Adhesive composition, adhesive layer, and vehicle protective film

Abstract

The present invention provides an adhesive composition, an adhesive layer, and a vehicle protective film, the adhesive composition comprising (A) a (meth) acrylic copolymer, (B) a metal chelate crosslinking agent, (C) a solvent having a boiling point of 100-200 DEG C and being a compound represented by formula (1), and (D) a monohydric alcohol solvent having 1-3 carbon atoms, the copolymer (A) contains 40-90% by mass of an alkyl (meth) acrylate monomer unit (a1) having 1-2 carbon atoms in the alkyl moiety with respect to all structural units, and contains 0.5-5.0% by mass of a monomer unit (a2) having a carboxyl group with respect to all structural units, the content of the crosslinking agent (B) being 0.1-1.0 part by mass with respect to 100 parts by mass of the copolymer (A), and the content of the crosslinking agent (B) being 0.1-1.0 part by mass with respect to 100 parts by mass of the copolymer (A). The content of the solvent (C) is 3-30 parts by mass per 100 parts by mass of the copolymer (A), and the ratio of the content of the solvent (C) to the content of the alcohol solvent (D) is 0.5-10.0. # imgabs0 #

Description

Technical Field

[0001] The present disclosure relates to adhesive compositions, adhesive layers, and vehicle protection films. Background Art

[0002] Vehicle protection films are adhesive films used to protect vehicles from external influences, preventing damage and contamination of the vehicle's painted surface. These films, also known as paint protection films (PPF), have become increasingly common in recent years. Vehicle protection films are required to have strong enough adhesion to prevent peeling immediately after application (so-called initial adhesion).

[0003] Furthermore, vehicle protective films are often removed from vehicles after being attached for a certain period of time (e.g., five years). Vehicle protective films that have been attached to vehicles for a certain period of time are exposed to high temperatures for a long period of time due to direct sunlight. Therefore, when the vehicle protective film is removed from the vehicle, the adhesive layer may transfer to the vehicle (so-called adhesive residue). Therefore, in addition to initial adhesion, vehicle protective films are also required to have long-term removability, allowing them to be removed from the vehicle without leaving adhesive residue after long-term exposure to high temperatures.

[0004] There are currently various reports on adhesives for vehicle protection films that aim to achieve both initial adhesion and long-term removability.

[0005] For example, Japanese Patent No. 7308166 discloses an adhesive composition for a vehicle protective film, comprising: a (meth)acrylic acid copolymer (A) containing specified structural units and having a weight-average molecular weight of 200,000 to 1.8 million; a (meth)acrylic acid copolymer (B) containing specified structural units and having a weight-average molecular weight of 3,000 to 10,000; and a metal chelate crosslinking agent, wherein the contents of the (meth)acrylic acid copolymer (B) and the metal chelate crosslinking agent are respectively in specified ratios relative to the content of the (meth)acrylic acid copolymer (A).

[0006] Japanese Patent No. 7402769 discloses an adhesive composition for a vehicle protective film, comprising: a (meth)acrylic copolymer (A) containing predetermined structural units and having a weight-average molecular weight of 200,000 to 2.5 million; a (meth)acrylic copolymer (B) containing predetermined structural units and having a weight-average molecular weight of 1,000 to 8,000; and at least one crosslinking agent selected from metal chelate crosslinking agents and isocyanate crosslinking agents (excluding toluene diisocyanate compounds and diphenylmethane diisocyanate compounds). The content of the (meth)acrylic copolymer (B) and the total content of the metal chelate crosslinking agent and the isocyanate crosslinking agent are each in a predetermined ratio relative to the content of the (meth)acrylic copolymer (A). Summary of the Invention

[0007] However, in recent years, the number of curved surfaces and the complexity of vehicle shapes have continued to increase, driven by the desire to enhance vehicle design. Consequently, vehicle protective films are required to conform to the vehicle's shape at a high level when applied to the vehicle. In other words, they are required to exhibit excellent flexibility when applied to the vehicle. However, since flexibility is disadvantageous in terms of impact resistance, vehicle protective films are also required to harden to a certain degree after application.

[0008] To meet these demands for vehicle protective films, a material with the property of softening when heated and hardening when cooled (so-called thermoplastic properties) (e.g., thermoplastic polyurethane (TPU)) can be used in the film's base material. Using a thermoplastic material for the film's base material allows the film to be softened by heating it with steam, for example, before being applied to the vehicle. This allows the film to conform to the vehicle's shape and ensure high impact resistance by cooling it after application.

[0009] However, when applying vehicle protective films to a vehicle by heating them with steam or other methods, wrinkles and / or voids may form on curved or complexly shaped surfaces, or air bubbles may be introduced, necessitating the film be peeled off and reapplied. Therefore, vehicle protective films are required to have high-temperature, short-term re-peelability, enabling them to be peeled off from the vehicle without leaving adhesive residue immediately after heating at high temperatures.

[0010] In order to improve the high-temperature short-term re-peelability of the vehicle protection film, it is necessary to increase the cohesive force of the adhesive layer possessed by the vehicle protection film so that the adhesive layer hardens and reduces the adhesion of the adhesive layer to the vehicle as the adherend. However, the viscosity of the adhesive layer heated by steam becomes higher, and the wettability to the adherend becomes higher. If only the design to improve the cohesive force of the adhesive layer is carried out, the adhesive force of the adhesive layer will increase excessively due to heating, and the high-temperature short-term re-peelability will decrease. In other words, to improve the high-temperature short-term re-peelability, it is important not to excessively increase the cohesive force of the adhesive layer. On the other hand, in order to achieve long-term re-peelability, a very high cohesive force is generally required. Therefore, it can be said that there is a so-called contradictory relationship between long-term re-peelability and high-temperature short-term re-peelability.

[0011] As described above, adhesive compositions for vehicle protective films are required to form adhesive layers that exhibit excellent short-term removability at high temperatures, in addition to the existing initial adhesion and long-term removability. However, it is known that initial adhesion and long-term removability have a conflicting relationship, and as mentioned above, long-term removability also has a conflicting relationship with short-term removability at high temperatures. Therefore, it is difficult to form an adhesive layer that exhibits excellent initial adhesion, short-term removability at high temperatures, and long-term removability.

[0012] It should be noted that Japanese Patent No. 7308166 and Japanese Patent No. 7402769 do not focus on high-temperature short-term re-peelability.

[0013] The present disclosure has been made in view of the above-mentioned circumstances.

[0014] An object of one embodiment of the present disclosure is to provide a PSA composition capable of forming a PSA layer having excellent initial adhesive strength, short-term re-peelability at high temperatures, and long-term re-peelability.

[0015] Another embodiment of the present disclosure aims to provide a pressure-sensitive adhesive layer and a vehicle protection film that are excellent in initial adhesive strength, short-term re-peelability at high temperatures, and long-term re-peelability.

[0016] Specific means for solving the problem include the following methods.

[0017] <1> An adhesive composition comprising: a (meth)acrylic acid copolymer (A), a metal chelate crosslinking agent (B), a solvent (C) having a boiling point of 100°C to 200°C and being a compound represented by the following formula (1), and a monohydric alcohol solvent (D) having 1 to 3 carbon atoms; wherein the (meth)acrylic acid copolymer (A) contains a structural unit (a1) derived from an alkyl (meth)acrylate monomer having 1 to 2 carbon atoms in the alkyl portion in a ratio of 40% to 90% by mass relative to the total structural units, and the metal chelate crosslinking agent (B) contains a structural unit (a1) derived from an alkyl (meth)acrylate monomer having 1 to 2 carbon atoms in the alkyl portion in a ratio of 40% to 90% by mass relative to the total structural units. The structural unit (a2) derived from a monomer having a carboxyl group is contained in an amount of 0.5 to 5.0% by mass of the structural unit. The content of the metal chelate crosslinking agent (B) is 0.1 to 1.0 parts by mass relative to 100 parts by mass of the (meth)acrylic copolymer (A). The content of the solvent (C) is 3 to 30 parts by mass relative to 100 parts by mass of the (meth)acrylic copolymer (A). The ratio of the mass content of the solvent (C) to the mass content of the alcohol solvent (D) is 0.5 to 10.0.

[0018]

[0019] In formula (1), R 1 and R 3 Each independently represents a hydrogen atom, a C1-C6 alkyl group, a C3-C6 cycloalkyl group, a C1-C6 hydroxyalkyl group, a C1-C6 alkoxy group, or an aromatic group which may be substituted with a C1-C6 alkyl group or a C1-C6 alkoxy group, and R 2 represents a hydrogen atom or a C1-C6 alkyl group.

[0020] <2> The adhesive composition according to <1>, wherein the (meth)acrylate monomer having 1 to 2 carbon atoms in the alkyl portion is at least one selected from methyl acrylate and ethyl acrylate.

[0021] <3> The adhesive composition according to <1> or <2>, wherein the (meth)acrylic copolymer (A) contains a structural unit (a3) ​​derived from an alkyl (meth)acrylate monomer other than the alkyl (meth)acrylate monomer having 1 to 2 carbon atoms in the alkyl portion.

[0022] <4> The adhesive composition according to any one of <1> to <3>, wherein the (meth)acrylic copolymer (A) has a weight average molecular weight of 200,000 to 1,800,000.

[0023] <5> A pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of <1> to <4>.

[0024] <6> A vehicle protection film comprising a substrate and the adhesive layer according to <5> provided on the substrate.

[0025] <7> The vehicle protection film according to <6>, wherein the substrate is made of a thermoplastic polyurethane elastomer.

[0026] According to one embodiment of the present disclosure, an adhesive composition capable of forming an adhesive layer excellent in initial adhesive force, high-temperature short-term re-peelability, and long-term re-peelability can be provided.

[0027] According to other embodiments of the present disclosure, a pressure-sensitive adhesive layer and a vehicle protection film having excellent initial adhesive force, short-term re-peelability at high temperature, and long-term re-peelability can be provided. DETAILED DESCRIPTION

[0028] The adhesive composition, adhesive layer, and vehicle protection film of the present disclosure are described in detail below. The following description of the elements may be based on representative embodiments of the present disclosure, but the present disclosure is not limited to such embodiments and can be implemented with appropriate modifications within the scope of the present disclosure.

[0029] In the present disclosure, a numerical range expressed using “to” means a range including the numerical values ​​described before and after “to” as the lower limit and the upper limit, respectively.

[0030] Within the numerical ranges described in this disclosure, the upper limit or lower limit described in a certain numerical range may be replaced by the upper limit or lower limit of another numerical range described in a certain stage. In addition, within the numerical ranges described in this disclosure, the upper limit or lower limit described in a certain numerical range may be replaced by the values ​​shown in the Examples.

[0031] In the present disclosure, a combination of two or more preferred aspects is a more preferred aspect.

[0032] In the present disclosure, when a plurality of substances belonging to each component are present in the adhesive composition, the amount of each component in the adhesive composition refers to the total amount of the plurality of substances present in the adhesive composition unless otherwise specified.

[0033] In the present disclosure, unless otherwise specified, "solid content" refers to the components contained in the composition excluding the solvent, and "solvent" refers to water and an organic solvent. In the present disclosure, "organic solvent" may be referred to as "solvent".

[0034] For example, when the solvent contained in the composition is only an organic solvent, the solid content refers to the components contained in the composition other than the organic solvent; when the solvent contained in the composition is water and an organic solvent, the solid content refers to the components contained in the composition other than water and the organic solvent.

[0035] In the present disclosure, a “(meth)acrylic copolymer” refers to a copolymer containing a structural unit derived from a (meth)acrylic monomer, wherein the ratio of the structural unit derived from the (meth)acrylic monomer to the copolymer is 50% by mass or more.

[0036] In the present disclosure, a "(meth)acrylic monomer" refers to a monomer having a (meth)acryloyl group.

[0037] In the present disclosure, “(meth)acrylic acid” is a term encompassing both “acrylic acid” and “methacrylic acid”, “(meth)acrylate” is a term encompassing both “acrylate” and “methacrylate”, and “(meth)acryloyl” is a term encompassing both “acryloyl” and “methacryloyl”.

[0038] In the present disclosure, "n-" refers to normal, "i-" refers to iso, "s-" refers to secondary, and "t-" refers to tertiary.

[0039] In the present disclosure, the expression "Ca to Cb (a and b represent integers greater than or equal to 1)" means that the number of carbon atoms is a to b. Specifically, "C1 to C6" means that the number of carbon atoms is 1 to 6, excluding the number of carbon atoms in substituents.

[0040] In the present disclosure, "monomer" has the same meaning as "monomer", and "polymer" has the same meaning as "polymer" and "copolymer".

[0041] In the present disclosure, “mass %” and “weight %” have the same meaning, and “parts by mass” and “parts by weight” have the same meaning.

[0042] In the present disclosure, the term "process" refers not only to an independent process but also to a process that cannot be clearly distinguished from other process regions as long as the intended purpose of the process can be achieved.

[0043] In this disclosure, "adhesive" and "adhesive composition" have the same meaning.

[0044] In the present disclosure, the "boiling point of a solvent" is a value at atmospheric pressure (ie, 101.325 kPa).

[0045] [Adhesive composition]

[0046] The adhesive composition of the present disclosure comprises: a (meth)acrylic acid copolymer (A), a metal chelate crosslinking agent (B), a solvent (C) having a boiling point of 100° C. to 200° C. and being a compound represented by formula (1), and a monohydric alcohol solvent (D) having 1 to 3 carbon atoms, wherein the (meth)acrylic acid copolymer (A) contains a structural unit (a1) derived from an alkyl (meth)acrylate monomer having 1 to 2 carbon atoms in the alkyl portion in a ratio of 40% to 90% by mass relative to the total structural units, and a metal chelate crosslinking agent (B) in a ratio of 40% to 90% by mass relative to the total structural units. The structural unit (a2) derived from a monomer having a carboxyl group is contained in an amount of 0.5% by mass to 5.0% by mass of the structural unit. The content of the metal chelate crosslinking agent (B) is 0.1 part by mass to 1.0 part by mass relative to 100 parts by mass of the (meth)acrylic copolymer (A). The content of the solvent (C) is 3 parts by mass to 30 parts by mass relative to 100 parts by mass of the (meth)acrylic copolymer (A). The ratio of the mass content of the solvent (C) to the mass content of the alcohol solvent (D) is 0.5 or more.

[0047] According to the adhesive composition of the present disclosure, an adhesive layer excellent in initial adhesive force, short-term re-peelability at high temperature, and long-term re-peelability can be formed.

[0048] In order to improve the initial adhesion of the adhesive layer, it is considered necessary to increase the initial cohesive force of the adhesive layer and improve the wettability of the adhesive layer to the adherend. In order to improve the high-temperature short-term removability of the adhesive layer, it is considered necessary to appropriately increase the initial cohesive force of the adhesive layer and weaken the interaction between the adhesive layer and the adherend. In order to improve the long-term removability of the adhesive layer, it is considered necessary to significantly increase the cohesive force of the adhesive layer after time and improve the temporal stability of the adhesive force of the adhesive layer.

[0049] In the present disclosure, by selecting a (meth)acrylic acid copolymer (A) containing specific structural units in a specific ratio, a relatively small amount of a metal chelate crosslinking agent (B), a solvent (C) with a specific structure and a specific boiling point, and a specific alcohol solvent (D) as components of the adhesive composition, and adjusting the quantitative ratio of the solvent (C) to the alcohol solvent (D), the initial cohesive force, wettability to the adherend, interaction with the adherend, cohesive force after aging, and temporal stability of the adhesive force of the formed adhesive layer are controlled, thereby achieving the formation of an adhesive layer with excellent initial adhesive force, short-term removability at high temperature, and long-term removability.

[0050] In the present disclosure, a "(meth)acrylic copolymer (A) comprising a structural unit (a1) derived from an alkyl (meth)acrylate monomer having 1 to 2 carbon atoms in the alkyl portion at a ratio of 40% by mass to 90% by mass relative to all structural units, and a structural unit (a2) derived from a monomer having a carboxyl group at a ratio of 0.5% by mass to 5.0% by mass relative to all structural units" is also referred to as a "specific (meth)acrylic copolymer (A)".

[0051] In the present disclosure, a "(meth)acrylic acid alkyl ester monomer having 1 to 2 carbon atoms in the alkyl portion" is also referred to as a "specific (meth)acrylic acid alkyl ester monomer."

[0052] In the present disclosure, “alkyl (meth)acrylate monomers other than the specific alkyl (meth)acrylate monomer” is also referred to as “other alkyl (meth)acrylate monomers”, and “structural units derived from other alkyl (meth)acrylate monomers” is also referred to as “structural unit (a3)”.

[0053] In the present disclosure, “specific (meth)acrylic acid alkyl ester monomers” and “other (meth)acrylic acid alkyl ester monomers” may be collectively referred to as “(meth)acrylic acid alkyl ester monomers”.

[0054] [Specific (meth)acrylic acid-based copolymer (A)]

[0055] The adhesive composition of the present disclosure comprises a (meth)acrylic copolymer (A) [i.e., a specific (meth)acrylic copolymer (A)], wherein the specific (meth)acrylic copolymer (A) comprises a structural unit (a1) derived from an alkyl (meth)acrylate monomer having 1 to 2 carbon atoms in the alkyl portion at a ratio of 40% to 90% by mass relative to all structural units, and a structural unit (a2) derived from a monomer having a carboxyl group at a ratio of 0.5% to 5.0% by mass relative to all structural units.

[0056] The pressure-sensitive adhesive composition of the present disclosure may contain only one specific (meth)acrylic copolymer (A), or may contain two or more specific (meth)acrylic copolymers (A).

[0057] <Structural unit (a1) derived from a specific (meth)acrylic acid alkyl ester monomer>

[0058] The specific (meth)acrylic copolymer (A) contains the structural unit (a1) derived from an alkyl (meth)acrylate monomer having 1 to 2 carbon atoms in the alkyl portion (i.e., a specific alkyl (meth)acrylate monomer) at a ratio of 40 to 90% by mass based on all structural units.

[0059] In the present disclosure, the “structural unit derived from an alkyl (meth)acrylate monomer” refers to a structural unit formed by addition polymerization of an alkyl (meth)acrylate monomer.

[0060] It should be noted that the term "alkyl (meth)acrylate monomer" in this disclosure does not include monomers that have a carboxyl group. Specifically, the term "alkyl (meth)acrylate monomer" in this disclosure refers to an alkyl (meth)acrylate monomer that does not have a carboxyl group, while an alkyl (meth)acrylate monomer that has a carboxyl group is classified as a monomer that has a carboxyl group, which will be described later.

[0061] The specific (meth)acrylic acid alkyl ester monomer may be an alkyl acrylate monomer or an alkyl methacrylate monomer.

[0062] The alkyl group contained in the specific alkyl (meth)acrylate monomer may be unsubstituted or may have a substituent, but is preferably unsubstituted.

[0063] The number of carbon atoms of 1 to 2 in the alkyl portion of the specific alkyl (meth)acrylate monomer referred to in the present disclosure does not include the number of carbon atoms in the substituent.

[0064] Specific examples of the specific (meth)acrylic acid alkyl ester monomer include methyl acrylate, methyl methacrylate, ethyl acrylate, and ethyl methacrylate.

[0065] The specific (meth)acrylic acid alkyl ester monomer is preferably at least one selected from methyl acrylate, methyl methacrylate, and ethyl acrylate, and more preferably at least one selected from methyl acrylate and ethyl acrylate.

[0066] The specific (meth)acrylic copolymer (A) may include only one type of structural unit (a1) or two or more types.

[0067] The content of the structural unit (a1) in the specific (meth)acryl-based copolymer (A) is 40% by mass to 90% by mass relative to all the structural units of the specific (meth)acryl-based copolymer (A).

[0068] Since the side chains of the specific (meth)acrylic acid alkyl ester monomer are very short, the polymer chains of the specific (meth)acrylic copolymer (A) tend to aggregate easily. If the polymer chains of the specific (meth)acrylic copolymer (A) aggregate, the cohesive force of the adhesive layer increases, thereby improving the removability. If the content of structural unit (a1) is 40% by mass or more relative to the total structural units of the specific (meth)acrylic copolymer (A), the aggregation of the polymer chains caused by the short side chains is not easily hindered by the steric hindrance of other monomers, and the cohesive force of the adhesive layer can be fully improved. As a result, the resulting adhesive layer tends to show excellent high-temperature short-term removability and long-term removability.

[0069] The content of the structural unit (a1) in the specific (meth)acrylic copolymer (A) is preferably 45% by mass or more, more preferably 50% by mass or more, based on all structural units of the specific (meth)acrylic copolymer (A).

[0070] If the content of the structural unit (a1) relative to the total structural units of the specific (meth)acrylic copolymer (A) is 90% by mass or less, the glass transition temperature of the specific (meth)acrylic copolymer (A) will not be too high, and the cohesive force of the adhesive layer will not be too high. Therefore, an adhesive layer having high wettability to an adherend can be formed in a relatively short time. As a result, the initial adhesive force of the formed adhesive layer tends to be excellent.

[0071] The content of the structural unit (a1) in the specific (meth)acrylic copolymer (A) is preferably 65% ​​by mass or less, more preferably 55% by mass or less, based on all structural units of the specific (meth)acrylic copolymer (A).

[0072] In one embodiment, the content of the structural unit (a1) in the specific (meth)acrylic copolymer (A) may be 40% by mass to 65% by mass, 45% by mass to 65% by mass, 50% by mass to 65% by mass, or 50% by mass to 55% by mass relative to all the structural units of the specific (meth)acrylic copolymer (A).

[0073] <Structural unit (a2) derived from a monomer having a carboxyl group>

[0074] The specific (meth)acrylic copolymer (A) contains the structural unit (a2) derived from the monomer having a carboxyl group at a ratio of 0.5% by mass to 5.0% by mass based on all the structural units.

[0075] In the present disclosure, the “structural unit derived from a monomer having a carboxyl group” refers to a structural unit formed by addition polymerization of a monomer having a carboxyl group.

[0076] The type of the monomer having a carboxyl group is not particularly limited.

[0077] Examples of the monomer having a carboxyl group include monomers having at least one carboxyl group and an ethylenically unsaturated group in one molecule.

[0078] 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.

[0079] Specific examples of monomers having a carboxyl 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 succinate).

[0080] The monomer having a carboxyl group is preferably at least one selected from (meth)acrylic acid and ω-carboxy-polycaprolactone mono(meth)acrylate, more preferably at least one selected from acrylic acid and ω-carboxy-polycaprolactone monoacrylate, and still more preferably acrylic acid.

[0081] The specific (meth)acrylic copolymer (A) may include only one type of structural unit (a2) or two or more types.

[0082] The content of the structural unit (a2) in the specific (meth)acryl-based copolymer (A) is 0.5% by mass to 5.0% by mass relative to all the structural units of the specific (meth)acryl-based copolymer (A).

[0083] The carboxyl group contained in the structural unit (a2) contributes to the crosslinking reaction with the metal chelate crosslinking agent. If the content of the structural unit (a2) is 0.5% by mass or greater relative to the total structural units of the specific (meth)acrylic copolymer (A), crosslinking can proceed sufficiently, allowing the adhesive layer to exhibit cohesive strength. Consequently, the resulting adhesive layer tends to exhibit excellent initial adhesive strength, short-term removability at high temperatures, and long-term removability.

[0084] The content of the structural unit (a2) in the specific (meth)acrylic copolymer (A) is preferably 0.8% by mass or more, more preferably 1.0% by mass or more, based on all structural units of the specific (meth)acrylic copolymer (A).

[0085] The carboxyl group included in the structural unit (a2) can produce interaction between the adhesive layer and the adherend. The interaction between the adhesive layer and the adherend brought by the carboxyl group has a trend of becoming stronger by heating. If the containing ratio of the structural unit (a2) is 5.0 mass % or less relative to the whole structural units of the specific (meth) acrylic copolymer (A), the heating after the adhesive layer and the adherend are adhered will not make the interaction between the adhesive layer and the adherend too strong, and the adhesion of the adhesive layer to the adherend will not be too high. Therefore, the high temperature short-term re-peelability and long-term re-peelability of the adhesive layer formed show an excellent trend.

[0086] The content of the structural unit (a2) in the specific (meth)acrylic copolymer (A) is preferably 4.5% by mass or less, more preferably 4.0% by mass or less, based on all structural units of the specific (meth)acrylic copolymer (A).

[0087] In a certain embodiment, the content of the structural unit (a2) in the specific (meth)acrylic copolymer (A) may be 0.5% by mass to 4.5% by mass, 0.5% by mass to 4.0% by mass, 0.8% by mass to 4.5% by mass, 0.8% by mass to 4.0% by mass, 1.0% by mass to 4.5% by mass, or 1.0% by mass to 4.0% by mass relative to all the structural units of the specific (meth)acrylic copolymer (A).

[0088] <Structural unit (a3) ​​derived from other alkyl (meth)acrylate monomers>

[0089] The specific (meth)acrylic copolymer (A) preferably contains a structural unit (a3) ​​derived from an alkyl (meth)acrylate monomer other than the specific alkyl (meth)acrylate monomer (ie, another alkyl (meth)acrylate monomer).

[0090] The types of other alkyl (meth)acrylate monomers are not particularly limited.

[0091] The other alkyl (meth)acrylate monomers may be alkyl acrylate monomers or alkyl methacrylate monomers.

[0092] The alkyl group contained in other alkyl (meth)acrylate monomers may be unsubstituted or may have a substituent, but is preferably unsubstituted.

[0093] The alkyl group contained in other alkyl (meth)acrylate monomers may be linear, branched, or cyclic.

[0094] The number of carbon atoms in the alkyl portion of the other alkyl (meth)acrylate monomer is, for example, preferably 3 to 18, more preferably 3 to 12, and even more preferably 3 to 8.

[0095] Specific examples of other (meth)acrylate alkyl ester monomers include n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, and isobornyl (meth)acrylate.

[0096] As the other alkyl (meth)acrylate monomer, at least one selected from n-butyl acrylate and 2-ethylhexyl acrylate is preferred, and 2-ethylhexyl acrylate is more preferred.

[0097] When the specific (meth)acrylic copolymer (A) includes the structural unit (a3), it may include only one type of the structural unit (a3) ​​or may include two or more types.

[0098] When the specific (meth)acrylic copolymer (A) contains the structural unit (a3), the content of the structural unit (a3) ​​is not particularly limited. For example, it is preferably 5.0% by mass to 59.5% by mass, more preferably 7.0% by mass to 57.0% by mass, and even more preferably 10.0% by mass to 50.0% by mass, relative to all the structural units of the specific (meth)acrylic copolymer (A).

[0099] <Structural units derived from other monomers>

[0100] The specific (meth)acrylic copolymer (A) may contain a structural unit derived from any of the monomers (so-called other monomers) that are not the specific (meth)acrylate alkyl ester monomer, the monomer having a carboxyl group, and other (meth)acrylate alkyl ester monomers, as needed, within a range that does not impair the effects of the adhesive composition of the present disclosure.

[0101] In the present disclosure, "a structural unit derived from another monomer" refers to a structural unit formed by addition polymerization of another monomer.

[0102] Examples of the 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 monovinyl groups such as styrene, α-methylstyrene, tert-butylstyrene, p-chlorostyrene, chloromethylstyrene, and vinyltoluene; structural units derived from vinyl cyanides such as acrylonitrile and methacrylonitrile; structural units derived from vinyl esters such as vinyl formate, vinyl acetate, vinyl propionate, and vinyl versatate; and the like.

[0103] When the specific (meth)acrylic copolymer (A) contains a structural unit derived from other monomers, it may contain only one type of the structural unit derived from other monomers, or may contain two or more types.

[0104] When the specific (meth)acrylic copolymer (A) contains structural units derived from other monomers, the ratio of the structural units derived from other monomers contained in the specific (meth)acrylic copolymer (A) can be appropriately set within a range that does not impair the effects of the pressure-sensitive adhesive composition of the present disclosure.

[0105] <<Weight Average Molecular Weight of Specific (Meth)Acrylic Copolymer (A)>>

[0106] The weight average molecular weight of the specific (meth)acrylic copolymer (A) is not particularly limited.

[0107] For example, from the viewpoint of the initial adhesive strength, short-term re-peelability at high temperature, and long-term re-peelability of the formed adhesive layer, the weight-average molecular weight of the specific (meth)acrylic copolymer (A) is preferably 200,000 or greater, more preferably 300,000 or greater, and even more preferably 400,000 or greater. Furthermore, for example, from the viewpoint of the initial adhesive strength of the formed adhesive layer, the weight-average molecular weight of the specific (meth)acrylic copolymer (A) is preferably 1.8 million or less, more preferably 1.5 million or less, and even more preferably 1.2 million or less.

[0108] In one embodiment, the weight average molecular weight of the specific (meth)acrylic copolymer (A) may be 200,000 to 1,800,000, 300,000 to 1,500,000, or 400,000 to 1,200,000.

[0109] The weight average molecular weight of the specific (meth)acrylic copolymer (A) is a value measured by the following method. Specifically, it is measured according to the following (1) to (3).

[0110] (1) A solution of a specific (meth)acrylic copolymer (A) is applied to a release paper and then dried at 100° C. for 1 minute to obtain a film-like specific (meth)acrylic copolymer (A).

[0111] (2) Using the film-like specific (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. It should be noted that the "solid content concentration" mentioned herein refers to the mass ratio of the specific (meth)acrylic copolymer (A) in the sample solution.

[0112] (3) The weight average molecular weight of the specific (meth)acrylic copolymer (A) was determined as a standard polystyrene equivalent value by gel permeation chromatography (GPC) under the following conditions.

[0113] ~Conditions~

[0114] Measuring apparatus: High-speed GPC [Model: HLC-8420GPC, manufactured by Tosoh Corporation]

[0115] Detector: Differential refractometer (RI) [Integrated into HLC-8420, manufactured by Tosoh Corporation]

[0116] Column: Two TSKgel GMH columns were used. XL [Made by Tosoh Corporation]

[0117] Column temperature: 40°C

[0118] Eluent: tetrahydrofuran

[0119] Injection volume of sample solution: 100 μL

[0120] Flow rate: 0.8 mL / min

[0121] The weight average molecular weight of the specific (meth)acrylic copolymer (A) can be adjusted to a desired value by adjusting the polymerization temperature, polymerization time, amount of organic solvent used, type and amount of polymerization initiator used, etc. during monomer polymerization.

[0122] <<Content of specific (meth)acrylic copolymer (A)>>

[0123] The content of the specific (meth)acrylic copolymer (A) in the adhesive composition of the present disclosure is not particularly limited, but is preferably 10% to 90% by mass, more preferably 20% to 70% by mass, and even more preferably 30% to 50% by mass, relative to the total amount of the adhesive composition.

[0124] [Method for producing specific (meth)acrylic acid-based copolymer (A)]

[0125] The method for producing the specific (meth)acrylic copolymer (A) is not particularly limited.

[0126] The specific (meth)acrylic copolymer (A) can be produced by polymerizing the above-mentioned monomers by a known polymerization method represented by, for example, a solution polymerization method, an emulsion polymerization method, a suspension polymerization method, and a bulk polymerization method.

[0127] As a polymerization method, a solution polymerization method is preferred because the handling process after production is relatively simple when preparing the adhesive composition of the present disclosure and can be performed in a short time.

[0128] In solution polymerization, a predetermined organic solvent, monomer, polymerization initiator, and, if necessary, chain transfer agent are generally added to a polymerization tank. The reaction is then heated and reacted for several hours, for example, at the reflux temperature of the organic solvent while stirring. In this case, at least a portion of the organic solvent, monomer, polymerization initiator, and, if necessary, chain transfer agent may be added sequentially. Alternatively, the reaction may be conducted under a nitrogen stream.

[0129] 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.

[0130] More specifically, examples of the organic solvent used in the polymerization reaction include aromatic hydrocarbon compounds represented by benzene, toluene, ethylbenzene, n-propylbenzene, tert-butylbenzene, o-xylene, m-xylene, p-xylene, tetralin, decalin, and aromatic naphtha; aliphatic or alicyclic hydrocarbon compounds represented by n-hexane, n-heptane, n-octane, isooctane, n-decane, dipentene, petroleum spirit, naphtha, and turpentine; ester compounds represented by methyl acetate, ethyl acetate, n-butyl acetate, n-amyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate, 3-methoxybutyl acetate, and methyl benzoate; and ketone compounds represented by acetone, methyl ethyl ketone, methyl isobutyl 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, alcohol compounds represented by methyl alcohol (so-called methanol), ethyl alcohol (so-called ethanol), n-propyl alcohol (so-called 1-propanol), isopropyl alcohol (so-called 2-propanol), n-butyl alcohol (so-called 1-butanol), isobutyl alcohol (so-called 2-butanol), sec-butyl alcohol and tert-butyl alcohol, and dicarbonyl compounds represented by acetylacetone, hexane-2,4-dione, ethyl acetoacetate, 1,3-bis(4-methoxyphenyl)-1,3-propanedione, diethyl malonate, isopropyl acetoacetate, ethyl 3-oxopentanoate and ethyl 2-methylacetoacetate.

[0131] When producing the specific (meth)acrylic copolymer (A), it is preferred to use an organic solvent such as an aromatic hydrocarbon compound, an ester compound, or a ketone compound that is less likely to cause chain transfer during the polymerization reaction. In particular, ethyl acetate is preferably used from the viewpoints of the solubility of the specific (meth)acrylic copolymer (A) and the ease of the polymerization reaction.

[0132] During the polymerization reaction, only one organic solvent may be used, or two or more organic solvents may be used.

[0133] Examples of the polymerization initiator include organic peroxides and azo compounds used in general solution polymerization methods. Specific examples of the organic peroxide include tert-butyl peroxy-2-ethylhexanoate, tert-butyl hydroperoxide, cumene hydroperoxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, hexanoyl peroxide, diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, tert-butyl peroxypivalate, 2,2-bis(4,4-di-tert-butylperoxycyclohexyl)propane, 2,2-bis(4,4-di-tert-amylperoxycyclohexyl)propane, 2,2-bis(4,4-di-tert-octylperoxycyclohexyl)propane, 2,2-bis(4,4-di-α-cumylperoxycyclohexyl)propane, 2,2-bis(4,4-di-tert-butylperoxycyclohexyl)butane, and 2,2-bis(4,4-di-tert-octylperoxycyclohexyl)butane. Specific examples of the 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(isobutyric acid)dimethyl ester.

[0134] During the polymerization reaction, only one polymerization initiator may be used, or two or more polymerization initiators may be used.

[0135] The amount of the polymerization initiator used is not particularly limited and can be appropriately set according to, for example, the molecular weight of the target specific (meth)acrylic copolymer (A).

[0136] When producing the specific (meth)acrylic copolymer (A), a chain transfer agent may be used as needed. 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 represented by α-methylstyrene, anthracene, phenanthrene, fluorene, and 9-phenylfluorene, aromatic nitro compounds represented by p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid, p-nitrophenol, and p-nitrotoluene, benzoquinone derivatives represented by benzoquinone and 2,3,5,6-tetramethyl-p-benzoquinone, borane derivatives represented by tributylborane, Halogenated hydrocarbon compounds represented by carbon tetrabromide, carbon tetrachloride, 1,1,2,2-tetrabromoethane, tribromoethylene, trichloroethylene, bromotrichloromethane, bromoform, and 3-chloro-1-propene; aldehyde compounds represented by chloral and furfural; alkyl mercaptan compounds having 1 to 18 carbon atoms; aromatic mercaptan compounds represented by thiophenol and toluene mercaptan; thioglycolic acid, alkyl ester compounds having 1 to 10 carbon atoms of thioglycolic acid; hydroxyalkyl mercaptan compounds having 1 to 12 carbon atoms; and terpene compounds represented by pinene and terpinolene.

[0137] When a chain transfer agent is used in producing the specific (meth)acrylic copolymer (A), the amount of the chain transfer agent used is not particularly limited and can be appropriately set according to, for example, the target molecular weight of the specific (meth)acrylic copolymer (A).

[0138] The polymerization temperature is not particularly limited and can be appropriately set according to, for example, the molecular weight of the target specific (meth)acrylic copolymer (A).

[0139] [Metal chelate crosslinking agent (B)]

[0140] The adhesive composition of the present disclosure contains a metal chelate crosslinking agent (B), and the content of the metal chelate crosslinking agent (B) is 0.1 to 1 parts by mass relative to 100 parts by mass of the specific (meth)acrylic copolymer (A).

[0141] In the present disclosure, a “metal chelate-based cross-linking agent” refers to a metal chelate compound that functions as a cross-linking agent.

[0142] The type of the metal chelate-based cross-linking agent (B) is not particularly limited.

[0143] Examples of the metal chelate-based crosslinking agent (B) include aluminum chelate compounds, titanium chelate compounds, zirconium chelate compounds, and cobalt chelate compounds.

[0144] For example, from the viewpoint of crosslinking speed, the metal chelate-based crosslinking agent (B) is preferably an aluminum chelate compound.

[0145] Specific examples of the aluminum chelate compound include aluminum tris(acetylacetonate), aluminum alkyl acetylacetate diisopropoxide, aluminum monoacetylacetonate bis(ethyl acetoacetate), and aluminum tris(ethyl acetoacetate).

[0146] As the metal chelate-based cross-linking agent, a commercially available product can be used.

[0147] Examples of commercially available metal chelate crosslinking agents include Alumichelate A [trade name, chemical name: aluminum tris(acetylacetonate), manufactured by Kawaken Fine Chemicals Co., Ltd.], Alumichelate D [trade name, chemical name: aluminum monoacetylacetonate bis(ethyl acetoacetate), manufactured by Kawaken Fine Chemicals Co., Ltd.], Alumichelate M [trade name, chemical name: aluminum alkyl acetoacetate diisopropoxide, manufactured by Kawaken Fine Chemicals Co., Ltd.], and ALCH-TR [trade name, chemical name: aluminum tris(ethyl acetoacetate), manufactured by Kawaken Fine Chemicals Co., Ltd.].

[0148] The adhesive composition of the present disclosure may contain only one metal chelate-based crosslinking agent (B), or may contain two or more types.

[0149] The content of the metal chelate crosslinking agent (B) in the adhesive composition of the present disclosure is 0.1 to 1.0 parts by mass relative to 100 parts by mass of the specific (meth)acrylic copolymer (A).

[0150] Since the metal chelate crosslinking agent (B) reacts quickly with carboxyl groups, the crosslinking reaction between the carboxyl groups in the specific (meth)acrylic copolymer (A) and the metal chelate crosslinking agent (B) tends to be completed after the drying step of drying the coated film of the adhesive composition. Therefore, the phenomenon in which the cohesive strength of the adhesive layer increases due to the progress of the crosslinking reaction after lamination to the adherend is less likely to occur.

[0151] When the content of the metal chelate crosslinking agent (B) is 0.1 parts by mass or more per 100 parts by mass of the specific (meth)acrylic copolymer (A), crosslinking can be sufficiently achieved, allowing the adhesive layer to exhibit cohesive strength. Consequently, the resulting adhesive layer tends to exhibit excellent initial adhesive strength, short-term removability at high temperatures, and long-term removability.

[0152] The content of the metal chelate crosslinking agent (B) in the adhesive composition of the present disclosure is preferably 0.2 parts by mass or more, more preferably 0.4 parts by mass or more, per 100 parts by mass of the specific (meth)acrylic copolymer (A).

[0153] If the content of the metal chelate crosslinking agent (B) is 1.0 part by mass or less per 100 parts by mass of the specific (meth)acrylic copolymer (A), excessive crosslinking will not occur, and the adhesive layer will not harden, thus less likely to impair the adhesive layer's wettability to the adherend. Furthermore, after lamination to the adherend, the crosslinking reaction will proceed, which will increase the cohesive force of the adhesive layer. As a result, the resulting adhesive layer tends to exhibit excellent initial adhesion and long-term removability.

[0154] The content of the metal chelate crosslinking agent (B) in the adhesive composition of the present disclosure is preferably 0.8 parts by mass or less, more preferably 0.6 parts by mass or less, per 100 parts by mass of the specific (meth)acrylic copolymer (A).

[0155] In one embodiment, the content of the metal chelate crosslinking agent (B) in the adhesive composition of the present disclosure may be 0.2 to 1.0 parts by mass, 0.2 to 0.8 parts by mass, or 0.4 to 0.6 parts by mass relative to 100 parts by mass of the specific (meth)acrylic copolymer (A).

[0156] [Solvent (C)]

[0157] The adhesive composition of the present disclosure contains a solvent (C) having a boiling point of 100° C. to 200° C. and being a compound represented by the following formula (1). The content of the solvent (C) is 3 to 30 parts by mass per 100 parts by mass of the specific (meth)acrylic copolymer (A).

[0158] The boiling point of the solvent (C) is 100°C to 200°C.

[0159] The boiling point of the solvent (C) is 100° C. or higher because the solvent (C) is likely to remain in the adhesive film after the drying step of drying the applied film of the adhesive composition.

[0160] The boiling point of the solvent (C) is preferably 110°C or higher, more preferably 120°C or higher, and even more preferably 130°C or higher.

[0161] From the viewpoint of easy availability, the boiling point of the solvent (C) is 200° C. or lower.

[0162] In one embodiment, the boiling point of the solvent (C) may be 110°C to 200°C, 120°C to 200°C, or 130°C to 200°C.

[0163] The solvent (C) is a compound represented by the following formula (1).

[0164] Since the solvent (C) is a compound represented by formula (1), it coordinates with the metal chelate crosslinking agent (B) when remaining in the adhesive film, and can appropriately inhibit the crosslinking reaction between the carboxyl groups in the specific (meth)acrylic copolymer (A) and the metal chelate crosslinking agent (B).

[0165]

[0166] In formula (1), R 1 and R 3 Each independently represents a hydrogen atom, a C1-C6 alkyl group, a C3-C6 cycloalkyl group, a C1-C6 hydroxyalkyl group, a C1-C6 alkoxy group, or an aromatic group which may be substituted with a C1-C6 alkyl group or a C1-C6 alkoxy group. 1 and R 3 It can be the same or different.

[0167] R 1 and R 3 It is preferably a C1-C6 alkyl group, a C1-C6 alkoxy group, or an aromatic group substituted with a C1-C6 alkoxy group.

[0168] R 1 and R 3 The C1 to C6 alkyl group may be a linear alkyl group or a branched alkyl group.

[0169] As R 1 and R 3 Examples of the C1-C6 alkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl and n-hexyl.

[0170] As R 1 The C1-C6 alkyl group is preferably a methyl group or an ethyl group.

[0171] As R 3 The C1-C6 alkyl group is preferably methyl.

[0172] As R 1 and R 3 Examples of the C3-C6 cycloalkyl group include cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl.

[0173] As R 1 and R 3 Examples of the C1-C6 hydroxyalkyl group include a hydroxymethyl group, a hydroxyethyl group, a hydroxypropyl group, and a hydroxybutyl group.

[0174] R 1 and R 3 The C1 to C6 alkoxy groups may be linear or branched.

[0175] As R 1 and R 3 Examples of the C1-C6 alkoxy groups include methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, tert-butoxy and n-pentoxy.

[0176] As R 1 The C1-C6 alkoxy group is preferably an ethoxy group.

[0177] As R 3 The C1-C6 alkoxy group is preferably ethoxy or isopropoxy.

[0178] R 1 and R 3 The aromatic group in the group may be unsubstituted or substituted by a C1-C6 alkyl group or a C1-C6 alkoxy group.

[0179] Specific examples of the C1-C6 alkyl group and C1-C6 alkoxy group as substituents are respectively as follows: 1 and R 3 Specific examples of the C1-C6 alkyl group are the same as those of the C1-C6 alkoxy group.

[0180] As R 1 and R 3 The aromatic group in , for example, is phenyl.

[0181] R 1 The aromatic group in is preferably a phenyl group substituted by a methoxy group.

[0182] R 3 The aromatic group in is preferably a phenyl group substituted by a methoxy group.

[0183] In formula (1), R 2 represents a hydrogen atom or a C1-C6 alkyl group.

[0184] R 2 Specific examples of the C1 to C6 alkyl groups in R 1 and R 3 The same is true for specific examples of the C1-C6 alkyl group.

[0185] R 2 Preferred is a hydrogen atom or a methyl group.

[0186] Specific examples of the solvent (C) include acetylacetone [boiling point: 141°C, R 1 =CH3, R 2 =H, R 3 =CH3], hexane-2,4-dione〔boiling point: 161℃, R 1 =C2H5, R2 =H, R 3 =CH3], ethyl acetoacetate〔boiling point: 184℃, R 1 =CH3, R 2 =H, R 3 =OC2H5〕、1,3-bis(4-methoxyphenyl)-1,3-propanedione〔Boiling point: 116℃、R 1 =C6H4-OCH3, R 2 =H, R 3 =C6H4-OCH3], diethyl malonate〔boiling point: 199℃, R 1 =OC2H5, R 2 =H, R 3 =OC2H5], isopropyl acetoacetate [boiling point: 187°C, R 1 =CH3, R 2 =H, R 3 =O-C3H7[O-iPr]〕、3-oxopentanoic acid ethyl ester〔boiling point: 191℃、R 1 =C2H5, R 2 =H, R 3 =OC2H5], and ethyl 2-methylacetoacetate [boiling point: 185°C, R 1 =CH3, R 2 =CH3, R 3 =OC2H5〕.

[0187] The adhesive composition of the present disclosure may contain only one solvent (C) or two or more. The solvent (C) may be contained in the adhesive composition of the present disclosure by, for example, using it as an organic solvent in the production of the specific (meth)acrylic copolymer (A), or by blending it during the preparation of the adhesive composition of the present disclosure.

[0188] The content of the solvent (C) in the pressure-sensitive adhesive composition of the present disclosure is 3 to 30 parts by mass relative to 100 parts by mass of the specific (meth)acrylic copolymer (A).

[0189] If the content of the solvent (C) is 3 parts by mass or greater per 100 parts by mass of the specific (meth)acrylic copolymer (A), a sufficient amount of the solvent (C) can remain in the adhesive film. By coordinating the solvent (C) remaining in the adhesive film with the metal chelate crosslinking agent (B), the crosslinking reaction between the carboxyl groups in the specific (meth)acrylic copolymer (A) and the metal chelate crosslinking agent (B) can be appropriately inhibited, thereby ensuring adequate wettability of the adhesive layer to the adherend. Consequently, the resulting adhesive layer tends to exhibit excellent initial adhesion.

[0190] The content of the solvent (C) in the pressure-sensitive adhesive composition of the present disclosure is preferably 5 parts by mass or more, more preferably 7.5 parts by mass or more, and even more preferably 10 parts by mass or more, per 100 parts by mass of the specific (meth)acrylic copolymer (A).

[0191] When the content of the solvent (C) is 30 parts by mass or less per 100 parts by mass of the specific (meth)acrylic copolymer (A), an excessive amount of the solvent (C) will not remain in the adhesive film, and the solvent (C) will not excessively inhibit the crosslinking reaction between the carboxyl groups in the specific (meth)acrylic copolymer (A) and the metal chelate crosslinking agent (B), thereby ensuring that the adhesive layer has a suitably high cohesive strength. As a result, the resulting adhesive layer tends to exhibit excellent initial adhesive strength.

[0192] The content of the solvent (C) in the pressure-sensitive adhesive composition of the present disclosure is preferably 25 parts by mass or less, more preferably 20 parts by mass or less, relative to 100 parts by mass of the specific (meth)acrylic copolymer (A).

[0193] In one embodiment, the content of the solvent (C) in the adhesive composition of the present disclosure may be 5 to 25 parts by mass, 7.5 to 20 parts by mass, or 10 to 20 parts by mass relative to 100 parts by mass of the specific (meth)acrylic copolymer (A).

[0194] [Alcohol solvent (D)]

[0195] The adhesive composition of the present disclosure contains a monohydric alcohol solvent (D) having 1 to 3 carbon atoms.

[0196] The alcohol solvent (D) has poor compatibility with the specific (meth)acrylic copolymer (A). Therefore, if the PSA composition of the present disclosure contains the alcohol solvent (D), it will synergistically act with the specific (meth)acrylic copolymer (A) containing the structural unit (a1) derived from the specific (meth)acrylic acid alkyl ester monomer, and polymer chains will tend to aggregate when the solution is formed, resulting in a tendency for the cohesive strength of the resulting PSA layer to increase.

[0197] Specific examples of the alcohol solvent (D) include methanol (carbon number: 1), ethanol (carbon number: 2), 1-propanol (carbon number: 3), and 2-propanol (carbon number: 3).

[0198] The alcohol solvent (D) is preferably at least one selected from the group consisting of methanol, ethanol, 1-propanol, and 2-propanol.

[0199] The adhesive composition of the present disclosure may contain only one alcohol solvent (D) or two or more. The alcohol solvent (D) may be contained in the adhesive composition of the present disclosure by, for example, using it as an organic solvent in the production of the specific (meth)acrylic copolymer (A), or by blending it during the preparation of the adhesive composition of the present disclosure.

[0200] The content of the alcohol solvent (D) in the adhesive composition of the present disclosure is not particularly limited as long as the ratio of the mass content of the solvent (C) to the mass content of the alcohol solvent (D) is 0.5 or more, and can be appropriately set according to the content of the solvent (C).

[0201] <Ratio of the mass content of the solvent (C) to the mass content of the alcohol solvent (D)>

[0202] The ratio of the mass content of the solvent (C) to the mass content of the alcohol solvent (D) in the adhesive composition of the present disclosure [mass content of the solvent (C) / mass content of the alcohol solvent (D)] is 0.5 or more.

[0203] If the ratio of the mass of the solvent (C) to the mass of the alcohol solvent (D) is 0.5 or more, the alcohol solvent (D) is not excessive, so the size of the aggregated particles formed by the aggregation of the polymer chains is small, which can fully improve the cohesive force of the adhesive layer. Therefore, the long-term re-peelability of the formed adhesive layer shows an excellent trend. In addition, since the size of the aggregated particles formed by the aggregation of the polymer chains is small, the distance between the carboxyl groups in the polymer chains and the adherend becomes larger, and the interaction between the adhesive layer and the adherend based on the carboxyl groups becomes weaker. Therefore, the high-temperature short-term re-peelability of the formed adhesive layer shows an excellent trend.

[0204] The upper limit of the ratio of the mass content of the solvent (C) to the mass content of the alcohol solvent (D) in the adhesive composition of the present disclosure is not particularly limited. For example, from the viewpoint of the initial adhesive strength, high-temperature short-term removability, and long-term removability of the formed adhesive layer, it is preferably 10.0 or less, more preferably 2.0 or less, and even more preferably 1.0 or less.

[0205] In one embodiment, the ratio of the mass content of the solvent (C) to the mass content of the alcohol solvent (D) in the adhesive composition of the present disclosure may be 0.5 to 10.0, 0.5 to 2.0, or 0.5 to 1.0.

[0206] 〔Other solvents〕

[0207] The adhesive composition of the present disclosure may contain a solvent (so-called other solvent) other than the solvent (C) and the alcohol solvent (D).

[0208] Other solvents are not particularly limited.

[0209] Examples of other solvents include solvents other than the solvent (C) and the alcohol solvent (D) among the organic solvents used in the polymerization reaction of the specific (meth)acrylic copolymer (A).

[0210] When the pressure-sensitive adhesive composition of the present disclosure contains another solvent, it may contain only one other solvent or two or more other solvents.

[0211] When the adhesive composition of the present disclosure contains other solvents, the content of the other solvents is not particularly limited and can be appropriately set according to the purpose, such as viscosity adjustment for coating.

[0212] [Other ingredients]

[0213] The adhesive composition of the present disclosure may contain components other than the above components (so-called other components) as needed within a range not impairing the effects thereof.

[0214] Other components include various additives such as polymers other than the specific (meth)acrylic copolymer (A), crosslinking agents other than the metal chelate crosslinking agent (B), crosslinking catalysts, antioxidants, colorants (e.g., dyes and pigments), light stabilizers (e.g., ultraviolet absorbers), and antistatic agents.

[0215] When the pressure-sensitive adhesive composition of the present disclosure contains other components, the content 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.

[0216] <<Application of Adhesive Composition>>

[0217] The use of the adhesive composition of the present disclosure is not particularly limited.

[0218] The adhesive composition of the present disclosure can form an adhesive layer having excellent initial adhesive strength, short-term removability at high temperatures, and long-term removability, and is therefore suitable as an adhesive composition for use in films for protecting vehicles (so-called adhesive compositions for vehicle protection films), for example.

[0219] The vehicle is not particularly limited, and examples thereof include cars, motorcycles, trains, and the like.

[0220] [Adhesive layer]

[0221] The adhesive layer of the present disclosure is formed from the adhesive composition of the present disclosure.

[0222] The adhesive layer of the present disclosure includes a cured product of the adhesive composition of the present disclosure. The cured product includes, for example, a crosslinked product of a specific (meth)acrylic copolymer (A) crosslinked and cured with a metal chelate crosslinking agent (B).

[0223] Since the adhesive layer of the present disclosure is formed of the adhesive composition of the present disclosure, it is excellent in initial adhesive force, high-temperature short-term re-peelability, and long-term re-peelability.

[0224] The thickness of the adhesive layer of the present disclosure is not particularly limited and can be appropriately set according to, for example, the type (eg, material and shape) of the adherend and the surface roughness of the adherend.

[0225] The thickness of the adhesive layer of the present disclosure is generally 1 μm to 100 μm, preferably 5 μm to 50 μm, and more preferably 10 μm to 40 μm.

[0226] The “thickness of the adhesive layer” in the present disclosure refers to the average thickness of the adhesive layer.

[0227] The average thickness of the pressure-sensitive adhesive layer is a value determined by the following method.

[0228] The thickness of the adhesive layer was measured at 10 randomly selected locations in the thickness direction using a film thickness meter. The arithmetic mean of the measured values ​​was calculated and the obtained value was defined as the average thickness of the adhesive layer.

[0229] [Vehicle protection film]

[0230] The vehicle protection film disclosed herein comprises a substrate and an adhesive layer disclosed herein disposed on the substrate. The vehicle protection film disclosed herein comprises the adhesive layer disclosed herein (i.e., an adhesive layer formed from the adhesive composition disclosed herein), thereby exhibiting excellent initial adhesion, high-temperature short-term removability, and long-term removability. The details of the adhesive layer disclosed herein are as described above.

[0231] The substrate is not particularly limited as long as the pressure-sensitive adhesive layer can be formed on its surface.

[0232] The substrate is preferably in the form of a film.

[0233] Examples of the material of the substrate include polyolefin resins [e.g., polyethylene (PE) and polypropylene (PP)], polyester resins [e.g., polyethylene terephthalate (PET)], acetate resins (e.g., cellulose triacetate), polyethersulfone resins, polycarbonate resins, polyamide resins, polyimide resins, (meth)acrylic resins, vinyl chloride resins, ABS (Acrylonitrile Butadiene Styrene: acrylonitrile-butadiene-styrene) resins, fluorine-based resins, polyurethane resins, and thermoplastic polyurethane elastomers (TPU).

[0234] For example, from the viewpoint of surface protection performance, the material of the substrate is preferably a thermoplastic polyurethane elastomer.

[0235] The substrate may contain various additives such as plasticizers, colorants (such as dyes and pigments), heat stabilizers, light stabilizers, antistatic agents, flame retardants, antioxidants, fillers, and the like.

[0236] The pattern may be applied to a portion or the entire substrate.

[0237] Antistatic layer can be set on the single side or both sides of base material.In addition, from the viewpoint of improving the adhesion of base material and adhesive layer, the face of the side that adhesive layer is set on of base material can be implemented surface treatments (so-called easy bonding process) such as corona discharge treatment, plasma discharge treatment.

[0238] The thickness of the substrate is not particularly limited, but is generally 500 μm or less, preferably 300 μm or less, and more preferably 200 μm or less.

[0239] For example, from the viewpoint of ensuring the strength of the vehicle protection film, the lower limit of the thickness of the substrate is preferably 5 μm or more, more preferably 10 μm or more.

[0240] The "thickness of a substrate" in the present disclosure refers to the average thickness of the substrate.

[0241] The average thickness of the substrate is a value determined by the following method.

[0242] The thickness of the substrate was measured at 10 randomly selected locations in the thickness direction using a film thickness meter. The arithmetic mean of the measured values ​​was calculated and the obtained value was defined as the average thickness of the substrate.

[0243] In the vehicle protection film of the present disclosure, the exposed surface of the adhesive layer can be protected by a release sheet. Generally, the release sheet protects the surface of the adhesive layer until the vehicle protection film is actually used and is removed during use.

[0244] The release sheet is not particularly limited as long as it can be easily released from the pressure-sensitive adhesive layer.

[0245] Examples of release sheets include resin films, paper, synthetic paper, and composite sheets obtained by laminating two or more of these, which have been surface-treated with a release agent on one or both sides (so-called easy-release treatment). In this disclosure, release sheets in which a resin film has been surface-treated with a release agent on one or both sides (so-called easy-release treatment) are also referred to as "release films."

[0246] Examples of the release agent include silicone-based release agents (eg, silicone), wax-based release agents (eg, paraffin), and fluorine-based release agents (eg, fluorine-based resins).

[0247] Examples of the resin film include polyester films typified by polyethylene terephthalate (PET) films.

[0248] Examples of paper include high-quality paper and coated paper.

[0249] The thickness of the release sheet is not particularly limited, but is generally 20 μm to 180 μm.

[0250] [Method for producing vehicle protective film]

[0251] The method for producing the vehicle protection film disclosed herein is not particularly limited.

[0252] The vehicle protection film of the present disclosure can be produced by a known method. For example, the following method can be used as a method for producing the vehicle protection film of the present disclosure.

[0253] The adhesive composition of the present disclosure is applied to one side of a substrate (preferably the side treated for easy adhesion) to form a coating film on the substrate. The formed coating film is then dried to form an adhesive film on the substrate. The exposed surface of the formed adhesive film is then laminated to the easily releasable surface of a release sheet and, if necessary, aged. This allows the production of the vehicle protective film of the present disclosure having a laminated structure of substrate / adhesive layer / release sheet.

[0254] As another method, for example, the following method can also be mentioned. The adhesive composition of the present invention is applied to the easily peelable surface of a release sheet to form a coating film on the release sheet. Next, the formed coating film is dried to form an adhesive film on the release sheet. Next, the exposed surface of the formed adhesive film is overlapped and attached to one side of the substrate (preferably the easily adhesive surface), and then aged as needed, thereby producing the vehicle protective film of the present invention having a laminated structure of substrate / adhesive layer / release sheet.

[0255] The method for applying the adhesive composition is not particularly limited.

[0256] Examples of the method for applying the 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, or applicator.

[0257] The coating amount of the adhesive composition is not particularly limited and can be appropriately set according to, for example, the thickness of the adhesive layer to be formed.

[0258] The method for drying the coating film is not particularly limited.

[0259] Examples of a method for drying the coating film include natural drying, heat drying, hot air drying, and vacuum drying.

[0260] The drying temperature and drying time of the coating film are not particularly limited and can be appropriately set according to the thickness of the coating film, the amount of the solvent contained in the coating film, and the like.

[0261] An example of drying conditions is drying for 2 minutes using a hot air circulation dryer in an environment at an ambient temperature of 100°C.

[0262] As a method for aging, for example, there is mentioned a method of leaving the mixture to stand for 2 to 7 days in an environment with an atmospheric temperature of 20° C. to 35° C. and a relative humidity of 45% to 55%.

[0263] Example

[0264] The adhesive composition, adhesive layer, and vehicle protection film of the present disclosure are described in more detail below with reference to examples. The present disclosure is not limited to the following examples unless it exceeds the scope of the present disclosure.

[0265] [Production of (meth)acrylic acid-based copolymer (A)]

[0266] [Production Example A-1]

[0267] A reactor equipped with a stirrer, reflux cooler, a sequential addition device, and a thermometer was charged with 63.9 parts by mass of ethyl acetate. Separately, 43.2 parts by mass of 2-ethylhexyl acrylate (2EHA), 53.8 parts by mass of methyl acrylate (MA), and 3.0 parts by mass of acrylic acid (AA) were added to a separate container and mixed to prepare 100.0 parts by mass of a monomer mixture. Next, 25.0% by mass of the prepared monomer mixture and 0.019 parts by mass of 2,2'-azobisisobutyronitrile (AIBN; polymerization initiator) were added to the reactor. The reactor was heated and refluxed at reflux for 10 minutes. The remaining 75.0% by mass of the monomer mixture, 29.2 parts by mass of ethyl acetate, and 0.146 parts by mass of AIBN were then added dropwise to the reactor at reflux over 90 minutes. After the additions were complete, the reaction was allowed to continue for 90 minutes to complete. The solution after completion of the reaction was diluted with ethyl acetate to a solid content concentration of 45.45% by mass to obtain a solution of the (meth)acrylic acid-based copolymer A-1.

[0268] The "solid content concentration" mentioned here refers to the mass ratio of the (meth)acrylic acid copolymer A-1 in the solution of the (meth)acrylic acid copolymer A-1. The same concept applies to the solutions of the (meth)acrylic acid copolymers A-2 to A-22 prepared below.

[0269] [Manufacturing Examples A-2 to A-12 and A-15 to A-22]

[0270] In Production Examples A-2 to A-12 and A-15 to A-22, the same procedures as in Production Example A-1 were performed, except that the monomer components of the (meth)acrylic acid-based copolymer (A) were changed to those shown in Table 1 and at least one of the amount of the organic solvent and the amount of the polymerization initiator used was adjusted to adjust the weight average molecular weight of the (meth)acrylic acid-based copolymer (A) to that shown in Table 1. Thus, solutions of (meth)acrylic acid-based copolymers A-2 to A-12 and A-15 to A-22 having a solid content concentration of 45.45% by mass were obtained.

[0271] [Production Examples A-13 and A-14]

[0272] In Production Examples A-13 and A-14, except that at least one of the amount of the organic solvent used and the amount of the polymerization initiator used was adjusted so that the weight average molecular weight of the (meth)acrylic copolymer (A) was adjusted to the weight average molecular weight shown in Table 1, the same procedures as in Production Example 1 were carried out to obtain solutions of (meth)acrylic copolymers A-13 and A-14 each having a solid content concentration of 45.45% by mass.

[0273] Table 1 shows the monomer components [unit: mass %] and weight average molecular weight (Mw) of the (meth)acrylic copolymers A-1 to A-22.

[0274] The weight average molecular weight of the (meth)acrylic copolymers A-1 to A-22 is measured by the same method as the method for measuring the weight average molecular weight of the above-mentioned specific (meth)acrylic copolymer (A).

[0275] Among the (meth)acrylic copolymers A-1 to A-22, the (meth)acrylic copolymers A-1 to A-18 belong to the specific (meth)acrylic copolymer (A) in the present disclosure.

[0276] [Table 1]

[0277]

[0278] The details of each monomer described in Table 1 are as follows.

[0279] <Specific (meth)acrylate alkyl ester monomer>

[0280] "MA": Methyl acrylate (number of carbon atoms in the alkyl group: 1)

[0281] "EA": Ethyl acrylate (number of carbon atoms in the alkyl group: 2)

[0282] "MMA": Methyl methacrylate (number of carbon atoms in the alkyl group: 1)

[0283] <Other alkyl (meth)acrylate monomers>

[0284] "2EHA": 2-ethylhexyl acrylate (number of carbon atoms in the alkyl portion: 8)

[0285] "n-BA": n-butyl acrylate (number of carbon atoms in the alkyl group: 4)

[0286] <Monomers having a carboxyl group>

[0287] "AA": acrylic acid

[0288] "MAA": methacrylic acid

[0289] "M-5300": ω-carboxy-polycaprolactone (n≈2) monoacrylate [trade name, ARONIX M-5300, manufactured by Toagosei Co., Ltd.]

[0290] In Table 1, "-" in the column of monomer components means that the monomer belonging to the column was not used.

[0291] [Preparation of Adhesive Composition]

[0292] [Example 1]

[0293] 220.0 parts by mass (100 parts by mass as solid content) of a solution of the (meth)acrylic copolymer A-1, 0.53 parts by mass (0.53 parts by mass as solid content) of Alumichelate A (trade name, aluminum tris(acetylacetonate), manufactured by Kawaken Fine Chemicals Co., Ltd.) as a metal chelate crosslinking agent, 15.0 parts by mass of acetylacetone, and 15.0 parts by mass of 2-propanol were thoroughly mixed to obtain an adhesive composition.

[0294] [Examples 2 to 15]

[0295] In Examples 2 to 15, the same operation as in Example 1 was carried out except that the mixed components were changed, thereby obtaining adhesive compositions having the compositions and solid content concentrations shown in Table 2.

[0296] [Example 16]

[0297] In Example 16, the same operation as in Example 1 was carried out except that the mixed components were changed and the solid content concentration was adjusted by adding ethyl acetate to obtain a PSA composition having the composition and solid content concentration shown in Table 2.

[0298] [Examples 17 to 20]

[0299] In Examples 17 to 20, the same operation as in Example 1 was carried out except that the mixed components were changed and the solid content concentration was adjusted by vacuum distillation of ethyl acetate to obtain adhesive compositions having the compositions and solid content concentrations shown in Table 2.

[0300] [Example 21]

[0301] In Example 21, the same operation as in Example 1 was carried out except that the mixed components were changed. The solid content concentration was adjusted by vacuum distillation of ethyl acetate and addition of methyl acetate to obtain an adhesive composition having the composition and solid content concentration shown in Table 3.

[0302] [Example 22]

[0303] In Example 22, the same operation as in Example 1 was carried out except that the mixed components were changed. The solid content concentration was adjusted by vacuum distillation of ethyl acetate and addition of toluene to obtain a PSA composition having the composition and solid content concentration shown in Table 3.

[0304] [Example 23]

[0305] In Example 23, the same operation as in Example 1 was carried out except that the mixed components were changed. The solid content concentration was adjusted by vacuum distillation of ethyl acetate and addition of acetone to obtain an adhesive composition having the composition and solid content concentration shown in Table 3.

[0306] [Examples 24 to 28 and 32 to 37]

[0307] In Examples 24 to 28 and 32 to 37, the same operation as in Example 1 was carried out except that the mixed components were changed, thereby obtaining adhesive compositions having the compositions and solid content concentrations shown in Table 3.

[0308] [Example 29]

[0309] In Example 29, the same operation as in Example 1 was carried out except that the mixed components were changed and the solid content concentration was adjusted by adding ethyl acetate to obtain a PSA composition having the composition and solid content concentration shown in Table 3.

[0310] [Example 30]

[0311] In Example 30, the same operation as in Example 1 was carried out, and the solid content concentration was adjusted by adding ethyl acetate to obtain a PSA composition having the composition and solid content concentration shown in Table 3.

[0312] [Example 31]

[0313] In Example 31, the same operation as in Example 1 was carried out, and the solid content concentration was adjusted by distilling ethyl acetate under reduced pressure to obtain a PSA composition having the composition and solid content concentration shown in Table 3.

[0314] [Comparative Examples 1 to 9 and 18]

[0315] In Comparative Examples 1 to 9 and 18, the same operation as in Example 1 was carried out except that the mixed components were changed, thereby obtaining adhesive compositions having the compositions and solid content concentrations shown in Table 4.

[0316] [Comparative Examples 10, 11, 14 to 17]

[0317] In Comparative Examples 10, 11, and 14 to 17, the same operation as in Example 1 was carried out except that the mixed components were changed and the solid content concentration was adjusted by adding ethyl acetate to obtain adhesive compositions having the compositions and solid content concentrations shown in Table 4.

[0318] [Comparative Examples 12 and 13]

[0319] In Comparative Examples 12 and 13, the same operation as in Example 1 was carried out except that the mixed components were changed and the solid content concentration was adjusted by vacuum distillation of ethyl acetate to obtain adhesive compositions having the compositions and solid content concentrations shown in Table 4.

[0320] Tables 2 to 4 show the ratio of the mass content of the solvent (C) to the mass content of the alcohol solvent (D) in the adhesive compositions of Examples 1 to 37 and Comparative Examples 1 to 18 (expressed as "C / D" in the tables).

[0321] As shown in Tables 2 to 4, the "solvent" in the table includes the organic solvent contained in the solution of the (meth)acrylic copolymer (A) (specifically, the organic solvent used in the polymerization reaction).

[0322]

[0323]

[0324]

[0325] The details of the cross-linking agents described in Tables 2 to 4 are shown below.

[0326] <Metal chelate crosslinking agents>

[0327] "Alumichelate A" [Trade name, Chemical name: Aluminum tris(acetylacetonate), Solid content concentration: 100% by mass, manufactured by Kawaken Fine Chemicals Co., Ltd.]

[0328] "Alumichelate M" [trade name, chemical name: aluminum alkyl acetoacetate diisopropylate, solid content concentration: 100% by mass, manufactured by Kawaken Fine Chemicals Co., Ltd.]

[0329] Isocyanate crosslinking agents

[0330] "CORONATE L-45E" [trade name, adduct of toluene diisocyanate (TDI) and trimethylolpropane (TMP), solid content concentration: 45% by mass, manufactured by Tosoh Corporation]

[0331] <Epoxy crosslinking agent>

[0332] "TETRAD-X" [trade name, solid content concentration: 100% by mass, manufactured by Mitsubishi Gas Chemical Co., Ltd.]

[0333] "CORONATE" and "TETRAD" are registered trademarks.

[0334] The details of the solvents described in Tables 2 to 4 are shown below.

[0335] Solvent (C)

[0336] "Acetylacetone" [boiling point: 141°C, manufactured by FUJIFILM Wako Pure Chemical Corporation] In formula (1), R 1 =CH3, R 2 =H, R 3 =CH3

[0337] "Hexane-2,4-dione" [boiling point: 161°C, manufactured by Alchem ​​Pharmtech., Inc.] In formula (1), R 1 =C2H5, R 2 =H, R 3 =CH3

[0338] "Ethyl acetoacetate" [boiling point: 184°C, manufactured by Tokyo Chemical Industry Co., Ltd.] In formula (1), R 1 =CH3, R 2 =H, R 3 =OC2H5

[0339] <Alcohol solvent (D)>

[0340] “Ethanol” [Boiling point: 79°C, number of carbon atoms: 2, manufactured by FUJIFILM Wako Pure Chemical Corporation]

[0341] “Methanol” [Boiling point: 65°C, number of carbon atoms: 1, manufactured by FUJIFILM Wako Pure Chemical Corporation]

[0342] "1-Propanol" [Boiling point: 97°C, number of carbon atoms: 3, manufactured by FUJIFILM Wako Pure Chemical Corporation]

[0343] "2-Propanol" [Boiling point: 82°C, number of carbon atoms: 3, manufactured by FUJIFILM Wako Pure Chemical Corporation]

[0344] <Other solvents>

[0345] "Ethyl acetate" [Boiling point: 77°C, manufactured by FUJIFILM Wako Pure Chemical Corporation]

[0346] "Methyl acetate" [Boiling point: 57°C, manufactured by FUJIFILM Wako Pure Chemical Corporation]

[0347] "Toluene" [Boiling point: 111°C, manufactured by FUJIFILM Wako Pure Chemical Corporation]

[0348] "Acetone" [Boiling point: 56°C, manufactured by FUJIFILM Wako Pure Chemical Corporation]

[0349] "1-Butanol" [Boiling point: 118°C, number of carbon atoms: 4, manufactured by FUJIFILM Wako Pure Chemical Corporation]

[0350] In Tables 2 to 4, the numerical values ​​described in the "compounding amount" column of the (meth)acrylic acid-based copolymer and the crosslinking agent are all values ​​converted to solid content.

[0351] In Tables 2 to 4, "-" in the column of the composition of the adhesive composition means that the component in that column was not blended.

[0352] In Table 4, “-” in the “C / D” column means that calculation could not be performed because at least one of the solvent (C) and the alcohol solvent (D) was not added.

[0353] [Preparation of PSA Sheet for Evaluation]

[0354] The adhesive composition prepared above was applied to the easily peelable surface of a release film [trade name: FILMBYNA (registered trademark) 100E-0010 No. 23, thickness: 100 μm, manufactured by Fujimori Industries, Ltd.] that had been surface-treated with a silicone-based release agent (so-called easy peeling treatment) to form a coating film. It should be noted that the amount of the adhesive composition applied was set to such an amount that the thickness of the adhesive film described later would be 30 μm. Next, a hot air circulation dryer was used to dry the formed coating film at an ambient temperature of 100°C for 2 minutes to form an adhesive film on the release film. Next, the exposed surface of the formed adhesive film was overlapped and bonded to one side of a thermoplastic polyurethane elastomer (TPU) film [trade name: SILKLON (registered trademark), category name: SNY97, thickness: 150 μm, manufactured by Okura Industries, Ltd.] serving as a substrate. Next, the laminate obtained by bonding was left to stand for 4 days (so-called aging period) under an environment of an atmospheric temperature of 23° C. and 50% RH to age the adhesive film.

[0355] As described above, a pressure-sensitive adhesive sheet for evaluation having a structure of release film / pressure-sensitive adhesive layer / substrate (TPU film) was prepared.

[0356] [Measurement and evaluation]

[0357] 1. Initial adhesion

[0358] The evaluation adhesive sheet prepared above was cut to prepare an evaluation adhesive sheet small piece of 25 mm × 150 mm (long side). The release film was peeled off from the prepared evaluation adhesive sheet small piece [composition: release film / adhesive layer / substrate (TPU film)] to obtain an evaluation adhesive sheet small piece X [composition: adhesive layer / substrate (TPU film)]. Next, the exposed adhesive layer surface of the evaluation adhesive sheet small piece X was overlapped and attached to one side of a stainless steel plate (SUS plate) [trade name: SUS304 (BA), manufactured by PALTEK Co., Ltd.] as an adherend, and then a 2 kg roller was pressed back and forth once to produce a laminate X. The prepared laminate X has a laminate structure of adherend (SUS plate) / evaluation adhesive sheet small piece X [composition: adhesive layer / substrate (TPU film)]. Next, the prepared laminate X was left to stand for 24 hours under an ambient temperature of 23°C and 50% RH. The laminate X after standing was used as a test piece for evaluating the initial adhesive force of the adhesive layer. The adhesive strength (unit: N / 25 mm) of the test piece when the evaluation pressure-sensitive adhesive sheet piece X was peeled 180° from the adherend (SUS plate) along the long side (150 mm) was measured using a single-column material testing machine (model: STA-1225) manufactured by A&D Corporation under the conditions of an ambient temperature of 23°C and 50% RH at a peeling speed of 300 mm / min.

[0359] The adhesive strength value obtained by the measurement was defined as the initial adhesive strength value, and based on this value, the initial adhesive strength of the pressure-sensitive adhesive layer was evaluated according to the following evaluation criteria.

[0360] Tables 5 and 6 show the measured values ​​and evaluation results of the initial adhesive force.

[0361] If the evaluation result is "A," "B," or "C," the pressure-sensitive adhesive layer is judged to have excellent initial adhesive strength. The evaluation result is most preferably "A."

[0362] -Evaluation Criteria-

[0363] A: The initial adhesive force is 20 N / 25 mm or more.

[0364] B: The initial adhesive force is within the range of 15 N / 25 mm or more and less than 20 N / 25 mm.

[0365] C: The initial adhesive force is within the range of 10 N / 25 mm or more and less than 15 N / 25 mm.

[0366] D: Initial adhesive force is less than 10 N / 25 mm.

[0367] 2. High temperature short-term re-peelability

[0368] The evaluation adhesive sheet prepared above was cut to prepare an evaluation adhesive sheet piece of 25 mm × 300 mm (long side) in size. The peeling film was peeled off from the prepared evaluation adhesive sheet piece [composition: peeling film / adhesive layer / substrate (TPU film)] to obtain an evaluation adhesive sheet piece Y [composition: adhesive layer / substrate (TPU film)]. Next, the exposed adhesive layer surface of the evaluation adhesive sheet piece Y was overlapped and bonded to one side of a stainless steel plate (SUS plate) [trade name: SUS304 (BA), manufactured by PALTEK Co., Ltd.] as an adherend, and then a 2 kg roller was moved back and forth once for pressing to produce a laminate Y. The laminate Y produced has a laminate structure of adherend (SUS plate) / evaluation adhesive sheet piece Y [composition: adhesive layer / substrate (TPU film)]. The produced laminate Y was left to stand in a constant temperature dryer at an ambient temperature of 100°C for 30 minutes. After this rest, the door of the constant temperature dryer was opened and the laminate Y inside the constant temperature dryer was immediately peeled off by hand. The evaluation adhesive tape piece Y was peeled off 180° from the adherend (SUS plate) along the long side (300 mm). The adhesive layer present on the surface of the adherend (SUS plate) after this peeling was observed using a microscope (Model: VHX-7000, manufactured by KEYENCE Co., Ltd.). If any adhesive layer remained on the surface of the adherend (SUS plate), the total area of ​​the remaining adhesive layer was calculated by image processing. The high-temperature short-term re-peelability of the adhesive layer was then evaluated according to the following evaluation criteria.

[0369] Tables 5 and 6 show the evaluation results of high-temperature short-term removability.

[0370] If the evaluation result is "A," "B," or "C," the PSA layer is judged to have excellent high-temperature short-term removability. The evaluation result is most preferably "A."

[0371] -Evaluation Criteria-

[0372] A: No adhesive layer remains on the surface of the adherend.

[0373] B: The total area of ​​the adhesive layer remaining on the adherend surface is greater than 0 mm 2 and 5mm 2 Within the following range.

[0374] C: The total area of ​​the adhesive layer remaining on the adherend surface is greater than 5 mm 2 and 10mm 2 Within the following range.

[0375] D: The total area of ​​the adhesive layer remaining on the adherend surface is greater than 10 mm 2 .

[0376] 3. Long-term re-peelability

[0377] The evaluation adhesive sheet prepared above was cut to prepare an evaluation adhesive sheet small piece of 25 mm × 300 mm (long side). The release film was peeled off from the prepared evaluation adhesive sheet small piece [composition: release film / adhesive layer / substrate (TPU film)] to obtain an evaluation adhesive sheet small piece Z [composition: adhesive layer / substrate (TPU film)]. Next, the exposed adhesive layer surface of the evaluation adhesive sheet small piece Z was overlapped and bonded to one side of a stainless steel plate (SUS plate) [trade name: SUS304 (BA), manufactured by PALTEK Co., Ltd.] as an adherend, and then a 2 kg roller was moved back and forth once for pressure bonding to produce a laminate Z. The prepared laminate Z has a laminate structure of adherend (SUS plate) / evaluation adhesive sheet small piece Z [composition: adhesive layer / substrate (TPU film)]. The prepared laminate Z was left to stand for 1 week in an environment with an ambient temperature of 70°C, and then left to stand for 1 hour in an environment with an ambient temperature of 23°C. After this rest, the evaluation adhesive tape piece Z was peeled off from the adherend (SUS plate) by hand at an angle of 180° along the long side (300 mm) of the laminate Z. The adhesive layer present on the surface of the adherend (SUS plate) after this peeling was observed using a microscope (Model: VHX-7000, manufactured by KEYENCE Co., Ltd.). If the adhesive layer remained on the surface of the adherend (SUS plate), the total area of ​​the remaining adhesive layer was calculated by image processing. The long-term removability of the adhesive layer was then evaluated according to the following evaluation criteria.

[0378] Tables 5 and 6 show the evaluation results of long-term removability.

[0379] If the evaluation result is "A," "B," or "C," the pressure-sensitive adhesive layer is judged to have excellent long-term removability. The evaluation result is most preferably "A."

[0380] -Evaluation Criteria-

[0381] A: No adhesive layer remains on the surface of the adherend.

[0382] B: The total area of ​​the adhesive layer remaining on the adherend surface is greater than 0 mm 2 and 5mm 2 Within the following range.

[0383] C: The total area of ​​the adhesive layer remaining on the adherend surface is greater than 5 mm 2 and 10mm 2 Within the following range.

[0384] D: The total area of ​​the adhesive layer remaining on the adherend surface is greater than 10 mm 2 .

[0385] [Table 5]

[0386]

[0387] [Table 6]

[0388]

[0389] As shown in Table 5, the adhesive layers formed from the adhesive compositions of Examples 1 to 37 were excellent in initial adhesive strength, high-temperature short-term re-peelability, and long-term re-peelability.

[0390] On the other hand, as shown in Table 6, the adhesive layers formed from the adhesive compositions of Comparative Examples 1 to 18 were inferior to the adhesive layers formed from the adhesive compositions of Examples in at least one of initial adhesive strength, high-temperature short-term removability, and long-term removability.

Claims

1. An adhesive composition comprising: (Meth) acrylic copolymer A, Metal chelate crosslinking agent B, Solvent C having a boiling point of 100°C to 200°C and being a compound represented by the following formula (1), and Monohydric alcohol solvent D having 1 to 3 carbon atoms; The (meth)acrylic copolymer A comprises a structural unit a1 derived from an alkyl (meth)acrylate monomer having 1 to 2 carbon atoms in the alkyl portion at a ratio of 40% to 90% by mass relative to all structural units, and a structural unit a2 derived from a monomer having a carboxyl group at a ratio of 0.5% to 5.0% by mass relative to all structural units. The content of the metal chelate crosslinking agent B is 0.1 to 1.0 parts by mass relative to 100 parts by mass of the (meth)acrylic copolymer A. The content of the solvent C is 3 to 30 parts by mass relative to 100 parts by mass of the (meth)acrylic copolymer A. The ratio of the mass of the solvent C to the mass of the alcohol solvent D is 0.5 to 10.

0. In formula (1), R 1 and R 3 Each independently represents a hydrogen atom, a C1-C6 alkyl group, a C3-C6 cycloalkyl group, a C1-C6 hydroxyalkyl group, a C1-C6 alkoxy group, or an aromatic group which may be substituted with a C1-C6 alkyl group or a C1-C6 alkoxy group, and R 2 represents a hydrogen atom or a C1-C6 alkyl group.

2. The adhesive composition according to claim 1, wherein The (meth)acrylic acid alkyl ester monomer having 1 to 2 carbon atoms in the alkyl portion is at least one selected from methyl acrylate and ethyl acrylate.

3. The adhesive composition according to claim 1, wherein The (meth)acrylic copolymer A includes a structural unit a3 derived from an alkyl (meth)acrylate monomer other than the alkyl (meth)acrylate monomer having 1 to 2 carbon atoms in the alkyl portion.

4. The adhesive composition according to claim 1, wherein The weight average molecular weight of the (meth)acrylic copolymer A is 200,000 to 1,800,000. 5 . An adhesive layer formed from the adhesive composition according to claim 1 .

6. A vehicle protective film comprising: substrate, and The adhesive layer according to claim 5 is provided on the substrate.

7. The vehicle protection film according to claim 6, wherein: The material of the substrate is thermoplastic polyurethane elastomer.

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