Release Adhesive Composition, Surface Protection Film, and Optical Member with Adhesive Layer

Abstract

An object of the present invention is to provide a pressure-sensitive adhesive composition for re-peeling that has excellent low contamination and adhesion balance. 【Means for Solving the Problem】 It contains a (meth)acrylic polymer (A) containing an alkyl group-containing unsaturated monomer (a1) having an alkyl group with 1 to 18 carbon atoms and a monomer (a2) having a functional group as constituent units, and a curing agent (B). The alkyl group-containing unsaturated monomer (a1) contains at least 2-octyl (meth)acrylate. The (meth)acrylic polymer (A) contains 30% by mass or more of the 2-octyl (meth)acrylate and 3.5 to 15% by mass of the monomer (a2) having a functional group in 100% by mass of all the monomers constituting the (meth)acrylic polymer (A). The monomer (a2) having a functional group does not contain a monomer having a carboxyl group. The curing agent (B) is contained in an amount of 5.0 to 30.0% by mass based on 100% by mass of the (meth)acrylic polymer (A).

Description

Technical Field

[0001] The present invention relates to a pressure-sensitive adhesive composition for re-peeling, a surface protection film, and an optical member with an adhesive layer.

Background Art

[0002] In the manufacturing process of an optical member (for example, a polarizing plate) constituting a liquid crystal display, a surface protection film is adhered to the optical member in order to temporarily protect the surface of the optical member. After use, the surface protection film is peeled off from the optical member by the user, so the surface protection film has a slightly sticky adhesive layer. Recently, as the size of liquid crystal displays has increased, the size of the surface protection film for optical members has also increased. Generally, the larger the size of the surface protection film, the more difficult it is to quickly peel the surface protection film from the optical member. Therefore, reduction of the adhesive force during high-speed peeling is required for the surface protection film.

[0003] However, since it is further required as the performance of the surface protection film that it cannot be peeled off from the adherend until it is used up, it is desirable that the adhesive force during low-speed peeling of the surface protection film is somewhat high. In addition, when the surface protection film is peeled off, it is required as the performance of the surface protection film that there is no adherend contamination (that is, the adhesive does not contaminate the adherend). Hereinafter, this performance is called low contamination.

[0004] Conventionally, when the pressure-sensitive adhesive composition contains butyl acrylate having a high glass transition temperature Tg (-55°C), the film becomes hard, so the low contamination is improved. However, since the adhesive force during high-speed peeling increases, the balance of the adhesive force deteriorates. Thus, it has been difficult to realize a pressure-sensitive adhesive composition excellent in both low contamination and adhesive force balance.

[0005] Therefore, Patent Document 1 proposes a pressure-sensitive adhesive composition containing 2-ethylhexyl acrylate having a low glass transition temperature Tg (-70°C) and a copolymerizable monomer containing a carboxyl group.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] In Patent Document 1, the adhesive force during high - speed peeling is reduced, but the adhesive force during low - speed peeling is too low, so the balance of the adhesive force deteriorates. Therefore, a re - peelable adhesive composition with excellent low - contamination property and adhesive - force balance has not yet been realized.

[0008] Therefore, an object of the present invention is to provide a re - peelable adhesive composition having excellent low - contamination property and adhesive - force balance.

Means for Solving the Problems

[0009] To achieve the object of the present invention, the re - peelable adhesive composition of the present invention has the following configuration. That is, it contains a (meth) acrylic polymer (A) containing an alkyl - group - containing unsaturated monomer (a1) having an alkyl group with 1 to 18 carbon atoms and a monomer (a2) having a functional group as constituent units, and a curing agent (B). The alkyl - group - containing unsaturated monomer (a1) contains at least 2 - octyl (meth) acrylate. The (meth) acrylic polymer (A) contains the 2 - octyl (meth) acrylate in 85 to 96.5 mass% and contains the monomer (a2) having a functional group in an amount of 3.5 to 15% by mass. The monomer (a2) having a functional group does not contain a monomer having a carboxyl group. and contains a monomer having at least a hydroxy group, The curing agent (B) is contained in an amount of 5.0 to 30.0% by mass with respect to 100% by mass of the (meth) acrylic polymer (A). and the alkyl group-containing unsaturated monomer (a1) is an alkyl (meth)acrylate.

Effects of the Invention

[0010] According to the present invention, it is possible to provide a pressure-sensitive adhesive composition for re-peeling that is excellent in the balance between low contamination and adhesive strength.

Mode for Carrying Out the Invention

[0011] Hereinafter, embodiments will be described in detail. It should be noted that the following embodiments do not limit the invention according to the claims, and not all combinations of the features described in the embodiments are essential to the invention. Two or more of the plurality of features described in the embodiments may be arbitrarily combined.

[0012] In this specification, the notation "A to B" representing a numerical range is synonymous with "A or more and B or less", and includes A and B.

[0013] In this specification, "(meth)acryl" means both "acryl" and "methacryl". Also, "(meth)acrylate" means both "acrylate" and "methacrylate".

[0014] In this specification, "mass%" has the same definition as "parts by mass", "parts by weight", and "parts". Therefore, "mass%" can be read as any of "parts by mass", "parts by weight", and "parts".

[0015] <Pressure-Sensitive Adhesive Composition for Re-Peeling> The pressure-sensitive adhesive composition for re-peeling is used as an adhesive layer of a surface protection film or an adhesive layer of an optical member after removing the solvent from the pressure-sensitive adhesive composition for re-peeling and drying it. The pressure-sensitive adhesive composition for re-peeling according to one embodiment contains at least a (meth)acrylic polymer (A) and a curing agent (B). Further, the pressure-sensitive adhesive composition for re-peeling can further contain at least one of a curing retarder (C) and an antistatic agent (D) according to the required performance of the user.

[0016] Here, re-peelability refers to the property including ease of peeling when peeling off the surface protection film having an adhesive layer composed of an adhesive composition for re-peeling from various adherends after a certain period of time, and difficulty in adhesive residue.

[0017] <(Meth)acrylic polymer (A)> The (meth)acrylic polymer (A) according to one embodiment includes an alkyl group-containing unsaturated monomer (a1) having an alkyl group with 1 to 18 carbon atoms and a monomer (a2) having a functional group as constituent units. Further, the (meth)acrylic polymer (A) can include a vinyl monomer (a3) and / or a polyalkylene glycol chain-containing mono(meth)acrylate (a4) in addition to the above constituent units. Note that the polyalkylene glycol chain-containing mono(meth)acrylate (a4) having at least one hydroxy group does not belong to the monomer (a2) having a functional group.

[0018] The (meth)acrylic polymer (A) according to one embodiment contains 2-octyl (meth)acrylate in an amount of 30% by mass or more and a monomer (a2) having a functional group in an amount of 3.5 to 15% by mass based on 100% by mass of all the monomers constituting the (meth)acrylic polymer (A). Here, the alkyl group-containing unsaturated monomer (a1) contains at least 2-octyl (meth)acrylate.

[0019] That is, the alkyl group-containing unsaturated monomer (a1) can further include 2-octyl (meth)acrylate and a monomer other than 2-octyl (meth)acrylate. The type and content of the monomer other than 2-octyl (meth)acrylate are not particularly limited. Further, the monomer (a2) having a functional group does not include a monomer having a carboxy group. Note that "the monomer (a2) having a functional group does not include a monomer having a carboxy group" means that a monomer having a carboxy group is not intentionally used, and it is allowable that a monomer having a carboxy group is included unintentionally.

[0020] (Meta)acrylic polymer (A) contains 2-octyl (meta)acrylate at 30% by mass or more, so that the Tg of (meta)acrylic polymer (A) can be increased and the film becomes hard. As a result, a pressure-sensitive adhesive composition for re-peeling excellent in the balance between low contamination and adhesiveness can be realized. In addition, since 2-octyl acrylate can be obtained from biomass-derived materials, the dependence on monomers derived from fossil resources can be reduced. Since the pressure-sensitive adhesive composition for re-peeling of the present invention contains 2-octyl acrylate which is a biomass-derived material, it is excellent in that it is friendly to both humans and the environment.

[0021] <An alkyl group-containing unsaturated monomer (a1) having an alkyl group with 1 to 18 carbon atoms> Examples of the alkyl group-containing unsaturated monomer (a1) having an alkyl group with 1 to 18 carbon atoms (hereinafter also referred to as the alkyl group-containing unsaturated monomer (a1)) include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, sec-butyl (meth)acrylate, n-amyl (meth)acrylate, isoamyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-octyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, n-undecyl (meth)acrylate, n-dodecyl (meth)acrylate, n-tridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, cetyl (meth)acrylate, and stearyl (meth)acrylate, etc., which are (meth)acrylic acid alkyl esters having a linear or branched alkyl group; (meth)acrylic acid esters having an alicyclic hydrocarbon group such as cyclohexyl (meth)acrylate, 4-tert-butylcyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclopentanyl (meth)acrylate, etc. These may be used alone or in combination of two or more. The alkyl group-containing unsaturated monomer (a1) having an alkyl group with 1 to 18 carbon atoms contains at least 2-octyl (meth)acrylate. The alkyl group-containing unsaturated monomer (a1) having an alkyl group with 1 to 18 carbon atoms preferably contains at least 2-octyl acrylate. Further, the alkyl group-containing unsaturated monomer (a1) having an alkyl group with 1 to 18 carbon atoms may further contain 2-ethylhexyl acrylate or butyl acrylate in addition to 2-octyl (meth)acrylate.

[0022] In one embodiment, the (meth)acrylic polymer (A) contains 2-octyl (meth)acrylate in an amount of 30% by mass or more based on 100% by mass of all the monomers constituting the (meth)acrylic polymer (A). When the amount of 2-octyl (meth)acrylate is less than 30% by mass, the Tg of the (meth)acrylic polymer (A) decreases, resulting in a brittle film and a reduction in low contamination property.

[0023] In one embodiment, when the alkyl group-containing unsaturated monomer (a1) is 2-octyl (meth)acrylate, the (meth)acrylic polymer (A) contains 2-octyl (meth)acrylate in an amount of 85 to 96.5% by mass based on 100% by mass of all the monomers constituting the (meth)acrylic polymer (A).

[0024] In one embodiment, when the alkyl group-containing unsaturated monomer (a1) further contains 2-ethylhexyl acrylate in addition to 2-octyl (meth)acrylate, the (meth)acrylic polymer (A) contains 2-octyl (meth)acrylate in an amount of 30 to 90% by mass and 2-ethylhexyl acrylate in an amount of 5 to 65% by mass based on 100% by mass of all the monomers constituting the (meth)acrylic polymer (A).

[0025] In one embodiment, when the alkyl group-containing unsaturated monomer (a1) further contains butyl acrylate in addition to 2-octyl (meth)acrylate, the (meth)acrylic polymer (A) contains 2-octyl (meth)acrylate in an amount of 40 to 90% by mass, preferably 48 to 90% by mass, and butyl acrylate in an amount of 5 to 47% by mass based on 100% by mass of all the monomers constituting the (meth)acrylic polymer (A).

[0026] The upper limit of the content of 2-octyl (meth) acrylate is 96.5% by mass or less, 94% by mass or less, 92% by mass or less, 90% by mass or less, 89% by mass or less, 87% by mass or less, 84% by mass or less, or 82% by mass or less. On the other hand, the lower limit of the content of 2-octyl (meth) acrylate is 30% by mass or more, 48% by mass or more, 76.5% by mass or more, 79% by mass or more, or 81.5% by mass or more. The predetermined range of the content of 2-octyl (meth) acrylate may be any combination of the above-mentioned lower limit and upper limit. When the content of 2-octyl (meth) acrylate is within the predetermined range, a pressure-sensitive adhesive composition for re-peeling that is excellent in both low contamination and adhesion balance can be realized. On the other hand, when the content of 2-octyl (meth) acrylate is outside the predetermined range (for example, when it is less than 30% by mass), the low contamination decreases or the adhesion balance deteriorates.

[0027] <Monomer (a2) having a functional group> The monomer (a2) having a functional group may be a monomer having a functional group other than a carboxy group, and for example, may include at least one of a monomer having a hydroxy group and a monomer having an amide group. The monomer (a2) having a functional group according to one embodiment does not include a monomer having a carboxy group. When the monomer (a2) having a functional group includes a monomer having a carboxy group, the low contamination decreases or the adhesion balance deteriorates.

[0028] The monomer (a2) having a functional group is a radically polymerizable monomer having a functional group capable of reacting with a curing agent (B) described later. A polymer network is formed by the crosslinking reaction between the functional group and the curing agent (B), and the cohesive force and re-peeling property of the pressure-sensitive adhesive composition for re-peeling can be improved. The monomer (a2) having a functional group is preferably a monomer having a hydroxy group from the viewpoint of improving the re-peeling property of the pressure-sensitive adhesive composition for re-peeling.

[0029] The monomer (a2) having a functional group according to one embodiment is a monomer having a hydroxy group.

[0030] The monomer (a2) having a functional group according to one embodiment includes a monomer having a hydroxy group and a monomer having an amide group.

[0031] In one embodiment, when the monomer (a2) having a functional group is a monomer having a hydroxy group, the (meth)acrylic polymer (A) contains the monomer (a2) having a functional group in an amount of 3.5 to 15% by mass based on 100% by mass of all the monomers constituting the (meth)acrylic polymer (A). By the content of the monomer (a2) having a functional group being within the predetermined range defined in the present invention, a pressure-sensitive adhesive composition for re-peeling excellent in low contamination property and adhesion balance can be realized. When the content of the monomer (a2) having a functional group is less than 3.5% by mass, the adhesive strength at high-speed peeling increases and the adhesion balance deteriorates. On the other hand, when the content of the monomer (a2) having a functional group exceeds 15% by mass, the adhesive strength at low-speed peeling increases and the adhesion balance deteriorates.

[0032] In one embodiment, when the monomer (a2) having a functional group includes a monomer having a hydroxy group and a monomer having an amide group, the (meth)acrylic polymer (A) contains the monomer having a hydroxy group in an amount of 2.5 to 14.9% by mass and the monomer having an amide group in an amount of 0.1 to 1% by mass based on 100% by mass of all the monomers constituting the (meth)acrylic polymer (A).

[0033] Examples of the monomer having a hydroxy group include (meth)acrylic esters having a hydroxy group such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate (hydroxyalkyl (meth)acrylate). These may be used alone or in combination of two or more. The monomer having a hydroxy group preferably contains at least one of 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate.

[0034] Examples of the monomer having an amide group include, for example, (meth)acrylamide, isopropyl (meth)acrylamide, dimethylaminopropyl (meth)acrylamide, hydroxyethyl (meth)acrylamide, and the like. These may be used alone or in combination of two or more. The monomer having an amide group is preferably methacrylamide.

[0035] <Vinyl monomer (a3)> The (meth)acrylic polymer (A) according to one embodiment further includes a vinyl monomer (a3) as a constituent unit in addition to the alkyl group-containing unsaturated monomer (a1) and the monomer (a2) having a functional group. Examples of the vinyl monomer (a3) include styrene, α-methylstyrene, vinyltoluene, vinylpyridine, vinylpyrrolidone, vinyl acetate, acrylonitrile, and the like. These may be used alone or in combination of two or more. The vinyl monomer (a3) is preferably vinyl acetate.

[0036] When the acrylic polymer (A) further includes vinyl acetate as the vinyl monomer (a3), the adhesion balance of the adhesive layer is further improved.

[0037] In one embodiment, when the (meth)acrylic polymer (A) further includes a vinyl monomer (a3) as a constituent unit, 2-octyl acrylate is contained in an amount of 70 to 89% by mass, preferably 79 to 89% by mass, and the vinyl monomer (a3) is preferably contained in an amount of 5 to 15% by mass in 100% by mass of all the monomers constituting the (meth)acrylic polymer (A).

[0038] In one embodiment, the vinyl monomer (a3) is vinyl acetate.

[0039] <Polyalkylene glycol chain-containing mono(meth)acrylate (a4)> The (meth)acrylic polymer (A) according to one embodiment further contains a polyalkylene glycol chain-containing mono(meth)acrylate (a4) as a constituent unit, in addition to an alkyl group-containing unsaturated monomer (a1) and a monomer (a2) having a functional group. Here, the polyalkylene glycol chain-containing mono(meth)acrylate (a4) having at least one hydroxy group shall not belong to the monomer (a2) having a functional group.

[0040] The polyalkylene glycol chain-containing mono(meth)acrylate (a4) may be a compound in which one hydroxy group out of a plurality of hydroxy groups of the polyalkylene glycol is esterified as (meth)acrylate. Since the acryloyl group of the polyalkylene glycol chain-containing mono(meth)acrylate (a4) is a polymerizable group, it can copolymerize with the polymerizable monomer of the (meth)acrylic polymer (A) described above. The other hydroxy groups may remain as hydroxy groups, or may be alkyl ethers such as methyl ether and ethyl ether, or saturated carboxylic acid esters such as acetic acid ester. Note that the polyalkylene glycol chain-containing mono(meth)acrylate (a4) in which the other hydroxy groups remain as hydroxy groups, that is, the polyalkylene glycol chain-containing mono(meth)acrylate (a4) having a hydroxy group, does not belong to the monomer (a2) having a functional group.

[0041] In the polyalkylene glycol chain-containing mono(meth)acrylate (a4), examples of the alkylene group of the polyalkylene glycol include, but are not limited to, an ethylene group, a propylene group, and a butylene group. The polyalkylene glycol may be a polyalkylene glycol having two or more types of alkylene groups in one molecule, such as polyethylene glycol-polypropylene glycol, polyethylene glycol-polybutylene glycol, or polypropylene glycol-polybutylene glycol. The polyalkylene glycol chain-containing mono(meth)acrylate (a4) is preferably at least one compound in which the average number of repeating units of the alkylene oxide constituting the polyalkylene oxide is 4 to 14.

[0042] As the polyalkylene glycol chain-containing mono(meth)acrylate (a4), for example, it is preferably at least one selected from polyalkylene glycol mono(meth)acrylate, methoxypolyalkylene glycol (meth)acrylate, and ethoxypolyalkylene glycol (meth)acrylate.

[0043] More specific examples of the polyalkylene glycol chain-containing mono(meth)acrylate (a4) include polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, polybutylene glycol mono(meth)acrylate, methoxypolyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, methoxypolybutylene glycol (meth)acrylate, ethoxypolyethylene glycol (meth)acrylate, ethoxypolypropylene glycol (meth)acrylate, and ethoxypolybutylene glycol (meth)acrylate. These may be used alone or in combination of two or more. The polyalkylene glycol chain-containing mono(meth)acrylate (a4) is preferably methoxypolyethylene glycol methacrylate.

[0044] When the acrylic polymer (A) further contains methoxypolyethylene glycol methacrylate as the polyalkylene glycol chain-containing mono(meth)acrylate (a4), the adhesion balance of the pressure-sensitive adhesive layer is further improved.

[0045] In one embodiment, when the (meth)acrylic polymer (A) further contains a polyalkylene glycol chain-containing mono(meth)acrylate (a4) as a constituent unit, 2-octyl (meth)acrylate is contained in an amount of 70.0 to 89.5% by mass, preferably 76.5 to 89.5% by mass, and the polyalkylene glycol chain-containing mono(meth)acrylate (a4) is preferably contained in an amount of 5 to 15% by mass, based on 100% by mass of all the monomers constituting the (meth)acrylic polymer (A). Note that the polyalkylene glycol chain-containing mono(meth)acrylate (a4) having at least one hydroxy group does not belong to the monomer (a2) having a functional group.

[0046] The polyalkylene glycol chain-containing mono(meth)acrylate (a4) according to one embodiment is methoxypolyethylene glycol methacrylate.

[0047] <Supplement to the embodiment> In one embodiment, in addition to the alkyl group-containing unsaturated monomer (a1) and the monomer (a2) having a functional group, the (meth)acrylic polymer (A) further contains at least one of butyl acrylate, a vinyl monomer (a3), and a polyalkylene glycol chain-containing mono(meth)acrylate (a4) as a constituent unit. That is, when the (meth)acrylic polymer (A) is composed of the following Compositions 1 to 4, the effect of improving the adhesion balance of the pressure-sensitive adhesive layer can be obtained.

[0048] Composition 1 is a composition in which the (meth)acrylic polymer (A) contains an alkyl group-containing unsaturated monomer (a1) other than butyl acrylate, a monomer (a2) having a functional group, and butyl acrylate. In one embodiment, the (meth)acrylic polymer (A) contains 2-octyl (meth)acrylate in an amount of 30.0 to 80.0% by mass, preferably 30.0 to 74.0% by mass, and contains butyl acrylate in an amount of 5 to 15% by mass, preferably 5 to 10% by mass. In this case, the mass % of the remaining monomers constituting the (meth)acrylic polymer (A) can include the mass % of the alkyl group-containing unsaturated monomer (a1) other than 2-octyl (meth)acrylate and butyl acrylate, the mass % of the monomer (a2) having a functional group, the mass % of the vinyl monomer (a3), and the mass % of the polyalkylene glycol chain-containing mono(meth)acrylate (a4). Note that the types and contents of the remaining monomers constituting the (meth)acrylic polymer (A) are not particularly limited as long as Composition 1 is satisfied.

[0049] Composition 2 is a composition in which the (meth)acrylic polymer (A) contains an alkyl group-containing unsaturated monomer (a1), a monomer (a2) having a functional group, and a vinyl monomer (a3). In one embodiment, the (meth)acrylic polymer (A) contains 2-octyl (meth)acrylate in an amount of 30.0 to 80.0% by mass, preferably 30.0 to 74.0% by mass, and contains the vinyl monomer (a3) in an amount of 5 to 15% by mass, preferably 5 to 10% by mass. In this case, the mass % of the remaining monomers constituting the (meth)acrylic polymer (A) can include the mass % of the alkyl group-containing unsaturated monomer (a1) other than 2-octyl (meth)acrylate, the mass % of the monomer (a2) having a functional group, and the polyalkylene glycol chain-containing mono(meth)acrylate (a4). Note that the types and contents of the remaining monomers constituting the (meth)acrylic polymer (A) are not particularly limited as long as Composition 2 is satisfied.

[0050] Composition 3 is a composition in which the (meth)acrylic polymer (A) contains an alkyl group-containing unsaturated monomer (a1), a monomer (a2) having a functional group, and a polyalkylene glycol chain-containing mono(meth)acrylate (a4). In one embodiment, the (meth)acrylic polymer (A) contains 2-octyl (meth)acrylate in an amount of 30.0 to 80.0% by mass, preferably 30.0 to 74.0% by mass, and the polyalkylene glycol chain-containing mono(meth)acrylate (a4) in an amount of 5 to 15% by mass, preferably 5 to 10% by mass. In this case, the mass percentage of the remaining monomers constituting the (meth)acrylic polymer (A) includes the mass percentage of the alkyl group-containing unsaturated monomer (a1) other than 2-octyl (meth)acrylate, the mass percentage of the monomer (a2) having a functional group, and the vinyl-based monomer (a3). The types and contents of the remaining monomers constituting the (meth)acrylic polymer (A) are not particularly limited as long as Composition 3 is satisfied.

[0051] Composition 4 refers to a composition in which the (meth)acrylic polymer (A) contains an alkyl group-containing unsaturated monomer (a1), a monomer (a2) having a functional group, a vinyl monomer (a3), and a polyalkylene glycol chain-containing mono(meth)acrylate (a4). In one embodiment, the (meth)acrylic polymer (A) contains 2-octyl (meth)acrylate in an amount of 30.0 to 80.0% by mass, preferably 30.0 to 74.0% by mass, the vinyl monomer (a3) in an amount of 5 to 15% by mass, preferably 5 to 10% by mass, and the polyalkylene glycol chain-containing mono(meth)acrylate (a4) in an amount of 5 to 15% by mass, preferably 5 to 10% by mass. In this case, the mass percentage of the remaining monomers constituting the (meth)acrylic polymer (A) includes the mass percentage of the alkyl group-containing unsaturated monomer (a1) other than 2-octyl (meth)acrylate and the mass percentage of the monomer (a2) having a functional group. More specifically, the alkyl group-containing unsaturated monomer (a1) further includes 2-ethylhexyl acrylate and butyl acrylate. The (meth)acrylic polymer (A) contains 2-ethylhexyl acrylate in an amount of 5 to 50% by mass, preferably 5 to 44% by mass, and butyl acrylate in an amount of 2 to 8% by mass, preferably 3 to 7% by mass, based on 100% by mass of all the monomers constituting the (meth)acrylic polymer (A). In one embodiment, the (meth)acrylic polymer (A) contains a monomer having a hydroxy group as the monomer (a2) having a functional group in an amount of 4 to 10% by mass, preferably 5 to 9% by mass. The monomer (a2) having a functional group preferably includes 4-hydroxybutyl acrylate. Here, the type and content of the monomer (a2) having a functional group are not particularly limited. Note that the polyalkylene glycol chain-containing mono(meth)acrylate (a4) having at least one hydroxy group does not belong to the monomer (a2) having a functional group.

[0052] <Other monomers> The (meth)acrylic polymer (A) according to one embodiment may further contain other monomers as constitutional units.

[0053] Examples of other monomers include (meth)acrylic acid alkoxyalkyl esters such as 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, and 2-phenoxyethyl (meth)acrylate; aralkyl (meth)acrylates such as benzyl (meth)acrylate, 2-phenylethyl (meth)acrylate, and naphthylmethyl (meth)acrylate; and aryl (meth)acrylates such as phenyl (meth)acrylate, tolyl (meth)acrylate, and naphthyl (meth)acrylate. These may be used alone or in combination of two or more.

[0054] <Hardener (B)> The pressure-sensitive adhesive composition for re-peeling according to one embodiment contains a hardener (B). By including the hardener (B) in the pressure-sensitive adhesive composition for re-peeling, the cohesive force of the pressure-sensitive adhesive composition for re-peeling is increased and the re-peelability is improved.

[0055] In one embodiment, the pressure-sensitive adhesive composition for re-peeling contains the hardener (B) in an amount of 5.0 to 30.0% by mass based on 100% by mass of the (meth)acrylic polymer (A). When the content of the hardener (B) is within the above-mentioned predetermined range, a pressure-sensitive adhesive composition for re-peeling with excellent low contamination property and adhesion balance can be realized. On the other hand, when the content of the hardener (B) is less than 5.0% by mass, the low contamination property decreases. Also, when the content of the hardener (B) exceeds 30.0% by mass, the adhesive force at low-speed peeling decreases, so the adhesion balance deteriorates.

[0056] The hardener (B) according to one embodiment is an isocyanate-based hardener.

[0057] Examples of the hardener (B) include isocyanate-based hardeners, epoxy-based hardeners, metal chelate-based hardeners, and aziridine-based hardeners. These may be used alone or in combination of two or more. The (meth)acrylic polymer (A) is preferably crosslinked with at least one of the above hardeners. The hardener (B) is preferably an isocyanate-based hardener.

[0058] Isocyanate-based curing agents include, for example, adducts of isocyanate compounds such as tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethylxylylene diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, and polymethylene polyphenyl isocyanate, etc., and polyol compounds such as trimethylolpropane, as well as their burette forms, and their isocyanurate forms, and adducts of the above isocyanate compounds and any of the polyols such as polyether polyol, polyester polyol, acrylic polyol, polybutadiene polyol, and polyisoprene polyol, etc., compounds having three or more isocyanate groups in the molecule; or compounds having two isocyanate groups in the molecule such as their allophanate forms, etc.

[0059] Epoxy-based curing agents include, for example, epoxy resins obtained from the reaction of bisphenol A and epichlorohydrin, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, N,N-diglycidylaniline, N,N,N',N'-tetraglycidyl-m-xylylenediamine, 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, and N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane, etc.

[0060] Metal chelate-based curing agents include, for example, coordination compounds of polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium, etc., and acetylacetone or ethyl acetoacetate.

[0061] Aziridine-based curing agents include, for example, N,N'-(4,4'-methylenediphenyl)bis(aziridine-1-carboxamide), 1,1'-isophthaloyl bis(2-methylaziridine), tris(1-aziridinyl)phosphine oxide, 1,1'-hexamethylenebis(iminocarbonyl)bisaziridine, trimethylolpropane-tris(2-aziridinylpropionate), 2,4,6-tris(1-aziridinyl)-1,3,5-triazine, and the like.

[0062] <Curing retarder (C)> The pressure-sensitive adhesive composition for re-peeling according to one embodiment further includes a curing retarder (C).

[0063] In one embodiment, the pressure-sensitive adhesive composition for re-peeling contains the curing retarder (C) in an amount of 4.1 to 14.1% by mass, preferably 6.1 to 12.1% by mass, more preferably 8.1 to 10.1% by mass, based on 100% by mass of the (meth)acrylic polymer (A).

[0064] The pressure-sensitive adhesive composition for re-peeling preferably further contains a keto-enol tautomer compound as the curing retarder (C). When a polyisocyanate compound such as a trifunctional or higher isocyanate compound is used as the curing agent (B), the keto-enol tautomer compound blocks the isocyanate groups of the curing agent (B). Thereby, excessive viscosity increase and gelation of the pressure-sensitive adhesive composition for re-peeling after the addition of the curing agent (B) can be suppressed, and the pot life of the pressure-sensitive adhesive composition for re-peeling can be extended.

[0065] Examples of the keto-enol tautomer compound include β-ketoesters such as methyl acetoacetate, ethyl acetoacetate, octyl acetoacetate, oleyl acetoacetate, lauryl acetoacetate, and stearyl acetoacetate, and β-diketones such as acetylacetone, 2,4-hexanedione, and benzoylacetone. These may be used alone or in combination of two or more. The keto-enol tautomer compound is preferably acetylacetone.

[0066] <Antistatic agent (D)> The pressure-sensitive adhesive composition for re-peeling according to one embodiment further contains an antistatic agent (D). The pressure-sensitive adhesive composition for re-peeling may contain an antistatic agent (D) in order to impart antistatic properties to the pressure-sensitive adhesive layer. Thereby, the surface protection film of the present invention can be suitably used as a surface protection film having antistatic properties.

[0067] The surface resistivity of the pressure-sensitive adhesive layer according to one embodiment is 1.0×10 +12 Ω / sq or less. The surface resistivity is an index indicating the ease of electric current passing through a unit area of a substance. A large surface resistivity indicates poor performance in releasing static electricity generated by charging when peeling the pressure-sensitive adhesive layer from the adherend. On the other hand, a small surface resistivity indicates high performance in releasing static electricity generated by charging when peeling the pressure-sensitive adhesive layer from the adherend. By making the surface resistivity of the pressure-sensitive adhesive layer as small as possible, peeling charge generated when peeling the pressure-sensitive adhesive layer from the adherend is reduced, so that damage and failure of the adherend (for example, an optical member) can be avoided. Note that the antistatic property of the pressure-sensitive adhesive layer is not an essential performance and may be an arbitrary performance depending on the type of the adherend.

[0068] In one embodiment, the pressure-sensitive adhesive composition for re-peeling contains 1.0 to 6.0% by mass, preferably 1.5 to 5.5% by mass, more preferably 2.0 to 5.0% by mass of the antistatic agent (D) with respect to 100% by mass of the (meth)acrylic polymer (A).

[0069] Examples of the antistatic agent (D) include cations such as pyridinium cation, imidazolium cation, ammonium cation, and alkali metal cation, and phosphates hexafluoride (PF 6 - ), thiocyanate (SCN - ), alkylbenzenesulfonate (RC 6 H 4 SO 3 - ), perchlorate (ClO 4 - ), tetrafluoroborate (BF 4 -) Ionic compounds having anions such as bis(fluorosulfonyl)imide salt (FSI), bis(trifluoromethanesulfonyl)imide salt (TFSI), tetrabutylammonium bis(trifluoromethanesulfonyl)imide salt, and trifluoromethanesulfonate salt (TF) can be mentioned. These may be used alone or in combination of two or more. The antistatic agent (D) preferably contains lithium bis(trifluoromethanesulfonyl)imide (TFSI) or tetrabutylammonium bis(trifluoromethanesulfonyl)imide.

[0070] <Other Additives> The pressure-sensitive adhesive composition for re-peeling of the present invention may contain various resins and additives as long as it does not affect the required performance defined in the present invention. Examples of the additives include tackifiers, antioxidants, silane coupling agents, heat or light stabilizers, ultraviolet absorbers, leveling agents, defoaming agents, antibacterial agents, moisturizing agents, pigments, dyes, and fragrances. These may be used alone or in combination of two or more.

[0071] <Physical Properties> In one embodiment, the adhesive force at low-speed peeling (when peeling at a tensile speed of 0.3 m / min) of the adhesive layer composed of the pressure-sensitive adhesive composition for re-peeling is 10.0 to 19.9 gf / 25 mm. The adhesive force at low-speed peeling is the adhesive force measured with the adherend being PET. More specifically, the adhesive force at low-speed peeling of the adhesive layer is 10.0 to 19.0 gf / 25 mm.

[0072] In one embodiment, the adhesive force at high-speed peeling (when peeling at a tensile speed of 30 m / min) of the adhesive layer composed of the pressure-sensitive adhesive composition for re-peeling is less than 150 gf / 25 mm. The adhesive force at high-speed peeling is the adhesive force measured with the adherend being PET. More specifically, the adhesive force at high-speed peeling of the adhesive layer is 8 to 137 gf / 25 mm.

[0073] In one embodiment, the adhesion balance of the pressure-sensitive adhesive layer made of the re-peeling pressure-sensitive adhesive composition is less than 10.0 and is calculated by the following formula. Adhesion balance = Adhesion at a tensile speed of 30 m / min / Adhesion at a tensile speed of 0.3 m / min... (Formula). Here, the adhesion balance refers to a parameter that quantitatively represents the relationship between two types of adhesions necessary for a user to comfortably use the surface protection film. The two types of adhesions include the adhesion during low-speed peeling and the adhesion during high-speed peeling. The adhesion during low-speed peeling refers to the adhesion required for the surface protection film not to peel off from the adherend until it is used up. On the other hand, the adhesion during high-speed peeling refers to the adhesion that can quickly and cleanly peel off the surface protection film attached to the adherend (for example, a large optical member). Thus, the adhesion balance is a parameter considering the adhesion of the surface protection film from before use to after use. The inventor of the present invention has found, through trial and error, a numerical value of the adhesion balance (less than 10.0) that provides high user satisfaction. By having the pressure-sensitive adhesive layer have the adhesion balance defined in the present invention, a surface protection film with high user satisfaction can be realized. A surface protection film with high user satisfaction refers to a surface protection film that is difficult to peel off before use and can be cleanly peeled off after use (after being used up).

[0074] In one embodiment, the pressure-sensitive adhesive layer made of the re-peeling pressure-sensitive adhesive composition has low contamination. Here, low contamination means that after sticking the surface protection film to the adherend and tracing an object (for example, a pencil) over the surface protection film through the pressure-sensitive adhesive layer, even when peeled off from the adherend, the pressure-sensitive adhesive does not detach and contaminate the adherend.

[0075] In one embodiment, the surface resistivity of the pressure-sensitive adhesive layer made of the re-peeling pressure-sensitive adhesive composition is 1.0×10 +12 Ω / □ or less.

[0076] <Manufacturing method of (meth)acrylic polymer (A)> (Meta)acrylic polymer (A) can be produced by a known method, but it is preferably produced by solution polymerization. Specifically, it is common to heat a solvent, monomer, polymerization initiator, etc. to a reaction temperature of about 50 to 90 °C under an inert gas atmosphere such as nitrogen gas and carry out a polymerization reaction for 4 to 12 hours. Examples of solvents used in solution polymerization include ester solvents such as methyl acetate, ethyl acetate, and butyl acetate, ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, and hydrocarbon solvents such as toluene, xylene, hexane, and heptane. These may be used alone or in combination of two or more.

[0077] The polymerization initiator may be any one having the ability to initiate radical polymerization, and conventionally known polymerization initiators can be used.

[0078] Examples of polymerization initiators include persulfates such as potassium persulfate, sodium persulfate, and ammonium persulfate; oil-soluble azo compounds such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(isobutyric acid)dimethyl, and 1,1'-azobis(cyclohexane-1-carbonitrile); water-soluble azo compounds such as 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide], 2,2'-azobis[2-(2-imidazolin-2-yl)propane] and its salts, 2,2'-azobis(2-methylpropionamidine) and its salts, and 4,4'-azobis(4-cyanovaleric acid) and its salts; and organic peroxides such as benzoyl peroxide, cumene hydroperoxide, t-butyl hydroperoxide, t-butyl peroxy-2-ethylhexanoate, and t-butyl peroxyisobutyrate. These may be used alone or in combination of two or more.

[0079] <Surface protection film> The surface protection film has an adhesive layer on a base material, which is a cured product of the pressure-sensitive adhesive composition for re-peeling of the present invention. The surface protection film can be manufactured, for example, by applying the pressure-sensitive adhesive composition for re-peeling on the base material and drying it. The adhesive layer may be provided on at least one surface of the base material. Further, a release sheet may be provided on the adhesive surface of the adhesive layer. Since the pressure-sensitive adhesive composition for re-peeling used for the surface protection film is as described above, detailed description thereof is omitted.

[0080] The adhesive layer is a layer having a slightly adhesive property for attaching the surface protection film to optical members such as a polarizing plate and a retardation plate. Further, the adhesive layer may have antistatic properties when the adherend dislikes static electricity. The reason for making the adhesive layer slightly adhesive is to make it easy to peel off and leave no adhesive residue when peeling the used surface protection film from the optical member. When the surface protection film is attached to an optical member, it is preferable that the adhesive layer has sufficient transparency. The size (area) of the optical member to which the surface protection film is attached is not particularly limited, and it may have a small area or a large area. Further, the shape of the optical member is not limited to a flat surface, and may have a curved surface and one or more irregularities.

[0081] <Optical member with an adhesive layer> The optical member with an adhesive layer according to one embodiment is obtained by laminating an adhesive layer obtained by curing the pressure-sensitive adhesive composition for re-peeling of the present invention on at least one surface of the optical member. Examples of the optical member include a polarizing film, a retardation film, an antireflection film, an antiglare film, an ultraviolet absorption film, an infrared absorption film, an optical compensation film, and a brightness enhancement film. Examples of the display device including the optical member include a liquid crystal display, an organic EL display, and a touch panel.

[0082] Examples of the liquid medium used when applying the pressure-sensitive adhesive composition for release include hydrocarbon solvents such as toluene, xylene, hexane, and heptane; ester solvents such as methyl acetate, ethyl acetate, and butyl acetate; ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; halogenated hydrocarbon solvents such as dichloromethane and chloroform; ether solvents such as diethyl ether, methoxytoluene, and dioxane; and other organic solvents such as hydrocarbon solvents. These may be used alone or in combination of two or more. Any liquid medium can be added to the pressure-sensitive adhesive composition for release to adjust the viscosity. Also, the viscosity of the pressure-sensitive adhesive composition for release can be reduced by heating.

[0083] Examples of the base material include cellophane, plastic sheet, rubber, foam, fabric, rubber cloth, resin-impregnated cloth, glass plate, and wood. The base material may be in the form of a plate or a film. Further, the base material may be composed of a single material, or may be a multilayer base material formed by laminating base materials of a plurality of materials. Further, a base material with its surface subjected to a release treatment can also be used. When the surface protection film is adhered to the optical member, the base material preferably has sufficient transparency.

[0084] Examples of the plastic sheet include films of polyolefin resins such as polyvinyl alcohol film, triacetyl cellulose film, polypropylene, polyethylene, polycycloolefin, and ethylene-vinyl acetate copolymer; films of polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; films of vinyl resins such as polyvinyl chloride; films of polycarbonate resins; films of polynorbornene resins; films of polyarylate resins; films of acrylic resins; films of polyphenylene sulfide resins; films of polystyrene resins; films of polyamide resins; films of polyimide resins; films of epoxy resins, etc. These may be used alone or in combination of two or more.

[0085] As a release sheet (separator) for protecting the adhesive surface of the adhesive layer, a resin film such as a polyester film can be used. The surface of the release sheet on the side that comes into contact with the adhesive surface of the adhesive layer can be subjected to a release treatment with a silicone-based or fluorine-based release agent or the like.

[0086] Examples of the coating method of the re-peeling adhesive composition include, for example, a Meyer bar, an applicator, a brush, a spray, a roller, a gravure coater, a die coater, a lip coater, a comma coater, a knife coater, a reverse coater, and a spin coater. Examples of the drying method include, for example, hot air drying, infrared rays, and a reduced pressure method. The drying conditions can be appropriately changed according to the curing form, film thickness, and type of solvent of the re-peeling adhesive composition, but for example, hot air drying at 60 to 130 °C may be used.

[0087] In one embodiment, the thickness of the adhesive layer is 1 to 200 μm, preferably 3 to 100 μm.

[0088] <Production of (Meth)acrylic Polymer (A) and Re-peeling Adhesive Composition> The definitions of the abbreviations in Tables 1 to 8 are as follows. Definition of Abbreviations 2OA 2-Octyl acrylate 2EHA 2-Ethylhexyl acrylate BA Butyl acrylate VAc Vinyl acetate MPEGMA Methoxypolyethylene glycol methacrylate 4HBA 4-Hydroxybutyl acrylate HEA 2-Hydroxyethyl acrylate AAc Acrylic acid mAM Methacrylamide Curing agent: Isocyanate-based curing agent manufactured by Siden Chemical Co., Ltd. Li-TFSI Lithium bis(trifluoromethanesulfonyl)imide FC-4400: Tetrabutylammonium bis(trifluoromethanesulfonyl)imide manufactured by 3M Company (A) Component (Meth)acrylic polymer (A) (a1) Component Alkyl group-containing unsaturated monomer (a1) having an alkyl group with 1 to 18 carbon atoms (a2) Component Monomer (a2) having a functional group (a3) Component Vinyl monomer (a3) (a4) Component Polyalkylene glycol chain-containing mono(meth)acrylate (a4) Adhesive strength (gf / 25 mm) Adhesive strength during low-speed peeling at 0.3 m / min, refer to Test 1 described below Adhesive strength (gf / 25 mm) Adhesive strength during high-speed peeling at 30 m / min, refer to Test 1 described below Adhesive strength balance Refer to Test 2 described below Low contamination Refer to Test 3 described below Surface resistivity (Ω / sq) Refer to Test 4 described below

[0089] Table 1 shows the raw material formulations of the (meth)acrylic polymers (A) of Production Examples 1 to 7. Table 2 shows the raw material formulations of the (meth)acrylic polymers (A) of Production Examples 8 to 14. Table 3 shows the raw material formulations of the (meth)acrylic polymers (A) of Production Examples 15 to 21. Table 4 shows the raw material formulations of the (meth)acrylic polymers (A) of Production Examples 22 to 28. The unit of the numerical values regarding the raw material formulations of the (A) component in Tables 1 to 4 is "parts".

[0090] Table 5 shows the raw material formulations and test results of the pressure-sensitive adhesive compositions for re-peeling of Examples 1 to 8. Table 6 shows the raw material formulations and test results of the pressure-sensitive adhesive compositions for re-peeling of Examples 9 to 16. Table 7 shows the raw material formulations and test results of the pressure-sensitive adhesive compositions for re-peeling of Examples 17 to 24. Table 8 shows the raw material formulations and test results of the pressure-sensitive adhesive compositions for re-peeling of Comparative Examples 1 to 9. The unit of the numerical values regarding the raw material formulations of the pressure-sensitive adhesive compositions for re-peeling in Tables 5 to 8 is "parts".

[0091] [Table 1]

[0092] [Table 2]

[0093]

Table 3

[0094]

Table 4

[0095]

Table 5

[0096]

Table 6

[0097]

Table 7

[0098]

Table 8

[0099] <Production Example 1: Method for Producing (Meth)Acrylic Polymer (A)> The method for producing the (meth)acrylic polymer (A) of Production Example 1 will be described with reference to Table 1. 37 parts of ethyl acetate, 10 parts of acetone, and 0.1 part of a polymerization initiator (azobisisobutyronitrile) were charged into a reaction apparatus equipped with a stirrer, a thermometer, a sequential dropping device, and a reflux condenser. On the other hand, a monomer and solvent mixture composed of 95 parts of 2-octyl acrylate, 5 parts of 4-hydroxybutyl acrylate, and 10 parts of ethyl acetate was prepared in a separate container. While stirring the reaction apparatus, the temperature was raised to 68°C, and the monomer and solvent mixture measured in the separate container was dropped over 90 minutes, and a polymerization reaction was carried out at 80°C for 7 hours. After completion of the reaction, it was cooled, and ethyl acetate was added for dilution to obtain a (meth)acrylic polymer solution having a solid content of 44.0% by mass.

[0100] <Production Examples 2 to 28: Production Method of (Meth)acrylic Polymer (A)> Based on the raw material formulations in Tables 1 and 2 and the same production method as in Production Example 1, the (meth)acrylic polymers (A) of Production Examples 2 to 28 were produced, so detailed descriptions are omitted.

[0101] <Example 1: Production Method of Pressure-Sensitive Adhesive Composition for Release> While referring to Table 5, the production method of the pressure-sensitive adhesive composition for release of Example 1 will be described. With respect to 100 parts by solid content of the (meth)acrylic polymer solution of Production Example 1, 6.1 parts by solid content of an isocyanate-based curing agent (manufactured by Siden Chemical Co., Ltd.) as the curing agent (B) and 9.1 parts of acetylacetone as the curing retarder (C) were added, and they were thoroughly mixed to obtain a pressure-sensitive adhesive composition for release.

[0102] <Example 1: Production Method of Surface Protection Film> The pressure-sensitive adhesive composition for release of Example 1 was directly applied to a 38-μm-thick polyethylene terephthalate (PET) film as the base material. Then, the solvent was removed by drying at 90°C to form an adhesive layer with a thickness of 15 μm. A silicone resin-coated polyester film (release sheet) was coated on the surface where this adhesive layer was formed to produce a surface protection film. Furthermore, the produced surface protection film was cured at 23°C for 3 days to obtain samples for each test.

[0103] <Examples 2 to 24: Production Method of Pressure-Sensitive Adhesive Composition for Release> Based on the raw material formulations in Tables 5, 6, and 7 and the same production method as in Example 1, the pressure-sensitive adhesive compositions for release of Examples 2 to 24 were produced, so detailed descriptions are omitted. In Examples 15, 16, 17, and 19, 2.2 parts of lithium bis(trifluoromethanesulfonyl)imide was added as the antistatic agent (D). In Examples 18, 23, and 24, 4.5 parts of tetrabutylammonium bis(trifluoromethanesulfonyl)imide was added as the antistatic agent (D).

[0104] <Examples 2 to 24: Production Method of Surface Protection Film> Based on the same manufacturing method as in Example 1, the surface protection films of Examples 2 to 24 were manufactured, so detailed descriptions are omitted.

[0105] <Comparative Examples 1 to 9: Manufacturing Method of Pressure-Sensitive Adhesive Composition for Re-Peeling> Based on the raw material formulations in Table 8 and the same manufacturing method as in Example 1, the pressure-sensitive adhesive compositions for re-peeling of Comparative Examples 1 to 9 were manufactured, so detailed descriptions are omitted.

[0106] <Comparative Examples 1 to 9: Manufacturing Method of Surface Protection Film> Based on the same manufacturing method as in Example 1, the surface protection films of Comparative Examples 1 to 9 were manufactured, so detailed descriptions are omitted.

[0107] <Test Method> The following Tests 1 to 4 were conducted using the surface protection films of Examples 1 to 24 and Comparative Examples 1 to 9.

[0108] (Test 1: Measurement of Adhesive Force) The sample (surface protection film) was cut into pieces with a width of 25 mm and a length of 70 mm to prepare test pieces. The release sheet was peeled off from the test pieces and adhered to the surface of PET as the adherend, and a 2 kg roll was reciprocated once for pressure bonding. Then, it was left standing in an atmosphere of 23°C and 50% for 24 hours. After standing, using a tensile testing machine, the adhesive force was measured under the conditions of a tensile speed of 0.3 m / min or 30 m / min and a peeling angle of 180°. [Evaluation Criteria] · Adhesive force (gf / 25 mm) during low-speed peeling, tensile speed 0.3 m / min 〇 ··· 10.0 to 19.9 gf / 25 mm × ··· Less than 10.0 gf / 25 mm or 20.0 gf / 25 mm or more · Adhesive force (gf / 25 mm) during high-speed peeling, tensile speed 30 m / min 〇 ··· Less than 150 gf / 25 mm × ··· 150 gf / 25 mm or more

[0109] (Test 2: Calculation of Adhesive Force Balance) Based on the measurement results of the adhesive force during low-speed peeling and high-speed peeling measured in Test 1 and the following formula, the adhesive force balance was calculated. Adhesive force balance = Adhesive force at a tensile speed of 30 m / min / Adhesive force at a tensile speed of 0.3 m / min [Evaluation criteria] 〇 ··· Less than 10.0 × ··· 10.0 or more, or less than 10.0 (however, when the determination of either the adhesive force during low-speed peeling or high-speed peeling in Test 1 is "×")

[0110] (Test 3: Confirmation of low contamination) The sample (surface protection film) was cut into pieces 15 mm long and 40 mm wide to obtain test pieces. The release sheet was peeled off from the adhesive sheet of the test piece, and it was attached to the surface of the polarizing plate and pressed with a 2 kg roll once back and forth. Then, it was left in an atmosphere of 23°C and 50% for 24 hours. After leaving, using an automatic pencil scratching tester (manufactured by Imoto Seisakusho), it was traced with a 3H pencil at a scratching speed of 30 mm / min and a load of 0.7 kg from above the surface protection film. [Evaluation criteria] 〇 ··· There is no contamination on the polarizing plate. × ··· Clear traces remain on the polarizing plate.

[0111] (Test 4: Measurement of surface resistivity) The release sheet was peeled off from the test piece (surface protection film) to expose the adhesive layer, and the surface resistivity of the adhesive layer was measured using a resistivity meter.

[0112] <Test results> While referring to Tables 5 to 8 above, the test results of Examples 1 to 24 and Comparative Examples 1 to 9 will be described.

[0113] Examples 1 to 24 were excellent in both the adhesive force balance and low contamination as shown by the results of Tests 1 to 4. On the other hand, Comparative Examples 1 to 9 were not excellent in both the adhesive force balance and low contamination. Hereinafter, the reasons why Comparative Examples 1 to 9 did not satisfy the required performance will be explained.

[0114] In Comparative Example 1, since it contains 2-ethylhexyl acrylate having a low Tg, the adhesion balance was slightly improved, but the adhesion during low-speed peeling was still low. Also, the film became brittle and the low contamination property decreased. It should be noted that Comparative Example 1 differs from Patent Document 1 described at the beginning of this specification in that it contains a monomer (4HBA) having a hydroxy group as the monomer (a2) having a functional group.

[0115] In Comparative Example 2, since it contains butyl acrylate having a high Tg, the film became hard and the low contamination property was improved. However, since the adhesion during high-speed peeling increased, the adhesion balance deteriorated. Note that Comparative Example 2 corresponds to the known technique described at the beginning of this specification.

[0116] In Comparative Example 3, since the monomer (a2) having a functional group was contained in an amount less than the lower limit defined in the present invention, the crosslink density was low and the film became soft. Therefore, the adhesion during high-speed peeling increased and the adhesion balance deteriorated.

[0117] In Comparative Example 4, since the monomer (a2) having a functional group was contained in an amount exceeding the upper limit defined in the present invention, the polarity of the adhesive layer increased and the intermolecular force with the surface of the adherend became strong. Therefore, the adhesion during low-speed peeling increased and the adhesion balance deteriorated.

[0118] In Comparative Example 5, since 2-octyl acrylate was contained in an amount less than the lower limit defined in the present invention, the Tg of the (meth)acrylic polymer (A) decreased. Therefore, the film became brittle and the low contamination property decreased.

[0119] In Comparative Example 6, since it contains a monomer having a carboxy group (acrylic acid), the polarity of the adhesive layer increased and the intermolecular force with the surface of the adherend became strong. The adhesion during low-speed peeling and high-speed peeling increased and the adhesion balance deteriorated. Also, the film became brittle and the low contamination property decreased.

[0120] In Comparative Example 7, since the monomer having a hydroxy group was included in an amount less than the lower limit defined in the present invention and the monomer having a carboxy group (acrylic acid) was included, the polarity of the adhesive layer became high and the intermolecular force with the surface of the adherend became strong. Therefore, the adhesive force at the time of low-speed and high-speed peeling increased, and the adhesive force balance deteriorated.

[0121] In Comparative Example 8, since the curing agent (B) was included in an amount less than the lower limit defined in the present invention, the cohesive force became low and the adhesive force at the time of low-speed peeling increased. Therefore, the adhesive force balance deteriorated. In addition, the film became brittle and the low contamination property decreased.

[0122] In Comparative Example 9, since the curing agent (B) was included in an amount exceeding the upper limit defined in the present invention, the cohesive force became high and the adhesive force at the time of low-speed peeling decreased. Therefore, the adhesive force balance deteriorated.

[0123] As described above, the pressure-sensitive adhesive composition for re-peeling of the present invention has remarkable effects such as excellent low contamination property and adhesive force balance.

[0124] In addition, since the present invention can provide an environmentally friendly pressure-sensitive adhesive composition for re-peeling using a biomass-derived raw material with a low dependence on fossil resources, it can contribute to Goal 12, "Responsible Production and Consumption," of the Sustainable Development Goals (SDGs) led by the United Nations.

[0125] The invention is not limited to the above-described embodiments, and various modifications and changes are possible within the scope of the gist of the invention.

Claims

1. (a1) an alkyl group-containing unsaturated monomer having an alkyl group having 1 to 18 carbon atoms; a (meth)acrylic polymer (A) containing, as a structural unit, a monomer (a2) having a functional group; A curing agent (B), The alkyl group-containing unsaturated monomer (a1) contains at least 2-octyl (meth)acrylate, The (meth)acrylic polymer (A) contains 85 to 96.5% by mass of the 2-octyl (meth)acrylate and 3.5 to 15% by mass of the monomer (a2) having a functional group, based on 100% by mass of all monomers constituting the (meth)acrylic polymer (A); the monomer (a2) having a functional group does not include a monomer having a carboxy group and includes at least a monomer having a hydroxy group, The curing agent (B) is contained in an amount of 5.0 to 30.0% by mass relative to 100% by mass of the (meth)acrylic polymer (A), The alkyl group-containing unsaturated monomer (a1) is a (meth)acrylic acid alkyl ester. A removable pressure-sensitive adhesive composition.

2. (a1) an alkyl group-containing unsaturated monomer having an alkyl group having 1 to 18 carbon atoms; a (meth)acrylic polymer (A) containing, as a structural unit, a monomer (a2) having a functional group; A curing agent (B), The alkyl group-containing unsaturated monomer (a1) contains at least 2-octyl (meth)acrylate, The (meth)acrylic polymer (A) contains the monomer (a2) having a functional group in an amount of 3.5 to 15 mass% based on 100 mass% of all monomers constituting the (meth)acrylic polymer (A), the monomer (a2) having a functional group does not include a monomer having a carboxy group and includes at least a monomer having a hydroxy group, The curing agent (B) is contained in an amount of 5.0 to 30.0% by mass relative to 100% by mass of the (meth)acrylic polymer (A), The alkyl group-containing unsaturated monomer (a1) further contains 2-ethylhexyl acrylate, The (meth)acrylic polymer (A) contains 30 to 90% by mass of the 2-octyl (meth)acrylate and 5 to 65% by mass of the 2-ethylhexyl acrylate, based on 100% by mass of all monomers constituting the (meth)acrylic polymer (A); The alkyl group-containing unsaturated monomer (a1) is a (meth)acrylic acid alkyl ester. A removable pressure-sensitive adhesive composition.

3. (a1) an alkyl group-containing unsaturated monomer having an alkyl group having 1 to 18 carbon atoms; a (meth)acrylic polymer (A) containing, as a structural unit, a monomer (a2) having a functional group; A curing agent (B), The alkyl group-containing unsaturated monomer (a1) contains at least 2-octyl (meth)acrylate, The (meth)acrylic polymer (A) contains the monomer (a2) having a functional group in an amount of 3.5 to 15 mass% based on 100 mass% of all monomers constituting the (meth)acrylic polymer (A), the monomer (a2) having a functional group does not include a monomer having a carboxy group and includes at least a monomer having a hydroxy group, The curing agent (B) is contained in an amount of 5.0 to 30.0% by mass relative to 100% by mass of the (meth)acrylic polymer (A), The alkyl group-containing unsaturated monomer (a1) further contains butyl acrylate, The (meth)acrylic polymer (A) contains 40 to 90% by mass of the 2-octyl (meth)acrylate and 5 to 47% by mass of the butyl acrylate, based on 100% by mass of all monomers constituting the (meth)acrylic polymer (A); or The 2-octyl (meth)acrylate is contained in an amount of 30.0 to 80.0% by mass, and the butyl acrylate is contained in an amount of 5 to 15% by mass, The alkyl group-containing unsaturated monomer (a1) is a (meth)acrylic acid alkyl ester. A removable pressure-sensitive adhesive composition.

4. The alkyl group-containing unsaturated monomer (a1) further includes 2-ethylhexyl acrylate. The removable pressure-sensitive adhesive composition according to claim 1 or 3.

5. The alkyl group-containing unsaturated monomer (a1) further includes butyl acrylate. The removable pressure-sensitive adhesive composition according to claim 1 or 2.

6. The monomer (a2) having a functional group includes a monomer having a hydroxy group and a monomer having an amide group. The removable pressure-sensitive adhesive composition according to claim 1 .

7. The monomer (a2) having a functional group includes a monomer having a hydroxy group and a monomer having an amide group, The (meth)acrylic polymer (A) contains the monomer having a hydroxy group in an amount of 2.5 to 14.9% by mass and the monomer having an amide group in an amount of 0.1 to 1% by mass, based on 100% by mass of all monomers constituting the (meth)acrylic polymer (A). The removable pressure-sensitive adhesive composition according to claim 1 .

8. The (meth)acrylic polymer (A) further contains at least one selected from the group consisting of styrene, α-methylstyrene, vinyltoluene, vinylpyridine, vinylpyrrolidone, vinyl acetate, and acrylonitrile as a structural unit. The removable pressure-sensitive adhesive composition according to claim 1 .

9. The (meth)acrylic polymer (A) further contains at least one selected from the group consisting of styrene, α-methylstyrene, vinyltoluene, vinylpyridine, vinylpyrrolidone, vinyl acetate, and acrylonitrile as a structural unit, The (meth)acrylic polymer (A) contains 70 to 89% by mass of the 2-octyl (meth)acrylate and 5 to 15% by mass of at least one selected from the group consisting of 1-(2-octyl)(meth)acrylate and 1-(2-octyl)(meth)acrylate, based on 100% by mass of all monomers constituting the (meth)acrylic polymer (A), or The composition contains 30.0 to 80.0% by mass of the 2-octyl (meth)acrylate and 5 to 15% by mass of at least one selected from the group. The removable pressure-sensitive adhesive composition according to claim 1 .

10. The (meth)acrylic polymer (A) further contains a polyalkylene glycol chain-containing mono(meth)acrylate (a4) as a constituent unit, Here, the monomer (a2) having a functional group does not include the polyalkylene glycol chain-containing mono(meth)acrylate (a4). The removable pressure-sensitive adhesive composition according to claim 1 .

11. The (meth)acrylic polymer (A) further contains a polyalkylene glycol chain-containing mono(meth)acrylate (a4) as a constituent unit, The (meth)acrylic polymer (A) contains 70.0 to 89.5% by mass of the 2-octyl (meth)acrylate and 5 to 15% by mass of a polyalkylene glycol chain-containing mono(meth)acrylate (a4) relative to 100% by mass of all monomers constituting the (meth)acrylic polymer (A); or The composition contains 30.0 to 80.0% by mass of the 2-octyl (meth)acrylate and 5 to 15% by mass of a polyalkylene glycol chain-containing mono(meth)acrylate (a4), Here, the monomer (a2) having a functional group does not include the polyalkylene glycol chain-containing mono(meth)acrylate (a4). The removable pressure-sensitive adhesive composition according to claim 1 .

12. The polyalkylene glycol chain-containing mono(meth)acrylate (a4) is methoxypolyethylene glycol methacrylate. The removable pressure-sensitive adhesive composition according to claim 11.

13. The curing agent (B) is an isocyanate-based curing agent. The removable pressure-sensitive adhesive composition according to claim 1 .

14. Further comprising a cure retarder (C), The removable pressure-sensitive adhesive composition according to claim 13.

15. Further comprising an antistatic agent (D), The removable pressure-sensitive adhesive composition according to claim 1 .

16. the adhesive layer made of the removable adhesive composition has an adhesive strength balance of less than 10.0; The adhesive force balance is calculated by the following formula: Adhesive strength balance = Adhesive strength at a pulling speed of 30 m / min / Adhesive strength at a pulling speed of 0.3 m / min Here, the adhesive strength at a pulling speed of 30 m / min and the adhesive strength at a pulling speed of 0.3 m / min are adhesive strengths measured using PET as the adherend, The adhesive strength at the pulling speed of 30 m / min is less than 150 gf / 25 mm; The adhesive strength at a tensile speed of 0.3 m / min is 10.0 to 19.9 gf / 25 mm. The removable pressure-sensitive adhesive composition according to claim 1 .

17. A substrate; and a pressure-sensitive adhesive layer comprising the removable pressure-sensitive adhesive composition according to any one of claims 1 to 3 and provided on at least one surface of the substrate. Surface protection film.

18. The adhesive strength balance of the pressure-sensitive adhesive layer is less than 10.0, The adhesive force balance is calculated by the following formula: Adhesive strength balance = Adhesive strength at a pulling speed of 30 m / min / Adhesive strength at a pulling speed of 0.3 m / min Here, the adhesive strength at a pulling speed of 30 m / min and the adhesive strength at a pulling speed of 0.3 m / min are adhesive strengths measured using PET as the adherend, The adhesive strength at the pulling speed of 30 m / min is less than 150 gf / 25 mm; The adhesive strength at a tensile speed of 0.3 m / min is 10.0 to 19.9 gf / 25 mm. The surface protective film according to claim 17.

19. An optical member; and a pressure-sensitive adhesive layer comprising the removable pressure-sensitive adhesive composition according to any one of claims 1 to 3 and provided on at least one surface of the optical member. An optical component with an adhesive layer.

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