Structure and method for producing same

Abstract

The present invention provides a structure that comprises an adhesive appropriate for suppressing adherend contamination. The structure according to an embodiment of the present invention comprises: a substrate containing a compound having a molecular weight of no greater than 1500; and an adhesive that is formed from a water-dispersible adhesive composition and that is in contact with the substrate. The content of the abovementioned compound in the adhesive is no greater than 20 µg with respect to 1 g of the adhesive.

Description

Structure and method for manufacturing the same

[0001] The present invention relates to a structure and a method for manufacturing the same.

[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] One method for forming an adhesive from a water-dispersible adhesive composition is to apply the water-dispersible adhesive composition onto a substrate and dry it. However, according to the inventors' research, when an adhesive prepared by the above method is applied to a substrate, the substrate tends to become contaminated.

[0006] The object of the present invention is to provide a structure equipped with an adhesive suitable for suppressing contamination of the adherend.

[0007] [1] A structure according to an embodiment of the present invention comprises a base material containing a compound with a molecular weight of 1500 or less, and an adhesive formed from a water-dispersible adhesive composition and in contact with the base material, wherein the content of the compound in the adhesive is 20 μg or less per 1 g of the adhesive. [2] In the structure described in [1], the content of the compound in the adhesive may be 0.1 μg or more per 1 g of the adhesive. [3] In the structure described in [1] or [2], the content of the compound in the base material may be 1.5% by weight or more. [4] In the structure described in any of [1] to [3], the base material may contain a polyester resin. [5] In the structure described in any of [1] to [4], the base material may contain polyethylene terephthalate. [6] In the structure described in any of [1] to [5], the water-dispersible adhesive composition may contain a (meth)acrylic polymer as a base polymer. [7] In the structure described in any of [1] to [6] above, the glass transition temperature of the adhesive may be -40°C to 15°C. [8] The structure described in any of [1] to [7] above may include an adhesive sheet made of the adhesive. [9] In the structure described in [8] above, the thickness of the adhesive sheet may be 50 μm or less.

[10] A method for manufacturing a structure according to an embodiment of the present invention is a method for manufacturing a structure described in any of [1] to [9] above, the manufacturing method comprising: a step of applying the water-dispersible adhesive composition onto the substrate; and a step of irradiating the water-dispersible adhesive composition with microwaves to dry the water-dispersible adhesive composition.

[0008] According to embodiments of the present invention, it is possible to provide a structure equipped with an adhesive suitable for suppressing contamination of the adherend.

[0009] This is a schematic cross-sectional view of a structure according to one embodiment of the present invention. This is a schematic cross-sectional view of a structure according to another embodiment of the present invention. This is a schematic cross-sectional view of a structure according to yet another embodiment of the present invention. This is a diagram illustrating an example of a method for manufacturing a structure according to an embodiment of the present invention. This is a diagram illustrating another example of a method for manufacturing a structure according to an embodiment 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. Structure≫≫ The structure according to the embodiment of the present invention comprises a base material containing compound P with a molecular weight of 1500 or less, and an adhesive formed from a water-dispersible adhesive composition and in contact with the base material. Furthermore, the content of compound P in the adhesive is 20 μg or less per 1 g of adhesive.

[0014] As described above, one method for forming an adhesive from a water-dispersible adhesive composition is to apply the water-dispersible adhesive composition onto a substrate and dry it. However, according to the inventors' studies, in the above method, when the water-dispersible adhesive composition dries, some of the compounds with a molecular weight of 1500 or less (typically oligomers) contained in the substrate migrate to the water-dispersible adhesive composition, and as a result, an adhesive containing the above compounds derived from the substrate tends to be formed. If the content of the above compounds in the adhesive is high, when the adhesive is bonded to an adherend, the above compounds may bleed out at the interface between the adhesive and the adherend, potentially contaminating the adherend. If the adherend is an optical component, contamination of the adherend may prevent the desired optical properties from being obtained.

[0015] As described above, in the adhesive of the structure of this embodiment, the content of compound P derived from the substrate is adjusted to 20 μg or less per gram of adhesive. Because the content of compound P in the adhesive is sufficiently low, the adherend tends not to be contaminated even when the adhesive is applied to the adherend.

[0016] ≪1-1. Overall Structure≫ Figure 1 is a typical schematic cross-sectional view of a structure according to an embodiment of the present invention. The structure 10 shown in Figure 1 is a laminate comprising a base material 5 and an adhesive sheet 1 made of an adhesive. In the structure 10, the adhesive sheet 1 is in contact with the base material 5. As an example, in the structure 10, the adhesive sheet 1 can be attached to a substrate by placing the substrate on the exposed surface of the adhesive sheet 1.

[0017] The structure 10 can be considered as a single-sided adhesive sheet with a base material. The base material 5 may function as a release liner that can be peeled off from the structure 10. The structure 10 may be wound up, so that the exposed surface of the adhesive sheet 1 is in contact with the back surface of the base material 5.

[0018] Figure 2 is another representative schematic cross-sectional view of a structure according to an embodiment of the present invention. The structure 11 shown in Figure 2 is a laminate comprising a release liner 6, an adhesive sheet 1, and a base material 5 in that order. As an example, the adhesive sheet 1 can be adhered to the adherend by peeling off the release liner 6 from the structure 11 and placing the adherend on the exposed surface of the adhesive sheet 1.

[0019] Figure 3 is another representative schematic cross-sectional view of a structure according to an embodiment of the present invention. The structure 12 shown in Figure 3 is a laminate comprising a release liner 6A, an adhesive sheet 1A, a base material 5, an adhesive sheet 1B, and a release liner 6B in that order. The structure 12 can be considered as a double-sided adhesive sheet with a base material. As an example, the release liner 6A can be peeled off from the structure 12, and the adhesive sheet 1A can be attached to the adherend by placing the adherend on the exposed surface of the adhesive sheet 1A.

[0020] The structure 12 does not necessarily have to include either the release liner 6A or the release liner 6B. In this case, the structure 12 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.

[0021] The structure according to the embodiment of the present invention may be configured in any suitable way, as long as it includes the base material described in section 1-2. Base Material and the adhesive sheet described in section 1-4. Adhesive Sheet, but typically it is the configuration shown in Figures 1 to 3 above. In Figures 1 to 3, the structure may, in some cases, include an adhesive (the adhesive described in section 1-3. Adhesive) arranged in a regular or random pattern such as dots or stripes instead of the adhesive sheet 1. Also, either the adhesive sheet 1A or 1B in Figure 3 may use a known adhesive.

[0022] The following describes the components of the structure.

[0023] ≪1-2. Substrate≫ The substrate is typically a supporting substrate that supports (backs) an adhesive (especially an adhesive sheet). The substrate may be in the form of a single sheet or a long strip.

[0024] As described above, the base material contains compound P having a molecular weight of 1500 or less. Preferably, the base material further contains a resin along with compound P. In this specification, "resin" is a polymer with a molecular weight greater than that of compound P, and for example, it may have a weight-average molecular weight of 5000 or more, or even 10000 or more.

[0025] The resin contained in the base material may be one type or two or more types. Examples of resins include polyolefin resins such as polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymer; polyester resins such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN); vinyl chloride resins; vinyl acetate resins; polyimide resins; polyamide resins; and fluororesins. From the viewpoint of handling and processability, the base material preferably contains polyester resins, and particularly preferably contains PET.

[0026] The base material preferably contains resin as its main component. In this specification, the main component means the component that is present in the base material in the most abundant weight ratio. The resin content in the base material may be, for example, 50% by weight or more, 80% by weight or more, or even 90% by weight or more. The above content may be, for example, 99% by weight or less, 98.5% by weight or less, 98% by weight or less, or even 95% by weight or less.

[0027] The compound P contained in the base material may be one type or two or more types. Compound P is, for example, at least one selected from the group consisting of monomers and oligomers, and is preferably an oligomer. When compound P is a monomer or oligomer, it may be a by-product generated when synthesizing the above resin or a decomposition product of the resin. As an example, the base material contains a polyester resin (particularly PET) along with a polyester oligomer (particularly PET oligomer) as compound P.

[0028] The molecular weight of compound P is 1500 or less, as described above, but may be 1300 or less, 1000 or less, or even 800 or less. The lower limit of the above molecular weight is, for example, 100 or more, but may be 200 or more, 300 or more, or even 500 or more.

[0029] If compound P is an oligomer, the oligomer may be, for example, a 2-7 mer, or a 2-6 mer, a 3-5 mer, or even a trimer.

[0030] The content of compound P in the base material is, for example, 0.1% by weight or more, and may be 0.5% by weight or more, 1.0% by weight or more, 1.2% by weight or more, 1.3% by weight or more, 1.4% by weight or more, 1.5% by weight or more, and even 1.7% by weight or more. The above content may be, for example, 5.0% by weight or less, 3.0% by weight or less, and even 2.0% by weight or less.

[0031] The base material may further contain other components besides the resin and compound P mentioned above. Examples of other components include various additives such as fillers (inorganic fillers, organic fillers, etc.), antioxidants, UV absorbers, antistatic agents, lubricants, plasticizers, and colorants (pigments, dyes, etc.). The base material may or may not contain other oligomers that do not correspond to compound P as other components.

[0032] The substrate is typically a resin film containing the above-mentioned resin and compound P. In this specification, "resin film" is typically a non-porous sheet and is a concept distinct from so-called nonwoven or woven fabrics (in other words, a concept excluding nonwoven or woven fabrics). The resin film may be an unoriented film, a uniaxially oriented film, or a biaxially oriented film. However, the substrate does not have to be a resin film as long as it contains compound P, and may be paper, cloth, rubber sheet, foam sheet, metal foil, composites thereof, etc.

[0033] The surface of the substrate (particularly the surface on which the adhesive is applied) 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 performed to improve the anchoring properties of the adhesive to the substrate.

[0034] The thickness of the base material can be appropriately selected depending on the purpose, and may be, for example, 200 μm or less, but may also be 100 μm or less, 80 μm or less, or even 50 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, but may also be 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.

[0035] ≪1-3. Adhesive≫ <1-3-1. Compound P> As described above, in the structure according to the embodiment of the present invention, the content of compound P in the adhesive is 20 μg or less per 1 g of adhesive. The above content is preferably 18 μg or less per 1 g of adhesive, and may be 15 μg or less, 13 μg or less, or even 10 μg or less. The adhesive does not have to substantially contain compound P. The above content may be 0.1 μg or more per 1 g of adhesive, and may be 0.5 μg or more, 1.0 μg or more, 3.0 μg or more, or even 5.0 μg or more. The above content can be determined by analyzing the extract obtained by extracting compound P from the adhesive using liquid chromatography.

[0036] Compound P, which may be present in the adhesive, is typically migrated from the substrate to the water-dispersible adhesive composition when the adhesive is formed from the water-dispersible adhesive composition. In other words, compound P in the adhesive is the same as compound P in the substrate. Therefore, the explanation in section 1-2. Substrate can be applied to compound P in the adhesive.

[0037] The adhesive may or may not contain other monomers or oligomers other than compound P derived from the substrate. Examples of other monomers or oligomers include by-products generated during the synthesis of the base polymer contained in the water-dispersible adhesive composition, and decomposition products of the base polymer. The adhesive may also contain a tackifier as another oligomer.

[0038] <1-3-2. Water-dispersible adhesive composition> As described above, the adhesive is formed from a water-dispersible adhesive composition. Specifically, the adhesive is a cured product or a dried product of the water-dispersible adhesive composition. Therefore, the adhesive contains materials derived from the water-dispersible adhesive composition.

[0039] (1-3-2-a. Base polymer) The water-dispersible adhesive composition (hereinafter sometimes simply referred to as "adhesive composition") typically contains a base polymer. The base polymer may be only one type or two or more types.

[0040] Examples of the base polymer include (meth)acrylic polymers, rubber polymers (natural rubber, synthetic rubber, mixtures thereof, etc.), polyester polymers, urethane polymers, polyether polymers, polyamide polymers, fluorine polymers, etc. The adhesive composition preferably contains a (meth)acrylic polymer as the base polymer. Hereinafter, the (meth)acrylic polymer as the base polymer will be described in detail.

[0041] The (meth)acrylic polymer preferably contains structural units derived from (meth)acrylic acid alkyl esters. The (meth)acrylic acid alkyl esters may be only one type or two or more types. The (meth)acrylic acid alkyl esters preferably have an alkyl group having 1 to 20 carbon atoms in the side chain. The number of carbon atoms of the alkyl group may be 1 to 14, may be 1 to 10, or may be 4 to 10. The number of carbon atoms of the alkyl group may be 4 to 12 in some cases. The alkyl group may be linear or branched.

[0042] Examples of the alkyl (meth)acrylate 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, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate, etc. The alkyl (meth)acrylate preferably includes 2-ethylhexyl acrylate.

[0043] The content rate of the structural unit derived from the alkyl (meth)acrylate 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 rate is, for example, 99% by weight or less, and may be 95% by weight or less in some cases, 90% by weight or less, and even 85% by weight or less.

[0044] Furthermore, the ratio of the content rate (by weight %) of the structural unit derived from the alkyl (meth)acrylate having an alkyl group with 4 to 12 carbon atoms in the side chain to the content rate (by weight %) of the structural unit derived from all the alkyl (meth)acrylates in the (meth)acrylic polymer is, for example, 70% or more, and may be 80% or more.

[0045] 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 strength. The carboxyl group-containing monomer may be one type or two or more types.

[0046] 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.

[0047] 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).

[0048] 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.

[0049] The (meth)acrylic polymer may further contain constituent units derived from alkoxysilyl group-containing monomers. The alkoxysilyl group-containing monomer may be one type or two or more types.

[0050] 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.

[0051] 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.

[0052] Examples of monomers containing an alkoxysilyl group include 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, and 3-(meth)acryloxypropylmethyldiethoxysilane.

[0053] 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 is, for example, 1.0% by weight or less, and may be 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. The (meth)acrylic polymer does not need to contain constituent units derived from alkoxysilyl group-containing monomers.

[0054] The (meth)acrylic polymer may further contain constituent units derived from a reactive surfactant. In this specification, a 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. The reactive surfactant can function, for example, as an emulsifier for synthesizing (meth)acrylic polymers by emulsion polymerization, and can also function as a monomer copolymerized with alkyl (meth)acrylates, etc. By using a reactive surfactant, the surfactant is less likely to bleed out from the adhesive, resulting in good stain resistance. In addition, the adhesive strength tends not to decrease.

[0055] 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 (1-3-2-b. 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.

[0056] Groups containing ethylenically unsaturated groups are typically polymerizable functional groups (especially radical polymerizable functional groups). Examples of groups containing ethylenically unsaturated groups include 1-propenyl group, 2-propenyl group (allyl group), isopropenyl group, (meth)acryloyl group, vinyl group, vinyl ether group (vinyloxy group), and allyl ether group (allyloxy group).

[0057] Examples of anionic reactive surfactants include polyoxyethylene (allyloxymethyl) alkyl ether sulfate (e.g., ammonium salt), polyoxyethylene styrene-phenyl ether sulfate, alkylallyl sulfosuccinate (e.g., sodium salt), methacryloxypolyoxypropylene sulfate (e.g., sodium salt), and polyoxyalkylene alkenyl ether sulfate (e.g., ammonium salt with an isopropenyl group at the end). When an anionic reactive surfactant forms a salt, the salt may be a metal salt such as a sodium salt, or a nonmetal salt such as an ammonium salt or an amine salt.

[0058] Examples of nonionic reactive surfactants include polyoxyethylene alkyl ethers.

[0059] Commercially available reactive surfactants include the following product names from Daiichi Kogyo Seiyaku Co., Ltd.: "Aqualon KH-10", "Aqualon KH-1025", "Aqualon KH-05", "Aqualon BC-0515", "Aqualon BC-10", "Aqualon BC-1025", "Aqualon BC-20", "Aqualon BC-2020", "Aqualon AR-10", "Aqualon AR-20", "Aqualon AR-1025", and "Aqualon Examples include "AR-2020", ADEKA Corporation's product names "Adekarya Soap SE-10N" and "Adekarya Soap SR-1025", Kao Corporation's product names "Latemul PD-104", "Latemul PD-420", "Latemul PD-430", and "Latemul PD-450", Sanyo Chemical Corporation's product names "Eleminol JS-20" and "Eleminol RS-3000", and Nippon Emulsifier Co., Ltd.'s product name "Antox MS-60".

[0060] The content of constituent units derived from reactive surfactants 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 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 does not need to contain constituent units derived from reactive surfactants.

[0061] (Meth)acrylic polymers may contain structural units derived from other copolymer monomers other than those described above. These other copolymer monomers may be one type or two or more types. Examples of these other copolymer monomers include functional group-containing monomers. Structural units derived from functional group-containing monomers can introduce crosslinking points and improve cohesive strength.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] (Meth)acrylic polymers can be synthesized, for example, by emulsion polymerization. Emulsion polymerization allows for the preparation of polymer emulsions in which (meth)acrylic polymers are dispersed in a dispersion medium. Methods of emulsion polymerization include a batch loading 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 may be, for example, 10 minutes to 24 hours.

[0068] 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 (1-3-2-b. Surfactants) may also be used.

[0069] 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 parts by weight or more, 1.5 parts by weight or more, and even 2.0 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, 4.5 parts by weight or less, and even 4.0 parts by weight or less. The above amount used is preferably 1 to 5 parts by weight per 100 parts by weight of monomer component, and is preferably 1.5 to 4.5 parts by weight, and even more preferably 2 to 4 parts by weight.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] (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.

[0077] The following section provides a detailed description of the physical properties of the base polymer (particularly the (meth)acrylic polymer) contained in the adhesive composition.

[0078] The glass transition temperature (Tg) of the base polymer, as a theoretically calculated value obtained by the FOX formula, is, for example, -70°C to 30°C, but may also be -60°C to 25°C, -50°C to 20°C, or even -40°C to 15°C.

[0079] 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.

[0080] In the adhesive composition, the average particle size of the particles containing the base polymer is, for example, 50 nm to 1000 nm, but may also be 75 nm to 700 nm, or even 100 nm to 300 nm. 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.

[0081] 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.

[0082] (1-3-2-b. Surfactants) The adhesive composition may 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.

[0083] The surfactant may be one type or two or more types. Preferably, the surfactant is a salt containing a cation. Examples of cations in the surfactant include Na. + Metal cations such as NH4 + Examples include the above. Examples of cation-containing salts include metal salts such as sodium salts, potassium salts, calcium salts, and magnesium salts (preferably monovalent metal salts), ammonium salts, and amine salts.

[0084] Surfactants that are cation-containing salts 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 (1-3-2-a. Base Polymers).

[0085] 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 include those mentioned above in section (1-3-2-a. Base Polymers).

[0086] 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.

[0087] (1-3-2-c. Dispersant) 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 along with 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 95% by weight.

[0088] (1-3-2-d. 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 thickeners, tackifiers, crosslinking agents, pH adjusters, hygroscopic agents, 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.

[0089] Examples of thickening agents include carboxylic acid copolymer thickeners, polyacrylic acid thickeners, urethane thickeners, and polyvinyl alcohol thickeners.

[0090] Examples of tackifiers include rosin-based resins, rosin derivative resins, petroleum-based resins, terpene-based resins, phenol-based resins, and ketone-based resins.

[0091] 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.

[0092] 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.

[0093] (1-3-2-e. Physical properties of the adhesive composition) The adhesive composition is preferably neutral to alkaline. In this adhesive composition, particles containing the base polymer (especially (meth)acrylic polymer) tend not to aggregate easily and have high stability. The pH of the adhesive composition is, for example, 6 to 10, and may be 6.5 to 9.5, or even 7 to 9.

[0094] 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.

[0095] <1-3-3. Physical Properties of Adhesives> The glass transition temperature (Tg) of the adhesive is, for example, -70°C to 30°C, and may also be -60°C to 25°C, -50°C to 20°C, or even -40°C to 15°C.

[0096] The Tg of an adhesive can be measured by the following method. First, a sample made of adhesive is prepared. The sample is disc-shaped. The sample has a base diameter of 8 mm and a thickness of 1 mm. The sample may also be a disc-shaped piece made by punching out a laminate of multiple adhesive sheets made of adhesive. Next, dynamic viscoelasticity measurement is performed on the sample under the following conditions. For dynamic viscoelasticity measurement, for example, TA Instruments' "ARES-G2" can be used. Measurement conditions Frequency: 1 Hz Deformation mode: Torsion Measurement temperature: -70°C to 150°C Heating rate: 5°C / min

[0097] Next, the storage modulus G' and loss modulus G'' of the adhesive are determined from the results of the dynamic viscoelasticity measurement. Based on the storage modulus G' and loss modulus G'', the tanδ (loss tangent) is calculated from the following formula, and its peak value can be considered as the Tg of the adhesive. tanδ (loss tangent) = G'' / G'

[0098] The gel fraction of the adhesive is, for example, 10% to 99%, and may be 80% or more, 85% or more, 90% or more, or even 95% or more.

[0099] The gel fraction can be measured by the following method. First, a small piece is obtained by scraping off a portion of the adhesive sheet made of adhesive. Next, the obtained piece is wrapped in a stretched porous film of polytetrafluoroethylene and tied with kite string. This gives a test specimen. Next, the total weight (weight A) of the adhesive piece, the stretched porous film, and the kite string is measured. The total weight of the stretched porous film 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 one week. After standing, the test specimen is removed from the container and dried in a dryer set to 130°C for two hours, and then the weight C of the test specimen is measured. The gel fraction of the adhesive can be calculated from weights A, B, and C based on the following formula: Gel fraction (weight %) = (C - B) / (A - B) × 100

[0100] ≪1-4. Adhesive Sheet≫ In this embodiment, the adhesive sheet is a sheet composed of the adhesive described in section ≪1-3. Adhesive≫. In other words, the adhesive sheet is an adhesive sheet formed from the adhesive composition described in section <1-3-2. Water-Dispersible Adhesive Composition>.

[0101] The thickness of the adhesive sheet may be, for example, 1 μm or more, but may also 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 may be, for example, 100 μm or less, but may also be 80 μm or less, or even 50 μm or less. Preferably, the thickness of the adhesive sheet is between 1 μm and 50 μm.

[0102] ≪1-5. Peel Liner≫ There are no particular restrictions on the material or composition of the peel liner, and a suitable one can be selected from known peel liners. For example, a peel liner having a peel treatment applied to at least one surface of the liner substrate can be suitably used. As the liner substrate, those described in section ≪1-2. Substrate≫ can be used, and examples include various plastic films, papers, cloths, rubber sheets, foam sheets, metal foils, and composites thereof.

[0103] 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.

[0104] 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.

[0105] ≪1-6. Method for Manufacturing a Structure≫ A method for manufacturing a structure according to an embodiment of the present invention includes, for example, a step of applying an adhesive composition (water-dispersible adhesive composition) onto a substrate (coating step), and a step of drying the adhesive composition by irradiating it with microwaves (drying step).

[0106] <1-6-1. Preparation Step> The method for manufacturing the structure may further include a step of preparing an adhesive composition (preparation step). The adhesive composition 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. The method for synthesizing the base polymer can be described in section (1-3-2-a. Base Polymer). Next, an adhesive composition can be prepared by adding various additives to this emulsion and mixing.

[0107] <1-6-2. Coating Process> As described above, in the coating process, the adhesive composition is applied onto the substrate. As shown in Figure 4, in the coating process, a coating film 2 may be formed by applying the adhesive composition onto the substrate 5. The thickness of the coating film 2 can be appropriately adjusted according to the desired thickness of the adhesive sheet.

[0108] In the coating process, the coating method for applying the adhesive composition onto the substrate 5 is not particularly limited, and examples include 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 methods 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 liquid metering device such as a dispenser.

[0109] <1-6-3. Drying Process> As described above, in the drying process, the adhesive composition is dried by irradiating it with microwaves. In this embodiment, since the adhesive composition contains water, which is a dielectric, when the adhesive composition is irradiated with microwaves, the water in the adhesive composition is heated. This heating dries the adhesive composition (specifically the coating film 2), and an adhesive (specifically the adhesive sheet) is formed.

[0110] The microwave irradiation conditions are not particularly limited and can be adjusted as appropriate depending on the composition of the adhesive composition. For example, the microwave power may be, for example, 1W to 10kW, 10W to 3000W, or even 100W to 200W. The microwave frequency may be, for example, 13MHz to 6GHz. A preferred example of the microwave frequency is 2.4GHz to 2.5GHz. Another preferred example of the microwave frequency is 902MHz to 928MHz. The microwave irradiation time may be, for example, 0.1 seconds to 10 minutes, or 0.1 seconds to 1 minute.

[0111] Examples of microwave sources include magnetrons and semiconductor solid-state devices. The microwave source may also be a VCO (Voltage-Controlled oscillator), VCXO (Voltage-Controlled Crystal Oscillator), or PLL (Phase-Locked Loop) oscillator. The microwave source may also include an amplifier.

[0112] Furthermore, during the drying process, the substrate 5 is also irradiated with microwaves. However, the substrate 5 tends not to heat up much even when irradiated with microwaves. In other words, in the manufacturing method of this embodiment, the water in the adhesive composition can be preferentially heated by the microwaves. According to the inventors' studies, preferential heating of the water in the adhesive composition tends to suppress the migration of compound P contained in the substrate 5 to the adhesive composition. Thus, the drying process using microwaves is suitable for reducing the content of compound P in the adhesive.

[0113] <1-6-4. Other Processes> The method for manufacturing the structure may further include other processes other than those described above. For example, the manufacturing method may further include a step of bonding a release liner onto the adhesive sheet formed by the drying process.

[0114] <1-6-5. Another Example of a Method for Manufacturing a Structure> Figure 5 is a diagram illustrating another example of a method for manufacturing a structure. As shown in Figure 5, in the coating step described above, an adhesive composition may be applied to one side of a long substrate 5 unwound from a winding body 31 using a coating device 32, thereby forming a coated film 2. In the drying step, the coated film 2 may be passed through a microwave heating device 33 while microwaves are irradiated onto the coated film 2. The structure 10 of the long adhesive sheet 1 and substrate 5 obtained in the drying step may be wound onto a winding body 34. It is preferable to carry out the above steps while transporting the substrate 5. The method in Figure 5 is suitable for mass production of the structure 10.

[0115] In addition, in the method shown in Figure 5, a long release liner may be attached to the adhesive sheet 1 of the structure 10 before winding the structure 10 onto the winding body 34.

[0116] ≪1-7. Physical Properties of the Structure≫ As described above, in the structure of this embodiment, the content of compound P in the adhesive is sufficiently low, so even when the adhesive is applied to the substrate, contamination of the substrate tends to be sufficiently suppressed. As an example, when the following test was performed on the structure, the amount of compound P attached to the plastic film was 0.20 ng / cm³. 2 The following is preferable. Test: A test specimen is prepared by attaching the adhesive in the structure to a plastic film. The test specimen is stored in a 50°C atmosphere for one week. After storage, the adhesive is peeled off the plastic film. The amount of compound P attached to the plastic film is determined.

[0117] The above test can be carried out in detail by the following method. First, a structure is prepared comprising a base material and an adhesive sheet made of an adhesive. If necessary, the release liner is peeled off the structure to expose the adhesive sheet. The structure is then placed on top of a plastic film via the adhesive sheet, and a 2 kg roller is passed back and forth once to press them together. As the plastic film, for example, a film made of cycloolefin polymer can be used.

[0118] The test piece obtained by the above operation is stored in an atmosphere of 50 °C for one week. After storage, the adhesive sheet is peeled off from the plastic film. Next, the plastic film is cut out into a 10 cm square, and its surface is immersed in acetonitrile overnight. The supernatant after immersion is filtered through a filter, and the obtained filtrate is analyzed by gas chromatography. From the obtained analysis results, the amount (ng / cm 2 ) of Compound P attached to the plastic film per 1 cm 2 of the surface of the plastic film can be specified.

[0119] When the above test is performed, the amount of Compound P attached to the plastic film is preferably 0.20 ng / cm 2 or less, more preferably 0. of 15 ng / cm 2 or less, 0.10 ng / cm ; 2 [[ID=E13]] or less, 0.05 ng / cm 2 or less, and even more preferably 0.01 ng / cm 2 or less. When the above test is performed, it is preferable that substantially no Compound P adheres to the plastic film.

[0120] <<1-8. Use of the Structure>> The structure (particularly, the adhesive provided in the structure) can be preferably used for uses such as fixing, joining, molding, decorating, protecting, and supporting products and members. The structure is preferably used for protecting the above products and the above members, and particularly preferably used for protecting members in electronic devices.

[0121] The structure is preferably a surface protection film. The surface protection film is provided on the surface of optical devices such as displays and imaging devices, electronic devices, and film and glass materials that are components of these devices for the purpose of providing surface protection and impact resistance. Examples of the surface protection film include a re-peelable surface protection film that is temporarily adhered in a state before use such as device assembly, processing, and transportation, and is re-peeled before use of the device.

[0122] 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.

[0123] [Polymer Emulsion] In a container, 30 parts by weight of water, 70 parts by weight of 2-ethylhexyl acrylate (2EHA), 30 parts by weight of methyl methacrylate (MMA), 3 parts by weight of acrylic acid (AA), and 12 parts by weight of anionic reactive surfactant (manufactured by Daiichi Kogyo Seiyaku, trade name "Aqualon KH-1025") were mixed and stirred using a homomixer to prepare a monomer emulsion.

[0124] Next, 50 parts by weight of water and 0.1 parts by weight of polymerization initiator (ammonium persulfate) were added to a reaction vessel equipped with a condenser, nitrogen inlet tube, thermometer, and stirrer, and the monomer emulsion was added over 3 hours while stirring. After the addition, the reaction was carried out at 75°C for 3 hours. Then, the mixture was cooled to 30°C, and 10% by weight aqueous ammonia was added to adjust the pH to 8, thereby preparing an aqueous dispersion (polymer emulsion) containing a (meth)acrylic polymer at a concentration of 55% by weight.

[0125] [Water-dispersible adhesive composition] To the above polymer emulsion, an epoxy crosslinking agent (manufactured by Mitsubishi Gas Chemical, trade name "TETRAD-C", 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, epoxy equivalent: 110, number of functional groups: 4), which is a water-insoluble crosslinking agent, was added in an amount of 0.5 parts by weight per 100 parts by weight of (meth)acrylic polymer. Next, the mixture was stirred and mixed using a stirrer under stirring conditions of 23°C, 300 rpm, and 10 minutes to prepare a water-dispersible adhesive composition.

[0126] (Comparative Example 1) First, a polyethylene terephthalate (PET) resin film (manufactured by Mitsubishi Chemical, product name "Diafoil T100", thickness 38 μm) was prepared as a base material. This resin film contained PET oligomer (compound P) with a molecular weight of 1500 or less at a content of 1.5% by weight. Next, the above water-dispersible adhesive composition was applied to the corona-treated surface of the resin film so that the thickness after drying was 5 μm, forming a coating film. An adhesive sheet was formed by drying the coating film at 130°C for 30 seconds using a hot air circulation oven. A release liner was attached to the adhesive sheet and cured (aged) at room temperature for one week to obtain the structure of Comparative Example 1.

[0127] (Comparative Examples 2-3) The structures of Comparative Examples 2-3 were obtained by the same method as in Comparative Example 1, except that the drying time of the coated film was changed as shown in Table 1.

[0128] (Example 1) First, a polyethylene terephthalate (PET) resin film (manufactured by Mitsubishi Chemical, product name "Diafoil MRF38", thickness 38 μm) was prepared as a base material. This resin film contained PET oligomer (compound P) with a molecular weight of 1500 or less at a content of 1.5% by weight. Next, the above water-dispersible adhesive composition was applied to the resin film so that the thickness after drying was 5 μm, forming a coated film. An adhesive sheet was formed by drying the coated film by irradiating it with microwaves for 18.4 seconds at a condition of 200 W using a microwave drying oven. A release liner was attached to the adhesive sheet and cured (aged) at room temperature for one week to obtain the structure of Example 1.

[0129] (Example 2) The structure of Example 2 was obtained by the same method as in Example 1, except that the microwave power was changed from 200W to 100W.

[0130] <Content of Compound P in the Adhesive> The content of compound P in the adhesive of the fabricated structure was determined by the following method. First, the release liner was peeled off the structure to expose the adhesive sheet. Using a spatula, approximately 0.01 g of the adhesive sheet was scraped off from the exposed surface to the substrate side. At this time, it was confirmed with an optical microscope that the substrate had not been scraped off. Next, the scraped adhesive was immersed in 1 mL of chloroform overnight. This yielded an extract containing compound P from the adhesive. 5 mL of acetonitrile was added to this extract to precipitate the polymer components, and the supernatant was filtered. The obtained filtrate was analyzed using a liquid chromatograph (Agilent Technologies, 1290 Infinity II). From the obtained analytical results (detection peaks), the content of compound P (μg / g) per 1 g of adhesive was determined. In Comparative Examples 1-3 and Examples 1-2, the adhesive contained only a trimer PET oligomer (molecular weight approximately 570) derived from the substrate as compound P.

[0131] <Drying State> The adhesive of the fabricated structure was visually inspected and its drying state was evaluated according to the following criteria. ○: The adhesive was transparent and sufficiently dry. ×: White cloudiness was observed in the adhesive and it was not sufficiently dry.

[0132] <Evaluation of Contamination of Adhered Surface> The fabricated structure was evaluated for contamination of the adherend using the following method. First, the release liner was peeled off the structure to expose the adhesive sheet. The structure was placed on a cycloolefin polymer plastic film (manufactured by Nippon Zeon, trade name "Zeonor") via the adhesive sheet, and a 2 kg roller was passed back and forth once to press them together. The test specimen obtained by this operation was stored in a 50°C atmosphere for one week. After storage, the adhesive sheet was peeled off the plastic film. Next, the plastic film was cut into 10 cm squares, and its surface was immersed in 4 mL of acetonitrile overnight. The supernatant after immersion was filtered, and the obtained filtrate was analyzed using a gas chromatograph (Waters, Acquity UPLC BEH C18). From the obtained analysis results, the surface of the plastic film was analyzed for 1 cm. 2 The amount of compound P attached to the plastic film (ng / cm³) 2 ) was identified. In each of Comparative Examples 1 to 3, the plastic film had only a trimer PET oligomer (molecular weight approximately 570) derived from the substrate attached as compound P.

[0133]

[0134] As can be seen from Table 1, in the example structures where the compound P content in the adhesive was 20 μg or less per gram of adhesive, the amount of compound P adhering to the adherend (plastic film) was below the detection limit even when the structures were bonded to the adherend. From these results, it can be said that the adhesive contained in the example structures is suitable for suppressing contamination of the adherend.

[0135] The structure of the present invention (in particular, the adhesive provided by the structure) can be used for fixing components within electronic devices.

Claims

1. A structure comprising: a base material containing a compound with a molecular weight of 1500 or less; and an adhesive formed from a water-dispersible adhesive composition and in contact with the base material, wherein the content of the compound in the adhesive is 20 μg or less per 1 g of the adhesive.

2. The structure according to claim 1, wherein the content of the compound in the adhesive is 0.1 μg or more per 1 g of the adhesive.

3. The structure according to claim 1, wherein the content of the compound in the base material is 1.5% by weight or more.

4. The structure according to claim 1, wherein the base material includes a polyester resin.

5. The structure according to claim 1, wherein the base material includes polyethylene terephthalate.

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

7. The structure according to claim 1, wherein the glass transition temperature of the adhesive is -40°C to 15°C.

8. The structure according to claim 1, comprising an adhesive sheet composed of the adhesive.

9. The structure according to claim 8, wherein the thickness of the adhesive sheet is 50 μm or less.

10. A method for manufacturing a structure according to any one of claims 1 to 9, the manufacturing method comprising: a step of applying the water-dispersible adhesive composition onto the substrate; and a step of irradiating the water-dispersible adhesive composition with microwaves to dry the water-dispersible adhesive composition.

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