Adhesive composition for decorative film and decorative film

Abstract

To provide an adhesive composition for a decorative film, which exhibits superior reworkability and is less prone to contaminate adherends, and a decorative film prepared using the adhesive composition.SOLUTION: An adhesive composition for a decorative film comprises: a (meth)acrylic polymer (A) having a glass transition temperature of -20°C or less; and a polymer (B) having a glass transition temperature of more than -20°C and less than 30°C, wherein the content of the polymer (B) is 0.1 to 100 pts.mass based on 100 pts.mass of the (meth)acrylic polymer (A).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a pressure-sensitive adhesive composition for decorative films and a decorative film using the pressure-sensitive adhesive composition for decorative films. [Background technology]

[0002] Due to the recent trend of reducing volatile organic compounds (VOCs), automobile manufacturers are actively replacing exterior paint with decorative films that have an adhesive layer. One of the requirements for the adhesive used in this decorative film is reworkability. Reworkability is the ability to easily peel off and reposition an adhesive-processed decorative film if it becomes misaligned when it is attached to an adherend. In addition, if the decorative film can be peeled off without contaminating the adherend, a different decorative film can be attached without cleaning, making it easy to impart a different design.

[0003] Patent Document 1 describes that an adhesive containing two specific acrylic polymers is suitable as an adhesive for decorative adhesive sheets used for advertising and decoration of items such as signs, buildings, and vehicles, and that the decorative sheet using this adhesive can be peeled off without leaving any adhesive residue after use. Specifically, it teaches that a decorative adhesive sheet having an adhesive layer formed from an adhesive composition containing 75 parts by mass of an acrylic polymer with Mw of 910,000 and Tg of -39°C obtained by copolymerizing 70 parts of n-butyl acrylate, 20 parts of methyl acrylate, 4 parts of 2-ethylhexyl acrylate, and 6 parts of acrylic acid, 25 parts by mass of an acrylic low molecular weight material, and an epoxy curing agent has good outdoor weather resistance, good adhesion to olefin materials, and can be peeled off without leaving any adhesive residue after use. However, even sheets using such adhesives have the problem of insufficient reworkability. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5434773 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a pressure-sensitive adhesive composition for decorative films which has good reworkability and does not easily contaminate an adherend, and a decorative film which uses the pressure-sensitive adhesive composition for decorative films. [Means for solving the problem]

[0006] Means for Solving the Problems The present inventors have conducted intensive research in light of the above-mentioned circumstances and have found that a (meth)acrylic polymer having a specific Tg and a pressure-sensitive adhesive composition containing a polymer having a specific Tg can solve the above-mentioned problems, thereby completing the present invention. The present invention relates to, for example, the following items [1] to [6].

[0007] [1] A pressure-sensitive adhesive composition for decorative films, comprising a (meth)acrylic polymer (A) having a glass transition temperature of -20°C or lower and a polymer (B) having a glass transition temperature of more than -20°C and less than 30°C, wherein the polymer (B) is contained in an amount of 0.1 to 100 parts by mass per 100 parts by mass of the (meth)acrylic polymer (A). [2] The pressure-sensitive adhesive composition for decorative films according to [1], wherein the content of structural units derived from alkoxyalkyl (meth)acrylate in all monomers constituting the (meth)acrylic polymer (A) is less than 50 mass%. [3] The pressure-sensitive adhesive composition for decorative films according to [1] or [2], wherein the polymer (B) does not contain a structural unit derived from a nitrogen atom-containing monomer. [4] The pressure-sensitive adhesive composition for decorative films according to any one of [1] to [3], wherein the polymer (B) has a number average molecular weight (Mn) of 13,000 to 100,000. [5] A decorative film comprising a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition for decorative films according to any one of [1] to [4], and a substrate layer. [6] The decorative film according to [5], which is for vacuum and pressure forming. Effect of the Invention

[0008] According to the present invention, it is possible to provide a decorative film adhesive composition having good reworkability and hardly contaminating the adherend, and a decorative film using the decorative film adhesive composition. The decorative film adhesive composition of the present invention can be suitably used in the adhesive layer of the decorative film, and the decorative film using the same has excellent reworkability and hardly contaminates the adherend. The decorative film according to the present invention can be used for surface decoration of various molded bodies, and is particularly suitable for use in the decoration of interior and exterior parts of vehicles such as automobiles and trains. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The present invention will be specifically described below. In the present invention, acrylic and methacrylic are collectively referred to as "(meth)acrylic", and acrylate and methacrylate are collectively referred to as "(meth)acrylate". In addition, in the present invention, A to B representing a numerical range means A or more and B or less, unless otherwise specified.

[0010] <Adhesive composition for decorative film> The pressure-sensitive adhesive composition for decorative films according to the present invention (hereinafter also referred to as "the composition") is a composition containing a (meth)acrylic polymer (A), a polymer (B), and, if necessary, other components.

[0011] [(Meth)acrylic polymer (A)] The (meth)acrylic polymer (A) is a polymer of a monomer component (a) containing a (meth)acrylic monomer as a main component, and has a glass transition temperature (Tg) of -20°C or lower. The (meth)acrylic polymer (A) used in the present composition may be one type or two or more types.

[0012] Examples of the monomer component (a) constituting the (meth)acrylic polymer (A) include (meth)acrylic monomers (a1) having no crosslinkable functional group, monomers (a2) having a crosslinkable functional group, and other monomers (a3). Among these, one or more kinds can be used.

[0013] ((Meth)acrylic monomer (a1) having no crosslinkable functional group) The (meth)acrylic monomer (a1) having no crosslinkable functional group is a (meth)acrylic monomer having no crosslinkable functional group that can react with a functional group in the crosslinking agent (C) preferably contained in the pressure-sensitive adhesive composition to form a crosslinked structure. Examples of the crosslinkable functional group include a carboxy group, an acid anhydride group, a hydroxy group, an amino group, an amide group, and a cyano group.

[0014] Examples of the (meth)acrylic monomer (a1) having no crosslinkable functional group include alkyl (meth)acrylates, alicyclic group-containing (meth)acrylates, aromatic ring-containing (meth)acrylates, alkoxyalkyl (meth)acrylates, and alkoxypolyalkylene glycol mono(meth)acrylates. Among these, alkyl (meth)acrylates are preferred.

[0015] The alkyl (meth)acrylate preferably has an alkyl group in an ester side chain of 1 to 12 carbon atoms, more preferably 1 to 8, and further preferably 1 to 4. The alkyl group may be either a linear alkyl group or a branched alkyl group.

[0016] Examples of the alkyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, iso-propyl (meth)acrylate, n-butyl (meth)acrylate, iso-butyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, iso-octyl (meth)acrylate, n-nonyl (meth)acrylate, iso-nonyl (meth)acrylate, n-decyl (meth)acrylate, iso-decyl (meth)acrylate, undeca(meth)acrylate, lauryl (meth)acrylate, oleyl (meth)acrylate, n-stearyl (meth)acrylate, and iso-stearyl (meth)acrylate.

[0017] Examples of the alicyclic group-containing (meth)acrylate include cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and adamantyl (meth)acrylate.

[0018] Examples of aromatic ring-containing (meth)acrylates include benzyl (meth)acrylate, phenyl (meth)acrylate, and phenoxyethyl (meth)acrylate.

[0019] Examples of alkoxyalkyl (meth)acrylates include 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 4-methoxybutyl (meth)acrylate, and 4-ethoxybutyl (meth)acrylate.

[0020] Examples of alkoxypolyalkylene glycol mono(meth)acrylates 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.

[0021] The (meth)acrylic polymer (A) may have one or more structural units derived from a (meth)acrylic monomer (a1) that does not have a crosslinkable functional group. In 100% by mass of the monomer component (a) used to form the (meth)acrylic polymer (A), the content of the (meth)acrylic monomer (a1) having no crosslinkable functional group is usually 30 to 100% by mass, preferably 40 to 99% by mass, more preferably 50 to 98% by mass, and even more preferably 60 to 97% by mass. When an alkoxyalkyl (meth)acrylate is used as the (meth)acrylic monomer (a1) having no crosslinkable functional group, the upper limit of the content thereof is preferably less than 50 mass %, more preferably less than 40 mass %. If the amount of the (meth)acrylic monomer (a1) having no crosslinkable functional group is within the above range, good reworkability can be easily obtained, which is preferable.

[0022] (Monomer (a2) Having a Crosslinkable Functional Group) The monomer (a2) having a crosslinkable functional group is a monomer having a crosslinkable functional group that can form a crosslinked structure by reacting with a functional group in the crosslinking agent (C) preferably contained in the pressure-sensitive adhesive composition. Examples of the monomer (a2) having a crosslinkable functional group include a carboxy group- or acid anhydride group-containing monomer, a hydroxy group-containing monomer, an amino group-containing monomer, an amide group-containing monomer, and a cyano group-containing monomer, and among these, a carboxy group- or acid anhydride group-containing monomer is preferred.

[0023] Examples of the carboxy group- or acid anhydride group-containing monomer include carboxy group-containing (meth)acrylates such as β-carboxyethyl (meth)acrylate, 5-carboxypentyl (meth)acrylate, succinic acid mono(meth)acryloyloxyethyl ester, and ω-carboxypolycaprolactone mono(meth)acrylate; monounsaturated fatty acids such as acrylic acid, methacrylic acid, and crotonic acid; diunsaturated fatty acids such as maleic acid, fumaric acid, itaconic acid, and citraconic acid, and acid anhydrides thereof.

[0024] Examples of hydroxyl group-containing monomers include hydroxyl group-containing (meth)acrylates, specifically hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, etc. The number of carbon atoms in the alkyl group in the hydroxyalkyl (meth)acrylate is usually 2 to 8, preferably 2 to 6.

[0025] Examples of amino group-containing monomers include N-alkylaminoalkyl(meth)acrylates such as N-methylaminoethyl(meth)acrylate and N-ethylaminoethyl(meth)acrylate.

[0026] Examples of amide group-containing monomers include (meth)acrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-propyl(meth)acrylamide, N-hexyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, and N,N-diethyl(meth)acrylamide.

[0027] An example of a cyano group-containing monomer is (meth)acrylonitrile.

[0028] The (meth)acrylic polymer (A) may have structural units derived from one or more types of monomers (a2) having a crosslinkable functional group. In 100% by mass of the monomer component (a) used to form the (meth)acrylic polymer (A), the content of the monomer (a2) having a crosslinkable functional group is usually 30% by mass or less, preferably 25% by mass or less, more preferably 0.1 to 20% by mass, and even more preferably 0.5 to 15% by mass. If the content of the monomer (a2) having a crosslinkable functional group is within the above range, the adherend tends not to be stained easily, which is preferable.

[0029] (Other monomers (a3)) The other monomer (a3) ​​is a monomer other than the (meth)acrylic monomer (a1) having no crosslinkable functional group and the monomer (a2) having a crosslinkable functional group.

[0030] Examples of the other monomers (a3) ​​include nitrogen-based heterocycle-containing monomers such as N-vinylpyrrolidone, N-vinylcaprolactam, (meth)acryloylmorpholine, etc.; vinyl esters such as vinyl acetate, vinyl propionate, etc.; olefins such as ethylene, propylene, isobutylene, etc.; halogenated olefins such as vinyl chloride, vinylidene chloride, etc.; styrene-based monomers such as styrene, α-methylstyrene, etc.; and diene-based monomers such as butadiene, isoprene, chloroprene, etc.

[0031] The (meth)acrylic polymer (A) may have structural units derived from one or more other monomers (a3). In 100% by mass of the monomer component (a) used to form the (meth)acrylic polymer (A), the content of the other monomer (a3) ​​is usually 30% by mass or less, preferably 25% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less.

[0032] [Method for producing (meth)acrylic polymer (A)] The (meth)acrylic polymer (A) is obtained by copolymerizing the monomer component (a). The production method is not particularly limited, and any known method can be used, for example, solution polymerization, bulk polymerization, emulsion polymerization, suspension polymerization, etc., and is preferably the solution polymerization method because it is easy to adjust the molecular weight and produces fewer impurities during production.

[0033] Specifically, a polymerization solvent, monomer component (a), and, if necessary, a chain transfer agent are charged into a reaction vessel, a polymerization initiator is added under an inert gas atmosphere such as nitrogen gas, the reaction initiation temperature is set to usually 40 to 100°C, preferably 50 to 90°C, and the reaction system is maintained at a temperature of usually 50 to 90°C, preferably 60 to 90°C, and the reaction is carried out for 3 to 20 hours to obtain the (meth)acrylic polymer (A).

[0034] Examples of the polymerization initiator include an azo-based initiator and a peroxide-based polymerization 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, 2,2'-azobis(2 -Amidinopropane) dihydrochloride, 2,2'-azobis(N,N'-dimethyleneisobutylamidine), 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)-propionamide], 2,2'-azobis(isobutylamide) dihydrate, 4,4'-azobis(4-cyanopentanoic acid), 2,2'-azobis(2-cyanopropanol), dimethyl-2,2'-azobis(2-methylpropionate), and 2,2'-azobis(2-methyl-N-(2-hydroxyethyl)propionamide).

[0035] Examples of peroxide-based polymerization initiators include t-butyl hydroperoxide, cumene hydroperoxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, caproyl peroxide, di-i-propyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, t-butyl peroxypivalate, and 2,2-bis(4,4-di-t-butylperoxycyclohexyl). Examples of the alkylperoxycyclohexyl include propane, 2,2-bis(4,4-di-t-amylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-octylperoxycyclohexyl)propane, 2,2-bis(4,4-di-α-cumylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)butane, and 2,2-bis(4,4-di-t-octylperoxycyclohexyl)butane.

[0036] The polymerization initiator may be used alone or in combination of two or more kinds. In addition, there is no restriction on adding the polymerization initiator multiple times during the polymerization. The polymerization initiator is used in an amount of usually 0.001 to 5 parts by mass, preferably 0.005 to 3 parts by mass, based on 100 parts by mass of the monomer component (a) forming the (meth)acrylic polymer (A). In addition, during the polymerization reaction, the polymerization initiator, the chain transfer agent, the polymerizable monomer, and the polymerization solvent may be appropriately added.

[0037] Examples of the chain transfer agent include alkyl mercaptans such as octyl mercaptan, nonyl mercaptan, decyl mercaptan, and dodecyl mercaptan; thioglycolic acid esters such as octyl thioglycolate, nonyl thioglycolate, and 2-ethylhexyl thioglycolate; 2,4-diphenyl-4-methyl-1-pentene, 1-methyl-4-isopropylidene-1-cyclohexene, α-pinene, and β-pinene. The chain transfer agent may be used alone or in combination of two or more kinds.

[0038] Examples of the polymerization solvent used in the solution polymerization 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, phenylethyl 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. The polymerization solvent may be used alone or in combination of two or more.

[0039] [Physical properties of (meth)acrylic polymer (A)] The (meth)acrylic polymer (A) has a Tg of -20°C or lower, preferably -70 to -20°C, more preferably -60 to -22°C, and further preferably -50 to -24°C. If the Tg of the (meth)acrylic polymer (A) is within the above range, good reworkability is easily obtained, which is preferable. The Tg of the (meth)acrylic polymer (A) is calculated from the monomer units constituting the (meth)acrylic polymer (A) and their content ratios according to the Fox formula.

[0040] Fox formula: 1 / Tg=(W1 / Tg1)+(W2 / Tg2)+…+(Wm / Tgm) W1+W2+…+Wm=1 In the above formula, Tg is the glass transition temperature (unit: K) of the polymer, Tg1, Tg2, ..., Tgm are the glass transition temperatures (unit: K) of homopolymers formed from each monomer, and W1, W2, ..., Wm are the mass fractions of the structural units derived from each monomer in the entire copolymer. The mass fractions of the structural units derived from each monomer can be determined by the ratio of each monomer to the total monomers used in the synthesis of the copolymer.

[0041] In the calculation of the Fox formula, the glass transition temperature (Tg) of the homopolymer formed from each monomer can be, for example, the value described in Polymer Handbook Fourth Edition (Wiley-Interscience 2003).

[0042] The weight average molecular weight (Mw) of the (meth)acrylic polymer (A) measured by gel permeation chromatography (GPC) is not particularly limited, but is usually 200,000 to 3,000,000, preferably 250,000 to 2,000,000, more preferably 300,000 to 1,500,000, and even more preferably 350,000 to 1,200,000, in terms of polystyrene. When the Mw of the (meth)acrylic polymer (A) is within the above range, good reworkability is easily obtained and the adherend tends not to be contaminated, which is preferable.

[0043] The molecular weight distribution (Mw / Mn) of the (meth)acrylic polymer (A) measured by GPC method is usually 15 or less, preferably 10 or less, and more preferably 2-8.

[0044] [Polymer (B)] The polymer (B) is a polymer having a glass transition temperature (Tg) of more than -20°C and less than 30°C. The polymer (B) used in the present composition may be one type, or two or more types.

[0045] The blending ratio of polymer (B) in the present composition is 0.1 to 100 parts by mass, preferably 0.5 to 80 parts by mass, more preferably 1 to 60 parts by mass, and further preferably 2 to 40 parts by mass, per 100 parts by mass of (meth)acrylic polymer (A). When the blending ratio of polymer (B) is within the above range, the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition exhibits good reworkability, which is preferable.

[0046] Examples of the monomer component (b) constituting the polymer (B) in the present composition include monomers (b1) having no crosslinkable functional group and no nitrogen atom, nitrogen-containing monomers (b2) and other monomers (b3), and one or more of these may be used.

[0047] (Monomer (b1) having no crosslinkable functional group and no nitrogen atom) The monomer (b1) having no crosslinkable functional group and no nitrogen atom is a monomer having no crosslinkable functional group capable of reacting with a functional group in the crosslinking agent (C) preferably contained in the pressure-sensitive adhesive composition to form a crosslinked structure, and having no nitrogen atom in the molecule. Examples of the crosslinkable functional group include a carboxy group, an acid anhydride group, a hydroxy group, an amino group, an amide group, and a cyano group.

[0048] Specific examples of the monomer (b1) having neither a crosslinkable functional group nor a nitrogen atom include the monomers described in the section entitled "(meth)acrylic monomer (a1) having no crosslinkable functional group" in the (meth)acrylic polymer (A), and the vinyl esters, olefins, halogenated olefins, styrene-based monomers, and diene-based monomers described in the section entitled "Other monomers (a3)."

[0049] The polymer (B) may have one or more types of constitutional units derived from a monomer (b1) that does not have a crosslinkable functional group and a nitrogen atom. In 100% by mass of the monomer component (b) used to form the polymer (B), the content of the monomer (b1) having no crosslinkable functional group and no nitrogen atom is usually 50 to 100% by mass, preferably 60 to 100% by mass, more preferably 70 to 100% by mass, and even more preferably 80 to 100% by mass. If the content of the monomer (b1) having neither a crosslinkable functional group nor a nitrogen atom is within the above range, good reworkability is easily obtained, which is preferable.

[0050] (Nitrogen atom-containing monomer (b2)) The nitrogen atom-containing monomer (b2) is a monomer having a nitrogen atom in the molecule, and examples thereof include amino group-containing monomers, amide group-containing monomers, nitrogen-based heterocycle-containing monomers, and cyano group-containing monomers.

[0051] Specific examples of the amino group-containing monomer, amide group-containing monomer, nitrogen-based heterocycle-containing monomer and cyano group-containing monomer include the amino group-containing monomers described in the section (a2) of the monomer having a crosslinkable functional group in the (meth)acrylic polymer (A), and the amide group-containing monomer, nitrogen-based heterocycle-containing monomer and cyano group-containing monomer described in the section (a3) ​​of other monomers.

[0052] The polymer (B) may have constitutional units derived from one or more nitrogen atom-containing monomers (b2). In 100% by mass of the monomer component (b) used to form the polymer (B), the content of the nitrogen atom-containing monomer (b2) is preferably 5% by mass or less, more preferably 2% by mass or less, and even more preferably the polymer (B) does not contain any nitrogen atom-containing monomer (b2). If the nitrogen atom-containing monomer (b2) is within the above range, the adherend tends not to be stained easily, which is preferable.

[0053] (Other monomers (b3)) The other monomer (b3) is a monomer other than the monomer (b1) having no crosslinkable functional group or nitrogen atom and the nitrogen-containing monomer (b2).

[0054] Specific examples of the other monomer (b3) include the carboxy group- or acid anhydride group-containing monomers and hydroxy group-containing monomers described in the section on the monomer (a2) having a crosslinkable functional group in the (meth)acrylic polymer (A).

[0055] The polymer (B) may have constitutional units derived from one or more other monomers (b3). In 100% by mass of the monomer component (b) used to form the polymer (B), the content of the other monomer (b3) is usually 30% by mass or less, preferably 25% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less. If the content of the other monomer (b3) is within the above range, the adherend tends not to be stained, which is preferable.

[0056] [Method for producing polymer (B)] The polymer (B) is obtained by copolymerizing the monomer component (b). The production method is not particularly limited, and any known method can be used, for example, solution polymerization, bulk polymerization, emulsion polymerization, suspension polymerization, etc., and is preferably the solution polymerization method because it is easy to adjust the molecular weight and produces fewer impurities during production. As specific production conditions, for example, the production conditions described in the (meth)acrylic polymer (A) section can be referred to.

[0057] [Physical properties of polymer (B)] The Tg of the polymer (B) is greater than -20°C and less than 30°C, preferably -15°C or more and less than -30°C, and more preferably -10°C or more and less than -30°C. It is preferable that the Tg of the polymer (B) is within the above range, since it is easy to obtain good reworkability and tends not to contaminate the adherend. The Tg of the polymer (B) is calculated by the above-mentioned Fox formula.

[0058] The number average molecular weight (Mn) of the polymer (B) measured by the GPC method is not particularly limited, but is preferably 13,000 to 100,000, more preferably 13,000 to 80,000, and even more preferably 14,000 to 60,000, in terms of polystyrene. When the Mn of the polymer (B) is within the above range, good reworkability is easily obtained and the adherend tends not to be contaminated, which is preferable.

[0059] The molecular weight distribution (Mw / Mn) of the polymer (B) measured by the GPC method is usually 10 or less, preferably 8 or less, and more preferably 2-6.

[0060] [Crosslinker (C)] The composition may contain a crosslinking agent (C). The crosslinking agent (C) is not particularly limited, but for example, an epoxy-based crosslinking agent, an isocyanate-based crosslinking agent, a metal chelate compound, etc. can be used, and among these, an epoxy-based crosslinking agent is preferred. The crosslinking agent (C) used in the present composition may be one type alone, or two or more types may be used.

[0061] (Epoxy crosslinking agent) Examples of epoxy crosslinking agents include epoxy compounds having two or more epoxy groups in one molecule, specifically ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-m-xylylenediamine, N,N,N',N'-tetraglycidylaminophenylmethane, triglycidyl isocyanurate, mN,N-diglycidylaminophenyl glycidyl ether, N,N-diglycidyl toluidine, and N,N-diglycidylaniline. The number of epoxy groups in one molecule of the epoxy compound is, for example, 2 to 10.

[0062] (Isocyanate-based crosslinking agent) Examples of isocyanate crosslinking agents include isocyanate compounds having two or more isocyanate groups in one molecule. Examples of diisocyanate compounds having two isocyanate groups in one molecule include aliphatic diisocyanates, alicyclic diisocyanates, and aromatic diisocyanates. Examples of isocyanate compounds having three or more isocyanate groups in one molecule include aromatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates. Examples of isocyanate compounds include multimers (e.g., dimers or trimers, biuret bodies, isocyanurates), derivatives (e.g., addition reaction products of polyhydric alcohols and two or more molecules of diisocyanate compounds), and polymers of the above isocyanate compounds having two or three or more isocyanate groups.

[0063] (Metal chelate compounds) Examples of metal chelate crosslinking agents include compounds in which components such as alkoxides, acetylacetone, and ethyl acetoacetate are coordinated with polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium. Among these, aluminum chelate compounds are preferred. Specific examples include aluminum isopropylate, aluminum secondary butylate, aluminum ethyl acetoacetate diisopropylate, aluminum trisethyl acetoacetate, and aluminum trisacetylacetonate.

[0064] In the present composition, the content of the crosslinking agent (C) is usually 10 parts by mass or less, preferably 0.01 to 8 parts by mass, and more preferably 0.05 to 5 parts by mass, based on 100 parts by mass of the (meth)acrylic polymer (A). When the crosslinking agent (C) is within the above range, a crosslinked structure is formed in the pressure-sensitive adhesive layer formed from the composition, which tends to provide a pressure-sensitive adhesive layer that has good reworkability and is less likely to contaminate the adherend.

[0065] [solvent] The present composition may contain a solvent to adjust the coating property, and the solvent is preferably an organic solvent.

[0066] 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, phenylethyl 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. The organic solvent may be used alone or in combination of two or more kinds.

[0067] In the present composition, the content of the solvent is usually 90% by mass or less, and preferably 10 to 80% by mass.

[0068] [Other ingredients] The present composition may further contain other components besides the (meth)acrylic polymer (A) and polymer (B) as long as the effects of the present invention are not impaired. When other components are used in the present composition, the number of types of each of the other components may be one or more.

[0069] Examples of other components include resin components other than the (meth)acrylic polymer (A) and polymer (B), and various additives such as antistatic agents, silane coupling agents, ultraviolet absorbers, antioxidants, tackifiers, plasticizers, defoamers, fillers, stabilizers, softeners, pigments, and wettability adjusters.

[0070] When the present composition contains other components, the amount of such components may be in the range of usually 50 parts by mass or less, preferably 40 parts by mass or less, and more preferably 30 parts by mass or less, per 100 parts by mass of the polymer (A).

[0071] [Method of manufacturing adhesive composition for decorative film] The present composition can be prepared by mixing the above-mentioned components sequentially or simultaneously by a known method.

[0072] The composition can be prepared by mixing the (meth)acrylic polymer (A) and the polymer (B) with the crosslinking agent (C), a solvent, and other components as required by a conventionally known method. In one embodiment, for example, a polymer solution containing the polymer and an organic solvent obtained when synthesizing the (meth)acrylic polymer (A) and the polymer (B) is mixed, and the crosslinking agent (C) and other components are added as required. The composition can be obtained by mixing each component all at once or sequentially, and the mixing time is not particularly limited, but from the viewpoint of workability and productivity, it is usually about 10 to 120 minutes at room temperature using a stirring device.

[0073] <Decorative film> The decorative film of the present invention has a pressure-sensitive adhesive layer obtained from the above-mentioned pressure-sensitive adhesive composition for decorative film and a substrate layer. The substrate layer preferably plays a role of decoration, but may have a decorative layer. In addition, in order to protect the pressure-sensitive adhesive layer until it is used, a release film may be provided on the pressure-sensitive adhesive layer. Furthermore, other layers may be provided as necessary.

[0074] (Adhesive layer) The pressure-sensitive adhesive layer of the decorative film according to the present invention is formed from the pressure-sensitive adhesive composition for decorative films according to the present invention described above. The pressure-sensitive adhesive layer can be obtained, for example, by applying the above-mentioned pressure-sensitive adhesive composition for decorative films onto a substrate or onto a decorative layer, and crosslinking the composition as necessary.

[0075] The adhesive layer may have an uneven surface on the side that comes into contact with the adherend (the release film side) to facilitate the escape of air bubbles between the adherend and the adhesive layer when the decorative film is attached to the adherend.

[0076] The thickness of the pressure-sensitive adhesive layer is usually 3 to 500 μm, preferably 5 to 300 μm.

[0077] (base material layer) The substrate layer usually constitutes the outermost layer of a decorated molded body obtained by attaching a decorative film to an adherend that is the object of decoration. The substrate constituting the substrate layer may be colored or colorless, and may be transparent, semi-transparent, or opaque. The substrate layer is usually in the form of a film or sheet, and may have a single layer structure or a multi-layer structure.

[0078] The base layer is preferably made of a thermoplastic resin, although it is not particularly limited thereto. Examples of the thermoplastic resin include polyvinyl chloride, polyester, polyethylene, polypropylene, polycarbonate, polymethyl methacrylate, and acrylonitrile / butadiene / styrene (ABS) resin, and the base layer may contain one or more of these.

[0079] The base layer may contain, as necessary, a functionality-imparting substance such as a filler such as particles, a plasticizer, a colorant, an ultraviolet absorber, etc. Furthermore, a pattern, letter, design, etc. may be printed on the surface of the base layer to impart design, and a pattern, letter, design, etc. may be formed inside the base layer.

[0080] The thickness of the substrate layer is usually 10 to 1000 μm, preferably 20 to 500 μm, and more preferably 30 to 300 μm.

[0081] (Decorative layer) The decorative film of the present invention can further have a decorative layer between the substrate layer and the adhesive layer, in the substrate layer or on the substrate layer. The decorative layer is a layer provided to impart design to the decorative film, and may be, for example, a metal layer to express a metallic tone, and may form a pattern, character, picture, etc. by a method such as printing. When forming a pattern on the decorative layer, it can be formed by a known printing method such as gravure printing with printing ink, offset printing, silk screen printing, transfer printing from a transfer sheet, sublimation transfer printing, and inkjet printing. It may also have a fine uneven shape such as an embossed pattern.

[0082] In order to express a variety of designs, the thickness of the decorative layer is usually 0.1 to 50 μm, preferably 0.5 to 40 μm, and more preferably 1 to 30 μm.

[0083] (Release film) The decorative film of the present invention may have a release film on the adhesive layer as necessary. The release film protects the surface of the adhesive layer until the decorative film is actually used, and is peeled off and removed when the decorative film is used. The release film is not particularly limited as long as it is a film that can be easily peeled off from the adhesive layer, and examples thereof include resin films such as polyester films such as polyethylene terephthalate and polybutylene terephthalate, polyolefin films such as polyethylene, polypropylene, and ethylene-vinyl acetate copolymer, and paper materials such as glassine paper, craft paper, and clay-coated paper. At least one side of the release film may be easily peeled off with a release treatment agent such as a silicone-based, fluorine-based, long-chain alkyl-based, or fatty acid amide-based.

[0084] In addition, a release film having an uneven shape can be used to facilitate the escape of air bubbles between the adherend and the adhesive layer when the decorative film is applied to the adherend. For example, an adhesive composition is applied to the uneven surface of a release film having an uneven shape, and dried to form an adhesive layer, thereby transferring the uneven shape to the adhesive layer, or a release film having an uneven shape and an adhesive layer are attached to each other to transfer the uneven shape to the adhesive layer, thereby imparting an uneven shape to the adhesive layer.

[0085] The thickness of the release film is usually 10 to 500 μm, preferably 20 to 300 μm.

[0086] (Other layers) The decorative film of the present invention may have other layers as necessary, such as a protective layer, an ultraviolet absorbing layer, an antistatic layer, and an impact buffer layer. When the other layer is present, the other layer may be one type or two or more types.

[0087] [Decorative film manufacturing method] The decorative film of the present invention can be obtained, for example, by a method of applying the adhesive composition for decorative films of the present invention to a release film, drying to form an adhesive layer, laminating an exposed surface of the obtained adhesive layer that is not in contact with the release film to a substrate, and curing to form a decorative film; or by a method of applying the composition to a substrate, drying to form an adhesive layer, laminating an exposed surface of the obtained adhesive layer that is not in contact with the substrate to a release film, and curing to form a decorative film.

[0088] The conditions for forming the pressure-sensitive adhesive layer are, for example, as follows: The composition is applied to a release film or a substrate and dried. Drying conditions vary depending on the type of solvent, but typically the drying temperature is 50 to 150° C. and the drying time is 1 to 10 minutes. Examples of methods for applying the pressure-sensitive adhesive composition include spin coating, knife coating, roll coating, bar coating, blade coating, die coating, and gravure coating.

[0089] The curing conditions are, for example, as follows. Curing is usually performed for one day or more, preferably for 2 to 10 days, usually at 5 to 60°C, preferably 15 to 50°C, usually at 30 to 70% RH, preferably 40 to 70% RH. Curing under these conditions ensures sufficient adhesion between the pressure-sensitive adhesive layer and the substrate. In addition, when the pressure-sensitive adhesive composition contains a crosslinking agent (C), a crosslinked body (network polymer) can be efficiently formed.

[0090] [Uses of decorative film] The object to which the decorative film of the present invention is applied includes a molded body such as an article having a three-dimensional shape, and an article having a three-dimensional curved surface is preferable.Specific examples include exterior and interior materials for moving objects, building materials, and decorative panels.Note that the moving object refers to a moving object in a broad sense, including, for example, a vehicle having wheels or tracks such as a passenger car, a bus, a dual mode vehicle, a truck, a motorcycle, a scooter, a motorized bicycle, a bulldozer, etc.; a railway such as a train, a monorail, and a linear motor car; an aircraft such as an airplane, a helicopter, and a drone; and a ship.

[0091] The decorative film of the present invention has good reworkability and is not likely to contaminate the substrate. For example, when replacing the decorative film, a different decorative film can be attached to the substrate without cleaning the surface of the substrate. Since different designs can be easily imparted, the decorative film is particularly preferably used as a film for vehicles, specifically as a film for the exterior of vehicles (e.g., a film for car wrapping).

[0092] The material of the adherend is not particularly limited, and examples thereof include metal materials; wood; and plastics such as ABS resin, polycarbonate resin, polyester resin, polypropylene resin, and polyethylene resin, the surface of which may be coated.

[0093] Methods for attaching the decorative film to the molded body as the adherend include, for example, manual attachment, vacuum molding, pressure molding, vacuum pressure molding, and hot high pressure molding. Among these, vacuum pressure molding is preferred because it allows the decorative film to be neatly wrapped around the end of the molded body having a curved surface. EXAMPLES

[0094] Specific examples embodying the disclosure of this specification are shown below. However, the disclosure of this specification is not limited to the following specific examples. In the following description, "parts" means parts by mass and "%" means % by mass.

[0095] [Molecular weight] The weight average molecular weight (Mw) and number average molecular weight (Mn) of (meth)acrylic polymer (A) and polymer (B) were determined by gel permeation chromatography (GPC) under the following conditions in terms of standard polystyrene. Measuring device: HLC-8220GPC (Tosoh Corporation) GPC column configuration: 5 columns in series (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: 1.0mg / cm 3 Dilute with tetrahydrofuran so that Mobile phase solvent: Tetrahydrofuran ·Flow rate: 1.0cm 3 / min Column temperature: 40℃

[0096] [Synthesis Example 1] (Production of (meth)acrylic polymer (A1)) A reactor equipped with a stirrer, reflux condenser, thermometer and nitrogen inlet tube was charged with 72 parts of n-butyl acrylate (BA), 20 parts of methyl acrylate (MA), 8 parts of acrylic acid (AA) and 200 parts of ethyl acetate, and the temperature was raised to 75°C while introducing nitrogen gas. Then, 0.15 parts of 2,2'-azobisisobutyronitrile (AIBN) was added, and a polymerization reaction was carried out for 4 hours at 75-76°C under a nitrogen atmosphere. After the reaction was completed, the reaction solution was diluted with ethyl acetate to prepare a polymer solution with a solid content concentration of 25% by mass. The weight average molecular weight (Mw) of the obtained (meth)acrylic polymer (A1) was 450,000, and the glass transition temperature (Tg) (calculated by Fox's formula) was -32°C.

[0097] [Synthesis Examples 2-3] Polymerization was carried out in the same manner as in Synthesis Example 1, except that the monomer composition was changed as shown in Table 1 (the unit of composition is parts by mass), to obtain (meth)acrylic polymers (A2) to (A3). Table 1 also shows the Mw and Tg of the obtained (meth)acrylic polymers (A2) to (A3).

[0098] [Table 1] BA: n-butyl acrylate 2EHA: 2-Ethylhexyl acrylate MEA: 2-Methoxyethyl acrylate MA: Methyl acrylate AA: Acrylic acid Vac: Vinyl acetate

[0099] [Synthesis Example 4] (Production of Polymer (B1)) In a reaction apparatus equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen inlet tube, 90 parts of n-butyl methacrylate (BMA), 10 parts of methyl methacrylate (MMA), 0.95 parts of N-dodecyl mercaptan (NDM) as a chain transfer agent, and 100 parts of ethyl acetate were charged, and the temperature was raised to 75°C while introducing nitrogen gas. Then, 0.15 parts of AIBN were added, and a polymerization reaction was carried out at 75 to 76°C for 4 hours under a nitrogen atmosphere. After the reaction was completed, the reaction solution was diluted with ethyl acetate to prepare a polymer solution with a solid content concentration of 45% by mass. The number average molecular weight (Mn) of the obtained polymer (B1) was 15,000, and Tg was 27°C.

[0100] [Synthesis Example 5, Synthesis Example 7] Polymers (B2) and (cB4) were obtained by polymerization in the same manner as in Synthesis Example 4, except that the monomer composition was changed as shown in Table 2 (the unit of composition is parts by mass). The Mn and Tg of the obtained polymers (B2) and (cB4) are also shown in Table 2.

[0101] [Synthesis Example 6] Polymer (B3) was obtained by carrying out polymerization in the same manner as in Synthesis Example 4, except that the monomer composition was changed as shown in Table 2 and the amount of NDM was changed to 0.98 parts. The Mn and Tg of the obtained polymer (B3) are also shown in Table 2.

[0102] [Table 2] BMA: n-Butyl methacrylate MMA: Methyl methacrylate DMAEA: Dimethylaminoethyl acrylate

[0103] [Example 1] A pressure-sensitive adhesive composition was obtained by adding and mixing the polymer solution of the polymer (B1) obtained in Synthesis Example 4 and N,N,N',N'-tetraglycidyl-m-xylylenediamine (Soken Chemical & Engineering Co., Ltd., E-AX) as a crosslinking agent to the polymer solution of the (meth)acrylic polymer (A1) obtained in Synthesis Example 1. The respective blend amounts were, in terms of solid content, 10 parts of polymer (B1) and 0.1 part of crosslinking agent per 100 parts of the (meth)acrylic polymer (A1).

[0104] Next, a decorative film was produced using the obtained pressure-sensitive adhesive composition as described below, and the staining resistance and reworkability were evaluated. The results are shown in Table 3.

[0105] [Creating decorative film] As the substrate, a resin composition was extruded from 100 parts by mass of polyvinyl chloride resin (ZEST1000Z, Shin-Daiichi Vinyl Corporation) to which 30 parts by mass of a polyester plasticizer (Adeka Cizer PN-7230, ADEKA Corporation) was added to produce a soft polyvinyl chloride (PVC) film with a thickness of 80 μm. Next, the adhesive composition was applied onto a release-treated PET film and dried at 90° C. for 4 minutes to form an adhesive layer having a thickness of 25 μm. The adhesive layer was then attached to the PVC film and aged at 40° C. for 3 days to produce a decorative film.

[0106] [Staining test] The obtained decorative film was set in a vacuum and compressed air forming machine (Fuse Vacuum Co., Ltd., NGF forming machine), and a stainless steel plate with a width of 100 mm, length of 100 mm, and thickness of 20 mm was decorated and formed under the conditions of a heating temperature of 110°C and a pressure of 0.2 MPa so that the stretching ratio was 200%. The stainless steel plate used was a stainless steel (SUS) 304 steel plate (hereinafter simply referred to as stainless steel plate) specified in JIS G 4305 that had been BA-treated (cold-rolled, then bright heat-treated) and had its surface degreased and washed with ethyl acetate. The obtained molded body was left in a 40°C environment for 24 hours, and then left in a 23°C / 50% RH environment for 1 hour. After that, a slit was made in the molded decorative film to a width of 25 mm, and one end was attached to the chuck of a tensile tester. The end of the decorative film was pulled at a peel angle of 180° to the stainless steel plate at a pulling speed of 300 mm / min in an environment of 23°C / 50% RH, and the contamination of the stainless steel plate surface was visually evaluated according to the following criteria. ◯: No traces of the adhesive were left on the surface of the stainless steel plate. Δ: A slight oily film-like mark was observed on the surface of the stainless steel plate, but this was not problematic for practical use. ×: An oily film-like attachment mark was clearly observed on the surface of the stainless steel plate.

[0107] [Reworkability test] The obtained decorative film was cut to a width of 25 mm and a length of 80 mm to prepare a test piece. The release-treated PET film was peeled off from the obtained test piece, and the exposed adhesive layer was attached to a stainless steel plate and pressed with a 2 kg roller three times. After pressing, the test piece was left in an environment of 23°C and 50% RH for 20 minutes. Then, in an environment of 23°C and 50% RH, the end of the test piece was pulled at an angle of 180° to the stainless steel plate at a pulling speed of 300 mm / min, and the reworkability was evaluated according to the following criteria. ◯: No adhesion failure such as lifting or peeling occurred at the interface between the PVC film and the pressure-sensitive adhesive layer. Δ: A small amount of lift occurred at the interface between the PVC film and the adhesive layer. ×: Adhesion failure such as lifting or peeling occurred at the interface between the PVC film and the adhesive layer.

[0108] [Examples 2 to 4, Comparative Examples 1 to 3] Pressure-sensitive adhesive compositions were obtained in the same manner as in Example 1, except that the blending composition was changed as shown in Table 3. The values ​​shown in Table 3 are solid contents. Next, decorative films were produced using each of the obtained pressure-sensitive adhesive compositions in the same manner as in Example 1, and the staining resistance and reworkability were evaluated. The results are also shown in Table 3.

[0109] [Table 3]

[0110] Examples 1 to 4 show that an adhesive composition containing a (meth)acrylic polymer (A) having a Tg of -20°C or less and a polymer (B) having a Tg of more than -20°C and less than 30°C is suitable as a decorative film because it has good resistance to contamination and reworkability when used as an adhesive layer of the decorative film.

[0111] Comparative Example 1 and Comparative Example 3, which do not contain a polymer (B) having a Tg of more than -20°C and less than 30°C, were insufficient for decorative film use in terms of both reworkability or staining property and reworkability. Comparative Example 2, which does not contain a (meth)acrylic polymer (A) having a glass transition temperature of -20°C or less, was insufficient in terms of staining property for decorative film use. This is considered to be due to the compatibility between the (meth)acrylic polymer (A) and the polymer (B). [Industrial Applicability]

[0112] The adhesive composition for decorative films of the present invention is suitable for forming an adhesive layer of decorative films. The decorative films of the present invention are suitable for surface decoration of molded articles such as exterior and interior materials for mobile objects, building materials, and decorative panels, and are particularly suitable for use as exterior films for vehicles such as car wrapping films.

Claims

1. A (meth)acrylic polymer (A) having a glass transition temperature of −20° C. or lower; A pressure-sensitive adhesive composition comprising a polymer (B) having a glass transition temperature of more than -20°C and less than 30°C, The polymer (B) is contained in an amount of 0.1 to 100 parts by mass based on 100 parts by mass of the (meth)acrylic polymer (A). Adhesive composition for decorative films.

2. 2. The pressure-sensitive adhesive composition for decorative films according to claim 1, wherein the content of structural units derived from alkoxyalkyl (meth)acrylate in all monomers constituting the (meth)acrylic polymer (A) is less than 50 mass%.

3. The pressure-sensitive adhesive composition for decorative films according to claim 1 , wherein the polymer (B) does not contain any structural unit derived from a nitrogen atom-containing monomer.

4. 2. The pressure-sensitive adhesive composition for decorative films according to claim 1, wherein the number average molecular weight (Mn) of the polymer (B) is 13,000 to 100,000.

5. A decorative film comprising a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition for decorative films according to any one of claims 1 to 4, and a substrate layer.

6. The decorative film according to claim 5, which is for vacuum and pressure forming.

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