Adhesive composition and adhesive sheet

Abstract

To provide an adhesive composition capable of forming an adhesive layer that exhibits light peelability in the initial stage of bonding, displays high adhesive strength after heating, and prevents wrinkling in a decorative film even when used in decorative molding heated to approximately 110°C.SOLUTION: An adhesive composition includes a polymer (A) with a Tg of lower than 0°C, and a polymer (B) with a Tg of 0°C or higher, which includes an organosiloxane skeleton-containing monomer unit. In the polymer (B), the organosiloxane skeleton-containing monomer unit has a Mn of 4000 or more and less than 20000. When an adhesive layer having a thickness of 20 μm is formed, the adhesive layer satisfies (a)-(c). [N1: adhesive strength after left standing for 30 minutes at 23°C, N2: adhesive strength after left standing for 5 minutes at 80°C, then 30 minutes at 23°C, N3: adhesive strength after left standing for 5 minutes at 110°C, then 30 minutes at 23°C]. (a) 0.01 N / 25 mm≤N1<1.0 N / 25 mm, (b) N2 / N1<2.0, (c) 10.0≤N3 / N2.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This disclosure relates to adhesive compositions and adhesive sheets. [Background technology]

[0002] Conventionally, adhesives have been used to fix articles to a substrate. When it is difficult to fix the position of an article to a substrate and there is a possibility of repositioning, the adhesive layer used must be controllable to exhibit slight peelability in the initial stages of bonding and high adhesive strength once the possibility of repositioning is eliminated. Various temperature-sensitive adhesives have been reported to meet these requirements.

[0003] For example, Patent Document 1 discloses an adhesive sheet having a base material and an adhesive layer laminated on at least one side of the base material, wherein the adhesive strength N1 after bonding the adhesive layer to stainless steel (430BA plate) and leaving it at 23°C for 10 seconds is 1.0 [N / 20mm] or less, the adhesive strength N2 after aging at 80°C for 5 minutes after bonding and then leaving it at 23°C for 30 minutes is 3.0 [N / 20mm] or more, and N2 / N1 is 5.0 or more, the adhesive layer contains a polymer (A) having a glass transition temperature of less than 0°C, the polymer (A) is an acrylic polymer, and the adhesive layer further contains a polymer (B) containing monomers as monomer units having a polyorganosiloxane skeleton with a functional group equivalent of 1000 g / mol or more and less than 15000 g / mol. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 6506193 [Overview of the project] [Problems that the invention aims to solve]

[0005] Incidentally, decorative films typically use strong adhesives to prevent them from easily peeling off the substrate. However, decorative films are prone to wrinkling when applied to a substrate and may need to be reapplied. Hot-melt adhesives, which spread and wet the substrate when heated and solidify to form a bond, are frequently used for such decorative films. However, the adhesive layer formed by hot-melt adhesives has poor heat resistance, and if heated again, it can peel off or shift from the substrate. For this reason, hot-melt adhesives are not suitable for decorative molding that involves heating. On the other hand, while thermosensitive adhesives, which exhibit high adhesive strength upon heating, have excellent heat resistance, when used in decorative molding, they already show high adhesive strength at the temperature at which positioning of the decorative film onto the substrate is required. Therefore, decorative films using thermosensitive adhesives for bonding to a substrate are prone to wrinkling due to stretching while only a portion of the film is firmly adhered to the substrate. Conventional thermosensitive adhesives, for example, when used in decorative molding heated to around 110°C (i.e., 100°C to 120°C), exhibit high adhesive strength in the adhesive layer even at around 80°C (i.e., 70°C to 90°C), the temperature at which the decorative film is softened and positioned onto the substrate, resulting in the problem of wrinkles easily forming in the decorative film.

[0006] This disclosure is made in light of the circumstances described above. The problem that the embodiments of this disclosure aim to solve is to provide an adhesive composition and an adhesive sheet that can form an adhesive layer that exhibits easy peelability in the initial stages of bonding to an adherend and high adhesive strength after heating, and that does not easily cause wrinkles in the decorative film even when used in decorative molding heated to a temperature of around 110°C. [Means for solving the problem]

[0007] The following are examples of specific means for solving the problem: <1> A (meth)acrylic polymer (A) having a glass transition temperature of less than 0°C, A (meth)acrylic polymer (B) containing constituent units derived from monomers having an organosiloxane skeleton and having a glass transition temperature of 0°C or higher, Includes, The number-average molecular weight of the monomer having the organosiloxane skeleton in the above (meth)acrylic polymer (B) is in the range of 4000 or more and less than 20000. An adhesive composition that, when an adhesive layer with a thickness of 20 μm is formed, satisfies the following requirements (a) to (c).

[0008] (a) 0.01 N / 25 mm ≤ N1 < 1.0 N / 25 mm (b) N2 / N1 < 2.0 (c) 10.0 ≤ N3 / N2

[0009] In (a) to (c) above, N1 indicates the adhesive strength after the adhesive layer is bonded to stainless steel 430 and left to stand for 30 minutes in an environment with an ambient temperature of 23°C, N2 indicates the adhesive strength after the adhesive layer is bonded to stainless steel 430, left to stand for 5 minutes in an environment with an ambient temperature of 80°C, and then left to stand for 30 minutes in an environment with an ambient temperature of 23°C, and N3 indicates the adhesive strength after the adhesive layer is bonded to stainless steel 430, left to stand for 5 minutes in an environment with an ambient temperature of 110°C, and then left to stand for 30 minutes in an environment with an ambient temperature of 23°C. N1, N2 and N3 are the adhesive strengths when the adhesive layer is peeled off from stainless steel 430 at a peeling speed of 300 mm / min in the 180° direction in accordance with JIS Z0237:2009.

[0010] <2> The monomer having the above organosiloxane skeleton is a compound represented by the following formula (1). <1> The adhesive composition described above.

[0011] [ka]

[0012] In formula (1), R 1 R represents a hydrogen atom or a methyl group. 2represents a monovalent organic group. m and n each independently represent an integer of 0 or more, but m and n do not simultaneously represent 0.

[0013] <3> The adhesive composition according to <1> or <2>, wherein the (meth)acrylic polymer (B) contains a structural unit derived from a (meth)acrylic acid alkyl ester monomer having a glass transition temperature of 40°C or higher when used as a homopolymer. <4> The adhesive composition according to <3>, wherein the content of the structural unit derived from the (meth)acrylic acid alkyl ester monomer in the (meth)acrylic polymer (B) is in the range of 10% by mass or more and 80% by mass or less based on all the structural units of the (meth)acrylic polymer (B). <5> The adhesive composition according to any one of <1> to <4>, wherein the content of the (meth)acrylic polymer (B) is in the range of 0.1 part by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the (meth)acrylic polymer (A). <6> An adhesive sheet including an adhesive layer formed of the adhesive composition according to any one of <1> to <5>.

Advantages of the Invention

[0014] According to an embodiment of the present disclosure, there are provided an adhesive composition and an adhesive sheet that form an adhesive layer which exhibits low peelability at the initial stage of bonding to an adherend and high adhesive strength after heating, and is difficult to cause wrinkles in the decorative film even when used for a decorative molding heated to a temperature near 110°C.

Modes for Carrying Out the Invention

[0015] Hereinafter, the adhesive composition and the adhesive sheet of the present disclosure will be described in detail. The description of the requirements described below may be made based on representative embodiments of the present disclosure, but the present disclosure is not limited to such embodiments, and modifications can be appropriately made and implemented within the scope of the object of the present disclosure.

[0016] In the present disclosure, the numerical range indicated by using "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value, respectively. In the numerical ranges described step by step in the present disclosure, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the upper limit value or the lower limit value of the numerical range described in other step-by-step descriptions. Further, in the numerical ranges described in the present disclosure, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the value shown in the examples.

[0017] In the present disclosure, the combination of two or more preferred embodiments is a more preferred embodiment.

[0018] In the present disclosure, the amount of each component in the adhesive composition means the total amount of the plurality of substances present in the adhesive composition, unless otherwise specified, when there are a plurality of substances corresponding to each component in the adhesive composition.

[0019] In the present disclosure, the "(meth)acrylic monomer" means a monomer having a (meth)acryloyl group. In the present disclosure, the "(meth)acrylic polymer" means a polymer containing a structural unit derived from a (meth)acrylic monomer and having a proportion of the structural unit derived from the (meth)acrylic monomer of 50% by mass or more.

[0020] In the present disclosure, "(meth)acrylic" is a term encompassing both "acrylic" and "methacrylic", "(meth)acrylate" is a term encompassing both "acrylate" and "methacrylate", "(meth)acryloyl" is a term encompassing both "acryloyl" and "methacryloyl", and "(meth)acrylamide" is a term encompassing both "acrylamide" and "methacrylamide".

[0021] In the present disclosure, "n-" means normal, "i-" means iso, "s-" means secondary, and "t-" means tertiary.

[0022] In this disclosure, "polymer" and "polymer" are synonymous, and "monomer" and "monomer" are synonymous. In this disclosure, "adhesive" and "adhesive composition" are synonymous.

[0023] [Adhesive composition] The adhesive composition of this disclosure comprises a (meth)acrylic polymer (A) having a glass transition temperature of less than 0°C and a (meth)acrylic polymer (B) having a glass transition temperature of 0°C or higher, wherein the number average molecular weight of the monomer having an organosiloxane skeleton in the (meth)acrylic polymer (B) is in the range of 4000 or more and less than 20000, and when an adhesive layer with a thickness of 20 μm is formed, the adhesive layer satisfies the following requirements (a) to (c). (a) 0.01 N / 25 mm ≤ N1 < 1.0 N / 25 mm (b) N2 / N1 < 2.0 (c) 10.0 ≤ N3 / N2

[0024] In (a) to (c) above, N1 indicates the adhesive strength after the adhesive layer is bonded to stainless steel 430 and left to stand for 30 minutes in an environment with an ambient temperature of 23°C, N2 indicates the adhesive strength after the adhesive layer is bonded to stainless steel 430, left to stand for 5 minutes in an environment with an ambient temperature of 80°C, and then left to stand for 30 minutes in an environment with an ambient temperature of 23°C, and N3 indicates the adhesive strength after the adhesive layer is bonded to stainless steel 430, left to stand for 5 minutes in an environment with an ambient temperature of 110°C, and then left to stand for 30 minutes in an environment with an ambient temperature of 23°C. N1, N2 and N3 are the adhesive strengths when the adhesive layer is peeled off from stainless steel 430 at a peeling speed of 300 mm / min in the 180° direction in accordance with JIS Z0237:2009.

[0025] The adhesive composition of this disclosure provides an adhesive layer that exhibits easy peelability in the initial stages of bonding to the adherend and high adhesive strength after heating, and even when used in decorative molding heated to a temperature of around 110°C, it is possible to form an adhesive layer that is less likely to cause wrinkles in the decorative film. Furthermore, the adhesive composition of this disclosure makes it possible to form an adhesive layer that is less likely to shift from the adherend when heated to a temperature of around 110°C and has excellent holding power.

[0026] In this disclosure, "(meth)acrylic polymer (A) having a glass transition temperature of less than 0°C" is also referred to as "specific (meth)acrylic polymer (A)". Furthermore, in this disclosure, "a (meth)acrylic polymer (B) that includes constituent units derived from monomers having an organosiloxane skeleton and has a glass transition temperature of 0°C or higher, wherein the number average molecular weight of the monomers having an organosiloxane skeleton in the (meth)acrylic polymer (B) is in the range of 4,000 or more and less than 20,000" is also referred to as "a specific (meth)acrylic polymer (B)". In this disclosure, "specific (meth)acrylic polymer (A) and specific (meth)acrylic polymer (B)" may be collectively referred to as "specific (meth)acrylic polymer."

[0027] <<Requirements (a)>> When the adhesive composition of this disclosure forms an adhesive layer with a thickness of 20 μm, the adhesive layer satisfies requirement (a), i.e., 0.01 N / 25 mm ≤ N1 < 1.0 N / 25 mm. N1 represents the adhesive strength (so-called initial adhesive strength) after the adhesive layer described above has been bonded to stainless steel 430 and left to stand for 30 minutes in an environment with an ambient temperature of 23°C.

[0028] A N1 value between 0.01 N / 25 mm and less than 1.0 N / 25 mm indicates that the adhesive layer exhibits slight peelability from the substrate during the initial stages of bonding. It is preferable that N1 is in the range of 0.01 N / 25 mm or more and less than 0.4 N / 25 mm (i.e., 0.01 N / 25 mm ≤ N1 < 0.4 N / 25 mm).

[0029] <<Requirements (b) and (c)>> When the adhesive composition of this disclosure forms an adhesive layer with a thickness of 20 μm, the adhesive layer satisfies requirement (b), i.e., N2 / N1 < 2.0. N2 represents the adhesive strength after the adhesive layer is bonded to stainless steel 430, left to stand for 5 minutes at an ambient temperature of 80°C, and then left to stand for 30 minutes at an ambient temperature of 23°C. N2 is not particularly limited as long as N2 / N1 < 2.0 is satisfied. It is preferable that N2 / N1 is in the range of 1.0 or more and less than 2.0 (i.e., 1.0 ≤ N2 / N1 < 2.0), and more preferable that it is in the range of 1.0 or more and 1.5 or less (i.e., 1.0 ≤ N2 / N1 ≤ 1.5).

[0030] When the adhesive composition of this disclosure forms an adhesive layer with a thickness of 20 μm, the adhesive layer satisfies requirement (c), i.e., 10.0 ≤ N3 / N2. N3 represents the adhesive strength after the adhesive layer is bonded to stainless steel 430, left to stand for 5 minutes at an ambient temperature of 110°C, and then left to stand for 30 minutes at an ambient temperature of 23°C. N3 is not particularly limited as long as it satisfies 10.0 ≤ N3 / N2. The N3 / N2 ratio is preferably 15.0 or higher. There is no particular upper limit to the N3 / N2 ratio.

[0031] A N2 / N1 ratio of less than 2.0 means that heating at 80°C for 5 minutes will not result in excessively high adhesion of the adhesive layer, while an N3 / N2 ratio of 10.0 or higher means that raising the temperature from around 80°C to around 110°C will result in high adhesion of the adhesive layer. When a decorative film is heated and stretched while only a portion of it is firmly adhered to the substrate, wrinkles tend to form in the decorative film. In contrast, when an adhesive layer that satisfies the requirements of (b) and (c) is used in decorative molding heated to a temperature of around 110°C, for example, the adhesive strength is not excessively high at around 80°C, the temperature at which positioning of the decorative film on the substrate is required. Therefore, wrinkles caused by the heating and stretching of the decorative film while only a portion of it is firmly adhered to the substrate can be suppressed.

[0032] N1, N2, and N3 represent the adhesive strength when the adhesive layer is peeled off the stainless steel 430 at a peeling speed of 300 mm / min in the 180° direction, in accordance with JIS Z0237:2009. Specifically, these are the adhesive strengths measured by the method described in the examples below.

[0033] N1, N2, and N3 can be controlled, for example, by the composition, glass transition temperature, weight-average molecular weight, and content of the specific (meth)acrylic polymer (A) and the specific (meth)acrylic polymer (B). In particular, the glass transition temperatures of the specific (meth)acrylic polymer (A) and the specific (meth)acrylic polymer (B), the content of constituent units derived from monomers having an organosiloxane skeleton in the specific (meth)acrylic polymer (B), and the mass ratio of the specific (meth)acrylic polymer (A) to the specific (meth)acrylic polymer (B) are preferred means of controlling N1, N2, and N3.

[0034] [Specific (meth)acrylic polymer (A)] The adhesive composition of this disclosure comprises a (meth)acrylic polymer (A) having a glass transition temperature of less than 0°C [i.e., a specific (meth)acrylic polymer (A)]. The adhesive composition of this disclosure may contain only one specific (meth)acrylic polymer (A), or it may contain two or more specific polymers.

[0035] The specific (meth)acrylic polymer (A) may be a homopolymer or a copolymer, provided that its glass transition temperature is less than 0°C, but it is preferably a copolymer. The following describes the physical properties of the specific (meth)acrylic polymer (A), such as its glass transition temperature, and then explains the constituent units that the specific (meth)acrylic polymer (A) may contain.

[0036] <<Glass transition temperature of a specific (meth)acrylic polymer (A)>> The glass transition temperature (also called "Tg") of the specific (meth)acrylic polymer (A) is less than 0°C, preferably in the range of -70°C or higher and less than 0°C, more preferably in the range of -70°C or higher and -10°C or lower, even more preferably in the range of -70°C or higher and -20°C or lower, and particularly preferably in the range of -70°C or higher and -30°C or lower. When the glass transition temperature of a specific (meth)acrylic polymer (A) is below 0°C, it tends to form an adhesive layer that is less likely to cause wrinkles in the decorative film, even when used in decorative molding heated to around 110°C.

[0037] The glass transition temperature of a specific (meth)acrylic polymer (A) is the absolute temperature (unit: K) calculated from Equation 1 below and converted to Celsius temperature (unit: °C). 1 / Tg=m1 / Tg1+m2 / Tg2+ +m(k-1) / Tg(k-1)+mk / Tgk (Formula 1)

[0038] In Equation 1, Tg1, Tg2, ..., Tg(k-1), and Tgk represent the glass transition temperatures expressed in absolute temperature when each monomer constituting the specific (meth)acrylic polymer (A) is a homopolymer. m1, m2, ..., m(k-1), and mk represent the mole fractions of each monomer constituting the specific (meth)acrylic polymer (A), where m1 + m2 + ... + m(k-1) + mk = 1. Furthermore, absolute temperature can be converted to Celsius temperature by subtracting 273 from it, and Celsius temperature can be converted back to absolute temperature by adding 273 to it.

[0039] In this disclosure, the "glass transition temperature when used as a homopolymer" shall be the value described in publicly available documents or the value measured using a differential scanning calorimetry (DSC). Specifically, the choice of which value to use is as follows:

[0040] For the "glass transition temperatures when the monomers listed below are homopolymers," the values ​​indicated for each monomer should be used. 2-Ethylhexyl acrylate: -70°C, 2-Ethylhexyl methacrylate: -10°C, n-Butyl acrylate: -54°C, n-Butyl methacrylate: 20°C, t-Butyl acrylate: 43°C, t-Butyl methacrylate: 118°C, i-Butyl methacrylate: 53°C, Methyl acrylate: 10°C, Methyl methacrylate: 105°C, Ethyl acrylate: -22°C, Ethyl methacrylate: 65°C, Methacrylic acid: 228°C, 4-Hydroxybutyl acrylate: -8°C 0℃, 2-hydroxyethyl acrylate: -15℃, 2-hydroxyethyl methacrylate: 85℃, acrylic acid: 106℃, n-octyl acrylate: -65℃, stearyl acrylate: 30℃, stearyl methacrylate: 38℃, lauryl acrylate: -3℃, lauryl methacrylate: -65℃, dimethylaminoethyl methacrylate: 18℃, ω-carboxy-polycaprolactone (n≒2) monoacrylate: -30℃, phenoxyethyl acrylate: -22℃.

[0041] For monomers other than those mentioned above, the "glass transition temperature when used as a homopolymer" will be based on the values ​​listed in the Polymer Handbook (4th edition, Wiley-Interscience; hereafter the same). If the value is not listed in the Polymer Handbook, the glass transition temperature of the homopolymer obtained by the following measurement method will be used.

[0042] -Measurement of glass transition temperature of homopolymers- A differential scanning calorimetry (DSC) was used to measure the glass transition temperature of the homopolymer under conditions of a nitrogen atmosphere, with a sample of 10 mg and a heating rate of 10°C / min. The inflection point of the resulting DSC curve was defined as the glass transition temperature of the homopolymer. As a differential scanning calorimetry device, for example, a differential scanning calorimeter (product name: Discovery DSC 2500) manufactured by T.A. Instrument Japan Co., Ltd. can be suitably used. However, the differential scanning calorimetry device is not limited to this.

[0043] The glass transition temperature of a specific (meth)acrylic polymer (A) can be appropriately adjusted, for example, by using two or more monomers that have different glass transition temperatures when used as a single polymer.

[0044] <<Weight-average molecular weight of specific (meth)acrylic polymer (A)>> The weight-average molecular weight (also called "Mw") of the specific (meth)acrylic polymer (A) is not particularly limited, but is preferably in the range of over 400,000 and up to 2,500,000, more preferably in the range of 450,000 to 2,500,000, and even more preferably in the range of 500,000 to 2,500,000. When the weight-average molecular weight of a specific (meth)acrylic polymer (A) exceeds 400,000, it tends to form an adhesive layer that exhibits better easy peelability in the initial stages of bonding to the adherend. When the weight-average molecular weight of the specific (meth)acrylic polymer (A) is 2.5 million or less, the viscosity of the adhesive composition does not increase excessively, and the coating properties of the adhesive composition tend to be better.

[0045] The weight-average molecular weight of a specific (meth)acrylic polymer (A) is a value measured by the following method. Specifically, it is measured according to (1) to (3) below. (1) A solution of the specific (meth)acrylic polymer (A) is applied to release paper and dried at 100°C for 1 minute to obtain a film-like specific (meth)acrylic polymer (A). (2) Using the film-like specific (meth)acrylic polymer (A) obtained in (1) above and tetrahydrofuran, a sample solution having a solid content concentration of 0.2% by mass is obtained. Here, "solid content concentration" refers to the mass ratio of the specific (meth)acrylic polymer (A) in the sample solution. (3) The weight-average molecular weight of the specific (meth)acrylic polymer (A) is determined as a standard polystyrene equivalent by gel permeation chromatography (GPC) under the following conditions.

[0046] ~Conditions~ Measurement device: High-speed GPC [Model number: HLC-8220 GPC, manufactured by Tosoh Corporation] Detector: Differential Refractometer (RI) [Integrated into HLC-8220, manufactured by Tosoh Corporation] Column: TSKgel GMH XL Four units manufactured by Tosoh Corporation were used. Column temperature: 40℃ Eluent: Tetrahydrofuran Sample solution injection volume: 100 μL Flow rate: 0.8mL / min

[0047] The weight-average molecular weight of a specific (meth)acrylic polymer (A) can be adjusted to a desired value by controlling the polymerization temperature, polymerization time, amount of organic solvent used, type of polymerization initiator, and amount of polymerization initiator used during the polymerization of the monomer.

[0048] <Constituent units derived from alkyl methacrylate monomers> The specific (meth)acrylic polymer (A) preferably contains constituent units derived from alkyl (meth)acrylate monomers. In this disclosure, "constituent units derived from (meth)acrylate alkyl ester monomers" means constituent units formed by the addition polymerization of (meth)acrylate alkyl ester monomers. In this disclosure, "(meth)acrylate alkyl ester monomers" do not include monomers having a hydroxyl group or monomers having a carboxyl group.

[0049] The type of alkyl (meth)acrylate monomer is not particularly limited. The alkyl (meth)acrylate monomer may be an alkyl acrylate monomer or an alkyl methacrylate monomer. The alkyl group in the alkyl (meth)acrylate monomer may be unsubstituted or may have substituents (excluding carboxyl and hydroxyl groups), but it is preferable that it be unsubstituted. The alkyl group in the alkyl (meth)acrylate monomer may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group of the (meth)acrylate monomer is preferably 1 to 18, more preferably 1 to 12, and even more preferably 1 to 8.

[0050] Specific examples of alkyl (meth)acrylate monomers include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, n-octyl (meth)acrylate, i-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, i-nonyl (meth)acrylate, n-decyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, and isobornyl (meth)acrylate. As the alkyl (meth)acrylate monomer, for example, from the viewpoint of easily producing (meth)acrylic polymers with a glass transition temperature of less than 0°C, at least one selected from the group consisting of n-butyl acrylate (n-BA), 2-ethylhexyl acrylate (2EHA), methyl acrylate (MA), and methyl methacrylate (MMA) is preferred.

[0051] If the specified (meth)acrylic polymer (A) contains constituent units derived from alkyl (meth)acrylate monomers, it may contain only one type of constituent unit derived from alkyl (meth)acrylate monomers, or it may contain two or more types.

[0052] When a specific (meth)acrylic polymer (A) contains constituent units derived from alkyl (meth)acrylate monomers, the content of constituent units derived from alkyl (meth)acrylate monomers in the specific (meth)acrylic polymer (A) is not particularly limited, but is preferably in the range of 50% by mass or more and 100% by mass or less, more preferably in the range of 60% by mass or more and 100% by mass or less, even more preferably in the range of 70% by mass or more and 100% by mass or less, and particularly preferably in the range of 80% by mass or more and 100% by mass or less, relative to the total constituent units of the specific (meth)acrylic polymer (A). Here, the content of constituent units derived from alkyl methacrylate monomers in the specific (meth)acrylic polymer (A) being 50% by mass or more relative to the total constituent units of the specific (meth)acrylic polymer (A) means that constituent units derived from alkyl methacrylate monomers are included as the main component of the constituent units of the specific (meth)acrylic polymer (A).

[0053] <Constituent units derived from monomers containing hydroxyl groups> The specific (meth)acrylic polymer (A) may contain constituent units derived from monomers having hydroxyl groups. In this disclosure, "constituent unit derived from a monomer having a hydroxyl group" means a constituent unit formed by the addition polymerization of monomers having a hydroxyl group.

[0054] The type of monomer having a hydroxyl group is not particularly limited. Examples of monomers having a hydroxyl group include monomers having at least one hydroxyl group and an ethylenically unsaturated group in one molecule. The ethylenically unsaturated group is not particularly limited and includes, for example, a vinyl group, an allyl group, a vinylphenyl group, a (meth)acrylamide group, and a (meth)acryloyl group. A (meth)acryloyl group is preferred as the ethylenically unsaturated group.

[0055] Specific examples of monomers having hydroxyl groups include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, 3-methyl-3-hydroxybutyl (meth)acrylate, 1,1-dimethyl-3-hydroxybutyl (meth)acrylate, 1,3-dimethyl-3-hydroxybutyl (meth)acrylate, 2,2,4-trimethyl-3-hydroxypentyl (meth)acrylate, 2-ethyl-3-hydroxyhexyl (meth)acrylate, N-hydroxyethyl (meth)acrylamide, glycerin mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, polyethylene glycol mono(meth)acrylate, and poly(ethylene glycol-propylene glycol) mono(meth)acrylate. As monomers having hydroxyl groups, hydroxyalkyl (meth)acrylates are preferred, for example, because they exhibit good copolymerization with other monomers. Furthermore, as hydroxyalkyl (meth)acrylates, hydroxyalkyl (meth)acrylates having a hydroxyalkyl group with 2 to 4 carbon atoms are preferred, and 2-hydroxyethyl acrylate is more preferred.

[0056] If the specific (meth)acrylic polymer (A) contains constituent units derived from monomers having hydroxyl groups, it may contain only one type of constituent unit derived from monomers having hydroxyl groups, or it may contain two or more types.

[0057] When the specific (meth)acrylic polymer (A) contains constituent units derived from monomers having hydroxyl groups, the content of constituent units derived from monomers having hydroxyl groups is not particularly limited, but for example, from the viewpoint of compatibility with the specific (meth)acrylic polymer (B), it is preferably in the range of 1% by mass or more and 30% by mass or less, more preferably in the range of 3% by mass or more and 25% by mass or less, and even more preferably in the range of 5% by mass or more and 20% by mass or less, relative to the total constituent units of the specific (meth)acrylic polymer (A).

[0058] <Other constituent units> Other constituent units that the specific (meth)acrylic polymer (A) may contain include: constituent units derived from monomers having a carboxyl group, such as (meth)acrylic acid; constituent units derived from (meth)acrylates having an aromatic ring, such as benzyl (meth)acrylate and phenoxyethyl (meth)acrylate; constituent units derived from alkoxyalkyl (meth)acrylates, such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; constituent units derived from aromatic monovinyls, such as styrene, α-methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene and vinyltoluene; constituent units derived from vinyl cyanides, such as acrylonitrile and methacrylonitrile; constituent units derived from vinyl esters, such as vinyl formate, vinyl acetate, vinyl propionate and vinyl versatate; and so on.

[0059] If the specified (meth)acrylic polymer (A) contains other constituent units, it may contain only one type of other constituent unit or two or more types.

[0060] If the specified (meth)acrylic polymer (A) contains other constituent units, the content of the other constituent units in the specified (meth)acrylic polymer (A) can be set appropriately within a range that does not impair the effect of the adhesive composition of this disclosure.

[0061] <<Content of specific (meth)acrylic polymer (A)>> The content of the specific (meth)acrylic polymer (A) in the adhesive composition of this disclosure is not particularly limited, but is preferably in the range of 40.0% by mass or more and 90.0% by mass or less, more preferably in the range of 43.0% by mass or more and 87.0% by mass or less, and even more preferably in the range of 45.0% by mass or more and 85.0% by mass or less, based on the total solid content in the adhesive composition.

[0062] In this disclosure, "total solid content in the adhesive composition" means the total mass of the adhesive composition if the adhesive composition does not contain a solvent, and the mass of the residue remaining after removing the solvent from the adhesive composition if the adhesive composition contains a solvent. In this disclosure, "solvent" means water and organic solvents.

[0063] [Specific (meth)acrylic polymer (B)] The adhesive composition of this disclosure includes a (meth)acrylic polymer (B) [i.e., a specific (meth)acrylic polymer (B)] which contains constituent units derived from monomers having an organosiloxane skeleton and has a glass transition temperature of 0°C or higher, wherein the number average molecular weight of the monomers having an organosiloxane skeleton in the specific (meth)acrylic polymer (B) is in the range of 4,000 or more and less than 20,000. The adhesive composition of this disclosure may contain only one specific (meth)acrylic polymer (B), or it may contain two or more specific polymers.

[0064] The specific (meth)acrylic polymer (B) contains constituent units derived from monomers having an organosiloxane skeleton, and has a glass transition temperature of 0°C or higher. It may be a homopolymer or a copolymer, but it is preferably a copolymer. The following describes the physical properties of the specific (meth)acrylic polymer (B), such as its glass transition temperature, and then explains the constituent units that the specific (meth)acrylic polymer (B) may contain.

[0065] <<Glass transition temperature of specific (meth)acrylic polymer (B)>> The glass transition temperature (Tg) of the specific (meth)acrylic polymer (B) is 0°C or higher. The glass transition temperature of the specific (meth)acrylic polymer (B) being 0°C or higher means that the specific (meth)acrylic polymer (B) is a different polymer from the specific (meth)acrylic polymer (A) described above.

[0066] The glass transition temperature of the specific (meth)acrylic polymer (B) was determined using a differential scanning calorimetry (DSC) under the following conditions: a measurement start temperature of -70°C, a measurement end temperature of 150°C, and a heating rate of 10°C / min, with an 8 mg sample being measured in a nitrogen atmosphere. The inflection point of the resulting DSC curve was defined as the glass transition temperature of the specific (meth)acrylic polymer (B). As a differential scanning calorimetry device, for example, the DSC2500 (model number) manufactured by T.A. Instruments Corporation can be suitably used. However, the differential scanning calorimetry device is not limited to this.

[0067] The glass transition temperature of a specific (meth)acrylic polymer (B) can be appropriately adjusted, for example, by using two or more monomers that have different glass transition temperatures when used as a single polymer.

[0068] <<Weight-average molecular weight of specific (meth)acrylic polymer (B)>> The weight-average molecular weight of the specific (meth)acrylic polymer (B) is not particularly limited, but is preferably in the range of 10,000 to 400,000, more preferably in the range of 30,000 to 350,000, and even more preferably in the range of 50,000 to 300,000. When the weight-average molecular weight of a specific (meth)acrylic polymer (B) is 10,000 or more, it tends to form an adhesive layer that is less prone to shifting from the bonded substrate even when heated to a temperature of around 110°C, and has superior holding power. When the weight-average molecular weight of a specific (meth)acrylic polymer (B) is 400,000 or less, it tends to form an adhesive layer that exhibits higher tackiness after heating.

[0069] The weight-average molecular weight of the specific (meth)acrylic polymer (B) is measured by the same method as the method for measuring the weight-average molecular weight of the specific (meth)acrylic polymer (A) described above.

[0070] The weight-average molecular weight of a specific (meth)acrylic polymer (B) can be adjusted to a desired value by controlling the polymerization temperature, polymerization time, amount of organic solvent used, type of polymerization initiator, amount of polymerization initiator used, etc.

[0071] <Constituent units derived from monomers having an organosiloxane skeleton> The specified (meth)acrylic polymer (B) contains constituent units derived from monomers having an organosiloxane skeleton (hereinafter also referred to as "constituent unit b1"). Furthermore, the number-average molecular weight of the monomers having an organosiloxane skeleton in the specified (meth)acrylic polymer (B) is in the range of 4,000 or more and less than 20,000. In this disclosure, "constituent unit derived from a monomer having an organosiloxane skeleton (i.e., constituent unit b1)" means a constituent unit formed by addition polymerization of monomers having an organosiloxane skeleton.

[0072] Monomers having an organosiloxane skeleton tend to cause (meth)acrylic polymers (B) to be unevenly distributed on the adhesive surface of the adhesive layer due to their low polarity derived from their structure. Here, "adhesive surface of the adhesive layer" can refer to, for example, the interface between the adhesive layer and the adherend. The constituent units derived from monomers having an organosiloxane skeleton contribute to the design of adhesive compositions that satisfy the requirements (a) to (c) described above by controlling the uneven distribution of the (meth)acrylic polymer (B) on the adhesive surface of the adhesive layer.

[0073] The type of monomer having an organosiloxane skeleton is not particularly limited, as long as the number average molecular weight of the monomer having an organosiloxane skeleton in the specific (meth)acrylic polymer (B) can be adjusted to a range of 4,000 or more and less than 20,000. Specific examples of monomers having an organosiloxane skeleton include compounds represented by the following formula (1).

[0074] [Chemical formula]

[0075] In formula (1), R 1 represents a hydrogen atom or a methyl group, and is preferably a methyl group.

[0076] In formula (1), R 2 represents a monovalent organic group. R 2 The monovalent organic group represented by R may be linear, branched, or cyclic. Examples of the monovalent organic group include an alkyl group, an alkenyl group, an alkynyl group, and an aryl group, and an alkyl group is preferred. R 2 When R represents an alkyl group, the alkyl group is preferably an alkyl group having 1 to 12 carbon atoms, more preferably an alkyl group having 1 to 6 carbon atoms, and even more preferably an alkyl group having 1 to 4 carbon atoms. Examples of the alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl group, an s-butyl group, and a t-butyl group, and a methyl group is preferred. R 2 When R represents an alkenyl group, examples of the alkenyl group include a vinyl group, an allyl group, and a 2-propenyl group, and a vinyl group is preferred. R 2 / / When R represents an alkynyl group, examples of the alkynyl group include an ethynyl group, a propargyl group, and a prop-2-yn-1-yl group, and an ethynyl group is preferred. R / / 2 When R represents an aryl group, examples of the aryl group include a phenyl group, a tolyl group, and a pyridyl group, and a phenyl group is preferred.

[0077] In formula (1), m and n each independently represent an integer of 0 or more, but m and n do not simultaneously represent 0. m is preferably an integer between 1 and 10, and more preferably an integer between 1 and 6. n is preferably an integer between 1 and 250, more preferably an integer between 5 and 200, and even more preferably an integer between 10 and 200.

[0078] Commercially available monomers with an organosiloxane skeleton can be used. Examples of commercially available monomers having an organosiloxane skeleton include X-22-174ASX (trade name, number average molecular weight: 1100, manufactured by Shin-Etsu Chemical Co., Ltd.), Cyraplane® FM-0711 (trade name, number average molecular weight: 1200, manufactured by JNC Corporation), Cyraplane® FM-0721 (trade name, number average molecular weight: 6500, manufactured by JNC Corporation), Cyraplane® FM-0725 (trade name, number average molecular weight: 15000, manufactured by JNC Corporation), KF-2012 (trade name, number average molecular weight: 5400, manufactured by Shin-Etsu Chemical Co., Ltd.), and X-22-2426 (trade name, number average molecular weight: 13800, manufactured by Shin-Etsu Chemical Co., Ltd.). All of the commercially available products listed above correspond to compounds represented by formula (1).

[0079] The number-average molecular weight (also referred to as "Mn") of monomers having an organosiloxane skeleton in the specific (meth)acrylic polymer (B) is in the range of 4,000 or more and less than 20,000, preferably in the range of 4,200 or more and less than 20,000, more preferably in the range of 4,500 or more and less than 20,000, and even more preferably in the range of 5,000 or more and less than 20,000. The number-average molecular weight of monomers having an organosiloxane skeleton in a specific (meth)acrylic polymer (B) is less than 20,000, for example, from the viewpoint of the availability of monomers having an organosiloxane skeleton. When the number-average molecular weight of monomers having an organosiloxane skeleton in a specific (meth)acrylic polymer (B) is 4000 or more, it tends to form an adhesive layer that is less likely to cause wrinkles in the decorative film, even when used in decorative molding heated to a temperature of around 110°C.

[0080] In this disclosure, the number-average molecular weight of monomers having an organosiloxane skeleton is a value measured by the following method. Specifically, it is measured according to (1) and (2) below. (1) A sample solution with a solid content concentration of 0.2% by mass is obtained using a monomer having an organosiloxane skeleton and tetrahydrofuran. Here, "solid content concentration" refers to the mass ratio of the monomer having an organosiloxane skeleton in the sample solution. (2) The number-average molecular weight of monomers having an organosiloxane skeleton is determined as a standard polystyrene equivalent by gel permeation chromatography (GPC) under the following conditions.

[0081] ~Conditions~ Measurement device: High-speed GPC [Model number: HLC-8220 GPC, manufactured by Tosoh Corporation] Detector: Differential Refractometer (RI) [Integrated into HLC-8220, manufactured by Tosoh Corporation] Column: TSKgel GMH XL Four units manufactured by Tosoh Corporation were used. Column temperature: 40℃ Eluent: Tetrahydrofuran Sample solution injection volume: 100 μL Flow rate: 0.8mL / min

[0082] Furthermore, if the specified (meth)acrylic polymer (B) contains monomers having two or more organosiloxane skeletons with different number-average molecular weights, the "number-average molecular weight of the organosiloxane skeleton monomers in the specified (meth)acrylic polymer (B)" refers to the arithmetic mean, specifically the value calculated by the following formula. The number-average molecular weight of monomers having an organosiloxane skeleton in a specific (meth)acrylic polymer (B) = [Number-average molecular weight of monomer 1 × Amount of monomer 1 + Number-average molecular weight of monomer 2 × Amount of monomer 2 + ... + Number-average molecular weight of monomer n × Amount of monomer n] / [Amount of monomer 1 + Amount of monomer 2 + ... + Amount of monomer n]

[0083] The specific (meth)acrylic polymer (B) may contain only one type of constituent unit b1, or it may contain two or more types.

[0084] The content of constituent unit b1 in the specific (meth)acrylic polymer (B) is not particularly limited, but is preferably in the range of 0.1% by mass or more and 10.0% by mass or less relative to the total constituent units of the specific (meth)acrylic polymer (B). When the content of constituent unit b1 in the specific (meth)acrylic polymer (B) is within the above range relative to all constituent units of the specific (meth)acrylic polymer (B), it tends to be easier to design an adhesive composition that satisfies the requirements (a) to (c) described above. The content of constituent unit b1 in the specified (meth)acrylic polymer (B) is more preferably in the range of 0.5% by mass or more and 10.0% by mass or less, more preferably in the range of 1.0% by mass or more and 5.0% by mass or less, and particularly preferably in the range of 1.0% by mass or more and 3.0% by mass or less, relative to the total constituent units of the specified (meth)acrylic polymer (B).

[0085] <Constituent units derived from alkyl (meth)acrylate monomers whose glass transition temperature is 40°C or higher when used as a homopolymer> The specific (meth)acrylic polymer (B) preferably contains a constituent unit (hereinafter also referred to as "constituent unit b2") derived from an alkyl (meth)acrylate monomer whose glass transition temperature when used as a homopolymer is 40°C or higher. When the specific (meth)acrylic polymer (B) contains the constituent unit b2, it tends to be easier to design adhesive compositions that satisfy the requirements (a) to (c) described above. In this disclosure, "constituent units derived from alkyl (meth)acrylate monomers having a glass transition temperature of 40°C or higher when used as a homopolymer (i.e., constituent unit b2)" means constituent units formed by addition polymerization of alkyl (meth)acrylate monomers having a glass transition temperature of 40°C or higher when used as a homopolymer.

[0086] The (meth)acrylate alkyl ester monomer having a glass transition temperature of 40°C or higher when used as a homopolymer may be either an alkyl acrylate monomer or an alkyl methacrylate monomer. The alkyl group in an alkyl (meth)acrylate monomer that has a glass transition temperature of 40°C or higher when used as a homopolymer is preferably unsubstituted. The alkyl group of an alkyl (meth)acrylate monomer having a glass transition temperature of 40°C or higher when used as a homopolymer may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group of an alkyl (meth)acrylate monomer having a glass transition temperature of 40°C or higher when used as a homopolymer is preferably 1 to 18, more preferably 1 to 12, even more preferably 1 to 8, and particularly preferably 1 to 4.

[0087] As a monomer of alkyl (meth)acrylate having a glass transition temperature of 40°C or higher when used as a homopolymer, alkyl (meth)acrylate monomers having a glass transition temperature in the range of 40°C to 120°C when used as a homopolymer are preferred, alkyl (meth)acrylate monomers having a glass transition temperature in the range of 50°C to 120°C when used as a homopolymer are more preferred, and alkyl (meth)acrylate monomers having a glass transition temperature in the range of 80°C to 120°C when used as a homopolymer are even more preferred.

[0088] Specific examples of alkyl (meth)acrylate monomers having a glass transition temperature of 40°C or higher when used as a homopolymer include t-butyl acrylate (t-BA, glass transition temperature when used as a homopolymer: 43°C), t-butyl methacrylate (t-BMA, glass transition temperature when used as a homopolymer: 118°C), i-butyl methacrylate (i-BMA, glass transition temperature when used as a homopolymer: 53°C), methyl methacrylate (MMA, glass transition temperature when used as a homopolymer: 105°C), and ethyl methacrylate (EMA, glass transition temperature when used as a homopolymer: 65°C).

[0089] If the specific (meth)acrylic polymer (B) contains constituent unit b2, it may contain only one type of constituent unit b2 or two or more types.

[0090] When the specific (meth)acrylic polymer (B) contains constituent unit b2, the content of constituent unit b2 is not particularly limited, but is preferably in the range of 10% by mass or more and 80% by mass or less relative to the total constituent units of the specific (meth)acrylic polymer (B). When the content of constituent unit b2 in the specific (meth)acrylic polymer (B) is within the above range relative to all constituent units of the specific (meth)acrylic polymer (B), it tends to be easier to design an adhesive composition that satisfies the requirements (a) to (c) described above. The content of constituent unit b2 in the specific (meth)acrylic polymer (B) is more preferably in the range of 20% by mass or more and 80% by mass or less, more preferably in the range of 30% by mass or more and 80% by mass or less, and particularly preferably in the range of 40% by mass or more and 80% by mass or less, relative to the total constituent units of the specific (meth)acrylic polymer (B).

[0091] <Constituent units derived from alkyl (meth)acrylate monomers whose glass transition temperature is less than 40°C when used as a homopolymer> The specified (meth)acrylic polymer (B) may contain constituent units (hereinafter also referred to as "constituent unit b3") derived from alkyl (meth)acrylate monomers whose glass transition temperature when used as a homopolymer is less than 40°C. When a specific (meth)acrylic polymer (B) contains constituent unit b3, it tends to be easier to design adhesive compositions that satisfy the requirements (a) to (c) described above. In this disclosure, "constituent units derived from alkyl (meth)acrylate monomers having a glass transition temperature of less than 40°C when used as a homopolymer (i.e., constituent unit b3)" means constituent units formed by addition polymerization of alkyl (meth)acrylate monomers having a glass transition temperature of less than 40°C when used as a homopolymer.

[0092] The alkyl (meth)acrylate monomer having a glass transition temperature of less than 40°C when used as a homopolymer may be an alkyl acrylate monomer or an alkyl methacrylate monomer. The alkyl group in an alkyl (meth)acrylate monomer that has a glass transition temperature of less than 40°C when used as a homopolymer is preferably unsubstituted. The alkyl group of an alkyl (meth)acrylate monomer having a glass transition temperature of less than 40°C when used as a homopolymer may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group of an alkyl (meth)acrylate monomer having a glass transition temperature of less than 40°C when used as a homopolymer is preferably 1 to 18, more preferably 1 to 12, even more preferably 1 to 8, and particularly preferably 1 to 4.

[0093] As a monomer of alkyl (meth)acrylate having a glass transition temperature of less than 40°C when used as a homopolymer, alkyl (meth)acrylate monomer having a glass transition temperature in the range of -40°C or higher and less than 40°C when used as a homopolymer is preferred, and alkyl (meth)acrylate monomer having a glass transition temperature in the range of -40°C or higher and 30°C or lower when used as a homopolymer is more preferred.

[0094] Specific examples of alkyl (meth)acrylate monomers having a glass transition temperature of less than 40°C when used as a homopolymer include 2-ethylhexyl acrylate (2EHA, glass transition temperature when used as a homopolymer: -70°C), 2-ethylhexyl methacrylate (2EHMA, glass transition temperature when used as a homopolymer: -10°C), n-butyl acrylate (n-BA, glass transition temperature when used as a homopolymer: -54°C), n-butyl methacrylate (n-BMA, glass transition temperature when used as a homopolymer: 20°C), methyl acrylate (MA, glass transition temperature when used as a homopolymer: 10°C), and ethyl acrylate (EA, glass transition temperature when used as a homopolymer: -22°C).

[0095] If the specific (meth)acrylic polymer (B) contains constituent unit b3, it may contain only one type of constituent unit b3 or two or more types.

[0096] When the specific (meth)acrylic polymer (B) contains constituent unit b3, the content of constituent unit b3 in the specific (meth)acrylic polymer (B) is not particularly limited and can be set appropriately depending on the purpose, for example, by designing the adhesive composition to satisfy the requirements of (a) to (c) described above.

[0097] <Other constituent units> Other constituent units that the specific (meth)acrylic polymer (B) may contain include: constituent units derived from monomers having hydroxyl groups, such as 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate; constituent units derived from monomers having carboxyl groups, such as (meth)acrylic acid; constituent units derived from (meth)acrylates having aromatic rings, such as benzyl (meth)acrylate and phenoxyethyl (meth)acrylate; constituent units derived from alkoxyalkyl (meth)acrylates, such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; constituent units derived from aromatic monovinyls, such as styrene, α-methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, and vinyltoluene; constituent units derived from vinyl cyanides, such as acrylonitrile and methacrylonitrile; constituent units derived from vinyl esters, such as vinyl formate, vinyl acetate, vinyl propionate, and vinyl versatate; and the like.

[0098] If the specified (meth)acrylic polymer (B) contains other constituent units, it may contain only one type of other constituent unit or two or more types.

[0099] If the specified (meth)acrylic polymer (B) contains other constituent units, the content of the other constituent units in the specified (meth)acrylic polymer (B) can be appropriately set within a range that does not impair the effect of the adhesive composition of this disclosure.

[0100] <<Content of specific (meth)acrylic polymer (B)>> The content of the specific (meth)acrylic polymer (B) in the adhesive composition of this disclosure is not particularly limited, but is preferably in the range of 0.1 parts by mass or more and 100 parts by mass or less per 100 parts by mass of the specific (meth)acrylic polymer (A). When the content of the specific (meth)acrylic polymer (B) in the adhesive composition of this disclosure is within the above range relative to 100 parts by mass of the specific (meth)acrylic polymer (A), it tends to be easier to design an adhesive composition that satisfies the requirements (a) to (c) described above. The content of the specific (meth)acrylic polymer (B) in the adhesive composition of this disclosure is more preferably in the range of 1 part by mass or more and 100 parts by mass or less, more preferably in the range of 10 parts by mass or more and 100 parts by mass or less, and particularly preferably in the range of 20 parts by mass or more and 100 parts by mass or less, per 100 parts by mass of the specific (meth)acrylic polymer (A).

[0101] [Meth)acrylic polymer manufacturing method] The method for producing the specific (meth)acrylic polymer (A) and the specific (meth)acrylic polymer (B) [i.e., the specific (meth)acrylic polymer] is not particularly limited. Specific (meth)acrylic polymers can be produced by polymerizing the monomers described above using known polymerization methods, such as solution polymerization, emulsion polymerization, suspension polymerization, and bulk polymerization. As for the polymerization method, solution polymerization is preferred because the processing steps are relatively simple and can be carried out in a short time when preparing the adhesive composition of this disclosure after the production of a specific (meth)acrylic polymer.

[0102] In solution polymerization, a predetermined organic solvent, monomer, polymerization initiator, and a chain transfer agent (if necessary) are generally placed in a polymerization tank, and the reaction is carried out by heating for several hours at, for example, the reflux temperature of the organic solvent while stirring. In this case, at least a portion of the organic solvent, monomer, polymerization initiator, and chain transfer agent (if necessary) may be added sequentially. Alternatively, the reaction may be carried out under a nitrogen atmosphere.

[0103] Examples of organic solvents used in polymerization reactions include aromatic hydrocarbon compounds, aliphatic hydrocarbon compounds, alicyclic hydrocarbon compounds, ester compounds, ketone compounds, glycol ether compounds, and alcohol compounds. More specifically, organic solvents used in polymerization reactions include aromatic hydrocarbon compounds such as benzene, toluene, ethylbenzene, n-propylbenzene, t-butylbenzene, o-xylene, m-xylene, p-xylene, tetralin, decalin, and aromatic naphtha; aliphatic or alicyclic hydrocarbon compounds such as n-hexane, n-heptane, n-octane, i-octane, n-decane, dipentene, petroleum spirits, petroleum naphtha, and turpentine oil; ester compounds such as methyl acetate, ethyl acetate, n-butyl acetate, n-amyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate, 3-methoxybutyl acetate, and methyl benzoate; acetone; and methyl Examples include ketone compounds represented by ethyl ketone, methyl-i-butyl ketone, isophorone, cyclohexanone, and methylcyclohexanone; glycol ether compounds represented by ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and diethylene glycol monobutyl ether; and alcohol compounds represented by methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, i-butyl alcohol, s-butyl alcohol, and t-butyl alcohol.

[0104] In the production of specific (meth)acrylic polymers, it is preferable to use organic solvents that do not easily cause chain transfer during polymerization reactions, such as aromatic hydrocarbon compounds, ester compounds, and ketone compounds. In particular, from the viewpoint of solubility of the specific (meth)acrylic polymer and ease of polymerization reaction, the use of ethyl acetate is preferred.

[0105] During the polymerization reaction, one organic solvent may be used, or two or more may be used.

[0106] Examples of polymerization initiators include organic peroxides and azo compounds commonly used in conventional solution polymerization methods. Specific examples of organic peroxides include t-butylperoxy-2-ethylhexanoate, t-butylhydroperoxide, cumenehydroperoxide, dicumylperoxide, benzoylperoxide, lauroylperoxide, caproylperoxide, di-i-propylperoxydicarbonate, di-2-ethylhexylperoxydicarbonate, t-butylperoxypivalate, and 2,2-bis(4,4-di-t-butylperoxy). Examples include chlorohexyl)propane, 2,2-bis(4,4-di-t-amylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-octylperoxycyclohexyl)propane, 2,2-bis(4,4-di-α-cumylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)butane, and 2,2-bis(4,4-di-t-octylperoxycyclohexyl)butane. Specific examples of azo compounds include 2,2'-azobisisobutyronitrile [AIBN], 2,2'-azobis(2,4-dimethylvaleronitrile) [ABVN], 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 1,1'-azobis(cyclohexane-1-carbonitride), 2,2'-azobis(2-methylpropionic acid)dimethyl, and 2,2'-azobis(isobutyric acid)dimethyl.

[0107] During the polymerization reaction, one polymerization initiator may be used, or two or more may be used.

[0108] The amount of polymerization initiator used is not particularly limited and can be appropriately set, for example, depending on the molecular weight of the target specific (meth)acrylic polymer.

[0109] In the production of specific (meth)acrylic polymers, chain transfer agents may be used as needed. Examples of chain transfer agents include cyanoacetic acid, alkyl ester compounds of cyanoacetic acid with 1 to 8 carbon atoms, bromoacetic acid, alkyl ester compounds of bromoacetic acid with 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, carbon tetrabromide, and tetra- Examples include halogenated hydrocarbon compounds represented by carbon chloride, 1,1,2,2-tetrabromoethane, tribromoethylene, trichloroethylene, bromotrichloromethane, tribromomethane, and 3-chloro-1-propene; aldehyde compounds represented by chloral and furaldihydes; alkyl mercaptan compounds having 1 to 18 carbon atoms; aromatic mercaptan compounds represented by thiophenol and toluene mercaptan; mercaptoacetic acid; alkyl ester compounds of mercaptoacetic acid having 1 to 10 carbon atoms; hydroxyalkyl mercaptan compounds having 1 to 12 carbon atoms; and terpene compounds represented by pinene and terpinolene.

[0110] When using a chain transfer agent in the production of a specific (meth)acrylic polymer, the amount of the chain transfer agent used is not particularly limited and can be appropriately set, for example, depending on the molecular weight of the target specific (meth)acrylic polymer.

[0111] The polymerization temperature is not particularly limited and can be set appropriately depending on the molecular weight of the target (meth)acrylic polymer, for example.

[0112] [Crosslinking agent] The adhesive composition of this disclosure may contain a crosslinking agent. The type of crosslinking agent is not particularly limited. Examples of crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, and metal chelate-based crosslinking agents.

[0113] In this disclosure, "isocyanate-based crosslinking agent" refers to a compound having two or more isocyanate groups in one molecule (a so-called polyisocyanate compound). Furthermore, "epoxy-based crosslinking agent" refers to a compound having two or more epoxy groups in one molecule (a so-called bifunctional or multifunctional epoxy compound). Furthermore, "metal chelate-based crosslinking agent" refers to a metal chelate compound that functions as a crosslinking agent.

[0114] As the crosslinking agent, isocyanate-based crosslinking agents (so-called polyisocyanate compounds) are preferred. Examples of polyisocyanate compounds include aliphatic polyisocyanate compounds, alicyclic polyisocyanate compounds, and aromatic polyisocyanate compounds.

[0115] Aliphatic polyisocyanate compounds include, for example, aliphatic polyisocyanate compounds, polymers of aliphatic polyisocyanate compounds, adducts of aliphatic polyisocyanate compounds and polyol compounds (e.g., trimethylolpropane (TMP); the same applies hereafter), and biuret compounds of aliphatic polyisocyanate compounds. Specific examples of aliphatic polyisocyanate compounds include hexamethylene diisocyanate (HMDI), pentamethylene diisocyanate (PDI), tetramethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate.

[0116] Alicyclic polyisocyanate compounds include, for example, alicyclic polyisocyanate compounds, polymers of alicyclic polyisocyanate compounds, adducts of alicyclic polyisocyanate compounds and polyol compounds, and biuret compounds of alicyclic polyisocyanate compounds. Specific examples of alicyclic polyisocyanate compounds include isophorone diisocyanate (IPDI), hydrogenated tolylene diisocyanate, hydrogenated xylene diisocyanate, hydrogenated 4,4'-diphenylmethane diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

[0117] Aromatic polyisocyanate compounds include, for example, aromatic polyisocyanate compounds, polymers of aromatic polyisocyanate compounds, adducts of aromatic polyisocyanate compounds and polyol compounds, and biuret compounds of aromatic polyisocyanate compounds. Specific examples of aromatic polyisocyanate compounds include tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), 4,4'-diphenylmethane diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

[0118] Aromatic polyisocyanate compounds are preferred as the polyisocyanate compounds. Furthermore, xylylene diisocyanate compounds are preferred as the aromatic polyisocyanate compounds. Xylylene diisocyanate compounds include, for example, XDI, polymers of XDI, adducts of XDI and polyol compounds, and biuret compounds of XDI. Among the xylylene diisocyanate compounds, adducts of XDI and TMP are preferred.

[0119] Commercially available isocyanate-based crosslinking agents can be used. Examples of commercially available isocyanate-based crosslinking agents include "Coronate® HX", "Coronate® HL-S", "Coronate® L", "Coronate® L-45E", "Coronate® 2031", "Coronate® 2037", "Coronate® 2234", "Coronate® 2785", "Aquanate® 200", and "Aquanate® 210" [all manufactured by Tosoh Corporation], "Sumijoule® N3300", "Desmodule® N3400", and "Sumijoule® N75" [all manufactured by Sumika Covestro Urethane Co., Ltd.], "Duranate® D201", "Duranate® E405-70B", "Duranate® E405-80T", and "Duranate® Examples include "AE700-100", "Duranate® 24A-100", and "Duranate® TSE-100" (all manufactured by Asahi Kasei Corporation), as well as "Takenate® D-110N", "Takenate® D-101E (45EA)", "Takenate® D-120N", "Takenate® D-140N", "Takenate® M-631N", "MT-Orestar® NP1200", and "Stavio® XD-340N" (all manufactured by Mitsui Chemicals, Inc.).

[0120] If the adhesive composition of this disclosure contains a crosslinking agent, it may contain only one crosslinking agent or two or more crosslinking agents.

[0121] If the adhesive composition of this disclosure contains a crosslinking agent, the content of the crosslinking agent is not particularly limited, but for example, from the viewpoint of suppressing shrinkage of the substrate over time and maintaining a good appearance, it is preferably 0.01 to 1.0 parts by mass, more preferably 0.1 to 0.7 parts by mass, and even more preferably 0.2 to 0.5 parts by mass per 100 parts by mass of the specific (meth)acrylic polymer (A).

[0122] [Organic solvents] The adhesive composition of this disclosure may contain an organic solvent. The adhesive composition of this disclosure may have improved applicability and pot life when it contains an organic solvent. Examples of organic solvents include those similar to those used in the polymerization reaction of the specific (meth)acrylic polymers described above.

[0123] If the adhesive composition of this disclosure contains an organic solvent, it may contain only one organic solvent or two or more organic solvents.

[0124] If the adhesive composition of this disclosure contains an organic solvent, the content of the organic solvent is not particularly limited and can be set as appropriate depending on the purpose.

[0125] [Other ingredients] The adhesive composition of this disclosure may, if necessary, contain components other than those described above (so-called other components), as long as they do not impair its effect. Other components include polymers other than specific (meth)acrylic polymers, crosslinking catalysts, tackifiers, antioxidants, colorants (e.g., dyes and pigments), light stabilizers (e.g., UV absorbers), antistatic agents, and various other additives.

[0126] If the adhesive composition of this disclosure contains other components, the content of these other components is not particularly limited and can be set as appropriate depending on the purpose.

[0127] <Application> The uses of the adhesive composition disclosed herein are not particularly limited. The adhesive composition of this disclosure can form an adhesive layer that exhibits easy peelability in the initial stages of bonding to an adherend and high adhesive strength after heating. Furthermore, the adhesive composition of this disclosure can form an adhesive layer that is less likely to cause wrinkles in the decorative film even when used in decorative molding heated to a temperature of around 110°C. Moreover, the adhesive composition of this disclosure is less likely to shift from the adherend even when heated to a temperature of around 110°C and has excellent holding power. Because the adhesive layer formed by the adhesive composition of this disclosure has the above-described properties, the adhesive composition of this disclosure is suitable, for example, as an adhesive composition used in decorative molding. Specific applications of the adhesive composition disclosed herein include, for example, bonding a decorative film to a molded product by decorative molding.

[0128] [Adhesive sheet] The adhesive sheet of this disclosure comprises an adhesive layer formed by the adhesive composition of this disclosure. Therefore, the adhesive sheet of this disclosure exhibits easy peelability to the adherend in the initial stages of bonding and high adhesive strength after heating. Furthermore, the adhesive sheet of this disclosure is less likely to cause wrinkles in the decorative film even when used in decorative molding heated to a temperature of around 110°C. Moreover, the adhesive sheet of this disclosure is less likely to shift from the adherend even when heated to a temperature of around 110°C and exhibits excellent holding power. The adhesive layer of the adhesive sheet of the present disclosure includes a cured product of the adhesive composition of the present disclosure. If the adhesive composition of the present disclosure includes a crosslinking agent, the cured product includes, for example, crosslinked products of a specific (meth)acrylic polymer (A) and a specific (meth)acrylic polymer (B) that have been crosslinked and cured by the crosslinking agent.

[0129] The thickness of the adhesive layer of the adhesive sheet of this disclosure is not particularly limited. The thickness of the adhesive layer is preferably, for example, 1 μm to 100 μm, more preferably 5 μm to 75 μm, and even more preferably 5 μm to 50 μm.

[0130] In this disclosure, "thickness of the adhesive layer" refers to the average thickness of the adhesive layer. The average thickness of the adhesive layer is determined by the following method. The thickness of the adhesive layer is measured at 10 randomly selected locations in the thickness direction using a film thickness gauge. The arithmetic mean of the measured values ​​is calculated, and this value is taken as the average thickness of the adhesive layer.

[0131] The adhesive sheet of this disclosure may be a non-substrate type adhesive sheet without a substrate, or a substrate type adhesive sheet having an adhesive layer on one or both sides of a substrate. If the adhesive sheet of the present disclosure is a non-substrate type adhesive sheet without a substrate, or a substrate type adhesive sheet having an adhesive layer on one side of a substrate, the exposed surface of the adhesive layer in the adhesive sheet of the present disclosure may be protected by a release sheet. Generally, a release liner protects the surface of the adhesive layer until the adhesive sheet is put into practical use, and is peeled off when in use.

[0132] The release sheet is not particularly limited as long as it can be easily peeled off from the adhesive layer. Examples of release sheets include resin films, paper, synthetic paper, and composite sheets made by laminating two or more of these materials, all of which have been surface-treated with a release agent on one or both sides (so-called easy-peel treatment). In this disclosure, a release sheet in which one or both sides of a resin film are subjected to a surface treatment with a release agent (so-called easy-release treatment) is also referred to as a "release film." Examples of release agents include silicone-based release agents (e.g., silicone), wax-based release agents (e.g., paraffin wax), and fluorine-based release agents (e.g., fluorine-based resins). Examples of resin films include polyester films, such as polyethylene terephthalate (PET) film. Examples of paper include high-quality paper and coated paper. The film thickness of the release sheet is not particularly limited, but is generally between 20 μm and 180 μm.

[0133] If the adhesive sheet of this disclosure includes a substrate, the substrate is not particularly limited as long as it is capable of forming an adhesive layer thereon. Examples of substrates include films containing resins such as polyolefins (e.g., polyethylene (PE) and polypropylene (PP)), polyesters (e.g., polyethylene terephthalate (PET)), acetate resins (e.g., triacetylcellulose), polyethersulfone, polycarbonate (PC), polyamide (PA), polyimide (PI), polyurethane, acrylic resin, polyvinyl chloride (PVC), acrylonitrile / butadiene / styrene resin (ABS resin), and fluororesins.

[0134] The side of the substrate on which the adhesive layer is provided may be subjected to surface treatment such as corona discharge treatment or plasma discharge treatment (so-called easy-adhesion treatment) from the viewpoint of improving the adhesion between the substrate and the adhesive layer.

[0135] The base material may contain various additives such as plasticizers, colorants (e.g., dyes and pigments), heat stabilizers, light stabilizers, antistatic agents, flame retardants, antioxidants, and fillers. The base material may have a pattern applied to part or all of it. When the adhesive sheet of this disclosure is used for decorative molding, the base material is preferably a decorative film. In this case, a preferred embodiment of the adhesive sheet of this disclosure comprises a decorative film and an adhesive layer provided on at least one side of the decorative film and formed from the adhesive composition of this disclosure.

[0136] The thickness of the substrate is not particularly limited, but is preferably 10 μm to 500 μm, more preferably 10 μm to 300 μm, even more preferably 10 μm to 200 μm, and particularly preferably 10 μm to 100 μm.

[0137] In this disclosure, "thickness of the substrate" refers to the average thickness of the substrate. The average thickness of the substrate is determined by the following method. The thickness of the substrate is measured at 10 randomly selected locations in the thickness direction using a film thickness gauge. The arithmetic mean of the measured values ​​is calculated, and this value is taken as the average thickness of the substrate.

[0138] [Method for making adhesive sheets] The method for producing the adhesive sheet described herein is not particularly limited. The adhesive sheet of this disclosure can be manufactured by known methods. Examples of methods for producing the adhesive sheet of this disclosure include the following:

[0139] If the adhesive sheet of this disclosure is a non-substrate type adhesive sheet, first, the adhesive composition of this disclosure is applied to the easily peelable surface of the 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. Then, the exposed surface of the formed adhesive film is placed on top of the easily peelable surface of a separately prepared release sheet and bonded together, and then curing is performed as necessary to produce the adhesive sheet of this disclosure having a laminated structure of release sheet / adhesive layer / release sheet.

[0140] If the adhesive sheet of this disclosure is a substrate-type adhesive sheet, first, the adhesive composition of this disclosure is applied to the easily adhesive treated surface of the substrate to form a coating film on the substrate. Next, the formed coating film is dried to form an adhesive film on the substrate. Then, the exposed surface of the formed adhesive film is placed on top of the easily peeled surface of the release sheet and bonded together, and then curing is performed as necessary to produce the adhesive sheet of this disclosure having a laminated structure of substrate / adhesive layer / release sheet.

[0141] If the adhesive sheet of this disclosure is a substrate-type adhesive sheet, another method, for example, is as follows: The adhesive composition of this disclosure is applied to the easily peelable surface of a release sheet to form a coating film on the release sheet. Then, 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 placed on top of the easily adhesive surface of the substrate and bonded together, and then curing is performed as necessary to produce the adhesive sheet of this disclosure having a laminated structure of substrate / adhesive layer / release sheet.

[0142] The method of applying the adhesive composition is not particularly limited. Examples of known methods for applying adhesive compositions include gravure roll coaters, reverse roll coaters, kiss roll coaters, dip roll coaters, knife coaters, spray coaters, bar coaters, applicators, and the like. The amount of adhesive composition applied is not particularly limited and can be appropriately set, for example, depending on the thickness of the adhesive layer to be formed.

[0143] The method for drying the coating film is not particularly limited. Methods for drying the coated film include, for example, natural drying, heat drying, hot air drying, and vacuum drying. The drying temperature and drying time of the coating film are not particularly limited and are set appropriately according to the thickness of the coating film, the amount of organic solvent in the coating film, etc. One example of drying conditions is to use a hot air circulation dryer and dry at 60°C to 120°C for 30 to 180 seconds.

[0144] When curing is performed, one possible method is to leave the product undisturbed for 2 to 7 days in an environment with an ambient temperature of 20°C to 35°C and a relative humidity of 45% to 55% (i.e., 45%RH to 55%RH). [Examples]

[0145] The adhesive compositions and adhesive sheets of this disclosure will be described in more detail below with reference to examples. This disclosure is not limited to the following examples unless it exceeds the spirit of the disclosure.

[0146] [Production of (meth)acrylic polymer (A)] [Manufacturing example A-3] 116.0 parts by mass of ethyl acetate [organic solvent for polymerization] was charged into a reaction vessel equipped with a stirrer, reflux condenser, sequential dropper, and thermometer. Next, 71.0 parts by mass of n-butyl acrylate [n-BA], 9.0 parts by mass of methyl acrylate [MA], and 20.0 parts by mass of 2-hydroxyethyl acrylate [2HEA] were added to a separate container and mixed to prepare a monomer mixture. 20% by mass of the prepared monomer mixture was added to the reaction vessel. Next, the monomer mixture in the reaction vessel was heated while stirring and refluxed at reflux temperature for 10 minutes. Then, under reflux temperature conditions, the remaining 80% by mass of the monomer mixture, 45.0 parts by mass of ethyl acetate [organic solvent for polymerization], and 0.026 parts by mass of 2,2'-azobis(2,4-dimethylvaleronitrile) [ABVN; polymerization initiator] were sequentially added dropwise over 120 minutes. After the dropwise addition was complete, the mixture was allowed to react for 30 minutes to complete the reaction. The solution after the reaction was diluted with ethyl acetate to a solid content concentration of 32% by mass to obtain a solution of (meth)acrylic polymer A-3.

[0147] Here, "solids concentration" refers to the mass ratio of (meth)acrylic polymer A-3 to the solution of (meth)acrylic polymer A-3. The same applies to the solutions of (meth)acrylic polymers A-1, A-2, and A-4 to A-7 prepared below.

[0148] [Manufacturing examples A-1, A-2, and A-4~A-7] In production examples A-1, A-2, and A-4 to A-7, the monomer composition of the (meth)acrylic polymer was changed to the monomer composition shown in Table 1, and the weight-average molecular weight of the (meth)acrylic polymer was adjusted to the weight-average molecular weight shown in Table 1 by adjusting at least one of the amount of organic solvent used and the amount of polymerization initiator used. The same procedure as in production example A-3 was followed to obtain solutions of (meth)acrylic polymers A-1, A-2, and A-4 to A-7, each with a solid content concentration of 32% by mass.

[0149] Table 1 shows the monomer composition [unit: mass%], glass transition temperature (denoted as "Tg") [unit: °C], and weight-average molecular weight (denoted as "Mw") of (meth)acrylic polymers A-1 to A-7.

[0150] The glass transition temperatures of (meth)acrylic polymers A-1 to A-7 were determined using the same method as described above for determining the glass transition temperature of the specific (meth)acrylic polymer (A). The weight-average molecular weights of (meth)acrylic polymers A-1 to A-7 were measured using the same method as the method for measuring the weight-average molecular weight of the specific (meth)acrylic polymer (A) described above.

[0151] Of the (meth)acrylic polymers A-1 to A-7, (meth)acrylic polymers A-1 to A-3 and A-5 to A-7 correspond to the specified (meth)acrylic polymer (A) in this disclosure.

[0152] [Table 1]

[0153] Details of each monomer listed in Table 1 are as follows: <(meth)acrylate alkyl monomer> "n-BA": n-butyl acrylate [Tg when homopolymer: -54℃] "2EHA": 2-ethylhexyl acrylate [Tg when used as a homopolymer: -70°C] "MA": Methyl acrylate [Tg: 10°C when used as a homopolymer] "MMA": Methyl methacrylate [Tg: 105°C when used as a homopolymer] <Monomers containing hydroxyl groups> "2HEA": 2-hydroxyethyl acrylate [Tg when used as a homopolymer: -15℃]

[0154] In Table 1, a "-" in the monomer composition column indicates that the monomer corresponding to that column was not used.

[0155] [(Meth)acrylic polymer (B) production] [Manufacturing example B-1] 67.5 parts by mass of ethyl acetate [organic solvent for polymerization] was charged into a reaction vessel equipped with a stirrer, reflux condenser, sequential dropper, and thermometer. Next, 0.1 parts by mass of an organosiloxane monomer [product name: Cyraplane® FM-0721, number average molecular weight: 5000, manufactured by JNC Corporation], 55.0 parts by mass of methyl methacrylate [MMA], 34.9 parts by mass of n-butyl methacrylate [n-BMA], 10.0 parts by mass of ethyl acrylate [EA], 1.58 parts by mass of 2,2'-azobis(isobutyrate)dimethyl [polymerization initiator], and 150 parts by mass of ethyl acetate [organic solvent for polymerization] were added to a separate container and mixed to prepare a solution containing the monomer mixture. This prepared solution was sequentially added dropwise to the reaction vessel over 180 minutes under reflux temperature conditions. After the addition was complete, the mixture was allowed to react for another 180 minutes to complete the reaction. The solution after the reaction was completed was diluted with ethyl acetate to a solid content concentration of 35% by mass to obtain a solution of (meth)acrylic polymer B-1.

[0156] Here, "solids concentration" refers to the mass ratio of (meth)acrylic polymer B-1 to the solution of (meth)acrylic polymer B-1. The same applies to the solutions of (meth)acrylic polymers B-2 to B-14 prepared below.

[0157] [Manufacturing examples B-2 to B-6 and B-10 to B-14] In production examples B-2 to B-6 and B-10 to B-14, the same procedure as in production example B-1 was followed, except that the monomer composition of the (meth)acrylic polymer was changed to the monomer composition shown in Table 2, to obtain solutions of (meth)acrylic polymers B-2 to B-6 and B-10 to B-14, each with a solid content concentration of 35% by mass.

[0158] [Manufacturing examples B-7 to B-9] In production examples B-7 to B-9, the monomer composition of the (meth)acrylic polymer was changed to the monomer composition shown in Table 2, and the weight-average molecular weight of the (meth)acrylic polymer was adjusted to the weight-average molecular weight shown in Table 2 by adjusting at least one of the amount of organic solvent used and the amount of polymerization initiator used. The same procedure as in production example B-1 was followed to obtain solutions of (meth)acrylic polymers B-7 to B-9, each with a solid content concentration of 35% by mass.

[0159] Table 2 shows the monomer composition [unit: mass%] and weight-average molecular weight (indicated as "Mw") of (meth)acrylic polymers B-1 to B-14. Note that the glass transition temperatures of all (meth)acrylic polymers B-1 to B-14 are 0°C or higher.

[0160] The weight-average molecular weights of (meth)acrylic polymers B-1 to B-14 were measured using the same method as the method for measuring the weight-average molecular weight of the specific (meth)acrylic polymer (A) described above.

[0161] Of the (meth)acrylic polymers B-1 to B-14, (meth)acrylic polymers B-1 to B-11 and B-14 correspond to the specified (meth)acrylic polymer (B) in this disclosure.

[0162] [Table 2]

[0163] Details of each monomer listed in Table 2 are as follows. <Monomers containing an organosiloxane skeleton> "FM-0721" [Product name: Cyraplane (registered trademark) FM-0721, number average molecular weight: 5000, compound represented by formula (1), manufactured by JNC Corporation] "FM-0725" [Product name: Cyraplane (registered trademark) FM-0725, number average molecular weight: 10000, compound represented by formula (1), manufactured by JNC Corporation] "X-22-174ASX" [Trade name, number-average molecular weight: 1200, compound represented by formula (1), manufactured by Shin-Etsu Chemical Co., Ltd.]

[0164] <Alkyl (meth)acrylate monomers with a glass transition temperature of 40°C or higher when used as a homopolymer> "MMA": Methyl methacrylate [Tg: 105°C when used as a homopolymer] "i-BMA": i-butyl methacrylate [Tg: 53°C when used as a homopolymer] <Alkyl (meth)acrylate monomers with a glass transition temperature of less than 40°C when used as a homopolymer> "n-BMA": n-butyl methacrylate [Tg: 20°C when used as a homopolymer] "EA": Ethyl acrylate [Tg when homopolymer: -22°C]

[0165] In Table 2, a "-" in the monomer composition column indicates that the monomer corresponding to that column was not used.

[0166] [Preparation of adhesive composition] [Example 1] The adhesive composition of Example 1 was obtained by thoroughly mixing 25.0 parts by mass (100 parts by mass as solids) of a solution of (meth)acrylic polymer A-3, 10.53 parts by mass (50 parts by mass as solids) of a solution of (meth)acrylic polymer B-1, and 0.04 parts by mass (0.4 parts by mass as solids) of a crosslinking agent [product name: Takenate® D-110N, xylylene diisocyanate (XDI), solid content concentration: 75% by mass, manufactured by Mitsui Chemicals, Inc.].

[0167] [Examples 2-19] Except for changing the composition of the adhesive composition to the composition shown in Table 3, the same procedure as in Example 1 was followed to obtain the adhesive compositions of Examples 2 to 19.

[0168] [Comparative Examples 1-4] The same procedure as in Example 1 was followed, except that the composition of the adhesive composition was changed to the composition shown in Table 4, to obtain the adhesive compositions of Comparative Examples 1 to 4.

[0169] [Preparation of adhesive sheets for evaluation] The adhesive composition prepared above was applied to the easily-peeled surface of a release film [product name: Film Vina®, model number: 100E-0010 No.23, thickness: 100 μm, manufactured by Fujimori Kogyo Co., Ltd.] using an applicator to form a coated film with a dry thickness of 20 μm. Next, the formed coated film was dried in a hot air circulation dryer under drying conditions of a drying temperature of 100°C and a drying time of 1 minute to form an adhesive film on the release film. Then, the surface with the exposed adhesive film was laminated onto the untreated surface of a separately prepared polyethylene terephthalate (PET) film [product name: Teijin® Tetron® Film, model number: G2P2, thickness: 50 μm, manufactured by Teijin Film Solutions Ltd.], and then cured for 4 days in an environment of 23°C and 50% RH to obtain an adhesive sheet for evaluation. The resulting evaluation adhesive sheet has a laminated structure consisting of a release film, an adhesive layer, and a PET film.

[0170] [Measurement and Evaluation] 1. Adhesion to the adherend (1) Initial adhesive strength (N1) The evaluation adhesive sheet prepared as described above was cut to a size of 25 mm x 150 mm to prepare evaluation adhesive sheet pieces. The release film was peeled off from the prepared evaluation adhesive sheet pieces [composition: release film / adhesive layer / PET film]. After the adhesive layer surface exposed by peeling was attached to a stainless steel (so-called SUS) plate, a 2 kg roller was rolled back and forth once to press it down and obtain test piece X-1. The obtained test piece X-1 was left to stand for 30 minutes in an environment with an ambient temperature of 23°C and 50% RH. For the test piece X-1 after standing, the adhesive strength (unit: N / 25 mm) when the evaluation adhesive sheet piece [composition: adhesive layer / PET film] was peeled from the SUS plate at a 180° angle in the long side (150 mm) direction was measured using a single-column type material testing machine (model number: STA-1225) manufactured by A&D Co., Ltd., under conditions of an ambient temperature of 23°C and 50% RH and a peeling speed of 300 mm / min. The evaluation was then conducted according to the following evaluation criteria. The measured and evaluated results of the adhesive strength are shown in Tables 3 and 4. If the evaluation result is "A" or "B", the adhesive layer is evaluated as exhibiting slight peelability in the initial stages of bonding to the substrate. An evaluation result of "A" is most preferable.

[0171] -Evaluation Criteria- A: The adhesive strength is 0.01 N / 25 mm or more and less than 0.40 N / 25 mm. B: The adhesive strength is 0.40 N / 25 mm or more and less than 1.00 N / 25 mm. C: The adhesive strength is 1.00 N / 25 mm or more.

[0172] (2) Adhesion after heating (N2) The evaluation adhesive sheet prepared as described above was cut to a size of 25 mm x 150 mm to prepare evaluation adhesive sheet pieces. The release film was peeled off from the prepared evaluation adhesive sheet pieces [composition: release film / adhesive layer / PET film]. The surface of the adhesive layer exposed by peeling was attached to a stainless steel (so-called SUS) plate, and then pressed down by passing a 2 kg roller back and forth once to obtain test piece X-2. The obtained test piece X-2 was left to stand in a dryer set at a temperature of 80°C for 5 minutes, and then removed from the dryer. Next, the removed test piece X-2 was left to stand for 30 minutes in an environment with an ambient temperature of 23°C and 50% RH. For test specimen X-2 after standing, the adhesive strength (unit: N / 25mm) was measured when an evaluation adhesive sheet [composition: adhesive layer / PET film] was peeled off from the SUS plate at a 180° angle along the long side (150mm) using a single-column type material testing machine (model number: STA-1225) manufactured by A&D Co., Ltd., under ambient temperature of 23°C, 50% RH, and peeling speed of 300mm / min. The measured values ​​of the adhesive strength are shown in Tables 3 and 4.

[0173] (3) Adhesion after heating (N3) The evaluation adhesive sheet prepared as described above was cut to a size of 25 mm x 150 mm to prepare evaluation adhesive sheet pieces. The release film was peeled off from the prepared evaluation adhesive sheet pieces [composition: release film / adhesive layer / PET film]. The surface of the adhesive layer exposed by peeling was attached to a stainless steel (so-called SUS) plate, and then pressed down by passing a 2 kg roller back and forth once to obtain test piece X-3. The obtained test piece X-3 was left to stand in a dryer set at a temperature of 110°C for 5 minutes, and then removed from the dryer. Next, the removed test piece X-3 was left to stand for 30 minutes in an environment with an ambient temperature of 23°C and 50% RH. For test specimen X-3 after standing, the adhesive strength (unit: N / 25mm) was measured when an evaluation adhesive sheet [composition: adhesive layer / PET film] was peeled off from the SUS plate at a 180° angle along the long side (150mm) using a single-column type material testing machine (model number: STA-1225) manufactured by A&D Co., Ltd., under ambient temperature of 23°C, 50% RH, and peeling speed of 300mm / min. The evaluation was then performed according to the evaluation criteria below. The measured and evaluated results of the adhesive strength are shown in Tables 3 and 4. If the evaluation result is "A" or "B", the adhesive layer is evaluated as exhibiting high adhesion to the adherend after heating. An evaluation result of "A" is most preferable.

[0174] -Evaluation Criteria- A: The adhesive strength is 7.0 N / 25 mm or more. B: The adhesive strength is 4.5 N / 25 mm or more and less than 7.0 N / 25 mm. C: The adhesive strength is less than 4.5 N / 25 mm.

[0175] Based on the measurements obtained in "(1) Initial adhesive strength (N1)", "(2) Adhesion strength after heating (N2)", and "(3) Adhesion strength after heating (N3)" above, "N2 / N1" and "N3 / N2" were calculated. The calculated values ​​were rounded to one decimal place by rounding to two decimal places.

[0176] 2.Holding power The evaluation adhesive sheet prepared as described above was cut to a size of 25 mm x 150 mm to prepare evaluation adhesive sheet pieces. A portion of the release film was peeled off from the prepared evaluation adhesive sheet piece [composition: release film / adhesive layer / PET film]. The surface of the adhesive layer exposed by peeling was attached to a stainless steel (so-called SUS) plate so that the bonding area was 10 mm x 25 mm, and then pressed down using a 2 kg roller to obtain test piece X-4. The obtained test piece X-4 was left to stand in a dryer set at a temperature of 110°C for 5 minutes, and then removed from the dryer. Next, a 1 kg weight was suspended from the evaluation adhesive sheet piece attached to the stainless steel plate of the removed test piece X-4, and with a static load of 1 kg applied in the long side (150 mm) direction, it was left in a constant temperature bath set at a temperature of 80°C for 1 hour. After the period of time, the distance of displacement of the evaluation adhesive sheet piece from the stainless steel plate (i.e., the distance the evaluation adhesive sheet piece moved) was measured. The evaluation was then conducted according to the following evaluation criteria. The measured distances traveled and the results of the evaluation are shown in Tables 3 and 4. If the evaluation result is "A" or "B", the adhesive layer is evaluated as having excellent holding power and is less likely to shift from the bonded substrate even when heated to 110°C. An evaluation result of "A" is most preferable.

[0177] -Evaluation Criteria- A: The distance traveled by the evaluation adhesive sheet is 0 mm. B: The distance traveled by the evaluation adhesive sheet is between 0 mm and 5 mm. C: The distance traveled by the evaluation adhesive sheet piece exceeds 5 mm.

[0178] 3. Wrinkles during molding The adhesive composition prepared above was applied to the easily peelable surface of a release film (product name: Film Vina®, model number: 100E-0010 No.23, thickness: 100 μm, manufactured by Fujimori Kogyo Co., Ltd.) using an applicator to form a coated film with a dry thickness of 20 μm. The formed coated film was then dried in a hot air circulation dryer at a drying temperature of 100°C for a drying time of 1 minute to form an adhesive film on the release film. The side with the exposed adhesive film was then laminated onto a polyvinyl chloride (PVC) film (thickness: 50 μm, manufactured by Nippon Carbide Industries Co., Ltd.), and cured for 4 days in an environment of 23°C and 50% RH to obtain an adhesive sheet for wrinkle evaluation. The obtained adhesive sheet for wrinkle evaluation has a laminated structure of release film / adhesive layer / PVC film.

[0179] The obtained adhesive sheet for wrinkle evaluation was cut to a size of 100 mm x 100 mm to prepare adhesive sheet pieces for wrinkle evaluation. The release film was peeled off the prepared adhesive sheet pieces for wrinkle evaluation [composition: release film / adhesive layer / PVC film]. Next, using a forming machine (480 type) manufactured by Seikou Sangyo Co., Ltd., the adhesive sheet pieces from which the release film had been peeled off were used to coat the surface of a three-dimensional structure made of acrylonitrile / butadiene / styrene resin (ABS resin) with a hemispherical shape of 30 mm radius at a surface elongation rate of 300%, and a molded body was produced by raising the molding temperature to 110°C. The presence and degree of wrinkle formation during the production of the molded body were observed visually and evaluated according to the evaluation criteria below. The evaluation results are shown in Tables 3 and 4. If the evaluation result is "A" or "B", the adhesive layer is evaluated as being less prone to wrinkles during molding. An evaluation result of "A" is most preferable.

[0180] -Evaluation Criteria- A: No wrinkles are visible at all. B: Slight wrinkles are visible. C: Large wrinkles are visible.

[0181] [Table 3]

[0182] [Table 4]

[0183] In Tables 3 and 4, the values ​​listed in the "Amount" column are all based on solid content.

[0184] As shown in Table 3, the adhesive layers formed by the adhesive compositions of Examples 1 to 19 were found to exhibit easy peelability to the adherend initially, and high adhesive strength after heating. Furthermore, the adhesive layers formed by the adhesive compositions of Examples 1 to 19 were found to be less prone to wrinkling of the substrate even when heated to a temperature of around 110°C. In addition, the adhesive layers formed by the adhesive compositions of Examples 1 to 19 were found to be less prone to shifting from the adherend even when heated to a temperature of around 110°C, demonstrating excellent holding power. On the other hand, as shown in Table 4, the adhesive layers formed by the adhesive compositions of Comparative Examples 1 to 4 exhibited slight peelability to the adherend in the initial stages of bonding and high adhesive strength after heating, but it was confirmed that they tended to cause wrinkles in the substrate when heated to a temperature of around 110°C.

Claims

1. A (meth)acrylic polymer (A) having a glass transition temperature of less than 0°C, A (meth)acrylic polymer (B) comprising constituent units derived from monomers having an organosiloxane skeleton and constituent units derived from alkyl (meth)acrylate monomers having a glass transition temperature of 40°C or higher when formed as a homopolymer, wherein the content of constituent units derived from alkyl (meth)acrylate monomers is in the range of 10% by mass or more and 80% by mass or less of the total constituent units, the content of constituent units derived from monomers having an organosiloxane skeleton is in the range of 0.1% by mass or more and 10.0% by mass or less of the total constituent units, and the glass transition temperature is 0°C or higher, Isocyanate-based crosslinking agents, Includes, The number-average molecular weight of the monomer having the organosiloxane skeleton in the (meth)acrylic polymer (B) is in the range of 4,000 or more and less than 20,000. The content of the (meth)acrylic polymer (B) is in the range of 20 parts by mass or more and 100 parts by mass or less per 100 parts by mass of the (meth)acrylic polymer (A), An adhesive composition that, when an adhesive layer with a thickness of 20 μm is formed, satisfies the following requirements (a) to (c). (a) 0.01N / 25mm≦N1<1.0N / 25mm (b) N2 / N1<2.0 (c) 10.0≦N3 / N2 In (a) to (c) above, N1 indicates the adhesive strength after the adhesive layer is bonded to the stainless steel 430 and left to stand for 30 minutes in an environment with an ambient temperature of 23°C, N2 indicates the adhesive strength after the adhesive layer is bonded to the stainless steel 430, left to stand for 5 minutes in an environment with an ambient temperature of 80°C, and then left to stand for 30 minutes in an environment with an ambient temperature of 23°C, and N3 indicates the adhesive strength after the adhesive layer is bonded to the stainless steel 430, left to stand for 5 minutes in an environment with an ambient temperature of 110°C, and then left to stand for 30 minutes in an environment with an ambient temperature of 23°C. N1, N2 and N3 are the adhesive strengths when the adhesive layer is peeled off the stainless steel 430 at a peeling speed of 300 mm / min in the 180° direction in accordance with JIS Z0237:2009.

2. The adhesive composition according to claim 1, wherein the monomer having an organosiloxane skeleton is a compound represented by the following formula (1). 【Chemistry 1】 In formula (1), R １ R represents a hydrogen atom or a methyl group. ２ m represents a monovalent organic group. m and n each independently represent non-negative integers, but m and n cannot both represent 0 at the same time.

3. An adhesive sheet comprising an adhesive layer formed by the adhesive composition according to claim 1 or claim 2.

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