Adhesive composition for decorative film and decorative film

Abstract

To provide an adhesive composition for a decorative film that exhibits superior adhesion immediately after application and demonstrates superior durability, and a decorative film prepared using the adhesive composition.SOLUTION: An adhesive composition for a decorative film comprises: a (meth)acrylic polymer (A) comprising 1 to 20 mass% of structural units derived from a carboxyl group-containing monomer; and a polymer (B) having a glass transition temperature of 30°C to 200°C and a number average molecular weight (Mn) of 500 to 10000, 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. The adhesive used in these decorative films is required to have low tack (stickiness) so that it can be easily repositioned if the adhesive-processed decorative film is misaligned when applied to the substrate. On the other hand, if the tack is too low, the film will peel off immediately after application, so it is also required to have a moderate adhesion. In particular, in low-temperature environments such as cold regions, the tack is low, so the adhesion immediately after application is likely to be insufficient.

[0003] Patent Document 1 discloses a decorative film having an adhesive layer containing a specific vinyl polymer and an acrylic adhesive polymer. Patent Document 2 discloses a decorative film having a pressure-sensitive adhesive layer containing a carboxyl group-containing (meth)acrylic polymer and an amino group-containing (meth)acrylic polymer capable of forming a metal complex with a metal ion generated from a metal substrate, and an acrylic resin film layer. It is taught that these decorative films and decorative films each have stable adhesive strength for a long period of time and are excellent in durability.

[0004] However, the reality is that no adhesive for decorative films has been found that has good adhesion immediately after application and excellent durability. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2019-112574 A [Patent Document 2] Patent No. 6574109 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a pressure-sensitive adhesive composition for decorative films which has good adhesion immediately after application and excellent durability, and a decorative film which uses the pressure-sensitive adhesive composition for decorative films. [Means for solving the problem]

[0007] Means for Solving the Problems The present inventors have conducted intensive research in light of the above-mentioned circumstances and have found that a pressure-sensitive adhesive composition containing a (meth)acrylic polymer having a predetermined structural unit and a polymer having a predetermined 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].

[0008] [1] A pressure-sensitive adhesive composition for decorative films, comprising: a (meth)acrylic polymer (A) containing 1 to 20 mass% of a structural unit derived from a carboxy group-containing monomer; and a polymer (B) having a glass transition temperature of 30 to 200°C and a number average molecular weight (Mn) of 500 to 10,000, the composition comprising 0.1 to 100 parts by mass of the polymer (B) 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 (meth)acrylic polymer (A) contains 6.5 to 20 mass % of structural units derived from an alkyl (meth)acrylate having a homopolymer glass transition temperature of less than -55°C. [3] The pressure-sensitive adhesive composition for decorative films according to [1] or [2], wherein the weight average molecular weight (Mw) of the (meth)acrylic polymer (A) is 200,000 or more and less than 800,000. [4] The pressure-sensitive adhesive composition for decorative films according to any one of [1] to [3], wherein the polymer (B) contains 65 mass % or more of structural units derived from methyl methacrylate. [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

[0009] According to the present invention, it is possible to provide a pressure-sensitive adhesive composition for decorative films that has good adhesion immediately after application and excellent durability, and a decorative film using the pressure-sensitive adhesive composition for decorative films. The pressure-sensitive adhesive composition for decorative films of the present invention can be suitably used in the pressure-sensitive adhesive layer of decorative films, and decorative films using the composition have good adhesion immediately after application and excellent durability. 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

[0010] 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.

[0011] <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.

[0012] [(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 containing 1 to 20 mass% of a carboxyl group-containing monomer (a1). Here, the main component means a component contained in an amount of more than 50 mass% of 100 mass% of the monomer component (a). The monomer component (a) may further contain an alkyl (meth)acrylate (a2) and other monomers (a3) ​​having a homopolymer glass transition temperature of less than -55°C. The (meth)acrylic polymer (A) used in the present composition may be one type or two or more types.

[0013] (Carboxy Group-Containing Monomer (a1)) Examples of the carboxy group-containing monomer (a1) 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 (meth)acrylic acid and crotonic acid; diunsaturated fatty acids such as maleic acid, fumaric acid, itaconic acid, and citraconic acid, and acid anhydrides thereof. Among these, (meth)acrylic acid is preferred. The carboxyl group-containing monomer (a1) may be used alone or in combination of two or more.

[0014] In 100% by mass of the monomer component (a), the content of the carboxy group-containing monomer (a1) is 1 to 20% by mass, preferably 2 to 18% by mass, more preferably 3 to 16% by mass, and even more preferably more than 5% by mass and less than 15% by mass. When the amount of the carboxyl group-containing monomer (a1) is within the above range, excellent durability is easily obtained, which is preferable.

[0015] (Alkyl (meth)acrylate (a2) having a homopolymer glass transition temperature of less than -55°C) Examples of alkyl (meth)acrylates (a2) having a homopolymer glass transition temperature of less than -55°C include n-hexyl acrylate (Tg: -57°C), n-octyl acrylate (Tg: -65°C), isooctyl acrylate (Tg: -58°C), 2-ethylhexyl acrylate (Tg: -70°C), nonyl acrylate (Tg: -58°C), and lauryl methacrylate (Tg: -65°C). The alkyl (meth)acrylate (a2) having a homopolymer glass transition temperature of less than −55° C. may be used alone or in combination of two or more kinds. In the present invention, the glass transition temperature of the homopolymer of each monomer may be, for example, the value described in Polymer Handbook, Fourth Edition (Wiley-Interscience 2003).

[0016] When an alkyl (meth)acrylate (a2) having a homopolymer glass transition temperature of less than -55°C is used in 100 mass% of the monomer component (a), the content thereof is usually 99 mass% or less, preferably 2 to 70 mass%, more preferably 4 to 40 mass%, and even more preferably 6.5 to 20 mass%, in 100 mass% of the monomer component (a). If the alkyl (meth)acrylate (a2) having a homopolymer glass transition temperature of less than −55° C. is within the above range, the adhesiveness immediately after application tends to be excellent, which is preferable.

[0017] (Other monomers (a3)) The other monomer (a3) ​​is a monomer selected from the group consisting of the carboxyl group-containing monomer (a1) and the homopolymer (a2). The polymer has a glass transition temperature of less than -55°C and is a monomer other than alkyl (meth)acrylate (a2).

[0018] Examples of the other monomer (a3) ​​include crosslinkable functional group-containing monomers other than alkyl (meth)acrylates, alicyclic group-containing (meth)acrylates, aromatic ring-containing (meth)acrylates, alkoxyalkyl (meth)acrylates, alkoxypolyalkylene glycol mono(meth)acrylates, and carboxy group-containing monomers, whose homopolymers have a glass transition temperature of −55° C. or higher.

[0019] Examples of alkyl (meth)acrylates having a homopolymer glass transition temperature of -55°C or higher include methyl acrylate (Tg: 8°C), ethyl acrylate (Tg: -24°C), n-propyl acrylate (Tg: 3°C), isopropyl acrylate (Tg: -3°C), n-butyl acrylate (Tg: -50°C), isobutyl acrylate (Tg: -40°C), t-butyl acrylate (Tg: 43°C), n-pentyl acrylate (Tg: 22°C), lauryl acrylate (Tg: -3°C), methyl methacrylate (Tg: 105°C), ethyl methacrylate (Tg : 65 ° C), n-propyl methacrylate (Tg: 35 ° C), isopropyl methacrylate (Tg: 81 ° C), t-butyl methacrylate (Tg: 118 ° C), n-butyl methacrylate (Tg: 20 ° C), isobutyl methacrylate (Tg: 48 ° C), n-pentyl methacrylate (Tg: -5 ° C), n-hexyl methacrylate (Tg: -5 ° C), n-octyl methacrylate (Tg: -20 ° C), isooctyl methacrylate (Tg: -45 ° C), 2-ethylhexyl methacrylate (Tg: -10 ° C), isodecyl methacrylate (Tg: -41 ° C).

[0020] Examples of the alicyclic group-containing (meth)acrylate include cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and adamantyl (meth)acrylate.

[0021] Examples of aromatic ring-containing (meth)acrylates include benzyl (meth)acrylate, phenyl (meth)acrylate, and phenoxyethyl (meth)acrylate.

[0022] 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.

[0023] 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.

[0024] The above-mentioned alkyl (meth)acrylates, alicyclic group-containing (meth)acrylates, aromatic ring-containing (meth)acrylates, alkoxyalkyl (meth)acrylates, and alkoxypolyalkylene glycol mono(meth)acrylates, each of which has a homopolymer glass transition temperature of -55°C or higher, may be used alone or in combination of two or more. When such a monomer is used, the content thereof is usually 99% by mass or less, preferably 1 to 95% by mass, more preferably 2 to 90% by mass, and further preferably 3 to 85% by mass, based on 100% by mass of the monomer component (a).

[0025] Examples of crosslinkable functional group-containing monomers other than carboxy group-containing monomers include hydroxy group-containing monomers, amino group-containing monomers, amide group-containing monomers, and cyano group-containing monomers.

[0026] Examples of hydroxy group-containing monomers include hydroxy group-containing (meth)acrylates, specifically 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 8-hydroxyoctyl (meth)acrylate.

[0027] Examples of amino group-containing monomers include N-alkylaminoalkyl(meth)acrylates such as N-methylaminoethyl(meth)acrylate and N-ethylaminoethyl(meth)acrylate.

[0028] 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.

[0029] An example of a cyano group-containing monomer is (meth)acrylonitrile.

[0030] The crosslinkable functional group-containing monomer other than the carboxy group-containing monomer may be used alone or in combination of two or more kinds. When a crosslinkable functional group-containing monomer other than a carboxy group-containing monomer is used, the content thereof is usually 20 mass % or less, preferably 15 mass % or less, more preferably 10 mass % or less, and even more preferably 5 mass % or less, based on 100 mass % of the monomer component (a).

[0031] Furthermore, the (meth)acrylic polymer (A) according to the present invention may contain, within the range that does not impair its physical properties, copolymerizable monomers such as 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., diene-based monomers such as butadiene, isoprene, chloroprene, etc., in the monomer component (a) of 100% by mass, when such copolymerizable monomers are used, the content ratio thereof is preferably 30% by mass or less, more preferably 20% 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 glass transition temperature (Tg) of the (meth)acrylic polymer (A) is usually from -80 to 0°C, preferably from -70 to -10°C, more preferably from -60 to -20°C, and further preferably from -50 to -30°C. If the Tg of the (meth)acrylic polymer (A) is within the above range, the adhesion and durability immediately after application tend to be excellent, 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] When calculating 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 2,000,000, preferably 200,000 to 1,500,000, more preferably 200,000 to 1,000,000, and even more preferably 200,000 or more and less than 800,000, in terms of polystyrene. If the Mw of the (meth)acrylic polymer (A) is within the above range, the adhesiveness immediately after application tends to be excellent, 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 30 to 200° C. and a number average molecular weight (Mn) of 500 to 10,000. The polymer (B) used in the present composition may be one type, or two or more types.

[0045] The blending ratio of the 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 the (meth)acrylic polymer (A). When the blending ratio of the polymer (B) is within the above range, it is preferred because the composition tends to have excellent adhesion immediately after application.

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

[0047] (Monomer (b1) having no crosslinkable functional group) The monomer (b1) having no crosslinkable functional group is a monomer having no 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 crosslinkable functional group include a carboxy group, a hydroxy group, an amino group, an amide group, and a cyano group.

[0048] Specific examples of the monomer (b1) that does not have a crosslinkable functional group include the monomers described in the alkyl (meth)acrylate (a2) column, which have a homopolymer glass transition temperature of less than -55°C in the (meth)acrylic polymer (A), and the alkyl (meth)acrylates described in the other monomers (a3) ​​column, which have a homopolymer glass transition temperature of -55°C or higher, alicyclic group-containing (meth)acrylates, aromatic ring-containing (meth)acrylates, alkoxyalkyl (meth)acrylates, alkoxypolyalkylene glycol mono(meth)acrylates, vinyl esters, olefins, halogenated olefins, styrene-based monomers, and diene-based monomers. Among these, methyl methacrylate is particularly preferred.

[0049] The monomer (b1) having no crosslinkable functional group may be used alone or in combination of two or more kinds. The content of the monomer (b1) having no crosslinkable functional group is usually 50 to 100 mass%, preferably 65 to 100 mass%, more preferably 80 to 100 mass%, and further preferably 90 to 100 mass%, in 100 mass% of the monomer component (b). If it is within such a range, it is preferable because the adhesiveness immediately after application tends to be excellent.

[0050] (Monomer (b2) having a crosslinkable functional group) The monomer (b2) having a crosslinkable functional group is a monomer having a 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.

[0051] Specific examples of the monomer (b2) having a crosslinkable functional group include the monomers described in the section entitled “carboxy group-containing monomer (a1)” for the (meth)acrylic polymer (A) above, and the hydroxy group-containing monomers, amino group-containing monomers, amide group-containing monomers, and cyano group-containing monomers described in the section entitled “Other monomers (a3).”

[0052] The monomer (b2) having a crosslinkable functional group may be used alone or in combination of two or more kinds. The content of the monomer (b2) having a crosslinkable functional group is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less, based on 100% by mass of the monomer component (b). If it is within such a range, it is preferable because the adhesiveness immediately after application tends to be excellent.

[0053] [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.

[0054] [Physical properties of polymer (B)] The Tg of the polymer (B) is from 30 to 200°C, preferably from 40 to 175°C, more preferably from 50 to 150°C, and further preferably from 60 to 125°C. When the Tg of the polymer (B) is within the above range, excellent durability is easily obtained, which is preferable. The Tg of the polymer (B) is calculated by the above-mentioned Fox formula.

[0055] The number average molecular weight (Mn) of the polymer (B) measured by the GPC method is, in terms of polystyrene, 500 to 10,000, preferably 1,000 to 9,500, more preferably 1,500 to 9,000, and further preferably 2,000 to 8,500. When the Mn of the polymer (B) is within the above range, the adhesion immediately after application tends to be excellent, which is preferable.

[0056] 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.

[0057] [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.

[0058] (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.

[0059] (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.

[0060] (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.

[0061] 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 content of the crosslinking agent (C) is within the above range, a crosslinked structure is formed in the pressure-sensitive adhesive layer formed from the present composition, which is preferable since it makes it easier to obtain excellent durability.

[0062] [solvent] The present composition may contain a solvent to adjust the coating property, and the solvent is preferably an organic solvent.

[0063] 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, 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 with two or more other organic solvents.

[0064] In the present composition, the content of the solvent is usually 90% by mass or less, and preferably 10 to 80% by mass.

[0065] [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.

[0066] 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.

[0067] 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).

[0068] [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.

[0069] 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.

[0070] <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.

[0071] (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.

[0072] 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.

[0073] The thickness of the pressure-sensitive adhesive layer is usually 3 to 500 μm, preferably 5 to 300 μm.

[0074] (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.

[0075] 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.

[0076] 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.

[0077] The thickness of the substrate layer is usually 10 to 1000 μm, preferably 20 to 500 μm, and more preferably 30 to 300 μm.

[0078] (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, or may express 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.

[0079] 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.

[0080] (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.

[0081] 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.

[0082] The thickness of the release film is usually 10 to 500 μm, preferably 20 to 300 μm.

[0083] (Other layers) The decorative film of the present invention may have other layers as necessary. Examples of the other layers include a protective layer, an ultraviolet absorbing layer, an antistatic layer, and an impact buffer layer. When the decorative film of the present invention has other layers, the other layers may be one type or two or more types.

[0084] [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.

[0085] 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.

[0086] 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.

[0087] [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.

[0088] The decorative film of the present invention has good adhesion immediately after application, making it less likely to cause adhesion problems such as lifting or peeling, and furthermore, it exhibits sufficient durability even after application, making it particularly suitable for use as a film for vehicles, specifically as a film for the exterior of a vehicle (e.g., a film for car wrapping).

[0089] 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.

[0090] 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

[0091] 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.

[0092] [Molecular weight] The weight average molecular weight (Mw) and number average molecular weight (Mn) of the (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 the mobile phase solvent is tetrahydrofuran. ·Flow rate: 1.0cm 3 / min Column temperature: 40℃

[0093] [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 57 parts of n-butyl acrylate (BA), 15 parts of 2-ethyl acrylate (2EHA), 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 -36°C.

[0094] [Synthesis Example 2] The monomer composition was changed as shown in Table 1 (the unit of the composition is parts by mass), and polymerization was carried out in the same manner as in Synthesis Example 1, except that AIBN was changed to 0.1 parts, to obtain a (meth)acrylic polymer (A2). The Mw and Tg of the obtained (meth)acrylic polymer (A2) are also shown in Table 1.

[0095] [Synthesis Examples 3 to 5] Polymerization was carried out in the same manner as in Synthesis Example 1 above, except that the monomer composition was changed as shown in Table 1, to obtain (meth)acrylic polymers (A3) to (cA5). Table 1 also shows the Mw and Tg of the obtained (meth)acrylic polymers (A3) to (cA5).

[0096] [Table 1] BA: n-butyl acrylate 2EHA: 2-Ethylhexyl acrylate MA: Methyl acrylate AA: Acrylic acid

[0097] [Synthesis Example 6] (Production of Polymer (B1)) A reactor equipped with a stirrer, reflux condenser, thermometer and nitrogen inlet tube was charged with 95 parts of methyl methacrylate (MMA), 5 parts of dimethylaminoethyl acrylate (DMAEA), 0.98 parts of N-dodecyl mercaptan (NDM) as a chain transfer agent, and 100 parts of ethyl acetate, and the temperature was raised to 75°C while introducing nitrogen gas. Then, 0.15 parts of AIBN was 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 Mw of the obtained polymer (B1) was 20000, Mn was 8000, and Tg was 105°C.

[0098] [Synthesis Example 7, Synthesis Example 9] Polymers (B2) and (cB4) were obtained by polymerization in the same manner as in Synthesis Example 6, except that the monomer composition was changed as shown in Table 2 (the unit of composition is parts by mass). The Mw, Mn and Tg of the obtained polymers (B2) and (cB4) are also shown in Table 2.

[0099] [Synthesis Example 8] Polymer (cB3) was obtained by carrying out polymerization in the same manner as in Synthesis Example 6, except that the monomer composition was changed as shown in Table 2 and the amount of NDM was changed to 0.95 parts. Table 2 also shows the Mw, Mn and Tg of the obtained polymer (cB3).

[0100] [Table 2] BMA: n-Butyl methacrylate MMA: Methyl methacrylate DMAEA: Dimethylaminoethyl acrylate

[0101] [Example 1] A pressure-sensitive adhesive composition was obtained by adding the polymer solution of the polymer (B1) obtained in Synthesis Example 6 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 and mixing them. The respective blend amounts were 10 parts of polymer (B1) and 0.1 part of crosslinking agent per 100 parts of the (meth)acrylic polymer (A1) in solid content.

[0102] The adhesive composition thus obtained was then used to prepare a decorative film in the manner described below, and the adhesion and adhesive strength were evaluated. The results are shown in Table 3.

[0103] [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.

[0104] [Adhesion test] The obtained decorative film was set in a vacuum pressurized air molding machine (NGF molding machine, Fuse Vacuum Co., Ltd.), and an ABS plate 100 mm wide x 100 mm long x 20 mm thick was molded with a heating temperature of 110°C and a pressure of 0.2 MPa so that the stretch ratio was 200%. Within 2 minutes after the decorative molding, a 5 cm long cross-shaped cut was made in the molded decorative film with a cutter, and the film was left in a 23°C / 50% RH environment for 5 hours. The appearance of the decorative film was then evaluated based on the following criteria. ○: No peeling or expansion of the notch occurred △: No peeling occurred, but a slight crack was enlarged ×: Peeling or significant notch enlargement occurred.

[0105] [Adhesive strength test] (durability) The obtained decorative film was cut into a width of 25 mm and a length of 80 mm to prepare a test piece. The peel-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. The stainless steel plate 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. After pressing, the test piece was left in a 40°C / 90%RH environment for 72 hours. Then, the test piece was left in a 23°C / 50%RH environment for 24 hours. Next, the end of the test piece was pulled at a peel angle of 180° against the stainless steel plate and at a pulling speed of 300 mm / min using a tensile tester in a 23°C / 50%RH environment, and the adhesive strength was evaluated according to the following criteria. ○: Adhesive strength was greater than 15N / 25mm △: Adhesive strength was 10-15N / 25mm ×: Adhesive strength was less than 10N / 25mm

[0106] [Examples 2 to 5, Comparative Examples 1 to 4] 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 adhesion and adhesive strength were evaluated. The results are also shown in Table 3.

[0107] [Table 3]

[0108] Examples 1 to 5 show that an adhesive composition containing a (meth)acrylic polymer (A) containing 1 to 20 mass% of structural units derived from a carboxy group-containing monomer and a polymer (B) having a glass transition temperature of 30 to 200°C and a number average molecular weight (Mn) of 500 to 10,000 is suitable as a decorative film because it provides good adhesion and durability immediately after application when used as an adhesive layer of a decorative film.

[0109] It is seen that Comparative Example 1 and Comparative Example 4, which do not contain the polymer (B) having a number average molecular weight (Mn) of 500 to 10,000, have insufficient adhesion immediately after application for use as a decorative film. It is also seen that Comparative Example 2, which does not contain the polymer (B) having a glass transition temperature of 30 to 200°C, and Comparative Example 3, which does not contain the (meth)acrylic polymer (A) containing 1 to 20 mass% of a structural unit derived from a carboxyl group-containing monomer, have insufficient durability for use as a decorative film. This is thought to be due to the compatibility of the (meth)acrylic polymer (A) and the polymer (B). [Industrial Applicability]

[0110] 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) containing 1 to 20% by mass of a structural unit derived from a carboxy group-containing monomer; A pressure-sensitive adhesive composition comprising a polymer (B) having a glass transition temperature of 30 to 200° C. and a number average molecular weight (Mn) of 500 to 10,000, 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. The (meth)acrylic polymer (A) contains 6.5 to 20 mass% of a structural unit derived from an alkyl (meth)acrylate having a homopolymer glass transition temperature of less than -55 ° C. The pressure-sensitive adhesive composition for decorative films according to claim 1.

3. The pressure-sensitive adhesive composition for decorative films according to claim 1, wherein the (meth)acrylic polymer (A) has a weight average molecular weight (Mw) of 200,000 or more and less than 800,000.

4. 2. The pressure-sensitive adhesive composition for decorative films according to claim 1, wherein the polymer (B) contains 65 mass % or more of structural units derived from methyl methacrylate.

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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