Adhesive composition and adhesive tape

Abstract

To provide an adhesive composition capable of forming an adhesive layer that exhibits light peelability from an adherend in the initial stage of bonding, displays high adhesive strength after heating, efficiently inhibits the entry of bubbles from the adherend, and ensures that the initial-stage light peelability of an adhesive tape from its own backing remains stable over time.SOLUTION: An adhesive composition includes a polymer A with a Tg of lower than 0°C, which includes a hydroxy group-containing monomer unit, a polymer B which includes 0.1-10 mass% of an organosiloxane skeleton-containing monomer unit, more than 50 mass % and 85 mass% or less of an alkyl (meth)acrylate monomer unit where the homopolymer has a Tg of 40°C or higher, and 0.01-0.5 mass% of a (meth)acrylic acid unit, wherein the Mw is 10000-400000 and Tg is 0°C or higher, and an HMDI compound and / or XDI compound. In the polymer B, the organosiloxane skeleton-containing monomer unit has an Mn of 4000 or more and less than 20000. The content of the polymer B is more than 20 pts.mass to 100 pts.mass or less relative to 100 pts.mass of the polymer A.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Conventionally, adhesives have been used to fix articles to a substrate. For adhesives used when it is difficult to fix the position of an article to a substrate and there is a possibility of repositioning, it is necessary to be able to form an adhesive layer that exhibits slight peelability in the initial stages of bonding and then exhibits 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 the adhesive layer is bonded to stainless steel (430BA plate) and left 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 is 3.0 [N / 20mm] or more, and the N2 / N1 ratio is 5.0 or more. According to the adhesive sheet described in Patent Document 1, the adhesive strength of the adhesive layer is low immediately after bonding, making it easy to reposition, and the adhesive strength of the adhesive layer increases over time, allowing for firm fixation. Furthermore, Patent Document 2 discloses an adhesive composition comprising 100 parts by mass of polymer (A) having a glass transition temperature of less than 0°C, and 0.1 to 20 parts by mass of polymer (B) containing monomer units of monomer (B1) having a polyorganosiloxane skeleton with a functional group equivalent of 1000 g / mol or more and 4600 g / mol or less, and monomer (B2) having a homopolymer glass transition temperature of 40°C or more, and having a weight-average molecular weight of 10000 or more and less than 100000, wherein polymer (B) contains 10% to 20% by mass of monomer (B1) and 30% to 50% by mass of monomer (B2). According to the adhesive composition described in Patent Document 2, the adhesive strength is low enough to allow rework in the initial stages of application, and after time has passed, it can adhere firmly to the adherend. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2015 / 163115 [Patent Document 2] Japanese Patent Publication No. 2017-203164 [Overview of the project] [Problems that the invention aims to solve]

[0005] In recent years, the development of products that address environmental issues has progressed, and environmental considerations are also required in the field of adhesives. For example, single-sided adhesive tapes generally have a release film to protect the surface of the adhesive layer until it is put into practical use. However, by creating an adhesive tape without a release film (hereinafter also called "separator-less adhesive tape"), for example, an adhesive tape in which the exposed surface of the adhesive layer formed on one side of the base material is brought into contact with the other side of the base material and wound into a roll, it is possible to reduce waste. However, adhesive layers formed with temperature-sensitive adhesives tend to increase in adhesive strength over time, so if a separator-less adhesive tape is used, the adhesive strength of the adhesive layer may increase during storage, making it difficult to peel the adhesive layer from the back of the adhesive tape.

[0006] Incidentally, in adhesive layers formed with temperature-sensitive adhesives, heating increases the adhesive strength. However, if heating is performed after bonding to the substrate, depending on the material of the substrate, outgassing (so-called volatile gas) may occur, causing air bubbles to be incorporated into the adhesive layer. The inclusion of air bubbles in the adhesive layer not only impairs the appearance but can also cause the adhesive layer to peel off the substrate.

[0007] 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 tape that provides an adhesive layer that exhibits easy peelability in the initial stages of bonding to an adherend and high adhesive strength after heating, which can effectively suppress the incorporation of air bubbles originating from outgassing generated from the adherend, and in addition, when used as a separator-less adhesive tape, can form an adhesive layer in which the easy peelability in the initial stages of bonding to the back surface of the adhesive tape is not easily impaired over time. [Means for solving the problem]

[0008] The following are examples of specific means for solving the problem: <1> A (meth)acrylic polymer (A) containing constituent units derived from monomers having hydroxyl groups and having a glass transition temperature of less than 0°C, and a (meth)acrylic polymer (A) containing constituent units derived from monomers having an organosiloxane skeleton in a range of 0.1% to 10% by mass relative to the total constituent units, constituent units derived from alkyl (meth)acrylate monomers having a glass transition temperature of 40°C or higher when homopolymerized in a range of more than 50% to 85% by mass relative to the total constituent units, and constituent units derived from (meth)acrylic acid in a range of 0.01% to 0.5% by mass relative to the total constituent units, wherein the weight-average molecular weight is An adhesive composition comprising a (meth)acrylic polymer (B) having a number average molecular weight in the range of 10,000 to 400,000 and a glass transition temperature of 0°C or higher, and at least one compound selected from hexamethylene diisocyanate compounds and xylylene diisocyanate compounds, wherein 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 to less than 20,000, and the content of the (meth)acrylic polymer (B) is in the range of more than 20 parts by mass and 100 parts by mass or less per 100 parts by mass of the (meth)acrylic polymer (A).

[0009] <2> The monomer having the above organosiloxane skeleton is a compound represented by the following formula (1). <1> The adhesive composition described above.

[0010] [ka]

[0011] In formula (1), R 1 R represents a hydrogen atom or a methyl group. 2 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.

[0012] <3> A base material, and provided on one surface of the base material, <1> or <2> An adhesive tape comprising an adhesive layer formed by the adhesive composition described above. <4> The adhesive tape according to <3>, which is a roll body formed by laminating the surface of the adhesive layer opposite to the base material and the other surface of the base material in contact with each other.

Advantages of the Invention

[0013] According to an embodiment of the present disclosure, there is provided an adhesive composition capable of forming an adhesive layer that exhibits low peelability at the initial stage of bonding to an adherend and high adhesive strength after heating, can preferably suppress the incorporation of bubbles derived from outgassing generated from the adherend, and in addition, can form an adhesive layer in which the low peelability at the initial stage of bonding of the adhesive tape to its own back surface is hardly impaired over time when used as a separatorless type adhesive tape, and an adhesive tape.

Embodiments for Carrying Out the Invention

[0014] Hereinafter, the adhesive composition and adhesive tape of the present disclosure will be described in detail. The description of the requirements described below may be made based on typical 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.

[0015] 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 stepwise 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 stepwise descriptions. Also, 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.

[0016] In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment.

[0017] 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.

[0018] 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 structural units derived from a (meth)acrylic monomer and having a proportion of structural units derived from the (meth)acrylic monomer of 50% by mass or more.

[0019] 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”.

[0020] In the present disclosure, “n-” means normal, “i-” means iso, “s-” means secondary, and “t-” means tertiary.

[0021] In the present disclosure, the “back surface of the substrate” refers to the surface of the substrate on the side where the adhesive layer is not coated and formed.

[0022] [Adhesive Composition] The adhesive composition of this disclosure comprises a (meth)acrylic polymer (A) containing constituent units derived from monomers having hydroxyl groups and having a glass transition temperature of less than 0°C, and constituent units derived from monomers having an organosiloxane skeleton in an amount of 0.1% to 10% by mass relative to the total constituent units, constituent units derived from alkyl (meth)acrylate monomers having a glass transition temperature of 40°C or higher when homopolymerized in an amount of more than 50% to 85% by mass relative to the total constituent units, and constituent units derived from (meth)acrylic acid in an amount of 0.01% to 0.5% by mass relative to the total constituent units. The (meth)acrylic polymer (B) comprises a (meth)acrylic polymer (B) having a weight-average molecular weight in the range of 10,000 to 400,000 and a glass transition temperature of 0°C or higher, and at least one compound selected from hexamethylene diisocyanate compounds and xylylene diisocyanate compounds, wherein 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 to less than 20,000, and the content of the (meth)acrylic polymer (B) is in the range of more than 20 parts by mass and 100 parts by mass or less per 100 parts by mass of the (meth)acrylic polymer (A). The adhesive composition of this disclosure provides an adhesive layer that exhibits easy peelability in the initial stages of bonding to an adherend and high adhesive strength after heating, effectively suppressing the incorporation of air bubbles originating from outgassing generated from the adherend, and, in the case of a separator-less adhesive tape, forming an adhesive layer in which the easy peelability in the initial stages of bonding to the back surface of the adhesive tape is not easily impaired over time. The reason why the adhesive composition of this disclosure may produce such effects is not clear, but the inventors speculate as follows. However, the following speculation is not intended to be restrictive to the adhesive composition of this disclosure, but is provided as an example.

[0023] 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, the "adhesive surface of the adhesive layer" can refer to, for example, the interface between the adhesive layer and the adherend. In the case of separator-less adhesive tapes, the "adhesive surface of the adhesive layer" can refer to, for example, the interface between the adhesive layer and the back surface of the adhesive tape (for example, the back surface of the substrate). In the adhesive composition of this disclosure, by adjusting the content of constituent units derived from monomers having an organosiloxane skeleton in the (meth)acrylic polymer (B), and the content ratio of (meth)acrylic polymer (B) to (meth)acrylic polymer (A), it is possible to appropriately unevenly distribute the (meth)acrylic polymer (B) on the adhesive surface of the adhesive layer. The adhesive layer formed by the adhesive composition of this disclosure is presumed to exhibit slight peelability in the initial stages of bonding to adherends such as SUS because the (meth)acrylic polymer (B) is appropriately unevenly distributed on the adhesive surface. Furthermore, the adhesive layer formed by the adhesive composition of this disclosure is presumed to exhibit slight peelability in the initial stages of bonding to the back surface of the adhesive tape (for example, the back surface of the substrate) because the (meth)acrylic polymer (B) is appropriately unevenly distributed on the adhesive surface, and the cohesive force is not excessively high due to the appropriate inclusion of (meth)acrylic polymer (A), which has a relatively low glass transition temperature.

[0024] Furthermore, in the adhesive composition of this disclosure, the monomer composition of (meth)acrylic polymer (A) and (meth)acrylic polymer (B), the glass transition temperature of (meth)acrylic polymer (A), etc., are adjusted to maintain an appropriate uneven distribution of specific (meth)acrylic polymer (B) on the adhesive surface of the adhesive layer, and to adjust the hardness of the adhesive surface of the adhesive layer. The adhesive layer formed by the adhesive composition of this disclosure maintains an appropriate uneven distribution of (meth)acrylic polymer (B) on the adhesive surface, and the adhesive surface does not become excessively hard, so it is presumed that the initial easy peelability of the adhesive tape against its own back surface (e.g., the back surface of the substrate) is not easily impaired over time.

[0025] Furthermore, in the adhesive composition of this disclosure, the (meth)acrylic polymer (B) is appropriately unevenly distributed on the adhesive surface of the adhesive layer by adjusting the content of constituent units derived from monomers having an organosiloxane skeleton in the (meth)acrylic polymer (B) and the content ratio of the (meth)acrylic polymer (B) to the (meth)acrylic polymer (A), and the wetting spread of the adhesive layer onto the adherend when heated is adjusted by adjusting the weight-average molecular weight of the (meth)acrylic polymer (B). The adhesive layer formed by the adhesive composition of this disclosure is presumed to exhibit high adhesive strength after heating because the (meth)acrylic polymer (B) is not excessively unevenly distributed on the adhesive surface and wetting spreads onto the adherend when heated.

[0026] Furthermore, in the adhesive composition of this disclosure, the (meth)acrylic polymer (B), which contains constituent units derived from monomers having an organosiloxane skeleton, contains constituent units derived from (meth)acrylic acid having a carboxyl group, and the (meth)acrylic polymer (A) contains constituent units derived from monomers having a hydroxyl group. The crosslinking reaction is controlled by selecting a specific compound that functions as a crosslinking agent, namely, at least one compound selected from hexamethylene diisocyanate compounds and xylylene diisocyanate compounds. In the adhesive composition of this disclosure, it is considered that the crosslinking reaction of the (meth)acrylic polymer (B) having a carboxyl group proceeds before the crosslinking reaction of the (meth)acrylic polymer (A) having a hydroxyl group. Since the (meth)acrylic polymer (B), which is appropriately unevenly distributed on the adhesive surface of the adhesive layer, crosslinks before the (meth)acrylic polymer (A), outgassing generated from the adherend is blocked, and therefore, it is presumed that the adhesive layer formed by the adhesive composition of this disclosure can effectively suppress the incorporation of air bubbles.

[0027] On the other hand, the adhesive compositions in Patent Document 1 (International Publication No. 2015 / 163115) and Patent Document 2 (Japanese Patent Publication No. 2017-203164) are designed so that the adhesive strength of the adhesive layer can increase after a certain period of time, even under normal temperature conditions (i.e., temperatures between 5°C and 35°C). It is believed that Patent Documents 1 and 2 do not focus on making the adhesive tape a separator-less type. Furthermore, Patent Documents 1 and 2 do not focus on suppressing the inclusion of bubbles originating from outgassing generated from the adherend by controlling the crosslinking reaction.

[0028] In this disclosure, "(meth)acrylic polymer (A) containing constituent units derived from monomers having hydroxyl groups and 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 contains constituent units derived from monomers having an organosiloxane skeleton in an amount of 0.1% to 10% by mass relative to the total constituent units, constituent units derived from alkyl (meth)acrylate monomers having a glass transition temperature of 40°C or higher as a homopolymer in an amount of more than 50% to 85% by mass relative to the total constituent units, and constituent units derived from (meth)acrylic acid in an amount of 0.01% to 0.5% by mass relative to the total constituent units, having a weight-average molecular weight in the range of 10,000 to 400,000, and having 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 to 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."

[0029] [Specific (meth)acrylic polymer (A)] The adhesive composition of this disclosure includes a (meth)acrylic polymer (A) [i.e., a specific (meth)acrylic polymer (A)] which contains constituent units derived from monomers having hydroxyl groups and has a glass transition temperature of less than 0°C. The adhesive composition of this disclosure may contain only one specific (meth)acrylic polymer (A), or it may contain two or more specific polymers.

[0030] The specific (meth)acrylic polymer (A) may be a homopolymer or a copolymer, but it is preferably a copolymer.

[0031] <Constituent units derived from monomers containing hydroxyl groups> The specific (meth)acrylic polymer (A) contains 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.

[0032] 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.

[0033] 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.

[0034] The specific (meth)acrylic polymer (A) may contain only one or more constituent units derived from monomers having hydroxyl groups.

[0035] The content of constituent units derived from monomers having hydroxyl groups in the specific (meth)acrylic polymer (A) is not particularly limited, but for example, from the viewpoint of easily increasing the adhesive strength of the formed adhesive layer after heating, it is preferably in the range of 5% by mass or more and 25% by mass or less, more preferably in the range of 10% by mass or more and 25% by mass or less, and even more preferably in the range of 15% by mass or more and 25% by mass or less, relative to the total constituent units of the specific (meth)acrylic polymer (A).

[0036] <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.

[0037] 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.

[0038] 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), and methyl acrylate (MA) is preferred.

[0039] 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.

[0040] 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 95% by mass or less, more preferably in the range of 60% by mass or more and 90% by mass or less, and even more preferably in the range of 70% by mass or more and 85% 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).

[0041] <Constituent units derived from monomers containing a carboxyl group> The specific (meth)acrylic polymer (A) may contain structural units derived from monomers having a carboxyl group, but it is preferable that it does not. In this disclosure, "constituent unit derived from a monomer having a carboxyl group" means a constituent unit formed by the addition polymerization of monomers having a carboxyl group.

[0042] The type of monomer having a carboxyl group is not particularly limited. Examples of monomers having a carboxyl group include monomers having at least one carboxyl 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. Specific examples of monomers having a carboxyl group include (meth)acrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, glutaconic acid, citraconic acid, ω-carboxy-polycaprolactone mono(meth)acrylate [e.g., ω-carboxy-polycaprolactone (n≒2) monoacrylate], and succinic acid derivatives (e.g., 2-acryloyloxyethyl succinic acid).

[0043] The specified (meth)acrylic polymer (A) preferably does not contain any constituent units derived from monomers having a carboxyl group, or the content of constituent units derived from monomers having a carboxyl group is in the range of more than 0% by mass and 1% by mass or less relative to the total constituent units of the specified (meth)acrylic polymer (A). It is more preferable that it does not contain any constituent units derived from monomers having a carboxyl group, or the content of constituent units derived from monomers having a carboxyl group is in the range of more than 0% by mass and 0.5% by mass or less relative to the total constituent units of the specified (meth)acrylic polymer (A). It is even more preferable that it does not contain any constituent units derived from monomers having a carboxyl group.

[0044] <Other constituent units> Other constituent units that the specific (meth)acrylic polymer (A) may contain include: 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.

[0045] 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.

[0046] 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 appropriately set within a range that does not impair the effect of the adhesive composition of this disclosure.

[0047] <<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 less than 0°C, the formed adhesive layer exhibits easy peelability in the initial stages of bonding to the back surface of the adhesive tape, and this easy peelability tends not to deteriorate over time.

[0048] 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)

[0049] 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.

[0050] 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:

[0051] 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℃.

[0052] 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.

[0053] -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.

[0054] 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.

[0055] <<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 the specific (meth)acrylic polymer (A) exceeds 400,000, the formed adhesive layer tends to exhibit better easy peelability in the initial stages of bonding to the adherend and the back surface of the adhesive tape. This is thought to be because the specific (meth)acrylic polymer (B) tends to be more unevenly distributed on the adhesive surface of the adhesive layer. 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.

[0056] 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.

[0057] ~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

[0058] 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.

[0059] <<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 82.9% by mass or less, more preferably in the range of 45.0% by mass or more and 82.7% by mass or less, and even more preferably in the range of 49.5% by mass or more and 82.5% by mass or less, based on the total solid content in the adhesive composition.

[0060] 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.

[0061] [Specific (meth)acrylic polymer (B)] The adhesive composition of this disclosure contains a (meth)acrylic polymer (B) [i.e., a specific (meth)acrylic polymer (B)] which has a weight-average molecular weight in the range of 10,000 to 400,000 and a glass transition temperature of 0°C or higher, and the number-average molecular weight of the monomers having an organosiloxane skeleton in the range of 4,000 to 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.

[0062] <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") in an amount of 0.1% to 10% by mass relative to the total number of constituent units. 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 4000 to less than 20000. 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.

[0063] 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).

[0064]

Chem.

[0065] In formula (1), R 1 represents a hydrogen atom or a methyl group, and is preferably a methyl group.

[0066] 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 still 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.

[0067] 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.

[0068] 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).

[0069] 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 the specific (meth)acrylic polymer (B) is 4000 or more, the formed adhesive layer tends to maintain its easy peelability over time, even in the initial stages of bonding to the back surface of the adhesive tape. This is thought to be because the polarity of the specific (meth)acrylic polymer (B) becomes sufficiently low, and the uneven distribution of the (meth)acrylic polymer (B) on the adhesive surface of the adhesive layer is sufficiently maintained.

[0070] 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.

[0071] ~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

[0072] 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]

[0073] The specific (meth)acrylic polymer (B) may contain only one type of constituent unit b1, or it may contain two or more types.

[0074] The content of constituent unit b1 in the specified (meth)acrylic polymer (B) is in the range of 0.1% by mass or more and 10% by mass or less relative to the total constituent units of the specified (meth)acrylic polymer (B). When the content of constituent unit b1 in the specific (meth)acrylic polymer (B) is 0.1% by mass or more relative to the total constituent units of the specific (meth)acrylic polymer (B), the formed adhesive layer tends to maintain its easy peelability over time, even in the initial stages of adhesion to the back surface of the adhesive tape. The content of constituent unit b1 in the specific (meth)acrylic polymer (B) is preferably 0.5% by mass or more, more preferably 1% by mass or more, even more preferably 2% by mass or more, and particularly preferably 3% by mass or more, 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 10% by mass or less relative to the total constituent units of the specific (meth)acrylic polymer (B), the formed adhesive layer tends to exhibit high adhesive strength to the adherend after heating. This is thought to be because the (meth)acrylic polymer (B) on the adhesive surface of the adhesive layer does not become excessively unevenly distributed, and the increase in adhesive strength of the adhesive layer due to heating is not suppressed. From this perspective, the content of constituent unit b1 in the specific (meth)acrylic polymer (B) is preferably 10% by mass or less, more preferably 9% by mass or less, more preferably 8% by mass or less, and even more preferably 7% by mass or less, relative to the total constituent units of the specific (meth)acrylic polymer (B).

[0075] <Constituent units derived from alkyl (meth)acrylate monomers whose glass transition temperature is 40°C or higher when used as a homopolymer> The specified (meth)acrylic polymer (B) contains constituent units derived from alkyl (meth)acrylate monomers, which have a glass transition temperature of 40°C or higher when used as a homopolymer (hereinafter also referred to as "constituent unit b2"), in an amount exceeding 50% by mass and not exceeding 85% by mass relative to the total constituent units. 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.

[0076] 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. It is preferable that the alkyl (meth)acrylate monomer, which has a glass transition temperature of 40°C or higher when used as a homopolymer, does not contain either a hydroxyl group or a carboxyl group.

[0077] 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.

[0078] 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, and alkyl (meth)acrylate monomers having a glass transition temperature in the range of 50°C to 110°C when used as a homopolymer are more preferred.

[0079] 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).

[0080] The specific (meth)acrylic polymer (B) may contain only one type of constituent unit b2, or it may contain two or more types.

[0081] The content of constituent unit b2 in the specified (meth)acrylic polymer (B) is in the range of more than 50% by mass and 85% by mass or less, preferably in the range of 55% by mass or more and 80% by mass or less, more preferably in the range of 60% by mass or more and 75% by mass or less, and even more preferably in the range of 60% by mass or more and 70% by mass or less, relative to the total constituent units of the specified (meth)acrylic polymer (B). When the content of constituent unit b2 in the specific (meth)acrylic polymer (B) exceeds 50% by mass relative to the total constituent units of the specific (meth)acrylic polymer (B), the formed adhesive layer tends to retain its easy peelability in the initial stages of bonding over time. When the content of constituent unit b2 in the specific (meth)acrylic polymer (B) is 85% by mass or less relative to the total constituent units of the specific (meth)acrylic polymer (B), the zipping phenomenon that may occur when peeling from the adherend after heating and when peeling from the substrate on the back of the adhesive tape over time tends to be suppressed. This is presumed to be because the glass transition temperature of the specific (meth)acrylic polymer (B) that is unevenly distributed on the adhesive surface of the adhesive layer does not become excessively high, the partial inhibition of the wetting spread of the adhesive layer is suppressed, and unevenness in the adhesive strength of the adhesive layer is less likely to occur.

[0082] <Constituent units derived from (meth)acrylic acid> The specified (meth)acrylic polymer (B) contains constituent units derived from (meth)acrylic acid (hereinafter also referred to as "constituent unit b3") in an amount of 0.01% by mass or more and 0.5% by mass or less relative to the total constituent units. In this disclosure, "(meth)acrylic acid-derived constituent units (i.e., constituent unit b3)" means constituent units formed by the addition polymerization of (meth)acrylic acid.

[0083] The specific (meth)acrylic polymer (B) may contain either methacrylic acid or acrylic acid, or it may contain both methacrylic acid and acrylic acid.

[0084] The content of constituent unit b3 in the specified (meth)acrylic polymer (B) is in the range of 0.01% by mass or more and 0.5% by mass or less, preferably in the range of 0.01% by mass or more and 0.4% by mass or less, more preferably in the range of 0.01% by mass or more and 0.3% by mass or less, and even more preferably in the range of 0.01% by mass or more and 0.25% by mass or less, relative to the total constituent units of the specified (meth)acrylic polymer (B). The content of constituent unit b3 in the specified (meth)acrylic polymer (B) being 0.01% by mass or more relative to the total constituent units of the specified (meth)acrylic polymer (B) means that the specified (meth)acrylic polymer (B) actively contains constituent unit b3. When the specified (meth)acrylic polymer (B) contains constituent unit b3, the resulting adhesive layer tends to effectively suppress the inclusion of bubbles originating from outgassing generated from the adherend. When the content of constituent unit b3 in the specific (meth)acrylic polymer (B) is 0.5% by mass or less relative to the total constituent units of the specific (meth)acrylic polymer (B), the formed adhesive layer tends to exhibit high adhesion to the adherend after heating. This is thought to be because the specific (meth)acrylic polymer (B) does not crosslink excessively, and the adhesive layer can easily wet and spread on the adherend.

[0085] <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 b4") derived from alkyl (meth)acrylate monomers whose glass transition temperature when used as a homopolymer is less than 40°C. 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 b4)" 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.

[0086] 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. (Meth)acrylate alkyl ester monomers that have a glass transition temperature of less than 40°C when used as a homopolymer preferably do not contain either a hydroxyl group or a carboxyl group.

[0087] 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.

[0088] 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.

[0089] 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).

[0090] If the specific (meth)acrylic polymer (B) contains constituent unit b4, it may contain only one type of constituent unit b4 or two or more types.

[0091] When the specific (meth)acrylic polymer (B) contains constituent unit b4, the content of constituent unit b4 in the specific (meth)acrylic polymer (B) is not particularly limited and can be set appropriately depending on the purpose, for example, by adjusting the glass transition temperature of the specific (meth)acrylic polymer (B).

[0092] <Other constituent units> Other constituent units that the specific (meth)acrylic polymer (B) may contain include: 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 so on.

[0093] 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.

[0094] 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.

[0095] <<Weight-average molecular weight of specific (meth)acrylic polymer (B)>> The weight-average molecular weight of the specific (meth)acrylic polymer (B) is in the range of 10,000 to 400,000. When the weight-average molecular weight of the specific (meth)acrylic polymer (B) is 10,000 or more, it tends to form an adhesive layer in which the adhesive strength of the adhesive tape to its own back surface does not increase easily over time. This is thought to be because the localization of the specific (meth)acrylic polymer at the interface of the adhesive layer is easily maintained. Furthermore, when the weight-average molecular weight of the specific (meth)acrylic polymer (B) is 10,000 or more, it tends to form an adhesive layer in which the incorporation of bubbles originating from outgassing generated from the adherend can be effectively suppressed. From this perspective, the weight-average molecular weight of the specific (meth)acrylic polymer (B) is preferably 10,000 or more, more preferably 30,000 or more, more preferably 50,000 or more, even more preferably 70,000 or more, and particularly preferably 90,000 or more. When the weight-average molecular weight of the specific (meth)acrylic polymer (B) is 400,000 or less, the resulting adhesive layer tends to exhibit high adhesion to the adherend after heating. This is thought to be because it is less likely to hinder the wetting and spreading of the adhesive layer onto the adherend. From this perspective, the weight-average molecular weight of the specific (meth)acrylic polymer (B) is 400,000 or less, preferably 350,000 or less, more preferably 300,000 or less, even more preferably 250,000 or less, and particularly preferably 200,000 or less.

[0096] 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.

[0097] 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.

[0098] <<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.

[0099] 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.

[0100] 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.

[0101] <<Content of specific (meth)acrylic polymer (B)>> The content of the specific (meth)acrylic polymer (B) in the adhesive composition of this disclosure is in the range of more than 20 parts by mass 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 exceeds 20 parts by mass per 100 parts by mass of the specific (meth)acrylic polymer (A), the formed adhesive layer tends to exhibit slight peelability in the initial stages of bonding to the back surface of the adhesive tape. This is thought to be because the specific (meth)acrylic polymer (B) is appropriately unevenly distributed on the adhesive surface of the adhesive layer, in addition to the adhesive layer having appropriate cohesive force. Furthermore, when the content of the specific (meth)acrylic polymer (B) in the adhesive composition of this disclosure exceeds 20 parts by mass per 100 parts by mass of the specific (meth)acrylic polymer (A), the formed adhesive layer tends to maintain its slight peelability in the initial stages of bonding to the back surface of the adhesive tape over time. This is thought to be because the appropriate uneven distribution of the specific (meth)acrylic polymer (B) suppresses the wetting and spreading of the adhesive layer over time to the back surface of the adhesive tape. From this viewpoint, the content of the specific (meth)acrylic polymer (B) in the adhesive composition of the present disclosure is preferably more than 20 parts by mass, 25 parts by mass or more, more preferably 30 parts by mass or more, even more preferably 35 parts by mass or more, and particularly preferably 40 parts by mass or more, based on 100 parts by mass of the specific (meth)acrylic polymer (A). In the adhesive composition of this disclosure, if the content of the specific (meth)acrylic polymer (B) is 100 parts by mass or less per 100 parts by mass of the specific (meth)acrylic polymer (A), the formed adhesive layer tends to exhibit high adhesion to the adherend after heating. This is thought to be because the specific (meth)acrylic polymer (B) is not excessively unevenly distributed on the adhesive surface of the adhesive layer, and the specific (meth)acrylic polymer (A) is present in an appropriate amount, allowing the adhesive layer to spread sufficiently over the adherend upon heating. From this viewpoint, the content of the specific (meth)acrylic polymer (B) in the adhesive composition of the present disclosure is 100 parts by mass or less, preferably 95 parts by mass or less, more preferably 90 parts by mass or less, even more preferably 85 parts by mass or less, and particularly preferably 80 parts by mass or less, per 100 parts by mass of the specific (meth)acrylic polymer (A).

[0102] [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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] During the polymerization reaction, one organic solvent may be used, or two or more may be used.

[0107] 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.

[0108] During the polymerization reaction, one polymerization initiator may be used, or two or more may be used.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] [At least one compound selected from hexamethylene diisocyanate compounds and xylylene diisocyanate compounds] The adhesive composition of this disclosure comprises at least one compound selected from hexamethylene diisocyanate compounds and xylylene diisocyanate compounds. In the adhesive composition of this disclosure, both the hexamethylene diisocyanate compound and the xylylene diisocyanate compound function as crosslinking agents. At least one compound selected from hexamethylene diisocyanate compounds and xylylene diisocyanate compounds can contribute to the formation of an adhesive layer that effectively suppresses the incorporation of bubbles originating from outgassing generated from the adherend.

[0114] Hexamethylene diisocyanate compounds include hexamethylene diisocyanate (HMDI), HMDI polymers, adducts of HMDI and polyol compounds, and biuret compounds of HMDI. Examples of polyol compounds include trimethylolpropane (TMP). While there are no particular limitations on the hexamethylene diisocyanate compound, biuret derivatives of HMDI are preferred.

[0115] Commercially available hexamethylene diisocyanate compounds can be used. Examples of commercially available hexamethylene diisocyanate compounds include "Sumijoule® N75," "Sumijoule® N3300," and "Sumijoule® N3400" manufactured by Sumika Covestro Urethane Co., Ltd., "Coronate® HX" manufactured by Tosoh Corporation, and "Duranate® D-201" manufactured by Asahi Kasei Chemicals Corporation.

[0116] Xylylene diisocyanate compounds include xylylene diisocyanate (XDI), XDI polymers, adducts of XDI and polyol compounds, and biuret compounds of XDI. While the xylylene diisocyanate compound is not particularly limited, an adduct of XDI and TMP is preferred. Commercially available xylylene diisocyanate compounds can be used. Examples of commercially available xylylene diisocyanate compounds include "Takenate® D-110N" and "Takenate® D-120N" manufactured by Mitsui Chemicals, Inc.

[0117] The adhesive composition of this disclosure may contain one or more hexamethylene diisocyanate compounds, one or more xylylene diisocyanate compounds, or one or more hexamethylene diisocyanate compounds and one or more xylylene diisocyanate compounds.

[0118] The total content of hexamethylene diisocyanate compounds and xylylene diisocyanate compounds in the adhesive composition of this disclosure is not particularly limited, but is preferably 0.01 to 1 part by mass, more preferably 0.01 to 0.8 parts by mass, and even more preferably 0.01 to 0.5 parts by mass, per 100 parts by mass of a specific (meth)acrylic polymer (A).

[0119] [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.

[0120] If the adhesive composition of this disclosure contains an organic solvent, it may contain only one organic solvent or two or more organic solvents.

[0121] 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.

[0122] [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.

[0123] 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.

[0124] <Application> The uses of the adhesive composition disclosed herein are not particularly limited. The adhesive composition of this disclosure provides an adhesive layer that exhibits easy peelability in the initial stages of bonding to an adherend and high adhesive strength after heating, effectively suppressing the incorporation of air bubbles originating from outgassing from the adherend, and in addition, when used as a separator-less adhesive tape, it forms an adhesive layer in which the easy peelability in the initial stages of bonding to the back surface of the adhesive tape is not easily impaired over time. For example, it is suitable for applications such as attaching decorative films such as stickers to cars, motorcycles, bicycles, etc., or attaching decorative films to mirrors.

[0125] [Adhesive tape] The adhesive tape of this disclosure comprises a base material and an adhesive layer provided on one surface of the base material and formed of the adhesive composition of this disclosure. The adhesive tape of this disclosure comprises an adhesive layer formed by the adhesive composition of this disclosure described above, and therefore exhibits easy peelability to the adherend in the initial stages of bonding and high adhesive strength after heating. Furthermore, the adhesive tape of this disclosure can effectively suppress the incorporation of air bubbles originating from outgassing generated from the adherend. Moreover, when the adhesive tape of this disclosure is a separator-less type adhesive tape, the easy peelability to the back surface in the initial stages of bonding is less likely to deteriorate over time. The adhesive layer of the adhesive tape of the present disclosure includes a cured product of the adhesive composition of the present disclosure. The cured product includes, for example, crosslinked products of specific (meth)acrylic polymers (A) and specific (meth)acrylic polymers (B) that are crosslinked and cured with a hexamethylene diisocyanate compound and / or a xylylene diisocyanate compound.

[0126] The substrates to which the adhesive tapes of this disclosure are applied are not particularly limited, but include, for example, metals, resins, and glass. The adhesive tape of this disclosure can effectively suppress the incorporation of bubbles originating from outgassing generated from the adherend, and can therefore be suitably used even with resins that tend to generate outgassing when heated, such as acrylonitrile / butadiene / styrene resin (ABS resin) and polycarbonate (PC). With the adhesive tape of this disclosure, even when the above-mentioned resins are used as adherends, problems such as appearance defects and peeling due to foaming are less likely to occur.

[0127] The substrate of the adhesive tape of this disclosure is not particularly limited. The substrate of the tape of this disclosure is preferably, for example, capable of forming an adhesive layer on one surface and being able to be wound up. 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.

[0128] 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.

[0129] The substrate may have a functional layer on its back side, to the extent that it does not impair the effectiveness of the adhesive tape of this disclosure. In this disclosure, "functional layer" means a layer that imparts a desired function to the substrate, and the functional layer constitutes a part of the substrate. Examples of functional layers include a hard coat layer, an easy-peel layer, and a low-friction layer.

[0130] 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.

[0131] The thickness of the substrate is not particularly limited, but is generally 10 μm to 500 μm, preferably 10 μm to 300 μm, more preferably 10 μm to 200 μm, and even more preferably 10 μm to 100 μm.

[0132] 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.

[0133] The thickness of the adhesive layer of the adhesive tape 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.

[0134] 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.

[0135] The adhesive tape of this disclosure is preferably a roll body in which the side of the adhesive layer opposite to the substrate is in contact with the other side of the substrate and laminated, that is, a separator-less adhesive tape. Since the adhesive tape of this disclosure comprises an adhesive layer formed by the adhesive composition of this disclosure described above, even when it is a separator-less adhesive tape, the initial easy peelability from its back surface is less likely to be impaired over time.

[0136] [Method for manufacturing adhesive tape] The method for manufacturing the adhesive tape described herein is not particularly limited. The adhesive tapes of this disclosure can be manufactured by reference to known methods. Examples of methods for manufacturing the adhesive tape of this disclosure include the following methods (1) and (2).

[0137] Method (1): The adhesive composition of this disclosure is applied to one side of a substrate (preferably the easily bonded surface) to form a coating film on one side of the substrate. Next, the formed coating film is dried to form an adhesive film on one side of the substrate. Then, the laminate having a substrate / adhesive film layer structure is wound into a roll with the substrate and adhesive film alternating, and after forming the roll, it is left to stand to complete the crosslinking reaction. Method (2): The adhesive composition of the present disclosure is applied to one side of a substrate (preferably the easy-adhesion treated side) to form a coating film on one side of the substrate. Next, the formed coating film is dried to form an adhesive film on one side of the substrate. Next, the exposed side of the formed adhesive film is placed on top of the easy-peel treated side of a separately prepared release film and bonded together to form a laminate having a substrate / adhesive film / release film layer structure, which is then wound into a roll. Next, the wound laminate is unwound, and while peeling off the release film, the laminate having a substrate / adhesive film layer structure is rewound into a roll with the substrate and adhesive film alternating, and then left to stand to complete the crosslinking reaction. According to the above methods (1) and (2), an adhesive tape of the present disclosure can be successfully manufactured, having a base material and an adhesive layer provided on one surface of the base material, wherein the adhesive layer on the side opposite to the base material and the other surface of the base material are in contact and laminated together to form a roll body.

[0138] 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.

[0139] 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.

[0140] The conditions for standing are not particularly limited, but it is preferable to stand the mixture 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). The crosslinking reaction is completed by standing. [Examples]

[0141] The adhesive compositions and adhesive tapes 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. Examples 1-4 and 6-24 below are embodiments of the present disclosure, while Example 5 is a reference example of the present disclosure.

[0142] [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.

[0143] 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-6 prepared below.

[0144] [Manufacturing examples A-1, A-2, and A-4~A-6] In production examples A-1, A-2, and A-4 to A-6, 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-6, each with a solid content concentration of 32% by mass.

[0145] 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-6.

[0146] The glass transition temperatures of (meth)acrylic polymers A-1 to A-6 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-6 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.

[0147] Of the (meth)acrylic polymers A-1 to A-6, (meth)acrylic polymers A-1 to A-3 and A-5 correspond to the specified (meth)acrylic polymer (A) in this disclosure.

[0148] [Table 1]

[0149] 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℃]

[0150] In Table 1, a "-" in the monomer composition column indicates that the monomer corresponding to that column was not used.

[0151] [(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 monomer having an organosiloxane skeleton [product name: Cyraplane® FM-0721, number average molecular weight: 6500, manufactured by JNC Corporation], 54.9 parts by mass of methyl methacrylate [MMA], 0.10 parts by mass of methacrylic acid [MAA], 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 another container and mixed to prepare a solution containing the monomer mixture. This prepared solution was sequentially added dropwise to the above reaction vessel over 180 minutes under reflux temperature conditions. After the dropwise addition was complete, the mixture was allowed to react for 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.

[0152] 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-30 prepared below.

[0153] [Manufacturing examples B-2 to B-6, B-10 to B-18, B-20 to B-28 and B-30] In production examples B-2 to B-6, B-10 to B-18, B-20 to B-28, and B-30, 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 or Table 3, to obtain solutions of the (meth)acrylic polymers B-2 to B-6, B-10 to B-18, B-20 to B-28, and B-30, each with a solid content concentration of 35% by mass.

[0154] [Manufacturing examples B-7 to B-9, B-19 and B-29] In production examples B-7 to B-9, B-19, and B-29, the monomer composition of the (meth)acrylic polymer was changed to the monomer composition shown in Table 2 or Table 3, and at least one of the amount of organic solvent used and the amount of polymerization initiator used was adjusted to adjust the weight-average molecular weight of the (meth)acrylic polymer to the weight-average molecular weight shown in Table 2 or Table 3. The same procedure as in production example B-1 was followed to obtain solutions of the (meth)acrylic polymers B-7 to B-9, B-19, and B-29, each with a solid content concentration of 35% by mass.

[0155] Tables 2 and 3 show the monomer composition [unit: mass%] and weight-average molecular weight (indicated as "Mw") of (meth)acrylic polymers B-1 to B-30. Note that the glass transition temperatures of all (meth)acrylic polymers B-1 to B-30 are 0°C or higher.

[0156] The weight-average molecular weights of (meth)acrylic polymers B-1 to B-30 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.

[0157] Of the (meth)acrylic polymers B-1 to B-30, (meth)acrylic polymers B-1 to B-14, B-23, B-24, B-26 and B-30 correspond to the specified (meth)acrylic polymer (B) in this disclosure.

[0158] [Table 2]

[0159] [Table 3]

[0160] Details of each monomer listed in Tables 2 and 3 are as follows. <Monomers containing an organosiloxane skeleton> "FM-0721" [Product name: Cyraplane (registered trademark) FM-0721, number average molecular weight: 6500, compound represented by formula (1), manufactured by JNC Corporation] "FM-0725" [Product name: Cyraplane (registered trademark) FM-0725, number average molecular weight: 15000, compound represented by formula (1), manufactured by JNC Corporation] "X-22-174ASX" [Trade name, number average molecular weight: 1100, compound represented by formula (1), manufactured by Shin-Etsu Chemical Co., Ltd.]

[0161] <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": n-butyl methacrylate [Tg: 53°C when used as a homopolymer] <(meth)acrylic acid> "MAA": Methacrylic acid [Tg: 228°C when used as a homopolymer] "AA": Acrylic acid [Tg: 106°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] <Monomers containing hydroxyl groups> "2HEA": 2-hydroxyethyl acrylate [Tg when used as a homopolymer: -15℃]

[0162] In Tables 2 and 3, a "-" in the monomer composition column indicates that the monomer corresponding to that column was not used.

[0163] [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.].

[0164] [Examples 2-24] Except for changing the composition of the adhesive composition to the composition shown in Table 4 in Example 1, the same procedure as in Example 1 was followed to obtain the adhesive compositions of Examples 2 to 24.

[0165] [Comparative Examples 1-17] 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 5, to obtain the adhesive compositions of Comparative Examples 1 to 17.

[0166] [Preparation of adhesive tape for evaluation] The adhesive composition prepared above was applied to the easily bonded surface of a polyethylene terephthalate (PET) film (P1) [product name: Teijin® Tetron® Film, model number: G2P2, thickness: 50 μm, manufactured by Teijin Film Solutions 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 at a drying temperature of 100°C for a drying time of 1 minute to form an adhesive film on the PET film. Then, the side with the exposed adhesive film was laminated onto the unbonded surface of a separately prepared polyethylene terephthalate (PET) film (P2) [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 tape for evaluation. The resulting evaluation adhesive tape has a laminated structure consisting of a PET film (P1) / adhesive layer / PET film (P2).

[0167] [Measurement and Evaluation] 1. Adhesion to the adherend (1) Initial adhesive strength The evaluation adhesive tape prepared as described above was cut to a size of 25 mm x 150 mm to prepare evaluation adhesive tape pieces. The PET film (P2) was peeled off from the prepared evaluation adhesive tape piece [composition: PET film (P1) / adhesive layer / PET film (P2)]. After the surface of the adhesive layer exposed by peeling was attached to a stainless steel (so-called SUS) plate, a 2 kg roller was passed 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 test specimen X-1 after standing, the adhesive strength (unit: N / 25mm) was measured when an evaluation adhesive tape piece [composition: adhesive layer / PET film (P1)] was peeled 180° along the long side (150mm) from the SUS plate. This was done 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 4 and 5. 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.

[0168] -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.

[0169] (2) Adhesion after heating The evaluation adhesive tape prepared as described above was cut to a size of 25 mm x 150 mm to prepare evaluation adhesive tape pieces. The PET film (P2) was peeled off from the prepared evaluation adhesive tape piece [composition: PET film (P1) / adhesive layer / PET film (P2)]. After the surface of the adhesive layer exposed by peeling was attached to a stainless steel (so-called SUS) plate, a 2 kg roller was passed back and forth once to press it down and obtain test piece X-2. The obtained test piece X-2 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-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 tape piece [composition: adhesive layer / PET film (P1)] was peeled 180° along the long side (150mm) from the SUS plate. This was done 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. Tables 4 and 5 show the measured and evaluated adhesive strength. When zipping occurred, the minimum and maximum measured adhesive strength values ​​are shown as a numerical range, and the term "zipping" is used. Zipping refers to the phenomenon where the material does not peel off smoothly but instead makes a crackling sound. 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.

[0170] -Evaluation Criteria- A: The adhesive strength is 7.0 N / 25 mm or more. B: The adhesive strength is 5.0 N / 25 mm or more and less than 7.0 N / 25 mm. C: The adhesive strength is less than 5.0 N / 25 mm, and / or the zipping phenomenon occurs.

[0171] 2. Adhesion to the back surface (1) Initial adhesive strength The evaluation adhesive tape prepared as described above was cut to a size of 25 mm x 150 mm to prepare evaluation adhesive tape pieces. The adhesive strength (unit: N / 25 mm) when the PET film (P2) was peeled off at a 180° angle along the long side (150 mm) from the prepared evaluation adhesive tape piece [composition: PET film (P1) / adhesive layer / PET film (P2)] 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, 50% RH, and a peeling speed of 300 mm / 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 4 and 5. If the evaluation result is "A" or "B", the adhesive layer is evaluated as exhibiting slight peelability at the initial stage of adhesion to the back surface of the adhesive tape (i.e., the back surface of the substrate). An evaluation result of "A" is most preferable.

[0172] -Evaluation Criteria- A: The adhesive strength is 0.01 N / 25 mm or more and less than 0.20 N / 25 mm. B: The adhesive strength is 0.20 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.

[0173] (2) Adhesion over time The evaluation adhesive tape prepared as described above was cut to a size of 25 mm x 150 mm to prepare evaluation adhesive tape pieces. The prepared evaluation adhesive tape pieces were left to stand for 7 days in an environment with an ambient temperature of 40°C. The adhesive strength (unit: N / 25 mm) when the PET film (P2) was peeled off at a 180° angle along the long side (150 mm) from the evaluation adhesive tape piece [composition: PET film (P1) / adhesive layer / PET film (P2)] 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, 50% RH, and a peeling speed of 300 mm / min. The evaluation was then performed according to the evaluation criteria below. Tables 4 and 5 show the measured and evaluated adhesive strengths. When zipping occurred, the minimum and maximum measured adhesive strengths were indicated as a numerical range, and the term "zipping" was added. If the evaluation result is "A" or "B", it is evaluated that the adhesive layer is one in which the initial easy peelability of the adhesive tape against its own back surface (i.e., the back surface of the substrate) does not deteriorate easily over time. An evaluation result of "A" is most preferable.

[0174] -Evaluation Criteria- A: The adhesive strength is 0.01 N / 25 mm or more and less than 0.20 N / 25 mm. B: The adhesive strength is 0.20 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, and / or the zipping phenomenon occurs.

[0175] 3. Foam suppression The evaluation adhesive tape prepared as described above was cut to a size of 25 mm x 150 mm to prepare evaluation adhesive tape pieces. The PET film (P2) was peeled off from the prepared evaluation adhesive tape piece [composition: PET film (P1) / adhesive layer / PET film (P2)]. After the adhesive layer surface exposed by peeling was attached to a polycarbonate (PC) plate, a 2 kg roller was rolled back and forth once to press it down and obtain test piece X-3. The PC plate side of the obtained test piece X-3 was heated using a hairdryer for 5 minutes until the surface temperature reached 110°C. After heating, the interface between the adhesive layer and the PC plate was observed visually. Then, evaluation was performed according to the evaluation criteria below. The evaluation results are shown in Tables 4 and 5. If the evaluation result is "A" or "B", the adhesive layer is evaluated as being able to effectively suppress the inclusion of air bubbles caused by outgassing from the adherend. An evaluation result of "A" is most preferable.

[0176] -Evaluation Criteria- A: No air bubbles were observed at the interface between the adhesive layer and the PC board. B: A small amount of air bubbles are observed at the interface between the adhesive layer and the PC board, but no peeling of the adhesive layer from the PC board is observed. C: Air bubbles were observed at the interface between the adhesive layer and the PC board, and peeling of the adhesive layer from the PC board due to these air bubbles was also observed.

[0177] [Table 4]

[0178] [Table 5]

[0179] Details of the crosslinking agents listed in Table 4 and / or Table 5 are as follows. "XDI" [Product name: Takenate® D-110N, xylylene diisocyanate compound (adduct of xylylene diisocyanate (XDI) and trimethylolpropane (TMP)), solid content: 75% by mass, manufactured by Mitsui Chemicals, Inc.] "HMDI" [Product name: Sumijoule (registered trademark) N75, hexamethylene diisocyanate compound (biuret form of hexamethylene diisocyanate (HMDI)), solid content concentration: 75% by mass, manufactured by Sumika Covestro Urethane Co., Ltd.] "TDI" [Product name: Coronate® L-45E, tolylene diisocyanate compound (adduct of tolylene diisocyanate (TDI) and trimethylolpropane (TMP)), solid content: 45% by mass, manufactured by Tosoh Corporation] The above terms, "Takenate," "Sumijule," and "Coronate," are all registered trademarks.

[0180] In Tables 4 and 5, the values ​​listed in the "Amount" column are all based on solid content.

[0181] As shown in Table 4, the adhesive layers formed by the adhesive compositions of Examples 1 to 24 were found to exhibit easy peelability in the initial stages of bonding to the adherend, and high adhesive strength after heating. Furthermore, the adhesive layers formed by the adhesive compositions of Examples 1 to 24 were found to effectively suppress the incorporation of air bubbles originating from outgassing generated from the adherend. In addition, when the adhesive layers formed by the adhesive compositions of Examples 1 to 24 were used as separator-less adhesive tapes, it was found that the easy peelability in the initial stages of bonding to the back surface of the adhesive tape was not easily impaired over time.

[0182] On the other hand, as shown in Table 5, it was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 1, which does not contain the constituent unit b1 of the (meth)acrylic polymer (B), was more prone to losing its initial easy peelability from the substrate, which is the back surface of the adhesive tape, over time, compared to the adhesive layer formed by the adhesive composition of the example. It was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 2, in which the content of constituent unit b1 in the (meth)acrylic polymer (B) exceeds 10% by mass relative to the total constituent units of the (meth)acrylic polymer (B), does not exhibit a high degree of adhesion to the adherend after heating, compared to the adhesive layer formed by the adhesive composition of the example. It was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 3, in which the content of constituent unit b2 in the (meth)acrylic polymer (B) is 50% by mass or less relative to the total constituent units of the (meth)acrylic polymer (B), is more prone to deterioration over time in terms of initial easy peelability from the substrate, which is the back surface of the adhesive tape, compared to the adhesive layer formed by the adhesive composition of the example.

[0183] It was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 4, in which the content of constituent unit b2 in the (meth)acrylic polymer (B) exceeds 85% by mass relative to the total constituent units of the (meth)acrylic polymer (B), exhibits a zipping phenomenon when peeled off from the adherend after heating, and when peeled off from the substrate, which is the back surface of the adhesive tape, after a period of time. The reason for this is presumed to be that the glass transition temperature of the (meth)acrylic polymer (B) becomes excessively high due to the high content of constituent unit b2, partially inhibiting the wetting spread of the adhesive layer and causing unevenness in the adhesive strength of the adhesive layer. It was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 5, in which the weight-average molecular weight of the (meth)acrylic polymer (B) exceeds 400,000, does not exhibit a high degree of adhesion to the adherend after heating, compared to the adhesive layer formed by the adhesive composition of the example. In Comparative Examples 6 and 16, the adhesive layers formed by the adhesive compositions in which the number-average molecular weight of monomers having an organosiloxane skeleton in the (meth)acrylic polymer (B) was less than 4000 were found to be more susceptible to deterioration over time compared to the adhesive layers formed by the adhesive compositions of the Examples, specifically in terms of the initial easy peelability of the adhesive tape from the substrate on the back surface.

[0184] The adhesive layer formed by the adhesive composition of Comparative Example 7, in which the content of (meth)acrylic polymer (B) is 20 parts by mass or less per 100 parts by mass of (meth)acrylic polymer (A), was found to have higher initial adhesion to the substrate on the back surface of the adhesive tape and to not exhibit easy peeling compared to the adhesive layer formed by the adhesive composition of the example. It was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 8, in which the content of (meth)acrylic polymer (B) exceeds 100 parts by mass per 100 parts by mass of (meth)acrylic polymer (A), does not easily develop high adhesive strength to the adherend after heating compared to the adhesive layer formed by the adhesive composition of the example. It was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 9, in which the glass transition temperature of the (meth)acrylic polymer (A) exceeds 0°C, had higher initial adhesion to the substrate, which is the back surface of the adhesive tape, and did not exhibit easy peeling properties, compared to the adhesive layer formed by the adhesive composition of the example.

[0185] It was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 10, in which the (meth)acrylic polymer (B) does not contain the constituent unit b3, does not effectively suppress the incorporation of bubbles originating from outgassing generated from the adherend, compared to the adhesive layer formed by the adhesive composition of the example. It was also confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 13, in which the (meth)acrylic polymer (B) contains a constituent unit derived from a monomer having a hydroxyl group instead of the constituent unit b3, does not effectively suppress the incorporation of bubbles originating from outgassing generated from the adherend, similar to the adhesive layer formed by the adhesive composition of Comparative Example 10. It was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 11, in which the content of constituent unit b3 in (meth)acrylic polymer (B) exceeds 0.5% by mass relative to the total constituent units of (meth)acrylic polymer (B), does not exhibit high adhesion to the adherend after heating compared to the adhesive layer formed by the adhesive composition of the example. It was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 12, which does not contain at least one compound selected from hexamethylene diisocyanate compounds and xylylene diisocyanate compounds, is unable to effectively suppress the incorporation of bubbles originating from outgassing generated from the adherend, compared to the adhesive layer formed by the adhesive composition of the example.

[0186] It was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 14, in which the (meth)acrylic polymer (A) does not contain constituent units derived from monomers having hydroxyl groups, does not exhibit high adhesion to the adherend after heating, compared to the adhesive layer formed by the adhesive composition of the example. It was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 15, which does not contain the constituent unit b1 of the (meth)acrylic polymer (B), is more prone to losing its initial easy peelability from the substrate, which is the back surface of the adhesive tape, over time, compared to the adhesive layer formed by the adhesive composition of the example. The adhesive layer formed by the adhesive composition of Comparative Example 17, in which the weight-average molecular weight of the (meth)acrylic polymer (B) is less than 10,000, was found to be more prone to deterioration over time in terms of initial easy peelability from the substrate (the back surface of the adhesive tape) compared to the adhesive layer formed by the adhesive composition of the Examples. Furthermore, it was found that the inclusion of air bubbles originating from outgassing from the adherend could not be effectively suppressed.

Claims

1. A (meth)acrylic polymer (A) containing constituent units derived from monomers having hydroxyl groups and 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 in an amount of 0.1% to 10% by mass relative to the total constituent units, constituent units derived from alkyl (meth)acrylate monomers having a glass transition temperature of 40°C or higher as a homopolymer in an amount of more than 50% to 85% by mass relative to the total constituent units, and constituent units derived from (meth)acrylic acid in an amount of 0.01% to 0.5% by mass relative to the total constituent units, having a weight-average molecular weight in the range of 10,000 to 400,000, and having a glass transition temperature of 0°C or higher, At least one compound selected from hexamethylene diisocyanate compounds and xylylene diisocyanate compounds, 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. An adhesive composition in which the content of the (meth)acrylic polymer (B) is in the range of 21 parts by mass or more and 100 parts by mass or less per 100 parts by mass of the (meth)acrylic polymer (A).

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. Substrate and An adhesive layer provided on one surface of the substrate and formed with the adhesive composition described in claim 1 or claim 2, Adhesive tape equipped with [a specific feature].

4. The adhesive tape according to claim 3, wherein the side of the adhesive layer opposite to the substrate is in contact with the other side of the substrate and the roll body is laminated.

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