the adherend on the exposed surface of the adhesive sheet 1, the adhesive sheet 1 can be bonded to the adherend. The laminate may also comprise the adhesive sheet 1 and a base material.

[0128] ≪4-1. Overall Structure of the Laminate≫ Figure 2 is a typical schematic cross-sectional view of a laminate according to an embodiment of the present invention. The laminate 10 shown in Figure 2 comprises a release liner 2A, an adhesive sheet 1, and a release liner 2B in that order. The laminate 10 can be considered as a substrate-less double-sided adhesive sheet. As an example, the release liner 2A can be peeled off from the laminate 10, and the adhesive sheet 1 can be attached to the adherend by placing the adherend on the exposed surface of the adhesive sheet 1.

[0129] In addition, in the laminate 10, either the release liner 2A or the release liner 2B may be a base material described later. In this case, the laminate 10 can be considered as a single-sided adhesive sheet with a base material. Furthermore, the laminate 10 does not have to include either the release liner 2A or the release liner 2B. In this case, the laminate 10 may be wound up, so that the exposed surface of the adhesive sheet 1 is in contact with the back surface of the release liner.

[0130] Figure 3 is another representative schematic cross-sectional view of a laminate according to an embodiment of the present invention. The laminate 11 shown in Figure 3 comprises a release liner 2A, an adhesive sheet 1A, a base material 5, an adhesive sheet 1B, and a release liner 2B in that order. The laminate 11 can be considered as a double-sided adhesive sheet with a base material. As an example, the adhesive sheet 1A can be bonded to the adherend by peeling off the release liner 2A from the laminate 11 and placing the adherend on the exposed surface of the adhesive sheet 1A.

[0131] The laminate 11 does not necessarily have to include either the release liner 2A or the release liner 2B. In this case, the laminate 11 may be wound up, so that the exposed surface of the adhesive sheet 1A or 1B is in contact with the back surface of the release liner.

[0132] The laminate according to the embodiment of the present invention may adopt any suitable configuration as long as it includes the adhesive sheet 1 described in section 3. Adhesive Sheet, but typically it is the configuration shown in Figures 2 to 3 above. In some cases, the laminate may include an adhesive (the adhesive described in section 2. Adhesive) arranged in a regular or random pattern such as dots or stripes instead of the adhesive sheet 1.

[0133] The following describes the components of the laminate.

[0134] ≪4-2. Adhesive Sheets≫ Adhesive sheet 1 in Figure 2, and adhesive sheets 1A and 1B in Figure 3 are preferably the adhesive sheets described in section ≪≪3. Adhesive Sheets≫≫. However, either adhesive sheet 1A or 1B in Figure 3 may use a known adhesive.

[0135] ≪4-3. Release Liner≫ Any suitable release liner can be used as the release liner, as long as it does not impair the effects of the present invention. The release liner may be the release liner described in section ≪3-2. Method for Manufacturing Adhesive Sheets≫.

[0136] ≪4-4. Substrate≫ The substrate is typically a supporting substrate that supports (backs) the adhesive sheet. Examples of substrates include porous materials such as plastic films, paper, cloth, and nonwoven fabrics, nets, foamed sheets, metal foils, and appropriate thin sheets such as laminates thereof. From the viewpoint of improving processability, it is preferable to use a non-foamed thermoplastic film as the substrate.

[0137] The thermoplastic film described above preferably contains at least one resin selected from the group consisting of flexible polyolefin resins, flexible urethane resins, flexible acrylic resins, flexible polyester resins such as polybutylene terephthalate, and flexible vinyl chloride resins. The base material may be a flexible polyolefin resin sheet composed of a flexible polyolefin resin, a flexible urethane resin sheet composed of a flexible urethane resin, a flexible acrylic resin sheet composed of a flexible acrylic resin, a flexible polyester resin sheet composed of a flexible polyester resin, or a flexible vinyl chloride resin sheet composed of a flexible vinyl chloride resin.

[0138] Examples of thermoplastic films include polyester resin sheets such as polyethylene terephthalate and polybutylene terephthalate; olefin resin sheets made from EMMA (ethylene-methyl methacrylate copolymer) resin and EVA (ethylene-vinyl acetate copolymer) resin; polyethylene resin sheets made using one or more of the following: low-density polyethylene, linear low-density polyethylene containing α-olefin components; polyolefin resin sheets made using one or more of the following: propylene polymers (single, block, random), propylene polymers blended with rubber components and reactors, ethylene-propylene copolymer, propylene-α-olefin copolymer, ethylene-propylene-α-olefin copolymer, etc.; and vinyl chloride resin sheets. The base material may be formed by mixing two or more of the above-mentioned resins.

[0139] For example, materials used in components of portable electronic devices are often required to be halogen-free. Therefore, it is preferable that the base material is substantially free of halogen substances.

[0140] As the base material, a non-woven fabric base material may be used. Examples of the non-woven fabric base material include non-woven fabrics composed of natural fibers such as wood pulp, cotton, and hemp (e.g., Manila hemp); non-woven fabrics composed of chemical fibers (synthetic fibers) such as polyester fibers, rayon, vinylon, acetate fibers, polyvinyl alcohol (PVA) fibers, polyamide fibers, polyolefin fibers, and polyurethane fibers; and non-woven fabrics composed of a combination of two or more fibers of different materials. Among them, a non-woven fabric base material composed of hemp (e.g., Manila hemp) is preferred. In this case, the amount of hemp contained in the non-woven fabric is preferably 90% by weight or more, more preferably 95% by weight or more. Particularly preferably, a non-woven fabric consisting substantially only of hemp is used.

[0141] The basis weight of the non-woven fabric is, for example, 10 g / m 2 or more, and may be 13 g / m 2 or more. The above basis weight is, for example, 25 g / m 2 or less, and may be 22 g / m 2 or less. The bulk density of the non-woven fabric is preferably in the range of 0.25 g / cm 3 to 0.50 g / cm 3 . Note that the bulk density of the non-woven fabric can be calculated by dividing the basis weight by the thickness.

[0142] The non-woven fabric preferably has a tensile strength in both the machine direction (MD) and the transverse direction (TD) of 8 N / 15 mm or more, and may be 12 N / 15 mm or more, and further 16 N / 15 mm or more. In particular, the MD tensile strength of the non-woven fabric is preferably 12 N / 15 mm or more, and may be 18 N / 15 mm or more, and further 24 N / 15 mm or more. The non-woven fabric having the above tensile strength is suitable for forming a laminate excellent in tensile strength.

[0143] During the manufacturing process of nonwoven fabrics, polymers such as viscose, starch, and cationic polymers (e.g., polyamides, amines, epichlorohydrin) may be used to improve the strength (e.g., tensile strength) of the nonwoven fabric. Such polymers may be added during the papermaking stage (the stage in which fibers are assembled), or they may be coated or impregnated after papermaking. Nonwoven fabrics formed using strength improvers are suitable for forming laminates with excellent tensile strength. These nonwoven fabrics are suitable, for example, for use in double-sided adhesive sheets with substrates that are attached to recycled parts.

[0144] The substrate may contain various additives as needed, such as fillers (inorganic fillers, organic fillers, etc.), anti-aging agents, antioxidants, UV absorbers, antistatic agents, lubricants, plasticizers, and colorants (pigments, dyes, etc.). The surface of the substrate (especially the surface on which the adhesive sheet is attached) may be subjected to known or conventional surface treatments, such as corona discharge treatment, plasma treatment, or application of a primer. Such surface treatments may, for example, be treatments to improve the anchoring properties of the adhesive sheet to the substrate.

[0145] The thickness of the base material can be appropriately selected depending on the purpose, and may be, for example, 200 μm or less, or 100 μm or less. When the thickness of the base material is small, the ability to conform to the surface shape (steps, etc.) of the adherend tends to improve. The above thickness may be, for example, 1 μm or more, or 2 μm or more, 4 μm or more, 10 μm or more, 20 μm or more, or even 30 μm or more. Increasing the thickness of the base material tends to increase strength and improve handling (processability) during manufacturing or use.

[0146] ≪4-5. Method for Manufacturing the Laminate≫ The laminate 11 shown in Figure 3 can be manufactured by providing adhesive sheets 1A and 1B on each surface of the base material 5. The method for providing the adhesive sheets on the surface of the base material 5 is not particularly limited and includes methods such as a method of transferring an adhesive sheet formed on a release liner to the base material by bonding it (transfer method), and a method of forming an adhesive sheet by directly applying an adhesive composition to the base material and drying it (direct method). As an example, adhesive sheets may be provided on both sides of the base material by the transfer method (transfer-transfer method), or adhesive sheets may be provided on one side of the base material by the transfer method and then on the other side by the direct method (transfer-direct method).

[0147] The present invention will be specifically described below with reference to examples, but the present invention is not limited in any way to these examples. Where "parts" is mentioned, it means "parts by weight" unless otherwise specified, and where "%" is mentioned, it means "percent by weight" unless otherwise specified.

[0148] [Polymer Emulsion A1] In a reaction vessel equipped with a thermometer, stirrer, nitrogen inlet tube, and reflux condenser, 0.07 parts (in terms of solid content) of an aqueous solution of polyoxyethylene-1-(allyloxymethyl) alkyl ether sulfate ammonium salt (manufactured by Daiichi Kogyo Seiyaku, trade name "Aqualon KH-1025", a 25% aqueous solution of Aqualon KH-10) and 61.1 parts of distilled water were added as a reactive surfactant, and the mixture was purged with nitrogen at 60°C for 1 hour while stirring. Then, 0.10 parts of 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]hydrate (manufactured by Fujifilm Wako Pure Chemical Industries, trade name "VA-057") was added as a polymerization initiator. Furthermore, 85 parts of 2-ethylhexyl acrylate (2EHA), 13 parts of methyl acrylate (MA), 1.22 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 (manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-503"), and 1.93 parts (solid content equivalent) of an aqueous solution of the above reactive surfactant were emulsified with 28 parts of distilled water, and emulsion polymerization was carried out by gradually adding this mixture dropwise at 60°C for 4 hours. After holding at 60°C for 3 hours, an additional 0.05 parts of the above polymerization initiator were added, and the mixture was held at 60°C for 2 hours. The reaction solution was cooled to room temperature, and 10% aqueous ammonia was added as a pH adjuster to adjust the pH of the reaction solution to 7. Furthermore, 0.0072 parts of a preservative (manufactured by Sumika Environmental Science Co., Ltd., product name "Neosynthol 2208") were added. This prepared an aqueous dispersion of (meth)acrylic polymer A1 (polymer emulsion A1).

[0149] [Polymer Emulsion A2] An emulsion of (meth)acrylic polymer A2 (polymer emulsion A2) was prepared using the same method as polymer emulsion A1, except that the types and contents of monomers and other components were changed as shown in Table 1.

[0150] <Measurement of Gel Fraction> The gel fraction of the prepared polymer emulsion was measured by performing the above-described test G. In detail, first, the polymer emulsion was applied to a release liner using an applicator to form a coating film. The coating film was dried at 130°C for 1 hour to obtain a solid. A small piece was obtained by scraping off a portion of this solid. Next, the small piece was wrapped in a stretched porous polytetrafluoroethylene membrane (Teflon sheet, size: 100 mm long x 100 mm wide) and tied with kite string to obtain a test specimen. Next, the total weight (weight A) of the small piece of solid, the stretched porous membrane, and the kite string was measured. The total weight of the stretched porous membrane and kite string used was defined as weight B. Next, the test specimen was immersed in a container filled with ethyl acetate and left to stand at 23°C for 5 days. After standing, the test specimen was removed from the container and dried in an oven set to 130°C for 1 hour, after which the weight C of the test specimen was measured. Based on the following formula, the gel fraction of the solid obtained by drying the polymer emulsion was calculated from weights A, B, and C: Gel fraction (weight %) = (C - B) / (A - B) × 100

[0151]

[0152] The abbreviations in Table 1 are as follows: 2EHA: 2-ethylhexyl acrylate nOA: n-octyl acrylate BA: n-butyl acrylate MA: methyl acrylate AA: acrylic acid MAA: methacrylic acid KBM503: 3-methacryloxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-503") KH1025: aqueous solution of polyoxyethylene-1-(allyloxymethyl)alkyl ether sulfate ammonium salt (manufactured by Daiichi Kogyo Seiyaku, product name "Aqualon KH-1025", 25% aqueous solution of Aqualon KH-10) VA-057: 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]hydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., product name "VA-057")

[0153] (Example 1) To 100 parts by weight of (meth)acrylic polymer A1 in polymer emulsion A1, 1 part by weight of 10% aqueous ammonia and 1 part by weight (in terms of solid content) of an aqueous dispersion of urethane polymer (manufactured by Mitsui Chemicals, trade name "Takelac WS-5000", solid content concentration 30%) were added and stirred and mixed. Furthermore, 0.5 parts by weight of a thickener (manufactured by Toagosei Co., Ltd., trade name "Aron B-500") was added to adjust the viscosity, and the mixture was degassed. This obtained the aqueous dispersion adhesive composition of Example 1. The urethane polymer contained in Takelac WS-5000 was an ester-type polyurethane containing a silanol group (functional group F) that can react with (meth)acrylic polymer A1.

[0154] (Examples 2-5) Except for changing the type and content of the polymer emulsion and urethane polymer as shown in Table 2, the water-dispersible adhesive compositions of Examples 2-5 were obtained by the same method as in Example 1. In Examples 3-4, Mitsui Chemicals Co., Ltd.'s product name "Takelac WS-6021" (solids content 30%) was used as the water-dispersion of the urethane polymer. The urethane polymer contained in Takelac WS-6021 was an ether-based polyurethane containing a silanol group (functional group F) that can react with (meth)acrylic polymer A1.

[0155] (Comparative Example 1) 1 part by weight of 10% aqueous ammonia was added to 100 parts by weight of (meth)acrylic polymer A1 in polymer emulsion A1. Furthermore, 0.5 parts by weight of a thickening agent (manufactured by Toagosei Co., Ltd., trade name "Aron B-500") was added to adjust the viscosity, and the mixture was mixed and degassed. This obtained the water-dispersible adhesive composition of Comparative Example 1.

[0156] (Comparative Examples 2-3) Water-dispersible adhesive compositions for Comparative Examples 2-3 were obtained by the same method as in Example 1, except that the type and content of the urethane polymer were changed as shown in Table 2. In Comparative Examples 2-3, ADEKA Corporation's product "ADEKA BONTITER HUX-380" (solid content concentration 38%) was used as the water-dispersion of the urethane polymer. The urethane polymer contained in ADEKA BONTITER HUX-380 was an ester-based polyurethane that did not contain functional group F which is reactable with (meth)acrylic polymer A1.

[0157] (Comparative Example 4) 1 part by weight of 10% aqueous ammonia was added to 100 parts by weight of (meth)acrylic polymer A2 in polymer emulsion A2. Furthermore, 0.5 parts by weight of a thickening agent (manufactured by Toagosei Co., Ltd., trade name "Aron B-500") was added to adjust the viscosity, and the mixture was mixed and degassed. This obtained the water-dispersible adhesive composition of Comparative Example 4.

[0158] <Glass Transition Temperature> The glass transition temperature (Tg) of the urethane polymers used in the examples and comparative examples was measured by differential scanning calorimetry (DSC) in accordance with the provisions of JIS K7121:1987. The DSC was performed under the conditions of a measurement temperature range of -100°C to 160°C and a heating rate of 20°C / min.

[0159] <Peeling Force F1 and F2> The adhesive compositions of the examples and comparative examples were subjected to the above-described test R1 by the following method. First, the adhesive composition was applied to a release liner (manufactured by Mitsubishi Chemical Corporation, trade name "MRF38") using an applicator to form a coating film. Next, the coating film was dried using a blow-air oven at 100°C for 3 minutes. This obtained a laminate of an adhesive sheet (thickness 30 μm) and a release liner. Furthermore, a release liner (manufactured by Mitsubishi Chemical Corporation, trade name "MRE38") was placed on top of the adhesive sheet, and these were pressed together using a hand roller.

[0160] Next, one of the release liners was peeled off, and the laminate was placed on top of a PET film (25 μm thick) via an adhesive sheet, and these were pressed together using a hand roller. This resulted in a laminate having the release liner / adhesive sheet / PET film in that order. Next, this laminate was cut into strips measuring 100 mm in length and 20 mm in width. The release liner was peeled off the laminate, and a stainless steel plate (SUS304BA plate) was placed on the exposed surface of the adhesive sheet, and these were pressed together by passing a 2 kg roller back and forth once.

[0161] Next, the laminate of stainless steel plate / adhesive sheet / PET film was placed in a tensile testing machine with a constant temperature chamber (Shimadzu Corporation, AG-X) and left to stand for 30 minutes in an atmosphere of 60°C and 95% RH. Immediately after standing, the adhesive sheet was peeled off the stainless steel plate using the above tensile testing machine in an atmosphere of 60°C and 95% RH under conditions of a peeling speed of 300 mm / min and a peeling angle of 180°. At this time, the maximum value of the force required to peel the adhesive sheet from the stainless steel plate (peel strength) was identified as the peeling force F1.

[0162] Furthermore, the adhesive compositions of the examples and comparative examples were subjected to the above-described test R2 by the following method. First, a laminate of stainless steel plate / adhesive sheet / PET film was prepared using the method described above for the peel force F1. This laminate was left to stand for 30 minutes in an atmosphere of 23°C and 50% RH. After standing, the adhesive sheet was peeled from the stainless steel plate using a tensile testing machine (Minebea, TCN-1kNB, 50N load cell) under conditions of a peel speed of 300 mm / min and a peel angle of 180° in an atmosphere of 23°C and 50% RH. At this time, the maximum value of the force required to peel the adhesive sheet from the stainless steel plate (peel strength) was identified as the peel force F2.

[0163]

[0164] The abbreviations in Table 2 are as follows: WS5000: Manufactured by Mitsui Chemicals, product name "Takerack WS-5000" WS6021: Manufactured by Mitsui Chemicals, product name "Takerack WS-6021" HUX380: Manufactured by ADEKA, product name "ADEKA BONTITER HUX-380"

[0165] As can be seen from Table 2, the adhesive sheet formed from the water-dispersible adhesive composition of the example, which includes a base polymer ((meth)acrylic polymer) and another polymer having a functional group that can react with the base polymer (a urethane polymer containing a silanol group), had a higher peel strength F1 compared to the comparative example. From this result, it can be seen that the water-dispersible adhesive composition of the example is suitable for producing an adhesive with improved adhesive strength when placed in a high-humidity environment.

[0166] The adhesive sheet formed from the water-dispersible adhesive composition of the present invention can be used to fix components inside electronic devices.

Claims

1. A water-dispersible adhesive composition comprising a base polymer and another polymer having a functional group that can react with the base polymer.

2. The water-dispersible adhesive composition according to claim 1, wherein the functional group comprises a silanol group.

3. The water-dispersible adhesive composition according to claim 1, wherein the other polymer includes a urethane-based polymer.

4. The water-dispersible adhesive composition according to claim 1, wherein the glass transition temperature of the other polymer is 100°C or less.

5. The water-dispersible adhesive composition according to claim 1, wherein the content of the other polymer is 0.1 parts by weight or more per 100 parts by weight of the base polymer.

6. The water-dispersible adhesive composition according to claim 1, wherein the base polymer comprises a (meth)acrylic polymer.

7. The water-dispersible adhesive composition according to claim 6, wherein the (meth)acrylic polymer has constituent units derived from alkyl (meth)acrylate.

8. The water-dispersible adhesive composition according to claim 6, wherein the (meth)acrylic polymer has structural units derived from a carboxyl group-containing monomer.

9. The water-dispersible adhesive composition according to claim 6, wherein the (meth)acrylic polymer has structural units derived from an alkoxysilyl group-containing monomer.

10. The water-dispersible adhesive composition according to claim 6, wherein the (meth)acrylic polymer has constituent units derived from a reactive surfactant.

11. An adhesive formed from a water-dispersible adhesive composition according to any one of claims 1 to 10.

12. An adhesive sheet comprising the adhesive described in claim 11.

13. The adhesive sheet according to claim 12, wherein the thickness is 50 μm or less.

14. The adhesive sheet according to claim 12, wherein the peeling force F1 determined by the following test R1 is 3.0 N / 20 mm or more. Test R1: The adhesive sheet is bonded to a stainless steel plate (SUS304BA plate) and left to stand for 30 minutes in an atmosphere of 60°C and 95% RH. After standing, the adhesive sheet is peeled off the stainless steel plate under the conditions of a peeling speed of 300 mm / min and a peeling angle of 180° in an atmosphere of 60°C and 95% RH. The maximum value of the force required at this time is identified as the peeling force F1.

15. The adhesive sheet according to claim 12, used for fixing components within electronic equipment.

16. A laminate comprising the adhesive sheet described in claim 12 and a base material.

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