JP2024085366A - Adhesive composition for decorative sheets, decorative sheet employing the same, decorative structure comprising that decorative sheet, and method for manufacturing the same - Google Patents

Abstract

To provide an adhesive composition for decorative sheets, a decorative sheet, a decorative structure and a method for manufacturing the same, which are used in decorating a molding to realize re-sticking before heating and durability at a high temperature, impart an excellent appearance to the molding, and realize excellent water-resistant adhesion retention on a curved surface.SOLUTION: An adhesive composition for decorative sheets comprises a (meth)acrylic ester copolymer (A) and a curing agent (B), the (meth)acrylic ester copolymer (A) being a copolymer of a monomer mixture, where a content of linear chain alkyl (meth)acrylates (a) whose alkyl group has 8 to 18 carbon atoms is 10 to 95 mass% in 100 mass% of the monomer mixture. Also there are provided a decorative sheet, a decorative structure, and a method for manufacturing the decorative structure that employ the adhesive composition.SELECTED DRAWING: None

Description

The present invention relates to a pressure-sensitive adhesive composition for decorative sheets, and to decorative sheets and decorative structures using the same, as well as methods for producing the same.

Pressure-sensitive adhesives (also known as pressure-sensitive adhesives) are processed into shapes such as tapes and labels and are used in a wide range of applications, including everyday items, packaging materials, optical components, automobiles, building materials, and medical applications.

On the other hand, when decorating the surfaces of automobile interior and exterior parts, home appliance parts, building material parts, etc., the conventional method involves applying paint to the surface of a molded body using spray painting or other methods, then drying and heating to harden it. However, this method has problems such as poor work environment due to the emission of volatile organic solvents, requiring work steps and production equipment for each molded product, and poor paint yield and low productivity due to the need to apply multiple coats of paint.

In recent years, there has been a shift from conventional spray painting to film decoration methods in order to further reduce the environmental impact and improve design. An adhesive is used to attach the decorative sheet to the molded body, and decoration methods using decorative sheets are attracting attention for a variety of applications, including the automotive field, as they can decorate the surface of molded bodies that have three-dimensional irregularities.

Methods for decorating molded products with three-dimensional shapes, such as automobile interior and exterior parts, using decorative sheets include, for example, insert molding, in-mold molding, vacuum molding, and vacuum-compressed air molding.

Insert molding and in-mold molding are characterized by the fact that the parts are decorated at the same time as they are molded, and are firmly integrated. On the other hand, vacuum molding and vacuum-pressure molding are methods of decorating parts by laminating them at room temperature after they are completed, and then heating and forming them. In other words, the decorative sheet is attached to the exterior surface of the molded product in a separate operation from the molding of the molded product, so a single machine can be used to attach the decorative sheet to molded products of various shapes. Furthermore, vacuum molding and vacuum-pressure molding are widely used because they allow continuous coating from the front to the back of the edges of the molded product, i.e., wrap-around coating, which is difficult to achieve with methods such as in-mold molding.

Patent Document 1 discloses that by using an adhesive composition containing two types of (meth)acrylic polymers with glass transition temperatures in a specific range in a specific ratio, it is possible to form an adhesive layer that has low tack, excellent repositionability, and excellent coating appearance.

Patent Document 2 discloses that an adhesive layer obtained by crosslinking an adhesive composition containing a vinyl polymer and an acrylic adhesive polymer in a specific ratio, the vinyl polymer having a glass transition temperature of 30°C or higher and 200°C or lower and a number average molecular weight of 500 to 10,000, with a crosslinking agent, has excellent adhesion under high temperature and humidity conditions, excellent coating appearance, and excellent adhesion to curved surfaces and uneven parts, if the adhesive layer satisfies specific glass transition temperature conditions.

International Publication No. 2021/049480 JP 2018-2891 A

Normally, when applying a decorative sheet to a molded product using the vacuum forming method or vacuum/compressed air forming method, it is not possible to reapply it after heat forming, so it is often reapplied before molding. For this reason, it is required to be able to be easily reapplied. Furthermore, since it is expected that interior and exterior parts of automobiles will be used in a variety of environments, it is also important that the sheet has excellent durability and adhesion so that it does not cause appearance defects such as lifting or peeling even when exposed to high temperatures or water.

The adhesive composition of Patent Document 1 has excellent repositionability and removability, but does not mention durability in high temperature environments, and is therefore insufficient in terms of practical performance.

The decorative film described in Patent Document 2 maintains its durability at 120°C for 24 hours, but there are concerns about its durability in higher temperature environments (e.g., 150°C) and for long periods of time. In addition, when a sample attached to a curved surface was exposed to water, the adhesive sheet lifted or peeled off, resulting in a poor appearance.

In other words, no adhesive composition has been developed to date that can provide excellent repositionability before heating, durability at high temperatures, and an excellent appearance to molded articles when decorating articles formed using vacuum molding or vacuum-pressure molding, while also providing excellent water-resistant adhesion to curved surfaces.

The present inventors conducted extensive research to solve the above problems and arrived at the present invention.
That is, the adhesive composition for decorative sheets is characterized by comprising a (meth)acrylic acid ester copolymer (A) and a curing agent (B), the (meth)acrylic acid ester copolymer (A) being a copolymer of a monomer mixture, and the content of linear alkyl (meth)acrylate (a) having an alkyl group of 8 to 18 carbon atoms in 100 mass % of the monomer mixture being 10 to 95 mass %.

The present invention makes it possible to provide a pressure-sensitive adhesive composition for decorative sheets, decorative sheets, decorative structures, and methods for producing the same, which can impart excellent repositionability before heating, durability at high temperatures, and appearance to molded products when decorating molded products using vacuum molding or vacuum-compressed air molding, and which also have excellent water-resistant adhesion to curved surfaces. It has been discovered that when a pressure-sensitive adhesive layer is formed from a pressure-sensitive adhesive composition containing a (meth)acrylic acid ester copolymer (A) containing a specified (meth)acrylate and a curing agent (B), its moderately high hydrophobicity and flexibility make it possible to improve water-resistant adhesion retention to curved surfaces while simultaneously achieving a high level of other performance.

The pressure-sensitive adhesive composition for decorative sheets, the decorative sheet, the decorative structure, and the method for producing a decorative structure according to the present disclosure have the following configurations [1] to [8].
[1] A pressure-sensitive adhesive composition for decorative sheets, comprising: a (meth)acrylic acid ester copolymer (A) and a curing agent (B), wherein the (meth)acrylic acid ester copolymer (A) is a copolymer of a monomer mixture, and the content of linear alkyl (meth)acrylate (a) having an alkyl group of 8 to 18 carbon atoms is 10 to 95 mass% relative to 100 mass% of the monomer mixture.
[2] The monomer mixture constituting the (meth)acrylic acid ester copolymer (A) further contains an alkyl (meth)acrylate (b) having an alkyl group with 1 to 4 carbon atoms,
The content of alkyl (meth)acrylate (b) in 100% by mass of the monomer mixture is 1 to 5
0% by mass of the pressure-sensitive adhesive composition for decorative sheets.
[3] The pressure-sensitive adhesive composition for decorative sheets, characterized in that the gel fraction after crosslinking is 50% or more.
[4] The pressure-sensitive adhesive composition for decorative sheets, which is for attaching a decorative sheet to an adherend by vacuum forming or vacuum/pressure forming.
[5] A decorative sheet comprising a substrate and an adhesive layer made of the adhesive composition for decorative sheets.
[6] A decorative structure comprising an adherend and the decorative sheet.
[7] A method for producing a decorated structure, characterized in that the decorative sheet is integrated with an adherend by vacuum forming or vacuum/pressure forming to form a decorated structure.

The present disclosure is described in detail below. Needless to say, other embodiments are also included within the scope of the present disclosure as long as they conform to the spirit of the present disclosure.

In this disclosure, "sheet" refers to a flexible laminate, and includes thin laminates known as "films."

In this disclosure, "(meth)acrylic" means either or both of "acrylic" and "methacrylic", and "(meth)acrylate" means either or both of "acrylate" and "methacrylate".

In this disclosure, a numerical range specified using "~" is intended to include the numerical values before and after "~" as the lower and upper limit values of the range.

In this specification, the adhesive composition for decorative sheets may be abbreviated as "adhesive composition."

In this specification, "Mw" is the weight average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC), and "Mn" is the number average molecular weight in terms of polystyrene measured by GPC.
The weight average molecular weight and number average molecular weight can be measured by the method described in the section [Examples].

The following describes in detail the embodiments of the present invention, but the following description is merely one example (representative example) of the embodiment of the present invention, and the present invention is not limited to these details as long as it does not exceed the gist of the invention.

<Adhesive composition for decorative sheet>
The adhesive composition for decorative sheets of the present invention comprises a (meth)acrylic acid ester copolymer (A) and a curing agent (B), and is characterized in that the (meth)acrylic acid ester copolymer (A) is a copolymer of a monomer mixture, and the content of linear alkyl (meth)acrylate (a) having an alkyl group of 8 to 18 carbon atoms is 10 to 95 mass% relative to 100 mass% of the monomer mixture.

<(Meth)acrylic acid ester copolymer (A)>
The (meth)acrylic acid ester copolymer (A) (hereinafter also referred to as copolymer (A)) contained in the pressure-sensitive adhesive composition of the present invention is a copolymer obtained by polymerizing all or a part of a mixture of monomers containing a (meth)acrylic acid alkyl ester.

The content of the (meth)acrylate (a) having a linear alkyl group having 8 to 18 carbon atoms in 100% by mass of the monomer mixture is 10 to 95% by mass, more preferably 30 to 85% by mass. By keeping it within the above range, it is possible to achieve a high degree of adhesion, durability at high temperatures, and water-resistant adhesion retention to curved surfaces.

Examples of (meth)acrylates (a) having a linear alkyl group with 8 to 18 carbon atoms include n-octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, and stearyl (meth)acrylate.

In addition to the (meth)acrylate (a) having a linear alkyl group having 8 to 18 carbon atoms, other monomers can also be used in the synthesis of the copolymer (A) depending on the purpose of adjusting the compatibility with other components, the dispersibility of other components, the adhesion to the substrate and the adherend, and the crosslinkability.
More specifically, the monomer mixture constituting the copolymer (A) preferably further contains (b) a (meth)acrylate having 1 to 4 carbon atoms. These may be used alone or in combination of two or more kinds.

Examples of (meth)acrylates (b) having 1 to 4 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, tert-butyl (meth)acrylate, and isobutyl (meth)acrylate.

In 100% by mass of the monomer mixture, the content of (meth)acrylate (b) having 1 to 4 carbon atoms is preferably 1 to 50% by mass, and more preferably 5 to 40% by mass. By keeping it within the above range, it is possible to achieve a high degree of adhesion, durability at high temperatures, and water-resistant adhesion to curved surfaces.

The monomer mixture constituting the copolymer (A) preferably further contains a monomer having a functional group that forms a crosslinked structure with the crosslinking group (B). Examples of the functional group include a hydroxyl group, an acidic group, an unsaturated double bond group, and an epoxy group. These may be used alone or in combination of two or more.
From the viewpoint of adhesion to substrates and durability at high temperatures, it is particularly preferable to use hydroxyl group-containing monomers and acidic group-containing monomers, and it is even more preferable to use acidic group-containing monomers.

Examples of acidic group-containing monomers include vinyl monomers having an acidic group, such as (meth)acrylic acid, 2-carboxyethyl acrylate, itaconic acid, maleic acid, styrenesulfonic acid, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxyethyl phthalic acid, 2-acryloyloxyethyl hexahydrophthalic acid, 2-(meth)acryloyloxyethyl acid phosphate, and 2-methacryloyloxyethyl acid phosphate.

The content of the acidic group-containing monomer in the monomer mixture constituting the copolymer (A) is preferably 2 to 25% by mass, more preferably 5 to 20% by mass, based on 100% by mass of the monomer mixture, from the viewpoints of repositionability, durability at high temperatures, and water-resistant adhesion retention to curved surfaces.

Examples of hydroxyl group-containing monomers include (meth)acrylic acid ester monomers having a hydroxyl group, such as 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, and polyalkylene glycol mono(meth)acrylate, as well as allyl ether monomers having a hydroxyl group, such as polyalkylene glycol allyl ether.

From the viewpoints of repositionability, durability at high temperatures, and adhesion to curved surfaces, the content of the hydroxyl group-containing monomer in the monomer mixture constituting the copolymer (A) is preferably 0.01 to 5 mass% and more preferably 0.1 to 3 mass% in 100 mass% of the monomer mixture.

Furthermore, examples of other monomers that can be included in the monomer mixture constituting copolymer (A) include the following:

Vinyl monomers such as vinyl acetate, vinyl propionate, styrene, vinyl laurate, vinyl caprate, vinyl caprylate, and vinyl nonanoate;
(meth)acrylates having a straight-chain or branched alkyl group having 5 to 26 carbon atoms, such as pentyl (meth)acrylate, isopentyl (meth)acrylate, 2-methylbutyl (meth)acrylate, hexyl (meth)acrylate, 4-methyl-2-pentyl (meth)acrylate, heptyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isononyl (meth)acrylate, isodecyl (meth)acrylate, isostearyl (meth)acrylate, behenyl acrylate, eicosanyl (meth)acrylate, and hexacosanyl (meth)acrylate (however, excluding straight-chain alkyl (meth)acrylate (a) having 8 to 18 carbon atoms);
(meth)acrylic acid ester monomers having an aliphatic ring, such as cyclohexyl (meth)acrylate, 4-t-butylcyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and 3,3,5-trimethylcyclohexyl acrylate;
(meth)acrylic acid ester monomers having an aromatic ring, such as benzyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, 2-(o-phenylphenoxy)ethyl (meth)acrylate, and nonylphenoxy polyethylene glycol acrylate;
(meth)acrylic acid ester monomers having an alkoxy group, such as 2-methoxymethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxymethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 4-methoxybutyl (meth)acrylate, and 4-ethoxybutyl (meth)acrylate;
(meth)acrylic acid ester monomers having a polyether chain, such as methoxypolyethylene glycol (meth)acrylate, ethoxypolyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, ethoxypolypropylene glycol (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, and phenoxypolypropylene glycol (meth)acrylate;
N-vinyl cyclic amide monomers such as N-vinyl-2-pyrrolidone, N-vinyl-2-piperidone, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxazin-2-one, and N-vinyl-3,5-morpholinedione;
(meth)acrylamide-based monomers such as (meth)acrylamide, N-alkyl(meth)acrylamide, N,N-dialkyl(meth)acrylamide, N-hydroxyalkyl(meth)acrylamide, and N-alkoxyalkyl(meth)acrylamide;
N,N-dialkyl(meth)acrylamide monomers such as N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide, N,N-di(n-butyl)(meth)acrylamide, and N,N-di(t-butyl)(meth)acrylamide;
N-hydroxyalkyl(meth)acrylamide monomers such as N-methylol(meth)acrylamide, N-(2)-hydroxyethyl)(meth)acrylamide, N-(2-hydroxypropyl)(meth)acrylamide, N-(1-hydroxypropyl)(meth)acrylamide, N-(3-hydroxypropyl)(meth)acrylamide, N-(2-hydroxybutyl)(meth)acrylamide, N-(3-hydroxybutyl)(meth)acrylamide, N-(4-hydroxybutyl)(meth)acrylamide, and N-methyl-N-2-hydroxyethyl(meth)acrylamide;
Examples of the compound include N-alkoxyalkyl(meth)acrylamides such as N-methoxymethyl(meth)acrylamide and N-butoxymethyl(meth)acrylamide.
These may or may not be included in the monomer mixture constituting the copolymer (A) as necessary, but when they are included in the monomer mixture, it is more preferable to use vinyl acetate from the viewpoint of the coatability of the pressure-sensitive adhesive composition, etc.

The content of other monomers in the monomer mixture constituting copolymer (A) is preferably 40% by mass or less, more preferably 30% by mass or less, based on 100% by mass of the monomer mixture. By keeping it within the above range, it is possible to achieve a high degree of compatibility between adhesive strength, durability at high temperatures, and water-resistant adhesion retention.

The polymerization form of the (meth)acrylic acid ester copolymer (A) is not particularly limited. That is, the copolymer (A) may be any of an alternating copolymer, a random copolymer, a block copolymer, and a graft copolymer of each monomer including an (meth)acrylic acid alkyl ester. For example, the block copolymer may be a diblock or a triblock.

Copolymer (A) can be synthesized by a conventionally known method, for example, by a known polymerization method such as solution polymerization, bulk polymerization, emulsion polymerization, or suspension polymerization. Copolymer (A) can also be synthesized by a known polymerization method such as living radical polymerization or active energy ray polymerization. In this case, the monomer mixture for synthesizing copolymer (A) can contain a photopolymerization initiator or a conventionally known additive. As the active energy ray, ultraviolet light, visible light, X-rays, gamma rays, or electron beams can be used. In addition, light sources such as low pressure mercury lamps, medium pressure mercury lamps, high pressure mercury lamps, ultra-high pressure mercury lamps, xenon lamps, metal halide lamps, electrodeless lamps, and LEDs can be used for ultraviolet irradiation.

The content of each structural unit (monomer component) of copolymer (A) can be determined using various instruments such as nuclear magnetic resonance analysis (NMR) and gas chromatography (GC).

The weight average molecular weight (Mw) of the (meth)acrylic acid ester copolymer (A) is preferably more than 300,000, more preferably 500,000 or more, and even more preferably 700,000 or more. The weight average molecular weight of the copolymer (A) is preferably 1,500,000 or less, more preferably 1,300,000 or less, and even more preferably 1,200,000 or less.
When the Mw of the copolymer (A) satisfies the above-mentioned lower limit condition, it is easy to ensure a viscosity suitable for coating, and it is also easy to prevent the decorative sheet portion from shifting after decoration of the molded article, which would cause deterioration in the appearance of the decorated molded article.

<Curing Agent (B)>
The pressure-sensitive adhesive composition of the present invention contains a curing agent (B). By providing the (meth)acrylic acid ester copolymer (A) with a crosslinking group and crosslinking it with the curing agent (B), the cohesive strength, adhesive strength, durability at high temperatures, and water resistance of the adhesive layer can be increased.

Examples of the curing agent contained in the pressure-sensitive adhesive composition of the present invention include isocyanate compounds, epoxy compounds, aziridine compounds, metal chelates, amine compounds, acrylate compounds, etc. Among these, from the viewpoints of adhesive strength and solution stability, isocyanate compounds, epoxy compounds, and metal chelates are more preferred, and from the viewpoint of durability in high-temperature environments, epoxy compounds are even more preferred.

Examples of isocyanate-based curing agents include adducts of diisocyanates such as tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethylxylylene diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, and polymethylene polyphenyl isocyanate with polyol compounds such as trimethylolpropane, as well as their biuret forms and their isocyanurates, as well as adducts of the above diisocyanates with polyether polyols, polyester polyols, acrylic polyols, polybutadiene polyols, and polyisocyanates. Compounds having three or more isocyanate groups in the molecule, such as adducts with any of polyols such as ene polyols and polyisoprene polyols; diisocyanates such as tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethyl xylylene diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, and polymethylene polyphenyl isocyanate, as well as compounds having two isocyanate groups in the molecule, such as allophanate compounds of hexamethylene diisocyanate; and the like. Among these, trimethylolpropane adducts of tolylene diisocyanate are preferred because the adhesive properties can be easily adjusted. The number of isocyanate groups is the average number.

Epoxy curing agents include, for example, bisphenol A-epichlorohydrin type epoxy resins, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, diglycidylaniline, N,N,N',N'-tetraglycidyl-m-xylylenediamine, 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, and N,N,N',N'-tetraglycidylaminophenylmethane.

Metal chelate curing agents include, for example, coordination compounds of polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium with acetylacetone or ethyl acetoacetate.

Examples of aziridine compounds include N,N'-hexamethylene bis(1-aziridinecarboxamide), methylene bis[N-(1-aziridinylcarbonyl)-4-aniline], tetramethylol methane tris(β-aziridinyl propionate), trimethylol propane tris(β-aziridinyl propionate), etc. In addition, examples of commercially available products include "TAZO" and "TAZM" manufactured by Sogo Pharmaceutical Co., Ltd., and "ChemiTite PZ-33" manufactured by Nippon Shokubai Co., Ltd.

Examples of amine compounds include hexamethylenediamine, triethyldiamine, polyethyleneimine, hexamethylenetetramine, diethylenetriamine, triethyltetramine, isophoronediamine, amino resins, and methylene resins.

Examples of acrylate compounds include multifunctional acrylates such as 1,6-hexanediol acrylate.

The content of the curing agent (B) may be changed as appropriate depending on the desired physical properties such as the type of copolymer (A) and the degree of crosslinking, but from the viewpoints of adhesive strength, repositionability, and durability at high temperatures, it is preferably 0.01 to 30 parts by mass, more preferably 0.02 to 10 parts by mass, even more preferably 0.03 to 5 parts by mass, and particularly preferably 0.05 to 3 parts by mass, per 100 parts by mass of copolymer (A). In particular, by keeping the content of the epoxy compound as the curing agent within the above range, it is possible to achieve a high degree of both adhesion and heat resistance in high-temperature environments up to 150°C.

The degree of crosslinking of the adhesive composition of the present invention is indicated by the gel fraction, and the method for measuring it is as shown in the Examples. Since the higher the gel fraction, the better the repositionability and durability in high temperature environments, the gel fraction after crosslinking of the adhesive composition of the present invention is preferably 50% or more. The gel fraction may be 100%. The degree of crosslinking of the adhesive composition can be appropriately adjusted by changing the amount of the curing agent (B) blended, etc.

In addition to the copolymer (A) and the curing agent (B), the adhesive composition of the present invention may contain any additives, such as a solvent, a tackifier, a resin other than the copolymer (A), a plasticizer, a silane coupling agent, a leveling agent, inorganic and/or organic fine particles, an ultraviolet absorber, a light stabilizer, and an antioxidant, as necessary. The amount of these additives added can be appropriately selected within a range in which the effects of the present disclosure can be obtained, and it is preferable to appropriately set the content of the copolymer (A) within the above range, for example.

Resins other than the (meth)acrylic acid ester copolymer (A) include known thermoplastic resins, such as low-density polyethylene, very low-density polyethylene, low-crystalline (amorphous) polypropylene, ionomer resins, ethylene copolymers such as ethylene-vinyl acetate copolymer, ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylic acid ester-maleic anhydride copolymer, and ethylene-glycidyl methacrylate copolymer, as well as olefin-based copolymers such as polyolefin-modified polymers, as well as thermoplastic elastomers such as butadiene-based elastomers, ester-based elastomers, styrene-based elastomers, styrene-butadiene-based elastomers, styrene-isoprene-based elastomers, and polyurethane-based elastomers, as well as thermoplastic polyesters, as well as polyamide-based resins such as polyamide-based copolymers, polyurethanes, polystyrene-based resins, cellophane, polyacrylonitrile, and polyvinyl chloride-based resins such as vinyl chloride-vinyl acetate copolymers. These resins may be used alone or in combination of two or more. The content of these other resins is preferably less than 10% by mass, based on 100% by mass of the solid content of the adhesive composition. If the content of these resins is less than 10% by mass, good compatibility is easily achieved, and appropriate adhesive strength can be easily obtained.

When applying the pressure-sensitive adhesive composition of the present invention to an object to be affixed, the solvent used in the polymerization of the (meth)acrylic acid ester copolymer (A) may be used as is, or a further solvent may be added, and any suitable solvent may be used.

Examples of the solvent include methyl acetate, ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, xylene, hexane, acetone, methyl ethyl ketone, methyl isobutyl ketone, methanol, ethanol, n-propanol, and isopropanol. These organic solvents may be used alone or in combination of two or more. The viscosity of the adhesive composition can be adjusted by adding these organic solvents, or the viscosity can be reduced by heating the adhesive composition.
From the viewpoint of solubility and drying property, it is preferable to use a solvent having an SP value of 9 or more. Examples of organic solvents having an SP value of 9 or more include ethyl acetate, butyl acetate, methyl ethyl ketone, isopropanol, etc. Among these, it is preferable to use ethyl acetate.
On the other hand, from the viewpoint of decreasing the viscosity of the pressure-sensitive adhesive composition, it is preferable to use a solvent having an SP value of less than 9. Examples of organic solvents having an SP value of less than 9 include hexane, heptane, and octane.

The adhesive composition of the present invention may contain a tackifier (tackifier resin) for the purpose of adjusting the adhesive strength. The tackifier is not particularly limited, but examples thereof include rosin-based resins, terpene-based resins, synthetic hydrocarbon-based resins, etc.

Examples of rosin-based resins include rosin esters, polymerized rosin, hydrogenated rosin, disproportionated rosin, maleic acid modified rosin, fumaric acid modified rosin, rosin phenolic resin, and natural rosin.

Terpene resins include, for example, α-pinene resin, β-pinene resin, dipentene resin, aromatic modified terpene resin, hydrogenated terpene resin, terpene phenol resin, acid modified terpene resin, styrenated terpene resin, and styrene-aliphatic hydrocarbon copolymer resin.

Examples of synthetic hydrocarbon resins include coumarone resins, coumarone-indene resins, styrene resins, xylene resins, phenol resins, and petroleum resins.

From the viewpoint of obtaining good adhesion to the object to which it is applied, it is preferable to use rosin-based resins and terpene-based resins as tackifiers. Tackifiers may be used alone or in combination of two or more types.

The content of the tackifier is preferably less than 30 parts by mass, more preferably 25 parts by mass or less, and even more preferably 20 parts by mass or less, per 100 parts by mass of the acrylic acid ester copolymer (A). By making the content of the tackifier less than 30 parts by mass, it is easy to obtain good compatibility, appropriate re-tensioning properties, and excellent appearance of the molded product.

The pressure-sensitive adhesive composition of the present invention preferably contains the (meth)acrylic acid ester copolymer (A) as a main component. The main component refers to the component that is mixed in the largest amount among all components contained in the target object (here, the pressure-sensitive adhesive composition of the present invention).
Specifically, the content of the (meth)acrylic acid ester copolymer (A) in 100% by mass of the solid content of the pressure-sensitive adhesive composition of the present invention is preferably 70 to 100% by mass, more preferably 80 to 100% by mass, and even more preferably 90 to 99% by mass. When the (meth)acrylic acid ester copolymer (A) is contained in 70% by mass or more in 100% by mass of the solid content of the pressure-sensitive adhesive composition of the present invention, it is possible to easily obtain an appropriate adhesive strength that allows repositioning at room temperature and is free of air bubble entrapment and foreign matter contamination.

The viscosity of the adhesive composition of the present invention is preferably 1000 to 10000 mPa·s, more preferably 1000 to 8000 mPa·s, and even more preferably 1000 to 5000 mPa·s, at 23°C and a relative humidity of 50% (hereinafter referred to as 50% RH). With a viscosity within the above range, coatability can be easily ensured. The method for measuring the viscosity is as shown in the examples.

<Decorative sheet>
The decorative sheet according to the present invention (hereinafter, also referred to as the present decorative sheet) comprises a substrate and an adhesive layer made of a cured product of the adhesive composition according to the present invention. If necessary, the exposed surface of the adhesive layer can be covered with a release sheet. The release sheet is peeled off when the adhesive sheet is attached to an adherend.
The substrate is not particularly limited, and may be a resin sheet, paper, metal foil, etc. The substrate may be a laminated sheet in which any one or more layers are laminated on at least one surface of the substrate. The surface of the substrate on which any adhesive layer is formed may be subjected to an easy-adhesion treatment such as corona discharge treatment and application of an anchor coating agent, if necessary.
The release sheet is not particularly limited, and any known release sheet can be used, which is obtained by subjecting the surface of a base sheet such as a resin sheet or paper to a known release treatment such as coating with a release agent.

The manufacturing method of the decorative sheet of the present invention having an adhesive layer can be appropriately used by a conventionally known method, and is not particularly limited. For example, the adhesive composition of the present invention, diluted with a solvent as necessary, is coated on a sheet on which a surface layer and a decorative layer are formed, by knife coating, bar coating, blade coating, doctor coating, roll coating, cast coating, etc., to form a coating film. Then, the adhesive layer (solidified product) can be formed on the sheet by heating and drying or curing as necessary.
In addition, when the copolymer (A) contained in the pressure-sensitive adhesive composition of the present invention needs to be crosslinked by active energy rays, the pressure-sensitive adhesive composition is applied to a sheet, and then the sheet is irradiated with active energy rays to form a pressure-sensitive adhesive layer (crosslinked product). At that time, for example, a belt conveyor type ultraviolet ray irradiation device is used to irradiate the pressure-sensitive adhesive composition applied to the sheet with ultraviolet rays to obtain a pressure-sensitive adhesive layer. The amount of ultraviolet irradiation can be, for example, 500 mJ/ ^cm2 or more and 5000 mJ/ ^cm2 or less.
The decorative sheet of the present invention has a suitable adhesive strength at room temperature (e.g., 25° C.), has excellent adhesive properties when bonded at high temperatures (e.g., 100 to 130° C.), and can maintain its properties for a long period of time at high temperatures (e.g., 100° C., 7 days). Therefore, the decorative sheet can be applied to the decoration of aircraft, automobiles, interior and exterior of building materials, nursing and medical fields, electrical appliances, etc., by three-dimensional surface decoration (Three Dimension Overlay Method: TOM molding).

<Decorative structure and method for producing same>
The decorative structure according to the present disclosure can be formed by attaching a decorative sheet to an adherend using the present pressure-sensitive adhesive composition. The adherend is not particularly limited, and various shapes of objects (e.g., molded products having three-dimensional shapes) can be used. The pressure-sensitive adhesive composition of the present invention can be preferably used for attachment to an adherend by a vacuum molding method and a vacuum-pressure molding method. Conventionally known methods can be appropriately applied to the vacuum molding method and the vacuum-pressure molding method.

More specifically, the decorated structure of the present invention can include, for example, a surface layer, a decorative layer, and an adhesive layer in this order.
The surface layer is a layer that becomes the surface of the decorated molded product, and any layer that is conventionally known in the field of decorative sheets can be used as appropriate. The surface layer can be made of various resins, such as acrylic resin, polyurethane, fluororesin, and polyvinyl chloride. The exposed surface of the surface layer may also be embossed.
The decorative layer is for decorating the object to be decorated, and various materials can be used depending on the intended use. The decorative layer can contain at least one resin selected from the group consisting of olefin resins, styrene resins, and vinyl chloride resins. The decorative layer may further contain other layers such as a design layer, a bulk layer, and a bonding layer as optional elements. The number of layers of the decorative sheet, the type, arrangement, thickness, etc. of each layer can be appropriately selected and are not particularly limited.
The adhesive layer is a layer for attaching a decorative sheet to an adherend (e.g., a molded product formed into a three-dimensional shape), and can be formed by drying the adhesive composition (e.g., after applying it to a substrate) or by crosslinking it by irradiating it with ultraviolet light, etc.

Next, the present disclosure will be described in more detail with reference to examples, but the present disclosure is not limited to these examples. In the examples, unless otherwise specified, "parts" refers to "parts by mass" and "%" refers to "% by mass". In addition, the blending amounts in the tables are parts by mass.

<Measurement of weight average molecular weight (Mw)>
The Mw of the (meth)acrylic acid ester copolymer (A) was measured by the following method. The copolymer (A) dissolved in tetrahydrofuran (THF) was subjected to liquid chromatography (gel permeation chromatography) for separating and quantifying based on the difference in molecular size, and the Mw was specified. The measurement device used was a LC-GPC system "Prominence" (product name) of GPC manufactured by Shimadzu Corporation. The weight average molecular weight was determined in terms of polystyrene. The columns were four GMHXL columns manufactured by Tosoh Corporation (product name: GMHXL) and one HXL-H column manufactured by Tosoh Corporation (product name: HXL-H) connected in series, and the measurement was performed at a flow rate of 1.0 ml/min and a column temperature of 40°C.

[Production Example of (Meth)Acrylic Acid Ester Copolymer (A)]
<Copolymer (A-1)>
A reaction vessel (hereinafter simply referred to as "reaction vessel") equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen inlet tube was charged with 90 parts of n-octyl acrylate, 10 parts of acrylic acid, 65 parts of ethyl acetate, 20 parts of MEK, and 0.03 parts of 2,2'-azobisisobutyronitrile under a nitrogen atmosphere. The mixture was heated with stirring to confirm the start of the polymerization reaction, and reacted at reflux temperature for 2 hours. Next, 0.03 parts of 2,2'-azobisisobutyronitrile was added to the reaction solution, and the reaction was continued for 6 hours. Thereafter, the reaction vessel was cooled, and ethyl acetate was added to adjust the nonvolatile content to 40%, to obtain a copolymer (A-1) solution having a weight average molecular weight of 700,000.

<Copolymers (A-2) to (A-19), (A'-1) to (A'-6)>
In producing copolymers (A-2) to (A-19) and (A'-1) to (A'-6), copolymers (A-2) to (A-19) and (A'-1) to (A'-6) were obtained in the same manner as in producing copolymer (A-1), except that the types of (meth)acrylate (a), (meth)acrylate (b) and other monomers and their compounding ratios shown in Tables 1 and 2 were changed.

<Copolymer (A-20)>
A reaction vessel (hereinafter simply referred to as "reaction vessel") equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen inlet tube was charged with 60 parts of lauryl methacrylate, 30 parts of methacrylic acid, 10 parts of acrylic acid, 30 parts of ethyl acetate, 55 parts of MEK, and 0.03 parts of 2,2'-azobisisobutyronitrile under a nitrogen atmosphere. The mixture was heated with stirring to confirm the start of the polymerization reaction, and reacted at the reflux temperature for 2 hours. Next, 0.03 parts of 2,2'-azobisisobutyronitrile was added to the reaction solution, and the reaction was continued for 6 hours. Thereafter, the reaction vessel was cooled, and ethyl acetate was added to adjust the nonvolatile content to 40%, to obtain a copolymer (A-20) solution having a weight average molecular weight of 150,000.

<Copolymer (A-21)>
A reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen inlet tube was charged with 60 parts of lauryl methacrylate, 30 parts of methacrylic acid, 10 parts of acrylic acid, 40 parts of ethyl acetate, 45 parts of MEK, and 0.03 parts of 2,2'-azobisisobutyronitrile under a nitrogen atmosphere. The mixture was heated with stirring to confirm the start of the polymerization reaction and reacted at reflux temperature for 2 hours. Next, 0.03 parts of 2,2'-azobisisobutyronitrile was added to the reaction solution and the reaction was continued for 6 hours. Thereafter, the reaction vessel was cooled, and ethyl acetate was added to adjust the non-volatile content to 40%, to obtain a copolymer (A-21) solution having a weight average molecular weight of 300,000.

<Copolymer (A-22)>
A reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen inlet tube was charged with 60 parts of lauryl methacrylate, 30 parts of methacrylic acid, 10 parts of acrylic acid, 85 parts of ethyl acetate, and 0.03 parts of 2,2'-azobisisobutyronitrile under a nitrogen atmosphere. The mixture was heated with stirring to confirm the start of the polymerization reaction, and reacted at reflux temperature for 2 hours. Next, 0.03 parts of 2,2'-azobisisobutyronitrile was added to the reaction solution, and the reaction was continued for 6 hours. Thereafter, the reaction vessel was cooled, and ethyl acetate was added to adjust the nonvolatile content to 40%, to obtain a copolymer (A-22) solution having a weight average molecular weight of 1.3 million.

<Copolymer (A-23)>
A reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen inlet tube was charged with 60 parts of lauryl methacrylate, 30 parts of methacrylic acid, 10 parts of acrylic acid, 20 parts of acetone, and 0.03 parts of 2,2'-azobisisobutyronitrile under a nitrogen atmosphere. The mixture was heated with stirring to confirm the start of the polymerization reaction, and reacted at reflux temperature for 2 hours. Next, 0.03 parts of 2,2'-azobisisobutyronitrile was added to the reaction solution, and the reaction was continued for 6 hours. Thereafter, the reaction vessel was cooled, and ethyl acetate was added to adjust the nonvolatile content to 40%, to obtain a copolymer (A-23) solution having a weight average molecular weight of 1.5 million.

<Copolymer (A-24)>
A reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen inlet tube was charged with 60 parts of lauryl methacrylate, 30 parts of methacrylic acid, 10 parts of acrylic acid, 55 parts of ethyl acetate, 30 parts of acetone, and 0.03 parts of 2,2'-azobisisobutyronitrile under a nitrogen atmosphere. The mixture was heated with stirring to confirm the start of the polymerization reaction, and reacted at the reflux temperature for 2 hours. Next, 0.03 parts of 2,2'-azobisisobutyronitrile was added to the reaction solution, and the reaction was continued for 6 hours. Thereafter, the reaction vessel was cooled, and ethyl acetate was added to adjust the nonvolatile content to 40%, to obtain a copolymer (A-24) solution having a weight average molecular weight of 1.8 million.

Example compounds are specifically shown in Tables 1 and 2 below, but are not limited to these.

The abbreviations in Tables 1 and 2 are listed below.
[(Meth)acrylate (a)]
NOA: n-octyl acrylate (alkyl group has 8 carbon atoms)
LA: Lauryl acrylate (alkyl group carbon number: 12)
LMA: Lauryl methacrylate (alkyl group has 12 carbon atoms)
STA: Stearyl acrylate (alkyl group carbon number: 18)
[(Meth)acrylate (b)]
MA: methyl acrylate (alkyl group carbon number 1)
BA: Butyl acrylate (alkyl group has 4 carbon atoms)
[Other monomers]
2EHA: 2-ethylhexyl acrylate VAc: vinyl acetate AA: acrylic acid HEA: hydroxyethyl acrylate ISTA: isostearyl acrylate BEA: behenyl acrylate (alkyl group has 21 carbon atoms)
CHA: cyclohexyl acrylate

Example 1
100 parts of the copolymer (A-1) obtained in the above Production Example was mixed with 0.1 parts (non-volatile content) of TETRAD-X (manufactured by Mitsubishi Gas Chemical Company, Inc.) as a curing agent (B), and ethyl acetate was further added as a solvent to adjust the non-volatile content to 30%, to obtain a pressure-sensitive adhesive composition of Example 1. The obtained pressure-sensitive adhesive composition was evaluated according to the measurement and evaluation methods shown below.

<Gel Fraction>
The obtained pressure-sensitive adhesive composition was applied to a release-treated surface of a polyethylene terephthalate (PET) film (thickness: 38 μm) having one side subjected to a release treatment so that the thickness after drying would be 25 μm. Then, after drying at 105° C. for 2 minutes, the coating film was laminated onto a substrate (made of polyethylene terephthalate) having a thickness of 50 μm and aged for 7 days in an atmosphere of 23° C. and 50% RH.
A test piece with a width of 3 mm and a length of 100 mm was cut out from the obtained pressure-sensitive adhesive sheet and its weight was measured. The release sheet was peeled off from the test piece, and the exposed pressure-sensitive adhesive layer was attached to a 300-mesh stainless steel wire mesh, which was folded so that the test piece would not peel off, and the test piece was wrapped in the wire mesh and immersed in ethyl acetate as an extraction solution and left to stand at 50°C for 24 hours. After immersion, the wire mesh was removed, washed with a small amount of ethyl acetate, and dried at 100°C for 30 minutes, and then its weight was measured. The gel fraction was calculated by the following formula (1).
(Gel fraction)={(W2−W0−W3)/(W1−W0−W3)}×100 (Equation 1)
W0: Weight of wire mesh W1: Weight of wire mesh + test piece W2: Weight of wire mesh + test piece after drying W3: Weight of substrate of test piece

<Viscosity>
The viscosity of the resulting pressure-sensitive adhesive composition was measured at 60 revolutions per minute using a Brookfield viscometer in an atmosphere of 23° C. and 50% RH.

<Method of producing decorative sheet>
The obtained pressure-sensitive adhesive composition was applied to the release-treated surface of a polyethylene terephthalate (PET) film (thickness: 38 μm) having one side subjected to a release treatment so that the thickness after drying would be 25 μm. Then, after drying at 105° C. for 2 minutes, the coating film was attached to a commercially available polyvinyl chloride film and aged for 7 days in an atmosphere of 23° C. and 50% RH to prepare a decorative sheet.

<Coatability>
The coatability of the pressure-sensitive adhesive composition when obtaining a decorative sheet by the above-mentioned method was evaluated based on the following evaluation criteria.
(Evaluation criteria)
AA: When coating was performed at coating speeds of 30 m/min and 50 m/min, the coated surface was smooth and no streaks occurred. Very good.
A: When coating was performed at a coating speed of 30 m/min, the coated surface was smooth and free of streaks, but when coating was performed at a coating speed of 50 m/min, one or two streaks occurred on the coated surface. Good.
B: When coating was performed at a coating speed of 30 m/min, one or two streaks occurred on the coated surface.
C: Three or more streaks occurred on the coated surface when coating was performed at a coating speed of 30 m/min. Not suitable for practical use.

<Repositionability>
The decorative sheet obtained by the above-mentioned method was evaluated for re-attachability to an ABS resin plate when attached to the frame of a TOM molding machine (NGF molding machine, manufactured by Fuse Vacuum Co., Ltd.) based on the following evaluation criteria.
(Evaluation criteria)
AA: No peeling marks were left on the sample surface and no peeling noise was heard. Very good.
A: No peeling marks were found on the sample surface, but there was a peeling sound. Good.
B: Peel marks remained partially on the sample surface. Practical use possible.
C: Peel marks remained on the entire surface of the sample. Not suitable for practical use.

<Durability after molding>
The decorative sheet obtained by the above method was attached to the frame of a TOM molding machine (NGF molding machine, manufactured by Fuse Vacuum Co., Ltd.), and then an ABS resin plate of 10 cm x 7 cm x 5 mm thickness was set in the frame. The ABS resin plate was then covered with the decorative sheet and molded at 130°C to obtain a molded product. The molded product was then left for 24 hours in a 23°C-50RH% atmosphere, and a 5 cm long cross was made on the surface of the molded product. The molded product was then left for 168 hours at high temperatures (100°C and 150°C), and was then evaluated for lifting and displacement based on the following criteria.
(Evaluation criteria)
AA: No lifting or peeling, but some misalignment of less than 1 mm occurred. Very good.
A: No lifting or peeling occurred, but there was a misalignment of 1 mm or more and less than 3 mm. Good.
B: No lifting or peeling occurred, but there was a displacement of 3 mm or more and less than 10 mm.
C: Lifting or peeling occurs. Not practical.

<Water-resistant curved surface adhesion retention>
The decorative sheet obtained by the above method was attached to the frame of a TOM molding machine (NGF molding machine, manufactured by Fuse Vacuum Co., Ltd.), and then a 10 cm x 7 cm x 5 mm thick ABS resin plate and a 50 mm diameter cylindrical polypropylene (PP) resin were set in the frame. The cylindrical polypropylene (PP) resin was then molded at 130°C so that the circumferential direction was covered with the decorative sheet to obtain a molded product. The molded product was then left for 24 hours in an atmosphere of 23°C and 50 RH%, after which a 4 cm long cross was made on the surface of the molded product, and the state of the cut part of the measurement sample after immersion in water at 40°C for 24 hours was evaluated based on the following evaluation criteria.
(Evaluation criteria)
AA: No lifting or peeling. Very good.
A: The length of lifting or peeling is more than 0 mm and less than 3 mm. Good.
B: The length of lifting or peeling is 3 mm or more and less than 8 mm.
C: The length of lifting or peeling is 8 mm or more. Not practical.

<Appearance of coating film after molding>
The decorative sheet obtained by the above method was attached to the frame of a TOM molding machine (NGF molding machine, manufactured by Fuse Vacuum Co., Ltd.), and then an ABS resin plate of 10 cm x 7 cm x 5 mm thickness was set in the frame. The ABS resin plate was then covered with the decorative sheet and molded at 130°C to obtain a molded product. The surface condition after molding was evaluated based on the following evaluation criteria.
(Evaluation criteria)
AA: No defects were observed. Very good.
A: 1 or more and less than 5 defects occurred. Good.
B: Five to nine defects occurred. Usable.
C: 10 or more defects occurred. Not practical.

(Examples 2 to 32, Comparative Examples 1 to 7)
The adhesive compositions and adhesive sheets of Examples 2 to 32 and Comparative Examples 1 to 7 were obtained in the same manner as in Example 1, except that the types and amounts of the (meth)acrylic acid ester copolymers (A) and (A') and the curing agent (B) and tackifier contained in the adhesive composition were changed to those shown in Tables 3 and 4. Note that, although the example compounds are specifically shown in Tables 3 and 4, they are not limited thereto.

The abbreviations in Tables 3 and 4 are described below.
[Curing agent (B)]
TETRAD-X: Epoxy crosslinking agent (manufactured by Mitsubishi Gas Chemical Company, Inc., N,N,N',N'-tetraglycidyl-m-xylylenediamine)
TETRAD-C: Epoxy crosslinking agent (manufactured by Mitsubishi Gas Chemical Company, Inc., N,N,N',N'-tetraglycidyl-1,3-bisaminomethylcyclohexane)
TDI-TMP: Trimethylolpropane adduct of tolylene diisocyanate
Aluminum chelate A: Aluminum trisacetylacetonate (Kawaken Fine Chemicals Co., Ltd.)
[Tackifier]
T-130: Terpene resin manufactured by Yasuhara Chemical Co., Ltd. D-125: Rosin resin manufactured by Arakawa Chemical Industries, Ltd. FTR6100: Aromatic hydrocarbon resin manufactured by Mitsui Chemicals, Inc.

The present invention is not limited to the above-described embodiments and examples, and appropriate design changes are possible without departing from the spirit of the present invention.

The pressure-sensitive adhesive composition of the present invention was excellent in coatability, repositionability, durability at high temperatures, water-resistant curved surface adhesion retention, and appearance of molded products, as shown in Examples 1 to 32 in Table 3. In contrast, Comparative Examples 1 to 7 in Table 4 were found to be inferior in the above-mentioned physical properties.
The adhesive composition having the above-mentioned excellent properties can be suitably used for various adhesive processed products such as adhesive films, adhesive sheets, adhesive tapes, and labels. Specific examples of adhesive processed products include adhesive sheets, adhesive films, adhesive tapes, pressure-sensitive tapes, surface protection films, surface protection tapes, masking tapes, electrical insulating tapes, laminates, and the like. Furthermore, the composition of the present invention can be suitably used for decoration of, for example, aircraft, automobiles, railways, interior and exterior building materials, nursing and medical fields, and electrical appliances, and its use is not particularly limited.

Claims (7)

Contains a (meth)acrylic acid ester copolymer (A) and a curing agent (B),
The (meth)acrylic acid ester copolymer (A) is a copolymer of a monomer mixture,
The content of the linear alkyl (meth)acrylate (a) having an alkyl group of 8 to 18 carbon atoms is 10 to 95 mass% in 100 mass% of the monomer mixture.
Adhesive composition for decorative sheets. the monomer mixture constituting the (meth)acrylic acid ester copolymer (A) further contains an alkyl (meth)acrylate (b) having an alkyl group with 1 to 4 carbon atoms;
2. The pressure-sensitive adhesive composition for decorative sheets according to claim 1, wherein the content of the alkyl (meth)acrylate (b) is 1 to 50 mass % based on 100 mass % of the monomer mixture. The adhesive composition for decorative sheets according to claim 1, characterized in that the gel fraction after crosslinking is 50% or more. The adhesive composition for decorative sheets according to claim 1, which is used for attaching decorative sheets to adherends by vacuum forming or vacuum/pressure forming. A decorative sheet comprising a substrate and an adhesive layer made of the adhesive composition for decorative sheets according to any one of claims 1 to 4. A decorative structure comprising an adherend and the decorative sheet according to claim 5. A method for producing a decorative structure, comprising forming a decorative structure by integrating the decorative sheet according to claim 5 with an adherend by vacuum forming or vacuum/pressure forming.