Decorative film

Abstract

One embodiment of the present invention relates to a decorative film comprising: a base material layer having a stress relaxation rate of 40% to 100% (inclusive) as measured by a stress relaxation test, a stress of 2.0 N or less after 30 seconds, and a pressure-sensitive adhesive layer having a pressure-sensitive adhesive layer, the stress relaxation rate being 40% to 100% (inclusive) as measured by a stress relaxation test; the ratio of the loss tangent value at 80 DEG C to the loss tangent value at 23 DEG C (80 DEG C loss tangent value / 23 DEG C loss tangent value) of the adhesive layer measured by a dynamic viscoelasticity test is 0.45-0.80, and the peeling distance of the adhesive layer measured by a constant load peeling test is less than 100 mm.

Description

Technical Field

[0001] One embodiment of the present invention relates to a decorative film. Background Art

[0002] Three-dimensional decorative molding (TOM molding) is a technique that enables affixing a decorative film while conforming to the surface of an adherend having a complex shape with curves or irregularities. For example, Patent Document 1 has been proposed as a decorative film used therein. However, during molding, the decorative film is adhered to the adherend in a heated and stretched state. Therefore, after molding, the base layer will generate shrinkage stress. Over time, the ends of the decorative film may shift, peel, float, and other undesirable conditions. These undesirable conditions may occur significantly, especially when placed in a high-temperature environment (such as outdoors in summer). Furthermore, avoiding these problems requires that the results vary not only depending on the type of adhesive layer, but also on the type of substrate layer and the type of adherend used. Therefore, conventionally, it has been impossible to evaluate the durability of decorative films other than through installation evaluation or similar evaluation methods. Prior art literature Patent Literature

[0003] Patent Document 1: Japanese Patent Application Laid-Open No. 2012-213891 Summary of the Invention Technical problem to be solved by the invention

[0004] It is clear that there is room for improvement in the durability of existing decorative films, and there is room for finding appropriate parameters for different constituent materials.

[0005] One of the technical problems of the present invention is to provide a decorative film which is less likely to cause adhesion failures such as shrinkage displacement, peeling, and lifting at the ends of the decorative film even in a high-temperature environment and can exhibit high durability. Technical solutions used to solve technical problems

[0006] The present inventors have conducted intensive studies and have found that the above-mentioned technical problems can be solved by combining a substrate layer having predetermined stress relaxation properties with a pressure-sensitive adhesive layer having excellent constant-load releasability for low-polarity adherends, thereby completing the present invention.

[0007] The present invention relates to, for example, the following [1] to [4]. [1] A decorative film comprising a base material layer and an adhesive layer, wherein: The stress relaxation rate of the substrate layer measured by the following stress relaxation test is 40% or more and 100% or less, and the stress after 30 seconds is 2.0N or less. The ratio of the loss tangent value at 80°C to the loss tangent value at 23°C (80°C loss tangent value / 23°C loss tangent value) of the adhesive layer measured by a dynamic viscoelasticity test is 0.45 to 0.80, and The peeling distance of the adhesive layer measured by the following constant load peeling test is less than 100 mm, [Stress relaxation test] When a 25 mm wide substrate is stretched 50% at a temperature 10°C higher than the softening temperature of the substrate, with a chuck distance of 5 mm and a stretching speed of 1000 mm / min, the stress immediately after stretching (initial stress) and the stress when the stretched state is maintained for 30 seconds (stress after 30 seconds) are measured. The stress relaxation rate is calculated using the following formula: Stress relaxation rate (%) = (([initial stress] - [stress after 30 seconds]) / [initial stress]) × 100 [Constant load peeling test] A 100 mm × 10 mm test piece was cut out from a PSA sheet for a constant load peelability test consisting of a 25 μm thick PSA layer and a 25 μm thick polyethylene terephthalate film on one side of the PSA layer. The PSA layer was attached to a polypropylene plate (test plate) and allowed to stand at 80°C for 20 minutes. The test plate was then horizontally positioned at 80°C with the surface to which the test piece was attached facing downward. A load of 50 g was applied to one end of the test piece in the longitudinal direction so that the peel angle of the test piece was 90 degrees. The distance (peel distance, mm) that the test piece peeled from the surface of the test plate 2 hours after the load was applied was measured.

[0008] [2] The decorative film according to [1], wherein the adhesive layer is composed of an adhesive composition comprising a (meth)acrylic copolymer (A) and a crosslinking agent (B).

[0009] [3] The decorative film according to [1] or [2], wherein the adhesive layer has a gel fraction of 40% or more.

[0010] [4] The decorative film according to any one of [1] to [3], which is used for three-dimensional decorative molding. Effects of the Invention

[0011] According to one embodiment of the present invention, a decorative film can be provided which is less likely to cause adhesion failures such as shrinkage displacement, peeling, and lifting at the edges of the decorative film even in a high-temperature environment and can exhibit high durability. DETAILED DESCRIPTION

[0012] Hereinafter, the present invention will be described in detail. In the present invention, "(meth)acrylic acid" is used as a general term for acrylic acid and methacrylic acid. For example, "(meth)acrylic acid" refers to acrylic acid or methacrylic acid. Furthermore, in the present invention, unless otherwise specified, "A to B" indicating a numerical range means greater than A and less than B.

[0013] [Decorative film] A decorative film according to one embodiment of the present invention includes a base material layer and an adhesive layer. The stress relaxation rate of the substrate layer measured by the following stress relaxation test is 40% or more and 100% or less, and the stress after 30 seconds is 2.0N or less. The ratio of the loss tangent value at 80°C to the loss tangent value at 23°C (80°C loss tangent value / 23°C loss tangent value) of the adhesive layer measured by a dynamic viscoelasticity test is 0.45 to 0.80, and The adhesive layer has a peeling distance of less than 100 mm as measured by the following constant load peeling test. [Stress relaxation test] When a 25 mm wide substrate is stretched 50% at a temperature 10°C higher than the softening temperature of the substrate, with a chuck distance of 5 mm and a stretching speed of 1000 mm / min, the stress immediately after stretching (initial stress) and the stress when the stretched state is maintained for 30 seconds (stress after 30 seconds) are measured. The stress relaxation rate is calculated using the following formula: Stress relaxation rate (%) = (([initial stress] - [stress after 30 seconds]) / [initial stress]) × 100 Here, the softening temperature of the base material is a value measured in accordance with JIS K 7196 (1991). [Constant load peeling test] A 100 mm × 10 mm test piece was cut out from a PSA sheet for a constant load peelability test consisting of a 25 μm thick PSA layer and a 25 μm thick polyethylene terephthalate film on one side of the PSA layer. The PSA layer was attached to a polypropylene plate (test plate) and allowed to stand at 80°C for 20 minutes. The test plate was then horizontally positioned at 80°C with the surface to which the test piece was attached facing downward. A load of 50 g was applied to one end of the test piece in the longitudinal direction so that the peel angle of the test piece was 90 degrees. The distance (peel distance, mm) that the test piece peeled from the surface of the test plate 2 hours after the load was applied was measured.

[0014] In one embodiment of the decorative film of the present invention, a base layer with a predetermined stress relaxation property is combined with an adhesive layer having excellent constant-load releasability for low-polarity adherends (e.g., polypropylene (PP)). This reduces the likelihood of poor adhesion at the interface with the low-polarity adherend. Furthermore, the adhesive layer itself exhibits excellent stress relaxation properties, thereby suppressing the occurrence of poor adhesion caused by the concentration of shrinkage stress in the base layer. Furthermore, the adhesive layer exhibits moderate viscoelasticity (loss tangent ratio) across a wide temperature range, from room temperature (23°C) to high temperatures (80°C), providing sufficient adhesive performance over a wide temperature range.

[0015] In the decorative film of one embodiment of the present invention, the base layer preferably plays a decorative role, but a decorative layer may also be provided. In addition, the decorative film of one embodiment of the present invention may also have a release film on the adhesive layer to protect the adhesive layer before use.

[0016] <Base Material Layer> The base layer typically forms the outermost layer of a decorative molded article, formed by attaching a decorative film to an adherend. The base material constituting the base layer can be colored or colorless, and can be transparent, translucent, or opaque. Furthermore, the base layer is typically in the form of a film or sheet and can be a single layer or comprise multiple layers, such as a decorative layer, primer, or hard coat.

[0017] The stress relaxation rate of the substrate layer, as measured by the aforementioned stress relaxation test, is 40% to 100%, preferably 45% to 95%, and more preferably 50% to 90%. If the stress relaxation rate is within this range, adhesion defects such as peeling or lifting of the decorative film over time are less likely to occur.

[0018] The stress of the substrate layer after 30 seconds, as measured by the aforementioned stress relaxation test, is 2.0 N or less, preferably 0.01 N to 1.5 N or less, and more preferably 0.01 N to 1.0 N or less. If the stress relaxation rate is within this range, adhesion defects such as peeling or lifting of the decorative film over time are less likely to occur.

[0019] The base layer is not particularly limited, but is preferably composed of a thermoplastic resin, more preferably composed of at least one selected from polyvinyl chloride, polyethylene, polypropylene, polycarbonate, polymethyl methacrylate, and acrylonitrile / butadiene / styrene (ABS) resin.

[0020] As required, the substrate layer can also contain inorganic particles such as silicon dioxide, plasticizers, colorants, ultraviolet absorbers and other functional materials. In addition, the substrate surface can be printed with patterns, characters and designs for giving design, or patterns, characters and designs can be formed inside the substrate. The substrate layer is preferably in the form of a film or a sheet. The thickness of the substrate layer is preferably 10 to 1000 μm, more preferably 20 to 500 μm, and even more preferably 50 to 300 μm.

[0021] <Adhesive Layer> The adhesive layer of the decorative film according to one embodiment of the present invention is formed from an adhesive composition described below, preferably an adhesive composition containing a (meth)acrylic copolymer (A) and a crosslinking agent (B).

[0022] In the Examples described below, the ratio of the loss tangent at 80°C to the loss tangent at 23°C (80°C loss tangent / 23°C loss tangent), as measured by a dynamic viscoelasticity test in accordance with JIS K7244, for the adhesive layer is 0.45 to 0.80, preferably 0.45 to 0.70, and more preferably 0.45 to 0.65. When the 80°C loss tangent / 23°C loss tangent is within this range, adhesion defects such as peeling and lifting of the decorative film over time are less likely to occur.

[0023] The peel distance of the adhesive layer measured by the above-mentioned constant load peelability test is less than 100 mm, preferably less than 75 mm, and more preferably less than 50 mm. If it exceeds 100 mm, the adhesive sheet may fall off. A peel distance of less than 100 mm is preferred because it is less likely to float or peel over time after application.

[0024] (Adhesive Sheet) The adhesive sheet includes the adhesive layer and a release film provided on one or both sides of the adhesive layer. The details of the method for preparing the adhesive sheet are described in the examples below. The pressure-sensitive adhesive sheet for a constant-load peelability test according to one embodiment of the present invention comprises the 25 μm-thick pressure-sensitive adhesive layer and a 25 μm-thick polyethylene terephthalate film located on one surface of the pressure-sensitive adhesive layer.

[0025] The PSA sheet can also be used to measure the gel fraction of the PSA layer. Details of the method for measuring the gel fraction are described in the Examples below. The gel fraction of the adhesive layer is preferably 40% or greater, more preferably 50% or greater, and even more preferably 55% or greater. On the other hand, the gel fraction of the adhesive layer is preferably 100% or less, more preferably 90% or less, and even more preferably 80% or less. When the gel fraction is within this range, the resulting adhesive layer exhibits adequate cohesive strength, and the decorative film exhibits high durability.

[0026] The adhesive layer can be obtained, for example, by applying the adhesive composition on a substrate or a decorative layer and crosslinking it as needed. That is, a known method can be used, for example, a method of applying the adhesive composition to a specified thickness and drying it by spin coating, knife coating, roller coating, rod coating, doctor blade coating, die coating, or gravure coating. More specifically, for example, the adhesive composition is applied to a substrate or a decorative layer, preferably dried at 60 to 120° C., more preferably at 70 to 110° C., preferably for 1 to 10 minutes, more preferably for 2 to 5 minutes, to form a coating film. Then, it is cured (aged) for preferably more than 1 day, more preferably for 2 to 10 days, under an environment of preferably 5 to 60° C., more preferably 15 to 50° C. and preferably 30 to 70% RH, more preferably 40 to 70% RH. If crosslinking is performed under the above-mentioned aging conditions, a crosslinked body (network polymer) can be efficiently formed. The thickness of the adhesive layer is preferably 3 to 1000 μm, more preferably 5 to 500 μm.

[0027] (Adhesive composition) The pressure-sensitive adhesive composition contains a (meth)acrylic copolymer (A) and other components as needed.

[0028] (Meth)acrylic acid copolymer (A) The (meth)acrylic copolymer (A) (hereinafter also referred to as "copolymer (A)") is a copolymer comprising monomer components of an alkyl (meth)acrylate monomer (a1) and a carboxyl group-containing monomer (a2), and is obtained by copolymerizing these monomer components. The monomer components may further comprise a hydroxyl group-containing monomer (a3), a nitrogen-containing monomer (a4), and / or other monomers in addition to the alkyl (meth)acrylate monomer (a1) and the carboxyl group-containing monomer (a2).

[0029] <<Alkyl (meth)acrylate monomer (a1)>> The (meth)acrylate alkyl ester monomer (a1) preferably has an alkyl group with a carbon number of 1 to 20, more preferably 1 to 10, and may be an alkyl (meth)acrylate. Specifically, the esters include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, oleyl (meth)acrylate, n-stearyl (meth)acrylate, and isostearyl (meth)acrylate.

[0030] The (meth)acrylic copolymer (A) may have one or two or more structural units derived from the (meth)acrylate monomer (a1). The content of the alkyl (meth)acrylate monomer (a1) in the total monomer components used to obtain the copolymer (A) is preferably in the range of 40 to 97% by mass, more preferably 50 to 97% by mass, even more preferably 60 to 97% by mass, and particularly preferably 70 to 97% by mass. Furthermore, the content of the structural units derived from the alkyl (meth)acrylate monomer (a1) in the copolymer (A) is preferably in the range of 40 to 97% by mass, more preferably 50 to 97% by mass, even more preferably 60 to 97% by mass, and particularly preferably 70 to 97% by mass.

[0031] 《Carboxyl group-containing monomer (a2)》 As the carboxyl group-containing monomer (a2), any monomer containing a carboxyl group and a polymerizable double bond can be used without particular limitation. Examples thereof include: (meth)acrylic acid, itaconic acid, crotonic acid, fumaric acid, and maleic acid; anhydride group-containing monomers such as phthalic anhydride and maleic anhydride; and carboxyl group-containing (meth)acrylates such as β-carboxyethyl (meth)acrylate, 5-carboxypentyl (meth)acrylate, mono(meth)acryloyloxyethyl succinate, and ω-carboxypolycaprolactone mono(meth)acrylate. The carboxyl group-containing monomer (a2) includes an anhydride group-containing monomer that generates a carboxyl group by ring-opening.

[0032] The (meth)acrylic copolymer (A) may have one or two or more structural units derived from the carboxyl group-containing monomer (a2). In the total monomer components used to obtain the copolymer (A), the content of the carboxyl group-containing monomer (a2) is preferably 1% by mass or more and less than 15% by mass, more preferably 1 to 12% by mass, further preferably 1 to 10% by mass, and particularly preferably 1 to 8% by mass. In addition, the structural units derived from the carboxyl group-containing monomer (a2) in the copolymer (A) are preferably 1% by mass or more and less than 15% by mass, more preferably 1 to 12% by mass, further preferably 1 to 10% by mass, and particularly preferably 1 to 8% by mass.

[0033] By using the adhesive composition containing the copolymer (A) obtained by copolymerizing the carboxyl group-containing monomer (a2) in the above amount, the adhesive layer of the resulting decorative film tends to have excellent durability.

[0034] 《Hydroxy-containing monomer (a3)》 Examples of the hydroxyl group-containing monomer (a3) ​​include hydroxyl group-containing (meth)acrylates of the (meth)acrylate type such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 8-hydroxyoctyl (meth)acrylate.

[0035] The content of the hydroxyl-containing monomer (a3) ​​in the total monomer components used to obtain the (meth)acrylic copolymer (A) is preferably 0.1 to 10% by mass, more preferably 0.1 to 5% by mass, and even more preferably 0.1 to 3% by mass. Furthermore, the content of the structural units derived from the hydroxyl-containing monomer (a3) ​​in the copolymer (A) is preferably 0.1 to 10% by mass, more preferably 0.1 to 5% by mass, and even more preferably 0.1 to 3% by mass.

[0036] In the adhesive composition, when the (meth)acrylic copolymer (A) is a copolymer containing a monomer component of the hydroxyl group-containing monomer (a3), the adhesive layer of the resulting decorative film tends to have excellent durability. When the content of the hydroxyl group-containing monomer (a3) ​​in the total monomer components for obtaining the copolymer (A) is preferably 10% by mass or less, more preferably 5% by mass or less, the durability of the adhesive layer of the resulting decorative film tends to be excellent. The (meth)acrylic copolymer (A) containing the nitrogen-containing monomer (a4) may also be a copolymer comprising the aforementioned alkyl (meth)acrylate monomer (a1), the carboxyl group-containing monomer (a2), and the hydroxyl group-containing monomer (a3), and further comprising a nitrogen-containing monomer (a4). Specifically, the copolymer (A) may have structural units derived from the nitrogen-containing monomer (a4).

[0037] As the nitrogen-containing monomer (a4), any monomer containing nitrogen and having a polymerizable double bond can be used without particular limitation. Examples thereof include amino group-containing monomers, amide group-containing monomers, nitrogen-containing heterocyclic monomers, and cyano group-containing monomers. Preferably, an amino group-containing monomer, i.e., a monomer containing an amino group and having a polymerizable double bond, is used. In this case, amino groups include, in addition to groups represented by -NH2, groups represented by -NHR, and groups represented by -NR2. Here, R is, for example, an alkyl group.

[0038] Examples of amino group-containing monomers include N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, and other N,N-dialkylaminoalkyl (meth)acrylates. Examples of amide group-containing monomers include N-alkyl (meth)acrylamides such as (meth)acrylamide, N-methyl (meth)acrylamide, N-ethyl (meth)acrylamide, N-propyl (meth)acrylamide, and N-hexyl (meth)acrylamide; and N,N-dialkyl (meth)acrylamides such as N,N-dimethyl (meth)acrylamide and N,N-diethyl (meth)acrylamide. Examples of nitrogen-containing heterocyclic monomers include N-vinylpyrrolidone, N-vinylcaprolactam, and (meth)acryloylmorpholine. Examples of cyano group-containing monomers include cyano (meth)acrylate and (meth)acrylonitrile.

[0039] Examples of the nitrogen-containing monomer (a4) include N,N-dialkylaminoalkyl (meth)acrylates such as N,N-dimethylaminoethyl (meth)acrylate and N,N-diethylaminoethyl (meth)acrylate. The number of carbon atoms in the dialkylaminoalkyl group in the N,N-dialkylaminoalkyl (meth)acrylate is preferably 3 to 20, more preferably 3 to 10.

[0040] The content of the nitrogen-containing monomer (a4) in the total monomer components used to obtain the (meth)acrylic copolymer (A) is preferably 0.1 to 10% by mass, more preferably 0.1 to 5% by mass, and even more preferably 0.1 to 3% by mass. Furthermore, the content of the structural unit derived from the nitrogen-containing monomer (a4) in the copolymer (A) is preferably 0.1 to 10% by mass, more preferably 0.1 to 5% by mass, and even more preferably 0.1 to 3% by mass.

[0041] In the adhesive composition, when the (meth)acrylic copolymer (A) is a copolymer containing a monomer component of the nitrogen-containing monomer (a4), the durability of the adhesive layer of the resulting decorative film tends to be excellent. When the content of the nitrogen-containing monomer (a4) in the total monomer components for obtaining the copolymer (A) is preferably 10% by mass or less, more preferably 5% by mass or less, the durability of the adhesive layer of the resulting decorative film tends to be excellent. <Other Monomers> The (meth)acrylic copolymer (A) may have structural units derived from monomers other than (a1) to (a4) described above. Examples of such other monomers include (meth)acrylates containing alicyclic hydrocarbon groups or aromatic hydrocarbon groups, alkoxypolyalkylene glycol mono(meth)acrylates, styrene monomers, vinyl acetate, and macromonomers.

[0042] Examples of the (meth)acrylate containing an alicyclic hydrocarbon group or an aromatic hydrocarbon group include cyclohexyl (meth)acrylate, benzyl (meth)acrylate and phenyl (meth)acrylate.

[0043] Examples of the alkoxypolyalkylene glycol mono(meth)acrylate include methoxydiethylene glycol mono(meth)acrylate, methoxydipropylene glycol mono(meth)acrylate, ethoxytriethylene glycol mono(meth)acrylate, ethoxydiethylene glycol mono(meth)acrylate and methoxytriethylene glycol mono(meth)acrylate.

[0044] Examples of the styrene monomer include styrene; alkyl styrenes such as methylstyrene, dimethylstyrene, trimethylstyrene, propylstyrene, butylstyrene, hexylstyrene, heptylstyrene, and octylstyrene; halogenated styrenes such as fluorostyrene, chlorostyrene, bromostyrene, and dibromostyrene; and functionalized styrenes such as nitrostyrene, acetylstyrene, and methoxystyrene.

[0045] The macromonomer has a polymerizable unsaturated group. Examples of the polymerizable unsaturated group include ethylenically unsaturated double bonds. One example is a polymer having a (meth)acryloyl group at the terminal.

[0046] The polymerizable unsaturated groups of the macromonomer are introduced into the copolymer (A) from the macromonomer, for example, through a free radical polymerization reaction with other monomers constituting the copolymer (A). Thus, side chains based on the macromonomer are formed in the copolymer (A). These side chains are believed to prevent the molecules of the copolymer (A) from being closely packed together, resulting in a more flexible structure for the adhesive layer.

[0047] The macromonomer is a polymer having a number average molecular weight (Mn) of preferably 500 to 100,000, more preferably 1,000 to 50,000, and even more preferably 2,000 to 20,000. In this specification, the number average molecular weight (Mn) refers to the standard ethylene-equivalent number average molecular weight measured by gel permeation chromatography (GPC).

[0048] The glass transition temperature (Tg) of the macromonomer is preferably 50 to 180° C., more preferably 80 to 150° C. The Tg of the macromonomer can be a value obtained by the Fox equation, or a value listed in a catalogue when a commercial product is used.

[0049] Fox formula: 1 / Tg=(W1 / Tg1)+(W2 / Tg2)+……+(Wm / Tgm)W1+W2+……+Wm=1 In the above formula, Tg is the glass transition temperature (K) of the (meth)acrylic copolymer (A), Tg1, Tg2, ..., Tgm are the glass transition temperatures (K) of the homopolymers formed from the respective monomers, and W1, W2, ..., Wm are the mass fractions of the structural units derived from the respective monomers in the copolymer (A). The mass fraction of the structural units derived from the respective monomers can be determined by the ratio of the monomers charged to the total monomers during copolymer synthesis.

[0050] When calculating using the Fox equation, the glass transition temperature (Tg) of a homopolymer formed from each monomer can be, for example, the value described in "Polymer Handbook Fourth Edition" (Wiley-Interscience 2003).

[0051] Examples of monomers that constitute the polymer chain (main chain) portion of the macromonomer include (meth)acrylate alkyl esters, preferably having an alkyl group with 1 to 20 carbon atoms, (meth)acrylonitrile, and styrene-based monomers such as styrene and α-methylstyrene. Preferred macromonomers include (meth)acrylic acid-based macromonomers, (meth)acrylonitrile-based macromonomers, and styrene-based macromonomers. Such macromonomers can be produced by various known methods, for example, by the method described in paragraph

[0039] of Japanese Patent Application Laid-Open No. 2013-018227.

[0052] Among other monomers, (meth)acrylates and styrene-based monomers containing an alicyclic hydrocarbon group or an aromatic hydrocarbon group are preferred.

[0053] The (meth)acrylic copolymer (A) may have one or two or more structural units derived from other monomers. The content of other monomers in the total monomer components used to obtain the (meth)acrylic copolymer (A) is preferably 47% by mass or less, more preferably 41% by mass or less, and even more preferably 35% by mass or less. Furthermore, the content of structural units derived from other monomers in the copolymer (A) is preferably 47% by mass or less, more preferably 41% by mass or less, and even more preferably 35% by mass or less.

[0054] <<Physical Properties and Production Method of (Meth)Acrylic Copolymer (A)>> The (meth)acrylic polymer (A) can be obtained by polymerizing the above-mentioned monomer components. Examples of the polymerization method include conventionally known methods such as solution polymerization, bulk polymerization, emulsion polymerization, and suspension polymerization, with solution polymerization being preferred.

[0055] For example, a polymerization solvent and monomer components are placed in a reaction vessel, a polymerization initiator is added, the reaction starting temperature is preferably set to 40 to 100° C., more preferably 50 to 90° C., the reaction system is maintained at a temperature of preferably 50 to 90° C., preferably 70 to 90° C., and the reaction is allowed to proceed for 2 to 20 hours. The polymerization reaction can be carried out under an inert gas atmosphere such as nitrogen.

[0056] The (meth)acrylic polymer (A) can be obtained by polymerizing the above-mentioned monomer components, but may be, for example, a random copolymer or a block copolymer. Among these, a random copolymer is preferred.

[0057] Examples of the polymerization solvent include aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as n-pentane, n-hexane, n-heptane, and n-octane; alicyclic hydrocarbons such as cyclopentane, cyclohexane, cycloheptane, and cyclooctane; ethers such as diethyl ether, isopropyl ether, 1,2-dimethoxyethane, butyl ether, tetrahydrofuran, dioxane, anisole, phenethyl ether, and diphenyl ether; halogenated hydrocarbons such as chloroform, carbon tetrachloride, 1,2-dichloroethane, and chlorobenzene; esters such as ethyl acetate, propyl acetate, butyl acetate, and methyl propionate; ketones such as acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, and cyclohexanone; amides such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; nitriles such as acetonitrile and benzonitrile; and sulfoxides such as dimethyl sulfoxide and sulfolane. One or more polymerization solvents may be used.

[0058] The polymerization initiator may, for example, be an azo initiator or a peroxide initiator. Examples of the azo initiator include 2,2'-azobisisobutyronitrile, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), 2-(carbamoylazo)isobutyronitrile, 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, and 2,2'-azobis(2-cyclopropylpropionitrile). 2'-Azobis(2-amidinopropane), 2,2'-azobis(N,N'-dimethyleneisobutylamidine), 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)-propionamide], 2,2'-azobis(isobutylamide) dihydrate, 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis(2-cyanopropanol), dimethyl-2,2'-azobis(2-methylpropionate), 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide].

[0059] Examples of the peroxide initiator include tert-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, benzoyl hydroperoxide, lauroyl hydroperoxide, hexyl hydroperoxide, diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, tert-butyl peroxypivalate, 2,2-bis(4,4-di-tert-butylperoxycyclohexyl)propane, 2,2-bis(4,4-di-tert-acylperoxycyclohexyl)propane, 2,2-bis(4,4-di-tert-octylperoxycyclohexyl)propane, 2,2-bis(4,4-di-α-cumylperoxycyclohexyl)propane, 2,2-bis(4,4-di-tert-butylperoxycyclohexyl)butane, and 2,2-bis(4,4-di-tert-octylperoxycyclohexyl)butane.

[0060] The polymerization initiator may be used alone or in combination of two or more. The polymerization initiator is preferably used in an amount within the range of 0.01 to 5 parts by mass, more preferably 0.05 to 3 parts by mass, per 100 parts by mass of the monomer components of the (meth)acrylic copolymer (A). Furthermore, one or more selected from the monomer components, polymerization initiator, and polymerization solvent may be added as appropriate during the polymerization reaction.

[0061] <<Physical Properties of (Meth)Acrylic Copolymer (A)>> The weight average molecular weight (Mw) of the (meth)acrylic copolymer (A) as measured by gel permeation chromatography (GPC) is preferably 200,000 to 2,000,000, more preferably 300,000 to 1,500,000, and even more preferably 400,000 to 1,200,000. Such a form tends to provide a pressure-sensitive adhesive having excellent durability.

[0062] The ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the (meth)acrylic copolymer (A), i.e., the molecular weight distribution (Mw / Mn), is preferably 2 to 15, more preferably 3 to 13, and even more preferably 4 to 11. With such a configuration, a PSA having excellent durability tends to be obtained. Mw, Mn and Mw / Mn can be measured by gel permeation chromatography (GPC).

[0063] The glass transition temperature (Tg) of the (meth)acrylic copolymer (A) is preferably -60°C or higher, more preferably -55 to -10°C, and even more preferably -50 to -15°C. Such a configuration tends to yield an adhesive with excellent removability. The glass transition temperature can be calculated using the aforementioned Fox equation.

[0064] Crosslinking agent (B) The pressure-sensitive adhesive composition may contain a crosslinking agent (B) in addition to the (meth)acrylic copolymer (A). The crosslinking agent (B) is not particularly limited as long as it is a component capable of undergoing a crosslinking reaction with the (meth)acrylic copolymer (A). Examples of the crosslinking agent (B) include epoxy crosslinking agents, metal chelate crosslinking agents, and isocyanate crosslinking agents.

[0065] The crosslinking agent (B) may be used alone or in combination of two or more. In the adhesive composition, the content of the crosslinking agent (B) is preferably 0.01 to 30 parts by mass, more preferably 0.01 to 20 parts by mass, and even more preferably 0.01 to 10 parts by mass, relative to 100 parts by mass of the (meth)acrylic copolymer (A). This configuration provides an adhesive having a sufficiently and appropriately formed crosslinked structure, high cohesive strength, an excellent balance of adhesive properties, and excellent durability.

[0066] Epoxy crosslinking agent Examples of epoxy crosslinking agents include epoxy compounds having two or more epoxy groups per molecule, specifically ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-m-xylenediamine, N,N,N',N'-tetraglycidylaminophenylmethane, triglycidyl isocyanurate, m-N,N-diglycidylaminophenylglycidyl ether, N,N-diglycidyltoluidine, and N,N-diglycidylaniline. The number of epoxy groups per molecule of these epoxy compounds is, for example, 2 to 10. One or more epoxy crosslinking agents may be used.

[0067] Metal chelate crosslinkers Examples of metal chelate crosslinking agents include compounds formed by coordination with polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium, such as alkoxides, acetylacetone, and ethyl acetoacetate. Among these, aluminum chelate compounds are preferred. Specific examples include aluminum isopropoxide, aluminum sec-butyrate, ethylaluminum diisopropyl acetoacetate, aluminum trisacetoacetate, and aluminum trisacetylacetonate. The metal chelate cross-linking agent may be used alone or in combination of two or more.

[0068] Isocyanate crosslinking agents The isocyanate crosslinking agent may, for example, be an isocyanate compound having two or more isocyanate groups in one molecule.

[0069] Examples of diisocyanate compounds having two isocyanate groups per molecule include aliphatic diisocyanates, alicyclic diisocyanates, and aromatic diisocyanates. Examples of isocyanate compounds having three or more isocyanate groups per molecule include aromatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates. Examples of isocyanate compounds include multimers (e.g., dimers or trimers, biuret forms, isocyanurate forms), derivatives (e.g., addition reaction products of polyols with two or more diisocyanate molecules), and polymers of the above-mentioned isocyanate compounds having two or more isocyanate groups. The isocyanate crosslinking agent may be used alone or in combination of two or more.

[0070] Viscosity imparting agent (C) The pressure-sensitive adhesive composition may further contain a tackifier (C) in addition to the (meth)acrylic copolymer (A) and the crosslinking agent (B). In the pressure-sensitive adhesive composition, the content of the tackifier (C) is preferably 1 to 50 parts by mass, more preferably 3 to 40 parts by mass, and even more preferably 5 to 30 parts by mass, based on 100 parts by mass of the (meth)acrylic copolymer (A). The tackifier is not particularly limited, and examples thereof include rosin-based tackifiers, terpene-based tackifiers, phenol-based tackifiers, hydrocarbon-based tackifiers, ketone-based tackifiers, polyamide-based tackifiers, epoxy-based tackifiers, and elastomer-based tackifiers. One or more tackifiers may be used.

[0071] Examples of rosin-based tackifiers include unmodified rosins (raw rosins) such as gum rosin, wood rosin, and tall oil rosin; modified rosins obtained by modifying these unmodified rosins by polymerization, disproportionation, hydrogenation, etc. (polymerized rosin, stabilized rosin, disproportionated rosin, fully hydrogenated rosin, partially hydrogenated rosin, and other chemically modified rosins); and various rosin derivatives. Examples of the rosin derivatives include rosin phenolic resins obtained by adding phenol to rosins (unmodified rosin, modified rosin, and various rosin derivatives) under the action of an acid catalyst and thermally polymerizing the rosin; Rosin ester resins such as rosin ester compounds obtained by esterifying unmodified rosin with alcohols (unmodified rosin esters), and modified rosin ester compounds (polymerized rosin esters, stabilized rosin esters, disproportionated rosin esters, fully hydrogenated rosin esters, partially hydrogenated rosin esters, etc.) obtained by esterifying modified rosins such as polymerized rosin, stabilized rosin, disproportionated rosin esters, fully hydrogenated rosin esters, partially hydrogenated rosin esters, etc. with alcohols; Unsaturated fatty acid-modified rosin resins obtained by modifying unmodified rosin or modified rosin (polymerized rosin, stabilized rosin, disproportionated rosin, fully hydrogenated rosin, partially hydrogenated rosin, etc.) with unsaturated fatty acids; Unsaturated fatty acid modified rosin ester resin obtained by modifying rosin ester resin with unsaturated fatty acid; Rosin alcohol resins obtained by reducing the carboxyl groups in unmodified rosin, modified rosin (polymerized rosin, stabilized rosin, disproportionated rosin, fully hydrogenated rosin, partially hydrogenated rosin, etc.), unsaturated fatty acid-modified rosin resins, or unsaturated fatty acid-modified rosin ester resins; Metal salts of rosin resins (especially rosin ester resins) such as unmodified rosin, modified rosin, and various rosin derivatives.

[0072] Examples of terpene viscosity-imparting agents include terpene resins such as α-pinene polymers, β-pinene polymers, and dipentene polymers, and modified terpene resins obtained by modifying these terpene resins (phenol modification, aromatic modification, hydrogenation modification, hydrocarbon modification, etc.) (e.g., terpene phenolic resins, styrene-modified terpene resins, aromatic-modified terpene resins, hydrogenated terpene resins, etc.).

[0073] Examples of the phenolic viscosity-imparting agent include condensates of various phenols (e.g., phenol, m-cresol, 3,5-xylenol, p-alkylphenol, resorcinol, etc.) with formaldehyde (e.g., alkylphenol-formaldehyde resins, xylene-formaldehyde resins, etc.), resol resins obtained by an addition reaction of the above-mentioned phenols with formaldehyde in the presence of an alkali catalyst, and novolac resins obtained by a condensation reaction of the above-mentioned phenols with formaldehyde in the presence of an acid catalyst.

[0074] Examples of hydrocarbon viscosity-imparting agents include various hydrocarbon resins such as aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic / aromatic petroleum resins (styrene-olefin copolymers, etc.), aliphatic / alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone resins, and coumarone-indene resins.

[0075] additive In addition to the above components, the adhesive composition may further contain at least one selected from a resin component other than the above-mentioned (meth)acrylic copolymer, an antistatic agent, a silane coupling agent, an ultraviolet absorber, an antioxidant, a plasticizer, a defoaming agent, a filler, a stabilizer, a softener, and a wettability modifier, within a range that does not impair the effects of the present invention.

[0076] organic solvents The adhesive composition preferably contains an organic solvent in order to adjust its coating properties. Examples of the organic solvent include aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as n-pentane, n-hexane, n-heptane, and n-octane; alicyclic hydrocarbons such as cyclopentane, cyclohexane, cycloheptane, and cyclooctane; ethers such as diethyl ether, diisopropyl ether, 1,2-dimethoxyethane, dibutyl ether, tetrahydrofuran, dioxane, anisole, phenethyl ether, and diphenyl ether; halogenated hydrocarbons such as chloroform, carbon tetrachloride, 1,2-dichloroethane, and chlorobenzene; esters such as ethyl acetate, propyl acetate, butyl acetate, and methyl propionate; ketones such as acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, and cyclohexanone; amides such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; nitriles such as acetonitrile and benzonitrile; and sulfoxides such as dimethyl sulfoxide and sulfolane.

[0077] One or more organic solvents may be used. The content of the organic solvent in the adhesive composition is preferably 0 to 90% by mass, more preferably 10 to 80% by mass.

[0078] (Method for producing adhesive composition) The adhesive composition can be produced by mixing the above-mentioned components sequentially or simultaneously by a known method. Specifically, the PSA composition can be prepared by mixing a (meth)acrylic copolymer (A) and, if necessary, other components such as a crosslinking agent (B), a tackifier (C), additives, and an organic solvent using a conventionally known method. In one embodiment, for example, the crosslinking agent (B), a tackifier (C), and additives can be added, if necessary, to a polymer solution containing the (meth)acrylic copolymer (A) and an organic solvent, obtained during the synthesis of the polymer.

[0079] <Decorative layer> The decorative film of one embodiment of the present invention may further include a decorative layer between the base layer and the adhesive layer or on the base layer. The decorative layer is provided to impart design to the decorative film and is a layer for displaying patterns, text, or designs.

[0080] <Release Film> The decorative film according to one embodiment of the present invention may, if desired, have a release film on the adhesive layer. The release film protects the adhesive surface before the decorative film is actually used and is removed when the decorative film is used. The release film is not particularly limited as long as it facilitates release from the adhesive layer. Examples include resin films, specifically films of polyesters such as polyethylene terephthalate and polybutylene terephthalate; and films of polyolefins such as polyethylene, polypropylene, and ethylene-vinyl acetate copolymer. At least one surface of the release film may be treated to facilitate release using a release treatment agent such as a silicone, fluorine-based, long-chain alkyl, or fatty acid amide-based release agent. The thickness of the release film is preferably 10 to 500 μm, more preferably 25 to 200 μm.

[0081] [Method for producing decorative film] In producing the decorative film according to one embodiment of the present invention, any method capable of forming a decorative film having a substrate layer and an adhesive layer can be employed without particular limitation. Examples include: a method in which an adhesive composition is applied to a substrate layer and dried to form an adhesive layer; a method in which a release film is attached to the adhesive layer of the decorative film obtained by this method, as needed; and a method in which an adhesive composition is applied to a release film and dried to form an adhesive layer, and the exposed surface of the resulting adhesive layer not in contact with the release film is attached to a substrate serving as the substrate layer and cured.

[0082] The adhesive layer can be obtained by applying the adhesive composition described above onto a substrate or a release film constituting the substrate layer and drying it. Drying conditions vary depending on the type of organic solvent contained in the composition, the thickness of the adhesive layer, etc., but are generally dried at a temperature of 50 to 150°C and for a time of 1 to 10 minutes.

[0083] Examples of a method for applying the adhesive composition include spin coating, knife coating, roll coating, bar coating, doctor blade coating, die coating and gravure coating.

[0084] Curing conditions are as follows, for example. Curing is preferably performed at 5 to 60°C, more preferably 15 to 50°C, and preferably at 30 to 70% RH, more preferably at 40 to 70% RH, for at least one day, more preferably 2 to 10 days. When crosslinking is performed under these curing conditions, a crosslinked product (network polymer) composed of the (meth)acrylic copolymer (A) and the crosslinking agent (B) can be efficiently formed.

[0085] <Applications and Decorative Molded Articles> The decorative film according to one embodiment of the present invention is preferably used for three-dimensional decoration (TOM) molding. The decorative molded body having the decorative film according to one embodiment of the present invention is a decorated molded body in which the decorative film is attached to at least a portion of the surface of a molded body serving as an adherend.

[0086] Adherends for the decorative film according to one embodiment of the present invention include shaped articles such as three-dimensional objects. Specifically, these include exterior and interior decorative materials for mobile objects, building materials, and vanity panels. Furthermore, the term "mobile object" broadly encompasses vehicles with wheels and endless tracks, such as passenger cars, buses, trucks, motorcycles, scooters, mopeds, and bulldozers; railways such as trams, monorails, and linear electric locomotives; aircraft such as airplanes, helicopters, and drones; and ships.

[0087] The adherend of the decorative film according to one embodiment of the present invention may be a low-polarity adherend such as an olefin resin, which may be surface-treated by a coating or the like. Examples of olefin resins include polypropylene (PP), polyethylene, and ethylene-propylene rubber (EPR). Olefin resins also include composite materials of PP and EPR, such as Toyota Super Olefin Polymer (TSOP).

[0088] Examples of a method for attaching the decorative film to a molded object as an adherend include manual attachment, vacuum forming, compressed air forming, and hot high-pressure forming. Among these, vacuum forming is preferred.

[0089] The decorative molded article comprises a molded article (the adherend) and a substrate with an adhesive layer, wherein the adhesive layer is formed by applying the adhesive layer to the surface of the molded article and removing a release film from the decorative film. More specifically, the decorative molded article comprises, in this order, a molded article, an adhesive layer, a decorative layer (if applicable), and a substrate. Example

[0090] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples.

[0091] <Synthesis Method of (Meth) Acrylic Copolymer (A)> [Synthesis example 1] In a reaction apparatus equipped with a stirrer, a reflux cooler, a thermometer, and a nitrogen inlet tube, 20 parts by mass of methyl methacrylate (MA), 72 parts by mass of n-butyl acrylate (BA), 8 parts by mass of acrylic acid (AA), and 100 parts by mass of ethyl acetate were added, and the temperature was raised to 70°C while introducing nitrogen. Subsequently, 0.1 parts by mass of 2,2'-azobisisobutyronitrile (hereinafter also referred to as "AIBN") was added, and a polymerization reaction was carried out at 75-76°C under a nitrogen atmosphere for 4 hours to synthesize a (meth)acrylic copolymer (A1). After the reaction was completed, the reaction solution was diluted with ethyl acetate to prepare a polymer solution. The resulting (meth)acrylic copolymer (A1) had a glass transition temperature (Tg) (calculated using the Fox equation) of -32°C, a weight-average molecular weight (Mw) of 850,000, and a molecular weight distribution (Mw / Mn) of 3.0. The weight-average molecular weight (Mw) and molecular weight distribution (Mw / Mn) were determined by the following methods.

[0092] [Weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn)] The weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of the obtained (meth)acrylic copolymer (A) in terms of standard polystyrene were determined by gel permeation chromatography (GPC) under the following conditions. ·Measuring device: HLC-8220GPC (manufactured by Tosoh Corporation) GPC column configuration: The following five columns (all manufactured by Tosoh Corporation) (1)TSK-GEL HXL-H (guard column) (2)TSK-GEL G7000HXL (3)TSK-GEL GMHXL (4)TSK-GEL GMHXL (5)TSK-GEL G2500HXL Sample concentration: Dilute with tetrahydrofuran to a concentration of 1.0 mg / cm 3 Mobile phase solvent: tetrahydrofuran Flow rate: 1.0cm 3 / minute Column temperature: 40°C

[0093] [Synthesis example 2] A (meth)acrylic copolymer (A2) was synthesized in the same manner as in Synthesis Example 1, except that the types and amounts of the monomers used were changed as described in Table 1, and the amount of AIBN was changed to 0.12 parts by mass. The Tg, Mw, and Mw / Mn of the resulting copolymer (A2) are also shown in Table 1.

[0094] [Synthesis Examples 3, 5, 6] (Meth)acrylic copolymers (A3), (Meth)acrylic copolymers (A5), and (Meth)acrylic copolymers (A6) were synthesized in the same manner as in Synthesis Example 1, except that the types and amounts of the monomers used were changed as described in Table 1, and the amount of AIBN was changed to 0.09 parts by mass. The Tg, Mw, and Mw / Mn of the resulting copolymers (A3), (A5), and (A6) are collectively shown in Table 1.

[0095] [Synthesis Example 4] A (meth)acrylic copolymer (A4) was synthesized in the same manner as in Synthesis Example 1, except that the types and amounts of the monomers used were changed as described in Table 1, and the amount of AIBN was changed to 0.16 parts by mass. The Tg, Mw, and Mw / Mn of the resulting copolymer (A4) are also shown in Table 1.

[0096] [Synthesis Examples 7 and 8] (Meth)acrylic acid copolymers (A7) and (Meth)acrylic acid copolymers (A8) were synthesized in the same manner as in Synthesis Example 1, except that the types and amounts of the monomers used were changed as described in Table 1. The Tg, Mw, and Mw / Mn of the resulting copolymers (A7) and (A8) are also shown in Table 1.

[0097] [Table 1]

[0098] The monomers used in the above Table 1 are as follows. MA: Methyl methacrylate BA: n-butyl acrylate 2EHA: 2-ethylhexyl acrylate AA: Acrylic acid HEA: 2-Hydroxyethyl Acrylate VAc: vinyl acetate

[0099] [Example 1] [Preparation of Adhesive Composition] To the polymer solution of the copolymer (A1) obtained in Synthesis Example 1, 5 parts by mass of an isocyanate crosslinking agent L-45K (manufactured by Soken Chemical Industries, Ltd.) in terms of solid content and 10 parts by mass of a tackifier D135 (manufactured by Arakawa Chemical Industries, Ltd.) in terms of solid content were added relative to 100 parts by mass of the copolymer (A1) to obtain an adhesive composition (I).

[0100] [Preparation of Adhesive Sheet] The degassed PSA composition (I) was applied to a release-treated polyethylene terephthalate (release film) using a doctor blade and dried at 80°C for 3 minutes to form a coating having a dry film thickness of 25 μm. A release film was further applied to the opposite side of the coating to the adhesive surface of the release film. After aging for 7 days in a 23°C / 50% RH environment, a PSA sheet having a 25 μm thick PSA layer sandwiched between two release films was obtained.

[0101] [Production of decorative film] The degassed PSA composition (I) was applied to a release-treated polyethylene terephthalate (release film) using a doctor blade and dried at 80°C for 5 minutes to produce a sheet having a 50 μm-thick coating. A 225 μm-thick polyvinyl chloride (PVC) film (substrate 1) was attached to the coated surface of the sheet and aged at 23°C / 50% RH for 7 days to produce a decorative film comprising the release film, a 50 μm-thick PSA layer, and the PVC film. The details of the substrates used are shown in Table 2.

[0102] [Table 2]

[0103] [Examples 2 to 9, Comparative Examples 1 to 9] A PSA composition was obtained in the same manner as in Example 1, except that the type and amount of the (meth)acrylic copolymer (A), the type and amount of the crosslinking agent (B), the type and amount of the tackifier (C), and the type of the substrate were changed as described in Tables 3 and 4. In Tables 3 and 4, the amount of the crosslinking agent is expressed as a solid content (parts by mass) per 100 parts of each (meth)acrylic copolymer. Next, using the obtained adhesive composition, an adhesive sheet and a decorative film were prepared in the same manner as in Example 1, and various physical properties were evaluated. The results are shown in Tables 3 and 4.

[0104] <Evaluation Methods of Physical Properties> [Measurement of gel fraction] Approximately 0.1 g of the adhesive layer was collected from the prepared adhesive sheet and placed in a sample bottle. 30 mL of ethyl acetate was added and shaken for 4 hours. The contents of the sample bottle were then filtered through a 200-mesh stainless steel mesh. The residue on the mesh was dried at 100°C for 2 hours, and the dry mass was measured. The gel fraction of the adhesive layer was calculated using the following formula. Gel fraction (%) = (dry weight / adhesive collection weight) × 100 (%)

[0105] [Evaluation of viscoelasticity] The adhesive layer for viscoelasticity evaluation was prepared using the following procedure. First, a 25 μm thick adhesive layer formed on a release film was laminated onto a 25 μm thick adhesive layer formed on another release film under a 23°C / 50% RH environment. The layer was then autoclaved at 50°C / 5 atm for 20 minutes to produce a 50 μm thick adhesive layer. One release film was peeled off, and the 25 μm thick adhesive layer formed on the other release film was laminated. This process was repeated to produce a total adhesive layer thickness of 1.0 mm. For this 1.0 mm thick adhesive layer, a viscoelastic spectrum was measured using the "Physica MCR300" manufactured by Anton Paar using the dynamic viscoelasticity measurement method in accordance with JIS K7244 (temperature range -40 to 180°C, heating rate 3.67°C / minute, frequency 1 Hz). The loss tangent (tan δ) at temperatures of 23°C and 80°C was measured, and the ratio of the loss tangent values ​​(80°C loss tangent value / 23°C loss tangent value) was calculated.

[0106] [Evaluation of Constant Load Peelability] The degassed adhesive composition was applied to a polyethylene terephthalate (PET) film having a thickness of 25 μm using a doctor blade and dried at 80°C for 3 minutes to form an adhesive layer having a dry film thickness of 25 μm, thereby forming an adhesive sheet for constant load peelability measurement. A 100 mm × 10 mm test piece was then cut out from the adhesive sheet, and the adhesive layer was attached to a polypropylene (PP) plate and placed under 80°C for 20 minutes. The test plate was then horizontally arranged at 80°C with the surface of the test piece facing downward, and a load of 50 g was applied to one end of the length direction of the test piece with the peeling angle of the test piece being 90 degrees. The distance (peeling distance, mm) of the test piece peeled off from the surface of the test plate 2 hours after the load was applied was measured. When the peeling distance was above 100 mm, the test piece fell off.

[0107] [Softening temperature] The softening temperature of the substrate was measured using a thermomechanical analyzer (TMA / SS6100, manufactured by Hitachi High-Technologies Corporation) in accordance with JIS K 7196 (1991) under the following conditions: an indenter diameter of 1.0 mm, a load of 0.5 N, and a heating rate of 5°C / min.

[0108] [Evaluation of stress relaxation rate] The stress (initial stress, N / mm) immediately after stretching a 25 mm wide substrate was measured when the substrate was stretched 50% at a temperature 10°C higher than the softening temperature of the substrate, with a chuck distance of 5 mm and a stretching speed of 1000 mm / min. 2) and the stress when the tensile state is maintained for 30 seconds (stress after 30 seconds, N / mm 2 ), the stress relaxation rate is calculated by the following formula: Stress relaxation rate (%) = (([initial stress] - [stress after 30 seconds]) / [initial stress]) × 100

[0109] [Durability Evaluation] Using a TOM molding machine (Fuse Vacuum Co., Ltd., NGF molding machine), the decorative film, with the single-sided release film removed, was molded onto an ABS sheet at an area stretching ratio of 20% to produce a decorative molded article. A 10 cm cross-section was then cut in the center of the molded decorative film using a cutter. The film was then left at 80°C for 400 hours. The film was then removed to a 23°C / 50% RH environment, and the appearance of the cut section was evaluated according to the following criteria. (Evaluation Criteria) ○: Displacement distance is less than 0.5mm △: Displacement distance is 0.5mm~2.0mm ×: Displacement distance is greater than 2.0 mm or peeling occurs

[0110] [Table 3]

[0111] [Table 4]

[0112] As the crosslinking agent (B) and tackifier (C) described in Tables 3 and 4 above, the commercially available products shown below were used. Crosslinking agent (B) L-45K: Isocyanate crosslinking agent (manufactured by Soken Chemical Co., Ltd.) E-5XM: Epoxy crosslinking agent (manufactured by Soken Chemical Co., Ltd.) Viscosity imparting agent (C) SEA-100: Rosin-based tackifier (manufactured by Arakawa Chemical Industries, Ltd.) KE-311: Rosin-based tackifier (manufactured by Arakawa Chemical Industries, Ltd.) D135: Rosin-based tackifier (manufactured by Arakawa Chemical Industries, Ltd.) D160: Rosin-based tackifier (manufactured by Arakawa Chemical Industries, Ltd.) DP2669: Rosin-based tackifier (manufactured by Harima Chemicals Co., Ltd.) FTR6100: Styrene-based tackifier (Mitsui Chemicals, Inc.)

[0113] In Examples 1 to 9, shrinkage displacement was suppressed even in a high-temperature environment, and decorative films having excellent durability were obtained. On the other hand, in Comparative Examples 1 to 9, the shrinkage displacement was large, and adhesion failures such as peeling occurred, resulting in insufficient durability.

Claims

1. A decorative film comprising a base material layer and an adhesive layer, wherein: The stress relaxation rate of the substrate layer measured by the following stress relaxation test is 40% or more and 100% or less, and the stress after 30 seconds is 2.0N or less. The ratio of the loss tangent value at 80°C to the loss tangent value at 23°C (80°C loss tangent value / 23°C loss tangent value) of the adhesive layer measured by a dynamic viscoelasticity test is 0.45 to 0.80, and The peeling distance of the adhesive layer measured by the following constant load peeling test is less than 100 mm, [Stress relaxation test] When a 25 mm wide substrate is stretched 50% at a temperature 10°C higher than the softening temperature of the substrate, with a chuck distance of 5 mm and a stretching speed of 1000 mm / min, the stress immediately after stretching (initial stress) and the stress when the stretched state is maintained for 30 seconds (stress after 30 seconds) are measured. The stress relaxation rate is calculated using the following formula: Stress relaxation rate (%) = (([initial stress] - [stress after 30 seconds]) / [initial stress]) × 100 [Constant load peeling test] A 100 mm × 10 mm test piece was cut out from a PSA sheet for a constant load peelability test consisting of a 25 μm thick PSA layer and a 25 μm thick polyethylene terephthalate film on one side of the PSA layer. The PSA layer was attached to a polypropylene plate (test plate) and allowed to stand at 80°C for 20 minutes. The test plate was then horizontally positioned at 80°C with the surface to which the test piece was attached facing downward. A load of 50 g was applied to one end of the test piece in the longitudinal direction so that the peel angle of the test piece was 90 degrees. The distance (peel distance, mm) that the test piece peeled from the surface of the test plate 2 hours after the load was applied was measured.

2. The decorative film according to claim 1, wherein The adhesive layer is composed of an adhesive composition containing a (meth)acrylic copolymer (A) and a crosslinking agent (B).

3. The decorative film according to claim 1 or 2, wherein: The gel fraction of the adhesive layer is greater than 40%. The decorative film according to any one of claims 1 to 3, which is used for three-dimensional decorative molding.

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