TW202030295A - Adhesive composition for protective film and protective film - Google Patents

Abstract

An adhesive composition for a protective film, comprising: a (meth)acrylic copolymer (A) that contains a structural unit derived from a monomer having a hydroxyl group, that has a glass transition temperature of -40°C or lower, and that has a weight average molecular weight in a range of from 300,000 to 1,500,000; a (meth)acrylic copolymer (B) that contains a structural unit derived from a monomer having a hydroxyl group, that has a glass transition temperature in a range of from -10°C to 45°C, and that has a weight average molecular weight in a range of from more than 10,000 to 200,000; and an isocyanate crosslinking agent, wherein a content of the (meth)acrylic copolymer (B) is in a range of from 5 parts by mass to 60 parts by mass with respect to 100 parts by mass of the (meth)acrylic copolymer (A), and a protective film are provided.

Description

Adhesive composition for protective film and protective film

The present invention relates to an adhesive composition for a protective film and a protective film.

In order to protect the surface of various articles, protective films with adhesive layers are widely used. In particular, various optical components represented by polarizing plates often use protective films.

For example, Japanese Patent Laid-Open No. 2005-146151 discloses a pressure-sensitive adhesive for protective sheets, which is formed by crosslinking a crosslinkable composition so that the gel fraction becomes 80% or more. The composition contains: (A) a (meth)acrylic polymer with a glass transition temperature of -40°C or less, which is copolymerized at least from an alkyl (meth)acrylate and a monomer containing a functional group, and (B) A (meth)acrylic polymer with a glass transition temperature of 80°C or higher and (C) a crosslinking agent with alkyl (meth)acrylate as the main component; the above (B) is relative to the above (A) 100 weight Parts, blended 5-20 parts by weight. In addition, Japanese Patent Application Laid-Open No. 2013-216769 discloses an adhesive composition containing: 100 parts by mass of polymer (A) having a glass transition temperature of less than 0°C, a weight average molecular weight of 1,000 or more and less than 50,000, and a glass transition temperature It is an organopolysiloxane compound (C) having a specific structure of a polyoxyalkylene chain and a (meth)acrylic polymer (B) of 30 to 300°C. In addition, Japanese Patent Application Laid-Open No. 2018-21127 discloses an adhesive containing: acrylic copolymer (A1) with a weight average molecular weight of 300,000 to 2 million, acrylic copolymer (A2) with a weight average molecular weight of 500 to 10,000, and Organic solvent; acrylic copolymer (A1) is a monomer mixture containing one or more selected from the group consisting of hydroxyl-containing monomers and carboxyl-containing monomers as monomers containing reactive functional groups ( The copolymer of B1), the acrylic copolymer (A2) is based on one of n-butyl acrylate or 2-ethylhexyl acrylate as the main component and contains monomers selected from hydroxyl-containing monomers and carboxyl-containing monomers. One or more of the group consisting of monomers is a copolymer of monomer mixture (B2) of monomers containing reactive functional groups, and the monomer mixture (B2) contains the above-mentioned monomers containing reactive functional groups 0.01~ 10% by weight, the reactive functional group-containing monomer contained in the monomer mixture (B1) and the reactive functional group-containing monomer contained in the monomer mixture (B2) contain one or more of the same monomer.

[The problem to be solved by the invention]

The adhesive composition used in the protective film (hereinafter also referred to as the "adhesive composition for protective film") is required to form an adhesive layer. After the protective film is attached to the surface of the adherend, protection is required During the period, it is not easy to peel off from the adherend, offset and other functional defects, and at the stage where protection is not needed, it can be effectively peeled off from the adherend. Here, the adhesive layer that is not prone to peeling off and shifting from the adherend can use the adhesive force measured when the protective film is peeled from the adherend at a low speed (0.3m/min) (the so-called low-speed peeling force) To evaluate. In addition, the adhesive layer that can be effectively peeled from the adherend can be evaluated by the adhesive force measured when the protective film is peeled from the adherend at a high speed (30 m/min) (so-called high-speed peel force).

In addition, when the protective film is peeled from the adherend, a phenomenon called zipping (hereinafter also referred to as a "zipping phenomenon") may occur when the protective film cannot be peeled off smoothly and a sound is made. If the zipper phenomenon occurs, striped defects may be observed on the surface of the adherend after the protective film is peeled off. Therefore, the adhesive composition for protective films is also required to form an adhesive layer that can suppress the zipper phenomenon.

In addition, in recent years, display devices with curved or curved shapes such as curved displays and flexible displays have gradually increased. Therefore, the adhesive composition for protective films is also required to form an adhesive layer, which shows that when the protective film is attached, it is not only attached to the adherend with a curved shape, even when the protective film is attached After the adherend has a flat shape, and the adherend with the protective film attached is bent, it is still not easy to peel off from the adherend, offset and other functionally poor adhesive strength. Hereinafter, the adhesion to the curved surface is also referred to as "curved surface adhesion".

However, when it is desired to control the low-speed peeling force and the high-speed peeling force of the adhesive layer of the protective film, since both exhibit the same behavior, it is difficult to adjust the balance between the low-speed peeling force and the high-speed peeling force. In addition, in recent years, considering the viewpoint of improving the workability, the peeling speed of the protective film from the adherend tends to be further increased. In addition, as the adherend (especially the optical member) becomes thinner, there is a tendency that surface defects of the adherend due to the zipper phenomenon when the protective film is peeled off are more likely to occur. The zipper phenomenon is thought to be caused by the strength of the adhesive layer. Generally, the adhesive force of the adhesive layer shows a tendency that the higher the peeling speed, the higher the adhesive force, so the zipper phenomenon is more likely to occur when the protective film is peeled from the adherend at a high speed. In addition, generally, the protective film attached to the curved surface is more likely to peel off from the adherend, offset and other functional failures than when attached to a flat surface.

Therefore, it is desired to form an adhesive that has a good balance between low-speed peeling force and high-speed peeling force, higher speed (for example, 100m/min; the same below) than ever before, which is less likely to cause zipper phenomenon, and has excellent curved surface adhesion. The adhesive composition for the protective film of the layer is difficult.

The problem to be solved by the present invention is to provide an adhesive composition for a protective film and a protective film. The adhesive composition for a protective film can form a good balance of low-speed peeling force and high-speed peeling force, even when peeling at a higher speed than before. Adhesive layer that sufficiently suppresses the zipper phenomenon and has excellent surface adhesion. [Means to solve the problem]

The specific methods used to solve the problem include the following aspects. >1>An adhesive composition for protective film, containing: The (meth)acrylic copolymer (A) contains a structural unit derived from a monomer having a hydroxyl group, has a glass transition temperature of -40°C or less and a weight average molecular weight in the range of 300,000 to 1.5 million, The (meth)acrylic copolymer (B) contains a structural unit derived from a monomer having a hydroxyl group, the glass transition temperature falls within the range of -10°C or more and 45°C or less, and the weight average molecular weight falls between more than 10,000 and 200,000 The following range, and Isocyanate series crosslinking agent; The content of the (meth)acrylic copolymer (B) is in the range of 5 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the (meth)acrylic copolymer (A). >2> The adhesive composition for a protective film as described in >1>, wherein the glass transition temperature of the (meth)acrylic copolymer (A) falls within the range of -75°C or more and -40°C or less. >3> The adhesive composition for a protective film as described in >1> or >2>, wherein the (meth)acrylic copolymer (A) contains the structural unit derived from the monomer having a hydroxyl group The ratio falls within the range of 0.5% by mass or more and 15% by mass or less with respect to all the structural units of the (meth)acrylic copolymer (A). >4> The adhesive composition for a protective film as described in any one of >1>~>3>, wherein the above-mentioned (meth)acrylic copolymer (B) is derived from a monomer having a hydroxyl group The content rate of the structural unit falls within the range of 0.5% by mass or more and 15% by mass or less with respect to all the structural units of the (meth)acrylic copolymer (B). >5> The adhesive composition for a protective film as described in any one of >1>~>4>, wherein the content of the (meth)acrylic copolymer (B) is relative to the (meth)acrylic acid 100 parts by mass of the copolymer (A) falls within the range of 5 parts by mass or more and 50 parts by mass or less. >6> The adhesive composition for a protective film as described in any one of >1>~>5>, wherein the isocyanate-based crosslinking agent is hexamethylene diisocyanate. >7> The adhesive composition for a protective film as described in any one of >1>~>6>, wherein the (meth)acrylic copolymer (A) contains a structural unit derived from a monomer having a carboxyl group . >8> The adhesive composition for a protective film as described in any one of >1>~>7>, wherein the (meth)acrylic copolymer (B) contains a structural unit derived from a monomer having a carboxyl group . >9>A protective film with: Substrate, and The adhesive layer is provided on the above-mentioned substrate and formed by using the adhesive composition for protective film as described in any one of >1>~>8>. [Effects of Invention]

According to the present invention, there is provided an adhesive composition for a protective film that can form an adhesive layer that has a good balance of low-speed peeling force and high-speed peeling force, fully suppresses the zipper phenomenon even when peeling at a higher speed than before, and has excellent curved surface adhesion. And provide protective film.

Hereinafter, specific embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and can be implemented by adding appropriate changes within the scope of the object of the present invention.

In this manual, the numerical range indicated by "~" means the range that includes the numerical values before and after "~" as the minimum and maximum values. In this specification, within the numerical range described in stages, the upper limit or lower limit of a certain numerical range can be replaced with the upper limit or lower limit of the numerical range described in another stage. In addition, in the numerical range described in this specification, the upper limit or lower limit described in a certain numerical range may be replaced with the values shown in the examples. In this specification, a combination of two or more ideal aspects is a more ideal aspect. In this specification, when there are multiple substances belonging to each component, the amount of each component means the total amount of multiple substances unless specifically limited.

In this specification, "(meth)acrylic copolymer" means that the content of structural units derived from a monomer having a (meth)acrylic acid group is the percentage of all structural units (that is, the (meth)acrylic polymer) All constituent units) are copolymers of 50% by mass or more.

In this manual, "(meth)acrylic" includes terms of both "acrylic" and "methacrylic", and "(meth)acrylate" includes "acrylate" and "methacrylate" "The terms of both, "(meth)acryloyl" is a term that includes both "acryloyl" and "methacryloyl".

In this manual, "n-" means normal, "i-" means iso (iso), "s-" means secondary (secondary), and "t-" means tertiary.

In this specification, "adhesive composition" means a liquid or paste substance before the end of the crosslinking reaction. In this specification, the "adhesive layer" means a film made of a substance after the crosslinking reaction of the adhesive composition is completed.

In this manual, "low-speed peeling force" means the adhesion measured when the protective film attached to the adherend is peeled off at a low speed (ie, 0.3m/min) at 180° in the longitudinal direction of the protective film from the adherend force. In addition, the detailed measurement method is shown in the Example mentioned later. In this specification, "appropriate low-speed peeling force" means an adhesive force with a strength that does not easily cause malfunctions such as peeling and offset from the adherend.

In this manual, "high-speed peeling force" means the adhesive force measured when the protective film attached to the adherend is peeled off at a high speed (that is, 30m/min) at 180° in the longitudinal direction of the protective film from the adherend . In addition, the detailed measurement method is shown in the Example mentioned later. In this specification, "appropriate high-speed peeling force" means the adhesive force with the strength that can be effectively peeled from the adherend.

In this specification, "adhesive layer with a good balance of low-speed peeling force and high-speed peeling force" means an adhesive layer with a strength that is not prone to peeling and shifting from the adherend and can effectively peel off from the adherend. The adhesive layer of strength.

[Adhesive composition for protective film] The adhesive composition for protective film of the present invention (hereinafter also referred to as "adhesive composition") contains: The (meth)acrylic copolymer (A) contains a structural unit derived from a monomer having a hydroxyl group, and has a glass transition temperature of -40°C or less and a weight average molecular weight in the range of 300,000 to 1.5 million [hereinafter also referred to as Is a specific (meth)acrylic copolymer (A)"], The (meth)acrylic copolymer (B) contains a structural unit derived from a monomer having a hydroxyl group, the glass transition temperature falls within the range of -10°C or more and 45°C or less, and the weight average molecular weight falls between more than 10,000 and 200,000 The following range [hereinafter also referred to as specific (meth)acrylic copolymer (B)"], and Isocyanate series crosslinking agent; The content of the specific (meth)acrylic copolymer (B) falls within the range of 5 parts by mass or more and 60 parts by mass relative to 100 parts by mass of the specific (meth)acrylic copolymer (A). According to the adhesive composition of the present invention, it is possible to form an adhesive layer with a good balance of low-speed peeling force and high-speed peeling force, and even when peeling at a higher speed than before, the zipper phenomenon is sufficiently suppressed and the adhesive layer is excellent in surface adhesion. The reason why the adhesive composition of the present invention can exert such effects has not yet been clarified, but the present inventors speculate as follows. However, the following hypothesis is not intended to limit the explanation of the adhesive composition of the present invention, and is only described as an example.

The glass transition temperature of the specific (meth)acrylic copolymer (B) contained in the adhesive composition of the present invention falls within the range of -10°C or more and 45°C or less, and the weight average molecular weight falls within the range of more than 10,000 and 20 The range below 10,000. In addition, the content of the specific (meth)acrylic copolymer (B) in the adhesive composition of the present invention is 5 parts by mass or more relative to 100 parts by mass of the specific (meth)acrylic copolymer (A), and The range of 60 parts by mass or less. Therefore, it is considered that in the adhesive layer formed by the adhesive composition of the present invention, the specific (meth)acrylic copolymer (B) moderately concentrates in the vicinity of the surface (the so-called vicinity of the interface with the adherend). It is presumed that if the specific (meth)acrylic copolymer (B) is moderately concentrated near the interface with the adherend in the adhesive layer, the adhesive layer will not wet the adherend excessively, so the adhesive layer will Demonstrate appropriate high-speed peel strength. In addition, it is considered that the glass transition temperature of the specific (meth)acrylic copolymer (B) is 45° C. or lower, so that the adhesive layer can properly wet the adherend. Therefore, it is speculated that the adhesive layer formed by the adhesive composition of the present invention can suppress the zipper phenomenon caused by insufficient wetting of the adhesive layer to the adherend.

The glass transition temperature of the specific (meth)acrylic copolymer (A) contained in the adhesive composition of the present invention falls below -40°C and the weight average molecular weight falls within the range of 300,000 to 1.5 million. Therefore, it is presumed that the adhesive layer formed using the adhesive composition of the present invention will exhibit an appropriate low-speed peeling force. In addition, it is estimated that the adhesive layer formed by the adhesive composition of the present invention can sufficiently suppress the zipper phenomenon that may be caused when peeling off at a high speed.

The specific (meth)acrylic copolymer (A) and the specific (meth)acrylic copolymer (B) contained in the adhesive composition of the present invention both contain structural units derived from a monomer having a hydroxyl group. Cross-linking reaction with isocyanate-based cross-linking agent appropriately proceeds. Therefore, it is estimated that the low-speed peeling force and the high-speed peeling force of the adhesive layer formed using the adhesive composition of the present invention have a good balance. In addition, it is estimated that the adhesive layer formed by the adhesive composition of the present invention can sufficiently suppress the zipper phenomenon that may be caused when peeling off at a high speed.

In addition, the surface adhesion can be evaluated using the result of a constant load test as an index. The behavior when the protective film is peeled under a fixed load condition is different from the behavior when the protective film is peeled under a fixed speed condition. In the constant load test, the wet state of the interface between the adherend and the adhesive layer has a great influence. In the adhesive layer formed using the adhesive composition of the present invention, as described above, the specific (meth)acrylic copolymer (B) is moderately concentrated near the interface with the adherend. It is believed that the adhesive layer will be resistant to peeling. Therefore, it is estimated that the adhesive layer formed using the adhesive composition of the present invention has excellent curved surface adhesiveness.

In contrast to the adhesive composition of the present invention, the pressure sensitive adhesive for protective sheets described in JP 2005-146151 A contains two types of (meth)acrylic polymers, but the (methyl) ) The glass transition temperature (Tg) of the acrylic polymer is 80°C or higher, and the content of the (meth)acrylic polymer of component (B) is relative to 100 weight of the (meth)acrylic polymer of component (A) The part is 5-20 parts by weight, so the formed adhesive layer does not wet enough to the adherend. For example, the zipper phenomenon cannot be sufficiently suppressed when the peeling speed is 100m/min. The adhesive composition described in JP 2013-216769 A contains two types of copolymers, but the glass transition temperature (Tg) of the (meth)acrylic polymer (B) is 59°C or higher, so it is considered to be compatible Similarly to the pressure-sensitive adhesive for protective sheets described in Japanese Patent Application Laid-Open No. 2005-146151, the formed adhesive layer does not wet the adherend sufficiently, for example, it cannot be sufficiently suppressed when the peeling speed is 100m/min. Zipper phenomenon. The adhesive composition described in JP 2018-21127 A contains two types of copolymers. The present inventors discovered that the glass transition temperature (Tg) of the acrylic copolymer (A2) contained in the adhesive composition described in JP 2018-21127 A is lower than the specific (meth)acrylic copolymer in the present invention. Outside the glass transition temperature (Tg) of the material (B). Therefore, it is believed that the adhesive layer formed by the adhesive composition described in Japanese Patent Application Laid-Open No. 2018-21127 has insufficient wetting of the adherend. For example, it cannot be sufficiently suppressed when the peeling speed is 100m/min. Zipper phenomenon.

Hereinafter, in this specification, "specific (meth)acrylic copolymer (A) and specific (meth)acrylic copolymer (B)" are collectively referred to as "specific (meth)acrylic copolymer".

[Specific (meth)acrylic copolymer (A)] The adhesive composition of the present invention contains a structural unit derived from a monomer having a hydroxyl group, a glass transition temperature of -40°C or less, and a (meth)acrylic copolymer with a weight average molecular weight falling within the range of 300,000 or more and 1.5 million or less (A) [that is, specific (meth)acrylic copolymer (A)].

>Constituted units from monomers with hydroxyl groups> The specific (meth)acrylic copolymer (A) contains a structural unit derived from a monomer having a hydroxyl group. In this specification, "a structural unit derived from a monomer having a hydroxyl group" means a structural unit formed by addition polymerization of a monomer having a hydroxyl group.

The type of monomer having a hydroxyl group is not particularly limited. Specific examples of monomers having a hydroxyl group include: 2-hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, (methyl) ) 3-hydroxypropyl acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, (meth)acrylic acid -12-Hydroxylauryl ester, 3-methyl-3-hydroxybutyl (meth)acrylate, 1,1-dimethyl-3-hydroxybutyl (meth)acrylate, (meth)acrylic acid- 1,3-Dimethyl-3-hydroxybutyl ester, (meth)acrylic acid-2,2,4-trimethyl-3-hydroxypentyl ester, (meth)acrylic acid-2-ethyl-3-hydroxyl Hydroxyalkyl (meth)acrylates such as hexyl ester, N-hydroxyethyl (meth)acrylamide, etc.; 1,4-cyclohexanedimethanol monoacrylate, dicaprolactone-2-propenyloxy Ether and so on. Among them, a monomer having a hydroxyl group, for example, when the specific (meth)acrylic copolymer (A) contains a structural unit derived from an alkyl (meth)acrylate monomer described later, it is considered to be From the viewpoint of good copolymerizability of the ester monomer, hydroxyalkyl (meth)acrylate is preferable. (Meth) hydroxyalkyl acrylate, for example, in consideration of good reactivity with isocyanate-based crosslinking agents, it is preferably hydroxyalkyl (meth)acrylate having a hydroxyalkyl group with a carbon number of 1 to 5. Hydroxyalkyl (meth)acrylates of hydroxyalkyl having 2 to 4 carbon atoms are more preferred.

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

The content rate (so-called content ratio; the same hereinafter) of the structural unit derived from the monomer having a hydroxyl group in the specific (meth)acrylic copolymer (A) is not particularly limited. For example, relative to the specific (meth)acrylic copolymer (A) All constituent units of the copolymer (A) should preferably fall within the range of 0.1% by mass or more and 20% by mass or less, more preferably within the range of 0.5% by mass or more and 15% by mass or less, and fall within the range of 1% by mass or more and 10% by mass. The range below% is even better. The content of the structural unit derived from the monomer having a hydroxyl group in the specific (meth)acrylic copolymer (A) is 0.1% by mass or more relative to all the structural units of the specific (meth)acrylic copolymer (A) It means that the specific (meth)acrylic copolymer (A) actively contains a structural unit derived from a monomer having a hydroxyl group. When the specific (meth)acrylic copolymer (A) has a hydroxyl-containing monomer-derived structural unit content of 20% by mass or less relative to all the structural units of the specific (meth)acrylic copolymer (A) , There is a tendency to form an adhesive layer that can more fully suppress the zipper phenomenon that may be caused when peeling off at a high speed. And there is a tendency to form an adhesive layer with better surface adhesion.

>Constituted units derived from alkyl (meth)acrylate monomers> The specific (meth)acrylic copolymer (A) preferably contains a structural unit derived from an alkyl (meth)acrylate monomer. The structural unit derived from the alkyl (meth)acrylate monomer contributes to the adjustment of the adhesive force of the adhesive layer.

In this specification, "a structural unit derived from an alkyl (meth)acrylate monomer" means a structural unit formed by addition polymerization of an alkyl (meth)acrylate monomer.

The type of the alkyl (meth)acrylate monomer is not particularly limited. The alkyl (meth)acrylate monomer is preferably an unsubstituted alkyl (meth)acrylate monomer. The alkyl group of the (meth)acrylic acid alkyl ester monomer may be linear, branched, or cyclic. In addition, the carbon number of the alkyl group is preferably 1-18, more preferably 1-12 from the viewpoint of the adhesion of the formed adhesive layer to the adherend and the adhesion to the base material of the protective film.

The alkyl (meth)acrylate monomers include: methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, (meth)acrylate Base) 2-butyl acrylate, tertiary butyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, ( N-nonyl meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, stearyl (meth)acrylate, (meth) ) Lauryl acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, etc. Among them, the alkyl (meth)acrylate monomer is preferably selected from the viewpoint of easily adjusting the glass transition temperature (Tg) of the (meth)acrylic copolymer (A) to -40°C or less, for example, At least one of the group consisting of n-butyl acrylate (n-BA) and 2-ethylhexyl acrylate (2EHA).

When the specific (meth)acrylic copolymer (A) contains a structural unit derived from an alkyl (meth)acrylate monomer, it may contain only one structural unit derived from an alkyl (meth)acrylate monomer, or Can contain more than two types.

When the specific (meth)acrylic copolymer (A) contains a structural unit derived from an alkyl (meth)acrylate monomer, the specific (meth)acrylic copolymer (A) is derived from (meth)acrylic acid alkyl The content of the structural unit of the base ester monomer is preferably in the range of 50% by mass to 99.9% by mass relative to all the structural units of the specific (meth)acrylic copolymer (A), and should be 70% by mass. The range of the above and 99.5 mass% or less is more preferable, and the range of 80 mass% or more and 99.1 mass% or less is still more preferable.

>Constituted units derived from monomers having carboxyl groups> The specific (meth)acrylic copolymer (A) may contain a structural unit derived from a monomer having a carboxyl group. In this specification, "a structural unit derived from a monomer having a carboxyl group" means a structural unit formed by addition polymerization of a monomer having a carboxyl group.

If the specific (meth)acrylic copolymer (A) contains the structural unit derived from a monomer having a crosslinkable functional group only the structural unit derived from a monomer having a hydroxyl group, there will be a specific (meth)acrylic The cross-linked structure formed by the cross-linking reaction between the copolymer (A) and the isocyanate-based cross-linking agent is tighter, and the adhesive layer tends to become harder. If the adhesive layer becomes hard, the high-speed peeling force will increase, so it is easy to damage the balance between the low-speed peeling force and the high-speed peeling force. On the other hand, if the specific (meth)acrylic copolymer (A) contains a structural unit derived from a monomer having a carboxyl group, it tends to form an adhesive layer with a better balance of low-speed peeling force and high-speed peeling force. If the specific (meth)acrylic copolymer (A) contains a structural unit derived from a monomer having a carboxyl group, it is considered that it is difficult to form an excessively dense cross-linked structure, the hardening of the adhesive layer is suppressed, and the high-speed peeling force is unlikely to increase s reason.

The type of the monomer having a carboxyl group is not particularly limited. Specific examples of monomers having a carboxyl group include: acrylic acid (AA), methacrylic acid (MAA), crotonic acid, maleic anhydride, fumaric acid, itaconic acid, glutaconic acid, citraconic acid, ω-carboxyl group -Polycaprolactone mono(meth)acrylate [e.g. ω-carboxy-polycaprolactone (n≒2) monoacrylate], succinate (e.g. 2-propenyloxyethyl-succinic acid) and the like. Among them, the monomer having a carboxyl group is preferably acrylic acid (AA) in view of good reactivity with an isocyanate-based crosslinking agent, for example.

When a specific (meth)acrylic copolymer (A) contains the structural unit derived from the monomer which has a carboxyl group, it may contain only 1 type of structural unit derived from the monomer which has a carboxyl group, and may contain 2 or more types.

When the specific (meth)acrylic copolymer (A) contains a structural unit derived from a monomer having a carboxyl group, the content of a structural unit derived from a monomer having a carboxyl group in the specific (meth)acrylic copolymer (A) With respect to all the structural units of the specific (meth)acrylic copolymer (A), it is preferable to fall within the range of 0.1% by mass to 5% by mass, and more preferably within the range of 0.3% by mass to 3% by mass, It is more preferable to fall within the range of 0.5% by mass or more and 1.5% by mass or less. When the specific (meth)acrylic copolymer (A) has a carboxyl-containing monomer-derived structural unit content of 0.1% by mass or more relative to all the structural units of the specific (meth)acrylic copolymer (A) , There is a tendency to form an adhesive layer with a better balance of low-speed peeling force and high-speed peeling force. When the specific (meth)acrylic copolymer (A) has a carboxyl-containing monomer-derived structural unit content of 5% by mass or less relative to all the structural units of the specific (meth)acrylic copolymer (A) , There is a tendency to form an adhesive layer that can more fully suppress the zipper phenomenon even when peeling at a higher speed than before.

>Other building blocks> The specific (meth)acrylic copolymer (A) may contain structural units other than the aforementioned structural units (so-called other structural units) within the range where the effects of the present invention can be exerted. The aforementioned structural units are also essential structural units. The structural unit derived from the monomer which has a hydroxyl group, the structural unit derived from the alkyl (meth)acrylate monomer of arbitrary structural units, and the structural unit derived from the monomer which has a carboxyl group.

The monomer constituting the other structural unit is not particularly limited as long as it can be copolymerized with the monomer constituting the aforementioned structural unit. Examples of monomers constituting other structural units include: (meth)acrylates with cyclic groups represented by benzyl (meth)acrylate and phenoxyethyl (meth)acrylate; Methoxyethyl acrylate and ethoxyethyl (meth)acrylate are represented by alkoxyalkyl (meth)acrylates; styrene, α-methylstyrene, tertiary butylstyrene, Aromatic monovinyl monomers represented by p-chlorostyrene, chloromethyl styrene, and vinyl toluene; vinyl cyanide monomers represented by acrylonitrile and methacrylonitrile; and vinyl formate, Vinyl acetate, vinyl propionate, and vinyl versatic acid are representative vinyl esters. Various derivatives of these monomers can also be cited.

>>Glass transition temperature of specific (meth)acrylic copolymer (A)>> The glass transition temperature (Tg) of the specific (meth)acrylic copolymer (A) is -40°C or lower, preferably -50°C or lower, more preferably -55°C or lower, and even more preferably -60°C or lower. If the glass transition temperature (Tg) of the specific (meth)acrylic copolymer (A) is below -40℃, the high-speed peeling force will not become too high, and it can form an adhesive with a good balance of low-speed peeling force and high-speed peeling force. Floor. In addition, an adhesive layer can be formed that can sufficiently suppress the zipper phenomenon that may be caused when peeling off at a high speed. The lower limit of the glass transition temperature (Tg) of the specific (meth)acrylic copolymer (A) is not particularly limited. For example, considering the adhesive force to the adherend, it is preferably -75°C or higher.

The glass transition temperature (Tg) of the specific (meth)acrylic copolymer (A) is the absolute temperature (unit: K; the same for the following) calculated by the following formula 1 converted into Celsius temperature (unit: °C; below Are the same). 1/Tg=m1/Tg1+m2/Tg2+...+m(k-1)/Tg(k-1)+mk/Tgk　(Equation 1)

In formula 1, Tg1, Tg2,..., Tg(k-1), and Tgk respectively represent the absolute temperature when each monomer constituting the specific (meth)acrylic copolymer (A) is made into a homopolymer (K) represents the glass transition temperature (Tg). m1, m2,..., m(k-1), and mk respectively represent the molar fraction of each monomer constituting the specific (meth)acrylic copolymer (A), and m1+m2+...+ m(k-1)+mk=1. In addition, by subtracting 273 from the absolute temperature (K), the absolute temperature (K) can be converted to Celsius (℃), and by adding 273 from the Celsius temperature (℃), the Celsius temperature (℃) can be converted to absolute temperature. (K).

In this specification, "the glass transition temperature (Tg) expressed in absolute temperature (K) when the homopolymer is made" means the absolute temperature (K) of the homopolymer obtained by polymerizing the monomer alone The glass transition temperature (Tg). The glass transition temperature (Tg) of the homopolymer was measured using a differential scanning calorimetry device (DSC) (model: EXSTAR6000, manufactured by Seiko Instruments (stock)) in a nitrogen stream, measuring a sample of 10 mg, and a heating rate of 10°C/min. The conditions are measured, and the inflection point of the obtained DSC curve is taken as the glass transition temperature (Tg) of the homopolymer.

For the representative monomer "Glass transition temperature (Tg) expressed in Celsius (°C) when it is made into a homopolymer", 2-ethylhexyl acrylate (2EHA) is -76°C. 2-ethylhexyl acrylate (2EHMA) at -10°C, n-butyl acrylate (n-BA) at -57°C, n-butyl methacrylate (n-BMA) at 21°C, tertiary butyl acrylate Ester (t-BA) is 41℃, tertiary butyl methacrylate (t-BMA) is 107℃, isobutyl methacrylate (i-BMA) is 48℃, and methyl acrylate (MA) is 5℃ , Methyl methacrylate (MMA) is 103°C, isobornyl methacrylate (IBXMA) is 155°C, isobornyl acrylate (IBXA) is 96°C, cyclohexyl methacrylate (CHMA) is 56°C, Ethyl acrylate (EA) is -27°C, ethyl methacrylate (EMA) is 42°C, methacrylic acid is 185°C, 4-hydroxybutyl acrylate (4HBA) is -39°C, 2-hydroxy acrylic acid Ethyl (2HEA) is -15°C, 2-hydroxyethyl methacrylate (2HEMA) is 55°C, acrylic acid (AA) is 163°C, isooctyl acrylate (i-OA) is -75°C, methyl Dimethylaminoethyl acrylate (DM) is 18℃, ω-carboxy-polycaprolactone (n≒2) monoacrylate is -30℃, and 2-propenoxyethyl-succinic acid is -40 ℃.

>>Weight average molecular weight of specific (meth)acrylic copolymer (A)>> The weight average molecular weight (Mw) of the specific (meth)acrylic copolymer (A) falls in the range of 300,000 or more and 1.5 million or less, preferably in the range of 330,000 or more and 800,000 or less, and falls in the range of 350,000 or more and The range below 550,000 is better. When the weight average molecular weight (Mw) of the specific (meth)acrylic copolymer (A) is 300,000 or more, it tends to be easy to obtain cohesive force. If the weight average molecular weight (Mw) of the specific (meth)acrylic copolymer (A) is 1.5 million or less, an adhesive layer can be formed that suppresses the zipper phenomenon even when it is peeled at a higher speed than before Propensity.

The weight average molecular weight (Mw) of the specific (meth)acrylic copolymer (A) is a value measured by the following method. Specifically, the measurement was performed according to the following (1) to (3). (1) The solution of the specific (meth)acrylic copolymer (A) is applied to release paper and dried at 100°C for 1 minute to obtain a film of the specific (meth)acrylic copolymer (A). (2) Using the film-like specific (meth)acrylic copolymer (A) obtained in (1) above and tetrahydrofuran, a sample solution with a solid content concentration of 0.2% by mass is obtained. (3) Using gel permeation chromatography (GPC), under the following conditions, the weight average molecular weight (Mw) of the specific (meth)acrylic copolymer (A) is measured as a standard polystyrene conversion value.

~Conditions~ Measuring device: High-speed GPC [Model: HLC-8220 GPC, manufactured by Tosoh Corporation] Detector: Differential Refractometer (RI) [Assembled in HLC-8220, manufactured by Tosoh Corporation] String: Connect 4 TSK-GEL GMHXL [manufactured by Tosoh Corporation] in series Column temperature: 40℃ Mobile phase: Tetrahydrofuran Sample concentration: 0.2% by mass Injection volume: 100μL Flow rate: 0.6mL/min

>>Specific (meth)acrylic copolymer (A) content rate>> The content rate of the specific (meth)acrylic copolymer (A) in the adhesive composition of the present invention is not particularly limited. For example, the content of the specific (meth)acrylic copolymer (A) in the adhesive composition is preferably 50% by mass or more relative to the total solid content in the adhesive composition. The range of 99 mass% or less is more preferably the range of 60 mass% or more and 90 mass% or less, and the range of 70 mass% or more and 80 mass% or less is even more preferable. If the content of the specific (meth)acrylic copolymer (A) in the adhesive composition of the present invention is 50% by mass or more relative to the total solid content in the adhesive composition, the formation can be more fully suppressed The tendency of the adhesive layer of the zipper phenomenon that may be caused by high-speed peeling. When the content of the specific (meth)acrylic copolymer (A) in the adhesive composition of the present invention is less than 99% by mass relative to the total solid content in the adhesive composition, the low-speed peeling force and the high-speed peeling force The balance will be better, and there will be a tendency to form an adhesive layer with better surface adhesion. In this specification, "the total solid content in the adhesive composition" means the total mass of the adhesive composition when the adhesive composition does not contain volatile components such as solvents. In terms of ingredients, it means the mass of the residue obtained by removing volatile components such as solvent from the adhesive composition.

[Specific (meth)acrylic copolymer (B)] The adhesive composition of the present invention contains structural units derived from a monomer having a hydroxyl group, the glass transition temperature falls within the range of -10°C or more and 45°C or less, and the weight average molecular weight falls within the range of more than 10,000 and less than 200,000. (Meth)acrylic copolymer (B) [that is, specific (meth)acrylic copolymer (B)]. In addition, the content of the specific (meth)acrylic copolymer (B) in the adhesive composition of the present invention is 5 parts by mass or more relative to 100 parts by mass of the specific (meth)acrylic copolymer (A), and The range of 60 parts by mass or less.

>Constituted units from monomers with hydroxyl groups> The specific (meth)acrylic copolymer (B) contains a structural unit derived from a monomer having a hydroxyl group. The type of monomer having a hydroxyl group is not particularly limited. The specific example of the monomer having a hydroxyl group is the same as the specific example of the monomer having a hydroxyl group in the specific (meth)acrylic copolymer (A), so the description thereof is omitted here.

The monomer having a hydroxyl group, for example, when the specific (meth)acrylic copolymer (B) has a constituent unit derived from an alkyl (meth)acrylate monomer described later, it is considered to be the same as the alkyl (meth)acrylate monomer From the viewpoint of good copolymerizability, hydroxyalkyl (meth)acrylate is preferable. (Meth) hydroxyalkyl acrylate, for example, in consideration of good reactivity with isocyanate-based crosslinking agents, it is preferably hydroxyalkyl (meth)acrylate having a hydroxyalkyl group with a carbon number of 1 to 5. Hydroxyalkyl (meth)acrylates of hydroxyalkyl having 2 to 4 carbon atoms are more preferred.

If the adhesive layer is too hard or too soft, the adhesiveness of the adhesive layer will decrease. If the adhesive layer is too hard, it will not wet the adherend and the surface adhesiveness will decrease. In addition, if the adhesive layer is too soft, the resistance to a certain load will be insufficient, and the adhesiveness of the curved surface will decrease. If the carbon number of the hydroxyalkyl group is 3 or less, there will be an adhesive layer due to the specific (meth)acrylic copolymer (B) concentrated near the surface of the adhesive layer (near the interface with the adherend) Tendency to harden easily. In addition, when the carbon number of the hydroxyalkyl group is 5 or more, since the crosslinking pitch in the specific (meth)acrylic copolymer (B) becomes long, the adhesive layer tends to become soft. Considering this point of view, the hydroxyalkyl (meth)acrylate is preferably a hydroxyalkyl (meth)acrylate having a hydroxyalkyl group with a carbon number of 4, that is, 4-hydroxybutyl (meth)acrylate is preferred. The ester is preferably 4-hydroxybutyl acrylate (4HBA).

The specific (meth)acrylic copolymer (B) may contain only one type of structural unit derived from a monomer having a hydroxyl group, or may contain two or more types.

The content rate of the structural unit derived from the monomer having a hydroxyl group in the specific (meth)acrylic copolymer (B) is not particularly limited, for example, relative to all the structural units of the specific (meth)acrylic copolymer (B) , Should fall within the range of 0.1% by mass or more and 20% by mass or less, more preferably within the range of 0.5% by mass or more and 15% by mass or less, and even more preferably within the range of 1% by mass or more and 10% by mass or less. The specific (meth)acrylic copolymer (B) has a content of structural units derived from a monomer having a hydroxyl group of 0.1% by mass or more with respect to all the structural units of the specific (meth)acrylic copolymer (B) It means that the specific (meth)acrylic copolymer (B) actively contains a structural unit derived from a monomer having a hydroxyl group. When the specific (meth)acrylic copolymer (B) has a hydroxyl-containing monomer-derived structural unit content of 20% by mass or less relative to all the structural units of the specific (meth)acrylic copolymer (B) , There is a tendency to form an adhesive layer with a better balance of low-speed peeling force and high-speed peeling force and better surface adhesion.

>Constituted units derived from alkyl (meth)acrylate monomers> The specific (meth)acrylic copolymer (B) preferably contains a structural unit derived from an alkyl (meth)acrylate monomer. The structural unit derived from the alkyl (meth)acrylate monomer contributes to the adjustment of the adhesive force of the adhesive layer.

The type of the alkyl (meth)acrylate monomer is not particularly limited. The alkyl (meth)acrylate monomer is preferably an unsubstituted alkyl (meth)acrylate monomer. The alkyl group of the (meth)acrylic acid alkyl ester monomer may be linear, branched, or cyclic. In addition, the carbon number of the alkyl group is preferably 1-18, more preferably 1-12 from the viewpoint of the adhesion of the formed adhesive layer to the adherend and the adhesion to the base material of the protective film.

The specific example of the alkyl (meth)acrylate monomer is the same as the specific example of the alkyl (meth)acrylate monomer in the specific (meth)acrylic copolymer (A), so its description is omitted here. The (meth)acrylic acid alkyl ester monomer, for example, considering easy adjustment of the glass transition temperature (Tg), is preferably selected from tertiary butyl acrylate (t-BA) and n-butyl methacrylate (n-BMA). ) At least one of the group consisting of.

When the specific (meth)acrylic copolymer (B) contains a structural unit derived from an alkyl (meth)acrylate monomer, it may contain only one structural unit derived from an alkyl (meth)acrylate monomer, or Two or more types can be included.

When the specific (meth)acrylic copolymer (B) contains a structural unit derived from an alkyl (meth)acrylate monomer, the specific (meth)acrylic copolymer (B) is derived from (meth)acrylic acid alkyl The content of the constituent units of the base ester monomer, for example, relative to all the constituent units of the specific (meth)acrylic copolymer (B), preferably falls within the range of 50% by mass to 99.9% by mass, and is 70% by mass. The range of the above and 99.5 mass% or less is more preferable, and the range of 90 mass% or more and 99.0 mass% or less is even more preferable.

>Constituted units derived from monomers having carboxyl groups> The specific (meth)acrylic copolymer (B) may contain a structural unit derived from a monomer having a carboxyl group.

If the specific (meth)acrylic copolymer (B) contains only the structural unit derived from the monomer having a crosslinkable functional group, the specific (meth)acrylic copolymer is When the substance (B) is concentrated near the surface of the adhesive layer (that is, near the interface with the adherend), the surface of the adhesive layer tends to become hard. If the surface of the adhesive layer becomes hard, it will not sufficiently wet the adherend, which will easily impair the surface adhesion. On the other hand, if the specific (meth)acrylic copolymer (B) contains a structural unit derived from a monomer having a carboxyl group, the surface of the adhesive layer is not easy to harden, and it is unlikely that the adherend is insufficiently wetted , So it can form the tendency of the adhesive layer with better surface adhesion.

The type of the monomer having a carboxyl group is not particularly limited. The specific example of the monomer having a carboxyl group is the same as the specific example of the monomer having a carboxyl group in the specific (meth)acrylic copolymer (A), so the description thereof is omitted here. The monomer having a carboxyl group is preferably acrylic acid (AA) from the viewpoint of good reactivity with an isocyanate-based crosslinking agent.

When a specific (meth)acrylic copolymer (B) contains the structural unit derived from the monomer which has a carboxyl group, it may contain only 1 type of structural unit derived from the monomer which has a carboxyl group, and may contain 2 or more types.

When the specific (meth)acrylic copolymer (B) contains a structural unit derived from a monomer having a carboxyl group, the content of a structural unit derived from a monomer having a carboxyl group in the specific (meth)acrylic copolymer (B) With respect to all the constituent units of the specific (meth)acrylic copolymer (B), the range is preferably 0.1% by mass to 10% by mass, and more preferably in the range of 0.3% by mass to 8% by mass. , It is more preferable to fall within the range of 0.5 mass% or more and 5 mass% or less. When the specific (meth)acrylic copolymer (B) has a carboxyl-containing monomer-derived structural unit content of 0.1% by mass or more relative to all the structural units of the specific (meth)acrylic copolymer (B) , There is a tendency to form an adhesive layer with better surface adhesion. When the specific (meth)acrylic copolymer (B) has a carboxyl-containing monomer-derived structural unit content of 10% by mass or less relative to all the structural units of the specific (meth)acrylic copolymer (B) , There is a tendency to form an adhesive layer that can more fully suppress the zipper phenomenon that may be caused when peeling off at a high speed.

>Other building blocks> The specific (meth)acrylic copolymer (B) may contain structural units other than the aforementioned structural units (so-called other structural units) within the range in which the effects of the present invention can be exerted. The aforementioned structural units are also essential structural units. The structural unit derived from the monomer which has a hydroxyl group, the structural unit derived from the alkyl (meth)acrylate monomer of arbitrary structural units, and the structural unit derived from the monomer which has a carboxyl group.

The monomer constituting the other structural unit is not particularly limited as long as it can be copolymerized with the monomer constituting the aforementioned structural unit. The specific examples of the monomers constituting the other structural units are the same as the specific examples of the monomers constituting the other structural units in the specific (meth)acrylic copolymer (A), so the description is omitted here.

>>Glass transition temperature of specific (meth)acrylic copolymer (B)>> The glass transition temperature (Tg) of the specific (meth)acrylic copolymer (B) falls in the range of -10°C or more and 45°C, preferably in the range of 5°C or more and 40°C, and falls in the range of 15°C or more And the range below 35°C is more preferable. When the glass transition temperature (Tg) of the specific (meth)acrylic copolymer (B) is -10°C or higher, an adhesive layer with a good balance of low-speed peeling force and high-speed peeling force can be formed. In addition, an adhesive layer with excellent surface adhesion can be formed. When the glass transition temperature (Tg) of the specific (meth)acrylic copolymer (B) is 45°C or less, an adhesive layer can be formed that can sufficiently suppress the zipper phenomenon that may be caused when peeling at high speed.

The glass transition temperature (Tg) of the specific (meth)acrylic copolymer (B) is calculated by the same method as the glass transition temperature (Tg) of the aforementioned specific (meth)acrylic copolymer (A) .

>>Weight average molecular weight of specific (meth)acrylic copolymer (B)>> The weight average molecular weight (Mw) of the specific (meth)acrylic copolymer (B) falls in the range of more than 10,000 and less than 200,000, preferably in the range of 15,000 to 150,000, and falls in the range of more than 20,000 and The range below 100,000 is better. When the weight average molecular weight (Mw) of the specific (meth)acrylic copolymer (B) exceeds 10,000, an adhesive layer with a good balance of low-speed peeling force and high-speed peeling force can be formed. When the weight average molecular weight (Mw) of the specific (meth)acrylic copolymer (B) is 200,000 or less, an adhesive layer can be formed that can sufficiently suppress the zipper phenomenon that may be caused when peeling at high speed.

The weight average molecular weight (Mw) of the specific (meth)acrylic copolymer (B) is a value measured by the same method as the weight average molecular weight (Mw) of the aforementioned specific (meth)acrylic copolymer (A).

>>Content of specific (meth)acrylic copolymer (B)>> The content of the specific (meth)acrylic copolymer (B) in the adhesive composition of the present invention is 5 parts by mass or more and 60 parts by mass relative to 100 parts by mass of the specific (meth)acrylic copolymer (A) The range of parts below preferably falls within the range of 5 parts by mass or more and 50 parts by mass or less, more preferably within the range of 10 parts by mass or more and 50 parts by mass or less, and falls within the range of 15 parts by mass or more and 40 parts by mass or less. Better. If the content of the specific (meth)acrylic copolymer (B) in the adhesive composition of the present invention is 5 parts by mass or more relative to 100 parts by mass of the specific (meth)acrylic copolymer (A), a low speed An adhesive layer with a good balance of peeling force and high-speed peeling force. In addition, an adhesive layer with excellent surface adhesion can be formed. If the content of the specific (meth)acrylic copolymer (B) in the adhesive composition of the present invention is 60 parts by mass or less with respect to 100 parts by mass of the specific (meth)acrylic copolymer (A), the Adhesive layer that sufficiently suppresses the zipper phenomenon that may be caused when peeling off at high speed. In addition, an adhesive layer with excellent surface adhesion can be formed.

[Method for manufacturing specific (meth)acrylic copolymer] The production method of the specific (meth)acrylic copolymer (A) and the specific (meth)acrylic copolymer (B) [that is, the specific (meth)acrylic copolymer] is not particularly limited. The specific (meth)acrylic copolymer can be produced by polymerizing the above-mentioned monomer by a known polymerization method typified by a solution polymerization method, an emulsion polymerization method, a suspension polymerization method, and a bulk polymerization method, for example.

The glass transition temperature (Tg) of a specific (meth)acrylic copolymer can be adjusted suitably by using 2 or more types of monomers which differ in the glass transition temperature (Tg) at the time of making a homopolymer, for example. In addition, the weight average molecular weight (Mw) of a specific (meth)acrylic copolymer can be adjusted by adjusting the polymerization temperature, polymerization time, the amount of organic solvent used, the type of polymerization initiator, and the amount of polymerization initiator used. Pick the desired value.

Regarding the polymerization method, considering that when preparing the adhesive composition of the present invention after manufacturing, the processing steps are relatively simple and can be implemented in a short time, the solution polymerization method is preferable. The solution polymerization method usually involves feeding predetermined organic solvents, monomers, polymerization initiators, and chain transfer agents as needed into the polymerization tank, and under nitrogen flow and/or the reflux temperature of the organic solvent, It is heated and reacted for several hours while stirring. At this time, at least a part of the organic solvent, monomer, polymerization initiator, and/or chain transfer agent may be added sequentially.

Examples of the organic solvent used in the polymerization reaction include aromatic hydrocarbon compounds, aliphatic or alicyclic hydrocarbon compounds, ester compounds, ketone compounds, glycol ether compounds, and alcohol compounds. More specifically, the organic solvent used in the polymerization reaction includes, for example, benzene, toluene, ethylbenzene, n-propylbenzene, tertiary butylbenzene, o-xylene, meta-xylene, p-xylene, tetralin Aromatic hydrocarbon compounds represented by, decalin, and aromatic naphtha; n-hexane, n-heptane, n-octane, isooctane, n-decane, dipentene, petroleum spirit, petroleum naphtha , And aliphatic or cycloaliphatic hydrocarbon compounds represented by turpentine; ethyl acetate, n-butyl acetate, n-pentyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate, acetic acid Ester compounds represented by -3-methoxybutyl ester and methyl benzoate; represented by acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone, cyclohexanone, and methyl cyclohexanone Ketone 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 Glycol ether compounds; and alcohol compounds represented by methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, secondary butanol, and tertiary butanol. During the polymerization reaction, these organic solvents may be used alone or in combination of two or more kinds.

When manufacturing specific (meth)acrylic copolymers, it is preferable to use organic solvents that are not prone to chain transfer during polymerization, such as aromatic hydrocarbon compounds, ester compounds, ketone compounds, and alcohol compounds. In particular, consider specific (meth)acrylic copolymers. Toluene, ethyl acetate, methyl ethyl ketone, tertiary butanol, etc. are suitable from the viewpoints of solubility of the copolymer and ease of polymerization.

Examples of the polymerization initiator include organic peroxides and azo compounds generally used in solution polymerization. Examples of organic peroxides include: tertiary butyl hydroperoxide, cumene hydroperoxide, dicumyl peroxide, benzyl peroxide, laurel peroxide, hexyl peroxide, and dicarbonic acid peroxide. Diisopropyl ester, di-2-ethylhexyl peroxydicarbonate, tertiary butyl peroxytrimethyl acetate, 2,2-bis(4,4-di(tertiary butyl)peroxycyclohexyl) )Propane, 2,2-bis(4,4-bis(tertiary pentyl)peroxycyclohexyl)propane, 2,2-bis(4,4-bis(tertiary octyl)peroxycyclohexyl)propane , 2,2-bis(4,4-bis-α-cumylperoxycyclohexyl)propane, 2,2-bis(4,4-bis(tertiarybutyl)peroxycyclohexyl)butane , And 2,2-bis(4,4-bis(tertiary octyl)peroxycyclohexyl)butane. Examples of azo compounds include: 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(2,4-dimethylvaleronitrile) (ABVN), 2,2'- Azobis(4-methoxy-2,4-dimethylvaleronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), and 2,2'-azobis( Isobutyric acid) dimethyl ester. During the polymerization reaction, these polymerization initiators may be used alone or in combination of two or more kinds.

When producing a specific (meth)acrylic copolymer, it is preferable to use a polymerization initiator that does not cause a graft reaction during the polymerization reaction, and it is particularly preferable to use an azobis-based polymerization initiator.

The amount of the polymerization initiator used is not particularly limited, and is appropriately set according to the molecular weight of the specific (meth)acrylic copolymer for the purpose.

In the production of a specific (meth)acrylic copolymer, a chain transfer agent may be used as needed, as long as it does not impair the purpose and effects of the present invention. Examples of chain transfer agents include: cyanoacetic acid, cyanoacetic acid alkyl ester compounds with carbon numbers 1 to 8, bromoacetic acid, bromoacetic acid alkyl ester compounds with carbon numbers 1 to 8, and α-methylstyrene, anthracene Aromatic compounds represented by phenanthrene, pyrene, and 9-phenyl pyridine; p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid, p-nitrophenol, and p-nitrotoluene are Representative aromatic nitro compounds; benzoquinone and benzoquinone derivatives represented by 2,3,5,6-tetramethyl-p-benzoquinone; borane derivatives represented by tributylborane; tetrabromo Halogenated hydrocarbons represented by carbon, carbon tetrachloride, 1,1,2,2-tetrabromoethane, tribromoethylene, trichloroethylene, bromotrichloromethane, tribromomethane, and 3-chloro-1-propene Compounds; aldehyde compounds represented by chloral and furan formaldehyde; aromatic thiol compounds represented by alkyl mercaptan compounds with carbon numbers of 1 to 18, thiophenol and toluene mercaptan; carbons of thioglycolic acid and thioglycolic acid Alkyl ester compounds with 1 to 10, hydroxyalkyl mercaptan compounds with 1 to 12 carbons; and terpene compounds represented by pinene and terpinolene.

When manufacturing a specific (meth)acrylic copolymer, in the case of using a chain transfer agent, the amount of the chain transfer agent used is not particularly limited, and it is appropriate according to the molecular weight of the specific (meth)acrylic copolymer for the purpose To set.

The polymerization temperature is not particularly limited, and is appropriately set according to the molecular weight of the specific (meth)acrylic copolymer for the purpose.

[Isocyanate-based crosslinking agent] The adhesive composition of the present invention contains an isocyanate-based crosslinking agent. In the present specification, "isocyanate-based crosslinking agent" means a compound having two or more isocyanate groups in the molecule (so-called polyisocyanate compound).

Examples of isocyanate-based crosslinking agents include aromatic polyisocyanate compounds such as xylylene diisocyanate (XDI), diphenylmethane diisocyanate, triphenylmethane triisocyanate, and toluene diisocyanate (TDI); hexamethylene diisocyanate (HMDI) ), aliphatic or alicyclic polyisocyanate compounds such as pentamethylene diisocyanate (PDI), isophorone diisocyanate, and hydrogenated aromatic polyisocyanate compounds. In addition, the isocyanate-based crosslinking agent may also include the dimer of the polyisocyanate compound, the trimer of the polyisocyanate compound, the pentamer of the polyisocyanate compound, the polyisocyanate compound and the polyol compound (for example, trimethylol Propyl propane), the biuret of the above-mentioned isocyanate compound, etc. Among them, the isocyanate-based crosslinking agent is preferably hexamethylene diisocyanate (HMDI) in consideration of the viewpoint that it is easy to exhibit a desired adhesive force, for example. In addition, if the isocyanate-based crosslinking agent is hexamethylene diisocyanate (HMDI), the haze is suppressed, so it can be applied to, for example, a protective film for protecting the surface of an optical member.

Commercial products can be used for the polyisocyanate compound. Examples of commercially available products of polyisocyanate compounds include: "CORONATE (registered trademark) HX", "CORONATE (registered trademark) HL-S", "CORONATE (registered trademark) L", "CORONATE (registered trademark) L-45E ", "CORONATE (registered trademark) 2031", "CORONATE (registered trademark) 2030", "CORONATE (registered trademark) 2234", "CORONATE (registered trademark) 2785", "AQUANATE (registered trademark) 200", and "AQUANATE (Registered trademark) 210" [the above is Tosoh (stock) system]; "SUMIDUR (registered trademark) N-3300", "DESMODUR (registered trademark) N-3400", and "SUMIDUR (registered trademark) N-75" [The above is Sumika Covestro Urethane (stock) system]; "DURANATE (registered trademark) E-405-80T", "DURANATE (registered trademark) AE700-100", "DURANATE (registered trademark) 24A-100", and "DURANATE (Registered trademark) TSE-100" [Above is Asahi Kasei Co., Ltd.]; and "TAKENATE (registered trademark) D-110N", "TAKENATE (registered trademark) D-120N", "TAKENATE (registered trademark) M-631N ", "MT-OLESTER (registered trademark) NP1200", and "STABiO (registered trademark) XD-340N" [above are manufactured by Mitsui Chemicals Co., Ltd.].

In the adhesive composition of the present invention, the isocyanate-based crosslinking agent may contain only one type or two or more types.

The content of the isocyanate-based crosslinking agent in the adhesive composition of the present invention is not particularly limited, and is preferably within the range of 0.5 parts by mass or more and 10.0 parts by mass relative to 100 parts by mass of the specific (meth)acrylic copolymer , It is more preferable to fall within a range of 0.8 parts by mass or more and 9.0 parts by mass or less, and even more preferably within a range of 1.5 parts by mass or more and 6.0 parts by mass or less. The content of the isocyanate-based crosslinking agent in the adhesive composition of the present invention is 0.5 parts by mass or more relative to 100 parts by mass of the specific (meth)acrylic copolymer, which means that the adhesive composition of the present invention actively contains isocyanate-based crosslinking agents. Joint agent. If the content of the isocyanate-based crosslinking agent in the adhesive composition of the present invention is 10.0 parts by mass or less relative to 100 parts by mass of the specific (meth)acrylic copolymer, there will be an adhesive layer that does not excessively cause the formation of The wetting of the adhesive body is reduced, and the adhesive layer will show a tendency of more appropriate low-speed peeling force. In addition, there is a tendency to more fully suppress the zipper phenomenon that may be caused when peeling off at a high speed.

[Organic solvents] The adhesive composition of the present invention may also contain an organic solvent. The organic solvent contributes to the improvement of the coatability of the adhesive composition. Examples of the organic solvent include the same organic solvents used in the polymerization reaction of the aforementioned specific (meth)acrylic copolymer.

When the adhesive composition of the present invention contains an organic solvent, the organic solvent may contain only one type or two or more types.

When the adhesive composition of the present invention contains an organic solvent, the content of the organic solvent is not particularly limited, and can be appropriately set according to the purpose.

[Other ingredients] The adhesive composition of the present invention may contain components other than the aforementioned components (so-called other components) as needed within a range that does not impair the effects of the present invention. Other components include: polymers other than specific (meth)acrylic copolymers, crosslinking agents other than isocyanate crosslinking agents (for example, metal chelate crosslinking agents), and crosslinking catalysts (for example, metal alkyl Catalysts), antistatic agents (such as ionic compounds), antistatic additives (such as polyether modified polysiloxane compounds), tackifiers, antioxidants, colorants (such as dyes and pigments), light stabilizers ( For example, ultraviolet absorbers) and so on. In addition, the details of the ionic compound and the polyether-modified polysiloxane compound can be referred to, for example, the description in JP 2017-128636 A.

[use] Since the adhesive composition of the present invention can form a good balance of low-speed peeling force and high-speed peeling force, even when peeling at a higher speed than before, it can fully suppress the zipper phenomenon and has excellent curved surface adhesiveness, so it is suitable for use in pasting. A film attached to an adherend with a curved shape and used to protect the surface of the adherend (that is, a protective film). The adherends suitable for the protective film using the adhesive composition of the present invention include not only those having a curved shape when the protective film is attached, but also those having a flat shape when the protective film is attached, and when the protective film is attached After attachment, the adherend with the protective film attached is bent to have a curved shape. When bending the adherend to which the protective film is attached, for example, processing (pressing, cutting, etc.), winding, etc. can be cited.

Specific examples of such adherends include: optical members with curved shapes (curved displays, wafers, etc.), curved optical members (flexible displays, optical films, etc.), and window glass with curved shapes (for vehicles) , Stores, etc.), various products with curved or curved shapes (home appliances, automotive products, daily necessities, etc.), etc. The material of the adherend can include, for example, polyester resin, acetate resin, polyether resin, polycarbonate resin, polyamide resin, polyimide resin, polyolefin resin, Acrylic resin, vinyl chloride resin, ABS (Acrylonitrile Butadiene Styrene) resin, fluorine resin and other resins, various glasses, various metals, etc.

[Protective Film] The protective film of the present invention includes a substrate and an adhesive layer provided on the substrate and formed using the adhesive composition of the present invention. That is, the protective film of the present invention is laminated with a substrate and an adhesive layer formed using the adhesive composition of the present invention. Since the protective film of the present invention is provided with the adhesive layer formed by the adhesive composition of the present invention, after being attached to the surface of the adherend, it is not easy to peel off and offset from the adherend during the period of protection It is not good, and it can be peeled off efficiently when peeling from the adherend without protection. In other words, the low-speed peel force and the high-speed peel force have a good balance. In addition, since the protective film of the present invention has an adhesive layer formed using the adhesive composition of the present invention, it is less likely to cause a zipper phenomenon when peeled from an adherend at a high speed, even at a higher speed than before (for example, 100m/min) The zipper phenomenon is still sufficiently suppressed when peeling off. In addition, since the protective film of the present invention has an adhesive layer formed using the adhesive composition of the present invention, it has excellent curved surface adhesiveness.

Regarding the substrate in the protective film of the present invention, if an adhesive layer can be formed on the substrate, there is no particular limitation. The base material may, for example, contain polyester resins, acetate resins (e.g., triacetyl cellulose resin), polyether ether resins, polycarbonate resins, polyamide resins, and polyimide resins. , Polyolefin resin, acrylic resin, vinyl chloride resin, ABS resin, fluorine resin and other resin films. For example, considering the viewpoint of inspection and management of optical components using perspective, the base material should preferably contain selected from polyester resins, acetate resins, polyether sulfite resins, polycarbonate resins, and polyamides. A film of at least one type of resin from the group consisting of polyimide resin, polyimide resin, polyolefin resin, and acrylic resin. In addition, for example, considering the surface protection performance, a film containing a polyester resin is preferable, and in consideration of practicality, a film containing polyethylene terephthalate (PET) is particularly preferable.

The substrate may also contain various additives such as plasticizers, colorants (such as dyes and pigments), heat stabilizers, light stabilizers, antistatic agents, flame retardants and the like. In addition, a pattern may be applied to a part or the entire base material.

The thickness of the substrate is generally 500 μm or less, preferably 300 μm or less, and more preferably 200 μm or less. The lower limit of the thickness of the base material is preferably 5 μm or more, and more preferably 10 μm or more in consideration of the strength of the protective film, for example.

An antistatic layer can also be provided on one or both sides of the substrate. In addition, the surface of the substrate on the side where the adhesive layer is provided may be subjected to surface treatments such as corona discharge treatment and plasma discharge treatment in consideration of improving the adhesion between the substrate and the adhesive layer.

The method of forming the adhesive layer is not particularly limited, and a commonly used method can be adopted. For the method of forming the adhesive layer on the substrate, for example, the following method can be adopted. The adhesive composition of the present invention is applied on a substrate in its own state or diluted with a solvent as needed, and a coating film is formed on the substrate. Then, the formed coating film is dried to remove the solvent, and then aged to form an adhesive layer on the substrate. In addition, the exposed surface of the adhesive layer can also be protected with a release film. The release film is not particularly limited as long as it can be easily released from the surface of the adhesive layer, and examples thereof include paper and resin film that have been surface-treated with a release agent on one or both sides. Examples of the resin film include polyester films represented by polyethylene terephthalate (PET) films. Examples of release agents include fluorine-based resins, paraffin wax, silicone, and long-chain alkyl compounds. The peeling film protects the surface of the adhesive layer during the period before the protective film is actually used, and is peeled off during use.

Another method of forming the adhesive layer on the substrate may be the following method, for example. The adhesive composition of the present invention is applied in its own state or in a state diluted with a solvent as required, on a release film such as paper or resin film that has been surface-treated with a release agent, and then peeled off The thin film forms a coating film. Then, the formed coating film is dried to remove the solvent. Then, the surface of the release film on the side where the adhesive layer is formed is brought into contact with the substrate and pressed, and the adhesive layer is transferred to the substrate, thereby forming an adhesive layer on the substrate. Then, aging is carried out.

The method of coating the adhesive composition on the substrate or the release film is not particularly limited. Examples include the use of a gravure roll coater, a reverse roll coater, a kiss roll coater, a dipping roll coater, and a knife coater. Well-known methods such as spraying machines, spraying machines, coating rods, and applicators. The amount of the adhesive composition applied to the substrate or the release film is appropriately set according to the thickness of the formed adhesive layer.

The thickness of the adhesive layer can be appropriately set according to the adhesive force required by the protective film, the type (such as material and shape) of the adherend, and the surface roughness of the adherend. The thickness of the adhesive layer usually falls within the range of 1 μm or more and 100 μm or less, preferably within the range of 5 μm or more and 50 μm or less, and more preferably within the range of 10 μm or more and 30 μm or less.

The method of drying the coating film formed on the substrate or the release film is not particularly limited, and examples include methods such as natural drying, heat drying, hot air drying, and vacuum drying. The drying temperature and drying time of the coating film are not particularly limited, and are appropriately set according to the thickness of the coating film, the amount of organic solvent in the coating film, and the like.

The maturation is carried out for 1 to 10 days in an environment of 23° C. and 50% RH, for example. After aging, the crosslinking reaction of the adhesive composition will end and an adhesive layer will be formed.

The adhesive force of the adhesive layer (so-called peeling force) when the protective film attached to the adherend is peeled off at 180°, when the peeling speed is 0.3m/min (that is, low-speed peeling), it is preferably 0.15N /25mm or more, more preferably 0.20N/25mm or more, and even more preferably 0.25N/25mm or more. If the adhesive force during low-speed peeling (so-called low-speed peeling force) is 0.15N/25mm or more, the protective film tends to be more restrained from peeling or shifting.

The adhesive force of the adhesive layer when the protective film attached to the adherend is peeled at 180° (the so-called peeling force), when the peeling speed is 30m/min (that is, high-speed peeling), it should be less than 2.00N /25mm, less than 1.80N/25mm is better, less than 1.50N/25mm is better. If the adhesive force during high-speed peeling (so-called high-speed peeling force) is less than 2.00N/25mm, since the protective film can be peeled from the adherend more efficiently, the workability can be improved.

In this specification, an adhesive layer with a good balance of low-speed peeling force and high-speed peeling force is evaluated based on the value (low-speed peeling force/high-speed peeling force) obtained by dividing the value of low-speed peeling force by the value of high-speed peeling force. (Low-speed peeling force/high-speed peeling force) is preferably 0.10 or more, more preferably 0.15 or more, and even more preferably 0.20 or more. [Example]

Hereinafter, the present invention will be explained more specifically using examples. The present invention is not limited to the following embodiments as long as it does not exceed the gist.

[Production of (meth)acrylic copolymer (A)] [Manufacturing Example A-1] 171.0 parts by mass of ethyl acetate and 249.0 parts by mass of tertiary butanol were put into a reaction vessel equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a reflux cooler. In addition, 360.0 parts by mass of n-butyl acrylate (n-BA; alkyl acrylate monomer), 217.8 parts by mass of 2-ethylhexyl acrylate (2EHA; alkyl acrylate monomer), and 4-hydroxy acrylate 18.0 parts by mass of butyl ester (4HBA; monomer having a hydroxyl group) and 4.2 parts by mass of acrylic acid (AA; monomer having a carboxyl group) were put into another container and mixed to prepare a monomer mixture. 20.0% by mass of the monomer mixture was added to the reaction vessel. Then, after replacing the air in the reaction vessel with nitrogen, 0.08 parts by mass of 2,2'-azobisisobutyronitrile [AIBN; polymerization initiator] was added, and the reaction vessel was stirred while stirring under a nitrogen atmosphere. The temperature of the contents was increased to 85°C and the initial reaction was started. While adding 80.0% by mass of the remaining monomer mixture, 88.0 parts by mass of ethyl acetate and 0.80 parts by mass of AIBN to the reaction vessel after the initial reaction was almost completed, the contents of the reaction vessel were gradually added over about 2 hours. After the addition, the reaction was allowed to react for another 2 hours to obtain the reaction product (a1). Thereafter, a solution prepared by dissolving 0.60 parts by mass of trimethyl acetic acid tertiary butyl peroxide (polymerization initiator) in 132.0 parts by mass of ethyl acetate was added dropwise to the reaction product in the reaction vessel ( In a1), after completion of the dropwise addition, the reaction was further carried out for 1.5 hours to obtain the reaction product (a2). The obtained reaction product (a2) was diluted with ethyl acetate to obtain a solution of (meth)acrylic copolymer A-1 having a solid content of 45% by mass. The term "solid content" here means a component remaining after volatile components such as a solvent are removed from the solution of the (meth)acrylic copolymer A-1. The same applies to the following solutions of (meth)acrylic copolymers A-2 to A-9.

[Manufacturing Examples A-2~A-9] In Production Example A-1, the monomer composition of the (meth)acrylic copolymer (A) was changed to the monomer composition shown in Table 1, and the amount of organic solvent used and the amount of polymerization initiator used were adjusted At least one of them is used to change the weight average molecular weight (Mw) of the (meth)acrylic copolymer (A) to the weight average molecular weight (Mw) shown in Table 1. In addition, implement and manufacture In the same manner as in Example A-1, solutions of (meth)acrylic copolymers A-2 to A-9 having a solid content of 45% by mass were obtained.

(Meth) acrylic copolymer A-1~A-9 monomer composition (unit: mass %), glass transition temperature (Tg, unit: °C), and weight average molecular weight [Mw, unit: ten thousand (in the table) Marked as "×10 ⁴ ")] as shown in Table 1. The glass transition temperature (Tg) of (meth)acrylic copolymer A-1~A-9 is calculated using the same method as the glass transition temperature (Tg) of the aforementioned specific (meth)acrylic copolymer (A) Got. In addition, the weight average molecular weight (Mw) of (meth)acrylic copolymers A-1 to A-9 is the same method as the weight average molecular weight (Mw) of the aforementioned specific (meth)acrylic copolymer (A) Measured.

Among the (meth)acrylic copolymers A-1 to A-9 obtained above, the (meth)acrylic copolymers A-1 to A-7 correspond to the specific (meth)acrylic copolymers in the present invention. Copolymer (A).

[Table 1] (Meth) acrylic copolymer (A) Monomer composition [mass%] Tg [℃] Mw [×10 ⁴ ] n-BA 2EHA MA 4HBA AA A-1 60.0 36.3 - 3.0 0.7 -63.0 45.1 A-2 60.0 39.1 - 0.2 0.7 -64.1 40.2 A-3 60.0 38.8 - 0.5 0.7 -64.0 39.9 A-4 60.0 24.3 - 15.0 0.7 -57.9 47.9 A-5 60.0 22.3 - 17.0 0.7 -57.1 36.6 A-6 60.0 37.0 - 3.0 - -58.2 37.7 A-7 - 96.3 - 3.0 0.7 -74.1 35.3 A-8 60.0 39.3 - - 0.7 -64.2 38.5 A-9 33.3 - 63.0 3.0 0.7 -20.1 39.2

The details of each monomer described in Table 1 are as follows. >(Meth)acrylic acid alkyl ester monomer> "N-BA": n-butyl acrylate "2EHA": 2-ethylhexyl acrylate "MA": methyl acrylate >Monomers with hydroxyl> "4HBA": 4-hydroxybutyl acrylate >Monomers with carboxyl group> "AA": Acrylic

In Table 1, "-" means the monomer in this column is not used. In Table 1, "Glass transition temperature (Tg)" is abbreviated as "Tg", and "weight average molecular weight (Mw)" is abbreviated as "Mw".

[Production of (meth)acrylic copolymer (B)] [Manufacturing Example B-1] Put 350.0 parts by mass of ethyl acetate and 150.0 parts by mass of tertiary butanol into a reaction vessel equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a reflux cooler. In addition, 577.8 parts by mass of tertiary butyl acrylate (t-BA; alkyl acrylate monomer), 18.0 parts by mass of 4-hydroxybutyl acrylate (4HBA; monomer having a hydroxyl group), and acrylic acid (AA; (Carboxyl monomer) 4.2 parts by mass was put into another container and mixed to prepare a monomer mixture. 20.0% by mass of the monomer mixture was added to the reaction vessel. Then, after replacing the air in the reaction vessel with nitrogen, 1.80 parts by mass of 2,2'-azobisisobutyronitrile [AIBN; polymerization initiator] was added, and the reaction vessel was stirred while stirring under a nitrogen atmosphere. The temperature of the contents was increased to 85°C and the initial reaction was started. While adding the remaining monomer mixture of 80.0% by mass, 80.0 parts by mass of ethyl acetate and 8.0 parts by mass of AIBN to the reaction vessel after the initial reaction was almost completed, the contents of the reaction vessel were gradually added over about 2 hours. After the addition, the reaction was allowed to react for 1 hour to obtain the reaction product (b1). Thereafter, a solution prepared by dissolving 0.60 parts by mass of trimethyl acetic acid tertiary butyl peroxide (polymerization initiator) in 132.0 parts by mass of ethyl acetate was added dropwise to the reaction product in the reaction vessel ( In b1), after the dropwise addition is completed, the reaction is further carried out for 2 hours to obtain a reaction product (b2). The obtained reaction product (b2) was diluted with ethyl acetate to obtain a solution of (meth)acrylic copolymer B-1 having a solid content of 45% by mass. The term "solid content" here means a component remaining after volatile components such as a solvent are removed from the solution of the (meth)acrylic copolymer B-1. The same applies to the following solutions of (meth)acrylic copolymers B-2 to B-24.

[Manufacturing examples B-2~B-5, B-9~B-18, and B-21~B-24] In Production Example B-1, the monomer composition of the (meth)acrylic copolymer (B) was changed to the monomer composition shown in Table 2, and the amount of organic solvent used and the amount of polymerization initiator used were adjusted At least one of them is used to change the weight average molecular weight (Mw) of the (meth)acrylic copolymer (B) to the weight average molecular weight (Mw) shown in Table 2. In addition, implement and manufacture In Example B-1, the same operation was performed to obtain (meth)acrylic copolymers B-2~B-5, B-9~B-18, and B-21~B-24 with a solid content of 45% by mass Solution.

[Manufacturing examples B-6~B-8, B-19, and B-20] In Production Example B-1, at least one of the used amount of the organic solvent and the used amount of the polymerization initiator was adjusted to adjust the weight average molecular weight (Mw) of the (meth)acrylic copolymer (B) Except changing to the weight average molecular weight (Mw) shown in Table 2, the same operation as in Production Example B-1 was carried out to obtain (meth)acrylic copolymer B-6 with a solid content of 45% by mass ~B-8, B-19, and B-20 solutions.

(Meth) acrylic copolymer B-1~B-24 monomer composition (unit: mass %), glass transition temperature (Tg, unit: °C), and weight average molecular weight [Mw, unit: ten thousand (in the table) Marked as "×10 ⁴ ")] as shown in Table 2. The glass transition temperature (Tg) of (meth)acrylic copolymer B-1~B-24 is calculated using the same method as the glass transition temperature (Tg) of the aforementioned specific (meth)acrylic copolymer (A) Got. In addition, the weight average molecular weight (Mw) of (meth)acrylic copolymers B-1 to B-24 is the same as the weight average molecular weight (Mw) of the aforementioned specific (meth)acrylic copolymer (A) Measured.

Among the (meth)acrylic copolymers B-1 to B-24 obtained above, the (meth)acrylic copolymers B-1 to B-18 correspond to the specific (meth)acrylic copolymers in the present invention. Copolymer (B).

[Table 2]

The details of each monomer described in Table 2 are as follows. >(Meth)acrylic acid alkyl ester monomer> "T-BA": tertiary butyl acrylate "MA": methyl acrylate "N-BMA": n-butyl methacrylate "T-BMA": tertiary butyl methacrylate "2EHMA": 2-ethylhexyl methacrylate "2EHA": 2-ethylhexyl acrylate "I-BMA": Isobutyl methacrylate "MMA": methyl methacrylate "CHMA": Cyclohexyl methacrylate >Monomers with hydroxyl> "4HBA": 4-hydroxybutyl acrylate "2HEA": 2-hydroxyethyl acrylate "2HEMA": 2-hydroxyethyl methacrylate "SR-495" [trade name, manufactured by SARTOMER ARKEMA]: Dicaprolactone-2-propenoxyethyl ether "CHDMMA" [manufactured by Mitsubishi Chemical Corporation]: 1,4-cyclohexanedimethanol monoacrylate >Monomers with carboxyl group> "AA": Acrylic "M-5300" [trade name, manufactured by Toagosei Co., Ltd.]: ω-carboxy-polycaprolactone (n≒2) monoacrylate

In Table 2, "-" means that the monomer in this column is not used. In Table 2, "Glass transition temperature (Tg)" is abbreviated as "Tg", and "weight average molecular weight (Mw)" is abbreviated as "Mw".

[Preparation of Adhesive Composition] [Example 1] The solution of (meth)acrylic copolymer A-1 was 222.2 parts by mass (100 parts by mass of solid content) and 33.3 parts by mass of the solution of (meth)acrylic copolymer B-1 (the solid content was 15 parts by mass) The feed was placed in a four-necked flask equipped with a stirring blade, a thermometer, a cooler, and a dropping funnel, and the liquid temperature in the flask was kept at around 25°C while stirring for 4 hours. Then, add SUMIDUR (registered trademark) N-3300 as an isocyanate-based crosslinking agent in the flask [trade name, diluent of the trimer of hexamethylene diisocyanate (HMDI), manufactured by Sumika Covestro Urethane (Stock)] 16.0 parts by mass (solid content: 4.00 parts by mass), fully stirred to obtain an adhesive composition.

[Examples 2~18] In Examples 2 to 18, the composition of the adhesive composition was changed to the composition shown in Table 3. Except that, the same operation as in Example 1 was performed to obtain the adhesive composition.

[Examples 19~38] In Examples 19 to 38, except that the composition of the adhesive composition was changed to the composition shown in Table 4, the same operation as in Example 1 was carried out to obtain the adhesive composition.

[Comparative Examples 1~12] In Comparative Examples 1 to 12, except that the composition of the adhesive composition was changed to the composition shown in Table 5, the same operation as in Example 1 was carried out to obtain the adhesive composition.

[table 3] Composition of adhesive composition (Meth) acrylic copolymer (A) (Meth) acrylic copolymer (B) Isocyanate-based crosslinking agent species Blending amount [parts by mass] species Blending amount [parts by mass] species Blending amount [parts by mass] Example 1 A-1 100 B-1 15 N-3300 4.00 Example 2 A-2 100 B-1 15 N-3300 9.00 Example 3 A-3 100 B-1 15 N-3300 9.00 Example 4 A-4 100 B-1 15 N-3300 4.00 Example 5 A-5 100 B-1 15 N-3300 4.00 Example 6 A-6 100 B-1 15 N-3300 9.00 Example 7 A-1 100 B-2 15 N-3300 4.00 Example 8 A-1 100 B-3 15 N-3300 4.00 Example 9 A-1 100 B-4 15 N-3300 4.00 Example 10 A-1 100 B-5 15 N-3300 4.00 Example 11 A-1 100 B-1 5 N-3300 4.00 Example 12 A-1 100 B-1 10 N-3300 4.00 Example 13 A-1 100 B-1 30 N-3300 4.00 Example 14 A-1 100 B-1 50 N-3300 4.00 Example 15 A-1 100 B-1 60 N-3300 4.00 Example 16 A-1 100 B-6 15 N-3300 4.00 Example 17 A-1 100 B-7 15 N-3300 4.00 Example 18 A-1 100 B-8 15 N-3300 4.00

[Table 4] Composition of adhesive composition (Meth) acrylic copolymer (A) (Meth) acrylic copolymer (B) Isocyanate-based crosslinking agent Other ingredients SH-3773M LiTFS DOTDL ALUMICHELATE species Blending amount [parts by mass] species Blending amount [parts by mass] species Blending amount [parts by mass] Blending amount [parts by mass] Blending amount [parts by mass] Blending amount [parts by mass] Blending amount [parts by mass] Example 19 A-1 100 B-9 30 N-3300 4.00 - - - - Example 20 A-1 100 B-10 30 N-3300 4.00 - - - - Example 21 A-1 100 B-11 30 N-3300 4.00 - - - - Example 22 A-1 100 B-12 30 N-3300 4.00 - - - - Example 23 A-1 100 B-13 30 N-3300 3.00 - - - - Example 24 A-1 100 B-14 30 N-3300 4.00 - - 0.02 - Example 25 A-1 100 B-15 15 N-3300 4.00 - - - - Example 26 A-1 100 B-16 30 N-3300 4.00 - - - - Example 27 A-1 100 B-17 10 N-3300 9.00 - - - - Example 28 A-7 100 B-18 30 N-3300 4.00 - - - - Example 29 A-1 100 B-1 30 N-3300 0.80 0.05 - - - Example 30 A-1 100 B-1 15 N-3300 10.00 - - - - Example 31 A-1 100 B-1 15 L-45E 4.00 - - - - Example 32 A-1 100 B-1 15 D-120 6.00 - - - - Example 33 A-1 100 B-1 15 N-3400 4.00 - - - - Example 34 A-1 100 B-1 15 N-3300 /N-3400 3.96 /0.04 - - - - Example 35 A-1 100 B-1 30 N-3300 4.00 - - - 0.10 Example 36 A-1 100 B-1 30 N-3300 4.00 - 3.00 - - Example 37 A-1 100 B-1 30 N-3300 1.50 0.30 - - - Example 38 A-1 100 B-1 30 N-3300 1.50 0.30 0.25 - -

[table 5] Composition of adhesive composition (Meth) acrylic copolymer (A) (Meth) acrylic copolymer (B) Isocyanate-based crosslinking agent Other ingredients TETRAD-X species Blending amount [parts by mass] species Blending amount [parts by mass] species Blending amount [parts by mass] Blending amount [parts by mass] Comparative example 1 A-1 100 - - N-3300 4.00 - Comparative example 2 A-8 100 B-1 15 N-3300 9.00 - Comparative example 3 A-9 100 B-1 15 N-3300 4.00 - Comparative example 4 A-1 100 B-19 15 N-3300 4.00 - Comparative example 5 A-1 100 B-20 15 N-3300 4.00 - Comparative example 6 A-1 100 B-21 15 N-3300 4.00 - Comparative example 7 A-1 100 B-22 15 N-3300 4.00 - Comparative example 8 A-1 100 B-23 1 N-3300 4.00 - Comparative example 9 A-1 100 B-24 5 N-3300 4.00 - Comparative example 10 A-1 100 B-1 70 N-3300 4.00 - Comparative example 11 A-1 100 B-1 3 N-3300 4.00 - Comparative example 12 A-1 100 B-1 15 - - 10.00

In Tables 3 to 5, "-" means that the ingredient is not included.

The details of the ingredients listed in Tables 3 to 5 are as follows. >Isocyanate-based crosslinking agent> "N-3300" [Trade name: SUMIDUR (registered trademark) N-3300, manufactured by Sumika Covestro Urethane (Stock)]: 4-fold dilution of the trimer of hexamethylene diisocyanate (HMDI), solid content: 25 quality% "L-45E" [trade name: CORONATE (registered trademark) L-45E, manufactured by Tosoh Corporation]: adduct of toluene diisocyanate (TDI) and trimethylolpropane (TMP), solid content: 45 quality% "D-120" [trade name: TAKENATE (registered trademark) D-120, manufactured by Mitsui Chemicals Co., Ltd.]: adduct of xylylene diisocyanate (XDI) and trimethylolpropane (TMP), solid content ：75% by mass "N-3400" [Trade name: DESMODUR (registered trademark) N-3400, manufactured by Sumika Covestro Urethane (Stock)]: 4-fold dilution of the dimer of hexamethylene diisocyanate (HMDI), solid content: 25 quality%

>Other ingredients>"SH-3773M" [trade name, manufactured by Toray Dow Corning Co., Ltd.]: polyether-modified polysiloxane compound (having a hydroxyl group at the end of the polyalkyleneoxy group as a reactive group) "LiTFS" [Morita Chemical Industry Co., Ltd.]: lithium trifluoromethanesulfonate [Li(CF ₃ SO ₃ )], ionic compound "DOTDL": dioctyltin dilaurate, cross-linking catalyst "TETRAD-X" [Trade name: TETRAD (registered trademark)-X, manufactured by Mitsubishi Gas Chemical Co., Ltd.]: Epoxy crosslinking agent "ALUMICHELATE" [Kawaken Fine Chemical Co., Ltd.]: Aluminium acetone, metal chelate Crosslinking agent

[Evaluation] Using the adhesive composition prepared above, the following evaluation was performed. The results are shown in Tables 6-8.

1. Peeling force>Production of protective film for evaluation> Polyethylene terephthalate (PET) film as substrate [trade name: TEIJIN (registered trademark) TETORON (registered trademark) film, model: G2, thickness : 38 μm, Teijin Film Solutions (manufactured by Teijin Film Solutions Co., Ltd.) is coated with an adhesive composition so that the coating amount after drying becomes 15 g/m ² , and a coating film is formed. Then, the formed coating film was dried at 100°C for 60 seconds using a hot air circulation dryer, and an adhesive film was formed on the PET film. Then, the exposed surface of the adhesive film formed on the PET film was laminated on a release film that has been surface-treated with a silicone release agent [trade name: FILMBYNA (registered trademark) 100E-0010N023, thickness: 100 μm, Fujimori Industrial (Stock) Co., Ltd.] surface treatment surface, made into a laminate. After the laminate was crimped and bonded by a pressure nip roller pair, it was aged for 96 hours under an ambient temperature of 23°C and 50% RH to allow the crosslinking reaction to proceed, thereby obtaining a substrate/adhesive layer /Protective film for evaluation of laminated structure of release film.

(1) Low speed peeling force The protective film for evaluation prepared above was cut into a size of 25 mm×150 mm to prepare a protective film sheet for evaluation of peeling force. Then, the peeling film was peeled from the prepared protective film sheet for peeling force evaluation, and the surface of the adhesive layer exposed by the peeling was laminated on a polyethylene terephthalate (PET) film [trade name: After the surface of COSMOSHINE (registered trademark) A4300, thickness: 300μm, manufactured by Toyobo Co., Ltd., it was crimped using a desktop laminator to prepare a test sample. The test sample was placed in an ambient temperature of 23°C and 50%RH for 24 hours. Then, using a single-column material testing machine [model: STA-1225, manufactured by A&D (stock)] as a measuring device, under the conditions of an ambient temperature of 23°C, 50%RH, and a peeling speed of 0.3m/min, The peeling force (unit: N/25mm) of the PET film when the protective film sheet (adhesive layer/base material) for peeling force evaluation is peeled at 180° along the long side (150 mm) direction. Then, the low-speed peel force was evaluated according to the following evaluation criteria. If the evaluation result is "AA", "A", or "B", it is determined that the low-speed peel strength is excellent.

-Evaluation criteria- AA: Peeling force is 0.25N/25mm or more. A: The peeling force is 0.20 N/25mm or more and less than 0.25 N/25mm. B: The peeling force is 0.15N/25mm or more and less than 0.20N/25mm. C: The peeling force is less than 0.15N/25mm.

(2) High-speed peeling force Obtain test samples using the same procedure as in "(1) Low-speed peel force" above. The test sample was placed in an ambient temperature of 23°C and 50%RH for 24 hours. Then, using a peeling tester [model: horizontal TE-720, manufactured by TESTER SANGYO (stock)] as a measuring device, under the conditions of an ambient temperature of 23°C, 50%RH, and a peeling speed of 30m/min, the measurement was made from PET The peeling force (unit: N/25mm) when the film is peeled 180° from the protective film sheet (adhesive layer/base material) for peeling force evaluation in the long side (150 mm) direction. Then, the high-speed peel force was evaluated according to the following evaluation criteria. If the evaluation result is "AA", "A", or "B", it is judged that the high-speed peel strength is excellent.

-Evaluation criteria- AA: Peeling force is less than 1.50N/25mm. A: The peeling force is 1.50 N/25mm or more and less than 1.80 N/25mm. B: The peeling force is 1.80 N/25mm or more and less than 2.00 N/25mm. C: The peeling force is 2.00 N/25mm or more.

(3) Balance of low-speed peeling force and high-speed peeling force Evaluate the balance of low-speed peeling force and high-speed peeling force based on the value of low-speed peeling force measured in the above "(1) Low-speed peeling force" and the value of high-speed peeling force measured in "(2) High-speed peeling force" above. Specifically, based on the value obtained by dividing the value of the low-speed peeling force by the value of the high-speed peeling force, and rounding the third digit below the decimal point, the following evaluation criteria are used to evaluate the low-speed peeling force and the high-speed peeling force. balance. If the evaluation result is "AA", "A", or "B", it is determined that the low-speed peel force and the high-speed peel force have a good balance.

-Evaluation criteria- AA: "Low-speed peeling force/high-speed peeling force" is 0.20 or more. A: "Low-speed peeling force/high-speed peeling force" is 0.15 or more and less than 0.20. B: "Low-speed peeling force/high-speed peeling force" is 0.10 or more and less than 0.15. C: "Low-speed peeling force/high-speed peeling force" is less than 0.10.

2. Inhibition of zipper phenomenon (1) High speed (Peeling speed: 30m/min) In the above-mentioned "(2) High-speed peeling force", it was confirmed whether or not there is a zipper sound when peeling the protective film sheet (adhesive layer/base material) for peeling force evaluation from the PET film and its degree. Then, the suppression of the zipper phenomenon was evaluated according to the following evaluation criteria. If the evaluation result is "AA", "A", or "B", it is determined that the zipper phenomenon that may be caused when peeling off at high speed is sufficiently suppressed.

-Evaluation criteria- AA: No sound can be heard at all. A: I hear the sound vaguely. B: A sound is heard slightly. C: A louder sound is heard.

(2) Super high speed (Peeling speed: 100m/min) Obtain test samples using the same procedure as in "(1) Low-speed peeling force" of "1. Peeling force" above. The test sample was placed in an ambient temperature of 23°C and 50%RH for 24 hours. Then, using a peeling tester [model: horizontal TE-720, made by TESTER SANGYO], the peeling force from the PET film was measured under the conditions of an ambient temperature of 23°C, 50% RH, and a peeling speed of 100m/min. The protective film sheet for evaluation (adhesive layer/base material) was peeled 180° along the long side (150 mm) direction, and it was confirmed whether there was a zipper sound and its degree during peeling. Then, the suppression of the zipper phenomenon was evaluated according to the same evaluation criteria as the above-mentioned "(1) High speed (peel speed: 30 m/min)". If the evaluation result is "AA", "A", or "B", it is determined that the zipper phenomenon is sufficiently suppressed even when peeled off at an ultra high speed.

3. Surface adhesion The surface adhesion is evaluated based on the result of a constant load test according to the following procedure as an index. For the evaluation of the adhesion to the curved surface, the same protective film as the protective film for evaluation prepared in the above "1. Peeling force" was used. The protective film for evaluation was cut into a size of 25 mm×150 mm to prepare a protective film sheet for evaluation of surface adhesiveness. Then, the release film was peeled from the prepared protective film sheet for evaluation of curved surface adhesiveness, and the surface of the adhesive layer exposed by the peeling was laminated on polyethylene terephthalate (PET) as the adherend. ) After the film [trade name: COSMOSHINE (registered trademark) A4300, thickness: 300 μm, manufactured by Toyobo Co., Ltd.], the surface was crimped using a desktop laminator to prepare a test sample. The test sample has a laminated structure of adherend (PET film)/protective film sheet [adhesive layer/substrate (PET film)]. The test sample was placed in an ambient temperature of 23°C and 50%RH for 24 hours. Using the test sample after placement, an evaluation test of the adhesion to the curved surface was performed. The method of the evaluation test will be described with reference to the diagram (Figure 1). In an environment with an ambient temperature of 23°C and 50%RH, peel off the end of the test sample and use cellophane tape S to hang the weight W on the protective film sheet (adhesive layer 20/substrate 30) to A load of 9.0 g was applied in a direction of 90° with respect to the PET film 10 that is the adherend (the normal direction of the adhered surface). After marking the starting position where the protective film sheet began to peel off, it was left for 2 minutes. After leaving for 2 minutes, the length (unit: cm) of the protective film sheet peeled off was measured. Then, the adhesion of the curved surface was evaluated according to the following evaluation criteria. If the evaluation result is "AA", "A", or "B", it is judged that the surface adhesion is excellent.

-Evaluation criteria- AA: The peeling length of the test sample does not reach 2.0cm. A: The peeling length of the test sample is 2.0cm or more and less than 2.5cm. B: The peeling length of the test sample is 2.5 cm or more and less than 3.0 cm. C: The peeling length of the test sample is 3.0 cm or more.

[Table 6] Evaluation Peel force Balance of low-speed peeling force and high-speed peeling force [low-speed peeling force/high-speed peeling force] Suppression of zipper phenomenon Surface adhesion [constant load test] Low speed [Peeling speed: 0.3m/min High speed [Peeling speed: 30m/min] High speed [Peeling speed: 30m/min] Super high speed [Peeling speed: 100m/min] Measured value [N/25mm] Evaluation results Measured value [N/25mm] Evaluation results Calculated Evaluation results Evaluation results Evaluation results Measured value [cm] Evaluation results Example 1 0.29 AA 1.30 AA 0.22 AA AA AA 1.5 AA Example 2 0.26 AA 1.98 B 0.13 B AA AA 0.0 AA Example 3 0.29 AA 1.98 B 0.15 A AA AA 0.2 AA Example 4 0.16 B 0.58 AA 0.28 AA A B 1.5 AA Example 5 0.15 B 0.55 AA 0.27 AA B B 2.7 B Example 6 0.23 A 1.97 B 0.12 B AA AA 0.0 AA Example 7 0.25 AA 1.92 B 0.13 B AA AA 0.2 AA Example 8 0.29 AA 1.62 A 0.18 A AA AA 0.2 AA Example 9 0.24 A 1.31 AA 0.18 A A A 2.3 A Example 10 0.19 B 1.29 AA 0.15 A A A 2.8 B Example 11 0.17 B 1.61 A 0.11 B AA AA 2.7 B Example 12 0.20 A 1.47 AA 0.14 B AA AA 2.6 B Example 13 0.30 AA 1.13 AA 0.27 AA A A 0.4 AA Example 14 0.31 AA 0.69 AA 0.45 AA A B 0.2 AA Example 15 0.28 AA 0.55 AA 0.51 AA B B 0.8 AA Example 16 0.19 B 1.51 A 0.13 B AA AA 1.1 AA Example 17 0.25 AA 1.21 AA 0.21 AA AA AA 2.8 B Example 18 0.26 AA 1.20 AA 0.22 AA AA AA 2.7 B

[Table 7] Evaluation Peel force Balance of low-speed peeling force and high-speed peeling force [low-speed peeling force/high-speed peeling force] Suppression of zipper phenomenon Surface adhesion [constant load test] Low speed [Peeling speed: 0.3m/min High speed [Peeling speed: 30m/min] High speed [Peeling speed: 30m/min] Super high speed [Peeling speed: 100m/min] Measured value [N/25mm] Evaluation results Measured value [N/25mm] Evaluation results Calculated Evaluation results Evaluation results Evaluation results Measured value [cm] Evaluation results Example 19 0.19 B 1.15 AA 0.17 A AA AA 2.3 A Example 20 0.32 AA 1.12 AA 0.29 AA AA AA 2.5 B Example 21 0.28 AA 1.90 B 0.15 A AA A 2.4 A Example 22 0.27 AA 1.19 AA 0.23 AA A B 2.1 A Example 23 0.32 AA 1.65 A 0.19 A AA AA 2.4 A Example 24 0.30 AA 1.15 AA 0.26 AA AA B 2.8 B Example 25 0.31 AA 0.98 AA 0.32 AA A A 0.5 AA Example 26 0.35 AA 1.12 AA 0.31 AA AA AA 1.1 AA Example 27 0.35 AA 1.89 B 0.19 A AA B 0.7 AA Example 28 0.30 AA 1.40 AA 0.21 AA B B 1.4 AA Example 29 0.40 AA 1.97 B 0.20 AA AA A 2.5 B Example 30 0.15 B 0.60 AA 0.25 AA B B 1.9 AA Example 31 0.31 AA 1.48 AA 0.21 AA A B 0.0 AA Example 32 0.30 AA 1.83 B 0.16 A A B 0.0 AA Example 33 0.21 A 1.43 AA 0.15 A AA A 0.0 AA Example 34 0.20 A 1.19 AA 0.17 A AA A 1.2 AA Example 35 0.17 B 0.73 AA 0.23 AA B B 1.5 AA Example 36 0.23 A 1.87 B 0.12 B AA B 0.6 AA Example 37 0.23 A 0.72 AA 0.32 AA AA AA 2.7 B Example 38 0.25 AA 0.85 AA 0.29 AA AA AA 2.8 B

[Table 8] Evaluation Peel force Balance of low-speed peeling force and high-speed peeling force [low-speed peeling force/high-speed peeling force] Suppression of zipper phenomenon Surface adhesion [constant load test] Low speed [Peeling speed: 0.3m/min High speed [Peeling speed: 30m/min] High speed [Peeling speed: 30m/min] Super high speed [Peeling speed: 100m/min] Measured value [N/25mm] Evaluation results Measured value [N/25mm] Evaluation results Calculated Evaluation results Evaluation results Evaluation results Measured value [cm] Evaluation results Comparative example 1 0.14 C 2.13 C 0.07 C AA AA 4.7 C Comparative example 2 0.60 AA 7.31 C 0.08 C A A 0.0 AA Comparative example 3 0.26 AA 2.81 C 0.09 C C C 2.4 A Comparative example 4 0.31 AA 1.12 AA 0.28 AA C C 2.8 B Comparative example 5 0.14 C 1.90 B 0.07 C AA AA 1.8 AA Comparative example 6 0.25 AA 2.64 C 0.09 C A A 2.3 A Comparative example 7 0.14 C 1.91 B 0.07 C AA AA 3.8 C Comparative example 8 0.32 AA 1.49 AA 0.21 AA C C 1.5 AA Comparative example 9 0.29 AA 1.31 AA 0.22 AA C C 0.3 AA Comparative example 10 0.28 AA 0.45 AA 0.62 AA C C 3.1 C Comparative example 11 0.15 B 1.76 A 0.09 C AA AA 4.1 C Comparative example 12 3.20 AA 8.90 C 0.36 AA C C 0.0 AA

As shown in Table 6 and Table 7, it is confirmed that the glass transition temperature is below -40°C and the weight average molecular weight falls within the range of 300,000 to 1.5 million (methyl ) Acrylic copolymer (A) [that is, specific (meth)acrylic copolymer (A)], containing structural units derived from a monomer having a hydroxyl group, the glass transition temperature falls between -10°C and 45°C (Meth)acrylic copolymer (B) [that is, specific (meth)acrylic copolymer (B)], and isocyanate-based cross-linked range and weight average molecular weight falling in the range of more than 10,000 and less than 200,000 An example in which the content of the specific (meth)acrylic copolymer (B) falls within the range of 5 parts by mass to 60 parts by mass relative to 100 parts by mass of the specific (meth)acrylic copolymer (A) The adhesive layer formed by the adhesive composition of 1 to Example 38 has a good balance between low-speed peeling force and high-speed peeling force. Even when peeling at a higher speed than before, the zipper phenomenon is sufficiently suppressed, and the curved surface adhesiveness is excellent .

On the other hand, as shown in Table 8, it was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 1 that does not contain the specific (meth)acrylic copolymer (B) has significantly lower low-speed peel strength. And the high-speed peeling force is obviously higher, and the balance between the low-speed peeling force and the high-speed peeling force is not good. In addition, it was confirmed that the adhesive layer formed using the adhesive composition of Comparative Example 1 had poor adhesion to the curved surface. It is confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 2 in which the (meth)acrylic copolymer (A) does not contain a structural unit derived from a monomer having a hydroxyl group has significantly higher high-speed peeling force and low-speed peeling The balance between force and high-speed peel force is poor. It is confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 3 whose glass transition temperature (Tg) of the (meth)acrylic copolymer (A) exceeds -40°C has significantly higher high-speed peeling force and low-speed peeling The balance between force and high-speed peel force is poor. In addition, it was confirmed that the adhesive layer formed using the adhesive composition of Comparative Example 3 cannot sufficiently suppress the zipper phenomenon that may be caused when peeling at high speed.

It was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 4 in which the weight average molecular weight of the (meth)acrylic copolymer (B) exceeds 200,000, cannot sufficiently suppress the zipper phenomenon that may be caused when peeling at high speed. It was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 5 whose weight average molecular weight of the (meth)acrylic copolymer (B) is 10,000 or less has significantly lower low-speed peeling force, and low-speed peeling force and high-speed Poor balance of peel force. It was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 6 in which the (meth)acrylic copolymer (B) does not contain a structural unit derived from a monomer having a hydroxyl group has significantly higher high-speed peeling force and low-speed peeling The balance between force and high-speed peel force is poor.

It was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 7 in which the glass transition temperature (Tg) of the (meth)acrylic copolymer (B) did not reach -10°C had significantly lower low-speed peeling force, and the low-speed The balance between peeling force and high-speed peeling force is poor. In addition, it was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 7 had poor adhesiveness on the curved surface. It was confirmed that the use of a (meth)acrylic copolymer (B) that does not contain a structural unit derived from a monomer having a hydroxyl group, has a glass transition temperature (Tg) exceeding 45°C and a weight average molecular weight of 10,000 or less, is relative to the specific (methyl) ) 100 parts by mass of the acrylic copolymer (A) is an adhesive layer formed by the adhesive composition of Comparative Example 8 with less than 5 parts by mass, which cannot sufficiently suppress the zipper phenomenon that may be caused when peeling off at a high speed. It was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 9 in which the glass transition temperature (Tg) of the (meth)acrylic copolymer (B) exceeds 45°C cannot sufficiently suppress the possibility of peeling at high speed Zipper phenomenon.

It is confirmed that the content of the specific (meth)acrylic copolymer (B) is more than 60 parts by mass relative to 100 parts by mass of the specific (meth)acrylic copolymer (A), which is formed by the adhesive composition of Comparative Example 10 The adhesive layer cannot sufficiently suppress the zipper phenomenon that may be caused when peeling off at a high speed. In addition, it was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 10 had poor adhesiveness on the curved surface. It is confirmed that the content of the specific (meth)acrylic copolymer (B) is less than 5 parts by mass relative to 100 parts by mass of the specific (meth)acrylic copolymer (A) to be formed by the adhesive composition of Comparative Example 11 In the adhesive layer, the balance between low-speed peeling force and high-speed peeling force is not good. In addition, it was confirmed that the adhesive layer formed using the adhesive composition of Comparative Example 11 had poor adhesiveness on the curved surface. It was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 12 that does not contain an isocyanate-based crosslinking agent cannot sufficiently suppress the zipper phenomenon that may be caused when peeling off at high speed.

10: Adhered body (PET film) 20: Adhesive layer 30: Substrate (PET film) S: Cellophane tape W: heavy

[Fig. 1] A schematic diagram illustrating a test method for evaluating the adhesion to a curved surface in an embodiment of the present invention.

Claims (9)

An adhesive composition for protective film, containing: The (meth)acrylic copolymer (A) contains a structural unit derived from a monomer having a hydroxyl group, has a glass transition temperature of -40°C or less and a weight average molecular weight in the range of 300,000 to 1.5 million, The (meth)acrylic copolymer (B) contains a structural unit derived from a monomer having a hydroxyl group, the glass transition temperature falls within the range of -10°C or more and 45°C or less, and the weight average molecular weight falls between more than 10,000 and 200,000 The following range, and Isocyanate series crosslinking agent; The content of the (meth)acrylic copolymer (B) falls within a range of 5 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the (meth)acrylic copolymer (A). The adhesive composition for a protective film of claim 1, wherein the glass transition temperature of the (meth)acrylic copolymer (A) falls within the range of -75°C or more and -40°C or less. The adhesive composition for a protective film of claim 1 or 2, wherein the (meth)acrylic copolymer (A) has a content rate of the structural unit derived from the monomer having a hydroxyl group relative to the (methyl) ) All the structural units of the acrylic copolymer (A) fall within the range of 0.5% by mass or more and 15% by mass or less. The adhesive composition for a protective film of claim 1 or 2, wherein the (meth)acrylic copolymer (B) has a content rate of the structural unit derived from the monomer having a hydroxyl group relative to the (methyl) ) All the structural units of the acrylic copolymer (B) fall within the range of 0.5% by mass to 15% by mass. The adhesive composition for a protective film of claim 1 or 2, wherein the content of the (meth)acrylic copolymer (B) is relative to 100 parts by mass of the (meth)acrylic copolymer (A). It is in the range of 5 parts by mass or more and 50 parts by mass or less. According to claim 1 or 2, the adhesive composition for a protective film, wherein the isocyanate-based crosslinking agent is hexamethylene diisocyanate. The adhesive composition for a protective film of claim 1 or 2, wherein the (meth)acrylic copolymer (A) contains a structural unit derived from a monomer having a carboxyl group. The adhesive composition for a protective film of claim 1 or 2, wherein the (meth)acrylic copolymer (B) contains a structural unit derived from a monomer having a carboxyl group. A protective film with: Substrate, and The adhesive layer is provided on the substrate and formed by using the adhesive composition for a protective film according to any one of claims 1 to 8.

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