Adhesive composition for overlaminate film, overlaminate film, and license plate

Abstract

To provide an adhesive composition for overlaminate films, enabling formation of an adhesive layer that exhibits strong adhesion to adherends and is less prone to cause visual defects during three-dimensional molding.SOLUTION: The present invention provides an adhesive composition for overlaminate films, comprising: a (meth)acrylic copolymer (A), a (meth)acrylic copolymer (B), and a blocked isocyanate compound as a crosslinking agent, wherein the copolymer (A) contains 1 to 15 mass% of monomer units having a carboxyl group based on all the structural units in the copolymer (A), and has a glass transition temperature (Tg) of -45°C to -5°C; the copolymer (B) contains monomer units having at least one selected from primary, secondary, and tertiary amino groups, and has a glass transition temperature (Tg) of 50°C to 100°C; the content of the copolymer (B) is 5 to 25 pts.mass based on 100 pts.mass of the copolymer (A); and the molar ratio of the isocyanate groups in the compound to the carboxyl groups in the copolymer (A) is 0.1 or more.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a pressure-sensitive adhesive composition for an overlaminate film, an overlaminate film, and a license plate. [Background technology]

[0002] Conventionally, inkjet-printed films have been used to decorate outdoor signs, vehicles (e.g., two-wheeled and four-wheeled vehicles), etc. Such films have a configuration including at least a printing film for printing and an overlaminate film for protecting the printing film, and in recent years have also been used for number plates (also called "license plates") (see, for example, Patent Documents 1 to 4). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-215672 A [Patent Document 2] JP 2017-177481 A [Patent Document 3] JP 2019-81330 A [Patent Document 4] JP 2019-206145 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, although commonly used overlaminate films have excellent adhesion to the adherend, during three-dimensional molding, cohesive failure and / or peeling of the pressure-sensitive adhesive layer may occur around the convex parts of the adherend, which may cause a loss of appearance.

[0005] The present disclosure has been made in consideration of the above circumstances. An object of one embodiment of the present disclosure is to provide a pressure-sensitive adhesive composition for an overlaminate film that has high adhesive strength to an adherend and is capable of forming a pressure-sensitive adhesive layer that is unlikely to cause poor appearance during three-dimensional molding. Another problem to be solved by another embodiment of the present disclosure is to provide an overlaminate film and a license plate having a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition for an overlaminate film. [Means for solving the problem]

[0006] Specific means for solving the problems include the following aspects. <1> A (meth)acrylic copolymer (A), a (meth)acrylic copolymer (B), and a blocked isocyanate compound as a crosslinking agent, Including, The (meth)acrylic copolymer (A) contains a structural unit derived from a monomer having a carboxy group in a proportion of 1% by mass to 15% by mass based on the total structural units of the (meth)acrylic copolymer (A), and has a glass transition temperature of -45°C to -5°C; The (meth)acrylic copolymer (B) contains a structural unit derived from a monomer having at least one amino group selected from the group consisting of a primary amino group, a secondary amino group, and a tertiary amino group, and has a glass transition temperature of 50° C. to 100° C.; the content of the (meth)acrylic copolymer (B) is 5 parts by mass to 25 parts by mass relative to 100 parts by mass of the (meth)acrylic copolymer (A); A pressure-sensitive adhesive composition for overlaminate films, wherein the ratio of the number of moles of isocyanate groups in the blocked isocyanate compound to the number of moles of carboxy groups in the (meth)acrylic copolymer (A) is 0.1 or more. <2> The weight average molecular weight of the (meth)acrylic copolymer (A) is 400,000 to 2,500,000. <1> 2. The pressure-sensitive adhesive composition for an overlaminate film according to claim 1 . <3> The weight average molecular weight of the (meth)acrylic copolymer (B) is 5,000 to 200,000. <1> or <2> 2. The pressure-sensitive adhesive composition for an overlaminate film according to claim 1 . <4> The total content of the structural units derived from the monomer having an amino group in the (meth)acrylic copolymer (B) is 3% by mass or more based on the total structural units of the (meth)acrylic copolymer (B). <1> ~ <3> 10. The pressure-sensitive adhesive composition for an overlaminate film according to claim 9 . <5> The dissociation temperature of the blocked isocyanate compound is 80°C to 180°C. <1> ~ <4> 10. The pressure-sensitive adhesive composition for an overlaminate film according to claim 9 . <6> A surface protection film; Provided on one side of the surface protective film, <1> ~ <5> A pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition for overlaminate films according to any one of the above items, An overlaminate film comprising: <7> A plate substrate; The plate substrate is provided on one side thereof. <6> An overlaminate film according to claim 1, A license plate comprising: Effect of the Invention

[0007] According to one embodiment of the present disclosure, there is provided a pressure-sensitive adhesive composition for an overlaminate film, which has high adhesive strength to an adherend and can form a pressure-sensitive adhesive layer that is less likely to cause poor appearance during three-dimensional molding. According to another embodiment of the present disclosure, there is provided an overlaminate film and a license plate comprising a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition for an overlaminate film. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of a configuration of an overlaminate film of the present disclosure. [Diagram 2]FIG. 1 is a schematic cross-sectional view showing an example of the configuration of a license plate of the present disclosure. [Diagram 3] FIG. 11 is a schematic cross-sectional view showing an example of another configuration of the license plate of the present disclosure. [Figure 4A] 1 is a photograph showing an example of the evaluation result "A" of cohesive failure in an example. [Figure 4B] 1 is a photograph showing an example of the evaluation result "B" of cohesive failure in an example. [Figure 4C] 1 is a photograph showing an example of the evaluation result "C" of cohesive failure in an example. [Diagram 5] 1 is a photograph showing an example of embossed letters in a peeling evaluation test in the Examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The adhesive composition for overlaminate film, the overlaminate film, and the license plate of the present disclosure will be described in detail below. The following description of the requirements may be based on a representative embodiment of the present disclosure, but the present disclosure is not limited to such an embodiment, and can be modified as appropriate within the scope of the purpose of the present disclosure.

[0010] In the present disclosure, when an embodiment is described with reference to the drawings, the configuration of the embodiment is not limited to the configuration shown in the drawings. In addition, the size of the members in each drawing is conceptual, and the relative relationship of the size between the members is not limited thereto. In addition, in each drawing, the same reference numerals are given to members having substantially the same functions, and duplicated descriptions may be omitted.

[0011] In the present disclosure, a numerical range indicated using "to" means a range that includes the numerical values ​​before and after "to" as the lower limit and upper limit, respectively. In the numerical ranges described in the present disclosure, the upper or lower limit value described in a certain numerical range may be replaced with the upper or lower limit value of another numerical range described in the present disclosure. In addition, in the numerical ranges described in the present disclosure, the upper or lower limit value described in a certain numerical range may be replaced with a value shown in the examples.

[0012] In the present disclosure, combinations of two or more preferred embodiments are more preferred embodiments.

[0013] In the present disclosure, the amount of each component in the pressure-sensitive adhesive composition for an overlaminate film means, unless otherwise specified, the total amount of the above-mentioned multiple substances present in the pressure-sensitive adhesive composition for an overlaminate film when multiple substances corresponding to each component are present in the pressure-sensitive adhesive composition for an overlaminate film.

[0014] In the present disclosure, unless otherwise specified, "solid content" means components other than the solvent contained in the composition. In this disclosure, "solvent" means water and / or an organic solvent.

[0015] In the present disclosure, "(meth)acrylic monomer" means a monomer having a (meth)acryloyl group. In the present disclosure, "(meth)acrylic copolymer" means a copolymer that contains structural units derived from (meth)acrylic monomers and in which the proportion of structural units derived from (meth)acrylic monomers is 50 mass% or more.

[0016] In this disclosure, "(meth)acrylic" is a term that encompasses both "acrylic" and "methacrylic", "(meth)acrylate" is a term that encompasses both "acrylate" and "methacrylate", and "(meth)acryloyl" is a term that encompasses both "acryloyl" and "methacryloyl".

[0017] In this disclosure, "n-" means normal, "i-" means iso, "s-" means secondary, and "t-" means tertiary.

[0018] In the present disclosure, "mass %" and "weight %" are synonymous, and "parts by mass" and "parts by weight" are synonymous.

[0019] In the present disclosure, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved.

[0020] In the present disclosure, the term "layer" includes cases where the layer is formed over the entire area when the area is observed, as well as cases where the layer is formed over only a part of the area. The same applies to the term "film." In this disclosure, the term "lamination" refers to stacking layers, and a "lamination" may be two or more layers bonded together, or two or more layers may be detachable.

[0021] In the present disclosure, "poor appearance" refers to poor appearance caused by cohesive failure and / or peeling of the pressure-sensitive adhesive layer, and "peeling" also includes a state in which part of the pressure-sensitive adhesive layer is lifted from the adherend.

[0022] In the present disclosure, the "(meth)acrylic copolymer (A) and the (meth)acrylic copolymer (B)" may be collectively referred to as the "specific (meth)acrylic copolymer."

[0023] [Adhesive composition for overlaminate film] The pressure-sensitive adhesive composition for an overlaminate film according to the present disclosure (hereinafter, also simply referred to as the "pressure-sensitive adhesive composition") comprises a (meth)acrylic copolymer (A), a (meth)acrylic copolymer (B), and a blocked isocyanate compound as a crosslinking agent, wherein the (meth)acrylic copolymer (A) comprises a structural unit derived from a monomer having a carboxy group in a proportion of 1% by mass to 15% by mass relative to the total structural units of the (meth)acrylic copolymer (A) and has a glass transition temperature of -45°C to -5°C, and the (meth)acrylic copolymer (B) contains a constituent unit derived from a monomer having at least one amino group selected from the group consisting of a primary amino group, a secondary amino group, and a tertiary amino group, and has a glass transition temperature of 50°C to 100°C, the content of the (meth)acrylic copolymer (B) is 5 parts by mass to 25 parts by mass per 100 parts by mass of the (meth)acrylic copolymer (A), and the ratio of the number of moles of isocyanate groups in the blocked isocyanate compound to the number of moles of carboxy groups in the (meth)acrylic copolymer (A) is 0.1 or more.

[0024] The pressure-sensitive adhesive composition of the present disclosure contains a combination, in specific ratios, of a (meth)acrylic copolymer (A) which contains structural units derived from a monomer having a carboxy group in a specific range and has a relatively low glass transition temperature, a (meth)acrylic copolymer (B) which contains structural units derived from a monomer having an amino group and has a relatively high glass transition temperature, and a blocked isocyanate compound which serves as a crosslinking agent. This allows the formation of a pressure-sensitive adhesive layer which has high adhesion to an adherend and is unlikely to cause poor appearance during three-dimensional molding. The reason why the pressure-sensitive adhesive composition of the present disclosure can exhibit such an effect is unclear, but the present inventors speculate as follows, however, the following speculation is not intended to limit the pressure-sensitive adhesive composition of the present disclosure, but is merely an example.

[0025] The pressure-sensitive adhesive composition of the present disclosure is used for forming a pressure-sensitive adhesive layer included in an overlaminate film. A pressure-sensitive adhesive layer formed by a conventional pressure-sensitive adhesive composition for a general overlaminate film has excellent adhesion to an adherend, but when the layer is laminated to an adherend and then three-dimensionally molded, cohesive failure and / or peeling may be observed around the protruding parts of the adherend after three-dimensional molding. In contrast, the adhesive composition of the present disclosure contains a (meth)acrylic copolymer (A) having a relatively low glass transition temperature, and therefore the adhesive layer formed has excellent wettability to the adherend, and is believed to adhere to the adherend when it is attached to the adherend. For this reason, the adhesive layer formed by the adhesive composition of the present disclosure can function suitably as an adhesive layer provided in an overlaminate film. In addition, since the adhesive composition of the present disclosure contains a blocked isocyanate compound as a crosslinking agent, the timing of crosslinking can be controlled by heating. For example, the adhesive layer before the crosslinking reaction is allowed to proceed has excellent wettability to the adherend due to the presence of the (meth)acrylic copolymer (A) having a relatively low glass transition temperature, and therefore is believed to adhere to the adherend when it is attached to the adherend. By allowing the crosslinking reaction to proceed by heating while the adhesive layer is in close contact with the adherend, the cohesive strength of the adhesive layer can be increased without decreasing the adhesive strength of the adhesive layer to the adherend, and therefore it is believed that it is possible to suppress the occurrence of cohesive failure and peeling around the protruding parts of the adherend due to three-dimensional molding. In addition, the isocyanate group deprotected by heating crosslinks with the carboxy group in the (meth)acrylic copolymer (A). In the pressure-sensitive adhesive composition of the present disclosure, the ratio of the molar number of the isocyanate group in the blocked isocyanate compound to the molar number of the carboxy group in the (meth)acrylic copolymer (A) is a specific value or more, so that the cohesive strength of the pressure-sensitive adhesive layer is increased to such an extent that cohesive failure is suppressed. In addition, the presence of a (meth)acrylic copolymer with a high glass transition temperature is also effective in suppressing cohesive failure of the pressure-sensitive adhesive layer that may occur during three-dimensional molding. The (meth)acrylic copolymer (B) contained in the pressure-sensitive adhesive composition of the present disclosure has a relatively high glass transition temperature and has excellent compatibility with the (meth)acrylic copolymer (A) due to the presence of an amino group, so that it can effectively function in suppressing cohesive failure of the pressure-sensitive adhesive layer that may occur during three-dimensional molding.

[0026] [(Meth)acrylic copolymer (A)] The pressure-sensitive adhesive composition of the present disclosure contains a (meth)acrylic copolymer (A). The (meth)acrylic copolymer (A) contains structural units derived from a monomer having a carboxy group in a ratio of 1% by mass to 15% by mass based on all structural units of the (meth)acrylic copolymer (A), and has a glass transition temperature of -45°C to -5°C. The pressure-sensitive adhesive composition of the present disclosure may contain only one type of (meth)acrylic copolymer (A), or may contain two or more types.

[0027] <Structural Unit Derived from Monomer Having a Carboxy Group> The (meth)acrylic copolymer (A) contains structural units derived from a monomer having a carboxy group in a proportion of 1% by mass to 15% by mass based on the total structural units of the (meth)acrylic copolymer (A). In the present disclosure, a "structural unit derived from a monomer having a carboxy group" refers to a structural unit formed by addition polymerization of a monomer having a carboxy group.

[0028] The type of the monomer having a carboxy group is not particularly limited. An example of a monomer having a carboxy group is a monomer having at least one carboxy group and an ethylenically unsaturated group in one molecule. The ethylenically unsaturated group is not particularly limited, and examples thereof include a vinyl group, an allyl group, a vinylphenyl group, a (meth)acrylamide group, and a (meth)acryloyl group. The ethylenically unsaturated group is preferably a (meth)acryloyl group.

[0029] Specific examples of monomers having a carboxy group include (meth)acrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, glutaconic acid, citraconic acid, ω-carboxy-polycaprolactone mono(meth)acrylate [e.g., ω-carboxy-polycaprolactone (n≒2) monoacrylate], and succinic acid derivatives (e.g., 2-acryloyloxyethyl-succinic acid). The monomer having a carboxy group is preferably a (meth)acrylic monomer having a carboxy group, more preferably (meth)acrylic acid, and even more preferably acrylic acid.

[0030] The (meth)acrylic copolymer (A) may contain only one type of structural unit derived from a monomer having a carboxy group, or may contain two or more types.

[0031] The content of the structural units derived from the monomer having a carboxy group in the (meth)acrylic copolymer (A) is 1% by mass to 15% by mass based on the total structural units of the (meth)acrylic copolymer (A). When the content of the structural unit derived from the monomer having a carboxyl group in the (meth)acrylic copolymer (A) is 1% by mass or more relative to the total structural units of the (meth)acrylic copolymer (A), the cohesive strength of the pressure-sensitive adhesive layer is sufficiently increased, so that the pressure-sensitive adhesive layer is less likely to undergo cohesive failure around the convex parts of the adherend during three-dimensional molding. From this viewpoint, the content of the structural unit derived from the monomer having a carboxyl group in the (meth)acrylic copolymer (A) is preferably 2% by mass or more, more preferably 3% by mass or more, and even more preferably 4% by mass or more relative to the total structural units of the (meth)acrylic copolymer (A). If the content of the structural unit derived from the monomer having a carboxyl group in the (meth)acrylic copolymer (A) is 15% by mass or less based on the total structural units of the (meth)acrylic copolymer (A), the cohesive strength of the pressure-sensitive adhesive layer does not become excessively high, and therefore the adhesive strength of the pressure-sensitive adhesive layer to the adherend tends to be suppressed from decreasing. From this viewpoint, the content of the structural unit derived from the monomer having a carboxyl group in the (meth)acrylic copolymer (A) is preferably 10% by mass or less, more preferably 8% by mass or less, and even more preferably 6% by mass or less based on the total structural units of the (meth)acrylic copolymer (A). In one embodiment, the content of structural units derived from a monomer having a carboxy group in the (meth)acrylic copolymer (A) may be 1% by mass to 10% by mass, 2% by mass to 15% by mass, 2% by mass to 10% by mass, 2% by mass to 8% by mass, 3% by mass to 10% by mass, 3% by mass to 8% by mass, 3% by mass to 6% by mass, 4% by mass to 8% by mass, or 4% by mass to 6% by mass, relative to all structural units of the (meth)acrylic copolymer (A).

[0032] <Structural Unit Derived from (Meth)acrylic Acid Alkyl Ester Monomer> The (meth)acrylic copolymer (A) preferably contains a structural unit derived from a (meth)acrylic acid alkyl ester monomer. In the present disclosure, the term "structural unit derived from a (meth)acrylic acid alkyl ester monomer" refers to a structural unit formed by addition polymerization of a (meth)acrylic acid alkyl ester monomer. In addition, the "(meth)acrylic acid alkyl ester monomer" in the (meth)acrylic copolymer (A) refers to a (meth)acrylic acid alkyl ester monomer that does not have a carboxy group. In other words, in the (meth)acrylic copolymer (A), the "(meth)acrylic acid alkyl ester monomer having a carboxy group" is classified as a monomer having a carboxy group.

[0033] The type of the (meth)acrylic acid alkyl ester monomer is not particularly limited. The (meth)acrylic acid alkyl ester monomer may be an acrylic acid alkyl ester monomer or a methacrylic acid alkyl ester monomer. From the viewpoint of facilitating the production of a (meth)acrylic copolymer (A) having a glass transition temperature of −45° C. to −5° C., for example, an acrylic acid alkyl ester monomer is preferred. The alkyl group in the (meth)acrylic acid alkyl ester monomer may be unsubstituted or may have a substituent, but is preferably unsubstituted. The alkyl group contained in the (meth)acrylic acid alkyl ester monomer may be linear, branched, or cyclic. The alkyl group of the (meth)acrylic acid alkyl ester monomer preferably has 1 to 18 carbon atoms, more preferably 1 to 12 carbon atoms, further preferably 1 to 8 carbon atoms, and particularly preferably 1 to 4 carbon atoms.

[0034] Specific examples of the (meth)acrylic acid alkyl ester monomer include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, n-octyl (meth)acrylate, i-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, i-nonyl (meth)acrylate, n-decyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, and isobornyl (meth)acrylate. The (meth)acrylic acid alkyl ester monomer preferably contains at least one of methyl acrylate and n-butyl acrylate, and more preferably contains both methyl acrylate and n-butyl acrylate.

[0035] When the (meth)acrylic copolymer (A) contains a structural unit derived from a (meth)acrylic acid alkyl ester monomer, it may contain only one type of structural unit derived from the (meth)acrylic acid alkyl ester monomer, or it may contain two or more types of structural units derived from the (meth)acrylic acid alkyl ester monomer.

[0036] When the (meth)acrylic copolymer (A) contains a structural unit derived from a (meth)acrylic acid alkyl ester monomer, the content of the structural unit derived from the (meth)acrylic acid alkyl ester monomer is not particularly limited, but is, for example, preferably 50 mass% or more, more preferably 50 mass% to 99 mass%, even more preferably 60 mass% to 97 mass%, and particularly preferably 70 mass% to 96 mass%, relative to all structural units of the (meth)acrylic copolymer (A). Here, the content of structural units derived from (meth)acrylic acid alkyl ester monomers in the (meth)acrylic copolymer (A) being 50 mass% or more relative to the total structural units of the (meth)acrylic copolymer (A) means that the structural units derived from (meth)acrylic acid alkyl ester monomers are contained as the main component of the structural units of the (meth)acrylic copolymer (A).

[0037] <Constituent units derived from other monomers> The (meth)acrylic copolymer (A) may contain a structural unit derived from a monomer (so-called other monomer) that does not fall into either the monomer having a carboxy group or the (meth)acrylic acid alkyl ester monomer. In the present disclosure, the term "structural units derived from other monomers" refers to structural units formed by addition polymerization of other monomers.

[0038] Examples of structural units derived from other monomers include structural units derived from (meth)acrylates having an aromatic ring, such as benzyl (meth)acrylate and phenoxyethyl (meth)acrylate; structural units derived from alkoxyalkyl (meth)acrylates, such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; structural units derived from aromatic monovinyls, such as styrene, α-methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, and vinyltoluene; structural units derived from vinyl cyanides, such as acrylonitrile and methacrylonitrile; and structural units derived from vinyl esters, such as vinyl formate, vinyl acetate, vinyl propionate, and vinyl versatate.

[0039] When the (meth)acrylic copolymer (A) contains a structural unit derived from another monomer, it may contain only one type of structural unit derived from the other monomer, or may contain two or more types of structural units derived from the other monomer.

[0040] When the (meth)acrylic copolymer (A) contains a structural unit derived from another monomer, the content of the structural unit derived from the other monomer can be appropriately set within a range that does not impair the effects of the pressure-sensitive adhesive composition of the present disclosure.

[0041] <<Glass transition temperature of (meth)acrylic copolymer (A)>> The glass transition temperature (also referred to as "Tg") of the (meth)acrylic copolymer (A) is -45°C to -5°C. If the (meth)acrylic copolymer (A) has a glass transition temperature of -45°C or higher, the pressure-sensitive adhesive layer is less likely to undergo cohesive failure around the convex portions of the adherend during three-dimensional molding. From this viewpoint, the (meth)acrylic copolymer (A) preferably has a glass transition temperature of -40°C or higher, more preferably has a glass transition temperature of -35°C or higher, and even more preferably has a glass transition temperature of -30°C or higher. If the (meth)acrylic copolymer (A) has a glass transition temperature of -5°C or lower, the pressure-sensitive adhesive layer exhibits sufficient wettability to the adherend, and the pressure-sensitive adhesive layer tends to have a sufficiently high adhesive strength to the adherend. From this viewpoint, the glass transition temperature of the (meth)acrylic copolymer (A) is preferably -10°C or lower, more preferably -15°C or lower. In one embodiment, the glass transition temperature of the (meth)acrylic copolymer (A) may be -40°C to -10°C, may be -35°C to -10°C, or may be -30°C to -15°C.

[0042] The glass transition temperature of the (meth)acrylic copolymer (A) is a value calculated from the following formula 1, which is calculated by converting the absolute temperature (unit: K) into Celsius temperature (unit: ° C.). 1 / Tg=m1 / Tg1+m2 / Tg2+ +m(k-1) / Tg(k-1)+mk / Tgk (Formula 1)

[0043] In formula 1, Tg1, Tg2, , Tg(k-1), and Tgk respectively represent the glass transition temperatures expressed as absolute temperatures when each monomer constituting the (meth)acrylic copolymer (A) is made into a homopolymer. m1, m2, , m(k-1), and mk respectively represent the molar fractions of each monomer constituting the (meth)acrylic copolymer (A), and m1+m2+···+m(k-1)+mk=1. Note that absolute temperatures can be converted to Celsius temperatures by subtracting 273 from the absolute temperature, and Celsius temperatures can be converted to absolute temperatures by adding 273 to the Celsius temperature.

[0044] In the present disclosure, the "glass transition temperature when made into a homopolymer" refers to a value described in a publicly known document or a value measured using a differential scanning calorimeter (DSC). The specific values ​​to be used are as follows:

[0045] For the "glass transition temperature when made into a homopolymer" of the monomers shown below, the respective values ​​shown are adopted. 2-Ethylhexyl acrylate: -70°C, 2-Ethylhexyl methacrylate: -10°C, n-butyl acrylate: -54°C, n-butyl methacrylate: 20°C, t-butyl acrylate: 43°C, t-butyl methacrylate: 118°C, i-butyl methacrylate: 53°C, methyl acrylate: 10°C, methyl methacrylate: 105°C, ethyl acrylate: -22°C, ethyl methacrylate: 65°C, methacrylic acid: 228°C, 4-hydroxybutyl acrylate: -80°C, 2-hydroxyethyl acrylate: -15°C, 2-hydroxyethyl methacrylate: acrylate: 85°C, acrylic acid: 106°C, n-octyl acrylate: -65°C, stearyl acrylate: 30°C, stearyl methacrylate: 38°C, lauryl acrylate: -3°C, lauryl methacrylate: -65°C, ω-carboxy-polycaprolactone (n≒2) monoacrylate: -30°C, phenoxyethyl acrylate: -22°C, methoxyethyl acrylate: -50°C, methoxypolyethylene glycol methacrylate: -60°C, 2-dimethylaminoethyl methacrylate: 18°C, 2-diethylaminoethyl methacrylate: 20°C.

[0046] Regarding the "glass transition temperature when made into a homopolymer" of a monomer other than the above-mentioned monomers, the value described in Polymer Handbook (4th edition, Wiley-Interscience; the same applies hereinafter) is adopted. When there is no description in the Polymer Handbook, the glass transition temperature of the homopolymer obtained by the following measurement method is adopted.

[0047] -Measurement of glass transition temperature of homopolymer- Using a differential scanning calorimeter (DSC), measurements are performed under conditions of a nitrogen gas flow, 10 mg of a measurement sample (i.e., homopolymer) and a heating rate of 10°C / min, and the inflection point of the obtained DSC curve is regarded as the glass transition temperature of the homopolymer. As the differential scanning calorimeter, for example, a differential scanning calorimeter (product name: Discovery DSC 2500) manufactured by TA Instruments Japan Co., Ltd. can be suitably used. However, the differential scanning calorimeter is not limited to this.

[0048] The glass transition temperature of the (meth)acrylic copolymer (A) can be appropriately adjusted, for example, by using two or more monomers having different glass transition temperatures when formed into homopolymers.

[0049] <<Weight average molecular weight of (meth)acrylic copolymer (A)>> The weight average molecular weight (also referred to as "Mw") of the (meth)acrylic copolymer (A) is not particularly limited, but is, for example, preferably 400,000 to 2.5 million, more preferably 500,000 to 2.5 million, and even more preferably 600,000 to 2.5 million. When the weight average molecular weight of the (meth)acrylic copolymer (A) is 400,000 or more, the pressure-sensitive adhesive layer tends to be less susceptible to heat shrinkage caused by a decrease in cohesive strength. When the weight average molecular weight of the (meth)acrylic copolymer (A) is 2.5 million or less, it tends to be easy to produce.

[0050] The weight average molecular weight of the (meth)acrylic copolymer (A) is a value measured by the following method, specifically, according to the following (1) to (3). (1) A solution of the (meth)acrylic copolymer (A) is applied to a release paper and dried at 100° C. for 1 minute to obtain a film of the (meth)acrylic copolymer (A). (2) Using the film-like (meth)acrylic copolymer (A) obtained in (1) above and tetrahydrofuran, a sample solution having a solid content concentration of 0.2% by mass is obtained. Note that the "solid content concentration" here means the mass ratio of the (meth)acrylic copolymer (A) in the sample solution. (3) The weight average molecular weight of the (meth)acrylic copolymer (A) is determined, in terms of standard polystyrene, by gel permeation chromatography (GPC) under the following conditions.

[0051] ~Conditions~ Measurement equipment: High-speed GPC [Model: HLC-8420 GPC, manufactured by Tosoh Corporation] Detector: Differential refractometer (RI) [installed in HLC-8420, manufactured by Tosoh Corporation] Column: TSKgel GMH XL Two Tosoh products are used. Column temperature: 40℃ Eluent: Tetrahydrofuran Sample solution injection volume: 100μL Flow rate: 0.8mL / min

[0052] The weight average molecular weight of the (meth)acrylic copolymer (A) can be adjusted to a desired value by adjusting the polymerization temperature, polymerization time, amount of organic solvent used, type of polymerization initiator, amount of polymerization initiator used, etc. when polymerizing the monomers.

[0053] <<Content of (meth)acrylic copolymer (A)>> The content of the (meth)acrylic copolymer (A) in the pressure-sensitive adhesive composition of the present disclosure is not particularly limited, but for example, it is preferably 60% by mass to 94% by mass, more preferably 60% by mass to 93% by mass, and even more preferably 60% by mass to 92% by mass, relative to the total solid content in the pressure-sensitive adhesive composition.

[0054] In the present disclosure, the "total solid content in the PSA composition" means the total mass of the PSA composition when the PSA composition does not contain a solvent, and means the mass of the residue remaining after removing the solvent from the PSA composition when the PSA composition contains a solvent.

[0055] [(Meth)acrylic copolymer (B)] The pressure-sensitive adhesive composition of the present disclosure contains a (meth)acrylic copolymer (B). The (meth)acrylic copolymer (B) contains a structural unit derived from a monomer having at least one amino group selected from the group consisting of a primary amino group, a secondary amino group, and a tertiary amino group, and has a glass transition temperature of 50°C to 100°C. The content of the (meth)acrylic copolymer (B) is 5 parts by mass to 25 parts by mass based on 100 parts by mass of the above-mentioned (meth)acrylic copolymer (A). The pressure-sensitive adhesive composition of the present disclosure may contain only one type of (meth)acrylic copolymer (B), or may contain two or more types.

[0056] <Structural Unit Derived from Monomer Having an Amino Group> The (meth)acrylic copolymer (B) contains a constituent unit derived from a monomer having at least one type of amino group selected from the group consisting of a primary amino group, a secondary amino group, and a tertiary amino group. In the present disclosure, a "structural unit derived from a monomer having an amino group" refers to a structural unit formed by addition polymerization of a monomer having an amino group.

[0057] The type of the monomer having an amino group is not particularly limited. An example of a monomer having an amino group is a monomer having at least one amino group and an ethylenically unsaturated group in one molecule. The ethylenically unsaturated group is not particularly limited, and examples thereof include a vinyl group, an allyl group, a vinylphenyl group, a (meth)acrylamide group, and a (meth)acryloyl group. The ethylenically unsaturated group is preferably a (meth)acryloyl group.

[0058] Specific examples of the monomer having an amino group include 2-dimethylaminoethyl (meth)acrylate, 2-diethylaminoethyl (meth)acrylate, 2-diisopropylaminoethyl (meth)acrylate, and dimethylaminopropyl (meth)acrylamide. As the monomer having an amino group, a (meth)acrylic monomer having an amino group is preferable, a (meth)acrylic acid alkyl ester monomer having an amino group is more preferable, at least one selected from the group consisting of 2-dimethylaminoethyl (meth)acrylate and 2-diethylaminoethyl (meth)acrylate is further preferable, and at least one selected from 2-dimethylaminoethyl methacrylate and 2-diethylaminoethyl methacrylate is particularly preferable.

[0059] The (meth)acrylic copolymer (B) may contain only one type of structural unit derived from a monomer having an amino group, or may contain two or more types.

[0060] The total content of structural units derived from monomers having an amino group in the (meth)acrylic copolymer (B) is not particularly limited, but from the viewpoint of compatibility between the (meth)acrylic copolymer (A) and the (meth)acrylic copolymer (B), for example, it is preferably 1.5 mass% or more, more preferably 2 mass% or more, even more preferably 2.5 mass% or more, and particularly preferably 3 mass% or more, based on the total structural units of the (meth)acrylic copolymer (B). The upper limit of the total content of structural units derived from monomers having an amino group in the (meth)acrylic copolymer (B) may be, for example, 20 mass% or less, 15 mass% or less, 12 mass% or less, 10 mass% or less, or 6 mass% or less, relative to all structural units of the (meth)acrylic copolymer (B). In one embodiment, the total content of structural units derived from monomers having an amino group in the (meth)acrylic copolymer (B) may be 1.5% by mass to 20% by mass, 2% by mass to 15% by mass, 2.5% by mass to 12% by mass, 3% by mass to 10% by mass, or 3% by mass to 6% by mass, relative to all structural units of the (meth)acrylic copolymer (B).

[0061] <Structural Unit Derived from (Meth)acrylic Acid Alkyl Ester Monomer> The (meth)acrylic copolymer (B) preferably contains a structural unit derived from a (meth)acrylic acid alkyl ester monomer. In addition, the "(meth)acrylic acid alkyl ester monomer" in the (meth)acrylic copolymer (B) refers to a (meth)acrylic acid alkyl ester monomer that does not have an amino group. In other words, in the (meth)acrylic copolymer (B), the "(meth)acrylic acid alkyl ester monomer having an amino group" is classified as a monomer having an amino group.

[0062] The type of the (meth)acrylic acid alkyl ester monomer is not particularly limited. The (meth)acrylic acid alkyl ester monomer may be an acrylic acid alkyl ester monomer or a methacrylic acid alkyl ester monomer. The alkyl group in the (meth)acrylic acid alkyl ester monomer may be unsubstituted or may have a substituent, but is preferably unsubstituted. The alkyl group contained in the (meth)acrylic acid alkyl ester monomer may be linear, branched, or cyclic. The alkyl group of the (meth)acrylic acid alkyl ester monomer preferably has 1 to 18 carbon atoms, more preferably 1 to 12 carbon atoms, further preferably 1 to 8 carbon atoms, and particularly preferably 1 to 4 carbon atoms.

[0063] Specific examples of the (meth)acrylic acid alkyl ester monomer are the same as those explained in the (meth)acrylic copolymer (A), and therefore explanation thereof will be omitted here. The (meth)acrylic acid alkyl ester monomer preferably contains at least one of methyl methacrylate and ethyl acrylate, and more preferably contains both methyl methacrylate and ethyl acrylate.

[0064] When the (meth)acrylic copolymer (B) contains a structural unit derived from a (meth)acrylic acid alkyl ester monomer, it may contain only one type of structural unit derived from the (meth)acrylic acid alkyl ester monomer, or it may contain two or more types of structural units derived from the (meth)acrylic acid alkyl ester monomer.

[0065] When the (meth)acrylic copolymer (B) contains a structural unit derived from a (meth)acrylic acid alkyl ester monomer, the content of the structural unit derived from the (meth)acrylic acid alkyl ester monomer is not particularly limited, but is, for example, preferably 50 mass% or more, more preferably 50 mass% to 98.5 mass%, even more preferably 60 mass% to 98 mass%, and particularly preferably 70 mass% to 97 mass%, relative to all structural units of the (meth)acrylic copolymer (B). Here, the content of structural units derived from (meth)acrylic acid alkyl ester monomers in the (meth)acrylic copolymer (B) being 50 mass% or more relative to the total structural units of the (meth)acrylic copolymer (B) means that the structural units derived from (meth)acrylic acid alkyl ester monomers are contained as the main component of the structural units of the (meth)acrylic copolymer (B).

[0066] <Constituent units derived from other monomers> The (meth)acrylic copolymer (B) may contain a structural unit derived from a monomer (so-called other monomer) that does not fall into either the category of a monomer having an amino group or a (meth)acrylic acid alkyl ester monomer.

[0067] Specific examples of the structural units derived from other monomers are the same as those explained in the (meth)acrylic copolymer (A) and therefore will not be explained here.

[0068] When the (meth)acrylic copolymer (B) contains a structural unit derived from another monomer, it may contain only one type of structural unit derived from the other monomer, or may contain two or more types of structural units derived from the other monomer.

[0069] When the (meth)acrylic copolymer (B) contains a structural unit derived from another monomer, the content of the structural unit derived from the other monomer can be appropriately set within a range that does not impair the effects of the pressure-sensitive adhesive composition of the present disclosure.

[0070] <<Glass transition temperature of (meth)acrylic copolymer (B)>> The (meth)acrylic copolymer (B) has a glass transition temperature (Tg) of 50°C to 100°C. If the (meth)acrylic copolymer (B) has a glass transition temperature of 50° C. or higher, the pressure-sensitive adhesive layer is less likely to undergo cohesive failure around the convex portions of the adherend during three-dimensional molding. From this viewpoint, the (meth)acrylic copolymer (B) preferably has a glass transition temperature of 60° C. or higher, more preferably 70° C. or higher. The glass transition temperature of the (meth)acrylic copolymer (B) is 100° C. or lower, preferably 95° C. or lower, from the viewpoint of manufacturability. In one embodiment, the glass transition temperature of the (meth)acrylic copolymer (B) may be 60°C to 100°C, 70°C to 100°C, 60°C to 95°C, or 70°C to 95°C.

[0071] The glass transition temperature of the (meth)acrylic copolymer (B) is a value determined by the same method as that for determining the glass transition temperature of the (meth)acrylic copolymer (A) described above.

[0072] The glass transition temperature of the (meth)acrylic copolymer (B) can be appropriately adjusted, for example, by using two or more monomers having different glass transition temperatures when formed into homopolymers.

[0073] <<Weight average molecular weight of (meth)acrylic copolymer (B)>> The weight average molecular weight (Mw) of the (meth)acrylic copolymer (B) is not particularly limited, but is, for example, preferably from 5,000 to 200,000, more preferably from 10,000 to 200,000, and even more preferably from 50,000 to 150,000. When the weight average molecular weight of the (meth)acrylic copolymer (B) is 5,000 or more, the (meth)acrylic copolymer (B) is more appropriately compatible with the (meth)acrylic copolymer (A), and therefore tends to exhibit more appropriate cohesive strength. When the weight average molecular weight of the (meth)acrylic copolymer (B) is 200,000 or less, production tends to be easier.

[0074] The weight average molecular weight of the (meth)acrylic copolymer (B) is a value measured by the same method as the above-mentioned method for measuring the weight average molecular weight of the (meth)acrylic copolymer (A).

[0075] The weight average molecular weight of the (meth)acrylic copolymer (B) can be adjusted to a desired value by adjusting the polymerization temperature, polymerization time, amount of organic solvent used, type of polymerization initiator, amount of polymerization initiator used, etc. when polymerizing the monomers.

[0076] <<Content of (meth)acrylic copolymer (B)>> The content of the (meth)acrylic copolymer (B) in the pressure-sensitive adhesive composition of the present disclosure is 5 to 25 parts by mass per 100 parts by mass of the above-mentioned (meth)acrylic copolymer (A). When the content of the (meth)acrylic copolymer (B) in the pressure-sensitive adhesive composition of the present disclosure is 5 parts by mass or more relative to 100 parts by mass of the (meth)acrylic copolymer (A), the cohesive strength of the pressure-sensitive adhesive layer is sufficiently increased, so that the pressure-sensitive adhesive layer is less likely to undergo cohesive failure around the convex parts of the adherend during three-dimensional molding. From this viewpoint, the content of the (meth)acrylic copolymer (B) in the pressure-sensitive adhesive composition of the present disclosure is preferably 8 parts by mass or more, more preferably 10 parts by mass or more, relative to 100 parts by mass of the (meth)acrylic copolymer (A). When the content of the (meth)acrylic copolymer (B) in the pressure-sensitive adhesive composition of the present disclosure is 25 parts by mass or less relative to 100 parts by mass of the (meth)acrylic copolymer (A), the cohesive strength of the pressure-sensitive adhesive layer does not become excessively high, and therefore the adhesive strength of the pressure-sensitive adhesive layer to the adherend tends to be suppressed from decreasing. From this viewpoint, the content of the (meth)acrylic copolymer (B) in the pressure-sensitive adhesive composition of the present disclosure is preferably 23 parts by mass or less, more preferably 20 parts by mass or less, relative to 100 parts by mass of the (meth)acrylic copolymer (A). In an embodiment, the content of the (meth)acrylic copolymer (B) in the pressure-sensitive adhesive composition of the present disclosure may be 5 parts by mass to 23 parts by mass, 5 parts by mass to 20 parts by mass, 8 parts by mass to 23 parts by mass, or 10 parts by mass to 20 parts by mass, per 100 parts by mass of the (meth)acrylic copolymer (A).

[0077] [Method for producing specific (meth)acrylic copolymer] The method for producing the (meth)acrylic copolymer (A) and the (meth)acrylic copolymer (B) [i.e., the specific (meth)acrylic copolymer] is not particularly limited. The specific (meth)acrylic copolymer can be produced by polymerizing the above-mentioned monomers by a known polymerization method typified by, for example, a solution polymerization method, an emulsion polymerization method, a suspension polymerization method, or a bulk polymerization method. As a polymerization method, a solution polymerization method is preferred in that the processing steps are relatively simple and can be carried out in a short time when preparing the pressure-sensitive adhesive composition of the present disclosure after production.

[0078] In the solution polymerization method, a predetermined organic solvent, a monomer, a polymerization initiator, and a chain transfer agent used as required are generally charged into a polymerization tank, and the mixture is heated and reacted for several hours with stirring at the reflux temperature of the organic solvent. In this case, at least a part of the organic solvent, the monomer, the polymerization initiator, and the chain transfer agent used as required may be added successively. The reaction may also be carried out in a nitrogen gas flow.

[0079] Examples of the organic solvent used in the polymerization reaction include aromatic hydrocarbon compounds, aliphatic hydrocarbon compounds, alicyclic hydrocarbon compounds, ester compounds, ketone compounds, glycol ether compounds, and alcohol compounds. More specifically, examples of the organic solvent used in the polymerization reaction include aromatic hydrocarbon compounds such as benzene, toluene, ethylbenzene, n-propylbenzene, t-butylbenzene, o-xylene, m-xylene, p-xylene, tetralin, decalin, and aromatic naphtha; aliphatic or alicyclic hydrocarbon compounds such as n-hexane, n-heptane, n-octane, i-octane, n-decane, dipentene, petroleum spirit, petroleum naphtha, and turpentine oil; ester compounds such as methyl acetate, ethyl acetate, n-butyl acetate, n-amyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate, 3-methoxybutyl acetate, and methyl benzoate; acetone, methyl Examples of the alcohol compounds include ketone compounds represented by ethyl ketone, methyl-i-butyl ketone, isophorone, cyclohexanone, and methylcyclohexanone; glycol ether compounds represented by ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and diethylene glycol monobutyl ether; and alcohol compounds represented by methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, i-butyl alcohol, s-butyl alcohol, and t-butyl alcohol.

[0080] In producing the specific (meth)acrylic copolymer, it is preferable to use an organic solvent that is unlikely to cause chain transfer during the polymerization reaction, such as an aromatic hydrocarbon compound, an ester compound, or a ketone compound. In particular, it is preferable to use methyl acetate and / or ethyl acetate from the viewpoints of the solubility of the specific (meth)acrylic copolymer, ease of polymerization reaction, etc.

[0081] During the polymerization reaction, only one type of organic solvent may be used, or two or more types may be used.

[0082] Examples of the polymerization initiator include organic peroxides and azo compounds that are used in ordinary solution polymerization methods. Specific examples of organic peroxides include t-butyl peroxy-2-ethylhexanoate, t-butyl hydroperoxide, cumene hydroperoxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, caproyl peroxide, di-i-propyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, t-butyl peroxypivalate, 2,2-bis(4,4-di-t-butyl peroxysilane), peroxycyclohexyl)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. Specific examples of azo compounds include 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(2,4-dimethylvaleronitrile) (ABVN), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), and 2,2'-azobis(isobutyrate) dimethyl.

[0083] In the polymerization reaction, only one type of polymerization initiator may be used, or two or more types may be used.

[0084] The amount of the polymerization initiator used is not particularly limited, and can be appropriately set depending on, for example, the molecular weight of the target specific (meth)acrylic copolymer.

[0085] In producing the specific (meth)acrylic copolymer, a chain transfer agent may be used, if necessary. Examples of the chain transfer agent include cyanoacetic acid, alkyl ester compounds of cyanoacetic acid having 1 to 8 carbon atoms, bromoacetic acid, alkyl ester compounds of bromoacetic acid having 1 to 8 carbon atoms, aromatic compounds such as α-methylstyrene, anthracene, phenanthrene, fluorene, and 9-phenylfluorene, aromatic nitro compounds such as p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid, p-nitrophenol, and p-nitrotoluene, benzoquinone derivatives such as benzoquinone and 2,3,5,6-tetramethyl-p-benzoquinone, borane derivatives such as tributylborane, carbon tetrabromide, ... Examples of the halogenated hydrocarbon compounds include carbon chloride, 1,1,2,2-tetrabromoethane, tribromoethylene, trichloroethylene, bromotrichloromethane, tribromomethane, and 3-chloro-1-propene, aldehyde compounds such as chloral and furaldehyde, alkyl mercaptan compounds having 1 to 18 carbon atoms, aromatic mercaptan compounds such as thiophenol and toluene mercaptan, mercaptoacetic acid, alkyl ester compounds of mercaptoacetic acid having 1 to 10 carbon atoms, hydroxyalkyl mercaptan compounds having 1 to 12 carbon atoms, and terpene compounds such as pinene and terpinolene.

[0086] When a chain transfer agent is used in producing the specific (meth)acrylic copolymer, the amount of the chain transfer agent used is not particularly limited and can be appropriately set depending on, for example, the molecular weight of the target specific (meth)acrylic copolymer.

[0087] The polymerization temperature is not particularly limited, and can be appropriately set depending on, for example, the molecular weight of the target specific (meth)acrylic copolymer.

[0088] [Blocked isocyanate compounds] The pressure-sensitive adhesive composition of the present disclosure contains a blocked isocyanate compound as a crosslinking agent. In the present disclosure, the term "blocked isocyanate compound" refers to a compound having two or more blocked isocyanate groups in one molecule. That is, a blocked isocyanate compound is a compound in which two or more isocyanate groups of a polyisocyanate compound are protected with a blocking agent. In addition, in the present disclosure, the term "blocked isocyanate group" refers to a group that is usually protected (so-called masked) with a blocking agent to suppress the reactivity of the isocyanate group, but can be deprotected when heated to generate an active isocyanate group.

[0089] The blocked isocyanate group has a partial structure represented by the following formula.

[0090] [ka]

[0091] In the above formula, X represents a structure obtained by removing a hydrogen atom from a blocking agent. The blocking agent is not particularly limited, and examples thereof include ketoxime compounds, amide compounds, nitrogen-containing heterocyclic compounds, and active methylene compounds.

[0092] Examples of the polyisocyanate compound before the isocyanate group is protected with a blocking agent include an aliphatic polyisocyanate compound, an alicyclic polyisocyanate compound, and an aromatic polyisocyanate compound.

[0093] The "aliphatic polyisocyanate compound" includes, for example, an aliphatic polyisocyanate compound, a polymer of an aliphatic polyisocyanate compound, an adduct of an aliphatic polyisocyanate compound and a polyol compound (e.g., trimethylolpropane (TMP); the same applies below), and a biuret of an aliphatic polyisocyanate compound. Specific examples of the aliphatic polyisocyanate compound include hexamethylene diisocyanate (HMDI), pentamethylene diisocyanate (PDI), tetramethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate.

[0094] The "alicyclic polyisocyanate compound" includes, for example, an alicyclic polyisocyanate compound, a polymer of an alicyclic polyisocyanate compound, an adduct of an alicyclic polyisocyanate compound and a polyol compound, and a biuret of an alicyclic polyisocyanate compound. Specific examples of the alicyclic polyisocyanate compound include isophorone diisocyanate (IPDI), hydrogenated tolylene diisocyanate, hydrogenated xylylene diisocyanate (H6XDI), hydrogenated 4,4'-diphenylmethane diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

[0095] The "aromatic polyisocyanate compound" includes, for example, an aromatic polyisocyanate compound, a polymer of an aromatic polyisocyanate compound, an adduct of an aromatic polyisocyanate compound and a polyol compound, and a biuret of an aromatic polyisocyanate compound. Specific examples of aromatic polyisocyanate compounds include tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), and 4,4'-diphenylmethane diisocyanate.

[0096] The polyisocyanate compound is preferably at least one selected from the group consisting of aliphatic polyisocyanate compounds and alicyclic polyisocyanate compounds, and more preferably at least one selected from the group consisting of hexamethylene diisocyanate compounds and hydrogenated xylylene diisocyanate compounds. The "hexamethylene diisocyanate-based compounds" include, for example, HMDI, HMDI polymers, adducts of HMDI and polyol-based compounds, and biuret forms of HMDI. As the hexamethylene diisocyanate compound, a polymer of HMDI or a biuret of HMDI is preferred. The "hydrogenated xylylene diisocyanate-based compound" includes, for example, H6XDI, an adduct of H6XDI and a polyol-based compound, and a biuret of H6XDI.

[0097] The dissociation temperature of the blocked isocyanate compound is not particularly limited, but is preferably 80° C. or higher from the viewpoint of commercial availability, for example. Also, the dissociation temperature of the blocked isocyanate compound is preferably 180° C. or lower from the viewpoint of suppressing deformation due to heating of a surface protection film provided in an overlaminate film attached to an adherend. The dissociation temperature of the blocked isocyanate compound is preferably 80°C to 180°C, more preferably 90°C to 180°C, and further preferably 100°C to 180°C. In the present disclosure, the "dissociation temperature of a blocked isocyanate compound" means the temperature at which the blocking agent dissociates.

[0098] Representative blocked isocyanate compounds and their dissociation temperatures are shown below. Dimethylpyrazole blocked isocyanate compounds (dissociation temperature: 100℃~120℃), active methylene blocked isocyanate compounds (dissociation temperature: 100℃~120℃), ketoxime blocked isocyanate compounds (dissociation temperature: 130℃~150℃), ε-caprolactam blocked isocyanate compounds (dissociation temperature: 160℃~180℃).

[0099] The dissociation temperature of a blocked isocyanate compound in the present disclosure means "the temperature of the endothermic peak accompanying the deprotection reaction of the blocked isocyanate when measured by DSC (Differential Scanning Calorimetry) analysis using a differential scanning calorimeter."

[0100] As the blocked isocyanate compound, commercially available products can be used. Examples of commercially available blocked isocyanate compounds include "Takenate (registered trademark) B-820NP" manufactured by Mitsui Chemicals, Inc., and "Duranate (registered trademark) 17B-60P," "Duranate (registered trademark) SBB-70P," "Duranate (registered trademark) TPA-B80E," and "Duranate (registered trademark) SBN-70D" manufactured by Asahi Kasei Corporation.

[0101] The pressure-sensitive adhesive composition of the present disclosure may contain only one type of blocked isocyanate compound as a crosslinking agent, or may contain two or more types.

[0102] The content of the blocked isocyanate compound in the pressure-sensitive adhesive composition of the present disclosure is not particularly limited, so long as the ratio of the number of moles of isocyanate groups in the blocked isocyanate compound to the number of moles of carboxy groups in the (meth)acrylic copolymer (A) is 0.1 or more. The content of the blocked isocyanate compound in the pressure-sensitive adhesive composition of the present disclosure may be, for example, 1 part by mass to 45 parts by mass relative to 100 parts by mass of the (meth)acrylic copolymer (A).

[0103] <<Ratio of the number of moles of isocyanate groups in the blocked isocyanate compound to the number of moles of carboxyl groups in the (meth)acrylic copolymer (A)>> When the ratio of the number of moles of isocyanate groups in the blocked isocyanate compound to the number of moles of carboxy groups in the (meth)acrylic copolymer (A) is 0.1 or more, the cohesive strength of the pressure-sensitive adhesive layer is sufficiently increased, so that the pressure-sensitive adhesive layer is less likely to suffer cohesive failure around the convex parts of the adherend during three-dimensional molding. From this viewpoint, the ratio of the number of moles of isocyanate groups in the blocked isocyanate compound to the number of moles of carboxy groups in the (meth)acrylic copolymer (A) is preferably 0.15 or more, more preferably 0.2 or more. The upper limit of the ratio of the number of moles of isocyanate groups in the blocked isocyanate compound to the number of moles of carboxyl groups in the (meth)acrylic copolymer (A) is not particularly limited, but if the amount of the blocked isocyanate compound is excessively large, the pressure-sensitive adhesive layer may become cloudy and the appearance may be impaired. From the viewpoint of the transparency of the pressure-sensitive adhesive layer, the upper limit is preferably 2.0 or less, more preferably 1.0 or less. In one embodiment, the ratio of the number of moles of isocyanate groups in the blocked isocyanate compound to the number of moles of carboxy groups in the (meth)acrylic copolymer (A) may be 0.1 to 2.0, 0.1 to 1.0, 0.15 to 2.0, 0.15 to 1.0, 0.2 to 2.0, or 0.2 to 1.0.

[0104] The ratio of the number of moles of isocyanate groups in the blocked isocyanate compound to the number of moles of carboxy groups in the (meth)acrylic copolymer (A) is calculated by the following formulas (1) to (3). In addition, the "isocyanate group" in the formula (1) refers to the isocyanate group in the blocked isocyanate group after the blocking agent is deprotected, that is, the isocyanate group in a state not protected by the blocking agent. In addition, when there are multiple types of monomers having carboxy groups that form the (meth)acrylic copolymer (A), calculations are performed for each monomer, and the obtained values ​​are then summed up.

[0105] Number of moles of isocyanate groups in blocked isocyanate compounds (unit: mmol) = [Isocyanate group content in blocked isocyanate compound (unit: mass%) / Solid content concentration of blocked isocyanate compound (unit: mass%) × Blocked isocyanate compound blend amount [amount as solid content] (unit: g)] / Molecular weight of isocyanate group (unit: g / mol) × 1000 (1)

[0106] Number of moles of carboxyl groups in (meth)acrylic copolymer (A) [unit: mmol] = [Content of the structural unit derived from the monomer having a carboxy group in the (meth)acrylic copolymer (A) (unit: mass%) / 100 × amount of the (meth)acrylic copolymer (A) (unit: g) / molecular weight of the structural unit derived from the monomer having a carboxy group (unit: g / mol) × number of carboxy groups (valence) in the structural unit derived from the monomer having a carboxy group × 1000] (2)

[0107] The ratio of the number of moles of isocyanate groups in the blocked isocyanate compound to the number of moles of carboxyl groups in the (meth)acrylic copolymer (A) = Value obtained by formula (1) / Value obtained by formula (2) (3)

[0108] [Organic Solvent] The pressure-sensitive adhesive composition of the present disclosure may contain an organic solvent. When the pressure-sensitive adhesive composition of the present disclosure contains an organic solvent, the coatability and pot life can be improved. As the organic solvent, for example, the same organic solvents as those used in the polymerization reaction of the above-mentioned specific (meth)acrylic copolymer can be mentioned.

[0109] When the pressure-sensitive adhesive composition of the present disclosure contains an organic solvent, it may contain only one type of organic solvent, or may contain two or more types of organic solvent.

[0110] When the pressure-sensitive adhesive composition of the present disclosure contains an organic solvent, the content of the organic solvent is not particularly limited and can be appropriately set depending on the purpose.

[0111] [Other ingredients] The pressure-sensitive adhesive composition of the present disclosure may contain components other than the components described above (so-called other components) as necessary, provided that the effects of the composition are not impaired. Examples of other components include various additives such as polymers other than the (meth)acrylic copolymer (A) and the (meth)acrylic copolymer (B), crosslinking agents other than blocked isocyanate compounds (e.g., epoxy crosslinking agents), crosslinking catalysts, antioxidants, light stabilizers (e.g., ultraviolet absorbers), and antistatic agents.

[0112] When the pressure-sensitive adhesive composition of the present disclosure contains other components, the contents of the other components can be appropriately set within a range that does not impair the effects of the pressure-sensitive adhesive composition of the present disclosure.

[0113] [Overlamination film] The overlaminate film of the present disclosure comprises a surface protective film, and a pressure-sensitive adhesive layer provided on one side of the surface protective film and formed from the pressure-sensitive adhesive composition of the present disclosure. The overlaminate film of the present disclosure has a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present disclosure, and therefore has high adhesive strength to an adherend and is less likely to cause poor appearance during three-dimensional molding.

[0114] The material of the adherend of the overlaminate film of the present disclosure is not particularly limited, and examples thereof include resins (such as polyurethane-based resins) and metals (such as aluminum plates).

[0115] The adhesive layer formed by the adhesive composition of the present disclosure shows excellent adhesion to the adherend when it is attached to the adherend, and when it is heated thereafter, the isocyanate group of the blocked isocyanate compound is deprotected, and an active isocyanate group is generated, which advances the crosslinking reaction and increases the cohesive strength of the adhesive layer. Due to such an action mechanism, the adhesive composition of the present disclosure has high adhesion to the adherend and can form an adhesive layer that is unlikely to cause poor appearance during three-dimensional molding, so that the method of using the overlaminate film of the present disclosure is preferably, for example, a method of heating after it is attached to the adherend, before molding, or during molding.

[0116] The material of the surface protection film is not particularly limited. Examples of the surface protection film include films containing resins such as polyolefin resins (e.g., polyethylene (PE) and polypropylene (PP)), polyester resins (e.g., polyethylene terephthalate (PET)), acetate resins (e.g., triacetyl cellulose), polyethersulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyurethane resins, (meth)acrylic resins, vinyl chloride resins, ABS (Acrylonitrile Butadiene Styrene) resins, and fluorine-based resins. The surface protection film is preferably a film containing a polyurethane resin, from the viewpoint of suppressing distortion of the molded portion that may occur during three-dimensional molding, for example.

[0117] The surface protective film may be colorless or colored, but is preferably colorless from the viewpoint of not interfering with the design of the decoration applied to the adherend. The surface protective film may be transparent or translucent, but is preferably transparent so as not to impair the visibility of the decoration applied to the adherend. In the present disclosure, "transparent" means that the average transmittance of visible light with a wavelength of 400 nm to 700 nm is 80% or more, and preferably 90% or more. In this disclosure, "transmittance" is a value measured using a spectrophotometer.

[0118] The surface of the surface protection film on which the adhesive layer is provided may be subjected to a surface treatment such as corona discharge treatment or plasma discharge treatment (so-called easy-adhesion treatment) in order to improve the adhesion between the surface protection film and the adhesive layer.

[0119] The surface protective film may contain various additives such as a crosslinking agent, a crosslinking catalyst, a plasticizer, a heat stabilizer, an ultraviolet absorber, a light stabilizer, an antistatic agent, a flame retardant, an antioxidant, a filler, an antifoaming agent, and a surfactant.

[0120] The thickness of the surface protection film is not particularly limited, but is, for example, preferably from 20 μm to 100 μm, more preferably from 25 μm to 90 μm, and further preferably from 30 μm to 80 μm.

[0121] In the present disclosure, the "thickness of the surface protection film" means the average thickness of the surface protection film. The average thickness of the surface protective film is a value determined by the following method. The thickness of the surface protection film is measured at five randomly selected locations in the thickness direction using a constant pressure thickness gauge (measuring probe diameter: 5 mm). The arithmetic mean of the measured values ​​is calculated, and the obtained value is regarded as the average thickness of the surface protection film.

[0122] The surface protective film may be a single layer film or may be formed of multiple layers. When the surface protection film is formed of a plurality of layers, the thickness of the surface protection film mentioned above refers to the total thickness of the plurality of layers forming the surface protection film.

[0123] The pressure-sensitive adhesive layer included in the overlaminate film of the present disclosure is a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present disclosure, and is provided on one side of the surface protection film. The adhesive layer provided in the overlaminate film of the present disclosure is formed from the adhesive composition of the present disclosure described above, and therefore has high adhesive strength to the adherend and is less likely to cause poor appearance during three-dimensional molding. The pressure-sensitive adhesive layer is preferably a layer made of the pressure-sensitive adhesive composition of the present disclosure, or a layer made of the solid content of the pressure-sensitive adhesive composition of the present disclosure.

[0124] The thickness of the pressure-sensitive adhesive layer is not particularly limited, but is, for example, preferably 3 μm to 40 μm, more preferably 5 μm to 35 μm, further preferably 8 μm to 30 μm, and particularly preferably 10 μm to 25 μm. When the thickness of the pressure-sensitive adhesive layer is 3 μm or more, the adhesive strength of the pressure-sensitive adhesive layer to an adherend tends to be more sufficiently increased. When the thickness of the pressure-sensitive adhesive layer is 40 μm or less, cohesive failure of the pressure-sensitive adhesive layer tends to be less likely to occur around the protrusions of the adherend during three-dimensional molding.

[0125] In the present disclosure, the "thickness of the pressure-sensitive adhesive layer" means the average thickness of the pressure-sensitive adhesive layer. The average thickness of the pressure-sensitive adhesive layer is a value determined by the following method. The thickness of the adhesive layer is measured at 5 randomly selected locations in the thickness direction using a constant pressure thickness gauge (measuring probe diameter: 5 mm). The arithmetic mean of the measured values ​​is calculated and the obtained value is regarded as the average thickness of the adhesive layer.

[0126] In the overlaminate film of the present disclosure, the exposed surface of the pressure-sensitive adhesive layer may be protected by a release sheet. In general, the release sheet protects the surface of the pressure-sensitive adhesive layer until the overlaminate film is put to practical use, and is peeled off when the film is used.

[0127] The release sheet is not particularly limited as long as it can be easily peeled off from the pressure-sensitive adhesive layer. Examples of release sheets include resin films, paper, synthetic paper, one or both sides of which have been surface-treated with a release agent (so-called easy-release treatment), and composite sheets obtained by laminating two or more of these. In the present disclosure, a release sheet in an embodiment in which one or both sides of a resin film have been surface-treated with a release treating agent (so-called easy-release treatment) is also referred to as a "release film". Examples of the release agent include silicone-based release agents (eg, silicone), wax-based release agents (eg, paraffin wax), and fluorine-based release agents (eg, fluorine-based resins). An example of the resin film is a polyester film, typically a polyethylene terephthalate (PET) film. Examples of the paper include fine paper and coated paper. The thickness of the release sheet is not particularly limited, and is generally 20 μm to 180 μm.

[0128] FIG. 1 is a schematic cross-sectional view showing an example of the configuration of the overlaminate film of the present disclosure. The overlaminate film 10 shown in Fig. 1 includes a surface protective film 20 and a pressure-sensitive adhesive layer 30 provided on one side of the surface protective film 20. Details of the surface protective film 20 and the pressure-sensitive adhesive layer 30 are as described above.

[0129] The overlaminate film of the present disclosure may include layers (also referred to as "other layers") other than the surface protective film and the pressure-sensitive adhesive layer, as necessary. Examples of other layers include a decorative layer provided on the surface protective film and / or between the surface protective film and the adhesive layer. In this case, the decorative layer is a layer provided to impart design to the overlaminate film, and is a layer that expresses patterns, characters, pictures, etc. The decorative layer can be formed by known printing methods such as inkjet printing, screen printing, gravure printing, hot stamp printing, and baking printing. When the overlaminate film of the present disclosure is used for a license plate described later, a layer on which characters (numbers, kanji, hiragana, alphabet, etc.) are formed is provided as a decorative layer on the surface protective film. The characters can be formed, for example, by baking printing.

[0130] The overlaminate film of the present disclosure comprises an adhesive layer formed from the adhesive composition of the present disclosure, i.e., an adhesive layer that has high adhesive strength to an adherend and is unlikely to cause poor appearance during three-dimensional molding, and therefore can be suitably used not only for flat-shaped articles but also for three-dimensionally shaped articles. The overlaminate film of the present disclosure can be used, for example, as a constituent member of the license plate of the present disclosure described below. The overlaminate film of the present disclosure can also be used for applications such as the interior or exterior of a vehicle such as an automobile, and the interior of a building such as a wall, floor, or ceiling.

[0131] [How to make overlaminate film] The method for producing the overlaminate film of the present disclosure is not particularly limited. The overlaminate film of the present disclosure can be produced by a known method using the pressure-sensitive adhesive composition of the present disclosure. Examples of the method for producing the overlaminate film of the present disclosure include the following methods.

[0132] The adhesive composition of the present disclosure is applied to the easy-adhesion treated surface of the substrate film to be the surface protection film, thereby forming a coating film on the substrate film. The formed coating film is then dried to form an adhesive layer on the substrate film. The exposed surface of the formed adhesive layer is then laminated on the easy-release treated surface of the release sheet, thereby producing the overlaminate film of the present disclosure having a laminated structure of substrate film (so-called surface protection film) / adhesive layer / release sheet.

[0133] Another method may be, for example, the following method. The adhesive composition of the present disclosure is applied to the easy-release treated surface of a release sheet to form a coating film on the release sheet. The formed coating film is then dried to form an adhesive layer on the release sheet. The exposed surface of the formed adhesive layer is then laminated onto the easy-adhesion treated surface of a substrate film to be a surface protective film, thereby producing an overlaminate film of the present disclosure having a laminated structure of substrate film (so-called surface protective film) / adhesive layer / release sheet.

[0134] The method for applying the pressure-sensitive adhesive composition is not particularly limited. Examples of methods for applying the pressure-sensitive adhesive composition include known methods using a gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, knife coater, spray coater, bar coater, applicator, and the like. The amount of the adhesive composition to be applied is not particularly limited, and is appropriately set depending on, for example, the thickness of the adhesive layer to be formed.

[0135] The method for drying the coating film is not particularly limited. Examples of methods for drying the coating film include natural drying, heat drying, hot air drying, and vacuum drying. The drying temperature and drying time of the coating film are not particularly limited, and are appropriately set depending on the thickness of the coating film, the amount of the organic solvent in the coating film, and the like. An example of the drying conditions is heating at 100° C. for 1 minute.

[0136] [License plate] The license plate of the present disclosure comprises a plate substrate and an overlaminate film of the present disclosure provided on one side of the plate substrate. Since the license plate of the present disclosure is equipped with the overlaminate film of the present disclosure, appearance defects due to the use of the overlaminate film are less likely to occur. Hereinafter, in the license plate of the present disclosure, the "adhesive layer formed from the adhesive composition of the present disclosure" provided on the overlaminate film of the present disclosure is also referred to as the "first adhesive layer."

[0137] The embodiment of the license plate of the present disclosure is not particularly limited as long as it comprises a plate substrate and an overlaminate film of the present disclosure provided on one side of the plate substrate. For example, it is preferable that the license plate has a surface protection film provided on the overlaminate film of the present disclosure as the outermost layer of the license plate. The license plate of the present disclosure may be, for example, an embodiment in which the first adhesive layer side of the overlaminate film of the present disclosure is attached to one side of the plate substrate, or an embodiment in which an image receiving layer capable of forming a decorative layer on the surface is provided between the plate substrate and the overlaminate film of the present disclosure. The image receiving layer may constitute an image receiving film together with a second adhesive layer that allows the image receiving layer to adhere to the plate substrate. In this case, the image receiving layer preferably contains a polyurethane resin and a (meth)acrylic resin, for example, from the viewpoint of imparting low-temperature impact resistance and printability. The image receiving layer preferably further contains a white pigment, for example, from the viewpoint of further improving whiteness. The second adhesive layer preferably contains a (meth)acrylic resin, for example, from the viewpoint of improving weather resistance, durability, and adhesion to the plate substrate. The second adhesive layer preferably further contains a pigment, for example, from the viewpoint of improving the appearance of the license plate. When the license plate of the present disclosure has an image receiving layer, a decorative layer may be provided on the image receiving layer as appropriate. In this case, the decorative layer is a layer provided to impart design to the license plate, and is a layer that expresses a pattern, a design, etc. As a method for forming a decorative layer on the image receiving layer, known printing methods such as inkjet printing, screen printing, and gravure printing can be applied. For example, a layer on which a design is formed by inkjet printing is provided as a decorative layer on the image receiving layer.

[0138] FIG. 2 is a schematic cross-sectional view showing an example of the configuration of the license plate of the present disclosure. The license plate 40 shown in Fig. 2 comprises a plate substrate 50 and an overlaminate film 10 of the present disclosure provided on one side of the plate substrate 50. The overlaminate film 10 comprises a surface protective film 20 and a first adhesive layer 30 provided on one side of the surface protective film 20. In the license plate 40, the surface of the overlaminate film 10 on the side of the first adhesive layer 30 is in contact with one side of the plate substrate 50. The license plate 40 also comprises a decorative layer 60 on the surface protective film 20 constituting the overlaminate film 10.

[0139] FIG. 3 is a schematic cross-sectional view showing an example of another configuration of the license plate of the present disclosure. The license plate 70 shown in FIG. 3 includes a plate substrate 50, an image receiving film 100 having an image receiving layer 80 and a second adhesive layer 90, and an overlaminate film 10 of the present disclosure. The overlaminate film 10 includes a surface protective film 20 and a first adhesive layer 30 provided on one side of the surface protective film 20. In the license plate 70, the surface of the image receiving film 100 on the second adhesive layer 90 side is in contact with one side of the plate substrate 50. In the license plate 70, the surface of the overlaminate film 10 on the first adhesive layer 30 side is in contact with the surface of the image receiving film 100 on the image receiving layer 80 side. The license plate 70 includes a decorative layer 60 on the surface protective film 20 that constitutes the overlaminate film 10. The license plate 70 also includes a decorative layer 60 on the image receiving layer 80 that constitutes the image receiving film 100. The details of the plate substrate 50 will be described later. The details of the overlaminate film 10, the decorative layer 60 and the image receiving film 100 are as described above.

[0140] The plate substrate may be a metal plate or a resin plate. Examples of the metal plate include an aluminum plate, a stainless steel plate, and an iron plate. Examples of resin plates include polycarbonate plates, polyester plates, polyvinyl chloride plates, acrylic plates, ABS plates, and PP plates. The plate substrate may be one obtained by forming the above-mentioned metal plate or resin plate into the shape of a frame or the like.

[0141] The method of manufacturing the license plate of the present disclosure is not particularly limited. The license plate of the present disclosure can be manufactured, for example, by the following method. First, the overlaminate film of the present disclosure is attached to a plate substrate before embossing the characters, etc. Next, the plate substrate to which the overlaminate film of the present disclosure is attached is heated, and then the plate substrate is embossed, or the plate substrate to which the overlaminate film of the present disclosure is attached is embossed while being heated. In this manner, the license plate of the present disclosure can be manufactured. EXAMPLES

[0142] The pressure-sensitive adhesive composition of the present disclosure will be described in more detail below with reference to examples. The present disclosure is not limited to the following examples as long as it does not deviate from the gist of the disclosure.

[0143] [Production of (meth)acrylic copolymer A] [Manufacturing example A-1] A reactor equipped with a stirrer, a reflux condenser, a successive dropping device, and a thermometer was charged with 25 mass% of a monomer mixture consisting of 53.0 parts by mass of n-butyl acrylate (n-BA), 43.0 parts by mass of methyl acrylate (MA), and 4.0 parts by mass of acrylic acid (AA), 45.0 parts by mass of ethyl acetate (organic solvent), and 0.015 parts by mass of 2,2'-azobisisobutyronitrile (AIBN; polymerization initiator), and the mixture was heated to carry out polymerization at the reflux temperature for 20 minutes. Next, the remaining 75% by mass of the monomer mixture and a polymerization initiator solution consisting of 30.0 parts by mass of ethyl acetate and 0.15 parts by mass of 2,2'-azobisisobutyronitrile were successively dropped into the polymerization reaction product in the reactor maintained at reflux temperature over 1.5 hours, and the polymerization reaction was continued for 1 hour, and then a polymerization initiator solution consisting of 25.0 parts by mass of ethyl acetate and 0.30 parts by mass of 2,2'-azobisisobutyronitrile was successively dropped into the polymerization reaction product in one hour, and the polymerization reaction was continued for another 2 hours to obtain a polymerization reaction product. The obtained polymerization reaction product was diluted to a solid concentration of 35% by mass using methyl ethyl ketone (MEK), and then cooled to obtain a solution of (meth)acrylic copolymer A-1.

[0144] The term "solid content" used herein means the mass ratio of the (meth)acrylic copolymer A-1 in the solution of the (meth)acrylic copolymer A-1. The same applies to each of the solutions of the (meth)acrylic copolymers A-2 to A-13 produced below.

[0145] [Manufacturing examples A-2 to A-13] In Production Examples A-2 to A-13, the same operations as in Production Example A-1 were carried out except that the monomer composition of (meth)acrylic copolymer A was changed to the monomer composition shown in Table 1, and solutions of (meth)acrylic copolymers A-2 to A-13 with solid concentrations of 35 mass% were obtained.

[0146] The monomer compositions (unit: mass%) and glass transition temperatures (represented as "Tg") (unit: °C) of the (meth)acrylic copolymers A-1 to A-13 are shown in Table 1. The weight average molecular weight of each of the (meth)acrylic copolymers A-1 to A-13 was 600,000.

[0147] The glass transition temperatures of the (meth)acrylic copolymers A-1 to A-13 were determined by the same method as that for determining the glass transition temperature of the (meth)acrylic copolymer (A) described above. The weight average molecular weights of the (meth)acrylic copolymers A-1 to A-13 were measured by the same method as the above-mentioned method for measuring the weight average molecular weight of the (meth)acrylic copolymer (A).

[0148] Among the (meth)acrylic copolymers A-1 to A-13, the (meth)acrylic copolymers A-1 to A-9 correspond to the (meth)acrylic copolymer (A) in the present disclosure.

[0149] [Table 1]

[0150] Details of each monomer listed in Table 1 are as follows. <(Meth)acrylic acid alkyl ester monomer> "n-BA": n-butyl acrylate "MA": Methyl acrylate "2EHA": 2-Ethylhexyl acrylate <Monomers having a carboxy group> "AA": acrylic acid

[0151] In Table 1, "-" in the monomer composition column means that the monomer in that column was not used.

[0152] [Production of (meth)acrylic copolymer B] [Manufacturing example B-1] A reactor equipped with a stirrer, a reflux condenser, a successive dropping device, and a thermometer was charged with 20 mass% of a monomer mixture consisting of 80.0 parts by mass of methyl methacrylate (MMA), 14.0 parts by mass of ethyl acrylate (EA), and 6.0 parts by mass of 2-dimethylaminoethyl methacrylate (DM), 45.0 parts by mass of ethyl acetate (organic solvent), and 0.15 parts by mass of 2,2'-azobisisobutyronitrile (AIBN; polymerization initiator), and the mixture was heated to carry out polymerization at the reflux temperature for 20 minutes. The polymerization reaction product in the reactor, which was kept at reflux temperature, was successively dropped over 1.5 hours with the remaining 80% by mass of the monomer mixture, 30.0 parts by mass of ethyl acetate, and 0.15 parts by mass of 2,2'-azobisisobutyronitrile, followed by polymerization reaction for 1 hour. The polymerization reaction product was then successively dropped over 1 hour with the polymerization reaction product consisting of 25.0 parts by mass of ethyl acetate and 0.30 parts by mass of 2,2'-azobisisobutyronitrile, followed by polymerization reaction for another 2 hours to obtain a polymerization reaction product. The obtained polymerization reaction product was diluted to a solid content concentration of 36% by mass using methyl ethyl ketone (MEK), and then cooled to obtain a solution of (meth)acrylic copolymer B-1.

[0153] The term "solid content" used herein means the mass ratio of the (meth)acrylic copolymer B-1 in the solution of the (meth)acrylic copolymer B-1. The same applies to each of the solutions of the (meth)acrylic copolymers B-2 to B-5 produced below.

[0154] [Manufacturing examples B-2 to B-5] In Production Examples B-2 to B-5, the same operations as in Production Example B-1 were carried out except that the monomer composition of (meth)acrylic copolymer B was changed to the monomer composition shown in Table 2, and solutions of (meth)acrylic copolymers B-2 to B-5 with solid concentrations of 36 mass% were obtained.

[0155] The monomer compositions (unit: mass%) and glass transition temperatures (represented as "Tg") (unit: °C) of the (meth)acrylic copolymers B-1 to B-5 are shown in Table 2. The weight average molecular weight of each of the (meth)acrylic copolymers B-1 to B-5 was 100,000.

[0156] The glass transition temperatures of the (meth)acrylic copolymers B-1 to B-5 were determined by the same method as that for determining the glass transition temperature of the (meth)acrylic copolymer (A) described above. The weight average molecular weights of the (meth)acrylic copolymers B-1 to B-5 were measured by the same method as the above-mentioned method for measuring the weight average molecular weight of the (meth)acrylic copolymer (A).

[0157] Of the (meth)acrylic copolymers B-1 to B-5, the (meth)acrylic copolymers B-1 to B-4 correspond to the (meth)acrylic copolymer (B) in the present disclosure.

[0158] [Table 2]

[0159] Details of each monomer listed in Table 2 are as follows. <(Meth)acrylic acid alkyl ester monomer> "MMA": Methyl methacrylate "EA": Ethyl acrylate <Monomers having amino groups> "DM": 2-Dimethylaminoethyl methacrylate "DE": 2-diethylaminoethyl methacrylate

[0160] In Table 2, "-" in the monomer composition column means that the monomer in that column was not used.

[0161] [Preparation of Adhesive Composition] Example 1 100 parts by mass (solid content equivalent) of (meth)acrylic copolymer A-1, 15 parts by mass (solid content equivalent) of (meth)acrylic copolymer B-1, and 4.4 parts by mass (solid content equivalent) of a blocked isocyanate compound (product name: Takenate B-820NP, manufactured by Mitsui Chemicals, Inc.) as a crosslinking agent were mixed by stirring to obtain a pressure-sensitive adhesive composition of Example 1.

[0162] [Examples 2 to 21] In Examples 2 to 21, the adhesive compositions of Examples 2 to 21 were obtained in the same manner as in Example 1, except that the formulation of the adhesive composition was changed to the formulation shown in Table 3.

[0163] [Comparative Examples 1 to 10] In Comparative Examples 1 to 10, the adhesive compositions of each of Comparative Examples 1 to 10 were obtained by the same procedure as in Example 1, except that the formulation of the adhesive composition was changed to the formulation shown in Table 4.

[0164] Tables 3 and 4 show the compositions of the pressure-sensitive adhesive compositions of Examples 1 to 21 and Comparative Examples 1 to 10, the number of moles of carboxy groups in the (meth)acrylic copolymer A [unit: mmol], the number of moles of isocyanate groups in the crosslinking agent [unit: mmol], and the ratio of the number of moles of isocyanate groups in the crosslinking agent to the number of moles of carboxy groups in the (meth)acrylic copolymer A [in the table, this is expressed as "number of moles of isocyanate groups in the crosslinking agent / number of moles of carboxy groups in (meth)acrylic copolymer A"].

[0165] [Table 3]

[0166] [Table 4]

[0167] Details of the components listed in Tables 3 and 4 are as follows. <Crosslinking agent> -Blocked isocyanate compounds- "Takenate B-820NP" [Product name, hydrogenated xylylene diisocyanate (H6XDI), solid content: 60% by mass, isocyanate group content (catalog value): 6.4% by mass, dissociation temperature: 100°C to 120°C, manufactured by Mitsui Chemicals, Inc.] "Duranate 17B-60P" [Product name, biuret of hexamethylene diisocyanate (HMDI), solid content: 60% by mass, isocyanate group content (catalog value): 9.4% by mass, dissociation temperature: 130°C, manufactured by Asahi Kasei Corporation] "Duranate SBB-70P" [Product name, biuret of hexamethylene diisocyanate (HMDI), solid content: 70% by mass, isocyanate group content (catalog value): 10.2% by mass, dissociation temperature: 110°C, manufactured by Asahi Kasei Corporation] "Duranate TPA-B80E" [Product name, hexamethylene diisocyanate (HMDI) nurate (trimer), solids concentration: 80% by mass, isocyanate group content (catalog value): 12.4% by mass, dissociation temperature: 130°C, manufactured by Asahi Kasei Corporation] "Duranate SBN-70D" [Product name, hexamethylene diisocyanate (HMDI) nurate (trimer), solids concentration: 70% by mass, isocyanate group content (catalog value): 10.2% by mass, dissociation temperature: 110°C, manufactured by Asahi Kasei Corporation]

[0168] -Unblocked isocyanate compounds- "Takenate D-140N" [product name, adduct of isophorone diisocyanate (IPDI) and trimethylolpropane (TMP), solid content: 75% by mass, isocyanate group content (catalog value): 10.5% by mass, manufactured by Mitsui Chemicals, Inc.] "Duranate E405-70B" [Product name, adduct of hexamethylene diisocyanate (HMDI) and trimethylolpropane (TMP), solid content: 70% by mass, isocyanate group content (catalog value): 6.2% by mass, manufactured by Asahi Kasei Corporation]

[0169] The above "Takenate" and "Duranate" are both registered trademarks.

[0170] [Preparation of base film] In a reactor equipped with a stirrer, 90 parts by mass of polyurethane resin 1 [product name: Resamine NE-8836, one-component curing polycarbonate-based urethane resin, manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.], 10 parts by mass of polyurethane resin 2 [product name: Resamine NE-8811, one-component curing polycarbonate-based urethane resin, manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.], 20 parts by mass of crosslinking agent [product name: Resamine X-100, isocyanate-based crosslinking agent, manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.], 0.1 parts by mass of crosslinking catalyst [product name: UA-38, tin 2-ethylhexyl acid, manufactured by TOKUSHIKI CORPORATION], and dilution solvent [N,N-dimethylformamide] were mixed and stirred for 10 minutes using a disper under an ambient temperature of 23° C. to obtain a composition for forming a base film. Next, the composition for forming a base film was applied to the easily peelable surface of a release film (trade name: P756050, polyethylene terephthalate (PET), thickness: 75 μm, manufactured by Lintec Corporation) that had been surface-treated (so-called easy peeling treatment) with a silicone-based release treatment agent, so that the thickness after drying would be 35 μm, forming a coating film. Next, the formed coating film was heated at 100° C. for 3 minutes using a hot air circulation dryer, and then further heated and dried at 160° C. for 3 minutes to produce a base film. In addition, the above-mentioned "Rezamin" is a registered trademark.

[0171] [Preparation of adhesive film for evaluation] Pressure-sensitive adhesive films for evaluation were produced using the pressure-sensitive adhesive compositions of Examples 1 to 21 and Comparative Examples 1 to 10 and base films as follows.

[0172] (1) In the case of the pressure-sensitive adhesive compositions of Examples 1 to 21 and Comparative Examples 1 to 8 A pressure-sensitive adhesive composition was applied to the easy-release treated surface of a release film (trade name: PET75GS, material: polyethylene terephthalate (PET), thickness: 75 μm, manufactured by Lintec Corporation) that had been surface-treated (so-called easy-release treatment) with a silicone-based release treatment agent, so that the thickness after drying (i.e., the thickness of the adhesive layer) was the thickness shown in Table 5, to form a coating film. Next, the formed coating film was dried by heating at 100 ° C. for 1 minute using a hot air circulation dryer, to form an adhesive layer on the release film. Next, a substrate film was attached to the exposed surface of the formed adhesive layer, to prepare an evaluation adhesive film having a substrate film / adhesive layer / release film configuration.

[0173] (2) In the case of the pressure-sensitive adhesive compositions of Comparative Examples 9 and 10 A pressure-sensitive adhesive composition was applied to the easy-release treated surface of a release film (trade name: PET75GS, material: polyethylene terephthalate (PET), thickness: 75 μm, manufactured by Lintec Corporation) that had been surface-treated (so-called easy-release treatment) with a silicone-based release agent, so that the thickness after drying (i.e., the thickness of the adhesive layer) was the thickness shown in Table 5, to form a coating film. Next, the formed coating film was dried by heating at 100 ° C. for 1 minute using a hot air circulation dryer, to form an adhesive film on the release film. Next, a base film was attached to the exposed surface of the formed adhesive film to prepare a laminate. Next, the prepared laminate was left to stand in an environment with an atmospheric temperature of 23 ° C. for 1 week to allow the adhesive film to mature, thereby preparing an evaluation adhesive film having a configuration of base film / adhesive layer / release film.

[0174] [Preparation of the substrate] A printing plate was prepared as an adherend to be used in the evaluation test, specifically, according to the following procedures (1) to (3).

[0175] (1) Formation of image-receiving layer In a reactor equipped with a stirrer, 100 parts by mass of a polyurethane resin (product name: REZAMIN NE-8811, one-component curing polycarbonate-based urethane resin, manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.), 15 parts by mass of a (meth)acrylic resin (product name: DIANAL MB-2593, methacrylic resin, manufactured by Mitsubishi Chemical Corporation), 42 parts by mass of a pigment (product name: NX-501, titanium oxide, manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.), and a dilution solvent (a mixed solvent of isopropyl alcohol and toluene (volume ratio 1:1)) were stirred and mixed for 10 minutes using a disper in an environment with an ambient temperature of 23° C. to obtain a composition for forming an image-receiving layer. Next, the composition for forming an image receiving layer was applied to the easily peelable surface of a release film (trade name: P756050, polyethylene terephthalate (PET), thickness: 75 μm, manufactured by Lintec Corporation) that had been surface-treated (so-called easily peelable) with a silicone-based release treatment agent, so that the thickness after drying would be 55 μm, forming a coating film. Next, the formed coating film was heated at 100° C. for 3 minutes using a hot air circulation dryer, and then further heated and dried at 160° C. for 3 minutes, thereby forming an image receiving layer on the release film. In addition, both "Rezamin" and "Dianal" are registered trademarks.

[0176] (2) Formation of the second adhesive layer 100 parts by mass of an acrylic copolymer obtained by polymerizing 90 parts by mass of n-butyl acrylate and 10.0 parts by mass of acrylic acid, 8.34 parts by mass of a white pigment [trade name: DAD-100, component: titanium dioxide, manufactured by DIC Corporation], 5.0 parts by mass of an isocyanate-based crosslinking agent [trade name: Coronate L-45E, manufactured by Mitsubishi Gas Chemical Co., Ltd.], and a dilution solvent [ethyl acetate] were mixed by stirring to obtain a composition for forming a second adhesive layer. Next, the composition for forming a second adhesive layer was applied to the easy-release treated surface of a release film [trade name: PET75GS, material: polyethylene terephthalate (PET), thickness: 75 μm, manufactured by Lintec Corporation] that had been surface-treated (so-called easy-release treatment) with a silicone-based release treatment agent, so that the thickness after drying was 40 μm, to form a coating film. The formed coating film was then dried by heating at 100° C. for 1 minute using a hot air circulation dryer, thereby forming a second pressure-sensitive adhesive layer on the release film. In addition, the above-mentioned "Coronate" is a registered trademark.

[0177] (3) Preparation of printing plates The exposed surface of the image receiving layer formed above was laminated to the exposed surface of the second adhesive layer to prepare an image receiving film. Next, in an environment of an atmospheric temperature of 23°C and 50% RH, the release film on the second adhesive layer side of the image receiving film was peeled off, and the exposed surface of the second adhesive layer was laminated to an aluminum plate. Next, the release film on the image receiving layer side of the image receiving film was peeled off, and solid printing of cyan and yellow was performed on the exposed surface of the image receiving layer using an inkjet printer [model number: JV-300, manufactured by Mimaki Engineering Co., Ltd.] to form a decorative layer. In this manner, a printing plate having a configuration of decorative layer / image receiving layer / second adhesive layer / aluminum plate was prepared.

[0178] [evaluation] 1. Adhesive strength The adhesive film for evaluation prepared above was cut to a size of 25 mm x 150 mm (long side), and the release film was peeled off. Next, the surface of the adhesive layer exposed by peeling was placed on the exposed surface of the decorative layer of the printing plate prepared above, and then the two were laminated by rolling a 2 kg roller back and forth twice. The laminate obtained by this lamination was subjected to a heat treatment at 120°C for 1 hour using a hot air circulation dryer, and used as a sample for adhesive strength evaluation test. For this adhesive strength evaluation test sample, the adhesive strength (unit: N / 25 mm) when the adhesive film for evaluation (structure: base film / adhesive layer) was peeled off from the printing plate at 180° in the long side (150 mm) direction was measured by a method conforming to JIS Z 0237:2000. Specifically, a single column type material testing machine [model number: RTG-1310] manufactured by A&D Co., Ltd. was used as the measuring device, and the measurement was performed under conditions of an atmospheric temperature of 23°C, 50% RH, and a peeling speed of 300 mm / min. Then, the adhesive strength to the adherend was evaluated according to the following evaluation criteria. The results are shown in Tables 5 and 6. In the following evaluation criteria, "A" and "B" are practically acceptable levels, with "A" being the most preferable.

[0179] -Evaluation criteria- A: The adhesive strength is 15N / 25mm or more. B: The adhesive strength is 5N / 25mm or more and less than 15N / 25mm. C: The adhesive strength is less than 5N / 25mm.

[0180] 2.Appearance during 3D molding 2-1. Cohesive failure The adhesive film for evaluation prepared above was cut to a size of 50 mm x 50 mm, and the release film was peeled off. Next, the surface of the adhesive layer exposed by peeling was placed on the exposed surface of the decorative layer of the printing plate prepared above, and then the two were laminated by rolling a 2 kg roller back and forth twice. The laminate obtained by this lamination was subjected to a heat treatment at 120°C for 1 hour using a hot air circulation dryer, and used as a sample for cohesive failure evaluation test. The cohesive failure evaluation test sample was subjected to a DuPont impact test from the aluminum plate side under the following conditions.

[0181] <DuPont impact test conditions> Falling weight: 1kg Drop height: 50cm Receiving jig: 1 / 4 inch recessed R shape Strike core: Flat tip, 1 / 2 inch diameter, 3 / 8 inch tip diameter

[0182] After the test, the evaluation adhesive film (structure: base film / adhesive layer) was stretched and deformed, and the deformed portion was observed under an optical microscope. The presence or absence and degree of air bubbles in the adhesive layer were confirmed, and the state of cohesive failure was evaluated according to the following evaluation criteria. The results are shown in Tables 5 and 6. The occurrence of air bubbles in the pressure-sensitive adhesive layer means that cohesive failure has occurred in the pressure-sensitive adhesive layer. In the following evaluation criteria, "A" and "B" are practically acceptable levels, with "A" being the most preferable.

[0183] -Evaluation criteria- A: No air bubbles were found in the adhesive layer (see FIG. 4A). B: A small amount of air bubbles were observed in the adhesive layer (see FIG. 4B). C: Air bubbles are noticeably generated in the adhesive layer (see FIG. 4C).

[0184] 2-2. Peeling The adhesive film for evaluation prepared above was cut to a size of 50 mm x 35 mm, and the release film was peeled off. Next, the surface of the adhesive layer exposed by peeling was placed on the exposed surface of the decorative layer of the printing plate prepared above, and then the two were laminated using a laminator. The laminate obtained by this lamination was subjected to a heat treatment at 120°C for 1 hour using a hot air circulation dryer, and used as a peel evaluation test sample. This peeling evaluation test sample was embossed with letters using a press machine and a die measuring 50 mm x 35 mm at a pressure of 1.3 t. An example of embossed letters is shown in Figure 5. Next, the peeling evaluation test sample 24 hours after embossing was subjected to a heat treatment at 120°C for 10 minutes using a hot air circulation dryer. After the heat treatment, the edges of the embossed letters were visually observed to confirm the presence or absence and the degree of lifting of the adhesive film (composition: base film / adhesive layer). The state of peeling was then evaluated according to the following evaluation criteria. The results are shown in Tables 5 and 6. In the following evaluation criteria, "A" and "B" are practically acceptable levels, with "A" being the most preferable.

[0185] -Evaluation criteria- A: No lifting was observed at all on the edges of the embossed letters. B: Slight lifting is observed at the edges of the embossed letters. C: The occurrence of lifting is clearly observed at the edges of the embossed letters.

[0186] [Table 5]

[0187] [Table 6]

[0188] In Table 5, "(a)", "(b)" and "(c)" in the column for Example 1 all refer to adhesive layers formed from the adhesive composition of Example 1, and have thicknesses of "3 μm", "12 μm" and "39 μm", respectively.

[0189] As shown in Table 5, it was confirmed that the pressure-sensitive adhesive layers formed from the pressure-sensitive adhesive compositions of Examples 1 to 21 had high adhesive strength to the adherend. It was also confirmed that the pressure-sensitive adhesive layers formed from the pressure-sensitive adhesive compositions of Examples 1 to 21 were less susceptible to cohesive failure and peeling around the protrusions of the adherend during three-dimensional molding, and were less likely to cause poor appearance.

[0190] On the other hand, as shown in Table 6, the adhesive layers formed using the adhesive compositions of Comparative Examples 1 to 10 were confirmed to be inferior to the adhesive layers formed using the adhesive compositions of Examples 1 to 21 in the evaluation results of either the adhesive strength to the adherend, or the cohesive failure and peeling around the convex portions of the adherend during three-dimensional molding. [Explanation of symbols]

[0191] 10: Overlamination film 20: Surface protection film 30: Adhesive layer (first adhesive layer) 40, 70: License plate 50: Plate substrate 60:Decorative layer 80: Image receiving layer 90:Second adhesive layer 100: Image receiving film

Claims

1. A (meth)acrylic copolymer (A), a (meth)acrylic copolymer (B), and a blocked isocyanate compound as a crosslinking agent, Including, The (meth)acrylic copolymer (A) contains a structural unit derived from a monomer having a carboxy group in a ratio of 1% by mass to 15% by mass based on all structural units of the (meth)acrylic copolymer (A), and has a glass transition temperature of −45° C. to −5° C.; The (meth)acrylic copolymer (B) contains a structural unit derived from a monomer having at least one amino group selected from the group consisting of a primary amino group, a secondary amino group, and a tertiary amino group, and has a glass transition temperature of 50° C. to 100° C.; The content of the (meth)acrylic copolymer (B) is 5 parts by mass to 25 parts by mass based on 100 parts by mass of the (meth)acrylic copolymer (A), A pressure-sensitive adhesive composition for overlaminate films, wherein the ratio of the number of moles of isocyanate groups in the blocked isocyanate compound to the number of moles of carboxy groups in the (meth)acrylic copolymer (A) is 0.1 or more.

2. The pressure-sensitive adhesive composition for overlaminate films according to claim 1, wherein the (meth)acrylic copolymer (A) has a weight average molecular weight of 400,000 to 2,500,000.

3. 2. The pressure-sensitive adhesive composition for overlaminate films according to claim 1, wherein the (meth)acrylic copolymer (B) has a weight average molecular weight of 5,000 to 200,000.

4. 2. The pressure-sensitive adhesive composition for overlaminate films according to claim 1, wherein the total content of structural units derived from the monomer having an amino group in the (meth)acrylic copolymer (B) is 3 mass% or more based on all structural units of the (meth)acrylic copolymer (B).

5. The pressure-sensitive adhesive composition for overlaminate films according to claim 1, wherein the dissociation temperature of the blocked isocyanate compound is 80°C to 180°C.

6. A surface protection film; A pressure-sensitive adhesive layer provided on one side of the surface protective film and formed from the pressure-sensitive adhesive composition for overlaminate films according to any one of claims 1 to 5; An overlaminate film comprising:

7. A plate substrate; The overlaminate film according to claim 6 provided on one surface side of the plate substrate; A license plate comprising:

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