Adhesive composition for decorative film and use thereof

Abstract

The present invention provides an adhesive composition for a finishing film, which has good initial re-adhesion, high durability, and excellent whitening resistance, a finishing film using the adhesive composition, and a molded body having the finishing film. The adhesive composition for a finishing film of the present invention contains a specific amount of a (meth)acrylic copolymer (A) and a specific amount of a (meth)acrylic copolymer (B), the (meth)acrylic copolymer (A) is obtained by copolymerization of a monomer component containing 50% by mass or more of a (meth)acrylic acid alkoxyalkyl ester monomer (a1) and 2% by mass or more of a carboxyl group-containing monomer (a2), the (meth)acrylic copolymer (B) is obtained by copolymerization of a monomer component containing 1 to 10% by mass of a nitrogen-containing monomer (b1), and the (meth)acrylic copolymer (B) has a glass transition point of 0°C or higher.

Description

Technical Field

[0001] The present invention relates to an adhesive composition for decorative film, a decorative film using the adhesive composition for decorative film, and a molded body having the decorative film. Background Technology

[0002] Recently, due to the trend of reducing volatile organic compounds (VOCs), there has been an increasing trend among automakers to use trim films with adhesive layers as a substitute for exterior coatings. One of the requirements for the adhesives used in these trim films is initial re-tack. Initial re-tack refers to the following property: easy to peel off and easy to re-apply in the event of misalignment when the trim film has been bonded to the substrate. Furthermore, it is required to have high durability and not peel off after the trim has been molded.

[0003] Patent Document 1 discloses a decorative film comprising an adhesive layer containing a specific vinyl polymer and an acrylic adhesive polymer. Furthermore, Patent Document 2 discloses a decorative film having a pressure-sensitive adhesive layer and an acrylic resin film layer, wherein the pressure-sensitive adhesive layer comprises a (meth)acrylic polymer containing carboxyl groups and a (meth)acrylic polymer having amino groups capable of forming metal complexes with metal ions generated based on a metal substrate. The teaching derived from this is that these decorative films or finishing films possess long-term stable adhesion and excellent durability.

[0004] In addition, in regions with high temperature and humidity throughout the year, the adhesive layer may whiten during use. In particular, when the substrate film is transparent or has low opacity, appearance defects may occur. Therefore, the adhesive layer of the decorative film is required to have whitening resistance.

[0005] However, in reality, no adhesive for decorative films has yet been found that exhibits good initial re-adhesion, high durability, and excellent resistance to whitening.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent document 1: Japanese Patent Application Publication No. 2019-112574.

[0009] Patent document 2: Japanese Patent No. 6574109. Summary of the Invention

[0010] The technical problem that the invention aims to solve

[0011] The technical problem of the present invention is to provide an adhesive composition for decorative films that has good initial tack, high durability and excellent whitening resistance, a decorative film using the adhesive composition for decorative films, and a molded body having the decorative film.

[0012] Technical solutions adopted to solve technical problems

[0013] The inventors have devoted themselves to research in order to solve the above-mentioned technical problems, and as a result, they discovered that the above-mentioned technical problems can be solved by using the following structure, thereby completing the present invention. The present invention relates, for example, to [1] to [7] below.

[0014] [1] An adhesive composition for decorative films, said adhesive composition comprising (meth)acrylic copolymer (A) and (meth)acrylic copolymer (B), said (meth)acrylic copolymer (A) being copolymerized from monomer components containing 50% by mass or more of (meth)acrylic alkoxyalkyl ester monomer (a1) and 2% by mass or more of carboxyl-containing monomer (a2),

[0015] The (meth)acrylic acid copolymer (B) is copolymerized from monomer components containing 1-10% by mass of a nitrogen-containing monomer (b1), and has a glass transition point above 0°C.

[0016] in,

[0017] The copolymer (B) comprises 2 or more parts by mass relative to 100 parts by mass of the (meth)acrylic copolymer (A).

[0018] [2] The adhesive composition for decorative films as described in [1], wherein the carboxyl-containing monomer (a2) in the monomer component constituting the (meth)acrylic copolymer (A) is 2 to 10% by mass.

[0019] The copolymer (B) comprises 2 to 20 parts by weight of the (meth)acrylic copolymer (A) relative to 100 parts by weight of the copolymer (A).

[0020] [3] A decorative film comprising: an adhesive layer formed of the adhesive composition for decorative films described in [1] or [2]; and a substrate layer.

[0021] [4] The decorative film as described in [3], wherein the substrate layer is composed of at least one selected from polyvinyl chloride, polyethylene, polypropylene, polycarbonate, polymethyl methacrylate, and ABS.

[0022] [5] The trimming film as described in [3] or [4], wherein the trimming film is used for interior or exterior parts of a vehicle.

[0023] [6] The decorative film as described in any one of [3] to [5], wherein the decorative film is used for exterior parts of a vehicle.

[0024] [7] A decorative molded article having any one of [3] to [6] decorative film.

[0025] Invention Effects

[0026] According to the present invention, an adhesive composition for finishing films that combines good initial re-adhesion, high durability, and excellent resistance to whitening is provided; a finishing film using the adhesive composition for finishing films; and a molded article having the finishing film. The adhesive composition for finishing films of the present invention is suitable for the adhesive layer of finishing films, and finishing films using it exhibit excellent initial re-adhesion, durability, and resistance to whitening. The finishing film of the present invention can be used for surface finishing of various molded articles, and is particularly suitable for finishing applications on interior and exterior parts of vehicles such as automobiles and trains. Detailed Implementation

[0027] The present invention will now be described in detail.

[0028] In this invention, "(meth)acrylic acid" is used collectively to refer to acrylic acid and methacrylic acid. For example, "(meth)acrylic acid" refers to either acrylic acid or methacrylic acid. Furthermore, in this invention, unless otherwise specified, the numerical range A to B refers to values ​​above A and below B.

[0029] <Adhesive Composition for Decorative Films>

[0030] The adhesive composition for decorative films of the present invention is a composition containing (meth)acrylic copolymer (A), (meth)acrylic copolymer (B), and other components as needed.

[0031] (Meth)acrylic acid copolymer (A)

[0032] (Meth)acrylic acid copolymer (A) is a copolymer of monomer components, which includes more than 50% by mass of (meth)acrylic acid alkoxyalkyl ester monomer (a1) and more than 2% by mass of carboxyl-containing monomer (a2). (Meth)acrylic acid copolymer (A) is obtained by copolymerizing the above monomer components.

[0033] Generally speaking, monomer components are monomers containing polymerizable double bonds.

[0034] Alkoxyalkyl (meth)acrylate monomers (a1)

[0035] The adhesive composition for decorative films of the present invention comprises a (meth)acrylic copolymer (A) with structural units derived from (meth)acrylic alkoxyalkyl ester monomer (a1) as the main component. Therefore, the adhesive layer obtained using this composition exhibits improved water absorption, and moisture absorbed into the adhesive layer under high humidity conditions is dispersed within the adhesive layer, thus suppressing moisture-induced whitening. Therefore, even when the decorative film of the present invention is used in applications such as vehicle interior and exterior trim materials exposed to external air, whitening of the adhesive layer is often suppressed for a long period.

[0036] Furthermore, the adhesive composition for decorative films of the present invention contains a (meth)acrylic copolymer (A) with structural units derived from (meth)acrylic alkoxyalkyl ester monomer (a1) as the main component. Therefore, the wettability of the obtained adhesive layer on the surface of the adherend is reduced, and the adhesive force immediately after bonding is suppressed to a lower level. As a result, the initial re-adhesion of the decorative film is often improved.

[0037] The number of carbon atoms in the alkoxyalkyl group of the (meth)acrylate alkoxyalkyl ester monomer (a1) is typically 2 to 18, preferably 2 to 12, and more preferably 2 to 10. Examples of (meth)acrylate alkoxyalkyl ester monomers (a1) include methoxymethyl methacrylate, 2-methoxyethyl methacrylate, 2-ethoxyethyl methacrylate, 3-methoxypropyl methacrylate, 3-ethoxypropyl methacrylate, 4-methoxybutyl methacrylate, and 4-ethoxybutyl methacrylate.

[0038] (Meth)acrylic copolymers (A) may have structural units derived from one or more (meth)acrylic alkoxyalkyl ester monomers (a1).

[0039] The amount of (meth)acrylate alkoxyalkyl ester monomer (a1) in all monomer components used to obtain the (meth)acrylate copolymer (A) is 50% by mass or more, preferably 50 to 98% by mass, more preferably 50 to 97% by mass, even more preferably 55 to 96% by mass, and particularly preferably 60 to 95% by mass. When the amount of (meth)acrylate alkoxyalkyl ester monomer (a1) is 50% by mass or more, the water absorption of the adhesive layer can be improved, and the water entering the adhesive layer can be dissolved and captured by the adhesive layer, which often improves the resistance to whitening. When it is 98% by mass or less, it is beneficial for high adhesion.

[0040] Furthermore, the (meth)acrylic acid copolymer (A) has 50% by mass or more of structural units derived from the (meth)acrylic acid alkoxyalkyl ester monomer (a1), preferably 50-98% by mass, more preferably 50-97% by mass, even more preferably 55-96% by mass, and particularly preferably 60-95% by mass. The amount of these structural units can be determined, for example, based on the amount of monomer components added. The same applies to the amounts of other structural units.

[0041] <Monomers containing carboxyl groups (a2)>

[0042] As the monomer containing a carboxyl group (a2), monomers containing both a carboxyl group and a polymerizable double bond can be used without restriction. However, preferred monomers include, for example, (meth)acrylic acid, itaconic acid, crotonic acid, fumaric acid, and maleic acid; phthalic anhydride and maleic anhydride, etc., monomers containing anhydride groups; β-carboxyethyl (meth)acrylic acid, 5-carboxypentyl (meth)acrylic acid; mono(meth)acryloyloxyethyl succinate, ω-carboxylated polycaprolactone mono(meth)acrylic acid, etc., which contain carboxyl groups. The monomer containing a carboxyl group (a2) includes monomers containing anhydride groups that generate a carboxyl group by ring-opening.

[0043] (Meth)acrylic acid copolymers (A) may have structural units derived from one or more carboxyl-containing monomers (a2).

[0044] The amount of carboxyl-containing monomer (a2) in all monomer components used to obtain the (meth)acrylic acid copolymer (A) is 2% by mass or more, preferably 2 to 15% by mass, more preferably 2 to 12% by mass, further preferably 3 to 10% by mass, even more preferably 4 to 10% by mass, and particularly preferably 5 to 8% by mass. Furthermore, the (meth)acrylic acid copolymer (A) has 2% by mass or more of structural units derived from the carboxyl-containing monomer (a2), preferably 2 to 15% by mass, more preferably 2 to 12% by mass, further preferably 3 to 10% by mass, even more preferably 4 to 10% by mass, and particularly preferably 5 to 8% by mass.

[0045] By using an adhesive composition for decorative films containing a (meth)acrylic copolymer (A), which is obtained by copolymerizing a monomer composition containing the above-mentioned amount of a carboxyl-containing monomer (a2), the wettability of the adhesive layer of the decorative film on the surface of the adhered object is reduced, and the adhesion force immediately after application is suppressed to a lower level. Therefore, the initial re-adhesion of the decorative film is often improved.

[0046] By using an adhesive composition for decorative films containing a (meth)acrylic copolymer (A), which is obtained by copolymerizing a carboxyl-containing monomer (a2) in the aforementioned amount, the adhesive layer of the resulting decorative film tends to have increased adhesive strength after a certain period of time from when it is applied to the substrate, thus exhibiting high adhesive strength.

[0047] <Other Individuals>

[0048] The (meth)acrylic acid copolymer (A) of the present invention may also have structural units derived from other monomers besides (a1) to (a2) described above. Examples of other monomers include, for instance, alkyl (meth)acrylic acid esters, (meth)acrylic acid esters containing alicyclic or aromatic hydrocarbon groups, alkoxy polyalkylene glycol mono(meth)acrylic acid esters, styrene monomers, monomers containing hydroxyl groups, monomers containing amino groups, monomers containing amide groups, monomers containing nitrogen heterocycles, monomers containing cyano groups, vinyl acetate, and polymerizable macromolecular monomers.

[0049] The alkyl group in alkyl methacrylates preferably has 1 to 20 carbon atoms. Examples of alkyl methacrylates include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, n-nonyl methacrylate, isononyl methacrylate, n-decyl methacrylate, isodecyl methacrylate, undecyl methacrylate, lauryl methacrylate, oleoyl methacrylate, stearyl methacrylate, and isostearyl methacrylate.

[0050] Examples of (meth)acrylates containing alicyclic or aromatic hydrocarbon groups include cyclohexyl (meth)acrylate, benzyl (meth)acrylate, and phenyl (meth)acrylate.

[0051] Examples of alkoxy polyalkylene glycol mono(meth)acrylates include, for example, methoxy diethylene glycol mono(meth)acrylate, methoxy dipropylene glycol mono(meth)acrylate, ethoxy triethylene glycol mono(meth)acrylate, ethoxy diethylene glycol mono(meth)acrylate, and methoxy triethylene glycol mono(meth)acrylate.

[0052] Examples of styrene monomers include: styrene; alkyl styrene such as methylstyrene, dimethylstyrene, trimethylstyrene, propylstyrene, butylstyrene, hexylstyrene, heptylstyrene, and octylstyrene; halogenated styrene such as fluorostyrene, chlorostyrene, bromostyrene, and dibromostyrene; and functionalized styrene such as nitrostyrene, acetylstyrene, and methoxystyrene.

[0053] Examples of monomers containing carboxyl groups include 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, 6-hydroxyhexyl methacrylate, 8-hydroxyoctyl methacrylate, and other hydroxyalkyl methacrylates containing carboxyl groups.

[0054] Examples of monomers containing an amino group include N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, and other N,N-dialkylaminoalkyl (meth)acrylates. Examples of monomers containing an amide group include (meth)acrylamide, N-methyl (meth)acrylamide, N-ethyl (meth)acrylamide, N-propyl (meth)acrylamide, N-hexyl (meth)acrylamide, and other N-alkyl (meth)acrylamides; N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, and other N,N-dialkyl (meth)acrylamides. Examples of monomers containing a nitrogen heterocycle include N-vinylpyrrolidone, N-vinylcaprolactam, and (meth)acryloylmorpholine. Examples of monomers containing a cyano group include (meth)acrylate cyanoester and (meth)acrylonitrile.

[0055] Examples of monomers constituting the polymer chain (main chain) portion of polymerizable macromonomers include alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, and tert-butyl methacrylate, wherein the alkyl group preferably has 1 to 20 carbon atoms. Other examples include styrene monomers such as methacrylonitrile, styrene, and α-methylstyrene. Preferably, the macromonomers are methacrylic acid macromonomers, methacrylonitrile macromonomers, and styrene macromonomers.

[0056] Among other monomers, alkyl (meth)acrylates, (meth)acrylates containing alicyclic hydrocarbon groups or aromatic hydrocarbon groups, and styrene monomers are preferred, with alkyl (meth)acrylates being more preferred.

[0057] (Meth)acrylic acid copolymers (A) may have structural units derived from one or more other monomers.

[0058] The amount of other monomers in all 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, in the (meth)acrylic copolymer (A), the amount of structural units derived from other monomers is preferably 47% by mass or less, more preferably 41% by mass or less, and even more preferably 35% by mass or less.

[0059] Physical Properties and Manufacturing Methods of (Meth)acrylic Acid Copolymers (A)

[0060] The weight-average molecular weight (Mw) of the (meth)acrylic acid copolymer (A), as determined by gel permeation chromatography (GPC), is typically 200,000 to 2,000,000, preferably 400,000 to 1,500,000, and more preferably 500,000 to 1,000,000. With such a configuration, adhesives exhibiting excellent high-temperature durability are often obtained.

[0061] The ratio of Mw to number-average molecular weight (Mn) of the (meth)acrylic acid copolymer (A), i.e., the molecular weight distribution (Mw / Mn), is typically 2 to 15, preferably 2.5 to 10, and more preferably 3 to 8. With such a configuration, adhesives with excellent high-temperature durability are often obtained.

[0062] Mw and Mw / Mn can be determined, for example, by the methods described in the examples.

[0063] The glass transition temperature (Tg) of (meth)acrylic acid copolymer (A) is generally above -70°C and below 0°C, preferably -70 to -30°C. Such a configuration often results in adhesives with excellent adhesion at room temperature. The glass transition temperature can be calculated using the so-called Fox formula. The same applies to (meth)acrylic acid copolymer (B), which will be discussed later.

[0064] Fox's formula: 1 / Tg=(W1 / Tg1)+(W2 / Tg2)+…+(Wm / Tgm)

[0065] W1 + W2 + ... + Wm = 1

[0066] In the above formula, Tg is the glass transition temperature (K) of the (meth)acrylic acid copolymer (A), Tg1, Tg2, ..., Tgm are the glass transition temperatures (K) of the homopolymers formed from each monomer, and W1, W2, ..., Wm are the mass fractions of the structural units derived from each monomer in the above (meth)acrylic acid copolymer (A). The mass fraction of the structural units derived from each monomer can be obtained by using the proportion of each monomer added during copolymer synthesis.

[0067] When performing calculations using the Fox formula, the glass transition temperature (Tg) of the homopolymer formed by each monomer can, for example, be the value described in the fourth edition of the Polymer Handbook (Wiley-Interscience 2003).

[0068] It is possible to use one or more (meth)acrylic acid copolymers (A).

[0069] In the adhesive composition for decorative films of the present invention, the total content of (meth)acrylic copolymer (A) and (meth)acrylic copolymer (B) (described later) is typically 60% by mass or more, preferably 65% ​​by mass or more, and more preferably 70% by mass or more, of 100% by mass of the solid components of the adhesive composition. Solid components refer to components excluding organic solvents.

[0070] (Meth)acrylic acid copolymers (A) can be manufactured by known methods, preferably by solution polymerization. Specifically, monomer components and polymerization solvents are added to a reaction vessel, a polymerization initiator is added, and the mixture is heated to a reaction temperature of approximately 50–90°C for 2–20 hours. For example, polymerization can be carried out in an inert gas environment such as nitrogen. Furthermore, polymerization initiators, chain transfer agents, monomer components, and polymerization solvents can be appropriately added to the polymerization reaction.

[0071] Organic solvents that can be listed as polymerization solvents are those described later.

[0072] As polymerization initiators, examples include organic polymerization initiators, specifically peroxides such as benzoyl peroxide and lauroyl peroxide, and azo compounds such as 2,2'-azobisisobutyronitrile. Among these, azo compounds are preferred. One or more polymerization initiators can be used.

[0073] Generally, the amount of polymerization initiator used is 0.01 to 5 parts by mass relative to 100 parts by mass of monomer. In this form, the Mw of the (meth)acrylic acid copolymer (A) can be adjusted to an appropriate range.

[0074] (Meth)acrylic acid copolymer (B)

[0075] (Meth)acrylic acid copolymers (B) are copolymers formed by copolymerizing monomer components containing nitrogen-containing monomers, and their glass transition temperature is above 0°C.

[0076] In the adhesive composition for decorative films of the present invention, a specific amount of (meth)acrylic copolymer (B) is contained as the adhesive resin relative to (meth)acrylic copolymer (A), thereby enabling the formation of an adhesive layer with excellent properties such as whitening resistance, adhesion, and initial re-tack.

[0077] Nitrogen-containing monomers (b1)

[0078] As the nitrogen-containing monomer (b1), monomers containing nitrogen and polymerizable double bonds are used without particular limitation. Examples include monomers containing amino groups, monomers containing amide groups, monomers containing nitrogen-containing heterocycles, and monomers containing cyano groups. However, monomers containing amino groups, i.e., monomers containing amino groups and polymerizable double bonds, are preferred. Here, amino groups include, in addition to groups represented by -NH2, groups represented by, for example, -NHR and -NR2. Here, R is, for example, an alkyl group.

[0079] Examples of monomers containing an amino group include N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, and other N,N-dialkylaminoalkyl (meth)acrylates. Examples of monomers containing an amide group include (meth)acrylamide, N-methyl (meth)acrylamide, N-ethyl (meth)acrylamide, N-propyl (meth)acrylamide, N-hexyl (meth)acrylamide, and other N-alkyl (meth)acrylamides; N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, and other N,N-dialkyl (meth)acrylamides. Examples of monomers containing a nitrogen-containing heterocycle include N-vinylpyrrolidone, N-vinylcaprolactam, and (meth)acryloylmorpholine. Examples of monomers containing a cyano group include (meth)acrylate cyanoester and (meth)acrylonitrile.

[0080] As a nitrogen-containing monomer (b1), preferably, for example, N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, and other N,N-dialkylaminoalkyl (meth)acrylates are examples. The number of carbon atoms in the dialkylaminoalkyl group of the N,N-dialkylaminoalkyl (meth)acrylate is preferably 3 to 20, more preferably 3 to 10.

[0081] The amount of nitrogen-containing monomer (b1) in all monomer components used to obtain the (meth)acrylic copolymer (B) is preferably 1 to 10% by mass, more preferably 3 to 10% by mass, and even more preferably 5 to 10% by mass. Furthermore, the (meth)acrylic copolymer (B) preferably has 1 to 10% by mass of structural units derived from the nitrogen-containing monomer (b1), more preferably 3 to 10% by mass, and even more preferably 5 to 10% by mass.

[0082] In the adhesive composition for decorative films of the present invention, by adding a (meth)acrylic copolymer (B) with a high glass transition temperature obtained by copolymerizing a nitrogen-containing monomer in the above-mentioned amount to the (meth)acrylic copolymer (A), the adhesion can be appropriately reduced, thereby improving the initial re-adhesion of the obtained decorative film.

[0083] Furthermore, through the interaction of acid and base groups such as carboxyl groups derived from the carboxyl-containing monomer (a2) in (meth)acrylic acid copolymer (A) and nitrogen-containing groups such as amino groups derived from the nitrogen-containing monomer (b1) in (meth)acrylic acid copolymer (B), the compatibility of the base polymer, namely (meth)acrylic acid copolymer (A), with (meth)acrylic acid copolymer (B) having a high glass transition temperature is often improved, and the whitening resistance is often improved.

[0084] If the amount of nitrogen-containing monomer (b1) in all monomer components used to obtain (meth)acrylic copolymer (B) is less than 10% by mass, the resulting adhesive layer has good resistance to whitening and is therefore preferred.

[0085] (Meth)acrylate (b2)

[0086] The (meth)acrylic copolymer (B) preferably also has structural units derived from (meth)acrylate (b2) (wherein excluding (meth)acrylate belonging to nitrogen-containing monomer (b1)).

[0087] As for (meth)acrylates (b2), examples include alkyl (meth)acrylates, (meth)acrylates containing alicyclic hydrocarbon groups or aromatic hydrocarbon groups, and alkoxy polyalkylene glycol mono(meth)acrylates. Specific examples of these can be listed in the "Other Monomers" column of (meth)acrylate copolymers (A).

[0088] The amount of (meth)acrylate (b2) in all monomer components used to obtain the (meth)acrylate copolymer (B) is preferably 50-99% by mass, more preferably 60-97% by mass, and even more preferably 70-95% by mass. Furthermore, the (meth)acrylate copolymer (B) preferably has 50-99% by mass of structural units derived from (meth)acrylate (b2), more preferably 60-97% by mass, and even more preferably 70-95% by mass.

[0089] Other Individuals

[0090] (Meth)acrylic copolymers (B) may also have structural units derived from monomers other than the nitrogen-containing monomer (b1) and (meth)acrylate (b2) mentioned above.

[0091] Other monomers include, for example, styrene monomers, monomers containing amide groups, monomers containing nitrogen-containing heterocycles, monomers containing cyano groups, and vinyl acetate. Monomers belonging to (meth)acrylates (b2) are excluded.

[0092] Physical Properties and Manufacturing Methods of (Meth)acrylic Acid Copolymers (B)

[0093] The weight-average molecular weight (Mw) of the (meth)acrylic acid copolymer (B), as determined by GPC, is typically 10,000 to 50,000, preferably 10,000 to 40,000, and more preferably 15,000 to 30,000. In this form, the (meth)acrylic acid copolymer (B) is less likely to become uneven in the adhesive layer and often achieves good compatibility.

[0094] The molecular weight distribution (Mw / Mn) of the (meth)acrylic acid copolymer (B) is typically 2 to 15, preferably 2.5 to 10, and more preferably 3 to 8. In this form, good compatibility is often achieved.

[0095] Mw and Mw / Mn can be determined, for example, by the methods described in the examples.

[0096] The glass transition temperature (Tg) of the (meth)acrylic acid copolymer (B) is 0°C or higher, preferably 50–200°C, and more preferably 80–150°C. When this is the case, an adhesive layer with excellent initial tack and durable adhesion is often obtained. The glass transition temperature can be calculated using the aforementioned Fox formula.

[0097] It is possible to use one or more (meth)acrylic acid copolymers (B).

[0098] In the adhesive composition for decorative films of the present invention, the content of (meth)acrylic copolymer (B) relative to 100 parts by weight of (meth)acrylic copolymer (A) is 2 parts by weight or more, preferably 2 to 20 parts by weight, more preferably 3 to 17 parts by weight, and even more preferably 3 to 15 parts by weight. If the content of (meth)acrylic copolymer (B) is 2 parts by weight or more, the adhesion tends to decrease appropriately, while the initial re-adhesion tends to increase. If the content of (meth)acrylic copolymer (B) is 20 parts by weight or less, an adhesive layer with excellent adhesion can often be obtained.

[0099] (Meth)acrylic acid copolymer (B) can be manufactured by known methods, preferably by solution polymerization. For specific manufacturing conditions, for example, the manufacturing conditions described in the (meth)acrylic acid copolymer (A) section can be referred to.

[0100] <Crosslinking agent (C)>

[0101] In addition to the above-mentioned (meth)acrylic copolymer (A) and (meth)acrylic copolymer (B), the adhesive composition for decorative films of the present invention may contain a crosslinking agent (C).

[0102] The crosslinking agent (C) is not particularly limited as long as it can undergo a crosslinking reaction with the (meth)acrylic acid copolymer (A). Examples of crosslinking agents (C) include epoxy crosslinking agents (C1), metal chelate crosslinking agents (C2), and isocyanate crosslinking agents.

[0103] It is possible to use one or more crosslinking agents (C).

[0104] In the adhesive composition for decorative films of the present invention, the content of crosslinking agent (C) is preferably 0.01 to 5 parts by weight, more preferably 0.01 to 3 parts by weight, and even more preferably 0.01 to 1 part by weight, relative to 100 parts by weight of (meth)acrylic polymer (A). When this is the case, an adhesive with a sufficiently and appropriate crosslinked structure, high cohesion, excellent balance of adhesive physical properties, and excellent durability can be obtained.

[0105] Epoxy crosslinking agents (C1)

[0106] As epoxy crosslinking agents (C1), examples include epoxy compounds with two or more epoxy groups per molecule. Specifically, examples include 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'-tetraglycidylm-phenylenediamine, N,N,N',N'-tetraglycidylaminobenzylmethane, triglycidyl isocyanurate, m-N,N-diglycidylaminophenylglycidyl ether, N,N-diglycidyltoluidine, and N,N-diglycidylaniline. The number of epoxy groups per molecule in the above epoxy compounds is, for example, 2 to 10.

[0107] It is possible to use one or more epoxy crosslinking agents (C1).

[0108] Metal chelate crosslinking agents (C2)

[0109] As a metal chelate crosslinking agent (C2), examples include compounds formed by coordinating polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium with alkoxides, acetylacetone, ethyl acetoacetate, etc. Among these, aluminum chelate compounds are preferred. Specifically, examples include aluminum isopropoxide, aluminum sec-butyrate, ethyl aluminum acetoacetate diisopropyl, ethyl triacetoacetate aluminum, and aluminum triacetoacetone.

[0110] It is possible to use one or more metal chelate crosslinking agents (C2).

[0111] Isocyanate crosslinking agents (C3)

[0112] As an isocyanate crosslinking agent (C3), for example, it is possible to list isocyanate compounds in which the number of isocyanate groups in a molecule is two or more.

[0113] Diisocyanate compounds having two isocyanate groups per molecule include, for example, aliphatic diisocyanates, alicyclic diisocyanates, and aromatic diisocyanates. Isocyanate compounds having three or more isocyanate groups per molecule include, for example, aromatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates. Furthermore, as isocyanate compounds, polymers (e.g., dimers or trimers, biuret forms, isocyanurate forms), derivatives (e.g., products of addition reactions of polyols with two or more molecules of diisocyanate compounds), and polymers can be included.

[0114] It is possible to use one or more isocyanate crosslinking agents (C3).

[0115] <Additives>

[0116] Without diminishing the effects of the present invention, the adhesive composition for decorative films of the present invention may contain, in addition to the above-mentioned components, at least one selected from resin components other than the above-mentioned (meth)acrylic copolymers (A) and (meth)acrylic copolymers (B), antistatic agents, silane coupling agents, ultraviolet absorbers, antioxidants, adhesive resins, plasticizers, defoamers, fillers, stabilizers, softeners, and wetting modifiers.

[0117] <Organic solvents>

[0118] To adjust its coatability, the adhesive composition for decorative films of the present invention preferably contains an organic solvent.

[0119] Examples of organic solvents 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.

[0120] It can use one or more organic solvents.

[0121] In the adhesive composition for decorative films of the present invention, the content of organic solvent is typically 0 to 90% by mass, preferably 10 to 80% by mass.

[0122] <Adhesive Composition for Decorative Films>

[0123] The adhesive composition for decorative films of the present invention is a composition containing the above-mentioned (meth)acrylic copolymer (A) and (meth)acrylic copolymer (B), comprising at least 2 parts by mass of (meth)acrylic copolymer (B) relative to 100 parts by mass of (meth)acrylic copolymer (A). The adhesive layer obtained from such an adhesive composition exhibits good initial re-adhesion, high durability, and excellent resistance to whitening.

[0124] Generally, when different polymers are added to a base polymer, their compatibility often becomes problematic. When polymers have poor compatibility, the adhesive layer may whiten, or even bleed from one side, resulting in decreased durability, which is a cause for concern.

[0125] However, in the adhesive composition for decorative films of the present invention, since the (meth)acrylic acid copolymer (A) has structural units derived from a monomer (a2) containing a carboxyl group, and the (meth)acrylic acid copolymer (B) has structural units derived from a monomer containing nitrogen, such as an amino group, the (meth)acrylic acid copolymer (A) and the (meth)acrylic acid copolymer (B) exhibit good compatibility through acid-base interactions. Therefore, the adhesive composition for decorative films of the present invention exhibits long-term stability, and the resulting adhesive layer possesses characteristics of good initial re-adhesion, high durability, and excellent resistance to whitening.

[0126] <Method for manufacturing adhesive composition for decorative film>

[0127] The adhesive composition for decorative films of the present invention can be manufactured by mixing the above-mentioned components sequentially or simultaneously using known methods.

[0128] That is, the adhesive composition of the present invention can be prepared by mixing (meth)acrylic acid copolymer (A) and (meth)acrylic acid copolymer (B) with other components such as crosslinking agent (C), additives, and organic solvents as needed, using existing known methods. In one embodiment, for example, it is possible to mix a polymer solution containing the polymer and an organic solvent obtained during the synthesis of (meth)acrylic acid copolymer (A) and (meth)acrylic acid copolymer (B), and to add crosslinking agent (C), additives, etc. as needed.

[0129] Adding a decorative film

[0130] The decorative film of the present invention comprises an adhesive layer and a substrate layer obtained by the above-described adhesive composition for decorative films. In the decorative film of the present invention, the substrate layer preferably serves as the decorative layer; however, it may also have a decorative layer. Furthermore, the decorative film of the present invention may also have a release liner on the adhesive layer, which protects the adhesive layer before use.

[0131] Adhesive layer

[0132] The adhesive layer of the decorative film of the present invention is formed from the adhesive composition for decorative films of the present invention described above.

[0133] The adhesive layer can be obtained, for example, by coating the aforementioned adhesive composition for decorative films onto a substrate or decorative layer and crosslinking it as needed. That is, the adhesive composition for decorative films can be coated and dried using known methods such as spin coating, blade coating, roller coating, rod coating, blade coating, mold coating, and gravure coating to form a specified thickness. Specifically, for example, the aforementioned adhesive composition for decorative films is coated onto a substrate or decorative layer and dried typically at 60–120°C, preferably 70–110°C, for 1–10 minutes, preferably 2–5 minutes, to form a coating film. Then, it is cured (matured) typically at 5–60°C, preferably 15–50°C, and typically at 30–70% RH, preferably 40–70% RH for at least one day, preferably 2–10 days. Crosslinking under these maturation conditions allows for efficient formation of a crosslinked polymer (network polymer).

[0134] The thickness of the adhesive layer is typically 3 to 1000 μm, preferably 5 to 500 μm.

[0135] Substrate Layer

[0136] Generally, the substrate layer forms the outermost layer of the decorated object, i.e., the molded body obtained by attaching the decorative film to the adhesive. The substrate layer can be colored or colorless, and can be transparent, translucent, or opaque. Furthermore, the substrate layer is usually in the form of a film or sheet, and can be a single-layer structure or composed of multiple layers. In this invention, the adhesive layer constituting the decorative film exhibits excellent resistance to whitening, making it suitable for using transparent or translucent substrate layers.

[0137] The substrate layer is not particularly limited, however, it is preferably made of a thermoplastic resin, and more preferably of at least one selected from polyvinyl chloride, polyethylene, polypropylene, polycarbonate, polymethyl methacrylate, and ABS.

[0138] Depending on the requirements, the substrate layer may also contain inorganic particles such as silica, plasticizers, colorants, ultraviolet absorbers, and other functional substances. Furthermore, patterns, text, and designs can be printed on the surface of the substrate to impart aesthetic appeal, and patterns, text, and designs can also be formed within the substrate itself.

[0139] The substrate layer is preferably in the form of a film or sheet. The thickness of the substrate layer is typically 10–1000 μm, preferably 20–200 μm, and more preferably 50–150 μm.

[0140] Decorative Layer

[0141] The decorative film of the present invention may also have a decorative layer between the substrate layer and the adhesive layer or on the substrate layer. The decorative layer is a layer provided to give the decorative film an appearance, and is a layer that presents patterns, text, and designs.

[0142] Peel-off membrane

[0143] Depending on the requirements, the decorative film of the present invention may also have a release film on the adhesive layer. The release film protects the surface of the adhesive layer before actual use of the decorative film and is peeled off and removed when the decorative film is used. As the release film, there are no particular limitations as long as it is a film that can be easily peeled off from the adhesive layer; resin films can be listed, specifically: polyester films such as polyethylene terephthalate and polybutylene terephthalate; polyolefin films such as polyethylene, polypropylene, and ethylene-vinyl acetate copolymer. At least one side of the release film can be treated with a release agent such as silicone, fluorine, long-chain alkyl, or fatty acid amide for easy peeling.

[0144] The thickness of the release film is typically 10–500 μm, preferably 25–200 μm.

[0145] Manufacturing Method of Decorative Film

[0146] For the manufacture of the decorative film of the present invention, methods for forming a decorative film having an adhesive layer and a substrate layer composed of the adhesive composition for decorative films of the present invention can be used without particular limitation. For example, methods can be listed as follows: forming an adhesive layer by applying and drying the adhesive composition for decorative films of the present invention onto a substrate layer; further bonding a release film onto the adhesive layer of the decorative film obtained by the above methods as needed; forming an adhesive layer by applying the adhesive composition for decorative films of the present invention to a release film and drying it, and bonding the exposed surface of the obtained adhesive layer that does not contact the release film to the substrate constituting the substrate layer and curing it, etc.

[0147] Generally, the adhesive layer can be obtained by applying the adhesive composition for the decorative film of the present invention to a substrate constituting the substrate layer or a release film and then drying it. The drying conditions vary depending on the type of organic solvent contained in the composition, the thickness of the adhesive layer, etc., but generally, the drying temperature is 50 to 150°C and the drying time is 1 to 10 minutes.

[0148] Methods for applying adhesive compositions for decorative films include, for example, spin coating, knife coating, roller coating, bar coating, blade coating, mold coating, and gravure coating.

[0149] The curing conditions are as follows: Curing is typically performed at 5–60°C, preferably 15–50°C, and at a relative humidity of 30–70%, preferably 40–70%, typically for more than one day, preferably 2–10 days. If crosslinking is performed under these curing conditions, a crosslinked polymer (network polymer) composed of a (meth)acrylic acid copolymer (A) and a crosslinking agent (C) can be efficiently formed.

[0150] Applications and decorative moldings

[0151] The decorative molded body of the present invention is formed by attaching the decorative film of the present invention to at least a portion of the surface of the substrate, i.e., the molded body.

[0152] As the adhered material for the decorative film of the present invention, shaped bodies such as articles with three-dimensional shapes can be included, and articles with three-dimensional curved surfaces are preferred. Specifically, vehicle bodies, vehicle interior materials, building materials, and decorative panels can be included. In addition, as for "vehicles", for example, four-wheeled vehicles such as cars, buses, and trucks; two-wheeled vehicles such as motorcycles, scooters, and electric bicycles; and trams can be included.

[0153] The decorative film of the present invention is particularly preferred for use as a vehicle film, and more specifically, particularly preferred for use as a vehicle exterior film (e.g., automotive wrapping film). When automotive wrapping film is applied to a vehicle body, large-sized films are mostly applied manually, and sometimes the film is peeled off the vehicle body after a long period of time since application. As described above, the decorative film of the present invention exhibits excellent initial re-adhesion and re-peelability, and is therefore ideal as an automotive wrapping film.

[0154] There are no particular limitations on the materials used to form the adhered material, including: metal materials; wood; plastics such as acrylonitrile / butadiene / styrene resin, polycarbonate resin, polyester resin, polypropylene resin, and polyethylene resin, and coatings can also be applied to their surfaces.

[0155] Methods for attaching decorative films to the substrate, i.e., the molded body, include, for example, manual bonding, vacuum forming, pneumatic forming, and thermo-high pressure forming. Among these, vacuum forming is preferred.

[0156] The decorative molded body of the present invention has a molded body (the adherend) and a substrate with an adhesive layer disposed on the surface of the molded body and formed by removing a release film from the decorative film. More specifically, the decorative molded body sequentially comprises a molded body, an adhesive layer, a decorative layer as needed, and a substrate.

[0157]

Example

[0158] The present invention will be further described in detail below based on embodiments; however, the present invention is not limited to these embodiments. In the following description of embodiments, etc., unless otherwise specified, "parts" means "parts by mass".

[0159] Each measured value was obtained using the following method.

[0160] [Metal-average molecular weight (Mw) and molecular weight distribution (Mw / Mn)]

[0161] For (meth)acrylic acid copolymers, the weight-average molecular weight (Mw) and molecular weight distribution (Mw / Mn) based on standard polystyrene were determined by gel permeation chromatography (GPC) under the following conditions.

[0162] • Measuring apparatus: HLC-8220GPC (Tosoh Corporation)

[0163] • GPC column configuration: The following five columns (all manufactured by Tosoh) are as follows: (1) TSK-GEL HXL-H (protective column) (2) TSK-GEL G7000HXL (3) TSK-GEL GMHXL (4) TSK-GEL GMHXL (5) TSK-GEL G2500HXL

[0164] • Sample concentration: diluted with tetrahydrofuran to 1.0 mg / cm³ 3

[0165] Mobile phase solvent: tetrahydrofuran

[0166] • Flow rate: 1.0 cm 3 / min

[0167] • Column temperature: 40℃

[0168] [Polymerization Example 1] (Preparation of (meth)acrylic acid copolymer (A-1))

[0169] In a reaction apparatus including a stirrer, reflux cooler, thermometer, and nitrogen inlet pipe, 92 parts of 2-methoxyethyl acrylate (MEA), 8 parts of acrylic acid (AA), and 200 parts of ethyl acetate were added, and the temperature was raised to 75°C while nitrogen was introduced. Then, 0.1 parts of 2,2'-azobisisobutyronitrile (2,2'-Azobisisobutyronitrile) were added, and polymerization was carried out for four hours under nitrogen atmosphere at 75–76°C. After the reaction, the reaction solution was diluted with ethyl acetate to prepare a polymer solution with a solid content of 39% by mass. The obtained (meth)acrylic acid copolymer (A-1) had a Mw of 700,000 and an Mw / Mn ratio of 7.5.

[0170] [Examples 2-6 of Aggregation]

[0171] Except for the monomer composition being changed as described in Table 1 (the composition is in parts by mass), polymerization was carried out in the same manner as in the polymerization example 1 above, to obtain (meth)acrylic acid copolymers (A-2) to (A-3), (A'-4) to (A'-6). The Tg, Mw, and Mw / Mn of each obtained (meth)acrylic acid copolymer are shown in Table 1.

[0172] Table 1

[0173] Table 1

[0174]

[0175] BA: n-Butyl acrylate

[0176] MEA: 2-Methoxyethyl Acrylate

[0177] HEA: 2-Hydroxyethyl acrylate

[0178] AA: Acrylic acid

[0179] [Example 7]

[0180] In a reaction apparatus including a stirrer, reflux cooler, thermometer, and nitrogen inlet pipe, 95 parts of methyl methacrylate (MMA), 5 parts of N-dimethylaminoethyl methacrylate (DM), 1 part of N-dodecyl mercaptan as a chain transfer agent, and 100 parts of ethyl acetate were added. The mixture was heated to 75°C while nitrogen was introduced. Then, 0.1 parts of 2,2'-azobisisobutyronitrile (2,2'-azobisisobutyronitrile) were added, and polymerization was carried out for four hours under nitrogen atmosphere at 75–76°C. After the reaction, the reaction solution was diluted with ethyl acetate to prepare a polymer solution with a solids content of 45% by mass. The obtained (meth)acrylic acid copolymer (B-1) had a Tg of 102°C, a Mw of 15000, and a Mw / Mn ratio of 4.5.

[0181] [Example 8]

[0182] Except for the monomer composition being changed as described in Table 2 (the composition is in parts by mass), polymerization was carried out in the same manner as in polymerization example seven above to obtain (meth)acrylic acid copolymer (B'-2).

[0183] Table 2

[0184] Table 2

[0185]

[0186] BA n-Butyl Acrylate

[0187] MMA methyl methacrylate

[0188] DM 2-Dimethylaminoethyl methacrylate

[0189] [Example 1]

[0190] A polymer solution of (meth)acrylic acid copolymer (A-1) obtained in polymerization example 7 and an epoxy compound "E-AX" as a crosslinking agent were added and mixed to a polymer solution of (meth)acrylic acid copolymer (A-1) obtained in polymerization example 1 to obtain an adhesive composition. The respective proportions were: 10 parts of (meth)acrylic acid copolymer (B-1) relative to 100 parts of (meth)acrylic acid copolymer (A-1) and 0.045 parts of the solid content of epoxy compound "E-AX".

[0191] Next, adhesive sheet samples were prepared using the obtained adhesive composition as follows, and their initial re-adhesion, whitening resistance, and durability were measured or evaluated. The results are shown in Table 3.

[0192] [Preparation of Adhesive Sheet Samples]

[0193] An adhesive composition was applied to a PET film that had undergone a peeling process and dried at 90°C for 4 minutes to form an adhesive layer with a thickness of 25 μm. This layer was then laminated to a PET film substrate with a thickness of 25 μm and cured at 40°C for 3 days to produce an adhesive sheet.

[0194] [Fast Adhesion (Initial Heavy Adhesion)]

[0195] The determination was performed using the inclined plane rolling ball method (J. Dow method). Specifically, a peeled PET film was removed from the prepared adhesive sheet, exposing the adhesive layer, and mounted on an inclined plane with a 30-degree inclination angle. Then, at 23°C and 65% RH, a steel ball was driven from the top of the inclined plane and allowed to slide along the adhesive surface (the adhesive layer surface). The driving distance and sliding distance were both set to 10 cm. The diameter of the steel ball was varied, and sliding tests were performed to determine the maximum diameter of the steel ball that stopped sliding at the adhesive surface. The diameter of the steel ball used was X / 32 inches (where X is an integer from 1 to 32), and the values ​​shown in Table 3 represent the values ​​of X. The judgment criteria are as follows.

[0196] Judgment criteria

[0197] AA: 2-4 (low viscosity, good heavy tack)

[0198] BB: 5-9 (slightly sticky but not problematic for use)

[0199] CC: 10 or higher (high viscosity, issues with heavy tack).

[0200] [Whitening resistance]

[0201] Cut 60mm x 50mm pieces from the prepared adhesive sheet, peel off the PET film that has undergone a release treatment, and adhere the exposed adhesive layer to a glass plate (the substrate). Then, prepare a test panel by maintaining the pressure at 50°C and 5 atmospheres for 20 minutes. The degree of whitening was measured using a haze meter (model "HM-150", manufactured by Murakami Color Technology Research Institute), and this was set as the initial haze level. Next, the test panel was placed at 85°C and 85% RH for 72 hours, and the degree of whitening was measured again using a haze meter (model "HM-150", manufactured by Murakami Color Technology Research Institute), and this was set as the post-durability haze level. The measurement results and judgment results are shown in Table 3.

[0202] Judgment criteria

[0203] AA: The difference in haze before and after damp heat treatment is less than 0.5.

[0204] BB: The difference in haze before and after damp heat treatment is greater than 0.5 but less than 1.0.

[0205] CC: The difference in haze before and after damp heat treatment is greater than 1.0.

[0206] [Durability Testing]

[0207] Cut a 25mm × 100mm piece from the prepared adhesive sheet, peel off the PET film that has undergone the peeling process, and adhere the exposed adhesive layer to the polycarbonate sheet. Next, maintain the mixture in an autoclave at 50°C and 5 atmospheres for 20 minutes to ensure strong adhesion. Then, place it at 85°C and 85% RH for 1000 hours and observe its appearance. The results are shown in Table 3.

[0208] Judgment criteria

[0209] AA: No blistering or peeling observed.

[0210] BB: Although slight bubbling and peeling were observed, there were no problems with its use.

[0211] CC: Blistering and peeling were clearly observed.

[0212] [Examples 2-5, Comparative Examples 1-6]

[0213] Except for the changes in formulation as described in Table 3, the adhesive composition was obtained in the same manner as in Example 1. In Table 3, the amounts of each component are relative to 100 parts by mass of the (meth)acrylic acid copolymer (A) or an equivalent 100 parts by mass of the comparative copolymer. The amounts of the crosslinking agent in Table 3 are solid components. Furthermore, in Table 3, "Y-75" is an isocyanate compound.

[0214] Next, adhesive sheet samples were prepared using the obtained adhesive compositions in the same manner as in Example 1, and their initial re-adhesion, whitening resistance, and durability were measured or evaluated. The results are shown in Table 3.

[0215] Table 3

[0216] Table 3

[0217]

[0218] Y-75: Isocyanate compound (isocyanate crosslinking agent; manufactured by Zongyan Chemical, isocyanurate form of hexamethylene diisocyanate: 75% solid content, ethyl acetate solution)

[0219] E-AX: Epoxy compounds (epoxy crosslinking agents; manufactured by Zongyan Chemical, 4-functional epoxy compounds: 5% solid content, toluene-isopropanol solution)

[0220] A comparison of Example 1 and Comparative Example 1 shows that when using a (meth)acrylic copolymer (A) containing structural units derived from (meth)acrylic alkoxyalkyl ester monomer (al), the whitening resistance is improved.

[0221] By comparing Example 1 with Comparative Examples 2 and 3, it can be seen that when using a (meth)acrylic acid copolymer (A) containing more than 2% by mass of structural units derived from a monomer (a2) containing a carboxyl group, the initial tackiness and durability are improved.

[0222] By comparing Examples 1-3 with Comparative Examples 1-3, it can be seen that by using a (meth)acrylic copolymer (A) containing more than 50% by mass of structural units derived from (meth)acrylic alkoxyalkyl ester units (a1) and more than 2% by mass of carboxyl-containing monomers (a2), the initial tackiness, whitening resistance and durability are improved.

[0223] A comparison between Example 1 and Comparative Example 4 shows that when using a (meth)acrylic acid copolymer (B) with a high glass transition temperature (Tg) above 0°C, initial tackiness and durability are improved.

[0224] By comparing Examples 1 and 4 with Comparative Examples 5 and 6, it can be seen that when more than 2 parts by mass of (meth)acrylic copolymer (B) are used relative to 100 parts by mass of (meth)acrylic copolymer (A), the initial tackiness and durability are improved.

[0225] As can be seen from the above, using an adhesive composition containing a specific amount of an adhesive composition containing a (meth)acrylic copolymer (A) having a high glass transition temperature (Tg) of 0°C or higher, relative to a structural unit derived from (meth)acrylic alkoxyalkyl ester monomer (a1) and a monomer containing a carboxyl group (a2), can form an adhesive layer with excellent initial tack, whitening resistance, and durability.

[0226] Industrial availability

[0227] The adhesive composition for decorative films of the present invention is ideal for the formation of the adhesive layer of the decorative film. The decorative film of the present invention is suitable for surface finishing of molded bodies such as vehicle bodies, vehicle interior materials, building materials, and decorative panels, and is particularly preferred for use as a film for vehicles, specifically, it is particularly preferred for use as a film for automotive packaging and exterior trim of vehicles.

Claims

1. An adhesive composition for decorative films, said adhesive composition comprising (meth)acrylic copolymer (A) and (meth)acrylic copolymer (B), The (meth)acrylic acid copolymer (A) is a monomer component containing 92-98% by mass of (meth)acrylic acid alkoxyalkyl ester monomer (a1) and more than 2% by mass of carboxyl-containing monomer (a2). The (meth)acrylic acid copolymer (B) is copolymerized from a monomer component containing 1-10% by mass of a nitrogen-containing monomer (b1). Its features are, The weight average molecular weight (Mw) of the (meth)acrylic acid copolymer (A) is 200,000 to 2,000,000. The (meth)acrylic acid copolymer (B) has a weight average molecular weight (Mw) of 10,000 to 50,000 and a glass transition temperature (Tg) of 50 to 200°C. The copolymer comprises 2 to 20 parts by weight of the (meth)acrylic acid copolymer (B) relative to 100 parts by weight of the copolymer (A). Nitrogen-containing monomers (b1) are amino-containing monomers having groups represented by -NH2, -NHR, or -NR2, wherein R is an alkyl group.

2. The adhesive composition for decorative films as described in claim 1, characterized in that, The carboxyl-containing monomer (a2) in the monomer component constituting the (meth)acrylic acid copolymer (A) is 2 to 8% by mass.

3. A decorative film, characterized in that, It comprises: an adhesive layer formed from the adhesive composition for decorative films as described in claim 1 or 2; and a substrate layer.

4. The decorative film as described in claim 3, characterized in that, The substrate layer is composed of at least one selected from polyvinyl chloride, polyethylene, polypropylene, polycarbonate, polymethyl methacrylate, and ABS.

5. The decorative film as described in claim 3, characterized in that, The decorative film is used on interior or exterior parts of a vehicle.

6. The decorative film as described in claim 4, characterized in that, The decorative film is used on interior or exterior parts of a vehicle.

7. The decorative film according to any one of claims 3 to 6, characterized in that, The decorative film is used on the exterior parts of the vehicle.

8. A decorated molded body, characterized in that, The decorative film having any one of claims 3 to 7.

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